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  <row Id="1" PostTypeId="1" AcceptedAnswerId="13" CreationDate="2009-10-28T03:18:50.070" Score="3" ViewCount="2830" Body="&lt;p&gt;How do use use an Arduino with a Stepper Motor? &lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-11-02T00:47:35.897" Title="Arduino Stepper Motor" Tags="&lt;arduino&gt;&lt;stepper&gt;&lt;motor&gt;" AnswerCount="3" />
  <row Id="2" PostTypeId="1" AcceptedAnswerId="5" CreationDate="2009-10-28T14:06:32.277" Score="3" ViewCount="256" Body="&lt;p&gt;How can you get the analogue sensor data into Max MSP with an Arduino?&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-01T04:54:23.773" LastActivityDate="2011-02-01T04:54:23.773" Title="How can you get the analogue sensor data into Max MSP?" Tags="&lt;arduino&gt;&lt;maxmsp&gt;" AnswerCount="4" />
  <row Id="3" PostTypeId="1" CreationDate="2009-10-28T15:00:37.867" Score="9" ViewCount="882" Body="&lt;p&gt;How do I know when to use lead, flux-core, lead-free, or any other kind of solder out there? Do you have any tips on solder gauge for specific applications? &lt;/p&gt;&#xA;" OwnerUserId="8" LastActivityDate="2011-05-17T08:03:14.820" Title="What are the different types of solder used for?" Tags="&lt;soldering&gt;" AnswerCount="4" FavoriteCount="4" />
  <row Id="4" PostTypeId="2" ParentId="3" CreationDate="2009-10-28T16:09:45.390" Score="9" ViewCount="" Body="&lt;p&gt;A great question, and since a textbook could probably be written to answer it, there's probably not going to be any single answer.  I want to provide a general answer tailored to hobbyists, and hope that people more knowledgeable can come in and tie up specifics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Summary&lt;/strong&gt;&lt;br&gt;&#xA;Solder is basically metal wire with a &quot;low&quot; melting point, where low for our purposes means low enough to be melted with a soldering iron.  For electronics, it is traditionally a mix of tin and lead.  Lead has a lower melting point than tin, so more lead means a lower melting point.  Most common lead-based solder you'll find at the gadget store will be 60Sn/40Pb (for 60% tin, 40% lead).  There's some other minor variations you're likely to see, such as 63Sn/37Pb, but for general hobbyist purposes I have used 60/40 for years with no issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Science Content&lt;/strong&gt;&lt;br&gt;&#xA;Now, molten metal is a tricky beast.  We melt solder to weld parts together, but molten metal behaves a bit like water: Of particular interest is its surface tension.  Molten metal will ball up if it doesn't find something to &quot;stick&quot; to.  That's why solder masks work to keep jumpers from forming, and why you see surface-mount soldering tricks.  In general, metal likes to stick to metal, but doesn't like to stick to oils or oxidized metals.  By simply being exposed to air, our parts and boards start to oxidize, and through handling they get exposed to grime (such as oils from our skin).  The solution to this is to clean the parts and boards first.  That's where flux cores come in to solder.  Flux cores melt at a lower temperature than the solder, and coat the area to be soldered.  The flux cleans the surfaces, and if they're not too dirty the flux is sufficient to make a good strong solder joint (makes it &quot;sticky&quot; enough).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Flux Cores&lt;/strong&gt;&lt;br&gt;&#xA;There are two common types of flux cores: Acid and Rosin.  Acid is for plumbing, and should NOT be used in electronics (it is likely to eat your components or boards).  You do need to keep an eye out for that, but in general if it's in the electronics section of a gadget store it's good, if it's in the plumbing section of a home supply/home improvement store, it's bad.  In general, for hobbyist use, as long as you keep your parts clean and don't let them sit around too long, a flux core isn't necessary.  However, if you are looking for solder then you probably should pick up something with a rosin core.  The only reason you wouldn't use a flux core solder as a hobbyist is if you knew exactly why you didn't need the flux in the first place, but again, if you have some solder without flux you can probably use it for hobbyist purposes without issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Lead Free&lt;/strong&gt;&lt;br&gt;&#xA;That's pretty much all a hobbyist needs to know, but it doesn't hurt to know about lead-free solder since things are going that way.  The EU now requires pretty much all commercially-available electronics (with exceptions for the health and aerospace industries, as I recall) to use lead-free components, including solder.  This is catching on, and while you can still find lead-based solder it can lead to confusion.  The purpose of lead-free solder is exactly the same: It's an evolution in the product meant to be more environmentally friendly.  The issue is that lead is used to reduce the melting point, so now different metals are used instead which aren't as effective.  In general, you can use lead-free and lead-based solder interchangeably for hobbyist uses, but lead-free solder is a bit harder to work with because it doesn't flow as nicely or at as low a temperature as its lead-based equivalent.  It's nothing that will stop you from successfully soldering something, and in general lead-free and lead-based solders are pretty interchangeable to the hobbyist.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Tutorials&lt;/strong&gt;&lt;br&gt;&#xA;There are plenty of soldering videos on YouTube, just plugging in &quot;soldering&quot; to the search should turn up plenty.  NASA has some old instructional videos that are great, because they deal with a lot of through-hole components.  Some of these are relevant because they discuss the techniques and how the solder types relate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, if you got it at the electronics hobby shop, it's good to use for hobbyist purposes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope that helps, and that this discussion continues to provide more information.&lt;/p&gt;&#xA;" OwnerUserId="11" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-17T08:03:14.820" LastActivityDate="2011-05-17T08:03:14.820" />
  <row Id="5" PostTypeId="2" ParentId="2" CreationDate="2009-10-28T20:55:16.697" Score="2" ViewCount="" Body="&lt;p&gt;Atleast &lt;a href=&quot;http://www.arduino.cc/playground/Interfacing/MaxMSP&quot; rel=&quot;nofollow&quot;&gt;Arduino2Max&lt;/a&gt; allows you to read analogue pins and also digital pins into a Max.&lt;/p&gt;&#xA;" OwnerUserId="13" LastActivityDate="2009-10-28T20:55:16.697" />
  <row Id="6" PostTypeId="2" ParentId="2" CreationDate="2009-10-28T20:56:58.210" Score="2" ViewCount="" Body="&lt;p&gt;While doing some surfing trying to find out more about Max MSP, I came across this site:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://file-error.net/1o1o1o1o1/?Physical_Computing_and_Interaction:Arduino:Arduino_VS_Max/MSP&quot; rel=&quot;nofollow&quot;&gt;http://file-error.net/1o1o1o1o1/?Physical_Computing_and_Interaction:Arduino:Arduino_VS_Max/MSP&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino2Max section of the page (near the bottom) has a patch for Max MSP and some sample code for the Arduino.  I don't know if that helps, because I don't have Max MSP available, but maybe it'll get the ball rolling. &lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-10-28T20:56:58.210" />
  <row Id="7" PostTypeId="1" CreationDate="2009-10-28T22:19:05.113" Score="3" ViewCount="645" Body="&lt;p&gt;What is the trick to soldering to aluminum bases (like are found on the older Luxeon LEDS?)&lt;/p&gt;&#xA;" LastActivityDate="2009-11-02T18:17:16.323" Title="Soldering to aluminum" Tags="&lt;soldering&gt;" AnswerCount="6" />
  <row Id="8" PostTypeId="2" ParentId="1" CreationDate="2009-10-28T22:47:48.063" Score="1" ViewCount="" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here you have a tutorial made my me in Portuguese but google translate it to english pretty well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://translate.google.pt/translate?js=y&amp;amp;prev=_t&amp;amp;hl=pt-PT&amp;amp;ie=UTF-8&amp;amp;u=http%3A%2F%2Fwww.lusorobotica.com%2Findex.php%2Ftopic%2C106.0.html&amp;amp;sl=pt&amp;amp;tl=en&amp;amp;history_state0=&amp;amp;swap=1&quot; rel=&quot;nofollow&quot;&gt;http://translate.google.pt/translate?js=y&amp;amp;prev=_t&amp;amp;hl=pt-PT&amp;amp;ie=UTF-8&amp;amp;u=http%3A%2F%2Fwww.lusorobotica.com%2Findex.php%2Ftopic%2C106.0.html&amp;amp;sl=pt&amp;amp;tl=en&amp;amp;history_state0=&amp;amp;swap=1&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The original language can be consulted to have the source without translation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best regards,&lt;/p&gt;&#xA;" LastActivityDate="2009-10-28T22:47:48.063" />
  <row Id="10" PostTypeId="2" ParentId="7" CreationDate="2009-10-28T23:54:27.300" Score="0" ViewCount="" Body="&lt;p&gt;As I understand it you need special flux to break through the oxide formed on the aluminium. The oxide forms so quickly that just cleaning the surface won't do it. I've never done it myself though!&lt;/p&gt;&#xA;" LastActivityDate="2009-10-28T23:54:27.300" />
  <row Id="11" PostTypeId="2" ParentId="7" CreationDate="2009-10-28T23:58:37.080" Score="2" ViewCount="" Body="&lt;p&gt;Soldering to aluminum is indeed tricky.  Aluminum oxidizes even worse than copper, so you need a different, stronger flux that you get with most solder.  Also, soldering to something like the base of a Luxeon LED means you are trying to solder to a heatsink - so it will be difficult to get the aluminum up to the melting point of solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The aluminum bases of LED modules, and other heatsinks, are normally electrically isolated.  They are just heat sinks.  So before you go to too much trouble, I'd question why you are even attempting to solder to aluminum.&lt;/p&gt;&#xA;" OwnerUserId="19" LastActivityDate="2009-10-28T23:58:37.080" />
  <row Id="12" PostTypeId="2" ParentId="3" CreationDate="2009-10-29T01:13:01.673" Score="7" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Lead vs Lead-free&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;60/40 lead solder melts at 315C and takes about 1.5 seconds to melt and form a bond, aka &quot;wet&quot;.  Good bonds are shiny and shaped like a &quot;tent&quot;, not a ball.  With just a little practice, you can get good or at least very competent using lead solder.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, lead is a toxic heavy metal, so extended skin contact isn't good for you (and terrible for the environment if disposed of improperly).  I like to wear very thin cotton gloves while soldering (but I don't always).  Note that lead does not &quot;evaporate&quot; during soldering.  The smoke you see is the flux.  But you shouldn't be breathing flux either.  I use a fan and filter when soldering.  There is also the &quot;breath out&quot; technique to avoid the fumes, which is fine for small jobs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lead-free solder melts at 340 to 370C (depending on the formula), and takes about 4 seconds to wet.  Good bonds are not shiny, and it is harder to visually detect a bad joint, at least at first.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simple answer: unless you are planning to sell the device you are soldering to someone in the EU, stick with lead-based solder.  Lower soldering temperature and faster wetting time of lead-based solder means less chance to thermally damage your board and parts (and its cheaper).  Electrically, you can use either.  You can even use lead solder to rework a lead-free board.  Of course, then it won't be RoHS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Diameter of solder&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Very thin solder, 0.020&quot; dia or less, gives you a lot of control over how much solder you are putting down, and melts a bit faster.  But you have to &quot;feed&quot; the solder into the joint at the right speed, and unrolling another foot from the roll every couple joints gets old.  I sometimes don't get enough solder into the joint with thin solder because I don't/can't feed it fast enough.  Good for hand-soldering fine SMT parts.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thick solder, 0.050&quot; dia or more, is good for making big joints, like heavy gauge wire or leads on a TO-220 regulator.  But it is easy to put down too much solder, and seems to melt slower as the solder itself acts as a heat sink.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I generally prefer &quot;mid sized&quot; solder, 0.025 - 0.031&quot; dia, for most work.  It gives me a balance of controlling how much I put on a joint, without the hassle of feeding the hair-thin stuff.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Flux&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Electronics flux can be rosin, water-based, or no-clean.  All are about the same quality as far as de-oxidizing the copper so a good solder bond can be made.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rosin flux leaves an ugly, sticky residue.  Cleaning it off takes either a LOT of water, or a (nasty) chemical solvent.  You shouldn't leave it on, as it is slightly corrosive, and can also be somewhat conductive.  This is falling out of usage due to the environmental impact of cleaning.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Water-based (aka Resin) flux is less ugly, not sticky.  The stuff I have used leaves a white film behind.  I have heard this film can cause problems with long term reliability.  Some people just leave it on, but removal takes only a moderate amount of water.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;No-clean&quot; flux is resin flux that burns or boils off, leaving almost no residue.  &lt;/p&gt;&#xA;" OwnerUserId="19" LastActivityDate="2009-10-29T01:13:01.673" CommentCount="2" />
  <row Id="13" PostTypeId="2" ParentId="1" CreationDate="2009-10-29T04:50:28.880" Score="3" ViewCount="" Body="&lt;p&gt;There are two kinds of stepper motors: unipolar and bipolar. Unipolar steppers have six wires coming off of them and bipolar ones have four wires. To control a unipolar stepper, you need to use a chip called a darlington array. To control a bipolar stepper you use an h-bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've never worked with unipolar steppers, but I can explain how to use bipolar ones. The first thing you need to do is find which wires are paired. Use a multimeter and one-by-once connect the meter to every possible pair of wires while measuring the resistance. On two of the pairings you'll find non-infinite amounts of resistance. These are the connected pairs. Attach each of these to the different halves of your h-bridge. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you've got your control circuit wired up (whether it be the h-bridge for the bipolar stepper or the darlington array for the unipolar), you use the Arduino Stepper Library to control it&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got a write-up of &lt;a href=&quot;http://www.urbanhonking.com/ideasfordozens/2009/10/real%5Fpen%5Fetchasketch%5Fwith%5Fstep.html&quot; rel=&quot;nofollow&quot;&gt;a recent project I did with steppers&lt;/a&gt; Since I'm only allowed to post one link here, refer there for links to many of the things I mentioned here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tom Igoe has a great write-up about steppers on his site.&lt;/p&gt;&#xA;" OwnerUserId="22" LastActivityDate="2009-10-29T04:50:28.880" />
  <row Id="14" PostTypeId="1" AcceptedAnswerId="15" CreationDate="2009-10-29T05:00:32.383" Score="3" ViewCount="2430" Body="&lt;p&gt;How do I get Arduino working on Windows 7?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-10-29T05:14:25.020" ClosedDate="2011-03-22T16:51:11.027" Title="How do I get Arduino working on Windows 7?" Tags="&lt;arduino&gt;&lt;windows&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="15" PostTypeId="2" ParentId="14" CreationDate="2009-10-29T05:14:25.020" Score="2" ViewCount="" Body="&lt;p&gt;1) Download Arduino V17 from: &lt;a href=&quot;http://arduino.googlecode.com/files/arduino-0017.zip&quot; rel=&quot;nofollow&quot;&gt;http://arduino.googlecode.com/files/arduino-0017.zip&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Fix the graphical glitches in the Arduino IDE. The Arduino IDE will actually work fine, but have graphical glitches. The fix is to download the latest (32-Bit, even if you're running 64-Bit Windows) JAVA JRE Update from &lt;a href=&quot;http://java.com/en/download/manual.jsp&quot; rel=&quot;nofollow&quot;&gt;http://java.com/en/download/manual.jsp&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Delete the JAVA folder from the Arduino folder and replace it with the one that the the JRE install places in your Program Files folder. (If the new java.exe is in your system path it is possible that you don't really need to move the folder.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) Reinstall the Arduino FTDI Chip drivers from &lt;a href=&quot;http://www.ftdichip.com/Drivers/VCP.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.ftdichip.com/Drivers/VCP.htm&lt;/a&gt; . The FTDI chip is the chip on the Arduino that translates your computer's USB to Serial.&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-10-29T05:14:25.020" CommunityOwnedDate="2009-10-29T05:14:25.020" />
  <row Id="16" PostTypeId="1" CreationDate="2009-10-29T10:21:32.420" Score="1" ViewCount="1286" Body="&lt;p&gt;We had a version of the &lt;a href=&quot;http://www.instructables.com/id/HDDJ%5FTurning%5Fan%5Fold%5Fhard%5Fdisk%5Fdrive%5Finto%5Fa%5Frotary/&quot; rel=&quot;nofollow&quot;&gt;HDDJ&lt;/a&gt; working with an arduino reading an old stepper motor (with 4 wires), then sending serial data to processing, using a midi library, and midiox + midiyoke. Having trouble getting reliable forward/back speed data from the newer HDD's (2 or 3 wires), I think they are brushless DC motors? anyone had any experiance with this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers,&#xA;Al &lt;/p&gt;&#xA;" OwnerUserId="24" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-10-30T02:17:08.970" LastActivityDate="2009-10-31T23:11:16.147" Title="How do you read newer HDD motors (DC/Brushless) into arduino? (like stepper motors)" Tags="&lt;arduino&gt;&lt;brushless&gt;&lt;dc&gt;&lt;stepper&gt;" AnswerCount="2" />
  <row Id="17" PostTypeId="2" ParentId="7" CreationDate="2009-10-29T22:49:14.240" Score="1" ViewCount="" Body="&lt;p&gt;In my experience, soldering to aluminum requires a lot of flux, and even then only really works when doing aluminum to aluminum. Otherwise I recommend using something like silver paste or some other sort of conductive epoxy.&lt;/p&gt;&#xA;" OwnerUserId="26" LastActivityDate="2009-10-29T22:49:14.240" />
  <row Id="18" PostTypeId="1" AcceptedAnswerId="20" CreationDate="2009-10-30T02:06:23.157" Score="4" ViewCount="2216" Body="&lt;p&gt;How do I setup a hardware watch dog timer with an Arduino?&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-22T16:52:24.787" LastActivityDate="2011-03-22T16:52:24.787" Title="Watch Dog Timer + Arduino" Tags="&lt;arduino&gt;&lt;timer&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="19" PostTypeId="2" ParentId="16" CreationDate="2009-10-30T03:50:08.860" Score="1" ViewCount="" Body="&lt;p&gt;I have used a brushless motor from a CD player for input.&#xA;The best info I found was this instructable &lt;a href=&quot;http://www.instructables.com/id/HDDJ_Turning_an_old_hard_disk_drive_into_a_rotary/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/HDDJ_Turning_an_old_hard_disk_drive_into_a_rotary/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They show how to use an op-amp to make the signals readable.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-10-30T03:50:08.860" CommunityOwnedDate="2009-10-30T03:50:08.860" CommentCount="2" />
  <row Id="20" PostTypeId="2" ParentId="18" CreationDate="2009-10-30T04:02:29.867" Score="5" ViewCount="" Body="&lt;p&gt;There are a number of dedicated hardware watchdog chips available, but it's easy enough to do using a regular 555 timer IC and a couple of supporting parts. With the 555 configured in astable mode with a very long &quot;HIGH&quot; period and a relatively short (perhaps 0.3 seconds) &quot;LOW&quot; period, the output can be connected to the Arduino's reset pin via a diode to make the watchdog an open-collector device. The Arduino can then periodically reset the watchdog using a digital output to turn on a transistor that discharges the timing capacitor attached to the 555, preventing it ever reaching a trigger point that will cause it to reset the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some basic information about a project to do this is available at &lt;a href=&quot;http://www.practicalarduino.com/news/id/471&quot; rel=&quot;nofollow&quot;&gt;http://www.practicalarduino.com/news/id/471&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="31" LastActivityDate="2009-10-30T04:02:29.867" CommentCount="2" />
  <row Id="22" PostTypeId="1" AcceptedAnswerId="31" CreationDate="2009-10-30T10:58:41.967" Score="7" ViewCount="2722" Body="&lt;p&gt;Is there any method to output VGA with Arduino?&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2010-10-18T13:59:48.210" Title="VGA Output from Arduino" Tags="&lt;arduino&gt;&lt;vga&gt;" AnswerCount="4" />
  <row Id="23" PostTypeId="1" AcceptedAnswerId="41" CreationDate="2009-10-30T10:59:30.220" Score="4" ViewCount="593" Body="&lt;p&gt;How do you send a tweet via Arduino using an Arduino Ethernet Shield? &lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:34:10.123" LastActivityDate="2011-03-09T22:17:11.653" Title="Arduino Twitter" Tags="&lt;arduino&gt;&lt;ethernet&gt;&lt;twitter&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="24" PostTypeId="1" AcceptedAnswerId="30" CreationDate="2009-10-30T11:02:47.427" Score="1" ViewCount="246" Body="&lt;p&gt;What's the correct DC Adapter to use with Arduino? Voltage etc?&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-10-30T13:12:05.680" Title="Correct DC Adapter type to use for Arduino" Tags="&lt;arduino&gt;&lt;dc&gt;&lt;power&gt;&lt;adapter&gt;&lt;voltage&gt;" AnswerCount="2" />
  <row Id="25" PostTypeId="1" AcceptedAnswerId="63" CreationDate="2009-10-30T11:04:38.293" Score="2" ViewCount="746" Body="&lt;p&gt;How do you make / connect an Analogue gauge with Arduino?&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-10T03:00:53.953" LastActivityDate="2010-03-10T03:00:53.953" Title="Analogue Gauge with Arduino" Tags="&lt;analog&gt;&lt;gauge&gt;&lt;arduino&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="26" PostTypeId="1" AcceptedAnswerId="86" CreationDate="2009-10-30T11:05:47.337" Score="1" ViewCount="536" Body="&lt;p&gt;How do you control an Arduino using Applescript?&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-11-24T04:38:13.190" Title="Applescript and Arduino" Tags="&lt;arduino&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="27" PostTypeId="1" AcceptedAnswerId="90" CreationDate="2009-10-30T11:07:13.747" Score="2" ViewCount="310" Body="&lt;p&gt;What is a good software package for interfacing Arduino's input pins to MAX/MSP?&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-01T04:53:50.607" LastActivityDate="2011-02-01T04:53:50.607" Title="Software package for interfacing Arduino with MAX MSP?" Tags="&lt;arduino&gt;&lt;maxmsp&gt;" AnswerCount="3" />
  <row Id="28" PostTypeId="1" AcceptedAnswerId="51" CreationDate="2009-10-30T11:08:34.883" Score="1" ViewCount="347" Body="&lt;p&gt;How do you burn the Arduino Boot Loader onto the Arduino BT? &lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-10-31T11:37:17.210" Title="Arduino BT (bluetooth) Boot Loader" Tags="&lt;arduino&gt;&lt;bluetooth&gt;" AnswerCount="1" />
  <row Id="29" PostTypeId="1" AcceptedAnswerId="36" CreationDate="2009-10-30T11:10:09.810" Score="3" ViewCount="1739" Body="&lt;p&gt;How do you program a sleep mode for your Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:41:13.703" LastActivityDate="2010-08-17T23:41:13.703" Title="How to Sleep Arduino" Tags="&lt;arduino&gt;&lt;programming&gt;&lt;sleep&gt;" AnswerCount="3" />
  <row Id="30" PostTypeId="2" ParentId="24" CreationDate="2009-10-30T11:15:15.250" Score="2" ViewCount="" Body="&lt;p&gt;You can find some documentation related to this on the Arduino Website here:&#xA;&lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardDuemilanove&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Main/ArduinoBoardDuemilanove&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Essentially.. the thing to know is that it is a 7805 regulator.. any excess voltage is being converted into heat.  The Arduino runs at 5V.. and in order for the regulator to work it needs to be a minimum of around 1.5 volts above that.. so your &quot;Minimum&quot; is about 6.5V DC.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You want to try be as close to that as possible - so 7.5 and 9 volts DC are fine .. you can run at 12 volts DC.. but the regulator will get a little warm.. and I wouldn't do this if you are powering much from the Arduino board as that will increase the heat output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bottom line: 7.5V DC is best, 9V and 12V DC are OK.  Anything about 12V is probably pushing it.  12V is the most common you will find &quot;lying around&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino uses a Barrel-style connector .. it is compatible with most reasonably sized plugpacks.. I am not sure what the size in millimeters is.&lt;/p&gt;&#xA;" OwnerUserId="33" LastActivityDate="2009-10-30T11:15:15.250" />
  <row Id="31" PostTypeId="2" ParentId="22" CreationDate="2009-10-30T11:21:30.160" Score="5" ViewCount="" Body="&lt;p&gt;This is quite difficult to do well.. there are a couple of examples.  The main difficulty is in the speed of the CPU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's one doing direct VGA output:&#xA;&lt;a href=&quot;http://blog.makezine.com/archive/2008/07/arduino_vga_demo.html&quot; rel=&quot;nofollow&quot;&gt;http://blog.makezine.com/archive/2008/07/arduino_vga_demo.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you google &quot;Arduino VGA&quot; there are a few demo projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A couple options are the &quot;TellyMate&quot; shield that lets you output Composite rather than VGA (the single yellow connector you find on your TV. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another is the &quot;PICASO Universal Base Board&quot; and &quot;PICASO VGA/SVGA Graphics Controller&quot; - this is not a direct shield but probably the best option I have seen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both the above items are available from Sparkfun and Little Bird Electronics among other places.&lt;/p&gt;&#xA;" OwnerUserId="33" LastActivityDate="2009-10-30T11:21:30.160" />
  <row Id="32" PostTypeId="1" CreationDate="2009-10-30T11:43:23.597" Score="2" ViewCount="473" Body="&lt;p&gt;Where can I find pin mappings for the ATMEGA168?&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2011-05-31T12:28:04.480" Title="ATMEGA168 Pin Mappings" Tags="&lt;atmega168&gt;&lt;atmega&gt;&lt;pin&gt;" AnswerCount="5" FavoriteCount="0" />
  <row Id="33" PostTypeId="1" AcceptedAnswerId="71" CreationDate="2009-10-30T11:44:36.307" Score="6" ViewCount="2130" Body="&lt;p&gt;Can you use the Arduino as an AVR programmer?&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2010-03-03T04:20:05.813" Title="Arduino as AVR Programmer" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;programmer&gt;" AnswerCount="5" FavoriteCount="3" />
  <row Id="34" PostTypeId="2" ParentId="32" CreationDate="2009-10-30T13:03:51.923" Score="6" ViewCount="" Body="&lt;p&gt;Page 2 of the ATMega168 data sheet has the pin mappings for all four packages of the chip, and pages 3 and 4 give a bit more information regarding some of the basic pin functions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2545.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/resources/prod_documents/doc2545.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-10-30T13:03:51.923" CommentCount="1" />
  <row Id="35" PostTypeId="2" ParentId="24" CreationDate="2009-10-30T13:12:05.680" Score="2" ViewCount="" Body="&lt;p&gt;The spec sheets for the Arduino Duemilanove says it is a 2.1mm barrel jack, if anyone needs to know (See the Power heading):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardDuemilanove&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Main/ArduinoBoardDuemilanove&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-10-30T13:12:05.680" />
  <row Id="36" PostTypeId="2" ParentId="29" CreationDate="2009-10-30T13:36:21.183" Score="4" ViewCount="" Body="&lt;p&gt;avr/sleep.h might have what you need - documentation is at &#xA;    &lt;a href=&quot;http://www.nongnu.org/avr-libc/user-manual/group__avr__sleep.html&quot; rel=&quot;nofollow&quot;&gt;http://www.nongnu.org/avr-libc/user-manual/group__avr__sleep.html&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some warnings about putting the CPU to sleep though :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="34" LastActivityDate="2009-10-30T13:36:21.183" />
  <row Id="37" PostTypeId="1" AcceptedAnswerId="39" CreationDate="2009-10-30T13:57:13.107" Score="2" ViewCount="777" Body="&lt;p&gt;I have purchased an ATMega328 from SparkFun with the Arduino bootloader pre-programmed (&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9217&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9217&lt;/a&gt;).  My intention is to replace the ATMega168 I currently have in my Duemilanove.  Is this as simple as swapping the chips, or will I need to take any additional steps?  As I recall, I am currently at Arduino 13 but am planning to upgrade to 17 (current version) concurrent with the part swap.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-11-04T10:13:07.123" Title="Upgrading an Arduino Duemilanove from ATMega168 to ATMega328" Tags="&lt;arduino&gt;&lt;atmega&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="38" PostTypeId="2" ParentId="1" CreationDate="2009-10-30T16:33:38.987" Score="3" ViewCount="" Body="&lt;p&gt;An alternative to crafting your own drivers and pushing out the correct order of controls to a stepper's pairs, is to use an off-the-shelf driver for your stepper.  Most feature a simple two-pin control, one for direction and one you pulse to take a step, that greatly reduces the number of pins you use on your arduino, and the amount of logic involved.  Not to mention, they also tend to support chopper (micro-stepping) driving, which reduces overall current consumption and allows you to run them at higher voltage, and gain smoother motions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some example of off-the-shelf drivers include: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Easydriver (a favorite among arduino folks)&#xA;Probotix Unipolar Stepper Drivers,&#xA;and Gecko drivers (Arguably the Rolls-Royce of stepper drivers)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I have not included links as it does not allow me to include more than one link, but they can easily be found via google.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An important point to note when you start driving steppers, which is often overlooked in the myriad tutorials out there: you &lt;em&gt;must&lt;/em&gt; ramp into and out of full-speed stepping when making a multiple step move.  I've seen many examples where they say to just send the same rate of steps to the motor at all times.  Not only will this result in greater vibrations and noise when moving at full-speed, it can also result in a failure to execute move, and under- or over-shooting position.  Apply proper linear (or otherwise) speed ramping to your movements.  (Start and end with a larger delay between steps than the delay used in full-speed movement.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;!c&lt;/p&gt;&#xA;" OwnerUserId="36" LastActivityDate="2009-10-30T16:33:38.987" />
  <row Id="39" PostTypeId="2" ParentId="37" CreationDate="2009-10-30T16:41:29.140" Score="4" ViewCount="" Body="&lt;p&gt;Yes, you may simply switch the chips.  Version 13 implemented support for the 328, so an IDE upgrade is not essential.&lt;/p&gt;&#xA;" OwnerUserId="36" LastActivityDate="2009-10-30T16:41:29.140" />
  <row Id="40" PostTypeId="1" CreationDate="2009-10-30T18:49:34.180" Score="3" ViewCount="275" Body="&lt;p&gt;I'm interested in a hand powered generator similar to the one in this Gakken Helicopter Kit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MKGK24&quot; rel=&quot;nofollow&quot;&gt;http://www.makershed.com/ProductDetails.asp?ProductCode=MKGK24&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are these easy to come by? Easy to make? Thanks. &lt;/p&gt;&#xA;" LastActivityDate="2009-11-07T14:07:44.267" Title="Hand Powered Generator" Tags="&lt;generator&gt;" AnswerCount="4" />
  <row Id="41" PostTypeId="2" ParentId="23" CreationDate="2009-10-30T21:06:22.837" Score="7" ViewCount="" Body="&lt;p&gt;There is a library available for twittering &lt;a href=&quot;http://www.arduino.cc/playground/Code/TwitterLibrary&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, it has info on how to set it up.  I am not sure about how to use the ethernet sheild as I am too broke to afford one, but I imagine it wouldn't be that hard with the library installed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the example code from the library page (looks nice and easy):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/* Post a simple message to Twitter  */&#xA;#include &amp;lt;Ethernet.h&amp;gt;&#xA;#include &amp;lt;Twitter.h&amp;gt;&#xA;&#xA;byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };&#xA;byte ip[] = { 10, 0, 0, 177 };&#xA;byte gateway[] = { 10, 0, 0, 1 };&#xA;byte subnet[] = { 255, 255, 0, 0 };&#xA;&#xA;Twitter twitter(&quot;YourID:Password&quot;);&#xA;char msg[] = &quot;Hello, World! I'm Arduino!&quot;;&#xA;&#xA;void setup()&#xA;{&#xA;  Ethernet.begin(mac, ip, gateway, subnet);&#xA;  Serial.begin(9600);&#xA;&#xA;  delay(1000);&#xA;&#xA;  Serial.println(&quot;connecting ...&quot;);&#xA;  if (twitter.post(msg)) {&#xA;    int status = twitter.wait();&#xA;    if (status == 200) {&#xA;      Serial.println(&quot;OK.&quot;);&#xA;    } else {&#xA;      Serial.print(&quot;failed : code &quot;);&#xA;      Serial.println(status);&#xA;  }&#xA;  } else {&#xA;  Serial.println(&quot;connection failed.&quot;);&#xA;  }&#xA;}&#xA;&#xA;void loop()&#xA;{&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="24" LastActivityDate="2009-10-30T21:06:22.837" CommentCount="1" />
  <row Id="42" PostTypeId="1" AcceptedAnswerId="46" CreationDate="2009-10-30T21:09:58.777" Score="7" ViewCount="591" Body="&lt;p&gt;I am a poor student, was wondering if anyone has any home-brew recipes for making conductive thread for use in wearable electronics?&lt;/p&gt;&#xA;" OwnerUserId="24" LastActivityDate="2009-12-15T00:40:28.063" Title="Is there a way to make your own conductive thread for wearable electronics?" Tags="&lt;conductive&gt;&lt;thread&gt;&lt;soldering&gt;" AnswerCount="4" />
  <row Id="43" PostTypeId="1" AcceptedAnswerId="45" CreationDate="2009-10-30T21:40:46.470" Score="5" ViewCount="439" Body="&lt;p&gt;Is there a way that I can make an Arduino or other Micro-controller detect a change in capacitance. I'm thinking of having a screen on my door that only turns on when you touch the  metal door handle. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2010-03-08T19:30:54.660" Title="Capacitive Sensing" Tags="&lt;capacitive&gt;&lt;capacitance&gt;&lt;arduino&gt;&lt;sensor&gt;" AnswerCount="4" FavoriteCount="4" />
  <row Id="44" PostTypeId="2" ParentId="40" CreationDate="2009-10-30T21:50:11.130" Score="1" ViewCount="" Body="&lt;p&gt;Most electrical motors generate electricity if you wind them,  There are examples of people using old treadmill motors for wind turbines... etc.  If you did a bit of research and went down to the second hand shop, grabbed a cheap old motor out of something, made a crank, it might be quite a cheap alternative to buying one.&lt;/p&gt;&#xA;" OwnerUserId="24" LastActivityDate="2009-10-30T21:50:11.130" />
  <row Id="45" PostTypeId="2" ParentId="43" CreationDate="2009-10-30T23:10:11.233" Score="5" ViewCount="" Body="&lt;p&gt;Yes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simplest way would be to use a high value resistor (1-10M) and follow the instructions on this old arduino forum post: &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1171076259&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1171076259&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="26" LastActivityDate="2009-10-30T23:10:11.233" />
  <row Id="46" PostTypeId="2" ParentId="42" CreationDate="2009-10-30T23:12:17.970" Score="6" ViewCount="" Body="&lt;p&gt;Well you could use some really low gauge wire, but I can't imagine that would save you any money.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;150 yards of conductive thread is only $20 at sparkfun.&lt;/p&gt;&#xA;" OwnerUserId="26" LastActivityDate="2009-10-30T23:12:17.970" CommentCount="3" />
  <row Id="47" PostTypeId="2" ParentId="42" CreationDate="2009-10-31T10:29:16.023" Score="5" ViewCount="" Body="&lt;p&gt;Instructables has a &lt;a href=&quot;http://www.instructables.com/id/How%5Fto%5Fmake%5Fconductive%5Fthread/&quot; rel=&quot;nofollow&quot;&gt;post&lt;/a&gt; on how to create conductive thread using very fine wire and thread, that combined together to create a strong, low resistance thread.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The principle idea is that you spin the the thread and the fibre together. As Andrew Parnell said, 150 yards of conductive thread is only $20 at sparkfun.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-10-31T10:29:16.023" />
  <row Id="48" PostTypeId="2" ParentId="43" CreationDate="2009-10-31T10:38:13.853" Score="6" ViewCount="" Body="&lt;p&gt;Here is a tutorial&#xA;&lt;a href=&quot;http://www.nerdkits.com/videos/halloween_capacitive_touch_sensor/&quot; rel=&quot;nofollow&quot;&gt;http://www.nerdkits.com/videos/halloween_capacitive_touch_sensor/&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2009-10-31T10:38:13.853" />
  <row Id="49" PostTypeId="1" AcceptedAnswerId="52" CreationDate="2009-10-31T11:02:33.090" Score="2" ViewCount="990" Body="&lt;p&gt;If I have a sketch compiled to hex, is it be possible to upload this sketch to an Arduino board using avrdude directly from command line? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pekkaa figured out that arduino ide executes the following command when uploading the sketch:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;./hardware/tools/avrdude -Chardware/tools/avrdude.conf -pm328p -cstk500v1 -P/dev/ttyUSB0 -b57600 -D -Uflash:w:/home/pekka/sketchbook/Blink2/applet/Blink2.hex&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-10-31T11:53:05.017" Title="Upload to an Arduino from the command line" Tags="&lt;arduino&gt;&lt;line&gt;&lt;avrdude&gt;&lt;serial&gt;" AnswerCount="1" />
  <row Id="50" PostTypeId="2" ParentId="33" CreationDate="2009-10-31T11:22:51.780" Score="3" ViewCount="" Body="&lt;p&gt;Yes, you can use the Arduino as a AVR programmer!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take a look at the &lt;a href=&quot;http://code.google.com/p/mega-isp/&quot; rel=&quot;nofollow&quot;&gt;mega-isp&lt;/a&gt; project.&lt;/p&gt;&#xA;" LastActivityDate="2009-10-31T11:22:51.780" />
  <row Id="51" PostTypeId="2" ParentId="28" CreationDate="2009-10-31T11:37:17.210" Score="1" ViewCount="" Body="&lt;p&gt;You need an AVR ISP programmer. You just plug it onto the 6-pin header on the arduino board and program it with the Arduino application.&lt;/p&gt;&#xA;" LastActivityDate="2009-10-31T11:37:17.210" />
  <row Id="52" PostTypeId="2" ParentId="49" CreationDate="2009-10-31T11:53:05.017" Score="3" ViewCount="" Body="&lt;p&gt;The arduino IDE resets the attached arduino before running avrdude. It does this by telling the FTDI device to pulse the DTR line which is attached to the arduino's reset pin. Pekkaa found the example perl code which does this and updated the thread on the Arduino forums.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For completeness here is the command they used to upload the .hex file:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;perl -MDevice::SerialPort -e 'Device::SerialPort-&amp;gt;new(&quot;/dev/ttyUSB0&quot;)-&amp;gt;pulse_dtr_on(1000)'; \&#xA;./hardware/tools/avrdude -Chardware/tools/avrdude.conf -q -q -pm328p -cstk500v1 -P/dev/ttyUSB0 -b57600 -D -Uflash:w:/home/pekka/sketchbook/Blink2/applet/Blink2.hex;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;There is also a &lt;a href=&quot;http://projects.cs.kent.ac.uk/projects/kroc/trac/browser/kroc/trunk/tvm/arduino/reset-arduino&quot; rel=&quot;nofollow&quot;&gt;python script for reseting arduinos&lt;/a&gt; which can be used in place of the perl one if you have trouble getting it to work on your system.&lt;/p&gt;&#xA;" OwnerUserId="15" LastActivityDate="2009-10-31T11:53:05.017" />
  <row Id="53" PostTypeId="2" ParentId="43" CreationDate="2009-10-31T12:21:15.237" Score="2" ViewCount="" Body="&lt;p&gt;Not an Arduino specific answer, but Microchip have an explanation of one way to do it on the PIC - which would possibly work on an AVR&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS%5FGET%5FPAGE&amp;amp;nodeId=1824&amp;amp;appnote=en545264&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en545264&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Only concern with these methods is lack of protection from static discharge&lt;/p&gt;&#xA;" OwnerUserId="52" LastActivityDate="2009-10-31T12:21:15.237" />
  <row Id="54" PostTypeId="1" CreationDate="2009-10-31T12:58:11.960" Score="2" ViewCount="2448" Body="&lt;p&gt;How can I save data retrieved from a sensor to a text file on the computer?&lt;/p&gt;&#xA;" OwnerUserId="55" LastActivityDate="2011-01-21T19:00:22.240" Title="Saving Arduino sensor data to a text file" Tags="&lt;arduino&gt;" AnswerCount="5" />
  <row Id="55" PostTypeId="2" ParentId="3" CreationDate="2009-10-31T13:14:49.783" Score="0" ViewCount="" Body="&lt;p&gt;&quot;60/40 lead solder melts at 315C&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rubbish.  60/40 Sn/Pb solder has a pasty range of a few degrees C and solidifies at 183 deg C.  A eutectic solder such as 63/37 Sn/Pb melts and solidifies at 183 deg C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;However, lead is a toxic heavy metal, so extended skin contact isn't good for you&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again, not true.  Lead cannot propagate through the skin.  It can only be ingested by transference from fingers to food or cigarettes, or through inhalation if atomised.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Lead-free solder melts at 340 to 370C&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alloy such as 96.5Sn/3.0Ag/0.5Cu is liquidous a t 217 deg C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Electronics flux can be rosin, water-based, or no-clean. All are about the same quality as far as de-oxidizing the copper so a good solder bond can be made.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wrong.  Different fluxes have different levels of activity and will help wetting and coalescence to different degrees.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;No-clean&quot; flux is resin flux that burns or boils off, leaving almost no residue.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are commonly synthetic fluxes that do not &quot;burn off' but remain after the joint has solidified and are inert so do not pose any long-term risk to the circuit from hygroscopic action or ionic contamination.&lt;/p&gt;&#xA;" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-07-15T10:29:22.760" LastActivityDate="2010-07-15T10:29:22.760" CommentCount="2" />
  <row Id="56" PostTypeId="1" AcceptedAnswerId="131" CreationDate="2009-10-31T14:04:01.707" Score="3" ViewCount="870" Body="&lt;p&gt;Hi all!  I am quite new to hardware hacking, and have chosen to use the Arduino for my first project. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am attempting to build a cat deterrent, something &lt;a href=&quot;http://www.emrktstore.com/products/petsupplies/catscram.html&quot; rel=&quot;nofollow&quot;&gt;akin to this&lt;/a&gt;.  I have figured out detection, and now realize that I need to use an ultrasonic transducer to produce the 'blast' that I need.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I am clueless as to how I would interface one of these with an arduino.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any advice?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for helping a newbie out. &lt;/p&gt;&#xA;" OwnerUserId="58" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:49:17.167" LastActivityDate="2010-08-17T23:49:17.167" Title="How do I Drive an Ultrasonic Transducer with an Arduino?" Tags="&lt;arduino&gt;&lt;ultrasound&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="57" PostTypeId="2" ParentId="40" CreationDate="2009-10-31T14:05:27.980" Score="3" ViewCount="" Body="&lt;p&gt;That generator is just a DC motor attached to a large gear. The large gear is connected to the handle and makes the DC motor spin really fast. Any DC motor can become a generator. Rip apart an old toy, etc. Simple.&lt;/p&gt;&#xA;" LastActivityDate="2009-10-31T14:05:27.980" />
  <row Id="58" PostTypeId="2" ParentId="29" CreationDate="2009-10-31T14:47:26.947" Score="3" ViewCount="" Body="&lt;p&gt;keep in mind that depending on your sleep mode there are a couple of interrupt sources running on your arduino.  timer0 generates an overflow interrupt that will wake your arduino approximately every millisecond and the uart will generate an interrupt everytime there's an incoming character.  ... and, of course, there are the external interrupts on pins 2 and 3 that you may or may not have enabled using the attachInterrupt function.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;when an interrupt occurs your sketch will be awakened from sleep and after the interrupt is serviced it will continue running from the point where it went to sleep.  the solution to this is to set up you sketch to put itself back to sleep everytime through loop unless it's really time to wake up.&lt;/p&gt;&#xA;" OwnerUserId="64" LastActivityDate="2009-10-31T14:47:26.947" />
  <row Id="59" PostTypeId="1" AcceptedAnswerId="64" CreationDate="2009-10-31T15:02:52.540" Score="9" ViewCount="1334" Body="&lt;p&gt;I am considering a project involving a fair share of digital signal processing. As far as I know, the best type of IC suited for this are the Digital Signal Processors. I have never worked with them before - can you recommend me any model that is simple enough for beginners? The project involves filtering hi-fi digital audio (44100Hz, 16 bit stereo) in several ways.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, do I need an additional uC to for example control an UI with an LCD panel and some buttons, or can the DSP handle this along its signal processing task?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers&lt;/p&gt;&#xA;" OwnerUserId="65" LastActivityDate="2011-03-09T13:19:27.633" Title="DSP recommendation for beginners" Tags="&lt;dsp&gt;&lt;audio&gt;&lt;lcd&gt;" AnswerCount="9" FavoriteCount="4" />
  <row Id="60" PostTypeId="2" ParentId="54" CreationDate="2009-10-31T15:17:13.750" Score="2" ViewCount="" Body="&lt;p&gt;The simplest method is to use the &lt;a href=&quot;http://www.arduino.cc/en/Serial/Begin&quot; rel=&quot;nofollow&quot;&gt;Serial library&lt;/a&gt; and output to that.  You can then capture the output to a text file using a terminal program.  Hyperterminal is available on Windows, Teraterm on Linux and Z Term on OS X.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Melanie&lt;/p&gt;&#xA;" OwnerUserId="5" LastActivityDate="2009-10-31T15:17:13.750" />
  <row Id="61" PostTypeId="2" ParentId="54" CreationDate="2009-10-31T15:20:31.440" Score="0" ViewCount="" Body="&lt;p&gt;The next step is to use either the ethernet shield or something like a WIZ810MJ board and internet enable your arduino.  You can then write data to that and send it to say a web server to collate it.  I do this in my &lt;a href=&quot;http://www.cyberspice.org.uk/blog/2009/10/29/boarduino-vivarium-temperature-monitor/&quot; rel=&quot;nofollow&quot;&gt;vivarium temperature monitor&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="5" LastActivityDate="2009-10-31T15:20:31.440" />
  <row Id="62" PostTypeId="2" ParentId="18" CreationDate="2009-10-31T16:20:27.947" Score="9" ViewCount="" Body="&lt;p&gt;There's already a watchdog timer built into the atmega chip; you can use &lt;a href=&quot;http://www.nongnu.org/avr-libc/user-manual/group%5F%5Favr%5F%5Fwatchdog.html&quot; rel=&quot;nofollow&quot;&gt;&lt;code&gt;avr/wdt.h&lt;/code&gt;&lt;/a&gt; to manipulate it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A quick example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;avr/wdt.h&amp;gt;&#xA;&#xA;void setup() {  &#xA;  wdt_enable(WDTO_500MS); // have the wdt reset the chip&#xA;  // if 500ms passes without a reset&#xA;}&#xA;&#xA;void loop() {   &#xA;  wdt_reset(); // reset the wdt&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="70" LastActivityDate="2009-10-31T16:20:27.947" />
  <row Id="63" PostTypeId="2" ParentId="25" CreationDate="2009-10-31T16:28:40.703" Score="3" ViewCount="" Body="&lt;p&gt;The simplest analog gauge is an &lt;a href=&quot;http://en.wikipedia.org/wiki/Ammeter&quot; rel=&quot;nofollow&quot;&gt;ammeter&lt;/a&gt;.  Connect one end to an analog output pin, the other to the middle pin of a potentiometer, and another pin of the pot to ground.  You'll need to tweak the potentiometer to calibrate the range of the output.  Make sure that you measure the resistance across the ammeter and don't short out the arduino's output pin.  You can use analogWrite() to move the needle.&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2009-10-31T16:28:40.703" />
  <row Id="64" PostTypeId="2" ParentId="59" CreationDate="2009-10-31T16:37:12.070" Score="5" ViewCount="" Body="&lt;p&gt;A couple good beginning DSP's are the C5505 DSP from TI and the C6713 also from TI.  I like the first cause it is only $55.00 and I like the second because there are whole books written around the chip (Digital Signal Processing and Applications with the C6713 and C6416 DSK )&#xA;Most Dsp evaluation boards have built in support for LCD's. &lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2009-10-31T16:37:12.070" CommentCount="1" />
  <row Id="65" PostTypeId="2" ParentId="7" CreationDate="2009-10-31T17:02:38.773" Score="1" ViewCount="" Body="&lt;p&gt;Soldering aluminum is hard but possible. Cover the aluminum surface with mineral oil and scrape the oxide. The oil will prevent it from reforming immediately through contact with oxygen. Then tin the surface with a hot iron and normal leaded solder. Then clean off the oil and solder as usual on your tinned surface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However as Jon Hirsch said, these bases are not intended to be soldered. You need to apply some heat conducting compound and affix them using screws to the heatsink.&lt;/p&gt;&#xA;" OwnerUserId="73" LastActivityDate="2009-10-31T17:02:38.773" />
  <row Id="66" PostTypeId="1" CreationDate="2009-10-31T17:17:26.497" Score="6" ViewCount="2031" Body="&lt;p&gt;Is it possible to save data from the Arduino to a SD Memory module?&lt;/p&gt;&#xA;" OwnerUserId="55" LastActivityDate="2011-05-16T14:29:59.037" Title="Arduino Saving Data to SD Memory Module" Tags="&lt;arduino&gt;&lt;sd&gt;&lt;memory&gt;" AnswerCount="7" FavoriteCount="3" />
  <row Id="67" PostTypeId="2" ParentId="66" CreationDate="2009-10-31T17:25:49.130" Score="3" ViewCount="" Body="&lt;p&gt;yes it is check this out &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1206874649/all&quot; rel=&quot;nofollow&quot;&gt;Arduino SD card&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2009-10-31T17:25:49.130" />
  <row Id="68" PostTypeId="2" ParentId="66" CreationDate="2009-10-31T17:39:04.643" Score="4" ViewCount="" Body="&lt;p&gt;If you wish to be able to read the card from your PC and not simply use it a a big EEPROM here's an &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1235125412/0&quot; rel=&quot;nofollow&quot;&gt;extensive thread on the Arduino forums&lt;/a&gt; which explains how to interface with an SD card with FAT support.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also take a look at this Arduino skectch to get you started on the software side. A lot of it has nothing to do with SD card I/O but I'm sure you'll figure it out : ht tp://docs.google.co m/Doc?id=dqhc6fg_0gmk96kdd&lt;/p&gt;&#xA;" OwnerUserId="73" LastActivityDate="2009-10-31T17:39:04.643" />
  <row Id="69" PostTypeId="2" ParentId="25" CreationDate="2009-10-31T18:41:29.737" Score="1" ViewCount="" Body="&lt;p&gt;Check this link out - pretty good solution.&#xA;&lt;a href=&quot;http://www.uchobby.com/index.php/2008/02/12/arduino-analog-gauge/&quot; rel=&quot;nofollow&quot;&gt;http://www.uchobby.com/index.php/2008/02/12/arduino-analog-gauge/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-10-31T18:41:29.737" />
  <row Id="70" PostTypeId="2" ParentId="33" CreationDate="2009-10-31T19:17:36.760" Score="3" ViewCount="" Body="&lt;p&gt;If you need hi-voltage programming (you have an otherwise dead chip) you can try this solution&#xA;&lt;a href=&quot;http://www.mightyohm.com/blog/2008/09/arduino-based-avr-high-voltage-programmer/&quot; rel=&quot;nofollow&quot;&gt;http://www.mightyohm.com/blog/2008/09/arduino-based-avr-high-voltage-programmer/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-10-31T19:17:36.760" />
  <row Id="71" PostTypeId="2" ParentId="33" CreationDate="2009-10-31T20:04:11.987" Score="5" ViewCount="" Body="&lt;p&gt;I use the mega-isp solution mentioned above - the Arduino avrisp sketch is here&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/mega-isp/downloads/list&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/mega-isp/downloads/list&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do not use the shield they have - I made up a simple cable using two 6 pin dual-in-line header sockets to fit the programming ISP connector on your Arduino. (I did not have two dil sockets so I used standard single in line and superglued two 3 pin sockets together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You then need a piece of ribbon cable or some wire.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;&lt;img src=&quot;http://john.crouchley.com/images/ISP%206%20way%20pinout.png&quot; alt=&quot;Arduino 6 pin ISP&quot; /&gt;&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Connect each pin on one socket the the corresponding one on the other, with the exception of pin 5 = Reset.&#xA;Connect one end of the cable to pin 5 - this is the end that will connect to the target AVR that you wish to program. Connect the other end of the pin 5 wire to a floating pin connector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To use connect the cable to the arduino by placing over the ISP programming connector and connecting the floating lead to digital 10, connect the other end to the target ISP connector. You need to ensure that the pin 1's match up.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;&lt;img src=&quot;http://john.crouchley.com/images/isp%20cable.jpg&quot; alt=&quot;Cable overview&quot; /&gt; &lt;img src=&quot;http://john.crouchley.com/images/isp%20socket%20closeup.jpg&quot; alt=&quot;cable detail&quot; /&gt;&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Program with avrdude using &lt;/p&gt;&#xA;&#xA;&lt;p&gt;avrdude -P com7 -p t2313 -c avrisp -b 19200 -U flash:w:fred.hex&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;where&#xA;com7 - the com port that the Arduino based programmer is on&#xA;t2313 - the type of AVR you wish to program (m328 for ATMega328).&#xA;fred.hex - the name of the hex file you wish to progam into the target.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I have used this to program Tiny2313 with no problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: The cable will carry 5v to power the target - if the target is already powered then do not connect pin 2 of the cable.&lt;/p&gt;&#xA;" OwnerUserId="9" LastEditorUserId="9" LastEditorDisplayName="" LastEditDate="2009-11-10T08:44:09.380" LastActivityDate="2009-11-10T08:44:09.380" />
  <row Id="72" PostTypeId="2" ParentId="16" CreationDate="2009-10-31T23:11:16.147" Score="1" ViewCount="" Body="&lt;p&gt;Check out &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1251656637/7#7&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1251656637/7#7&lt;/a&gt;&#xA;It has the arduino version of the instructable, a video, and a diagram of how to set it up.&lt;/p&gt;&#xA;" OwnerUserId="95" LastActivityDate="2009-10-31T23:11:16.147" CommentCount="1" />
  <row Id="73" PostTypeId="1" AcceptedAnswerId="165" CreationDate="2009-10-31T23:24:03.613" Score="1" ViewCount="139" Body="&lt;p&gt;How can you control a Servo using a Basic Stamp?&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-11-02T23:59:13.533" Title="Serial Servo Controller using Basic Stamp" Tags="&lt;servo&gt;&lt;basic&gt;" AnswerCount="1" />
  <row Id="74" PostTypeId="1" AcceptedAnswerId="95" CreationDate="2009-10-31T23:28:52.823" Score="9" ViewCount="1324" Body="&lt;p&gt;How can I start PIC Microcontroller Programming on Mac OS X. Can I use an Arduino connected to my Mac has a programmer? Or do I need to buy specific programmer board and serial adapters?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2011-01-20T11:26:22.817" Title="PIC Microcontroller Programming on Mac OS X" Tags="&lt;pic&gt;&lt;microcontroller&gt;&lt;mac&gt;&lt;os&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="75" PostTypeId="2" ParentId="7" CreationDate="2009-10-31T23:44:45.303" Score="1" ViewCount="" Body="&lt;p&gt;One problem with soldering aluminum that has oxidized is that the melting point of aluminum oxide is (2072 °C) much higher than aluminum itself(660.32 °C) , so by the time you melted the outer coating of aluminum the inside is liquid already.   this can be a problem with thin walled parts like tubes etc.&lt;/p&gt;&#xA;" LastActivityDate="2009-10-31T23:44:45.303" />
  <row Id="76" PostTypeId="1" CreationDate="2009-10-31T23:55:40.727" Score="4" ViewCount="952" Body="&lt;p&gt;Hi i am trying to make a UPS for a project that requires 12Volts. &#xA;I'm currently using a replay diode and capacitor. &#xA;My problem is that when the switchover occurs, the voltage drops from &#xA;12Volts to 7Volts, and back up again. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have a good circuit design, that will minimise the drop off? &lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-19T01:05:06.717" LastActivityDate="2011-01-19T01:05:06.717" Title="DIY 12 Volt UPS" Tags="&lt;circuit&gt;&lt;design&gt;&lt;ups&gt;&lt;12v&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="77" PostTypeId="1" AcceptedAnswerId="111" CreationDate="2009-10-31T23:59:41.607" Score="14" ViewCount="1604" Body="&lt;p&gt;I'm looking to make a battery life indicator that I can use in conjunction with a micro-controller. I'm hoping that I can then read the current battery life remaining and increasingly put the micro-controller to sleep to preserve battery life.&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-08T07:09:47.807" LastActivityDate="2010-12-08T07:09:47.807" Title="Low Battery Indicator" Tags="&lt;microcontroller&gt;&lt;sleep&gt;&lt;indicator&gt;&lt;low-battery&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="5" />
  <row Id="78" PostTypeId="1" AcceptedAnswerId="82" CreationDate="2009-11-01T00:01:33.320" Score="8" ViewCount="255" Body="&lt;p&gt;Are there any special requirements for charging lead-acid batteries? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2010-04-14T19:00:27.220" Title="Charging lead-acid batteries?" Tags="&lt;battery&gt;&lt;charging&gt;&lt;batteries&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="79" PostTypeId="2" ParentId="78" CreationDate="2009-11-01T00:18:07.047" Score="4" ViewCount="" Body="&lt;p&gt;Don't boil it dry!  If it's a sealed unit it should have a maximum charging rate, usually printed on it's side or available on the makers website.  If it's a &quot;car type&quot; then just don't let the electrolyte boil off.  Dry plates mean disaster for the life span of the battery.&lt;/p&gt;&#xA;" OwnerUserId="101" LastActivityDate="2009-11-01T00:18:07.047" />
  <row Id="80" PostTypeId="2" ParentId="32" CreationDate="2009-11-01T00:19:12.400" Score="1" ViewCount="" Body="&lt;p&gt;You may find it at &lt;a href=&quot;http://www.msarnoff.org/chipdb/atmega168&quot; rel=&quot;nofollow&quot;&gt;http://www.msarnoff.org/chipdb/atmega168&lt;/a&gt;. Very plain and simple site. They will also link you to the original ATMega PDF document if you need more than just a pinout.&lt;/p&gt;&#xA;" OwnerUserId="102" LastActivityDate="2009-11-01T00:19:12.400" />
  <row Id="81" PostTypeId="2" ParentId="74" CreationDate="2009-11-01T00:26:16.700" Score="2" ViewCount="" Body="&lt;p&gt;I don't think you can do it from an Arduino board. There are various specs around the internet for serial based pic programmer boards, or you can get them from Microchip (the manufacturers of PIC chips), if you go to their site &lt;a href=&quot;http://www.microchipdirect.com&quot; rel=&quot;nofollow&quot;&gt;http://www.microchipdirect.com&lt;/a&gt; you should find most of their offerings under development tools, including USB based programmers. I'm not sure what software there is available as an IDE for the Mac but Google is your friend in situations like this.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-20T04:09:34.803" LastActivityDate="2011-01-20T04:09:34.803" />
  <row Id="82" PostTypeId="2" ParentId="78" CreationDate="2009-11-01T00:30:54.453" Score="7" ViewCount="" Body="&lt;p&gt;Charging lead-acid batteries with a power supply&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lead-acid batteries can be charged manually with a commercial power supply featuring voltage regulation and current limiting. Calculate the charge voltage according to the number of cells and desired voltage limit. Charging a 12-volt battery (6 cells) at a cell voltage limit of 2.40V, for example, would require a voltage setting of 14.40V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The charge current for small lead-acid batteries should be set between 10% and 30% of the rated capacity (30% of a 2Ah battery would be 600mA). Larger batteries, such as those used in the automotive industry, are generally charged at lower current ratings. Cells constructed of a non-antimonial lead grid material allow higher charge currents but have a lower capacity. The cylindrical Cyclone is sealed and can sustain a pressure of up to 3.5 Bar (50 psi). A pressurized cell assists in the recombination of gases. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Observe the battery temperature, voltage and current during charge. Charge only at ambient temperatures and in a ventilated room. Once the battery is fully charged and the current has dropped to 3% of the rated current, the charge is completed. A good car battery will drop to about 40mA when fully charged; a bad battery may not fall below 100mA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After full charge, remove the battery from the charger. If float charge is needed for operational readiness, lower the charge voltage to about 13.50V (2.25V/cell). Most chargers perform this function automatically. The float charge can be applied for an unlimited time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--Information found &lt;a href=&quot;http://www.batteryuniversity.com/partone-13.htm&quot; rel=&quot;nofollow&quot; title=&quot;Here&quot;&gt;link text&lt;/a&gt;&#xA;Hope This Helps!&lt;/p&gt;&#xA;" OwnerUserId="102" LastActivityDate="2009-11-01T00:30:54.453" />
  <row Id="83" PostTypeId="1" AcceptedAnswerId="88" CreationDate="2009-11-01T00:34:17.887" Score="4" ViewCount="348" Body="&lt;p&gt;I've just hidden away our entertainment centre electronics including our Infrared controlled DVD Player, Amp and Mac Mini .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was wondering if there is any IR Remote code for Arduino, that I can use to eventually control the entertainment centre. I plan to write a simple iPhone app, that talks to an Arduino with an Ethernet shield. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2010-07-08T17:18:37.143" Title="IR Remote code for Arduino" Tags="&lt;infrared&gt;&lt;ir&gt;&lt;arduino&gt;&lt;library&gt;&lt;remote&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="84" PostTypeId="2" ParentId="74" CreationDate="2009-11-01T00:41:58.503" Score="3" ViewCount="" Body="&lt;p&gt;You will need a special programmer and you can use &lt;a href=&quot;http://sdcc.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;SDCC&lt;/a&gt; and xcode which you can get from apple.&lt;/p&gt;&#xA;" OwnerUserId="81" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-20T11:26:22.817" LastActivityDate="2011-01-20T11:26:22.817" CommentCount="1" />
  <row Id="86" PostTypeId="2" ParentId="26" CreationDate="2009-11-01T01:48:09.223" Score="3" ViewCount="" Body="&lt;p&gt;The USB cable used to connect your Mac to the Arduino acts as a serial port, and can be used for communication.  (For example, see &lt;a href=&quot;http://www.gardenvillesoftware.com/?q=node/4&quot; rel=&quot;nofollow&quot;&gt;Make an Arduino talk to your Mac&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a thread that appears relevant: &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1201066343&quot; rel=&quot;nofollow&quot;&gt;AppleScript serial communication with arduino&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, you could go see this blog entry: &lt;a href=&quot;http://todbot.com/blog/2006/12/06/arduino-serial-c-code-to-talk-to-arduino/&quot; rel=&quot;nofollow&quot;&gt;Arduino-serial: C code to talk to Arduino&lt;/a&gt;.  You could compile the application [downloading xcode, first, if needs be] and then use it to communicate from applescript by using the &quot;&lt;a href=&quot;http://developer.apple.com/mac/library/technotes/tn2002/tn2065.html&quot; rel=&quot;nofollow&quot;&gt;do shell script&lt;/a&gt;&quot; command. &lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="106" LastEditorDisplayName="" LastEditDate="2009-11-01T02:04:58.997" LastActivityDate="2009-11-01T02:04:58.997" />
  <row Id="87" PostTypeId="2" ParentId="37" CreationDate="2009-11-01T01:50:47.910" Score="3" ViewCount="" Body="&lt;p&gt;Yes, you can just swap it in. I've also upgraded a Diecimila without any problems. If you have an AVR programmer (such as the one from Adafruit) you can also upgrade it with a fresh unprogrammed chip.&lt;/p&gt;&#xA;" OwnerUserId="105" LastActivityDate="2009-11-01T01:50:47.910" />
  <row Id="88" PostTypeId="2" ParentId="83" CreationDate="2009-11-01T01:55:56.567" Score="5" ViewCount="" Body="&lt;p&gt;This might help: &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1209565937&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1209565937&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect the Mac Mini will not respond to the same sort of signals that your audio equiptment does.&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-11-01T01:55:56.567" />
  <row Id="89" PostTypeId="1" AcceptedAnswerId="104" CreationDate="2009-11-01T04:02:41.727" Score="4" ViewCount="3528" Body="&lt;p&gt;I'm trying to make an onboard system for my bike using an Arduino or maybe the Lilypad boards....I'm want to output my speed to an LCD display and am wondering the best way to go about this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mad &lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T16:02:29.740" LastActivityDate="2010-10-22T16:02:29.740" Title="How do i use a Hall Effect Sensor to measure the RPM of a wheel?" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;hall-effect&gt;" AnswerCount="6" />
  <row Id="90" PostTypeId="2" ParentId="27" CreationDate="2009-11-01T04:04:37.550" Score="2" ViewCount="" Body="&lt;p&gt;SimpleMessageSystem is a library for the Arduino that allows you to send, receive and parse characters, integers and lists between Arduino and Max/Msp or Pure Data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Source: &lt;a href=&quot;http://www.arduino.cc/playground/Interfacing/MaxMSP&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/Interfacing/MaxMSP&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="26" LastActivityDate="2009-11-01T04:04:37.550" />
  <row Id="91" PostTypeId="1" AcceptedAnswerId="94" CreationDate="2009-11-01T04:06:50.863" Score="2" ViewCount="132" Body="&lt;p&gt;I want to make a vest that has LED all over it (for the purpose of night time cycling) but i want to be able to easily wash it.&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-12-15T00:55:11.063" Title="With Lilypad boards, whats the best way to put them into clothing so they can be easiy taken out?" Tags="&lt;lilypad&gt;&lt;clothing&gt;" AnswerCount="4" />
  <row Id="92" PostTypeId="1" AcceptedAnswerId="103" CreationDate="2009-11-01T04:08:58.713" Score="3" ViewCount="213" Body="&lt;p&gt;If you have a funky Lilypad clothing and it gets rained on or you spontaneously decide to go for a swim in it  :)   what happen?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-01T11:36:58.993" Title="What happens to Lilypads in the rain?" Tags="&lt;lilypad&gt;&lt;clothing&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="93" PostTypeId="2" ParentId="89" CreationDate="2009-11-01T05:28:20.890" Score="3" ViewCount="" Body="&lt;p&gt;A magnet can be mounted on the edge of the wheel's rim and the Hall Effect sensor mounted very close to (but not contacting) the magnet. As the wheel spins and the magnet passes the sensor, the sensor will pick up the variation in the magnetic field.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-01T05:28:20.890" />
  <row Id="94" PostTypeId="2" ParentId="91" CreationDate="2009-11-01T05:59:35.070" Score="4" ViewCount="" Body="&lt;p&gt;Use metal snaps.&lt;/p&gt;&#xA;" OwnerUserId="26" LastActivityDate="2009-11-01T05:59:35.070" />
  <row Id="95" PostTypeId="2" ParentId="74" CreationDate="2009-11-01T06:09:41.587" Score="7" ViewCount="" Body="&lt;p&gt;You can use the PICKit Flash Starter Key (USB!). Check this website: www.teammojo.org/PICkit/pickit1.html&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There used to be a Cocoa GUI to program the PICKit made by someone at Microchip, but I can't find it now... (source code was available!).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can compile your code using gpasm (gputils.sourceforge.net), and then flash it into the PIC using the PICKit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found also this simulator that runs perfect on the mac: www.feertech.com/misim/homepage.html&lt;/p&gt;&#xA;" OwnerUserId="110" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-20T04:09:24.087" LastActivityDate="2011-01-20T04:09:24.087" />
  <row Id="96" PostTypeId="1" CreationDate="2009-11-01T06:19:43.487" Score="3" ViewCount="302" Body="&lt;p&gt;Hi there,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Special needs kids have big troubles with potty training. A 'wee-wee' alarm would be of a lot of help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be a good way of detecting 'it' without electrocuting nobody? A possibility would be to detect humidity or temperature, but it really has to be a sturdy sensor... any ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks!&#xA;roberto&lt;/p&gt;&#xA;" OwnerUserId="110" LastActivityDate="2009-11-01T15:30:57.167" Title="Best humidity/temperature sensor for a nappy?" Tags="&lt;sensor&gt;&lt;humidity&gt;&lt;temperature&gt;" AnswerCount="3" />
  <row Id="97" PostTypeId="2" ParentId="76" CreationDate="2009-11-01T07:18:45.660" Score="4" ViewCount="" Body="&lt;p&gt;How about running the project off of the battery and charging the battery?&#xA;We used to do this for critical radio setups in the old days.  If you have a trickle charge potential greater than that of your load, and set a cutoff for over charging you have it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an aside, there is supposed to be a &quot;hum&quot; or small ripple in the charging current to improve the battery life, but you could also have the battery at 14 or 16 volts and then place a regulator to get the 12 volts you are needing.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-01T07:18:45.660" CommentCount="1" />
  <row Id="98" PostTypeId="2" ParentId="76" CreationDate="2009-11-01T09:11:28.257" Score="4" ViewCount="" Body="&lt;p&gt;Use Schottky diodes (which have a lower forward voltage) and you should only lose 0.5V or so. The voltage clearly shouldn't fall all the way to 7V anyhow - perhaps your diode is underrated, or you don't have enough battery current capacity?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When choosing Schottky diodes, choose one with a reverse breakdown voltage close to the maximum which you're likely to encounter (so not more than 20V) so that you get a low forward voltage too.&lt;/p&gt;&#xA;" OwnerUserId="112" LastActivityDate="2009-11-01T09:11:28.257" />
  <row Id="99" PostTypeId="2" ParentId="96" CreationDate="2009-11-01T09:16:40.810" Score="2" ViewCount="" Body="&lt;p&gt;Conductivity is the obvious choice - running the electronics with a 1.5V battery and connecting the electrodes through a high-valued resistor should stop anything bad happening (though don't take that as a guarantee ;)&lt;/p&gt;&#xA;" OwnerUserId="112" LastActivityDate="2009-11-01T09:16:40.810" />
  <row Id="101" PostTypeId="2" ParentId="32" CreationDate="2009-11-01T10:25:30.977" Score="2" ViewCount="" Body="&lt;p&gt;You can either go to &lt;a href=&quot;http://www.atmel.com&quot; rel=&quot;nofollow&quot;&gt;the manufacturers website&lt;/a&gt; directly and search for your device (&lt;a href=&quot;http://www.atmel.com/dyn/products/Product_card.asp?part_id=3303&quot; rel=&quot;nofollow&quot;&gt;ATMega168 is here&lt;/a&gt;, with link to the &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2545.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;)).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another very good resource for everything AVR is the &lt;a href=&quot;http://www.avrfreaks.net/&quot; rel=&quot;nofollow&quot;&gt;AVR Freaks&lt;/a&gt; community. &lt;strike&gt;They have a &lt;a href=&quot;http://www.avrfreaks.net/index.php?module=Freaks%20Devices&amp;amp;func=viewDev&quot; rel=&quot;nofollow&quot;&gt;Device list&lt;/a&gt;&lt;/strike&gt; (Gone, use Atmel's &lt;a href=&quot;http://atmel.com/dyn/products/param_table.asp?category_id=163&amp;amp;family_id=607&amp;amp;subfamily_id=760&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) (ATMega168 is &lt;a href=&quot;http://www.avrfreaks.net/index.php?module=Freaks%20Devices&amp;amp;func=displayDev&amp;amp;objectid=78&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) where you can get a quick overview of the chips features, the pin mappings, and of course the official data sheet, too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I prefer AVR Freaks for my projects. Ironically, the default search on Atmel.com is google-wide - and directly links to AVR Freaks, too.&lt;/p&gt;&#xA;" OwnerUserId="45" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-31T12:24:18.913" LastActivityDate="2011-05-31T12:24:18.913" CommentCount="4" />
  <row Id="102" PostTypeId="2" ParentId="92" CreationDate="2009-11-01T11:22:11.940" Score="2" ViewCount="" Body="&lt;p&gt;Not owning one myself, I'd need to guess.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardLilyPad&quot; rel=&quot;nofollow&quot;&gt;the arduino website&lt;/a&gt;, the pad itself won't get harmed:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Washability&lt;/strong&gt;&lt;br /&gt;&#xA;  Wash at your own risk - we do ;). We recommend washing projects by hand with a mild detergent. Drip dry. Make sure you remove your power supply first! &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Electronics and water don't mix usually for two reasons:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;short circuits: the ions in the water short circuit the board, rendering it infunctional or even destroying it. The latter happens when power from the supply voltage goes to places it shouldn't go. This is especially important for high voltage devices.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;rust: water reacts with certain materials and corrosion occurs over time&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'd guess that a coated PCB designed to be washed won't rust (that easily) and probably also don't react to short circuits that easily. So in rain there is a good propability that it will work as expected. Submerged under water, however, I'd expect it to fail (primarily due to the open pins on the outside) and you should specially protect your power supply and leads. (hence the warning in above quote)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have to make similar reasonings about the other components of your clothing. If they are designed to withstand washing they'll probably work in some rain, too. But only really waterproof connections will work with that much water you have when swimming.&lt;/p&gt;&#xA;" OwnerUserId="45" LastActivityDate="2009-11-01T11:22:11.940" />
  <row Id="103" PostTypeId="2" ParentId="92" CreationDate="2009-11-01T11:36:58.993" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;If the circuit is powered when you put it in water&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Water would add random paths where the current can flow in your circuit. Most probably something will short out. If you're lucky, the circuit will just not work, in the worst case you can damage the chip on the Lilypad. If you predict that your circuit will have contact with water, you can experiment with:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;enclosing it in something waterproof&#xA;(some synthetic material, maybe?)&lt;/li&gt;&#xA;&lt;li&gt;using waterproof fixatives from art supplies (these are in spray and coat your electronics with a thin waterproof film of chemicals). There are also some specialty products for coating electronics, although I haven't tried them.&lt;/li&gt;&#xA;&lt;li&gt;to make your LilyPad really safe, you can cast it into epoxy resin or something of the like.&lt;/li&gt;&#xA;&lt;li&gt;be sure to insulate every exterior wire, too. (For example wires that go to an LED somewhere)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;If the circuit is not powered when you put it in water&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It shouldn't be a big problem. The circuit will be okay AS LONG as you let it dry completely before powering up again. Most cell phones can survive trips to the bottom of the lake (the batteries don't). It is a good idea, if you consider spontaneous swimming, to put the battery out. The problem you may have is the circuit rusting prematurely, but that shouldn't be the case of arduino and lilypad.&lt;/p&gt;&#xA;" OwnerUserId="65" LastActivityDate="2009-11-01T11:36:58.993" />
  <row Id="104" PostTypeId="2" ParentId="89" CreationDate="2009-11-01T11:38:47.000" Score="5" ViewCount="" Body="&lt;p&gt;Using a hall effect sensor as Starliner suggested will be one way to interface with the wheel. Achim and Shutterdrone's suggestion to use a reed switch makes more sense though, given the supporting hardware a hall effect sensor requires to get a clean digital signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might be able to pickup a magnet and sensor from a broken bicycle computer but if you can't, a local component store should have one of each in stock. The advantage of a recycled sensor and magnet is the you will already have the mounting hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a page on the arduino wiki on &lt;a href=&quot;http://www.arduino.cc/playground/Main/ReadingRPM&quot; rel=&quot;nofollow&quot;&gt;ReadingRPM&lt;/a&gt; signals. To calculate the speed multiply the RPM value by the circumference of the wheel (2 * pi * radius [in meters]). The result will be in meters per minute.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I've notice that the linked code is for systems with two pulses per revolution. One magnet is sufficient for your task. Additionally, for a bicycle computer you'll probably want the result to be in KPH (or MPH if you live somewhere that still thinks that's civilised). I've made some (untested) mods to the code on the wiki to print out KPH and pasted them bellow.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;volatile byte revolutions;&#xA;&#xA;unsigned int rpmilli;&#xA;float speed;&#xA;&#xA;&#xA;unsigned long timeold;&#xA;&#xA;void setup()&#xA;{&#xA;  Serial.begin(9600);&#xA;  attachInterrupt(0, rpm_fun, RISING);&#xA;&#xA;  revolutions = 0;&#xA;  rpmilli = 0;&#xA;  timeold = 0;&#xA;}&#xA;&#xA;void loop()&#xA;{&#xA;  if (revolutions &amp;gt;= 20) { &#xA;    //Update RPM every 20 counts, increase this for better RPM resolution,&#xA;    //decrease for faster update&#xA;&#xA;    // calculate the revolutions per milli(second)&#xA;    rpmilli = (millis() - timeold)/revolutions;&#xA;    timeold = millis();&#xA;    rpmcount = 0;&#xA;&#xA;    // WHEELCIRC = 2 * PI * radius (in meters)&#xA;    // speed = rpmilli * WHEELCIRC * &quot;milliseconds per hour&quot; / &quot;meters per kilometer&quot;&#xA;&#xA;    // simplify the equation to reduce the number of floating point operations&#xA;    // speed = rpmilli * WHEELCIRC * 3600000 / 1000&#xA;    // speed = rpmilli * WHEELCIRC * 3600&#xA;&#xA;    speed = rpmilli * WHEELCIRC * 3600;&#xA;&#xA;    Serial.print(&quot;RPM:&quot;);&#xA;    Serial.print(rpmilli * 60000,DEC);&#xA;    Serial.print(&quot; Speed:&quot;);&#xA;    Serial.print(speed,DEC);&#xA;    Serial.println(&quot; kph&quot;);&#xA;  }&#xA;}&#xA;&#xA;void rpm_fun()&#xA;{&#xA;  revolutions++;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Also, I've enabled 'community wiki' on this, which I think means other users can edit it. If my maths is wrong (and you can prove it!) jump in and fix it for me. :)&lt;/p&gt;&#xA;" OwnerUserId="15" LastEditorUserId="15" LastEditorDisplayName="" LastEditDate="2009-11-03T20:41:06.587" LastActivityDate="2009-11-03T20:41:06.587" CommunityOwnedDate="2009-11-01T23:13:20.920" />
  <row Id="105" PostTypeId="1" CreationDate="2009-11-01T12:42:40.187" Score="10" ViewCount="1858" Body="&lt;p&gt;Inspired by projects such as the &lt;a href=&quot;http://www.tweetingcatdoor.com/&quot; rel=&quot;nofollow&quot;&gt;tweeting cat door&lt;/a&gt; and &lt;a href=&quot;http://www.nermal.org/projects/catalog/&quot; rel=&quot;nofollow&quot;&gt;CATaLOG&lt;/a&gt; [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Full Disclosure: This is a &lt;a href=&quot;http://www.michevan.id.au/content/petting-problem&quot; rel=&quot;nofollow&quot;&gt;reprint from my blog&lt;/a&gt; where I first wrote up the problem, but all feedback is welcome!)&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;The Players&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;We currently have three cats, one dog and one pet door.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;The Mischievous Mutt&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg&quot; width=&quot;200&quot; height=&quot;150&quot; alt=&quot;Toby&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and &lt;a href=&quot;http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg&quot; rel=&quot;nofollow&quot;&gt;other amenities&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;The Clutter Kittens&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg&quot; width=&quot;200&quot; height=&quot;150&quot; alt=&quot;Bazyl&quot; /&gt; &lt;img src=&quot;http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg&quot; width=&quot;200&quot; height=&quot;150&quot; alt=&quot;Kismet&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;&lt;strike&gt;The Wanderer&lt;/strike&gt;&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg&quot; width=&quot;200&quot; height=&quot;150&quot; alt=&quot;Murray&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE 2010/01/17: Unfortunately, Murray is &lt;a href=&quot;http://www.michevan.id.au/content/memory-murray&quot; rel=&quot;nofollow&quot;&gt;no longer with us&lt;/a&gt;. Old age finally caught up with him.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strike&gt;Murray, the venerable 17 year old veteran of the family &lt;a href=&quot;http://www.michevan.id.au/content/do-you-have-cat-named-murray&quot; rel=&quot;nofollow&quot;&gt;who has a habit of going walkabout&lt;/a&gt;. At this stage in his life, it would be best if he stayed indoors.&lt;/strike&gt;&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;The Portcullis&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg&quot; width=&quot;200&quot; height=&quot;150&quot; alt=&quot;Pet Door Outside View&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Our pet door, that allows the rabble to go out on the deck and into the backyard.  The door is fixed in a wooden panel in the frame of what was originally a window.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Requirements Summary&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, &lt;strike&gt;and any time Murray is in proximity&lt;/strike&gt;.  We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below.  (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg&quot; width=&quot;200&quot; height=&quot;150&quot; alt=&quot;Pet Door Inside View&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm planning on using an &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; board as the control unit, and think I need &lt;strike&gt;two&lt;/strike&gt;one RFID tag&lt;strike&gt;s&lt;/strike&gt; &amp;ndash; one for Toby &lt;strike&gt;and one for Murray&lt;/strike&gt; &amp;ndash; at the minimum to handle the rules I've outlined above.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the preliminary parts list is:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;One &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; controller board.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;One light sensor for sensing daylight hours.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;One RFID scanner.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Two RFID tags that can be attached to the animals' collar.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;One solenoid or something else that can be used to stop the flap opening to the outside.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;A red/green LED to indicate if the door is currently locked or not.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The concerns I have are finding the right RFID scanner and tags that'll work in this environment.  I've no experience with RFID but hear a bit about range issues.  One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference.  The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option might be bluetooth.  This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range.  The disadvantage is batteries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any other ideas for proximity sensors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other thing is the mechanism to block the door.  Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open.  Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed.  Should only need to apply voltage to change state, not maintain state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing.  To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, any and all feedback on the above would be welcome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of &lt;a href=&quot;http://www.practicalarduino.com/&quot; rel=&quot;nofollow&quot;&gt;Practical Arduino&lt;/a&gt; which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then.&lt;/p&gt;&#xA;" OwnerUserId="117" LastEditorUserId="117" LastEditorDisplayName="" LastEditDate="2010-01-17T09:43:44.203" LastActivityDate="2010-12-03T17:21:26.247" Title="Electronic pet-door access control - RFID" Tags="&lt;arduino&gt;&lt;rfid&gt;&lt;bluetooth&gt;" AnswerCount="8" FavoriteCount="4" />
  <row Id="106" PostTypeId="2" ParentId="96" CreationDate="2009-11-01T14:27:34.263" Score="0" ViewCount="" Body="&lt;p&gt;I remember visiting a young relative once who had a similar issue (was very young at the time).  I recall 2 electrodes that would snap into each other with part of his underwear in between.  When it would get wet, it would conduct and a little buzzer would go off.  Perhaps you could do something similar?&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2009-11-01T14:27:34.263" />
  <row Id="107" PostTypeId="2" ParentId="96" CreationDate="2009-11-01T15:30:57.167" Score="3" ViewCount="" Body="&lt;p&gt;I would just use a surface mount temp sensor on a piece of cloth and some conductive wire. Actually, I would go a non tech route.  With my son, we made him go every hour, then every 1.5, then every 2 until we found where his max range was.  Then 10 or 15 minutes before he hit that max, we would prompt him to pay attention to how his boy parts were feeling. In pretty short order (month or two) he got used to what it felt like when he needed to go and potty training was done. &lt;/p&gt;&#xA;" OwnerUserId="120" LastActivityDate="2009-11-01T15:30:57.167" />
  <row Id="108" PostTypeId="2" ParentId="89" CreationDate="2009-11-01T16:30:04.127" Score="1" ViewCount="" Body="&lt;p&gt;The magnet can be mounted on a spoke, and the sensor on one of your forks, or the chainstay. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rather than multiplying by pi etc, the method suggested by my last bike computer was to measure one revolution's linear distance (chalk on the tyre, measure between the two chalk marks), then you can just multiply the revolutions by the circumference direct.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[EDIT]I've just found this &lt;a href=&quot;http://www.piclist.com/techref/piclist/biketut/index.htm&quot; rel=&quot;nofollow&quot;&gt;guide&lt;/a&gt; on the piclist site for implementing a bike computer using a PIC, maybe some of the information might be of use to you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Amos&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-01-14T11:41:58.387" LastActivityDate="2010-01-14T11:41:58.387" />
  <row Id="109" PostTypeId="2" ParentId="54" CreationDate="2009-11-01T16:38:23.813" Score="6" ViewCount="" Body="&lt;p&gt;you can write the sensor data to the serial port using serial-lib and &#xA;write a small processing program that reads the data from the serial port and writes it to a file. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;in the arduino code initalize the serial lib in the setup method &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Serial.begin(9600);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;and write your sensor values to the serial interface using &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Serial.println(value);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;in your loop method&lt;/p&gt;&#xA;&#xA;&lt;p&gt;on the processing side use a PrintWriter to write the data read from the serial port to a file &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;import processing.serial.*;&#xA;Serial mySerial;&#xA;PrintWriter output;&#xA;void setup() {&#xA;   mySerial = new Serial( this, Serial.list()[0], 9600 );&#xA;   output = createWriter( &quot;data.txt&quot; );&#xA;}&#xA;void draw() {&#xA;    if (mySerial.available() &amp;gt; 0 ) {&#xA;         String value = mySerial.readString();&#xA;         if ( value != null ) {&#xA;              output.println( value );&#xA;         }&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="123" LastActivityDate="2009-11-01T16:38:23.813" />
  <row Id="110" PostTypeId="1" AcceptedAnswerId="125" CreationDate="2009-11-01T16:47:20.203" Score="8" ViewCount="5011" Body="&lt;p&gt;Is it possible to drive a brushless motor directly with Arduino? Or should I revert on controlling a brushless motor ESC with PWM pulses? &lt;/p&gt;&#xA;" OwnerUserId="94" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2010-05-27T21:03:52.010" LastActivityDate="2011-01-01T16:08:57.147" Title="How to drive drive brushless motor with Arduino?" Tags="&lt;arduino&gt;&lt;brushless&gt;&lt;motor&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="111" PostTypeId="2" ParentId="77" CreationDate="2009-11-01T17:57:03.760" Score="8" ViewCount="" Body="&lt;p&gt;To the primary question, as to how to measure the voltage of a battery, the most simple method is to use one of the ADC pins on the arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're providing 5v from the battery (unlikely), then you can run the + straight to one of the analog in pins, and use analogRead() - each increment in value (from 0-1023) will represent 4.9mV.  So multiply the read value by .0049 to get the volts read.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're running higher than 5v (more likely), you can use a voltage divider circuit (see: &lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage_divider&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Voltage_divider&lt;/a&gt;) to bring the voltage you're sending to the analog input to &amp;lt;= 5v.  If you're running 12V, you'll want to divide the voltage into roughly 1/3.  Then, after multiplying the ADC value, multiply by 3 to get actual voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thus, if using 12V, and a 1/3rd voltage divider:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define BAT_PIN 14&#xA;&#xA;float read_batt_volts(void) {&#xA;&#xA;  int val = analogRead(BAT_PIN);&#xA;&#xA;  float volts = (float) val * (float) 0.0049 * (float) 3;&#xA;&#xA;  return(volts)&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;!c&lt;/p&gt;&#xA;" OwnerUserId="36" LastActivityDate="2009-11-01T17:57:03.760" CommentCount="1" />
  <row Id="112" PostTypeId="2" ParentId="59" CreationDate="2009-11-01T20:07:05.803" Score="9" ViewCount="" Body="&lt;p&gt;The dsPIC30F line of microcontrollers from Microchip are excellent introductory DSPs.  They are programmed in C or assembly in the same way that other PICs are, but include DSP libraries that help with filtering, etc.  They have all the necessary peripherals for most projects (ADC, DAC, serial communications, timers, the list goes on and on). They are fairly cheap (no more than $10), can be sampled in through-hole packaging, and can be programmed with standard PIC programmers and debuggers.&lt;/p&gt;&#xA;" OwnerUserId="126" LastActivityDate="2009-11-01T20:07:05.803" CommentCount="3" />
  <row Id="113" PostTypeId="2" ParentId="110" CreationDate="2009-11-01T20:34:47.810" Score="4" ViewCount="" Body="&lt;p&gt;I have gone back and forth on this for like 30 minutes.  I think you probably want to use an ESC unless you are just doing it as a learning experience.  To properly control the motor would tie up more resources from your arduino than I could imagine justifying.  Plus you would be limiting the responsiveness of the motor to that of the adc polling. I wouldn't think of using an ESC as reverting, that is the way it is supposed to be done.  &lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2009-11-01T20:34:47.810" />
  <row Id="114" PostTypeId="1" AcceptedAnswerId="115" CreationDate="2009-11-01T20:51:43.910" Score="1" ViewCount="211" Body="&lt;p&gt;Anyone got a good tutorial on using and Arduino to capture the Wii nunchuck accelerometer data?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:37:08.357" LastActivityDate="2010-08-17T23:37:08.357" Title="Using a Wii Numchuck for data collection" Tags="&lt;arduino&gt;&lt;wii&gt;&lt;nunchuck&gt;&lt;accelerometer&gt;&lt;tutorial&gt;" AnswerCount="3" />
  <row Id="115" PostTypeId="2" ParentId="114" CreationDate="2009-11-01T21:16:36.400" Score="2" ViewCount="" Body="&lt;p&gt;Check the Windmeadow Labs blog post titled &lt;a href=&quot;http://www.windmeadow.com/node/42&quot; rel=&quot;nofollow&quot;&gt;&quot;Read wii nunchuck data into arduino&quot;&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2009-11-01T21:16:36.400" />
  <row Id="116" PostTypeId="2" ParentId="114" CreationDate="2009-11-01T21:17:04.197" Score="1" ViewCount="" Body="&lt;p&gt;I just searched for wii nuNchuck arduino on Google and got about 90 000 hits, including this one : &lt;a href=&quot;http://www.windmeadow.com/node/42&quot; rel=&quot;nofollow&quot;&gt;http://www.windmeadow.com/node/42&lt;/a&gt; which may do what you want. Notice the second n in nunchuck not m (this may be why you weren't finding anything decent on Google et al).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Amos&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:[Damn tuupola beat me to it by seconds]&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2009-11-01T21:27:33.443" LastActivityDate="2009-11-01T21:27:33.443" />
  <row Id="117" PostTypeId="2" ParentId="66" CreationDate="2009-11-01T21:30:25.327" Score="6" ViewCount="" Body="&lt;p&gt;There are also couple of hardware solutions which should be usable with Arduino:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://dosonchip.com/&quot; rel=&quot;nofollow&quot;&gt;DOSonCHIP&lt;/a&gt; which is FAT32 &amp;amp; FAT16 compatible. It will be really cool when they update the firmware to support I2C SparkFun also has a &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8215&quot; rel=&quot;nofollow&quot;&gt;breakout board&lt;/a&gt; for it. &lt;/li&gt;&#xA;&lt;li&gt;4D systems makes &lt;a href=&quot;http://www.4dsystems.com.au/prod.php?id=22&quot; rel=&quot;nofollow&quot;&gt;micro-DRIVE&lt;/a&gt;. Also this seems to be be &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8567&quot; rel=&quot;nofollow&quot;&gt;available&lt;/a&gt; from SparkFun.&lt;/li&gt;&#xA;&lt;li&gt;GHI Electronics has &lt;a href=&quot;http://www.ghielectronics.com/product/102&quot; rel=&quot;nofollow&quot;&gt;uALFAT MicroSD Board&lt;/a&gt;. It has an easy I2C interface and also supports long filenames.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="94" LastActivityDate="2009-11-01T21:30:25.327" />
  <row Id="118" PostTypeId="2" ParentId="105" CreationDate="2009-11-01T21:44:03.457" Score="3" ViewCount="" Body="&lt;p&gt;At Uni I did a talk on RFID chips as part of one module for my course. Based on the research I did then, and never actually having used them in real life, you probably will need to research/play with different chips to find ones that work. some chips can be blocked by a bottle of water, so whether a dog or cat's neck will do the same thing depends. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Possible problems that spring to mind:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does the position of the chip on the collar (top, bottom, side etc) relative to the sensor(s?) have an effect on detection?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will you need more than 1 sensor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What happens if your dog is in proximity to the flap, when the older cat wants to get out? Are you thinking that the chips will only be on cats which are not allowed out, thereby locking the flap whilst in proximity?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there are commercially available versions of this technology, see if you can find out what they use, including which brand/type of chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A book which was particularly useful whilst researching RFID as a topic (it seemed to have lots of case studies of implementations in it too) was RFID for Dummies which is &lt;a href=&quot;http://www.amazon.co.uk/RFID-Dummies-Patrick-J-Sweeney/dp/076457910X/ref=sr%5F1%5F2?ie=UTF8&amp;amp;s=books&amp;amp;qid=1257111710&amp;amp;sr=8-2&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; on Amazon in the UK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(That pretty much exhausts my knowledge of RFID, let us know how you get on, somehow.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers&#xA;Amos&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-01T21:44:03.457" />
  <row Id="119" PostTypeId="1" AcceptedAnswerId="123" CreationDate="2009-11-01T23:38:56.817" Score="4" ViewCount="2284" Body="&lt;p&gt;I've just bought a bag of random resistors from Maplin, and can't work out which way round the six band ones should be read.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance I have one which is either:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Violet Orange Red Brown Brown Red&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Red Brown Brown Red Orange Violet&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The red band at either the right or left appears thicker than the others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anybody point me to somewhere with a clear explanation (or provide one themselves) as searching on Google isn't finding me anything lucid.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers&#xA;Amos&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:42:30.050" LastActivityDate="2010-08-17T23:42:30.050" Title="6 Band Resistors, which way should the bands be read." Tags="&lt;resistor&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="120" PostTypeId="2" ParentId="105" CreationDate="2009-11-01T23:51:39.660" Score="5" ViewCount="" Body="&lt;p&gt;I am be very interested to see how this works out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am currently making an RFID controlled lock for a door and I know from my work on that,that RFID have range limitations(depending on what type of reader and chip you use) so the position of both reader and chip may be very important especially because you're planning on using it on an unpredictable living thing. That might be a big challenge and may require more than one RFID reader.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as a locking mechanism you can make one really cheap by taking apart an old cd drive and using the slots drive system.&lt;/p&gt;&#xA;" OwnerUserId="81" LastEditorUserId="81" LastEditorDisplayName="" LastEditDate="2009-11-01T23:57:54.453" LastActivityDate="2009-11-01T23:57:54.453" CommentCount="4" />
  <row Id="121" PostTypeId="2" ParentId="105" CreationDate="2009-11-01T23:52:07.140" Score="4" ViewCount="" Body="&lt;p&gt;I can't really help you with the issue of identifying you pets but for the latching mechanism you should look into linear actuators. The friction in the ball/screw drive of the actuator will be enough to hold the lock in place without applying power to the motor. A simple DC  actuator (with built in limit switches) and a throw of 1cm-2cm should be enough to operate a set of bolts. Linear actuators are typically slower than servos and solenoids but have more power and will stall the mechanism without using power.&lt;/p&gt;&#xA;" OwnerUserId="15" LastActivityDate="2009-11-01T23:52:07.140" CommentCount="1" />
  <row Id="122" PostTypeId="2" ParentId="119" CreationDate="2009-11-02T00:22:59.833" Score="3" ViewCount="" Body="&lt;p&gt;The Gold or Silver band is always set to the right, then you read from left to right. Sometimes there will be no tolerance band -- Simply find the side that has a band closest to a lead and make that the first band.&quot;  [1].  Also, usually you'll see one band off by itself, that is the tolerance band.&lt;/p&gt;&#xA;" OwnerUserId="30" LastEditorUserId="30" LastEditorDisplayName="" LastEditDate="2009-11-02T00:32:30.053" LastActivityDate="2009-11-02T00:32:30.053" CommentCount="1" />
  <row Id="123" PostTypeId="2" ParentId="119" CreationDate="2009-11-02T00:35:45.933" Score="5" ViewCount="" Body="&lt;p&gt;The folks at &lt;a href=&quot;http://itll.colorado.edu/ITLL/index.cfm?fuseaction=ResistorChart&quot; rel=&quot;nofollow&quot;&gt;itll.colorado.edu&lt;/a&gt; have a resistor chart that includes how to read 6 Band Resistors. You should start with the thick band! You can always test with a Multimeter too!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://img.skitch.com/20100609-bujatf2aujmekus9pa2632jkj8.png&quot; alt=&quot;Resistor Chart&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2010-06-09T07:28:19.440" LastActivityDate="2010-06-09T07:28:19.440" CommentCount="3" />
  <row Id="125" PostTypeId="2" ParentId="110" CreationDate="2009-11-02T01:47:57.727" Score="6" ViewCount="" Body="&lt;p&gt;You should definitely use the ESC. Brushless motors works best when driven with a sine wave (or as close as possible to a sine wave). They also require a fairly accurate and complicated set of signals. Generating the proper wave forms and timing from an arduino would be difficult, and unless you really need to it, is probably not worth it. You can always arrange to control the ESC from your arduino, which would give you programmatic control plus the efficiency and power of the ESC.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-02T01:47:57.727" CommentCount="1" />
  <row Id="126" PostTypeId="1" AcceptedAnswerId="127" CreationDate="2009-11-02T04:18:54.630" Score="3" ViewCount="525" Body="&lt;p&gt;Does anyone have a pin out diagram for the NES Controller? I'd like to connect the NES controller to an Arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2010-11-04T00:57:48.957" Title="Use an old NES Controller as an input device" Tags="&lt;controller&gt;&lt;pin&gt;&lt;layout&gt;&lt;arduino&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="127" PostTypeId="2" ParentId="126" CreationDate="2009-11-02T04:50:21.290" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://pinouts.ru/Game/snescontroller_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;http://pinouts.ru/Game/snescontroller_pinout.shtml&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-02T04:50:21.290" />
  <row Id="129" PostTypeId="1" CreationDate="2009-11-02T06:20:50.370" Score="5" ViewCount="2122" Body="&lt;p&gt;What are some recommendations on an ideal WiFi to Serial bridge? My ideal qualities would be:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Simple connectivity, SPI or Serial&lt;/li&gt;&#xA;&lt;li&gt;Reasonable fast speed, at least 1mbit/sec ideally (though probably wouldn't always need that fast)&lt;/li&gt;&#xA;&lt;li&gt;Inexpensive, I'm thinking under $50&lt;/li&gt;&#xA;&lt;li&gt;Low power -- it should use at most 100mA, if we could get it even lower like say 20 or 30ma, even better.&lt;/li&gt;&#xA;&lt;li&gt;Built-in protocol stack -- I want it to handle the WiFi protocol, along with DHCP, TCP/IP, DNS, etc, so that all I have to do is tell it what IP/port to connect to, and then handle the data myself.&lt;/li&gt;&#xA;&lt;li&gt;If at all possible, 5V-tolerant I/O's...to make it easy to interface to our old-school microcontrollers.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So far I've found:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.lantronix.com/device-networking/embedded-device-servers/matchport.html&quot; rel=&quot;nofollow&quot;&gt;Matchport b/g&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.rovingnetworks.com/wifly-gsx.php&quot; rel=&quot;nofollow&quot;&gt;WiFly GSX&lt;/a&gt; &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Anyone have any experience with other possibilities?&lt;/p&gt;&#xA;" OwnerUserId="131" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-04-16T18:20:46.223" LastActivityDate="2010-07-27T00:26:28.517" Title="Ideal WiFi to Serial (or SPI) bridge?" Tags="&lt;serial&gt;&lt;avr&gt;&lt;pic&gt;&lt;wifi&gt;&lt;wireless&gt;" AnswerCount="7" FavoriteCount="3" />
  <row Id="130" PostTypeId="2" ParentId="66" CreationDate="2009-11-02T08:28:30.067" Score="2" ViewCount="" Body="&lt;p&gt;Look at this:&#xA;&lt;a href=&quot;http://www.libelium.com/tienda/catalog/product%5Finfo.php?cPath=21&amp;amp;products%5Fid=66&amp;amp;language=en&quot; rel=&quot;nofollow&quot;&gt;Libelium SD module&lt;/a&gt; ; check &quot;&lt;em&gt;Documentation:&lt;/em&gt;&quot; section, there you will find everything you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used this module, you can even build it yourself. It works perfectly and you have developed libraries for use FAT as you can see.&lt;/p&gt;&#xA;" OwnerUserId="132" LastActivityDate="2009-11-02T08:28:30.067" />
  <row Id="131" PostTypeId="2" ParentId="56" CreationDate="2009-11-02T08:54:06.007" Score="1" ViewCount="" Body="&lt;p&gt;Just looking at the ultrasonic transducer without having open one ever it looks like it ha similar functionality to a standard movement activated light. That means that in the top half of the transducer you see the lens which detects movement using a Passive infra red (PIR) sensor. When this detects any motion it switches a signal pin which triggers the ultrasonic burst. Of course you can take advantage of this and switch the signal pin using an arduino or any other microcontroller using your own cat detection method. Might be a good idea to put in a optocoupler between the arduino and the ultrasonic transducer to protect both circuits from each other. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1255548587/3&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; is some info about some optocoupler and I cant post the link about the pir since chiphacker dosnt trust me enough... But just go into arduino.cc and search for pir and you will find it&lt;/p&gt;&#xA;" OwnerUserId="134" LastActivityDate="2009-11-02T08:54:06.007" />
  <row Id="132" PostTypeId="2" ParentId="29" CreationDate="2009-11-02T09:12:26.043" Score="2" ViewCount="" Body="&lt;p&gt;here, my arduino sleep library&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/arms22/downloads/list&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/arms22/downloads/list&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2009-11-02T09:12:26.043" />
  <row Id="133" PostTypeId="1" AcceptedAnswerId="137" CreationDate="2009-11-02T11:37:44.100" Score="2" ViewCount="851" Body="&lt;p&gt;I'm looking for a list of cool projects that people have made with the arduino that twitter...i have read about plants that tweet when they need watering or pets who have a button to let you know when they are hungry....whole houses which twitter the power usage etc....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So is there a place to go for a list of these....? Or could people just link the individual projects here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mad&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:33:59.513" LastActivityDate="2010-12-10T22:33:59.513" Title="Arduino Twitters" Tags="&lt;arduino&gt;&lt;twitter&gt;" AnswerCount="6" />
  <row Id="134" PostTypeId="2" ParentId="133" CreationDate="2009-11-02T14:06:19.853" Score="2" ViewCount="" Body="&lt;p&gt;Here, play around with mine.  &lt;a href=&quot;http://ka1kjz.com/?p=129&quot; rel=&quot;nofollow&quot;&gt;http://ka1kjz.com/?p=129&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll need to Base64 encode your username and password, there are plenty of sites to do that, just google around, you'll see the line in the code where you need to stick it.&lt;/p&gt;&#xA;" OwnerUserId="139" LastActivityDate="2009-11-02T14:06:19.853" />
  <row Id="136" PostTypeId="2" ParentId="129" CreationDate="2009-11-02T15:43:26.577" Score="1" ViewCount="" Body="&lt;p&gt;It's a bit unclear what this project is for but I think your best bet is a premade WiFi router with OpenWRT or some similar other open-source firmware. WiFi routers have the WiFi interface and they usually have a pinheader on the board for (TTL level) serial.&lt;/p&gt;&#xA;" OwnerUserId="140" LastActivityDate="2009-11-02T15:43:26.577" CommentCount="1" />
  <row Id="137" PostTypeId="2" ParentId="133" CreationDate="2009-11-02T15:49:33.220" Score="2" ViewCount="" Body="&lt;p&gt;Hello again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.botanicalls.com/kits/&quot; rel=&quot;nofollow&quot;&gt;Botanicalls&lt;/a&gt; is a open project that takes time working.&#xA;You can buy the kit and assemble or otherwise you have &lt;a href=&quot;http://www.botanicalls.com/archived%5Fkits/twitter/&quot; rel=&quot;nofollow&quot;&gt;all information&lt;/a&gt; on the web to build and why not make improvements?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The project where arduino is a twitter notification as better success at marketing today is &lt;a href=&quot;http://www.bakertweet.com/&quot; rel=&quot;nofollow&quot;&gt;BakerTweet&lt;/a&gt;. This is a funny device where the baker select that product just out of the oven and this is published in twitter. &#xA;What to does this serve? Those who do not live in town many times when we go to buy bread bakers are selling day-old bread. By this we know when we can go for fresh bread, cakes, buns, croissants, ... ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another open project is the &lt;a href=&quot;http://www.ladyada.net/make/tweetawatt/&quot; rel=&quot;nofollow&quot;&gt;Tweet a Watt&lt;/a&gt;, this project is very interesting and useful because we can monitor the consumption of a device by the Twitter. From my point of view is an expensive project, but with a little imagination we can reduce cost if we are forced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/playground/Code/TwitterLibrary&quot; rel=&quot;nofollow&quot;&gt;Oficial Tiwitter library&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Silly projects (my point of view ;) ):&lt;br&gt;&#xA;&lt;a href=&quot;http://www.mcqn.com/bubblino&quot; rel=&quot;nofollow&quot;&gt;Bubblino&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://portfolio.menscher.com/itp/kickbee/&quot; rel=&quot;nofollow&quot;&gt;KickBee&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="132" LastEditorUserId="132" LastEditorDisplayName="" LastEditDate="2009-11-02T17:06:15.630" LastActivityDate="2009-11-02T17:06:15.630" />
  <row Id="138" PostTypeId="2" ParentId="25" CreationDate="2009-11-02T17:05:05.383" Score="2" ViewCount="" Body="&lt;p&gt;I did this recently with a few gauges I picked up from a friend. I found the best solution was to drive the base of a transistor (BC547, in my case) with PWM from the Arduino.  Connect the collector to Vcc (+5, +3.3, etc.), and put a resistor between the positive side of the gauge and the emitter to limit the current to the value that will result in a full swing of the needle (and obviously the negative side of the gauge goes to ground).  Then the PWM output of the Arduino will swing the gauge ratiometrically between 0 and 100%.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-11-02T17:05:05.383" />
  <row Id="139" PostTypeId="2" ParentId="133" CreationDate="2009-11-02T17:29:02.087" Score="1" ViewCount="" Body="&lt;p&gt;The next upgrade to my &lt;a href=&quot;http://chaos.trader.name/accessories/chaos-controller/&quot; rel=&quot;nofollow&quot;&gt;Chaos Machine Controller&lt;/a&gt; will have a webserver and Twitter updates, so that anyone who's interested in the Chaos Machine can keep track of how long the machine has been running, and how many balls have passed through the machine during the installation.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-02T17:29:02.087" />
  <row Id="140" PostTypeId="2" ParentId="77" CreationDate="2009-11-02T17:51:37.007" Score="7" ViewCount="" Body="&lt;p&gt;shutterdrone's suggestion is very good, but is missing a detail, as it implies that the analog voltage reference is the same as the voltage being measured (aside from assuming that an Arduino is being used, which is not explicitly stated).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll need an ADC, whether it's integral to your uC or an external component.  The ADC needs an analog voltage reference (ARef) to compare the input with.  You don't want the ARef to be the same as the voltage you're sensing because then the ADC will always see the input and reference voltages as being equal, so the analog value for the sensed voltage will always be the maximum.  What you need is a very accurate analog voltage reference that won't change as the power supply voltage changes.  The ADC will compare that reference voltage to the battery voltage; you can use a voltage divider to reduce the battery voltage being sensed into the range of the ARef.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino (Atmega8/168/328/etc.) has a built-in ADC and a built-in 1.1V analog reference, so the only external components you'd need are resistors for the voltage divider.  I think you would also want to use very high values for the resistors to reduce the current drain on the battery.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-11-02T17:51:37.007" CommentCount="1" />
  <row Id="141" PostTypeId="2" ParentId="126" CreationDate="2009-11-02T18:00:03.510" Score="3" ViewCount="" Body="&lt;p&gt;Here's another &lt;a href=&quot;http://www.mit.edu/~tarvizo/nes-controller.html&quot; rel=&quot;nofollow&quot;&gt;page with some helpful information&lt;/a&gt;, including a signal diagram.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;          +----&amp;gt; Power  (white)&#xA;          |&#xA;5 +---------+  7    &#xA;  | x  x  o   \     &#xA;  | o  o  o  o |    &#xA;4 +------------+ 1  &#xA;    |  |  |  |&#xA;    |  |  |  +-&amp;gt; Ground (brown)&#xA;    |  |  +----&amp;gt; Pulse  (red)&#xA;    |  +-------&amp;gt; Latch  (orange)&#xA;    +----------&amp;gt; Data   (yellow)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-02T18:00:03.510" />
  <row Id="142" PostTypeId="2" ParentId="7" CreationDate="2009-11-02T18:17:16.323" Score="3" ViewCount="" Body="&lt;p&gt;The primary problem in soldering or brazing aluminum is cleanliness...oxidation and cross contamination must be prevented. In aviation we use a hydrogen flame instead of acetylene for better heat control. Larger pieces are welded using heli-arc or tig (tungsten inert gas) processes. A skilled operator can &quot;glue&quot; razorblades together.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-02T18:17:16.323" />
  <row Id="143" PostTypeId="2" ParentId="129" CreationDate="2009-11-02T18:45:59.663" Score="1" ViewCount="" Body="&lt;p&gt;As pointed out by Dago, I personally use a Fon (La Fonera) or Meraki router (with OpenWRT) for connecting Wifi to a serial connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.geocities.jp/arduino_diecimila/wifi/a2p_ddwrt_en.html&quot; rel=&quot;nofollow&quot;&gt;http://www.geocities.jp/arduino_diecimila/wifi/a2p_ddwrt_en.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="144" LastEditorUserId="144" LastEditorDisplayName="" LastEditDate="2009-11-02T19:14:25.547" LastActivityDate="2009-11-02T19:14:25.547" />
  <row Id="144" PostTypeId="2" ParentId="59" CreationDate="2009-11-02T18:49:45.077" Score="1" ViewCount="" Body="&lt;p&gt;To answer the second part of your question, yes, you'll probably need a general-purpose microcontroller to handle your user interface.  DSPs are dedicated processors:  they do one thing very well (signal processing) but don't do anything else.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-02T18:49:45.077" CommentCount="3" />
  <row Id="145" PostTypeId="2" ParentId="66" CreationDate="2009-11-02T21:01:23.763" Score="3" ViewCount="" Body="&lt;p&gt;Saving data on a SD card is not that difficult without premade boards/solutions but saving data on a filesystem (meaning that you can just mount it as a regular partition on your computer) on a SD card is much harder because you have to be able to manipulate the filesystem itself which is much harder, but there are readymade libraries for this which make it easier. So it depends on what you want to do.&lt;/p&gt;&#xA;" OwnerUserId="140" LastActivityDate="2009-11-02T21:01:23.763" CommentCount="1" />
  <row Id="146" PostTypeId="1" AcceptedAnswerId="154" CreationDate="2009-11-02T21:30:17.370" Score="2" ViewCount="2239" Body="&lt;p&gt;So i started this project a while back where i made a remote controlled car that i could control with the directional buttons on my keyboard via an Arduino -&gt;  now the next step i want to do is to get the tilt control in my iPhone to be driving the car  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone got a good tutorial on this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mad&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2010-09-08T11:17:22.967" Title="Using the iPhone to control a remote controlled car via Arduino" Tags="&lt;arduino&gt;&lt;iphone&gt;&lt;remote&gt;&lt;control&gt;&lt;tutorial&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="147" PostTypeId="1" AcceptedAnswerId="631" CreationDate="2009-11-02T21:34:36.743" Score="3" ViewCount="396" Body="&lt;p&gt;How do i go about using the joystick with an Arduino?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-25T10:13:12.647" Title="Joystick with the Arduino" Tags="&lt;arduino&gt;" AnswerCount="5" />
  <row Id="148" PostTypeId="1" AcceptedAnswerId="151" CreationDate="2009-11-02T21:37:44.747" Score="3" ViewCount="1322" Body="&lt;p&gt;If i'm running out of Pins to put things in on the Arduino  -&gt; short of buying a second one or getting a Mega - is there a way to get more happening on the one board?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do i need to worry about overloading it?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2010-03-06T19:56:15.083" Title="Pins in the Arduino" Tags="&lt;pins&gt;&lt;arduino&gt;" AnswerCount="8" />
  <row Id="149" PostTypeId="1" AcceptedAnswerId="176" CreationDate="2009-11-02T21:43:18.160" Score="3" ViewCount="1245" Body="&lt;p&gt;To get full resolution from Arduino ADC when using 3.3V sensors you must do two things.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Connect 3.3V power supply to AREF pin.&lt;/li&gt;&#xA;&lt;li&gt;Call &lt;em&gt;analogReference(EXTERNAL)&lt;/em&gt; in the code.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;But what about if I must mix 3.3V and 5V outputting sensors. What are my options?&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2009-11-09T16:24:44.883" Title="How to use 3.3V and 5V outputting sensors with Arduino?" Tags="&lt;arduino&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="150" PostTypeId="2" ParentId="77" CreationDate="2009-11-02T22:07:55.747" Score="13" ViewCount="" Body="&lt;p&gt;tinker.it published a &quot;secret&quot; voltage level meter in the Atmega168/atmega328. With a little trick an Arduino is able to compare VCC against an internal precision 1.1v reference. The explanation and the code is here: &lt;a href=&quot;http://code.google.com/p/tinkerit/wiki/SecretVoltmeter&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/tinkerit/wiki/SecretVoltmeter&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-02T22:07:55.747" />
  <row Id="151" PostTypeId="2" ParentId="148" CreationDate="2009-11-02T22:19:46.987" Score="5" ViewCount="" Body="&lt;p&gt;Have you used up all your analog pins as well? They can also be used as digital input/output by just referring to them as digital pins pins 14 to 19. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After you used all of them as well you might consider using a shift register IC. These chips will convert serial data into parallel data. The 8 bit versions will take serial data on three pins and output parallel data on 8 pins, giving you 5 extra pins. A very nice explanation is done by &lt;a href=&quot;http://www.nycresistor.com/category/oscilloscope/&quot; rel=&quot;nofollow&quot;&gt;Dave Clausen at NYC Resistor&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is actually a possibility of overloading your arduino. Not by using too much pins, but by drawing too much current from the pins, by hooking up too much stuff to your pins. The Atmega168 datasheet says that the pins have an absolute maximum current of 40mA. This would be equivalent to two LED's in parallel. Anything more than one LED (20mA) should be switched through a transistor or transistor array. This is also explained in the video mentioned above and by &lt;a href=&quot;http://www.tigoe.net/pcomp/code/input-output/controlling-high-current-circuits&quot; rel=&quot;nofollow&quot;&gt;Tom Igoe&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="10" LastEditorUserId="10" LastEditorDisplayName="" LastEditDate="2009-11-02T22:54:12.900" LastActivityDate="2009-11-02T22:54:12.900" CommentCount="1" />
  <row Id="152" PostTypeId="2" ParentId="147" CreationDate="2009-11-02T22:20:05.943" Score="2" ViewCount="" Body="&lt;p&gt;I'm assuming you are using a non-USB joystick.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;See &lt;a href=&quot;http://www.built-to-spec.com/blog/2009/09/10/using-a-pc-joystick-with-the-arduino/&quot; rel=&quot;nofollow&quot;&gt;http://www.built-to-spec.com/blog/2009/09/10/using-a-pc-joystick-with-the-arduino/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-11-02T22:20:05.943" />
  <row Id="153" PostTypeId="2" ParentId="148" CreationDate="2009-11-02T22:22:43.637" Score="2" ViewCount="" Body="&lt;p&gt;If you are driving LEDS, you might look into charlieplexing.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-02T22:22:43.637" />
  <row Id="154" PostTypeId="2" ParentId="146" CreationDate="2009-11-02T22:30:03.800" Score="4" ViewCount="" Body="&lt;p&gt;The biggest problem you've got is how to get data from the iPhone to the Arduino.  The main possibilities are to:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Physically interface the iPod Touch/iPhone to the Arduino.  (&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1207058161&quot; rel=&quot;nofollow&quot;&gt;See this thread&lt;/a&gt;).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Send a signal from the iPod Touch/iPhone via WiFi (or, I believe, from the iPhone via Bluetooth) to a computer (likely running a webserver) or directly to the Arduino (provided it has additional hardware to receive bluetooth or WiFi signals.)  (&lt;a href=&quot;http://hackedgadgets.com/2008/10/20/iphone-controlled-rc-car-using-an-arduino/&quot; rel=&quot;nofollow&quot;&gt;See this blog entry&lt;/a&gt;).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-11-02T22:30:03.800" />
  <row Id="155" PostTypeId="2" ParentId="114" CreationDate="2009-11-02T22:45:36.553" Score="4" ViewCount="" Body="&lt;p&gt;Todbot wrote a &lt;a href=&quot;http://todbot.com/blog/2008/02/18/wiichuck-wii-nunchuck-adapter-available/&quot; rel=&quot;nofollow&quot;&gt;tutorial&lt;/a&gt; for this a while ago. He also made a small nunchuck-breadboard adapter so you wouldn't have to cut off the connector of your nunchuck to get to the wires. &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9281&quot; rel=&quot;nofollow&quot;&gt;Sparkfun.com&lt;/a&gt; sells these. If you really want to demolish your nunchuck, make sure you get a &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.24529&quot; rel=&quot;nofollow&quot;&gt;cheap one&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-02T22:45:36.553" />
  <row Id="156" PostTypeId="2" ParentId="32" CreationDate="2009-11-02T22:48:44.260" Score="3" ViewCount="" Body="&lt;p&gt;Of course this can be found in the atmega168 datasheet from Atmel but sometimes it is also handy to know which Arduino pins correspond to the Atmega168 pin numbers. This reference can be found on the &lt;a href=&quot;http://www.arduino.cc/en/Hacking/PinMapping&quot; rel=&quot;nofollow&quot;&gt;Arduino site&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-02T22:48:44.260" />
  <row Id="157" PostTypeId="2" ParentId="148" CreationDate="2009-11-02T23:07:50.423" Score="3" ViewCount="" Body="&lt;p&gt;There are many options for expanding the number of inputs and outputs you have available. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For analog input, it is common to use analog multiplexers (like the &lt;a href=&quot;http://www.arduino.cc/playground/Learning/4051&quot; rel=&quot;nofollow&quot;&gt;4051&lt;/a&gt;, available as 74HC4051 and CD4051) which allow you to switch between 8 analog sources using 3 digital lines and 1 analog input. One commonly used option for digital IO is to add TTL (or CMOS) shift registers. Shift registers come in two main varieties, the &quot;serial in, parallel out&quot; (like the &lt;a href=&quot;http://www.arduino.cc/en/Tutorial/ShiftOut&quot; rel=&quot;nofollow&quot;&gt;74HC595&lt;/a&gt;) which are useful for extending the number of digital outputs your project has and &quot;parallel in, serial out&quot; (like the &lt;a href=&quot;http://www.arduino.cc/playground/Code/ShiftRegSN74HC165N&quot; rel=&quot;nofollow&quot;&gt;74HC165&lt;/a&gt;) which allows you to add more digital inputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tom Igeo has a nice write up on &lt;a href=&quot;http://www.tigoe.net/pcomp/code/category/arduinowiring/486&quot; rel=&quot;nofollow&quot;&gt;Controlling Lots of Outputs from a Microcontoller&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can overload the arduino's output by trying to 'fanout' too far. Each IC you connect to an output draws current from that output. If you load lots of ICs onto the same output (or set of outputs) they might try to draw more than the arduino's outputs can handle. To remedy this problem you can place non'inverting buffer chips (like the 74ls07) between some of ICs.&lt;/p&gt;&#xA;" OwnerUserId="15" LastEditorUserId="15" LastEditorDisplayName="" LastEditDate="2009-11-02T23:35:58.557" LastActivityDate="2009-11-02T23:35:58.557" CommunityOwnedDate="2009-11-02T23:07:50.423" />
  <row Id="158" PostTypeId="1" AcceptedAnswerId="247" CreationDate="2009-11-02T23:09:14.000" Score="1" ViewCount="242" Body="&lt;p&gt;I am making an application using the DIY Force Sensitive Resistor (FSR) taken from &lt;a href=&quot;http://www.instructables.com/id/DIY-Force-Sensitive-Resistor-FSR/?ALLSTEPS&quot; rel=&quot;nofollow&quot;&gt;this instructable&lt;/a&gt;. The resistance of this sensor typycally ranges from 20kOhm when at rest to 9kOhm when pressed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would I convert these resistance values to a signal where 0v corresponds to the rest condition and 5v corresponds to the &quot;pressed&quot; condition so that I can read it with an Arduino?&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-06T09:20:23.070" Title="How would I get a full range voltage reading from a pressure sensor?" Tags="&lt;sensor&gt;&lt;arduino&gt;" AnswerCount="2" />
  <row Id="159" PostTypeId="1" AcceptedAnswerId="164" CreationDate="2009-11-02T23:20:57.270" Score="4" ViewCount="390" Body="&lt;p&gt;What sort of LCD should should i be using to go with my Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used the HD44780-compatible LCD in the past, but heard that the Serial Enabled LCDs make life a lot easier.&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-10T02:58:20.623" LastActivityDate="2011-02-27T22:45:06.773" Title="Serial Enabled LCD" Tags="&lt;arduino&gt;&lt;serial&gt;&lt;lcd&gt;" AnswerCount="6" />
  <row Id="160" PostTypeId="2" ParentId="149" CreationDate="2009-11-02T23:29:31.137" Score="2" ViewCount="" Body="&lt;p&gt;Two things, live with the reduced resolution from the 3.3v sensors and keep your reference at 5V.  Thats what I usually do and its good enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also switch your analogReference on the fly when reading each respective sensor.  I do recall reading about mixing external references and internal references and having a series limiting resistor on your AREF, so read that part of the Arduino reference carefully.&lt;/p&gt;&#xA;" OwnerUserId="139" LastActivityDate="2009-11-02T23:29:31.137" />
  <row Id="161" PostTypeId="2" ParentId="32" CreationDate="2009-11-02T23:32:45.113" Score="1" ViewCount="" Body="&lt;p&gt;Be aware, shameless promotion ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a cheat sheet with the ATmega-Arduino pin mapping on it.&#xA;&lt;a href=&quot;http://tinkerlog.com/2009/06/18/microcontroller-cheat-sheet/&quot; rel=&quot;nofollow&quot;&gt;http://tinkerlog.com/2009/06/18/microcontroller-cheat-sheet/&lt;/a&gt;&lt;/p&gt;&#xA;" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-31T12:28:04.480" LastActivityDate="2011-05-31T12:28:04.480" />
  <row Id="162" PostTypeId="2" ParentId="66" CreationDate="2009-11-02T23:43:24.513" Score="2" ViewCount="" Body="&lt;p&gt;You can get a simple SD card reader/writer from the &lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MKSEEED6&amp;amp;Click=37845&quot; rel=&quot;nofollow&quot;&gt;Maker Shed&lt;/a&gt;.&#xA;You can get an SD card reader/writer with audio out with the &lt;a href=&quot;http://www.adafruit.com/index.php?main%5Fpage=product%5Finfo&amp;amp;cPath=17%5F21&amp;amp;products%5Fid=94&quot; rel=&quot;nofollow&quot;&gt;Adafruit WaveShield&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="143" LastEditorUserId="143" LastEditorDisplayName="" LastEditDate="2009-11-03T16:14:35.350" LastActivityDate="2009-11-03T16:14:35.350" />
  <row Id="163" PostTypeId="2" ParentId="158" CreationDate="2009-11-02T23:50:39.167" Score="2" ViewCount="" Body="&lt;p&gt;I think the simplest way would be a voltage divider that gives you 5V at 9k and decreases as the resistance increases.  You can play with various resistor combinations in this [voltage divider calculator][1]. It's going to be a linear progression, however.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;[1] &lt;a href=&quot;http://www.raltron.com/cust/tools/voltage_divider.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.raltron.com/cust/tools/voltage_divider.asp&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-11-02T23:50:39.167" />
  <row Id="164" PostTypeId="2" ParentId="159" CreationDate="2009-11-02T23:51:52.327" Score="4" ViewCount="" Body="&lt;p&gt;It really depends upon what you want to do with the Arduino, besides displaying information on the LCD.  Like you, I used an HD44780-compatible LCD for my first project, and while it worked fine, it consumed half of my digital I/O pins, and seriously limited what I could do with my project.  If you don't really need a lot of I/O, that can be fine.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, if you want to do more than that, a serial LCD interface may make more sense.  They cost twice as much, but as you can see from this &lt;a href=&quot;http://store.fungizmos.com/index.php?main%5Fpage=product%5Finfo&amp;amp;products%5Fid=210&quot; rel=&quot;nofollow&quot;&gt;example&lt;/a&gt;, you can daisy chain with I2C.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/* Quick example to use FunGizmos serial LCD in I2C mode&#xA;*&#xA;* Connections between LCD &amp;amp; Arduino &#xA;* LCD P2&#xA;*   Pin1 not connected&#xA;*   Pin2 not connected&#xA;*   Pin3 SCL -&amp;gt; Analog in 5 (Arduino has internal pullup resistor)&#xA;*   Pin4 SDA -&amp;gt; Analog in 4 (Arduino has internal pullup resistor)&#xA;*   Pin5 VSS -&amp;gt; gnd&#xA;*   Pin6 VDD -&amp;gt; +5V&#xA;*&#xA;* To enable I2C mode of LCD Pads of R1 must be jumpered on back of LCD &#xA;* (Between R6 &amp;amp; R14 right below the black IC glob)&#xA;*&#xA;*/&#xA;&#xA;#include &amp;lt;Wire.h&amp;gt;&#xA;&#xA;int lcd_addr = 0x50; //default I2C hex address from datasheet&#xA;int blink;&#xA;&#xA;void setup(){&#xA;  delay(1000); //allow lcd to wake up.&#xA;&#xA;  Wire.begin(); //initialize Wire library&#xA;&#xA;  // Wire library expects 7-bit value for address and shifts left appending 0 or 1 for read/write&#xA;  // Lets adjust our address to match what Wire is expecting (shift it right one bit)&#xA;  lcd_addr = lcd_addr &amp;gt;&amp;gt; 1;&#xA;&#xA;  //Send lcd clear command&#xA;  Wire.beginTransmission(lcd_addr);&#xA;  Wire.send(0xFE); //Cmd char&#xA;  Wire.send(0x51); //Home and clear&#xA;  Wire.endTransmission();&#xA;&#xA;  Wire.beginTransmission(lcd_addr);&#xA;  Wire.send(0xFE); //Cmd char&#xA;  Wire.send(0x70); //Display LCD firmware version&#xA;  Wire.endTransmission();&#xA;&#xA;  delay(2000);&#xA;&#xA;  //Send lcd clear command&#xA;  Wire.beginTransmission(lcd_addr);&#xA;  Wire.send(0xFE); //Cmd char&#xA;  Wire.send(0x51); //Home and clear&#xA;  Wire.endTransmission();&#xA;&#xA;  Wire.beginTransmission(lcd_addr);&#xA;  Wire.send(&quot;Hi I'm using I2C&quot;);&#xA;  Wire.endTransmission();&#xA;&#xA;  Wire.beginTransmission(lcd_addr);&#xA;  Wire.send(0xFE); //Cmd char&#xA;  Wire.send(0x45); //Set Cursor pos&#xA;  Wire.send(0x40); //Line 2&#xA;  Wire.endTransmission();&#xA;&#xA;  Wire.beginTransmission(lcd_addr);&#xA;  Wire.send(&quot;FunGizmos.com&quot;);&#xA;  Wire.endTransmission();&#xA;&#xA;}&#xA;&#xA;&#xA;&#xA;void loop(){&#xA;&#xA;  Wire.beginTransmission(lcd_addr);&#xA;  Wire.send(0xFE); //Cmd char&#xA;  Wire.send(0x45); //Set Cursor pos&#xA;  Wire.send(0x40+15); //Line 2 last char&#xA;  Wire.endTransmission();&#xA;&#xA;  Wire.beginTransmission(lcd_addr);&#xA;  if(blink)&#xA;     Wire.send('*');&#xA;  else&#xA;     Wire.send(' ');&#xA;  Wire.endTransmission();&#xA;  blink = !blink;&#xA;&#xA;  delay(500);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-02T23:51:52.327" />
  <row Id="165" PostTypeId="2" ParentId="73" CreationDate="2009-11-02T23:59:13.533" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://forums.parallax.com/forums/default.aspx?f=6&amp;amp;m=164400&quot; rel=&quot;nofollow&quot;&gt;http://forums.parallax.com/forums/default.aspx?f=6&amp;amp;m=164400&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="157" LastActivityDate="2009-11-02T23:59:13.533" />
  <row Id="166" PostTypeId="2" ParentId="159" CreationDate="2009-11-03T00:42:46.467" Score="1" ViewCount="" Body="&lt;p&gt;I use serial lcd's and they're very easy to use and helpful, but if your not using an Arduino Mega you will only have one serial port.This can be solved by using software serial though as long ads you only need to do a write not a read. A good software serial library can be found &lt;a href=&quot;http://arduiniana.org/libraries/NewSoftSerial/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2009-11-03T00:42:46.467" />
  <row Id="167" PostTypeId="1" AcceptedAnswerId="397" CreationDate="2009-11-03T00:53:06.820" Score="3" ViewCount="1905" Body="&lt;p&gt;Does anyone know how to access the Iphones serial port, from a program on the Ipod to allow that application to send signals. The idea is that the ipod could be used as the brain for some kind of robot by using the serial port to tell an arduino what to do.&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2011-02-17T18:37:32.060" Title="Iphone hardware serial port access" Tags="&lt;arduino&gt;&lt;iphone&gt;&lt;serial&gt;" AnswerCount="6" FavoriteCount="4" />
  <row Id="168" PostTypeId="2" ParentId="59" CreationDate="2009-11-03T01:56:17.743" Score="5" ViewCount="" Body="&lt;p&gt;If you go with one of the dsPIC parts, you can have both interface and processing in one (the make great general purpose MCU's as well).  They come in SOIC and DIP packages which makes prototyping easy, and some of the dsPIC 33 range have almost all their pins re-mappable which makes routing a board a breeze.&lt;/p&gt;&#xA;" OwnerUserId="159" LastActivityDate="2009-11-03T01:56:17.743" CommentCount="2" />
  <row Id="169" PostTypeId="2" ParentId="167" CreationDate="2009-11-03T02:01:33.280" Score="3" ViewCount="" Body="&lt;p&gt;This looks like what you want:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://devdot.wikispaces.com/Iphone+Serial+Port+Tutorial&quot; rel=&quot;nofollow&quot;&gt;http://devdot.wikispaces.com/Iphone+Serial+Port+Tutorial&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-11-03T02:01:33.280" CommentCount="1" />
  <row Id="170" PostTypeId="2" ParentId="148" CreationDate="2009-11-03T04:30:20.907" Score="3" ViewCount="" Body="&lt;p&gt;I've been toying with using this... &lt;a href=&quot;http://www.neufeld.newton.ks.us/electronics/?p=241&quot; rel=&quot;nofollow&quot;&gt;http://www.neufeld.newton.ks.us/electronics/?p=241&lt;/a&gt;  Arduino I/O expansion using I2C.  Looks real promising, I havent gotten around to ordering the chips yet.  It's also a really good tutorial on using I2C.&lt;/p&gt;&#xA;" OwnerUserId="139" LastActivityDate="2009-11-03T04:30:20.907" />
  <row Id="171" PostTypeId="2" ParentId="159" CreationDate="2009-11-03T04:47:12.637" Score="1" ViewCount="" Body="&lt;p&gt;I have used one serial LCD before, the 20x4 black on green one from SparkFun. The 3-wire interface is very easy to work with but be warned, the back-light draws a &lt;strong&gt;lot&lt;/strong&gt; of power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if you connect it to a PICAXE the serial 1/0 vs high/low is around the wrong way and you will have to put a logic inverter inline.&lt;/p&gt;&#xA;" OwnerUserId="25" LastActivityDate="2009-11-03T04:47:12.637" />
  <row Id="172" PostTypeId="2" ParentId="89" CreationDate="2009-11-03T05:38:13.800" Score="2" ViewCount="" Body="&lt;p&gt;The parts in bicycle computers are reed-contacts not hall effect sensors. They are copmplete different. But i think you all talk about the reed-contacts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Greetings 0815achim&lt;/p&gt;&#xA;" OwnerUserId="162" LastActivityDate="2009-11-03T05:38:13.800" />
  <row Id="173" PostTypeId="2" ParentId="159" CreationDate="2009-11-03T08:29:23.297" Score="4" ViewCount="" Body="&lt;p&gt;I use a parallel LCD display unit which I converted to I2C by using the BV4208 I2C LCD Controller IC chip from ByVac&#xA;&lt;a href=&quot;http://www.byvac.com/di_i2c.php&quot; rel=&quot;nofollow&quot;&gt;http://www.byvac.com/di_i2c.php&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a library for use with this unit.&#xA;&lt;a href=&quot;http://john.crouchley.com/blog/archives/264&quot; rel=&quot;nofollow&quot;&gt;http://john.crouchley.com/blog/archives/264&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I2C only uses two wires - Analog 4 and Analog 5, you can connect a number of devices from these wires each with their own I2C address. This is a very easy way to extend the Arduino.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-03T08:29:23.297" />
  <row Id="174" PostTypeId="2" ParentId="133" CreationDate="2009-11-03T08:35:43.730" Score="1" ViewCount="" Body="&lt;p&gt;I have a twittering home monitoring system, it also logs to Pachube. I am constantly upgrading this and expect to have more tweets and also SMS over the next few weeks.&#xA;Block diagram of system &lt;a href=&quot;http://john.crouchley.com/blog/archives/445&quot; rel=&quot;nofollow&quot;&gt;http://john.crouchley.com/blog/archives/445&lt;/a&gt;&#xA;Arduino code &lt;a href=&quot;http://john.crouchley.com/blog/archives/404&quot; rel=&quot;nofollow&quot;&gt;http://john.crouchley.com/blog/archives/404&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-03T08:35:43.730" />
  <row Id="175" PostTypeId="2" ParentId="167" CreationDate="2009-11-03T08:41:18.703" Score="1" ViewCount="" Body="&lt;p&gt;since OS 3.0 there is an API for the hardware port. might wanna use that,&lt;/p&gt;&#xA;" LastActivityDate="2009-11-03T08:41:18.703" CommentCount="3" />
  <row Id="176" PostTypeId="2" ParentId="149" CreationDate="2009-11-03T09:01:19.193" Score="4" ViewCount="" Body="&lt;p&gt;A simple solution is to use a resistor divider (ratio approx 1:1.94) and reduce the 5v signal to a peak of 3.3v&#xA;That way you would retain full resolution whilst not needing to switch reference.&#xA;Suitable divider would be to use a 18k from the sensor to the analog input and a 33k from the analog input to ground. This would translate the 5v input to a 3.23v input. Use of higher precision resistors would get this closer to 3.3v if needed.&#xA;You need to ensure that the sensor can supply the current needed for a given value - in this case about 0.1mA.&#xA;The input resistance of the ATMega analog inputs is about 100M ohms so you could increase these values (reducing the load on the sensor) significantly before worrying about the effect of the input resistance.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-03T09:01:19.193" />
  <row Id="177" PostTypeId="2" ParentId="148" CreationDate="2009-11-03T09:47:49.830" Score="3" ViewCount="" Body="&lt;p&gt;If you do end up getting another microcontroller, I like the &lt;a href=&quot;http://sanguino.cc/&quot; rel=&quot;nofollow&quot;&gt;sanguino&lt;/a&gt; for at least four reasons:  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;it has a bunch more I/O than the&#xA;Atmega 168/368 (32 general purpose&#xA;pins, up from 14).  Like the&#xA;Arduino, 8 pins can do ADC, 6 can do&#xA;PWM, but there is an additional&#xA;hardware serial port.&lt;/li&gt;&#xA;&lt;li&gt;it's $5 cheaper*, &lt;/li&gt;&#xA;&lt;li&gt;with 64K of flash, I never even come&#xA;    close to running out of memory, and&lt;/li&gt;&#xA;&lt;li&gt;you get to put it together yourself&#xA;    from a kit.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The Arduino Mega &lt;em&gt;does&lt;/em&gt; have more PWM pins -- 14, but I don't think you'd multiplex those.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*Sanguino seems to go for $25, Arduino for $30, although you'll need a $20 USB-to-TTL cable if you need to use a USB port to program it, where the Arduino has USB built in.&lt;/p&gt;&#xA;" OwnerUserId="165" LastActivityDate="2009-11-03T09:47:49.830" />
  <row Id="178" PostTypeId="2" ParentId="149" CreationDate="2009-11-03T16:04:58.753" Score="1" ViewCount="" Body="&lt;p&gt;You may also consider looking for newer versions of your sensors.  You may be able to acquire sensors that both work with the same voltage limits, or you may find out that newer versions of the sensors are available which will give you digital outputs and can be polled with I2C or other simple serial communication protocols.  It would require buying a new chip, of course, but they're not terribly expensive and not only would you eliminate the problem, but you would likely provide your project with a greater level of precision since you don't have to worry about noise in your circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Short of redesigning your entire project to fit new chips, John C and the ham provide excellent, simple solutions.  In my experience, I have run a 3v3 sensor with a 5v supply and reference and have had larger issues with noise than with lost resolution for casual projects.  This is the easiest way out, but does require you to do some math, and I have voted ka1kjz's post up accordingly (do check the reference sheets).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as the voltage divider solution goes, as long as you use higher-precision resistors you get the advantage of having all of your measurements be in the same voltage range and you get the ratiometric correction benefit of using AREF to follow any voltage ripple.  In practice, however, I've found that noise and lack of calibration techniques in my projects have contributed more error than a little voltage ripple or 10% resistors could reasonably cause.  For that reason I have voted JohnC's solution up as well, since he covers all this in more detail.&lt;/p&gt;&#xA;" OwnerUserId="11" LastEditorUserId="11" LastEditorDisplayName="" LastEditDate="2009-11-09T16:24:44.883" LastActivityDate="2009-11-09T16:24:44.883" />
  <row Id="179" PostTypeId="2" ParentId="54" CreationDate="2009-11-03T16:36:39.893" Score="1" ViewCount="" Body="&lt;p&gt;Yet another option is to use an SD Card reader / writer, and write your file to a SD card.  When you're done collecting data, swap out SD cards with your workstation computer.  This approach will allow you to run your project disconnected from a computer, and will provide for non-volatile storage of large amounts of data.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-03T16:36:39.893" />
  <row Id="180" PostTypeId="2" ParentId="89" CreationDate="2009-11-03T17:22:12.337" Score="4" ViewCount="" Body="&lt;p&gt;Actually, Achim has made a very good point here. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a big difference between a Reed (magnetic) relay (switch), and a Hall effect sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Primarily, a Reed relay will connect a switch whenever enough magnetic force is acting upon it, giving you an on/off signal.  A Hall effect sensor provides a voltage level indicating how much magnetic force is being applied to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The code shown above would only 'directly' work with a Reed relay, which is not to say that it won't work at all for a hall effect sensor, but that it would provide additional challenges using a hall-effect sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The primary challenge will be that you're treating an analog device as a digital one - expecting to trigger on rise of a pulse.  Now, the signal won't be pulsed - it will be generally like a bell-curve, with all sorts of fluctuations.  You might trip past the minimal voltage for a high signal (around 3.5v, IIRC?) several times as the magnet passes the hall-effect sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, our first instinct when using something like a hall effect sensor is to use the ADC and read the voltage level on an analog pin.  However, you're limited to 10,000 reads, roughly, per second on an analog pin (each read takes 100uS). That assumes also that all you do is loop and read values - doesn't leave you much other time to update a display, calculate, etc. Not to mention, if you read at the wrong time, you missed your signal!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm sure it's possible to use interrupts somehow linked to the ADC, but I don't have such knowledge handy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead, if you wish to use an &lt;em&gt;actual&lt;/em&gt; Hall Effect sensor, I'd suggest feeding it into a Schmitt trigger to convert it to a digital (on/off) signal at a calibrated level that indicates &quot;directly under the magnet.&quot;  Additionally, depending on the level of hysteresis implemented in the Schmitt trigger, you may need to do some de-bouncing that would change the rate of de-bounce based on current speed.  Then you could treat it like a normal Reed relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;!c&lt;/p&gt;&#xA;" OwnerUserId="36" LastEditorUserId="36" LastEditorDisplayName="" LastEditDate="2009-11-03T17:37:47.353" LastActivityDate="2009-11-03T17:37:47.353" CommentCount="2" />
  <row Id="181" PostTypeId="1" AcceptedAnswerId="206" CreationDate="2009-11-03T20:48:38.947" Score="1" ViewCount="207" Body="&lt;p&gt;Has anyone got a diagram of the layout of the Robosapien v2?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-04T18:50:45.027" Title="Modding a robosapien" Tags="&lt;diagram&gt;&lt;layout&gt;" AnswerCount="1" />
  <row Id="182" PostTypeId="2" ParentId="105" CreationDate="2009-11-03T20:54:53.587" Score="2" ViewCount="" Body="&lt;p&gt;ZigBee could be a decent alternative for RFID.  I've never used it, but it's designed for situations like yours.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-03T20:54:53.587" CommentCount="1" />
  <row Id="183" PostTypeId="1" AcceptedAnswerId="187" CreationDate="2009-11-03T21:46:57.550" Score="4" ViewCount="482" Body="&lt;p&gt;Does anyone have an easy to use Servo Torque Calculator?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-02T02:24:09.107" LastActivityDate="2011-02-02T02:24:09.107" Title="Servo Torque Calculator" Tags="&lt;servo&gt;&lt;torque&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="184" PostTypeId="1" AcceptedAnswerId="196" CreationDate="2009-11-03T22:04:04.583" Score="3" ViewCount="311" Body="&lt;p&gt;I'm looking for an alternative to the conductive thread (since i lack some sowing skills).  I have seen this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/silver-conductive-pen&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/silver-conductive-pen&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but i'm wondering if it could be used for clothing?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-11-03T22:19:28.833" LastActivityDate="2010-07-17T05:16:25.457" Title="Is there a way to print / draw a circuit on to clothing?" Tags="&lt;conductive&gt;&lt;thread&gt;&lt;clothing&gt;&lt;circuit&gt;" AnswerCount="7" FavoriteCount="1" />
  <row Id="185" PostTypeId="2" ParentId="167" CreationDate="2009-11-03T22:15:57.860" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Related:&lt;/strong&gt; Here is a &lt;a href=&quot;http://pargon.nl/&quot; rel=&quot;nofollow&quot;&gt;tutorial&lt;/a&gt; on how to boot a Jailbroken iPod 2G using a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-11-03T22:15:57.860" />
  <row Id="186" PostTypeId="2" ParentId="184" CreationDate="2009-11-03T22:19:14.683" Score="2" ViewCount="" Body="&lt;p&gt;Xerox has &lt;a href=&quot;http://digital.venturebeat.com/2009/10/26/xerox-developers-a-silver-ink-that-can-be-used-to-wearable-or-throwaway-electronics/&quot; rel=&quot;nofollow&quot;&gt;just announced&lt;/a&gt; a silver ink for wearable and throwaway electronics. I think it's a bit early to use in your projects. The Silver Pen is an interesting idea. I don't know if it'll work! &lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-11-03T22:19:14.683" />
  <row Id="187" PostTypeId="2" ParentId="183" CreationDate="2009-11-03T22:31:30.903" Score="2" ViewCount="" Body="&lt;p&gt;Does this &lt;a href=&quot;http://agert.homelinux.org/~fredrik/flyg/servo.html&quot; rel=&quot;nofollow&quot;&gt;http://agert.homelinux.org/~fredrik/flyg/servo.html&lt;/a&gt; fit the bill or not?&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-03T22:31:30.903" CommentCount="2" />
  <row Id="188" PostTypeId="1" CreationDate="2009-11-04T00:58:14.640" Score="4" ViewCount="2668" Body="&lt;p&gt;Hi, I have 2 &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=682&quot; rel=&quot;nofollow&quot;&gt;8x8 LED Matrix&lt;/a&gt;, a MAX7219 Chip. I just wonder how can  I connect that to the Arduino Duemilanove? I have been googling but I couldn't find out how. Thanks.&lt;/p&gt;&#xA;" LastActivityDate="2010-10-07T15:09:41.153" Title="How to connect LED Matrix into Arduino using MAX 7219 ?" Tags="&lt;arduino&gt;" AnswerCount="7" />
  <row Id="189" PostTypeId="2" ParentId="188" CreationDate="2009-11-04T02:47:04.963" Score="7" ViewCount="" Body="&lt;p&gt;Hey Vic, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Brian Chung has a &lt;a href=&quot;http://www.bryanchung.net/?p=177&quot; rel=&quot;nofollow&quot;&gt;tutorial&lt;/a&gt; on how to connect the a LED Matrix into Arduino using MAX 7219.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Here is an experiment with an 8×8 LED&#xA;  matrix, driven by a MAX7219 IC,&#xA;  controlled through an Arduino&#xA;  micro-controller board. A custom PCB&#xA;  has been made by Tan from DinoTech to&#xA;  tidy up all the wires connecting the&#xA;  LED matrix and the IC. It comes with a&#xA;  separate 12V power supply, in order&#xA;  not to drain everything from the&#xA;  Arduino board.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Only 4 wires are necessary to control&#xA;  the MAX7219 driver IC. They are the&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Data Clock Latch/load Ground&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The data and clock pins should match&#xA;  those for the shiftOut() command in&#xA;  Arduino. The latch pin will give a LOW&#xA;  to HIGH pulse after the shiftOut&#xA;  command. I have written the original&#xA;  program for Javelin Stamp. Since&#xA;  Arduino can only shift 8 bits of data,&#xA;  I have to use 2 separate commands to&#xA;  shift both the upper and lower bytes&#xA;  to the MAX7219, which needs a 2 bytes&#xA;  control for each command.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;For the data structure of the 8×8 LED&#xA;  matrix, I use a byte array – matrix of&#xA;  length 8. Each row in the matrix&#xA;  corresponds to the Y dimension. Each&#xA;  bit in a row corresponds to the X&#xA;  dimension. Digit 1 is on; 0 is off.&#xA;  The X direction is reversed and there&#xA;  is also an 1 bit shift. The&#xA;  updateLED() function caters for this.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The first program is an animation of a&#xA;  single line motion.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int CLOCK = 12;&#xA;int LATCH = 13;&#xA;int DATA  = 11;&#xA;byte matrix[8];&#xA;int idx = 0;&#xA;&#xA;void setup() {&#xA;  pinMode(CLOCK, OUTPUT);&#xA;  pinMode(LATCH, OUTPUT);&#xA;  pinMode(DATA,  OUTPUT);&#xA;  digitalWrite(CLOCK, LOW);&#xA;  digitalWrite(LATCH, LOW);&#xA;  digitalWrite(DATA,  LOW);&#xA;  initLED();&#xA;  clearLED();&#xA;}&#xA;&#xA;void loop() {&#xA;  for (int j=0;j&amp;lt;8;j++) {&#xA;    updateLED(idx, j, true);&#xA;  }&#xA;  refreshLED();&#xA;  delay(200);&#xA;  for (int j=0;j&amp;lt;8;j++) {&#xA;    updateLED(idx, j, false);&#xA;  }&#xA;  refreshLED();&#xA;  delay(100);&#xA;  idx++;&#xA;  idx %= 8;&#xA;}&#xA;&#xA;void ledOut(int n) {&#xA;  digitalWrite(LATCH, LOW);&#xA;  shiftOut(DATA, CLOCK, MSBFIRST, (n&amp;gt;&amp;gt;8));&#xA;  shiftOut(DATA, CLOCK, MSBFIRST, (n));&#xA;  digitalWrite(LATCH, HIGH);&#xA;  delay(1);&#xA;  digitalWrite(LATCH, LOW);&#xA;}&#xA;&#xA;void initLED() {&#xA;  ledOut(0x0B07);&#xA;  ledOut(0x0A0C);&#xA;  ledOut(0x0900);&#xA;  ledOut(0x0C01);&#xA;}&#xA;&#xA;void clearLED() {&#xA;  for (int i=0;i&amp;lt;8;i++) {&#xA;    matrix[i] = 0x00;&#xA;  }&#xA;  refreshLED();&#xA;}&#xA;&#xA;void refreshLED() {&#xA;  int n1, n2, n3;&#xA;  for (int i=0;i&amp;lt;8;i++) {&#xA;    n1 = i+1;&#xA;    n2 = matrix[i];&#xA;    n3 = (n1&amp;lt;&amp;lt;8)+n2;&#xA;    ledOut(n3);&#xA;  }&#xA;}&#xA;&#xA;void updateLED(int i, int j, boolean b) {&#xA;  int t = 1;&#xA;  int n = 0;&#xA;  int m = 0;&#xA;  if (j==0) {&#xA;    m = 7;&#xA;  }&#xA;  else {&#xA;    m = j-1;&#xA;  }&#xA;  n = t&amp;lt;&amp;lt;m;&#xA;  if (b) {&#xA;    matrix[i] = n | matrix[i];&#xA;  }&#xA;  else {&#xA;    n = ~n;&#xA;    matrix[i] = n &amp;amp; matrix[i];&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-11-04T02:47:04.963" />
  <row Id="190" PostTypeId="1" AcceptedAnswerId="192" CreationDate="2009-11-04T04:49:59.410" Score="3" ViewCount="312" Body="&lt;p&gt;How do I detect the pattern of the knock on a door, and use it as a signature to unlock a door?&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-11-04T15:41:50.503" Title="How do I detect the pattern of the knock on a door, and use it as a signature to unlock a door?" Tags="&lt;sound&gt;&lt;microcontroller&gt;&lt;arduino&gt;&lt;sensor&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="191" PostTypeId="2" ParentId="190" CreationDate="2009-11-04T05:02:40.797" Score="1" ViewCount="" Body="&lt;p&gt;I think the easy way would be to measure time between knocks using a microcontroller.&lt;br&gt;To detect the knocks you can use an electret microphone connected to a Diferential Amplifier, and its output shuld be the trigger of a 555 timer configured as monostable.&lt;br&gt;&#xA;The monostable output then is connected to a &quot;Capture And Compare Pin&quot; of the microcontroller.&lt;br&gt;&#xA;All the rest is just coding.&lt;/p&gt;&#xA;" OwnerUserId="168" LastActivityDate="2009-11-04T05:02:40.797" />
  <row Id="192" PostTypeId="2" ParentId="190" CreationDate="2009-11-04T05:25:20.593" Score="3" ViewCount="" Body="&lt;p&gt;This site has fairly detailed answers to how they did it&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://grathio.com/2009/11/secret-knock-detecting-door-lock.html&quot; rel=&quot;nofollow&quot;&gt;http://grathio.com/2009/11/secret-knock-detecting-door-lock.html&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2009-11-04T05:25:20.593" />
  <row Id="193" PostTypeId="2" ParentId="188" CreationDate="2009-11-04T06:15:20.523" Score="1" ViewCount="" Body="&lt;p&gt;Thanks, my problem is, I don't have the breakout board for the LED Matrix. &lt;/p&gt;&#xA;" LastActivityDate="2009-11-04T06:15:20.523" CommentCount="1" />
  <row Id="194" PostTypeId="2" ParentId="129" CreationDate="2009-11-04T06:43:23.633" Score="4" ViewCount="" Body="&lt;p&gt;Hi Davr,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you considered using a Lantronix Wiport (Wifi to Serial Module). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Little Bird Electronics used to sell the Little Bird Brain Arduino Wifi Shield. Which was&#xA;an Lantronix Wiport on an Arduino shield.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-11-04T06:43:23.633" CommentCount="2" />
  <row Id="195" PostTypeId="1" AcceptedAnswerId="203" CreationDate="2009-11-04T07:44:35.957" Score="5" ViewCount="300" Body="&lt;p&gt;Ok, so I don't really want to turn the TV-B-Gone into a universal remote, &lt;em&gt;specifically&lt;/em&gt;, but I would like to know/learn how I could go about creating a universal remote (I merely thought that working off of the TV-B-Gone would be a good point to start).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So yeah, anyone have any ideas as to how to go about making a universal remote? (ie: Can change channels, volume, on/off, maybe even the tv source...)&lt;/p&gt;&#xA;" OwnerUserId="172" LastActivityDate="2011-01-11T01:52:33.823" Title="Turning the TV-B-Gone into a universal remote" Tags="&lt;microcontroller&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="196" PostTypeId="2" ParentId="184" CreationDate="2009-11-04T09:11:38.913" Score="3" ViewCount="" Body="&lt;p&gt;Maybe conductive glue will work on fabric. It is definitely cheaper than the CirquitWriter pen so if it doesn't work, there's not much harm :) &quot;&lt;a href=&quot;http://www.wireglue.us/&quot; rel=&quot;nofollow&quot;&gt;Wire Glue&lt;/a&gt;&quot; is being sold in the US but you can also try to make your own by mixing graphite and glue. There is an &lt;a href=&quot;http://www.instructables.com/id/Make-Conductive-Glue-and-Glue-a-Circuit/&quot; rel=&quot;nofollow&quot;&gt;instructable&lt;/a&gt; that explains the process.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-04T09:11:38.913" />
  <row Id="197" PostTypeId="1" CreationDate="2009-11-04T09:31:56.067" Score="1" ViewCount="1087" Body="&lt;p&gt;I have a Samsung 170L40AA1 VFD, but no controller. So I wondered if it is possible to use an arduino to control it instead. I've found the &lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=69620&quot; rel=&quot;nofollow&quot;&gt;code&lt;/a&gt; for controlling an Futaba NA202MD13AA, which I want to try, but I can't figure out how to connect the VFD to the arduino&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any pointers would be greatly appreciated!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best regards,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pieter&lt;/p&gt;&#xA;" OwnerUserId="173" LastActivityDate="2009-11-10T17:58:50.133" Title="How to control a VFD with arduino" Tags="&lt;arduino&gt;" AnswerCount="3" />
  <row Id="198" PostTypeId="2" ParentId="188" CreationDate="2009-11-04T09:51:53.983" Score="1" ViewCount="" Body="&lt;p&gt;There's a schematic for the board at the bottom of the tutorial mentioned in littlebirdceo's reply above, which I've reproduced below.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.bryanchung.net/images/arduino/max7219.gif&quot; alt=&quot;Schematic for breakout board&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe you could build your own.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-04T09:51:53.983" />
  <row Id="199" PostTypeId="2" ParentId="188" CreationDate="2009-11-04T10:01:12.793" Score="0" ViewCount="" Body="&lt;p&gt;Firstly, thanks for the quick reply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are 12 pins on the LED Matrix I have each row. Do I just ignore the last 4 pins ? &lt;/p&gt;&#xA;" LastActivityDate="2009-11-04T10:01:12.793" />
  <row Id="200" PostTypeId="2" ParentId="37" CreationDate="2009-11-04T10:13:07.123" Score="4" ViewCount="" Body="&lt;p&gt;Make sure you change the &quot;Tools/Board&quot; setting in the Arduino IDE to &quot;Arduino Duemilanove or Nano w/ Atmega328&quot;&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-04T10:13:07.123" />
  <row Id="201" PostTypeId="2" ParentId="188" CreationDate="2009-11-04T10:29:37.627" Score="0" ViewCount="" Body="&lt;p&gt;I have no idea. But does putting voltage through the first pins make an LED light up? If so just try and see if the 12th one does anything. Or get something flashing with the first 4 pins and then move the connections to the extra pins and see what happens.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-04T10:29:37.627" CommentCount="1" />
  <row Id="202" PostTypeId="2" ParentId="147" CreationDate="2009-11-04T11:39:36.817" Score="1" ViewCount="" Body="&lt;p&gt;Non-analog joysticks aren't that hard to make by yourself. There is an &lt;a href=&quot;http://www.instructables.com/id/Mini-Joystick-with-Fire-Button/&quot; rel=&quot;nofollow&quot;&gt;instructable&lt;/a&gt; that explains how to do this.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-04T11:39:36.817" />
  <row Id="203" PostTypeId="2" ParentId="195" CreationDate="2009-11-04T14:48:58.850" Score="2" ViewCount="" Body="&lt;p&gt;I don't know much about the TV-B-Gone, but really you're looking to build an modulated infrared emitter.  Infrared LEDs are pretty inexpensive, and I imagine they could be directly driven by the PWM available on the Arduino.  Range may be an issue, and I don't have the time to do the math right now, but you may end up building a driver circuit where the PWM will drive an amplifier to power several IR LEDs as the per-pin limit is 40mA (iirc).  You may be able to drive the TV-B-Gone this way, but you may very well find it satisfying to build the IR emitter by yourself, and it shouldn't be too hard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as the remote itself goes, my understanding is that the vast majority of consumer electronics all work on a 38kHz modulation.  The protocol used to convey data may vary, but once you get your PWM set to send the data at the right rate that's just an issue of how you turn the LED on an off, which is just a series of pulses that need to be in memory.  One way of capturing this data is, using a working remote control, build an IR receiver circuit (or attach an oscilloscope) to read the signals it sends.  This is tedious, but definitely something you can do on your work bench if you try.  Another method would be to try and find the breakdown of remote protocols on the Internet.  The Linux IR group might be able to help with that, at &lt;a href=&quot;http://www.lirc.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.lirc.org/&lt;/a&gt;.  It will require tearing through some source code, and may not give you all the answers you want, but will avoid the tedious nature of brute-forcing the protocols out of existing remotes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A quick Google query turned up this article on a home-built IR remote control: &lt;a href=&quot;http://www.designnews.com/article/327993-Gadget_Freak_Case_147_The_Ultimate_Universal_Remote_Control.php?nid=2337&amp;amp;rid=2897067&quot; rel=&quot;nofollow&quot;&gt;http://www.designnews.com/article/327993-Gadget_Freak_Case_147_The_Ultimate_Universal_Remote_Control.php?nid=2337&amp;amp;rid=2897067&lt;/a&gt;&lt;br /&gt;&#xA;The article and build itself may not be useful, since it goes a different hardware route, but the pdf attached on the build theory is sound and probably something worth reading (follow the link &quot;build instructions&quot;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the same Google search turned up this Arduino &quot;Universal Remote&quot;.  A quick perusal only showed it controlling a ceiling fan, but there's lots of good information in the article:&#xA;&lt;a href=&quot;http://zovirl.com/2008/11/12/building-a-universal-remote-with-an-arduino/&quot; rel=&quot;nofollow&quot;&gt;http://zovirl.com/2008/11/12/building-a-universal-remote-with-an-arduino/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck, and keep us posted on how the build goes!  By the time the project is done, perhaps all the information necessary will be in this thread, including a link to common codes.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-11-04T14:48:58.850" />
  <row Id="204" PostTypeId="2" ParentId="190" CreationDate="2009-11-04T15:41:50.503" Score="0" ViewCount="" Body="&lt;p&gt;From &lt;a href=&quot;http://blog.makezine.com/archive/2009/11/secret%5Fknock%5Fdetector.html&quot; rel=&quot;nofollow&quot;&gt;Make magazine's blog&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;img src=&quot;http://blog.makezine.com/knock%5Fsensor%5Flayout%5Fand%5Fparts%5Flist.jpg&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;RFID card readers becoming passé?&#xA;  Maybe what you need to guard the door&#xA;  to your high-tech lair is a &lt;a href=&quot;http://grathio.com/2009/11/secret-knock-detecting-door-lock.html&quot; rel=&quot;nofollow&quot;&gt;secret&#xA;  knock detecting door lock&lt;/a&gt;. Using&#xA;  an Arduino and a bunch of parts found&#xA;  around the lab, Steve Hoefer built a&#xA;  device that unlocks your door when it&#xA;  receives a certain knock pattern. It&#xA;  works by counting the time between&#xA;  successive knocks, and can be&#xA;  re-programmed at the touch of a&#xA;  button.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Of course, this system is susceptible&#xA;  to a &lt;a href=&quot;http://en.wikipedia.org/wiki/Replay%5Fattack&quot; rel=&quot;nofollow&quot;&gt;replay attack&lt;/a&gt;, because&#xA;  anyone can listen to the knock pattern&#xA;  and then know how to get in. If you&#xA;  are planning to use something like&#xA;  this, I would recommend either&#xA;  incorporating a &lt;a href=&quot;http://en.wikipedia.org/wiki/Timestamp&quot; rel=&quot;nofollow&quot;&gt;timestamp&lt;/a&gt; into&#xA;  the message, or using a series of &lt;a href=&quot;http://en.wikipedia.org/wiki/One-time%5Fpassword&quot; rel=&quot;nofollow&quot;&gt;one&#xA;  time knocks&lt;/a&gt;, in order to make it&#xA;  harder to break into. Actually, that&#xA;  might make it more secure than a&#xA;  regular lock.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-04T15:41:50.503" />
  <row Id="205" PostTypeId="2" ParentId="197" CreationDate="2009-11-04T18:39:30.680" Score="0" ViewCount="" Body="&lt;p&gt;Any VFD is going to need a high voltage driver circuit, so be prepared for that. The link you posted talks about building a controller/driver so there is probably som ehardware work to be done.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This may serve to get you a little closer: &lt;a href=&quot;http://www.m-display.co.kr/Productindex/newproduct/sdi/product/vfd/tech/vfd_tech_gra01.html&quot; rel=&quot;nofollow&quot;&gt;http://www.m-display.co.kr/Productindex/newproduct/sdi/product/vfd/tech/vfd_tech_gra01.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It says your VFD is compatible with one made by NEC so perhaps you can continue your search in that direction.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-04T18:39:30.680" />
  <row Id="206" PostTypeId="2" ParentId="181" CreationDate="2009-11-04T18:43:23.097" Score="1" ViewCount="" Body="&lt;p&gt;I'd suggest starting with &lt;a href=&quot;http://www.evosapien.com/robosapien-hack/nocturnal/RoboSapienV2/&quot; rel=&quot;nofollow&quot;&gt;Robosapien V2 Hacks&lt;/a&gt;, which includes a number of documented mods, along with documentation of all of the parts and connections that make up a Robosapien.  I also found a site with good photos of a &lt;a href=&quot;http://www.markcra.com/robot/hackrobos.php&quot; rel=&quot;nofollow&quot;&gt;Robosapien dissection&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="143" LastEditorUserId="143" LastEditorDisplayName="" LastEditDate="2009-11-04T18:50:45.027" LastActivityDate="2009-11-04T18:50:45.027" />
  <row Id="207" PostTypeId="1" CreationDate="2009-11-04T21:06:34.293" Score="1" ViewCount="134" Body="&lt;p&gt;What is the i2c speed?&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-04T21:11:26.740" LastActivityDate="2009-11-04T23:17:44.443" Title="Has anyone been able to get a Picaxe working with the blinkM?" Tags="&lt;picaxe&gt;&lt;blinkm&gt;" AnswerCount="2" />
  <row Id="208" PostTypeId="2" ParentId="207" CreationDate="2009-11-04T21:17:40.310" Score="3" ViewCount="" Body="&lt;p&gt;Do you mean standard i2c speeds or something specific to picaxes or blinkM?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;The standard clock (SCL) speed for I2C up to 100KHz. Philips do define faster speeds: Fast mode, which is up to 400KHz and High Speed mode which is up to 3.4MHz.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;quoted from &lt;a href=&quot;http://www.robot-electronics.co.uk/htm/using_the_i2c_bus.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.robot-electronics.co.uk/htm/using_the_i2c_bus.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Found this: &lt;a href=&quot;http://getsatisfaction.com/thingm/topics/picaxe_communication&quot; rel=&quot;nofollow&quot;&gt;http://getsatisfaction.com/thingm/topics/picaxe_communication&lt;/a&gt; which should give you at least something to test your setup with.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2009-11-04T21:36:53.193" LastActivityDate="2009-11-04T21:36:53.193" />
  <row Id="209" PostTypeId="2" ParentId="197" CreationDate="2009-11-04T21:56:17.967" Score="0" ViewCount="" Body="&lt;p&gt;You might have a look at &lt;a href=&quot;http://spritesmods.com/?art=vfdcontroller&quot; rel=&quot;nofollow&quot;&gt;http://spritesmods.com/?art=vfdcontroller&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2009-11-04T21:56:17.967" />
  <row Id="210" PostTypeId="1" CreationDate="2009-11-04T23:15:25.423" Score="3" ViewCount="191" Body="&lt;p&gt;Can i use a Bluetooth USB AVR and send audio over Bluetooth to multiple receivers?&lt;/p&gt;&#xA;" LastActivityDate="2009-11-08T21:54:55.617" Title="Audio via Bluetooth" Tags="&lt;bluetooth&gt;&lt;audio&gt;&lt;avr&gt;" AnswerCount="1" />
  <row Id="211" PostTypeId="2" ParentId="207" CreationDate="2009-11-04T23:17:44.443" Score="2" ViewCount="" Body="&lt;p&gt;This was useful:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://getsatisfaction.com/thingm/topics/picaxe_communication&quot; rel=&quot;nofollow&quot;&gt;http://getsatisfaction.com/thingm/topics/picaxe_communication&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2009-11-04T23:17:44.443" />
  <row Id="212" PostTypeId="2" ParentId="25" CreationDate="2009-11-04T23:57:23.853" Score="2" ViewCount="" Body="&lt;p&gt;Inspired by this question, I wrote the following arduino routine and made the following circuit.  Linky... &lt;a href=&quot;http://ka1kjz.com/?p=430&quot; rel=&quot;nofollow&quot;&gt;http://ka1kjz.com/?p=430&lt;/a&gt;  This is basically what Blalor said.&lt;/p&gt;&#xA;" OwnerUserId="139" LastActivityDate="2009-11-04T23:57:23.853" />
  <row Id="213" PostTypeId="2" ParentId="184" CreationDate="2009-11-05T00:01:15.347" Score="1" ViewCount="" Body="&lt;p&gt;I'm not sure how practical this would be, but screenprinting might be an option. Using a screen with a coarse mesh you can print with silver paint. You would need to do a test to make sure the paint is conducting in the way you expect. I have some &lt;a href=&quot;http://mintmedia.co.nz/Category:Screenprinting&quot; rel=&quot;nofollow&quot;&gt;articles and notes on my blog pages&lt;/a&gt; that might help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Screenprinting has the advantage that you can quickly make many prints of your circuit or make t-shirts to promote your event/exhibition/party.&lt;/p&gt;&#xA;" OwnerUserId="178" LastActivityDate="2009-11-05T00:01:15.347" />
  <row Id="214" PostTypeId="1" CreationDate="2009-11-05T00:39:54.410" Score="1" ViewCount="85" Body="&lt;p&gt;I'm trying to create something similar to this project:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2009/01/10/wireless-blinkm-control/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2009/01/10/wireless-blinkm-control/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and was looking for something cheap to use in place of the Relay Tester Box....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any Ideas?&lt;/p&gt;&#xA;" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-11-05T02:01:57.743" LastActivityDate="2009-11-05T11:16:05.430" Title="Relay Tester Box with BlinkM" Tags="&lt;arduino&gt;&lt;blinkm&gt;&lt;relay&gt;" AnswerCount="1" />
  <row Id="215" PostTypeId="1" AcceptedAnswerId="217" CreationDate="2009-11-05T02:19:43.833" Score="3" ViewCount="687" Body="&lt;p&gt;How do i connect a Wii remote to my Mac via Bluetooth?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-12-09T14:28:44.753" Title="Connecting the Wii remote to a computer via Bluetooth" Tags="&lt;bluetooth&gt;&lt;wii&gt;&lt;remote&gt;&lt;mac&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="216" PostTypeId="1" CreationDate="2009-11-05T02:45:13.430" Score="8" ViewCount="1039" Body="&lt;p&gt;How often should i tin my soldering iron?  It doesnt seem to pick up the solder quickly any more....i have to hold it there for 10seconds before it melts.&lt;/p&gt;&#xA;" LastActivityDate="2010-07-15T14:33:57.163" Title="Soldering Iron Maintenance" Tags="&lt;soldering&gt;" AnswerCount="11" CommentCount="1" FavoriteCount="3" />
  <row Id="217" PostTypeId="2" ParentId="215" CreationDate="2009-11-05T02:51:51.603" Score="2" ViewCount="" Body="&lt;p&gt;Looks like you just need to pair the Wiimote to the Mac via BT, but you need an application to actually read the data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mactricksandtips.com/2008/02/use-your-wii-remote-on-your-mac.html&quot; rel=&quot;nofollow&quot;&gt;http://www.mactricksandtips.com/2008/02/use-your-wii-remote-on-your-mac.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-11-05T02:51:51.603" />
  <row Id="218" PostTypeId="2" ParentId="216" CreationDate="2009-11-05T05:04:25.790" Score="8" ViewCount="" Body="&lt;p&gt;Here's a really good &lt;a href=&quot;http://www.curiousinventor.com/guides/How%5FTo%5FSolder&quot; rel=&quot;nofollow&quot;&gt;video and comprehesive FAQ&lt;/a&gt; that explains all about soldering (and when and how to tin your iron).&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-05T05:04:25.790" CommentCount="1" />
  <row Id="219" PostTypeId="2" ParentId="184" CreationDate="2009-11-05T10:18:49.727" Score="3" ViewCount="" Body="&lt;p&gt;The Arduino Lilypad is a microcontroller board designed for wearables and e-textiles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;google this one and you will find tutorials and details &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also here is a good book about making electronics click with clothes &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://harkopen.com/news/open-softwear&quot; rel=&quot;nofollow&quot;&gt;http://harkopen.com/news/open-softwear&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope it helps you! let us know what you acomplished :)&lt;/p&gt;&#xA;" OwnerUserId="182" LastActivityDate="2009-11-05T10:18:49.727" />
  <row Id="220" PostTypeId="2" ParentId="214" CreationDate="2009-11-05T11:16:05.430" Score="1" ViewCount="" Body="&lt;p&gt;It looks like the relay tester is a glorified set of potentiometers, with a switch or two; the inputs to the Arduino appear to all be analog lines, so you should be able to craft your own, and give it a funky patina of age as you see fit. :-)  The schematic of the original relay tester is even included in the author's original post, so designing something similar or identical to the original would be pretty straightforward.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-11-05T11:16:05.430" />
  <row Id="221" PostTypeId="2" ParentId="216" CreationDate="2009-11-05T11:46:46.897" Score="10" ViewCount="" Body="&lt;p&gt;A much cheaper option than the metal shavings coated in flux, is to put a pan scourer like this one:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.hospitalitywholesale.com.au/products/scourer1.jpg&quot; alt=&quot;Pan scourer&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;in a small container, and use that to clean the excess solder off of the tip, it seems to do a reasonable job and doesn't cool the tip excessively. Although you don't get the benefit of the flux which coats the shavings either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(A tip: make sure that the scourer isn't plastic!) ;-P&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-05T11:46:46.897" CommentCount="1" />
  <row Id="222" PostTypeId="2" ParentId="215" CreationDate="2009-11-05T16:17:11.210" Score="0" ViewCount="" Body="&lt;p&gt;You didn't say where the data would go after it got to your Mac, but there is Osculator &lt;a href=&quot;http://www.osculator.net/wp/&quot; rel=&quot;nofollow&quot;&gt;http://www.osculator.net/wp/&lt;/a&gt; which outputs OSC and MIDI messages if it's for musical applications (as well as others)&#xA;If you program in Python there are a number of implementations there&#xA;If you are using micros here is an interface board for Arduino that connects to the numchuck&lt;/p&gt;&#xA;" LastActivityDate="2009-11-05T16:17:11.210" />
  <row Id="223" PostTypeId="2" ParentId="195" CreationDate="2009-11-05T18:07:42.520" Score="1" ViewCount="" Body="&lt;p&gt;Here's a pointer to an &lt;a href=&quot;http://www.instructables.com/&quot; rel=&quot;nofollow&quot;&gt;Instructable&lt;/a&gt; on how to create an &lt;a href=&quot;http://www.instructables.com/id/DIY-Apple-Remote-Shield-for-the-Arduino/&quot; rel=&quot;nofollow&quot;&gt;Apple IR Remote&lt;/a&gt; from an Arduino -- a similar problem, with a step-by-step solution.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-05T18:07:42.520" />
  <row Id="224" PostTypeId="1" AcceptedAnswerId="246" CreationDate="2009-11-05T21:19:56.163" Score="4" ViewCount="363" Body="&lt;p&gt;Has anyone got an example of coating a Lilypad or some other electronics in resin to make them waterproof.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wanting to make something that is really resilient -&gt; Being lazy i want to be able to chuck it in the washing machine...hand washing is far too much effort.&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-16T12:10:28.507" Title="Coating a Lilypad in resin" Tags="&lt;lilypad&gt;&lt;waterproof&gt;&lt;clothing&gt;" AnswerCount="8" />
  <row Id="225" PostTypeId="1" AcceptedAnswerId="228" CreationDate="2009-11-05T21:30:35.987" Score="4" ViewCount="485" Body="&lt;p&gt;Can you recommend an inexpensive product for flashing an in circuit (read: powered) ATMEGA32 via JTAG. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a parallel port available on my laptop dock/port replicator, which I am guessing may be the cheapest form of these. I intend to use PonyProg to flash the ATMEGA32. I do not need the capability to debug in line, but simply to load someone else's off the shelf program (monome firmware) to the ATMEGA32.&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-12T23:56:34.583" LastActivityDate="2009-11-12T23:56:34.583" Title="ATMEGA32 Jtag flash" Tags="&lt;atmega&gt;&lt;jtag&gt;&lt;flash&gt;&lt;parallel&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="226" PostTypeId="1" AcceptedAnswerId="242" CreationDate="2009-11-05T21:42:51.407" Score="9" ViewCount="717" Body="&lt;p&gt;Can anyone advise what hardware and software is required for debugging AVR in circuit.&lt;/p&gt;&#xA;" OwnerUserId="9" LastEditorUserId="9" LastEditorDisplayName="" LastEditDate="2009-11-11T22:11:43.063" LastActivityDate="2009-11-12T08:07:26.767" Title="Jtag debugging AVR" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;jtag&gt;&lt;debugwire&gt;&lt;debug&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="227" PostTypeId="1" CreationDate="2009-11-05T21:51:02.670" Score="4" ViewCount="1518" Body="&lt;p&gt;Was looking for a bluetooth adapter to use with my Arduinos but everything is so expensive.&#xA;Sparkfun has &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=158&quot; rel=&quot;nofollow&quot;&gt;Bluetooth Modem - BlueSMiRF RP-SMA&lt;/a&gt; for $65.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there alternatives in the $30 to $40 range?&lt;/p&gt;&#xA;" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:27:04.237" LastActivityDate="2011-06-02T02:27:04.237" ClosedDate="2011-04-10T14:10:29.467" Title="bluetooth adapter for arduino" Tags="&lt;arduino&gt;&lt;bluetooth&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="2" />
  <row Id="228" PostTypeId="2" ParentId="225" CreationDate="2009-11-05T22:00:35.900" Score="3" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://ladyada.net/make/usbtinyisp/&quot; rel=&quot;nofollow&quot;&gt;Lady Ada's USBtinyISP&lt;/a&gt; with &lt;a href=&quot;http://www.nongnu.org/avrdude/&quot; rel=&quot;nofollow&quot;&gt;avrdude&lt;/a&gt;.  The &lt;a href=&quot;http://www.adafruit.com/index.php?main%5Fpage=product%5Finfo&amp;amp;cPath=16&amp;amp;products%5Fid=46&quot; rel=&quot;nofollow&quot;&gt;kit&lt;/a&gt; cost $22 and supports both the 6-pin and 10-pin interfaces.  You can learn a lot more about making &lt;a href=&quot;http://www.evilmadscientist.com/article.php/avrtargetboards&quot; rel=&quot;nofollow&quot;&gt;AVR target boards&lt;/a&gt; courtesy of the &lt;a href=&quot;http://www.evilmadscientist.com/&quot; rel=&quot;nofollow&quot;&gt;Evil Mad Scientist(s)&lt;/a&gt;.  I also found an Instructable for a &lt;a href=&quot;http://www.instructables.com/id/Ghetto-Programming%3a-Getting-started-with-AVR-micro/&quot; rel=&quot;nofollow&quot;&gt;truly bare-bones parallel port programmer&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-05T22:00:35.900" />
  <row Id="229" PostTypeId="1" CreationDate="2009-11-05T22:11:22.190" Score="3" ViewCount="207" Body="&lt;p&gt;I want to build a BlinkM as a simple temperature indicator as seen at&#xA;&lt;a href=&quot;http://thingm.com/products/blinkm/project-gallery.html&quot; rel=&quot;nofollow&quot;&gt;http://thingm.com/products/blinkm/project-gallery.html&lt;/a&gt;&#xA;Anyone know where I can get a schematic &amp;amp; parts list?   The link on the page doesn't take me anywhere useful.&lt;/p&gt;&#xA;" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-07-08T16:59:21.770" LastActivityDate="2010-07-08T16:59:21.770" Title="BlinkM temperature indicator" Tags="&lt;blinkm&gt;&lt;sensor&gt;&lt;temperature&gt;&lt;diagram&gt;&lt;schematics&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="230" PostTypeId="2" ParentId="226" CreationDate="2009-11-05T22:13:48.410" Score="4" ViewCount="" Body="&lt;p&gt;For the hardware, see my &lt;a href=&quot;http://chiphacker.com/questions/225/atmega32-jtag-flash/228#228&quot; rel=&quot;nofollow&quot;&gt;answer to a similar question&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the software, you can start with &lt;a href=&quot;http://www.atmel.com/dyn/products/tools%5Fcard.asp?tool%5Fid=2725&quot; rel=&quot;nofollow&quot;&gt;AVR Studio&lt;/a&gt; on Windows.  If you're using Linux for your development platform, then read this Linux Journal &lt;a href=&quot;http://www.linuxjournal.com/article/7289&quot; rel=&quot;nofollow&quot;&gt;article&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-05T22:13:48.410" />
  <row Id="231" PostTypeId="2" ParentId="229" CreationDate="2009-11-05T22:26:00.617" Score="3" ViewCount="" Body="&lt;p&gt;The link to the write-up went through a re-direct and doesn't come out right.  I do believe it is this:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.adafruit.com/blog/2008/02/03/valenthrowiem-tempm/&quot; rel=&quot;nofollow&quot;&gt;ValenThrowieM + TempM&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-11-05T22:26:00.617" />
  <row Id="232" PostTypeId="2" ParentId="224" CreationDate="2009-11-05T22:27:55.573" Score="1" ViewCount="" Body="&lt;p&gt;I think one common solution is to make the electronics be able to unplug from the clothing, so that the only thing left on the clothing are stuff like wires or resistors or other simple things that wont be hurt by water or by rolling around inside the washing machine.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-05T22:27:55.573" />
  <row Id="233" PostTypeId="2" ParentId="229" CreationDate="2009-11-05T22:31:31.870" Score="3" ViewCount="" Body="&lt;p&gt;Lady Ada wrote an extensive &lt;a href=&quot;http://www.adafruit.com/blog/2008/02/03/valenthrowiem-tempm/&quot; rel=&quot;nofollow&quot;&gt;blog post&lt;/a&gt; on this topic (which is what your article was referencing).  She shows how to work with the BlinkM, and mentions a sketch, but doesn't provide a link to it.  I can describe what the sketch must have looked like (in pseudo code):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;setup:&#xA;  Initialize thermal sensor port&#xA;  Initialize I2C interface (for the BlinkM)&#xA;&#xA;loop:&#xA;  Read and scale the temperature from the thermal sensor&#xA;  Send an appropriate color to the BlinkM, via I2C&#xA;  Sleep for a while&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-05T22:31:31.870" />
  <row Id="234" PostTypeId="2" ParentId="224" CreationDate="2009-11-05T23:56:37.797" Score="2" ViewCount="" Body="&lt;p&gt;This is kinda along the lines of what i'm thinking.....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is going even further with the idea of the electronics actually working while in water!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.plusplasticelectronics.com/SmartFabTextiles/Wearable-electronics-in-swimming.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.plusplasticelectronics.com/SmartFabTextiles/Wearable-electronics-in-swimming.aspx&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-05T23:56:37.797" />
  <row Id="236" PostTypeId="2" ParentId="59" CreationDate="2009-11-06T01:53:28.293" Score="5" ViewCount="" Body="&lt;p&gt;Check out &lt;a href=&quot;http://www.analog.com/en/embedded-processing-dsp/sigmadsp/processors/index.html#Audio_Signal_Processors&quot; rel=&quot;nofollow&quot;&gt;Analog Devices DSP page&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And the &lt;a href=&quot;http://www.analog.com/en/embedded-processing-dsp/sigmadsp/processors/CU_over_SigmaStudio_graphical_dev_tool_overview/fca.html&quot; rel=&quot;nofollow&quot;&gt;free development tools&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No programing required, just drag and drop GUI objects.&lt;/p&gt;&#xA;" OwnerUserId="193" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-09T13:19:27.633" LastActivityDate="2011-03-09T13:19:27.633" />
  <row Id="237" PostTypeId="1" AcceptedAnswerId="238" CreationDate="2009-11-06T03:28:07.247" Score="1" ViewCount="102" Body="&lt;p&gt;Is there a site in English which describes their products?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found something that might be useful for making clothing in place of conductive thread.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.talk2myshirt.com/blog/archives/154&quot; rel=&quot;nofollow&quot;&gt;http://www.talk2myshirt.com/blog/archives/154&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-06T04:09:07.243" Title="Has anyone ever used these Novonic conductive threads?" Tags="&lt;conductive&gt;&lt;thread&gt;&lt;clothing&gt;" AnswerCount="2" />
  <row Id="238" PostTypeId="2" ParentId="237" CreationDate="2009-11-06T03:57:50.353" Score="2" ViewCount="" Body="&lt;p&gt;This is a great site for finding all sorts of conductive threads:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.margaritabenitez.com/etextiles/resources.html&quot; rel=&quot;nofollow&quot;&gt;http://www.margaritabenitez.com/etextiles/resources.html&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2009-11-06T03:57:50.353" />
  <row Id="239" PostTypeId="2" ParentId="237" CreationDate="2009-11-06T04:09:07.243" Score="0" ViewCount="" Body="&lt;p&gt;also the site in English is here: (but doesn't appear to have pricing)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.novonic.de/web/novonic.nsf/id/pa_home_e.html&quot; rel=&quot;nofollow&quot;&gt;http://www.novonic.de/web/novonic.nsf/id/pa_home_e.html&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2009-11-06T04:09:07.243" />
  <row Id="240" PostTypeId="2" ParentId="215" CreationDate="2009-11-06T04:40:54.203" Score="0" ViewCount="" Body="&lt;p&gt;connecting the remote to via bluetooth at the driver level is rather typical.  but the question is how you wish to use the remote. as others have suggested you can use python, arduino or etc.  I would suggest using processing, if you are atune to a little programming and bit twiddling.  I have some &lt;a href=&quot;http://ittybits.blogspot.com/2008/06/visualization-of-accelerometer-objects.html&quot; rel=&quot;nofollow&quot;&gt;code over here&lt;/a&gt; that will give a 3D representation of the current orientation of the wii remote (see image). This was written in Processing and the code is documented so that beginners to Processing can understand it.&lt;/p&gt;&#xA;" OwnerUserId="196" LastActivityDate="2009-11-06T04:40:54.203" />
  <row Id="242" PostTypeId="2" ParentId="226" CreationDate="2009-11-06T05:27:20.067" Score="4" ViewCount="" Body="&lt;p&gt;Normal ISP programmers have no JTAG debugging capabilities. For this you will need slightly more expensive hardware. A JTAG in circuit emulator will enable you to let your circuit communicate with your PC while you are running the firmware. This way you can set breakpoints, watch the memory, enable/disable pins and see the exact status of your micro controller. The ISP programmers from EMSL and Adafruit will not let you do this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the cheapest programmers that have in-circuit emulation capabilities is the &lt;a href=&quot;http://www.atmel.com/dyn/Products/tools%5Fcard.asp?tool%5Fid=3891&quot; rel=&quot;nofollow&quot;&gt;AVR Dragon&lt;/a&gt;. It will cost you &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&amp;amp;site=US&amp;amp;WT.z%5Fhomepage%5Flink=hp%5Fgo%5Fbutton&amp;amp;KeyWords=avr+dragon&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;about $50,-&lt;/a&gt;. It is cheap for a reason though: it's too easy to overload the circuit and break the programmer. If you get one I recommend that you find some form of protection like a &lt;a href=&quot;http://www.ecrostech.com/AtmelAvr/DragonRider/&quot; rel=&quot;nofollow&quot;&gt;DragonRider&lt;/a&gt; or a &lt;a href=&quot;http://aplomb.nl/TechStuff/Dragon/Dragon.html&quot; rel=&quot;nofollow&quot;&gt;DragonHide&lt;/a&gt;. (I already killed my first dragon which is surprisingly easy to do)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A more robust solution would be an &lt;a href=&quot;http://www.atmel.com/dyn/Products/tools%5Fcard.asp?tool%5Fid=3353&quot; rel=&quot;nofollow&quot;&gt;AVR-JTAG-ICE-MKII&lt;/a&gt; but this thing is much more &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2621880&amp;amp;k=avr%20jtag%20ice%20mkII&quot; rel=&quot;nofollow&quot;&gt;expensive&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also try and &lt;a href=&quot;http://www.google.com/search?hl=en&amp;amp;q=diy+avr+jtag+programmer&amp;amp;aq=f&amp;amp;oq=&amp;amp;aqi=&quot; rel=&quot;nofollow&quot;&gt;build one yourself&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="10" LastEditorUserId="10" LastEditorDisplayName="" LastEditDate="2009-11-06T13:49:35.500" LastActivityDate="2009-11-06T13:49:35.500" />
  <row Id="243" PostTypeId="2" ParentId="227" CreationDate="2009-11-06T05:34:27.263" Score="0" ViewCount="" Body="&lt;p&gt;Have a look at BTM-222 Module.&#xA;You find many informations about other projects who use this one.&#xA;It's cheap and easy to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;0815Achim&lt;/p&gt;&#xA;" OwnerUserId="162" LastActivityDate="2009-11-06T05:34:27.263" />
  <row Id="244" PostTypeId="2" ParentId="227" CreationDate="2009-11-06T05:37:24.843" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardBluetooth&quot; rel=&quot;nofollow&quot;&gt;bluetooth enabled arduinos&lt;/a&gt; use &lt;a href=&quot;http://www.bluegiga.com/WT11%5FClass%5F1%5FBluetooth%5FModule&quot; rel=&quot;nofollow&quot;&gt;a chip from bluegiga&lt;/a&gt;. Google suggests that these can be bought for &lt;a href=&quot;http://www.google.com/products?source=ig&amp;amp;hl=en&amp;amp;rlz=&amp;amp;q=bluegiga+wt12+buy&amp;amp;um=1&amp;amp;ie=UTF-8&amp;amp;ei=7LTzSsT6N4O24Qb-t%5FDQAw&amp;amp;sa=X&amp;amp;oi=product%5Fresult%5Fgroup&amp;amp;ct=title&amp;amp;resnum=4&amp;amp;ved=0CCIQrQQwAw&quot; rel=&quot;nofollow&quot;&gt;about $26.-&lt;/a&gt; They are quite easy to work with.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-06T05:37:24.843" />
  <row Id="245" PostTypeId="2" ParentId="224" CreationDate="2009-11-06T07:22:27.900" Score="2" ViewCount="" Body="&lt;p&gt;I don't know how well conductive thread holds up when washed, but the resin part is certainly doable. Check out this guy who cast an entire arduino in resin. &lt;a href=&quot;http://dotmatrixdesign.tumblr.com/&quot; rel=&quot;nofollow&quot;&gt;http://dotmatrixdesign.tumblr.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could certainly make a smaller mold that would give you a streamlined cast Lilypad.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-06T07:22:27.900" />
  <row Id="246" PostTypeId="2" ParentId="224" CreationDate="2009-11-06T08:16:08.620" Score="5" ViewCount="" Body="&lt;p&gt;Simply searching for &quot;resin&quot; in Instructables provided several good results.&#xA;I would recommend using Resin as well. I honestly can't think of any other way to cover a circuit board, and have it clear at the same time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/USB-casting-in-transparent-resin/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/USB-casting-in-transparent-resin/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if you have a need for &lt;em&gt;a lot&lt;/em&gt; of resin, here's another good link:&#xA;&lt;a href=&quot;http://www.instructables.com/id/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/&lt;/a&gt;[Video]-Mixing-Polyester-Resin/&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One last thing. Different types/amounts of sanding will result in the resin becoming foggy. If you don't want this, both links discuss how to make it clear.&lt;/p&gt;&#xA;" OwnerUserId="172" LastActivityDate="2009-11-06T08:16:08.620" />
  <row Id="247" PostTypeId="2" ParentId="158" CreationDate="2009-11-06T09:20:23.070" Score="2" ViewCount="" Body="&lt;p&gt;If you really want to read from 0 to 5V you will have to use a voltage divider plus an amplifier with offset (more info: &lt;a href=&quot;http://www.maxim-ic.com/appnotes.cfm/an%5Fpk/803&quot; rel=&quot;nofollow&quot;&gt;http://www.maxim-ic.com/appnotes.cfm/an_pk/803&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use blalor's link to check min and max values of the voltage divider, which using a 20k resistor as R1 and R2 being from 9k and 20k:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Vmin = 5V * (9k / 29k) = 1.55V&#xA;Vmax = 5V * (20K / 29K) = 3.45V&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;For the min value you will have to apply an ofset of -1.55V. Then, for a 1 gain, you will reach a range from 0 to 1.9V. You can then configure the amplifier for a gain of 2.6.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;1.9 * 2.6 = 5V&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Also, an elegant method is to use a RC circuit. If you measure the time of the capacitor's discharge through your sensor, you can reach huge resolutions. It's been used for capacitance measurement but if you keep the C constant and change R, it is exactly the same. Search in arduino.cc for this.&lt;/p&gt;&#xA;" OwnerUserId="198" LastActivityDate="2009-11-06T09:20:23.070" />
  <row Id="248" PostTypeId="2" ParentId="110" CreationDate="2009-11-06T09:47:11.887" Score="2" ViewCount="" Body="&lt;p&gt;I think it would be a great learning exercise, but ESCs use back EMF to detect rotation, although you can use optical or magnetic sensors for this. Basically you have to generate 3 AC phases and activate/deactivate them in the right moment. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The speed of the rotation of the magnetic field needs to be the adapted to the motor's, i.e. if you want to accelerate, the field has to run a bit earlier and quicker. You can also break, doing the opposite.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a thorough explanation: &lt;a href=&quot;http://www.embedded.com/columns/technicalinsights/196701832?_requestid=137540&quot; rel=&quot;nofollow&quot;&gt;http://www.embedded.com/columns/technicalinsights/196701832?_requestid=137540&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a practical job, get an ESC.&lt;/p&gt;&#xA;" OwnerUserId="198" LastActivityDate="2009-11-06T09:47:11.887" />
  <row Id="249" PostTypeId="2" ParentId="40" CreationDate="2009-11-06T09:57:36.890" Score="2" ViewCount="" Body="&lt;p&gt;I used the motor from an old electric drill. It has a gear reductor and you can easily adapt a crank to the chuck. It was capable of feeding a dc motor and some little incandescent lights.&lt;/p&gt;&#xA;" OwnerUserId="198" LastActivityDate="2009-11-06T09:57:36.890" />
  <row Id="250" PostTypeId="1" CreationDate="2009-11-06T16:21:30.857" Score="4" ViewCount="445" Body="&lt;p&gt;For the life of me I am unable to find or determine who makes the chip with the label shown in the image:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://img21.imageshack.us/img21/5620/picture16cy.png&quot; alt=&quot;image here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;HLi, HL Inc, KLi?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="205" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-06-02T15:10:33.510" LastActivityDate="2010-10-17T16:18:41.497" Title="Who is the CPU or FPGA maker in this picture?" Tags="&lt;design&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="251" PostTypeId="2" ParentId="250" CreationDate="2009-11-06T17:41:34.593" Score="3" ViewCount="" Body="&lt;p&gt;I don't recognize the logo.  Most likely the chip is an &lt;a href=&quot;http://en.wikipedia.org/wiki/ASIC&quot; rel=&quot;nofollow&quot;&gt;ASIC&lt;/a&gt;.  There's only a couple of &lt;a href=&quot;http://en.wikipedia.org/wiki/FPGA#Major%5Fmanufacturers&quot; rel=&quot;nofollow&quot;&gt;FPGA manufacturers&lt;/a&gt; (Xilinx and Altera are the big ones).  Likewise, there aren't a lot of CPU manufacturers.  On the other hand, there are LOTS of ASIC vendors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you could provide an image of the entire chip (size, form-factor, part numbers) it might be possible to better identify it (and therefore the manufacturer).  If the only thing printed on the chip is the logo, then that's more evidence in favor of an ASIC -- since it's an application-specific chip, there's no need to provide part numbers (since it's not for sale) or documentation.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-06T17:41:34.593" />
  <row Id="252" PostTypeId="2" ParentId="227" CreationDate="2009-11-06T20:10:17.750" Score="0" ViewCount="" Body="&lt;p&gt;Did you look at all the modules on Sparkfun? They have one which is $35, the &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8497&quot; rel=&quot;nofollow&quot;&gt;Roving Networks module&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-06T20:10:17.750" />
  <row Id="253" PostTypeId="1" AcceptedAnswerId="389" CreationDate="2009-11-06T20:51:15.640" Score="1" ViewCount="479" Body="&lt;p&gt;I'm brainstorming a new project with my wife and was wondering&#xA;what type of laser I could use to cut multiple layers of fabric?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;F.Y.I.&#xA;I'm a total noob when it comes to lasers and integrated electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;The laser would be mounted on something that moves it on the x and y axis.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I want to cut through stacked layers of fabric.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I want to build a machine to cut out patterns on fabric to make cloths and what not.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;P.S.&#xA;You should really let new users create tags.&#xA;I wanted to tag this question &quot;lasers&quot; and couldn't.&lt;/p&gt;&#xA;" OwnerUserId="208" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-11-07T09:37:48.110" LastActivityDate="2009-11-13T06:54:26.017" Title="What kind of laser should I get to cut fabric?" Tags="&lt;laser&gt;&lt;cutting&gt;&lt;fabric&gt;&lt;wearable&gt;" AnswerCount="6" />
  <row Id="254" PostTypeId="1" CreationDate="2009-11-06T21:07:09.767" Score="1" ViewCount="215" Body="&lt;p&gt;I am a software developer and need to work with a partner who will design and develop a device (SIMPLE device) to interface with the iPhone hardware port.  I am not sure of the best place to find such a person.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would be a part-time thing - it won't take much to develop it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I already have the Apple hardware spec (through the Apple program) and now just need someone willing to design this.&lt;/p&gt;&#xA;" OwnerUserId="209" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-12T23:54:16.177" LastActivityDate="2009-11-13T07:40:00.960" Title="How do I find an E.E. to partner with for a product?" Tags="&lt;iphone&gt;&lt;interface&gt;&lt;mac&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="255" PostTypeId="2" ParentId="253" CreationDate="2009-11-06T21:33:43.407" Score="1" ViewCount="" Body="&lt;p&gt;For clarification, are you asking about CNC laser cutters? Or just about a (stationary) burning laser?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, are you talking about stacked layers of fabric? (And if so: why?)&lt;/p&gt;&#xA;" OwnerUserId="26" LastActivityDate="2009-11-06T21:33:43.407" />
  <row Id="256" PostTypeId="2" ParentId="254" CreationDate="2009-11-06T21:42:37.910" Score="3" ViewCount="" Body="&lt;p&gt;You could approach a local University's, electronics (or electrical engineering or computing) department to see if they might have some reasonably competent students who might be interested in a part time project of this nature (think hands on work experience which pays). Depending on the nature of the project you might also be able to partner up with the uni to offer it as a project to students for some aspect of their course.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just my tuppence worth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Amos&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-06T21:42:37.910" CommentCount="1" />
  <row Id="257" PostTypeId="2" ParentId="126" CreationDate="2009-11-06T22:08:33.637" Score="4" ViewCount="" Body="&lt;p&gt;The NES Pad library not only has a pinout, but is a great arduino class for using the NES controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/nespad/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/nespad/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="26" LastActivityDate="2009-11-06T22:08:33.637" />
  <row Id="258" PostTypeId="2" ParentId="254" CreationDate="2009-11-06T22:55:31.057" Score="3" ViewCount="" Body="&lt;p&gt;You're going to need more than just an EE.  You'll need someone who's experienced at packaging electronics (housing, connectors, etc NOT cardboard boxes and plastic blister packs), and someone who can shepard a device through the FCC approval process.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-06T22:55:31.057" />
  <row Id="259" PostTypeId="1" AcceptedAnswerId="4131" CreationDate="2009-11-07T00:38:37.233" Score="6" ViewCount="2195" Body="&lt;p&gt;Anyone know of a good source for capacitive touchscreens in low quantity at a reasonable price? Just something to play around with in projects, I'm interested in either small (eg for portable applications, 3-5&quot;) or large (eg for kiosk or standalone applications, 10-20&quot;). I know I can get a resistive touchscreen for pennies these days, but I want a capacitive one (for various reasons).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: The reasons I'm interested in are basically just the main reasons people use capacitive screens in general. Things like more durable (a solid piece of glass instead of a flexible piece of plastic), Multitouch capable, etc. &lt;/p&gt;&#xA;" OwnerUserId="131" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2009-11-09T19:16:48.593" LastActivityDate="2011-05-04T15:29:39.973" Title="Capacitive Touchscreen for DIY usage?" Tags="&lt;capacitive&gt;&lt;controller&gt;" AnswerCount="6" CommentCount="2" FavoriteCount="3" />
  <row Id="260" PostTypeId="2" ParentId="253" CreationDate="2009-11-07T00:40:39.597" Score="1" ViewCount="" Body="&lt;p&gt;I'm not sure this would work out well...aren't most fabrics flammable? Seems like 'cutting' fabric with a laser would burn/singe the edges of the fabric, which is probably not what you want.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-07T00:40:39.597" />
  <row Id="261" PostTypeId="2" ParentId="253" CreationDate="2009-11-07T04:22:47.810" Score="1" ViewCount="" Body="&lt;p&gt;That definitely sounds like a CNC laser cutter.  I'm afraid I don't know about the specifics.  They can be used to cut wood, paper, cardboard and composite, so it seems reasonable that they could be used on fabric.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-11-07T04:22:47.810" />
  <row Id="262" PostTypeId="2" ParentId="216" CreationDate="2009-11-07T04:32:36.883" Score="3" ViewCount="" Body="&lt;p&gt;(grrrr... not enough rep to comment) I used to wipe my tip on a wet sponge after every couple solder joints.  You definitely don't want it to look dirty. &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8966&quot; rel=&quot;nofollow&quot;&gt;This retinner&lt;/a&gt; can be used if things get really bad (it seemed like that happened every couple hundred joints).  If you don't want to buy that, then just melting a bit of resin core solder onto the tip works almost as well (but adds its own dirt...).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More recently, I've been using a brass sponge on a temperature controlled soldering iron.  I haven't needed to retin at all.  I don't know if it's the better iron or the brass sponge.  In other news, I'm completely in love with that soldering iron.  It heats up very quickly and then stops without getting too hot.  The tip doesn't show any wear, despite quite a bit of use.  One of the best purchases I've made in this hobby.&lt;/p&gt;&#xA;" OwnerUserId="213" LastEditorUserId="213" LastEditorDisplayName="" LastEditDate="2009-11-07T14:46:16.063" LastActivityDate="2009-11-07T14:46:16.063" />
  <row Id="263" PostTypeId="1" AcceptedAnswerId="277" CreationDate="2009-11-07T04:46:28.383" Score="3" ViewCount="1043" Body="&lt;p&gt;I'm setting up an attiny2313 to drive an array of LEDs and blink them in different patterns.  Rather than putting a series resistor in line with each LED (they'll be controlled separately, so I can't do tricks like putting them in series with each other), I was wondering about just using a couple diodes to get the voltage down to the right range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The system is running at 3.3V (with a regulator to keep it pretty constant), and two 1N4001 diodes will drop that down to 1.9V - right in line with the lower end of the 1.8 - 2.2V these LEDs are specced for.  Since the diodes will always want to maintain the same voltage drop across themselves, I don't have to worry about that voltage changing as I turn the LEDs on or off.  Overall I save 6 components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone else tried something like this?  Any gotchas I've overlooked?  I realize the diodes will have to dissipate the full current from all the LEDs, but for this small amount of current that doesn't seem like it will be an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(edit:  I'm putting these diodes between the common cathode of the LEDs and ground)&lt;/p&gt;&#xA;" OwnerUserId="213" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-06-29T06:25:04.660" LastActivityDate="2010-06-29T06:25:04.660" Title="Using diodes to limit current to LEDs" Tags="&lt;avr&gt;&lt;led&gt;&lt;diode&gt;" AnswerCount="10" CommentCount="1" />
  <row Id="264" PostTypeId="2" ParentId="253" CreationDate="2009-11-07T07:33:50.537" Score="1" ViewCount="" Body="&lt;p&gt;There are a variety of manufacturers who make laser cutters that would work well for cutting fabric. One of the most well known is Epilog. You can also try putting one together yourself. Although, if you want to cut stacked fabric, you are looking at a quite complicated project.&#xA;Here are a couple of links that might help.&#xA;On the low and simple end&#xA;&lt;a href=&quot;http://www.instructables.com/id/Laser-cutter-start-slicing-stuff-for-under-50-dol/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Laser-cutter-start-slicing-stuff-for-under-50-dol/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the high complicated and expensive end&#xA;&lt;a href=&quot;http://www.instructables.com/id/SXX5616F18DW8Q7/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/SXX5616F18DW8Q7/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-07T07:33:50.537" />
  <row Id="265" PostTypeId="2" ParentId="263" CreationDate="2009-11-07T09:23:31.987" Score="0" ViewCount="" Body="&lt;p&gt;If you are able to run your complete circuit at the forward voltage of the led then there is no problem - it will work fine. Why not use a variable regulator and get the voltage down that way rather than 3.3v and two diodes?&#xA;Alternatively you could use the diodes between the common cathode of the leds and ground - again no problem.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-07T09:23:31.987" CommentCount="3" />
  <row Id="266" PostTypeId="2" ParentId="263" CreationDate="2009-11-07T13:49:28.973" Score="4" ViewCount="" Body="&lt;p&gt;It occurs to me that one nice property of series resistors is that when the input voltage starts to sag (e.g. when batteries run low) they will gradually account for less of the total voltage as the current through the LEDs falls.  That will have the effect of making the LEDs stay brighter longer.  The diodes won't have that flexibility.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-11-07T13:49:28.973" />
  <row Id="267" PostTypeId="1" AcceptedAnswerId="271" CreationDate="2009-11-07T14:01:21.300" Score="8" ViewCount="1249" Body="&lt;p&gt;I've been writing Linux character device drivers for other people's stuff for some time. I'd like to find a new hobby and the thought of making my own USB gizmos seems really neat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would be thrilled to be able to control some LEDs, servos, and step motors. I really enjoy learning new things on my own and the excitement when something finally works. I've not done any serious MC programming, but do know my way around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone recommend some kits that would be helpful to a complete noob? Ideally, they are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Linux Friendly&lt;/li&gt;&#xA;&lt;li&gt;Able to ship internationally (I'm currently living in Asia)&lt;/li&gt;&#xA;&lt;li&gt;Offer breadboard kits&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you have the time and inclination, links to projects on other people's sites that include schematics and parts lists would be greatly appreciated. I want to study from examples, but &lt;em&gt;good&lt;/em&gt; examples, which is why I'm asking here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My eventual goal is to make my own data collectors - everything from rainfall to average decibels to light levels. Sorry if this has been asked before, I did search (and searched tags).&lt;/p&gt;&#xA;" OwnerUserId="216" LastActivityDate="2010-09-14T11:26:17.267" Title="I'd like to learn how to make my own USB gadgets" Tags="&lt;motor&gt;&lt;led&gt;&lt;servo&gt;" AnswerCount="9" FavoriteCount="4" />
  <row Id="268" PostTypeId="2" ParentId="40" CreationDate="2009-11-07T14:07:44.267" Score="2" ViewCount="" Body="&lt;p&gt;I made one once from taking apart three completely busted RC cars. It had three simple DC motors, enough gears were salvaged to make the crank turn all three, after adding several larger (2&quot;) gears that I had laying around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for the question, it brought back memories of a HS Science project :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the morbidly curious, it was a 'field rechargeable battery recharger'&lt;/p&gt;&#xA;" OwnerUserId="216" LastActivityDate="2009-11-07T14:07:44.267" />
  <row Id="270" PostTypeId="2" ParentId="216" CreationDate="2009-11-07T14:17:06.637" Score="2" ViewCount="" Body="&lt;p&gt;My soldering station has a sponge, a small steel wool pad and a little block of very fine grit sand paper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sponge and steel wool explain themselves. The tiny bit of sand paper is for the odd instance where I accidentally come in contact with some kind of plastic or insulation after using flux .. which the steel wool just seems to roll around on the tip and the sponge won't catch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The tip on a good iron (i.e. Weller) should last for years if taken care of properly, what kind are you using?&lt;/p&gt;&#xA;" OwnerUserId="216" LastActivityDate="2009-11-07T14:17:06.637" CommentCount="4" />
  <row Id="271" PostTypeId="2" ParentId="267" CreationDate="2009-11-07T14:25:51.923" Score="13" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; is really popular, and it is open-source hardware, so &lt;a href=&quot;http://arduino.cc/en/Main/Hardware&quot; rel=&quot;nofollow&quot;&gt;there are variations&lt;/a&gt;, including the third-party &lt;a href=&quot;http://moderndevice.com/freeduino&quot; rel=&quot;nofollow&quot;&gt;Freeduinos&lt;/a&gt; called &lt;a href=&quot;http://moderndevice.com/&quot; rel=&quot;nofollow&quot;&gt;Bare Bones Board&lt;/a&gt;, the &lt;a href=&quot;http://moderndevice.com/RBBB%5FrevB&quot; rel=&quot;nofollow&quot;&gt;Really Bare Bones Board&lt;/a&gt;, and the &lt;a href=&quot;http://www.ladyada.net/make/boarduino/&quot; rel=&quot;nofollow&quot;&gt;Boarduino&lt;/a&gt;, which are very nice for using with breadboards.  The standard Arduino is adapted using things called Shields.  You can &lt;a href=&quot;http://todbot.com/blog/2006/07/11/arduino-breadboard-shield/&quot; rel=&quot;nofollow&quot;&gt;make your own breadboard shield&lt;/a&gt; or buy something like this &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=7914&quot; rel=&quot;nofollow&quot;&gt;ProtoShield Kit.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino uses an &lt;a href=&quot;http://www.ftdichip.com/&quot; rel=&quot;nofollow&quot;&gt;FTDI&lt;/a&gt; USB-RS232 chip or cable.  [The standard Arduino has it build in, while the most of the bread board ones use a special cable that has the chip inside, and saves you some money.]  There is a built-in driver for Linux, and Mac OS X and Windows users can download a driver.  Effectively, this means that the Arduino acts as a device communicating on a serial port, and so it is very easy to communicate with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To use it, you also download software.  It comes with an IDE, an AVR-GCC toolchain, a really nice library, and software to upload your program on to the chip.  It hides most of the details from you, and has a great community.  It is programmed in a language called &quot;Wiring&quot;, but it is really C++.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lastly, being open-source hardware, there are schematics out there.  Indeed, I seem to recall reading that it was fairly easy to build an earlier model.  Searching for &quot;Arduino schematics&quot; in your favourite search engine will give you good results.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for kits, the &lt;a href=&quot;http://www.makershed.com/&quot; rel=&quot;nofollow&quot;&gt;Maker Shed&lt;/a&gt; offers a lot of &lt;a href=&quot;http://www.makershed.com/SearchResults.asp?Cat=43&quot; rel=&quot;nofollow&quot;&gt;Arduino-related items&lt;/a&gt; in stock.  They appear to ship around the world.  Some ones of interest include:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MSAPK2&quot; rel=&quot;nofollow&quot;&gt;Advanced Arduino Starter Kit&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MKSP8&quot; rel=&quot;nofollow&quot;&gt;Arduino Electronic Brick - Starter Kit&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MSAPK&quot; rel=&quot;nofollow&quot;&gt;Arduino Projects Pack&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MKSP9&quot; rel=&quot;nofollow&quot;&gt;Arduino Protoshield Kit&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MSGSA&quot; rel=&quot;nofollow&quot;&gt;Getting Started with Arduino Kit&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://wulfden.org/TheShoppe/freeduino/starting.shtml&quot; rel=&quot;nofollow&quot;&gt;Shoppe at Wulfden&lt;/a&gt; (USA) has a nice experimenters kits, and appears to ship internationally.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.solarbotics.com/&quot; rel=&quot;nofollow&quot;&gt;Solarbotics&lt;/a&gt; (Canada) has a &lt;a href=&quot;http://www.solarbotics.com/products/ardx/&quot; rel=&quot;nofollow&quot;&gt;ARDX Arduino Experimenter's Kit&lt;/a&gt;, a &lt;a href=&quot;http://www.solarbotics.com/products/28931/&quot; rel=&quot;nofollow&quot;&gt;Freeduino Starter Bundle - Ultimate&lt;/a&gt; and an &lt;a href=&quot;http://www.solarbotics.com/products/28935/&quot; rel=&quot;nofollow&quot;&gt;Arduino Starter Bundle - Basic&lt;/a&gt; (and &lt;a href=&quot;http://www.solarbotics.com/products/28936/&quot; rel=&quot;nofollow&quot;&gt;Ultimate&lt;/a&gt;), and appears to ship internationally.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The &lt;a href=&quot;http://arduino.cc/en/Main/Buy&quot; rel=&quot;nofollow&quot;&gt;main Arduino's &quot;buy&quot; page&lt;/a&gt; lists Arduino vendors in all areas of the globe.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other places I would check include &lt;a href=&quot;http://www.adafruit.com/index.php?main%5Fpage=index&amp;amp;cPath=19&quot; rel=&quot;nofollow&quot;&gt;Adafruit Industries&lt;/a&gt; (in the US), &lt;a href=&quot;http://www.hvwtech.com&quot; rel=&quot;nofollow&quot;&gt;HVW Technologies&lt;/a&gt; (in Canada), and &lt;a href=&quot;http://www.sparkfun.com&quot; rel=&quot;nofollow&quot;&gt;Sparkfun Electronics&lt;/a&gt; (in the US).&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="106" LastEditorDisplayName="" LastEditDate="2009-11-07T14:55:14.360" LastActivityDate="2009-11-07T14:55:14.360" CommentCount="2" />
  <row Id="272" PostTypeId="1" AcceptedAnswerId="344" CreationDate="2009-11-07T15:55:24.957" Score="1" ViewCount="328" Body="&lt;p&gt;I'm starting a project using the Realtek RTL8305SC ethernet switch. Does anybody have a good idea of how to use it, some code for it, or even a flow diagram of how it should be used in conjunction with an Ethernet enabled PIC?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be appreciated! I'm currently wondering what I need to do to get it working with the PIC, specifically the order of events. Do I need to reset the switch before enabling the ethernet in the PIC, or do I enable the ethernet on the PIC while the switch is in reset mode? &lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2009-11-11T12:20:39.920" Title="Using a RealTek Ethernet Switch" Tags="&lt;pic&gt;&lt;ethernet&gt;&lt;microcontroller&gt;" AnswerCount="3" />
  <row Id="274" PostTypeId="2" ParentId="267" CreationDate="2009-11-07T18:41:13.060" Score="7" ViewCount="" Body="&lt;p&gt;The Arduino is a great tool to start with when you want to build electronic gadgets and it might lead you to your eventual goal of building a &lt;a href=&quot;http://www.google.com/search?hl=en&amp;amp;q=arduino+data+logger&amp;amp;aq=f&amp;amp;oq=&amp;amp;aqi=&quot; rel=&quot;nofollow&quot;&gt;datalogger&lt;/a&gt;. However, it is not suitable for real USB development as it emulates an old fashioned serial port. It won't let you make it into anything else (like a Human Interface Device (mouse/keyboard) or a Mass Storage Device (cardreader/removable drive)).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to make &quot;real&quot; USB gadgets check out the site of &lt;a href=&quot;http://www.lvr.com/&quot; rel=&quot;nofollow&quot;&gt;Jan Axelson&lt;/a&gt;. He writes &quot;beginners&quot; books about USB. Developing gadgets that use USB on this level might not be suitable for beginners though so Arduino experience will definitely get you on your way.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-07T18:41:13.060" CommentCount="1" />
  <row Id="275" PostTypeId="2" ParentId="259" CreationDate="2009-11-07T18:47:46.517" Score="3" ViewCount="" Body="&lt;p&gt;I don't know much about capacitive touch screens but DealExtreme sells ridiculously cheap &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.21907&quot; rel=&quot;nofollow&quot;&gt;replacement touchscreens for the nintendo DS&lt;/a&gt;. These touchscreens &lt;a href=&quot;http://www.google.com/search?hl=en&amp;amp;q=arduino+nintendo+DS+touchscreen&amp;amp;aq=f&amp;amp;oq=&amp;amp;aqi=&quot; rel=&quot;nofollow&quot;&gt;work with an Arduino&lt;/a&gt; and &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9105&quot; rel=&quot;nofollow&quot;&gt;connectors&lt;/a&gt; and &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9170&quot; rel=&quot;nofollow&quot;&gt;breakout boards&lt;/a&gt; can be found at sparkfun.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-07T18:47:46.517" />
  <row Id="276" PostTypeId="1" AcceptedAnswerId="282" CreationDate="2009-11-07T19:43:52.063" Score="4" ViewCount="1646" Body="&lt;p&gt;Has anyone used the &lt;a href=&quot;http://pjrc.com/teensy/index.html&quot; rel=&quot;nofollow&quot;&gt;teensy&lt;/a&gt;? - I have a need for a serial port as well as USB connection and this looks good. Any opinions welcome.&#xA;Is it difficult to use with the Arduino IDE? What are the downsides compared with the Arduino?&lt;/p&gt;&#xA;" OwnerUserId="9" LastEditorUserId="9" LastEditorDisplayName="" LastEditDate="2009-11-11T22:11:06.293" LastActivityDate="2009-12-02T15:47:59.233" Title="Teensy development" Tags="&lt;arduino&gt;&lt;avr&gt;" AnswerCount="5" FavoriteCount="3" />
  <row Id="277" PostTypeId="2" ParentId="263" CreationDate="2009-11-08T03:11:27.013" Score="8" ViewCount="" Body="&lt;p&gt;I must confess I never tried this. But the series resistor has an important role: it is there to limit the current through the LED. If there's no resistor, the current may be limited in the end to a value which is too high for the LED or for the driver transistor. Theoretically you should graphically add the U-I characteristics of the diodes and the LED, and see on the the resulting characteristic what's the current for your Vcc value. But the main problem is that this current cannot be reliable predicted, since the U-I catalog characteristics of the diodes and LED give you an typical curve, and this curve will also shift with the temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So while it may work, I wouldn't count on it working in every instance. But you may have some help from an unexpected place: the IC driving your LEDs. Sometimes the digital outputs have internal resistors or other ways to limit the output current, in order to avoid overloading them. So check the spec sheet for your attiny2313.&lt;/p&gt;&#xA;" OwnerUserId="218" LastActivityDate="2009-11-08T03:11:27.013" CommentCount="1" />
  <row Id="278" PostTypeId="1" AcceptedAnswerId="281" CreationDate="2009-11-08T04:21:36.503" Score="1" ViewCount="97" Body="&lt;p&gt;I'm trying to get the Lilypad working on my machine but i get the following error.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had a google for it but everything keeps pointing to a problem with the board.  I swapped it out and tried another lilypad but got the same error....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the one i am using is the first Lilypad with the FTDI connection:&#xA;&lt;a href=&quot;http://web.media.mit.edu/~leah/LilyPad/01_computer_attach.html&quot; rel=&quot;nofollow&quot;&gt;http://web.media.mit.edu/~leah/LilyPad/01_computer_attach.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the error message i am getting:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;avrdude: stk500_recv(): programmer is not responding&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any thoughts?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-08T07:00:14.253" Title="Lilypad upload error" Tags="&lt;lilypad&gt;&lt;ftdi&gt;&lt;programmer&gt;&lt;avrdude&gt;" AnswerCount="1" />
  <row Id="279" PostTypeId="2" ParentId="276" CreationDate="2009-11-08T04:24:48.243" Score="1" ViewCount="" Body="&lt;p&gt;They do look great. I have a couple in the mail so I can't speak first hand but I see mainly upsides when compared to the Arduino. They have real USB so you wouldn't need to install drivers to use the device with a computer that you have not been developing on. They have more IO and memory, and they are nice and small. You can also select 3.3v or 5v operation. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I imagine some library code written specifically for the 168 or 328 might not work out of the box, but that should be easily fixed. If there's a specific library that you plan to use with your project let me know and I can test it once my boards arrive.&lt;/p&gt;&#xA;" OwnerUserId="105" LastActivityDate="2009-11-08T04:24:48.243" />
  <row Id="280" PostTypeId="2" ParentId="267" CreationDate="2009-11-08T05:12:53.837" Score="6" ViewCount="" Body="&lt;p&gt;I highly recommend &lt;a href=&quot;http://tuxgraphics.org/electronics/200810/avr-usb-slideshow-presenter.shtml&quot; rel=&quot;nofollow&quot;&gt;the Tuxgraphics AVR USB slideshow presenter tutorial.&lt;/a&gt; It uses an Atmel AVR microcontroller, which has a large hobbyist community (avrfreaks etc), and an open-source software-only usb1.1 stack from obdev.org. It can't scale up very high (mass storage, for example), but the final product is a little USB HID keyboard with two assignable pushbuttons. It would be trivial use it as a datalogger, and a few of the examples at obdev.org are just that ( www.obdev.at/products/vusb/projects.html ). It's written in clean c, and the parts list is a few dollars at most.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the same time, I recommend building or buying the tuxgraphics avrusb500 programmer. It's a joy to use, and one of the most reliable pieces of equipment I own. (I'm not affiliated -- just a very satisfied customer!)&lt;/p&gt;&#xA;" OwnerUserId="220" LastActivityDate="2009-11-08T05:12:53.837" />
  <row Id="281" PostTypeId="2" ParentId="278" CreationDate="2009-11-08T07:00:14.253" Score="2" ViewCount="" Body="&lt;p&gt;It sounds like you're not selecting the correct board within the Arduino IDE.&#xA;Be sure to: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Download the latest version of Arduino from &lt;a href=&quot;http://arduino.cc/en/Main/Software&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Main/Software&lt;/a&gt;&#xA;2) Install the Arduino IDE and FTDI drivers&#xA;3) Select Tools&gt;Board&gt;LilyPad Arduino W/ATMega328&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-11-08T07:00:14.253" />
  <row Id="282" PostTypeId="2" ParentId="276" CreationDate="2009-11-08T12:19:12.983" Score="3" ViewCount="" Body="&lt;p&gt;I have not used the Teensy hardware.  That said, from the specifications, it looks like a nicely designed piece of hardware.  The Teensy developers have done their own &lt;a href=&quot;http://pjrc.com/teensy/teensyduino.html&quot; rel=&quot;nofollow&quot;&gt;comparison with the Arduino&lt;/a&gt;, from which I'll quote:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Teensy uses a similar Atmel AVR&#xA;  processor as the Arduino board, but&#xA;  there are differences. The most&#xA;  important is direct, built-in USB on&#xA;  the Teensy compared to serial&#xA;  converted to USB by a separate chip on&#xA;  the Arduino. Teensy communications&#xA;  MUCH faster than Arduino. Starting&#xA;  with Teensyduino 0.6, Teensy can&#xA;  communicate as a USB keyboard and&#xA;  mouse, which is impossible with an&#xA;  Arduino board that has a fixed USB to&#xA;  serial converter chip.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Teensy is designed for easy use on&#xA;  breadboards in the smallest possible&#xA;  size, which is incompatible with the&#xA;  form-factor used by Arduino shields.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;While many types of sketches can run,&#xA;  Teensy is NOT an &quot;Arduino clone&quot; due&#xA;  to the substantial technical&#xA;  differences. The Teensy hardware and&#xA;  Teensyduino software add-on are NOT&#xA;  endorsed or supported by the Arduino&#xA;  developer team.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Here are some other advantages that the Arduino has over the Teensy:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;strong&gt;Standalone operation&lt;/strong&gt;:  The Teensy can only be powered by the USB port.  Therefore whatever you build around it will need to be plugged into a USB port (and most likely, a computer); if you want/need more power, you'll have to design and build your own power circuits.  Arduinos offer many power options (USB, battery, wall-wart, etc) on-board.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Easier Development Tools&lt;/strong&gt;:  Out of the box, both the Teensy and Arduino depend upon GCC and &lt;a href=&quot;http://www.nongnu.org/avr-libc/&quot; rel=&quot;nofollow&quot;&gt;AVR-Libc&lt;/a&gt;.  Arduino then adds the Arduino IDE, sketches, and other libraries that make getting started faster and simpler.  (You can use those tools to develop with Teensy, but they aren't supported and have limitations).&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Standardized physical form-factor&lt;/strong&gt;: The consistent Arduino form-factor allows people to develop processor and extension boards (shields) that can be shared and reused.  You can see lists of those boards &lt;a href=&quot;http://arduino.cc/en/Main/Hardware&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoShields&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, and &lt;a href=&quot;http://www.arduino.cc/playground/Main/SimilarBoards&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  Those lists are necessarily incomplete, because there are developers actively developing new boards continuously.  Even the Arduino Mega can use shields designed for the earliest Arduinos.  Different versions of Teensy use different &lt;a href=&quot;http://pjrc.com/teensy/pinout.html&quot; rel=&quot;nofollow&quot;&gt;physical forms and pinouts&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Open development model&lt;/strong&gt;: All of the Arduino hardware, firmware, and software are available with Open licenses that allow you to modify, enhance, and distribute your changes without fear of legal reprisals.  Teensy does not offer the same protections.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Community&lt;/strong&gt;: There are &lt;strong&gt;LOTS&lt;/strong&gt; of Arduino developers, along with websites, tutorials, books, kits, etc.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;On the other hand, don't let all of that discourage your from using the Teensy if it meets your needs -- the Teensy platform looks well-designed for many applications where the Arduino would be too large or bulky.&lt;/p&gt;&#xA;" OwnerUserId="143" LastEditorUserId="143" LastEditorDisplayName="" LastEditDate="2009-11-08T15:50:03.787" LastActivityDate="2009-11-08T15:50:03.787" CommentCount="1" />
  <row Id="283" PostTypeId="2" ParentId="259" CreationDate="2009-11-08T17:15:35.380" Score="5" ViewCount="" Body="&lt;p&gt;A basic search turned up a couple of companies offering touch screen kits, but almost all are resistive. I think the main reason that the resistive screens are so common is that the control and sense electronics are much harder with the capacitive screens. You can do a resistive screen interface with just the analog input pins of a microcontroller, but for capacitive screens you must have dedicated electronics. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out this article which runs down a list of development boards and manufacturers &lt;a href=&quot;http://www.edn.com/blog/1590000759/post/1070050307.html&quot; rel=&quot;nofollow&quot;&gt;http://www.edn.com/blog/1590000759/post/1070050307.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have sometimes seen touch screens on the surplus market that look like capacitive units:&#xA;&lt;a href=&quot;http://www.goldmine-elec-products.com/prodinfo.asp?number=G17048&quot; rel=&quot;nofollow&quot;&gt;http://www.goldmine-elec-products.com/prodinfo.asp?number=G17048&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-08T17:15:35.380" />
  <row Id="284" PostTypeId="2" ParentId="272" CreationDate="2009-11-08T18:44:56.433" Score="0" ViewCount="" Body="&lt;p&gt;Switch is just a switch. You plug ethernet connected device to it and it automagically starts to route packets. It does not matter if the device is a Powerbook, PC or a PIC gadget with ethernet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your gadget &amp;lt;---&gt; Switch &amp;lt;---&gt; Intenet&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For you gadget to talk to the Intterwebs your PIC gadget of course know how to handle the TCP/IP layer.&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2009-11-08T18:44:56.433" CommentCount="1" />
  <row Id="285" PostTypeId="2" ParentId="267" CreationDate="2009-11-08T18:48:34.207" Score="3" ViewCount="" Body="&lt;p&gt;You might also want to check &lt;a href=&quot;http://pjrc.com/teensy/index.html&quot; rel=&quot;nofollow&quot;&gt;Teensy&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2009-11-08T18:48:34.207" />
  <row Id="286" PostTypeId="1" AcceptedAnswerId="291" CreationDate="2009-11-08T19:28:57.457" Score="3" ViewCount="336" Body="&lt;p&gt;Is there any cheap and very extensible robot kit, which can work with Microsoft Robotics?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to have a great choice of cool parts for a robot to buy :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;hr /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If where is no such robot kit which can work with MS Robotics, is there any chance to buy a very extensible robot which just can be programmed, maybe even in assembler?&lt;/p&gt;&#xA;" OwnerUserId="224" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T06:50:09.123" LastActivityDate="2011-01-29T06:50:09.123" Title="microsoft robotics: cheap but very extensible robot?" Tags="&lt;robotics&gt;&lt;programmer&gt;&lt;kit&gt;&lt;microsoft&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="287" PostTypeId="2" ParentId="227" CreationDate="2009-11-08T19:29:55.673" Score="1" ViewCount="" Body="&lt;p&gt;Have you considered this adapter from EBay?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://cgi.ebay.co.uk/Bluetooth-serial-converter-UART-interface_W0QQitemZ350276327853QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item518e1899ad&quot; rel=&quot;nofollow&quot;&gt;http://cgi.ebay.co.uk/Bluetooth-serial-converter-UART-interface_W0QQitemZ350276327853QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item518e1899ad&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can't get much cheaper.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-08T19:29:55.673" />
  <row Id="288" PostTypeId="2" ParentId="225" CreationDate="2009-11-08T21:23:09.753" Score="1" ViewCount="" Body="&lt;p&gt;Are you sure you need a JTAG programmer?&#xA;On most AVRs are two methods available to program the flash.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Isp Programming&lt;/li&gt;&#xA;&lt;li&gt;Jtag Programming&#xA;Isp programmer are cheaper, but JTAG supports debugging&#xA;For Jtag are mainly two Programmer available: Dragon and JTAGice mkii &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="225" LastActivityDate="2009-11-08T21:23:09.753" />
  <row Id="289" PostTypeId="2" ParentId="210" CreationDate="2009-11-08T21:54:55.617" Score="2" ViewCount="" Body="&lt;p&gt;This might be helpful:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://forum.sparkfun.com/viewtopic.php?t=17472&quot; rel=&quot;nofollow&quot;&gt;http://forum.sparkfun.com/viewtopic.php?t=17472&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;USB AVR chips can operate in host mode, so in theory it would be possible. In practice, it might take a LOT of work to write the AVR drivers for the dongle, unless the protocol has been published or someone else has already figured out how to do it with that particular dongle.&quot;&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-08T21:54:55.617" />
  <row Id="290" PostTypeId="2" ParentId="272" CreationDate="2009-11-08T22:14:33.753" Score="0" ViewCount="" Body="&lt;p&gt;Microchip offer a free licensed tcp/ip stack for certain chips. More information from their website &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS%5FGET%5FPAGE&amp;amp;nodeId=2505&amp;amp;param=en535724&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. This specific page is in the middle of a group of pages discussing pic and ethernet connections.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-08T22:14:33.753" />
  <row Id="291" PostTypeId="2" ParentId="286" CreationDate="2009-11-09T00:13:24.730" Score="4" ViewCount="" Body="&lt;p&gt;A little basic research on your part would have turned up the Wikipedia entry for &lt;a href=&quot;http://en.wikipedia.org/wiki/Microsoft%5FRobotics%5FDeveloper%5FStudio&quot; rel=&quot;nofollow&quot;&gt;Microsoft Robotics Developer Studio&lt;/a&gt;, which lists no fewer than 16 robotics platforms that are compatible (to lesser or greater degree) with MRDS.  A little more browsing would have turned up Microsoft's list of &lt;a href=&quot;http://msdn.microsoft.com/en-us/library/bb905437.aspx&quot; rel=&quot;nofollow&quot;&gt;Supported Robots&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Frankly, if you want cheap, then using a Microsoft tool may look like the solution, but it will end up costing you more in the long run, because you'll be paying the &lt;a href=&quot;http://en.wikipedia.org/wiki/Criticism%5Fof%5FMicrosoft&quot; rel=&quot;nofollow&quot;&gt;Microsoft tax&lt;/a&gt;, but that's your choice.  Every one of the 'supported robots' has a primary way of being programmed -- Microsoft is merely providing an alternative set of tools, in a desperate bid to capture more users of its OS, software, and tools.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-09T00:13:24.730" CommentCount="4" />
  <row Id="292" PostTypeId="1" AcceptedAnswerId="293" CreationDate="2009-11-09T02:40:31.313" Score="1" ViewCount="885" Body="&lt;p&gt;What is the difference between Codevision AVR C and Atmel AVR C compiler?&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-12T23:52:05.240" LastActivityDate="2009-11-12T23:52:05.240" Title="Codevision AVR C and Atmel AVR C compiler" Tags="&lt;avr&gt;&lt;compiler&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="293" PostTypeId="2" ParentId="292" CreationDate="2009-11-09T04:04:20.407" Score="3" ViewCount="" Body="&lt;p&gt;There isn't really much difference there may be some differences in which chips are supported under Codevision so you may want to check for the chip you plan to use. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are different IDE's available Codevsion has its own IDE and there are different IDE to choose from for Atmel's avr C (like &lt;a href=&quot;http://www.atmel.com/dyn/products/tools%5Fcard.asp?tool%5Fid=2725&quot; rel=&quot;nofollow&quot;&gt;AVR Studio 4&lt;/a&gt;) But you could also use &lt;a href=&quot;http://winavr.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;WinAVR&lt;/a&gt; which is uses &lt;a href=&quot;http://gcc.gnu.org/install/specific.html#avr&quot; rel=&quot;nofollow&quot;&gt;GCC&lt;/a&gt;, or you could use GCC with another IDE of your choice or you can go without the IDE entirely. If you do use GCC this is a good website to check out &lt;a href=&quot;http://www.nongnu.org/avr-libc/&quot; rel=&quot;nofollow&quot;&gt;AVR Libc&lt;/a&gt;. For even more information and tutorials about AVR you should check &lt;a href=&quot;http://www.avrfreaks.net/&quot; rel=&quot;nofollow&quot;&gt;AVR Freaks&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2009-11-09T04:04:20.407" />
  <row Id="294" PostTypeId="2" ParentId="263" CreationDate="2009-11-09T08:49:05.170" Score="2" ViewCount="" Body="&lt;p&gt;A typical max current of a microcontroller is 40mA. Sometimes this is limited and sometimes it will shut down the uc. That's why sometimes you can connect a LED directly to a uc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are driving a LED, the voltage is not important because it's constant. It will let (almost) all the current that you provide pass, until breakage. So that's why you have to limit it somehow and a diode won't do it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Asuming you are limiting the power supply it to, for example, 40mA, if you don't use a resistor for each LED, current will be distributed so if you light one diode it will be very bright and when turning 10 leds on they will be ten times dimmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's why every LED tutorial you see on the net, regulates current with simple resistors.&lt;/p&gt;&#xA;" OwnerUserId="198" LastActivityDate="2009-11-09T08:49:05.170" CommentCount="1" />
  <row Id="295" PostTypeId="2" ParentId="259" CreationDate="2009-11-09T13:24:51.313" Score="4" ViewCount="" Body="&lt;p&gt;Your question is a bit ambiguous, and that makes it hard to answer.  What is a reasonable price?  Because of the electronics required to control and sense capacitive screens (See jkopel), they are by nature more expensive to deliver a complete product.  In my experience, your choices are either pay a good bit for a touch screen ready to go (which sounds like it is outside of your reasonable range) or buy some surplus components (again, see jkopel) and try to figure out all of the particulars yourself.  The first way is pricier, the second way is fraught with headaches and does not even guarantee you will be able to use the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps you could list the reasons you want a capacitive touch screen?  If you did, then perhaps we could suggest alternatives.  There are all sorts of methods to do proximity sensing on all sorts of materials for less than a dollar, for example, and if we had a better idea of the kinds of things you are trying to accomplish perhaps we could point you to solutions you would find reasonably priced.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-11-09T13:24:51.313" />
  <row Id="296" PostTypeId="2" ParentId="267" CreationDate="2009-11-09T17:59:26.663" Score="6" ViewCount="" Body="&lt;p&gt;Another device I've wanted to look into is the &lt;a href=&quot;http://www.atmel.com/dyn/products/tools%5Fcard.asp?tool%5Fid=3879&quot; rel=&quot;nofollow&quot;&gt;AT90USBKey&lt;/a&gt;.  It has been a while since I've looked into it, and I'm not certain if you can program for it without Windows, but it will act as a USB device (like a keyboard or mass storage device) or as a USB host that you plug other devices into.  There are sample programs available, and it looks reasonably easy to work with, provided you know a little bit about electronics and can code in C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A google search for AT90USBKey and Linux yileds promising results.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know you can get it from &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&amp;amp;site=CA&amp;amp;WT.z%5Fhomepage%5Flink=hp%5Fgo%5Fbutton&amp;amp;KeyWords=at90usbkey&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;DigiKey.ca&lt;/a&gt;.  I looked up a &lt;a href=&quot;http://digikeyasia.blogspot.com/&quot; rel=&quot;nofollow&quot;&gt;digikey equivalent for Asia&lt;/a&gt;; you can get the part from &lt;a href=&quot;http://www.farnell.com/&quot; rel=&quot;nofollow&quot;&gt;Farnell&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-11-09T17:59:26.663" CommentCount="1" />
  <row Id="297" PostTypeId="1" AcceptedAnswerId="343" CreationDate="2009-11-09T18:53:27.737" Score="9" ViewCount="2377" Body="&lt;p&gt;What is a good microcontroller for doing Ethernet applications?  Or do I just need a good Ethernet library to connect with an Ethernet MAC/PHY?&lt;/p&gt;&#xA;" OwnerUserId="204" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:00:11.790" LastActivityDate="2010-12-10T22:00:11.790" Title="What is a good microcontroller for Ethernet applications?" Tags="&lt;microcontroller&gt;&lt;ethernet&gt;&lt;tcp-ip&gt;" AnswerCount="11" FavoriteCount="9" />
  <row Id="298" PostTypeId="2" ParentId="297" CreationDate="2009-11-09T19:43:11.553" Score="6" ViewCount="" Body="&lt;p&gt;Generally ethernet is not built in to microcontrollers. First you need a jack which can convert ethernet signals into signals read by a microcontroller (this is generally called 'magnetics'). Then you need a TCP/IP stack, and then on top of that you need DHCP, DNS, and whatever other protocols you want to use. So the actual microcontroller you use doesn't matter a whole lot. If you get something very powerful like an ARM with Linux running on it, then developing for it would be very simple, almost the same as writing a network application running on a desktop PC running Linux. Or you could go with something less powerful &amp;amp; cheaper like an AVR or PIC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ethernet and TCP/IP can be quite complex if you want to implement an entire TCP/IP stack in software. One common solution is to use something like Wiznet's W5100 chip, which handles all the low level TCP/IP stuff for you. You can buy it in a pre-made module that includes the ethernet connector and everything for pretty cheap, around &lt;a href=&quot;http://www.nkcelectronics.com/wiznet-wiz812mj-tcpip-network-mod812.html&quot; rel=&quot;nofollow&quot;&gt;$20 for the WIZ812MJ module&lt;/a&gt;. You can communicate with it using only SPI, so it wont take a lot of I/O pins on your mcu.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lantronix also provides some more powerful modules that look even simpler to use, but they are a bit more pricey ($50-$100 depending on the model). See their &lt;a href=&quot;http://www.lantronix.com/device-networking/embedded-device-servers/xport.html&quot; rel=&quot;nofollow&quot;&gt;XPort&lt;/a&gt; for example.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-09T19:43:11.553" CommentCount="4" />
  <row Id="299" PostTypeId="2" ParentId="297" CreationDate="2009-11-09T19:46:15.070" Score="2" ViewCount="" Body="&lt;p&gt;It depends what you want to do with it. The main thing to look out for is the amount of RAM (can limit individual message size) and if you want to serve web pages then the amount of storage available for that.&#xA;I use an Arduino Duemilanova &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/&lt;/a&gt; - ATMega328 micro controller, 2Kbytes RAM. You can connect up a SD card if you want significant storage. The ethernet shield will support upto 4 concurrent sessions. Don't expect to be able to serve up complex pages but works fine uploading to Pachube, twitter etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a more powerful solution I would recommend the Marvel SheevaPlug &lt;a href=&quot;http://www.marvell.com/products/embedded_processors/developer/kirkwood/sheevaplug.jsp&quot; rel=&quot;nofollow&quot;&gt;http://www.marvell.com/products/embedded_processors/developer/kirkwood/sheevaplug.jsp&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-09T19:46:15.070" />
  <row Id="300" PostTypeId="2" ParentId="276" CreationDate="2009-11-09T19:50:21.040" Score="1" ViewCount="" Body="&lt;p&gt;I got one about a week ago, it works quite well for me so far. I haven't done a whole lot besides play with serial ports and blink some LEDs, but I have plans for it. Basically I bought it because I didn't need everything the arduino board has, the teensy chip actually has more ram and flash than the arduino chip, and it's a couple bucks cheaper. Also the fact that it has native USB instead of using an external FT chip for USB is nice.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-09T19:50:21.040" />
  <row Id="301" PostTypeId="2" ParentId="263" CreationDate="2009-11-09T19:57:02.037" Score="8" ViewCount="" Body="&lt;p&gt;Sorry, but the whole premise of the question won't work, because diodes do not limit current. You seem to be somewhat confusing voltage and current. Without a resistor, there will be nothing to limit the current. In the best case, the LEDs will work fine, but will wear out much sooner due to overcurrent. In the worst case, it will pop the LED from too much current, and in the very worst case it will fry your microcontroller by trying to sink or source too much current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically the answer is that you always need to limit the current using resistors, unless you are using a special LED driver IC that handles it for you (often called 'constant current sink' or 'constant current source'). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used &lt;a href=&quot;http://www.allegromicro.com/en/products/Categories/ICs/leddriver.asp&quot; rel=&quot;nofollow&quot;&gt;Allegro's LED driver ICs&lt;/a&gt; before, they work quite well. You can control 16 individual LEDs using only 3 pins on your microcontroller (or many more if using matrixing or multiplexing). Various other vendors also make LED driving ICs as well. Or you can do it yourself just using a combination of shift registers, transistors, and resistors.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-09T19:57:02.037" />
  <row Id="302" PostTypeId="2" ParentId="297" CreationDate="2009-11-09T20:43:35.370" Score="6" ViewCount="" Body="&lt;p&gt;Regarding having a TCP/IP stack, there are two projects you should look at:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://www.sics.se/contiki/about-contiki.html&quot; rel=&quot;nofollow&quot;&gt;Contiki&lt;/a&gt; Operating System&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Contiki is an open source, highly&#xA;  portable, multi-tasking operating&#xA;  system for memory-efficient networked&#xA;  embedded systems and wireless sensor&#xA;  networks. Contiki has been used is a&#xA;  variety of projects, such as road&#xA;  tunnel fire monitoring, intrusion&#xA;  detection, water monitoring in the&#xA;  Baltic Sea, and in surveillance&#xA;  networks.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Contiki is designed for&#xA;  microcontrollers with small amounts of&#xA;  memory. A typical Contiki&#xA;  configuration is 2 kilobytes of RAM&#xA;  and 40 kilobytes of ROM.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://www.sics.se/~adam/uip/index.php/Main%5FPage&quot; rel=&quot;nofollow&quot;&gt;uIP TCP/IP Stack&lt;/a&gt;:&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The open-source uIP TCP/IP stack&#xA;  provides TCP/IP connectivity to tiny&#xA;  embedded 8-bit microcontrollers, with&#xA;  maintained interoperability and RFC&#xA;  standards compliance.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-11-09T20:43:35.370" />
  <row Id="303" PostTypeId="2" ParentId="297" CreationDate="2009-11-09T21:36:12.347" Score="4" ViewCount="" Body="&lt;p&gt;Microchip have a number of Pic microcontrollers with inbuilt ethernet capabilities, there's a list &lt;a href=&quot;http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=121&amp;amp;mid=10&amp;amp;lang=en&amp;amp;pageId=74&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. They also have a series of pages concerning design solutions for ethernet and their products &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS%5FGET%5FPAGE&amp;amp;nodeId=2504&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, which also includes details of their full TCP/IP stack (with integrated MAC and PHY).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2009-11-09T22:18:58.263" LastActivityDate="2009-11-09T22:18:58.263" />
  <row Id="304" PostTypeId="1" AcceptedAnswerId="305" CreationDate="2009-11-09T22:35:03.667" Score="3" ViewCount="854" Body="&lt;p&gt;I'm using an ATTiny2313 to act as a serial concentrator. It only has 128bytes of RAM. I think I'm running out of RAM during the ISR. My question is how much RAM (stack) does an ISR use to save the context (registers). I.e. if I use ISRs how much will I have left out of 128 bytes.&#xA;Is there a way to detect stack overflow?&lt;/p&gt;&#xA;" OwnerUserId="9" LastEditorUserId="9" LastEditorDisplayName="" LastEditDate="2009-11-11T22:10:33.067" LastActivityDate="2009-11-11T22:10:33.067" Title="ATTiny2313 ISR stack usage" Tags="&lt;avr&gt;&lt;microcontroller&gt;&lt;memory&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="305" PostTypeId="2" ParentId="304" CreationDate="2009-11-10T00:15:51.593" Score="4" ViewCount="" Body="&lt;p&gt;Well, checking the &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod%5Fdocuments/DOC2543.PDF&quot; rel=&quot;nofollow&quot;&gt;ATTiny2313 documentation&lt;/a&gt;, on page 15, it states:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The interrupt execution response for&#xA;  all the enabled AVR interrupts is four&#xA;  clock cycles minimum. After four clock&#xA;  cycles the program vector address for&#xA;  the actual interrupt handling routine&#xA;  is executed. During this four clock&#xA;  cycle period, the Program Counter is&#xA;  pushed onto the Stack. The vector is&#xA;  normally a jump to the interrupt&#xA;  routine, and this jump takes three&#xA;  clock cycles. If an interrupt occurs&#xA;  during execution of a multi-cycle&#xA;  instruction, this instruction is&#xA;  completed before the interrupt is&#xA;  served. If an interrupt occurs when&#xA;  the MCU is in sleep mode, the&#xA;  interrupt execution response time is&#xA;  increased by four clock cycles. This&#xA;  increase comes in addition to the&#xA;  start-up time from the selected sleep&#xA;  mode.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;A return from an interrupt handling&#xA;  routine takes four clock cycles.&#xA;  During these four clock cycles, the&#xA;  Program Counter (two bytes) is popped&#xA;  back from the Stack, the Stack Pointer&#xA;  is incremented by two, and the I-bit&#xA;  in SREG is set.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Thus you're really only looking at 2 bytes on the stack during an interrupt (the PC); anything else that an ISR puts on the stack is up to the ISR itself.  I wouldn't expect a well-written interrupt handler to need a whole lot of stack space.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the Stack Pointer itself, on page 13, it states:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The Stack is mainly used for storing temporary data, for storing local &#xA;  variables and for storing return addresses after interrupts and subroutine &#xA;  calls. The Stack Pointer Register always points to the top of the Stack. &#xA;  Note that the Stack is implemented as growing from higher memory locations &#xA;  to lower memory locations. This implies that a Stack PUSH command decreases &#xA;  the Stack Pointer.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The Stack Pointer points to the data SRAM Stack area where the Subroutine &#xA;  and Interrupt Stacks are located. This Stack space in the data SRAM must be &#xA;  defined by the program before any subroutine calls are executed or interrupts &#xA;  are enabled. The Stack Pointer must be set to point above 0x60. The Stack &#xA;  Pointer is decremented by one when data is pushed onto the Stack with the PUSH &#xA;  instruction, and it is decremented by two when the return address is pushed &#xA;  onto the Stack with subroutine call or interrupt.  The Stack Pointer is &#xA;  incremented by one when data is popped from the Stack with the POP instruction, &#xA;  and it is incremented by two when data is popped from the Stack with &#xA;  return from subroutine RET or return from interrupt RETI.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The AVR Stack Pointer is implemented as two 8-bit registers in the I/O space. &#xA;  The number of bits actually used is implementation dependent. Note that the &#xA;  data space in some implementations of the AVR architecture is so small that &#xA;  only SPL is needed. In this case, the SPH Register will not be present.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;In your case, I think there's only SPL present (128 bytes of RAM = 7 bits).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Beyond the hardware, it depends upon your framework, which for most AVR parts is going to involve GCC, &lt;a href=&quot;http://www.gnu.org/software/binutils/&quot; rel=&quot;nofollow&quot;&gt;GNU Binutils&lt;/a&gt;, and &lt;a href=&quot;http://www.nongnu.org/avr-libc/&quot; rel=&quot;nofollow&quot;&gt;avr-libc&lt;/a&gt;.  A quick look at the avr-libc FAQ turned up two good questions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_reg_usage&quot; rel=&quot;nofollow&quot;&gt;http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_reg_usage&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;What registers are used by the C compiler?&lt;/strong&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;&lt;p&gt;Data types:&#xA;  char is 8 bits, int is 16 bits, long is 32 bits, long long is 64 bits, float and double are 32 bits (this is the only supported floating point format), pointers are 16 bits (function pointers are word addresses, to allow addressing up to 128K program memory space). There is a -mint8 option (see Options for the C compiler avr-gcc) to make int 8 bits, but that is not supported by avr-libc and violates C standards (int must be at least 16 bits). It may be removed in a future release.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;Call-used registers (r18-r27, r30-r31):&#xA;  May be allocated by gcc for local data. You may use them freely in assembler subroutines. Calling C subroutines can clobber any of them - the caller is responsible for saving and restoring.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;Call-saved registers (r2-r17, r28-r29):&#xA;  May be allocated by gcc for local data. Calling C subroutines leaves them unchanged. Assembler subroutines are responsible for saving and restoring these registers, if changed. r29:r28 (Y pointer) is used as a frame pointer (points to local data on stack) if necessary. The requirement for the callee to save/preserve the contents of these registers even applies in situations where the compiler assigns them for argument passing.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;Fixed registers (r0, r1):&#xA;  Never allocated by gcc for local data, but often used for fixed purposes: &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;r0 - temporary register, can be clobbered by any C code (except interrupt handlers which save it), may be used to remember something for a while within one piece of assembler code&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;r1 - assumed to be always zero in any C code, may be used to remember something for a while within one piece of assembler code, but must then be cleared after use (clr r1). This includes any use of the [f]mul[s[u]] instructions, which return their result in r1:r0. Interrupt handlers save and clear r1 on entry, and restore r1 on exit (in case it was non-zero).&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;Function call conventions:&#xA;  Arguments - allocated left to right, r25 to r8. All arguments are aligned to start in even-numbered registers (odd-sized arguments, including char, have one free register above them). This allows making better use of the movw instruction on the enhanced core. &lt;/p&gt;&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;  &#xA;  &lt;p&gt;If too many, those that don't fit are passed on the stack.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Return values: 8-bit in r24 (not r25!), 16-bit in r25:r24, up to 32 bits in r22-r25, up to 64 bits in r18-r25. 8-bit return values are zero/sign-extended to 16 bits by the called function (unsigned char is more efficient than signed char - just clr r25). Arguments to functions with variable argument lists (printf etc.) are all passed on stack, and char is extended to int. &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_ramoverlap&quot; rel=&quot;nofollow&quot;&gt;http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_ramoverlap&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;How to detect RAM memory and variable overlap problems?&lt;/strong&gt;&#xA;  You can simply run avr-nm on your output (ELF) file. Run it with the -n option, and it will sort the symbols numerically (by default, they are sorted alphabetically).&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Look for the symbol _end, that's the first address in RAM that is not allocated by a variable. (avr-gcc internally adds 0x800000 to all data/bss variable addresses, so please ignore this offset.) Then, the run-time initialization code initializes the stack pointer (by default) to point to the last available address in (internal) SRAM. Thus, the region between _end and the end of SRAM is what is available for stack. (If your application uses malloc(), which e. g. also can happen inside printf(), the heap for dynamic memory is also located there. See Memory Areas and Using malloc().)&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The amount of stack required for your application cannot be determined that easily. For example, if you recursively call a function and forget to break that recursion, the amount of stack required is infinite. :-) You can look at the generated assembler code (avr-gcc ... -S), there's a comment in each generated assembler file that tells you the frame size for each generated function. That's the amount of stack required for this function, you have to add up that for all functions where you know that the calls could be nested.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="143" LastEditorUserId="143" LastEditorDisplayName="" LastEditDate="2009-11-10T21:43:08.513" LastActivityDate="2009-11-10T21:43:08.513" CommentCount="2" />
  <row Id="306" PostTypeId="2" ParentId="276" CreationDate="2009-11-10T02:59:23.760" Score="2" ViewCount="" Body="&lt;p&gt;Do you know if it is possible to rig these to work at lower voltages? 2.8, 1.8?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;as suggested in this thread the USB part of the device will not work under 3v. I spoke with paul after ordering a couple of these. The standard Teensy has a location on the bottom to add a 3.3v regulator. On the Teensy++ (lot more i/o pins) Paul suggests I either follow the + and - lines from the USB to install a voltage regulator or I can try to splice a USB cable and add voltage regulation. To simplify matters in the future they will release a version of Teensy++ that has the spot to install a 3.3v regulator.  My plan of action (for the next day or two) is to try to splice a cable. I will program the device with a normal 5v cable and then power it with a 3.3v cable for opperation. To others, my suggestion is that if you need 3.3v and do NOT need 38 i/o pins, get the standard Teensy. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Modification:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This picture shows how to manually modify the Teensy++ ver 1.0 board to install a voltage regulator and jumper so that it can be switched between 5V and 3.3v.&#xA;&lt;img src=&quot;http://farm3.static.flickr.com/2648/4152517331%5Fe8d9176f62%5Fo.jpg&quot; alt=&quot;teensypp 3.3v modifcation&quot; /&gt; (&lt;a href=&quot;http://farm3.static.flickr.com/2648/4152517331%5Fe8d9176f62%5Fo.jpg&quot; rel=&quot;nofollow&quot;&gt;full size&lt;/a&gt; or &lt;a href=&quot;http://www.flickr.com/photos/deadhacker/4152517331/&quot; rel=&quot;nofollow&quot;&gt;see flickr for embedded notes&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="196" LastEditorUserId="196" LastEditorDisplayName="" LastEditDate="2009-12-02T15:47:59.233" LastActivityDate="2009-12-02T15:47:59.233" CommentCount="1" />
  <row Id="307" PostTypeId="2" ParentId="297" CreationDate="2009-11-10T05:46:47.130" Score="2" ViewCount="" Body="&lt;p&gt;There are many projects using the ENC28J60 and ATMEL Cips.&#xA;The most of them are well documented and using C or BASCOM.&#xA;You could also buy complete kits to start with.&#xA;I by myself own such a kit and learned much about the programming from the forums.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Greetings...  0815achim&lt;/p&gt;&#xA;" OwnerUserId="162" LastActivityDate="2009-11-10T05:46:47.130" />
  <row Id="308" PostTypeId="2" ParentId="197" CreationDate="2009-11-10T07:06:48.753" Score="1" ViewCount="" Body="&lt;p&gt;If you want to experiment, you can drive a VFD using an Arduino without a controller chip. If you can't find a datasheet for your display it'll take a bit of trial and error. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, you'll need a couple volts across the filament. This will most likely be the first and last pin. For best results this should be AC, but DC is usually acceptable. The 5v from your Arduino will be too much so put a small resistor in series with the filament, for my display, I used a 47ohm resistor. If you skip the resistor you'll see the filament glow red hot. Since these displays are not designed to be light bulbs, you shouldn't do this for more than a couple seconds, but it might be useful to confirm that you've found the filament. I found that the display was brighter if I hooked up the first pin to ground and the last pin to 5v via the resistor. I'm not sure why this is the case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you probably won't be able to drive the grids with 5v, but depending on your display you might not need much higher. I have a display lit to a decent brightness at the moment with only 7v which I've pulled directly from the supply rather than going through a regulator. (If you can't do this with your Arduino, or your particular display needs 20v or something, you can use two different power supplies by connecting the ground together, though this is not a good idea long term.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your display will be broken into separate grids and it will probably be obvious which pins are connected to which since these things made of glass and you can look right inside. So you'll have one pin for each grid and the remaining pins connect to the individual segments that light up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So here's where VFDs differ from LED displays. In an LED display you'll have a common anode or cathode and the individual segments will be the reverse. In VFDs, both the grids and segments are anodes. So hook up your higher voltage to at least one grid and one segment. Doing this, you can map out which pins light which segment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This can all be done without an Arduino at all. What you'll notice now is that you can only light up the same configuration of segments for each grid. Not very useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll need to multiplex the display: light up the grids in rapid succession, changing the segments that are turned on each time. This is where a controller chip can be handy but it can be fun to write using just the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have enough free pins on the Arduino for the anodes that you need, you can use a transistor on each as a switch for the higher voltage. You can use the analog pins as digital pins as well, just refer to them as pins 14-19.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best way to multiplex a display is using an interrupt on a timer, so read up on those.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Here's a circuit with a calculator to build a voltage booster for powering VFDs&#xA;&lt;a href=&quot;http://www.ladyada.net/library/diyboostcalc.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/library/diyboostcalc.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="105" LastEditorUserId="105" LastEditorDisplayName="" LastEditDate="2009-11-10T17:58:50.133" LastActivityDate="2009-11-10T17:58:50.133" />
  <row Id="309" PostTypeId="2" ParentId="292" CreationDate="2009-11-10T07:28:07.653" Score="1" ViewCount="" Body="&lt;p&gt;Overall they're fairly similar&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a few things that I'm aware of:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;In Codevision you can refer to the individual bits (pins) in a port directly like: &lt;code&gt;PINA.1&lt;/code&gt; rather than shifting them in.&lt;/li&gt;&#xA;&lt;li&gt;Storing data in program memory is a little more user friendly in Codevision&lt;/li&gt;&#xA;&lt;li&gt;The Codevision compiler supplies a few pseudo registers that you can use to make sure a read from a 16-bit register is atomic.&lt;/li&gt;&#xA;&lt;li&gt;Interrupts are installed differently&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="105" LastActivityDate="2009-11-10T07:28:07.653" />
  <row Id="310" PostTypeId="1" AcceptedAnswerId="327" CreationDate="2009-11-10T08:36:13.987" Score="11" ViewCount="1232" Body="&lt;p&gt;What's a good circuit to use to generate a square wave? The exact waveform isn't too important - I just want to get a piezo buzzer cranking at 150 kHz. I also want efficiency and adjustable amplitude.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Motivation: I want to vaporize some oil in order to burn it. I choose 150 kHz after the Glade Wisp as hacked in Make.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest I found was &lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/Electronic/square.html&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; consisting of a capacitor, 3 resistors and &lt;s&gt;an op amp&lt;/s&gt; a comparator. Is this design a good way to go? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming so, according to the same page, it has a period of &lt;/p&gt;&#xA;&#xA;&lt;p&gt;T = 2RC ln ((1+L)/(1-L)) where L = R1 / (R1+R2)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Choosing R1 = R2 gives L = 1/2, giving (1+L)/(1-L) = approximately e, giving the simpler&lt;/p&gt;&#xA;&#xA;&lt;p&gt;T = 2RC&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm in the woods here, but I'll suppose that R1 = R2 = R is a good choice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The T I want is 1/150kHz; thus RC = 3.33e-6&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another abitrary choice presents itself. Say, a 100 ohm resistor and a 0.033 uF capacitor? Is this choice important? Is choice of op amp important?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry for the long question, but if someone who knows what they're doing could walk with me here, I'd surely appreciate it.&lt;/p&gt;&#xA;" OwnerUserId="84" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-07T23:46:24.103" LastActivityDate="2010-08-07T23:46:24.103" Title="What's a good square wave generator?" Tags="&lt;generator&gt;&lt;wave&gt;" AnswerCount="7" CommentCount="3" FavoriteCount="1" />
  <row Id="311" PostTypeId="2" ParentId="310" CreationDate="2009-11-10T10:11:21.760" Score="17" ViewCount="" Body="&lt;p&gt;If you google for 555 square wave generator you'll get thousands of hits for circuits based on a 555 chip that produce a square wave. There's a square wave calculator &lt;a href=&quot;http://www.csgnetwork.com/ne555timer2calc.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, which should allow you to experiment with the calculations. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plus as an added bonus 555 chips are dirt cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or look at 556 chips which are basically two 555s on the same chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Amos&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2009-12-11T10:34:44.517" LastActivityDate="2009-12-11T10:34:44.517" CommentCount="1" />
  <row Id="312" PostTypeId="1" CreationDate="2009-11-10T10:23:32.140" Score="1" ViewCount="609" Body="&lt;p&gt;Am considering the WRL-08770 module for use in a project. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where can I find:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Datasheet&lt;/li&gt;&#xA;&lt;li&gt;Programming Guide&lt;/li&gt;&#xA;&lt;li&gt;and sample C code&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Kind Regards,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stefan&lt;/p&gt;&#xA;" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-11-10T10:27:27.507" LastActivityDate="2009-11-10T10:27:27.507" Title="FM Receiver Breakout Board Documents - AR1010" Tags="&lt;datasheet&gt;&lt;fm&gt;" AnswerCount="1" />
  <row Id="313" PostTypeId="2" ParentId="297" CreationDate="2009-11-10T10:24:59.423" Score="3" ViewCount="" Body="&lt;p&gt;I would suggest using the ENC28J60 together with one of the pic 18 micro-controllers because microchip offers a TCP/IP stack for this combination and there should be plenty of information available through google on implementing this.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-10T10:24:59.423" />
  <row Id="314" PostTypeId="2" ParentId="312" CreationDate="2009-11-10T10:26:07.833" Score="2" ViewCount="" Body="&lt;p&gt;Hi Stefan, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find the &lt;a href=&quot;http://www.littlebirdelectronics.com/products/fm-receiver-breakout-board-ar1010&quot; rel=&quot;nofollow&quot;&gt;FM Receiver Breakout Board&lt;/a&gt; Documents following here:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/datasheets/Wireless/General/SPK-TFM-1010%20SPECIFICATION.pdf&quot; rel=&quot;nofollow&quot;&gt;Datasheet&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/datasheets/Wireless/General/AR1000ATMega168v11.zip&quot; rel=&quot;nofollow&quot;&gt;sample C code&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-11-10T10:26:07.833" CommentCount="3" />
  <row Id="315" PostTypeId="2" ParentId="297" CreationDate="2009-11-10T11:18:03.583" Score="2" ViewCount="" Body="&lt;p&gt;i've tried the microchip stack using the picdem.net 2 develpment card and i was not satisfied at all, it's not optimised and not well documented.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i think that the best solution in market now is wiznet that have the first Ethernet based TCP/IP hardware chip that save a lot of time and give you more efficiency&lt;/p&gt;&#xA;&#xA;&lt;p&gt;this link gives all the solutions availables and compare them:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.beyondlogic.org/etherip/ip.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.beyondlogic.org/etherip/ip.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;good luck&lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2009-11-10T11:18:03.583" CommentCount="1" />
  <row Id="316" PostTypeId="2" ParentId="310" CreationDate="2009-11-10T12:22:21.043" Score="6" ViewCount="" Body="&lt;p&gt;If you are wanting to build an A-stable vibrator, then the circuit you chose is fine. You will want to keep the R value from loading the op amp. This means selecting R so that it doesn't load an op amp. I would suggest that mean staying in the 10k-100k region of resistance keeps you safe if you use a baseband op amp like a TL072(FET) or an LM358(BJT).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With your circuit you will need trim resistors to get the thing to 'load up' right. A potentiometer in line with R (your feedback resistor) will probably be necessary for tuning.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you will find that it is a lot of trouble to make an oscillator circuit this way. I would only do it if you have some very compelling reason not to use a micro controller. A basic stamp, propeller, or Atmel based mcu circuit would be able to create this same squarewave much more accurately. A 555 timer would also work but I would just go the MCU route, an ATtiny 8 pin is 3 bucks so why not just use that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But multivibrators are fun to play with if you are just playing, remember to buffer the output so you don't load the thing! Good Luck.&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2009-11-10T12:22:21.043" CommentCount="1" />
  <row Id="317" PostTypeId="1" CreationDate="2009-11-10T13:40:12.913" Score="4" ViewCount="358" Body="&lt;p&gt;I am looking for a motion sensor device that can track person/animal walking by it and record time/date of the event(s).  It needs to be able to run on a small battery or two (maybe 2 AA's or a 9 volt).  It does not have to have a screen, just an input connection for a screen to hook up to in order to read the information and set the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Total cost would be only like $10 to $15.  My initial research on the internet points me to look at a pyroelectric infrared sensor or some kind of passive infrared sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible?&lt;/p&gt;&#xA;" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:28:40.100" LastActivityDate="2011-06-02T02:28:40.100" Title="low voltage motion sensor" Tags="&lt;sensor&gt;&lt;voltage&gt;&lt;infrared&gt;&lt;motion&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="318" PostTypeId="2" ParentId="310" CreationDate="2009-11-10T13:49:02.567" Score="3" ViewCount="" Body="&lt;p&gt;I agree with Scott above: A micro is the way to go here, unless you're just playing about with the specific intention of learning oscillators.  Making the amplitude adjustable could be a bit tricky, though.  Can you tell us more about that?  Does it need to be adjusted once (or very infrequently) for calibration purposes, or do you need to be able to change it frequently?  Does it need to be user-adjustable, or will it adjust based on parameters in the circuit?  What is the range of the amplitude you need, and the resolution (or rather, how many steps) you need in that range?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest method is to just build an adjustable gain amplifier using a potentiometer for the adjustment, if you only need the amplitude adjustable for calibration purposes or for infrequent manual adjustment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to make it adjustable is to use the PWM output of the micro and feed that to a filter, but you'd have to build a filter that passed 150kHz and smoothed out anything at your PWM frequency (which will depend on your micro frequency).  This will be difficult and will strictly limit your resolution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need a square wave above the micro voltage, you'll definitely need an amplifier circuit, and you can probably just control the gain of the amplifier with the micro as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Come to think of it, are you sure you need to control amplitude?  You can probably control whatever you are trying to control through other tricks as well.  If you could share more information, we can probably give you other control ideas.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-11-10T13:49:02.567" CommentCount="5" />
  <row Id="319" PostTypeId="2" ParentId="317" CreationDate="2009-11-10T14:10:21.503" Score="4" ViewCount="" Body="&lt;p&gt;I'm thinking a PIR sensor (available from many places - &#xA;ebay $9.99 &lt;a href=&quot;http://cgi.ebay.co.uk/Pyroelectric-Infrared-PIR-Motion-Sensor-Detector-Module%5FW0QQitemZ110423920715QQcmdZViewItemQQptZBI%5FSecurity%5FFire%5FProtection?hash=item19b5c7504b&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;&#xA; Adafruit $10 + P&amp;amp;P &lt;a href=&quot;http://www.adafruit.com/index.php?main%5Fpage=product%5Finfo&amp;amp;cPath=35&amp;amp;products%5Fid=189&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt; )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Together with a microprocessor with a serial interface e.g. ATTiny2313v $1.48 from mouser &lt;a href=&quot;http://www2.mouser.com/ProductDetail/Atmel/ATtiny2313V-10PI/?qs=sGAEpiMZZMvu0Nwh4cA1wUVlLgw9m2DPnWKVJPG9t94%3d&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;. The ATTiny will run with no additional components, using an internal oscillator. You may need a bit more memory (RAM/Flash) than this but even an ATMega168 is not too expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use a SD card to store the data in (fast and non-volatile) - can be interfaced directly to ATTIny via SPI (need a SD card holder). No need to use FAT as the data can be read out by the controller into the serial interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use the serial interface to plug your laptop into (bring a USB-TTL serial convertor).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So with enclosure and assorted connectors etc you will probably come in at about $20.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PIR operates at 3.3v (you can bypass the 3.3v regulator to do this) and the ATTiny will work quite happily at that voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Battery consumption is the only other issue here - PIR consumption is the one to worry about here - the microcontroller can run in full sleep mode (micro amps) almost all the time, waking the microcontroller up via an interrupt when the PIR detects something.&#xA;The PIR is rated at 4.7mA when run from 12v. You can get rechargable AA cells with around 2000 mAH, or LiPoly cells - so these would last just over two weeks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So all in all yes it is possible - but it may cost a few $ more than your budget.&lt;/p&gt;&#xA;" OwnerUserId="9" LastEditorUserId="9" LastEditorDisplayName="" LastEditDate="2009-11-10T14:18:04.430" LastActivityDate="2009-11-10T14:18:04.430" CommentCount="2" />
  <row Id="320" PostTypeId="2" ParentId="91" CreationDate="2009-11-10T14:18:48.893" Score="1" ViewCount="" Body="&lt;p&gt;You could get some industrial velcro and sew it both onto the lilypad and the clothing. Some of the Thinkgeek screenshirts work this way: they have the loop-part on the shirt and the hook part on the hardware.&lt;/p&gt;&#xA;" OwnerUserId="236" LastActivityDate="2009-11-10T14:18:48.893" />
  <row Id="321" PostTypeId="1" AcceptedAnswerId="461" CreationDate="2009-11-10T14:31:39.517" Score="5" ViewCount="1111" Body="&lt;p&gt;What is the best way I can hook &lt;a href=&quot;http://cid-acbfe2d16cd0ace8.skydrive.live.com/self.aspx/Public/18068op.pdf&quot; rel=&quot;nofollow&quot;&gt;this 5x7 LED matrix&lt;/a&gt; to an Arduino board?&lt;/p&gt;&#xA;" OwnerUserId="6" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2011-02-05T05:00:38.577" LastActivityDate="2011-02-05T05:00:53.337" Title="How to hook up a 5x7 LED matrix to Arduino?" Tags="&lt;arduino&gt;&lt;led&gt;&lt;matrix&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="322" PostTypeId="2" ParentId="263" CreationDate="2009-11-10T15:17:33.763" Score="1" ViewCount="" Body="&lt;p&gt;I enjoy your idea, and I think it is an excellent one, I would just change the hardware just a little.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have heard of a zener diode, I think it is more what you are looking for. They hold a constant voltage over a wide range of currents, and you can get one for 1.8 V. A zener is a diode that has a reverse breakdown voltage that is very controlled, and does not change a noticeable amount. The 5.1V zener diodes are the most temperature independent due to the physical parameters, but a 1.8 can be also.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LED you are using have a decently large operating rage, so a variance in your power supply should not be a large problem for circuit, which removes the reason people normally use resistors, as a power limiter, but we often measure that as a current/voltage limiting device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing I worry about you overlooking is the maximum current your micro-controller can output, but this has been brought up in other posts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a Zener to drop a voltage down to an operating range for another device is a common practice I read about and have used myself. I am sure you will be happy with the result.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-10T15:17:33.763" CommentCount="2" />
  <row Id="323" PostTypeId="2" ParentId="91" CreationDate="2009-11-10T15:40:24.593" Score="1" ViewCount="" Body="&lt;p&gt;Take a look at &lt;a href=&quot;http://speedvest.com/&quot; rel=&quot;nofollow&quot;&gt;http://speedvest.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;it about a vest with EL wire from coolight.com showing speed of bycicle&lt;/p&gt;&#xA;&#xA;&lt;p&gt;good luck&lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2009-11-10T15:40:24.593" />
  <row Id="324" PostTypeId="2" ParentId="263" CreationDate="2009-11-10T16:38:35.203" Score="3" ViewCount="" Body="&lt;p&gt;davr has the best answer here.  Diodes in forward bias have a current that is very sensitive to voltage. ( and temperature ... )  So you do not regulate the voltage, you regulate the current.  A resistor is the simplest ( and not very energy efficient way to do this ).  &lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-10T16:38:35.203" CommentCount="1" />
  <row Id="325" PostTypeId="2" ParentId="321" CreationDate="2009-11-10T17:47:14.980" Score="6" ViewCount="" Body="&lt;p&gt;A quick look at the datasheet shows that the individual LEDs are multiplexed, meaning that a single line can drive more than one LED.  In this case, all of the anodes in a column are electrically connected, and all of the cathodes in a row are electrically connected (or vice versa, depending on the model).  That means, whenever you manipulate a pin, you are manipulating that whole row or that whole column.  By choosing one column and one row, you can control an individual LED.  You can then manipulate all rows and one column, which will allow you to control a whole column at once.  To control all of them, you'll need to switch each column in sequence, changing which rows are active.  If you do this fast enough, it will look like they're always on.  This is called time multiplexing, or time-division multiplexing, since each column gets a slice of time in sequence.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an example of a project that uses a 5x7 matrix and time mulitplexing:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://heim.ifi.uio.no/haakoh/avr/&quot; rel=&quot;nofollow&quot;&gt;http://heim.ifi.uio.no/haakoh/avr/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Run with that for a while, and come on back if you have further questions or add comments to refine the question.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-11-10T17:47:14.980" />
  <row Id="326" PostTypeId="2" ParentId="276" CreationDate="2009-11-10T17:57:13.697" Score="9" ViewCount="" Body="&lt;p&gt;Hello, Paul here, Teensy developer.  Obviously my opinion about whether you should use a Teensy is biased, but in terms of technical accuracy, well, I do know the details!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, Teensy definitely does work with the Arduino IDE when you install the Teensyduino add-on package.  There is a very easy-to-use an automated installer.  Then you can just choose Teensy from the Tools-&gt;Boards menu.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Definitely if you are looking to interface a serial device, like a GPS with NEMA 0183 output, a PLC with Modbus, or any number of other serial devices, Teensy is much easier than Arduino with the '168 or '328 chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Arduino uses the serial port for downloading code.  You need the RXD and TXD pins connected to the FTDI USB-serial converter chip on the Arduino, at least while you're loading new code.  So your first issue is how your device will drive the RXD pin and not conflict.  You can, for example, modify the Arduino with a DPDT toggle switch, so you can flip the RXD/TXD signals between the USB-serial converter and your device.  Then you have to flip the switch every time, unless you come up with something more automated.  There are other approaches, but fundamentally, the Arudino uses the serial port, so if you want to use it too, you have to go to some effort to somehow share.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With Teensy, there is a direct USB port that is used for all development.  You can directly connect to the Teensy's serial RXD/TXD because it's not used for anything else.  You use the serial port in the same functions (begin, available, read, write), but you do have to add one line to define the name you want.  This page has the details:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.pjrc.com/teensy/td_uart.html&quot; rel=&quot;nofollow&quot;&gt;http://www.pjrc.com/teensy/td_uart.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While your program is running, you can use Serial.print(), which will print through the USB to to the Arduino Serial Monitor.  It works just like Serial.print(), except it's much faster at full USB speed than Arduino's serial which has a 115.2 kbps maximum.  The USB is also double buffered, so a typical call to Serial.print() will return control to your program very quickly, whereas Arduino waits (the serial port does buffer 2 bytes).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Teensy has real USB, which in theory can implement almost any type of device.  In practice, with Teensyduino you're limited to the types provided in the Tools-&gt;Boards menu.  Currently, the choice is either USB Serial (which gives you something almost exactly like Arduino, but much faster), or USB Keyboard/Mouse.  Both support Serial.print() to the Serial Monitor.  With keyboard/mouse, the Teensy becomes a keyboard and mouse while it's running your program.  You can type with Keyboard.print() (caution: save your work first!) and use funtions like Mouse.move(x, y).  Other device types are planned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One way the Teensy differs from Arudino is the USB changes every time you load new code and reboot (Arduino always appears as a USB-serial chip).  Teensyduino tries very hard to give you an experience very close to a real Arduino.  However, there is no physical reset signal (Arduino uses the DTR signal from its USB-serial chip).  Auto-reset is emulated in software, so in most cases you can just click the upload button.  But if it's not running previously-loaded code or it crashed with interrupts disabled, you do have to physically press the reset button on the Teensy (much like the older Arduinos before auto-reset was added).  A message tells you if you need to push the button.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are planning to reuse existing Arduino code, in most cases it works great on the Teensy.  Especially if that code uses the Arduino (wiring) functions like pinMode, digitalWrite, etc, it will almost certainly work.  The Teensy has a very similar set of AVR timers and peripherals, so most code that directly accesses the hardware works with little or no modification.  However, some Arduino programs (and even some poorly designed libraries) hard-code assumptions, for example, the RXD and TXD pins corresponding to Arduino pins 0 and 1.  If you're planning to re-use code or use certain libraries, it's worth checking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Teensy does not really work below 2.5 volts, and the USB can't work with less than 3 volts.  It can be powered externally by simply applying power to the pins, but that power must be regulated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried hard not to make this into a sales pitch.  I hope you'll consider the technical details and make the choice that's best for your project.&lt;/p&gt;&#xA;" OwnerUserId="237" LastActivityDate="2009-11-10T17:57:13.697" CommentCount="2" />
  <row Id="327" PostTypeId="2" ParentId="310" CreationDate="2009-11-10T20:42:36.367" Score="3" ViewCount="" Body="&lt;p&gt;As advised by @Scott Murphy and @Lou, I'm going to implement this with an Arduino (with which I'm familiar) running into an amplifier. Depending on power consumption it may make sense to switch to some other circuit later, but I'll cross that bridge when I come to it - if the oil burns and power use is higher than it could be. In that case I'll try a 555 circuit or modify the astable multivibrator I mentioned, as advised.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For amplification, for now, I'll use a headphone amp, and put together an op amp circuit if needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will update here as the implementation comes together (or falls apart).&lt;/p&gt;&#xA;" OwnerUserId="84" LastActivityDate="2009-11-10T20:42:36.367" CommunityOwnedDate="2009-11-10T20:42:36.367" CommentCount="1" />
  <row Id="328" PostTypeId="1" AcceptedAnswerId="345" CreationDate="2009-11-10T20:58:01.757" Score="4" ViewCount="219" Body="&lt;p&gt;I've been playing around with a Lego Mindstorms NXT robot, gearing it for speed and power.  To my dismay, when geared for power, it wasn't any harder to stop than when geared for speed -- I suspect that it doesn't have very good traction (as there really isn't much mass pushing down on the wheels).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be nice to be able make quantitative statements about how much force (and thus, how much torque) a robot puts out.  Does anyone know how I can do this?  Would, for example, a spring scale or force gauge &lt;a href=&quot;http://www.spectrumed.com/viewer/?id=09SecScience&amp;amp;p=248&amp;amp;zl=2&quot; rel=&quot;nofollow&quot;&gt;like one of these&lt;/a&gt; work well for this purpose, and if so, what is a good maximum rating to look for?&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-12T23:45:52.933" LastActivityDate="2009-11-12T23:45:52.933" Title="Measuring force developed by a robot" Tags="&lt;motor&gt;&lt;torque&gt;&lt;indicator&gt;&lt;robotics&gt;&lt;measurement&gt;" AnswerCount="3" />
  <row Id="329" PostTypeId="2" ParentId="328" CreationDate="2009-11-10T21:35:09.170" Score="0" ViewCount="" Body="&lt;p&gt;It would at least provide a starting point, but if your Robot has poor traction you don't want the weight of your Newton Balance to affect your results in either direction, if possible. There are devices which measure breaking strain on ropes etc (I'm not sure what they're called), they measure up to a value but don't decrease until you reset it, that might be more use, but I don't know whether they come in a small enough (or accurate enough) version. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Strain Gauges?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit(2): Maybe a Secondary School Physics Textbook might have some suggestions for experiments that could be adapted to measure this.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-10T21:35:09.170" />
  <row Id="330" PostTypeId="1" AcceptedAnswerId="331" CreationDate="2009-11-10T22:56:24.180" Score="1" ViewCount="991" Body="&lt;p&gt;Do the Arduino Duemilanove USB Board with Atmega328 come with the Arduino bootloader?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-10T23:04:00.417" Title="ATMega chips come with the Arduino bootloader" Tags="&lt;arduino&gt;&lt;atmega&gt;&lt;bootloader&gt;&lt;duemilanove&gt;" AnswerCount="1" />
  <row Id="331" PostTypeId="2" ParentId="330" CreationDate="2009-11-10T23:04:00.417" Score="2" ViewCount="" Body="&lt;p&gt;Yes - all boards with ATMega labelled Arduino come with the bootloader. Individual chips will say specifically, generaly if ordered from an Arduino supplier then they will have bootloader, whilst if ordered from generic electronic supplier they will not.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-10T23:04:00.417" CommentCount="4" />
  <row Id="332" PostTypeId="1" CreationDate="2009-11-10T23:26:43.387" Score="8" ViewCount="993" Body="&lt;p&gt;I'm a student studying electronics and I'm having trouble understanding the concept behind current sourcing and current sinking. We've covered it in a lab using a 7404 and an LED and all that. Just having trouble getting an intuitive understanding of what exactly is happening. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone can take a crack at explaining, it would be greatly appreciated. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just to be sure, I understand what the process is, in terms of current flow and from input to output and vice versa. Just not getting why one is preferred over the other, and what it has to do with having a floating Hi input or why I wouldn't want to have a floating Hi.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Input would be greatly appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="217" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-12T23:42:39.783" LastActivityDate="2010-04-29T22:28:33.573" Title="current sourcing, current sinking" Tags="&lt;led&gt;&lt;electronics&gt;&lt;current&gt;&lt;sinking&gt;&lt;sourcing&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="333" PostTypeId="1" CreationDate="2009-11-10T23:38:21.307" Score="5" ViewCount="503" Body="&lt;p&gt;Hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I implement (or maybe there is an IC that already does that) a board whose input would be I2C and output would be analog voltage (0V - 5V) ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Eventually I would like to connect a couple of those to the IO pins of an arduino effectively creating digital to analog outputs.&lt;/p&gt;&#xA;" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-06-11T15:17:39.370" LastActivityDate="2010-06-11T15:17:39.370" Title="Implementing I2C to analog" Tags="&lt;arduino&gt;&lt;i2c&gt;&lt;voltage&gt;&lt;analog&gt;&lt;dac&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="334" PostTypeId="2" ParentId="333" CreationDate="2009-11-11T00:00:20.983" Score="4" ViewCount="" Body="&lt;p&gt;You'd need an I2C based digital to analog convertor (DAC) of some type, a quick search turned up the following:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8736&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=8736&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2009-11-11T00:00:20.983" />
  <row Id="335" PostTypeId="2" ParentId="333" CreationDate="2009-11-11T00:03:04.727" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Digital%5Fpotentiometer&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a Wikipedia entry on digital Potentiometers. These digital pots can act as analog output on the arduino. It would act as a regular potentiometer sweeping across all voltages from 0 - 5V through serial(of some sort) commands. If you didn't have to have I2C then you could use &lt;a href=&quot;http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/potentiometer/List/0/SortField/4/ProductID/246/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; digital pot from Parralax or &lt;a href=&quot;http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&amp;amp;storeId=10001&amp;amp;catalogId=10001&amp;amp;productId=1777604&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; chip from Jameco. The only I2C chips I have seen are all surface mount instead of through-hole, this makes them harder to work with and. &lt;a href=&quot;http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?langId=-1&amp;amp;storeId=10001&amp;amp;catalogId=10001&amp;amp;freeText=digital%20potentiometers%20i2c&amp;amp;search%5Ftype=jamecoall&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is the link to all of Jameco's I2C digital potentiometers. I hope this was helpful and the best of luck!&lt;/p&gt;&#xA;" OwnerUserId="92" LastActivityDate="2009-11-11T00:03:04.727" CommentCount="1" />
  <row Id="336" PostTypeId="2" ParentId="333" CreationDate="2009-11-11T00:19:49.680" Score="3" ViewCount="" Body="&lt;p&gt;Just so you know, an AVR (the chip used in an Arduino) can already produce 'analog' voltages via using PWM + a capacitor to smooth the waveform (capacitor is not even needed in some cases). It's not quite as high resolution as a dedicated DAC chip, but it is good enough for many needs.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-11T00:19:49.680" />
  <row Id="337" PostTypeId="2" ParentId="332" CreationDate="2009-11-11T01:23:32.877" Score="13" ViewCount="" Body="&lt;p&gt;short version: current sources connect things to Vcc, current sinks connect them to ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;longer version:&#xA;The following is a practical explanation of current-sources/sinks as used in microcontrollers &amp;amp; TTL logic. For a more theoretical description, see the &lt;a href=&quot;http://en.wikipedia.org/wiki/Current%5Fsource&quot; rel=&quot;nofollow&quot;&gt;Wikipedia page on current source&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some devices are very good at creating a connection to ground. (or whatever the lowest voltage is in the system, e.g. 0V)  Other devices are very good at creating a connection to Vcc. (or whatever is the highest voltage in the system, e.g. +5V)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Those devices that are good connecting to ground are called current sinks; those good at connecting to Vcc are called current sources.  Until recently (the last decade or so), it was unusual for integrated circuits to be good at being both.  Most were good at being current sinks but were terrible at being current sources.  So at lot of circuits were designed so all the chip had to do was connect to ground to make the circuit do its thing.  Many chips still have an asymmetric current drive ability and function better switching to ground than switching to Vcc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To me a good example of current source and current since are the standard &quot;switch&quot; configuration of a PNP and NPN transistor.  A PNP is a good current source: you almost always connect its collector to Vcc, and it switches it on/off.  A NPN is a good current sink: its emitter is almost always connected to ground and it switches the ground connection on/off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why you choose one over the other often depends on the capabilities of the parts available to you.  For instance, an RGB LED is often a &quot;common-anode&quot; type where the anode (positive lead) is connected on all three LED elements, so to turn on an element you need to connect its lead to ground.  You can use three pins on a microcontroller to do this (or three NPN transistors) and they would be acting as current sinks.&lt;/p&gt;&#xA;" OwnerUserId="215" LastEditorUserId="215" LastEditorDisplayName="" LastEditDate="2009-11-11T02:45:20.887" LastActivityDate="2009-11-11T02:45:20.887" />
  <row Id="338" PostTypeId="2" ParentId="328" CreationDate="2009-11-11T01:37:50.013" Score="3" ViewCount="" Body="&lt;p&gt;A cheap way to do it would be to have the robot pulling on a string  which runs over the edge of the the table (or to a pulley), and gradually add weights (such as washers) to the end of the string until the robot can't lift any more.&lt;/p&gt;&#xA;" OwnerUserId="222" LastActivityDate="2009-11-11T01:37:50.013" />
  <row Id="339" PostTypeId="1" AcceptedAnswerId="340" CreationDate="2009-11-11T10:59:32.737" Score="1" ViewCount="440" Body="&lt;p&gt;Does the Arduino chip get wiped of any (uploaded) code when you press the reset button?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you retrieve the code that is currently on the chip?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-11T11:32:59.910" Title="Arduino chip wipe on reset" Tags="&lt;arduino&gt;&lt;reset&gt;" AnswerCount="2" />
  <row Id="340" PostTypeId="2" ParentId="339" CreationDate="2009-11-11T11:08:31.140" Score="3" ViewCount="" Body="&lt;p&gt;No, nothing gets wiped and yes you can read the code and data currently on the chip. You do lose the contents of RAM when the chip loses power.&#xA;Avrdude is a useful program that will allow you to read and write the chip contents. The Arduino IDE uses avrdude to program the chip.&#xA;Lady Ada has a very good tutorial on &lt;a href=&quot;http://www.ladyada.net/learn/avr/avrdude.html&quot; rel=&quot;nofollow&quot;&gt;Avrdude&lt;/a&gt; - indeed her tutorials are all very good.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-11T11:08:31.140" CommentCount="1" />
  <row Id="341" PostTypeId="2" ParentId="339" CreationDate="2009-11-11T11:32:59.910" Score="1" ViewCount="" Body="&lt;p&gt;You can retrieve the compiled hex code from the chip (like an exe file for the microcontroller), but reconstructing the original Arduino sketch from it is nearly impossible.&lt;/p&gt;&#xA;" OwnerUserId="243" LastActivityDate="2009-11-11T11:32:59.910" CommentCount="4" />
  <row Id="342" PostTypeId="2" ParentId="333" CreationDate="2009-11-11T12:01:08.633" Score="8" ViewCount="" Body="&lt;p&gt;Consider the Microchip &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010547&quot; rel=&quot;nofollow&quot;&gt;TC1321&lt;/a&gt; it's an I2C digital to analog converter (DAC) with 10 bits of resolution (4.88mV/step), available in &lt;a href=&quot;http://en.wikipedia.org/wiki/Small-outline%5Fintegrated%5Fcircuit&quot; rel=&quot;nofollow&quot;&gt;SOIC8&lt;/a&gt; (you'll need an easy to solder adapter board [eg &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=494&quot; rel=&quot;nofollow&quot;&gt;sparkfun's&lt;/a&gt; or &lt;a href=&quot;http://futurlec.com/SMD%5FAdapters.shtml&quot; rel=&quot;nofollow&quot;&gt;futurlec's&lt;/a&gt;) and operates from 5 volts. If you're OK with only 8 bits (19.5mV/step) consider the &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010546&quot; rel=&quot;nofollow&quot;&gt;TC1320&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both chips are available from &lt;a href=&quot;http://ca.mouser.com/Semiconductors/Integrated-Circuits-ICs/Logic-ICs/%5F/N-6j77x?Keyword=TC132&amp;amp;FS=True&quot; rel=&quot;nofollow&quot;&gt;Mouser&lt;/a&gt; or &lt;a href=&quot;http://www.microchipdirect.com/productsearch.aspx?Keywords=tc132&quot; rel=&quot;nofollow&quot;&gt;Microchip Direct&lt;/a&gt; for around $2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can use SPI instead of I2C, your options are easier, the MCP4821 and MCP4822 are single and dual SPI DAC chips that come in nice PDIP8 packages. Again they cost about $2 from the usual places (mouser, digikey, microchip direct, farnell).&lt;/p&gt;&#xA;" OwnerUserId="243" LastEditorUserId="243" LastEditorDisplayName="" LastEditDate="2009-11-20T16:09:12.017" LastActivityDate="2009-11-20T16:09:12.017" CommentCount="6" />
  <row Id="343" PostTypeId="2" ParentId="297" CreationDate="2009-11-11T12:08:56.107" Score="6" ViewCount="" Body="&lt;p&gt;Microchip's PIC18s with built-in ethernet are excellent for this, just add a magjack (or other connector with built in magnetics) and download their TCP/IP stack. You'll be pinging things in no time. For more grunt, the PIC24 and PIC32 also have TCP/IP stacks designed to run with one of the SPI Ethernet MAC/PHY parts they offer (ENC624J600 or ENC628J60).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ST also recently enhanced their ARM Cortex based STM32 line to include on-chip ethernet, but you'll need an external PHY and magnetics. It's an option if you're already looking at the PIC32.&lt;/p&gt;&#xA;" OwnerUserId="243" LastActivityDate="2009-11-11T12:08:56.107" />
  <row Id="344" PostTypeId="2" ParentId="272" CreationDate="2009-11-11T12:20:39.920" Score="3" ViewCount="" Body="&lt;p&gt;The RTL8305SC doesn't require any actual code, but you need to read through it's &lt;a href=&quot;http://realtek.info/pdf/rtl8305sc.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; for a good description of how to wire it up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, connect the output of the PIC's ethernet to one of the RTL8305's ports in a cross-over (or enable auto crossover on the RTL8305). Connect the rest f the RTL8305's ports to ethernet jacks (w/ magnetics).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While I haven't used this particular switch, it's usually easier if you release the switch from reset, then enable the PIC's ethernet core. But if you do things the other way, it will just look like an unplugged cable to the PIC.&lt;/p&gt;&#xA;" OwnerUserId="243" LastActivityDate="2009-11-11T12:20:39.920" />
  <row Id="345" PostTypeId="2" ParentId="328" CreationDate="2009-11-11T12:54:43.960" Score="4" ViewCount="" Body="&lt;p&gt;I've always used a standard spring kitchen scale rotated. Put the scale between the robot and a wall (or another fixed object) and let the robot push... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW: This is one of the tips that are also suggested in the robotic sumo chapter of &quot;Building Robots With Lego Mindstorms&quot; book by Mario and Giulio Ferrari (two italian RCX gurus). So, it's really &quot;in topic&quot; with the original question. &lt;/p&gt;&#xA;" OwnerUserId="244" LastEditorUserId="244" LastEditorDisplayName="" LastEditDate="2009-11-11T19:43:00.950" LastActivityDate="2009-11-11T19:43:00.950" CommentCount="1" />
  <row Id="346" PostTypeId="2" ParentId="333" CreationDate="2009-11-11T14:09:57.123" Score="6" ViewCount="" Body="&lt;p&gt;Depending on what you are driving, if you have an Arduino you already have three to six Analog outputs, as you can use the AnalogWrite function to set the duty cycle of the PWM pins.  The frequency is approximately 490 Hz, more than sufficient for LEDs (again, it depends on your application).  You can set the value from 0 to 255, giving you a resolution of (5v / 256 =) .020V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to determine if 490 Hz is a sufficient rate, but PWM is used to simulate analog voltage for many applications, and it may fit yours without extra parts or programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may also consider using a filter (capacitor-resistor network) to smooth out the square wave.  It'll give you more leeway in the applications you can control, and passives are cheap, but depending on your application it may not even be necessary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/en/Reference/AnalogWrite&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Reference/AnalogWrite&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-11-11T14:09:57.123" />
  <row Id="347" PostTypeId="1" AcceptedAnswerId="348" CreationDate="2009-11-11T16:44:12.617" Score="3" ViewCount="547" Body="&lt;p&gt;If I upgrade my arduino from the ATMega 168 to ATMega 328 will I be able to use the ATMega 168 like a stock chip from the factory or will the bootloader prohibit this? In other words, will I be able to overwrite the bootloader, with my usbtiny ISP programmer, on the 168 to use as a Atmel stock chip with Avrdude? Is there any special steps I would need to take like reseting fuses?&lt;/p&gt;&#xA;" OwnerUserId="92" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-12T23:38:26.200" LastActivityDate="2009-11-15T15:21:56.140" Title="Arduino Bootloader" Tags="&lt;avr&gt;&lt;arduino&gt;&lt;bootloader&gt;&lt;atmega168&gt;&lt;atmega328&gt;" AnswerCount="3" />
  <row Id="348" PostTypeId="2" ParentId="347" CreationDate="2009-11-11T17:19:02.673" Score="3" ViewCount="" Body="&lt;p&gt;Yes, you can reprogram the chip.  I did the same when I upgraded my Arduino from a 168 to a 328 two weeks ago.  The chip works great in another application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take note, of course, that you may need to change fuses depending on what kind of board you had and what kind of board you are moving it to.  The most common, I would imagine (and the ones I had to reset) dealt with changing to the internal oscillator and setting dividers instead of using an external crystal.  There is no comprehensive list of fuse changes, though, because it depends on what kind of circuit you're moving the chip to.  YMMV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--Edit--&#xA;As JohnC said, yes, reprogramming of fuses should be done BEFORE you remove it from the Arduino.  Since the Arduino is fused to use an external oscillator, the chip will not do a darn thing if placed on a board without an oscillator.&lt;/p&gt;&#xA;" OwnerUserId="11" LastEditorUserId="11" LastEditorDisplayName="" LastEditDate="2009-11-11T17:56:03.940" LastActivityDate="2009-11-11T17:56:03.940" />
  <row Id="349" PostTypeId="2" ParentId="347" CreationDate="2009-11-11T17:48:51.550" Score="2" ViewCount="" Body="&lt;p&gt;I would reset the fuses to factory default whilst the 168 is still in the Arduino board. If the fuses are configured for an external oscillator (as they are in the Arduino) and there isn't one then you will not be able to re-program without using a high voltage programmer. Setting to factory default sets the chip up to use an internal oscillator.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-11T17:48:51.550" />
  <row Id="350" PostTypeId="1" AcceptedAnswerId="353" CreationDate="2009-11-11T19:29:00.990" Score="3" ViewCount="613" Body="&lt;p&gt;If I have an unkown device which talk I2C or SPI how can I reverse engineer the protocol. Basically I am looking for something similar as &lt;em&gt;snoop&lt;/em&gt; or &lt;em&gt;tcpdump&lt;/em&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For software Mac is preferred but can also run PC under parallels.&lt;/p&gt;&#xA;" OwnerUserId="94" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-12T23:36:46.760" LastActivityDate="2009-11-12T23:36:46.760" Title="How to reverse engineer I2C and SPI protocols?" Tags="&lt;serial&gt;&lt;mac&gt;&lt;pc&gt;&lt;spi&gt;&lt;i2c&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="351" PostTypeId="2" ParentId="350" CreationDate="2009-11-11T19:47:32.280" Score="1" ViewCount="" Body="&lt;p&gt;First off you need something to capture the signals. The standard way of doing this is with a &lt;a href=&quot;http://en.wikipedia.org/wiki/Logic%5Fanalyzer&quot; rel=&quot;nofollow&quot;&gt;Logic Analyzer&lt;/a&gt;. I've collected &lt;a href=&quot;http://spreadsheets.google.com/pub?key=rmNr4Eeren8jBG7MXfHYxsQ&amp;amp;output=html&quot; rel=&quot;nofollow&quot;&gt;a list of PC-based logic analyzers&lt;/a&gt;, basically how they work is they capture the signal data and transfer it for display and processing on your PC. Most of them include software for decoding SPI and I2C, showing you what bytes were sent and received by the devices. &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-11T19:47:32.280" CommentCount="2" />
  <row Id="352" PostTypeId="2" ParentId="350" CreationDate="2009-11-11T20:12:46.143" Score="3" ViewCount="" Body="&lt;p&gt;Just about any of the modern USB-based logic analyzers also have protocol analyzers for common serial protocols like RS-232, SPI, &amp;amp; I2C.  I know of none that have shipping Mac OS X drivers.  However, the &lt;a href=&quot;http://www.saleae.com/logic/&quot; rel=&quot;nofollow&quot;&gt;Saleae Logic&lt;/a&gt; logic analyzer has been getting good press and they promise some cross-platform drivers in the future.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an Intronix LogicPort USB analyzer and it's okay. I run it out of either a VMWare WinXP VM on my Mac or on an old throw-away laptop running WinXP.  If you're a Mac user doing hardware hacking, I highly recommend getting VMWare or similar so you can run the occasional bit of Windows-only software.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-11T20:12:46.143" />
  <row Id="353" PostTypeId="2" ParentId="350" CreationDate="2009-11-11T21:05:41.147" Score="5" ViewCount="" Body="&lt;p&gt;i think that you have to consider using the pirate bus an open hardware project that cost just 30 dollars including worldwide shipping&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/the-bus-pirate/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/the-bus-pirate/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;it work with a gui for mac osx and windows&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i hope that will help&lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2009-11-11T21:05:41.147" CommentCount="1" />
  <row Id="354" PostTypeId="1" CreationDate="2009-11-11T22:29:58.363" Score="2" ViewCount="174" Body="&lt;p&gt;Will they survive wet weather?&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-11T22:37:24.963" LastActivityDate="2010-08-06T22:32:40.063" Title="Has anyone used a SpokePOV in the rain?" Tags="&lt;waterproof&gt;" AnswerCount="4" />
  <row Id="355" PostTypeId="1" CreationDate="2009-11-11T22:33:44.677" Score="4" ViewCount="1419" Body="&lt;p&gt;I am using an Arduino to read a keypad and open an electric strike upon keypad PIN entry. For this sketch I wanted to use some sort of lightweight encryption to store the PINs in EEProm.&#xA;Does anyone know of such a library? I have heard it may be possible using TwoFish.&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-12T23:35:31.457" LastActivityDate="2009-11-13T17:13:05.530" Title="Encryption Library for Arduino" Tags="&lt;arduino&gt;&lt;microcontroller&gt;&lt;encryption&gt;&lt;pin&gt;" AnswerCount="7" />
  <row Id="356" PostTypeId="2" ParentId="354" CreationDate="2009-11-11T22:44:30.173" Score="2" ViewCount="" Body="&lt;p&gt;There's a discussion about waterproofing etc &lt;a href=&quot;http://forums.adafruit.com/viewtopic.php?f=17&amp;amp;t=12497&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, in the SpokePOV Forum on ladyada's site.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-11T22:44:30.173" />
  <row Id="357" PostTypeId="2" ParentId="354" CreationDate="2009-11-11T22:50:13.003" Score="2" ViewCount="" Body="&lt;p&gt;Here is someones feedback from when they were using it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://forums.adafruit.com/viewtopic.php?f=17&amp;amp;t=12283&quot; rel=&quot;nofollow&quot;&gt;http://forums.adafruit.com/viewtopic.php?f=17&amp;amp;t=12283&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;The contacts and components will corrode. You will need to waterproof it.&quot;&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-11T22:50:13.003" />
  <row Id="358" PostTypeId="2" ParentId="355" CreationDate="2009-11-11T23:05:43.927" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.osix.net/modules/article/?id=96&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a method of simple encription in C that could easily be ported to the Arduino. This seems like the easiest way to encrypt data with the arduino's limited resources.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-EDIT- To keep the key out of your program you could make half of the PIN the key. This means that your program takes the key half of the PIN to decrypt the encrypted 1/2 PIN stored in EEProm. If the decrypted key from EEProm match the part of your pin that is not the key, the door would unlock. This would only work in a situation where it is not possible for the intruders to break down the door or reprogram the Arduino. &lt;/p&gt;&#xA;" OwnerUserId="92" LastEditorUserId="92" LastEditorDisplayName="" LastEditDate="2009-11-12T11:40:20.207" LastActivityDate="2009-11-12T11:40:20.207" CommentCount="1" />
  <row Id="359" PostTypeId="2" ParentId="355" CreationDate="2009-11-11T23:06:39.560" Score="1" ViewCount="" Body="&lt;p&gt;The problem I forsee is that if they can see your pins they can also see your program which encrypts/checks/decrypts your pins. Plus if they have your chip, can they not just alter the program to always give a positive result (effectively bypassing the check) for any pin entered.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-11T23:06:39.560" />
  <row Id="360" PostTypeId="2" ParentId="355" CreationDate="2009-11-11T23:46:46.170" Score="1" ViewCount="" Body="&lt;p&gt;How do you plan to decode the encrypted PINs, in order to check if the user entered a valid PIN? You'll need to store the decryption key...at which point if the attacker can read your eeprom, he can also read your flash to find the encryption key. Basically rendering your entire encryption completely useless. Also as the other people said, if he already has the ability to read your chip, he could just write a new program. Much simpler to just kick the door open, I doubt anyone would ever go to the trouble of trying to hack your chip.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-11T23:46:46.170" />
  <row Id="365" PostTypeId="2" ParentId="355" CreationDate="2009-11-12T01:26:22.783" Score="8" ViewCount="" Body="&lt;p&gt;That link Hristos posted, while possibly useful, certainly doesn't count as &quot;encryption&quot;. It's really only &quot;obfuscation&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Proper cryptography is notoriously easy to get wrong, even for people who know the math.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In response to the original post - what are the attack methods that would let someone get access to the PINs in the EEProm? Surely if they've got &lt;em&gt;that&lt;/em&gt; far into your electronics they can just &quot;snip the red wire&quot; and open the door?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you somehow &lt;em&gt;do&lt;/em&gt; have a system where attackers might get hold of the EEProm contents without already having enough access to open your door, you probably want to redesign it. You &lt;em&gt;could&lt;/em&gt; look at one-way hash functions similar to Unix password hashing - that way the EEProm doesn't need t contain a decryption key - the problem is the search space for PINs is &lt;em&gt;very&lt;/em&gt; small - if I can download the hashed version of the PIN, I can pretty quickly try all 10,000 possible PINs, I suspect any modern-ish laptop will run all of them in a few seconds.&lt;/p&gt;&#xA;" OwnerUserId="20" LastActivityDate="2009-11-12T01:26:22.783" CommentCount="1" />
  <row Id="367" PostTypeId="2" ParentId="297" CreationDate="2009-11-12T02:49:49.367" Score="2" ViewCount="" Body="&lt;p&gt;checkout &lt;a href=&quot;http://tuxgraphics.org/electronics/200606/article06061.shtml&quot; rel=&quot;nofollow&quot;&gt;tuxgraphics&lt;/a&gt; for a nice solution.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-12T02:49:49.367" CommentCount="2" />
  <row Id="370" PostTypeId="2" ParentId="224" CreationDate="2009-11-12T04:38:16.177" Score="1" ViewCount="" Body="&lt;p&gt;Altho its not very strong, I have had great results with liquid latex.&#xA;It can be found at costume shops and dries to a latex coating not unlike a condom.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The coolest thing about it is if you need to modify anything it is easially peeled off and &#xA;reapplied with as many coats as you think you require.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In australia its about $8au for 30ml which has so far done 3 4 by 6&quot; pcbs and 2 zombie costumes... hehe&lt;/p&gt;&#xA;" LastActivityDate="2009-11-12T04:38:16.177" />
  <row Id="372" PostTypeId="1" AcceptedAnswerId="393" CreationDate="2009-11-12T07:10:41.983" Score="3" ViewCount="561" Body="&lt;p&gt;How do i connect bluetooth to Lilypad Arduino?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-12T23:40:02.250" Title="Connecting bluetooth to Lilypad Arduino" Tags="&lt;arduino&gt;&lt;lilypad&gt;&lt;bluetooth&gt;" AnswerCount="2" />
  <row Id="374" PostTypeId="2" ParentId="226" CreationDate="2009-11-12T08:07:26.767" Score="5" ViewCount="" Body="&lt;p&gt;Another option for hardware may be the Bus Pirate at $27.15(sold though seedstudio) which also do other things. I haven't used it for JTAG yet, but this is what the manual says: &lt;a href=&quot;http://dangerousprototypes.com/bus-pirate-manual/bus-pirate-jtag-guide/&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-12T08:07:26.767" />
  <row Id="376" PostTypeId="1" CreationDate="2009-11-12T09:26:42.110" Score="8" ViewCount="662" Body="&lt;p&gt;How do you unit test your assembly code?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm working on a serial servo controller as part of a hexapod robot project and the code has got to the point where it's becoming complicated ;) Anyway, I'm used to using unit tests in my day job as a C++ server developer and so have been trying to apply the same kinds of testing to my AVR assembly code. I've worked out a way that works OK for me (see &lt;a href=&quot;http://www.lhexapod.com/blog/2009/10/repeatable-unit-testing-with-avr-assembler-and-avr-studio.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) but I'm interested if there are any standard tools or techniques that I'm missing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Updated:&lt;/strong&gt; For those of you that are interested the full source to the servo controller and the unit tests are now available &lt;a href=&quot;http://www.lhexapod.com/blog/2009/11/atmega168-64-channel-servo-controller-with-advanced-servo-commands.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="255" LastEditorUserId="255" LastEditorDisplayName="" LastEditDate="2009-11-30T18:45:23.380" LastActivityDate="2009-11-30T18:45:23.380" Title="Unit testing AVR assembly language" Tags="&lt;avr&gt;&lt;robotics&gt;&lt;serial&gt;&lt;servo&gt;" AnswerCount="2" />
  <row Id="378" PostTypeId="2" ParentId="376" CreationDate="2009-11-12T12:16:41.833" Score="1" ViewCount="" Body="&lt;p&gt;Interesting. After Christmas I was planning on looking into doing some Assembler with Pics, when I've got a bit more time I'll have a good look at your system. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One way I could see would be to script some sort of framework in a different language to create and tear down the mock objects etc, but how you would interface this to the chip/simulation would be a problem. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it becomes too onerous though then that will outweigh the benefits of unit testing and also make you less keen to use it.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-12T12:16:41.833" CommentCount="6" />
  <row Id="379" PostTypeId="2" ParentId="372" CreationDate="2009-11-12T13:07:01.763" Score="2" ViewCount="" Body="&lt;p&gt;There's a discussion &lt;a href=&quot;http://thehighlowtech.com/LilyPad/extend.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; with suggestions for various ways of extending a lilypad with a Sparkfun BlueSMiRF Bluetooth board.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-12T13:07:01.763" />
  <row Id="380" PostTypeId="2" ParentId="355" CreationDate="2009-11-12T13:27:24.233" Score="1" ViewCount="" Body="&lt;p&gt;These comments are really spot-on.  There's nothing wrong with trying to experiment to learn about encryption, but this isn't really a good project for learning such things.  You really want a good textbook and a computer, and as @bigiain says, the math is notoriously easy to get wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a better understanding of how cryptography works and what you're up against, the Handbook of Applied Cryptography is excellent and free:&#xA;&lt;a href=&quot;http://www.cacr.math.uwaterloo.ca/hac/&quot; rel=&quot;nofollow&quot;&gt;http://www.cacr.math.uwaterloo.ca/hac/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you just want to secure your project, this is an inefficient way of doing so.  If you're interested in cryptography, start with this book and a computer.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-11-12T13:27:24.233" CommentCount="2" />
  <row Id="387" PostTypeId="2" ParentId="355" CreationDate="2009-11-12T17:59:44.463" Score="1" ViewCount="" Body="&lt;p&gt;I hate not answering the question while asking another, but ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there some reason why your device is not tamper proof? I've seen push button switches in screw holes implemented 'on the bench' to detect the kind of tampering you are worried about. Then .. here comes the kid with a butane micro torch that manages to get your chip without unscrewing anything (or damaging the chip).. somehow, he knew the design of your tamper proof system which (also, hopefully) includes detecting changes in ambient light and / or sound. When the cover comes off, both become quite different .. day or night.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that's the case, it should be a two part system where the exposed pieces communicate with something where encryption is more easily implemented. Plus, checksums (help) account for the kid with the torch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you are asking a screwdriver to be a hammer.&lt;/p&gt;&#xA;" OwnerUserId="216" LastActivityDate="2009-11-12T17:59:44.463" />
  <row Id="388" PostTypeId="2" ParentId="267" CreationDate="2009-11-12T19:27:48.773" Score="4" ViewCount="" Body="&lt;p&gt;There are a number of AVR-USB based developer boards now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've personally used the before-mentioned Teensy and &lt;a href=&quot;http://fletchtronics.net/bumble-b&quot; rel=&quot;nofollow&quot;&gt;Bumble-B&lt;/a&gt; and think they're both great.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Teensy is nice, because it integrates really well with the Arduino environment.  This means you can do things like &quot;Mouse.init; Mouse.move(x,y)&quot;  instead of dealing with the low-level USB code yourself.  Both will run LUFA if you want it, though.&lt;/p&gt;&#xA;" OwnerUserId="265" LastActivityDate="2009-11-12T19:27:48.773" />
  <row Id="389" PostTypeId="2" ParentId="253" CreationDate="2009-11-12T20:08:00.030" Score="2" ViewCount="" Body="&lt;p&gt;I built a home made CO2 laser that would work. It's only 40 Watts but it can cut through thin plywood, luon, basla, and fabric as well.It can also score granite marble etc.  I had an old pair of jeans I cut the legs off with the laser to make a pair of shorts. It worked ok, but this is before I had a XY table so I had to move the jeans by hand. (dangerous!) The trick is to focus the beam to a very small spot. At that point its soo hot (&gt;3000 F) that the fabric just vaporizes and there is no chance for it to singe or catch on fire especially if the beam is traveling. I am just finishing an XY table with a flying beam design to go with the laser. It's controlled by a AVR microcontoller that talks to a PC through a serial port, and will interpret standard &quot;NC G-Codes&quot;. Then I can play with cutting patterns in all sorts of things. A YAG laser might work too and there is a lot less plumbing. If your intrested go to sams laser faq &lt;a href=&quot;http://repairfaq.org/sam/lasersam.htm&quot; rel=&quot;nofollow&quot;&gt;http://repairfaq.org/sam/lasersam.htm&lt;/a&gt; and you will find more information about building fixing using lasers than you ever tought. Also you can post to ALT.LASERS Just BE CAREFUL if you want to do this, lasers and their equipment can put a real hurting on you.&#xA;And remember &quot;Don't stare into the beam with the remaining eye!&quot;&lt;/p&gt;&#xA;" LastActivityDate="2009-11-12T20:08:00.030" />
  <row Id="390" PostTypeId="2" ParentId="355" CreationDate="2009-11-12T22:39:33.590" Score="6" ViewCount="" Body="&lt;p&gt;You don't want to encrypt passwords (PINs) -- you want to &lt;a href=&quot;http://en.wikipedia.org/wiki/Cryptographic%5Fhash%5Ffunction&quot; rel=&quot;nofollow&quot;&gt;hash&lt;/a&gt; them.  When someone enters a password, you hash that password, and compare the hash against the stored hash.  The advantage to this method (used for over 30 years) is that even if someone gets hold of the source and the hashes, they still can't tell what PINs match the hashes, as long as you choose a strong enough &lt;a href=&quot;http://en.wikipedia.org/wiki/Cryptographic%5Fhash%5Ffunction&quot; rel=&quot;nofollow&quot;&gt;hash function&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't want to implement encryption yourself -- you want to use someone else's library, particularly one with an open implementation that has been tested by a large community.  Encryption is hard, testing is hard, and testing encryption is damned hard, so get someone else to do it for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should checkout the &lt;a href=&quot;http://www.das-labor.org/wiki/AVR-Crypto-Lib/en&quot; rel=&quot;nofollow&quot;&gt;AVR Crypto Library&lt;/a&gt;, which is licensed with GPLv3.  There's also an implementation of &lt;a href=&quot;http://www.efton.sk/crypt/skein.htm&quot; rel=&quot;nofollow&quot;&gt;Skein for AVR&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="143" LastEditorUserId="143" LastEditorDisplayName="" LastEditDate="2009-11-13T17:13:05.530" LastActivityDate="2009-11-13T17:13:05.530" CommentCount="1" />
  <row Id="391" PostTypeId="1" AcceptedAnswerId="395" CreationDate="2009-11-12T23:06:04.733" Score="3" ViewCount="301" Body="&lt;p&gt;Hey,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to use bluetooth to grab the info off my 3pi rather then have it display on the small LCD.&#xA;Pololu provides a lib for serial communication.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wondering what the best bluetooth/serial module to use is?   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A friend recommended the Xbee module - Any thoughts?&lt;/p&gt;&#xA;" OwnerUserId="267" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-12T23:39:31.330" LastActivityDate="2009-11-13T07:47:25.427" Title="3pi Robot with Bluetooth" Tags="&lt;serial&gt;&lt;bluetooth&gt;&lt;robotics&gt;&lt;xbee&gt;&lt;3pi&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="393" PostTypeId="2" ParentId="372" CreationDate="2009-11-12T23:40:02.250" Score="3" ViewCount="" Body="&lt;p&gt;Without knowing which BT module you are using it will be a little difficult to help, but. As mentioned above using the BlueSMiRF board and some jumper wires you can attach&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;5v to PWR&lt;/li&gt;&#xA;&lt;li&gt;(-) to GND&lt;/li&gt;&#xA;&lt;li&gt;tx to RX - I &lt;/li&gt;&#xA;&lt;li&gt;rx to TX - O&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you have a specific BT module you are working with update your question and we can try to be more helpful.&lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-11-12T23:40:02.250" />
  <row Id="394" PostTypeId="2" ParentId="391" CreationDate="2009-11-12T23:48:53.073" Score="2" ViewCount="" Body="&lt;p&gt;Depends on your requirements but Xbee's wouldn't be a bad choice. They have a better range than Bluetooth &lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-11-12T23:48:53.073" CommentCount="1" />
  <row Id="395" PostTypeId="2" ParentId="391" CreationDate="2009-11-13T00:16:21.813" Score="4" ViewCount="" Body="&lt;p&gt;I would use bluetooth, it is easier to communicate with a computer. All you need for bluetooth is the module such as the BlueSMiRF from sparkfun and a Bluetooth usb dongle. Then all you would do is use the serial capabilities on the 3pi to communicate with the computer through the Bluetooth serial connection with a program like Hyperterminal. On the other hand, with the xbee you would need two transmitters and a way for the data to be read by a computer. One way to do this is through the &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8687&quot; rel=&quot;nofollow&quot;&gt;Xbee Explorer&lt;/a&gt;. Both options would be the same cost but the Xbee route takes more components and is more complex. &lt;a href=&quot;http://www.acroname.com/garcia/tutorials/bluetooth/connection/connection.html&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; page shows you how to establish the virtual serial port, and &lt;a href=&quot;http://thehighlowtech.com/LilyPad/extend.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; page shows the connection, although it is for the Lillypad. You connect the VCC and Grounds of the 3pi and the Bluetooth then connect the RX and TX of the 3pi to the TX and RX of the Bluetooth module respectably. Hope this helps. Also &lt;a href=&quot;http://www.pololu.com/docs/0J18/9&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is the tutorial for the 3pi serial communication.&lt;/p&gt;&#xA;" OwnerUserId="92" LastActivityDate="2009-11-13T00:16:21.813" />
  <row Id="396" PostTypeId="1" CreationDate="2009-11-13T00:22:09.813" Score="3" ViewCount="171" Body="&lt;p&gt;How do I connect an LCD monitor to be the display for a VHS VCR?&lt;/p&gt;&#xA;" LastActivityDate="2010-07-08T16:54:20.930" Title="VGA monitor as the display for VHS player" Tags="&lt;lcd&gt;&lt;vga&gt;" AnswerCount="3" />
  <row Id="397" PostTypeId="2" ParentId="167" CreationDate="2009-11-13T00:24:50.763" Score="3" ViewCount="" Body="&lt;p&gt;Most of the suggestions need a jail-broken phone. &lt;a href=&quot;http://www.uchobby.com/index.php/2009/09/06/iphone-audio-breadboard-adaptor/&quot; rel=&quot;nofollow&quot;&gt;ucHobby&lt;/a&gt; has a different approach using the audio jack of the phone or ipod.&lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-11-13T00:24:50.763" />
  <row Id="398" PostTypeId="2" ParentId="396" CreationDate="2009-11-13T00:39:07.793" Score="3" ViewCount="" Body="&lt;p&gt;I think you need a TV Tuner card, because monitors are designed for a higher refresh rate so the picture would have to be digitized. The bonus though is that you would get to also watch tv on it. I picked one up on eBay for about $15 and I set it to record all my shows as a DVR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your monitor has composite cables on it, you could hook it up through those, but the pic quality is not going to be so great coming off VHS.&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-11-13T00:39:07.793" CommentCount="1" />
  <row Id="399" PostTypeId="2" ParentId="396" CreationDate="2009-11-13T00:40:24.530" Score="5" ViewCount="" Body="&lt;p&gt;If your VCR has RCA video out you will need an &lt;a href=&quot;http://www.amazon.com/Console-Converter-monitor-RCA2VGA-1L9/dp/B000V58F9M&quot; rel=&quot;nofollow&quot;&gt;RCA to VGA (d-sub) converter&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I never tried these but there are many out there. Depending on your budget and video quality needed. &lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-11-13T00:40:24.530" />
  <row Id="400" PostTypeId="2" ParentId="396" CreationDate="2009-11-13T00:41:27.590" Score="3" ViewCount="" Body="&lt;p&gt;There are any number of video to VGA converters like &lt;a href=&quot;http://www.ramelectronics.net/audio-video/audio-video-computer/video-to-vga/c10000-c11300-c11302-p1.html&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt;. Google around and you can find more. Prices vary widely and I don't have any direct experience to recommend one over another.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2009-11-13T00:41:27.590" />
  <row Id="401" PostTypeId="1" CreationDate="2009-11-13T01:36:24.567" Score="9" ViewCount="1000" Body="&lt;p&gt;I'm designing a board that can be powered either by USB or an ATX power supply.  They can both be plugged in at the same time, independently.  I'd like the ATX to provide 5V if its plugged in, but fall back to the USB if possible.  The chips in the circuit will all be running at 5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T21:46:15.797" LastActivityDate="2010-12-10T21:46:15.797" Title="Switch between 5V power supplies?" Tags="&lt;power-supply&gt;&lt;usb&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="402" PostTypeId="2" ParentId="401" CreationDate="2009-11-13T01:49:09.740" Score="3" ViewCount="" Body="&lt;p&gt;What you may need to do is hook up the USB power through some sort of buffer with a chip select pin or something.  Then have an AND gate that if it sees 5V from both the USB power (before the buffer chip) and 5V from the ATX power supply, 1 and 1 = 1 (and chip selects are typically active low meaning that a '1' will turn OFF the USB supply).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit:  I didnt mean buffer chip.  I meant to say some IC to 'clean' the voltage coming from the USB.  Really any chip you can use to supply the power and has a chip select pin&lt;/p&gt;&#xA;" OwnerUserId="107" LastEditorUserId="107" LastEditorDisplayName="" LastEditDate="2009-11-14T01:18:23.347" LastActivityDate="2009-11-14T01:18:23.347" CommentCount="1" />
  <row Id="403" PostTypeId="1" AcceptedAnswerId="407" CreationDate="2009-11-13T03:06:19.533" Score="2" ViewCount="95" Body="&lt;p&gt;Has anyone had much experience with the &lt;a href=&quot;http://www.pololu.com/&quot; rel=&quot;nofollow&quot;&gt;Pololu&lt;/a&gt; Robots  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which are the coolest? what do you recommend i get?   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to hear about some cool projects with these Robots  :)&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-04T00:30:02.330" LastActivityDate="2011-02-04T00:30:02.330" Title="Experience with Pololu Robots" Tags="&lt;pololu&gt;" AnswerCount="2" />
  <row Id="404" PostTypeId="1" CreationDate="2009-11-13T03:33:06.843" Score="3" ViewCount="138" Body="&lt;p&gt;If I built a coil like the one in this crystal set &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://scitoys.com/scitoys/scitoys/radio/radio.html#crysta&quot; rel=&quot;nofollow&quot;&gt;http://scitoys.com/scitoys/scitoys/radio/radio.html#crystal&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How could I use a micro to detect which point the alligator clip is on?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically I wan't to use the crystal set as a user interface for an audio playback system. &lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-13T05:07:24.547" LastActivityDate="2009-11-13T16:03:24.590" Title="Crystal radio as user interface problem." Tags="&lt;microcontroller&gt;&lt;crystal&gt;&lt;radio&gt;&lt;interface&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="405" PostTypeId="2" ParentId="167" CreationDate="2009-11-13T03:43:41.300" Score="3" ViewCount="" Body="&lt;p&gt;One thing to note is that you cannot use the official External Accessory Framework to communicate with accessories, unless the accessory that you're communicating with has been designed under the Made For iPod, or Works With iPhone programs&lt;/p&gt;&#xA;" OwnerUserId="271" LastActivityDate="2009-11-13T03:43:41.300" />
  <row Id="406" PostTypeId="1" AcceptedAnswerId="414" CreationDate="2009-11-13T03:46:12.637" Score="3" ViewCount="1133" Body="&lt;p&gt;I have an old apple keyboard that I would like to use but it uses the ADB bus instead of the newer USB bus. Griffin used to produce a product called the iMate which was an ADB-to-USB converter but have since discontinued it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I've decided to build one. It shouldn't be that difficult right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://pinouts.ru/Slots/apple%5Fadb%5Fpinout.shtml&quot; rel=&quot;nofollow&quot;&gt;pinouts.ru&lt;/a&gt; has the bus specs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The pinouts are pretty straight forward:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pin&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;Name&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;Description&lt;br/&gt;&#xA;1&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;ADB&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;Apple Desktop Bus&lt;br/&gt;&#xA;2&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;PSW&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;Power Switch&lt;br/&gt;&#xA;3&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;+5V&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;Power +5V&lt;br/&gt;&#xA;4&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;GND&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;Ground&lt;br/&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would I go about building something like this? Would I need to get a FTDI chip to do the interface?&lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-11-13T17:33:12.150" Title="Apple Desktop Bus (ADB) to USB Adapter" Tags="&lt;adapter&gt;&lt;serial&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="407" PostTypeId="2" ParentId="403" CreationDate="2009-11-13T03:46:14.100" Score="3" ViewCount="" Body="&lt;p&gt;The 3pi:&#xA;this has an awesome design and is great for programming practice.  I'd recommend it for any high school studients or uni students just getting into electronics&#xA;&lt;a href=&quot;http://www.pololu.com/catalog/product/975&quot; rel=&quot;nofollow&quot;&gt;http://www.pololu.com/catalog/product/975&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="267" LastActivityDate="2009-11-13T03:46:14.100" />
  <row Id="408" PostTypeId="2" ParentId="404" CreationDate="2009-11-13T04:01:13.173" Score="2" ViewCount="" Body="&lt;p&gt;If you used a very thin gauge wire you could measure the resistance from one end of the coil to the connection point.  However, even with 28 gauge wire you're looking at a total of 6 ohms for the entire coil, so reading that with a micro is going to require additional components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternately you can measure the inductance of the coil from one end to the tap, which would vary based on which tap was chosen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you're just building an interface.  Does it have to be a real coil, or does it just have to &lt;em&gt;look&lt;/em&gt; like a coil?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Were I in your shoes, I'd cut the back side of the coil around the taps and use one of many methods for determining which tap was connected.  This could be done with one input per tap, or with an analog input if you added resistors to the coil so the resistance significantly increased between each tap.&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="161" LastEditorDisplayName="" LastEditDate="2009-11-13T16:03:24.590" LastActivityDate="2009-11-13T16:03:24.590" CommentCount="2" />
  <row Id="409" PostTypeId="2" ParentId="286" CreationDate="2009-11-13T04:05:18.447" Score="2" ViewCount="" Body="&lt;p&gt;We built this autonomous robot with an Arduino.&#xA;&lt;a href=&quot;http://www.youtube.com/watch?v=6J_eh1HPu54&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=6J_eh1HPu54&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Granted its a hobby robot, but you can get more advanced.&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-11-13T04:05:18.447" />
  <row Id="410" PostTypeId="2" ParentId="403" CreationDate="2009-11-13T04:25:13.783" Score="2" ViewCount="" Body="&lt;p&gt;This was a really good starter kit:&#xA;Elenco 21-880 Line-Tracking Mouse &#xA;&lt;a href=&quot;http://www.pololu.com/catalog/product/301&quot; rel=&quot;nofollow&quot;&gt;http://www.pololu.com/catalog/product/301&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="267" LastActivityDate="2009-11-13T04:25:13.783" />
  <row Id="411" PostTypeId="2" ParentId="33" CreationDate="2009-11-13T04:33:27.470" Score="3" ViewCount="" Body="&lt;p&gt;This solution works great too:  &lt;a href=&quot;http://www.geocities.jp/arduino%5Fdiecimila/bootloader/index%5Fen.html&quot; rel=&quot;nofollow&quot;&gt;Kimio Kosaka avrdude-serjtag method&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have assembled you own computers you may have spare case mounted USB cables/connectors that often come with new moherboards.  Just wack off the USB end and you can use the motherboard connector as the ISP connector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A batch file like this can be used:  (This is for the 328 chips, will set the fuses for high speed transfer and then upload the bootloader, and setting the lock bits when finished.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;avrdude -c diecimila -P ft0 -p m328p -B 4800 -U lock:w:0x3F:m -U efuse:w:0x05:m&#xA;-U hfuse:w:0xDA:m -U lfuse:w:0xFF:m&#xA;&#xA;avrdude -c diecimila -P ft0 -p m328p -U flash:w:ATmegaBOOT_168_atmega328.hex -U&#xA;efuse:w:0x05:m -U hfuse:w:0xDA:m -U lfuse:w:0xFF:m -U lock:w:0x0F:m&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="272" LastActivityDate="2009-11-13T04:33:27.470" />
  <row Id="412" PostTypeId="2" ParentId="401" CreationDate="2009-11-13T04:54:25.953" Score="8" ViewCount="" Body="&lt;p&gt;You should be able to use the same circuit that an &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardDuemilanove&quot; rel=&quot;nofollow&quot;&gt;Arduino Duemilanove&lt;/a&gt; uses; you can get the schematic in &lt;a href=&quot;http://arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf&quot; rel=&quot;nofollow&quot;&gt;PDF&lt;/a&gt; or as &lt;a href=&quot;http://arduino.cc/en/uploads/Main/arduino-duemilanove-reference-design.zip&quot; rel=&quot;nofollow&quot;&gt;Eagle files&lt;/a&gt;.  The Arduino designs are licensed under a Creative Commons license &lt;a href=&quot;http://creativecommons.org/licenses/by-sa/2.5/&quot; rel=&quot;nofollow&quot;&gt;Attribution-ShareAlike 2.5&lt;/a&gt;.  Here's a description of the Duemilanove's power options:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The Arduino Duemilanove can be powered&#xA;  via the USB connection or with an&#xA;  external power supply. The power&#xA;  source is selected automatically.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;External (non-USB) power can come&#xA;  either from an AC-to-DC adapter&#xA;  (wall-wart) or battery. The adapter&#xA;  can be connected by plugging a 2.1mm&#xA;  center-positive plug into the board's&#xA;  power jack. Leads from a battery can&#xA;  be inserted in the Gnd and Vin pin&#xA;  headers of the POWER connector.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The board can operate on an external&#xA;  supply of 6 to 20 volts. If supplied&#xA;  with less than 7V, however, the 5V pin&#xA;  may supply less than five volts and&#xA;  the board may be unstable. If using&#xA;  more than 12V, the voltage regulator&#xA;  may overheat and damage the board. The&#xA;  recommended range is 7 to 12 volts.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The power pins are as follows:&lt;/p&gt;&#xA;  &#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;&lt;p&gt;VIN. The input voltage to the Arduino board when it's using an&#xA;  external power source (as opposed to 5&#xA;  volts from the USB connection or other&#xA;  regulated power source). You can&#xA;  supply voltage through this pin, or,&#xA;  if supplying voltage via the power&#xA;  jack, access it through this pin.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;5V. The regulated power supply used to power the microcontroller and other&#xA;  components on the board. This can come&#xA;  either from VIN via an on-board&#xA;  regulator, or be supplied by USB or&#xA;  another regulated 5V supply.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;3V3. A 3.3 volt supply generated by the on-board FTDI chip. Maximum&#xA;  current draw is 50 mA.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;GND. Ground pins.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-13T04:54:25.953" CommentCount="4" />
  <row Id="413" PostTypeId="2" ParentId="167" CreationDate="2009-11-13T05:02:08.303" Score="3" ViewCount="" Body="&lt;p&gt;Here are some of the commands and pin outs of the serial port&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Commands: &lt;a href=&quot;http://nuxx.net/wiki/Apple_Accessory_Protocol&quot; rel=&quot;nofollow&quot;&gt;http://nuxx.net/wiki/Apple_Accessory_Protocol&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Pin outs: &lt;a href=&quot;http://www.pinouts.ru/PortableDevices/ipod_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;www.pinouts.ru/PortableDevices/ipod_pinout.shtml&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="212" LastEditorUserId="1202" LastEditorDisplayName="" LastEditDate="2011-02-17T18:37:32.060" LastActivityDate="2011-02-17T18:37:32.060" />
  <row Id="414" PostTypeId="2" ParentId="406" CreationDate="2009-11-13T05:06:03.327" Score="3" ViewCount="" Body="&lt;p&gt;Are you expecting it to act as a normal keyboard, or just as something that works with special software?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using an Arduino (say) with an FTDI cable, it will act like a device talking over a serial port.  You can send interpreted keypresses, and any application listening will see them.  (You would probably be best off to use '&lt;a href=&quot;http://embeddedfreak.wordpress.com/2008/08/12/using-gnu-screen-to-debug-your-serial-port/&quot; rel=&quot;nofollow&quot;&gt;screen&lt;/a&gt;').  However, an application will not be listening to the serial port for keyboard input under normal conditions, and you may find yourself disappointed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want it to pretend to be a USB keyboard, you'll need a chip in there that has a USB registration code as a keyboard device.  (I don't remember the proper term; probably some sort of HID -- Human Interface Device -- thing.)  In which case, the question, &quot;&lt;a href=&quot;http://chiphacker.com/questions/267/id-like-to-learn-how-to-make-my-own-usb-gadgets&quot; rel=&quot;nofollow&quot;&gt;I’d like to learn how to make my own USB gadgets&lt;/a&gt;&quot; has some relevance to you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using a standard AVR chip, you can use the &lt;a href=&quot;http://www.obdev.at/products/vusb/index.html&quot; rel=&quot;nofollow&quot;&gt;V-USB&lt;/a&gt; firmware to make it talk like a USB device.  See their &lt;a href=&quot;http://www.obdev.at/products/vusb/prjhid.html&quot; rel=&quot;nofollow&quot;&gt;examples of human input devices&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you could use an &lt;a href=&quot;http://www.atmel.com/dyn/products/tools%5Fcard.asp?tool%5Fid=3879&quot; rel=&quot;nofollow&quot;&gt;AT90USBKey&lt;/a&gt; and check out their &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod%5Fdocuments/doc7602.pdf&quot; rel=&quot;nofollow&quot;&gt;USB Keyboard Demonstration [pdf]&lt;/a&gt;.  &lt;a href=&quot;http://fletchtronics.net/bumble-b&quot; rel=&quot;nofollow&quot;&gt;Bumble-B&lt;/a&gt; sounds somewhat similar.&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-11-13T05:06:03.327" CommentCount="1" />
  <row Id="415" PostTypeId="2" ParentId="401" CreationDate="2009-11-13T05:20:13.087" Score="12" ViewCount="" Body="&lt;p&gt;Usually, if you can stand the voltage drop, you use a diode from each supply to the circuit.  This way the supplies won't back feed into each other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't stand the voltage drop, then you would use FETs to switch them into the circuit, using a little logic to turn on whichever FET you want based on which combination of supplies is attached.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if you're just starting out in electronics, and are not sure of power supply design then go for the diodes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i288.photobucket.com/albums/ll164/stienman/diode%5Fpower%5Fcombine.png&quot; alt=&quot;Circuit diagram showing two power sources leading into individual diodes (anode side), with the output of the diodes connected together (cathodes)&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each diode will have a voltage drop, a current rating, and a wattage for dissipation.  Since you're drawing from a USB port, your current isn't going to be over 500mA, and that current with the voltage drop is less than a watt in power dissipation, so as long as you choose power diodes you should be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The voltage drop for a standard 1N4001 diode ($0.30 each at &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=1N4001DICT-ND&quot; rel=&quot;nofollow&quot;&gt;Digikey&lt;/a&gt;) is about 1V, so the output to your circuit would be 4V.  If you wanted to get a lower voltage drop you would move to Schottky diode, such as a &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=1N5817FSCT-ND&quot; rel=&quot;nofollow&quot;&gt;1N5817&lt;/a&gt; which has a drop closer to 450mV, so the voltage on the output side would be 4.55V.  That diode is only a few cents more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If, however, you require exactly 5 volts to the circuit, you'll have to look at other switching methods, such as FETs.  Keep in mind, however, that it'll be more expensive, and nearly every other simple option still includes a voltage drop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most 5V devices and circuits will run fine at 4.5V, though, just check their specifications carefully and do some testing.&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="161" LastEditorDisplayName="" LastEditDate="2009-11-13T16:08:51.233" LastActivityDate="2009-11-13T16:08:51.233" CommentCount="1" />
  <row Id="418" PostTypeId="2" ParentId="406" CreationDate="2009-11-13T05:44:52.950" Score="3" ViewCount="" Body="&lt;p&gt;The Apple Desktop Bus is well documented on Apple's website (&lt;code&gt;http://developer.apple.com/legacy/mac/library/technotes/hw/hw_01.html&lt;/code&gt;).  It's a single wire communications bus - the other wires are for power and ground, and the computer polls the devices continuously for data after an initial setup period.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be relatively straightforward to do this with a variety of microcontrollers, and most USB capable microcontroller manufacturers have at least one application note on how to make a keyboard HID device (ie, USB keyboard).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip's app note TB056 has a PS2 to USB keyboard adaptor.  Replace all the PS2 code and circuit interface with ADB code and interface, and you should be able to accomplish exactly what you need without a great deal of effort.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en011984&lt;/code&gt; is the current page for that app note, but if the link stops working you can search for TB056 and find it.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2009-11-13T05:44:52.950" />
  <row Id="419" PostTypeId="2" ParentId="253" CreationDate="2009-11-13T06:54:26.017" Score="1" ViewCount="" Body="&lt;p&gt;Cutting a single layer of lightweight fabric should be easy at 20 watts.  Cutting stacked fabric will take significantly more since the focal point of the laser won't be optimum for all the layers.  Still, fabric is easy to cut, so a 60 watt or so should be able to handle it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are people with laser cutters all over the place - poke around in your local maker hotspots, or ask on makezine.com to find someone that is willing to do some tests for you.  You may even find someone willing to do the laser cutting for you much more economically than you could build/buy a machine for yourself, at least to do a proof of concept, and get enough business to decide whether the machine investment is worth it.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2009-11-13T06:54:26.017" />
  <row Id="420" PostTypeId="2" ParentId="254" CreationDate="2009-11-13T07:40:00.960" Score="2" ViewCount="" Body="&lt;p&gt;I would suggest doing this with an electrical department at a university or with a company. Work out a deal for IP first (ie. talk about the reward you want for your time), and if it is a good project, the university will normally take over the FCC and patenting process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means less money for you if it is a good product, as you share rights, but the university effectively acts as an investor, giving the money required for the process and in return expecting some profit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will need a larger university, although I cannot be specific on what size as this type of thing varies with location, but if you are in Oklahoma I can get you in contact with a professor for OSU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope it helps.&#xA;-Max&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-13T07:40:00.960" CommentCount="2" />
  <row Id="421" PostTypeId="2" ParentId="391" CreationDate="2009-11-13T07:47:25.427" Score="2" ViewCount="" Body="&lt;p&gt;For the most part I agree with Hristos, but must disagree about Xbee. I have done this with both devices and there was not a significant difference in complexity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would point out, there is a good rule to remember here, like occam's razor for electronics, try to stick with the most common and accessible technology. Many computers have bluetooth removing the need for a dongle, it is a very common tech, and by that fact has more available in development.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Range relation, most people think Xbee has greater range, but bluetooth also can have radiated power of up to 100mW in class 1, although saying a device is class 1 does not imply this to be true, it just defines a maximum, if you want range you MUST read about the devices actual radiated power. Most people also overlook receiver sensitivity, you will find out with testing it often has more to do with range than the radiated power, although both are important.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope I helped. -Max&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-13T07:47:25.427" />
  <row Id="423" PostTypeId="2" ParentId="404" CreationDate="2009-11-13T08:32:01.560" Score="2" ViewCount="" Body="&lt;p&gt;Resistance is a good solution, it also might be interesting to treat the coil like a resonator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try using a uC to give it a rising edge on the end clipped into and measure the rising edge on the other side. I could simulate this and see if it was feasible, but it would probably save hours to use a function generator and an Oscope, or just use a uC. A capture pin on a PIC and a PWM output would be my choice, pin goes high from PWM on a PIC at timer overflow, capture is relative to timers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just an Idea, if I think of any others I will let you know. If it could be done you could have two simple interrupts and just w check the variable they wrote to before doing any audio out.&#xA;-Max&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2009-11-13T10:36:46.097" LastActivityDate="2009-11-13T10:36:46.097" CommunityOwnedDate="2009-11-13T10:36:46.097" CommentCount="1" />
  <row Id="424" PostTypeId="2" ParentId="376" CreationDate="2009-11-13T08:57:05.887" Score="2" ViewCount="" Body="&lt;p&gt;I would also describe this as elegant, but would like to add the the problem, if you will forgive my intrusion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know there are very pricey software packages to work through situations like this, but at the company I work at we cannot afford the cost unless we are sure it does what we need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Test Driven Development(TDD) is one of the better systems I have heard of for development, and I enjoy it, but the problems that take up my time are normally caused by complex interrupt and hardware events that many would call glitches. It seems like a minor thing to have a problem every 2 hours when the stars align, but if your phone just froze once a week,you would curse the engineers name. In our case, we have to trek into a feed lot when things really break, which, as you can imagine, I like to avoid.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have seen very intelligent solutions for checking functionality of subsystems, which, if implemented properly, would probably save me 3 hours out of a 50 hour work week, but if there was an intelligent way to find glitch situations it would save me weeks of work looking for the &quot;bug&quot; that happens in the field occasionally under heavy load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This post probably does not help a large amount, but I find bringing everything into the light makes everything easier to resolve. If there was a TDD method for finding glitch situations, I could get 10s of thousands allocated to pay for it.&#xA;-Max&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-13T08:57:05.887" CommentCount="7" />
  <row Id="428" PostTypeId="2" ParentId="406" CreationDate="2009-11-13T17:33:12.150" Score="1" ViewCount="" Body="&lt;p&gt;If you want it to behave like a USB keyboard, you're going to have to have a microcontroller that translates between the &lt;a href=&quot;http://en.wikipedia.org/wiki/Apple%5Fdesktop%5Fbus&quot; rel=&quot;nofollow&quot;&gt;ADB protocol&lt;/a&gt; and the &lt;a href=&quot;http://en.wikipedia.org/wiki/USB&quot; rel=&quot;nofollow&quot;&gt;USB protocol&lt;/a&gt;, and which implements the keyboard profile for the HID class.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-13T17:33:12.150" />
  <row Id="430" PostTypeId="1" CreationDate="2009-11-14T01:48:08.460" Score="4" ViewCount="978" Body="&lt;p&gt;Sorry for the question, I'm just starting out in robotics - as a hobby- and I was just interested in what I'll be able to actually do, please let me know, &lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-04T00:29:15.950" LastActivityDate="2011-02-04T00:29:15.950" Title="What sort of things can an Arduino do?" Tags="&lt;arduino&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="2" />
  <row Id="431" PostTypeId="2" ParentId="430" CreationDate="2009-11-14T02:33:57.990" Score="2" ViewCount="" Body="&lt;p&gt;Arduino's can do a variety of things for robots, including but not limited to: process data from sensors and control servos/motors. For some general examples take a look at&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.freeduino.org/&quot; rel=&quot;nofollow&quot;&gt;Freeduino.org&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/en/Tutorial/HomePage&quot; rel=&quot;nofollow&quot;&gt;Arduino.cc Examples&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You can connect other modules to an Arduino using what is called a &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoShields&quot; rel=&quot;nofollow&quot;&gt;shield&lt;/a&gt;. Shields are available from several small businesses like &lt;a href=&quot;http://www.littlebirdelectronics.com/&quot; rel=&quot;nofollow&quot;&gt;LittleBird Electronics&lt;/a&gt;, &lt;a href=&quot;http://www.adafruit.com&quot; rel=&quot;nofollow&quot;&gt;AdaFruit Industries&lt;/a&gt;, &lt;a href=&quot;http://www.sparkfun.com&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt;, etc.&lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-11-14T02:33:57.990" />
  <row Id="432" PostTypeId="2" ParentId="59" CreationDate="2009-11-14T02:50:46.980" Score="4" ViewCount="" Body="&lt;p&gt;I'm looking for the same thing.  &lt;a href=&quot;http://www.dsprelated.com/showmessage/91989/1.php&quot; rel=&quot;nofollow&quot;&gt;This thread&lt;/a&gt; has some suggestions.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also TI's TAS3202 System-on-a-Chip, which seems to have everything you would need for filtering stereo audio.  Converters and everything are built-in.  The chip itself is about $5, but the eval board is about &lt;strong&gt;$500&lt;/strong&gt;.  Sheesh.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(You can get a single TAS3204 &lt;a href=&quot;http://mouser.com/ProductDetail/Texas-Instruments/TAS3204PAG/?qs=sGAEpiMZZMuTgk%252bQPI7Id0LpqHj%252bX0I4&quot; rel=&quot;nofollow&quot;&gt;for about $10&lt;/a&gt;.  TAS3202 I can't even find in low quantities.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also the &lt;a href=&quot;http://www.asahi-kasei.co.jp/akm/en/product/ak7742/ak7742.html&quot; rel=&quot;nofollow&quot;&gt;AK7742&lt;/a&gt;, which has &lt;a href=&quot;http://www.nuhorizons.com/development/devtool.asp?board=100&quot; rel=&quot;nofollow&quot;&gt;a very convenient GUI&lt;/a&gt;, but you'd need to buy the eval board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd love to find a hobbyist-dedicated open source DSP board like the BASIC Stamp, Arduino, Chameleon, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to learn the high-level fundamentals of DSP, though, you'll want to start with your computer, using tools like &lt;a href=&quot;http://www.mathworks.com/&quot; rel=&quot;nofollow&quot;&gt;MATLAB&lt;/a&gt; or its free clones &lt;a href=&quot;http://www.scilab.org/&quot; rel=&quot;nofollow&quot;&gt;Scilab&lt;/a&gt;, &lt;a href=&quot;http://www.gnu.org/software/octave/&quot; rel=&quot;nofollow&quot;&gt;Octave&lt;/a&gt;, &lt;a href=&quot;http://freemat.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;Freemat&lt;/a&gt;, etc. to do simulations.  I've been playing around with &lt;a href=&quot;http://www.scipy.org/&quot; rel=&quot;nofollow&quot;&gt;SciPy&lt;/a&gt; a lot lately.  That way you can learn the theoretical stuff without being bogged down by the implementation details.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-04-28T02:18:40.447" LastActivityDate="2010-04-28T02:18:40.447" CommentCount="1" />
  <row Id="433" PostTypeId="1" AcceptedAnswerId="436" CreationDate="2009-11-14T03:51:47.953" Score="13" ViewCount="742" Body="&lt;p&gt;I've noticed, with regards to microcontrollers, there are several way to program them. I am sorta familiar with USB as my Arduino's can be programmed via USB. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is a JTAG or SPI interface? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ultimately I know that these interfaces provide a means to flash the chip with new instructions but how do they differ? Are there any advantages of one over another?&lt;/p&gt;&#xA;" OwnerUserId="245" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-29T00:18:16.257" LastActivityDate="2010-12-29T16:01:30.783" Title="JTAG, SPI, USB oh my!?" Tags="&lt;jtag&gt;&lt;spi&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="2" />
  <row Id="435" PostTypeId="2" ParentId="433" CreationDate="2009-11-14T09:36:52.463" Score="2" ViewCount="" Body="&lt;p&gt;From an overall point of view these interfaces only differ in which programmers and which micro-controllers support them. As long as you have a match between the programmer and the micro-controller I wouldn't worry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you get into it more you will find that it is the pins the interface uses on the micro-controller that matter more - if you are using these pins for sensors then the signals can interfere when you are programming the device. The simplest solution should this be a problem is to disconnect the sensors during programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some interfaces (including JTAG) allow for debugging the device - but then you need a programmer (and software to drive it) that also supports this. In a &lt;a href=&quot;http://chiphacker.com/questions/226/jtag-debugging-avr&quot; rel=&quot;nofollow&quot;&gt;previous question&lt;/a&gt; I was pointed at the Dragon for debugging AVR devices - I intend to get one and play when my current round of projects nears completion.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-14T09:36:52.463" CommentCount="0" />
  <row Id="436" PostTypeId="2" ParentId="433" CreationDate="2009-11-14T09:49:23.177" Score="12" ViewCount="" Body="&lt;p&gt;ATMEGA microcontrollers like the one in the arduino that are coming straight from the factory can only be programmed using the SPI or JTAG interface. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Serial%5FPeripheral%5FInterface%5FBus&quot; rel=&quot;nofollow&quot;&gt;SPI&lt;/a&gt; stands for Serial Peripheral Interface and is a way for microcontrollers to communicate with each other or with the outside world. It's also called 3-wire sometimes because it uses three wires to communicate. To program a chip, you will need a special programmer which reads commands from USB to drive the SPI lines to program the chip. A popular one seems to be the &lt;a href=&quot;http://www.adafruit.com/index.php?main%5Fpage=product%5Finfo&amp;amp;cPath=16&amp;amp;products%5Fid=46&amp;amp;zenid=50c51732c87bc5d1395a5166c09e4ddd&quot; rel=&quot;nofollow&quot;&gt;USBTinyISP from Adafruit&lt;/a&gt;. A very good introduction into SPI programming is at &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial%5Finfo.php?tutorials%5Fid=93&quot; rel=&quot;nofollow&quot;&gt;SparkFun&lt;/a&gt;. The most popular applications for programming Atmel AVR chips are avrdude (cmd line), ponyprog (doesn't work with newer programmers) and in some cases AVR Studio (if your programmer supports it). The advantage of SPI programming is that you can program any Atmel chip straight from the factory so you wouldn't always need an Arduino in your projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where SPI is &quot;just another&quot; serial protocol, &lt;a href=&quot;http://en.wikipedia.org/wiki/Jtag&quot; rel=&quot;nofollow&quot;&gt;JTAG&lt;/a&gt; is a protocol which is especially designed to program and debug microcontrollers. Not all Atmel micro's support JTAG but the ones that are used in the Arduino do. The JTAG protocol can be used for cool things like &quot;in circuit emulation&quot; and debugging which means that it enables you to see the state of the program in your microcontroller while it's actually running. To do this you'll need a special programmer. Seen my answer for &lt;a href=&quot;http://chiphacker.com/questions/226/jtag-debugging-avr&quot; rel=&quot;nofollow&quot;&gt;another question&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To program a chip using USB, you'll have to program it first with a &quot;bootloader&quot; using SPI or JTAG. Once loaded with the bootloader, the system will be programmable from any PC using a USB-Serial converter. The downside is that the bootloader takes up some memory space and this method does not allow you to see the state of the chip while it's running.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-14T09:49:23.177" CommentCount="1" />
  <row Id="437" PostTypeId="1" AcceptedAnswerId="480" CreationDate="2009-11-14T14:29:26.360" Score="3" ViewCount="475" Body="&lt;p&gt;I'm building a &lt;a href=&quot;http://www.lhexapod.com/blog/2009/08/a-timer-driven-pwm-servo-controller---part-4.html&quot; rel=&quot;nofollow&quot;&gt;serial servo controller&lt;/a&gt; to learn about electronics and assembly language as part of my &lt;a href=&quot;http://www.lhexapod.com&quot; rel=&quot;nofollow&quot;&gt;hexapod robot project&lt;/a&gt;. Quite early on I decided that I needed more I/O channels than my ATTiny2313 that I was using at the time supported so I investigated some 3-8 line demultiplexer chips (&lt;a href=&quot;http://pdfdata.datasheetsite.com/web/124672/CD74HCT238E.pdf&quot; rel=&quot;nofollow&quot;&gt;CD74HCT238E&lt;/a&gt;'s) which have allowed me to create a 64 channel PWM servo controller with just 8 I/O pins for the PWM channels and 3 address lines. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway. I also bought some &lt;a href=&quot;http://pdfdata.datasheetsite.com/web/124672/CD74HCT238E.pdf&quot; rel=&quot;nofollow&quot;&gt;CD74HCT138E&lt;/a&gt;'s which are active low rather than the active high CD74HCT238E's. I understand, in principal, the differences &lt;a href=&quot;http://chiphacker.com/questions/332/current-sourcing-current-sinking/337#337&quot; rel=&quot;nofollow&quot;&gt;between the current sourcing chip that I'm using and the current sinking chips&lt;/a&gt; but I don't really know how to adjust my circuit to use the current sinking chips instead of the current sourcing chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The schematic for the active high chips is here:&#xA;&lt;img src=&quot;http://www.lhexapod.com/blog/pictures/ATTiny2313-24ChannelServoController.png&quot; alt=&quot;alt text&quot; /&gt;&#xA;What do I need to change to swap the &lt;a href=&quot;http://pdfdata.datasheetsite.com/web/124672/CD74HCT238E.pdf&quot; rel=&quot;nofollow&quot;&gt;CD74HCT238E&lt;/a&gt;'s for &lt;a href=&quot;http://pdfdata.datasheetsite.com/web/124672/CD74HCT238E.pdf&quot; rel=&quot;nofollow&quot;&gt;CD74HCT138E&lt;/a&gt;'s?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that the reason for asking this question is that I bought a tube of the active low ICs by mistake and I'm curious at how much more complex the schematic and circuit design would need to be for me to make use of them. &lt;/p&gt;&#xA;" OwnerUserId="255" LastEditorUserId="255" LastEditorDisplayName="" LastEditDate="2009-11-15T18:59:42.350" LastActivityDate="2009-11-16T09:57:57.213" Title="How to redesign a circuit to use a current sinking IC rather than a current sourcing IC" Tags="&lt;avr&gt;&lt;electronics&gt;&lt;current&gt;&lt;sinking&gt;&lt;sourcing&gt;" AnswerCount="2" />
  <row Id="438" PostTypeId="2" ParentId="430" CreationDate="2009-11-14T15:17:30.423" Score="1" ViewCount="" Body="&lt;p&gt;Go to instructables and search on arduino.  Lots of hits.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-14T15:17:30.423" />
  <row Id="439" PostTypeId="2" ParentId="332" CreationDate="2009-11-14T19:14:22.973" Score="3" ViewCount="" Body="&lt;p&gt;Transistors are like water valves.  They can either block a flow of water, or allow a flow of water to pass through them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current sources and current sinks both have these valves at the output, to either block current or allow current from outside devices.  The difference is simple:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A current sink has a valve that internally connects to a low pressure&lt;/li&gt;&#xA;&lt;li&gt;A current source has a valve that internally connects to a high pressure&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you connect a current sink to a component that's connected to a low pressure, nothing will happen.  Both sides are at the same pressure, so it doesn't matter whether the valve is open or closed, no current will flow.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2009-11-15T04:34:41.087" LastActivityDate="2009-11-15T04:34:41.087" />
  <row Id="440" PostTypeId="2" ParentId="430" CreationDate="2009-11-14T19:16:07.353" Score="11" ViewCount="" Body="&lt;p&gt;Arduino is very flexible.  You can do a lot of neat stuff with it.  It's one of the best tools for interfacing software to the real world.  However, it might be useful to also ask &quot;&lt;em&gt;What can an Arduino &lt;strong&gt;not&lt;/strong&gt; do?&lt;/em&gt;&quot;.  Arduino has very limited memory and I/O compared to modern computers.  So some of the things the Arduino cannot do or cannot do easily are things that require a lot of memory or access to complex peripherals, like:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;video recording, processing &amp;amp; output&lt;/li&gt;&#xA;&lt;li&gt;high-fidelity audio recording &amp;amp; processing&lt;/li&gt;&#xA;&lt;li&gt;act as USB host for USB devices like flash drives, disk drives, cameras, keyboards, etc.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So, you can't easily make a video game system that hooks to your TV with an Arduino.  That doesn't mean people haven't done it, but that level of hacking is in the realm of deep voodoo, and the results still end up looking like a 1980s videogame.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Often you see Arduino boards hooked up as peripherals to a larger computer.  The computer does the A/V and the Arduino handles all the other physical world interfacing.  Another common use is the fully embedded system where a more mundane device is made &quot;smart&quot; with a hidden Arduino. (&quot;Your coffee table now knows when you set cups on it and buzzes you if you don't use a coaster&quot;)  This is where Arduino seems happiest.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-14T19:16:07.353" />
  <row Id="441" PostTypeId="1" AcceptedAnswerId="505" CreationDate="2009-11-14T20:32:29.257" Score="3" ViewCount="423" Body="&lt;p&gt;How does the propeller stack up against other multi core solutions.  I just saw an article about the open stomp project that won their design contest.  I wanted to see what other people thought of the chip.  Any similar better products? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How does spin rate?&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2009-11-17T14:40:39.700" Title="Is propeller a good product" Tags="&lt;microcontroller&gt;" AnswerCount="6" FavoriteCount="2" />
  <row Id="442" PostTypeId="1" AcceptedAnswerId="448" CreationDate="2009-11-14T22:12:21.940" Score="4" ViewCount="1159" Body="&lt;p&gt;I've been looking into doing some PIC Programming, but unlike some of the other microcontrollers available the sheer number of different chips available has caused me some confusion. It also appears that some of the chips suggested on some sites as good choices for people starting out with PIC programming may have been superseded (or I may just be getting even more confused). So my question boils down to three parts:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;a) What would be a good PIC chip to start out with?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;b) I'm quite happy doing either assembler or some other language, so what IDEs/languages would you suggest for Linux?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C) What would you recommend in terms of getting the code onto the chip, over a USB connection from a Linux laptop (PicKit 2? was one possibility) and what circuit/board configuration will I need to do this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;for extra credit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;d) What sites/books/forums would you recommend in terms of learning about PICs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: After a long discussion with Kortuk (see comments below) on the merits of various bits of kit, I've decided to start with the PicKit2 Starter Kit. This comes with a PIC16f690 chip installed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anybody point me towards some good tutorials or books for programming PICs using Assembler for people with a computer programming background.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plus does anyone know of a good &lt;a href=&quot;http://piklab.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;PikLab&lt;/a&gt; Tutorial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Amos&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2009-11-18T11:04:53.063" LastActivityDate="2010-07-21T07:17:16.477" Title="Starting out PIC Programming" Tags="&lt;pic&gt;&lt;programmer&gt;&lt;microcontroller&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="443" PostTypeId="2" ParentId="229" CreationDate="2009-11-15T02:29:48.413" Score="0" ViewCount="" Body="&lt;p&gt;I too want to build a BlinkM as a simple temperature indicator. I am willing to pay for schematic and sketch code needed for complete project. &lt;/p&gt;&#xA;" LastActivityDate="2009-11-15T02:29:48.413" />
  <row Id="444" PostTypeId="1" CreationDate="2009-11-15T03:31:23.263" Score="1" ViewCount="500" Body="&lt;p&gt;A little while ago I desoldered a 900 MHz phone and its base's RF modules and was wondering if anyone could help me to interface them with an Arduino, or just help find a datasheet. I put a picture of the modules on my website at &lt;a href=&quot;http://devin.gotdns.com/images/IMG_4975.JPG&quot; rel=&quot;nofollow&quot;&gt;http://devin.gotdns.com/images/IMG_4975.JPG&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The numbers on the base's module are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;PQLZ10006ZBM&lt;/li&gt;&#xA;&lt;li&gt;RU0903B15JBB&lt;/li&gt;&#xA;&lt;li&gt;SS9951&lt;/li&gt;&#xA;&lt;li&gt;S/N:0026130F&lt;/li&gt;&#xA;&lt;li&gt;1740M ABT&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The numbers on the phone's module are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;PQLZ10005ZBM&lt;/li&gt;&#xA;&lt;li&gt;RU0927H15JBB&lt;/li&gt;&#xA;&lt;li&gt;SS9951&lt;/li&gt;&#xA;&lt;li&gt;S/N:0037256A&lt;/li&gt;&#xA;&lt;li&gt;1740M ABT&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="280" LastActivityDate="2009-11-16T17:09:22.530" Title="Phone RF Module Interfacing with an Arduino" Tags="&lt;arduino&gt;&lt;radio&gt;&lt;interface&gt;" AnswerCount="2" />
  <row Id="445" PostTypeId="2" ParentId="442" CreationDate="2009-11-15T03:45:37.277" Score="2" ViewCount="" Body="&lt;p&gt;For chip look at the 18F series, allmost as cheap as the 16F a lot more guts. 18F2550 is a nice chip and includes USB, there are others in the same series.  Take a look at microchips selection charts on their website.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Free IDE from microchip including C which you should use over assembler IMHO.  Not sure if microchip IDE runs on Linux but it may.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PicKit may be good for programming, may want to burn a bootloader the first time then bootload over usb.  The Bitwacker ( google it ) is a nice setup to use or copy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a ton of forums and other sites, just google.  One problem with the PIC is that there are so many languages and none are quite the same ( even within c compilers )  If you can write a good question ask on piclist.com, but do your homework first.  Forums are not the best place for learning, look for tutorial sites for that ( again the bitwacher site is good, also google &quot;Embedded Adventures&quot; the guy has done a lot in C ( but not the microchip one )&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-15T03:45:37.277" CommentCount="1" />
  <row Id="447" PostTypeId="1" CreationDate="2009-11-15T07:38:44.750" Score="2" ViewCount="589" Body="&lt;p&gt;I am attempting to have an Arduino interpret an AFSK signal, this is very vague but can anyone just point me in the right direction for detecting the frequency of the AFSK signal with an arduino?&lt;/p&gt;&#xA;" OwnerUserId="81" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-11-15T08:52:06.440" LastActivityDate="2010-05-07T16:00:32.213" Title="Audio Frequency Shift Keying to Arduino" Tags="&lt;arduino&gt;&lt;electronics&gt;&lt;audio&gt;&lt;frequency&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="448" PostTypeId="2" ParentId="442" CreationDate="2009-11-15T08:39:36.187" Score="5" ViewCount="" Body="&lt;p&gt;I agree with PIC18s, but for someone just starting it may be a bit intense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I currently teach senior level electrical engineers PIC and even with the same classes, their range of backgrounds can be astounding.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you could give me a little more information on your background I would love to give you a more detailed response. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I currently Teach People with the CCS PIC-C compiler. &lt;a href=&quot;http://www.ccsinfo.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.ccsinfo.com/&lt;/a&gt; is their site, but it costs money. It is unbelievable simple which was chosen as most of our students have only worked in a lab setting with basic assembly or x86 programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a feeling a very simple pic16 may be a better fit, but it will depend on your background. pic16f688 is a very simple pic we use for our first project to warm people up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I look forward to hear more.&#xA;-Max Murphy&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-15T08:39:36.187" CommentCount="17" />
  <row Id="449" PostTypeId="2" ParentId="433" CreationDate="2009-11-15T08:51:52.837" Score="2" ViewCount="" Body="&lt;p&gt;I would like to add one more thing to the discussion. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;SPI is a very common interface for chips. The allusion to 3-wire is the mode of SPI where you do not use the chip's select pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I2C is the main contest for interface as it only uses 2-wires no matter the number of chips, while the SPI requires another wire per interface, but is slower.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When teaching I consider teaching about interfaces one of the most important tasks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Community wiki available for those that want to expand on my information.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-29T16:01:30.783" LastActivityDate="2010-12-29T16:01:30.783" CommunityOwnedDate="2009-11-15T08:51:52.837" CommentCount="2" />
  <row Id="450" PostTypeId="2" ParentId="447" CreationDate="2009-11-15T08:59:23.337" Score="3" ViewCount="" Body="&lt;p&gt;Can you give any more detail on the frequency of the signal. A 60 and 100 Hz signal is a different ball game than 60 and 61 Hz which is significantly harder to diagnose and is completely different from 6 and 7 GHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For 60 and 100Hz of dependable amplitude I would just use a schmitt trigger and count the time between rising edges.&#xA;-Max Murphy&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-15T08:59:23.337" CommentCount="5" />
  <row Id="451" PostTypeId="2" ParentId="444" CreationDate="2009-11-15T09:07:16.407" Score="1" ViewCount="" Body="&lt;p&gt;Devin, you have definitely found modules that they do not put a datasheet out on. It may be because they are older though. I will look more, but I only found a &lt;a href=&quot;http://www.faqs.org/rulings/rulings2000NYF81535.html&quot; rel=&quot;nofollow&quot;&gt;tariff ruling&lt;/a&gt; which defines the devices as full duplex FM voice modulators. You may be able to learn a lot with a scope, or it may be a waste of you time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will look into it more, interesting part.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2009-11-16T16:56:32.600" LastActivityDate="2009-11-16T16:56:32.600" />
  <row Id="452" PostTypeId="2" ParentId="437" CreationDate="2009-11-15T09:35:14.170" Score="1" ViewCount="" Body="&lt;p&gt;They are the same thing excluding the output. The active low is exactly the same as the active high with an inverted input on all pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a few app's with servos, this would require I put an inverter on each path or changed out my servos. With info for your servo I might be able to help more but I doubt this change is worth it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I took a look through your site, I have enjoyed it both times I have visited it, but I did not find more hardware information, if I missed anything, I apologize.&#xA;-Max Murphy&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-15T09:35:14.170" CommentCount="5" />
  <row Id="453" PostTypeId="2" ParentId="224" CreationDate="2009-11-15T09:40:09.260" Score="3" ViewCount="" Body="&lt;p&gt;I have one very hard earned piece of advice to share.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is very easy to make something water proof, but water vapour can ruin your world.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you put clothes through the drier and there are rapid temperature changes you can very quickly get water to condense on your circuit board under coating. This can cause catastrophic failure that is near impossible to track down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you would like more information, just ask and I will go into greater detail.&#xA;-Max Murphy&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-15T09:40:09.260" />
  <row Id="454" PostTypeId="2" ParentId="229" CreationDate="2009-11-15T10:55:06.007" Score="2" ViewCount="" Body="&lt;p&gt;This is pretty cool, we just has a student build one of these for an arm board. We took the I2C to RGB LED chip and pick an RGB LED. Linux was driving the LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On that note, if this is something people are not able to find more information on easily, I will do it for a PIC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope everyone enjoys their project.&#xA;-Max&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-15T10:55:06.007" />
  <row Id="455" PostTypeId="2" ParentId="224" CreationDate="2009-11-15T11:14:44.007" Score="4" ViewCount="" Body="&lt;p&gt;I've had some luck with these two products: &lt;a href=&quot;http://jaycar.com.au/productView.asp?ID=NM2832&quot; rel=&quot;nofollow&quot; title=&quot;jaycar.com.au&quot;&gt;liquid electrical tape&lt;/a&gt; and &lt;a href=&quot;http://jaycar.com.au/productView.asp?ID=NP4260&quot; rel=&quot;nofollow&quot; title=&quot;jaycar.com.au&quot;&gt;polymorph pellets&lt;/a&gt;. They are cheap and easy to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The pellets can be melted with a low heat and molded directly onto the circuit board. The liquid electrical tape adds a degree of waterproofing and extra knock protection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Washing machines can be pretty hash. Have you considered a quick release system for the main board? It might be easier than trying to make it rugged and waterproof?&lt;/p&gt;&#xA;" OwnerUserId="274" LastActivityDate="2009-11-15T11:14:44.007" />
  <row Id="456" PostTypeId="2" ParentId="332" CreationDate="2009-11-15T12:01:04.513" Score="1" ViewCount="" Body="&lt;p&gt;Adding to todbot's answer. The reason you see thinks better at current sinking was not arbitrary, the transistor is physically one step faster to make with older processes. I also believe it's mobility of electrons is higher, but that is probably a bit too much device physics.&#xA;-Max&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-15T12:01:04.513" />
  <row Id="457" PostTypeId="2" ParentId="347" CreationDate="2009-11-15T15:21:56.140" Score="1" ViewCount="" Body="&lt;p&gt;I've done this - pulled the 168 from an arduino, programmed it with the USBtinyISP.  You'll need some form of target board for the USBtiny ISP.  I used &lt;a href=&quot;http://evilmadscience.com/tinykitlist/74-atmegaxx8&quot; rel=&quot;nofollow&quot;&gt;one of these from Evil Mad Scientist Labs&lt;/a&gt;, along with a ZIF socket from Sparkfun.  The actual circuit needed to program them is simple enough that you can build it on a protoboard without much trouble.  EMSL also has a handy article on just what that circuit needs to be so you can DIY.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order for a target board to work, it needs to be set up with at least an approximation of how the chip is already fused.  That means having the right amount of power (if the brownout detection circuit is enabled) and having an oscillator if the chip is set to use an external one (AFAIK the chip will ignore an external oscillator if not fused to use it).  You either need to first set the fuses to use the internal oscillator before removing from the Arduino or put an oscillator on your target board.  I don't think the Arduino comes with brownout detect enabled, so you're probably safe on that score.  I'd suggest just using the jumper on the USBtiny to supply power to the target board, rather than bothering with an external power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't recommend using the Arduino board as the programmer target because it has a normal socket instead of a ZIF socket. I find that I'm much less likely to mangle the pins on my MCU when I use a ZIF socket.  Going in and out of a breadboard is bad enough.  Sparkfun seems to have the cheapest prices on ZIF sockets, if you decide to go that route.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you already have an ISP programmer, you can save a little money on your 328 chip and buy one without the Arduino bootloader.  Just use the Arduino software to burn the appropriate bootloader to it once you've got it installed.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-11-15T15:21:56.140" />
  <row Id="459" PostTypeId="2" ParentId="430" CreationDate="2009-11-15T15:35:09.920" Score="4" ViewCount="" Body="&lt;p&gt;It depends on whether you're only talking about the bare Arduino, or Arduinos with shields or other augmented bits attached.  One great thing about Arduinos is that it's relatively easy to design shields that add capabilities to the Arduino.  Without anything attached, the Arduino is pretty useless.  It has no way to interact with the outside world other than USB serial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you've got peripherals added to your Arduino you communicate wirelessly, read sensors, trigger motors, audio outputs, light shows, etc.  The sky's the limit.  I especially like being able to put an entire microcontroller development environment, including programmer and an assortment of components (jumper wires, resistors, etc) in my laptop bag and go off to a coffee shop to hack on it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What the stock arduino doesn't do well:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;heavy processing - like face or motion detection from a camera.  It just doesn't have the processing power or RAM for it.&lt;/li&gt;&#xA;&lt;li&gt;super low power consumption - the stock arduino tends to draw too much current for really long-lived battery powered applications.  For those you have to switch to an arduino compatible device (e.g. Arduino Pro Mini), at which point running for months on some AAs is easily achievable (and you can still prototype with the stock arduino).&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-11-15T15:35:09.920" />
  <row Id="460" PostTypeId="1" AcceptedAnswerId="465" CreationDate="2009-11-15T17:00:13.657" Score="7" ViewCount="981" Body="&lt;p&gt;I'm putting together a design for a hardware random number generator that will utilize multiple sources of entropy (&lt;strong&gt;combined&lt;/strong&gt;):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Ambient light&lt;/li&gt;&#xA;&lt;li&gt;Ambient sound (and sound levels)&lt;/li&gt;&#xA;&lt;li&gt;Ambient temp&lt;/li&gt;&#xA;&lt;li&gt;Ambient humidity&lt;/li&gt;&#xA;&lt;li&gt;Position of the device itself (upside down, tilted left, titled right, etc)&lt;/li&gt;&#xA;&lt;li&gt;Other sources in the future, possibly even GPS data (marked possible because two users may be standing next to each other, hence possibly deterministic if you know them.)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;My idea is to make an entropy pool 'recharger' that people can carry around with them during their day while it continues to write to a USB drive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After a few hours, the user will have a nice ~4GB entropy pool that can be plugged in to a PC and used. I can't afford the really expensive QRNG's based on light or radioactive decay, so I'm trying to come up with something cheaper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your opinion, is Arduino the best choice for prototyping this? If not, what would you recommend?&lt;/p&gt;&#xA;" OwnerUserId="216" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-10T04:32:24.593" LastActivityDate="2011-05-19T14:15:51.303" Title="Is Arduino ideal for making a HRNG (hardware random number generator)?" Tags="&lt;arduino&gt;&lt;generator&gt;" AnswerCount="10" CommentCount="1" FavoriteCount="1" />
  <row Id="461" PostTypeId="2" ParentId="321" CreationDate="2009-11-15T17:57:09.820" Score="2" ViewCount="" Body="&lt;p&gt;I used a very similar 5x7 matrix on Arduino a while ago.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is how I hooked it up and a small sample sketch, &#xA;&lt;a href=&quot;http://www.local-guru.net/blog/2009/04/03/5x7-led-matrix-on-my-arduino&quot; rel=&quot;nofollow&quot;&gt;http://www.local-guru.net/blog/2009/04/03/5x7-led-matrix-on-my-arduino&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="123" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2011-02-05T05:00:53.337" LastActivityDate="2011-02-05T05:00:53.337" />
  <row Id="462" PostTypeId="2" ParentId="460" CreationDate="2009-11-15T18:15:31.687" Score="4" ViewCount="" Body="&lt;p&gt;There are some interesting circuits for HRNG without the need for ambient entropy sources: &#xA;&lt;a href=&quot;http://www.cryogenius.com/hardware/rng/&quot; rel=&quot;nofollow&quot;&gt;http://www.cryogenius.com/hardware/rng/&lt;/a&gt;&#xA;&lt;a href=&quot;http://robseward.com/itp/adv%5Ftech/random%5Fgenerator/&quot; rel=&quot;nofollow&quot;&gt;http://robseward.com/itp/adv_tech/random_generator/&lt;/a&gt;&#xA;&lt;a href=&quot;http://www.google.com/search?source=ig&amp;amp;hl=en&amp;amp;rlz=&amp;amp;=&amp;amp;q=random+number+generator+circuit&amp;amp;aq=f&amp;amp;oq=&amp;amp;aqi=g-m1&quot; rel=&quot;nofollow&quot;&gt;and more...&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's definitely possible to adapt one of these circuits to an &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoShields&quot; rel=&quot;nofollow&quot;&gt;Arduino shield&lt;/a&gt;. The Arduino would then act as a gateway between the HRNG and a PC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really need ambient entropy input, the arduino has 6 &lt;a href=&quot;http://arduino.cc/en/Tutorial/AnalogInput&quot; rel=&quot;nofollow&quot;&gt;analog input channels&lt;/a&gt; so you can read out &lt;a href=&quot;http://www.freeduino.org/&quot; rel=&quot;nofollow&quot;&gt;almost any sensor that you can think of&lt;/a&gt; and use the data as a source for a random seed.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-15T18:15:31.687" CommentCount="0" />
  <row Id="463" PostTypeId="2" ParentId="321" CreationDate="2009-11-15T19:04:19.593" Score="1" ViewCount="" Body="&lt;p&gt;I have not done it yet, but you can address 5x7 matrix's using a maxim max7221 IC.  This can be controlled via a serial port connection to the duino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/playground/Main/LEDMatrix&quot; rel=&quot;nofollow&quot;&gt;There are more details here&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have just ordered an arduino and have the max chip sat beside me.  I will be driving Common Cathode LED 7 segment displays with mine.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-15T19:04:19.593" />
  <row Id="464" PostTypeId="1" AcceptedAnswerId="469" CreationDate="2009-11-15T19:05:30.727" Score="17" ViewCount="933" Body="&lt;p&gt;When working with AVR microcontrollers or Arduinos, what is something that if you had known sooner would have saved you a lot of time or frustration?&lt;/p&gt;&#xA;" OwnerUserId="105" LastActivityDate="2010-08-05T10:46:19.090" CommunityOwnedDate="2009-11-17T17:36:44.030" Title="What did you wish you knew?" Tags="&lt;avr&gt;&lt;microcontroller&gt;&lt;arduino&gt;" AnswerCount="16" FavoriteCount="7" />
  <row Id="465" PostTypeId="2" ParentId="460" CreationDate="2009-11-15T19:38:18.650" Score="10" ViewCount="" Body="&lt;p&gt;I think you'll want to go down the path busz suggests. Search for the concept &quot;diode noise&quot;. The PN junctions in diodes and transistors can produce close to perfect Gaussian white noise.  Sampling that should be a source of entropy that's better than any environmental source.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem with most environmental/ambient data is the values just don't change that much over time: temperature, humidity, light and sound all have less than an order-of-magnitude of variability with really strong modes. An accelerometer to measure motion might be a good source of variability if mounted on a person, but you'd likely have to do a bit of signal processing to remove the normal modes of oscillation that are present in how humans move.  An ambient light &amp;amp; sound source might have some pretty high variability if placed in an high-density urban space, but again I think there would be a lot of repetition.  I still think the best source of entropy would be going down towards fundamental physical properties of materials like diode noise than going up in scale and looking at environmental factors capable of being read by a microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-15T19:38:18.650" />
  <row Id="466" PostTypeId="1" AcceptedAnswerId="470" CreationDate="2009-11-15T21:43:52.733" Score="3" ViewCount="553" Body="&lt;p&gt;&lt;strike&gt;&lt;a href=&quot;http://data:image/svg+xml;base64,[encoded data, 10204 characters]&quot; rel=&quot;nofollow&quot;&gt;Here's a circuit diagram.&lt;/a&gt;&lt;/strike&gt; Circuit diagram is below.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a signal response test circuit from the spec sheet for a HA-5195 op amp and looks like a non-inverting amplifier circuit with a gain of 5, plus the 200Ω resistor between Vout and ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone explain the purpose of the 200Ω resistor? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully you can see the circuit diagram. If not, it's the canonical (I assume?) non-inverting amplifier circuit with R1 = 400Ω and Rf = 1.6kΩ, plus the resistor I'm asking about.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;em&gt;Actually that's a secondary purpose for this question, to try out the idea of posting schematics as SVG data. This should work in most browsers, but not IE (unless you have the Google Chrome Frame installed). It was drawn using &lt;a href=&quot;http://svg-edit.googlecode.com/svn-history/r877/trunk/editor/svg-editor.html&quot; rel=&quot;nofollow&quot;&gt;this online svg editor&lt;/a&gt;, which is an alpha version of &lt;a href=&quot;http://code.google.com/p/svg-edit/&quot; rel=&quot;nofollow&quot;&gt;svg-edit&lt;/a&gt;. It's my idea that this editor could be customized a little to be a decent way to post circuit diagrams here. The image is all in the URL - no image hosting is required.&lt;/em&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;strike&gt;Here is the diagram inline, but it doesn't seem to work, at least on Safari: &lt;img src=&quot;http://data:image/svg+xml;base64,[encoded data, 10204 characters]&quot; alt=&quot;Circuit diagram&quot; /&gt;&lt;/strike&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: No luck clicking the obove link to the diagram for me. I think the URL is too gigantic - it encodes the entire diagram. I give up. Here's an image of the one in the spec.&#xA;&lt;img src=&quot;http://grumdrig.com/image/amptest.png&quot; alt=&quot;Circuit diagram&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="84" LastEditorUserId="84" LastEditorDisplayName="" LastEditDate="2009-11-16T17:20:37.343" LastActivityDate="2009-11-16T18:27:02.443" Title="Why the resistor in this op-amp circuit?" Tags="&lt;circuit&gt;&lt;resistor&gt;&lt;op-amp&gt;&lt;amplifier&gt;" AnswerCount="3" CommentCount="9" />
  <row Id="467" PostTypeId="2" ParentId="466" CreationDate="2009-11-15T21:54:34.093" Score="3" ViewCount="" Body="&lt;p&gt;Maybe to give a fixed, known impedance to the opamp?&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-15T21:54:34.093" />
  <row Id="468" PostTypeId="2" ParentId="464" CreationDate="2009-11-15T22:12:58.167" Score="3" ViewCount="" Body="&lt;p&gt;I have used the Arduino a fair bit and I wish I had known how difficult serial IO was on arbitrary pins. I eventually settled on a 3rd party library but it took weeks to get to that point and even then it was not rock-solid reliable.&lt;/p&gt;&#xA;" OwnerUserId="25" LastActivityDate="2009-11-15T22:12:58.167" />
  <row Id="469" PostTypeId="2" ParentId="464" CreationDate="2009-11-15T22:13:09.887" Score="16" ViewCount="" Body="&lt;p&gt;For me it's the other way around: I wish I knew about Arduino's and AVR's before they tried to teach me electronics in secondary school. Learning Ohms law without ever having seen or used an actual resistor was not a pretty exercise. Back then it would be ideal to have an Arduino around to play around with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because of this, I would have like to have known more about basic electronics. Simple questions as: why should I care about current? (because things blow up if you don't) Why should I care about resistors? (same here and other stuff) Why should I care about caps? (all kinds of reasons) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having the ability to play with micros (and frying them in the process) has tought me most of these things but I wish I had learned them sooner. (Classic chicken and egg problem I guess)&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-11-15T22:13:09.887" CommentCount="3" />
  <row Id="470" PostTypeId="2" ParentId="466" CreationDate="2009-11-15T22:14:05.090" Score="10" ViewCount="" Body="&lt;p&gt;It is a load resistor probably. Often op-amp circuits have the &quot;load&quot; placed as a resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current an op-amp drives can greatly increase it's non-ideal property. The finite gain becomes more apparent as you drive more current, along with the output resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When simulating an OP-amp you should always attempt to place a load resistor across the output for the effective load you are connecting to. If you want to look up a method of doing something like this, &lt;a href=&quot;http://en.wikipedia.org/wiki/Th%C3%A9venin%27s%5Ftheorem&quot; rel=&quot;nofollow&quot;&gt;Thevenin equivalent circuits&lt;/a&gt; are a good example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope I helped, let me know if you need more detail.&#xA;-Max Murphy&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Community Wiki is on if anyone wants to expand.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-15T22:14:05.090" CommunityOwnedDate="2009-11-15T22:14:05.090" CommentCount="2" />
  <row Id="471" PostTypeId="2" ParentId="59" CreationDate="2009-11-16T00:19:47.120" Score="1" ViewCount="" Body="&lt;p&gt;You could also use a &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;BeagleBoard&lt;/a&gt; available for only $150 from &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9444&quot; rel=&quot;nofollow&quot;&gt;sparkfun&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2009-11-16T00:19:47.120" CommentCount="1" />
  <row Id="472" PostTypeId="1" CreationDate="2009-11-16T00:49:10.710" Score="6" ViewCount="1208" Body="&lt;p&gt;Hi all.&lt;br /&gt;&#xA;Not entirely sure if this applies to ChipHacker, if it doesn't, I apologise for posting. But it definitely applies to the subject of electronics in general.&lt;br /&gt;&#xA;Im currently working on my first PCB prototyping by using some pre-sensitized PCB board, purchased here - &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.maplin.co.uk/Module.aspx?ModuleNo=2033&quot; rel=&quot;nofollow&quot;&gt;Maplins UK&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However I'm having terrible trouble exposing and developing the board, it just never seems to turn out right. I haven't even reached the etching stage yet because I'm not happy with the presensitized developing results.&lt;br /&gt;&#xA;I'm looking for general tips and tricks, and how to follow the right 'path' to success - I seem to be getting worse at it for some reason! ;-)&lt;br /&gt;&#xA;I am using inkjet transparency sheets with the darkest tone applied for the mask, and after noticing you can see light thru the printed areas on the mask, I decided to double up, and sellotaped two identical transparencies aligned on top of each other. You can hold it up to the light and still see a kind of dull purple glow, but it is mostly opaque. I acknowledge this may be one of the causes of my troubles!&lt;br /&gt;&#xA;I started off using a normal 100watt lightbulb, with little success, exposures seemed to take 40 mins and beyond to have any effect at all and get very warm.&lt;br /&gt;&#xA;I used to hold the mask down onto the board using glass, but after realising glass blocks a lot of UV light, I decided to switch to a sheet of clear acrylic.&lt;br /&gt;&#xA;I then found a cheap portable UV sterilizer, which actually claims to emit UV-C light, I know UV-A is the type required to expose the board as far as I can work out but it seems to be having a much quicker effect, I see an effect even after just two minutes exposure.&#xA;The manual states it uses a &quot;Long life 4 watt germicidal UV lamp&quot;, and yes, its not what you'd call bright. The longest exposure I have done so far is about six minutes, and I still saw the same problem (See below).&lt;br /&gt;&#xA;According to their site, the boards are supposedly developed using a caustic soda solution.&#xA;On all of my attempts, I am seeing the circuit pattern appear, but the developed copper which is to be etched away ends up nowhere near as shiny as I'd expect it to be - I am expecting the photoresist layer to completely dissipate resulting in exposed shiny copper - going by a lot of those reference pcb etching sites on the internet. Instead I end up with varying degrees of random areas of shiny copper but mostly dull copper (partially disolved photoresist), and other areas complete bluey greeny photoresist layer.&lt;br /&gt;&#xA;I haven't tried etching yet, but its not difficult to see why I expect such a poorly exposed and developed board to poorly etch too. I can't imagine the 'mostly dull copper' areas will etch at all given the photoresist is only partially dissipated.&lt;br /&gt;&#xA;I'm cutting off small areas of my two medium sized pre-sensitized boards for testing purposes, and I'm running out quickly!&lt;br /&gt;&#xA;So I am unclear and am proceeding very slowly because of all these variables -&lt;br /&gt;&#xA;-Not sure about exposure time (for my lamp).&lt;br /&gt;&#xA;-Not sure about UV light position and height required.&lt;br /&gt;&#xA;-Not sure if my mask pattern is opaque enough (to UV light).&lt;br /&gt;&#xA;-Not sure about correct proportions of caustic soda to water&lt;br /&gt;&#xA;-Not sure about time to leave the board in the caustic soda - whether I'm going too far developing.&lt;br /&gt;&#xA;-Not sure about dipping in water to stop the development - Can you put it back in the caustic soda to continue development if you didn't leave it in long enough? Also how can you tell!?&lt;br /&gt;&#xA;-I also dont know if a developed pre-sensitized board stays so, and wont fade as its left in daylight over time. How long before normal daylight affects a pre-sensitized developed board?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help anybody could give me would be appreciated. I haven't kept a decent log of my activities, to learn effectively, because I thought I'd have nailed it by now! However I can provide pictures of my efforts so far, if need be.&lt;br /&gt;&#xA;Thanks so much!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stu&lt;/p&gt;&#xA;" OwnerUserId="284" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-16T01:33:47.020" LastActivityDate="2010-09-07T06:40:15.667" Title="PCB prototyping with Presensitized copper boards" Tags="&lt;pic&gt;&lt;prototyping&gt;&lt;board&gt;&lt;pcb&gt;&lt;electronics&gt;" AnswerCount="5" CommentCount="4" FavoriteCount="1" />
  <row Id="475" PostTypeId="2" ParentId="472" CreationDate="2009-11-16T08:56:03.063" Score="3" ViewCount="" Body="&lt;p&gt;Inkjet on transparency is indeed weak for this application.  You need to use a laser printer, or print it on your inkjet at 2X and positive on paper.  Take it to a local print shop and they can reduce it 2:1 and make a negative for $10 or less.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your supplier's web page clearly says 1 teaspoon sodium hydroxide (caustic soda) to 0.5 liters water for the developer solution.  Since you say you don't know the concentration, it tells me you haven't read their directions carefully enough, so that is your next step.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck.&lt;/p&gt;&#xA;" OwnerUserId="286" LastActivityDate="2009-11-16T08:56:03.063" CommentCount="2" />
  <row Id="476" PostTypeId="2" ParentId="472" CreationDate="2009-11-16T09:04:55.270" Score="7" ViewCount="" Body="&lt;p&gt;&lt;em&gt;-Not sure about exposure time (for my lamp).&#xA;-Not sure about UV light position and height required.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With these you just have to experiment, I'd suggest putting the board fairly close to the lamp (20-50mm or so). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suggest you take one longish strip of photoresist PCB and put something on top of it that blocks UV light, then expose the strip while moving the UV blocker away at predefined intervals (say, every 10 seconds). What you will end up with is a PCB exposed in steps for different exposure times (10s, 20s, 30s, 40s, 50s etc.), then just pick the exposure time that gives off the best result.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;-Not sure if my mask pattern is opaque enough (to UV light).&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's a normal transparency sheet it should be fine. Printing to these with a laser printer works but this depends on your printer. Large areas of black might get overexposed but this depends on your printer. If your quality of black is bad you can print two sheets and align them on top of eachother.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;-Not sure about correct proportions of caustic soda to water&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been using a 3% solution of NaOH (KOH works too) which seems to work well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;-Not sure about time to leave the board in the caustic soda - whether I'm going too far developing.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You just basically move it around in the solution until it seems developed (black stuff comes off the board), usually it develops quite quickly (under 30s) but this depends on your solution. If your solution is too strong or you develop it too long it will strip off all the photoresist if you keep it in the solution too long. A solution not concentrated enough won't successfully develop the board (again, 3% solution seems to work well). Washing the board under a faucet afterwards works well. You can continue developing after taking it away from the solution. You can actually even continue developing after etching the board a bit, just remember to wash the board. Putting the board in the etching solution shows you pretty well where the board has photoresist and where it doesn't, the copper exposed to the etching solution goes to this &quot;dull&quot; color/texture in under a minute in the etching solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;-I also dont know if a developed pre-sensitized board stays so, and wont fade as its left in daylight over time. How long before normal daylight affects a pre-sensitized developed board?&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A board with the plastic shield &lt;em&gt;SHOULDNT&lt;/em&gt; be affected by daylight but to be sure I'd keep them in a place shielded from light (like a drawer).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Btw. I'd suggest you try to expose your boards with a 11W fluorescent table lamp (the ones with a &quot;U&quot;-shaped lamp, they should be pretty common and cost like 10e from Ikea). Put the lamp quite close to the board (like 50mm close, and have a thin plate of glass over the board to keep the mask close to the board). You can get suitable plate of glass from picture frames (again, Ikea is a good place to get these), just make sure its real glass and not plastic. Expose for 12-15min (I've used 13,5min for my boards and setup). I have been using  this method succesfully for a long time. Won't work for large boards due to the lamp being so narrow but for small boards it works well.&lt;/p&gt;&#xA;" OwnerUserId="140" LastActivityDate="2009-11-16T09:04:55.270" CommentCount="7" />
  <row Id="478" PostTypeId="2" ParentId="460" CreationDate="2009-11-16T09:20:14.830" Score="2" ViewCount="" Body="&lt;p&gt;I agree with the above two responses.  Human activities and ambient readings will make a terrible random pool.  But it sounds like you will only be convinced of this by trying it and checking the resulting randomness yourself. It will be a great learning experience for you!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Arduino is fine for this application.  All of the sensors you are interested in can be attached to Arduino and there are Arduino libraries available for those sensors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out these tutorials on connecting sensors to Arduino: &lt;a href=&quot;http://www.ladyada.net/learn/sensors/&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/learn/sensors/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="286" LastActivityDate="2009-11-16T09:20:14.830" CommentCount="0" />
  <row Id="480" PostTypeId="2" ParentId="437" CreationDate="2009-11-16T09:57:57.213" Score="1" ViewCount="" Body="&lt;p&gt;The '238 have only one of eight outputs logic high, sourcing current, the rest of the pins will be logic low, sinking current.  The '138 is precisely the opposite, one of eight pins can be low, sinking current, the rest will be high, sourcing current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To &quot;invert&quot; the function of the '138, you could use eight PNP transistors with the bases each tied to an output of the '138 with a resistor, the emitters all connected to +5 and the collectors each connected to one of your servo connectors.  Or use a bunch of inverters (74HCT04 or octal 74HCT240) to change the sense of the outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your choice of 1 of 8 decoders will limit what you can do with your servos, as your circuit can only activate one output at a time.  Max speed of any one servo will be limited by the number of servos that you want active.  If you wanted all 64 channels on, for example, they would all be running at at average of 1/64th speed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PCF8575C is very handy for expanding digital IO using serial I2C protocol from devices like Arduino.  You could run 64 servos using 2 pins on the Arduino and 4 PCF8575Cs.  This would give you more flexibility in setting your PWM duty cycles.&lt;/p&gt;&#xA;" OwnerUserId="286" LastActivityDate="2009-11-16T09:57:57.213" CommentCount="3" />
  <row Id="481" PostTypeId="2" ParentId="464" CreationDate="2009-11-16T10:23:07.730" Score="11" ViewCount="" Body="&lt;p&gt;I wish I had known that every math class I would ever take I would use again, and more than once, and I sure as hell wish I had paid a bit more attention.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wish I had a lot of hands on experience programming and using FPGAs. They are the new wave of embedded system development and I have only basic class experience with them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wish I had been taught how to use all of the modules of Microcontrollers in classes before my boss expected me to use them all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I sure as hell wish that my university's electrical engineering department started design classes before senior year.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2009-11-17T11:09:00.793" LastActivityDate="2009-11-17T11:09:00.793" CommentCount="2" />
  <row Id="482" PostTypeId="2" ParentId="464" CreationDate="2009-11-16T11:55:49.043" Score="11" ViewCount="" Body="&lt;p&gt;I wish I'd known how much FUN it was :) If I had I would have started playing with this stuff much sooner!&lt;/p&gt;&#xA;" OwnerUserId="255" LastActivityDate="2009-11-16T11:55:49.043" />
  <row Id="483" PostTypeId="2" ParentId="224" CreationDate="2009-11-16T11:56:57.343" Score="6" ViewCount="" Body="&lt;p&gt;Is there a reason you want to use resin as opposed to a product made for the purpose?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mouser.com/Search/Refine.aspx?Keyword=conformal+coating&quot; rel=&quot;nofollow&quot;&gt;Conformal coating&lt;/a&gt; is what we use in the electronics industry.  One advantage of this is that some types of coating are made to be removable with solvents, which would allow you to modify your repair your board after it was coated. &lt;/p&gt;&#xA;" OwnerUserId="222" LastEditorUserId="222" LastEditorDisplayName="" LastEditDate="2009-11-16T12:10:28.507" LastActivityDate="2009-11-16T12:10:28.507" CommentCount="1" />
  <row Id="484" PostTypeId="1" AcceptedAnswerId="10514" CreationDate="2009-11-16T12:32:18.903" Score="5" ViewCount="189" Body="&lt;p&gt;Has anyone had any experiences with laser cutting services in the UK? I've googled but most of the results seem to be for expensive industrial setups. What I'm looking for is someone who can do pretty much what the Pololu service &lt;a href=&quot;http://www.pololu.com/catalog/product/749&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; does but nearer to me to reduce shipping time and costs. &lt;/p&gt;&#xA;" OwnerUserId="255" LastActivityDate="2011-02-21T17:52:07.627" Title="Reasonably priced laser cutting service in the UK?" Tags="&lt;laser&gt;&lt;cutting&gt;&lt;robotics&gt;" AnswerCount="4" />
  <row Id="485" PostTypeId="2" ParentId="444" CreationDate="2009-11-16T17:09:22.530" Score="2" ViewCount="" Body="&lt;p&gt;I've done work with similar full duplex RF modules, and without the datasheet you're going to have a hard time working with them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to implement multiple channels there's usually a PLL in there controlled by a microcontroller, which you would talk to via SPI.  It takes a chunk of SPI data to set the radios up in the first place, and then you have to pair them which takes another smaller chunk of data to perform basic communications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Further, they may or may not have data slicers in them, but even if they do you'll still end up needing to implement manchester encoding or another RF suitable data stream encoding in order to transmit data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lastly, they are very, very noisy.  The phone and base station have a ton of filtering and compression in order to overcome the noise these modules typically have.  This means your data stream has to be exceptionally robust.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you are really committed to dealing them with no data sheet, you need to do one or both of the following:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Probe the lines with it connected and working in the handset and base station, and record all the digital setup data it uses.  Also record when it pairs to see if you can understand how it handles that.  Try to duplicate the setup, and dissect the pairing traffic so you can understand how to set the send and receive channel/frequency for each module.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Take the can apart and see if you can decode the circuit and read the chip part numbers.  You may be able to get enough information from the circuit and chip data sheets to set it up yourself.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you are merely interested in modules like that, but want to save yourself the frustrating and time, you should consider these:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.laipac.com/easy_900dv_eng.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.laipac.com/easy_900dv_eng.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are easy to work with, though you still have to deal with the noise and data slicing issues.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2009-11-16T17:09:22.530" />
  <row Id="486" PostTypeId="2" ParentId="466" CreationDate="2009-11-16T18:27:02.443" Score="8" ViewCount="" Body="&lt;p&gt;Right above that diagram, in the &lt;strong&gt;NOTES&lt;/strong&gt; section, it says R&lt;sub&gt;L&lt;/sub&gt; = 200&amp;Omega;.  &quot;R&lt;sub&gt;L&lt;/sub&gt;&quot; means &quot;load resistor&quot;.  You'll see that they show it in all the other diagrams, too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This op-amp is specified for high-frequency video applications, and in these cases you generally have low impedance loads like this so the &lt;a href=&quot;http://en.wikipedia.org/wiki/Impedance%5Fmatching&quot; rel=&quot;nofollow&quot;&gt;sources and loads can be matched&lt;/a&gt; to avoid reflections back up cables.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In &lt;a href=&quot;http://www.intersil.com/data/an/an551.pdf&quot; rel=&quot;nofollow&quot;&gt;Recommended Test Procedures for Operational Amplifiers&lt;/a&gt; they describe using a load resistance when measuring transient response, and have a table of recommended values for each part (0.2 k&amp;Omega; for this part).  I guess the high-speed transient response is affected by the load (I don't work with high-speed stuff), so they're showing it in-circuit to show a real-life application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The overall gain will also be decreased, since the output impedance of the op-amp is 25-30 &amp;Omega; (as shown in page 2 of the datasheet), and the maximum output level will be decreased, as shown in Figure 13.  In the &lt;a href=&quot;http://www.intersil.com/data/an/an9510.pdf&quot; rel=&quot;nofollow&quot;&gt;application notes&lt;/a&gt;, it says: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;In Figure 19, R&lt;sub&gt;IN&lt;/sub&gt; is usually the&#xA;  terminating resistance for the input&#xA;  cable, and it is usually 50Ω or 75Ω .&#xA;  R&lt;sub&gt;M&lt;/sub&gt; is the matching resistance for the&#xA;  cable being driven, and R&lt;sub&gt;T&lt;/sub&gt; is the&#xA;  terminating resistance for the driven&#xA;  cable. R&lt;sub&gt;T&lt;/sub&gt; is often shown here for gain&#xA;  calculations while it is physically&#xA;  placed at the cable end.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;In this case, R&lt;sub&gt;T&lt;/sub&gt; is the same as R&lt;sub&gt;L&lt;/sub&gt; in the datasheet.  So it's being shown &quot;here&quot; for its effect on the gain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, in general, they're showing the load in the circuit to demonstrate that their measurements were tested in a real-life video situation.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2009-11-16T18:27:02.443" CommentCount="1" />
  <row Id="487" PostTypeId="2" ParentId="484" CreationDate="2009-11-16T19:12:09.520" Score="2" ViewCount="" Body="&lt;p&gt;I have used Ponoko.com and they are very good. I am in the US, but I use the UK company. They are very good with their support and that is highly valuable to me!&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-11-16T19:12:09.520" CommentCount="2" />
  <row Id="488" PostTypeId="2" ParentId="472" CreationDate="2009-11-16T19:17:16.597" Score="3" ViewCount="" Body="&lt;p&gt;I use an Inkjet printer and it works great. You need 3M Inkjet transparency paper because it is textured. I have an instructable located at:&#xA;&lt;a href=&quot;http://www.instructables.com/id/Creating-Printed-Circuit-Boards-with-a-INKJET-Prin/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Creating-Printed-Circuit-Boards-with-a-INKJET-Prin/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-11-16T19:17:16.597" CommentCount="7" />
  <row Id="489" PostTypeId="1" AcceptedAnswerId="499" CreationDate="2009-11-16T19:48:15.433" Score="1" ViewCount="700" Body="&lt;p&gt;I'm trying to control a DC (pager) motor with a sound signal so that I can use an audio synthesizer to control the speed of the motor. I'm hoping to modulate the speed of the motor at audio rate (1-200hz). I need to do a few things. &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Convert AC -&gt; DC. A rectifier will chop the negative or fold it up, but how can I shift the waveform up, per se? What is the circuit equivalent of f(x)+1? (or will a rectifier be good enough)&lt;/li&gt;&#xA;&lt;li&gt;I could send the rectified signal straight to the motor, but this might be a waste of energy. Two strategies present themselves:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Use a comparator to send only the peaks&lt;/li&gt;&#xA;&lt;li&gt;Use PWM (Frequency -&gt; Pulsewidth)&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Which do you think will work better? Can you think of other strategies? Should I implement this with, say, a small AVR chip, or with analog electronics?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An additional constraint is that the circuit has to be small. Ideally my motor + battery + circuit would be quarter-sized. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Any advice would be appreciated.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I'll also need to do some lowpass filtering to avoid overwhelming the motors with information they can't respond to. Thoughts on this would be appreciated as well.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will be using &lt;a href=&quot;http://www.solarbotics.com/products/vpm2/&quot; rel=&quot;nofollow&quot;&gt;this pager motor&lt;/a&gt; from Solarbotics possibly in conjunction with &lt;a href=&quot;http://www.precisionmicrodrives.com/product_info.php?products_id=172&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; from Precision Microdrives, who specialize in &lt;a href=&quot;http://www.precisionmicrodrives.com/vibration_motors.php&quot; rel=&quot;nofollow&quot;&gt;vibration motors&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2009-11-17T04:18:09.470" LastActivityDate="2010-07-29T07:17:40.407" CommunityOwnedDate="2009-11-17T04:18:09.470" Title="Controlling DC (Pager) Motor with Audio Signal" Tags="&lt;fm&gt;&lt;sound&gt;&lt;audio&gt;&lt;motor&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="490" PostTypeId="2" ParentId="447" CreationDate="2009-11-16T19:49:22.867" Score="1" ViewCount="" Body="&lt;p&gt;At the 4000Hz and 8000Hz, you're looking at 125 microseseconds and 62.5 microseconds pulse width, respectively.  That might be slow enough for &lt;a href=&quot;http://www.arduino.cc/en/Reference/PulseIn&quot; rel=&quot;nofollow&quot;&gt;Arduino's built-in pulseIn() function&lt;/a&gt;.  There's some setup and teardown time of the function, so if your signal switches between 4kHz &amp;amp; 8kHz too rapidly, you might miss some bits.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-16T19:49:22.867" />
  <row Id="491" PostTypeId="1" CreationDate="2009-11-16T20:09:00.977" Score="1" ViewCount="467" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/317/low-voltage-motion-sensor&quot;&gt;low voltage motion sensor&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I am looking for a motion sensor device that can track person/animal walking by it and record time/date of the event(s). It needs to be able to run on a small battery or two (maybe 2 AA's or a 9 volt). It does not have to have a screen, just an input connection for a screen to hook up to in order to read the information and set the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Total cost would be only like $10 to $15. My initial research on the internet points me to look at a pyroelectric infrared sensor or some kind of passive infrared sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can it also detect and record which direction something walked past?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible?&lt;/p&gt;&#xA;" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:32:05.137" LastActivityDate="2011-06-02T02:32:05.137" ClosedDate="2011-06-02T12:41:37.630" Title="low voltage motion sensor" Tags="&lt;sensor&gt;&lt;voltage&gt;&lt;infrared&gt;&lt;motion&gt;" AnswerCount="0" CommentCount="1" FavoriteCount="0" />
  <row Id="492" PostTypeId="2" ParentId="317" CreationDate="2009-11-16T20:18:06.503" Score="2" ViewCount="" Body="&lt;p&gt;This should be fairly simple to make with a microcontroller (maybe an arduino) and a premade motion sensor. Just interface them together and make the microcontroller save the time to the eeprom everytime motion is seen. Data could be uploaded with a computer through a serial connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Recording the direction might be possible with two sensors spaced some distance away from eachother (the person/animal is moving to the direction of the sensor that picked it up last) but this might not be too reliable, at least not if the sensors are overlapping.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A cheap and a simple solution would be to use a premade motion sensor and an old computer/laptop and connect the sensor to the parallel port or to the serial port and just log stuff with the computer, but it would not be battery powered.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think making a motion sensor yourself is worth the hassle, premade modules are cheap and plentiful and should be easy to interface with.&lt;/p&gt;&#xA;" OwnerUserId="140" LastEditorUserId="140" LastEditorDisplayName="" LastEditDate="2009-11-16T20:23:16.183" LastActivityDate="2009-11-16T20:23:16.183" />
  <row Id="493" PostTypeId="2" ParentId="489" CreationDate="2009-11-16T21:12:52.930" Score="1" ViewCount="" Body="&lt;p&gt;Quarter-sized is pretty small, you're going to need to go all surface mount components on a PCB to get to that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically you want to create vibrations that is related to sound...you know there are actually some devices out there that already do this, but they aren't exactly PG-rated, so I'm not sure if I can link to them here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you want to go based simply on the volume of the audio signal, or something else? Volume is pretty easy to sense, you simply measure the voltage peaks, you could do this with the ADC on an AVR for example, then use PWM to drive the motor, as you suggested. They have some pretty small AVR chips (like 8-pin TSSOP is the tiniest I think), but the tiny tiny ones might not have both ADC and PWM, so you might need a tiny bit larger.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-16T21:12:52.930" CommentCount="1" />
  <row Id="494" PostTypeId="2" ParentId="484" CreationDate="2009-11-16T21:31:56.037" Score="3" ViewCount="" Body="&lt;p&gt;I suppose this question boils down to what you consider a reasonable rate, too? I have no experience of the going rate, are we talking a couple of quid, or £50-100? If there just isn't anyone you can find locally then maybe it's time to build your own. It's been posted before, but here's the link to the Instructable about &lt;a href=&quot;http://www.instructables.com/id/Laser-cutter-start-slicing-stuff-for-under-50-dol/&quot; rel=&quot;nofollow&quot;&gt;building your own laser cutter for less than 50 dollars&lt;/a&gt;, I suppose it also depends how many times you'll need to use it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some Secondary schools have access to laser cutters, maybe trawling through some of your local schools or colleges might throw some up. You may be able to do a deal with them, ie share some of your technological know how with them in exchange for some laser cutting, maybe a robot building session or a talk about programming to some VI Formers. What about the University of Surrey, do they not have anything?&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-16T21:31:56.037" CommentCount="1" />
  <row Id="495" PostTypeId="1" CreationDate="2009-11-16T22:07:26.143" Score="7" ViewCount="584" Body="&lt;p&gt;The title pretty much says it all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an idea to try out involving a op-amp differentiator circuit and a diode bridge, but I am flying blind.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also I am trying to accomplish this without a micro-controller.&lt;/p&gt;&#xA;" OwnerUserId="290" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-11-17T23:03:07.913" LastActivityDate="2009-12-04T18:06:04.053" Title="How can I convert the output from a momentary switch to a pulse on push and a pulse on release?" Tags="&lt;op-amp&gt;&lt;circuit&gt;&lt;momentary&gt;&lt;switch&gt;" AnswerCount="6" CommentCount="2" />
  <row Id="496" PostTypeId="2" ParentId="495" CreationDate="2009-11-16T22:49:06.200" Score="4" ViewCount="" Body="&lt;p&gt;There might be a way to do it with a 555 timer set up as a one-shot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One D flip flop and one XOR gate will also do it.  Exact logic left as an exercise to the reader.&lt;/p&gt;&#xA;" OwnerUserId="286" LastActivityDate="2009-11-16T22:49:06.200" />
  <row Id="497" PostTypeId="2" ParentId="317" CreationDate="2009-11-16T23:13:05.170" Score="1" ViewCount="" Body="&lt;p&gt;Parallax sells a PIR motion sensor for $9.99 and it is simple to hook up. You just have +5V, GND and then a signal pin. If you use an Arduino (&lt;a href=&quot;http://www.arduino.cc&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc&lt;/a&gt;) you can just hook that pin to one of the digital pins. You can build your own Arduino for pretty cheap as well. You can use an SD card to log the data to; and that can be hooked up to the Arduino as well. There is a SD Card shield in the Maker store for $13.95 &lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MKSEEED6&amp;amp;Click=37845&quot; rel=&quot;nofollow&quot;&gt;http://www.makershed.com/ProductDetails.asp?ProductCode=MKSEEED6&amp;amp;Click=37845&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-11-16T23:13:05.170" />
  <row Id="498" PostTypeId="2" ParentId="495" CreationDate="2009-11-17T00:31:07.990" Score="5" ViewCount="" Body="&lt;p&gt;Allowing a 555 but rejecting a microcontroller is silly, you can get a microcontroler in the same or smaller package than a 555, and as a bonus you can do debouncing in software, saving some extra components which would be required to debounce the signal for the 555. Same thing goes for D flip-flop and XOR gate...that's 2 ICs you need, in addition to the debouncing components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is your reason for wanting to avoid a microcontroller? The simplest ones are $1, probably much less in high quantities. If it's space, there is an 8-pin TSSOP AVR which is like 3x5 mm, pretty tiny.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-17T00:31:07.990" CommentCount="5" />
  <row Id="499" PostTypeId="2" ParentId="489" CreationDate="2009-11-17T02:41:35.810" Score="3" ViewCount="" Body="&lt;p&gt;Use PWM to drive the pager motor, at a frequency above human hearing (so you don't get audio whine from the PWM).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll need to choose  pager motor, and then characterize it to find what duty cycle produces what approximate frequency of spin.  Each motor will be slightly different, but motors manufactured at the same time should be close.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You won't be able to get an exact frequency without some form of feedback.  If you can get ahold of 3 phase pager motors then you can set the exact frequency of vibration, but they aren't easy to find, and are harder to drive properly.  They are the same type of motor used to run hard drive platters and CD/DVD discs.  If you rip apart a CD burner you should be able to take this motor, and you may be able to hack the motor drive circuitry to do what you need - but then you have to attach your own eccentric weight to the motor, and the whole assembly is going to be much larger than a pager motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if you're just looking for a close approximation, you may be able to characterize a particular pager motor and be satisfied with that.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2009-11-17T02:41:35.810" CommentCount="2" />
  <row Id="501" PostTypeId="2" ParentId="267" CreationDate="2009-11-17T04:00:35.577" Score="5" ViewCount="" Body="&lt;p&gt;If you end up using the Arduino I have ported the V-USB (formerly AVR-USB) library to run on it. It is also wrapped with a class to make interaction easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can create USB HID devices with it, e.g. keyboard, mouse, or joystick. You can also create a generic device that uses libusb on the host to control it--from Python, C, Processing etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My site has a PCB shield you can make that uses a USB socket and a few resistors etc:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.rancidbacon.com/ProjectLogArduinoUSB&quot; rel=&quot;nofollow&quot;&gt;http://code.rancidbacon.com/ProjectLogArduinoUSB&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can write Arduino code to send keystrokes as easily as:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;UsbKeyboard.sendKeyStroke(KEY_ENTER);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;or with a libusb &quot;driver&quot; you can send data like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;UsbStream.write(0xff)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;or read data with:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;UsbStream.read()&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;--Philip;&lt;/p&gt;&#xA;" OwnerUserId="294" LastActivityDate="2009-11-17T04:00:35.577" />
  <row Id="502" PostTypeId="2" ParentId="464" CreationDate="2009-11-17T04:14:57.340" Score="4" ViewCount="" Body="&lt;p&gt;I'm with Kortuk. I wish we'd started simple design classes before final year of university, but specifically I wish we'd gotten to use an Arduino board in my classes!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We used a specially configured board designed at University of Wollongong based on an old Motorola chip, all programmed in assembler via a monitoring application. Pain in the arse!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, I look up the course content for digital design now and they're all using Atmel AVR chips. &lt;em&gt;sigh&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also wish I had more time to tinker with 'em, 'cause that's the best way to learn!&lt;/p&gt;&#xA;" OwnerUserId="295" LastActivityDate="2009-11-17T04:14:57.340" CommentCount="3" />
  <row Id="503" PostTypeId="2" ParentId="495" CreationDate="2009-11-17T05:14:27.640" Score="6" ViewCount="" Body="&lt;p&gt;Depending on how much you want to invest in learning, the debouncing, xor, flip-flop solution would be the most &quot;basic&quot;. The 555 is a great circuit to learn about though.&#xA;Here is a page that walks through about a large number of applications for it: &lt;a href=&quot;http://www.kpsec.freeuk.com/555timer.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.kpsec.freeuk.com/555timer.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you look for &quot;Edge-triggering&quot; under the monostable section you will find what seems to be the solution you are looking for.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-17T05:14:27.640" CommentCount="1" />
  <row Id="504" PostTypeId="2" ParentId="184" CreationDate="2009-11-17T05:46:39.323" Score="5" ViewCount="" Body="&lt;p&gt;See &lt;a href=&quot;http://www.plusea.at/&quot; rel=&quot;nofollow&quot;&gt;http://www.plusea.at/&lt;/a&gt; for all kinds of wearable electronics.  &lt;a href=&quot;http://www.flickr.com/photos/plusea/4050956299/in/set-72157615409091847/&quot; rel=&quot;nofollow&quot;&gt;Gluing strips of conductive fabric&lt;/a&gt; is probably better than &lt;a href=&quot;http://www.flickr.com/photos/plusea/4107731597/in/set-72157622299881137/&quot; rel=&quot;nofollow&quot;&gt;conductive glue&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.kobakant.at/DIY/&quot; rel=&quot;nofollow&quot;&gt;How To Get What You Want&lt;/a&gt; by the same people has more details: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.kobakant.at/DIY/?cat=38&quot; rel=&quot;nofollow&quot;&gt;Traces&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.kobakant.at/DIY/?cat=24&quot; rel=&quot;nofollow&quot;&gt;Conductive materials&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm4.static.flickr.com/3087/2759097679%5Fd59b91f365.jpg?v=0&quot; alt=&quot;alt text&quot; /&gt;&lt;img src=&quot;http://farm4.static.flickr.com/3340/3608026021%5Fe276861736.jpg?v=0&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2009-11-19T00:41:38.927" LastActivityDate="2009-11-19T00:41:38.927" />
  <row Id="505" PostTypeId="2" ParentId="441" CreationDate="2009-11-17T06:05:07.650" Score="5" ViewCount="" Body="&lt;p&gt;It does what it does very well. Spin is a nice easy language to get your head around and as an interpreted language, quite efficient with a nice compact bytecode. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Spin is not blazingly fast, but raw PASM is pretty sprightly (50ns instruction cycle).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having 8 identical cores with a completely deterministic instruction cycle makes for a very versatile little chip. As long as you remember it is a microcontroller and play within its limits, it's an incredibly nice chip to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I keep a stack of proto-boards handy for rapid prototypes. The ability to do crash and burn compile/test cycles in a matter of seconds (it takes about 7 seconds to download the absolute largest program into the chip and huge compiles rarely take more than 2 seconds - more often in the hundreds of milliseconds) makes for a very fast turnaround development cycle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Parallax really concentrates on the beginner market, so along with being a pretty potent little machine, it is &lt;em&gt;very&lt;/em&gt; easy for a greenhorn to get working in short order.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Native 32 bit integer math is nice too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt; I did not mean that to sound like Parallax products are only suitable for the beginner. The Propeller is a &quot;grown ups&quot; processor with plenty of oomph in the right places, it's just that Parallax provides a lot of hand holding for the beginner to help them get started.&lt;/p&gt;&#xA;" OwnerUserId="299" LastEditorUserId="299" LastEditorDisplayName="" LastEditDate="2009-11-17T06:16:50.823" LastActivityDate="2009-11-17T06:16:50.823" />
  <row Id="506" PostTypeId="2" ParentId="441" CreationDate="2009-11-17T06:17:28.080" Score="3" ViewCount="" Body="&lt;p&gt;Spin is fast enough to bit-bang serial I/O at 19200 Baud.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a large library of routines, mostly I/O drivers, but with a vocal tract synthesis program that sings in 4-part harmony and a variety of video drivers for TV and VGA displays among other things.  There's even a floating point library including the usual transcendental functions.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-17T06:17:28.080" />
  <row Id="507" PostTypeId="2" ParentId="441" CreationDate="2009-11-17T06:31:53.210" Score="2" ViewCount="" Body="&lt;p&gt;I agree with Brad Campbell's post above. I started Propeller programming about a year and a half ago and have become a big fan of this MCU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are a couple of additional items.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Speed: DC to 80 MHZ.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The software is a FREE download on Parallax's web site. You will need to purchase a programmer, such as the PROP PLUG, for a modest price.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All the documentation, including numerous tutorials, are also free to download. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out Parallax's forum. The design engineers are very active on the forum and very available for help questions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Parallax also has great customer service.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-17T06:31:53.210" />
  <row Id="508" PostTypeId="2" ParentId="441" CreationDate="2009-11-17T06:43:57.960" Score="2" ViewCount="" Body="&lt;p&gt;You mention other multi core solutions, but do not give any area to compare with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any solution can possibly be better depending on what process is. The Propeller has a vast following, with some very knowledgeable people. It has a broad range of functions already found, and some yet to be discovered. The chip has actually surprised the designers in some areas, and that within itself is a huge positive mark.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For most items to be controlled with a micro, it will hand almost any task. It's not the fastest, nor the most expensive, but I find it hard to beat for the price.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-17T06:43:57.960" />
  <row Id="510" PostTypeId="2" ParentId="441" CreationDate="2009-11-17T07:29:17.107" Score="5" ViewCount="" Body="&lt;p&gt;Big difference to other MCUs is that the propeller has very little hardware add-ons. No I2C, no serial interface, no AD and so on ... oh .. not to forget NO INTERRUPTS. Only a video generator per COG and 2 counters per COG (COG is the name of a core). On the first glance this does not sound very good! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But that's exactly what the 8 COGs are meant for. Instead of adding hardware here and there and offering thousands of different types of microcontrollers for every possibly useful combination, the propeller is designed to do all that in software or get support by external chips that do things much better than the internal circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SPIN supports modular software development by so called Objects. And Parallax supports the developers by offering a internet platform for Object Exchange. So, if you need a chip with 8 serial ports ... pick an object that implements 4 serial prots per COG, use it in 2 COGs and there you are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did PIC programming and AVR programming before, but the propeller is so easy to use and you get results much faster than with other controllers. Mainly because the Objects can be used without changes in most cases. Interrupt driven controller software most times needs to be adapted to fit in the own environment.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Brian stated:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The software is a FREE download on Parallax's web site. You will need to purchase a programmer, such as the PROP PLUG, for a modest price.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That could be missunderstood. You don't have to buy a PROP PLUG. I'm still running my propeller on a breadboard with a non Parallax USB to serial converter. In their documents you can also find a serial interface which only needs some resistors &amp;amp; transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a start with the propeller you only need:&#xA;1. the propeller&#xA;2. a interface (serial or USB to serial)&#xA;THAT'S IT! Very inexpensive.&#xA;Of course some Objects will not run at that low speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Add on:&#xA;A 5 MHz crystal to get the full 80MHz internal speed generated with PLL. (full speed means the speed given in the spec as max. frequency ;o)&#xA;A min. 32kByte serial EEPROM to store one program.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ah ... EEPROM ... another difference to other microcontrollers. The propeller does not have any internal non-volatile memory to store programs on, like FLASH or internal EEPROM. It's booting from external EEPROM -or FRAM- into it's internal RAM. I already damaged AVRs just by programming to often, which I think is very usual when developing programs. This won't happen with the propeller! EEPROM gone? Well .. attach the next one.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-17T12:12:51.587" />
  <row Id="511" PostTypeId="1" AcceptedAnswerId="513" CreationDate="2009-11-17T13:36:47.157" Score="3" ViewCount="498" Body="&lt;p&gt;I've attempted installation of AVR studio 32 (for AVR32 UC3 development) and it doesn't appear to work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone here gotten this to work in Vista 64?&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-20T03:57:15.913" LastActivityDate="2009-11-20T03:57:15.913" Title="Running AVRStudio 32 and JTAGICE MKII on Vista 64" Tags="&lt;avr&gt;&lt;windows&gt;" AnswerCount="1" />
  <row Id="512" PostTypeId="2" ParentId="441" CreationDate="2009-11-17T14:40:39.700" Score="1" ViewCount="" Body="&lt;p&gt;Another multicore option is XMOS - 1600 MIPS from four cores, with eight 100/50 MIPS hardware threads per core. They start at $7.50 for a single-core 400 MIPS QFP device. The (excellent) development tools are free.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Leon&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-11-17T14:40:39.700" />
  <row Id="513" PostTypeId="2" ParentId="511" CreationDate="2009-11-17T14:57:57.127" Score="3" ViewCount="" Body="&lt;p&gt;Personally I use a virtual machine running XP...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I notice that Dean Camera (a regular over at AVRFreaks) has been playing with getting AVR tools to work on x64 boxes. See this posting on his blog: &lt;a href=&quot;http://fourwalledcubicle.com/blog/archives/467&quot; rel=&quot;nofollow&quot;&gt;http://fourwalledcubicle.com/blog/archives/467&lt;/a&gt;. He also mentions that he's recently installed a beta of AVR Studio (&lt;a href=&quot;http://www.atmel.no/beta%5Fware&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.no/beta_ware&lt;/a&gt;) which supports Windows 7 and x64.&lt;/p&gt;&#xA;" OwnerUserId="255" LastActivityDate="2009-11-17T14:57:57.127" CommentCount="2" />
  <row Id="514" PostTypeId="1" AcceptedAnswerId="517" CreationDate="2009-11-17T17:04:55.840" Score="3" ViewCount="912" Body="&lt;p&gt;Thinking of building a device for sending text and probably mouse movement into a computer, but I want it to be wireless and compatible with many computers/PDAs/phones without a specialized dongle, etc.  So I thought &quot;Hey, Bluetooth is a standard for input devices and lots of computers/PDAs/phones have it built in!&quot;  But how to get the data into the Bluetooth on the other end?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I could buy a &lt;a href=&quot;http://www.bluepacket.net/BluePacket/solutions/solutions.aspx&quot; rel=&quot;nofollow&quot;&gt;Bluetooth&lt;/a&gt; &#xA;&lt;a href=&quot;http://www.broadcom.com/products/Bluetooth/Bluetooth-RF-Silicon-and-Software-Solutions/BCM2042&quot; rel=&quot;nofollow&quot;&gt;IC&lt;/a&gt; and build a PCB for it, but I&#xA;can't even find a place to buy them&#xA;in small quantities, or find documentation without being part of a company and signing NDAs, etc.&lt;/li&gt;&#xA;&lt;li&gt;I could learn the&#xA;very popular Arduino with the&#xA;&lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8255&quot; rel=&quot;nofollow&quot;&gt;Bluetooth adapter&lt;/a&gt;, but this&#xA;would cost $149.95, which is not what I had&#xA;in mind, and I don't know if it can even act as a keyboard/mouse.&lt;/li&gt;&#xA;&lt;li&gt;I could buy a cheap USB&#xA;keyboard and &lt;a href=&quot;http://www.flickr.com/photos/56868697@N00/sets/72157602444167525/&quot; rel=&quot;nofollow&quot;&gt;take it apart&lt;/a&gt;, figure&#xA;out how the keys map to the data&#xA;lines, and just stimulate them&#xA;appropriately.  Mouse is not so easy,&#xA;though.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The last seems like the best, but do you have any other ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do &lt;strong&gt;not&lt;/strong&gt; want a generic serial-over-Bluetooth board, unless it can be configured to look like a standard Bluetooth keyboard/mouse at the other end.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-20T03:58:59.237" LastActivityDate="2011-04-23T22:39:41.893" Title="Cheapest, simplest way to implement a Bluetooth keyboard/mouse?" Tags="&lt;bluetooth&gt;&lt;wearable&gt;&lt;wireless&gt;&lt;keyboard&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="515" PostTypeId="1" AcceptedAnswerId="516" CreationDate="2009-11-17T18:09:25.687" Score="12" ViewCount="1198" Body="&lt;p&gt;I am designing a circuit that needs to output 5VDC @ 1A.  I'm trying to use a wall transformer to step the voltage down to 12VAC.  The next step is the diode bridge and ripple capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ripple voltage equation is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Vripple = I / (2 * f * C)&#xA;I = load current (1A)&#xA;f = AC frequency (60Hz)&#xA;C = Filter Capacitor (? uF)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If I choose a C of 1000 uF, the ripple voltage is 8.3 V!  Do I really need to put more capacitance to lower the ripple voltage?  Is there another method of converting AC to DC?&lt;/p&gt;&#xA;" OwnerUserId="204" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-25T06:25:09.427" LastActivityDate="2011-01-25T06:25:09.427" Title="How to convert AC to DC" Tags="&lt;power-supply&gt;&lt;capacitor&gt;&lt;voltage-regulator&gt;&lt;frequency&gt;&lt;rectifier&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="2" />
  <row Id="516" PostTypeId="2" ParentId="515" CreationDate="2009-11-17T18:30:39.070" Score="27" ViewCount="" Body="&lt;p&gt;1000 µF at this voltage isn't terribly big.  Are you limited by size or something? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To completely get rid of the ripple and produce 5 V, you need to add a voltage regulator after the capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;12 V&lt;sub&gt;RMS&lt;/sub&gt; = 17 V&lt;sub&gt;Peak&lt;/sub&gt;, which, minus the two diode drops, is the peak DC voltage you'll see at the output of the rectifiers: 17 - 1.1 - 1.1 = 14.8 V.  So there's no threat of exceeding the input limits of the regulator (35 V input).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the ripple is 8.3 V, then the DC voltage will be varying from 6.5 V to 15 V.  This is just barely high enough to feed into the regulator without dropping out of regulation, since the 7805 has about 1.5 V dropout at 1 A (depending on temperature).  So yes, you should use a slightly higher capacitor (or multiple capacitors in parallel, if space is an issue).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://homepage.ntlworld.com/alanet.marshall1/WS-page/X1CNC/X1CNCpage2.htm&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://homepage.ntlworld.com/alanet.marshall1/WS-page/X1CNC/5VPSupply.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.kpsec.freeuk.com/powersup.htm&quot; rel=&quot;nofollow&quot;&gt;Here's a guide&lt;/a&gt; to each stage of the power supply circuit.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-19T21:36:52.333" LastActivityDate="2010-05-19T21:36:52.333" CommentCount="8" />
  <row Id="517" PostTypeId="2" ParentId="514" CreationDate="2009-11-17T18:36:50.367" Score="5" ViewCount="" Body="&lt;p&gt;You'll find this is often the case, when you try to build something from off the shelf parts that duplicates an existing product, almost always the parts alone will cost more than the existing product. The reason being that they can mass produce their product, buying parts in bulk cuts down on costs etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Look closely at the 'serial-over-Bluetooth boards', some of them do in fact support different profiles. What you are looking for is a module that supports the Bluetooth HID profile (Human Interface Device, aka mouse, keyboard, joystick, wii remote, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out &lt;a href=&quot;http://chiphacker.com/questions/227/bluetooth-adapter-for-arduino&quot; rel=&quot;nofollow&quot;&gt;this previous question&lt;/a&gt;, it lists several bluetooth modules, which you can buy in single quantities for fairly reasonable prices, some or all of them should support HID.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-17T18:36:50.367" CommentCount="3" />
  <row Id="518" PostTypeId="1" CreationDate="2009-11-17T19:56:19.677" Score="2" ViewCount="136" Body="&lt;p&gt;Hi!  I apologize if this is not welcome in this forum, but Im looking for someone who can help me...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a little project that I'd like to put together, however I lack the engineering expertise.  I was trained as a computer scientist/engineer and I am looking to create a simple device that can communicates with my phone!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please let me know if anyone is interested by emailing me or responding to this thread.  I am based in the nyc area&lt;/p&gt;&#xA;" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-07-08T16:39:35.743" LastActivityDate="2010-07-08T16:39:35.743" Title="Seeking an electrical engineer with bluetooth experience for a small side project..." Tags="&lt;bluetooth&gt;&lt;phone&gt;&lt;communication&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="519" PostTypeId="2" ParentId="518" CreationDate="2009-11-17T20:12:00.830" Score="1" ViewCount="" Body="&lt;p&gt;I am not sure what phone you are operating with, but I will let you know if you expect the iPhone to be fully functional over BT, prepare to be surprised. They do not want people making projects that bypass things they like to charge subscription for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rovingnetworks.com/bluetooth-modules.php&quot; rel=&quot;nofollow&quot;&gt;Bluetooth Module from Roving Networks&lt;/a&gt; are fantastic modules for working with bluetooth and allow you to use it like a serial connection. If I was not in OK I would be willing to help you out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wish you luck.&#xA;-Max Murphy&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-17T20:12:00.830" />
  <row Id="520" PostTypeId="2" ParentId="495" CreationDate="2009-11-17T20:43:22.843" Score="6" ViewCount="" Body="&lt;p&gt;If you'd like a nice analog solution, there's this circuit that's used by flight simmers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.simprojects.nl/images/Image12.gif&quot; alt=&quot;&amp;quot;Sorry, new users aren't allowed to use image tags&amp;quot;&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The schematic shows the arrangement for a toggle switch, but it could be easily substituted for a momentary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each time the switch changes positions, the capacitor has to charge and discharge. During this time, a voltage is developed across the relay contacts, closing the switch. Once the capacitor has charged, the relay turns off again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More info here:&#xA;&lt;a href=&quot;http://www.simprojects.nl/toggle%5Fto%5Fmomentary.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.simprojects.nl/toggle_to_momentary.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="307" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-11-17T22:24:15.027" LastActivityDate="2009-11-17T22:24:15.027" CommentCount="1" />
  <row Id="521" PostTypeId="2" ParentId="514" CreationDate="2009-11-17T21:28:54.210" Score="-1" ViewCount="" Body="&lt;p&gt;It is not likely the solution you are looking for, but I thought it was relevant to the question:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://serverfault.com/questions/43615/setup-a-linux-computer-to-act-as-a-bluetooth-keyboard-mouse&quot; rel=&quot;nofollow&quot;&gt;http://serverfault.com/questions/43615/setup-a-linux-computer-to-act-as-a-bluetooth-keyboard-mouse&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-11-17T21:28:54.210" />
  <row Id="522" PostTypeId="2" ParentId="515" CreationDate="2009-11-17T21:47:01.970" Score="7" ViewCount="" Body="&lt;p&gt;If your capacitor is big enough to get the ripple down, your Vdc will be around 15V as shown by Endolith. Let's consider it drops a little under load, and use 12V as an example. If the output needs to be 5V, the regulator should take 7V at 1A, which means it should be able to &lt;em&gt;continuously&lt;/em&gt; dissipate 7W of power. Depending on your application, this may or may not be an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why don't you just use a switching power adapter? These days there are a lot of routers, network switches/hubs, harddrive enclosures, etc. which use 5V. Their power supplies are usually not bigger then a regular wall transformer, are more efficient and the output voltage is well regulated.&lt;/p&gt;&#xA;" OwnerUserId="218" LastEditorUserId="218" LastEditorDisplayName="" LastEditDate="2009-11-30T14:39:21.270" LastActivityDate="2009-11-30T14:39:21.270" />
  <row Id="523" PostTypeId="2" ParentId="184" CreationDate="2009-11-17T22:48:11.830" Score="1" ViewCount="" Body="&lt;p&gt;Here is a source for all sorts of conductive paints. &lt;a href=&quot;http://www.lessemf.com/paint.html&quot; rel=&quot;nofollow&quot;&gt;http://www.lessemf.com/paint.html&lt;/a&gt;&#xA;Some of them would probably work for painting directly on fabric.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-17T22:48:11.830" />
  <row Id="524" PostTypeId="2" ParentId="495" CreationDate="2009-11-17T23:05:49.687" Score="6" ViewCount="" Body="&lt;p&gt;You may use a simple xor gate, and one of the inputs connected to the switch directly, while the other input through a R-C circuit which provides the delay. This works OK as an &quot;edge detector&quot;, but it doesn't do any debouncing - you didn't ask for this :-). It's probably the cheapest way if you already have an unused xor gate in your design.&lt;/p&gt;&#xA;" OwnerUserId="218" LastActivityDate="2009-11-17T23:05:49.687" />
  <row Id="525" PostTypeId="2" ParentId="464" CreationDate="2009-11-18T01:36:28.367" Score="6" ViewCount="" Body="&lt;p&gt;I think of loop as being the arduino's substutitue for main in C.  So I declared some variables at the top of loop.  Bad idea, they get re-initialized each time around the loop.  Instead declare as globals before any subroutine.  Not a big deal, but it took a few minutes to figure out what was happening.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastEditorUserId="819" LastEditorDisplayName="" LastEditDate="2010-06-25T23:37:09.280" LastActivityDate="2010-06-25T23:37:09.280" CommunityOwnedDate="2009-11-18T01:36:28.367" />
  <row Id="526" PostTypeId="2" ParentId="515" CreationDate="2009-11-18T01:42:08.987" Score="3" ViewCount="" Body="&lt;p&gt;If you do not want to go the switching route a 5 or 6 volt transformer with lots of cap. and a low drop out regulator would help effiency a lot.  You have to do some calculations to get the values and see if they are reasonable.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-18T01:42:08.987" />
  <row Id="527" PostTypeId="1" AcceptedAnswerId="539" CreationDate="2009-11-18T02:01:54.657" Score="3" ViewCount="563" Body="&lt;p&gt;has anyone used the arduino to convert text to speech?&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-19T04:06:04.830" LastActivityDate="2009-11-24T19:29:26.997" Title="Arduino Text to Speech" Tags="&lt;arduino&gt;&lt;speech&gt;&lt;convert&gt;" AnswerCount="4" />
  <row Id="528" PostTypeId="1" AcceptedAnswerId="530" CreationDate="2009-11-18T02:40:34.107" Score="3" ViewCount="334" Body="&lt;p&gt;I need to build a programmable current source from a 8051 microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It needs an output current from 0 to 10mA maximun. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do i go about doing this?  what circuits do i need to build?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was going to do a 20 steps - with 0.5mA so from 0 to 10mA is 20 steps.&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-20T04:02:13.867" LastActivityDate="2009-11-20T04:02:13.867" Title="Programmable current source" Tags="&lt;microcontroller&gt;&lt;programmer&gt;&lt;current&gt;&lt;output&gt;&lt;circuit&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="529" PostTypeId="2" ParentId="527" CreationDate="2009-11-18T04:09:34.177" Score="1" ViewCount="" Body="&lt;p&gt;I think it should be possible to use the PWM (Pulse Width Modulation) to playback audio samples - but at very low quality. I've heard this done on the BBC Micro game &lt;a href=&quot;http://en.wikipedia.org/wiki/Exile%5F%28arcade%5Fadventure%29&quot; rel=&quot;nofollow&quot;&gt;Exile&lt;/a&gt;, on a 6502 CPU way back in the day. Text to speech seems like quite a lot to ask of an ATMEGA series chip. But who knows what clever people are out there to prove me wrong!&lt;/p&gt;&#xA;" OwnerUserId="178" LastActivityDate="2009-11-18T04:09:34.177" />
  <row Id="530" PostTypeId="2" ParentId="528" CreationDate="2009-11-18T04:56:17.677" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.analog.com/en/verifiedcircuits/CN0117/vc.html&quot; rel=&quot;nofollow&quot;&gt;Here's an example&lt;/a&gt; that goes from -15V to +15V with +/- 18mA, so unless you need higher or lower voltages it should do the trick with two chips and a handful of passives.  It provides a great deal of resolution and stability, and requires positive and negative supplies, so it may be overkill.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you let us know what voltage range you're looking for, though, a simpler circuit may better fit the bill.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's another option, 100mA and 9V: &lt;a href=&quot;http://www.discovercircuits.com/DJ-Circuits/100ma-current-source.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.discovercircuits.com/DJ-Circuits/100ma-current-source.htm&lt;/a&gt; 1 chip, two fets, and a handful of components.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2009-11-18T04:56:17.677" />
  <row Id="531" PostTypeId="2" ParentId="495" CreationDate="2009-11-18T05:25:59.110" Score="6" ViewCount="" Body="&lt;p&gt;XOR gate:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.muc.de/~hm/music/Wireless-GK/XOR.png&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used the &lt;a href=&quot;http://www.fairchildsemi.com/pf/NC/NC7SZ58.html&quot; rel=&quot;nofollow&quot;&gt;NC7SZ58&lt;/a&gt; for this, which is cheap ($0.04) and tiny and has Schmitt trigger inputs so the pulses are roughly the same length.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2009-12-04T18:06:04.053" LastActivityDate="2009-12-04T18:06:04.053" />
  <row Id="532" PostTypeId="1" AcceptedAnswerId="534" CreationDate="2009-11-18T07:04:31.783" Score="4" ViewCount="298" Body="&lt;p&gt;I have recently purchased a sparkfun protoboard that I wish to stack above an ethernet shield. (I have 2 different ethernet shields, an Arduino one and a seeed studio enc28j60 shield.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem I have is that if I use the supplied headers, or even the longer &quot;Arduino Stackable header&quot; then the magjack from the ethernet shield below contacts the protoboard. This happens before adding the components at the front of the board, I suspect that if I solder those in the header won't even make reliable contact.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I'd like to source some extra long headers, either male-male or male-female would be fine. I did notice that the Arduino ethernet shield has extra long headers - does anyone know where to source those or any other 1.5cm long headers from? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be awesome if the supplier had a reasonable shipping rate to Australia, but I'll take whatever I can get. :) I have searched farnell without luck so far, but the number of products is a bit bewildering so there is a chance I have overlooked the perfect header.&lt;/p&gt;&#xA;" OwnerUserId="298" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-16T06:01:16.923" LastActivityDate="2010-12-16T20:11:14.447" Title="Where can I source extra long headers from." Tags="&lt;arduino&gt;&lt;sourcing&gt;&lt;header&gt;&lt;protoboard&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="533" PostTypeId="2" ParentId="532" CreationDate="2009-11-18T08:58:08.360" Score="2" ViewCount="" Body="&lt;p&gt;Is &lt;a href=&quot;http://www.littlebirdelectronics.com/products/arduino-stackable-header-8-pin&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; the sort of thing you had in mind or do you need longer ones still? They appear to have other options too, I searched for Headers on the site these were on the second page.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-18T08:58:08.360" CommentCount="4" />
  <row Id="534" PostTypeId="2" ParentId="532" CreationDate="2009-11-18T09:28:34.243" Score="5" ViewCount="" Body="&lt;p&gt;I use a second set of long headers, push them into the ethernet board and then push the protoboad into them.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-18T09:28:34.243" CommentCount="1" />
  <row Id="535" PostTypeId="1" CreationDate="2009-11-18T09:40:29.143" Score="12" ViewCount="1860" Body="&lt;p&gt;I am looking for tool to draw circuits on Mac OS X. I mostly need it so I can add it into presentations. So the requirements are that it looks preety.&lt;/p&gt;&#xA;" OwnerUserId="311" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-11-18T09:47:35.560" LastActivityDate="2011-03-22T09:12:08.193" Title="Good tool for Mac OS X to draw circuits." Tags="&lt;circuit&gt;&lt;mac&gt;&lt;osx&gt;&lt;software&gt;" AnswerCount="9" FavoriteCount="6" />
  <row Id="536" PostTypeId="2" ParentId="535" CreationDate="2009-11-18T09:52:19.247" Score="11" ViewCount="" Body="&lt;p&gt;For drawing circuits I use &lt;a href=&quot;http://www.omnigroup.com/applications/OmniGraffle/&quot; rel=&quot;nofollow&quot;&gt;Omnigraffle&lt;/a&gt; and the &lt;a href=&quot;http://www.omnigroup.com/ftp/pub/software/MacOSX/Extras/OmniGraffle/Electronics.dmg&quot; rel=&quot;nofollow&quot;&gt;Electronics&lt;/a&gt; Extra.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.damhave.com/Stencils/files/page3_1.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For physical hardware diagrams I use &lt;a href=&quot;http://fritzing.org/&quot; rel=&quot;nofollow&quot;&gt;Fritzing&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Checkout a &lt;a href=&quot;http://www.youtube.com/watch?v=Hxhd4HKrWpg&quot; rel=&quot;nofollow&quot;&gt;video on Fritzing here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-22T09:12:08.193" LastActivityDate="2011-03-22T09:12:08.193" CommunityOwnedDate="2011-03-22T09:19:47.623" CommentCount="1" />
  <row Id="537" PostTypeId="2" ParentId="535" CreationDate="2009-11-18T10:09:58.367" Score="5" ViewCount="" Body="&lt;p&gt;There is also OSX version of &lt;a href=&quot;http://www.cadsoft.de/&quot; rel=&quot;nofollow&quot;&gt;Eagle Cad&lt;/a&gt;. Although software itself is not very Mac-like nor exactly easy to use.&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2009-11-18T10:09:58.367" CommentCount="1" />
  <row Id="538" PostTypeId="2" ParentId="535" CreationDate="2009-11-18T10:12:42.480" Score="0" ViewCount="" Body="&lt;p&gt;You may be able to access some of the Linux stuff which is around, through things like MacPorts.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-18T10:12:42.480" />
  <row Id="539" PostTypeId="2" ParentId="527" CreationDate="2009-11-18T10:22:15.333" Score="6" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/tinkerit/wiki/Cantarino&quot; rel=&quot;nofollow&quot;&gt;Cantarino&lt;/a&gt; is a work in progress software speech synthesizer for Arduino. You could also interface with several &lt;a href=&quot;http://www.speechchips.com/shop/&quot; rel=&quot;nofollow&quot;&gt;speech synth chips&lt;/a&gt; available. Devantech &lt;a href=&quot;http://www.robot-electronics.co.uk/htm/Sp03doc.shtml&quot; rel=&quot;nofollow&quot;&gt;SP03&lt;/a&gt; module has been popular but it is hard to find. What makes it especially cool is the I2C interface.&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2009-11-18T10:22:15.333" />
  <row Id="540" PostTypeId="2" ParentId="528" CreationDate="2009-11-18T15:23:24.363" Score="2" ViewCount="" Body="&lt;p&gt;One cheap solution is to create a PWM signal, filter it with a RC cell, and then feed it to a voltage-to-current converter. In the simplest case, this can be a transistor with a resistor in the emitter, and the load in the collector. But you can also use an op amp for this. Since you only need a 20-step scale, this may be enough for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A better but more expensive solution is to connect a DAC to 5 of your digital outputs, and feed the output of the DAC to a voltage-to-current converter as before. I think there are even some DACs which directly control their output current. Since you only need 5-bit resolution, you can even build a R-2R DAC yourself, as described &lt;a href=&quot;http://www.ikalogic.com/dac08.php&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, the optimal solution depends on your project's constraints (time? price? size?). &lt;/p&gt;&#xA;" OwnerUserId="218" LastEditorUserId="218" LastEditorDisplayName="" LastEditDate="2009-11-18T15:38:43.653" LastActivityDate="2009-11-18T15:38:43.653" />
  <row Id="541" PostTypeId="2" ParentId="532" CreationDate="2009-11-18T17:31:15.893" Score="2" ViewCount="" Body="&lt;p&gt;Digikey has &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1442672&quot; rel=&quot;nofollow&quot;&gt;lots of different sizes&lt;/a&gt;. Here's a really really long one: &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=SAM1067-50-ND&quot; rel=&quot;nofollow&quot;&gt;SAM1067-50-ND&lt;/a&gt; (not exactly cheap though, $18 for 10pcs, with 50 pins each)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://davr.org/pics/TSW-150-17-T-S.JPG&quot; alt=&quot;long header&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No idea on Digikey's policy of shipping to Australia though, but it's quite reasonable pricing for in the USA.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-18T17:31:15.893" CommentCount="1" />
  <row Id="542" PostTypeId="2" ParentId="535" CreationDate="2009-11-18T18:25:41.920" Score="5" ViewCount="" Body="&lt;p&gt;There is always &lt;a href=&quot;http://opencircuitdesign.com/xcircuit/&quot; rel=&quot;nofollow&quot;&gt;XCircuit&lt;/a&gt; and &lt;a href=&quot;http://macspice.com/&quot; rel=&quot;nofollow&quot;&gt;MacSpice&lt;/a&gt;.  They maybe overkill for whatever your needs are, but might as well learn from them too.&lt;/p&gt;&#xA;" OwnerUserId="151" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-22T07:57:05.660" LastActivityDate="2011-03-22T07:57:05.660" />
  <row Id="543" PostTypeId="2" ParentId="532" CreationDate="2009-11-18T20:12:14.070" Score="2" ViewCount="" Body="&lt;p&gt;Are these long enough: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In one salvage job I found some &quot;double ended&quot; headers, long pins on both ends. These can be very handy because once plugged in they can be used to let you plug in female connectors ( like those on hard drive cables ( but just one of the two sides ) to the board.  Hard part to find. But wait, you can solder two regular headers back to back.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.opencircuits.com/Solderless_protoboard#More_Tips&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/Solderless_protoboard#More_Tips&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-18T20:12:14.070" />
  <row Id="544" PostTypeId="2" ParentId="442" CreationDate="2009-11-18T21:24:26.623" Score="1" ViewCount="" Body="&lt;p&gt;For the PIC, there is an open source compiler called JAL (Just Another Language)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like other programming languages it allows the possibility to use hardware libraries to greatly simplify the process of attaching your chosen PIC to other hardware.  The software also will allow you to compile and upload programs via your PIC2 (or a clone of this programmer) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;JAL is a Pascal based language and is free software (always nice if your just starting out)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/JAL%5F%28compiler%29&quot; rel=&quot;nofollow&quot;&gt;JAL Wiki Entry&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for books, &quot;PIC Microcontrollers, 50 projects for beginners and experts&quot; By Bert Van Dam is worth a look at as an introduction to JAL&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far I have used just the 16F877A chip from PIC, a good beginners chip apparently.  Pretty cheap and lots of ports available.  &lt;/p&gt;&#xA;" OwnerUserId="312" LastActivityDate="2009-11-18T21:24:26.623" CommentCount="3" />
  <row Id="545" PostTypeId="2" ParentId="535" CreationDate="2009-11-18T21:26:07.707" Score="2" ViewCount="" Body="&lt;p&gt;I recommend Eagle from Cadsoft. It's the best free schematic/layout editor there is in my opinion.&lt;/p&gt;&#xA;" OwnerUserId="140" LastActivityDate="2009-11-18T21:26:07.707" />
  <row Id="546" PostTypeId="1" AcceptedAnswerId="547" CreationDate="2009-11-18T22:20:17.147" Score="3" ViewCount="906" Body="&lt;p&gt;I need to make a voltage level shifter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;it needs to translate a TTL logic level into a 12v logigc level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;what I've done is to apply the 5v at the base and 12v Vcc and to take the output from the collector &#xA;(not using any emitter resistor)&#xA;Output was good but the current was 0mA when the Vc was 12v -&gt; the phase was shifted&#xA;I've tried connecting the load at the emitter and the voltage was just 5V or less&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-&gt; voltage level translator?&lt;/p&gt;&#xA;" OwnerUserId="267" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-19T04:02:13.463" LastActivityDate="2011-01-08T05:56:49.417" Title="Voltage level shifter" Tags="&lt;voltage&gt;&lt;shifter&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="547" PostTypeId="2" ParentId="546" CreationDate="2009-11-18T22:44:25.103" Score="6" ViewCount="" Body="&lt;p&gt;Check out Sparkfun's &lt;a href=&quot;http://www.sparkfun.com/products/8745&quot; rel=&quot;nofollow&quot;&gt;Logic Level converter&lt;/a&gt;. It includes a schematic, you should be able to do almost exactly the same thing by hand, but you'll probably need to use different resistor values to get the correct voltages. It includes two circuits, one for connecting a low voltage transmitter to a high voltage receiver, and one for connecting a high voltage transmitter to a low voltage receiver. It sounds like the former is what you're asking for.&lt;/p&gt;&#xA;" OwnerUserId="131" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-01-08T05:56:49.417" LastActivityDate="2011-01-08T05:56:49.417" />
  <row Id="548" PostTypeId="2" ParentId="527" CreationDate="2009-11-18T22:48:09.423" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.speechchips.com/shop/&quot; rel=&quot;nofollow&quot;&gt;speechchips.com&lt;/a&gt; sells a few IC's programmed to handle text-to-speech for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your application though...you can probably get much better quality simply using pre-recorded audio stored on a SD card or something. Sure it might take a couple hundred MB for all your different speech recordings, but that's just pennies at today's SD card prices, and SD cards can be interfaced via SPI.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-18T22:48:09.423" />
  <row Id="549" PostTypeId="2" ParentId="535" CreationDate="2009-11-18T22:48:35.373" Score="2" ViewCount="" Body="&lt;p&gt;I use Omnigraffle for drawing the simple circuits I use in my Arduino classes.  For circuit design, I use Eagle. It's a &quot;real&quot; schematic capture program (i.e. CAD program for circuits) that you can also use to produce circuit boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Omnigraffle is great for producing really nice looking schematics, as long as they are not too complex, because it doesn't have the intelligence that a real schematic capture program does on how to maintain connection between components.  Omnigraffle also doesn't have very many components in its library so you have to make your own for even simple things.  Eagle's part library is so big it's daunting.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-18T22:48:35.373" />
  <row Id="550" PostTypeId="2" ParentId="546" CreationDate="2009-11-18T22:53:08.143" Score="2" ViewCount="" Body="&lt;p&gt;It sounds like you might have been using an NPN transistor where a PNP would be more appropriate. Try changing to a PNP transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that's not it, we'll need a schematic or at least more information.&lt;/p&gt;&#xA;" OwnerUserId="105" LastActivityDate="2009-11-18T22:53:08.143" />
  <row Id="551" PostTypeId="2" ParentId="515" CreationDate="2009-11-18T22:57:35.043" Score="3" ViewCount="" Body="&lt;p&gt;Your Vripple equation is only an approximation, and only good for small amounts of ripple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Find a better equation, or solve it graphically, and you will see your ripple isn't as much as you think.  &lt;/p&gt;&#xA;" OwnerUserId="19" LastActivityDate="2009-11-18T22:57:35.043" CommentCount="2" />
  <row Id="552" PostTypeId="2" ParentId="515" CreationDate="2009-11-19T04:12:27.470" Score="6" ViewCount="" Body="&lt;p&gt;Another method is to add a choke (inductor) in series before the final filter cap.  Something like 100 uH would do a world of good.   A coil resists changes in current, just like a cap resists changes in voltage. Put the two together and you get a much more effective filter. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have an error in your Vripple equation.  As you are using a full wave bridge, your freq is not 60 hz, but 120. &lt;/p&gt;&#xA;" OwnerUserId="313" LastActivityDate="2009-11-19T04:12:27.470" CommentCount="4" />
  <row Id="553" PostTypeId="2" ParentId="546" CreationDate="2009-11-19T04:17:15.123" Score="4" ViewCount="" Body="&lt;p&gt;a single common emitter transistor amp is described. This inverts the signal. You need 2 stages. Duplicate your circuit, feed the output of what you have now into another common emitter amp.  Adjust bias and increase negative feedback to reduce gain.  Usually these things are done with totem poles. &lt;/p&gt;&#xA;" OwnerUserId="313" LastActivityDate="2009-11-19T04:17:15.123" />
  <row Id="554" PostTypeId="1" AcceptedAnswerId="555" CreationDate="2009-11-19T06:23:33.180" Score="7" ViewCount="2166" Body="&lt;p&gt;What's involved in building your own RFID reader? As you guys would know industrial RFID readers aren't cheap, how do you energise the antenna, then read back the output?&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-30T00:55:09.833" LastActivityDate="2011-01-30T00:55:09.833" Title="How do you build your own RFID reader?" Tags="&lt;rfid&gt;&lt;antenna&gt;" AnswerCount="4" FavoriteCount="6" />
  <row Id="555" PostTypeId="2" ParentId="554" CreationDate="2009-11-19T09:39:46.623" Score="5" ViewCount="" Body="&lt;p&gt;There's a Uni level final project detailing one &lt;a href=&quot;http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2006/cjr37/Website/index.htm&quot; rel=&quot;nofollow&quot;&gt;here.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a more general RFID eavesdropper/reader &lt;a href=&quot;http://cq.cx/proxmark3.pl&quot; rel=&quot;nofollow&quot;&gt;here.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[EDIT] This page &lt;a href=&quot;http://memweb.newsguy.com/~rhuang/RFID/rfid.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; appears to have detailed instructions for building your own reader.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2009-12-08T21:22:21.173" LastActivityDate="2009-12-08T21:22:21.173" />
  <row Id="556" PostTypeId="1" CreationDate="2009-11-19T09:43:07.950" Score="4" ViewCount="1494" Body="&lt;p&gt;The cheapest USB device (with Linux support) that can control the color of a RGB Led strip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this:&#xA;&lt;a href=&quot;http://www.ledtuning.nl/catalog/product_info.php?cPath=93&amp;amp;products_id=437&quot; rel=&quot;nofollow&quot;&gt;http://www.ledtuning.nl/catalog/product_info.php?cPath=93&amp;amp;products_id=437&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone do better?&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-20T04:05:38.700" LastActivityDate="2011-05-16T14:11:23.433" ClosedDate="2011-05-16T15:28:38.923" Title="Cheap USB RGB Led Strip Controller" Tags="&lt;pic&gt;&lt;rgb&gt;&lt;usb&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="558" PostTypeId="2" ParentId="554" CreationDate="2009-11-19T11:59:26.880" Score="2" ViewCount="" Body="&lt;p&gt;SparkFun has a lot of &lt;a href=&quot;http://www.sparkfun.com/commerce/advanced%5Fsearch%5Fresult.php?keywords=rfid&amp;amp;x=0&amp;amp;y=0&amp;amp;search%5Fsection=products&quot; rel=&quot;nofollow&quot;&gt;parts and boards&lt;/a&gt; that can help you as well.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-11-19T11:59:26.880" />
  <row Id="559" PostTypeId="2" ParentId="556" CreationDate="2009-11-19T14:22:20.570" Score="2" ViewCount="" Body="&lt;p&gt;I prefer to build than buy.  I would do this by using a usb uC.  For output you would need some sort of amplification set up to be constant current.  I would be willing to buy the uC, either an Arduino or BitWacker ( some preference if you have not used PIC's to the Arduino ) Program in C or other HHL.  If this does not make sense then buy the best one you can find, the Burning Man guys/gals love this kind of thing, poke around on their sites.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-19T14:22:20.570" />
  <row Id="560" PostTypeId="2" ParentId="556" CreationDate="2009-11-19T17:05:44.267" Score="4" ViewCount="" Body="&lt;p&gt;The interface linked to in the question doesn't have a true USB interface: you need a USB-to-serial adapter.  Not a big deal, but something to note.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A &lt;a href=&quot;http://thingm.com/products/blinkm-maxm.html&quot; rel=&quot;nofollow&quot;&gt;BlinkM MaxM&lt;/a&gt; can control arbitrary RGB LED strips and it can be plugged into an Arduino to give it a USB interface.  &lt;a href=&quot;http://www.flickr.com/photos/todbot/3552701124/in/set-72157605675213625/&quot; rel=&quot;nofollow&quot;&gt;Here's a picture of it&lt;/a&gt; controlling an LED strip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(disclaimer: my company makes the MaxM)&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-19T17:05:44.267" />
  <row Id="561" PostTypeId="2" ParentId="554" CreationDate="2009-11-19T21:04:03.867" Score="4" ViewCount="" Body="&lt;p&gt;If you are looking for something cheap &lt;a href=&quot;http://www.seeedstudio.com/depot/125khz-rfid-module-uart-p-171.html?zenid=09bfb99d14c91f240ff5e9077a3d0d0e&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; may do the trick.&lt;/p&gt;&#xA;" OwnerUserId="212" LastActivityDate="2009-11-19T21:04:03.867" CommentCount="1" />
  <row Id="562" PostTypeId="1" AcceptedAnswerId="570" CreationDate="2009-11-19T21:18:08.270" Score="3" ViewCount="176" Body="&lt;p&gt;I'm working on making a sign that will be outdoors in full sunlight and I want it to have the longest range visibility.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a project for uni and I will probably need 100 LEDs or so - &#xA;I need the cheapest possible but I really want people to be able to see it from afar!&lt;/p&gt;&#xA;" OwnerUserId="267" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-20T04:06:29.963" LastActivityDate="2009-11-21T16:06:11.780" Title="LEDs for full daylight" Tags="&lt;led&gt;" AnswerCount="4" CommentCount="4" />
  <row Id="563" PostTypeId="1" AcceptedAnswerId="566" CreationDate="2009-11-19T22:12:07.957" Score="4" ViewCount="95" Body="&lt;p&gt;Where can i get a high temperature humidity sensor for  temperatures up to 700 or 800 degree Fahrenheit?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-19T22:29:05.690" Title="High Temperature Humidity Sensor" Tags="&lt;temperature&gt;&lt;humidity&gt;" AnswerCount="1" />
  <row Id="564" PostTypeId="2" ParentId="562" CreationDate="2009-11-19T22:14:29.720" Score="2" ViewCount="" Body="&lt;p&gt;The super bright white LED may be a good bet, only 20 ma or so to light.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-19T22:14:29.720" />
  <row Id="565" PostTypeId="1" AcceptedAnswerId="568" CreationDate="2009-11-19T22:28:24.540" Score="6" ViewCount="584" Body="&lt;p&gt;My friend Jules asks:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The aim is to get as many servo motor controls as possible - looks like the maximum an Arduino will output is 14?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardMega&quot; rel=&quot;nofollow&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Digital I/O Pins54 (of which 14 provide PWM output)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;/a&gt;&#xA;I guess then it becomes a software issue to synchronise multiple Mega boards?&#xA;- ie 14 x 14 array using 14 boards&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-06T22:21:10.947" LastActivityDate="2011-02-06T22:21:10.947" Title="Synchronise multiple Mega boards to run multiple servo motors" Tags="&lt;arduino&gt;&lt;motor&gt;&lt;servo&gt;" AnswerCount="5" />
  <row Id="566" PostTypeId="2" ParentId="563" CreationDate="2009-11-19T22:29:05.690" Score="3" ViewCount="" Body="&lt;p&gt;There's these ones &lt;a href=&quot;http://www.macinstruments.com/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; which apparently will do up to 1200&lt;sup&gt;o&lt;/sup&gt;F.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-19T22:29:05.690" />
  <row Id="567" PostTypeId="2" ParentId="565" CreationDate="2009-11-19T22:43:14.450" Score="7" ViewCount="" Body="&lt;p&gt;If you want to drive multiple servos, the better route might be to hook a few dedicated servo controllers to a single Arduino.  There are many open source examples of servo controllers out there, but you can also buy fulling built ones.  For instance, here's a &lt;a href=&quot;http://www.pololu.com/catalog/product/208&quot; rel=&quot;nofollow&quot;&gt;Polulu 8-servo controller&lt;/a&gt; and a &lt;a href=&quot;http://www.pololu.com/catalog/product/240&quot; rel=&quot;nofollow&quot;&gt;Pololu 16-servo controller&lt;/a&gt;.  Get a few of those, hook them up to any digital pins of the Arduino and use the SoftSerial library to send commands to them.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-19T22:43:14.450" CommentCount="1" />
  <row Id="568" PostTypeId="2" ParentId="565" CreationDate="2009-11-19T22:49:34.947" Score="10" ViewCount="" Body="&lt;p&gt;I would also go for same route todbot suggested. However since I am a big fan of I2C I am using &lt;a href=&quot;http://www.google.com/search?q=sd21+servo+controller&quot; rel=&quot;nofollow&quot;&gt;SD21 servo controller&lt;/a&gt; which can drive 21 servos. If you need even more there is &lt;a href=&quot;http://www.google.com/search?q=SD84+Servo+Controller&quot; rel=&quot;nofollow&quot;&gt;SD84 servo controller&lt;/a&gt; which can drive (you guessed it) 84 servos.&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2009-11-19T22:49:34.947" />
  <row Id="569" PostTypeId="2" ParentId="267" CreationDate="2009-11-19T23:14:31.577" Score="3" ViewCount="" Body="&lt;p&gt;Here's a simple PIC USB project of mine:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.leonheller.com/usb&quot; rel=&quot;nofollow&quot;&gt;http://www.leonheller.com/usb&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PCBs are available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Leon&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-11-19T23:14:31.577" />
  <row Id="570" PostTypeId="2" ParentId="562" CreationDate="2009-11-19T23:35:33.473" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.superbrightleds.com/leds.htm&quot; rel=&quot;nofollow&quot;&gt;SuperBrightLeds.com&lt;/a&gt; have a wide variety, at least. I haven't bought from them much, but they have LEDs in pretty much any size and output you'd want. Make sure you pay attention to viewing angle as well as output power - for a sign you probably want something with a wide viewing angle.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2009-11-19T23:35:33.473" />
  <row Id="571" PostTypeId="2" ParentId="562" CreationDate="2009-11-20T03:39:42.833" Score="2" ViewCount="" Body="&lt;p&gt;I've had good luck with ledshoppe.com.  100 5mm super-bright LEDs them should come in around $5-$8, shipping included.  They can take a couple weeks to arrive (they ship from Hong Kong or Taiwan), but all 3 orders I've done with them have arrived reliably.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd suggest buying some extras - for only twice as much you can get 200 LEDs and have plenty of extras in case you toast a few along the way.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-11-20T03:39:42.833" />
  <row Id="572" PostTypeId="2" ParentId="565" CreationDate="2009-11-20T05:39:51.277" Score="1" ViewCount="" Body="&lt;p&gt;I Use a SSC32 from Lynxmotion&lt;a href=&quot;http://www.lynxmotion.com/Product.aspx?productID=395&quot; rel=&quot;nofollow&quot;&gt;link text&lt;/a&gt;&#xA;It uses a ATMEGA8 or ATMEGA168 and can control up to 32 Servos.&#xA;You find everything (circuit diagram, firmware) to build it on there page.&#xA;I build one by myself and it worked fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Greetings... 0815achim&lt;/p&gt;&#xA;" OwnerUserId="162" LastActivityDate="2009-11-20T05:39:51.277" />
  <row Id="573" PostTypeId="2" ParentId="565" CreationDate="2009-11-20T09:36:25.033" Score="1" ViewCount="" Body="&lt;p&gt;I agree with the other guys, use a dedicated servo controller. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm in the process of building my own for my hexapod robot, see &lt;a href=&quot;http://www.lhexapod.com/cgi-bin/mt/mt-search.cgi?blog%5Fid=1&amp;amp;tag=servo%20controllers&amp;amp;limit=20&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; source code and schematics available.&lt;/p&gt;&#xA;" OwnerUserId="255" LastActivityDate="2009-11-20T09:36:25.033" />
  <row Id="574" PostTypeId="2" ParentId="554" CreationDate="2009-11-20T11:36:05.977" Score="4" ViewCount="" Body="&lt;p&gt;before beginning, you have to know that there are mainly two type of RFID Reader:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;125 khz : antenna of 100 turn coil&lt;/li&gt;&#xA;&lt;li&gt;13.6 Mhz : antenna of 3-5 turn coil, more sofisticated can include communication protocol and security issues&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;if it just to open a door or something like that you can use the 125 khz&lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2009-11-20T11:36:05.977" />
  <row Id="575" PostTypeId="2" ParentId="535" CreationDate="2009-11-20T16:58:35.563" Score="1" ViewCount="" Body="&lt;p&gt;Someone asked Make a similar question (that was not Mac-specific).  &lt;a href=&quot;http://blog.makezine.com/archive/2009/11/ask%5Fmake%5F3.html&quot; rel=&quot;nofollow&quot;&gt;Their answer&lt;/a&gt; suggests Fritzing, too, and there are other tools mentioned in the post and in the comments.&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-11-20T16:58:35.563" />
  <row Id="576" PostTypeId="1" AcceptedAnswerId="578" CreationDate="2009-11-21T01:08:59.770" Score="6" ViewCount="363" Body="&lt;p&gt;I'm anxiously awaiting the delivery of my second set of custom designed PCBs from BatchPCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first board I designed was pretty darn simple and didn't have any problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This second set includes a full on arduino compatible board plus two shields for it.  Somehow I suspect I made a mistake somewhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is:  what sorts of things have other folks gotten wrong?  When I start debugging why that board doesn't work, what kind of things should I be looking for?  What are the first things that you check?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;hr /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As it turns out, my boards have two problems.  The first is that there's a cap too close to the ISP header.  I just didn't allow enough space.  The second is that the holes I specified, while large enough for all my normal through-hole components, are too small for breakaway headers to fit into without manually reaming them out a little bit (almost like it's just the thickness of the plating layer that covers the copper).  Other than that, everything is good.  I very carefully checked all the power connections before doing anything to make sure I wasn't about to short something badly, and held the various boards up to the light and verified alignment of stacking headers.&lt;/p&gt;&#xA;" OwnerUserId="213" LastEditorUserId="213" LastEditorDisplayName="" LastEditDate="2009-11-25T18:18:38.703" LastActivityDate="2009-11-25T18:18:38.703" Title="Custom PCBs... what can go wrong?" Tags="&lt;pcb&gt;&lt;arduino&gt;" AnswerCount="7" FavoriteCount="2" />
  <row Id="577" PostTypeId="2" ParentId="576" CreationDate="2009-11-21T01:30:06.637" Score="6" ViewCount="" Body="&lt;p&gt;First thing I'd check is make sure Power and Ground are not shorted. Should probably check this again after soldering the components, just to be sure.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-21T01:30:06.637" />
  <row Id="578" PostTypeId="2" ParentId="576" CreationDate="2009-11-21T01:55:13.667" Score="12" ViewCount="" Body="&lt;p&gt;After you make sure power/ground aren't shorted, make sure that any silk screen or pin 1 markings for polarized components are correct - you don't want to go soldering that kind of stuff in backwards. After that it's really kind of random. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was involved in bringing up a number of multi-layer boards over the years (not my designs) and we had pretty much any kind of screw-up you could make - traces that didn't go where they should, traces that simply weren't there, pads that weren't connected to their traces, etc, etc. I once even saw an issue where a broken trace was caused by the guys who built up the board gripping it wrong with pliers to break off a break-away section.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We were doing high layer-count designs, so we also had a lot of internal layer foolishness that you aren't going to see on a 2 or 4 layer board (registration can be...interesting when you've got 10 or more layers).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you get past the power/ground thing, you're probably not going to have too much trouble. Just take your time, test each bit of functionality one by one, and you should be good to go. If you're feeling paranoid, you could try building up the board one bit at a time (first put on and test the power, then the CPU and it's communications. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're feeling REALLY paranoid, you can sit down with the schematic and a meter and buzz-out the entire board. But unless the board is really small, that's gonna take a while.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You definitely want to get the main board working before you start on the secondary boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2009-11-21T01:55:13.667" />
  <row Id="579" PostTypeId="2" ParentId="576" CreationDate="2009-11-21T02:35:14.600" Score="2" ViewCount="" Body="&lt;p&gt;One of the best methods to creating an error free PCB is to create a schematic first.  A schematic will give you a better representation of what you're trying to achieve.  Then you can check the PCB against the schematic which will be easier and many PCB apps now can check against your schematic to make sure that you have everything connected properly (or at least the same way it was in the schematic).&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2009-11-21T02:35:14.600" />
  <row Id="580" PostTypeId="1" CreationDate="2009-11-21T03:58:42.000" Score="6" ViewCount="725" Body="&lt;p&gt;I am trying to build a robot and i have been having trouble getting a working h-bridge for my motors and i was wondering if anyone could help me work this out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i have 2 motors to drive with either a pic or a c-stamp pwm. the motors are HG16-120-AA Operating Voltage 5.4v-6.6v Rated Current 350ma Stall Current 1600ma.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i have some irf530 and irf9630 power mosfets that i think will work for those motors but i am not sure as i have yet to have any luck getting it to work right. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;i also have some irl510 mostfets if they would help?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i plan on driving the motors off 4 AA battery's&lt;/p&gt;&#xA;&#xA;&lt;p&gt;any help would be greatly appreciated&lt;/p&gt;&#xA;" LastActivityDate="2009-11-25T03:06:40.777" Title="H-bridge motor driver" Tags="&lt;robotics&gt;&lt;voltage&gt;&lt;servo&gt;&lt;motor&gt;" AnswerCount="5" CommentCount="1" />
  <row Id="581" PostTypeId="1" AcceptedAnswerId="582" CreationDate="2009-11-21T04:18:47.013" Score="3" ViewCount="167" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am building a distance sensor..I have the ucontroller portion done. I was going to use IR to reflect a beam and get a proportional analog voltage to estimate distance but...it has no range&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas/methods? &lt;/p&gt;&#xA;" LastActivityDate="2009-11-21T16:17:41.440" Title="Distance sensor IR" Tags="&lt;voltage&gt;&lt;sensor&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="582" PostTypeId="2" ParentId="581" CreationDate="2009-11-21T05:25:50.717" Score="6" ViewCount="" Body="&lt;p&gt;You want an IR distance sensor like this &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=35&amp;amp;products_id=164&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=35&amp;amp;products_id=164&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I am sure there are lots of sources).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just hook it up to an analog pin of your UC and you will get your proportional voltage.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-21T05:25:50.717" />
  <row Id="583" PostTypeId="2" ParentId="580" CreationDate="2009-11-21T09:03:55.737" Score="12" ViewCount="" Body="&lt;p&gt;In many cases, building your own H-bridge out of discrete transistors is more work than you need to do. (See &lt;a href=&quot;http://www.cadvision.com/blanchas/hexfet/&quot; rel=&quot;nofollow&quot;&gt;this page on H-bridge issues&lt;/a&gt; which also has an example schematic that would work with your FETs)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead, look into using one of the many H-bridge chips out there.  These chips are designed to make quick work of controlling a motor and contain protection circuitry for both the motor and the power transistors.  A really common H-bridge chip is the L293.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find a few examples of how to use H-bridge chips on the &lt;a href=&quot;http://arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino.cc&lt;/a&gt; site.  For example, here's &lt;a href=&quot;http://itp.nyu.edu/physcomp/Labs/DCMotorControl#toc6&quot; rel=&quot;nofollow&quot;&gt;an example using an L293E H-bridge chip on a breadboard&lt;/a&gt; and here's &lt;a href=&quot;http://www.ladyada.net/make/mshield/&quot; rel=&quot;nofollow&quot;&gt;Adafruit's Arduino motor shield kit&lt;/a&gt; which has four H-bridges (two L293Ds) on it.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-21T09:03:55.737" />
  <row Id="584" PostTypeId="2" ParentId="576" CreationDate="2009-11-21T09:19:00.227" Score="11" ViewCount="" Body="&lt;p&gt;Common non-obvious problems that crop up specifically with Arduino shield PCBs:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Not connecting the Gnd pins on the analog side with the Gnd pin on the digital side&lt;/li&gt;&#xA;&lt;li&gt;Component placement makes them short against metal of Arduino (USB jack &amp;amp; ISP connector usually)&lt;/li&gt;&#xA;&lt;li&gt;Headers flipped 180º (digital 7 -&gt; 0, 6-&gt;1, 5-&gt;2, etc.)&lt;/li&gt;&#xA;&lt;li&gt;Bad header spacing so it the shield doesn't plug in to Arduino&lt;/li&gt;&#xA;&lt;li&gt;Board larger than Arduino, making Arduino+shield assembly not fit enclosures&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Many of these errors can be discovered by printing out the PCB (both top &amp;amp; bottom) on paper at 1:1 scale, cutting it out, and laying it on top of an real Arduino. It makes it physical.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-21T09:19:00.227" CommentCount="1" />
  <row Id="585" PostTypeId="2" ParentId="576" CreationDate="2009-11-21T10:40:16.850" Score="4" ViewCount="" Body="&lt;p&gt;I have been pretty lucky with PCBs that I have sent to fab houses, though I verge on the paranoid when I am preparing the design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Big rule as said before is begin with a schematic.  Once that is correct, the software will to an extent look after you.  I personally use DIptrace which includes error checking tools, even in the free editions.  I am pretty sure that most of the packages do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are designing Arduino shields it might be worth looking at the &lt;a href=&quot;http://fritzing.org/&quot; rel=&quot;nofollow&quot;&gt;Fritzing Project&lt;/a&gt;.  It is software that allows you to design either in schematic, breadboard or PCB layout specifically for the Arduinio.  Templates are already there for board sizes and pinouts.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have not done more than play with it, and it does seem at first glance to be a little basic PCB design wise.  However it also seems very convenient.&lt;/p&gt;&#xA;" OwnerUserId="312" LastActivityDate="2009-11-21T10:40:16.850" />
  <row Id="586" PostTypeId="2" ParentId="576" CreationDate="2009-11-21T13:47:15.540" Score="5" ViewCount="" Body="&lt;p&gt;When you start populating the board the first thing you want to do is to make sure all the chips get power (build the PSU section first and then make sure it is not shorted, then measure all the power pins for the chips get power). Next thing you want to do is to measure every &quot;output&quot; pin on chips that they are not shorted to anything because that will kill them. And generally building everything in sections and making sure every section works by itself is a good practice.&lt;/p&gt;&#xA;" OwnerUserId="140" LastActivityDate="2009-11-21T13:47:15.540" />
  <row Id="587" PostTypeId="2" ParentId="562" CreationDate="2009-11-21T16:06:11.780" Score="2" ViewCount="" Body="&lt;p&gt;If you want to go a slightly different route, you can buy LED fixtures from Philips Color Kinetics (www.colorkinetics.com).  They make string lights (&quot;Flex&quot; is the name of the series), and you can talk to them using one of their power supply/controllers via Ethernet or DMX (an RS-485 based protocol).  Its an option rather than hardcoding it yourself.  You could then mount the Flex lights how you want them.  They should be bright enough to see far away in daylight.  Just another option...&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2009-11-21T16:06:11.780" />
  <row Id="588" PostTypeId="2" ParentId="581" CreationDate="2009-11-21T16:17:41.440" Score="3" ViewCount="" Body="&lt;p&gt;I think a key to this kind of thing is to modulate the IR.  Then in the detector have a lot of gain in the band you used to modulate the signal.  This lets you extend the range without picking up a lot of other light noise.  Reflection can depend a lot on the surface you are reflecting from so distance is still uncertain.  Using time of flight is a different method, but to measure 30 cm involves measureing down to 1 nano second with light, easier to apply to sound.  There is also triangulation using light, do not know any simple, reliable systems using this.  Unless you are really into buiding your own I would consider buying one, perhaps as the earlier suggestion.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-21T16:17:41.440" />
  <row Id="589" PostTypeId="2" ParentId="460" CreationDate="2009-11-21T17:16:07.183" Score="3" ViewCount="" Body="&lt;p&gt;This may be an option for you.  Its from sparkfun and not cheap, but it will probably be excellent as a 'true' random number generator.  It uses a geigercounter to generate the random numbers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;https://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=132&quot; rel=&quot;nofollow&quot;&gt;https://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=132&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2009-11-21T17:16:07.183" CommentCount="1" />
  <row Id="590" PostTypeId="2" ParentId="580" CreationDate="2009-11-21T17:25:14.917" Score="3" ViewCount="" Body="&lt;p&gt;I thought I would include this for the people searching for H-Bridge stuff. Another good resource about h-bridges is at the &lt;a href=&quot;http://www.societyofrobots.com/schematics%5Fh-bridgedes.shtml&quot; rel=&quot;nofollow&quot;&gt;Society of Robots&lt;/a&gt; site.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-11-21T17:25:14.917" />
  <row Id="591" PostTypeId="2" ParentId="556" CreationDate="2009-11-21T18:13:36.153" Score="3" ViewCount="" Body="&lt;p&gt;You could make your own. I recently built an LED notifier for my netbook using an AVR chip and a RGB LED.  The AVR code came from a similar project elsewhere by Dave Hillier.  It is easily controlled, even from the command line in either Windows or Linus (I have done both)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was only controlling a single LED, but with high power transistors, the projet could be very easily adpted to running strips of LEDs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can see what I did here... &#xA;&lt;a href=&quot;http://www.justblair.co.uk/the-attiny45-usb-led-e-mail-twitter-and-pidgin-notifier.html&quot; rel=&quot;nofollow&quot;&gt;LED Notifier&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used some code written by a chap Dennis that I know online to control mine.&lt;/p&gt;&#xA;" OwnerUserId="312" LastActivityDate="2009-11-21T18:13:36.153" />
  <row Id="592" PostTypeId="1" AcceptedAnswerId="593" CreationDate="2009-11-21T20:01:19.477" Score="11" ViewCount="1794" Body="&lt;p&gt;Hi, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;can anyone point me to a tutorial for electronic noobs that &#xA;explains how to use op-amps and what i can do with them, besides&#xA;amplification?&lt;/p&gt;&#xA;" OwnerUserId="123" LastActivityDate="2011-06-02T23:16:15.600" Title="op-amp tutorial for electronic noobs?" Tags="&lt;electronics&gt;&lt;op-amp&gt;" AnswerCount="11" FavoriteCount="8" />
  <row Id="593" PostTypeId="2" ParentId="592" CreationDate="2009-11-21T20:41:54.667" Score="9" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/Electronic/opampvar.html&quot; rel=&quot;nofollow&quot;&gt;http://hyperphysics.phy-astr.gsu.edu/hbase/Electronic/opampvar.html&lt;/a&gt; Hyperphysics has a pretty good section about opamps.&lt;/p&gt;&#xA;" OwnerUserId="140" LastActivityDate="2009-11-21T20:41:54.667" CommentCount="2" />
  <row Id="594" PostTypeId="2" ParentId="592" CreationDate="2009-11-21T21:30:04.057" Score="3" ViewCount="" Body="&lt;p&gt;Check out: &lt;a href=&quot;http://www.opencircuits.com/Op_amp&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/Op_amp&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-21T21:30:04.057" />
  <row Id="595" PostTypeId="2" ParentId="592" CreationDate="2009-11-21T23:28:14.737" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.amazon.co.uk/IC-Op-Amp-Cookbook-Walter-Jung/dp/0138896011&quot; rel=&quot;nofollow&quot;&gt;Op amp Cookbook&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This book is considered to be a key text on the subject.  I dont think there is an online version available... £30 (where I come from) is around the &quot;reasonable&quot; price range for such books.&lt;/p&gt;&#xA;" OwnerUserId="312" LastActivityDate="2009-11-21T23:28:14.737" CommentCount="1" />
  <row Id="596" PostTypeId="2" ParentId="592" CreationDate="2009-11-21T23:40:59.393" Score="5" ViewCount="" Body="&lt;p&gt;Try &lt;a href=&quot;http://focus.ti.com/lit/an/slod006b/slod006b.pdf&quot; rel=&quot;nofollow&quot;&gt;link text&lt;/a&gt;  (warning -- large pdf, and some TI bias)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has lots to teach, covers beginning to somewhat advanced topics, and it's free. &lt;/p&gt;&#xA;" OwnerUserId="227" LastActivityDate="2009-11-21T23:40:59.393" />
  <row Id="597" PostTypeId="1" AcceptedAnswerId="598" CreationDate="2009-11-22T08:35:13.680" Score="4" ViewCount="95" Body="&lt;p&gt;&quot;The MAX6960–MAX6963 are compact cathode-row display drivers&quot;&#xA;What does cathode-row mean?&lt;/p&gt;&#xA;" OwnerUserId="322" LastEditorUserId="215" LastEditorDisplayName="" LastEditDate="2009-11-24T02:12:06.777" LastActivityDate="2011-03-15T18:56:18.670" Title="Cathode-Row Meaning" Tags="&lt;max&gt;&lt;led&gt;" AnswerCount="2" />
  <row Id="598" PostTypeId="2" ParentId="597" CreationDate="2009-11-22T10:10:20.923" Score="6" ViewCount="" Body="&lt;p&gt;If you think of a matrix of LEDs (8*8) having rows and columns, where all the cathodes are linked in a row and all the anodes are linked in a column. &#xA;This range of ICs will drive such a matrix with no other components (apart from a microprocessor etc.). &#xA;I realise that the the terminology of rows vs columns is arbitrary.&#xA;The terminology exists to help to understand which pins to connect up, the pictures shown and also how to send data.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-22T10:10:20.923" />
  <row Id="599" PostTypeId="1" AcceptedAnswerId="604" CreationDate="2009-11-22T16:07:04.200" Score="3" ViewCount="244" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an old CD-burner (HP 9100 plus) where I would like to control the BLDC motor from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My idea is to use the original IC of the burner as the driver and use an ATtiny13 for controlling it. There are however some problems. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found out that the IC is similar to the LB11699H &lt;a href=&quot;http://www.alldatasheet.com/datasheet-pdf/pdf/267193/SANYO/LB11699H.html&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;, only lower model.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I hook the CD-burner up to the power the motor spins up and down by itself a couple of times and then stops. I disconnected the cable to the laser head for safety. During the time the motor spins I can make it stop and spin a bit faster by changing pins 1 and 2, but when the motor is stopped by the on-board circuit, I can do nothing... I don't get the motor spinning. What is going wrong?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also I need to have an analog signal between 0 and 2 volt to control the IC. Can this signal be generated with a smoothed PWM from ATtiny13 or do I need to use something else? Perhaps two batteries with voltage dividers and transistor connect to ATtiny13 pins? How do I do this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could someone help me out here? :D&lt;/p&gt;&#xA;" OwnerUserId="323" LastActivityDate="2009-11-23T03:23:59.227" Title="Hacking/Controlling BLDC from CD-burner" Tags="&lt;avr&gt;&lt;analog&gt;&lt;microcontroller&gt;" AnswerCount="1" />
  <row Id="600" PostTypeId="2" ParentId="580" CreationDate="2009-11-22T16:19:01.917" Score="3" ViewCount="" Body="&lt;p&gt;I have an H-Bridge tutorial on Instructables. Its for Arduino but might still help you out.&#xA;&lt;a href=&quot;http://www.instructables.com/id/Duel-Motor-Driver-with-Arduino-using-a-SN754410NE-/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Duel-Motor-Driver-with-Arduino-using-a-SN754410NE-/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-11-22T16:19:01.917" />
  <row Id="601" PostTypeId="1" CreationDate="2009-11-22T21:07:03.760" Score="4" ViewCount="436" Body="&lt;p&gt;Been trying to figure out how to implement trig functions in my PicBasic projects.  I could use a lookup table but that limits my output.  I need to be able to use sin, cos, tan, and their inverses in order to do a time based calculation.  Should I just give up and start looking at programming PICs in C?  I've got a programmer and a couple PICs next ot me and would rather use these before jumping on the Arduino bandwagon.....Or would it really be that much easier to do Arduinio?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-11-22T21:13:27.480" LastActivityDate="2009-12-01T00:23:08.157" Title="Trig Functions In PicBasic" Tags="&lt;pic&gt;&lt;math&gt;" AnswerCount="4" />
  <row Id="602" PostTypeId="2" ParentId="601" CreationDate="2009-11-22T22:00:23.440" Score="0" ViewCount="" Body="&lt;p&gt;Depending on whether time is a factor bear in mind that all trig functions have Taylor series for them, for instance Sine has:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/math/2/9/c/29cb648e96291f52707c7225630c1a17.png&quot; alt=&quot;taylor series for sine&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The terms continue so the next would be + x^9/9! you increase the number of terms to get more accuracy. But if you need to do the calculation in any reasonable amount of time then this might not be the best solution. There's a long discussion about accuracy etc at the &lt;a href=&quot;http://en.wikipedia.org/wiki/Taylor%5Fseries&quot; rel=&quot;nofollow&quot;&gt;Taylor Series Wikipedia Page&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As ever YMMV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[EDIT] There's an Arduino implementation of an accurate sine wave generator &lt;a href=&quot;http://interface.khm.de/index.php/lab/experiments/arduino-dds-sinewave-generator/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and from the looks of things they're using a lookup table too.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2009-11-30T23:41:06.137" LastActivityDate="2009-11-30T23:41:06.137" CommentCount="1" />
  <row Id="603" PostTypeId="2" ParentId="601" CreationDate="2009-11-23T00:02:37.407" Score="1" ViewCount="" Body="&lt;p&gt;You are coding on a PIC, how many bits is your angle? if you have an 8 bit number coming in, a look up table can be easy, if you have a 16 bit number coming in, then it is a different story.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally in PICs 8 or 10 bit number is about as big as you will get, a look up table is probably okay. People often get lost in getting a high accuracy number, normally you do not need one. I had someone reading a 12 bit number of a sensor, using doubles and getting a really accurate conversion out. It worked perfectly when he used a voltage source as an input for testing, but you add a real sensor with it's error and you find all of the accuracy is a waste of time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are cases where I would suggest using a high quality sin/cos/tan function, I have never encountered one on a PIC. Forgive me if you need a high quality sign function, I am just answering what would be the right answer for 95% of cases.&#xA;-Max Murphy&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-23T00:02:37.407" CommentCount="2" />
  <row Id="604" PostTypeId="2" ParentId="599" CreationDate="2009-11-23T03:09:26.683" Score="2" ViewCount="" Body="&lt;p&gt;(I really have no experience with this particular application, so this is a bit of a shot in the dark - hopefully it'll give you some ideas)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How thoroughly have you separated this from the rest of the drive circuitry?  From the part where you say you disconnected the wires from the laser head, it sounds like it's still in the drive.  If so, you're probably fighting against the automatic drive startup behaviour where it spins up and checks to see if there's a disk before shutting down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the very least, check to see if something is happening on pin 7 (BRAKE).  It looks like that pin going high will brake the motor.  You want it to be low the whole time.  If you can see it transition low to high right when the motor stops, you've got your culprit :)  If that doesn't seem to be it, try checking the other pins on the controller to see if one of them does it (they might have changed the pinout between chip versions).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for how to get your 0 - 2V level, smoothing a PWM output is pretty tricky and the exact capacitance needed varies based on how much current is being drawn.  If you don't need to vary the voltage, I'd do a voltage divider.  If you do need to vary it, but can live with discrete steps I'd look at doing several voltage dividers, either on multiple pins of the Attiny, or attached to something like a ripple counter where you could select which output pin is ON and thus control which one of several resistors is used as the top half of the voltage divider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck on this project.  Salvaging parts can be tricky.  I've got immense respect for the folks who pull it off.&lt;/p&gt;&#xA;" OwnerUserId="213" LastEditorUserId="213" LastEditorDisplayName="" LastEditDate="2009-11-23T03:23:59.227" LastActivityDate="2009-11-23T03:23:59.227" CommentCount="1" />
  <row Id="605" PostTypeId="1" AcceptedAnswerId="608" CreationDate="2009-11-23T11:06:04.533" Score="5" ViewCount="1163" Body="&lt;p&gt;I was wondering if there was a single IC like the MAX6960 that could control a whole 8x8 RGB LED Matrix because the MAX6960 can only control a RGY.&lt;/p&gt;&#xA;" OwnerUserId="322" LastActivityDate="2011-03-18T15:30:06.150" Title="Is there a single IC that can control a 8x8 RGB LED Matrix" Tags="&lt;rgb&gt;&lt;led&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="606" PostTypeId="1" CreationDate="2009-11-23T11:42:09.123" Score="3" ViewCount="461" Body="&lt;p&gt;After etching a PCB I discovered a big spot across some of the traces - probably from a finger. I transferred the PCB layout from a transparent film. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be the best way to remove &quot;finger&quot; and others from both the PCB and the film before etching without destroying them?&lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-02T02:18:27.880" LastActivityDate="2011-02-02T02:18:27.880" Title="PCB etching with transparent film" Tags="&lt;pcb-fabrication&gt;" AnswerCount="5" />
  <row Id="607" PostTypeId="2" ParentId="601" CreationDate="2009-11-23T11:45:14.780" Score="1" ViewCount="" Body="&lt;p&gt;Have a look at the CORDIC algorithms in section 31.2 of the fxtbook: &lt;a href=&quot;http://www.jjj.de/fxt/&quot; rel=&quot;nofollow&quot;&gt;http://www.jjj.de/fxt/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="23" LastActivityDate="2009-11-23T11:45:14.780" />
  <row Id="608" PostTypeId="2" ParentId="605" CreationDate="2009-11-23T11:54:49.660" Score="5" ViewCount="" Body="&lt;p&gt;The Holtek HT1632 chip controls a 24*16 panel of LEDs - so it would control a 8*16 matrix of RGB leds. I'm not sure how easy they are to get hold of.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also interesting RGB application of the TI TLC5490 &lt;a href=&quot;http://macetech.com/blog/?q=node/36&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-11-23T11:54:49.660" CommentCount="1" />
  <row Id="609" PostTypeId="2" ParentId="576" CreationDate="2009-11-23T13:46:39.470" Score="1" ViewCount="" Body="&lt;p&gt;Make sure all the mounting holes are in the correct location.  Also check all the components that need to poke through the enclosure such as LEDs and switches and connectors are in the correct location.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2009-11-23T13:46:39.470" />
  <row Id="610" PostTypeId="2" ParentId="605" CreationDate="2009-11-23T15:34:57.770" Score="3" ViewCount="" Body="&lt;p&gt;I found no easy and affordable way to do this with a single IC, so I've &quot;used&quot; a project like this as an &quot;excuse&quot; to learn the use of FPGAs. I've managed to handle a single array of 20x16 led with 16 &quot;gray&quot; levels, driven from a PC via RS232 port with 50 Hz refresh rate with an Altera CycloneII EP2C5 and a transistor for each row and column. I don't think it costs much more than a dedicated IC. &lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2009-11-23T15:34:57.770" CommentCount="2" />
  <row Id="611" PostTypeId="2" ParentId="606" CreationDate="2009-11-23T17:39:35.287" Score="5" ViewCount="" Body="&lt;p&gt;We wash with a mild detergent and then put the PCB through a very quick bath in etchant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After this point, we use gloves. The gloves are an attempt to keep our body oils off of the board. The board is very clean and nice for the photo-resist at this point, and it has paid off well.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-23T17:39:35.287" />
  <row Id="612" PostTypeId="2" ParentId="606" CreationDate="2009-11-23T17:40:00.747" Score="1" ViewCount="" Body="&lt;p&gt;I would say it is impossible and you just need to expose a new board or try to fix the old one after etching. I'd just try etching the board and then just scraping the traces off from each other with a dremel or some other tool, depending where the fingerprint is.&lt;/p&gt;&#xA;" OwnerUserId="140" LastActivityDate="2009-11-23T17:40:00.747" CommentCount="1" />
  <row Id="613" PostTypeId="2" ParentId="605" CreationDate="2009-11-23T21:00:13.367" Score="2" ViewCount="" Body="&lt;p&gt;Yes, well sort of  The Maxim &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/1339&quot; rel=&quot;nofollow&quot;&gt;MAX7219 or MAX7221&lt;/a&gt; IC's can be cascaded to give you control of up to 8 8x8 LED matrix via SPI&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not perfect, but code examples are available...  That should make it least the programming a bit easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/playground/LEDMatrix/Max7219&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/LEDMatrix/Max7219&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="312" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-07-20T19:00:22.910" LastActivityDate="2010-07-20T19:00:22.910" CommentCount="1" />
  <row Id="614" PostTypeId="1" CreationDate="2009-11-23T21:05:38.700" Score="3" ViewCount="150" Body="&lt;p&gt;Does anybody know of any online resources that go over the setup of driving ultrasonic transducers, as well as how to receive an ultrasonic echo, and pick it out (for rangefinding)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found one article online...but it glosses over it almost too much.&#xA;&lt;a href=&quot;http://www.ee.latrobe.edu.au/~djc/UltraSonics/Ultrasonics.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.ee.latrobe.edu.au/~djc/UltraSonics/Ultrasonics.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="326" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:49:33.440" LastActivityDate="2010-08-20T11:43:30.267" Title="ultrasonic setup guide" Tags="&lt;ultrasound&gt;&lt;setup&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="615" PostTypeId="2" ParentId="614" CreationDate="2009-11-23T21:35:49.653" Score="3" ViewCount="" Body="&lt;p&gt;Have you considered an ultrasonic &quot;module&quot; like one of these? &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8502&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=8502&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will take care of most of the details for you.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-23T21:35:49.653" />
  <row Id="616" PostTypeId="1" CreationDate="2009-11-23T22:21:39.657" Score="30" ViewCount="1495" Body="&lt;p&gt;I need basic electronics books  (diodes,transistors,current..etc) as I am just starting out with electronics and want to have something to read over the holiday.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions of good beginners' books?&lt;/p&gt;&#xA;" OwnerUserId="326" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-18T02:28:23.780" LastActivityDate="2011-05-13T20:10:20.723" CommunityOwnedDate="2011-03-24T07:55:53.500" Title="Basic Electronics Book" Tags="&lt;electronics&gt;&lt;books&gt;" AnswerCount="12" CommentCount="2" FavoriteCount="28" />
  <row Id="617" PostTypeId="2" ParentId="616" CreationDate="2009-11-23T22:38:25.680" Score="6" ViewCount="" Body="&lt;p&gt;Check out &lt;a href=&quot;http://hardware.slashdot.org/article.pl?sid=08/05/06/2333256&quot; rel=&quot;nofollow&quot;&gt;this slashdot question&lt;/a&gt; on the almost exact same topic. Make sure to set the comments threshold to see only comments rated +5, and you'll see all the most popular suggestions.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-23T22:38:25.680" CommunityOwnedDate="2011-03-24T07:55:53.500" />
  <row Id="618" PostTypeId="2" ParentId="616" CreationDate="2009-11-23T22:53:35.907" Score="27" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/The%5FArt%5Fof%5FElectronics&quot; rel=&quot;nofollow&quot;&gt;The Art of Electronics:Paul Horowitz and Winfield Hill&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Often described as the Bible of Electronics.  Its fair to say that if you buy this one, you wont need another for a while!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Contents:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Foundations&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;voltage and current; passive components; signals; complex analysis made simple. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Transistors&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;an easy-to-use transistor model&lt;/li&gt;&#xA;&lt;li&gt;extensive discussion of useful subcircuits, such as followers, switches, current sources, current mirrors, differential amplifiers, push-pull, cascode. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Field Effect Transistors&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;JFETs and MOSFETs: types and properties; low-level and power applications; FET vs bipolar transistors; ESD.&lt;/li&gt;&#xA;&lt;li&gt;how to design amplifiers, buffers, current sources, gain controls, and logic switches.&lt;/li&gt;&#xA;&lt;li&gt;everything you wanted to know about analog switching -- feedthrough and crosstalk, bandwidth and speed, charge injection, nonlinearities, capacitance and on-resistance, latchup. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Feedback and Operational Amplifiers&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&quot;golden rules&quot; for simple design, followed by in-depth treatment of real op-amp properties.&lt;/li&gt;&#xA;&lt;li&gt;circuit smorgasbord; design tradeoffs and cautions.&lt;/li&gt;&#xA;&lt;li&gt;easy to understand discussion of single-supply op-amp design and op-amp frequency compensation.&lt;/li&gt;&#xA;&lt;li&gt;special topics such as active rectifiers, logarithmic converters, peak detectors, dielectric absorption. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Active Filters and Oscillators&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;simplified design of active filters, with tables and graphs.&lt;/li&gt;&#xA;&lt;li&gt;design of constant-Q and constant-BW filters, switched-capacitor filters, zero-offset LPFs, single-control tunable notch.&lt;/li&gt;&#xA;&lt;li&gt;oscillators: relaxation, VCO, RF VCO, quadrature, switched-capacitor, function generator, lookup table, state-variable, Wein bridge, LC, parasitic, quartz crystal, ovenized. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Voltage Regulators and Power Circuits&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;discrete and integrated regulators, current sources and current sensing, crowbars, ground meccas.&lt;/li&gt;&#xA;&lt;li&gt;power design: parallel operation of bipolar and MOSFET transistors, SOA, thermal design and heatsinking.&lt;/li&gt;&#xA;&lt;li&gt;voltage references: bandgap/zener: stability and noise; integrated/discrete.&lt;/li&gt;&#xA;&lt;li&gt;all about switching supplies: configurations, design, and examples.&lt;/li&gt;&#xA;&lt;li&gt;flying-capacitor, high-voltage, low-power, and ultra stable power supplies.&lt;/li&gt;&#xA;&lt;li&gt;full analysis of a commercial line-powered switcher. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Precision Cicruits and Low-Noise Techniques&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;an easy-to-use section on precision linear design.&lt;/li&gt;&#xA;&lt;li&gt;a section on noise, shielding, and grounding.&lt;/li&gt;&#xA;&lt;li&gt;a unique graphical method for streamlined low-noise amplifier analysis.&lt;/li&gt;&#xA;&lt;li&gt;autonulling amplifiers, instrumentation amplifiers, isolation amplifiers. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Digital Electronics&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;combinational and sequential design with standard ICs, and with PLDs.&lt;/li&gt;&#xA;&lt;li&gt;all you wanted to know about timing, logic races, runt pulses, clocking skew, and metastable states.&lt;/li&gt;&#xA;&lt;li&gt;monostable multivibrators and their idiosyncrasies.&lt;/li&gt;&#xA;&lt;li&gt;a collection of digital logic pathology, and what to do about it. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Digital Meets Analog&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;an extensive discussion of interfacing between logic families, and between logic and the outside world.&lt;/li&gt;&#xA;&lt;li&gt;a detailed discussion of A/D and D/A conversion techniques.&lt;/li&gt;&#xA;&lt;li&gt;digital noise generation.&lt;/li&gt;&#xA;&lt;li&gt;an easy-to-understand discussion of phase-locked loops, with design examples and applications.&lt;/li&gt;&#xA;&lt;li&gt;optoelectronics: emitters, detectors, couplers, displays, fiber optics.&lt;/li&gt;&#xA;&lt;li&gt;driving buses, capacitive loads, cables, and the outside world. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Microcomputers&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;IBM PC and Intel family: assembly language, bus signals, interfacing (with many examples).&lt;/li&gt;&#xA;&lt;li&gt;programmed I/O, interrupts, status registers, DMA.&lt;/li&gt;&#xA;&lt;li&gt;RS-232 cables that really work.&lt;/li&gt;&#xA;&lt;li&gt;serial ports, ASCII, and modems.&lt;/li&gt;&#xA;&lt;li&gt;SCSI, IPI, GPIB, parallel ports.&lt;/li&gt;&#xA;&lt;li&gt;local-area networks. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Microprocessors&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;68000 family: actual design examples and discussion -- how to design them into instruments, and how to make them do what you want.&lt;/li&gt;&#xA;&lt;li&gt;complete general-purpose instrument design, with programming.&lt;/li&gt;&#xA;&lt;li&gt;peripheral LSI chips; serial and parallel ports; D/A and A/D converters.&lt;/li&gt;&#xA;&lt;li&gt;memory: how to choose it, how to use it. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Electronic Construction Techniques&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;prototyping methods.&lt;/li&gt;&#xA;&lt;li&gt;printed-circuit and wire-wrap design, both manual and CAD.&lt;/li&gt;&#xA;&lt;li&gt;instrument construction: motherboards, enclosures, controls, wiring, accessibility, cooling.&lt;/li&gt;&#xA;&lt;li&gt;electrical and construction hints. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;High-Frequency and High-Speed Techniques&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;transistor high-frequency design made simple.&lt;/li&gt;&#xA;&lt;li&gt;modular RF components -- amplifiers, mixers, hybrids, etc.&lt;/li&gt;&#xA;&lt;li&gt;modulation and detection.&lt;/li&gt;&#xA;&lt;li&gt;simplified design of high-speed switching circuits. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Low-Power Design&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;extensive discussion of batteries, solar cells, and &quot;signal-current&quot; power sources.&lt;/li&gt;&#xA;&lt;li&gt;micropower references and regulators.&lt;/li&gt;&#xA;&lt;li&gt;low-power analog circuits -- discrete and integrated.&lt;/li&gt;&#xA;&lt;li&gt;low-power digital circuits, microprocessors, and conversion techniques. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Measurements and Signal Processing&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;what you can measure and how accurately, and what to do with the data.&lt;/li&gt;&#xA;&lt;li&gt;bandwidth-narrowing methods made clear: signal averaging, multichannel scaling, lock-in amplifiers, and pulse-height analysis. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;It takes a bit of a commitment to read it all, but it is the sort of book that you can pick from.  Not to heavy on the maths.&lt;/p&gt;&#xA;" OwnerUserId="312" LastActivityDate="2009-11-23T22:53:35.907" CommunityOwnedDate="2011-03-24T07:55:53.500" CommentCount="7" />
  <row Id="619" PostTypeId="2" ParentId="616" CreationDate="2009-11-23T23:05:37.780" Score="8" ViewCount="" Body="&lt;p&gt;So to sum up the /. article and add a few cents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Highest recommended were the following:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Art of Electronics, Horowitz&lt;/p&gt;&#xA;&#xA;&lt;p&gt;get an Arduino and play/walk through the plethora of howtos&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Practical Electronics for Inventors: Paul Scherz&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting Started in Electronics: Forrest M. Mims III&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was surprised to not see &quot;Black Art of Game Console Design&quot;, &quot;Physical Computing&quot; or &quot;Making things Talk&quot;.  Course my filters may have knocked them off, or folks might consider them to be a bit too practical.&lt;/p&gt;&#xA;" OwnerUserId="151" LastActivityDate="2009-11-23T23:05:37.780" CommunityOwnedDate="2011-03-24T07:55:53.500" />
  <row Id="620" PostTypeId="2" ParentId="616" CreationDate="2009-11-23T23:16:00.077" Score="5" ViewCount="" Body="&lt;p&gt;I really enjoyed &lt;strong&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0070580782&quot; rel=&quot;nofollow&quot;&gt;Practical Electronics For Inventors&lt;/a&gt;&lt;/strong&gt; by Paul Sherz. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's easy to read and fun without being simplistic and glossing over important details. As the title suggests it's geared toward hands on practical electronics rather than someone studying for an EE degree. For example there's a page comparing the types of capacitors available and how to recognize each. It has a good amount of detail without getting dry and textbookish.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's not very much detail on modern microcontrollers in this book, but don't let that stop you, just grab another book dedicated to that topic if you're interested. You'll need to learn what's in this book to get the most out of using microcontrollers anyway.&lt;/p&gt;&#xA;" OwnerUserId="105" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T19:12:34.363" LastActivityDate="2011-05-13T19:12:34.363" CommunityOwnedDate="2011-03-24T07:55:53.500" />
  <row Id="621" PostTypeId="1" AcceptedAnswerId="624" CreationDate="2009-11-23T23:23:49.390" Score="13" ViewCount="1444" Body="&lt;p&gt;What are the advantages of stranded vs solid wire?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;what should i be using for prototyping circuits?&lt;/p&gt;&#xA;" OwnerUserId="267" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-01T19:46:50.950" LastActivityDate="2011-01-01T19:46:50.950" Title="Stranded vs solid wire" Tags="&lt;circuit&gt;&lt;wire&gt;&lt;prototyping&gt;" AnswerCount="10" CommentCount="1" />
  <row Id="622" PostTypeId="1" AcceptedAnswerId="625" CreationDate="2009-11-23T23:30:15.870" Score="7" ViewCount="815" Body="&lt;p&gt;So I've been reading a few threads here and on other forums.  I understand there are various solutions for stepping down or up a voltage.  What I have found are the LVC series shift regs that give a constant ouput, &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en531457&quot; rel=&quot;nofollow&quot;&gt;MCP1825&lt;/a&gt; which will step down 5 to 3.3 (and other versions which have different increments) the 74LCX245 which will step 2.5 or 3.3 to 5v and perhaps some others I am forgetting. Then there are ready made boards such as the &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8745&quot; rel=&quot;nofollow&quot;&gt;Sparkfun converters&lt;/a&gt; or this &lt;a href=&quot;http://www.futurlec.com/Mini%5FLogic.shtml&quot; rel=&quot;nofollow&quot;&gt;8 pin to 8 pin converter&lt;/a&gt;. But all of these are one direction only, or bi-direction switched by a jumper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would I convert voltages down or up in both directions without requiring a pin select. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;5--3.3&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5--2.5&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5--1.8&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks&lt;/p&gt;&#xA;" OwnerUserId="196" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-24T01:39:43.363" LastActivityDate="2010-07-25T20:37:01.013" Title="Bi-Directional Step up and Step down (3.3v &lt;-&gt; 5, etc)" Tags="&lt;voltage&gt;&lt;convert&gt;&lt;stepper&gt;" AnswerCount="4" CommentCount="0" />
  <row Id="623" PostTypeId="2" ParentId="621" CreationDate="2009-11-23T23:36:54.327" Score="12" ViewCount="" Body="&lt;p&gt;Advantages&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stranded-More Flexible, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Non-Stranded-Easy to solder, will fit into breadboard.  Trying to insert stranded into a breadboard is like trying to push string!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I prefer non stranded, in fact I have a good tip here for a cheap source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Buy Solid Core Cat 5 or 6 Network cable, a couple of meters goes a long way... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Strip it out and you get 8 differently coloured/marked sets of good quality cable in 4 twisted pairs.  Very cheap compared to buying hookup cable in small quantities, and generally better quality!&lt;/p&gt;&#xA;" OwnerUserId="312" LastEditorUserId="312" LastEditorDisplayName="" LastEditDate="2009-11-24T22:34:24.707" LastActivityDate="2009-11-24T22:34:24.707" CommentCount="5" />
  <row Id="624" PostTypeId="2" ParentId="621" CreationDate="2009-11-23T23:38:30.160" Score="19" ViewCount="" Body="&lt;p&gt;Solid wire (24 gauge) is good for use as jumpers in solderless breadboards.  Trying to push in stranded wire is frustrating.  Solid wire holds its shape, so you can route wires along a path and they'll stay there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use stranded wire for everything else.  It is flexible so it's good for cables going between a circuit board and knobs/switches on an enclosure, connecting cables between circuit boards, or any time you might have physical flexing in a wire.  24 gauge is a good all-around size for stranded too.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-23T23:38:30.160" />
  <row Id="625" PostTypeId="2" ParentId="622" CreationDate="2009-11-23T23:40:58.047" Score="7" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial%5Finfo.php?tutorials%5Fid=65&quot; rel=&quot;nofollow&quot;&gt;Sparkfun has a tutorial on sensor interfacing/logic-level conversion&lt;/a&gt; that might be useful to you.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-23T23:40:58.047" CommentCount="4" />
  <row Id="626" PostTypeId="2" ParentId="622" CreationDate="2009-11-23T23:59:26.963" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.maxim-ic.com/&quot; rel=&quot;nofollow&quot;&gt;Maxim&lt;/a&gt; has a bunch of &lt;a href=&quot;http://para.maxim-ic.com/en/search.mvp?fam=bidirtranslators&amp;amp;hs=1&quot; rel=&quot;nofollow&quot;&gt;Logic Level Translators&lt;/a&gt;, most of which are bidirectional. The speeds vary, the fastest supports 100 MBit/sec max data rate, which should cover pretty much anything you'd ever want to do at a hobby level. Voltages range from 0.9V to 5.5V. &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-23T23:59:26.963" CommentCount="2" />
  <row Id="627" PostTypeId="1" AcceptedAnswerId="629" CreationDate="2009-11-24T00:00:23.110" Score="7" ViewCount="305" Body="&lt;p&gt;I'm looking to start a few different projects and stock up on some basic components - I was just wondering if anyone knows a good supplier of DC motors, stepper motors and servos?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm in vicinity of Sydney in Australia, so big pats on the back if they ship here. Thanks!&lt;/p&gt;&#xA;" OwnerUserId="295" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T21:45:55.110" LastActivityDate="2010-12-10T21:45:55.110" Title="Good motor supplier?" Tags="&lt;motor&gt;&lt;stepper&gt;&lt;servo&gt;&lt;sourcing&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="628" PostTypeId="2" ParentId="621" CreationDate="2009-11-24T00:01:59.730" Score="1" ViewCount="" Body="&lt;p&gt;It depends...if you are wiring up 100 connections, you really want to use stranded wire, since you can get it thinner and more flexible. If it's just a few connections, thicker non-stranded wire is easier to deal with.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-24T00:01:59.730" />
  <row Id="629" PostTypeId="2" ParentId="627" CreationDate="2009-11-24T00:09:05.403" Score="7" ViewCount="" Body="&lt;p&gt;I've been most impressed with the &lt;a href=&quot;http://www.pololu.com/catalog/category/21&quot; rel=&quot;nofollow&quot;&gt;Pololu&lt;/a&gt; range of motors and servos.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Their site has clear specs for each of the parts and other parts to accompany the motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: Gratuitous plug &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/collections/robotics&quot; rel=&quot;nofollow&quot;&gt;Little Bird Electronics&lt;/a&gt; is starting to get these in stock if you want cheaper shipping in Australia but it might be a while before the full range is in.&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-24T00:09:05.403" CommentCount="1" />
  <row Id="631" PostTypeId="2" ParentId="147" CreationDate="2009-11-24T01:49:29.897" Score="4" ViewCount="" Body="&lt;p&gt;This is brilliant!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;a new &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9490&quot; rel=&quot;nofollow&quot;&gt;Joystick from Sparkfun&lt;/a&gt; with the example code to getting it running on the &lt;a href=&quot;http://www.sparkfun.com/Code/Joystick%5FShield%5FExample.zip&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-24T01:49:29.897" CommentCount="1" />
  <row Id="632" PostTypeId="1" AcceptedAnswerId="642" CreationDate="2009-11-24T02:19:50.567" Score="22" ViewCount="767" Body="&lt;p&gt;I do a lot of firmware work at my job, but I'm looking for more advanced books on the topic.  Things not like the basics of &quot;what is an interrupt&quot;.  I'm reading the O'Reilly book on embedded systems development which is OK, but not advanced enough.  For instance, its rare for books to discuss things like Flash pages (which can be really useful), how to put a section of code in a specific area of memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps something with some tips and tricks.  I do primarily PIC programming.&lt;/p&gt;&#xA;" OwnerUserId="107" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-24T02:27:48.287" LastActivityDate="2011-03-18T23:07:45.397" Title="Good book for non-beginner firmware development" Tags="&lt;pic&gt;&lt;microcontroller&gt;&lt;books&gt;&lt;development&gt;" AnswerCount="7" FavoriteCount="11" />
  <row Id="633" PostTypeId="2" ParentId="621" CreationDate="2009-11-24T02:20:56.773" Score="5" ViewCount="" Body="&lt;p&gt;One thing I have not seen mentioned is that solid wire (when bent many many times) is more likely to break than stranded wire.&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2009-11-24T02:20:56.773" CommentCount="2" />
  <row Id="634" PostTypeId="2" ParentId="580" CreationDate="2009-11-24T02:24:55.750" Score="1" ViewCount="" Body="&lt;p&gt;Whatever you decide, I would recommend against using the &quot;typical&quot; H-bridge design with 4 transistors (FETS) as this can cause &quot;shoot through&quot; where you are shorting the power supply.  This can cause major damage to both the power supply and your circuit (and some fire in the process).&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2009-11-24T02:24:55.750" CommentCount="1" />
  <row Id="635" PostTypeId="2" ParentId="621" CreationDate="2009-11-24T04:15:32.813" Score="7" ViewCount="" Body="&lt;p&gt;As todbot says, if you are prototyping on a breadboard then solid core is easier.&#xA;Except that when you are making connections between the breadboard and something else (like a sensor, or an Arduino, or another breadboard) the wires tend to jump out of the breadboard.&#xA;The solution is to use flexible stranded wire for those runs, and solder a single pin from a male header on each end to make jumpers. A short piece of shrink wrap will provide some strain relief and keep the pins from breaking off. You can also buy these jumper wires  pre-made from adafruit or sparkfun, but they are easy to make.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-24T04:15:32.813" CommunityOwnedDate="2009-11-24T04:15:32.813" CommentCount="2" />
  <row Id="636" PostTypeId="2" ParentId="616" CreationDate="2009-11-24T04:16:04.980" Score="2" ViewCount="" Body="&lt;p&gt;I really liked &quot;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596510519&quot; rel=&quot;nofollow&quot;&gt;Make things talk&lt;/a&gt;&quot;. it doesn't explain to much theory, but&#xA;helps you to get your first projects started.&lt;/p&gt;&#xA;" OwnerUserId="123" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T19:08:28.187" LastActivityDate="2011-05-13T19:08:28.187" CommunityOwnedDate="2011-03-24T07:55:53.500" />
  <row Id="637" PostTypeId="2" ParentId="464" CreationDate="2009-11-24T04:32:40.330" Score="4" ViewCount="" Body="&lt;p&gt;I wish i had arduinos and &quot;make things talk&quot; when i was a kid. I would have automated everything!&lt;/p&gt;&#xA;" OwnerUserId="123" LastActivityDate="2009-11-24T04:32:40.330" CommunityOwnedDate="2009-11-24T04:32:40.330" />
  <row Id="638" PostTypeId="2" ParentId="26" CreationDate="2009-11-24T04:38:13.190" Score="1" ViewCount="" Body="&lt;p&gt;You can use your scripting-language of choice (python, ruby, perl, ... ) and execute &#xA;the script from applescript.&lt;/p&gt;&#xA;" OwnerUserId="123" LastActivityDate="2009-11-24T04:38:13.190" />
  <row Id="639" PostTypeId="1" AcceptedAnswerId="644" CreationDate="2009-11-24T06:41:53.750" Score="5" ViewCount="132" Body="&lt;p&gt;I am trying to minimize interference in a sensor project. Can anyone recommend a good shielded wire I can solder into my board?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:44:32.573" LastActivityDate="2010-08-17T23:44:32.573" Title="Wire to use with Sensors" Tags="&lt;sensor&gt;&lt;wire&gt;&lt;interference&gt;&lt;shielding&gt;&lt;soldering&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="640" PostTypeId="2" ParentId="632" CreationDate="2009-11-24T08:07:58.503" Score="6" ViewCount="" Body="&lt;p&gt;I wish I had a good suggestion, I will watch the thread hoping a great book shows up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a side not, the manual that comes with your compiler is one of the most important books you can read. In general this is where you learn the nitty-gritty of placing code in certain areas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Learning about how to use flash at a basic level, like what pages are, you can learn from the datasheet. If you need to learn more advanced topics, well, I guess looking for a good book is the right way to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will let you know that there is a very very large amount of educational materials on the microchip website. Most microcomputer sites put a lot of material up to help boost new users to learn their system.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-18T23:07:45.397" LastActivityDate="2011-03-18T23:07:45.397" CommentCount="6" />
  <row Id="641" PostTypeId="2" ParentId="616" CreationDate="2009-11-24T10:29:22.747" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0750678127&quot; rel=&quot;nofollow&quot;&gt;Electrical Engineering 101, Second Edition: Everything You Should Have Learned in School...but Probably Didn't - Darren Ashby&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="6" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T19:09:04.317" LastActivityDate="2011-05-13T19:09:04.317" CommunityOwnedDate="2011-03-24T07:55:53.500" />
  <row Id="642" PostTypeId="2" ParentId="632" CreationDate="2009-11-24T11:33:45.340" Score="15" ViewCount="" Body="&lt;p&gt;Jack Ganssle's &lt;em&gt;The Firmware Handbook&lt;/em&gt; has some good bits and pieces. Best of all you can find a lot of the good parts from the book (and more) on his &lt;a href=&quot;http://www.ganssle.com/articles.htm&quot; rel=&quot;nofollow&quot;&gt;website&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-11-24T11:33:45.340" CommentCount="4" />
  <row Id="643" PostTypeId="2" ParentId="621" CreationDate="2009-11-24T13:27:10.103" Score="1" ViewCount="" Body="&lt;p&gt;If you tin stranded wire, it'll work well enough in a breadboard.  I often do this as I build up components (like a remote sensor) and prototype/test each piece along the way.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-11-24T13:27:10.103" CommentCount="3" />
  <row Id="644" PostTypeId="2" ParentId="639" CreationDate="2009-11-24T16:19:54.713" Score="6" ViewCount="" Body="&lt;p&gt;I am assuming you are sending the sensor data some distance.  May not be the best but easily available is cat5 networking wire.  Ideal wire probably has twisted pair with a shield, just enough conductors to get by.  You may be able to find some audio wire set up this way.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can some processing of the sensor data prior to transmission can help.  For example converting to a differential signal, or taking a voltage and converting to a frequency.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-24T16:19:54.713" CommentCount="1" />
  <row Id="646" PostTypeId="2" ParentId="639" CreationDate="2009-11-24T18:15:01.320" Score="4" ViewCount="" Body="&lt;p&gt;Depending upon the length of the wire, and the type of signal you could try either twisted pair or shielded coaxial cable (coax). If you want to experiment you can find solid-core twisted pair in cat-5 cable (as russ_hensel says), and small diameter coax can be scrounged from microphone or headphone/earbud cables. The coax has a braided shield that you can connect to ground which shields the inner wires from interference. With twisted pair you use one wire for signal and the other for ground which minimizes (but can't eliminate) interference).&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-11-24T18:15:01.320" />
  <row Id="647" PostTypeId="2" ParentId="639" CreationDate="2009-11-24T19:01:52.700" Score="3" ViewCount="" Body="&lt;p&gt;Simple twisted pair (with no shielding) might be all you need.  The twists in the wire make noise common to both wires be out of phase with each other and thus cancel each other out.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-24T19:01:52.700" />
  <row Id="648" PostTypeId="1" AcceptedAnswerId="660" CreationDate="2009-11-24T19:25:43.637" Score="4" ViewCount="109" Body="&lt;p&gt;Is there a good book that talks about memory (SDRAM, DDR, NVRAM, flash etc) from a hardware/system perspective? Most of what I've been able to find deal with memory at the transistor level. I am looking for overview of the different types of memories, power requirements and PCB guidelines.&lt;/p&gt;&#xA;" OwnerUserId="327" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-25T23:26:51.237" LastActivityDate="2009-11-25T23:26:51.237" Title="Book on memory from hardware perspective?" Tags="&lt;memory&gt;&lt;books&gt;&lt;hardware&gt;&lt;system&gt;" AnswerCount="3" />
  <row Id="649" PostTypeId="2" ParentId="527" CreationDate="2009-11-24T19:29:26.997" Score="1" ViewCount="" Body="&lt;p&gt;Just discovered this blog post on LMR. Looks pretty cool.&#xA;&lt;a href=&quot;http://letsmakerobots.com/node/11969&quot; rel=&quot;nofollow&quot;&gt;SpeakJet&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-11-24T19:29:26.997" />
  <row Id="650" PostTypeId="2" ParentId="605" CreationDate="2009-11-24T19:37:02.967" Score="1" ViewCount="" Body="&lt;p&gt;Driving large LED arrays is one of the &quot;killer&quot; applications for &lt;a href=&quot;http://www.xmos.com/applications/led-signs-and-displays&quot; rel=&quot;nofollow&quot;&gt;XMOS devices&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Leon&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-11-24T19:37:02.967" CommentCount="1" />
  <row Id="651" PostTypeId="2" ParentId="648" CreationDate="2009-11-24T20:48:36.497" Score="1" ViewCount="" Body="&lt;p&gt;There's always wikipedia, it gives a decent overview of the different types of memories. What is your application that you are planning to use the memory for? &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-11-24T20:48:36.497" CommentCount="2" />
  <row Id="652" PostTypeId="2" ParentId="648" CreationDate="2009-11-24T21:31:09.093" Score="2" ViewCount="" Body="&lt;p&gt;Try looking in the datasheets for the devices you are interested in. Many manufactures will also have application notes that have more general information.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-11-24T21:31:09.093" CommentCount="1" />
  <row Id="653" PostTypeId="2" ParentId="621" CreationDate="2009-11-25T01:01:04.583" Score="3" ViewCount="" Body="&lt;p&gt;Most connectors are designed to be used for stranded wire. Crimp tools in particular are often precision-machined and are not guaranteed to work properly on solid-core wire.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-11-25T01:01:04.583" CommentCount="1" />
  <row Id="654" PostTypeId="2" ParentId="460" CreationDate="2009-11-25T01:14:09.470" Score="1" ViewCount="" Body="&lt;p&gt;Two comments:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Look into Bruce Schneier's &lt;a href=&quot;http://www.schneier.com/yarrow.html&quot; rel=&quot;nofollow&quot;&gt;Yarrow&lt;/a&gt; PRNG algorithm. The main point is that you can have a really lousy source of &quot;true&quot; random information; as long as you accumulate enough of it over time, the resulting uncertainty can be combined with software pseudo-random number generation techniques to yield decent random numbers.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;On the other hand, I have to agree with most other answerers. Slowly-changing signals from environmental sensors are lousy sources of entropy, and could easily be influenced. Make sure you use something that is based on intrinsic device noise, and it will be insensitive of environmental changes.  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-11-25T01:14:09.470" />
  <row Id="655" PostTypeId="2" ParentId="515" CreationDate="2009-11-25T01:24:26.767" Score="14" ViewCount="" Body="&lt;p&gt;The thing is that these days switching power supply adapters are such a commodity item that unless you really want to get into the design for learning purposes, just buy one. Digikey has a few that are under $10 in single quantities (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=T1038-P5RP-ND&quot; rel=&quot;nofollow&quot;&gt;here's one from CUI&lt;/a&gt;) and will give you regulated DC output, with high efficiency, complete with all the safety and EMI/RFI certifications. &lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-11-25T01:24:26.767" />
  <row Id="656" PostTypeId="2" ParentId="606" CreationDate="2009-11-25T02:56:29.363" Score="1" ViewCount="" Body="&lt;p&gt;Make sure you have the transparency in direct contact with your photosensitive board.  Any distance between them will cause distortions.  Similarily, you will want a glass plate on top of the transparency to keep it flat.  Remember, your etching will only be as good as the artwork.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-25T02:56:29.363" />
  <row Id="657" PostTypeId="2" ParentId="460" CreationDate="2009-11-25T03:00:44.457" Score="1" ViewCount="" Body="&lt;p&gt;I have read recently a very interesting discussion of using resistors to generate random noise.  Due to quantum effects, a resistor will produce a very small voltage.  This can be amplified with an op-amp to produce a high quality source of random noise.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-25T03:00:44.457" />
  <row Id="658" PostTypeId="2" ParentId="580" CreationDate="2009-11-25T03:06:40.777" Score="1" ViewCount="" Body="&lt;p&gt;I will echo the recommendation of a pre-built H-bridge chip.  Driving an inductive load with transistors carries many risks, and the L293 and friends carry circuitry to deal with transients and prevent latch-up.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-25T03:06:40.777" />
  <row Id="659" PostTypeId="2" ParentId="147" CreationDate="2009-11-25T03:40:01.833" Score="1" ViewCount="" Body="&lt;p&gt;If you're interested in using a Wii nunchuk as a joystick controller for your Arduino, you might want to check out these sources:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://todbot.com/blog/2008/02/18/wiichuck-wii-nunchuck-adapter-available/&quot; rel=&quot;nofollow&quot;&gt;http://todbot.com/blog/2008/02/18/wiichuck-wii-nunchuck-adapter-available/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.windmeadow.com/node/42&quot; rel=&quot;nofollow&quot;&gt;http://www.windmeadow.com/node/42&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="295" LastActivityDate="2009-11-25T03:40:01.833" />
  <row Id="660" PostTypeId="2" ParentId="648" CreationDate="2009-11-25T06:57:24.550" Score="1" ViewCount="" Body="&lt;p&gt;After some searching, I found a website that gives a very good overview of memory: &lt;a href=&quot;http://www.pcguide.com/ref/ram/index.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.pcguide.com/ref/ram/index.htm&lt;/a&gt;. Also has some good info on other components of a PC.&lt;/p&gt;&#xA;" OwnerUserId="327" LastActivityDate="2009-11-25T06:57:24.550" CommentCount="1" />
  <row Id="661" PostTypeId="1" AcceptedAnswerId="663" CreationDate="2009-11-25T09:51:31.393" Score="3" ViewCount="134" Body="&lt;p&gt;I'm looking to power a remote controlled car with a solar panel on its back.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What size to power am I going to get?  Is there one light enough that it wont slow the car down?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-12-01T21:56:06.860" Title="Size to power trade off with solar panels" Tags="&lt;solar-cell&gt;&lt;voltage&gt;" AnswerCount="2" />
  <row Id="662" PostTypeId="2" ParentId="147" CreationDate="2009-11-25T10:13:12.647" Score="1" ViewCount="" Body="&lt;p&gt;take a look here  &lt;a href=&quot;http://www.liquidware.com/projects/26/TouchShield+Tetris&quot; rel=&quot;nofollow&quot;&gt;http://www.liquidware.com/projects/26/TouchShield+Tetris&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;it's a project about TouchShield Tetris &lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2009-11-25T10:13:12.647" />
  <row Id="663" PostTypeId="2" ParentId="661" CreationDate="2009-11-25T11:43:23.307" Score="5" ViewCount="" Body="&lt;p&gt;This is dependent on what you are willing to pay. A remote controlled car pulls Amps of power normally, you will not be able to sustain this with a solar panel you can afford and is not too large.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to use a solar panel for recharging the battery during down time this is very possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Solar panels are based on a watts per square inch they can achieve. They are still normally sold with a wattage rating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The amount of available power is quite variable. Most marketing give you an absolute best case. Things that cause great variance are...&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Alignment to light source. Yes,&#xA;being off-angle from the sun is bad.&lt;/li&gt;&#xA;&lt;li&gt;Amount of light available. Small&#xA;variance of conditions can have a&#xA;large affect.&lt;/li&gt;&#xA;&lt;li&gt;Light source. florescent and the sun&#xA;are very different, there are panels&#xA;for each.&#xA;There can be many more variables, but these alone will account for  you getting less than 10% of what it is rated in most cases.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If I get a chance tomorrow I will look up more information for you.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-11-25T11:43:23.307" />
  <row Id="664" PostTypeId="2" ParentId="310" CreationDate="2009-11-25T14:12:13.480" Score="6" ViewCount="" Body="&lt;p&gt;Please note: the circuit you linked to uses a &lt;strong&gt;comparator&lt;/strong&gt;, not an op-amp. You can use op-amps in comparator circuits but they aren't up to the job for various reasons: op-amps are optimized for amplification applications where the inputs are driven to the same voltage through feedback, and may take a long time to recover from saturation when their inputs zoom apart through positive feedback like in this circuit. A comparator will be faster and will do the right thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for circuits: I'd either use a &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=LM393MXFSTR-ND&quot; rel=&quot;nofollow&quot;&gt;LM393&lt;/a&gt; comparator or a 555 (hard to beat: lots of manufacturers and you can get it from Radio Shack or in &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=568-1818-2-ND&quot; rel=&quot;nofollow&quot;&gt;high quantities from Digikey&lt;/a&gt; at 11c) or a 74xx123 (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=296-18758-2-ND&quot; rel=&quot;nofollow&quot;&gt;this one from TI&lt;/a&gt; is 16c in large quantity). The comparator will need a few more parts than the other two.&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-11-28T03:48:46.097" LastActivityDate="2009-11-28T03:48:46.097" CommentCount="4" />
  <row Id="665" PostTypeId="2" ParentId="317" CreationDate="2009-11-25T16:29:30.033" Score="2" ViewCount="" Body="&lt;p&gt;It is above your $15 price limit, but you can pick up a can of SSScat! automated cat repellent at many pet centers (WalMart included) for around $25:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Premier-SSSCAT-Automated-Cat-Deterrent-Kit/dp/B0002XI7CI&quot; rel=&quot;nofollow&quot;&gt;http://www.amazon.com/Premier-SSSCAT-Automated-Cat-Deterrent-Kit/dp/B0002XI7CI&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The battery operated motion sensor can be removed from the canned air and connected to the microcontroller platform of your choice (either electrically, or mechanically using the built-in actuator).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One option would be a $20 AVR Butterfly running Butteruino so that it can be programmed via the Arduino platform. The Butterfly includes 512KB of flash memory, an LCD, pin-header serial output, a 5-way joystick, and watch crystal, so it makes a decent all-in-one data logger platform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Total cost for that configuration would be about $45, but build time would be minimal as there is essentially no electronics integration to do.&lt;/p&gt;&#xA;" OwnerUserId="332" LastActivityDate="2009-11-25T16:29:30.033" />
  <row Id="683" PostTypeId="1" AcceptedAnswerId="736" CreationDate="2009-11-25T23:13:16.863" Score="2" ViewCount="74" Body="&lt;p&gt;I'm looking for players of &lt;a href=&quot;http://www.roboticfootballleague.com/site/index.php&quot; rel=&quot;nofollow&quot;&gt;Robotic Football League&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just got one of these:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/collections/frontpage/products/rfl-robot&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/collections/frontpage/products/rfl-robot&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and I'm looking for any groups set up who play in Sydney  (or Aus)&lt;/p&gt;&#xA;" OwnerUserId="267" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-25T23:25:59.833" LastActivityDate="2009-11-28T11:06:08.817" Title="Is there an RFL in australia?" Tags="&lt;robotics&gt;&lt;australia&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="684" PostTypeId="1" CreationDate="2009-11-25T23:27:28.043" Score="3" ViewCount="248" Body="&lt;p&gt;Hello everyone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a problem with a sbc that I am repairing, the sbc is controlled by an 8-bit OTP microcontroller which I think is broken.&#xA;I only get 200 ohms between pin Vcc and Vss, specifically the chip is &lt;a href=&quot;http://www.national.com/opf/CO/COP87L84BC.html#Overview&quot; rel=&quot;nofollow&quot;&gt;COP87L84BC&lt;/a&gt; and is out of production. &#xA;What I try is to read the registers of the microcontroller with a cable ISP and any similar software &lt;a href=&quot;http://www.winpic800.com/&quot; rel=&quot;nofollow&quot;&gt;WinPic800&lt;/a&gt; but for this chip.&#xA;I never use the COP8s OPT of National Semiconductor so I wanted information about this MCU or web sites where I can find information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks to all!!&lt;/p&gt;&#xA;" OwnerUserId="132" LastActivityDate="2010-10-08T02:52:12.813" Title="COP8 MCU National Semiconductor" Tags="&lt;microcontroller&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="686" PostTypeId="2" ParentId="460" CreationDate="2009-11-26T02:18:40.700" Score="0" ViewCount="" Body="&lt;p&gt;Here is the ultimate in random number generation:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.idquantique.com/products/quantis.htm&quot; rel=&quot;nofollow&quot;&gt;link text&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They aren't all that expensive.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-11-26T02:18:40.700" CommentCount="1" />
  <row Id="687" PostTypeId="1" AcceptedAnswerId="694" CreationDate="2009-11-26T04:14:12.467" Score="3" ViewCount="76" Body="&lt;p&gt;Looking in Sydney in particular.&lt;/p&gt;&#xA;" OwnerUserId="337" LastActivityDate="2009-11-26T09:56:30.823" ClosedDate="2011-05-05T07:53:42.460" Title="Is there a Robot Fighting League in Australia?" Tags="&lt;robotics&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="688" PostTypeId="1" AcceptedAnswerId="692" CreationDate="2009-11-26T05:13:16.090" Score="2" ViewCount="216" Body="&lt;p&gt;Hi I've done some dev using AVR's. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd really like to use the arduino but continue using atmel tools. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this straightforward? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a converter that I can use my 910 programmer with? I think it's a 10 pin connector&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-26T06:54:14.967" Title="Arduino with atmel tools" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;atmel&gt;&lt;convert&gt;&lt;programmer&gt;" AnswerCount="1" />
  <row Id="690" PostTypeId="2" ParentId="464" CreationDate="2009-11-26T05:47:50.127" Score="6" ViewCount="" Body="&lt;p&gt;I wished I'd had a clearer understanding of Fuse bits. I spent half my time early on terrified that I'd brick my mega32. Oh and ditto with regards to serial IO.&lt;/p&gt;&#xA;" LastActivityDate="2009-11-26T05:47:50.127" CommunityOwnedDate="2009-11-26T05:47:50.127" CommentCount="1" />
  <row Id="691" PostTypeId="2" ParentId="263" CreationDate="2009-11-26T06:35:59.060" Score="8" ViewCount="" Body="&lt;p&gt;using another diode to &quot;match&quot; the source voltage to the LED voltage: &lt;strong&gt;NO NO NO!&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An LED is basically a voltage sink: it draws no current until the voltage across it forward-biases the diode junction, and then all of a sudden when you get enough voltage the current through it rises dramatically. The light output of an LED is strongly dependent on the amount of current you put through it: more current = more light output. The voltage drop, although approximately constant, varies with temperature and from device to device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In almost all applications you want to set the light output, and hence the current, to a fixed value, independent of supply voltage variations and LED voltage drop variations. &lt;strong&gt;This means the ideal source for an LED load is a constant current source&lt;/strong&gt; -- which you can implement, it's just that it's a pain to do so without a few additional components. In practice we just tend to use a voltage source (switched on and off by a logic gate or a MOSFET or a bipolar transistor) and a resistor to set the current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The key equation is &lt;strong&gt;V&lt;sub&gt;supply&lt;/sub&gt; - V&lt;sub&gt;LED&lt;/sub&gt; = I&lt;sub&gt;LED&lt;/sub&gt;*R&lt;/strong&gt;, or I&lt;sub&gt;LED&lt;/sub&gt; = (V&lt;sub&gt;supply&lt;/sub&gt; - V&lt;sub&gt;LED&lt;/sub&gt;)/R&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The term on the left-hand side is the difference between supply voltage and LED voltage drop. This can vary with temperature and part-to-part variation. A sensitivity analysis here is fairly easy: &amp;Delta;I = &amp;Delta;V/R -- the change in current is equal to 1/R times the change in voltage. If you want your LED current to be less sensitive to changes in voltage, that means the value of R should be higher... for a particular nominal LED current (usually between 5mA and 20mA), the current will be less sensitive to changes in voltage if the source voltage is higher and the resistance is higher. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;By dropping the supply voltage using a second diode, you are doing the exact opposite: to get the desired current, you have to reduce the value of R, which makes the load current more sensitive to voltage variation. AND you are also introducing another circuit element (this new diode) which has additional voltage tolerances, making those voltage variations larger. &lt;strong&gt;You'd be adding extra components which serve no purpose but to make the light output more sensitive to supply voltage variations, temperature, and part variations.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only other things worth considering here are power dissipation. If you have a fixed voltage source (say 5V) and an LED or other circuit element that uses only a fraction of that voltage (say 1.2V) then only a fraction of the power (1.2/5V = 24% in this example) is dissipated in the LED, and the rest (76%) is dissipated in something else that you need to connect the two together. That's true for any &lt;em&gt;linear&lt;/em&gt; power supply (see below for a comment about switchers). This goes into heat, which needs to be properly dissipated, and in most cases the cheapest easiest way to dissipate a given amount of heat in a controlled fashion is in a resistor. They work properly over a higher temperature range (most diodes/transistors work up to about 150 C max) and their behavior varies less with temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The exception to all of this thinking is a switching power supply. Many LED drivers are going the switcher route, and using pulse-width modulation + a switching transistor and an inductor to get the efficiencies up. This lets essentially all of the power dissipation occur in the LED (with a little bit of loss in a switching MOSFET and inductor). You still treat the LED as a voltage sink, though, with the switching transistor + inductor acting as a current source, varying its duty cycle to control the LED brightness (in high-quality visual displays there is also a light-sensor chip so that the current can be varied to compensate for the LED's aging over time so that white light does not drift in color towards red or green or blue). A switching LED driver costs $$, though, so unless you need the efficiency I wouldn't bother.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bottom line: keep it simple, use the resistor by itself.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-11-26T06:35:59.060" CommentCount="2" />
  <row Id="692" PostTypeId="2" ParentId="688" CreationDate="2009-11-26T06:54:14.967" Score="2" ViewCount="" Body="&lt;p&gt;I'm pretty sure that you can.  All the schematics for the AVR910 programmer that I have found show it with a 6 pin interface.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://microcontrollershop.com/product%5Finfo.php?products%5Fid=1918&quot; rel=&quot;nofollow&quot;&gt;10 Pin to 6 Pin Converter&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A converter ought to do it.  Some programmers come with both interfaces, for instance the Adafruit Attiny USB programmer.  Loooking at its schematic, I can see that the 10 pin programmer has the same connections on it as the 6 pin, just a few not connected pins.  I assume that the 10 pin connectors pinout is standardised.  You of course could convert it yourself or build a similar converter as above without too much difficulty.&lt;/p&gt;&#xA;" OwnerUserId="312" LastActivityDate="2009-11-26T06:54:14.967" />
  <row Id="693" PostTypeId="1" AcceptedAnswerId="996" CreationDate="2009-11-26T09:22:19.893" Score="3" ViewCount="695" Body="&lt;p&gt;I'm working on a &lt;a href=&quot;http://www.obdev.at/products/vusb/index.html&quot; rel=&quot;nofollow&quot;&gt;V-USB&lt;/a&gt; (aka AVR-USB) -based circuit running at 5V (i.e. two 3.6V Zeners across D+ &amp;amp; D-) and at 12MHz.  I tried an ATmega88P instead of the ATmega88 chips I normally use and I can't get the circuit to enumerate.  The Atmel appnotes on mega88-&gt;mega88P migration don't describe any obvious gotchas. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone have any experience/tips with the differences in ATmega88P chips?&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-11T21:39:19.027" Title="Issues migrating from ATmega88 to ATmega88P, with V-USB/AVR-USB?" Tags="&lt;atmega&gt;&lt;avr&gt;&lt;usb&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="694" PostTypeId="2" ParentId="687" CreationDate="2009-11-26T09:56:30.823" Score="3" ViewCount="" Body="&lt;p&gt;I guess you are looking to hook up with the &lt;a href=&quot;http://www.robowars.org/forum/viewforum.php?f=2&quot; rel=&quot;nofollow&quot;&gt;Robot Wars&lt;/a&gt; people.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have some really interesting discussions in their &lt;a href=&quot;http://www.robowars.org/forum/viewforum.php?f=1&quot; rel=&quot;nofollow&quot;&gt;forum&lt;/a&gt; about the technical side of things too!&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-26T09:56:30.823" />
  <row Id="695" PostTypeId="1" AcceptedAnswerId="697" CreationDate="2009-11-26T10:56:40.500" Score="4" ViewCount="940" Body="&lt;p&gt;Is it possible to monitor a block of code and determine the number of processor clock cycles that code took on an Arduino and/or AVR atmel processor? or, should I rather monitor microseconds passed before and after code run? Note: I'm not concerned with real time (as in, how many real seconds passed) as much as I am in &quot;how many clock cycles does this code require from the CPU&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current solution I can come up with is from time.c:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define clockCyclesPerMicrosecond() ( F_CPU / 1000000L )&#xA;#define clockCyclesToMicroseconds(a) ( (a) / clockCyclesPerMicrosecond() )&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;wiring.c adds:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define microsecondsToClockCycles(a) ( (a) * clockCyclesPerMicrosecond() )&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;By this account i could calculate clock cyles passed by monitoring microseconds passed and then pass that to microsecondsToClockCycles(). My question is, is there a better way?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;sidenote: are there good resources for performance monitoring of the AVR. lmgtfy.com and various forums searches do not provide any obvious results, other than exploration of timers&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks&lt;/p&gt;&#xA;" OwnerUserId="196" LastEditorUserId="196" LastEditorDisplayName="" LastEditDate="2009-11-26T11:20:52.550" LastActivityDate="2009-11-26T20:16:47.713" Title="Monitor clock cycles for code on arduino/AVR?" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;atmel&gt;&lt;timer&gt;" AnswerCount="3" />
  <row Id="696" PostTypeId="2" ParentId="695" CreationDate="2009-11-26T11:06:37.173" Score="4" ViewCount="" Body="&lt;p&gt;What do you mean by &quot;monitor&quot;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It shouldn't be hard to count clock cycles for AVR for small pieces of assembly code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also set a port before the code is executed and reset it afterwards, and monitor that with a logic analyzer or an oszilloscope to get the timing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And you could also read the time from a fast-running timer, as you say.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2009-11-26T11:06:37.173" CommentCount="2" />
  <row Id="697" PostTypeId="2" ParentId="695" CreationDate="2009-11-26T12:19:53.130" Score="3" ViewCount="" Body="&lt;p&gt;This is an example for Arduino using the clockCyclesPerMicrosecond() function to calculate the clocks that have passed. This code will wait 4 seconds, then print the time passed since start of program.  Left 3 values are total time (microseconds, milliseconds, total clock cycles) and right most 3 are elapsed times:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Output:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;clocks for 1us:16&#xA;runtime us, ms, ck :: elapsed tme us, ms ck&#xA;4003236 4002	64051776	::	4003236	4002	64051760&#xA;8006668 8006	128106688	::	4003432	4004	64054912&#xA;12010508    12010	192168128	::	4003840	4004	64061440&#xA;16014348    16014	256229568	::	4003840	4004	64061440&#xA;20018188    20018	320291008	::	4003840	4004	64061440&#xA;24022028    24022	384352448	::	4003840	4004	64061440&#xA;28026892    28026	448430272	::	4004864	4004	64077824&#xA;32030732    32030	512491712	::	4003840	4004	64061440&#xA;36034572    36034	576553152	::	4003840	4004	64061440&#xA;40038412    40038	640614592	::	4003840	4004	64061440&#xA;44042252    44042	704676032	::	4003840	4004	64061440&#xA;48046092    48046	768737472	::	4003840	4004	64061440&#xA;52050956    52050	832815296	::	4004864	4004	64077824&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I'm sure there is a reasonable explanation why the first too loops had shorter elapsed clock cycles than most and why all other loops toggle between two lengths of clock cycles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;unsigned long us, ms, ck;&#xA;unsigned long _us, _ms, _ck;&#xA;unsigned long __us, __ms, __ck;&#xA;void setup() {&#xA;        Serial.begin(9600);&#xA;}&#xA;boolean firstloop=1;&#xA;void loop() { &#xA;        delay(4000);&#xA;&#xA;        if (firstloop) {&#xA;                Serial.print(&quot;clocks for 1us:&quot;);&#xA;                ck=microsecondsToClockCycles(1);&#xA;                Serial.println(ck,DEC);&#xA;                firstloop--;&#xA;                Serial.println(&quot;runtime us, ms, ck :: elapsed tme us, ms ck&quot;);&#xA;        }&#xA;&#xA;        _us=us;&#xA;        _ms=ms;&#xA;        _ck=ck;&#xA;&#xA;        us=micros(); // us since program start&#xA;        ms=millis();&#xA;        //ms=us/1000;&#xA;        ck=microsecondsToClockCycles(us);&#xA;        Serial.print(us,DEC);&#xA;        Serial.print(&quot;\t&quot;);&#xA;        Serial.print(ms,DEC);&#xA;        Serial.print(&quot;\t&quot;);&#xA;        Serial.print(ck,DEC);     &#xA;        Serial.print(&quot;\t::\t&quot;);&#xA;&#xA;        __us = us - _us;&#xA;        __ms = ms - _ms;&#xA;        __ck = ck - _ck;&#xA;        Serial.print(__us,DEC);&#xA;        Serial.print(&quot;\t&quot;);&#xA;        Serial.print(__ms,DEC);&#xA;        Serial.print(&quot;\t&quot;);&#xA;        Serial.println(__ck,DEC);     &#xA;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Sidenote:&#xA;if you remove the 4 second delay you will start to see the effects of the Serial.print() much more clearly. Note, here 2 runs are compared. I've only included 4 samples near each other from their respective logs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Run 1:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;5000604 5000	80009664	::	2516	2	40256&#xA;6001424 6001	96022784	::	2520	3	40320&#xA;7002184 7002	112034944	::	2600	3	41600&#xA;8001292 8001	128020672	::	2600	3	41600&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Run 2:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;5002460 5002	80039360	::	2524	3	40384&#xA;6000728 6000	96011648	::	2520	2	40320&#xA;7001452 7001	112023232	::	2600	3	41600&#xA;8000552 8000	128008832	::	2604	3	41664&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The elapsed time increases over total run time. After a second has elapsed the clocks increase on average from 40k to 44k. This happens consistently a few milliseconds after 1 second and the elapsed clocks remains around 44k for at least the next 10 seconds (I havent tested it further). This is why monitoring is useful or needed. Perhaps the decreased efficiency has to do with configuration or bugs in serial? Or perhaps the code is not using memory properly and has a leak that effects performance, etc.&lt;/p&gt;&#xA;" OwnerUserId="196" LastEditorUserId="196" LastEditorDisplayName="" LastEditDate="2009-11-26T17:04:13.563" LastActivityDate="2009-11-26T17:04:13.563" />
  <row Id="699" PostTypeId="2" ParentId="695" CreationDate="2009-11-26T20:16:47.713" Score="3" ViewCount="" Body="&lt;p&gt;The simplest method is to make your code pull some pin up before it executes the code you want to time, and pull it low after it has finished doing whatever. Then make the code loop (or use digital oscilloscope with memory in single-shot mode) and just scope then pin. The length of the pulse tells you how long it took to execute the piece of code plus one clock cycle from changing the pin state (I think it takes one cycle, not 100% sure).&lt;/p&gt;&#xA;" OwnerUserId="140" LastActivityDate="2009-11-26T20:16:47.713" CommentCount="1" />
  <row Id="700" PostTypeId="1" AcceptedAnswerId="702" CreationDate="2009-11-26T22:49:42.460" Score="5" ViewCount="919" Body="&lt;p&gt;How would I need to set my fuse bits on a ATMega328p  to use a 16MHz crystal?  I tried this on my own and killed the last atmega I had.  I'd like some advice this time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The crystal I am using is &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=536&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am assuming this is a &quot;Full Swing Crystal Oscillator&quot; as listed in the datasheet, so CKSEL3..1 should be 011&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then I need to set the startup time.  I'm assuming the &quot;Crystal Oscillator, slowly&#xA;rising power&quot; is the safer option so CKSEL0 should be 1 and SUT1..0 should be 11.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't want to divide the clock by 8 so CKDIV8 should be 1&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CKOUT I will leave at the default of 1&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If my assumptions are correct (and how do I verify that?) my lfuse bit settings will be 0xf7.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I doing this right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;hr /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This didn't work.  See &lt;a href=&quot;http://chiphacker.com/questions/717/troubleshooting-an-atmega328p-clock-setting&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="202" LastEditorUserId="202" LastEditorDisplayName="" LastEditDate="2009-11-28T00:38:43.590" LastActivityDate="2009-11-28T00:38:43.590" Title="Using a 16 MHz crystal on a ATMega328p" Tags="&lt;atmega328&gt;" AnswerCount="4" />
  <row Id="701" PostTypeId="2" ParentId="700" CreationDate="2009-11-26T23:09:27.237" Score="2" ViewCount="" Body="&lt;p&gt;For ATmega*8 chips, one of the best resources to crib from is the &lt;a href=&quot;http://code.google.com/p/arduino/source/browse/trunk/hardware/boards.txt&quot; rel=&quot;nofollow&quot;&gt;Arduino &quot;boards.txt&quot; file&lt;/a&gt;  It contains settings for many common chips and configurations.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-26T23:09:27.237" />
  <row Id="702" PostTypeId="2" ParentId="700" CreationDate="2009-11-26T23:25:24.107" Score="4" ViewCount="" Body="&lt;p&gt;Arduino uses low fuse setting of 0xff for ATMega328p, which is the same as 0xf7 except crystal is not programmed as full swing. Full swing is recommended for speeds over 8MHz and especially if multiple units use same clock source.&lt;/p&gt;&#xA;" OwnerUserId="13" LastActivityDate="2009-11-26T23:25:24.107" />
  <row Id="703" PostTypeId="2" ParentId="700" CreationDate="2009-11-26T23:33:19.970" Score="2" ViewCount="" Body="&lt;p&gt;Try using &lt;a href=&quot;http://www.vonnieda.org/software/avrfuses&quot; rel=&quot;nofollow&quot;&gt;AVRFuses&lt;/a&gt;. Thats what I use for all my fuses and it works fine.&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2009-11-26T23:33:19.970" />
  <row Id="704" PostTypeId="1" CreationDate="2009-11-27T03:02:14.760" Score="5" ViewCount="157" Body="&lt;p&gt;I was trying to design a data logging application using something like a www.ruggedcircuits.com gator+ board with some sort of rugged zigbee module&#xA;for measuring principally steam pressure (to 110 bar) and temperature (to 380 C).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course this is a development project with limited funding so I am trying to design a low cost R &amp;amp; D system rather than a big iron industrial control system as this stage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know where to get or have suggestions for:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;A rugged zigbee module similar to the rugged circuit gator+ board approach?&lt;/li&gt;&#xA;&lt;li&gt;Good bomb proof enclosures for connecting sensors that would house the board, zigbee module and power supply?&lt;/li&gt;&#xA;&lt;li&gt;Pressure and temperature sensors to cope with this sort of environment?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I know that there are really expensive sensors for plant installations, but they are not likely to be in budget as we will need lots of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas or leads would be appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Harley&lt;/p&gt;&#xA;" OwnerUserId="297" LastActivityDate="2009-11-30T01:03:24.970" Title="Steam plant data logging" Tags="&lt;sensor&gt;&lt;avr&gt;&lt;wire&gt;" AnswerCount="4" />
  <row Id="705" PostTypeId="2" ParentId="704" CreationDate="2009-11-27T08:38:52.647" Score="4" ViewCount="" Body="&lt;p&gt;As a grade 1 steam engineer, I hope you are well experienced and highly educated with steam before you start this project.  At 110 bar, you have almost 1300 kJ/kg of energy.  By the time you can generate this much energy, your boilers must be at least 25k lbs/hr capacity. At this energy level if anything goes even slightly wrong, the chances of killing everyone contained within a building of 75,000 cubic feet would be 100 percent. The time it would take to increase the room temperature of that space to over 125 degrees C would be less than .15 second. I know that if I were to attempt this kind of prototype work here in Seattle, the city would shut me down. Not to mention the effect it would have on your insurance carrier. Look to Burnham Boilers, Cleaver Brooks, or Cannon Boiler works for support.   &lt;/p&gt;&#xA;" LastActivityDate="2009-11-27T08:38:52.647" CommentCount="1" />
  <row Id="707" PostTypeId="2" ParentId="700" CreationDate="2009-11-27T15:25:11.593" Score="5" ViewCount="" Body="&lt;p&gt;I use this: &lt;a href=&quot;http://www.engbedded.com/fusecalc/&quot; rel=&quot;nofollow&quot;&gt;http://www.engbedded.com/fusecalc/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="255" LastActivityDate="2009-11-27T15:25:11.593" />
  <row Id="708" PostTypeId="1" AcceptedAnswerId="714" CreationDate="2009-11-27T20:45:08.053" Score="12" ViewCount="1700" Body="&lt;p&gt;I'm trying to interface a 3.3V \$I^2C\$ device to a 5V Arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't have any problem with SCL line.&#xA;I can use a simple voltage divider but I have an issue with the SDA line as this is bi-directional. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not at all sure how to handle this. I have though of adding a pair of diodes, with a voltage divider on the slave input side and nothing extra on the master input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any other solutions?&lt;/p&gt;&#xA;" OwnerUserId="9" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:30:15.123" LastActivityDate="2011-06-02T02:30:15.123" Title="\$I^2C\$ 3.3 to 5.0 V conversion" Tags="&lt;arduino&gt;&lt;voltage&gt;&lt;i2c&gt;" AnswerCount="4" FavoriteCount="5" />
  <row Id="709" PostTypeId="2" ParentId="704" CreationDate="2009-11-27T21:05:12.397" Score="3" ViewCount="" Body="&lt;p&gt;Why not just use temperature?  If you are dealing with saturated steam, it's much safer.  Since you are near the saturation point you should easily be able to convert the difference.  Even if you have a lot of superheat going in the system that can be subtracted easily.  Each sensor may have it's own offset temp due to heat losses but once calibrated you should be able to determine usage, loss or any other useful info without the danger of getting into the pressure stream. Strap on thermocouples are way safer than attaching to a pipe.  If you need to attach to a pipe remember to install velocity checks!  then run very small diameter pipe to the sensor so as to limit the volume of OOPS. There is a whole bunch of info in the Babcock and Wilcox book on steam and its generation which will help.  That company is extremely easy to work with and will also help with your project. How about infrared heat guns?  Cheap fast, easy and safe.  Or even crayon temp sticks?&lt;/p&gt;&#xA;" OwnerUserId="343" LastActivityDate="2009-11-27T21:05:12.397" CommentCount="1" />
  <row Id="710" PostTypeId="1" AcceptedAnswerId="715" CreationDate="2009-11-27T21:09:38.487" Score="6" ViewCount="377" Body="&lt;p&gt;I'd like to design a PCB for an analog loop controller.. something with an A/D, D/A, and processor on board.  (Either DSP or FPGA, I haven't decided.)  Since this should modulate analog signals at 10 kHz, it needs to be quite a fast processor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I understand, designing a board for processors running above 150 MHz or so can be very challenging due to RF problems.  What are some advice you can provide in designing such a board?  What problems due to layout can occur?  Are there any good online resources that have knowledge bases for this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="344" LastActivityDate="2010-05-08T22:03:21.340" Title="What are some 'gotchas' of high-frequency board design?" Tags="&lt;board&gt;&lt;layout&gt;&lt;pcb&gt;" AnswerCount="6" CommentCount="4" FavoriteCount="1" />
  <row Id="711" PostTypeId="2" ParentId="710" CreationDate="2009-11-27T21:16:59.160" Score="2" ViewCount="" Body="&lt;p&gt;Read up on ham radio or find an Extra Class operator to help.  We deal with these problems all the time at much higher frequencies.  We also use DSP processing in nearly all of our equipment. Try the AARL education stuff online, or QRZ. The problems aren't that hard to correct for but there are a lot of possible problem areas to watch out for.&lt;br /&gt;&#xA;73,&#xA;KF7BYU&lt;/p&gt;&#xA;" OwnerUserId="343" LastActivityDate="2009-11-27T21:16:59.160" />
  <row Id="712" PostTypeId="2" ParentId="710" CreationDate="2009-11-27T21:17:30.003" Score="5" ViewCount="" Body="&lt;p&gt;I know very little about high-speed layout. But the thre common things I've heard are: Avoid right angles for signal traces (they cause reflections), have a ground plane over as much of your circuit as much as possible, and partition your board to have similar signal types (low-speed digital, high-speed digital, analog) into different areas, with &quot;choke points&quot; in your ground plane to minimize interference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for good online resources, I would imagine the datasheets &amp;amp; appnotes for the DSP or FPGA you're considering will have some good tips.  I remember Xilinx having good stuff.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-27T21:17:30.003" CommentCount="6" />
  <row Id="714" PostTypeId="2" ParentId="708" CreationDate="2009-11-27T22:08:41.287" Score="15" ViewCount="" Body="&lt;p&gt;Good document about the subject is &lt;a href=&quot;http://www.standardics.nxp.com/support/documents/i2c/pdf/an97055.pdf&quot; rel=&quot;nofollow&quot;&gt;Bi-directional level shifter for I2C-bus and other systems&lt;/a&gt; which uses a single mosfet as a bi-directional level shifter.&lt;/p&gt;&#xA;" OwnerUserId="13" LastActivityDate="2009-11-27T22:08:41.287" CommentCount="1" />
  <row Id="715" PostTypeId="2" ParentId="710" CreationDate="2009-11-27T23:14:09.047" Score="9" ViewCount="" Body="&lt;p&gt;If you're interested in high speed digital, get a copy of &lt;a href=&quot;http://www.amazon.com/High-Speed-Digital-Design-Handbook/dp/0133957241/&quot; rel=&quot;nofollow&quot;&gt;High Speed Digital Design&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Key points:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The main determining factor of you circuit is the rise time of the logic. Even if you operate at a slow clock rate, fast edges can create problems.&lt;/li&gt;&#xA;&lt;li&gt;The maximum rise time of your system then gives you the critical length of your circuit. Essentially if the propagation delay of your signal over the length of the circuit is longer than the rise time of the signal, you need to worry about the high frequency aspect of the design.&lt;/li&gt;&#xA;&lt;li&gt;If it turns out the critical length is shorter than the circuit layout, then you need to use controlled impedance layout. This includes:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Track geometry (track width and hight above a ground plane) to give the circuit a defined characteristic impedance.&lt;/li&gt;&#xA;&lt;li&gt;Terminating the drivers and/or recievers with the line's characteristic impedance.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-11-27T23:14:09.047" CommentCount="1" />
  <row Id="716" PostTypeId="2" ParentId="708" CreationDate="2009-11-27T23:43:32.977" Score="6" ViewCount="" Body="&lt;p&gt;Many arduino's have onboard support to run at 3.3v. Actually, all can run at 3.3 and the FTDI chip schematic explains how in an example.  Paul, who made the Teensy USB arduino, had suggested that I could splice the USB cable open and  supply a 3.3v voltage in place of the VCC line of the cable. You could try this. But there are also other options. &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Check the logic levels for the Arduino. I believe they support 3.3v as logic HIGH even on 5v sourced Atmel. &lt;a href=&quot;http://www.rocketnumbernine.com/2009/04/10/5v-33v-bidirectional-level-converter/&quot; rel=&quot;nofollow&quot;&gt;Sparkfun article&lt;/a&gt;: &quot;&lt;em&gt;Connecting a 3.3V digital output pin to a 5V input pin is often straightforward. Most devices are fairly tolerant to the minimum voltage that they will accept as a digital high value. Most Atmel microcontrollers, for example, accept anything above 0.6&lt;/em&gt;Vcc as high, so the 3.3V device must output a level above 3V (0.6*5V).*&quot;&lt;/li&gt;&#xA;&lt;li&gt;Purchase one of the arduino cloans that has jumpered 3.3v and 5v selectors. I use the &lt;a href=&quot;http://moderndevice.com/RBBB%5FrevB&quot; rel=&quot;nofollow&quot;&gt;RBBB cloan&lt;/a&gt; which i have set the supply cables ftdi chip to 3.3v. But there are many others that have actual 3.3v configuration options, including one of the recent official arduinos if i remember correctly. You could also use the Teensy USB with his Arduino plugin and follow the directions on his site to install a &lt;a href=&quot;http://www.pjrc.com/teensy/3volt.html&quot; rel=&quot;nofollow&quot;&gt;3.3v regulator&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;Splice the USB cable and provide a lab quality 3.3v source in place of the VCC line of the USB cable. It should be low current, as Paul has suggested. Hence, either a good quality voltage source.  You could also just put a couple batteries in series to get the desired voltage.&lt;/li&gt;&#xA;&lt;li&gt;If you are interested I can try to examine the schematic of your arduino and perhaps it is possible to make a change to the FTDI configuration that would allow for 3.3v.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Lastly, we have a discussion that might interest you about this over &lt;a href=&quot;http://chiphacker.com/questions/622/bi-directional-step-up-and-step-down-3-3v-5-etc&quot; rel=&quot;nofollow&quot;&gt;here on chiphacker about uni-directional and bi-directional solutions&lt;/a&gt; for voltage step down. &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial%5Finfo.php?tutorials%5Fid=65&quot; rel=&quot;nofollow&quot;&gt;This article on Sparkfun&lt;/a&gt; mentioned by todbot is usefull, as is the discussion on bidrectional mosfet article linked from sparkfun.  To summarize the sparkfun article:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Inline Resistor. Uni-directional. Step-down only. -- reduces current, IC's i/o clamping diodes can them limit max input. &lt;/li&gt;&#xA;&lt;li&gt;Series Resistors. Uni-directional. Step-down only, but granular. &lt;/li&gt;&#xA;&lt;li&gt;Diode. Uni-directional. Step-down. Safer. High from 5v blocks Diode; 3.3v side then ties to high. But, if you reverse diode configuration couldnt you also step-up? &lt;/li&gt;&#xA;&lt;li&gt;Mosfet. Bi-directional. Step-down or Step-up. &lt;/li&gt;&#xA;&lt;li&gt;In comments: Optical isolation example: 4N25. high current. &lt;/li&gt;&#xA;&lt;li&gt;In comments: Zener diode example: 1N4728A &lt;/li&gt;&#xA;&lt;li&gt;In comments: 74HC244/125 Uni-directional &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="196" LastEditorUserId="196" LastEditorDisplayName="" LastEditDate="2009-11-27T23:56:33.767" LastActivityDate="2009-11-27T23:56:33.767" />
  <row Id="717" PostTypeId="1" CreationDate="2009-11-28T00:26:58.200" Score="3" ViewCount="813" Body="&lt;p&gt;I am trying to run my ATMega at 16MHz using &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=536&quot; rel=&quot;nofollow&quot;&gt;this crystal&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I set the lfuse bit to F7 (see &lt;a href=&quot;http://chiphacker.com/questions/700/using-a-16-mhz-crystal-on-a-atmega328p&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The command I used to set the lfuse bit was &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;C:\&amp;gt;avrdude -p m328p -P lpt1 -c stk200 -U lfuse:w:0xf7:m&#xA;&#xA;avrdude: AVR device initialized and ready to accept instructions&#xA;&#xA;Reading | ################################################## | 100% 0.02s&#xA;&#xA;avrdude: Device signature = 0x1e950f&#xA;avrdude: reading input file &quot;0xf7&quot;&#xA;avrdude: writing lfuse (1 bytes):&#xA;&#xA;Writing | ################################################## | 100% 0.00s&#xA;&#xA;avrdude: 1 bytes of lfuse written&#xA;avrdude: verifying lfuse memory against 0xf7:&#xA;avrdude: load data lfuse data from input file 0xf7:&#xA;avrdude: input file 0xf7 contains 1 bytes&#xA;avrdude: reading on-chip lfuse data:&#xA;&#xA;Reading | ################################################## | 100% 0.00s&#xA;&#xA;avrdude: verifying ...&#xA;avrdude: 1 bytes of lfuse verified&#xA;&#xA;avrdude: safemode: Fuses OK&#xA;&#xA;avrdude done.  Thank you.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I had code on the chip that was blinking a LED once every second.  After I set the lfuse bit it stopped.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried to read the lfuse bit via &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;C:\Documents and Settings\admin&amp;gt;avrdude -p m328p -P lpt1 -c stk200 -U lfuse:r:-:&#xA;h -U hfuse:r:-:h&#xA;&#xA;avrdude: AVR device not responding&#xA;avrdude: initialization failed, rc=-1&#xA;         Double check connections and try again, or use -F to override&#xA;         this check.&#xA;&#xA;&#xA;avrdude done.  Thank you.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I believe I have the crystal setup correctly on pins 9 (TOSC1) &amp;amp; 10 (TOSC2).  I am using 22 pF caps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am seeing 5V on pin 10 and 0V on pin 9&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What steps can I take to troubleshoot this?&lt;/p&gt;&#xA;" OwnerUserId="202" LastEditorUserId="202" LastEditorDisplayName="" LastEditDate="2009-11-28T00:40:36.813" LastActivityDate="2009-11-29T22:01:02.167" Title="Troubleshooting an ATMega328p clock setting" Tags="&lt;atmega328&gt;&lt;avr&gt;&lt;atmega&gt;" AnswerCount="2" />
  <row Id="718" PostTypeId="1" AcceptedAnswerId="772" CreationDate="2009-11-28T01:00:08.897" Score="5" ViewCount="295" Body="&lt;p&gt;I have a project where I'd like to convert a .5V, 800mA supply (a solar cell) to at least 3V with as much efficiency as possible. I've seen DC boost converters, but all the ones I've seen are designed for a higher voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any tips on a good low voltage one?&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-11-30T16:36:50.830" Title="DC Boost for low voltage?" Tags="&lt;dc&gt;&lt;power&gt;&lt;solar-cell&gt;" AnswerCount="3" />
  <row Id="719" PostTypeId="2" ParentId="718" CreationDate="2009-11-28T01:19:47.767" Score="9" ViewCount="" Body="&lt;p&gt;You're going to struggle with only 0.5 V. Look for a different solar cell or array that can supply at least 1.5 V. There are a few existing solutions aimed at running off a single 1.5 V cell. Have a look at the &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1031,C1060,P2412&quot; rel=&quot;nofollow&quot;&gt;LTC3400&lt;/a&gt; from Linear Technology.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that it's hard to even turn on a transistor with only 0.5 V, so even if you could get the converter running correctly, it would be pretty challenging to bootstrap itself into starting at such a low voltage.&lt;/p&gt;&#xA;" OwnerUserId="328" LastEditorUserId="328" LastEditorDisplayName="" LastEditDate="2009-11-28T03:07:18.257" LastActivityDate="2009-11-28T03:07:18.257" CommentCount="4" />
  <row Id="721" PostTypeId="2" ParentId="718" CreationDate="2009-11-28T03:51:27.963" Score="8" ViewCount="" Body="&lt;p&gt;You're not the only one who has this problem, given the recent interest in solar energy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out the &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tps61200.html&quot; rel=&quot;nofollow&quot;&gt;TPS61200&lt;/a&gt; from TI. It needs 0.5V for startup, but once started can operate down to 0.3V. I haven't used this part myself but TI's a very reputable player in the power management IC business (among many others).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Clint is correct, though, in that you'll have better efficiency (and more part choices!) if you string several cells in series to get to 1.5V or 2V.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-11-28T03:51:27.963" CommentCount="2" />
  <row Id="724" PostTypeId="1" AcceptedAnswerId="733" CreationDate="2009-11-28T04:21:04.377" Score="13" ViewCount="1757" Body="&lt;p&gt;I'm looking for some cheap beginners projects that show the uses of an arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;things like turning on and off an LED&lt;/p&gt;&#xA;&#xA;&lt;p&gt;getting back sensor data&lt;/p&gt;&#xA;&#xA;&lt;p&gt;...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;if anyone has come across useful youtube video tutorials that would be perfect!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;that sort of thing&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-22T08:13:56.017" LastActivityDate="2011-03-22T23:42:44.553" Title="What are the best beginner project using an arduino" Tags="&lt;arduino&gt;" AnswerCount="8" FavoriteCount="7" />
  <row Id="725" PostTypeId="1" AcceptedAnswerId="748" CreationDate="2009-11-28T04:24:08.057" Score="9" ViewCount="180" Body="&lt;p&gt;Does anyone know how to create a cf controller in order to read data from cf card?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-04T03:58:34.727" LastActivityDate="2011-02-05T05:01:41.760" Title="Creating a compact flash controller" Tags="&lt;flash&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="3" />
  <row Id="726" PostTypeId="1" AcceptedAnswerId="737" CreationDate="2009-11-28T04:33:27.210" Score="0" ViewCount="861" Body="&lt;p&gt;How do you interface a VGA camera to a FPGA? &lt;/p&gt;&#xA;" OwnerUserId="337" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-01T22:05:14.017" LastActivityDate="2011-02-19T20:13:15.943" Title="Interface a VGA camera to a FPGA" Tags="&lt;interface&gt;&lt;vga&gt;&lt;camera&gt;&lt;fpga&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="727" PostTypeId="2" ParentId="708" CreationDate="2009-11-28T04:34:27.563" Score="7" ViewCount="" Body="&lt;p&gt;To expand upon sivu's answer, this is a common use for so-called &quot;bus switches&quot; which are basically logic-controlled MOSFETs. Using discrete MOSFETs has some drawbacks (parasitic capacitance / capacitive coupling being one) and it can be tricky to choose a good MOSFET. The bus switches are optimized for use in high-speed logic circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Several manufacturers make them, including Fairchild, TI, IDT, and Pericom. Take a look at the &lt;a href=&quot;http://www.fairchildsemi.com/pf/NC/NC7SZ384.html&quot; rel=&quot;nofollow&quot;&gt;NC7SZ384&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See the following appnotes, among others:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.fairchildsemi.com/an/AN/AN-996.pdf&quot; rel=&quot;nofollow&quot;&gt;Fairchild AN-996&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://focus.ti.com/lit/an/scda003b/scda003b.pdf&quot; rel=&quot;nofollow&quot;&gt;TI SCDA003B&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.idt.com/products/getdoc.cfm?docid=7464&quot; rel=&quot;nofollow&quot;&gt;IDT AN-157&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.pericom.com/pdf/applications/AB008.pdf&quot; rel=&quot;nofollow&quot;&gt;Pericom AB-008&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-11-28T04:34:27.563" />
  <row Id="728" PostTypeId="2" ParentId="621" CreationDate="2009-11-28T04:42:33.977" Score="1" ViewCount="" Body="&lt;p&gt;When it comes to network installations (such as CAT5 in-wall) solid wire is the way to go, provided the wire is not intended to move, such as in a B&amp;amp;M business or a home.  In the marine industry they use stranded wire for everything, as even at rest the boat moves and flexes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Patch cables are made with stranded wire as its intended to move around. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically its much easier to breadboard with solid wire, but easier to prototype (solder) with stranded. &lt;/p&gt;&#xA;" OwnerUserId="313" LastActivityDate="2009-11-28T04:42:33.977" />
  <row Id="730" PostTypeId="2" ParentId="710" CreationDate="2009-11-28T04:56:06.247" Score="4" ViewCount="" Body="&lt;p&gt;To address your application rather than the question you asked directly (the other answers have talked about this):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;10 kHz DSP for a loop controller isn't too fast. (we use 5 or 10kHz control loops for motor controllers) With a decent device, my guess is you should be able to handle it with a clock frequency of 40-80MHz if you had to, and the neat thing about the newer series of DSPs and microcontrollers is that they use phase-locked loop (PLL) clock multipliers to boost the clock frequency internally, so that externally there don't actually need to be any really fast signals. TI's TMS320F28xx series of DSPs (see the 28044 and 28235) have a 5x PLL (half-steps from 0.5x to 5x), so you can get a 100MHz clock with a 20MHz crystal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the digital side, what you need to watch out for most, is making sure you provide a good solid pair of power and ground planes for your processor, and make sure you add bypass capacitors as close as possible to the processor's power supply pins. Also instead of just sprinkling a bunch of 0.1uF capacitors, use a variety of 0.1uF, 0.01uF, and 0.001uF capacitors. The 0.1uF capacitors provide more charge but their parasitic inductance comes into play at a lower frequency than what you'll see on a 0.01uF or 0.001uF capacitor. The latter two will not provide as much charge, but will work properly as bypass caps out to a higher frequency. We had a board design that was working but had a moderate amount of noise on the DSP's analog-to-digital converter. One of our engineers actually made some high frequency measurements with a scope probe with the &quot;witch's hat probe tip off&quot;, directly with the probe terminal and ground ring, and modified the bypass capacitors until he saw the power supply voltage noise reduced sufficiently.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The analog to digital conversion is going to be the weakest spot in your system. You probably won't have to work too hard to get the digital system working ok. But unless you're careful, you'll get mediocre noise performance on your ADC. (I'm afraid I don't have much experience personally dealing with this; other engineers at our company handle the layout, so what I'm telling you is second-hand.) How to handle ground planes is something that is argued by two separate approaches: whether to use one huge ground plane for the whole system, vs. two separate ground planes, one analog + one digital, tied together at the ADC -- the former is fine for 8-10 bit systems, and I hear separating digital/analog areas of the circuit is more important when you get to higher bit counts (16bit or higher). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't skimp on # of board layers. Ground and power planes are your friends.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-11-28T04:56:06.247" CommentCount="1" />
  <row Id="731" PostTypeId="2" ParentId="148" CreationDate="2009-11-28T05:09:48.567" Score="3" ViewCount="" Body="&lt;p&gt;I wrote a &lt;a href=&quot;http://github.com/dustin/arduino-2406&quot; rel=&quot;nofollow&quot;&gt;library&lt;/a&gt; to control DS2406 1wire switches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With one of these, you can use a single pin to switch a much larger number of devices.  It'll be slower than flipping the IO pin directly, of course, and it'll use more memory since you have to address the devices over that port (this can be traded off for more speed if you'd like).&lt;/p&gt;&#xA;" OwnerUserId="347" LastActivityDate="2009-11-28T05:09:48.567" />
  <row Id="732" PostTypeId="2" ParentId="148" CreationDate="2009-11-28T09:01:13.197" Score="3" ViewCount="" Body="&lt;p&gt;Sparkfun sells a &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9056&quot; rel=&quot;nofollow&quot;&gt;digital/analog multiplexer&lt;/a&gt; that allows 16 pins to be controlled by five on the Arduino. It is bidirectional so you may also use it for input.&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2009-11-28T09:01:13.197" />
  <row Id="733" PostTypeId="2" ParentId="724" CreationDate="2009-11-28T09:10:28.700" Score="9" ViewCount="" Body="&lt;p&gt;Start with the sparkfun tutorial &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=145&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and do a google search. There are tons of different options for starting out with the Arduino, you can try a &lt;a href=&quot;http://www.sparkfun.com/products/10174&quot; rel=&quot;nofollow&quot;&gt;starter kit&lt;/a&gt;. Go on to the &lt;a href=&quot;http://arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino website&lt;/a&gt; there is a ton of information there.&lt;/p&gt;&#xA;" OwnerUserId="81" LastEditorUserId="81" LastEditorDisplayName="" LastEditDate="2010-12-10T06:57:11.803" LastActivityDate="2010-12-10T06:57:11.803" CommentCount="2" />
  <row Id="734" PostTypeId="2" ParentId="724" CreationDate="2009-11-28T09:51:47.173" Score="7" ViewCount="" Body="&lt;p&gt;Yes definately the sparkfun tutorial.  Another source of good starter projects is the free e-book &lt;a href=&quot;http://www.earthshineelectronics.com/files/ASKManualRev4.pdf&quot; rel=&quot;nofollow&quot;&gt;&quot;The Complete Beginners Guide to the Arduino&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also worth downloading (or you can buy a hard copy) of the &lt;a href=&quot;http://www.lulu.com/content/1108699&quot; rel=&quot;nofollow&quot;&gt;Arduino Programming Notebook&lt;/a&gt;.  It is a very good walk through of the main code.&lt;/p&gt;&#xA;" OwnerUserId="312" LastEditorUserId="1609" LastEditorDisplayName="" LastEditDate="2011-03-22T07:55:43.623" LastActivityDate="2011-03-22T07:55:43.623" CommentCount="2" />
  <row Id="735" PostTypeId="2" ParentId="724" CreationDate="2009-11-28T10:37:42.637" Score="7" ViewCount="" Body="&lt;p&gt;I like the &quot;How to Tuesday&quot; projects from Make:&#xA;&lt;a href=&quot;http://www.youtube.com/watch?v=HYUYbN2gRuQ&amp;amp;feature=related&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=HYUYbN2gRuQ&amp;amp;feature=related&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-11-28T10:37:42.637" />
  <row Id="736" PostTypeId="2" ParentId="683" CreationDate="2009-11-28T11:06:08.817" Score="2" ViewCount="" Body="&lt;p&gt;I don't think there is an official RFL set up in Aus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on what Uni you are at and what course you are doing, you may be able to start one for yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They give full instructions for setting up a field / what you will need on the &lt;img src=&quot;http://www.roboticfootballleague.com/site/docs/FieldConstruction%5FCurrent.pdf&quot; alt=&quot;RFL site&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-11-28T11:06:08.817" CommentCount="1" />
  <row Id="737" PostTypeId="2" ParentId="726" CreationDate="2009-11-28T11:43:39.190" Score="4" ViewCount="" Body="&lt;p&gt;I think this would depend on the connection of the camera. Will you be interfacing a ccd chip or try to have the FPGA act as an usb host for a webcam...&lt;/p&gt;&#xA;" OwnerUserId="348" LastActivityDate="2009-11-28T11:43:39.190" CommentCount="2" />
  <row Id="739" PostTypeId="1" CreationDate="2009-11-28T17:38:37.107" Score="16" ViewCount="820" Body="&lt;p&gt;I need to do digital signal processing on 8 analog lines at 10 kHz.  This is quite a demanding task, and I was thinking that an FPGA might be the right approach. I am currently looking at dev kits from Xilinx, and since I have no experience with FPGA, I find it really hard to know how to choose the right chip.  I imagined using a dev kit and expanding it using the I/O pins to connect to an 8-channels A/D chip and 8-channel D/A chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the differences between using Spartan, Virtex, Altera, etc.?  I don't even know how to estimate how many gates I will need.  Are there any rules of thumb for that?  How do I make sure the clock speed will be enough (as a function of the number of adds and multiplies).  Is it difficult to do floating-point processing on an FPGA, should I stick to fixed point math?  What's the best way to get started?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I require a solution that's programmable using Linux.  Xilinx provides this, but I'm not sure what the limitations are.&lt;/p&gt;&#xA;" OwnerUserId="349" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-04-09T13:48:48.770" LastActivityDate="2010-11-04T09:04:05.910" Title="How to choose an FPGA?" Tags="&lt;kit&gt;&lt;development&gt;&lt;fpga&gt;&lt;xilinx&gt;" AnswerCount="9" CommentCount="2" FavoriteCount="6" />
  <row Id="740" PostTypeId="2" ParentId="739" CreationDate="2009-11-28T18:42:06.323" Score="10" ViewCount="" Body="&lt;p&gt;I would not use an FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You mention you have no experience with FPGA's, and yet you are interested in doing digital signal processing on an FPGA... numerical manipulation + signal processing are difficult enough to get right on a computer/DSP/microprocessor, where the programming tools are conventional programming. It seems to me that using a digital signal processing project for a first FPGA project is likely a recipe for frustration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to learn FPGAs, try doing something more suited to the development tools, like state machines or communications packet processing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a DSP project like what you've described, I'd recommend a DSP or a &lt;a href=&quot;http://www.cypress.com/?id=1353&quot; rel=&quot;nofollow&quot;&gt;Cypress PSOC&lt;/a&gt; or an &lt;a href=&quot;http://www.analog.com/en/analog-microcontrollers/analog-microcontrollers/products/index.html&quot; rel=&quot;nofollow&quot;&gt;Analog Devices Microconverter&lt;/a&gt; (=microcontroller with ADC+DAC builtin) instead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(full disclosure, which provides some context for my advice: I do not use FPGAs myself. I have used programmable logic = PLDs on rare occasions. My officemate does use FPGAs frequently, and I've seen enough VHDL/Verilog code looking over his shoulder to know that it is well suited for bit manipulations. He is a seasoned engineer with lots of experience with FPGAs; in a recent conversation with him where he was doing some fairly simple math on integers with different bit widths, I told him he needed to do sign-extending on the shorter bit width number in order to subtract it properly, and he got this look on his face, like &quot;oh man, I don't want to have to do sign extension...&quot; Adding and subtracting is not very hard in an FPGA. Beyond addition and subtraction, you really need to know the tools and libraries. And floating-point processing??!?!!??!?!!?)&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-11-28T18:51:38.113" LastActivityDate="2009-11-28T18:51:38.113" CommentCount="2" />
  <row Id="741" PostTypeId="2" ParentId="724" CreationDate="2009-11-28T22:20:18.683" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.linuxformat.co.uk/&quot; rel=&quot;nofollow&quot;&gt;Linux Format&lt;/a&gt; had 4 or 5 issues with some Arduino Tutorials in. There are versions of the first two available on Tux Radar &lt;a href=&quot;http://www.tuxradar.com/content/arduino-hardware-hacking-part-1&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://www.tuxradar.com/content/arduino-hardware-hacking-part-2&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. The first one gets some LEDs blinking, whilst the second one showed you how to create a simplified Simon Says game (only 3 LEDs and no sound). Unfortunately they don't appear to have the later ones which extended the project to include sound and a score counter. The same articles also appeared in a Linux Format Special called You Can Code!, so if you can find a copy of that maybe you could follow it there.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-11-28T22:20:18.683" />
  <row Id="742" PostTypeId="1" AcceptedAnswerId="747" CreationDate="2009-11-28T22:27:18.637" Score="4" ViewCount="187" Body="&lt;p&gt;I've been using a Motoman and I'm wondering what is the best way to recover when the encoder position has been lost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried lining up all the reference marks on the joins but this can be a bit dodgy.&lt;/p&gt;&#xA;" OwnerUserId="337" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-11-30T02:15:57.277" LastActivityDate="2009-11-30T02:15:57.277" Title="Robot Encoder Position" Tags="&lt;robotics&gt;&lt;encoder&gt;" AnswerCount="1" />
  <row Id="743" PostTypeId="2" ParentId="724" CreationDate="2009-11-29T00:47:01.800" Score="8" ViewCount="" Body="&lt;p&gt;You could also check the soon to be release book &quot;Practical Arduino&quot; by Jonathan Oxer and Hugh Blemings. Check out the blog to see some cool projects that is going to be on the book (&lt;a href=&quot;http://www.practicalarduino.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.practicalarduino.com/&lt;/a&gt;).&lt;/p&gt;&#xA;" OwnerUserId="351" LastActivityDate="2009-11-29T00:47:01.800" />
  <row Id="744" PostTypeId="2" ParentId="724" CreationDate="2009-11-29T01:10:45.750" Score="4" ViewCount="" Body="&lt;p&gt;I have also been thinking about this. I had thought to give a arduino kit of some sort to family and friends for christmas but wanted to include an interesting project.  This is by no means full answer but here are my current thoughts. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The project should be limited to use a sensor and control (motor). I'd like to have a project which can be applied in every day use. Hence, not something that teaches you the basics of controlling components, but something that tells you how to apply them. For example, a temp. sensor that logs the data to your computer so you can monitor energy efficiency of various parts of your house. Or, an IR sensor and motor to detect when your child gets home late at night. Rig a sensor so that you can monitor when your baby moves in their sleep, and log this. Audio sensor that detects when your partner snores and has a string attached to it which pulls their toe. Etc.&lt;/p&gt;&#xA;" OwnerUserId="196" LastActivityDate="2009-11-29T01:10:45.750" />
  <row Id="746" PostTypeId="2" ParentId="717" CreationDate="2009-11-29T08:25:00.120" Score="2" ViewCount="" Body="&lt;p&gt;That's a really odd response you're seeing.  Of course there's the obvious suggestion of: have you tried power cycling everything in the chain? (PC-&gt;STK200-&gt;devboard)  But also, do you have another AVR programmer you can try?  Do you have another ATmega328P you can try reading &amp;amp; writing?  Have you ever been able to read fuse settings with any programmer?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other things to try:&#xA;Can you remove the crystal and see if you can communicate with the chip then?&#xA;Does your programmer have the ability to adjust SCK speed?  (the STK500 can do this, not sure about STK200)  It may be the chip got in a really low speed mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a last resort, you'll need to put the chip in a high-voltage programmer.  I know at least the STK500 can do that, and there are a few circuits out there for hacking a HVP out of an Arduino or LPT port.  I've had to resuscitate a few AVR chips that way because of an electrical glitch or I flubbed settings.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-29T08:25:00.120" />
  <row Id="747" PostTypeId="2" ParentId="742" CreationDate="2009-11-29T09:41:43.760" Score="4" ViewCount="" Body="&lt;p&gt;I've played with these a bit and found some useful documents in the past.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have a look at the &lt;a href=&quot;http://www.robot-forum.com/robotforum/empty-t417.0.html&quot; rel=&quot;nofollow&quot;&gt;robot forum&lt;/a&gt; on it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically run the 'home' job on the robot, you need the absolute position from each axis and this is found on a sticker on the inside of the controller.&#xA;At the home position you should have all the ref arrows alligned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the home position has been lost the encoder memory is lost.  It counts 4000 points for each revolution - if the encoder memoery is lost it doesnt know how many have passed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take the difference between the new and old encoder home position and divide by 4000 - this will give you how many it is out by.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the example given was:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Original home encoder count: -119771 New home encoder count (after lining up reference marks and setting the data for that axis): -95834 Difference: -23937 Divided by 4000: 5.98425 Therefore, number of revolutions out was 6 My new home position should then be -119771 + (6)x(4000) = -95771&lt;/p&gt;&#xA;" OwnerUserId="267" LastActivityDate="2009-11-29T09:41:43.760" />
  <row Id="748" PostTypeId="2" ParentId="725" CreationDate="2009-11-29T18:22:31.783" Score="10" ViewCount="" Body="&lt;p&gt;Look at Sparkfun's compact flash breakouts &lt;a href=&quot;http://www.sparkfun.com/products/195&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://www.sparkfun.com/products/493&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and check out &lt;a href=&quot;http://www.sparkfun.com/datasheets/BreakoutBoards/c0201mspdf.pdf&quot; rel=&quot;nofollow&quot;&gt;this article&lt;/a&gt; on interfacing with a compact flash card.&lt;/p&gt;&#xA;" OwnerUserId="81" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-02-05T05:01:41.760" LastActivityDate="2011-02-05T05:01:41.760" />
  <row Id="749" PostTypeId="1" CreationDate="2009-11-29T21:54:44.193" Score="8" ViewCount="279" Body="&lt;p&gt;I want to work on a project where you could replace a magstripe with another item which can change the data stored on it via a PIC but still be read by a magstripe reader.  This means that the PIC could 'write' another value to the different tracks on a magstripe to replicate different cards.  So what method could be used to do this?  Would a magstripe be used?&lt;/p&gt;&#xA;" OwnerUserId="107" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-04T03:56:42.267" LastActivityDate="2011-02-04T10:22:57.477" Title="Replicating a Magstripe?" Tags="&lt;pic&gt;&lt;magstripe&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="750" PostTypeId="2" ParentId="717" CreationDate="2009-11-29T22:01:02.167" Score="1" ViewCount="" Body="&lt;p&gt;A couple thoughts.  What were the fuses set to before you changed them?  have you confirmed your wiring with the schematic?  Remember, it needs the crystal connected to program it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Checking the datasheet, it looks like 0xF7 was the wrong setting to use.  CKSEL 3..0 is set to 1000 by 0xF7.  There is a table in the datasheet, which recommends this value for oscillators from .8 to .9MHz, and specificially states that this setting is &lt;em&gt;not&lt;/em&gt; to be used with crystals.  The correct setting for the low byte of the fuses was 0xF1, this puts CKSEL 3..1 at 111, which is recommended for 16MHz quartz crystal.  The relevant info is on page 29 of the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll probably need an old-school programmer to fix the issue, otherwise you've bricked the chip.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-29T22:01:02.167" />
  <row Id="751" PostTypeId="2" ParentId="749" CreationDate="2009-11-29T22:05:45.467" Score="4" ViewCount="" Body="&lt;p&gt;The basic hardware behind magstripes is really the same as a tape recorder.  It is divided into several tracks, and has a strobe track to sync everything up.  You can buy the reader hardware, and I am aware of variants that are designed for writing.  Check digikey.  Make sure the reader/writer hardware you buy can read/write the track you intend.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-29T22:05:45.467" CommentCount="8" />
  <row Id="752" PostTypeId="2" ParentId="725" CreationDate="2009-11-29T22:09:51.510" Score="2" ViewCount="" Body="&lt;p&gt;I'm told that compact flash has an interface very similar to IDE, that being said IDE is not trivial to communicate over.  The easiest way is to do as zklapow recommends, buy a pre-made control chip.  Sparkfun has boards that even have filesystem support builtin.  &lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-29T22:09:51.510" CommentCount="1" />
  <row Id="753" PostTypeId="2" ParentId="724" CreationDate="2009-11-29T22:13:40.100" Score="3" ViewCount="" Body="&lt;p&gt;Arduino.cc is the place to go, it has a lot of different tutorials and information.  The arduino is very easy to work with.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-29T22:13:40.100" />
  <row Id="754" PostTypeId="2" ParentId="133" CreationDate="2009-11-29T22:18:50.103" Score="2" ViewCount="" Body="&lt;p&gt;You can do a lot of cool things by having devices twitter programmatically.  I had a server configured to twitter it's uptime and disk usage.  A couple ideas:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Twitter status of coffee pot in a nearby kitchen/breakroom&lt;/li&gt;&#xA;&lt;li&gt;Room temperature&lt;/li&gt;&#xA;&lt;li&gt;Weekly rainfall&lt;/li&gt;&#xA;&lt;li&gt;Cat entrances/exits from the building&lt;/li&gt;&#xA;&lt;li&gt;toilet flushes&lt;/li&gt;&#xA;&lt;li&gt;Daily electricity usage.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;A pile of neat stuff!&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-29T22:18:50.103" />
  <row Id="755" PostTypeId="2" ParentId="704" CreationDate="2009-11-29T22:30:53.700" Score="2" ViewCount="" Body="&lt;p&gt;Does the controller/wireless need to be close to the point of measurement?  A thermocouple should do yeoman service in this application, and allows some distance between the logger and  the high heat.  Sparkfun has chips to interface with thermocouples that do the linearization internally, even have the cold junction.  A qualified pipefitter can put a thermowell into a legline or something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mind, most pressure tranducers in this application will need a coil of tube to isolate it from the heat.  1500 psi steam is hot stuff.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-29T22:30:53.700" CommentCount="2" />
  <row Id="756" PostTypeId="2" ParentId="263" CreationDate="2009-11-29T22:37:30.347" Score="2" ViewCount="" Body="&lt;p&gt;I would like to add a suggestion: build a current mirror.  The problem with the resistors is that they will resist the same amount at all time.  You lose a certain amount of energy to resisting current flow even when the LEDs wouldn't normally be drawing too much.  A current mirror, or constant current source, is much more efficient and allows you select a specific current to run at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Further, you may consider using a driver chip like the ULN2803, linky:&#xA;&lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=312&quot; rel=&quot;nofollow&quot;&gt;ULN2803&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will find it can handle much more current than a microcontroller, and allows you drive some pretty big loads.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-29T22:37:30.347" CommentCount="2" />
  <row Id="757" PostTypeId="2" ParentId="704" CreationDate="2009-11-30T01:03:24.970" Score="2" ViewCount="" Body="&lt;p&gt;Unless you really need some specific custom capabilities, there should be lots of off the self options that can be used for logging. We regularly use a &lt;a href=&quot;http://www.datataker.com/&quot; rel=&quot;nofollow&quot;&gt;Data Taker&lt;/a&gt; at work, which is quite flexible. It can run standalone or over a network. I find the software for it hard to use, but once it's set up it works reliably.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;National instruments also have lots of small and cheap (or not so cheap too) DAQ products that could help. I realise you were looking for a more DIY solution, but if this is an R&amp;amp;D project having a reliable proven solution can be cheaper in the long run.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-11-30T01:03:24.970" />
  <row Id="758" PostTypeId="1" AcceptedAnswerId="759" CreationDate="2009-11-30T03:03:53.963" Score="8" ViewCount="3239" Body="&lt;p&gt;G'day all!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an Arduino Duemilanove hanging around spare at the moment and thought I might try a few audio interfacing projects. I'm just wondering what sort of sampling frequency I can achieve using a single analog input and applying some simple algorithms on chip, then reporting using a few digital outputs tied to LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to sample in at ~44.1 kHz if possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For reference the first thing I want to try is a simple guitar tuner.&lt;/p&gt;&#xA;" OwnerUserId="295" LastActivityDate="2011-02-17T08:14:28.710" Title="Maximum sample rate of Arduino Duemilanove?" Tags="&lt;audio&gt;&lt;arduino&gt;&lt;duemilanove&gt;&lt;analog&gt;&lt;frequency&gt;" AnswerCount="8" CommentCount="3" FavoriteCount="1" />
  <row Id="759" PostTypeId="2" ParentId="758" CreationDate="2009-11-30T03:48:32.240" Score="10" ViewCount="" Body="&lt;p&gt;I don't think you can sample that fast at full resolution. The ATMega168 can only sample at 15 ksps at its full resolution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having said that, you should be able to get a suitable sample rate to get a functioning guitar tuner. 44.1 kHz is most likely a fair bit faster than you will need given that the fundamental of the high E string an a guitar is around 330 Hz.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-11-30T03:48:32.240" CommentCount="2" />
  <row Id="760" PostTypeId="2" ParentId="758" CreationDate="2009-11-30T05:03:25.887" Score="5" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;It takes about 100 us (0.0001 s) to&#xA;  read an analog input, so the maximum&#xA;  reading rate is about 10,000 times a&#xA;  second.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://arduino.cc/en/Reference/AnalogRead&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Reference/AnalogRead&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rob.&lt;/p&gt;&#xA;" OwnerUserId="356" LastActivityDate="2009-11-30T05:03:25.887" />
  <row Id="761" PostTypeId="1" CreationDate="2009-11-30T05:08:22.000" Score="4" ViewCount="399" Body="&lt;p&gt;I am looking at designing a low-power project that will have an ATMega328 running at a low speed for lower power consumption.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current plan is to have the UART hooked up to a &lt;a href=&quot;http://www.littlebirdelectronics.com/products/rf-link-2400bps-receiver-315mhz&quot; rel=&quot;nofollow&quot;&gt;RF Link Reciever&lt;/a&gt; for communication at 1200baud.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'm wondering, though, is what the minimum speed is that I can run an ATMega328 at and still have a 1200baud UART running. Is 1MHz fast enough?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rob.&lt;/p&gt;&#xA;" OwnerUserId="356" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T16:12:49.133" LastActivityDate="2010-10-22T16:12:49.133" Title="Minimum ATMega328 speed with UART" Tags="&lt;atmega328&gt;&lt;low-power&gt;" AnswerCount="1" />
  <row Id="762" PostTypeId="2" ParentId="761" CreationDate="2009-11-30T05:48:13.640" Score="5" ViewCount="" Body="&lt;p&gt;The UART clock runs at 16 times the baud rate. So you would could get possibly get away with 19.2 kHz. 1 MHz will be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most often you would run at a clock rate that gives a convenient divider to generate the UART baud rate clock and is still faster enough for any other processing you need to get done. Each time a byte or packet is transmitted via the UART, put the CPU into a low power mode and wake up again on an interrupt when more data is ready.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-11-30T05:48:13.640" CommentCount="1" />
  <row Id="763" PostTypeId="2" ParentId="758" CreationDate="2009-11-30T06:11:53.967" Score="3" ViewCount="" Body="&lt;p&gt;If you use an analog comparator (either the internal one in the AVR or an external opamp one) that turns the analog input into a square wave, you can sample oscillations at much higher speeds.  While this isn't true audio sampling, for building a guitar tuner it's often all you need since all your code would be doing anyway would be counting zero crossings per unit time.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-11-30T06:11:53.967" CommentCount="5" />
  <row Id="764" PostTypeId="2" ParentId="133" CreationDate="2009-11-30T10:31:35.763" Score="2" ViewCount="" Body="&lt;p&gt;Baker Tweet is a nice arduino / Twitter project: &lt;a href=&quot;http://www.bakertweet.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.bakertweet.com/&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2009-11-30T10:43:01.820" />
  <row Id="765" PostTypeId="1" AcceptedAnswerId="766" CreationDate="2009-11-30T11:00:08.153" Score="14" ViewCount="1314" Body="&lt;p&gt;How do i measure the level of a water tank with a microcontroller?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-03-22T19:36:00.213" LastActivityDate="2010-11-07T02:59:02.960" Title="Level of a water tank with a microcontroller" Tags="&lt;microcontroller&gt;&lt;measurement&gt;&lt;sensor&gt;" AnswerCount="11" CommentCount="1" FavoriteCount="4" />
  <row Id="766" PostTypeId="2" ParentId="765" CreationDate="2009-11-30T11:45:42.900" Score="12" ViewCount="" Body="&lt;p&gt;Well, assuming you are operating here on earth (as opposed to in orbit), you can use a float sensor that you measure using the micro. The question is: Do you need to know the exact level, or do you just need some sort of trip when it gets to high/low? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the 'trip at specific level' theme, you can get switches &lt;a href=&quot;http://www.waterloo-biofilter.com/spec%20sheets/float%20switches/SJE%20Sensor.pdf&quot; rel=&quot;nofollow&quot;&gt;like this&lt;/a&gt; - generally the float contains some kind of attitude sensing switch. When the water level is lower, the float ends up on it's side, and the switch is 'off', while raising the level forces the float upright, and therefore 'on'. These are often used for sump pumps. They are pretty reliable and very easy to deal with, though you have to be careful to anchor them correctly, and you have to be sure that nothing gets in the way of the float.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to know the actual level, then you've got lots of choices, but it's less simple. You can go with something like an ultrasonic sensor (ultrasound beam firing down from the top of the tank to reflect off the water level). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tankindicator.com/&quot; rel=&quot;nofollow&quot;&gt;These guys&lt;/a&gt; seem to make level indicators for BIG tanks which consist of a float and an external weight cabled together. As the float rides up and down on the fluid, the external indicator moves appropriately. You could build something similar, with nothing more complicated than photo-cells to read the level (if it's a large tank, or you want lots of granularity, you'd need a log of photo-cells).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternately, taking the cabled float idea, you could put an idler wheel that moves whenever the cable moves, and then attach an encoder to that. This would allow you to track the level with pretty high accuracy.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2009-11-30T11:45:42.900" />
  <row Id="767" PostTypeId="2" ParentId="765" CreationDate="2009-11-30T11:56:22.160" Score="5" ViewCount="" Body="&lt;p&gt;One way of doing this is to place an led at the bottom of the tank pointing to the top, and a photodiode at the top of the tank, facing the LED. The LED will be attenuated by the water in the tank, you'll need to experiment to determine how much. Also, it's best to take a series of rapid measurements and average them when using this method.&lt;/p&gt;&#xA;" OwnerUserId="358" LastActivityDate="2009-11-30T11:56:22.160" CommentCount="1" />
  <row Id="768" PostTypeId="2" ParentId="725" CreationDate="2009-11-30T15:02:28.547" Score="2" ViewCount="" Body="&lt;p&gt;I assume you are looking for an embedded solution, since you could easily get a reader for a desktop or laptop computer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;People have written SPI IDE interfaces, which you might be able to run on an AVR.  I will link to one that runs on an ATMega32.  It may be too big for an ATMega168, but it should fit on a 328, though it may need a bit of cleanup to account for the Arduino bootloader if you go that route:&#xA;&lt;a href=&quot;http://forum.6502.org/viewtopic.php?p=8343&amp;amp;sid=a06dc948bd456b223cf8a93d175d37e1&quot; rel=&quot;nofollow&quot;&gt;http://forum.6502.org/viewtopic.php?p=8343&amp;amp;sid=a06dc948bd456b223cf8a93d175d37e1&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have seen a lot of work on this for the PIC series of microcontrollers as well.  A simple search on PIC and CF should return plenty of details, though the hardware and article linked above by zklapow should be more than sufficient to complete the project.  I just wanted to add in an AVR solution for those who are looking since I know there is a big Arduino community here.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-11-30T15:02:28.547" />
  <row Id="769" PostTypeId="2" ParentId="765" CreationDate="2009-11-30T15:03:50.137" Score="5" ViewCount="" Body="&lt;p&gt;There are a surprising number of ways to check for level.  There are sensors that use RF, sending a pulse down a waveguide and detecting the reflection off the surface of the liquid in the tank.  There's ultrasound, floats, bubbler tubes, pressure taps...  The method used depends on the size of the tank, the contents, ambient environment and other factors.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-30T15:03:50.137" />
  <row Id="770" PostTypeId="2" ParentId="765" CreationDate="2009-11-30T15:03:59.613" Score="7" ViewCount="" Body="&lt;p&gt;A method I like, but have not tried is to put two insulated plates in the liquid.  No condution, electrolosis, contanimation....... They form the plates of a cap. and are used in some sort of oscillator ( choice up to you )  Because water is a good dialetric the frquency depends strongly on the amount of water between the plates.  Meaure the frequency to get the depth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might be able to get a similar result by applying an ac signal and measureing the current thru the cap. &lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-11-30T15:03:59.613" CommentCount="2" />
  <row Id="771" PostTypeId="2" ParentId="758" CreationDate="2009-11-30T15:40:27.327" Score="3" ViewCount="" Body="&lt;p&gt;There are a number of ADCs available that are serial, I2S is NXP's standard based on I2C.  They allow you to pretty easily pull in analog even at much higher speeds.  This link should get you to an NXP part that is designed for audio:&#xA;&lt;a href=&quot;http://www.nxp.com/#/pip/pip=%5Bpip=UDA1361TS%5D|pp=%5Bt=pip,i=UDA1361TS%5D&quot; rel=&quot;nofollow&quot;&gt;UDA1361TS&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Free samples are your friend :)&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-11-30T15:40:27.327" CommentCount="1" />
  <row Id="772" PostTypeId="2" ParentId="718" CreationDate="2009-11-30T16:36:50.830" Score="2" ViewCount="" Body="&lt;p&gt;Over at &lt;a href=&quot;http://electronics.stackexchange.com/questions/170/5v-800ma-to-at-least-3v&quot; rel=&quot;nofollow&quot;&gt;Electronics Exchange&lt;/a&gt;, &lt;a href=&quot;http://electronics.stackexchange.com/users/14/rex-logan&quot; rel=&quot;nofollow&quot;&gt;Rex Logan&lt;/a&gt; had a great answer - the &lt;a href=&quot;http://www.dimensionengineering.com/lvboost.htm&quot; rel=&quot;nofollow&quot;&gt;LVBoost&lt;/a&gt; is exactly what I'm looking for.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-11-30T16:36:50.830" CommunityOwnedDate="2009-11-30T16:36:50.830" />
  <row Id="773" PostTypeId="2" ParentId="765" CreationDate="2009-11-30T17:35:03.677" Score="7" ViewCount="" Body="&lt;p&gt;More details would help, but I think the ultrasonic method is probably the simplest, conceptually, anyway (hence the need for more details :-]).  I threw together a level sensor for the fuel oil tank in my basement using a MaxSonar ultrasonic transducer.  I'm switching to a Parallax Ping sensor, as soon as I can get my hands on one.  The MaxSonar unit has proved to be somewhat of a pain; turns out it's only got a resolution of one inch (2.54cm), which equates to nearly 7 gallons in my tank.  I put the MaxSonar unit in a PVC cap at the top of the tank pointing down (out of reach of the liquid).&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-11-30T17:35:03.677" />
  <row Id="774" PostTypeId="2" ParentId="739" CreationDate="2009-11-30T19:25:47.157" Score="9" ViewCount="" Body="&lt;p&gt;They're all pretty much good. You won't need too much out of the FPGA to do something simple like that, so any beginner FPGA (like the Spartan-3 line) should suffice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just a word of warning though, programming an FPGA is a LOOOOTTTTTT different than something like C++, C, perl... I'd suggest starting out with verilog because it's probably the easier to transition into... VHDL is very COBOL like but verilog is more similar to modern programming languages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;About the clock speed: don't worry about it. The advantage to using FPGAs is that they are massively parallel, so while a 50MHz clock may seem ridiculously slow by today's standards, keep in mind that they can do hundreds of things at once, whereas a &quot;normal&quot; CPU at 3GHz has to queue things up one at a time. This is the advantage to using FPGA: parallelism. So for something specialized, you don't need to worry about speed so much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But like the other comment, it's a whole different paradigm. The learning curve is steep, but once you grasp the language, it all makes sense (just make sure you understand the building blocks).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Happy FPGA'ing :)&lt;/p&gt;&#xA;" OwnerUserId="364" LastActivityDate="2009-11-30T19:25:47.157" CommentCount="3" />
  <row Id="775" PostTypeId="2" ParentId="765" CreationDate="2009-11-30T22:59:41.907" Score="9" ViewCount="" Body="&lt;p&gt;I know that the soon to be released book &lt;a href=&quot;http://www.practicalarduino.com/&quot; rel=&quot;nofollow&quot;&gt;Practical Arduino&lt;/a&gt; has a &lt;a href=&quot;http://www.practicalarduino.com/projects/water-tank-depth-sensor&quot; rel=&quot;nofollow&quot;&gt;water tank depth sensor&lt;/a&gt; project included, which uses a differential pressure transducer to measure the water pressure at the bottom of the tank, and from that to calculate how full the tank is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Schematics are on the above link, along with a link to the source code on github.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Full disclosure: I have no association with the book, but have met one of the authors a couple of times at our local hackerspaces.)&lt;/p&gt;&#xA;" OwnerUserId="117" LastActivityDate="2009-11-30T22:59:41.907" />
  <row Id="776" PostTypeId="2" ParentId="601" CreationDate="2009-12-01T00:16:48.000" Score="3" ViewCount="" Body="&lt;p&gt;This topic has been discussed at length on StackOverflow, and is fairly processor-independent and language-independent except for the relative costs of multiplication/addition/lookup, which will make certain implementations more attractive.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://stackoverflow.com/questions/345085/how-do-trigonometric-functions-work/394512#394512&quot; rel=&quot;nofollow&quot;&gt;How do Trigonometric Functions work?&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://stackoverflow.com/questions/523531/fast-transcendent-trigonometric-functions-for-java&quot; rel=&quot;nofollow&quot;&gt;Fast transcendent / trigonometric functions for Java&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://stackoverflow.com/questions/1571502/trigonometric-functions-on-embedded-system&quot; rel=&quot;nofollow&quot;&gt;Trigonometric functions on embedded systems&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://stackoverflow.com/questions/99620/books-on-the-algorithims-needed-for-calculating-trancendental-functions&quot; rel=&quot;nofollow&quot;&gt;Book(s) on the algorithms needed for calculating transcendental functions&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://stackoverflow.com/questions/639283/how-should-i-tackle-arctan-and-prevent-deviding-by-zero-without-the-convenience&quot; rel=&quot;nofollow&quot;&gt;How should I tackle ARCTAN...&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The atan2() function, or rectangular-to-polar conversion, is not completely implementable by lookup tables of reasonable size; CORDIC is one option.&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-12-01T00:23:08.157" LastActivityDate="2009-12-01T00:23:08.157" />
  <row Id="777" PostTypeId="2" ParentId="758" CreationDate="2009-12-01T02:41:22.823" Score="3" ViewCount="" Body="&lt;p&gt;Google for 'AVR guitar tuner', there are a couple projects out there that do this already, and they seem to be able to do it without too much trouble with the speed of the AVR.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-01T02:41:22.823" />
  <row Id="778" PostTypeId="1" AcceptedAnswerId="780" CreationDate="2009-12-01T05:33:38.630" Score="5" ViewCount="205" Body="&lt;p&gt;I have no vocabulary for this, so forgive my clumsiness in explaining.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to hook up a power supply to use with solenoids and an Arduino, but I'm not sure where to cut it. Just before the power plug there is a thing (not sure of the name, bottom right of picture in the link below), do I need to cut before or after it? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.allelectronics.com/mas_assets/image_cache/height.500_width.500_modified.1237373195.3188.PS-1233.jpg&quot; rel=&quot;nofollow&quot;&gt;Here is a link to the picture&lt;/a&gt;, I'm a new user so I can't embed it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you know the name of the mystery thing, I'd also love to know.&lt;/p&gt;&#xA;" OwnerUserId="370" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-09T18:42:17.460" LastActivityDate="2011-03-09T18:42:17.460" Title="Where to cut my power supply for Arduino?" Tags="&lt;arduino&gt;&lt;power-supply&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="779" PostTypeId="2" ParentId="778" CreationDate="2009-12-01T06:43:50.953" Score="6" ViewCount="" Body="&lt;p&gt;The thing just before the power plug is a common mode choke. It is used to reduce EMI that could be conducted on the power cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can leave it in that would be better, but if it gets in the way, or the cable isn't long enough just chop it off.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-12-01T06:43:50.953" />
  <row Id="780" PostTypeId="2" ParentId="778" CreationDate="2009-12-01T06:49:48.173" Score="11" ViewCount="" Body="&lt;p&gt;That thing is a Ferrite Filter. It's there to dampen Electromagnetic Interference (EMI) or high frequency noise from your power lines from interfering with your circuit. If you're not doing audio (or radio) work or you're not picky you can cut it off. If you are and it gets in the way, you can cut it off and add a ferrite bead elsewhere in your circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Better than cutting it would be to add a proper plug to your circuit, but you've probably already considered that. If you're using a breadboard, this type of terminal block works well: &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=ED2580-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=ED2580-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A bit of warning: That looks like a laptop power supply, so it's probably capable of sourcing a fair amount of current. It's a little more powerful than a typical &quot;wall wart&quot;. Be careful not to short anything, and don't work on your project while it's powered up.&lt;/p&gt;&#xA;" OwnerUserId="105" LastActivityDate="2009-12-01T06:49:48.173" />
  <row Id="781" PostTypeId="2" ParentId="749" CreationDate="2009-12-01T07:30:28.917" Score="3" ViewCount="" Body="&lt;p&gt;I remember watching a presentation by Acidus on his Stripe Snoop project... but I can't remember which con it was at.  He had various types of readers, but he had one constructed out of an old cassette tape head.  The head was manually moved to read the multiple tracks on the card.  I know this is not quite the answer you are looking for, but it may help point you in the right direction!  Here are some links to DIY mag card reading, software and hardware:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://stripesnoop.sourceforge.net/hardware/hardware.html&quot; rel=&quot;nofollow&quot;&gt;http://stripesnoop.sourceforge.net/hardware/hardware.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="368" LastActivityDate="2009-12-01T07:30:28.917" CommunityOwnedDate="2009-12-01T07:30:28.917" CommentCount="2" />
  <row Id="782" PostTypeId="1" AcceptedAnswerId="791" CreationDate="2009-12-01T09:53:19.223" Score="6" ViewCount="591" Body="&lt;p&gt;How would i set up an Arduino to do time lapse photography?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-24T21:46:04.803" LastActivityDate="2010-08-24T21:46:04.803" Title="Arduino for time lapse photography" Tags="&lt;arduino&gt;&lt;timer&gt;" AnswerCount="5" />
  <row Id="783" PostTypeId="2" ParentId="782" CreationDate="2009-12-01T10:34:00.890" Score="2" ViewCount="" Body="&lt;p&gt;There is a great example of &lt;a href=&quot;http://luckylarry.co.uk/2009/07/arduino-motion-triggered-camera/&quot; rel=&quot;nofollow&quot;&gt;Arduino motion tiggered camera&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It uses a PIR (Pyroelectric InfraRed) sensor to switch the camera on when the motion is detected.&lt;/p&gt;&#xA;" OwnerUserId="337" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-01T20:47:34.813" LastActivityDate="2009-12-01T20:47:34.813" CommentCount="2" />
  <row Id="784" PostTypeId="2" ParentId="782" CreationDate="2009-12-01T11:01:50.643" Score="5" ViewCount="" Body="&lt;p&gt;Google for &quot;arduino intervalometer&quot;.  The triggering method depends on what kind of camera you have.  Most (hopefully &lt;em&gt;all&lt;/em&gt;) dSLRs have external remotes, and most of those are electronic, so you can drive an optoisolator from the Arduino to make the shutter connection.  Canon's consumer line of dSLRs (like the Rebel XT) have an IR remote, so you could use an IR LED to send the shutter command.  Failing either of those, you could always use a servo to press the button.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-12-01T11:01:50.643" />
  <row Id="785" PostTypeId="1" CreationDate="2009-12-01T11:10:28.853" Score="4" ViewCount="664" Body="&lt;p&gt;I am looking to power a PIC microcontroller with a supply voltage that ranges from 4.5V to 18V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will be a battery powered device so I would like to conserve power, ie. linear regulators like the 7805 is less desirable. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also the application will be producing quite a bit of heat in an enclosed space so no need to add to heat generation with the linear regulator dissipating excess voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After some hunting I suppose I am after a switch mode DC-DC converter, a step down one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been looking at an LM2575 based circuit, but wondering what Vout would be if my supply Vin drops below the minimum 7V for regulation. The PIC I am working with have an operating range of 2V to 5.5V so I am OK with Vout being equal to Vin when Vin &amp;lt; regulation threshold. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is, what happens to Vout when Vin &amp;lt; regulation threshold?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also are there any additional things/circuits I should be considering?&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-01T22:03:22.457" LastActivityDate="2010-06-15T23:46:12.290" Title="Wide voltage supply for PIC microcontroller" Tags="&lt;pic&gt;&lt;power&gt;&lt;voltage&gt;&lt;microcontroller&gt;&lt;battery&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="786" PostTypeId="2" ParentId="785" CreationDate="2009-12-01T12:22:35.883" Score="5" ViewCount="" Body="&lt;p&gt;When Vin goes below your minimum Vin you are going to have your output drop. I have seen many times that people think it will be a small drop and it ends up dropping very quickly when the Vin goes to low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want something that give you 5 out from 4.5 to 18V in, then you should just pick a simple Buck-Boost DC-DC converter. They will be able to handle from 2V to higher than 18 without a problem. By grace of being a buck boost, they can step your voltage either direction and it should make your life quite easy.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2009-12-01T23:13:56.963" LastActivityDate="2009-12-01T23:13:56.963" />
  <row Id="787" PostTypeId="2" ParentId="739" CreationDate="2009-12-01T12:40:18.277" Score="4" ViewCount="" Body="&lt;p&gt;A fellow named Anthony Burch has put together a &lt;a href=&quot;http://www.burched.com/freevideos.ag.php&quot; rel=&quot;nofollow&quot;&gt;descent series of videos about FPGAs&lt;/a&gt;. One of the free ones includes information about how to choose an FPGA.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-12-01T12:40:18.277" />
  <row Id="788" PostTypeId="2" ParentId="739" CreationDate="2009-12-01T15:48:48.007" Score="1" ViewCount="" Body="&lt;p&gt;Have a look at &lt;a href=&quot;http://www.xmos.com&quot; rel=&quot;nofollow&quot;&gt;XMOS&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They may be used to replace FPGAs in many applications.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-03T14:16:14.340" LastActivityDate="2010-11-03T14:16:14.340" />
  <row Id="790" PostTypeId="2" ParentId="765" CreationDate="2009-12-01T18:45:20.940" Score="6" ViewCount="" Body="&lt;p&gt;I use a cheap stud sensor from the local hardware store with a photo transistor to sense the indicator led.  With this glued to the side of the tank it senses when the level rises above the sensor and alerts us to a high water condition.&lt;/p&gt;&#xA;" OwnerUserId="375" LastActivityDate="2009-12-01T18:45:20.940" />
  <row Id="791" PostTypeId="2" ParentId="782" CreationDate="2009-12-01T18:45:38.040" Score="6" ViewCount="" Body="&lt;p&gt;I did this by splicing into my Canon's remote shutter release (it has 3 conductors, so I used an 1/8&quot; stereo headphone jack as the connector).  That way I can put the ends back together and use it like normal, or I can plug it into an arduino and control it digitally. I drive it by connecting a digital output from the arduino to the base of a transistor (the other two connectors on the transistor went to ground and another of the conductors from the cable).  You'll have to experiment with your cable to find what works&#xA;on your particular camera model.  If I'd had an optoisolator it would have made sense&#xA;to use that instead of the transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that, it's a matter of figuring out how to sleep your arduino.  You can start with&#xA;a basic call to delay().  For truly long runs you may wish to use the watchdog timer or&#xA;a RTC to the system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tips:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You want to keep the button &quot;pressed&quot;&#xA;for just long enough to trip the&#xA;shutter - 100ms is probably good.&lt;/li&gt;&#xA;&lt;li&gt;Turn off auto-focus.  Set your lens&#xA;on manual focus, otherwise you'll &#xA;get unpredictable results.  In low&#xA;light you may not get anything at all.&lt;/li&gt;&#xA;&lt;li&gt;Alternatively, set the camera to single&#xA;exposure mode and leave the button down&#xA;except for a short period before each new&#xA;exposure.  You won't know when the exposure&#xA;goes off each time, but you'll have a good&#xA;chance of getting one some time while&#xA;you have it down. &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-12-01T18:45:38.040" CommentCount="1" />
  <row Id="792" PostTypeId="2" ParentId="708" CreationDate="2009-12-01T18:45:47.900" Score="5" ViewCount="" Body="&lt;p&gt;There are ICs available specifically for level-shifting I2C:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;LTC4300A-2 (&lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1007,C1070,P2296&quot; rel=&quot;nofollow&quot;&gt;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1007,C1070,P2296&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;li&gt;PCA9306 (&lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/pca9306.html&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/docs/prod/folders/print/pca9306.html&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I don't know what kind of constraints you have on your design, but I would think using a dedicated IC would be easier then coming up with your own solution.&lt;/p&gt;&#xA;" OwnerUserId="327" LastActivityDate="2009-12-01T18:45:47.900" />
  <row Id="793" PostTypeId="2" ParentId="464" CreationDate="2009-12-01T18:51:35.937" Score="4" ViewCount="" Body="&lt;p&gt;The CAN bus communication scheme and CANOpen.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2009-12-01T18:51:35.937" CommunityOwnedDate="2009-12-01T18:51:35.937" CommentCount="3" />
  <row Id="794" PostTypeId="2" ParentId="782" CreationDate="2009-12-01T20:39:03.663" Score="3" ViewCount="" Body="&lt;p&gt;If you're using a compact canon camera, try using &lt;a href=&quot;http://chdk.wikia.com/wiki/CHDK&quot; rel=&quot;nofollow&quot;&gt;chdk&lt;/a&gt;. This project provides hacked firmware for many different models and allows for things like time lapse control. It's not an Arduino, but it will get the job done.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-12-01T20:39:03.663" />
  <row Id="795" PostTypeId="1" AcceptedAnswerId="835" CreationDate="2009-12-01T21:40:06.523" Score="6" ViewCount="354" Body="&lt;p&gt;We have been given a project at uni to create a multi touch display.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done some research into this and a lot of them call for special film on the glass or use a &lt;a href=&quot;http://www.instructables.com/id/interactive-Multitouch-Display/&quot; rel=&quot;nofollow&quot;&gt;projector&lt;/a&gt; (meaning it needs a certain amount of darkness).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to make a multi touch screen that can be used in full daylight (outdoors) and not more than a few cm behind glass - has anyone come across such a project?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It needs to be about a 42&quot; screen size - so not a small pre-made one.&lt;/p&gt;&#xA;" OwnerUserId="267" LastEditorUserId="143" LastEditorDisplayName="" LastEditDate="2009-12-03T04:00:45.247" LastActivityDate="2010-07-17T01:59:05.293" Title="Create multi touch display for full light" Tags="&lt;projects&gt;&lt;display&gt;&lt;light&gt;&lt;homework&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="796" PostTypeId="2" ParentId="726" CreationDate="2009-12-01T21:42:54.977" Score="3" ViewCount="" Body="&lt;p&gt;Yes, it completely depends on the interface of the camera. Do you already have a VGA camera? Tell us about it, and maybe we can give you some tips. But overall, this question is very vague, and hints that you haven't really done any work yourself. Try getting something done, and then come back when you have a specific question.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-01T21:42:54.977" />
  <row Id="797" PostTypeId="2" ParentId="661" CreationDate="2009-12-01T21:56:06.860" Score="2" ViewCount="" Body="&lt;p&gt;Yeah, average solar panels wont put out enough power to run most RC cars. The exception are expensive high quality solar panels, combined with very carefully engineered lightweight &amp;amp; efficient car. &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-01T21:56:06.860" />
  <row Id="798" PostTypeId="2" ParentId="782" CreationDate="2009-12-01T22:51:11.607" Score="4" ViewCount="" Body="&lt;p&gt;I had written a little while back a detailed guide to implementing one's first arduino intervalometer.  The link is here: &lt;a href=&quot;http://openmoco.org/node/88&quot; rel=&quot;nofollow&quot;&gt;Arduino Intervalometer Basics&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The difference between this and other examples, is that it provides not only the standard &quot;pinmode, delay, pinmode&quot;-style control, but also introduces the reader to non-blocking timing concepts, and discusses the benefits and drawbacks of each programming method.  In addition, it walks the reader through a series of tests to make sure they understand the concept well before they try to hook up the camera.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, no one can tell you how to control your camera, unless you tell us what kind of camera you are using.  But, in most cases, it is pretty simple.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, once you really get into it, check out the whole openmoco project, which does a lot more than just interval shooting. =)&lt;/p&gt;&#xA;" OwnerUserId="36" LastActivityDate="2009-12-01T22:51:11.607" />
  <row Id="799" PostTypeId="2" ParentId="627" CreationDate="2009-12-01T23:26:47.557" Score="2" ViewCount="" Body="&lt;p&gt;Another good resource is &lt;a href=&quot;http://anaheimautomation.com/&quot; rel=&quot;nofollow&quot;&gt;Anaheim Automation&lt;/a&gt; - especially if you're looking for a wide variety of stepper form factors at an excellent price.  While they don't do online ordering, they are very easy to deal with as a hobbyist on the phone.  They also provide CAD and full diagrams on their motor models, making it easy to determine what will fit in your project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Full disclosure: I am not an employee of AA, but I am a satisfied customer =)&lt;/p&gt;&#xA;" OwnerUserId="36" LastActivityDate="2009-12-01T23:26:47.557" CommentCount="1" />
  <row Id="800" PostTypeId="1" AcceptedAnswerId="810" CreationDate="2009-12-01T23:46:31.113" Score="2" ViewCount="155" Body="&lt;p&gt;I can't get data off my ARM LPC2378 microcontroller - does it need UART or can any GPIO be used?&lt;/p&gt;&#xA;" OwnerUserId="267" LastActivityDate="2009-12-02T23:56:50.813" Title="Reading a ARM microcontroller" Tags="&lt;microcontroller&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="801" PostTypeId="1" CreationDate="2009-12-02T00:46:09.940" Score="6" ViewCount="802" Body="&lt;p&gt;I've recently bought an Olimx ARM-USB-OCD JTAG programmer but I've had difficulty getting it to work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My primary system is linux, but I've tested it in window with no luck there either. I'm using OpenOCD to communicate with the device, but it does not detect the ftdi chip on the programmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect the hardware is dodgy, for two reasons. The programmer has the ability to power a board at 5V,9V or 12V, but when I measure the output voltage it is only at 0.7~1V (when connected to USB, tested on 3 different computers and one usb hub); additionally, when conncted to linux, the ftdi chip is detected, but it connects and disconnect quickly leaving a number of errors in syslog.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are (and I'm most interested in anyone who has the same programmer): is the hardware broken? If not, what am I likely to be doing wrong?&lt;/p&gt;&#xA;" OwnerUserId="378" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2010-04-13T11:28:20.013" LastActivityDate="2010-04-13T11:28:20.013" Title="Olimex Arm USB JTAG Programmer Problems" Tags="&lt;jtag&gt;&lt;linux&gt;&lt;detection&gt;&lt;programmer&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="802" PostTypeId="2" ParentId="801" CreationDate="2009-12-02T01:35:30.217" Score="7" ViewCount="" Body="&lt;p&gt;Check how much current your board needs. From memory, the ARM-USB-OCD can only supply a few 10's of milliamps. It is not uncommon for a dev board to use a couple of hundred. As a trouble shooting step, try getting openocd to communicate with the JTAG adapter without it connected to the board. &lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-12-02T01:35:30.217" CommentCount="2" />
  <row Id="804" PostTypeId="1" CreationDate="2009-12-02T06:50:44.730" Score="6" ViewCount="195" Body="&lt;p&gt;I need some ideas of sensors to use so my tank can drive towards humans and seek them out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Distinguishing them from the background.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assume the human is standing still / quitely&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;looking to use an Arduino as the controller - though if there are better options please let me know.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="337" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-02T07:37:00.370" LastActivityDate="2009-12-09T17:05:17.677" Title="Robot picking a person from other objects" Tags="&lt;robotics&gt;&lt;sensor&gt;" AnswerCount="7" FavoriteCount="2" />
  <row Id="805" PostTypeId="2" ParentId="804" CreationDate="2009-12-02T07:19:33.647" Score="3" ViewCount="" Body="&lt;p&gt;What kind of platform are you using to run the robot. If you are running a like an ARM processor (with linux) than you can use a camera and OpenCV, but if you are using an Arduino or somethings along those lines that wont work. An arduino will be tough and definitely wont run OpenCV.&lt;/p&gt;&#xA;" OwnerUserId="81" LastEditorUserId="81" LastEditorDisplayName="" LastEditDate="2009-12-07T05:44:29.293" LastActivityDate="2009-12-07T05:44:29.293" />
  <row Id="806" PostTypeId="2" ParentId="785" CreationDate="2009-12-02T07:32:49.973" Score="1" ViewCount="" Body="&lt;p&gt;The LM2575 has a drop out voltage of less than 1.5 V. You could stick with the simple buck regulator and set its output voltage to 3 V, assuming you have the adjustable type. &lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-12-02T07:32:49.973" />
  <row Id="807" PostTypeId="2" ParentId="401" CreationDate="2009-12-02T07:43:22.063" Score="2" ViewCount="" Body="&lt;p&gt;Take a look at ORing MOSFET controllers like the LTC4412 (&lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1142,C1079,P2220&quot; rel=&quot;nofollow&quot;&gt;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1142,C1079,P2220&lt;/a&gt;) and Maxim's MAX5079 (&lt;a href=&quot;http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4606&quot; rel=&quot;nofollow&quot;&gt;http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4606&lt;/a&gt;). A little more complicated (and expensive) then using diodes in parallel. However, the supply voltage drop and power dissipation will be minimal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do go ahead with the diodes, remember that no two diodes have the exact same forward voltage. So, the tolerances could work out such that the circuit is powered by the USB even if ATX is plugged in.&lt;/p&gt;&#xA;" OwnerUserId="327" LastActivityDate="2009-12-02T07:43:22.063" />
  <row Id="809" PostTypeId="2" ParentId="804" CreationDate="2009-12-02T10:25:31.143" Score="3" ViewCount="" Body="&lt;p&gt;OpenCV as zklapow says will allow you to use Haar Training to train the camera/controller to recognise faces or other shapes (this is how face recognition is done on my camera I think) but I'm not sure what resources there are available for Arduino. There's what looks like a fairly detailed discussion &lt;a href=&quot;http://note.sonots.com/SciSoftware/haartraining.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; using OpenCV. There's an interesting looking page &lt;a href=&quot;http://www.quotientrobotics.com/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; which is talking about haartraining and robots (recognising hands to be specific).&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-02T10:25:31.143" CommentCount="1" />
  <row Id="810" PostTypeId="2" ParentId="800" CreationDate="2009-12-02T10:32:36.980" Score="3" ViewCount="" Body="&lt;p&gt;You need a level converter to actually use the UART (connecting to a PC, for example).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out this schematic &lt;a href=&quot;http://www.keil.com/mcb2300/mcb2300-schematics.pdf&quot; rel=&quot;nofollow&quot;&gt;Keil eval board&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="379" LastActivityDate="2009-12-02T10:32:36.980" />
  <row Id="811" PostTypeId="2" ParentId="804" CreationDate="2009-12-02T12:04:14.970" Score="3" ViewCount="" Body="&lt;p&gt;An infrared camera would be perfect.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-12-02T12:04:14.970" CommentCount="3" />
  <row Id="812" PostTypeId="1" CreationDate="2009-12-02T13:17:10.393" Score="4" ViewCount="625" Body="&lt;p&gt;I am running a battery powered device, and would like my microcontroller (PIC) to report on the supply voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is so I can determine how many batteries is used in the supply, and also the state of charge of the battery pack. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Supply voltage ranges from 4xD (either 1.2V nominal NiMH or 1.5V Alkalines making about 6V) to 12xAA (1.2V NiMH for 14.4V or 1.5V Alkaline for 18V). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My PIC is running off a regulated 5V supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I plan to use one of the ADC ports to measure the voltage, and therefore believe I should map the 18V f.s.d. to the range 0-5V, so roughly I'd need to divide the input voltage by 3.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've heard of using a resistor voltage divider, but know that it can be wasteful in terms of energy consumed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wondering if there is a better way to achieve this voltage division without too much energy loss/wastage?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-02T20:56:50.653" LastActivityDate="2009-12-02T20:56:50.653" Title="PIC voltage measurement" Tags="&lt;pic&gt;&lt;voltage&gt;&lt;battery&gt;&lt;energy&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="813" PostTypeId="2" ParentId="785" CreationDate="2009-12-02T13:21:43.970" Score="1" ViewCount="" Body="&lt;p&gt;Thanks for the responses everyone. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll check out the adjustable mode for the LM2575 Clint.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Kortuk: are there any buck-boost solutions you recommend or can point me to? The primary criterion would be low part count, secondary criterion being good efficiency. &lt;/p&gt;&#xA;" LastActivityDate="2009-12-02T13:21:43.970" CommentCount="4" />
  <row Id="814" PostTypeId="2" ParentId="812" CreationDate="2009-12-02T14:25:36.230" Score="7" ViewCount="" Body="&lt;p&gt;you want a voltage divider. if you care about power dissipation, there are a couple of things you can do:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;use a fairly high impedance voltage divider, with a capacitor on the output terminal, and buffer it with a low-power op-amp. Make sure you use an RC filter between op-amp and ADC, values of this RC filter are typically around 50-200 ohms, 1000pf. This serves to keep voltage stable when the ADC is switching between channels and charge is transferred between the ADC's internal capacitor and the outside pin. An op-amp alone cannot do this. If you don't buffer the high-impedance voltage divider, you will get errors due to ADC leakage current and charge transfer.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;switch the voltage divider, e.g. connect/disconnect it to the supply voltage, so you can do this only occasionally when you want. A PFET would work, just be careful with how you drive it.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-02T14:25:36.230" CommentCount="4" />
  <row Id="815" PostTypeId="1" CreationDate="2009-12-02T16:23:11.323" Score="9" ViewCount="1265" Body="&lt;p&gt;is there any project of an rtos that works on arduino ?&lt;/p&gt;&#xA;" OwnerUserId="199" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:32:14.507" LastActivityDate="2010-12-10T22:32:14.507" Title="RTOS for Arduino ?" Tags="&lt;arduino&gt;&lt;rtos&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="4" />
  <row Id="816" PostTypeId="2" ParentId="815" CreationDate="2009-12-02T16:31:18.523" Score="4" ViewCount="" Body="&lt;p&gt;I have been using &lt;a href=&quot;http://femtoos.org/&quot; rel=&quot;nofollow&quot;&gt;FemtoOS&lt;/a&gt; in few projects and it works very well.&lt;/p&gt;&#xA;" OwnerUserId="13" LastActivityDate="2009-12-02T16:31:18.523" />
  <row Id="817" PostTypeId="2" ParentId="815" CreationDate="2009-12-02T16:33:03.593" Score="5" ViewCount="" Body="&lt;p&gt;Here is a good summary of the &lt;a href=&quot;http://www.out--there.com/blog/rtos-for-arduino/&quot; rel=&quot;nofollow&quot;&gt;current offerings&lt;/a&gt; - the favorite looks like &lt;a href=&quot;http://robotgroup.com.ar/noticias/20091102/duinos-sistema-operativo-multitarea-para-arduino&quot; rel=&quot;nofollow&quot;&gt;DuinOS&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also consider &lt;a href=&quot;http://github.com/geekscape/Aiko&quot; rel=&quot;nofollow&quot;&gt;Aiko&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-12-02T16:33:03.593" />
  <row Id="818" PostTypeId="2" ParentId="627" CreationDate="2009-12-02T18:51:46.450" Score="1" ViewCount="" Body="&lt;p&gt;American Science and Surplus!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sciplus.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.sciplus.com/&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2009-12-02T18:51:46.450" CommentCount="1" />
  <row Id="820" PostTypeId="2" ParentId="627" CreationDate="2009-12-02T20:26:01.753" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.solarbotics.com/&quot; rel=&quot;nofollow&quot;&gt;Solarbotics&lt;/a&gt; has a nice selection of &lt;a href=&quot;http://www.solarbotics.com/motors%5Faccessories/&quot; rel=&quot;nofollow&quot;&gt;Motors and accessories&lt;/a&gt;.  They appear to ship internationally (from Canada).&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-12-02T20:26:01.753" />
  <row Id="821" PostTypeId="2" ParentId="804" CreationDate="2009-12-02T20:30:04.233" Score="6" ViewCount="" Body="&lt;p&gt;A smart sensor might help -- take a look at the &lt;a href=&quot;http://www.cmucam.org/&quot; rel=&quot;nofollow&quot;&gt;CMUcam&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-12-02T20:30:04.233" />
  <row Id="822" PostTypeId="2" ParentId="812" CreationDate="2009-12-02T20:37:18.270" Score="4" ViewCount="" Body="&lt;p&gt;Jason S has provided a good suggestion for how you can reduce the power if required. But before making life more complicated for youself, it's possible to determine how much power you can really afford.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For any low power design, you should consider the overall power budget. For a battery powered device this will usually be determined by the desired life of the batteries. If the combined power of the rest of the circuit is significantly more than the resistor divider, then either you don't need to worry about it or you've got other power hungry parts of the circuit to worry about.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-12-02T20:37:18.270" CommentCount="4" />
  <row Id="823" PostTypeId="1" CreationDate="2009-12-02T20:56:03.223" Score="4" ViewCount="871" Body="&lt;p&gt;I'm running Virtual Wire between two Arduino's and, so far I've been able to  send characters and receive them on the other side.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Problem is, how do I turn this received 'A' (or whatever I send) into an action to operate a few digital outputs. (it's a relay circuit configured as an H-bridge)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Below is the sample receiver program included with VirtualWire.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// receiver.pde&#xA;//&#xA;// Simple example of how to use VirtualWire to receive messages&#xA;// Implements a simplex (one-way) receiver with an Rx-B1 module&#xA;&#xA;&#xA;#include &amp;lt;VirtualWire.h&amp;gt;&#xA;&#xA;int twoPin = 2;     //the two pins to be used to control the relays&#xA;int fourPin = 4;&#xA;&#xA;void setup()&#xA;{&#xA;  pinMode(twoPin, OUTPUT);&#xA;  pinMode(fourPIn, OUTPUT);&#xA;&#xA;  Serial.begin(9600);   // Debugging only&#xA;  Serial.println(&quot;setup&quot;);&#xA;&#xA;  // Initialise the IO and ISR&#xA;  vw_set_ptt_inverted(true); // Required for DR3100&#xA;  vw_setup(2000);    // Bits per sec&#xA;&#xA;  vw_rx_start();       // Start the receiver PLL running&#xA;}&#xA;&#xA;void loop()&#xA;{&#xA;  uint8_t buf[VW_MAX_MESSAGE_LEN];&#xA;  uint8_t buflen = VW_MAX_MESSAGE_LEN;&#xA;&#xA;  if (vw_get_message(buf, &amp;amp;buflen)) // Non-blocking&#xA;  {&#xA;    int i;&#xA;&#xA;    digitalWrite(13, true); // Flash a light to show received good message&#xA;    // Message with a good checksum received, dump it.&#xA;    Serial.print(&quot;Got: &quot;);&#xA;&#xA;    for (i = 0; i &amp;lt; buflen; i++)&#xA;    {&#xA;      Serial.print(buf[i], HEX);&#xA;      Serial.print(&quot; &quot;);&#xA;    }&#xA;    Serial.println(&quot;&quot;);&#xA;    digitalWrite(13, false);&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-04-23T04:30:09.477" LastActivityDate="2011-04-23T04:30:09.477" Title="Virtual Wire Control" Tags="&lt;wire&gt;&lt;arduino&gt;&lt;wireless&gt;&lt;relay&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="824" PostTypeId="1" AcceptedAnswerId="837" CreationDate="2009-12-02T20:59:25.127" Score="28" ViewCount="1013" Body="&lt;p&gt;I have seen many articles that tell me I should be using RTOS for time management and resource management. My time has not permitted my own research, so I come to chiphacker for advice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use low resource microcontrollers(MSP430, PIC) and was looking for RTOSs I can use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To the point:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Resource cost of system&lt;/li&gt;&#xA;&lt;li&gt;Advantages of system&lt;/li&gt;&#xA;&lt;li&gt;Disadvantages of system&lt;/li&gt;&#xA;&lt;li&gt;Implementation Tricks&lt;/li&gt;&#xA;&lt;li&gt;Situations the RTOS should/should&#xA;not be used in.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I do not use systems like the arduino, the projects I work with cannot support the cost of such a system.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2009-12-03T03:01:57.717" LastActivityDate="2011-03-16T15:15:26.077" Title="RTOS for Embedded Systems" Tags="&lt;pic&gt;&lt;rtos&gt;&lt;embedded&gt;&lt;microcontroller&gt;" AnswerCount="9" CommentCount="3" FavoriteCount="11" />
  <row Id="825" PostTypeId="1" AcceptedAnswerId="826" CreationDate="2009-12-02T21:17:17.587" Score="7" ViewCount="500" Body="&lt;p&gt;Anyone have any recommendations on a good rs232-to-usb converter. There are a lot out there and from the looks of it some are hit or miss. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good driver support is a must.&lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2010-07-09T14:29:28.423" Title="RS232-to-USB Converter" Tags="&lt;usb&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="826" PostTypeId="2" ParentId="825" CreationDate="2009-12-02T21:27:34.560" Score="17" ViewCount="" Body="&lt;p&gt;Any FT232 chip is good(ie FT232R). The drivers are publicly available and windows will download automatically. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will show up as a serial port and there are many pre-built solutions available. The Company that makes the FT232 chips, &lt;a href=&quot;http://www.ftdichip.com/&quot; rel=&quot;nofollow&quot;&gt;FTDI&lt;/a&gt;, will sell many solutions they developed in-house, also.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2009-12-02T21:56:44.567" LastActivityDate="2009-12-02T21:56:44.567" CommentCount="6" />
  <row Id="827" PostTypeId="2" ParentId="825" CreationDate="2009-12-02T22:38:58.087" Score="3" ViewCount="" Body="&lt;p&gt;I have used the Prolific chipset in &lt;a href=&quot;http://www.serialio.com/products/adaptors/usb%5Fserial%5FWinDesk.php&quot; rel=&quot;nofollow&quot;&gt;this product&lt;/a&gt; and it is extremely reliable. Like the FT232, it shows up as a serial port. I have used it in many of my projects without problems, the best example would be &lt;a href=&quot;http://thisismyrobot.blogspot.com/search/label/project%3A%20google%20calculator&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; where it survived me pulling the rs232 end apart to connect directly to some of the pins.&lt;/p&gt;&#xA;" OwnerUserId="25" LastActivityDate="2009-12-02T22:38:58.087" />
  <row Id="828" PostTypeId="1" CreationDate="2009-12-02T23:44:40.130" Score="5" ViewCount="663" Body="&lt;p&gt;Hiya :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to get my ArduinoBT to be a bit more power friendly, I have it running in a sensor network and it is constantly drawing power.  I want to be able to turn off or put the Bluetooth module to sleep for durations when it isn't in use.&lt;br /&gt;&#xA;I've tried &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Serial.println(&quot;SET CONTROL CONFIG 103d&quot;);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;In my setup method which should put the module into deep sleep mode but it doesn't seem to do anything in terms of power consumption (still draws about 30mA).&lt;br /&gt;&#xA;Am I not waiting long enough for it to kick in?  Does the WT11 iWRAP version not support deep sleep? Am I putting it in the wrong spot in my code?  Am I doing something else incredibly ditzy that is stopping it from working??&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-03T07:38:38.273" LastActivityDate="2010-01-07T00:20:11.473" Title="Bluetooth power saving mode for ArduinoBT" Tags="&lt;bluetooth&gt;&lt;arduino&gt;&lt;power&gt;&lt;save&gt;&lt;sleep&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="829" PostTypeId="2" ParentId="800" CreationDate="2009-12-02T23:56:50.813" Score="1" ViewCount="" Body="&lt;p&gt;If you're talking about connecting the processor's UART to a PC's serial port, you can now get USB to RS232/TTL converters. One end goes into your PC's USB socket, and appears as a normal serial port; the other comes out to 5 V or 3.3 V signals that can be connected directly to your processor, with no level-shifting required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We've used &lt;a href=&quot;http://www.ftdichip.com/Products/EvaluationKits/TTL-232R-3V3.htm&quot; rel=&quot;nofollow&quot;&gt;TTL-232R-3V3&lt;/a&gt; from FDTI Chip, which works perfectly for this kind of application.&lt;/p&gt;&#xA;" OwnerUserId="387" LastActivityDate="2009-12-02T23:56:50.813" />
  <row Id="830" PostTypeId="2" ParentId="825" CreationDate="2009-12-03T00:00:53.050" Score="3" ViewCount="" Body="&lt;p&gt;I agree with Kortuk's recommendation for FDTI, such as the &lt;a href=&quot;http://www.ftdichip.com/Products/EvaluationKits/TTL-232R-3V3.htm&quot; rel=&quot;nofollow&quot;&gt;TTL-232R-3V3&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Don't yet have the rep to comment or upvote).&lt;/p&gt;&#xA;" OwnerUserId="387" LastActivityDate="2009-12-03T00:00:53.050" CommentCount="1" />
  <row Id="831" PostTypeId="2" ParentId="824" CreationDate="2009-12-03T00:05:08.160" Score="16" ViewCount="" Body="&lt;p&gt;Have you tried &lt;a href=&quot;http://www.freertos.org/&quot; rel=&quot;nofollow&quot;&gt;FreeRTOS&lt;/a&gt;? It's &lt;strong&gt;free&lt;/strong&gt; (subject to T&amp;amp;C), and has been ported to both the MSP430, and several flavours of PIC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's small compared to some others, but this also makes it easy to learn, especially if you haven't used an RTOS before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A (non-free) commercial license is available, as well as a IEC 61508/SIL 3 version.&lt;/p&gt;&#xA;" OwnerUserId="387" LastActivityDate="2009-12-03T00:05:08.160" CommentCount="1" />
  <row Id="832" PostTypeId="2" ParentId="825" CreationDate="2009-12-03T01:31:31.770" Score="5" ViewCount="" Body="&lt;p&gt;USB-to-serial adapters live and die by their driver support.  In my experience, FTDI has great support on all three OSes (Mac OS X, Windows, Linux), but the chips are a bit more expensive.  I remember Prolific having great support on Linux, but the Mac drivers kinda sucked.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-03T01:31:31.770" CommentCount="1" />
  <row Id="833" PostTypeId="2" ParentId="825" CreationDate="2009-12-03T03:33:56.720" Score="3" ViewCount="" Body="&lt;p&gt;Are you looking for a chip, or an actual device?  Keyspan used to make great devices - usually a USB to DB-9 adapter.  I haven't had cause to buy a new one lately.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the chip front I've been nothing but happy with the various FTDI based solutions I've tried (though they were all going to TTL-serial, instead of RS-232).&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-12-03T03:33:56.720" CommentCount="1" />
  <row Id="834" PostTypeId="2" ParentId="828" CreationDate="2009-12-03T03:55:20.220" Score="4" ViewCount="" Body="&lt;p&gt;The code I'm running at the moment is just&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;setup()&#xA;{&#xA;    Serial.println(&quot;SET CONTROL CONFIG 103d&quot;);&#xA;}&#xA;&#xA;loop()&#xA;{&#xA;    Serial.println(&quot;SLEEP&quot;);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;but I've also tried the SLEEP command in the setup, and putting this code in the ArduinoBT bootloader.  I left the Arduino with sleep enabled running for several hours and it made no difference to the consumption, also &quot;SET CONTROL CONFIG 102d&quot; doesn't make any change.  Perhaps I'm issuing the commands in data mode?  I understand that data mode is when there is a Bluetooth connection and command is when there isn't a connection but I might be mistaken.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry I've taken so long had my exams and holidays.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My code eventually evolved to be something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int input = 0;    &#xA;int resetPin = 7;&#xA;int ledPin = 13;&#xA;&#xA;void setup()&#xA;{&#xA;  pinMode(resetPin, OUTPUT);&#xA;  Serial.begin(115200);&#xA;  Serial.println(&quot;SET CONTROL ESCAPE 43 00 0&quot;);&#xA;  Serial.println(&quot;SET CONTROL CONFIG 103D&quot;);&#xA;  digitalWrite(ledPin, HIGH);&#xA;}&#xA;&#xA;void loop()&#xA;{&#xA;  if (!input)&#xA;  {&#xA;    delay(2000);&#xA;    Serial.print(&quot;+++&quot;);&#xA;    delay(2000);&#xA;    Serial.println(&quot;TEST DEEPSLEEP&quot;);&#xA;    delay(10000);&#xA;    Serial.print(&quot;+++&quot;);&#xA;    delay(2000);&#xA;    input = 1;&#xA;    digitalWrite(ledPin, LOW);&#xA;  }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Which doesn't work (YAY!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I then found some code &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1199569902/0&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; which had successful iWRAP communication, I modified it to include the iWRAP I wanted, started with &quot;INFO&quot; and found out the version of iWRAP (WRAP THOR AI 2.2.0 build 60) obtained the correct datasheet found that deepsleep was  feature of the module and that you could test it using the &quot;TEST DEEPSLEEP&quot; command.  I used that command and the board slept! I think... the current sat at around 36mA which is higher than normal unconnected use but the board was incommunicable.  The test returned an OK so I'm confident that I can make the board sleep now.  Unfortunately issuing the &quot;SLEEP&quot; command doesn't seem to do anything atm, though I don't know if my initial setup commands are being issued yet.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyhoo here is the (barely) modified code I'm using now.  Basically run it then enter &quot;&amp;amp;&quot; into the serial monitor and it goes to command mode and issues the commands you put in the code, enter &quot;@&quot; and it tells you the response to those commands.  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;EEPROM.h&amp;gt;&#xA;&#xA;int ledPin = 13;    	    // LED connected to digital pin 13&#xA;int resetPin = 7;   		// BT module uses pin 7 for reset&#xA;char inByte = 0;    	    // incoming serial byte&#xA;int  infoSize = 0 ;&#xA;void setup()    		  // run once, when the sketch starts&#xA;{&#xA;  pinMode(ledPin, OUTPUT);  // sets the digital pin as output&#xA;  pinMode(resetPin, OUTPUT);  &#xA;  Serial.begin(115200);   // start serial at 115200 kbs&#xA;&#xA;  Serial.println(&quot;SET CONTROL ESCAPE 43 00 0&quot;);&#xA;  Serial.println(&quot;SET CONTROL CONFIG 103D&quot;);&#xA;}&#xA;&#xA;void loop()&#xA;{&#xA;  // if we get a valid byte, read analog ins:&#xA;  if (Serial.available() &amp;gt; 0) {    &#xA;    inByte = getbyte();  // get incoming byte&#xA;    if (inByte == '&amp;amp;' ) { // look for a &amp;amp;&#xA;      Serial.print(&quot;Got an &amp;amp;  &quot;);&#xA;    infoSize = getInfo();&#xA;      Serial.println(&quot;Done&quot;);&#xA;    }&#xA;    else if (inByte == '@' ) { // look for a 0&#xA;    digitalWrite(ledPin, LOW); // set led LOW&#xA;        Serial.print(&quot;Get string:  &quot;);  &#xA;    for(int i=0;i&amp;lt;infoSize;i++)&#xA;        {&#xA;      Serial.print(EEPROM.read(i));&#xA;        }&#xA;    Serial.println();&#xA;    Serial.print(&quot;Cleared string  size: &quot;);&#xA;    Serial.println(infoSize);&#xA;    }     &#xA;  }&#xA;}&#xA;&#xA;int getInfo()&#xA;{&#xA;  int j=0;&#xA;  digitalWrite(ledPin, HIGH); // set led HIGH&#xA;  delay(2000);  &#xA;  Serial.print(&quot;+++&quot;);&#xA;  delay(2000);&#xA;&#xA;&#xA;  Serial.println(&quot;SLEEP&quot;);  //THIS IS WHERE YOU ENTER THE COMMANDS&#xA;                            //&quot;INFO&quot; and &quot;TEST DEEPSLEEP&quot; are both successful&#xA;                            //&quot;SLEEP&quot; isn't successful yet&#xA;&#xA;&#xA;  for (int i=0; i &amp;lt;= 10; i++){&#xA;    delay(1000);&#xA;    while (Serial.available() &amp;gt; 0 &amp;amp;&amp;amp; j &amp;lt;512) {    &#xA;    inByte = getbyte();  // get incoming byte    &#xA;    EEPROM.write(j, inByte);&#xA;    j++;&#xA;    }&#xA;    delay(1000);&#xA;  }  &#xA;  delay(2000);&#xA;  Serial.print(&quot;+++&quot;);&#xA;  delay(2000);&#xA;  digitalWrite(ledPin, LOW); // set led low&#xA;  return j;&#xA;}&#xA;&#xA;char getbyte()&#xA;{&#xA;  while (Serial.available() == 0) { //look for aviable data&#xA;    // do nothing, wait for incoming data&#xA;  }&#xA;  return Serial.read(); //return data if aviable&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Yay epic edit!&#xA;Thanks so much for your help, it's been invaluable to my journey :) &lt;/p&gt;&#xA;" OwnerUserId="386" LastEditorUserId="386" LastEditorDisplayName="" LastEditDate="2010-01-07T00:20:11.473" LastActivityDate="2010-01-07T00:20:11.473" CommentCount="3" />
  <row Id="835" PostTypeId="2" ParentId="795" CreationDate="2009-12-03T03:59:46.420" Score="4" ViewCount="" Body="&lt;p&gt;Most multi-touch displays have some form of an input unit, and a display.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The display can be a front-screen projector, a rear-screen projector, or a flat panel (LCD or plasma).  These are all well understood technologies, and your choice will be driven by cost and how it interacts with the input unit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The input unit can have more implementations.  When I write 'light' understand that it can be visible light or infrared.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Rear-projected light, reflected by touch points, read by rear camera.&lt;/li&gt;&#xA;&lt;li&gt;Front-projected light, interrupted by touch points, read by rear camera.&lt;/li&gt;&#xA;&lt;li&gt;Front-projected light, reflected by the surface, interrupted by touch points, read by front camera.&lt;/li&gt;&#xA;&lt;li&gt;Side-mounted LEDs and photo-transistors, with row/column scanning.&lt;/li&gt;&#xA;&lt;li&gt;Touch-sensitive, capacitive grid.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;That's just what I can think of off the top of my head.  Any of the back-projection modes can use visible light; for front-projection you'll be better off using infrared.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a more in-depth review, I suggest you do more research here:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Multi-touch&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Multi-touch&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://multi-touchscreen.com/&quot; rel=&quot;nofollow&quot;&gt;http://multi-touchscreen.com/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.billbuxton.com/multitouchOverview.html&quot; rel=&quot;nofollow&quot;&gt;http://www.billbuxton.com/multitouchOverview.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://electronics.howstuffworks.com/iphone2.htm&quot; rel=&quot;nofollow&quot;&gt;http://electronics.howstuffworks.com/iphone2.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.google.com/search?hl=en&amp;amp;q=multi-touch+technology&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/search?hl=en&amp;amp;q=multi-touch+technology&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="143" LastEditorUserId="143" LastEditorDisplayName="" LastEditDate="2009-12-03T04:15:17.230" LastActivityDate="2009-12-03T04:15:17.230" />
  <row Id="836" PostTypeId="2" ParentId="795" CreationDate="2009-12-03T05:06:53.320" Score="3" ViewCount="" Body="&lt;p&gt;Using it in sunlight rules out pretty much anything that uses infrared for detecting the&#xA;touch points. I used a DIY one and a surface and both are pretty useless as soon as sunlight &#xA;comes even if it shines trough a window.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What does work even in sunlight is the detection of special markers (color, form, etc) if that is an option.&lt;/p&gt;&#xA;" OwnerUserId="123" LastActivityDate="2009-12-03T05:06:53.320" CommentCount="1" />
  <row Id="837" PostTypeId="2" ParentId="824" CreationDate="2009-12-03T05:07:37.903" Score="15" ViewCount="" Body="&lt;p&gt;I haven't had much personal experience with RTOS's other than QNX (which is great on the whole but it's not cheap and I have had a really bad experience with a particular board vendor and QNX's we-don't-care attitude for systems other than their most common) which is too large for PICs and MSP430's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where you will benefit from an RTOS is in areas such as&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;thread management/scheduling&lt;/li&gt;&#xA;&lt;li&gt;inter-thread communications + synchronization&lt;/li&gt;&#xA;&lt;li&gt;I/O on systems with stdin/stdout/stderr or serial ports or ethernet support or a filesystem (not an MSP430 or PIC for the most part, except for the serial ports)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For peripherals of a PIC or MSP430: for serial ports I'd use a ring buffer + interrupts... something I write once per system and just reuse; other peripherals I don't think you'd find much support from an RTOS, as they are so vendor-specific.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need timing that is rock-solid to the microsecond, an RTOS probably won't help -- RTOS's have bounded timing, but typically do have timing jitter in their scheduling due to context switching delays... QNX running on a PXA270 had jitter in the tens of microseconds typical, 100-200us maximum, so I wouldn't use it for stuff that has to run faster than about 100Hz or which needs timing much more accurate than about 500us. For that kind of stuff you probably will have to implement your own interrupt handling. Some RTOS's will play nicely with that, and others will make it a royal pain: your timing and their timing may not be able to coexist well. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the timing/scheduling is not too complex, you may be better off using a well-designed state machine. I would highly recommend reading &lt;a href=&quot;http://books.google.com/books?id=gto-LlDP5TUC&quot; rel=&quot;nofollow&quot;&gt;Practical Statecharts in C/C++&lt;/a&gt; if you haven't already. We've used this approach in some of our projects where I work, and it's got some real advantages over traditional state machines for managing complexity.... which is really the only reason you need an RTOS.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-03T05:07:37.903" CommentCount="5" />
  <row Id="838" PostTypeId="1" CreationDate="2009-12-03T12:56:18.380" Score="6" ViewCount="230" Body="&lt;p&gt;Hi Guys, I'm putting together a cheat sheet. What are the essential equations to get on there? &lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2009-12-04T16:48:33.980" Title="Essential Equations for Cheat Sheet?" Tags="&lt;math&gt;&lt;electronics&gt;" AnswerCount="4" />
  <row Id="839" PostTypeId="2" ParentId="838" CreationDate="2009-12-03T13:52:12.517" Score="2" ViewCount="" Body="&lt;p&gt;For the workbench or for school?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Capacitor#DC%5Fcircuits&quot; rel=&quot;nofollow&quot;&gt;Exponential discharge of a capacitor.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/math/b/b/c/bbced795d66b70261dd6c365701b2468.png&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage%5Fdivider#Resistive%5Fdivider%5F2&quot; rel=&quot;nofollow&quot;&gt;Resistive Voltage divider.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/math/5/7/e/57eea512679f9735bace7bfc8959839c.png&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="198" LastEditorUserId="198" LastEditorDisplayName="" LastEditDate="2009-12-04T10:08:59.323" LastActivityDate="2009-12-04T10:08:59.323" CommentCount="1" />
  <row Id="840" PostTypeId="2" ParentId="838" CreationDate="2009-12-03T13:54:09.777" Score="4" ViewCount="" Body="&lt;p&gt;These are some from my classes that we use.&#xA;&lt;a href=&quot;http://cid-acbfe2d16cd0ace8.skydrive.live.com/self.aspx/Public/equations.pdf&quot; rel=&quot;nofollow&quot;&gt;equations.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-12-03T13:54:09.777" CommentCount="2" />
  <row Id="841" PostTypeId="2" ParentId="838" CreationDate="2009-12-03T14:01:50.413" Score="5" ViewCount="" Body="&lt;p&gt;Don't just put equations, for a workbench cheat sheet I would find other reference information  useful as well: Resistor color codings are great, as are the different value-encoding schemes used on capacitors.  I can't count the number of times I've had a brain fart and have had to pull out a cheat sheet to look up these things, and since you want to capture starting hobbyists as well these types of things are invaluable.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-12-03T14:01:50.413" />
  <row Id="842" PostTypeId="2" ParentId="828" CreationDate="2009-12-03T14:18:16.967" Score="1" ViewCount="" Body="&lt;p&gt;The spec sheet for the BlueGiga module gives an average supply current of 1.5 mA when the module is IDLE and Deep Sleep is ON.    The ArduinoBT page, though a bit light on details, implies the ArduinoBT  does support any configuration modes the BlueGiga is capable of, and the spec sheet on the BlueGiga site does say it is capable of the Deep Sleep mode, so that's out.  I doubt the Arduino is consuming 28.5 mA when idling, so  unless you have something else in the circuit it's probably somewhere in the code.  Would you post your code and schematic for further review?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;---EDIT---&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I looked a bit further into the iWire document I linked in the comment below.  Your understanding seems correct, but there's an override to force command mode: Issue the escape character three times (See Page 15).  Have you tried issuing three escape characters?  It also says on Page 15 that &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;When iWRAP enters to command mode&#xA;  READY event occurs (Unless masked away&#xA;  with “SET CONTROL ECHO” command.)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Are you listening for READY events?  On Page 23, for example, it appears that READY is issued over the serial port and you could quite easily listen for it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll also ask if you've reviewed your setup and connection code.  For example, serial communications with the BT module need to be at 115200 bps (&lt;a href=&quot;http://www.arduino.cc/en/Guide/ArduinoBT&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Guide/ArduinoBT&lt;/a&gt;).  I didn't see that line in your setup code, but you could try adding &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Serial.begin(115200)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;before the println statement in your setup() method.  You said that you posted all of the code, so this is probably the first thing I'd try.  If you don't set the baud rate properly, you're just sending garbage.  Keep us posted!&lt;/p&gt;&#xA;" OwnerUserId="11" LastEditorUserId="11" LastEditorDisplayName="" LastEditDate="2009-12-04T13:45:49.180" LastActivityDate="2009-12-04T13:45:49.180" CommentCount="1" />
  <row Id="843" PostTypeId="2" ParentId="823" CreationDate="2009-12-03T14:37:13.900" Score="5" ViewCount="" Body="&lt;p&gt;Unless I misunderstood the question, it should be as simple as extending the code where you print out what's in the buffer with some if-then statements.  For example your code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;for (i = 0; i &amp;lt; buflen; i++)&#xA;{&#xA;    Serial.print(buf[i], HEX);&#xA;    Serial.print(&quot; &quot;);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;goes through the received string and prints it out bit by bit.  If, instead, you want to know if you received an &quot;A&quot;, you can use:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if (buf[0] = &quot;A&quot;)&#xA;{&#xA;  //flip bits here&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You could also use a Case-Switch block to define several letters.  There are many ways to improve this code, including using strcmp so that you can send full words and not worry about case or terminations, but it's best to worry about that once you're off the ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I misunderstood the question, I apologize.  I'll be glad to try again with more information.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-12-03T14:37:13.900" CommentCount="1" />
  <row Id="844" PostTypeId="1" CreationDate="2009-12-03T14:50:03.020" Score="2" ViewCount="300" Body="&lt;p&gt;when a capacitor is connected in a network with dc source,if initially the switch is open at time t=0,does the capacitor act as an open ckt or short ckt at time t=0+?and why?wat abt the inductor? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;additional info:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i meant the same behaviour for the inductor. and i did try it out,what i got was this:initially when i opened the switch,the capacitor acted like a sc,but that shud not be happening right?coz,a capacitor shud behave as an open ckt to dc...and i tried with different caps........this bit has resulted in me being very confused......and the couple of people i asked cud not answer it very satisfactorily!&lt;/p&gt;&#xA;" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-03T20:48:33.177" LastActivityDate="2009-12-03T20:48:33.177" Title="capacitor behaviour" Tags="&lt;electronics&gt;&lt;homework&gt;&lt;capacitor&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="846" PostTypeId="2" ParentId="844" CreationDate="2009-12-03T15:22:54.043" Score="7" ViewCount="" Body="&lt;p&gt;A capacitors charge is given by Vt=V(1-e^(-t/RC)) where V is the applied voltage to the circuit, R is the series resistance and C is the parallel capacitance. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the exact instant power is applied, the capacitor has 0v of stored voltage and so consumes a theoretically infinite current limited by the series resistance. (A short circuit) As time continues and the charge accumulates, the capacitors voltage rises and it's current consumption drops until the capacitor voltage and the applied voltage are equal and no current flows into the capacitor (open circuit). This effect may not be immediately recognizable with smaller capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A nice page with graphs and some math explaining this is &lt;a href=&quot;http://webphysics.davidson.edu/physlet_resources/bu_semester2/c11_rc.html&quot; rel=&quot;nofollow&quot;&gt;http://webphysics.davidson.edu/physlet_resources/bu_semester2/c11_rc.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an inductor, the opposite is true, at the moment of power-on, when voltage is first applied, it has a very high resistance to the changed voltage and carries little current (open circuit), as time continues, it will have a low resistance to the steady voltage and carry lots of current (short circuit).&lt;/p&gt;&#xA;" OwnerUserId="243" LastActivityDate="2009-12-03T15:22:54.043" />
  <row Id="847" PostTypeId="2" ParentId="844" CreationDate="2009-12-03T15:26:26.730" Score="1" ViewCount="" Body="&lt;p&gt;When you turn on an ideal switch from an ideal voltage source, to an ideal capacitor you get some odd solutions, in this case infinite current for an infantessimal ( sp ) time. So it looks like a short for no time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More realistic solutions include more ideal element to model the real world, the first might be a series resistance.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-12-03T15:26:26.730" />
  <row Id="848" PostTypeId="1" AcceptedAnswerId="850" CreationDate="2009-12-04T06:26:07.350" Score="3" ViewCount="343" Body="&lt;p&gt;I am planning on an automation project that will be using several different sensors including but not limited to: Temperature, Barometric Pressure, Air flow, Humidity, etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As I was talking with someone they mentioned that I should look into RS-485 as a means to connecting my sensors to my controller. Then ultimately to the PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After a quick search I gathered some information about RS-485 but now I am wondering if it's over kill or if it's even used now a days?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Couldn't I just use a microcontroller that has enough inputs and interface with the PC using USB?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thoughts? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Ok if distance to controller and environment (in my case an industrial application) then RS485 might be useful. Are there other bus alternatives that might be more useful?&lt;/p&gt;&#xA;" OwnerUserId="245" LastEditorUserId="245" LastEditorDisplayName="" LastEditDate="2009-12-04T19:36:16.053" LastActivityDate="2009-12-04T21:09:55.807" Title="Should I consider using RS-485 for my next project" Tags="&lt;serial&gt;&lt;sensor&gt;" AnswerCount="7" />
  <row Id="849" PostTypeId="2" ParentId="848" CreationDate="2009-12-04T07:04:36.227" Score="2" ViewCount="" Body="&lt;p&gt;I would say the short answer is sensors-&gt;micro-controller-&gt;USB&#xA;But, you don't give us a lot of detail as to the environment you will be working in, or how robust the entire system needs to be. If you have a noisy environment, long distances between the sensors, or a requirement for high reliability then you might want to look at professionally built equipment and something like RS-485. If you want to track the micro-climate around your tomatoes then some sensors and an arduino might be all you need.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-12-04T07:04:36.227" CommentCount="1" />
  <row Id="850" PostTypeId="2" ParentId="848" CreationDate="2009-12-04T07:11:13.497" Score="4" ViewCount="" Body="&lt;p&gt;I've used RS485 to connect multiple data-loggers together over distances of up to 100m. In this application it worked perfectly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't used RS485 to connect sensors directly to a controller but if you have sensors with RS485 outputs + a controller that supports RS485 and you have more than 10 sensors or the sensors need to be more than a short distance from the controller I would definitely use RS485 instead of analogue wiring. I found that as you add more and more analogue sensors to a controller (in my case, a data-logger) small issues with power supply noise, wire impedance and environmental interference suddenly become big issues.&lt;/p&gt;&#xA;" OwnerUserId="25" LastActivityDate="2009-12-04T07:11:13.497" CommentCount="1" />
  <row Id="851" PostTypeId="1" AcceptedAnswerId="854" CreationDate="2009-12-04T10:31:25.477" Score="8" ViewCount="163" Body="&lt;p&gt;I'm thinking about selling a small batch of a simple gadget that would have some electronics inside.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I want to use an online shop and sell it worldwide, what are the certifications and licenses to be aware of? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I qualify something for the UE, can it be sold to the USA?&lt;/p&gt;&#xA;" OwnerUserId="198" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-04T10:57:00.253" LastActivityDate="2009-12-04T18:24:28.680" Title="Manufacturing, qualification and sale" Tags="&lt;prototyping&gt;&lt;development&gt;&lt;manufacturing&gt;" AnswerCount="2" CommentCount="6" FavoriteCount="2" />
  <row Id="852" PostTypeId="2" ParentId="848" CreationDate="2009-12-04T11:19:57.523" Score="2" ViewCount="" Body="&lt;p&gt;If your sensors are near the PC, then USB could be OK, but it's not always the case. I have an energy meter in my house basement, and the computer that reads energy values is in my apartment (4th floor) ... No problem with RS485 (or a CAN bus), but try this with USB :-) &lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2009-12-04T11:19:57.523" CommentCount="1" />
  <row Id="853" PostTypeId="2" ParentId="848" CreationDate="2009-12-04T11:28:14.873" Score="1" ViewCount="" Body="&lt;p&gt;RS-485 is very useful in situations where the devices (sensors in your case) need to be remote from the controller. In general it's used where the device has it's own brains (i.e. an on-board microcontroller) and it's reporting to a PC. You can get 232 to 485 adapters that will let your PC talk RS-485. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can get the sensors into the same box as the microcontroller, then you could use 485 to talk back to the PC. It's not high-speed, but it's very robust and well understood in a lot of situations, and it pretty easily allows for additional devices. If you just have the one device, then 232 will do you just fine.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2009-12-04T11:28:14.873" />
  <row Id="854" PostTypeId="2" ParentId="851" CreationDate="2009-12-04T14:18:18.667" Score="9" ViewCount="" Body="&lt;p&gt;If it's a consumer gadget/toy (and not a medical device which has much more stringent standards!) you probably just need to worry about safety standards and EMC standards.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;CE certification for Europe&lt;/li&gt;&#xA;&lt;li&gt;EMC certification: in the USA, &lt;a href=&quot;http://en.wikipedia.org/wiki/Title%5F47%5FCFR%5FPart%5F15&quot; rel=&quot;nofollow&quot;&gt;FCC class B&lt;/a&gt; radiated emissions &lt;/li&gt;&#xA;&lt;li&gt;Europe now requires &lt;a href=&quot;http://en.wikipedia.org/wiki/Restriction%5Fof%5FHazardous%5FSubstances%5FDirective&quot; rel=&quot;nofollow&quot;&gt;RoHS&lt;/a&gt; to limit Cd, Pb, Hg and some other hazardous substances&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Safety standards will include things like pinch points, sharp edges; if it's a toy and there are children involved, there's a standard container used for choke hazards, etc. If the gadget plugs into the wall for power, you need to worry about shock hazards and fire hazards (&lt;a href=&quot;http://www.ul.com/global/eng/pages/&quot; rel=&quot;nofollow&quot;&gt;UL&lt;/a&gt; in the USA), although you can probably deal with this by using a UL/CE approved wall transformer so voltages entering your device are limited.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-04T14:18:18.667" CommentCount="1" />
  <row Id="855" PostTypeId="2" ParentId="848" CreationDate="2009-12-04T16:46:57.993" Score="1" ViewCount="" Body="&lt;p&gt;RS485 is the equivalent of I2C but in larger scale, both have bus architecture with node adresses:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;RS-485 is excellent out to 4000+ feet of sensor wire. You can implement it for anything you would use I2C for. It has a wide variety of EMF and optical isolation options. RS-485 need a signal adapter to work&lt;/li&gt;&#xA;&lt;li&gt;I2C is faster not adapted for long distance, don't need  a line driver to work and therfore comsume less&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;i hope it's clearer now&lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2009-12-04T16:46:57.993" />
  <row Id="856" PostTypeId="2" ParentId="838" CreationDate="2009-12-04T16:48:33.980" Score="3" ViewCount="" Body="&lt;p&gt;Something else that might be useful is standard IC packages and their pin numberings/footprints.  If it's a workbench cheat sheet, you can probably stick with DIPs and the like, but when you're looking at part specs it's handy to be able to look and say, &quot;Oh, yeah, that's an SOT-32, I can use that&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I included this as a separate answer so it can be judged on its own merit.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-12-04T16:48:33.980" />
  <row Id="857" PostTypeId="2" ParentId="848" CreationDate="2009-12-04T17:27:37.800" Score="2" ViewCount="" Body="&lt;p&gt;What about dallas one wire?  I think they have a lot of sensors and that the network is fairly long range.  I have never used it but always thought it was interesting.  If you already have you sensors this does not make as much sense.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-12-04T17:27:37.800" />
  <row Id="858" PostTypeId="2" ParentId="851" CreationDate="2009-12-04T18:24:28.680" Score="5" ViewCount="" Body="&lt;p&gt;If it's a small batch, and you're using an approved wall transformer as mentioned by Jason S, you probably don't have to worry about anything. I've seen all sorts of sites selling little gadgets they make in small quantity, that I am 99% sure they didn't do any kind of certification. It all depends on the scale...does 'small batch' mean 20 or 2000?&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-04T18:24:28.680" />
  <row Id="859" PostTypeId="2" ParentId="848" CreationDate="2009-12-04T21:09:55.807" Score="2" ViewCount="" Body="&lt;p&gt;I think the big difference has to do with how far away your sensors are on your network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If they're close, and likely not to be affected by electrical noise, then I don't think it matters too much.  &lt;strong&gt;USB, RS-232, SPI, I2C, parallel, Bluetooth&lt;/strong&gt;... all would be good options.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If they're far away, and likely to be around electrical noise, a system that utilizes a differential communication scheme (like &lt;strong&gt;CAN, RS-485, Ethernet&lt;/strong&gt;) is probably a better route to go.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2009-12-04T21:09:55.807" />
  <row Id="860" PostTypeId="2" ParentId="616" CreationDate="2009-12-04T21:32:36.653" Score="13" ViewCount="" Body="&lt;p&gt;While this isn't a book, the online &lt;a href=&quot;http://www.allaboutcircuits.com&quot; rel=&quot;nofollow&quot;&gt;All About Circuits&lt;/a&gt; site is fantastic.  The examples are simple and easy to learn from.  I use that in conjunction with some of the other books I have (which all have some pluses/minuses):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0070580782&quot; rel=&quot;nofollow&quot;&gt;Paul Scherz's &lt;em&gt;Pratical Electronics for Inventors&lt;/em&gt;&lt;/a&gt;.  I inherited this book from my late cousin.  Very concise, almost too concise, but has a ridiculous amount of data/information that is useful for designing practical circuits.  However, it's not very good at explaining concepts in an easy-to-understand fashion.  That said, this book was easy to use in a pinch at RS to learn enough about transistors to select some for a project in 10 mins after asking for help from the clueless salesperson, and its data tables can be useful.  Great as a reference, but might be overwhelming to learn/teach yourself from.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;em&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0521370957&quot; rel=&quot;nofollow&quot;&gt;The Art of Electronics&lt;/a&gt;&lt;/em&gt; is the ultimate reference/explanation.  Pretty much anything that you &lt;em&gt;really&lt;/em&gt; need to know when designing circuits is in there.  But it's not very good at learning book, more as a reference.  But if you need to think about &lt;em&gt;all&lt;/em&gt; the aspects of a design, they've got you covered.  It's a must-have.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The &lt;em&gt;Getting Started With Electronics&lt;/em&gt; book from RS, I've found, is probably the worst reference I own.  It has cute pictures, but is extremely terse in its explanations.  After taking a class on electronics, and re-looking at the book, I find it only useful as a way to jog my memory in remembering formulas, basic circuits and such.  He also bucks tradition:  all current flow is labeled non-conventionally, which is really confusing when using his reference with others.  That confused the heck out me when learning about transistors.  That said, it's easy to find and cheap.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="374" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T19:11:53.133" LastActivityDate="2011-05-13T19:11:53.133" CommunityOwnedDate="2011-03-24T07:55:53.500" />
  <row Id="861" PostTypeId="1" CreationDate="2009-12-04T21:57:57.570" Score="8" ViewCount="335" Body="&lt;p&gt;I am playing with an ATtiny13 and I thought it would be good to use it with an external 8Mhz ceramic oscillator instead of the 1.2 Mhz built-in one. (I want to do a soft-uart at 9600 bps, so I figured 1.2 Mhz was too slow)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To change to an external oscillator, I ran 'avrdude -c usbtiny -p attiny13 -U lfuse:w:0x70:m -U hfuse:w:0xff:m'&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately I can't access the device anymore now. The 'Blink the LED on PB0' program that was in there does not run anymore and the programmer can't connect to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure what to do here. Can I throw away this chip or is there a way to rescue it?&lt;/p&gt;&#xA;" OwnerUserId="393" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-03T16:30:31.423" LastActivityDate="2011-01-03T16:30:31.423" Title="Recovering an ATtiny13" Tags="&lt;avr&gt;&lt;programmer&gt;&lt;fuse-bits&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="862" PostTypeId="2" ParentId="861" CreationDate="2009-12-04T22:33:33.347" Score="7" ViewCount="" Body="&lt;p&gt;Have you tried to set the chip up with an external oscillator? Once the chip is programmed to use an external oscillator it will not work unless one is present. If you do not do this you will need &lt;a href=&quot;http://www.mightyohm.com/blog/2008/09/arduino-based-avr-high-voltage-programmer/&quot; rel=&quot;nofollow&quot;&gt;hi voltage programming&lt;/a&gt; to reset the fuses.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-12-04T22:33:33.347" />
  <row Id="863" PostTypeId="2" ParentId="861" CreationDate="2009-12-05T00:55:07.643" Score="5" ViewCount="" Body="&lt;p&gt;You should absolutely be able to recover it.  In the worst case, you might need a high voltage (12V?) programmer, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fuse settings you used don't seem problematic to me.  Brown-out detect is off (that can be a gotcha) and SPI is enabled, so you should be able to reprogram it just fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main thing is that it looks like you set it to need an external oscillator.  You were trying for that, so you probably have one around.  You need it hooked up in the system you're using for ISP programming, but that should be the only issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IOW, you're not doing anything weird.  It should all work.  Double-check that you don't have any problems in your setup.  Loose connections, that kind of thing.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-12-05T00:55:07.643" />
  <row Id="864" PostTypeId="1" AcceptedAnswerId="879" CreationDate="2009-12-05T04:55:08.833" Score="3" ViewCount="476" Body="&lt;p&gt;Can you brick an Arduino just through code?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-07T06:33:30.753" LastActivityDate="2011-02-07T06:33:30.753" Title="Frying an Arduino" Tags="&lt;arduino&gt;&lt;software&gt;" AnswerCount="3" />
  <row Id="865" PostTypeId="1" AcceptedAnswerId="890" CreationDate="2009-12-05T04:59:03.087" Score="4" ViewCount="1025" Body="&lt;p&gt;Where do i put the Arduino &quot;Library&quot; folder on a Mac?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-12-05T22:00:10.877" Title="Arduino Libaries folder" Tags="&lt;arduino&gt;&lt;library&gt;&lt;mac&gt;&lt;osx&gt;" AnswerCount="2" />
  <row Id="866" PostTypeId="1" AcceptedAnswerId="925" CreationDate="2009-12-05T05:01:20.867" Score="4" ViewCount="292" Body="&lt;p&gt;What are the key differences between Wiring and Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would you recommend?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T10:07:18.487" LastActivityDate="2011-01-23T10:07:18.487" Title="Wiring vs Arduino" Tags="&lt;arduino&gt;&lt;wiring&gt;" AnswerCount="1" />
  <row Id="867" PostTypeId="1" CreationDate="2009-12-05T05:03:54.247" Score="4" ViewCount="355" Body="&lt;p&gt;Is there a way (other than restarting the computer) to clear a Serial Port Lock?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-12-07T17:07:55.873" Title="Serial Port Lock" Tags="&lt;serial&gt;&lt;port&gt;" AnswerCount="3" />
  <row Id="868" PostTypeId="1" AcceptedAnswerId="887" CreationDate="2009-12-05T05:05:39.420" Score="6" ViewCount="629" Body="&lt;p&gt;Do you need to use different resistors against each of the colours on an RGB LED?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2010-07-23T01:52:32.517" Title="Red Green Blue LED" Tags="&lt;rgb&gt;&lt;led&gt;&lt;resistor&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="869" PostTypeId="1" AcceptedAnswerId="886" CreationDate="2009-12-05T05:08:23.893" Score="25" ViewCount="1191" Body="&lt;p&gt;What are the items you have in your personal electronics tool kit?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2011-05-16T10:38:19.167" Title="Personal electronics tool kit" Tags="&lt;electronics&gt;&lt;tools&gt;&lt;kit&gt;" AnswerCount="7" FavoriteCount="16" />
  <row Id="870" PostTypeId="2" ParentId="865" CreationDate="2009-12-05T05:19:44.463" Score="0" ViewCount="" Body="&lt;p&gt;I can't find a folder called 'Library' for my own version (0017).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you mean the preferences.txt that goes in &quot;/Users//Library/Arduino&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise all libraries are inside the package (right click on the Arduino icon to access) then contained in &quot;/Contents/Resources/Java&quot; there are 'lib' and 'libaries' folders.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope that helps a little :)&lt;/p&gt;&#xA;" OwnerUserId="386" LastActivityDate="2009-12-05T05:19:44.463" />
  <row Id="871" PostTypeId="1" CreationDate="2009-12-05T05:53:30.900" Score="3" ViewCount="188" Body="&lt;p&gt;I'm looking for a 2 or 4 bit shift register that I can shift data into, and on the 5th shift into the device it will shift the previous data back out on the Dout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking for a shift register that acts a lot like the MAX6969 from Maxim, yet is smaller than that.&lt;/p&gt;&#xA;" OwnerUserId="373" LastActivityDate="2009-12-09T14:27:35.753" Title="2/4 Bit Shift Register" Tags="&lt;electronics&gt;&lt;shifter&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="872" PostTypeId="2" ParentId="868" CreationDate="2009-12-05T07:00:48.373" Score="2" ViewCount="" Body="&lt;p&gt;Or one resistor in line with all of them, determined by if they are common cathode or common annode. I have seen high qualify RGB LEDs where you can use one resistor, i have seen low quality ones where an intelligent driver cannot make them look good.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-12-05T07:00:48.373" CommentCount="2" />
  <row Id="873" PostTypeId="2" ParentId="869" CreationDate="2009-12-05T07:09:23.953" Score="7" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;1k, 10k resistors, i rarely need&#xA;other values, maybe 100s if I have&#xA;LEDs.&lt;/li&gt;&#xA;&lt;li&gt;caps, 4.7uF, 1000pF, .1uF&lt;/li&gt;&#xA;&lt;li&gt;PICs, just some PICs, i think I have&#xA;some pic16F876As, but I have access&#xA;to three others also.&lt;/li&gt;&#xA;&lt;li&gt;LEDS, a few cheap ~10mA LEDs&lt;/li&gt;&#xA;&lt;li&gt;FLash memory, I never know when my&#xA;project will need memory, I keep&#xA;simple ATMEL memory, I can give a&#xA;part number if wanted.&lt;/li&gt;&#xA;&lt;li&gt;ft232R, never know when I want some&#xA;USB connectivity.&lt;/li&gt;&#xA;&lt;li&gt;I have other random parts, but they&#xA;probably cycle pretty constantly.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I try to get a professor or my boss at work to buy my components, I do not tinker a large amount at home, but build little projects for my professor, or students in the class I help teach, to use, or I will build little projects to speed up a task at my job.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2009-12-05T10:06:28.050" LastActivityDate="2009-12-05T10:06:28.050" CommentCount="1" />
  <row Id="874" PostTypeId="2" ParentId="871" CreationDate="2009-12-05T07:18:29.963" Score="6" ViewCount="" Body="&lt;p&gt;have you tried looking in the 74xx series of logic? Pick your favorite flavor. 74HC194 and 74HC195 are 4-bit shift registers; 74HC174 (quad flip-flop) and 74HC175 (hex flip-flop) can be made into shift registers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: based on your comments, why don't you use an HC594 (output) or HC597 (input)? They're 8-bit registers, easily cascadable to arbitrary lengths, compatible with a SPI interface as well as plain old clocking.&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-12-09T14:27:35.753" LastActivityDate="2009-12-09T14:27:35.753" CommentCount="1" />
  <row Id="875" PostTypeId="1" AcceptedAnswerId="876" CreationDate="2009-12-05T09:04:58.050" Score="7" ViewCount="701" Body="&lt;p&gt;I'm building a hexapod robot using simple servos and I was wondering how feasible it was to measure the current flow to each servo (5-6V DC to a maximum of 0.25-1A (I haven't found the spec for the servo's stall current yet)) using, say, an ATMega168. What kind of circuit would I need to build in series with each of the servo's power lines to give me a useful readout? I assume I'd get a voltage drop across this circuit, what's it likely to be? etc. &lt;/p&gt;&#xA;" OwnerUserId="255" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2009-12-06T03:57:14.907" LastActivityDate="2010-09-09T14:32:28.503" Title="How do I measure the current flow to a component?" Tags="&lt;avr&gt;&lt;measurement&gt;&lt;robotics&gt;&lt;servo&gt;" AnswerCount="3" />
  <row Id="876" PostTypeId="2" ParentId="875" CreationDate="2009-12-05T09:56:47.507" Score="13" ViewCount="" Body="&lt;p&gt;Honestly, People often use a simple sense resistor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You place an in series very low resistance resistor(&amp;lt;1 ohm often) and you measure voltage drop. This allows you to monitor motor current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many many motor control algorithms if you want to control the motor yourself, otherwise, if you are measuring for just knowing current draw, you just need to make sure you sample often enough to get an accurate measurement, or use a circuit with a lowpass filter effect(make sure you buffer the voltage).&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2009-12-05T22:12:50.850" LastActivityDate="2009-12-05T22:12:50.850" CommentCount="3" />
  <row Id="877" PostTypeId="2" ParentId="868" CreationDate="2009-12-05T10:27:57.210" Score="7" ViewCount="" Body="&lt;p&gt;Voltage drop is different. You can use a single resistor if it keeps current below safe values for each of the 3 leds.&#xA;Downside effect: the RED led will be brighter than the green LED, and much brighter than the BLUE led.&#xA;I always use 3 separate resistors if the &quot;color quality&quot; is an issue.&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2009-12-05T10:27:57.210" CommentCount="4" />
  <row Id="878" PostTypeId="1" AcceptedAnswerId="881" CreationDate="2009-12-05T15:13:17.883" Score="3" ViewCount="199" Body="&lt;p&gt;I'm using Maxim's DS18x20 (I've actually got more than one variant) one-wire temperature sensors to log the temperatures in various rooms in my house once a minute.  About one reading in a thousand, I get something completely bogus back.  In the middle of a sequence that's gradually rising from 65F to 70F I get something like -32.1F or 15.64F.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone else had that kind of problem, or is this something wrong with my setup?  If this is just a known issue with these things, I'll have to do something like taking three readings and throwing out the outlier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just a few statements about my setup:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I'm running at 3.3V&lt;/li&gt;&#xA;&lt;li&gt;I'm checking the checksum of the reading as it comes back to the arduino, and it matches (or I think it does - there could always be a bug in that code).&lt;/li&gt;&#xA;&lt;li&gt;These are running off of normal power, not parasite power.&lt;/li&gt;&#xA;&lt;li&gt;I have the 4.7K pullup resistor in place.&lt;/li&gt;&#xA;&lt;li&gt;I'm only using a single sensor on each sensing platform.&lt;/li&gt;&#xA;&lt;li&gt;The sensor is on a PCB attached to the arduino that's reading it.&lt;/li&gt;&#xA;&lt;li&gt;I see the same problem reading from a variety of different arduinos (diecimilla, pro-mini, homemade custom)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-12-07T12:20:46.217" Title="Reliability of DS18x20 temperature sensors" Tags="&lt;arduino&gt;&lt;temperature&gt;&lt;one-wire&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="879" PostTypeId="2" ParentId="864" CreationDate="2009-12-05T15:19:31.553" Score="10" ViewCount="" Body="&lt;p&gt;I don't think you can brick it without hooking up some extra hardware.  Shorting power to ground will do it.  Trying to source or drain too much power through a single pin might do it, but would be more likely to just burn out that one pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you do in software shouldn't be able to actually brick the Arduino itself.  Repeated EEPROM reads/writes could burn out the EEPROM cells, but that wouldn't brick the whole thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wackyvorlon is right that you can set fuses to make it impossible to program in the usual fashion.  Even that is reversible with the use of a high-voltage programmer, though.  The Arduino IDE hides the fuses from you, so this isn't too much of a worry.  Once you start programming AVRs directly or editing the boards file in the Arduino environment this can be more of an issue.&lt;/p&gt;&#xA;" OwnerUserId="213" LastEditorUserId="213" LastEditorDisplayName="" LastEditDate="2009-12-27T16:34:13.627" LastActivityDate="2009-12-27T16:34:13.627" />
  <row Id="880" PostTypeId="2" ParentId="867" CreationDate="2009-12-05T17:59:11.080" Score="0" ViewCount="" Body="&lt;p&gt;What's a Serial Port Lock? Is that where one application takes exclusive control of the serial port? You could try closing or killing that application.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-05T17:59:11.080" />
  <row Id="881" PostTypeId="2" ParentId="878" CreationDate="2009-12-05T18:05:01.130" Score="2" ViewCount="" Body="&lt;p&gt;I have see this with occasionally with the DS18B20. For my application, it was simple enough to filter out the spurious results with code.&lt;/p&gt;&#xA;" OwnerUserId="274" LastActivityDate="2009-12-05T18:05:01.130" CommentCount="3" />
  <row Id="882" PostTypeId="2" ParentId="868" CreationDate="2009-12-05T18:15:00.580" Score="0" ViewCount="" Body="&lt;p&gt;There is a lot of variation in RGB LEDs. You need to consult the data sheet.&lt;/p&gt;&#xA;" OwnerUserId="274" LastActivityDate="2009-12-05T18:15:00.580" CommentCount="1" />
  <row Id="883" PostTypeId="2" ParentId="869" CreationDate="2009-12-05T18:15:32.500" Score="5" ViewCount="" Body="&lt;p&gt;Tool wise I have: Multimeter, probe, pocket oscilloscope from seed studio, solder iron, screw drivers, and other various hand tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bench wise I have: tektronix oscilloscope (from school), programmable power supply(from school), function generator&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Component wise: Too many to list here. I am one of those people that stores love to see coming. I see something and think to myself &quot;I might be able to use that later&quot; and so I stock up in bulk. Or my neighbors throw out stuff and I take it and rip parts off it (my wife hates that). She thinks I could be on that show called &quot;Hoarders&quot; but for electronic components. Then I lucked out because my school upgraded their labs, and my professor gave me everything they had because the school was just going to throw them out!&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-12-05T18:15:32.500" CommentCount="2" />
  <row Id="884" PostTypeId="1" AcceptedAnswerId="1007" CreationDate="2009-12-05T18:46:31.313" Score="6" ViewCount="783" Body="&lt;p&gt;How do you get the SparkFun FTDI Basic Breakout board to auto reset?&#xA;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9115&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9115&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I still have to hit the rest button for any Arduino clones when I use the breakout board. I have tried connecting to the DTR pin and other methods of trial and error but I am just not getting it.&lt;/p&gt;&#xA;" OwnerUserId="6" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-06T01:18:31.657" LastActivityDate="2009-12-14T01:02:14.340" Title="Arduino reset with FTDI breakout question" Tags="&lt;arduino&gt;&lt;ftdi&gt;&lt;reset&gt;" AnswerCount="3" />
  <row Id="885" PostTypeId="2" ParentId="884" CreationDate="2009-12-05T18:58:24.303" Score="3" ViewCount="" Body="&lt;p&gt;I use the Sparkfun FTDI 5V basic board with my Arduino Mini Pro 328 boards and I have no problems with auto reset, I plug it in and upload using the Ardunio IDE (I use 017) - it works fine. Is this an issue with your clone Arduino boards? You do not say which clones you have.&lt;/p&gt;&#xA;" OwnerUserId="9" LastEditorUserId="9" LastEditorDisplayName="" LastEditDate="2009-12-05T19:13:39.730" LastActivityDate="2009-12-05T19:13:39.730" />
  <row Id="886" PostTypeId="2" ParentId="869" CreationDate="2009-12-05T20:28:27.347" Score="22" ViewCount="" Body="&lt;p&gt;Most important tool:  A quality soldering iron.  Mine's a Weller.  Those Radio Shack pencil irons are useless, and will only make life more difficult.  I have both desoldering braid and a solder sucker.  Plenty of 60/40 solder, the silver bearing stuff doesn't flow nearly as well.  A well stocked junkbox is extremely important.  The more components you have to hand, the faster you can work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good digital multimeter, I love my Fluke.  Add to that a good analog multimeter, digital meters offer no sense of change over time.  A dual channel 100MHz oscilloscope(mine's a tektronix mainframe that I scavenged).  Good lighting!  A third-hand rig or similar to hold parts and boards that are being soldered.  A spectrum analyzer is very useful for radio work.  Also a function generator.  A sharp pair of flush cutting nippers, several spools of different coloured 20 gauge hookup wire.  Some people keep flux to hand, but I've never found I needed it.  Assorted scraps of printed circuit board, or strip board - breadboards are very finicky and can add circuit-killing parasitic capacitance.  The absolute best tool I've found for cutting PCB is a jeweler's saw.  You can buy them from Contenti, and aren't very expensive.  I've never seen anything use produce a better or faster cut.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A wet sponge for cleaning the iron tip, several tips for the iron.  I think that covers the bulk of it, it may seem like a lot of stuff but it's mostly small stuff.  An LCR meter is handy, too.  I have a foredom flexshaft, it's kind of like a dremel but more powerful and higher quality. They're not cheap machines, but are a real life saver for modifying circuit boards.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-12-05T20:28:27.347" CommentCount="4" />
  <row Id="887" PostTypeId="2" ParentId="868" CreationDate="2009-12-05T20:29:46.347" Score="12" ViewCount="" Body="&lt;p&gt;Yes, you need a separate resistor per LED. (or per color of an RGB LED, which just just 3 LEDs in one package)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Due to the physics of the LED, different colored LEDs have different &quot;forward voltage&quot;s (a primary characteristic of an LED).  &lt;a href=&quot;http://www.oksolar.com/led/led%5Fcolor%5Fchart.htm&quot; rel=&quot;nofollow&quot;&gt;This site's LED color chart&lt;/a&gt; gives the forward voltages for their LEDs, but it does really depend on the LED in question.  In general, the higher in frequency light an LED makes (the bluer it is), the higher the forward voltage.  Often, a red LED's forward voltage is ~2V, a green one ~3V, and a blue one is ~3.4V, but it really does depend on the LED manufacturer and the exact frequency of the light emitted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you know the forward voltage of an LED, you can use Ohm's Law to calculate the resistor you need for a given power supply voltage.  Or you can use a &lt;a href=&quot;http://led.linear1.org/1led.wiz&quot; rel=&quot;nofollow&quot;&gt;handy LED calculator&lt;/a&gt; to help.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-05T20:29:46.347" CommentCount="7" />
  <row Id="888" PostTypeId="2" ParentId="884" CreationDate="2009-12-05T20:36:26.707" Score="3" ViewCount="" Body="&lt;p&gt;I've been using the FTDI 3.3V breakout from sparkfun, the 5V cable from FTDI and the 3.3v cable from sparkfun with an RBBB arduino clone.  they all reset the board without problem.  the auto-reset is a feature of the arduino bootloader as i understand.  perhaps your cloan has a different bootloader&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps you could mention which arduino clone you are using and maybe someone has some specific experience with this issue on it, or we can checkout what the bootloader supports&lt;/p&gt;&#xA;" OwnerUserId="196" LastEditorUserId="196" LastEditorDisplayName="" LastEditDate="2009-12-07T03:17:00.037" LastActivityDate="2009-12-07T03:17:00.037" CommentCount="1" />
  <row Id="889" PostTypeId="2" ParentId="864" CreationDate="2009-12-05T20:44:36.237" Score="6" ViewCount="" Body="&lt;p&gt;You can come pretty close to bricking it using the fuses.  My understanding is that frobbed fuse settings can be corrected with a high-voltage programmer.  &lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-12-05T20:44:36.237" />
  <row Id="890" PostTypeId="2" ParentId="865" CreationDate="2009-12-05T22:00:10.877" Score="5" ViewCount="" Body="&lt;p&gt;Libraries should go to &lt;em&gt;~/Documents/Arduino/libraries/&lt;/em&gt; folder. This way when you upgrade Arduino IDE it wont overwrite your libraries. If Arduino IDE does not show your recently added library you need to restart the IDE.&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2009-12-05T22:00:10.877" />
  <row Id="891" PostTypeId="2" ParentId="875" CreationDate="2009-12-05T23:19:22.980" Score="7" ViewCount="" Body="&lt;p&gt;Sense resistor is good. Usually they're placed on the high side of the circuit, so that the supply voltage return can be shared between source and load, and usually you size the sense resistor so it's small enough not to affect the circuit, but large compared to voltage errors (typical op-amp input offsets are in the neighborhood of 0.5-5mV). This makes it a little harder to amplify and translate to a &quot;ground&quot;-referenced signal. Take a look at these &lt;a href=&quot;http://www.diodes.com/products/catalog/browse.php?parent-id=78&quot; rel=&quot;nofollow&quot;&gt;current sense monitor ICs from Zetex&lt;/a&gt; (now part of Diodes Inc) -- I had to design a current sense circuit a few months ago and these looked like the best fit (project got changed so I never had a chance to use it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For layout, make sure you use a pseudo-Kelvin connection -- connect the current sense signal lines directly to the pads of the resistors (preferably the inner edges of the pads) and don't use those sense traces for anything else except the amplification circuit. (A true Kelvin connection would be the same thing except it would require a &lt;a href=&quot;http://en.wikipedia.org/wiki/Four-terminal%5Fsensing&quot; rel=&quot;nofollow&quot;&gt;4-terminal resistor&lt;/a&gt; with 2 load terminals and 2 sense terminals -- this isn't usually necessary unless you get into really accurate or low-resistance circuits.)&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-05T23:19:22.980" CommentCount="10" />
  <row Id="892" PostTypeId="2" ParentId="867" CreationDate="2009-12-06T00:46:28.383" Score="2" ViewCount="" Body="&lt;p&gt;This has happened to me before with java, but normally termination of the program fixes the problem. If I do not have that option, you need some try...catch blocks to handle unlocking the serial port in error conditions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this is what you were speaking of. What operating system you are using may allow more detailed answers.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-12-06T00:46:28.383" />
  <row Id="893" PostTypeId="1" AcceptedAnswerId="894" CreationDate="2009-12-06T01:02:42.253" Score="6" ViewCount="654" Body="&lt;p&gt;I have a relay operated by an NPN transistor that needs some voltage applied to the base.  I'm working with an arduino and if I give it a digital port, all's well.  The circuit looks like the one in &lt;a href=&quot;http://www.kpsec.freeuk.com/images/diopro.gif&quot; rel=&quot;nofollow&quot;&gt;this picture&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I want to replace the arduino port with a &lt;a href=&quot;http://www.maxim-ic.com/quick%5Fview2.cfm/qv%5Fpk/2907&quot; rel=&quot;nofollow&quot;&gt;DS2406&lt;/a&gt; (the TO92 kind).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This seemed to get really complicated fast.  &lt;a href=&quot;http://github.com/dustin/arduino-2406&quot; rel=&quot;nofollow&quot;&gt;My library&lt;/a&gt; for operating the 2406 is fine, but I can't figure out how to wire it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now that both pieces independently work, my goal is to get some current fed into the base of the transistor so it throws the relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've run into the following issues:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DS2406 closes to ground.  That's the only option, so I can't map it directly to the base pin of the transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The TO-92 package doesn't have a vcc pin, so I have to have a pull up resistor between vcc and the data pin.  This causes stuff to get hot and smelly when I power it up hooked up to the collector of the transistor with the base wired to the relay power.  I could be using the wrong kind of resistor, but I don't have a strong sense of what's right here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I &lt;em&gt;may&lt;/em&gt; be able to run the relay strictly off the DS2406, but I'm afraid it will have too much draw, which is why I want it to go through the transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the easiest way to go from a switch that opens and closes ground to a transistor base that wants current?&lt;/p&gt;&#xA;" OwnerUserId="347" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-06T01:19:35.933" LastActivityDate="2010-04-29T22:12:14.183" Title="Need help operating a transistor" Tags="&lt;switch&gt;&lt;transistor&gt;&lt;current&gt;&lt;voltage&gt;" AnswerCount="3" />
  <row Id="894" PostTypeId="2" ParentId="893" CreationDate="2009-12-06T04:49:24.487" Score="8" ViewCount="" Body="&lt;p&gt;Your basic NPN transistor switch circuit is an inverter, if you put a pull-up resistor (maybe 10k?) between the collector and 5V. (i.e. the resistor replaces the relay in your linked diagram)  When you switch on the base of the transistor (put it to 5V), the voltage at the collector goes to ~0V, and when you switch off the base (0V), the voltage at the collector goes to 5V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you could stick such a transistor inverter in between the DS2406 and the transistor driving the relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I still think you should be able to use the DS2406 with only one transistor though.  Perhaps if you had a pull-up resistor (10k) going from the transistor's base to 5V.  This keeps the transistor turned on, unless the DS2406 pulls the base down.  Also, don't forget to put the current limiting resistor at the front of the base.  If you don't have this, the transistor will &quot;get hot and smelly&quot; as you say. ;)&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-06T04:49:24.487" CommentCount="4" />
  <row Id="895" PostTypeId="2" ParentId="878" CreationDate="2009-12-06T09:02:36.240" Score="2" ViewCount="" Body="&lt;p&gt;Hi.  For what it's worth, I did a bit of work with the DS18B20 a few months back.  I shot a short video and did a write-up on my blog, which has links to examples and sample code.  Hope this may help a bit!&#xA;&lt;a href=&quot;http://dailyduino.com/archives/552&quot; rel=&quot;nofollow&quot;&gt;http://dailyduino.com/archives/552&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="368" LastActivityDate="2009-12-06T09:02:36.240" />
  <row Id="897" PostTypeId="1" CreationDate="2009-12-06T23:25:27.300" Score="4" ViewCount="123" Body="&lt;p&gt;Hi everyone, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought three spring-return, push-type solenoid. I can't remember them being sticky from the start because I only was using one at a time, but they may have been. Now that I tried to work them together, two are so sticky that they have become unusable (even by themselves).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to know whether this may have happened progressively because of pushing them a bit hard (I hardly used them though), or wrong components or because I hooked the three up at the same time. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a bit of info on my setup:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Spring-return, push-type solenoid. 14 Ohm, 12-24Vdc coil. Intermittent duty&lt;/li&gt;&#xA;&lt;li&gt;RECT DIODE 1AMP/400PIV&lt;/li&gt;&#xA;&lt;li&gt;12VDC 3.33A SWITCHING POWER SUPPLY &lt;/li&gt;&#xA;&lt;li&gt;N-CHANNEL MOSFET, 55V 22A .06OHM &lt;/li&gt;&#xA;&lt;li&gt;Resistors&lt;/li&gt;&#xA;&lt;li&gt;Arduino Duemillenove &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="370" LastActivityDate="2009-12-07T12:03:26.443" Title="Can Solenoids Get Sticky From Improper Usage?" Tags="&lt;arduino&gt;&lt;circuit&gt;&lt;electronics&gt;" AnswerCount="2" />
  <row Id="898" PostTypeId="2" ParentId="804" CreationDate="2009-12-07T01:31:25.797" Score="3" ViewCount="" Body="&lt;p&gt;Could you use an array of &lt;a href=&quot;http://en.wikipedia.org/wiki/Passive%5Finfrared%5Fsensor&quot; rel=&quot;nofollow&quot;&gt;passive infrared sensors&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ladyada's got &lt;a href=&quot;http://www.ladyada.net/learn/sensors/pir.html&quot; rel=&quot;nofollow&quot;&gt;a bunch of stuff on interfacing with them&lt;/a&gt;, including Arduinos.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the Arduino only has 6 analog inputs, but you could multiplex more sensors in and out using FETs if you need them.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2009-12-07T01:37:54.893" LastActivityDate="2009-12-07T01:37:54.893" />
  <row Id="899" PostTypeId="2" ParentId="897" CreationDate="2009-12-07T01:32:40.380" Score="5" ViewCount="" Body="&lt;p&gt;The potential exists to melt some parts on the interior.  I would wash the rod of the solenoid in acetone to remove any residue, and check for visible charring within.  If worse comes to worse, try some powdered graphite or white lithium grease to lubricate it.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-12-07T01:32:40.380" />
  <row Id="900" PostTypeId="2" ParentId="804" CreationDate="2009-12-07T01:41:56.400" Score="4" ViewCount="" Body="&lt;p&gt;I don't believe the arduino has the horsepower to do this.  It's a very difficult task you propose.&lt;/p&gt;&#xA;" OwnerUserId="331" LastActivityDate="2009-12-07T01:41:56.400" />
  <row Id="901" PostTypeId="2" ParentId="869" CreationDate="2009-12-07T03:00:33.010" Score="8" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92020&quot; rel=&quot;nofollow&quot;&gt;Harbor Freight multimeter&lt;/a&gt;.  They actually work quite well.  RS has some slip-over test lead IC-hooks that work with the bundled test leads, totally worth the extra cost.  More expensive meters are better, but these are accurate enough (esp. for digital work: is it high? is it low?  it's cheaper than a logic probe!) and small enough to go in a small tackle/toolbox, and if something goes wrong it's easy to replace.  The transistor tester saved me when I picked up some 2N2222's at RS and discovered that the package had the pinout backwards.  Seriously, even if you have a nicer meter, you &lt;em&gt;will&lt;/em&gt; find uses for one of these.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Lots of IC-hook wires&lt;/strong&gt;.  Those things are fantastic, and are great for probing and prototyping.  You can never have too many of those.  I prefer these over alligator clips.&lt;/li&gt;&#xA;&lt;li&gt;Small/jewelers screwdrivers.&lt;/li&gt;&#xA;&lt;li&gt;Wire stripper.&lt;/li&gt;&#xA;&lt;li&gt;Small needle-nose pliers.&lt;/li&gt;&#xA;&lt;li&gt;Analog o-scope that was a cast-off from school.&lt;/li&gt;&#xA;&lt;li&gt;RS soldering irons.  Honestly though, it's not worth getting the RS.  Get a good iron.  And solder wick, not that silly solder sucker bulb thing.  I think this is the area I regret the most in my toolkit.  I've used the small pencil iron three times and I botched a board with it because it didn't get hot enough.&lt;/li&gt;&#xA;&lt;li&gt;Arudino + Protoshield.  Nice, small little prototyping platform.&lt;/li&gt;&#xA;&lt;li&gt;6500K desk lamp lighting.  Really, the daylight color helps.  Very bright.&lt;/li&gt;&#xA;&lt;li&gt;Plastic compartment boxes for holding parts.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2009-12-15T16:21:31.353" LastActivityDate="2009-12-15T16:21:31.353" />
  <row Id="902" PostTypeId="1" AcceptedAnswerId="905" CreationDate="2009-12-07T06:57:42.730" Score="15" ViewCount="541" Body="&lt;p&gt;How do I detect light with an LED?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-12-07T09:58:10.077" Title="Detecting light with an LED" Tags="&lt;led&gt;&lt;light&gt;&lt;detection&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="9" />
  <row Id="903" PostTypeId="2" ParentId="902" CreationDate="2009-12-07T07:07:06.190" Score="2" ViewCount="" Body="&lt;p&gt;Photocells are a dead simple way to detect light. It's resistance varies proportionally to the amount of light shining on it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;LadyAda has a very nice write-up on photocells including Arduino implementation: &lt;a href=&quot;http://www.ladyada.net/learn/sensors/cds.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/learn/sensors/cds.html&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="327" LastActivityDate="2009-12-07T07:07:06.190" />
  <row Id="904" PostTypeId="1" CreationDate="2009-12-07T09:01:56.660" Score="5" ViewCount="473" Body="&lt;p&gt;I was wondering if you can use an inductive proximity sensor to detect aluminum or if a capacitive sensor must be used? I wasn't sure if inductive sensors were reserved for ferrous metals only.&lt;/p&gt;&#xA;" OwnerUserId="337" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-07T11:11:18.537" LastActivityDate="2009-12-07T21:06:57.290" Title="Detect aluminum using an inductive sensor" Tags="&lt;sensor&gt;&lt;inductive&gt;&lt;detection&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="905" PostTypeId="2" ParentId="902" CreationDate="2009-12-07T09:26:22.150" Score="22" ViewCount="" Body="&lt;p&gt;It is possible to use a led as a light sensor as well as a light emitter. Essentially a reverse biased led will act as a capacititor, if it is then disconnected the charge will drain at a rate roughly proportional to the light hitting it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We can use this with a microcontroller - utilising the multi state ability of the ports.&#xA;&lt;img src=&quot;http://john.crouchley.com/images/ledsensor.png&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistor should be about 100 ohms, I have only used this with red leds - it may work with others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use the following sequence:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Set Port A output high&#xA;set Port B output low   // this makes sure the led is discharged&#xA;wait 1mS&#xA;set Port A output low&#xA;set Port B output high  // reverse bias and charge&#xA;wait 1mS&#xA;set Port B as input     // Port B is high impedance input&#xA;time how long for Port B to read low&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The length of time will be dependant on the amount of light hitting the led.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several examples of this on the web - I will list them here as I find them again:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.edn.com/article/CA6387024.html&quot; rel=&quot;nofollow&quot;&gt;LED senses and displays ambient-light intensity&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.edn.com/article/CA6541376.html?nid=2551&quot; rel=&quot;nofollow&quot;&gt;Red LEDs function as light sensors&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://cs.nyu.edu/~jhan/ledtouch/index.html&quot; rel=&quot;nofollow&quot;&gt;Multi-Touch Sensing through LED Matrix Displays&lt;/a&gt; - very cool video&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://projects.dimension-x.net/technology-and-projects/ledsensors&quot; rel=&quot;nofollow&quot;&gt;LEDs As Sensors&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.merl.com/publications/TR2003-035/&quot; rel=&quot;nofollow&quot;&gt;Very Low-Cost Sensing and Communication Using Bidirectional LEDs&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="9" LastEditorUserId="9" LastEditorDisplayName="" LastEditDate="2009-12-07T09:51:15.830" LastActivityDate="2009-12-07T09:51:15.830" />
  <row Id="906" PostTypeId="1" CreationDate="2009-12-07T09:39:04.620" Score="4" ViewCount="1764" Body="&lt;p&gt;Hey guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wanting to use one of the Arduino's PWM output to control a high-powered LED. I can't remember the exact specifications, but it was considerably more current than the ATMega328 can provide.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I realise that this would usually be achieved with the use of a transistor, and a resistor to current-control the LED. However, I'm not wanting the LED to become less bright as the battery voltage sags, and therefore I'm wanting to use a constant current source instead of the resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first thought was to use an LM317. What I'm wanting to know, though, is if it can respond at the 64KHz it would need to?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, could I use a simple MOSFET to achieve the same thing cheaper and simpler? (Then I wouldn't need a transistor nor constant current source, as the MOSFET would do both of these)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&#xA;Rob.&lt;/p&gt;&#xA;" OwnerUserId="356" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-20T19:02:46.757" LastActivityDate="2011-05-20T19:02:46.757" Title="Arduino PWM controlling high-power LED" Tags="&lt;arduino&gt;&lt;led&gt;&lt;current&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="907" PostTypeId="2" ParentId="902" CreationDate="2009-12-07T09:58:10.077" Score="5" ViewCount="" Body="&lt;p&gt;Here is a good video describing how LEDs can be used as a light sensor&#xA;&lt;a href=&quot;http://www.youtube.com/watch?v=VZUvoLDlMS0&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=VZUvoLDlMS0&lt;/a&gt;&#xA;Also Forest M.Mims III has wrote about simple projects using LEDs as touch sensors as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I have read that SMD LEDs work better as light sensors than through hole LEDs...&lt;/p&gt;&#xA;" OwnerUserId="368" LastActivityDate="2009-12-07T09:58:10.077" />
  <row Id="908" PostTypeId="2" ParentId="904" CreationDate="2009-12-07T09:58:57.093" Score="6" ViewCount="" Body="&lt;p&gt;I've used years ago an inductive proximity sensor for a test, and I remember that it sensed aluminium and copper way better than iron. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just found this doc.&#xA;&lt;a href=&quot;http://www.rselectronics.com/SEO/Selecting%5FProx.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.rselectronics.com/SEO/Selecting_Prox.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2009-12-07T09:58:57.093" />
  <row Id="909" PostTypeId="2" ParentId="897" CreationDate="2009-12-07T12:03:26.443" Score="3" ViewCount="" Body="&lt;p&gt;Are they in any kind of hostile environment? Dusty? Wet? Have you verified the voltage at the solenoid to make sure it really is within spec? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have any side-side forces on the solenoid? Something that would make it harder to move?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, your spec on the solenoid says 'Intermittent duty'. What does the manufacturer say that means? Do you ever exceed that spec (leaving it 'on' for long periods of time)?&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2009-12-07T12:03:26.443" />
  <row Id="910" PostTypeId="2" ParentId="878" CreationDate="2009-12-07T12:20:46.217" Score="2" ViewCount="" Body="&lt;p&gt;Hi. I have 13 of them running in my house since about four years now. The database is hard to handle anymore (I kept track of all samples). But, I didn't see this kinda behavior. Instead, every now and than one sensor freezes and blocks all the others, the only way out of this (that I found) was to shut down supply voltage for a few seconds. So I added a tiny relay to my board and whenever the micro senses this behavior it resets the whole chain of sensors. That happens a few times a week.  &lt;/p&gt;&#xA;" LastActivityDate="2009-12-07T12:20:46.217" CommentCount="1" />
  <row Id="911" PostTypeId="2" ParentId="906" CreationDate="2009-12-07T12:23:33.713" Score="4" ViewCount="" Body="&lt;p&gt;You don't need 64kHz for this application, 200Hz is enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used the following design, for about 200mA current:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;+5V --- LED --- transistor -(1)- shunt (1 Ohm) --- GND&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(1) goes to the negativ input of an LM358 OpAmp. It is important that the OpAmp works down to the lower rail (GND), because there is only a small voltage on the shunt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output of the OpAmp drives the transistor via some appropriate resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The positive input is connected to a voltage divider which is fed from the port pin. The voltage divider and the shunt determine the current through the LED.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2009-12-07T12:23:33.713" CommentCount="1" />
  <row Id="912" PostTypeId="2" ParentId="906" CreationDate="2009-12-07T12:35:13.003" Score="3" ViewCount="" Body="&lt;p&gt;The data sheet for a LM317 shows that its step response time is in the order of 10 uS. This will be too slow to modulate at 64 kHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A current source is the right approach. Depending on the total power you need to drive the LED a linear current source like starblue suggested might work, but if the power is higher you might need to use a buck regulator.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-12-07T12:35:13.003" CommentCount="1" />
  <row Id="913" PostTypeId="1" CreationDate="2009-12-07T14:53:35.780" Score="6" ViewCount="1099" Body="&lt;p&gt;Hi everybody&lt;/p&gt;&#xA;&#xA;&lt;p&gt;is there any software working on PC with a gui that can control the outputs and read the inputs of an arduino in realtime? &lt;/p&gt;&#xA;" OwnerUserId="199" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-08T00:55:05.383" LastActivityDate="2009-12-08T17:27:56.830" Title="Software to control an Arduino" Tags="&lt;arduino&gt;&lt;pc&gt;&lt;software&gt;&lt;output&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="915" PostTypeId="2" ParentId="913" CreationDate="2009-12-07T15:33:42.500" Score="3" ViewCount="" Body="&lt;p&gt;I've not tried this but there are several links on the web to control/read Arduino from PC. They mostly seem to use Firmata on the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.acraigie.com/programming/firmatavb/&quot; rel=&quot;nofollow&quot;&gt;Arduino &amp;lt;&gt; Firmata &amp;lt;&gt; Visual Basic .NET&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.firmata.org/wiki/Main%5FPage&quot; rel=&quot;nofollow&quot;&gt;Firmata main site&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-12-07T15:33:42.500" />
  <row Id="916" PostTypeId="1" CreationDate="2009-12-07T16:19:58.357" Score="4" ViewCount="472" Body="&lt;p&gt;After looking over &lt;a href=&quot;http://chiphacker.com/questions/906/ardiono-pwm-controlling-high-power-led&quot; rel=&quot;nofollow&quot;&gt;this question&lt;/a&gt; and the answers received, it prompted me to wonder:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Given pulse signals generated by a uC, what kind of slew rate on an op-amp will you need to reproduce the waveform cleanly?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example:  Assume you have a project where you generate pulses 10uS in length on a uC pin that go into an op-amp in a buffer configuration.  What is the minimum slew rate required to reproduce the waveform at the output of the buffer without introducing an integrating effect?  What is a good rule of thumb to use?&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2009-12-07T17:00:17.480" LastActivityDate="2009-12-07T17:29:26.980" Title="Op-Amp Slew Rate Requirements" Tags="&lt;op-amp&gt;&lt;microcontroller&gt;" AnswerCount="1" />
  <row Id="917" PostTypeId="2" ParentId="913" CreationDate="2009-12-07T17:07:29.680" Score="0" ViewCount="" Body="&lt;p&gt;Hey, are you are familiar with Max/MSP (paid) and Pure Data (free)? They are graphical programming environments. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I put together a tutorial to set it up if you're interested in testing it: &lt;a href=&quot;http://www.soundplusdesign.com/?p=1305&quot; rel=&quot;nofollow&quot;&gt;http://www.soundplusdesign.com/?p=1305&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers.&lt;/p&gt;&#xA;" OwnerUserId="370" LastActivityDate="2009-12-07T17:07:29.680" />
  <row Id="918" PostTypeId="2" ParentId="867" CreationDate="2009-12-07T17:07:55.873" Score="3" ViewCount="" Body="&lt;p&gt;You'll have to figure out what application has locked the port.  Assuming your'e running windows, check out &lt;a href=&quot;http://technet.microsoft.com/en-us/sysinternals/bb896644.aspx&quot; rel=&quot;nofollow&quot;&gt;PortMon&lt;/a&gt;.  That should tell you what application is using the port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, if a custom app you wrote locked the port, and then crashed/closed without unlocking the port, there might not be a way to unlock it without rebooting.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2009-12-07T17:07:55.873" />
  <row Id="919" PostTypeId="2" ParentId="916" CreationDate="2009-12-07T17:29:26.980" Score="9" ViewCount="" Body="&lt;p&gt;You need to specify more information. This depends on &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;signal consumer requirements&#xA;&lt;ul&gt;&#xA;&lt;li&gt;what bandwidth is needed?&lt;/li&gt;&#xA;&lt;li&gt;is error at a particular sampling point important?&lt;/li&gt;&#xA;&lt;li&gt;is this being used by a digital or analog circuit?&lt;/li&gt;&#xA;&lt;li&gt;is linearity important?&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;signal producer capabilities / signal properties&#xA;&lt;ul&gt;&#xA;&lt;li&gt;what is power supply voltage?&lt;/li&gt;&#xA;&lt;li&gt;what is source slew rate?&lt;/li&gt;&#xA;&lt;li&gt;what is source waveform timing?&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If I just want to look on a scope, a 1us slew rate for a 10us pulse might be fine. If I'm sampling at particular instants in time, maybe the error during a particular sample might be important.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your consumer is a digital circuit, you should be using a digital buffer, not an op-amp. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also I challenge your problem statement:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;blockquote&gt;&#xA;    &lt;p&gt;Given pulse signals generated by a uC, what kind of slew rate on an op-amp will you need to reproduce the waveform cleanly?&lt;/p&gt;&#xA;  &lt;/blockquote&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Microcontroller outputs do not have &quot;clean&quot; voltage levels, so it really doesn't make sense to try to buffer their output waveform &quot;cleanly&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to maintain precise timing &lt;em&gt;and&lt;/em&gt; particular reference voltage levels rather than the somewhat-indeterminate &quot;Vol&quot; and &quot;Voh&quot; output voltage levels of a microcontroller, which can drift, bounce, etc. as long as they stay within spec, then I would highly recommend using a fast analog SPDT multiplexer. (FSA4157 / NLAS4157 are really good choices) Hook the A/B inputs to stiff reference voltages of your choice, and hook the switching input to your microcontroller output. The multiplexer output is your analog output signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't think of any good reason whatsoever to spend money on a fast op-amp to buffer a cruddy microcontroller output signal.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-07T17:29:26.980" CommentCount="5" />
  <row Id="920" PostTypeId="2" ParentId="893" CreationDate="2009-12-07T19:03:30.580" Score="3" ViewCount="" Body="&lt;p&gt;You could also change your transistor from a NPN to a PNP.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2009-12-07T19:03:30.580" />
  <row Id="921" PostTypeId="2" ParentId="904" CreationDate="2009-12-07T21:06:57.290" Score="6" ViewCount="" Body="&lt;p&gt;Yes - inductive sensors work on the same principles as a comercially avaliable metal detector. They have an LC circuit which oscillates in a particular frequencey range, when a conductive material is near by, eddy currents form in the material which then produce their own magnetic field which then dampens the oscillation of the sensor.&lt;/p&gt;&#xA;" OwnerUserId="267" LastActivityDate="2009-12-07T21:06:57.290" />
  <row Id="922" PostTypeId="1" AcceptedAnswerId="924" CreationDate="2009-12-07T21:22:52.240" Score="13" ViewCount="1373" Body="&lt;p&gt;How do most voltage regulator ICs work? Are they the same as hooking up a variable resistor and a voltmeter and turning the knob until you get the desired voltage?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-25T06:34:35.030" LastActivityDate="2011-01-25T06:34:35.030" Title="How does an LM7805 voltage regulator work?" Tags="&lt;resistor&gt;&lt;voltage-regulator&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="923" PostTypeId="2" ParentId="922" CreationDate="2009-12-07T21:37:30.433" Score="8" ViewCount="" Body="&lt;p&gt;This is an excellent way to understand the theory. A linear regulator will use a transistor to step the voltage down as an inline resistor(the transistor can be modeled as a variable resistance) with feedback changing its resistance to get a very dependable output voltage. This method is very low noise but not power efficient in general.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Linear%5Fregulator&quot; rel=&quot;nofollow&quot;&gt;wikipedia&lt;/a&gt; page is not half bad to learn about them. Switching regulators use a method that can be though of more as a charge pump, taking advantage of inductors changing voltage to push a continuous current.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-12-07T21:37:30.433" CommentCount="2" />
  <row Id="924" PostTypeId="2" ParentId="922" CreationDate="2009-12-07T21:49:40.050" Score="15" ViewCount="" Body="&lt;p&gt;Voltage regulators achieve &quot;stiffness&quot; via a feedback control loop, where &quot;stiffness&quot; means that a large change in load current causes a small change in voltage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both switching and linear regulators include a control loop (historically analog... some of the newer switchers use digital control loops) to adjust some parameter of the circuit so that the output voltage remains constant in the presence of load current changes and input voltage changes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a linear regulator the circuit parameter is the pass transistor drive circuit (which produces base current for an NPN/PNP power transistor, gate voltage for a MOSFET).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a switching regulator the circuit parameter is the duty cycle of the switching element(s).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So there's really two areas you need to understand if you want to get into the details of  how regulators work:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;topology design (achieve required limits of current/voltage/etc)&lt;/li&gt;&#xA;&lt;li&gt;control loop tuning + stability&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-07T21:49:40.050" CommentCount="1" />
  <row Id="925" PostTypeId="2" ParentId="866" CreationDate="2009-12-07T23:06:51.017" Score="5" ViewCount="" Body="&lt;p&gt;Wiring was an older attempt at what the Arduino has succeeded in doing. It was designed to be an educational platform for learning about microprocessors, software, and physical computing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Wiring board has a different processor and more robust hardware then the Aduino Duemilanove. It has more I/O pins, more memory, more interrupts, etc (although fewer then an Arduino Mega). It is also quite a bit more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The language is essentially the same, and each has an IDE based on the one written for processing. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a page comparing the Wiring board to (older) arduinos and other platforms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://wiring.org.co/hardware/compare.html&quot; rel=&quot;nofollow&quot;&gt;http://wiring.org.co/hardware/compare.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-12-07T23:06:51.017" />
  <row Id="926" PostTypeId="2" ParentId="913" CreationDate="2009-12-07T23:37:51.113" Score="2" ViewCount="" Body="&lt;p&gt;As JohnC says, Firmata is probably what you want.  Firmata is a special sketch you load onto your Arduino.  It has a &lt;a href=&quot;http://www.firmata.org/wiki/Protocol&quot; rel=&quot;nofollow&quot;&gt;set of commands&lt;/a&gt; you send it over the Arduino's serial port to read and write the Arduino's inputs and outputs. There's a &lt;a href=&quot;http://www.arduino.cc/playground/Interfacing/Processing&quot; rel=&quot;nofollow&quot;&gt;Processing library&lt;/a&gt; that you can use so you can write Processing apps to directly control the Arduino, as well as many other libraries for other computer languages running on your desktop computer (like the VB .NET one JohnC mentions).  Even if you don't have a library, you can send the commands from any language that knows how to talk to serial ports (like with Max/Pd as Andrew mentions)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I like the Processing library because Processing is open source and similar to Arduino.  A Processing sketch talking to a Firmata'd Arduino looks something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;import cc.arduino.*;&#xA;Arduino myArduino = new Arduino(this, &quot;/dev/tty.usbserial&quot;, 57600);&#xA;myArduino.digitalWrite(ledPin, Arduino.HIGH);&#xA;delay(1000);&#xA;myArduino.digitalWrite(ledPin, Arduino.HIGH);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-07T23:37:51.113" CommentCount="1" />
  <row Id="927" PostTypeId="1" AcceptedAnswerId="928" CreationDate="2009-12-08T04:48:47.253" Score="5" ViewCount="517" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an Arduino Duemilanove (ATMEGA328) and ethernet shield (based on the wiznet w5100). My network gateway is a D-Link DSL-G604T.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using this setup I can contact computers on my local network fine, however when I attempt to contact computers on the public internet the device times out. I traced the packets going back and forward using wireshark and the problem appears to be that the gateway is not responding to the w5100's ARP request.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I saved the ARP packet that the w5100 is sending and the ARP packet that my computer is sending and compared them. The only different that is not a timestamp, address, length or sequence number is that the w5100 is sending a Trailer at the end of the Ethernet II frame.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to &lt;a href=&quot;http://www.faqs.org/rfcs/rfc1122.html&quot; rel=&quot;nofollow&quot;&gt;http://www.faqs.org/rfcs/rfc1122.html&lt;/a&gt; section 2.3.1 a trailer may only be used if both hosts have previously agreed to use them. I suspect that my gateway is not able to handle trailers and is ignoring the packet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a way to disable trailers in the w5100?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hamish&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update: Here are the arp packets that are sent by a computer on my network that is able to make internet connections and the Arduino device. I have also provided a diff of the two packets. In the case of the packet that is sent by the computer, the gateway responds, in the case of the packet sent by the Arduino, the gateway does not respond. Note that I have changed the hardware addresses, but that's all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Computer Packet:&#xA;&lt;a href=&quot;http://chiphacker.pastebin.com/f37faeff5&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.pastebin.com/f37faeff5&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Arduino Packet:&#xA;&lt;a href=&quot;http://chiphacker.pastebin.com/f779740ba&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.pastebin.com/f779740ba&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Diff:&#xA;&lt;a href=&quot;http://img38.imageshack.us/img38/8179/packetdiff.jpg&quot; rel=&quot;nofollow&quot;&gt;http://img38.imageshack.us/img38/8179/packetdiff.jpg&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="298" LastEditorUserId="298" LastEditorDisplayName="" LastEditDate="2009-12-09T04:28:27.703" LastActivityDate="2009-12-10T11:34:55.780" Title="Disabling Trailer Protocol when using w5100 ethernet shield." Tags="&lt;arduino&gt;&lt;ethernet&gt;" AnswerCount="2" />
  <row Id="928" PostTypeId="2" ParentId="927" CreationDate="2009-12-08T13:47:22.470" Score="2" ViewCount="" Body="&lt;p&gt;Are you sure that the trailer isn't just there to pad the packet to the appropriate size, or as some form of CRC checksum?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[EDIT] In fact looking at the RFC it looks to me like a host which wishes to use trailers would send the trailer request during ARP, and if the other host understands trailers then it will add it to it's list of hosts which understand/utilise trailers. Therefore in theory it wouldn't be the trailer which was causing your problem. However I can't categorically rule it out as this is based on my memories of my networking course and a superficial reading of the RFC you linked to and wikipedia.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2009-12-08T13:54:14.607" LastActivityDate="2009-12-08T13:54:14.607" CommentCount="4" />
  <row Id="929" PostTypeId="2" ParentId="869" CreationDate="2009-12-08T15:58:14.267" Score="4" ViewCount="" Body="&lt;p&gt;I make sure I have a 1/8&quot; stereo jack on a length of wire so I can plug my breadboard projects straight into my computers audio input. I also have some paperclips, that I normally use for bending into little brackets, that can hold various strange shaped components onto the breadboard, i.e little piezo buzzers or speakers. &#xA;And last but not least, Blue Tac, I can't stress enough how many times it's helped me out in a tight spot, it's useful for all sorts, not to mention holding wires in place whilst soldering.&#xA;I also have a lamp, it's an eco-friendly 2.5w super massive LED thingy. It's got a swan neck, it's really bright and at £20 from Ikea it's a darn site cheaper than a proper technicians desk lamp. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jim.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-08T15:58:14.267" CommentCount="1" />
  <row Id="930" PostTypeId="2" ParentId="442" CreationDate="2009-12-08T16:15:37.557" Score="1" ViewCount="" Body="&lt;p&gt;The Dwengo board is based on the PIC18F4550, they also have a low-cost PICkit2 clone and some very good tutorials to get you started: &lt;a href=&quot;http://www.dwengo.org/tutorials&quot; rel=&quot;nofollow&quot;&gt;http://www.dwengo.org/tutorials&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="401" LastActivityDate="2009-12-08T16:15:37.557" CommentCount="2" />
  <row Id="931" PostTypeId="2" ParentId="824" CreationDate="2009-12-08T16:16:22.107" Score="5" ViewCount="" Body="&lt;p&gt;I have used &lt;a href=&quot;http://www.pumpkininc.com&quot; rel=&quot;nofollow&quot;&gt;Salvo&lt;/a&gt; on the MSP430.  This was very light on processor resources and, providing that you obey the implementation rules, very easy to use and reliable.  This is a co-operative OS and requires that task switches are performed at the outer function call level of the task functions.  This constraint allows the OS to work in very small memory devices without using vast amounts of stack space maintaining task contexts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the AVR32 I am using FreeRTOS.  Again very reliable so far but I have had some configuration/version discrepancies between the version that FreeRTOS publish and the version supplied with the Atmel framework.  This however has the advantage that it is free!&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2009-12-08T16:16:22.107" />
  <row Id="932" PostTypeId="2" ParentId="913" CreationDate="2009-12-08T17:27:56.830" Score="0" ViewCount="" Body="&lt;p&gt;I'd agree with the other answers, Processing is a good one because it's so similar to the Arduino environment. I use Max Msp 5 myself, and I can certainly recommend it, you can download it from the cycling74 website -&gt; &lt;a href=&quot;http://cycling74.com/downloads/&quot; rel=&quot;nofollow&quot;&gt;http://cycling74.com/downloads/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You get a free 30 day trial of the full version plus the runtime environment, it works on both mac os and windows.&#xA;It's super easy to learn, and it allows you to program whilst your program is running! - no more compiling!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use an object called serial to talk with the Arduino, and Max comes packed with handy pre made objects and GUI components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plus you can then export stand alone applications, or you can share them in text format.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jim.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-08T17:27:56.830" />
  <row Id="933" PostTypeId="1" AcceptedAnswerId="1034" CreationDate="2009-12-08T21:36:04.020" Score="6" ViewCount="891" Body="&lt;p&gt;Hey there Chiphackers, this is my first post, and I need some help/advice finding the right integrated circuits.&#xA;I'll start by describing the project background a bit. I've received a fellowship to develop an open source electroencephalograph, the finished hardware will provide a platform for people to develop various creative and therapeutic uses for an EEG system i.e music controllers, game controllers or brain training programs.&#xA;I want to use an Atmel MCU for the analogue to digital conversion, I'd like it to connect to a computer via USB and I'd also like the unit to be powered by the USB connection.&#xA;I need help finding a suitable op-amp IC to amplify the signals from the electrodes prior to the MCU. The finished device will be 16 channels, so I'd like to find an IC with multiple op-amps. The electrical activity picked up by the electrodes will be in the region of 200mV and less, so I'll need a lot of gain.&#xA;Is it possible to adjust the gain of an op-amp circuit with an MCU by using a digital resistor program? It would be nice if the hardware could be reprogrammed to work with various audio and sensor inputs. &#xA;Any help or advice would be fantastic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jim.&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-29T16:44:51.843" LastActivityDate="2010-07-27T21:54:42.217" Title="RnD on an EEG, Help required, what op-amp?" Tags="&lt;op-amp&gt;&lt;usb&gt;&lt;atmel&gt;" AnswerCount="7" CommentCount="2" FavoriteCount="2" />
  <row Id="934" PostTypeId="2" ParentId="933" CreationDate="2009-12-08T21:49:02.590" Score="5" ViewCount="" Body="&lt;p&gt;Any reason you aren't using &lt;a href=&quot;http://openeeg.sourceforge.net/doc/&quot; rel=&quot;nofollow&quot;&gt;OpenEEG&lt;/a&gt;, a low cost &amp;amp; open source EEG system? They've been around for a while, and have lots of useful information on their website.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-08T21:49:02.590" CommentCount="1" />
  <row Id="935" PostTypeId="2" ParentId="933" CreationDate="2009-12-09T00:25:15.200" Score="6" ViewCount="" Body="&lt;p&gt;For such situations I think you generally want to use an &lt;a href=&quot;http://en.wikipedia.org/wiki/Instrumentation%5Famp&quot; rel=&quot;nofollow&quot;&gt;instrumentation amplifier&lt;/a&gt; type of op-amp.  They're made for differential signals, so you can easily subtract out the noise, they have really high-gain, so you can amplify the weak signals, and they have really high impedances, so they can sense delicate signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a &lt;a href=&quot;http://openeeg.sourceforge.net/doc/modeeg/modEEGamp-v1.0.png&quot; rel=&quot;nofollow&quot;&gt;quick perusal&lt;/a&gt; of the &lt;a href=&quot;http://openeeg.sourceforge.net/doc/&quot; rel=&quot;nofollow&quot;&gt;OpenEEG&lt;/a&gt; site as davr suggests, it looks like they use a &lt;a href=&quot;http://www.chipcatalog.com/TI/INA114AP.htm&quot; rel=&quot;nofollow&quot;&gt;TI INA114AP&lt;/a&gt; instrumentation amp as the main amp.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-09T00:25:15.200" CommentCount="5" />
  <row Id="936" PostTypeId="2" ParentId="933" CreationDate="2009-12-09T00:31:51.887" Score="4" ViewCount="" Body="&lt;p&gt;AD620 op amp has a schematic in the &lt;a href=&quot;http://www.analog.com/static/imported-files/data%5Fsheets/AD620.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; for an ECG circuit. Here you can also find class sheets that use the AD620 to build an ECG (&lt;a href=&quot;http://www.cs.wright.edu/%7Ephe/EGR199/Lab%5F1/&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt;, &lt;a href=&quot;http://www.cs.wright.edu/%7Ephe/EGR199/Lab%5F2/&quot; rel=&quot;nofollow&quot;&gt;2&lt;/a&gt;, &lt;a href=&quot;http://www.cs.wright.edu/%7Ephe/EGR199/Lab%5F3/&quot; rel=&quot;nofollow&quot;&gt;3&lt;/a&gt;, &lt;a href=&quot;http://www.cs.wright.edu/%7Ephe/EGR199/Lab%5F4/&quot; rel=&quot;nofollow&quot;&gt;4&lt;/a&gt;). Similar to the schematic in the datasheet just a lot more verbose.&#xA;It is only single channel. Cant quickly answer the rest of your question but hope that helps.&lt;/p&gt;&#xA;" OwnerUserId="196" LastEditorUserId="196" LastEditorDisplayName="" LastEditDate="2009-12-09T00:37:19.230" LastActivityDate="2009-12-09T00:37:19.230" CommentCount="4" />
  <row Id="937" PostTypeId="1" AcceptedAnswerId="959" CreationDate="2009-12-09T05:18:18.990" Score="9" ViewCount="2754" Body="&lt;p&gt;I've recently built some fiber-optic bend sensors and I want to read the values I get from them into a computer via an Arduino. I'm measuring the light with &lt;a href=&quot;http://i-fiberoptics.com/pdf/IFD91.pdf&quot; rel=&quot;nofollow&quot;&gt;this photodiode&lt;/a&gt; from &lt;a href=&quot;http://i-fiberoptics.com/Fiber_optic_led_photodetectors.php#photodetectors&quot; rel=&quot;nofollow&quot;&gt;Industrial Fiber Optics&lt;/a&gt;. Currently, I'm giving the LED on the other end as well as the photodiode 2.2V. My question has to do with the fact that the voltage fluctuations as measured by a multi-meter on the photodiode are linear, but rather small as the fiber is deformed, even quite radically. With the fiber straight, depending on the fiber (its hard to score them identically), the voltage hovers around 1.92V, for instance, and with bending it will it will go up to, say, 1.93-1.94V. I'm not worried about getting the voltages identical as I can scale in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I am worried about is losing resolution when doing A/D with the Arduino. If my voltage fluctuations are on the order of 10mV, won't the Arduino's 10-bit A/D quantize the hell out of it, even if I step the voltage up to 5V with a voltage divider? What I'm looking for is an analog scaler. How can I stretch out that range between 1.92 and 1.94 to cover the full range, from 0V to 5V so that I can take advantage of the full range of the Arduino A/D?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I feel like this has got to be a common operation in electronics, but I've never studied it formally, so a lot of things are lost on me. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(You may be thinking, as davr was, &quot;why are you using fiber optics for bend sensing? Why would you expect a voltage change when the fiber is bent?&quot; The trick is to remove the cladding on one side of the fiber optic cable. This lets light spill out. When the cable is bent away from the scoring, even more light is let out of the cable, causing a voltage drop in the receiver, and vice versa. There is little documentation of this technique online, so I plan on making an Instructable after my project is finished. See below.)&lt;br /&gt;&lt;br /&gt;&#xA;&lt;a href=&quot;http://rgel.posterous.com/progress-201&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://posterous.com/getfile/files.posterous.com/rgel/3q1yGJMpNJq7BPNkThti5ThzDDfs7rTlpW1r5lcay9Ud9hgDJeIwYfC93so3/rgel-091204-03.jpg&quot; width=&quot;300&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2009-12-13T01:08:02.263" LastActivityDate="2009-12-13T01:08:02.263" CommunityOwnedDate="2009-12-09T08:33:26.663" Title="Scaling Voltage for Arduino Analog In, Beyond Voltage Dividers" Tags="&lt;arduino&gt;&lt;sensor&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="2" />
  <row Id="938" PostTypeId="2" ParentId="937" CreationDate="2009-12-09T05:45:05.500" Score="2" ViewCount="" Body="&lt;p&gt;Using fiber optics as a bend sensor might be a poor choice, isn't the whole point of fiber optics to easily allow you to bend light around corners with minimal loss?&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-09T05:45:05.500" CommentCount="1" />
  <row Id="939" PostTypeId="2" ParentId="937" CreationDate="2009-12-09T06:05:10.957" Score="10" ViewCount="" Body="&lt;p&gt;Signal conditioning in this sense is extremely common. You want to use an amplifier in order to make that 10mV range span (for example) the entire 0-5V range of the arduino. This can be done using op-amps such as the LM741. You'll proabably also want to use a &quot;voltage clamp&quot; (ex: two zener diodes) on the output of your signal conditioner/input into the ADC to make sure that the value does not exceed 5V. If you look around online at op-amp data sheets and/or signal conditioning circuits, you should find guides as to exactly what you are looking for.&lt;/p&gt;&#xA;" OwnerUserId="403" LastActivityDate="2009-12-09T06:05:10.957" />
  <row Id="940" PostTypeId="1" AcceptedAnswerId="941" CreationDate="2009-12-09T08:12:33.267" Score="8" ViewCount="413" Body="&lt;p&gt;How do you get around the annoying pin spacing on the Arduino?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where pin 7 and pin 8 are not standard spacing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why is it set up like this?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-12-09T20:54:44.853" Title="Arduino pin spacing." Tags="&lt;arduino&gt;&lt;pin&gt;&lt;spacing&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="941" PostTypeId="2" ParentId="940" CreationDate="2009-12-09T10:06:10.937" Score="13" ViewCount="" Body="&lt;p&gt;Hi, I got to meet Massimo at Flourish Conf in Chicago this year... and I  actually asked him this same question.  What is up with the odd pin spacing?!  This had been a subject of debate among friends, with the general agreement being that it help you from putting shields on backwards.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Turns out, the actual reason for the odd pin spacing was an error in the original CAD/gerber file.  So yea, the odd pin spacing was completely unintentional.  Massimo also mentioned that there was a proposal to remove the odd pin spacing starting  with the Duemilanove, Mega and future models (a so called &quot;restart&quot;), but was voted down in favor of reverse compatibility with old shields, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps with the odd pin spacing question.&lt;/p&gt;&#xA;" OwnerUserId="368" LastActivityDate="2009-12-09T10:06:10.937" CommunityOwnedDate="2009-12-09T10:06:10.937" CommentCount="2" />
  <row Id="942" PostTypeId="2" ParentId="824" CreationDate="2009-12-09T11:09:17.590" Score="4" ViewCount="" Body="&lt;p&gt;The December edition of &lt;a href=&quot;http://www.epemag.co.uk/&quot; rel=&quot;nofollow&quot;&gt;Everyday Practical Electronics&lt;/a&gt; has part 3 of a series on Real Time Operating Systems for PICs (in the PIC n' Mix Column) and has details of setting up FreeRTOS with MPLAB and a PICKit 2. The previous two articles (which I haven't seen) appear to have discussed the merits of various RTOSes and settled on FreeRTOS. Once the current article has setup the development environment they go on to start designing a binary digital clock. It appears that there's at least one more part to come on this topic. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure how available EPE is in the US, but there does appear to be a US Store linked to from their site and there may be electronic copies available.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-09T11:09:17.590" />
  <row Id="944" PostTypeId="2" ParentId="215" CreationDate="2009-12-09T14:28:44.753" Score="0" ViewCount="" Body="&lt;p&gt;I use a wiiremote with my mac mini, all you ned to do is pair the device. I then use MAX MSP to handle all the data, you could just access the bluetooth port directly, but there's a handy object called aka.wiiremote, it's available for free here -&gt; &lt;a href=&quot;http://www.iamas.ac.jp/~aka/max/&quot; rel=&quot;nofollow&quot;&gt;http://www.iamas.ac.jp/~aka/max/&lt;/a&gt; this object will allow MAX MSP to receive and send data to the remote, without any ugly scaling or formating, it makes the whole programming process 100x faster. I've got a whole bunch of programs I've made to turn the wiiremote into a music controller, I mostly use it to wiiJ (wii DJing) using Ableton live. I also use the wiiremote as an infra red camera for a digital graffiti setup, you just pair it with the mac then download the whiteboard software from here -&gt; &lt;a href=&quot;http://www.uweschmidt.org/wiimote-whiteboard&quot; rel=&quot;nofollow&quot;&gt;http://www.uweschmidt.org/wiimote-whiteboard&lt;/a&gt; it's free and works really well, the setup is simple.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-09T14:28:44.753" />
  <row Id="945" PostTypeId="2" ParentId="795" CreationDate="2009-12-09T14:54:50.940" Score="3" ViewCount="" Body="&lt;p&gt;In the past, I've used a laminated piece of glass which has a frosty acetate middle layer, they're not too cheap unfortunately but they work well. I then used a projector to back project the screen on, and I had infra red LEDs lining the edge of the glass, then I used the IR camera on a Wiiremote to pick up the light reflected from the fingertips. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mine works fine in any lighting, I once did a demo at a local pub, and the halogen lights above the pool tables kept setting it off, So I took an image of the room (on the IR camera) and subtracted it from the real time image, it worked fine after that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's true multi-touch using fTIR, and it's really smooth and responsive, if you experiment to remove the light related gremlins, it's more than worth it for the results, I wouldn't use any other method myself, SAW, multi-layer resistive and capacitive just don't compare&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-09T14:54:50.940" />
  <row Id="946" PostTypeId="2" ParentId="940" CreationDate="2009-12-09T15:05:33.240" Score="4" ViewCount="" Body="&lt;p&gt;I actually noticed a side benefit to it.  I made my own Arduino compatible with standard spacing everywhere and promptly put the shield on backwards.  That odd spacing means that you cannot physically put the shield in backwards (never mind that you have the wrong number of pins on both sides).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, I'm not redoing my board to prevent doing that.  I'm just going to be more careful :)&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-12-09T15:05:33.240" />
  <row Id="947" PostTypeId="2" ParentId="310" CreationDate="2009-12-09T15:27:51.600" Score="2" ViewCount="" Body="&lt;p&gt;If you just want simple gain adjustment, I'd go with the 555 timer. Then use a potentiometer in parallel with a resistor on the output, to create a log pot, (don't buy log pots, they're a rubbish estimation of a log curve, unless you spend mega bucks) the potentiometer set up is here -&gt; &lt;a href=&quot;http://sound.westhost.com/project01.htm&quot; rel=&quot;nofollow&quot;&gt;http://sound.westhost.com/project01.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want accurate control, I'd agree with the other answers, an Arduino type board or an MCU would be much better. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget, volume is not linear!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've made an open source pocket oscillator, called a Posc, it features two square waves produced by a pair of 555 timers, have a look, it may help -&gt; &lt;a href=&quot;http://www.sonodrome.co.uk/tutorials.html&quot; rel=&quot;nofollow&quot;&gt;http://www.sonodrome.co.uk/tutorials.html&lt;/a&gt;&#xA;There's a couple of PDFs on this page that show the circuit and component layout. &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-09T15:27:51.600" CommentCount="1" />
  <row Id="948" PostTypeId="2" ParentId="804" CreationDate="2009-12-09T17:05:17.677" Score="0" ViewCount="" Body="&lt;p&gt;You can hook up a camera that sends serial data to the Arduino (available from Sparkfun, I think they are normally used for cell phones, it looks similar to the CMUcam solution) then send data to your computer via usb, or you can use a wireless module if your feeling swanky. Then you could download a facial tracking program, that would process the images from the Arduino. Facial tracking is a well established method of real time video processing, it should be relatively easy to find one.&#xA;That's the only way I can think of that may get around the Arduino's lack of horsepower, you will need to be hooked up to a proper computer tho, if you want to process realtime video. It would be more expense and effort compared to using NIR sensors, but the results may be more suited for your application.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-09T17:05:17.677" />
  <row Id="949" PostTypeId="2" ParentId="27" CreationDate="2009-12-09T17:40:17.523" Score="2" ViewCount="" Body="&lt;p&gt;I'd agree SimpleMessageSystem looks like the easiest to impalement. 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       }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;]&#xA;    }&lt;/p&gt;&#xA;&#xA;&lt;p&gt;}&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This MAX 5 patch will receive data from Arduino's serial monitor, I think it was used to connect a pot to one of the analogue inputs, that could then be used to control the cutoff frequency of a filter in MAX MSP.&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2009-12-09T17:52:20.880" LastActivityDate="2009-12-09T17:52:20.880" CommentCount="1" />
  <row Id="950" PostTypeId="2" ParentId="2" CreationDate="2009-12-09T18:12:17.370" Score="2" ViewCount="" Body="&lt;p&gt;Send/print the analogue pin data to Arduino's serial monitor, then use MAX MSP's serial object to recieve it. It's quite simple, no externals are required. Make sure you specify arguments to select the appropriate channel and Baud rate to match your Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have fun!  &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-09T18:12:17.370" />
  <row Id="951" PostTypeId="2" ParentId="940" CreationDate="2009-12-09T20:54:44.853" Score="4" ViewCount="" Body="&lt;p&gt;I found a couple of interesting points on the adafruit forum on this when i started looking into it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On this one the guy soldered another header on to the arduino as an '&lt;a href=&quot;http://forums.adafruit.com/viewtopic.php?f=25&amp;amp;t=13666&quot; rel=&quot;nofollow&quot;&gt;outrigger&lt;/a&gt;' - so that the new header lines up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And this one....  the guy has created his own &lt;a href=&quot;http://www.adafruit.com/index.php?main%5Fpage=product%5Finfo&amp;amp;cPath=17%5F21&amp;amp;products%5Fid=187&quot; rel=&quot;nofollow&quot;&gt;bent header&lt;/a&gt; which slots in so that you can make your own shield.&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-12-09T20:54:44.853" />
  <row Id="952" PostTypeId="1" CreationDate="2009-12-09T21:44:29.300" Score="31" ViewCount="1353" Body="&lt;p&gt;There are some great blogs out there for programmers (Joel on Software, Paul Graham's Essays, etc.). I would love to know about any similar quality content for electronics. Do you have any great blogs or podcasts you love?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(submit one answer for each blog)&lt;/p&gt;&#xA;" OwnerUserId="238" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-02-24T21:31:59.427" LastActivityDate="2010-10-20T21:45:59.547" CommunityOwnedDate="2009-12-09T21:44:45.007" Title="Electronics Blogs and Podcasts" Tags="&lt;electronics&gt;&lt;education&gt;" AnswerCount="30" CommentCount="1" FavoriteCount="22" />
  <row Id="953" PostTypeId="2" ParentId="952" CreationDate="2009-12-09T21:48:50.040" Score="10" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://chrisgammell.com/&quot; rel=&quot;nofollow&quot;&gt;Chris Gammell's Analog Life&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-12-09T21:48:50.040" CommunityOwnedDate="2009-12-09T21:48:50.040" CommentCount="1" />
  <row Id="954" PostTypeId="2" ParentId="952" CreationDate="2009-12-09T21:49:22.933" Score="20" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.eevblog.com/&quot; rel=&quot;nofollow&quot;&gt;Electronics Engineering Video Blog Podcast&lt;/a&gt;(eevblog)&lt;/p&gt;&#xA;" OwnerUserId="238" LastEditorUserId="238" LastEditorDisplayName="" LastEditDate="2009-12-10T01:22:58.483" LastActivityDate="2009-12-10T01:22:58.483" CommunityOwnedDate="2009-12-09T21:49:22.933" CommentCount="8" />
  <row Id="955" PostTypeId="2" ParentId="952" CreationDate="2009-12-09T21:49:56.543" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://electricio.us/&quot; rel=&quot;nofollow&quot;&gt;http://electricio.us/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-12-09T21:49:56.543" CommunityOwnedDate="2009-12-09T21:49:56.543" />
  <row Id="956" PostTypeId="2" ParentId="952" CreationDate="2009-12-09T22:25:14.223" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.neufeld.newton.ks.us/electronics/&quot; rel=&quot;nofollow&quot;&gt;Keith's Electronics Blog&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2009-12-09T22:25:14.223" CommunityOwnedDate="2009-12-09T22:25:14.223" />
  <row Id="957" PostTypeId="2" ParentId="952" CreationDate="2009-12-09T22:29:51.203" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://flyingflux.blogspot.com/&quot; rel=&quot;nofollow&quot;&gt;Flying Flux&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2009-12-09T22:29:51.203" CommunityOwnedDate="2009-12-09T22:29:51.203" />
  <row Id="958" PostTypeId="1" AcceptedAnswerId="961" CreationDate="2009-12-09T22:37:36.933" Score="2" ViewCount="692" Body="&lt;p&gt;Anyone used one of the &lt;a href=&quot;http://www.ftdichip.com/Products/FT2232H.htm&quot; rel=&quot;nofollow&quot;&gt;FT2232H&lt;/a&gt; chips from FTDI?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically, how do you figure out the permissible baud rates?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The data sheet is kind of vague, and I have to pick something in the 1-3 MBaud range but need to know what my options are.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-09-10T12:52:07.617" Title="FTDI FT2232H (USB &lt;-&gt; UART) baud rates?" Tags="&lt;usb&gt;&lt;uart&gt;&lt;ftdi&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="959" PostTypeId="2" ParentId="937" CreationDate="2009-12-09T22:49:52.927" Score="8" ViewCount="" Body="&lt;p&gt;So if I understand correctly, you want to be able to &quot;read&quot; a 10 mV variation on top of a 1.9V signal? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that is the case then I would suggest two separate stages. The first will be a &lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;ct=res&amp;amp;cd=1&amp;amp;ved=0CA0QFjAA&amp;amp;url=http%3A%2F%2Fwww.national.com%2Fonlineseminar%2F2004%2Fphotodiode%2FPhotodiodeAmplifers.pdf&amp;amp;ei=XicgS8fzDYmINuayycQC&amp;amp;usg=AFQjCNH-DJSgW4AUO7cFLUX7teuU64orAg&amp;amp;sig2=dzgHdIw49xXgAOMOd9o7ww&quot; rel=&quot;nofollow&quot;&gt;photodiode amplifier&lt;/a&gt; (page 9 is the most standard of circuits). This will help to get the current from your photodiode translated into voltage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second stage will be an instrumentatation amplifier, such as the INA family from Texas Instruments (the best but also can be expensive). This will help to remove your &quot;common mode&quot; signal, which in this case is the 1.9 V. You can also add gain in to the instrumentation amp or alternately add a simple op amp in a non-inverting configuration at the end to help gain your signal up to the necessary 5 V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not saying it'll be perfect, but I think that's a good start.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a final note, I like David's idea above about the clamps, even though those can cause some measurement errors at the A/D converter. What is more important though is if you can swing it, try a better op amp than the 741. Those are common but the specs are terrible. The 3 or 4 mV of offset voltage at the input terminals could really mess up a small signal like you're trying to measure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;~Chris Gammell&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2009-12-09T22:49:52.927" CommunityOwnedDate="2009-12-09T22:49:52.927" CommentCount="2" />
  <row Id="960" PostTypeId="2" ParentId="952" CreationDate="2009-12-09T23:15:23.140" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.embedded.com/columns/archive/?content%5Ftype=bp&quot; rel=&quot;nofollow&quot;&gt;Jack Ganssle's column&lt;/a&gt; on embedded.com - and indeed, &lt;a href=&quot;http://www.embedded.com/&quot; rel=&quot;nofollow&quot;&gt;embedded.com&lt;/a&gt; itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the collection of &lt;a href=&quot;http://www.ganssle.com/articles-subj.htm&quot; rel=&quot;nofollow&quot;&gt;articles on his website&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Admittedly these are mostly (though not entirely) software-oriented - but specifically embedded software.&lt;/p&gt;&#xA;" OwnerUserId="387" LastActivityDate="2009-12-09T23:15:23.140" CommunityOwnedDate="2009-12-09T23:15:23.140" />
  <row Id="961" PostTypeId="2" ParentId="958" CreationDate="2009-12-09T23:27:02.510" Score="4" ViewCount="" Body="&lt;p&gt;I had this problem too. FTDI considers it more a driver issue than a chip issue.  Head over to the &lt;a href=&quot;http://www.ftdichip.com/Documents/AppNotes.htm&quot; rel=&quot;nofollow&quot;&gt;FTDI App Notes&lt;/a&gt; area and look at the &quot;AN_120 Aliasing VCP Baud Rates&quot; PDF appnote.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-09T23:27:02.510" CommentCount="5" />
  <row Id="962" PostTypeId="2" ParentId="937" CreationDate="2009-12-09T23:28:52.630" Score="3" ViewCount="" Body="&lt;p&gt;Suggest you look at the combination of a differential PGA (programmable gain amplifier) and a DAC, with the sensor output going to the &quot;+&quot; input and the DAC going to the &quot;-&quot; input. (Or something integrated that gives you equivalent functionality.) Basically, look at the signal with low gain, figure out what its offset is, put that voltage on the DAC, and crank the gain up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/pga308.html&quot; rel=&quot;nofollow&quot;&gt;TI's PGA308&lt;/a&gt; looks like it might be a nice solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want a less expensive solution, use a fixed-gain differential amplifier (the standard 4-resistor + op-amp would do) + a stable, quiet 8-bit DAC (stability/noise characteristics more important than accuracy), again put the sensor output on the &quot;+&quot; input to the diff amp and the DAC output on the &quot;-&quot; input. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Exercise for the reader: show that you can bring the diff-amp output out of saturation and into a linear range by using a binary search technique with the DAC, and ensuring that the gain is not larger than G1 = the fullscale ADC input voltage, divided by the sum of the DAC's nominal step size and its DNL (differential nonlinearity). I'd probably use the smaller of (G1/2) and G2, where G2 = the fullscale ADC input voltage divided by the sensor output voltage range that you care about.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-09T23:28:52.630" CommunityOwnedDate="2009-12-09T23:28:52.630" CommentCount="3" />
  <row Id="963" PostTypeId="2" ParentId="952" CreationDate="2009-12-09T23:47:47.280" Score="5" ViewCount="" Body="&lt;p&gt;There are lots of blogs that people use to talk about their own projects.&#xA;They may not be &quot;general education&quot; but you wil certainly learn something.&#xA;Some of my favorites:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://mightyohm.com/blog/&quot; rel=&quot;nofollow&quot;&gt;http://mightyohm.com/blog/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://projects.dimension-x.net/&quot; rel=&quot;nofollow&quot;&gt;http://projects.dimension-x.net/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://interactive-matter.org/&quot; rel=&quot;nofollow&quot;&gt;http://interactive-matter.org/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This one is more engineering oriented&#xA; - &lt;a href=&quot;http://www.eevblog.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.eevblog.com/&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2009-12-09T23:47:47.280" CommunityOwnedDate="2009-12-09T23:47:47.280" />
  <row Id="964" PostTypeId="2" ParentId="592" CreationDate="2009-12-09T23:59:55.623" Score="5" ViewCount="" Body="&lt;p&gt;I know it's not all online, but &lt;a href=&quot;http://books.google.com/books?id=bkOMDgwFA28C&amp;amp;printsec=frontcover&amp;amp;source=gbs%5Fnavlinks%5Fs#v=onepage&amp;amp;q=&amp;amp;f=false&quot; rel=&quot;nofollow&quot;&gt;the Art of Electronic by Horowitz and Hill&lt;/a&gt; is fantastic. It's basically the only book you need for the first 2 years of learning electronics (especially if you don't have any math requirements). The second edition of the book was published back in the late 80s and a lot of the example circuits using op amps are spectacular examples.&lt;/p&gt;&#xA;" OwnerUserId="404" LastEditorUserId="404" LastEditorDisplayName="" LastEditDate="2009-12-15T23:46:07.410" LastActivityDate="2009-12-15T23:46:07.410" CommentCount="5" />
  <row Id="965" PostTypeId="2" ParentId="952" CreationDate="2009-12-10T01:19:52.627" Score="3" ViewCount="" Body="&lt;p&gt;Although rather infrequent &lt;a href=&quot;http://www.adafruit.com/blog/feed/adacast&quot; rel=&quot;nofollow&quot;&gt;Adafruit Industries - Citizen Engineer&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-12-10T01:19:52.627" CommunityOwnedDate="2009-12-10T01:19:52.627" />
  <row Id="966" PostTypeId="1" CreationDate="2009-12-10T01:30:24.133" Score="42" ViewCount="1751" Body="&lt;p&gt;I am thinking about ordering up some parts for every day use. I am thinking about making one big purchase so as to minimize on shipping and other charges. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are some of the components that any electronics hobbyist should have around ALL the time?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To put a little more scope: typically working with Arduino's, PICs and sensors. 5V - low current projects. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking for: component, value or range (if any), manufacturer (optional) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example -  Resistors, 1K through 100K 5W&lt;/p&gt;&#xA;" OwnerUserId="245" LastEditorUserId="328" LastEditorDisplayName="" LastEditDate="2009-12-10T10:38:44.207" LastActivityDate="2011-05-13T19:28:34.783" CommunityOwnedDate="2009-12-15T18:49:36.233" Title="Which electronics components should I always have on hand?" Tags="&lt;electronics&gt;&lt;components&gt;" AnswerCount="18" CommentCount="1" FavoriteCount="24" />
  <row Id="967" PostTypeId="2" ParentId="966" CreationDate="2009-12-10T03:52:07.247" Score="14" ViewCount="" Body="&lt;p&gt;I really enjoy having a few BJTs and a few MOSFETs around. If you are used to using them, building a very high gain amplifier with an offset to put it in the middle of your ADC range will always pay off. The number of times 1 cap, 2 resistors and a BJT replaced 4 op-amps with an entire range of components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make a list:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Resistors&lt;/strong&gt;, the normal set you can get, I like to have 1 ohm through 10 Meg, but I have a lot of resistors, they never hurt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Caps&lt;/strong&gt;, the basic values, 1000pF, .1uF, 4.7uF, there are a few more, but you get the idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;inductors&lt;/strong&gt;, I honestly never have any, I only used them in projects specific to a professor assigning them(RFID).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;BJTs&lt;/strong&gt;, just get some cheap through hole ones, I would keep one that can handle pretty high current, and them some that are designed for the 100uA - 500mA range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;op-amps&lt;/strong&gt;, there are many times where they help, comparator operation is my most common. I like rail-to-rail op-amps. There are many other things to look for, but for my use, rail-rail is the most important.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some 5V and 3.3V &lt;strong&gt;linear regulators&lt;/strong&gt;, it is nice to be able to step from a wall converter that is something around 9V to a usable range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Heatsinks&lt;/strong&gt; can be nice to have, especially for those linear regulators.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;LEDs&lt;/strong&gt; and &lt;strong&gt;Photodiodes&lt;/strong&gt;, LEDs for debugging and so forth, photodiodes because you never know when you need to measure light(I like to have a few IR and some general visible light ones).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://mouser.com/ProductDetail/SST/SST25VF080B-50-4C-PAE/?qs=UWkW%252b1WCrVryuwkQtgw4gQ%3d%3d&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;Flash&lt;/strong&gt;, for example, this PDIP 1MB chip&lt;/a&gt; is a 1.34 a piece and can really improve the memory of your system. You can get a little larger for about the same if you do not mind a SOIC-16 package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know Flash memory seems a bit odd, but I have so many different projects where non-volatile memory helps, and often I just need more space, it meets both bills.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this list helps.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-12-10T03:52:07.247" CommentCount="5" />
  <row Id="968" PostTypeId="2" ParentId="966" CreationDate="2009-12-10T05:31:56.890" Score="6" ViewCount="" Body="&lt;p&gt;I would vote for having a 5K or 10K twenty turn pot on hand. It can be useful for things like nulling offsets tweaks during breadboarding. I doubt you'll be using the pots much in the final circuits however, so just a couple will probably do you.&lt;/p&gt;&#xA;" OwnerUserId="227" LastActivityDate="2009-12-10T05:31:56.890" CommentCount="1" />
  <row Id="969" PostTypeId="2" ParentId="2" CreationDate="2009-12-10T07:15:35.637" Score="2" ViewCount="" Body="&lt;p&gt;This is a particularly clean implementation for automagic analog and digital input with some built-in code for using a 4051 multiplexer on the analog pins:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://pixlpa.com/blog/arduino-sensorbox-firmware&quot; rel=&quot;nofollow&quot;&gt;SensorBox&lt;/a&gt; by Andrew Benson&#xA;(via &lt;a href=&quot;http://cycling74.com/forums/topic.php?id=22767#post-116559&quot; rel=&quot;nofollow&quot;&gt;C74 forum&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2009-12-10T07:15:35.637" />
  <row Id="970" PostTypeId="2" ParentId="966" CreationDate="2009-12-10T10:37:56.190" Score="29" ViewCount="" Body="&lt;p&gt;Here is my general collection. Apart from the components listed below, when ever I by parts I usually by a few extras. It doesn't take long to build odds and ends that way.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;1/2 W 1% Metal Film Resistors. All E12 values between about 100 R and 1 Meg. Random collection of values in 5W.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;1, 10, 22, 33, 68, 100, 220, 330 nF 63 V film caps. A random assortment of electrolytics - 1, 10, 100 uF in voltages between 16 V to 63 V. A hand full of different value ceramics less than 1 nF.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;General purpose PNP and NPN transistors. I typically have BC337/327s laying around, but just about anything will do.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;2N7000 N-fet&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Which ever high power BJTs and FET you come across. But it's hand to keep at least one decent N-FET laying around.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;LM7805 and LM317s. These are almost indestructible. The 317's with a single resistor makes a really hand current source that's good when you want to protect an output or power supply but don't need anything to accurate. (The circuit is in the datasheet)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Opamps - TL072 or TL074 for a general purpose, low input current. LM358 are easy to get and while not rail-to-rail, can be used for many applications of a single rail. I also have a sampling of different rail-to-rail op-amps that get used occasionally.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Some shunt references. LM336, TL431 or many others. Adjustable ones are hand to keep on standby so you set them to the value you need.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;1N4148's and 1N4007's.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;A couple of spare micro-controller in you favorite flavor.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Crystals and load caps to suit your favorite micro-controller.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="328" LastActivityDate="2009-12-10T10:37:56.190" CommentCount="4" />
  <row Id="971" PostTypeId="2" ParentId="927" CreationDate="2009-12-10T11:34:55.780" Score="1" ViewCount="" Body="&lt;p&gt;Wiznet have stated that it is not possible to disable the trailers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://wiznet.co.kr/rg4%5Fboard/view.php?&amp;amp;bbs%5Fcode=en%5Fqna&amp;amp;bd%5Fnum=21321&quot; rel=&quot;nofollow&quot;&gt;http://wiznet.co.kr/rg4_board/view.php?&amp;amp;bbs_code=en_qna&amp;amp;bd_num=21321&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="298" LastActivityDate="2009-12-10T11:34:55.780" CommentCount="6" />
  <row Id="972" PostTypeId="2" ParentId="952" CreationDate="2009-12-10T12:46:18.077" Score="3" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.allaboutcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.allaboutcircuits.com/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.eetimes.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.eetimes.com/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/tutorials.php&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/tutorials.php&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://itp.nyu.edu/physcomp/Tutorials/Tutorials&quot; rel=&quot;nofollow&quot;&gt;http://itp.nyu.edu/physcomp/Tutorials/Tutorials&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-12-10T12:46:18.077" CommunityOwnedDate="2009-12-10T12:46:18.077" />
  <row Id="973" PostTypeId="2" ParentId="952" CreationDate="2009-12-10T14:29:56.490" Score="9" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.hackaday.com&quot; rel=&quot;nofollow&quot;&gt;http://www.hackaday.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="406" LastActivityDate="2009-12-10T14:29:56.490" CommunityOwnedDate="2009-12-10T14:29:56.490" />
  <row Id="974" PostTypeId="2" ParentId="966" CreationDate="2009-12-10T14:38:09.680" Score="18" ViewCount="" Body="&lt;p&gt;I feel like the component left off this list is the almighty zener (maybe some 1V and 5V so you can build up voltages you need). You can use them for grunt references for DACs (assuming you don't care about drift) and they are useful for setting up voltages wherever you need them. They also work great as clamps in the event you want to protect your circuit from overvoltage at one point or another (the zener will kick in and start sinking current whenever the node it is on goes above the voltage of the zener). You can also use them to set up current sources in conjuction with a resistor and a transistor to have a very stable current source for other parts of your circuits (works much better than just a resistor and a voltage source).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I never really realized the power of them until I started using them.&lt;/p&gt;&#xA;" OwnerUserId="404" LastEditorUserId="404" LastEditorDisplayName="" LastEditDate="2009-12-10T14:51:45.213" LastActivityDate="2009-12-10T14:51:45.213" CommentCount="2" />
  <row Id="975" PostTypeId="2" ParentId="966" CreationDate="2009-12-10T14:47:27.563" Score="14" ViewCount="" Body="&lt;p&gt;I keep around breakaway pins and headers.  They're great for dev boards, orders from SparkFun and for working with an Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also suggest some male-male jumper wires if you plan on using breadboards with an Arduino.  They're very handy.  Instead of jumper wires, I use solid-core hook-up wire in various colors (I believe 22-ga, but the size isn't critical).  I find I have made quite a collection of varying-length jumpers this way and saved a few bucks, but having them soldered to pins prevents you from breaking off an overused wire in a header, which is quite frustrating.  It's only a few bucks, so it's probably worth it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, a box of those pre-cut and tinned breadboard jumper wires are really handy.  They come in varying colors and lengths, which makes it easy to build prototypes quickly.  I do keep a box of these around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For small but versatile circuits, such as proven power regulators, those tiny breadboards can't be beat.  I have a few around with common circuits that I frequently use as building blocks for larger composite circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know these aren't components, &lt;em&gt;per se&lt;/em&gt;, but I find them very handy to have around to use with my components and felt it was within the spirit of the question to include them.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-12-10T14:47:27.563" CommentCount="2" />
  <row Id="976" PostTypeId="2" ParentId="952" CreationDate="2009-12-10T15:01:53.760" Score="2" ViewCount="" Body="&lt;p&gt;Not specifically electronics but plenty of projects:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/&quot; rel=&quot;nofollow&quot;&gt;Instructables&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-10T15:01:53.760" CommunityOwnedDate="2009-12-10T15:01:53.760" />
  <row Id="977" PostTypeId="2" ParentId="952" CreationDate="2009-12-10T15:03:52.397" Score="4" ViewCount="" Body="&lt;p&gt;Very inspiring:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.makezine.com/&quot; rel=&quot;nofollow&quot;&gt;Make:Blog&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-10T15:03:52.397" CommunityOwnedDate="2009-12-10T15:03:52.397" />
  <row Id="978" PostTypeId="2" ParentId="952" CreationDate="2009-12-10T15:07:43.780" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://ericarcher.net/&quot; rel=&quot;nofollow&quot;&gt;Eric Archer's Site&lt;/a&gt; especially the Devices section.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-10T15:07:43.780" CommunityOwnedDate="2009-12-10T15:07:43.780" />
  <row Id="979" PostTypeId="2" ParentId="952" CreationDate="2009-12-10T15:10:51.067" Score="1" ViewCount="" Body="&lt;p&gt;If you've ever wanted to build your own Synth:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.musicfromouterspace.com/&quot; rel=&quot;nofollow&quot;&gt;Music From Outer Space&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out the Virtual Breadboard Designer under the Electronic Bubblegum section if nothing else.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-10T15:10:51.067" CommunityOwnedDate="2009-12-10T15:10:51.067" />
  <row Id="980" PostTypeId="2" ParentId="952" CreationDate="2009-12-10T15:26:56.313" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.soldersmoke.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.soldersmoke.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A lovely little ham radio podcast that I've been listening to for years. I'm not a ham radio guy at all, so there's plenty of interest to the general technologist here.&lt;/p&gt;&#xA;" LastActivityDate="2009-12-10T15:26:56.313" CommunityOwnedDate="2009-12-10T15:26:56.313" />
  <row Id="981" PostTypeId="2" ParentId="952" CreationDate="2009-12-10T16:24:18.650" Score="9" ViewCount="" Body="&lt;p&gt;I'm surprised that nobody mentioned The Fat Man and Circuit Girl:&#xA;&lt;a href=&quot;http://www.fatmanandcircuitgirl.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.fatmanandcircuitgirl.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd say it's more along the lines of Joel on Software, where they're really sharing a lot of information on things they've tried and how it's worked out, but the community goes above and beyond.  It's a very entertaining and educational group.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-12-10T16:24:18.650" CommunityOwnedDate="2009-12-10T16:24:18.650" />
  <row Id="982" PostTypeId="2" ParentId="952" CreationDate="2009-12-10T18:07:06.147" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://tinkerlog.com&quot; rel=&quot;nofollow&quot;&gt;http://tinkerlog.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="407" LastActivityDate="2009-12-10T18:07:06.147" CommunityOwnedDate="2009-12-10T18:07:06.147" CommentCount="2" />
  <row Id="983" PostTypeId="2" ParentId="966" CreationDate="2009-12-10T19:50:54.970" Score="7" ViewCount="" Body="&lt;p&gt;If your working with Pics and Arduinos it's probably a good idea to get some shift registers, you never know when your going to need a load of extra ins and outs.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-10T19:50:54.970" />
  <row Id="984" PostTypeId="1" AcceptedAnswerId="988" CreationDate="2009-12-10T22:32:15.080" Score="14" ViewCount="969" Body="&lt;p&gt;I just recently started using a Sparkfun serial LCD. I am able to control it through an arduino, but I want to be able to control it through a terminal on my computer. To be able to move the cursor or clear the screen, you need to be able to send hexadecimal code to it, for example, 0xFE. I am unable to find an open source terminal program for Windows that will give me this functionality. An example of a program that works very well is &lt;a href=&quot;http://www.eltima.com/products/serial-port-monitor/&quot; rel=&quot;nofollow&quot;&gt;Eltima serial port monitor&lt;/a&gt;, although it is rather expensive for just a student. I have a USB to serial FTDI breakout board to get the signal to the LCD. Any suggestions as for programs, under Windows 7, will be greatly appreciated.&lt;/p&gt;&#xA;" OwnerUserId="92" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-22T10:52:24.560" LastActivityDate="2011-03-22T10:52:24.560" Title="Best serial monitor?" Tags="&lt;serial&gt;&lt;lcd&gt;" AnswerCount="11" FavoriteCount="4" />
  <row Id="985" PostTypeId="2" ParentId="966" CreationDate="2009-12-10T22:41:46.293" Score="12" ViewCount="" Body="&lt;p&gt;adjustable shunt voltage reference:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;TLVH431 -- I highly recommend this one, it's inexpensive and works up to 18V while using a 1.25V reference pin threshold (original TL431's are 2.5V) and reference pin current is very low. TLV431 is less expensive if you only need up to 6V operation.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Analog multiplexers:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;HC4051/4052/4053 series -- these are good for general-purpose, low-source-impedance (&amp;lt;1kohm) input voltages (leakage current spec is 1uA which is pretty lousy)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;FSA4157 / NLAS4157 -- these are good for micropower circuits, they specify leakage current much lower than the HC405x series.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;dual opamps that are relatively inexpensive but decent (look at specs to see what you like):&#xA;I prefer duals as they are more economical than singles but easier to layout than quads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;rail-to-rail input and output (RRIO):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;MCP6242&lt;/li&gt;&#xA;&lt;li&gt;MCP6022&lt;/li&gt;&#xA;&lt;li&gt;TS922&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;rail-to-rail output (RRO)&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;MCP602&lt;/li&gt;&#xA;&lt;li&gt;MCP617&lt;/li&gt;&#xA;&lt;li&gt;LMV358&lt;/li&gt;&#xA;&lt;li&gt;LMV822&lt;/li&gt;&#xA;&lt;li&gt;LMV722&lt;/li&gt;&#xA;&lt;li&gt;LMV772&lt;/li&gt;&#xA;&lt;li&gt;TLC2272&lt;/li&gt;&#xA;&lt;li&gt;TLV2442&lt;/li&gt;&#xA;&lt;li&gt;LVC342&lt;/li&gt;&#xA;&lt;li&gt;TLV272&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-10T22:41:46.293" CommentCount="1" />
  <row Id="986" PostTypeId="2" ParentId="984" CreationDate="2009-12-10T23:55:00.460" Score="3" ViewCount="" Body="&lt;p&gt;See &lt;a href=&quot;http://www.opencircuits.com/PC-Microcontroller_Communications&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/PC-Microcontroller_Communications&lt;/a&gt; for a discussion of serial monitors, mostly free.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-12-10T23:55:00.460" />
  <row Id="987" PostTypeId="2" ParentId="984" CreationDate="2009-12-11T00:55:44.543" Score="2" ViewCount="" Body="&lt;p&gt;My current favorite is MTTTY and can be downloaded from &#xA;&lt;a href=&quot;http://www.netburner.com/support/public_downloads.html&quot; rel=&quot;nofollow&quot;&gt;http://www.netburner.com/support/public_downloads.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2009-12-11T00:55:44.543" />
  <row Id="988" PostTypeId="2" ParentId="984" CreationDate="2009-12-11T01:41:02.630" Score="16" ViewCount="" Body="&lt;p&gt;I just write short Python programs using &lt;a href=&quot;http://pyserial.sourceforge.net/index.html&quot; rel=&quot;nofollow&quot; title=&quot;pySerial&quot;&gt;pySerial&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;&amp;gt;&amp;gt;&amp;gt; import serial&#xA;&amp;gt;&amp;gt;&amp;gt; ser = serial.Serial(0)  # open first serial port&#xA;&amp;gt;&amp;gt;&amp;gt; print ser.portstr       # check which port was really used&#xA;&amp;gt;&amp;gt;&amp;gt; ser.write(&quot;hello&quot;)      # write a string&#xA;&amp;gt;&amp;gt;&amp;gt; ser.write(0xa4)         # write a byte&#xA;&amp;gt;&amp;gt;&amp;gt; ser.close()             # close port&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="86" LastActivityDate="2009-12-11T01:41:02.630" />
  <row Id="989" PostTypeId="2" ParentId="984" CreationDate="2009-12-11T02:25:06.310" Score="8" ViewCount="" Body="&lt;p&gt;You want something like  &lt;a href=&quot;http://www.chiark.greenend.org.uk/~sgtatham/putty/&quot; rel=&quot;nofollow&quot;&gt;PuTTY&lt;/a&gt; or &lt;a href=&quot;http://ttssh2.sourceforge.jp/&quot; rel=&quot;nofollow&quot;&gt;TeraTerm&lt;/a&gt; for human-readable serial i/o, or a good programming environment that makes it easy to open/access serial ports. I'm not a Python expert but MrEvil has a good point. Also the &lt;a href=&quot;http://www.jsdb.org/&quot; rel=&quot;nofollow&quot;&gt;jsdb Javascript shell&lt;/a&gt; has an easy-to-use COM port feature:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;S = new Stream('com1://115200');&#xA;S.write(0xf4);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-11T02:25:06.310" CommentCount="1" />
  <row Id="990" PostTypeId="2" ParentId="984" CreationDate="2009-12-11T17:05:01.170" Score="3" ViewCount="" Body="&lt;p&gt;take a look at bray terminal at &lt;a href=&quot;http://hw-server.com/software/termv19b.html&quot; rel=&quot;nofollow&quot;&gt;http://hw-server.com/software/termv19b.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i think it's the best free terminal&lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2009-12-11T17:05:01.170" />
  <row Id="991" PostTypeId="1" CreationDate="2009-12-11T17:19:49.097" Score="15" ViewCount="2578" Body="&lt;p&gt;I am planning to migrate to the NXP Cortex M3 architecture and I'm a little lost between the existant development tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keil is expensive and I don't know if it's worth it.&#xA;Anyone who has tried some compiler can give any advice?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this compiler &lt;a href=&quot;http://www.code-red-tech.com/red-suite-2.php&quot; rel=&quot;nofollow&quot;&gt;http://www.code-red-tech.com/red-suite-2.php&lt;/a&gt; it seems good and not expensive.&#xA;Anyone who tried it or know about it can give me more info?&lt;/p&gt;&#xA;" OwnerUserId="199" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-02T00:07:46.920" LastActivityDate="2010-11-30T23:23:48.247" Title="ARM Cortex-M3 development tools ?" Tags="&lt;compiler&gt;&lt;arm&gt;" AnswerCount="8" CommentCount="2" FavoriteCount="7" />
  <row Id="992" PostTypeId="1" AcceptedAnswerId="995" CreationDate="2009-12-11T17:50:36.977" Score="6" ViewCount="292" Body="&lt;p&gt;I've noticed that in analog signal acquisition hardware you see two paradigms: AC-coupled and DC-coupled.  Typically AC-coupled hardware is less expensive, and basically has a 20 Hz high-pass filter to remove the DC component.  DC-coupled hardware, which is good for reading sensor signals for example, tends to be in the hundreds or thousands of dollars, whereas AC-coupled hardware like computer sound cards is very inexpensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the electrical challenges in designing high-quality circuits for sampling DC-frequency analog signals?  I'm trying to understand why there is this huge difference in cost.&lt;/p&gt;&#xA;" OwnerUserId="344" LastActivityDate="2009-12-11T21:05:20.290" Title="What's the difference (electrically) between AC- and DC-coupled sampling circuits?" Tags="&lt;analog&gt;&lt;electronics&gt;" AnswerCount="2" />
  <row Id="993" PostTypeId="2" ParentId="992" CreationDate="2009-12-11T18:32:18.440" Score="3" ViewCount="" Body="&lt;p&gt;Being DC-accurate (or at least accurate for frequency content below a few Hz) is tough -- you need absolute references + amplifiers that have low offset errors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In addition, the major market for high-accuracy AC sampling circuits is audio, so ADCs for AC circuits have additional economies of scale.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-11T18:32:18.440" CommentCount="1" />
  <row Id="994" PostTypeId="1" AcceptedAnswerId="1004" CreationDate="2009-12-11T20:02:13.650" Score="7" ViewCount="844" Body="&lt;p&gt;I'm a long time AVR user.  I really like that AVR-GCC works on the two main OSes I use (Mac OS X and Linux), is open-source, and is supported by Atmel.  I'd like to get back into PIC programming (used them in the 90s) since there are some pretty good PICs out there, like the PIC18F4550-class of chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, most all the compilers for PIC18s seem to be Windows-only and for-pay.  And they almost always have an IDE that I do not need.  I prefer command-line compilers and Makefiles so I can tell by glancing at a single file how code gets built. (and not wade through a twisty maze of dialog boxes)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I poked around at &lt;a href=&quot;http://sdcc.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;SDCC&lt;/a&gt; but it doesn't appear to have PIC18F4550 support and even if it did, grumblings on the net make it sound like its PIC18 support is weak, or at best very confusing to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, what's a good cross-platform command-line C-compiler with PIC18F4550 support out there?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Failing that, what's the best-of-breed C-compiler for PIC18F4550 and how does one use it with Makefiles?&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-13T09:31:20.807" Title="PIC18F4550 C-compiler that's open-source &amp; cross-platform?" Tags="&lt;pic&gt;&lt;compiler&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="995" PostTypeId="2" ParentId="992" CreationDate="2009-12-11T21:05:20.290" Score="4" ViewCount="" Body="&lt;p&gt;Components are always a big cost. When you need high accuracy resistors, you can run up your BOM cost quickly. Add in some pricey op amps (which are also my favorite, unfortunately), and you can have a 100 dollar board in no time. If you want to match the high speed A/D technology of the AC coupled circuits you speak of and want to do it at a high resolution you also will be paying through the nose. Just the other day I was looking at an 18 bit, 1 MSPS A/D that topped 25 dollars. You could build a lot of cool stuff with that same 25 bucks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, a key thing to remember is 1/f noise. As you go towards (absolute) DC noise goes through the roof. DC is a tough field, but I work with it everyday so if you have any other questions, give me a shout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;~Chris Gammell&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2009-12-11T21:05:20.290" CommentCount="3" />
  <row Id="996" PostTypeId="2" ParentId="693" CreationDate="2009-12-11T21:39:19.027" Score="1" ViewCount="" Body="&lt;p&gt;The problem is that the AVR-GCC library file &quot;iom88p.h&quot; for the ATmega88P (and similar files for ATmega168P and ATmega328P) is broken.  It doesn't define the SIG_INTERRUPT0 interupt vector handler and only defines the alternate handler name of INT0_vect.  The V-USB assembly code uses SIG_INTERRUPT0 and for some reason avr-as doesn't pick up the null define.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This library problem is also why you can no longer use defines like &quot;PC3&quot; in Arduino and must instead use &quot;PORTC3&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The solution in the case of V-USB is to go into the &quot;usbconfig.h&quot; for your project and add:&lt;pre&gt;&#xA;     #define USB_INTR_VECTOR         INT0_vect&#xA;&lt;/pre&gt;&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-11T21:39:19.027" />
  <row Id="997" PostTypeId="1" AcceptedAnswerId="999" CreationDate="2009-12-12T16:16:19.007" Score="7" ViewCount="275" Body="&lt;p&gt;I'm working on a little sensor platform that runs off of batteries.  I'd love to be able to trigger an alert when the voltage gets too low.  The problem is that anything I use to measure that voltage will be powered by that same voltage source.  FWIW, I'm running arduino pro-mini clones (3.3V) off of 4xAA rechargeables (4.8V to start with, but the system seems to work right down to 2V or so, including the XBee transmitter).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any clever ideas for how to work this?  It seems like anything using the analog inputs of the Atmega chip will just be comparing the input voltage with itself.  Maybe checking the difference between what comes from the regulator and what comes from the batteries themselves?&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-12-18T03:30:49.003" Title="Monitoring voltage without a known reference" Tags="&lt;battery&gt;&lt;power&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="998" PostTypeId="2" ParentId="997" CreationDate="2009-12-12T17:34:26.540" Score="5" ViewCount="" Body="&lt;p&gt;How about a supply supervisor like &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tps3836x.html&quot; rel=&quot;nofollow&quot;&gt;these Texas ones&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Typically, they monitor the supply, and if it dips below a fixed threshold, an output pin changes state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can then connect this to your processor's non-maskable interrupt (or reset) pin.&lt;/p&gt;&#xA;" OwnerUserId="387" LastActivityDate="2009-12-12T17:34:26.540" CommentCount="4" />
  <row Id="999" PostTypeId="2" ParentId="997" CreationDate="2009-12-12T18:01:01.040" Score="7" ViewCount="" Body="&lt;p&gt;Most (all?) AVR's with an ADC have an internal reference voltage which is regulated to a constant value, independent of the voltage supply. Check your datasheet...in the chip I'm using, it's 2.56V. There's a register that picks between comparing against Vcc, AREF, or internal voltage reference. You'd just set it to compare against internal voltage reference, along with using a voltage divider so the maximum voltage is never over 2.56V. &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-12T18:01:01.040" CommentCount="3" />
  <row Id="1000" PostTypeId="2" ParentId="966" CreationDate="2009-12-12T20:01:33.443" Score="11" ViewCount="" Body="&lt;p&gt;Lots of 10K resistors.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2009-12-12T20:01:33.443" CommentCount="3" />
  <row Id="1001" PostTypeId="1" AcceptedAnswerId="1002" CreationDate="2009-12-13T01:25:17.230" Score="7" ViewCount="459" Body="&lt;p&gt;I'm currently an undergraduate student in a design/engineering focussed fine art program. I do projects along the lines of what you might find at the &lt;a href=&quot;http://www.media.mit.edu/&quot; rel=&quot;nofollow&quot;&gt;MIT Media Lab&lt;/a&gt;. Recently I've become interested in circuit design, signal processing, and networks for sensing applications. &quot;How can we sense aspects of the environment while retaining the richness of the phenomena under observation&quot; is a guiding question for me. Observing the people around me who do research along these lines, I find that most have an electrical engineering, mathematics, or physics background. A select few might have studied music or a less related science. Those who studied fine art typically stick to the 'experience' side of design. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a few years left in which to take classes. I'm wondering: I've had access to a particular research community and it seems that on my current track, devoid of any math or engineering classes, I can learn what it takes to do what I want on my own through books, the internet, and helpful lab technicians. However, I'm not sure that I can teach myself enough that I could find a job designing electrical systems (not that I necessarily want a job doing this, but it's a good arbitrary measure of ability and confidence). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This project, for instance, is something I would be delighted to work on: &lt;a href=&quot;http://www.hpl.hp.com/research/quantum_systems/&quot; rel=&quot;nofollow&quot;&gt;HP Central Nervous System for the Earth&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I plan on taking some math or electronics classes in the coming years? Or perhaps after university I could do a short technical program to compensate for my lack of 'hard' classes in undergrad? I have math through Calculus II (I should review series' though) and basic linear algebra. (One thing to note is that I originally was an engineering student, but I can't stand the way the classes are taught, so I dropped it for a program that let me learn things at my own pace.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What classes did you find particularly useful to your work? Could I just read the textbook, or is it necessary to take the class?&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2009-12-16T18:11:13.480" CommunityOwnedDate="2009-12-13T01:25:29.217" Title="Do I Need to Study Electronics to Get a Job in Signal Processing or Sensor Network Design?" Tags="&lt;education&gt;&lt;sensor&gt;&lt;dsp&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="1002" PostTypeId="2" ParentId="1001" CreationDate="2009-12-13T04:21:09.033" Score="13" ViewCount="" Body="&lt;p&gt;I think in general, yes you will need to, but not necessarily for the actual learning aspects of it. The sad fact is, if you want to work on certain things, you'll need certain credentials. I think if you're trying to do sensor type stuff you'd need a BS. If you're going to do DSP type stuff, you'll need more. If you want to be a system architect, you'll need a bunch of degrees, experience and luck. But that is just what I've seen so far in my career.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, aside from the idea that you MUST take classes or MUST graduate with A, B, or C degree, I think it's better to look at it from what you can learn. You say you have calculus II (good), but there are more advanced topics in the math area and much more in the ways you can apply that knowledge. For DSP type situations, I feel like the math is even more important. Plus I feel like if I never went to school but was still interested in this field, I would be most lacking because it's a lot easier to just wave my hand sometimes and say &quot;It works because it works&quot; than actually explaining it. Also, I have a limited sample size, but haven't met any that work on DSP yet that weren't stellar at applying their knowledge to their field. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Classes I think you should take a look at:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Signals: if you want to touch DSP, you need to understand all of the mathematical models that are used and how to manipulate signals. There are some great programs out there like MATLAB, but if you don't understand the math behind a Fourier transform, for instance, you'll just be pushing buttons.&lt;/li&gt;&#xA;&lt;li&gt;Advanced circuits: You can learn the simple stuff on your own, and I'm guessing you already have. However, it's important again to realize how the mathematical models fit in here. Having exposure to low component count, high complexity system (think two transistor amplifiers) can require a lot of math. I don't know how small you would want to go on the component level (down to the silicon?) but if you're down in that region, you'll need tons o' math.&lt;/li&gt;&#xA;&lt;li&gt;Electrical Design: Any class involving electrical system design--analog, digital, DSP or otherwise--is important. This is where most schools are truly lacking, for good reason. It's hard to emulate what you'd encounter outside the classroom when designing something with classroom-like constraints. It's important, though, because you need to understand the working in a team, the time involved and how to create something that not only works, but works in a variety of situations. Like I said, this might not necessarily happen in a design class, but it's more likely than would happen in a French literature class.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;A class that isn't on this list because I don't think that any school offers it is networking. If you want to touch a program like that HP one you mentioned, get to know people working on it early and figure out what you'd need to do. And keep in touch with them. And meet others there and get THEM to recommend you too. The thing that no school teaches is that no matter how many courses you take and how well you do in school, if you don't get your butt in the door somehow, you'll never work there. The other thing they don't teach you is that there are likely others wanting to work on the exact same project as you and might be as good or better than you at it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, learn your EE stuff well (it'll pay off in most anything you do) and get to know people that work on projects that you think you'd enjoy (ask them if they enjoy it too). That's probably the simplest advice I can offer.&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2009-12-13T04:21:09.033" CommunityOwnedDate="2009-12-13T04:21:09.033" />
  <row Id="1003" PostTypeId="2" ParentId="1001" CreationDate="2009-12-13T04:40:24.470" Score="6" ViewCount="" Body="&lt;p&gt;signals &amp;amp; systems (feedback/control/signal processing) is almost completely disjunct from electronics. If you're interested in DSP you don't necessarily need much electronics. (&lt;em&gt;edit, based upon comments&lt;/em&gt;: but learning electronics is good for you anyway!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;sensors: electronics is much more relevant here.&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-12-14T00:42:14.573" LastActivityDate="2009-12-14T00:42:14.573" CommunityOwnedDate="2009-12-13T04:40:24.470" CommentCount="6" />
  <row Id="1004" PostTypeId="2" ParentId="994" CreationDate="2009-12-13T09:31:20.807" Score="5" ViewCount="" Body="&lt;p&gt;SDCC works fine for the 18F4550.  The code it produces is maybe not as compact as the expensive compilers.  But recent builds of SDCC seem to be doing a pretty good job.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://vivara.net/blog/?p=55&quot; rel=&quot;nofollow&quot;&gt;Here's a project&lt;/a&gt; I did with SDCC and the 18f2550. &lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2009-12-13T09:31:20.807" CommentCount="1" />
  <row Id="1005" PostTypeId="2" ParentId="1001" CreationDate="2009-12-13T13:39:23.677" Score="3" ViewCount="" Body="&lt;p&gt;For DSP related stuff, it's all math. I found the Lathi books (&lt;a href=&quot;http://www.amazon.com/Systems-Signals-Electrical-Computer-Engineering/dp/0195158334/ref=sr%5F1%5F2?ie=UTF8&amp;amp;s=books&amp;amp;qid=1260711423&amp;amp;sr=1-2&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt; &lt;a href=&quot;http://www.amazon.com/gp/product/0195158334/ref=pd%5Flpo%5Fk2%5Fdp%5Fsr%5F1?pf%5Frd%5Fp=486539851&amp;amp;pf%5Frd%5Fs=lpo-top-stripe-1&amp;amp;pf%5Frd%5Ft=201&amp;amp;pf%5Frd%5Fi=0195219171&amp;amp;pf%5Frd%5Fm=ATVPDKIKX0DER&amp;amp;pf%5Frd%5Fr=0T3FEDNK97HHQEY32P0Y&quot; rel=&quot;nofollow&quot;&gt;2&lt;/a&gt;) very readable - suitable for independent learning.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-12-13T13:39:23.677" CommunityOwnedDate="2009-12-13T13:39:23.677" />
  <row Id="1006" PostTypeId="2" ParentId="991" CreationDate="2009-12-13T23:05:52.780" Score="10" ViewCount="" Body="&lt;p&gt;I have been playing with an STM32 (also Cortex M3) lately in my spare time and using the CodeSourcery distribution of GCC, which has worked out pretty well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A colleague who has worked with ARM micros professionally in the past told me that he was satisfied with the IAR toolchain, although I don't know what the cost is like or how the Cortex support is.&lt;/p&gt;&#xA;" OwnerUserId="412" LastActivityDate="2009-12-13T23:05:52.780" CommentCount="1" />
  <row Id="1007" PostTypeId="2" ParentId="884" CreationDate="2009-12-14T01:02:14.340" Score="2" ViewCount="" Body="&lt;p&gt;What I did to get my breadboard arduino to reset was to go into the device manager (Windows 7) and highlighted the FTDI device (A virtual COM port) and then went to Properties, Port settings, Advanced. I then checked off the box that said &quot;Set Rts on close&quot;. After I did this my arduino reset itself no problem.&#xA;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="92" LastActivityDate="2009-12-14T01:02:14.340" CommentCount="2" />
  <row Id="1008" PostTypeId="2" ParentId="1001" CreationDate="2009-12-14T01:11:45.610" Score="4" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;What classes did you find particularly useful to your work? Could I just read the textbook, or is it necessary to take the class?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I don't think it's completely necessary to take a class on DSP**, but I do think you need to have a good background on signals/systems (read as: TAKE A COURSE!) so that you can understand Laplace and Fourier transforms, the relationship between the time-content and frequency-content of a signal, and what those pesky &quot;s&quot; and &quot;z&quot; variables are for, because you'll run into them in filter design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Books you might look at:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://books.google.com/books?id=f%5FyCQgAACAAJ&quot; rel=&quot;nofollow&quot;&gt;&lt;em&gt;Understanding Digital Signal Processing&lt;/em&gt;&lt;/a&gt;, Lyons &amp;mdash; note there's a 2nd ed. (2004)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://books.google.com/books?id=hf1SAAAAMAAJ&quot; rel=&quot;nofollow&quot;&gt;&lt;em&gt;Signals and Systems Made Ridiculously Simple&lt;/em&gt;&lt;/a&gt;, Karu&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.dspguide.com/&quot; rel=&quot;nofollow&quot;&gt;&lt;em&gt;The Scientist and Engineer's Guide to Digital Signal Processing&lt;/em&gt;&lt;/a&gt;, Smith &amp;mdash; note that you can &lt;a href=&quot;http://www.dspguide.com/&quot; rel=&quot;nofollow&quot;&gt;read this book online&lt;/a&gt; and download it if you wish.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Beware of books that have much of their space devoted to matrices or equations or proving theorems &amp;mdash; these may be welcome to academics but they're about as welcome as coyote urine to the rest of us (and serve the same function, to repel), in my opinion. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;hr /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;sub&gt;**I say this because I never took a class on DSP and I've learned the material enough through books and self-study to use digital filters and control systems in my career. My college roommate and I were both looking forward to a DSP course back in 1994, but the professor &amp;mdash; a prominent academic and the primary author of a well-known book on signal processing, who shall remain semi-anonymous &amp;mdash; was a complete hardass and announced on the first day that there was now a prerequisite course you had to take first, which had only just been offered the previous semester on an experimental basis. Or you could take it if you were a grad student, because that meant you were &quot;mature&quot;. Thanks, Dr. O. :p :p :p&lt;/sub&gt;&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-12-14T01:16:50.100" LastActivityDate="2009-12-14T01:16:50.100" CommunityOwnedDate="2009-12-14T01:11:45.610" CommentCount="1" />
  <row Id="1009" PostTypeId="1" CreationDate="2009-12-14T03:05:46.377" Score="10" ViewCount="534" Body="&lt;p&gt;In reviewing possible approaches for my data logging project, I have found the book &quot;Practical UML statecharts in C/C++&quot; to be very interesting for more serious work with the Arduino. QP is a family of ultra-light, open source, state machine-based frameworks for embedded systems and they distribute code and ports for their frameworks (GNU GPL2) at &lt;a href=&quot;http://www.state-machine.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.state-machine.com/&lt;/a&gt; where they have a port for the AVR and AVR mega using the WinAVR/Gnu C++ tool set. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although the chip specific headers are appropriate, has anyone created a board BSP file or had any experience with these frameworks? I am just starting with the book, so any comments greatly appreciated.&lt;/p&gt;&#xA;" OwnerUserId="297" LastEditorUserId="625" LastEditorDisplayName="" LastEditDate="2010-03-26T16:06:25.233" LastActivityDate="2010-11-18T05:02:58.347" Title="Anyone ported the QP state framework for Arduino?" Tags="&lt;arduino&gt;&lt;avr&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="3" />
  <row Id="1010" PostTypeId="2" ParentId="1001" CreationDate="2009-12-14T08:06:14.307" Score="3" ViewCount="" Body="&lt;p&gt;I did Mechatronics, for sensor design and control system design, That might help..&lt;/p&gt;&#xA;" OwnerUserId="413" LastActivityDate="2009-12-14T08:06:14.307" CommunityOwnedDate="2009-12-14T08:06:14.307" />
  <row Id="1011" PostTypeId="1" CreationDate="2009-12-14T17:03:02.313" Score="12" ViewCount="500" Body="&lt;p&gt;I'm wondering how much company work (not personal projects) you typically do after hours. &lt;/p&gt;&#xA;" OwnerUserId="238" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-12-14T18:20:00.157" LastActivityDate="2011-05-17T14:11:36.667" CommunityOwnedDate="2009-12-14T17:03:02.313" Title="Professional Engineers: How much of your work comes home?" Tags="&lt;electronics&gt;&lt;careers&gt;" AnswerCount="15" CommentCount="1" FavoriteCount="2" />
  <row Id="1012" PostTypeId="2" ParentId="1011" CreationDate="2009-12-14T18:21:13.240" Score="9" ViewCount="" Body="&lt;p&gt;Zero. I gotta draw the line somewhere!&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2010-09-30T12:30:27.980" LastActivityDate="2010-09-30T12:30:27.980" CommunityOwnedDate="2009-12-14T18:21:13.240" CommentCount="4" />
  <row Id="1013" PostTypeId="2" ParentId="966" CreationDate="2009-12-14T18:36:11.810" Score="15" ViewCount="" Body="&lt;p&gt;Don't forget test equipment!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Besides a good DMM (4 1/2 or 4 3/4 digits are worth it, also look for one that has capacitance sensing), get some patch cords. I highly recommend items from &lt;a href=&quot;http://www.pomonaelectronics.com/index.php&quot; rel=&quot;nofollow&quot;&gt;Pomona&lt;/a&gt;. We just made a recent purchase, mostly of patch cords (minigrabber on both ends, banana-to-banana, and banana-to-alligator), but also a few quirky things from them:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;#1296 (BNC-to-binding post adapter) &lt;a href=&quot;http://www.pomonaelectronics.com/images/large/1296.jpg&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://www.pomonaelectronics.com/images/thumbs/1296.jpg&quot; alt=&quot;alt text&quot; /&gt;&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;#5143-K-48 (SMD tweezers) &lt;a href=&quot;http://www.pomonaelectronics.com/images/large/5143K.jpg&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://www.pomonaelectronics.com/images/thumbs/5143K.jpg&quot; alt=&quot;alt text&quot; /&gt;&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;#5953A (&quot;pointy-probes&quot;) &lt;a href=&quot;http://www.pomonaelectronics.com/images/large/5953.jpg&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://www.pomonaelectronics.com/images/thumbs/5953.jpg&quot; alt=&quot;alt text&quot; /&gt;&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;#6342 (probes with &quot;pogo&quot; tips) -- these are spring-loaded probe tips that add some compliance so when you are pressing onto a circuit board, it exerts a more controlled force.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-14T18:36:11.810" CommentCount="3" />
  <row Id="1014" PostTypeId="2" ParentId="1011" CreationDate="2009-12-14T21:55:06.460" Score="7" ViewCount="" Body="&lt;p&gt;Personal research or education often (ideally) overlaps with work so I work about 2 weekends a month from home.  Personally, if they do not overlap I get depressed so my home life depends on having a progressive work life.  Does that sound depressing in itself?  It's not.  It's a personality type.  I enjoy working on new topics in the hopes of sharing or publishing so, I work from home a lot.&lt;/p&gt;&#xA;" OwnerUserId="196" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2010-09-29T20:17:56.443" LastActivityDate="2010-09-29T20:17:56.443" CommunityOwnedDate="2009-12-14T21:55:06.460" />
  <row Id="1015" PostTypeId="1" AcceptedAnswerId="1016" CreationDate="2009-12-14T23:36:09.117" Score="3" ViewCount="881" Body="&lt;p&gt;Does anyone have additional Tutorials for learning Arduino Programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I started with the &lt;a href=&quot;http://www.ladyada.net/learn/arduino&quot; rel=&quot;nofollow&quot;&gt;ladyada&lt;/a&gt; one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And done bits an pieces of the &lt;a href=&quot;http://arduino.cc/en/Reference/HomePagem&quot; rel=&quot;nofollow&quot;&gt;arduino.cc&lt;/a&gt; ones&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any others out there?&lt;/p&gt;&#xA;" OwnerUserId="267" LastActivityDate="2011-03-09T13:19:19.660" Title="Steps to learning Arduino Programming" Tags="&lt;arduino&gt;&lt;tutorial&gt;&lt;beginner&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="1016" PostTypeId="2" ParentId="1015" CreationDate="2009-12-15T00:07:55.210" Score="2" ViewCount="" Body="&lt;p&gt;Arduino uses a programming language called Wiring (&lt;a href=&quot;http://wiring.org.co/learning/&quot; rel=&quot;nofollow&quot;&gt;http://wiring.org&lt;/a&gt;) that is a lot like C. If you've programmed in C you shouldn't have a problem programming the Arduino. Along with the material that's available on the web there are a couple of good books, for example:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://oreilly.com/catalog/9780596510510&quot; rel=&quot;nofollow&quot;&gt;Making Things Talk&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-12-15T00:07:55.210" CommentCount="1" />
  <row Id="1017" PostTypeId="2" ParentId="42" CreationDate="2009-12-15T00:17:45.003" Score="3" ViewCount="" Body="&lt;p&gt;while it's not so much about making conductive thread, here is a good post talking about the different types of commercially available conductive thread.  Gives a good run down of various comparisons, where to buy and what they cost.  hope this helps!&#xA;&lt;a href=&quot;http://www.fashioningtech.com/page/conductive-thread&quot; rel=&quot;nofollow&quot;&gt;http://www.fashioningtech.com/page/conductive-thread&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="368" LastActivityDate="2009-12-15T00:17:45.003" />
  <row Id="1018" PostTypeId="2" ParentId="42" CreationDate="2009-12-15T00:40:28.063" Score="4" ViewCount="" Body="&lt;p&gt;Step 1: Find a conductive sheep or conductive cotton plant&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Step 2: Extract the fibers from said conductive fiber source&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Step 3: Spin conductive fibers into conductive thread&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-15T00:40:28.063" CommentCount="1" />
  <row Id="1019" PostTypeId="2" ParentId="91" CreationDate="2009-12-15T00:46:21.937" Score="2" ViewCount="" Body="&lt;p&gt;I have a Lilly Pad, along with several Arduino boards.  I've been wanting to do some sewable/wearable projects but just didn't want to ruin the Lilly Pad on a mistake.  So after reading Pulsea's instructable: &lt;a href=&quot;http://www.instructables.com/id/Sewable%5FArduino%5FInterface/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Sewable_Arduino_Interface/&lt;/a&gt;&#xA;I decided to make a &quot;fabric shield&quot; for a regular Arduino.  It's currently a work in progress, but here are some pics:&#xA;&lt;img src=&quot;http://farm3.static.flickr.com/2664/4182789768%5Fc41f92cf32.jpg&quot; alt=&quot;http://www.flickr.com/photos/morgellon/4182789768&quot; /&gt;&#xA;&lt;img src=&quot;http://farm3.static.flickr.com/2783/4182769288%5F81360aaa64.jpg&quot; alt=&quot;http://www.flickr.com/photos/morgellon/4182769288&quot; /&gt;&#xA;&lt;img src=&quot;http://farm3.static.flickr.com/2772/4169401395%5Fdd74202e80.jpg&quot; alt=&quot;http://www.flickr.com/photos/morgellon/4169401395&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="368" LastEditorUserId="368" LastEditorDisplayName="" LastEditDate="2009-12-15T00:55:11.063" LastActivityDate="2009-12-15T00:55:11.063" />
  <row Id="1020" PostTypeId="2" ParentId="1011" CreationDate="2009-12-15T02:27:59.500" Score="4" ViewCount="" Body="&lt;p&gt;Yeah, I take lots of work home. If you are an engineer working on systems or design, you will take work home.  In fact, you might do your best work from home, you can't relegate finding the solution to a difficult design problem to work hours.  If I think of how to solve something at home then I need to write it down and start on it right then.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think people who work in test and on-site engineering are more able to leave work at work than those doing product design.  I could be wrong about this, I just have a few friends who work in research/test areas and they never seem to have work for the weekend.&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2009-12-15T02:27:59.500" CommunityOwnedDate="2009-12-15T02:27:59.500" CommentCount="1" />
  <row Id="1021" PostTypeId="2" ParentId="1011" CreationDate="2009-12-15T03:05:13.790" Score="2" ViewCount="" Body="&lt;p&gt;I work with at a startup where we do R&amp;amp;D and I live with a EE(my girlfriend), so yes, I bring a lot of it home. I normally try to limit it to discussing my day, I occasionally do a little work at home. I will occasionally do what Scott does, I have an epiphany and immediately try to get details worked out and written down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a few friends that do not bring their work home, but at my job it just seems to be the personality type. If I have a problem at work I think about it for a long time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a less positive note, if you are referring to bringing stress home, this has happened to me and is something I occasionally have a hard time limiting. I love working at a small company but sometimes when there are employees that cause problems you cannot simply remove them, the time it would take to hire someone and allow them to learn how to fill the slot is too great when you are behind schedule.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-12-15T03:05:13.790" CommunityOwnedDate="2009-12-15T03:05:13.790" />
  <row Id="1022" PostTypeId="2" ParentId="1015" CreationDate="2009-12-15T03:21:19.673" Score="2" ViewCount="" Body="&lt;p&gt;There is a good book by Massimo Banzi &lt;a href=&quot;http://oreilly.com/catalog/9780596155520&quot; rel=&quot;nofollow&quot;&gt;http://oreilly.com/catalog/9780596155520&lt;/a&gt;&#xA;and another good book by Brian Evans at &lt;a href=&quot;http://www.lulu.com/content/1108699&quot; rel=&quot;nofollow&quot;&gt;http://www.lulu.com/content/1108699&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a few projects on my blog at &lt;a href=&quot;http://www.ArduinoFun.com&quot; rel=&quot;nofollow&quot;&gt;http://www.ArduinoFun.com&lt;/a&gt; and here are some other great Arduino sites:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://lab.guilhermemartins.net/&quot; rel=&quot;nofollow&quot;&gt;http://lab.guilhermemartins.net/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://blog.makezine.com/archive/arduino/&quot; rel=&quot;nofollow&quot;&gt;http://blog.makezine.com/archive/arduino/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduinoshow.com/show/&quot; rel=&quot;nofollow&quot;&gt;http://www.arduinoshow.com/show/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://tinker.it/now/&quot; rel=&quot;nofollow&quot;&gt;http://tinker.it/now/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://arduinocollective.com/&quot; rel=&quot;nofollow&quot;&gt;http://arduinocollective.com/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://todbot.com/blog/&quot; rel=&quot;nofollow&quot;&gt;http://todbot.com/blog/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://delicious.com/ArduinoFun/Arduino&quot; rel=&quot;nofollow&quot;&gt;http://delicious.com/ArduinoFun/Arduino&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://letsmakerobots.com&quot; rel=&quot;nofollow&quot;&gt;http://letsmakerobots.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.uchobby.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.uchobby.com/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-12-15T03:21:19.673" CommentCount="2" />
  <row Id="1023" PostTypeId="2" ParentId="23" CreationDate="2009-12-15T03:34:33.610" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;What does the &quot;0x&quot; represent in the MAC address?&lt;/strong&gt; When I first set mine up I was confused about that. As soon as I added the &quot;0x&quot; in front, everything started tweeting with no problems. I was just curious if this was a parity bit or some sort of place holder or what.&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-12-15T03:34:33.610" CommentCount="3" />
  <row Id="1024" PostTypeId="1" AcceptedAnswerId="2050" CreationDate="2009-12-15T03:40:14.550" Score="43" ViewCount="2143" Body="&lt;p&gt;I was going to add a bit of information to my post on a previous day using schematics and some instructions. What programs are being employed for this purpose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mostly want to see what others are using and that I can easily use to give descriptive schematics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a perfect world, and I know this is a case of me wishing, it would be:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Free.&lt;/li&gt;&#xA;&lt;li&gt;Extremely easy to draw schematics&#xA;in.&lt;/li&gt;&#xA;&lt;li&gt;Allows simple production of&#xA;waveforms for the inputs/outputs.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Would enjoy any pointers people could toss me.&#xA;-Max Murphy&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-16T17:41:27.893" LastActivityDate="2011-05-17T12:51:48.800" CommunityOwnedDate="2011-03-22T20:53:31.463" Title="Good Tools for Drawing Schematics" Tags="&lt;schematics&gt;&lt;education&gt;&lt;eda&gt;" AnswerCount="19" CommentCount="18" FavoriteCount="35" />
  <row Id="1025" PostTypeId="2" ParentId="1011" CreationDate="2009-12-15T03:50:48.790" Score="2" ViewCount="" Body="&lt;p&gt;I agree with Scott also. I bring work home in my head and will usually keep grinding it out over the evening, thought usually passively. It's really bad when I start dreaming about it. I was fixing electronics for 3 nights straight a few months ago...that's just not cool.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also write about electronics, so that's sort of a separate &quot;work&quot; that I do, still related to electronics, just not my day-job kind of stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I think I should state that I completely figure that as my career progresses and job responsibilities mount that I will be expected to work more and more from home possibly. Doesn't mean I won't push back, just means I expect a little bit more stuff that needs doin' as I get better at what I do.&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2009-12-15T03:50:48.790" CommunityOwnedDate="2009-12-15T03:50:48.790" CommentCount="2" />
  <row Id="1026" PostTypeId="2" ParentId="1024" CreationDate="2009-12-15T03:55:26.547" Score="7" ViewCount="" Body="&lt;p&gt;Usually whenever I'm doing this, I'd just plop out a circuit in SPICE and then print to a PDF. Not the most elegant solution, but not the most difficult either. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;LTSpice is free and pretty great. Also, I hear they keep waveforms inside some of those circle and triangle things on the schematics, just need to push some buttons to let them out :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this what you meant? Or did you mean something that is modifiable like a GoogleDocs for schematics? That'd be nice, wouldn't it?&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2009-12-15T03:55:26.547" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="3" />
  <row Id="1027" PostTypeId="2" ParentId="1024" CreationDate="2009-12-15T04:18:17.763" Score="8" ViewCount="" Body="&lt;p&gt;Probably not the best solution, but most of time I use Eagle to make schematics. Now, that doesn't really cover points 2 and 3 of your requirements, but it's what I use. Additionally I frequently use OrCad PSPICE.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would, however, strongly recommend gEDA &lt;a href=&quot;http://www.gpleda.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.gpleda.org/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="403" LastActivityDate="2009-12-15T04:18:17.763" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="2" />
  <row Id="1028" PostTypeId="2" ParentId="592" CreationDate="2009-12-15T04:33:07.113" Score="2" ViewCount="" Body="&lt;p&gt;This one helped me a lot for a Devices class which included op-amps. Really good animations, and covers most types (inverter, differentiator...) needed for a starting point.[link text]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.wisc-online.com/Search.asp?search=op+amp&quot; rel=&quot;nofollow&quot;&gt;http://electronics.wisc-online.com/Search.asp?search=op+amp&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[1] &lt;/p&gt;&#xA;" LastActivityDate="2009-12-15T04:33:07.113" />
  <row Id="1029" PostTypeId="2" ParentId="1024" CreationDate="2009-12-15T05:36:17.627" Score="8" ViewCount="" Body="&lt;p&gt;I personally use Eagle but the learning curve is somewhat high.  You might want to check out &lt;a href=&quot;http://fritzing.org/&quot; rel=&quot;nofollow&quot;&gt;Fritzing&lt;/a&gt;, it's open source and built with the beginner in mind.&lt;/p&gt;&#xA;" OwnerUserId="86" LastActivityDate="2009-12-15T05:36:17.627" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="4" />
  <row Id="1030" PostTypeId="1" AcceptedAnswerId="1031" CreationDate="2009-12-15T08:03:03.230" Score="9" ViewCount="892" Body="&lt;p&gt;I am an EE student and can write [at least simple] programs in more languages than I have fingers. I have just started learning VHDL and I was wondering what a good project would be to really get to know the language and the relevant tools? I am having trouble coming up with one because it is a really different style of programming for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have made simple things like adders, but I am looking for a more long term (ie a month or so) project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In case it is relevent, I have Xilinx Webpack and a Digilent Spartan3 board.&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-04-09T13:48:12.187" LastActivityDate="2011-05-19T14:15:35.997" Title="Project to learn VHDL" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;vhdl&gt;" AnswerCount="7" FavoriteCount="4" />
  <row Id="1031" PostTypeId="2" ParentId="1030" CreationDate="2009-12-15T08:55:12.520" Score="3" ViewCount="" Body="&lt;p&gt;My &quot;hello world&quot; FPGA project was a LED array controller with PWM and serial stream input. &#xA;The final result was nice (&lt;a href=&quot;http://lbw.axe-man.org/led1.wmv&quot; rel=&quot;nofollow&quot;&gt;http://lbw.axe-man.org/led1.wmv&lt;/a&gt;) but I admit that I've done a part of it with the Altera Quartus Schematic Editor to see how VHDL parts were described.&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2009-12-15T08:55:12.520" CommentCount="2" />
  <row Id="1033" PostTypeId="2" ParentId="1015" CreationDate="2009-12-15T11:30:20.123" Score="1" ViewCount="" Body="&lt;p&gt;tuupola - I am primarily a programmer who develops in Python, Java and C/C++, however I think arduino is a good little kit because it lets me explore my imagination without making a hole in my pocket. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;True, it's used by artists but how should that limit a programmer? If you want to integrate OLEDs+arduino and do nice little setup, how about that? Or, have sensing stuffs integrated (I think my atmel328P can handle that), wouldn't that be cool? And from the projects I've read through that arduino will probably let me do that (with other kits). I've developed for FPGAs (Xilinx, VHDL, Handle-C) in the past so it should technically speaking be a breeze for me but we'll see about that.&lt;/p&gt;&#xA;" OwnerUserId="419" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-09T13:19:19.660" LastActivityDate="2011-03-09T13:19:19.660" CommentCount="3" />
  <row Id="1034" PostTypeId="2" ParentId="933" CreationDate="2009-12-15T12:00:39.567" Score="7" ViewCount="" Body="&lt;p&gt;Your average instrumentation amp can easily do 1MHz bandwidth; and your EEG should be no more than 2kSPS. So a multiplexer / Sample and Hold ahead of the the instrumentation amp ought to save you there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But consider that the amp should be only a few dollars.  Is it worth the multiplexing?  If you do Surface Mount, the size will be quite minimal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino cannot digitise faster than about 10kSPS, so you would need a faster A/D to do 16 channels.  Something that can do 12 bits at 100kSPS would be nice.  They are also fairly cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that for patient safety you need optical isolation on signals, and a good isolated supply (battery or similar).  Don't mess with safety in this area - if you need to get a high speed data stream out, build your own isolators or use fibreoptics to transmit the signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards,&#xA;Tony Barry&lt;/p&gt;&#xA;" OwnerUserId="420" LastActivityDate="2009-12-15T12:00:39.567" CommentCount="8" />
  <row Id="1035" PostTypeId="2" ParentId="1030" CreationDate="2009-12-15T12:08:47.673" Score="4" ViewCount="" Body="&lt;p&gt;I enjoyed working with Hans at &lt;a href=&quot;http://hardhack.org/&quot; rel=&quot;nofollow&quot;&gt;hardhack&lt;/a&gt; this year on the &lt;a href=&quot;http://code.google.com/p/rekonstrukt/&quot; rel=&quot;nofollow&quot;&gt;Rekonstrukt&lt;/a&gt; project to build a basic synthisizer in an FPGA. LED projects are also good but there is nothing like plugging up the FPGA to a stereo. It isn't building from the ground up, as an LED project would, because the project is based on a open core processor that supports forth. So at the beginning you are learning how to basically load the FPGA with the project, then you can play with the envelopes in FORTH.  But where you start to learn more about the FPGA internals is when you want to add functionality, which then requires digging into the VHDL.&lt;/p&gt;&#xA;" OwnerUserId="196" LastEditorUserId="196" LastEditorDisplayName="" LastEditDate="2009-12-15T12:42:44.303" LastActivityDate="2009-12-15T12:42:44.303" />
  <row Id="1036" PostTypeId="2" ParentId="1030" CreationDate="2009-12-15T12:54:40.427" Score="3" ViewCount="" Body="&lt;p&gt;Hi! You should check out &lt;a href=&quot;http://opencores.org&quot; rel=&quot;nofollow&quot;&gt;opencores.org&lt;/a&gt; and find an interesting project there. You can also download the &lt;a href=&quot;http://www.sigasi.com&quot; rel=&quot;nofollow&quot;&gt;Sigasi HDT&lt;/a&gt;, which will help you up to speed on VHDL grammar.&lt;/p&gt;&#xA;" OwnerUserId="421" LastEditorUserId="923" LastEditorDisplayName="" LastEditDate="2011-05-06T16:34:29.040" LastActivityDate="2011-05-06T16:34:29.040" />
  <row Id="1037" PostTypeId="2" ParentId="1030" CreationDate="2009-12-15T13:00:37.267" Score="1" ViewCount="" Body="&lt;p&gt;I wrote vhdl code for xilinx virtex core sometime ago. it was an alarm clock implementation. This is what i did:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt; Read a lot through vhdl manual - i'd have to revise on it now but i found it pretty straightforward and easy to use hdl :-) &lt;/li&gt;&#xA;&lt;li&gt; Used xilinx suite (compiler, synthesizer) to get the bitstream&lt;/li&gt;&#xA;&lt;li&gt; Uploaded the bitstreams using jtag &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Rinsed, Repeated 1-3. I'd point out that bitstream generation is very much all integrated in Xilinx's IDE. You just have to have clear set of logic to implement in HDL; all the rest of the stuffs are done by the IDE.&lt;/p&gt;&#xA;" OwnerUserId="419" LastActivityDate="2009-12-15T13:00:37.267" />
  <row Id="1038" PostTypeId="2" ParentId="1024" CreationDate="2009-12-15T13:43:51.310" Score="17" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.gpleda.org/tools/gschem/index.html&quot; rel=&quot;nofollow&quot;&gt;gschem&lt;/a&gt; of &lt;a href=&quot;http://www.gpleda.org/&quot; rel=&quot;nofollow&quot;&gt;geda&lt;/a&gt; makes nice schematics, with real fonts.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;It's free software (GPL license).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;It's as easy as it gets. All the schematic capture programs need some learning.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I've not tried that, but there ought to be something in the gEDA suite.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="339" LastActivityDate="2009-12-15T13:43:51.310" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="3" />
  <row Id="1039" PostTypeId="1" AcceptedAnswerId="1083" CreationDate="2009-12-15T13:47:21.890" Score="7" ViewCount="471" Body="&lt;p&gt;Can someone suggest a source and part number for insulated, stranded small-gauge wire (around 22AWG) that is flexible and doesn't hold its shape?  Something along the lines of the wire found on multimeter probes.  I want something to connect to my bench power supply that will lay flat on the workbench; standard stranded hookup wire is too stiff and retains the shape of the spool.  When &lt;a href=&quot;http://mouser.com/Wire-Cable/Wire-Single-Conductor/_/N-5ggs?P=1z0wxmeZ1z0wxmfZ1yzvwzvZ1z0wxluZ1z0wxjo&quot; rel=&quot;nofollow&quot;&gt;searching Mouser&lt;/a&gt;, there are multiple choices for stranding, jacket material, and wire type, but I don't know how to correlate those to my needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&#xA;Brian&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-12-18T18:58:05.350" Title="Source for flexible, stranded wire" Tags="&lt;wire&gt;&lt;components&gt;&lt;sourcing&gt;" AnswerCount="4" />
  <row Id="1040" PostTypeId="2" ParentId="1030" CreationDate="2009-12-15T13:49:54.843" Score="4" ViewCount="" Body="&lt;p&gt;Since you seem interested in programming you could build a simple microprocessor.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2009-12-15T13:49:54.843" CommentCount="1" />
  <row Id="1041" PostTypeId="2" ParentId="1039" CreationDate="2009-12-15T15:19:57.817" Score="6" ViewCount="" Body="&lt;p&gt;For how little of it I use, I usually just run to Radio Shack and pick up whatever stranded wire they have in the electronic component section.  If you're in the U.S., that should be sufficient.  By the time you pay shipping, you're not saving any money getting it from Mouser, and if you're not using it in large quantities there's no bulk pricing advantage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other thing you can do is look for other types of wire.  I've used speaker wire in a pinch for things like power.  You can usually find pretty thin, stranded speaker wire at most general-goods retailers (Wal-Mart, for example) or electronics specialty retailers.  As long as it's just for power, it should be quite sufficient.  Again, it probably won't be any more expensive and will save you time to go pick this up at the store rather than order it from Mouser.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you just want a few feet, I'd be tempted to hit up my local hardware store.  They usually have stranded wire by the foot.  You might have to settle for something of a slightly larger size, but my local Home Depot and Lowe's (again, U.S. stores) have 22-ga stranded wire available by the foot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Direct from Mouser, well, there's a whole ton of options.  The following link will show you all 22-ga hook-up wire options on 100' spools that Mouser sells.  There are 205 results returned, they should in large part be sufficient for your needs, and start at $20.  You'll excuse me if I don't go through each one individually:&#xA;&lt;a href=&quot;http://www.mouser.com/Wire-Cable/Wire-Single-Conductor/%5F/N-5ggs?P=1z0jnerZ1z0juksZ1z0wxmfZ1yzvwzvZ1z0xg0i&quot; rel=&quot;nofollow&quot;&gt;http://www.mouser.com/Wire-Cable/Wire-Single-Conductor/_/N-5ggs?P=1z0jnerZ1z0juksZ1z0wxmfZ1yzvwzvZ1z0xg0i&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there are smaller spools available, I missed them.  Also, you could easily use other wire  gauges as well (20, for example).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FWIW, I have taken solid-core wire and wound it &quot;backwards&quot; around a spool to remove the curves, and other objects can be used to give it other shapes (as well as simply pinching).  I find that 22ga wire can be bent to pretty much any shape I want this way, if that helps.&lt;/p&gt;&#xA;" OwnerUserId="11" LastEditorUserId="11" LastEditorDisplayName="" LastEditDate="2009-12-15T21:28:39.467" LastActivityDate="2009-12-15T21:28:39.467" CommentCount="6" />
  <row Id="1042" PostTypeId="2" ParentId="1030" CreationDate="2009-12-15T15:34:32.080" Score="2" ViewCount="" Body="&lt;p&gt;A project that I enjoyed doing was implementing the Milton Bradley Simon Game on a FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At my university, our EDA class uses the same board you mention. Some of the projects implemented included:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Image processing: median filter, histogram stretching, edge detection&lt;/li&gt;&#xA;&lt;li&gt;Cryptography: AES, various hashing algorithms, etc.&lt;/li&gt;&#xA;&lt;li&gt;Communication: Ethernet, USB, I2C, etc.&lt;/li&gt;&#xA;&lt;li&gt;Games: Pong, space invaders, etc.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;That may give you some ideas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll second the opencores.org idea as well as implementing your own microprocessor. Since you have a Xilinx FPGA, you might also look at doing something with microblaze or picoblaze.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: formatting.&lt;/p&gt;&#xA;" OwnerUserId="403" LastActivityDate="2009-12-15T15:34:32.080" />
  <row Id="1043" PostTypeId="1" AcceptedAnswerId="1047" CreationDate="2009-12-15T18:33:11.030" Score="7" ViewCount="1107" Body="&lt;p&gt;I want to control lava lamps using Arduino. I think it shouldn't be hard project, but I have no experience with hardware projects so I'm not sure witch design will feet best for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I consider using S202T01 Series Solid State Relays (I already have two of them).  I think it's the easiest way to do it (Am I right?, Are my SSR good for that?). Probably I could use LED blinking example and use SSR instead of LEDs. I think there are some other advantages of this approach. It's safety because of optoisolation, and it can switch very fast. Unfortunately SSR are quiet expensive and I need control ten devices.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for cheaper solution (but not much harder to use, and also safety). Me by I should use TRIACs (if yes what models)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And one more question: how about cooling? Should I use radiator on Solid State Relays or TRIACs?&lt;/p&gt;&#xA;" OwnerUserId="422" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-05-19T20:50:22.300" LastActivityDate="2011-05-19T20:50:22.300" Title="Controlling High Voltage device with Arduino" Tags="&lt;arduino&gt;&lt;control&gt;&lt;triac&gt;&lt;solid-state-relay&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="1044" PostTypeId="2" ParentId="1043" CreationDate="2009-12-15T18:56:17.023" Score="3" ViewCount="" Body="&lt;p&gt;Take a look at this thread on &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1236998971/0&quot; rel=&quot;nofollow&quot;&gt;arduino.cc forums&lt;/a&gt;. Someone is in the process of developing a AC Shield for the arduino using TRIAC's. &lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-12-15T18:56:17.023" />
  <row Id="1045" PostTypeId="2" ParentId="1011" CreationDate="2009-12-15T20:31:02.150" Score="2" ViewCount="" Body="&lt;p&gt;Very little.  I work 9-6, though, so I'm already at work plenty.  :'(&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I am working on something at home, it's likely something that interests me on a hobbyist level, too, and isn't strictly necessary for work, so that doesn't really count.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2009-12-15T20:31:02.150" CommunityOwnedDate="2009-12-15T20:31:02.150" />
  <row Id="1046" PostTypeId="2" ParentId="933" CreationDate="2009-12-15T20:47:01.263" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://openeeg.sourceforge.net/doc/modeeg/modEEGamp-v1.0.png&quot; rel=&quot;nofollow&quot;&gt;ModularEEG&lt;/a&gt; uses &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/ina114.html&quot; rel=&quot;nofollow&quot;&gt;INA114&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://openeeg.sourceforge.net/doc/hw/sceeg/DualChannelFMUnit-Sheet1.jpg&quot; rel=&quot;nofollow&quot;&gt;Soundcard EEG&lt;/a&gt; uses &lt;a href=&quot;http://www.analog.com/en/amplifiers-and-comparators/instrumentation-amplifiers/AD8221/products/product.html&quot; rel=&quot;nofollow&quot;&gt;AD8221 instrumentation amp&lt;/a&gt;.  Yes, you can adjust the gain with a digital pot, &#xA;but why would you want to?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.analog.com/static/imported-files/images/verified%5Fcircuits/CN0114%5F00%5F0415.gif&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, a search: &lt;a href=&quot;http://www.google.com/search?q=site%3Ati.com+PHYSIOLOGICAL+AMPLIFIERS%3A+EEG&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/search?q=site%3Ati.com+PHYSIOLOGICAL+AMPLIFIERS%3A+EEG&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2009-12-21T21:46:55.973" LastActivityDate="2009-12-21T21:46:55.973" CommentCount="3" />
  <row Id="1047" PostTypeId="2" ParentId="1043" CreationDate="2009-12-15T21:31:10.920" Score="5" ViewCount="" Body="&lt;p&gt;I would recommend sticking with SSRs. You can get them for somewhat cheap from ebay or allelectronics.com. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, if you want to use TRIACs, you can obviously do that as well. You will want to use an optoisolator to separate the high and low voltages. I found this (&lt;a href=&quot;http://www.epanorama.net/circuits/semiconductor_relays.html&quot; rel=&quot;nofollow&quot;&gt;http://www.epanorama.net/circuits/semiconductor_relays.html&lt;/a&gt;) to be a very useful resource on how to use TRIACs as a relay/switch.&lt;/p&gt;&#xA;" OwnerUserId="403" LastActivityDate="2009-12-15T21:31:10.920" />
  <row Id="1051" PostTypeId="2" ParentId="1043" CreationDate="2009-12-15T23:21:57.153" Score="2" ViewCount="" Body="&lt;p&gt;I would stick with the SSR's too. It will be less parts and the opto-isolation is already&#xA;built-in.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-01T03:44:26.683" LastActivityDate="2011-02-01T03:44:26.683" />
  <row Id="1052" PostTypeId="2" ParentId="1030" CreationDate="2009-12-15T23:27:52.997" Score="1" ViewCount="" Body="&lt;p&gt;Numerically Controlled Oscillator would be fun. I just did &#xA;a design with my Arduino compatible board (see &lt;a href=&quot;http://tinyurl.com/ydmz2su&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/ydmz2su&lt;/a&gt;)&#xA;but this would be perfect for an FPGA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are a couple of design references.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Snell, John 1988 &quot;Design of a Digital Oscillator That Will Generate up to 256 Low-Distortion Sine Waves in Real Time&quot; Foundations of Computer Music. Cambridge, Mass.: MIT Press&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Moore, F. Richard 1988 &quot;Table Lookup Noise for Sinusoidal Digital Oscillators&quot; Foundations of Computer Music. Cambridge, Mass.: MIT Press&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:15:35.997" LastActivityDate="2011-05-19T14:15:35.997" />
  <row Id="1053" PostTypeId="2" ParentId="906" CreationDate="2009-12-15T23:41:21.190" Score="1" ViewCount="" Body="&lt;p&gt;I would use an op-amp, resistor and FET to create a constant current sink.&#xA;As the voltage drops the op-amp will drive the gate of the FET to&#xA;maintain a constant-current through the sense resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you scroll down to the &quot;Electronic Load&quot; section at &lt;a href=&quot;http://tinyurl.com/6cbn6h&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/6cbn6h&lt;/a&gt;&#xA;you will see a schematic of a &quot;load cell&quot; which is a constant current&#xA;sink. You can PWM the sink by periodically setting the programmed current&#xA;to zero.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have my prototype working. It is in the &quot;not-quite-ready&quot; section at the&#xA;wiblocks site.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:17:24.267" LastActivityDate="2011-05-19T14:17:24.267" />
  <row Id="1055" PostTypeId="2" ParentId="460" CreationDate="2009-12-15T23:50:53.477" Score="1" ViewCount="" Body="&lt;p&gt;A number of the white noise generators in the analog music synthesizers (Moog and Arp) would&#xA;avalanche a transistor. If you query online for the Minimoog schematic or the ARP4027 you&#xA;should find the schematics. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did a PCB layout for the ARP4027. If you can't find the schematic send me an email.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;National had made a digital random number generator -- the MM5437. IIRC there were&#xA;some programs for an AT-tiny that would do this too. Could be a fun little project.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:15:51.303" LastActivityDate="2011-05-19T14:15:51.303" />
  <row Id="1057" PostTypeId="2" ParentId="592" CreationDate="2009-12-15T23:56:56.827" Score="4" ViewCount="" Body="&lt;p&gt;There are a couple of very good tutorials at Analog Devices and Texas Instruments.&#xA;The TI one is called &quot;Handbook of Operational Amplifiers&quot; (IIRC it is sboa092a.pdf).&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:57:01.290" LastActivityDate="2011-05-17T12:57:01.290" />
  <row Id="1058" PostTypeId="2" ParentId="1011" CreationDate="2009-12-16T00:00:00.317" Score="3" ViewCount="" Body="&lt;p&gt;Since I work at home -- 100% ;)&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:56:03.447" LastActivityDate="2011-05-17T12:56:03.447" CommunityOwnedDate="2009-12-16T00:00:00.317" CommentCount="3" />
  <row Id="1060" PostTypeId="1" AcceptedAnswerId="1063" CreationDate="2009-12-16T01:11:45.480" Score="14" ViewCount="399" Body="&lt;p&gt;I've seen a lot of people talking about FPGA's before and I know that it stands for field-programmable gate array but how does it work and what is the purpose of using an FPGA?&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2010-02-22T21:03:15.130" Title="What is an FPGA?" Tags="&lt;fpga&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="1063" PostTypeId="2" ParentId="1060" CreationDate="2009-12-16T01:37:51.787" Score="16" ViewCount="" Body="&lt;p&gt;Those are electronic components that adds some logic to Your circuits (so they are similar to  micro controllers). But the design  approach is completely then in uC (micro controllers). In uC You can not change internal uC design, You can only run &quot;classical&quot; programs on it. Programing FPGAs is more like crating new hardware. You crate now connections between logical gates and crate new specialized processor. And You can do it all in Your home on Your desk and Your PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sounds cool? Yes, but there are some disadvantaged. For example price (but I think it's hard to compare it), higher power consumption and lower clock speeds (but you can design your application in smart way and do more operations in one clock cycle).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Useful links:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://members.optushome.com.au/jekent/FPGA.htm&quot; rel=&quot;nofollow&quot;&gt;http://members.optushome.com.au/jekent/FPGA.htm&lt;/a&gt; - good tutorials&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Digital_electronics&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Digital_electronics&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Semiconductor_intellectual_property_core&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Semiconductor_intellectual_property_core&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/PicoBlaze&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/PicoBlaze&lt;/a&gt; - example of soft processor core&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;//edit:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;example usage: &lt;a href=&quot;http://nsa.unaligned.org/&quot; rel=&quot;nofollow&quot;&gt;http://nsa.unaligned.org/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="422" LastEditorUserId="422" LastEditorDisplayName="" LastEditDate="2009-12-16T11:53:44.307" LastActivityDate="2009-12-16T11:53:44.307" CommentCount="2" />
  <row Id="1065" PostTypeId="1" AcceptedAnswerId="1066" CreationDate="2009-12-16T02:52:37.580" Score="7" ViewCount="68" Body="&lt;p&gt;Is the &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8549&quot; rel=&quot;nofollow&quot;&gt;conductive thread&lt;/a&gt; non toxic?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Safe to wear up against your skin for extended periods of time?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2009-12-16T04:46:33.830" LastActivityDate="2009-12-16T04:46:33.830" Title="Conductive Thread - non toxic?" Tags="&lt;conductive&gt;&lt;thread&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="1066" PostTypeId="2" ParentId="1065" CreationDate="2009-12-16T03:19:38.523" Score="9" ViewCount="" Body="&lt;p&gt;I believe that the thread sold by Sparkfun is made by &lt;a href=&quot;http://www.shieldextrading.net&quot; rel=&quot;nofollow&quot;&gt;ShieldEx&lt;/a&gt;. According to the &lt;a href=&quot;http://www.shieldextrading.net/images/pdfs/STATEX%5F%5F%5FMATERIAL%5FSAFETY%5FDATA%5FAg.pdf&quot; rel=&quot;nofollow&quot;&gt;material safety data sheet&lt;/a&gt; for the silver-coated thread:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Eye Protection: SHIELDEX® silver&#xA;  coated non-woven/or/woven nylon fabric&#xA;  and yarns does not cause significant&#xA;  eye irritation or eye toxicity&#xA;  requiring special protection. Use good&#xA;  industrial practice to avoid eye&#xA;  contact.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Skin Protection: SHIELDEX®&#xA;  silver-coated non-woven/or/woven nylon&#xA;  fabric and yarns does not present a&#xA;  significant skin concern requiring&#xA;  special protection.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Comprehensive &lt;a href=&quot;http://www.fashioningtech.com/page/conductive-thread&quot; rel=&quot;nofollow&quot;&gt;review&lt;/a&gt; of other conductive threads&lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-12-16T03:19:38.523" CommentCount="3" />
  <row Id="1069" PostTypeId="1" AcceptedAnswerId="1070" CreationDate="2009-12-16T03:58:52.437" Score="25" ViewCount="638" Body="&lt;p&gt;The datasheet for the ATTiny13A, for instance, lists Min frequency of 0 MHz.  Does this mean the clock can be run at any arbitrarily low frequency with no ill effects?  I'm assuming it draws lower current at lower clock speeds?  Does 0 MHz mean you can stop the clock completely, and as long as power is still applied, it will remember its state indefinitely?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-04-09T17:11:49.193" Title="Can microcontrollers be run at arbitrarily low clock frequencies?" Tags="&lt;clock&gt;&lt;microcontroller&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="1070" PostTypeId="2" ParentId="1069" CreationDate="2009-12-16T04:07:32.247" Score="22" ViewCount="" Body="&lt;p&gt;Yes. If the datasheet says &quot;fully static operation&quot;, then you can clock it at any speed, even 0 Hz.  A &quot;dynamic&quot; chip needs to have a clock at a specific rate or it loses its state.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-16T04:07:32.247" CommentCount="7" />
  <row Id="1071" PostTypeId="2" ParentId="1069" CreationDate="2009-12-16T04:41:34.473" Score="13" ViewCount="" Body="&lt;p&gt;I am posting another answer, just because the last question you had was not answered before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Todbot is completely correct. It will also draw lower power at lower speeds. It also means if you supply it's clock from another processor, for example, you could stop supplying it at any point and then start clocking it later, as long as you do not go faster than max speed, you will be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Chips I have get an order of magnitude change between 32768Hz oscillator and a 1MHz one. I have had applications where I did not need speed, I just needed another little guy doing some basic data handling for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-12-16T04:41:34.473" CommentCount="6" />
  <row Id="1073" PostTypeId="2" ParentId="1060" CreationDate="2009-12-16T08:19:26.373" Score="9" ViewCount="" Body="&lt;p&gt;If you are familiar with basic logic gates, you should know that they're virtually instantaneous. The operation A and B OR C changes instantly when A, B or C change.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An FPGA is (sort of) a matrix of programmable logic gates. You can define the inputs and outputs (as a combination of the inputs).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a uC, A+B/C*sqrt(D) would take several clock cycles and some memory. In an FPGA, the result is almost inmediate. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are great for video, DSP, cryptography...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's the main advantage. Modern FPGAs are suited now with memory and there are uC/FPGA hybrids.&lt;/p&gt;&#xA;" OwnerUserId="198" LastActivityDate="2009-12-16T08:19:26.373" CommentCount="3" />
  <row Id="1075" PostTypeId="2" ParentId="1024" CreationDate="2009-12-16T16:43:53.037" Score="15" ViewCount="" Body="&lt;p&gt;My favorite schematic capture tool is a pencil on green-gridded engineering paper, and a camera.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once I have the schematic how I like it, it goes into gschem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But for just sketching up circuits, paper is the way to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/nfuL0.jpg&quot; alt=&quot;linear drivers rock&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-11-24T05:00:03.730" LastActivityDate="2010-11-24T05:00:03.730" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="6" />
  <row Id="1077" PostTypeId="2" ParentId="869" CreationDate="2009-12-16T17:46:28.990" Score="5" ViewCount="" Body="&lt;p&gt;A couple of people have asked me about tools&#xA;so I put together this list (below). I will put&#xA;it on my site soon. If you think you may want&#xA;to do SMD I would invest in a better iron &#xA;than listed below (also a good light and&#xA;a magnifier). My SMD tool recommendations&#xA;are at &lt;a href=&quot;http://tinyurl.com/5foeou&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/5foeou&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Tools&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;(1) Weller WESD51 Soldering Station      &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;or Hakko 936ESD (diy list)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(1) Well WSA350  Weller Smoke Absorber&lt;br&gt;&#xA;(5) WSA350F filter 3-pack&lt;br&gt;&#xA;(1) Panavise 308 Base Mount&lt;br&gt;&#xA;(1) Panavise 305 Base &#xA;(1) Panavise 366 Jaws&lt;br&gt;&#xA;(1) Cooper Tools &quot;Xcelite&quot; 170M cutter&lt;br&gt;&#xA;(1) Ideal T-6 16-26AWG wire stripper&lt;br&gt;&#xA;(1) Ideal T-8 8-16AWG wire stripper&lt;br&gt;&#xA;(1) X-Acto x3201    No. 1 Knife&lt;br&gt;&#xA;(1) X-Acto x411 No. 11 Fine Point Blade&lt;br&gt;&#xA;    Needle Nose Pliers, narrow tip&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Supplies&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Kester 24-6337-6422 Solder&lt;br&gt;&#xA;Kester 2331-ZX Flux&lt;br&gt;&#xA;Chemtronics 5-25L Solder Wick&lt;br&gt;&#xA;    Could add Chemtronics 10-25L Solder Wick&lt;br&gt;&#xA;3M 2214 Wrist Strap&lt;br&gt;&#xA;3M 8214 Anti-static Matt&lt;br&gt;&#xA;5854/7 BL005 100ft 24AWG Blue Wire, Teflon&lt;br&gt;&#xA;299 SV005   24AWG Bus Wire&lt;br&gt;&#xA;Extech EX330 Multimeter&lt;br&gt;&#xA;  or Extech XTC-MM560 (sdiy list)&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Custom circuits (not kits)&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;169P84WE (unclad) Vector board&lt;br&gt;&#xA;Vector T42-1 Clips&lt;br&gt;&#xA;Vector K24A Push pins&lt;br&gt;&#xA;299/3 SV005 30AWG Bus Wire&lt;br&gt;&#xA;Extech Power Supply 382213         &lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:38:19.167" LastActivityDate="2011-05-16T10:38:19.167" CommentCount="2" />
  <row Id="1079" PostTypeId="2" ParentId="1011" CreationDate="2009-12-16T18:02:28.273" Score="1" ViewCount="" Body="&lt;p&gt;I work for myself, and I'm continuously surrounded by electronics at home, so I can often be found hunched over a breadboard at 5 in the morning, scowling at an IC. For me work and play often cross paths. &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-16T18:02:28.273" CommunityOwnedDate="2009-12-16T18:02:28.273" />
  <row Id="1081" PostTypeId="2" ParentId="1001" CreationDate="2009-12-16T18:11:13.480" Score="1" ViewCount="" Body="&lt;p&gt;Taking the academic approach has many advantages, including networking with your peers. However, many self taught electrical engineers go on to work in industry or open there own businesses. If you wanna learn DSP on your own this link is great -&gt; &lt;a href=&quot;http://www.dspdimension.com/admin/dft-a-pied/&quot; rel=&quot;nofollow&quot;&gt;http://www.dspdimension.com/admin/dft-a-pied/&lt;/a&gt;&#xA;Even though I studied DSP design at University, I still found these tutorials extremely helpful for filling in the gaps in my knowledge.     &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-16T18:11:13.480" CommunityOwnedDate="2009-12-16T18:11:13.480" CommentCount="1" />
  <row Id="1083" PostTypeId="2" ParentId="1039" CreationDate="2009-12-17T05:12:50.927" Score="4" ViewCount="" Body="&lt;p&gt;I think this is what you want, &lt;a href=&quot;http://www.bulkwire.com/product.asp?ProdID=21718&amp;amp;CtgID=6578&quot; rel=&quot;nofollow&quot;&gt;http://www.bulkwire.com/product.asp?ProdID=21718&amp;amp;CtgID=6578&lt;/a&gt;  I was looking for teflon wire for a project, but noticed they seemed to have a decent selection of other types of wire.  No idea if they are the best price, but seem reasonable (I welcome feedback on this).  They only seem to have 18 gauge wire but it is the type of wire you are asking about.  Hope this helps!&lt;/p&gt;&#xA;" OwnerUserId="368" LastActivityDate="2009-12-17T05:12:50.927" CommentCount="3" />
  <row Id="1084" PostTypeId="2" ParentId="105" CreationDate="2009-12-17T07:28:58.767" Score="2" ViewCount="" Body="&lt;p&gt;i'm working on something like this myself.  i have an id-12 in hand that does not seem to read my cat's tag.  i have a couple of other rfid tags on hand that it will not read, and one that it can read from 6&quot; away (no antenna on everything).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i'm not certain of the khz of the tag in my cat, or any of my others except for the &quot;control&quot; card i bought with the reader for testing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the id12 is the easiest thing in the world to use in ASCII mode, and this is all ive tried.  i think i might have to find a 134khz model and or a proper antenna to get any farther.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;feel free to contact me.  turbohoje@h0tmail&lt;/p&gt;&#xA;" LastActivityDate="2009-12-17T07:28:58.767" CommentCount="1" />
  <row Id="1085" PostTypeId="2" ParentId="1011" CreationDate="2009-12-17T07:30:51.553" Score="-1" ViewCount="" Body="&lt;p&gt;If bathroom is taken into account as home, Yes. I found solutions to work problems when I was shitting, on several occasions. Other than that, I don't bring work related things to my home.&lt;/p&gt;&#xA;" OwnerUserId="379" LastActivityDate="2009-12-17T07:30:51.553" CommunityOwnedDate="2009-12-17T07:30:51.553" />
  <row Id="1086" PostTypeId="2" ParentId="922" CreationDate="2009-12-17T15:48:34.857" Score="4" ViewCount="" Body="&lt;p&gt;Essentially, yes. There is a pass transistor that changes in resistance so that the output voltage stays constant. It's like a variable resistor, though, not a potentiometer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.techitoutuk.com/knowledge/electronics/components/resist/symbolsvarpot.gif&quot; alt=&quot;variable resistor vs pot&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The amount of resistance is controlled by a feedback amplifier. It adjusts the resistance so that the voltage at the output is constant, regardless of changes in the source voltage or the load resistance.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2009-12-17T15:48:34.857" />
  <row Id="1087" PostTypeId="2" ParentId="1024" CreationDate="2009-12-17T16:41:59.570" Score="4" ViewCount="" Body="&lt;p&gt;I use gEDA as well. gschem for schematics and PCB for printed circuit board&#xA;layout. As an open source example I did a remix of the ladyada Drawdio circuit.&#xA;The files and documentation are at &lt;a href=&quot;http://tinyurl.com/bq8pq4&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/bq8pq4&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My PCB footprint library and various EDA automation scripts are at&#xA;&lt;a href=&quot;http://www.luciani.org&quot; rel=&quot;nofollow&quot;&gt;http://www.luciani.org&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:51:48.800" LastActivityDate="2011-05-17T12:51:48.800" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="1" />
  <row Id="1088" PostTypeId="2" ParentId="1024" CreationDate="2009-12-17T17:32:51.697" Score="17" ViewCount="" Body="&lt;p&gt;Another option is &lt;a href=&quot;http://sourceforge.net/projects/ktechlab/&quot; rel=&quot;nofollow&quot;&gt;KTechlab&lt;/a&gt;.  I suspect most people have never heard of it, but it's a free electronics simulation program that lets you do simple circuits.  Schematics are easy to draw and it produces waveforms easily.  I find it more intuitive and quick than a SPICE simulator, but of course it's not as powerful.  It's more a system for thinking about idealized circuits, while SPICE is more a system for modeling real-life circuits, along with all their flaws and frailties.  It's Linux-only, but you can run it in Virtualbox or something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://linuxislife.files.wordpress.com/2007/03/ktechlab%5F1.png&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://linuxislife.files.wordpress.com/2007/03/ktechlab%5F1.png&quot; alt=&quot;alt text&quot; /&gt;&lt;/a&gt;&#xA;&lt;a href=&quot;http://linuxislife.files.wordpress.com/2007/03/51443.png&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://linuxislife.files.wordpress.com/2007/03/51443.png&quot; alt=&quot;alt text&quot; /&gt;&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2009-12-18T03:06:40.950" LastActivityDate="2009-12-18T03:06:40.950" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="5" />
  <row Id="1089" PostTypeId="2" ParentId="1060" CreationDate="2009-12-17T18:26:05.570" Score="2" ViewCount="" Body="&lt;p&gt;They are used for cracking encryption keys much faster than a general-purpose computer could.  :D&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2009-12-17T18:26:05.570" CommentCount="2" />
  <row Id="1090" PostTypeId="2" ParentId="1039" CreationDate="2009-12-17T19:22:13.507" Score="3" ViewCount="" Body="&lt;p&gt;I use this wire:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rapidonline.com/Cables-Connectors/Equipment-Wire/Test-Cable/Extra-flexible-cable/62327/kw/flexible+cable&quot; rel=&quot;nofollow&quot;&gt;http://www.rapidonline.com/Cables-Connectors/Equipment-Wire/Test-Cable/Extra-flexible-cable/62327/kw/flexible+cable&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2009-12-17T19:43:08.097" LastActivityDate="2009-12-17T19:43:08.097" CommentCount="1" />
  <row Id="1091" PostTypeId="2" ParentId="991" CreationDate="2009-12-17T19:26:03.627" Score="5" ViewCount="" Body="&lt;p&gt;I use Rowley software for ARM and MSP430 development:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rowley.co.uk/&quot; rel=&quot;nofollow&quot;&gt;http://www.rowley.co.uk&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's excellent. Cortex-M3 is supported.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2009-12-17T19:38:39.183" LastActivityDate="2009-12-17T19:38:39.183" CommentCount="2" />
  <row Id="1092" PostTypeId="1" AcceptedAnswerId="1093" CreationDate="2009-12-17T21:18:22.430" Score="22" ViewCount="2941" Body="&lt;p&gt;What's the difference between a microcontroller and a microprocessor?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T10:06:44.510" LastActivityDate="2011-01-23T10:06:44.510" Title="What's the difference between a microcontroller and a microprocessor?" Tags="&lt;microcontroller&gt;&lt;microprocessor&gt;" AnswerCount="5" FavoriteCount="3" />
  <row Id="1093" PostTypeId="2" ParentId="1092" CreationDate="2009-12-17T21:28:09.353" Score="40" ViewCount="" Body="&lt;p&gt;A microprocessor generally does not have Ram, ROM and IO pins. It usually uses its pins as a bus to interface to peripherals such as RAM, ROM, Serial ports, Digital and Analog IO. It is expandable at the board level due to this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A microcontroller is 'all in one', the processor, ram, IO all on the one chip, as such you cannot (say) increase the amount of RAM available or the number of IO ports. The controlling bus is internal and not available to the board designer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means that a microprocessor is generally capable of being built into bigger general purpose applications than a microcontroller. The microcontroller is usually used for more dedicated applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of this is very general statements, there are chips available that blur the boundaries.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-12-17T21:28:09.353" CommentCount="1" />
  <row Id="1094" PostTypeId="2" ParentId="1092" CreationDate="2009-12-17T21:54:17.680" Score="7" ViewCount="" Body="&lt;p&gt;As was mentioned microcontrollers are essentially systems on a chip.&#xA;Except for some specialized peripherals everything is in one&#xA;package. Interface to external peripherals is almost always&#xA;done using serial connections. This keeps the package sizes&#xA;small (less pins) and the PCB size small (less pins to connect&#xA;between packages).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the last Boston Barcamp (MIT 2009) I did an &quot;Intro to Microcontrollers&quot;&#xA;talk. A copy of the handout is at &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.luciani.org/not-quite-ready/doc/intro-to-uC.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.luciani.org/not-quite-ready/doc/intro-to-uC.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-23T15:29:19.693" LastActivityDate="2010-11-23T15:29:19.693" />
  <row Id="1095" PostTypeId="2" ParentId="1092" CreationDate="2009-12-17T22:14:58.683" Score="6" ViewCount="" Body="&lt;p&gt;Mostly marketing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's some other weird terms; Analog Devices has (or had) something they called &quot;microconverters&quot; which were like ADC/DACs with a microprocessor built in. TI is now calling some of their DSPs (the C2000 series) Digital Signal Controllers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise what JohnC said.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-17T22:14:58.683" CommentCount="4" />
  <row Id="1096" PostTypeId="2" ParentId="1092" CreationDate="2009-12-18T01:01:44.040" Score="4" ViewCount="" Body="&lt;p&gt;Microcontrollers:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;are typically 8-bit, but may be 4-, 16-, or 32-bit&lt;/li&gt;&#xA;&lt;li&gt;run at speeds less than 60 MHz&lt;/li&gt;&#xA;&lt;li&gt;use very little power&lt;/li&gt;&#xA;&lt;li&gt;may provide enough current to operate an LED&lt;/li&gt;&#xA;&lt;li&gt;are useful to interface with sensors and motors&lt;/li&gt;&#xA;&lt;li&gt;are readily replaced, being inexpensive ($0.10 to $10)&lt;/li&gt;&#xA;&lt;li&gt;are really constrained for RAM and persistent storage (flash space)&lt;/li&gt;&#xA;&lt;li&gt;are really nice for electronics hobbyists&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Microprocessors:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;are at least 16-bit, and typically 32-bit or 64-bit&lt;/li&gt;&#xA;&lt;li&gt;many will be able to do floating point math in hardware&lt;/li&gt;&#xA;&lt;li&gt;run at speeds measured in hundreds of MHz&lt;/li&gt;&#xA;&lt;li&gt;are designed to be the brains of a system (and need a whole system to support them)&lt;/li&gt;&#xA;&lt;li&gt;need special hardware to interface with sensors, motors, LEDs, etc.&lt;/li&gt;&#xA;&lt;li&gt;are expensive (think $50 - $250)&lt;/li&gt;&#xA;&lt;li&gt;are designed for external RAM and persistent storage (hard drives)&lt;/li&gt;&#xA;&lt;li&gt;are not as easily worked with by a hobbyist&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I find it interesting that the LEGO Mindstorms NXT set has a microprocessor [32-bit AT91SAM7S256 (ARM7TDMI) main microprocessor @ 48 MHz (256 KB flash memory, 64 KB RAM)] for doing the thinking, and a microcontroller [8-bit ATmega48 microcontroller @ 4 MHz (4 KB flash memory, 512 Bytes RAM)] for interfacing with the sensors and motors.  See &lt;a href=&quot;http://en.wikipedia.org/wiki/Lego_Mindstorms_NXT#Technical_specifications&quot; rel=&quot;nofollow&quot;&gt;technical specifications on Wikipedia&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-23T15:21:57.483" LastActivityDate="2010-11-23T15:21:57.483" CommunityOwnedDate="2009-12-18T15:48:52.130" CommentCount="6" />
  <row Id="1097" PostTypeId="2" ParentId="997" CreationDate="2009-12-18T03:30:49.003" Score="1" ViewCount="" Body="&lt;p&gt;If your Arduino doesn't support measuring the internal bandgap reference, just use an external reference.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.national.com/mpf/LM/LM431.html&quot; rel=&quot;nofollow&quot;&gt;http://www.national.com/mpf/LM/LM431.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.national.com/mpf/LM/LM4040.html&quot; rel=&quot;nofollow&quot;&gt;http://www.national.com/mpf/LM/LM4040.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1002,C1223,P1209&quot; rel=&quot;nofollow&quot;&gt;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1002,C1223,P1209&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Or just a Zener or two regular diodes in series&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The voltage at the input pin will be held constant by the reference diode, but the value you read will vary depending on the supply, since the ADCs are referenced to the supply.  If your reference is 1.0 V, for instance, and your ADC reads 512 out of 1024, then you know the voltage rails are at 2 V.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2009-12-18T03:30:49.003" />
  <row Id="1098" PostTypeId="1" AcceptedAnswerId="1104" CreationDate="2009-12-18T04:41:57.950" Score="6" ViewCount="405" Body="&lt;p&gt;This is intended to be the hardware equivalent of this question: &lt;a href=&quot;http://stackoverflow.com/questions/34785/when-if-to-seek-a-patent&quot; rel=&quot;nofollow&quot;&gt;&quot;When/if to seek a [software] patent?&quot;&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are some possible ways to make money from a hardware project that you've worked on yourself?  Do patents make sense for individual inventors?  Is it easy or lucrative to work as a freelancer?  What other options are there?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.adafruit.com/&quot; rel=&quot;nofollow&quot;&gt;Selling open source kits&lt;/a&gt; seems to be very successful for a small operation, but is sort of a specialty niche.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-10T03:01:32.080" LastActivityDate="2011-05-16T10:36:49.930" Title="How to make money without working for someone else? Patents?" Tags="&lt;electronics&gt;&lt;careers&gt;" AnswerCount="6" CommentCount="4" FavoriteCount="2" />
  <row Id="1099" PostTypeId="1" AcceptedAnswerId="1101" CreationDate="2009-12-18T04:50:02.847" Score="4" ViewCount="1536" Body="&lt;p&gt;Hello, i know there are tons of projects that use WIFI oder simple LAN shields to send sensor data of the arduino as twitter messages. How could this work with a mobile phone connection? are there libraries or handware layers that enable tcp via gsm or gprs? &#xA;if not with twitter, could i email the data or send to other apis, which would be http requests?&lt;/p&gt;&#xA;" LastActivityDate="2010-10-05T20:13:22.620" Title="how to connect the Arduino with Twitter via GSM/GPRS?" Tags="&lt;arduino&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="1100" PostTypeId="2" ParentId="1098" CreationDate="2009-12-18T04:58:55.730" Score="6" ViewCount="" Body="&lt;p&gt;I work at a small company which spends a lot of effort on patents + intellectual property. It is NOT an easy endeavor. Patents take a lot of time and money; I'm not sure how I could do it if I were off on my own.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the very least, you should keep a notebook of your ideas, document them as best you can (sign + date), and get someone you trust to witness those ideas. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you do with them is a whole other story, anyone's guess... If you're lucky enough to think of something in a niche field, it might be worth something.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-18T04:58:55.730" CommentCount="2" />
  <row Id="1101" PostTypeId="2" ParentId="1099" CreationDate="2009-12-18T05:11:03.763" Score="3" ViewCount="" Body="&lt;p&gt;You can get a &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9533&quot; rel=&quot;nofollow&quot;&gt;gsm/gprs module from sparkfun&lt;/a&gt;.  It looks like that'd be pretty easy to get going.  You would, of course, need data service to run it.&lt;/p&gt;&#xA;" OwnerUserId="347" LastActivityDate="2009-12-18T05:11:03.763" />
  <row Id="1103" PostTypeId="2" ParentId="1099" CreationDate="2009-12-18T06:42:14.673" Score="2" ViewCount="" Body="&lt;p&gt;Along with what Dustin stated take a look at &lt;a href=&quot;http://chiphacker.com/questions/133/arduino-twitters&quot; rel=&quot;nofollow&quot;&gt;Arduino Twitter Examples on ChipHacker&lt;/a&gt; for possible ideas or inspiration&lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-12-18T06:42:14.673" />
  <row Id="1104" PostTypeId="2" ParentId="1098" CreationDate="2009-12-18T07:00:59.833" Score="11" ViewCount="" Body="&lt;p&gt;Patents only make you money if your idea is good enough that someone wants to license it and make it in volume. Or if someone rips it off, is successful, and you sue.&#xA;If you are the only one who wants to manufacture and sell something then you don't need a patent, you just need to do it. That is the root of the open source model. Don't worry about what everyone else might do, just go do it yourself. The chances of getting rich either way are pretty damn small.  Better to aim for success as a small operation and be pleasantly surprised when you grow large!&lt;/p&gt;&#xA;" OwnerUserId="12" LastEditorUserId="12" LastEditorDisplayName="" LastEditDate="2009-12-18T07:13:22.067" LastActivityDate="2009-12-18T07:13:22.067" CommentCount="8" />
  <row Id="1105" PostTypeId="2" ParentId="627" CreationDate="2009-12-18T13:29:06.470" Score="2" ViewCount="" Body="&lt;p&gt;Even though they are in Victoria, you might consider &lt;a href=&quot;http://www.oceancontrols.com.au&quot; rel=&quot;nofollow&quot;&gt;http://www.oceancontrols.com.au&lt;/a&gt;. They have a few types of motors including some interesting stepper motors.&lt;/p&gt;&#xA;" OwnerUserId="427" LastActivityDate="2009-12-18T13:29:06.470" />
  <row Id="1106" PostTypeId="2" ParentId="1098" CreationDate="2009-12-18T13:31:16.873" Score="5" ViewCount="" Body="&lt;p&gt;I would say your best bet would be a small time marketing campaign on the internet using social media and such to get the word out about your product (and generate interest and possibly funding). Then ship your design out to be fabricated in China or elsewhere (&lt;em&gt;GASP&lt;/em&gt;...the US??). Perhaps even try to create a partnership with a design house to defray costs. Then try to sell the darn thing. If it's good and the right people find out about it at the beginning...a lot more people will find out about it. All these skills are very different and time consuming than designing the widget.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Patents are useful if you're making something REALLY special...but if that's the case, why are you shipping it to China? It's probably one or the other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.chumby.com/&quot; rel=&quot;nofollow&quot;&gt;Example company&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.boingboing.net/2006/09/11/chumby-chairman-inte.html&quot; rel=&quot;nofollow&quot;&gt;Interview with said company&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2009-12-18T13:31:16.873" />
  <row Id="1107" PostTypeId="1" CreationDate="2009-12-18T14:03:12.117" Score="7" ViewCount="2618" Body="&lt;p&gt;Does anyone even care about what you're developing on? I just wonder because there is such a strong contingent for AVRs in the Arduino family. I understand that they are the official processor but there isn't a reason the code couldn't be ported to an ARM or a Freescale architecture other than cost, right? As long as there is onboard memory, I figured there could be easy migration into those parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see a lot of ARM in industry (seems like every vendor is pushing one into their designs) and was wondering why there wasn't more uptake in the Arduino developer world. Thoughts?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;~Chris&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2011-05-19T14:19:23.443" CommunityOwnedDate="2011-05-19T14:16:24.430" Title="AVR vs ARM vs Others" Tags="&lt;arm&gt;&lt;avr&gt;&lt;freescale&gt;&lt;arduino&gt;" AnswerCount="6" CommentCount="3" FavoriteCount="1" />
  <row Id="1108" PostTypeId="2" ParentId="1107" CreationDate="2009-12-18T14:17:36.123" Score="3" ViewCount="" Body="&lt;p&gt;I know you said &quot;other than cost&quot;, but really that is the most important thing for hobbyists. You don't need more than one UART or more than one SPI on what is meant to be a cheap, generic platform. Once you start needing &gt;20mhz speeds, you really should be looking at a custom setup (ymmv of course)&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2009-12-18T14:17:36.123" CommunityOwnedDate="2011-05-19T14:16:24.430" />
  <row Id="1109" PostTypeId="2" ParentId="1107" CreationDate="2009-12-18T14:25:06.600" Score="6" ViewCount="" Body="&lt;p&gt;Arm development is coming along - take a look at the following projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blogs.leaflabs.com/2009/08/maple-prototype/&quot; rel=&quot;nofollow&quot;&gt;Maple Leaf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xduino.com/&quot; rel=&quot;nofollow&quot;&gt;XDuino&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.bugblat.com/products/cor.html&quot; rel=&quot;nofollow&quot;&gt;Cortino&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.liquidware.com/category/Illuminato+X+Machina&quot; rel=&quot;nofollow&quot;&gt;Illuminato&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.coridiumcorp.com/ARMduino.php&quot; rel=&quot;nofollow&quot;&gt;ARMmite PRO / ArmDuino&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-12-18T14:25:06.600" CommunityOwnedDate="2011-05-19T14:16:24.430" />
  <row Id="1110" PostTypeId="2" ParentId="1107" CreationDate="2009-12-18T14:41:00.173" Score="3" ViewCount="" Body="&lt;p&gt;A major advantage to the ATmel uCs is that there is a free compiler&#xA;available for Linux, PC and MAC. Add to that a simple cross-platform&#xA;GUI and you have a free development system that runs on all platforms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cost is a major factor for the hobbyist boards. Since you want to have&#xA;a starter price in the $30 range you need to have a uC cost that is no&#xA;more than a couple of dollars.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ARM would be a excellent candidate for the higher end boards. A lot of&#xA;companies license the ARM core and add peripherals. I believe there&#xA;are free compilers for Linux, PC and MAC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really like the Freescale Coldfire for high end boards. I worked on&#xA;a board for test equipment that used a 5206e. We added some DRAM and&#xA;high accuracy A/D and D/A converters. It was a cost-effective&#xA;solution. I have not recently compared Coldfire to the wide variety of&#xA;ARM's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of the 8-bit Freescale uCs are nice but I am not sure if they&#xA;have free tools.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:12:16.767" LastActivityDate="2011-05-19T14:12:16.767" CommunityOwnedDate="2011-05-19T14:16:24.430" CommentCount="2" />
  <row Id="1111" PostTypeId="2" ParentId="1107" CreationDate="2009-12-18T17:09:41.060" Score="8" ViewCount="" Body="&lt;p&gt;Part of the reason for the large community interest in the Arduino is the physical standardization.  As screwy as the physical layout is, by including a standardized expansion option, the Arduino developers allowed people to come up with their own solutions.  If you want to replace the base Arduino board with another board that uses a different microcontroller, you can.  IIRC, someone has already built a PIC-based board that uses the Arduino form-factor.  (The &lt;a href=&quot;http://www.circuitlake.com/pinguino-pic-based-arduino.html&quot; rel=&quot;nofollow&quot;&gt;PIC Ardunio board&lt;/a&gt; doesn't have the same form factor, but is otherwise similar.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another reason for the success of the Arduino is in its openness -- most of the PIC-based microcontrollers were closed; They used proprietary hardware implementations, so if you wanted to redesign the board to better fit into a specific space, you were out of luck.  They used custom firmware and proprietary development tools, so that if you had bugs or wanted to expand the capabilities, you were out of luck.  With the Arduino, every single piece of the puzzle is open:  you can buy parts anywhere, rearrange them as you need, improve or modify the firmware AND the development tools.  You can start simple with the Arduino IDE, but you can still shift to C or Assembly anytime you need it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I like the Arduino because it gets a lot of things 'just right':  It's not too expensive, it's not locked into proprietary tools, it's easy to start with, it's got a lot of capability, and it has a large user community, which continues to expand and do neat things.&lt;/p&gt;&#xA;" OwnerUserId="143" LastActivityDate="2009-12-18T17:09:41.060" CommunityOwnedDate="2011-05-19T14:16:24.430" CommentCount="1" />
  <row Id="1112" PostTypeId="2" ParentId="1107" CreationDate="2009-12-18T18:29:57.950" Score="9" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;em&gt;Does anyone even care about what&#xA;  you're developing on?&lt;/em&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes and no.  I've been developing on the AVR32 for a particular project, and the development environment (in particular the compile/program/debug cycle) is horrendous compared to, for instance, PIC32.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The customers don't care, except for cost and maintenance, and in the case of an arduino-like system the programmers wouldn't care because the arduino environment and development cycle is leaps and bounds better than the current AVR32 setup.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;em&gt;I just wonder because there is such a&#xA;  strong contingent for AVRs in the&#xA;  Arduino family. I understand that they&#xA;  are the official processor but there&#xA;  isn't a reason the code couldn't be&#xA;  ported to an ARM or a Freescale&#xA;  architecture other than cost, right?&#xA;  As long as there is onboard memory, I&#xA;  figured there could be easy migration&#xA;  into those parts.&lt;/em&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;There's no reason another processor &lt;em&gt;couldn't&lt;/em&gt; be used, but there's a very good reason they've chosen a low end 8 bit device rather than an ARM, MIPS, PowerPC, etc device: Ease of use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you've looked at the setup for the even the low end arms, it's an order of magnitude more complex (memory mapping, caching, etc) than an 8 bit processor.  But even more importantly - at the time there were no DIP arm processors, and these were meant to be used and buildable by artists and hackers, not necessarily electronic technicians and engineers who feel comfortable with even a 48 pin TQFP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason the AVR was chosen over the PIC is that the PIC doesn't really have a widely used, open source, free C compiler, among other things (the SDCC port isn't mature).&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;em&gt;I see a lot of ARM in industry (seems&#xA;  like every vendor is pushing one into&#xA;  their designs) and was wondering why&#xA;  there wasn't more uptake in the&#xA;  Arduino developer world. Thoughts?&lt;/em&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Mainly it's due to ease of use - complexity, easy to solder, cost, and the fact that there's not much need for it.  Developers like the idea of having a lot of power, but at the end of the day when all you need to do is move some servos and flash some lights with a low-end FFT, an 8 bit processor is just fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even the low end cortex ARMS coming out in 28 pin packages are still SOIC, not DIP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the AVR had all the right features:  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Easy to solder&lt;/li&gt;&#xA;&lt;li&gt;Easy to get via mail order all over the world&lt;/li&gt;&#xA;&lt;li&gt;Free GCC C compiler&lt;/li&gt;&#xA;&lt;li&gt;Easy to understand the processor and peripheral setup and usage&lt;/li&gt;&#xA;&lt;li&gt;Cheap&lt;/li&gt;&#xA;&lt;li&gt;Ubiquitous - lots of people and experience surrounding the AVR family&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Largely this is still true - I don't know of an ARM in a dip format, and the adapters make it significantly more expensive than the AVR.  For the most part, manufacturers don't think that a DIP packaged 32 bit processor is going to be very profitable.&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-19T14:19:23.443" LastActivityDate="2011-05-19T14:19:23.443" CommunityOwnedDate="2011-05-19T14:16:24.430" CommentCount="3" />
  <row Id="1113" PostTypeId="1" AcceptedAnswerId="1115" CreationDate="2009-12-18T18:44:08.030" Score="8" ViewCount="204" Body="&lt;p&gt;I'm looking at a cheap board to start on and I'm wondering if I'll be able to fit a Picoblaze, LEON, S1, or OpenRISC core on there. Is there any way to tell?&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2010-02-12T17:18:02.810" Title="How do you tell if an FPGA is capable of running an ip core?" Tags="&lt;fpga&gt;" AnswerCount="2" />
  <row Id="1114" PostTypeId="2" ParentId="1039" CreationDate="2009-12-18T18:58:05.350" Score="5" ViewCount="" Body="&lt;p&gt;So that you understand why test lead wire meets your needs where general purpose wires don't:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wire flexibility is determined by two things:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The wire&lt;/li&gt;&#xA;&lt;li&gt;The insulation&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The insulation aspect is pretty easy to understand - the stiffer the insulation, the stiffer the wire.  Test lead wire uses a tough, but very pliable rubber for insulation, so not only is it flexible, it's also heavy so it drapes on the workbench rather than standing up stiffly where it's stressed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The wire is a little bit more interesting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice that the test lead wire has the property:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;Stranding&#xA;Gauge   Strands/Gauge&#xA;18      65/36&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If you look at a comparable standard stranded hookup wire you'll find this parameter as:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;Stranding&#xA;Gauge   Strands/Gauge&#xA;18      16/30&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This means that the test lead wire is composed of 65 individual 36 awg wires, while the appliance wire (which is still pretty flexible, just not limp noodle flexible) only has 16 wires of 30 awg each.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With AWG gauges when you drop the gauge by 3 (ie, from 30 to 33 gauge) the area of a slice of the wire (thin disc) drops by a factor of 2 (which, among other things, means the current carrying capacity drops by 2).  This area affects the stiffness similarly, so from 30 gauge to 36 gauge, the wire's flexibility increases by almost 4 times, while the current carrying capacity decreases by 4 times.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, that also means you need over 4 times the number of wires (more than 4x since it's not solid copper) to attain the same 'awg' gauge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the flexibility increase is worth the extra cost for many applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So when you're looking for wire, keep in mind that this parameter (strands/awg per strand) is important.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2009-12-18T18:58:05.350" CommentCount="1" />
  <row Id="1115" PostTypeId="2" ParentId="1113" CreationDate="2009-12-18T19:03:45.497" Score="10" ViewCount="" Body="&lt;p&gt;Yes, you can synthesize IP cores without actually needing the hardware. In your synthesis tool you get to pick which FPGA chip you are targeting, and when you synthesize it will tell you what % of the FPGA's resources it used to fit it on there, or if it could not fit it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In fact, it's a good idea to use the synthesis tool and run everything in simulation before you plunk down money on a board. It's not like AVR where you can get a whole setup for $20, the range for decent starter FPGA boards is $100 - $200 depending on the number of features and helper chips you need.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-18T19:03:45.497" CommentCount="2" />
  <row Id="1116" PostTypeId="2" ParentId="1060" CreationDate="2009-12-18T20:10:36.750" Score="9" ViewCount="" Body="&lt;p&gt;An FPGA is literally an array of logic gates that can be programmed in the field. Flip flops, multiplexers, 4-bit look up tables, etc. that can be connected any way you want, using a C-like language (Verilog).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A uC, such as an AVR, is also made of similar logic gates, but they are configured when the device is made.  Sure, it has RAM and Flash so you can write software to read inputs and control outputs, but you can't change the actual arrangements of the gates.  The gates will always be arranged into an ALU, a memory controller, a serial port, etc.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The benefit of the uC is that you can program it in the field (at your desk), with an easy to use, familiar, high level language such as C.  The problem is, software is &quot;slow&quot;.  To have an input control an output, in the simplest case, you might write:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;void loop(){&#xA;   buttonState = digitalRead(buttonPin);&#xA;   if (buttonState == HIGH) {&lt;br /&gt;&#xA;     digitalWrite(ledPin, HIGH);&lt;br /&gt;&#xA;   } &#xA;   else {&#xA;     digitalWrite(ledPin, LOW); &#xA;   }&#xA; }&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That would be turned into a dozen assembly instructions, so the loop would take a microsecond or so to control that one output from one input.  And it takes the whole uC chip to do it that fast.  Sure, you can do much much more, but then your ability to control that output will slow down as the uC gets busy doing other things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In an FPGA, I could configure the gates to have an input control an output in 1 clock.  So the output would follow the input with a delay of perhaps 25 nanoseconds.  That's 40X faster, using the same clock period.  And the rest of the gates in the FPGA are available to do many other things, which won't affect the speed of this little function.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The code for the FPGA would be a simple flip flop:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;always @ (posedge clock)&#xA;    ledPin &amp;lt;= buttonPin;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would take only 1 FPGA cell, about 40 gates, out of tens of thousands in an FPGA.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can reprogram my FPGA to do something else, for example control the led based on a combination of four inputs, still in one clock, still using that 1 FPGA cell.  Or control the led based on a serial stream from the input, in a few FPGA cells, which would be 100's of gates. So I could control the LED based on serial data, say &quot;ON&quot; or &quot;OFF&quot;, with the serial stream at a very high rate (easily 20MHz), and still only use a tiny fraction of the FPGA's capacity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the advantage of an FPGA is clearly speed. It can do anything a uC can do, and it can do it much faster, with everything done in parallel. Complex things that a uC would take milliseconds do to, an FPGA could do in microseconds or less.  As long as there are gates left over in the FPGA, I can add more functions to it without affecting the speed or operation of previous functions in the FPGA.  By the way, an FPGA can very easily run a clock rate of 20MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cost is not a differentiator.  I can buy an FPGA that could implement almost any Arduino design I have ever seen for about $5, about the same as an Arduino AVR chip.  There are also free toolchains (IDE, compiler, debugger) for FPGAs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Power is not a differentiator.  Since I can run the FPGA at a much lower clock rate to get the same function as a uC, and use a small portion of its gates (unused gates use only leakage power), an FPGA can beat the power of almost any uC-based design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The biggest downside to an FPGA is that it is much more complex and time consuming to define, write the code, and debug a non-trivial FPGA design than a uC program.  A typical uC project that you might do in an evening could take days on an FPGA.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other, potentially fixable problems are that most people are trained in software programming, but few understand hardware programming.  You can learn Verilog fairly easily.  But you would also need to think in terms of hardware design instead of software design.  The design patterns are much different.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another issue is that FPGA's don't come in little 8 to 20 pin DIP packages.  They tend to come in 100-pin or larger surface mount packages, so building the boards is harder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And a final problem is that a whole lot of interesting projects can be implemented just fine in those easy to use uC's, so why bother with an FPGA?  &lt;/p&gt;&#xA;" OwnerUserId="19" LastActivityDate="2009-12-18T20:10:36.750" />
  <row Id="1117" PostTypeId="1" AcceptedAnswerId="1127" CreationDate="2009-12-19T05:47:15.027" Score="4" ViewCount="1049" Body="&lt;p&gt;Okay, here's some background info leading up to the [obvious] question with further elaboration:&#xA;I have been using a 28 pin PICAXE for small projects here and there for the last couple of years and am ready to move up.  My current project is the PICAXE as a data acquisition module.  I have simply mounted the board inside an enclosure, and run the inputs and outputs to [a lot] of screw terminals on the outside for quick and painless component swapping.  (And for further visualization, I also built in a 5V regulator and put in a DC jack so i can hook up a universal wall wart for power and wired the USB connection to a mini-usb that can be plugged into from the outside.)  Well, interfacing with the computer is pretty much a pain with the PICAXE, and it can only be programmed with their official program.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I am going to upgrade to Arduino.  I was thinking &lt;a href=&quot;http://amzn.com/w/2O8ZU4GC7X4C&quot; rel=&quot;nofollow&quot;&gt;the Arduino Mega Starter Kit&lt;/a&gt; because it seems like the most versatile, and I know that whatever board I get will be the board I will be using for a good while.  If I could do it over again, I would have started with the Arduino.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The things I am most interested in is data acquisition and sending data back to my computer, as well automation, which I know will not be an issue.  I have experience with C and BASIC but I prefer C; I am not sure if the there is a difference in language across Arduino's or not.  So, what would you recommend as the most versatile Arduino that will accomplish my current goals and keep me fat and happy on capabilities for whatever strange things I desire doing next?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a secondary question:  is it possible to interface any (or all) of the Arduino's with LabVIEW?     &lt;/p&gt;&#xA;" OwnerUserId="429" LastActivityDate="2011-05-17T12:57:22.380" Title="Recommendation for Arduino" Tags="&lt;arduino&gt;&lt;beginner&gt;" AnswerCount="7" FavoriteCount="1" />
  <row Id="1118" PostTypeId="1" AcceptedAnswerId="1120" CreationDate="2009-12-19T06:07:42.927" Score="5" ViewCount="231" Body="&lt;p&gt;I have been considering using Nitinol wire for some experimentation as a component in an autonomous system.  My understanding is that it will return to its original, contracted state when it reaches ~70°C, which seems to be capable of some pretty neat applications by passing current across it.  I assume that if I were to buy some, I should purchase the stuff with the thinnest diameter for maximum resistance in relatively short (&amp;lt;20cm) lengths.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, for those of you who have been able to play with the stuff, is Nitinol the nerdy engineer-candy it appears to be?  &lt;/p&gt;&#xA;" OwnerUserId="429" LastActivityDate="2009-12-21T11:38:16.023" Title="Nitinol: Useful stuff?" Tags="&lt;electronics&gt;&lt;robotics&gt;" AnswerCount="2" />
  <row Id="1119" PostTypeId="2" ParentId="1117" CreationDate="2009-12-19T06:26:40.837" Score="2" ViewCount="" Body="&lt;p&gt;If you are only doing data acquisition the Mega would seem a bit superfluous, unless of course you are using tons of sensors and or need multiple serial ports. I would say that for just simply data acquisition you would do OK with just the Diecimila(again depending on what you actually need to do with it)&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2009-12-19T06:26:40.837" CommentCount="2" />
  <row Id="1120" PostTypeId="2" ParentId="1118" CreationDate="2009-12-19T08:03:09.350" Score="6" ViewCount="" Body="&lt;p&gt;I've been told two things:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;It gets very hot, which imposes some limitations (the person who told me this was &lt;a href=&quot;http://www.xslabs.net/skorpions/&quot; rel=&quot;nofollow&quot;&gt;using it in clothing&lt;/a&gt;).&lt;/li&gt;&#xA;&lt;li&gt;It contracts and expands disappointingly slowly.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;However, I recently came across a device developed at the (late) Haptics Laboratory at McGill University called a &lt;a href=&quot;http://www.cim.mcgill.ca/~haptic/devices.html#SMA-Actuator&quot; rel=&quot;nofollow&quot;&gt;&quot;high strain shape memory allow actuator&quot;&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;They consist of thin NiTi fibers woven in a counter-rotating helical pattern around supporting disks. This structure accomplishes a highly efficient transformation between force and displacement overcoming the main mechanical drawback of shape memory alloys, that of limited strain. They are as fast as the fibers are thin, while preserving the humph due to the many fibers in parallel. Because fibers can be made very thin indeed, they can twitch and relax in milliseconds. Various variable structure controllers were successful at controlling position, force and acceleration for vibration control. Thus we have high strain, high speed, high precision Shape Memory Actuators amazingly simple to build and to control.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="207" LastActivityDate="2009-12-19T08:03:09.350" CommentCount="2" />
  <row Id="1121" PostTypeId="2" ParentId="27" CreationDate="2009-12-19T08:09:13.603" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://pixlpa.com/blog/arduino-sensorbox-firmware&quot; rel=&quot;nofollow&quot;&gt;SensorBox&lt;/a&gt; is a particularly elegant solution. Includes [serial]-based Max patches as well as Arduino code. &lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2009-12-19T08:09:13.603" />
  <row Id="1122" PostTypeId="2" ParentId="1117" CreationDate="2009-12-19T10:15:19.430" Score="1" ViewCount="" Body="&lt;p&gt;Yeah I would get two regular Arduinos instead of the Arduino MEGA, unless you specifically have a project that requires lots of I/O.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's easy to make a project you want to keep around, so instead of tearing up your circuit to make a new project, keep it and just get another Arduino.  If the cost of a regular Arduino is too much, you can build a Freeduino kit. And if &lt;em&gt;that's&lt;/em&gt; too much, you can make a minimal Arduino setup using just an ATmega8, a resistor and a capacitor.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-19T10:15:19.430" />
  <row Id="1123" PostTypeId="2" ParentId="1117" CreationDate="2009-12-19T10:19:12.670" Score="1" ViewCount="" Body="&lt;p&gt;A slightly different solution to your question is to bear in mind that your PicAXEs are just a preprogrammed PIC,the manual lists the following equivalences: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;PICAXE-28X1 = PIC16F886 &lt;/li&gt;&#xA;&lt;li&gt;PICAXE-28X2 = PIC18F2520 (3V version PIC18F25K20)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;and obsolete chips:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;PICAXE-28A = PIC16F872 (Superseded by 28X1)&lt;/li&gt;&#xA;&lt;li&gt;PICAXE-28X = PIC16F873A (Superseded by 28X1)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So in theory you could get a Programmer which supports these PICs and reprogram them either in C or Assembler, wiping out the PicAXE bootloader and use them as standard PICs. This way you can program your chips with much more flexibility.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you could take the chip in your datalogger for instance, reprogram it in C to do whatever it is that you want, and replace it in the same circuit. Although you might have to remove the PicAXE programming circuit if you have it in place I don't know how closely it mimics the PICs ICSP circuit (you won't be using the audio jack I think).&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2009-12-20T09:54:11.137" LastActivityDate="2009-12-20T09:54:11.137" />
  <row Id="1124" PostTypeId="2" ParentId="1117" CreationDate="2009-12-19T13:18:13.440" Score="3" ViewCount="" Body="&lt;p&gt;To date, all of the Arduino's and compatible systems consist of a board with an Atmel chip (such as an '168 or 328), a bootloader, a high level library and a cross-platform GUI. The bootloader enables you to download programs developed on the host using the uC serial port. Most people convert the uC serial port to a USB connection using some variety of FTDI USB to serial interface. The serial/USB interface could be used with LabView.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use these boards as Arduinos or as embedded systems. Most of these boards have a 3x2 header that conforms to Atmels ICSP specification. Using a USB to ICSP adapter (such as the ATmel AVRISPMKII) you can program the board without the bootloader or the Arduino libraries. There are a wide variety of Atmel libraries that you can use for stand-alone C development. Most of my development is done using the ICSP port, gcc and a Makefile. The Arduino libraries do an excellent job of providing hardware control at a high level. Sometimes the trade-off is performance. In a recent application I noticed a major speed improvement when I changed digitalWrite statements to bitset and bitclear operations. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The correct board depends more on your application --&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How many digital I/Os do you require?&lt;/li&gt;&#xA;&lt;li&gt;Is the uC A/D sufficient accuracy and resolution?&lt;/li&gt;&#xA;&lt;li&gt;Do you require analog output? What accuracy and resolution?&lt;/li&gt;&#xA;&lt;li&gt;Do you require signal conditioning?&lt;/li&gt;&#xA;&lt;li&gt;Do you require isolation?&lt;/li&gt;&#xA;&lt;li&gt;Do you require timestamping of data on the uC board or can that be handled by the host?&lt;/li&gt;&#xA;&lt;li&gt;How many serial interfaces do you require? (The last two applications I have done&#xA;could have used one more UART ;)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If you cannot use the A/D on the uC, and you don't need the UARTs you may be better of&#xA;with the smaller board. The last large data acquisition system I did used a uC with only a few peripherals. We needed a 16-bit A/D and a 14-bit DAC. There was no sense in paying for an internal 10-bit A/D or 8-bit DAC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I make a couple of Arduino compatible boards that bring out all the I/O connections to a single header. You can make a system that has co-planar boards, stacked boards, remote boards (one ribbon cable) or a backplane. The backplane could be useful for a data acquisition system that uses peripheral cards. My boards are at &lt;a href=&quot;http://www.wiblocks.com&quot; rel=&quot;nofollow&quot;&gt;http://www.wiblocks.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:57:22.380" LastActivityDate="2011-05-17T12:57:22.380" />
  <row Id="1125" PostTypeId="2" ParentId="1098" CreationDate="2009-12-19T14:08:25.320" Score="5" ViewCount="" Body="&lt;p&gt;If you believe you have a great idea you should talk to an attorney (even if you have to pay for the short meeting). If you are at a University they probably have an IP lawyer you can talk to for free.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can patent things yourself but it is time consuming and there are a lot of details. If you do not write the claims properly you could end up with no protection. The wording is critical. The claims need to be broad to prevent someone from copying your idea by making only a minor change.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example using &quot;consist&quot; instead of &quot;comprise&quot; would narrow your claim to a specific set of conditions. You want to be descriptive without being restrictive. Read through the claims sections of some patents that are online. This will give you an idea about the details.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A provisional patent can give you some protection for a short period of time. A lot of people just choose to make there design proprietary instead. Once you patent your design it is public. Unless you have the resources to protect it could be copied.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is an excellent book by Pressman called &quot;Patent it Yourself&quot;. You may want to take a look.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:36:49.930" LastActivityDate="2011-05-16T10:36:49.930" />
  <row Id="1126" PostTypeId="2" ParentId="1117" CreationDate="2009-12-19T16:12:20.937" Score="0" ViewCount="" Body="&lt;p&gt;Consider some barebones boards in kit form, work nicely with breadboard, very inexpensive.  Drawbacks: they are rs232 ttl and do not take shields.  Maker shed has some adapters from std 232.  Moderndevice.com sources the board.  Under 15 dollars as I recally.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2009-12-19T16:12:20.937" />
  <row Id="1127" PostTypeId="2" ParentId="1117" CreationDate="2009-12-19T18:52:43.617" Score="4" ViewCount="" Body="&lt;p&gt;It seems like you've largely answered your own question.  The Mega is by far the biggest and most powerful of the Arduinos.  Personally I lean more towards quantity instead of quality, so I'd get two less expensive Arduinos.  I find the female headers on the arduinos somewhat limiting, so the various breadboard Arduinos tend to get my nod (&lt;a href=&quot;http://www.moderndevice.com/products/rbbb-kit&quot; rel=&quot;nofollow&quot;&gt;Really Bare Bones Boarduino&lt;/a&gt; and &lt;a href=&quot;http://www.adafruit.com/index.php?main%5Fpage=product%5Finfo&amp;amp;cPath=19&amp;amp;products%5Fid=91&quot; rel=&quot;nofollow&quot;&gt;Boarduino&lt;/a&gt;).  You're usually choosing two things when you pick an Arduino:  how many inputs/outputs it has and how to communicate with it.  You're obviously on top of the i/o questions, but you might want to think about whether you're going to use USB or serial (probably via USB -&gt; serial adapter) to program the Arduino.  If you're only going to buy one or two boards, then USB is the easiest and cheapest.  If you're going to end up with 3 or more boards, it's probably cheaper to buy serial-only boards and a separate USB -&gt; serial converter (&lt;a href=&quot;http://www.adafruit.com/index.php?main%5Fpage=product%5Finfo&amp;amp;products%5Fid=70&quot; rel=&quot;nofollow&quot;&gt;FTDI cable&lt;/a&gt; or &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8772&quot; rel=&quot;nofollow&quot;&gt;FTDI basic breakout board&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The base Arduino is amazingly capable and it's pretty easy to add additional inputs with cheap multiplexer ICs.  If you don't have immediate need for the extra inputs, it might be worth starting with a cheaper board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're using the Arduino IDE, then you'll be programming in C++ on all the Arduinos.  The Arduino documentation tends to encourage using only slightly more than the C subset of C++ (basically C with just one or two extras), so a C programmer should feel very comfortable.  As an added bonus, you can do things like declare variables right before you use them, rather than having to do so at the start of functions.  On the other hand, watch out for differences from the C standard library.  sprintf(&quot;%f&quot;, foo) and some other things don't work by default.  When in doubt, hit arduino.cc and search.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for communicating back to the computer, I'm personally using Ruby on Rails to talk to my Arduino projects, but most folks seem to prefer Processing.  It all boils down to a serial port, so you can use whatever you feel most comfortable with.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-12-19T18:52:43.617" CommentCount="1" />
  <row Id="1128" PostTypeId="1" AcceptedAnswerId="1130" CreationDate="2009-12-19T19:00:55.147" Score="14" ViewCount="215" Body="&lt;p&gt;Can anyone give me a rundown of the various licenses that are well-suited to open hardware?  I've designed a few circuit boards and would like to make them available for others to use, so I need to choose a license for them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Things I'm concerned about:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Attribution.  Are others required to credit me?  If so, how?  I know this turned out to be a big issue with some BSD licenses for software.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Commercial use. Can folks copies of my work, or not?  I don't really care if they do, but I'd like some credit if so :)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Can others take my work and make &quot;closed&quot; derivatives of it?  Similar to #2, but for when people start changing things.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;How &quot;strong&quot; is this license?  2 lines made up by a random hacker can constitute a license, but I'd prefer someone with legal training to have looked at it.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="213" LastActivityDate="2011-05-16T10:33:00.697" Title="Best licenses for Open Hardware" Tags="&lt;hardware&gt;&lt;legal&gt;&lt;licensing&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="3" />
  <row Id="1129" PostTypeId="2" ParentId="1128" CreationDate="2009-12-19T19:18:35.733" Score="7" ViewCount="" Body="&lt;p&gt;Have you looked at the Creative Commons license pages &lt;a href=&quot;http://creativecommons.org&quot; rel=&quot;nofollow&quot;&gt;http://creativecommons.org&lt;/a&gt; ?&#xA;The first three items in your list are condition options on the license page. &#xA;It almost sounds like the -- &quot;by attribution&quot; &quot;share alike&quot; license meets your requirements. You can also add other terms and conditions to the license.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless there are patents involved in your work there may not be a lot of protection&#xA;anyways. Although someone may not be able to create derivative works using your&#xA;schematics or layout files they could redraw the schematics and do their own layout&#xA;of the board. Of course if you have a 12 layer board with 4/4 design rules and buried&#xA;vias not many people will have the resources to copy it anyways ;)&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:33:00.697" LastActivityDate="2011-05-16T10:33:00.697" />
  <row Id="1130" PostTypeId="2" ParentId="1128" CreationDate="2009-12-20T00:03:29.567" Score="8" ViewCount="" Body="&lt;p&gt;I use the creative commons license and the GNU LGPL version 3, which is normally used for software but has now been extended to hardware also. &lt;a href=&quot;http://www.gnu.org/licenses/lgpl.html&quot; rel=&quot;nofollow&quot;&gt;http://www.gnu.org/licenses/lgpl.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even though people can copy your work, the license will protect you if someone rips off your idea without accrediting you even if they take your idea and change it (proving this could be difficult). The license also protects against people copying your work for any commercial exploits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As with all licenses, trademarks and copyright they are only a strong as the legal team you can afford to back them up with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even a patent is pretty pathetic when faced with the legal team of a large corporation. A company I used to work for in the UK had £50,000 worth of patents on a new loud speaker system, just to have some big company bring out an almost identical, but slightly different system, 6 months after. &#xA;Patents and Licenses are all good, if your a massive company, for the average joe it's a waste of cash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I make and sell all my work with both the CC and LGPL licenses - &lt;a href=&quot;http://www.sonodrome.co.uk&quot; rel=&quot;nofollow&quot;&gt;http://www.sonodrome.co.uk&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I know they are the most comprehensive free licenses available online.     &lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2009-12-20T00:08:38.907" LastActivityDate="2009-12-20T00:08:38.907" CommentCount="5" />
  <row Id="1132" PostTypeId="2" ParentId="1098" CreationDate="2009-12-20T11:49:47.300" Score="4" ViewCount="" Body="&lt;p&gt;W.r.t. free-lancing, from the perspective of a free-lancing German software developer:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;You could offer your services via some social networking site, it is free and easy. I'm a software developer in Germany and use Xing (which is somewhat business-oriented), but you might want to check what's appropriate where you live.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If you got the qualifications (for hardware an EE degree) and some nice projects to show it shouldn't be too hard to get a job, though the first one is the most difficult. Depending on where you live it may be necessary to travel to work.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Don't sell yourself too cheaply.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You won't get filthy rich, but you can make a decent living.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="339" LastActivityDate="2009-12-20T11:49:47.300" CommentCount="3" />
  <row Id="1133" PostTypeId="1" CreationDate="2009-12-20T13:41:54.823" Score="16" ViewCount="318" Body="&lt;p&gt;Hey, i was wondering for a project of mine if i can order components&#xA;that are made for a long time of usage. would Mil-spec components fit under this&#xA;category?&#xA;What i basically want are parts that are good for a very long time, and have a very high reliability, in addition to high life cycle (amount of times it is used)&#xA;I can count out electrolytics, as they don't last long. Components with high power ratings are also probably better. Does anyone know if there are companies that manufacture these?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;p.s. Is there an alternative to relays that i can use to switch high amounts of power? because relays have a low amount of switchings.&lt;/p&gt;&#xA;" OwnerUserId="346" LastActivityDate="2011-04-30T10:22:37.190" Title="Long-Life Electronics" Tags="&lt;electronics&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="3" />
  <row Id="1134" PostTypeId="2" ParentId="1133" CreationDate="2009-12-20T14:12:00.440" Score="3" ViewCount="" Body="&lt;p&gt;Depending on your application you can use a transistor to &quot;turn things on&quot;.  Also, you can always use a Solid State relay.  (no moving parts).  However this is limited to DC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as the rest of your question.  I am sorry I do not know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope that helps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ril3y&lt;/p&gt;&#xA;" OwnerUserId="29" LastActivityDate="2009-12-20T14:12:00.440" />
  <row Id="1135" PostTypeId="2" ParentId="1133" CreationDate="2009-12-20T14:56:07.617" Score="15" ViewCount="" Body="&lt;p&gt;The life of your electronics will probably be more a function of your design&#xA;then it will be of the components. You can review the component reliability data&#xA;from the manufacturer's websites. Without a proper design you will not achieve&#xA;the specified reliability. Without process controls in manufacturing you will&#xA;not be able to manufacture a reliable product. A strategy of trying to test the quality into a product is doomed to failure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A lot of components will follow the Arrhenius activiation law which estimates&#xA;the component life based on the operating temperature and the maximum operating&#xA;temperature specification of the component. Reducing the operating temperature will have a dramatic affect&#xA;on life. For example -- reducing the operating temperature of  electrolytic capacitors &#xA;by 10degC will increase the capacitor life by roughly a factor of 2. &#xA;A 105degC rated capacitor run at 85degC will last roughly 4 times as long as&#xA;running an 85degC rated capacitor at 85degC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can switch high amounts of power with MOSFETs and IGBTs. For reliability heat&#xA;will be your enemy. You want to transition the semiconductor from off to on and on to off quickly&#xA;to minimize the heating. There are transient thermal curves at the back of the datasheet.&#xA;The thermal mass of the die is small. Switching the transistor in 10uS versus 1mS will have a dramatic affect on the junction temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general -- &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Design review -- thermal, electrical stress, environmental stress&lt;/li&gt;&#xA;&lt;li&gt;Design qualification&lt;/li&gt;&#xA;&lt;li&gt;Choose components with a wide temperature.&lt;/li&gt;&#xA;&lt;li&gt;Choose quality component manufacturers. &lt;/li&gt;&#xA;&lt;li&gt;Handle your components properly -- ESD, humidity, environment&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="424" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-30T10:22:37.190" LastActivityDate="2011-04-30T10:22:37.190" CommentCount="1" />
  <row Id="1136" PostTypeId="2" ParentId="1133" CreationDate="2009-12-20T14:58:02.340" Score="4" ViewCount="" Body="&lt;p&gt;First off, many times the life of a specific electronics product boils down to 1 or 2 components on a board, and usually those can be the capacitors used on a project.  Capacitor lifetimes are very dependent on which type you choose (tantalum being the best, I think, but someone correct me if I'm wrong).  Also, you want to keep these items cool as many times the life of the component doubles for every 10 °C below the maximum operating temperature.  So if any part of the product will be getting hot (&gt; 50-60 °C) try to find ways to keep it cool through heat sinking or through other means.&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2009-12-20T14:58:02.340" CommentCount="1" />
  <row Id="1137" PostTypeId="2" ParentId="1024" CreationDate="2009-12-20T15:08:02.417" Score="6" ViewCount="" Body="&lt;p&gt;Personally I don't like the traditional electronics schematics, because I'm normally making stuff for non engineers. So I use Photographs and a regular drawing program to label the components. Thought it may be of interest to people checking out this thread &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://sonodrome.co.uk/Pboard-01.png&quot; alt=&quot;Posc Board&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I like this method as it's easy to understand and quick to draw up. (obviously this picture comes with a key describing each label)  &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-20T15:08:02.417" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="9" />
  <row Id="1138" PostTypeId="2" ParentId="1024" CreationDate="2009-12-20T15:20:34.443" Score="6" ViewCount="" Body="&lt;p&gt;Try &lt;a href=&quot;http://tinycad.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;TinyCAD&lt;/a&gt;: it's open-source. For schematic capture (this doesn't do simulation, although you can export netlists to PSPICE).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(disclosure of bias: I work with the project maintainer)&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-20T15:20:34.443" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="1" />
  <row Id="1139" PostTypeId="2" ParentId="1133" CreationDate="2009-12-20T15:31:39.483" Score="2" ViewCount="" Body="&lt;p&gt;I suppose it depends on how long is long. Do you need this device to go on well after your life span? certain components, for example a back electret microphone capsule, will die of over usage before you do. I'd imagine the majority chips and discreet components will probably outlast all of us, as long as you don't abuse them. Be very careful to only operate within your components power ratings, if your worried about damage from static discharge then avoid CMOS chips.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got a 22 year old Atari computer, still works perfect to this day and I'm sure it has a good few delicate chips inside.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Things like electrolytic capacitors have come a long way in the last 10-20 years, a modern one probably lasts substantially longer than the ones in my Atari. You could always go overkill on the power rating of your components, i'd imagine they would put up a better fight in the long run.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Come to think of it, my uncle has a 30 year old electric guitar, it may have something to do with having passive circuitry, but it's fine to this day, it probably sounds better now. I don't think it's ever been repaired.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-20T15:31:39.483" />
  <row Id="1140" PostTypeId="1" AcceptedAnswerId="1143" CreationDate="2009-12-20T16:10:32.043" Score="7" ViewCount="1122" Body="&lt;p&gt;I would like to start using PICs in my projects and was wondering which programmer I should get. I have plenty of experience using micro-controllers (68k, avr), I also have lots of experience with electronics (so building a programmer is possible).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to be able to use MPLAB, icsp, and the in-circuit debugging feature seems pretty neat. USB would also be convenient, but is not necessary. In your answer, I would appreciate a comparison of the pros and cons of your recommendation.&lt;/p&gt;&#xA;" OwnerUserId="403" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-08-09T17:18:44.520" LastActivityDate="2010-08-09T17:18:44.520" Title="Best PIC programmer?" Tags="&lt;pic&gt;&lt;programmer&gt;&lt;isp&gt;&lt;microcontroller&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="1141" PostTypeId="2" ParentId="1128" CreationDate="2009-12-20T17:04:18.410" Score="4" ViewCount="" Body="&lt;p&gt;One thing to remember is that you, as copyright holder, can multi-license things.  You can release it to the general public under a CC non-commercial license, for instance, and then turn around and sell it to a corporation under whatever terms you want.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;So if you choose to license your work under a Creative Commons license that includes the “noncommercial use” option, you impose the ”noncommercial” condition on the users (licensees). However, you, the creator of the work and/or licensor, may at any time decide to use it commercially. People who want to copy or adapt your work, &quot;primarily for monetary compensation or financial gain&quot; must get your separate permission first. - &lt;a href=&quot;http://wiki.creativecommons.org/Frequently%5FAsked%5FQuestions&quot; rel=&quot;nofollow&quot;&gt;wiki&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Another thing to remember is that you're only copyrighting the schematics and PCB layout.  Anyone can &quot;paraphrase&quot; your work by re-drawing it, and it won't be a copyright violation.  If you patent it, on the other hand, they can't duplicate the same functionality regardless of PCB layout.  (The idea that source code and PCB layouts can be covered by copyright law has always seemed flawed to me.  They're utilitarian designs, not creative works.)&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2009-12-20T17:09:56.900" LastActivityDate="2009-12-20T17:09:56.900" CommentCount="5" />
  <row Id="1142" PostTypeId="2" ParentId="1140" CreationDate="2009-12-20T17:51:27.160" Score="13" ViewCount="" Body="&lt;p&gt;Get a Microchip PICkit 2, about $35. It has USB, ICSP, and in-circuit debugging via MPLAB. It can also act as a standalone ICSP programmer, and can also be used as a serial port analyser and simple logic analyser.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en023805&amp;amp;redirects=pickit2&quot; rel=&quot;nofollow&quot;&gt;PICkit 2&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a newer PICkit 3, but it has a few problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, get one of the new ICD 3 units, about $150. I've replaced my old ICD 2 with one, and it's a marvelous piece of kit - very fast (high-speed USB) with several nice new features. It's a more professional unit than the PICkits; for instance, Microchip replaces them free if they ever develop a fault even if the user has done something silly to it.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-07-19T21:39:36.610" LastActivityDate="2010-07-19T21:39:36.610" CommentCount="3" />
  <row Id="1143" PostTypeId="2" ParentId="1140" CreationDate="2009-12-20T18:23:40.683" Score="5" ViewCount="" Body="&lt;p&gt;If you are looking for the best in-circuit programmer/debugger for your own productivity, either ICD3 or RealICE is best. (these are pricier, but you get what you pay for!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are faster (+therefore quicker to recover from bugs/weirdness) than the older ICD2, which in turn is lightyears better than the original ICD1 (ugh!)&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-20T18:23:40.683" />
  <row Id="1144" PostTypeId="2" ParentId="472" CreationDate="2009-12-20T20:01:53.480" Score="3" ViewCount="" Body="&lt;p&gt;I get excellent results with a cheap HP DeskJet 5940 printer and Mega Electronics JetStar Premium film, using positive pre-coated boards in a home-made UV exposure unit made from MDF and a few strips of wood. I use a sheet of glass in the exposure unit - it's transparent to long-wave UV. I keep meaning to add another tube to decrease the exposure time, it takes 11 minutes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's best to have the UV tubes some distance from the artwork/PCB, as it increases the resolution due to the collimation effect. I have done 5 mil tracks as an experiment, but usually use 10 mil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Leon&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.leonheller.com/Photos/UV%20unit.jpg&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2009-12-20T20:08:13.540" LastActivityDate="2009-12-20T20:08:13.540" />
  <row Id="1145" PostTypeId="1" CreationDate="2009-12-21T05:40:47.787" Score="6" ViewCount="668" Body="&lt;p&gt;Hi All,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to connect my Lilypad Arduino to a WiFi 802.11 network that provides internet. What is the best way of achieving this? Can I use a XBee module and somehow interface with my home router? Is there a WiFi option available?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks so much all!&lt;/p&gt;&#xA;" OwnerUserId="431" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-10T02:58:29.500" LastActivityDate="2010-03-10T02:58:29.500" Title="Connecting a Lilypad to a WiFi network?" Tags="&lt;lilypad&gt;&lt;arduino&gt;&lt;beginner&gt;" AnswerCount="4" />
  <row Id="1146" PostTypeId="2" ParentId="1145" CreationDate="2009-12-21T06:50:06.570" Score="5" ViewCount="" Body="&lt;p&gt;You can buy &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9290&quot; rel=&quot;nofollow&quot;&gt;WiFi modules with a serial interface&lt;/a&gt;, but they're a little pricy. Basically you control them via UART, and you send them AT commands similar to how you controlled dial-up modems in the olden days.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://static.sparkfun.com/images/products/09290-1%5Fi%5Fma.jpg&quot; alt=&quot;WiFi module&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-21T06:50:06.570" CommentCount="1" />
  <row Id="1147" PostTypeId="1" CreationDate="2009-12-21T06:56:37.123" Score="14" ViewCount="930" Body="&lt;p&gt;I'm looking for a new soldering iron. What is the best all rounder soldering iron (soldering station) &amp;lt; $200 USD?&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:35:25.193" LastActivityDate="2011-06-02T02:35:25.193" Title="Choosing a new soldering iron" Tags="&lt;soldering&gt;&lt;iron&gt;" AnswerCount="8" FavoriteCount="4" />
  <row Id="1148" PostTypeId="1" CreationDate="2009-12-21T07:11:40.263" Score="2" ViewCount="307" Body="&lt;p&gt;Does anyone know a way to get Tango schematics into Eagle? Even if it is a hard way (other than entering from scratch)... Of course, an easy way would be nice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2010-01-18T19:15:51.797" Title="Tango to Eagle Schematic import" Tags="&lt;eagle&gt;&lt;cad&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="1149" PostTypeId="1" CreationDate="2009-12-21T07:14:15.707" Score="3" ViewCount="871" Body="&lt;p&gt;Would like to communicate between an Arduino and a PC but over a &#xA;distance of 2500+ feet outside in the open, wirelessly. What would be &#xA;the best way of doing this? The communcation devices I have found &#xA;(xbee,...) dont go the distance.&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-07-03T22:50:59.087" LastActivityDate="2011-06-05T13:08:33.873" Title="Wireless communication over long distances" Tags="&lt;communication&gt;&lt;wireless&gt;&lt;arduino&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="1150" PostTypeId="1" CreationDate="2009-12-21T07:17:25.343" Score="8" ViewCount="1043" Body="&lt;p&gt;I'm considering taking on a project that would involve individually addressing 500 LEDs, optimally with PWM support for each. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm planning on using an Arduino since I already have one, but I'm open to suggestions if anyone thinks a different platform would be a better match.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Shift registers would need to be employed. What is a good shift register to use in this situation? If PWM makes this project a lot more expensive, I'm alright to do without it. I want to try to spend less than $100. Here are the LEDs I'd buy:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://cgi.ebay.com/Lot-of-500-X-5mm-Amber-LED-10000-mcd-Free-Resistors_W0QQitemZ250521718989QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3a544210cd#ht_2131wt_939&quot; rel=&quot;nofollow&quot;&gt;http://cgi.ebay.com/Lot-of-500-X-5mm-Amber-LED-10000-mcd-Free-Resistors_W0QQitemZ250521718989QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3a544210cd#ht_2131wt_939&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is your opinion on the best way to control such a large number of LEDs? Also, how would I go about providing the power? I'd appreciate any help. I'm fairly experienced with electronics, I've just never done anything on such a large scale.&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-06-29T06:24:35.267" LastActivityDate="2011-03-16T17:38:25.657" Title="Controlling 500 LEDs with PWM" Tags="&lt;led&gt;&lt;multiplexing&gt;&lt;arduino&gt;" AnswerCount="8" />
  <row Id="1151" PostTypeId="1" AcceptedAnswerId="1173" CreationDate="2009-12-21T07:19:30.943" Score="13" ViewCount="2115" Body="&lt;p&gt;I just spent about 20 minutes trying to cut through a PCB with a hacksaw. These things are really tough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the correct tool to cut PCB material, and get a nice straight line?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I saw something about a guillotine, but can't find a vendor.&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-02T00:13:46.240" LastActivityDate="2010-12-02T00:13:46.240" Title="How do you cut PCB?" Tags="&lt;pcb&gt;&lt;cutting&gt;" AnswerCount="14" CommentCount="3" FavoriteCount="2" />
  <row Id="1152" PostTypeId="2" ParentId="1147" CreationDate="2009-12-21T07:20:08.337" Score="3" ViewCount="" Body="&lt;p&gt;I think Circuit Specialists has some good deals on soldering stations.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.circuitspecialists.com/level.itml/icOid/6388&quot; rel=&quot;nofollow&quot;&gt;http://www.circuitspecialists.com/level.itml/icOid/6388&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got the CSI-STATION1A and CSI-STATION2A models.  (Identical except for analog / digital display.  I prefer analog.) They are well made, and work as well as the more expensive Weller and Pace units I've used before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All the Chinese soldering stations seem to use the same kind of tip, and I've been able to buy 10-packs of replacement tips on eBay.  Tip life seems to be about one year of daily use.  I'm sure they would last longer if I could remember to turn the iron off when I'm not using it.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2009-12-21T07:20:08.337" />
  <row Id="1153" PostTypeId="2" ParentId="1150" CreationDate="2009-12-21T07:21:12.963" Score="6" ViewCount="" Body="&lt;p&gt;Just copy :-) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.evilmadscientist.com/article.php/peggy2&quot; rel=&quot;nofollow&quot;&gt;http://www.evilmadscientist.com/article.php/peggy2&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the &quot;peggy 2&quot; version is, IIRC, Arduino friendly ... &lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2009-12-21T07:21:12.963" CommentCount="1" />
  <row Id="1154" PostTypeId="1" AcceptedAnswerId="1156" CreationDate="2009-12-21T07:22:04.530" Score="6" ViewCount="2436" Body="&lt;p&gt;A customer has asked:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I want to slow down a small hobby&#xA;  sized DC motor to a user variable&#xA;  range that runs from slow to zero&#xA;  RPM. I would simply use a wall wart&#xA;  for a power supply and a potentiometer&#xA;  to set the speed but the load on the&#xA;  motor might change slightly. Although&#xA;  the drag on the motor will be very&#xA;  low, if that drag does change, I would&#xA;  like the speed of the motor to stay&#xA;  fairly steady in spite of this.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;A couple of people told me to use a&#xA;  PWM controller for this purpose&#xA;  because a PWM has a range of 0 to&#xA;  100%. Of course this in not in RPM.&#xA;  One other person said that the motor&#xA;  might not slow down properly because&#xA;  the hertz rating on the PWM could be&#xA;  to high to allow this or because the&#xA;  pulses might not have an adequate&#xA;  amount of strength to excite motor&#xA;  enough to move it at all when the&#xA;  motor speed is set near zero.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;I thought about using a steper motor so&#xA;  I looked a an Adafruit&#xA;  Motor/Stepper/Servo Shield for Arduino&#xA;  kit - v1.0 but I know almost nothing&#xA;  about this stuff so I don't know if&#xA;  this would be just the right thing&#xA;  either.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;I want to turn a knob to vary the&#xA;  speed of a motor form a few parts of&#xA;  an RPM up to a &quot;slow&quot; speed ...say 60&#xA;  RPM? ...maybe?&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Oh ...comparatively inexpensive and&#xA;  simple to set up would be great as&#xA;  well !&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Any thoughts? &lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-02-23T21:59:40.787" LastActivityDate="2011-02-23T21:59:40.787" Title="Very Slow Electric Motor" Tags="&lt;motor&gt;&lt;dc&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="1155" PostTypeId="2" ParentId="1147" CreationDate="2009-12-21T07:53:48.743" Score="8" ViewCount="" Body="&lt;p&gt;Are you looking for best bang for the buck or solid reliability?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best bang for the buck:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Chinese 2-in-1 or 3-in-1 that has soldering iron, hot air station and (with 3-in-1) smoke absorber. I went for the Kada 952D on eBay however after reading some more about the reliability, the lower risk of buying from a reputable dealer closer to home is attractive. The Aoyue apparently is made in the same factory and seems to be slightly more common so it might be worth going for an Aoyue over the Kada. Supposedly, the soldering irons on these offerings are compatible with the Hakko tips. Opinions differ on the included tips. I've ordered up a selection of genuine Hakko tips to compare.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Kada 852D+ or 952D:&#xA;See eBay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Aoyue 968:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://hackaday.com/2009/02/20/tools-aoyue-968-3-in-1-soldering-and-rework-station/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2009/02/20/tools-aoyue-968-3-in-1-soldering-and-rework-station/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;www.sparkfun.com/commerce/product_info.php?products_id=76&lt;/li&gt;&#xA;&lt;li&gt;store.sra-solder.com/product.php/6267/0&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Solid reliability:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Weller WES51:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;www.amazon.com/Weller-WES51-Analog-Soldering-Station/dp/B000BRC2XU&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Hakko 936:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;www.amazon.com/Hakko-936-ESD-Soldering-Station/dp/B000ARU9HW&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You could combine one of the above with a hot air station (say Aoyue 850++) and still be under $200 (at least if you're in the US and talking USD $200).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no experience with any of these products but did recently face the same decision. I'm waiting on the Kada 952D and crossing my fingers that it isn't going to be faulty. I can only post one link in my first post.&lt;/p&gt;&#xA;" OwnerUserId="432" LastEditorUserId="432" LastEditorDisplayName="" LastEditDate="2009-12-21T07:59:55.837" LastActivityDate="2009-12-21T07:59:55.837" CommentCount="5" />
  <row Id="1156" PostTypeId="2" ParentId="1154" CreationDate="2009-12-21T07:56:09.973" Score="13" ViewCount="" Body="&lt;p&gt;DC motors don't work well at low RPMs.  They stall and have horrible torque. (i.e. they can't turn very hard)  So people have created gear motors: motors with integrated gearing.  The result looks like a slightly bulkier motor, but one that has low RPMs and high torque.  If you were to take apart a running a gear motor, you'd see the motor part actually runs at several thousand RPMs, but it's geared down to something like 60 RPM max.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A common specialized one is the standard hobby servo, which has some additional electronic bits but is fundamentally a gear motor.  Check out any place that sells motors for robotics or surplus electronics and you'll see several different gear motors to choose from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC gear motors are controlled just like normal DC motors, so an Arduino motor shield works just fine with them.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2009-12-21T07:56:09.973" CommentCount="2" />
  <row Id="1157" PostTypeId="2" ParentId="1149" CreationDate="2009-12-21T08:16:30.177" Score="3" ViewCount="" Body="&lt;p&gt;Wifi maybe if you used range extenders for your network, or if you have the funds you can use the cell network with a module like &lt;a href=&quot;http://www.sparkfun.com/commerce/categories.php?c=66&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; from sparkfun.&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2009-12-21T08:16:30.177" />
  <row Id="1158" PostTypeId="2" ParentId="1151" CreationDate="2009-12-21T08:28:17.693" Score="15" ViewCount="" Body="&lt;p&gt;I don't know if this is the best way, but I usually score it multiple times with a heavy-duty knife (on both sides) and snap it by hand. Obviously this won't work for any non-straight cuts. The knife I use is similar to one of these &lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Cutter%5FStanley.jpeg/800px-Cutter%5FStanley.jpeg&quot; alt=&quot;Stanley knife&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="25" LastActivityDate="2009-12-21T08:28:17.693" CommentCount="3" />
  <row Id="1159" PostTypeId="2" ParentId="1149" CreationDate="2009-12-21T08:31:58.280" Score="3" ViewCount="" Body="&lt;p&gt;There are XBees that communicate about 1 mile (~4800 feet?). &#xA;&lt;a href=&quot;http://www.ladyada.net/make/xbee/modules.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/make/xbee/modules.html&lt;/a&gt;&#xA;Maybe you can even improve the range with a better antenna.&lt;/p&gt;&#xA;" OwnerUserId="409" LastActivityDate="2009-12-21T08:31:58.280" CommentCount="1" />
  <row Id="1160" PostTypeId="2" ParentId="1145" CreationDate="2009-12-21T08:44:06.143" Score="3" ViewCount="" Body="&lt;p&gt;Expanding a bit more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Davr suggested what I was going to suggest also. Roving Networks also makes a good set of BT modules.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To Expand. &lt;a href=&quot;http://en.wikipedia.org/wiki/ZigBee&quot; rel=&quot;nofollow&quot;&gt;ZigBee&lt;/a&gt; is a separate protocol completely from Wi-Fi. ZigBee is similar to BT in radiated power, which relates a large amount to range, but is different in that it is designed to allow multiple nodes to create a network, each node effectively expanding the network out by it's range. I hope this clears up that they are similar but not related.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2009-12-21T08:44:06.143" CommentCount="1" />
  <row Id="1161" PostTypeId="2" ParentId="1151" CreationDate="2009-12-21T08:46:39.687" Score="5" ViewCount="" Body="&lt;p&gt;I use a big scissor (originally meant for metal sheets, I don't know the english name, see the picture &lt;a href=&quot;http://www.usag.it/prodotti/zoom_foto_prodotto.htm?foto=204.jpg&amp;amp;nome=Cesoie%20per%20lamiere&quot; rel=&quot;nofollow&quot;&gt;http://www.usag.it/prodotti/zoom_foto_prodotto.htm?foto=204.jpg&amp;amp;nome=Cesoie%20per%20lamiere&lt;/a&gt; ) that's perfect for the scope. &lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2009-12-21T08:46:39.687" CommentCount="1" />
  <row Id="1162" PostTypeId="2" ParentId="1149" CreationDate="2009-12-21T08:56:46.967" Score="3" ViewCount="" Body="&lt;p&gt;One factor your options depend on is how the data transfer rate you need over that distance.  More of the long range, low power applications reduce in throughput as the distance increases.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, the XBee Pro 50mW Series 2.5  operates at 2.4GHz with a range of 1 mile and has a data transfer rate of 250kbps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The longer range &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9085&quot; rel=&quot;nofollow&quot;&gt;XBee Pro 900 XSC&lt;/a&gt; operates at 900MHz and has a range of over 15 miles, but a data transfer rate of only 9.6kbps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also look into directional antennas and signal amplifiers.&lt;/p&gt;&#xA;" OwnerUserId="433" LastActivityDate="2009-12-21T08:56:46.967" CommentCount="3" />
  <row Id="1163" PostTypeId="2" ParentId="1150" CreationDate="2009-12-21T09:09:54.303" Score="3" ViewCount="" Body="&lt;p&gt;What layout do you want the LEDs in? You can save a lot of work if you buy some LED matrixes, you can get single-color 8x8 LED matrixes (64 LEDs) &lt;a href=&quot;http://cgi.ebay.com/10pcs-8x8-LED-Dot-Matrix-20mm-Square-RED-10-x-pcs-USA%5FW0QQitemZ150386988451QQcmdZViewItemQQptZLH%5FDefaultDomain%5F0?hash=item2303c355a3&quot; rel=&quot;nofollow&quot;&gt;for a buck&lt;/a&gt; or &lt;a href=&quot;http://futurlec.com/LED/LEDMS88Opr.shtml&quot; rel=&quot;nofollow&quot;&gt;two&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You're not gonna get real PWM with an AVR and shift registers on this many LEDs, but you may be able to squeeze 2-4 levels of brightness. You'd have to run the numbers and see what's possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Allegro makes some handy &lt;a href=&quot;http://www.allegromicro.com/en/Products/Part%5FNumbers/6276/index.asp&quot; rel=&quot;nofollow&quot;&gt;constant current sink shift registers&lt;/a&gt; specifically designed for controlling arrays of LEDs, so that you don't need the extra resistors, that will make things simpler as well. You might not be able to drive the LEDs directly from the AVR output if it can't provide enough power, so you'll need to use transistors. You can get them in &lt;a href=&quot;http://www.allegromicro.com/en/Products/Part%5FNumbers/2981/index.asp&quot; rel=&quot;nofollow&quot;&gt;arrays in a single IC&lt;/a&gt;, that saves some work too.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-21T09:09:54.303" CommentCount="1" />
  <row Id="1164" PostTypeId="1" CreationDate="2009-12-21T09:15:51.310" Score="1" ViewCount="210" Body="&lt;p&gt;Hi everybody&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I' a technician since 4 years, for a compagny focused on defense electronics in france.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;-My job is to analyse , and repair electronics boards down to component level.&#xA;-Recommend process improvements or procedure modifications.&#xA;-Suggest modifications to testing equipment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;for about 2730$USD/month &lt;/p&gt;&#xA;&#xA;&lt;p&gt;i just wondering about other people like me over the world ...&lt;/p&gt;&#xA;" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-12-21T12:43:55.517" LastActivityDate="2009-12-21T15:56:37.477" CommunityOwnedDate="2009-12-21T13:04:12.020" Title="How much do you earn (only electronics job...)" Tags="&lt;electronics&gt;&lt;careers&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="1166" PostTypeId="2" ParentId="1147" CreationDate="2009-12-21T10:57:19.937" Score="2" ViewCount="" Body="&lt;p&gt;I just got one that has a ceramic tip, it seems to heat up really fast and it's lasted much longer. &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-21T10:57:19.937" CommentCount="1" />
  <row Id="1167" PostTypeId="2" ParentId="1149" CreationDate="2009-12-21T11:05:54.630" Score="3" ViewCount="" Body="&lt;p&gt;What sort of data rate do you need to maintain?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Long range communication is quite possible in open areas with very low power - a project I am currently working on incorporates data transmission over 500 KM using only 25 mW (miliwatts) of tx power - this of course relies on a line of sight, and data transmission is at only 50 baud. Even without line of sight, omnidirectional communications outdoors are quite easily achievable over the range you're looking for. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As others have mentioned, matching your antennas with your intend usage patterns is important - can you give us more detail as to requirements/use patterns?&lt;/p&gt;&#xA;" OwnerUserId="358" LastActivityDate="2009-12-21T11:05:54.630" />
  <row Id="1168" PostTypeId="2" ParentId="1099" CreationDate="2009-12-21T11:25:38.470" Score="2" ViewCount="" Body="&lt;p&gt;I connected an Arduino to a Telit GM862 (GPRS/GPS) module. It's a breadboard setup but I know that shields are coming for these modules.&#xA;There is a bit of code the lets you connect to twitter via GPRS. Not really a library but maybe a starting point.&#xA;&lt;a href=&quot;http://tinkerlog.com/2009/05/15/interfacing-arduino-with-a-telit-gm862/&quot; rel=&quot;nofollow&quot;&gt;http://tinkerlog.com/2009/05/15/interfacing-arduino-with-a-telit-gm862/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="409" LastActivityDate="2009-12-21T11:25:38.470" />
  <row Id="1169" PostTypeId="2" ParentId="1118" CreationDate="2009-12-21T11:38:16.023" Score="1" ViewCount="" Body="&lt;p&gt;here's a video of it being used as an inch worm bot&#xA;&lt;a href=&quot;http://www.youtube.com/watch?v=k9f-W6Xi%5FWo&quot; rel=&quot;nofollow&quot;&gt;Youtube Video&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the fact that it's an inch worm says something about the effectiveness of Nitinol, it's still pretty cool in my opinion&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-21T11:38:16.023" CommentCount="1" />
  <row Id="1170" PostTypeId="2" ParentId="1150" CreationDate="2009-12-21T11:49:47.183" Score="2" ViewCount="" Body="&lt;p&gt;I've no idea of the range of PWM you need for an LED but I've been working on a 64 channel PWM controller for a servo control application that can give me pulses of between 600us and 2.4ms. This uses CD74HCT238E's (3-8 line demultiplexors) to generate 64 channels from 8 I/O pins on an ATMega168 and is controllable via simple serial commands. I guess you could chain multiple versions of a modified version this controller together on a serial line and address all 500 LEDs... You could probably use the ATTiny2313 version of the controller as your firmware requirements would be simpler.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My &lt;a href=&quot;http://www.lhexapod.com&quot; rel=&quot;nofollow&quot;&gt;blog&lt;/a&gt; contains the assembly source and schematics and details of the design process.&lt;/p&gt;&#xA;" OwnerUserId="255" LastActivityDate="2009-12-21T11:49:47.183" />
  <row Id="1171" PostTypeId="2" ParentId="1164" CreationDate="2009-12-21T11:51:55.310" Score="1" ViewCount="" Body="&lt;p&gt;I'm not the best person to compare wages with as I've just open my own company two months ago and I just make enough to scrape by. I was intrigued by the description of your job role tho. I was wondering what kind of equipment you mostly repair? &#xA;Do you work with weapons systems? If so, is this something that raises moral questions about the use of the equipment you maintain? (in your experience) &#xA;Sorry if i'm overstepping the mark a bit, just tell me to get lost if you want. &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-21T11:51:55.310" CommunityOwnedDate="2009-12-21T13:04:12.020" CommentCount="3" />
  <row Id="1172" PostTypeId="2" ParentId="1149" CreationDate="2009-12-21T12:21:06.720" Score="1" ViewCount="" Body="&lt;p&gt;As was mentioned the XBee with the 50mW antenna should do this. You want to make sure&#xA;you order the high gain antenna. There is a series of XBees that come with a coax connecter&#xA;on the top. IIRC the highest gain antenna is the whip antenna with the coax cable. &#xA;The document that discusses the antenna gains is application note XST-AN019a from MaxStream.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:17:53.330" LastActivityDate="2011-05-19T14:17:53.330" />
  <row Id="1173" PostTypeId="2" ParentId="1151" CreationDate="2009-12-21T12:31:36.087" Score="13" ViewCount="" Body="&lt;p&gt;The first thing I should mention is safety. You need to wear breathing&#xA;protection since the dust created by cutting is very hazardous to breath.&#xA;Safety glasses should always be worn. As Norm would say -- read and understand&#xA;all the manufacturers instructions for your tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use either a hacksaw, bandsaw or tin-snips. Since I primarily use the&#xA;bandsaw for wood I only use it if the blade needs to changed anyways. &#xA;After cutting 10 linear inches of FR4 the blade will be useless for wood.&#xA;I hate changing bandsaw blades. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hacksaw is what I usually use. I leave 50mils between board edges.&#xA;I place copper no closer than 25mils to the edge. The hacksaw blade is&#xA;apx 35mils wide. I use a magnifying visor. This is fine for prototypes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes I snip the edges with tin-snips. A scroll-saw would be ideal.&#xA;Quick change carbide blades. Also I have heard of people using shears.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-02T00:12:47.973" LastActivityDate="2010-12-02T00:12:47.973" CommentCount="3" />
  <row Id="1174" PostTypeId="2" ParentId="1164" CreationDate="2009-12-21T14:38:08.380" Score="1" ViewCount="" Body="&lt;p&gt;You can find some good information about salaries for various occupations from &lt;a href=&quot;http://salary.com&quot; rel=&quot;nofollow&quot;&gt;Salary.com&lt;/a&gt; and the U.S. Bureau of Labor Statistic's &lt;a href=&quot;http://www.bls.gov/oco/&quot; rel=&quot;nofollow&quot;&gt;Occupational Outlook Handbook&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-12-21T14:38:08.380" CommunityOwnedDate="2009-12-21T14:38:08.380" />
  <row Id="1175" PostTypeId="1" CreationDate="2009-12-21T15:21:08.913" Score="4" ViewCount="345" Body="&lt;p&gt;I'm aware that different companies have different definitions for job titles, but in general, is &quot;logic design&quot; the same thing as &quot;digital circuit design&quot;?&lt;/p&gt;&#xA;" OwnerUserId="238" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T19:40:10.993" LastActivityDate="2011-02-08T19:40:10.993" Title="&quot;Logic Design&quot; vs. &quot;Digital Circuit Design&quot;" Tags="&lt;vhdl&gt;&lt;verilog&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="1176" PostTypeId="2" ParentId="1164" CreationDate="2009-12-21T15:56:37.477" Score="1" ViewCount="" Body="&lt;p&gt;Not nearly as much as I'm supposed to.  :'(  I go to salary.com and I'm not even in the 10th percentile.  This is entirely my own fault, though.  Salary.com is pretty accurate, according to the other engineers I know.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2009-12-21T15:56:37.477" CommunityOwnedDate="2009-12-21T15:56:37.477" />
  <row Id="1177" PostTypeId="2" ParentId="1150" CreationDate="2009-12-21T15:57:17.287" Score="2" ViewCount="" Body="&lt;p&gt;Check out &quot;LED driver&quot; ICs on mouser/digikey. TI, for example, makes a bunch of drivers with a variety of interfaces (I2C, SPI) that would certainly meet your needs. Most of these drivers are designed to be daisy chained so the serial out from one is fed into the serial in of another.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, something like the TLC5940 offers 16 channel PWM control. So, basically it's a constant current 16-bit shift register with 12-bit grayscale PWM control. I can recommend that particular IC as I helped design an 80x16 display with it.&lt;/p&gt;&#xA;" OwnerUserId="403" LastActivityDate="2009-12-21T15:57:17.287" />
  <row Id="1178" PostTypeId="2" ParentId="1154" CreationDate="2009-12-21T15:58:27.533" Score="6" ViewCount="" Body="&lt;p&gt;Generally speaking, a potentiometer will &lt;em&gt;not&lt;/em&gt; be a good choice for controlling the speed of a DC motor, unless it's a very small one (think a few 100 mA draw) as the pot must be rated for the current drawn by the motor. Additionally, as you restrict current, you're also sapping power from the motor.  So, at slow speeds using a current-limiting mechanism, you'll find it can only elicit a small fraction of the torque it can at high speeds.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC Gear motors, as pointed out, are more appropriate for reducing speed.  Alternatively, you can fashion your own gear chain, but it's not likely to be cost-effective. Dayton makes a well-priced range of 12V DC gear motors going as low as 0.6RPM (IIRC). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, if you wish to use the rated speed as the max speed, then a PWM speed controller can be quite handy.  While there's nothing wrong with the adafruit motor shield for DC motor control, I do prefer an external speed controller, like the L298 Compact Driver from Solarbotics for larger DC gear motors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your friend is right, that each motor will have different characteristics as to the lowest PWM duty cycle it will reliably respond to.  For most of my motors, it seems to limit around 25-35% duty cycle. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, another excellent way to control output speed is by using a stepper. It lets you take discrete steps whensoever you choose. While a servo also lets you take discrete steps, less expensive ones tend to be limited to 1degree minimum movements, and are designed to move as quickly as possible from the current position to the defined position.  A standard 200-step stepper motor, with an 8x microstepping driver, will give you effectively about 4 times the resolution, and therefor the ability to make smoother, smaller increments.  &lt;/p&gt;&#xA;" OwnerUserId="36" LastActivityDate="2009-12-21T15:58:27.533" />
  <row Id="1179" PostTypeId="2" ParentId="1151" CreationDate="2009-12-21T16:03:32.637" Score="7" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/Slice%5FCircuit%5FBoards%5Fwith%5Fa%5FPaper%5FCutter/&quot; rel=&quot;nofollow&quot;&gt;Use a paper cutter&lt;/a&gt;!&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2009-12-21T16:03:32.637" CommentCount="2" />
  <row Id="1180" PostTypeId="2" ParentId="1175" CreationDate="2009-12-21T16:11:52.640" Score="6" ViewCount="" Body="&lt;p&gt;To me, the job titles are very similar, but not exactly the same. &quot;Logic design,&quot; in my opinion, implies writing VHDL or Verilog to design digital logic to go onto FPGAs, CPLDs, or maybe even ASICs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Digital Circuit Design,&quot; on the other hand, means to me that in addition to (potentially working on) the HDL stuff, you are also designing the entire digital part of the board/chip/system - including working on the interfaces to the analog stuff. I would also think &quot;digital circuit design&quot; includes less &quot;logic design&quot; and more using ICs and off-the shelf components/IP blocks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, this obviously does not have to be the case. The two job titles could certainly describe the exact same position, that's just my interpretation. If you're looking for a job in that area, the job description can probably provide some more information on what the particular job entails. If it's still not clear, apply to both and then in the interview you can ask for clarification.&lt;/p&gt;&#xA;" OwnerUserId="403" LastActivityDate="2009-12-21T16:11:52.640" CommentCount="2" />
  <row Id="1181" PostTypeId="2" ParentId="1151" CreationDate="2009-12-21T16:25:30.683" Score="6" ViewCount="" Body="&lt;p&gt;I score it deeply with a Stanley knife on both sides and snap it, as well. A tungsten carbide tile cutter also works, but I prefer the Stanley knife. It blunts the blade very quickly, I resharpen mine with a diamond hone and can keep using the same blade indefinitely.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-02T00:13:05.600" LastActivityDate="2010-12-02T00:13:05.600" CommentCount="2" />
  <row Id="1182" PostTypeId="2" ParentId="1147" CreationDate="2009-12-21T16:31:29.527" Score="2" ViewCount="" Body="&lt;p&gt;Metcal arguably makes the best soldering equipment. It is expensive new, but perfectly good older models can often be picked up on Ebay for about the same price as a new Weller system. I paid £125 (GBP) for a second-hand STSS power unit with a new MX-500 handpiece and several new cartridges a few years ago from a UK supplier. I subsequently bought a second STSS unit on Ebay for £70. The cartridges are expensive, but they last a very long time, and there is one made for virtually every soldering job.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Leon&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-12-21T16:31:29.527" />
  <row Id="1183" PostTypeId="2" ParentId="1150" CreationDate="2009-12-21T16:36:52.497" Score="0" ViewCount="" Body="&lt;p&gt;XMOS uses the Macroblock MBI5026 with their LED tile kits. I think that they are used in most other professional systems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Leon&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-12-21T16:36:52.497" />
  <row Id="1184" PostTypeId="1" AcceptedAnswerId="1187" CreationDate="2009-12-21T16:40:39.010" Score="11" ViewCount="2591" Body="&lt;p&gt;I've read quite a few write ups on converting toaster ovens or skillets for reflowing SMT components. The important parts appeared to be:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Attempting to match a reflow profile (temperature pattern to ramp up and then down that gets hot enough to reflow but not hot enough to damage components/PCB)&lt;/li&gt;&#xA;&lt;li&gt;To make applying paste easier to specific areas: use a template (laser cut appears to be popular)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;SparkFun even &lt;a href=&quot;http://www.sparkfun.com/products/81&quot; rel=&quot;nofollow&quot;&gt;offers a kit&lt;/a&gt; to control an oven or skillet but apparently due to liability concerns, the kit uses a 12v relay instead of a 110/120v or 220v relay (adapting it to full voltage is left up to the DIYer).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is your personal experience with this? It would be great to hear actual experience on what works and what to avoid.&lt;/p&gt;&#xA;" OwnerUserId="432" LastEditorUserId="2770" LastEditorDisplayName="" LastEditDate="2011-02-15T19:18:12.803" LastActivityDate="2011-02-15T19:18:12.803" Title="DIY SMT Reflow: Toaster Oven, Skillet or ?" Tags="&lt;soldering&gt;&lt;surface-mount&gt;" AnswerCount="7" FavoriteCount="6" />
  <row Id="1185" PostTypeId="2" ParentId="1147" CreationDate="2009-12-21T16:48:01.210" Score="0" ViewCount="" Body="&lt;p&gt;At work we have &lt;a href=&quot;http://www.hakkousa.com/detail.asp?PID=1250&amp;amp;Page=1&quot; rel=&quot;nofollow&quot;&gt;Hakko 936&lt;/a&gt;, which works quite well.  (Google says $75 new)  SparkFun sells &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9672&quot; rel=&quot;nofollow&quot;&gt;a copy of the Hakko 936&lt;/a&gt; for $40, which is what I would recommend.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At home, I have a &lt;a href=&quot;http://www.eham.net/reviews/detail/2671&quot; rel=&quot;nofollow&quot;&gt;Weller WES50&lt;/a&gt;, which is ok, but not super great. (Google says $125.00 new)&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-29T21:53:55.520" LastActivityDate="2010-10-29T21:53:55.520" />
  <row Id="1186" PostTypeId="2" ParentId="1148" CreationDate="2009-12-21T16:59:15.757" Score="1" ViewCount="" Body="&lt;p&gt;Is Tango open source? Is their format documented? If so, Eagle has a scripting language, depending on how many schematics you have, it might be worth spending the time learning the scripting language and writing a tool to import it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should also ask on the Eagle newsgroups, it's on usenet which is kind of obscure, but you can use Mozilla Thunderbird to read/post to them.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-21T16:59:15.757" />
  <row Id="1187" PostTypeId="2" ParentId="1184" CreationDate="2009-12-21T17:47:48.287" Score="14" ViewCount="" Body="&lt;p&gt;From a hobbyist perspective:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just picked up a toaster oven with a convection bake mode, no mods at all.  The convection bake mode is important, as it more evenly distributes the temperature in the oven which prevents hot spots from frying components or cold spots from forming cold solder joints.  I have used older toaster ovens, and they work just fine for hobbyist work, but if you're going to pick up a new one then spend the extra $10 or so to get convection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have successfully reflowed many boards with different ICs and have never had an issue.  I can't remember the specifics, but I usually give it roughly 90 seconds to come to a &quot;warm-up&quot; temperature, then jack it up to my final baking temperature (I think it spends about a minute or two in that phase).  Check your datasheets to make sure your components can handle whatever temperature your solder paste melts at, and for how long.  I pretty much eyeball it when I first do a board of a given type to see when different parts reflow based on the amount of solder paste I use, but it's all been pretty similar in my smallish projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as templates/stencils go, I don't bother unless I have lots of fine-pitched ICs.  Get yourself a solder paste kit with a syringe and different tips, and play with those (I used this one from Celeritous: &lt;a href=&quot;http://www.celeritous.com/estore/index.php?main_page=product_info&amp;amp;products_id=47&quot; rel=&quot;nofollow&quot;&gt;http://www.celeritous.com/estore/index.php?main_page=product_info&amp;amp;products_id=47&lt;/a&gt; there's also a lead-free version).  All you need is a sufficient blob of solder paste, surface tension really does 90% of the work if you don't put too much on.  I figured out &quot;how much&quot; through trial and error on a few spare boards. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think if you're not trying to sell stuff and you're not working with sensitive components, no mods are required.  In my experience, components are pretty darn robust all things considered, and nothing beats the learning process of watching solder paste reflow on some old boards (and SMT components, if you have some to spare).  You'll know when you really need to address the issues you brought up.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-12-21T17:47:48.287" />
  <row Id="1188" PostTypeId="2" ParentId="1184" CreationDate="2009-12-21T17:50:28.613" Score="3" ViewCount="" Body="&lt;p&gt;I have used the skillet method at a friends house. It works very well. He made&#xA;a stencil by etching thin brass using the same process he uses to make PCBs.&#xA;We spread the paste on the PCB using the stencil. I placed the parts on the&#xA;PCB. After the parts are placed I carefully pushed the PCB+solder+parts onto the&#xA;preheated skillet using a dowel. When the solder started to melt I pushed the &#xA;PCB off the skillet. It is important to have the infeed area and outfeed area&#xA;at the same height as the skillet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A negative of the skillet is that you can only solder components on one-side. With&#xA;a toaster oven you could do both sides. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A big positive of the skillet is that you are heating through the PCB. The component&#xA;body will be at a lot lower temperature than in the oven method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a fellow I now that laser cuts Kapton stencils. $25 for an 8.5 x 11 stencil.&#xA;Some PCB manufacturer will also sell you a stencil.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-30T02:12:13.093" LastActivityDate="2011-01-30T02:12:13.093" CommentCount="1" />
  <row Id="1189" PostTypeId="2" ParentId="1151" CreationDate="2009-12-21T17:55:21.900" Score="3" ViewCount="" Body="&lt;p&gt;If you have access to one, a router table with a straight bit will do a great job.  You can probably pick up a decent router and table used for a reasonable price (varies by location) and they don't take up much space.  The table allows you to assure your boards are squared, and the router itself will allow you to make funky shapes if you wish.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IT's a bit more involved than, say, an Xacto knife or tin snips, which also work quite well, but the results are really great and very quick.  If you plan on processing a lot of boards, it's worth the investment.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-12-21T17:55:21.900" />
  <row Id="1190" PostTypeId="2" ParentId="952" CreationDate="2009-12-21T18:31:46.460" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.hackedgadgets.com&quot; rel=&quot;nofollow&quot;&gt;http://www.hackedgadgets.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="403" LastActivityDate="2009-12-21T18:31:46.460" CommunityOwnedDate="2009-12-21T18:31:46.460" />
  <row Id="1191" PostTypeId="2" ParentId="1184" CreationDate="2009-12-21T18:45:43.390" Score="2" ViewCount="" Body="&lt;p&gt;OMG!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Look, if it works for you, great, but I wouldn't touch this kind of approach with a 10' (3m ;-) pole. Stick to hand-soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess the exception to this is BGA parts or other devices with pads under the chip. For power devices with a single pad, some sort of solder paste + heat gun might work, I guess. For a BGA I wouldn't bother, as the quality control issues involved with BGAs are out of range of DIY techniques in my opinion.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-21T18:45:43.390" CommentCount="6" />
  <row Id="1192" PostTypeId="1" CreationDate="2009-12-21T19:19:24.603" Score="10" ViewCount="392" Body="&lt;p&gt;What software do you suggest for visualizing sensor data on OSX. For example bunch of sensors connected to Arduino and sent to MacBook via serial. Realtime graphing preferred but would be interested also in log-and-graph-later solutions.&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2011-05-19T14:17:40.227" Title="Visualizing sensor data with OSX?" Tags="&lt;sensor&gt;&lt;osx&gt;" AnswerCount="9" CommentCount="1" FavoriteCount="2" />
  <row Id="1193" PostTypeId="2" ParentId="1192" CreationDate="2009-12-21T20:07:26.393" Score="7" ViewCount="" Body="&lt;p&gt;One that comes to mind is &lt;a href=&quot;http://processing.org/exhibition/index.html&quot; rel=&quot;nofollow&quot;&gt;Processing&lt;/a&gt;. The development environment is similar to the Arduino's and it is cross platform (Java). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to see a native OSX app but haven't found it yet :)&lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2009-12-21T20:07:26.393" CommentCount="2" />
  <row Id="1194" PostTypeId="2" ParentId="1192" CreationDate="2009-12-21T20:30:08.100" Score="3" ViewCount="" Body="&lt;p&gt;hon is both open source and cross-platform. You can use &lt;a href=&quot;http://pyserial.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;pyserial&lt;/a&gt; to connect to an Arduino and there are libraries available to graph the data.&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2009-12-21T20:30:08.100" CommentCount="1" />
  <row Id="1195" PostTypeId="2" ParentId="739" CreationDate="2009-12-21T20:43:35.077" Score="8" ViewCount="" Body="&lt;p&gt;A while back I put together a &lt;a href=&quot;http://blog.davr.org/2009/05/18/comparison-of-entry-level-aka-cheap-fpga-boards/&quot; rel=&quot;nofollow&quot;&gt;comparison chart of entry level FPGA boards&lt;/a&gt;, from the two FPGA vendors Xilinx and Altera. They're the two major players in FPGAs, sort of like PIC vs AVR or Sony vs Nintendo. They provide the best bang-for-buck. There are other vendors that provide specific features, but you usually end up either paying more, or losing features/processing power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this doesn't directly answer your specific question, but it should be helpful to anybody who is looking to get started with a FPGA board.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-21T20:43:35.077" />
  <row Id="1196" PostTypeId="1" CreationDate="2009-12-21T23:10:31.607" Score="5" ViewCount="279" Body="&lt;p&gt;What is this &lt;em&gt;Arduino&lt;/em&gt; concept that I keep hearing about? Is it a microcontroller family, or a demoboard?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please include pictures in your answer, and if there are multiple possible items known as &lt;em&gt;Arduino&lt;/em&gt;, then let me into the secret :) .. and tell us about a few of those items.&lt;/p&gt;&#xA;" OwnerUserId="333" LastActivityDate="2011-05-17T12:57:59.563" Title="What is the Arduino?" Tags="&lt;arduino&gt;&lt;atmel&gt;&lt;microcontroller&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="1197" PostTypeId="2" ParentId="1196" CreationDate="2009-12-21T23:11:15.867" Score="5" ViewCount="" Body="&lt;p&gt;To quote their &lt;a href=&quot;http://www.arduino.cc/en/Guide/Introduction&quot; rel=&quot;nofollow&quot;&gt;Introduction page&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Arduino is a tool for making computers that can sense and control more of the physical world than your desktop computer. It's an open-source physical computing platform based on a simple microcontroller board, and a development environment for writing software for the board. &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;It consists of a demo board with (depending on the version) either an Atmel ATMega328, ATMega168, ATMega8 or an ATMega1280. These chips have the Arduino Bootloader burnt into them, which makes it easy to load your own programs onto them (called sketches in Arduino parlance). It also has a crossplatform IDE to allow you to develop for it, the language is based on a subset of C/C++. There are a large number of add-on boards (normally referred to as shields) which allow you to interact with the Arduino or extend its' capabilities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of this is open source including the board designs, so you can either buy a premade board, or make your own. The boards are relatively cheap (about £25 for a Duemilanove at the moment) and there is a thriving community of people using/developing/hacking with them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a picture of one:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://arduino.cc/en/uploads/Main/arduino316.jpg&quot; alt=&quot;Duemanilove&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="333" LastActivityDate="2009-12-21T23:11:15.867" CommentCount="1" />
  <row Id="1198" PostTypeId="2" ParentId="1196" CreationDate="2009-12-21T23:17:30.503" Score="3" ViewCount="" Body="&lt;p&gt;The Arduino is a development board for either the Atmel ATMega168 or ATMega328 microcontrollers.  It offers a standard USB serial port as well as headers for a variety of 'shields' that fit over the dev board to offer additional functionality such as motor drivers, SD cards, etc.  It comes with its own variant of C programming language that aims to make things a bit easier for people who haven't ever programmed before. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several different versions of it both official and unofficial.  Some of the unofficial versions use surface mount components and have a different layout that precludes the use of the shields.  There is also a 'mega' version that uses the ATMega1280 uC and has many more timers, UARTs and other peripherals than the original version.  Most shields are compatible with the mega version but some are not.&lt;/p&gt;&#xA;" OwnerUserId="333" LastActivityDate="2009-12-21T23:17:30.503" />
  <row Id="1199" PostTypeId="1" CreationDate="2009-12-21T23:52:31.977" Score="22" ViewCount="1649" Body="&lt;p&gt;I have experience with assembly and C programming for microcontrollers, but I'm not familiar with the various MCU and DSP families offered by today's companies. (eg: Texas Instruments, Atmel, Renesas)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to know about the good microcontrollers / DSPs, and what its like to develop with them. Please summarize your understandings about the various MCU / DSP families, one &lt;strong&gt;family&lt;/strong&gt; per answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be very interesting also if you detail what is(are) the main application(s) for this(ese) microcontroller please.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;(This is a &quot;community-wiki&quot;, so anyone with &gt;100 reputation can refine and improve answers)&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="333" LastEditorUserId="1416" LastEditorDisplayName="" LastEditDate="2010-10-07T12:56:22.817" LastActivityDate="2010-12-16T18:09:40.230" CommunityOwnedDate="2009-12-21T23:55:24.450" Title="What are good microcontrollers available today?" Tags="&lt;microcontroller&gt;&lt;development&gt;&lt;design&gt;&lt;dsp&gt;" AnswerCount="18" CommentCount="3" FavoriteCount="13" />
  <row Id="1200" PostTypeId="2" ParentId="1199" CreationDate="2009-12-21T23:54:05.920" Score="13" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;TI MSP430&lt;/strong&gt; series&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Hardware&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The variety of hardware peripherals is not as flexible as the Microchip PICs, but the software debugging toolchain support is much much better than Microchip's parts. TI recently released their new version of Code Composer for the MSP430 microcontrollers and TMS320F28xx DSPs, which uses Eclipse. The debugging support is excellent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are also very easy to setup the control registers, much easier than the 28xx DSPs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The MSP430 can be excellent for timing intensive applications as it will normally have more Capture/Compare Registers available for use. This can greatly simplify systems where you need to deal with many many timing intensive peripherals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Development&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy a development system for $150 (there's a cheaper $20 MSP430-on-a-USB-stick variant, but it's kinda limiting), and you get a real hardware + debugger prototyping system. You can also get the new TI &lt;a href=&quot;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_%28MSP-EXP430G2%29?DCMP=launchpad&amp;amp;HQS=Other+OT+launchpadwiki&quot; rel=&quot;nofollow&quot;&gt;launchpad&lt;/a&gt; which comes with 2 chips, and costs on $4.30.&lt;/p&gt;&#xA;" OwnerUserId="333" LastEditorUserId="81" LastEditorDisplayName="" LastEditDate="2010-06-23T19:58:30.383" LastActivityDate="2010-06-23T19:58:30.383" CommunityOwnedDate="2009-12-21T23:54:05.920" CommentCount="4" />
  <row Id="1201" PostTypeId="2" ParentId="1192" CreationDate="2009-12-21T23:57:42.917" Score="4" ViewCount="" Body="&lt;p&gt;You can use Grapher for simple graphs. It comes with OSX. &#xA;Although it's not really powerful, it's ok to take a quick look at some samples.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;@zklapow do you have a link?&lt;/p&gt;&#xA;" OwnerUserId="409" LastActivityDate="2009-12-21T23:57:42.917" CommentCount="1" />
  <row Id="1202" PostTypeId="2" ParentId="1199" CreationDate="2009-12-21T23:59:32.553" Score="9" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.analog.com/en/embedded-processing-dsp/blackfin/processors/index.html&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;Blackfin&lt;/strong&gt; by Analog Devices&lt;/a&gt;&#xA;The Blackfin family is a hybrid DSP/microcontroller with a strong RISC core as well as support video/signal processing instructions. Some instructions support SIMD.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Hardware&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has a RISC core. Speeds range from 200MHz single-core to 600MHz dual-core. It has may peripherals: 10/100 Ethernet MAC, UARTS, SPI, CAN controller, Timers with PWM support, Watchdog Timer, Real-Time Clock, and a glueless synchronous and asynchronous memory controller. It has dynamic power management - automatically shutting down parts of the processor that are not used. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Development&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The two primary development tools are AD's VisualDSP++ and the GNU toolchain. There is also an SDK with plenty of code and application notes. The SDK code serves either as a framework or as good code examples. There are several operating systems, including uCLinux, that will run on it. There are a number of &lt;a href=&quot;http://www.analog.com/en/embedded-processing-dsp/blackfin/content/blackfin%5Fdevelopment%5Ftools/fca.html&quot; rel=&quot;nofollow&quot;&gt;eval boards&lt;/a&gt; available. The &lt;a href=&quot;http://www.analog.com/en/embedded-processing-dsp/blackfin/processors/manuals/resources/index.html&quot; rel=&quot;nofollow&quot;&gt;manuals&lt;/a&gt; are indispensable.&lt;/p&gt;&#xA;" OwnerUserId="333" LastEditorUserId="238" LastEditorDisplayName="" LastEditDate="2009-12-22T03:15:52.963" LastActivityDate="2009-12-22T03:15:52.963" CommunityOwnedDate="2009-12-21T23:59:32.553" CommentCount="2" />
  <row Id="1203" PostTypeId="2" ParentId="1199" CreationDate="2009-12-22T00:05:00.670" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;TI TMS320F28xx&lt;/strong&gt; series of DSPs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Target market&lt;/em&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Motor control and digitally-controlled power converters: they have very flexible PWM peripherals and fast ADCs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Hardware&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These DSPs have two major drawbacks:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;More complex to setup -- the linker files and all the registers (memory wait states, etc.) have too many options and you really have to know what you're doing to make sure you're doing it right&lt;/li&gt;&#xA;&lt;li&gt;Needs two power supply voltages, 3.3V for I/O and peripherals, and 1.8-1.9V for the DSP core.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Development tools&lt;/em&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Real-time debugging through JTAG port, using Code Composer v4 (Eclipse-based!!!).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI's DSPs used to be really expensive to prototype because you needed a $1500 real-time-debugging pod (JTAG adapter), but the price of that has come way down (there's an inexpensive one for $150-200) and they sell eval boards with built-in JTAG adapters.&lt;/p&gt;&#xA;" OwnerUserId="333" LastActivityDate="2009-12-22T00:05:00.670" CommunityOwnedDate="2009-12-22T00:05:00.670" CommentCount="2" />
  <row Id="1204" PostTypeId="2" ParentId="1145" CreationDate="2009-12-22T00:19:58.263" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Can I use a XBee module and somehow interface with my home router?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes but You need to connect XBee module to Your router. You can try to find serial port on Your router board or by USB to serial adapter if Your router has USB port. Also your router should work under Linux (probably openWRT).&lt;/p&gt;&#xA;" OwnerUserId="422" LastActivityDate="2009-12-22T00:19:58.263" />
  <row Id="1205" PostTypeId="2" ParentId="1199" CreationDate="2009-12-22T00:22:39.357" Score="8" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Microchip PIC 16F/18F&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Target market&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inexpensive 8-bit microprocessors. The 16F is one of Microchip's earlier lines of processors and is not particularly amenable to programming in C / C++ due to:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;its instruction set core and memory architecture&lt;/li&gt;&#xA;&lt;li&gt;the necessity of switching banks&lt;/li&gt;&#xA;&lt;li&gt;lack of support for common pointer operations&lt;/li&gt;&#xA;&lt;li&gt;poor performance in C / C++ due to architecture&lt;/li&gt;&#xA;&lt;li&gt;requires larger program size to implement algorithms&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The 18F series is newer and should be considered if you can afford it for your project. It's similar in target market, peripheral set, IC packages, development tools, and price to the 16F series. The 18F core was designed to be more amenable to C and C++, due to:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;support for indirection&lt;/li&gt;&#xA;&lt;li&gt;particular RAM banks that are always accessible (no need of bank switching)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Software&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Quite easy to program, you can write using its set of 30 assembly instructions, or use a &lt;a href=&quot;http://www.electro-tech-online.com/micro-controllers/25909-what-best-c-compiler-pic16f877a.html&quot; rel=&quot;nofollow&quot;&gt;C compiler&lt;/a&gt;. These are 8-bit MCUs so if you want to work with values &gt;255 you will have to find/write 2 byte addition / subtraction / multiplication / division code yourself. Its RAM has 4 &quot;banks&quot; so if you write in assembly, you have to keep switching back and forth to access variables stored in banks other than the current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Hardware&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These MCUs run quite slow, with a typical speed of 4 MIPS and maximum speed of 20 MIPS. They have a few in-built hardware features that work okay if configured properly, like the ADC, Serial port, Parallel port, CAN bus, I2C bus, SPI bus, Voltage comparison, EEPROM, and of course, all purpose I/O ports.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Documentation&lt;/em&gt;  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Datasheets have all required info (pinouts, registers for configuration, etc) neatly categorized and well documented. A &lt;a href=&quot;http://ww1.microchip.com/downloads/en/devicedoc/33023a.pdf&quot; rel=&quot;nofollow&quot;&gt;manual&lt;/a&gt; also explains in-depth about the features. &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Development tools&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Microchip has a new tool, the &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/01033B%2044.pdf&quot; rel=&quot;nofollow&quot;&gt;VDI&lt;/a&gt; that makes it easier configure the MCU's various hardware features, which generates assembly or C code. Better than pouring over the datasheets.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Microchip has offered its &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en019469&amp;amp;part=SW007002&quot; rel=&quot;nofollow&quot;&gt;MPLAB IDE&lt;/a&gt; for many years, and although the program has been slowly improving, compared to PC development tools (Visual C++, Eclipse/NetBeans for Java/etc) the user interface is very poor and the software is still particularly buggy. It also does not support C++, despite the fact that the difference between C and the majority of C++ features (excluding dynamic-memory allocation, virtual functions, and a few other features) is very slight and C++ encourages programming modularity. There are 3rd-party IDE vendors, particularly IAR, but they are pricey. (Hi-Tech got bought out by Microchip recently.)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;In-circuit debugging is offered in some parts by Microchip's ICD interface, a 2-pin serial interface that can be accessed through debugging adapters ICD2, &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en537580&quot; rel=&quot;nofollow&quot;&gt;ICD3&lt;/a&gt;, &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en028120&quot; rel=&quot;nofollow&quot;&gt;REAL ICE&lt;/a&gt;, &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en023805&quot; rel=&quot;nofollow&quot;&gt;PICkit2&lt;/a&gt;/3, etc. &lt;strong&gt;Be sure to check if the part you choose has the ICD features!&lt;/strong&gt; The debugging features are somewhat limiting and have &quot;skid&quot; where you set a breakpoint on one instruction and the program stops a few instructions later. However, ICD is better than nothing.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Support&lt;/em&gt;  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1469&quot; rel=&quot;nofollow&quot;&gt;Application notes&lt;/a&gt; describe code and circuitry for various common applications&lt;/li&gt;&#xA;&lt;li&gt;Active community of users at the &lt;a href=&quot;http://www.microchip.com/forums/tt.aspx?forumid=-2&quot; rel=&quot;nofollow&quot;&gt;Microchip Forums&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Free 24/7 &lt;a href=&quot;http://support.microchip.com/scripts/slxweb.dll/external?name=webticketcust&quot; rel=&quot;nofollow&quot;&gt;Tech Support&lt;/a&gt; website where you send in your problems (tickets) and technical staff will respond free of cost, and even let you call if you need more help&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://techtrain.microchip.com/webseminars/QuickList.aspx&quot; rel=&quot;nofollow&quot;&gt;Presentations&lt;/a&gt; (web seminars) which explain the various modules and applications&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="333" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-10-04T15:13:09.423" LastActivityDate="2010-10-04T15:13:09.423" CommunityOwnedDate="2009-12-22T00:22:39.357" CommentCount="4" />
  <row Id="1206" PostTypeId="1" CreationDate="2009-12-22T00:24:02.770" Score="10" ViewCount="1673" Body="&lt;p&gt;Does anyone know of a freeware SPICE / circuit simulator?&lt;/p&gt;&#xA;" OwnerUserId="333" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-12-22T03:12:08.757" LastActivityDate="2011-04-01T16:22:07.020" CommunityOwnedDate="2011-04-01T14:55:18.717" Title="What are the freeware SPICE simulators available?" Tags="&lt;software&gt;&lt;electronics&gt;&lt;simulation&gt;" AnswerCount="7" CommentCount="4" FavoriteCount="5" />
  <row Id="1207" PostTypeId="2" ParentId="1206" CreationDate="2009-12-22T00:27:13.187" Score="8" ViewCount="" Body="&lt;p&gt;I found an excellent online &lt;a href=&quot;http://www.falstad.com/circuit/&quot; rel=&quot;nofollow&quot;&gt;circuit simulator&lt;/a&gt; written in Java, and its free-and-open-source. You can play with the software by visiting the link, and wait for the applet to pop-up. (you need the &lt;a href=&quot;http://www.java.com/getjava/&quot; rel=&quot;nofollow&quot;&gt;Java Player&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit components and connections by right-clicking anywhere/on a component. You can build entire circuits using this and simulate it visually to understand how the circuit works. (voltage is shown in green/red, simply amazing) If you start with one of the gate &lt;a href=&quot;http://www.falstad.com/circuit/e-index.html&quot; rel=&quot;nofollow&quot;&gt;circuit examples&lt;/a&gt;, (choose it from the &lt;em&gt;Circuits&lt;/em&gt; menu), then you can click on gates or digital signals to switch them on/off, and see your circuit react.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can setup oscilloscope views on any connection too. &lt;em&gt;(see bottom of the pic)&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i34.tinypic.com/2nknxc.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="333" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-01T16:22:07.020" LastActivityDate="2011-04-01T16:22:07.020" CommunityOwnedDate="2011-04-01T14:55:18.717" CommentCount="3" />
  <row Id="1208" PostTypeId="2" ParentId="1196" CreationDate="2009-12-22T00:28:17.707" Score="3" ViewCount="" Body="&lt;p&gt;The wikipedia page at &lt;a href=&quot;http://en.wikipedia.org/wiki/Arduino&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Arduino&lt;/a&gt;&#xA;provides an excellent description of the Arduino and&#xA;variants.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:57:59.563" LastActivityDate="2011-05-17T12:57:59.563" CommentCount="2" />
  <row Id="1209" PostTypeId="2" ParentId="1206" CreationDate="2009-12-22T00:36:55.117" Score="14" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;ngSpice is available for gEDA. &#xA;&lt;li&gt;gnuCAP is also available for gEDA.&#xA;&lt;li&gt;LTSpice is free from Linear Technology.&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I thought that one of the other analog chip makers had a spice too but I can't remember&#xA;who :(&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been to a few talks on simulation given by physicists and EEs who have done&#xA;chip design. Each of the talks seems to end like this ---&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Except for simple circuits you will spend most of your getting models&#xA;    and determining where the models need to be modified for your application.&#xA;&lt;li&gt;Unless you are doing work for an IC manufacturer the manufacturer will not&#xA;    give you detailed models.&#xA;&lt;li&gt;You will not be able to avoid a prototype.&#xA;&lt;li&gt;You should only simulate subsections of your design. Simulating the entire&#xA;    design is not usually practical.&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Also most of the free simulators are not distributed with models. Re-distribution of&#xA;the models is usually a copyright violation. LTspice is distributed with models of&#xA;the Linear Tech parts. I am not sure the quality of the models. Most manufacturers &#xA;do not want to reveal too many details about their process.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-01T14:54:07.107" LastActivityDate="2011-04-01T14:54:07.107" CommunityOwnedDate="2011-04-01T14:55:18.717" />
  <row Id="1210" PostTypeId="2" ParentId="1206" CreationDate="2009-12-22T00:41:34.937" Score="8" ViewCount="" Body="&lt;p&gt;A free version of TINA, which includes Spice, is available from TI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use SIMetrix Spice, it is an option with the Pulsonix PCB software I use. It's a very good implementation, and a free demo version is available that is suitable for small circuits:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.simetrix.co.uk/&quot; rel=&quot;nofollow&quot;&gt;SIMetrix&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.spiceopus.si/&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is a very nice SPICE that I investigated some years ago. It can be used with Eagle schematics.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-01T14:54:26.513" LastActivityDate="2011-04-01T14:54:26.513" CommunityOwnedDate="2011-04-01T14:55:18.717" CommentCount="1" />
  <row Id="1211" PostTypeId="2" ParentId="1192" CreationDate="2009-12-22T00:42:06.513" Score="1" ViewCount="" Body="&lt;p&gt;I will suggest using some RIA framework (&lt;a href=&quot;http://en.wikipedia.org/wiki/Rich_Internet_application&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Rich_Internet_application&lt;/a&gt;). Strictly speaking I recommend Data Visualization framework on top of RIA framework (&lt;a href=&quot;http://www.insideria.com/2009/12/28-rich-data-visualization-too.html&quot; rel=&quot;nofollow&quot;&gt;http://www.insideria.com/2009/12/28-rich-data-visualization-too.html&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the best approach will be Flash. I suggest Flex or Air (if You need more desktop integration).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To connect with flash You need ser2net or something like this. Fore example You can use as3glu (&lt;a href=&quot;http://code.google.com/p/as3glue/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/as3glue/&lt;/a&gt;) that hes ser2net build in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another interesting project is NETLab Toolkit (&lt;a href=&quot;http://newecologyofthings.wik.is/NETLab_Toolkit&quot; rel=&quot;nofollow&quot;&gt;http://newecologyofthings.wik.is/NETLab_Toolkit&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="422" LastActivityDate="2009-12-22T00:42:06.513" CommentCount="1" />
  <row Id="1212" PostTypeId="2" ParentId="1199" CreationDate="2009-12-22T01:07:07.473" Score="0" ViewCount="" Body="&lt;p&gt;I use PIC, ARM, MSP430, AVR and a few others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip has excellent support and good hardware and software tools, debugging is especially easy and fast. The 8-bit architecture is a bit dated. Their newer 16-bit chips are excellent. They are the market leader in 8-bit MCUs.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2009-12-22T01:21:34.717" LastActivityDate="2009-12-22T01:21:34.717" CommunityOwnedDate="2009-12-22T01:07:07.473" CommentCount="1" />
  <row Id="1213" PostTypeId="2" ParentId="1199" CreationDate="2009-12-22T01:22:45.993" Score="19" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/ARM_architecture&quot; rel=&quot;nofollow&quot;&gt;ARM&lt;/a&gt; is the industry standard for 32-bit controllers, although the &lt;a href=&quot;http://www.microchip.com/PIC32/&quot; rel=&quot;nofollow&quot;&gt;PIC32&lt;/a&gt; has some nice features. They are quite easy to use. I like the NXP LPC2000 and LPC1000 ARM chips, but the new Energy Micro &lt;a href=&quot;http://www.energymicro.com/technology/arm-cortex-m3&quot; rel=&quot;nofollow&quot;&gt;ARM Cortex-M3&lt;/a&gt; chip is very interesting because of its very low power consumption - as good as the &lt;a href=&quot;http://www.youtube.com/watch?v=ZxGZIiyyxrM&quot; rel=&quot;nofollow&quot;&gt;MSP430&lt;/a&gt; [Youtube]. Support is very variable, the NXP chips have the &lt;a href=&quot;http://tech.groups.yahoo.com/group/lpc2000/&quot; rel=&quot;nofollow&quot;&gt;LPC2000&lt;/a&gt; group which I run, which people seem to like - we have over 8,000 members!&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-15T12:26:03.570" LastActivityDate="2010-12-15T12:26:03.570" CommunityOwnedDate="2009-12-22T01:22:45.993" CommentCount="2" />
  <row Id="1214" PostTypeId="2" ParentId="1199" CreationDate="2009-12-22T01:24:58.927" Score="0" ViewCount="" Body="&lt;p&gt;Atmel's own support for the AVR isn't very good and their hardware tools are a bit flaky.The chips are nice, though, and the AVR Freaks forum is very good. They have serious delivery problems with their newer chips like the XMega and the 6-pin Tiny chips.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-12-22T01:24:58.927" CommunityOwnedDate="2009-12-22T01:24:58.927" CommentCount="4" />
  <row Id="1215" PostTypeId="2" ParentId="1199" CreationDate="2009-12-22T01:25:57.067" Score="2" ViewCount="" Body="&lt;p&gt;XMOS makes a range of very powerful 32-bit parallel processing chips (1600 MIPS from four cores with 32 hardware threads). They are fast enough to do high-speed USB and Ethernet in software. Their tools are very good, the chips are superb, they are reasonably priced (they start at $7.50), and the people there are very helpful. They have two very good support forums; one is run by the company, the other is independent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Leon&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2009-12-22T02:18:23.653" LastActivityDate="2009-12-22T02:18:23.653" CommunityOwnedDate="2009-12-22T01:25:57.067" CommentCount="1" />
  <row Id="1216" PostTypeId="2" ParentId="1199" CreationDate="2009-12-22T01:31:31.707" Score="5" ViewCount="" Body="&lt;p&gt;The 16-bit MSP430 is the market leader for very low-power applications. People don't find it very easy to use. Support via the MSP430 forum is very good. TI is having manufacturing problems with some of the chips at present.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-12-22T01:31:31.707" CommunityOwnedDate="2009-12-22T01:31:31.707" CommentCount="2" />
  <row Id="1217" PostTypeId="2" ParentId="1206" CreationDate="2009-12-22T02:40:39.577" Score="8" ViewCount="" Body="&lt;p&gt;my favorite spice engine is the one made by linear technology.  I saw ngSpice mentioned above but there is no good port to windows.  Its cool if you have the linux box.  But I find it has some compatibility issues and library import issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.linear.com/designtools/&quot; rel=&quot;nofollow&quot;&gt;http://www.linear.com/designtools/&lt;/a&gt;&#xA;That is where LTspice is, they have filter design tools there too.  &lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2009-12-22T02:40:39.577" CommunityOwnedDate="2011-04-01T14:55:18.717" CommentCount="3" />
  <row Id="1218" PostTypeId="2" ParentId="1147" CreationDate="2009-12-22T02:43:27.407" Score="2" ViewCount="" Body="&lt;p&gt;I wouldn't bother with hot air stuff.  Just get a Weller or Hakko, those are both good brands.  I would save up to get a de-soldering gun.  They make life so much easier for so many applicatons.  &lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2009-12-22T02:43:27.407" CommentCount="5" />
  <row Id="1219" PostTypeId="2" ParentId="1147" CreationDate="2009-12-22T03:04:20.240" Score="2" ViewCount="" Body="&lt;p&gt;I bought one of these &lt;a href=&quot;http://www.mpja.com/prodinfo.asp?number=15845+TL&quot; rel=&quot;nofollow&quot;&gt;ZD Electronic Tools ZD-929C&lt;/a&gt; and have been fairly happy with it. I accidentally wound the cord too tight around the handle once and it pulled loose, but I see that as my own fault. The tips are good quality and the iron heats up quickly and seems to hold a fiarly constant temp. A pretty good deal for $50.&lt;/p&gt;&#xA;" OwnerUserId="12" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-29T21:49:44.980" LastActivityDate="2010-10-29T21:49:44.980" CommentCount="1" />
  <row Id="1220" PostTypeId="2" ParentId="1199" CreationDate="2009-12-22T03:04:33.297" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Microchip 18F&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Similar in target market, peripheral set, IC packages, development tools, and price to the 16F series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 18F core was designed to be more amenable to C and C++, due to:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;support for indirection&lt;/li&gt;&#xA;&lt;li&gt;particular RAM banks that are always accessible (no need of bank switching)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="333" LastActivityDate="2009-12-22T03:04:33.297" CommunityOwnedDate="2009-12-22T03:04:33.297" CommentCount="1" />
  <row Id="1221" PostTypeId="2" ParentId="1206" CreationDate="2009-12-22T03:10:43.097" Score="7" ViewCount="" Body="&lt;p&gt;There are a couple of heavy-duty packages and a lightweight program for Linux.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The serious packages are &lt;strong&gt;GEDA&lt;/strong&gt; and &lt;strong&gt;KiCAD&lt;/strong&gt;. They are each a collection of programs that work well together (like Orcad); they include a schematic capture, a simulator, a waveform viewer, and a PCB layout tool. They are very sufficient except my professor requires the &quot;.out&quot; file generated by pspice, so I still have to use that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The lightweight program is &lt;strong&gt;Oregano&lt;/strong&gt;. It's great for quick simulations. The libraries are quick and easy to use and find parts from. The schematic capture is much easier to use and prettier than the other programs. It uses either gnucap or ngspice for the simulations, so they're pretty good. One major drawback that I have found is that the waveform viewer does not provide a logarithmic view and there's no way to get data out of it.&lt;/p&gt;&#xA;" OwnerUserId="333" LastActivityDate="2009-12-22T03:10:43.097" CommunityOwnedDate="2011-04-01T14:55:18.717" />
  <row Id="1222" PostTypeId="1" CreationDate="2009-12-22T03:14:12.293" Score="17" ViewCount="896" Body="&lt;p&gt;Do you know of any freeware or low cost circuit / PCB design software?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know a few which I have listed below but I was wondering if there were more of its kind. Please mention the good features and issues you've faced with the software.&lt;/p&gt;&#xA;" OwnerUserId="333" LastActivityDate="2011-01-26T20:11:00.967" Title="What are low cost circuit and PCB design software?" Tags="&lt;software&gt;&lt;circuit&gt;&lt;pcb&gt;&lt;design&gt;&lt;development&gt;" AnswerCount="12" CommentCount="1" FavoriteCount="12" />
  <row Id="1223" PostTypeId="2" ParentId="1222" CreationDate="2009-12-22T03:15:06.457" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.ohioautomation.com/images/epcmontage0.gif&quot; rel=&quot;nofollow&quot;&gt;Easy PC&lt;/a&gt; from Number One Systems works really well for small/medium sized projects, it supports multi-layer PCBs, includes a Schematic editing tool, and has an entry level Autorouter, or you can buy the pro Autorouter as an addon. Grab a free demo from their site.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PCB routing by hand is quick and intuitive, and you can create the netlist right in the PCB editor itself, by simply wiring any pin to another. All unconnected wires show up as a ratsnest. Then as you connect wires with tracks, the ratsnest line disappears.&lt;/p&gt;&#xA;" OwnerUserId="333" LastActivityDate="2009-12-22T03:15:06.457" />
  <row Id="1224" PostTypeId="2" ParentId="1222" CreationDate="2009-12-22T03:18:11.037" Score="9" ViewCount="" Body="&lt;p&gt;This may not count as a PCB design software, but it takes a new, creative approach to circuit and PCB design, and lets you prototype around with a breadboard view.&lt;br/&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's called &lt;a href=&quot;http://fritzing.org/&quot; rel=&quot;nofollow&quot;&gt;Fritzing&lt;/a&gt; and there are versions for Windows, Linux and Mac.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;View screenshots of the main feature modes:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Breadboard view (see below)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.svgopen.org/2009/abstracts/33-SVG%5Fin%5FFritzing%5Fa%5FCase%5FStudy/fritzing%5Fschematic%5Fview.jpg&quot; rel=&quot;nofollow&quot;&gt;Schematic view&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.svgopen.org/2009/abstracts/33-SVG%5Fin%5FFritzing%5Fa%5FCase%5FStudy/fritzing%5Fpcb%5Fview.jpg&quot; rel=&quot;nofollow&quot;&gt;PCB view&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.svgopen.org/2009/abstracts/33-SVG%5Fin%5FFritzing%5Fa%5FCase%5FStudy/fritzing%5Fbreadboard%5Fview.jpg&quot; alt=&quot;Breadboard view &quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="333" LastEditorUserId="333" LastEditorDisplayName="" LastEditDate="2009-12-22T03:27:42.907" LastActivityDate="2009-12-22T03:27:42.907" CommentCount="1" />
  <row Id="1225" PostTypeId="2" ParentId="1222" CreationDate="2009-12-22T03:34:06.130" Score="16" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.cadsoft.de/&quot; rel=&quot;nofollow&quot;&gt;Eagle&lt;/a&gt; seems to be the most popular free PCB tool.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-12-22T03:34:06.130" CommentCount="3" />
  <row Id="1226" PostTypeId="2" ParentId="1222" CreationDate="2009-12-22T08:02:20.700" Score="10" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.lis.inpg.fr/realise_au_lis/kicad/&quot; rel=&quot;nofollow&quot;&gt;Kicad&lt;/a&gt; is free and open source, and it is a relatively well-integrated package of schematics and layout editor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.gpleda.org/&quot; rel=&quot;nofollow&quot;&gt;gEDA&lt;/a&gt; is free and open source. It is older than Kicad, has more tools which produce nicer output, but is less well integrated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since they are open-source packages there are no arbitrary restrictions on the free version (like e.g. board size in Eagle) and no license hassles.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2009-12-22T08:02:20.700" />
  <row Id="1227" PostTypeId="2" ParentId="1222" CreationDate="2009-12-22T11:18:43.447" Score="2" ViewCount="" Body="&lt;p&gt;If you don't need gerber output, the demo of omnyglyph (formerly circad) at &lt;a href=&quot;http://www.holophase.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.holophase.com/&lt;/a&gt; should be enough. I've used this almost unknown software from the very first version for MS-DOS.&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2009-12-22T11:18:43.447" />
  <row Id="1228" PostTypeId="2" ParentId="1222" CreationDate="2009-12-22T11:43:31.120" Score="5" ViewCount="" Body="&lt;p&gt;I use gEDA/PCB. The file formats are open an ASCII. The open file formats make&#xA;a wide variety of EDA automation tasks possible. The ASCII format makes them&#xA;easy. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have switched from Eagle to gEDA/PCB. I have found gEDA to be a more productive&#xA;tool. The schematic capture is better but the PCB layout seems more difficult.&#xA;The scriptability is what has made the difference. There are also tools for&#xA;simulation. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be careful of choosing a free version of an EDA tool that is crippled&#xA;or a tool that locks you in to a specific PCB vendor. There is a learning curve&#xA;associated with any EDA tool or other complex piece of software. It will be very&#xA;time consuming to switch tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The footprint library that I use is available at &lt;a href=&quot;http://www.luciani.org&quot; rel=&quot;nofollow&quot;&gt;http://www.luciani.org&lt;/a&gt;&#xA;Also I have a variety of EDA automation scripts on my site.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an example of gEDA/PCB I did a remix of the Drawdio circuit design that&#xA;ladyada did. The remix includes the EDA files and documentation. &#xA;All of the files are at &lt;a href=&quot;http://tinyurl.com/bq8pq4&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/bq8pq4&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-25T07:57:27.893" LastActivityDate="2011-01-25T07:57:27.893" CommentCount="1" />
  <row Id="1230" PostTypeId="2" ParentId="1196" CreationDate="2009-12-22T13:25:55.797" Score="0" ViewCount="" Body="&lt;p&gt;Presented without comment, the home page for the Arduino platform:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-12-22T13:25:55.797" />
  <row Id="1231" PostTypeId="1" AcceptedAnswerId="1233" CreationDate="2009-12-22T13:43:11.987" Score="4" ViewCount="1200" Body="&lt;p&gt;Anyone got any super simple circuit designs for converting 1.5v dc to 9v dc?&#xA;Maybe something that uses a couple of transistors would be good?&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-23T11:43:42.700" Title="simple circuits 1.5v dc to 9v dc" Tags="&lt;dc&gt;&lt;circuit&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="1232" PostTypeId="2" ParentId="1231" CreationDate="2009-12-22T14:33:20.420" Score="6" ViewCount="" Body="&lt;p&gt;I did a brief review of the TL499A, and I believe (from the data sheet) it will do what you need:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tl499a.html&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/docs/prod/folders/print/tl499a.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a DIP package available, and the data sheet gives a pretty complete application example on page 4.  Mouser shows these chips available for $1.50 with plenty of availability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should definitely figure out your current requirements as well.  Handy charts are in the data sheet to help you determine if this chip can supply the current you need.&lt;/p&gt;&#xA;" OwnerUserId="11" LastEditorUserId="11" LastEditorDisplayName="" LastEditDate="2009-12-22T14:39:56.320" LastActivityDate="2009-12-22T14:39:56.320" CommentCount="5" />
  <row Id="1233" PostTypeId="2" ParentId="1231" CreationDate="2009-12-22T16:48:11.560" Score="4" ViewCount="" Body="&lt;p&gt;If you just need a few milliamps, it looks like maybe the &lt;a href=&quot;http://www.onsemi.com/PowerSolutions/product.do?id=NCP1403SNT1G&quot; rel=&quot;nofollow&quot;&gt;NCP1403&lt;/a&gt; would do. Otherwise, TI doesn't seem to have anything besides the TL499A; maybe Linear Tech or Maxim or Micrel or National Semiconductor would have something useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: Linear has the &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1060,P1775&quot; rel=&quot;nofollow&quot;&gt;LT1615-1&lt;/a&gt;, looks promising but pricey as most of Linear's stuff is. I don't like Maxim (have been burned by pricey unobtainable products too many times).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;National has the &lt;a href=&quot;http://www.national.com/pf/LM/LM2621.html#Overview&quot; rel=&quot;nofollow&quot;&gt;LM2621&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;hr /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;update (based on comments):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Consider using the 1.5V of an AAA battery directly, along with a low-voltage version of a 555 (e.g. &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tlc551.html&quot; rel=&quot;nofollow&quot;&gt;TLC551&lt;/a&gt; -- not a typo, it's a little different from TLC555 -- or &lt;a href=&quot;http://www.national.com/mpf/LM/LMC555.html#Overview&quot; rel=&quot;nofollow&quot;&gt;LMC555&lt;/a&gt; or &lt;a href=&quot;http://www.diodes.com/zetex/?ztx=3.0/3-3-2b@rid~112&quot; rel=&quot;nofollow&quot;&gt;ZSCT555&lt;/a&gt;), and a buzzer/piezo rated at 1.5V.... the latter is kinda difficult to find (I guess they spec 15Vp-p usually) and we ran into the same problem on a project at work. You'll get twice the peak-to-peak voltage if you drive both sides of the piezo. Drive one end from the 555 directly, the other end from an inverted version of the 555 output: pick a 74xx14 from a logic series that can run off 1.5V and has high drive capability. You can generally parallel up the output of inverters with identical inputs (for a home project fine, on a &quot;real&quot; project i'd probably put some 1-5ohm resistors in series to limit short circuit current somewhat)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may not be as LOUD as running the piezo off 9V but maybe that's ok.... :-)&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-12-23T00:06:27.670" LastActivityDate="2009-12-23T00:06:27.670" CommentCount="4" />
  <row Id="1234" PostTypeId="1" AcceptedAnswerId="1237" CreationDate="2009-12-22T18:47:50.420" Score="2" ViewCount="167" Body="&lt;p&gt;Looking to play around with the &lt;a href=&quot;http://www.cree.com/products/xlamp%5Fxpg.asp&quot; rel=&quot;nofollow&quot;&gt;CREE Xlamp series LED&lt;/a&gt; and was wondering what would I need to drive them off 110V household power?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Output current needs to be in the range of 800-900mA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I am looking to do this for creating lighting for a NanoReef tank. I would be combining several of these in series. &lt;/p&gt;&#xA;" OwnerUserId="245" LastEditorUserId="245" LastEditorDisplayName="" LastEditDate="2009-12-22T19:47:05.143" LastActivityDate="2011-05-19T14:11:08.170" Title="Current source for CREE XLamp XP-G" Tags="&lt;led&gt;&lt;driver&gt;" AnswerCount="3" />
  <row Id="1235" PostTypeId="2" ParentId="1234" CreationDate="2009-12-22T19:02:04.573" Score="2" ViewCount="" Body="&lt;p&gt;I would not advise driving the led directly with household voltage - it is far too high for this low voltage device. A further consideration is that the led requires DC to drive it and the household power is AC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These LEDs will draw 800-900mA at a forward voltage of around 3.2 v. If you use a wall wart (plug and voltage regulator all in one) with an output of 5v DC (a common value) then a 1.8 ohm 2 watt (or greater wattage) resistor in series with the led would do the trick. Note the led will need a heatsink as it will need to dissipate about 3W.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-12-22T19:02:04.573" CommentCount="3" />
  <row Id="1236" PostTypeId="2" ParentId="1234" CreationDate="2009-12-22T19:48:03.303" Score="1" ViewCount="" Body="&lt;p&gt;At that power I'd use some kind of switching regulator for efficiency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wouldn't dare to go directly from household power to the LED without a lot more research. For a start I'd rather use some wall wart to provide say 12V and step that down to the LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, make sure to cool them sufficiently.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2009-12-22T19:48:03.303" />
  <row Id="1237" PostTypeId="2" ParentId="1234" CreationDate="2009-12-22T21:12:21.013" Score="2" ViewCount="" Body="&lt;p&gt;As was suggested twice already you do not want to power this directly from the line.&#xA;You should have an isolated low voltage supply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would use a current-sink to provide a regulated current. An easy way&#xA;to make a current-sink is to use an op-amp, resistor and FET. I have been working on a prototype that is four channels at 20A per channel. For an LED application the practical limits would be around 2A per channel (due to cooling). A picture of my prototype that is powering 5 1W LEDs is at &lt;a href=&quot;http://tinyurl.com/yzg9kd7&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/yzg9kd7&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have mounted the LEDs on a heatsink. I use thermal grease between the LEDs and&#xA;heatsink. I have a schematic of a current-sink (a.k.a. load cell) at &#xA;&lt;a href=&quot;http://tinyurl.com/6cbn6h&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/6cbn6h&lt;/a&gt; (scroll down to the &quot;Electronic Load&quot; section.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:11:08.170" LastActivityDate="2011-05-19T14:11:08.170" />
  <row Id="1241" PostTypeId="2" ParentId="1145" CreationDate="2009-12-22T22:33:38.060" Score="3" ViewCount="" Body="&lt;p&gt;Just wanted to share my current solution with you all:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After chatting with Marcus and Madeleine at LittleBirdElectronics, we have come up with the following possible solution:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Xbee on The lilypad,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) USB Arduino, Ethernet Sheild and Xbee combo to transfer messages to the WWW.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is just one of many possible solutions, but for me this seems to provide the benefits of the low power and size requirements on the lilypad end by using the xbee instead of using 802.11 directly on the lilypad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Besides, I already had a spare Arduino and Ethernet shield going unused, and wanted an excuse to play with xbee anyway! ;-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks all for your input! It was very useful in devising a solution.&lt;/p&gt;&#xA;" OwnerUserId="431" LastActivityDate="2009-12-22T22:33:38.060" CommentCount="2" />
  <row Id="1242" PostTypeId="2" ParentId="1192" CreationDate="2009-12-22T22:50:07.577" Score="3" ViewCount="" Body="&lt;p&gt;You could take a look at &lt;a href=&quot;http://puredata.info/&quot; rel=&quot;nofollow&quot;&gt;Pure Data&lt;/a&gt; a Max like language (it's not just for music generation) there's a Wikipedia page &lt;a href=&quot;http://en.wikipedia.org/wiki/Pure%5FData&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; with a bit more information about it. It's fully supported on Mac OSX and there's even a subforum &lt;a href=&quot;http://puredata.hurleur.com/index.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; dedicated to linking it to things like Arduinos.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-22T22:50:07.577" CommentCount="0" />
  <row Id="1245" PostTypeId="1" AcceptedAnswerId="1247" CreationDate="2009-12-23T01:01:58.163" Score="6" ViewCount="108" Body="&lt;p&gt;Can a LED change colour over time?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've had a blue LED set up for some time and it use to be a much brighter (ultramarine blue) now it's heading to a more greenish dull colour.  How is this happening?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2009-12-23T04:18:34.373" Title="LED changing colour over time" Tags="&lt;led&gt;&lt;colour&gt;" AnswerCount="2" />
  <row Id="1246" PostTypeId="1" AcceptedAnswerId="1252" CreationDate="2009-12-23T01:20:08.820" Score="3" ViewCount="997" Body="&lt;p&gt;I have a bunch of green LEDs (not super bright), the plastic around the actual LED is physically green, but they did not come with a turn on voltage. 3V seems to work but they're not too bright, is there any way I can figure it out? What's the standard turn-on voltage for non super bright green LEDs?&lt;/p&gt;&#xA;" OwnerUserId="337" LastActivityDate="2009-12-23T04:52:51.057" Title="Turn-on voltage for LED" Tags="&lt;led&gt;&lt;voltage&gt;" AnswerCount="2" />
  <row Id="1247" PostTypeId="2" ParentId="1245" CreationDate="2009-12-23T01:25:42.893" Score="6" ViewCount="" Body="&lt;p&gt;My guess is over-voltage or over-current, both of which can be caused by using an incorrect resistor with the LED, or by a power supply giving more voltage than you thought. Slightly overdriving a LED will often work at first, but it will wear it out much sooner than if the specs were followed.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-23T01:25:42.893" />
  <row Id="1248" PostTypeId="2" ParentId="1246" CreationDate="2009-12-23T01:27:12.327" Score="7" ViewCount="" Body="&lt;p&gt;Brightness depends mostly on current, not on voltage. As long as you've got the correct voltage, you can adjust brightness by changing how much current the LED is given. If you have a set voltage, then changing the resistor will give you different currents. Google for &quot;LED calculator&quot; to see how to find the correct values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The term you are looking for is &quot;Forward voltage&quot;, here is a &lt;a href=&quot;http://www.kpsec.freeuk.com/components/led.htm#data&quot; rel=&quot;nofollow&quot;&gt;chart of some common values&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-23T01:27:12.327" CommentCount="1" />
  <row Id="1250" PostTypeId="2" ParentId="1245" CreationDate="2009-12-23T04:18:34.373" Score="3" ViewCount="" Body="&lt;p&gt;Sadly, not all LEDs are well made, and some will deteriorate over time even without mishandling. How long have you had this LED running? If it's just a few hundred hours, it probably was damaged by something, but if it has been in use for thousands of hours, it may just be aging. &lt;/p&gt;&#xA;" OwnerUserId="227" LastActivityDate="2009-12-23T04:18:34.373" />
  <row Id="1251" PostTypeId="1" AcceptedAnswerId="1260" CreationDate="2009-12-23T04:47:38.953" Score="6" ViewCount="332" Body="&lt;p&gt;For my projects I have always used hacky power supplies: wall plug + 7805, a usb port or an ATX PSU. I am looking at getting into 3.3v circuits and I am having trouble getting hold of the necessary regulators where I am located. Can anyone recommend a good lab/benchtop PSU or alternatively a cheap way of getting 3.3v?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I am in Australia&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="417" LastEditorDisplayName="" LastEditDate="2009-12-23T13:37:16.330" LastActivityDate="2011-05-19T14:18:05.797" Title="Investing in a benchtop PSU" Tags="&lt;power&gt;" AnswerCount="8" CommentCount="1" FavoriteCount="1" />
  <row Id="1252" PostTypeId="2" ParentId="1246" CreationDate="2009-12-23T04:52:51.057" Score="6" ViewCount="" Body="&lt;p&gt;A good way to think about an LED is as a variable resistance (or impedances, more commonly). At very low voltages, it has very high impedance, so not a lot of current will flow through the device. If you have a current source, as davr suggests, the current flowing through the LED times the impedance will create a voltage (Ohm's law). If you force enough current, the voltage will quickly rise and the impedance will drop. The point where current seems to flow easily is past the &quot;turn-on&quot; voltage you speak of. Past this point the impedance of the device is very low and large changes in current will create small changes in voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this can still be confusing, but I would suggest staring at an I-V curve for a while (current plotted versus voltage). This is a simple looking chart but is in fact quite complex.  The thing that I did not grasp until much further into my career is that the instantaneous slope of the line is actually the impedance. Once you grasp that concept, what I said earlier may become clearer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.utc.edu/Faculty/Tatiana-Allen/IVfig6.gif&quot; alt=&quot;Simple IV Curve&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2009-12-23T04:52:51.057" />
  <row Id="1253" PostTypeId="1" AcceptedAnswerId="1266" CreationDate="2009-12-23T05:26:28.077" Score="3" ViewCount="474" Body="&lt;p&gt;How can I sense the touch of a hand through a thick surface? I'm working on a device that has to be completely enclosed in a 1-2&quot; thick wooden casing (or 1-3mm thick metal) due to design requirements, so no chance of pushbuttons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I thought we could use capacitance touch sensing, but I don't know what will work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="333" LastActivityDate="2011-05-19T14:18:25.093" Title="Sensing touch through a thick surface?" Tags="&lt;sensor&gt;" AnswerCount="7" />
  <row Id="1257" PostTypeId="2" ParentId="1251" CreationDate="2009-12-23T08:10:33.967" Score="3" ViewCount="" Body="&lt;p&gt;You could use an LM317 and set that to 3.3V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The standard part for 3.3V would be the 1117 at 3.3V I suppose. It is indeed somewhat hard to get, even here in Germany (for example, Reichelt only has the SOT 223 variant of the LT1117).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a lab supply I have &lt;a href=&quot;http://gsmserver.com/shop/equipment/power_supply_device/hy1503d_dc_power_supply_lcd_display_0_15v_0_3a.php&quot; rel=&quot;nofollow&quot;&gt;a cheap chinese 15V 3A unit&lt;/a&gt;. That should also be ok, though I prefer the regulator approach.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2009-12-23T08:10:33.967" />
  <row Id="1258" PostTypeId="2" ParentId="1253" CreationDate="2009-12-23T08:34:11.100" Score="2" ViewCount="" Body="&lt;p&gt;It should be possible to pick up the minimal bending of the metal with a strain gauge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen them register the minuscule bending of a cm think steel bar pushed lightly with a finger. Though I don't know what quality of strain gauge and amplifier you need to achieve that. In any case it will be rather expensive (~10$ up).&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2009-12-23T08:34:11.100" CommentCount="0" />
  <row Id="1259" PostTypeId="2" ParentId="1251" CreationDate="2009-12-23T08:56:07.090" Score="3" ViewCount="" Body="&lt;p&gt;For quick prototyping designs with dual rails supply voltage (i.e. 3.3V and 5.0V), I have recently been using a breadboard with an &lt;a href=&quot;http://www.seeedstudio.com/depot/adjustable-breadboard-power-supply-p-566.html?cPath=11&quot; rel=&quot;nofollow&quot;&gt;adjustable breadboard power supply&lt;/a&gt;. With this, I can use it with a USB plug or with an ac-dc power adapter and a JST-DC adapter, or for more portability, I use a 9V battery with the JST connector. Search &quot;JST&quot; at seeedstudio for the adapters.&lt;/p&gt;&#xA;" OwnerUserId="437" LastActivityDate="2009-12-23T08:56:07.090" />
  <row Id="1260" PostTypeId="2" ParentId="1251" CreationDate="2009-12-23T09:53:33.433" Score="8" ViewCount="" Body="&lt;p&gt;Decent bench power supplies are quite expensive.  However, you've said that you have used an ATX power supply in the past.  This is what I've done - I've modified an ATX supply to have a switch, an LED and some 4mm sockets on it with +12V, -12V, +5V, -5V and 3.3V.  It's a cheap and very effective way of having a range of voltages available for development.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ATX supply pin-out is &lt;a href=&quot;http://wiki.xtronics.com/index.php/ATX%5FPinout&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, there are a wide range of 3.3V regulators available, including switching ones like the LM2574 or linear ones like the 78L33.  Farnell or RS will ship to most places (and they stock both of these parts); alternatively some bits are on ebay (search for 78L33 and you get a few links from &quot;international sellers&quot;) and you can probably get them shipped pretty much anywhere.  Where are you located?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apologies for the lack of links for Farnell, RS or ebay: it'll only let me add one hyperlink as I'm a new chiphacker.com user!&lt;/p&gt;&#xA;" OwnerUserId="201" LastActivityDate="2009-12-23T09:53:33.433" CommentCount="2" />
  <row Id="1261" PostTypeId="2" ParentId="1253" CreationDate="2009-12-23T10:26:08.093" Score="1" ViewCount="" Body="&lt;p&gt;I've used the old Qprox QT110 (well, it's not really touch sense, but near proxy) to detect touch through a wood board 4 cm thick. I had to carefully tune Cx and Rs by trials, but the final result was good enough. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the metal is non-magnetic, you can use reed relays inside and small magnet outside to operate controls.&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2009-12-23T10:26:08.093" />
  <row Id="1262" PostTypeId="1" AcceptedAnswerId="1263" CreationDate="2009-12-23T10:42:19.433" Score="9" ViewCount="701" Body="&lt;p&gt;What are Fuses in Atmel microprocessors and when I should or need to change the default settings.&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2010-06-14T04:09:15.140" Title="What are Atmel Fuses?" Tags="&lt;atmel&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="1263" PostTypeId="2" ParentId="1262" CreationDate="2009-12-23T10:53:41.260" Score="12" ViewCount="" Body="&lt;p&gt;They're essentially configuration parameters, or like the chip's BIOS.  There's a fantastic fuse calculator for Atmega AVRs here: &lt;a href=&quot;http://www.engbedded.com/fusecalc/&quot; rel=&quot;nofollow&quot;&gt;http://www.engbedded.com/fusecalc/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They control things like which oscillator to use, and what speed to run at (ie. the internal 8MHz oscillator, or an external crystal), brownout detection, and the size of the boot flash.  &lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-12-23T10:53:41.260" CommentCount="3" />
  <row Id="1264" PostTypeId="2" ParentId="1231" CreationDate="2009-12-23T11:43:42.700" Score="0" ViewCount="" Body="&lt;p&gt;I had a look at the 551 timers and I don't think they will be that loud when hooked up to a regular piezo buzzer. So I've decided to try and boost the voltage, I couldn't find most of the ICs available locally at short notice, but I did manage to find some NCP1403s that can be delivered tomorrow. So I'll try them out with the trusty 555 timer and I'll let y'all know if it works well. The only thing I'm worried about is the lack of current!&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-23T11:43:42.700" />
  <row Id="1265" PostTypeId="2" ParentId="1262" CreationDate="2009-12-23T13:15:41.797" Score="7" ViewCount="" Body="&lt;p&gt;They can be a bit of a pain if you make a mistake with them, and configure your chip for use with an external oscillator when it uses a crystal or internal oscillator. You then find that you can't program your chip, and need to inject a clock signal into the oscillator pin to recover it, by setting the fuse correctly.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-12-23T13:15:41.797" />
  <row Id="1266" PostTypeId="2" ParentId="1253" CreationDate="2009-12-23T13:23:11.173" Score="7" ViewCount="" Body="&lt;p&gt;If you really need to detect touch through a metal surface, you could possibly do it using 4 insulated Piezoelectric pickups. There is a technique for detecting touch that cross references the frequency detected by 4 equidistant piezo pickups. It's a technique called SAW or surface acoustic wave. It's normally used for touch screens that are 3 dimensional or have surfaces that are prone to damage or deformation. It can detect location of a touch point, velocity of a touch (It can distinguish a tap from a press, to emulate a mouse click for instance) and it can detect a dragging or moving point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you wanted you could have a very simplified version to implement a few basic buttons or tap sensors. Instead of doing all the annoying frequency calculations, you could just position a few piezoelectric pickups where you want the actual buttons, then use a threshold detection to determine which has been pressed (the one with the largest signal peak). They are quite affective as they don't pickup any airborne vibration, so you don't have to worry about any loud noises setting it off, although dropping it on the floor would probably do it.     &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2009-12-23T13:23:11.173" CommentCount="1" />
  <row Id="1267" PostTypeId="2" ParentId="1253" CreationDate="2009-12-23T13:24:27.833" Score="2" ViewCount="" Body="&lt;p&gt;(my answer migrated from &lt;a href=&quot;http://electronics.stackexchange.com/questions/111/sensing-touch-through-a-thick-surface/117#117&quot; rel=&quot;nofollow&quot;&gt;electronics-exchange&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Through 2&quot; thick wood: Also tough, but not impossible. I assume you mean distinguishing between a finger/hand touching the box, and a finger/hand placed 1mm away from the box.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can place one or more metal plates on the outside of the box &amp;mdash; not providing a total covering of the entire box! &amp;mdash; then there are a number of possibilities using electromagnetic fields. I can think of a few (no guarantee that either would work!). Put your thinking cap on, and imagine how the touch of a person's skin can alter an electromagnetic circuit network. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The biggest thing that can make a difference is whether you can bring a conductor out from the inside of a box, through the wall, and connected to earth ground, or to a metal plate on the outside of the box.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) &lt;strong&gt;The resistance of a person's skin can close an electric circuit&lt;/strong&gt; -- Have two semicircular plates, separated by a small gap. The impedance between the plates is a very large resistance in parallel with a small capacitance. If you bridge the gap between the plates with your skin, you drastically reduce that resistance. If you can somehow measure that resistance, you're done:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can connect wires through the box walls to the plates, that's easy, just use a voltage divider and a source of DC or AC voltage that is small (don't hurt the person).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't connect wires through the box walls to the plates, you might still be able to distinguish touch vs. no touch, but it'll be tougher. Maybe have another pair of plates, this time on the inside of the box, on the other side of the box wall from the first pair of plates, but with a much larger gap. Measure the capacitance between the inner plates. There may be a large enough change in the capacitance between the two inner plates with / without a person bridging the gap on the outside, that you could distinguish. There are a number of techniques/chips that can do capacitive sensing. Cypress has CapSense, Atmel has QTouch, ST Micro has S-Touch, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) &lt;strong&gt;A person's body is a reasonably good antenna and will pick up noise.&lt;/strong&gt; (Look at an oscilloscope probe when you touch the tip with your finger.) If you have a plate on the outside of the box, and you touch it, you transfer that noise to the plate's electric potential. Think of this case as a person &quot;shaking&quot; electric potential up and down. If you can sense this shaking relative to a reference potential, you've got a sensor. The problem here is that finding a reference potential is touch. You really need a connection to earth ground, since a box floating in the air doesn't have access to a fixed reference voltage. You might be able to sense the differential voltage between two plates... dunno though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;hr /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just my two cents.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-23T13:24:27.833" CommentCount="0" />
  <row Id="1268" PostTypeId="2" ParentId="1253" CreationDate="2009-12-23T13:27:00.187" Score="-1" ViewCount="" Body="&lt;p&gt;(my answer migrated from &lt;a href=&quot;http://electronics.stackexchange.com/questions/111/sensing-touch-through-a-thick-surface/113#113&quot; rel=&quot;nofollow&quot;&gt;electronics-exchange&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Through a 2&quot; thick conductor? No feasible way, unless you have another electrode that the user is attached to or standing on. (in which case you could use an electrometer-type approach; that's kind of how those touch-activated lamps work)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think about it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;People are essentially non-magnetic so that rules out a solution that uses magnetic fields/circuits. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're talking electric fields, a 2&quot; thick conductor is millions (probably billions) of times more conductive than the human body. Any electric field you try to generate from inside the box, whether DC or AC, will be greatly attenuated by the time it gets outside, and the incremental effect of a human body touching or not touching it is insignificant. Capacitive effects are small (low picofarads) and if you could get the frequency high enough to measure it, you lose because of &lt;a href=&quot;http://en.wikipedia.org/wiki/Skin%5Feffect&quot; rel=&quot;nofollow&quot;&gt;skin effect&lt;/a&gt;: a metal box attenuates AC fields more as you go higher in frequency. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you try to sense environmental fields originating outside the box, (e.g. treat the box as an antenna, whose reception characteristics change with the addition of a human body touching it) you also lose because of skin effect attenuation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Aside from electromagnetic fields, you have thermal: possible if you touch a box long enough to sense heating it up. Or radioactivity, or light, or....&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-23T13:27:00.187" CommentCount="5" />
  <row Id="1269" PostTypeId="1" CreationDate="2009-12-23T13:53:26.857" Score="4" ViewCount="169" Body="&lt;p&gt;What do I need to develop hardware that can run embedded software developed with the &lt;a href=&quot;http://www.microsoft.com/switzerland/education/en/academiczone/students/robotics.mspx&quot; rel=&quot;nofollow&quot;&gt;Microsoft Robotics&lt;/a&gt; studio? I thought only certain high-end off-the-shelf robots that support embedded Linux were capable of running such software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have any experience with MS Robotics? and is it possible for me to develop my own custom-built hardware in-house so I don't have to buy some expensive robot simply to play with the MS Robotics studio and the Visual Programming Language (VPL) that is included within the package?&lt;/p&gt;&#xA;" OwnerUserId="333" LastActivityDate="2009-12-23T19:51:46.550" Title="How easy is it to develop hardware to run Microsoft Robotics?" Tags="&lt;microsoft&gt;&lt;robotics&gt;&lt;electronics&gt;&lt;embedded&gt;&lt;software&gt;" AnswerCount="2" FavoriteCount="3" />
  <row Id="1270" PostTypeId="1" AcceptedAnswerId="1329" CreationDate="2009-12-23T14:26:58.793" Score="10" ViewCount="589" Body="&lt;p&gt;I'm always looking for interesting electronics kits with a music or audio based theme. I've recently started an online shop selling a basic electronics kit, the Posc pocket oscillator, and I'm in the process of developing a multipurpose Biofeedback system (EEG, ECG, EMG etc). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd love to hear some ideas and thoughts from everyone on Chiphacker, about what kind of kits you would like to see available. The kits will be aimed at all different ages, skill levels and can implement a wide range of technologies.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd welcome any ideas, but I'd love to see something associated with sound, however Robots and visuals would also be cool. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although I'd be using your input for a commercial product any resulting work from your ideas would be released under GNU LGPLv3 and the Creative Commons Licenses. &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-01-10T23:27:27.147" CommunityOwnedDate="2009-12-23T14:26:58.793" ClosedDate="2011-03-22T11:26:30.287" Title="Electronics kits, any requests?" Tags="&lt;kit&gt;&lt;electronics&gt;&lt;audio&gt;&lt;sound&gt;" AnswerCount="13" CommentCount="1" FavoriteCount="3" />
  <row Id="1271" PostTypeId="2" ParentId="1270" CreationDate="2009-12-23T14:34:06.167" Score="5" ViewCount="" Body="&lt;p&gt;Well, with sound as your primary focus:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to see a device I can send encoded digital audio (PCM, perhaps) to (over I2C), and have the sound either come out of a speaker or a headphone jack (or line out).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, it is a drop in sound module; all your microcontroller has to do is send it waveform data.  (If I could send it musical notes and phonemes to play, that'd be even cooler!)&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-12-23T14:34:06.167" CommunityOwnedDate="2009-12-23T14:34:06.167" CommentCount="5" />
  <row Id="1272" PostTypeId="2" ParentId="1269" CreationDate="2009-12-23T15:26:50.257" Score="3" ViewCount="" Body="&lt;p&gt;According to the documentation on the site in Tutorial #6 (&lt;a href=&quot;http://msdn.microsoft.com/en-us/library/bb483043.aspx&quot; rel=&quot;nofollow&quot;&gt;http://msdn.microsoft.com/en-us/library/bb483043.aspx&lt;/a&gt;), it seems that you can create control applications if your robot doesn't run the .NET framework (likely if you decide to roll your own).  From the tutorial, it looks like it would be possible to write an interface to control pretty much anything you can come up with, though I admit I didn't give it an exhaustive consideration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, it does seem to support a wide array of robots according to Wikipedia (&lt;a href=&quot;http://en.wikipedia.org/wiki/Microsoft_Robotics_Developer_Studio#Supported_robots&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Microsoft_Robotics_Developer_Studio#Supported_robots&lt;/a&gt;) and several of those models aren't exactly &quot;high-end&quot;.  You may find something up your alley, and it would undoubtedly be easier to start out with, say, a Parallax BOE-Bot (&lt;a href=&quot;http://en.wikipedia.org/wiki/Boe-Bot&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Boe-Bot&lt;/a&gt;) than building something from scratch and creating all the interfaces.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is, apparently, a simulated robot environment as well.  According to the Wikipedia article linked above, you can, &quot;simulate the behavior  of robots in a virtual world using NVIDIA PhysX technology (3D engine originally written by Ageia) that includes advanced physics.&quot;  Microsoft makes extensive reference to the Ageia physics engine on their site as well.  If you have an idea you want to try out, this might be a free way of doing so.  I haven't really looked at this environment, though, so anything other than what I quoted from the sources is speculation here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have not used the MS Robotics environment at all, so all of this comes from the documentation.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2009-12-23T15:26:50.257" />
  <row Id="1273" PostTypeId="2" ParentId="1192" CreationDate="2009-12-23T17:14:26.873" Score="4" ViewCount="" Body="&lt;p&gt;I use either &lt;a href=&quot;http://oss.oetiker.ch/rrdtool/&quot; rel=&quot;nofollow&quot;&gt;RRD TOOL&lt;/a&gt; which is good for monitoring of continuous streams of data.  When I want to produce one off graphs I usually go with &lt;a href=&quot;http://matplotlib.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;matplotlib&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://matplotlib.sourceforge.net/%5Fimages/mri%5Fwith%5Feeg1.png&quot; alt=&quot;matplotlib&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://oss.oetiker.ch/rrdtool/stream-pop.png&quot; alt=&quot;RRD Tool&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="86" LastActivityDate="2009-12-23T17:14:26.873" CommentCount="1" />
  <row Id="1274" PostTypeId="2" ParentId="1269" CreationDate="2009-12-23T19:51:46.550" Score="2" ViewCount="" Body="&lt;p&gt;Ther must be better way, but since roomba protocol specification is open and it uses serial interface it should be not very hard to implement roombas api in your robot and lay to MSRS (that has support for Roomba) that it is true Roomba.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;useful links:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.irobot.com/images/consumer/hacker/Roomba_SCI_Spec_Manual.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.irobot.com/images/consumer/hacker/Roomba_SCI_Spec_Manual.pdf&lt;/a&gt; protocol specification&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://hackingroomba.com/code/roombacomm/&quot; rel=&quot;nofollow&quot;&gt;http://hackingroomba.com/code/roombacomm/&lt;/a&gt; open source Roomba client implementation&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="422" LastActivityDate="2009-12-23T19:51:46.550" />
  <row Id="1275" PostTypeId="2" ParentId="1140" CreationDate="2009-12-23T20:55:43.437" Score="5" ViewCount="" Body="&lt;p&gt;For hobby use, the PICkit2 is certainly a very good option. It's a modern design, USB, integrates with MPLab, does in-circuit debugging, it's cheap (with even cheaper clones available), and both the design and firmware are open source so you can build your own or integrate one for debugging into your own board designs.&lt;/p&gt;&#xA;" OwnerUserId="401" LastActivityDate="2009-12-23T20:55:43.437" />
  <row Id="1276" PostTypeId="2" ParentId="1222" CreationDate="2009-12-23T22:22:59.950" Score="5" ViewCount="" Body="&lt;p&gt;I personally prefer using Diptrace &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.diptrace.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.diptrace.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is available for non-commercial use in a limited form (250 pins) for free and then hasd a scale of different costs depending on use and scope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried Eagle and find diptrace easier to use with a fairly extensive library and more importantly an easy to use parts designer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used this to create gerbers which I had turned into PCB's with no issues whatsoever.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would thoroughly recommend giving it a try, I think it is as powerful as Eagle and simpler to use...&lt;/p&gt;&#xA;" OwnerUserId="312" LastActivityDate="2009-12-23T22:22:59.950" />
  <row Id="1277" PostTypeId="2" ParentId="1251" CreationDate="2009-12-23T22:53:33.970" Score="1" ViewCount="" Body="&lt;p&gt;I use one of these:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.lascarelectronics.com/temperaturedatalogger.php?location=uk&amp;amp;datalogger=125&quot; rel=&quot;nofollow&quot;&gt;PSU 140&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's very good. The only shortcoming is the sockets, I'd have preferred terminals with sockets.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-12-23T22:53:33.970" />
  <row Id="1278" PostTypeId="2" ParentId="1251" CreationDate="2009-12-23T23:20:45.473" Score="1" ViewCount="" Body="&lt;p&gt;The surplus company Marlin P. Jones (http://www.mpja.com) sells a variety&#xA;of supplies made by MasTech. I don't know the quality of this brand but&#xA;if they meet the specs and are reliable they would be a good value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Extech power supplies look good. Same caveats.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:18:05.797" LastActivityDate="2011-05-19T14:18:05.797" />
  <row Id="1279" PostTypeId="2" ParentId="1270" CreationDate="2009-12-24T00:43:47.447" Score="5" ViewCount="" Body="&lt;p&gt;I'd buy an EEG,ECG etc kit! especially if built around a *duino core.&lt;/p&gt;&#xA;" LastActivityDate="2009-12-24T00:43:47.447" CommunityOwnedDate="2009-12-24T00:43:47.447" CommentCount="5" />
  <row Id="1280" PostTypeId="2" ParentId="1253" CreationDate="2009-12-24T11:55:34.770" Score="1" ViewCount="" Body="&lt;p&gt;Detecting the change in frequency of an RF oscillator might work through wood, due to the change in capacitance caused by the proximity of a hand to the oscillator tank circuit. It won't work with a metal case, of course.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-12-24T11:55:34.770" />
  <row Id="1281" PostTypeId="2" ParentId="1253" CreationDate="2009-12-24T12:59:20.463" Score="1" ViewCount="" Body="&lt;p&gt;As Leon mentioned the RF oscillator will work. I would use a heterodyne&#xA;oscillator which consists of a fixed frequency oscillator, a variable&#xA;frequency oscillator and a non-linear mixer (such as a diode). &#xA;Your body acts as a small capacitor to change the frequency of the&#xA;variable oscillator. It is easier to measure the change in frequency &#xA;of the mixed frequency. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the way a Theremin works. The Theremin is sensitive at distances&#xA;of a foot or two and the antenna will work inside a wood case. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Q-touch sensors may work too. Can you mill a feature in the &#xA;wood so that the contact was a closer than the thickness of the wood?&#xA;Q-touch sells springs made for this purpose. One end of the spring&#xA;attaches to the PCB and the other end rests just below the top&#xA;of the surface.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:18:25.093" LastActivityDate="2011-05-19T14:18:25.093" CommentCount="1" />
  <row Id="1285" PostTypeId="2" ParentId="1117" CreationDate="2009-12-26T01:33:45.443" Score="1" ViewCount="" Body="&lt;p&gt;an almost fully functional arduino clone (eg; a &lt;a href=&quot;http://store.fundamentallogic.com/ecom/index.php?main%5Fpage=product%5Finfo&amp;amp;cPath=15&amp;amp;products%5Fid=29&quot; rel=&quot;nofollow&quot;&gt;duinostamp by Fundamentalogic&lt;/a&gt;) can be had for as little as $10-12 ... and once you are done prototyping, it is easy enough to embed it in your project and release it in the wild. Embedding a full Arduino(TM) would be overkill imo. I'd say get the cheapest ones and get an FTDI cable for uploading 'sketches' (via the arduino IDE) etc. You may also want to get an ISP programmer if you plan to put custom bootloaders etc (or just save a buck a chip by burning the bootloader yourself)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am a beginner and I got the Duemilanove board at first, but ended up getting a boarduino also after playing with the original, as it is much easier to prototype with it right on the breadboard. In the future, I intend to build just the barebones &quot;duino&quot; stamp or equivalent for embedding in any projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Arduino(tm) is great to start out with, but I found very quickly that for actual projects that I intend to release into the wild I'd need something more flexible ... and cheaper (plus the female headers can get a bit unweildy, though they're great for beginners)&lt;/p&gt;&#xA;" LastActivityDate="2009-12-26T01:33:45.443" />
  <row Id="1287" PostTypeId="1" AcceptedAnswerId="1289" CreationDate="2009-12-26T19:40:52.050" Score="3" ViewCount="136" Body="&lt;p&gt;I have a project where I want to be able to cook food (very similar to a crock pot).  What would anybody here recommend to use to convert AC to useable DC and what should I use to heat the food?  Should I use cartridge heaters?  How many watts would be OK?  Also, I would need to turn on/off the heating element so what should I watch out for?&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2009-12-27T09:21:55.437" Title="Electronics used for cooking" Tags="&lt;microcontroller&gt;&lt;heating&gt;" AnswerCount="3" />
  <row Id="1288" PostTypeId="1" CreationDate="2009-12-26T20:31:30.807" Score="4" ViewCount="186" Body="&lt;p&gt;I&quot;m working on an app that uses text messaging (SMS) in an embedded application and I'd like to source a SIM card where I just pay per text (dont really care about the rates) but I refuse to pay a monthly fee for it.  Does anyone know of any SIM card suppliers where I only need text messaging and am willing to pay a lot for it ($1 per text) but no monthly fee.&lt;/p&gt;&#xA;" OwnerUserId="107" LastEditorUserId="81" LastEditorDisplayName="" LastEditDate="2009-12-26T21:41:12.850" LastActivityDate="2010-01-02T00:59:29.313" Title="SIM card for SMS messaging application. Just pay per text (SMS) rather than monthly fee?" Tags="&lt;wireless&gt;&lt;microcontroller&gt;&lt;phone&gt;" AnswerCount="3" />
  <row Id="1289" PostTypeId="2" ParentId="1287" CreationDate="2009-12-26T21:38:25.477" Score="5" ViewCount="" Body="&lt;p&gt;nearly all simple cookers use AC power to directly run a heating element. The elements are usually just wire coils, or sometimes flat resistance wire types. since the quantity of food being heated varies it is nearly always necessary to incorporate a thermostatic controller in order to vary the power.  On toasters this is accomplished with a simple variable timer to allow you to adjust how long the bread is exposed to the heat.  On crock pots and the like there is a variable thermostat which keeps the contents being cooked at a steady temperature. If you do use a heating element with exposed wire remember to keep it well insulated.  The coils are live power and can be lethal if you come in contact with them.  Also remember to use a thermostat which can handle the load presented to it by the heating element. If you can't easily find a thermostat for the current needed, then use a relay to handle the power.  The amount of power needed will be influenced by several factors. The quantity of food to be cooked, the size of the oven, the final desired temperature, how fast it needs to cook, and other factors.  If you look at similar sized units you can find out a good approximation of what you need by taking notes of their power needs.&lt;/p&gt;&#xA;" OwnerUserId="445" LastActivityDate="2009-12-26T21:38:25.477" CommentCount="1" />
  <row Id="1290" PostTypeId="2" ParentId="1288" CreationDate="2009-12-26T22:28:35.077" Score="3" ViewCount="" Body="&lt;p&gt;This is prepaid plan. However you must bay some credits (even if you have a few left) every month (that maybe different period in various carriers) to keep Your account active. But You can spend all credits for sms so technicality there isn't any &quot;monthly fee&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I think much cheaper and reliable solution would be using some Internet sms gateway for example &lt;a href=&quot;http://www.clickatell.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.clickatell.com/&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="422" LastActivityDate="2009-12-26T22:28:35.077" CommentCount="1" />
  <row Id="1291" PostTypeId="1" AcceptedAnswerId="1293" CreationDate="2009-12-26T23:05:29.577" Score="5" ViewCount="969" Body="&lt;p&gt;I am looking for some input into getting a good integrated development environment set up for AVR programming under Linux (Assembly and C).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My studies gave me some limited practical experience with AVRs but I fear I am getting a bit rusty so want to get busy with some projects but also want to persist in performing all development under Linux.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use Ladyada's USBtinyISP and have been programming my chips using AVRdude but have yet to find an IDE that works as I like under Linux so have been compiling and building via my Windows lappie and AVRstudio. (This is why I love Arduino, good IDE &amp;amp; works straight away!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, does anyone have any first hand experience using an IDE with Linux that they have successfully developed their AVR projects with start to finish?&lt;/p&gt;&#xA;" OwnerUserId="443" LastActivityDate="2010-08-31T21:30:56.210" Title="Firsthand experience with Linux AVR IDE" Tags="&lt;avr&gt;&lt;avrdude&gt;&lt;linux&gt;&lt;projects&gt;&lt;development&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="1292" PostTypeId="2" ParentId="1287" CreationDate="2009-12-27T02:02:34.760" Score="3" ViewCount="" Body="&lt;p&gt;Consider buying a crock pot of suitable size (should only be US$15-$30, less than if you try to construct one from your own parts) and modify it as necessary to automatically turn on/off the AC power to meet your cooking needs.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-27T02:02:34.760" />
  <row Id="1293" PostTypeId="2" ParentId="1291" CreationDate="2009-12-27T02:49:33.487" Score="6" ViewCount="" Body="&lt;p&gt;The thing about linux based developers is that they usually have their own unique workflow (vim vs emacs, etc). In my opinion, linux is one big IDE that you add your own parts to. With that in mind:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using a debian-based distro, run this in your command line: sudo apt-get install build-essential avr-gcc avrdude&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then find a text editor you like (google is your friend but here are a few: vim/gvim, emacs, geany, kate, jedit) and write some C. When you are ready to compile, jump onto &lt;a href=&quot;http://www.avrfreaks.net/&quot; rel=&quot;nofollow&quot;&gt;avrfreaks&lt;/a&gt; and have a look at other peoples &lt;a href=&quot;http://en.wikipedia.org/wiki/Makefile&quot; rel=&quot;nofollow&quot;&gt;makefiles&lt;/a&gt;. You can probably just steal a makefile from someone else's project and modify the target device, XTAL frequency and source filenames. After you run make and have a .hex file, use avrdude to program your chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To go into detail would take much more space than I have, but that is the basic process. When you are comfortable with the process you can do extra cool stuff in the makefile like having a single command that compiles and downloads your code. Some text editors (like geany) let you set custom make commands to GUI menu options so you could have a compile+download button like I do. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the fantastic thing about this process is that it is pretty much the same whether you are building for ARM, AVR, x86, SPARC, whatever. Once you have makefiles and gcc down, the rest of linux development is a piece of cake!&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2009-12-27T02:49:33.487" CommentCount="3" />
  <row Id="1294" PostTypeId="2" ParentId="1251" CreationDate="2009-12-27T05:49:57.947" Score="3" ViewCount="" Body="&lt;p&gt;LittleBirdElectronics in australia sells a &lt;a href=&quot;http://www.littlebirdelectronics.com/products/breadboard-power-supply-5v-3-3v&quot; rel=&quot;nofollow&quot;&gt;simple, build it yourself kit&lt;/a&gt; capable of taking in DC from a standard 2.1mm center pin positive barrel and outputting selectable 5v or 3.3v. I myself have one and find it extremely reliable.&lt;/p&gt;&#xA;" OwnerUserId="446" LastActivityDate="2009-12-27T05:49:57.947" />
  <row Id="1295" PostTypeId="2" ParentId="1151" CreationDate="2009-12-27T08:15:08.980" Score="4" ViewCount="" Body="&lt;p&gt;While many of these have already been addressed I'll put my 2 cents worth in as I have had some good and bad experiences with this problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of the basic options like Hacksaw, coping saw, tinsnips and scoring with a knife work for small jobs they are not my favourite for larger scale runs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are just blanking out a large sheet for etching/developing etc. then a PCB guillotine, as you stated, is good for quick, straight and accurate cuts. See &lt;a href=&quot;http://www.getlofi.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.getlofi.com/&lt;/a&gt; &lt;strong&gt;How We Make Circuit Boards – Video November 5th, 2009&lt;/strong&gt; entry for good vids on DIY PCB manufacturing including how they cut boards down. &lt;a href=&quot;http://www.farnell.com&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;Farnell&lt;/strong&gt;&lt;/a&gt; carry PCB specific guillotines but they are frighteningly priced, further googlage to the effect of &quot;PCB guillotine&quot; might elicit cheaper results. If you want to try paper guillotines Officeworks or other stationary suppliers will carry them for ~$60AU but I cannot vouch for this method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I was working at a signshop and had small circuits to produce I would use a bandsaw for all my cuts (including straight cuts, takes practice or a jig or both). As stated by &lt;strong&gt;&lt;em&gt;jluciani&lt;/em&gt;&lt;/strong&gt; safety should always be considered first! Wear a good breathing mask and not just a cheap one, just don't bother if your not going to spend the money and get a proper mask! I say this from experience because I developed breathing problems when I worked in this environment and the company didn't look after my health, lesson: look after yourself. If you can smell the fibre glass then you are breathing it in!!! Use an extractor too, even if you can't get a fancy industrial one Gaffer tape the hose of a normal vacuum to the table and you will eliminate most dust. Small bandsaws are available from Bunnings warehouse and Total Tools Industrial in Australia and should be available worldwide from any good industrial tool suppliers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this helps :)&lt;/p&gt;&#xA;" OwnerUserId="443" LastActivityDate="2009-12-27T08:15:08.980" />
  <row Id="1296" PostTypeId="2" ParentId="1287" CreationDate="2009-12-27T09:21:55.437" Score="2" ViewCount="" Body="&lt;p&gt;Another good choice is an old 2 gallon type coffee pot.  it's temperature setting works off of a thermo-switch at about 180 degrees F.  They can be had for pennies at your local thrift store.  I have used them from such sources my entire life and they seem to last decades in hard use. If you do build your own, consider using a solid-state type relay from your local electronics supplier.  if you get one which is slightly overkill it should last forever and it can be switched on and off using low voltage sources.&lt;/p&gt;&#xA;" OwnerUserId="447" LastActivityDate="2009-12-27T09:21:55.437" />
  <row Id="1297" PostTypeId="2" ParentId="1291" CreationDate="2009-12-27T15:48:25.907" Score="2" ViewCount="" Body="&lt;p&gt;I haven't got any first-hand experience with it, but &lt;a href=&quot;http://www.cadmaniac.org/projectMain.php?projectName=kontrollerlab&amp;amp;section=main&quot; rel=&quot;nofollow&quot;&gt;KontrollerLab&lt;/a&gt; sounds interesting.&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-12-27T15:48:25.907" CommentCount="1" />
  <row Id="1298" PostTypeId="2" ParentId="1270" CreationDate="2009-12-27T16:13:04.173" Score="4" ViewCount="" Body="&lt;p&gt;I'd like a kit where:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;the input is an audio source (such as a simple microphone)&lt;/li&gt;&#xA;&lt;li&gt;the output is several LEDs (say, 8), each of which light up when a different frequency range is present in the input signal&#xA;&lt;ul&gt;&#xA;&lt;li&gt;for example, LED 1 might light up when a frequency in the 40-80 Hz range is present&lt;/li&gt;&#xA;&lt;li&gt;LED 2 might light up when a frequency in the 80-160 Hz range is present&lt;/li&gt;&#xA;&lt;li&gt;LED 8 might light up when a frequency ending at 16 kHZ is present&lt;/li&gt;&#xA;&lt;li&gt;I really don't have a good feel for what ranges would be suitable, and it likely depends upon how the kit takes a time-domain signal and gives several frequency domain signals&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;the 'brains' of the kit could, I believe, be implemented using LC circuits or a DSP running a Fast-Fourier Transform.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The device should certainly have a threshold mode -- lights turn on when the threshold is exceeded.  (Or, the output could be read [in parallel] by a microcontroller!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would also be neat if it had an intensity mode, where the LEDs grow brighter or dimmer depending on how much of the corresponding frequency range is in present.&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2009-12-27T16:13:04.173" CommunityOwnedDate="2009-12-27T16:13:04.173" CommentCount="1" />
  <row Id="1299" PostTypeId="1" AcceptedAnswerId="1318" CreationDate="2009-12-27T16:46:46.567" Score="16" ViewCount="1196" Body="&lt;p&gt;I'm contemplating a project that would require several AVRs talking to each other over a bus.  They'd be separated by as much as 6 feet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems like both I2C and SPI can let a series of micros communicate over a bus, but I haven't seen anything talking about how long that will be.  Has anyone tried connecting these protocols over distances of several feet?&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2011-02-25T17:15:41.740" Title="SPI or I2C... which to use for a longish bus" Tags="&lt;avr&gt;&lt;spi&gt;&lt;i2c&gt;" AnswerCount="10" FavoriteCount="4" />
  <row Id="1300" PostTypeId="2" ParentId="1299" CreationDate="2009-12-27T17:26:02.990" Score="6" ViewCount="" Body="&lt;p&gt;Several feet shouldn't be problematic, just use twisted wires if you can. SPI is much easier to buffer (if you need to) than I2C since SPI signals are all unidirectional, whereas I2C's signals are on shared lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;can the AVR microcontrollers handle I2C and SPI slave modes as well as master modes? (you'd need both)&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-27T17:26:02.990" />
  <row Id="1301" PostTypeId="2" ParentId="1291" CreationDate="2009-12-27T17:31:55.543" Score="2" ViewCount="" Body="&lt;p&gt;There is an Eclipse module for the AVR, but I used it and it seemed to be much more trouble than it was worth. (Like the majority of other Eclipse modules I've used)&lt;/p&gt;&#xA;" OwnerUserId="449" LastActivityDate="2009-12-27T17:31:55.543" CommentCount="2" />
  <row Id="1302" PostTypeId="2" ParentId="864" CreationDate="2009-12-27T20:55:39.530" Score="3" ViewCount="" Body="&lt;p&gt;While using 10 of the Decimalia units in a large sensor array, I had 2 of them from different manufacturing runs die in the course of development.  The inputs and outputs were externally opto-isolated, so it wasn't because of current or stray voltage.  I put the failures down to two possible sources.  One is that they bricked because of manufacturing failures, probably internally in the I.C.'s. The second was because it might have been possible to brick the unit by damaging the boot loader.  After the failures the units failed to be recognized as a legitimate device by the programming computer.  I still use them for sensor and data logging. I haven't had any further troubles on any other project.&lt;/p&gt;&#xA;" OwnerUserId="447" LastActivityDate="2009-12-27T20:55:39.530" />
  <row Id="1303" PostTypeId="2" ParentId="1299" CreationDate="2009-12-27T21:06:53.487" Score="3" ViewCount="" Body="&lt;p&gt;While both I2C and SPI are designed for short-distance hauls (a few inches), both can be utilized on longer hauls with proper cable and attention to overall bus capacitance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While I have little experience with SPI, I2C isn't terribly difficult given that you always need to calculate the proper size for your pull-up resistor.  Additionally, there are dedicated, and inexpensive I2C buffers that are quite easy to use.  However, you will still have to use a properly-sized pull-up resistor for your network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used I2C to network between two AVRs at a distance of 8 feet, using only pull-up resistors and high-quality, well-shielded, twisted cable.&lt;/p&gt;&#xA;" OwnerUserId="36" LastActivityDate="2009-12-27T21:06:53.487" CommentCount="1" />
  <row Id="1304" PostTypeId="2" ParentId="1288" CreationDate="2009-12-27T22:58:57.710" Score="3" ViewCount="" Body="&lt;p&gt;Can you not just get a pay-as-you go SIM card (which is possibly what msawicki is suggesting)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or in the UK I'm fairly sure that you could also get a SIM card from one of the networks on a pay monthly tariff (not expensive if you only go for the SIM) and pay about £5 a month for unlimited (sort of) text messages.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-27T22:58:57.710" />
  <row Id="1305" PostTypeId="2" ParentId="460" CreationDate="2009-12-27T23:33:14.343" Score="1" ViewCount="" Body="&lt;p&gt;I just spotted this &lt;a href=&quot;http://home.comcast.net/~hourglass/index.html&quot; rel=&quot;nofollow&quot;&gt;Random Number Generator&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://home.comcast.net/~hourglass/IMG%5F0718s.JPG&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;over on &lt;a href=&quot;http://blog.makezine.com/&quot; rel=&quot;nofollow&quot;&gt;Make:Blog&lt;/a&gt; and thought you might be interested.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-27T23:33:14.343" />
  <row Id="1306" PostTypeId="2" ParentId="1299" CreationDate="2009-12-27T23:47:20.590" Score="7" ViewCount="" Body="&lt;p&gt;For I2C over long distances you might want to seek out some &quot;I2C bus repeater&quot; solutions. Keep in mind that any maximum distance you might find for I2C or SPI communication is mostly referring to the total bus distance and not the to distance between two nodes in a bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might want to look into RS485 for these kinds of problems. It's a serial bus protocol which communicates over differential lines, so when using twisted wires, the chances of noise are minimized. Very long distances can be reached this way. The downside would be that you would need an extra RS485 encoder IC (like a MAX485 ,not very expensive) in your circuit. &lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2009-12-27T23:47:20.590" CommentCount="3" />
  <row Id="1307" PostTypeId="2" ParentId="1291" CreationDate="2009-12-28T00:15:56.083" Score="2" ViewCount="" Body="&lt;p&gt;As the makefile approach seems to deal with the C side of my question I did a little more experimenting here (such as it was) and found that I had the resources to build assembly code also.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using &lt;a href=&quot;http://sourceforge.net/projects/avra/&quot; rel=&quot;nofollow&quot;&gt;AVRA&lt;/a&gt;, a command line assembler, I have tested the building of an old school project of mine and output an identical *.hex file comparing it to my original AVRstudio output. While I haven't actually programmed the AVR micro, based on the output alone I am happy to say I have firsthand xp now, albeit limited :)&lt;/p&gt;&#xA;" OwnerUserId="443" LastActivityDate="2009-12-28T00:15:56.083" CommentCount="1" />
  <row Id="1308" PostTypeId="1" AcceptedAnswerId="1310" CreationDate="2009-12-28T02:04:18.800" Score="4" ViewCount="835" Body="&lt;p&gt;I am working on an Arduino project where I would like to use an output pin to control a 12v load with a mosfet.  I think it should be an n-fet, but am not sure.  I have been looking at specs, and don't know how to pic a fet that will do what I want.  Can anyone point me at a part I could use?&lt;/p&gt;&#xA;" OwnerUserId="451" LastActivityDate="2011-05-13T12:48:18.670" Title="picking a FET for 12v use with Arduino" Tags="&lt;arduino&gt;&lt;12v&gt;" AnswerCount="1" />
  <row Id="1309" PostTypeId="2" ParentId="1222" CreationDate="2009-12-28T02:19:53.273" Score="2" ViewCount="" Body="&lt;p&gt;I have now tried Eagle and Fritzing.  Fritzing does not yet have a library big enough for me, so I am sticking with Eagle.  I found an Eagle library from Sparkfun that made it a lot easier to use.  A footprint for nearly every part I use is in this library.  &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial%5Finfo.php?tutorials%5Fid=108&quot; rel=&quot;nofollow&quot;&gt;It is here.&lt;/a&gt; It has made Eagle redeemable for me.  There is also a shortcut script they make that I intend to try.&lt;/p&gt;&#xA;" OwnerUserId="451" LastActivityDate="2009-12-28T02:19:53.273" />
  <row Id="1310" PostTypeId="2" ParentId="1308" CreationDate="2009-12-28T02:20:56.650" Score="7" ViewCount="" Body="&lt;p&gt;How much current do you require? &#xA;For specs you want a FET with a breakdown voltage (BVDSS) above 12V and a current&#xA;rating that exceeds your load. A logic-level FET can sometimes be better but it&#xA;probably will not matter if your current requirement is only a few amps.&#xA;N-channel is usually what you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use the On-Semi NTP65N02 with a 3.3V gate drive level for a current-sink.&#xA;TO-220 package and a fairly low Rds(on) at that level.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:48:18.670" LastActivityDate="2011-05-13T12:48:18.670" CommentCount="4" />
  <row Id="1312" PostTypeId="2" ParentId="1251" CreationDate="2009-12-28T03:26:36.590" Score="1" ViewCount="" Body="&lt;p&gt;Electronics Express has some power supplies.  &lt;a href=&quot;http://elexp.com/tst-pwr.htm&quot; rel=&quot;nofollow&quot;&gt;http://elexp.com/tst-pwr.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also sell some kits such as this one.&#xA;&lt;a href=&quot;http://www.elexp.com/tst%5F3010.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.elexp.com/tst_3010.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="6" LastActivityDate="2009-12-28T03:26:36.590" />
  <row Id="1313" PostTypeId="1" AcceptedAnswerId="1314" CreationDate="2009-12-28T07:04:54.887" Score="4" ViewCount="194" Body="&lt;p&gt;I recently got hold of an LED matrix that I would really like to use in a project. The problem I have is that it uses a 2mm (not 2.54mm) pitch pin header connection for which I can find no standard sockets close by. Making a pcb would be the next best option but by the time it gets fabbed and shipped my holidays will be over. Are there any secret tricks around that would allow me to solder this matrix onto veroboard? &lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="81" LastEditorDisplayName="" LastEditDate="2009-12-28T08:49:02.180" LastActivityDate="2010-08-20T13:37:04.827" Title="Dealing with weird connectors" Tags="&lt;hardware&gt;&lt;connector&gt;" AnswerCount="2" />
  <row Id="1314" PostTypeId="2" ParentId="1313" CreationDate="2009-12-28T07:34:32.783" Score="10" ViewCount="" Body="&lt;p&gt;If I was in your situation I would probably solder ribbon cable or individual wires to each pin and run to the board.  Or etch my own PCB.&lt;/p&gt;&#xA;" OwnerUserId="451" LastActivityDate="2009-12-28T07:34:32.783" CommentCount="2" />
  <row Id="1315" PostTypeId="1" CreationDate="2009-12-28T11:29:51.047" Score="5" ViewCount="718" Body="&lt;p&gt;What's the proper way to solder with bus wire on perfboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used perfboard for the first time on a project recently. I designed a great layout and started soldering the components to the copper pads; the joints were perfect and beautiful. Then I realized I still needed to add the connections. So I put the bus wire down and was successful in getting the device working, but it was pretty ugly underneath.&lt;/p&gt;&#xA;" OwnerUserId="238" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-01T02:43:53.420" LastActivityDate="2011-02-01T02:53:26.540" Title="Soldering with bus wire on perfboard." Tags="&lt;soldering&gt;&lt;protoboard&gt;" AnswerCount="2" />
  <row Id="1316" PostTypeId="1" CreationDate="2009-12-28T11:41:37.333" Score="7" ViewCount="269" Body="&lt;p&gt;For a project of mine I need to use infrared LED markers to identify locations of points in space with stereovision algorithms and multiple IR cameras.  I also need each LED marker to have a unique recognizable ID, which is my current problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My thought was to have each LED flash between two states of brightness (is this possible?) in a recognizable sequence but still be bright enough to track in the lower brightness state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know how to implement this or really where to start looking.  I am a programmer but have never worked with actual circuits before.  Can you help me get started?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" LastActivityDate="2011-01-29T04:16:06.023" Title="Identifying LED markers by modulating brightness - How?" Tags="&lt;led&gt;" AnswerCount="6" />
  <row Id="1317" PostTypeId="2" ParentId="1316" CreationDate="2009-12-28T11:50:19.937" Score="3" ViewCount="" Body="&lt;p&gt;Hi Sebastien!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Everyone seems to be starting off with Arduinos these days, so something like &lt;a href=&quot;http://arduino.cc/en/Tutorial/Fading&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; is probably what you are looking for. However it seems as if you are intending to use a &lt;strong&gt;lot&lt;/strong&gt; of LEDs in this project which would be difficult with an arduino. This is all off the top of my head* here, but it may be possible to use a transistor and a large resistor in parallel so that when the transistor is off, the current flows through the large resistor and you get a dim light. When you turn it on though, current flows through the transistor due to the lower resistance and you get the brighter state. Assuming this works, you could use digital components like microcontrollers to control the transistors and achieve the flashing that you require. Attached is a schematic of what I mean (the values are arbitrary, you will probably have to change them for your circuit):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://img15.imageshack.us/img15/1224/schw.png&quot; alt=&quot;Schematic of transistor circuit&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whichever way you do it, its going to be quite hard considering you've not done much electronics. Good luck!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*it is late; this could be completely wrong and not work at all. ymmv.&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="417" LastEditorDisplayName="" LastEditDate="2009-12-28T13:04:39.670" LastActivityDate="2009-12-28T13:04:39.670" CommentCount="2" />
  <row Id="1318" PostTypeId="2" ParentId="1299" CreationDate="2009-12-28T12:23:04.807" Score="11" ViewCount="" Body="&lt;p&gt;As others have said, SPI and I2C can be used over long distances as long as the pull-up resistors, clock frequencies and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main alternatives (which will give better noise immunity) are &lt;a href=&quot;http://en.wikipedia.org/wiki/Rs485&quot; rel=&quot;nofollow&quot;&gt;RS485&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/Canbus&quot; rel=&quot;nofollow&quot;&gt;CAN&lt;/a&gt;.  Both of these use differential lines in order to minimise noise issues and are better suited to this length of data transmission than I2C or SPI.  However, I don't think many (any?) AVRs come with built-in CAN peripherals, which make CAN use much easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would say that the most important thing to consider when picking a bus is to ensure that the protocol you use for communicating between devices includes a &lt;a href=&quot;http://en.wikipedia.org/wiki/Cyclic%5Fredundancy%5Fcheck&quot; rel=&quot;nofollow&quot;&gt;CRC&lt;/a&gt; or equivalent so that you can determine whether a message has been received correctly (CAN has this as part of the packet).  Considering this, it's also useful to have an ACK/NACK type response as part of the protocol so that a corrupted message can be re-transmitted.&lt;/p&gt;&#xA;" OwnerUserId="201" LastActivityDate="2009-12-28T12:23:04.807" CommentCount="5" />
  <row Id="1319" PostTypeId="2" ParentId="1316" CreationDate="2009-12-28T12:39:58.777" Score="3" ViewCount="" Body="&lt;p&gt;If you could flash each LED on and off at a different frequency this would probably simplify things a lot as you could use 555 based circuits to flash each one at the required frequency.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-28T12:39:58.777" CommentCount="3" />
  <row Id="1320" PostTypeId="2" ParentId="1315" CreationDate="2009-12-28T13:07:09.813" Score="5" ViewCount="" Body="&lt;p&gt;I put together some &quot;Breadboard Hints&quot; at &#xA;&lt;a href=&quot;http://www.luciani.org/eng-notes/ee-notes/ee-notes-index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.luciani.org/eng-notes/ee-notes/ee-notes-index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a combination of clips (Vector T42-1) and pins (Vector K24A)&#xA;you can put together some neat perfboards. The hints at the site&#xA;list the supplies and show an example breadboard.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-01T02:53:26.540" LastActivityDate="2011-02-01T02:53:26.540" CommentCount="2" />
  <row Id="1321" PostTypeId="2" ParentId="1316" CreationDate="2009-12-28T13:33:05.830" Score="2" ViewCount="" Body="&lt;p&gt;I would do a variation of penjuin's idea. I would use an on and off state to generate&#xA;the two levels. Rather than trying to track the LED in the off state (or low state) &#xA;make the off state short and just track in the on-state. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also didn't mention how many LEDs you need to track and how fast they&#xA;are moving.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T04:16:06.023" LastActivityDate="2011-01-29T04:16:06.023" />
  <row Id="1322" PostTypeId="2" ParentId="1316" CreationDate="2009-12-28T13:40:57.860" Score="8" ViewCount="" Body="&lt;p&gt;if all your LEDs are being controlled from the same source, consider using a microcontroller + &lt;a href=&quot;http://en.wikipedia.org/wiki/Differential%5FManchester%5Fencoding&quot; rel=&quot;nofollow&quot;&gt;differential Manchester encoding&lt;/a&gt; + your high/low LED states to encode bitstrings of repeating sequences like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;id #0: 1000000000000000[10000000000000001000000000000000....]&#xA;id #1: 1000000000000001[10000000000000011000000000000001....]&#xA;id #2: 1000000000000010&#xA;id #3: 1000000000000011&#xA;id #4: 1000000000000100&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;to encode ID numbers as a 16-bit bitsequence consisting of a 1, then 7 zeros, and an 8-bit ID#. Then when decoding, look for a 1 followed by 7 zeros, then take the subsequent subsequent bits. This works for all 8-bit ID#s (even #128 = 10000000 which encodes as 1000000010000000 which can't necessarily be synced properly but for that number it doesn't matter).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(If you have fewer potential LEDs, use fewer bits; this scheme is pretty simple and generalizes to a 1 + (N-1) zeros + an N-bit number) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Manchester encoding is self-clocking so you should be able to synchronize a receiver to it (even if it's another microcontroller not sure of the frequency, sample several times per bit so you can stay locked).&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2009-12-28T13:40:57.860" />
  <row Id="1323" PostTypeId="2" ParentId="1270" CreationDate="2009-12-28T14:16:56.490" Score="4" ViewCount="" Body="&lt;p&gt;I'd like a device similar to Clinton Blackmore's except with a video output and a microcontroller. This would let the user program some interesting Winamp-style visualizations and plug it into a screen at a concert.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-12-28T14:16:56.490" CommunityOwnedDate="2009-12-28T14:16:56.490" CommentCount="2" />
  <row Id="1324" PostTypeId="1" AcceptedAnswerId="1570" CreationDate="2009-12-28T16:32:44.733" Score="6" ViewCount="496" Body="&lt;p&gt;I'm looking for a very low cost barometric pressure sensor. The SCP1000-D01 available at Sparkfun and elsewhere is around $25 but I was hoping to find something in the $5-10 range. I am only interested in rough relative pressure change, so it does not have to have high precision or be calibrated. Basically something like the thermistor equivalent for pressure...&lt;/p&gt;&#xA;" OwnerUserId="354" LastEditorUserId="354" LastEditorDisplayName="" LastEditDate="2009-12-28T17:08:32.627" LastActivityDate="2010-02-04T22:35:32.020" Title="Low cost barometric pressure sensor" Tags="&lt;sensor&gt;" AnswerCount="5" CommentCount="3" />
  <row Id="1325" PostTypeId="2" ParentId="1315" CreationDate="2009-12-28T19:06:20.447" Score="8" ViewCount="" Body="&lt;p&gt;One suggestion I can give is to use the thinnest wire possible, and to cut your wires to the exact length you need to route them around your perfboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another clever technique, which I have not personally tried, is to make a &quot;Wiring Pen&quot; as in &lt;a href=&quot;http://www.instructables.com/id/Wiring-Pen/&quot; rel=&quot;nofollow&quot;&gt;this instructables&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2009-12-28T19:06:20.447" />
  <row Id="1326" PostTypeId="2" ParentId="1324" CreationDate="2009-12-28T20:05:41.360" Score="5" ViewCount="" Body="&lt;p&gt;I would take a look at the sensors from Freescale.  I bought an &lt;a href=&quot;http://www.mouser.com/Search/ProductDetail.aspx?R=MPX4115Avirtualkey55700000virtualkey841-MPX4115A&quot; rel=&quot;nofollow&quot;&gt;MPX4115A from Mouser.com&lt;/a&gt; for about $10.  This is (supposedly) suitable for use as an altimeter; I haven't gotten to that project, yet. :-)&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2009-12-28T20:05:41.360" />
  <row Id="1327" PostTypeId="2" ParentId="1324" CreationDate="2009-12-28T21:37:56.577" Score="1" ViewCount="" Body="&lt;p&gt;Those Freescale devices are very easy to use - I'd interface it to a small MCU with an ADC. Alternatively, you could just connect it to a voltmeter.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2009-12-28T23:38:18.300" LastActivityDate="2009-12-28T23:38:18.300" />
  <row Id="1328" PostTypeId="2" ParentId="1270" CreationDate="2009-12-28T23:56:31.427" Score="1" ViewCount="" Body="&lt;p&gt;I like the look of your Posc, and as I also like the look of a lot of the kits on &lt;a href=&quot;http://www.musicfromouterspace.com/&quot; rel=&quot;nofollow&quot;&gt;Music From Outer Space&lt;/a&gt;, so if you could come up with some sort of derivative of the Weird Sound Generator maybe with some LDRs thrown in then I might go for that. Sort of a Super Weird Posc.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2009-12-28T23:56:31.427" CommunityOwnedDate="2009-12-28T23:56:31.427" CommentCount="1" />
  <row Id="1329" PostTypeId="2" ParentId="1270" CreationDate="2009-12-29T00:10:10.180" Score="8" ViewCount="" Body="&lt;p&gt;I would like to see a starter kit for a digitally controlled analog synthesizer. Essentially:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Arduino with control software (with built in sequencer, MIDI, or external computer control options)&lt;/li&gt;&#xA;&lt;li&gt;digitally controlled analog oscillator&lt;/li&gt;&#xA;&lt;li&gt;digitally controlled analog filter&lt;/li&gt;&#xA;&lt;li&gt;digitally controlled amplifier&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Ideally this would be built so that the components were modular, allowing you to easily add more oscillators, filters, and amplifiers. &lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2009-12-29T00:10:10.180" CommunityOwnedDate="2009-12-29T00:10:10.180" CommentCount="4" />
  <row Id="1330" PostTypeId="2" ParentId="1299" CreationDate="2009-12-29T00:14:29.740" Score="3" ViewCount="" Body="&lt;p&gt;I worked on a project involving about 80 AVR-based nodes in a star network communicating over I2C. It was a total mess and didn't work in the end. Getting updates to all the nodes took seconds and one faulty connection would throw off the whole network. Last I spoke to the guy who made the nodes, he said he's stopped using I2C for projects like this. Unfortunately I don't know why specifically I2C was inadequate here. &lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2009-12-29T00:14:29.740" CommentCount="1" />
  <row Id="1331" PostTypeId="2" ParentId="1192" CreationDate="2009-12-29T00:27:10.480" Score="3" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://cycling74.com/products/maxmspjitter/&quot; rel=&quot;nofollow&quot;&gt;Max&lt;/a&gt; for all my sensor processing and visualizing. Both Max and its younger open source sibling &lt;a href=&quot;http://puredata.info/&quot; rel=&quot;nofollow&quot;&gt;Pd&lt;/a&gt; have libraries for advanced graphics programming (Jitter and GEM respectively). Jitter is its own graphics system based on 'jitter matrices', but includes a suite of OpenGL based tools. GEM is based on OpenGL. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative (again OpenGL-based) dataflow language that comes with OSX is &lt;a href=&quot;http://developer.apple.com/graphicsimaging/quartz/quartzcomposer.html&quot; rel=&quot;nofollow&quot;&gt;Quartz Composer&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Along with &lt;a href=&quot;http://processing.org/&quot; rel=&quot;nofollow&quot;&gt;Processing&lt;/a&gt;, &lt;a href=&quot;http://vvvv.org/tiki-index.php&quot; rel=&quot;nofollow&quot;&gt;vvvv&lt;/a&gt;, and &lt;a href=&quot;http://en.wikipedia.org/wiki/Adobe%5FFlash&quot; rel=&quot;nofollow&quot;&gt;Flash&lt;/a&gt; these are the standard realtime video programming environments for artists. All great choices for rapidly developing sensor data visualization applications. &lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2009-12-29T00:27:10.480" />
  <row Id="1332" PostTypeId="1" AcceptedAnswerId="1334" CreationDate="2009-12-29T01:48:12.750" Score="7" ViewCount="2413" Body="&lt;p&gt;Hi,&#xA;I need to control 25 groups of 3 LEDs or 25 RGB LEDs. Each group will be dismissed from the uC by up to 20 cm (about 8 inches). 20 cm is very safe assumption but I think it will be 10 cm or less. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I think If it be even 5 cm, it will be hard to create in matrix way, so I think using MAX7219 likie IC (&lt;a href=&quot;http://www.arduino.cc/playground/Main/MAX72XXHardware&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/Main/MAX72XXHardware&lt;/a&gt;) is not best idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will probably use shift registers (&lt;a href=&quot;http://www.arduino.cc/en/Tutorial/ShiftOut&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Tutorial/ShiftOut&lt;/a&gt;). I can connect multiple 74HC595 or use something like STP16C596.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I prefer STP16C596 but they are obsolete. I found SCT2026 (&lt;a href=&quot;http://zefiryn.tme.pl/dok/a04/sct2026.pdf&quot; rel=&quot;nofollow&quot;&gt;http://zefiryn.tme.pl/dok/a04/sct2026.pdf&lt;/a&gt;) but I'm not sure is It right choice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One more note.&#xA;My current project requires only &quot;2 bit control&quot; over each group (3 LEDs off, or selected and turned on only one of them), but I don't think it make my project easier or cheaper, also controlling each LED separately will give much more flexibility in case of changes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What solution will be fit best for my requirements. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will be nice if parts will be available in this shop - &lt;a href=&quot;http://www.tme.eu/en/katalog/?&amp;amp;page=1,20#main&quot; rel=&quot;nofollow&quot;&gt;http://www.tme.eu/en/katalog/?&amp;amp;page=1,20#main&lt;/a&gt; or &lt;a href=&quot;http://eu.mouser.com/&quot; rel=&quot;nofollow&quot;&gt;http://eu.mouser.com/&lt;/a&gt; (but i prefer first one).&lt;/p&gt;&#xA;" OwnerUserId="422" LastActivityDate="2011-04-06T02:40:47.087" Title="Best way to control 75 LEDs with Arduino" Tags="&lt;arduino&gt;&lt;led&gt;&lt;driver&gt;&lt;avr&gt;" AnswerCount="4" />
  <row Id="1333" PostTypeId="2" ParentId="1332" CreationDate="2009-12-29T04:01:58.190" Score="2" ViewCount="" Body="&lt;p&gt;I don't know of any chips off the top of my head, but perhaps some of those I2C GPIO/output expander chips might be the way to go. It has been a while but I'm sure I saw 4bit ones around. Of course, going this avenue may not be as cheap as some other solutions but it would be easy to expand it in the future and use minimal arduino pins.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apologies for the lack of detail, I am posting from my phone. &lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2009-12-29T04:01:58.190" CommentCount="1" />
  <row Id="1334" PostTypeId="2" ParentId="1332" CreationDate="2009-12-29T04:39:10.080" Score="5" ViewCount="" Body="&lt;p&gt;I would suggest going the matrix route with a driver like the MAX7219 you mentioned or maybe, if you wanted a lot more control, the TLC5951DAP, a TI LED driver meant for RGB leds that will give you 24 channels with a 12 bit resolution (4096 different steps of brightness for each channel). This will allow you to turn on each of the R, G, and B LEDs to different brightnesses to mix the colors to what you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use ribbon cable for the wiring to each of the LEDs (I'm assuming wiring is why you do not like the idea of the matrix) and have all of the cables plug into a controller board. For something like this, I would definitely recommend that you make a pcb for the controller because that's a lot of connections to try to do by hand. That's just what I would do though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The STC2026 looks to be directly compatible with the STP16C596, so that's a perfectly good replacement if you want to use it. I would agree that controlling each LED individually will probably be cheaper and easier than trying to use some sort of MUX to have 2bits control which LED is on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope that helps.&lt;/p&gt;&#xA;" OwnerUserId="403" LastActivityDate="2009-12-29T04:39:10.080" CommentCount="6" />
  <row Id="1335" PostTypeId="2" ParentId="1270" CreationDate="2009-12-29T15:25:17.193" Score="4" ViewCount="" Body="&lt;p&gt;I'd love a signal generator kit.  Something that would let me do sine, saw and square waves over a range of amplitudes and frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That'd be very useful for all sorts of things.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2009-12-29T15:25:17.193" CommunityOwnedDate="2009-12-29T15:25:17.193" CommentCount="1" />
  <row Id="1336" PostTypeId="2" ParentId="1270" CreationDate="2009-12-29T16:49:49.747" Score="5" ViewCount="" Body="&lt;p&gt;Not a specific kit request, but some types of kits I like:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Breadboardable and componentized.  If you're doing an analog synth, rather than having a monolithic PCB, why not have the oscillators, LFO, amp, etc. as separate breadboardable PCBs? This makes the whole system much more prototype friendly. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Hackable PCBs. If you're not going for a breadboard friendly approach, at least allow the PCB to have holes and room for optional sub-systems and tie-in points. The Freeduino board does a good job of this (e.g. optional trimpot for AREF, programmer bit-bang posts can be soldered in, etc.).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I rarely want the kit to do exactly what the designer intended, so any ways to make it more flexible are useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also +1 to msutherl's idea. &lt;/p&gt;&#xA;" OwnerUserId="354" LastActivityDate="2009-12-29T16:49:49.747" CommunityOwnedDate="2009-12-29T16:49:49.747" CommentCount="1" />
  <row Id="1337" PostTypeId="1" CreationDate="2009-12-29T21:37:57.160" Score="5" ViewCount="699" Body="&lt;p&gt;I want to create a simple square wave oscillator similar to what one would do with a 555, but I want to use interrupt based pwm support to control pulse width and frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been studying the datasheet, avr api and whatever pwm examples I can find, but I haven't quite been able to put it all together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to create such an oscillator with the built in avr pwm functionality and if so how. I friend of mine did something similar with an 8 pin PIC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My reasoning is that I will get interesting sounds by changing the pulse-width and therefore the wave form at a given frequency. Similar to how the Atari Punk Console works but hopefully in a more stable way (i.e. changing the pulse width, but leaving the frequency constant or vise versa).&lt;/p&gt;&#xA;" OwnerUserId="290" LastEditorUserId="290" LastEditorDisplayName="" LastEditDate="2009-12-30T02:43:07.987" LastActivityDate="2011-05-19T14:11:46.237" Title="Program an ATTiny13 as an audio oscillator with variable frequency and pulse-width." Tags="&lt;avr&gt;&lt;audio&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="1" />
  <row Id="1338" PostTypeId="2" ParentId="1337" CreationDate="2009-12-29T22:47:43.930" Score="1" ViewCount="" Body="&lt;p&gt;Basicly a PWM dosn't change the frequency. PWM are mostly used to control the &quot;intensity&quot; of a signal.&#xA;To generate an interrupt for different frequencys ill sugest to use the timer in &quot;ctc&quot;-mode.&#xA;it will run to your &quot;top&quot;-mark, togle an interrupt, clear and restart itselfs. ('till run to your top mark again...)&#xA;Every interupt you can switch one or more ports and the rest of the time (the timer still runs automaticly) you may watch your input of any kind...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may still &quot;modulate&quot; your squareform with a PWM to control the &quot;gain&quot;. But one of them has to be done &quot;by hand&quot; because the ATtiby13 has only one hardwaretimer...&lt;/p&gt;&#xA;" LastActivityDate="2009-12-29T22:47:43.930" CommentCount="2" />
  <row Id="1339" PostTypeId="2" ParentId="1337" CreationDate="2009-12-29T23:55:15.527" Score="2" ViewCount="" Body="&lt;p&gt;Not a direct answer to your question but this may be apropos and provide some hints --&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just created a numerically controlled oscillator (NCO) using an ATmega uC and a DAC.&#xA;An array of integers is used to store one cycle of a waveform (wavetable). A phase&#xA;accumulator (long int) is used to determine the address of the output data in&#xA;the wavetable. Each timer interrupt increments the phase accumulator by a fixed value.&#xA;The phase increment determines the frequency. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my application I used a 64 byte wavetable that contained one cycle of a sinewave.&#xA;It is easy to extend the wavetable and to add more resolution to the samples.&#xA;My application note is at &lt;a href=&quot;http://tinyurl.com/ydmz2su&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/ydmz2su&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:11:46.237" LastActivityDate="2011-05-19T14:11:46.237" />
  <row Id="1340" PostTypeId="2" ParentId="1270" CreationDate="2009-12-30T01:08:36.253" Score="2" ViewCount="" Body="&lt;p&gt;ECG with recordable output!  I know at least a half dozen G.P.'s that would die for one.  Instead of having old junk taking up valuable office space a small unit which could produce records would be greatly appreciated.  The cost of used units is extreme and most family docs will never use one except when someone drops over in their waiting room.  I know it's somewhat suicidal for me to ask since I repair them, but I also know it would improve the state of health care to have one at every office.  If you do create something, consider the first several units pre-sold!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" LastActivityDate="2009-12-30T01:08:36.253" CommunityOwnedDate="2009-12-30T01:08:36.253" CommentCount="1" />
  <row Id="1341" PostTypeId="2" ParentId="1270" CreationDate="2009-12-30T14:50:29.357" Score="2" ViewCount="" Body="&lt;p&gt;I would love to see some processing module kits, like re-verb, delay, distortion, ring modulation, etc.&lt;/p&gt;&#xA;" OwnerUserId="290" LastActivityDate="2009-12-30T14:50:29.357" CommunityOwnedDate="2009-12-30T14:50:29.357" CommentCount="3" />
  <row Id="1342" PostTypeId="1" AcceptedAnswerId="1343" CreationDate="2009-12-30T15:33:39.847" Score="6" ViewCount="521" Body="&lt;p&gt;From the &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod%5Fdocuments/doc0838.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;, I though the AT90S1200 had current-limited pins and when running at 5V would sink the proper amount of current through a green LED attached to + (0 turns on the LED, 1 turns it off) without any external resistors. Unfortunately when I attached 8 of them the IC burned out after a few minutes. I also have a dodgy solderless breadboard and may have otherwise shorted out the part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What did I misunderstand about that &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod%5Fdocuments/doc0838.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2011-05-17T12:58:19.217" Title="Is it OK to attach an LED directly to a 5V Attiny?" Tags="&lt;atmel&gt;&lt;led&gt;&lt;current&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="1" />
  <row Id="1343" PostTypeId="2" ParentId="1342" CreationDate="2009-12-30T15:57:48.440" Score="4" ViewCount="" Body="&lt;p&gt;From the data sheet&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC Current per I/O Pin ............................................... 40.0 mA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC Current VCC and GND Pins................................ 200.0 mA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now each led will be over driven at 40mA (as there is no current limiting resistor) - enough to shorten the life of the led but otherwise not too bad. However running 8 leds will draw a total of 320mA from the microcontroller - together with any current it itself requires to run (depends on clock speed). This is enough to greatly exceed the 200mA total allowed, hence your burned out chip.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2009-12-30T15:57:48.440" CommentCount="4" />
  <row Id="1344" PostTypeId="2" ParentId="1342" CreationDate="2009-12-30T16:12:20.550" Score="4" ViewCount="" Body="&lt;p&gt;It's fine to attach LEDs to your micro without current limiting resistors as long as you don't mind spending money on replacing the micro every once in a while. You will continue to break them if you just hook up LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Chip manufacturers put current limits on their output pins so you don't burn up the part or make it drift from all the heating that will result from pulling so much (relative) power through it. Resistors are very cheap and I can't think of a situation that would make sense not to put one in line with the LEDs. &lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2009-12-30T16:12:20.550" CommentCount="1" />
  <row Id="1345" PostTypeId="2" ParentId="1192" CreationDate="2009-12-30T17:03:12.077" Score="1" ViewCount="" Body="&lt;p&gt;I would use a database (like PostgreSQL) and a web interface. Run Apache and serve&#xA;up graphs and tables. Any device with a browser could view the graphs, tables or&#xA;raw data. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also provide a query interface to the data.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:17:40.227" LastActivityDate="2011-05-19T14:17:40.227" />
  <row Id="1346" PostTypeId="2" ParentId="1342" CreationDate="2009-12-30T18:43:35.920" Score="3" ViewCount="" Body="&lt;p&gt;I have not looked in a while but you may be able to get LEDs with internal current limiting resistors.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:58:19.217" LastActivityDate="2011-05-17T12:58:19.217" />
  <row Id="1347" PostTypeId="1" AcceptedAnswerId="1348" CreationDate="2009-12-30T22:20:52.347" Score="6" ViewCount="785" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to run/control a BLDC motor from a DVD/CD-rom player and found a schematic how to do this, the so called three phase inverter (see right schematic on this page: &lt;a href=&quot;http://en.wikipedia.org/wiki/Inverter_%28electrical%29#Three_phase_inverters&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Inverter_%28electrical%29#Three_phase_inverters&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I already made it with some some different types of transistors and an ATtiny2313 for the signal/timing and opening of the transistors, but I don't get the BLDC running. I can get LED's burning correctly, but not enough power for BLDC, I think. There are no 'anti-parallel diodes' in this set-up of my.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now my question, do you think I can make the NPN's in the schematic with BC639 's? I can get 50 for 3,50 euro, so I can use them also for other stuff. What about the 'anti-parallel diodes' for back EMF, do I need those? The motor doesn't need to turn very fast, easy speed is enough. And what about timings, how long should the open/pulse take (how many ms)? Or do I need to use other stuff/different transistors/schematics?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for the help.&lt;/p&gt;&#xA;" OwnerUserId="323" LastActivityDate="2009-12-31T17:39:07.740" Title="BLDC and three phase inverter" Tags="&lt;avr&gt;&lt;motor&gt;&lt;driver&gt;" AnswerCount="2" />
  <row Id="1348" PostTypeId="2" ParentId="1347" CreationDate="2009-12-31T00:20:05.863" Score="8" ViewCount="" Body="&lt;p&gt;uh oh... I should warn you that you have stepped into the wonderful and wild world of motor control. Getting a motor with an &quot;easy&quot; load like a fan or pump to turn is not too difficult, but you need to be aware of a couple of things, and unfortunately what you find on the Internet glosses over some important subtleties.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to control a BLDC motor (which is better to call a PMSM = permanent-magnet synchronous motor), you need to manage these aspects:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;power devices (the wikipedia page shows NPN transistors but nobody really uses those anymore, instead MOSFETs get used in sub-200V applications, IGBTs at higher voltages)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;gate drives (interfacing signals from your controller to the power devices)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;commutation (cycling current through different phases of the motor as it turns)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;current control (making sure you allow safe levels of current through the motor and transistors)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;motion control (making the motor turn at a desired speed or stay at a desired position)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I would highly recommend that you buy an integrated 3-phase bridge which takes in logic signals from a microcontroller, and turns on and off MOSFETs. ST is a decent manufacturer + has several of these, often including overcurrent protection. The &lt;a href=&quot;http://www.st.com/stonline/products/literature/ds/1107/l6234.htm&quot; rel=&quot;nofollow&quot;&gt;L6234&lt;/a&gt; is one that might suit your needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you aren't going to use an integrated bridge, use MOSFETs but BE CAREFUL. The lower ones aren't too hard to control, but the upper ones can't be driven directly from a microcontroller output unless you use P-channel MOSFETs and the supply voltage is the same as the supply for the microcontroller. (In any case it's dangerous to drive directly from a micro; if you have a fault you can easily damage the microcontroller.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(NPN transistors would be a real pain to drive; the lower ones may need more current than the micro can source, and the upper ones need some kind of circuitry to drive them correctly.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The anti-parallel or &quot;free-wheeling&quot; diodes allow current to flow from the motor, which is an inductive load, to the power supply. If you don't have them and you turn off a transistor while current is flowing through the motor, you will probably damage the transistor due to the inductive voltage spike during turnoff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also you'll probably need to use PWM (pulse-width modulation) -- if you just use on/off control for each of the 6 transistor, you will probably get an overcurrent condition because you're putting the entire battery voltage across the motor, and when it's at a standstill, the back-emf is 0 so the current is only limited by the transistors and the motor's winding resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding commutation: if you don't have a position sensor on the motor, you will have to use a sensorless commutation technique, which can be interesting... the basic ones measure the motor terminal voltage and use that to measure the approximate back-emf. Nothing really works at zero speed; at low speed the algorithms are complicated, and at high speed it's not so bad. If your motor has an &quot;easy&quot; load (low load torque at low speeds, smoothly changing torque at higher speeds), then you can drive it open loop at low speeds like a stepper motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All this is just the tip of the iceberg for motor control.... fortunately you have a pretty small motor so it shouldn't be that difficult or dangerous to work with. Good luck!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit:&lt;/strong&gt; &lt;a href=&quot;http://www.allegromicro.com/en/products/Categories/ICs/motor.asp&quot; rel=&quot;nofollow&quot;&gt;Allegro&lt;/a&gt; is another company that makes motor drive ICs.&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2009-12-31T17:39:07.740" LastActivityDate="2009-12-31T17:39:07.740" />
  <row Id="1349" PostTypeId="1" CreationDate="2009-12-31T00:48:14.767" Score="3" ViewCount="337" Body="&lt;p&gt;I've been trying to learn a bit of electronics theory and have been studying a textbook (very basic level).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;could someone help me with this question please!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My Image is Here of my textbook printscreen: &lt;a href=&quot;https://www.7chan.org/sci/src/126218141429.jpg&quot; rel=&quot;nofollow&quot;&gt;https://www.7chan.org/sci/src/126218141429.jpg&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i'm not allowed to post image tags as I'm new&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the book was very brief and hardly said more than that when a diodes reversed biased current won't flow until the diode breaks and that when it is forward biased it follows a characteristic curve.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I must admit, I can do some of the sub questions, but since I have gotten others wrong for not explainable reason, I think that my errors lie far deeper...I'd appreciate a good explanation = )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have the solutions but they weren't much help and would be difficult to post&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks!&lt;/p&gt;&#xA;" LastEditorUserId="215" LastEditorDisplayName="" LastEditDate="2009-12-31T01:11:55.367" LastActivityDate="2009-12-31T01:55:34.163" Title="high school level electronics theory (diodes)" Tags="&lt;electronics&gt;&lt;homework&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="1351" PostTypeId="2" ParentId="1349" CreationDate="2009-12-31T01:40:05.187" Score="6" ViewCount="" Body="&lt;p&gt;a) Since you are told that 4mA is passing through the diode, by using the graph given, you can easily determine that the voltage drop is 0.6V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;b) Since you have a 6V battery and the diode is dropping 0.6V of that, the resistor is dropping the remaining 5.4V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;c) Since the resistor is passing the same 4mA of current that the diode is, Ohm's law tells us that the resistor is R = V/I, or 5.4V / 4mA = 1350 Ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;d &amp;amp; e) The figure for these questions is not shown, so I can only assume that it is the same, only the diode is reversed. If the diode is reversed, current will not flow unless the reverse voltage exceeds the reverse breakdown voltage, which the graph indicates is past the -6V mark. This would indicate to me that the diode is dropping the entire 6V (reverse biased), and there is no current flowing.&lt;/p&gt;&#xA;" OwnerUserId="458" LastActivityDate="2009-12-31T01:40:05.187" />
  <row Id="1352" PostTypeId="2" ParentId="1349" CreationDate="2009-12-31T01:55:34.163" Score="5" ViewCount="" Body="&lt;p&gt;The characteristic curve is the plot that is shown with the problem. It simply relates the voltage drop across the diode with the current through it. A resistor also has a characteristic curve; it just happens to be linear with a slope of 1/R. We have measured a current of 4mA through the circuit (it may be necessary to convince yourself that the current is the same through all the elements by Kirchoff's current law). If 4mA is going through the diode, we can find how much voltage must be dropped across it by looking at the characteristic curve - find 4mA on the I axis, trace it over to the curve, and find the value off the V axis. In this case, it is about 0.65V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To find the voltage drop across the resistor, think about Kirchoff's voltage law. We know the sum of the voltages must be 0. In this case, we are considering the ammeter to be ideal - it has 0 volts across it. We know the battery contributes -6V and the diode contributes 0.65V. The only element left is the resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once we know the voltage drop across the resistor, we have both I and V and can use ohm's law to find its resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the diode is reversed, no current is flowing (we are assuming it is not broken). If no current is flowing, you can figure out the voltage drop across the resistor through ohm's law. Using the known voltage drops across the battery and the resistor, you can find the drop across the diode using Kirchoff's voltage law.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2009-12-31T01:55:34.163" />
  <row Id="1353" PostTypeId="2" ParentId="1347" CreationDate="2009-12-31T16:56:53.127" Score="3" ViewCount="" Body="&lt;p&gt;Microchip makes devices specifically for that sort of application:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS%5FGET%5FPAGE&amp;amp;nodeId=2125&amp;amp;param=en542235&quot; rel=&quot;nofollow&quot;&gt;Microchip BLDC control&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2009-12-31T16:56:53.127" CommentCount="2" />
  <row Id="1354" PostTypeId="2" ParentId="1288" CreationDate="2010-01-02T00:59:29.313" Score="2" ViewCount="" Body="&lt;p&gt;I was looking for a similar type plan but could not find one in the U.S., the cheapest one that I found was by boost mobile. You still need to pay periodically but its only every 3 months.&lt;/p&gt;&#xA;" OwnerUserId="212" LastActivityDate="2010-01-02T00:59:29.313" />
  <row Id="1355" PostTypeId="2" ParentId="1270" CreationDate="2010-01-02T03:34:47.517" Score="2" ViewCount="" Body="&lt;p&gt;I would love to have a kit to play around with speech synthesis. There are people still hacking on the ancient TI Speak and Spell chip; there must be something better and network-able out there by now.&lt;/p&gt;&#xA;" LastActivityDate="2010-01-02T03:34:47.517" CommunityOwnedDate="2010-01-02T03:34:47.517" CommentCount="1" />
  <row Id="1356" PostTypeId="1" AcceptedAnswerId="1357" CreationDate="2010-01-02T19:50:46.403" Score="4" ViewCount="137" Body="&lt;p&gt;I'm using Nichrome wire for a heating application and just using some scavenged parts from a slow cooker.  What would be the easiest way to turn on/off the Nichrome?  I'm thinking of just having a microcontroller switch 120VAC via a solid state relay (SSR) which would feed the Nichrome wire directly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any inductance issues I need to worry about?  The nichrome is just one long strip and not coiled in any way.&lt;/p&gt;&#xA;" OwnerUserId="107" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-05-19T20:50:36.467" LastActivityDate="2011-05-19T20:50:36.467" Title="Interfacing with Nichrome heater" Tags="&lt;microcontroller&gt;&lt;relay&gt;&lt;solid-state-relay&gt;&lt;heating&gt;" AnswerCount="1" />
  <row Id="1357" PostTypeId="2" ParentId="1356" CreationDate="2010-01-02T21:34:15.227" Score="6" ViewCount="" Body="&lt;p&gt;I think triacs are the normal semi conductor, maybe the one in the solid state relay.  In any case inductance is not much of an issue.  If the current rating of the ssr is ok and so is the isolation voltage ( 200 volts would be good ) I think you can go ahead.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-01-02T21:34:15.227" />
  <row Id="1358" PostTypeId="1" AcceptedAnswerId="1359" CreationDate="2010-01-02T22:57:49.723" Score="3" ViewCount="569" Body="&lt;p&gt;The answer to this question is probably staring me in the face, but I just can't see it.  I'm attempting to interface with an LM335AZ temperature sensor (&lt;a href=&quot;http://www.st.com/stonline/books/pdf/docs/2158.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;) at 3.3V.  The datasheet clearly states that the output voltage is 10mV/1°C, and that at 25°C and 1mV it should output between 2.92V and 3.04V.  What I do &lt;b&gt;not&lt;/b&gt; see specified is the minimum voltage it will operate at, and the sensor I have in hand doesn't appear to work correctly at 3.3V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a 3.3KΩ resistor the current to the LM335 should be 1mA at 3.3V. If I directly measure the output voltage when supplying 3.3V, I get 2.46V, which correlates to −27°C; if I supply 5V I get 2.93V, or about 20°C.  Suffice it to say that I'm not performing these tests outside at the North Pole. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does the LM335AZ only work on 5V, or 5V and up?&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-05-16T10:39:38.510" Title="What is the minimum supply voltage for an LM335?" Tags="&lt;temperature&gt;&lt;analog&gt;&lt;sensor&gt;&lt;lm335&gt;" AnswerCount="1" />
  <row Id="1359" PostTypeId="2" ParentId="1358" CreationDate="2010-01-03T00:16:53.150" Score="5" ViewCount="" Body="&lt;p&gt;With 3.3K you are not getting 1mA. You are getting around 100uA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At 25DegC the LM335 is at 3V. With a Vin of 3.3V you getting 0.3V across the resistor.&#xA;0.3V / 3.3K is apx 100uA. If you use a 300Ohm resistor you should be at about 1mA.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:39:38.510" LastActivityDate="2011-05-16T10:39:38.510" CommentCount="1" />
  <row Id="1360" PostTypeId="1" CreationDate="2010-01-03T08:47:08.963" Score="3" ViewCount="159" Body="&lt;p&gt;For a project we want to create a group of 'flocking' robots.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Between 5 - 10 robots to be interacting with each other -&gt; what is the best value robot for this kind of project.&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2010-01-03T08:55:52.763" LastActivityDate="2010-01-03T11:46:35.923" Title="Flocking Robots" Tags="&lt;robotics&gt;&lt;projects&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="1361" PostTypeId="2" ParentId="1360" CreationDate="2010-01-03T11:46:35.923" Score="4" ViewCount="" Body="&lt;p&gt;Take a look at &lt;a href=&quot;http://warrantyvoidifremoved.com/formica&quot; rel=&quot;nofollow&quot;&gt;Formica&lt;/a&gt;, they have tiny relatively cheap robots.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-01-03T11:46:35.923" CommentCount="3" />
  <row Id="1362" PostTypeId="2" ParentId="1270" CreationDate="2010-01-03T21:24:11.993" Score="1" ViewCount="" Body="&lt;p&gt;A Decent LED Matrix kit, including or excluding LED's...&#xA;(something a lil cooler than 8x8 please, lol)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ive been looking to build an LED message board for so long, its almost rocket science this business of multiplexing w/ shift registers etc, etc.. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;ive never seen a well written guide or comprehensive tutorial on the subject.&lt;/p&gt;&#xA;" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-01-04T13:44:24.720" LastActivityDate="2010-01-04T13:44:24.720" CommunityOwnedDate="2010-01-03T21:24:11.993" CommentCount="2" />
  <row Id="1363" PostTypeId="1" CreationDate="2010-01-04T10:19:58.260" Score="3" ViewCount="497" Body="&lt;p&gt;I have been looking for suppliers of STP16C596, 16 bit shift register with constant current output.  I have read that these are out of date and to get SCT2026 chips.  Can anyone recommend a supplier or any other options?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks&lt;/p&gt;&#xA;" LastActivityDate="2010-01-04T17:58:51.380" ClosedDate="2011-04-05T21:46:54.893" Title="Hard to find chips" Tags="&lt;hardware&gt;" AnswerCount="4" />
  <row Id="1364" PostTypeId="2" ParentId="1363" CreationDate="2010-01-04T11:13:09.463" Score="3" ViewCount="" Body="&lt;p&gt;Neither of those appear to be available at either DigiKey or Mouser, but I did find a category of similar LED driver chips &lt;a href=&quot;http://www.mouser.com/Optoelectronics/Drivers/LED-Drivers/_/N-6hpc2Zscv7Zlls6?FS=True&quot; rel=&quot;nofollow&quot;&gt;at Mouser&lt;/a&gt;.  You can see the specs and a link to the datasheet for the STP16C596 &lt;a href=&quot;http://www.mouser.com/ProductDetail/STMicroelectronics/STP16C596TTR/?qs=sGAEpiMZZMu8%252bGBKj8XSFGNuj%2fthX3kT70m8nQ7hi1k%3d&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  Hope that's helpful…&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-01-04T11:13:09.463" />
  <row Id="1365" PostTypeId="2" ParentId="1363" CreationDate="2010-01-04T15:01:42.060" Score="3" ViewCount="" Body="&lt;p&gt;Just use &lt;a href=&quot;http://www.findchips.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.findchips.com/&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;it will simultaneously query over 20 distributors, and return the responses (pricing and availability) to you in real time&lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2010-01-04T15:01:42.060" />
  <row Id="1366" PostTypeId="2" ParentId="1363" CreationDate="2010-01-04T17:20:57.147" Score="2" ViewCount="" Body="&lt;p&gt;Along with findchips.com, try &lt;a href=&quot;http://octopart.com/&quot; rel=&quot;nofollow&quot;&gt;Octopart&lt;/a&gt; to find your parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also check out Allegro, they have several &lt;a href=&quot;http://www.allegromicro.com/en/Products/Applications/Lighting/displays%5Fand%5Fsignage.asp&quot; rel=&quot;nofollow&quot;&gt;constant current shift registers&lt;/a&gt;. They're designed for controlling LEDs, which you didn't mention, but they should work for other things too.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-04T17:20:57.147" />
  <row Id="1367" PostTypeId="2" ParentId="1363" CreationDate="2010-01-04T17:58:51.380" Score="4" ViewCount="" Body="&lt;p&gt;Watch out for frauds too. I'm not sure how often the Chiphacker community encounters fake chips, but if there is any money in it, you can be sure there will be someone trying to sneak a fake one in with the good. They either take similar package parts and wipe the markings or give you packages with no silicon inside. It can be confusing and frustrating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not speaking for any of the sites listed. I'm just saying that as you go deeper into the markets for obsolete and/or hard to find parts, the price and the likelihood of fraud are proportional. Many times it's tempting to try and find the exact part number listed (moreso with digital than analog parts because the guts have very precise functions); however, I think taking the time to try a modern(ish) day replacement for parts makes sense for overall time spent on a problem.&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-01-04T17:58:51.380" />
  <row Id="1368" PostTypeId="2" ParentId="1342" CreationDate="2010-01-04T20:22:49.553" Score="2" ViewCount="" Body="&lt;p&gt;They did not build a current limiting function into the chip, however they are CMOS drivers, and by their nature increase their resistance the warmer they get, so they will generally safely self-limit on a per-port basis (although you could end up driving more than 20mA through a given LED, which might exceed the LED's rating) as long as you keep the voltage low (ie, each port doesn't have to drop more than a volt or two above the diode).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the supply lines internal to the chip cannot handle all 8 lines being maxed out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not ideal to do this, as you are stressing the part, but if you really want to drive an LED without the resistor, as long as you don't exceed the aggregate current, you are ok.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you can get around this by running the LEDs in a PWM manner.  Only drive one LED at a time, but sequence through them quickly enough that they appear constantly on to humans, even though you're actually blinking them at 30+ times per second individually.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Still, resistors are cheap, so unless you have a great reason to drive them directly with no current limiting, it's best to design the circuit so that both the microcontroller and the LEDs are operating within their design limits.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-01-04T20:22:49.553" />
  <row Id="1369" PostTypeId="1" CreationDate="2010-01-05T05:56:59.953" Score="4" ViewCount="686" Body="&lt;p&gt;I found a sensor recently that emits ±90V (AC) on stimulus.  How would I go about reading this from an arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I didn't think there were so many options.  :)  The kind of thing I'm looking at is a &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9196&quot; rel=&quot;nofollow&quot;&gt;piezo vibration sensor&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current is small, but 90V sounds like a lot (and I'm kind of new to electronics, so I don't really understand what high voltage/low current means in terms of damaging stuff).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it were just 90V DC then I'd get the voltage divider idea, but reversing polarity sounds like it could be a bad thing.  Perhaps voltage divider + a diode or two (or a rectifier) would work?&lt;/p&gt;&#xA;" OwnerUserId="347" LastEditorUserId="347" LastEditorDisplayName="" LastEditDate="2010-01-05T17:18:25.373" LastActivityDate="2011-05-16T10:40:20.193" Title="How do I read analog devices that produce relatively high voltage?" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;voltage&gt;" AnswerCount="5" />
  <row Id="1370" PostTypeId="2" ParentId="1369" CreationDate="2010-01-05T07:12:48.953" Score="3" ViewCount="" Body="&lt;p&gt;Is it only +90V or -90V? Or is it a range from -90V to +90V? If it's a binary +/-, you could use a voltage comparator (aka an op-amp), otherwise you could use a voltage divider (aka two resistors).&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-05T07:12:48.953" CommentCount="1" />
  <row Id="1371" PostTypeId="2" ParentId="1369" CreationDate="2010-01-05T13:02:35.357" Score="5" ViewCount="" Body="&lt;p&gt;If this sensor is connected to line voltage I would not connect it to&#xA;the Arduino with any circuit that does not provide isolation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One safe way to measure the voltage is to use a step-down&#xA;transformer. This provides isolation and lowers the voltage. You could&#xA;use a rectifier to convert the AC to DC. You would need to check&#xA;the transformer loading on the sensor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A resistor divided followed by an isolation amplifier would work&#xA;too. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There was an article in the April 2002 of Poptronics called&#xA;&quot;Build this Home Appliance Watt Meter/Watt-Hour Meter&quot;. The&#xA;article documented how to safely measure line voltage (with &#xA;a step-down transformer) and how to safely measure line&#xA;current with a current transformer.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:40:20.193" LastActivityDate="2011-05-16T10:40:20.193" CommentCount="6" />
  <row Id="1372" PostTypeId="2" ParentId="1369" CreationDate="2010-01-05T13:36:11.383" Score="2" ViewCount="" Body="&lt;p&gt;Check out the &lt;a href=&quot;http://www.fairchildsemi.com/pf/MI/MID400.html&quot; rel=&quot;nofollow&quot;&gt;MID400 8-Pin DIP AC Line Monitor Logic Output Optocoupler&lt;/a&gt;.  There's a very good &lt;a href=&quot;http://www.fairchildsemi.com/an/AN/AN-3007.pdf&quot; rel=&quot;nofollow&quot;&gt;application note&lt;/a&gt; for this device. I use it for monitoring my furnace, which operates (in part) at 24VAC.  You'd need a 22.5k 0.5W resistor in series with the input to give a high output when voltage is present.  That'll give you a binary output if you just need to sense whether there's voltage or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to actually measure the voltage, however, the MID400 won't really work (or, at least, I'm not sure if the output will be linear with the voltage; it may just pulse if the input current drops too low).  For my home power monitor, I'm planning to measure RMS values for voltage and current with an &lt;a href=&quot;http://www.analog.com/en/other-products/rms-to-dc-converters/ad737/products/product.html&quot; rel=&quot;nofollow&quot;&gt;AD737 RMS-to-DC converter&lt;/a&gt;.  You'd probably need a transformer and/or voltage divider to get the voltage down to the 200mV input required by the AD737.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or you could go the cheap way: step down the voltage and feed it through a diode into a capacitor and resistor, which will give you a half-rectified somewhat-smoothed DC output correlating to the input...&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-01-05T13:36:11.383" CommentCount="2" />
  <row Id="1373" PostTypeId="2" ParentId="1369" CreationDate="2010-01-05T19:03:32.540" Score="5" ViewCount="" Body="&lt;p&gt;Piezo vibration sensors produce a high voltage, but very low current.  Further, you are generally interested in sensing only a few things - level of vibration, frequency, amplitude, shocks, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the interface will depend greatly on what you want to sense.  Assuming you only want to know one or more of the following, then the interface suggested below will work.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A vibration event such as a shock or sudden G force&lt;/li&gt;&#xA;&lt;li&gt;The vibration level&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The general interface is to push the signal through a diode, then a resistor into a capacitor that's attached to ground.  In parallel with the capacitor is a clamping diode that limits the voltage spikes to a more reasonable voltage (5V, for instance).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now each time a spike happens, the capacitor will charge a little bit.  If you have continuous vibration it will charge more quickly.  It'll eventually reach the level of the clamping diode as long as the vibration exceeds the capacitor's self discharge rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sense the voltage on the capacitor, and you'll learn about the signal coming in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you put a resistor in parallel with the capacitor then you can define how quickly the capacitor discharges.  A small resistor will discharge quickly, and you can count how often the piezo is hit or dropped.  A large resistor will allow the charge to build up so you won't see individual events, but instead get a higher voltage with more vigorous vibration, a lower voltage with less vibration, and no voltage with no vibration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need more information than this simple technique, then you'll want to use a signal transformer to bring the signal down into the 5V range, and a precision op-amp and ADC.&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="161" LastEditorDisplayName="" LastEditDate="2010-01-05T19:10:46.253" LastActivityDate="2010-01-05T19:10:46.253" />
  <row Id="1374" PostTypeId="1" CreationDate="2010-01-06T08:42:24.083" Score="3" ViewCount="1229" Body="&lt;p&gt;Hi Guys, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the best Arduino Operating System? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastActivityDate="2010-02-25T14:23:06.103" Title="What is the best Arduino Operating System?" Tags="&lt;arduino&gt;&lt;os&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="1375" PostTypeId="2" ParentId="1251" CreationDate="2010-01-06T10:23:59.573" Score="1" ViewCount="" Body="&lt;p&gt;I recently picked up a kenwood bench psu for a very low price on ebay as new old stock, it's only 1A 60V but that's quite enough for 99% of things I will ever do and it cost about 10% of it's list price. So ebay might be worth a look.&lt;/p&gt;&#xA;" LastActivityDate="2010-01-06T10:23:59.573" />
  <row Id="1376" PostTypeId="2" ParentId="1192" CreationDate="2010-01-06T10:30:32.683" Score="2" ViewCount="" Body="&lt;p&gt;You can have a look at my Processing based sketch, I &lt;a href=&quot;http://interactive-matter.org/2009/07/arduino-ad7746/&quot; rel=&quot;nofollow&quot;&gt;used for visualizing AD7746 data&lt;/a&gt;. It is very simple - but perhaps just the thing you need.&#xA;It takes values from the serial püorts, decodes strings and generates data sets.&#xA;Just contact me if you have questions.&lt;/p&gt;&#xA;" OwnerUserId="407" LastActivityDate="2010-01-06T10:30:32.683" />
  <row Id="1377" PostTypeId="2" ParentId="1324" CreationDate="2010-01-06T10:37:49.557" Score="3" ViewCount="" Body="&lt;p&gt;You can check out the Bosch Sensortec BMP085 sensor. It is SMT, but it gave me &lt;a href=&quot;http://interactive-matter.org/2009/12/arduino-barometric-pressure-sensor-bmp085/&quot; rel=&quot;nofollow&quot;&gt;good results.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="407" LastActivityDate="2010-01-06T10:37:49.557" CommentCount="2" />
  <row Id="1378" PostTypeId="1" AcceptedAnswerId="1382" CreationDate="2010-01-06T13:44:58.180" Score="5" ViewCount="882" Body="&lt;p&gt;So I have this friend with a problem...I swear...it's not me! I like Arduino. I wasn't sold on the concept at first but I'm firmly in the &quot;it's awesome&quot; camp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, what I'm really looking for is a pitch to some (tech) friends about the benefits of Arduino over going out and rolling a different solution from scratch (or ordering a eval kit from a uC vendor). I'm also trying to convince a school that Arduino is a great way to teach kids programming over other starter kits and such. They also want to do some robotics eventually, so I figured I could sell them on that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have some ideas on what to tell them, but I really want to hear what others have to say. And before anyone says it, I understand the best way would be to show them. But some things need to be explained before that and that's what I hope to hear from everyone. Thanks!&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2011-05-17T12:57:43.807" Title="How do you convince people to use Arduino" Tags="&lt;arduino&gt;&lt;beginner&gt;" AnswerCount="6" FavoriteCount="2" />
  <row Id="1379" PostTypeId="2" ParentId="1378" CreationDate="2010-01-06T14:25:19.383" Score="4" ViewCount="" Body="&lt;p&gt;The main advantage of Arduino over other platforms is the community of&#xA;users and developers that openly share and advance the&#xA;platform. Currently no other platform has that breadth and depth of&#xA;support.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some bullets -- &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The software tools are free and run on Linux, MAC and PC. Easy programming&#xA;using a USB port.&lt;/li&gt;&#xA;&lt;li&gt;Software is open and easily modified to create custom examples. &lt;/li&gt;&#xA;&lt;li&gt;The schematics of the boards and numerous peripherals are freely available.&#xA;There are a wide variety of compatible boards available that can&#xA;be tailored to specific applications.&lt;/li&gt;&#xA;&lt;li&gt;Plenty of mentoring on arduino.cc and sites like chiphacker Lots of local&#xA;user groups.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I make some standard Arduino/Sanguino compatible boards that integrate a &#xA;variety of peripherals (Zigbee (XBee), RTC, DAC). I also do custom designs.&#xA;My application hints and documentation are at &lt;a href=&quot;http://www.wiblocks.com&quot; rel=&quot;nofollow&quot;&gt;http://www.wiblocks.com&lt;/a&gt;&#xA;If you have specific questions about my boards or want to discuss your&#xA;program further please send me an email.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:57:43.807" LastActivityDate="2011-05-17T12:57:43.807" />
  <row Id="1380" PostTypeId="2" ParentId="1378" CreationDate="2010-01-06T15:12:25.527" Score="4" ViewCount="" Body="&lt;p&gt;The Arduino platform was my first exposure to electronics of any kind.  I'm a Java developer by trade and I found the clear, self-documenting, high-level Arduino &quot;language&quot; (API, really) to be the key.  I think &lt;i&gt;anyone&lt;/i&gt;, even if they've never seen a line of code, can grok the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;void loop() {&#xA;    digitalWrite(LED_PIN, HIGH);&#xA;    delay(1000);&#xA;    digitalWrite(LED_PIN, LOW);&#xA;    delay(1000);&#xA;}&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I'm starting to understand that there are port registers behind those digitalWrite calls, but I don't need to.  You can accomplish a &lt;em&gt;lot&lt;/em&gt; with the AVR just by using this simple API.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Aside from the intrinsic value of having a development environment that runs out of the box on the vast majority of computing environments in use today (a la John's first comment; the openness is nice and key to the Arduino's success, but not a selling point for someone who just wants to dive in), you've also got hardware that communicates with a host PC as easily as writing to stdout.  Have you seen the code behind Serial.println()?  It's not intuitive or easy!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The hardware is almost couch-cushion-change cheap.  If your friends are considering an eval kit from any uC vendor, they're probably looking at spending an order of magnitude more for the initial purchase over an Arduino; if they get an Arduino and don't like it, they're out like thirty bucks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's an interesting ecosystem where you see a Lego-like set of modular building blocks (shields) that lets you build things without ever lifting a soldering iron; buy, build, visualize, play.  If you want to get your hands dirty, you can start breadboarding, and when you run out of breadboards, it's time to start protoboarding and then designing your own boards.  That's the route I've taken. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The barriers to entry are almost non-existent: just a willingness to learn.  &lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-01-06T15:12:25.527" />
  <row Id="1381" PostTypeId="2" ParentId="1378" CreationDate="2010-01-06T15:13:41.797" Score="4" ViewCount="" Body="&lt;p&gt;A great point about the Arduino platform is made by Dave Jones on his &lt;a href=&quot;http://www.eevblog.com/tag/arduino/&quot; rel=&quot;nofollow&quot;&gt;Electronics Engineering Video Blog&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;His opinion is from a professional standpoint and he even dares to mock the Arduino name to prove that he is not a fanboy. He states that the Arduino is very interesting because it doesn't make use of some sort of strange parallel development environment, like the PICAXE. Even beginners are learning to program the Arduino platform in real C, albeit somewhat simplified. If you want you can actually program AVR C directly from the Arduino IDE and the step from Arduino to AVR studio is not that big either.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2010-01-06T15:13:41.797" CommentCount="4" />
  <row Id="1382" PostTypeId="2" ParentId="1378" CreationDate="2010-01-06T15:18:13.610" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;I understand the best way would be to show them. But some things need to be explained before that.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I disagree, unless you have to pitch the Arduino over a phone.  A small kit is portable enough that it can be brought to any meeting or chat, and even set up and played with on a small table with enough room for lunch for a lunch meeting.  In fact you can bring a model than illustrates each point I'm going to make below, and it'll all still fit in a small box, lay out completely on a small table, powered by batteries, and be durable enough to be handled without breaking by the person you are pitching to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A pitch is a conversation that is largely one-way due to you anticipating and answering all their needs and issues before they voice them, and often before they even know they have that need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have two audiences, technical people, and schools.  You're going to have to understand their needs before you can develop the pitches, and while there will be some overlap, you'll find that the pitches will focus on fundamentally different needs/issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For technical friends:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Arduino is FUN&lt;/li&gt;&#xA;&lt;li&gt;Arduino is EASY&lt;/li&gt;&#xA;&lt;li&gt;Arduino is FAST&lt;/li&gt;&#xA;&lt;li&gt;Arduino is CHEAP&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Hobbyists are, above all, in it for the fun.  Show them that it's fun to build with arduino, and the reason it's fun is that it's easy and fast.  They are concerned about price, but most are willing to pay a bit more if it makes it easy to build something with complex behavior.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For schools:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Arduino is ROBUST&lt;/li&gt;&#xA;&lt;li&gt;Arduino is EASY AND FUN TO LEARN&lt;/li&gt;&#xA;&lt;li&gt;Arduino teaches important TECHNOLOGY&lt;/li&gt;&#xA;&lt;li&gt;Arduino is EASY TO TEACH&lt;/li&gt;&#xA;&lt;li&gt;Arduino is CHEAP&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Schools are not as concerned about cost as they say they are.  Check out the science catalogs to see that educational products are more expensive, partly because they are more robust (last longer in a student environment) and partly because they are built into a curriculum so the teachers can spend more time teaching and less time preparing to teach.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the school needs to know that it's hard for a student to break an arduino (intentionally or not), they need to know that it's easy for the students to learn, which is helped by the fact that it's fun.  They need to know that &lt;em&gt;important&lt;/em&gt; skills students absolutely &lt;em&gt;need&lt;/em&gt; in the future will be taught by the process of learning about the arduino.  They need to know that it's easy to teach - they don't have to send teachers to a training course, non-technical teachers will be able to solve most arduino problems (or there's a good community that will support the teacher), and that the curriculum is already in place with the suggested parts and kits.  Lastly, it still has to be cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, the arduino fails rather spectacularly at two of these tasks, and is complicated by a few others: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;It's not robust.&lt;/strong&gt;  Place a stray wire between one of the pins set to output high and ground, and you may fry a single port.  It might not be caught, but could 'spoil' the results of later student projects for months or years before it's noticed, diagnosed, and repaired.  Damage needs to be very difficult, and when it occurs it needs to be instantly noticeable, and easily and cheaply repairable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;It's not easy to teach.&lt;/strong&gt;  There's no established curriculum.  Any teacher doing this will need to make their own curriculum up as they go, which means they need to be at an advanced level of understanding with the Arduino, which requires training.  Teaching may be a labor of love, but it's also a job, and the school isn't going to pay for them to learn it on school time, and they aren't going to spend their free time to learn it.  There isn't enough support to get a new, untrained teacher going even if the curriculum was already set.  They would constantly be stymied by small problems and would lose days trying to diagnose problems and get students re-started on their projects because they can't call a mentor (or technical support) and get an instant diagnosis and fix.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Forming a curriculum is hard, but making it teach technology principles that are general and arguably useful for the average student is very difficult work to do well.  Then you have to add fun and interesting on top of it so students actually learn the principles, rather than just following instructions, getting the expected results, and moving on having gained no significant knowledge.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This doesn't even begin to touch infrastructure issues - computer lab use, safety issues, dealing with IT for the software and drivers that need to be installed, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The point should not be to train them to use arduino (ie, rote memory or mere knowledge).  The point should be to increase their ability to understand a system/principle (analysis), and then leap from there to new thoughts, ideas, and concepts (synthesis).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not trivial work.  But you have to start somewhere, and showing them a 6 month cirriculum in a 5 minute presentation on a table during lunch is going to be your best bet.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-01-06T15:18:13.610" />
  <row Id="1383" PostTypeId="1" CreationDate="2010-01-06T15:34:47.760" Score="4" ViewCount="263" Body="&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/1374/what-is-the-best-arduino-operating-system&quot; rel=&quot;nofollow&quot;&gt;This question&lt;/a&gt; seems to suggest that people are developing Operating Systems for the Arduino platform.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;What Arduino OS projects are you aware of?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&lt;em&gt;Please list only one project or OS per answer&lt;/strong&gt;, and give a short list of goals or features of that OS.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the purposes of this question software frameworks, task handling utilities, and similar projects are considered Operating Systems.  While there are many AVR frameworks and OS projects that work on Arduino hardware, please only list those that work within the Arduino software development tools and platform without modification.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-01-06T17:46:50.067" Title="What Operating Systems are available for Arduino?" Tags="&lt;arduino&gt;&lt;os&gt;&lt;avr&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="1384" PostTypeId="2" ParentId="460" CreationDate="2010-01-06T17:09:57.490" Score="1" ViewCount="" Body="&lt;p&gt;You could use the sensor input as seeds to a pseudo-random number generator.  The Linux OS uses input from the keyboard/mouse as seeds to /dev/random.  Just an idea.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-01-06T21:00:51.063" LastActivityDate="2010-01-06T21:00:51.063" />
  <row Id="1385" PostTypeId="2" ParentId="1383" CreationDate="2010-01-06T17:46:50.067" Score="6" ViewCount="" Body="&lt;p&gt;Here is a good run-down of four different OS for the Arduino&#xA;&lt;a href=&quot;http://antipastohw.blogspot.com/2009/11/4-operating-systems-for-arduino.html&quot; rel=&quot;nofollow&quot;&gt;http://antipastohw.blogspot.com/2009/11/4-operating-systems-for-arduino.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2010-01-06T17:46:50.067" />
  <row Id="1386" PostTypeId="1" CreationDate="2010-01-06T21:41:49.250" Score="2" ViewCount="669" Body="&lt;p&gt;I have an MP3 development board I picked up from sparkfun that runs off the LPC2148 ARM processor. In looking through the code, I see a function to force a watchdog reset. My question is, how do you figure out what values to feed to the watchdog register? I looked through the LPC2148 data sheet and couldn't figure it out. I don't just want to use other people's code, I want to understand why they did what they did and how they figured out what to do.&lt;/p&gt;&#xA;" LastActivityDate="2010-07-20T20:58:55.147" Title="ARM watchdog reset" Tags="&lt;arm&gt;" AnswerCount="6" />
  <row Id="1387" PostTypeId="2" ParentId="1222" CreationDate="2010-01-06T22:07:40.087" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.mentor.com/products/pcb-system-design/design-flows/pads/pads-evaluation&quot; rel=&quot;nofollow&quot;&gt;Mentor PADS&lt;/a&gt; is another one with a free eval. It has unlimited size and 8 layers. Its limitation is the number of devices: 30.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2010-01-06T22:07:40.087" />
  <row Id="1388" PostTypeId="1" AcceptedAnswerId="1390" CreationDate="2010-01-06T22:55:40.560" Score="6" ViewCount="529" Body="&lt;p&gt;Is there a tutorial that shows different techniques and the dos/don't of soldering?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was doing a kit last night that just said heat up both components for 5 seconds then put the solder close and let it oose into the join -&gt; they all worked nicely....but as instructions go they are a bit basic,  and from past experience there are certain components that you shouldn't heat up too much.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I was doing Through-hole soldering but Surface Mount would also be great to learn about.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-01T02:41:59.367" LastActivityDate="2011-02-01T02:53:37.367" Title="What are the best Electronics Soldering Techniques?" Tags="&lt;soldering&gt;" AnswerCount="8" FavoriteCount="2" />
  <row Id="1389" PostTypeId="2" ParentId="1378" CreationDate="2010-01-06T23:43:31.953" Score="2" ViewCount="" Body="&lt;p&gt;By far the best way is to get Silicon Chip magazine to support it. The PICAXE is a classic example - it's far more popular in this part of the world than anywhere else - even in the UK where it was developed - because an enthusiastic PICAXE user (Stan Swan) got Silicon Chip interested and starting writing articles about it.&#xA;So if there is a real Arduino nut out there who can write good articles he/she should write a beginner's guide to Arduino and send it to the magazine. If it is good enough/interesting enough, they will publish it (and I speak from experience!).&#xA;You might not make a fortune but you will help spread the Arduino gospel.&lt;/p&gt;&#xA;" LastActivityDate="2010-01-06T23:43:31.953" />
  <row Id="1390" PostTypeId="2" ParentId="1388" CreationDate="2010-01-07T00:01:13.610" Score="3" ViewCount="" Body="&lt;p&gt;I use a Metcal system. Provided that the correct cartridge is used, I get a perfect joint every time, with minimal risk of damaging parts. Metcal uses RF heating with very accurate temperature control built into the cartridges. They have excellent tutorials on soldering techniques, like this one:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.metcal.com/images/Tech%20Note%20-%20SMT%20Techniques%20Using%20Metcal%20MX-5000.pdf&quot; rel=&quot;nofollow&quot;&gt;Metcal tips&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-07T00:01:13.610" CommentCount="5" />
  <row Id="1391" PostTypeId="2" ParentId="1386" CreationDate="2010-01-07T00:07:04.510" Score="1" ViewCount="" Body="&lt;p&gt;This is the code I use for an LPC2148:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;WDTC = 0x00000FFF;  // very short timeout&lt;/p&gt;&#xA;&#xA;&lt;p&gt;WDMOD = 0x03;       // watchdog resets CPU&lt;/p&gt;&#xA;&#xA;&lt;p&gt;WDFEED = 0xAA;      // start watchdog&lt;/p&gt;&#xA;&#xA;&lt;p&gt;WDFEED = 0x55;&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-01-07T00:14:14.963" LastActivityDate="2010-01-07T00:14:14.963" />
  <row Id="1392" PostTypeId="2" ParentId="1388" CreationDate="2010-01-07T00:14:15.690" Score="3" ViewCount="" Body="&lt;p&gt;Are you doing SMD or TH soldering? This is an excellent SMD instructional video --- &lt;a href=&quot;http://www.youtube.com/watch?v=wQXhny3R7lk&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=wQXhny3R7lk&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-01T02:53:37.367" LastActivityDate="2011-02-01T02:53:37.367" />
  <row Id="1393" PostTypeId="1" AcceptedAnswerId="1396" CreationDate="2010-01-07T00:20:42.440" Score="12" ViewCount="945" Body="&lt;p&gt;This is a pretty open-ended question intentionally. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of the soldering I've done to this point has been with through-hole components. I hope to move up to some smaller surface-mount parts at some point in the future.  I've got a Weller WES51 soldering station that came with a &quot;screwdriver&quot; tip (ETA, I think) that's starting to feel a bit like working with a sausage as my skills (incrementally) improve.  There is a &lt;a href=&quot;http://www.cooperhandtools.com/brands/weller/index.cfm?model_list=1&amp;amp;att_id=WEL007%20%20%20%20%20%20%20%20%20%20%20%20&amp;amp;att1=Tips%20and%20Nozzles%20%20%20%20%20%20%20%20%20%20%20%20%20%20&amp;amp;att2=ET%20Series%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20&quot; rel=&quot;nofollow&quot;&gt;large number of ET series tips available&lt;/a&gt;.  How do I choose the right tip for the components I'll be working with?  &lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-11-09T22:11:31.997" Title="Which soldering iron tip should I use?" Tags="&lt;soldering&gt;&lt;tools&gt;" AnswerCount="5" FavoriteCount="6" />
  <row Id="1394" PostTypeId="2" ParentId="1393" CreationDate="2010-01-07T00:55:55.037" Score="2" ViewCount="" Body="&lt;p&gt;Get the biggest one that is comfortable to use for the parts you are soldering. Obviously for smaller SMD parts, you'll need a smaller tip, but smaller tips are also slower to transfer heat, making it harder to solder. &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-07T00:55:55.037" />
  <row Id="1395" PostTypeId="2" ParentId="1393" CreationDate="2010-01-07T01:51:50.633" Score="2" ViewCount="" Body="&lt;p&gt;I like the 20mil tip with a 30deg bend. Great for SMD. I use wider&#xA;parts of the tip for larger leads. The Metcal heats the tip mass very&#xA;quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I am soldering a lot of connector pins I keep the 20+year old&#xA;Weller on. Large chisel tip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The part numbers for the tips and my tools are at &lt;a href=&quot;http://tinyurl.com/5foeou&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/5foeou&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-09T15:10:12.067" LastActivityDate="2010-11-09T15:10:12.067" />
  <row Id="1396" PostTypeId="2" ParentId="1393" CreationDate="2010-01-07T04:54:36.463" Score="2" ViewCount="" Body="&lt;p&gt;It depends on what you're soldering, and how skilled you are at soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can, in fact, solder a 0.4mm pitch TQFP with a tip that spans several pins, such as the ETA you mention, but it takes a lot more skill (and flux!).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're doing mostly through hole components, the ETA is perfectly fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm also doing SMT and very fine SMT work, so I also purchased the 0.030&quot; and 0.015&quot; conical tips.  I use these under a microscope to do the 0.4mm (about 0.016&quot;) pitch TQFP chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is worthwhile getting the biggest chisel tip you can, as well, for the occasional need to deal with soldered heatsinks, or parts soldered to ground planes or PCB heatsinks.  These can pump all 40+ watts of your iron into the joint, allowing you to remove it without heating the component up too much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that typical wet sponge tip cleaners can lower the tip's temperature significantly, especially with the small tips.  I use a gold tip cleaner similar to &lt;a href=&quot;http://www.google.com/search?q=HAKKO%20599B&quot; rel=&quot;nofollow&quot;&gt;this Hakko product&lt;/a&gt;, which doesn't soak as much heat from the iron on each wipe.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-01-07T04:54:36.463" CommentCount="4" />
  <row Id="1397" PostTypeId="1" CreationDate="2010-01-07T08:18:23.497" Score="2" ViewCount="159" Body="&lt;p&gt;I'm trying to build something Arduino-based which can (among other things) detect when a user touches two specific fingers together.  The best idea I can come up with is to have a wire on each finger that forms a circuit when they touch each other.  I'm afraid that some kind of static discharge or other accident applied to the wires could fry the Arduino.  I read that using a Zener diode attached to ground before the input would work but that it might not catch very fast spikes (as in the case of an ESD, I would presume).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a better way to protect the chip from such circumstances?  Or better yet how can I improve my design so that this doesn't become an issue?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2010-01-07T12:49:15.640" LastActivityDate="2011-05-19T14:18:38.510" Title="Non-isolated input conditioning for a crude switch" Tags="&lt;esd&gt;&lt;zener&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="1398" PostTypeId="2" ParentId="1386" CreationDate="2010-01-07T10:05:42.413" Score="2" ViewCount="" Body="&lt;p&gt;From the LPC23XX datasheet, should be the same for LPC2148 ::&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Watchdog feed sequence register.&#xA;  Writing 0xAA  followed by 0x55 to this&#xA;  register reloads the  Watchdog timer&#xA;  with the value contained in  WDTC.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="379" LastActivityDate="2010-01-07T10:05:42.413" />
  <row Id="1399" PostTypeId="2" ParentId="1397" CreationDate="2010-01-07T12:48:36.573" Score="3" ViewCount="" Body="&lt;p&gt;standard practice is both of the following:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;zener diode connected from outer input to ground&lt;/li&gt;&#xA;&lt;li&gt;small resistor connected from outer input to CPU pin (20-100ohms?)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The zener diode clamps outer input between (ground - Vbe diode drop, where Vbe = between 0.7-1.0V) and (ground + zener clamp voltage at high current). The small resistor helps limit current from outer input into CPU pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ESD-clamping diodes (more commonly known as TVS = &lt;a href=&quot;http://en.wikipedia.org/wiki/Transient%5Fvoltage%5Fsuppressor&quot; rel=&quot;nofollow&quot;&gt;transient voltage suppressors&lt;/a&gt;; tons of companies make them, good mfrs are &lt;a href=&quot;http://www.onsemi.com/PowerSolutions/parametrics.do?id=824&quot; rel=&quot;nofollow&quot;&gt;ON Semi&lt;/a&gt; and &lt;a href=&quot;http://www.diodes.com/products/catalog/list.php?parent-id=46&quot; rel=&quot;nofollow&quot;&gt;Diodes Inc&lt;/a&gt; and &lt;a href=&quot;http://www.fairchildsemi.com/sitesearch/fsc.jsp?command=eq&amp;amp;attr1=AAAFamily&amp;amp;attr2=Transient+Voltage+Suppressor+%28TVS%29&quot; rel=&quot;nofollow&quot;&gt;Fairchild&lt;/a&gt;) are really just zener diodes optimized for this use, that can handle high surge power w/o getting damaged. If you are concerned (or if you are working on a commercial product), I'd use one of them, but a regular zener will almost certainly work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure you use minimum wire/lead length from outer input to ground: the more inductance you introduce in series with the clamping diode, the worse it will perform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(&lt;em&gt;NOTE&lt;/em&gt;: regular zeners add capacitance, maybe a few hundred pF. If you have a communication line or other circuit node which is sensitive to capacitance, you'll need a special clamping diode that is designed for low-capacitance. These usually have the following topology internal to the part:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;*-----+---&amp;gt;Z------|&amp;lt;------+------*&#xA;      |                   |&#xA;      +------&amp;gt;|-----------+&#xA;&#xA; --&amp;gt;Z--   = zener&#xA; --&amp;gt;|--   = regular diode&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The regular diode in series with the zener reduces the capacitance, and you then need another diode in parallel with those two, in order to clamp in the other direction.)&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2010-01-08T21:27:33.570" LastActivityDate="2010-01-08T21:27:33.570" CommentCount="5" />
  <row Id="1400" PostTypeId="2" ParentId="1397" CreationDate="2010-01-07T12:50:38.463" Score="1" ViewCount="" Body="&lt;p&gt;I would use a capacitive sense IC like the Atmel Q-touch devices. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general for transient suppression I would use a transient voltage suppressor (TVS) with&#xA;a series current limiting resistor. I like the Littefuse SP-7xx devices. Very fast.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:18:38.510" LastActivityDate="2011-05-19T14:18:38.510" />
  <row Id="1401" PostTypeId="2" ParentId="1388" CreationDate="2010-01-07T13:00:12.947" Score="2" ViewCount="" Body="&lt;p&gt;I learned to solder components to circuit boards by touching the iron to the component pin, and then touching the solder to the pin, until the solder flows into the pad or hole. You don't need to preheat components except in special situations where there's lots of metal. If you do it this way rather than touching the solder directly to the iron, it will make sure you don't get a cold solder joint (where the solder melts and then freezes but doesn't bond to the tinned component/board.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are soldering two components together, twist the leads together, then touch iron to the leads and touch solder to the leads until the solder flows.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-01-07T13:00:12.947" />
  <row Id="1402" PostTypeId="1" AcceptedAnswerId="1405" CreationDate="2010-01-07T14:47:19.407" Score="3" ViewCount="767" Body="&lt;p&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4066/4252490413_f480929c6e.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought about 10 ATMEGA168V's (which I thought were P's) and tried to flash with TinyISP via the Arduino IDE with the arduino mini pro board selected.  Well this fails for the obvious reason that the mini does not use the ATMEGA168V.  The lilypad actually uses the V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now when I try to:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;avrdude -c tinypisp -p m168 &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I get an error that tells me to recheck the connections.  However I know the connections are fine since I was able to get the fuses set msg with this very same command BEFORE I tried to flash it with the Arduino IDE.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I applaud you for getting this far into my rambling back story.  The question is are these chips now dead?  Is there something I can do to get these guys talking to avrdude again?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ril3y&lt;/p&gt;&#xA;" OwnerUserId="29" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-04T15:56:05.467" LastActivityDate="2011-05-19T14:18:52.177" Title="ATMEGA168 (P/V/ 10/20 AU?) + Arduino Booloader Flashing via AVRDUDE?" Tags="&lt;arduino&gt;&lt;atmega&gt;" AnswerCount="3" />
  <row Id="1403" PostTypeId="2" ParentId="1402" CreationDate="2010-01-07T15:27:09.653" Score="1" ViewCount="" Body="&lt;p&gt;I had a similar problem with the TinyISP. I am not sure whether it was the TinyISP or a Linux configuration problem. I switched to the Atmel AVRISPMKII and have not seem the problem.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:18:52.177" LastActivityDate="2011-05-19T14:18:52.177" />
  <row Id="1404" PostTypeId="1" AcceptedAnswerId="1406" CreationDate="2010-01-07T15:53:53.797" Score="8" ViewCount="909" Body="&lt;p&gt;What is the lowest cost way to add a Bluetooth integrated radio to an embedded system?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using a BlueGiga WT12 which works well. IIRC these are in the $20-$25 range. Are there comparable modules that are less expensive?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, I've also considered the Zigbee integrated radios (e.g. XBee).  However, everything seems to be in the $20-$25 range.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-06-01T19:43:35.177" LastActivityDate="2011-06-01T19:43:35.177" Title="Low Cost Bluetooth" Tags="&lt;bluetooth&gt;" AnswerCount="6" CommentCount="2" FavoriteCount="4" />
  <row Id="1405" PostTypeId="2" ParentId="1402" CreationDate="2010-01-07T17:04:20.637" Score="4" ViewCount="" Body="&lt;p&gt;It looks like the breadboard where you're burning doesn't have a crystal, although that could be hidden behind something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Burning the bootloader will also set the fuses... which will set it to require an external oscillator.  You'll have to add an oscillator to the system to get it to talk to the ISP again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could that be your problem?&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2010-01-07T17:04:20.637" />
  <row Id="1406" PostTypeId="2" ParentId="1404" CreationDate="2010-01-07T17:41:08.870" Score="6" ViewCount="" Body="&lt;p&gt;Bluetooth is somewhat complex to implement, there's a whole protocol stack etc. $20 is probably the minimum you are going to pay at this point, the only way to go much cheaper is to mass produce (and I'm talking like tens of thousands of modules).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your question is basically a duplicate of this one, see the answers for what people found as the cheapest BT modules:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/227/bluetooth-adapter-for-arduino&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/227/bluetooth-adapter-for-arduino&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you really need Bluetooth? You could try using a slower, cheaper, RF radio, depending on your application. For example, the least expensive wireless mice and keyboards generally do not use bluetooth, they use custom RF which requires a separate USB dongle on your PC, but even with the separate piece it's cheaper for them to produce than bluetooth.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-07T17:41:08.870" CommentCount="1" />
  <row Id="1407" PostTypeId="2" ParentId="1378" CreationDate="2010-01-07T23:30:54.543" Score="0" ViewCount="" Body="&lt;p&gt;As a teacher for 17 years (Maths not Technology or ICT) in the UK, if I wanted schools to focus on using Arduinos to teach basic electronics then I would need to do one of two things (or both):&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Convince the School Improvement Officer/Advisor who deals with Technology teaching for a particular Local Authority that the Arduino was the best match for his Schools' Electronics needs, in fact I would probably need to convince a number of them which means getting to them at a conference. The people who would need to be doing this convincing would themselves probably need to be experienced Technology Teachers who may or may not have used Arduinos in a classroom situation and are able to provide practical demonstrations as well as field what-if questions. Unfortunately if there weren't experienced people demonstrating to me, I would just assume that the demonstrators were salesmen and that at most 50% (and that's being generous) of what they were telling me was doable. &#xA;The Advisors/School Improvement Officers are the people who in England at least organise much of the In Service Training so getting them on board would be a first step. If you manage to sell them on the idea of Arduinos then they would need to organise more demonstrations/training at a more regional level to disseminate ideas/techniques/suggested course content to the teachers themselves. It might be worth showing people how to build there own Arduino clones too so that they can get started with little monetary cost.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Another route would be to persuade either the Government's Key Stage 3 Technology people or one or more of the Major Exam boards that Arduinos are the thing that has been missing from Electronics teaching all these years. Again this would involve demonstrations to relevant people first, which would then need to result in training for the actual teachers &quot;at the chalk face&quot; (I haven't had a blackboard in my room in 7 years but it's still know as being at the chalk face). &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In practical terms at the school where I work each Key Stage 3 pupil will get about 12-18 weeks of electronics education, which revolves around basic circuits, basic soldering, and designing an electronic game which uses a PCB designed by each pupil (a technician handles the actual etching). That's it for the first 3 years of secondary school technology, there might be some work on circuits in science too, there are no microcontrollers involved. If they want to pupils who choose to take Technology at GCSE can create a more complex version of this electronic game for their GCSE coursework, but that's it. In ICT the focus is on using various software packages to solve common problems, with a brief whistle stop tour of flow charts and simple programming. If they do anything more complicated than LOGO I'd be surprised.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other schools may do more electronics but I'm not actually sure how far they take it, much of the Technology curriculum seems to be focused on Design techniques and using skills which are taught to solve specific problems rather than saying lets equip people to use these specific tools or pieces of technology.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-01-07T23:30:54.543" />
  <row Id="1408" PostTypeId="1" AcceptedAnswerId="1415" CreationDate="2010-01-08T00:18:54.537" Score="3" ViewCount="238" Body="&lt;p&gt;I put together the a Herbie the &lt;a href=&quot;http://www.solarbotics.com/products/k%5Fhm/&quot; rel=&quot;nofollow&quot;&gt;Mousebot&lt;/a&gt; the other day and he is FAST!  Too fast to demonstrate in a small area.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have a look a this &lt;a href=&quot;http://www.youtube.com/watch?v=KVaVRlmiQUs&amp;amp;feature=player%5Fembedded&quot; rel=&quot;nofollow&quot;&gt;video&lt;/a&gt; to see just how he zips around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Documentation: &lt;a href=&quot;http://www.solarbotics.com/assets/documentation/khm%5Fherbie%5Fthe%5Fmousebot%5Fmanual.pdf&quot; rel=&quot;nofollow&quot;&gt;Mousebot&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is - how should i go about slowing him down a bit - so i can demonstrate it in a 1m x 1m area.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mad_z&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2010-01-29T15:18:10.687" Title="Slowing down a motor - Mousebot" Tags="&lt;motor&gt;&lt;speed&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="1409" PostTypeId="1" AcceptedAnswerId="1416" CreationDate="2010-01-08T02:38:44.183" Score="9" ViewCount="616" Body="&lt;p&gt;I've made a couple of PCBs which need the odd few 10 mil tracks, but are mostly 20/30 mil. Unfortunately the etching process isn't fantastic and there are numerous breaks in the traces, most of them small.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've managed to convince solder lumps to go over the top of the smaller gaps, and have used components legs to bridge some of the larger ones. The solder lumps don't feel particularly reliable though, and there are some gaps which are too small and awkward to get a piece of wire across but too big to be bridged with just the iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any standard ways to reliably fix up broken traces?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;b&gt;Update:&lt;/b&gt; Thanks for the suggestions everyone!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found and tried out a silver conductive pen. As a first time user I found it difficult to dispense, and obviously I didn't use enough of it or mix it properly because it didn't even end up being conductive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems like the main problem was that I was trying to use pieces of wire which are too short. I found some small gauge tinned wire and used longer lengths, running it over significant lengths of good track on either side of the fault. That makes it much easier to position, and you can tack them down one end at a time.&lt;/p&gt;&#xA;" OwnerUserId="470" LastEditorUserId="470" LastEditorDisplayName="" LastEditDate="2010-01-10T23:52:24.793" LastActivityDate="2010-07-15T10:38:08.303" Title="Best methods to fix broken tracks" Tags="&lt;pcb&gt;&lt;soldering&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="1410" PostTypeId="2" ParentId="1386" CreationDate="2010-01-08T02:55:10.130" Score="1" ViewCount="" Body="&lt;p&gt;Leon: that's the code I'm using. The thing is that I don't want to just use other people's code without understanding &lt;em&gt;why&lt;/em&gt; it's being used. I understand the code just fine. What I don't understand is where the numbers came from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Malkocoglu: is there a master NXP ARM datasheet I'm not seeing that tells you these things? How would I know to look in the LPC23XX datasheet, or is it just something you happen across?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I found the actual user manual. All my searches before were just giving me the data sheet, the site for the kit that I was using just had the data sheet, and I wasn't aware that there was a user manual. I didn't realize that the data sheet and user manual were separate, now I get it. Thanks for the help! &lt;/p&gt;&#xA;" LastActivityDate="2010-01-08T22:37:40.433" CommunityOwnedDate="2010-01-08T02:55:10.130" CommentCount="1" />
  <row Id="1411" PostTypeId="2" ParentId="1402" CreationDate="2010-01-08T03:14:39.743" Score="2" ViewCount="" Body="&lt;p&gt;I ran into the same issue with a regular atmega168. I was able to initially communicate with it using avrdude, then I plugged it into the arduino board and tried to flash it using the IDE. The error I got was:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;avrdude: initialization failed, rc=-1&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was using the wiring scheme from a Sparkfun tutorial which does not contain an external oscillator. I rewired everything multiple times with no luck. I finally decided to try this circuit with an external 16Mhz oscillator and it worked:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://upvector.com/atmega/&quot; rel=&quot;nofollow&quot;&gt;http://upvector.com/atmega/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="354" LastActivityDate="2010-01-08T03:14:39.743" />
  <row Id="1412" PostTypeId="1" CreationDate="2010-01-08T04:40:14.533" Score="3" ViewCount="208" Body="&lt;p&gt;Is there any way to monitor what is being sent to the WT-11 module via UART?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to implement deep sleep on the WT-11 and can run the iWRAP &quot;TEST DEEPSLEEP&quot; command successfully but the deep sleep lasts for less than a minute.  The iWRAP &lt;a href=&quot;http://www.sparkfun.com/datasheets/Wireless/Bluetooth/iWRAP%5F2.2.0%5FUser%5FGuide.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; says that this command &quot;Puts the module into deep-sleep after a delay of half a second until woken by a reset or activity on UART.&quot;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think I'm doing anything that should end deep sleep.  Is there something lower level on the ArduinoBT that may be interferring?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also can't get the &quot;SLEEP&quot; command to work, this may be related.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(The code I'm running is &lt;a href=&quot;http://chiphacker.com/questions/828/bluetooth-power-saving-mode-for-arduinobt/834#834&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="386" LastActivityDate="2010-01-08T12:29:33.610" Title="ArduinoBT UART Communications" Tags="&lt;arduino&gt;&lt;bluetooth&gt;&lt;sleep&gt;&lt;power&gt;&lt;save&gt;" AnswerCount="1" />
  <row Id="1413" PostTypeId="2" ParentId="1409" CreationDate="2010-01-08T06:46:16.093" Score="1" ViewCount="" Body="&lt;p&gt;One option is a &quot;&lt;a href=&quot;http://www.maplin.co.uk/module.aspx?moduleno=33837&quot; rel=&quot;nofollow&quot;&gt;conductive pen&lt;/a&gt;&quot; or &quot;&lt;a href=&quot;http://www.action-electronics.com/conductivepaint.htm&quot; rel=&quot;nofollow&quot;&gt;conductive paint&lt;/a&gt;&quot;...dunno how well they work though.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-08T06:46:16.093" />
  <row Id="1414" PostTypeId="2" ParentId="1409" CreationDate="2010-01-08T08:44:10.890" Score="4" ViewCount="" Body="&lt;p&gt;I've had the same problem in the past, if you really don't want to etch another one, I'd just solder a jumper wire across the gap (use single strand/bell wire, it holds it's shape better)&#xA;I've tried conductive pens in the past and they can be a bit hit and miss, not sure about the paint tho, it may work well if you build up a few layers&lt;/p&gt;&#xA;&#xA;&lt;p&gt;here's an example -&gt; &lt;a href=&quot;http://www.nexlogic.com/Portals/0/PCB-Rework2.png&quot; rel=&quot;nofollow&quot;&gt;PCBrepair&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's ugly but it works!&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-01-08T08:44:10.890" CommentCount="1" />
  <row Id="1415" PostTypeId="2" ParentId="1408" CreationDate="2010-01-08T08:50:24.847" Score="4" ViewCount="" Body="&lt;p&gt;I'd imagine a resistor on the positive connection to the motors would do the trick. You will probably need to experiment with the value to get it right.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-01-08T08:50:24.847" CommentCount="2" />
  <row Id="1416" PostTypeId="2" ParentId="1409" CreationDate="2010-01-08T11:16:54.990" Score="12" ViewCount="" Body="&lt;p&gt;I use wire-wrap wire to fix broken tracks, or to modify boards. It's very thin, and easy to solder because of the silver coating. It breaks easily so some sort of glue to hold the wires in place is advisable, I just use masking tape, sometimes.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-08T11:16:54.990" CommentCount="4" />
  <row Id="1417" PostTypeId="2" ParentId="1386" CreationDate="2010-01-08T11:23:43.993" Score="1" ViewCount="" Body="&lt;p&gt;You need the User Manual! You won't find that stuff in the data sheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What don't you understand about my code? It's commented.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-08T11:23:43.993" CommentCount="1" />
  <row Id="1418" PostTypeId="2" ParentId="1412" CreationDate="2010-01-08T12:29:33.610" Score="1" ViewCount="" Body="&lt;p&gt;In answer to your first question, looking at the schematic for the ArduinoBT (available &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardBluetooth&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;), there is a connector called J1 that has the UART connections on Pins 1 &amp;amp; 2.  You could make a connector that links these two pins up to a monitor cable (something like one of  &lt;a href=&quot;http://www.lammertbies.nl/comm/cable/RS-232-spy-monitor.html&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; with level shifting if you're using a PC to monitor and aren't using a USB TTL UART cable).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use the full duplex one, you can use &lt;a href=&quot;http://www.docklight.de&quot; rel=&quot;nofollow&quot;&gt;Docklight&lt;/a&gt; to monitor both ports at the same time*; with the half duplex one any serial terminal software will work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to monitor the reset line (pin 11 of J1), you'll have to use an correctly triggered oscilloscope probably.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;* Note that if you use USB serial leads like the ones &lt;a href=&quot;http://www.ftdichip.com/Products/EvaluationKits/USB-Serial.htm&quot; rel=&quot;nofollow&quot;&gt;FTDI&lt;/a&gt; manufacture, the UART communication is buffered, so you can't tell in what order the data arrives with a full duplex monitor cable.&lt;/p&gt;&#xA;" OwnerUserId="201" LastActivityDate="2010-01-08T12:29:33.610" />
  <row Id="1419" PostTypeId="2" ParentId="1386" CreationDate="2010-01-08T22:58:23.497" Score="1" ViewCount="" Body="&lt;p&gt;0xAA and 0x55 are often used in this sort of code which affects an application in a big way, as they are unlikely to be encountered during normal code execution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll find the LPC2000 Yahoo group very useful for this sort of question. It has over 8,000 members!&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-08T22:58:23.497" />
  <row Id="1420" PostTypeId="1" AcceptedAnswerId="1641" CreationDate="2010-01-08T23:34:19.600" Score="4" ViewCount="1228" Body="&lt;p&gt;So I just got my &lt;strong&gt;TI eZ430-Chronos&lt;/strong&gt; Dev kit (a runners watch &amp;amp; eZ430 micro dev combined), and I am chomping at the bit to start playing around with my new toy. I have just a few issues the recommended tools from TI are Windows based, and I am lacking a valid windows OS right now.  Also I brought the watch back to work, but left the programmer and AP at home.  So I am left reading articles and links to wiki's, but unable to try anything out for myself.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stuff I have read so far:&lt;br&gt;&#xA;&lt;a href=&quot;http://www.linuxjournal.com/article/8682&quot; rel=&quot;nofollow&quot;&gt;http://www.linuxjournal.com/article/8682&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://wiki.msp430.com/index.php/EZ430-Chronos&quot; rel=&quot;nofollow&quot;&gt;http://wiki.msp430.com/index.php/EZ430-Chronos&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://sourceforge.net/projects/mspgcc4&quot; rel=&quot;nofollow&quot;&gt;http://sourceforge.net/projects/mspgcc4&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://blog.makezine.com/archive/2010/01/ti_ez430_-_chronos_development_kit.html&quot; rel=&quot;nofollow&quot;&gt;http://blog.makezine.com/archive/2010/01/ti_ez430_-_chronos_development_kit.html&lt;/a&gt;&lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also searched the mspgcc sf mailing-list, it had no mention of the chronos.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone been able to get mspgcc or mspgcc4 to work with the Chronos. I have searched for &#xA;information about this on the various sites, but found no answers.  It should be very straight forward, but I will give it a shot later and report back if I don't hear back.&lt;br&gt;&lt;/p&gt;&#xA;" OwnerUserId="151" LastActivityDate="2010-08-25T22:35:06.617" Title="eZ430-Chronos Development on *nix?" Tags="&lt;linux&gt;&lt;microcontroller&gt;" AnswerCount="6" CommentCount="2" FavoriteCount="3" />
  <row Id="1421" PostTypeId="2" ParentId="1420" CreationDate="2010-01-09T00:10:23.397" Score="1" ViewCount="" Body="&lt;p&gt;I got mine yesterday. They have only just started shipping them in quantity (I know several people who have just got them), so I think it will be some time before anyone has a go at porting the software to Linux.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-09T00:10:23.397" />
  <row Id="1422" PostTypeId="2" ParentId="1404" CreationDate="2010-01-09T00:16:41.783" Score="0" ViewCount="" Body="&lt;p&gt;Microchip has a new low-cost ($10) wirelesss module:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en535967&quot; rel=&quot;nofollow&quot;&gt;MRF24J40MA&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-09T00:16:41.783" CommentCount="2" />
  <row Id="1423" PostTypeId="2" ParentId="216" CreationDate="2010-01-09T00:23:02.963" Score="1" ViewCount="" Body="&lt;p&gt;I use Multicore Tip Cleaner. It's solder powder mixed with an aggressive flux and does a very good job with my Metcal cartridges when they need tinning. I just poke the tip in the cleaner and wipe it on the sponge. My cat seems to like the taste of the stuff so I have to keep it covered when I'm not using it, otherwise he licks it, which isn't very good for him.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-09T00:23:02.963" />
  <row Id="1424" PostTypeId="2" ParentId="216" CreationDate="2010-01-09T14:57:34.183" Score="2" ViewCount="" Body="&lt;p&gt;I think it can depend on what type of iron/tip you have. I've got a ceramic tip and the manufacturers instructions say not to use an abrasive to clean it. I use a wet natural sponge to clean off dirt whilst soldering, and I tin the tip with pre fluxed solder after every use, when it gets dirty I clean it off with the natural sponge, then leave it to cool down. Once cooled I use isopropyl alcohol and a cloth to polish the tip. Normally I'd clean it in this way once a week, and I use my iron daily. Over all this method seems to preserve the tip for longer I've been using the same one for nearly three months now and it shows no signs of letting up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'd say the first port of call for finding out how to look after your tip, is to contact the manufacturer and see what they recommend. &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-01-09T14:57:34.183" CommentCount="1" />
  <row Id="1425" PostTypeId="2" ParentId="1420" CreationDate="2010-01-09T16:05:45.963" Score="0" ViewCount="" Body="&lt;p&gt;I don't know specifically what you need, WINE might help you somewhat, but if you need access to USB ports etc then you may be stuck (I had a similar problem whereMPLAB appears to function properly under WINE but can't access the USB port - but for PICs there are Linux alternatives). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully when you get home you'll be able to check if you can connect to the device from the command line etc, as mspgcc etc appear to work under Linux.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-01-09T16:27:58.573" LastActivityDate="2010-01-09T16:27:58.573" />
  <row Id="1426" PostTypeId="2" ParentId="216" CreationDate="2010-01-09T16:49:24.490" Score="2" ViewCount="" Body="&lt;p&gt;Metcal recommends de-ionised water on the sponge, but I don't bother. Most of my cartridges have lasted for a couple of years, which is a good thing as they are rather expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They supply a brass cleaner with their new MX-5000 system, so that is probably the thing to use with other systems.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-01-09T16:55:17.723" LastActivityDate="2010-01-09T16:55:17.723" />
  <row Id="1427" PostTypeId="2" ParentId="216" CreationDate="2010-01-09T19:32:02.480" Score="2" ViewCount="" Body="&lt;p&gt;You should tin the soldering iron whenever any part of the tip does not have a shiny appearance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Flux is a good tinner, so if you don't have soldering iron tinner then just keep melting solder with flux onto the tip wherever it's not shiny and let the bubbling flux do its job.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use a brass pad type tip cleaner rather than a sponge - water will corrode the tip quickly, so I've completely moved away from damp sponges.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also add a little solder to the tip every time I place it in the stand (and wipe the excess off when I pull it out) this puts a layer of solder coating the tip so it doesn't oxidize in the air while it's sitting there waiting for me to pick it up again.  When I turn it off, the solder blob stays on the tip and protects it long term when not in use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since starting this technique I haven't had to fully re-tin my tip in years, and my tips do not develop the pitting and corrosion I used to experience.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that to solder some things it'll heat up a little faster if you keep a bit of solder on the tip, and touch that to the part and PCB pad - the solder blob will transfer heat more effectively than the bare metal will.  If the tip won't hold solder, it won't heat the joint effectively.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-01-09T19:32:02.480" />
  <row Id="1428" PostTypeId="2" ParentId="1369" CreationDate="2010-01-10T19:38:37.300" Score="1" ViewCount="" Body="&lt;p&gt;Just use a voltage divider.  You can measure thousands of volts that way.  &lt;a href=&quot;http://www.rossengineeringcorp.com/hv_dividers.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.rossengineeringcorp.com/hv_dividers.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And yes, dividers work for AC, too.  :D  They just make the signal smaller.  You'll want a capacitor coupling the piezo to your input to block DC and bias it to the Arduino's reference voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I doubt it will do any damage, because the arduino input already has clamping diodes, and the current will be very low (piezos are high impedance sources, plus your divider provides a large impedance), but you can always add an extra clamping diode to protect the input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually, depending on what you're doing, you might want a high-impedance amplifier right at the piezo to prevent it from being loaded down or picking up interference.  What specifically are you trying to do?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-01-10T19:46:22.963" LastActivityDate="2010-01-10T19:46:22.963" />
  <row Id="1429" PostTypeId="2" ParentId="1270" CreationDate="2010-01-10T23:27:27.147" Score="1" ViewCount="" Body="&lt;p&gt;I'd love to buy and build a kit that converts S/PDIF to analog audio and it is small enough to mount inside an old hi-fi amplifier and can be connected directly into its pre-amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In other words, I'm thinking about kits for digitizing vintage audio devices.&lt;/p&gt;&#xA;" OwnerUserId="65" LastActivityDate="2010-01-10T23:27:27.147" CommunityOwnedDate="2010-01-10T23:27:27.147" CommentCount="1" />
  <row Id="1430" PostTypeId="2" ParentId="1409" CreationDate="2010-01-11T03:54:34.037" Score="2" ViewCount="" Body="&lt;p&gt;I use solder lumps and component legs. :)&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-01-11T03:54:34.037" />
  <row Id="1431" PostTypeId="1" CreationDate="2010-01-11T06:06:57.577" Score="4" ViewCount="1409" Body="&lt;p&gt;customer question:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have had no success with the ethernet &amp;amp; saw some fine print&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Please note that the current design of the ethernet shield is not compatible with the Arduino Mega &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoEthernetShield&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Main/ArduinoEthernetShield&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Is that correct? Is there a workaround?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-02T07:43:06.160" LastActivityDate="2011-02-02T07:43:06.160" Title="Making an Ethernet Shield work with an Arduino Mega" Tags="&lt;arduino&gt;&lt;ethernet&gt;" AnswerCount="2" />
  <row Id="1432" PostTypeId="2" ParentId="1431" CreationDate="2010-01-11T06:21:26.753" Score="5" ViewCount="" Body="&lt;p&gt;There is some discussion &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1239058804/0&quot; rel=&quot;nofollow&quot;&gt; here &lt;/a&gt; on the Arduino forum (From NKC Electronics) about a fairly simple work around.&lt;/p&gt;&#xA;" OwnerUserId="272" LastActivityDate="2010-01-11T06:21:26.753" />
  <row Id="1433" PostTypeId="2" ParentId="1324" CreationDate="2010-01-11T06:22:36.593" Score="1" ViewCount="" Body="&lt;p&gt;Another vote for the MPX4115 family - I'm using one, they're very simple to use &amp;amp; cheap.&lt;/p&gt;&#xA;" OwnerUserId="358" LastActivityDate="2010-01-11T06:22:36.593" />
  <row Id="1434" PostTypeId="2" ParentId="1431" CreationDate="2010-01-11T16:54:33.210" Score="1" ViewCount="" Body="&lt;p&gt;you can also just buy the nkc shield already hacked, i have it and it work great&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.nkcelectronics.com/nkc-ethernet-shield-for-arduino-mega--duemilanove--diecimila-diy-kit.html&quot; rel=&quot;nofollow&quot;&gt;http://www.nkcelectronics.com/nkc-ethernet-shield-for-arduino-mega--duemilanove--diecimila-diy-kit.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2010-01-11T16:54:33.210" />
  <row Id="1435" PostTypeId="1" AcceptedAnswerId="1436" CreationDate="2010-01-12T00:49:35.933" Score="2" ViewCount="208" Body="&lt;p&gt;Hi All, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I came across this post on the todbot blog about controlling BlinkMs over an I2C bus:&#xA;&lt;a href=&quot;http://todbot.com/blog/2008/06/17/get-on-the-blinkm-bus-with-a-blinkm-cylon/&quot; rel=&quot;nofollow&quot;&gt;http://todbot.com/blog/2008/06/17/get-on-the-blinkm-bus-with-a-blinkm-cylon/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I LOVE his connectors, but cannot find a good source for the ribbon cable/push through connectors...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone seen where I can get these easily? Its such an elegant solution.&lt;/p&gt;&#xA;" OwnerUserId="431" LastActivityDate="2010-01-12T10:41:08.260" Title="Source for parts to make a BlinkM I2C bus cable? (from todbot blog)" Tags="&lt;blinkm&gt;&lt;i2c&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="1436" PostTypeId="2" ParentId="1435" CreationDate="2010-01-12T00:57:46.163" Score="2" ViewCount="" Body="&lt;p&gt;Hi funk_e,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are the sources I list at the bottom of my post not working for you?  Or are you looking for something local to Australia or Europe?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ribbon cable is bog standard ribbon cable for IDC connectors.  I use a roll of 40-wire wide cable that I peel off the number of wires I need (eight in the case of the 2x4 IDC connectors I use in that post)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the 2x4 IDC connectors, they are a very standard form-factor as well, special only in that they are 2x4 instead of the more common 2x5 or 2x8 sizes.  You can use those longer sizes if you want (or even the 2x20 kind used by IDE hard drives), but then you have to be more careful about alignment. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Updated:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Jaycar link that penjuin has for a 2x5 connector will work.  &lt;a href=&quot;http://au.farnell.com&quot; rel=&quot;nofollow&quot;&gt;Au.farnell.com&lt;/a&gt; has an entry for the exact part I use: &lt;a href=&quot;http://au.farnell.com/fci/71600-308lf/pcb-connector/dp/1630555?Ntt=FCI71600-308LF&quot; rel=&quot;nofollow&quot;&gt;FCI 71600-308LF&lt;/a&gt;, but currently show none in stock local to you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus, if Little Bird Electronics wanted to get into stocking various kinda weird connectors like these, you should check out &lt;a href=&quot;http://www.4uconnector.com&quot; rel=&quot;nofollow&quot;&gt;4ucon&lt;/a&gt;. They have the &lt;a href=&quot;http://www.4uconnector.com/online/itemagrid.asp?seriesdesp=2.54++IDC+SOCKET&amp;amp;seriesno=0413&amp;amp;GroupNo=04&amp;amp;groupdesp=IDC+Plug+%2F+Socket+%2F+Latch+Header+%2F+Box+Header&amp;amp;itemnum=906&amp;amp;sample=0&amp;amp;seriesnum=46&amp;amp;&quot; rel=&quot;nofollow&quot;&gt;2x8 IDC connector&lt;/a&gt; as well as many many others.  There lead time is at least a month usually and minimum order quantity is several hundred, but their prices are very good.&lt;/p&gt;&#xA;" OwnerUserId="215" LastEditorUserId="215" LastEditorDisplayName="" LastEditDate="2010-01-12T10:41:08.260" LastActivityDate="2010-01-12T10:41:08.260" CommentCount="3" />
  <row Id="1437" PostTypeId="1" CreationDate="2010-01-12T01:28:57.977" Score="3" ViewCount="1482" Body="&lt;p&gt;I have been coding and using Arduinos for quite some time now.  However I am ready to move up to using straight AVR chips without the arduino bootloader.  My question is what are resources to do this?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to use linux / mac so winavr is out of the picture as is avrstudio.  If there is no such thing as what I am after I will settle for a windows virtual machine.  But until I know for sure.  What I want is some type of IDE that uses avr-gcc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a bonus to this question does anyone have any good resources on learning C for avr?  Specifically how to configure Makefiles etc for the various different chips?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Riley&lt;/p&gt;&#xA;" OwnerUserId="29" LastActivityDate="2011-05-17T12:55:27.687" Title="Linux / Mac AVR Programming Suite?" Tags="&lt;atmega&gt;&lt;avr&gt;&lt;linux&gt;&lt;osx&gt;" AnswerCount="8" FavoriteCount="1" />
  <row Id="1438" PostTypeId="2" ParentId="1437" CreationDate="2010-01-12T01:36:43.483" Score="3" ViewCount="" Body="&lt;p&gt;If you install &lt;a href=&quot;http://www.obdev.at/products/crosspack/index.html&quot; rel=&quot;nofollow&quot;&gt;crosspack&lt;/a&gt; you can use Apple's Xcode for mac, which is a great IDE. If you want learn c for AVR check out the &lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewforum&amp;amp;f=11&amp;amp;sid=874ba8239b6a193c5a97677ab5ab5189&quot; rel=&quot;nofollow&quot;&gt;tutorials forum at AVR Freaks&lt;/a&gt;. Also as for linux check out &lt;a href=&quot;http://chiphacker.com/questions/1291/firsthand-experience-with-linux-avr-ide&quot; rel=&quot;nofollow&quot;&gt;this question&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2010-01-12T01:36:43.483" />
  <row Id="1439" PostTypeId="2" ParentId="1437" CreationDate="2010-01-12T02:32:49.560" Score="3" ViewCount="" Body="&lt;p&gt;Since you have been using the Arduino everything you need is already installed. &#xA;I compile Arduino sketches from the command line using a Makefile. I also compile&#xA;code without the Arduino bootloader.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Makefile I use to compile the Arduino bootloader for my boards&#xA;is at &lt;a href=&quot;http://wiblocks.luciani.org/docs/app-notes/bootloader.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/docs/app-notes/bootloader.html&lt;/a&gt;&#xA;You could modify it to compile your program rather than the&#xA;ATmegaBOOT_xx8.c file. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My Makefile is modified from the file I found at this site -- &lt;a href=&quot;http://mjo.tc/atelier/2009/02/arduino-cli.html&quot; rel=&quot;nofollow&quot;&gt;http://mjo.tc/atelier/2009/02/arduino-cli.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While answering this same question (just yesterday;) on twitter I came across a makefile&#xA;at dorbotpdx. See &lt;a href=&quot;http://dorkbotpdx.org/blog/ax/arduino_0017_makefile&quot; rel=&quot;nofollow&quot;&gt;http://dorkbotpdx.org/blog/ax/arduino_0017_makefile&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also a well documented shell script at &#xA;&lt;a href=&quot;http://arkku.com/misc/arduino_make.sh&quot; rel=&quot;nofollow&quot;&gt;http://arkku.com/misc/arduino_make.sh&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would probably use a Makefile rather than a shell script.&#xA;The fellow that did this script has done an excellent&#xA;job of commenting the flow. It is work a look just to understand the&#xA;flow.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:55:27.687" LastActivityDate="2011-05-17T12:55:27.687" CommentCount="2" />
  <row Id="1440" PostTypeId="2" ParentId="1437" CreationDate="2010-01-12T03:46:36.953" Score="3" ViewCount="" Body="&lt;p&gt;I agree with zklapow but check the projects section on AVR Freaks too. That's how I learnt back in the day before arduinos. Also, you will almost certainly have to read the datasheet for your chip to get anything useful done. There are no nice functions that, for example, read an analog pin in because there are so many parameters that the arduino environment hides from you. Let me give you an example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; int ledPin =  13;    // LED connected to digital pin 13&#xA; // The setup() method runs once, when the sketch starts&#xA; void setup()   {                &#xA;   // initialize the digital pin as an output:&#xA;   pinMode(ledPin, OUTPUT);     &#xA; }&#xA; // the loop() method runs over and over again,&#xA; // as long as the Arduino has power&#xA; void loop()                     &#xA; {&#xA;   digitalWrite(ledPin, HIGH);   // set the LED on&#xA;   delay(1000);                  // wait for a second&#xA;   digitalWrite(ledPin, LOW);    // set the LED off&#xA;   delay(1000);                  // wait for a second&#xA; }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;is roughly similar to the following C (not tested):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int main(void) {&#xA;    // I just randomly picked pin 6 on PORTB, this may not be the same on an arduino&#xA;    DDRB = (1&amp;lt;&amp;lt;6); // set pin to output in data direction register&#xA;    int i; // have to do this outside the for loop because of C standard&#xA;&#xA;    while(1) {&#xA;        PORTB |= (1&amp;lt;&amp;lt;6); // send pin 6 high and leave other pins in their current state&#xA;        for (i=0; i&amp;lt;10000; i++); // delay&#xA;&#xA;        PORTB &amp;amp;= ~(1&amp;lt;&amp;lt;6); // send pin 6 low&#xA;        for (i=0; i&amp;lt;10000; i++); // delay&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Sure, there are delay functions in some libraries and there may be output functions in other ones, but get used to writing code like this. The only way you can possibly know what all this PORTB and DDRB stuff means is to read the datasheet. I'm sorry to drone on about this but not enough people realize that the datasheet is a goldmine for information.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-01-12T03:46:36.953" CommentCount="2" />
  <row Id="1441" PostTypeId="2" ParentId="1435" CreationDate="2010-01-12T03:58:21.793" Score="2" ViewCount="" Body="&lt;p&gt;You mentioned you are in Australia; try searching Jaycar for &quot;IDC Line Socket&quot; and &quot;IDC Cable&quot;. The smallest connector they sell is &lt;a href=&quot;http://jaycar.com.au/productView.asp?ID=PS0984&amp;amp;keywords=idc&amp;amp;form=KEYWORD&quot; rel=&quot;nofollow&quot;&gt;2x5&lt;/a&gt; and the smallest ribbon cable is &lt;a href=&quot;http://jaycar.com.au/productView.asp?ID=WM4502&amp;amp;keywords=IDC+ribbon&amp;amp;form=KEYWORD&quot; rel=&quot;nofollow&quot;&gt;16 wires&lt;/a&gt; but you can easily tear that cable apart. You just get some connectors, run the ribbon through and put them in a vice; simple!&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-01-12T03:58:21.793" />
  <row Id="1442" PostTypeId="2" ParentId="1420" CreationDate="2010-01-12T08:50:50.313" Score="1" ViewCount="" Body="&lt;p&gt;The Rowley crossworks toolset is a very high performance development system for the MSP430.  It is available for Linux, MAC OS-X and Solaris as well as Windows.  It is not free, prices according to license type:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$1500 — Commercial License&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$300 — Educational License&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$150 — Personal License  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This supports both the 430 and 430X (larger memory) architectures.  IIRC the GCC port only supports the 430.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-01-12T08:50:50.313" CommentCount="2" />
  <row Id="1443" PostTypeId="2" ParentId="1437" CreationDate="2010-01-12T08:55:57.937" Score="2" ViewCount="" Body="&lt;p&gt;I found CodeLite (www.codelite.org) IDE nice and full featured; still, to program AVR microchips you need to create your own Makefile.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could try &lt;a href=&quot;http://www.bertos.org/discover/&quot; rel=&quot;nofollow&quot;&gt;BeRTOS Wizard&lt;/a&gt;, which will create a BeRTOS project and related Makefiles, which you can then use with CodeLite. To flash your target, just use &quot;make flash&quot; and you're done. We work on Linux on a daily basis, if you have further question please post them on the mailing list.&#xA;Disclaimer: I'm a BeRTOS developer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best regards,&#xA;Luca&lt;/p&gt;&#xA;" OwnerUserId="482" LastActivityDate="2010-01-12T08:55:57.937" CommentCount="1" />
  <row Id="1444" PostTypeId="1" AcceptedAnswerId="1474" CreationDate="2010-01-12T08:58:06.330" Score="4" ViewCount="242" Body="&lt;p&gt;Anyone had any experience with the programmable system on chip by Cypress? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cypress.com/?id=1353&quot; rel=&quot;nofollow&quot;&gt;http://www.cypress.com/?id=1353&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers.&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T16:47:33.187" LastActivityDate="2011-01-23T19:46:19.770" CommunityOwnedDate="2010-01-12T08:58:06.330" ClosedDate="2011-01-25T18:52:16.560" Title="PSoc by Cypress" Tags="&lt;system-on-chip&gt;&lt;psoc&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="1445" PostTypeId="2" ParentId="1437" CreationDate="2010-01-12T12:17:01.407" Score="4" ViewCount="" Body="&lt;p&gt;You should also check out &lt;a href=&quot;http://www.eclipse.org/downloads/packages/eclipse-ide-cc-developers/galileor&quot; rel=&quot;nofollow&quot;&gt;Eclipse for C/C++&lt;/a&gt; and the &lt;a href=&quot;http://avr-eclipse.sourceforge.net/wiki/index.php/The%5FAVR%5FEclipse%5FPlugin&quot; rel=&quot;nofollow&quot;&gt;AVR-Eclipse plugin.&lt;/a&gt; Works flawlessly for me, especially with crosspack. I use it for about a year now and I really like it.&lt;/p&gt;&#xA;" OwnerUserId="407" LastActivityDate="2010-01-12T12:17:01.407" CommentCount="1" />
  <row Id="1446" PostTypeId="2" ParentId="1444" CreationDate="2010-01-12T13:15:36.840" Score="1" ViewCount="" Body="&lt;p&gt;I've played with them a couple of times since they first came out. The early chips weren't much cop, and the development tools were very clunky, but the current PSOC 1 chips aren't bad in spite of the grotty CPU, and the tools have improved. The new ones look interesting, but it's a very niche market, and I can't see them being very widely used.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-12T13:15:36.840" CommunityOwnedDate="2010-01-12T13:15:36.840" CommentCount="1" />
  <row Id="1447" PostTypeId="2" ParentId="1444" CreationDate="2010-01-12T14:07:32.633" Score="2" ViewCount="" Body="&lt;p&gt;The chips are great! The development tools are not very good. I'm a professional EE and I am very interested in devices like these but have limited bursts of time, and with a 3hr time bubble I had available, I could not do anything significant with the parts (forget whether I even got an LED to blink).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully they'll fix this.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-01-12T14:07:32.633" CommunityOwnedDate="2010-01-12T14:07:32.633" />
  <row Id="1448" PostTypeId="2" ParentId="216" CreationDate="2010-01-12T19:54:59.547" Score="1" ViewCount="" Body="&lt;p&gt;If you're holding the solder to the tip and it's not melting it's because 1) the tip's not hot or 2) it's really dirty.  Both are things worth checking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other answers talk about the range of options to clean the tip, all good, all dependent on your particular tip.  The point of all of them though is that you don't want to score the tip, you want it clean and intact, without pitting or scrapes, so be gentle.  In nearly all cases, the tip will be hot when you're cleaning it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A trick I learned from an aerospace tech is to use a lot of solder when I clean the tip, using the excess solder to almost 'flush' off the tip.  Flux or Rosin is your friend to help distribute heat, but don't leave it on, as it will corrode.  Alcohol cleans rosin up nicely. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just as a note too, you'll buy &quot;flux&quot;, but make sure it's a &quot;rosin&quot; flux. There are many kinds of flux, and the rest are unsuitable for soldering irons and pcbs.  They might work in the short term, but cause endless headaches in the long run with corroded parts.&lt;/p&gt;&#xA;" OwnerUserId="483" LastActivityDate="2010-01-12T19:54:59.547" />
  <row Id="1449" PostTypeId="2" ParentId="1388" CreationDate="2010-01-12T20:03:49.217" Score="4" ViewCount="" Body="&lt;p&gt;I'm going to second and expand on Jason S's answer.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Clean and tin the iron&lt;/li&gt;&#xA;&lt;li&gt;(rosin) flux the joint to be soldered&lt;/li&gt;&#xA;&lt;li&gt;with your third hand, touch the iron to the part to be soldered, and simultaneously, touch the solder to the part - not to the iron.&lt;/li&gt;&#xA;&lt;li&gt;Hold until you see the solder &quot;flow&quot; and fill the joint/through hole/twisted wire/etc&lt;/li&gt;&#xA;&lt;li&gt;pull the iron away quickly&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;You'll know when it's good if you can still see the parts of the joint, and it's shiny. As in, if you still can see the two wire twisting together.  You don't want to make a super-full 'ball' of solder, since then no one else can, by inspection, see that it's a good solder joint.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Worst case is if you get a ball of solder where the joint is with a dull sheen.  That's a cold solder joint and needs to be redone.&lt;/p&gt;&#xA;" OwnerUserId="483" LastActivityDate="2010-01-12T20:03:49.217" />
  <row Id="1450" PostTypeId="1" AcceptedAnswerId="1453" CreationDate="2010-01-13T05:12:38.853" Score="7" ViewCount="1555" Body="&lt;p&gt;I am looking for a cheap but powerful dev board for an ARM9 processor. It needs to be able to run linux. I am unsure about the exact specifications for RAM and such(thats partly why I'm posting this question). I would however like it to have SD, Ethernet(or WIFI) and USB. Any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2011-06-02T02:37:41.213" Title="Best development board for ARM9?" Tags="&lt;arm&gt;&lt;microprocessor&gt;&lt;development&gt;&lt;board&gt;&lt;ethernet&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="4" />
  <row Id="1451" PostTypeId="2" ParentId="1388" CreationDate="2010-01-13T06:05:54.290" Score="2" ViewCount="" Body="&lt;p&gt;If your looking at SMD, you could look at using a solder reflow technique using solder paste.&#xA;Here's a video of a simple version using a kitchen hot plate -&gt; &lt;a href=&quot;http://www.youtube.com/watch?v=lqYjPJJBiZo&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=lqYjPJJBiZo&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A hot gun can also be useful for concentrating heat on a particular part of your PCB&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Solder paste ROCKS! &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-01-13T06:05:54.290" />
  <row Id="1452" PostTypeId="2" ParentId="1450" CreationDate="2010-01-13T06:49:14.690" Score="10" ViewCount="" Body="&lt;p&gt;Does it have to be ARM9? The &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;beagleboard&lt;/a&gt; is pretty powerful for the price. $150 gets you a 500MHz ARM Cortex A8 (two generations newer than ARM9), 256MByte of RAM, 256MByte of NAND Flash storage, DVI video output, SDHC card slot, USB (Host &amp;amp; Device), audio in &amp;amp; audio out, and a bunch of I/O ports. It doesn't have built in ethernet, but you can use an inexpensive USB Ethernet adaptor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sparkfun also has an &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9047&quot; rel=&quot;nofollow&quot;&gt;ARM9 board&lt;/a&gt;, but it costs more and IMO is less powerful (180MHz ARM9 / 64MB RAM / 512MB storage / no video out / does have built in ethernet though)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to buy a Nintendo DS...you get a 66MHz ARM9 + 33MHz ARM7 + 4MB ram + 2D/3D graphics hardware rendering w/ ~0.75MB of VRAM (which you can reuse as RAM if you need it all for gfx) two 256x192 LCDs (one has a touchscreen), WiFi, and microSD card storage (with an inexpensive adapter, under $20 these days), built in battery + charger, speakers, mic. Downside is you have limited interfaces to the outside world...either SPI in Slot-1, or the GBA Cart Bus in Slot-2. There is a &lt;a href=&quot;http://www.devkitpro.org/&quot; rel=&quot;nofollow&quot;&gt;free gcc port + libraries&lt;/a&gt; available, you just compile a program, and drop it on the microSD card, put it in the adapter, and put it in the DS. Retail price is $130 these days, you can get the original (bulkier) NDS for probably around $50-70 used on ebay.&lt;/p&gt;&#xA;" OwnerUserId="131" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:37:41.213" LastActivityDate="2011-06-02T02:37:41.213" CommentCount="2" />
  <row Id="1453" PostTypeId="2" ParentId="1450" CreationDate="2010-01-13T09:21:44.063" Score="8" ViewCount="" Body="&lt;p&gt;Another option is a &lt;a href=&quot;http://www.friendlyarm.net/&quot; rel=&quot;nofollow&quot;&gt;mini2440 or a micro2440&lt;/a&gt;.&#xA;I bought mine (including an LCD touch screen) for 85$ on Ebay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Support is very extensive, it includes what you need/wanted (ethernet adapter)&lt;/p&gt;&#xA;" OwnerUserId="485" LastActivityDate="2010-01-13T09:21:44.063" CommentCount="2" />
  <row Id="1454" PostTypeId="1" CreationDate="2010-01-13T09:33:06.750" Score="11" ViewCount="3460" Body="&lt;p&gt;I'm thinking about getting an oscilloscope as my next tool purchase but I don't really know what I should be looking for or what the options are. Ideally I'd prefer something that was stand alone, but I expect a device that hooks up to a PC for the display would be cheaper and offer more functionality. Right now my projects are reasonably simple but I'd prefer to buy a tool that I wont outgrow too quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for all the answers so far, that's a lot of information to look at!&lt;/p&gt;&#xA;" OwnerUserId="255" LastEditorUserId="255" LastEditorDisplayName="" LastEditDate="2010-01-16T11:06:41.553" LastActivityDate="2011-01-04T01:24:20.027" Title="Opinions on an oscilloscope suitable for hobby electronics on a budget" Tags="&lt;oscilloscope&gt;&lt;tools&gt;" AnswerCount="9" CommentCount="1" FavoriteCount="2" />
  <row Id="1455" PostTypeId="2" ParentId="1454" CreationDate="2010-01-13T12:09:31.083" Score="14" ViewCount="" Body="&lt;p&gt;You don't mention exactly what work you do, but a good DSO will last you a while (and I guarantee it won't go out of date for a while). Sure, you can grab a Tek analog scope 2nd hand but my storage scope has saved my frustration bacon more than once. I have a Rigol DS1052E (a good review from a proper EE &lt;a href=&quot;http://www.eevblog.com/2009/04/05/full-review-of-the-rigol-ds1052e/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) which is a 50mhz 1GSa/s scope direct from the factory; they are about 675$AU on ebay. In my opinion they are the best high end hobbyist scopes on the market; considering what you get for the price I wouldn't trade mine for anything.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-01-13T12:09:31.083" CommentCount="5" />
  <row Id="1456" PostTypeId="2" ParentId="1454" CreationDate="2010-01-13T14:43:35.623" Score="4" ViewCount="" Body="&lt;p&gt;I never had any luck finding a good used 'scope on eBay or Craigslist; there are tons out there, but they're typically missing probes or documentation.  I ended up buying an &lt;a href=&quot;http://linkinstruments.com/mso19.htm&quot; rel=&quot;nofollow&quot;&gt;MSO-19 from Link Instruments&lt;/a&gt; for about $250.  It's a computer-based USB single-channel digital storage oscilloscope and 7-channel logic analyzer.  It works well on Windows XP running in VMWare Fusion on my MacBook Pro running Snow Leopard.  I have not found any USB-based 'scope with OS X-native software.  I find the fact that it's a single-channel scope to be a limitation: it'd be really nice to compare a raw signal to one that's been processed in some way (through an RC filter or op-amp), but it's proven to be extremely useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Parallax has two oscilloscopes, the $250 &lt;a href=&quot;http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/oscilloscope/List/0/SortField/4/ProductID/586/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;PropScope&lt;/a&gt;, and $140 &lt;a href=&quot;http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/oscilloscope/List/0/SortField/4/ProductID/46/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;USB Oscilloscope&lt;/a&gt;.  I don't have any experience with either of these.  They do appear to both be 2-channel scopes, but neither seem to have any kind of logic analyzer.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-01-13T14:43:35.623" CommentCount="1" />
  <row Id="1457" PostTypeId="2" ParentId="1454" CreationDate="2010-01-13T17:05:02.040" Score="3" ViewCount="" Body="&lt;p&gt;Do you need the analog oscilloscope features, or are you planning to use it more for digital logic analysis? There are some decent PC-based logic analyzers that you can get for very cheap considering their capabilities, if you don't mind forgoing the ability to do analog signal analysis.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as actual analog-capable PC-based oscilloscopes, this is the only one I know of that has decent capabilities at a reasonable price: &lt;a href=&quot;http://www.linkinstruments.com/mso19.htm&quot; rel=&quot;nofollow&quot;&gt;Link Instruments MSO-19&lt;/a&gt;. It actually combines 1 channel oscilloscope with an 8-bit digital logic analyzer, so you're getting a good set of features. Supposedly it can sample the oscilloscope at 2GHz, and the digital logic analyzer channels at 200MHz. It's mentioned by another poster above, for $250.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you just want a digital logic analyzer, the best low priced one I've found is the &lt;a href=&quot;http://www.nkcelectronics.com/zeroplus-lap16032u-logic-ana16032.html&quot; rel=&quot;nofollow&quot;&gt;Zeroplus Logic Cube LAP-C 16032&lt;/a&gt; with a 32kbit/channel buffer, 16 digital channels, and can sample up to 100MHz, it's only $120.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-13T17:05:02.040" />
  <row Id="1458" PostTypeId="2" ParentId="1454" CreationDate="2010-01-13T17:25:10.320" Score="7" ViewCount="" Body="&lt;p&gt;Since no-one has mentioned it yet, I'll post the link to the afrotechmods guide on purchasing an oscilloscope thinga-ma-jiggy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.afrotechmods.com/groovy/oscilloscope_tutorial/oscilloscope_tutorial.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.afrotechmods.com/groovy/oscilloscope_tutorial/oscilloscope_tutorial.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;first video on that page is the discussion about what kind you should buy etc.&lt;/p&gt;&#xA;" LastActivityDate="2010-01-13T17:25:10.320" />
  <row Id="1460" PostTypeId="1" AcceptedAnswerId="1462" CreationDate="2010-01-13T21:20:36.990" Score="6" ViewCount="356" Body="&lt;p&gt;My college undergraduate electronics classes covered some analog design, and I'd like to further my knowledge and experience. What would be a good project that would require significant effort as far as research and learning new material? Ideally, the project, when finished, would also serve as evidence that I have analog design skills.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2011-05-13T12:48:01.120" CommunityOwnedDate="2011-05-13T20:44:33.280" Title="Good analog design learning project." Tags="&lt;analog&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="1461" PostTypeId="2" ParentId="1454" CreationDate="2010-01-13T22:09:45.813" Score="1" ViewCount="" Body="&lt;p&gt;There's an article in the January edition of &lt;a href=&quot;http://www.elektor.com&quot; rel=&quot;nofollow&quot;&gt;Elektor Magazine&lt;/a&gt; about building your own multi channel Logic Analyzer based on ATM18 board that they sell(?). This in turn is based on an earlier article about building your own Storage Oscilloscope using the same board. Depending on your requirements, either of these might be suitable as a stop gap until you settle on a final one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You appear to have about a week to get to WHSmith's before the next issue comes out, alternatively you can pay about £1.10 to download the article about the Logic Analyser &lt;a href=&quot;http://www.elektor.com/magazines/2010/january/atm18-logic-analyzer.1191291.lynkx&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; or the Storage Oscilloscope &lt;a href=&quot;http://www.elektor.com/magazines/2009/april/scoping-with-the-atm18.875739.lynkx&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; (you need to buy Elektor credits from the left hand menu). The board it's based on appears to be &lt;a href=&quot;http://www.elektor.com/magazines/2008/april/atm18-avr-board.399044.lynkx&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-01-13T22:09:45.813" />
  <row Id="1462" PostTypeId="2" ParentId="1460" CreationDate="2010-01-13T22:27:41.177" Score="9" ViewCount="" Body="&lt;p&gt;Music ... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An analog synthesizer has a number of functional blocks --&#xA;  voltage controlled oscillator, voltage controlled amplifier, mixer, envelope generator,&#xA;  filter with voltage control over the cutoff frequency, noise generator, &#xA;  analog multiplication&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Power Electronics ...   DC to DC converter, DC to AC converter, motor control&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Audio .... Amplifier pre-amp&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:48:01.120" LastActivityDate="2011-05-13T12:48:01.120" CommunityOwnedDate="2011-05-13T20:44:33.280" CommentCount="3" />
  <row Id="1463" PostTypeId="2" ParentId="1454" CreationDate="2010-01-14T01:38:53.327" Score="3" ViewCount="" Body="&lt;p&gt;Just get a used one on eBay.  It's much cheaper than a PC scope.  My family got me an old &quot;Lizen&quot; 20 MHz scope, which works well enough for what I do.  I suspect it was under $50.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also this thing for $89, if it meets your requirements: &lt;a href=&quot;http://www.seeedstudio.com/depot/micro-digital-storage-oscilloscopedso-nano-p-512.html&quot; rel=&quot;nofollow&quot;&gt;http://www.seeedstudio.com/depot/micro-digital-storage-oscilloscopedso-nano-p-512.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a &lt;a href=&quot;http://www.endolith.com/wordpress/2008/06/17/bitscope/&quot; rel=&quot;nofollow&quot;&gt;BitScope&lt;/a&gt;, because I saw one for cheap on eBay, but I rarely use it.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-01-14T19:05:46.470" LastActivityDate="2010-01-14T19:05:46.470" CommentCount="1" />
  <row Id="1464" PostTypeId="2" ParentId="1454" CreationDate="2010-01-14T08:58:23.253" Score="1" ViewCount="" Body="&lt;p&gt;I've got a dual trace PC based one made by Parallax. It has very limited capabilities because it's limited to the speed of the USB bus while taking samples. This makes it easy to use when you have a laptop or desktop PC handy, but also makes it useless when working on any higher speed signals. In all I only spent about a hundred $ on mine and it has served my prototype and hobby needs quite well.  It just isn't any good for radio or microwave work.&lt;/p&gt;&#xA;" LastActivityDate="2010-01-14T08:58:23.253" />
  <row Id="1465" PostTypeId="1" AcceptedAnswerId="1466" CreationDate="2010-01-14T16:27:47.420" Score="3" ViewCount="1143" Body="&lt;p&gt;I'm trying to find an off the shelf plug in ac/dc power supply unit to work with my project.&#xA;I want to power an Arduino Duemilanove and six 12v 1A solenoids.&#xA;Here's the solenoids -&gt; &#xA;&lt;a href=&quot;http://www.rapidonline.com/productinfo.aspx?&amp;amp;tier1=Electronic+Components&amp;amp;tier2=Relays+%26+Solenoids&amp;amp;tier3=Solenoids&amp;amp;tier4=PCB+miniature+solenoids&amp;amp;moduleno=29536&amp;amp;catref=60-3210&quot; rel=&quot;nofollow&quot;&gt;http://www.rapidonline.com/productinfo.aspx?&amp;amp;tier1=Electronic+Components&amp;amp;tier2=Relays+%26+Solenoids&amp;amp;tier3=Solenoids&amp;amp;tier4=PCB+miniature+solenoids&amp;amp;moduleno=29536&amp;amp;catref=60-3210&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to buy one of the power supply units from this page -&gt;&#xA;&lt;a href=&quot;http://www.rapidonline.com/Electrical-Power/Power-Supplies/Plug-In-PSUs&quot; rel=&quot;nofollow&quot;&gt;http://www.rapidonline.com/Electrical-Power/Power-Supplies/Plug-In-PSUs&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I don't know how to work out the right one. Cheers  &lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-04-01T14:39:38.443" LastActivityDate="2010-04-01T14:39:38.443" Title="power supply unit for Arduino/solenoid project" Tags="&lt;power-supply&gt;&lt;arduino&gt;" AnswerCount="2" />
  <row Id="1466" PostTypeId="2" ParentId="1465" CreationDate="2010-01-14T19:54:27.427" Score="3" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Figure out what voltages you need. You say the solenoid needs 12V, then you need to check the Arduino Duemilanove. Will it work with 12V, or does it require a different voltage.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Figure out the maximum power you will need. 12V * 1A = 12W, seems high for a small solenoid, but I don't have a lot of experience with them. Sum this for all the components you will be running simultaneously. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Select a power supply that provides the required voltage(s), plus at least the maximum current you need. You should probably pick something that provides a bit more than what you need, because running a component at 100% is generally a bad practice.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-14T19:54:27.427" CommentCount="4" />
  <row Id="1467" PostTypeId="2" ParentId="1465" CreationDate="2010-01-14T20:12:24.277" Score="3" ViewCount="" Body="&lt;p&gt;It might be a good idea to use two power supplies, otherwise transients from the solenoids will affect the Arduino's operation. A single power supply could be used, but you need to design it carefully.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-14T20:12:24.277" CommentCount="3" />
  <row Id="1468" PostTypeId="1" CreationDate="2010-01-14T21:02:07.413" Score="2" ViewCount="922" Body="&lt;p&gt;Pat asks:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9332&quot; rel=&quot;nofollow&quot;&gt;Accelerometer Breakout Board - ADXL193 +/-250g&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;could you tell me if this is correct.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at the data sheet the mid sensitivity is about 8mv/G @ 5volts. If I use a 10bit adc @ 5volts then 5/1024=4.9 mV, so 1g=8mV so in bits 8/4.9=1.63 bits/g. Then if I have a zero adc reading of say 500 and I get a reading of 530, then&lt;/p&gt;&#xA;&#xA;&lt;p&gt;530-500- 30/1.63=18 g's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is that the way to calculate G's from this Breakout Board.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;the data sheet says that voltage as low as 3.5 could be used and I was thinking of trying both 3.7v and see if 3.3v will work. Any idea what this will do for the calculations and that maximum range. I know the sensitivity is ratiometric so that will drop based on a lower input voltage.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-02T02:23:21.213" LastActivityDate="2011-02-02T02:23:21.213" Title="Calculate G's of an Accelerometer" Tags="&lt;accelerometer&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="1469" PostTypeId="2" ParentId="1468" CreationDate="2010-01-14T22:02:05.807" Score="2" ViewCount="" Body="&lt;p&gt;At 1024 steps (10 bit ADC) over a 5v range, that's 4.88mV per step.  You can measure a range of 500 Gs (-250 to +250), so at 1024 steps you have (1024/500) = 2.048 units per G, or roughly 9.99 mV.  Depending on your accuracy requirements, you can probably get away with assuming 2 steps per G.  At +/-250G, you will be off by 12 steps, or 6G, and the error is linear across your readings.  For example, if you assumed 2 steps per G, a reading of 1012 would be mistakenly read as 250G when the sensor is actually reporting closer to 244G.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, remember that you will undoubtedly be fighting noise and you can be inaccurate to a few units from that as well.  This doesn't really play in to how to calculate readings, but is an important consideration when dealing with ADCs.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2010-01-14T22:02:05.807" />
  <row Id="1470" PostTypeId="2" ParentId="1468" CreationDate="2010-01-14T22:21:00.447" Score="1" ViewCount="" Body="&lt;p&gt;I once tried a similar SFE breakout board for another accelerometer and found it to be unusable, because of the noise it picked up due to the long connections. I designed my own PCB with the accelerometer close to the MCU ADC inputs, and all the noise disappeared.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-14T22:21:00.447" />
  <row Id="1471" PostTypeId="2" ParentId="1468" CreationDate="2010-01-14T22:21:49.423" Score="3" ViewCount="" Body="&lt;p&gt;If you use a 10 bit a/d converter to digitise a voltage in the range 0 to 5V then each count will represent 5/1024 = 4.88mV&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sensor data sheet gives an output of 8mV per g acceleration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case that you are stating then the offset from the zero reading is 30 counts.  This equates to 30*4.88 = 146.5&lt;/p&gt;&#xA;&#xA;&lt;p&gt;at 8mV per g this is 18.3g&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a system level I would have a number of concerns (and these really depend upon the end application for which the device is being used)&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;+/-250g is one hell of an acceleration.  This sort of acceleration can only be seen for a very short time.  In order to capture this you would have to have a fast A/D converter, but then the sensor has a 400Hz filter on the output which will remove the fast transients from the output.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The resolution of the A/D only allows the determination of the acceleration to steps of 0.61g.  Is this resolution sufficient.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;Any noise on the A/D input can give a 1 or 2 count error in the A/D conversion resulting in a large error in the measured value.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If you scale/amplify the output from the accelerometer and limit its value to to lie in the A/D converter input range then you can, at the cost of a reduced dynamic range, improve the sensitivity of yor device without having to increase the resolution and cost of your converter.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-01-14T22:21:49.423" />
  <row Id="1472" PostTypeId="2" ParentId="1468" CreationDate="2010-01-14T22:52:09.867" Score="1" ViewCount="" Body="&lt;p&gt;Thanks for your help.. one other question about the voltage, the data sheet says that voltage as low as 3.5 could be used and I was thinking of trying both 3.7v and see if 3.3v will work. Any idea what this will do for the calculations and that maximum range. I know the sensitivity is ratiometric so that will drop based on a lower input voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&#xA;Pat&lt;/p&gt;&#xA;" LastActivityDate="2010-01-14T22:52:09.867" CommentCount="2" />
  <row Id="1473" PostTypeId="2" ParentId="1460" CreationDate="2010-01-14T23:19:48.800" Score="1" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;a log-amplifier (output voltage increases by V0 volts every time input voltage doubles)&lt;/li&gt;&#xA;&lt;li&gt;an optical interrupter (put two LEDs on either end of a tube with a slot cut through it; put current into the transmit LED, amplify the current produced by the receive LED)&lt;/li&gt;&#xA;&lt;li&gt;a thermocouple temperature reader (amplifier + cold-junction compensation + ADC) &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-01-14T23:19:48.800" CommunityOwnedDate="2011-05-13T20:44:33.280" />
  <row Id="1474" PostTypeId="2" ParentId="1444" CreationDate="2010-01-15T03:05:19.773" Score="3" ViewCount="" Body="&lt;p&gt;I'm actually working on a project with PSoC chips right now.  I can say that there are definite pros and cons to it.  The capsense works pretty well, but takes a while to tune it, but they do provide a USB to I2C &quot;bridge&quot; which allows you to tune it fairly easily (gets you 80% of the way there and you can fine tune it by hand afterwards).  The good thing about the capsense is that you get &quot;free&quot; buttons, meaning that the cost of adding a button onto a PCB is just adding some traces rather than the cost of an actual button (if that matters).  But there are a lot of app notes to read to learn the best way to lay out your board for capsense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The IDE is not so great.  I've had it crash several times on me.  The documentation is pretty good, and the personnel have been good to respond to my questions.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One major &quot;gotcha&quot; is that not all of the chips have in circuit debugging capabilities (a must these days!) so be careful which chip you select.  Also, I've run into some issues with their compiler as well (it &quot;optimized&quot; some of its own I2C bootloader code right into oblivion).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All in all, my recommendation would be that unless you really really want capsense buttons for your project I would just go with something more standard like Atmel or PIC. &lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2010-01-15T03:05:19.773" CommunityOwnedDate="2010-01-15T03:05:19.773" CommentCount="4" />
  <row Id="1475" PostTypeId="1" AcceptedAnswerId="1477" CreationDate="2010-01-15T11:47:25.130" Score="3" ViewCount="308" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I got some static LCD's from an old cheap clock, calculator and the like and now I would like to use them for displaying simple things like temperature. They are connected with those pink with grey connector bars, if you know what I mean.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this article: &lt;a href=&quot;http://www.ubasics.com/driving%5Fstatic%5Flcds&quot; rel=&quot;nofollow&quot;&gt;http://www.ubasics.com/driving_static_lcds&lt;/a&gt; but he talks about non-multiplexed LCD's. How can I see/test/check what for static LCD I have?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be great if I could use these static LCD's, do you guys got more info on how to use these things (multiplexed or not)? Can I use it with an ATtiny2313?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="323" LastActivityDate="2010-01-15T20:58:54.500" Title="How to test if it is a non-multiplexed (static) LCD?" Tags="&lt;lcd&gt;&lt;driver&gt;&lt;atmel&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="1476" PostTypeId="2" ParentId="1475" CreationDate="2010-01-15T18:04:10.577" Score="4" ViewCount="" Body="&lt;p&gt;Try counting the number of pins compared to the number of LCD display segments? That should be one way to possibly determine. There should be at least as many pins as segments, plus a one or more extra for the common pin(s). If there are significantly fewer pins than display segments, it must be multiplexed.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-15T18:04:10.577" />
  <row Id="1477" PostTypeId="2" ParentId="1475" CreationDate="2010-01-15T20:58:54.500" Score="3" ViewCount="" Body="&lt;p&gt;You can hook up the LCD as described in that article, and start testing pins by hooking the common up to one pin, and the drive up to another pin.  Map out the whole LCD this way and you should soon see which segments go to which pins.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A static LCD will have one pin, common, that will drive all other segments (should be easy to find) and another pin for each segment on the display.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A multiplexed display will have 2 or more common pins that each drive a number of segments, an each other pin will drive a few segments.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-01-15T20:58:54.500" />
  <row Id="1478" PostTypeId="1" AcceptedAnswerId="1479" CreationDate="2010-01-15T21:10:20.187" Score="14" ViewCount="1288" Body="&lt;p&gt;How do I calculate how long a battery operated product will run?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's what I've got:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;2 AA, 1.5V, 2700mAH batteries&lt;/li&gt;&#xA;&lt;li&gt;Voltage Regulator with a Iq of 25 uA&lt;/li&gt;&#xA;&lt;li&gt;Voltage Regulator Eff = 80%&lt;/li&gt;&#xA;&lt;li&gt;Active Current = 50mA &lt;/li&gt;&#xA;&lt;li&gt;Sleep Current = 1uA &lt;/li&gt;&#xA;&lt;li&gt;Duty Cycle = 99.9% (only active 0.1% of the time) &lt;/li&gt;&#xA;&lt;li&gt;Active Voltage is 3.3V&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I've gone the current route and got an answer.  I went the power route and got a TOTALLY different answer (days vs years different).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you do this?&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-06-02T02:41:13.597" Title="How to calculate battery life" Tags="&lt;power&gt;&lt;battery&gt;" AnswerCount="2" FavoriteCount="5" />
  <row Id="1479" PostTypeId="2" ParentId="1478" CreationDate="2010-01-16T00:21:33.933" Score="9" ViewCount="" Body="&lt;p&gt;My calculation, probably missing something, but here's what I did:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;\$1\mu A + (50mA \times 0.1\%) + 25&#xA;\mu A = 76 \mu A\$&lt;/li&gt;&#xA;&lt;li&gt;\$\frac{76 \mu A}{  80\% \mbox{&#xA;efficiency}} = 88 uA\$&lt;/li&gt;&#xA;&lt;li&gt;Round up to \$100 \mu A = 0.1mA\$&lt;/li&gt;&#xA;&lt;li&gt;\$\frac{2700mAh}{  0.1mA} \approx 3 \mbox{ years}\$&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you're using rechargeable batteries, they'll discharge on their own long before that. Or if any of your other calculations are off (like maybe it's a 98% instead of 99.9% sleep), that will affect it a lot too.&lt;/p&gt;&#xA;" OwnerUserId="131" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:41:13.597" LastActivityDate="2011-06-02T02:41:13.597" CommentCount="4" />
  <row Id="1480" PostTypeId="2" ParentId="1478" CreationDate="2010-01-16T13:47:17.050" Score="8" ViewCount="" Body="&lt;p&gt;The output current required from the 3.3V &#xA;regulator is &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1uA * 0.999 + 50mA * 0.001 + 25uA = 75.999uA &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output power is&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3.3V * 75.999uA = 250.8uW&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The input power to the regulator is&lt;/p&gt;&#xA;&#xA;&lt;p&gt;250.8uW / 0.8 = 313.5uW&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the batteries are fully charged &#xA;the input current to the regulator is&lt;/p&gt;&#xA;&#xA;&lt;p&gt;313.5uW / 3V = 104uA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the batteries have a flat discharge&#xA;curve then you will get a life of&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2700mAh / 104uA = 25837hours &#xA;                  = 2.95 years&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since your batteries are 2700mAh 1.5V AA&#xA;I am guessing that the discharge curve&#xA;is not flat. You will need to draw&#xA;higher currents as the voltage drops.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also your regulator efficiency probably&#xA;drops at lower voltages. Again I am&#xA;guessing since I have not seen the&#xA;design. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be careful when calculating using currents.&#xA;You may be inadvertently assuming that &#xA;the input and output voltage of the regulator&#xA;is the same. With an input of 3V and an output&#xA;of 3.3V it is not a big error. If you do&#xA;a more accurate estimate of the battery&#xA;discharge curve it will matter.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-30T10:20:06.630" LastActivityDate="2011-04-30T10:20:06.630" CommentCount="3" />
  <row Id="1481" PostTypeId="2" ParentId="1437" CreationDate="2010-01-16T19:44:03.187" Score="2" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://www.obdev.at/products/crosspack/index.html&quot; rel=&quot;nofollow&quot;&gt;ObDev's CrossPack&lt;/a&gt; as well.  It's a great bundling of all the tools needed to write AVR-GCC C code.  They're the same tools present in a standard Arduino installation, so sometimes I've used the guts of the Arduino build system to write plain AVR-GCC code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally when I write C code, the &quot;IDE&quot; I use is a text editor, command-line commands, and Makefiles.  I'm just more efficient that way.  I have one window open that's the text editor (emacs), another window that's compilation, and a third or fourth that's doing serial monitor or similar.  But all that can be done in a single command-line window, in which case the commands look something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;% emacs foo.c [edit file]&#xA;% make        [compile code]&#xA;% make flash  [upload to chip]&#xA;% screen /dev/tty.usbserial 9600  [talk to chip]&#xA;... and then repeat as needed...&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Also, you may want to check out &lt;a href=&quot;http://smileymicros.com/&quot; rel=&quot;nofollow&quot;&gt;SmileyMicros.com&lt;/a&gt;.  He wrote a really nice book on intro AVR GCC programming based on the AVR Butterfly board, before the Arduino, and has since been updating his examples to incorporate Arduino.  It's a nice comparison to see how AVR C programming is done on a more complex chip than the one in Arduino.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-01-16T19:44:03.187" />
  <row Id="1482" PostTypeId="1" CreationDate="2010-01-17T12:00:28.813" Score="5" ViewCount="1631" Body="&lt;p&gt;I was just wondering if there was a tutorial anywhere on how to make your own USB Flash Drive and I don't mean take apart a USB and put the guts into something else, I mean put together the flash memory and controller.&lt;/p&gt;&#xA;" OwnerUserId="322" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-23T16:39:14.850" LastActivityDate="2011-03-23T16:39:14.850" Title="DIY USB Mass Storage Tutorial" Tags="&lt;usb&gt;&lt;memory&gt;&lt;flash&gt;" AnswerCount="6" CommentCount="2" FavoriteCount="2" />
  <row Id="1483" PostTypeId="2" ParentId="1482" CreationDate="2010-01-17T12:51:22.897" Score="3" ViewCount="" Body="&lt;p&gt;You could base it on this project of mine:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.leonheller.com/usb&quot; rel=&quot;nofollow&quot;&gt;http://www.leonheller.com/usb&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-01-17T12:51:22.897" />
  <row Id="1484" PostTypeId="2" ParentId="1482" CreationDate="2010-01-17T13:29:49.700" Score="4" ViewCount="" Body="&lt;p&gt;A question about general USB devices was asked &lt;a href=&quot;http://chiphacker.com/questions/267/id-like-to-learn-how-to-make-my-own-usb-gadgets/274#274&quot; rel=&quot;nofollow&quot;&gt;a while ago&lt;/a&gt;, but you are specifically referring to a USB mass storage device (MSD)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jan Axelson (from &lt;a href=&quot;http://www.lvr.com&quot; rel=&quot;nofollow&quot;&gt;http://www.lvr.com&lt;/a&gt;) has written a book about it: &lt;a href=&quot;http://www.lvr.com/mass_storage.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.lvr.com/mass_storage.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="10" LastEditorUserId="10" LastEditorDisplayName="" LastEditDate="2010-01-17T14:08:54.307" LastActivityDate="2010-01-17T14:08:54.307" />
  <row Id="1485" PostTypeId="1" CreationDate="2010-01-17T21:56:15.267" Score="3" ViewCount="143" Body="&lt;p&gt;I have an idea for a project where I use a pc fan to make an oscillator. The oscillation is created by the cycle of light/dark falling on a light sensor as the blades of the fan rotate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My initial research points to the use of the photodiode in combination with a op-amp to provide a suitable line audio output. My question is: What are the critical parameters for the circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the datasheet for the photodiode i'm prototyping: &lt;a href=&quot;http://www.jaycar.co.nz/products_uploaded/ZD1948.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.jaycar.co.nz/products_uploaded/ZD1948.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rob&lt;/p&gt;&#xA;" OwnerUserId="178" LastActivityDate="2010-01-18T14:15:02.833" Title="sensing light and outputing voltage suitable for audio" Tags="&lt;light&gt;&lt;audio&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="1486" PostTypeId="2" ParentId="1485" CreationDate="2010-01-17T22:43:41.323" Score="2" ViewCount="" Body="&lt;p&gt;The critical parameters are the light and dark currents.&#xA;The dark current has a maximum value of 30nA. The&#xA;light current has a minimum value of 30uA and a &#xA;typical value of 40uA. Since the ratio is 1000:1&#xA;there will be a large difference between on and off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use an op-amp to output a line level I would set &#xA;the gain resistor so that a 40uA current gives you 80-90% &#xA;of the line voltage level. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The downside is that the level may be different for different diodes.&#xA;You could put a pot in the feedback loop for adjustment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to get more complicated you could have the&#xA;photodiode trigger an analog switch (SPDT). The precise &#xA;line level could be set by adjusting the inputs of the switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the Hamamatsu site there is some good technical information&#xA;and application hints for photodiodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(* jcl *)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.wiblocks.com&quot; rel=&quot;nofollow&quot;&gt;http://www.wiblocks.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="424" LastEditorDisplayName="" LastEditDate="2010-01-17T23:08:34.470" LastActivityDate="2010-01-17T23:08:34.470" CommentCount="2" />
  <row Id="1487" PostTypeId="1" CreationDate="2010-01-17T23:01:52.430" Score="5" ViewCount="1112" Body="&lt;p&gt;When I was a teen, I joined an electronics club and built a disco board.  I had 5 light bulbs, I painted them different colors.  Then I built a board which was connected to these light bulbs.  I'd connect my stereo to the board and the each light bulb would flash when a specific instrument would play (e.g. green for drums, etc...).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to build something similar with my son now, but I totally and utterly forgot how to do this.  Can someone point me in the right direction?  &lt;/p&gt;&#xA;" OwnerUserId="231" LastActivityDate="2011-04-27T20:23:29.293" Title="How to build disco lights?" Tags="&lt;light&gt;" AnswerCount="3" />
  <row Id="1489" PostTypeId="1" CreationDate="2010-01-18T04:31:52.693" Score="3" ViewCount="354" Body="&lt;p&gt;It do provide the full set of logic functionality,but its arithmetic functionalities are not so clear,which do not contain &lt;code&gt;a minus b&lt;/code&gt; and &lt;code&gt;a plus b&lt;/code&gt; at the same time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you provide some history background about how it was designed?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks.&lt;/p&gt;&#xA;" OwnerUserId="493" LastActivityDate="2010-01-18T20:12:04.307" Title="Why 74181 was designed to function as it now?" Tags="&lt;circuit&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="1490" PostTypeId="2" ParentId="1487" CreationDate="2010-01-18T12:28:44.610" Score="3" ViewCount="" Body="&lt;p&gt;You could look at triggering different lights with amplitude, like a VU meter. This is a cheap 5 LED digital VU meter -&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.littlediode.com/components/LB1403N_LB1403_Integrated_Circuit_.html?NO_COOKIE_WARNING=2&amp;amp;ti=646e9cc97c539a96ef3257fa2cc49a19&amp;amp;xid=5c2ec922e32bf8c66047b98f481d025f&quot; rel=&quot;nofollow&quot;&gt;http://www.littlediode.com/components/LB1403N_LB1403_Integrated_Circuit_.html?NO_COOKIE_WARNING=2&amp;amp;ti=646e9cc97c539a96ef3257fa2cc49a19&amp;amp;xid=5c2ec922e32bf8c66047b98f481d025f&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used it before to drive some LEDs on a kinda birthday card thing, I plugged the card into my Ipod output, and the 5 LED flowers on the card flashed with the music!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could hook the output pins to some transistors which could then drive your colored light bulbs, it would be much cheaper and easier than using a micro controller. This would give you a regular audio level meter much like the one on a mixing desk, you could however change the order and color of the lights to mix it up a bit, so it's more of a light show. The lights also fade in with the increase of amplitude rather than just flashing on at a set value, so it would look cool. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise you would have to take a look at frequency analysis, whereby the lights could be triggered by the audio level at different frequency bands (one per light). This system would closest resemble a disco light that flashes with the different instruments in an audio track, but it's much harder to implement when compared to amplitude analysis. I'm sure a modern MCU would do the job with ease tho, with only 5 lights the resolution on the analogue inputs would not be a huge issue. If you could find some code to steal this option wouldn't be that hairy, if you're familiar with micro controllers.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-01-18T12:28:44.610" CommentCount="4" />
  <row Id="1491" PostTypeId="2" ParentId="1485" CreationDate="2010-01-18T13:02:03.293" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/users/156/alex&quot; rel=&quot;nofollow&quot;&gt;Alex&lt;/a&gt; who is a member here has details over on his &lt;a href=&quot;http://tinkerlog.com&quot; rel=&quot;nofollow&quot;&gt;tinkerlog site&lt;/a&gt; of something he calls &lt;a href=&quot;http://tinkerlog.com/howto/synchronizing-firefly-how-to/&quot; rel=&quot;nofollow&quot;&gt;Synchronizing Fireflies&lt;/a&gt;, these may have some useful details in. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But of more use to you is probably &lt;a href=&quot;http://chiphacker.com/users/399/jim&quot; rel=&quot;nofollow&quot;&gt;Jim&lt;/a&gt;'s site &lt;a href=&quot;http://www.sonodrome.co.uk&quot; rel=&quot;nofollow&quot;&gt;Sonodrome&lt;/a&gt; which has details of his Posc on it. This has two oscillators controlled by light dependent resistors and can output to a stereo. There is a schematic etc in there somewhere.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-01-18T13:02:03.293" CommentCount="2" />
  <row Id="1492" PostTypeId="2" ParentId="1485" CreationDate="2010-01-18T13:53:15.343" Score="2" ViewCount="" Body="&lt;p&gt;If you just use a 555 timer you won't need to amplify it, you can plug it directly into a line level input (microphone in on computer, aux in on hifi etc). By putting the photocell on the bottom of the fan and a light source above the fan you could get some interesting results. The speed of the fan would create an oscillation, also the 'brightness' (pitch of harmonic content) of the oscillator could be adjusted by changing the intensity of the overhead light source. Amos is right, you could use a very similar circuit to the one in my Posc, I'll draw up an example just give me a mo....&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-01-18T13:53:15.343" CommentCount="3" />
  <row Id="1493" PostTypeId="2" ParentId="1485" CreationDate="2010-01-18T14:15:02.833" Score="0" ViewCount="" Body="&lt;p&gt;Sorry it's not too clear, but you should get the idea, just ask if you wanna know more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i19.servimg.com/u/f19/14/39/80/39/photo%5F10.jpg&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-01-18T14:15:02.833" CommentCount="8" />
  <row Id="1494" PostTypeId="1" AcceptedAnswerId="1496" CreationDate="2010-01-18T15:20:12.047" Score="5" ViewCount="149" Body="&lt;p&gt;I'm trying to find a powerful MCU that has multiple analogue to digital converters. I want around a 14 bit resolution to do some serious audio sampling.&#xA;Any suggestions or comments would be great, cheers.   &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-01-18T20:22:52.710" CommunityOwnedDate="2010-01-18T15:20:12.047" Title="What MCU, need hi res ADCs?" Tags="&lt;microcontroller&gt;&lt;adc&gt;" AnswerCount="2" />
  <row Id="1495" PostTypeId="2" ParentId="1494" CreationDate="2010-01-18T16:38:12.950" Score="12" ViewCount="" Body="&lt;p&gt;If you REALLY require 14 bit resolution then doing conversions on the MCU is probably not a good idea.  Maintaining signal conversion to this sort of accuracy is not a trivial undertaking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Highly sensitive analogue circuitry on the same silicon as the MCU with all its clocks and associated noise sources is not a good combination - that is one reason why most MCUs have 10 or 12 bit ADCs.  Another reason is that the silicon process used for the MCU is optimised for high speed digital signals.  This process does not work so well for high accuracy analogue processing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are wanting to process analogue signals to this level of resolution then you should keep the analogue signals away from the digital sections, with their own converters, low noise reference and quiet power supply rails so that you do not add noise to the signal being analysed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember, if your analogue signal has a peak value of 1V (corresponding to adc full scale) then each bit is only 60uV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In addition, you really need to have a handle on your power supply and might want to consider a separate supply for the analog side and the DC side.  It might be overkill if your supply is designed right, but if not you could easily have several &quot;bits&quot; of discrepancy due to voltage ripple and the micro and other components making small but meaningful changes on the load and the supply voltage of their own.  Remember, the higher the resolution the larger those fluctuations are.&lt;/p&gt;&#xA;" OwnerUserId="400" LastEditorUserId="11" LastEditorDisplayName="" LastEditDate="2010-01-18T18:04:07.367" LastActivityDate="2010-01-18T18:04:07.367" CommunityOwnedDate="2010-01-18T16:38:12.950" CommentCount="2" />
  <row Id="1496" PostTypeId="2" ParentId="1494" CreationDate="2010-01-18T16:53:00.363" Score="7" ViewCount="" Body="&lt;p&gt;Use a serial ADC (preferably SPI-based). There are many good 14 or 16 bit ADCs (I like the 14-bit &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tlc3541.html&quot; rel=&quot;nofollow&quot;&gt;TLC3541&lt;/a&gt; -- you can substitute with the TLC4541 for 16bits, or TLV2541 for 12bits) that are very easy to use with a microcontroller that you are already familiar with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many microcontrollers have SPI master peripherals, and even if yours doesn't, SPI is really easy to control via bitbanging. &lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-01-18T16:53:00.363" CommunityOwnedDate="2010-01-18T16:53:00.363" CommentCount="2" />
  <row Id="1497" PostTypeId="1" CreationDate="2010-01-18T18:47:37.800" Score="2" ViewCount="1148" Body="&lt;p&gt;&lt;img src=&quot;http://farm3.static.flickr.com/2794/4277616111%5F1e8e96c5cf.jpg&quot; alt=&quot;AVRISP MKII Custom  Enclosure&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a AVRISP MKII that I wish to program avr chips with through avrstudio 4 with.  However on the &quot;select platform&quot; the only think that resembles MKII is JTAGICE MKII which is not what I have?  Am I missing something here?  When I plug in the AVRISP MKII the drivers are all working and says it &quot;sees&quot; the device at least in windows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ril3y&lt;/p&gt;&#xA;" OwnerUserId="29" LastActivityDate="2010-01-18T22:35:59.783" Title="AVRISP MKII does not appear in AVRStudio 4 (latest build 4.18 SP1)" Tags="&lt;avr&gt;" AnswerCount="2" />
  <row Id="1498" PostTypeId="2" ParentId="1148" CreationDate="2010-01-18T19:15:51.797" Score="1" ViewCount="" Body="&lt;p&gt;I think your best bet is to import the netlist into Eagle, then get everything sorted back out into a usable schematic.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-01-18T19:15:51.797" />
  <row Id="1499" PostTypeId="2" ParentId="1497" CreationDate="2010-01-18T19:35:28.020" Score="2" ViewCount="" Body="&lt;p&gt;Programmer selection in AVRStudio is user experience nightmare.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you going to Tools -&gt; Program AVR -&gt; Connect ?&#xA;And in the &quot;Platform&quot; list you should see &quot;AVRISP mkII&quot; as one of the options with &quot;USB&quot; as the only available port.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This should appear whether or not you have the programmer plugged in.  If you're missing it, it sounds like you may have an incomplete install of AVRStudio.  (I don't recall, but I think AVRStudio might install a USB driver or two during its install)&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-01-18T19:35:28.020" />
  <row Id="1500" PostTypeId="2" ParentId="1489" CreationDate="2010-01-18T20:12:04.307" Score="2" ViewCount="" Body="&lt;p&gt;&lt;code&gt;A minus B minus 1&lt;/code&gt; is used for subtraction, and the complement of the carry flag can be viewed as a borrow flag.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-01-18T20:12:04.307" CommentCount="2" />
  <row Id="1502" PostTypeId="2" ParentId="1497" CreationDate="2010-01-18T22:35:59.783" Score="2" ViewCount="" Body="&lt;p&gt;The menu you are currently in is for selecting which emulator/simulator/debugger. AVRISP MKII doesn't support that, it's &quot;only&quot; a programmer. So simply pick whatever option in that menu, then later, pick the programmer in a different menu.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-18T22:35:59.783" />
  <row Id="1503" PostTypeId="2" ParentId="1487" CreationDate="2010-01-19T23:43:59.833" Score="3" ViewCount="" Body="&lt;p&gt;Hi Angryhacker;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your question stirred some cobwebs deep in the recesses of my dusty brain. I seem to remember building such a thing myself way back when. I don't remember the specifics, but if I recall correctly, we used RC filters to segment the incoming audio signal and SCRs to trigger short strings of 110V AC Christmas lights. Probably a transistor to drive the SCR. These things were all the rage, along with strobe lights, back in the late 70's.&lt;/p&gt;&#xA;" OwnerUserId="425" LastActivityDate="2010-01-19T23:43:59.833" CommentCount="1" />
  <row Id="1504" PostTypeId="1" CreationDate="2010-01-20T18:31:47.173" Score="9" ViewCount="1167" Body="&lt;p&gt;I'm looking for some not too expensive, easy to control color graphics LCD I can use for various hobby projects, along with an AVR microcontroller or maybe an ARM in the future. The cheaper the better, but I want to be able to either control it with a serial connection, or a low-speed parallel connection. Some LCDs require multiple MHz parallel control signals to drive each pixel individually, I probably can't manage that with a single AVR. This unfortunately rules out super cheap LCDs like replacement Nintendo DS LCDs or whatever. Recommendations on LCDs that you've personally used &amp;amp; liked will be especially appreciated. Thanks.&lt;/p&gt;&#xA;" OwnerUserId="131" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T06:56:10.160" LastActivityDate="2011-01-29T06:56:10.160" Title="Easily controlled color LCD for hobby projects?" Tags="&lt;avr&gt;&lt;lcd&gt;&lt;display&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="1505" PostTypeId="2" ParentId="1504" CreationDate="2010-01-21T16:58:05.920" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8600&quot; rel=&quot;nofollow&quot;&gt;This LCD assembly&lt;/a&gt; works with serial commands and is only about $35 [USD].  There are other options as well, but even once you get past the command set, interfacing to small LCDs physically is difficult due to the FPC connectors they use.  If that is not a problem, you might find more variety with low cost color displays from &lt;a href=&quot;http://www.newhavendisplay.com/&quot; rel=&quot;nofollow&quot;&gt;Newhaven Display International&lt;/a&gt;.  I've used two of their products so far.  Digikey carries some of them, but some seem to have a large minimum order quantity, so you might have to order directly from newhaven.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-01-21T16:58:05.920" CommentCount="2" />
  <row Id="1506" PostTypeId="1" CreationDate="2010-01-21T23:55:26.617" Score="3" ViewCount="763" Body="&lt;p&gt;I am using Arduino and Ardumoto dc motor controller to drive a DC motor. I am kind of at lost because i have gone through 10 different motors. They either don't work( not enough power ) or not powerful enough to drive the robot. Can anyone tell me, max voltage and amps provided to the motors AFAIK power to the motors are supplied through VIN pin? and are there any way to supply my own power and still use ardumoto to control the dc motor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9213&quot; rel=&quot;nofollow&quot;&gt;Ardumoto - Motor Driver Shield&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="496" LastActivityDate="2010-01-22T11:41:03.737" Title="Arduino Ardumoto" Tags="&lt;arduino&gt;&lt;motor&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="1507" PostTypeId="2" ParentId="1506" CreationDate="2010-01-22T00:12:47.537" Score="2" ViewCount="" Body="&lt;p&gt;Refer to the data sheet.  50v max at 2 amp ( or anything less ) This is like 100 watts.  The board ( chip ) should have its own power supply capable of what ever voltage your motor needs at 2 amp ( per channel I think or 4 amp total )  100 wats is about 1/8 hp. Should drive a small robot.  What is the size and weight of your robot.  Can you drive the motor directly off a power supply?&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-01-22T00:12:47.537" CommentCount="1" />
  <row Id="1508" PostTypeId="1" AcceptedAnswerId="1509" CreationDate="2010-01-22T07:14:10.690" Score="5" ViewCount="339" Body="&lt;p&gt;I'm thinking about putting together something simple for my young son's soccer team. I'd like to build a simple circuit that could be placed on/underneath the laces of their shoes and plays a sound when the kids kick the ball on the laces.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas on what would be the simplest route to do something like this? I'm wondering what kind of contact sensor would work best and how bulky I'd have to make things to produce a sound loud enough for the kids to hear. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for any advice!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tom&lt;/p&gt;&#xA;" OwnerUserId="365" LastActivityDate="2010-01-31T01:14:50.467" Title="Simple (?) pressure activated sound" Tags="&lt;sound&gt;&lt;sensor&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="1509" PostTypeId="2" ParentId="1508" CreationDate="2010-01-22T10:32:46.177" Score="4" ViewCount="" Body="&lt;p&gt;A Piezoelectric sensor is enough for the detection of a kick.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Piezoelectric%5Fsensor&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Piezoelectric_sensor&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are cheap, easy to attach to a shoe and you can even use it as a buzzer to produce the sound. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This simple circuit will help you:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.discovercircuits.com/DJ-Circuits/motionalarm2.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.discovercircuits.com/DJ-Circuits/motionalarm2.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.discovercircuits.com/DJ-Circuits/images/MOTIONALARM2.jpg&quot; alt=&quot;alt text&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="198" LastActivityDate="2010-01-22T10:32:46.177" CommentCount="3" />
  <row Id="1510" PostTypeId="2" ParentId="1506" CreationDate="2010-01-22T11:41:03.737" Score="2" ViewCount="" Body="&lt;p&gt;You could drive the motors with a separate power supply, then you can use a Darlington pair NPN transistor on the Arduino output pin, when the output switches on, the transistor supplies the necessary power to the motors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your wanting to use a single power supply, you could have a more suitable ac/dc PSU for the motors, then you can get a dc/dc converter to lower the voltage for powering your Arduino. &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-01-22T11:41:03.737" />
  <row Id="1511" PostTypeId="1" CreationDate="2010-01-22T16:14:29.820" Score="3" ViewCount="1012" Body="&lt;p&gt;This maybe a very stupid question but, how much power is available via Vin pin? I am assuming it is 5 volts, but how much amps are provided?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to run a dc motor using ardumoto shield, AFAIK it gets power from vin, arduino is connected to a power source that provides 9v 2amps, so i am assuming say if i have x volts and y amps on the vin pin, i can get a motor according to this spec?&#xA;&lt;a href=&quot;http://chiphacker.com/questions/1506/arduino-ardumoto&quot; rel=&quot;nofollow&quot;&gt;in this&lt;/a&gt; question someone said ardumoto supports up to 50v and 2 amps, i am trying to figure out how pass more current to the driver shield to run a dc motor in a RC car.&lt;/p&gt;&#xA;" OwnerUserId="496" LastEditorUserId="496" LastEditorDisplayName="" LastEditDate="2010-01-22T18:29:04.230" LastActivityDate="2010-01-23T21:30:33.423" Title="Arduino Vin Pin" Tags="&lt;arduino&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="1512" PostTypeId="2" ParentId="1511" CreationDate="2010-01-22T16:33:49.080" Score="3" ViewCount="" Body="&lt;p&gt;Vin pin is connected directly to the external power supply you use (if you are not powering from USB). Voltage is therefore down to the the supply itself. Amps available is also down to the supply (less a bit for the Arduino consumption). In general I would not advise drawing more than 1 amp through the board - if you need that sort of power then you should be connecting directly to power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are powering from USB then there is nothing on Vin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you (say) use a power adapter giving 9V and 2A then you will get 9V and a little under 2A, say 1.9A at the Vin pin.&lt;/p&gt;&#xA;" OwnerUserId="9" LastEditorUserId="9" LastEditorDisplayName="" LastEditDate="2010-01-23T21:30:33.423" LastActivityDate="2010-01-23T21:30:33.423" CommentCount="4" />
  <row Id="1513" PostTypeId="2" ParentId="1508" CreationDate="2010-01-22T17:49:38.553" Score="2" ViewCount="" Body="&lt;p&gt;I'd try something simpler - you just want to detect when the ball presses on top of the foot, which would require nothing more than a large, thin pushbutton.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not many off the shelf solutions for that, but you can take a small surface mount pushbutton, sandwich it between two pieces of plastic, and then the plastic surface becomes the pushbutton.  You can make this plastic disc as large or as small as you want, which will determine how precisely the soccer player must hit the ball to trigger it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should be less susceptible to false positives than many other shock detection solutions such as piezo or accelerometers, which might also be triggered with a particularly hard kick that isn't on the surface of the shoe.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-01-22T17:49:38.553" CommentCount="1" />
  <row Id="1514" PostTypeId="1" CreationDate="2010-01-23T20:55:54.280" Score="3" ViewCount="335" Body="&lt;p&gt;Hello, everyone!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Background information:&lt;br /&gt;&#xA;I tried hard to get a Schmitt-trigger working, but it kept failing. By accident I figured out, that my AC-to-DC adapter produces a very irregular voltage output (I could hear the 50Hz very clearly). After putting a strong electrolyte capacitor (over 4000 microF) on the DC output, it started working.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I'm asking myself, if the DC output it stable enough that way, or if I could experience difficulties in the future when building (let's say) a radio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are common ways of stabilizing the DC output of such an adapter?&lt;/p&gt;&#xA;" OwnerUserId="491" LastActivityDate="2011-05-13T12:49:42.647" Title="How to deal with a DC adapter with irregular voltage output?" Tags="&lt;adapter&gt;&lt;dc&gt;&lt;frequency&gt;&lt;capacitor&gt;" AnswerCount="5" />
  <row Id="1515" PostTypeId="2" ParentId="1514" CreationDate="2010-01-23T21:16:00.503" Score="2" ViewCount="" Body="&lt;p&gt;Sparkfun has a good &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial%5Finfo.php?tutorials%5Fid=57&quot; rel=&quot;nofollow&quot;&gt;tutorial on power supplies&lt;/a&gt; that covers these types of issues.&lt;/p&gt;&#xA;" OwnerUserId="347" LastActivityDate="2010-01-23T21:16:00.503" />
  <row Id="1516" PostTypeId="2" ParentId="1514" CreationDate="2010-01-23T22:22:18.533" Score="2" ViewCount="" Body="&lt;p&gt;In my understanding, the more load you draw off a power supply, the less effective a particular-sized capacitor will be at stabilising the voltage. So, if you had a low load, the current capacitor might be fine, but if the &quot;radio&quot; had a decent amplifier and speaker incorporated the load might be enough to reduce the capacitor's effectiveness and cause noise to make its way into the circuit. The solution in that case is to increase the capacitor size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the DC output from the adapter is higher than what is needed in the circuit, another option that will help stabilise the output is to regulate the voltage down as required, after the capacitor, using a standard voltage regulator.&lt;/p&gt;&#xA;" OwnerUserId="25" LastActivityDate="2010-01-23T22:22:18.533" />
  <row Id="1517" PostTypeId="2" ParentId="1514" CreationDate="2010-01-23T23:54:21.597" Score="8" ViewCount="" Body="&lt;p&gt;What is the voltage and current rating of the supply? Is there any other load on the&#xA;supply? Is the supply a regulated or unregulated supply?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most of these supplies require a minimum load before the output voltage is within&#xA;a specified range. Other than the schmitt-triger was there any other load on the&#xA;supply? If not you are probably not loading the supply to the specified minimum&#xA;current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In most applications these supplies are followed with a linear regulator to provide a stable voltage. You still need a minimum load and some filtering capacitors. 4000uF is excessive and possibly dangerous. Typical capacitors are in the 1-100uF range. &#xA;The size and type of capacitor is dependent on the linear regulator. Follow the manufacturers ecommendation exactly. Some devices have very specific capacitance and ESR (effective series resistance) requirements.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:49:42.647" LastActivityDate="2011-05-13T12:49:42.647" CommentCount="3" />
  <row Id="1518" PostTypeId="2" ParentId="1514" CreationDate="2010-01-24T14:55:01.570" Score="2" ViewCount="" Body="&lt;p&gt;Make sure you use a power supply which is properly regulated for your application. (jluciani's comments are good ones) Ripple voltage should be one of the specs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's not good enough for your purposes, get a different one -- you can't really fix a power supply in a way that's guaranteed to work in all cases.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-01-24T14:55:01.570" />
  <row Id="1519" PostTypeId="2" ParentId="1487" CreationDate="2010-01-24T16:38:53.533" Score="1" ViewCount="" Body="&lt;p&gt;Hi,&#xA;I might be able to help you with one of my latest projects. Take a look at my Blog and give me a shout if you are interested.&#xA;&lt;a href=&quot;http://www.mendingthings.com&quot; rel=&quot;nofollow&quot;&gt;www.mendingthings.com&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-01-24T16:38:53.533" CommentCount="1" />
  <row Id="1520" PostTypeId="2" ParentId="1388" CreationDate="2010-01-24T16:58:18.407" Score="3" ViewCount="" Body="&lt;p&gt;Just a note, pull the solder away from the joint before removing the iron.&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-01-24T16:58:18.407" />
  <row Id="1521" PostTypeId="2" ParentId="1409" CreationDate="2010-01-24T17:04:52.947" Score="3" ViewCount="" Body="&lt;p&gt;Sometimes it is best to run a wire between the two nearest solder pads along that trace rather than try to fix it in a very tight area. If you do this then put a few drops of super glue on the wire after you are done to hold it in place and prevent vibration from breaking the connections.&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-01-24T17:04:52.947" />
  <row Id="1522" PostTypeId="2" ParentId="952" CreationDate="2010-01-24T17:11:41.280" Score="1" ViewCount="" Body="&lt;p&gt;I have a new Blog, &lt;a href=&quot;http://www.mendingthings.com&quot; rel=&quot;nofollow&quot;&gt;www.mendingthings.com&lt;/a&gt; not a lot of content yet but I will keep adding. Someone has already mentioned HackADay. That is a great blog.&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-01-24T17:11:41.280" CommunityOwnedDate="2010-01-24T17:11:41.280" />
  <row Id="1523" PostTypeId="2" ParentId="952" CreationDate="2010-01-24T19:37:38.273" Score="1" ViewCount="" Body="&lt;p&gt;I have collected many blogs about electronics over the three years and I have made an aggregated list of RSS feeds available through &lt;a href=&quot;http://www.google.com/reader/shared/user/12805417219521926745/label/public%5Felectronics&quot; rel=&quot;nofollow&quot;&gt;Google Reader&lt;/a&gt;. Most of the blogs in this list are already mentioned here here but you might encounter some less familiar ones. I have also linked this feed to a &lt;a href=&quot;http://www.twitter.com/knurdstuff&quot; rel=&quot;nofollow&quot;&gt;twitter account&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2010-01-24T19:37:38.273" CommunityOwnedDate="2010-01-24T19:37:38.273" CommentCount="1" />
  <row Id="1524" PostTypeId="2" ParentId="1454" CreationDate="2010-01-25T06:06:00.567" Score="2" ViewCount="" Body="&lt;p&gt;Owon standalone oscilloscopes are pretty cheap (25MHz less than $200 if ordered from the manufacturer) and quite good for their price. &lt;a href=&quot;http://www.owon.com.cn/eng/pdsSeries.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.owon.com.cn/eng/pdsSeries.asp&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="13" LastActivityDate="2010-01-25T06:06:00.567" CommentCount="1" />
  <row Id="1525" PostTypeId="2" ParentId="310" CreationDate="2010-01-25T21:19:51.027" Score="4" ViewCount="" Body="&lt;p&gt;Can't you just use a standard &lt;a href=&quot;http://en.wikipedia.org/wiki/Crystal%5Foscillator&quot; rel=&quot;nofollow&quot;&gt;crystal oscillator&lt;/a&gt; circuit, like the &lt;a href=&quot;http://en.wikipedia.org/wiki/Pierce%5Foscillator&quot; rel=&quot;nofollow&quot;&gt;Pierce oscillator&lt;/a&gt;, and drive the piezo at its natural resonant frequency?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a circuit for an &lt;a href=&quot;http://www.repairfaq.org/sam/samschem.htm#schahv5&quot; rel=&quot;nofollow&quot;&gt;ultrasonic cleaner&lt;/a&gt;, which would seem to be the same principle as your vaporizer.  You can also look at &lt;a href=&quot;http://www.google.com/patents?id=das0AAAAEBAJ&quot; rel=&quot;nofollow&quot;&gt;patents&lt;/a&gt; for things like ultrasonic humidifiers, atomizer, nebulizer, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No matter what you use, you should have a resonant inductor in series with the piezo to get the hundreds of volts to drive it.  &lt;a href=&quot;http://www.techmind.org/sl/#electric&quot; rel=&quot;nofollow&quot;&gt;http://www.techmind.org/sl/#electric&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Surely a microcontroller is overkill when the micro has exactly this kind of oscillator inside it to run the clock.  You'd be using a crystal oscillator to drive a computer to drive a crystal oscillator.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-01-25T21:31:03.130" LastActivityDate="2010-01-25T21:31:03.130" CommentCount="1" />
  <row Id="1526" PostTypeId="1" CreationDate="2010-01-26T04:25:15.737" Score="1" ViewCount="893" Body="&lt;p&gt;Can you program a PICAXE microcontroller with an Arduino Duemilanove&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe with the ICSP (6 pin) header?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2010-05-12T10:48:48.423" Title="Programming a PICAXE with an Arduino" Tags="&lt;arduino&gt;&lt;picaxe&gt;" AnswerCount="2" />
  <row Id="1527" PostTypeId="1" CreationDate="2010-01-26T04:39:51.420" Score="5" ViewCount="669" Body="&lt;p&gt;I want to create an Arduino Weather Station with&#xA;Temperature&#xA;Rain Gauge&#xA;Wind Speed&#xA;Wind Direction&#xA;Humidity&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What peripherals should I be looking at getting?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally I want this project to tweet the results - how do I do this?&lt;/p&gt;&#xA;" OwnerUserId="337" LastActivityDate="2010-02-01T17:32:28.423" Title="Arduino Tweeting Weather Station" Tags="&lt;arduino&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="1528" PostTypeId="2" ParentId="1527" CreationDate="2010-01-26T05:15:23.573" Score="2" ViewCount="" Body="&lt;p&gt;Sparkfun has a pretty comprehensive weather meter package that sounds like what you want &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8942&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and as for tweeting it depends on where it is if you have WiFi you can get a wifi shield or if you have ethernet and ethernet shield or if none of these are available you can use a cell phone data connection.&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2010-01-26T05:15:23.573" />
  <row Id="1529" PostTypeId="2" ParentId="1397" CreationDate="2010-01-26T15:24:08.407" Score="2" ViewCount="" Body="&lt;p&gt;A circuit like sketched below shurly will work too.&#xA;The two diodes clamp the voltage against VCC and GND and the Resistor limits the current&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;&#xA;------------------------*-------- VCC&#xA;                        | &#xA;            	       ---&#xA;             	        ^&#xA;                       / \&#xA;                       ---&#xA;             ----       |&#xA;Ext Input --|    |------*-------- Arduino Input&#xA;             ----       |&#xA;             10k        |&#xA;           	       ---&#xA;    	                ^&#xA;    	               / \&#xA;    	               ---&#xA;    		        |&#xA;------------------------*-------- GND   		 &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="495" LastActivityDate="2010-01-26T15:24:08.407" />
  <row Id="1530" PostTypeId="1" AcceptedAnswerId="1534" CreationDate="2010-01-26T17:32:59.633" Score="3" ViewCount="529" Body="&lt;p&gt;More components are only available in SMD packages. &#xA;For hobbyist assembly the options are to buy breakout boards or &#xA;solder SMD.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since components are usually packaged in a couple of SMD&#xA;package types I am trying to put together a set of guidelines&#xA;for choosing packages that are compatible with hobbyist&#xA;skills and tools. I would consider hobbyist level tools for SMD&#xA;assembly as -- soldering iron in the $50-$100 range (new), &#xA;for magnification a $40 visor (like the B&amp;amp;L) and tweezers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the kits I make now I use the following guidelines --&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Passives 0805 or larger&lt;/li&gt;&#xA;&lt;li&gt;Min Lead Pitch for SOIC or QFP -- 0.5mm&lt;/li&gt;&#xA;&lt;li&gt;No QFN, LGA or BGA&lt;/li&gt;&#xA;&lt;li&gt;Prefered package for gates, BJT, FET --- SOT23&lt;/li&gt;&#xA;&lt;li&gt;Diodes SOD123 (or larger)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I am interested in recommendations on component selection,&#xA;minimum tool requirements and assembly issues. &#xA;Specific tool changes (like solder tip size) that enabled you to do SMD assembly with your existing tools would be useful too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-08T00:49:57.863" LastActivityDate="2011-01-08T00:49:57.863" Title="Sizing SMD components for Hobbyist Kits" Tags="&lt;soldering&gt;&lt;surface-mount&gt;&lt;pcb-assembly&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="1531" PostTypeId="1" AcceptedAnswerId="1532" CreationDate="2010-01-26T19:16:30.663" Score="2" ViewCount="179" Body="&lt;p&gt;Hi,&#xA;I need a really small 2-pin connector, a cable connector on one side, and a surface-mount jack on the other.  These two items at AllElectronics are pretty close:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://www.allelectronics.com/make-a-store/item/SBC-1/SMALL-BATTERY-CONNECTOR-WHITE/-/1.html&quot; rel=&quot;nofollow&quot;&gt;Small Battery Connector, 2mm spacing&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://www.allelectronics.com/make-a-store/item/SBH-1/HEADER-FOR-SMALL-BATTERY-CON-2MM-SPACING-WHITE/-/1.html&quot; rel=&quot;nofollow&quot;&gt;Header for Small Battery Connector&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;What is the general name for these two items, so I can search Digikey or Molex?  And anyone know the exact part numbers of the above parts?  (AllElectronics doesn't know)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As per jluciani's awesome answer, these are definitely JST parts.  Mouser doesn't carry JST, but &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=455-1704-ND&quot; rel=&quot;nofollow&quot;&gt;Digikey does&lt;/a&gt; as does AlliedElec.   And it looks like &lt;a href=&quot;http://www.jst.com/&quot; rel=&quot;nofollow&quot;&gt;JST&lt;/a&gt; makes SMT variants of the PCB mount header as well as small pitch connectors too.&lt;/p&gt;&#xA;" OwnerUserId="215" LastEditorUserId="215" LastEditorDisplayName="" LastEditDate="2010-01-26T21:16:10.970" LastActivityDate="2011-05-16T10:35:05.860" Title="Help with connector part numbers" Tags="&lt;connector&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="1532" PostTypeId="2" ParentId="1531" CreationDate="2010-01-26T19:28:21.267" Score="6" ViewCount="" Body="&lt;p&gt;Those are headers and receptacles. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The parts in the pictures look like the common 2mm battery connectors&#xA;made by JST. If those connectors will work then I would search&#xA;for JST and 2 pins and 2mm pitch. The exact pn's for the TH&#xA;parts should be&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;B2B-PH-K-S for a top entry header&lt;/li&gt;&#xA;&lt;li&gt;S2B-PH-K-S for a side entry header&lt;/li&gt;&#xA;&lt;li&gt;PHR-2 for a cable mount recptacle (without contacts)&#xA;The contacts are SPH-002T-P0.5L for the 24-28AWG crimp&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You may want to double check those pn's at Digikey and Mouser.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connectors are one place where all the search engines fall short.&#xA;The printed catalog can sometimes be a lot quicker.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:35:05.860" LastActivityDate="2011-05-16T10:35:05.860" CommentCount="4" />
  <row Id="1533" PostTypeId="2" ParentId="1526" CreationDate="2010-01-26T22:15:23.017" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://forums.adafruit.com/viewtopic.php?f=24&amp;amp;p=70039&quot; rel=&quot;nofollow&quot;&gt;This post&lt;/a&gt; on the Adafruit Forum would suggest not. I've used PICAXE's a bit, but not extensively (I felt restricted using BASIC) but usage boils down to the following.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PICAXE's contain bootstrap code which simplifies programming of them, basically as long as they have power being supplied you need three wires to program them, here's a diagram for an 08 chip:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.thebackshed.com/Windmill/articles/images/PicAxeCircuit.gif&quot; alt=&quot;Programming circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The USB cable which they supply (AXE 027) contains a circuit in the molded USB plug which converts the signal to what the circuit needs (I think the Serial version doesn't require any conversion).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The software supplied (either the Windows based Programming Editor or the AxePad Editor which works on Linux too) allows for programming in BASIC, which it then converts to Hex. This is then loaded onto the chip using the cable/bootstrap code, whichever editor is used the type of chip is detected prior to the Hex being uploaded, probably prior to it being compiled in fact.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Programming a PICAXE using a normal programmer will erase the bootstrap code thus reverting it to being a standard PIC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can find a way of using the Duemilanove to program a PIC then you may be able to modify this to enable PICAXEs to be programmed the same way (since PICAXEs are just PICs plus the bootstrap code). I've had a quick Google for it and nothing obvious leaps out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt; In response to Tom Hargrave's question, the PICAXE website is here: &lt;a href=&quot;http://www.rev-ed.co.uk/&quot; rel=&quot;nofollow&quot;&gt;http://www.rev-ed.co.uk/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have lots of different options, there may be something there that meets your requirements, if not then post back here and we'll see what we can do. I have an Experimenter Kit which was about £30 or £40 and can take most if not all sizes of PICAXE, setting up the programming circuit on a breadboard is quite straightforward though and the cables are quite cheap.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-05-12T10:48:48.423" LastActivityDate="2010-05-12T10:48:48.423" />
  <row Id="1534" PostTypeId="2" ParentId="1530" CreationDate="2010-01-26T23:31:05.423" Score="7" ViewCount="" Body="&lt;p&gt;0603 isn't too bad to solder by hand (I won't do 0402 or smaller though).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SOT23 is probably a good guideline (for diodes too, not just transistors); there are some SOT323s that are smaller that are a pain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would avoid certain SOT23-6 parts because it can be very difficult to determine which way the package is supposed to go. (For some dual MOSFET packages it doesn't matter.) We had one where there was a slight bevel along one edge. Grrr.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also avoid SOD123 because of the backwards nature, if possible. SMA/SMB/SMC aren't as much of a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And avoid those cylindrical diodes (LL-34 / MELF) like the plague! they will roll off the board.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-01-26T23:31:05.423" CommentCount="3" />
  <row Id="1535" PostTypeId="2" ParentId="1530" CreationDate="2010-01-27T00:29:41.210" Score="4" ViewCount="" Body="&lt;p&gt;As far as my skills, to add a point of data. Using a $40 soldering iron, and lots of flux (I have a 'pen' with the liquid kind inside), and the occasional desoldering braid.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Easy: 0805 passives , 0.7mm pitch ICs&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doable if careful, but have ruined a couple: 0603, 0.5mm pitch ICs&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Haven't tried smaller than those yet, I think that's about my limit.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-27T00:29:41.210" />
  <row Id="1536" PostTypeId="1" CreationDate="2010-01-27T05:58:39.950" Score="3" ViewCount="641" Body="&lt;p&gt;Has anyone used this data logger (or similar) with &lt;a href=&quot;http://www.obdev.at/products/vusb/index.html&quot; rel=&quot;nofollow&quot;&gt;v-usb&lt;/a&gt; to collect data?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9147&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9147&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If so, what is the maximum times per second voltage data can be sent at HID messages? (I can't understand the spec sheets)&#xA;And can it work with an ultrasonic rangefinder (or similar) also from sparkfun?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-05T22:54:23.083" LastActivityDate="2010-06-05T22:54:23.083" Title="AVR Stick Data Logger Usage" Tags="&lt;usb&gt;&lt;avr&gt;&lt;datalogger&gt;" AnswerCount="2" />
  <row Id="1537" PostTypeId="1" AcceptedAnswerId="1540" CreationDate="2010-01-27T07:49:32.573" Score="2" ViewCount="1119" Body="&lt;p&gt;Hi all - been using picaxe for a few years but now playign with arduino and trying to learn how it all works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a couple of arduinos talking via the HOPERF library successfully and now want to send some meaningful data over the link.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have the code for the DS18B20 running on the client aurduino and &quot;printing&quot; the temp value to the PC via USB but just not sure how to get it into the HOPERF commands to send over the RF.&#xA;Here is a bit of the code. The 2nd line is where the data is sent over the HOPERF.&#xA;What i need to do is replace the string &quot;test&quot; with the data returned by the (sensors.getTebyCByIndex(0)) command from the 4th line.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;sensors.requestTemperatures();            // Send the command to get temperatures&#xA;client.sendto(11, (uint8_t*)&quot;test\n&quot;, 6); // Includes the NUL at the end of the string&#xA;Serial.print(&quot;sending\n&quot;);&#xA;Serial.print(sensors.getTempCByIndex(0)); //prints the temp value over the USB&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Any clues anyone?? I prefer to learn but doing stuff like this - and yes i did do the &quot;BLINK&quot; thing first! I find doing something i find useful helps me learn faster :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am struggling a bit with working out the docs as there doesnt seem to be a nice &quot;manual&quot; liek the picaxes to follow :-(&lt;/p&gt;&#xA;" OwnerUserId="503" LastActivityDate="2010-01-28T05:56:46.357" Title="newbie code query =&gt; Arduino &amp; DS18B20" Tags="&lt;arduino&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="1538" PostTypeId="2" ParentId="1537" CreationDate="2010-01-27T10:41:46.103" Score="0" ViewCount="" Body="&lt;p&gt;What does sensors.getTempCByIndex(0) return? If it's a string you should be able to cast it in the same way as your test string. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not is it a number (float?), does the second argument to client.sendto() have to be a uint8_t*? Can you cast from one to the other? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you need to cast it? I don't know whether the client.sendto() function and whatever is receiving it are in the library or written by you. If you've written them, you could modify them to accept the type of value returned by sensors.getTempCByIndex(0), then you wouldn't need a cast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[EDIT (in response to the first two comments below)]I know that Arduino Sketches are a subset of C, but I'm not certain which bits of C work and which don't. There is a discussion &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1189536064&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; about casting a float (floating point number) to a string on the Arduino, but it appears to be saying that the method may be very memory intensive. A cast is basically when you change the type of a variable (eg float -&gt; string), in C you typically do this by putting the new type in brackets immediately preceding the variable to change.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at the code you've got:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;client.sendto(11, (uint8_t*)&quot;test\n&quot;, 6);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;which appears to be casting the string &quot;test\n&quot; (typically called a string literal) to a uint8_t*, which appears to be a pointer to an 8 bit wide byte of data or possibly the first byte of an array of uint8_t bytes. This whole function call I'm guessing is converting the string into 6 bytes to transmit with 6 being the length of string. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does the receiver automatically decode the message back to a string? The comments in the source code for your library appear to suggest that you can send any binary encoded data as the packet in your datagram/message, so rather than converting your existing float to a string you could convert the whole number part to an integer and send it, then take the first 2 or so digits of the decimal part and send them as an integer and then reconstruct the float at the far end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the bottom of &lt;a href=&quot;http://www.arduino.cc/playground/Code/LCD&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; there's mention of the standard C function itoa which is used to convert an integer (whole number) to an ascii string, if you can split your number into a whole number part and decimal part you can encode them using this as a string and concatenate them (computer programmer speak for join them together) into &quot;wholenumberstring&quot;+&quot;.&quot;+&quot;decimalstring&quot; and then put the resulting string into client.sendto() making sure that the final argument to client.sendto() is the length of the newly formed string. It also tells you on that page what the overhead will be in terms of memory of using different implementations of itoa.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A further thought, how is your temperature data coming into the Arduino? Do you get a float, or do you actually get an analogue value (eg in the range 0 to 255 depending on the resolution) which is then converted to a decimal value. It might be easier to send the raw data as a string over the link and convert it at the other end.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-01-27T15:01:08.423" LastActivityDate="2010-01-27T15:01:08.423" CommentCount="3" />
  <row Id="1539" PostTypeId="2" ParentId="1537" CreationDate="2010-01-27T17:46:27.673" Score="1" ViewCount="" Body="&lt;p&gt;You may want to spend some time learning C or C++ on a PC first, with a standard programming book/course, before you start adding more complex things like microcontrollers and RF links and USB and so on. Without a solid foundation, you will run into many problems like this where you'll get stuck on the most basic items. Of course, if your goal is just to quickly hack together this one item, and you don't want to spend time learning or plan to use these skills in the long term, then my suggestion might not be useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a random free book on C++: &lt;a href=&quot;http://www.mindview.net/Books/TICPP/ThinkingInCPP2e.html&quot; rel=&quot;nofollow&quot;&gt;Thinking in C++&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-01-27T17:46:27.673" CommentCount="3" />
  <row Id="1540" PostTypeId="2" ParentId="1537" CreationDate="2010-01-27T20:21:40.037" Score="2" ViewCount="" Body="&lt;p&gt;In C, just about any data type can be represented as an array of bytes.  Without getting into a complete course on data types and pointers in C (which I'm not really qualified to do, anyway), the following should work on the transmitting end:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;float tempC = sensors.getTempCByIndex(0);&#xA;client.sendto(11, (uint8_t *)&amp;amp;tempC, sizeof(tempC));&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;On the receiving end, you'd do something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;float tempC;&#xA;server.recv((uint8_t *)&amp;amp;tempC, sizeof(tempC));&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-01-27T20:21:40.037" CommentCount="5" />
  <row Id="1541" PostTypeId="1" CreationDate="2010-01-28T02:53:34.473" Score="2" ViewCount="129" Body="&lt;p&gt;As a sort of weird side project, I'd like to make an oven timer that has selectable food stuffs and associated timing information. Now while this device would be simple to make I would like to stick it on the oven which means it would have to deal with some significant but not ridiculous temperatures (gas oven, metal structure). Has anyone has any experience heat proofing things like HD44780 LCDs, AVRs and other delicate components or do I have to go and get hold of those military grade parts?&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-01-29T15:47:26.367" Title="Dealing with excess heat" Tags="&lt;heat-protection&gt;" AnswerCount="4" />
  <row Id="1542" PostTypeId="2" ParentId="1537" CreationDate="2010-01-28T05:56:46.357" Score="0" ViewCount="" Body="&lt;p&gt;Thanks all who contributed.&#xA;My code works and I have learnt about hardware serial, rf comms, software serial, cast, floats, serial LCD and dallas onewire all in 2 days :-)&lt;/p&gt;&#xA;" OwnerUserId="503" LastActivityDate="2010-01-28T05:56:46.357" />
  <row Id="1543" PostTypeId="1" CreationDate="2010-01-28T10:09:04.647" Score="3" ViewCount="77" Body="&lt;p&gt;I have been gifted about 2/3 of a reel (2000-ish) of these SOT-23 parts but I cannot locate any data for them.  Can anyone point me in the right direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Through the various datasheet sites I have determined that they are probably an N channel JFet that was obsoleted in 2007.  The local dealer in siliconix products was unable (or unwilling) to help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the label on the reel reads:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;        SILICONIX&#xA;17856             SSTC34-T1&#xA;G45004  (E10)     E9612&#xA;QA D/C Q9613E     QTY 3000&#xA;PHILIPPINES       30 MAR 96&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The case marking on these is C34&lt;/p&gt;&#xA;" OwnerUserId="505" LastActivityDate="2010-01-28T14:36:43.593" Title="Specs on Siliconix SSTC34-T1" Tags="&lt;datasheet&gt;&lt;surface-mount&gt;" AnswerCount="1" />
  <row Id="1544" PostTypeId="2" ParentId="1530" CreationDate="2010-01-28T10:58:45.780" Score="5" ViewCount="" Body="&lt;p&gt;I would recommend using a SMD rework tool for small projects, and a reflow oven (you can make one from a toaster oven) for larger boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reflow makes sense because you have far less problems with solder bridges and it's actually harder to destroy components.  Components tend to pull themselves into position, so placement of smaller components becomes less critical (than with soldering by hand).  0805 and 0603 are a breeze.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For reflow it makes sense if you have a tool to deposit accurate amounts of solder.  Using a syringe by hand and really a bad idea.  The smaller the component the more critical this is.&lt;/p&gt;&#xA;" OwnerUserId="505" LastActivityDate="2010-01-28T10:58:45.780" />
  <row Id="1545" PostTypeId="2" ParentId="1543" CreationDate="2010-01-28T13:18:05.313" Score="2" ViewCount="" Body="&lt;p&gt;A tough problem... it's very annoying that manufacturers &quot;unpublish&quot; their datasheets. I have had to go down this road, and I would recommend calling up the manufacturer's rep (Vishay Siliconix) and ask them if they can provide a datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit:&lt;/strong&gt; just noticed you mentioned the local siliconix dealer was unwilling to help. Do you mean a distributor or a sales rep? I'd get on the phone with someone (sales rep or tech support) direct from Vishay. If they still don't help, let us know; it's good to share pluses and minuses about various IC / component companies.&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2010-01-28T14:36:43.593" LastActivityDate="2010-01-28T14:36:43.593" CommentCount="1" />
  <row Id="1546" PostTypeId="2" ParentId="1541" CreationDate="2010-01-28T20:12:18.140" Score="2" ViewCount="" Body="&lt;p&gt;Do you really need to put the electronics in that environment? Couldn't you simply use high temperature wire for the sensors and such, then mount the electronics in a slightly cooler location? Not trying to be mister obvious here just asking to understand. An oven is a rather dangerous appliance to automate, not that it can't be done safely, just that you need to make sure you have proper fail safes and such. I have built some very large kilns that were gas fired so I do understand some of the challenges with dealing with the heat. I always tried to remove any electronics to a temperature friendly zone. &lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-01-28T20:12:18.140" CommentCount="3" />
  <row Id="1547" PostTypeId="2" ParentId="1541" CreationDate="2010-01-29T15:01:26.863" Score="1" ViewCount="" Body="&lt;p&gt;why not use some insulation between the electronics and the thing that sticks to the oven? e.g. take a square potholder, affix electronics to one side and an applicance magnet to the other side.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-01-29T15:01:26.863" CommentCount="1" />
  <row Id="1548" PostTypeId="2" ParentId="1408" CreationDate="2010-01-29T15:18:10.687" Score="2" ViewCount="" Body="&lt;p&gt;Decreasing the voltage going into the motor will cause it to go slower. As Jim said putting a resistor just before going into the motor is an excellent way but you will need to switch resistors each time you want to speed back up. Better then using just a regular resistor you may try a potentiometer which is a variable resistor. You use it the same way but you can turn the potentiometers up or down to give more speed or less&lt;/p&gt;&#xA;" OwnerUserId="507" LastActivityDate="2010-01-29T15:18:10.687" />
  <row Id="1549" PostTypeId="2" ParentId="1541" CreationDate="2010-01-29T15:46:18.727" Score="3" ViewCount="" Body="&lt;p&gt;Typical ovens with electronics use a back panel to place the electronic components on. Putting an additional panel above or to the side of this panel will provide the best location. Mark has a good point though test the temp experienced at the location you plan to put the project before you start to build. Each component you use should have a rating given by the manufacture of the max heat the component should be exposed to. You may also consider using an old pc fan to place in the enclosure to aid in keeping everything cool.&lt;/p&gt;&#xA;" OwnerUserId="507" LastActivityDate="2010-01-29T15:46:18.727" />
  <row Id="1550" PostTypeId="2" ParentId="1541" CreationDate="2010-01-29T15:47:26.367" Score="1" ViewCount="" Body="&lt;p&gt;There's always and only three ways for heat to transfer: radiation, conduction and convection.  Account for all three by shielding, isolating, and &quot;mitigating&quot;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, sticking electronics (of any kind) in an oven is not a great idea; out-gassing could occur with the plastic parts and thermal cycling is a great way to check the reliability of parts and their interconnects.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For temperatures above the 'normal' industrial range (say 70C), it's not just the military grade parts you'll need, but (perhaps) the ceramic PCBs, the heavy traces and bomb-proof assembly.  It's why they're so expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Much, much cheaper is what Mark B said, get the electronics outside, and just sense the temperature.&lt;/p&gt;&#xA;" OwnerUserId="483" LastActivityDate="2010-01-29T15:47:26.367" CommentCount="2" />
  <row Id="1551" PostTypeId="2" ParentId="1508" CreationDate="2010-01-29T16:27:51.217" Score="1" ViewCount="" Body="&lt;p&gt;PPVI solution is a good one in my opinion but you may use a 2032 watch battery instead of two AA batteries to reduce weight&lt;/p&gt;&#xA;" OwnerUserId="507" LastActivityDate="2010-01-29T16:27:51.217" />
  <row Id="1552" PostTypeId="1" AcceptedAnswerId="1555" CreationDate="2010-01-29T17:21:00.293" Score="4" ViewCount="613" Body="&lt;p&gt;This may be a lame question but, Speed controllers on big RC cars can they be controlled from Arduino? If yes, do they have a standart? do I control them using PWM values? What should i look for if I am going to buy one?&lt;/p&gt;&#xA;" OwnerUserId="496" LastActivityDate="2010-01-30T00:02:23.910" Title="Arduino Speed Controllers for RC Cars" Tags="&lt;arduino&gt;&lt;motor&gt;" AnswerCount="1" />
  <row Id="1553" PostTypeId="2" ParentId="1154" CreationDate="2010-01-29T18:16:04.880" Score="3" ViewCount="" Body="&lt;p&gt;Stepper motor would be perfect for what it sounds like you want to do. The typical drawback of a stepper is their slow speeds. Considering however that you said you want to go from slow to slower it would work&lt;/p&gt;&#xA;" OwnerUserId="507" LastActivityDate="2010-01-29T18:16:04.880" />
  <row Id="1554" PostTypeId="1" CreationDate="2010-01-29T20:11:23.700" Score="4" ViewCount="959" Body="&lt;p&gt;Hi, I found you via the Yahoo group for MSP430s. (&lt;a href=&quot;http://tech.groups.yahoo.com/group/msp430/message/21260&quot; rel=&quot;nofollow&quot;&gt;http://tech.groups.yahoo.com/group/msp430/message/21260&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was hoping you would share with me info on making my own board for programming. I recently came into a handful of MSP430F20xx that I'd like to play around with, but my student budget isn't offering me the option of purchasing a decent board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please and thanks for your time&lt;/p&gt;&#xA;" LastEditorUserId="985" LastEditorDisplayName="" LastEditDate="2010-07-20T18:38:55.633" LastActivityDate="2011-04-30T23:35:23.293" Title="MSP430 programmer" Tags="&lt;board&gt;&lt;msp&gt;&lt;msp430&gt;" AnswerCount="5" CommentCount="1" />
  <row Id="1555" PostTypeId="2" ParentId="1552" CreationDate="2010-01-30T00:02:23.910" Score="4" ViewCount="" Body="&lt;p&gt;They should be controlled by pwm, in particular the same pwm that is used for servos.  Typically built in pwm units are not accurate enough, instead interrupt driven timer routines are usually the way to go.  Should be lots of info on the web for arduino and servos.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-01-30T00:02:23.910" CommentCount="2" />
  <row Id="1556" PostTypeId="2" ParentId="1554" CreationDate="2010-01-30T14:44:36.687" Score="3" ViewCount="" Body="&lt;p&gt;Hmm. I don't quite see how you could beat US$99 for the &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/msp-fet430uif.html&quot; rel=&quot;nofollow&quot;&gt;MSP-FET430UIF&lt;/a&gt; USB debugging/programming interface from TI, or US$49 for the &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/msp-fet430pif.html&quot; rel=&quot;nofollow&quot;&gt;MSP-FET430PIF&lt;/a&gt; parallel-port debugging/programming interface, by trying to design/build/test something yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The MSP-FET430UIF also is part of TI's &lt;a href=&quot;http://focus.ti.com/general/docs/university/univ.tsp?templateId=5807&amp;amp;navigationId=10543&amp;amp;path=templatedata/cm/univgen/data/univ%5Fpricing%5Fovw&quot; rel=&quot;nofollow&quot;&gt;university discount program&lt;/a&gt; and is 50% off ($49.50 instead of the $99), not sure what the details to qualify, but contact your TI rep.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I like MSP430's; for a basic low-end microcontroller they have been the easiest series for me to use/debug because of the development tool set.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-01-30T14:44:36.687" CommentCount="1" />
  <row Id="1557" PostTypeId="2" ParentId="1554" CreationDate="2010-01-30T23:28:44.173" Score="7" ViewCount="" Body="&lt;p&gt;Also if you have a chance check out &lt;a href=&quot;http://goodfet.sf.net/&quot; rel=&quot;nofollow&quot;&gt;http://goodfet.sf.net/&lt;/a&gt; . Travis Goodspeed developed an MSP430 JTAG programmer that is completely open source. If you contact him via email he might send you some boards at which point all you need to do is gather the various components so that you can build it.&lt;/p&gt;&#xA;" OwnerUserId="373" LastActivityDate="2010-01-30T23:28:44.173" />
  <row Id="1558" PostTypeId="2" ParentId="1508" CreationDate="2010-01-31T01:14:50.467" Score="1" ViewCount="" Body="&lt;p&gt;I agree that the piezo sensor that PPVI suggested is a very cost effective way to go at less than $3 ea. However I would suspect it would not be discrete enough to distinguish between a ball being struck on the laces versus the toe or instep. I am a long time soccer coach as well and understand the precision you are looking for. Although it would be a much more expensive alternative I think you could use a softpot membrane potentiometer. Sparkfun has them for about $13ea. &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8680&quot; rel=&quot;nofollow&quot;&gt;Check them out Here&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However for the price difference you may want to try the piezo first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck and let us know how it works.&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-01-31T01:14:50.467" />
  <row Id="1559" PostTypeId="2" ParentId="1527" CreationDate="2010-02-01T17:32:28.423" Score="3" ViewCount="" Body="&lt;p&gt;Get yourself an Arduino board + ethernet shield. You'll need sensors (temperature, wind, humidity,...) aswell. You'll find a huge selection in your preffered online tech store. Then, learn some low level programming on Arduino, involving the ethernet library, code a small webclient and off you go. It's not rocket science ;)&lt;/p&gt;&#xA;" LastActivityDate="2010-02-01T17:32:28.423" />
  <row Id="1560" PostTypeId="2" ParentId="801" CreationDate="2010-02-03T10:09:08.677" Score="6" ViewCount="" Body="&lt;p&gt;For future reference, I've solved this problem. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Turns out the two USB cables I'd been trying to use have a high impedance (~6 ohms), when I used a cable with an impedance closer to 1 ohm it worked fine...&lt;/p&gt;&#xA;" OwnerUserId="378" LastActivityDate="2010-02-03T10:09:08.677" />
  <row Id="1561" PostTypeId="1" AcceptedAnswerId="1562" CreationDate="2010-02-03T17:00:45.363" Score="11" ViewCount="1006" Body="&lt;p&gt;How do I incorporate a hobby-style motor into a project, physically.  How do I mount it and connect a wheel to it?  (Assume that I have a working H-bridge or even switches, and am not concerned about how to use the motor electrically, just physically.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've purchased small, hobby style motors at various times.  Typically, they run on 1.5 V to 12 V, and many of them have no built-in gearing (and thus spin really fast with very low torque).  How do I connect a wheel to it, or a gear or pully?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, most motors of this sort are round.  Round!  If it was flat on one side, I could glue it down.  It looks like they are designed to be screwed into something at the front or back, but I don't know how I'd make a surface to mate to it nor make marks to drill holes through it precisely enough.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What have you found works for when you want to make an electronics project move around on its own?&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2010-02-23T19:49:08.567" Title="How do I physically work with a hobby motor?" Tags="&lt;motor&gt;&lt;mount&gt;" AnswerCount="5" FavoriteCount="3" />
  <row Id="1562" PostTypeId="2" ParentId="1561" CreationDate="2010-02-03T23:06:28.120" Score="11" ViewCount="" Body="&lt;p&gt;I would suggest you look at some shapelock. &lt;a href=&quot;http://shapelock.com/&quot; rel=&quot;nofollow&quot;&gt;Shapelock.com&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can mold any type of mount you want with this. You could also buy gearboxes that are designed to mount on these hobby motors. But as cheap as they are you may want to consider buying some with the gearbox already attached. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most hobby supply stores have assortments of wheels, sprockets, gears and pulleys for these or you can find them on ebay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck and let us know what you build.&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-02-03T23:06:28.120" CommentCount="4" />
  <row Id="1563" PostTypeId="1" AcceptedAnswerId="1567" CreationDate="2010-02-03T23:50:50.950" Score="3" ViewCount="1637" Body="&lt;p&gt;I have an Arduino (NG) board with an ATMEGA168 AVR micro. The board has a 6 pin ICSP header. Here is what I propose to do, please tell me if it is possible:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Remove current ATMEGA168 IC&lt;/li&gt;&#xA;&lt;li&gt;Replace with a new AT AVR of similar series&lt;/li&gt;&#xA;&lt;li&gt;Plug in the programmer to the ICSP header on the Arduino&lt;/li&gt;&#xA;&lt;li&gt;Use avrdude software to program the AVR&lt;/li&gt;&#xA;&lt;li&gt;Remove AVR and install in a socket on my project board and replace the original ATMEGA168 AVR&lt;/li&gt;&#xA;&lt;li&gt;Continue to use the Arduino as normal&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I have also thought about installing the 6 pin ICSP header on my project board so I can tweek the software with the chip in place. If I implement this part of the arduino circuit on my project would this be possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://mintmedia.co.nz/File:ATMEGA168%5FICSP%5Fschematic.png&quot; rel=&quot;nofollow&quot;&gt;Schematic&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="178" LastActivityDate="2010-02-09T03:27:42.267" Title="Using Arduino to program Amtel AVRs via ICSP header" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;avrdude&gt;&lt;prototyping&gt;" AnswerCount="3" />
  <row Id="1564" PostTypeId="2" ParentId="1563" CreationDate="2010-02-04T00:50:02.327" Score="1" ViewCount="" Body="&lt;p&gt;Would be much simpler to just program your ATMEGA directly via adding your own ICSP header. If you already have a standalone AVR programmer, all that's needed is to connect 4 pins from the programmer to the ATMEGA (the two power pins VCC/GND are not required if your ATMEGA already has its own power supply).&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-02-04T00:50:02.327" />
  <row Id="1565" PostTypeId="1" CreationDate="2010-02-04T02:02:00.153" Score="2" ViewCount="187" Body="&lt;p&gt;At my Company, we are using the BL2600 (&lt;a href=&quot;http://www.rabbit.com/products/bl2600/&quot; rel=&quot;nofollow&quot;&gt;Seen here&lt;/a&gt;) to create a new automation controller to replace our older controller. Rather than have electricians have to terminate wires into a Molex connector and snap on the side, we'd rather have boards snap into the sockets seen in the picture and then allow simple green screw-in connectors. How can we create this ourselves or purchase from somewhere?&lt;/p&gt;&#xA;" OwnerUserId="514" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-08-09T13:58:51.440" LastActivityDate="2011-05-17T12:55:08.363" Title="Develop Snap-On Board For Easy Connections - Rabbit SBC" Tags="&lt;pic&gt;" AnswerCount="1" />
  <row Id="1566" PostTypeId="2" ParentId="1565" CreationDate="2010-02-04T04:13:56.270" Score="3" ViewCount="" Body="&lt;p&gt;It looks like the receptacles are in parallel with the Molex connectors. &#xA;Is that true? Also it looks like the receptacles are top and bottom&#xA;entry. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If those are bottom entry then you could build a single interface&#xA;board that the Rabbit will plug into. The board would have long-pin&#xA;headers to interface to the Rabbit and screw terminals for your wires.&#xA;The interface board would also make replacing the Rabbit easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you sure Rabbit doesn't sell an accessory like this?&#xA;If you could purchase the board without the Molex connectors&#xA;you could probably solder on screw terminals.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:55:08.363" LastActivityDate="2011-05-17T12:55:08.363" CommentCount="5" />
  <row Id="1567" PostTypeId="2" ParentId="1563" CreationDate="2010-02-04T08:42:06.697" Score="2" ViewCount="" Body="&lt;p&gt;Adding your own ICSP header is easy, however your solution will work just fine, you are just using the Arduino board as a socket with an ICSP already wired up. If your programmer will supply power to the ATMega then do not power the Arduino board any other way (do not connect USB).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Further to Davr's answer - you must always attach ground, but you can leave the V+ free if your board is powered independently.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2010-02-04T08:42:06.697" />
  <row Id="1568" PostTypeId="2" ParentId="1561" CreationDate="2010-02-04T10:09:14.343" Score="7" ViewCount="" Body="&lt;p&gt;get some cardboard or even decent paper &amp;amp; push the axle through it without enlarging the hole. You may need to place masking tape to reinforce the hole once you've made it.  The idea here is to maintain the accuracy of the centre hole. After this get a pencil &amp;amp; rub it on the paper  so as to make a kind of 'picture' of the surface end of the motor, making sure you can see the mounting holes in the picture.  You can then use this paper as a  template to make a right-angle mounting bracket for it.  careful not to use too long a mounting screws into the end of the motor as they may foul the commutator brushes or the armature.  I find a good source of tiny little self-tappers in cheap import shops, not available separately but in carefully chosen throw-away cheap plastic toys etc.  Just choose yourself a toy with lotsa little screws! &lt;/p&gt;&#xA;" OwnerUserId="515" LastActivityDate="2010-02-04T10:09:14.343" CommentCount="1" />
  <row Id="1569" PostTypeId="2" ParentId="1554" CreationDate="2010-02-04T15:39:06.177" Score="1" ViewCount="" Body="&lt;p&gt;I've got one of those MSP-FET430UIF interfaces, it's an excellent piece of kit. I use it with Rowley CrossWorks under Windows 7 x64. It also works OK with the free IAR tools available from TI.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-02-04T15:39:06.177" />
  <row Id="1570" PostTypeId="2" ParentId="1324" CreationDate="2010-02-04T22:35:32.020" Score="2" ViewCount="" Body="&lt;p&gt;Futurlec has a few barometric sensor in the $5-10 range. These use I2C interface though, so a bit more involved in the MCU side than a simple analog voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.futurlec.com/Pressure_Sensors.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.futurlec.com/Pressure_Sensors.shtml&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're in Australia, you can buy from their Australian website as well.&lt;/p&gt;&#xA;" OwnerUserId="516" LastActivityDate="2010-02-04T22:35:32.020" />
  <row Id="1571" PostTypeId="1" CreationDate="2010-02-05T21:48:35.193" Score="3" ViewCount="369" Body="&lt;p&gt;i have a 1.25 to 28 V variable power supply I'm working on. here's the schematic:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.circuit-projects.com/power-supply/125v-to-25v-15a-lm317-power-supply.html&quot; rel=&quot;nofollow&quot;&gt;Schematic link&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'd like to do is put in a fan (12v 0.16A) so it runs when i turn it on, however&#xA;i don't know where to insert it so that it doesn't blow. I was also thinking of putting in a small bulb as an indicator light - when i turn it up, the light gets brighter. I have quite a few different rated lights, so i'm good for that, but still- don't know how to set it up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll be using a cheap multimeter as a voltmeter - i don't have a standalone voltmeter on it's own and they are quite expensive actually for something so simple.&lt;/p&gt;&#xA;" OwnerUserId="346" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T21:44:30.603" LastActivityDate="2011-06-03T12:32:10.537" Title="1.25-28V var. power supply mod" Tags="&lt;power-supply&gt;" AnswerCount="4" />
  <row Id="1572" PostTypeId="2" ParentId="1571" CreationDate="2010-02-05T22:53:16.293" Score="4" ViewCount="" Body="&lt;p&gt;You can get a simple LCD panel voltmeter from &lt;a href=&quot;http://futurlec.com/Panel%5FMeters.shtml&quot; rel=&quot;nofollow&quot;&gt;Futurlec&lt;/a&gt;, they have various models. The PM128E for $7.90 looks like it would do what you want. I'd suggest using this instead of trying to use the brightness of a bulb to show the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For your fan, probably you should just have a separate voltage regulator to supply power to it, since it needs a constant voltage, and not an adjustable one.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-02-05T22:53:16.293" CommentCount="1" />
  <row Id="1573" PostTypeId="2" ParentId="1571" CreationDate="2010-02-07T00:51:20.510" Score="2" ViewCount="" Body="&lt;p&gt;You can also get a fan that runs off 115VAC and put it before the transformer T1.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-02-07T00:51:20.510" />
  <row Id="1574" PostTypeId="2" ParentId="1571" CreationDate="2010-02-07T21:26:28.473" Score="1" ViewCount="" Body="&lt;p&gt;The unregulated voltage (across the 1000 μF capacitor) is about sqrt(2) * 25V, or 35V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you could wire three 12V fans in series.  Lots of cooling!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or you could put a (35-12)/0.16, or 150 ohm resistor in series with the fan.  This resistor will dissipate 150*(0.16)^2, or 3.8 watts.  You would need a 5 or 10 watt resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you could connect a three-terminal 12V regulator (e.g., LM7812).  It's not too hard to use, just read the datasheet.  The regulator will still dissipate the 3.8 watts, so it should be heatsinked, and in the airflow of the fan.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a cheap meter, you can buy little Chinese DMMs for &amp;lt; $10 at the right places.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90899&quot; rel=&quot;nofollow&quot;&gt;http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90899&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-02-07T21:26:28.473" />
  <row Id="1575" PostTypeId="1" AcceptedAnswerId="1576" CreationDate="2010-02-08T16:43:15.937" Score="2" ViewCount="208" Body="&lt;p&gt;Are there cases for Phidgets IO boards such as the &lt;a href=&quot;http://www.phidgets.com/products.php?category=0&amp;amp;product%5Fid=1019&quot; rel=&quot;nofollow&quot;&gt;1019&lt;/a&gt; ?&lt;/p&gt;&#xA;" OwnerUserId="329" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-02-08T22:46:06.710" LastActivityDate="2010-02-09T02:44:57.903" Title="Cases for Phidgets boards" Tags="&lt;board&gt;&lt;cases&gt;&lt;enclosure&gt;" AnswerCount="1" />
  <row Id="1576" PostTypeId="2" ParentId="1575" CreationDate="2010-02-09T02:44:57.903" Score="2" ViewCount="" Body="&lt;p&gt;If you mean prefabbed with bezel and all, I am not aware of any. I have used some standard project boxes for my phidget projects and they work pretty well. They just take a little work. I use a dremmel to carve the openings.&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-02-09T02:44:57.903" CommentCount="1" />
  <row Id="1577" PostTypeId="2" ParentId="1563" CreationDate="2010-02-09T03:27:42.267" Score="3" ViewCount="" Body="&lt;p&gt;It sounds like you've already got an AVR ISP programmer and you're just looking for something to go from that to the AVR.  Adding the ICSP header to your project is easy, but if you don't want to do that, I'd suggest checking out the &lt;a href=&quot;http://evilmadscience.com/tinykitlist/74-atmegaxx8&quot; rel=&quot;nofollow&quot;&gt;Simple AtmegaXX8 Mini Dev kit&lt;/a&gt;.  I'd get the version with the ZIF socket included - it's much easier to work with than a traditional socket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you can &lt;a href=&quot;http://www.evilmadscientist.com/article.php/avrtargetboards&quot; rel=&quot;nofollow&quot;&gt;wire your own&lt;/a&gt; up on a piece of protoboard pretty easily, though again I'd suggest getting a ZIF socket.  &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9175&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt; has the cheapest ZIF sockets.  You'll probably also want to add a crystal (&lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=538&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt;) since the ICSP won't work without one if you've set the fuse bits to expect an external crystal (so having one means it will always work).&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2010-02-09T03:27:42.267" />
  <row Id="1578" PostTypeId="2" ParentId="1561" CreationDate="2010-02-09T04:24:49.130" Score="2" ViewCount="" Body="&lt;p&gt;Mounting motors can be a pain. One ugly, but workable trick in some situations is using hose clamps. &lt;/p&gt;&#xA;" OwnerUserId="227" LastActivityDate="2010-02-09T04:24:49.130" />
  <row Id="1580" PostTypeId="1" CreationDate="2010-02-09T19:23:32.390" Score="2" ViewCount="1309" Body="&lt;p&gt;Has anyone got a really clear diagram of the way to link up a 16x2 LCD screen to an Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically I have an LCD for which the back light is coming on, but I am not getting any words appearing on the screen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which Pins should I be focusing on to test this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the screen i'm using&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/basic-16x2-character-lcd-yellow-on-blue-5v&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/basic-16x2-character-lcd-yellow-on-blue-5v&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="21" LastEditorDisplayName="" LastEditDate="2010-02-09T21:10:34.707" LastActivityDate="2011-05-19T14:15:19.853" Title="Hooking up an LCD to Arduino Diagram" Tags="&lt;lcd&gt;&lt;diagram&gt;&lt;arduino&gt;&lt;setup&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="1581" PostTypeId="2" ParentId="1580" CreationDate="2010-02-09T19:38:45.560" Score="2" ViewCount="" Body="&lt;p&gt;Check this link out - &lt;a href=&quot;http://www.ladyada.net/learn/arduino/lcd.html&quot; rel=&quot;nofollow&quot;&gt;very good tutorial exactly what you want from LadyAda.&lt;/a&gt; Her LCD has a block of pins at the end, most LCDs have 16 pins along the top with pin 1 at the top left (looking from the front). Note LadyAda pins are reversed from normal but if you have the back light sorted then the code below will help a lot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also another &lt;a href=&quot;http://www.uchobby.com/index.php/2007/07/07/arduino-lcd-interfacing-part-1/&quot; rel=&quot;nofollow&quot;&gt;tutorial&lt;/a&gt; but no wiring diagram&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From &lt;a href=&quot;http://www.alfonsomartone.itb.it/kwztcq.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; I copied this -  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// my pinout from L (LCD pin) to A (Arduino pin):&#xA;// LCD pin 1: Vss --&amp;gt; to Arduino GND&#xA;// LCD pin 2: Vdd --&amp;gt; to Arduino +5V&#xA;// LCD pin 3: V0 (contrast) --&amp;gt; to GND (I chose the PWM pin 10, see below)&#xA;// LCD pin 4: RS (register select) --&amp;gt; to Arduino pin 11&#xA;// LCD pin 5: R/W- (read/write) --&amp;gt; to Arduino pin 2&#xA;// LCD pin 6: E (H/L enable) --&amp;gt; to Arduino pin 3&#xA;// LCD pin 7: DB0 (data bit 0) --&amp;gt; to Arduino PIN 4&#xA;// LCD pin 8: DB1 (data bit 1) --&amp;gt; to Arduino PIN 5&#xA;// LCD pin 9: DB2 --&amp;gt; to Arduino PIN 6&#xA;// LCD pin 10: DB3 --&amp;gt; to Arduino PIN 7&#xA;// LCD pin 11: DB4 --&amp;gt; to Arduino PIN 14&#xA;// LCD pin 12: DB5 --&amp;gt; to Arduino PIN 15&#xA;// LCD pin 13: DB6 --&amp;gt; to Arduino PIN 16&#xA;// LCD pin 14: DB7 --&amp;gt; to Arduino PIN 17&#xA;// LCD pin 15: A/Vee (backlight+) --&amp;gt; to a 4.2Vcc source (see documentation)&#xA;// LCD pin 16: K (backlight-) --&amp;gt; to Arduino GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;note you can ignore the R/W line (connect it to ground) and use 4 bit mode (with the &lt;a href=&quot;http://www.arduino.cc/playground/Code/LCD4BitLibrary&quot; rel=&quot;nofollow&quot;&gt;LCD 4bit library&lt;/a&gt;) by disconnecting LCD pin 7, 8, 9 &amp;amp; 10. The pin assignments for the 4-bit library are mentioned in the library code. The mistake I made initially here was to wire up the lower nibble (DB0 to DB3) instead of the high nibble (DB4 to DB7).&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// --------- PINS -------------------------------------&#xA;//is the RW pin of the LCD under our control?  If we're only ever going to write to the LCD, we can use one less microcontroller pin, and just tie the LCD pin to the necessary signal, high or low.&#xA;//this stops us sending signals to the RW pin if it isn't being used.&#xA;int USING_RW = false;&#xA;&#xA;//RS, RW and Enable can be set to whatever you like&#xA;int RS = 4;&#xA;int RW = 11;&#xA;int Enable = 5;&#xA;//DB should be an unseparated group of pins  - because of lazy coding in pushNibble()&#xA;int DB[] = {6, 7, 8, 9};  //wire these to DB4~7 on LCD.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="9" LastEditorUserId="9" LastEditorDisplayName="" LastEditDate="2010-02-09T20:02:32.393" LastActivityDate="2010-02-09T20:02:32.393" />
  <row Id="1582" PostTypeId="2" ParentId="1580" CreationDate="2010-02-09T19:54:05.490" Score="1" ViewCount="" Body="&lt;p&gt;JohnC got most of it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One LCD I own has the pins in reverse order from the datasheet.  Since there are power and ground on both ends (mirrored, even), it still powers on even with it hooked up &quot;backwards&quot;.  It's worth checking that possibility if you're pretty sure you have the basic stuff hooked up correctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, for 4 pin mode, you'll want DB4-7 connected.  I always forget and hook up DB0-3 instead.  That doesn't work as well :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck.  These are trickier than they seem.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2010-02-09T19:54:05.490" CommentCount="1" />
  <row Id="1583" PostTypeId="2" ParentId="1580" CreationDate="2010-02-09T20:18:57.193" Score="1" ViewCount="" Body="&lt;p&gt;I have looked at a number of LCDs and the pin-out can vary quite&#xA;a bit. Which display are you using? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you have the contrast pin connected? I am not sure what display&#xA;you are using but on the Optrex 51505 that I use the pin is labeled&#xA;VLCD. I connect VLCD to the wiper of a 10K pot. One side of the pot&#xA;is connected to 5V the other is connected to GND. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should be able to adjust the pot all the way in one direction&#xA;and see black blocks all the way in the other and you will see&#xA;nothing.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:15:19.853" LastActivityDate="2011-05-19T14:15:19.853" />
  <row Id="1584" PostTypeId="2" ParentId="1482" CreationDate="2010-02-10T04:19:16.793" Score="7" ViewCount="" Body="&lt;p&gt;Dean Camera has written a USB stack for the AVR.  It includes a mass storage driver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.fourwalledcubicle.com/LUFA.php&quot; rel=&quot;nofollow&quot;&gt;http://www.fourwalledcubicle.com/LUFA.php&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="524" LastActivityDate="2010-02-10T04:19:16.793" CommentCount="2" />
  <row Id="1585" PostTypeId="2" ParentId="1561" CreationDate="2010-02-10T12:06:30.323" Score="1" ViewCount="" Body="&lt;p&gt;Get one of the Tamiya Double Gearbox kits. They are quite cheap, and come with two motors and two gearboxes, with shafts for attaching wheels. I've got a couple of them, but haven't got round to assembling them. When it's put together all you need do is build it into a little cart, add a couple of H-bridge drivers and start programming.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-02-10T12:06:30.323" CommentCount="1" />
  <row Id="1586" PostTypeId="1" AcceptedAnswerId="1590" CreationDate="2010-02-11T06:36:32.967" Score="2" ViewCount="458" Body="&lt;p&gt;&lt;a href=&quot;http://www.sics.se/%7Eadam/contiki/docs-uipv6/a01107.html&quot; rel=&quot;nofollow&quot;&gt;This tutorial&lt;/a&gt; starts with programming the Ravens and Jackdaw with a Windows box.  Can I do those initial steps with a Linux or OS X machine instead?  If so, how?  Is there any risk of bricking the hardware if I just try?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a USB JTAG ICE MKii clone, which is supposed to work for this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm totally new to AVR, but very experienced with C/C++ programming on Linux or OS X, up to and including kernel programming.&lt;/p&gt;&#xA;" OwnerUserId="526" LastActivityDate="2010-03-01T23:12:07.120" Title="How do I program an AVR Raven with Linux or a Mac?" Tags="&lt;avr&gt;&lt;linux&gt;" AnswerCount="3" />
  <row Id="1587" PostTypeId="1" AcceptedAnswerId="1589" CreationDate="2010-02-11T11:00:51.367" Score="4" ViewCount="197" Body="&lt;p&gt;I am a programmer with only basic understanding of electronics/electricity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to install &lt;a href=&quot;http://www.teltonika.lt/en/pages/view/?id=955&quot; rel=&quot;nofollow&quot;&gt;this device&lt;/a&gt; into my vehicle. The device accepts a wide DC power input (10V to 30V), but has a maximum power supply rating of 12W &lt;em&gt;(Edit: had typed 1W)&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am assuming that means the input current should be somehow controlled, external to the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What do I need to do this? A &lt;strong&gt;current limiting circuit&lt;/strong&gt;? A fuse for extreme situations?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A current limiting circuit as described in wikipedia will dissipate power? Are there off-the-shelf components for this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is a separate spike guard required?&lt;/p&gt;&#xA;" OwnerUserId="527" LastEditorUserId="527" LastEditorDisplayName="" LastEditDate="2010-02-12T06:44:53.413" LastActivityDate="2011-05-17T12:55:44.197" Title="How to supply power from vehicle to a low power device?" Tags="&lt;current&gt;" AnswerCount="3" />
  <row Id="1588" PostTypeId="2" ParentId="1587" CreationDate="2010-02-11T13:15:57.710" Score="6" ViewCount="" Body="&lt;p&gt;I am mostly self taught on this stuff so someone please correct me if I am wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you have a slight misunderstanding as to how current flow works. Unless there is something seriously wrong with your circuit, that rating means that it will use at most 1W of power from whatever supply system it is hooked up to (so don't hook it up to a 0.5W supply). I guess the best way to think of it is that the device is responsible for how much current it draws; the PSU will not &quot;force&quot; extra current down into it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current limiting circuits and fuses are used to protect against short circuits because when you short out the power supply (connect the two terminals together), the load resistance drops to essentially 0 and current flow theoretically approaches infinity. You can see how infinity amps of current could break something!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think about it: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;V = I * R&lt;/p&gt;&#xA;&#xA;&lt;p&gt;if V = 30V and R = 0 ohms,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;V/R = I (rearranged equation)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;30/0 = I (a divide by zero situation)&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-02-11T13:15:57.710" CommentCount="3" />
  <row Id="1589" PostTypeId="2" ParentId="1587" CreationDate="2010-02-11T16:22:34.913" Score="3" ViewCount="" Body="&lt;p&gt;Have you checked with the manufacturer for installation instructions and &#xA;application notes? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the flyer lists a wide range input ( and has a big picture of a car ;) &#xA;you may not need anything. A fuse won't hurt but you will need the manufacturer&#xA;to tell you the value. The device may have a high in-rush current that could&#xA;blow a fuse that is sized for the maximum operating current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also an EMI filter or transient protection component may be recommended. Again the&#xA;manufacturer will tell you this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The device may have an internal fuse and filtering.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:55:44.197" LastActivityDate="2011-05-17T12:55:44.197" CommentCount="1" />
  <row Id="1590" PostTypeId="2" ParentId="1586" CreationDate="2010-02-11T16:42:42.630" Score="1" ViewCount="" Body="&lt;p&gt;Under Linux, you'd probably use &lt;a href=&quot;http://www.nongnu.org/avrdude/&quot; rel=&quot;nofollow&quot;&gt;&lt;code&gt;avrdude&lt;/code&gt;&lt;/a&gt; to program them. It supports most programmers and most AVR chips. The main thing to watch out for, is that I think you need to use &lt;code&gt;avr-objcopy&lt;/code&gt; to extract the data from the 'ELF' binary files, you can't program the 'ELF' directly with avrdude.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;hr /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Random googling for avr-objcopy / avrdude commandlines comes up with this, which looks like it might work:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;# create demo.bin from demo.elf&#xA;avr-objcopy -j .text -j .data -O binary demo.elf demo.bin&#xA;&#xA;# program demo.bin to the 'flash' memory in an 'atmega128' chip,&#xA;# using a 'stk200' programmer connected to the 'lpt1' port on your computer&#xA;avrdude -p atmega128 -c stk200 -P lpt1 -U flash:w:demo.bin:r&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="131" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-02-12T05:50:43.850" LastActivityDate="2010-02-12T05:50:43.850" CommentCount="4" />
  <row Id="1591" PostTypeId="2" ParentId="1587" CreationDate="2010-02-11T18:13:37.370" Score="4" ViewCount="" Body="&lt;p&gt;You are good to hook it up without any other circuit, although a fuse is never a bad idea. It is actually to prevent damage to the wiring or other devices in you car in the event your device shorts out. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless there is a defect in your circuit it will never consume more than the 1 watt it is rated at. Are you sure the rating you looked at didn't say a &quot;minimum power supply rating&quot; instead of maximum? Most likely it was stating the maximum power the unit would consume.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't loose sight that your unit will be draining the battery if you are not running the car unless you hook it up to a switched circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck.&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-02-11T18:13:37.370" CommentCount="2" />
  <row Id="1592" PostTypeId="2" ParentId="188" CreationDate="2010-02-12T16:11:16.750" Score="0" ViewCount="" Body="&lt;p&gt;quick question what is K1....K4 in the schematic is that just the three pins that i need to connect to my Arduino. I assume you just showed us how to incorporate multiple ways of changing the LEDs like a two player game or something&lt;/p&gt;&#xA;" LastActivityDate="2010-02-12T16:11:16.750" />
  <row Id="1593" PostTypeId="2" ParentId="1113" CreationDate="2010-02-12T17:18:02.810" Score="3" ViewCount="" Body="&lt;p&gt;Look in the documentation for the cores.  See how many LUTs (Look Up Tables) or registers they have.  See if the requirements are less than the cheap board provides.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Picoblaze will fit on virtually anything.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-02-12T17:18:02.810" />
  <row Id="1594" PostTypeId="1" CreationDate="2010-02-13T16:40:31.007" Score="8" ViewCount="1075" Body="&lt;p&gt;For the last few days I have been trying without any luck to find a good tutorial on simple circuit simulations. I am a relatively new hobbyist and I figure if I use simulations and play around the circuit and see the output I would learn more. Can you please direct me to a simple tutorial which teaches simulation of circuits.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2011-03-06T23:45:42.840" Title="Simple Circuit Simulation tutorial" Tags="&lt;circuit&gt;&lt;simulation&gt;" AnswerCount="3" />
  <row Id="1595" PostTypeId="2" ParentId="1594" CreationDate="2010-02-13T18:04:45.530" Score="9" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.falstad.com/circuit/&quot; rel=&quot;nofollow&quot;&gt;http://www.falstad.com/circuit/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a java applet that allows you to simulate your circuits, I find it very useful, (dont have to make a whole new SPICE simulation.. :P )&lt;/p&gt;&#xA;" OwnerUserId="413" LastActivityDate="2010-02-13T18:04:45.530" CommentCount="5" />
  <row Id="1596" PostTypeId="2" ParentId="1594" CreationDate="2010-02-13T22:58:33.800" Score="13" ViewCount="" Body="&lt;p&gt;If you are on Windows I would download a copy of LTspice from Linear Technology. &#xA;IIRC there is a tutorial in the download. If not it is on their website.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LTspice is very quick to get started with. A major advantage is that the package&#xA;comes with all of the semiconductor models for the LT parts. &#xA;Most models are copyright and end up having to download them from the manufacturer.&#xA;This can be a major source of difficulty for people getting started.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have the software I would start with a very simple circuit like a voltage&#xA;source in series with a resistor in series with a capacitor. Setup your&#xA;probes to plot the voltage across the capacitor and the voltage across the resistor.&#xA;This will enable you to learn the quirks of the tool and hopefully get some instant&#xA;gratification.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make a copy of the simple circuit and start to add new elements to the new circuit.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-06T23:45:42.840" LastActivityDate="2011-03-06T23:45:42.840" CommentCount="3" />
  <row Id="1597" PostTypeId="1" CreationDate="2010-02-15T16:44:45.073" Score="3" ViewCount="115" Body="&lt;p&gt;I have some nice gear motors that run on 12 to 24 volts, and want to use them in a medium-sized mobile robot -- maybe 30 cm * 30 cm for the base.  I only expect it to run indoors, or possibly outside in nice weather.  If it had a half-hour run time, that'd be fine.  [If this is successful, though, I'd like to make a bigger robot that can withstand the out-of-doors, but probably only in nice weather].&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wondering what sort of batteries to use to power the motors.  These are the choices I can see in order from what I think is best to worst.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Use one or two 12 V (lead-acid) batteries.  This is sort of what I'm leaning towards, but I'm worried about how bulky and heavy it would be.  A car battery would be far too large and heavy.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I already have a charger that claims to be &quot;ideal for car, SUV, light truck, farm equipment, boat, deep-cycle, RV, motorcycle, ATV, snowmobile and lawn tractor batteries.&quot;  I imagine it would charge any 12-V lead-acid battery.  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Use some 9-V rechargeable batteries.  They appear to typically be a little less than 9V, but it appears that there are &lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9081&quot; rel=&quot;nofollow&quot;&gt;9V&lt;/a&gt; and &lt;a href=&quot;http://www.paulsfinest.com/Maha-PowerEX-9.6V-230-mAh-NiMH-Battery-p-34.html&quot; rel=&quot;nofollow&quot;&gt;9.6V varieties&lt;/a&gt;.  I would have to get a charger.  These would be light, compact, but they won't last long.  (230 mAH seems paltry compared to a &lt;s&gt;5 AH&lt;/s&gt; 50 AH car battery.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would need to have two in series, and, I suspect, have two or even three series in parallel.  That adds up to quite a few batteries and starts to negate the benefit of the small, compact batteries.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I could use 2 to 4 6-V batteries.  (I didn't realize you could get rechargeable 6V batteries).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;AA batteries, and lots of them.  10 to 20 1.2V NiMH batteries, though, will take a fair bit of space and mass and be take a long time to charge.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Specialty batteries (like those used in RC vehicles).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Some combination of the above -- say, two 9V batteries and a 6V battery.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Any sort of battery and a DC-to-DC adapter.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The first two options seem like my best choices.  What would you recommend?&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="106" LastEditorDisplayName="" LastEditDate="2010-02-15T19:43:25.657" LastActivityDate="2010-02-15T19:43:25.657" Title="Batteries for 12- to 24-V motors" Tags="&lt;batteries&gt;&lt;motor&gt;" AnswerCount="2" />
  <row Id="1598" PostTypeId="2" ParentId="1597" CreationDate="2010-02-15T17:52:39.960" Score="5" ViewCount="" Body="&lt;p&gt;I'm just going to say that 9V batteries are a bad idea, they generally have a very small amount of power stored in them. You're better off going with a bunch of AA batteries than with 9V batteries, if you're looking to get the best ratio. 9V are only good for the cases where you need the higher voltage of 9V, but have very low current requirements. A small SLA (sealed lead acid) battery is a good choice, I've seen these used before on medium sized robots. They are good for when you need a lot of power to drive motors and such, are very cheap compared to NiMh or LiPo rechargeable batteries, and you don't mind the extra weight. Make sure it's 'sealed', they cost a tiny bit more, and have slightly worse performance, but they are safer and don't require any maintenance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If space &amp;amp; weight are at a premium, and you don't mind spending lots of $$$, then you can upgrade to LiPo (Lithium Polymer). For example, you could get four of these &lt;a href=&quot;http://www.seeedstudio.com/depot/lithium-ion-polymer-batteries-6a-p-602.html&quot; rel=&quot;nofollow&quot;&gt;3.6V 6Ah LiPo batteries&lt;/a&gt;, equivilent of a 14.8V 6Ah battery, and it would weigh less than 1lb, whereas a &lt;a href=&quot;http://www.zbattery.com/CSB-12V-7-2Ah-SLA-Battery-Fire-Resistant&quot; rel=&quot;nofollow&quot;&gt;12V 7.2Ah SLA&lt;/a&gt; battery would weigh around 6lbs. Of course, the LiPo's will run you about $80 versus $20 for the SLA. So as always, there's a tradeoff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, your numbers above are wrong...a standard (huge) car battery is closer to 50 Ah than 5 Ah. But those weigh like 40 lbs, versus the smaller 6lb one I linked above.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-02-15T17:52:39.960" CommentCount="2" />
  <row Id="1599" PostTypeId="2" ParentId="1597" CreationDate="2010-02-15T18:59:40.467" Score="3" ViewCount="" Body="&lt;p&gt;You can usually run motors at a lower voltage than their rating and they'll work fine, they just turn slower.  So if you find a lower-voltage battery that is otherwise perfect, but not 12V, try that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On that note, I'd recommend looking into the battery packs used in R/C cars. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, here's a &lt;a href=&quot;http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10917&amp;amp;Product_Name=JR_AA_1500mah_Transmitter_Battery_Ni-MH_9.6V_&quot; rel=&quot;nofollow&quot;&gt;9.6V NiMH 1500mAh battery pack&lt;/a&gt; for $3.99 (but currently out of stock).  &lt;br/&gt;&#xA;And here's a &lt;a href=&quot;http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8936&amp;amp;Product_Name=Turnigy_1300mAh_3S_25C_Lipo_Pack&quot; rel=&quot;nofollow&quot;&gt;11.1V LiPoly 1300mAh battery pack&lt;/a&gt; for $9.99.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want something right away and are in the US, you might have a &lt;a href=&quot;http://hobbypeople.net/prdcls/battcl01.asp&quot; rel=&quot;nofollow&quot;&gt;Hobby People&lt;/a&gt; near you.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-02-15T18:59:40.467" />
  <row Id="1600" PostTypeId="1" CreationDate="2010-02-15T19:06:56.787" Score="11" ViewCount="2038" Body="&lt;p&gt;I'm prototyping a simple layout for a small project on matrix board, but figured there must be a better way than drawing it all out on paper. Are there any aimed at matrix board?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found the following software for stripboard, but nothing explicitly for matrix board:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://diy-fever.com/software/&quot; rel=&quot;nofollow&quot;&gt;DIY Layout Creator&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://3dreplicators.com/New%20Front%20Page/Documentation/Tools/Stripboard%20designer.htm&quot; rel=&quot;nofollow&quot;&gt;Stripboard Designer&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Stripboard Magic (seems to be abandonware, but there's page about it &lt;a href=&quot;http://www.marlwifi.org.nz/other/stripboard-magic/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://veecad.com/&quot; rel=&quot;nofollow&quot;&gt;VeeCAD&lt;/a&gt; Stripboard Editor Limited free version, designed to integrate well with &lt;a href=&quot;http://tinycad.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;TinyCAD&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.heyrick.co.uk/software/verodes/&quot; rel=&quot;nofollow&quot;&gt;VeroDes&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Any more I've missed? Any recommendations?&lt;/p&gt;&#xA;" OwnerUserId="542" LastEditorUserId="542" LastEditorDisplayName="" LastEditDate="2011-01-03T20:55:26.653" LastActivityDate="2011-01-03T21:31:44.777" Title="Stripboard/veroboard/matrix board design software" Tags="&lt;design&gt;&lt;stripboard&gt;&lt;stripboard&gt;&lt;matrix-board&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="1601" PostTypeId="1" CreationDate="2010-02-15T19:26:58.963" Score="6" ViewCount="410" Body="&lt;p&gt;I have an Airwave &lt;a href=&quot;http://www.active-robots.co.uk/airwave-58ghz-wireless-rf-av-receiver-module-p-1263.html&quot; rel=&quot;nofollow&quot;&gt;AWM682RX&lt;/a&gt; 5.8GHz video received and matching AWM683TX transmitter module. Oddly, one has pins spaced at 0.1&quot;, the other at 2mm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, &lt;strong&gt;what's the best way to make a part with 2mm spaced pins fit on 0.1&quot; matrix board?&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="542" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-04-14T19:06:39.647" LastActivityDate="2011-05-16T10:35:33.067" Title="Prototyping a part with 2mm spacing on 0.1&quot; matrix board?" Tags="&lt;prototyping&gt;&lt;pin&gt;&lt;spacing&gt;&lt;breadboard&gt;" AnswerCount="3" />
  <row Id="1602" PostTypeId="2" ParentId="1601" CreationDate="2010-02-15T20:01:30.617" Score="3" ViewCount="" Body="&lt;p&gt;I make my own PCBs at home, so I'd just make a little adapter.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-02-15T20:01:30.617" />
  <row Id="1603" PostTypeId="2" ParentId="1600" CreationDate="2010-02-15T20:03:16.720" Score="1" ViewCount="" Body="&lt;p&gt;You could use one of the PCB design programs.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-02-15T20:03:16.720" />
  <row Id="1604" PostTypeId="1" AcceptedAnswerId="1608" CreationDate="2010-02-15T20:16:49.963" Score="5" ViewCount="604" Body="&lt;p&gt;Here's the circuit I'm working on, it's a robotic stringed musical instrument thing, that uses 6 DC motors and an Arduino Duemilanove - &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i69.servimg.com/u/f69/14/39/80/39/pictur10.png&quot; alt=&quot;Circuit&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistors are 0.25w 1KΩ &#xA;The transistors are TIP122 Darlington PNP&#xA;The diodes are N5401&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The motors require 3v and 1.17A each, but the Arduino likes to work on about 6v-9v and only a few mA. I'd like to know the easiest way to use a single DC power supply unit (Of any appropriate spec), to power the whole circuit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers.&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T21:44:11.587" LastActivityDate="2011-04-30T10:23:55.597" Title="Can I combine the power supply?" Tags="&lt;arduino&gt;&lt;motor&gt;&lt;power-supply&gt;&lt;dc&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="1605" PostTypeId="2" ParentId="1604" CreationDate="2010-02-15T20:40:07.730" Score="3" ViewCount="" Body="&lt;p&gt;You could use a small DC-DC converter to convert the 3V supply to something the Arduino can use.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-02-15T20:40:07.730" />
  <row Id="1606" PostTypeId="2" ParentId="1600" CreationDate="2010-02-15T20:47:39.143" Score="3" ViewCount="" Body="&lt;p&gt;As Leon suggested I would use PCB design program. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have done this in two ways. &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Create a land pattern that is a strip of holes or a matrix of holes &#xA;(no silkscreen). Place a couple of these patterns down and you have a &#xA;large grid.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Sometimes I just use vias to create a matrix.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I made two footprints for vector pins. One for the Vector T42-1 micro clips&#xA;another for the K24A gold pins. I place these pins on the 100mil x 100mil&#xA;grid. I use the copper routes on different PCB layers (with different colors)&#xA;to represent wires. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The nice thing about the PCB program is you can check connectivity against your schematic.&#xA;You won't have that benefit in a drawing program.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-03T21:04:42.870" LastActivityDate="2011-01-03T21:04:42.870" />
  <row Id="1607" PostTypeId="2" ParentId="1601" CreationDate="2010-02-15T20:54:30.337" Score="6" ViewCount="" Body="&lt;p&gt;The best way would be the adapter. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A quick way would be to take a dremel tool to the &#xA;Vector board and route a slot. Epoxy the 2mm sockets to the&#xA;board and then run jumper wires to Vector K24A pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do not have many pins you could take a wire-wrap header&#xA;with 0.1&quot; centers and bend the leads on one end to 2mm centers.&#xA;Solder the socket to bent leads.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:35:33.067" LastActivityDate="2011-05-16T10:35:33.067" />
  <row Id="1608" PostTypeId="2" ParentId="1604" CreationDate="2010-02-15T21:23:22.887" Score="10" ViewCount="" Body="&lt;p&gt;If you are sure of the motor voltage and currents and all the motors&#xA;may need to be on at the same time you really want two voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a single a 7V supply you would need to drop&#xA;4V to power a 3V motor. 4V * 1.17A * 6 motors = 28W. That is&#xA;a lot of power to dissipate. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get dual output wall warts. Get one with a 7-10V output&#xA;and a 3-5V high current output. If size is not a factor you&#xA;could get a PC power supply. Use the 3.3V for the motors&#xA;and use the 12V for the Arduino with an regulator to drop&#xA;the voltage to 7V or so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also get a single 3.3V supply and use a boost&#xA;converter to generate 7V. It would be a small boost converter&#xA;since the Arduino wouldn't need much power. These are&#xA;easy to build. Something like a MAX34063 or LT1302 would work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would do the boost converter solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One more note -- I would not use Darlingtons to drive the motors. Darlingtons&#xA;have a very high saturation voltage and you are going to&#xA;dissipate a lot of power. A better choice would be a MOSFET.&#xA;The IR IRLB8748PBF is a 40A MOSFET with an Rds(on) of 7mOhms (at logic levels).&#xA;At 1A you will dissipate around 7mW compared to over 1W in&#xA;the Darlington. They are about 90cents from Digikey.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-30T10:23:55.597" LastActivityDate="2011-04-30T10:23:55.597" CommentCount="1" />
  <row Id="1609" PostTypeId="1" AcceptedAnswerId="1610" CreationDate="2010-02-16T02:20:03.450" Score="8" ViewCount="2091" Body="&lt;p&gt;I want to use a regular Arduino board to control LEDs - what is the most lights I can control individually from the board?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a tutorial on how to hook it up?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2011-03-19T03:16:13.083" Title="How many individual lights can an arduino control" Tags="&lt;arduino&gt;&lt;led&gt;&lt;tutorial&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="1" />
  <row Id="1610" PostTypeId="2" ParentId="1609" CreationDate="2010-02-16T02:37:57.237" Score="14" ViewCount="" Body="&lt;p&gt;I believe using Charlie-plexing N lines controls N*(N-1) LEDs.&#xA;There is a good article on Wikipedia.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A friend of mine, Jimmie P. Rodgers, fit 126 LEDs on an Arduino Shield. &#xA;He uses charlie-plexing to control the LEDs.&#xA;Some information on his board is at -- &#xA;&lt;a href=&quot;http://jimmieprodgers.com/2009/12/my-development-process/&quot; rel=&quot;nofollow&quot;&gt;http://jimmieprodgers.com/2009/12/my-development-process/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;At the last Boston Arduino User Group meeting Jimmie P. Rodgers drew a&#xA;Charlie-plexing diagram as a matrix with labeled nets. Schematics drawn in this&#xA;manner seemed to do a good job of communicating the concept. I created&#xA;a couple of similar schematics -- See &lt;a href=&quot;http://wiblocks.luciani.org/FAQ/faq-charlie-plex.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/FAQ/faq-charlie-plex.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-10T09:09:17.783" LastActivityDate="2011-03-10T09:09:17.783" CommentCount="2" />
  <row Id="1611" PostTypeId="2" ParentId="1601" CreationDate="2010-02-16T03:21:51.990" Score="4" ViewCount="" Body="&lt;p&gt;If you want to avoid soldering and just want to connect some devices up quick to breadboard, try this: &lt;a href=&quot;http://www.seeedstudio.com/depot/4-pin-254mm-to-20mm-female-jumper-wire-100mm-p-403.html&quot; rel=&quot;nofollow&quot;&gt;2.54mm to 2mm jumper wire&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="437" LastActivityDate="2010-02-16T03:21:51.990" />
  <row Id="1612" PostTypeId="1" AcceptedAnswerId="1613" CreationDate="2010-02-16T17:32:52.037" Score="5" ViewCount="248" Body="&lt;p&gt;I recently bought a CNC mini-mill at an auction. It is fitted with steppers on the three axis. The X and Y are the same, and the Z is a bit smaller (physically). All the markings were removed from the motors and they are painted flat black. Yet another reason to hate proprietary hardware :-) The machine was originally designed to use a custom controller which is missing. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, can I figure out what voltage the motors were intended to run at? &#xA;Does the coil resistance offer any clues?&#xA;I have a good quality multi-meter, and I have already reverse engineered the wiring. I don't want to fry the motors though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for any advice!&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2011-03-09T13:25:28.697" Title="is there any way to determine the correct voltage for a stepper motor" Tags="&lt;stepper&gt;&lt;motor&gt;&lt;reverse-engineering&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="1613" PostTypeId="2" ParentId="1612" CreationDate="2010-02-16T18:36:50.243" Score="2" ViewCount="" Body="&lt;p&gt;If you use a good driver circuit that has current limiting and chopper features, it really won't matter. Basically you can slowly crank up the current on these drivers while checking the stepper motor temperature and usually you can operate them at a voltage MUCH higher then they were intended with the right circuit. I am currently in a CNC build project and I am about to do that very thing. You can follow me on my Blog. &lt;a href=&quot;http://www.mendingthings.com&quot; rel=&quot;nofollow&quot;&gt;WWW.MENDINGTHINGS.COM&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck.&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-02-16T18:36:50.243" CommentCount="4" />
  <row Id="1614" PostTypeId="2" ParentId="1609" CreationDate="2010-02-16T18:39:43.203" Score="8" ViewCount="" Body="&lt;p&gt;You can use Shift Registers (&lt;a href=&quot;http://en.wikipedia.org/wiki/Shift%5Fregister&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Shift_register&lt;/a&gt;) to get as many parallel outputs from a single serial stream as you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will need to be concerned with your power constraints. I have actually never used an Arduino myself but I am assuming it has a current limit just like PICs do. Also, shift registers will have a current limit themselves. If you run into this, you will need to look at using something like a MOSFET to allow you to control the LEDs without having to pull much power directly from your micro controller. &lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-02-16T18:39:43.203" />
  <row Id="1615" PostTypeId="2" ParentId="1612" CreationDate="2010-02-16T19:55:28.170" Score="1" ViewCount="" Body="&lt;p&gt;The total weight of the motor and the coil resistance might be a good guide.  See if you can find some specs on the web and match them to your motor.  I have done similiar things with rechargeable batteries matching chemistry and weight.  I also think that Mark B's advice is pretty good, but suggests an over sized driver.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-02-16T19:55:28.170" />
  <row Id="1616" PostTypeId="1" AcceptedAnswerId="1617" CreationDate="2010-02-16T23:50:40.550" Score="7" ViewCount="357" Body="&lt;p&gt;I remember with fondness the X-10 days, when you could connect your computer to every wall plate in your house, using power-line carrier to transmit signals to addressable receivers (with varying degrees of success).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK, so maybe I don't need to turn on my microwave from my computer remotely, but I still think it would be cool to have a wireless controller scheme for some home automation, maybe even put a webcam on my Roomba, or some temperature sensors outside.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is a sensible overall way to approach this?  Wifi endpoints are really attractive, but they seem a little pricey.  Are there alternative approaches using radio?  Or is power-line carrier still the way to go?&lt;/p&gt;&#xA;" OwnerUserId="544" LastActivityDate="2011-05-17T12:54:41.403" Title="What is a sensible approach to connecting devices to your computer via wireless technology?" Tags="&lt;wireless&gt;&lt;embedded&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="1617" PostTypeId="2" ParentId="1616" CreationDate="2010-02-17T00:00:48.487" Score="6" ViewCount="" Body="&lt;p&gt;Check out the &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial%5Finfo.php?tutorials%5Fid=128&quot; rel=&quot;nofollow&quot;&gt;sparkfun wireless&lt;/a&gt; guide.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been playing with &lt;a href=&quot;http://news.jeelabs.org/tag/jeelink/&quot; rel=&quot;nofollow&quot;&gt;jeenodes&lt;/a&gt; for most of my low-end stuff and think it might be the best cost/power ratio.  I get mine through &lt;a href=&quot;http://www.moderndevice.com/products/jeenode-kit&quot; rel=&quot;nofollow&quot;&gt;modern device&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="347" LastActivityDate="2010-02-17T00:00:48.487" CommentCount="2" />
  <row Id="1618" PostTypeId="2" ParentId="1616" CreationDate="2010-02-17T00:22:16.437" Score="3" ViewCount="" Body="&lt;p&gt;ZigBee works quite well for sensor networks and home automation. ZigBee&#xA;is the network layer for the physical and MAC layer defined&#xA;in IEEE 802.15.4-2003. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The raw, over-the-air data rate is 250 kbit/s per channel (2.4 GHz band), 100 kbit/s per   channel in the 915 MHz band, and 20 kbit/s in the 868 MHz band.&#xA;&lt;li&gt;Transmission range is rougly 300ft (1mW) and 4000ft (60mW).&#xA;&lt;li&gt;The basic channel access mode is &quot;carrier sense, multiple access/collision avoidance&quot; (CSMA/CA).&#xA;&lt;li&gt;In the 2.4GHz band there are 16 channels each requiring 5MHz of bandwidth.&#xA;&lt;li&gt;IEEE 802.15.4-2003 short (16-bit) and long (64-bit) address modes supported. &#xA;bandwidth, low power network &#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;There are number of ways to deploy ZigBee. Most people buy a system on a chip like an XBee&#xA;that you talk to using a UART. The XBee integrates a uC, radio and antenna. You can&#xA;use the XBee with a board like an Arduino or you in a standalone mode. In standalone&#xA;mode the XBee can be set to periodically wake, collect data, transmit the data and go back to sleep. The XBee uC has digital I/O capabilities and an ADC. At a 0.1% duty cycle a couple of AA's will last 2-3 years. With some better power management longer battery life&#xA;is easily possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did a little write-up on ZigBee a few weeks ago. The write-up is at &lt;a href=&quot;http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also make a uC board that integrates an XBee with an Arduino compatible uC &lt;a href=&quot;http://wiblocks.luciani.org/ZB1/index.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/ZB1/index.html&lt;/a&gt; On my site are some XBee programming&#xA;examples.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:54:41.403" LastActivityDate="2011-05-17T12:54:41.403" />
  <row Id="1619" PostTypeId="2" ParentId="1616" CreationDate="2010-02-17T00:36:26.183" Score="3" ViewCount="" Body="&lt;p&gt;For wireless comms inside a house, the Nordic nRF24L01+ chips (modules available from Sparkfun) or the TI CC2500 (modules available from TI) are ideal. They are quite cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The TI modules actually come with sensor network software that is easily adapted for a particular application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Leon&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-02-17T18:49:35.933" LastActivityDate="2010-02-17T18:49:35.933" />
  <row Id="1620" PostTypeId="1" AcceptedAnswerId="1621" CreationDate="2010-02-17T19:04:16.423" Score="9" ViewCount="895" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a 17&quot; laptop monitor with a 1920x1200 (WUXGA I beleive it's called? or just UXGA?) resolution which I simply love. Now, assuming the laptop dies before the monitor does, would anyone know if it would be possible to salvage the monitor? Are the interfaces somehow standardized (can I simply solder some cable to a DVI connector and plug it in, more or less) or do they all depend on make and model? I'm guessing the power supply will be the least of my problems..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this particular case, it's a Dell Inspiron 9300.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wasn't sure how to tag it, and 'new users can't create tags', so sorry about that. :)&lt;/p&gt;&#xA;" OwnerUserId="546" LastEditorUserId="11" LastEditorDisplayName="" LastEditDate="2010-02-17T20:31:00.867" LastActivityDate="2010-02-20T11:03:17.587" Title="Reusing laptop monitors" Tags="&lt;electronics&gt;&lt;computers&gt;&lt;lcd&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="1621" PostTypeId="2" ParentId="1620" CreationDate="2010-02-17T20:29:45.800" Score="5" ViewCount="" Body="&lt;p&gt;I wish I could give you more information, but here's what I have seen in the laptops I have ripped open:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually the LCD itself is no different than any other LCD panel you would pick up at, say, SparkFun (aside from the obvious size and resolution).  This in and of itself isn't much, because there are many different interfaces and you would have to identify the panel itself and hope you could weasel something out of the manufacturer.  If so, you could probably build something to handle the interfacing, but it would not be an easy task.  It's probably right in the wheelhouse of an FPGA, but now I'm really speculating just to give a sense of project scale.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, the panel usually has a ribbon cable which interfaces with some part of the laptop proper, and in some cases it appears as if there is a daughter board that handles the work between the CPU/GPU and the panel.  If this is the case, you may find that you can hack together some kind of interface on the far side of the daughter board from the LCD.  It seems unlikely but possible, and you'd still be stuck with the task of identifying the interface that is actually used (DVI sounds like a good place to start on a newer laptop) and you'd still have to create a board from scratch to interface with a &quot;normal&quot; video cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even after you figure out the interface, you'd still need to address power to both the LCD and to the backlight.  If you can solve the interface issues, these should be a walk in the park.  However, it's something to consider since you'll be powering some interface circuit anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again, my knowledge on this is limited to the few models of laptops I've had in pieces, and I've never looked that closely at the video.  Someone else may be able to give you more details and there may be some easier solutions than I've suggested.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--EDIT--&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did some poking around on the Internet, because your question really got me thinking.  I don't have any more real knowledge than I did a few hours back, but I did run across this site which talks about different LCD types and how you can build custom interfaces with them.  It was last updated 3 January 2008 at the time of this post and I have no first-hand experience with this, I'm linking because it describes the lengths someone went through to make a certain subset of panels work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.fpga4fun.com/GraphicLCDpanel1.html&quot; rel=&quot;nofollow&quot;&gt;http://www.fpga4fun.com/GraphicLCDpanel1.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="11" LastEditorUserId="11" LastEditorDisplayName="" LastEditDate="2010-02-17T22:03:04.113" LastActivityDate="2010-02-17T22:03:04.113" CommentCount="2" />
  <row Id="1622" PostTypeId="2" ParentId="1620" CreationDate="2010-02-17T20:34:52.427" Score="4" ViewCount="" Body="&lt;p&gt;Can you simply solder a DVI or VGA cable?  No.  You basically need to hook up a video chip with LCD panel driver to the many wires going to LCD.  These might exist but I've never seen them.  It's a bummer because I've got a few busted laptops that I'd love to reuse the displays on.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-02-17T20:34:52.427" CommentCount="1" />
  <row Id="1629" PostTypeId="1" AcceptedAnswerId="1637" CreationDate="2010-02-18T13:34:15.337" Score="7" ViewCount="668" Body="&lt;p&gt;Hi everyone,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm pretty new to all this, only having used an Arduino for a couple of weeks now.  Having said that I'm preparing to build my first &quot;proper&quot; circuit from the ground up, and many people talk of sending designs off to a PCB house and getting a finished board back.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This sounds exciting and preferable to dealing with all the chemicals to etch the board myself.  However I'm located in Australia (specifically Brisbane) and Google hasn't been particularly helpful in pointing out any local places that can produce PCBs for hobbyists.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there anyone here from Australia who knows of a place that can do this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, how much does it normally cost?  The only local place I could find charges about AU$\$$275 (US$\$$245) for a basic board which seems a bit pricey to me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions would be much appreciated!&lt;/p&gt;&#xA;" OwnerUserId="548" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-05-12T05:32:34.483" LastActivityDate="2011-05-17T12:54:54.227" ClosedDate="2011-05-12T13:54:46.540" Title="Where can you get PCBs fabricated in Australia?" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;&lt;australia&gt;" AnswerCount="11" />
  <row Id="1630" PostTypeId="1" AcceptedAnswerId="1633" CreationDate="2010-02-18T13:58:33.243" Score="7" ViewCount="407" Body="&lt;p&gt;Hi everyone,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many people seem to run their projects off the mains (e.g. with a wall wart) or from a battery, but there doesn't seem to be too much discussion about how to run a device off the mains, charging a battery, but then switching over to the battery in the event of a power outage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I imagine that with NiCD/NiMH batteries you could just hook them up in parallel with the power supply (more or less), however since LiPo batteries hold more power for their size I would like to use them instead in a project like this - but they don't seem quite so simple to use in this way!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone offer some pointers as to how LiPo batteries might be used for backup power?  I imagine you would need some logic to power a charger and switch over to the batteries when the mains disappears, but I'm not sure how this might work.  I imagine you'd also need a large capacitor to avoid a momentary dropout during the switch over as well.  Or perhaps there's some cheap IC that can do all this for me?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for any suggestions!&lt;/p&gt;&#xA;" OwnerUserId="548" LastActivityDate="2011-05-16T10:36:05.250" Title="How might you use a LiPo battery as backup for mains power loss?" Tags="&lt;battery&gt;&lt;power&gt;" AnswerCount="2" />
  <row Id="1631" PostTypeId="2" ParentId="1630" CreationDate="2010-02-18T14:36:00.667" Score="4" ViewCount="" Body="&lt;p&gt;There are many ways to do this.  One way you may want to consider is a dedicated battery management / battery backup IC.  This link to Mouser should give you many options:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://mouser.com/Search/Refine.aspx?Keyword=battery+management+backup&amp;amp;FS=True&quot; rel=&quot;nofollow&quot;&gt;http://mouser.com/Search/Refine.aspx?Keyword=battery+management+backup&amp;amp;FS=True&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should look for the &quot;Backup for LP Processor&quot; ICs.  Read the data sheets closely, but they should provide sufficient specs to give you what you need.  The downside is that I didn't see any through-hole chips (though I didn't give an exhaustive search).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To do this, you will either need to get a proper LiPoly charging circuit to keep the battery properly charged while power is applied to the circuit or find one of these chips that can handle charging a LiPoly as well as perform fail-over functions.  I think I saw one on Digikey that does everything for $20, but that seemed like it was an unnecessarily expensive solution.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2010-02-18T14:36:00.667" />
  <row Id="1632" PostTypeId="2" ParentId="1629" CreationDate="2010-02-18T16:02:58.297" Score="2" ViewCount="" Body="&lt;p&gt;I'm a newbie when it comes to electronics, but $275 is very, very expensive. I can't help you find addresses in Australia, but I found &lt;a href=&quot;http://blog.makezine.com/archive/2010/02/circuit%5Fskills%5Fcircuit%5Fboard%5Fetchin.html&quot; rel=&quot;nofollow&quot;&gt;this blog entry&lt;/a&gt; very interesting and rather easy to follow if you want to do it yourself.&lt;/p&gt;&#xA;" OwnerUserId="545" LastActivityDate="2010-02-18T16:02:58.297" />
  <row Id="1633" PostTypeId="2" ParentId="1630" CreationDate="2010-02-18T16:09:43.133" Score="6" ViewCount="" Body="&lt;p&gt;There are a number of ICs that will do these functions. I would go to the Maxim and &#xA;Linear Technology sites. The downside is that most of these devices is that they &#xA;are only in surface mount packages and a lot of them come in packages without leads (QFN, LGA).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A part like the LTC4088 is nice. It has an input for the battery, an input for the&#xA;USB (or wall adapter) and a switching regulator. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also use separate ICs (but you are probably better off with a single).&#xA;There is a device that Linear Tech calls a PowerPath controller (LTC4412)&#xA;that performs the switchover function. You could add a MAX1555 Li-ion charger&#xA;for a low cost charger and add the LTC4412. Also there are devices called &quot;Ideal Diodes&quot;&#xA;that will perform switchover. These devices are FETs so you get a much&#xA;lower voltage drop than a Schottky. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best solution depends on a couple of things you haven't mentioned -- system current,&#xA;battery capacity and recharge rates.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:36:05.250" LastActivityDate="2011-05-16T10:36:05.250" CommentCount="2" />
  <row Id="1634" PostTypeId="2" ParentId="1629" CreationDate="2010-02-18T16:20:13.197" Score="1" ViewCount="" Body="&lt;p&gt;That seems really expensive.  I don't know what import tariffs/taxes/fees/stamps/etc. you guys have in Australia, but Gold Phoenix does all the boards for BatchPCB and they will print up a 100 sq. cm board for $110 (USD).  Add $10 for shipping and $30 for multiple designs (you might as well make multiple designs) and that still comes out to $150, a lot less than $275.  It's not ideal, and there may be a better local solution, but it's worth mentioning.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.goldphoenixpcb.biz/quote2.php&quot; rel=&quot;nofollow&quot;&gt;http://www.goldphoenixpcb.biz/quote2.php&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2010-02-18T16:20:13.197" CommentCount="4" />
  <row Id="1635" PostTypeId="1" AcceptedAnswerId="1681" CreationDate="2010-02-18T16:23:19.933" Score="11" ViewCount="3115" Body="&lt;p&gt;I'm learning electronics (and basic electricity) and I wondered if a 1MHz oscilloscope like the &lt;a href=&quot;http://www.seeedstudio.com/depot/micro-digital-storage-oscilloscopedso-nano-p-512.html&quot; rel=&quot;nofollow&quot;&gt;DSO Nano&lt;/a&gt; is enough for (very) basic electrical and/or electronic circuits. I'm almost broke and I need a cheap portable oscilloscope to try various circuits (wherever I am, hence the required portable property) with resistors, capacitors, transistors, and microcontrollers (if I study hard enough). I don't thing I need a more powerful oscilloscope because I'm learning and I'm just following the exercises in various books right now. This would be my first oscilloscope and I would eventually buy a 20MHz portable oscilloscope later.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you!&lt;/p&gt;&#xA;" OwnerUserId="545" LastActivityDate="2011-01-27T15:44:13.717" Title="Cheap 1MHz oscilloscope" Tags="&lt;oscilloscope&gt;" AnswerCount="9" CommentCount="3" FavoriteCount="3" />
  <row Id="1636" PostTypeId="2" ParentId="1635" CreationDate="2010-02-18T16:37:58.937" Score="9" ViewCount="" Body="&lt;p&gt;Your typical hobbyist microcontroller can range anywhere from KHz up to 40MHz or more. So if you are wanting to have a microcontroller running at lets say 40MHz and be able to see what a PWM looks like, you may be out of luck.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you are just wanting to see a general idea of what is happening on your analog circuits or simple digital circuits then the DSO Nano will work just fine for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option to consider is an OScope on a computer. You can use the sound card on your computer to interface with a program (&lt;a href=&quot;http://www.ledametrix.com/oscope/index.html&quot; rel=&quot;nofollow&quot;&gt;Here is an example&lt;/a&gt;). The down side to this is that computer sound cards tend to be very noisy and many times only have a sample rate of about 96KHz or lower in some cases.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-02-18T16:37:58.937" CommentCount="3" />
  <row Id="1637" PostTypeId="2" ParentId="1629" CreationDate="2010-02-18T16:56:19.000" Score="8" ViewCount="" Body="&lt;p&gt;Yeah, local places are almost always gonna cost more. The best deals will be places in other countries. Here's a few places that are much much cheaper than $245 (note these prices are examples, may be a bit higher/lower depending on what exactly you order)&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.goldphoenixpcb.biz/quote2.php&quot; rel=&quot;nofollow&quot;&gt;goldphoenix&lt;/a&gt; - $110 for 155 sq inch&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.olimex.com/pcb/index.html&quot; rel=&quot;nofollow&quot;&gt;olimex&lt;/a&gt; - $55 for 25 sq inch&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.batchpcb.com/&quot; rel=&quot;nofollow&quot;&gt;batchpcb&lt;/a&gt; - $2.50 per sq inch plus $10 fee (eg $35 for 10 sq inch)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.makepcb.net/&quot; rel=&quot;nofollow&quot;&gt;makepcb&lt;/a&gt; - $50 for 23 sq inch&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.myropcb.com/&quot; rel=&quot;nofollow&quot;&gt;myropcb&lt;/a&gt; &lt;/li&gt;&#xA;&lt;li&gt;Also see &lt;a href=&quot;http://www.ladyada.net/library/pcb/costcalc.html&quot; rel=&quot;nofollow&quot;&gt;ladyada's PCB cost calculator&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you could give us more details about what you want, we might be able to find more specific places. For example, if you are buying 1000 PCBs, they might only cost $1 each, but if you just want 1 PCB, it might cost $50. What size PCB do you want, how many pieces, and what size tracks do you need? &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-02-18T16:56:19.000" CommentCount="1" />
  <row Id="1638" PostTypeId="2" ParentId="1635" CreationDate="2010-02-18T16:59:06.050" Score="4" ViewCount="" Body="&lt;p&gt;A good rule of thumb is you need a minimum of 4x the speed of the signal you are watching, and higher (up to 10x) is better. So if you want to watch a signal that's running at 1MHz, you need a 4-10MHz scope. &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-02-18T16:59:06.050" CommentCount="1" />
  <row Id="1639" PostTypeId="2" ParentId="1629" CreationDate="2010-02-18T17:39:40.067" Score="3" ViewCount="" Body="&lt;p&gt;I don't have a suggestion for an Australian vendor. I have been using using PCB Express&#xA;and Advanced Circuits. I believe these guys ship international. Not sure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One way I save on PCB costs is to panelize designs. I place multiple copies of multiple&#xA;designs on a sheet. If you space the designs 50mils apart a single cut with a hacksaw&#xA;blade will cut two edges. &lt;strong&gt;You need to wear breathing and eye protection when you cut FR4&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The board I am doing now will have about 15-20 designs. Some new, some revisions. &#xA;It will be about $25 per design (at least two copies of each). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have friends that require PCBs of their own designs you could pool the work. &#xA;When the panels come in each person would cut their own board and pass it to &#xA;the next person.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Advanced Circuits has a 5 for $133(US) deal every now and then. Five 30in^2 boards&#xA;with silkscreen and soldermask. If you panelize they charge you another $50. If&#xA;you do a lot of baords PCB Express has a price of about $500 for two 12&quot; x 14&quot; panels.&#xA;No fee for panelizing. For a couple small boards &amp;lt; 10in^2 PCB Express also has a good&#xA;price. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Advanced Circuits and PCB Express are excellent vendors. I choose between them based&#xA;solely on price and delivery.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:54:54.227" LastActivityDate="2011-05-17T12:54:54.227" CommentCount="2" />
  <row Id="1640" PostTypeId="2" ParentId="1635" CreationDate="2010-02-18T19:28:41.370" Score="2" ViewCount="" Body="&lt;p&gt;Depends on what you're designing.  If you only need 1 MHz bandwidth it should work fine.  You can get a cheap analog scope on eBay though, and it will have a higher bandwidth.  Just bulkier and harder to carry around.  The shipping on my old 20 MHz analog scope was more than the scope itself.  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also have a &lt;a href=&quot;http://www.bitscope.com/product/BS50/&quot; rel=&quot;nofollow&quot;&gt;Bitscope BS50U&lt;/a&gt;, which I carry around with me, but I almost never use it and don't recommend it.  The software is the weakest link.  It's hard to navigate, unintuitive, hard to get a good trigger, etc.  A software-based oscilloscope should be &lt;em&gt;more&lt;/em&gt; powerful than a hardware scope, not less.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-04T14:15:11.517" LastActivityDate="2010-11-04T14:15:11.517" />
  <row Id="1641" PostTypeId="2" ParentId="1420" CreationDate="2010-02-18T21:06:01.980" Score="4" ViewCount="" Body="&lt;p&gt;check out mspdebug it should get your code onto the device and do some debugging there. I also saw that someone patched mspgcc v3.2.3 to handle the cc430 in the chronos. &lt;/p&gt;&#xA;" OwnerUserId="549" LastActivityDate="2010-02-18T21:06:01.980" />
  <row Id="1642" PostTypeId="2" ParentId="1620" CreationDate="2010-02-19T21:12:29.477" Score="6" ViewCount="" Body="&lt;p&gt;Some laptop display panels use DVI, but even when that's the case you'll find that the signaling isn't quite the same as DVI.  It's generally an LVDS electrical interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other displays still use an LVDS interface, but a different set of signals than DVI, putting most of the brains in the video chip, and removing the need for a lot of conversion and signaling on the display itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you are partially in luck.  That particular display uses the same interface as the 15&quot; WUXGA display used in the Dell Inspiron series of that vintage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These 1920x1200 displays are widely used by hobbyists building their own projectors, and so input boards exist for them that accept a wide variety of video inputs (usually HDMI, composite, VGA, DVI, etc) and drive the display for you.  It's not such a big hobby (especially now that 1080p projectors are under $1000) that they are readily available, but sometimes there are group buys, and often someone buys the interface board but never gets around to using it.  One resource for such a hobbyist community is &lt;a href=&quot;http://www.lumenlab.com/forums/index.php?showforum=54&quot; rel=&quot;nofollow&quot;&gt;http://www.lumenlab.com/forums/index.php?showforum=54&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Poke around those forums and you should have some luck finding what you need, but don't expect to be able to do this on the cheap - when I last looked the boards were $100-$200, and you can get a nice 1920x1200 monitor for that much, though none as small as 17&quot;.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-02-19T21:12:29.477" />
  <row Id="1643" PostTypeId="1" AcceptedAnswerId="1646" CreationDate="2010-02-20T10:10:32.170" Score="2" ViewCount="579" Body="&lt;p&gt;Can anyone suggest a 330uH inductor and associated Eagle .lbr for use with an LM2575? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been looking all day for this! Any suggestions would be appreciated.&lt;/p&gt;&#xA;" OwnerUserId="551" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-05-05T23:57:30.530" LastActivityDate="2011-05-17T12:53:56.163" Title="Inductor for LM2575" Tags="&lt;eagle&gt;&lt;power-supply&gt;&lt;components&gt;&lt;power&gt;" AnswerCount="2" />
  <row Id="1644" PostTypeId="2" ParentId="1620" CreationDate="2010-02-20T11:03:17.587" Score="4" ViewCount="" Body="&lt;p&gt;I looked into this a few years ago, although I was trying to hook up one of the panels to a PC then.  I found &lt;a href=&quot;http://store.earthlcd.com/LCD-Products&quot; rel=&quot;nofollow&quot;&gt;EarthLCD&lt;/a&gt;, who sell various interface cards designed to work with obscure LCD panels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately they're not cheap, and most are designed to connect to a PC or have a composite video signal applied, but it might give you an idea of the complexity involved.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe the new DisplayPort connector is designed to work with laptop panels as well, so in maybe 10 years time we'll reach a point where old laptop screens can simply have a new plug wired on to them.&lt;/p&gt;&#xA;" OwnerUserId="548" LastActivityDate="2010-02-20T11:03:17.587" />
  <row Id="1645" PostTypeId="2" ParentId="1643" CreationDate="2010-02-20T13:48:09.453" Score="2" ViewCount="" Body="&lt;p&gt;the &lt;a href=&quot;http://www.national.com/mpf/LM/LM2575.html#Overview&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; suggests a &lt;a href=&quot;http://www.mouser.com/search/ProductDetail.aspx?qs=96C2vqMyhuqmP4c6N2Ancw%3D%3D&quot; rel=&quot;nofollow&quot;&gt;Pulse PE-52627&lt;/a&gt; for most designs. If you use National's Webench, and put in your exact design requirements (input/output voltage, current) then I'm pretty sure it will suggest a part number.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-02-20T13:48:09.453" />
  <row Id="1646" PostTypeId="2" ParentId="1643" CreationDate="2010-02-20T15:54:31.040" Score="3" ViewCount="" Body="&lt;p&gt;On-Semi is a second source for this part. There may be some additional&#xA;information at &lt;a href=&quot;http://www.onsemi.com/PowerSolutions/product.do?id=LM2575&quot; rel=&quot;nofollow&quot;&gt;http://www.onsemi.com/PowerSolutions/product.do?id=LM2575&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you choosing the LM2575 because you want a through hole buck converter? &#xA;If you can do SMD parts there are parts that offer much better performance.&#xA;A higher frequency part will let you use much smaller capacitors and inductors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI also makes some buck converter modules (TH packages) that are very inexpensive. Checkout&#xA;the PTR and PTN series devices.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:53:56.163" LastActivityDate="2011-05-17T12:53:56.163" CommentCount="3" />
  <row Id="1647" PostTypeId="1" AcceptedAnswerId="1662" CreationDate="2010-02-20T23:28:19.073" Score="8" ViewCount="1311" Body="&lt;p&gt;Some sound card audio jacks can now inform recent Windows OS's that an audio device is plugged in.  Anyone know how it does this?  I'm thinking it uses some kind of voltage comparator or resistance measurement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This question was asked at &lt;a href=&quot;http://superuser.com/questions/110933/how-does-a-sound-card-determine-if-headphones-are-plugged-in&quot; rel=&quot;nofollow&quot;&gt;Superuser&lt;/a&gt;.  My gut feeling is that the circuit is not as trivial as one of the participants is suggesting, but I'm a bit rusty on circuits.&lt;/p&gt;&#xA;" OwnerUserId="553" LastActivityDate="2010-02-22T16:55:53.273" Title="How does an audio jack detect when a speaker is plugged in?" Tags="&lt;audio&gt;&lt;detection&gt;&lt;circuit&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="1648" PostTypeId="2" ParentId="1647" CreationDate="2010-02-21T01:31:23.737" Score="13" ViewCount="" Body="&lt;p&gt;Most all jacks (DC power or audio) have an extra terminal that is switched on plug insertion.  This is a mechanical switch.  Some designs use this extra terminal to switch between battery and external power (in the case of DC jacks) or to switch between headphones and speakers (in the case of audio jacks).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the photo of &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=CP-008A-ND&quot; rel=&quot;nofollow&quot;&gt;this DC jack on Digikey&lt;/a&gt; you can almost get a good view of the internals.  The two lugs on the back of the jack are for the two DC power connections.  The third lug on the bottom is the switch input.  Audio jacks have a similar arrangement.&lt;/p&gt;&#xA;" OwnerUserId="215" LastEditorUserId="215" LastEditorDisplayName="" LastEditDate="2010-02-21T05:49:01.153" LastActivityDate="2010-02-21T05:49:01.153" />
  <row Id="1649" PostTypeId="2" ParentId="1647" CreationDate="2010-02-21T03:23:15.733" Score="3" ViewCount="" Body="&lt;p&gt;Take one apart and find out.   :)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several things it could be doing, depending on whether it's just measuring the presence of a plug (just a jack switch will do), or if it knows the difference between a mic and a headphone, etc (resistance measurement?).&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-02-21T03:23:15.733" />
  <row Id="1650" PostTypeId="2" ParentId="1647" CreationDate="2010-02-21T11:45:07.777" Score="5" ViewCount="" Body="&lt;p&gt;Does it not measure the impedance of whatever is plugged in and then determines what it is based on known values ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;when I insert my speaker jack into the plug, i can hear all the speakers &quot;clicking&quot; one by one, as if the computer is testing to see if they are there...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this on &lt;a href=&quot;http://www.freepatentsonline.com/7579832.html&quot; rel=&quot;nofollow&quot;&gt;http://www.freepatentsonline.com/7579832.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;An audio system includes a CODEC audio&#xA;  jack having left and right audio ports&#xA;  and a jack sense circuit. The jack&#xA;  sense circuit includes left and right&#xA;  amplifiers and a cross-drive impedance&#xA;  sensing circuit. This cross-drive&#xA;  impedance sensing circuit, which is&#xA;  electrically coupled to the left and&#xA;  right audio ports and the left and&#xA;  right amplifiers, detects the&#xA;  resistances of left and right output&#xA;  loads in order to determine&#xA;  characteristics of a device connected&#xA;  to the CODEC audio jack. The&#xA;  cross-drive impedance circuit is&#xA;  configured to measure a resistance of&#xA;  a left output load electrically&#xA;  coupled to the left audio port, in&#xA;  response to a “right” test signal&#xA;  generated by the right amplifier, and&#xA;  is further configured to measure a&#xA;  resistance of a right output load&#xA;  electrically coupled to the right&#xA;  audio port in response to a “left”&#xA;  test signal generated by the left&#xA;  amplifier.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="413" LastActivityDate="2010-02-21T11:45:07.777" />
  <row Id="1651" PostTypeId="2" ParentId="1609" CreationDate="2010-02-21T22:01:38.553" Score="7" ViewCount="" Body="&lt;p&gt;Any given AVR microcontroller pin is allowed to source up to 40 mA, and the total power supply sourced or sunk by the chip (i.e., at the ground and Vcc pins) needs to be below 200 mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Charlieplexing is a great solution for situations where you need lots of LEDs, but can get by with only one LED &lt;em&gt;lit&lt;/em&gt; at a time.  A standard Arduino board (like a Duemilanove) provides 17 &quot;free&quot; I/O pins, not counting TX, RX, Reset, or pin 13.  So, you can hook up 17*16=272 LEDs.  This can work well, especially if you're keeping one LED lit, or quickly scanning between just a few.  But if you're trying to light the whole matrix with a pattern, you'll find that each is on (slightly less than) 1/272 of the time, so if your drive current were 30 mA at any given moment, each LED's average current would be about 0.1 mA-- pretty dim.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't need that many LEDs but instead need more brightness, traditional multiplexing may be a better option.  In this case, you use some of your lines as rows and some as columns in a matrix.   If you use a 10 mA LED current, you could define a matrix of 4 columns and 13 rows, where all 4 LEDs in one row can be on at a time, and you scan through the rows.   Then each row is on 1/13 of the time at 10 mA current, so the average LED current can be as high as 0.76 mA, BUT you only get 4*13=104 LEDs.  (Definitely brighter per LED than with charlieplexing.)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The limit in the last example is the 40 mA per pin on the AVR-- since each row driving pin sources 4x10=40 mA.  If you allow external transistors (which can be cheap and small) to be added to the row outputs, then you can avoid that particular limit and go brighter.  For example, you could make an 8x9 array, with 8 rows and 9 columns, 72 LEDs altogether.  One of the 8 rows is on at a time, selected through the transistor.  Up to all 9 LEDs in a given row can be on at a time, driven at 20 mA, so 180 mA comes from the transistor, and you stay under the current limits of the AVR.  The average current per LED is now 20 mA/8 =  2.5 mA-- usually reasonably bright.&lt;/p&gt;&#xA;" OwnerUserId="484" LastActivityDate="2010-02-21T22:01:38.553" />
  <row Id="1652" PostTypeId="2" ParentId="1629" CreationDate="2010-02-21T23:43:32.380" Score="2" ViewCount="" Body="&lt;p&gt;I've used &lt;a href=&quot;http://pcbcart.com&quot; rel=&quot;nofollow&quot;&gt;pcbcart.com&lt;/a&gt; a number of times and found them to be quite good. Looking through the other links, their site is quite similar to makepcb.com and I wouldn't be surprised to learn that they're the same people (or one orders from the other).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The great thing is that both sites have online quoting systems (makepcb's is faster but has less options). So you can play with the options and work out the best price point. Often it's cheaper (total cost - not just per board) to get more boards made. For example at makepcb.com a single 20x20mm board is 23.13 €, but you can get 20 boards for 25.56 € (1.28 ea)! &lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-02-21T23:43:32.380" />
  <row Id="1653" PostTypeId="2" ParentId="1586" CreationDate="2010-02-21T23:59:29.077" Score="2" ViewCount="" Body="&lt;p&gt;If you're developing projects on Linux, do some searching for a good Makefile that supports avr-gcc and avrdude. You should then just have to edit the Makefile to specify your hardware and source files and you're away.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To build a binary you generally just call &lt;code&gt;make&lt;/code&gt;, to program a device is often &lt;code&gt;make program&lt;/code&gt; and sometimes &lt;code&gt;make fuse&lt;/code&gt; to set the fuses on the AVR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used &lt;a href=&quot;http://www.sax.de/~joerg/mfile/&quot; rel=&quot;nofollow&quot;&gt;Mfile&lt;/a&gt; for generating Makefiles on Windows, but it looks like they support *nix also.&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-02-21T23:59:29.077" />
  <row Id="1654" PostTypeId="1" AcceptedAnswerId="1656" CreationDate="2010-02-22T00:29:17.460" Score="6" ViewCount="1403" Body="&lt;p&gt;I'd like to be able to daisy chain multiple devices using just the power supply wires and then inject a communications signal over the power lines to turn it into a half duplex network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any common methods of achieving this? The simpler the better and it would be great if it used the UART on the microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: There are actually two projects that I'm working on that I think would benefit from this - one is a low power sensor network. The other is a LED lighting project. In both cases the objective is to simplify wiring, but if the solution is too complex then it probably makes more sense to use three wires (pwr, gnd, comms).&lt;/p&gt;&#xA;" OwnerUserId="554" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-05-02T02:29:53.810" LastActivityDate="2011-06-05T13:25:48.480" Title="Injecting a communication signal over DC power supply lines" Tags="&lt;communication&gt;&lt;uart&gt;&lt;powerline&gt;" AnswerCount="8" CommentCount="2" FavoriteCount="1" />
  <row Id="1655" PostTypeId="2" ParentId="1374" CreationDate="2010-02-22T00:48:44.893" Score="2" ViewCount="" Body="&lt;p&gt;Dunno which one is the best, but I really liked DuinOS when I played with it a while back. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It didn't quite work right out of the box and required some tweaking, but I don't remember it being difficult to use.&lt;/p&gt;&#xA;" OwnerUserId="555" LastActivityDate="2010-02-22T00:48:44.893" />
  <row Id="1656" PostTypeId="2" ParentId="1654" CreationDate="2010-02-22T00:58:45.233" Score="6" ViewCount="" Body="&lt;p&gt;Have you looked into the Maxim 1-Wire protocol? It is really low speed and if you device takes relatively little current then you can get away with using parasitic power and power the device with the data lines.&lt;/p&gt;&#xA;" OwnerUserId="555" LastActivityDate="2010-02-22T00:58:45.233" CommentCount="3" />
  <row Id="1657" PostTypeId="2" ParentId="1654" CreationDate="2010-02-22T01:59:07.013" Score="2" ViewCount="" Body="&lt;p&gt;There are lots of questions I could ask before giving any advice. I guess the first thing for us to try to understand is, what is your goal here? Low build cost, long communication runs thereby saving wiring, proof of concept or something else. They all would have different recommendations. For example if you aren't worried about cost then maybe go with a Zigbee solution or if it is long runs then that creates problems with most single wire transmitions and now you need to look at other options. I guess the thing that worries me the most about your question is that you say &quot;the simpler the better&quot;. What you are asking is possible in some situations, but I dare to say it won't be simple. Mainly due to the real world problems you will encounter, such as signal loss, noise and current management. If you have more specifics then we could be of more assistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best of luck.&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-02-22T01:59:07.013" CommentCount="1" />
  <row Id="1658" PostTypeId="2" ParentId="1654" CreationDate="2010-02-22T02:14:36.383" Score="2" ViewCount="" Body="&lt;p&gt;Are you sure some sort of USB solution is not workable? You have around 2-2.5W available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are a couple of other ideas --&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Power over ethernet (POE) integrates power and ethernet signals. There are a variety of semiconductors and DC/DC converters designed for these devices. This is probably your best option since there are off-the-shelf parts for this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe some of the home automation companies integrate AC power and communications signals. Maybe some of that is adaptable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The audio folks have &quot;phantom&quot; powering of microphones. 48VDC plus audio over a microphone cable.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-03-09T16:16:20.877" LastActivityDate="2011-03-09T16:16:20.877" CommentCount="2" />
  <row Id="1659" PostTypeId="2" ParentId="1654" CreationDate="2010-02-22T04:01:03.937" Score="3" ViewCount="" Body="&lt;p&gt;I would recommend thinking about it as a signal that you are adding and removing a DC Offset. You can use capacitors to block DC by placing them in series with your circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Beyond that it is hard to say what you will need to do because it will be dependent upon your application. You may need to use an opamp to separate your coupling capacitor from what ever is receiving your signal. If your DC offset voltage is large compared to your signal voltage you may not even need to do any power conditioning on it to remove the ripple, this is all dependent on your application though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a pair of speakers that use this same technique to light a power LED on a secondary speaker. If I turn the volume up loud enough I can actually notice the LED get brighter. In this particular application they would need to be worried about what type of RC filter is being created. &lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-02-22T04:01:03.937" CommentCount="1" />
  <row Id="1660" PostTypeId="2" ParentId="1654" CreationDate="2010-02-22T08:44:59.670" Score="3" ViewCount="" Body="&lt;p&gt;I've built something like this for a train controller system (model train, of course). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It was a monodirectional low speed protocol (a single entity sends data, all others are receivers only) and transmission was done by simply reversing rail polarity. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On every &quot;client&quot; there was a simple circuit done with a pic (16C54, years ago!), a rectifier and some dip switches to set address. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't have source codes anymore, but system was really easy, and worked flawless for years, allowing easy control of every single locomotive, raiload barrier, semaphore etc. from a the main control panel without additional wires.&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2010-02-22T08:44:59.670" CommentCount="2" />
  <row Id="1661" PostTypeId="2" ParentId="1654" CreationDate="2010-02-22T16:50:42.177" Score="5" ViewCount="" Body="&lt;p&gt;You essentially need to push AC signals onto the DC power line, and separate them out again.  This is common in homes with TV antennas - the power amplifier is put near the antenna, and DC power is pushed up the antenna wire while TV signals come down the antenna wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't give enough details for an example circuit, but here are the basics:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The power source should have an inductor in series going to the output to block high frequency signals feeding into the power supply and possibly causing regulation problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each unit's power input should be similarly protected with an inductor to filter out the AC signals.  Feeding that into a diode and capacitor will make sure the AC signals don't jeopardize your module power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Prior to the inductor, you'll also attach a capacitor.  It'll probably be a low value so that most of the AC signals on the line pass the capcitor, but none of the DC will.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output of this capacitor MIGHT be usable directly into a microcontroller (with diode clamping) if you have the skills to implement the necessary software to read the now-mutilated data off the line.  Likewise you can send pulses directly into the capacitor with the I/O pin.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out what that looks like on a scope - the square wave going into the capacitor will look like a decaying spike on the power line.  When it comes out another capacitor on the network it will be further changed - just a spike on the line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reading these spikes can be difficult, and filtering out noise can be difficult, so if you're running long lines, have a noisy power supply, or running lines near other noise sources then you'll have to implement significant signal processing.  Usually this takes the form of AM (ASK - Amplitude shift keying) or FM (FSK - Frequency shift keying) on the line, with data slicers, comparators, tone generators and detectors, etc.  Or the equivalent processing in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may seem like a lot of work, but start off with a simple pulse detector on the receiving end and send square waves when transmitting.  Use an oscilloscope to understand what's happening, and if you find you need a more complex solution ask again about ASK or FSK detection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A pulse detector might be a simple software interrupt on change input pin, or a 555 set up as a pulse stretcher.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-02-22T16:50:42.177" CommentCount="2" />
  <row Id="1662" PostTypeId="2" ParentId="1647" CreationDate="2010-02-22T16:55:53.273" Score="10" ViewCount="" Body="&lt;p&gt;While audio jacks often have switches that can be used for plug detection, most codecs now implement jack sensing that measures the impedance and other characteristics of the plugged in device and make that information available to the processor they are connected to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is also very helpful in preventing an audio amplifier from trying to drive speakers outside its impedance range and damaging the amp or the speakers.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-02-22T16:55:53.273" CommentCount="2" />
  <row Id="1663" PostTypeId="1" AcceptedAnswerId="1664" CreationDate="2010-02-22T19:34:31.793" Score="8" ViewCount="659" Body="&lt;p&gt;Are &lt;a href=&quot;http://en.wikipedia.org/wiki/Plug%5Fcomputer&quot; rel=&quot;nofollow&quot;&gt;plug computers&lt;/a&gt; useful for anything besides network-attached storage?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that you can hang a bunch of drives off them, maybe set up your own web server.  But those uses have limited attractiveness in a home environment, and in a corporate environment, I suspect that ordinary servers would be used.  I could see them used in an industrial environment, perhaps as environmental controllers or energy management devices, but the lack of I/O (keyboard and display) appears to limit their usefulness.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I missing something?  Or do I simply lack imagination?  Do you envision a way to use these in a home environment, other than as a media server/poor man's Tivo?&lt;/p&gt;&#xA;" OwnerUserId="544" LastActivityDate="2010-07-20T18:31:22.310" Title="What are some of the more compelling use cases for plug computers?" Tags="&lt;computers&gt;&lt;microcontroller&gt;&lt;embedded&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="1664" PostTypeId="2" ParentId="1663" CreationDate="2010-02-22T19:53:09.220" Score="6" ViewCount="" Body="&lt;p&gt;There are quite a few people (including me) using them with arduinos. Currently it's only being a temperature sensor. I run a MQTT Server on the sheevaplug and use php scripts to get data from the arduino and send messages into the server for receipt by a few clients. I also monitor the sheevaplug usage via MQTT and post it all to &lt;a href=&quot;http://www.pachube.com/users/chemicaloliver/feeds&quot; rel=&quot;nofollow&quot;&gt;pachube&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My plug also acts as a testing platform for testing websites and an ssh gateway to my network. Other than that you've pretty much outlined the uses, using &amp;lt;5W is a big advantage over anything if you're running a computer 24/7. A lot of people are doing home monitoring these days and it could become the next cult computer for that after the viglen mplc or the linksys slug&lt;/p&gt;&#xA;" OwnerUserId="558" LastActivityDate="2010-02-22T19:53:09.220" />
  <row Id="1665" PostTypeId="2" ParentId="1060" CreationDate="2010-02-22T21:03:15.130" Score="2" ViewCount="" Body="&lt;p&gt;To save money and risk vs. an ASIC.  Unless you&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Deeply care about power or&lt;/li&gt;&#xA;&lt;li&gt;Are building a bunch of them (say &gt;10k units)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;the fixed (NRE) costs of doing an ASIC make it cost prohibitive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you can change a FPGA easily, you can simulate the design less and get into lab quicker.  Also you can do a partial design and build on it, as in software.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-02-22T21:03:15.130" />
  <row Id="1666" PostTypeId="2" ParentId="1663" CreationDate="2010-02-22T21:04:42.790" Score="4" ViewCount="" Body="&lt;p&gt;Hi, here are some past experiences + ideas I have been entertaining concerning homeplugs.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Although I agree that lack of keyboard I/O may limit its usefulness, in some cases, it is actually a good idea. For example, one past project I had worked on involved an embedded thin-client (it wasn't called plug computer back then...) with only an uart IR barcode scanner. And it worked magic for the guys on manufacturing / logistic sites. There was little to no training required. It is directly connected and bootloaded off of the network so it can be easily re-programed for different inventory sets. It was cheap and extremely portable. It can also serve as a cheap &quot;rugged&quot; computer replacement. &lt;/li&gt;&#xA;&lt;li&gt;For home use, it can be easily used to as a gateway to home automation like X10 / Homeplug. It can also be used to make a mother of all twitter-enabled devices (although you can do it much easier with arduino + ethernet shield or a microchip enc28j60). &lt;/li&gt;&#xA;&lt;li&gt;I have also been entertaining the notion of using Xdmx / VNC and a homeplug to create &quot;extra&quot; monitors for my linux workstation at home. Of course, most plug computer does not have video out, but some do, and you can probably get away with using a beagleboard for this purpose as well. The beagleboard has HDMI out IIRC and runs a full blown Cortex-A8 processor. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;As always, treat my ideas with a LOT of skepticism.&lt;/p&gt;&#xA;" OwnerUserId="555" LastActivityDate="2010-02-22T21:04:42.790" />
  <row Id="1667" PostTypeId="2" ParentId="1663" CreationDate="2010-02-22T21:10:19.440" Score="4" ViewCount="" Body="&lt;p&gt;Right now you can get a plug computer for $50.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a few years they'll be $5 or less.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At that point, you might as well buy the plug with the computer built in and use it for home energy insight, automation, and control.  Or build it into every appliance, or both.  Once the appliances can talk to the plugs and the internet, lowering your carbon footprint from your PDA in real time will be trivial.  Leave the house and you can know that you're only consumption is to keep the pipes from freezing.  If you notice a surge in usage when no one is supposed to be home, then you can check on things and see if the police are needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But keep in mind that it's just a development platform.  It's a small, low cost, easy to use, low energy computer.  Remove the plug and you've got a $50 computer that can be run off solar cells and an SLA battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Get a wifi or cellular model, buy a few thousand of them, attach a cheap webcam, and mount them on utility poles pointing at gas station signs.  Viola!  A real-time gas price website for all the gas stations along a few hundred miles of freeway corridor.  If you get each of a thousand people to pay $0.99 per month for the iPhone gas app for that one freeway, you've just made an income source that will keep you in the black for your next project, and you can sell your data to many other services.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connect one to several cameras and GPS on top of your car, use another inside your car as the NAS, and build your own Google streetview car on the cheap for $200.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ignore the fact that you plug them in - that's just part of the built-in development kit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are $50 linux computers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What &lt;em&gt;can't&lt;/em&gt; you use them for?&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-02-22T21:10:19.440" CommentCount="3" />
  <row Id="1668" PostTypeId="1" AcceptedAnswerId="1678" CreationDate="2010-02-23T17:08:25.300" Score="8" ViewCount="223" Body="&lt;p&gt;So a friend and I were talking about schematics at work and how we can better communicate among us and our co-workers. I know &lt;a href=&quot;http://chiphacker.com/questions/1024/uploading-schematics-for-chip-hacker/&quot; rel=&quot;nofollow&quot;&gt;Kortuk had asked a question previously&lt;/a&gt; that was similar, but that question was more about how to make the schematics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead, I'm now asking if anyone knows a good way to collaborate on schematics that are already complete. Kind of like the &lt;a href=&quot;http://chiphacker.com/questions/1024/uploading-schematics-for-chip-hacker/1026#1026&quot; rel=&quot;nofollow&quot;&gt;&quot;Google Docs for Schematics&quot; I talked about in response to Kortuk's question&lt;/a&gt;. I have a bunch of schematics in pdf form that I want to be able to mark up and show to someone with a link as opposed to sending it to them. I also want the content to be secure and probably on an internal server.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think what I really want is a wiki plugin that would allow me to do something like this. Has anyone heard of any program that could achieve something like this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FYI, I've seen software such as &lt;a href=&quot;http://a.nnotate.com/index.html&quot; rel=&quot;nofollow&quot;&gt;a.nnotate&lt;/a&gt;, but don't know if I can swing the price they ask (to keep it behind my firewall). So I'd appreciate open source but am willing to pay something.&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2011-05-17T12:54:11.337" Title="Sharing and Notating Schematics?" Tags="&lt;schematics&gt;&lt;communication&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="1669" PostTypeId="1" AcceptedAnswerId="1679" CreationDate="2010-02-23T17:53:26.050" Score="5" ViewCount="210" Body="&lt;p&gt;I've built a temperature sensor module that runs off of 4xAA batteries and sends data back to a computer via XBee.  Works great, until the weather gets cold.  At that point, the rechargeable AA batteries (I've tried duracell and eneloop) die very quickly.  At 40 or so it seems like they can hardly muster the 3.3V needed to power the wireless.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This needs to be battery powered - running a wire to it isn't an option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying plain old alkalines right now, but I was wondering if anyone had any tips on getting enough power out of batteries during the winter.  Do I just need to double up and use 8 batteries?  Do NiCad or LiPo cells work better than NiMH?  Would switching to a different wireless module that can handle lower voltage solve the problem?&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2011-05-17T12:54:24.867" Title="Cold weather battery power" Tags="&lt;battery&gt;&lt;wireless&gt;" AnswerCount="3" />
  <row Id="1670" PostTypeId="2" ParentId="1669" CreationDate="2010-02-23T18:14:44.630" Score="6" ViewCount="" Body="&lt;p&gt;Lithium-Ion batteries might be your best option for rechargeables...They have a low self-discharge rate, and apparently work better in cold weather.  Unfortunately, all of the popular types of batteries basically stop working at temperatures approaching freezing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you might consider doing is putting up a small solar cell for trickle charging, and insulating the batteries.  If you can get the insulation right, the trickle charge will warm the batteries during the day, and the insulation will keep them warm at night.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Energizer claims that their &lt;a href=&quot;http://www.energizer.com/PRODUCTS/HIGHTECH-BATTERIES/LITHIUM/Pages/lithium-batteries.aspx&quot; rel=&quot;nofollow&quot;&gt;Ultimate Lithium&lt;/a&gt; works well all the way down to -40ºC&lt;/p&gt;&#xA;" OwnerUserId="544" LastEditorUserId="544" LastEditorDisplayName="" LastEditDate="2010-02-23T18:21:46.727" LastActivityDate="2010-02-23T18:21:46.727" />
  <row Id="1671" PostTypeId="2" ParentId="1668" CreationDate="2010-02-23T18:51:40.210" Score="1" ViewCount="" Body="&lt;p&gt;There's tons of web-based services like a.nnotate, while most of them offer free or very cheap usage, they generally charge lots more for an &quot;enterprise&quot; solution where you host it yourself. IMO unless you're working at Intel or NVidia or something, probably industrial espionage is not really a threat to you, and you can probably trust 3rd parties with your data.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-02-23T18:51:40.210" CommentCount="2" />
  <row Id="1672" PostTypeId="2" ParentId="1561" CreationDate="2010-02-23T19:49:08.567" Score="1" ViewCount="" Body="&lt;p&gt;If nothing else you can buy motors from Roombas rather cheap here: &lt;a href=&quot;http://www.protechrobotics.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.protechrobotics.com/&lt;/a&gt; or even cheaper here at roombarecycle  The Roomba motors either have gearheads on them or a head to use a rubber pulley. Most mechanical parts can also be found there.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-02-23T19:49:08.567" />
  <row Id="1673" PostTypeId="2" ParentId="1668" CreationDate="2010-02-23T19:50:25.130" Score="3" ViewCount="" Body="&lt;p&gt;A revision control system (e.g. git) would let engineers checkout a branch, annotate&#xA;and change the files and then merge the changes back. Not the same as marking up &#xA;a PDF file or a piece of paper but it could be useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of my schematic and PCB files are in ASCII. I know there are a number &#xA;of people who use git for revision control of their EDA work.&#xA;Open source, runs on a local or remote server. You would also get redundancy.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:54:11.337" LastActivityDate="2011-05-17T12:54:11.337" />
  <row Id="1674" PostTypeId="1" CreationDate="2010-02-23T21:07:46.460" Score="7" ViewCount="825" Body="&lt;p&gt;Is there a common netlist format that is portable between different schematic/pcb/EDA/CAD tools, and if so where is the format or reference so I can implement it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not, does each package implement it differently, or are there a few standards that, if implemented, might give greater compatibility with a broad range of tools?&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:45:09.047" LastActivityDate="2011-03-24T00:41:25.730" Title="Is there a common netlist format?" Tags="&lt;schematics&gt;&lt;cad&gt;&lt;pcb&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="1675" PostTypeId="2" ParentId="1674" CreationDate="2010-02-23T21:53:04.800" Score="4" ViewCount="" Body="&lt;p&gt;I have not seen any standards. Each package implements their own format.&#xA;Fortunately the format is very simple making it easy to translate between &#xA;packages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example the gEDA netlist consists of records in the following&#xA;format --&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NETNAME  REFDES-PIN REFDES-PIN ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;here is a sample from one of my boards -- &lt;/p&gt;&#xA;&#xA;&lt;p&gt;unnamed_net39   J28-3 U11-12 &lt;/p&gt;&#xA;&#xA;&lt;p&gt;unnamed_net38   J28-1 J16-2 J27-1 &lt;/p&gt;&#xA;&#xA;&lt;p&gt;GND J16-3 C16-2 J15-3 C15-2&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could easily read this netlist file into a data structure and translate it&#xA;to a different format.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-24T00:41:25.730" LastActivityDate="2011-03-24T00:41:25.730" CommentCount="1" />
  <row Id="1676" PostTypeId="2" ParentId="1674" CreationDate="2010-02-23T23:55:35.090" Score="2" ViewCount="" Body="&lt;p&gt;If they are saved in ASCII form it is quite easy to convert them, I can import most formats into the Pulsonix PCB software I use. The only awkward one is Eagle; Eagle schematics, PCBs and libraries have to be converted by a specially written ULP.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-02-23T23:55:35.090" />
  <row Id="1677" PostTypeId="1" CreationDate="2010-02-24T01:32:48.480" Score="4" ViewCount="1691" Body="&lt;p&gt;Hi,&#xA;I found vary nice open source avr emulator ( &lt;a href=&quot;http://gitorious.org/simavr&quot; rel=&quot;nofollow&quot;&gt;http://gitorious.org/simavr&lt;/a&gt;). Since there is uart emulation implemented it can simulate Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is board_simduino example, but I have some problems with it. I hooked up virtual leds to port B (pins 8-13) - &lt;a href=&quot;http://gitorious.org/~viroos/simavr/viroos-simduino-simavr/commit/bfaeac1e61f1d6678b3daab7fede9a783d01c098&quot; rel=&quot;nofollow&quot;&gt;http://gitorious.org/~viroos/simavr/viroos-simduino-simavr/commit/bfaeac1e61f1d6678b3daab7fede9a783d01c098&lt;/a&gt;, and they works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But serial connection looks broken. I can upload sketch (I added &lt;code&gt;,link=/dev/ttyUSB0&lt;/code&gt; to socat command for that), but after that communication stops working. For example I can upload &quot;physical pixel&quot; sketch but I can't turn on leds. I tried to connect using serial monitor in build in IDE and from pySerial. It's looks like commends are being ignored.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also in &quot;blink&quot; sketch I in main loop:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void loop()&#xA;{&#xA; digitalWrite(ledPin, HIGH);   // set the LED on&#xA; delay(1000);                  // wait for a second&#xA; digitalWrite(ledPin, LOW);    // set the LED off&#xA; delay(1000);                  // wait for a second&#xA;}&quot;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I have to remove &lt;code&gt;delay(1000);&lt;/code&gt; command because they hangups emulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will appreciate any help. Most important form me for now is uart fixing (run &quot;physical pixel&quot; sketch). &lt;/p&gt;&#xA;" OwnerUserId="422" LastEditorUserId="422" LastEditorDisplayName="" LastEditDate="2010-02-24T08:50:15.740" LastActivityDate="2010-03-22T04:07:57.623" Title="How can I use avrsim to simulate Arduino?" Tags="&lt;arduino&gt;&lt;simulation&gt;" AnswerCount="1" />
  <row Id="1678" PostTypeId="2" ParentId="1668" CreationDate="2010-02-24T01:42:25.933" Score="3" ViewCount="" Body="&lt;p&gt;There's a wiki plugin (&lt;a href=&quot;http://wikitex.org/&quot; rel=&quot;nofollow&quot;&gt;WikiTeX&lt;/a&gt;) for including schematics inline, but it seems abandoned and not really what you're looking for.  You'd paste the source code of a gschem circuit into the page, which is then rendered as an image by the backend, and then you could make modifications to it and they'd be saved in the wiki's version control.  The gschem code is not at all user-friendly, though, and the only examples I can find are broken, even on their own example site:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://wikisophia.org/wiki/Schem&quot; rel=&quot;nofollow&quot;&gt;http://wikisophia.org/wiki/Schem&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.organicdesign.co.nz/WikiTeX_music_and_schematics&quot; rel=&quot;nofollow&quot;&gt;http://www.organicdesign.co.nz/WikiTeX_music_and_schematics&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;There's also the &lt;a href=&quot;http://commons.wikimedia.org/wiki/Help%3aGadget-ImageAnnotator&quot; rel=&quot;nofollow&quot;&gt;image annotator for Mediawiki&lt;/a&gt;...&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-02-25T14:58:06.700" LastActivityDate="2010-02-25T14:58:06.700" CommentCount="1" />
  <row Id="1679" PostTypeId="2" ParentId="1669" CreationDate="2010-02-24T12:58:49.153" Score="3" ViewCount="" Body="&lt;p&gt;Are the batteries actually dead or will they start to work if the temperature&#xA;is increased? Is the XBee on all the time or does it spend most of its time &#xA;sleeping?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming the batteries just need to be warmed -- &#xA;if the XBee does not have to be on all the time you may be able &#xA;to perform a startup sequence that consists of drawing current &#xA;from the batteries to warm them up and then enabling the XBee. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A wide input range DC-DC converter would also enable you to startup&#xA;at lower voltages. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One other note the XBees can be run at 3V. They also draw very low&#xA;currents in the hibernate modes when run at 3V. I have some plots &#xA;of duty-cycle and current draw for different operating modes at &lt;a href=&quot;http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:54:24.867" LastActivityDate="2011-05-17T12:54:24.867" CommentCount="2" />
  <row Id="1680" PostTypeId="2" ParentId="1674" CreationDate="2010-02-24T17:21:31.247" Score="2" ViewCount="" Body="&lt;p&gt;I haven't seen a standard format anywhere, either. However, as others have mentioned, netlist formats are very simple and usually text-based, and thus trivial to translate between various forms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A netlist is simply a list of nets (wires), with a list of ports (pins of components) that attach on each wire. Although the details differ, it's all a variation of the same theme. In the past I've written several scripts in Perl and Python that easily manipulate netlists. As a matter of fact, netlist files are a great exercise in beginner-level text processing.&lt;/p&gt;&#xA;" OwnerUserId="560" LastActivityDate="2010-02-24T17:21:31.247" />
  <row Id="1681" PostTypeId="2" ParentId="1635" CreationDate="2010-02-24T17:27:02.717" Score="8" ViewCount="" Body="&lt;p&gt;IMHO for its low price, the DSO Nano is actually a good first-time scope. As others have mentioned, you will have problems with showing anything faster than 100-250KHz coherently, but this is pretty high for quite a lot of uses. Yes, you won't be able to see system clocks or PWMs with it, but in my experience a scope is more useful for analog signals, and as long as they don't rise and fall too quickly, you'll be fine with the DSO Nano. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you get more money and become more serious about the projects, you should invest in a 2nd hand scope, something real with at least 100MHz bandwidth.&lt;/p&gt;&#xA;" OwnerUserId="560" LastActivityDate="2010-02-24T17:27:02.717" />
  <row Id="1682" PostTypeId="2" ParentId="1635" CreationDate="2010-02-24T20:48:03.597" Score="8" ViewCount="" Body="&lt;h2&gt;The DSO Nano is a poor choice for a hobbyist's oscilloscope.&lt;/h2&gt;&#xA;&#xA;&lt;h3&gt;Capabilities&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;It's really only good for audio bandwidth signals - anything above 100kHz is going to be visible, but unmeasurable.  By most standards you want the sampling rate to be 10x the bandwidth of the signal in order to get close to measuring significant parameters of the signal (peaks, rise time, frequency, duty cycle, etc).  While you can see signals with as poor as a 5x sampling rate, you can't reliably measure such signals and expect to get good results.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Competition, New Oscilloscopes&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that a very low end entry oscilloscope NEW is only about $400 - so if you can spend more then a 2 channel 50MHz Rigol would be a fine choice as a beginner:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.30573&quot; rel=&quot;nofollow&quot;&gt;http://www.dealextreme.com/details.dx/sku.30573&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that the 50MHz rating is the fastest signal it can measure.  It measures at 1 billion samples per second for one channel, or 500 million samples per second for both channels, which means you'll be able to see signals much faster than the rated 50MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compared to the single channel, 1 million samples per second Nano this is worlds better.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Competition, Used Oscilloscopes&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;But even if that's too much, you can get a $50-$100 used oscilloscope on ebay that is significantly better than the nano.  For the same price you can easily find a 2 channel 20MHz scope (which can be used to measure the clock of a 40MHz micro, just not precisely) and there are many scopes in the 50-60MHz range for under $100.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;What is it good for?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;The nano is NOT an oscilloscope replacement.  The major reasons to get one are&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You want one (it's open source, and could be fun to hack)&lt;/li&gt;&#xA;&lt;li&gt;You need a portable device that can function as a simple oscilloscope for audio bandwidth applications&lt;/li&gt;&#xA;&lt;li&gt;You are only interested in high-level overview of the signals you measure, and won't really be doing significant work with it (ie, beginning hobbyist) so don't want something bulky that you might only use a few times a year.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;That being said, despite its severe limitations, I can see it as an additional tool for the workbench after you've invested in a good oscilloscope and other gear.  Keep in mind that many tasks, such as SPI, can be slowed down to within the range of the oscilloscope, and even though it's only good up to 100kHz analog signals, one could reasonably measure up to 500kHz digital signals (if they wrote software for the Nano that synchronized the ADC clock to the input signal).&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Conclusion&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;The price to performance of the device is just so low that I can't see it being worth the cost except to tinkerers that might want to hack it.  Your money is better spent on a used oscilloscope.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-02-24T20:48:03.597" CommentCount="3" />
  <row Id="1683" PostTypeId="2" ParentId="952" CreationDate="2010-02-24T20:58:49.247" Score="1" ViewCount="" Body="&lt;p&gt;Lattice Semiconductor (an FPGA company) has &lt;a href=&quot;http://latticeblogs.typepad.com/&quot; rel=&quot;nofollow&quot;&gt;this blog&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-02-24T20:58:49.247" CommunityOwnedDate="2010-02-24T20:58:49.247" />
  <row Id="1684" PostTypeId="2" ParentId="952" CreationDate="2010-02-24T21:02:26.980" Score="1" ViewCount="" Body="&lt;p&gt;This &lt;a href=&quot;http://fpgacomputing.blogspot.com/&quot; rel=&quot;nofollow&quot;&gt;one on reconfigurable computing&lt;/a&gt; in FPGAs.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-02-24T21:02:26.980" CommunityOwnedDate="2010-02-24T21:02:26.980" />
  <row Id="1685" PostTypeId="2" ParentId="1654" CreationDate="2010-02-24T22:09:55.003" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/X10_%28industry_standard%29&quot; rel=&quot;nofollow&quot;&gt;X-10 protocol&lt;/a&gt; does exactly this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also some of the suggestions above aren't safe or certainly can't be used in approved (UL/CE mark) devices.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-02-24T22:09:55.003" CommentCount="2" />
  <row Id="1686" PostTypeId="2" ParentId="1668" CreationDate="2010-02-24T22:31:25.460" Score="1" ViewCount="" Body="&lt;p&gt;We print to Adobe and use its review features of the full edition.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-02-24T22:31:25.460" CommentCount="1" />
  <row Id="1687" PostTypeId="2" ParentId="1663" CreationDate="2010-02-25T00:15:08.340" Score="1" ViewCount="" Body="&lt;p&gt;&quot;Classic&quot; ideas: &lt;a href=&quot;http://www.openplug.org/index.php/us/resources/innovation-plans&quot; rel=&quot;nofollow&quot;&gt;http://www.openplug.org/index.php/us/resources/innovation-plans&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But If You connect Arduino to it then skyt is the limit ;). Most advantage over using ethernet shield or even openWRT base router for it is having full Linux distro already installed. You can ssh to it install python, pySerial, cherrypy and You got perfect web controller. I did exactly the same using Asus WL-500W but it was much harder, router took more place on my desk, I had to use pen drive for storage and router was more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course lack of WiFi is disappointing, but GuruPlug will have it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I all ready prerecorded GuruPlug and I will use my SheevaPlug as base for internet radio (I will connect it to good external sound card like sound blaster extigy or similar)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;//edit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One more interesting idea: &lt;a href=&quot;http://groups.google.com/group/wview/web/tutorial---wview-on-the-sheeva&quot; rel=&quot;nofollow&quot;&gt;http://groups.google.com/group/wview/web/tutorial---wview-on-the-sheeva&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also think about replacing power supply with battery (ther is also solar panel example on the Wiki), and use it in robot.&lt;/p&gt;&#xA;" OwnerUserId="422" LastEditorUserId="422" LastEditorDisplayName="" LastEditDate="2010-02-25T22:01:05.413" LastActivityDate="2010-02-25T22:01:05.413" />
  <row Id="1688" PostTypeId="2" ParentId="1374" CreationDate="2010-02-25T14:23:06.103" Score="1" ViewCount="" Body="&lt;p&gt;check out this question&#xA;&lt;a href=&quot;http://chiphacker.com/questions/815/rtos-for-arduino&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/815/rtos-for-arduino&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2010-02-25T14:23:06.103" />
  <row Id="1689" PostTypeId="1" AcceptedAnswerId="1694" CreationDate="2010-02-25T14:31:07.060" Score="5" ViewCount="673" Body="&lt;p&gt;Are there any alternatives to this ancient yet still popular way of communication?&lt;/p&gt;&#xA;" OwnerUserId="561" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-28T21:14:49.797" LastActivityDate="2011-02-28T21:14:49.797" Title="It's been more than 10 years (since I designed hardware with RS-232), and we're still using RS-232?" Tags="&lt;uart&gt;&lt;communication&gt;&lt;rs232&gt;" AnswerCount="8" CommentCount="0" FavoriteCount="2" />
  <row Id="1690" PostTypeId="2" ParentId="1689" CreationDate="2010-02-25T15:07:33.203" Score="10" ViewCount="" Body="&lt;p&gt;There are many alternatives.  USB is the one that seems most commonly used nowadays.  I2C is another.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RS-232 still exists for legacy reasons.  If you can put up with the mishmash of different data rates, stop bits, parity settings and wiring configurations, it is actually quite a simple, solid and reliable interface for low data rate applications. &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;I listened to a podcast recently that discussed the handling of audio at a seminar.  All of the audio pros still use XLR connectors and conventional microphone cables, a technology that's at least &lt;a href=&quot;http://www.rane.com/par-c.html#XLR&quot; rel=&quot;nofollow&quot;&gt;50 years old&lt;/a&gt;, even though newer alternatives are available. They use it because it is stable, proven, reliable, and industry-standard.&lt;/p&gt;&#xA;" OwnerUserId="544" LastEditorUserId="544" LastEditorDisplayName="" LastEditDate="2010-02-25T22:07:35.063" LastActivityDate="2010-02-25T22:07:35.063" />
  <row Id="1691" PostTypeId="2" ParentId="1689" CreationDate="2010-02-25T15:26:37.533" Score="3" ViewCount="" Body="&lt;p&gt;A lot of systems will convert the RS-232 to USB using a converter IC. &#xA;The ones that seem to be the most popular are the FTDI devices.&#xA;FTDI sells a cable with a USB connector on one end and six pin header&#xA;on the other (FTDI TTL-232R-3V3). This converts from a USB to RS232 at &lt;strong&gt;TTL levels&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FTDI also makes an IC to perform the same function -- FTDI FT232RL. This&#xA;is in an SMD package. You connect the data inputs to the USB connector and the &#xA;outputs to an RS232 at &lt;strong&gt;TTL Levels&lt;/strong&gt;. The cable is in the $15-$20 range.&#xA;The IC is around $2.50 (100). The IC requires a half dozen passives. I&#xA;also like to add a TVS IC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It you need to get true RS232 levels you would need a driver IC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;More of the hobbyist parts are now starting to integrate USB into the low&#xA;end controllers. RS232 will start to be used only where you need a large&#xA;number of simple UARTs. &lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-28T21:13:56.163" LastActivityDate="2011-02-28T21:13:56.163" />
  <row Id="1692" PostTypeId="2" ParentId="1689" CreationDate="2010-02-25T15:34:34.357" Score="23" ViewCount="" Body="&lt;p&gt;What do you mean - just 10 years.  RS-232 was defined in 1962 and so is coming up to its 48th birthday.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RS-232 uses a simple asynchronous serial data transfer method that requires very little silicon, is easy to code in software and can be used on micros with minute amounts of RAM or program memory.  It has also had the advantage in the past that all computers and dumb terminals had RS-232 interfaces so using it for debug output was a no-brainer.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you needed higher speed or long distance transmission then you just replace the line drivers with RS-422 or RS-485 differential driver/receivers and no change to the software was needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Implementing USB on tiny micros is just not possible.  The processing/memory/silicon overhead is just too costly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SPI or I2C are possible (and used in some places) but the interface cards for your pc are unusual and expensive.  I2C has a nasty lockup state that can make it die if the clock stops halfway through a slave data output cycle and the data bit is low.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-02-25T15:34:34.357" CommentCount="1" />
  <row Id="1693" PostTypeId="2" ParentId="1689" CreationDate="2010-02-25T16:06:33.710" Score="11" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;Very reliable.&lt;/li&gt;&#xA;&lt;li&gt;Easy to implement.&lt;/li&gt;&#xA;&lt;li&gt;Requires only 3 wires, most of the time.&lt;/li&gt;&#xA;&lt;li&gt;Uses wide voltage swing.&lt;/li&gt;&#xA;&lt;li&gt;It has many devices that have used it.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;mice&lt;/li&gt;&#xA;&lt;li&gt;printers &lt;sup&gt;&lt;sub&gt;I have at least one&lt;/sub&gt;&lt;/sup&gt;&lt;/li&gt;&#xA;&lt;li&gt;modems&lt;/li&gt;&#xA;&lt;li&gt;scanners&lt;/li&gt;&#xA;&lt;li&gt;bar-code scanners&lt;/li&gt;&#xA;&lt;li&gt;multi-meters&lt;/li&gt;&#xA;&lt;li&gt;GPS units&lt;/li&gt;&#xA;&lt;li&gt;various scientific equipment&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Can be used to transfer data between two computers with only changing around a few wires.&#xA;&lt;sup&gt;&lt;sub&gt;( Just try that with USB )&lt;/sub&gt;&lt;/sup&gt;&lt;/li&gt;&#xA;&lt;li&gt;Has been implemented in many different micro-controllers&lt;/li&gt;&#xA;&lt;li&gt;Doesn't require expensive cable. Except in extreme circumstances, including high speeds.&lt;/li&gt;&#xA;&lt;li&gt;You can easily make your own cable, without special tools.&lt;/li&gt;&#xA;&lt;li&gt;Can be easily adapted for longer cable runs, by using RS-422 or RS-485 signalling.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Frankly with that record, I would be surprised if it ever goes away entirely.&lt;/p&gt;&#xA;" OwnerUserId="1301" LastEditorUserId="1301" LastEditorDisplayName="" LastEditDate="2010-02-25T21:09:51.353" LastActivityDate="2010-02-25T21:09:51.353" CommentCount="2" />
  <row Id="1694" PostTypeId="2" ParentId="1689" CreationDate="2010-02-25T17:03:40.477" Score="18" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;It’s been more than 10 years, and we’re still using RS-232?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;It's just a communications standard, and very bare-bones at that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your statement is not much different than, &quot;It’s been more than 10 years, and we’re still using wires?&quot;  Despite optical and RF solutions being available, wire still has some very distinct advantages, just like RS-232.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main advantages are &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;It's cheap&lt;/li&gt;&#xA;&lt;li&gt;It's trivially easy to use&lt;/li&gt;&#xA;&lt;li&gt;It uses fewer wires than parallel data transmission&lt;/li&gt;&#xA;&lt;li&gt;It goes long distances (measured in &lt;a href=&quot;http://www.marcspages.co.uk/tech/long232.htm&quot; rel=&quot;nofollow&quot;&gt;hundreds of feet/tens of meters&lt;/a&gt;, rather than inches/cm for most TTL/CMOS signals)&lt;/li&gt;&#xA;&lt;li&gt;It's widely used in many products&lt;/li&gt;&#xA;&lt;li&gt;Compatibility issues are rare&lt;/li&gt;&#xA;&lt;li&gt;It's standardized, and a UART is included on all but the most simple microcontrollers&lt;/li&gt;&#xA;&lt;li&gt;Lots of converters are available to convert it to other standards (such as USB)&lt;/li&gt;&#xA;&lt;li&gt;Uses trivial NRZ encoding, so it's easy to interpret even without a UART&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Disadvantages include&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Slow&lt;/li&gt;&#xA;&lt;li&gt;Doesn't specify protocol or higher layers of the communications stack&lt;/li&gt;&#xA;&lt;li&gt;Standard connectors are bulky&lt;/li&gt;&#xA;&lt;li&gt;Doesn't supply power&lt;/li&gt;&#xA;&lt;li&gt;No standard identification mechanism (ie, can't plug it in and have the host know what was plugged in and its capabilities)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Are there any alternatives to this ancient yet still popular way of communication?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;There are certainly alternatives, but no competitors that have &lt;em&gt;all&lt;/em&gt; the above advantages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We could list off the thousands of communication standards one might use in place of RS-232, but the bottom line is that RS-232 hasn't been replaced or superceded.  USB is the closest thing to it, but is severely limited in terms of distance, cost, ease of use, and included silicon on most microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;USB has other significant advantages that RS-232 doesn't have, though.  They aren't replacements for each other, and in fact happily coexist on many computers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The key point is that RS-232 is a tool, and as such isn't intrinsically bad, or in need of replacement.  It's getting less use these days as people want more advanced features, or faster speeds, or have some other requirement which RS-232 doesn't fulfill.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But that doesn't mean that it should or will go away, because there are still a lot of &lt;em&gt;new&lt;/em&gt; applications where RS-232 is the perfect fit.&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="161" LastEditorDisplayName="" LastEditDate="2010-03-01T13:59:33.093" LastActivityDate="2010-03-01T13:59:33.093" />
  <row Id="1695" PostTypeId="2" ParentId="1689" CreationDate="2010-02-25T20:22:35.700" Score="2" ViewCount="" Body="&lt;p&gt;I'm a fan of USB &amp;lt;--&gt; Serial IC's, handles all the dirty work of implementing USB, and you can pump up the bitrates to extreme levels (official RS232 tops out at what, 115k? I've seen USB&amp;lt;--&gt;serial do several mbit/sec before)&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-02-25T20:22:35.700" CommentCount="2" />
  <row Id="1696" PostTypeId="1" CreationDate="2010-02-26T00:52:37.460" Score="7" ViewCount="921" Body="&lt;p&gt;Lately I've been doing a lot of work with &lt;a href=&quot;http://en.wikipedia.org/wiki/Intel_HEX&quot; rel=&quot;nofollow&quot;&gt;Intel HEX&lt;/a&gt; files.  I want a program that can import an Intel HEX file and allow me to view the byte contents at each address.  There are a handful of programs I've seen that do this, but are there any that are good which are free and also allow you to see the contents at an absolute address, not a relative address to the start of the hex file (for example, if the intel hex file starts writing at address 200, the application should signify that addresses 0-199 are blank and not show as if it starts at address 0).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: So I posted this question quite a while ago and the best tool I've found is not really a tool meant to view HEX files, but Segger's J-Link Flash programming software.  Its really meant to program chips, but it reads HEX files beautifully.  Find it here: &lt;a href=&quot;http://www.segger.com/cms/jlink-software.html&quot; rel=&quot;nofollow&quot;&gt;http://www.segger.com/cms/jlink-software.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll keep the question open so folks can post their favorite intel HEX viewers&lt;/p&gt;&#xA;" OwnerUserId="107" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-02T17:29:30.093" LastActivityDate="2011-02-02T17:29:30.093" CommunityOwnedDate="2011-02-09T13:48:06.387" Title="Intel HEX (.hex) Viewer/Readers" Tags="&lt;microcontroller&gt;" AnswerCount="10" CommentCount="3" FavoriteCount="2" />
  <row Id="1697" PostTypeId="1" AcceptedAnswerId="1699" CreationDate="2010-02-26T07:55:52.210" Score="4" ViewCount="358" Body="&lt;p&gt;Which websites/blogs/tools/books/manuals would you recommend for getting into the Freescale microcontrollers, especially the 32-bit models?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the best development tools (IDEs, compilers) for this environment.  There is so much out there for the AVRs, ARMs, PICs but not too much for Freescale.  I admit, I need to spend more time with Google on this and just thought I'd save myself plenty of time by asking the &quot;experts&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="561" LastEditorUserId="11" LastEditorDisplayName="" LastEditDate="2010-02-26T13:21:53.773" LastActivityDate="2011-05-19T14:13:55.047" Title="How to get into Freescale 32-bit MicroControllers?" Tags="&lt;microcontroller&gt;&lt;freescale&gt;" AnswerCount="3" />
  <row Id="1698" PostTypeId="2" ParentId="1696" CreationDate="2010-02-26T11:02:31.793" Score="1" ViewCount="" Body="&lt;p&gt;I've not used any of these, so I'm not sure if they meet your requirements or not:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hexplorer.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;Hexplorer&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sf-soft.de/hex-editor.html&quot; rel=&quot;nofollow&quot;&gt;WinHex&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There also seem to be some links at the bottom of the &lt;a href=&quot;http://en.wikipedia.org/wiki/Intel_HEX&quot; rel=&quot;nofollow&quot;&gt;Intel HEX page on wikipedia&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope these give you some more starting points, although you've probably looked at them already.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-02-26T11:02:31.793" CommunityOwnedDate="2011-02-09T13:48:06.387" />
  <row Id="1699" PostTypeId="2" ParentId="1697" CreationDate="2010-02-26T11:58:48.247" Score="3" ViewCount="" Body="&lt;p&gt;The Freescale devices aren't very popular, hence there isn't much support for them, and the tools are expensive. If you want to get into 32-bit MCUs you would be better off with ARM. The new NXP Cortex-M0 chips are very cheap, and you have lots of choice with the development tools, some of which are free. I've been playing with the new NXP LPCXpresso board - £18 each (!), with a nice (free) development environment.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-02-26T11:58:48.247" CommentCount="3" />
  <row Id="1700" PostTypeId="2" ParentId="1697" CreationDate="2010-02-26T13:21:14.960" Score="3" ViewCount="" Body="&lt;p&gt;A while ago I did a large project with Coldfire chips &#xA;(64 uCs per system, lots of RS232 lines ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used EMACS, a Makefile and gcc. It ran on Linux and Windows. I am not sure how&#xA;actively Coldfire gcc is developed. At the time the Coldfire chips were a very good&#xA;value. Haven't looked at them in a while. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;IIRC there was a commercial compiler with an IDE available for Windows. It was around $2K. Since&#xA;some development was on Linux and some on Windows we ended up using gcc.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:13:55.047" LastActivityDate="2011-05-19T14:13:55.047" />
  <row Id="1701" PostTypeId="2" ParentId="1696" CreationDate="2010-02-26T15:04:10.620" Score="0" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://www.hhdsoftware.com/Products/home/hex-editor-free.html&quot; rel=&quot;nofollow&quot;&gt;Hex Editor Neo&lt;/a&gt;.  It has some unique properties that make it useful for my particular brand of work, such as the ability to handle large files, unlimited undo/redo, and the ability to create patches.  It can display data as bytes, words, double words, and floating point numbers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't believe it has any awareness of the Intel Hex File format.  It can make relative jumps, however.  So if your file starts at address 200, you can jump absolute to your specified address, and then jump relative minus 200, and that should take you to the exact byte.&lt;/p&gt;&#xA;" OwnerUserId="544" LastEditorUserId="544" LastEditorDisplayName="" LastEditDate="2010-02-26T15:25:32.700" LastActivityDate="2010-02-26T15:25:32.700" CommunityOwnedDate="2011-02-09T13:48:06.387" />
  <row Id="1702" PostTypeId="2" ParentId="1504" CreationDate="2010-02-26T15:32:00.120" Score="1" ViewCount="" Body="&lt;p&gt;Hello,&#xA;I have a large qty. of LCD screens available, with datasheet, source code, and a sample program to drive the LCD through the parallel port. It is a 1.5&quot; 128x128 LCD Screen with 65K color and the contacts are a good size for soldering to. The link is here:&#xA;&lt;a href=&quot;http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&amp;amp;rd=1&amp;amp;item=170408432092&amp;amp;ssPageName=STRK%3aMESE%3aIT&quot; rel=&quot;nofollow&quot;&gt;http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&amp;amp;rd=1&amp;amp;item=170408432092&amp;amp;ssPageName=STRK:MESE:IT&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-02-26T15:37:20.647" CommentCount="2" />
  <row Id="1703" PostTypeId="2" ParentId="1696" CreationDate="2010-02-26T15:50:19.950" Score="4" ViewCount="" Body="&lt;p&gt;If you have access to a KDE computer you should try Okteta.  It interprets hex in 3 or 4 formats at once.  Very very nice, esp if you are looking at mixed meaning hex code.&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2010-02-26T15:50:19.950" CommunityOwnedDate="2011-02-09T13:48:06.387" CommentCount="1" />
  <row Id="1704" PostTypeId="2" ParentId="952" CreationDate="2010-02-26T18:12:43.813" Score="2" ViewCount="" Body="&lt;p&gt;I feel a little self-serving by adding this one, but I write it and I do try to mostly put in useful information without too much commercial type content. &lt;a href=&quot;http://blog.screamingcircuits.com&quot; rel=&quot;nofollow&quot;&gt;http://blog.screamingcircuits.com&lt;/a&gt;. It's predominantly about how to avoid common design and layout things that trip a lot of people up when they get to the point of building a board.&lt;/p&gt;&#xA;" OwnerUserId="425" LastActivityDate="2010-02-26T18:12:43.813" CommunityOwnedDate="2010-02-26T18:12:43.813" />
  <row Id="1705" PostTypeId="1" AcceptedAnswerId="1731" CreationDate="2010-02-27T11:21:11.373" Score="0" ViewCount="468" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a couple of years experience in designing/developing hardware solutions.  It's such a pity that I don't have the creativity nor the time to figure out what a feasible project would be to spend my time on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you find it frustrating having all the power and nothing to spend it on that will be worth while?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, in essence, I guess I'm asking for ideas.  Ideas you don't want to implement.  Ideas that can be implemented by a single guy and not an army.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking forward to your responses.&lt;/p&gt;&#xA;" OwnerUserId="561" LastActivityDate="2010-06-05T22:21:45.897" Title="Looking for a hardware project idea that actually sells" Tags="&lt;hardware&gt;&lt;projects&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="2" />
  <row Id="1706" PostTypeId="2" ParentId="1705" CreationDate="2010-02-27T16:42:55.993" Score="7" ViewCount="" Body="&lt;p&gt;If any of us had such great easy money making ideas, why would we give them to you for free instead of getting rich ourselves?&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-02-27T16:42:55.993" CommentCount="2" />
  <row Id="1707" PostTypeId="1" CreationDate="2010-02-27T17:18:11.877" Score="4" ViewCount="973" Body="&lt;p&gt;How much current do you require in Arduino/Sanguino or other embedded &#xA;systems projects?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After responding to the LM2575 inductor question I started to take &#xA;a closer look at the TI power DC-DC converters. It would not be&#xA;difficult to replace the linear regulator + or'ing diodes on all&#xA;my Arduino/Sanguino compatible boards with a TI step-down converter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would provide a &gt;90% efficient conversion, input voltages from 5-15V&#xA;and a 2.5A output that is regulated and adjustable. What would be&#xA;sacrificed would be the ability to power off of the USB. The incremental&#xA;cost would be in the $5-$8 range. Wider range inputs are also &#xA;possible. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the 500mA you can get from the USB port all you ever need? &#xA;Would this be useful in your projects or is it too little current?&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-31T05:25:17.810" LastActivityDate="2011-01-31T05:27:45.497" Title="How much current do you require in Arduino and embedded systems projects?" Tags="&lt;arduino&gt;&lt;power-supply&gt;&lt;smps&gt;" AnswerCount="5" />
  <row Id="1708" PostTypeId="2" ParentId="1705" CreationDate="2010-02-28T01:03:49.887" Score="13" ViewCount="" Body="&lt;p&gt;I have a spreadsheet on google documents with my ever-growing list of ideas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No, you can't have it.  Mostly because the vast majority of ideas won't make money and are useless, but more importantly because &lt;em&gt;you&lt;/em&gt; will best succeed with an idea you believe in, not someone else's idea, especially if you are only interested in the profit, and not the motive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I keep adding ideas to the list to stimulate the creative portion of my brain, and to have an outlet for all those random thoughts and ideas.  This is one thing I do to keep my 'creativity' knife sharp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are lots of articles on the internet on how to be creative, start here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://google.com/search?q=practicing+creativity&quot; rel=&quot;nofollow&quot;&gt;http://google.com/search?q=practicing+creativity&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the main things is to ignore whether it'll make money or not.  You can't start off saying, &quot;I want an idea right now, and it has to be profitable&quot; because you'll discard every idea - even the profitable ones - because the profitable ones will look unprofitable at first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have to have an idea, develop it, brainstorm, transform it, polish it, dig into the core to find the kernel or seed of the idea, then replant it in fertile ground, ponder it, apply it to new areas, and only &lt;em&gt;then&lt;/em&gt; can you really know if it's a worthwhile idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you throw it out and start again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Knowing that you're going to be throwing 99% of your ideas out the window gives you real freedom to brainstorm and reach beyond what is possible or reasonable and find something new.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do it enough, eventually something will squeek through, and you'll have your profitable idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But it won't happen unless you come up with a thousand other ideas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lastly, even if we handed you a profitable idea on a platter, it would not be profitable for you, because you were not the creator of it.  I could give you my spreadsheet, but it would be nothing more to you than a springboard for your own creative ideas.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't really &lt;em&gt;own&lt;/em&gt; the idea in terms of excitement and desire for success - not financial success, but success of the idea - then you simply aren't going to be able to put enough of yourself into the development to make it successful.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-02-28T01:03:49.887" CommentCount="2" />
  <row Id="1709" PostTypeId="1" AcceptedAnswerId="1710" CreationDate="2010-02-28T02:45:18.017" Score="8" ViewCount="276" Body="&lt;p&gt;I Need help confirming some hunches.  I'm trying to figure out what type of circuit this is: &lt;img src=&quot;http://img442.imageshack.us/img442/1000/78389584.jpg&quot; alt=&quot;diagram&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;br&gt;&#xA;Also, I think the logic expression for this is:&#xA;D = (A AND B) OR (NOT(B) AND C)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does that look right?&lt;/p&gt;&#xA;" LastEditorUserId="708" LastEditorDisplayName="" LastEditDate="2011-03-20T04:10:47.197" LastActivityDate="2011-03-20T04:10:47.197" Title="What type of Boolean logic circuit is this?" Tags="&lt;circuit&gt;&lt;homework&gt;" AnswerCount="1" />
  <row Id="1710" PostTypeId="2" ParentId="1709" CreationDate="2010-02-28T03:18:38.743" Score="15" ViewCount="" Body="&lt;p&gt;There are only two intermediate signals, so it's relatively easy to break down.  We'll call the left input to the bottom &lt;code&gt;OR&lt;/code&gt; gate &lt;code&gt;X&lt;/code&gt; and the right input &lt;code&gt;Y&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm going to use some shorthand here - &lt;code&gt;NOT&lt;/code&gt; = &lt;code&gt;!&lt;/code&gt;, &lt;code&gt;AND&lt;/code&gt; = &lt;code&gt;&amp;amp;&lt;/code&gt;, &lt;code&gt;OR&lt;/code&gt; = &lt;code&gt;|&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;X = A &amp; B&#xA;&#xA;Y = !B &amp; C&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Those two lead into the &lt;code&gt;OR&lt;/code&gt; gate that produces D:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;D = (A &amp; B) | (!B &amp; C)&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Which is the result you came up with, so you are correct.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One application of this logic circuit is to act as a selector:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;When &lt;code&gt;B&lt;/code&gt; is asserted, then &lt;code&gt;A&lt;/code&gt; is output on &lt;code&gt;D&lt;/code&gt;, and &lt;code&gt;C&lt;/code&gt; is ignored.&lt;/li&gt;&#xA;&lt;li&gt;When &lt;code&gt;B&lt;/code&gt; is de-asserted, then &lt;code&gt;C&lt;/code&gt; is output on &lt;code&gt;D&lt;/code&gt;, and &lt;code&gt;A&lt;/code&gt; is ignored.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-02-28T03:18:38.743" CommentCount="1" />
  <row Id="1711" PostTypeId="2" ParentId="1707" CreationDate="2010-02-28T15:11:44.887" Score="3" ViewCount="" Body="&lt;p&gt;I've been using my own custom arduino compatible.  I've actually gone with a 150mA voltage regulator because I generally don't need more than 75mA or so.  I have done a couple projects that required more than that - one that needs ~250mA and another that actually needed a full amp.  I've got another in the works that'll need considerably more to drive a motor, but I intend to bypass the regulator and only use the regulator for the ATtiny chip on that one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So... 90% of the time I've needed 75mA or less.  If I need more, I've been able to get away with swapping out for a heavier voltage regulator like a 7805 (I picked my smaller regulator to fit in the same footprint).&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2010-02-28T15:11:44.887" />
  <row Id="1712" PostTypeId="2" ParentId="1705" CreationDate="2010-02-28T19:47:52.857" Score="4" ViewCount="" Body="&lt;p&gt;I am going to take a slightly different tack from the previous answers and say that this may not be a bad idea. In fact, maltrap if you create more specialized posts like &quot;projects ideas: arduino&quot; and &quot;project ideas: sensor networks&quot; I would contribute my ideas gladly. It would be more meaningful and less generic than just &quot;project ideas that sell&quot;, and may garner less criticism. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually, for my ideas for plug computer see &lt;a href=&quot;http://chiphacker.com/questions/1663/what-are-some-of-the-more-compelling-use-cases-for-plug-computers&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/1663/what-are-some-of-the-more-compelling-use-cases-for-plug-computers&lt;/a&gt;. Of course, I make no guarantees that those ideas will sell XD.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nonetheless, I do want to caution that the motivation should not be things that sell, but rather for the sake of doing interesting projects. Not all of us are in this for the money... especially those of us who have a day job already in an EE company and are using hobbyist electronics as a way to put some pizazz back into my life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, I think most people require some amount of motivation and excitement before they can get started. What better way for people to get motivated than to have ppl vet your ideas or offer/criticisms before the idea even take off? I think chiphacker can serve that purpose. And, if you do make money off my ideas that I never implemented, more power to you! Although, it does beg the question how come I didn't have guts to pursue the implementation myself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;my 2 cents...&lt;/p&gt;&#xA;" OwnerUserId="555" LastActivityDate="2010-02-28T19:47:52.857" CommentCount="2" />
  <row Id="1713" PostTypeId="2" ParentId="1707" CreationDate="2010-02-28T20:52:07.060" Score="3" ViewCount="" Body="&lt;p&gt;About the worst case current draw I have seen from a higher-end micro controller is about ~200 to 300 mA. This was the LPC2388 (ARM7, 32-bits) with the usb, emc, and all the more power hungry peripherals turned on running at the highest clock speed (288MHz internal PLL divided down to 72MHz). Generally, I would highly recommend going to switching regulators if cost, noise, and complexity is not an issue.&lt;/p&gt;&#xA;" OwnerUserId="555" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-31T05:27:34.860" LastActivityDate="2011-01-31T05:27:34.860" />
  <row Id="1714" PostTypeId="1" AcceptedAnswerId="1715" CreationDate="2010-03-01T10:19:06.683" Score="8" ViewCount="690" Body="&lt;ul&gt;&#xA;&lt;li&gt;How could I achieve this?  &lt;/li&gt;&#xA;&lt;li&gt;What are the stepper motor facts&#xA;and principless that I have to&#xA;keep in mind to design a circuit&#xA;to achive this goal?  &lt;/li&gt;&#xA;&lt;li&gt;Are there any readymade/open source&#xA;alternatives and circuits available&#xA;to achieve this task?  &lt;/li&gt;&#xA;&lt;li&gt;Do I have to    approach design for&#xA;geared and    non-geared stepper&#xA;motors?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="444" LastActivityDate="2011-03-09T19:15:14.633" Title="Is it possible to drive a stepper motor greater than 1000 rpm?" Tags="&lt;stepper&gt;&lt;motor&gt;&lt;driver&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="1715" PostTypeId="2" ParentId="1714" CreationDate="2010-03-01T15:08:31.720" Score="16" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;How can I drive a stepper motor greater than 1000 rpm?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;A 200 step per revolution motor, running at 1,000 RPM must have a stepper drive capable of doing full steps at 3.4kHz, which is well within the range of most motor drive circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, keep in mind that if you start out the motor at 3.4kHz, it will merely vibrate due to inertia - you don't start a car at 60 miles per hour, you start at 0 and ramp up to 60 MPH, otherwise you just spin your tires.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you have to design your circuit to ramp the frequency up from 0 to 3.4kHz slowly enough that the motor can keep up.  This means you'll also have to take into account the whole drive train - stepper motor, gears, belts, and anything else the stepper motor is moving.  This may be a large platform if you're doing CNC, and the inertia may require a very slow ramp up to avoid skipping steps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lastly, if the motor isn't powerful enough to move the load at 1,000RPM, then you'll need a more powerful stepper motor.  Torque falls as speed increases due to internal motor losses.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;What are the stepper motor facts and principless that I have to keep in mind to design a circuit to achive this goal?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Gecko has a decent &lt;a href=&quot;http://www.geckodrive.com/images/fck_uploads/Step%20Motor%20Basics%20Guide.pdf&quot; rel=&quot;nofollow&quot;&gt;basic introduction to stepper motors&lt;/a&gt;.  Power supply design, matching the drive with the motor so you don't lose too much power in mismatch problems, etc are covered in very basic terms there.  Once you understand the basics, ask more detailed questions for specific answers.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Are there any readymade/open source alternatives and circuits available to achieve this task?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If you are running a low power design, the RepRap project has some reasonable stepper motor drivers.  Alternately, a &lt;a href=&quot;http://www.google.com/search?q=open%20source%20stepper%20control&quot; rel=&quot;nofollow&quot;&gt;simple google search&lt;/a&gt; gives a lot of open source stepper driver information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you don't provide any more detail as to what you're driving, and what motor you're using, I can't suggest anything specific.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Do I have to approach design for geared and non-geared stepper motors?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Not in terms of driver design - the only difference is that a gear train adds more mass to the drive line, requiring a slower ramp-up time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the larger the gear train, the more backlash you might experience, so there's a lot more to the mechanical design if you require speed &lt;em&gt;and&lt;/em&gt; accuracy.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the stepper driver design is the same in either case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want more speed and/or power, you should consider looking at CNC servo motors rather than steppers.&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-09T19:15:14.633" LastActivityDate="2011-03-09T19:15:14.633" CommentCount="2" />
  <row Id="1716" PostTypeId="1" AcceptedAnswerId="1728" CreationDate="2010-03-01T17:13:12.710" Score="5" ViewCount="288" Body="&lt;p&gt;Does anyone know of an ARM Cortex-M3 microcontroller with both the 3.3V peripheral and 1.8V core voltages supplied by external sources?  Everything I have found so far has an internal regulator for the 1.8V CPU core.  My problem is that I'm working in a high temperature environment and the internal regulators all have a thermal shutdown circuit to protect the chip which shuts the 1.8V off at 125C.  I would like to supply the 1.8V with my own extended thermal protection that will run up to 200C but have not been able to find a microcontroller that will accept one.&lt;/p&gt;&#xA;" OwnerUserId="529" LastEditorUserId="529" LastEditorDisplayName="" LastEditDate="2010-03-01T20:53:49.883" LastActivityDate="2010-04-11T20:01:51.623" Title="Is there a Cortex-M3 with external voltage regulators?" Tags="&lt;microcontroller&gt;&lt;arm&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="1" />
  <row Id="1717" PostTypeId="2" ParentId="1716" CreationDate="2010-03-01T17:19:53.127" Score="5" ViewCount="" Body="&lt;p&gt;Even if you do, you will be violating the maximum temperature for the part.  It will not necessarily work, even at lower frequencies above its maximum temperature.  Remember the &quot;absolute maximum&quot; is for damage, not functioning.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-03-01T17:19:53.127" CommentCount="1" />
  <row Id="1718" PostTypeId="2" ParentId="1716" CreationDate="2010-03-01T18:25:57.253" Score="1" ViewCount="" Body="&lt;p&gt;The maximum operating temperature of the cortex M3 chips I've looked at is 125C - which is right about where you found the thermal shutdown protection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll have to call the manufacturer for use beyond those conditions, but I expect that you won't get the answer you need.  You may need to locate the computing elements away from the heat, or use some active cooling solution because there are very few microcontrollers that operate above 125C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to play with pushing them beyond your limits, though, you're right, you need one that allows an external regulator.  I believe both the PIC32 and AVR32 have internal regulators, but they are on accessible external pins and may be bypassed with your own power supply.  They aren't ARMs, though, so if that's a core requirement then you may simply need to contact a manufacturer.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-01T18:25:57.253" />
  <row Id="1719" PostTypeId="2" ParentId="1716" CreationDate="2010-03-01T20:02:36.293" Score="3" ViewCount="" Body="&lt;p&gt;Microchip has &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2844&amp;amp;param=en544822&quot; rel=&quot;nofollow&quot;&gt;MCUs&lt;/a&gt; that are qualified for 150C operation.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-01T20:02:36.293" CommentCount="1" />
  <row Id="1720" PostTypeId="2" ParentId="1009" CreationDate="2010-03-01T22:52:29.250" Score="5" ViewCount="" Body="&lt;p&gt;I would avoid this kind of thing like the plague.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most &quot;serious&quot; low level software I've encountered has been a state machine in this form:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;stdio.h&amp;gt;&#xA;&#xA;typedef enum&#xA;{&#xA;    STATE_INIT,     // Description&#xA;    STATE_RUNNING,  // Description&#xA;    STATE_COMPLETE  // Description&#xA;} state_t;&#xA;&#xA;int main(void)&#xA;{&#xA;    state_t state = STATE_INIT; // setup the initial state&#xA;&#xA;    while(1)&#xA;    {&#xA;        os_run(); // call the OS services (poll the UART, check buttons, etc.)&#xA;&#xA;        switch(state)&#xA;        {&#xA;            case STATE_INIT:&#xA;                state = STATE_RUNNING;&#xA;                puts(&quot;init&quot;);&#xA;                break;&#xA;            case STATE_RUNNING:&#xA;                state = STATE_COMPLETE;&#xA;                puts(&quot;running&quot;);&#xA;                break;&#xA;            case STATE_COMPLETE:&#xA;                puts(&quot;complete&quot;);&#xA;                break;&#xA;        }&#xA;    }&#xA;    return 0;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;There are plenty of other good approaches in C/C++, but they're not my favourite.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The big problem with tools like QP is that it's often very hard to do things they don't want you to. If you do choose to fiddle with code manually you'll have to maintain the special case forever.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd say, UML statecharts are a fantastic tool for documentation, teaching and analysis. But, not for actual programming - there are much better tools for that :)&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-01T22:52:29.250" CommentCount="2" />
  <row Id="1721" PostTypeId="2" ParentId="1586" CreationDate="2010-03-01T23:12:07.120" Score="2" ViewCount="" Body="&lt;p&gt;Avrdude works just fine on OSX too. Just,&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;port install avrdude avr-gcc avr-binutils avr-gdb avr-libc&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And you're ready to do everything that WinAVR does.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-01T23:12:07.120" />
  <row Id="1722" PostTypeId="1" AcceptedAnswerId="1723" CreationDate="2010-03-02T16:33:39.190" Score="2" ViewCount="1076" Body="&lt;p&gt;Is the main way of programming the Arduino's Atmel MCU thru a Visual Programming environment such as Max/MSP? Or do you have to write typical C code?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the different ways available?&lt;/p&gt;&#xA;" OwnerUserId="333" LastEditorUserId="333" LastEditorDisplayName="" LastEditDate="2010-03-02T16:43:12.667" LastActivityDate="2011-05-16T10:33:57.687" Title="How do you develop software for the Arduino?" Tags="&lt;arduino&gt;&lt;software&gt;&lt;programming&gt;&lt;max&gt;&lt;msp&gt;" AnswerCount="6" FavoriteCount="2" />
  <row Id="1723" PostTypeId="2" ParentId="1722" CreationDate="2010-03-02T16:44:30.620" Score="11" ViewCount="" Body="&lt;p&gt;The main way of programming the atmel chips is using avrstudio a windows IDE or avr-gcc. In C or assembly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The arduino simplifies this to use a simple variation of c++ in its own simple IDE. There is no visual programming method for arduino/avrs as far as I know.&lt;/p&gt;&#xA;" OwnerUserId="558" LastActivityDate="2010-03-02T16:44:30.620" CommentCount="1" />
  <row Id="1724" PostTypeId="2" ParentId="1722" CreationDate="2010-03-02T17:02:20.193" Score="2" ViewCount="" Body="&lt;p&gt;Here's a good tutorial for programming the AVR ATMega chips in C, without the Arduino IDE.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;https://www.mainframe.cx/~ckuethe/avr-c-tutorial/&quot; rel=&quot;nofollow&quot;&gt;https://www.mainframe.cx/~ckuethe/avr-c-tutorial/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-02T17:02:20.193" />
  <row Id="1725" PostTypeId="1" CreationDate="2010-03-02T17:23:48.007" Score="4" ViewCount="485" Body="&lt;p&gt;Hey I have a circuit like this, &lt;img src=&quot;http://farm2.static.flickr.com/1137/758565223_c8c8119cdd.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am powering this circuit with a 6v alkaline battery, the circuit works just fine with 100uf capacitors. But the problem is I want to replace the LED with a dpdt relay, I tried a 6v one I had laying around but it wont budge. Also when I tried the circuit with a 12v battery, the circuit just remains active for all the time. How do I get this to work?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2011-05-20T10:59:17.527" Title="how to get more power out of a astable multivibrator?" Tags="&lt;power&gt;" AnswerCount="4" />
  <row Id="1726" PostTypeId="2" ParentId="1725" CreationDate="2010-03-02T18:48:26.950" Score="1" ViewCount="" Body="&lt;p&gt;Add a transistor to supply current to the load:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Emitter_follower&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Emitter_follower&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-03-02T18:48:26.950" />
  <row Id="1727" PostTypeId="2" ParentId="1725" CreationDate="2010-03-02T20:02:47.757" Score="3" ViewCount="" Body="&lt;p&gt;You'll need to use a transistor or other switching element to drive the relay.  One common circuit is here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.dnatechindia.com/index.php/Tutorials/8051-Tutorial/Relay-Interfacing.html&quot; rel=&quot;nofollow&quot;&gt;http://www.dnatechindia.com/index.php/Tutorials/8051-Tutorial/Relay-Interfacing.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just treat the output of your oscillator as the output of the microcontroller in the above circuit.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-02T20:02:47.757" />
  <row Id="1728" PostTypeId="2" ParentId="1716" CreationDate="2010-03-02T21:17:01.287" Score="3" ViewCount="" Body="&lt;p&gt;I found one so far.  It looks like the Atmel SAM3S series allows for external regulators to provide power for both the I/O and the CPU core.  The down side is that is does not have as much RAM (only 48 k bytes) as most competitors (typically 64 k bytes).&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-03-02T21:17:01.287" CommentCount="1" />
  <row Id="1729" PostTypeId="2" ParentId="1725" CreationDate="2010-03-02T21:57:22.233" Score="0" ViewCount="" Body="&lt;p&gt;How fast are you trying to turn the relay on and off? There is a turn-on and turn-off&#xA;delay. If you are operating at frequencies above 10Hz or so I would look for&#xA;a different solution. If you are at frequencies below that the transistor buffer&#xA;should work.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T10:59:17.527" LastActivityDate="2011-05-20T10:59:17.527" CommentCount="2" />
  <row Id="1730" PostTypeId="2" ParentId="1722" CreationDate="2010-03-03T00:52:52.270" Score="6" ViewCount="" Body="&lt;p&gt;I program the Arduinos and Atmel chips a couple of different ways --&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The quickest and easiest way is to use a uC with the Arduino bootloader&#xA;and use the Arduino IDE and libraries. Quick and easy but can can be&#xA;lower performance depending on your task.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You can use the Arduino bootloader and libraries from AVR studio or&#xA;the command line. I find the command line a lot quicker than the Arduino&#xA;IDE. Haven't played with AVR studio. When I develop Arduino libraries I usually&#xA;use this method.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Program the uC using just AVR studio or from the command line.&#xA;No Arduino bootloader or libraries. Porting the Atmel&#xA;application code is easy. This is my preferred method. &#xA;C from the command-line using Make. EMACS for editing files.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:33:57.687" LastActivityDate="2011-05-16T10:33:57.687" CommentCount="1" />
  <row Id="1731" PostTypeId="2" ParentId="1705" CreationDate="2010-03-03T03:27:56.353" Score="4" ViewCount="" Body="&lt;p&gt;I've always liked the idea of providing essential technology for medical purposes. Whilst researching for my current project I've spoken to many people who work with medical tech. The general consensus is that the equipment is just too expensive. &#xA;One of the main reasons this equipment is so expensive, is because of the cost of testing/trialing such equipment to strictly set government guidelines. As a result many GPs, care workers and lab technicians have to go without access to certain devices/technologies. (It really is a massive joke, it's that disproportionate! many government standards agencies are raking in the cash at the expense of the patients/service users)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the UK (where I live) and in many other countries, Technologies sold as kits, with disclaimers and explicit instructions for intended use (i.e education or experimentation - for arguments sake) come under different guidelines and government legislation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess my point is - if you can spot one of these essential medical electronic devices, (that are in high demand) and you can reach your market (the hard bit!), then people will buy them out of necessity - despite the faux guidelines for intended use. In doing so you can undercut the competition by vastly reducing the cost of manufacture, compared to the certified manufacturing route. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another point to bear in mind, is that some patients/service users require constant monitoring, and thusly constant access to certain equipment, and they may not have the money to buy the certified technology. &#xA;I mention this because I've had commission work in the past to make components for medical equipment - such as head bands for sensors and mounting cradles for electrodes (they're essentially consumables but suppliers are charging more than £100 pound sterling for replacements) - plus it's a good cause. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully, in there somewhere (the preceding ramble) there's a useful idea or starting point. Remember tho - it's always easier said than done (arrggghh, the dreaded and inevitable hard work!), so you can't just make it &lt;em&gt;all about the money&lt;/em&gt; - you'll have to find something you're at least mildly passionate about, not just the cash! I guess it all swings on what kind of stuff/technology you &lt;em&gt;really&lt;/em&gt; like, so that probably means all that stuff I wrote earlier was *!'(&amp;amp;^@£ (insert random expletive)&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-03-03T03:27:56.353" CommentCount="3" />
  <row Id="1732" PostTypeId="2" ParentId="33" CreationDate="2010-03-03T04:20:05.813" Score="1" ViewCount="" Body="&lt;p&gt;FYI: The mega-isp sketch is now included with the Arduino software as of version 0018 and no longer needs to be downloaded separately; it's located under File|Examples, named ArduinoISP.&lt;/p&gt;&#xA;" OwnerUserId="480" LastActivityDate="2010-03-03T04:20:05.813" />
  <row Id="1733" PostTypeId="2" ParentId="1669" CreationDate="2010-03-03T06:38:15.270" Score="4" ViewCount="" Body="&lt;p&gt;Use something like the Energizer Lithium AA's - they're rated to 40 below zero, and they're not too expensive if you look around. I use them in high altitude balloons where temperatures can get as low as -55 C, and they work a treat for me :)&lt;/p&gt;&#xA;" OwnerUserId="358" LastActivityDate="2010-03-03T06:38:15.270" CommentCount="1" />
  <row Id="1734" PostTypeId="2" ParentId="1716" CreationDate="2010-03-03T10:38:45.183" Score="8" ViewCount="" Body="&lt;p&gt;Have you looked into Honeywell's HT83C51. It is a 8051 compatible microcontroller rated to work up to 225C (and derated up to 300C). I believe this chip is designed from the ground up to work in harsh conditions.&lt;/p&gt;&#xA;" OwnerUserId="555" LastActivityDate="2010-03-03T10:38:45.183" CommentCount="1" />
  <row Id="1735" PostTypeId="2" ParentId="1689" CreationDate="2010-03-03T13:33:45.970" Score="6" ViewCount="" Body="&lt;p&gt;Distinguish serial UART communication from the various voltage levels used to transmit it: RS232, RS485, LVDS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Serial UART communication is reliable and simple.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-03-03T13:33:45.970" />
  <row Id="1736" PostTypeId="2" ParentId="1725" CreationDate="2010-03-03T15:43:43.243" Score="6" ViewCount="" Body="&lt;p&gt;This should work. You may have to change the values of the resistors, as adding another transistor affects the functioning of the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/b2gills/4404458667/&quot; rel=&quot;nofollow&quot; title=&quot;Astable multivibrator relay by b2gills, on Flickr&quot;&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4010/4404458667_2a39c7e64b_o.png&quot; width=&quot;340&quot; height=&quot;220&quot; alt=&quot;Astable multivibrator relay&quot; /&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have actually used a similar circuit to operate a relay at about twice a second, at 12 volts. I plan on using it for a trailer wiring tester. &lt;/p&gt;&#xA;" OwnerUserId="1301" LastEditorUserId="1301" LastEditorDisplayName="" LastEditDate="2010-03-03T23:20:28.650" LastActivityDate="2010-03-03T23:20:28.650" CommentCount="3" />
  <row Id="1737" PostTypeId="2" ParentId="1705" CreationDate="2010-03-04T16:28:24.723" Score="1" ViewCount="" Body="&lt;p&gt;Maltrap,&#xA;I think it is more of an issue that this site and others like it, are geared towards information sharing not profit making. Most people that contribute here could very easily take the stance that why share what I know if I can use it to make money, however they don't because their motives are more around helping and learning from each other. In that spirit your post has a slightly out of character approach for this venue. On the other hand it is always good to share ideas to see what comes from it (without the tie to how I can SELL the idea).&#xA;I, like others here have our own off screen ideas we are working on but that doesn't preclude us from helping someone else get off the ground with something of their own. I agree with Terry though in the since it would be much better if you gave a direction that you had interest in, or some personal insight.&#xA;As for my recommendation, work on ways to help others, for example: handicap enabling devices, energy for under developed areas, anything that reduces the cost of living.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck with what ever you do and let us know if you make a fortune on it :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS: All of my ideas are always available on my blog www.mendingthings.com&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-03-04T16:28:24.723" />
  <row Id="1738" PostTypeId="1" AcceptedAnswerId="1741" CreationDate="2010-03-04T23:37:36.143" Score="17" ViewCount="1269" Body="&lt;p&gt;I'd like to make a single board computer capable of booting Linux, with my low-tech garage tools (2 sided PCBs, reflow skillet, no plating through holes).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the simplest hardware design I could choose?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any microcontrollers with enough onboard flash/RAM to run Linux/uCLinux?&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-01T23:53:30.650" Title="What's the simplest Linux capable board I could make at home?" Tags="&lt;linux&gt;&lt;pcb&gt;" AnswerCount="7" FavoriteCount="2" />
  <row Id="1739" PostTypeId="2" ParentId="472" CreationDate="2010-03-04T23:59:53.523" Score="1" ViewCount="" Body="&lt;p&gt;I also use a cheap inkjet with JetStar film and get great results. For developing and removing the etch-resist, I use Seno's boot polish style applicators from Mega UK. Exposure takes me 3 minutes (per side) under 2 8W UV bulbs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://blog.hodgepig.org/articles/000028-reflow/goodpcb.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-04T23:59:53.523" />
  <row Id="1740" PostTypeId="2" ParentId="1738" CreationDate="2010-03-05T00:00:25.160" Score="5" ViewCount="" Body="&lt;p&gt;Personally, I think it would be simpler to buy one rather than make one.  A &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;BeagleBoard&lt;/a&gt; is a pretty popular solution at $149.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-03-05T00:00:25.160" CommentCount="2" />
  <row Id="1741" PostTypeId="2" ParentId="1738" CreationDate="2010-03-05T01:06:41.453" Score="9" ViewCount="" Body="&lt;p&gt;I'd like to see this too, but my gut instinct is to say &quot;maybe, but it's a &lt;em&gt;lot&lt;/em&gt; of work&quot;.  Even the smallest Linux distro is going to need around a megabyte of RAM to run.  This means at least 30 or so additional pins for the RAM controller in the microcontroller, and a couple of big RAM chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the simplest architectures I know that has Linux for it is the Atmel AVR32 series of parts.  The smallest, the &lt;a href=&quot;http://atmel.com/dyn/products/product_card_mcu.asp?part_id=4126&quot; rel=&quot;nofollow&quot;&gt;AT32UC3A0128&lt;/a&gt; comes in a relatively hacker-friendly 100-pin TQFP package.  This is at least amenable to hand-soldering, unlike most of the OS-capable embedded microcontrollers that come in BGA packages. (the chips that have the little solder balls underneath them)  You can get an idea as to the complexity of a circuit using that chip by examining the &lt;a href=&quot;http://atmel.com/dyn/products/tools_card_mcu.asp?tool_id=4114&quot; rel=&quot;nofollow&quot;&gt;EVK1100&lt;/a&gt; eval board.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-03-05T01:06:41.453" CommentCount="2" />
  <row Id="1742" PostTypeId="1" CreationDate="2010-03-05T05:28:33.767" Score="3" ViewCount="486" Body="&lt;p&gt;Hi Guys n Gals,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for a solution for &quot;flyback&quot; protection when driving a 2 wire DC latching solenoid. You cant use the traditional diode solution as the polarity of the coil is reversed to open or close the solenoid.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My cct uses two relays to switch the solenoid - the first (SPST) applies power to the second relays contacts (DPDT) which does the polarity reversal for the power to the solenoid coil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course my relay coils already have conventional flyback diodes connected - what i'm looking to protect against is the back EMF from the actual solenoid coil itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stocky&lt;/p&gt;&#xA;" OwnerUserId="503" LastActivityDate="2010-03-05T12:36:01.243" Title="Flyback protection for a dc latching soelnoid?" Tags="&lt;relay&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="1743" PostTypeId="2" ParentId="1742" CreationDate="2010-03-05T06:31:52.740" Score="6" ViewCount="" Body="&lt;p&gt;You can use four diodes to the supply rails like for motors in an H-bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See for example &lt;a href=&quot;http://www.cs.uiowa.edu/~jones/step/circuits.html#bipolar&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="339" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2010-03-05T06:43:46.210" LastActivityDate="2010-03-05T06:43:46.210" CommentCount="1" />
  <row Id="1744" PostTypeId="2" ParentId="1742" CreationDate="2010-03-05T07:21:09.897" Score="4" ViewCount="" Body="&lt;p&gt;There are a number of ways you could do this.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Two series connected zeners diodes. With the diodes connected with opposite polarity (either both anodes connected or both cathodes connected) the voltage will be clamped in both directions. The zener voltage should be at least a volt or two greater that the supply voltage used to drive the solenoid. Increasing the zener voltage up to the voltage rating of your relay contacts will permit a faster response from the solenoid.&lt;/li&gt;&#xA;&lt;li&gt;Four diodes clamping to the power supply, as suggested by starblue. With this approach you will want to make sure that the power supply can sink the current supplied by the solenoid when it switches off.&lt;/li&gt;&#xA;&lt;li&gt;An RC snubber. You will have to calculate or experiment to get a suitable RC combination that trades off the peak voltage and time constant.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;My preference would be for the back to back zeners. Unlike the four diode clamp, it keeps the flyback current contained, away from the power supply. The advantage over the RC snubber is the the voltage is well defined and it is easy to specify.&lt;/p&gt;&#xA;" OwnerUserId="328" LastEditorUserId="328" LastEditorDisplayName="" LastEditDate="2010-03-05T12:36:01.243" LastActivityDate="2010-03-05T12:36:01.243" CommentCount="3" />
  <row Id="1745" PostTypeId="2" ParentId="1738" CreationDate="2010-03-05T08:04:42.387" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://shop.ngxtechnologies.com/product_info.php?products_id=72&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is something a lot cheaper. If you really want to make your own, the schematic will be available.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-05T08:04:42.387" CommentCount="1" />
  <row Id="1746" PostTypeId="1" CreationDate="2010-03-05T12:04:14.910" Score="7" ViewCount="263" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to make a device that uses several motors all with an arrow fixed on top that has 8 fixed positions (N,NE,E,SE,S,SW,W,NW). I am trying to avoid servos and steppers because of the price, so I was wondering if anyone had ideas on how this could be achieved. The only way I can think of is to calibrate pulses to the amount of rotation that the motor would experience. It seems like there should be a better solution than this!&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-03-08T22:04:56.260" Title="Precise motor positioning" Tags="&lt;motor&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="1747" PostTypeId="2" ParentId="1746" CreationDate="2010-03-05T12:39:40.950" Score="6" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;The only way I can think of is to calibrate pulses to the amount of rotation that the motor would experience.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I have difficulty thinking that this would work, which means you should definitely get a motor and try it out!  Set it up with a stop so you can apply a long pulse and get it to rest on the stop at a known position, then apply pulses of various lengths, currents, etc and see if you can get repeatable results.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that friction will change slightly with temperature, humidity, and other factors depending on the motor design, but since you only need 8 positions you may have enough room for error that it won't matter.  Your biggest problem is likely to be that you have to calibrate each motor, even if they're the same type, since they'll all have slightly different torque/A characteristics, and that this will change over time as the motor ages and how the environment affects it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, to get better results, you'll need some sort of feedback loop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The easiest/cheapest is probably to attach a potentiometer and read its position with an a/d converter.  Since the potentiometer will be too hard to turn, make your own with a piece of cardboard and pencil.  Draw a thick black circle almost all the way around the cardboard, cut a hole in the center and attach it to the motor.  Attach a wire to one end of the semicircle, and drag a wire along the other end so as the motor turns you get varying resistance.  Use that with an A/D.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also reverse this - put the moving contact on the arrow with the thick black line below it (so you don't have to turn the cardboard, just the moving contact).  If you are creative with your design people will just think the black semicircle is part of the display face.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will be very, very noisy and unreliable, though, depending on construction, and won't last for a long time, but it is cheap and easy and with your low resolution positioning requirements it should give you enough feedback to get in the right 45 degree area.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another (more reliable) option would be to use one optical sensor with notches cut in the rotating cardboard.  Just count the pulses until you're in the right spot.  You can get rid of the (expensive) optical encoder and use two wires that touch in the notches, and are separated when there's no notch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck, and please tell us what you tried and how it worked!&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-05T12:39:40.950" />
  <row Id="1748" PostTypeId="1" AcceptedAnswerId="1785" CreationDate="2010-03-05T14:12:14.260" Score="3" ViewCount="856" Body="&lt;p&gt;I have been trying to get the &lt;a href=&quot;http://www.sxlist.com/techref/io/stepper/linistep/index.htm&quot; rel=&quot;nofollow&quot;&gt;Linistepper&lt;/a&gt; to work, however I can't seem the understand the working of the circuit.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit is &lt;a href=&quot;http://techref.massmind.org/images/member/RB-ezy-Q33/LiniV2_sch.gif&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The issues that I'm unclear about are:  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What are the diodes D1-D6 for?  &lt;/li&gt;&#xA;&lt;li&gt;How does one calculate the resistors R18 - R23 for setting different microstepping current levels? (It is currently set to 0, 25, 55 ,100 % respectively).  &lt;/li&gt;&#xA;&lt;li&gt;How does current regulation in the circuit work.&lt;/li&gt;&#xA;&lt;li&gt;PWM is used to achieve 3600 steps, how is this done?  &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="444" LastEditorUserId="444" LastEditorDisplayName="" LastEditDate="2010-03-05T14:22:59.697" LastActivityDate="2011-04-05T03:09:44.023" Title="How does the Linistepper, open source linear Stepper Motor Drive work?" Tags="&lt;stepper&gt;&lt;motor&gt;&lt;driver&gt;" AnswerCount="4" />
  <row Id="1749" PostTypeId="1" AcceptedAnswerId="1756" CreationDate="2010-03-05T14:21:49.713" Score="6" ViewCount="783" Body="&lt;p&gt;I'm sure there are plenty of schematic tools available.  Which ones do you use/prefer?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Feel free to also list tools which aren't completely free but very popular.&lt;/p&gt;&#xA;" OwnerUserId="561" LastActivityDate="2010-03-06T13:04:26.613" Title="What are the best free schematic tools out there?" Tags="&lt;schematics&gt;&lt;software&gt;&lt;design&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="1750" PostTypeId="2" ParentId="1749" CreationDate="2010-03-05T14:42:11.707" Score="1" ViewCount="" Body="&lt;p&gt;I don't use it (I have a very good PCB CAD package), but &lt;a href=&quot;http://tinycad.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;TinyCAD&lt;/a&gt; is very popular. I tried it once, and it was quite easy to use.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-05T14:42:11.707" />
  <row Id="1751" PostTypeId="2" ParentId="1748" CreationDate="2010-03-05T14:49:17.803" Score="2" ViewCount="" Body="&lt;p&gt;Different output voltages are achieved by turning the PIC outputs on and off. The diodes prevent current flowing the wrong way when some outputs are high and some are low. It's a clever idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 3600 steps are achieved with &quot;micro-stepping&quot;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-03-05T14:54:30.467" LastActivityDate="2010-03-05T14:54:30.467" CommentCount="2" />
  <row Id="1752" PostTypeId="2" ParentId="1746" CreationDate="2010-03-05T15:00:56.763" Score="7" ViewCount="" Body="&lt;p&gt;You want an arrow to point in one of 8 fixed positions?  Just use magnetized needles and 8 minimal electromagnets to pull the needle in the direction you want?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-03-05T15:00:56.763" CommentCount="1" />
  <row Id="1753" PostTypeId="2" ParentId="1749" CreationDate="2010-03-05T15:01:14.627" Score="4" ViewCount="" Body="&lt;p&gt;The de facto standard (at least acc. to my impressions) is &lt;a href=&quot;http://cadsoft.de/&quot; rel=&quot;nofollow&quot;&gt;Eagle CAD&lt;/a&gt;. It is not open source, but there is a free non-commercial license availlaible. It is limited in PCB production (2 Layers, 10x16cm) and can handle only one schematic sheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I like it a lot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good open source alternative is &lt;a href=&quot;http://www.lis.inpg.fr/realise_au_lis/kicad/&quot; rel=&quot;nofollow&quot;&gt;Kicad&lt;/a&gt;. But I have not used it often enough to give good advice.&lt;/p&gt;&#xA;" OwnerUserId="407" LastActivityDate="2010-03-05T15:01:14.627" CommentCount="1" />
  <row Id="1754" PostTypeId="1" CreationDate="2010-03-05T16:08:48.497" Score="10" ViewCount="327" Body="&lt;p&gt;Can you recommend a readable and educational implementation of a CPU in VHDL or Verilog? Preferably something well documented.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. I know I can look at &lt;code&gt;opencores&lt;/code&gt;, but I'm specifically interested in stuff people have actually looked at and found interesting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S.2. Sorry about the sucky tags, but as a new user I can't create new ones&lt;/p&gt;&#xA;" OwnerUserId="560" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:46:55.410" LastActivityDate="2010-11-16T05:39:27.573" Title="Readable and educational implementations of a CPU in a HDL" Tags="&lt;microprocessor&gt;&lt;fpga&gt;&lt;softcore&gt;&lt;verilog&gt;&lt;vhdl&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="3" />
  <row Id="1755" PostTypeId="2" ParentId="1754" CreationDate="2010-03-05T16:56:26.617" Score="3" ViewCount="" Body="&lt;p&gt;Get &lt;a href=&quot;http://users.ece.gatech.edu/~hamblen/book/bookse.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; book, I've got the first edition. A few years ago I implemented their CPU in a little Flex 10K10 FPGA on a PCB I designed, with a couple of push buttons and a single 7-segment display for entering data and displaying the results.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-05T16:56:26.617" />
  <row Id="1756" PostTypeId="2" ParentId="1749" CreationDate="2010-03-05T17:29:46.087" Score="5" ViewCount="" Body="&lt;p&gt;I use gEDA/PCB. The file formats are open an ASCII. The open file&#xA;formats make a wide variety of EDA automation tasks possible. The&#xA;ASCII format makes them easy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have switched from Eagle to gEDA/PCB. I have found gEDA to be a more&#xA;productive tool. The schematic capture is better but the PCB layout&#xA;seems more difficult. The scriptability is what has made the&#xA;difference. There are also tools for simulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be careful of choosing a free version of an EDA tool that is crippled&#xA;or a tool that locks you in to a specific PCB vendor. There is a&#xA;learning curve associated with any EDA tool or other complex piece of&#xA;software. It will be very time consuming to switch tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The footprint library that I use is available at&#xA;&lt;a href=&quot;http://www.luciani.org&quot; rel=&quot;nofollow&quot;&gt;http://www.luciani.org&lt;/a&gt; Also I have a variety of EDA automation scripts&#xA;on my site.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an example of gEDA/PCB I did a remix of the Drawdio circuit design&#xA;that ladyada did (CC 3.0 BY-SA). The remix includes the EDA files and&#xA;documentation. All of the files are at&#xA;&lt;a href=&quot;http://wiblocks.luciani.org/remix/index.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/remix/index.html&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;A couple of additions --&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;XCircuit &lt;a href=&quot;http://opencircuitdesign.com/xcircuit&quot; rel=&quot;nofollow&quot;&gt;http://opencircuitdesign.com/xcircuit&lt;/a&gt; is an open source&#xA;package that produces some very nice looking schematics. The&#xA;most extensive example would be the open textbook at &lt;a href=&quot;http://www.ibiblio.org/kuphaldt/electricCircuits&quot; rel=&quot;nofollow&quot;&gt;http://www.ibiblio.org/kuphaldt/electricCircuits&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use La/TeX you can create inline schematics using macros.&#xA;This could be useful for very simple schematics but I can see&#xA;this getting very cumbersome very quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(* jcl *)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.wiblocks.com&quot; rel=&quot;nofollow&quot;&gt;http://www.wiblocks.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="424" LastEditorDisplayName="" LastEditDate="2010-03-06T13:04:26.613" LastActivityDate="2010-03-06T13:04:26.613" />
  <row Id="1757" PostTypeId="2" ParentId="1749" CreationDate="2010-03-05T20:00:04.930" Score="1" ViewCount="" Body="&lt;p&gt;You haven't said what your schematic is for.  If it's purely an &lt;em&gt;illustrative&lt;/em&gt; schematic-- one that won't be used to generate a netlist (and/or PCB) --then you may find that general-purpose drawing tools work very well, often much better than engineering applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, we often publish circuit diagrams on our blog, and write up projects that we contribute to books and magazines as well.  In situations like this, I use &lt;a href=&quot;http://inkscape.org/&quot; rel=&quot;nofollow&quot; title=&quot;Inkscape&quot;&gt;Inkscape&lt;/a&gt; to make &lt;em&gt;great looking&lt;/em&gt; schematic diagrams that show exactly what I want to show. (You can see a few examples in &lt;a href=&quot;http://www.evilmadscientist.com/article.php/ADXL335&quot; rel=&quot;nofollow&quot; title=&quot;this article&quot;&gt;this article&lt;/a&gt;.)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to use a dedicated schematic package, as part of a PCB layout, then I'd also recommend gschem, part of the gEDA suite.  It produces very clean vector-pdf output that make for good looking printouts.  It has the limitations that other EDA tools have-- a learning curve and less control over the visual output than an illustration package like Inkscape.&lt;/p&gt;&#xA;" OwnerUserId="484" LastActivityDate="2010-03-05T20:00:04.930" />
  <row Id="1758" PostTypeId="2" ParentId="1629" CreationDate="2010-03-05T20:33:17.427" Score="1" ViewCount="" Body="&lt;p&gt;You can get 2 layer 100 square inches for $94 at PCB International. In addition you have cool standard specs like Free-test, your choice of color for soldermask/silkscreen. In their about us, it states they are United States based with manufacturing in Taiwan. I've ordered from them before, their quality is outstanding.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.pcbinternational.com&quot; rel=&quot;nofollow&quot;&gt;http://www.pcbinternational.com&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-03-05T20:33:17.427" />
  <row Id="1759" PostTypeId="2" ParentId="1629" CreationDate="2010-03-05T22:33:48.053" Score="2" ViewCount="" Body="&lt;p&gt;How big are your boards? &lt;a href=&quot;http://seeedstudio.com&quot; rel=&quot;nofollow&quot;&gt;Seeedstudio&lt;/a&gt; has their FusionPCB service:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.seeedstudio.com/depot/fusion-pcb-2-layer-5cm5cm-max-10pcs-p-513.html?cPath=64_12&quot; rel=&quot;nofollow&quot;&gt;5cm by 5cm&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.seeedstudio.com/depot/fusion-pcb-2-layer-10cm10cm-max-10pcs-p-396.html?cPath=64_12&quot; rel=&quot;nofollow&quot;&gt;10cm by 10cm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$20 and $50 for 10 boards respectively. They do different colours PCB, silkscreen both sides, soldermask both sides, and are pretty fast. Generally a 7 day turn around time. I've used them for some of my boards and they are absolutely fantastic!&lt;/p&gt;&#xA;" OwnerUserId="373" LastActivityDate="2010-03-05T22:33:48.053" CommentCount="1" />
  <row Id="1760" PostTypeId="1" AcceptedAnswerId="1761" CreationDate="2010-03-06T16:00:50.327" Score="2" ViewCount="326" Body="&lt;p&gt;I'm using the &lt;a href=&quot;http://courses.missouristate.edu/KenVollmar/MARS/&quot; rel=&quot;nofollow&quot;&gt;MARS simulator&lt;/a&gt; to explore the MIPS cpu.  I have a simple assembly program:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;.data&#xA;ascii1: .asciiz &quot;8C@2&quot;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I expect the value in the memory address for ascii1 to be  0x38434032 (the hex equivalent for the ascii bit pattern for &quot;8C@2&quot;).  But it's not.  Here's a screenshot of what MARS shows:&#xA;&lt;a href=&quot;http://img442.imageshack.us/i/mars1.jpg/&quot; rel=&quot;nofollow&quot;&gt;http://img442.imageshack.us/i/mars1.jpg/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone explain why the value in 0x1001000 is not 0x38434032.&lt;/p&gt;&#xA;" LastActivityDate="2010-08-10T21:16:04.927" Title="MIPS: MARS editor not showing correct value for ASCII string?" Tags="&lt;assembly&gt;" AnswerCount="2" />
  <row Id="1761" PostTypeId="2" ParentId="1760" CreationDate="2010-03-06T16:44:53.687" Score="4" ViewCount="" Body="&lt;p&gt;You have encountered the concept of &lt;a href=&quot;http://en.wikipedia.org/wiki/Endianness&quot; rel=&quot;nofollow&quot;&gt;Big-Endian and Little-Endian byte order&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You expect:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;0x38434032&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;But got:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;0x32404338&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that the bytes are simply in reverse order:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;38 43 40 32&#xA;32 40 43 38&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Wikipedia explains it succinctly:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;In computing, endianness is the ordering of individually addressable sub-units (words, bytes, or even bits) within a longer data word stored in external memory. The most typical cases are the ordering of bytes within a 16-, 32-, or 64-bit word, where endianness is often simply referred to as byte order. &lt;a href=&quot;http://en.wikipedia.org/wiki/Endianness&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt; The usual contrast is between most versus least significant byte first, called big-endian and little-endian respectively. &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;MIPS is generally Big Endian, while the processors you may be used to (such as Intel) are Little Endian.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many processors allow you to set whether they are big endian or little endian in some configuration bits.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-06T16:44:53.687" CommentCount="1" />
  <row Id="1762" PostTypeId="2" ParentId="148" CreationDate="2010-03-06T19:56:15.083" Score="1" ViewCount="" Body="&lt;p&gt;This product is a simple and cheap way to add pins to your Arduino.  There is an easy-to-use open source library for accessing the new pins:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://nootropicdesign.com/ez-expander/&quot; rel=&quot;nofollow&quot;&gt;http://nootropicdesign.com/ez-expander/&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-03-06T19:56:15.083" />
  <row Id="1763" PostTypeId="1" AcceptedAnswerId="1764" CreationDate="2010-03-06T22:55:21.323" Score="12" ViewCount="567" Body="&lt;p&gt;When I started programming back in the '90s, I found the variety of magazines on the shelves of my bookstore really useful for learning about a lot of technologies.  What magazines do you read these days to help with your hardware hacking?&lt;/p&gt;&#xA;" OwnerUserId="574" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-05T22:45:57.450" LastActivityDate="2011-06-02T21:56:49.853" Title="What are the best hardware hacking magazines?" Tags="&lt;beginner&gt;" AnswerCount="6" FavoriteCount="7" />
  <row Id="1764" PostTypeId="2" ParentId="1763" CreationDate="2010-03-06T23:04:17.483" Score="13" ViewCount="" Body="&lt;p&gt;This one's easy, Make magazine &lt;a href=&quot;http://makezine.com/magazine/&quot; rel=&quot;nofollow&quot;&gt;http://makezine.com/magazine/&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="327" LastActivityDate="2010-03-06T23:04:17.483" CommentCount="3" />
  <row Id="1765" PostTypeId="2" ParentId="1705" CreationDate="2010-03-06T23:07:02.313" Score="1" ViewCount="" Body="&lt;p&gt;I'd look into doing some open-source hardware kits.  There's a growing number of companies like &lt;a href=&quot;http://www.adafruit.com/&quot; rel=&quot;nofollow&quot;&gt;Adafruit Industries&lt;/a&gt; and &lt;a href=&quot;http://www.nkcelectronics.com/&quot; rel=&quot;nofollow&quot;&gt;NKC Electronics&lt;/a&gt; that are making completely open designs, publishing everything about them online, and then selling the kits.  Most people who want to make them will buy the kit, often at a 50% markup over the PC board and parts costs, just to avoid the problem of sourcing everything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many of the kits are fairly simple.  You could probably do pretty well just making a bunch of breakout boards for popular surface-mount chips, similar to many of the designs at SparkFun.&lt;/p&gt;&#xA;" OwnerUserId="574" LastActivityDate="2010-03-06T23:07:02.313" />
  <row Id="1766" PostTypeId="2" ParentId="1763" CreationDate="2010-03-06T23:17:07.067" Score="15" ViewCount="" Body="&lt;p&gt;Ones that I read frequently:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.nutsvolts.com/&quot; rel=&quot;nofollow&quot;&gt;Nuts &amp;amp; Volts&lt;/a&gt;, great monthly with lots of microcontroller projects&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.servomagazine.com/&quot; rel=&quot;nofollow&quot;&gt;Servo&lt;/a&gt;, sister publication to N&amp;amp;V with focus on robotics&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.circuitcellar.com&quot; rel=&quot;nofollow&quot;&gt;Circuit Cellar&lt;/a&gt;, more professional than N&amp;amp;V, lots of great hardware info&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.elektor.com/&quot; rel=&quot;nofollow&quot;&gt;Elektor&lt;/a&gt;, just started distribution of English translation in US&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.epemag3.com/&quot; rel=&quot;nofollow&quot;&gt;Everyday Practical Electronics&lt;/a&gt;, British magazine full of construction projects&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="574" LastActivityDate="2010-03-06T23:17:07.067" CommentCount="1" />
  <row Id="1767" PostTypeId="2" ParentId="1332" CreationDate="2010-03-06T23:25:13.930" Score="0" ViewCount="" Body="&lt;p&gt;I've used a bank of three TLC5490 chips to do individual control of 16 RGB LEDs.  It's used in my &lt;a href=&quot;http://combee.net/rgbshield&quot; rel=&quot;nofollow&quot;&gt;RGB LED Shield project&lt;/a&gt;.  If I were reimplementing it now, I'd use the easier-to-program TLC5497 chip which has 24 output channels, versus the 5490's 16 channels.  &lt;a href=&quot;http://www.macetech.com/blog/node/90&quot; rel=&quot;nofollow&quot;&gt;MaceTech is selling those&lt;/a&gt; in small quantities with immediate availability.  I'm planning on using one with a FT232R to make a LED USB dongle for the Chumby. &lt;/p&gt;&#xA;" OwnerUserId="574" LastActivityDate="2010-03-06T23:25:13.930" />
  <row Id="1768" PostTypeId="2" ParentId="1697" CreationDate="2010-03-06T23:33:24.273" Score="1" ViewCount="" Body="&lt;p&gt;Joe Grand has used the Freescale 32-bit MCU chips &lt;a href=&quot;http://www.grandideastudio.com/portfolio/defcon-16-badge/&quot; rel=&quot;nofollow&quot;&gt;for a couple of&lt;/a&gt; &lt;a href=&quot;http://www.grandideastudio.com/portfolio/defcon-17-badge&quot; rel=&quot;nofollow&quot;&gt;his DefCon badges&lt;/a&gt;.  His articles on developing the badges in Nuts &amp;amp; Volts are a good intro to what the chips can do.  He also did &lt;a href=&quot;http://www.defcon.org/html/links/dc-archives/dc-17-archive.html#Grand&quot; rel=&quot;nofollow&quot;&gt;a presentation at DefCon&lt;/a&gt; about the badge.&lt;/p&gt;&#xA;" OwnerUserId="574" LastActivityDate="2010-03-06T23:33:24.273" />
  <row Id="1769" PostTypeId="2" ParentId="1629" CreationDate="2010-03-07T02:08:02.640" Score="1" ViewCount="" Body="&lt;p&gt;I'd go with PCB International &lt;a href=&quot;http://www.pcbinternational.com&quot; rel=&quot;nofollow&quot;&gt;http://www.pcbinternational.com&lt;/a&gt; their quality is much better than gold phoenix and if you factor in all their standard specs they are much less expensive as well (what I got for around $160 at GP before I got for $100 at PCB International). Plus if your designs are more complex they go down to 5/5 trace and space at no extra charge. &lt;/p&gt;&#xA;" LastActivityDate="2010-03-07T02:08:02.640" />
  <row Id="1770" PostTypeId="1" AcceptedAnswerId="1774" CreationDate="2010-03-07T03:38:11.457" Score="3" ViewCount="519" Body="&lt;p&gt;I just got an arduino and have been working through some of the exercises in the tutorials, making good progress.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I'm learning a new programming language or tool, I usually work through a few steps: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;do the tutorials,&lt;/li&gt;&#xA;&lt;li&gt;modify the tutorial programs, get them to do new stuff, and&lt;/li&gt;&#xA;&lt;li&gt;solve a problem not covered in the how-to to make myself figure out how to do stuff.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;With Arduino, I have a bit of a chicken-and-egg problem. I don't have a good enough idea what I &lt;em&gt;can&lt;/em&gt; do with it to come up with interesting problems to solve.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are some good problems/exercises I can tackle as a beginner to help myself learn more about what Arduino can do and how to do it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Problem statements only, please. Any instructions for solving them would defeat the purpose (though, it might make sense to point out what hardware is required.)&lt;/p&gt;&#xA;" OwnerUserId="577" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-17T03:05:24.220" LastActivityDate="2011-02-17T07:53:38.883" CommunityOwnedDate="2011-02-17T03:28:35.710" Title="Suggested exercises for learning with Arduino" Tags="&lt;arduino&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="1" />
  <row Id="1771" PostTypeId="2" ParentId="1770" CreationDate="2010-03-07T05:36:09.723" Score="3" ViewCount="" Body="&lt;p&gt;One suggestion is to get one of &lt;a href=&quot;http://www.zachhoeken.com/danger-shield-v1-0&quot; rel=&quot;nofollow&quot;&gt;Zach Hoeken's Danger Shields&lt;/a&gt; from &lt;a href=&quot;http://store.makerbot.com/featured-products/danger-shield-v1-0-1-kit.html&quot; rel=&quot;nofollow&quot;&gt;the MakerBot Store&lt;/a&gt; and try to do something awesome with it.  I used that to get started with the Arduino and going through its examples and modifying the code taught me a lot about interfacing with more than just LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a problem you can try to solve, how about building your own special purpose PC keyboard that hooks into a PS2 port for controlling a game?&lt;/p&gt;&#xA;" OwnerUserId="574" LastActivityDate="2010-03-07T05:36:09.723" CommunityOwnedDate="2011-02-17T03:28:35.710" />
  <row Id="1772" PostTypeId="2" ParentId="22" CreationDate="2010-03-07T05:41:17.387" Score="3" ViewCount="" Body="&lt;p&gt;I'd suggest using a &lt;a href=&quot;http://www.brielcomputers.com/wordpress/?cat=6&quot; rel=&quot;nofollow&quot;&gt;PockeTerm kit from Briel Computing&lt;/a&gt; to interface with the serial port of the Arduino.  It's a Parallax Propeller-based system that acts like a VT100 terminal, with VGA output and PS/2 keyboard input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plus, when you're done with that project, you can reuse the PockeTerm or even load other Propeller software on it for experimentation.&lt;/p&gt;&#xA;" OwnerUserId="574" LastActivityDate="2010-03-07T05:41:17.387" CommentCount="1" />
  <row Id="1773" PostTypeId="2" ParentId="22" CreationDate="2010-03-07T07:34:46.253" Score="5" ViewCount="" Body="&lt;p&gt;Yes, but getting the VGA timings right is all about carefully timing your instructions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd recommend the AVGA library, it can output VGA and CVBS/Composite PAL and NTSC from a humble ATMega168. It handles everything under interrupt, so you can just write your application in C and not worry about VGA timing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://avga.prometheus4.com/&quot; rel=&quot;nofollow&quot;&gt;http://avga.prometheus4.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It even does sound.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I built a little pong game using it: &lt;a href=&quot;http://blog.hodgepig.org/2009/08/17/510/&quot; rel=&quot;nofollow&quot;&gt;http://blog.hodgepig.org/2009/08/17/510/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-18T13:59:48.210" LastActivityDate="2010-10-18T13:59:48.210" />
  <row Id="1774" PostTypeId="2" ParentId="1770" CreationDate="2010-03-07T15:46:36.070" Score="7" ViewCount="" Body="&lt;p&gt;To learn what you &lt;strong&gt;can&lt;/strong&gt; do we should start with hardware capabilities of&#xA;the platform. The Arduino (and other uC system that uses the ATmega328 or ATmega644) have a basic set of resources that are brought out to pins on the uC --&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;digital inputs&lt;/strong&gt; - You use this to read a binary signal. A voltage greater than&#xA;around two volts is a one and less than 0.8V is zero. These are used to read &#xA;the state of a binary device like a switch (mechanical, tilt, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;digital outputs&lt;/strong&gt; Binary outputs. Use to turn on or off a device. LEDs, motors, etc.&#xA;With high current devices you usually need to add additional circuitry (like a transistor&#xA;or motor driver).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;analog inputs&lt;/strong&gt; These are used to read signals from analog outputs -- such as from &#xA;a sensor. Low cost temperature sensors can have analog outputs, light sensors, etc.&#xA;The analog input converts the analog signal into a digital value that can be used&#xA;by your program.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;communications ports&lt;/strong&gt; To communicate to the outside world a UART is provided. This&#xA;enables you to send ASCII strings to an external device (most people convert the UART&#xA;to a USB port). There are two other protocols available -- SPI and I2C. These are&#xA;primarily used for communications within a system. Using these two communciations&#xA;interfaces additional capabilities can be added to a system such as high current&#xA;latches, analog outputs, real-time clock, SD storage. The list of SPI and I2C&#xA;peripherals is long.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I presented an &quot;Intro to Microcontrollers&quot; at the MIT Barcamp in 2009.&#xA;The handout is at --&#xA;&lt;a href=&quot;http://www.luciani.org/not-quite-ready/not-quite-ready-index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.luciani.org/not-quite-ready/not-quite-ready-index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now that we have a summary of most of the capabilities what are your &#xA;interests? Here are some example projects -- &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;robots&lt;/strong&gt; A lot of people do simple robots with their Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;art&lt;/strong&gt; A number of artists create interactive pieces with the Arduino. Add motion,&#xA;motion sensing, leds, sound&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;music&lt;/strong&gt; You can create a numerically controlled oscillator (see &lt;a href=&quot;http://wiblocks.luciani.org/docs/app-notes/nb1a-nco.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/docs/app-notes/nb1a-nco.html&lt;/a&gt; ). You could create&#xA;a midi device or an analog output sequencer that controls an analog&#xA;synth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;datalogger&lt;/strong&gt; A number of people are doing datalogging applications. Temperature, humidity, light. Performance measurements for physical activity, etc. Energy monitoring.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;control&lt;/strong&gt; A number of people are doing CNC control with the Arduino or Sanguino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I were starting I would purchase a copy of &quot;Making Things Talks&quot; (MTT) from O'Reilly&#xA;and extend the examples. MTT works as a cookbook and a reference.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-15T09:58:15.663" LastActivityDate="2011-02-15T09:58:15.663" CommunityOwnedDate="2011-02-17T03:28:35.710" />
  <row Id="1776" PostTypeId="1" AcceptedAnswerId="1780" CreationDate="2010-03-07T23:45:22.550" Score="4" ViewCount="197" Body="&lt;p&gt;Which uclinux community has the largest userbase/is the most active?&#xA;Is it the ARM9 one? &lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-03-08T11:16:16.687" ClosedDate="2011-04-01T16:09:28.600" Title="what is the largest embedded linux community" Tags="&lt;linux&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="1777" PostTypeId="2" ParentId="1696" CreationDate="2010-03-08T00:12:56.627" Score="2" ViewCount="" Body="&lt;p&gt;I'd comment on the earlier answer, but can't yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.x-ways.net/winhex/&quot; rel=&quot;nofollow&quot;&gt;WinHex&lt;/a&gt; will convert (&lt;strong&gt;Ctrl+R&lt;/strong&gt;) to/from Intel format, and uses 0xff as the empty data value (as &lt;a href=&quot;http://home.kpn.nl/newlife-software/Binex/binex.htm&quot; rel=&quot;nofollow&quot;&gt;Binex&lt;/a&gt; does).  It's also a fantastic tool if you need to do anything else with binaries or hard drive structures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hexplorer is a bit clunky, and strangely complains if there isn't a start address.&lt;/p&gt;&#xA;" OwnerUserId="257" LastActivityDate="2010-03-08T00:12:56.627" CommunityOwnedDate="2011-02-09T13:48:06.387" />
  <row Id="1778" PostTypeId="2" ParentId="1748" CreationDate="2010-03-08T02:41:37.193" Score="3" ViewCount="" Body="&lt;p&gt;You might try this forum &lt;a href=&quot;http://www.electro-tech-online.com/&quot; rel=&quot;nofollow&quot;&gt;Electro-tech-online&lt;/a&gt; The creator of Linistepper, Roman Black, frequents it. He goes by MR RB. Who better to get your answers from?&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-03-08T02:41:37.193" CommentCount="1" />
  <row Id="1779" PostTypeId="2" ParentId="1707" CreationDate="2010-03-08T09:10:14.410" Score="2" ViewCount="" Body="&lt;p&gt;My worst case current draw is around 320mA - Arduino, Ethernet shield, XBee, SD Card, and a few I2C devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would seriously consider a switching regulator - in fact I often power Arduino mini pro + peripherals from a 5v switching regulator and bypass the on board linear regulator.&lt;/p&gt;&#xA;" OwnerUserId="9" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-31T05:27:45.497" LastActivityDate="2011-01-31T05:27:45.497" />
  <row Id="1780" PostTypeId="2" ParentId="1776" CreationDate="2010-03-08T11:16:16.687" Score="5" ViewCount="" Body="&lt;p&gt;There are active communities of embedded Linux developers on many platforms. If you're interested in applications and tools rather than Linux kernel development, take a look at some of the embedded Linux distributions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.angstrom-distribution.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.angstrom-distribution.org/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.openembedded.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.openembedded.org/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://openwrt.org&quot; rel=&quot;nofollow&quot;&gt;http://openwrt.org&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.nslu2-linux.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.nslu2-linux.org/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;uClinux is a port of the Linux kernel to microcontrollers with no MMU (Memory Management Unit).&#xA;The ARM9 has an MMU, so can run a full Linux kernel.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-08T11:16:16.687" />
  <row Id="1781" PostTypeId="1" CreationDate="2010-03-08T15:23:18.807" Score="7" ViewCount="553" Body="&lt;p&gt;Idea:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take one oscilloscope probe, and one USB cable.  Cut the BNC connector off the oscilloscope probe, and the USB B connector off the USB jack and splice them together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mount all the USB &amp;lt;--&gt; analog circuitry inside the scope probe body and/or the USB A connector body.  It would essentially compete with all the other USB oscilloscopes out there, but it would be in a single cable design - no extra boxes, etc.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is this a product you would like?&lt;/li&gt;&#xA;&lt;li&gt;What are your minimum specifications for this type of product?&lt;/li&gt;&#xA;&lt;li&gt;What are your ideal specifications for this type of product?&lt;/li&gt;&#xA;&lt;li&gt;Would this be any more useful or desirable than the current USB oscilloscopes available?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;My biggest concerns are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Obtaining the speed necessary to be reasonably useful without requiring a lot of components&lt;/li&gt;&#xA;&lt;li&gt;Synchronizing multiple probes into the computer (Getting nS accuracy without wiring the probes together seems problematic...)&lt;/li&gt;&#xA;&lt;li&gt;Fitting it all into the form factor and power limitations of a USB port (ideally 100mA unpowered hub ~0.5W)&lt;/li&gt;&#xA;&lt;li&gt;Keeping the assembled cost low&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'd appreciate feedback on any or all of the above (what you want vs how to implement it).  Ideally it'd be completely open source, but using very tiny surface mount parts it might not be easily assembled by hand.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-15T08:14:34.073" Title="USB scope probe - request for comments and ideas" Tags="&lt;oscilloscope&gt;&lt;probe&gt;&lt;usb&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="1782" PostTypeId="1" AcceptedAnswerId="1793" CreationDate="2010-03-08T15:48:37.223" Score="2" ViewCount="808" Body="&lt;p&gt;The impression I get is that PICAXE is based on the PIC cores, but geared to beginners, but I wanted to make sure before committing to any particular platform. Thank you!&lt;/p&gt;&#xA;" LastActivityDate="2010-03-08T21:57:42.523" Title="What is the difference between PIC and PICAXE?" Tags="&lt;pic&gt;&lt;picaxe&gt;&lt;microcontroller&gt;&lt;electronics&gt;&lt;beginner&gt;" AnswerCount="2" />
  <row Id="1783" PostTypeId="2" ParentId="1770" CreationDate="2010-03-08T16:03:20.923" Score="4" ViewCount="" Body="&lt;p&gt;The best beginners guide I have found is&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.earthshinedesign.co.uk/ASKManual/Site/ASKManual.html&quot; rel=&quot;nofollow&quot;&gt;http://www.earthshinedesign.co.uk/ASKManual/Site/ASKManual.html&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-03-08T16:03:20.923" CommunityOwnedDate="2011-02-17T03:28:35.710" CommentCount="1" />
  <row Id="1784" PostTypeId="2" ParentId="1781" CreationDate="2010-03-08T16:22:31.257" Score="5" ViewCount="" Body="&lt;p&gt;Multiple inputs are pretty important.  If you could figure out how to use one probe to trigger the others there would be some good potential.  A single probe useful but on a pretty limited basis.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-03-08T16:22:31.257" />
  <row Id="1785" PostTypeId="2" ParentId="1748" CreationDate="2010-03-08T16:30:20.917" Score="4" ViewCount="" Body="&lt;p&gt;The how it works page from the Linistepper home page might help:&#xA;&lt;a href=&quot;http://www.piclist.com/techref/io/stepper/linistep/lini_wks.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.piclist.com/techref/io/stepper/linistep/lini_wks.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="587" LastActivityDate="2010-03-08T16:30:20.917" CommentCount="1" />
  <row Id="1786" PostTypeId="2" ParentId="1738" CreationDate="2010-03-08T17:04:19.800" Score="6" ViewCount="" Body="&lt;p&gt;The Nintendo DS is capable of running uCLinux. You can get a used one for cheap, the only peripheral you need to run Linux on it is a microSD adapter (can be had for $15 from dealextreme.com) and a microSD (small ones are basically free these days)&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-03-08T17:04:19.800" />
  <row Id="1787" PostTypeId="2" ParentId="622" CreationDate="2010-03-08T18:49:34.447" Score="0" ViewCount="" Body="&lt;p&gt;On one of our boards we use a &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/txs0104e.html&quot; rel=&quot;nofollow&quot;&gt;TXS0104E&lt;/a&gt; to translate between 3.3V and 5V on an I2C bus (bi-directional).&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-03-08T18:49:34.447" />
  <row Id="1788" PostTypeId="2" ParentId="1738" CreationDate="2010-03-08T18:58:25.093" Score="6" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.opencircuits.com/Linuxstamp&quot; rel=&quot;nofollow&quot;&gt;Linuxstamp&lt;/a&gt; is probably your best bet.  It's open and has the PCB drawings, schematics, etc available.  But as far as doing it at home - probably not.  There's some very fine pitches on some of the parts.  You're welcome to try, but it seems like a fair bit of consternation to me.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-03-08T18:58:25.093" />
  <row Id="1789" PostTypeId="2" ParentId="1746" CreationDate="2010-03-08T19:07:45.303" Score="4" ViewCount="" Body="&lt;p&gt;Use a &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=425-1950-5-ND&quot; rel=&quot;nofollow&quot;&gt;photointerrupters&lt;/a&gt; like the one in the link.  Attach a thin 'arm' to the motor shaft that points the direction you want to point.  Then place 8 of the photointerrupters at the angles you want to point to, positioned such that the arm moves through the interrupter when it's at the right position.  Then, just move the motor until you detect that the correct interrupter has been interrupted.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-03-08T19:07:45.303" />
  <row Id="1790" PostTypeId="2" ParentId="43" CreationDate="2010-03-08T19:30:54.660" Score="3" ViewCount="" Body="&lt;p&gt;One of the best ways that I've found to measure capacitance is to use an RC circuit. Use a digital I/O port on a microprocessor to charge and discharge the capacitive sensor through a fixed resistor. Start a timer when you begin the charge/discharge cycle. Then use a comparator to detect when the capacitor has fully charged/discharged. Stop the timer when the comparator trips. The value stored in the timer can then be used to calculate the capacitance of the sensor.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-03-08T19:30:54.660" />
  <row Id="1791" PostTypeId="2" ParentId="1696" CreationDate="2010-03-08T19:39:55.527" Score="1" ViewCount="" Body="&lt;p&gt;I'm not familiar with the format of Intel hex files, but when I need to modify/view a binary I use &lt;a href=&quot;http://www.chmaas.handshake.de/delphi/freeware/xvi32/xvi32.htm&quot; rel=&quot;nofollow&quot;&gt;XVI32&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-08-18T12:35:25.343" LastActivityDate="2010-08-18T12:35:25.343" CommunityOwnedDate="2011-02-09T13:48:06.387" />
  <row Id="1792" PostTypeId="1" AcceptedAnswerId="1798" CreationDate="2010-03-08T21:11:29.363" Score="4" ViewCount="1071" Body="&lt;p&gt;I've had a number of issues getting good stable analog readings from an RTD temperature sensor. The temperature readings have a tendency to bounce as much as +/- 5 Deg C. The circuit is very basic, a voltage divider is formed between a fixed resistor and an RTD connected to ground. The voltage at the RTD is then fed into a programmable gain amplifier set at 16 V/V. The analog signal output from the programmable gain amplifier is then fed into a 10-bit ADC on a PIC microprocessor. I've implemented a low pass filter in software to attempt to fix the problem, but the temperature readings are still very unstable. Does anyone have any suggestions about where I could look to find the source of the problem and correct it?&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-04-27T13:45:50.277" LastActivityDate="2011-04-27T13:45:50.277" Title="Reading RTD Temperature Sensor" Tags="&lt;pic&gt;&lt;sensor&gt;&lt;analog&gt;&lt;temperature&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="1793" PostTypeId="2" ParentId="1782" CreationDate="2010-03-08T21:33:44.483" Score="4" ViewCount="" Body="&lt;p&gt;The various Picaxe chips are actually Pic chips with a small piece of code burnt in. This code acts as a bootloader for the chip, which simplifies things when it comes time to upload your code to the chip. You are restricted to using Picaxe's version of BASIC, or a flowchart based system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pics on the other hand are a number of different families of chips. The ones the Picaxes are based on are 8 bit chips, although there are dozens more to choose from in that range too. There are also 16 bit and 32 bit chips too. They can be programmed in Assembler or C (and various other languages if you can find compilers or bootloaders for them) using various tools available direct from Microchip their manufacturer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In terms of programming tools there are free IDEs for Picaxe for both Windows and Linux available from the Picaxe website. To get the code onto the chip you need either a Serial cable and a simple circuit to connect to the chip, or a USB cable from the Picaxe site which connects to the same circuit. There are quite a few extra items you can get, which can be interfaced to Picaxes all from their site.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As previously stated there is a free IDE for Windows which can be downloaded from the Microchip website and used to write either C programs or Assembler programs at least for the 8 bit chips (I've no idea whether it'll target the 16 &amp;amp; 32 bit chips I'll check later). There are various solutions available for Linux including Piklab and Pikdev. To get your code onto your chip you'll need either one of the traditional Serial or Parallel port programmers of which there seem to be hundreds on the internet, or a USB solution such as the Pickit 2 or 3 which as available from Microchip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although the Picaxes seem better suited if you are working with school children or have very little programming experience I'd say the Pics offer a greater flexibility and variety of products. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may also want to investigate whether ATMEL chips or the Arduino which is based on them offer a better fit for your requirements. I found the Wikipedia pages detailing the various different families of microchip to be very useful for getting a handle on what was what with the various types of chip. I'll try and add some useful links when I'm back at my computer.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-03-08T21:57:42.523" LastActivityDate="2010-03-08T21:57:42.523" CommentCount="2" />
  <row Id="1794" PostTypeId="2" ParentId="1782" CreationDate="2010-03-08T21:53:56.597" Score="1" ViewCount="" Body="&lt;p&gt;The same MPLAB IDE can be used for all Microchip parts - 8-bit PIC10, PIC12, PIC16 and PIC18, 16-bit PIC24 and dsPIC, and 32-bit PIC32. It includes simulators and debuggers. Free development software that runs under MPLAB is available for all devices.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-08T21:53:56.597" CommentCount="1" />
  <row Id="1795" PostTypeId="2" ParentId="1746" CreationDate="2010-03-08T22:04:56.260" Score="4" ViewCount="" Body="&lt;p&gt;If you want cheap...&#xA;I have messed around with pulling simple DC motors out of inkjet printers and then using the inkjet's optical encoders for positioning.&#xA;I used an Arduino for testing, but you could use any microcontroller.&#xA;&lt;a href=&quot;http://abigmagnet.blogspot.com/2008/10/dc-motor-control-part-one.html&quot; rel=&quot;nofollow&quot;&gt;http://abigmagnet.blogspot.com/2008/10/dc-motor-control-part-one.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2010-03-08T22:04:56.260" />
  <row Id="1796" PostTypeId="2" ParentId="1792" CreationDate="2010-03-08T22:30:24.883" Score="3" ViewCount="" Body="&lt;p&gt;There are a few places to look.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First of all you should have some analogue filtering before you sample. Temperature measurements are usually slow changing so it should be possible to filter fairly aggressively. Even a simple RC can be very effective.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Consider how much cable you have between the circuit and the RTD. Where is that cable running in relation to other (potentially noisy) cables? Separation between wiring looms and reducing the length of the cable can both help in this case. As can better quality shielded and/or twisted pair wiring.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have access to an oscilloscope you should try and measure the voltage signal that you see going into the adc. Assuming that there is noise present, the nature of the noise will give some hint as to where it's coming from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Consider how the sensor and you uC circuit are grounded with regard to what ever it is you're measuring. If the RTD is connected to an earthed object it is possible that the noise is being coupled as a result of an earth loop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can post more details of the circuit you have, how you're filtering the samples and the application, it should be possible to provide some more specific feedback.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2010-03-08T22:30:24.883" CommentCount="2" />
  <row Id="1797" PostTypeId="2" ParentId="1781" CreationDate="2010-03-09T11:31:29.453" Score="3" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;Yes&lt;/li&gt;&#xA;&lt;li&gt;1MHz, 1Msps, completely isolated from my PC's USB port&lt;/li&gt;&#xA;&lt;li&gt;10Mhz, 10Msps&lt;/li&gt;&#xA;&lt;li&gt;Only if it were a lot cheaper. The DSO nano is $89 and is self-contained.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-09T11:31:29.453" />
  <row Id="1798" PostTypeId="2" ParentId="1792" CreationDate="2010-03-09T15:24:31.293" Score="2" ViewCount="" Body="&lt;p&gt;The first thing I'd look at is ripple in your voltage rail.  Noisy voltages are killer with a voltage divider.  A higher-quality measurement system might use a regulated constant current source to drive the RTD instead of a voltage divider.  An LM317 can be used to do this - hook a resistor between the OUTPUT and ADJ terminal, and hook the RTD between ADJ and GND.  The value of the resistor between output and adjust will set the current going through the RTD - use a precise resistor to be certain of the amount of current.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise, attempt to do the filtering in hardware if possible.  You first have to figure out where the noise is coming from to make it effective.  Determine what frequencies of noise you're seeing and then probe at the input to the gain stage, the output, and the input to the ADC.  If there's noise everywhere, then it's in the source, otherwise it's being injected somewhere else.  Make sure all of your IC's have bypass capacitors to start with.  Then make sure that you don't have any long ground loops - make everything as direct (high current) of a connection to ground as possible.  Don't daisy chain grounds - everything should get its own connection to ground that doesn't run through other chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're seeing noise at the source, chances are it's your voltage source for the divider.  To combat this, you could put a capacitor in parallel with the RTD to make a simple filtering circuit.  Just figure out what frequencies of noise you're seeing and match the capacitor to the resistance of the RTD and figure it out. &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-03-09T15:24:31.293" CommentCount="1" />
  <row Id="1799" PostTypeId="2" ParentId="1536" CreationDate="2010-03-09T16:49:11.107" Score="1" ViewCount="" Body="&lt;p&gt;The driver is based on V-USB I would ask at their &lt;a href=&quot;http://forums.obdev.at/viewforum.php?f=8&quot; rel=&quot;nofollow&quot;&gt;forum&lt;/a&gt; regarding the speed.&#xA;As far as the range finder it uses serial communication so you won't be able to read it out directly as a voltage.  You should be able to change the firmware on the usb stick to send the proper serial commands to get a distance reading from the ultrasonic rangefinder though and output that over the USB HID interface.&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-03-09T16:49:11.107" />
  <row Id="1800" PostTypeId="2" ParentId="1792" CreationDate="2010-03-09T17:26:00.330" Score="3" ViewCount="" Body="&lt;p&gt;One common culprit is charge coupling between channels of the ADC (disregard if you are only using 1 channel). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most microcontrollers with multichannel ADCs have a multiplexer and a sampling capacitor. The sampling capacitor might be in the 1-10pf range. When you switch from one channel to the next, that sampling capacitor initially retains charge from the previous channel's voltage. The sampling capacitor then has to charge up/down to the voltage on the next channel, and has a time constant that depends on the external impedance on the ADC channel input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is good practice to use an RC circuit right on the ADC channel inputs. (&lt;strong&gt;edit:&lt;/strong&gt; if you have a voltage divider, you don't need the R; the Thevenin equivalent resistance acts as a resistor, so a 10K and a 1K divider will yield an equivalent resistance of 909 ohms.) I tend to use something in the neighborhood of 499 ohms, 100-300pf. What happens is the external capacitor in the RC network acts as a storage reservoir, so when the ADC multiplexer switches, the external capacitor very quickly charges the sampling capacitor. There's a tradeoff between using a small capacitance (fast time constant, but initial transient when ADC mux switches is very large) vs. a large capacitance (very little initial transient on external capacitor when ADC mux switches, but a long time constant) and you can solve this yourself to optimize.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You generally need to do this &lt;em&gt;even if you are using an op-amp to buffer the voltage leading into the ADC&lt;/em&gt;. This is because op-amps aren't great at dealing with high-frequency nonlinear loads like a multiplexer + sampling capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are &lt;em&gt;not&lt;/em&gt; buffering the voltage leading into the ADC with an op-amp, note that high source resistance can be a problem. This charge coupling causes a current that flows between one channel and the next, with current equal to f * C * deltaV, where f = sampling frequency, C = internal sampling capacitance, and deltaV = voltage between successive channels sampled by the ADC. Example: deltaV &amp;lt;= +/-3V, C = 5pf, f = 1000Hz yields a charge-coupling current of up to +/- 15nA. If your source impedance is 10K, you'll get an offset voltage of up to +/-150uV depending on the voltage difference between channels. (This really only becomes a problem with high sampling rates or high source impedances)&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-03-09T17:26:00.330" CommentCount="3" />
  <row Id="1801" PostTypeId="2" ParentId="1781" CreationDate="2010-03-09T18:41:38.853" Score="5" ViewCount="" Body="&lt;p&gt;I would certainly be interested in this.  Particular things that would appeal to me:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Isolation from PC and from other channels&lt;/li&gt;&#xA;&lt;li&gt;Multiple synchronised channels&lt;/li&gt;&#xA;&lt;li&gt;Polished cross-platform interface software&lt;/li&gt;&#xA;&lt;li&gt;Cheaper than the competition: the other self-contained units such as the &lt;a href=&quot;http://www.picotech.com/handheld-oscilloscope.html&quot; rel=&quot;nofollow&quot;&gt;handheld picoscopes&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I've used quite a few USB scopes, but the (single- and dual-channel) picoscopes trump the rest simply on the software at the moment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To be honest, personally I'm not that bothered by the self-contained thing or the unpowered hub thing.  If I could find some good, cost-effective, multi-channel USB scopes that worked on any platform, had good software, reasonable specs and isolation between the channels, I'd be over the moon.&lt;/p&gt;&#xA;" OwnerUserId="201" LastActivityDate="2010-03-09T18:41:38.853" />
  <row Id="1802" PostTypeId="2" ParentId="984" CreationDate="2010-03-09T19:13:22.420" Score="3" ViewCount="" Body="&lt;p&gt;I find that RealTerm works for all of my serial port applications. I'm not sure if you are looking to programatically control the LCD or just manually send data/commands to it. RealTerm will let you send hex or ASCII values to to the serial port. It's a little buggy sometimes, but it's great for the price (free).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://realterm.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;http://realterm.sourceforge.net/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-03-09T19:13:22.420" CommentCount="3" />
  <row Id="1804" PostTypeId="2" ParentId="1388" CreationDate="2010-03-09T19:38:57.327" Score="4" ViewCount="" Body="&lt;p&gt;Best is using the various techniques above, practice for a few hours using junk PCB's and parts. &lt;/p&gt;&#xA;" OwnerUserId="591" LastActivityDate="2010-03-09T19:38:57.327" />
  <row Id="1805" PostTypeId="2" ParentId="966" CreationDate="2010-03-09T21:31:35.200" Score="2" ViewCount="" Body="&lt;p&gt;and to above&#xA;22 gauge solid hook-up wire, various colors&#xA;3220 point &lt;strong&gt;QUALITY&lt;/strong&gt; breadboard&#xA;assorted relays&lt;/p&gt;&#xA;" OwnerUserId="591" LastActivityDate="2010-03-09T21:31:35.200" CommunityOwnedDate="2010-03-09T21:31:35.200" />
  <row Id="1806" PostTypeId="2" ParentId="1151" CreationDate="2010-03-09T21:40:49.950" Score="3" ViewCount="" Body="&lt;p&gt;Nice cordless dremel tool like the 300 works fantastic. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The various cut off wheels work great on lots of other hobby chores/cuts.&lt;/p&gt;&#xA;" OwnerUserId="591" LastActivityDate="2010-03-09T21:40:49.950" />
  <row Id="1807" PostTypeId="1" AcceptedAnswerId="1811" CreationDate="2010-03-09T23:44:39.487" Score="4" ViewCount="647" Body="&lt;p&gt;Hello&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have build a prototype with the Arduino Duemilanove and a Ethernet shield. It works great, now I want to get it redesigned in to a single board with a few extra connectors. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Screw terminal for power, &lt;/li&gt;&#xA;&lt;li&gt;Screw terminal for a few of the digital pins, &lt;/li&gt;&#xA;&lt;li&gt;RS232 connection to the serial port. &lt;/li&gt;&#xA;&lt;li&gt;RJ-45 port &lt;/li&gt;&#xA;&lt;li&gt;I also want an enclosure for this new board.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Q: Why do I want to redesign the board?&lt;/strong&gt;&#xA;I can't have a barrel connector for power, its a requirement from the site where I want to install this product. I also want a nice metal enclosure ( I couldn't find one for the Arduino that was reasonably priced. &#xA;&#xA;&lt;p&gt;&lt;strong&gt;Q: How many units would you be making&lt;/strong&gt;&#xA;100-250 to start and more as time goes on. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is; Where should I post this job posting?&lt;/p&gt;&#xA;" OwnerUserId="592" LastActivityDate="2010-07-02T06:20:25.610" Title="Redesigning the Arduino Duemilanove and Ethernet shield in to a single board." Tags="&lt;arduino&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="1808" PostTypeId="1" AcceptedAnswerId="1823" CreationDate="2010-03-10T02:36:30.310" Score="8" ViewCount="1645" Body="&lt;p&gt;Okay, having decided to pitch myself at the PIC family (including dsPIC), I now have a question about programmers. I've been hearing a lot of bad things about the new PICKit 3, and am wondering if I should get that or the apparently more venerable PICKit 2? If I want to be able to use the newest PICs, I think I might need to buy the latest, but I'm not so sure. Thank you!&lt;/p&gt;&#xA;" LastActivityDate="2011-03-08T19:21:41.820" Title="Should I get the PICKit 2 or 3?" Tags="&lt;pic&gt;&lt;programmer&gt;&lt;microcontroller&gt;&lt;electronics&gt;" AnswerCount="7" FavoriteCount="1" />
  <row Id="1809" PostTypeId="2" ParentId="1098" CreationDate="2010-03-10T04:00:43.170" Score="4" ViewCount="" Body="&lt;p&gt;Freelancing through websites like Rentacoder could be an interesting alternative. These websites tend to have embedded/EE jobs in addition to programming jobs. Personally, I had an experience with an interesting VHDL project there on which I actually earned a solid amount per hour. &lt;/p&gt;&#xA;" OwnerUserId="560" LastActivityDate="2010-03-10T04:00:43.170" CommentCount="1" />
  <row Id="1810" PostTypeId="2" ParentId="1808" CreationDate="2010-03-10T05:03:53.773" Score="1" ViewCount="" Body="&lt;p&gt;You need the PK3 if you are going to use the latest chips, as the PK2 software isn't being updated. You can see if the chips you want to use are supported by either unit by checking from within MPLAB. The main thing that people don't like about the PK3 is that the useful applications for the PK2 that configure it as a simple logic analyser and serial I/F haven't been ported to it. The ICD 3 I use is another option. It works with all Microchip devices and is a lot faster than the PK2/PK3, but costs a lot more. It's also replaced free if it ever develops a fault, even if I do something silly to it.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-10T05:03:53.773" />
  <row Id="1811" PostTypeId="2" ParentId="1807" CreationDate="2010-03-10T05:16:50.083" Score="2" ViewCount="" Body="&lt;p&gt;You could try one of the freelance design sites like &lt;a href=&quot;http://www.freelancer.com/projects/by-job/PCB-Layout.html&quot; rel=&quot;nofollow&quot;&gt;Freelancer&lt;/a&gt;. You need to take into account the cost of EMC conformity in the country where you live; CE conformance is required in the EU, and can be quite expensive- something like £3,000 in the UK for that sort of item.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-10T05:16:50.083" CommentCount="1" />
  <row Id="1813" PostTypeId="2" ParentId="1808" CreationDate="2010-03-10T13:59:22.833" Score="1" ViewCount="" Body="&lt;p&gt;Like Leon I also use an ICD3, but I want to try a PK2. The PK2 has a PK2-to-go option that allows you to download a hex file to the programmer and then program a microcontroller without a PC. This is an important feature for my company since we sometimes want to do firmware updates in the field. I think the PK3 has the same feature, but I have not been able to confirm that from just looking at the microchip website. Is there anyone out there who has tried both the PK2/PK3?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just tried the PK2. It's good, but there are a few things that don't exactly meet my expectations:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;PK2-to-go option limited in supported&#xA;hex file size &amp;lt; 100kb&lt;/li&gt;&#xA;&lt;li&gt;PK2-to-go option still requires power via USB&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Haven't tried the PK3 yet.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-04-15T15:23:48.620" LastActivityDate="2010-04-15T15:23:48.620" CommentCount="0" />
  <row Id="1814" PostTypeId="2" ParentId="1770" CreationDate="2010-03-10T14:49:17.300" Score="0" ViewCount="" Body="&lt;p&gt;You should get a waveshield and make an xmas decoration that says 'braaaaainsss' when you push a button on santa's hat.  Or a different saying if you push his hands first.  How about that as a problem?&lt;/p&gt;&#xA;" LastActivityDate="2010-03-10T14:49:17.300" CommunityOwnedDate="2011-02-17T03:28:35.710" />
  <row Id="1815" PostTypeId="1" CreationDate="2010-03-10T14:58:47.947" Score="5" ViewCount="1261" Body="&lt;p&gt;Hi, where I live one cannot buy an arduino very ceap. I figure if I make one for my own purpose on a pcb that would be much cheaper and would be much more fun. Now I cannot find any etch-able pdf on the internet so can anyone point me to some?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-03-13T21:17:18.853" Title="Arduino PCB etchable pdf" Tags="&lt;arduino&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="1816" PostTypeId="2" ParentId="1815" CreationDate="2010-03-10T15:34:00.880" Score="2" ViewCount="" Body="&lt;p&gt;I don't believe that the board layout files for the Arduino are available, but you can pick up the design files for the Freeduino &lt;a href=&quot;http://www.freeduino.org/freeduino_open_designs.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  It's not the Arduino, but it should be compatible enough.  I don't know if it's the sort of thing you'd want to etch yourself at home but you're welcome to try.  So far as I saw, the boards don't come in PDF format - just Gerber and Eagle, so pick up Gerbv from Sourceforge to convert to PDF.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-03-10T15:34:00.880" />
  <row Id="1817" PostTypeId="2" ParentId="1808" CreationDate="2010-03-10T16:48:22.227" Score="1" ViewCount="" Body="&lt;p&gt;I have had a PK2 for nearly 4 years now and I'm pretty happy with it. It works for low end PICs as well as the 18F usb series which are all I have at my disposal.&#xA;The UART and logic analyzer are really useful tools, but I have yet to use the PK2-to-go option.&#xA;I think these are all the tools any starting PIC hobbyist will need and because it's an older model than PK3 I guess you might be able to get hold of them cheaper.&lt;/p&gt;&#xA;" OwnerUserId="348" LastActivityDate="2010-03-10T16:48:22.227" />
  <row Id="1818" PostTypeId="2" ParentId="984" CreationDate="2010-03-10T17:45:10.970" Score="5" ViewCount="" Body="&lt;p&gt;As everyone said before: Realterm.  It's my #1 serial terminal program PERIOD.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from that you may get good results with several other programs/hardware combinations:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bus Pirate has a built-in LCD mode and can interface to nearly any serial device on any serial interface.  You communicate with it via terminal software or Python, C, etc&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Docklight is a terminal spying program/terminal scripting program that you may like.  I've only begun to look into it but it seems like it has some good features.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-03-10T17:45:10.970" CommentCount="1" />
  <row Id="1819" PostTypeId="2" ParentId="1815" CreationDate="2010-03-10T19:50:55.167" Score="3" ViewCount="" Body="&lt;p&gt;There's a single-sided arduino PCB that you can etch at home:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardSerialSingleSided&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Main/ArduinoBoardSerialSingleSided&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A smaller alternative is the Really Bare Bones Board (RBBB), it's Arduino compatible and comes with design files:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.moderndevice.com/products/rbbb-kit&quot; rel=&quot;nofollow&quot;&gt;http://www.moderndevice.com/products/rbbb-kit&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, you could do without a PCB and go for a Paperduino:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://lab.guilhermemartins.net/2009/05/06/paperduino-prints/&quot; rel=&quot;nofollow&quot;&gt;http://lab.guilhermemartins.net/2009/05/06/paperduino-prints/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-10T19:50:55.167" CommentCount="1" />
  <row Id="1820" PostTypeId="1" AcceptedAnswerId="1821" CreationDate="2010-03-10T20:28:54.370" Score="3" ViewCount="232" Body="&lt;p&gt;&lt;a href=&quot;http://imgur.com/WVhCg&quot; rel=&quot;nofollow&quot;&gt;This piece of metal&lt;/a&gt; was packaged with my new soldering iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody know what is it ? Is it a stand ?&lt;/p&gt;&#xA;" OwnerUserId="595" LastActivityDate="2010-03-10T20:48:47.047" Title="Mysterious piece of metal shipped with a soldering iron" Tags="&lt;soldering&gt;&lt;iron&gt;" AnswerCount="2" />
  <row Id="1821" PostTypeId="2" ParentId="1820" CreationDate="2010-03-10T20:42:57.010" Score="3" ViewCount="" Body="&lt;p&gt;Yes it is a stand, if you push out the center piece so that it is about 45 degrees or more from the rest of the metal then you have a stand which will hold the iron off the surface.&#xA;This tends to come with the Maplin irons in the UK.&lt;/p&gt;&#xA;" OwnerUserId="9" LastActivityDate="2010-03-10T20:42:57.010" CommentCount="3" />
  <row Id="1822" PostTypeId="2" ParentId="1820" CreationDate="2010-03-10T20:48:47.047" Score="1" ViewCount="" Body="&lt;p&gt;The holes are for securing it to the bench with a couple of screws.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-10T20:48:47.047" CommentCount="1" />
  <row Id="1823" PostTypeId="2" ParentId="1808" CreationDate="2010-03-10T22:22:51.630" Score="2" ViewCount="" Body="&lt;p&gt;I think the main reason behind PK3 hate is from &lt;a href=&quot;http://www.eevblog.com/2009/10/21/eevblog-39-pickit-3-programmerdebugger-review/&quot; rel=&quot;nofollow&quot;&gt;this review by D.L. Jones&lt;/a&gt;.  If you read (watch?) between the lines, D.L. Jones is upset because, well, the &lt;em&gt;PK3 isn't the PK2&lt;/em&gt;.  My response:  It's a PIC chip programmer for hobby use, not for production work!  Yes the physical UI is different between the two, but hey, your'e getting a OEM-supplied programmer for very little money that programs just about everything in their lineup (PK2 doesn't), so I wouldn't complain.  Take what they give you!  In the not-too-distant past, programmers were waay more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At work, we use ICD2 and ICD3 &quot;hockey pucks&quot; and the main reason we don't use PK2 is because the PK2 didn't support a particular micro we wanted to use in the past (the PK3 supports it now), so they had to upgrade.  All of my coworkers said PK3 is probably a good way to start, since the part support problem seems to be resolved.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-04-15T22:11:03.703" LastActivityDate="2010-04-15T22:11:03.703" CommentCount="2" />
  <row Id="1824" PostTypeId="2" ParentId="1808" CreationDate="2010-03-10T22:24:24.607" Score="1" ViewCount="" Body="&lt;p&gt;There's a video podcast &lt;a href=&quot;http://www.eevblog.com/2009/10/21/eevblog-39-pickit-3-programmerdebugger-review/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; where David L Jones an Australian Electronics Design Engineer compares the PICkit2 and PICkit3 (he prefers the PICkit2 and rants uncontrollably about how Microchip have stuffed up with the PICkit3). He has a tendency to rant in many of his podcasts but is very funny in the process (he swears a lot as well so be warned).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a PICkit2 and am very happy with it.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-03-10T22:24:24.607" />
  <row Id="1826" PostTypeId="2" ParentId="592" CreationDate="2010-03-11T14:23:38.350" Score="3" ViewCount="" Body="&lt;p&gt;Falstad  &lt;a href=&quot;http://www.falstad.com/circuit/e-index.html&quot; rel=&quot;nofollow&quot;&gt;Falstad Circuit index&lt;/a&gt; has an excellent Java applet that allows you to do virtual prototyping with various types of circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has a nice section on &lt;strong&gt;Op amps&lt;/strong&gt;, whats great is the built in O'scope, volt and current meters. Right clicking on a template component in the applet brings up menu where you can experiment/substitute with different values, add remove components. &lt;/p&gt;&#xA;" OwnerUserId="591" LastEditorUserId="591" LastEditorDisplayName="" LastEditDate="2010-03-11T14:36:52.113" LastActivityDate="2010-03-11T14:36:52.113" CommentCount="1" />
  <row Id="1827" PostTypeId="1" AcceptedAnswerId="1839" CreationDate="2010-03-11T15:03:29.577" Score="2" ViewCount="334" Body="&lt;p&gt;Does anyone else use the PIC18F97J60 Ethernet capability? If so what kind of RX/TX performance is typical for that chip? I was running the TCPPerformanceRX/TX applications provided as part of the Microchip TCP/IP stack and getting between 1500-2000 bytes/sec TX and 60-80 bytes/sec RX. Receive seems way slower than it should be.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-03-11T23:48:33.253" Title="PIC18F97J60 Ethernet performance" Tags="&lt;ethernet&gt;&lt;pic&gt;" AnswerCount="1" />
  <row Id="1828" PostTypeId="2" ParentId="592" CreationDate="2010-03-11T15:32:10.290" Score="1" ViewCount="" Body="&lt;p&gt;I always simulate my op amp and other analogue circuits with SPICE before building and testing them. Free SPICE implementations are available, and many PCB packages include it.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-11T15:32:10.290" />
  <row Id="1829" PostTypeId="1" AcceptedAnswerId="1844" CreationDate="2010-03-11T16:28:35.410" Score="3" ViewCount="347" Body="&lt;p&gt;I know there are plenty of references, tutorials and projects posted on line. I'm looking for a decent Arduino reference/project paperback I can read while traveling, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="591" LastActivityDate="2010-03-12T21:34:48.900" Title="Best Arduino pocket reference" Tags="&lt;arduino&gt;&lt;books&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="1830" PostTypeId="1" AcceptedAnswerId="1833" CreationDate="2010-03-11T16:55:33.813" Score="5" ViewCount="601" Body="&lt;p&gt;Does anyone have any examples of the &lt;a href=&quot;http://en.wikipedia.org/wiki/MD5&quot; rel=&quot;nofollow&quot;&gt;MD5 algorithm&lt;/a&gt; for a microcontroller (preferably an 8-bit one)?  Our project is going to use a Microchip PIC18 series device.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-03-11T21:37:07.563" LastActivityDate="2010-03-15T00:43:21.163" Title="MD5 implementation for microcontroller" Tags="&lt;microcontroller&gt;&lt;pic&gt;" AnswerCount="5" />
  <row Id="1831" PostTypeId="2" ParentId="1830" CreationDate="2010-03-11T17:33:02.043" Score="2" ViewCount="" Body="&lt;p&gt;You can find a good description and some pseudocode for the MD5 algorithm wikipedia at &lt;a href=&quot;http://en.wikipedia.org/wiki/MD5&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/MD5&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also consider posting this question on &lt;a href=&quot;http://stackoverflow.com/&quot;&gt;stackoverflow&lt;/a&gt; since it is geared more towards programming questions.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-03-11T17:33:02.043" />
  <row Id="1832" PostTypeId="2" ParentId="1829" CreationDate="2010-03-11T18:06:31.413" Score="2" ViewCount="" Body="&lt;p&gt;The only two printed books that I know are the &lt;a href=&quot;http://oreilly.com/catalog/9780596155520&quot; rel=&quot;nofollow&quot;&gt;Getting Started with Arduino&lt;/a&gt; and &lt;a href=&quot;http://www.lulu.com/content/1108699&quot; rel=&quot;nofollow&quot;&gt;this programming reference&lt;/a&gt; book (although this is really a reference book, not something fun to read while travelling). &lt;/p&gt;&#xA;" OwnerUserId="595" LastActivityDate="2010-03-11T18:06:31.413" />
  <row Id="1833" PostTypeId="2" ParentId="1830" CreationDate="2010-03-11T18:49:39.470" Score="9" ViewCount="" Body="&lt;p&gt;If you are looking for a C implementation, the Microchip TCP/IP stack has an implementation of MD5 in the Hashes.c file.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-03-11T18:49:39.470" CommentCount="1" />
  <row Id="1834" PostTypeId="1" CreationDate="2010-03-11T20:24:54.990" Score="4" ViewCount="311" Body="&lt;p&gt;I am using a qtr8-rc sensor array on a line following robot, When I use it on a black line on a white surface it works but when i try to use it on a black surface with white line i can't get correct results, i have extracted the following code from my robot to test it separately but no matter what i do i can not get it to detect white line on a black surface...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;pre&gt;&lt;code&gt;&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;include &quot;PololuQTRSensors.h&quot;&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;PololuQTRSensorsRC qtr;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;void setup(){&#xA;  Serial.begin(9600);&#xA;  qtr.init((unsigned char[]) {2,3,4,5,6,7,9}, 7);&lt;/p&gt;&#xA;&#xA;&lt;p&gt;int i;&#xA;  for (i = 0; i &amp;lt; 250; i++){  // make the calibration take about 5 seconds&#xA;    qtr.calibrate(QTR_EMITTERS_ON);&#xA;    delay(20);&#xA;  }&#xA;}&lt;/p&gt;&#xA;&#xA;&lt;p&gt;void loop(){&lt;/p&gt;&#xA;&#xA;&lt;p&gt;unsigned int val[7];&#xA;  qtr.readCalibrated(val);&#xA;  int line = qtr.readLine(val,QTR_EMITTERS_ON,true);&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Serial.print(line);&#xA;  Serial.print(&quot; R&amp;lt; &quot;);&#xA;  Serial.print(val[0]); Serial.print(&quot; &quot;);&#xA;  Serial.print(val[1]); Serial.print(&quot; &quot;);&#xA;  Serial.print(val[2]); Serial.print(&quot; &quot;);&#xA;  Serial.print(val[3]); Serial.print(&quot; &quot;);&#xA;  Serial.print(val[4]); Serial.print(&quot; &quot;);&#xA;  Serial.print(val[5]); Serial.print(&quot; &quot;);&#xA;  Serial.print(val[6]); Serial.print(&quot; &quot;);&#xA;  Serial.print(val[7]); Serial.print(&quot; &quot;);&#xA;  Serial.println(&quot; &gt;L &quot;);&lt;/p&gt;&#xA;&#xA;&lt;p&gt;}&#xA;&lt;/pre&gt;&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some sample reading I am getting,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;pre&gt;&lt;code&gt;&#xA;3200 R&amp;lt; 553 473 397 113 120 533 304 104  &gt;L&#xA;3432 R&amp;lt; 567 514 474 113 120 393 82 104  &gt;L&#xA;3494 R&amp;lt; 572 625 544 94 100 487 69 104  &gt;L&#xA;3418 R&amp;lt; 543 421 506 88 93 305 64 104  &gt;L&#xA;3407 R&amp;lt; 529 403 487 69 73 290 50 104  &gt;L&#xA;3403 R&amp;lt; 524 397 480 62 67 284 46 104  &gt;L&#xA;3506 R&amp;lt; 538 561 474 37 40 264 27 104  &gt;L&#xA;3503 R&amp;lt; 538 543 455 18 20 248 13 104  &gt;L&#xA;3519 R&amp;lt; 558 567 474 44 46 269 32 104  &gt;L&#xA;3537 R&amp;lt; 577 590 500 69 73 290 50 104  &gt;L&#xA;3545 R&amp;lt; 577 614 532 94 100 310 69 104  &gt;L&#xA;3466 R&amp;lt; 611 497 397 94 100 310 69 104  &gt;L&#xA;3534 R&amp;lt; 572 584 500 62 67 284 46 104  &gt;L&#xA;3534 R&amp;lt; 572 584 500 62 67 284 46 104  &gt;L&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;/pre&gt;&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All numbers are way too close so readLine does not return a correct position.  One of the pins on my arduino does not work so I skipped connecting one of the sensors(sensor 7)&lt;/p&gt;&#xA;" OwnerUserId="496" LastActivityDate="2011-02-17T08:15:00.220" Title="QTR 8RC White line detection" Tags="&lt;arduino&gt;&lt;pololu&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="1835" PostTypeId="2" ParentId="1830" CreationDate="2010-03-11T20:33:30.690" Score="7" ViewCount="" Body="&lt;p&gt;Here's the MD5 implementation from the EtherNut (AVR based)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ethernut.svn.sourceforge.net/viewvc/ethernut/trunk/nut/gorp/hashes/md5.c?revision=2555&amp;amp;view=markup&quot; rel=&quot;nofollow&quot;&gt;http://ethernut.svn.sourceforge.net/viewvc/ethernut/trunk/nut/gorp/hashes/md5.c?revision=2555&amp;amp;view=markup&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-11T20:33:30.690" />
  <row Id="1836" PostTypeId="2" ParentId="1829" CreationDate="2010-03-11T21:05:35.110" Score="4" ViewCount="" Body="&lt;p&gt;There is a quite good pdf document: &lt;a href=&quot;http://www.earthshinedesign.co.uk/ASKManual/Site/ASKManual.html&quot; rel=&quot;nofollow&quot;&gt;ASKManual&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can download and print it in pocket size for free :)&lt;/p&gt;&#xA;" OwnerUserId="598" LastActivityDate="2010-03-11T21:05:35.110" />
  <row Id="1837" PostTypeId="2" ParentId="1792" CreationDate="2010-03-11T21:25:33.330" Score="0" ViewCount="" Body="&lt;p&gt;You might also be running into EMI susceptibility. Active components (such as your PGA) are prone to a phenomenon called RF rectification where an AC disturbance at high frequencies at the input amplifier causes a DC disturbance at the output of an amplifier. This is very common in high-gain circuits (you'll see it a lot in thermocouple amplifiers) in an electrically noisy environment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is the problem, shunt out high-frequency noise by putting one or more good high-frequency bypass capacitors (1000pf-10000pf ceramic probably best) across the closest points that are inputs of your circuit. (for instance, if you have a 4-resistor one-op-amp differential amplifier:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/Opamp-differential.svg/200px-Opamp-differential.svg.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;then put 2 capacitors at the input of the resistors -- from V1 to GND and V2 to GND, you may need a 3rd one from V1 to V2 if there is a lot of differential noise -- and NOT across the op-amp inputs)&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-03-11T21:25:33.330" />
  <row Id="1838" PostTypeId="2" ParentId="1830" CreationDate="2010-03-11T22:04:56.713" Score="2" ViewCount="" Body="&lt;p&gt;I would stick with a known reputable implementation of MD5, and stay away from libraries you find from 3rd-party vendors. The original &lt;a href=&quot;http://tools.ietf.org/html/rfc1321&quot; rel=&quot;nofollow&quot;&gt;RFC 1321&lt;/a&gt; which described MD5 has a sample C implementation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reminder: the known weaknesses for MD5 are collision attacks, and &lt;em&gt;not&lt;/em&gt; &lt;a href=&quot;http://en.wikipedia.org/wiki/Preimage_attack&quot; rel=&quot;nofollow&quot;&gt;preimage attacks&lt;/a&gt;, so it is suitable for some cryptographic applications but not others. If you don't know the difference you shouldn't be using it, but don't discard it altogether. See &lt;a href=&quot;http://www.vpnc.org/hash.html&quot; rel=&quot;nofollow&quot;&gt;http://www.vpnc.org/hash.html&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2010-03-15T00:43:21.163" LastActivityDate="2010-03-15T00:43:21.163" CommentCount="3" />
  <row Id="1839" PostTypeId="2" ParentId="1827" CreationDate="2010-03-11T23:48:33.253" Score="3" ViewCount="" Body="&lt;p&gt;I have used the same chip from the same family (18F67J60) and I don't have quantitative data from its use, but your values are definitely significantly lower than I have seen (certainly my RX is many times faster than that).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One application I use with the chip is do bootloading via TFTP and I can receive information on the PIC at ~20k/sec or so.  I would look at how you're setting up your ethernet.  Perhaps the registers are set up incorrectly?  Is your ethernet hub bad?  I would try importing one of the basic examples from microchip (its on the C: in the microchip folder and has a few example applications) and see how fast its going.  Maybe use the Wireshark application to see the data going back and forth, maybe that will give you a clue as to whats happening.&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2010-03-11T23:48:33.253" CommentCount="2" />
  <row Id="1840" PostTypeId="1" CreationDate="2010-03-12T00:27:30.117" Score="2" ViewCount="113" Body="&lt;p&gt;I am developing a school project to make a rechargeable outdoor light for use at BBQ's etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea being, on the wall is a mains powered charging dock, with 4 battery powered lights attached.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once one of the light is removed from the dock, it lights, giving 2-3 hours of light.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Returned to the dock to charge again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have the product design part sorted , just need some help with electronics. Would any of you guru's be able to help me out?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess the lights would be a series of super bright LED's, running off NiMH rechargeable battery pack in each, these charging through a 'connector' to the charging dock. The simpler the better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To switch them on automatically , once removed from charging dock ? I am not sure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your time and help would be greatly appreciated,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for your time&lt;/p&gt;&#xA;" LastActivityDate="2011-05-19T14:15:06.187" Title="Lighting project advice." Tags="&lt;led&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="1841" PostTypeId="2" ParentId="1840" CreationDate="2010-03-12T03:45:29.773" Score="1" ViewCount="" Body="&lt;p&gt;You need to pick the LEDs first so that you quantify how much power &quot;super bright&quot; &#xA;requires. Once that is defined then you can look at the power control circuitry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not sure of your budget but you may want to look at Li-Ion batteries too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should not be difficult to have the light switch on automatically when &#xA;removed from a charging doc.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:15:06.187" LastActivityDate="2011-05-19T14:15:06.187" />
  <row Id="1842" PostTypeId="1" AcceptedAnswerId="1843" CreationDate="2010-03-12T18:02:04.860" Score="4" ViewCount="872" Body="&lt;p&gt;I'm looking into building a temperature monitoring system, and I want the sensor to have the ability to be submersed into boiling water. Can a thermocouple handle this?  I'm looking into &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=251&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; one now, but I'm not sure if it's waterproof.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My other idea would be to drop a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8227&quot; rel=&quot;nofollow&quot;&gt;small temperature sensor&lt;/a&gt; into an aluminum tube and seal it off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas or suggestions?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt;  Sorry, I should have provided more context with my question. To clarify some things, the sensor will be used to monitor and control water temperatures ranging from 30F to 230F, not just to test when water is boiling :).  Also, the water being monitored is consumable, so the sensor needs to be food safe as well, and since this is a hobby project, I'm trying to keep the sensor as cheap as possible.&lt;/p&gt;&#xA;" OwnerUserId="602" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T11:13:42.153" LastActivityDate="2011-05-20T19:18:01.230" Title="Waterproof Temperature Probe" Tags="&lt;sensor&gt;&lt;temperature&gt;&lt;waterproof&gt;" AnswerCount="11" CommentCount="7" FavoriteCount="1" />
  <row Id="1843" PostTypeId="2" ParentId="1842" CreationDate="2010-03-12T18:45:52.487" Score="3" ViewCount="" Body="&lt;p&gt;Sealing it inside a tube would be ideal.  The thermocouple you've linked isn't waterproof.  You can buy thermocouple probes in sealed housings from several sources.  One popular source fo industrial users is &lt;a href=&quot;http://www.omega.com/guides/thermocouples.html&quot; rel=&quot;nofollow&quot;&gt;http://www.omega.com/guides/thermocouples.html&lt;/a&gt; .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rolling your own is fine as long as you select good high temperature materials for the sealant.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-12T18:45:52.487" CommentCount="3" />
  <row Id="1844" PostTypeId="2" ParentId="1829" CreationDate="2010-03-12T21:34:48.900" Score="2" ViewCount="" Body="&lt;p&gt;The ASKManual linked by usecide is really good.  If you want something with even more pictures and really big type, you might like the PDFs of the slides from my Arduino classes &quot;&lt;a href=&quot;http://todbot.com/blog/spookyarduino/&quot; rel=&quot;nofollow&quot;&gt;Spooky Arduino&lt;/a&gt;&quot; and &quot;&lt;a href=&quot;http://todbot.com/blog/bionicarduino/&quot; rel=&quot;nofollow&quot;&gt;Bionic Arduino&lt;/a&gt;&quot;.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-03-12T21:34:48.900" />
  <row Id="1845" PostTypeId="2" ParentId="1842" CreationDate="2010-03-13T03:58:35.477" Score="3" ViewCount="" Body="&lt;p&gt;A thermocouple must be put into a thermowell if you wish to submerse it in water. However there are options, does the fluid have to be water? A dialectic oil would be fine and you could get much higher temperatures. If it must be water and you intend to make your own thermowell, then you should fill the well with oil and leave enough room for expansion before sealing. The oil will transfer the heat from the outside walls of the thermowell more efficiently than air. Also make sure the thermocouple is supported properly so not to short against the well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I take it from the nature of your question that you may have not used thermocouples much. If that is true, then you should do some reading first. There are a lot of pitfalls you need to avoid. Such as dissimilar metal junctions in your wiring, and the proper metallurgy wire for the series TC you are using.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps and good luck with your project.&lt;/p&gt;&#xA;" OwnerUserId="498" LastActivityDate="2010-03-13T03:58:35.477" CommentCount="2" />
  <row Id="1846" PostTypeId="2" ParentId="1830" CreationDate="2010-03-13T09:41:32.963" Score="2" ViewCount="" Body="&lt;p&gt;from the wikipedia page on &lt;a href=&quot;http://en.wikipedia.org/wiki/Md5&quot; rel=&quot;nofollow&quot;&gt;MD5&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;... it has been shown that MD5 is not collision resistant as such, MD5 is not suitable for applications like SSL certificates or digital signatures that rely on this property.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;and from the SSL researchers on the same page:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;We also hope that use of MD5 in other applications will be reconsidered as well.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I understand that you probably don't want to hear this, but do you really need MD5? It shouldn't be used for cryptographic purposes as it is too insecure (and there are boatloads of rainbow tables available). If you are looking for something to just validate data, look into &lt;a href=&quot;http://en.wikipedia.org/wiki/Cyclic_redundancy_check&quot; rel=&quot;nofollow&quot;&gt;CRC&lt;/a&gt; (code &lt;a href=&quot;http://www.netlib.org/crc/crc.c&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) which is computationally cheaper. If you &lt;em&gt;are&lt;/em&gt; using it for cryptographic purposes though, then may I suggest moving to &lt;a href=&quot;http://en.wikipedia.org/wiki/SHA_hash_functions&quot; rel=&quot;nofollow&quot;&gt;SHA&lt;/a&gt;? The only problem is that most cryptographically secure algorithms do not run particularly well on microcontrollers. I know it may seem like MD5 is &quot;good enough&quot;, but the engineering way is to err on the side of caution.&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="417" LastEditorDisplayName="" LastEditDate="2010-03-13T09:49:35.537" LastActivityDate="2010-03-13T09:49:35.537" CommentCount="2" />
  <row Id="1847" PostTypeId="1" AcceptedAnswerId="1862" CreationDate="2010-03-13T12:27:32.273" Score="10" ViewCount="420" Body="&lt;p&gt;For example when you build a circuit you have the board and the components between them is air.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a clay like material that will act like air does?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Application: you could bundle simple circuits into a ball, attach adhesive to the outside and throw them at things (LED throwie)&lt;/p&gt;&#xA;" OwnerUserId="605" LastEditorUserId="327" LastEditorDisplayName="" LastEditDate="2010-04-22T14:20:19.950" LastActivityDate="2011-05-17T12:53:02.170" Title="Does this exist: Insulating material to cover circuit." Tags="&lt;circuit&gt;" AnswerCount="10" />
  <row Id="1848" PostTypeId="1" AcceptedAnswerId="1853" CreationDate="2010-03-13T12:48:28.623" Score="5" ViewCount="234" Body="&lt;p&gt;I would like to fab some custom LEDs Assemblies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Embed a resistor in the plastic, is there a smart way to go about doing this? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know Alibaba other than that nothing really.&lt;/p&gt;&#xA;" OwnerUserId="605" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-01-29T03:16:19.243" LastActivityDate="2011-01-29T03:16:19.243" Title="Custom LED Assembly manufacturing?" Tags="&lt;led&gt;&lt;manufacturing&gt;" AnswerCount="4" />
  <row Id="1849" PostTypeId="1" AcceptedAnswerId="1852" CreationDate="2010-03-13T13:36:33.733" Score="9" ViewCount="2109" Body="&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/21203P.pdf&quot; rel=&quot;nofollow&quot;&gt;The datasheet&lt;/a&gt; of the 24LC256 EEPROM states that:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The SDA bus requires a pull-up resistor to VCC (typical 10 kΩ for 100 kHz, 2 kΩ for 400 kHz and 1 MHz).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I thought that any resistor with a kΩ value would do the job (and it seems that my EEPROM works fine at different frequencies with a 10 kΩ resistor).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;is there a correct value for pull-up resistors ?&lt;/li&gt;&#xA;&lt;li&gt;is there a law/rule to determine this value ?&lt;/li&gt;&#xA;&lt;li&gt;how do different resistance values affect the I²C data bus ?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="595" LastActivityDate="2011-05-13T12:45:04.130" Title="Is there a correct resistance value for pull-up resistors ?" Tags="&lt;i2c&gt;&lt;resistor&gt;" AnswerCount="4" FavoriteCount="4" />
  <row Id="1850" PostTypeId="2" ParentId="1847" CreationDate="2010-03-13T14:15:16.993" Score="10" ViewCount="" Body="&lt;p&gt;There are plenty of things out there that you could use as a conformal coating to insulate the circuit (just search digikey). As far as getting something sticky on the outside for use in throwies I would do that as a separate step once the circuit is insulated so you have more options and you can be more creative.&lt;/p&gt;&#xA;" OwnerUserId="606" LastActivityDate="2010-03-13T14:15:16.993" />
  <row Id="1851" PostTypeId="2" ParentId="1847" CreationDate="2010-03-13T15:10:44.650" Score="4" ViewCount="" Body="&lt;p&gt;There are also soft epoxy materials for electronic assemblies. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;IIRC Epoxy Technologies (http://www.epotek.com) makes soft epoxy.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:53:02.170" LastActivityDate="2011-05-17T12:53:02.170" />
  <row Id="1852" PostTypeId="2" ParentId="1849" CreationDate="2010-03-13T15:27:32.387" Score="9" ViewCount="" Body="&lt;p&gt;The correct pullup resistance for the I2C bus depends on the total capacitance on the bus&#xA;and the frequency you want to operate the bus at. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The formula from the ATmega168 datasheet (which I believe comes from the official I2C spec)&#xA;is -- &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Freq &amp;lt; 100KHz  Rmin = (Vcc - 0.4V) / 3mA   Rmax = 1000nS / Cbus&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Freq &gt; 100KHz  Rmin = (Vcc - 0.4V) / 3mA   Rmax = 300nS / Cbus&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Microchip 24LC256 specifies a maximum pin capacitance of 10pF (which is fairly&#xA;typical). Count up the number of devices you have in parallel on the bus and&#xA;use the formula above to calculate a range of values that will work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are powering off of batteries I would use values that are at the high&#xA;end of the range. If there are no power limits on the power source or&#xA;power dissipation issues in the ICs I would use values on the lower end&#xA;of the range. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I sell some kits with an I2C RTC (DS1337). I include 4.7K resistors in the kit which &#xA;seems like a reasonable compromise for most users.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:45:04.130" LastActivityDate="2011-05-13T12:45:04.130" CommentCount="2" />
  <row Id="1853" PostTypeId="2" ParentId="1848" CreationDate="2010-03-13T15:31:27.323" Score="5" ViewCount="" Body="&lt;p&gt;Custom plastic could be expensive. I would find a lens you like&#xA;and fabricate a small PCB with an SMD resistor and SMD LED. Glue the &#xA;lens to the PCB. Add two pins for the external connection.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T02:12:36.817" LastActivityDate="2011-01-29T02:12:36.817" CommentCount="2" />
  <row Id="1854" PostTypeId="2" ParentId="1842" CreationDate="2010-03-13T15:40:41.283" Score="0" ViewCount="" Body="&lt;p&gt;Analog Devices use to make a stainless steel temperature probe that contained&#xA;an AD590 - temperature to current transducer. A little easier to use than&#xA;a thermocouple. Not sure if they make it anymore. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The range on the AD590 is -55degC to 150degC. 1uA per degK. They are laser&#xA;trimmed but we use to do a boiling point and freezing point calibration.&#xA;As was mentioned you need to allow for the additional thermal mass when&#xA;doing your measurements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the AD590 in the TO-52 package you could glue the package to a tube&#xA;that is a thermal insulator and run the wires inside the tube. The tube&#xA;would not add mass and would insulate the wires.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T11:11:58.083" LastActivityDate="2011-05-20T11:11:58.083" />
  <row Id="1856" PostTypeId="1" CreationDate="2010-03-13T19:39:28.830" Score="2" ViewCount="124" Body="&lt;p&gt;I have an autoranging multimeter and many AA batteries.... how do I interpret the readings when deciding to keep or discard AA (1.5 volt) batteries?&lt;/p&gt;&#xA;" LastEditorUserId="424" LastEditorDisplayName="" LastEditDate="2010-03-13T20:40:12.490" LastActivityDate="2011-05-20T11:00:22.457" Title="How to I determine/ interpret values of autoranging multimter" Tags="&lt;battery&gt;&lt;capacity&gt;&lt;discharge&gt;&lt;voltage&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="1857" PostTypeId="2" ParentId="1856" CreationDate="2010-03-13T20:43:41.473" Score="0" ViewCount="" Body="&lt;p&gt;I am assuming Alkaline batteries -- In the Energizer datasheets &#xA;the capacity is specified down to 0.8V. I would discard them&#xA;if they are less the 0.8V. If it is a battery that I may not&#xA;check too often then I might set the limit at a volt or so.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T11:00:22.457" LastActivityDate="2011-05-20T11:00:22.457" />
  <row Id="1858" PostTypeId="2" ParentId="1856" CreationDate="2010-03-13T21:12:35.997" Score="5" ViewCount="" Body="&lt;p&gt;Look up voltage curves for the chemistry of your batteries. Depends on the exact battery, but you can gauge how much power is left based on the voltage:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.powerstream.com/z/AA-500mA.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From this graph, when it reads 1.0V, there is roughly 20% power left, and when it reads 0.8V, roughly 5% power left. Of course, it's hard to extract 100% of the power from a battery, since many devices require a certain voltage level to operate, and when it drops too low, they cannot run. Depends on the design of the device.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-03-13T21:12:35.997" />
  <row Id="1859" PostTypeId="2" ParentId="1815" CreationDate="2010-03-13T21:17:18.853" Score="3" ViewCount="" Body="&lt;p&gt;In fact, the layout files to (almost) all the Arduino boards are available on their respective pages, linked here: &lt;a href=&quot;http://arduino.cc/en/Main/Hardware&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Main/Hardware&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would recommend the updated version of the Arduino Single-Sided Serial board, described here: &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardSerialSingleSided3&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Main/ArduinoBoardSerialSingleSided3&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="609" LastActivityDate="2010-03-13T21:17:18.853" CommentCount="2" />
  <row Id="1860" PostTypeId="2" ParentId="1808" CreationDate="2010-03-13T22:12:09.397" Score="1" ViewCount="" Body="&lt;p&gt;Get the PK3. Microchip has responded to the rants with some rollbacks and improvements. Also you get a safer system with less zapping of target boards and better future compatibility.&lt;/p&gt;&#xA;" OwnerUserId="610" LastActivityDate="2010-03-13T22:12:09.397" CommentCount="1" />
  <row Id="1861" PostTypeId="2" ParentId="1849" CreationDate="2010-03-13T22:40:54.907" Score="2" ViewCount="" Body="&lt;p&gt;For low frequencies the value doesn't really matter, but for high frequencies it can have a filtering effect on the signal, in combination with other capacitances in the circuit, which is why they recommend different values for different speeds.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-03-13T22:40:54.907" />
  <row Id="1862" PostTypeId="2" ParentId="1847" CreationDate="2010-03-13T22:45:33.863" Score="8" ViewCount="" Body="&lt;p&gt;If you want something like clay, what's wrong with clay?  Just check it to make sure it's not conductive.  I think you'd have more difficulty finding &lt;em&gt;conductive&lt;/em&gt; clay than non-conductive...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's &lt;a href=&quot;http://flic.kr/p/4JWJfE&quot; rel=&quot;nofollow&quot;&gt;Elmer's Tac 'N Stik&lt;/a&gt;, which is probably more like what you want:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://flic.kr/p/4JWJ33&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://farm3.static.flickr.com/2227/2455040590_3e004e56d2.jpg&quot; alt=&quot;sticky-tack measured with a multimeter&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, here are instructions for cooking up &lt;a href=&quot;http://courseweb.stthomas.edu/apthomas/SquishyCircuits/INSULATING.htm&quot; rel=&quot;nofollow&quot;&gt;insulating dough&lt;/a&gt; and &lt;a href=&quot;http://courseweb.stthomas.edu/apthomas/SquishyCircuits/CONDUCTING.htm&quot; rel=&quot;nofollow&quot;&gt;conductive dough&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-07-19T16:35:58.300" LastActivityDate="2010-07-19T16:35:58.300" CommentCount="5" />
  <row Id="1863" PostTypeId="2" ParentId="1856" CreationDate="2010-03-13T23:00:41.543" Score="4" ViewCount="" Body="&lt;p&gt;Be careful not to confuse voltage with the amount of charge left in a battery. The open circuit voltage of a battery probably changes very little until it's virtually dead. However, over the same period of time the internal resistance of the battery my increase a great deal. Also notice that in the interesting graph davr posted that it's for batteries discharging 500 mA. So that means if you have a nominal 1.5V battery, you will want to short it with 3 ohm load and measure the voltage. Careful, that means if you use a resistor, that resistor will need to be rated for greater than 3/4 Watts. This also means you are using up your charge during your test.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might want to run an experiment yourself and short a battery with a load mimicking a likely current draw for your purpose, and logging the voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Determining the charge left in a battery is a non-trivial problem. Many consumer products don't quite get battery monitoring right.&lt;/p&gt;&#xA;" OwnerUserId="227" LastActivityDate="2010-03-13T23:00:41.543" CommentCount="1" />
  <row Id="1864" PostTypeId="2" ParentId="1388" CreationDate="2010-03-13T23:09:23.220" Score="0" ViewCount="" Body="&lt;p&gt;More tips,  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use a damp sponge to keep the tip clean. When soldering normal components (not SMD) use a powerful hot iron (I use an Antex 25w for general work). When wiring up a big job I'll often use a 40w iron with a fine tip. It stays hot and I can get a good rhythm going. The quicker you get the joint done the less chance of damage/excess heat transfer to other parts etc.&lt;/p&gt;&#xA;" OwnerUserId="611" LastActivityDate="2010-03-13T23:09:23.220" />
  <row Id="1865" PostTypeId="2" ParentId="991" CreationDate="2010-03-13T23:19:23.133" Score="5" ViewCount="" Body="&lt;p&gt;I've started using one of these (MBED developer board). The big selling points for me were that I could code in C or C++, straightforward connection vis USB and a slick on-line development environment (no local tool installation required at all!).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://mbed.org/&quot; rel=&quot;nofollow&quot;&gt;http://mbed.org/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Five minutes afer opening box I had a sample blinky program (the 'hello world' of the emedded world) running the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &quot;mbed.h&quot;&#xA;&#xA;DigitalOut myled(LED1);&#xA;&#xA;int main()&#xA;{&#xA;    while(1)&#xA;    {&#xA;        myled = 1;&#xA;        wait(0.2);&#xA;        myled = 0;&#xA;        wait(0.2);&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;That's it! Above is the complete program!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's based on ARM Cortex M3, fast and plenty of memory for embedded projects (100mhz, 256k flash &amp;amp; 32k ram). The online dev tools have a very good library and plenty of examples and theres a very active forum. Plenty of help on connecting devices to MBED etc&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even though I have plenty of experience with embedded systems (ARM 7/9, Renases M8/16/32, Coldfire, Zilog, PIC etc) I still found this a refreshingly easy system to get to grips with while having serious capability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After initially playing with it on a basic breadboard I bought a base board from these guys: &lt;a href=&quot;http://www.embeddedartists.com/products/lpcxpresso/xpr_base.php?PHPSESSID=lj20urpsh9isa0c8ddcfmmn207&quot; rel=&quot;nofollow&quot;&gt;http://www.embeddedartists.com/products/lpcxpresso/xpr_base.php?PHPSESSID=lj20urpsh9isa0c8ddcfmmn207&lt;/a&gt;. This has a pile of I/O devices (including a miniture OLED and a 3axis accelerometer). From the same site I also bought one of the LCPExpresso processor boards which is cheap, less power/memory than the MBED but perfect for smaller jobs (still hammers the crap out of PIC/Atmega processors). The base board supports both the LCPExpresso and the MBED. Purchasing the LCPExpress processor board also got me me an attached JTAG debugger and an offline dev envoronment (Code Red's GCC/Eclipse based dev kit). This is much more complex than the online MBED dev environment but is a logical progression after you've gained expeience with the MBED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With reference to my original point noite that the MBED controller is much more capable than the the LPCExpresso controller BUT is much simpler to use and learn with.&lt;/p&gt;&#xA;" OwnerUserId="611" LastActivityDate="2010-03-13T23:19:23.133" />
  <row Id="1866" PostTypeId="1" AcceptedAnswerId="1923" CreationDate="2010-03-14T08:29:58.940" Score="2" ViewCount="315" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to get the &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/DS1077.pdf&quot; rel=&quot;nofollow&quot; title=&quot;DS1077 datasheet&quot;&gt;DS1077&lt;/a&gt; to work, but I can't for the life of me figure out what I'm doing wrong.  I'm using the defaults for the MUX and BUS registers, and programming in my own DIV frequency has no effect.  I can read out the registers over I2C and they return the values I set, but the oscillator output (as measured on my scope) is nothing like what it should be.  I tried copying the values in from &lt;a href=&quot;http://www.sparkfun.com/datasheets/BreakoutBoards/DS1077v2.c&quot; rel=&quot;nofollow&quot; title=&quot;C code&quot;&gt;SparkFun's example&lt;/a&gt; (I'm using their breakout board) but the &quot;40kHz&quot; output is way above the 60MHz bandwidth of my scope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found an &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/171&quot; rel=&quot;nofollow&quot;&gt;example on Maxim's website&lt;/a&gt; and they recommend you tie CTRL0 and CTRL1 to GND if you're not using them - but if I tie CTRL1 to GND mine stops responding to I2C messages!  I have to tie CTRL1 to VCC to get it to respond over I2C (no mention of that in the datasheet), but that disables the oscillator output.  Otherwise my &quot;circuit&quot; is the same as their example - SDA/SCL go to an Arduino, and the OUT pins go to my scope.  VCC and GND are connected correctly and within spec.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got no idea what's going on, it seems really simple but I still can't get it to work :'-(  Has anyone encountered anything like this before?  Any ideas to help narrow down the problem?&lt;/p&gt;&#xA;" OwnerUserId="548" LastActivityDate="2010-03-17T15:22:31.973" Title="Can't get DS1077 programmable oscillator to work" Tags="&lt;i2c&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="1868" PostTypeId="2" ParentId="1781" CreationDate="2010-03-14T15:19:50.687" Score="2" ViewCount="" Body="&lt;p&gt;See this &lt;a href=&quot;http://yveslebrac.blogspot.com/2008/10/cheapest-dual-trace-scope-in-galaxy.html&quot; rel=&quot;nofollow&quot;&gt;interesting little AtmelTiny45 CPU based scope&lt;/a&gt;. This could easily fit in a probe shell and gives basic functionality for a few bucks...&lt;/p&gt;&#xA;" OwnerUserId="611" LastActivityDate="2010-03-14T15:19:50.687" CommentCount="1" />
  <row Id="1869" PostTypeId="1" AcceptedAnswerId="1882" CreationDate="2010-03-14T19:36:57.303" Score="3" ViewCount="304" Body="&lt;p&gt;so if you add enough caps can you emulate what an inductor is doing, ie. Lead the current so far that it appears to be lagging? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume this doesn't work, why not?&lt;/p&gt;&#xA;" OwnerUserId="605" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-06-14T14:15:42.823" LastActivityDate="2010-06-14T14:15:42.823" Title="Theory: With an AC circuit adding capacitors will cause the current trend towards leading..." Tags="&lt;current&gt;&lt;capacitor&gt;&lt;inductive&gt;&lt;impedance&gt;" AnswerCount="4" />
  <row Id="1870" PostTypeId="1" AcceptedAnswerId="1875" CreationDate="2010-03-14T20:38:49.153" Score="1" ViewCount="287" Body="&lt;p&gt;I got this chip and didn't realize the pins were not the normal spacing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.themountainfold.com/test/03142010046.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anybody know where to find a header for it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW the chip is a re-issue of the old sound chip SN76477&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.themountainfold.com/test/IMG_1119.png&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="605" LastEditorUserId="424" LastEditorDisplayName="" LastEditDate="2010-03-14T21:26:52.247" LastActivityDate="2011-05-19T14:14:18.057" Title="Where can I fnd a header for this goofy chip" Tags="&lt;ic&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="1871" PostTypeId="2" ParentId="1870" CreationDate="2010-03-14T20:52:42.870" Score="0" ViewCount="" Body="&lt;p&gt;Hard to tell from the photo, but looks like common 0.1&quot; pin spacing to me.  So it should plug into a breadboard just fine.  If it's the SN76477NF, which is the 0.4&quot; across narrow version of the chip, then yes, a normal socket (that come in 0.3&quot; &amp;amp; 0.6&quot; widths and is what I assume you mean by &quot;header&quot;) won't work.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But you can take a &lt;a href=&quot;http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&amp;amp;storeId=10001&amp;amp;catalogId=10001&amp;amp;productId=40301&quot; rel=&quot;nofollow&quot;&gt;28-pin 0.6&quot; width socket like this one from Jameco&lt;/a&gt;, cut it into two pieces along the three cross-braces, and remake it into a 0.4&quot; width socket.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-03-14T20:52:42.870" CommentCount="3" />
  <row Id="1872" PostTypeId="1" CreationDate="2010-03-14T20:53:41.620" Score="4" ViewCount="219" Body="&lt;p&gt;This is what I want....problem is that they are expensive, really expensive ($500). Is there a more economical version?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tequipment.net/ELCADET2.html&quot; rel=&quot;nofollow&quot;&gt;http://tequipment.net/ELCADET2.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://tequipment.net/ProductImages/E&amp;amp;L/CADET2_mid.jpg&quot;&gt;&#xA;Features:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;* Expanded Removeable breadboard area&#xA;* Two open collector pulsers&#xA;* Built-in multi-waveform function generator&#xA;* Quad voltage power supply: Three DC &amp;amp; one low voltage AC&#xA;* Functions with optional electronics trainer boards&#xA;* Built-in logic probe with pulse capture&#xA;* BCD to 7 segment decoder/display&#xA;* 8 channel logic indicatorsSpecifications &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The C.A.D.E.T. II is a Complete Electronics Trainer that includes all the functions needed to teach basic AC/DC, Linear and Digital Electronics courses. The unit contains all the functions of our highly acclaimed original C.A.D.E.T. plus frequently requested features from educators worldwide.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The breadboard area is 33% larger than original C.A.D.E.T., holds up to 32 IC's and comes standard as a removable socket plate with velcro. If you prefer, it can be ordered withour bread boards for use with the extensive line of E&amp;amp;L Trainer Boards. The built-in logic probe will detect narrow logic pulses and eliminate the need for extra lab equipment. The BCD to 7 segment display/decoder saves students time when constucting circuits. The Quad Voltage Power Supply has +5 VDC, two variable DC outputs, and a fixed 12.6 VAC center tapped output. The trainer also includes 8 TTL compatible logic switches and two pulsers.&lt;/p&gt;&#xA;" OwnerUserId="605" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-04-14T19:04:52.987" LastActivityDate="2010-04-29T14:23:20.230" Title="Is there a more economical version of this powersource prototyper the CADET" Tags="&lt;prototyping&gt;&lt;breadboard&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="1873" PostTypeId="1" AcceptedAnswerId="1877" CreationDate="2010-03-14T21:12:19.607" Score="4" ViewCount="873" Body="&lt;p&gt;I'm going to start a new project and I wonder if the concept makes sense.&#xA;(I'm not so familiar with ATA specifications to answer this by myself :))&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The concept:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;b&gt;HW design:&lt;/b&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;SATA connector on motherboard&quot; &amp;lt;-&gt; &quot;SATA cable&quot; &amp;lt;-&gt; &quot;SATA/IDE HW converter&quot; &amp;lt;-&gt; &quot;ATMEGA168&quot;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&quot;SATA connector on motherboard&quot; &amp;lt;-&gt; &quot;SATA cable&quot; - Device would be connected to SATA port on PC motherboard with typical SATA cable&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&quot;SATA/IDE HW converter&quot; - on my PCB I will use one of SATA/IDE controllers, so far I've found:&#xA;JMicron - JM20330,&lt;br&gt;&#xA;Atmel - AT78C5010,&lt;br&gt;&#xA;ACARD - ARC-770&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&quot;ATMEGA168&quot; - as programmable unit I'd like to use ATmega168 (or any other cheap 8-bit microcontroller)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;b&gt;Purpose&lt;/b&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With this device I'd like to simulate presence of hard drive in a system. As I want SATA/SCSI stack to be used by OS I need to use SATA ports on motherboard.&#xA;AFAIK connecting to SATA interface without SATA/IDE converter is impossible with ATMega microcontrollers due to big speed of SATA bus interface.&#xA;Nevertheless I've found IDE/ATA implementation for 8-bit uC:&#xA;&lt;a href=&quot;http://www.opend.co.za/hardware/avride/avride.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.opend.co.za/hardware/avride/avride.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;b&gt;Wonders&lt;/b&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My biggest concern is the SATA/IDE converter, I wonder if it can be easly used with micro-controllers as ATMega?&lt;/p&gt;&#xA;" OwnerUserId="598" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-01T19:50:09.837" LastActivityDate="2011-01-01T19:50:09.837" Title="Simulate HDD using ATMega168." Tags="&lt;atmega&gt;&lt;hardware&gt;&lt;simulation&gt;&lt;ide&gt;&lt;sata&gt;" AnswerCount="1" />
  <row Id="1874" PostTypeId="2" ParentId="1870" CreationDate="2010-03-14T21:22:34.763" Score="2" ViewCount="" Body="&lt;p&gt;What you seem to have there is a &quot;thin body&quot; SN76477N. Radio Shack/Tandy had it &quot;custom packaged&quot; in the USA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It being an antique, I doubt you'll find anyone selling an adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could make one...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Buy a piece of copper clad board, a fine tipped etch-resist pen and some etchant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Drill holes spaced correctly for the chip, draw on the tracks with the pen, submerse in etchant until all of the unwanted copper is gone.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-03-23T17:41:06.140" LastActivityDate="2010-03-23T17:41:06.140" CommentCount="1" />
  <row Id="1875" PostTypeId="2" ParentId="1870" CreationDate="2010-03-14T21:23:26.933" Score="2" ViewCount="" Body="&lt;p&gt;That looks like the 0.070 spacing on 600mil centers. Mill-max makes&#xA;a socket for that. See &#xA;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=ED90227-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=ED90227-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After you get the socket I would route a slot in the Vector board with a &#xA;Dremel tool and glue the socket in place. Run short jumper wires from the socket&#xA;pins to pins on the Vector board. (like Vector K24A or T42-1)&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:14:18.057" LastActivityDate="2011-05-19T14:14:18.057" />
  <row Id="1876" PostTypeId="2" ParentId="1870" CreationDate="2010-03-14T21:43:52.093" Score="2" ViewCount="" Body="&lt;p&gt;Thanks that is exactly what it is thanks Jluciani except it's .4 &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://es.digikey.com/1/1/790559-ic-socket-30-pin-400-hi-density-117-43-430-41-005000.html&quot; rel=&quot;nofollow&quot;&gt;http://es.digikey.com/1/1/790559-ic-socket-30-pin-400-hi-density-117-43-430-41-005000.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;for other peoples reference.&lt;/p&gt;&#xA;" OwnerUserId="605" LastActivityDate="2010-03-14T21:43:52.093" CommentCount="1" />
  <row Id="1877" PostTypeId="2" ParentId="1873" CreationDate="2010-03-14T22:38:42.763" Score="4" ViewCount="" Body="&lt;p&gt;Wow, I would've expected the 133MHz ATA/IDE interface would be too fast for an ATmega chip, but it looks like they use it in ATA33 (33MHz) mode, somehow getting it to work with a 4MHz(!) ATmega32.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this case you shouldn't have any problems with a SATA to IDE converter, since they're designed to support older ATA33 devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note however that the OS SCSI stack is only used for SATA devices.  IDE uses a different command set, so you won't see SCSI commands arriving at your ATmega, if that's your intention.  (The host PC will certainly issue SCSI commands though, and the SATA to IDE device will translate.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative that might be easier to achieve is to use a USB interface chip to make your ATmega appear as a USB hard drive.  AFAIK this &lt;em&gt;does&lt;/em&gt; use the SCSI protocol (perhaps a limited subset of it though), so you would see SCSI commands arriving on your device.  Recent PCs can boot off a USB hard drive too, if that's your need for connecting directly to SATA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This solution would be much less sensitive to timing too, as the USB chip would talk over the USB bus at the correct speeds, allowing you to talk to the chip at whatever speed you can manage.&lt;/p&gt;&#xA;" OwnerUserId="548" LastActivityDate="2010-03-14T22:38:42.763" CommentCount="2" />
  <row Id="1878" PostTypeId="2" ParentId="984" CreationDate="2010-03-15T01:09:03.210" Score="1" ViewCount="" Body="&lt;p&gt;Cool Term is pretty good and win/os x cross platform. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://freeware.the-meiers.org/&quot; rel=&quot;nofollow&quot;&gt;http://freeware.the-meiers.org/&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-03-15T01:09:03.210" />
  <row Id="1879" PostTypeId="2" ParentId="1870" CreationDate="2010-03-15T03:57:13.907" Score="1" ViewCount="" Body="&lt;p&gt;This is not a header, but it is a cheap and easy way to get standard spacing: &lt;a href=&quot;http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&amp;amp;ProdID=12925&amp;amp;HS=1&quot; rel=&quot;nofollow&quot;&gt;http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&amp;amp;ProdID=12925&amp;amp;HS=1&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also have the chips themselves:&#xA;&lt;a href=&quot;http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&amp;amp;ProdID=12924&amp;amp;HS=1&quot; rel=&quot;nofollow&quot;&gt;http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&amp;amp;ProdID=12924&amp;amp;HS=1&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2010-03-15T03:57:13.907" />
  <row Id="1880" PostTypeId="2" ParentId="1870" CreationDate="2010-03-15T06:00:12.427" Score="1" ViewCount="" Body="&lt;p&gt;You guys made go dig through the shop to find my old project that used that chip.  Luckily my soldering skills have improved a bit since then.  &lt;a href=&quot;http://www.flickr.com/photos/loco539/4433957405/in/set-72157623623035876/&quot; rel=&quot;nofollow&quot;&gt;Sound Synth Project on Flickr&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That was a fun chip!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sounds like they found a few options for your special package size.  Have fun.&lt;/p&gt;&#xA;" OwnerUserId="272" LastActivityDate="2010-03-15T06:00:12.427" />
  <row Id="1881" PostTypeId="2" ParentId="1781" CreationDate="2010-03-15T08:14:34.073" Score="3" ViewCount="" Body="&lt;p&gt;You might also be interested in: &lt;a href=&quot;http://www.fpga4fun.com/digitalscope.html&quot; rel=&quot;nofollow&quot;&gt;Digital Oscilloscope&lt;/a&gt; at fpga4fun.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers,&#xA;Matt&lt;/p&gt;&#xA;" LastActivityDate="2010-03-15T08:14:34.073" />
  <row Id="1882" PostTypeId="2" ParentId="1869" CreationDate="2010-03-15T12:20:32.483" Score="4" ViewCount="" Body="&lt;p&gt;You can &lt;em&gt;simulate&lt;/em&gt; an inductor with capacitors, but you need additional circuitry to invert its impedance, and there are limitations on what you can simulate with it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Gyrator&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Gyrator&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-16T00:49:10.797" LastActivityDate="2010-03-16T00:49:10.797" />
  <row Id="1883" PostTypeId="2" ParentId="1869" CreationDate="2010-03-15T12:32:33.563" Score="6" ViewCount="" Body="&lt;p&gt;Because with a resistive / capacitive parallel load, the total current is the vector sum of pure resistive current (current in phase with voltage) and pure capacitive current (current 90 degree lead from voltage). If the two components are Ir and Ic then the lead angle is atan2(Ic,Ir) which is 0 for Ic = 0, Ir &gt; 0, and pi/2 = 90 degrees for Ir = 0, Ic &gt; 0. So you are always between 0 and 90 degrees lead for RC parallel loads. It's not like the lead angle is proportional to the capacitance.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-03-15T12:32:33.563" />
  <row Id="1884" PostTypeId="2" ParentId="1842" CreationDate="2010-03-15T12:39:47.537" Score="3" ViewCount="" Body="&lt;p&gt;I use one of these kitchen thermometers for my home-scale maple sugaring equipment:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://ecx.images-amazon.com/images/I/41V4FKV1rhL._AA260_.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.target.com/gp/detail.html/181-2465896-2946763?asin=B0001BFJ54&quot; rel=&quot;nofollow&quot;&gt;http://www.target.com/gp/detail.html/181-2465896-2946763?asin=B0001BFJ54&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The probe is foodsafe and works fine in boiling sap, although after one or two seasons it starts to pick up scale from the calcium impurities in the maple sap. (a tough problem to get around)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure if the probe contains a thermistor or a thermocouple, but in any case it's a cheap off-the shelf solution that I'm sure you could use with your own circuitry if you experimented a bit.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-03-15T12:39:47.537" />
  <row Id="1885" PostTypeId="1" AcceptedAnswerId="1900" CreationDate="2010-03-15T13:56:16.457" Score="7" ViewCount="928" Body="&lt;p&gt;Are there any low-cost (&amp;lt;50$USD) wireless ambient temperature sensors available?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like a simple to interface to the sensor i.e. IP over Wifi if at all possible.&lt;/p&gt;&#xA;" OwnerUserId="329" LastActivityDate="2011-05-13T12:48:38.653" Title="wireless temperature sensor" Tags="&lt;temperature&gt;&lt;sensor&gt;&lt;wireless&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="8" />
  <row Id="1886" PostTypeId="1" AcceptedAnswerId="4056" CreationDate="2010-03-15T16:45:52.723" Score="12" ViewCount="582" Body="&lt;p&gt;CMOS greatly reduces the current draw of ICs because one of the complementary FETs is always in the non-conducting mode, so there is only a flow of current during the transition between states, which is just the amount of charge on the gate's equivalent capacitance and maybe some leakage when both gates are open momentarily.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it theoretically possible to make a logic gate that has zero leakage while changing states (using any realistic technology), and the signal is just passed through the circuit as changes in voltage causing other changes in voltage?  If not, what's the theoretical minimum?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T10:03:13.080" LastActivityDate="2011-01-23T10:03:55.450" Title="In theory, is it possible to make a logic gate that uses zero current?" Tags="&lt;current&gt;&lt;cmos&gt;&lt;energy&gt;&lt;theory&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="1887" PostTypeId="1" AcceptedAnswerId="2100" CreationDate="2010-03-15T17:29:47.520" Score="1" ViewCount="732" Body="&lt;p&gt;There is some information on chiphacker about using an arduino to control stepper motors (I'm driving Bipolar, 4 wire, motors), however I'm finding it hard to know how to control a stepper motor using my &lt;a href=&quot;http://mbed.org&quot; rel=&quot;nofollow&quot;&gt;mbed device&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fact that I'm using an mbed is really by-the-by, I've rigged up an H-Bridge so that I have 4 pinouts of my microcontroller/microprocessor going to the required pins of the H-Bridge (like this: http:/[I'm new here, can't post URLs]/www.tigoe.net/pcomp/img/stepper-bipolar-hbridge.jpg) What pulses should I send to which of the pins when? I can PwmOut if thats more useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any advice would be very welcome, even if its just a URL to a reasonably detailed tutorial. Thanks!&lt;/p&gt;&#xA;" OwnerUserId="617" LastActivityDate="2010-06-12T02:58:55.133" Title="Stepper Motors (on mbed, not arduino)" Tags="&lt;mbed&gt;&lt;stepper&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="1888" PostTypeId="1" AcceptedAnswerId="1892" CreationDate="2010-03-15T17:38:26.157" Score="2" ViewCount="463" Body="&lt;p&gt;&lt;em&gt;For those of you that haven't heard of the &lt;a href=&quot;http://mbed.org&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt; I'd highly recommend having a look at it for rapid prototyping!&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, the mbed is a 100MHz microprocessor that appears as a usb mass storage device when you plug it into a computer via USB. You can program it by using an online IDE which spits out compiled binary files you can drag-drop into the drive (on any OS) making it a very versatile and very easy to use tool for beginners (like myself!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As with all of these programmable ICs they have a limited number of IO pins, so if you wanted to drive 150 LEDs individually you'd need to have some kind of intermediatry control device. I'm considering using ATtiny devices to do just that:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is using ATtiny devices a good way to achieve control over a large number of LEDs? (considering my lack of experience with hardware)&lt;/li&gt;&#xA;&lt;li&gt;Would it be hard to port the code from the arduino ISP so that I could use my mbed as a programmer for programming ATtiny?&lt;/li&gt;&#xA;&lt;li&gt;Am I better off using PIC chips?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Many thanks!&lt;/p&gt;&#xA;" OwnerUserId="617" LastActivityDate="2010-05-07T19:33:02.793" Title="mbed as a programmer" Tags="&lt;mbed&gt;&lt;programmer&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="1889" PostTypeId="2" ParentId="1885" CreationDate="2010-03-15T17:44:11.783" Score="1" ViewCount="" Body="&lt;p&gt;You might want to consider building such a device yourself. If you need the communication to be over TCP/IP networks then the &lt;a href=&quot;http://mbed.org&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt; has in-built ethernet capabilities and could communicate temperature data (and a lot more!), but you would need to buy a wifi adaptor for wireless comms. As davr points out, thats going to be a power drain at the least!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively you could use an arduino and a &lt;a href=&quot;http://www.sparkfun.com/commerce/categories.php?c=111&quot; rel=&quot;nofollow&quot;&gt;zigbee module&lt;/a&gt; to send the data over potentially large distances back to a controller device with the lower power 802.15.4 protocol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Either way I think you're going to have to get your hands dirty and build the thing yourself. The bonus of that approach is that depending on how far to need to communicate wirelessly over, you could keep the cost down.&lt;/p&gt;&#xA;" OwnerUserId="617" LastActivityDate="2010-03-15T17:44:11.783" CommentCount="4" />
  <row Id="1890" PostTypeId="2" ParentId="1885" CreationDate="2010-03-15T18:26:07.847" Score="2" ViewCount="" Body="&lt;p&gt;One solution would be to use a a &lt;a href=&quot;http://shop.jeelabs.com/products/jeenode&quot; rel=&quot;nofollow&quot;&gt;JeeNode&lt;/a&gt; and a &lt;a href=&quot;http://shop.jeelabs.com/products/jeelink&quot; rel=&quot;nofollow&quot;&gt;JeeLink&lt;/a&gt; (plugged into a PC or router). Cheap, open-source and programmable from the Arduino IDE.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-15T18:26:07.847" CommentCount="2" />
  <row Id="1891" PostTypeId="2" ParentId="1888" CreationDate="2010-03-15T18:39:23.060" Score="3" ViewCount="" Body="&lt;p&gt;Why not use something like these?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PCF8574 I2C IO Expander&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is an I2C 8 bit IO expander, which you can add up to 8 of to a single I2C bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://mbed.org/projects/cookbook/browser/PCF8574/doc/PCF8574Interface.png?format=raw&quot; alt=&quot;image&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://mbed.org/projects/cookbook/wiki/PCF8574&quot; rel=&quot;nofollow&quot;&gt;http://mbed.org/projects/cookbook/wiki/PCF8574&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a 16-bit version, too.  Then you can control one LED with each output pin, and put several on each I2C bus?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depends on what you need to do with the LEDs, though.  If you can get away with persistence of vision effects, you can multiplex a small number of LEDs and cycle through them, for instance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.best-microcontroller-projects.com/led-dot-matrix-display.html&quot; rel=&quot;nofollow&quot;&gt;http://www.best-microcontroller-projects.com/led-dot-matrix-display.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Charlieplexing&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Charlieplexing&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-07T19:33:02.793" LastActivityDate="2010-05-07T19:33:02.793" CommentCount="2" />
  <row Id="1892" PostTypeId="2" ParentId="1888" CreationDate="2010-03-15T18:56:18.553" Score="3" ViewCount="" Body="&lt;p&gt;I'd would rather use a shift register for this purpose (such as &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=733&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;they are cheaper than a microcontroller&lt;/li&gt;&#xA;&lt;li&gt;they are handier to drive a large number of led&lt;/li&gt;&#xA;&lt;li&gt;code will be located only on the Mbed. Think that you'll have to update code on both the Mbed and the ATtiny at some point: juggling with different microcontrollers, tools and languages may become a real hassle.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="595" LastActivityDate="2010-03-15T18:56:18.553" CommentCount="1" />
  <row Id="1893" PostTypeId="1" AcceptedAnswerId="1897" CreationDate="2010-03-15T18:57:27.653" Score="9" ViewCount="1293" Body="&lt;p&gt;I've been milling over the different options for sourcing professionally manufactured PCBs. I've just started a business and I'm looking to make a few electronic kits, for now were looking at around 100 units at a time - until we secure more finance. Currently we are making simple 1 sided through hole but the next few boards will be SMD double sided, two things are a must tho - a variety of different colour solder masks and custom images in the copper etch not just the silk screen. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing I was struggling with, in choosing a supplier, is the fact that I'd have to order it from the far east or china to get it at a good price, i'm in the UK and manufacturers are not so cheap for a small run, plus a lot of them out source to china and the far east anyway. I don't have a problem with who manufactures it - as long at the quality is good and the company is not a total moral write-off (with regard to workers' rights). My main issue has been the fact that the PCBs will cost a lot in fuel, air miles or shipping from so far (not to mention clogging all the roads with dangerous lorries).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've started to come to the realization that commercial globalization might have crushed all hope of making the sensible option viable, or am I wrong? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any thoughts on where to get my supplies for electronics and PCBs in particular would be greatly appreciated. Bear in mind I'm located in England, the UK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If my fears are true &amp;amp; it's my only option - can anyone recommend a foreign manufacturer that will do a good deal? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks Chiphackers.      &lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2011-03-28T19:12:40.317" LastActivityDate="2011-03-28T19:12:40.317" CommunityOwnedDate="2010-03-15T18:57:27.653" ClosedDate="2011-03-28T16:39:46.843" Title="Cheap PCB manufacture (100 units at a time)" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;&lt;manufacturing&gt;" AnswerCount="9" CommentCount="3" FavoriteCount="7" />
  <row Id="1894" PostTypeId="2" ParentId="1888" CreationDate="2010-03-15T19:01:25.587" Score="2" ViewCount="" Body="&lt;p&gt;To do this you'd be better to investigate shift registers which would let you control many leds from a couple of pins this is the first example I came accross&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/LED-matrix-using-shift-registers/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/LED-matrix-using-shift-registers/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="558" LastActivityDate="2010-03-15T19:01:25.587" />
  <row Id="1895" PostTypeId="2" ParentId="1893" CreationDate="2010-03-15T19:40:20.873" Score="8" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;I've started to come to the realization that commercial globalization might have crushed all hope of making the sensible option viable, or am I wrong?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I disagree that making your own board is the sensible option. Unless you make all your&#xA;chemistry you still need to transport chemicals and raw materials in as well as waste out. Transportation of the finished goods is probably a lot less transportation. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing to look at is the percentage of cost that the PCB is in your bill of materials. If it is a small percentage I would go with a local supplier that may have better process controls. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately I don't have any non-U.S. suppliers to recommend. I have been using Advanced Circuits and PCB Express (both in the U.S.). I switch between the two based solely on price&#xA;and delivery. Small and Large boards to PCB Express. Medium boards to Advanced Circuits.&#xA;Quick turns usually go to PCB Express. Excellent quality, service and delivery.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-28T16:40:13.063" LastActivityDate="2011-03-28T16:40:13.063" CommunityOwnedDate="2010-03-15T19:40:20.873" CommentCount="1" />
  <row Id="1896" PostTypeId="2" ParentId="1888" CreationDate="2010-03-15T19:41:06.270" Score="2" ViewCount="" Body="&lt;p&gt;See these three previous questions about controlling a large number of LEDs from a single microcontroller:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/605/is-there-a-single-ic-that-can-control-a-8x8-rgb-led-matrix&quot; rel=&quot;nofollow&quot;&gt;Is there a single IC that can control a 8x8 RGB LED Matrix?&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/321/how-to-hook-up-a-5x7-led-matrix-to-arduino&quot; rel=&quot;nofollow&quot;&gt;How to hook up a 5x7 LED matrix to arduino?&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/1332/best-way-to-control-75-leds-with-arduino&quot; rel=&quot;nofollow&quot;&gt;Best way to control 75 LEDs with Arduino&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Yes they mention arduino in the questions, but the answers apply to whatever microcontroller you are using.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-03-15T19:41:06.270" />
  <row Id="1897" PostTypeId="2" ParentId="1893" CreationDate="2010-03-15T19:43:54.550" Score="3" ViewCount="" Body="&lt;p&gt;PCB Cart in China has a good reputation for production boards. I haven't used them myself as I mainly require prototype boards.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-15T19:43:54.550" CommunityOwnedDate="2010-03-15T19:43:54.550" CommentCount="2" />
  <row Id="1898" PostTypeId="2" ParentId="1888" CreationDate="2010-03-15T19:48:57.330" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;https://www.xmos.com/products/development-kits/led-reference-design-kit&quot; rel=&quot;nofollow&quot;&gt;XMOS chips&lt;/a&gt; are used for driving large LED arrays. They are used in conjunction with Macroblock shift registers.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-15T19:48:57.330" />
  <row Id="1899" PostTypeId="2" ParentId="1887" CreationDate="2010-03-15T19:54:00.207" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2125&amp;amp;param=en026178&quot; rel=&quot;nofollow&quot;&gt;Microchip &lt;/a&gt; has a lot of information on motor control, including steppers:&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-15T19:54:00.207" />
  <row Id="1900" PostTypeId="2" ParentId="1885" CreationDate="2010-03-15T20:16:44.503" Score="7" ViewCount="" Body="&lt;p&gt;Not wifi but a standalone XBee + temperature sensor will do this for around $30-$40 or so. &#xA;The XBee has a uC + A/D converter and could read an analog sensor. At a 0.1% duty cycle (transmitting for 1 second every 1000 seconds) you can get around two years on two&#xA;AA's with a fairly simple design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a short ZigBee writeup at&#xA;&lt;a href=&quot;http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:48:38.653" LastActivityDate="2011-05-13T12:48:38.653" CommentCount="4" />
  <row Id="1901" PostTypeId="2" ParentId="1885" CreationDate="2010-03-15T20:48:36.963" Score="2" ViewCount="" Body="&lt;p&gt;Another vote for a JeeNode radio and receiver. I suggest you review this weather station wireless implementation:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://jaagpad.blogspot.com/2010/01/weather-station.html&quot; rel=&quot;nofollow&quot;&gt;JeeNode Weather Station&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="591" LastActivityDate="2010-03-15T20:48:36.963" />
  <row Id="1902" PostTypeId="2" ParentId="1886" CreationDate="2010-03-15T21:00:52.710" Score="5" ViewCount="" Body="&lt;p&gt;No, it is not possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The gate capacitance is a function of the transistor geometry and the properties of the transistor materials. There will always be capacitance. In an effort to minimise capacitance there will always be trade off between transistor speed, voltage breakdown, gain and other device properties.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not only that, but in order to use the output of the gate, the transistor must drive any output capacitance. Again, the output capacitance is a function of the wire geometry and the properties of the surrounding materials.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also other leakage effects. Across the drain and source of any transistor in the off state and even some leakage current into the gate. While these effects are for the most part negligible in actual silicon parts, you would come up against them sooner or later in your quest for a zero-current gate.&lt;/p&gt;&#xA;" OwnerUserId="328" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-05T22:46:04.483" LastActivityDate="2010-05-05T22:46:04.483" CommentCount="7" />
  <row Id="1903" PostTypeId="2" ParentId="1893" CreationDate="2010-03-15T21:33:26.363" Score="2" ViewCount="" Body="&lt;p&gt;If you do decide to make your own PCBs, I'd recommend &lt;a href=&quot;https://www.megauk.com/&quot; rel=&quot;nofollow&quot;&gt;MegaUK&lt;/a&gt;. They sell both professional and high end hobby kit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For UK manufacturing, try &lt;a href=&quot;http://www.angliacircuits.com/&quot; rel=&quot;nofollow&quot;&gt;Anglia Circuits&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-15T21:33:26.363" CommunityOwnedDate="2010-03-15T21:33:26.363" CommentCount="1" />
  <row Id="1904" PostTypeId="1" AcceptedAnswerId="1905" CreationDate="2010-03-15T22:13:03.210" Score="26" ViewCount="1135" Body="&lt;p&gt;I do a fair bit of soldering (lead-free). Is breathing in solder/flux/paste fumes actually going to harm me?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are cheap fume extractors worth buying?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-03-15T22:21:21.907" LastActivityDate="2011-05-02T21:03:42.363" Title="Are solder fumes bad for me?" Tags="&lt;soldering&gt;&lt;pcb&gt;" AnswerCount="8" CommentCount="3" FavoriteCount="6" />
  <row Id="1905" PostTypeId="2" ParentId="1904" CreationDate="2010-03-15T23:31:18.680" Score="18" ViewCount="" Body="&lt;p&gt;They aren't very good for you. Some people can become sensitized to flux fumes, especially from the older rosin flux used in cored solder, and get breathing problems:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.hse.gov.uk/pubns/indg249.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.hse.gov.uk/pubns/indg249.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The no-clean flux isn't as bad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I once felt quite ill after assembling about 30 boards that I had to do myself as my distributor wanted them very quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Breathing out whilst you are soldering each joint helps a lot, if you don't have fume extraction.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-15T23:31:18.680" />
  <row Id="1906" PostTypeId="2" ParentId="1886" CreationDate="2010-03-15T23:47:00.443" Score="3" ViewCount="" Body="&lt;p&gt;au contraire:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your posed headline question can be solved with out using current, or any type of circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=SudixyugiX4&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=SudixyugiX4&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="605" LastActivityDate="2010-03-15T23:47:00.443" CommentCount="1" />
  <row Id="1907" PostTypeId="2" ParentId="1904" CreationDate="2010-03-15T23:49:13.783" Score="6" ViewCount="" Body="&lt;p&gt;You could always try building one. I've been meaning to one of these days, but I haven't done a whole lot of soldering recently. Googling turns up a bunch of people that have done this before in different ways. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://outroot.com/blog/2009/12/01/high-performance-diy-fume-extractor/&quot; rel=&quot;nofollow&quot;&gt;http://outroot.com/blog/2009/12/01/high-performance-diy-fume-extractor/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.lumenlab.com/forums/index.php?showtopic=11941&quot; rel=&quot;nofollow&quot;&gt;http://www.lumenlab.com/forums/index.php?showtopic=11941&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://web.archive.org/web/20051123062351/&quot; rel=&quot;nofollow&quot;&gt;http://web.archive.org/web/20051123062351/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.waldemeyer.com/soldrx.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.waldemeyer.com/soldrx.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.raphnet.net/divers/fume_extractor/index_en.php&quot; rel=&quot;nofollow&quot;&gt;http://www.raphnet.net/divers/fume_extractor/index_en.php&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-03-15T23:49:13.783" />
  <row Id="1908" PostTypeId="2" ParentId="1904" CreationDate="2010-03-16T00:25:13.360" Score="11" ViewCount="" Body="&lt;p&gt;Breathing the fumes is not good for you. With the additional flux required to get&#xA;good SMD solder joints there are more fumes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just bought a Weller WSA350 smoke absorber. It was $50 new. A three pack&#xA;of filters is pn WSA350F. This works OK. A unit with a stronger fan would&#xA;be better. After a few hours of soldering there is a fair amount of white&#xA;powder on the carbon filter. The fan looks like a standard 5&quot; boxed fan so&#xA;I may try getting a more powerful one. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the weather is good I have cross ventilation so I put an exhaust &#xA;fan in the window near my bench.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-04T03:47:25.827" LastActivityDate="2010-11-04T03:47:25.827" />
  <row Id="1909" PostTypeId="2" ParentId="1904" CreationDate="2010-03-16T01:04:02.377" Score="9" ViewCount="" Body="&lt;p&gt;At the very least, put a fan near your work area to blow the fumes away from your face.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-03-16T01:04:02.377" />
  <row Id="1910" PostTypeId="2" ParentId="1886" CreationDate="2010-03-16T01:17:24.910" Score="6" ViewCount="" Body="&lt;p&gt;Yes. You can make a gate that switches with zero current if you don't&#xA;mind waiting an infinite amount of time ;) Since current is change&#xA;in charge over change in time, as the change in time goes to infinity the&#xA;current goes to zero. Run your logic as slow as you can while meeting&#xA;your other system specifications. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your homework assignment for tonight is to read the &quot;Thermodynamics of&#xA;Computing&quot; chapter from &quot;Feynman's Lectures on Computation&quot; ;)&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T10:03:55.450" LastActivityDate="2011-01-23T10:03:55.450" CommentCount="3" />
  <row Id="1911" PostTypeId="1" AcceptedAnswerId="1914" CreationDate="2010-03-16T01:51:31.173" Score="4" ViewCount="987" Body="&lt;p&gt;I'm a bit confused between the microprogramming level vs machine language level.  For example:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Where do both types of programs reside while being executed?&lt;/li&gt;&#xA;&lt;li&gt;Do either have a 1:1 mapping to assembly language true-op instructions?&lt;/li&gt;&#xA;&lt;li&gt;Is the format of either defined by the processor architecture?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" LastActivityDate="2011-03-21T17:08:25.097" Title="Microprogramming vs. Machine Language programming" Tags="&lt;assembly&gt;&lt;microprocessor&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="1912" PostTypeId="2" ParentId="1911" CreationDate="2010-03-16T15:15:30.203" Score="2" ViewCount="" Body="&lt;p&gt;Basically, microcode expands a limited CPU instruction set to contain higher level instructions that would be cumbersome to implement in hardware, but relatively easy to build with existing instructions.  Microcode allows a processor with a small instruction set to function like one with a larger instruction set.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lets say you're working with a &lt;a href=&quot;http://cs.hbg.psu.edu/mspapers/sources/julia-lobur.pdf&quot; rel=&quot;nofollow&quot;&gt;MARIE instruction set&lt;/a&gt; and you would like an Add x,y function, but the architecture only allows a Add x (which just adds what's currently in the register to x)  so you add a microcode instruction:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;LOAD x //Load x into the register&#xA;ADD y //Add y to the value in the register&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Now when your machine language code says:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ADD x,y&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;it looks up the ADD function you added to ROM (your microcode) and executes it.  This is great because it increases your instruction set, which allows more readable machine code, and since your microcode is stored in ROM, it's also a little faster than calling the LOAD and ADD from RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used to work at a company that actually wrote microcode to perform custom measurements at very high speeds on their older systems.  However, with the advances in FPGAs they have switched over to those, which are much faster (since you actually are implementing the &quot;custom instructions&quot; in hardware instead of ROM).&lt;/p&gt;&#xA;" OwnerUserId="602" LastEditorUserId="602" LastEditorDisplayName="" LastEditDate="2011-03-21T17:08:25.097" LastActivityDate="2011-03-21T17:08:25.097" />
  <row Id="1913" PostTypeId="2" ParentId="1885" CreationDate="2010-03-16T18:52:11.123" Score="1" ViewCount="" Body="&lt;p&gt;Why not use a standard remote sensor for a consumer-grade weather station? Most of the ones you find in stores are made by &lt;a href=&quot;http://www2.oregonscientific.com/cat-Weather-sub-Classic-Weather-Stations-prod-Wireless-Temperature-and-Humidity-Sensor-with-Display.html&quot; rel=&quot;nofollow&quot;&gt;Oregon Scientific&lt;/a&gt;. I'm not sure of the wireless band and the protocol, but it ought to be fairly simple and probably documented somewhere out there on the internet.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-03-16T18:52:11.123" CommentCount="1" />
  <row Id="1914" PostTypeId="2" ParentId="1911" CreationDate="2010-03-16T19:17:32.047" Score="2" ViewCount="" Body="&lt;p&gt;Micro-code is another level of abstraction beyond machine code.  The actual CPU is running microcode, and a translation engine converts machine code into microcode on the fly.  This is done for a variety of reasons, including faster, smaller processors, easier to create a complex processor with less debugging, and for backwards compatibility.  For instance, the x86 instruction set contains some string processing instructions that are rarely used.  However, to remain backwards compatible, they must still be available in modern x86 processors.  Rather than hardwiring an execution path for these instructions, they are converted into microcode and executed.  This saves silicon, while still remaining backwards compatible.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Where do both types of programs reside while being executed?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The machine code resides in the cache (after being pulled from RAM).  The micro code resides in a micro code cache, depending on the particular machine architecture.  The cache may only be large enough to hold enough microcode to hold the converted microcode from the largest possible machine code instruction, or it may be a larger cache that stores the converted results of many machine codes so that it doesn't need to reconvert all the machine code on each iteration for small loops.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In some architectures the converted microcode isn't stored anywhere - the fetch/translate unit simply spits out a series of microcode instructions based on the currently executing machine code.  In this case the microcode is executing from a ROM of some sort, and the machine code is essentially an index into the ROM - pointing to the series of microcode instructions that must be run in order to fully execute the machine code instruction.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Do either have a 1:1 mapping to assembly language true-op instructions?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Machine code and assembly code, &lt;em&gt;in general&lt;/em&gt; are 1:1 mapped to assembly instructions.  It depends on the assembler.  High level assemblers may have a large set of macros that allow one to write one line of assembly code and the assembler will produce several machine codes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But in general &quot;pure&quot; assembly language can be converted directly into machine code using the instruction set table in the processor's manual.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure what you mean by &quot;true-op instructions&quot; though.  Perhaps you can explain the reference.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Is the format of either defined by the processor architecture?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The format of both machine code and microcode are defined by the processor architecture.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-16T19:17:32.047" CommentCount="2" />
  <row Id="1915" PostTypeId="2" ParentId="1893" CreationDate="2010-03-16T19:40:18.897" Score="1" ViewCount="" Body="&lt;p&gt;I like &lt;a href=&quot;http://apcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;APCircuits.com&lt;/a&gt; for prototype and light production stuff.  They're based in Alberta, Canada.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-03-16T19:40:18.897" CommunityOwnedDate="2010-03-16T19:40:18.897" CommentCount="1" />
  <row Id="1916" PostTypeId="1" CreationDate="2010-03-16T22:03:18.187" Score="5" ViewCount="115" Body="&lt;p&gt;I am new to the whole Arduino thing and am having problems loading 'Processing'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I attempt to run the Processing program it says 'This Program requires Java Development Kit 1.5.0'.  When I go the the Sun site to load this, I can't find SDK 1.5.0.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know the exact name of the app I have to load in order to successfully run Processing?  A web link to the correct app would be greatly appreciated.&lt;/p&gt;&#xA;" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-11T01:31:21.030" LastActivityDate="2011-01-11T01:31:21.030" Title="Problems installing 'Processing'" Tags="&lt;arduino&gt;&lt;processing&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="1917" PostTypeId="2" ParentId="1916" CreationDate="2010-03-16T22:22:48.103" Score="5" ViewCount="" Body="&lt;p&gt;You need the sun JDK 1.5 or above (current is 1.6) there &lt;a href=&quot;http://java.sun.com/javase/downloads/index.jsp&quot; rel=&quot;nofollow&quot;&gt;http://java.sun.com/javase/downloads/index.jsp&lt;/a&gt; you may need the JRE too, I can't remember if it's included with the JDK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're on linux then it's easier to use your distributions own packaging system to install.&lt;/p&gt;&#xA;" OwnerUserId="558" LastActivityDate="2010-03-16T22:22:48.103" />
  <row Id="1918" PostTypeId="2" ParentId="1916" CreationDate="2010-03-16T22:29:25.373" Score="2" ViewCount="" Body="&lt;p&gt;You want &quot;Java for your Desktop&quot;, as they call it on the Java.com homepage.  The easiest way to get that is to go to Java.com's &quot;Free Java Download&quot; page: &lt;a href=&quot;http://java.com/en/download/&quot; rel=&quot;nofollow&quot;&gt;http://java.com/en/download/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just accept all the defaults (but probably uncheck installing the Yahoo toolbar), and in a few minutes you'll have Java on your system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(btw, you don't need Processing to use Arduino) &lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-03-16T22:29:25.373" />
  <row Id="1919" PostTypeId="2" ParentId="1916" CreationDate="2010-03-16T22:35:23.520" Score="2" ViewCount="" Body="&lt;p&gt;Go to &lt;a href=&quot;http://www.java.com/getjava/&quot; rel=&quot;nofollow&quot;&gt;http://www.java.com/getjava/&lt;/a&gt; and follow the download link.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-16T22:35:23.520" CommentCount="1" />
  <row Id="1920" PostTypeId="1" AcceptedAnswerId="1921" CreationDate="2010-03-17T02:37:20.043" Score="3" ViewCount="604" Body="&lt;ol&gt;&#xA;&lt;li&gt;What is the best way to protect code flashed onto any AVR based device from reverse engineering? &lt;/li&gt;&#xA;&lt;li&gt;What is an easy way to provide updates to end users to flash on their own without disclosing the code? (Is it with a bootloader that decrypts an encrypted image?)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Don't flame me for promoting DRM, I am in favor of open platforms--I am just curious how this would work.&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-03-22T00:15:02.480" Title="Securing code on an AVR/Arduino and delivering updates" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;encryption&gt;&lt;reverse-engineering&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="1921" PostTypeId="2" ParentId="1920" CreationDate="2010-03-17T03:19:54.840" Score="2" ViewCount="" Body="&lt;p&gt;First:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are fuses on the chip that can be set to prevent external tools from reading the code off the chip.  Look for the protection fuses in your datasheet and/or programmer documentation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not perfect, but it protects you from simple attacks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You cannot download firmware securely.  The AVR cannot self-program protected areas:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc1644.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/resources/prod_documents/doc1644.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best you might be able to do is to use an encrypted token language (such as basic, or forth) and have the interpreter protected on the chip with a bootloader that can program the encrypted tokens into an open area.  When running, the chip would decrypt and execute the instructions on the fly.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-17T03:19:54.840" CommentCount="1" />
  <row Id="1922" PostTypeId="2" ParentId="1920" CreationDate="2010-03-17T04:30:42.687" Score="1" ViewCount="" Body="&lt;p&gt;If you wrote your own bootloader which accepted encrypted data over the serial port, decrypted it and stored it into code storage area, you could have secure code firmware update. Each device could even have its own unique decryption key in your custom bootloader.&lt;/p&gt;&#xA;" LastActivityDate="2010-03-17T04:30:42.687" CommentCount="3" />
  <row Id="1923" PostTypeId="2" ParentId="1866" CreationDate="2010-03-17T15:16:20.107" Score="1" ViewCount="" Body="&lt;p&gt;I would recommend reading the datasheet again for that device. It sounds like CTRL0 and CTRL1 can also be used as output enables depending on the devices control registers MUX and BUS. This would explain why when you assert CTRL0/CTRL1 the oscillator output is disabled. Another thing to note is that the datasheet says the register values are store on an internal EEPROM, but only after a write command is executed. It could be possible that you think the registers are set one way, but when you power cycle the board the previous values are being loaded from EEPROM. I've worked a lot with I2C clock chips and every time things weren't working it was because I miss interpreted one of the register values. Write each register out on initialization then read them all back to make sure you initialized them properly. Compare the results to the datasheet to see if they make sense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: It appears that the CTRL pins can also be used to place the device in a power-down mode which would explain why it's not responding to I2C at times.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-03-17T15:22:31.973" LastActivityDate="2010-03-17T15:22:31.973" CommentCount="1" />
  <row Id="1924" PostTypeId="2" ParentId="1722" CreationDate="2010-03-17T16:39:53.273" Score="4" ViewCount="" Body="&lt;p&gt;I use Eclipse as my main IDE for my Arduino projects and write C/C++. I wrote a tutorial on how to &lt;a href=&quot;http://www.chipkin.com/articles/using-eclipse-with-arduino-duemilanove&quot; rel=&quot;nofollow&quot;&gt;set up Eclipse with Arduino&lt;/a&gt; that you might find interesting. &lt;/p&gt;&#xA;" OwnerUserId="592" LastActivityDate="2010-03-17T16:39:53.273" />
  <row Id="1925" PostTypeId="2" ParentId="1847" CreationDate="2010-03-17T18:02:33.513" Score="6" ViewCount="" Body="&lt;p&gt;We use this &lt;a href=&quot;http://www.hmcelectronics.com/cgi-bin/scripts/product/8591-0008/tech-spray-2211-8SQ/&quot; rel=&quot;nofollow&quot;&gt;pink stuff&lt;/a&gt; as a conformal coating.  It is removable, which is great if you messed up and need to redo it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:  We've discovered that when the pink stuff is exposed to temperature changes in a vehicular environment, it can crack and moisture gets through and can cause damage to the board.  &lt;em&gt;You'll want to use something else (probably something that isn't totally hard) if you're project is used outside and/or on a vehicle.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-07-19T13:52:06.020" LastActivityDate="2010-07-19T13:52:06.020" />
  <row Id="1926" PostTypeId="1" CreationDate="2010-03-17T19:35:18.007" Score="6" ViewCount="1385" Body="&lt;p&gt;Hey folks, &#xA;I'm working on a device using arm-elf-gcc to compile code for a MakingThings prototype board.  My development machine is a Linux box running Ubuntu 9.10. On a different linux box using Ubuntu I got arm-elf-gcc running ok by manually building and installing gcc, after 3 or 4 tries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to pick the best way to install the toolchain, but there doesn't seem to be a best way AFAIK. Setting up on 9.08 and 9.10, both seem to fail except for when I manually build and install the environment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried  Emdebian packages and CodeSourery, and neither of those worked well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any other good suggestions for doing an arm-elf-gcc setup on a Linux box?&lt;/p&gt;&#xA;" OwnerUserId="626" LastActivityDate="2010-04-13T11:13:26.847" Title="Best way to install arm-elf-gcc onto a Linux machine" Tags="&lt;linux&gt;&lt;compiler&gt;&lt;arm&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="1927" PostTypeId="2" ParentId="1926" CreationDate="2010-03-17T20:44:04.810" Score="2" ViewCount="" Body="&lt;p&gt;I think the best way is to manually build and install gcc in one try. ;-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though this requires that you do it a couple of times for practice, and my own score was two tries last time (makeinfo was missing when building binutils, again). I use my own scripts, which are similar but separate download and build.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-03-17T20:44:04.810" CommentCount="2" />
  <row Id="1928" PostTypeId="2" ParentId="1926" CreationDate="2010-03-17T21:00:24.213" Score="2" ViewCount="" Body="&lt;p&gt;I'd say CodeSourcery Lite is the easiest way. The Lite version is just the GNU tools (no fancy IDEs, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It installs cleanly into a single directory, you just need to set your PATH to point at it.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-17T21:00:24.213" />
  <row Id="1929" PostTypeId="1" CreationDate="2010-03-17T21:31:19.050" Score="2" ViewCount="395" Body="&lt;p&gt;Hi, I inherited a Weller WTCPL soldering station a while ago:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tinypic.com/r/acllj/5&quot; rel=&quot;nofollow&quot;&gt;Picture of iron&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It was my grandpa's, and although I can't find a direct reference to it anywhere on the net, I'm guessing it's anywhere from 40 to 60 years old. It worked for some time, but sadly, it recently has stopped. When I was soldering the other day, I noticed the wand getting progressively colder, until it eventually wouldn't even melt solder. Now, it turns on (or at least the indicator light does), but the iron does not heat up. Is this fixable or do I need a new iron?&lt;/p&gt;&#xA;" LastActivityDate="2010-03-18T00:15:05.847" Title="Older Weller soldering iron won't heat!" Tags="&lt;soldering&gt;&lt;iron&gt;" AnswerCount="3" />
  <row Id="1930" PostTypeId="2" ParentId="1929" CreationDate="2010-03-17T22:02:01.560" Score="4" ViewCount="" Body="&lt;p&gt;Check the resistance of the element, it's probably failed. You might be able to get a replacement from Weller.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-17T22:02:01.560" CommentCount="1" />
  <row Id="1931" PostTypeId="2" ParentId="1926" CreationDate="2010-03-17T22:03:38.563" Score="2" ViewCount="" Body="&lt;p&gt;Place your toolchain in something like /usr/local/arm-elf-toolchain and put the appropriate prefixes in your makefiles and you should be alright.&#xA;I can really recommend putting the toolchain in a seperate directory so you won't mess up your current toolchain(s).&lt;/p&gt;&#xA;" OwnerUserId="348" LastActivityDate="2010-03-17T22:03:38.563" />
  <row Id="1932" PostTypeId="2" ParentId="1929" CreationDate="2010-03-17T23:37:02.023" Score="0" ViewCount="" Body="&lt;p&gt;Answer found &lt;a href=&quot;http://forum.sparkfun.com/viewtopic.php?f=14&amp;amp;t=20773&amp;amp;start=0&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Some Weller irons as part of the&#xA;  temperature control have a small&#xA;  spring loaded magnetic plate that the&#xA;  tip attracts. I have seen binding in&#xA;  the movement of the plate over time.&#xA;  If your iron is one of these, unscrew&#xA;  the end of the rod and carefully clean&#xA;  the tip and make sure that the&#xA;  mechanism works smoothly. I used to&#xA;  slide the tip in and out to make sure&#xA;  that the tip could attract the&#xA;  magnetic plate.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" LastActivityDate="2010-03-17T23:37:02.023" />
  <row Id="1933" PostTypeId="2" ParentId="1929" CreationDate="2010-03-18T00:15:05.847" Score="7" ViewCount="" Body="&lt;p&gt;The WTCPL uses the same soldering pencil as the WTCPT, which I inherited some time ago, and Weller (now part of Cooper) still makes new replacement parts and tips for these old workhorses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which I think is fantastic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, you'll find the datasheet for your model here, including troubleshooting guide, assembly diagram and parts list:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.action-electronics.com/pdf/wtcpltechsheet.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.action-electronics.com/pdf/wtcpltechsheet.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my case the magnetic switch was still working (there's instructions on how to test each part) but the heater barrel was open.  I replaced the barrel and the nut (the newer barrels are slightly larger in diameter, so you might as well get a barrel nut at the same time) and the iron works perfectly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get these parts from Digikey:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&amp;amp;lang=en&amp;amp;site=us&amp;amp;keywords=EC234-ND&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;EC234-ND - HEATER ASSY FOR A TC201T IRON&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1310804&amp;amp;k=BA60-ND&quot; rel=&quot;nofollow&quot;&gt;BA60-ND - ASSY BARREL NUT FOR PES51&amp;amp;50&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1310804&amp;amp;k=sw60&quot; rel=&quot;nofollow&quot;&gt;SW60-ND - SWITCH ASSM FOR SOLD PENCIL&lt;/a&gt; (magnetic heater switch)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some are listed as 0 quantity, but they order them and I got mine in about 2 weeks.  Other replacement parts are available, but if you have to replace too much (or the more expensive parts) on the iron you might as well buy a new iron.  When mine broke, I fixed it and purchased a &lt;a href=&quot;http://microcenter.com/single_product_results.phtml?product_id=0246904&quot; rel=&quot;nofollow&quot;&gt;new weller&lt;/a&gt; that was adjustable for $100.  Now my old one is the backup, and I don't mind bringing it to electronics group meetings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, this is a worthwhile iron to fix if the cost is not too great.  The new fancier models have more features, but you really can't beat how durable and usable these old wellers are.  While you're at it, you might as well get another &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1311719&amp;amp;k=TC201T&quot; rel=&quot;nofollow&quot;&gt;tip or two&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;sup&gt;Not affiliated with digikey, but they are a reasonable online supplier if you are in North America&lt;/sup&gt;&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-18T00:15:05.847" />
  <row Id="1934" PostTypeId="2" ParentId="1926" CreationDate="2010-03-18T15:21:20.863" Score="2" ViewCount="" Body="&lt;p&gt;Here's a pretty good &lt;a href=&quot;http://www.ibm.com/developerworks/edu/l-dw-linux-embedded-distro-i.html&quot; rel=&quot;nofollow&quot;&gt;article&lt;/a&gt; that partly covers building your own cross compiler toolchain using &lt;a href=&quot;http://ymorin.is-a-geek.org/projects/crosstool&quot; rel=&quot;nofollow&quot; title=&quot;crosstool-ng&quot;&gt;crosstool-ng&lt;/a&gt;.  You may find it helpful as I did.&lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2010-03-18T15:21:20.863" />
  <row Id="1935" PostTypeId="1" AcceptedAnswerId="1937" CreationDate="2010-03-18T22:08:57.397" Score="2" ViewCount="586" Body="&lt;p&gt;I have a hall effect sensor which outputs 0V when on the North pole of a magnet, 5V when on the South pole. It idles at 2.5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to connect 2 LEDs to show the reading, one activated from 0-2.5V, the other from 2.5V to 5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could use the ADC on a microcontroller to read the sensor then drive the LEDs with two PWM channels. But, this seems like overkill to me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone suggest a better way? Without using a microcontroller?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T16:02:21.237" LastActivityDate="2010-10-22T16:02:21.237" Title="How to convert a voltage range to LED brightness without a microcontroller?" Tags="&lt;led&gt;&lt;sensor&gt;&lt;adc&gt;&lt;hall-effect&gt;" AnswerCount="3" />
  <row Id="1936" PostTypeId="2" ParentId="1935" CreationDate="2010-03-18T22:38:56.570" Score="2" ViewCount="" Body="&lt;p&gt;Maybe one of those tiny 6 or 8 pin SMD microcontrollers that are like a quarter inch square. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That wouldn't really be overkill, it might be $1, but to do it from standalone components you'd probably need quite a few different pieces. The main issue is that the way to vary LED brightness is via PWM, so you'd need some kind of oscillator that you could vary the frequency based on input voltage. Then use the output of the oscillator to drive the base of a transistor which is driving the LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example this uber tiny microcontroller:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/dyn/products/product_card_mcu.asp?PN=ATtiny5&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;ATtiny5&lt;/strong&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;512 Bytes of In-System Programmable Flash&lt;/li&gt;&#xA;&lt;li&gt;32 Bytes Internal SRAM. &lt;/li&gt;&#xA;&lt;li&gt;One 16-bit Timer/Counter with PWM channels &lt;/li&gt;&#xA;&lt;li&gt;8-bit ADC&lt;/li&gt;&#xA;&lt;li&gt;Analog Comparator. &lt;/li&gt;&#xA;&lt;li&gt;Up to 12 MIPS throughput at 12 MHz. &lt;/li&gt;&#xA;&lt;li&gt;1.8 - 5.5 V operation.&lt;/li&gt;&#xA;&lt;li&gt;Max I/O Pins:  4 &lt;/li&gt;&#xA;&lt;li&gt;Package: &lt;a href=&quot;http://www.atmel.com/dyn/products/packagecard.asp?family_id=607&amp;amp;part_id=4606&amp;amp;package_id=1041&amp;amp;green=1&quot; rel=&quot;nofollow&quot;&gt;SOT23 6&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Dimensions: 1.6mm x 2.9mm, thickness: 1.1mm&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="131" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-03-18T22:44:06.813" LastActivityDate="2010-03-18T22:44:06.813" CommentCount="4" />
  <row Id="1937" PostTypeId="2" ParentId="1935" CreationDate="2010-03-18T22:47:13.910" Score="1" ViewCount="" Body="&lt;p&gt;Simplest but probably worst method: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connect the LEDs back-to-back, connect one leg to your signal voltage, and connect the other leg through a few kΩ resistor to a fixed 2.5 V source.  Then one LED will be on from 0 V to 0.5 V, off from 0.5 V to 4.5 V, and the other LED on from 4.5 V to 5 V.  Actual voltages would be &lt;a href=&quot;http://www.oksolar.com/led/led_color_chart.htm&quot; rel=&quot;nofollow&quot;&gt;determined by the color of the LED&lt;/a&gt;, and I think the brightness would only vary a little.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could probably get exactly what you want with some kind of combination of the ideas of &lt;a href=&quot;http://en.wikipedia.org/wiki/Precision_rectifier&quot; rel=&quot;nofollow&quot;&gt;precision rectifier&lt;/a&gt; (using feedback for turn-on with no dead zone) and &lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage-to-current_converter&quot; rel=&quot;nofollow&quot;&gt;voltage-to-current converter&lt;/a&gt; (brightness proportional to voltage), but I'm having trouble thinking up a circuit.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-19T01:30:12.330" LastActivityDate="2010-03-19T01:30:12.330" />
  <row Id="1938" PostTypeId="2" ParentId="1935" CreationDate="2010-03-19T00:01:37.937" Score="4" ViewCount="" Body="&lt;p&gt;If you want to do this with just a single LED you could just use a simple comparitor to generate a PWM signal to power the LED. Connect the positive lead of the comparitor to the output of your hall effect sensor and the other lead to a RC triangle wave generator. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a good example of this type of circuit see &lt;a href=&quot;http://www.solarbotics.net/library/circuits/bot_ornament_qlf.html&quot; rel=&quot;nofollow&quot;&gt;http://www.solarbotics.net/library/circuits/bot_ornament_qlf.html&lt;/a&gt;. Just replace the connection to the lower frequency oscillator to your hall effect IC and you will have a PWM LED fader with 0 digital electronics!&lt;/p&gt;&#xA;" OwnerUserId="631" LastActivityDate="2010-03-19T00:01:37.937" CommentCount="1" />
  <row Id="1939" PostTypeId="2" ParentId="801" CreationDate="2010-03-19T00:57:36.107" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;... can be used as power supply to your target board with three jumper&#xA;  selectable power supplies: 5V 9V and&#xA;  12VDC, USB source current is limited&#xA;  with resetable fuse at 300mA, at the&#xA;  different output voltage the maximum&#xA;  current is different: 5V/200mA,&#xA;  9V/100mA, 12V/70mA, note that this&#xA;  also depend on your USB host current&#xA;  capabilities, if other USB devices are&#xA;  attached to your computer or if the&#xA;  laptop is running on batteries these&#xA;  figures may be different and depend on&#xA;  your computer USB host.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;(from &lt;a href=&quot;http://www.olimex.com/dev/arm-usb-ocd.html&quot; rel=&quot;nofollow&quot;&gt;http://www.olimex.com/dev/arm-usb-ocd.html&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-19T00:57:36.107" />
  <row Id="1940" PostTypeId="1" AcceptedAnswerId="1941" CreationDate="2010-03-19T02:57:48.203" Score="1" ViewCount="164" Body="&lt;p&gt;I'm after a wireless PIR sensor for outdoor security use.  The PIR sensor should communicate via RF to a receiver which has a TTL output.  I'd like to eventually connect this output to a micro or directly to a PC (parallel port).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, hopefully I'll be able to connect up multiple of these PIRs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there anything like this out there?  Just a PIR sensor with casing, wireless.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="561" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-05-12T22:23:57.163" LastActivityDate="2011-05-12T22:44:20.077" ClosedDate="2011-05-13T04:06:34.937" Title="Where can I find good wireless (RF) PIRs sensors?" Tags="&lt;microcontroller&gt;" AnswerCount="3" />
  <row Id="1941" PostTypeId="2" ParentId="1940" CreationDate="2010-03-19T03:31:55.267" Score="1" ViewCount="" Body="&lt;p&gt;Hi There, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Combine a &lt;a href=&quot;http://www.littlebirdelectronics.com/search.php?search_query=PIR&amp;amp;x=43&amp;amp;y=9&quot; rel=&quot;nofollow&quot;&gt;PIR&lt;/a&gt; with a wireless &lt;a href=&quot;http://www.littlebirdelectronics.com/search.php?search_query=Arduino&amp;amp;x=37&amp;amp;y=10&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; &amp;amp; &lt;a href=&quot;http://www.littlebirdelectronics.com/search.php?search_query=lithium&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;Lithium Ion Battery&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Parts List: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;PIRs&lt;/strong&gt;&lt;br /&gt;&#xA;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/PIR-Motion-Sensor.html&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/PIR-Motion-Sensor.html&lt;/a&gt;&#xA;http://www.littlebirdelectronics.com/products/ePIR.html&#xA;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Passive-Infrared-Detector-SE%252d10.html&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/Passive-Infrared-Detector-SE%252d10.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Wireless Arduinos&lt;/strong&gt;&lt;br /&gt;&#xA;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Arduino-Bluetooth.html&quot; rel=&quot;nofollow&quot;&gt;Arduino Bluetooth&lt;/a&gt;&lt;br /&gt;&#xA;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/YellowJacket-1.0-.html&quot; rel=&quot;nofollow&quot;&gt;Yellow Jacket (Arduino Wifi)&lt;/a&gt;&lt;br /&gt;&#xA;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/BlackWidow-1.0-.html&quot; rel=&quot;nofollow&quot;&gt;Black Widow (Arduino Wifi, Duemilanove compatible)&lt;/a&gt;&lt;br /&gt;&lt;br /&gt;&#xA;&lt;strong&gt;Lithium Ion Batteries&lt;/strong&gt;&lt;br /&gt;&#xA;&lt;a href=&quot;http://www.littlebirdelectronics.com/search.php?search_query=lithium&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;Assorted Lithium Ion Batteries&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-12T20:03:32.650" LastActivityDate="2011-05-12T20:03:32.650" />
  <row Id="1942" PostTypeId="1" AcceptedAnswerId="1945" CreationDate="2010-03-19T04:11:00.617" Score="7" ViewCount="1168" Body="&lt;p&gt;How does one go about building an interface for a USB device that allows interfacing pots, linear/log tapers, and momentary/toggle switches to a computer?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If someone could give me a high-level description, I would appreciate it.  I can read spec sheets, so understanding details is not a problem as long as I know where to find the sheets.&lt;/p&gt;&#xA;" OwnerUserId="544" LastActivityDate="2010-09-21T04:43:41.280" Title="How to build a USB controller having knobs, sliders, and switches" Tags="&lt;usb&gt;&lt;interface&gt;" AnswerCount="7" FavoriteCount="2" />
  <row Id="1943" PostTypeId="2" ParentId="1942" CreationDate="2010-03-19T04:51:57.740" Score="4" ViewCount="" Body="&lt;p&gt;I would use a microcontroller board like an Arduino. You read the ADC and digital I/O&#xA;and send ASCII characters to the PC using the UART-&gt;USB connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How much external hardware you need depends on the accuracy you require. I would think&#xA;for most applications the hardware internal to the microcontroller would be sufficient.&#xA;I would debounce the switches in hardware. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the USB interface just write a simply parser so that you can query the readings.&#xA;For example if the PC sent the string &quot;A00?&quot; the uC could send back the reading&#xA;on analog channel 0. &quot;D00?&quot; the uC could send back the state of digital input 0.&#xA;To change a digital output maybe something like &quot;D00=1&quot; or &quot;D00=0&quot;.&#xA;These are short strings in a fixed length. Should be very easy to parse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(* jcl *)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.wiblocks.com&quot; rel=&quot;nofollow&quot;&gt;http://www.wiblocks.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastActivityDate="2010-03-19T04:51:57.740" />
  <row Id="1944" PostTypeId="2" ParentId="1940" CreationDate="2010-03-19T05:05:49.410" Score="0" ViewCount="" Body="&lt;p&gt;You could probably combine a PIR with an XBee. The XBee has a uC and can monitor analog&#xA;and digital lines. Add a Li-ion battery and a 3.3V regulator. If you run the XBee&#xA;at 3V you will consume quite a bit less current.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-12T20:03:00.420" LastActivityDate="2011-05-12T20:03:00.420" />
  <row Id="1945" PostTypeId="2" ParentId="1942" CreationDate="2010-03-19T09:35:41.933" Score="12" ViewCount="" Body="&lt;p&gt;I'd use one of the &lt;a href=&quot;http://www.pjrc.com/teensy/index.html&quot; rel=&quot;nofollow&quot;&gt;Teensy&lt;/a&gt; boards. These are Arduino-like microcontroller boards which have USB support. Unlike the Arduino, they can appear to a PC as any sort of USB device. This means that you can create your own custom USB keyboard, joystick, MIDI device, etc and have the PC use standard drivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Teensy supports the &lt;a href=&quot;http://www.pjrc.com/teensy/teensyduino.html&quot; rel=&quot;nofollow&quot;&gt;Arduino IDE&lt;/a&gt;, or you can program in C and use &lt;a href=&quot;http://www.fourwalledcubicle.com/LUFA.php&quot; rel=&quot;nofollow&quot;&gt;LUFA&lt;/a&gt; (for USB support) directly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some &lt;a href=&quot;http://www.pjrc.com/teensy/projects.html&quot; rel=&quot;nofollow&quot;&gt;project links&lt;/a&gt; to help.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-19T09:35:41.933" CommentCount="1" />
  <row Id="1946" PostTypeId="2" ParentId="1942" CreationDate="2010-03-19T16:16:45.990" Score="3" ViewCount="" Body="&lt;p&gt;I like using Arduinos, they're simple to program and you can easily send data to your computer from the various inputs via the onboard USB connection. The data can be sent to the Arduino programming environments Serial Monitor - which is useful for debugging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I then use a program like Pure Data (PD) or Max MSP to receive the serial data. Data can be sent out from these programs in all kinds of useful formats. Cuz it's simple enough to do any kind of log curves or scaling in the software - you don't have to worry about buying expensive log pots or using hard to find values - just buy a job-lot of the same value and worry about the specifics later (1K or 10K is normally easy to get). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This one's free:&#xA;&lt;a href=&quot;http://puredata.info/&quot; rel=&quot;nofollow&quot;&gt;http://puredata.info/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This one is the payed for swanky version, but it has a good demo:  &lt;a href=&quot;http://cycling74.com/downloads/&quot; rel=&quot;nofollow&quot;&gt;http://cycling74.com/downloads/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-03-19T16:16:45.990" />
  <row Id="1947" PostTypeId="2" ParentId="1942" CreationDate="2010-03-19T17:59:13.217" Score="4" ViewCount="" Body="&lt;p&gt;Get an &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=666&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Get a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9597&quot; rel=&quot;nofollow&quot;&gt;DangerShield&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Write code to send DangerShield sensor data to PC via RS-232 over USB connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Write custom app in like VB.NET or something to translate data into something useful on PC, like Win32 window messages or something.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-03-19T17:59:13.217" />
  <row Id="1948" PostTypeId="2" ParentId="1926" CreationDate="2010-03-19T18:55:25.327" Score="1" ViewCount="" Body="&lt;p&gt;I've installed the toolchain using tutorial from &lt;a href=&quot;http://www.madox.net/blog/2008/11/26/compiling-a-toolchain-for-arm7-under-ubuntu/&quot; rel=&quot;nofollow&quot;&gt;Madox&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After manual compilation and installation as described in this link everything worked like a charm. &lt;/p&gt;&#xA;" OwnerUserId="598" LastActivityDate="2010-03-19T18:55:25.327" />
  <row Id="1949" PostTypeId="1" AcceptedAnswerId="1960" CreationDate="2010-03-20T11:57:33.850" Score="5" ViewCount="587" Body="&lt;p&gt;I'm looking around for a large LCD character display (metre-ish long, 10-15cm high), and on the cheap side (of course)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually I think I meant LED display, max $150ish&lt;/p&gt;&#xA;" OwnerUserId="601" LastEditorUserId="601" LastEditorDisplayName="" LastEditDate="2010-03-20T22:30:45.017" LastActivityDate="2010-06-24T06:22:37.410" Title="Source a really big LCD character display" Tags="&lt;lcd&gt;&lt;display&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="1950" PostTypeId="2" ParentId="1949" CreationDate="2010-03-20T12:16:37.453" Score="2" ViewCount="" Body="&lt;p&gt;Could you work with these: &#xA;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/7%252dSegment-Red-6.5%22-Display.html&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/7%252dSegment-Red-6.5%22-Display.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="3" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2010-06-24T06:22:37.410" LastActivityDate="2010-06-24T06:22:37.410" CommentCount="3" />
  <row Id="1951" PostTypeId="2" ParentId="1949" CreationDate="2010-03-20T17:58:54.393" Score="4" ViewCount="" Body="&lt;p&gt;An LCD TV might be the cheapest option, with an MCU generating VGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it has to be LEDs, you could base it on &lt;a href=&quot;https://www.xmos.com/products/development-kits/xc-3-led-tile-kit&quot; rel=&quot;nofollow&quot;&gt;this XMOS kit&lt;/a&gt;, using your own LED array.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-03-21T04:30:10.487" LastActivityDate="2010-03-21T04:30:10.487" CommentCount="2" />
  <row Id="1952" PostTypeId="2" ParentId="1949" CreationDate="2010-03-21T04:06:23.547" Score="3" ViewCount="" Body="&lt;p&gt;How about hooking several LCDs with a 10-15cm dimension together to form a larger screen. Software can easily handle splitting the text to multiple such screens.&lt;/p&gt;&#xA;" OwnerUserId="560" LastActivityDate="2010-03-21T04:06:23.547" CommentCount="1" />
  <row Id="1953" PostTypeId="1" CreationDate="2010-03-21T08:32:46.613" Score="3" ViewCount="185" Body="&lt;p&gt;Hi all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are to create an 8051 microcontroller based system as a university project. We have the specs, which says we need an Atmel 89C51 chip. But Atmel &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=1930&quot; rel=&quot;nofollow&quot;&gt;recommends&lt;/a&gt; that we use AT89S51 instead of AT89C51. Why is it so? What is the difference between the two?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, what other hardware do we need to connect the microcontroller to a laptop in order to burn the program? What is a &quot;programmer&quot;, do we need to build it ourselves? I've also read about ISPs and &quot;off-the-shelf development boards&quot; but I'm a bit confused here regarding what hardware exactly we need to buy. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" LastActivityDate="2010-03-26T18:01:23.973" Title="New to embedded systems: help selecting the right chip for 8051 project?" Tags="&lt;8051&gt;&lt;atmel&gt;&lt;beginner&gt;" AnswerCount="4" />
  <row Id="1954" PostTypeId="2" ParentId="1953" CreationDate="2010-03-21T11:29:45.737" Score="2" ViewCount="" Body="&lt;p&gt;The former chip is obsolete, you should use the newer one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Programming details are &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc3ae686c15593f.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-21T11:29:45.737" />
  <row Id="1955" PostTypeId="2" ParentId="1953" CreationDate="2010-03-21T15:49:23.600" Score="3" ViewCount="" Body="&lt;p&gt;&quot;Not recommended for new designs&quot; means &quot;we aren't going to make this anymore&quot;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's for something low-quantity, go ahead and use it, but don't use it in something you intend to make thousands of over the next decade.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-03-21T15:49:23.600" />
  <row Id="1956" PostTypeId="2" ParentId="1953" CreationDate="2010-03-21T23:54:17.303" Score="2" ViewCount="" Body="&lt;p&gt;As to the second part of your question:&#xA;A programmer is required to interface with the micro so you can write the code you develop on a PC to the micro for execution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some chips, particularly in prototype systems, use a 'drop in' programmer that you physically remove the microcontroller chip from the system and drop into a chip mount on the programmer to write your software to memory, and then replace the chip in the system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ISP's achieve this without having to remove the chip from the system, usually by reserving a pair of Tx/Rx ports on the controller and requiring the designer to include a small interface plug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dev boards come in a variety of flavours. At the most basic end of the scale, bare-bones kits that have appropriate breakouts for a certain chip on an otherwise blank PCB with a hole grid drilled in it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think what you're probably looking at is a development kit that has the chip premounted and a set of breakouts and support components already included. Support components may include a typical power supply, a USB controller and interface port, line balancing resistors on I/O channels, etc. In these cases, there's usually a method setup to quickly reprogram the board without having to remove it from everything else (via USB for instance). Some of these boards will even let you run a monitoring host program that executes your code and reports it back to the PC for debugging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For your project, don't look at ISPs unless you're planning to SMD solder everything but anticipate changes to microcontroller software later (it's the &quot;inflexible&quot; solution). A dev kit is excellent for initial prototyping, but you may be paying for excess functionality that you won't need in your final product (hence &quot;development&quot; board). Barebones kits will give you a decent final prototype to present, but will take the most effort and extra component buy-in to build.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So... Try to strike a balance, I guess?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(sorry for wall of text!)&lt;/p&gt;&#xA;" OwnerUserId="295" LastActivityDate="2010-03-21T23:54:17.303" />
  <row Id="1957" PostTypeId="2" ParentId="1920" CreationDate="2010-03-22T00:15:02.480" Score="0" ViewCount="" Body="&lt;p&gt;If it's that important and you're particularly worried about competitors stealing your code, take out IP protection on your code segments. You should be looking into this if you're going to try and make money out of a project anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Certain elements of code can be either patented (for specific processing methods and novel algorithms) or registered as industrial designs (the look, layout and application of your code to a device). You may wish to consult an IP lawyer on this.&lt;/p&gt;&#xA;" OwnerUserId="295" LastActivityDate="2010-03-22T00:15:02.480" />
  <row Id="1958" PostTypeId="2" ParentId="1738" CreationDate="2010-03-22T02:48:40.367" Score="3" ViewCount="" Body="&lt;p&gt;You pretty much need a decent size piece of RAM and flash outside the MCU/MPU.  If I was going to make a bare bones Linux system, I think I would go with simple cheap ARM with a serial port.  You could make a tiny PCB with 4MB of RAM, 2MB of FLASH, RS-232 transceiver, COM port, and the ARM.  You could get real fancy by adding ethernet, but that won't add too much real estate to the PCB.&lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2010-03-22T02:48:40.367" />
  <row Id="1959" PostTypeId="2" ParentId="1677" CreationDate="2010-03-22T04:07:57.623" Score="2" ViewCount="" Body="&lt;p&gt;While I haven't use a hardware simulator for a while, it think what s happen is something like this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each clock cycle of the AVR is simulated which takes multiple clock cycles on the host PC. Hence time on the simulated AVR is running slower than real time. This could explain why the delay loop would appear to hang the AVR simulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A similar scenario could be the case with the serial port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I'm not sure if the simulating modern processors with flash memory is productive as it's quicker to just load the program into the system and &quot;let it run&quot; to see what happens.&lt;/p&gt;&#xA;" OwnerUserId="640" LastActivityDate="2010-03-22T04:07:57.623" />
  <row Id="1960" PostTypeId="2" ParentId="1949" CreationDate="2010-03-22T04:40:15.123" Score="4" ViewCount="" Body="&lt;p&gt;Hmmm. I'll assume that you mean an LED display.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are wanting to display a full character set, you might want to consider using several 5x7 led matrix. See &lt;a href=&quot;http://www.best-microcontroller-projects.com/led-dot-matrix-display.html&quot; rel=&quot;nofollow&quot;&gt;http://www.best-microcontroller-projects.com/led-dot-matrix-display.html&lt;/a&gt; for an introduction. MAX7221 driver chips can be used to instead of multiplexing the rows and columns. While the extra chip does add to the parts costs, it will mean bright letters and less pins being used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Give the dimension of the display that you are after, you'd need to find a LED matrix which contains 10mm LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't see this as a cheap project by the time you assemble the LED matrix displays. Good luck as it sounds like fun.&lt;/p&gt;&#xA;" OwnerUserId="640" LastActivityDate="2010-03-22T04:40:15.123" />
  <row Id="1961" PostTypeId="1" AcceptedAnswerId="1963" CreationDate="2010-03-22T08:46:29.090" Score="5" ViewCount="317" Body="&lt;p&gt;I am wanting to design a circuit that uses an astable multivibrator as a clock source. However the difference being that over time the clock is gradually sped up until it reaches some multiple frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have found circuits that have a speed that that decreases to zero (an addition of a cap) but not one that speeds up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas or help to point me in the right direction would be great!&#xA;Thanks&#xA;jme&lt;/p&gt;&#xA;" OwnerUserId="641" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T16:22:17.397" LastActivityDate="2010-10-22T16:22:17.397" Title="Astable multivibrator with increasing frequency" Tags="&lt;frequency&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="1962" PostTypeId="2" ParentId="1961" CreationDate="2010-03-22T08:50:10.883" Score="0" ViewCount="" Body="&lt;p&gt;Do you mean something that ramps the frequency up, from zero, until it reaches a maximum value? I'd use a small MCU for that, like a PIC or AVR.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-22T08:50:10.883" CommentCount="1" />
  <row Id="1963" PostTypeId="2" ParentId="1961" CreationDate="2010-03-22T10:19:42.780" Score="3" ViewCount="" Body="&lt;p&gt;One approach would be to use a voltage controlled oscillator (VCO) and a ramp generating circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The CD4046 has a VCO block in it or there are some function generator ics, like the MAX038. You'll need to find something that covers that range of frequency you need. To produce a ramp, it could be as simple as a capacitor pulled up (or down) to the input of the VCO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need a linear ramp, then driving the capacitor with a current source would be more suitable.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2010-03-22T10:19:42.780" CommentCount="1" />
  <row Id="1964" PostTypeId="1" AcceptedAnswerId="1966" CreationDate="2010-03-22T15:30:29.053" Score="5" ViewCount="349" Body="&lt;p&gt;Hello, I'm having an argument with a classmate and we can't agree.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;He tells me that it's not possible for the amplifier of a radio station to amplify the input signal &quot;instantaneously&quot; (at the speed of light), because they work with very big powers (tens of kilowatts) and you can't accelerate the electrons that quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I insist that since it's an analog device, it will work at speed of light, and that you don't need to accelerate the individual electrons, but only the electric/magnetic fields.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So which one of us is right in this particular case? Is there a delay in amplifying a signal for a high powered radio station? The radio station part is important. He agrees for example that a typical home audio amplifier is instantaneously.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be great if you could provide a reference link for an answer (if possible). Wikipedia would be fine. But don't waste your time searching for one.&lt;/p&gt;&#xA;" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-22T19:34:30.043" LastActivityDate="2010-10-16T12:38:18.047" Title="Does a radio station main amplifier work at the speed of light?" Tags="&lt;radio&gt;&lt;amplifier&gt;&lt;theory&gt;&lt;electromagnetism&gt;" AnswerCount="6" FavoriteCount="2" />
  <row Id="1965" PostTypeId="2" ParentId="1964" CreationDate="2010-03-22T15:48:49.270" Score="3" ViewCount="" Body="&lt;p&gt;I think the answer depends on the media and not the amplitude of the output signal; the amplifiers, in this case, and not the signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Electromagnetic waves (like the signals described) travel at the speed of:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(speed_of_light) / sqrt(permittivity_of_material * permeability_of_material)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The speed of the signal depends on the permittivity (electric attribute) and the permeability (magnetic attribute) of the media, not attributes of the signal itself (it's amplitude, frequency, phase shift).  So it depends on the amplifiers themselves, and the differences in permittivity and/or permeability between the two, but not the amplitude of the output signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your reasoning is better than your friend's in this case.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Source:  &lt;a href=&quot;http://wiki.answers.com/Q/Do_all_electromagnetic_waves_travel_at_the_same_rate&quot; rel=&quot;nofollow&quot;&gt;http://wiki.answers.com/Q/Do_all_electromagnetic_waves_travel_at_the_same_rate&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-03-22T22:10:16.597" LastActivityDate="2010-03-22T22:10:16.597" />
  <row Id="1966" PostTypeId="2" ParentId="1964" CreationDate="2010-03-22T16:10:54.127" Score="11" ViewCount="" Body="&lt;p&gt;It really depends on what you're talking about.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The signal does not travel at the speed of light in the cables connecting to the antenna.  Cable &lt;a href=&quot;http://en.wikipedia.org/wiki/Wave_propagation_speed&quot; rel=&quot;nofollow&quot;&gt;propagation speeds&lt;/a&gt; are often around 2/3 the speed of light, for instance.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It doesn't travel at the speed of light through an amplifier, either.  Any filtering incurs &lt;a href=&quot;http://en.wikipedia.org/wiki/Group_delay_and_phase_delay&quot; rel=&quot;nofollow&quot;&gt;a small delay&lt;/a&gt;, for instance, which is why filters are implemented using &lt;a href=&quot;http://en.wikipedia.org/wiki/Digital_delay_line&quot; rel=&quot;nofollow&quot;&gt;delay lines&lt;/a&gt; in the digital realm.  (It's not instantaneous through a home audio amplifier, either, so you're both wrong.)  :D&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After it gets out of the antenna it should travel at the speed of light in air, which is almost &lt;em&gt;c&lt;/em&gt;, and I don't know of any reason why this would vary with the amount of energy.  The sun puts out a lot more electromagnetic energy than a radio tower, and it still travels at &lt;em&gt;c&lt;/em&gt; through space.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-22T16:18:35.953" LastActivityDate="2010-03-22T16:18:35.953" CommentCount="2" />
  <row Id="1967" PostTypeId="1" CreationDate="2010-03-22T16:18:02.773" Score="4" ViewCount="215" Body="&lt;p&gt;What is the best plug computer to get that exists today? &lt;/p&gt;&#xA;" LastActivityDate="2010-03-22T22:06:17.253" ClosedDate="2011-03-22T11:27:33.410" Title="Plug computer question" Tags="&lt;linux&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="1968" PostTypeId="1" AcceptedAnswerId="1989" CreationDate="2010-03-22T16:27:39.187" Score="2" ViewCount="103" Body="&lt;p&gt;The normal musical instrument pickup uses a magnet inside a coil, and the movement of a ferromagnetic string causes changes in the magnetic field, which then induce currents in the coil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another possibility would be to use just a strong magnet near a string, and measuring induced currents in the string itself.  This would only require a conductive string, not a ferromagnetic one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone actually use this method?  Is there a name for it, or is it useless, so no one talks about it?  I tried it last night, and it works, but the signal is very low (-50 dBV, for instance, vs -5 dBV for a magnetic electric guitar pickup).&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-25T14:30:34.603" LastActivityDate="2010-03-25T14:30:34.603" Title="Amplifying instruments by measuring current in conductive strings" Tags="&lt;audio&gt;&lt;electromagnetism&gt;" AnswerCount="2" />
  <row Id="1970" PostTypeId="2" ParentId="1964" CreationDate="2010-03-22T18:00:43.640" Score="12" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;you can't accelerate the electrons that quickly.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I think the problem lies in a misconception.  The electrons don't move at the speed of light, in fact if you could 'tag' an individual electron coming into a wire and then sense when it leaves you could measure it with a stop watch in a reasonable length of cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;em&gt;effect&lt;/em&gt; of the electron, or in other words the wave that is generated when an electron is pushed into a conductor, can be sensed almost at the speed of light on the other end of the conductor, but the individual electron you pushed onto the cable will not appear there for some time based on current, voltage, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the amplifier does &lt;em&gt;not&lt;/em&gt; accelerate electrons to anywhere near the speed of light.  It induces waves in the electrons in the cables, or amplifier, which are sensed by the semiconductors which induce waves in other cables and other semiconductors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is some inherent delay with every amplifier, but it's so small as to be unnoticeable by human ears.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that if amplifier introduced significant delay, then BBC broadcasts on NPR stations in the US would be delayed much more than the few hundred mS it already is.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-22T18:00:43.640" CommentCount="4" />
  <row Id="1971" PostTypeId="2" ParentId="1964" CreationDate="2010-03-22T18:03:36.190" Score="4" ViewCount="" Body="&lt;p&gt;Actually you do need to move the electrons around in the active component of the amplifier, for example the junction of a bipolar transistor, as the amplifying effect depends on that. The junction is small, but you still get a delay in the pico- to nanoseconds range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Along wires the signal runs at the speed of light in that medium, which is somewhat lower than the speed of light in vacuum.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-03-22T18:03:36.190" />
  <row Id="1972" PostTypeId="1" CreationDate="2010-03-22T19:08:52.437" Score="5" ViewCount="96" Body="&lt;p&gt;Does anyone know or of use a standard set of source files for a simple embedded console?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been doing embedded work for a few years now, and I have a set of console code files I have reused in several situations.  I've searched the web before for common console code, and I have not found a standard library.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried using different RTOS solutions, and I have written my own console's that work A-OK. I'm just hoping to find a standard reference implementation to recommend to others, or to work on and with to improve quality and number of developers on a project.&lt;/p&gt;&#xA;" OwnerUserId="626" LastActivityDate="2010-03-22T20:06:17.653" Title="Is there a common embedded console library" Tags="&lt;embedded&gt;&lt;standard&gt;&lt;library&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="1973" PostTypeId="2" ParentId="1964" CreationDate="2010-03-22T19:21:49.150" Score="7" ViewCount="" Body="&lt;p&gt;The signal may travel fast but the electrons do not.  Google electron drift velocity.  Speeds are measured in cm per sec or perhaps cm per hour.  Here is one pretty good hit&#xA;&lt;a href=&quot;http://www.eskimo.com/~billb/miscon/speed.html&quot; rel=&quot;nofollow&quot;&gt;http://www.eskimo.com/~billb/miscon/speed.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-03-22T19:21:49.150" CommentCount="1" />
  <row Id="1974" PostTypeId="2" ParentId="1972" CreationDate="2010-03-22T20:01:39.403" Score="1" ViewCount="" Body="&lt;p&gt;Atmel have an appnote and some software to implement a simple ANSI console. (AVR244)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?module=Freaks%20Tools&amp;amp;func=viewItem&amp;amp;item_id=501&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?module=Freaks%20Tools&amp;amp;func=viewItem&amp;amp;item_id=501&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-22T20:01:39.403" />
  <row Id="1975" PostTypeId="2" ParentId="1972" CreationDate="2010-03-22T20:02:35.960" Score="0" ViewCount="" Body="&lt;p&gt;I've always just written a custom console for my applications. I do reuse code between them a lot though depending on what type of support they need to provide. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I base most of my consoles on a command/response format where the system provides a prompt '&gt;' then the user enters a command which is buffered. When the user enters a 'CR' the buffered command is executed. The system generates a reply and provides another prompt. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the interface to the console is automated and binary transfers are required you will need to come up with a way to escape the 'CR' so that it is not interpreted as an end of command.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I can tell the basic components of any console are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Interrupt for receiving and buffering input&lt;/li&gt;&#xA;&lt;li&gt;Task for processing buffered input and printing the response&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-03-22T20:02:35.960" />
  <row Id="1976" PostTypeId="2" ParentId="1967" CreationDate="2010-03-22T20:03:30.043" Score="2" ViewCount="" Body="&lt;p&gt;So far as I know, the Marvell SheevaPlug is the only one available to buy online.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-22T20:03:30.043" CommentCount="1" />
  <row Id="1978" PostTypeId="2" ParentId="1967" CreationDate="2010-03-22T22:06:17.253" Score="0" ViewCount="" Body="&lt;p&gt;The most powerful one on the market at the moment is the guruplug, it's around the same price as the sheevaplug, same chip, just more connectivity. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.newit.co.uk/shop/products.php?cat=11&quot; rel=&quot;nofollow&quot;&gt;http://www.newit.co.uk/shop/products.php?cat=11&lt;/a&gt; (in the uk)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Later this year there will be a version on the sheevaplug with a 2GHz chip, wifi, bluetooth and hd for around 400 dollars..but it's not in production yet.&lt;/p&gt;&#xA;" OwnerUserId="558" LastActivityDate="2010-03-22T22:06:17.253" />
  <row Id="1979" PostTypeId="2" ParentId="1968" CreationDate="2010-03-22T23:04:30.307" Score="0" ViewCount="" Body="&lt;p&gt;Moving coil and moving magnet &lt;a href=&quot;http://en.wikipedia.org/wiki/Magnetic_cartridge&quot; rel=&quot;nofollow&quot;&gt;phonograph cartridges&lt;/a&gt; (and other similar transducers) embody essentially the same principles as what you are describing.  As you would expect from your experiments, moving coil cartridges have a much lower output than moving magnet.  However, the fidelity is presumably better with moving coil cartridges.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can get an acceptable signal to noise ratio, I don't see any reason why this wouldn't work.  I &lt;em&gt;would&lt;/em&gt; expect the timbre to be somewhat different, however.  You will most likely need an additional 10 to 20 db of voltage gain.  You might (carefully) try a high-impedance microphone input, or placing an op-amp in the signal path to get a bit more gain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given the eclectic nature and history of pickup coils (such as humbuckers) and the demands put on musical instruments by the stage environment, I would characterize your application as a &quot;specialized use.&quot;  There's no way to know ahead of time if the strings will be more sensitive to feedback, for example, without testing it first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I once put a condenser microphone on a pillow, set an autoharp on top of it, and cranked up the treble.  The resulting recording was awesome.  Keep experimenting!&lt;/p&gt;&#xA;" OwnerUserId="544" LastEditorUserId="544" LastEditorDisplayName="" LastEditDate="2010-03-22T23:17:22.253" LastActivityDate="2010-03-22T23:17:22.253" CommentCount="2" />
  <row Id="1980" PostTypeId="1" AcceptedAnswerId="1988" CreationDate="2010-03-22T23:13:59.587" Score="4" ViewCount="580" Body="&lt;p&gt;I recently purchased a Weller WES51 soldering iron as my first temperature controlled iron and I'm looking for recommendations on the best default temperature to use when soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using mainly .031 inch 60/40 solder on through-hole components.&lt;/p&gt;&#xA;" OwnerUserId="647" LastEditorUserId="647" LastEditorDisplayName="" LastEditDate="2010-03-23T00:35:39.533" LastActivityDate="2010-03-23T21:10:24.690" Title="What’s the proper soldering iron temperature for standard .031&quot; 60/40 solder?" Tags="&lt;beginner&gt;&lt;soldering&gt;&lt;temperature&gt;&lt;soldering&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="1981" PostTypeId="2" ParentId="1980" CreationDate="2010-03-22T23:14:14.330" Score="2" ViewCount="" Body="&lt;p&gt;I found these two links, with the following information:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.technick.net/public/code/cp_dpage.php?aiocp_dp=how_to_solder&quot; rel=&quot;nofollow&quot;&gt;Basic Soldering Guide&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The melting point of most solder is in&#xA;  the region of 188°C (370°F) and the&#xA;  iron tip temperature is typically&#xA;  330°C to 350°C (626°F to 662°F).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.circuitrework.com/guides/7-1-1.shtml&quot; rel=&quot;nofollow&quot;&gt;Soldering Basics&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Although tip temperature is not the&#xA;  key element in soldering you should&#xA;  always start at the lowest temperature&#xA;  possible. A good rule of thumb is to&#xA;  set the soldering iron tip temperature&#xA;  at 260°C (500°F) and increase the&#xA;  temperature as needed to obtain the&#xA;  desired result.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;With these as a guide and a bit of experimentation I've found that 550°F generally heats the lead and pad up to the appropriate temperature within a couple seconds.&lt;/p&gt;&#xA;" OwnerUserId="647" LastActivityDate="2010-03-22T23:14:14.330" />
  <row Id="1982" PostTypeId="2" ParentId="1980" CreationDate="2010-03-22T23:21:41.743" Score="2" ViewCount="" Body="&lt;p&gt;My strategy is to always have the iron as hot as possible, then try to minimise the time I have in contact with components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A hot iron will melt solder immediately on contact. Whereas, a cooler iron will need to be held in contact for a while first, which might do damage to the PCB or parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though, apparently, between 600 and 700°F is ideal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any higher and you might:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Damage components&lt;/li&gt;&#xA;&lt;li&gt;Reduce the lifespan of the tip&lt;/li&gt;&#xA;&lt;li&gt;Melt insulating wire&lt;/li&gt;&#xA;&lt;li&gt;Burn off flux&lt;/li&gt;&#xA;&lt;li&gt;Vapourise lead&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.tubedepot.com/?p=226&quot; rel=&quot;nofollow&quot;&gt;http://blog.tubedepot.com/?p=226&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Despite the risks - I'd still recommend short bursts at high temperature for surface mount and through hole construction. Works for me.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-03-23T02:29:18.287" LastActivityDate="2010-03-23T02:29:18.287" CommentCount="2" />
  <row Id="1983" PostTypeId="1" AcceptedAnswerId="1996" CreationDate="2010-03-22T23:43:16.537" Score="9" ViewCount="549" Body="&lt;p&gt;When driving an LED with PWM, the brightness (as I perceive it) does not scale linearly with duty cycle.&#xA;The brightness is slow to ramp up, then increases exponentially with duty cycle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone suggest a rule of thumb to use as a correction factor, or other workaround?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-09-27T13:16:39.873" LastActivityDate="2011-03-30T12:37:06.573" Title="Correcting for non-linear brightness in LEDs when using PWM" Tags="&lt;led&gt;&lt;pwm&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="1984" PostTypeId="1" AcceptedAnswerId="1985" CreationDate="2010-03-23T00:08:51.650" Score="2" ViewCount="101" Body="&lt;p&gt;I have some RGB LEDs (eBay - no datasheet, 4 pin, common cathode, 5mm). I am colourblind.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to create a palette of colours which appear distinctly for most people's eyes, perhaps 16 colours or more. How could I generate this palette?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess that the colour produced will be far from a perfect match to the duty cycle applied.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The human eye is apparently more sensitive to green, could I use this (and other factors) to improve the colour output?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-03-23T00:59:34.807" LastActivityDate="2010-03-23T00:59:34.807" Title="Colour correcting RGB LEDs - possibly with science" Tags="&lt;led&gt;&lt;rgb&gt;&lt;colour&gt;" AnswerCount="1" />
  <row Id="1985" PostTypeId="2" ParentId="1984" CreationDate="2010-03-23T00:52:03.167" Score="3" ViewCount="" Body="&lt;p&gt;Well, the easy method would be to find a friend who can see colors and ask him to pick 16 colors for you. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first 8 colors (7 if you don't count black) are easy...just run through all the possible combinations of on/off LEDs. To get more than that, you'll need to vary the brightness of the individual colors. Generally you vary LED brightness not via voltage, but via PWM (very quickly turning the LED on and off. Spending more time off to make it appear dimemr)&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-03-23T00:52:03.167" CommentCount="1" />
  <row Id="1987" PostTypeId="2" ParentId="1983" CreationDate="2010-03-23T01:05:40.987" Score="4" ViewCount="" Body="&lt;p&gt;I found &lt;a href=&quot;http://www.youtube.com/watch?v=sZ1saomKYus&quot; rel=&quot;nofollow&quot;&gt;this guy&lt;/a&gt; who uses a method he calls &quot;Anti-Log Drive&quot;. Here is the &lt;a href=&quot;http://www.juno.dti.ne.jp/~mkatsube/download/files/AntiLogDrive.zip&quot; rel=&quot;nofollow&quot;&gt;direct download link&lt;/a&gt; for his info.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-03-23T01:05:40.987" />
  <row Id="1988" PostTypeId="2" ParentId="1980" CreationDate="2010-03-23T01:42:16.393" Score="4" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;What’s the proper soldering iron temperature for standard .031&quot; 60/40 solder?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;There is no proper soldering iron temperature &lt;em&gt;just&lt;/em&gt; for a given type of solder - the iron temperature should be set for both the component and the solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When soldering surface mount components, a small tip and 600F should be sufficient to quickly solder the joint well without overheating the component.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When soldering through hole components, 700F is useful to pump more heat into the wire and plated hole to solder it quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A negative capacitor lead to a heatsinking solid pour ground plane is going to need a big fat tip at the highest temperature your iron will go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I don't micromanage my soldering temperature, and simply keep mine at 700F.  I'll change the tips according to what I'm soldering, and the tip size really ends up determining how much heat gets into the joint in a given period of contact.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you'll find that very few soldering jobs will really require you to change your tip temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that I'm talking about prototyping, hobbyist, and one-off projects.  If you are planning on doing final assembly with the iron, repair work for critical projects, etc, then you'll need to consider what you're doing more carefully than you might ordinarily do.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-23T01:42:16.393" CommentCount="1" />
  <row Id="1989" PostTypeId="2" ParentId="1968" CreationDate="2010-03-23T01:51:30.147" Score="5" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Does anyone actually use this method? &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;For stringed instruments, no, but the principle is used in many, many places.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;is it useless, so no one talks about it? &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;It's not useless, but it has some significant disadvantages, and other methods are simply far superior.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I tried it last night, and it works, but the signal is very low.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That is the main disadvantage.  Others are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You are measuring low induced voltages in the string that is in contact with a conductor (human) which messes up the measurement&lt;/li&gt;&#xA;&lt;li&gt;More advanced measuring techniques induce a voltage in the string, but again the human conductor is in the way&lt;/li&gt;&#xA;&lt;li&gt;The strings are more variable in terms of electrical properties (resistance, capacitance, inductance) all of which affect the sound, and mean that two instruments might sound very different&lt;/li&gt;&#xA;&lt;li&gt;The strings, being long, are not unlike antennas and inductors and are very good at picking up stray noise in electrical and magnetic fields.  You can be much closer to a lamp ballast with a coil pickup before picking up the AC hum than you can with a string pickup.&lt;/li&gt;&#xA;&lt;li&gt;There's no galvanic isolation, so the amp has to be isolated from the AC line and high voltage sources, which pretty much rules out tube based amps.&lt;/li&gt;&#xA;&lt;li&gt;Electrostatic discharge from the user into the string and conducted into the equipment is damaging, but even if it's suppressed you can't easily filter out the additional noise it causes.&lt;/li&gt;&#xA;&lt;li&gt;Getting a good electrical connection to the string in a performance environment is difficult since it's hard to tin the metals used in many strings, and vibration, corrosion, and other environmental factors complicate it.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;That's just the start.  Don't misunderstand, coil pickups have disadvantages too, but they are superior in many areas.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-23T01:51:30.147" />
  <row Id="1990" PostTypeId="1" CreationDate="2010-03-23T03:52:13.080" Score="6" ViewCount="635" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am at the point that my projects are becoming limited by the space on my breadboard. Rather than buying more, I have decided to look into PCB fabrication. My question is this: is it cheaper to make your own PCBs for prototyping, or should I send my plans away and have them fabbed elsewhere? If you do make your own boards at home, how much does it cost per square unit (approximately) and what method do you use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it helps, I am in Australia so I don't have many fab businesses close by.&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-30T00:53:49.117" LastActivityDate="2011-03-10T03:53:43.897" Title="How much does it cost to etch your own PCBs?" Tags="&lt;pcb-fabrication&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="4" />
  <row Id="1991" PostTypeId="2" ParentId="1990" CreationDate="2010-03-23T04:01:16.500" Score="1" ViewCount="" Body="&lt;p&gt;i have the same question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but more to the place of GOOD Australian fabrication places that are cheap and have no minimum order.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i have tried futurlec, but their customer service is....... not good. i havent been able to get a quote, but i have been able to get some email full of bad English and answers avoiding the question.&lt;/p&gt;&#xA;" LastActivityDate="2010-03-23T04:01:16.500" CommentCount="1" />
  <row Id="1992" PostTypeId="2" ParentId="1893" CreationDate="2010-03-23T05:07:08.043" Score="3" ViewCount="" Body="&lt;p&gt;I use Gold Phoenix (A well known fab house) - it is based out of china and they produce very cheap boards in under a week. Their website is &lt;a href=&quot;http://www.goldphoenixpcb.biz/&quot; rel=&quot;nofollow&quot;&gt;http://www.goldphoenixpcb.biz/&lt;/a&gt; - check out their special offers. One design, 100sq inches worth of pieces, unlimited vias and TH, etc all for under $100. The only problem I had was the communication, since it is obvious English isn't their strongest language. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also recommend Advanced Circuits - they produce exceptional quality boards, but cost more than Gold Phoenix. &lt;/p&gt;&#xA;" LastActivityDate="2010-03-23T05:07:08.043" CommunityOwnedDate="2010-03-23T05:07:08.043" CommentCount="2" />
  <row Id="1993" PostTypeId="1" CreationDate="2010-03-23T06:09:39.767" Score="2" ViewCount="103" Body="&lt;p&gt;How to make a picaxe service remote for a pioneer ir controller for a DVR - 660H and DVP 540H DVD recorder&lt;/p&gt;&#xA;" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-03-23T13:26:15.130" LastActivityDate="2010-04-06T14:23:19.057" Title="How to make a picaxe service remote for a pioneer ir controller for a DVR - 660H and DVP 540H DVD recorder" Tags="&lt;picaxe&gt;&lt;infrared&gt;" AnswerCount="1" />
  <row Id="1994" PostTypeId="2" ParentId="1990" CreationDate="2010-03-23T06:53:24.930" Score="5" ViewCount="" Body="&lt;p&gt;I often make my own prototype PCBs at home. I made my own UV exposure unit for about £20, and use a cheap HP inkjet printer with Mega Electronics (UK) Jetstar Premium film for the transparencies and Mega's FPC16 positive resist pre-coated boards, developed in sodium hydroxide solution and etched in ferric chloride. The FPC16 costs about 1p a sq. inch, and the film costs roughly the same. I can make a PCB in about 30 minutes (not including drilling), and can do 8/8 mil tracks without any problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Join the Homebrew PCB Yahoo group if you need more information on the various techniques that are available.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-23T06:53:24.930" />
  <row Id="1995" PostTypeId="2" ParentId="1980" CreationDate="2010-03-23T07:02:31.977" Score="1" ViewCount="" Body="&lt;p&gt;I use a Metcal system and the cartridges for standard lead solder deliver 600F. It's important to use the correct size tip for the job in hand, Metcal recommends one that is about the same size as the object being soldered, to avoid damage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Metcal has &lt;a href=&quot;http://www.metcal.com/images/Tech%20Note%20-%20SMT%20Techniques%20Using%20Metcal%20MX-5000.pdf&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; useful document on soldering techniques&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-03-23T07:08:40.733" LastActivityDate="2010-03-23T07:08:40.733" />
  <row Id="1996" PostTypeId="2" ParentId="1983" CreationDate="2010-03-23T08:34:06.303" Score="8" ViewCount="" Body="&lt;p&gt;For 16 levels it's easy to do a simple look-up table &quot;by hand&quot; and convert the 4 bit value in an 8 bit value to pass to PWM controller: this is the component i've used in my FPGA led array driver.&#xA;For an 8 bit level controller, you'll need at least 11-12 bit output from the look-up table.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;library IEEE;&#xA;use IEEE.Std_logic_1164.all;&#xA;&#xA;entity Linearize is&#xA;port ( reqlev : in std_logic_vector (3 downto 0) ;&#xA;    pwmdrive : out std_logic_vector (7 downto 0) );&#xA;    end Linearize;&#xA;&#xA;architecture LUT of Linearize is&#xA;    begin&#xA;    with reqlev select&#xA;        pwmdrive &amp;lt;= &quot;00000000&quot; when &quot;0000&quot;,&#xA;                    &quot;00000010&quot; when &quot;0001&quot;,&#xA;                    &quot;00000100&quot; when &quot;0010&quot;,&#xA;                    &quot;00000111&quot; when &quot;0011&quot;,&#xA;                    &quot;00001011&quot; when &quot;0100&quot;,&#xA;                    &quot;00010010&quot; when &quot;0101&quot;,&#xA;                    &quot;00011110&quot; when &quot;0110&quot;,&#xA;                    &quot;00101000&quot; when &quot;0111&quot;,&#xA;                    &quot;00110010&quot; when &quot;1000&quot;,&#xA;                    &quot;01000001&quot; when &quot;1001&quot;,&#xA;                    &quot;01010000&quot; when &quot;1010&quot;,&#xA;                    &quot;01100100&quot; when &quot;1011&quot;,&#xA;                    &quot;01111101&quot; when &quot;1100&quot;,&#xA;                    &quot;10100000&quot; when &quot;1101&quot;,&#xA;                    &quot;11001000&quot; when &quot;1110&quot;,&#xA;                    &quot;11111111&quot; when &quot;1111&quot;,&#xA;                    &quot;00000000&quot; when others;&#xA;    end LUT;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="244" LastActivityDate="2010-03-23T08:34:06.303" CommentCount="2" />
  <row Id="1997" PostTypeId="2" ParentId="1993" CreationDate="2010-03-23T10:02:45.473" Score="1" ViewCount="" Body="&lt;p&gt;You could have a look at the TV Be Gone project there are various schematics available (including one &lt;a href=&quot;http://www.instructables.com/id/Double-the-Range-of-Your-TV-B-Gone/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) plus other information, maybe one of these might have some information you could use to help you.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-03-23T10:02:45.473" />
  <row Id="1998" PostTypeId="1" CreationDate="2010-03-23T15:49:02.713" Score="7" ViewCount="161" Body="&lt;p&gt;I have a PDF of a PCB I want to etch using toner transfer (photo inkjet paper in a laser printer). The design is fairly small, but I have 8.5x11 paper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'd like to do is print a grid of the design on one sheet. How do I do this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make things complicated, the pdf is a secure pdf.&lt;/p&gt;&#xA;" OwnerUserId="550" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-31T04:53:48.287" LastActivityDate="2011-01-31T04:53:48.287" Title="How can I print a grid of PDF PCBs" Tags="&lt;pcb-fabrication&gt;" AnswerCount="2" />
  <row Id="1999" PostTypeId="2" ParentId="1998" CreationDate="2010-03-23T15:56:06.247" Score="3" ViewCount="" Body="&lt;p&gt;In Mac OSX you can cut and paste sections from PDFs from the Preview app. I paste them into OmniGraffle and arrange by hand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Under Linux, you could try converting the PDF to postscript (pdf2ps) then manipulating it with Inkscape. Or, you may be able to do it from a script using &lt;a href=&quot;http://linux.die.net/man/1/poster&quot; rel=&quot;nofollow&quot;&gt;poster&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you could just save the image as a bitmap at the resolution you need, then edit the bitmap.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-23T15:56:06.247" CommentCount="1" />
  <row Id="2000" PostTypeId="1" AcceptedAnswerId="2001" CreationDate="2010-03-23T18:30:30.107" Score="4" ViewCount="476" Body="&lt;p&gt;I want to take a NTSC/PAL component video and overlay graphics over it.&lt;br&gt;&#xA;I am aware of solutions that either use the max7456 overlay chip, or accomplish it &lt;a href=&quot;http://www.viennawireless.org/balloon/hardware/overlay/index.php&quot; rel=&quot;nofollow&quot;&gt;with just an AVR&lt;/a&gt; &#xA;but these seem to have limited resolution and are monochromatic.  Ideally I would like to have something comparable to the performance of &lt;a href=&quot;http://www.diydrones.com/video/hud-test-on-a-trex-500?xg_source=activity&quot; rel=&quot;nofollow&quot;&gt;this setup&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is what I know I will need:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Video decoder (to digitize NTSC/PAL)&lt;/li&gt;&#xA;&lt;li&gt;Some sort of buffer/processor to overlay graphics onto the digitized frame&lt;/li&gt;&#xA;&lt;li&gt;Video Encoder (to re-encode to NTSC/PAL)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The middle part is what I am not sure how to setup.  Are there existing chips that will automatically do this overlaying for me somehow, or do I just need a sufficiently powerful MCU and RAM to buffer/manually manipulate a bitmap? Ideally I would like to have something low cost, and preferably a single chip solution.&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-12-28T20:04:22.300" Title="Video overlay / on screen display architecture" Tags="&lt;video&gt;&lt;display&gt;" AnswerCount="5" />
  <row Id="2001" PostTypeId="2" ParentId="2000" CreationDate="2010-03-23T19:28:16.010" Score="3" ViewCount="" Body="&lt;p&gt;Something like an ADI Blackfin could do that, or an FPGA with some fast RAM.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-23T19:28:16.010" />
  <row Id="2002" PostTypeId="2" ParentId="1980" CreationDate="2010-03-23T21:10:24.690" Score="2" ViewCount="" Body="&lt;p&gt;I normally set my WSD81 to 350°C, for leadless solder or big stuff I've used 360°C and for small SMD stuff 340°C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The solder doesn't just need to melt, it also needs to wet the surfaces, which happens faster at higher temperatures.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-03-23T21:10:24.690" />
  <row Id="2003" PostTypeId="2" ParentId="1983" CreationDate="2010-03-23T21:17:08.210" Score="4" ViewCount="" Body="&lt;p&gt;In theory it should be exponential, but I've got best results for fading by using a quadratic function.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also think you got it backwards. At low duty cycle the perceived increase in brightness is much bigger than at almost full duty cycle, where the increase in brightness is almost imperceivable.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-03-23T21:17:08.210" CommentCount="1" />
  <row Id="2004" PostTypeId="1" AcceptedAnswerId="2005" CreationDate="2010-03-23T21:41:10.080" Score="4" ViewCount="299" Body="&lt;p&gt;I want now to start developing devices, but I don't know too of electronics, just some good knowledge in MIPS, x86, 6502 and ARM Assembly languages, but where can I find some good resources to learn how to enter on this world of the hardware?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;PS: I just want to develop some simple things, but useful&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="654" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-27T19:52:41.757" LastActivityDate="2011-02-27T19:52:41.757" Title="Beginning On This Magic World" Tags="&lt;hardware&gt;&lt;books&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="2" />
  <row Id="2005" PostTypeId="2" ParentId="2004" CreationDate="2010-03-23T21:50:47.157" Score="9" ViewCount="" Body="&lt;p&gt;this is perhaps a duplicate question to an earlier question:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/616/basic-electronics-book&quot; rel=&quot;nofollow&quot;&gt;Basic Electronics Book&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;where you will find several introductory books on electronics. (I vote for Horowitz &amp;amp; Hill.)&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-03-23T21:50:47.157" />
  <row Id="2006" PostTypeId="2" ParentId="1998" CreationDate="2010-03-23T22:48:30.783" Score="3" ViewCount="" Body="&lt;p&gt;Do you really need an entire grid?  If you can live with etching one at a time, I would print the design on a regular piece of paper and then cut out the toner transfer (inkjet) paper just slightly larger than the design and tape it over the printed area on the plain paper.  Feed it back through the printer, and viola! as they say.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could possibly get around the security by printing to (yet another) PDF and then manipulating that with Gimp, Preview, or some other image editing program.  Just seems like you could run the risk of getting the scaling and resolution out of whack…&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-03-23T22:48:30.783" CommentCount="2" />
  <row Id="2007" PostTypeId="1" CreationDate="2010-03-23T23:59:13.997" Score="7" ViewCount="1696" Body="&lt;p&gt;&lt;strong&gt;The general question:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I open and close CD-Rom drives (about 20-30) in reaction to various sensor input?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Some more specific questions (based on the assumption that I should to tackle this with an Arduino):&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would I go about figuring out which pins on an IDE connector are the ones that need to receive a signal?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would I figure out what signal needs to be sent to those pins?  And how would I make an arduino send that signal?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Some context:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm working on a pine tree kinetic sculpture made of old CD-ROM drives. Basically, each &quot;branch&quot; of the tree is a CD-ROM drive pointing away from the trunk. The drives will open and close based on feedback via:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;a microphone. An algorithm would open and close the drives based on analysis of the audio input. One idea, blowing into the mic (like the wind) would simulate the wind blowing pine tree limbs (they would shutter open and close)&lt;/li&gt;&#xA;&lt;li&gt;alternate (or perhaps complementary input): a small model of a tree with touch sensors. If you put your hand around the entire small tree and cover all the sensors, all the drives close. Basically, each sensor is mapped to one drive, cover it and the drive closes.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What I've got so far:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this IDE Pinout diagram:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://img191.imageshack.us/img191/9240/ide44pinout.gif&quot; alt=&quot;IDE Pinout&quot;&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-03-24T06:52:32.743" Title="CD-ROMs open/close in response to sensors" Tags="&lt;ide&gt;&lt;arduino&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="2008" PostTypeId="2" ParentId="2007" CreationDate="2010-03-24T00:11:57.810" Score="4" ViewCount="" Body="&lt;p&gt;Unfortunately, it's not as easy as just closing a connection on that connector.  You need to send a &quot;media eject&quot; ATAPI command over the ATA/IDE bus.  &lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-03-24T00:11:57.810" />
  <row Id="2009" PostTypeId="2" ParentId="2007" CreationDate="2010-03-24T00:17:18.010" Score="6" ViewCount="" Body="&lt;p&gt;If you don't mind breaking the drives you could simply open it up strip out what you don't need and solder leads directly to the motor that opens and closes the drive. Use an H-bridge like the l293d and you're good to go for control from a microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2010-03-24T00:17:18.010" />
  <row Id="2010" PostTypeId="1" CreationDate="2010-03-24T04:26:45.170" Score="4" ViewCount="633" Body="&lt;p&gt;Is it possible to use a transistor with AC?&#xA;if you put a diode in there so no current flowed through it when the current reversed, but what could I do about the difference between the base and collector?&lt;/p&gt;&#xA;" LastActivityDate="2011-05-29T19:14:11.477" Title="Using a transistor with AC?" Tags="&lt;transistor&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="2011" PostTypeId="2" ParentId="2010" CreationDate="2010-03-24T05:01:05.390" Score="4" ViewCount="" Body="&lt;p&gt;No, as you said a transistor acts like a diode when it is &quot;on&quot; but as a subsitute you could either use a triac for low current applications or a solid state relay for higher current applications.&lt;/p&gt;&#xA;" OwnerUserId="212" LastActivityDate="2010-03-24T05:01:05.390" CommentCount="3" />
  <row Id="2012" PostTypeId="1" CreationDate="2010-03-24T05:22:27.930" Score="5" ViewCount="1283" Body="&lt;p&gt;I have a ATmega32 board laying around and I figure it would be perfect to start off with microcontrollers. I once did some babbling in embedded C (thats when I got this board) but the flow was stopped due to some things. Now I have two questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;What is the best free resource to start off with C for the avr series. I know of AVR-GCC but was looking for some tutorials or free books to start me off.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Should I directly jump to C or go through ASM first? I see there are many asm books around. So what is a better option?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;While searching the Internet, I found the Arduino bootloader for ATmega32 here &lt;a href=&quot;http://retrointerfacing.com/?p=30&quot; rel=&quot;nofollow&quot;&gt;http://retrointerfacing.com/?p=30&lt;/a&gt; but the problem is I a hesitant to do some tinkering with the fuse bits and all.  Is it safe to do so? &lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-27T05:29:09.963" LastActivityDate="2011-01-27T05:29:09.963" Title="Start off with embedded C with ATmega32 (ATmega AVR series)" Tags="&lt;avr&gt;&lt;atmega&gt;&lt;books&gt;&lt;c&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="2013" PostTypeId="2" ParentId="2012" CreationDate="2010-03-24T06:19:32.997" Score="4" ViewCount="" Body="&lt;p&gt;Join &lt;a href=&quot;http://www.avrfreaks.net/&quot; rel=&quot;nofollow&quot;&gt;AVR Freaks&lt;/a&gt;. You'll find lots of resources and help if you get stuck.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-24T06:19:32.997" />
  <row Id="2014" PostTypeId="2" ParentId="2007" CreationDate="2010-03-24T06:52:32.743" Score="5" ViewCount="" Body="&lt;p&gt;As is goes here is the dirty way. Every CD rom has a eject button right? Rip out the button and directly wire it using whatever input you have.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-03-24T06:52:32.743" CommentCount="3" />
  <row Id="2015" PostTypeId="2" ParentId="2012" CreationDate="2010-03-24T07:58:15.077" Score="4" ViewCount="" Body="&lt;p&gt;I would go with Arduino first. Lots of books, tutorials and example code. And a great and nice community. Then if you are familiar with Arduino, try out C with AVR-GCC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can not recommend ASM these days. There maybe some corners where you may have to use ASM but most things can be solved with plain C. With ASM you can learn some very details about how a microcontroller is working, but if you want to make things happen faster, I would stick to C or C++.     &lt;/p&gt;&#xA;" OwnerUserId="409" LastActivityDate="2010-03-24T07:58:15.077" CommentCount="2" />
  <row Id="2016" PostTypeId="2" ParentId="2012" CreationDate="2010-03-24T09:04:35.233" Score="4" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.nongnu.org/avr-libc/user-manual/index.html&quot; rel=&quot;nofollow&quot;&gt;avr-libc documentation&lt;/a&gt; is a great source of information for C on AVRs.&#xA;Here's &lt;a href=&quot;https://www.mainframe.cx/~ckuethe/avr-c-tutorial/&quot; rel=&quot;nofollow&quot;&gt;another one&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I prefer working in C. Making use of avr-libc gives you good code portability within the AVR family. However, if you're doing anything timing critical, you may have to resort to ASM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a parallel or &quot;high voltage&quot; &lt;a href=&quot;http://elm-chan.org/works/avrx/report_e.html&quot; rel=&quot;nofollow&quot;&gt;AVR programmer&lt;/a&gt; then you can always reprogram the fuse bits. If you're using serial (In-System-Programming, ISP) then be careful not to disable the SPIEN or RESETENABLE bits as these will prevent you from being able to reprogram.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's an &lt;a href=&quot;http://mightyohm.com/blog/2008/09/arduino-based-avr-high-voltage-programmer/&quot; rel=&quot;nofollow&quot;&gt;Arduino HV programming shield&lt;/a&gt; available.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-24T09:04:35.233" />
  <row Id="2017" PostTypeId="2" ParentId="2004" CreationDate="2010-03-24T09:10:26.797" Score="10" ViewCount="" Body="&lt;p&gt;On the practical side - get an Arduino. It's a great platform for sensor interfacing, rapid prototyping and exploring hardware.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-24T09:10:26.797" CommentCount="2" />
  <row Id="2018" PostTypeId="2" ParentId="1990" CreationDate="2010-03-24T12:39:33.850" Score="3" ViewCount="" Body="&lt;p&gt;I'm in Australia too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are no Australian fab houses (as far as I know) which will do small runs without large setup costs. I have used BatchPCB for commercially produced boards and found them to be good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I etch my own boards where I can - it's quite easy to do using toner transfer - a laser printer, some magazine pages, &amp;amp; some copper clad + ferric chloride etchant. It probably costs a dollar or two a board - I don't really think about the cost, given that I only do low volumes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm in Adelaide, I buy my stuff from Aztronics - it usually costs about $5 for a largish copper clad offcut, which lasts me a while, and about $10 for a few hundred mL of ferric chlroide, which again, lasts a while.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want more precision than you can get with toner transfer, you can use UV exposure for better results, combined with a bubble etching tank - you'll be able to do double sided boards too then.  &lt;/p&gt;&#xA;" OwnerUserId="358" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-10T03:53:43.897" LastActivityDate="2011-03-10T03:53:43.897" />
  <row Id="2019" PostTypeId="2" ParentId="2000" CreationDate="2010-03-24T14:12:58.960" Score="1" ViewCount="" Body="&lt;p&gt;I'm not sure about the overlay part, but you can generate an NTSC/PAL video signal on an AVR using &lt;a href=&quot;http://avga.prometheus4.com/&quot; rel=&quot;nofollow&quot;&gt;AVGA&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-24T14:12:58.960" />
  <row Id="2020" PostTypeId="2" ParentId="2012" CreationDate="2010-03-24T14:34:41.850" Score="4" ViewCount="" Body="&lt;p&gt;I would start off with C. You may need an occasional snippet of ASM but&#xA;for most applications that would be about it. The exception would be&#xA;a bootloader if you decide to roll your own.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dave Mellis put an AVR tutorial up on the MIT HLT wiki. He discusses&#xA;setting up the tools for the ATmega328 but it seems generic enough&#xA;to help you with different devices. See&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hlt.media.mit.edu/wiki/index.php/AVR_Programming&quot; rel=&quot;nofollow&quot;&gt;http://hlt.media.mit.edu/wiki/index.php/AVR_Programming&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The libraries and examples at the Atmel site seem to be good.&#xA;I have used a number of snippets from their app-notes. The I2C (TWI)&#xA;library I use in my RTC code comes from the Atmel site.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-27T03:30:16.943" LastActivityDate="2011-01-27T03:30:16.943" />
  <row Id="2021" PostTypeId="1" AcceptedAnswerId="2023" CreationDate="2010-03-24T14:35:12.020" Score="4" ViewCount="830" Body="&lt;p&gt;Could someone explain what &quot;bias&quot; is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And why do some devices need an external bias resistor?&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-05-18T11:30:49.203" Title="What is the purpose of a bias resistor?" Tags="&lt;bias&gt;&lt;resistor&gt;" AnswerCount="3" />
  <row Id="2022" PostTypeId="2" ParentId="2021" CreationDate="2010-03-24T14:46:51.483" Score="4" ViewCount="" Body="&lt;p&gt;The bias is the operating point. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a bipolar transistor (BJT) the bias resistor will maintain enough current into&#xA;the base so that the transistor is neither saturated (fully on) or cut-off (fully off).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some BJTs come with an internal bias resistor to reduce&#xA;the parts count in a design. If you are switching BJTs on or off you don't&#xA;need a &quot;bias&quot; resistor but you may need a resistor to limit &#xA;the current into the base.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:30:49.203" LastActivityDate="2011-05-18T11:30:49.203" />
  <row Id="2023" PostTypeId="2" ParentId="2021" CreationDate="2010-03-24T16:38:58.900" Score="7" ViewCount="" Body="&lt;p&gt;If your device is powered from a single voltage and ground, it can't output anything below ground.  In order to reproduce a signal that varies between +V and -V, you need to shift it upwards so that it varies from 0 to +2V instead.  The DC offset is the bias.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Biasing&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Biasing&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-03-24T16:38:58.900" CommentCount="3" />
  <row Id="2024" PostTypeId="1" AcceptedAnswerId="2026" CreationDate="2010-03-24T17:00:38.373" Score="6" ViewCount="1310" Body="&lt;p&gt;I believe that the answer is no, but I wanted to check before I put effort into rectifying it (and no, no promises!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there anything like &lt;a href=&quot;http://scratch.mit.edu&quot; rel=&quot;nofollow&quot;&gt;Scratch&lt;/a&gt; that one can use to program an Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Scratch is a graphical coding environment that makes learning to program fun, and is certainly suitable for elementary students.  It is put out by the Lifelong Kindergarten Group at MIT).&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-24T03:44:48.663" LastActivityDate="2011-05-13T12:47:32.460" Title="Is there a Scratch-like Arduino IDE?" Tags="&lt;arduino&gt;&lt;ide&gt;" AnswerCount="7" />
  <row Id="2025" PostTypeId="2" ParentId="2024" CreationDate="2010-03-24T17:09:27.777" Score="2" ViewCount="" Body="&lt;p&gt;This has been discussed at some length (for AVRs) here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;p=484219&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;p=484219&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-24T17:09:27.777" />
  <row Id="2026" PostTypeId="2" ParentId="2024" CreationDate="2010-03-24T17:11:00.777" Score="8" ViewCount="" Body="&lt;p&gt;It's in the works. A friend of mine, Ed Baafi, is working on a Scratch-like&#xA;interface for Arduino. I believe he may be presenting something in Cambridge (MA) at the&#xA;science festival this April.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a python shell script we (by we I mean Ed) were able to interface&#xA;one of my USB+XBee interfaces with the my ZB1 (arduino compatible board + XBee).&#xA;Text typed into an entry box was displayed on an LCD.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;His site is &lt;a href=&quot;http://www.modk.it&quot; rel=&quot;nofollow&quot;&gt;http://www.modk.it&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:47:32.460" LastActivityDate="2011-05-13T12:47:32.460" CommentCount="3" />
  <row Id="2028" PostTypeId="1" CreationDate="2010-03-24T18:05:35.700" Score="11" ViewCount="332" Body="&lt;p&gt;I'm looking into alternatives to LEGO Mindstorms for the robotics classes I teach (in an effort to find something less expensive and thus more readily accessible.)  I am working with children aged 11 and up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found a couple of interesting things lately, that one might call &quot;plug and play&quot; electronics.  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Seeed Studio puts out &lt;a href=&quot;http://www.seeedstudio.com/depot/electronic-brick-c-48.html&quot; rel=&quot;nofollow&quot;&gt;Electronic Bricks&lt;/a&gt;.  These look cool -- the components go together with cables (which I hope can not be attached incorrectly [without additional effort]) -- and the parts are reasonably inexpensive ($3-$15, instead of $35 to $65 for additional mindstorms sensors.]  The cables can then be plugged into a protoshield on an arduino, and voila!, you've got sensors.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Inex puts out &lt;a href=&quot;http://www.robotshop.ca/inex-en.html&quot; rel=&quot;nofollow&quot;&gt;some items&lt;/a&gt; that look a little bit similar, but not as extensive.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I should admit that I've got nothing against LEGO.  My main two ideas for getting the body of a robot include:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;using an arduino &lt;a href=&quot;http://letsmakerobots.com/node/15459&quot; rel=&quot;nofollow&quot;&gt;2WD&lt;/a&gt; or &lt;a href=&quot;http://www.seeedstudio.com/depot/4wd-arduino-robot-platform-global-free-shipping-p-554.html&quot; rel=&quot;nofollow&quot;&gt;4WD&lt;/a&gt; driving base.  (The downside to this is that you can't rebuild your robot in imaginative ways).&lt;/li&gt;&#xA;&lt;li&gt;using LEGO, with, say, a &lt;a href=&quot;http://www.mindsensors.com/index.php?module=pagemaster&amp;amp;PAGE_user_op=view_page&amp;amp;PAGE_id=117&amp;amp;MMN_position=41:41&quot; rel=&quot;nofollow&quot;&gt;servo-to-LEGO adapter&lt;/a&gt; (or possibly by using existing LEGO motors and interfacing them to an arduino/MCU).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;What other hardware-related electronics/robotics things should I be considering?&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="106" LastEditorDisplayName="" LastEditDate="2010-03-24T20:58:45.060" LastActivityDate="2010-03-24T22:40:30.803" Title="Newbie-friendly electronics (and robotics)" Tags="&lt;arduino&gt;&lt;robotics&gt;" AnswerCount="1" FavoriteCount="6" />
  <row Id="2029" PostTypeId="1" CreationDate="2010-03-24T19:06:56.243" Score="6" ViewCount="157" Body="&lt;p&gt;Does anyone know if it is possible to file physical objects under creative commons or something similar?  I don't want to make money off anything I make, I want to show the public how to make it and if someone uses one of my creations for a not for profit cause then all the better. That being said I also don't want someone else profiting off something I have created.  Any suggestions would be great!&lt;/p&gt;&#xA;" OwnerUserId="657" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-29T16:42:18.167" LastActivityDate="2011-05-18T11:31:02.913" Title="Creative Commons for physical objects?" Tags="&lt;licensing&gt;&lt;legal&gt;" AnswerCount="6" />
  <row Id="2030" PostTypeId="2" ParentId="2029" CreationDate="2010-03-24T19:47:26.663" Score="3" ViewCount="" Body="&lt;p&gt;Similar question: &lt;a href=&quot;http://chiphacker.com/questions/1128/best-licenses-for-open-hardware&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/1128/best-licenses-for-open-hardware&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Creative Commons can be applied to anything that's copyrightable.  PCB layouts are copyrighted all the time, which is what most companies try to do to protect their designs, but anyone can re-design the same circuit and it won't be a violation, just like paraphrasing text.  You can copyright creative expression, but you can't copyright an idea.  To protect a circuit, you need to get a patent on it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even &lt;a href=&quot;http://en.wikipedia.org/wiki/Copyright_in_architecture_in_the_United_States&quot; rel=&quot;nofollow&quot;&gt;architecture can be copyrighted&lt;/a&gt; in some places.  The number of things you can copyright and the length of time they're protected is increasing all the time...&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-03-24T19:47:26.663" />
  <row Id="2031" PostTypeId="2" ParentId="2029" CreationDate="2010-03-24T19:50:21.777" Score="3" ViewCount="" Body="&lt;p&gt;Unless you patent your idea and grant rights there is no legal&#xA;way (in the U.S.) to prevent someone from using your idea for&#xA;any purpose. Creative Commons (copyright protection) only &#xA;protects the documentation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If someone rewrites the documentation then they hold&#xA;the copyright to the new documentation. If they copy &#xA;significant pieces you may have some recourse.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:31:02.913" LastActivityDate="2011-05-18T11:31:02.913" />
  <row Id="2032" PostTypeId="2" ParentId="2029" CreationDate="2010-03-24T20:10:49.440" Score="5" ViewCount="" Body="&lt;p&gt;I understand your concerns, but even if you were able to protect your ideas (see @endolith, @jluciani) you would still face the &quot;make me&quot; crowd.  That is, people who will make money off your design anyway.  When you remind them that they can't (if you've gone through the effort and expense of a patent), they may just say &quot;make me&quot;.  Then you have court costs on TOP of everything else.  Sure, if it's a clear-cut case you may be able to get a lawyer to take on your case without charge (knowing the reward will be huge), but it's still an incredible time sink, and that's if you're lucky.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd say, just go ahead and say your work is under the spirit of the license.  People may try to make money off of it anyway, and by just putting it out there you save yourself a lot of time, money and effort.  Honestly, you're more likely to get some consulting side gigs out of it if you build something really cool.  Of course, that's my opinion on the subject and it doesn't really give you the answer you were looking for.&lt;/p&gt;&#xA;" OwnerUserId="11" LastActivityDate="2010-03-24T20:10:49.440" />
  <row Id="2033" PostTypeId="2" ParentId="2029" CreationDate="2010-03-24T20:14:37.560" Score="2" ViewCount="" Body="&lt;p&gt;&quot;I also don't want someone else profiting off something I have created.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that's the wrong attitude.&#xA;Making and selling something usually requires more effort (and is IMHO less fun) than designing something, so using your idea commercially wouldn't be freeloading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And you gain more the more your design is used.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-03-24T20:14:37.560" CommentCount="2" />
  <row Id="2034" PostTypeId="2" ParentId="2028" CreationDate="2010-03-24T22:40:30.803" Score="5" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.pololu.com/catalog/product/975&quot; rel=&quot;nofollow&quot;&gt;Pololu 3pi&lt;/a&gt; looks interesting. Arduino-compatible and speedy. It's not dissimilar to the Logo turtle or Big-Trak I had as a kid :-)&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-24T22:40:30.803" CommentCount="1" />
  <row Id="2035" PostTypeId="2" ParentId="2029" CreationDate="2010-03-24T22:46:06.570" Score="4" ViewCount="" Body="&lt;p&gt;Try this one, it should do the trick -&gt; &lt;a href=&quot;http://creativecommons.org/licenses/by-nc/3.0/&quot; rel=&quot;nofollow&quot;&gt;Non-commercial CC license&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's more effective than any patent for what you need - as an individual or small business you couldn't afford to do anything in the way protecting your product from the big guns.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The big boys use multiple patents and trade marks - plus they have a colossal legal team to back them up in a court of law. So from that point of view, there's fairly little you can do to protect your ideas. However - the Non-commercial CC license should protect you from the majority of idiots from running off with your hard work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good Luck!&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-03-24T22:54:41.290" LastActivityDate="2010-03-24T22:54:41.290" />
  <row Id="2036" PostTypeId="1" AcceptedAnswerId="2037" CreationDate="2010-03-24T23:12:27.253" Score="22" ViewCount="3353" Body="&lt;p&gt;Can anyone recommend a low cost or DIY buildable logic analyzer?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mostly, it would be for debugging serial protocols (SPI, I2C, RS232) at low voltages.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-18T02:29:31.530" LastActivityDate="2011-02-18T02:29:31.530" Title="Beginner's logic analyzer?" Tags="&lt;logic&gt;&lt;logic-analyzer&gt;&lt;equipment&gt;" AnswerCount="13" FavoriteCount="14" />
  <row Id="2037" PostTypeId="2" ParentId="2036" CreationDate="2010-03-24T23:47:44.357" Score="28" ViewCount="" Body="&lt;p&gt;The Bus Pirate is probably your best bet - open source software and hardware, easy to build if you don't mind SMT, cheap if you buy it assembled ($30 shipped worldwide).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/the-bus-pirate/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/the-bus-pirate/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lots of variants, with a lot of people supporting it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/search?q=bus+pirate&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/search?q=bus+pirate&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bus pirate is mostly useful for serial work, though it can do some small amount of simple logic analyzer functions.  If you need to do a lot of logic analyzer work, this product looks very nice:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dangerousprototypes.com/open-logic-sniffer/&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com/open-logic-sniffer/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Open source, but has very good capabilities.  Pre-ordering right now, so it's not immediately available.  Very inexpensive, though.&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="161" LastEditorDisplayName="" LastEditDate="2010-03-25T00:01:50.757" LastActivityDate="2010-03-25T00:01:50.757" CommentCount="5" />
  <row Id="2038" PostTypeId="2" ParentId="2036" CreationDate="2010-03-25T00:35:58.300" Score="8" ViewCount="" Body="&lt;p&gt;Not sure if this matches your definition of low-cost but the Saleae Logic Pod is around&#xA;$150. Eight channels and works well for decoding SPI and I2C. Haven't tried any&#xA;other protocols. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The software is OK but the interface seems a little strange compared to an oscilloscope&#xA;or real logic analyzer. On the website there was mention of an API definition so that&#xA;you could write your software interface or scripted data collection. I haven't had time &#xA;to look into this any further. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure if the levels go negative for true RS232 work.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-12-23T00:23:46.090" LastActivityDate="2010-12-23T00:23:46.090" CommentCount="5" />
  <row Id="2039" PostTypeId="2" ParentId="2036" CreationDate="2010-03-25T09:34:09.737" Score="8" ViewCount="" Body="&lt;p&gt;There is the &lt;a href=&quot;http://www.sump.org/projects/analyzer/&quot; rel=&quot;nofollow&quot;&gt;Sump.org&lt;/a&gt; logic analyser, using a low-cost ($99) Digilent Spartan 3 board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For slow stuff like I2C and SPI, you could use a Microchip PICkit 2 ($35). It comes with three-channel logic analyser software.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-25T09:34:09.737" CommentCount="2" />
  <row Id="2040" PostTypeId="2" ParentId="2029" CreationDate="2010-03-25T14:10:10.927" Score="2" ViewCount="" Body="&lt;p&gt;Very, very few ideas are worth commercializing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Those ideas that are worth it are very hard to commercialize.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given that, you can release everything of yours into the public domain, and it's such a low chance that someone will profit off it that it's probably not worrying about.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you will reap great rewards through simply showing people that you can do particular work well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Further, the people who would rip you off are not your customers - in fact they could likely do the work themselves, but are seeking a shortcut for an idea they already have.  Your customers are people who can't do what you can do, and can't do what the people who would rip you off can do.  So there's really no conflict of interest.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you successfully protect your work from being used commercially, it doesn't mean those people are going to fall in line and license your design - it just makes them look for another way to accomplish their goals without being caught, or without doing something that would fall afoul of the law.  Any effort you put into protecting your work is wasted - you should instead spend it on creating more, and protecting less.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So there's no benefit to protecting your work:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Ideas are rarely worth commercializing&lt;/li&gt;&#xA;&lt;li&gt;Good ideas are very hard to commercialize&lt;/li&gt;&#xA;&lt;li&gt;The people who would steal it aren't your target audience&lt;/li&gt;&#xA;&lt;li&gt;Your target audience isn't going to be able to steal it&lt;/li&gt;&#xA;&lt;li&gt;The people who steal it will find a way around any roadblock you put up anyway&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-25T14:10:10.927" />
  <row Id="2041" PostTypeId="1" CreationDate="2010-03-25T14:50:01.050" Score="5" ViewCount="945" Body="&lt;p&gt;Under what circumstances should I prefer a continuous rotation 'servo' to a DC motor, or vice versa?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems to me that to use a DC motor, I'm going to need three pins from an MCU -- two for forward/backward/brake/coast and one for PWM.  On top of that, I'll need an H-Bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a continuous rotation servo, I'll only need one signal pin and some code to send proper timing signals.  I can't control the speed of the servo, can I?  Also, it must have something akin to an h-bridge inside the motor, which surely ups the cost, but the motor will always be geared, which is a plus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, what are the pros and cons of each, and when should I choose one over the other?&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2010-05-27T21:28:09.857" Title="Continuous rotation 'servo' vs DC motor" Tags="&lt;motor&gt;&lt;servo&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="1" />
  <row Id="2042" PostTypeId="2" ParentId="2041" CreationDate="2010-03-25T16:19:10.790" Score="6" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;I can't control the speed of the servo, can I?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes, you can, but not to a very good degree of control&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Also, it must have something akin to an h-bridge inside the motor, which surely ups the cost, but the motor will always be geared, which is a plus.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Continuous rotation servo:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Gearing&lt;/li&gt;&#xA;&lt;li&gt;Built in motor driver&lt;/li&gt;&#xA;&lt;li&gt;Single pin control (forward, reverse, speed)&lt;/li&gt;&#xA;&lt;li&gt;Easy to mount the servo, and to attach movements to the horn&lt;/li&gt;&#xA;&lt;li&gt;Hard to 'center' due to temperature drift - ie, without feedback you can't ever fully stop a servo, and even with feedback it continues to hunt for 0, and induces vibration into the mechanism&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Motor:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Cheaper (even with gearing, especially in quantity)&lt;/li&gt;&#xA;&lt;li&gt;Greater degree of control with a good motor driver&lt;/li&gt;&#xA;&lt;li&gt;Doesn't require a PWM signal&lt;/li&gt;&#xA;&lt;li&gt;Smaller&lt;/li&gt;&#xA;&lt;li&gt;Lower power consumption for most applications&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-25T16:19:10.790" />
  <row Id="2043" PostTypeId="2" ParentId="1869" CreationDate="2010-03-25T17:19:35.843" Score="3" ViewCount="" Body="&lt;p&gt;The gyrator thing is a lot less useful than it looks in theory (I have never encountered one in an application).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jason is right that you can only get +/-90 phase shift from one capacitor/inductor. On the other hand you can easily make a chain by combining several such RC/RL networks and get a phase shift of any angle (just be aware that in a passive network the stages influence each other so calculating the required circuit may not be an easy task).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The real problem is that you cannot change the frequency dependency of a capacitor so you can always easily discriminate between them by changing the input signal frequency.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-03-25T17:19:35.843" />
  <row Id="2044" PostTypeId="1" AcceptedAnswerId="2058" CreationDate="2010-03-25T18:05:56.020" Score="3" ViewCount="1117" Body="&lt;p&gt;I am looking for a way to put a Arduino with an Ethernet shield inside a DIN rail enclosure while exposing the RJ45 and a few screw terminals. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bare min: 55mm Width, 75mm length, 30mm height. &#xA;Looks similar this &lt;a href=&quot;http://arduino.cc/en/uploads/Guide/ArduinoWithEthernetShield.jpg&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/uploads/Guide/ArduinoWithEthernetShield.jpg&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Parts list: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9026&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9026&lt;/a&gt; sitting on top of &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=666&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=666&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The problem we are having is how to expose the RJ45 connector. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We were thinking of finding an enclosure that supports a RJ45 Keystone and running wires from the board to the exposed terminals but we haven't found anything like that yet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We where also thinking about getting the two boards &lt;a href=&quot;http://chiphacker.com/questions/1807/redesigning-the-arduino-duemilanove-and-ethernet-shield-in-to-a-single-board&quot; rel=&quot;nofollow&quot;&gt;redesigned in to a single board&lt;/a&gt; that fits a existing enclosure. But that would cost 1000s of dolors. Or at lest thats what I been quoted.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I been searching and phoning people for about a week without finding an answer. I'm  looking for suggestions, hints, wild guess, anything?&lt;/p&gt;&#xA;" OwnerUserId="592" LastActivityDate="2011-05-18T11:39:17.467" Title="DIN rail enclosure for a Arduino + Ethernet shield" Tags="&lt;arduino&gt;&lt;enclosure&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="2045" PostTypeId="2" ParentId="2044" CreationDate="2010-03-25T22:50:17.350" Score="2" ViewCount="" Body="&lt;p&gt;There are variety of blank DIN enclosures. Are you saying you&#xA;couldn't find one large enough for the combination of boards?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a feedthru connector something like the Neutrik NE8FDP &#xA;should work. You just need to drill three round holes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a professional to design, prototype and document a single&#xA;board it would probably be in the $2K-$3K range.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:39:17.467" LastActivityDate="2011-05-18T11:39:17.467" />
  <row Id="2046" PostTypeId="2" ParentId="1990" CreationDate="2010-03-26T04:27:08.663" Score="5" ViewCount="" Body="&lt;p&gt;Yeah I do the laser printer transfer method, if you work in an office with a laser printer you could probably sneak a couple of prints for prototypes.  I would highly suggest using a laminator and not an iron for the transfers, you will get much more crisp results.  I regularly use the method for smd components with small lead spaces without any problems.  I use a mixture of muriatic acid, hydrogen peroxide, and water for my etching.  I would also suggest a fish tank air pump with a ceramic (not the blue ones, they will dissolve) aerator.  It will etch a 3.5 by 5 inch pcb board in about 8 min and the solution can be used over and over again if the aerator is left on in solution.  Laser printer $80, laminator $30, fish tank pump and aerator $15, muriatic acid and hydrogen peroxide $8 and stack of 10 12&quot; x 6&quot; copper clad boards about $15 dollars on ebay so it's about a $150 dollar investment in the beginning but you can cut most of your costs by borrowing a laser printer. It is more than worth it though because you can design and test out your boards all within an afternoon so the prototype phase is much shorter.  I know this is a shameless plug but here are some example results from my website &lt;a href=&quot;http://www.aaronalai.com/ultrasonic-navigation&quot; rel=&quot;nofollow&quot;&gt;http://www.aaronalai.com/ultrasonic-navigation&lt;/a&gt; and &lt;a href=&quot;http://www.aaronalai.com/business-card&quot; rel=&quot;nofollow&quot;&gt;http://www.aaronalai.com/business-card&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="657" LastActivityDate="2010-03-26T04:27:08.663" />
  <row Id="2047" PostTypeId="1" AcceptedAnswerId="2048" CreationDate="2010-03-26T05:03:37.087" Score="5" ViewCount="798" Body="&lt;p&gt;BGA seems to be somewhat of a showstopper for the diy community, especially with the newer more powerful parts being almost exclusively bga.  I know it can be done with the skillet/toaster oven method, but it seems like there is no way of inspecting for defects without an x-ray machine except   for maybe this method &lt;a href=&quot;http://www.jlime.com/mw4/index.php/Accessing_BGA_pins&quot; rel=&quot;nofollow&quot;&gt;using toothbrush bristles&lt;/a&gt;.  So is reflowing using these methods relatively high yielding or is this just not worth doing at home?&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-03-26T17:13:09.587" Title="DIY BGA soldering feasability" Tags="&lt;reflow&gt;&lt;bga&gt;&lt;soldering&gt;" AnswerCount="3" />
  <row Id="2048" PostTypeId="2" ParentId="2047" CreationDate="2010-03-26T05:11:37.273" Score="6" ViewCount="" Body="&lt;p&gt;I've heard of people doing it successfully, so it can be done, with some care and the right equipment. When the solder paste melts the chip aligns itself better than a fine-pitch QFP, so it can actually be easier than the latter. I'd be happier about doing it with an FPGA, as any missing connections could be corrected by rerouting the signals. The PCB has to be properly designed, of course.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd start with a QFN chip, they have some similarities to a BGA. If that works, I'd have some confidence that a BGA would be successful.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-03-26T05:19:37.087" LastActivityDate="2010-03-26T05:19:37.087" CommentCount="1" />
  <row Id="2049" PostTypeId="2" ParentId="2047" CreationDate="2010-03-26T06:32:17.480" Score="0" ViewCount="" Body="&lt;p&gt;You could try to do a JTAG boundary scan, if the chip supports that.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-03-26T06:32:17.480" />
  <row Id="2050" PostTypeId="2" ParentId="1024" CreationDate="2010-03-26T06:45:31.507" Score="13" ViewCount="" Body="&lt;p&gt;Surprised no one mentioned &lt;a href=&quot;http://kicad.sourceforge.net&quot; rel=&quot;nofollow&quot;&gt;KiCAD&lt;/a&gt;.  It doesn't do &lt;a href=&quot;http://en.wikipedia.org/wiki/ISO_15504&quot; rel=&quot;nofollow&quot;&gt;SPICE&lt;/a&gt; simulations, but handles pretty much everything else.  You might be able to use other &lt;a href=&quot;http://en.wikipedia.org/wiki/ISO_15504&quot; rel=&quot;nofollow&quot;&gt;SPICE&lt;/a&gt; tools with it's netlist, but I haven't tried.&lt;/p&gt;&#xA;" OwnerUserId="625" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-04-19T16:59:37.373" LastActivityDate="2011-04-19T16:59:37.373" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="6" />
  <row Id="2051" PostTypeId="2" ParentId="1009" CreationDate="2010-03-26T07:04:50.057" Score="1" ViewCount="" Body="&lt;p&gt;I personally have not used the QP framework/library, because of the GPL license.  At the time, I didn't think my employer was ready to cough up the dough for me to experiment with HSM's (hierarchical state machines) using QP.  I had to implement my own that was similar to QP when I was refactoring an awful state machine that took up hundreds of lines of code like Joby's example but times 1000. The old design which was borrowed to get features up in running on a tight deadline was a terrible pain to maintain.  I dreaded trying to add something new to it for fear of breaking something else.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I redesigned the code into an HSM that made a lot more sense to me personally on how the system should behave. It worked far better than I could imagine.  It was so much easier to modify and maintain then I could ever dream.  I even had to almost redo much of the state machine, because of unexpected behavior in system.  It was so much easier to fix with the framework I had made, and I'm sure it would have been just as easy in QP.  The framework I built became popular and spread to some other complex state machines inside our codebase.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did have a friend implement the quantum framework using Java in a robot that worked out pretty well.  It was part of the robot's decision making algorithm based on certain inputs. It was natural fit, given the decisions it had to make based on the robot's state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I understand of the beauty of QP is the ability to have a ready to framework for a state machine design that is optimized for your processor and not have to rely on CASE tools spitting out inefficient boilerplate code.  But, I would only use QP if you have set of complex set of state machines to implement that describe your design. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If all you have is something as simple as Joby's example, then just do it like he explained.  But if you find your state machine growing and growing with all kinds of &quot;if else&quot; statements wrapped around different conditions...then it might be time to try something like QP to break it down into HSM's.&lt;/p&gt;&#xA;" OwnerUserId="625" LastEditorUserId="625" LastEditorDisplayName="" LastEditDate="2010-03-26T07:09:54.327" LastActivityDate="2010-03-26T07:09:54.327" />
  <row Id="2052" PostTypeId="2" ParentId="2047" CreationDate="2010-03-26T17:13:09.587" Score="4" ViewCount="" Body="&lt;p&gt;As part of my old job I had to build some boards with the Foxconn 478 pin BGA socket for the old P4s.  It was the first component I put on the board.  My technician and I did it by hand, using a little jig he made to line everything up right.  You'll need a mask for screen printing the solder.  I used post-it notes to set the snapoff distance, I think it was 2 or 3 post it notes thick.  Reflow with a toaster oven (I had a nice reflow oven back then).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We yielded about 8/10 boards, maybe a little less.  Usually the fails had everything off a row, but occasionally one would line up between pads and short everything (big mess, obviously my pad masking wasn't quite right).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it's doable, by hand, if you are careful.  Do it first, with nothing else on the board.  If there are more than one BGA on the board your yield will be poor unless the pad spacing is large enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It just occurred to me that we could have tried buzzing out the board; there were a pair of voltage sense pins that we could have used.  That might have prevented some of the off-by-one-row alignment errors and shorting that we experienced, but the sockets were only about 5$ a piece.&lt;/p&gt;&#xA;" LastActivityDate="2010-03-26T17:13:09.587" />
  <row Id="2053" PostTypeId="2" ParentId="1009" CreationDate="2010-03-26T17:37:54.957" Score="1" ViewCount="" Body="&lt;p&gt;Expanding on Joby's example a cleaner way to implement a very large state machine is to replace the case statement with an array of function pointers. Then you can isolate all of the code for a particular state inside a function. I've found that implementing it this way requires far less program memory.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-03-26T17:37:54.957" />
  <row Id="2054" PostTypeId="2" ParentId="1953" CreationDate="2010-03-26T18:01:23.973" Score="0" ViewCount="" Body="&lt;p&gt;Another option for programming your microcontroller is to create a bootstrap/bootloader code that fits in the 4K flash of the chip. That code will contain serial port driver, xmodem/ymodem protocol support for downloads, and flash programming code. Put a bigger flash on the board for holding your main program code.  All this boot code (4k internal flash) does it start the chip with a boot output to the serial port giving the user a boot options to reprogram the bigger flash or just go ahead and boot from the big flash (main code resides).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We've used similar setups at my previous employers with 8051, but we usually didn't have internal flashes.  Of course we always had serial port boot options for reprogramming our external flash.&lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2010-03-26T18:01:23.973" />
  <row Id="2055" PostTypeId="1" AcceptedAnswerId="2071" CreationDate="2010-03-26T21:12:20.463" Score="5" ViewCount="519" Body="&lt;p&gt;I've been thinking about doing some electronic learning classes for my very large homeschool group.  The age range would be 12-18 years of age, and possibly broken up into separate age groups.  I would like to incorporate the full gambit of practical hardware and software.  I'm looking for other great ideas that some of you hackers may have if you were going to teach the younger generation.  How you format the class, and how would you go about it? What kind of material would you cover based on age range? Let your imagination go wild if you want!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone has actually done something like this before college, let me know your experience please as to what was good and what was bad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some project ideas that I have had:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Build a robot (of course that's obvious) along with possible BEST/Lego league competitions.&lt;/li&gt;&#xA;&lt;li&gt;Build a rocket with camera and sensors onboard.&lt;/li&gt;&#xA;&lt;li&gt;Homemade mp3 player&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I also require this to be as low cost as possible, so I can use good ideas as well in various areas.  I know Chiphacker has covered some this low cost areas in other questions such as PCB manufacturing, schematic entry, development boards, and toolchains.&lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2011-05-16T10:42:44.187" Title="Any good suggestions for a beginning electronics class for youth?" Tags="&lt;beginner&gt;&lt;electronics&gt;" AnswerCount="4" FavoriteCount="4" />
  <row Id="2056" PostTypeId="2" ParentId="297" CreationDate="2010-03-27T00:03:53.860" Score="2" ViewCount="" Body="&lt;p&gt;Lots of the TI Luminary microcontrollers (ARM Cortex-M3) have an onboard ethernet MAC. It needs an external crystal and ethernet PHY (connector + magnetics).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GCC and openOCD (JTAG flashing/debugging) support them well and they're pretty cheap in quantity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have cheap hardware devkits too...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.farnell.com/luminary-micro/ekt-lm3s811/kit-eval-lm3s811-code-red/dp/1712254&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/luminary-micro/ekt-lm3s811/kit-eval-lm3s811-code-red/dp/1712254&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-03-27T00:03:53.860" />
  <row Id="2057" PostTypeId="1" CreationDate="2010-03-27T00:15:07.940" Score="9" ViewCount="974" Body="&lt;p&gt;I can make monophonic sounds by toggling a single pin (&lt;a href=&quot;http://www.phy.mtu.edu/~suits/notefreqs.html&quot; rel=&quot;nofollow&quot;&gt;at a varying rate&lt;/a&gt;) connected to a piezo buzzer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I generate two mixed audio signals in software to create polyphony?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the code I'm using to play a simple tune.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define F_CPU 8000000UL // 8MHz&#xA;#include &amp;lt;avr/io.h&amp;gt;&#xA;#include &amp;lt;avr/interrupt.h&amp;gt;&#xA;#include &amp;lt;avr/delay.h&amp;gt;&#xA;&#xA;// number of timer0 overflows/sec&#xA;#define INT_PER_SEC 31250&#xA;&#xA;// Frequencies (in Hz) of notes&#xA;#define F_FSH_4 370&#xA;#define F_A_4 440&#xA;#define F_B_4 494&#xA;#define F_E_4 330&#xA;#define F_CSH_5 554&#xA;#define F_D_5 587&#xA;#define F_FSH_5 740&#xA;#define F_CSH_4 277&#xA;#define F_GSH_4 415&#xA;&#xA;// number of timer0 overflows for notes&#xA;#define REST -1 // special case&#xA;#define FSH_4 INT_PER_SEC/F_FSH_4&#xA;#define A_4 INT_PER_SEC/F_A_4&#xA;#define B_4 INT_PER_SEC/F_B_4&#xA;#define E_4 INT_PER_SEC/F_E_4&#xA;#define CSH_5 INT_PER_SEC/F_CSH_5&#xA;#define D_5 INT_PER_SEC/F_D_5&#xA;#define FSH_5 INT_PER_SEC/F_FSH_5&#xA;#define CSH_4 INT_PER_SEC/F_CSH_4&#xA;#define GSH_4 INT_PER_SEC/F_GSH_4&#xA;&#xA;#define SEMIQUAVER_TIME 60  // ms&#xA;#define BREATH_TIME 20      // ms&#xA;&#xA;volatile uint32_t intrs = 0;&#xA;volatile int32_t curNote = REST;&#xA;&#xA;// TIMER0 overflow&#xA;ISR(TIMER0_OVF_vect)&#xA;{&#xA;    if (curNote == REST)&#xA;        intrs = 0;&#xA;    else&#xA;    {&#xA;        intrs++;&#xA;        if (intrs &amp;gt;= curNote)&#xA;        {&#xA;            PORTD ^= _BV(PD4);&#xA;            intrs = 0;&#xA;        }&#xA;    }&#xA;}&#xA;&#xA;&#xA;void play(int32_t note, uint32_t len)&#xA;{&#xA;    int i;&#xA;    curNote = note;&#xA;    for (i = 0; i&amp;lt; len; i++)&#xA;        _delay_ms(SEMIQUAVER_TIME);&#xA;    curNote = REST;&#xA;    _delay_ms(BREATH_TIME);&#xA;}&#xA;&#xA;int main(void)&#xA;{&#xA;    /* setup clock divider. Timer0 overflows on counting to 256.&#xA;     * 8Mhz / 1 (CS0=1) = 8000000 increments/sec. Overflows every 256, so 31250&#xA;     * overflow interrupts/sec */&#xA;    TCCR0B |= _BV(CS00);&#xA;&#xA;    // enable overflow interrupts&#xA;    TIMSK0 |= _BV(TOIE0);&#xA;&#xA;    // PD4 as output&#xA;    DDRD = _BV(PD4);&#xA;&#xA;    TCNT0 = 0;&#xA;    intrs = 0;&#xA;&#xA;    curNote = REST;&#xA;&#xA;    // enable interrupts&#xA;    sei();&#xA;&#xA;    while (1)&#xA;    {&#xA;        // Axel F&#xA;        play(FSH_4, 2);&#xA;        play(REST, 2);&#xA;        play(A_4, 3);&#xA;        play(FSH_4, 2);&#xA;        play(FSH_4, 1);&#xA;        play(B_4, 2);&#xA;        play(FSH_4, 2);&#xA;        play(E_4, 2);&#xA;        play(FSH_4, 2);&#xA;        play(REST, 2);&#xA;        play(CSH_5, 3);&#xA;        play(FSH_4, 2);&#xA;        play(FSH_4, 1);&#xA;        play(D_5, 2);&#xA;        play(CSH_5, 2);&#xA;        play(A_4, 2);&#xA;        play(FSH_4, 2);&#xA;        play(CSH_5, 2);&#xA;        play(FSH_5, 2);&#xA;        play(FSH_4, 1);&#xA;        play(E_4, 2);&#xA;        play(E_4, 1);&#xA;        play(CSH_4, 2);&#xA;        play(GSH_4, 2);&#xA;        play(FSH_4, 6);&#xA;        play(REST, 12);&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="566" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-03-28T03:42:26.743" LastActivityDate="2011-06-04T22:16:42.760" Title="Polyphonic sounds from a microcontroller?" Tags="&lt;music&gt;&lt;sound&gt;&lt;audio&gt;" AnswerCount="12" CommentCount="7" FavoriteCount="4" />
  <row Id="2058" PostTypeId="2" ParentId="2044" CreationDate="2010-03-27T01:14:48.617" Score="2" ViewCount="" Body="&lt;p&gt;You could design and build your own with laser cut panels. This guy's arduino and shield look the same as yours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.iheartrobotics.com/search/label/A%20Case&quot; rel=&quot;nofollow&quot;&gt;http://www.iheartrobotics.com/search/label/A%20Case&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.iheartrobotics.com/2010/03/case-for-arduino-laser-cutouts.html?utm_source=feedburner&amp;amp;utm_medium=feed&amp;amp;utm_campaign=Feed%3A+IHeartRobotics+%28I+Heart+Robotics%29&quot; rel=&quot;nofollow&quot;&gt;http://www.iheartrobotics.com/2010/03/case-for-arduino-laser-cutouts.html?utm_source=feedburner&amp;amp;utm_medium=feed&amp;amp;utm_campaign=Feed%3A+IHeartRobotics+%28I+Heart+Robotics%29&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.shapeways.com/model/85671/arduino_case.html&quot; rel=&quot;nofollow&quot;&gt;http://www.shapeways.com/model/85671/arduino_case.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-03-27T08:03:47.837" LastActivityDate="2010-03-27T08:03:47.837" />
  <row Id="2059" PostTypeId="2" ParentId="2057" CreationDate="2010-03-27T01:56:02.713" Score="1" ViewCount="" Body="&lt;p&gt;They used to do this on old game systems and in the days of &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/PC_speaker&quot; rel=&quot;nofollow&quot;&gt;PC speakers&lt;/a&gt;&quot;, but I don't know how.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First guess: Think of the wave you would ideally make, then imagine distorting it into a heavily clipped square shape, then create that square shape by toggling your output at the appropriate times.  Would have lots of &lt;a href=&quot;http://en.wikipedia.org/wiki/Intermodulation&quot; rel=&quot;nofollow&quot;&gt;intermodulation&lt;/a&gt;, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second thought: Can you greatly increase the frequency of oscillation and &lt;a href=&quot;http://en.wikipedia.org/wiki/Class_D_amplifier&quot; rel=&quot;nofollow&quot;&gt;output analog signals PWM-style&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-03-27T01:56:02.713" CommentCount="2" />
  <row Id="2060" PostTypeId="2" ParentId="2057" CreationDate="2010-03-27T02:21:39.150" Score="1" ViewCount="" Body="&lt;p&gt;I believe there is a tone library for the Arduino that does two tones. &#xA;You should be able to adapt the code to the AVR chip you are using.&#xA;There are also a couple of excellent waveform generation threads&#xA;at arduino.cc&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you decide to add a DAC I have a numerically controlled&#xA;oscillator example at &lt;a href=&quot;http://wiblocks.luciani.org/docs/app-notes/nb1a-nco.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/docs/app-notes/nb1a-nco.html&lt;/a&gt;&#xA;Four independent output channels. The quad DAC and reference is only&#xA;about $2 or so.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-03T08:39:53.880" LastActivityDate="2011-02-03T08:39:53.880" />
  <row Id="2061" PostTypeId="2" ParentId="2055" CreationDate="2010-03-27T02:30:00.727" Score="5" ViewCount="" Body="&lt;p&gt;I would take a look at &quot;Make: Electronics&quot; by Charles Platt. For the younger&#xA;kids you could start at the beginning. For the older kids you could either&#xA;go rapidly through the beginning or skip it. The Arduino book could also work too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may be able to get some projects ideas from Making Things Talk. I would add&#xA;some audio projects -- something that beeps and buzzes. A drawdio is always a hit&#xA;and is a very easy first project.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:42:44.187" LastActivityDate="2011-05-16T10:42:44.187" CommentCount="2" />
  <row Id="2062" PostTypeId="2" ParentId="2057" CreationDate="2010-03-27T05:24:33.450" Score="7" ViewCount="" Body="&lt;p&gt;Well one easy trick is to use two pins with PWM, and tie them to the opposite sides of the speaker. Then modulate each pin at a different speed, and you can play two notes at once...basically the speaker is mixing them together for you. More than two notes and you will have to do it in software as mentioned.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-03-27T05:24:33.450" CommentCount="1" />
  <row Id="2063" PostTypeId="2" ParentId="2055" CreationDate="2010-03-27T06:08:38.483" Score="4" ViewCount="" Body="&lt;p&gt;I second @jluciani. These are excellent books. Anything from Make is always good I think. Making things talk is fun to go through. I think you have a constrain over time so the project I would suggest are:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;Experiment 31 : One Radio, No Solder, No Power&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically a Crystal Radio. Can anyone please tell me if the frequencies it can catch are still around? I think it can catch only AM. But you can teach them how to make an AM transmitter (see here for a simple one&lt;a href=&quot;http://sci-toys.com/scitoys/scitoys/radio/am_transmitter.html&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt; ) or make on your own and have something like a Fox Hunt (game details below).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;Experiment 34: Hardware Meets Software&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nice starting point in microcontrollers.Uses PicAxes but they are hard to find I think. But you know &quot;where there is a will there is a way&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One Game for your Class&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;Fox Hunt:&lt;/em&gt;&lt;/strong&gt; This is one game we had in the recent techfest of your college. We did this with proper trasmitters and recivers but you can use crystal radios and AM transmitters.&#xA;(here is a slightly modified version for one transmitter)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hide one transmitter somewhere in the building. Set it to transmit pulses like a homing beacon (but audio pulses for crystal radio receiving and keep the power low if you have a small one). Now crystal radio has a property that reception becomes better as you approach the transmitter. Make a group of 2 students (or if everyone can make the cheap radio you can have every man/woman of there own). Set them free and whoever finds the transmitter first wins. You can give some clues as to where is the transmitter in the form of a riddle(don't give away the whole thing just give general directions). Make it a point that the transmitter power is very low or they will have full signal everywhere in a small area.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="1200" LastEditorDisplayName="" LastEditDate="2010-03-27T13:58:20.297" LastActivityDate="2010-03-27T13:58:20.297" CommentCount="2" />
  <row Id="2064" PostTypeId="2" ParentId="297" CreationDate="2010-03-27T07:20:42.550" Score="4" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;https://www.xmos.com/products/development-kits/xc-2-ethernet-kit&quot; rel=&quot;nofollow&quot;&gt;XMOS XC-2 kit&lt;/a&gt; is an interesting way to do it. Everything is done in software, apart from the PHY. The software should run on the $7.50 XS1-L1 chip.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-27T07:20:42.550" CommentCount="2" />
  <row Id="2065" PostTypeId="1" CreationDate="2010-03-27T07:30:55.447" Score="2" ViewCount="229" Body="&lt;p&gt;I was wanting to get a bulk lot of small LED lights similar to&#xA;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Basic-LED-%252d--5mm-Yellow.html&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/Basic-LED-%252d--5mm-Yellow.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to put them in balloons so that the balloons appear to glow in&#xA;a dark environment, so I have a few questions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Would the heat produced by these lights be likely to burst the&#xA;balloons? I understand that most LED's produce little to no heat&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Is there a decent and inexpensive alternative that have a power&#xA;supply &quot;built in&quot; or attached? (so we dont have wires running from the&#xA;balloons) Failing this is there an alternative that just needs a small&#xA;battery to be connected?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2010-04-07T22:46:35.397" Title="LED producting heat and best power supply" Tags="&lt;led&gt;&lt;power&gt;&lt;heat&gt;" AnswerCount="4" />
  <row Id="2066" PostTypeId="2" ParentId="2057" CreationDate="2010-03-27T08:03:16.523" Score="1" ViewCount="" Body="&lt;p&gt;As has been mentioned you could do this the same way it used to be done &lt;a href=&quot;http://en.wikipedia.org/wiki/PC_speaker#Pulse-width_modulation&quot; rel=&quot;nofollow&quot; title=&quot;Wikipedia&quot;&gt;with a PC speaker&lt;/a&gt; (which only supports on/off optionally attached to a PWM controller.)  Basically my understanding of the method is that you switch the speaker on and off fast enough that it's never fully on or off (a bit like how a switch-mode power supply works.)  This leaves the speaker constantly moving between on and off, generating an analogue signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only gotchas are that you need a real speaker (I think a piezo moves so fast it reaches full on and full off too quickly) and you need to be able to toggle the bit fast enough.  I did some experiments and came up with &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1264861636/4#4&quot; rel=&quot;nofollow&quot; title=&quot;Arduino forum&quot;&gt;a maximum speed of around 5MHz&lt;/a&gt; which should be ample for an 11,025 Hz audio signal (probably the best quality you could hope to get.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course 11025Hz @ 8-bit is 11 kilobytes/second, which is much faster than the speed of a serial port.  It would only allow maybe a second or two worth of audio to be stored in the flash, so you're pretty much limited to playing audio generated on the fly, providing that leaves enough spare CPU time to twiddle the speaker!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a couple of other methods to achieve this too, and it looks like there's &lt;a href=&quot;http://www.arduino.cc/playground/Code/PCMAudio&quot; rel=&quot;nofollow&quot; title=&quot;Arduino PCMAudio library&quot;&gt;already an implementation for the Arduino&lt;/a&gt; of the method described above.&lt;/p&gt;&#xA;" OwnerUserId="548" LastActivityDate="2010-03-27T08:03:16.523" CommentCount="1" />
  <row Id="2067" PostTypeId="2" ParentId="2065" CreationDate="2010-03-27T08:05:29.530" Score="5" ViewCount="" Body="&lt;p&gt;1) The LED would be fine and never produce enough heat to pop the balloon.&#xA;2) You could make them into &lt;a href=&quot;http://www.instructables.com/id/LED-Throwies/&quot; rel=&quot;nofollow&quot;&gt;LED throwies&lt;/a&gt;. Just a small coin cell batter and an LED.&lt;/p&gt;&#xA;" OwnerUserId="641" LastActivityDate="2010-03-27T08:05:29.530" />
  <row Id="2068" PostTypeId="1" CreationDate="2010-03-27T12:31:42.157" Score="2" ViewCount="178" Body="&lt;p&gt;Where can I get information on an Electromate CM1401C &quot;Smart Intelligent Auto Function Meter&quot;? Mine has developed a fault where it will only measure negative voltages.&lt;/p&gt;&#xA;" LastActivityDate="2010-04-12T07:19:14.497" Title="Information on Electromate Multimeter" Tags="&lt;tools&gt;" AnswerCount="1" />
  <row Id="2069" PostTypeId="2" ParentId="2065" CreationDate="2010-03-27T12:48:12.163" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/LED-Floaties-That-float-away/&quot; rel=&quot;nofollow&quot;&gt;LED floaties&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-03-27T12:48:12.163" />
  <row Id="2070" PostTypeId="2" ParentId="2021" CreationDate="2010-03-27T13:03:21.407" Score="2" ViewCount="" Body="&lt;p&gt;In analogue working, transistors (and before that, valves (or vacuum tube devices)) do not have a fully linear response, ie the output is not exactly proportional to the input over the full operating range.  If you are wanting a linear response, you move the input signal into the middle of the linear part of the operating range by using bias resistors (and you restrict the input signal such that it does not go outside the linear range).&lt;/p&gt;&#xA;" LastActivityDate="2010-03-27T13:03:21.407" />
  <row Id="2071" PostTypeId="2" ParentId="2055" CreationDate="2010-03-27T14:44:38.670" Score="4" ViewCount="" Body="&lt;p&gt;I had thought to ask a question like this, too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My current thoughts are implied in two questions here:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/2028/newbie-friendly-electronics-and-robotics&quot; rel=&quot;nofollow&quot;&gt;Newbie-friendly electronics (and robotics)&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/2024/is-there-a-scratch-like-arduino-ide&quot; rel=&quot;nofollow&quot;&gt;Is there a Scratch-like Arduino IDE?&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Two asides that I have to mention, having met a group called &lt;a href=&quot;http://www.cs.uleth.ca/lumacs/&quot; rel=&quot;nofollow&quot;&gt;LUMACS&lt;/a&gt; at my local university last night, which does outreach activities and week-long camps for kids:&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;em&gt;they said it is easier to teach counting in binary and algorithms to young children than to adults&lt;/em&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;they recently got some &lt;a href=&quot;http://www.picocricket.com/index.html&quot; rel=&quot;nofollow&quot;&gt;PicoCrickets&lt;/a&gt; and the groups that used them did not want to move on to anything else [and I got the impression that the same did not hold true for Mindstorms robots]&lt;/em&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For the youngest groups I would want to work with (maybe as young as 9, 11 might be better), I'd think I would:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Teach them procedural thinking -- ie. &lt;a href=&quot;http://scratch.mit.edu/&quot; rel=&quot;nofollow&quot;&gt;Scratch&lt;/a&gt;, on the computer.&lt;/li&gt;&#xA;&lt;li&gt;Use a Arduino platform that is designed for plug and play [ie. the Seeed Studio &lt;a href=&quot;http://www.seeedstudio.com/depot/electronic-brick-starter-kit-p-506.html?cPath=48_69&quot; rel=&quot;nofollow&quot;&gt;Electronics Brick shield&lt;/a&gt;]&lt;/li&gt;&#xA;&lt;li&gt;Use a forthcoming Scratch-like programming environment for the Arduino&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For an older group (perhaps 14 and up), I think I'd:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;still start with Scratch, and/or possibly teach them &lt;a href=&quot;http://alice.org/&quot; rel=&quot;nofollow&quot;&gt;Alice&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;use a breadboard-friendly Arduino -- a &lt;a href=&quot;http://www.moderndevice.com/products/bbb-bub-cable-package&quot; rel=&quot;nofollow&quot;&gt;Bare Bones Board&lt;/a&gt; kit or a &lt;a href=&quot;http://www.ladyada.net/make/boarduino/&quot; rel=&quot;nofollow&quot;&gt;Boarduino&lt;/a&gt; or an &lt;a href=&quot;http://www.solarbotics.com/products/kardw/&quot; rel=&quot;nofollow&quot;&gt;Ardweeny&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;Get an experimenters kit of parts.  (See bottom of &lt;a href=&quot;http://wulfden.org/TheShoppe/accessories.shtml&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;li&gt;Or go for &lt;a href=&quot;http://www.solarbotics.com/freeduino_arduino/starter_bundles/&quot; rel=&quot;nofollow&quot;&gt;a bundle&lt;/a&gt; -- this &lt;a href=&quot;http://www.solarbotics.com/products/ardy/&quot; rel=&quot;nofollow&quot;&gt;ARDX experimenters kit with an arduino and breadboard overlays&lt;/a&gt; sounds great!&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Edit&lt;/em&gt;:  I just tried out &lt;a href=&quot;http://processing.org/&quot; rel=&quot;nofollow&quot;&gt;Processing&lt;/a&gt;, on which the Arduino programming environment is based.  You may well be able to teach them Processing and then move on to the real Arduino environment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This age might just be ready for a real text-based language, such as Processing and NodeBox.  Processing, in particular, would be a good intro for the regular Arduino environment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, on to robotics.  I have taught three extra-curricular robotics courses, and most of my students have been homeschoolers.  They range the gamat from kids who can hardly read (an major liability to learning) to incredible kids that I want mine to be like.  I was amazed at how beneficial it was to have parents attend with their children in the last class I ran; I would highly recommend it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The biggest advantage to working with homeschool students (at least where I live) is they have some say in how their educational dollars are distributed; I was able to offer a LEGO Mindstorms NXT-based course, and, with a teacher to sign off on it, they were able to put their educational money towards it to fund it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having taught three beginner NXT courses, allow me to say:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;the NXT platform is great&lt;/li&gt;&#xA;&lt;li&gt;the NXT-G programming environment is ... unsuitable ... for anything beyond beginner work.  When it is not downright buggy, it is very tedious.&lt;/li&gt;&#xA;&lt;li&gt;step back and have students work through things at &lt;a href=&quot;http://www.nxtprograms.com&quot; rel=&quot;nofollow&quot;&gt;nxtprograms.com&lt;/a&gt;.  They are simple, whimsical, and well-built.  [I'd tended to think, &quot;okay, lets make a line following robot&quot; and &quot;now a sumo bot&quot;; now I am thinking, &quot;lets build something simple, fun, and creative&quot;]&lt;/li&gt;&#xA;&lt;li&gt;teaching Scratch beforehand is really helpful.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Only one of the twenty-one students I've taught was a girl.  If I were to try to include more girls, I'd strongly consider using PicoCrickets (due to their crafty nature) and LilyPad Arduinos (same reason).  I'd also read &quot;&lt;a href=&quot;http://llk.media.mit.edu/papers.php&quot; rel=&quot;nofollow&quot;&gt;New Pathways Into Robotics&lt;/a&gt;&quot; [pdf], a paper from the Lifelong Kindergarten Group at MIT (the same people who make Scratch).  It indicates taking a exhibition-related approach, where you choose a theme (say, &quot;A Day In The Park&quot;) and have pupils build robots to display related to the theme (like a robotic caterpillar, or flowers that turn to face you).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With an older group, I'd consider  &lt;a href=&quot;http://www.google.ca/search?ie=UTF-8&amp;amp;q=beam+robotics&quot; rel=&quot;nofollow&quot;&gt;BEAM robotics&lt;/a&gt;.  It is robotics where you repurpose scavenged parts to build things, and typically use solar panels to power things.  The best book on the topic I'm aware of is Junkbots, Bugbots, and Bots On Wheels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Three other points:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;I'd want to go with hardware that is cheap and modular.  I'd rather, say, buy a special FTDI cable that has a USB-to-serial converter on it, and use a Freeduino that expects that signal, than use a regular A-to-B USB cable with an Arduino that has the converter chip.  The cables are a one-time-cost.  You save on every board.  If you let the magic smoke out (and I expect you will and shouldn't fear it), then you buy another board.  I'd also consider going for motor controllers on a separate board, so if the fry, only one part has to be replaced.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;As for books, my recommendations will re-iterate what others have said:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/en/Guide/HomePage&quot; rel=&quot;nofollow&quot;&gt;Getting Started With Arduino&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Make: Electronics&lt;/li&gt;&#xA;&lt;li&gt;Anything by &lt;a href=&quot;http://www.forrestmims.com/&quot; rel=&quot;nofollow&quot;&gt;Forrest Mims&lt;/a&gt; (ie. Getting Started In Electronics, from the 70s or 80s)&lt;/li&gt;&#xA;&lt;li&gt;Junkbots, Bugbots, and Bots on Wheels&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;It is not hard to host a robotics event.  I've run two in conjunction with a science fair.    Line following, an obstacle course, and mini sumo have proven to be fun.  I've also hosted a &lt;a href=&quot;http://robofest.net/&quot; rel=&quot;nofollow&quot;&gt;robofest&lt;/a&gt; event, and working with Lawrence Technological University was great -- they provide almost everything and you provide space and volunteers.  [You need to be in contact with them by October to get on the poster for events held in March/April].&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Do let us know if you have any luck with such a course.  I'll try to remember to edit this post if I do myself.&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="106" LastEditorDisplayName="" LastEditDate="2010-04-02T13:45:02.640" LastActivityDate="2010-04-02T13:45:02.640" CommentCount="2" />
  <row Id="2073" PostTypeId="1" CreationDate="2010-03-27T18:53:08.733" Score="1" ViewCount="565" Body="&lt;p&gt;I'm trying to understand pipelining on a 32 bit 5 cycle MIPS chip. If register writes were not performed in the first half of the cycle and reads in the second half, how many additional pipeline bubbles would be caused by data dependencies? &lt;/p&gt;&#xA;" LastActivityDate="2011-06-02T02:45:27.177" Title="MIPS pipelining and data hazards" Tags="&lt;cpu&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="2075" PostTypeId="2" ParentId="2065" CreationDate="2010-03-27T23:25:27.783" Score="3" ViewCount="" Body="&lt;p&gt;Don't forget the resistor! If you add a resistor, it will last for much longer on a single battery, and is less likely to damage the LED.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-03-27T23:25:27.783" />
  <row Id="2076" PostTypeId="2" ParentId="2044" CreationDate="2010-03-28T00:24:25.903" Score="2" ViewCount="" Body="&lt;p&gt;Thanks for mentioning the Arduino Case project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the next week or so the design should be finalized for the injection molded version.&#xA;After that we are going to have pre-orders available via Kickstarter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The goal of the project is to produce a case for Arduino project that can hold a shield and can support 80% of the projects people are working on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have suggestions or changes you would like to see, let us know sooner rather than later.&lt;/p&gt;&#xA;" LastActivityDate="2010-03-28T00:24:25.903" />
  <row Id="2077" PostTypeId="2" ParentId="2036" CreationDate="2010-03-28T02:27:28.110" Score="4" ViewCount="" Body="&lt;p&gt;I stumbled across this at &lt;a href=&quot;http://www.seeedstudio.com&quot; rel=&quot;nofollow&quot;&gt;www.seeedstudio.com&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.seeedstudio.com/depot/preorder-open-workbench-logic-sniffer-p-612.html?cPath=61_76&quot; rel=&quot;nofollow&quot;&gt;Open Workbench Logic Sniffer (pre-order only)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really don't know anything about it beyond their description. It might be worth looking into. &lt;/p&gt;&#xA;" OwnerUserId="227" LastActivityDate="2010-03-28T02:27:28.110" CommentCount="2" />
  <row Id="2078" PostTypeId="2" ParentId="2057" CreationDate="2010-03-28T14:18:29.063" Score="2" ViewCount="" Body="&lt;p&gt;This might help -&gt; &lt;a href=&quot;http://www.actel.com/documents/DAC_AB.pdf&quot; rel=&quot;nofollow&quot;&gt;simple PWM DAC&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-03-28T14:18:29.063" CommentCount="1" />
  <row Id="2079" PostTypeId="2" ParentId="2057" CreationDate="2010-03-28T16:39:57.873" Score="3" ViewCount="" Body="&lt;p&gt;I think this nice old little PC DOS game gem used real polyphonic sound through the PC speaker: &lt;a href=&quot;http://www.digger.org/&quot; rel=&quot;nofollow&quot; title=&quot;Digger&quot;&gt;Digger&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know how they made it, but you can download the C source code from the site.&lt;/p&gt;&#xA;" LastActivityDate="2010-03-28T16:39:57.873" CommentCount="1" />
  <row Id="2080" PostTypeId="1" CreationDate="2010-03-28T19:44:40.810" Score="3" ViewCount="156" Body="&lt;p&gt;Hi, &#xA;I'm trying to create an outdoor installation with simple embedded electronics. I was hoping to use conductive paint to connect leds. The leds would be covered (waterproof) but the conductive paint would be exposed. However, I was wondering: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) if conductive paint being exposed to water is just as a bad as exposing regular electronics being exposed to water, or if it would be ok for outdoor use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) if not, what would be a good alternative for waterproofing electronics?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="570" LastActivityDate="2010-03-28T21:32:11.700" Title="conductive paint + water = ?" Tags="&lt;conductive&gt;&lt;waterproof&gt;" AnswerCount="2" />
  <row Id="2081" PostTypeId="2" ParentId="2080" CreationDate="2010-03-28T20:31:40.170" Score="0" ViewCount="" Body="&lt;p&gt;Conformal coating is usually used on PCBs, and/or IP68 enclosures.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-28T20:31:40.170" />
  <row Id="2082" PostTypeId="2" ParentId="2036" CreationDate="2010-03-28T20:56:16.000" Score="4" ViewCount="" Body="&lt;p&gt;The pickit2 has a simple logic analyzer (as well as a programmer for pic uC's and a UART tool)&lt;/p&gt;&#xA;" OwnerUserId="348" LastActivityDate="2010-03-28T20:56:16.000" CommentCount="1" />
  <row Id="2083" PostTypeId="2" ParentId="2080" CreationDate="2010-03-28T21:32:11.700" Score="3" ViewCount="" Body="&lt;p&gt;I'm not sure if conductive paint will tarnish - but I do know that the &lt;a href=&quot;http://graffitiresearchlab.com/&quot; rel=&quot;nofollow&quot;&gt;Graffiti Research Lab&lt;/a&gt; uses conductive spray paint to add tracks for LEDs around their work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I've seen some of the work is on a regular exterior building walls.&#xA;Even if there's no information on the website about your questions, I'd imagine they would probably know - maybe you should contact them if you don't have any luck by other means  &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-03-28T21:32:11.700" />
  <row Id="2084" PostTypeId="2" ParentId="2073" CreationDate="2010-03-28T21:42:17.957" Score="3" ViewCount="" Body="&lt;p&gt;I'm assuming a few things because I'm mot sure that you gave enough info for an exact answer. I will describe a system that will allow me to give you an answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Suppose this MIPS chip has an ADD instruction that adds two registers, and stores the result in a third. In the pipeline, the data would be read from the register file on cycle 3, and the result would be written on cycle 5. The assembler code for adding three numbers would generate a hazard:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Add registers $11, $12, and $13 and store the result in register $10)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;add $10, $13, $12   # $13 + $12 -&amp;gt; $10 &#xA;add $9, $10, $11   # $11 + $10 -&amp;gt; $9&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The code has a Read after Write hazard on register $10. The processor would detect the data hazard and stall the second addition one cycle. This assumes that each cycle begins with a write, and ends with a read. If the order was reversed, then the data wouldn't be in the register in time for the 5th clock reading time, and an additional stall cycle would be necessary to get the correct result. Below is an example time-line for a &quot;Write, then Read&quot; system.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Read first add instruction&lt;/li&gt;&#xA;&lt;li&gt;Read second add instruction&lt;/li&gt;&#xA;&lt;li&gt;Read operands for first add instruction&lt;/li&gt;&#xA;&lt;li&gt;Pipeline stall for second add&lt;/li&gt;&#xA;&lt;li&gt;Write result of first add, read operands for second add&lt;/li&gt;&#xA;&lt;li&gt;...&lt;/li&gt;&#xA;&lt;li&gt;Write result of second add&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Wikipedia has a good article about &lt;a href=&quot;http://en.wikipedia.org/wiki/Pipeline_hazard&quot; rel=&quot;nofollow&quot;&gt;pipeline hazards&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:45:27.177" LastActivityDate="2011-06-02T02:45:27.177" />
  <row Id="2086" PostTypeId="1" CreationDate="2010-03-29T09:00:13.993" Score="4" ViewCount="727" Body="&lt;p&gt;Hey,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Got a new MicroSD shield from LittleBird, having some troubles with it,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Downloaded the sample library that it said to used threw in a MicroSD card and expected it to work... It won't initialise for some reason done a bit of googling and can't see how to get it working every one just say use this library, uses that one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone had any luck on get these set up&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hardware&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;MicroSD Shield&lt;/li&gt;&#xA;&lt;li&gt;Arduino Duemilanove (ATMEGA328)&lt;/li&gt;&#xA;&lt;li&gt;SanDisk (4GB) MicroSD card (HC) &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Is the SDHC part the problem?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I work off a mac even formatted the card in a Win XP machine to fat 16 still no luck&lt;/p&gt;&#xA;" OwnerUserId="665" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-24T21:42:58.580" LastActivityDate="2011-05-18T13:12:59.847" Title="Micro SD Shield" Tags="&lt;microsd&gt;&lt;memory&gt;&lt;arduino&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="1" />
  <row Id="2087" PostTypeId="2" ParentId="2086" CreationDate="2010-03-29T11:19:02.027" Score="1" ViewCount="" Body="&lt;p&gt;I got one of these, too, from Sparkfun, and it only kinda worked.  I checked out the comments at the bottom of the product page, and there might be a couple of issues.  a) the size of your card, and b) 3.3v-&gt;5V incompatibility.  The last comment looks promising.  I used Sparkfun's diode scheme to connect a 3.3Vpressure sensor to an Arduino and it worked just fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9520&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9520&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-03-29T11:19:02.027" CommentCount="1" />
  <row Id="2088" PostTypeId="2" ParentId="2086" CreationDate="2010-03-29T13:15:26.663" Score="2" ViewCount="" Body="&lt;p&gt;I was about to ask a similar question ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am adding a uSD card to my new '644 board to make a low-cost datalogger.&#xA;All my boards are 3.3V so I won't have the 5V issues. I have tried three&#xA;different libraries and none of these initialize the cards :(&#xA;I have also tried three different cards SD and SDHC from two different&#xA;manufacturers (all large capacity) and none initialize. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have my logic analyzer on the board now and I am reviewing the&#xA;spec. It looks like the initialization procedure is different for &#xA;the newer card. I am almost certain that the SDHC is different. &#xA;There is no response to the initialization routine. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;From &lt;strong&gt;a lot&lt;/strong&gt; of googling I have found out the following -- &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;NB&lt;/strong&gt;: I have not verified this information only found it ;)&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Using the resistor dividers to translate from 5V to 3.3V&#xA;can be problematic due to loss of edge speed due to the&#xA;series resistance. Not sure how much edge speed is lost&#xA;or how sensitive different cards are to this. &#xA;Since this is not an issue for my 3.3V board I wasn't&#xA;worried. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If the IO pins are not at 0V when power is applied to the&#xA;card the card may be startup in an unknown state. Unfortunately&#xA;the datasheet does not mention if there is a software&#xA;initialization procedure that can be used to reset the&#xA;card to a known state. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;In Version 2.00 of the SD specificaiton the initialization &#xA;procedure changed. Not sure if the libraries support &#xA;these changes.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Some people have reported success changing to low capacity&#xA;cards. I was hoping to find a low capacity at the office&#xA;supply store but the smallest they had in stock was 2GB.&#xA;I am suspecting that it may not be the size of the card&#xA;but the age (since most smaller cards are &#xA;also older cards). &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;SPI support is optional for uSD. I would be surprised if&#xA;cards didn't support SPI since if is required for the other&#xA;formats. I was hoping to find a list of cards that were&#xA;known to support SPI but could not find it.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;That is where I am at. Unfortunately I probably won't have&#xA;much time to work on this during the week. My next step&#xA;is to go through the specification and write a simple&#xA;initialization function and verify the output on the&#xA;logic analyzer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you discover anything please post back or send me an email.&#xA;I will post back anything I find.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:31:52.307" LastActivityDate="2011-05-18T11:31:52.307" CommentCount="3" />
  <row Id="2089" PostTypeId="1" AcceptedAnswerId="2090" CreationDate="2010-03-29T14:21:17.983" Score="9" ViewCount="1645" Body="&lt;p&gt;LEDs with a concave cone-shaped lens are sometimes called &quot;straw hat&quot; LEDs. What is the advantage compared to the more common hemispherical lens?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-03-29T15:09:25.733" Title="What is a &quot;straw hat&quot; LED?" Tags="&lt;led&gt;" AnswerCount="2" />
  <row Id="2090" PostTypeId="2" ParentId="2089" CreationDate="2010-03-29T15:06:18.433" Score="10" ViewCount="" Body="&lt;p&gt;The straw hat LED lenses have a much more even light distribution pattern than the typical hemisphere lens. The hemisphere lens usually focus the light into a narrow cone of maybe 20 or so degrees. One application that workes very well is Christmas tree lights. The straw hat lenses make the LED disperse light like an incandescent bulb. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-03-29T15:06:18.433" />
  <row Id="2091" PostTypeId="2" ParentId="2089" CreationDate="2010-03-29T15:09:25.733" Score="6" ViewCount="" Body="&lt;p&gt;Straw-hat LEDs have a wider viewing angle (typically 100 degrees).&lt;/p&gt;&#xA;" OwnerUserId="544" LastActivityDate="2010-03-29T15:09:25.733" />
  <row Id="2092" PostTypeId="2" ParentId="616" CreationDate="2010-03-29T15:27:00.850" Score="4" ViewCount="" Body="&lt;p&gt;If you're just starting out I would recommend both &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0945053282&quot; rel=&quot;nofollow&quot;&gt;Getting Started in Electronics&lt;/a&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596153740&quot; rel=&quot;nofollow&quot;&gt;Make: Electronics: Learning Through Discovery&lt;/a&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Getting Started in Electronics book as become a standard in the electronics world since it's initial release in the 1980's.  It's easy to read and follow and has taught electronics to a lot of folks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make: Electronics is a little more hands on and will introduce you to the theories as you are building real circuits.  It's a fun book but be warned to get all the parts you need for the book you will end up spending about two hundred dollars.  Don't let that scare you though because if you are wanting to learn electronics you're going to have to invest money at somewhat to get the basic stuff this book is asking you to get at some point anyway.  Doing it this way at least helps you get a list of things that you will need together.  It's not as proved as the Getting Started in Electronics book but I think it will be another standard for anyone getting started in a few years.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Art of Electronics that was mentioned by another person is a good book but it may be to technical for folks just starting out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is my 2 cents.  Good luck with your learning and have fun,&lt;/p&gt;&#xA;" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T19:13:45.363" LastActivityDate="2011-05-13T19:13:45.363" CommunityOwnedDate="2011-03-24T07:55:53.500" CommentCount="1" />
  <row Id="2093" PostTypeId="1" AcceptedAnswerId="2095" CreationDate="2010-03-29T17:21:53.137" Score="5" ViewCount="278" Body="&lt;p&gt;I'm trying to use a power relay (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=425-2359-2-ND&quot; rel=&quot;nofollow&quot;&gt;PR26MF&lt;/a&gt;) to turn on and off a device. The device takes a 9v supply and typically draws ~250mA. I'm finding that the relay turns on just fine, but when I try to turn it off, it won't: it remains latched in the on state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet mentions that a snubber circuit across the load may be necessary. I tried adding one (with a ~2ms time constant). It had no effect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I measured the resistance across the output port of the relay without the load attached; it works as you would expect: ~inf resistance when it's off and low resistance when on. It seems to turn on and off just fine in that setup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried a different load - using the SSR to drive a 5V mechanical relay. The SSR still exhibited the latching behavior.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2010-03-29T17:58:03.843" Title="How can I stop a solid state relay from latching up?" Tags="&lt;power&gt;&lt;relay&gt;" AnswerCount="1" />
  <row Id="2095" PostTypeId="2" ParentId="2093" CreationDate="2010-03-29T17:55:38.160" Score="12" ViewCount="" Body="&lt;p&gt;One big question is whether this is an AC load or not.  The solid state relay you are using is meant to switch AC loads only and WILL NOT shut off until the zero crossing occurs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using it for a DC load, then it'll stay on once switched on, and will not turn off until the current goes to 0 (usually at zero crossing with an AC power supply).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it is an AC load, then you may need to design your snubber more carefully to match your load and power supply. You haven't given us enough information to help you with that part, though.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are trying to switch a DC load, then you need a different type of solid state relay.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-29T17:55:38.160" CommentCount="1" />
  <row Id="2096" PostTypeId="2" ParentId="933" CreationDate="2010-03-29T19:01:56.457" Score="1" ViewCount="" Body="&lt;p&gt;TI has a &lt;a href=&quot;http://www.ti.com/ww/en/analog/ads1298/index.shtml&quot; rel=&quot;nofollow&quot;&gt;new chip&lt;/a&gt; for EEG and ECG front ends.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-29T19:01:56.457" CommentCount="2" />
  <row Id="2097" PostTypeId="1" AcceptedAnswerId="2101" CreationDate="2010-03-29T20:02:13.910" Score="4" ViewCount="259" Body="&lt;p&gt;I have a +5V power supply and need to invert to a -5V supply sourcing about 25mA. I've got an &lt;a href=&quot;http://www.national.com/mpf/LM/LMC7660.html#Overview&quot; rel=&quot;nofollow&quot;&gt;LMC7660&lt;/a&gt; running now. It's ok for the short term, it outputs -4.4V with 100mV p-p switching noise, but that's unacceptible for my long-term needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Anyone have any experience with LMC7660 / ICL7660 - like switched capacitor inverters?&lt;/strong&gt; There must be some better parts on the market nowadays, we've had those LMC7660's in a drawer for at least 12 years. I can probably hunt something down, but figured I'd ask here.&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-05-05T23:56:19.580" LastActivityDate="2011-05-16T10:42:30.070" Title="best quick&amp;cheap power supply inverter" Tags="&lt;power-supply&gt;&lt;components&gt;&lt;power&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="2098" PostTypeId="2" ParentId="2097" CreationDate="2010-03-29T21:21:33.313" Score="5" ViewCount="" Body="&lt;p&gt;I use the Analog Devices ADM660 which does about 100mA. Wasn't concerned with the switching noise in my application since I followed it with an LDO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could check out the LT1046 which also does 100mA. The ICL7660S looked interesting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your best bet is probably the Linear Technology site. If you can get one of the 100mA&#xA;devices you may able to get an adjustable LDO to remove the switching noise. &#xA;For the LTC660 the graph show -4.8V at 30mA. That gives you a few hundred mV&#xA;of dropout at 30mA.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:42:30.070" LastActivityDate="2011-05-16T10:42:30.070" />
  <row Id="2099" PostTypeId="2" ParentId="2097" CreationDate="2010-03-30T00:06:52.810" Score="1" ViewCount="" Body="&lt;p&gt;You can do it with a 4009 and a few capacitors and diodes. I have to do this when using the ICL7107 chip - I've copied the circuit to here for you. &lt;a href=&quot;http://www.flickr.com/photos/tronixstuff/4474249137/&quot; rel=&quot;nofollow&quot;&gt;http://www.flickr.com/photos/tronixstuff/4474249137/&lt;/a&gt;&#xA;However, you might get a bit less than -5V&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-03-30T00:06:52.810" />
  <row Id="2100" PostTypeId="2" ParentId="1887" CreationDate="2010-03-30T03:13:46.310" Score="2" ViewCount="" Body="&lt;p&gt;Check out &quot;&lt;a href=&quot;http://www.cs.uiowa.edu/~jones/step/types.html&quot; rel=&quot;nofollow&quot;&gt;jones on stepping motors&lt;/a&gt;&quot; a pretty complete source of information including pulse tables for a variety of motor types.&lt;/p&gt;&#xA;" OwnerUserId="12" LastActivityDate="2010-03-30T03:13:46.310" />
  <row Id="2101" PostTypeId="2" ParentId="2097" CreationDate="2010-03-30T12:39:14.973" Score="2" ViewCount="" Body="&lt;p&gt;After looking around I think I'm going to use a &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tps60403.html&quot; rel=&quot;nofollow&quot;&gt;TPS60403&lt;/a&gt;, it's got a higher switching frequency (250kHz) than the LMC7660.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-03-30T12:39:14.973" />
  <row Id="2102" PostTypeId="2" ParentId="2086" CreationDate="2010-03-30T12:58:14.377" Score="0" ViewCount="" Body="&lt;p&gt;It is unlikely that this is your problem, but the microSD standard does not list SPI compatibility as compulsory. A while back I had a specific microSD that wasn't talking to my AVR and I could have sworn it was because it was missing an SPI interface. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps try another card of a different brand?&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-03-30T12:58:14.377" />
  <row Id="2103" PostTypeId="1" AcceptedAnswerId="2107" CreationDate="2010-03-30T16:49:34.643" Score="21" ViewCount="1084" Body="&lt;p&gt;What are the cases where one should avoid using a breadboard? e.g. high frequency, noise prone circuits etc.&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-12-26T12:41:30.310" Title="When to avoid using a breadboard" Tags="&lt;breadboard&gt;&lt;prototyping&gt;" AnswerCount="11" CommentCount="1" FavoriteCount="4" />
  <row Id="2104" PostTypeId="2" ParentId="2103" CreationDate="2010-03-30T18:17:03.950" Score="3" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;When you want to use surface mount parts&lt;/li&gt;&#xA;&lt;li&gt;When you want something that won't fall apart&lt;/li&gt;&#xA;&lt;li&gt;When you've only got one breadboard...&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I use breadboards to help with circuit design, then make a PCB at home when I'm confident.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For surface mount parts, I often make adapter boards which can go into a breadboard.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-03-30T19:38:03.880" LastActivityDate="2010-03-30T19:38:03.880" />
  <row Id="2105" PostTypeId="2" ParentId="2103" CreationDate="2010-03-30T18:31:00.890" Score="3" ViewCount="" Body="&lt;p&gt;I never use them. I make a PCB at home if I need a prototype quickly.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-03-30T18:31:00.890" CommentCount="5" />
  <row Id="2106" PostTypeId="2" ParentId="2103" CreationDate="2010-03-30T18:59:14.583" Score="1" ViewCount="" Body="&lt;p&gt;I try to avoid them all the time. I have found when I use the breadboard &#xA;I spend 90% of the time troubleshooting the breadboard. I like to use&#xA;Vectorboard and hardwire the circuitry. It does not take too much longer.&#xA;An advantage is that Vectorboard is inexpensive enough so that you can leave&#xA;your circuits assembled. See my &lt;a href=&quot;http://www.luciani.org/getting-it-done/assembly-hints/assembly-hints-index.html#breadboard-hints&quot; rel=&quot;nofollow&quot; title=&quot;breadboard hints&quot;&gt;Breadboard hints&lt;/a&gt; for an example and a list&#xA;of supplies. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would avoid a breadboard for all of the examples you listed -- high frequency,&#xA;low-level signals, high impedance nodes. I would add power applications.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-12-26T03:14:34.300" LastActivityDate="2010-12-26T03:14:34.300" />
  <row Id="2107" PostTypeId="2" ParentId="2103" CreationDate="2010-03-30T19:15:31.913" Score="21" ViewCount="" Body="&lt;p&gt;Areas where the common breadboard does poorly:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;High voltage&lt;/li&gt;&#xA;&lt;li&gt;High frequency (above 10MHz)&lt;/li&gt;&#xA;&lt;li&gt;Where the additional breadboard capacitance would present problems (oscillators, etc)&lt;/li&gt;&#xA;&lt;li&gt;Where glitches due to poor wire connections would result in poor operation&lt;/li&gt;&#xA;&lt;li&gt;Where most of the parts are not through hole 0.1&quot; (2.54mm) centers&lt;/li&gt;&#xA;&lt;li&gt;For anything but on-the-bench prototyping (ie, don't take it out of the lab and expect it to work)&lt;/li&gt;&#xA;&lt;li&gt;Sensitive analog electronics, such as sensor usage&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-30T19:15:31.913" CommentCount="1" />
  <row Id="2108" PostTypeId="2" ParentId="2103" CreationDate="2010-03-30T19:37:35.393" Score="9" ViewCount="" Body="&lt;p&gt;Perhaps a better way to phrase the question would be when IS it ok to use a breadboard.&#xA;I'd say if the following cases are true it's probably ok to use a breadboard.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Rapid prototyping (not built to last)&lt;/li&gt;&#xA;&lt;li&gt;Few connections external to the breadboard&lt;/li&gt;&#xA;&lt;li&gt;Mostly thru-hole components&lt;/li&gt;&#xA;&lt;li&gt;Low voltage &amp;lt;= 12VDC&lt;/li&gt;&#xA;&lt;li&gt;Low frequency &amp;lt;= 10Mhz&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;There are a few exceptions for example you can have more external connections if you use cables with multiple wires and good thru-hole style connectors like ribbon cables. Don't try running lots of jumper wires from the breadboard to other devices or you will spend lots of time checking for broken connections. Many SMD -&gt; thru-hole adaptor boards are available online that will allow you to use SMD parts with a breadboard. This also helps with the frequency issues as the clock circuit can be built on the SMD board while only the low frequency analog/digital circuits are passed to the breadboard.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-03-30T19:37:35.393" />
  <row Id="2109" PostTypeId="2" ParentId="2103" CreationDate="2010-03-31T03:31:39.337" Score="0" ViewCount="" Body="&lt;p&gt;what Adam said, but also high current. The protoboards have high parasitic capacitance and inductance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use them to test pieces of circuits I know are OK, but not for larger systems.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-03-31T03:31:39.337" />
  <row Id="2110" PostTypeId="2" ParentId="2086" CreationDate="2010-03-31T15:22:55.267" Score="2" ViewCount="" Body="&lt;p&gt;Unless the library specifically includes SDHC support, it won't work. SDHC and SD have different addressing modes and a few differences in their initialization routines, and it's enough to keep it from working. Get a 2GB or smaller SD.&lt;/p&gt;&#xA;" OwnerUserId="610" LastActivityDate="2010-03-31T15:22:55.267" CommentCount="1" />
  <row Id="2111" PostTypeId="2" ParentId="2024" CreationDate="2010-03-31T18:23:07.357" Score="4" ViewCount="" Body="&lt;p&gt;There is a program called Catenary that allows Scratch programs to talk to an Arduino board. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are more details and a user guide found here:&#xA;&lt;a href=&quot;http://scratchconnections.wik.is/User:Chalkmarrow/Catenary&quot; rel=&quot;nofollow&quot;&gt;http://scratchconnections.wik.is/User:Chalkmarrow/Catenary&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-03-31T18:23:07.357" CommentCount="3" />
  <row Id="2112" PostTypeId="1" CreationDate="2010-03-31T21:30:08.147" Score="1" ViewCount="327" Body="&lt;p&gt;I've been taking a close look at PSoC chips (series 1 in particular). With the reconfigurable analog blocks, they seem like a great solution for general data acquisition needs for &lt;strong&gt;prototype&lt;/strong&gt; projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking about &lt;a href=&quot;http://www.nkcelectronics.com/cy3210-miniprog1-pso32101.html&quot; rel=&quot;nofollow&quot;&gt;buying the programmer&lt;/a&gt; ($37 academic) and a few PSoC 1 chips so that I can avoid building amplifiers and filters and design electronics in a more intuitive way (more like Max/MSP).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the signal chain I'm looking at for my current project:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(noisy) textile resistive sensors =&gt; voltage divider =&gt; PSoC(amplifier =&gt; lowpass filter) =&gt; (Xbee =&gt; Xbee?) =&gt; Teensy((decodeXbee|ADC) =&gt; &lt;a href=&quot;http://cnmat.berkeley.edu/research/uosc&quot; rel=&quot;nofollow&quot;&gt;micro-OSC code&lt;/a&gt; =&gt; USB) =&gt; Max/MSP/Jitter&lt;/p&gt;&#xA;&#xA;&lt;p&gt;People didn't have much good to say about PSoC in the &lt;a href=&quot;http://chiphacker.com/questions/1444/psoc-by-cypress&quot; rel=&quot;nofollow&quot;&gt;last thread&lt;/a&gt;. Do you think they're overkill for general signal processing tasks in prototypes? Not worth the convenience? Wait a few years for the bugs to be ironed out?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit 1:&lt;/strong&gt; I'm not looking for the best solution for my current project, I'm curious as to whether you think PSoC is a good investment for general prototyping. I see two advantages for myself:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;I get to learn (and share with the local community) a new technology&lt;/li&gt;&#xA;&lt;li&gt;When I need to do signal processing in prototypes, rather than hunting for circuits, spec'ing parts, ordering them, waiting, then assembling them, I can whip out a PSoC, configure the blocks I need, and plug it into a breadboard&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;This was prompted by the answers to &lt;a href=&quot;http://chiphacker.com/questions/937/scaling-voltage-for-arduino-analog-in-beyond-voltage-dividers&quot; rel=&quot;nofollow&quot;&gt;a previous question I asked here&lt;/a&gt;. I thought, rather than buying and learning to use PGAs and instrumentation amplifiers, I could get to know PSoC and turn a hardware problem into a software problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit 2:&lt;/strong&gt; I ordered the MiniProg1 kit from &lt;a href=&quot;http://www.nkcelectronics.com/psoc.html&quot; rel=&quot;nofollow&quot;&gt;NKC Electronics&lt;/a&gt;. I'll let you know how it goes.&lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2010-04-16T17:21:28.240" LastActivityDate="2011-05-20T10:56:52.643" Title="PSoC as General Data Acquisition Block" Tags="&lt;psoc&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="2113" PostTypeId="2" ParentId="2024" CreationDate="2010-03-31T21:39:38.830" Score="1" ViewCount="" Body="&lt;p&gt;Cypress PSoC chips are programmed with a &lt;a href=&quot;http://en.wikipedia.org/wiki/PSoC&quot; rel=&quot;nofollow&quot;&gt;visual dataflow style IDE&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2010-03-31T21:39:38.830" CommentCount="1" />
  <row Id="2114" PostTypeId="2" ParentId="2112" CreationDate="2010-03-31T21:44:58.160" Score="1" ViewCount="" Body="&lt;p&gt;Unfortunately I can't comment much on PSoC - it hasn't really solved a major problem for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I can say is that you can connect you noisy resistive sensors to a PIC or AVR and then filter in software, so the PSoC isn't really solving a problem for you either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For some sensors where a real amplifier is necessary before the A/D, then a PSoC might be useful, but I don't see it being important to your particular design, and may well be more expensive than the equivalent PIC/AVR solution.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-03-31T21:44:58.160" CommentCount="3" />
  <row Id="2115" PostTypeId="1" AcceptedAnswerId="2150" CreationDate="2010-03-31T21:57:37.977" Score="2" ViewCount="185" Body="&lt;p&gt;Is it possible to have two antennas connected to the antenna port of an RF transceiver through some sort of mux? I want to be able to switch to a different antenna if the signal is weak on one.  I would just use two of the RF modules but they are somewhat expensive.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ant2-----------------------------                          |---------|&#xA;                                 \________|2:1MUX|_________|RF module|&#xA;ant1-----------------------------/                         |---------| &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;edit:&#xA;this will be for a 500-900Mhz system&#xA;and both antennas are oriented differently, the case isn't that one antenna is high gain and the other not.&lt;/p&gt;&#xA;" OwnerUserId="582" LastEditorUserId="582" LastEditorDisplayName="" LastEditDate="2010-04-01T06:02:57.253" LastActivityDate="2011-05-20T10:58:03.470" Title="Multiplexing an antenna" Tags="&lt;antenna&gt;&lt;analog&gt;&lt;radio&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="2116" PostTypeId="2" ParentId="2112" CreationDate="2010-03-31T22:16:31.433" Score="1" ViewCount="" Body="&lt;p&gt;You haven't mentioned how many sensors, what voltage/current levels or data acquisition &#xA;speed you require. Also cost and size. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possibly to condition the noisy sensor near the sensor? If you can put&#xA;a filter at the noise source and buffer the signal with an op-amp (which will&#xA;have a low output impedance) you will have a cleaner signal path. Filtering at the noise source is the opposite of what you would get with a PSoC (unless the PSoC is &#xA;near the noise source). I don't have enough information on your application to know&#xA;if this would make a quantifiable difference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Moving the op-amps (and other analog components) to the PSoC will help with some of &#xA;the wiring but you will probably still need to change external passive components&#xA;and observe good analog design practices. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most of my work has been with systems that combine a minimally integrated uC&#xA;with high resolution peripherals (16/18/20 bit DACS and ADCS) or systems that &#xA;can use the 8/10 bit resources that all uCs seem to have. I occasional add an&#xA;op-amp or instrument amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On my last design a uC with a single (or dual op-amp) would have been extremely&#xA;handy but most times it is not an issue.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T10:56:52.643" LastActivityDate="2011-05-20T10:56:52.643" CommentCount="3" />
  <row Id="2118" PostTypeId="2" ParentId="2115" CreationDate="2010-04-01T02:09:26.253" Score="0" ViewCount="" Body="&lt;p&gt;Why wouldn't you just have the high gain antenna connected all the time?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some reference designs for Chipcon (now TI) radios that have a co-ax connector&#xA;and a PCB F antenna on them. The design is meant to be used with one&#xA;or the other. IIRC you install jumper resistors or replace a balun. &#xA;These designs are hardwired not meant to be switched based on signal strength.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T10:58:03.470" LastActivityDate="2011-05-20T10:58:03.470" CommentCount="1" />
  <row Id="2119" PostTypeId="2" ParentId="2115" CreationDate="2010-04-01T04:22:50.193" Score="0" ViewCount="" Body="&lt;p&gt;If you don't specifically need the different reception patterns provided by the different antennas it may be an option to use the single high gain antenna and a switched attenuator.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2010-04-01T04:22:50.193" />
  <row Id="2120" PostTypeId="2" ParentId="2103" CreationDate="2010-04-01T06:25:19.407" Score="0" ViewCount="" Body="&lt;p&gt;Absolutely. Just got burned trying out a large breadboard. Honestly, I threw it away last night! Still have a small one for the quickies though. Will never buy one from eBay again... craptacular.&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-04-01T06:25:19.407" />
  <row Id="2121" PostTypeId="2" ParentId="966" CreationDate="2010-04-01T06:28:27.747" Score="10" ViewCount="" Body="&lt;p&gt;74HC595&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a bit old school - don't forget your 555 timers.&lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T19:28:34.783" LastActivityDate="2011-05-13T19:28:34.783" CommunityOwnedDate="2010-04-01T06:28:27.747" CommentCount="2" />
  <row Id="2122" PostTypeId="1" CreationDate="2010-04-01T13:54:10.863" Score="1" ViewCount="803" Body="&lt;p&gt;Are there any chips or simple circuits available for removing the 50/60Hz mains hum from a regular power supply unit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I've got a few bits of audio equipment that have bad PSUs and they have a bit of mains hum, it seems to be a common problem with cheaper audio equipment - so I'm just curious to find out about any cheap or simple solutions to this common problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far I've used basic RC filters and Op Amp based ones too.  &lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-05-05T23:55:12.793" LastActivityDate="2010-05-05T23:55:12.793" CommunityOwnedDate="2010-04-01T13:54:10.863" Title="Mains Hum Filter" Tags="&lt;power-supply&gt;&lt;filter&gt;&lt;power&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="2123" PostTypeId="2" ParentId="2122" CreationDate="2010-04-01T14:12:30.690" Score="3" ViewCount="" Body="&lt;p&gt;Better filter caps?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not always the power supply.  Grounding can be a common problem in these kinds of units, &lt;a href=&quot;http://en.wikipedia.org/wiki/Ground_loop_%28electricity%29&quot; rel=&quot;nofollow&quot;&gt;ground loops&lt;/a&gt; in particular.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the following circuit is representative of your power supply...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.circuit-projects.com/cimg/symmetric_power_supply_for_op-amp_applications.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;...C1 and C2 are the filter caps.  You can try increasing the values of those to reduce the hum.  They are typically electrolytics.  If your power supply doesn't have voltage regulators like this circuit does, adding voltage regulators should lower the hum considerably, &lt;em&gt;if it's not a ground loop.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="544" LastEditorUserId="544" LastEditorDisplayName="" LastEditDate="2010-04-01T20:32:40.350" LastActivityDate="2010-04-01T20:32:40.350" CommunityOwnedDate="2010-04-01T14:12:30.690" CommentCount="6" />
  <row Id="2124" PostTypeId="1" AcceptedAnswerId="2125" CreationDate="2010-04-02T01:07:52.247" Score="5" ViewCount="513" Body="&lt;p&gt;I can't seem to get over this but this seems to be the basics in electronics.&#xA;I have an NPN darlington transistor TIP122 and have built to simple test circuit around it with Rb = 150 ohm, Rc = 80 ohm and Re = 6.8 ohm.&#xA;My base supply Vbb = 3.3V and collector supply Vcc = 20V.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used the equation from &lt;a href=&quot;http://www.allaboutcircuits.com/vol_3/chpt_4/10.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; site as mentioned for emitter biasing.  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Ie = (Vbb - Vbe)/(Rb/beta + Re)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;However I am getting different values theoretically and practically.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With Re = 6.8 I get theoretical Ie = 273mA and practical Ie = 222mA then&#xA;With Re = 6.8||6.8 I get theoretical Ie = 535mA and practical Ie = 228ma.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't understand why could this be happening, how does the emitter resistor work in the transistor circuit... can you help me out?&lt;/p&gt;&#xA;" OwnerUserId="444" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-03T00:54:21.707" LastActivityDate="2011-02-03T00:54:21.707" Title="Transistor with emitter resistor calculation" Tags="&lt;transistor&gt;&lt;bias&gt;" AnswerCount="1" />
  <row Id="2125" PostTypeId="2" ParentId="2124" CreationDate="2010-04-02T02:53:36.370" Score="5" ViewCount="" Body="&lt;p&gt;The simplified equations only work when you observe some basic assumptions. The most important being that the transistor is operating in it's linear region.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Leave out the transitor for a moment. How much current would you get through Rc if it was connected directly between the 20V supply and ground?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then add in Re. You should end up with 20/(80 + 6.8) = 230 mA. This will be the maximum current that can possibly flow through the transistor. Given that there will be a small voltage drop across the transistor and errors from the resistor tolerance, that is very close to the measured value of 222mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on what you are trying to achieve you may need to reduce the collector resistor or reduce the targeted collector current.&lt;/p&gt;&#xA;" OwnerUserId="328" LastEditorUserId="328" LastEditorDisplayName="" LastEditDate="2010-04-02T03:56:04.710" LastActivityDate="2010-04-02T03:56:04.710" CommentCount="3" />
  <row Id="2126" PostTypeId="2" ParentId="2055" CreationDate="2010-04-02T14:43:24.717" Score="3" ViewCount="" Body="&lt;p&gt;I've got some interesting but simple kits available on my website. We sell the kits - but all of the information for making them for yourself is available for free - &#xA;&lt;a href=&quot;http://www.sonodrome.co.uk/hardware.html&quot; rel=&quot;nofollow&quot;&gt;Sonodrome Hardware Page&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recommend the Posc pocket oscillator and Mr Kogawa's Micro FM Transmitter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done a few workshops with these kits and Mr Kogawa has spent 14 years doing micro FM transmitter workshops - so they should be more than suitable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the big issues with doing electronics with a group of beginners - is the time factor (It's easy to forget how long things can take when doing them for the first time).&#xA;If you have people for a course of workshops or a few days you can tackle something bigger, but in my experience you wanna keep it basic but effective - or you won't get done in time!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;People want to go home with a fully working device - there's nothing worse than running out of time and participants feeling dissatisfied with their project, then not bothering finishing it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a link to some shots of a workshop we did at the Maker Faire in Newcastle England -&#xA;&lt;a href=&quot;http://forum.sonodrome.co.uk/general-discussion-f1/maker-faire-t57.htm&quot; rel=&quot;nofollow&quot;&gt;Maker Faire Forum Page&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this is of some help &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ps. I do electronics kits and workshops solely because I was also gravely dissatisfied with the stuff we did at school - they seemed uninterested in the intended use for the device and were more focused on demonstrating a principal (As a result I found it hard to engage with the projects and I didn't learn much - if anything.) &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-04-02T14:43:24.717" CommunityOwnedDate="2010-04-02T14:43:24.717" />
  <row Id="2127" PostTypeId="1" CreationDate="2010-04-02T15:00:43.010" Score="2" ViewCount="293" Body="&lt;p&gt;My mother-in-law has sent my sons several singing, dancing plush toys (not unlike &lt;a href=&quot;http://www.cartoonfansclub.com/fabble-frog-27593.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; or &lt;a href=&quot;http://www.youtube.com/watch?v=WY50PVVXPaY&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;), which are well enjoyed until the batteries go.  Every time we get one, I can't help but think, &quot;I must be able to hack this, to reprogram it or change the music.&quot;  I don't imagine that I will any time soon, but I was wondering if anyone knows of a tutorial or blog post where someone goes through hacking one of these, or even a tear down.  [Granted, they likely use several different chips, and they might not be rewritable, or may require hardware I don't have, but I can't imagine that someone hasn't done it and documented it!] &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, I haven't looked deeply into it.  I suppose I'm wondering if it is likely to be something simple to do -- say, in a couple of hours or on a weekend -- or likely to be something to difficult to be worth the bother.&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-04-02T17:32:32.997" LastActivityDate="2010-04-06T16:57:43.360" Title="Hacking a singing, dancing plush toy" Tags="&lt;hack&gt;" AnswerCount="2" />
  <row Id="2128" PostTypeId="2" ParentId="2122" CreationDate="2010-04-02T15:38:17.620" Score="0" ViewCount="" Body="&lt;p&gt;Are you sure that the noise is coming from your power lines? One other thing to consider is that with cheap sound equipment it tends to be that all of the components and design are cheaper. This can include anything from resistors to opamps, even the PCB used. There also tends to be little shielding on cheaper boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it is the case that your components are cheap with no shielding there could be noise from florescent lights getting into your system. (This is of course if you are in a room with florescent)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have also noticed hum being introduced to audio systems when cheap dimmers are used for the lighting in the room.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-04-02T15:43:56.637" LastActivityDate="2010-04-02T15:43:56.637" CommunityOwnedDate="2010-04-02T15:38:17.620" CommentCount="1" />
  <row Id="2129" PostTypeId="2" ParentId="2127" CreationDate="2010-04-02T17:31:37.257" Score="3" ViewCount="" Body="&lt;p&gt;There are lots of circuit bending resources linked to &lt;a href=&quot;http://www.synthtopia.com/content/tag/circuit-bending/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also a link on that page to something called &lt;a href=&quot;http://www.synthtopia.com/content/2009/05/13/plush-toy-circuit-bending-with-the-bach-bot-9000/&quot; rel=&quot;nofollow&quot;&gt;Plush Toy Circuit Bending&lt;/a&gt;, but I can't access it from my phone to see if it's any good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A quick Google for 'circuit bending' should get you some resources,  I remember coming across a description of a circuit bent Staples 'Easy Button' somewhere which is similar to what you want but I can't remember where.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;[EDIT]&lt;/strong&gt; Right I see, that links to a video giving an example of a soft toy (I think in the UK we'd use the term soft toy to describe what you would call a plush toy) designed specifically for letting children experiment with circuit bending. You might be better looking at some of Eric archer's &lt;a href=&quot;http://ericarcher.net/devices/&quot; rel=&quot;nofollow&quot;&gt;Devices&lt;/a&gt;, (my favourite is the circuit bent tabla machine although that's not really what you're looking for) or maybe searching for the many, many experiments with circuit bent Speak and Spell toys.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-04-02T21:18:31.213" LastActivityDate="2010-04-02T21:18:31.213" />
  <row Id="2130" PostTypeId="1" AcceptedAnswerId="2133" CreationDate="2010-04-04T09:36:54.083" Score="5" ViewCount="203" Body="&lt;p&gt;Does anyone know of a maker of Conductive Fabric?&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2010-05-16T09:16:35.117" Title="Conductive Fabric" Tags="&lt;conductive&gt;&lt;fabric&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="2131" PostTypeId="2" ParentId="2130" CreationDate="2010-04-04T10:00:10.947" Score="3" ViewCount="" Body="&lt;p&gt;Becky Stern sells conductive thread... perhaps you could sew that in to your fabric?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://sternlab.org/store/&quot; rel=&quot;nofollow&quot;&gt;http://sternlab.org/store/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-04-04T10:00:10.947" />
  <row Id="2132" PostTypeId="2" ParentId="2130" CreationDate="2010-04-04T13:59:06.050" Score="0" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://wires.co.uk/&quot; rel=&quot;nofollow&quot;&gt;Scientific Wire Co.&lt;/a&gt; sells knitted copper wire.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-04T13:59:06.050" />
  <row Id="2133" PostTypeId="2" ParentId="2130" CreationDate="2010-04-04T14:52:39.083" Score="5" ViewCount="" Body="&lt;p&gt;Copying my answer from &lt;a href=&quot;http://chiphacker.com/questions/184/is-there-a-way-to-print-draw-a-circuit-on-to-clothing&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/184/is-there-a-way-to-print-draw-a-circuit-on-to-clothing&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See &lt;a href=&quot;http://www.plusea.at/&quot; rel=&quot;nofollow&quot;&gt;http://www.plusea.at/&lt;/a&gt; for all kinds of wearable electronics, including conductive fabric, thread, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.kobakant.at/DIY/&quot; rel=&quot;nofollow&quot;&gt;How To Get What You Want&lt;/a&gt; by the same people has more details: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.kobakant.at/DIY/?cat=38&quot; rel=&quot;nofollow&quot;&gt;Traces&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.kobakant.at/DIY/?cat=24&quot; rel=&quot;nofollow&quot;&gt;Conductive materials&lt;/a&gt;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.kobakant.at/DIY/?p=376&quot; rel=&quot;nofollow&quot;&gt;Conductive fabrics&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm4.static.flickr.com/3087/2759097679_d59b91f365.jpg?v=0&quot; alt=&quot;alt text&quot;&gt;&lt;img src=&quot;http://farm4.static.flickr.com/3340/3608026021_e276861736.jpg?v=0&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-04-04T14:52:39.083" />
  <row Id="2134" PostTypeId="2" ParentId="2130" CreationDate="2010-04-04T18:33:40.063" Score="4" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.lessemf.com/fabric.html&quot; rel=&quot;nofollow&quot;&gt;Less EMF&lt;/a&gt; has the largest selection in the States&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://eeonyx.com/&quot; rel=&quot;nofollow&quot;&gt;Eeonyx&lt;/a&gt; sells a range of high performance materials that you can order to spec.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.fine-silver-productsnet.com/&quot; rel=&quot;nofollow&quot;&gt;Fine Silver Products&lt;/a&gt; sells silver-doped fabrics&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.kobakant.at/DIY/?p=376&quot; rel=&quot;nofollow&quot;&gt;How To Get What You Want&lt;/a&gt; gives a good overview of the known conductive fabric merchants&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://fashioningtechnology.ning.com/&quot; rel=&quot;nofollow&quot;&gt;Fashioning Technology blog&lt;/a&gt; should give you some inspiration&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;A trip to the store with a multi-meter can be enlightening. Various commonly available tapes, fabrics, gels, packages etc. are conductive.&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2010-04-04T18:33:40.063" />
  <row Id="2135" PostTypeId="1" CreationDate="2010-04-05T15:29:36.807" Score="1" ViewCount="638" Body="&lt;p&gt;How do I determine how powerful an H-Bridge I need to control a DC-motor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In particular, does an H-Bridge need to be able to supply the full amount of current a motor will use when stalled, or would it be okay to use an H-Bridge that supplies enough power for a motor under standard load (and then some, but not stall conditions), and if so, what happens if the motor wants to draw more power than is available?  (Does the H-Bridge fry, or does the motor just stop?)&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2010-04-13T14:14:46.013" Title="H-Bridges and Motor Stall Current" Tags="&lt;motor&gt;" AnswerCount="3" />
  <row Id="2136" PostTypeId="2" ParentId="2135" CreationDate="2010-04-05T15:41:56.910" Score="2" ViewCount="" Body="&lt;p&gt;A current sensor, such as a resistor in series with the load, is often used to protect the system. A better solution is &lt;a href=&quot;http://cds.linear.com/docs/Design%20Note/dn407f.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-04-05T16:22:53.083" LastActivityDate="2010-04-05T16:22:53.083" />
  <row Id="2137" PostTypeId="2" ParentId="2057" CreationDate="2010-04-05T17:43:48.443" Score="2" ViewCount="" Body="&lt;p&gt;you could simply add two square waves, and use fast pwm to output the &quot;analog&quot; signal to the speaker. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;here's yet another different method if you like game sound, quick and dirty:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;https://gitweb.bl0rg.net/cgi-bin/gitweb.cgi?p=arduinisten.git;a=blob;f=projekte/soundz/arpeggio/arpeggio.pde;h=6ceb64a57916c094e87e5983c07b5dd1b4623083;hb=HEAD&quot; rel=&quot;nofollow&quot;&gt;https://gitweb.bl0rg.net/cgi-bin/gitweb.cgi?p=arduinisten.git;a=blob;f=projekte/soundz/arpeggio/arpeggio.pde;h=6ceb64a57916c094e87e5983c07b5dd1b4623083;hb=HEAD&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-04-05T17:43:48.443" />
  <row Id="2138" PostTypeId="1" CreationDate="2010-04-05T21:35:09.023" Score="4" ViewCount="290" Body="&lt;p&gt;Where do I find such a module? All of the embedded PC modules I've seen so far have only a slow 10/100 Mbit Ethernet interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;: this is for a scanner application. I get incoming data at a rate of 2 MByte/s, which I need to store locally e.g. on a SD-Card. The whole image is over 10 GByte, which is why I need a fast interface to transfer it to a PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update #2&lt;/strong&gt;: here's one I just found: Technologic Systems &lt;a href=&quot;http://www.embeddedarm.com/products/board-detail.php?product=TS-7800&quot; rel=&quot;nofollow&quot;&gt;TS-7800&lt;/a&gt;, it even features an user-programmable FPGA. There are other &lt;a href=&quot;http://www.embeddedarm.com/products/index.php&quot; rel=&quot;nofollow&quot;&gt;models&lt;/a&gt; available.&lt;/p&gt;&#xA;" OwnerUserId="672" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T16:22:30.263" LastActivityDate="2010-10-22T16:22:30.263" Title="Embedded PC with Gigabit Ethernet and SD-Card interface?" Tags="&lt;embedded&gt;&lt;sd&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="2139" PostTypeId="2" ParentId="2057" CreationDate="2010-04-05T22:06:00.600" Score="1" ViewCount="" Body="&lt;p&gt;You can just add the streams as described here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.vttoth.com/digimix.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.vttoth.com/digimix.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2010-04-05T22:06:00.600" />
  <row Id="2140" PostTypeId="2" ParentId="2138" CreationDate="2010-04-06T04:22:48.637" Score="1" ViewCount="" Body="&lt;p&gt;Check out &lt;a href=&quot;http://routerboard.com/pricelist.php?started_from_home=1&quot; rel=&quot;nofollow&quot;&gt;RouterBOARD&lt;/a&gt; -- These are custom designed hardware meant to be used with the Linux-based &lt;a href=&quot;http://www.mikrotik.com/index.html&quot; rel=&quot;nofollow&quot;&gt;MikroTik&lt;/a&gt; router software, but no reason you couldn't put your own software on there. You didn't really say anything at all about your application, so it's hard to give a specific recommendation, but the &lt;a href=&quot;http://routerboard.com/index.php?showProduct=90&quot; rel=&quot;nofollow&quot;&gt;RB750G&lt;/a&gt; is a good combination of price &amp;amp; power I think. 680MHz CPU, 32MB RAM, with 5 gigabit LAN ports. &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-04-06T04:22:48.637" />
  <row Id="2141" PostTypeId="2" ParentId="2138" CreationDate="2010-04-06T11:14:17.480" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.globalscaletechnologies.com/t-guruplugdetails.aspx&quot; rel=&quot;nofollow&quot;&gt;Guruplug Server&lt;/a&gt;. Dual gigabit, usb, esata, external sd interface and a bunch of other ports. Runs linux too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Guruplug Server Plus will set you back $130USD. Mine has already been ordered!&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-04-06T11:14:17.480" CommentCount="1" />
  <row Id="2142" PostTypeId="2" ParentId="2135" CreationDate="2010-04-06T11:43:32.697" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;How do I determine how powerful an H-Bridge I need to control a DC-motor?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If you want to provide full stall current, measure the DC resistance of the motor leads. (e.g. a 0.3 ohm motor connected to a 12V battery will draw 40A at stall) If you want to be able to drive the motor to full speed, then reverse it, it will draw twice that current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a current sensor, you can (with suitable control circuitry) limit the current to any value you choose, for a &quot;soft-start&quot;. This is usually a good idea. A less complicated route is to have a current trip sensor which then turns off the H-bridge (do NOT short the motor out, it will overcurrent if it is spinning) if there is an overcurrent detected, then retry some time period later. This has inferior performance to current limiting but will generally be adequate.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-04-06T11:43:32.697" />
  <row Id="2143" PostTypeId="2" ParentId="2127" CreationDate="2010-04-06T16:05:10.127" Score="2" ViewCount="" Body="&lt;p&gt;Probably the best way to figure out how to hack it would be to do a bit of reverse engineering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While the toy still works, I'd expose the circuit board and do some probing with a multimeter/logic analyzer/oscilloscope to see which lines change their voltage level and what that moves / makes sound.  Identify the ground bus on the board, and try probing various points on the main IC (usually it's an epoxy block blob).  Write down on a sheet of paper what moves and how the voltage on various pins change wrt ground, and you should have a pretty good idea of what lines control what...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A line that goes high when something moves, and low when it moves back controls the movement.  If it jiggles while a line is high, that line makes it jiggle, etc.  Take down the current requirements used when driving the lines.  Write down what the logic levels are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you can replace the main IC with your own &quot;brains&quot; that meet the same specs (current output, logic levels) as the main IC, and make it do whatever you want.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-04-06T16:57:43.360" LastActivityDate="2010-04-06T16:57:43.360" />
  <row Id="2144" PostTypeId="2" ParentId="2103" CreationDate="2010-04-07T12:01:11.133" Score="5" ViewCount="" Body="&lt;p&gt;You may want to read this great old article by Bob Pease, &lt;a href=&quot;http://www.national.com/rap/Story/0,1562,8,00.html&quot; rel=&quot;nofollow&quot;&gt;What's All This &quot;SMWISICDSI&quot; Stuff, Anyhow?&lt;/a&gt;, that speaks to the question.&lt;/p&gt;&#xA;" OwnerUserId="484" LastActivityDate="2010-04-07T12:01:11.133" />
  <row Id="2145" PostTypeId="1" AcceptedAnswerId="2146" CreationDate="2010-04-07T12:52:03.027" Score="9" ViewCount="417" Body="&lt;p&gt;I have a small hw product and I would like to find a plastic enclosure company that do small runs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Recommendations with experience please (i.e. not a simple Google Search result dump!)&lt;/p&gt;&#xA;" OwnerUserId="329" LastActivityDate="2011-05-18T11:38:03.193" Title="Plastic enclosure for small product" Tags="&lt;enclosure&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="4" />
  <row Id="2146" PostTypeId="2" ParentId="2145" CreationDate="2010-04-07T13:19:58.730" Score="8" ViewCount="" Body="&lt;p&gt;I would say that to keep costs to a minimum you need to try to fit your product to one of the standard enclosure boxes made by (for example) &lt;a href=&quot;http://www.okw.co.uk&quot; rel=&quot;nofollow&quot; title=&quot;OKW&quot;&gt;OKW&lt;/a&gt;.  The problem with a bespoke mould for your product you are looking at a large NRE charge for the design and some thousands of pounds for the tooling costs.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-04-07T13:19:58.730" CommentCount="1" />
  <row Id="2147" PostTypeId="2" ParentId="1609" CreationDate="2010-04-07T17:25:48.027" Score="3" ViewCount="" Body="&lt;p&gt;There are many I/O Expanders out there that use either SPI or I2C buses. With a single MSSP module you can control almost an infinite amount of digital outputs like LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See the Microchip datasheets or application notes for the following parts:&lt;br&gt;&#xA;SPI - &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en021817&quot; rel=&quot;nofollow&quot;&gt;MCP23S08&lt;/a&gt;&lt;br&gt;&#xA;I2C - &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en021393&quot; rel=&quot;nofollow&quot;&gt;MCP23008&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-07T17:25:48.027" />
  <row Id="2148" PostTypeId="2" ParentId="2065" CreationDate="2010-04-07T22:46:35.397" Score="1" ViewCount="" Body="&lt;p&gt;Depending on the type of LED, &lt;em&gt;you may or may not&lt;/em&gt; need a resistor in a throwie configuration. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wrote up &lt;a href=&quot;http://www.evilmadscientist.com/go/throw&quot; rel=&quot;nofollow&quot;&gt;an article&lt;/a&gt; examining some of the subtleties involved in that question; you may want to take a look. (Spoiler: For red or yellow LEDs, DEFINITELY use a resistor.)  &lt;/p&gt;&#xA;" OwnerUserId="484" LastActivityDate="2010-04-07T22:46:35.397" />
  <row Id="2149" PostTypeId="2" ParentId="621" CreationDate="2010-04-08T00:09:12.440" Score="1" ViewCount="" Body="&lt;p&gt;I think, it depends on the project 100%.  For example, attempting to solder stranded on to a diode... you either pop the diode or get too mush soldier.  When using diodes... I always use solid core... same with capacitors etc...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stranded works when you can crimp onto large diodes like the old Germanium types.  But the newer High Output Diode does not like to be crimped... it needs all the electrons it can get.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stranded is for 'handling' or 'the monkey principle'.  If you plan to lay the wire once and forget it in a place where very little vibration occures, then solid is the way to go, the variance will not change over time as the wire oxidizes.  Stranded cable because of the tiny bits of air that surround the strands, will oxidize much faster and in maybe 3 years, it will be brown and lacking conductivity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same with 'tinning' on small component type circuits.  You don't want to change the behavior of the electrons as they flows.  There is a reason we moved away from Tin wire Heavily used up until say 1985 or so... it would become brittle and in a lot of cases degrade the copper so that you would get pitting between the tin and copper.  But still today, professors and engineers who earned their degrees in prior to say 1990 or 1995 are taught that tinning has a positive effect.  Like Marconi invented the Radio or Edison invented the Light bulb.  They teach this as 'right'.  There is a reason why Cu is far away from Sn.  Germanium vs Silicon... I remember my micorprocessor professor swearing Germanium will out live Silicon as the semi-conductor of the future.  That is where we are with Tinning wire.  Stranded vs Solid core applications for wire.  If it was better then modern engineers would insist on tinned stranded cable... but we know they prefer the purist copper cable they can find for their applications.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stranded vs Solid Core wire arguments&#xA;- Stranded wire good for only applications where heavy vibrations would crack a solid core wire (I have no idea what that would be, the wire would have to be strung pretty tight)&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Lots of handling (monkey principle) &lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;cheaper for industry to to install and forget, there is a huge market for replacement LED's for Marine equipment because of outdated engineering data REQUIRES stranded core wires... and engineers have to use the old Germanium LED's so they can meet this standard... (wave my magic wand: &quot;ridiculous&quot;) Maybe this made sense when we had locomomitive engines driving boats... Have you been on a boat lately, they are built like Rolls Royces... same with cars... when was the last time you sat in a new car and you thought, man I hope it holds together long enough to drive it off the lot?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;How much vibration is needed (even over a long time to break a 24AWG wire?) &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;Lots of bending back and forth... like installed on a moveable arm or some moveable device... but bending around lots of corners is not a good enough excuese.  &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;[I remember a study about stranded vs Solid core about which one would heat up and break faster when bent at 45 degrees but, I forget what the out come was] &lt;/p&gt;&#xA;&#xA;&lt;p&gt;[CAT 5 has been in buildings since... 1994/5 (earlier?) and is now after 15 years starting be replaced on a massive scale by CAT 7 and fiber.  If stranded was better, engineers would have switched to it long ago.]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Breadboard technology - CAT 5 comes in 22AWG to 24AWG - 24AWG holds firmly unless you have plugged house wire into the holes ;-P.  Or larger than 24AWG - like 20AWG wire will fit in the breadboard and 'electronic' kits come with 20AWG and will stretch out a breadboard.  Expiriment - get new board and plug different size wires into holes and see which ones stretch out the holes.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;oh well, this MIT grad has worn himself out here... but I enjoyed reading peoples responses... and the 'war' continues over Stranded vs Solid core ... your biggest rival SAE and ABYC are very outdated... as is UL... and the IEEE and ISO.  They were great when they were young, but good jobs create a need for job security and it is easier to go with 'what you know' even if that is not the 'best' way to go.  In a way it makes sense.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" LastActivityDate="2010-04-08T00:09:12.440" />
  <row Id="2150" PostTypeId="2" ParentId="2115" CreationDate="2010-04-08T04:19:49.510" Score="3" ViewCount="" Body="&lt;p&gt;What you're probably looking for is a SPDT RF switch of some sort.  You can find RF relays that are designed for low loss and good isolation.  These are usually a few hundred dollars, but you may be able to find one on ebay or surplussed for cheap. The driving of a relay is very straightforward, but may require higher voltages than anything else in your system. Another option is using PIN diodes to act as RF switches. I'm not familiar with actual applications, but it may be easier or cheaper to try and make a switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the frequencies you're interested in, a simple mechanical relay may give you issues with loss and isolation. I'm also guessing you couldn't manually swap out the antennas either. Good luck.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-04-08T04:19:49.510" CommentCount="2" />
  <row Id="2151" PostTypeId="1" AcceptedAnswerId="2152" CreationDate="2010-04-08T09:16:44.313" Score="3" ViewCount="194" Body="&lt;p&gt;Here is a picture of two crystals: &lt;img src=&quot;http://imgur.com/EO6bP.jpg&quot; alt=&quot;two crystals&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does the difference of frequency explain why the 6Mhz crystal on the right has a lower profile than the 5Mhz one ?&lt;/p&gt;&#xA;" OwnerUserId="595" LastEditorUserId="595" LastEditorDisplayName="" LastEditDate="2010-04-08T20:01:12.597" LastActivityDate="2011-03-11T23:26:17.903" Title="Does the frequency of a crystal influence its height ?" Tags="&lt;crystal&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="2152" PostTypeId="2" ParentId="2151" CreationDate="2010-04-08T09:26:42.683" Score="6" ViewCount="" Body="&lt;p&gt;Influence, yes. Determine, no. For example, here's a tiny surface mount 16MHz crystal...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.chinafronter.com/admin/images/product/4025.jpg&quot; alt=&quot;http://www.chinafronter.com/admin/images/product/4025.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The frequency is determined by the size, shape and cut of the quartz crystal as well as where the electrodes are placed on it.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-04-08T14:41:38.380" LastActivityDate="2010-04-08T14:41:38.380" />
  <row Id="2153" PostTypeId="2" ParentId="621" CreationDate="2010-04-08T10:28:53.613" Score="0" ViewCount="" Body="&lt;p&gt;These are great for solderless breadboards:&#xA;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Jumper-Wires-Premium-12%22-M%7B47%7DM--Pack-of-10.html&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/Jumper-Wires-Premium-12%22-M%7B47%7DM--Pack-of-10.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-04-08T10:28:53.613" />
  <row Id="2154" PostTypeId="2" ParentId="2151" CreationDate="2010-04-08T11:18:57.327" Score="2" ViewCount="" Body="&lt;p&gt;And the size of the crystal! With the usual AT-cut crystals the size is inversely  proportional to the frequency - low-frequency crystals are larger than high-frequency ones.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-04-08T19:28:51.577" LastActivityDate="2010-04-08T19:28:51.577" CommentCount="5" />
  <row Id="2155" PostTypeId="1" CreationDate="2010-04-08T22:51:16.540" Score="1" ViewCount="327" Body="&lt;p&gt;Was wondering if someone could give me a hand with a project that I am undertaking. I have searched forums high and low and am yet to find the information to solve my problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically I have an RFID Reader (an ID20) and I have an Arduino Duemilanove.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to read the RFID data in, but I am not able to use Digital Pin 0 because I am using 1 and 0 to connect to a PC for Serial Communication. My assumed solution for this was to use a UART of some type to store the information until it is ready to be read by the Arduino (perhaps through SoftwareSerial). I cannot use SoftwareSerial because I need other actions to be performed between receiving RFID data, and SoftwareSerial pauses the Arduino until it receives data from the RFID.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure if I can use an FTDI USB UART ... can I?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?&lt;/p&gt;&#xA;" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-04-09T07:23:24.833" LastActivityDate="2010-04-09T07:23:24.833" Title="RFID Reader UART" Tags="&lt;arduino&gt;&lt;rfid&gt;&lt;uart&gt;&lt;serial&gt;" AnswerCount="1" />
  <row Id="2156" PostTypeId="1" AcceptedAnswerId="2166" CreationDate="2010-04-09T02:57:35.953" Score="1" ViewCount="377" Body="&lt;p&gt;I am looking at creating a USB host devices to talk to a standalone printer.&#xA;Basically my devices would feed out commands to the USB chip and the pritner would print it without interaction of a PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What chips would you recommend for the USB/MCU? &#xA;I am leaning towards an ATMEGA micro with a Vinculum USB interface.&#xA;Would it be easier to use a all in one chip or have a seperate MCU and USB chip?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="641" LastActivityDate="2010-04-12T12:54:13.080" Title="USB Host device" Tags="&lt;usb&gt;&lt;host&gt;&lt;atmega&gt;" AnswerCount="5" />
  <row Id="2157" PostTypeId="2" ParentId="2156" CreationDate="2010-04-09T03:52:17.270" Score="1" ViewCount="" Body="&lt;p&gt;You might be able to use an MCU with USB OTG to drive the printer. It will be a lot cheaper than using a separate chip like the Vinculum.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-09T03:52:17.270" />
  <row Id="2158" PostTypeId="2" ParentId="2156" CreationDate="2010-04-09T07:16:31.417" Score="1" ViewCount="" Body="&lt;p&gt;Have a look at &lt;a href=&quot;http://www.fourwalledcubicle.com/LUFA.php&quot; rel=&quot;nofollow&quot;&gt;LUFA&lt;/a&gt;, it has some support for USB host on MCUs. However, I expect that the printer driver you create might end up being tied to one particular model of printer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your project requirements, it might be easier to drive a serial or parallel printer interface than USB.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-04-09T07:16:31.417" />
  <row Id="2159" PostTypeId="2" ParentId="2155" CreationDate="2010-04-09T07:21:51.777" Score="1" ViewCount="" Body="&lt;p&gt;It sounds like you need a software serial driver which runs under interrupt rather than polling the pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://arduiniana.org/libraries/NewSoftSerial/&quot; rel=&quot;nofollow&quot;&gt;http://arduiniana.org/libraries/NewSoftSerial/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-04-09T07:21:51.777" />
  <row Id="2160" PostTypeId="2" ParentId="2036" CreationDate="2010-04-09T07:23:57.593" Score="3" ViewCount="" Body="&lt;p&gt;The scanalogic is a simple but nice 4 channel logic analyzer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ikalogic.com/scanalogic_home.php&quot; rel=&quot;nofollow&quot;&gt;http://www.ikalogic.com/scanalogic_home.php&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-04-09T07:23:57.593" />
  <row Id="2161" PostTypeId="1" CreationDate="2010-04-09T07:37:48.360" Score="6" ViewCount="254" Body="&lt;p&gt;I hate reading datasheets or user manuals on the screen, and printing such documents tends to waste a lot of paper/ink. Has anyone tried to use an eBook Reader for this purpose? Are they good enough to display the sometimes complex diagrams found on datasheets?&lt;/p&gt;&#xA;" OwnerUserId="672" LastActivityDate="2010-04-09T10:12:54.590" Title="eBook Reader for Datasheets" Tags="&lt;datasheet&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="2162" PostTypeId="2" ParentId="2161" CreationDate="2010-04-09T10:12:54.590" Score="6" ViewCount="" Body="&lt;p&gt;I've used a Kindle DX to read datasheets, and it has been a relatively pleasant experience. Typically, on a datasheet, the text is reasonably large enough that it looks OK. I've also used it on journal papers, and found that the text is small enough that it can be hard to read. Figures with very fine lines don't show up, but again, datasheets typically aren't too bad about this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The zoom ability is limited, which makes it difficult to zoom in just enough to cut out the margins. One workaround is to &quot;print&quot; the PDF using a PDF printer on a smaller virtual page. It might be worth it to figure out the correct settings for something large, like a book or microcontroller datasheet, or for a particular manufacturer you use frequently, but it's a clunky hack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think I would lay down $480 USD for &lt;em&gt;just&lt;/em&gt; reading datasheets. The experience feels second-class compared to the rest of the e-book features. I view it as a nice perk of the device.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-04-09T10:12:54.590" CommentCount="3" />
  <row Id="2163" PostTypeId="2" ParentId="2156" CreationDate="2010-04-09T13:12:21.243" Score="0" ViewCount="" Body="&lt;p&gt;My experience is primarily with Microchip, but Atmel may have chips with integrated USB as well. Microchip has a few products with integrated USB. You'll want one that supports USB on-the-go or embedded host. Microchip also provides the USB host stack that will help get you up and running with a few basic device classes.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-09T13:12:21.243" />
  <row Id="2164" PostTypeId="2" ParentId="1133" CreationDate="2010-04-09T14:06:05.277" Score="-1" ViewCount="" Body="&lt;p&gt;All semiconductor companies have an EOL (End Of life) notification program.  You can sign up for that to know when the parts go away.  Talk to your semiconductor distributor too; Arrow and Avnet can both notify you across most (all?) of the vendors they carry.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-04-09T14:06:05.277" />
  <row Id="2165" PostTypeId="1" CreationDate="2010-04-09T14:33:01.367" Score="4" ViewCount="239" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Recently I have been trying to get myself an arduino made by hand (as where I live the original one costs about 10x and its fun to make things on your own). I made a compatible on the breadboard and tested it using the blinky program. Now I want to make it on a PCB. The problem is getting a PCB manufactured is also not so cheap (if you are getting only one board). So I was thinking I would use a prototype board. I have used those once before and it was a clear mess. I kept shorting IC pins while connecting lines to them fried a whole PCB (actually fried it, the LEDs went BOOT, the IC went WOOSH and the wires turned to a general copper ting). All in all it was a not so good experience. I attribute this failure to my incompetence in soldering on the prototype boards. I can do a clean solder on any PCB in a kit but I think prototype boards are a different ball game. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I ask you all of any tips you may have on using such boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2011-05-18T11:38:41.820" Title="Tips on using a Prototype PCB" Tags="&lt;pcb&gt;&lt;protoboard&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="2166" PostTypeId="2" ParentId="2156" CreationDate="2010-04-09T14:45:37.390" Score="1" ViewCount="" Body="&lt;p&gt;I've never used one, but I'd look into the &lt;a href=&quot;http://www.atmel.com/dyn/Products/Product_card.asp?part_id=3875&quot; rel=&quot;nofollow&quot;&gt;AT90USB1287&lt;/a&gt; chip.  It even comes in an handy evaluation board called the &lt;a href=&quot;http://www.atmel.com/dyn/products/tools_card.asp?tool_id=3879&quot; rel=&quot;nofollow&quot;&gt;AT90USBKey&lt;/a&gt;.  While the chip itself is supposed to be able to act as a &lt;a href=&quot;http://en.wikipedia.org/wiki/USB_On-The-Go&quot; rel=&quot;nofollow&quot;&gt;USB-OTG&lt;/a&gt; Host, it isn't clear to me that the demo board supports that.&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2010-04-09T14:45:37.390" CommentCount="1" />
  <row Id="2167" PostTypeId="2" ParentId="2165" CreationDate="2010-04-09T14:49:01.700" Score="1" ViewCount="" Body="&lt;p&gt;When using perfboard use wire-wrap wire to make the connections. Ideally you could wire wrap the wire to the terminal before soldering it too. You always want a good mechanical connection for the wire prior to making the solder connection. By using wire wrap wire you will reduce the amount of excess wire you have and reduce the chances of creating shorts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Protoboard&quot; rel=&quot;nofollow&quot;&gt;Protoboard/Breadboard&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Perfboard&quot; rel=&quot;nofollow&quot;&gt;Perfboard&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-09T14:49:01.700" />
  <row Id="2168" PostTypeId="2" ParentId="2165" CreationDate="2010-04-09T15:30:14.207" Score="2" ViewCount="" Body="&lt;p&gt;I like to start with a piece of graph paper with a 100mil grid. You &#xA;can set the components out and draw connections and start with&#xA;a good layout plan. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make wiring and changes easy I like to use a lot of micro-clips (Vector T42-1)&#xA;and pins (Vector K24A). I run short jumpers to the clips and pins. I then solder&#xA;the components to the clips and pins. I use bus wire and teflon sleeving (where &#xA;necessary). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I put together some hints, a supply list and example pics. See &lt;a href=&quot;http://www.luciani.org/getting-it-done/assembly-hints/assembly-hints-index.html#breadboard-hints&quot; rel=&quot;nofollow&quot; title=&quot;breadboard hints&quot;&gt;breadboard hints&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:38:41.820" LastActivityDate="2011-05-18T11:38:41.820" />
  <row Id="2169" PostTypeId="1" CreationDate="2010-04-09T15:48:32.457" Score="3" ViewCount="104" Body="&lt;p&gt;Using software while PWMing a coil with feedback going to an A/D input,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1)  &lt;strong&gt;how can you detect a state where the coil is an open circuit?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2)  &lt;strong&gt;how can you detect a state where the coil is a short circuit?&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-04-09T18:03:11.587" Title="Detecting opens/shorts when driving coils" Tags="&lt;pwm&gt;&lt;detection&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="2170" PostTypeId="1" CreationDate="2010-04-09T17:23:31.970" Score="6" ViewCount="317" Body="&lt;p&gt;Hello!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have read that varicaps (capacity diodes) are a &quot;modern&quot; alternative to variable capacitors. In several electronics books only positive properties of varicaps are mentioned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But several major distributors (here in Germany) simply don't offer varicaps, or just have less than 5 of SOT-23 models. &lt;em&gt;(For comparison: same distributor offers around 1000 different diode models.)&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At three largest German distributors of electronic components I couldn't find a single &lt;em&gt;DO-xxx&lt;/em&gt; case varicap. Only SOT-xxx.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does it mean that varicaps are obsolete? If so, what do people use in today's circuits as &quot;replacement&quot;? Or, more general, is there some more common &quot;concept&quot; to vary capacity?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you.&lt;/p&gt;&#xA;" OwnerUserId="491" LastEditorUserId="491" LastEditorDisplayName="" LastEditDate="2010-04-10T20:23:17.803" LastActivityDate="2011-05-06T17:21:01.770" Title="Are varicaps (capacity diodes) obsolete?" Tags="&lt;capacity&gt;&lt;diode&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="2171" PostTypeId="2" ParentId="2169" CreationDate="2010-04-09T18:03:11.587" Score="2" ViewCount="" Body="&lt;p&gt;I'm guessing that your sensing is based on measuring the voltage drop across a series resistor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With an open circuit, you would not have any voltage drop across the sense resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a short circuit that shorts a large portion of the coil, you would notice a difference in the current when the PWM is at the &quot;off&quot; portion of the cycle. The series current should remain at a near constant level when the PWM is off. A short circuit would result in the series current dropping to 0 quickly after the PWM shuts off. Alternatively, you could look for a gradual increase in current after switching on the PWM. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't change the PWM modulation rapidly (so the circuit has time to reach equilibrium), you could build a table of currents corresponding to each PWM code. If you're not getting the current you're expecting, you may have an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A different approach using a magnetic field strength sensor, such as a Hall Effect device, would actually verify that coil is generating a magnetic field, but it may be more difficult to set up. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-04-09T18:03:11.587" CommentCount="1" />
  <row Id="2173" PostTypeId="2" ParentId="1754" CreationDate="2010-04-09T18:46:44.577" Score="0" ViewCount="" Body="&lt;p&gt;You may have a look at the Xilinx &lt;a href=&quot;http://www.xilinx.com/ipcenter/processor_central/picoblaze/picoblaze_user_resources.htm&quot; rel=&quot;nofollow&quot;&gt;PicoBlaze&lt;/a&gt; processor. It's a minimal 8-bit embedded microcontroller, and the source code should be available.&lt;/p&gt;&#xA;" OwnerUserId="672" LastActivityDate="2010-04-09T18:46:44.577" CommentCount="1" />
  <row Id="2174" PostTypeId="2" ParentId="2170" CreationDate="2010-04-09T22:20:11.987" Score="7" ViewCount="" Body="&lt;p&gt;They are still widely used in VCOs in phase-locked loop frequency synthesisers.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-09T22:20:11.987" CommentCount="1" />
  <row Id="2175" PostTypeId="2" ParentId="1893" CreationDate="2010-04-10T15:59:11.537" Score="1" ViewCount="" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.pcbwing.com/&quot; rel=&quot;nofollow&quot;&gt;pcbwing.com&lt;/a&gt; is a good one!&lt;/p&gt;&#xA;" LastActivityDate="2010-04-13T10:43:35.797" CommunityOwnedDate="2010-04-10T15:59:11.537" />
  <row Id="2176" PostTypeId="1" CreationDate="2010-04-10T18:15:37.967" Score="6" ViewCount="404" Body="&lt;p&gt;I need to implement a simple lowpass filter for a data acquisition circuit (using stretch conductive fabric as a resistive sensor). Various sources have recommended that the best way to go about this is to use filter design software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't found a filter design tool (calculator) that I like yet. The online ones I've found have been buggy/obnoxious. The best solution would be one with a nice GUI that works with Mac OS X. Alternatively a Unix/Linux solution could work. Windows is a no-go for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this list: &lt;a href=&quot;http://www.circuitsage.com/filter.html&quot; rel=&quot;nofollow&quot;&gt;http://www.circuitsage.com/filter.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; I'm using &lt;a href=&quot;http://astro.u-strasbg.fr/~koppen/radio/Activee.html&quot; rel=&quot;nofollow&quot;&gt;this web-based one&lt;/a&gt; right now, specifically for active filters (which are more applicable for sensors as they are more stable with low frequencies). &lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2011-02-09T11:17:06.703" LastActivityDate="2011-02-09T19:02:27.267" CommunityOwnedDate="2010-04-11T14:37:39.990" Title="Good filter design software for Mac OS X/Unix?" Tags="&lt;design&gt;&lt;software&gt;&lt;filter&gt;&lt;tools&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="2177" PostTypeId="2" ParentId="2176" CreationDate="2010-04-10T19:19:26.997" Score="2" ViewCount="" Body="&lt;p&gt;Depends what you mean by &quot;simple lowpass filter&quot; and what you need the software to do.  If you just want the -3 dB frequency for an LC filter:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/search?q=1%2F%282%2api%2asqrt%2850+millihenry+%2a+1+microfarad%29%29+in+Hz&quot; rel=&quot;nofollow&quot;&gt;Google Calculator&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.wolframalpha.com/input/?i=1%2F%282%2api%2asqrt%2850+mH+%2a+1+uF%29%29+in+Hz&quot; rel=&quot;nofollow&quot;&gt;Wolfram Alpha&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-04-10T19:19:26.997" />
  <row Id="2178" PostTypeId="1" AcceptedAnswerId="2261" CreationDate="2010-04-10T23:37:33.973" Score="7" ViewCount="1036" Body="&lt;p&gt;Hey,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've build a small three wheel robot with an Arduino Mega to drive the thing.&#xA;I'm looking to keep this bot mobile as much as I can without needing to interact with it for charging etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the moment I am running on a collection of normal AA batteries as the power source.&#xA;I'd like to replace this with an appropriate rechargeable battery pack, and a charging circuit of some kind.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'm after two things.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Information on charging circuits. I feel like I am searching for the wrong thing, and am not coming up with anything useful.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Inductive charging. I really would like to be able to park the robot on a charging base, and leave it there, and have it just drive off the base when its done. Most articles I can find say to rip apart an electric toothbrush for this. But I would love to do it myself.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Cheers!&lt;/p&gt;&#xA;" LastActivityDate="2011-04-20T20:11:35.380" Title="Inductive Charging" Tags="&lt;charging&gt;&lt;batteries&gt;&lt;arduino&gt;&lt;inductive&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="3" />
  <row Id="2179" PostTypeId="2" ParentId="2178" CreationDate="2010-04-10T23:55:12.230" Score="4" ViewCount="" Body="&lt;p&gt;Make a nice fat NiMH battery pack, use a MAX712 fast charge controller (http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1666/t/al). Not sure about inductive charging; imagine if you could program your robot to find its way home back to the charging base for a top-up! That'd be cool :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also came across this today, it may be of interest:&#xA;&lt;a href=&quot;http://www.cse.unsw.edu.au/~acra2005/proceedings/papers/emami.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.cse.unsw.edu.au/~acra2005/proceedings/papers/emami.pdf&lt;/a&gt;&#xA;http://ratslam.itee.uq.edu.au/&lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-04-14T06:10:33.383" LastActivityDate="2010-04-14T06:10:33.383" CommentCount="3" />
  <row Id="2180" PostTypeId="1" AcceptedAnswerId="2181" CreationDate="2010-04-11T03:29:59.097" Score="6" ViewCount="481" Body="&lt;p&gt;I am trying to understand the principles of a RC charging / discharging circuit however I'm at loss regarding certain aspects of its operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a square wave generator giving 0v to 5V levels at certain frequency, say 1Khz at 50% duty cycle.  My R = 3.3K and C = 100nf.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My thinking is that if the capacitor charges during the high state of the generator and discharges equally during the low state of the generator. Then it shouldn't have any charge left and should remain at that level(uncharged). However when I try it practically I find that eventually the capacitor charges to some mid level, that is 2V which my mind can't really comprehend.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does the capacitor charge and discharge and different rates in an RC circuit what exactly is going on over then I can't really explain, can you?&lt;/p&gt;&#xA;" OwnerUserId="444" LastActivityDate="2010-05-03T06:14:11.477" Title="RC circuit understandings" Tags="&lt;rc&gt;&lt;charging&gt;&lt;discharge&gt;&lt;circuit&gt;" AnswerCount="4" />
  <row Id="2181" PostTypeId="2" ParentId="2180" CreationDate="2010-04-11T04:57:19.183" Score="7" ViewCount="" Body="&lt;p&gt;The key is the RC time constant. This is the product of the resistance and capacitance in series. For your example, that would be 3,300 ohms * 0.0000001 farads, which results in 0.00033 seconds. In order for the capacitor to fully charge or discharge, you need to wait for 5 time constants. In your example, the capacitor will reach only about 75% of full charge / discharge during the half period of the 1 kHz square wave. Consider decreasing your frequency, or using a smaller capacitor or resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other possible issues can include:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Incorrectly connecting the circuit. The capacitor, resistor, and function generator should all be in series.&lt;/li&gt;&#xA;&lt;li&gt;Using the wrong tool for measuring the voltage. For the results you are expecting, you need an oscilloscope. A multimeter won't give you the same results unless your time constant is near a second in magnitude.&lt;/li&gt;&#xA;&lt;li&gt;The pattern generator has a high output impedance. This is unlikely, but if the impedance is close to your resistor value, that will throw off your calculations.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-04-12T06:08:23.547" LastActivityDate="2010-04-12T06:08:23.547" />
  <row Id="2182" PostTypeId="2" ParentId="2180" CreationDate="2010-04-11T14:24:05.647" Score="5" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;When you are charging the voltage difference on the resistor is 5V (cap = 0V, output = 5V). When you switch the output to 0V the cap had some voltage X which was lower than 5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;During the discharge the voltage across the resistor is smaller than 5V, the current is also smaller and so less charge gets removed from the capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So charge and discharge rates are not the same.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;When will they be the same? When the voltages across the resistor are the same. This happens when the average voltage across the capacitor is Vcc/2 which is what you have measured.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The general rule is that the voltage on the capacitor equals to the averaged input voltage. If you use a bigger capacitor and/or resistor, the longer it will take for the average to settle (the circuit will have more &quot;inertia&quot; or &quot;memory&quot;).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-04-11T14:24:05.647" CommentCount="1" />
  <row Id="2183" PostTypeId="2" ParentId="1754" CreationDate="2010-04-11T19:24:49.783" Score="3" ViewCount="" Body="&lt;p&gt;You may try examining some Forth CPU designs. Forth is a simple programming language whose specification and implementation is defined by means of two stacks stack (one for data and one for return addresses).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Several small VHDL/Verilog processors are freely available:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ultratechnology.com/4thvhdl.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.ultratechnology.com/4thvhdl.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.jwdt.com/~paysan/b16.html&quot; rel=&quot;nofollow&quot;&gt;http://www.jwdt.com/~paysan/b16.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.jwdt.com/~paysan/4stack.html&quot; rel=&quot;nofollow&quot;&gt;http://www.jwdt.com/~paysan/4stack.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.cse.cuhk.edu.hk/~phwl/mt/public/archives/old/msl16/msl16.html&quot; rel=&quot;nofollow&quot;&gt;http://www.cse.cuhk.edu.hk/~phwl/mt/public/archives/old/msl16/msl16.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Some more links can be found here:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ultratechnology.com/chips.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.ultratechnology.com/chips.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;PS. Despite Forth being a fairly old and obscure language many modern stack-based VMs (Java, fast JavaScript VMs) have similar low-level design so learning about it can be fruitful.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-04-11T19:24:49.783" />
  <row Id="2184" PostTypeId="2" ParentId="1716" CreationDate="2010-04-11T20:01:51.623" Score="2" ViewCount="" Body="&lt;p&gt;Not a Cortex-M3 but LPC2101 ARM7TDMI from NXP requires external 1,8V regulation.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-04-11T20:01:51.623" />
  <row Id="2185" PostTypeId="1" AcceptedAnswerId="2186" CreationDate="2010-04-11T22:25:36.390" Score="2" ViewCount="364" Body="&lt;p&gt;Does anyone know of any good I2C 7segment display drivers. I swear a previous answer referenced a chip for this on chiphacker but I cannot find it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also be happy with SPI, but I I2C would work better as I plan to use many 7Seg.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-04-13T03:40:26.043" LastActivityDate="2010-04-13T03:40:26.043" Title="I2C 7seg driver" Tags="&lt;i2c&gt;&lt;7segmentdisplay&gt;&lt;spi&gt;" AnswerCount="3" />
  <row Id="2186" PostTypeId="2" ParentId="2185" CreationDate="2010-04-11T22:48:10.243" Score="2" ViewCount="" Body="&lt;p&gt;The Maxim &lt;a href=&quot;http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3540&quot; rel=&quot;nofollow&quot;&gt;MAX6955&lt;/a&gt; might be suitable.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-11T22:48:10.243" CommentCount="1" />
  <row Id="2187" PostTypeId="2" ParentId="2185" CreationDate="2010-04-11T22:55:14.610" Score="2" ViewCount="" Body="&lt;p&gt;On the simple side of things, you could use serial-to-parallel shift register chips to drive the 7 segment displays. The SPI interface can probably be set up to send out the data without any issues. It's chain-able as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 74HC164 is an example of one of these chips, and with 8 outputs per chip, it would be able to drive the 7 segments plus a decimal point.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-04-11T22:55:14.610" CommentCount="3" />
  <row Id="2188" PostTypeId="2" ParentId="2068" CreationDate="2010-04-12T07:19:14.497" Score="3" ViewCount="" Body="&lt;p&gt;This place sells &quot;Electromate&quot; Multimeters (or meters with &quot;Electromate&quot; in their title)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Products Unlimited&#xA;2215 11th Street&#xA;Peru&#xA;Illinois 61354&#xA;United States&#xA;Phone: 815-224-8285&#xA;Fax: 815-224-8289&#xA;Email: cservice@productsunlimited.com&#xA;&lt;a href=&quot;http://www.productsunlimited.com&quot; rel=&quot;nofollow&quot;&gt;http://www.productsunlimited.com&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps email them for manufacturer details?&#xA;'t.&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-04-12T07:19:14.497" />
  <row Id="2189" PostTypeId="2" ParentId="2156" CreationDate="2010-04-12T12:54:13.080" Score="0" ViewCount="" Body="&lt;p&gt;Atmel provide host and device firmware for their AVR32B family of processors.  These have built in USB 2.0 OTG hardware.  The EVK1101 development board is a good hardware target and the AVR studio is a free GNU development environment.  FreeRTOS has been ported to this platform and is a good stable base to work from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also ARM Cortex-M3 parts that have the same capability and cheap/free tools.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-04-12T12:54:13.080" />
  <row Id="2190" PostTypeId="1" CreationDate="2010-04-12T13:19:55.393" Score="7" ViewCount="1168" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to build a small battery powered device containing a servo. I would like to be able to turn off the servo to save battery life. I have read previously that MOSFETs can be used to do this, but I am having trouble finding example circuits that are detailed enough (missing resistor values with no way to calculate them) and to be honest I am not too sure what sort of circuit I am looking for (I have never used any FETs before). Can someone please give me a nudge in the right direction?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;potentially relevant info:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;code running on a mega88 @ 3.3V&lt;/li&gt;&#xA;&lt;li&gt;4.8-6V servo connected straight into the 6V battery pack (I would like to change this)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="417" LastActivityDate="2011-05-13T12:44:26.017" Title="MOSFETs for dummies" Tags="&lt;fet&gt;&lt;mosfet&gt;&lt;servo&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="2191" PostTypeId="1" CreationDate="2010-04-12T13:27:53.113" Score="8" ViewCount="1907" Body="&lt;p&gt;What would be a good HW platform for running Linux? I am considering Marvell's SheevaPlug but I am sure many other exists.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like the following features:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;capable of running Linux kernel &gt;= 2.6&lt;/li&gt;&#xA;&lt;li&gt;At least Fast Ethernet UTP&lt;/li&gt;&#xA;&lt;li&gt;Serial port: UART / SD / SPI&lt;/li&gt;&#xA;&lt;li&gt;Nice to have: USB 2.0&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="329" LastActivityDate="2010-07-02T09:08:21.730" Title="Options for a small Linux HW platform" Tags="&lt;linux&gt;&lt;platform&gt;" AnswerCount="10" CommentCount="1" FavoriteCount="2" />
  <row Id="2192" PostTypeId="1" AcceptedAnswerId="2196" CreationDate="2010-04-12T13:31:44.487" Score="4" ViewCount="714" Body="&lt;p&gt;For growing crystals it is important that there are no vibrations. Is there a cheap and easy way to measure vibrations in the floor, like people walking, doors closing etc.?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps an accelerometer is possible, but those are pretty expensive (Nun chuck is less expensive).&lt;/p&gt;&#xA;" OwnerUserId="323" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-31T04:50:44.220" LastActivityDate="2011-01-31T04:50:44.220" Title="Vibration sensor (accelerometer?)" Tags="&lt;sensor&gt;&lt;measurement&gt;&lt;accelerometer&gt;" AnswerCount="7" CommentCount="3" FavoriteCount="1" />
  <row Id="2193" PostTypeId="2" ParentId="2190" CreationDate="2010-04-12T13:42:57.827" Score="10" ViewCount="" Body="&lt;p&gt;You didn't mention how much current you require. &#xA;Here is a quick guide -- &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For most switching applications the important parameters&#xA;  are the voltage rating (BVdss), the maximum drain current (Id(on))&#xA;  and the gate turn-on voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a 6V battery you want a breakdown voltage at least 6V. Make this&#xA;  a bit higher in case switching produces transient voltages. Since &#xA;  the majority of FETs have voltages of 20V or greater this should&#xA;  not be a problem. Choose a 20V or 30V FET.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Choose a maximum drain current above what the servo requires. &#xA;  The maximum drain current is usually limited by the thermal&#xA;  performance of the system not the device. How much current do&#xA;  you need? How large a device can you use? Do you have room for &#xA;  a heatsink?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To use the FET as a switch in a 3.3V system you want a logic level&#xA;  device. This will insure that the device is fully on (lowest &#xA;  on resistance) at 3.3V levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For circuitry I will usually put a pull-down resistor on the&#xA;  gate so that the gate is never floating. For some applications&#xA;  I will place a zener diode across the gate for transient protection.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:44:26.017" LastActivityDate="2011-05-13T12:44:26.017" CommentCount="5" />
  <row Id="2194" PostTypeId="1" AcceptedAnswerId="2202" CreationDate="2010-04-12T13:50:29.263" Score="3" ViewCount="425" Body="&lt;p&gt;I've seen circuit diagrams that use a polarize electrolytic to remove DC offsets from an input audio signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The cap is polarized. Why is this ok?&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2010-04-12T17:55:59.620" Title="Why is it ok to use polarized caps to remove DC offset from an audio input?" Tags="&lt;audio&gt;&lt;capacitor&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="2195" PostTypeId="2" ParentId="2191" CreationDate="2010-04-12T14:02:23.033" Score="3" ViewCount="" Body="&lt;p&gt;Here's the list of supported devices from the OpenWRT project - &lt;a href=&quot;http://wiki.openwrt.org/oldwiki/tableofhardware&quot; rel=&quot;nofollow&quot;&gt;http://wiki.openwrt.org/oldwiki/tableofhardware&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also some suggestions in this thread:&#xA;&lt;a href=&quot;http://chiphacker.com/questions/1738/whats-the-simplest-linux-capable-board-i-could-make-at-home&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/1738/whats-the-simplest-linux-capable-board-i-could-make-at-home&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-04-12T14:20:09.067" LastActivityDate="2010-04-12T14:20:09.067" />
  <row Id="2196" PostTypeId="2" ParentId="2192" CreationDate="2010-04-12T14:13:01.940" Score="6" ViewCount="" Body="&lt;p&gt;You can use a cheap piezo sounder to detect vibration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/en/Tutorial/KnockSensor&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Tutorial/KnockSensor&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-04-12T21:29:45.833" LastActivityDate="2010-04-12T21:29:45.833" CommentCount="1" />
  <row Id="2197" PostTypeId="2" ParentId="2194" CreationDate="2010-04-12T15:04:57.147" Score="0" ViewCount="" Body="&lt;p&gt;Why &lt;em&gt;wouldn't&lt;/em&gt; it be ok?  In the usual configuration, the DC voltage on the positive side of the cap is always higher than the DC voltage on the negative side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if you connect it with no bias, electrolytics can still withstand a small reverse voltage.  It's only after they are reversed continuously at 1 V or more that the dielectric starts to degrade.  See &lt;a href=&quot;http://en.wikipedia.org/wiki/Electrolytic_capacitor#Polarity&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Electrolytic_capacitor#Polarity&lt;/a&gt;  &lt;a href=&quot;http://en.wikipedia.org/wiki/Capacitive_coupling&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Capacitive_coupling&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-04-12T15:27:23.010" LastActivityDate="2010-04-12T15:27:23.010" CommentCount="0" />
  <row Id="2198" PostTypeId="2" ParentId="2191" CreationDate="2010-04-12T15:54:17.230" Score="12" ViewCount="" Body="&lt;p&gt;Depending on what you are wanting to use it for, you can check out the Gumstix: &lt;a href=&quot;http://www.gumstix.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.gumstix.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a very small board (about the size of a gum stick) that you then place on an expansion board. You can get expansion boards with USB, serial, touch screen, Ethernet, etc. Just look around and see if it meets what you are wanting to do.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-04-12T15:54:17.230" />
  <row Id="2199" PostTypeId="2" ParentId="2192" CreationDate="2010-04-12T16:12:46.513" Score="-1" ViewCount="" Body="&lt;p&gt;iPhone? Similar to @W5VO's suggestion for a Wii.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-04-12T16:12:46.513" CommentCount="1" />
  <row Id="2200" PostTypeId="2" ParentId="2191" CreationDate="2010-04-12T17:14:34.950" Score="11" ViewCount="" Body="&lt;p&gt;A beagle board is a good option also.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;http://beagleboard.org/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However not native ethernet support (need a usb or an expansion board).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ril3y&lt;/p&gt;&#xA;" OwnerUserId="29" LastActivityDate="2010-04-12T17:14:34.950" CommentCount="1" />
  <row Id="2201" PostTypeId="2" ParentId="2185" CreationDate="2010-04-12T17:14:49.187" Score="1" ViewCount="" Body="&lt;p&gt;There are many I/O Expanders out there that use either SPI or I2C buses. With a single MSSP module you can control almost an infinite amount of digital outputs like LEDs. Depending on the current draw of the LEDs in your 7seg display you may be able to control them with an I/O expander like the &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en021393&quot; rel=&quot;nofollow&quot;&gt;MCP23008&lt;/a&gt;. Check the datasheets for your display and the MCP23008.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-12T17:14:49.187" />
  <row Id="2202" PostTypeId="2" ParentId="2194" CreationDate="2010-04-12T17:42:16.793" Score="5" ViewCount="" Body="&lt;p&gt;As long as the DC level is positive, the AC amplitude of the audio signal is of no consequence because it is a &quot;coupling&quot; capacitor, in the sense that the RC time constant is much higher than the highest 1/f of the audio signal (excluding dc of course), so the capacitor never gets &quot;charged up&quot; to the audio ac signal voltage (only to its dc value).  Instead, the voltage across its terminals remains approximately constant. In other words, the capacitor rides with the input, and if the RC constant was not high enough, audio would be distorted.  For example, you could have 1V of dc offset and 10V of ac amplitude.  If RC is high enough, the voltage accross the capacitor will ALWAYS be very near 1V,NOT 11V to -9V as the comment to the first answer seemed to imply.  Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="688" LastEditorUserId="688" LastEditorDisplayName="" LastEditDate="2010-04-12T17:55:59.620" LastActivityDate="2010-04-12T17:55:59.620" CommentCount="1" />
  <row Id="2203" PostTypeId="2" ParentId="2165" CreationDate="2010-04-12T18:34:24.797" Score="1" ViewCount="" Body="&lt;p&gt;Consider barebonespcb.com .  You didn't mention your budget but this is as cheap as it gets in the US from my experience (e.g. two 2&quot;x2&quot; boards for $54 total).  No stop mask though.  &lt;/p&gt;&#xA;" OwnerUserId="688" LastEditorUserId="688" LastEditorDisplayName="" LastEditDate="2010-04-12T18:40:27.400" LastActivityDate="2010-04-12T18:40:27.400" />
  <row Id="2204" PostTypeId="2" ParentId="2191" CreationDate="2010-04-12T19:09:21.897" Score="3" ViewCount="" Body="&lt;p&gt;Another option is &lt;a href=&quot;http://armkits.com/&quot; rel=&quot;nofollow&quot;&gt;Armkits.com&lt;/a&gt; by Embest.  I've ordered one of their boards, and I have been impressed with how much quickly they ship out and material they provide. You might get cheaper shipping from their US distributor (as opposed to China) at &lt;a href=&quot;http://www.IESdistribution.com&quot; rel=&quot;nofollow&quot;&gt;IES&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2010-04-12T19:09:21.897" CommentCount="1" />
  <row Id="2205" PostTypeId="1" AcceptedAnswerId="2207" CreationDate="2010-04-12T19:10:12.333" Score="1" ViewCount="324" Body="&lt;p&gt;The ATMEGA datasheet suggests filtering the ADC reference voltage with an LC network, in other words VCC - L - AREF - C - GND. How does the inductor smooth the voltage better than just a capacitor?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2011-05-16T10:42:14.000" Title="How does an LC network filter power?" Tags="&lt;capacitor&gt;&lt;microcontroller&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="2206" PostTypeId="2" ParentId="2205" CreationDate="2010-04-12T19:24:38.540" Score="4" ViewCount="" Body="&lt;p&gt;It acts as a low-pass filter, removing high frequency noise much better than if just a capacitor was used.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-12T19:24:38.540" CommentCount="1" />
  <row Id="2207" PostTypeId="2" ParentId="2205" CreationDate="2010-04-12T19:54:22.767" Score="5" ViewCount="" Body="&lt;p&gt;At high frequency the impedance of the inductor increases and the impedance&#xA;of the capacitor decreases. For high frequency signals most of the signal voltage drop&#xA;is across the inductor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The VCC (in a properly designed system) will have a very low impedance. By raising the impedance between VCC and AREF the capacitor will reduce more of any high frequency&#xA;noise that is on VCC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On my boards I use a 10-20uH inductor and 0.1uF capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[corrected the first paragraph mistake that leon commented about]&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:42:14.000" LastActivityDate="2011-05-16T10:42:14.000" CommentCount="2" />
  <row Id="2208" PostTypeId="2" ParentId="2192" CreationDate="2010-04-12T20:25:09.793" Score="2" ViewCount="" Body="&lt;p&gt;A microphone might work. Cover it in hot glue and stick it to the object you're monitoring. That will keep out air vibrations (to a degree) and couple it to the conducted vibrations. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, it SHOULD anyway!&lt;/p&gt;&#xA;" OwnerUserId="610" LastActivityDate="2010-04-12T20:25:09.793" />
  <row Id="2209" PostTypeId="1" AcceptedAnswerId="2213" CreationDate="2010-04-12T21:50:24.553" Score="5" ViewCount="217" Body="&lt;p&gt;I see a lot of device specific JTAG cables such as AVR jtag or specific ARM JTAG.  Is there any such thing as a 'standard' JTAG cable that will work on multiple devices? I want something that will work with xilinx FPGAs, STM32s and AVR microcontrollers&lt;/p&gt;&#xA;" OwnerUserId="582" LastEditorUserId="582" LastEditorDisplayName="" LastEditDate="2010-04-12T22:31:09.930" LastActivityDate="2010-11-16T16:47:16.607" Title="JTAG cable and device interchangeability" Tags="&lt;jtag&gt;" AnswerCount="3" />
  <row Id="2210" PostTypeId="2" ParentId="2209" CreationDate="2010-04-12T22:47:07.313" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.amontec.com/chameleon.shtml&quot; rel=&quot;nofollow&quot;&gt;Amontec&lt;/a&gt; makes a reconfigurable JTAG. I've got one, and have used it with ARM chips and Xilinx FPGAs and CPLDs.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-12T22:47:07.313" />
  <row Id="2211" PostTypeId="1" AcceptedAnswerId="2214" CreationDate="2010-04-13T02:45:35.763" Score="4" ViewCount="779" Body="&lt;p&gt;Hi everyone,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've recently begun experimenting with AVRs and am keen to progress beyond making blinkies to making things &lt;em&gt;move&lt;/em&gt;.  I've tried to start with something easy, but it seems I'm already foiled!  What I'd like to know is this: is it possible to drive both an AVR and a motor from the same power source and without them interfering with one another?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The schematic below illustrates my initial attempt at doing this. The ATtiny is generating a ~3kHz PWM signal (1/3 duty cycle) on pin 5, with the intent of supplying a time-averaged voltage of 3V to the motor via the power transistor.  When I wire this up though, the motor just seems to cough and sputter.&#xA;&lt;img src=&quot;http://i42.tinypic.com/iy314k.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks heaps in advance,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tim&lt;/p&gt;&#xA;&#xA;&lt;p&gt;p.s. I'm just wondering about the fundamental possibility/impossibility of what I'm trying to do: I don't expect anybody to debug my circuit for me! :-)&lt;/p&gt;&#xA;" OwnerUserId="504" LastActivityDate="2010-05-18T08:23:45.637" Title="Driving a DC hobby motor using an AVR and a single power supply" Tags="&lt;avr&gt;&lt;motor&gt;&lt;beginner&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="2212" PostTypeId="2" ParentId="2192" CreationDate="2010-04-13T03:16:00.200" Score="5" ViewCount="" Body="&lt;p&gt;Purpose-built piezo vibration sensors (e.g. &lt;a href=&quot;http://www.littlebirdelectronics.com/products/Piezo-Vibration-Sensor-%252d-Large.html&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;) are cheap and fairly sensitive.&lt;/p&gt;&#xA;" OwnerUserId="504" LastActivityDate="2010-04-13T03:16:00.200" />
  <row Id="2213" PostTypeId="2" ParentId="2209" CreationDate="2010-04-13T04:58:28.150" Score="3" ViewCount="" Body="&lt;p&gt;In general, the &quot;JTAG&quot; cables for different families of devices are not compatible. However as Leon notes, there are some 3rd party companies that produce &quot;JTAG&quot; cables that can be reconfigured to support different families of devices.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-04-13T04:58:28.150" CommentCount="1" />
  <row Id="2214" PostTypeId="2" ParentId="2211" CreationDate="2010-04-13T05:09:00.693" Score="2" ViewCount="" Body="&lt;p&gt;It's &lt;em&gt;possible&lt;/em&gt;, sure.  Is the 9 V drooping a lot under load and dropping it out of regulation?  Is the voltage on both sides of the motor what you expect?  You might need bigger capacitors to keep the supplies &quot;stiff&quot;, and make sure the voltage drop caused by the motor's current in the ground wire isn't affecting the AVR's ground.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-04-13T05:09:00.693" CommentCount="6" />
  <row Id="2215" PostTypeId="1" CreationDate="2010-04-13T05:15:30.083" Score="16" ViewCount="735" Body="&lt;p&gt;Given a board like &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=17_21&amp;amp;products_id=187&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; with soldering pads but no traces, how would you connect adjacent components (including the ends of the jumpers for longer stretches)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some possibilities I've come up with:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Solder the individual leads as usual, then bridge the pads with solder.&lt;/li&gt;&#xA;&lt;li&gt;For each connection wrap one of the leads around the adjacent component's lead before soldering the two pads (ensuring there's more than just solder joining the two components).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I started with the former before I came up with the latter (which seems like at least an improvement), but I'm wondering if there's some even better solution I haven't come up with yet.&lt;/p&gt;&#xA;" OwnerUserId="647" LastEditorUserId="647" LastEditorDisplayName="" LastEditDate="2010-04-19T01:28:39.800" LastActivityDate="2010-04-19T01:28:39.800" Title="How do I connect components when using a circuit board with pads but no traces?" Tags="&lt;soldering&gt;&lt;best-practice&gt;&lt;prototyping&gt;" AnswerCount="4" FavoriteCount="4" />
  <row Id="2216" PostTypeId="2" ParentId="2215" CreationDate="2010-04-13T05:42:20.847" Score="6" ViewCount="" Body="&lt;p&gt;I have tried both the methods listed above, and I can certainly recommend the second one over the first. Trying to create solder bridges across the pads is &lt;em&gt;not&lt;/em&gt; fun! The solder tends to blob onto the pads, and it does not like forming bridges. Heaven forbid if you have to make more than one bridge, then you end up creating one bridge, then destroying it as you try to create the second!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perfboarding is an art, and requires a lot of thinking and forward planning to get neat. Never try to create solder bridges without something conductive in between. The best option is to use component leads to form the connections. Most through-hole components come with leads much longer than necessary, so you can use this to your advantage. If you need more material, you can use the snipped off ends of resistor legs, if you have them lying around. In addition, you can use hookup wire on the top of the board for longer connections. This is much less tedious than trying to carefully arrange multiple resistor legs along the bottom of the board, not to mention a better use of space. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your circuit can be less compact, then you can use strip board (a.k.a. Veroboard) which has long continuous copper strips along the board. You can break the lines by grinding off the copper with a knife, scalpel or drill bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really want to be embarrassed about your perfboarding skills then look no further than: &lt;a href=&quot;http://www.headphoneamp.co.kr/ftp/sijosae/Gallery/&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;. This guy knows the art!&lt;/p&gt;&#xA;" OwnerUserId="307" LastActivityDate="2010-04-13T05:42:20.847" CommentCount="2" />
  <row Id="2217" PostTypeId="2" ParentId="2191" CreationDate="2010-04-13T05:48:07.570" Score="3" ViewCount="" Body="&lt;p&gt;How about the LinuxStamp?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.opencircuits.com/Linuxstamp&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/Linuxstamp&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.opencircuits.com/Linuxstamp_II_9260&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/Linuxstamp_II_9260&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-13T05:48:07.570" />
  <row Id="2218" PostTypeId="2" ParentId="1893" CreationDate="2010-04-13T05:52:07.443" Score="1" ViewCount="" Body="&lt;p&gt;How about &lt;a href=&quot;http://olimex.com/&quot; rel=&quot;nofollow&quot;&gt;Olimex&lt;/a&gt;?&#xA;(You have probably heard of their cheap dev kits)&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-13T05:52:07.443" CommunityOwnedDate="2010-04-13T05:52:07.443" CommentCount="1" />
  <row Id="2219" PostTypeId="2" ParentId="2103" CreationDate="2010-04-13T07:31:18.740" Score="3" ViewCount="" Body="&lt;p&gt;I'd also remind you that along with the stray capacitance issues already mentioned, &lt;a href=&quot;http://www.boston.com/news/globe/city_region/breaking_news/2007/09/mit_student_arr.html&quot; rel=&quot;nofollow&quot;&gt;breadboards can get you hastily arrested if you wear them to the airport&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="504" LastActivityDate="2010-04-13T07:31:18.740" CommentCount="2" />
  <row Id="2220" PostTypeId="2" ParentId="2215" CreationDate="2010-04-13T08:36:28.817" Score="3" ViewCount="" Body="&lt;p&gt;I always bridge pads with solder, even for big circuits. It comes automatically after some practice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are two boards I've recently done (both of them deals with 220VAC)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://lbw.axe-man.org/solder/thumb/t_RELAYV2B.jpg&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://lbw.axe-man.org/solder/thumb/t_RELAYV2F.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://lbw.axe-man.org/solder/thumb/t_RELAYV3B.jpg&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://lbw.axe-man.org/solder/thumb/t_RELAYV3F.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've built the second one directly from this breadboard version &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://lbw.axe-man.org/solder/thumb/t_RELAYV3P.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first realizations were more &quot;fuzzy&quot; ... this was a 8x8 led matrix I made more than 18 years ago, with NO MULTIPLEX: each led was directly connected to buffer output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://lbw.axe-man.org/solder/thumb/t_LEDB.jpg&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://lbw.axe-man.org/solder/thumb/t_LEDF.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And this is my most &quot;knotty&quot; array cabling: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://lbw.axe-man.org/solder/thumb/t_FPGA.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(full size pictures are on &lt;a href=&quot;http://lbw.axe-man.org/solder/thumb.html&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="244" LastEditorUserId="244" LastEditorDisplayName="" LastEditDate="2010-04-14T17:36:37.330" LastActivityDate="2010-04-14T17:36:37.330" />
  <row Id="2221" PostTypeId="2" ParentId="1926" CreationDate="2010-04-13T11:13:26.847" Score="0" ViewCount="" Body="&lt;p&gt;I agree with Joby Taffey that CodeSourcery probably is a good choice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, some time back I started to play a little bit with the stm32 (ST:s arm Cortex M3 mcu) and in the process I create this page.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.fun-tech.se/stm32/&quot; rel=&quot;nofollow&quot;&gt;http://www.fun-tech.se/stm32/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.fun-tech.se/stm32/gcc/index.php&quot; rel=&quot;nofollow&quot;&gt;http://www.fun-tech.se/stm32/gcc/index.php&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Maybe it can help you in some sense?&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-13T11:13:26.847" />
  <row Id="2222" PostTypeId="2" ParentId="2215" CreationDate="2010-04-13T11:28:45.930" Score="3" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;Take a length of wire-wrap wire (30ga or so).&lt;/li&gt;&#xA;&lt;li&gt;Strip end of wire long enough to bridge the two pads. This leaves a short length of stripped wire and the remaining insulation, which now ends at point X.&lt;/li&gt;&#xA;&lt;li&gt;Solder end of wire to one pad.&lt;/li&gt;&#xA;&lt;li&gt;Cut wire at point X.&lt;/li&gt;&#xA;&lt;li&gt;Solder point X to the other pad.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-04-13T11:28:45.930" CommentCount="1" />
  <row Id="2223" PostTypeId="2" ParentId="2135" CreationDate="2010-04-13T14:14:46.013" Score="1" ViewCount="" Body="&lt;p&gt;I like the above, but if you want the best protection try using a PTC resettable fuse in line with the motor that will break before your H-bridge is damaged.  Ideally you never want to stall your motor, so I'd design for ideal conditions, add 25-50% of overhead and then put a PTC in line with the motor that will trip when those conditions are exceeded.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suggest the overhead because you never know what your robot is going to see.  I have a roomba that had a failing motor - the shaft kept getting stuck with friction.  The H-bridge couldn't drive it loose when it got like that, but if I applied the voltage directly to the motor with a 3A source then it would break free for a bit and continue running.  It was likely operating under increased load conditions before that occurred - but it kept running.  The overhead will ensure that if you've misjudged the power requirements your robot won't just stop dead if it hits a snag.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-04-13T14:14:46.013" />
  <row Id="2224" PostTypeId="2" ParentId="2112" CreationDate="2010-04-13T14:51:42.707" Score="1" ViewCount="" Body="&lt;p&gt;I've had good luck with some of the older PSoCs in certain circumstances.  I used it for a serial distribution board since we could load it up with multiple UARTs.  I didn't make much use of the analog blocks though.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, I didn't like the GUI they had for programming/configuring.  My colleagues say it has changed for the better with newer versions, but I haven't tried it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another problem I had was that those older PSoCs were SLOW!  24MHz yes, but each operation takes at least 4 clock cycles, probably more, and if you're programming in C you can just forget about any great speed.  Yeah, you've got interrupts and all that but you will NOT be able to do any complicated real-time processing or fast serial communication.  As before, the newer chips are supposedly faster, but I haven't used them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're seeking precision and accuracy then a PSoC may not be the right choice.  If it's just general data acquisition that you're having a hard time doing with another chip without adding multiple &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-04-13T14:51:42.707" />
  <row Id="2225" PostTypeId="2" ParentId="2215" CreationDate="2010-04-13T15:59:42.180" Score="11" ViewCount="" Body="&lt;p&gt;Here's another interesting method of perfboarding, this guy does it with SMD components and really tiny wires. He made a special little wiring pen for laying down the wires:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://elm-chan.org/docs/wire/wiring_e.html&quot; rel=&quot;nofollow&quot;&gt;Progressive Wiring Techniques&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://davr.org/pics/wiring5.jpeg&quot; alt=&quot;example&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally I make solder bridges for pins that are in adjacent holes, for things further away I use thin wires (though not as thin as the ones above) in adjacent holes to the things I want to connect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://picasaweb.google.com/drorex/AVR#5337603159881543362&quot; rel=&quot;nofollow&quot;&gt;Top of my board:&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://lh3.ggpht.com/_aA3BITGORuE/ShL5y0i97sI/AAAAAAAAGUs/McxOBAneY5A/s288/IMG_0676.JPG&quot; alt=&quot;board top&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://picasaweb.google.com/drorex/AVR#5337603171502551634&quot; rel=&quot;nofollow&quot;&gt;Bottom of my board:&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://lh4.ggpht.com/_aA3BITGORuE/ShL5zf1oclI/AAAAAAAAGUw/gmAiJBJ2iHA/s288/IMG_0678.JPG&quot; alt=&quot;board bottom&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And no, I didn't just wire those pins all on the fly, I had drawn up a detailed schematic in advance. There's no way I could keep track of so many wires just in my head.&lt;/p&gt;&#xA;" OwnerUserId="131" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-04-13T16:41:16.203" LastActivityDate="2010-04-13T16:41:16.203" CommentCount="1" />
  <row Id="2226" PostTypeId="1" AcceptedAnswerId="2228" CreationDate="2010-04-13T16:54:06.347" Score="3" ViewCount="287" Body="&lt;p&gt;A bit of background: We have a system currently in production, but the original programmer passed away, and the current hardware manufacturer cannot find hardware to run the (currently) DOS system, so I need to re-implement this in a more modern platform. I can only change the programming and the motherboard hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I asked over in StackOverflow and was suggested I ask here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am new to the locating hardware side of embedded programming and so after being completely overwhelmed with all the choices out there (pc104, arduino, rabbit, custom boards, a zillion options for each board, beagle, volume discounts, devel kits, ahhh!!) I am asking here for some direction borrowing from your experience. (What would you do?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, I must find a new motherboard and (most likely) re-implement the program logic. Rewriting this in C/C++/Java/C#/Pascal/BASIC is not a problem for me. so my real problem is finding the hardware. This motherboard will have several other devices attached to it. Here is a summary of what I need to do:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Software requirements: Very minimal. No need for RTOS or multitasking, very low CPU requirements, I just need something I can program and something I can put a remote update mechanism into (updates to the code will be downloaded via modem maybe 1-4 times a year).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Required hardware:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;2 RS232 serial ports (one used all the time for primary UI, the second one not continuous use [it's a serial printer])&lt;/li&gt;&#xA;&lt;li&gt;1 modem (9600+ baud ok) [Modem will be in simultaneous use with only one of the serial port devices (UI), so interrupt sharing issues with one serial port is OK, but not both]&lt;/li&gt;&#xA;&lt;li&gt;Minimum permanent/long term storage: Whatever O/S requires + 1 MB (executable) + 512 KB (Data files)&lt;/li&gt;&#xA;&lt;li&gt;RAM: Minimal, whatever the O/S requires plus maybe 1MB for executable.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Nice to have:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;USB port(s)&lt;/li&gt;&#xA;&lt;li&gt;Ethernet network port&lt;/li&gt;&#xA;&lt;li&gt;Wireless network&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Implementation languages (any O/S I will adapt to):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;First choice Java/C# (Mono ok)&lt;/li&gt;&#xA;&lt;li&gt;Second choice is C/C++/Pascal&lt;/li&gt;&#xA;&lt;li&gt;Third is BASIC&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Ok, given all this, I am having a lot of trouble finding hardware that will support this that is low in cost. Every manufacturer site I visit has a lot of options, and it's difficult to see if their offering will even satisfy my must-have requirements (for example they sometimes list 3 &quot;serial ports&quot;, but it appears that only one of the three is RS232, for example, and don't mention what the other two are, or how much it costs (or is even possible) to make it RS232). The #1 constraint is cost, #2 is size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone help me with this? This little task has left me thinking I should have gone for EE and not CS :-).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, please let me know if I can phrase my question any better.&lt;/p&gt;&#xA;" OwnerUserId="691" LastActivityDate="2011-05-18T11:30:02.550" Title="How to find an embedded platform?" Tags="&lt;platform&gt;&lt;microcontroller&gt;&lt;system&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="0" />
  <row Id="2228" PostTypeId="2" ParentId="2226" CreationDate="2010-04-13T19:33:15.000" Score="3" ViewCount="" Body="&lt;p&gt;I don't know of a exact match for this spec, but there is some quite nice embedded Linux cards out there that may fit your need. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just have a look at this page: &lt;a href=&quot;http://chiphacker.com/questions/2191/options-for-a-small-linux-hw-platform&quot; rel=&quot;nofollow&quot;&gt;chiphacker.com - options-for-a-small-linux-hw-platform&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A bonus of using Linux is that you could use most languages, but I would recommend using C or C++. Maybe Java if you can find a &lt;a href=&quot;http://jamvm.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;JavaVM&lt;/a&gt; port for the hardware you select. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could even use pascal if you feel like it (see &lt;a href=&quot;http://www.freepascal.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.freepascal.org/&lt;/a&gt;), &#xA;but I don't think that it is a good idea... &lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2010-04-13T19:40:21.380" LastActivityDate="2010-04-13T19:40:21.380" />
  <row Id="2232" PostTypeId="2" ParentId="2145" CreationDate="2010-04-14T10:03:48.710" Score="3" ViewCount="" Body="&lt;p&gt;If you want something custom, I've had great experience in the past with a process called &lt;a href=&quot;http://en.wikipedia.org/wiki/Selective_laser_sintering&quot; rel=&quot;nofollow&quot;&gt;Selective Laser Sintering&lt;/a&gt;.  Assuming you have CAD files for the parts, the setup costs are much less than any kind of injection molding process.  The surface quality is very similar to a generic laptop power brick.  The parts are nylon, so they can't be surface worked, but are otherwise mechanically equal to injection molded parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you move to higher volumes, you might consider injection molding using aluminum tools, rather than steel.  The setup costs are lower, as are the setup times.  The draft angles need to be a little shallower than with steel tools, otherwise the process is pretty similar to any mass-produced part.  There's a company in the US called &lt;a href=&quot;http://www.protomold.com/&quot; rel=&quot;nofollow&quot;&gt;Protomold&lt;/a&gt; that's done great work for some projects I've worked on in the past.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For both of these, I'd highly recommend working with a Mechanical Engineer who has prior experience in prototyping and/or model building.  Getting the CAD files in order, making the subtle changes to the design to ensure the part is suited for the process, and dealing with the production shop questions, take a fair amount of experience.&lt;/p&gt;&#xA;" OwnerUserId="696" LastActivityDate="2010-04-14T10:03:48.710" CommentCount="2" />
  <row Id="2233" PostTypeId="2" ParentId="2178" CreationDate="2010-04-14T10:19:21.810" Score="1" ViewCount="" Body="&lt;p&gt;Have a look here: &lt;a href=&quot;http://www.instructables.com/id/Low-Power-Wireless-Charging/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Low-Power-Wireless-Charging/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plenty of references too.&lt;/p&gt;&#xA;" LastActivityDate="2010-04-14T10:19:21.810" />
  <row Id="2234" PostTypeId="2" ParentId="2145" CreationDate="2010-04-14T11:28:58.940" Score="0" ViewCount="" Body="&lt;p&gt;I agree with Ian, try to use a existing box.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A tip is to get a label-printer that can print labels with a nice graphical logo, &#xA;a productname, serienumber etc etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a cheap way of transforming a boring black box into something that looks a little bit more professional.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe something like this? &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://global.dymo.com/enGB/Products/LabelWriter_4XL.html&quot; rel=&quot;nofollow&quot;&gt;Dymo - LabelWriter 4XL&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.brother.se/g3.cfm/s_page/64510/s_level/23730/s_product/QL580NZW1&quot; rel=&quot;nofollow&quot;&gt;Brother - QL-580N&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-14T11:28:58.940" />
  <row Id="2235" PostTypeId="1" AcceptedAnswerId="2241" CreationDate="2010-04-14T16:52:06.607" Score="5" ViewCount="313" Body="&lt;p&gt;I am hoping someone here can help me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am having trouble with a RFID kit I bought from SparkFun. I purchased the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8852&quot; rel=&quot;nofollow&quot;&gt;USB RFID (SEN-08852)&lt;/a&gt; with the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8419&quot; rel=&quot;nofollow&quot;&gt;RFID Reader ID-12 (SEN-08419)&lt;/a&gt; and some RFID cards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I hook up the reader or try to use it, it goes into a constant &quot;read&quot; mode. The green &quot;Read&quot; LED flashes constantly and the buzzer clicks with each flash. This will not stop until I unhook the USB cable. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have found that if I connect the USB part without the reader and then connect the reader to the board, the device works properly for the very first RFID card (and I can read the serial output using PuTTY). As soon as the first card is read, it starts the read loop again. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas as to why this is happening? Is my device broken, or am I just doing something wrong? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have Windows 7 x64, and I did not install any drivers when I hooked up the reader - Windows downloaded them for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; Apparently the port I was using wasn't providing enough power for the reader - once I tried a powered hub (and eventually another port on my laptop), it was working flawlessly! I now have no problems swiping a card more than once:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://img512.imageshack.us/img512/5195/putty.png&quot; alt=&quot;PuTTY reading the RFID card&quot; title=&quot;Too bad the reader beeps so loud!&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="693" LastEditorUserId="693" LastEditorDisplayName="" LastEditDate="2010-04-15T22:31:55.570" LastActivityDate="2010-04-15T22:31:55.570" Title="Problems with a RFID reader from SparkFun" Tags="&lt;rfid&gt;&lt;sensor&gt;&lt;usb&gt;" AnswerCount="3" />
  <row Id="2237" PostTypeId="2" ParentId="2235" CreationDate="2010-04-14T18:04:13.310" Score="0" ViewCount="" Body="&lt;p&gt;Try the Sparkfun &lt;a href=&quot;http://forum.sparkfun.com/&quot; rel=&quot;nofollow&quot;&gt;forum&lt;/a&gt;. Lots of people there seem to be using them successfully.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-14T18:04:13.310" CommentCount="2" />
  <row Id="2238" PostTypeId="2" ParentId="78" CreationDate="2010-04-14T19:00:27.220" Score="1" ViewCount="" Body="&lt;p&gt;Be careful.  You generate hydrogen, &lt;strong&gt;which can explode.&lt;/strong&gt;  Accordingly use a good quality charger at a minimum.  If you have banks of batteries, get a hydrogen sensor.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-04-14T19:00:27.220" />
  <row Id="2239" PostTypeId="1" CreationDate="2010-04-14T19:06:27.557" Score="9" ViewCount="907" Body="&lt;p&gt;I see this circuit a lot on electret microphone preamps, but I don't quite understand it.  The FET is operated as a &lt;a href=&quot;http://en.wikipedia.org/wiki/Common_source&quot; rel=&quot;nofollow&quot;&gt;common source&lt;/a&gt; amplifier, so it has gain, inverts, and has relatively high output impedance.  So it would make sense to follow it by a buffer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The BJT is &lt;a href=&quot;http://en.wikipedia.org/wiki/Common_collector&quot; rel=&quot;nofollow&quot;&gt;common collector&lt;/a&gt;/emitter follower, so it would seem to be acting as just such a buffer, right?  It would be non-inverting, with near unity voltage gain, and low output impedance to drive other things without being degraded.  The voltage signal from the FET is passed through the capacitor to the base of the BJT, where it's then buffered and shows up at the output of the BJT.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I don't get is why the FET's drain resistor is connected to the &lt;em&gt;output&lt;/em&gt; of the BJT, rather than to the power supply.  Is this some kind of feedback?  Wouldn't it be positive feedback?  (As the FET's output voltage increases, it pushes the base voltage upwards through the cap, which then pushes the output voltage upwards from the BJT, which then pulls the FET voltage upwards, and so on.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/0aF9A.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What advantage does it have over a circuit like this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/qeEZw.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-21T14:58:57.417" LastActivityDate="2010-05-21T14:58:57.417" Title="I don't quite understand this FET-BJT preamp circuit" Tags="&lt;fet&gt;&lt;bjt&gt;&lt;amplifier&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="2240" PostTypeId="2" ParentId="2235" CreationDate="2010-04-14T21:09:23.363" Score="2" ViewCount="" Body="&lt;p&gt;I have used one of these before, specifically the one from Sparkfun and it worked correctly. I suggest at this point that you try to wire it up in your own circuit with the ID12 for testing (the &lt;a href=&quot;http://www.sparkfun.com/datasheets/Sensors/ID-12-Datasheet.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; has all the pinout information you should need). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't need to connect an antenna; just wire pin 10 to an LED and try swiping some cards. If it works fine I would consider contacting sparkfun for a replacement USB board because there is something funky going on there (after trying it in another PC of course).&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-04-14T21:09:23.363" />
  <row Id="2241" PostTypeId="2" ParentId="2235" CreationDate="2010-04-14T22:57:19.277" Score="3" ViewCount="" Body="&lt;p&gt;Have you tried using a powered USB hub?&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-04-14T22:57:19.277" CommentCount="2" />
  <row Id="2242" PostTypeId="2" ParentId="1872" CreationDate="2010-04-15T14:08:45.937" Score="1" ViewCount="" Body="&lt;p&gt;Going with @Veuvius' suggestion of getting the parts&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The protoype board is Twin Industries &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=438-1048-ND&quot; rel=&quot;nofollow&quot;&gt;TW-E41-1060&lt;/a&gt; $37.45.&lt;/li&gt;&#xA;&lt;li&gt;Logic probe BK Precision &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=DP-21-ND&quot; rel=&quot;nofollow&quot;&gt;DP 21&lt;/a&gt; $37.00&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-04-15T14:15:10.010" LastActivityDate="2010-04-15T14:15:10.010" />
  <row Id="2243" PostTypeId="2" ParentId="1872" CreationDate="2010-04-15T14:20:59.983" Score="1" ViewCount="" Body="&lt;p&gt;A similar but cheaper solution is &lt;a href=&quot;http://www.tequipment.net/GlobalSpecialtiesPB-501.html&quot; rel=&quot;nofollow&quot;&gt;Global Specialties PB-501 Logic Design Trainer&lt;/a&gt; $182.70.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-04-15T14:20:59.983" />
  <row Id="2244" PostTypeId="2" ParentId="129" CreationDate="2010-04-15T15:15:24.727" Score="3" ViewCount="" Body="&lt;p&gt;Microchip/ZeroG Wireless Module&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't used this module, but we are planning on using it. I have used the Microchip TCP/IP stack and it works pretty well. It's inexpensive and interfaces to uP via SPI bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2664&amp;amp;param=en540851&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2664&amp;amp;param=en540851&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-15T15:15:24.727" CommentCount="5" />
  <row Id="2245" PostTypeId="1" AcceptedAnswerId="2248" CreationDate="2010-04-15T19:38:22.717" Score="5" ViewCount="1034" Body="&lt;p&gt;Hello All,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i want to start a home automation project, so finally i choose zigbee as the communication system between the devices.&#xA;I need something easy to start, so, what do you recomend to buy? there is some nice starter or development kit, with something like RS232 or USB output, just to forget about the zigbee protocols and issues, &#xA;i need something that almost works out-of-the-box...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks!&#xA;Br&lt;/p&gt;&#xA;" OwnerUserId="699" LastActivityDate="2011-05-20T08:43:00.403" Title="Zigbee starter kit, any suggestions?" Tags="&lt;zigbee&gt;&lt;development&gt;&lt;board&gt;&lt;wireless&gt;" AnswerCount="7" FavoriteCount="3" />
  <row Id="2246" PostTypeId="2" ParentId="2086" CreationDate="2010-04-15T19:57:48.100" Score="1" ViewCount="" Body="&lt;p&gt;I believe I have found my microSD problem! Hopefully this will help someone&#xA;else. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My main problem was a schematic error :( While looking for the schematic error&#xA;I found a couple of other potential issues --&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;For SPI operation all the RSV lines (pins 1 and 8) need to have&#xA;pull-ups even though they are not used (Samsung microSD datasheet&#xA;pg 14 (version 0.3, Mar 7 2007)).  I am not sure if this is a&#xA;Samsung requirement or a MicroSD requirement.  Also recommended are&#xA;pullups on all the RDAT lines and the RCMD line.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;At least 8 clock pulses are required before the card will give a response&#xA;to a command. This wait is labeled NCR in the Samsung DS and has a minumum&#xA;value of 8 (pulses) and a maximum value of 64 (pulses). &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I have tried a Transcend 1GB and SanDisk 2GB uSD card. Both initialize to&#xA;idle state. I am now going to finish the uSD libraries for my '328 and '644&#xA;boards. If I discover any other hardware or software issues I will try&#xA;to update this post.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:31:25.053" LastActivityDate="2011-05-18T11:31:25.053" />
  <row Id="2247" PostTypeId="2" ParentId="2245" CreationDate="2010-04-15T20:13:34.013" Score="1" ViewCount="" Body="&lt;p&gt;I would recommend one of my &lt;a href=&quot;http://wiblocks.luciani.org/ZB1/ZB1-index.html&quot; rel=&quot;nofollow&quot; title=&quot;ZB1&quot;&gt;ZB1 Boards&lt;/a&gt; ;) The ZB1 is an Arduino&#xA;compatible board with an XBee (Maxstream Zigbee) radio and a USB port.&#xA;There are a variety of accessories and software examples on the site.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The XBee's are very easy to start with. There are a variety of&#xA;antenna options and a couple of power levels. The downside is that&#xA;XBee's cost around $20-$25 each. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;XBee's can also run standalone. You can setup the devices&#xA;to periodically wake, perform a measurement or control task, transmit&#xA;data and go back to sleep. With a 0.1% duty cycle (transmit 1sec &#xA;and sleep 1000 seconds) you can get around a year or two on 2AA cells.&#xA;I did a &lt;a href=&quot;http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html&quot; rel=&quot;nofollow&quot;&gt;Zigbee Overview&lt;/a&gt; for the last MIT IAP.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:20:48.430" LastActivityDate="2011-05-19T14:20:48.430" CommentCount="2" />
  <row Id="2248" PostTypeId="2" ParentId="2245" CreationDate="2010-04-15T22:49:36.867" Score="3" ViewCount="" Body="&lt;p&gt;Digi's online store has an &lt;a href=&quot;http://store.digi.com/index.cfm?fuseaction=product.display&amp;amp;product_id=621&quot; rel=&quot;nofollow&quot;&gt;XBee 802.15.4 Starter Kit&lt;/a&gt; that includes:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;(2) XBee 802.15.4 w/ Wire Antenna&lt;/li&gt;&#xA;  &lt;li&gt;(1) RS-232 Development Board&lt;/li&gt;&#xA;  &lt;li&gt;(1) USB Development Board&lt;/li&gt;&#xA;  &lt;li&gt;(1) RS-232 Serial Cable&lt;/li&gt;&#xA;  &lt;li&gt;(1) USB Cable&lt;/li&gt;&#xA;  &lt;li&gt;(1) Power Adapter&lt;/li&gt;&#xA;  &lt;li&gt;(1) 9V Battery Clip&lt;/li&gt;&#xA;  &lt;li&gt;(3) Adapters&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This kit will not only let you start talking with the XBee modules, but actually program them as well.You can see a complete review of the kit from &lt;a href=&quot;http://zigbeeproject.org/?p=132&quot; rel=&quot;nofollow&quot;&gt;&lt;em&gt;The ZigBee Project&lt;/em&gt;&lt;/a&gt; blog.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also a more basic kit &lt;a href=&quot;http://www.trossenrobotics.com/p/Xbee-Communication-Starter-Kit.aspx&quot; rel=&quot;nofollow&quot;&gt;XBee Wireless Communication Starter Kit&lt;/a&gt; at Trossen Robotics:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;[2x] XBee 1mW Communication Module&lt;/li&gt;&#xA;  &lt;li&gt;XBee Explorer USB&lt;/li&gt;&#xA;  &lt;li&gt;XBee Explorer Regulated&lt;/li&gt;&#xA;  &lt;li&gt;A to Mini B USB Cable&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;And as always, you can pick up individual modules, Arduino shields, and accessories at &lt;a href=&quot;http://www.sparkfun.com/commerce/advanced_search_result.php?keywords=xbee&amp;amp;x=0&amp;amp;y=0&amp;amp;search_section=products&quot; rel=&quot;nofollow&quot;&gt;SparkFun.com&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="693" LastEditorUserId="4244" LastEditorDisplayName="" LastEditDate="2011-05-13T15:44:03.693" LastActivityDate="2011-05-13T15:44:03.693" CommentCount="4" />
  <row Id="2249" PostTypeId="2" ParentId="129" CreationDate="2010-04-15T23:43:29.347" Score="3" ViewCount="" Body="&lt;p&gt;Roving Networks offers the &lt;a href=&quot;http://www.rovingnetworks.com/wifly-gsx.php&quot; rel=&quot;nofollow&quot;&gt;RN-131G/C&lt;/a&gt; for $45/$40 WiFi - UART.  It uses 100 mA when awake, and 10 uA asleep.  I'm using a related system on a project and it works quite well.  The C variant is commercial temp range, the G is industrial.  I think they have RS-232 as well as SPI/I2C versions as well.  I'm not sure if this is the WiFly GSX you mentioned in your original question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, we looked at the modules from &lt;a href=&quot;http://www.redpinesignals.com/products.html#modules&quot; rel=&quot;nofollow&quot;&gt;Redpine Signals&lt;/a&gt;.  I'm not sure what their power consumption is, but the Connect-i-on series of products has the other functionality you're looking for.&lt;/p&gt;&#xA;" OwnerUserId="696" LastEditorUserId="696" LastEditorDisplayName="" LastEditDate="2010-04-16T01:27:39.600" LastActivityDate="2010-04-16T01:27:39.600" CommentCount="1" />
  <row Id="2250" PostTypeId="2" ParentId="1722" CreationDate="2010-04-15T23:55:32.410" Score="1" ViewCount="" Body="&lt;p&gt;There is a visual studio addin in beta at the moment. its free, if you want to be part of the beta then you just need to email beta @ visualmicro.com or take a look at &lt;a href=&quot;http://www.visualmicro.com&quot; rel=&quot;nofollow&quot;&gt;http://www.visualmicro.com&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The arduino addin for visual studio provides intellisense and allows you to select arduino boards, libraries. it also supports compile and upload from visual studio directly to the arduino&lt;/p&gt;&#xA;" LastActivityDate="2010-04-15T23:55:32.410" />
  <row Id="2251" PostTypeId="2" ParentId="616" CreationDate="2010-04-16T00:49:03.430" Score="8" ViewCount="" Body="&lt;p&gt;I &lt;strong&gt;don't&lt;/strong&gt; recommend &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0945053282&quot; rel=&quot;nofollow&quot;&gt;&lt;em&gt;Getting Started in Electronics&lt;/em&gt; by Forrest M. Mims III&lt;/a&gt;.  I tried to use this to learn electronics as a kid and I think it mislead me more than it taught.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I remember being frustrated by my inability to make simple circuits work, and I think this book's simplistic descriptions are partially to blame.  Some examples:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;It uses electron current in all the descriptions instead of conventional current.  This isn't really wrong, but &lt;a href=&quot;http://electronics.stackexchange.com/questions/42/books-for-beginners-starting-electronics&quot;&gt;it's not any more right, either&lt;/a&gt;, and adds an unnecessary layer of confusion when looking at circuits anywhere else.&lt;/li&gt;&#xA;&lt;li&gt;&quot;The minus side of our homemade capacitor is charged with electrons almost immediately.&quot;  So &lt;a href=&quot;http://amasci.com/emotor/cap1.html&quot; rel=&quot;nofollow&quot;&gt;why don't we&lt;/a&gt; store electrons on the other plate too, and get twice as much?  :)&lt;/li&gt;&#xA;&lt;li&gt;The drawings show little cartoon electrons jumping out of wires, getting &quot;stuck&quot; inside resistors, being blocked by the field of an FET, or stuck on one side of a thyristor with none being able to get to the other side, etc.  Likewise, &quot;When bombarded with light, heat, electrons and other forms of energy, most semi-conductor crystals will emit visible or infrared light.&quot;  Electrons are &lt;a href=&quot;http://amasci.com/miscon/energ1.html&quot; rel=&quot;nofollow&quot;&gt;&lt;em&gt;not&lt;/em&gt; a &quot;form of energy&quot;&lt;/a&gt;, and they don't &quot;bombard&quot; the semi-conductor.  I imagined that electrons went into components like light bulbs or LEDs, got &quot;used up&quot;, and turned into photons, like the illustrations in the book.  So why then, do they need a second return wire if there's nothing left to return?&lt;/li&gt;&#xA;&lt;li&gt;&quot;Transistors can be used as amplifiers&quot; ... &quot;Therefore a very small emitter-base current will cause a much larger emitter-collector current to flow.&quot;  This made me think that the emitter-collector junction can &lt;em&gt;source&lt;/em&gt; a current.  (It's a regulating valve, not an amplifier.  There is no energy source inside a transistor.)  None of my transistor circuits ever worked.&lt;/li&gt;&#xA;&lt;li&gt;&quot;Ground&quot; is described as &quot;the point in a circuit at zero voltage, whether or not it's connected to ground&quot;.  So what causes it to be at zero voltage?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I struggled with these descriptions for years. Only when I got to college did I finally start to learn this stuff, rather than poke in the dark and hope that things worked.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think William Beaty's &lt;a href=&quot;http://www.eskimo.com/~billb/miscon/elect.html&quot; rel=&quot;nofollow&quot;&gt;Electricity Misconceptions&lt;/a&gt; pages are much better at explaining electricity in an intuitive, but accurate way, and helped &quot;unteach&quot; all the incorrect things I learned from other books.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another book I &lt;strong&gt;don't&lt;/strong&gt; recommend is &lt;a href=&quot;http://www.sedrasmith.org/&quot; rel=&quot;nofollow&quot;&gt;Sedra &amp;amp; Smith's &lt;em&gt;Microelectronic Circuits&lt;/em&gt;&lt;/a&gt;.  Their teaching method for transistors is very unintuitive and impractical, for instance.  If you want to memorize a bunch of equations without actually learning anything you can use to build circuits, this is the book for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;a href=&quot;http://www.google.com.br/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CBwQFjAA&amp;amp;url=http://www.amazon.com/Art-Electronics-Paul-Horowitz/dp/0521370957&amp;amp;ei=WoPNTaTsGKbc0QHn98TfDQ&amp;amp;usg=AFQjCNFH1Ijguy7mmHOs0SJJomvlHZX6Ig&amp;amp;sig2=tc5aNhAEOsph0xCHjECnJw&quot; rel=&quot;nofollow&quot;&gt;Art of Electronics&lt;/a&gt;&lt;/em&gt; does a much better job of teaching transistor circuits.  It's good and practical.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T19:15:53.117" LastActivityDate="2011-05-13T19:15:53.117" CommunityOwnedDate="2011-03-24T07:55:53.500" CommentCount="1" />
  <row Id="2252" PostTypeId="2" ParentId="2245" CreationDate="2010-04-16T02:44:02.247" Score="3" ViewCount="" Body="&lt;p&gt;After spending the last 8 months working on my engineering project involving XBees for my degree, I would recommend a &lt;a href=&quot;http://www.ladyada.net/make/xbee/index.html&quot; rel=&quot;nofollow&quot;&gt;breakout board from ladyada&lt;/a&gt; with an FTDI usb to serial cable for programming and an XBee. The board exposes DTR, RST, CTS, RTS, TX and RX for the XBee and regulates the supply voltage down to 3.3V. For automation purposes, there's no reason to go pro unless you live in a mansion imo.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The breakout board uses a level converter to switch between RS232 levels and TTL levels required by the XBee, but if your controller outputs serial on TTL levels, I believe you can omit the MAX232 chip or something to keep it at TTL.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2010-04-16T02:44:02.247" CommentCount="1" />
  <row Id="2253" PostTypeId="2" ParentId="2245" CreationDate="2010-04-16T05:05:33.500" Score="0" ViewCount="" Body="&lt;p&gt;How about the &lt;a href=&quot;http://www.atmel.com/dyn/Products/tools_card.asp?tool_id=4291&quot; rel=&quot;nofollow&quot;&gt;Atmel Raven&lt;/a&gt;? It's a usb stick with zigbee.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-16T05:05:33.500" CommentCount="2" />
  <row Id="2254" PostTypeId="1" AcceptedAnswerId="2256" CreationDate="2010-04-16T14:34:11.220" Score="2" ViewCount="295" Body="&lt;p&gt;I'm having a problem programming a PIC18F97J60 with pk2cmd.exe. Using the same hex file I can program the device fine with MPLAB and the PicKit2 programming utility, but I'd like to be able to program the chip from the command line. The chip will program, but verify fails. I should mention that I have the code protect bits set on the PIC18F97J60.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Original Configuration:&lt;br&gt;&#xA; - PK2CMD.EXE v1.20&lt;br&gt;&#xA; - Device File v1.55.00&lt;br&gt;&#xA; - PICkit2 Firmware v2.32.00&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-04-16T15:15:52.387" LastActivityDate="2010-04-16T15:15:52.387" Title="Problem programming PIC18F97J60 with PicKit2" Tags="&lt;pic&gt;&lt;programmer&gt;" AnswerCount="1" />
  <row Id="2255" PostTypeId="2" ParentId="2245" CreationDate="2010-04-16T15:06:28.820" Score="1" ViewCount="" Body="&lt;p&gt;I'd check out the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8687&quot; rel=&quot;nofollow&quot;&gt;XBee USB Explorer&lt;/a&gt; from Sparkfun, an &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=29&amp;amp;products_id=126&quot; rel=&quot;nofollow&quot;&gt;XBee Adapter kit from Adafruit&lt;/a&gt;, an Arduino, plus 2 XBee units.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That gives you a way to have your computer directly talk over Xbee (with the USB explorer) and then a microcontroller that can carry out actions on your behalf (the XBee Adapter + arduino).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not recommending the Arduino XBee shield, because it blocks a lot of the outputs from the Arduino.  That XBee adapter kit from AdaFruit looks to be a lot more flexible, even if it does require you to breadboard things together instead of having the nice shield stacking action.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2010-04-16T15:06:28.820" />
  <row Id="2256" PostTypeId="2" ParentId="2254" CreationDate="2010-04-16T15:14:03.077" Score="2" ViewCount="" Body="&lt;p&gt;Apparently there is a problem with the device file that comes with v1.20 of pk2cmd.exe.&lt;br&gt;&#xA;Reverting to the device file that comes v1.01b of pk2cmd.exe fixes the issue.&lt;br&gt;&lt;br&gt;&#xA;Working configuration:&lt;br&gt;&#xA; - PK2CMD.EXE v1.20&lt;br&gt;&#xA; - Device File v1.42.00 (Comes with PK2CMD.EXE v1.01b)&lt;br&gt;&#xA; - PICkit2 Firmware v2.32.00&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-16T15:14:03.077" />
  <row Id="2257" PostTypeId="1" CreationDate="2010-04-17T00:23:56.213" Score="2" ViewCount="670" Body="&lt;p&gt;I have a &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/ina126.html&quot; rel=&quot;nofollow&quot;&gt;TI INA126&lt;/a&gt; (&lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/ina126.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;) instrumentation amplifier that I want to use to amplify a noisy, low-level signal from a fabric-based resistive stretch sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistance ranges for the fabric sensors vary depending on how they are cut. Sometimes the range is 50Ω-100Ω. Ideally it is 300Ω-600Ω. &lt;em&gt;Let's assume the range &lt;strong&gt;200Ω-300Ω&lt;/em&gt;&lt;/strong&gt; at first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a simple voltage divider (R2=250Ω) and working with 5V, I get a voltage range of about 0.5V from &lt;strong&gt;2.27V to 2.77V&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;(250/(250+200))*5 - (250/(250+300))*5 = 0.5&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I need to remove the common-mode of 2.77V and amplify the difference into the output swing of the INA126 (0.8V-4.2V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The equation for the INA126 is: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Vo = (Vin+ - Vin-)*G&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;G = 5+(80kΩ/Rg)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Setting the gain is very easy (one resistor across pins 1 and 8). A table is provided in the datasheet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm having trouble figuring out how to set everything up. I have it set up as follows:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Rg (no resistor for 5x amplification)&lt;/li&gt;&#xA;&lt;li&gt;V-in (3.3V? 5V? 2.7V? grnd?)&lt;/li&gt;&#xA;&lt;li&gt;V+in (sensor in)&lt;/li&gt;&#xA;&lt;li&gt;V- (grnd)&lt;/li&gt;&#xA;&lt;li&gt;Ref (grnd)&lt;/li&gt;&#xA;&lt;li&gt;Vout (output)&lt;/li&gt;&#xA;&lt;li&gt;V+ (+5V)&lt;/li&gt;&#xA;&lt;li&gt;Rg (no resistor for 5x amplification)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;With the above setup and V-in connected to 2.2V from a DC power supply and V+ connected to the Arduino 5V supply, the output range becomes:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;2.65-2.98&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This doesn't make sense according to the calculations:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;(2.27-2.1)*5 = 0.85&lt;/strong&gt;&#xA;&lt;br&gt;&lt;strong&gt;(2.77-2.1)*5 = 3.35&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally the amp doesn't seem to do what I want it to. What am I doing wrong?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT1:&lt;/strong&gt; I have access to a DC Power Supply (w/ negative voltage). Perhaps this will help me?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT2:&lt;/strong&gt; I'm going to try once more with a Wheatstone bridge and the dual power supply. If that doesn't work, I'm ordering amplifiers that are less fussy in single-supply mode (along with some 1% resistors) and trying again on Monday. &lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2010-04-18T05:38:47.640" LastActivityDate="2011-05-19T14:21:06.433" CommunityOwnedDate="2010-04-17T00:52:20.197" Title="Configuring INA126 Instrumentation Amplifier for Data Acquisition" Tags="&lt;op-amp&gt;&lt;arduino&gt;&lt;sensor&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="2258" PostTypeId="2" ParentId="2257" CreationDate="2010-04-17T01:22:26.663" Score="1" ViewCount="" Body="&lt;p&gt;I don't really see a reason for this not to work the way you expect with the connections you have listed here. Might I suggest some debugging steps?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) See what happens to the output range when you put a large-ish Rg ( say 27k ohms) in the circuit. Does the output swing change at all?&#xA;2) Have you checked the inputs to make sure they are as you expect with the amplifier connected? If so, how about using a larger resistance POT to simulate your resistor divider just to remove the sensor from the picture until you get the circuit working.&#xA;3) Perhaps the simplest explaination might be that the INA126 itself is bad. Do you have a spare you can drop in to test?&lt;/p&gt;&#xA;" OwnerUserId="631" LastActivityDate="2010-04-17T01:22:26.663" CommunityOwnedDate="2010-04-17T01:22:26.663" CommentCount="3" />
  <row Id="2259" PostTypeId="2" ParentId="2257" CreationDate="2010-04-17T01:38:10.627" Score="1" ViewCount="" Body="&lt;p&gt;I don't believe you can operate that instrument amp (IA) in single supply mode. Take a &#xA;look at page 8 of the datasheet (Input Common-Mode Range). It states that &#xA;the low rail of A2 (the bottomr amp in the diff amp) is &lt;/p&gt;&#xA;&#xA;&lt;p&gt;VO2 = 1.25 * VIN- + (VIN+ - VIN-) * 10K/RG &lt;/p&gt;&#xA;&#xA;&lt;p&gt;which for your setup would be VO2 = 1.25 * 2.1 + 0 = 2.625&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2.625 is essentially the low value you get in your experiment. &#xA;The voltage difference is invalid due to the voltage limiting of A2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need a single supply instrument amp (and preferable a &#xA;rail-to-rail IA). A couple of my favorites are the AD623 and AD8235.&#xA;I am sure TI (BB division), Linear Tech or ADI will have a number&#xA;of other options.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[EDIT] I may have spoke too soon on the single supply operation. Take a look &#xA;at page 9. You may be able to bias the reference pin up to offset the A2 output&#xA;voltage. Unfortunately the example that is shown looks a bit different&#xA;than an Arduino ADC.[/EDIT]&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:21:06.433" LastActivityDate="2011-05-19T14:21:06.433" CommunityOwnedDate="2010-04-17T01:38:10.627" CommentCount="15" />
  <row Id="2260" PostTypeId="2" ParentId="2257" CreationDate="2010-04-17T01:39:11.983" Score="1" ViewCount="" Body="&lt;p&gt;what i would do is build a ladder such that you get the voltage differential you want across a resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.kegs-tapped.com/images/opamp.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R1 would be the variable resistance of your sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R2 + R3 would be chosen for the desired current level&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R2 is chosen to produce the desired voltage drop based on the current range you just defined.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vref could be tied to a voltage reference supplied by the ADC (buffered with an op amp) or tied to ground.  Note that Vref sets DC offset of the amps output so its to be used to make sure the output ends up in the range the ADC can handle.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-04-17T01:39:11.983" CommunityOwnedDate="2010-04-17T01:39:11.983" CommentCount="5" />
  <row Id="2261" PostTypeId="2" ParentId="2178" CreationDate="2010-04-17T02:13:21.103" Score="5" ViewCount="" Body="&lt;p&gt;Inductive charging stations is a very neat idea, and one I hope you are able to pull off with your robot platform. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although I have never built a inductive charger myself, I have put together several home-made, from scratch RFID type devices and what I have learned is that the key to getting good coupling between the primary coil of the charging station and the pickup coil on your robot is having a well tuned (high-Q) resonant network on the primary. I think you will be best off coupling this with a non-resonant pickup coil on the robot, that way the load introduced by the robot will have minimal impact on the resonance of your primary coil. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Give this paper a read: &lt;a href=&quot;http://www.hizook.com/files/publications/PowerSurface-CameraReady.pdf&quot; rel=&quot;nofollow&quot;&gt;Surface Based Wireless Power Transmission and Bidirectional Communication for Autonomous Robot Swarms&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have put together a basic system that should have all of the parts you need to provide power to charge your robot. On the base they use a two-coil setup with a primary driver coil being driven by a power MOSFET coupled to a resonant secondary coil. Since the secondary coil is electrically isolated from the driver they are able to preserve the resonance and improve the Q of the secondary system better than if they were just driving it directly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the receiver end they are using a non-resonant pickup coil (basically coiled wire) connected to a &lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage_multiplier&quot; rel=&quot;nofollow&quot;&gt;cascade multiplier&lt;/a&gt; which boosts the voltage picked up by the coil to a level they can use on their robots. I have built similar pickups for the RFID projects and they work surprisingly well with the right combination of Schottky diodes and capacitor values (ceramic work best here). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the challenge in your case would be to get the output voltage high enough to trickle charge whatever battery pack you are using. Since I don't know if you are using LiPo, NiMH, or even lead acid I couldn't say if this would work for sure. I imagine with enough tweaking you can easily get 4-5V out of this type of setup and that should be enough for LiPo or NiMH.&lt;/p&gt;&#xA;" OwnerUserId="631" LastActivityDate="2010-04-17T02:13:21.103" />
  <row Id="2262" PostTypeId="1" CreationDate="2010-04-17T09:14:03.220" Score="10" ViewCount="812" Body="&lt;p&gt;Hey all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lots of chips nowadays require smoothing capacitors between VCC and GND for proper function. Given that my projects run at all sorts of different voltage and current levels, I was wondering if anyone had any rules of thumb for a) how many and b) what size capacitors should be used to ensure that power supply ripple doesn't affect my circuits?&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2011-02-12T17:52:17.180" Title="Smoothing capacitors: what size and how many?" Tags="&lt;power&gt;&lt;capacitor&gt;" AnswerCount="3" FavoriteCount="5" />
  <row Id="2263" PostTypeId="2" ParentId="2178" CreationDate="2010-04-17T09:28:46.577" Score="3" ViewCount="" Body="&lt;p&gt;I worked at a company where we developed and eventually manufactured an electric toothbrush with inductive charging, so your comment about ripping apart a toothbrush caught my attention. It should be noted that most (all?) electronic toothbrush inductive charging systems are very inefficient. The are trickle charging the batteries. They just need to charge the batteries enough to power a led charging indicator and run the brush about four minutes a day. The circuitry is generally quite simple, especially on the toothbrush side which consists of little more than a full wave rectifier, a coil, and a ferrite. Often a led is used as one of the diodes of the rectifier so it does double duty as a charging indicator. I doubt there is anything in the toothbrush that you couldn't easily put together yourself. The charging bases are slightly more complex, but still pretty simple oscillating circuits, often not very well optimized. Chinese companies often reuse charger designs with little sensitivity to maximizing efficiency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do get the urge to take apart a toothbrush, keep in mind taking apart most electric toothbrushes be harder than you expect. They are typically ultrasonically welded, so you'll need to cut it open. Pipe cutters are a good tool for this.&lt;/p&gt;&#xA;" OwnerUserId="227" LastActivityDate="2010-04-17T09:28:46.577" />
  <row Id="2264" PostTypeId="2" ParentId="2226" CreationDate="2010-04-17T11:25:11.717" Score="1" ViewCount="" Body="&lt;p&gt;Maybe you can use an ARM Cortex-M3? The peripherals would not be a problem but your code size/memory requirements may be. Take a look at the &lt;a href=&quot;http://mbed.org/nxp/lpc1768/quick-reference/&quot; rel=&quot;nofollow&quot;&gt;mbed board&lt;/a&gt;. It is priced at $60 (DigiKey) or €53 (Farnell) and has 3 serial ports and ethernet. It has 512kB of Flash (program) memory and 64kB of RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can give us more details about the device you have to replace, we may be able to tell if the Flash and RAM memory will be sufficient or do you have to search for a bigger device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. I will try to help you as much as I can but in case you later decide you don't want to do it yourself, feel free to contact me (I can help with both the hardware and the software).&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:30:02.550" LastActivityDate="2011-05-18T11:30:02.550" />
  <row Id="2265" PostTypeId="2" ParentId="2262" CreationDate="2010-04-17T11:58:38.030" Score="10" ViewCount="" Body="&lt;p&gt;You need to add a couple of more questions -- (c) what dielectric should I use and&#xA;(d) where do I place the capacitor in my layout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The amount and size varies by application. For power supply components&#xA;the ESR (effective series resistance) is a critical component. For example the MC33269 LDO datasheet lists an ESR recommendation of 0.2Ohms to 10Ohms. There is a minimum amount&#xA;of ESR required for stability. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For most logic ICs and op-amps I use a 0.1uF ceramic capacitor. I place the capacitor&#xA;very close to the IC so that there is very short path from the capacitor leads&#xA;to the ground. I use extensive ground and power planes to provide low impedance&#xA;paths. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For power supply and high current components each application is different. &#xA;I follow the manufacturer recommendations and place the capacitors very close&#xA;to the IC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For bulk filtering of power inputs coming into the board I will typically use a&#xA;10uF ceramic X7R capacitor. Again this varies with application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless there is an minimum ESR requirement for stability or I need very large&#xA;values of capacitance I will use either X7R or X5R dielectrics. Capacitance&#xA;varies with voltage and temperature. Currently it is not difficult to get&#xA;affordable 10uF ceramic capacitors. You do not need to over specify the voltage &#xA;rating on ceramic capacitors. At the rated voltage the capacitance is within&#xA;the tolerance range. Unless you increase the voltage above the dielectric breakdown&#xA;you are only losing capacitance. Typically the dielectric strength is 2 to 3 times&#xA;the rated voltage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a very good application note about grounding and decoupling&#xA;by Paul Brokaw called &quot;An IC Amplifier User's Guide to Decoupling,&#xA;Grounding,. and Making Things Go Right for a Change&quot;. It is at&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.analog.com/UploadedFiles/Application_Notes/135208865AN-202.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.analog.com/UploadedFiles/Application_Notes/135208865AN-202.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-12T17:52:17.180" LastActivityDate="2011-02-12T17:52:17.180" />
  <row Id="2266" PostTypeId="1" CreationDate="2010-04-17T12:14:58.513" Score="1" ViewCount="438" Body="&lt;p&gt;how to interface barcode scanner to AVR AT90usb1287 microcontroller.&lt;/p&gt;&#xA;" LastActivityDate="2010-04-18T07:36:16.960" Title="At90usb1287 USB \Barcode scanner interface" Tags="&lt;avr&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="2267" PostTypeId="1" CreationDate="2010-04-17T13:28:19.527" Score="1" ViewCount="119" Body="&lt;p&gt;I want to interface a cc2500 module with the 3pi robot...How do i do that...I just have the cc2500 module(the one &lt;a href=&quot;http://thinklabs.in/shop/product_info.php?cPath=67&amp;amp;products_id=186&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;)&#xA;I want my 3pi to move accordingly to the instruction given by another transciever. &lt;/p&gt;&#xA;" LastActivityDate="2010-04-17T20:14:11.560" Title="To receive data wirelessly by 3pi robot" Tags="&lt;3pi&gt;&lt;robotics&gt;&lt;wireless&gt;" AnswerCount="1" />
  <row Id="2268" PostTypeId="2" ParentId="2262" CreationDate="2010-04-17T14:04:15.123" Score="1" ViewCount="" Body="&lt;p&gt;If you're using big electrolytics to smooth out a power supply, don't forget to add small ceramic caps in parallel for the high frequencies.  Electrolytic caps actually look like inductors at high frequencies.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.boostbuck.com/BypassingaCapacitor.html&quot; rel=&quot;nofollow&quot;&gt;http://www.boostbuck.com/BypassingaCapacitor.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amccaps.com/leaded-capacitors/switch-mode-ceramic-capacitors/impedance-vs-frequency.html&quot; rel=&quot;nofollow&quot;&gt;http://www.amccaps.com/leaded-capacitors/switch-mode-ceramic-capacitors/impedance-vs-frequency.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://enjeti.tamu.edu/conf-papers/electrolytic-cap-pwm-asd.pdf&quot; rel=&quot;nofollow&quot;&gt;http://enjeti.tamu.edu/conf-papers/electrolytic-cap-pwm-asd.pdf&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-04-17T14:18:46.453" LastActivityDate="2010-04-17T14:18:46.453" />
  <row Id="2269" PostTypeId="2" ParentId="2262" CreationDate="2010-04-17T15:27:08.450" Score="3" ViewCount="" Body="&lt;p&gt;I use the following rules of thumb for my digital circuits:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each pair of power supplies should get its X7R ceramic 100nF capacitor. It should be as close as possible to the pins. Best is if the supply line passes by the capacitor first before it goes to the pin, but most of the time this is not necessary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output of the power supply should typically get a 10µF capacitor. Check the data sheet of the voltage regulator data sheet for the required ESR value, if you do it wrong the regulator may oscillate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the circuit is big you may need more 10µF capacitors for subgroups of chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/atmel/acrobat/doc1619.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/atmel/acrobat/doc1619.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For analog circuits X7R may not be the right material, because it has a relatively large piezoelectric effect. That is, mechanical vibrations can cause voltage changes and vice versa. C0G is better in that respect. Though this caveat mostly applies to signal paths.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-04-17T15:27:08.450" />
  <row Id="2270" PostTypeId="1" AcceptedAnswerId="2288" CreationDate="2010-04-17T18:34:04.213" Score="3" ViewCount="215" Body="&lt;p&gt;I am just getting started with Arduino...I figure this is kind of a newbie question but here goes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a Duemilanove and the Sparkfun Speakjet shield.  I've got some breakaway headers (not the stackable headers) for connecting the Duemilanove with the Speakjet shield.  But then I want to interface a bunch of other stuff like switches and LEDs to the Arduino pins that are not used by the Speakjet shield.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it required to get the stackable headers to wire up my switches and LEDs to the Arduino pins?  Or is it advisable to just solder wires for my switches and LEDs onto the tiny nubs of the breakaway headers where they poke through the top of the Speakjet shield?&lt;/p&gt;&#xA;" OwnerUserId="707" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-24T21:42:25.867" LastActivityDate="2010-08-24T21:42:25.867" Title="Tapping into unused Arduino pins with a shield in place" Tags="&lt;arduino&gt;&lt;arduino&gt;" AnswerCount="1" />
  <row Id="2271" PostTypeId="2" ParentId="2267" CreationDate="2010-04-17T20:14:11.560" Score="1" ViewCount="" Body="&lt;p&gt;The board looks as though it has an AVR controlling the transceiver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to interface the AVR on one transceiver board to the robot. You will then need to develop software for the AVRs on both units, to control the robot according to received commands, and to send commands via the transceiver on the second transceiver board.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-17T20:14:11.560" />
  <row Id="2272" PostTypeId="1" AcceptedAnswerId="2274" CreationDate="2010-04-17T23:47:47.080" Score="18" ViewCount="3680" Body="&lt;p&gt;What is a decoupling capacitor (or smoothing capacitor as referred to in the link below)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I know if I need one and if so, what size and where it needs to go? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/2262/smoothing-capacitors-what-size-and-how-many&quot; rel=&quot;nofollow&quot;&gt;This question&lt;/a&gt; mentions many chips needing one between VCC and GND; how do I know if a specific chip is one? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would an &lt;a href=&quot;http://pdf1.alldatasheet.com/datasheet-pdf/view/27391/TI/SN74195N.html&quot; rel=&quot;nofollow&quot;&gt;SN74195N&lt;/a&gt; 4-bit parallel access shift register used with an Arduino need one? (To use my current project as an example) Why or why not?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I feel like I'm starting to understand the basics of resistors and some places they're used, what values should be used in said places, etc, and I'd like to understand capacitors at the basic level as well.&lt;/p&gt;&#xA;" OwnerUserId="647" LastEditorUserId="647" LastEditorDisplayName="" LastEditDate="2010-04-20T05:19:48.230" LastActivityDate="2011-05-13T19:22:03.007" Title="What is a decoupling capacitor and how do I know if I need one?" Tags="&lt;capacitor&gt;&lt;decoupling-capacitor&gt;&lt;beginner&gt;" AnswerCount="10" CommentCount="3" FavoriteCount="7" />
  <row Id="2273" PostTypeId="2" ParentId="869" CreationDate="2010-04-18T00:04:27.627" Score="1" ViewCount="" Body="&lt;p&gt;Here are some of the tools I find myself using most often:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Weller WES51 soldering iron&lt;/li&gt;&#xA;&lt;li&gt;Panavise Jr.&lt;/li&gt;&#xA;&lt;li&gt;Fluke 87V multimeter&lt;/li&gt;&#xA;&lt;li&gt;PHT-PYT-4 wire strippers (&lt;em&gt;don't&lt;/em&gt; buy the cheap chinese knockoffs. Mine were unusable.)&lt;/li&gt;&#xA;&lt;li&gt;Rigol DS1052E oscilloscope (somewhat expensive, but even as a relative beginner it's been an invaluable learning tool for showing what's actually going on with the voltage levels inside a circuit.)&lt;/li&gt;&#xA;&lt;li&gt;Cooper Tools &quot;Xcelite&quot; 170M cutter&lt;/li&gt;&#xA;&lt;li&gt;Elexp 060210 long nose pliers (I find myself using these constantly. Best $2 I ever spent.)&lt;/li&gt;&#xA;&lt;li&gt;Soldapullt deluxe&lt;/li&gt;&#xA;&lt;li&gt;Scotch tape for holding components in whilst I'm soldering them on the underside of the board.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I use a 12V computer fan hooked up to my three output variable power supply to dissipate solder fumes. Seems to work fine for now.&lt;/p&gt;&#xA;" OwnerUserId="647" LastActivityDate="2010-04-18T00:04:27.627" />
  <row Id="2274" PostTypeId="2" ParentId="2272" CreationDate="2010-04-18T02:51:35.863" Score="10" ViewCount="" Body="&lt;p&gt;Hi, I was the one that asked that question. Here is my rudimentary understanding:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You attach capacitors across $V_{CC}$/GND to try and keep the voltage more constant. Under a DC circuit, a capacitor acts like an open circuit so there is no problem with shorting there. As your device is powered up ($V_{CC}$=5V), the capacitor is charged to capacity and waits until there is a change in the voltage between $V_{CC}$ and GND ($V_{CC}$=4.5V). At this point, the capacitor will discharge to try and bring the voltage back to the level of charge inside the capacitor (5V). This is called &quot;smoothing&quot; (or at least that is what I call it) because the change in voltage will be less pronounced. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ultimately, the voltage will not ever return to 5V through a capacitor, rather the capacitor will discharge until the charge inside it is equal to the supply voltage (to an equilibrium). A similar mechanism is responsible for smoothing if $V_{CC}$ increases too far beyond its average ($V_{CC}$=5.5V perhaps).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for why you need them, they are very important in high speed digital and analog circuits. I can't imagine you would need one for a SN74195, but it can't hurt!&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T19:22:03.007" LastActivityDate="2011-05-13T19:22:03.007" CommentCount="1" />
  <row Id="2275" PostTypeId="2" ParentId="2272" CreationDate="2010-04-18T02:55:04.953" Score="8" ViewCount="" Body="&lt;p&gt;A smoothing capacitor (a.k.a. decoupling capacitor) is used to reduce the change in &#xA;power supply voltage. When you draw high currents from your power supply (like when digital logic switches state) you will see a change in supply voltage. Switching tries to draw&#xA;large instantaneous currents and produces a voltage drop due to the impedance of the voltage source and the connection between the voltage source and the IC. A decoupling capacitor will help to maintain (or smooth) the supply voltage at the device. Placing this storage&#xA;element close to the IC reduces the change in voltage at the IC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless you measure the supply voltage at each IC when the IC is drawing its maximum&#xA;switching currents it is difficult to say how effective the capacitor will be. For&#xA;most digital devices the recommendation is 0.1uF ceramic very close to the device.&#xA;Since the capacitors are small and low-cost most designers will just add the capacitors.&#xA;Sometimes if I have two logic devices that are very close you may be able to orient&#xA;a single capacitor between two ICs. This is usually not the case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Power supply ICs have larger smoothing capacitor requirements since the swithing&#xA;currents are larger. For those devices you need to look closer at the application&#xA;ripple requirements to determine the appropriate filtering capacitor.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:47:11.963" LastActivityDate="2011-05-13T12:47:11.963" />
  <row Id="2276" PostTypeId="2" ParentId="2272" CreationDate="2010-04-18T04:20:14.750" Score="3" ViewCount="" Body="&lt;p&gt;I would like to emphasis one of jluciani's points. It is very important to put the capacitor as close to the chips power input as possible. This can help eliminate any noise that is introduced any where else, either in your circuit, from the power supply, or even some noise being radiated from a source off of your board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;jluciani is correct that 0.1uF is very common for being placed next to ICs. Simply think of the capacitance as how much charge the capacitor can hold, so the bigger the capacitance the more charge it is holding. If you put capacitors in parallel, you add more capacity resulting in a higher effective capacitance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as your question about if that chip needs it or not, I would say, it wouldn't hurt. The datasheet will usually specify if the chip needs decoupling (aka smoothing) capacitors and if so what the recommended value is.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-04-18T04:20:14.750" />
  <row Id="2277" PostTypeId="1" AcceptedAnswerId="2293" CreationDate="2010-04-18T05:20:38.253" Score="2" ViewCount="722" Body="&lt;p&gt;Hello, I am trying to get a Multiplexer to work with the Arduino. &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9056&quot; rel=&quot;nofollow&quot;&gt;Description at sparkfun&lt;/a&gt; &lt;a href=&quot;http://www.sparkfun.com/datasheets/IC/cd74hc4067.pdf&quot; rel=&quot;nofollow&quot;&gt;Datasheet&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I thought the wiring was pretty simple and as a basic test, I have AREF connected to C1(multiplexer) and a floating wire connected to C0. Everything on the interfacing side maps almost 1 to 1 with the arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using this simple code for switching the multiplexer&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void select_wire(char which){&#xA;    digitalWrite(S0,which&amp;amp;0x01);&#xA;    digitalWrite(S1,which&amp;amp;0x02);&#xA;    digitalWrite(S2,which&amp;amp;0x04);&#xA;    digitalWrite(S3,which&amp;amp;0x08);&#xA;    digitalWrite(EN,0);&#xA;    delay(1); //required?&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;and then I just read from the Analog pin at &lt;code&gt;S&lt;/code&gt; on the multiplexer. My problem is that it is not switching! How do I fix this so that it will behave as intended and give a zero(or close) whenever I do &lt;code&gt;select_wire(1)&lt;/code&gt; and read the analog pin? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I am not using the Wiring &quot;language&quot; but I am using the Wiring library. I have also set all the appropriate &lt;code&gt;pinMode&lt;/code&gt;s  in the &lt;code&gt;init&lt;/code&gt;&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2010-04-20T04:08:46.657" Title="Using Multiplexer with an Arduino" Tags="&lt;arduino&gt;&lt;multiplexing&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="2278" PostTypeId="2" ParentId="2272" CreationDate="2010-04-18T05:23:20.583" Score="7" ViewCount="" Body="&lt;p&gt;Normally called a &quot;bypass cap&quot;, because the high-frequency noise bypasses the IC and flows directly to ground, or a &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/Decoupling_capacitor&quot; rel=&quot;nofollow&quot;&gt;decoupling cap&lt;/a&gt;&quot;, because it prevents the current draw of one IC from coupling into another IC's power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;how do I know if a specific chip is one?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just assume they all do.  :)  If a chip is drawing current intermittently, it will cause the supply voltage to droop intermittently.  If another chip is &quot;downstream&quot;, it will see that noise on its power pins.  If it's bad enough, it can cause errors or noise or whatever.  So generally we put bypass caps on everything, &quot;upstream&quot; from the IC.  (Yes, the orientation of the traces and the locations of the components matters, since copper is not a perfect conductor.)&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-04-18T05:23:20.583" CommentCount="3" />
  <row Id="2279" PostTypeId="2" ParentId="2266" CreationDate="2010-04-18T07:36:16.960" Score="1" ViewCount="" Body="&lt;p&gt;Depends on what barcode scanner it is?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are unsure maybe goodle can be your friend?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.google.com/search?q=ATMega+barcode&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/search?q=ATMega+barcode&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-18T07:36:16.960" />
  <row Id="2280" PostTypeId="2" ParentId="2191" CreationDate="2010-04-18T15:48:14.807" Score="5" ViewCount="" Body="&lt;p&gt;If Beagle board looks like it may work for you, then check the &lt;a href=&quot;http://www.igep-platform.com/&quot; rel=&quot;nofollow&quot;&gt;IGEPv2 board&lt;/a&gt;. It has Ethernet and WiFi and is cheaper still. :)&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-04-18T15:48:14.807" CommentCount="3" />
  <row Id="2281" PostTypeId="2" ParentId="2272" CreationDate="2010-04-18T18:35:44.663" Score="2" ViewCount="" Body="&lt;p&gt;Just to add a few points to the other answers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To measure the effects of the current spikes on the supply voltage you'd need a fast oscilloscope. It depends on the speed of the circuits, but I guess you'd need 200MHz to 1GHz bandwidth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if the power supply circuit carrying the current spikes is large then it will cause radio emissions, which is frowned upon for various technical and legal reasons. A bypass capacitor acts like a shortcut for these spikes, so there is much less emission.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-04-18T18:35:44.663" CommentCount="1" />
  <row Id="2282" PostTypeId="2" ParentId="2272" CreationDate="2010-04-18T23:18:59.593" Score="7" ViewCount="" Body="&lt;p&gt;Just to add more on EM emissions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most companies will recommend 0.1uF caps at each power input.  Keep in mind this is only the bare minimum required to avoid voltage dips that could effect operation.  If your building a PCB board that needs to pass FCC part 15 for emissions you need to go further.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ultimately you need to calculate the entire capacitance needed on the power supply plane based on the PCB design and power usage.  A general rule of thumb i use as a starting place is 1 10uF tantalum cap per major IC (microcontroller, ADC, DAC, etc) and then a 0.1uF and a 10nF cap at every power pin on every IC and the 10nF caps need to be small, preferable 0402 or at most 0603 sized to avoid the lead inductance from the package nullifying the effect of the capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I highly recommend &lt;a href=&quot;http://www.amazon.com/High-Speed-Digital-Design-Handbook/dp/0133957241&quot; rel=&quot;nofollow&quot;&gt;this book&lt;/a&gt; if you plan to get into high speed digital design, high speed meaning anything over 1mhz really.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-04-18T23:18:59.593" CommentCount="1" />
  <row Id="2283" PostTypeId="1" CreationDate="2010-04-19T01:28:11.830" Score="8" ViewCount="334" Body="&lt;p&gt;I understand the basic use of a pull-up or pull-down resistor, including the specific case of using it with a tact switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When both are an option I was wondering whether I should favor one over the other and if so, why?&lt;/p&gt;&#xA;" OwnerUserId="647" LastActivityDate="2011-05-16T17:20:55.527" Title="Should I default to pull-up or pull-down resistor with tact switches?" Tags="&lt;resistor&gt;&lt;beginner&gt;&lt;best-practice&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="2284" PostTypeId="2" ParentId="2283" CreationDate="2010-04-19T02:08:22.130" Score="6" ViewCount="" Body="&lt;p&gt;Some times you can gain a reduction in current by choosing one over the other.&#xA;For a momentary switch this would not be the case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If all other things are equal I would favor a pull-up resistor. Some microcontrollers (like the Atmega series) have inputs that can be configured with an internal pull-up. &#xA;Using only pull-ups (internal or external) does provide some consistency.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:41:17.527" LastActivityDate="2011-05-16T10:41:17.527" CommentCount="1" />
  <row Id="2285" PostTypeId="1" CreationDate="2010-04-19T04:49:04.560" Score="4" ViewCount="554" Body="&lt;p&gt;Hi. Is it possible to extend the 1mW Wire Antenna XBEE's from the short wire antenna, to a longer wire antenna? Will this harm the output stage of the XBEE? The point being that I have an XBEE in a metal box and I need to place the antenna outside the box. Due to the placement of the XBEE, the wire antenna needs to be about 10cm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or alternatively, is it just a matter of replacing the wire antenna on the XBEE with a U.FL connector such as this... &lt;a href=&quot;http://www.littlebirdelectronics.com/products/U.FL-SMD-Connector.html&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/U.FL-SMD-Connector.html&lt;/a&gt;. Is that the identical connector used on XBEEs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd appreciate any thoughts on this. Cheers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Terry.&lt;/p&gt;&#xA;" LastActivityDate="2010-04-19T12:55:10.543" Title="XBEE short wire antenna replacement to longer wire?" Tags="&lt;xbee&gt;&lt;antenna&gt;" AnswerCount="1" CommentCount="0" FavoriteCount="1" />
  <row Id="2286" PostTypeId="2" ParentId="2283" CreationDate="2010-04-19T05:27:59.697" Score="2" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;When both are an option I was&#xA;  wondering whether I should favor one&#xA;  over the other and if so, why?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If both are a option, then I like to ground stuff.&#xA;It just feels better since ground tend to have less noise (even thou this is not always true)&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-19T05:27:59.697" CommentCount="4" />
  <row Id="2287" PostTypeId="2" ParentId="2285" CreationDate="2010-04-19T12:55:10.543" Score="3" ViewCount="" Body="&lt;p&gt;The xbee website shows various different antenna options - including an option that supports using an external antenna via a UFL RF Connector (such as the one on littlebirdelectronics.com). I'm sure it would be fine to attach your own antenna, the connectors look like a good choice and have the option of being disconnected, but even if you just soldered it directly on, as long as it's a suitable frequency/length it should be ok. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you extend the length of the antenna you could mess up the transmission strength, range or quality - the length of the antenna has a direct relationship to the wavelength of the transmission frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you come to fit the external antenna - any wire connecting the antenna to the xbee module must be well shielded so it does not add to the antennas overall length, you can't just increase the antennas length till it reaches the outside of the metal box &amp;lt;- it may seem obvious to most, but if ya don't know about it, it can be easily overlooked.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a web site with various prebuilt coax cables that are used for connecting antennas to wireless modules, thought it may help to have a peek - &lt;a href=&quot;http://www.gradconn.com/rf-cable/rf-cable-assembly.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.gradconn.com/rf-cable/rf-cable-assembly.asp&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-04-19T12:55:10.543" CommentCount="1" />
  <row Id="2288" PostTypeId="2" ParentId="2270" CreationDate="2010-04-19T13:14:28.593" Score="1" ViewCount="" Body="&lt;p&gt;Last time I looked the Sparkfun Speakjet shield did have stackable headers? Anyhoo aside from that moot point- It depends on how permanent your project is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to be able to use the Arduino again with different projects or shields - it's definitely recommended you get some stackable headers because of the cheap cost and ease of use. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the project is relatively permanent and you don't intend on using the Arduino again in another project, soldering the wires on might be better for you, it will be cheaper in the short run and will be affective for making good connections - it's just fiddly to do and not the most professional looking way of hooking stuff up. &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-04-19T13:14:28.593" CommentCount="1" />
  <row Id="2289" PostTypeId="1" AcceptedAnswerId="2291" CreationDate="2010-04-19T15:57:01.897" Score="2" ViewCount="251" Body="&lt;p&gt;I was wondering how does the protocol mapping work between the USB side and the UART side when dealing with the Microchip MCP2200?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What sort of USB transfer type is used?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;bulk?&lt;/li&gt;&#xA;&lt;li&gt;isochronous?&lt;/li&gt;&#xA;&lt;li&gt;interrupt?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Thanks for any clues!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;update&lt;/strong&gt;: I found a bit more info &lt;a href=&quot;http://www.lvr.com/usb_virtual_com_port.htm&quot; rel=&quot;nofollow&quot;&gt;Virtual COM port&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="329" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:02:08.170" LastActivityDate="2010-12-10T22:02:08.170" Title="USB-to-UART bridge: protocol mapping?" Tags="&lt;usb&gt;&lt;uart&gt;&lt;microchip&gt;" AnswerCount="2" />
  <row Id="2290" PostTypeId="2" ParentId="2289" CreationDate="2010-04-19T17:02:39.113" Score="0" ViewCount="" Body="&lt;p&gt;As it's an HID class device, it won't use bulk or isochronous transfers.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-19T17:02:39.113" />
  <row Id="2291" PostTypeId="2" ParentId="2289" CreationDate="2010-04-19T17:27:30.170" Score="3" ViewCount="" Body="&lt;p&gt;It looks to me like the &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en546923&quot; rel=&quot;nofollow&quot;&gt;MCP2200&lt;/a&gt; is also supported as a CDC class device. In that mode bulk and isochronous transfers should also be supported.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-19T17:27:30.170" CommentCount="1" />
  <row Id="2292" PostTypeId="2" ParentId="2191" CreationDate="2010-04-20T01:19:09.533" Score="1" ViewCount="" Body="&lt;p&gt;As per the reference to the OpenWRT project, I would suggest the Dlink DIR-320 might be of interest. It's cheap (about $80), readily available, it has USB 2.0, and it's listed as 'partially suppported'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://wiki.openwrt.org/oldwiki/openwrtdocs/hardware/d_link/dir_320&quot; rel=&quot;nofollow&quot;&gt;http://wiki.openwrt.org/oldwiki/openwrtdocs/hardware/d_link/dir_320&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't tried it myself, it's just an idea at this stage.&lt;/p&gt;&#xA;" LastActivityDate="2010-04-20T01:19:09.533" />
  <row Id="2293" PostTypeId="2" ParentId="2277" CreationDate="2010-04-20T04:00:56.890" Score="1" ViewCount="" Body="&lt;p&gt;As rzrgenesys187 said:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If pin C0 floats HIGH and C1 is&#xA;  connected to AREF which is also HIGH,&#xA;  then there shouldn't be any change.&#xA;  Did you try connecting C1 to ground to&#xA;  get zero when you run select_wire(1)?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yea, so it actually was switching the entire time.. however, there is a lot more distortion, so the wire connected to ground floated somewhere in the 10s. And AREF isn't high, so I don't understand how that works. AREF for me gave about the same values as ground when using&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;analogReference(DEFAULT);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;so not sure why, but AREF is giving me near-ground values... very strange, but the MUX does infact switch, so this question is answered.. and I actually never had any problems.. meh. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually, hooking straight into AREF does make it the input go high to 1023, so I have no idea why the input won't go that high with the MUX. maybe some kinda voltage limit, idk. I have to read up on it..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT2:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ok, finally think I'm figuring it out. Apparently breadboards leak a lot of current, so that if I was connected to C0 and it was reading C1, then a &lt;em&gt;lot&lt;/em&gt; of voltage would leak to C1. Anyway though, connecting to AREF to C3 makes both inputs go high, so now I'm just even more confused.  &lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="708" LastEditorDisplayName="" LastEditDate="2010-04-20T04:08:46.657" LastActivityDate="2010-04-20T04:08:46.657" />
  <row Id="2294" PostTypeId="1" CreationDate="2010-04-20T12:01:05.027" Score="6" ViewCount="389" Body="&lt;p&gt;Hi All,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to replace the bulb based tail/brake light and rear indicators/flashers on my bike with one integrated LED unit (flashers in brake light).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are pretty expensive, and since I'm on a budget I'm looking at building one myself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found some seemingly suitable 12v LEDs. I was hoping to use these to save me bothering with limiting resistors. However, one thing that bothers me is the max voltage rating of the LEDs and the rather unpredictable supply voltage. I've not yet measured it on my bike, but usually you would expect about 13v with the engine running. The absolute max voltage rating of the LEDs I'm looking at is 14v - do you think this is too close? Would the LEDs stand a higher voltage for short periods? (e.g. poss slightly higher V when at high engine revs when overtaking)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would you protect against this? Would one resistor for the whole set of LEDs suffice? (one resistor supplying multiple parallel LEDs). Any suggestions on what kind of resistor to use? Perhaps it would just be better to use standard votage LEDs if I am forced to use resistors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway - any advice appreciated!&lt;/p&gt;&#xA;" OwnerUserId="715" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-06-29T06:23:52.307" LastActivityDate="2010-06-29T06:23:52.307" Title="12v LEDs and use on a motorbike" Tags="&lt;led&gt;&lt;automotive&gt;" AnswerCount="5" />
  <row Id="2295" PostTypeId="2" ParentId="2192" CreationDate="2010-04-20T12:15:51.993" Score="0" ViewCount="" Body="&lt;p&gt;There is an app for setting up record decks.   Shows the vibrations on the display&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mulit Siesmometer. looks good with an alarm but ihave never used it. &lt;/p&gt;&#xA;" LastActivityDate="2010-04-20T12:22:31.377" />
  <row Id="2296" PostTypeId="2" ParentId="2294" CreationDate="2010-04-20T12:45:14.590" Score="2" ViewCount="" Body="&lt;p&gt;I think the magic is to put a lot of led:s in series, that what you spread the voltage over a handful of led:s.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;14V/7led:s = 2V over each led.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But my gut feeling tells me that you need to do more than this....&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-20T12:45:14.590" />
  <row Id="2297" PostTypeId="2" ParentId="2294" CreationDate="2010-04-20T12:45:16.427" Score="6" ViewCount="" Body="&lt;p&gt;If the voltage from the battery is fluctuating - you could look at using a &lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage_regulator&quot; rel=&quot;nofollow&quot;&gt;voltage regulator&lt;/a&gt; to keep it stable. You can get fixed value regulators (no resistors or other components required!) or variable ones (2 resistors are used to set them, but they're both quite easy to use). The one I've used, &lt;a href=&quot;http://www.national.com/mpf/LM/LM317.html#Overview&quot; rel=&quot;nofollow&quot;&gt;LM317T adjustable voltage regulator&lt;/a&gt;, requires the input voltage to be around 2v more than the output voltage (in order to stay stable) and they have a maximum input to output differential of 40v. In other words - you want to have LEDs that are rated at a lower voltage than your supply - then use the voltage regulator to reduce the supply and provide the correct voltage for the LEDs.&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-04-20T12:50:31.090" LastActivityDate="2010-04-20T12:50:31.090" CommentCount="1" />
  <row Id="2298" PostTypeId="2" ParentId="2294" CreationDate="2010-04-20T12:53:14.897" Score="3" ViewCount="" Body="&lt;p&gt;Hello. First of all, run the LEDs in parallel to share the current load, and also if one dies only the dead LED will not come on; if you have them in series if one dies they all switch off, which makes finding the dead one a PITA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Secondly, Jim's suggestion of using an LM317T is a good one, don't forget to use a nice smoothing capacitor on it. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-04-20T12:53:14.897" />
  <row Id="2299" PostTypeId="2" ParentId="2294" CreationDate="2010-04-20T13:27:51.293" Score="5" ViewCount="" Body="&lt;p&gt;There will probably be some fast high-voltage transients on the supply, which will kill any LEDs. Transient suppressors would be advisable.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-20T13:27:51.293" CommentCount="1" />
  <row Id="2300" PostTypeId="1" CreationDate="2010-04-20T15:13:47.020" Score="10" ViewCount="353" Body="&lt;p&gt;So far, we have built progressively more complicated wheel/treads mobile bots. The kids get to play with them at the end of class.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Today we started the ambitious alpha-rex. I tried splitting off one of the brightest students with another who was ready to follow him (or so I thought). We got maybe 5% through the project between the two groups.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So scratch that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For some context it's an after school program in VT where today, it was sunny and half the kids in my class went out to play soccer. Today it was just what I would deem, the 'best' kids of the 'class'.. plus a random 1st grade boy who took a liking to me right away (but was always trying to talk to me when all the kids had to stop talking), and a little girl with dreadlocks (I'm not making this up)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am thinking now of just building something fun and letting them play with it for the hour or make some small modification that adds functionality.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hadn't used mindstorms when I proposed/applied for the after school program. In fact I had never opened a box until ~25 minutes before the first class, but I had things printed out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I definitely don't know their potential. I could put a fair amount of time into this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ramps and pullies and what not moving a ball around, or a controllable claw come to mind.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mostly 2nd and some 3rd grade, all boys.&lt;/p&gt;&#xA;" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-15T02:38:13.460" LastActivityDate="2010-11-15T02:38:13.460" Title="so i have a lego mindstorms 8547 and 10 kids for an hour a week, what should I do?" Tags="&lt;lego-mindstorms&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="4" />
  <row Id="2301" PostTypeId="2" ParentId="2300" CreationDate="2010-04-20T22:46:26.643" Score="2" ViewCount="" Body="&lt;p&gt;I don't know enough about the actual bot you've got, but my plan would be to do something along the following lines:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Work out some non-trivial task that you want the robot to be able to do (something that will take a good few weeks to do).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Work out some smaller tasks that you can build up towards the main task - some physical and some code.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Get them to work at the smaller tasks with the target in mind over a series of weeks. Maybe split them into groups, get them to rotate different weeks on different tasks.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Alternatively depending on resources get them into teams and competing against each other at simpler tasks over the course of a few weeks with an overall prize for the winning team.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I think of any other ideas I'll add them later.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-04-20T22:46:26.643" />
  <row Id="2302" PostTypeId="2" ParentId="2300" CreationDate="2010-04-21T04:50:42.300" Score="2" ViewCount="" Body="&lt;p&gt;You might get some ideas from here: &lt;a href=&quot;http://mindstorms.lego.com/&quot; rel=&quot;nofollow&quot;&gt;http://mindstorms.lego.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would suggest trying to come up with some large objective that you would like them to accomplish, but show them how to break that into small pieces and learn how to do each piece individually. From there you can help teach them how to use what they learned in each small piece to complete a much more complex objective using simple steps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;10 People on a group is a lot, so you can break them into smaller groups and then they can compete to find who can make theirs the &quot;best&quot;. Hopefully with this technique you will have a final system that incorporates work from all of the kids.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--My boss has asked me to consider taking on a group very similar to this, so I would be interested to know any other comments.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-04-21T04:50:42.300" />
  <row Id="2303" PostTypeId="2" ParentId="2300" CreationDate="2010-04-21T05:08:15.570" Score="0" ViewCount="" Body="&lt;p&gt;You have a problem with the kids/computer ratio... If you had at least 2 of them you can split the team in two and have a &quot;robot challenge&quot; :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something like &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;-&quot;Build a robot that can lift this XXX and put it into XXX after doing XXX.&quot;&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you can mix both basic mechanics and programming in a a natural way.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-21T05:08:15.570" />
  <row Id="2304" PostTypeId="1" AcceptedAnswerId="2305" CreationDate="2010-04-21T13:19:38.540" Score="4" ViewCount="379" Body="&lt;p&gt;I've got a battery powered synth that uses two 9v batteries to make a split rail power supply (±9 and ground). I'm trying to use a regular AC-DC power adaptor to replace the batteries. The adaptor outputs 12v and I'm regulating it down to 9v with the LM317 voltage regulator. To get the required -9v I'm using the ICL7660 CMOS voltage converter. The problem I have is with the noise created by the power supply, when i hook up the synth it works, but there's some oscillations and artifacts on the audio output. Does anyone know if there's a way I can filter out this noise?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;here's the circuit so far -&lt;br&gt;&#xA;&lt;img src=&quot;http://i69.servimg.com/u/f69/14/39/80/39/splitp10.jpg&quot; alt=&quot;da circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;cheers.&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-05-13T00:30:58.497" LastActivityDate="2011-05-13T12:49:57.767" CommunityOwnedDate="2010-04-21T13:19:38.540" Title="Can I Filter This Split Power Supply?" Tags="&lt;power-supply&gt;&lt;voltage-regulator&gt;&lt;cmos&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="2305" PostTypeId="2" ParentId="2304" CreationDate="2010-04-21T13:39:34.303" Score="6" ViewCount="" Body="&lt;p&gt;Add capacitors between each power rail and ground. They'll act like short circuits to the high-frequency noise. I see that you have one between the -9 V rail and ground-- that's a good start.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The type of capacitor you use can make a difference. Electrolytic caps, for example, are relatively cheap, but they only deliver their rated capacitance at low frequencies, so they're not as good for filtering out high-frequency noise. I've had good luck with tantalum capacitors in this kind of application, but be careful that you don't plug them in backwards, as they will explode. Be double careful with the negative rail, because &quot;backwards&quot; might be the reverse of what you think. For both rails, you want the plus on the capacitor connected to the more positive terminal, which is ground for the -9 V rail.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-21T13:39:34.303" CommunityOwnedDate="2010-04-21T13:39:34.303" CommentCount="3" />
  <row Id="2306" PostTypeId="2" ParentId="2304" CreationDate="2010-04-21T13:40:35.777" Score="7" ViewCount="" Body="&lt;p&gt;I would use the ICL7660S instead. A couple of benefits --&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;The S version switches at 35KHz which is above the audio range.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The S version can switch 12V. If you did a +-12V conversion you &#xA;could do a +-9V linear regulation on the output. This will reduce&#xA;the noise. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You should be able to add a series inductor and another capacitor&#xA;on the output. I am assuming you are using ceramic caps (X5R or X7R).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The load regulation of these switched capacitor converters is not that&#xA;good under load. I am assuming that your synth only needs currents around 20mA or&#xA;so. Check the specs for the voltage and current limit specs.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:49:57.767" LastActivityDate="2011-05-13T12:49:57.767" CommunityOwnedDate="2010-04-21T13:40:35.777" CommentCount="7" />
  <row Id="2307" PostTypeId="2" ParentId="2294" CreationDate="2010-04-21T14:11:39.683" Score="3" ViewCount="" Body="&lt;p&gt;Using a linear voltage regulator like an LM317T is a decent idea, but it means you're guaranteed to throw away 2 V, which is a little disappointing. You might instead try a low-dropout regulator like the LT3085-- with that, you'd only lose 0.275 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But in both cases, you'll be limited by the relatively low current limit of the regulator (1.5 A for the LM317T, only 500 mA for the LT3085). For a bike light, either would work fine, but I think you could build a more robust circuit without a regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's what I'd suggest.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, cap the voltage with a 13 V zener diode between power and ground. A zener diode is a diode that acts mostly like a normal diode-- a one-way valve. However, in the no-flow direction, it blocks current until you hit a certain threshold voltage. Once you hit that voltage, it opens up with very low resistance until you drop below the threshold again. It's great for capping voltage spikes. Be sure to get one that can handle the power you'll me pumping through it. Maybe start with a 5 W diode and then buy a fatter one if that burns?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, you need to limit the current through the LEDs. (If you did this part right, you might not even need the zener, but zeners are cheap.) LEDs burn out because they get too hot, and prolonged high current is what makes them hot. They can handle very high currents for short periods. Whatever LEDs you buy will have a current rating, like 20 mA at 4 V. There are no LEDs with voltages over roughly 5 V. The higher voltage LEDs you see advertised are either multiple LEDs in series or LEDs packaged with a current-limiting resistor. You can do better with discrete LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you should do is put LEDs in series until you get close to your supply voltage-- maybe 3 of them, so you're trying to supply 3 * 4 V = 12 V, 20 mA. Then, take the remaining voltage between the cap (13 V) and the LED voltage (12 V) and pick a resistor that allows the right amount of current. In this case, 13 - 12 is 1 V, and you want 20 mA, so that's 1/0.020 = 50 ohms. I'd build one string like this and test it. Once that's working, build a few more. You can tweak the resistor value to make the LEDs a little brighter or dimmer (but don't burn them out).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Putting LEDs in parallel without giving each series string its own resistor is risky. LEDs are nonlinear elements-- raise the voltage a little near a certain threshold and the current changes dramatically. This means that they tend to not share current evenly. You might be able to pull it off if the LEDs are all from the same manufacturing run, but resistors are almost free; I wouldn't think it would be worth the savings.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-21T14:11:39.683" />
  <row Id="2308" PostTypeId="2" ParentId="2191" CreationDate="2010-04-21T15:23:23.100" Score="2" ViewCount="" Body="&lt;p&gt;The boards from Technologic Systems in Arizona are good and cheap. I've been using the TS-7550 recently; it's worked well. Being able to load a Debian filesystem image on a microSD card is convenient.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.embeddedarm.com/products/board-detail.php?product=TS-7550&quot; rel=&quot;nofollow&quot;&gt;http://www.embeddedarm.com/products/board-detail.php?product=TS-7550&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-21T15:23:23.100" />
  <row Id="2309" PostTypeId="2" ParentId="2300" CreationDate="2010-04-21T16:53:58.983" Score="4" ViewCount="" Body="&lt;p&gt;Here are a couple of things to get you started.  &lt;s&gt;(BTW, how old are your students?)&lt;/s&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;work through projects on &lt;a href=&quot;http://www.nxtprograms.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.nxtprograms.com/&lt;/a&gt; .  These start with simple and fun things you can build, and have documented programs you can download.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;take a look at &lt;a href=&quot;http://www.thenxtclassroom.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.thenxtclassroom.com/&lt;/a&gt; and sign up for the robotics in education mailing list.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;take a look at &lt;a href=&quot;http://www.legoengineering.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.legoengineering.com/&lt;/a&gt; &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;There are many other good sites out there (that I can't think of offhand).  I really enjoy following &lt;a href=&quot;http://www.thenxtstep.blogspot.com/&quot; rel=&quot;nofollow&quot;&gt;The NXT Step blog&lt;/a&gt;.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;There are a lot of good NXT books out there.  I haven't had a chance to look at many of the new ones focusing on the Mindstorms NXT 2.0 kit.  [Be aware that there are currently &lt;a href=&quot;http://static.robotclub.ab.ca/pages/nxt/InventoryComparison/nxt_1_vs_2_vs_edu.html&quot; rel=&quot;nofollow&quot;&gt;three different NXT sets&lt;/a&gt; with different pieces in them (ie. they are not backwards compatible, you can't build NXT 1.0 models with an NXT 2.0 kit without making adjustments).]&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I highly recommend teaching the kids &lt;a href=&quot;http://scratch.mit.edu/&quot; rel=&quot;nofollow&quot;&gt;Scratch&lt;/a&gt;.  It is free, they can use it at home, and it helps them understand how programming works.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;you might also find some of my ideas in the &lt;a href=&quot;http://chiphacker.com/questions/2055/any-good-suggestions-for-a-beginning-electronics-class-for-youth/2071#2071&quot; rel=&quot;nofollow&quot;&gt;answer to &quot;Any good suggestions for a beginning electronics class for youth?&quot;&lt;/a&gt; to be interesting.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Am I correct in thinking that you have a single Mindstorms kit?&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="106" LastEditorDisplayName="" LastEditDate="2010-04-21T17:03:19.490" LastActivityDate="2010-04-21T17:03:19.490" />
  <row Id="2310" PostTypeId="2" ParentId="2272" CreationDate="2010-04-21T19:06:18.477" Score="9" ViewCount="" Body="&lt;p&gt;Power supplies are slow...they take roughly 10 us to respond (i.e. bandwidth up to 100 kHz).  So when your big, bad, multi-MHz microcontroller switches a bunch of outputs from high to low, it will draw from the power supply, causing the voltage to start drooping until it realizes (10 us later!) that it needs to do something to correct the drooping voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To compensate for slow power supplies, we use decoupling capacitors.  Decoupling capacitors add fast &quot;charge storage&quot; near the IC.  So when your micro switches the outputs, instead of drawing charge from the power supply, it will first draw from the capacitors.  This will buy the power supply some time to adjust to the changing demands.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;speed&quot; of capacitors varies.  Basically, smaller capacitors are faster; inductance tends to be the limiting factor, which is why everyone recommends putting the caps as close as possible to VCC/GND with the shortest, widest leads that are practical.  So pick the largest capacitance in the smallest package, and they will provide the most charge as fast as possible.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-04-21T19:06:18.477" />
  <row Id="2311" PostTypeId="1" AcceptedAnswerId="2312" CreationDate="2010-04-21T20:14:37.157" Score="5" ViewCount="184" Body="&lt;p&gt;When ordering a desktop stencil for laying down solder paste, there is an option to specify the stencil's aperture.  Rectangular, home plate, trapezoidal...what's the difference between them?  Is there one that is preferred for hand-populating surface mount parts?&lt;/p&gt;&#xA;" OwnerUserId="1278" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-04-21T20:31:04.707" LastActivityDate="2010-05-24T16:29:41.847" Title="Stencil apertures" Tags="&lt;soldering&gt;&lt;surface-mount&gt;&lt;surface-mount&gt;" AnswerCount="2" />
  <row Id="2312" PostTypeId="2" ParentId="2311" CreationDate="2010-04-21T20:27:46.500" Score="6" ViewCount="" Body="&lt;p&gt;If you choose rectangular, the stencil will come back with exactly the geometry you've specified in your Gerber files. If you specify &quot;home plate&quot; the manufacturer will shrink the pads by 10% or thereabouts, but make the pads 5 sided, which improves soldering success rates in automated board stuffing. I've not heard of trapezoidal pads before, but I assume it's a similar tweak to improve solderability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For hand soldering surface-mount parts, you can safely stick with rectangular. The biggest improvement you can make is to get access to a stereo microscope for soldering. It makes a huge difference. You'll probably find that the limiting factor on your soldering ability is not your hand-eye coordination, but your vision. Obviously, a microscope improves your vision substantially.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update: I just ran into this today-- &quot;trapezoidal&quot; does not refer to the the footprint of the stencil hole. It refers to adding a slope to the cut, so if you were to look at the stencil from the side, you would see a trapezoid. &quot;Laser cutting apertures with trapezoidal walls and also rounding corners will offer better paste release,&quot; according to a Texas Instruments datasheet.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-05-24T16:29:41.847" LastActivityDate="2010-05-24T16:29:41.847" CommentCount="1" />
  <row Id="2313" PostTypeId="2" ParentId="2311" CreationDate="2010-04-21T20:45:15.187" Score="5" ViewCount="" Body="&lt;p&gt;Trapezoidal means that the edges of the stencil openings have a slope. This improves the solder paste distribution.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-21T20:45:15.187" CommentCount="1" />
  <row Id="2314" PostTypeId="1" AcceptedAnswerId="2315" CreationDate="2010-04-22T00:08:11.910" Score="5" ViewCount="425" Body="&lt;p&gt;I'm building a project that needs both 5V and 12V rails which will draw about 1A on the 12V and 0.5A on the 5V. I was thinking of using a 7805 to produce the required 5V but this could generate some significant heat. I am not so much asking if it is acceptable to use a 7805 (I just need a mini heatsink), but rather: are there any ways of doing it cooler? Any tips would be great.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-04-22T04:56:14.000" Title="What is the coolest way (using passive cooling only) to step 12V DC down to 5V DC" Tags="&lt;power&gt;&lt;heat&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="2315" PostTypeId="2" ParentId="2314" CreationDate="2010-04-22T00:40:16.257" Score="11" ViewCount="" Body="&lt;p&gt;Instead of using a linear regulator, which has relatively low efficiency (~50%), use a switching DC-DC converter (efficiency around 80-90%). A decent one to start with is National's &quot;simple switcher.&quot; It looks like the LMZ12001 would do the job-- up to 1 A at 5 V, and it accepts input voltages from 0.8-20 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.national.com/pf/LM/LMZ12001.html&quot; rel=&quot;nofollow&quot;&gt;http://www.national.com/pf/LM/LMZ12001.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-22T00:40:16.257" CommentCount="3" />
  <row Id="2316" PostTypeId="2" ParentId="2314" CreationDate="2010-04-22T00:40:49.397" Score="4" ViewCount="" Body="&lt;p&gt;Switching regulators (aka DC/DC converters) can step down 12V to 5V step without generating too much heat. Since you only need 2.5W on your 5V, don't think you need a heatsink too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lineage has some good DC/DC regulators: &lt;a href=&quot;http://www.lineagepower.com/category.aspx?NID=5e1812f4-fb02-49f4-ba31-6e312010f40d&quot; rel=&quot;nofollow&quot;&gt;http://www.lineagepower.com/category.aspx?NID=5e1812f4-fb02-49f4-ba31-6e312010f40d&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm assuming here that you need a non-isolated converter ie. your 5V does not need be electrically isolated with a transformer from the 12V. Non-isolated dc/dc are cheaper and smaller.&lt;/p&gt;&#xA;" OwnerUserId="327" LastEditorUserId="327" LastEditorDisplayName="" LastEditDate="2010-04-22T04:56:14.000" LastActivityDate="2010-04-22T04:56:14.000" />
  <row Id="2317" PostTypeId="2" ParentId="2314" CreationDate="2010-04-22T00:56:02.930" Score="5" ViewCount="" Body="&lt;p&gt;One of the main issues with regulators like the LM7805 (and linear regulators in general) when you step down from large voltages is that a lot of the energy is dissipated as heat. If you are limited to passive cooling only and you have some significant power draw from your load, you might risk thermal overload.&#xA;Fear not, because if you are willing to put up with a bit more complexity and cost there is another option: &lt;a href=&quot;http://www.national.com/appinfo/power/files/f5.pdf&quot; rel=&quot;nofollow&quot;&gt;Switching regulators&lt;/a&gt;, specifically in this case buck converters, which work off of a completely different principle. Depending on what your other requirements are, like noise, stability, EMI considerations, you might look into some of the highly integrated switching regulator modules offered by TI, like the &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/ptn78000w.pdf&quot; rel=&quot;nofollow&quot;&gt;PTN78000W family&lt;/a&gt;. That part in particular is nice because of the adjustable output, so you can produce a variety of supply rails off of one part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers!&lt;/p&gt;&#xA;" OwnerUserId="631" LastActivityDate="2010-04-22T00:56:02.930" />
  <row Id="2318" PostTypeId="1" AcceptedAnswerId="2330" CreationDate="2010-04-22T01:31:46.577" Score="5" ViewCount="192" Body="&lt;p&gt;What shielding techniques would be best suited for a digital sensor (3 wires - Pwr, Gnd, Sig) in a noisy environment (specifically fluorescent lighting)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Twisted pair (trio in this case) works well for differential voltages, but I suspect it won't be effective here even though the current in the wires is balanced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does shielded wire require a separate ground wire, or is it acceptable to use the shielding as ground? Should the shielding be ground at both ends, or only at the PCB?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Sensor is connected to PCB via ~1m of cable.&lt;/p&gt;&#xA;" OwnerUserId="554" LastEditorUserId="554" LastEditorDisplayName="" LastEditDate="2010-04-22T01:37:02.767" LastActivityDate="2010-04-23T06:40:37.377" Title="Shielding Techniques for Digital Sensor" Tags="&lt;shielding&gt;&lt;wire&gt;&lt;sensor&gt;" AnswerCount="6" CommentCount="3" />
  <row Id="2319" PostTypeId="2" ParentId="2318" CreationDate="2010-04-22T01:47:44.170" Score="1" ViewCount="" Body="&lt;p&gt;You can use the shielding as the ground wire. Given that the sensor current is probably tiny, the impedance of the shield will be very low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should ground the shield at least on the PCB. It doesn't matter whether you ground it at the sensor or not. What you're trying to do is reduce the size and impedance of loops in noise can be induced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a digital signal, you should be relatively impervious to noise, anyway.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-22T01:47:44.170" CommentCount="3" />
  <row Id="2320" PostTypeId="1" CreationDate="2010-04-22T01:55:23.300" Score="9" ViewCount="584" Body="&lt;p&gt;I would like to buy an assortment of IC's to use for PIC Microcontrollers projects that I want to make and use code for.  What is a good assortment to have on hand?&lt;/p&gt;&#xA;" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:37:31.977" LastActivityDate="2011-01-07T10:30:21.543" ClosedDate="2011-04-24T20:26:54.453" Title="What are the best useful variety IC's to have around for PIC Microcontrollers?" Tags="&lt;pic&gt;&lt;microcontroller&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="3" />
  <row Id="2321" PostTypeId="2" ParentId="1184" CreationDate="2010-04-22T02:00:54.197" Score="1" ViewCount="" Body="&lt;p&gt;I've found a cheap hotplate to be good:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The Sparkfun guys said that even with a cheap commercial reflow oven, some of their components with plastic housings (a USB type B connector from memory) would melt. This problem was fixed by using a skillet.&lt;/li&gt;&#xA;&lt;li&gt;Skillets tend not to be very flat and change shape in the heat. I've found the hot plate to be slightly better here.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As others have mentioned, most components are quite durable and controlling the temperature profile is not critical for hobbyist work, however be sure to raise the heat slowly at first and keep and eye on the paste. As the board is being heated from one side, it may bow upwards and you'll need to rock it to ensure even heat across the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Applying the solder paste by hand works fine for small batches and one offs, but a stencil does drastically speed up the process when you're doing a few boards with fine pitch components. Laser cut mylar (plastic) stencils are cheap and effective - I'd also suggest getting a stencil with a few common SMT footprints for microcontrollers etc (32 &amp;amp; 48 pin QFN; BGA; SOIC) as you often have one of these components on a board that you can stencil and then do the rest by hand.&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-04-22T02:00:54.197" />
  <row Id="2322" PostTypeId="2" ParentId="2320" CreationDate="2010-04-22T02:09:34.050" Score="9" ViewCount="" Body="&lt;p&gt;Here are some chips I've found useful for microcontroller prototyping:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Motor driver: LMD18200D&lt;/li&gt;&#xA;&lt;li&gt;Darlington transistors for driving actuators: ULN2003&lt;/li&gt;&#xA;&lt;li&gt;External temperature sensor: TMP102&lt;/li&gt;&#xA;&lt;li&gt;Quadrature decoder: HCTL2020&lt;/li&gt;&#xA;&lt;li&gt;LED bar graph driver: LM3914&lt;/li&gt;&#xA;&lt;li&gt;Basic transistors: 2N3904, 2N3906&lt;/li&gt;&#xA;&lt;li&gt;Schmitt trigger inverting buffer: 74HC14&lt;/li&gt;&#xA;&lt;li&gt;Shift register: 74HC595&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If there are other specific types of chips you're interested in, comment, and I'll add to the list.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-22T02:09:34.050" CommentCount="3" />
  <row Id="2323" PostTypeId="2" ParentId="1199" CreationDate="2010-04-22T05:31:36.260" Score="5" ViewCount="" Body="&lt;p&gt;How about the &lt;a href=&quot;http://www.st.com/mcu/familiesdocs-110.html&quot; rel=&quot;nofollow&quot;&gt;STM32&lt;/a&gt;, another Cortex-M3 based mcu family?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's cheap to get started since I found some good stuff from Olimex.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.olimex.com/dev/stm32-h103.html&quot; rel=&quot;nofollow&quot;&gt;http://www.olimex.com/dev/stm32-h103.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.olimex.com/dev/arm-usb-ocd.html&quot; rel=&quot;nofollow&quot;&gt;http://www.olimex.com/dev/arm-usb-ocd.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Then I use gcc as a compiler, and OpenOCD to control the jtag.&lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-04-22T12:50:54.743" LastActivityDate="2010-04-22T12:50:54.743" CommunityOwnedDate="2010-04-22T05:31:36.260" />
  <row Id="2324" PostTypeId="1" AcceptedAnswerId="2329" CreationDate="2010-04-22T09:25:48.910" Score="6" ViewCount="618" Body="&lt;p&gt;A recent question asked about the advantages/disadvantages of various types of MCU. AVRs seemed not even worth a mention given the answers.  Why then does it seem to an outsider that AVRs are experiencing a rush of popularity?  Is this solely due to the Arduino, or is there something else that makes the AVR an especially good microcontroller?&lt;/p&gt;&#xA;" OwnerUserId="504" LastActivityDate="2011-05-17T12:45:19.507" CommunityOwnedDate="2010-04-23T01:00:21.630" Title="Why are Atmel AVRs so popular?" Tags="&lt;microcontroller&gt;&lt;avr&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="2" />
  <row Id="2325" PostTypeId="2" ParentId="2324" CreationDate="2010-04-22T09:30:03.200" Score="4" ViewCount="" Body="&lt;p&gt;Microchip's PIC is number one in 8-bit MCU sales and the AVR is fifth. That could explain why the AVR doesn't get mentioned as often as other devices.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-04-22T09:35:08.177" LastActivityDate="2010-04-22T09:35:08.177" CommentCount="5" />
  <row Id="2326" PostTypeId="2" ParentId="2324" CreationDate="2010-04-22T11:01:10.140" Score="10" ViewCount="" Body="&lt;p&gt;I started out using PICs but later switched to AVRs. I switched because there's GCC for AVRs. This gave me an environment that I was used to, for free, and let me compile code on Linux/OSX, not just Windows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although there are plenty of C compilers for PICs these days, some even for Linux - they all have their own quirks which I didn't want to learn.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-04-22T18:50:08.707" LastActivityDate="2010-04-22T18:50:08.707" CommentCount="3" />
  <row Id="2327" PostTypeId="2" ParentId="2320" CreationDate="2010-04-22T11:05:02.880" Score="5" ViewCount="" Body="&lt;p&gt;The MCP23S17 is a handy chip. It's an SPI/I2C driven port expander, giving 16 extra GPIO lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the SPI version, you can chain up to 8 on the bus, giving 128 GPIO pins per chip select.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Very useful for those projects where you need more I/O but don't want to change your microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-04-22T11:05:02.880" CommentCount="1" />
  <row Id="2328" PostTypeId="2" ParentId="2324" CreationDate="2010-04-22T11:26:20.680" Score="4" ViewCount="" Body="&lt;p&gt;From what I have seen AVRs have experienced a rush of popularity only in niche markets&#xA;like hobbyist tools and rapid prototyping applications. AVR has done an excellent&#xA;job of getting cross-platform tool support on Linux, MAC and PC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Everyone I talked to that is using microcontrollers in OEM applications is either&#xA;using PIC, some sort of ARM variant or an MSP430 (only for low power applications). &#xA;I have yet to come across anyone using an AVR.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:45:19.507" LastActivityDate="2011-05-17T12:45:19.507" CommentCount="5" />
  <row Id="2329" PostTypeId="2" ParentId="2324" CreationDate="2010-04-22T11:32:58.033" Score="14" ViewCount="" Body="&lt;p&gt;The AVR family has a lot of good, inexpensive, hobbyist-friendly devices with nice peripherals, low power consumption, and good cross-platform support.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, Arduino is a big part of it.  But I think that Arduino came to exist the way that it did -- and to the success that it has -- partly due to those features.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Good:  They work well.  Easy to program in C for most basic functions.   Adequate documentation.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Inexpensive:  Lots of $3-$5 parts, available from major distributors in small quantity.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Hobbyist friendly:  Parts in through-hole packages-- a big contrast to many of the chip families out there today.  Newer AVR (e.g., xmega) devices are less so.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Nice peripherals:  Built-in oscillator, flash memory, on-board RAM, serial ports, ADC, EEPROM, and the other goodies that make it possible to run a single MCU on a protoboard to do basic stuff, without too much hassle.  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Low power consumption.  AVR's major pitch point these days.  Suckers can run on a battery almost forever if you know what you're doing.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Good cross-platform support:  The AVR was designed with C support in mind-- not as an afterthought.  GCC support came early, and a big open source community developed around that.  It's still one of the best MCUs that you can develop from any platform with free tools.  This is a &lt;em&gt;big&lt;/em&gt; one with respect to the other families, many of which use proprietary compilers or have lackluster gcc support.  Even PIC was pretty late to the game with good free C compilers.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As for why there wasn't much about it in the replies to your earlier question, I think that (1) you're seeing small sample bias and (2) many of the answers were specifically to discuss non-AVR solutions-- because so much of the discussion on this site is AVR/Arduino-centric.   &lt;em&gt;Most&lt;/em&gt; of the microcontroller families aren't represented in your list as of this writing-- including some that I use regularly, and others that are among the most popular in the world.&lt;/p&gt;&#xA;" OwnerUserId="484" LastActivityDate="2010-04-22T11:32:58.033" />
  <row Id="2330" PostTypeId="2" ParentId="2318" CreationDate="2010-04-22T12:36:10.693" Score="4" ViewCount="" Body="&lt;p&gt;I suggest you purchase / check out a copy of Henry Ott's &quot;Noise Reduction Techniques in Electronic Systems&quot;. It talks about these things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Don't&lt;/em&gt; ground the shield at both ends, as this creates a ground loop. The PCB end is probably the best place to ground the shield.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-04-22T12:36:10.693" CommentCount="3" />
  <row Id="2331" PostTypeId="2" ParentId="1847" CreationDate="2010-04-22T15:07:22.937" Score="2" ViewCount="" Body="&lt;p&gt;Silicone, like &lt;a href=&quot;http://www.smooth-on.com/Silicone-Rubber-an/c2_1115_1129/index.html&quot; rel=&quot;nofollow&quot;&gt;Dragon Skin&lt;/a&gt; from &lt;a href=&quot;http://www.smooth-on.com/&quot; rel=&quot;nofollow&quot;&gt;Smooth-On&lt;/a&gt;, works great. It's expensive though. And if you don't want it to cure with tiny bubbles in it, you need to use a vacuum chamber (I have access to one at my university).&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2010-04-22T15:07:22.937" />
  <row Id="2332" PostTypeId="1" CreationDate="2010-04-22T15:36:10.857" Score="6" ViewCount="883" Body="&lt;p&gt;I need low power wifi for a not-very-data-intensive application.  What modules or chipsets should I look at?  Other than low cost and low power, I have no restrictions.  The cheaper the better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is for a high volume product, so both hobby level (since I can trace it back to an oem module) and oem level suggestions are welcome.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-05-05T21:08:34.877" Title="Cheapest way to add wifi to a project" Tags="&lt;wifi&gt;&lt;rf&gt;" AnswerCount="7" CommentCount="3" FavoriteCount="1" />
  <row Id="2333" PostTypeId="2" ParentId="2320" CreationDate="2010-04-22T15:39:35.973" Score="5" ViewCount="" Body="&lt;p&gt;MAX232 chip to communicate with a serial port&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Infrared LED and infrared receiver, for faking a remote control&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Accelerometer/gyroscope, for motion sensitivity&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Photoresistor, for light sensitivity&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Real time clock chip, in case time is important&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2-line text LCD (cheap-o $5 kind)&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-04-22T15:39:35.973" CommentCount="2" />
  <row Id="2334" PostTypeId="2" ParentId="2318" CreationDate="2010-04-22T15:43:53.570" Score="1" ViewCount="" Body="&lt;p&gt;Try using some ferrite beads.  They're the big lump at the end of some cords, like USB cords and power cords.  They filter noise pretty well.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-04-22T15:43:53.570" />
  <row Id="2335" PostTypeId="2" ParentId="2318" CreationDate="2010-04-22T16:01:29.433" Score="1" ViewCount="" Body="&lt;p&gt;You could probably try filtering out the 60Hz noise using a simple RC filter.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2010-04-22T16:01:29.433" CommentCount="1" />
  <row Id="2336" PostTypeId="2" ParentId="2332" CreationDate="2010-04-22T16:05:18.320" Score="3" ViewCount="" Body="&lt;p&gt;I haven't used this chip myself, but I've looked at the Epcos B30810 series before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://bit.ly/9E2vNj&quot; rel=&quot;nofollow&quot;&gt;http://bit.ly/9E2vNj&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They're about $6 in low quantity, and below $2.50 in large quantities. Digikey has them in stock. Unfortunately, their datasheets are behind a signup form.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd also look at the Atheros chips. I think the most recent low-power one is the AR6003. I don't know how much it costs; I suspect you'd have to buy it from Atheros directly. I'd be a little wary of the 0.4 mm spacing on the BGA pads-- below 0.5 mm generally costs extra.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-04-22T16:13:09.220" LastActivityDate="2010-04-22T16:13:09.220" />
  <row Id="2337" PostTypeId="1" CreationDate="2010-04-22T18:04:18.107" Score="4" ViewCount="324" Body="&lt;p&gt;I came across this page on &lt;a href=&quot;http://users.telenet.be/davshomepage/current-source.htm&quot; rel=&quot;nofollow&quot;&gt;building your own current source&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are current sources used for in real-world applications?  The only places I've seen them used are textbooks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have any suggestions for some fun weekend projects involving a current source?&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-04-22T20:48:37.377" LastActivityDate="2011-05-16T10:33:44.487" Title="Current Sources - Usage and Projects" Tags="&lt;current-source&gt;&lt;projects&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="2338" PostTypeId="2" ParentId="2332" CreationDate="2010-04-22T18:05:16.703" Score="8" ViewCount="" Body="&lt;p&gt;See related chiphacker question:&lt;br&gt;&#xA;&lt;a href=&quot;http://chiphacker.com/questions/129/ideal-wifi-to-serial-or-spi-bridge&quot; rel=&quot;nofollow&quot;&gt;ideal-wifi-to-serial-or-spi-bridge&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-22T18:05:16.703" />
  <row Id="2339" PostTypeId="2" ParentId="2337" CreationDate="2010-04-22T18:19:14.303" Score="6" ViewCount="" Body="&lt;p&gt;The page you point to uses a current source to drive an LED which is a very popular&#xA;real-world application and is also a good weekend project ;)&#xA;The color temperature of the LEDs changes with current so keeping the current &#xA;constant is useful for some applications. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Current sources can also be used in battery charging applications where you&#xA;need to maintain a constant current to properly charge a particular chemistry &#xA;of battery. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I have used current sinks to test power supplies. A typically power supply test&#xA;will be to run the power supply at it's rated current to verify proper voltage&#xA;regulation.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Your multimeter may use a current source to measure resistance. Pass a current&#xA;through an unknown resistance and measure a voltage.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Within circuits a current source (and sink) can be used to bias transistors (like&#xA;a differential amplifier circuit).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:33:44.487" LastActivityDate="2011-05-16T10:33:44.487" CommentCount="1" />
  <row Id="2340" PostTypeId="2" ParentId="2337" CreationDate="2010-04-22T18:19:57.063" Score="3" ViewCount="" Body="&lt;p&gt;Solar cells behave like current sources-- their voltage remains relatively constant across different light levels, while the current changes roughly linearly. I've seen current sources used in solar call testing before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LED brightness is proportional to current, so if you made an adjustable current source, you could make a dimmable LED flashlight-- that would be pretty cool.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-22T18:19:57.063" CommentCount="3" />
  <row Id="2341" PostTypeId="2" ParentId="2332" CreationDate="2010-04-22T18:38:49.450" Score="0" ViewCount="" Body="&lt;p&gt;If you only need a few metres range, the Nordic nRF24L01+ chips are cheap and quite easy to use.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-22T18:38:49.450" CommentCount="1" />
  <row Id="2342" PostTypeId="2" ParentId="2337" CreationDate="2010-04-22T19:37:37.270" Score="3" ViewCount="" Body="&lt;p&gt;Current sources are used to &lt;a href=&quot;http://www.zen22142.zen.co.uk/Design/config2.htm&quot; rel=&quot;nofollow&quot;&gt;linearize transistor amplifiers&lt;/a&gt;, and as I understand it are used all over the place &lt;a href=&quot;http://en.wikipedia.org/wiki/Operational_amplifier#Internal_circuitry_of_741_type_op-amp&quot; rel=&quot;nofollow&quot;&gt;inside of ICs&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-04-22T19:37:37.270" CommentCount="1" />
  <row Id="2343" PostTypeId="2" ParentId="2337" CreationDate="2010-04-22T21:52:25.140" Score="4" ViewCount="" Body="&lt;p&gt;Stepper motor drivers are constant current sources made by switching the motor windings on and off at high-frequency. They monitor the current on sense resistors and adjust the duty cycle appropriately.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want some examples of the loosy (not switch-mode) kind then Ethernet and CAN use simple resistor current sources and current mirror circuits to limit the current spikes and reduce EMI when transmitting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another example are laser diode power supplies. The diodes are extremely sensitive to over-currents and have a sharp U(I) characteristic at the operating point. Even small fluctuations in voltage can cause large currents and destroy the diode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One more example is the diode testing mode of a multimeter. It will source a little more than 1mA to allow you to check diode and transistor polarity and forward voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. All these examples are really constant current/constant voltage since their maximum output voltage is limited by the power supply voltage. In fact both kinds of real sources have a limit: current sources won't work if the load resistance is too high and voltage sources won't work if the load resistance is too low.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-04-22T21:52:25.140" />
  <row Id="2344" PostTypeId="2" ParentId="2304" CreationDate="2010-04-22T22:22:05.887" Score="1" ViewCount="" Body="&lt;p&gt;Not really an answer but an alternative.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For low current circuits you can use an AC adaptor without the rectifying bridge (the one that gives a low-voltage sine wave on it's output) or just a 220/110V-&gt;12V transformer and add two half-wave rectifiers (one diode for +12 and one for -12V). This way won't need two separate secondary windings on the transformer. Then you can regulate the voltage using one 7809 and one 7909 (but don't forget the capacitors on these).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. You could probably just remove some components from your adaptor but be extra careful when dealing with 220/110V circuits.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-04-22T22:22:05.887" CommunityOwnedDate="2010-04-22T22:22:05.887" />
  <row Id="2345" PostTypeId="2" ParentId="2332" CreationDate="2010-04-22T22:55:06.493" Score="2" ViewCount="" Body="&lt;p&gt;Check the &lt;a href=&quot;http://www.wiznet.co.kr/Sub_Modules/en/product/Product_Detail.asp?cate1=5&amp;amp;cate2=43&amp;amp;cate3=0&amp;amp;pid=1020&quot; rel=&quot;nofollow&quot;&gt;WIZnet WIZ610wi modules&lt;/a&gt;. It is not clear from the website but AFAIK they have a normal TCP/IP stack hardwired in addition to the WiFi&amp;lt;-&gt;Serial bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Unfortunately it seems it does not have a TCP/IP stack for client use. You need to connect to the MII interface with their W5300 (which handles TCP/IP with 8 sockets) or some other MAC to get TCP/IP.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2010-04-23T07:10:41.453" LastActivityDate="2010-04-23T07:10:41.453" />
  <row Id="2346" PostTypeId="1" CreationDate="2010-04-23T00:29:04.550" Score="3" ViewCount="347" Body="&lt;p&gt;This question is really aimed at computer cases, but I suppose it also applies to other PCB cases. Most of the Computer cases I come across are aluminium, or else some other metal; As I understand it this is because of the following properties:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) thermal, a metal case will nicely dissipate heat applied to any point, and conduct it to the cooler areas (outside). Also, doesn't burn (though many cases have plastic on them too)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) RF, a metal case will shield from outside interference, and also keep inside EMF from interfering with other things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) strength, to keep heavy equipment in-place and protect them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) earthed, add a level of electrical protection by having an earthed metal case around components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question it this: why can't other materials be used if these are the only concerns?&#xA;Other materials may be cheaper, easier to get or work with, lighter and importantly &lt;em&gt;cheaper&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, Wood has good properties for #3, it can be strong, and servers don't need to be portable much, so it only needs to be as strong as not falling apart when just standing there. #4 isn't really needed, #1 is important, but most computers use fans and heatsinks (rarely the case itself is used as a heatsink) already, so with well planned airflow the cases needn't also be thermally conductive (maybe thermal sensors may be more important though); which leaves #2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, would it be possible to use some kind of metallic tape on the insides of the case? I've seen thick RF tape, but that stuff's expensive. As far as I know, aluminium (baking) foil is actually mainly plastic with a thin layer of aluminium. I've seen cheap aluminium tape (for the roof) but I assume that's much like the baking foil; Just how thick &lt;em&gt;does&lt;/em&gt; the layer need to be, and can it be done cheaply? Could I even use something like chicken wire?&lt;/p&gt;&#xA;" OwnerUserId="733" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:44:19.797" LastActivityDate="2010-09-07T04:16:20.427" Title="Non-metal cases." Tags="&lt;computers&gt;&lt;cases&gt;&lt;rf&gt;&lt;interference&gt;&lt;shielding&gt;" AnswerCount="3" />
  <row Id="2347" PostTypeId="2" ParentId="2318" CreationDate="2010-04-23T00:39:35.657" Score="0" ViewCount="" Body="&lt;p&gt;If your question is one of signal integrity, are you sure you have a problem? If so by how much and at what frequencies?  Are you doing impedance matching between the driver and the transmission line? If so how?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your worried about EM emissions from the cable, which i bet are quite high with a single ended digital signal then the best solution is to create a small pcb for the sensor to live on along with a differential line driver.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;General question, whats the clock frequency of the signal?&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-04-23T00:39:35.657" />
  <row Id="2348" PostTypeId="1" AcceptedAnswerId="2360" CreationDate="2010-04-23T00:46:20.960" Score="3" ViewCount="427" Body="&lt;p&gt;I am looking for an AC or DC output wall wart power supply&#xA;that provides an isolated output and brings out the earth &#xA;ground connection to the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specs --&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Either single output or bipolar output&lt;/li&gt;&#xA;&lt;li&gt;Any voltage 7V to 18V (preferable 7V)&lt;/li&gt;&#xA;&lt;li&gt;100mA of current&lt;/li&gt;&#xA;&lt;li&gt;Must be new and in production (no surplus)&lt;/li&gt;&#xA;&lt;li&gt;Must have UL/CSA/TUV approval&lt;/li&gt;&#xA;&lt;li&gt;Must be encapsulated or closed (no open frame designs)&lt;/li&gt;&#xA;&lt;li&gt;Earth ground can be a separate connection or tied to&#xA;the power supply return.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I haven't seen these made in a long while. All of the &#xA;wall-wart type supplies that seem to be made are isolated&#xA;and there is no earth ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for your help.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T21:43:47.607" LastActivityDate="2010-12-10T21:43:47.607" Title="Looking for a Wall Wart Power Supply with an Earth Ground Connection on the Output" Tags="&lt;power-supply&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="2349" PostTypeId="2" ParentId="2346" CreationDate="2010-04-23T01:18:05.127" Score="1" ViewCount="" Body="&lt;p&gt;The biggest reason is mass-manufacturability.  It's so cheap and easy to stamp aluminum enclosures once you've done the tooling, while wood requires milling each piece.  But if you're doing something one-off or for aesthetic reasons, the reproduction cost shouldn't be a concern.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the other reasons: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Thermal - you're right.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;RF - chicken wire would allow high frequencies through.  If the wavelength of the EM wave is smaller than the opening in the metal, it can get through.  Aluminum foil doesn't, AFAIK, have a plastic layer.  It should be good enough.  But it tears easily, so you have to be pretty vigilant to get good coverage.  Also, you need some spring mesh or something around any flanges or lids etc to ensure the electrical connection carries around the corner.  Note contact should be continuous all the way around any opening.  In theory, the thickness of the metal shouldn't impact the shielding (as long as the metal doesn't tear) but I don't know enough RF engineering to really assert this. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Strength - if your box sits on the floor, wood should do fine.  If it mounts in a rack, you'll have to decide what to do about the mounting flange.  The shear strength of wood is not as good as metal, so you might have to fabricate the flange out of metal, and use a lot of bolts to connect it to the wood.  Wood is  heavier for a given volume so the flange will have to carry more load.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Earth - I'm not too sure about this one.  I guess lightening strikes are the biggest reason you need to worry about this, and I'm not sure how much protection the metal case would give you anyway in that situation.  Anyway, your RF cage needs to be connected to ground so maybe you'll just end up with some charred aluminum foil to clean up.  If someone pokes something metal through the case and makes contact with the power supply, thicker metal on the RF cage would help.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="696" LastEditorUserId="696" LastEditorDisplayName="" LastEditDate="2010-04-23T06:32:16.987" LastActivityDate="2010-04-23T06:32:16.987" CommentCount="3" />
  <row Id="2351" PostTypeId="2" ParentId="2272" CreationDate="2010-04-23T06:37:00.800" Score="1" ViewCount="" Body="&lt;p&gt;In a general case, some or many ICs, transistors or valves (tubes) will be connected to the same power supply. As a device in these situations operates, it draws varying amounts of current from the power supply in accordance with the signal passing through it. As power supplies are not perfect, the varying current causes a varying voltage to appear on the supply rails. All the other devices connected to the same power supply will then feel this voltage ie. a noise signal will be coupled into them. This may cause instability in analogue circuits or wrong switching in digital ones. By placing DEcoupling capacitors at points described above, the power supply voltage becomes more stable, and the devices are decoupled from each other.&lt;/p&gt;&#xA;" LastActivityDate="2010-04-23T06:37:00.800" />
  <row Id="2352" PostTypeId="2" ParentId="2318" CreationDate="2010-04-23T06:40:37.377" Score="0" ViewCount="" Body="&lt;p&gt;Are you sure the problem is noise coupling onto the cable?  Is there any chance the ballast is producing a big enough magnetic field to saturate the sensor itself?&lt;/p&gt;&#xA;" OwnerUserId="696" LastActivityDate="2010-04-23T06:40:37.377" />
  <row Id="2353" PostTypeId="2" ParentId="2192" CreationDate="2010-04-23T06:49:32.650" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.analog.com/en/mems/low-g-accelerometers/products/index.html&quot; rel=&quot;nofollow&quot;&gt;iMEMs sensors&lt;/a&gt; from Analog Devices and/or ST are available for &amp;lt; $10 from Digi-Key.  Depending on the package you pick, you can get all three axes digitized and output on a SPI bus.&lt;/p&gt;&#xA;" OwnerUserId="696" LastActivityDate="2010-04-23T06:49:32.650" />
  <row Id="2354" PostTypeId="2" ParentId="2192" CreationDate="2010-04-23T09:18:21.783" Score="1" ViewCount="" Body="&lt;p&gt;How about a cheap dev kit that has a accelerometer?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a couple of them to choose from but maybe the &lt;a href=&quot;http://www.st.com/mcu/contentid-105-110-STM3210B_PRIMER.html&quot; rel=&quot;nofollow&quot;&gt;STM32 Primer&lt;/a&gt;, and &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=497-6049-ND&quot; rel=&quot;nofollow&quot;&gt;digikey&lt;/a&gt; sells those for approx 48$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A extra little feature is that this is a usb-based dev kit, so you can send the data to a computer and create a &quot;data-logger&quot;.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-23T09:18:21.783" />
  <row Id="2355" PostTypeId="1" CreationDate="2010-04-23T16:03:13.763" Score="5" ViewCount="209" Body="&lt;p&gt;I have a keyboard from an old Silent 700 TTY that I'm trying to bring to life.  The problem is that each individual keyswitch appears to be a hall effect sensor.  There are no part numbers; the chip dies are individually bonded to the carrier boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the switch.  The carrier board fits into a slot in the back of the switch in the orientation shown:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm3.static.flickr.com/2425/4500817139_2c078dbaf2.jpg&quot; alt=&quot;Image of the switch&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And here's the die:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm3.static.flickr.com/2712/4500815187_3f95624b26.jpg&quot; alt=&quot;Image of the die&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any thoughts on how to drive a switch like this?&lt;/p&gt;&#xA;" OwnerUserId="70" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T16:01:57.047" LastActivityDate="2010-10-22T16:01:57.047" Title="Old Hall-Effect Keyswitches?" Tags="&lt;switch&gt;&lt;keyboard&gt;&lt;hall-effect&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="2356" PostTypeId="2" ParentId="2332" CreationDate="2010-04-23T17:10:32.203" Score="0" ViewCount="" Body="&lt;p&gt;Wifi is a pain in the butt, with the TCP/IP stack and all that.  You should consider Bluetooth instead.  They have RS232-&gt;Bluetooth modules...BlueSnap is their name, I think.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-04-23T17:10:32.203" />
  <row Id="2357" PostTypeId="2" ParentId="2355" CreationDate="2010-04-23T19:11:49.453" Score="3" ViewCount="" Body="&lt;p&gt;Analog hall sensors are 4-pin so maybe this is one? If this is the case then you should drive constant current through one pair of contacts and measure the voltage on the other (I think they are unfortunately not interchangeable so you would have to guess).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand the die layout looks a little complicated for a simple analog hall sensor.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-04-23T19:11:49.453" />
  <row Id="2358" PostTypeId="2" ParentId="1199" CreationDate="2010-04-23T20:40:26.627" Score="5" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;dsPIC33F&lt;/strong&gt; and &lt;strong&gt;PIC24&lt;/strong&gt;: Microchip has a family of 16-bit, 40 MIPS microcontrollers called dsPIC33F which combine their PIC24F instruction set and peripherals with DSP features such as two 40-bit accumulators with rounding and saturation options; single-cycle multiply and accumulate; and up to ±16-bit shifts for up to 40-bit data. Prices are low (as low as $2 in volume).  One thing I like about Microchip microcontrollers is many of their devices are available in DIP packages which are ideal for breadboarding.  I have used one of these in a project where I needed to decode DTMF signals; it was more cost-effective than a dedicated DTMF decoder hardware solution.&#xA;A PIC24 is used in the amazing &lt;a href=&quot;http://www.calcwatch.com/&quot; rel=&quot;nofollow&quot;&gt;uWatch&lt;/a&gt;, &quot;The world's most powerful (and only!) programmable RPN/Algebraic scientific calculator watch&quot;.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2010-06-23T20:27:29.623" LastActivityDate="2010-06-23T20:27:29.623" CommunityOwnedDate="2010-04-23T20:40:26.627" CommentCount="1" />
  <row Id="2359" PostTypeId="2" ParentId="632" CreationDate="2010-04-23T23:37:33.593" Score="2" ViewCount="" Body="&lt;p&gt;For the 16-bit PICs, I recommend &quot;Microcontrollers: From Assembly Language to C Using the PIC24 Bit Family&quot; by R. Reese, J. Bruce and B. Jones, ISBN 978-1584505839.  It has a lot of hardware (including schematics) mixed in with the firmware discussions and is not just a rehash of datasheets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're using one of the newer 8-bit PICs (PIC18F family) the following book looks fairly good: &quot;Advanced PIC Microcontroller Projects in C: From USB to RTOS with the PIC 18F Series&quot; by D. Ibrahim, ISBN 978-1584503781.  I don't have that one myself though.  Both books are quite recent (published in 2008).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-- Tom&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-04-23T23:37:33.593" />
  <row Id="2360" PostTypeId="2" ParentId="2348" CreationDate="2010-04-23T23:43:28.353" Score="4" ViewCount="" Body="&lt;p&gt;The only places i've seen wall wart supplies with an earth ground terminal are on supplies built for the alarm system industry and normally only on the 16.5/24V AC supplies.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.elkproducts.com/products/elk-trg1640_2440.htm&quot; rel=&quot;nofollow&quot;&gt;Here is an example&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As to why you don't see them.  The ground terminal on mains power is intended to be used to earth ground the enclosures of devices operating at mains, or high voltage.  For example a blender with a 120V motor and a metal case.  This prevents the chassis from ever being at dangerous voltages due to wiring faults or shorts within the product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC supplies normally have a floating ground that can be at a much different potential level than earth ground.  There normally isn't a use for a earth ground in such systems.  You'd have to be very careful with it to not cause a ground loop and grounding the chassis to the floating ground is normally done but more for emissions issues as unsafe chassis voltages aren't a concern in low voltage DC systems. &lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-04-23T23:43:28.353" CommentCount="2" />
  <row Id="2361" PostTypeId="2" ParentId="632" CreationDate="2010-04-24T03:26:23.503" Score="2" ViewCount="" Body="&lt;p&gt;Linkers and Loaders by John R. Levine (ISBN 1-55860-496-0) is quite good. It's about the low-level details of memory, code relocation, symbol management, and the like, but not exclusively for embedded development. Still, it's the best book on such low-level details that I know of. At this point, it might be a little dated-- I don't think it has anything about modern Flash file systems, for example.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-24T03:26:23.503" />
  <row Id="2362" PostTypeId="1" CreationDate="2010-04-24T03:33:32.173" Score="6" ViewCount="272" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been hanging around chiphacker for quite a while. I have asked interesting questions, got much more interesting answers and had fun generally. Chiphacker is great, sure, but for discussions by the electronics nerds, but thats where it ends.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been hanging around on Hacker news&lt;a href=&quot;http://news.ycombinator.com&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt; for some time and like it there. they post (or used to post, anyway) interesting stuff about startups and CS. Isn't there such sites for electronics? I know about individual blogs and sites, but I much prefer the community rating model of HN. If anyone knows of such sites please let me know.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-04-24T19:57:26.930" LastActivityDate="2010-04-28T14:03:21.287" Title="News gathering site for electronics hacking and other electronics geeky stuff?" Tags="&lt;website&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="2364" PostTypeId="2" ParentId="2362" CreationDate="2010-04-24T06:49:30.220" Score="1" ViewCount="" Body="&lt;p&gt;Hi Rick,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you like Hacker News, I'd suggest sub-reddits dedicated to electronics. Here is a list of the sub-reddits I follow:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.reddit.com/r/ECE/&quot; rel=&quot;nofollow&quot;&gt;http://www.reddit.com/r/ECE/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.reddit.com/r/electronics/&quot; rel=&quot;nofollow&quot;&gt;http://www.reddit.com/r/electronics/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.reddit.com/r/arduino/&quot; rel=&quot;nofollow&quot;&gt;http://www.reddit.com/r/arduino/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.reddit.com/r/avr/&quot; rel=&quot;nofollow&quot;&gt;http://www.reddit.com/r/avr/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Hope this helps :-)&lt;/p&gt;&#xA;" OwnerUserId="595" LastActivityDate="2010-04-24T06:49:30.220" CommentCount="1" />
  <row Id="2365" PostTypeId="2" ParentId="2362" CreationDate="2010-04-24T11:51:07.243" Score="3" ViewCount="" Body="&lt;p&gt;To be honest some of the most interesting work I've come across has been sent to me as an email news letter from &lt;a href=&quot;http://blog.makezine.com/&quot; rel=&quot;nofollow&quot;&gt;Make Magazine&lt;/a&gt;. I know it's not just electronics and it's aimed at DIYers - but at least they show interesting new technologies, unusual implementations and occasionally - the people behind the tech. I recommend scanning through the blog - there's all sorts of goodies. It's not Hacker news1 with a simple collation of relevant tech news, but i'm not sure that's out there - i'd love to be proved wrong tho&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-04-24T11:51:07.243" />
  <row Id="2367" PostTypeId="2" ParentId="2337" CreationDate="2010-04-24T14:31:21.380" Score="3" ViewCount="" Body="&lt;p&gt;Many sensors and transducers out there are easy to instrument with constant current sources. RTDs are the first thing that come to mind, but really any resistive based transducer can be driven with a constant current source and then all you need to do is monitor the voltage drop across the element with something like an instrumentation amplifier to measure its output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like endolith mentioned, current sources are very important in many IC's, especially analog IC's including, amplifiers, op-amps, digital-to-analog converters. If I am remembering my basic amplifier design correctly constant current sources are common in the input stages of many designs to ensure proper biasing in the input FETs or BJTs. &lt;/p&gt;&#xA;" OwnerUserId="631" LastActivityDate="2010-04-24T14:31:21.380" />
  <row Id="2368" PostTypeId="2" ParentId="2362" CreationDate="2010-04-24T15:40:29.853" Score="3" ViewCount="" Body="&lt;p&gt;The main sites I follow are the Make Blog as mentioned previously, and Hack A Day. Unfortunately HAD is very pro-software-piracy, which annoys me, but they have a good collection of electronics related discussions.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-04-24T15:40:29.853" CommentCount="8" />
  <row Id="2369" PostTypeId="1" AcceptedAnswerId="2371" CreationDate="2010-04-24T20:04:30.963" Score="4" ViewCount="568" Body="&lt;p&gt;I'm designing an embedded Linux board for use as a web-based controller. It will be based around an Atmel AT91SAM9G20, which uses an ARM926EJ-S core. Anyone have particularly good or bad experiences with bootloaders? More broadly, how should I go about building/choosing a Linux distribution for this board?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-24T20:39:24.803" Title="What's the best bootloader for an embedded Linux board?" Tags="&lt;linux&gt;&lt;bootloader&gt;&lt;arm&gt;" AnswerCount="2" />
  <row Id="2370" PostTypeId="2" ParentId="2346" CreationDate="2010-04-24T20:20:50.187" Score="2" ViewCount="" Body="&lt;p&gt;Regarding the thickness of metal required for shielding: the conductor used as a shield has to be thicker than the &quot;skin depth&quot; of the metal at the frequencies you're trying to block out. According to a textbook[1] I have here, 1 micron is enough in practice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[1]: Engineering Electromagnetics, Inan and Inan, 1999, p. 322.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-24T20:20:50.187" CommentCount="9" />
  <row Id="2371" PostTypeId="2" ParentId="2369" CreationDate="2010-04-24T20:38:18.003" Score="5" ViewCount="" Body="&lt;p&gt;Both the bootloader and Linux distribution depend on what your final application is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RedBoot and uBoot are both popular bootloaders for embedded Linux. They support writing to flash, loading code over serial/ethernet etc. But, for a deeply embedded device, a very minimal loader might be better, leaving everything else to linux.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need access to a lot of software packages, you might try Debian's ARM port. For anything else, I'd recommend OpenEmbedded or Buildroot - both are configurable build systems for generating linux kernels and filesystems with only what you need and nothing else in.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-04-24T20:38:18.003" CommentCount="3" />
  <row Id="2372" PostTypeId="2" ParentId="2369" CreationDate="2010-04-24T20:39:24.803" Score="3" ViewCount="" Body="&lt;p&gt;I think your best bet for bootloader is &lt;a href=&quot;http://www.denx.de/wiki/U-Boot&quot; rel=&quot;nofollow&quot;&gt;U-Boot&lt;/a&gt;  It has a port for the processor you're looking for in it's &quot;arch&quot; folder, and it's probably one of the most popular bootloaders. You might look into the atmel board folder of the source for an idea on how to configure your code around your chip.&lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2010-04-24T20:39:24.803" CommentCount="1" />
  <row Id="2373" PostTypeId="1" AcceptedAnswerId="2376" CreationDate="2010-04-24T22:01:38.443" Score="3" ViewCount="154" Body="&lt;p&gt;I have a switch marked as having a max current of 2A at 240Vac, and 6A at 125Vac.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would its max current rating be at 12Vdc?&lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-03T00:57:13.093" LastActivityDate="2011-02-03T00:57:39.927" Title="What's the max current for this component?" Tags="&lt;maximum-ratings&gt;" AnswerCount="3" />
  <row Id="2374" PostTypeId="2" ParentId="2373" CreationDate="2010-04-24T22:23:07.947" Score="1" ViewCount="" Body="&lt;p&gt;Impossible to say, but it would be OK for 6A. You could measure the resistance through the contacts and estimate it from that.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-24T22:23:07.947" CommentCount="3" />
  <row Id="2375" PostTypeId="2" ParentId="2373" CreationDate="2010-04-24T22:23:43.230" Score="5" ViewCount="" Body="&lt;p&gt;The general rule of thumb for switches with 125VAC or 240VAC ratings is that the switch&#xA;will operate satisfactory up to 30VDC at the highest rating listed on the&#xA;switch. IIRC I read this rule at the carlingtech.com site.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-03T00:57:39.927" LastActivityDate="2011-02-03T00:57:39.927" />
  <row Id="2376" PostTypeId="2" ParentId="2373" CreationDate="2010-04-25T01:02:34.403" Score="6" ViewCount="" Body="&lt;p&gt;Technically, it is impossible to tell: switch manufacturers have to deal with the subtleties of arcing when designing circuits, and AC behavior is different than DC behavior. Arcs will be extinguished much more easily with AC (since voltage passes through zero) than with DC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's odd that the rating drops so much at 240VAC from the 6A rating at 125VAC. If the limiting factor were thermal behavior, I would expect the current rating would be the same. So I'm guessing they're probably using a particular test condition, like opening the switch with maximum rated current, assuming there's bouncing in the switch which may cause an arc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ask the manufacturer....&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-04-25T01:02:34.403" CommentCount="1" />
  <row Id="2377" PostTypeId="1" AcceptedAnswerId="2382" CreationDate="2010-04-25T02:19:27.283" Score="7" ViewCount="1784" Body="&lt;p&gt;Hi, I'm trying to write a program for the ATTiny13. My problem is that it has huge size constraints. Well, when making my first Hello World program, it took 100 bytes of program space just to make a light turn on and off! Are there any options I can give to avr-gcc to shrink this size down? Also, what is in the crt0? I'm not too keen on AVR assembly so I don't understand it much.. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do not want to have to drop to assembly for this project.. &lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="708" LastEditorDisplayName="" LastEditDate="2010-04-25T02:51:30.610" LastActivityDate="2011-04-09T21:20:40.237" Title="ATTiny13 -- avr-gcc Hello World uses over 100 bytes!?" Tags="&lt;avr&gt;&lt;attiny&gt;&lt;programming&gt;&lt;compiler&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="2378" PostTypeId="2" ParentId="2377" CreationDate="2010-04-25T02:56:43.547" Score="13" ViewCount="" Body="&lt;p&gt;What is your eventual application?  An ATtiny13 has 1kB of flash and you can do a lot with that in C.  The crt0 is the avr-libc C runtime.  It contains things like stack handling so you can use functions with arguments and return values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;100 bytes for embedded C setup isn't too bad, and it's constant size.  Doubling the lines of program logic won't necessarily make it 200 bytes.  What optimization level are you compiling at?  You should be at &quot;-Os&quot;.  And how are you compiling this?  The Makefiles in the demo projects available from the avr-libc site are pretty good and comprehensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simple LED on/off program below takes 62 bytes on an ATtiny13 with &quot;-Os&quot; on the avr-gcc 4.3.3. from CrossPack-AVR:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;#include &amp;lt;avr/io.h&amp;gt;&#xA;#include &amp;lt;avr/delay.h&amp;gt;&#xA;&#xA;int main(void)&#xA;{&#xA;    DDRB |= _BV( PB3 );&#xA;    while( 1 ) { &#xA;        PORTB |=  _BV( PB3 );&#xA;        _delay_ms(200);&#xA;        PORTB &amp;=~ _BV( PB3 );&#xA;        _delay_ms(200);&#xA;    }&#xA;}&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Removing the _delay_ms() calls makes it 46 bytes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A larger example on the ATtiny13 are my &lt;a href=&quot;http://todbot.com/blog/2007/03/25/smart-led-prototypes/&quot; rel=&quot;nofollow&quot;&gt;Smart LED prototypes&lt;/a&gt;.  This code contains a 3-channel software PWM, an HSV-to-RGB color conversion, a state machine, and reads two buttons.  It's not written particularly well and comes in at 864 bytes.  Under avr-gcc 3.x it was even smaller. (for some reason avr-gcc 4 has made almost all programs grow by a few bytes)&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-04-25T02:56:43.547" CommentCount="2" />
  <row Id="2379" PostTypeId="1" AcceptedAnswerId="2385" CreationDate="2010-04-25T09:11:30.550" Score="5" ViewCount="342" Body="&lt;p&gt;I'm soldering up some boards with smd parts, using a hot plate to reflow, and I'm (inevitably) realizing that I got some of the wrong parts. Now, is it better to leave the boards with smd components stuck on them (sitting in wet solder paste) until I can get the other parts, and then do the reflow all at once, or to reflow now, and then paste and heatgun (or just solder iron) the other parts in later? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I only have a few parts for which I need to do this, and I can stick the boards in a quiet refrigerator until I get the parts. I might not have ready access to a heat gun later, which is why this isn't a no-brainer (I'm imagining soldering iron+paste isn't the best way to do things, since I can't get to pads under the parts). Personally, I think the real question is whether reflowing twice negatively affects smd components, but context might prove it otherwise. &lt;/p&gt;&#xA;" OwnerUserId="471" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T06:52:58.917" LastActivityDate="2011-01-29T06:52:58.917" Title="SMD solder now or later?" Tags="&lt;soldering&gt;&lt;surface-mount&gt;&lt;reflow&gt;&lt;solder-paste&gt;" AnswerCount="5" />
  <row Id="2380" PostTypeId="2" ParentId="2379" CreationDate="2010-04-25T11:00:57.023" Score="2" ViewCount="" Body="&lt;p&gt;Personally, I'd solder all the parts now and add the missing parts when they arrive. The paste might dry out.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-04-25T13:20:14.503" LastActivityDate="2010-04-25T13:20:14.503" CommentCount="2" />
  <row Id="2381" PostTypeId="1" AcceptedAnswerId="2383" CreationDate="2010-04-25T12:25:00.503" Score="3" ViewCount="554" Body="&lt;p&gt;I am trying to include a DC jack on one of my PCBs. I am just setting up the footprints now, and I am not quite sure which pin is which. What do the symbols on the drawing mean?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have included a snap of the schematic below, it has been taken directly from the &lt;a href=&quot;http://www.farnell.com/datasheets/457135.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://imgur.com/KqGiq.png&quot; alt=&quot;DC jack schematic&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="484" LastEditorDisplayName="" LastEditDate="2010-08-18T00:21:46.943" LastActivityDate="2011-05-16T10:40:47.697" Title="Deciphering a DC jack schematic" Tags="&lt;power&gt;&lt;schematics&gt;&lt;connector&gt;" AnswerCount="4" FavoriteCount="0" />
  <row Id="2382" PostTypeId="2" ParentId="2377" CreationDate="2010-04-25T12:33:19.987" Score="8" ViewCount="" Body="&lt;p&gt;crt0 is the startup routine for the uC. The routines performs the setup of the registers&#xA;and also the initialization of data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does the 100 bytes include the interrupt vector table? I am not sure about the &#xA;ATtiny13 but the ATtiny25/45/85 has 15 interrupts vectors. This would take up&#xA;30 bytes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;gcc has an option to link in your crt0. You could take the AVR crt0.S file and modify&#xA;it. It is not very long so it should not be difficult to do.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-20T15:48:07.860" LastActivityDate="2010-12-20T15:48:07.860" CommentCount="6" />
  <row Id="2383" PostTypeId="2" ParentId="2381" CreationDate="2010-04-25T12:36:56.257" Score="5" ViewCount="" Body="&lt;p&gt;Pin 3 is the center pin, pin one connects to the barrel and pin 2 is used&#xA;to detect if there is a plug inserted. The lower left drawing shows the physical&#xA;pins looking at the bottom side.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:40:47.697" LastActivityDate="2011-05-16T10:40:47.697" CommentCount="1" />
  <row Id="2384" PostTypeId="2" ParentId="2381" CreationDate="2010-04-25T13:15:44.473" Score="2" ViewCount="" Body="&lt;p&gt;I generally connect pins 1 and 2 together.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-25T13:15:44.473" />
  <row Id="2385" PostTypeId="2" ParentId="2379" CreationDate="2010-04-25T13:25:06.447" Score="4" ViewCount="" Body="&lt;p&gt;I've left wet paste on a board overnight in cool weather without problems, but I'd be worried it would dry out over a few days - especially if left uncovered in a refrigerator (although I'm not sure if this would adversely effect the reflowing).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there are pads under the parts, then soldering with an iron is out of the question, but a hot air rework gun should work fine. Depending on the complexity and the number of missing parts, I would either:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Flow now and solder the additional parts later (you can place a cube of metal under specific parts of the board to reflow individual parts on the hotplate).&lt;/li&gt;&#xA;&lt;li&gt;Clean the board and restart when you've got the new parts&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-04-25T13:25:06.447" />
  <row Id="2386" PostTypeId="2" ParentId="2381" CreationDate="2010-04-25T13:37:29.853" Score="6" ViewCount="" Body="&lt;p&gt;It's a visual representation of how the socket works.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Pin 3 represents the pin that mates with the center of the plug (typically V+)&lt;/li&gt;&#xA;&lt;li&gt;Pin 1 is the sprung contact that connects to the outside of the plug (typically Gnd)&lt;/li&gt;&#xA;&lt;li&gt;Pin 2 contacts to Pin 1 (Gnd) but breaks contact when the plug is inserted (as the Pin 1 contact springs away)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-04-25T13:37:29.853" />
  <row Id="2387" PostTypeId="2" ParentId="2377" CreationDate="2010-04-25T22:15:37.910" Score="11" ViewCount="" Body="&lt;p&gt;You can use avr-objdump -d .elf to see what's being generated:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's analyze it a little:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;[jpc@jpc ~] avr-objdump -d avr.elf | sed -e 's/^/    /' | pbcopy&#xA;&#xA;avr.elf:     file format elf32-avr&#xA;&#xA;Disassembly of section .text:&#xA;&#xA;00000000 &amp;lt;__vectors&amp;gt;:&#xA;   0:   09 c0           rjmp    .+18        ; 0x14 &amp;lt;__ctors_end&amp;gt;&#xA;   2:   0e c0           rjmp    .+28        ; 0x20 &amp;lt;__bad_interrupt&amp;gt;&#xA;   4:   0d c0           rjmp    .+26        ; 0x20 &amp;lt;__bad_interrupt&amp;gt;&#xA;   6:   0c c0           rjmp    .+24        ; 0x20 &amp;lt;__bad_interrupt&amp;gt;&#xA;   8:   0b c0           rjmp    .+22        ; 0x20 &amp;lt;__bad_interrupt&amp;gt;&#xA;   a:   0a c0           rjmp    .+20        ; 0x20 &amp;lt;__bad_interrupt&amp;gt;&#xA;   c:   09 c0           rjmp    .+18        ; 0x20 &amp;lt;__bad_interrupt&amp;gt;&#xA;   e:   08 c0           rjmp    .+16        ; 0x20 &amp;lt;__bad_interrupt&amp;gt;&#xA;  10:   07 c0           rjmp    .+14        ; 0x20 &amp;lt;__bad_interrupt&amp;gt;&#xA;  12:   06 c0           rjmp    .+12        ; 0x20 &amp;lt;__bad_interrupt&amp;gt;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;20 bytes interrupt vector table (at least some of the entries could be omitted if you insisted and promised you would never enable the corresponding interrupts).&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;00000014 &amp;lt;__ctors_end&amp;gt;:&#xA;  14:   11 24           eor r1, r1&#xA;  16:   1f be           out 0x3f, r1    ; 63&#xA;  18:   cf e9           ldi r28, 0x9F   ; 159&#xA;  1a:   cd bf           out 0x3d, r28   ; 61&#xA;  1c:   02 d0           rcall   .+4         ; 0x22 &amp;lt;main&amp;gt;&#xA;  1e:   05 c0           rjmp    .+10        ; 0x2a &amp;lt;_exit&amp;gt;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Clears SREG (I am not sure this is really needed), writes 0x9f (RAMEND) to SPL (the stack pointer) and jumps to main. The last rjmp is kind of redundant. (you could promise never to return from main)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;00000020 &amp;lt;__bad_interrupt&amp;gt;:&#xA;  20:   ef cf           rjmp    .-34        ; 0x0 &amp;lt;__vectors&amp;gt;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Default interrupt procedure for those interrupts than do not have one overwritten in C. (same rules as for __vectors)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;00000022 &amp;lt;main&amp;gt;:&#xA;  22:   bb 9a           sbi 0x17, 3 ; 23&#xA;  24:   c3 9a           sbi 0x18, 3 ; 24&#xA;  26:   c3 98           cbi 0x18, 3 ; 24&#xA;  28:   fd cf           rjmp    .-6         ; 0x24 &amp;lt;main+0x2&amp;gt;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Your main proc. Tight.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;0000002a &amp;lt;_exit&amp;gt;:&#xA;  2a:   f8 94           cli&#xA;&#xA;0000002c &amp;lt;__stop_program&amp;gt;:&#xA;  2c:   ff cf           rjmp    .-2         ; 0x2c &amp;lt;__stop_program&amp;gt;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This two are not very useful. _exit is probably required by the C standard and __stop_program is needed for it to work as it should.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-09T21:18:17.923" LastActivityDate="2011-04-09T21:18:17.923" />
  <row Id="2388" PostTypeId="1" CreationDate="2010-04-25T22:46:38.597" Score="8" ViewCount="249" Body="&lt;p&gt;I need to produce a small batch (less than 100) of custom enclosures, each made up of 5-6 pieces of plastic.  I need surfaces to look smooth and hard (think the quality of a computer keyboard) and one of the pieces needs to be see-through, while another needs to contain several labels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the places you guys are using for this?  Also, what is the price range I'm looking at?&lt;/p&gt;&#xA;" OwnerUserId="729" LastEditorUserId="729" LastEditorDisplayName="" LastEditDate="2010-04-25T23:51:14.813" LastActivityDate="2010-04-29T11:28:23.353" Title="Custom enclosures" Tags="&lt;enclosure&gt;" AnswerCount="7" CommentCount="2" FavoriteCount="3" />
  <row Id="2389" PostTypeId="2" ParentId="2388" CreationDate="2010-04-26T00:39:30.450" Score="0" ViewCount="" Body="&lt;p&gt;Getting custom made plastic anything has a very high startup cost. It's usually not worth it if you need less than a thousand or more.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-04-26T00:39:30.450" CommentCount="3" />
  <row Id="2390" PostTypeId="2" ParentId="2388" CreationDate="2010-04-26T02:45:57.283" Score="1" ViewCount="" Body="&lt;p&gt;I've used a place in Colorado called Protogenic for SLA'd parts before. They'll paint and sand models so they look really good, and I believe they can do transparent parts as well. Unfortunately, I suspect that the cost would be quite high-- maybe $150-200 per enclosure?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.protogenic.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.protogenic.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-26T02:45:57.283" CommentCount="2" />
  <row Id="2391" PostTypeId="2" ParentId="2388" CreationDate="2010-04-26T07:29:51.363" Score="5" ViewCount="" Body="&lt;p&gt;I gave the following answer to &lt;a href=&quot;http://chiphacker.com/questions/2145/plastic-enclosure-for-small-product&quot; rel=&quot;nofollow&quot;&gt;this earlier question&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I would say that to keep costs to a minimum you need to try to fit your product to one of the standard enclosure boxes made by (for example) OKW. The problem with a bespoke mould for your product you are looking at a large NRE charge for the design and some thousands of pounds for the tooling costs.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;For a two part moulding the tooling cost was around £6-8k.  The design time was a couple of weeks - you do your own sums on the cost of that.  You are talking of what sounds like quite a complicated design if it is made up of 6 parts, so expect the costs to rise accordingly.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-04-26T07:29:51.363" CommentCount="1" />
  <row Id="2392" PostTypeId="2" ParentId="2388" CreationDate="2010-04-26T08:28:49.713" Score="0" ViewCount="" Body="&lt;p&gt;You can sandpaper the surface  manually&lt;/p&gt;&#xA;" LastActivityDate="2010-04-26T08:28:49.713" />
  <row Id="2393" PostTypeId="1" CreationDate="2010-04-26T08:43:42.117" Score="1" ViewCount="128" Body="&lt;p&gt;I want to hack my Samsung DVD player. But the IC used it a Sanyo LC87F5NC8A. I don't have a programmer that can dump or program this UC. Any advice ??&lt;/p&gt;&#xA;" LastActivityDate="2010-04-27T00:19:34.750" Title="Programmer for Sanyo LC87F5NC8A Microcontroller" Tags="&lt;programmer&gt;&lt;isp&gt;" AnswerCount="4" />
  <row Id="2394" PostTypeId="2" ParentId="2393" CreationDate="2010-04-26T11:16:10.607" Score="2" ViewCount="" Body="&lt;p&gt;The programming algorithm should be in the documentation for the chip. You could implement it on another MCU.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-26T11:16:10.607" />
  <row Id="2395" PostTypeId="2" ParentId="2388" CreationDate="2010-04-26T12:14:01.770" Score="1" ViewCount="" Body="&lt;p&gt;Depending on your design constraints, you can accomplish nice things with laser cut acrylic - for example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.positron.org/projects/juicebox/&quot; rel=&quot;nofollow&quot;&gt;http://www.positron.org/projects/juicebox/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Laser etching would then be natural for labels/artwork, or printed artwork inside the clear panels.&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-04-26T12:14:01.770" CommentCount="1" />
  <row Id="2396" PostTypeId="2" ParentId="2393" CreationDate="2010-04-26T12:37:33.370" Score="0" ViewCount="" Body="&lt;p&gt;You could buy a different DVD player which somebody else has already hacked/reverse engineered. In terms of effort and time, that's going to be a lot easier.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-04-26T12:37:33.370" />
  <row Id="2397" PostTypeId="2" ParentId="2393" CreationDate="2010-04-26T12:42:29.423" Score="3" ViewCount="" Body="&lt;p&gt;The datasheet is available via Google. Page 4 has lists part numbers for Flash ROM programmers that can program the chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's one company that makes them: &lt;a href=&quot;http://www.j-fsg.co.jp/en/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.j-fsg.co.jp/en/index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They don't appear to sell the exact models listed in the datasheet, but the AF9709C looks like it might do the job. I bet it's expensive, but you might be able to find out how it operates it, and then emulate it with something cheaper.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-04-27T00:19:34.750" LastActivityDate="2010-04-27T00:19:34.750" CommentCount="6" />
  <row Id="2398" PostTypeId="2" ParentId="2393" CreationDate="2010-04-26T17:08:46.203" Score="2" ViewCount="" Body="&lt;p&gt;I found the datasheet by doing a Google search for the part online. In the datasheet it references a number of different programmers to use with that chip.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-26T17:08:46.203" />
  <row Id="2400" PostTypeId="2" ParentId="2145" CreationDate="2010-04-26T19:30:12.533" Score="2" ViewCount="" Body="&lt;p&gt;Here are a few that I have bookmarked --&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.pactecenclosures.com&quot; rel=&quot;nofollow&quot;&gt;http://www.pactecenclosures.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.polycase.com&quot; rel=&quot;nofollow&quot;&gt;http://www.polycase.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.tekoenclosures.com&quot; rel=&quot;nofollow&quot;&gt;http://www.tekoenclosures.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I don't have experience with any of these manufacturers (which is why &#xA;I didn't post for the original question). I did receive samples from&#xA;each company and all the cases look good and feel solid. Each company&#xA;seems to have one or two styles that I like.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:38:03.193" LastActivityDate="2011-05-18T11:38:03.193" CommentCount="1" />
  <row Id="2401" PostTypeId="2" ParentId="2379" CreationDate="2010-04-26T21:04:31.300" Score="2" ViewCount="" Body="&lt;p&gt;To the best of my knowledge, solder paste is kept chilled not because the flux dries out quickly, but to help keep the very fine bits of solder in suspension.  You're probably okay waiting a few days to solder.&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2010-04-26T21:04:31.300" />
  <row Id="2402" PostTypeId="2" ParentId="2332" CreationDate="2010-04-27T02:53:02.203" Score="-1" ViewCount="" Body="&lt;p&gt;Maplin Electronics sells an Item &lt;a href=&quot;http://www.maplin.co.uk/Module.aspx?moduleno=267370&quot; rel=&quot;nofollow&quot;&gt;Low Cost 2.4GHz Transceiver Module&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think it includes encryption, but it's cheap for a whole module.&lt;/p&gt;&#xA;" OwnerUserId="733" LastActivityDate="2010-04-27T02:53:02.203" CommentCount="1" />
  <row Id="2405" PostTypeId="2" ParentId="1842" CreationDate="2010-04-27T09:20:40.930" Score="0" ViewCount="" Body="&lt;p&gt;Actually I don't think there's any problem with submersing a thermocouple in water. It's just wires, and as long as the thermoelectric effect can still take place at the point where the two metals touch, then it doesn't matter what they're surrounded by. I guess the water needs to be properly grounded though... you don't want freak voltage spikes etc getting into your thermocouple circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: woops, yes, if you're looking for something that's food-safe then it's not such a good idea. Bits of food likely to get stuck in the wires, etc.&lt;/p&gt;&#xA;" LastActivityDate="2010-04-27T09:20:40.930" />
  <row Id="2407" PostTypeId="1" AcceptedAnswerId="2408" CreationDate="2010-04-27T20:40:55.380" Score="7" ViewCount="562" Body="&lt;p&gt;Looking for a shunt resistor for measuring power usage and was wondering if anyone had any experience with these. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should be capable of handling 110V/20A in-home circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Energy monitors are the rage these days and I was thinking about putting a simple circuit together to try out. This would be used to measure a typical appliance or electronic device such as stereo or television. Similar to a Kill-a-watt or multimeter. I haven't really thought about accuracy as much as getting something to work well. I haven't thought this all the way through just thought maybe some here may have already &quot;been there done that&quot;.&lt;/p&gt;&#xA;" OwnerUserId="245" LastEditorUserId="245" LastEditorDisplayName="" LastEditDate="2010-04-27T23:55:48.903" LastActivityDate="2011-05-17T12:45:35.747" Title="Best shunt resistor for power meter application?" Tags="&lt;power-meter&gt;&lt;resistor&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="2408" PostTypeId="2" ParentId="2407" CreationDate="2010-04-27T21:07:12.707" Score="4" ViewCount="" Body="&lt;p&gt;The key is finding one with low enough resistance that it doesn't have to dissipate much power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two of these in parallel would do the job: &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=TMC5-.10-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=TMC5-.10-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With two in parallel, the resistance will be 0.05 ohms, so at 20 A, you'll have to dissipate 20 * 20 * 0.05 = 20 W. They're rated for 5 W continuous, or 10 W for the two of them. As long as you don't have to maintain 20 A, they'd work fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll see if I can dig up something better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: here's a better solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try one of these: &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=MR50.01FTR-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=MR50.01FTR-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistance is 0.01 ohms, so at 20 A, you'll dissipate 20 * 20 * 0.01 = 4 W. The part is rated for 5 W continuous, so you're safe.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-27T21:07:12.707" CommentCount="2" />
  <row Id="2409" PostTypeId="2" ParentId="2407" CreationDate="2010-04-27T23:07:14.117" Score="4" ViewCount="" Body="&lt;p&gt;You haven't stated the accuracy you require or the range of currents you want&#xA;to want to measure. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are looking for a 5% measurement you may want to look at a current transformer&#xA;or a hall effect device. The nice thing about these is they give you isolation&#xA;from the line. Take a look at the various power meter application notes on&#xA;the TI, Microchip and ADI sites. They will probably have some specific&#xA;recommendations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a resistor be careful of the power dissipation. You need to derate for dissipation&#xA;and you may need to look at the temperature coefficient for accuracy. Also some power&#xA;resistors have very specific mounting recommendations -- height off the PCB, the amount of&#xA;power being dissipated by adjacent components. If you need an accurate measurement&#xA;you will want a resistor with Kelvin connections (four terminal). If you need&#xA;a wide range of currents you may also need an instrumentation amplifier.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:45:35.747" LastActivityDate="2011-05-17T12:45:35.747" CommentCount="1" />
  <row Id="2410" PostTypeId="2" ParentId="2407" CreationDate="2010-04-28T02:02:25.067" Score="1" ViewCount="" Body="&lt;p&gt;Ah, you actually want to build a power meter-- take a look at the STPM01. It's an IC designed to be the core of a residential power meter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.st.com/stonline/products/families/analog_and_mixed_signal/interface_ics/related_info/stpm01.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.st.com/stonline/products/families/analog_and_mixed_signal/interface_ics/related_info/stpm01.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digikey has them in stock for $9.94 in qty. 1. You'd need to connect it to a microcontroller of some sort via SPI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect that there are also other ICs like this available-- maybe check Analog Devices, Linear Technology, and TI.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-28T02:02:25.067" />
  <row Id="2411" PostTypeId="1" CreationDate="2010-04-28T02:04:32.743" Score="2" ViewCount="162" Body="&lt;p&gt;So I want to make my own version of the &lt;a href=&quot;http://www.thinkgeek.com/stuff/41/iCade.shtml&quot; rel=&quot;nofollow&quot;&gt;iCade&lt;/a&gt; Any thoughts on how I go about doing the hardware side? Has anyone done an unofficial version of this? I'm thinking a combination of:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Concave-Button-%252d-Red.html&quot; rel=&quot;nofollow&quot;&gt;Concave Button&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Arcade-Joystick-%252d-Short-Handle.html&quot; rel=&quot;nofollow&quot;&gt;Arcade Joystick&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/PodBreakout.html&quot; rel=&quot;nofollow&quot;&gt;PodBreakout&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Arduino-Mega.html&quot; rel=&quot;nofollow&quot;&gt;Arduino Mega&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Any suggestions would be greatly appreciated!&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-06T22:18:37.657" LastActivityDate="2011-02-06T22:18:37.657" Title="iCade - making it a reality" Tags="&lt;arduino&gt;&lt;ipad&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="2412" PostTypeId="2" ParentId="2411" CreationDate="2010-04-28T03:47:30.503" Score="4" ViewCount="" Body="&lt;p&gt;The main problem I see is that wouldn't the arcade games on the iPad would have to be specifically coded to accept external inputs? Which means not only will you be building the hardware, you'll have to write the software too. You might want to consider using something else than the iPad that runs a standard OS that you can run something like &lt;a href=&quot;http://mamedev.org/&quot; rel=&quot;nofollow&quot;&gt;MAME&lt;/a&gt; on.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-04-28T03:47:30.503" CommentCount="0" />
  <row Id="2413" PostTypeId="2" ParentId="1885" CreationDate="2010-04-28T09:38:09.310" Score="1" ViewCount="" Body="&lt;p&gt;The book 'Practical Arduino', available from little bird electronics (and elsewhere) contains information on how to decode the data from wireless temperature probes as sold with consumer weather stations.&lt;/p&gt;&#xA;" LastActivityDate="2010-04-28T09:38:09.310" />
  <row Id="2414" PostTypeId="2" ParentId="464" CreationDate="2010-04-28T13:36:08.673" Score="2" ViewCount="" Body="&lt;p&gt;Similar to the accepted answer, I wish I had known about Arduino's sooner.  There were some designs I was looking at doing around the house.  I have no problem designing my own boards with uC's, but I just didn't want to pay for the PCB costs at the time and then mounting SMT chips.  So, those projects fell by the way side.  However, now that I know about Arduino and all the shields for it, I'm considering them once again.&lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2010-04-28T13:36:08.673" CommunityOwnedDate="2010-04-28T13:36:08.673" />
  <row Id="2415" PostTypeId="2" ParentId="2411" CreationDate="2010-04-28T13:38:11.913" Score="1" ViewCount="" Body="&lt;p&gt;The tricky part here is likely the software.  In addition to being able to put together the hardware, you'll need to have some knowledge of writing software for the iPad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll need to make sure you can:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Put together the joystick, buttons, and microcontroller to present the joystick/button data to the iPad via the dock port.&lt;/li&gt;&#xA;&lt;li&gt;Use an API to get the button presses / joystick movements from the external hardware.&lt;/li&gt;&#xA;&lt;li&gt;Take the output of that API as input into arcade software.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;davr's recommendation of MAME is likely a good place to start, but I don't know about MAME's support for hardware like the iPad.  Considering that there is already a &lt;a href=&quot;http://www.appsafari.com/games/851/mame/&quot; rel=&quot;nofollow&quot;&gt;iPhone app for MAME&lt;/a&gt; (although its level of operation seems minimal/in-beta right now), there is a good bet you'll get it to work with some effort (at least for Pacman, Qbert);  I believe the iPad supports iPhone OS apps.  Since the MAME port appears to be open-source, you could integrate your joystick/button data through some custom code modules that you've written yourself.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-04-28T13:38:11.913" />
  <row Id="2416" PostTypeId="2" ParentId="2362" CreationDate="2010-04-28T14:03:21.287" Score="1" ViewCount="" Body="&lt;p&gt;the adafruit forums aren't too bad, a lot of things are discussed there, and the moderation keeps the nutjobs under control. &lt;a href=&quot;http://forums.adafruit.com/&quot; rel=&quot;nofollow&quot;&gt;http://forums.adafruit.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-04-28T14:03:21.287" />
  <row Id="2417" PostTypeId="1" AcceptedAnswerId="2418" CreationDate="2010-04-28T15:01:14.633" Score="3" ViewCount="357" Body="&lt;p&gt;I've seen news articles talking about how SanDisk released Write Once Read Many (WORM) SD cards, but I can't find anywhere to buy them!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking of building a project where I'll want to write reasonably small amounts of data (amounting to maybe 64 MB at most) to permanent storage, for retrieval via USB — can anyone think of a suitable IC for this?&lt;/p&gt;&#xA;" OwnerUserId="617" LastActivityDate="2010-09-05T14:41:33.523" Title="Write Once Memory" Tags="&lt;memory&gt;&lt;ic&gt;" AnswerCount="6" CommentCount="3" />
  <row Id="2418" PostTypeId="2" ParentId="2417" CreationDate="2010-04-28T15:25:53.387" Score="3" ViewCount="" Body="&lt;p&gt;Using a microSD card seems like the best idea to me (using a socket or soldering directly to the contacts). You could add an AT90USB162 or LPC1342 for the USB mass-storage interface. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;DataFlash chips may be an alternative but their cost per megabyte is much higher.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-04-28T15:25:53.387" />
  <row Id="2419" PostTypeId="2" ParentId="2417" CreationDate="2010-04-28T15:59:56.387" Score="1" ViewCount="" Body="&lt;p&gt;If you need the write once implemented on the chip itself you may have a hard time finding the part you need. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are ok with writing some code you could use a separate chip to enforce the write once read many policy. I'd suggest pairing a Microchip part (&lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en533925&quot; rel=&quot;nofollow&quot;&gt;PIC18F13K50&lt;/a&gt;&#xA;) with built in USB support with a data flash chip (&lt;a href=&quot;http://www.sst.com/products/?inode=41337&quot; rel=&quot;nofollow&quot;&gt;SST25VF032B&lt;/a&gt;). That will give you 8MB of storage. If you need more memory just keep adding SST25VF032B's to the SPI bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Total system cost &amp;lt; $5.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-28T15:59:56.387" />
  <row Id="2420" PostTypeId="2" ParentId="464" CreationDate="2010-04-28T19:37:26.460" Score="5" ViewCount="" Body="&lt;p&gt;I wish I'd known how useful a board vise and a really good soldering iron would be.  My Panavise Jr and Aoyue soldering station cost &amp;lt; $100 together, but they've paid that back many times over by making it a lot more pleasant to build things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't absolutely need them, but they're much much better than helping hands and $15 cheapo soldering irons.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2010-04-28T19:37:26.460" CommunityOwnedDate="2010-04-28T19:37:26.460" />
  <row Id="2421" PostTypeId="2" ParentId="2417" CreationDate="2010-04-28T20:30:04.543" Score="0" ViewCount="" Body="&lt;p&gt;They are such a niche market you will have real trouble finding any such parts or cards unless you need millions.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-04-28T20:30:04.543" />
  <row Id="2422" PostTypeId="2" ParentId="2417" CreationDate="2010-04-28T22:03:42.747" Score="3" ViewCount="" Body="&lt;p&gt;The SDCard spec allows for WORM via its various write-protect techniques.  Most regular SDCards implement the mechanical write-protect switch, making it the host's responsibility to abide by the switch position.  But the SDCard spec also specifies two techniques done only by the card: one is an optional &quot;Card Internal Write Protection&quot; mechanism which I bet hardly any SDCard supports.  The other is the ability to password-protect an SDCard (the password is actually stored on the card)  After a card is locked with a password, if you don't have the password it can only be erased.&lt;/p&gt;&#xA;" OwnerUserId="215" LastActivityDate="2010-04-28T22:03:42.747" />
  <row Id="2423" PostTypeId="2" ParentId="464" CreationDate="2010-04-28T22:12:49.920" Score="3" ViewCount="" Body="&lt;p&gt;One thing I wish I knew better is analog circuit theory.  1s and 0s are easy...hook pin 1 of device A to pin 2 of device B.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A second-order band-pass Butterworth multiple-feedback filter...not so much.  And then you have to worry about the characteristics of the op-amp, like whether the capacitive load on the output combined with the output impedance of the op-amp creates a pole which makes the output oscillate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or let's say you want to send an audio signal to headphones.  You must carefully choose a DC-blocking cap, because it will combine with the impedance of the headphones to form a single-pole low-pass filter.  Pick the wrong cap and you will neuter the bass frequencies.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-04-28T22:12:49.920" CommunityOwnedDate="2010-04-28T22:12:49.920" />
  <row Id="2424" PostTypeId="2" ParentId="1482" CreationDate="2010-04-28T22:15:35.373" Score="1" ViewCount="" Body="&lt;p&gt;You could also consider the Cypress FX2.  It's a Hi-Speed USB chip that comes with Mass Storage Driver support.  Dunno about any tutorials for it, but it's a pretty popular chip.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-04-28T22:15:35.373" />
  <row Id="2425" PostTypeId="1" AcceptedAnswerId="2433" CreationDate="2010-04-28T23:59:17.803" Score="6" ViewCount="1120" Body="&lt;p&gt;I was looking over the schematic for the &lt;a href=&quot;http://www.gumstix.com/store/catalog/product_info.php?products_id=229&quot; rel=&quot;nofollow&quot;&gt;GumStix Palo 43&lt;/a&gt; and noticed they used a common mode choke coil on the data lines coming in from USB. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand how this design can help remove noise coming in on the USB lines, but I wonder if it is actually something I should start doing on my designs. The &lt;a href=&quot;http://www.ftdichip.com/Documents/DataSheets/DS_FT232R_V205.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; for the FT232R has no mention of adding common mode choke coils, and I have used this chip before with out one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, would you recommend I change my USB design or keep it the way it is?&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-04T00:50:57.427" Title="Are Common Mode Choke Coils needed on USB?" Tags="&lt;usb&gt;" AnswerCount="4" CommentCount="6" />
  <row Id="2426" PostTypeId="2" ParentId="2425" CreationDate="2010-04-29T00:27:53.673" Score="4" ViewCount="" Body="&lt;p&gt;There's a good chance that the choke is included on the Gumstix board because they have to pass FCC &lt;a href=&quot;http://en.wikipedia.org/wiki/Title_47_CFR_Part_15&quot; rel=&quot;nofollow&quot;&gt;Title 47 CFR Part 15&lt;/a&gt; emissions testing for unintentional radiators to sell their device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might not care about that, but if it's for a commercial product I think it's cheaper to add the choke now and then remove it if you discover it's not needed.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-04-29T00:33:47.467" LastActivityDate="2010-04-29T00:33:47.467" />
  <row Id="2427" PostTypeId="2" ParentId="1482" CreationDate="2010-04-29T05:07:20.780" Score="1" ViewCount="" Body="&lt;p&gt;How about a good book on how usb works?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.lvr.com/usbc.htm&quot; rel=&quot;nofollow&quot;&gt;USB Complete - Jan Axelson&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Then when you start to program, you know how things are supposed to work...&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-04-29T05:07:20.780" />
  <row Id="2428" PostTypeId="1" AcceptedAnswerId="2429" CreationDate="2010-04-29T07:49:13.640" Score="6" ViewCount="234" Body="&lt;p&gt;So after staring at a few ICs today, I was wondering what the &quot;e3&quot; or &quot;e4&quot; stands for on the top of an IC. For example, here is an e3 - &lt;a href=&quot;http://tronixstuff.files.wordpress.com/2010/04/lt1302small.jpg?w=300&amp;amp;h=281&quot; rel=&quot;nofollow&quot;&gt;http://tronixstuff.files.wordpress.com/2010/04/lt1302small.jpg?w=300&amp;amp;h=281&lt;/a&gt;. Thanks, 't&lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-04-30T13:50:25.213" LastActivityDate="2010-04-30T13:50:25.213" Title="What does the e3 or e4 printed on an IC mean?" Tags="&lt;electronics&gt;&lt;markings&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="2429" PostTypeId="2" ParentId="2428" CreationDate="2010-04-29T08:06:53.730" Score="14" ViewCount="" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe it is regarding the lead content or plating finish.  Here is an exerpt from ti.com&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e0 - contains intentionally added lead (Pb)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e1 - SnAgCu (shall not be included in category e2)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e2 - Sn alloys with no Bi or Zn excluding SnAgCu&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e3 - Sn&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e4 - Preplated (e.g., Ag, Au, NiPd, NiPdAu)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e5 - SnZn, SnZnx (no Bi)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e6 - contains Bi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e7 - low temperature solder (&#xA;&#xA;&lt;p&gt;e8, e9 symbols are unassigned at this time**&lt;/p&gt;&#xA;" OwnerUserId="272" LastActivityDate="2010-04-29T08:06:53.730" CommentCount="2" />
  <row Id="2430" PostTypeId="1" AcceptedAnswerId="2435" CreationDate="2010-04-29T08:19:50.893" Score="4" ViewCount="279" Body="&lt;p&gt;I need a quick heads up on a problem I am trying to solve at work. I'm trying to connect to a parallel data port on an interface module we use to access smart cards. The port has an 8bit input and an 8 bit output with associated strobe/ready pins. I have a microcontroller board with an ARM cortex (mbed.org) which would be perfect to interface to these ports to my PC for test purposes. The ARM board has loads of i/o but its a 3.3v part. I have used it with your typical 2 line LCD display (5v part) with no problem (I know the ARM i/o is 5v tolerant) and I can control the LCD no problem. What I'm wondering is, is it ok to assume that I can drive any 5v TTL level input from a 3.3v output pin ? I'm happy that I can read the 5v ttl levels as I said the ARM Cortex chip's documentation says it 5v tolerent. The connection will be very short (&amp;lt;10cm).&lt;/p&gt;&#xA;" OwnerUserId="611" LastActivityDate="2010-04-29T18:39:00.087" Title="Is it possible to drive TTL inputs from 3.3v microcontroller..." Tags="&lt;arm&gt;&lt;3.3v&gt;" AnswerCount="3" CommentCount="0" FavoriteCount="1" />
  <row Id="2431" PostTypeId="2" ParentId="765" CreationDate="2010-04-29T09:13:49.647" Score="3" ViewCount="" Body="&lt;p&gt;I'm surprised at all the complicated electronic solutions here, I would use a simple potentiometer. Most micro controllers have a basic analog i/p.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; +V&#xA;-----&#xA;  |&#xA;  |&#xA;  /&#xA;  \&#xA;  /&amp;lt;----------&amp;gt; to analog i/p&#xA;  \&#xA;  |&#xA;  |&#xA;-----&#xA; GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Use a standard water tank valve float (there may already be one). The remaining problem is coupling the float to the pot to get maximum swing (you could also use a slider pot).&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;                  |-|&#xA;                  | |&#xA;                  |o| &amp;lt;--------Slider pot.&#xA;                  |||&#xA;                  |||&#xA;                   |&#xA;                   |  &amp;lt;--------Coupling.&#xA;                   |&#xA;   ____            |&#xA;  (float)----------o-----o  &amp;lt;--Anchor point of float.&#xA;   ----&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="611" LastActivityDate="2010-04-29T09:13:49.647" />
  <row Id="2432" PostTypeId="2" ParentId="2430" CreationDate="2010-04-29T09:44:41.427" Score="1" ViewCount="" Body="&lt;p&gt;&quot;is it ok to assume&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;your number of assumptions should be inversely proportional to the amount of money invested in your work. I am not sure how much is in this project but I always try to keep that in mind.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the device: are you reading, writing or both? If reading, should be ok since you said your device is 5V tolerant. If you are writing then I would still stick with some sort of level shifter like &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8745&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;. You really can't know what will happen if you use a device out of spec (could get lucky but you could also get really really unlucky). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used one of the level converters and they work great!&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-04-29T09:44:41.427" />
  <row Id="2433" PostTypeId="2" ParentId="2425" CreationDate="2010-04-29T09:50:26.593" Score="11" ViewCount="" Body="&lt;p&gt;The USB signal is not entirely differential, so it's not a great idea.  (The end-of-packet (EOP) signal is both pins pulled low, which, I believe, is why there's always noise at 1 kHz and harmonics in USB systems, since it's sending common-mode signals every 1 ms.)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;A common mode (CM) choke should be used to terminate the high speed USB&#xA;  bus if they are need to pass EMI&#xA;  testing. Place the CM choke as close&#xA;  as possible to the connector pins. See&#xA;  Section 5.1 for details. &lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Note: Common&#xA;  mode chokes degrade signal quality,&#xA;  thus they should only be used if EMI&#xA;  is a known problem.&lt;/strong&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Common mode chokes distort full speed&#xA;  and high-speed signal quality. The eye&#xA;  diagram above shows full speed signal&#xA;  quality distortion of the end of&#xA;  packet, but still within the&#xA;  specification. As the common mode&#xA;  impedance increases, this distortion&#xA;  will increase, so you should test the&#xA;  effects of the common mode choke on&#xA;  full speed and high-speed signal&#xA;  quality.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.usb.org/developers/docs/hs_usb_pdg_r1_0.pdf&quot; rel=&quot;nofollow&quot;&gt;High Speed USB Platform Design&#xA;Guidelines&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Note:&#xA;  additional filtering may be achieved by winding the 4 wires through the ferrite bead an additional turn. As&#xA;  with the use of ferrite beads in signal paths, care should be taken to insure that the signaling meets rise&#xA;  and fall times, especially the EOP signaling. EOP signaling is single ended and may be strongly affected&#xA;  by a single bead, which acts as a common mode only filter.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ti.com/sc/docs/apps/msp/intrface/usb/emitest.pdf&quot; rel=&quot;nofollow&quot;&gt;Intel EMI Design Guidelines for USB Components&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-30T20:48:38.310" LastActivityDate="2010-08-30T20:48:38.310" CommentCount="5" />
  <row Id="2434" PostTypeId="2" ParentId="2388" CreationDate="2010-04-29T09:55:52.467" Score="1" ViewCount="" Body="&lt;p&gt;I have made specifically sized enclosures using resins.  I made a silicone cast using Smooth-Sil 950 from Smooth On &lt;a href=&quot;http://www.smooth-on.com/Silicone-Rubber-an/c2_1115_1131/index.html&quot; rel=&quot;nofollow&quot;&gt;Smooth On&lt;/a&gt;.  With the silicone compound you can make negatives of the parts you want and then assemble them to form your enclosure.  Smooth on has a bunch of different resins probably with similar properties to what you are looking for, and their technical support is great if you are still not sure if the material will act the way you expect.  This way you just build one set of negatives allowing you to make as many enclosures as you want!&lt;/p&gt;&#xA;" OwnerUserId="657" LastActivityDate="2010-04-29T09:55:52.467" />
  <row Id="2435" PostTypeId="2" ParentId="2430" CreationDate="2010-04-29T10:05:35.033" Score="6" ViewCount="" Body="&lt;p&gt;The datasheets should tell you the minimum voltage required to register as a digital high for your receiver, and the minimum voltage guaranteed at the output for a high from your sender.  Just make sure they're within each other's limits.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;A TTL input signal is defined as &quot;low&quot;&#xA;  when between 0 V and 0.8 V with&#xA;  respect to the ground terminal, and&#xA;  &quot;high&quot; when between 2.2 V and 5 V&#xA;  (precise logic levels vary slightly&#xA;  between sub-types). TTL outputs are&#xA;  typically restricted to narrower&#xA;  limits of between 0 V and 0.4 V for a&#xA;  &quot;low&quot; and between 2.6 V and 5 V for a&#xA;  &quot;high&quot;, providing 0.4V of noise&#xA;  immunity.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Transistor-transistor_logic#Interfacing_problems&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Transistor-transistor_logic#Interfacing_problems&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-04-29T13:34:57.060" LastActivityDate="2010-04-29T13:34:57.060" />
  <row Id="2436" PostTypeId="2" ParentId="2388" CreationDate="2010-04-29T11:28:23.353" Score="1" ViewCount="" Body="&lt;p&gt;A bit of an answer from left-field, but the things you can do at Ponoko might be suitable, if you can design something that snaps together or can be assembled... &lt;a href=&quot;http://www.ponoko.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.ponoko.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-04-29T11:28:23.353" />
  <row Id="2437" PostTypeId="1" CreationDate="2010-04-29T13:26:09.450" Score="2" ViewCount="568" Body="&lt;p&gt;Where can I find a female RJ45 connector that can be crimped to another cable rather than being soldered to a PCB or installed in a wall or plastic enclosure?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something like this: &lt;a href=&quot;http://www.pcpartscollection.com/rjcrmatofeca.html&quot; rel=&quot;nofollow&quot;&gt;http://www.pcpartscollection.com/rjcrmatofeca.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While we're at it, I'd love to find female RJ11 and RJ12 connectors with the same property.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://ep.yimg.com/ca/I/pcpartscollection_2101_7442622&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2010-04-29T22:14:52.603" Title="RJ45 Female Crimp Connector" Tags="&lt;connector&gt;" AnswerCount="3" />
  <row Id="2438" PostTypeId="2" ParentId="2437" CreationDate="2010-04-29T13:28:17.387" Score="3" ViewCount="" Body="&lt;p&gt;One solution is a female-to-female coupler:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Belkin-R6D011-Female-Inline-Coupler/dp/B00006HTTE&quot; rel=&quot;nofollow&quot;&gt;http://www.amazon.com/Belkin-R6D011-Female-Inline-Coupler/dp/B00006HTTE&lt;/a&gt;&#xA;&lt;img src=&quot;http://g-ecx.images-amazon.com/images/G/01/ciu/b7/f5/3d95729fd7a058cdc509d010.L.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2010-04-29T13:28:17.387" />
  <row Id="2439" PostTypeId="2" ParentId="2437" CreationDate="2010-04-29T14:35:21.730" Score="2" ViewCount="" Body="&lt;p&gt;Found this at my local electronics store. RJ45 female on one side, crimps on the other. Now, online?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://msutherl.net/images/rj45.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2010-04-29T14:35:21.730" />
  <row Id="2440" PostTypeId="1" AcceptedAnswerId="2442" CreationDate="2010-04-29T15:29:45.913" Score="11" ViewCount="569" Body="&lt;p&gt;I am reading a basic electronics book: &quot;There are no Electrons: Electronics for Earthlings&quot; and I came across a clever passage about the fact that you need a closed circuit in order for current to flow.  Here is the passage I am curious about:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;This has always bothered me: If the negative terminals of batteries have excess electrons (a negative charge) and the positive terminals of batteries have too few electrons (a positive charge) and opposites attract, why can't I hook a wire between the negative side of one battery and the positive side of a different battery and get any current?  This truth is it won't work. No current will flow.  Had someone been able to explain that to me, I probably would never have written this book.&quot;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Does anyone have a straight-forward answer to this question.  Is there a better stack exchange forum to ask this on?&lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="mike" LastEditDate="2011-02-22T08:15:10.867" LastActivityDate="2011-02-22T08:15:10.867" Title="Current flow in batteries?" Tags="&lt;current&gt;&lt;batteries&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="2" />
  <row Id="2441" PostTypeId="2" ParentId="2440" CreationDate="2010-04-29T15:58:23.533" Score="3" ViewCount="" Body="&lt;p&gt;Technically, current may or may not flow when a wire is connected that way.  It all depends on whether or not there is a &lt;a href=&quot;http://www.allaboutcircuits.com/vol_1/chpt_1/4.html&quot; rel=&quot;nofollow&quot;&gt;potential difference in charges&lt;/a&gt; between those two terminals.  If the difference is small, little/no current will flow.  This holds true for any wire connected between any two terminals, anywhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, current more than likely won't (depending upon the age/use of the battery).  The reason why is because the voltage potential difference - the &quot;excess holes on the positive end&quot; and the &quot;excess electrons on the negative end&quot; - &lt;em&gt;is relative to a given battery&lt;/em&gt;.  There are excess electrons/holes on the ends of a given battery with respect to each other.  That relationship may or may not hold true between one battery's negative terminal and another's positive terminal.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-04-29T16:03:45.940" LastActivityDate="2010-04-29T16:03:45.940" CommentCount="3" />
  <row Id="2442" PostTypeId="2" ParentId="2440" CreationDate="2010-04-29T16:54:28.867" Score="20" ViewCount="" Body="&lt;p&gt;The confusion here is from the initial poor description of how a battery works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A battery consists of three things: a positive electrode, a negative electrode, and an electrolyte in between. The electrodes are made of materials that strongly want to react with each other; they are kept apart by the electrolyte.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The electrolyte acts like a filter that blocks the flow of electrons, but allows ions (positively charged atoms from the electrodes) to pass through. If the battery is not connected to anything, the chemical force is pulling on the ions, trying to draw them across the electrolyte to complete the reaction, but this is balanced by the electrostatic force-- the voltage between the electrodes. Remember-- a voltage between two points means there is an electric field between those points which pushes charged particles in one direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you add a wire between the ends of the batteries, electrons can pass through the wire, driven by the voltage. This reduces the electrostatic force, so ions can pass through the electrolyte. As the battery is discharged, ions move from one electrode to the other, and the chemical reaction proceeds until one of the electrodes is used up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thinking about two batteries next to each other, linked by one wire-- there is no voltage between the two batteries, so there is no force to drive electrons. In each battery, the electrostatic force balances the chemical force, and the battery stays at steady state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I kind of glossed over what it means for two materials to &quot;want&quot; to react with each other.  Google &quot;Gibbs free energy&quot; for more details on that. You might also google &quot;Nernst equation.&quot;)&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-04-30T00:38:34.967" LastActivityDate="2010-04-30T00:38:34.967" />
  <row Id="2443" PostTypeId="1" AcceptedAnswerId="2444" CreationDate="2010-04-29T18:29:59.780" Score="8" ViewCount="577" Body="&lt;p&gt;What does it mean to &quot;tristate a pin&quot; on a CMOS microcontroller?&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-05-05T09:37:04.563" Title="&quot;Tristate a pin&quot;" Tags="&lt;microcontroller&gt;&lt;pins&gt;&lt;cmos&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="2444" PostTypeId="2" ParentId="2443" CreationDate="2010-04-29T18:33:25.083" Score="14" ViewCount="" Body="&lt;p&gt;&quot;Tristate&quot; means a state of high impedance. A pin can either pull to 0 V (sinking current, generally), pull to 5 V (sourcing current, generally), or become high impedance, like an input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea is that if a pin is in high impedance state, it can be pulled to high or low by an external device without much current flow. You see this kind of thing on bidirectional serial lines, where sometimes a pin is an output and sometimes an input. When it's an input, it's &quot;tristated,&quot; allowing the external chip to control its logic level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does that make sense in your situation?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-29T18:33:25.083" CommentCount="8" />
  <row Id="2445" PostTypeId="2" ParentId="2430" CreationDate="2010-04-29T18:39:00.087" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.pericom.com/pdf/applications/AN066.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a useful application note on logic family interfacing. It covers driving TTL from 3.3V CMOS.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-04-29T18:39:00.087" CommentCount="1" />
  <row Id="2446" PostTypeId="1" AcceptedAnswerId="2477" CreationDate="2010-04-29T19:05:46.150" Score="3" ViewCount="482" Body="&lt;p&gt;We all have(mostly) 32-bit machines at our homes. But the 32-bit machines have a microprocessor in them. I was reading an article about the ARM Cortex. Its a 32-bit microcontroller. Now that intrigued a question inside me. Microcontrollers were made to decrease the external circuitry around a microprocessor, then the microprocessors became more powerful while microcontrollers remained in there 8 bit forms for too long a while. But now that we have 32-bit microcontrollers can't we have like a computer based around those things?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2010-05-01T12:19:47.883" LastActivityDate="2010-12-07T05:44:44.270" Title="Can you base a computer around a 32-bit microcontroller?" Tags="&lt;microcontroller&gt;&lt;computers&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="2447" PostTypeId="2" ParentId="2446" CreationDate="2010-04-29T19:10:00.153" Score="4" ViewCount="" Body="&lt;p&gt;We definitely can. The iPad, for example, uses an ARM Cortex A8 processor for its brain.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-04-29T19:10:00.153" CommentCount="1" />
  <row Id="2448" PostTypeId="2" ParentId="2440" CreationDate="2010-04-29T19:31:20.043" Score="5" ViewCount="" Body="&lt;p&gt;Forget the batteries for a second, thats just one of a thousand analogies you could use to describe voltage/current and the reason that no current flows has nothing to do with the electro-chemical properties of batteries, its far simpler.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The easiest way to think of it is this: Current will only ever flow in a loop, even in very complex circuits you can always break it down into loops of current, if there is no path for current to return to its source, there will be no current flow.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your battery example, there is no return current path so no current will flow. There is obviously a more deep physics reason for why this works but as the question asked for a simple answer I'll skip the math, google Maxwell's Equations and how they are used in the derivation of Kirchhoff's voltage law.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Batteries do make a good example for this simply because they are current sources with completely isolated grounds.  This example would be equally true of any other power source with a completely isolated &quot;ground&quot;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, this is not an easy thing to find, for instance doing this with 2 bench supplies would likely make one of the bench supplies very unhappy, but thats not because the effect is different, the difference is that the bench supplies are likely both grounded to the electrical wiring in the building and as such there is a return path for current to flow through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The water analogy for this also effective.  Think of your battery example this way:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have a water pump (battery A) connected to a pipe (the wire), and you have another water pump (battery B) connected to the same pipe (the wire) .  Now in your example the there is no return path in the system so imagine that the pipe is full of water but capped off on both ends.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You hit the power switch on the pumps, what happens? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The answer is nothing, there is no where to move the water to, the pumps don't even spin. (ignore water turbulence like effects for this analogy).   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now if you were to connect the pipe in a loop and hit the switch the pumps would spin up (voltage) and water would flow (current).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you used 2 difference speed pumps (different voltage batteries) and faced them toward each other one will over power and cause the other to spin in the wrong direction (burn out just like connecting a 9V and 6V battery in parallel).       &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you connected both pumps pointing in the same direction you would get more water pressure (voltage) because the pumps are helping each other out (2 batteries in series).&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-04-29T20:14:55.417" LastActivityDate="2010-04-29T20:14:55.417" />
  <row Id="2449" PostTypeId="1" AcceptedAnswerId="2456" CreationDate="2010-04-29T19:52:46.087" Score="3" ViewCount="134" Body="&lt;p&gt;I'm learning about superscalar CPUs and I had a question about that and data dependencies. Given the dependencies, RAW  (read after write), WAR  (write after read), WAW  (write after write), when would the ROB (re-order buffer) NOT be used?&lt;/p&gt;&#xA;" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-05-04T14:16:10.470" LastActivityDate="2010-05-17T23:17:21.623" Title="superscalar CPUs and data dependencies" Tags="&lt;cpu&gt;&lt;homework&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="2450" PostTypeId="2" ParentId="2446" CreationDate="2010-04-29T20:29:43.797" Score="10" ViewCount="" Body="&lt;p&gt;Absolutely! Take a look as almost every cell phone out there.  For example, the  Motorola Droid uses the TI OMAP ARM based microcontroller running Android on top of Linux.  Basically, a full blown computer operating system is on it and many other gadgets. On some of the products my client builds, they use FreeScale PowerQuicc I &amp;amp; II 32-bit processor/controllers that can run Linux on them.  The PowerQuicc's basically have a PowerPC core along with a separate RISC processor for handling all the peripherals in a highly configurable way.  It's a glorified microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also have to remember that years ago computers weren't running on 32-bit processors, but more like 8-bit processors (4-bits way back then) like the Commodore 64. Then they migrated to 16-bit, 32-bit, etc.  There's really not much difference between a microcontroller versus a microprocessor of equivalent bit architecture and speed.  Microcontrollers usually lack the floating point unit, but that can be made up for with fixed point math.  For example, the original Motorola 68000 processor (16-bits) was used to power those old time Macintosh computers and then spun into a microcontroller version for many embedded electronic applications for years. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to look at the role of microcontroller to understand how it is used.  Normally, when you're designing with a microcontroller, you have a highly specialized application in mind and you're trying to fit it in a smaller space than say a PC Tower. Whereas, the computer is very general purpose: crunch numbers and process user input.  When you look for a microcontroller, you're looking for one that will support the kind of interface you're building for your application.  Do you need 3 USB ports, 2 ethernet, 2 UARTs, SPI port, ATM, and CAN interface?  Some of these interfaces don't come on a typical computer such as SPI, ATM, and CAN, and a microcontroller has them built in to reduce board space.  You can look at microcontrollers as processors designed for a specific solution. &lt;/p&gt;&#xA;" OwnerUserId="625" LastEditorUserId="625" LastEditorDisplayName="" LastEditDate="2010-04-29T20:39:41.763" LastActivityDate="2010-04-29T20:39:41.763" />
  <row Id="2451" PostTypeId="1" AcceptedAnswerId="2461" CreationDate="2010-04-29T20:33:30.123" Score="5" ViewCount="240" Body="&lt;p&gt;I've seen any number of nixie tube designs on the web that use regulated 170V supplies for the nixie tube anode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wouldn't it be possible to use unregulated, half-wave rectified 170V peak power for this? Yes, the illumination wouldn't be continuous, it would in fact flicker at 60Hz, but this is fast enough that it shouldn't matter to the human eye. The brightness would vary with line voltage, but since that doesn't usually vary more than a couple of percent, this effect also should go unnoticed to the casual observer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The up-side of this would be that you could dispense with the relatively costly regulated supply, and use a simple 1:1 isolation transformer and a single rectifier diode to get the anode supply, since sqrt(2) * 120 gives very close to 170. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In fact, if you used SCR's to pull the cathodes to ground, you could do away with the rectifier, because when the AC reverses direction, the SCR will cut off just like a diode. A single current limiting resistor should suffice if placed on the anode side of the tube.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would it work? If not, why not?&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-05-13T00:30:06.937" LastActivityDate="2011-05-13T00:30:06.937" Title="Isn't it overkill to use a regulated power supply for a nixie tube?" Tags="&lt;nixie&gt;&lt;power-supply&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="2452" PostTypeId="1" AcceptedAnswerId="2466" CreationDate="2010-04-29T21:01:11.423" Score="4" ViewCount="170" Body="&lt;p&gt;Does anyone have a circuit that will trigger a strobe light to flash in response to a TTL logic signal? Specifically, if I have a strobe circuit capable of flashing 1000 times per second, it seems like it should be possible, under logic control, to get pairs of flashes at say, 5 msec apart, with the pairs separated by much longer intervals, e.g., 100 msec.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most strobe circuits I've seen use some kind of relaxation oscillator to periodically trigger the flash tube. These are fine if all you want are single flashes at a not-too-specific rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know there are camera flash units that will flash in response to a switch closure, but these don't usually recharge fast enough to put two flashes together in the space of 10msec or less. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My hunch is that if I dump the charge from a small cap into the primary of a trigger transformer, through a switching device of some kind, the tube can be made to flash. The problem is dumping the cap charge quickly enough to get the trigger spike, and not toast the semiconductor with the backlash from the transformer input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other concern is that since the trigger circuit basically produces nasty voltage spikes, how to go about isolating the control logic from the spikes.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-04-30T22:57:36.117" Title="logic triggerable strobe light circuit" Tags="&lt;logic&gt;&lt;analog&gt;&lt;interface&gt;" AnswerCount="2" />
  <row Id="2453" PostTypeId="2" ParentId="2211" CreationDate="2010-04-29T21:11:59.950" Score="4" ViewCount="" Body="&lt;p&gt;Not sure you need the diode in series with the motor the way you've shown. All it's going to do is drop some voltage and generate heat (unless it's an LED).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You probably do want a diode in parallel with the motor, oriented with the cathode toward the positive supply. The diode will clamp any high voltage excursions caused by inductance in the motor, so that the collector of the pass transistor will never see a voltage higher than one diode drop above the supply voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you should probably have a small capacitor with good high-frequency response tied directly across the motor, to cut down on EMI caused by arcing in the brushes. Usually 0.01uF or 0.1uF disc ceramics are used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Larger transistors sometimes take a bit more drive, so consider the resistor from PB0 to the base of the TIP 122. Not sure what the specs are for the TIP 122, but you want to make sure that when the level on PB0 is at its high state, the collector should be very close to ground, not more than about 0.2V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, how big is this motor, and how big is the battery? Nine-volt alkaline batteries aren't known for having a lot of current capability, so I'm assuming the motor is quite small. You should be able to take a wire and short across the collector and emitter of the transistor w/o harming anything, and if you do, the motor should turn.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-04-29T21:19:55.457" LastActivityDate="2010-04-29T21:19:55.457" CommentCount="1" />
  <row Id="2454" PostTypeId="2" ParentId="2449" CreationDate="2010-04-29T21:21:24.520" Score="1" ViewCount="" Body="&lt;p&gt;It's been a long time since I took a course in computer architecture so I'm not even going to attempt to answer your question from memory. However I do remember talking extensively about super scalars and the textbook we used was great.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/gp/product/B001KYEI0I/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&amp;amp;pf_rd_s=lpo-top-stripe-1&amp;amp;pf_rd_t=201&amp;amp;pf_rd_i=0123704901&amp;amp;pf_rd_m=ATVPDKIKX0DER&amp;amp;pf_rd_r=122VJHM98MJBB4BT1TQP&quot; rel=&quot;nofollow&quot;&gt;Computer Architecture: A Quantitative Approach, 4th Edition &#xA;~ David A. Patterson, John L. Hennessy&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-04-29T21:21:24.520" />
  <row Id="2455" PostTypeId="2" ParentId="2103" CreationDate="2010-04-29T21:47:10.647" Score="1" ViewCount="" Body="&lt;p&gt;Anything more than maybe 100mA of current. You could probably push an entire amp through if you had to, but with just those little spring-grippers for contact, you could get some hot spots.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mainly though, if your circuit can't take noise introduced by loose wires, a breadboard is not the right medium. When I see a blog with an entire 8-bit micro wired up on a breadboard, I have to marvel at the sheer tenacity involved.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-04-29T21:47:10.647" CommentCount="1" />
  <row Id="2456" PostTypeId="2" ParentId="2449" CreationDate="2010-04-29T21:57:53.430" Score="1" ViewCount="" Body="&lt;p&gt;It's been a while for me, too, so take this with a grain of salt.  But I don't see why you would need the ROB for WAW and WAR.  Register renaming can get around those dependencies while executing in-order.  Only for RAW would the CPU potentially have to wait for the result, and so CPU would go searching through the instruction window for something else to execute out-of-order.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-04-29T21:57:53.430" />
  <row Id="2457" PostTypeId="2" ParentId="893" CreationDate="2010-04-29T22:12:14.183" Score="2" ViewCount="" Body="&lt;p&gt;If you want the relay to close when the DS2406 output closes:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;replace the NPN transistor with an equivalent PNP,&#xA;tie the PNP's base to the +12V supply through maybe 10k to 50k ohms.&#xA;tie the PNP's base to the DS2406 output through maybe 4.7k to 5.1k ohms.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;When the DS2406 is high impedance, the first resistor biases the PNP off. When the DS2406 output goes to zero, it pulls about 2mA of current through the base of the transistor and the relay should close.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want the relay to close when the DS2406 output opens:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;tie the base of the NPN transistor to +12V through about 5k ohms.&#xA;connect the output of the DS2406 directly to the base of the NPN&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;When the DS2406 is high-Z, the resistor should dump about 2mA into the NPN, turning it, and the relay both on. When the DS2406 goes to ground, it will 'steal' that 2mA from the base of the NPN and turn it and the relay off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The above resistor values are all calculated assuming that 1.5 or 2mA of base current is enough to drive the transistor into saturation. The collector-emitter drop should either be the full supply voltage in the OFF state, or something around 0.2V in the ON state. If not, resistor values should be changed.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-04-29T22:12:14.183" />
  <row Id="2458" PostTypeId="2" ParentId="2440" CreationDate="2010-04-29T22:13:25.850" Score="3" ViewCount="" Body="&lt;p&gt;Let's say you have AA batteries, with 1.5 V each.  Further, let's label them battery A and battery B.  If you hook A+ to B-, what you actually get is a 3 V difference across A- to B+.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;B+  -------------------&#xA;|                     |&#xA;B- _ A+  --           | 3V&#xA;     |    | 1.5 V     |&#xA;     A-  --------------&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;When you hook B- to A+, they are both at the same potential (they're hooked up with a wire, after all).  B+ is 1.5V higher than this potential, and A- is 1.5V lower.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's important to remember that a voltage is not an &lt;strong&gt;absolute&lt;/strong&gt; value.  It's a &lt;strong&gt;relative&lt;/strong&gt; value.  The B- _ A+ wire will be at one potential, and B+ and A- are &lt;strong&gt;relative&lt;/strong&gt; to that potential.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-04-29T22:13:25.850" CommentCount="3" />
  <row Id="2459" PostTypeId="2" ParentId="2437" CreationDate="2010-04-29T22:14:52.603" Score="3" ViewCount="" Body="&lt;p&gt;@msutherl I wouldn't exactly call what you found in the local electronics store a crimp connector. Technically that would be a punch down connection. This wouldn't have the same strain resistance that true crimped on connector would have.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2010-04-29T22:14:52.603" CommentCount="1" />
  <row Id="2460" PostTypeId="2" ParentId="332" CreationDate="2010-04-29T22:28:33.573" Score="1" ViewCount="" Body="&lt;p&gt;If your output is either sourcing current or sinking it, it means the device is actively trying to drive the voltage on that output to one of the supply rails; the positive supply when sourcing, the ground/return when sinking. I.e., that the output is at a low impedance relative to one of the supply lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A floating line is one that has a &lt;em&gt;high&lt;/em&gt; impedance to the supply/ground system. Floating inputs can behave a bit like little antennas, and pick up random noise from your circuit. This is why unused inputs should either be pulled to +V or ground.  Most inputs are high impedance anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're connecting standard CMOS outputs to the next devices inputs, there isn't too much to worry about, as the CMOS output stage will have the next device's input driven hard to one or the other logic levels. The output stage has two transistors, one that can drive the output to the +V rail, another that can pull it to ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A problem you might encounter, though, is when you have an 'open collector' (OC) or 'open drain' (OD) output stage. These devices basically only have the capability to pull the output to ground. When the output is at logic low, zero volts, the next device's input will be held at ground as the output sinks current. But when the output needs to be a logic '1', the output transistor shuts off, leaving you with .. a floating input. So with this kind of connection, you usually see a pull-up resistor to ensure that the voltage on the input doesn't wag around in response to whatever EMI is at hand. The resistor value is usually toward the smaller end of what you can get away with to not overwhelm the current sink capability of the OC/OD output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other common situation is 'tri-state' outputs. These are devices that have two transistor output stages, so they can drive '0' or '1' logic levels without aid of a pull-up resistor, but internally to the device there are controls that can turn off BOTH output transistors, resulting in the 'hi-Z' output condition. If you connect a single tri-stateable output to a single input, and conditions allow the output to go into tri-state mode, you get another case of floating input. You'd probably see a pull-up resistor under these circumstances too, for the same reasons as for the OC device. However, tri-stateable outputs are most often seen in 'bus' situations, where one of several devices asserts the logic level, and all others sit in their hi-Z state. Examine the schematic and there's usually a pull-up resistor on that line somewhere.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-04-29T22:28:33.573" />
  <row Id="2461" PostTypeId="2" ParentId="2451" CreationDate="2010-04-30T07:04:39.990" Score="6" ViewCount="" Body="&lt;p&gt;Sure, it would work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used a slight step-up transformer (120v to 130v) to drive a nixie supply. It also had a 6.3v filament tap which was really convenient for the 5v ttl logic supply. However, I used a full-bridge rectifier followed by a electrolytic capacitor to filter both supplies. Here's why I would recommend that setup over what you're suggesting:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;It's cheap. For $1.25, you can have decent regulation of your supply voltage. I'm assuming the isolation transformer is already accounted for.&lt;/li&gt;&#xA;&lt;li&gt;You can/will see the nixie tubes flicker at 60 Hz.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The motivation for fancier regulation circuits is to protect the nixie tubes. They are usually the focal point of any design using them, so it's in the designer's best interest to make sure nothing bad happens to the tubes. I've seen people drive nixie tubes with expensive regulated bench supplies, and read about people using unisolated circuits. Somewhere in that range is a cost-benefit-paranoia tradeoff. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-04-30T07:04:39.990" CommentCount="5" />
  <row Id="2463" PostTypeId="2" ParentId="2452" CreationDate="2010-04-30T14:10:02.570" Score="0" ViewCount="" Body="&lt;p&gt;Not having looked at strobe light circuitry, I would say look into solid state relays or optoisolators as  starting point and see how to fit them into the design.&lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2010-04-30T14:10:02.570" />
  <row Id="2464" PostTypeId="1" AcceptedAnswerId="2465" CreationDate="2010-04-30T19:59:08.520" Score="7" ViewCount="226" Body="&lt;p&gt;On a VGA connector, there are numerous 'ground' pins. Three of these are Red return, Green return and Blue return; But why does each color component have its own ground pin?&lt;/p&gt;&#xA;" OwnerUserId="733" LastActivityDate="2010-05-11T05:42:54.240" Title="What are 'return' pins?" Tags="&lt;vga&gt;&lt;pins&gt;" AnswerCount="2" />
  <row Id="2465" PostTypeId="2" ParentId="2464" CreationDate="2010-04-30T20:13:59.817" Score="12" ViewCount="" Body="&lt;p&gt;Probably so that the voltages induced by the ground currents don't interfere with each other.  Copper is not a perfect conductor, so a current transmitted through copper results in a small voltage change.  If they all returned through the same wire, the ground voltage would be affected by all three signals, and allow the colors to bleed into each other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also this would allow each pair of wires to be tightly twisted, so that the magnetic fields created from the currents going up one and down the other cancel each other out, reducing emissions.  If they all used a common ground wire, there would be more loop space between them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh yeah.  Impedance is important, too, at video frequencies. The pairs need to have a given characteristic impedance so that there are no reflections when the signal gets to the monitor.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-01T03:13:01.823" LastActivityDate="2010-05-01T03:13:01.823" CommentCount="3" />
  <row Id="2466" PostTypeId="2" ParentId="2452" CreationDate="2010-04-30T22:57:36.117" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://sound.westhost.com/project65.htm&quot; rel=&quot;nofollow&quot;&gt;This circuit&lt;/a&gt; uses an SCR to trigger the strobe.  There is an optoisolator between the SCR and the trigger circuitry, so as long as the SCR is rated at a high enough voltage (400V in this case), you should be able to easily trigger the SCR through the optoisolator using TTL voltages without problems.&lt;/p&gt;&#xA;" OwnerUserId="544" LastActivityDate="2010-04-30T22:57:36.117" />
  <row Id="2467" PostTypeId="1" AcceptedAnswerId="2468" CreationDate="2010-05-01T01:06:39.827" Score="15" ViewCount="841" Body="&lt;p&gt;I'm wondering what distributors exist for DIY electronics supplies that I don't know about.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For large distributors, I know about Digikey, Mouser, and Newark, plus Jameco for surplus stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For smaller firms that cater to the hobbyist market, I know about Sparkfun and Adafruit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I'm most interested in places that will ship to Boston, USA, but answers for the rest of the globe are certainly welcome.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-11-03T08:40:04.923" LastActivityDate="2010-11-03T17:12:36.150" CommunityOwnedDate="2010-05-01T01:06:39.827" ClosedDate="2011-04-14T14:27:16.087" Title="Good distributors for electronic components?" Tags="&lt;components&gt;&lt;distributors&gt;" AnswerCount="15" CommentCount="1" FavoriteCount="5" />
  <row Id="2468" PostTypeId="2" ParentId="2467" CreationDate="2010-05-01T01:28:31.533" Score="11" ViewCount="" Body="&lt;p&gt;I ship to Boston ( and live here too ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Besides the ones you mention I use Allied, Future, Arrow and Avnet. What I usually do is type the mfg pn into findchips and it searches the 20 or so distributor's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually I end up with Mouser (often better for semis, wire) or Digikey (better for passives, tools) since for one or two part numbers the shipping costs negate the price advantages. Newark can have some good deals in the clearance departments. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget the MIT Swap ;)&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-03T17:12:36.150" LastActivityDate="2010-11-03T17:12:36.150" CommunityOwnedDate="2010-05-01T01:28:31.533" CommentCount="5" />
  <row Id="2469" PostTypeId="2" ParentId="2467" CreationDate="2010-05-01T01:38:36.180" Score="3" ViewCount="" Body="&lt;p&gt;Here are a couple of vendors I've found useful&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;http://www.allelectronics.com/&#xA;http://www.bgmicro.com/&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-01T01:38:36.180" CommunityOwnedDate="2010-05-01T01:38:36.180" CommentCount="3" />
  <row Id="2470" PostTypeId="1" CreationDate="2010-05-01T03:55:24.317" Score="1" ViewCount="258" Body="&lt;p&gt;I just bought a &lt;a href=&quot;http://www.amazon.com/CSF-3-Super-Feeder-Stand-Timer/dp/B000NOLD18&quot; rel=&quot;nofollow&quot;&gt;cat feeder&lt;/a&gt; from the united states, and brought it to Israel. Israel has 220V power sockets, and the device (that came with the timer below) doesn't fit, obviously.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is I don't know which adapter to buy. I guess we have the standard European sockets, but the first converter I bought simply wouldn't fit because it had room for only two pins, and the timer in the picture has a third pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone help me find which adapter I need in order to plug the timer in the picture to Israel (= European) power output?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://sphotos.ak.fbcdn.net/hphotos-ak-sjc1/hs336.snc3/29405_360690984158_690184158_3248527_3179436_n.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="750" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-01T04:58:19.063" LastActivityDate="2010-05-01T11:05:00.383" CommunityOwnedDate="2010-09-10T08:20:13.227" Title="Help me find an adapter USA --&gt; Israel" Tags="&lt;power&gt;" AnswerCount="2" />
  <row Id="2472" PostTypeId="2" ParentId="2470" CreationDate="2010-05-01T10:29:29.470" Score="3" ViewCount="" Body="&lt;p&gt;Yeah Israel is not a standard European socket it's an H type (SI 32 Israel), European plugs only have two pins and they're not angled, the cat feeder looks like it has a B type mains plug (NEMA 5-15 USA 3 pin)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find all the different types on &lt;a href=&quot;http://en.wikipedia.org/wiki/Mains_power_around_the_world&quot; rel=&quot;nofollow&quot;&gt;wikipedia&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing about travel plug adaptors is it's best to buy them in the country you intend to use them in, because they are generally cheaper and easier to find, try your local airport or tourist shop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not here's one on &lt;a href=&quot;http://cgi.ebay.com/USA-UK-Euro-AUS-Israel-Travel-Adapter-AC-Power-Plug-/260594120059?cmd=ViewItem&amp;amp;pt=LH_DefaultDomain_0&amp;amp;hash=item3cac9eb57b&quot; rel=&quot;nofollow&quot;&gt;Ebay&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-05-01T11:05:00.383" LastActivityDate="2010-05-01T11:05:00.383" CommentCount="1" />
  <row Id="2473" PostTypeId="2" ParentId="2470" CreationDate="2010-05-01T10:42:55.077" Score="4" ViewCount="" Body="&lt;p&gt;Well, I think you have three problems.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The timer and cat feeder are not rated for wide voltage operation. Both parts are only designed for 120 volt operation. Simply plugging it in to a 220 volt outlet using a plug adapter will result in a dead timer and cat feeder. I'm not sure if you knew this, but I'm not assuming anything. At a minimum, you will need a voltage converter of some sort.&lt;/li&gt;&#xA;&lt;li&gt;The round bottom pin is the ground terminal of the socket. You could probably bypass it, although if your sockets have a ground, its best to connect it. &lt;/li&gt;&#xA;&lt;li&gt;The timer probably uses the ac frequency as a time standard. I'm guessing your power is 50 Hz, so the timer would run slower. If this is the case, that's going to be hard to fix.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I would recommend getting a lamp timer in your country, and then using a voltage converter to run the cat feeder. In a pinch, removing the ground pin will make things fit, but it's less safe.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-05-01T10:42:55.077" />
  <row Id="2474" PostTypeId="2" ParentId="2446" CreationDate="2010-05-01T11:12:49.477" Score="2" ViewCount="" Body="&lt;p&gt;It worth noting that the mentioned ARMs (OMAP and A8) are microprocessors without Flash memory and RAM (not totally true for the A8). The Cortex-M3 microcontroller is smaller, has small built-in memory and easier access to peripherals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is quite a large gap (performance- and feature-wise) between them.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-05-01T11:12:49.477" CommentCount="2" />
  <row Id="2475" PostTypeId="2" ParentId="1482" CreationDate="2010-05-01T11:19:03.863" Score="1" ViewCount="" Body="&lt;p&gt;IMHO the easiest way is to use an AT90USB or LPC1343. The latter has mass-storage device firmware stored in ROM so you only need to supply some details for the device descriptor and 2 or 3 Flash access procedures.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2010-05-02T16:44:07.153" LastActivityDate="2010-05-02T16:44:07.153" />
  <row Id="2476" PostTypeId="2" ParentId="2467" CreationDate="2010-05-01T17:07:41.297" Score="7" ViewCount="" Body="&lt;p&gt;For Europe: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://farnell.com/&quot; rel=&quot;nofollow&quot;&gt;Farnell&lt;/a&gt; &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://mouser.com&quot; rel=&quot;nofollow&quot;&gt;Mouser&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;https://www1.elfa.se/elfa3~eu_en/index.jsp?ignorecookie=true&quot; rel=&quot;nofollow&quot;&gt;Elfa&lt;/a&gt; (Sells to: Sweden, Norway, Finland, Denmark, Poland, Estonia, Latvia, Lithuania, Ukraine)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-05-01T17:07:41.297" CommunityOwnedDate="2010-05-01T17:07:41.297" />
  <row Id="2477" PostTypeId="2" ParentId="2446" CreationDate="2010-05-01T17:31:50.030" Score="6" ViewCount="" Body="&lt;p&gt;It depends on how you define 'computer'..  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the smaller end of the scale, what you might call traditional micro-controllers, you don't get memory management and seldom see any more RAM than the tiny amount embedded in the chip. I'll admit to very little knowledge about the architecture of the more capable micro-controllers now available, but the existence (or lack thereof) of these features is probably key to distinguishing between a device best suited for embedded applications or for general purpose computation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By 'memory management' I'm referring to the capability to run programs in virtual address spaces and map these to the physical RAM available in the system, a function carried out by what's usually called a memory management unit (MMU).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without an MMU, if you try to run multiple processes, all of them are forced to share a single address space, and this means that unless all processes involved adhere to your memory allocation scheme, one process can very easily crash another. So if you're in total control of designing all the processes, as with an embedded system, this isn't as much of a concern. However, if you're trying to support general purpose computation, you can't guarantee that all the code that will be executed will respect the memory allocation scheme, and the system will be rather fragile.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lack of RAM is also not much of a problem for embedded systems, (1) because there's usually lots of flash, and (2) not being a general purpose computer means you don't have to worry about running un-anticipated programs at the behest of a user. You know ahead of time the sum total of all the software that will run on the system, and only need RAM for variables for that software. When you try to make your system into a general purpose computer, though, users are going to expect to be able to run whatever suits them, and this requires RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, it's absolutely fine to do general purpose computation on devices without an MMU, and not much memory. The original 128K RAM, 8088 based (16 bit) IBM PC got away with this, as long as you only needed to run one program at a time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if you want to define 'computer' as something like 1982 technology, the answer is definitely yes. Or if you have a closed system where you can mitigate the problems of not having an MMU and/or much ram (e.g., cell phones) by carefully controlling the design of the software, also yes. Or, if your micro-controller has a built-in MMU and gobs of RAM (or can accommodate these externally), you should be able to construct a system that more resembles current computers.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-01T17:31:50.030" />
  <row Id="2478" PostTypeId="1" CreationDate="2010-05-01T19:24:23.140" Score="4" ViewCount="204" Body="&lt;p&gt;How would I add support for a new MSP430 processor type on MSP430-gcc? E.g. msp430x5xx series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand I must produce the relevant &lt;em&gt;.h/.o&lt;/em&gt; files but how do I generate/integrate those in msp430-gcc ?&lt;/p&gt;&#xA;" OwnerUserId="329" LastEditorUserId="329" LastEditorDisplayName="" LastEditDate="2010-05-01T21:03:11.927" LastActivityDate="2010-07-30T15:29:59.400" Title="Support for MSP430x5xx processors on MSP430-gcc" Tags="&lt;msp&gt;&lt;msp430&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="2479" PostTypeId="2" ParentId="2467" CreationDate="2010-05-01T19:44:21.563" Score="4" ViewCount="" Body="&lt;p&gt;In the UK &lt;a href=&quot;http://bitsbox.co.uk/&quot; rel=&quot;nofollow&quot;&gt;http://bitsbox.co.uk/&lt;/a&gt;&#xA;(otherwise there's just eBay or Maplins)&lt;/p&gt;&#xA;" LastActivityDate="2010-05-01T19:44:21.563" CommunityOwnedDate="2010-05-01T19:44:21.563" CommentCount="1" />
  <row Id="2480" PostTypeId="2" ParentId="2467" CreationDate="2010-05-01T21:07:50.427" Score="6" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.seeedstudio.com/depot/&quot; rel=&quot;nofollow&quot;&gt;Seeeeeed Studio&lt;/a&gt; has some good cheap stuff. They are similar to Sparkfun in products offered. Usually a few $ cheaper than sparkfun, but it ships from china so you have to wait a bit. They also have an interesting inexpensive PCB service.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.nkcelectronics.com/&quot; rel=&quot;nofollow&quot;&gt;NKC Electronics&lt;/a&gt; is another one of a similar sort.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then there's &lt;a href=&quot;http://goldmine-elec.com/&quot; rel=&quot;nofollow&quot;&gt;Electronic Goldmine&lt;/a&gt;, similar to all-electronics as mentioned above, has lots of random surplus components, sometimes very good prices, sometimes not.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-05-01T21:07:50.427" CommunityOwnedDate="2010-05-01T21:07:50.427" />
  <row Id="2481" PostTypeId="2" ParentId="2467" CreationDate="2010-05-01T21:25:27.540" Score="6" ViewCount="" Body="&lt;p&gt;Here in the UK we have &lt;a href=&quot;http://rswww.com&quot; rel=&quot;nofollow&quot;&gt;RS&lt;/a&gt;, &lt;a href=&quot;http://www.farnell.com&quot; rel=&quot;nofollow&quot;&gt;Farnell&lt;/a&gt; and &lt;a href=&quot;http://www.rapidonline.com/&quot; rel=&quot;nofollow&quot;&gt;Rapid&lt;/a&gt;, as well as many others.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-05-01T21:25:27.540" CommunityOwnedDate="2010-05-01T21:25:27.540" CommentCount="1" />
  <row Id="2482" PostTypeId="1" AcceptedAnswerId="2489" CreationDate="2010-05-01T23:28:09.513" Score="4" ViewCount="403" Body="&lt;p&gt;Hello!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to run both USB Host and USB Device controllers on top of an AVR (ATMega64)?&#xA;Specifically, what I'm looking for is to receive data from a usb keyboard, and simultaneously sending keystrokes to a PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I've seen, both VUSB &amp;amp; LUFA stacks support USB host modes, but they work with a single usb port only.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help is appreciated!&#xA;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="752" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-24T21:29:33.397" LastActivityDate="2010-08-24T21:29:33.397" Title="Dual Role USB device on AVR" Tags="&lt;usb&gt;&lt;usb-device&gt;&lt;host&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="2483" PostTypeId="2" ParentId="2482" CreationDate="2010-05-02T02:42:04.793" Score="4" ViewCount="" Body="&lt;p&gt;You might consider using a PS/2 keyboard, they are simple to interface with, it's basically just a serial protocol. Then you can still use USB in Device mode to connect to the host PC.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-05-02T02:42:04.793" CommentCount="3" />
  <row Id="2484" PostTypeId="2" ParentId="2446" CreationDate="2010-05-02T03:29:49.173" Score="1" ViewCount="" Body="&lt;p&gt;Recent netbooks are ARM-based: &lt;a href=&quot;http://www.google.com/search?client=safari&amp;amp;rls=en&amp;amp;q=arm+netbook&amp;amp;ie=UTF-8&amp;amp;oe=UTF-8&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/search?client=safari&amp;amp;rls=en&amp;amp;q=arm+netbook&amp;amp;ie=UTF-8&amp;amp;oe=UTF-8&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2010-05-02T03:29:49.173" CommentCount="1" />
  <row Id="2485" PostTypeId="1" CreationDate="2010-05-02T10:04:08.787" Score="2" ViewCount="120" Body="&lt;p&gt;I made a google custom search engine: &#xA;&lt;a HREF=&quot;http://www.google.com/cse/home?cx=009577865717141731876%3Agtymb6odhyk&amp;amp;auth=DQAAAOMAAABJPdvJt1AVHRfLMw2AEQaQ7KGrnEvJGzuuUqanqSy941B2zxC4mHKH9O3puT_e6EtoHBFRInW0JjWjAyq04BHD99PeDNr28EdUPphEOvbfxIcpLqH5FK2wNDGjnZMPTgLle1mLGgddCYBh9Yp8im2lF_1Ezgt_aZBOKn_x_xOfwsabLuAF7IHf261KPQlxy9_YjApOYtYThqhCs7ONuKWgAYj21fYxXnF1bNq594mYIXYPb-t6IDvw1xl73JItXV_SFzp89TCvVukDn0y5t9sICCCpPrURVVe5zYU0tmgCRH4m0-KAakR7O_rbyDGSJgs&quot; rel=&quot;nofollow&quot;&gt;robot cse&lt;/a&gt;. Any sites I should add to the list.&lt;br&gt;&#xA; &lt;a href=&quot;http://forum.microchip.com/&quot; rel=&quot;nofollow&quot;&gt;http://forum.microchip.com/&lt;/a&gt;    &lt;br&gt;&#xA; &lt;a href=&quot;http://www.avrfreaks.net&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net&lt;/a&gt;    &lt;br&gt;&#xA; &lt;a href=&quot;http://www.societyofrobots.com/robotforum/&quot; rel=&quot;nofollow&quot;&gt;http://www.societyofrobots.com/robotforum/&lt;/a&gt;    &lt;br&gt;&lt;/p&gt;&#xA;" OwnerUserId="754" LastActivityDate="2010-05-02T15:18:21.373" CommunityOwnedDate="2010-05-05T23:02:13.490" Title="Robotics custom search engine" Tags="&lt;robotics&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="2486" PostTypeId="2" ParentId="2467" CreationDate="2010-05-02T11:02:57.767" Score="6" ViewCount="" Body="&lt;p&gt;In Australia I get all my electronic components from&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://littlebirdelectronics.com&quot; rel=&quot;nofollow&quot;&gt;Little Bird Electronics&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://jaycar.com&quot; rel=&quot;nofollow&quot;&gt;Jaycar&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://freetronics.com&quot; rel=&quot;nofollow&quot;&gt;Freetronics&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also worth mentioning&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://au.farnell.com/&quot; rel=&quot;nofollow&quot;&gt;Farnell Australia&lt;/a&gt; (free shipping on internet orders)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;https://www.soanarplus.com/&quot; rel=&quot;nofollow&quot;&gt;Soanar Plus&lt;/a&gt; (relative of &amp;amp; cheaper than Jaycar, but not a retail outlet)&lt;/p&gt;&#xA;" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-05-13T14:48:14.653" LastActivityDate="2010-05-13T14:48:14.653" CommunityOwnedDate="2010-05-02T11:02:57.767" CommentCount="2" />
  <row Id="2488" PostTypeId="2" ParentId="2485" CreationDate="2010-05-02T15:18:21.373" Score="3" ViewCount="" Body="&lt;p&gt;Perhaps &lt;a href=&quot;http://forums.makezine.com/&quot; rel=&quot;nofollow&quot;&gt;http://forums.makezine.com/&lt;/a&gt; and &lt;a href=&quot;http://electronics.stackexchange.com/&quot; rel=&quot;nofollow&quot;&gt;http://electronics.stackexchange.com/&lt;/a&gt; ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe the Make forums are too broad in their coverage?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-02T15:18:21.373" />
  <row Id="2489" PostTypeId="2" ParentId="2482" CreationDate="2010-05-02T16:35:14.657" Score="1" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;I don't think that V-USB supports host (OTG) mode and LUFA host mode will require at least an AT90USB646 which is quite expensive.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I don't know about a cheap micro that has 2 USB port but you may try using two. Just connect them via an UART and exchange the needed information.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;That said, davr is probably right that using a PS/2 keyboard would be simpler.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-05-02T16:35:14.657" />
  <row Id="2490" PostTypeId="1" AcceptedAnswerId="2503" CreationDate="2010-05-02T16:51:36.950" Score="3" ViewCount="187" Body="&lt;p&gt;Are the control signals for a given instruction generated within a single cycle &#xA;for the pipelined, the multicycle as well as the single-cycle implementations of the MIPS32 datapath?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think they are for the single cycle implementation but not for the pipelined and multicycle implementation.&lt;/p&gt;&#xA;" LastActivityDate="2010-05-03T18:46:24.633" Title="When are MIPS control signals generated?" Tags="&lt;cpu&gt;&lt;controller&gt;" AnswerCount="1" />
  <row Id="2491" PostTypeId="1" AcceptedAnswerId="2494" CreationDate="2010-05-02T22:22:23.023" Score="4" ViewCount="228" Body="&lt;p&gt;Suppose I connect a logic analyzer to D+ or D- line, will I see a valid data?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="752" LastActivityDate="2010-05-03T19:43:51.150" Title="Is it possible to passively listen on low speed USB communication?" Tags="&lt;usb&gt;&lt;logic-analyzer&gt;" AnswerCount="3" />
  <row Id="2492" PostTypeId="2" ParentId="2491" CreationDate="2010-05-03T00:24:32.753" Score="3" ViewCount="" Body="&lt;p&gt;Yes, it should work. Ideally you'd use a logic analyzer that can capture &amp;amp; decode USB traffic, otherwise you will have trouble finding the data you are interested in.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-05-03T00:24:32.753" />
  <row Id="2493" PostTypeId="2" ParentId="2337" CreationDate="2010-05-03T00:24:44.690" Score="1" ViewCount="" Body="&lt;p&gt;Op-amps often (always?) use a current-source driven differential amplifier as the input stage, and it is this that confers the high-impedance to the input of the op-amp. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A current source provides a fixed current, regardless of the voltage across it. So the impedance of a current source is the ratio of change in voltage divided by the resulting change in current. Since for a current source, current doesn't change, the ideal current source therefore has infinite impedance. Real world current sources do pretty well, 10's of megohms being easily achieved.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-03T00:24:44.690" />
  <row Id="2494" PostTypeId="2" ParentId="2491" CreationDate="2010-05-03T00:25:54.180" Score="4" ViewCount="" Body="&lt;p&gt;I'm not certain about this, but I believe that if you look at the differential voltage between the two lines, you will see data, but it will be NRZI encoded. This means that the bits are encoded by whether the bus level changes or not. Change (in either direction) means 0 and no change (for one bit-time) means 1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe there are also CRCs and other signaling bytes at the beginning and end of packets.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-03T00:25:54.180" CommentCount="3" />
  <row Id="2495" PostTypeId="1" AcceptedAnswerId="2496" CreationDate="2010-05-03T00:31:08.117" Score="2" ViewCount="124" Body="&lt;p&gt;I'm designing a robot gripper that needs to pickup an electronic device (the size of half a laptop) and move it around. The problem is that when the device gets picked up, I need to establish a USB connection (the device has one of those small USB connectors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking about designing a PCB with an SMD right angle USB connector in one side and a few fat pads on the other. I would manually attach the connector to the device before the robot picks it up, and I would have some sort of spring on the gripper to make the USB connection. Something like the ones used in the SD cards, but bigger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Question is: do you have another suggestion or know what component to use to make the electrical contact?&lt;/p&gt;&#xA;" OwnerUserId="1267" LastActivityDate="2011-05-17T12:47:49.783" Title="What type of connector to use for pressure contact?" Tags="&lt;connector&gt;&lt;usb&gt;&lt;robotics&gt;" AnswerCount="1" />
  <row Id="2496" PostTypeId="2" ParentId="2495" CreationDate="2010-05-03T01:48:52.827" Score="4" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Mill-max makes spring probe strips and buttons (See &lt;a href=&quot;http://www.mill-max.com&quot; rel=&quot;nofollow&quot;&gt;http://www.mill-max.com&lt;/a&gt; )&#xA;If you had two little PCBs you could put use the spring probes to hit large &#xA;pads. You would need to apply constant pressure to insure the contacts&#xA;stay mated. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;There are conductive elastomer strips in a variety of sizes. The elastomer&#xA;would connect two PCB pads. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Spring probes for in-circuit testing could work too. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I would look at the Mill-max contact strips first.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:47:49.783" LastActivityDate="2011-05-17T12:47:49.783" CommentCount="3" />
  <row Id="2497" PostTypeId="2" ParentId="2180" CreationDate="2010-05-03T02:34:52.483" Score="4" ViewCount="" Body="&lt;p&gt;How are you measuring this 2V? From context it sounds like you may be using a multimeter rather than an oscilloscope. To really see what's going on in a circuit like this, the oscilloscope is the instrument of choice. You would be able to see from the symmetry of the charge and discharge curves that the the rates are indeed the same.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But it sounds like you are using a meter, and with a device that just gives you a number, understanding what's going on requires some interpretation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems reasonable to interpret the input signal you described as a 5V peak-to-peak square wave riding on a 2.5V DC offset. So if you use a DC measuring device, you might expect to measure this 2.5V DC level across the capacitor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your measuring device happens to be a DVM, you can reasonably ignore the effects of the meter on the circuit. Even cheap digital meters have megohms of impedance and will not load down the k-ohm scale circuit under test. However, these kinds of meters vary widely in their ability to make sense of time-varying inputs. Some are good just for checking batteries. Some will give you a fair DC reading in the presence of sinusoidal AC, but not with more complex AC. Some will give you true RMS no matter what the shape of the waveform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And if you are measuring using an old mechanical-movement type meter, you have to bear in mind that, as volt-meters, these meters are equivalent to a few k-ohms, maybe 10's of k-ohms at best. Hooking this kind of a meter into the circuit you describe will very certainly load the circuit and change its behavior significantly. You will get readings to be sure, but you have to interpret these knowing how the circuit is affected. In the case of the R-C setup you describe, this kind of meter would read lower than a DVM, on the basis that its resistance would help discharge the cap while contributing nothing to charging it.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-03T02:34:52.483" />
  <row Id="2498" PostTypeId="2" ParentId="2180" CreationDate="2010-05-03T06:14:11.477" Score="2" ViewCount="" Body="&lt;p&gt;I assume your circuit has the resistor in series with the cap and the cap is tied to ground, that is you've built a single pole low pass filter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With R = 3.3k and C = 100nF the -3db point will be ~482Hz.  At 1kHz the response will be ~ -6dB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With that time constant i would expect the voltage across the cap to be a rough sinusoid with a low peak to peak level (0.5-1.0v maybe?) and a DC offset of 2-2.5V, depending on the quality and type of capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As to why this happens....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the input is high, the cap is charging but never reaches 5V because of the time constant you've chosen.  When the input goes low the cap begins to discharge but again it never fully discharges.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Move the -3db point up to maybe 9kHz and you'll likely see more of what your expecting, which is a squareish wave looking thing with charge and discharge tails instead of sharp edges. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can think of this in the frequency domain if you want to make it easier to think of.  A square wave is made of its fundamental frequency + only odd harmonics.  To retain the shape of the signal you'll want its fundamental (1kHz in your case) and at least its first few harmonics (3k,5k,7k,9k,etc) intact.  The higher order harmonics give the signal its sharp square edges so if you filter those out you'll get the charge/discharge tails you were expecting.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-05-03T06:14:11.477" />
  <row Id="2499" PostTypeId="1" CreationDate="2010-05-03T14:01:46.860" Score="8" ViewCount="238" Body="&lt;p&gt;I was at Fry's yesterday, and was looking to get some thin solder for work on a kit (through-hole components).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two of the solders I was looking at (in the soldering gear isle section) were labeled &lt;em&gt;RA Flux&lt;/em&gt; and &lt;em&gt;No Clean&lt;/em&gt;.  I asked a engineer-in-the-isle for help, and after explaining my application (building an &lt;a href=&quot;http://adafruit.com/&quot; rel=&quot;nofollow&quot;&gt;adafruit.com&lt;/a&gt; kit), he said I should choose &lt;em&gt;No Clean&lt;/em&gt;, as I wouldn't need to clean the board afterwards(?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Can anyone clarify how one should select solder based on flux type?&lt;/strong&gt;  I had always been under the impression that you just use some sort of rosin-core solder with flux (one size fits all?) built in for basic board work, so I was confused at the different flux labels.  I didn't think you had to clean your board (although I do know that after soldering yellow gunk can be left behind, and I suspect this is a flux byproduct).  I also know that you should avoid solder with an acidic core for electronics work, as that is for pipes + household plumbing.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;The wikipedia page for soldering classifies many of the different &lt;a href=&quot;http://adafruit.com/&quot; rel=&quot;nofollow&quot;&gt;types of fluxes&lt;/a&gt;, most of which require cleaning:  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;R (non-activated)&lt;/li&gt;&#xA;&lt;li&gt;RMA (mildly-activated)&lt;/li&gt;&#xA;&lt;li&gt;RA (activated)&lt;/li&gt;&#xA;&lt;li&gt;No Clean&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Can someone explain why/how you should choose a flux type for a given application?&lt;/strong&gt;  Most of the answers below answer &quot;what.&quot;  I'd like to learn a bit of the theory.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-05-03T17:38:54.717" LastActivityDate="2011-05-16T10:41:02.393" Title="Solder Flux Classifications" Tags="&lt;soldering&gt;&lt;flux&gt;" AnswerCount="2" />
  <row Id="2500" PostTypeId="2" ParentId="2499" CreationDate="2010-05-03T16:00:07.893" Score="3" ViewCount="" Body="&lt;p&gt;RA flux contains activated rosin, and is the most active flux. It's probably more suitable for hobbyists as it'll be easier to get good joints. Use 99% isopropyl alcohol for removing it.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-05-03T16:00:07.893" CommentCount="3" />
  <row Id="2501" PostTypeId="2" ParentId="2499" CreationDate="2010-05-03T16:48:33.360" Score="6" ViewCount="" Body="&lt;p&gt;For thru-hole work (which it sounds like you are doing) I would go with an active &#xA;flux that is water soluble. You need to wash the residue off since it is corrosive &#xA;and can cause shorts. I have had a number of boards mysteriously come back to life after&#xA;a good cleaning. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For thru-hole parts that may get damaged by cleaning (LED lenses) or SMD parts&#xA;with heatsink pads I would use the no clean flux.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been using the flux pens from Kester. 2331-ZX for water soluble flux and&#xA;the 951 for no-clean. To clean the water soluble flux I use an &quot;acid&quot; brush with&#xA;the bristles clipped to around 0.5&quot;. I run the board under the hottest tap water&#xA;I get (probably around 140-160degF) and scrub with the brush. If I do a small&#xA;repair job I will clean with the isopropyl alcohol I have on my bench.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here some of the whys --&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why you need flux -- to get a quality joint at a lower soldering temperature.&#xA;  Using a liquid flux lets you spread the flux better over the two surfaces&#xA;  to be soldered. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why choose an aggressive flux -- an aggresive flux is more tolerant of soldering&#xA; temperatures. As Leon mentioned this would be a good candidate for a hobbyist.&#xA; I like the 2331-ZX for this. Since these leave ionic compounds you need to clean. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why choose no-clean -- eliminates a process step and the issues associated with&#xA; the extra process step. For example for soldering XLamp LEDs I use a no-clean&#xA; flux rather than risk scratching the lens. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For more details take a look at &lt;a href=&quot;http://www.finishing.com/Library/flux.html&quot; rel=&quot;nofollow&quot;&gt;http://www.finishing.com/Library/flux.html&lt;/a&gt;&#xA;and the Kester website.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:41:02.393" LastActivityDate="2011-05-16T10:41:02.393" CommentCount="1" />
  <row Id="2503" PostTypeId="2" ParentId="2490" CreationDate="2010-05-03T18:46:24.633" Score="3" ViewCount="" Body="&lt;p&gt;The control signals are generated by the Decode stage.  If I remember correctly (it's been like seven years...) the control signals are then passed through the pipeline registers between each stage, so they propagate down the pipeline with the rest of the instruction's data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the question is actually asking how many cycles it takes to generate the control signals.  For a single-cycle and pipelined implementation, it only takes one cycle to decode the instruction (for the pipeline, the results of the decode are passed to each stage in succession once generated).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the multi-cycle processor will generate different control signals during each cycle.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-03T18:46:24.633" />
  <row Id="2504" PostTypeId="2" ParentId="2491" CreationDate="2010-05-03T19:43:51.150" Score="2" ViewCount="" Body="&lt;p&gt;This is what you need &lt;a href=&quot;http://www.totalphase.com/products/beagle_usb480/&quot; rel=&quot;nofollow&quot;&gt;http://www.totalphase.com/products/beagle_usb480/&lt;/a&gt;, it is a USB 2.0 protocol analyzer, comes with software that will parse out USB traffic, and will be much easier to use than a logic analyzer.  I have one of these for I2C/SPI and it works well, plus, bunnie uses it &lt;a href=&quot;http://andrew.huang.usesthis.com/&quot; rel=&quot;nofollow&quot;&gt;http://andrew.huang.usesthis.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mateja&lt;/p&gt;&#xA;" OwnerUserId="97" LastActivityDate="2010-05-03T19:43:51.150" />
  <row Id="2505" PostTypeId="1" CreationDate="2010-05-04T02:48:44.837" Score="5" ViewCount="446" Body="&lt;p&gt;I'm studying the MIPS CPU and I have a very basic question about the datapath.  Since the MIPS CPU uses a 5 stage pipeline, that means that the pipeline is using a multicycle datapath, correct?  If a CPU has instructions where the Cycles Per Instruction is greater than 1, the CPU is using a multicycle datapath.  Correct? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess I'm trying to understand if there's ever a case where you can have a pipelined CPU that's NOT using a multicycle datapath.  In my mind, pipelining always implies a multicycle datapath.  Is that the case?  Or are there exceptions?&lt;/p&gt;&#xA;" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-05-04T14:11:56.787" LastActivityDate="2010-05-04T21:38:04.687" Title="Does CPU pipelining always imply a multicycle datapath?" Tags="&lt;cpu&gt;&lt;homework&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="2507" PostTypeId="1" CreationDate="2010-05-04T06:47:51.120" Score="6" ViewCount="363" Body="&lt;p&gt;How do you read the numbers on a rectifier diode? It only says &quot;06&quot; (or &quot;90&quot;) on it (twice, once horizontally and once vertically). I figure I'm supposed to assume this is a 1N4006, but I'm a bit of a newb and not really sure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone confirm this is correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's some pictures:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/NrO8b.jpg&quot; alt=&quot;Rectifier Diode&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/f12ew.jpg&quot; alt=&quot;Rectifier Diode&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="756" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-17T14:39:06.037" LastActivityDate="2011-05-17T14:39:06.037" Title="Reading a Rectifier Diode" Tags="&lt;diode&gt;&lt;rectifier&gt;&lt;identification&gt;" AnswerCount="2" CommentCount="8" />
  <row Id="2508" PostTypeId="2" ParentId="2505" CreationDate="2010-05-04T10:38:52.677" Score="2" ViewCount="" Body="&lt;p&gt;Many of the old 8 bit microprocessors (before the 8086, let's say) had instructions that took more than one cycle to execute and no pipeline capability. Each instruction would go through fetch, decode, execution, and write-back phases, but each one would run to completion before the next one could start. A bit like having a highway from NY to DC and only letting one car on it at a time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pipelining takes advantage of the fact that you could, for instance, be using the instruction fetching logic to get the &lt;em&gt;next&lt;/em&gt; instruction while executing the current one. This is know as instruction level parallelism, since you have more than one instruction executing at a time. Now in the highway analogy, you don't have to wait for the 1st car to arrive in DC before letting another one on at NY. This sort of thing started happening around the time of the 8086/8088. (and there were no doubt others, but I offer the 8086 merely as a reference point in time)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, no, having instructions that require more than one cycle does not imply pipelining.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, if all your instructions could be executed in a single cycle, there would be no advantage to pipelining, as there would effectively be no way to run different stages of different instructions at the same time. So pipelining seems to imply that instructions can be decomposed into different phases that can be parallelized.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(It's actually hard to envision what kind of instruction could be done in a single cycle, beyond a simple NOP. Even plain register-to-register transfers would require one cycle to pull the opcode into the chip and another cycle to achieve the effect.)&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-05-04T21:38:04.687" LastActivityDate="2010-05-04T21:38:04.687" CommentCount="7" />
  <row Id="2509" PostTypeId="2" ParentId="2507" CreationDate="2010-05-04T12:37:43.177" Score="5" ViewCount="" Body="&lt;p&gt;This is difficult because the 1N400x series of diodes is made by a number of different manufacturers all of which seem to have different component marking conventions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ON-semi have a 3 line set of markings with the full part number as the second line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fairchild have a 2 line marking again with the part number in full.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other manufacturers do not seem to specify their markings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edited to add&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now that you have added the picture it does not look like a 1N4006. The normal package for the device is a DO-41 which has a body length of between 1.6 and 2.05 inches.  Your device looks like it is 0.1 inches long.&lt;/p&gt;&#xA;" OwnerUserId="400" LastEditorUserId="400" LastEditorDisplayName="" LastEditDate="2010-05-05T07:34:11.480" LastActivityDate="2010-05-05T07:34:11.480" CommentCount="1" />
  <row Id="2510" PostTypeId="2" ParentId="2507" CreationDate="2010-05-04T13:12:40.877" Score="4" ViewCount="" Body="&lt;p&gt;My guess is the first 06 is for the part number (1N4006) and the last 06 is&#xA;some sort of date code. If both pairs of digits where in the same orientation&#xA;I would assume they were one string and formed a part number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should post a picture.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:46:06.947" LastActivityDate="2011-05-17T12:46:06.947" CommentCount="2" />
  <row Id="2511" PostTypeId="1" CreationDate="2010-05-04T20:00:29.257" Score="3" ViewCount="96" Body="&lt;p&gt;Hi there,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for the best option to develop a medium current (approx 1-2 amps) prototype board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I be using perfboard, Vero/stripboard or etching a custom board? Or are there any other options available?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="758" LastActivityDate="2011-05-18T11:39:32.817" Title="Prototype Options For Medium Current Application" Tags="&lt;prototyping&gt;" AnswerCount="3" />
  <row Id="2512" PostTypeId="1" CreationDate="2010-05-04T20:57:24.003" Score="4" ViewCount="561" Body="&lt;p&gt;Can this board be used to upload sketches to the Arduino. I tried by hooking the TX port on the FTDI Basic Breakout  to RX port(Pin 2 on the Arduino) and RX port to pin 3 on the Arduino. But so far I am not abl to upload anything. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The driver for the board loads fine. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for any feed back.&lt;/p&gt;&#xA;" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-07-11T08:40:13.533" LastActivityDate="2010-07-11T08:40:13.533" Title="FTDI Basic Breakout - 5V" Tags="&lt;basic&gt;&lt;breakout&gt;&lt;arduino&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="2513" PostTypeId="1" AcceptedAnswerId="2517" CreationDate="2010-05-04T21:00:47.887" Score="5" ViewCount="455" Body="&lt;p&gt;I've been considering using a NANDrive by SST in a new design, however I wasn't sure how complicated it would be to connect a PIC to the ATA interface on the NANDrive. I did a quick Google search and found a couple of forums with people who had done it, but I was wondering if anyone here had experience with it and could suggest a standard software library for PIC C18 that implements ATA.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-05-04T22:30:43.580" Title="ATA Interface for PIC" Tags="&lt;pic&gt;&lt;memory&gt;&lt;flash&gt;" AnswerCount="2" />
  <row Id="2514" PostTypeId="2" ParentId="2511" CreationDate="2010-05-04T21:05:24.907" Score="2" ViewCount="" Body="&lt;p&gt;How complex is your circuit? How much voltage drop can you tolerate&#xA;along the current carrying wires? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the circuit is not complex you can keep the wire length short &#xA;and use perf-board or strip board. 22AWG works well the&#xA;Vector T42-1 and K2A pins. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also use vectorboard with the copper plane on it.&#xA;Remove strips of copper to form traces and planes. A lot&#xA;more work to build (especially with a complex circuit).&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:39:32.817" LastActivityDate="2011-05-18T11:39:32.817" />
  <row Id="2515" PostTypeId="2" ParentId="2512" CreationDate="2010-05-04T21:13:56.193" Score="3" ViewCount="" Body="&lt;p&gt;This board can be used to connect to the Arduino and transmit serial data, yes. I don't know much about how the Arduino loads sketches, but here's some suggestions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check your pins for TX and RX, &lt;a href=&quot;http://profmason.com/?p=611&quot; rel=&quot;nofollow&quot;&gt;this diagram&lt;/a&gt; suggests that they might be labelled &quot;pin 0&quot; and &quot;pin 1&quot;. But, this may depend on your make/model of Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://profmason.com/wp-content/uploads/2008/09/arduinopins.jpg&quot; alt=&quot;http://profmason.com/wp-content/uploads/2008/09/arduinopins.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check that the FTDI breakout's Ground is connected to the Arduino Ground pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check that the Arduino is powered up.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-05-04T21:13:56.193" />
  <row Id="2516" PostTypeId="2" ParentId="2505" CreationDate="2010-05-04T21:35:15.873" Score="2" ViewCount="" Body="&lt;p&gt;A pipelined CPU implies a multi-cycle datapath, precisely because it takes five clock cycles for an instruction to go from Fetch to Writeback.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Where I'm getting confused is here &quot;unlike the multi cycle cpu, the pipelined datapath requires that every instruction use all five stages of execution.&quot;&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should finish reading the next paragraph you're quoting.  That requirement is just to prevent two instructions from finishing at the same time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;suppose we use the latencies from our multi-cycle cpu, and we try to run a load instruction followed by an add instruction. the &lt;strong&gt;load instruction will require five cycles to execute, and the add instruction will require four cycles&lt;/strong&gt;. so, if we start running the load instruction on cycle 1, it will finish execution on cycle 5. we are pipelining, so we can start running the add instruction on cycle 2, and it will finish on cycle 5. this is a problem: &lt;strong&gt;we have two instructions finishing on cycle 5&lt;/strong&gt;: they will both try to write to the register file on cycle 5. this is a problem, because our register file only has one write port.&lt;/em&gt; &lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-04T21:35:15.873" CommentCount="3" />
  <row Id="2517" PostTypeId="2" ParentId="2513" CreationDate="2010-05-04T21:58:45.337" Score="6" ViewCount="" Body="&lt;p&gt;I wouldn't recommend it outside of an academic exorcise.  You'll need 24pins (16 data 8 interface) and most likely bit bang the interface protocol as i don't think there is a PIC18 with any sort of 16bit parallel port.  Bit banging the interface, managing the ATA command layer and managing the file system could consume almost all the PIC's time if your trying to get any sort of reasonable transfer rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really want to go this route a quick google search for &quot;PIC IDE&quot; came up with a few places to look for code that supports ATA/IDE on PIC's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;www.pjrc.com/tech/8051/ide/wesley.html &lt;/p&gt;&#xA;&#xA;&lt;p&gt;www.telegraphics.com.au/sw/info/picide.html&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternately, interfacing to a SD card is really easy via a SPI port and there are PIC18's with SPI interfaces with DMA that would require much less work from the PIC to manage the interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your worried about reliability there are industrial grade SD cards and board mount locking SD connectors.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-05-04T22:04:36.800" LastActivityDate="2010-05-04T22:04:36.800" CommentCount="1" />
  <row Id="2518" PostTypeId="2" ParentId="2513" CreationDate="2010-05-04T22:14:31.710" Score="2" ViewCount="" Body="&lt;p&gt;Some 16-bit PICs have an 8/16-bit parallel port with up to 11 address lines. The &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en520629&quot; rel=&quot;nofollow&quot;&gt;PIC24FJ16GA002&lt;/a&gt; is an example.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-05-04T22:30:43.580" LastActivityDate="2010-05-04T22:30:43.580" CommentCount="2" />
  <row Id="2519" PostTypeId="2" ParentId="2511" CreationDate="2010-05-04T22:30:13.317" Score="4" ViewCount="" Body="&lt;p&gt;1 or 2A is not that much. If you are worried you can solder some moderately thick wire on the parts carrying larger currents.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-05-04T22:30:13.317" />
  <row Id="2520" PostTypeId="2" ParentId="2512" CreationDate="2010-05-05T07:54:42.977" Score="4" ViewCount="" Body="&lt;p&gt;As Joby Taffey suggests, the rx &amp;amp; tx pins of the AVR are 2 &amp;amp; 3 respectively, but on the Arduino headers they are pins 0 &amp;amp; 1. You also want to connect DTR to the reset pin of the arduino to enable automatic programming.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  FTDI        Arduino&#xA;Breakout        (5V)&#xA;&#xA;     GND &amp;lt;--&amp;gt; GND&#xA;     CTS &amp;lt;--&amp;gt; (not connected)&#xA;      5V &amp;lt;--&amp;gt; 5V (if you want the breakout to power the arduino)&#xA;     TXO &amp;lt;--&amp;gt; RX (pin 0)&#xA;     RXO &amp;lt;--&amp;gt; TX (pin 1)&#xA;     DTR &amp;lt;--&amp;gt; RESET (possibly through a 100nF cap*)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;On the FTDI TTL232R cable, DTR is not present so you have to manually reset the board before flashing. By default the Arduino will stay in the bootloader for 6-8s, but some boards rely on the automatic reset and have much shorter timeouts (0.25s say). For these boards, set &lt;code&gt;upload.verbose = true&lt;/code&gt; in your Arduino conf file, and learn to time the reset the moment the software attempts to flash the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove&quot; rel=&quot;nofollow&quot;&gt;* Arduino Wiki&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-05-05T07:54:42.977" />
  <row Id="2521" PostTypeId="2" ParentId="2443" CreationDate="2010-05-05T09:37:04.563" Score="6" ViewCount="" Body="&lt;p&gt;The idea of tri-state is to allow multiple output devices to share a single bus. For example, multiple RAM/ROM chips can be connected to a data bus. Only the selected chip will have active outputs (high or low), the other chips (not selected) will have all their outputs set to the hi impedence state (the third state). For outputs devices to share a bus they must be tri-state capable (usually controlled by chip-enable/direction pins). For microprocessors, micro controllers their hi impendence state allows other devices to use the bus (common for smart I/O devices, DMA etc).&lt;/p&gt;&#xA;" OwnerUserId="611" LastActivityDate="2010-05-05T09:37:04.563" />
  <row Id="2522" PostTypeId="1" CreationDate="2010-05-05T11:56:24.110" Score="1" ViewCount="910" Body="&lt;p&gt;I have been messing with AVR's xmega line. They are pretty amazing uC's howevet ATMEL changed much with this new line.  What I am trying to do is detect a pin going low.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I set the PINnCTRL register to every combination with no luck.  I can detect the pin going HIGH but not the other way around?  Below is the working code for turning on the LED on pin5 when pin6 goes high.  However I wanted to do the same thing just instead of when pin6 goes high I would like to have pin 6 go low and turn on the led on pin5.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyhow, have not seen a lot of XMEGA stuff on here thought I would try.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using AVR-Studio&#xA;ATXmega256A3 uC&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;AVR PINnCTRL Configuration Register Table (at least for the pull sections 0b00xxx000)&#xA;FULL DATASHEET HERE: &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8077.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/resources/prod_documents/doc8077.pdf&lt;/a&gt;. &lt;P&gt;&#xA;On page 131 (section 13.4) this lists the definition of all of table below.  NOTE: the PINxCTRL register contains more than just the pullups for settings.  The bits I am working with are these: &#xA;00xxx000 The x's correspond with the listing below.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Table 13-4. Output/Pull Configuration&#xA;                                                          Description&#xA;  OPC[2:0]  Group Configuration       Output configuration        Pull configuration&#xA;     000    TOTEM                     Totempole                   (N/A)&#xA;     001    BUSKEEPER                 Totempole                   Bus keeper&#xA;     010    PULLDOWN                  Totempole                   Pull-down (on input)&#xA;     011    PULLUP                    Totempole                   Pull-up (on input)&#xA;     100    WIREDOR                   Wired OR                    (N/A)&#xA;     101    WIREDAND                  Wired AND                   (N/A)&#xA;     110    WIREDORPULL               Wired OR                    Pull-down&#xA;     111    WIREDANDPULL              Wired AND                   Pull-up&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;stdio.h&amp;gt;&#xA;#include &amp;lt;avr\io.h&amp;gt;&#xA;#define F_CPU 32000000UL&#xA;#include &amp;lt;util\delay.h&amp;gt;&#xA;&#xA;void Config32MHzClock(void);&#xA;&#xA;&#xA;&#xA;int main(void)&#xA;{&#xA;&#xA;  //Init stuff..&#xA;  Config32MHzClock();&#xA;  CLK.PSCTRL = 0x00; // no division on peripheral clock&#xA;  PORTCFG.CLKEVOUT = PORTCFG_CLKOUT_PE7_gc;&#xA;&#xA;  PORTA.DIR = (1 &amp;lt;&amp;lt; 5);  //Sets pin5 as an output (led)&#xA;&#xA;  //011 PULLUP Totempole Pull-up (on input) is what is set&#xA;  PORTA.PIN6CTRL = (0x30);  //Sets Pullup on Input on pin 6 &#xA;  PORTA.OUT = (1&amp;lt;&amp;lt;5);       //Turn on the LED&#xA;&#xA;  while(1){                     //Never ending main loop&#xA;    if (PORTA.IN &amp;amp; (1&amp;lt;&amp;lt;6))      //If pin 6 goes HIGH&#xA;        PORTA.OUT = (0x00); //Turn off led&#xA;&#xA;&#xA;  PORTA.OUT = (1 &amp;lt;&amp;lt; 5); //Turn LED back on&#xA;   }&#xA;}&#xA;&#xA;//Function to setup clock..&#xA;void Config32MHzClock(void)&#xA;{&#xA;  CCP = CCP_IOREG_gc; //Security Signature to modify clock &#xA;  // initialize clock source to be 32MHz internal oscillator (no PLL)&#xA;  OSC.CTRL = OSC_RC32MEN_bm; // enable internal 32MHz oscillator&#xA;  while(!(OSC.STATUS &amp;amp; OSC_RC32MRDY_bm)); // wait for oscillator ready&#xA;  CCP = CCP_IOREG_gc; //Security Signature to modify clock &#xA;  CLK.CTRL = 0x01; //select sysclock 32MHz osc&#xA;};&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="29" LastEditorUserId="29" LastEditorDisplayName="" LastEditDate="2010-05-05T15:11:34.527" LastActivityDate="2010-05-19T21:23:08.240" Title="Reading a pin as an INPUT on AVR Xmegas" Tags="&lt;xmega&gt;&lt;avr&gt;&lt;microcontroller&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="2523" PostTypeId="2" ParentId="2511" CreationDate="2010-05-05T13:41:37.100" Score="2" ViewCount="" Body="&lt;p&gt;If there's significant power conversion / switching electronics, you may have to use a &quot;real&quot; (custom etched) PCB to get good ground planes and keep the parasitic inductances down. This can be the case even in the 0.5A-1A range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are other applications where you may need to keep voltage drops low, so plan carefully. We had a &quot;smart&quot; battery charger that used charging currents of 1.25A. The voltage drop along our charger cable was only about 0.1V, but we had SMBus (=I2C more or less) signals referenced to the ground return, and with a 0.1V difference between the ground return potential at either end of the cable, it ate into the SMBus voltage level margin, which isn't that much. Voltage drop along the positive power input wasn't a significant issue, but drops along the ground return had a big effect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bottom line: it depends. You need to study your system and decide what kind of voltage drops along the supply lines can be problematic. Then design your system around it. (e.g. star grounds rather than daisy chains in some circuits) Measure the drops in the final system to make sure you are doing OK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise, what the other answers said.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-05-05T13:41:37.100" />
  <row Id="2524" PostTypeId="1" CreationDate="2010-05-05T14:43:03.000" Score="5" ViewCount="202" Body="&lt;p&gt;I don't have much experience with electronics, but I think what I want to do could be cobbled together from a Radioshack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a Dig 5006-IP automatic sprinkler controller. It controls 24V DC valves. It has two &quot;SENSOR&quot; terminals, that when closed will put the unit in bypass mode. Basically a rain sensor is attatched to this, and is normally open. When it rains, the circuit goes closed and trips the rain mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, the Hunter Rain-Clik I bought is normally closed, and goes into open mode when it rains. Its more designed to be used inline with the valve. Something I don't want to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So how can I reverse this? How can I swap rainclik's signal, so that when it's closed, the dig sees it as open. And when its open, it sees it as closed? I have a soldering gun and basic knowledge of putting things together.&lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-31T04:48:13.270" LastActivityDate="2011-01-31T04:48:13.270" Title="logical not circuit?" Tags="&lt;circuit&gt;&lt;logic&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="2525" PostTypeId="2" ParentId="2524" CreationDate="2010-05-05T14:51:02.293" Score="0" ViewCount="" Body="&lt;p&gt;There are a lot of ways you could solve this. I think a decent solution would be to buy a cheap, simple microcontroller like the Arduino and use it to watch the rain sensor, and then close a relay that's attached to the sprinkler. That would be the fun way to solve the problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can imagine a few other possibilities. I suspect that it would be cheaper and easier to just buy the right sensor. There may also exist some sort of relay inverter that's designed for this type of situation. I've never actually seen one, but I bet it exists. (Edit: see Johan's answer for confirmation that this exists!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're interested in the fun solution, you can find out more about Arduinos here:&#xA;&lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also take a look at this example: &lt;a href=&quot;http://www.glacialwanderer.com/hobbyrobotics/?p=9&quot; rel=&quot;nofollow&quot;&gt;http://www.glacialwanderer.com/hobbyrobotics/?p=9&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-05-05T15:07:54.220" LastActivityDate="2010-05-05T15:07:54.220" CommentCount="3" />
  <row Id="2526" PostTypeId="2" ParentId="2524" CreationDate="2010-05-05T14:58:51.963" Score="7" ViewCount="" Body="&lt;p&gt;Use a old school 24VDC relay, that has NC (normaly closed) and NO (normally open), &#xA;then the put that like a inverter in the middle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That way when the circuit is closed, the relay is open, and vice verse.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-05-05T14:58:51.963" CommentCount="5" />
  <row Id="2527" PostTypeId="1" AcceptedAnswerId="2529" CreationDate="2010-05-05T16:36:26.110" Score="4" ViewCount="297" Body="&lt;p&gt;&lt;strong&gt;Disclaimer&lt;/strong&gt;: I have very little (almost none, really) electronics experience.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;I purchased a set of IR illuminator boards off of eBay. The only information that the seller provided was that the board had an operating voltage of 12 VDC and that the board has a built-in auto protection circuit that prevents damage from high voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have two questions. One directly related to this PCB, and one general:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How can I figure out how much current these boards will draw?&lt;/li&gt;&#xA;&lt;li&gt;Suppose the seller omitted the required voltage information. How would I go about figuring out how much juice a certain board needs without frying it?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;The board in question is sold by a lot of eBay sellers. &lt;a href=&quot;http://cgi.ebay.com/New-18-Infrared-LED-Lamp-Bulb-Camera-5mm-12V-/130388274468?cmd=ViewItem&amp;amp;pt=LH_DefaultDomain_2&amp;amp;hash=item1e5bbf2d24&quot; rel=&quot;nofollow&quot;&gt;Here's&lt;/a&gt; one listing with decent pictures.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;: Thanks for your answers everyone; you were all helpful.&lt;/p&gt;&#xA;" LastActivityDate="2011-05-17T12:48:26.227" Title="How to Determine a PCB's Power Requirements?" Tags="&lt;pcb&gt;&lt;power&gt;&lt;led&gt;" AnswerCount="5" CommentCount="1" />
  <row Id="2528" PostTypeId="2" ParentId="2527" CreationDate="2010-05-05T16:59:17.973" Score="1" ViewCount="" Body="&lt;p&gt;You can hook it up to any 12V power supply, but it might not work. It won’t work if the board draws more current than the power supply can source. This might burn out your power supply, but not your board. Additionally most power supplies have over current protection that will shut down the supply if a short or over-current is detected. If you have a multi-meter and know the max current of your power supply you can measure the current draw of the board and if it is approaching or exceeds the max current of the supply then chances are you are going to need a bigger power supply. Try one with a higher maximum current, but make sure to keep the voltage at 12V&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-05-05T16:59:17.973" CommentCount="2" />
  <row Id="2529" PostTypeId="2" ParentId="2527" CreationDate="2010-05-05T17:06:07.220" Score="4" ViewCount="" Body="&lt;p&gt;You can measure the amount of current the board draws using the current measurement capability of a multimeter. If your multimeter does not have a fuse on the current input you should put one in series. You place the multimeter in series with either the positive or negative line of your power supply. I would use the negative line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When first powering a device I would use a supply with a current limit. This limits&#xA;the current if there is a fault or if the vendor really meant 5V and not 12V, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Did the vendor mention if the device has an internal current limit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is not clear what the &quot;high voltage&quot; protection is. It could be a transient protection&#xA;device that will not protect the device if you apply a continuous voltage that is&#xA;beyond the input voltage range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is not really practical to determine the input voltage specification unless you&#xA;have a reasonable idea what it is before you start. You will not be able to determine&#xA;the maximum input voltage reliably.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:48:26.227" LastActivityDate="2011-05-17T12:48:26.227" />
  <row Id="2530" PostTypeId="2" ParentId="2527" CreationDate="2010-05-05T18:04:33.030" Score="2" ViewCount="" Body="&lt;p&gt;For the specific case of IR LEDs, you could count the number of LEDs wired in a series string. (Google &quot;series versus parallel wiring&quot; for details on what &quot;series&quot; means.) IR LEDs can tolerate a voltage in the range of 1.3-1.7 V per LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a 5-LED string, you could start with 5 * 1.3 = 6.5 V and increase from there. They'll get brighter as you increase the voltage*. Eventually the LEDs will overheat and burn out. If you're willing to buy a few and risk burning them, you should be able to figure out the peak voltage a PCB can tolerate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*(I'm eliding some details here-- the LEDs brightness is actually more linearly related to current than voltage, but you said you were new to electronics, so don't worry about that. I'm also presuming you have some sort of IR camera that can see the IR output.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-05T18:04:33.030" CommentCount="1" />
  <row Id="2531" PostTypeId="2" ParentId="2522" CreationDate="2010-05-05T20:35:47.163" Score="1" ViewCount="" Body="&lt;p&gt;There are a few concerns I have.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Unless you start counting pins from 0, (1 &amp;lt;&amp;lt; 5) is actually pin 6.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) According to the code, pin 6 going high causes the LED to turn off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Immediately after turning the LED off, you turn it back on.  Turning it back on should probably be in an else block.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) This part of your question is confusing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;I wanted to do the same thing just instead of when pin6 goes high I would like to have pin 6 go low and turn on the led on pin5.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason it is confusing is because you say that pin 6 is an input, and then you say you want to drive pin 6 low (which implies an output).&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-05T20:35:47.163" />
  <row Id="2532" PostTypeId="2" ParentId="2527" CreationDate="2010-05-05T20:47:47.287" Score="2" ViewCount="" Body="&lt;p&gt;1) Use an ammeter in series with the power supply to measure how much current the device uses.  You will have to break the circuit in order for this to work.  Breaking the circuit is not always easy.  You may need to cut the power supply wires in order to break the circuit.  Since you're a novice, I would be very, very, very careful with cutting the power supply wires.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) If you do not know what voltage a device takes, try to follow the circuit from the DC power plug to the nearest regulator (it should be in close proximity to the DC power plug).  Google the part number, find the datasheet, and see what the minimum input voltage requirement is for the regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Linear regulators require some extra room, so a 9V regulator might require 10V or more, which is why they would suggest a 12V supply.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-05T20:47:47.287" />
  <row Id="2533" PostTypeId="2" ParentId="2527" CreationDate="2010-05-05T20:54:41.683" Score="2" ViewCount="" Body="&lt;p&gt;Looking at the board there is not much there besides the LEDs and a couple of parts which I am guessing are resistors. It look like there are two groups of 9 LEDs and then a current limiting resistor. So measure the voltage across the resistors and use ohms law to work out the current. Each group should not pull more than around 50mA so I am guessing the board in total will be less than 100mA. Looking at a &lt;a href=&quot;http://www.vishay.com/docs/81012/tsal7200.pdf&quot; rel=&quot;nofollow&quot;&gt;data sheet for an IR led&lt;/a&gt; for 100% on you should not exceed 20mA or you will be damaging the LEDs.&lt;/p&gt;&#xA;" OwnerUserId="540" LastActivityDate="2010-05-05T20:54:41.683" />
  <row Id="2534" PostTypeId="2" ParentId="2332" CreationDate="2010-05-05T21:08:34.877" Score="1" ViewCount="" Body="&lt;p&gt;The problem you are going to run into is that the big boys like Marvell and Broadcom will not talk you unless you are someone like Apple. What I have has luck with is someone like &lt;a href=&quot;http://www.wi2wi.com/wireless.php&quot; rel=&quot;nofollow&quot;&gt;Wi2Wi&lt;/a&gt; who acts as the bridge to vendors like Marvell.&lt;/p&gt;&#xA;" OwnerUserId="540" LastActivityDate="2010-05-05T21:08:34.877" />
  <row Id="2535" PostTypeId="1" AcceptedAnswerId="2536" CreationDate="2010-05-06T02:41:27.800" Score="6" ViewCount="558" Body="&lt;p&gt;I have a couple of potentiometers that haven't been touched in quite some time. In fact, probably not in 15 years. So now they produce noisy output, presumably from oxides or some other crud that has built up on the contact surfaces. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Outright replacement might be an option, but these are quite large relative by current standards, they are in fact about the diameter of a quarter and are probably 1/4&quot; inch thick, real 1970's technology. Might be hard to get the same form factor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Certain retailers used to carry this stuff that came in a can like wd-40, complete with a little red tube for injecting the stuff into exactly this kind of part. You'd squirt a tiny amount into the noisy pot, wiggle the knob 2-3 times, and no more noisy output. So there's the proof of concept that it can be done, but this magic stuff seems to have vanished from the shelves.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It had to just be some kind of solvent, like xylene or something. Any ideas on what would clean the corrosion (dust? dirt? &lt;em&gt;fungus&lt;/em&gt;?) off a potentiometer, without damaging it?&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-08T02:42:52.353" Title="How to clean a potentiometer?" Tags="&lt;device&gt;" AnswerCount="6" />
  <row Id="2536" PostTypeId="2" ParentId="2535" CreationDate="2010-05-06T03:11:13.467" Score="7" ViewCount="" Body="&lt;p&gt;Just spray contact cleaner on it and wiggle it back and forth.  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It hasn't vanished:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.caig.com/&quot; rel=&quot;nofollow&quot;&gt;DeoxIT&lt;/a&gt;&#xA;&lt;a href=&quot;http://www.google.com/products?q=contact+cleaner&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/products?q=contact+cleaner&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-05-06T03:11:13.467" CommentCount="3" />
  <row Id="2537" PostTypeId="2" ParentId="1024" CreationDate="2010-05-06T09:44:01.220" Score="15" ViewCount="" Body="&lt;p&gt;For more limited media there's AACircuit&#xA;&lt;a href=&quot;http://www.tech-chat.de/aacircuit.html&quot; rel=&quot;nofollow&quot;&gt;http://www.tech-chat.de/aacircuit.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;                        ___&#xA;                   .---|___|-----.&#xA;                   |             |&#xA;                   |             |&#xA;             ___   |  |\|        |&#xA;           -|___|-----|-\        |&#xA;                      |  &amp;gt;-------'&#xA;                   .--|+/&#xA;                   |  |/|&#xA;                   |    |&#xA;                  ===  ===&#xA;                  GND  GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2010-05-06T09:44:01.220" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="5" />
  <row Id="2538" PostTypeId="2" ParentId="2535" CreationDate="2010-05-06T11:17:52.560" Score="2" ViewCount="" Body="&lt;p&gt;Isopropyl alcohol works well too - You can submerge the pot and give it a good soaking, then just turn the wiper backward and forward a few times to make sure it's well worked in. Then just leave it to dry before turning the electrical equipment back on. &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-05-06T11:17:52.560" />
  <row Id="2539" PostTypeId="1" CreationDate="2010-05-06T11:27:57.160" Score="6" ViewCount="224" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a design which expects a TTL level square wave from a radio reciever which is fed into a microcontroller. There is some TTL level noise as no encoding is done on the transmit end. I was wondering if anyone had any pointers on how you could decrease the noise in software? (I understand there are a number of hardware solutions, but I am interested more in learning) I am not looking for anyone to solve my problem for me, just for some advice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Names/articles/topics would be great!&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-06-02T03:29:24.810" Title="Removing digital noise in software" Tags="&lt;dsp&gt;&lt;noise&gt;&lt;software&gt;" AnswerCount="5" CommentCount="4" FavoriteCount="1" />
  <row Id="2540" PostTypeId="2" ParentId="2539" CreationDate="2010-05-06T11:55:10.060" Score="6" ViewCount="" Body="&lt;p&gt;There are many ways to work with noise in software, and they are becoming more and more effective to implement in software instead of hardware, reducing system cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead of attempting to explain it myself, I am going to pass you on to &lt;a href=&quot;http://www.ganssle.com/&quot; rel=&quot;nofollow&quot;&gt;Jack Ganssle&lt;/a&gt;, an embedded systems consultant that I have grown from reading the articles of. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;He has a listing of his articles online, the first one I would like you to is about &lt;a href=&quot;http://www.ganssle.com/articles/An_noise.htm&quot; rel=&quot;nofollow&quot;&gt;analog noise in embedded systems&lt;/a&gt;. The second article I have to link you to is about &lt;a href=&quot;http://www.ganssle.com/articles/anoise.htm&quot; rel=&quot;nofollow&quot;&gt;using software to reduce noise in your system&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also suggest his article in &lt;a href=&quot;http://www.ganssle.com/articles/adbounce.htm&quot; rel=&quot;nofollow&quot;&gt;smoothing digital inputs&lt;/a&gt; and &lt;a href=&quot;http://www.ganssle.com/articles/aselfcal.htm&quot; rel=&quot;nofollow&quot;&gt;self calibrating systems&lt;/a&gt;. After spending time working with embedded systems I hard picked up some of this information from my own errors, but I really enjoyed reading his ways of thinking. The self calibrating system was very obvious to me, but the way he suggested going about it was valuable to me. You may not need the information, but his articles have helped me.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-05-06T11:55:10.060" />
  <row Id="2541" PostTypeId="2" ParentId="2539" CreationDate="2010-05-06T12:13:39.713" Score="4" ViewCount="" Body="&lt;p&gt;I've found Digital Signal Processing and the Microcontroller by Grover and Deller to be the only book on filters that I can understand. Unfortunately, it's hard to find cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/books?id=GzVmQgAACAAJ&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/books?id=GzVmQgAACAAJ&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-06T12:13:39.713" CommentCount="2" />
  <row Id="2542" PostTypeId="2" ParentId="2535" CreationDate="2010-05-06T12:59:41.053" Score="1" ViewCount="" Body="&lt;p&gt;I don't know if I'd say it's vanished... in the US, at least, I've seen DeoxIT at Radioshack and Fry's Electronics carries a couple of types of electronics cleaner.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I picked up some stuff (not DeoxIT) that did a cleaning, but it didn't last very long (maybe a couple of months).  Deoxit is better, I hear.  I was cleaning potentiometers in a 1970s Marantz amplifier.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-05-06T18:08:23.823" LastActivityDate="2010-05-06T18:08:23.823" CommentCount="1" />
  <row Id="2543" PostTypeId="2" ParentId="2539" CreationDate="2010-05-06T14:15:01.590" Score="0" ViewCount="" Body="&lt;p&gt;Perhaps the &quot;noise&quot; is a problem caused by the lack of encoding. Simple transmitters and receivers require NRZ - Manchester code is often used.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-05-06T14:15:01.590" CommentCount="6" />
  <row Id="2544" PostTypeId="2" ParentId="2535" CreationDate="2010-05-06T14:35:07.587" Score="2" ViewCount="" Body="&lt;p&gt;I have used CRC Electronic Contact Cleaner, to just plain old Windex to clean potentiometers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It doesn't really matter that much what cleaner you use, provided that it doesn't leave behind any film. So I wouldn't use WD40 or anything that says that it lubricates.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Soak it by spraying it with your favorite cleaner.&lt;/li&gt;&#xA;&lt;li&gt;Rotate it several times.&lt;/li&gt;&#xA;&lt;li&gt;Spray it some more to get anything that broke loose out.&lt;/li&gt;&#xA;&lt;li&gt;Repeat steps 2. &amp;amp; 3. as necessary.&lt;/li&gt;&#xA;&lt;li&gt;Let it dry &lt;strong&gt;completely&lt;/strong&gt;.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;After you have cleaned it you &lt;em&gt;could&lt;/em&gt; put in some dielectric grease.&lt;/p&gt;&#xA;" OwnerUserId="1301" LastActivityDate="2010-05-06T14:35:07.587" CommentCount="1" />
  <row Id="2545" PostTypeId="1" CreationDate="2010-05-06T14:51:59.370" Score="3" ViewCount="312" Body="&lt;p&gt;Hey,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Today I bought a new Wi-Fi modem for my ADSL connection. Now the old UTStar UT300RU ethernet router is unoccupied. I was just thinking for any of you people had any idea what can I do with this thing? Any cool project which will utilize this thing is welcome.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="327" LastEditorDisplayName="" LastEditDate="2010-05-07T01:30:34.217" LastActivityDate="2010-05-07T01:30:34.217" Title="Cool things to do with a ADSL ethernet Router" Tags="&lt;projects&gt;" AnswerCount="3" />
  <row Id="2546" PostTypeId="2" ParentId="2545" CreationDate="2010-05-06T15:42:07.323" Score="2" ViewCount="" Body="&lt;p&gt;I'm not familiar with that specific router, but I would suspect that it's not hackable without substantial effort. If I understand correctly, it's an ADSL modem, which usually runs proprietary firmware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it were a Linksys WRT54, you could turn it into all sorts of fun stuff: &lt;a href=&quot;http://en.wikipedia.org/wiki/Linksys_WRT54G_series&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Linksys_WRT54G_series&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-06T15:42:07.323" CommentCount="2" />
  <row Id="2547" PostTypeId="2" ParentId="2545" CreationDate="2010-05-06T16:04:34.553" Score="3" ViewCount="" Body="&lt;p&gt;Here's some ideas:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Recycle the case for random electronics projects&lt;/li&gt;&#xA;&lt;li&gt;Desolder any useful components from the PCB&lt;/li&gt;&#xA;&lt;li&gt;Doorstop&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-05-06T16:04:34.553" />
  <row Id="2548" PostTypeId="2" ParentId="1707" CreationDate="2010-05-06T21:08:44.100" Score="0" ViewCount="" Body="&lt;p&gt;The only time I ever need more than 500 mA is if I'm driving a bunch of LEDs.  Even running an FPGA, microcontroller, and RAM only draws ~200-300 mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though, if this device ever needs to be certified by the USB IF (i.e. you want to go commercial with it), you should be aware that during enumeration, a USB device is only allowed to draw 100 mA.  After enumerating successfully, it can request 500 mA from the host.  The host can deny this request.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, most USB ports will feed you your 500 mA before enumerating, so you probably won't ever experience this limitation...unless you send your device to the USB IF for testing, in which case they will most certainly fail you.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-06T21:08:44.100" />
  <row Id="2549" PostTypeId="1" AcceptedAnswerId="2586" CreationDate="2010-05-06T21:21:30.597" Score="2" ViewCount="292" Body="&lt;p&gt;I am looking for an IC that can be used to drive high voltage/high current digital outputs from a microprocessor. I currently use an MC33298 in one of my designs, but Frescale now says the part is not recommended for new designs. The requirements are as follows:&lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Must have capability to sink ~1A of current&lt;/li&gt;&#xA;&lt;li&gt;Must support output voltage between 12V and 24V&lt;/li&gt;&#xA;&lt;li&gt;Must support 3.3V CMOS logic levels on inputs&lt;/li&gt;&#xA;&lt;li&gt;Must support 8 digital outputs&lt;/li&gt;&#xA;&lt;li&gt;Must cost less than $5&lt;/li&gt;&#xA;&lt;li&gt;Should have SPI or I2C interface&lt;/li&gt;&#xA;&lt;li&gt;Should be a single chip package&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Anyone have any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-05-11T12:23:15.403" Title="High voltage/current open-drain output driver" Tags="&lt;power&gt;&lt;driver&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="2550" PostTypeId="2" ParentId="2545" CreationDate="2010-05-07T00:10:29.527" Score="5" ViewCount="" Body="&lt;p&gt;Perhaps you could give it away using Freecycle - good karma and all that. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-05-07T00:10:29.527" />
  <row Id="2551" PostTypeId="1" CreationDate="2010-05-07T04:43:51.963" Score="4" ViewCount="428" Body="&lt;p&gt;I want to build a frequency meter which will measure the horizontal &#xA;oscillation frequency of a golf shaft tip when the butt of the shaft &#xA;is clamped  in a vice. Commercial golf shaft  frequency analysers are &#xA;very expensive, and basically the way they work is as follows: you &#xA;clamp the butt of the shaft in a vice, pull and release the tip, which &#xA;oscillates in a horizontal plane over a plate, or within a frame. The &#xA;digital readout gives the oscillation frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I build this?&lt;/p&gt;&#xA;" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-02-10T18:39:33.813" LastActivityDate="2011-02-10T18:40:19.133" Title="Golf shaft frequency metre" Tags="&lt;frequency&gt;&lt;frequency-measurement&gt;" AnswerCount="7" CommentCount="1" />
  <row Id="2552" PostTypeId="2" ParentId="2551" CreationDate="2010-05-07T05:49:38.613" Score="2" ViewCount="" Body="&lt;p&gt;Sounds like a job for an accelerometer and a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to make sure it is accurate enough.&lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-02-10T18:40:19.133" LastActivityDate="2011-02-10T18:40:19.133" />
  <row Id="2553" PostTypeId="2" ParentId="2551" CreationDate="2010-05-07T11:35:14.320" Score="3" ViewCount="" Body="&lt;p&gt;You could use an analog output accelerometer and the counter/timer &#xA;in a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to adjust the bandwidth filter capacitors appropriately&#xA;and add a comparator to give you a clean square wave for input into&#xA;the microcontroller counter/timer.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-01T03:38:46.813" LastActivityDate="2011-02-01T03:38:46.813" />
  <row Id="2554" PostTypeId="2" ParentId="2551" CreationDate="2010-05-07T12:54:30.797" Score="3" ViewCount="" Body="&lt;p&gt;Perhaps you could measure frequency with a homemade stroboscope?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.epanorama.net/circuits/strobo.html&quot; rel=&quot;nofollow&quot;&gt;http://www.epanorama.net/circuits/strobo.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-07T12:54:30.797" CommentCount="1" />
  <row Id="2555" PostTypeId="2" ParentId="18" CreationDate="2010-05-07T14:24:51.350" Score="2" ViewCount="" Body="&lt;p&gt;I have heard about some problems being reported with the WDT and the regular bootloader, so you may want to try another bootloader with it, for eg Adaboot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you can do a bunch more stuff with the WDT besides just a reset. I recommend &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2551.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/resources/prod_documents/doc2551.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-05-07T14:24:51.350" />
  <row Id="2556" PostTypeId="2" ParentId="2551" CreationDate="2010-05-07T14:25:40.350" Score="6" ViewCount="" Body="&lt;p&gt;If you're just trying to measure one golf club (not build a product), I'd try attaching a microphone and measuring the vibration with an oscilloscope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Quick and dirty.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-05-07T14:25:40.350" CommentCount="1" />
  <row Id="2557" PostTypeId="2" ParentId="1707" CreationDate="2010-05-07T14:50:06.043" Score="1" ViewCount="" Body="&lt;p&gt;You are really asking two separate questions:&#xA;1. How much current can you drive through the Arduino and &#xA;2. How much current do you expect your project to use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Answering 1. is easier: Max current is 50mA / pin on the 328. The Arduino has a fuse at 500mA total: &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There really is no simple answer to 2 - this discussion leads into the importance of signal level vs drive level currents. One goal should be to keep signal currents as low as you can get away with. (This is really a separate discussion).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can easily switch an amp with a TO-220 package transistor, and if you need more you can use relays to drive whatever current you like. However, as a general rule of thumb I like to take extra safety precautions if I am going above about 12v / 1amp. &lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-05-07T14:50:06.043" />
  <row Id="2558" PostTypeId="2" ParentId="2551" CreationDate="2010-05-07T14:55:55.767" Score="1" ViewCount="" Body="&lt;p&gt;One more for the quick and dirty...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a high speed camera (not so difficult to have nowadays), you can use your frame count to calculate the frequency.&lt;/p&gt;&#xA;" OwnerUserId="1267" LastActivityDate="2010-05-07T14:55:55.767" />
  <row Id="2559" PostTypeId="1" AcceptedAnswerId="2561" CreationDate="2010-05-07T15:26:45.690" Score="2" ViewCount="133" Body="&lt;p&gt;Hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody know what the rotational span of the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9065&quot; rel=&quot;nofollow&quot;&gt;ROB-09065 servo&lt;/a&gt; from SparkFun?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And even better, is there a datasheet available anywhere?&lt;/p&gt;&#xA;" OwnerUserId="718" LastActivityDate="2010-05-07T15:54:55.130" Title="Rotation span of SparkFun ROB-09065 servo." Tags="&lt;servo&gt;&lt;rc&gt;&lt;robotics&gt;" AnswerCount="1" />
  <row Id="2560" PostTypeId="2" ParentId="2539" CreationDate="2010-05-07T15:49:31.573" Score="6" ViewCount="" Body="&lt;p&gt;From your latest comment, I would suggest oversampling the input.  Record several consecutive samples, and then your output should be whatever the majority of the recorded samples are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, say you record 10 samples.  If you get a noise spike, only one or two of the samples will be corrupted, while the majority of them are the correct value.  If you get actual data, then eventually the 1s will outnumber the 0s and the output will change.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-07T15:49:31.573" />
  <row Id="2561" PostTypeId="2" ParentId="2559" CreationDate="2010-05-07T15:54:55.130" Score="2" ViewCount="" Body="&lt;p&gt;They claim that it's similar to the HS-55, which has a 180 degree span.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.servocity.com/html/hs-55_sub-micro.html&quot; rel=&quot;nofollow&quot;&gt;http://www.servocity.com/html/hs-55_sub-micro.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-05-07T15:54:55.130" />
  <row Id="2562" PostTypeId="2" ParentId="447" CreationDate="2010-05-07T16:00:32.213" Score="0" ViewCount="" Body="&lt;p&gt;You could try using two op amps in a band-pass configuration.  This would allow you to split the AFSK signal into two separate amplitude modulated signals.  As a bonus, you could also amplify the input signal if it's too low.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-07T16:00:32.213" />
  <row Id="2563" PostTypeId="2" ParentId="710" CreationDate="2010-05-07T16:37:31.553" Score="3" ViewCount="" Body="&lt;p&gt;Use a full ground and power plane.  Bypass caps are limited by inductance, which is mostly determined by package size, traces, and vias.  So pick the smallest package size that you can work with, then go for the largest capacitance that doesn't break your budget.  If you need more bypassing, go up a package size or two and get the biggest capacitance in that package.  When connecting the cap to the ground/power planes, use two vias on either side of each pad; vias + cap will look kinda like an H.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Splitting the planes can help isolate the analog and digital sections.  &lt;strong&gt;Never cross a split plane with a signal trace!!!&lt;/strong&gt;  Keep signals away from the edge of the board.  Keep signals at least 2x trace width apart to prevent crosstalk (simulations are helpful here).  Keep signals 5x trace width away from highly noisy signals (i.e. clocks) or extremely sensitive signals (i.e. analog inputs).  Use grounded guard traces around noisy/sensitive signals if necessary.  Avoid vias and stubs with noisy/sensitive signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally, provide one ground wire per signal in a connector.  Terminate connector signals, because they like to spew EMI.  Ferrite beads around the wire can help with connector noise, too.  Keep signals from going underneath connectors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ground plane allows you to create microstrip traces, which have a well-defined impedance.  You can also use termination resistors if your trace is long.  I think the general rule of thumb is for every nS of rise time, you can go 2.5&quot; without a termination resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use IBIS simulations to determine whether you need termination resistors.  Modern FPGAs have nice tricks for this sort of thing; they can control their output driver strength, sometimes even with a &quot;Digitally Controlled Impedance&quot; (Xilinx term for the technology).  IBIS simulations help here, too, when figuring out the appropriate drive strength.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out Dr. Howard Johnson's humongous list of High Speed Digital Design newsletters.  Truly awesome.  &lt;a href=&quot;http://www.sigcon.com/pubsAlpha.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.sigcon.com/pubsAlpha.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-07T16:37:31.553" />
  <row Id="2564" PostTypeId="2" ParentId="2551" CreationDate="2010-05-07T19:58:02.480" Score="7" ViewCount="" Body="&lt;p&gt;Glue a magnet on the club, put a coil near it.  The coil will generate AC from the motion of the club&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-05-07T19:58:02.480" CommentCount="1" />
  <row Id="2565" PostTypeId="2" ParentId="2549" CreationDate="2010-05-07T23:08:17.877" Score="0" ViewCount="" Body="&lt;p&gt;If you mean 1 A total across the 8 inputs, I think the TI TPL9202 fits the bill.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tpl9202.html&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/docs/prod/folders/print/tpl9202.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need 8 x 1 A, you could cascade that to 2 L293D Darlington arrays-- if I recall correctly, they have 4 Darlingtons per package.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-07T23:08:17.877" CommentCount="1" />
  <row Id="2566" PostTypeId="2" ParentId="2000" CreationDate="2010-05-08T06:47:56.687" Score="0" ViewCount="" Body="&lt;p&gt;I'm also looking for similar application. I want to add text in different font and some speedometer like graphics.&#xA;Please update me on this sachin.pukale@gmail.com&lt;/p&gt;&#xA;" LastActivityDate="2010-05-08T06:47:56.687" />
  <row Id="2567" PostTypeId="1" AcceptedAnswerId="2570" CreationDate="2010-05-08T13:43:32.213" Score="3" ViewCount="340" Body="&lt;p&gt;My motor-scooter has a built in radio, with a small speak either side of the front panel, below the handlebars.  It's a JonWay, i.e. cheap Chinese, so I suspect the radio is more suited to developing countries where helmets are not yet mandatory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For me to listen while wearing a helmet, I need zero traffic, or a headphone jack, and I'd like to do the jack myself.  I may not find the radio board without too much dismantling, but the speakers are very accessible, so I may have to grab my input signal directly from them.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My electronics knowledge has all but evaporated after 15 years of non-use, so all I can start with is that I'll need a high impedance input, to make the increased load on the amp negligible, and my own power amp stage.  Where do I go from here?  I would like to do a rough design myself, maybe make the amp component a kit, but nothing ready made.&lt;/p&gt;&#xA;" OwnerUserId="768" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-08T15:43:17.063" LastActivityDate="2011-05-18T11:21:48.443" Title="Piggy-backing off power amplifier outputs." Tags="&lt;amplifier&gt;&lt;audio&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="2568" PostTypeId="2" ParentId="2567" CreationDate="2010-05-08T14:38:27.577" Score="3" ViewCount="" Body="&lt;p&gt;You can grab the input signal off of the speaker or replace the speaker &#xA;with a power resistor. The radio is designed to drive a low-impedance &#xA;so you want to keep a low impedance on the output and amplify from there.&#xA;I did this with a car radio/cassette deck so that I could listen&#xA;to some old cassettes on my home stereo.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the amplifier you could use an amplifier IC like the TDA7056A from Phillips (and IIRC&#xA;others). There may be single package audio amp ICs from National&#xA;and TI that could. The TDA7056A is a large through-hole package&#xA;with a metal-tab for heatsinking. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may be better-off using a small portable radio or ipod like gadget&#xA;and coming off of the headphone jack.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:21:48.443" LastActivityDate="2011-05-18T11:21:48.443" />
  <row Id="2569" PostTypeId="1" CreationDate="2010-05-08T14:53:57.410" Score="7" ViewCount="99" Body="&lt;p&gt;Recently I have been watching Robert Full's talks on TED. He has some obscenely interesting works on robot locomotion. This has intrigued my curiosity and I have been trying to understand his works. I have tried to read many papers on these type of works but I have been unable to understand as I don't have the basics of these things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone please direct me to a resource (ebooks, websites, video/audio lectures, forums etc.) where I can understand the basics of Robot Locomotion and gait functions?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-05-10T12:29:56.353" CommunityOwnedDate="2010-05-10T12:26:44.307" Title="Resources to understand robot locomotion and Gait functions" Tags="&lt;robotics&gt;&lt;autonomous&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="2570" PostTypeId="2" ParentId="2567" CreationDate="2010-05-08T16:14:05.827" Score="5" ViewCount="" Body="&lt;p&gt;Don't worry about the input impedance of the stage.  Even a low 1 kΩ impedance will only decrease the load from 8 Ω to 7.94 Ω.  A more typical 10 kΩ will be invisible to the power amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Power amp for driving headphones is pretty easy.  In fact, you could just do it all in one stage.  See the CMoy amp for a popular and simple design:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://tangentsoft.net/audio/cmoy-tutorial/&quot; rel=&quot;nofollow&quot;&gt;http://tangentsoft.net/audio/cmoy-tutorial/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://gilmore2.chem.northwestern.edu/projects/cmoy2_prj.htm&quot; rel=&quot;nofollow&quot;&gt;http://gilmore2.chem.northwestern.edu/projects/cmoy2_prj.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://headwize.com/images2/cmoy2_3.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your headphone amp will be battery-powered and mono, just connect the input of this schematic to the red wire of the speaker, and the ground to the black wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to run stereo, or power it from the same supply so you don't need batteries, then you need to check whether the speakers are driven &lt;a href=&quot;http://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers#Bridged_amplifier&quot; rel=&quot;nofollow&quot;&gt;bridged&lt;/a&gt; or not.  With a signal coming through them, you should always see an AC voltage between the two terminals of a speaker (to make sure you're measuring right).  Then check if there's also a voltage between each terminal and ground.  If there is, then it's bridged.  If one wire has zero volts to ground, then it's ground.  You can make sure with a resistance check.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's not bridged, then you can just do the same thing with two amps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it &lt;em&gt;is&lt;/em&gt; bridged, you can't use that circuit.  You don't want to short the active speaker outputs to ground or short the left and right outputs to each other. So you'd need to build a &lt;a href=&quot;http://en.wikipedia.org/wiki/Operational_amplifier_applications#Differential_amplifier&quot; rel=&quot;nofollow&quot;&gt;diff amp&lt;/a&gt; for each input stage, and connect ground to ground, V1 to one speaker wire (red), and V2 to the other (black):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Op-Amp_Differential_Amplifier.svg/300px-Op-Amp_Differential_Amplifier.svg.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then Vout of this circuit connects to Vin of the previous headphone amplifier circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the speakers are driven &lt;a href=&quot;http://en.wikipedia.org/wiki/Class_D_Amplifier&quot; rel=&quot;nofollow&quot;&gt;class D&lt;/a&gt;, you might need additional filtering, but probably not.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-06-01T18:28:59.510" LastActivityDate="2010-06-01T18:28:59.510" />
  <row Id="2571" PostTypeId="2" ParentId="2569" CreationDate="2010-05-08T16:45:49.123" Score="3" ViewCount="" Body="&lt;p&gt;Here's one source - Tilden's BEAM/Solarbotics stuff tends to be low-power, low-tech, but the flip side of this is that it is simple. I believe he even had a six-leg gait generator built using a single hex-inverter chip. A quick googling produced&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://faq.solarbotics.net/nvnet.html&quot; rel=&quot;nofollow&quot;&gt;http://faq.solarbotics.net/nvnet.html&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://faq.solarbotics.net/FAQ.html&quot; rel=&quot;nofollow&quot;&gt;http://faq.solarbotics.net/FAQ.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, Valentino Braitenberg's &quot;Vehicles&quot; is a completely amazing book where the starting point is a simple reflexive control system and as the book progresses, increasing complexity is added. Google for 'braitenberg vehicles' and you will also find a simulator related to the book.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/exec/obidos/ASIN/0262521121/johnwiseman&quot; rel=&quot;nofollow&quot;&gt;http://www.amazon.com/exec/obidos/ASIN/0262521121/johnwiseman&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-05-08T16:54:02.227" LastActivityDate="2010-05-08T16:54:02.227" CommentCount="1" />
  <row Id="2572" PostTypeId="2" ParentId="710" CreationDate="2010-05-08T22:03:21.340" Score="0" ViewCount="" Body="&lt;p&gt;As already mentioned you can use a fast processor with a PLL and still have only your 10kHz signals + a 12MHz quartz oscillator (close to the CPU) on your board. To lay this out will not be a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many people (me included) did 48kHz stereo audio output on an ARM7TDMI (streaming from an SPI connected SD card in my case). I even saw mp3 decoding in software on a 50MHz ARM7 running from RAM (there may be wait-states when working from Flash).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe buy an mbed LPC1768 board (100MHz, very fast ADC/DAC and PWMs on-chip, cheap: 50€) and make a prototype? Only if this is not sufficient start playing with other (more costly and difficult) stuff.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-05-08T22:03:21.340" />
  <row Id="2573" PostTypeId="1" AcceptedAnswerId="2577" CreationDate="2010-05-09T03:08:39.187" Score="2" ViewCount="159" Body="&lt;p&gt;Hello,  I would like to use an LT3080 as current source (see datasheet pg 16 in Typical Applications Section).  However, I need to be able to shut it off.  Since Iout=10uA*Rset/Rout, it seems just a matter of shorting Rset with a PMOS.  The problem is that for all PMOS I review the best I've found for zero gate leakage current  of 1uA, and at high temperatures of 10uA, so depending on the temperature it will suck all the current from the 10uA current source, thereby killing the output current when it is not supposed to.  I thought of using a PNP but the problem is that Vce(sat) will be comparable to the 0.5V-1V I intend to drop accross Rset, so it will not shut off Iout effectively.  The only solution I have at the moment is to shut off the input voltage.  Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="688" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T16:19:35.850" LastActivityDate="2011-05-19T14:19:20.720" Title="Shutdown for LT3080 current source" Tags="&lt;current-source&gt;" AnswerCount="1" />
  <row Id="2574" PostTypeId="1" CreationDate="2010-05-09T05:35:52.380" Score="4" ViewCount="650" Body="&lt;p&gt;I am using this LCD: &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9053&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9053&lt;/a&gt;               &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plus I am using an Arduino. I am trying to hook this up but without a 10K pot. How is this possible? Every tutorial I found involved the 10K potentiometer&lt;/p&gt;&#xA;" OwnerUserId="769" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-10T04:31:33.573" LastActivityDate="2010-05-13T16:26:00.313" Title="Arduino hooking up LCD without POT" Tags="&lt;arduino&gt;&lt;lcd&gt;" AnswerCount="6" />
  <row Id="2575" PostTypeId="2" ParentId="2574" CreationDate="2010-05-09T06:15:29.913" Score="6" ViewCount="" Body="&lt;p&gt;Is there any reason why you don't want to use the 10k pot? It really is needed for the screen contrast control. If you don't have a 10k, you could experiment with a variety of fixed resistors to get the required contrast level. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-05-09T06:15:29.913" CommentCount="2" />
  <row Id="2576" PostTypeId="2" ParentId="2574" CreationDate="2010-05-09T10:03:45.763" Score="6" ViewCount="" Body="&lt;p&gt;You could start by using the variable resistor to find the sweet spot for the screen contrast, then use a multimeter to measure the resistance at that point, that should give you a good value for a fixed resistor. Otherwise you could look at using a digital potentiometer chip that could set the screen contrast and could be controlled by the Arduino   &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-05-09T10:03:45.763" />
  <row Id="2577" PostTypeId="2" ParentId="2573" CreationDate="2010-05-09T12:16:27.370" Score="2" ViewCount="" Body="&lt;p&gt;Depending on your load you may be able to just force the&#xA;SET pin to GND. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you pull the SET pin to GND the LT3080 &#xA;will force the OUT pin to 0V. The internal schematic shows &#xA;that the SET pin connects to the positive input of the control &#xA;amplifier and the OUT pin connects to the control amplifier &#xA;output (through a transistor buffer). The OUT&#xA;pin follows the voltage on the SET pin. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use an N channel FET to short the SET pin to ground.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:19:20.720" LastActivityDate="2011-05-19T14:19:20.720" />
  <row Id="2578" PostTypeId="2" ParentId="430" CreationDate="2010-05-10T05:01:21.687" Score="1" ViewCount="" Body="&lt;p&gt;have a look at: &lt;a href=&quot;http://tronixstuff.com/tutorials&quot; rel=&quot;nofollow&quot;&gt;http://tronixstuff.com/tutorials&lt;/a&gt; :)&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-05-10T05:01:21.687" CommentCount="1" />
  <row Id="2579" PostTypeId="2" ParentId="2574" CreationDate="2010-05-10T09:14:50.863" Score="3" ViewCount="" Body="&lt;p&gt;Just do a voltage divider between GND and Vcc with two 4.7kOhm, and connect the divider center with the LCD contrast pin. Every LCD I've used works perfectly and with the right contrast.&lt;/p&gt;&#xA;" OwnerUserId="244" LastEditorUserId="244" LastEditorDisplayName="" LastEditDate="2010-05-11T07:25:17.380" LastActivityDate="2010-05-11T07:25:17.380" CommentCount="1" />
  <row Id="2580" PostTypeId="1" CreationDate="2010-05-10T12:22:52.890" Score="3" ViewCount="184" Body="&lt;p&gt;Not really related to chips, but hopefully I'll get some directions to follow from here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I got a chunk of code, but I don't know what processor it intended for. &#xA;Are there tools available that can help me identify the code type? &#xA;What statistic methods can help? Byte distribution? Pairs distribution, etc?&#xA;Markov chains maybe?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help appreciated!&#xA;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="752" LastActivityDate="2010-05-11T18:47:21.097" Title="Identify processor type from raw binary code?" Tags="&lt;code&gt;&lt;processor&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="2581" PostTypeId="2" ParentId="2569" CreationDate="2010-05-10T12:29:56.353" Score="0" ViewCount="" Body="&lt;p&gt;I did some more digging and found out this PDF on MIT OCW. Its the course notes for Underactuated systems. I have not yet read the whole book but it is a nice resource to understand concepts of walking as most of the legged locomotion problems require underactuated control. You can find it here &lt;a href=&quot;http://ocw.mit.edu/OcwWeb/Electrical-Engineering-and-Computer-Science/6-832Spring-2009/CourseHome/index.htm&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-05-10T12:29:56.353" CommunityOwnedDate="2010-05-10T12:29:56.353" />
  <row Id="2582" PostTypeId="2" ParentId="2580" CreationDate="2010-05-10T12:35:01.527" Score="8" ViewCount="" Body="&lt;p&gt;Try running it through GNU file. If it's got any standard header, it'll pick it up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Eg.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;jrt@lin:~/src$ file foo&#xA;foo: ELF 32-bit LSB executable, Atmel AVR 8-bit, version 1 (SYSV), statically linked, not stripped&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-05-10T14:30:49.460" LastActivityDate="2010-05-10T14:30:49.460" CommentCount="2" />
  <row Id="2583" PostTypeId="2" ParentId="2574" CreationDate="2010-05-10T17:09:36.293" Score="5" ViewCount="" Body="&lt;p&gt;just PWM something to make a contrast that suit your needs. hook up the pot pin of the LCD to a PWM pin of the arduino, sending a stable 0-127 signal. Just try.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ciao davide&lt;/p&gt;&#xA;" OwnerUserId="772" LastActivityDate="2010-05-10T17:09:36.293" />
  <row Id="2584" PostTypeId="2" ParentId="2464" CreationDate="2010-05-11T05:42:54.240" Score="3" ViewCount="" Body="&lt;p&gt;The colour channels are sent over 75Ω coax (it's an RF signal running with a high bandwidth - up to 250MHz - so it goes over coax).  The ground pin next to each colour pin is the coax ground. It needs to be close to the centre pin to minimise impedance mismatch in the DB-15H connector (which is NOT a great connector for RF - it does not provide a coaxial join for the three colour channels).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Long runs of video cable (~30 metres) require low loss coax to function correctly.  Poor cable quality results in degraded images (smearing and ghosting,etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards,&#xA;Tony Barry &lt;/p&gt;&#xA;" LastActivityDate="2010-05-11T05:42:54.240" />
  <row Id="2585" PostTypeId="1" AcceptedAnswerId="2588" CreationDate="2010-05-11T10:54:24.133" Score="5" ViewCount="460" Body="&lt;p&gt;According to the datasheet, the ATMega168 can only execute self-programming instructions when running code from the bootloader block.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once the bootloader is complete and the application starts, can the application then jump back into a subroutine in the bootloader block and have it write to the flash?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, is it the case that once the program leaves the boot block it's not allowed to self-program again until after a reset?&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-05-13T18:23:19.333" Title="AVR self-programming" Tags="&lt;avr&gt;&lt;bootloader&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="2586" PostTypeId="2" ParentId="2549" CreationDate="2010-05-11T12:23:15.403" Score="3" ViewCount="" Body="&lt;p&gt;I would have recommended &lt;a href=&quot;http://www.allegromicro.com/en/Products/Categories/ICs/sink.asp&quot; rel=&quot;nofollow&quot;&gt;Allegro's relay/solenoid drivers&lt;/a&gt;, but they have been deemed &quot;pre-end-of-life&quot; and shouldn't be used for new designs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.infineon.com/cms/en/product/channel.html?channel=ff80808112ab681d0112ab69dfb9034d&quot; rel=&quot;nofollow&quot;&gt;Infineon SPIDER ic's&lt;/a&gt; look interesting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3042&quot; rel=&quot;nofollow&quot;&gt;MAX4896&lt;/a&gt; might work but I avoid Maxim ic's like the plague as they tend to be made out of unobtainium.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-05-11T12:23:15.403" />
  <row Id="2587" PostTypeId="2" ParentId="1808" CreationDate="2010-05-11T12:46:13.797" Score="1" ViewCount="" Body="&lt;p&gt;I had to make the same decision a while ago when I broke my old PICKit2.&#xA;Finally I decided to buy the PICKit2 again.&#xA;Why?&#xA;- it supports most Microchip devices&#xA;-you can even program AVR MCUs with it see here &lt;a href=&quot;http://pickit2.isgreat.org&quot; rel=&quot;nofollow&quot;&gt;http://pickit2.isgreat.org&lt;/a&gt;&#xA;-you can use the PICKit2 as a USB to serial converter (see link above)&#xA;-has its own PC programming software and the pk2cmd command line tool (Linux support too)&#xA;-PK3 is not mature yet&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its not like buying a house.. if you dont like it, buy the other one.&lt;/p&gt;&#xA;" LastActivityDate="2010-05-11T12:46:13.797" />
  <row Id="2588" PostTypeId="2" ParentId="2585" CreationDate="2010-05-11T16:26:47.457" Score="5" ViewCount="" Body="&lt;p&gt;well... you can always execute a software initiated reset ala exploitation of the watchdog timer... and put data in eeprom to communicate to your bootloader code as to what you wanted it to do...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cs.mun.ca/~paul/cs4723/material/atmel/avr-libc-user-manual-1.6.5/FAQ.html#faq_softreset&quot; rel=&quot;nofollow&quot;&gt;http://www.cs.mun.ca/~paul/cs4723/material/atmel/avr-libc-user-manual-1.6.5/FAQ.html#faq_softreset&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Looking at page 272 of the ATMega168 manual (section 6: Entering the Boot Loader Program), the first line states:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Entering the Boot Loader takes place&#xA;  by a jump or call from the application&#xA;  program. This may be initiated by a&#xA;  trigger such as a command received via&#xA;  USART, or SPI interface.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So it would seem to me that definitively you &lt;em&gt;can and must&lt;/em&gt; be able to call the bootloader functions from application code. As long as you are executing code that resides in the Boot Loader section of memory, SPM instructions can be executed, and therefore you should be able to self-program any time your application program jumps into the boot loader code.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-05-13T18:23:19.333" LastActivityDate="2010-05-13T18:23:19.333" CommentCount="0" />
  <row Id="2589" PostTypeId="2" ParentId="2580" CreationDate="2010-05-11T18:47:21.097" Score="2" ViewCount="" Body="&lt;p&gt;Idea:  do you know the &lt;em&gt;age&lt;/em&gt; of the sourcecode, ie, around what time/year it was created?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it was old enough, it might give you a clue as to which processor it was written for.  You could take the age / year it was written and determine what processor(s) were popular around that time period, and try loading/executing the hex file on those.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On second thought, given the mass proliferation of processors in just the last 20 years, this might be a needle-in-a-haystack technique and not be very fruitful.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-05-11T18:47:21.097" />
  <row Id="2590" PostTypeId="1" AcceptedAnswerId="2593" CreationDate="2010-05-11T23:15:05.523" Score="4" ViewCount="364" Body="&lt;p&gt;I'm relatively new to electronics, and I'm trying to make a thermometer using a LM335 temperature sensor. By reading the datasheet I thought it was simple, connect up 5V to a resister, then to the V+, connect up V- to GND, and I should get somewhere just below 3V when reading the V+ pin. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, when I do this, I'm actually getting 4.08. I've tried two different sensors, so I'm reasonably sure that it's not just a DOA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas about what I could be doing wrong? What I can do to try to work it out?&lt;/p&gt;&#xA;" OwnerUserId="776" LastActivityDate="2011-05-16T10:42:57.687" Title="LM335 doesn't seem to work" Tags="&lt;lm335&gt;&lt;diode&gt;&lt;zener&gt;&lt;temperature&gt;" AnswerCount="2" />
  <row Id="2591" PostTypeId="1" AcceptedAnswerId="2596" CreationDate="2010-05-11T23:45:19.973" Score="3" ViewCount="231" Body="&lt;p&gt;I want to get started with embedded development and for my first project I thought of making a caller-ID type of appliance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's why I want a SBC for this:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I want to be able to locally serve this data (i.e., caller log) via HTTP&lt;/li&gt;&#xA;&lt;li&gt;I thought of maybe extending this appliance and adding an answering machine of some sort at a later time, so I guess I'll need &quot;advanced&quot; modem capabilities&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;From what I understand, all I really need is a SBC and a USB modem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone recommend the cheapest and most lightweight SBC that would be able to fulfill these requirements?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;: &lt;a href=&quot;http://andahammer.com/micro2440-oem/&quot; rel=&quot;nofollow&quot;&gt;This board&lt;/a&gt; looks cheap enough. Though it's only the &quot;brains&quot; of what I'm after. How hard would it be to hook up OEM ethernet, USB, and serial connectors to something like this?&lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="jfl207" LastEditDate="2011-02-04T00:28:44.190" LastActivityDate="2011-02-05T04:58:19.400" Title="SBC Recommendations" Tags="&lt;ethernet&gt;&lt;sbc&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="2592" PostTypeId="2" ParentId="2590" CreationDate="2010-05-11T23:47:30.733" Score="1" ViewCount="" Body="&lt;p&gt;What value resistor are you using?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the datasheet, LM335 needs about 400uA to 5mA of current. Assuming the diode will drop 3V, 2V is dropped across the resistor. To give between 400uA to 5mA, your resistor value should be between 400ohm to 5kohms.&lt;/p&gt;&#xA;" OwnerUserId="327" LastActivityDate="2010-05-11T23:47:30.733" CommentCount="1" />
  <row Id="2593" PostTypeId="2" ParentId="2590" CreationDate="2010-05-12T00:40:45.850" Score="6" ViewCount="" Body="&lt;p&gt;Are you sure you have it connected properly? If you are getting 4.83V at V+ and&#xA;4.88V at your supply it sounds like you have an open circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check the pinout against the datasheet. On page two they are showing the &lt;strong&gt;bottom&lt;/strong&gt; views&#xA;of the package.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:42:57.687" LastActivityDate="2011-05-16T10:42:57.687" CommentCount="3" />
  <row Id="2594" PostTypeId="1" CreationDate="2010-05-12T00:40:51.643" Score="6" ViewCount="612" Body="&lt;p&gt;I am trying to simulate button presses on a cell phone by using the Arduino to complete the button circuit thus simulating a button press. I figured out I have to use a transistor but I can't get it to work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please help&lt;/p&gt;&#xA;" OwnerUserId="769" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-05T22:53:51.477" LastActivityDate="2010-06-05T22:53:51.477" Title="Arduino with cell phone" Tags="&lt;arduino&gt;&lt;gsm&gt;&lt;cellphone&gt;" AnswerCount="4" />
  <row Id="2596" PostTypeId="2" ParentId="2591" CreationDate="2010-05-12T01:30:18.637" Score="3" ViewCount="" Body="&lt;p&gt;I'd say you'd want a cheap embedded Linux board, like the Technologic Systems TS-7550: &lt;a href=&quot;http://www.embeddedarm.com/products/board-detail.php?product=TS-7550&quot; rel=&quot;nofollow&quot;&gt;http://www.embeddedarm.com/products/board-detail.php?product=TS-7550&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used one recently to make thermostat for my house that serves up temperature data via HTTP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure what to recommend on the modem side of things.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-12T01:30:18.637" CommentCount="12" />
  <row Id="2597" PostTypeId="2" ParentId="2594" CreationDate="2010-05-12T01:41:16.523" Score="4" ViewCount="" Body="&lt;p&gt;Here's a test I would do before I tried to replace the button with a transistor: check to see whether the closing of the circuit pulls the joined contacts high or low. Once you know that, you can design the right replacement circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To explain a little more: when the button is not pressed, one terminal will be high (3.3 V, maybe?) and the other will be low (0 V). When you press the button, does the low one get pulled up to 3.3 V, or does the high one get pulled to 0 V?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're trying to pull a terminal low when you should actually be pulling the other terminal high, I don't think the circuit will behave like you want.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-12T02:37:23.973" LastActivityDate="2010-05-12T02:37:23.973" CommentCount="3" />
  <row Id="2599" PostTypeId="2" ParentId="1526" CreationDate="2010-05-12T06:20:20.150" Score="0" ViewCount="" Body="&lt;p&gt;Seems easy enough. Does anyone know if a pre-assembled programmer that can be used to program a small qualtity of picaxe chips? Everything I see is based on one chip.&lt;/p&gt;&#xA;" LastActivityDate="2010-05-12T06:20:20.150" />
  <row Id="2600" PostTypeId="2" ParentId="2585" CreationDate="2010-05-12T09:02:07.890" Score="2" ViewCount="" Body="&lt;p&gt;You can just jump to the bootloader block and everything should be fine. (just remember to move the interrupt vectors as well)&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-05-12T09:02:07.890" CommentCount="1" />
  <row Id="2601" PostTypeId="1" CreationDate="2010-05-12T11:12:22.563" Score="4" ViewCount="451" Body="&lt;p&gt;Suppose I have a circuit that draws its power from a LiPo Battery.&#xA;I would like to know how much power the battery still has in it.&#xA;Ideally a circuit of power level to voltage will be best .. this way I can connect the output of that circuit to a ADC input in my Arduino.&lt;/p&gt;&#xA;" LastEditorUserId="198" LastEditorDisplayName="" LastEditDate="2010-05-12T12:16:17.853" LastActivityDate="2010-11-03T18:47:44.770" Title="How can I tell how much juice a LiPo battery still has in it ?" Tags="&lt;battery&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="2602" PostTypeId="2" ParentId="2601" CreationDate="2010-05-12T12:00:39.000" Score="6" ViewCount="" Body="&lt;p&gt;To be honest, if you manage to find a way to do this reliably, just measuring the voltage, and patent it, then you will never have to work again.  The available energy left in a battery is loosely related to the terminal voltage but also depends on the battery temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A common method of determining the battery charge state is to use a coulomb counter to count the charge going into and out of the cell.  This gives a better estimate of the charge state of the battery, although the actual energy available is still temperature dependant.  At low temperatures the battery capacity can be less than 50% of the nominal.  An example device is the &lt;a href=&quot;http://www.st.com/stonline/products/families/power_management/battery_management/related_info/stc3100.htm&quot; rel=&quot;nofollow&quot;&gt;ST STC3100&lt;/a&gt;.  This uses an I2C interface to communicate with the processor.  The coulomb counting is performed by integrating the current in and out of the cell over the charge/discharge cycle.  If you know when the battery is full then you can estimate the amount of charge that has been used.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-05-12T12:00:39.000" CommentCount="3" />
  <row Id="2603" PostTypeId="1" CreationDate="2010-05-12T12:12:04.797" Score="4" ViewCount="721" Body="&lt;p&gt;I have been struggling with making an arduino for a while (was successful in making a breadboard version using ISP programmer cable). They say that Arduino bootloader is made so that no external circuitry is required to program the atmega8. But when I looked into the schematics there is the normal circuit required for the serial connection. Then what does the bootloader actually do?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-05-12T12:35:23.080" LastActivityDate="2010-05-12T13:03:12.063" Title="I don't get the arduino concept" Tags="&lt;arduino&gt;&lt;bootloader&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="2604" PostTypeId="2" ParentId="2603" CreationDate="2010-05-12T12:20:12.643" Score="7" ViewCount="" Body="&lt;p&gt;The bootloader is a small program in the AVR's flash which is never overwritten and runs on powerup. The job of the bootloader is to read program data from the UART and write it to the internal flash. Without a bootloader, the only way to load code is using ISP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The AVR ATMega8 comes with no code in the flash. Code can be uploaded via the ISP (in-system-programming) pins, using an AVR ISP programmer (or even another Arduino).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For Arduino, the ISP is used only once (at manufacture) - to upload a small bootloader. On powerup, the bootloader runs and communicates with the serial UART (TX + RX pins). Now, Arduino can be programmed via the serial pins using the STK500 protocol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the serial pins are (typically) connected to an FTDI USB to serial chip, the Arduino can also be programmed over USB.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-05-12T13:03:12.063" LastActivityDate="2010-05-12T13:03:12.063" CommentCount="11" />
  <row Id="2605" PostTypeId="2" ParentId="2603" CreationDate="2010-05-12T12:28:11.613" Score="3" ViewCount="" Body="&lt;p&gt;You can buy ATmega328 chips with the boot-loader on them &lt;a href=&quot;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&amp;amp;searchTerm=ATmega328&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-05-12T12:28:11.613" CommentCount="1" />
  <row Id="2606" PostTypeId="2" ParentId="2467" CreationDate="2010-05-12T15:03:07.077" Score="3" ViewCount="" Body="&lt;p&gt;In addition to Jameco (has practically everything) I added another vote for &lt;a href=&quot;http://allelectronics.com&quot; rel=&quot;nofollow&quot;&gt;All Electronics&lt;/a&gt;, they don't have everything but what they do have is very fairly priced.&lt;/p&gt;&#xA;" OwnerUserId="591" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-05-12T20:06:25.067" LastActivityDate="2010-05-12T20:06:25.067" CommunityOwnedDate="2010-05-12T15:03:07.077" />
  <row Id="2607" PostTypeId="2" ParentId="2467" CreationDate="2010-05-12T15:30:02.017" Score="3" ViewCount="" Body="&lt;p&gt;Funny no one has mentioned RadioShack.  Pricy but awful convenient sometimes&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-05-12T15:30:02.017" CommunityOwnedDate="2010-05-12T15:30:02.017" CommentCount="5" />
  <row Id="2608" PostTypeId="2" ParentId="2601" CreationDate="2010-05-12T16:07:42.640" Score="0" ViewCount="" Body="&lt;p&gt;What I am doing right now on a big battery consisting of a lot of Lipo cells is the following.&#xA;I first charge it up (see datasheet of the cells for maximum voltage). Next I will drain the battery with a big resistor whilst using a current clamp connected to a scope as well as measuring the battery voltage. There is a power supply in parallel with the battery rated at the cutoff voltage for the battery so I can leave the setup to drain the battery right up till the point where it is not recommended to go further.&#xA;With the scope(some Fluke, don't know the model) I can record the current over time, and thus determine the capacity.&#xA;When the capacity is determined I am going to log the current and voltage constantly when it is in use, and thus I can more accurately find the charge left.&#xA;But this setup will be monitored by a fancy industrial computer so I am not sure if that is the best way to go about at home.&lt;/p&gt;&#xA;" OwnerUserId="348" LastActivityDate="2010-05-12T16:07:42.640" />
  <row Id="2609" PostTypeId="2" ParentId="2467" CreationDate="2010-05-12T16:07:44.917" Score="3" ViewCount="" Body="&lt;p&gt;India&lt;/p&gt;&#xA;&#xA;&lt;p&gt;robokits.co.in&lt;/p&gt;&#xA;&#xA;&lt;p&gt;www.kitsnspares.com&lt;/p&gt;&#xA;&#xA;&lt;p&gt;please if anyone else knows some expand this list&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="1200" LastEditorDisplayName="" LastEditDate="2010-05-12T16:13:12.123" LastActivityDate="2010-05-12T16:13:12.123" CommunityOwnedDate="2010-05-12T16:07:44.917" />
  <row Id="2610" PostTypeId="2" ParentId="2467" CreationDate="2010-05-12T17:18:56.617" Score="4" ViewCount="" Body="&lt;p&gt;For South Africa:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://za.rs-online.com&quot; rel=&quot;nofollow&quot;&gt;RS&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.fort777.co.za&quot; rel=&quot;nofollow&quot;&gt;Yebo&lt;/a&gt; (Cape Town only)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.mantech.co.za&quot; rel=&quot;nofollow&quot;&gt;Mantech&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="781" LastActivityDate="2010-05-12T17:18:56.617" CommunityOwnedDate="2010-05-12T17:18:56.617" CommentCount="1" />
  <row Id="2611" PostTypeId="2" ParentId="2574" CreationDate="2010-05-12T17:26:46.050" Score="0" ViewCount="" Body="&lt;p&gt;I run mine with a single 1k5 resistor to ground. Seems to be good. Play around with different sizes if you have.&lt;/p&gt;&#xA;" OwnerUserId="781" LastActivityDate="2010-05-12T17:26:46.050" />
  <row Id="2612" PostTypeId="1" AcceptedAnswerId="2613" CreationDate="2010-05-12T22:14:14.113" Score="6" ViewCount="177" Body="&lt;p&gt;Let's say I have an open source project with a license that prohibits commercial uses.  Then comes along a commercial product with &lt;em&gt;striking&lt;/em&gt; similarities in functionality/hardware.  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How would I go about inspecting the commercial product to see if they are using parts of my source code?&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I realize I could do an image dump, but is that really useful, or easily obfuscated?&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Are there any simple tricks I could use, such as adding strange corner case behaviors, that would allow me to easily detect if anyone has copied the source verbatim, and are not overly obvious?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Bonus legal question: can I somehow subpoena the source code, if so what do I need to have to present 'reasonable doubt'?&lt;/p&gt;&#xA;" OwnerUserId="582" LastEditorUserId="582" LastEditorDisplayName="" LastEditDate="2010-05-12T22:19:53.537" LastActivityDate="2010-05-13T11:21:29.087" Title="How do I detect open-source licence violations by companies?" Tags="&lt;open-source&gt;&lt;licensing&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="2613" PostTypeId="2" ParentId="2612" CreationDate="2010-05-12T22:23:00.013" Score="3" ViewCount="" Body="&lt;p&gt;Perhaps try this: &lt;a href=&quot;http://www.binaryanalysis.org/en/home&quot; rel=&quot;nofollow&quot;&gt;http://www.binaryanalysis.org/en/home&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the legal question, I would try emailing the Software Freedom Law Center: &lt;a href=&quot;http://www.softwarefreedom.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.softwarefreedom.org/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-12T22:23:00.013" />
  <row Id="2614" PostTypeId="2" ParentId="2612" CreationDate="2010-05-13T05:36:54.140" Score="3" ViewCount="" Body="&lt;p&gt;Often running &lt;code&gt;strings&lt;/code&gt; on the two binaries and comparing the results can yield telling results:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;strings &amp;lt;filename&amp;gt;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;From the strings man page:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;strings - find the printable strings in a object, or other binary, file&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The results may not be identical, but it may show key similarities between the files.&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-05-13T05:36:54.140" />
  <row Id="2615" PostTypeId="2" ParentId="2612" CreationDate="2010-05-13T09:04:56.977" Score="1" ViewCount="" Body="&lt;p&gt;How about a poker bluff inspired by Apple? (Their lawyers sends a lot of papermail, even if their cases are bogus :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You simply write them a letter where you claim that they are doing copyright violation on your code, and then offer them a deal to settle &quot;out of court&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe mentioned that the case will be handed over to someone like the &lt;a href=&quot;http://www.eff.org/&quot; rel=&quot;nofollow&quot;&gt;EFF&lt;/a&gt; within XX days if they don't replay. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And if you are lucky they will contact you and you can get some money out of this situation.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-05-13T09:04:56.977" />
  <row Id="2616" PostTypeId="1" CreationDate="2010-05-13T10:18:31.167" Score="3" ViewCount="271" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have recently discovered that my AVR dragon has a busted voltage regulator (see &lt;a href=&quot;http://www.aplomb.nl/TechStuff/Dragon/Dragon.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;). I am trying to remove the voltage regulator IC so I can perform the mod specified on that page, however it is an &lt;a href=&quot;http://focus.ti.com/lit/ml/mpds117g/mpds117g.pdf&quot; rel=&quot;nofollow&quot;&gt;SON package&lt;/a&gt; with what looks like all of the pins under the chip. Is there any way I can desolder this with a (very good) temp controlled iron? I have given it a whirl with some extra solder + braid with no luck.&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-17T08:03:38.970" LastActivityDate="2011-05-17T11:52:37.270" Title="Desoldering an SON package" Tags="&lt;soldering&gt;" AnswerCount="4" />
  <row Id="2617" PostTypeId="2" ParentId="2616" CreationDate="2010-05-13T11:18:38.837" Score="3" ViewCount="" Body="&lt;p&gt;Sounds like a job for hot air.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've had success with removing components using a cheap craft tool, &lt;a href=&quot;http://papermilldirect.co.uk/heat-it-up-dual-speed-purple-heat-gun&quot; rel=&quot;nofollow&quot;&gt;http://papermilldirect.co.uk/heat-it-up-dual-speed-purple-heat-gun&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's another that you can make &lt;a href=&quot;http://www.futuretimes.org.uk/air_pencil.html&quot; rel=&quot;nofollow&quot;&gt;http://www.futuretimes.org.uk/air_pencil.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-05-13T11:42:28.007" LastActivityDate="2010-05-13T11:42:28.007" CommentCount="3" />
  <row Id="2618" PostTypeId="2" ParentId="2612" CreationDate="2010-05-13T11:21:29.087" Score="2" ViewCount="" Body="&lt;p&gt;Here is a &lt;a href=&quot;http://multimedia.cx/eggs/poking-at-youtube/&quot; rel=&quot;nofollow&quot;&gt;nice article by Multimedia Mike (ffmpeg/mplayer)&lt;/a&gt; about the second trick you mentioned (exploring corner cases). There are no GPL violations on YouTube side, but it is fun nevertheless.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-05-13T11:21:29.087" />
  <row Id="2619" PostTypeId="2" ParentId="2616" CreationDate="2010-05-13T13:08:34.053" Score="2" ViewCount="" Body="&lt;p&gt;If it has these &quot;exposed metalized features&quot; shown in the PDF then you can probably get it off just by heating those up.  I just put big solder globs all around the chip so that I can keep the entire glob heated at once, and when it comes loose, push it off.  If the chip is already bad, you don't need to worry about ruining it.  You might knock off nearby parts in the process, and if the PCB quality is poor, you might overheat and remove the protective mask? layer, but these can be dealt with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually, if you don't care about the chip, just destroy it.  :)  When I blew up an IC with a solder pad under it, for instance, I &lt;a href=&quot;http://www.instructables.com/id/How-to-hand-solder-a-PowerPad-IC/step1/Remove-the-old-chip/&quot; rel=&quot;nofollow&quot;&gt;cut off all the regular leads first&lt;/a&gt; to make the job easier.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-13T19:44:32.243" LastActivityDate="2010-05-13T19:44:32.243" CommentCount="1" />
  <row Id="2620" PostTypeId="2" ParentId="2616" CreationDate="2010-05-13T14:33:50.317" Score="2" ViewCount="" Body="&lt;p&gt;I've had good success using solder wick to draw off as much solder as possible. Then slip the tip of a dental pick under the side of the chip and gently pry up while heating the chip with a hair dryer. You might make a heat shield for the rest of the board by loosely covering it in aluminum foil with a cutout slightly bigger than the chip you're removing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it helps, solder melts around 218 C. It starts to melt below that, but it's fully liquid (above the &quot;liquidus point&quot;) at 218.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-13T14:33:50.317" />
  <row Id="2621" PostTypeId="2" ParentId="2574" CreationDate="2010-05-13T16:26:00.313" Score="0" ViewCount="" Body="&lt;p&gt;Ditto to leppie, but a 1k resistor to gnd. Something in that range should do the trick, depends on the lighting of the environment where you're using it.&lt;/p&gt;&#xA;" LastActivityDate="2010-05-13T16:26:00.313" />
  <row Id="2622" PostTypeId="2" ParentId="430" CreationDate="2010-05-13T16:32:40.373" Score="1" ViewCount="" Body="&lt;p&gt;check out the arduino playground &lt;a href=&quot;http://www.arduino.cc/playground/&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/&lt;/a&gt;, and for robotics in particular &lt;a href=&quot;http://www.arduino.cc/playground/Main/InterfacingWithHardware#Physical_Mechanical&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/Main/InterfacingWithHardware#Physical_Mechanical&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-05-13T16:32:40.373" />
  <row Id="2623" PostTypeId="2" ParentId="430" CreationDate="2010-05-13T17:55:41.327" Score="2" ViewCount="" Body="&lt;p&gt;The Arduino is good at a particular class of problems. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are situations where you receive a bunch of inputs, make a decision based on them, and as a result output something. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can do many things, but is especially good at this. Fortunately this is a very wide class of problems.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to understand this is &quot;&lt;strong&gt;What is the Ardunio NOT good at&lt;/strong&gt;&quot;. There are two main classes of problem it does not do well at:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;It is not good at processing intensive applications, or &lt;/li&gt;&#xA;&lt;li&gt;Where a general purpose system is required - one that can switch between many different applications on demand. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;So it has more in common with your washing machine than it does with your laptop. You can think of it as a &lt;em&gt;computer appliance&lt;/em&gt;, not a PC.&lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-05-13T17:55:41.327" />
  <row Id="2628" PostTypeId="1" CreationDate="2010-05-13T21:53:50.517" Score="5" ViewCount="194" Body="&lt;p&gt;I am overwhelmed with the variety of switching devices. MOSFETS/BJTS Relays(mechanical/solidstate),optoisolated solutions, etc..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to support 15V, 60A bursts, should be high efficiency, and switching time is not important since it wont be changing very often.  Noise is also not a large issue.&#xA;This will serve the function of a battery cut off in a circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Based on these requirements, what would you guys recommend?&lt;/p&gt;&#xA;" OwnerUserId="582" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2010-05-14T00:28:38.020" LastActivityDate="2011-01-04T23:02:06.610" Title="Choosing a switching device" Tags="&lt;switch&gt;&lt;relay&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="2629" PostTypeId="2" ParentId="2628" CreationDate="2010-05-14T00:28:15.663" Score="4" ViewCount="" Body="&lt;p&gt;I would suggest a mechanical relay. There are relays for automotive uses that can handle your load. You will typically need a small MOSFET or BJT to drive the relay coil (connect one end of the coil to +12V and drive the other to ground using the MOSFET/BJT).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use a high-current MOSFET but I don't think you can beat the price and low losses of the relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit:&lt;/strong&gt; JustJeff is right that when switching full 60A (especially if the load is inductive or the wires are long) the relay will need additional protection from inductive spikes to prevent arcing at the contacts (which may result in a permanently-on relay). With a MOSFET you could try making the turn-off slower (the dissipation should not be an issue if you rarely switch) by increasing the gate resistor.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2010-05-14T01:00:35.383" LastActivityDate="2010-05-14T01:00:35.383" />
  <row Id="2630" PostTypeId="2" ParentId="2628" CreationDate="2010-05-14T00:31:40.187" Score="6" ViewCount="" Body="&lt;p&gt;Almost definitely a MOSFET. The only issue really is what voltage is available to drive it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's say you have a 15V battery with a 5V on/off signal referenced to battery negative. If your load can float and can attach directly to the battery positive, then you can use an N-channel MOSFET: tie MOSFET source to battery negative, drain to the side of the load not connected to the battery, and the gate to the on/off signal through a small (50-200 ohm) resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the load needs to be grounded, you need to use a P-channel MOSFET with drain tied to the ungrounded end of the load, the source tied to battery positive, and the gate drive circuit may be a little more complicated (* = I might post details later).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 15V battery is small enough that you can get away with a MOSFET rated for 25-40V range and there are super-low on-resistances that can handle 60A loads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit:&lt;/strong&gt; you don't say what kind of packaging you are looking for. If you are planning on using a circuit board for other things, go with a MOSFET in an SO8, DPAK, or D2PAK package. SO8 sounds iffy for 60A loads unless it's for a really brief time, but it's probably the most cost-effective, though the worst for thermal dissipation. DPAK and D2PAK are beefier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're not planning on using a circuit board, an automotive relay would probably be much easier to use. &lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2010-05-14T00:41:43.613" LastActivityDate="2010-05-14T00:41:43.613" CommentCount="3" />
  <row Id="2631" PostTypeId="2" ParentId="2628" CreationDate="2010-05-14T03:34:06.527" Score="1" ViewCount="" Body="&lt;p&gt;Interrupting 60 A is a non-trivial task. I'd use a DC contactor, like those used in electric vehicles. McMaster sells a pile of them: &lt;a href=&quot;http://www.mcmaster.com/#dc-voltage-contactors/=72v7eh&quot; rel=&quot;nofollow&quot;&gt;http://www.mcmaster.com/#dc-voltage-contactors/=72v7eh&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In particular, I think part 7995K42 would work.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-14T03:34:06.527" />
  <row Id="2632" PostTypeId="1" AcceptedAnswerId="2638" CreationDate="2010-05-14T11:03:37.023" Score="4" ViewCount="257" Body="&lt;p&gt;After my embarrassing mistake by having the &lt;a href=&quot;http://chiphacker.com/questions/2590/lm335-doesnt-seem-to-work&quot; rel=&quot;nofollow&quot;&gt;component in backwards&lt;/a&gt;, I'm wondering if anyone has advice for the newbie (or expert) on reading datasheets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What conventions are there which aren't obvious.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the first thing you should check when something's not working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What can I safely ignore and what should I worry about?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anything else?&lt;/p&gt;&#xA;" OwnerUserId="776" LastActivityDate="2010-12-01T22:58:31.183" Title="Any advice on reading datasheets" Tags="&lt;datasheet&gt;&lt;electronics&gt;" AnswerCount="8" />
  <row Id="2634" PostTypeId="2" ParentId="2632" CreationDate="2010-05-14T12:47:38.410" Score="6" ViewCount="" Body="&lt;p&gt;Read the datasheet &lt;em&gt;carefully&lt;/em&gt;.  Details matter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Be Humble:&lt;/em&gt;  Don't assume there is something wrong with the part right away, assume the problem is in the way you used it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Frequently, I find that when things aren't working, I've either not read the manual well-enough, or &lt;em&gt;I&lt;/em&gt; did something wrong.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-05-14T12:47:38.410" CommentCount="2" />
  <row Id="2637" PostTypeId="2" ParentId="2632" CreationDate="2010-05-14T14:47:20.490" Score="4" ViewCount="" Body="&lt;p&gt;I like to print them out, or at least print the useful pages. Scribble in the margins.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-05-14T15:16:41.613" LastActivityDate="2010-05-14T15:16:41.613" />
  <row Id="2638" PostTypeId="2" ParentId="2632" CreationDate="2010-05-14T14:56:39.440" Score="8" ViewCount="" Body="&lt;p&gt;Look hard at where pin one is.  Make sure you understand if the diagram is a top or bottom view ( top is I think most common.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-05-14T14:56:39.440" CommentCount="2" />
  <row Id="2639" PostTypeId="2" ParentId="2632" CreationDate="2010-05-14T15:08:54.967" Score="3" ViewCount="" Body="&lt;p&gt;One thing with data sheets is that the manufacturer usually goes out of the way to make &lt;em&gt;everything&lt;/em&gt; obvious. This means that often times you have to look around to find a specific parameter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing about data sheets is that they usually only put the things that actually are important on them (unlike marketing material!). Point being that it's usually worth reading the entire thing through, at least once.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really want to prioritize, check the 'absolute maximum electrical ratings' first. This helps keep from frying the part. You might defer wading through tables of timing parameters or expected waveforms, or look at selected ones first that relate to whatever basic function you're trying to get up and running. But, even the application notes are often useful.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-14T15:08:54.967" />
  <row Id="2640" PostTypeId="2" ParentId="2632" CreationDate="2010-05-14T15:40:29.707" Score="6" ViewCount="" Body="&lt;p&gt;Have another engineer review your work.  You will not catch everything.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-05-14T15:40:29.707" CommentCount="1" />
  <row Id="2641" PostTypeId="1" AcceptedAnswerId="2644" CreationDate="2010-05-14T17:21:59.663" Score="13" ViewCount="1855" Body="&lt;p&gt;How cheap do FPGAs get? I know they're more expensive than microprocessors of comparable capability, but I wonder if there exist FPGAs that could contain a Microblaze soft core running Linux, while leaving gates available for implementing DSP functionality (media codecs, for example) at a cost competitive with, say, a Cortex A8 ($20-30 in qty. ~100).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Apologies if my terminology is non-idiomatic i.e. wrong. Please comment with corrections, or edit directly.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-01T23:26:08.183" Title="Cheapest FPGAs?" Tags="&lt;fpga&gt;&lt;cost&gt;&lt;softcore&gt;" AnswerCount="9" CommentCount="2" FavoriteCount="3" />
  <row Id="2642" PostTypeId="2" ParentId="2641" CreationDate="2010-05-14T17:35:44.867" Score="2" ViewCount="" Body="&lt;p&gt;My best guess so far is something like a Xilinx XC3S400A, which costs around $16, but I'm not sure that it could handle a MicroBlaze.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-14T17:35:44.867" CommentCount="4" />
  <row Id="2643" PostTypeId="2" ParentId="2641" CreationDate="2010-05-14T17:58:05.683" Score="8" ViewCount="" Body="&lt;p&gt;Generally FPGA will cost a lot more than the same device implemented in silicon, because there's a lot of overhead due to the reconfigurability. So no, you wont find a FPGA for $20-30 that has the same power as an ARM CPU that's $20-30. Now, you may find a FPGA for $20-30 that can perform specific tasks much faster than that $20-30 ARM, but it wont be able to beat it in general computing tasks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is why it's common to see people sticking a microcontroller and a FPGA on the same board. ARM and PPC are the two most commonly combined with a FPGA. &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-05-14T17:58:05.683" CommentCount="1" />
  <row Id="2644" PostTypeId="2" ParentId="2641" CreationDate="2010-05-14T18:20:17.090" Score="3" ViewCount="" Body="&lt;p&gt;Xilinx has recently done a &lt;a href=&quot;http://www.arm.com/about/newsroom/26179.php&quot; rel=&quot;nofollow&quot;&gt;deal&lt;/a&gt; with ARM, which will enable them to put ARM cores on FPGAs. Unfortunately, they will only be available for the top-of-the-range Virtex devices.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-05-14T18:20:17.090" CommentCount="3" />
  <row Id="2645" PostTypeId="1" CreationDate="2010-05-14T21:16:09.100" Score="3" ViewCount="167" Body="&lt;p&gt;I have installed the Labjack package and I got it to work for my needs, but now I need to use the EI-1050 humidity probe. The basic package has 2 examples for this, ljsht and ljsht-multi, but I can't figure out how to see their source code, and the user guide isn't that enlightening either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is, does anyone have an example of using this probe with Labjack in a C-like language (C, C++ or C#)?&lt;/p&gt;&#xA;" OwnerUserId="787" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-10T15:24:23.817" LastActivityDate="2010-11-10T15:24:23.817" ClosedDate="2010-11-22T05:17:40.750" Title="Labjack Humidity Probe Example" Tags="&lt;c&gt;" CommentCount="1" />
  <row Id="2646" PostTypeId="1" CreationDate="2010-05-15T01:28:13.437" Score="2" ViewCount="239" Body="&lt;p&gt;I just bought a DC gear motor- I'm trying to spin a 20 pound disk. I realize I need to hook it up to a power source, but I'm having trouble figuring out the proper source. PS I also got a DC speed controller and I'd like to use the two in conjunction. How do I do that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are the specs on the motor I've got&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PM DC Gear &#xA;90 vdc&#xA;input hp 1/30&#xA;full load amps 0.35&#xA;47 rpm&#xA;26 lb full load torque&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are the speed controller specs&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC Speed Control&lt;/p&gt;&#xA;&#xA;&lt;p&gt;HP 1/50 to 1/6&#xA;Voltage Output 90&#xA;Input Voltage 115&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" LastActivityDate="2010-05-15T18:39:41.660" Title="DC Gear motor Operation" Tags="&lt;dc&gt;&lt;speedcontroller&gt;&lt;motor&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="2647" PostTypeId="2" ParentId="2646" CreationDate="2010-05-15T04:11:00.337" Score="3" ViewCount="" Body="&lt;p&gt;Using it is as easy as it sounds. You will connect it to power, hopefully through a switch. You need something like nickel metal hydride batteries(forgive my spelling). You need high current at a relatively low voltage, and the first time you do it, do it in pulses of increasing length, checking for heat in each component of the system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, the motor controller should have a pair of pins for power(one from battery, other from ground of battery), pair for the motor, pair for control. control is done by a 50Hz square wave(20ms period) that has a duty cycle between 1.1 and 1.9 mS. The minimum being full reverse, maximum is full forward, 1.5mS will be idle. There are also controllers that use on and off, but you probably have one of the nicer ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To control it electrically I suggest a power MOSFET or BJT. MOSFET is probably more what you will want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PLEASE NOTE: when you use any sort of electrical control(a MOSFET you pick or such) you need to have a diode, reverse biased in normal opperation, pointing from ground pin of the motor to the high side. This needs to be a relatively large diode in operating current. The motor will act as a voltage source and can generate very high voltages, as it is pretty much a large inductor. This diode will allow the current a path that does not involve over-voltage'ing your motor.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-05-15T04:11:00.337" CommentCount="1" />
  <row Id="2648" PostTypeId="1" AcceptedAnswerId="2666" CreationDate="2010-05-15T11:03:01.680" Score="2" ViewCount="1094" Body="&lt;p&gt;Hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking to better understand basic RF receiver circuits, and I thought building a basic AM 77.5 kHz receiver seemed like a good challenge. I do however have had quite a challenge in finding any resources on this. Do you know any good starting points for the basic circuits involved in building this, in discrete components if possible, as I would like to understand the details of the system?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I understand correctly it should be possible without any kind of phase locked loop, and just with &quot;simple&quot; envelope detection as it is low frequency amplitude modulation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't worry about the actual demodulation, I'm going to sample the signal and do it digitally. This is what I know how to do. ;) So I'm only looking for the RF to baseband part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="718" LastActivityDate="2010-05-16T13:26:22.250" Title="DCF77 (AM 77.5 kHz) receiver in discrete components?" Tags="&lt;rf&gt;&lt;radio&gt;&lt;circuit&gt;" AnswerCount="2" />
  <row Id="2649" PostTypeId="1" AcceptedAnswerId="2658" CreationDate="2010-05-15T11:53:36.973" Score="6" ViewCount="573" Body="&lt;p&gt;My current project involves using 74HC595 shift registers to control an LED display, however the display could be up to 5 or so metres away from the Arduino board. The plan is to use some DB9/RS232 cables between a box with the Arduino, and an enclosure with the display. Would the length be too long for the digital signal to travel from the digital out pins to the shift register without degradation? Thanks, John&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-05-16T04:16:50.720" Title="How long between Arduino digital pin and IC?" Tags="&lt;arduino&gt;&lt;74hc595&gt;" AnswerCount="5" CommentCount="1" />
  <row Id="2650" PostTypeId="2" ParentId="2649" CreationDate="2010-05-15T12:04:57.000" Score="3" ViewCount="" Body="&lt;p&gt;You will probably need buffers to drive that length of cable - something like the 74HC244 buffer/line driver should be suitable.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-05-15T12:04:57.000" />
  <row Id="2651" PostTypeId="2" ParentId="2649" CreationDate="2010-05-15T12:50:40.410" Score="3" ViewCount="" Body="&lt;p&gt;What's the bit rate/speed of the transmission?  Have you tried it and looked at the waves on a scope?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-05-15T12:50:40.410" />
  <row Id="2652" PostTypeId="2" ParentId="2648" CreationDate="2010-05-15T13:01:02.760" Score="1" ViewCount="" Body="&lt;p&gt;Well, a crystal radio is the simplest possible AM receiver, which just uses simple envelope detection.  &lt;a href=&quot;http://en.wikipedia.org/wiki/Crystal_radio#The_naive_circuit&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Crystal_radio#The_naive_circuit&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You've probably already seen this: &lt;a href=&quot;http://www.giangrandi.ch/electronics/dcf77/dcf77.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.giangrandi.ch/electronics/dcf77/dcf77.shtml&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Very simple AM receiver using envelope detection: &lt;a href=&quot;http://www.next.gr/inside-circuits/Simple-Coil-less-AM-receiver-l6022.html&quot; rel=&quot;nofollow&quot;&gt;http://www.next.gr/inside-circuits/Simple-Coil-less-AM-receiver-l6022.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But this is just regurgitating Google results.  Can you give more details about what kind of circuit you're looking to build and what information you need?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-05-15T13:01:02.760" CommentCount="2" />
  <row Id="2653" PostTypeId="1" AcceptedAnswerId="12107" CreationDate="2010-05-15T13:01:39.557" Score="6" ViewCount="243" Body="&lt;p&gt;Its been quite while since I have been listening about Amateur(Ham) radio. I think its a good hobby to dabble into to develop an understanding of Communication technology and electronics. But what ever research I have done turns up things which tell about it for someone who buys ready made radios. I want to dive into the electronics and understand how all of it works, I don't want to think too abstract.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone please guide me to some website or book which can guide a beginner to get started in radio technology but also provide at least a basic understanding of how everything works and how to get your hands dirty.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Before anyone mentions it, I know I have to get a licence and I am preparing for the exam).&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-27T22:07:26.320" LastActivityDate="2011-03-28T15:34:47.070" Title="Getting started in Ham radio" Tags="&lt;ham-radio&gt;" AnswerCount="6" CommentCount="5" FavoriteCount="1" />
  <row Id="2654" PostTypeId="2" ParentId="2653" CreationDate="2010-05-15T14:57:28.623" Score="11" ViewCount="" Body="&lt;p&gt;A book that meets your requirements would be the ARRL Handbook for Radio Communication. I haven't looked at this year's edition, but they typically have a section on electronics and radio theory, radio construction projects, antenna projects, and other side projects like power supplies. The projects run through the whole frequency range, though the HF projects are usually easier to build. The nice part is that not a lot of initial knowledge is assumed, and the theory sections are readable.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-05-15T14:57:28.623" />
  <row Id="2655" PostTypeId="2" ParentId="2653" CreationDate="2010-05-15T15:17:13.917" Score="4" ViewCount="" Body="&lt;p&gt;It's also a good idea to join your local amateur radio club. I'm on the committee of &lt;a href=&quot;http://www.radioclubs.net/herc/&quot; rel=&quot;nofollow&quot;&gt;HERC&lt;/a&gt;, the Hastings Electronics and Radio Club, and we provide free training for all three levels of the UK Amateur Radio License. Students get free club membership! Most other clubs do the same.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-05-15T16:06:34.923" LastActivityDate="2010-05-15T16:06:34.923" CommentCount="9" />
  <row Id="2657" PostTypeId="2" ParentId="2649" CreationDate="2010-05-15T16:25:11.320" Score="4" ViewCount="" Body="&lt;p&gt;My feeling is you should be fine at this length. Your best bet might be to try it and see if it works. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it does not work, there are a few things you can do to help:&#xA;- use shielded, twisted pair cables, or twist cables together.&#xA;- Put a small cap (0.01 uF or thereabouts) at the end. This should help cancel some of the noise (using too large a capacitor will not work, so bigger is not better in this case).&#xA;- Use slightly lower valued resistors than you would normally for your pulldowns.&#xA;- Use low impedance cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a datapoint, an Arduino can run 9600 serial over unshielded cable for 50' (maybe more?).&lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-05-15T16:25:11.320" />
  <row Id="2658" PostTypeId="2" ParentId="2649" CreationDate="2010-05-15T16:28:11.893" Score="5" ViewCount="" Body="&lt;p&gt;The 74HC595 is CMOS technology so it should take almost nothing in the way of current to drive it, so IR drop wouldn't be a concern. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As long as you keep the frequency of the signals down below say 100kHz, you shouldn't have to worry about transmission line effects. Assuming your intended observer for the LEDs to be the human eye, you shouldn't have to worry about high speeds anyway. For example, 8 digits at 7 segments and a decimal point each is 64 LED elements, and at a mere 9600 bps, you could update the display in just under 7 msec. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only thing I would worry about is whether the digital high output level from the Arduino will register as a high input at your shift register. As long as the shift register is running from a 5V supply (and not something odd like 6) you should be fine there, too. (and if &lt;em&gt;this&lt;/em&gt; was going to be a problem, it would manifest itself over a mere 10cm of wire so that's easy to check)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Short answer: very high probability you can go from arduino to cable to 74HC595s no problem.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-15T16:28:11.893" />
  <row Id="2660" PostTypeId="2" ParentId="2646" CreationDate="2010-05-15T17:47:06.883" Score="0" ViewCount="" Body="&lt;p&gt;Greg, this is an answer to your later question, &quot;Determining Power Source for DC Gear Motor?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm hoping you'll merge that question into this question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's start with the battery. 90 V is high enough to be dangerous. You can run the motor with a lower voltage, but with two side effects-- the top speed will decrease, and the torque will drop. I'd start with a few &lt;a href=&quot;http://www.amazon.com/Rayovac-6V-GP-Lantern-Battery-General/dp/B0017HVRUC&quot; rel=&quot;nofollow&quot;&gt;lantern batteries&lt;/a&gt; connected in a series string (+-+-+-) and turning it on and off by hand with a wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can tell us a little more about your DC speed controller, we might be able to help with that too. (For example: What does it look like? Where did you get it? Are there any words written on it?)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-15T17:47:06.883" CommunityOwnedDate="2010-05-15T17:47:06.883" />
  <row Id="2662" PostTypeId="2" ParentId="2649" CreationDate="2010-05-16T04:16:50.720" Score="3" ViewCount="" Body="&lt;p&gt;You should scope it anyway to ensure its performing correctly but here is the thought process/math you need to take into account to determine transmission line effects.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Edge rise and fall time, in opposition what some have posted here, the frequency of the signal does not matter at all when determining when you need to take transmission line effects into account.  It is generally true that high frequency signals have faster rise/fall times but low frequency signals can also have very fast rise and fall times if they are being driven at low frequency by a transceiver with a high slew rate.  As always use the slowest rise/fall times possible to stay within spec for the parts you are using, you can reduce the rise and fall times with an RC filter at the source.  In general you need to consider transmission line effects if the length of the wire is greater than Tr/(2*Td) with Tr = to the signal rise time at the source and Td = to the propagation delay per unit length of the cable you are using.  You may also need to properly terminate the signal lines on shorter cables if the load is highly capacitive,  this is kind of difficult to calculate upfront as there are many items with capacitive effects in such a system.  If you have this problem you will notice ringing (under and over shoot on edges) in the signal.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Current in the cable, this will be defined in the spec sheet of the receiving IC as the input current.  This combined with the resistance of the cable will tell you if the voltage drop is acceptable given the specs of the receiving IC.  This only an average current value.  The actual peak current can depend on the type of termination used and needs to be considered when deciding if the driving IC can handle the load or if you need a line driver.  The peak current should only last as long as the round trip propagation delay of the circuit. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you need to take the transmission line effects into account you also need to know the characteristic impedance of the cable and the output impedance of the driving IC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do need to handle the transmission line effects there are a few options for termination style.  The only two i would consider are source termination and AC biased end termination.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In source termination you need to place a resistor as close as possible to the driving IC with value equal to the characteristic impedance of the cable minus the output impedance of the driving IC, you may have to tune this a bit to hit spec dead on as the impedance of the cable connectors will also impact the system and as always place the driving and receiving IC's as close to the connectors as possible to reduce reflections.  This is probably the easiest method and probably the best method in this case.  Peak current will be (Vhigh - Vlow)/(2*Z0) with Z0 = to the characteristic impedance of the cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In AC biased end termination you connect to the signal line as close to the receiving IC as possible a resistor in series with a capacitor with the capacitor tied to ground.  The value of the resistor should be the characteristic impedance of the cable, the value of the capacitor is determined by the frequency of the signal (the R and C form a low pass filter).  The peak drive current is the same as for source termination.  The average drive current is dependent on the duty cycle of the signal, if its very close to 50% then it will be roughly equal to to the input current of the receiving IC, if it is over 50% the average drive current will be higher.  As the R and C form a low pass filter this termination style will filter out some high frequency noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Couple other things to keep in mind:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Using twisted pairs for a single ended signals does not reduce noise pick up at all.  It does result in a more consistent characteristic impedance for the transmission line.  This may make the output look better if you really should have properly terminated the signal but didn't.  It does nothing to reduce outside EM noise on the line.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Use of shielded cable on a single ended system is iffy at best.  You can often create a situation where outside noise capacitively couples to the shield resulting in current flow on the shield which then couples to the signal wire.  I wouldn't bother using a shielded cable unless your using differential signaling.  Also the usefulness of a shield on high frequency noise is dependent on the inductance to ground, low inductance paths usually require special connectors.  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You can use very much the same thought processing on any line be it a cable or a 2 inch PCB trace.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-05-16T04:16:50.720" CommentCount="2" />
  <row Id="2663" PostTypeId="2" ParentId="2632" CreationDate="2010-05-16T07:56:37.863" Score="2" ViewCount="" Body="&lt;p&gt;best advice i can give you is to read them carefully but take them with a grain of salt.  Don't just blindly do what they tell you, even with it comes to example circuits.  I've seen multiple datasheets with blatant errors in example circuits.  one famous one i remember called for a 470uF cap instead of a 470nF cap in a reconstruction filter, which the designer(me) followed without questioning resulting is a massive aluminium cap on the rev 1 pcb instead of a 0402 SMD package cap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also keep in mind that they are written by people who work on specific parts in specific sectors and usually have a distorted view of what the overall system design calls for.  A common example is devices that do A to D or D to A.  They will almost always call for separate and isolated digital and analog ground.  While in theory this is fine but in practice designing a PCB with segmented ground planes is almost always a terrible idea unless you have massive amounts of board space to play with.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-05-16T07:56:37.863" />
  <row Id="2664" PostTypeId="2" ParentId="2130" CreationDate="2010-05-16T09:16:35.117" Score="0" ViewCount="" Body="&lt;p&gt;Sparkfun are now selling &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9770&quot; rel=&quot;nofollow&quot;&gt;conductive fabric&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2010-05-16T09:16:35.117" />
  <row Id="2665" PostTypeId="2" ParentId="1834" CreationDate="2010-05-16T10:13:30.027" Score="3" ViewCount="" Body="&lt;p&gt;I haven't used the QTR sensors myself, but I noticed that the main difference between your code and the &lt;a href=&quot;http://www.pololu.com/docs/0J20/6.m&quot; rel=&quot;nofollow&quot;&gt;examples&lt;/a&gt; I found floating around is that you are calling readCalibrated(val) before readLine and the examples don't. I looked through the &lt;a href=&quot;http://www.pololu.com/file/download/PololuArduinoLibraries-080826.zip?file_id=0J127&quot; rel=&quot;nofollow&quot;&gt;source for the libary&lt;/a&gt; and readLine calls readCalibrated in the first couple of lines anyway. Maybe pre-loading val is with the calibration values is causing the problem?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, are you passing the sensor over both the white and black surfaces during the calibration? A trick could be to get the bot to slowly spin on the spot during calibration, while sitting on the line, allowing the sensor to see both the line and the surrounding area.&lt;/p&gt;&#xA;" OwnerUserId="25" LastActivityDate="2010-05-16T10:13:30.027" />
  <row Id="2666" PostTypeId="2" ParentId="2648" CreationDate="2010-05-16T13:26:22.250" Score="2" ViewCount="" Body="&lt;p&gt;I was looking into it some time ago and it seems that the 77.5kHz band is very noisy (SMSPs and stuff) and it makes it quite difficult to build a good receiver for DCF77. Most projects are based on ready-made modules.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to make something simple try building an analog AM receiver for local radio broadcasts. It should be easier (the signal will be stronger) and there are plenty resources on the net.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://elm-chan.org/works/rsm/report_e.html&quot; rel=&quot;nofollow&quot;&gt;Radio Spectrum Monitor&lt;/a&gt; may also be interesting to you albeit it is much more advanced project.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-05-16T13:26:22.250" CommentCount="3" />
  <row Id="2667" PostTypeId="2" ParentId="2632" CreationDate="2010-05-16T21:11:29.737" Score="6" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Terminology&lt;/strong&gt; There is industry standard terminology that has evolved&#xA;for electronic components. It is important to understand the&#xA;definitions.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Absolute Maximum Ratings&lt;/strong&gt; Understand the limitations of the&#xA;component.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Specification Conditions&lt;/strong&gt; Although the terminology is standard the&#xA;specific test conditions for each specification are not. It is&#xA;important to account for these differences when (1) determining the&#xA;proper component and (2) when comparing devices.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Application Notes&lt;/strong&gt; Most datasheets have a variety of application circuits.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Reference Designs&lt;/strong&gt; A good reference design will demonstrate the&#xA;proper application of a component and the proper circuit layout to&#xA;achieve the specified performance.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Component Package Specifications&lt;/strong&gt; Review the component&#xA;packages and the recommended PCB land patterns.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I have placed some additional details at &lt;a href=&quot;http://wiblocks.luciani.org/FAQ/faq-reading-datasheets.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/FAQ/faq-reading-datasheets.html&lt;/a&gt;&#xA;I will try to add some details about the datasheet&#xA;specifications that deal with thermal calculations --&#xA;thermal resistance, transient thermal response and switching&#xA;losses. There seems to be quite a few thermal questions&#xA;(on a variety of sites). &lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-01T22:04:18.910" LastActivityDate="2010-12-01T22:04:18.910" />
  <row Id="2668" PostTypeId="1" CreationDate="2010-05-17T08:03:17.043" Score="1" ViewCount="2586" Body="&lt;p&gt;I recently got an XBee Pro Series 2.5 and another XBee Series 2.5 as listed here:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/XBee-2mW-Series-2.5-Chip-Antenna.html&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/XBee-2mW-Series-2.5-Chip-Antenna.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/XBee-Pro-50mW-Series-2.5-U.FL-Connection.html&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/XBee-Pro-50mW-Series-2.5-U.FL-Connection.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I then downloaded the latest version of X-CTU so that I could attempt to configure the XBees for use as a serial communication between two Arduinos.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I launch X-CTU, the 'com test' works fine, and I see my modems with firmware version 1247 for both, and types 'XB24-B' and 'XBP24-B' for the normal and 'pro' XBees respectively.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, here's the problem: when I click the 'Modem Configuration' tab, and then click 'Read', I am repeatedly told that &quot;The modem configuration file was not found. Would you like to check the website for updates? (Recommended)&quot; and then, on clicking 'Yes', &quot;Modem configuration file not found after update&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Digi people have weirdly fobbed me off with some comment about my hardware no longer being supported... but it's brand new stuff as far as I can tell. The Pro XBee says &quot;Model:XBEEPRO2&quot; and the regular XBee says &quot;IC:4214-XBEE2&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone got any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="791" LastEditorUserId="791" LastEditorDisplayName="" LastEditDate="2010-05-18T05:34:33.883" LastActivityDate="2010-05-18T05:34:33.883" Title="Using X-CTU to setup XBee modem" Tags="&lt;xbee&gt;&lt;arduino&gt;&lt;zigbee&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="2669" PostTypeId="1" AcceptedAnswerId="2670" CreationDate="2010-05-17T13:01:38.880" Score="9" ViewCount="346" Body="&lt;p&gt;The attached screenshot is from a schematic in a datasheet.  I know that the flat-topped arrow is a diode, but I don't know what the pair of looped circles are.  Can anyone help me out?  If there's a good online symbol reference, please share the link!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://img.skitch.com/20100517-1n6cnjiecqkfgd4rpx85ii87m8.jpg&quot; alt=&quot;unknown symbol&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="51" LastEditorUserId="51" LastEditorDisplayName="" LastEditDate="2010-05-17T14:30:31.087" LastActivityDate="2011-05-16T10:49:30.240" Title="Can you help me identify this symbol?" Tags="&lt;schematics&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="2670" PostTypeId="2" ParentId="2669" CreationDate="2010-05-17T13:10:32.987" Score="10" ViewCount="" Body="&lt;p&gt;I believe that would be a diode (the triangle and horizontal line) in series with a current source (the two circles).&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-17T13:10:32.987" />
  <row Id="2671" PostTypeId="2" ParentId="2669" CreationDate="2010-05-17T13:15:44.680" Score="5" ViewCount="" Body="&lt;p&gt;A diode in series with a constant current source. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There was a symbol guide published by the ARRL at &lt;a href=&quot;http://www.arrl.org/qst/qs4hd.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.arrl.org/qst/qs4hd.pdf&lt;/a&gt;&#xA;but that link appears to be broken :(&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:49:30.240" LastActivityDate="2011-05-16T10:49:30.240" />
  <row Id="2672" PostTypeId="2" ParentId="2669" CreationDate="2010-05-17T13:27:18.940" Score="7" ViewCount="" Body="&lt;p&gt;The two circles are DC Current power Source&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electricalwhat.com/power-source/dc-current/&quot; rel=&quot;nofollow&quot;&gt;http://electricalwhat.com/power-source/dc-current/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="792" LastActivityDate="2010-05-17T13:27:18.940" CommentCount="2" />
  <row Id="2673" PostTypeId="2" ParentId="2467" CreationDate="2010-05-17T13:41:29.670" Score="4" ViewCount="" Body="&lt;p&gt;You can find larger components and a lot of cheap tools from &lt;a href=&quot;http://www.mpja.com&quot; rel=&quot;nofollow&quot;&gt;MPJA&lt;/a&gt;.  I most frequently use them to order $9 breadboard kits with jumper wires for classes at NYC Resistor.&lt;/p&gt;&#xA;" OwnerUserId="574" LastActivityDate="2010-05-17T13:41:29.670" CommunityOwnedDate="2010-05-17T13:41:29.670" />
  <row Id="2675" PostTypeId="1" AcceptedAnswerId="2676" CreationDate="2010-05-17T16:25:13.513" Score="9" ViewCount="330" Body="&lt;p&gt;If I've got a device that uses a single battery, and with that single battery, the device lasts an hour, and I want the device to last for two hours, I'm assuming I can wire two batteries up and it should work. But how? Do I want to double the voltage (so serial) or double the current? (so parallel.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Either way, if the device takes two batteries normally, and I want to double the running time, I do a combo of 2 parallel series of 2 serial batteries, right? But if I want to triple the run time, is that 3p2s or 2p3s?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="793" LastEditorUserId="3552" LastEditorDisplayName="" LastEditDate="2011-05-19T10:24:36.197" LastActivityDate="2011-05-19T10:24:36.197" Title="How do I connect two identical batteries to increase the consumer lifetime?" Tags="&lt;battery&gt;&lt;batteries&gt;&lt;basic&gt;&lt;power&gt;" AnswerCount="3" />
  <row Id="2676" PostTypeId="2" ParentId="2675" CreationDate="2010-05-17T16:46:40.523" Score="16" ViewCount="" Body="&lt;p&gt;When you connect two batteries in parallel you are effectively having your discharge rate and doubling your capacity. Effectively doubling life, as you are intending to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Serial connection does not increase life but increases operating voltage, which some devices need. If your device has 2 serial batteries then you need to connect another two serial batteries in parallel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If they are not going to be recharged in the configuration you are putting them in, then you should be able to connect them in parallel. They will end up using a small amount of power charging each-other small amounts, but you will probably see more than a doubling of life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are pulling a lot of power from a battery you will find that it's battery capacity decreases and causes excess current draw to decrease life and decreased capacity to decrease life. &lt;a href=&quot;http://www.batteryuniversity.com/&quot; rel=&quot;nofollow&quot;&gt;There are some excellent explanations about batteries online.&lt;/a&gt; The link I gave is more lithium focused, but the general knowledge applies to most batteries. &lt;a href=&quot;http://www.batteryuniversity.com/partone-16.htm&quot; rel=&quot;nofollow&quot;&gt;This link&lt;/a&gt; is specifically about discharge rates and their effect on battery life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps. If you comment on anything that is not clear I will edit and expand on it.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-05-17T17:00:43.470" LastActivityDate="2010-05-17T17:00:43.470" CommentCount="4" />
  <row Id="2677" PostTypeId="2" ParentId="2675" CreationDate="2010-05-17T16:47:04.583" Score="4" ViewCount="" Body="&lt;p&gt;You want to add batteries in parallel, keeping a constant voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are correct that if a device takes two batteries in series, you want to add additional series pairs in parallel.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-17T16:47:04.583" />
  <row Id="2678" PostTypeId="2" ParentId="2675" CreationDate="2010-05-17T17:04:31.933" Score="3" ViewCount="" Body="&lt;p&gt;The capacity (i.e. milliamp-hours or mAh) is what governs the lifetime. Capacity adds in parallel, so wire + to + and - to -.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-05-17T17:04:31.933" />
  <row Id="2679" PostTypeId="1" AcceptedAnswerId="2683" CreationDate="2010-05-17T19:25:51.523" Score="6" ViewCount="360" Body="&lt;p&gt;What software is generally used in industry to design cases for pcb boards?&lt;/p&gt;&#xA;" OwnerUserId="582" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-05-17T22:02:56.830" LastActivityDate="2011-05-02T21:48:14.680" Title="3d modelling software for case design" Tags="&lt;cases&gt;&lt;cad&gt;&lt;software&gt;" AnswerCount="9" FavoriteCount="4" />
  <row Id="2680" PostTypeId="2" ParentId="2679" CreationDate="2010-05-17T19:29:46.707" Score="4" ViewCount="" Body="&lt;p&gt;auto-cad Inventor.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-05-17T19:29:46.707" />
  <row Id="2681" PostTypeId="2" ParentId="2679" CreationDate="2010-05-17T19:45:43.707" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.ptc.com/products/proengineer/&quot; rel=&quot;nofollow&quot;&gt;Pro/Engineer&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-05-17T19:45:43.707" />
  <row Id="2682" PostTypeId="2" ParentId="2679" CreationDate="2010-05-17T20:03:25.213" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.solidworks.com&quot; rel=&quot;nofollow&quot; title=&quot;SolidWorks&quot;&gt;SolidWorks&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-05-17T20:03:25.213" />
  <row Id="2683" PostTypeId="2" ParentId="2679" CreationDate="2010-05-17T20:04:09.960" Score="13" ViewCount="" Body="&lt;p&gt;Generally, you need software that can export STL files.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Solidworks: $\$$4000 + $\$$1300/year&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ProEngineer: $\$$5000? + something per year?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Autocad Inventor: $\$$5200? + something per year?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Google Sketchup: Free or $\$$500, but can't export STL directly. I've seen mention of a plugin that can convert Sketchup files to STL, but I haven't used it myself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(From Peter Gibson) Blender: Free, but alleged to have a steep learning curve.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-02T21:07:08.743" LastActivityDate="2011-05-02T21:07:08.743" CommentCount="2" />
  <row Id="2684" PostTypeId="2" ParentId="2449" CreationDate="2010-05-17T23:17:21.623" Score="0" ViewCount="" Body="&lt;p&gt;In superscalar processors we use register renaming to avoid WAW and WAR hazards and we prefer using ROB for RAW. so iff you assume we are using register renaming we will not be using ROB in WAR and WAW.&lt;/p&gt;&#xA;" LastActivityDate="2010-05-17T23:17:21.623" CommunityOwnedDate="2010-05-17T23:17:21.623" />
  <row Id="2685" PostTypeId="2" ParentId="2668" CreationDate="2010-05-18T05:34:01.890" Score="3" ViewCount="" Body="&lt;p&gt;I made some progress on this after chatting live with Eric from Digi support, and also reading around HOWTOs on the net.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First point is that the XBee 2.5 model is discontinued and no longer supported by Digi, even though it's still pretty widely sold. Eric mentioned that there are some better and more up-to-date models available, I think the 'ZB' line rather than the 'ZNet' is what you want. But I'm not completely clear on that yet (and I have the 2.5 which I wanted to get working).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, because the XBee 2.5 and XBee PRO 2.5 are no longer supported, the firmware is not available automatically from the X-CTU program. To get the firmware, you can still download it manually, and then use the 'File' option in the X-CTU download tool to get X-CTU to use the latest firmware. The firmware I needed was on this page: &lt;a href=&quot;http://www.digi.com/support/productdetl.jsp?pid=3261&amp;amp;osvid=0&amp;amp;s=269&amp;amp;tp=2&amp;amp;tp2=0&quot; rel=&quot;nofollow&quot;&gt;http://www.digi.com/support/productdetl.jsp?pid=3261&amp;amp;osvid=0&amp;amp;s=269&amp;amp;tp=2&amp;amp;tp2=0&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, you can follow the information in the 'Xbee Configuration guide', see link at &lt;a href=&quot;http://www.arduino.cc/en/Guide/ArduinoXbeeShield&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Guide/ArduinoXbeeShield&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have to set up one XBee as 'ZNET 2.5 COMMUNICATOR AT' (the 'home base' xbee) and the other as 'ZNET 2.5 ROUTER/ENDPOINT AT' (the 'remote' xbee). You can assign names (ID) and network IDs (PAN ID) to both XBees using X-CTU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using this approach, the serial test worked OK, so it's looking good. According to Eric, what one should really be doing here is upgrading the firmware to the new 'ZB' feature set, for which instructions are here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ftp1.digi.com/support/documentation/upgradingfromznettozb.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ftp1.digi.com/support/documentation/upgradingfromznettozb.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm entirely sure why one should do that, other than to enable digi to support you better, because they don't actually support the ZNet modules, which apparently date from year 2006.&lt;/p&gt;&#xA;" OwnerUserId="791" LastActivityDate="2010-05-18T05:34:01.890" CommentCount="1" />
  <row Id="2686" PostTypeId="2" ParentId="263" CreationDate="2010-05-18T07:58:14.837" Score="0" ViewCount="" Body="&lt;p&gt;Stop guessing. Calculate it, simulate it, test it!&lt;/p&gt;&#xA;" OwnerUserId="796" LastActivityDate="2010-05-18T07:58:14.837" />
  <row Id="2687" PostTypeId="2" ParentId="2324" CreationDate="2010-05-18T08:17:30.157" Score="2" ViewCount="" Body="&lt;p&gt;Arduino is irrelevant or you'd be asking why is Arduino so popular and not why AVR. AVR's have been &quot;popular&quot; for a while completely regardless of Arduino. Arduino is a product of the same things that made AVR attractive. It's another product, another devkit. AVR is not pouplar in units delivered where 8051's in devices and pic's in smartcards or whatnot have massive numbers or in cellphone and PC markets where the AVR doesn't even compete.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead of &lt;em&gt;popular&lt;/em&gt;, you could say AVR is &lt;em&gt;attractive&lt;/em&gt;. And it is. The main points already came out: It's available and inexpensive, requires very little components or board features (clocks, buses...), is easily ISP and above all, there's good software support. You get a real compiler, programming software and hw designs, docs, samples, libraries, all free as in freedom. You don't have to fight vendors and wonder if you're code size limited or hear that your compiler has been discontinued or won't run on any operating system from this decade. If not before, then once you've been bitten enough times, you'll appreciate open tools and docs where nobody dictates what you can and can't do or know.&lt;/p&gt;&#xA;" OwnerUserId="796" LastActivityDate="2010-05-18T08:17:30.157" CommunityOwnedDate="2010-05-18T08:17:30.157" />
  <row Id="2688" PostTypeId="2" ParentId="2211" CreationDate="2010-05-18T08:23:45.637" Score="0" ViewCount="" Body="&lt;p&gt;I'm late, but I'd say:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Divide and conquer. You tried the motor without the controller, try the controller without the motor: put in a simpler dummy load (resistor).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stop thinking and look! Did you measure the pwm waveform? Make sure you're getting what you're expecting. Maybe add a heartbeat led or something else to see if the program is running or if it's doing something like resetting spuriously.&lt;/p&gt;&#xA;" OwnerUserId="796" LastActivityDate="2010-05-18T08:23:45.637" />
  <row Id="2689" PostTypeId="2" ParentId="2239" CreationDate="2010-05-18T08:31:53.813" Score="1" ViewCount="" Body="&lt;p&gt;I'd say the BJT is just a CCS.&lt;/p&gt;&#xA;" OwnerUserId="796" LastActivityDate="2010-05-18T08:31:53.813" CommentCount="1" />
  <row Id="2690" PostTypeId="2" ParentId="2190" CreationDate="2010-05-18T08:33:45.760" Score="1" ViewCount="" Body="&lt;p&gt;Instead of trying to find examples, I'd go looking for simple mosfet tutorials. They should quickly tell you how to control one.&lt;/p&gt;&#xA;" OwnerUserId="796" LastActivityDate="2010-05-18T08:33:45.760" />
  <row Id="2691" PostTypeId="2" ParentId="1299" CreationDate="2010-05-18T08:40:53.673" Score="1" ViewCount="" Body="&lt;p&gt;It should be easy with that short distances. What you could do is figure out what those distances and your cabling means in terms of capacitance and line impedance and see what kind of frequencies (rise/fall times) you can get through them. Beyond certain point, it's best to treat them as transmission lines. If it looks bad, you could indeed switch to some other serial line like EIA-232 or 422. That might mean an extra chip at both ends but will stretch far. If you really need to go fast and far, you'll need something more (ethernet, don't count out radio or laser :).&lt;/p&gt;&#xA;" OwnerUserId="796" LastActivityDate="2010-05-18T08:40:53.673" />
  <row Id="2692" PostTypeId="2" ParentId="1337" CreationDate="2010-05-18T08:51:59.913" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=89843&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=89843&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=50106&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=50106&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=68302&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=68302&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These should get you pretty far and the rest you can do with the datasheet. Start building piece by piece, from blinky to waveform to waveform that changes over time to tones. Some source might help with filtering and driving audio outputs (active LPF might do both neatly).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suggest coming back with more specific questions.&lt;/p&gt;&#xA;" OwnerUserId="796" LastActivityDate="2010-05-18T08:51:59.913" />
  <row Id="2693" PostTypeId="2" ParentId="2239" CreationDate="2010-05-18T12:50:04.810" Score="4" ViewCount="" Body="&lt;p&gt;Here's the deal. The capacitor provides constant voltage at high frequencies across the BJT base-emitter + resistor combination. This causes fairly constant current through the BJT and resistor, with some high impedance Z, probably determined mostly by the BJT base resistor Rb. The FET has a high transconductance (gm = Iout / Vin), and the net gain is gm * Z. This is the voltage &lt;em&gt;across the FET drain-source&lt;/em&gt;. The BJE emitter resistor has constant voltage across it, so there's a bias voltage added to that. The constant current allows the BJT to act as a low-impedance output buffer (=Rb/beta).&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-05-18T12:50:04.810" CommentCount="4" />
  <row Id="2694" PostTypeId="1" AcceptedAnswerId="2695" CreationDate="2010-05-18T13:56:56.353" Score="8" ViewCount="1126" Body="&lt;p&gt;I have a small circuit using a PIC18F14F50 microcontroller chip which is logging data into an external EEPROM chip over an i2c interface (which I can then read back later over the USB interface). One sample is recorded every 15 minutes and doesn't need to be particualrly accurately timed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's ok if samples are missed or mis-timed while batteries are being changed, but it's not great if the batteries expire and no data is recorded for several days until someone notices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'd like to warn the user when the battery is low in plenty of time for them to replace them. The average current is under 2mA and I'm running in from 3 AA alkaline batteries in series to give 4.5volts so I'd expect them to last quite a number of days.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I'm wondering how to detect that the battery is low? I presume the voltage will drop as the batteries reache the end of life. I'm thinking that this PIC has a 1.024v reference voltage so I can divide down the supply voltage and feed it to an analogue input and when the divided voltage drops below that trigger a warning.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I don't know enough about batteries to know how well this will work? And I don't know what voltage to choose that would indicate that perhaps 10-20% battery life is left. Will that even work at all? Is there a better approach?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This doesn't need to be at all accurate, I just want to give a good warning in plenty of time without getting people to disard batteries that still have life left in them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As my current usage is fairly constant, would a simple timer be reasonable if I can work out how long the batteries last on average and then pick 85% of that time before I give the warning? Or does battery life vary more than that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any thoughts would be welcome.&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2010-07-23T02:38:30.297" Title="Battery life monitor on PIC circuit" Tags="&lt;pic&gt;&lt;battery&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="4" />
  <row Id="2695" PostTypeId="2" ParentId="2694" CreationDate="2010-05-18T14:52:28.340" Score="5" ViewCount="" Body="&lt;p&gt;First, let me comment on the timer circuit. This will work, as long as your batteries are all of relatively the same age and kept in the same conditions. In 6 months when you are still using this and your batteries are all 6 months older you will need to update the timer. Functional solution, but not the best one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can divide down the voltage for your input with a resistor network that has a high enough voltage not to affect your lifetime(you can use a network that does load, you just replace your batteries more often). There is one catch, you need to Load a battery to see a true value of it's life left. You will find the more loaded a battery is the more the discharge curve looks like a line. It will never be a line, there will still be clear phases, but you can dependably correlate a loaded batteries voltage with your life left.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your PIC is on during the measurement you will probably get a decent measurement. Have the pic spend time measuring your battery and look at the resulting voltage curve until your device dies. If the curve stays relatively flat, and then suddenly drops and your batteries die then you will want to use a transistor and load resistor to increase current draw during battery measurements. &lt;a href=&quot;http://www.batteryuniversity.com/partone-16a.htm&quot; rel=&quot;nofollow&quot;&gt;There is a large amount of information on batteries on battery university.&lt;/a&gt; Often microcontrollers fail to pull enough current to get a curve that is sloped the entire way(I have seen this problem with ultra low power uC like MSP430). You will probably be fine with just your PIC running.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.powerstream.com/AA-tests.htm&quot; rel=&quot;nofollow&quot;&gt;Research into AA battery chemistry has fielded some results.&lt;/a&gt; It does look like they show pretty flat discharge curves with low currents(&amp;lt;500 mA). This will mean that you will likely want a resistor discharge circuit coupled with a transistor to allow the voltage measurements to be more valuable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please forgive me if this was not clear enough. If you comment and questions or suggestions I will update it.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-05-18T14:58:10.310" LastActivityDate="2010-05-18T14:58:10.310" CommentCount="4" />
  <row Id="2696" PostTypeId="2" ParentId="2694" CreationDate="2010-05-18T14:53:02.457" Score="4" ViewCount="" Body="&lt;p&gt;Yes, the battery voltage will drop, but the drop is small, say half a volt:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.powerstream.com/z/AA-100mA.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use a voltage divider to get this into the ADC range, you're dividing the range as well.  I guess this is still measurable with the ADC directly.  5 V / (2^10) = 0.005 V, with ± 3 LSb offset and gain errors, so there are still a number of measurement levels between full and empty?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To measure battery charging and discharging accurately, people keep a log of how much current is being drawn with a current-sensing resistor, and decide that the battery is low after a certain amount of charge has passed by.  If your current draw is relatively constant, then yes, you could just use a timer to do the same thing.  Run it a few times, measure the amount of time until you consider the battery to be dead, and then use a timer in the future to guess when it's about to die.  You are using fresh batteries each time?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-18T15:57:01.557" LastActivityDate="2010-05-18T15:57:01.557" CommentCount="6" />
  <row Id="2697" PostTypeId="2" ParentId="2679" CreationDate="2010-05-18T16:02:14.000" Score="2" ViewCount="" Body="&lt;p&gt;At my university the students use Solidworks to design cases to house my PCBs. But as that is very expensive I would try Blender first if it is just for home use.&lt;/p&gt;&#xA;" OwnerUserId="348" LastActivityDate="2010-05-18T16:02:14.000" />
  <row Id="2698" PostTypeId="2" ParentId="2239" CreationDate="2010-05-18T17:05:47.223" Score="2" ViewCount="" Body="&lt;p&gt;The current flowing through the BJT (i.e. from collector to emitter) is going to be equal to the current flowing into the base times the amplification factor of the transistor.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;I_ce = beta * I_b&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;... if my memory serves me correctly. The FET, on the other hand, can be generally thought of as &quot;on&quot; (letting current flow) or &quot;off&quot; (preventing current flow). If the FET is &quot;off&quot; there will not be a path to ground for the current and no current will flow through the BJT (or conversely any current will flow to ground. The capacitor provides a path to ground (drawing current away from the base of the BJT) for &quot;high frequency&quot; signals. The impedence of the capacitor decreases in proportion to the product of the signal frequency and capacitance.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Z_cap = -j * omega * C&#xA;|Z_cap| = omega * C = 2 * pi * f * C&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I guess that's not really much of an answer to the question, but it's what I remember from &quot;base principles.&quot;&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-05-18T17:05:47.223" />
  <row Id="2699" PostTypeId="2" ParentId="1337" CreationDate="2010-05-18T17:44:21.713" Score="3" ViewCount="" Body="&lt;p&gt;The period of the PWM is determined by the rate of overflow of your timer. There are lots of settings on the Modes of Operation section to think about. If all you want to do is generate a constant period square wave, with variable duty cycle, I think you're going to want to use the CTC (Clear Timer on Compare Match) mode. Basic idea is to set OCR0A to the number of timer ticks until you want the pin to toggle next, and use the Compare Match interrupt to change that value for the next time around. So in avr-gcc it would look something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;avr/io.h&amp;gt;&#xA;#include &amp;lt;avr/interrupt.h&amp;gt;&#xA;#include &amp;lt;stdint.h&amp;gt;&#xA;&#xA;// global variables defining number of ticks on and off&#xA;uint8_t on_time_ticks, off_time_ticks, csxx_bits=0; &#xA;&#xA;&#xA;void setup_timer(double p_ms, double duty){&#xA;  TCCR0A = _BV(COM0A0) // toggle OC0A on Compare Match&#xA;  TCCR0B = _BV(WGM02); // set CTC mode WGM0[2,1,0] = 0b100&#xA;&#xA;  // ... do some stuff based on your CPU frequency&#xA;  // to define the csxx_bits of TCCR0B when the timer is running&#xA;  // and consequently, to set on_time_ticks and off_time_ticks&#xA;  OCR0A = on_time_ticks;&#xA;  TCCR0B |= your_settings_here;&#xA;}&#xA;&#xA;&#xA;void start_timer(){&#xA;  //start the timer running at the desired rate&#xA;  TCCR0B |= csxx_bits; &#xA;}&#xA;&#xA;&#xA;int main(int argc, char **argv){&#xA;  double period_ms, duty_cycle;&#xA;  setup_timer(period_ms, duty cycle);&#xA;  start_timer();  &#xA;  for(;;){&#xA;    //spin or sleep or whatever&#xA;  }&#xA;}&#xA;&#xA;&#xA;ISR(TIM0_COMPA_vect){&#xA;  if(OCR0A == on_time_ticks){&#xA;    OCR0A = off_time_ticks;&#xA;  }&#xA;  else{&#xA;    OCR0A = on_time_ticks;&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Warning, this is untested code but I think the idea is right. By no means is this the &lt;em&gt;only&lt;/em&gt; way to do it either. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is one thing you should know about the ATTiny13, by the way. The internal RC Oscillator is only guaranteed to be accurate to within 10% off the factory floor. There's a user-calibration process you can go through (described by an atmel &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2555.pdf&quot; rel=&quot;nofollow&quot;&gt;appnote&lt;/a&gt;) that will get you to 2% accuracy for the ATTiny13. If you want to do better than that you're probably going to need to use a chip that accomodates an external crystal...&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-05-18T17:44:21.713" />
  <row Id="2700" PostTypeId="2" ParentId="1299" CreationDate="2010-05-18T18:09:25.940" Score="1" ViewCount="" Body="&lt;p&gt;If you can control the clock speed and you don't need high-speed data transfer, you should try to slow the clock down.  This will make it less susceptible to noise.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-18T18:09:25.940" />
  <row Id="2701" PostTypeId="2" ParentId="2641" CreationDate="2010-05-18T18:32:43.970" Score="3" ViewCount="" Body="&lt;p&gt;When purchasing an FPGA, do not forget to factor in the cost of the Flash memory that holds the FPGA program.  That's easy to forget.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a PCB designer, FPGAs are a million times easier to lay out, because you can rearrange the pinout however you want even after the board is made.  There are potential cost savings associated with the fewer layers needed to route an FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To the others who poo-poo FPGA vs. CPU performance, I agree to a certain extent.  An actual processor will be faster at doing actual processor-y things than an FPGA that's programmed to act like a processor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's not really fair to an FPGA, though.  CPUs are &quot;time-limited&quot;; if you want to do more work, you need more time, or a faster processor.  FPGAs are usually &quot;area-limited&quot;; if you want to do more work, you need a bigger FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, let's say you make a spectral analyzer that handles a mono audio signal.  Let's say it takes 70% of CPU time, and you're already as fast as the CPU can go.  You can't add stereo support, because the CPU just isn't fast enough to do the second channel before it must handle the first channel again.  But if you're using 70% of the FPGA, you can just buy a bigger FPGA and drop the second channel in.  It doesn't need to go faster.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, if you ported the problem into the Digital Design domain, using Finite State Machines and Datapaths instead of a CPU, I would bet dollars to pesos that the FPGA will &lt;strong&gt;crush&lt;/strong&gt; the CPU, at the expense of increasing complexity in the design.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-18T18:32:43.970" CommentCount="1" />
  <row Id="2702" PostTypeId="1" AcceptedAnswerId="2705" CreationDate="2010-05-18T23:34:34.253" Score="5" ViewCount="845" Body="&lt;p&gt;I'm new to Arduino - and electronics in general - and am having a frustrating problem with two serial-to-parallel 74HC595 chips trying to drive two 7-segment LED displays. The LEDs are both common cathode, and each LED input has its own 510 ohm resistor, connected up to an output of a 74HC595. If I unplug the common cathode from A, I see the correct display in B. If I unplug the common cathode from B, I see the correct display in A. But when both common cathodes are plugged in, B starts displaying rubbish (mostly it's just blank though) while A displays correctly. It's like there's not enough power to go around. I'm using the 5V power output, because that's what the 74HC595 chips need (actually it can be between 2V and 6) and I don't want to start frying chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone can point out what I'm doing wrong (or what I could potentially try to get it working) that would be great. I am working on a hobby project where I was hoping to have 6 of these LED and 74HC595 chips hooked up.&lt;/p&gt;&#xA;" OwnerUserId="770" LastActivityDate="2010-05-19T00:49:56.093" Title="Multiple 74HC595 chained together won't light all LEDs" Tags="&lt;arduino&gt;&lt;led&gt;&lt;74hc595&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="2703" PostTypeId="2" ParentId="2702" CreationDate="2010-05-19T00:18:37.807" Score="3" ViewCount="" Body="&lt;p&gt;From what you said about the resistor, figuring nearly-to-the-rail output from the CMOS 74hc595 and about 1.25V diode drop, each segment probably is pulling about 7mA. If you get two full displays going that's starting to add up. Just 14 segments at this current (not even two full digits worth) you're already breaking 100mA. Not to mention that if you are powering the 74HC595's off the same 5V source that's still more current, though thankfully not too much since it is a CMOS device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd have to look at the specs of the arduino to be sure, but it wouldn't be surprising if the tiny little regulated supply on the arduino isn't up to it. Even if it were rated for it, I'd probably try to at least feed the 74HC595's with a separate 5V supply. To use a separate supply, be sure to tie the grounds together. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you plan on running 6 digits, accounting for all segments on, you'd want something with at least 500mA or even better 1000mA. It's better to have the amp-capacity and not need it, than need it and not have it.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-05-19T00:33:27.587" LastActivityDate="2010-05-19T00:33:27.587" CommentCount="1" />
  <row Id="2704" PostTypeId="1" AcceptedAnswerId="2712" CreationDate="2010-05-19T00:46:52.763" Score="9" ViewCount="1044" Body="&lt;p&gt;What is the cheapest ARM processor with an MMU so I don't have to use uCLinux?&#xA;Bonus for non-bga and integrated RAM/Flash&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-07-09T07:16:09.853" Title="Cheapest ARM with an MMU" Tags="&lt;arm&gt;&lt;linux&gt;" AnswerCount="4" />
  <row Id="2705" PostTypeId="2" ParentId="2702" CreationDate="2010-05-19T00:49:56.093" Score="3" ViewCount="" Body="&lt;p&gt;Have a look at chapters four, five and six at &lt;a href=&quot;http://tronixstuff.com/tutorials&quot; rel=&quot;nofollow&quot;&gt;http://tronixstuff.com/tutorials&lt;/a&gt; - we run through using 74HC595s and Arduino to light LEDs, 7-segment displays and so on. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-05-19T00:49:56.093" CommentCount="5" />
  <row Id="2706" PostTypeId="2" ParentId="2704" CreationDate="2010-05-19T01:06:24.197" Score="5" ViewCount="" Body="&lt;p&gt;The AT91RM9200 used to be a popular choice (ARM9 + MMU). It's non-BGA, but doesn't have integrated RAM/Flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://opencircuits.com/Linuxstamp&quot; rel=&quot;nofollow&quot;&gt;http://opencircuits.com/Linuxstamp&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-05-19T01:06:24.197" />
  <row Id="2707" PostTypeId="2" ParentId="2704" CreationDate="2010-05-19T01:24:36.457" Score="6" ViewCount="" Body="&lt;p&gt;I think the answer is chips in the ARM926EJ-S family, like the &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=4337&quot; rel=&quot;nofollow&quot;&gt;AT91SAM9G20&lt;/a&gt;. The G20 costs around $10 in relatively low quantity, and it has an MMU. Unfortunately, it's only available in a BGA package, and you'll need external memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The good news is that the ball pitch on the G20 is 0.5 mm (edit: there's a 0.8 mm pitch version too), which is just within the limit of what most assembly houses will do without a surcharge. If you go to an ARM Cortex A8, like the OMAP35xx, you have to deal with 0.4 mm ball pitch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are at least 5 companies that are making SBCs using the G20. Here are a few:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.emacinc.com/som/som9G20.htm&quot; rel=&quot;nofollow&quot;&gt;Emac SoM-9G20&lt;/a&gt;, Illinois, USA&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.taskit.de/en/products/stamp9g20/index.htm&quot; rel=&quot;nofollow&quot;&gt;Taskit Stamp9G20&lt;/a&gt;, Berlin, Germany&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.propox.com/products/t_232.html?lang=en&quot; rel=&quot;nofollow&quot;&gt;Propox MMnet1002&lt;/a&gt;, Poland&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;(I'm actually working on an open hardware board based around this chip, but it won't be ready for a few months at least. But that at least explains why I have all this crap in my head!)&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-06-23T01:41:17.083" LastActivityDate="2010-06-23T01:41:17.083" CommunityOwnedDate="2010-05-19T01:24:36.457" />
  <row Id="2708" PostTypeId="1" AcceptedAnswerId="2711" CreationDate="2010-05-19T02:03:34.160" Score="5" ViewCount="411" Body="&lt;p&gt;I'm trying to build a latching switch connected to a door and would appreciate ideas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The switch is connected to a microcontroller input pin, and I'd like it to operate as follows: When a person opens and closes the door, it latches on. It remains on until it is reset in software. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic idea is to time how long since the door was opened and closed again, and do something based on that. Once I have done this, I can reset the switch again. It does not matter if the door is opened or closed several times.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure where to start, so any ideas welcome.&lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-05-19T17:38:22.547" Title="Latching switch ideas" Tags="&lt;arduino&gt;&lt;switch&gt;&lt;microcontroller&gt;&lt;avr&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="2709" PostTypeId="2" ParentId="2708" CreationDate="2010-05-19T02:16:13.927" Score="3" ViewCount="" Body="&lt;p&gt;To clarify, you're not talking about latching the door shut, right? You just mean that the switch latches?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming yes: I'd start with an optical slot sensor and a piece of cardboard attached to the door, and then do the latching in software. Try something like the &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&amp;amp;site=US&amp;amp;WT.z_homepage_link=hp_go_button&amp;amp;KeyWords=%09511-1339-ND&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;Rohm RPI-131&lt;/a&gt; from Digikey.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-19T02:16:13.927" CommentCount="4" />
  <row Id="2710" PostTypeId="1" AcceptedAnswerId="2713" CreationDate="2010-05-19T02:41:25.687" Score="4" ViewCount="263" Body="&lt;p&gt;&lt;img src=&quot;http://imgur.com/2SLTd.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I came across a test pattern a few years back in a robotics laboratory that I remember being told was some sort of test pattern to train cameras for robotic vision.  It was like some sort of checkerboard pattern but it was not a uniform pattern. &#xA;The image is my best rendition of it.  Does anyone know what this type of pattern is called and what its use is?&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-05-22T02:22:12.537" Title="What is this test pattern used for? (Computer vision, camera distortion mapping)" Tags="&lt;camera&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="2711" PostTypeId="2" ParentId="2708" CreationDate="2010-05-19T03:16:26.510" Score="8" ViewCount="" Body="&lt;p&gt;Most modern MCUs like the Atmel AVR (used in Arduino) have the ability to sleep in a very low power state (&amp;lt; 1 uA) and wake up from a variety of sources including low-power timer driven by 32 kHz crystal or pin change interrupts.  Using a pin change interrupt or a low level triggered interrupt can wake up the AVR microcontroller from deep power down.  Then the state can be saved in a program variable.  See &lt;a href=&quot;http://www.atmel.com/avr&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/avr&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative hardware-only approach to a latching switch is the RS latch built from two 2 input NOR or NAND gates with output fed back to one of the 2 inputs.  Whenever the output goes high, the feedback holds it in that state until the other input is pulled high to reset the latch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Atmelfaebrian&lt;/p&gt;&#xA;" OwnerUserId="797" LastActivityDate="2010-05-19T03:16:26.510" CommentCount="1" />
  <row Id="2712" PostTypeId="2" ParentId="2704" CreationDate="2010-05-19T03:26:02.500" Score="6" ViewCount="" Body="&lt;p&gt;The Atmel AT91SAM9260B comes in a LQFP package and may be a little bit lower in price than the SAM9G20.  It has a MMU and the same peripherals as the SAM9G20 but runs at 200 MHz rather than a max of 400 MHz.  Pay attention to the details in the Atmel Application note Schematic Checklists and you will be successful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also try the AT91SAM9XE512 with flash on-chip.  But 512KB isn't going to be enough even for uCLinux, so the most cost effective thing to do is use the flash-less SAM9G20 or SAM9260B with external flash and SDRAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/at91&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/at91&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="797" LastActivityDate="2010-05-19T03:26:02.500" />
  <row Id="2713" PostTypeId="2" ParentId="2710" CreationDate="2010-05-19T03:39:09.620" Score="5" ViewCount="" Body="&lt;p&gt;A &lt;a href=&quot;http://en.wikipedia.org/wiki/Fiduciary_marker&quot; rel=&quot;nofollow&quot;&gt;fiducial&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.augmentedenvironments.org/lab/wp-content/uploads/2007/10/fiducial.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;img src=&quot;http://www.madbrewlabs.com/wp-content/uploads/2009/08/PennState-300x300.gif&quot; alt=&quot;alt text&quot;&gt;&lt;img src=&quot;http://adfo.eurorscg4d.nl/wp-content/uploads/2009/06/10-kumpany_small.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;img src=&quot;http://nodebox.net/code/data/media/fiducial_example.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A &lt;a href=&quot;http://astrophysics.gsfc.nasa.gov/cai/coded_intr.html&quot; rel=&quot;nofollow&quot;&gt;coded aperture&lt;/a&gt; for &lt;a href=&quot;http://en.wikipedia.org/wiki/Computational_photography&quot; rel=&quot;nofollow&quot;&gt;computational photography&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://groups.csail.mit.edu/graphics/CodedAperture/source_imgs/coded_kernel_rot.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A &lt;a href=&quot;http://en.wikipedia.org/wiki/Barcode#Matrix_.282D.29_barcodes&quot; rel=&quot;nofollow&quot;&gt;2D barcode&lt;/a&gt; or &lt;a href=&quot;http://en.wikipedia.org/wiki/Bokode&quot; rel=&quot;nofollow&quot;&gt;bokode&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.alexmil.de/wp-content/bokode.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-19T21:28:11.183" LastActivityDate="2010-05-19T21:28:11.183" CommentCount="1" />
  <row Id="2714" PostTypeId="2" ParentId="2710" CreationDate="2010-05-19T05:33:56.300" Score="1" ViewCount="" Body="&lt;p&gt;Ok turns out it was a &lt;a href=&quot;http://www.hitl.washington.edu/artoolkit/documentation/usercalibration.htm&quot; rel=&quot;nofollow&quot;&gt;camera calibration pattern&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: NM my mistake &lt;/p&gt;&#xA;" OwnerUserId="582" LastEditorUserId="582" LastEditorDisplayName="" LastEditDate="2010-05-19T22:47:37.507" LastActivityDate="2010-05-19T22:47:37.507" CommentCount="3" />
  <row Id="2715" PostTypeId="2" ParentId="2679" CreationDate="2010-05-19T05:46:32.513" Score="2" ViewCount="" Body="&lt;p&gt;Apparently K-3D also does STL export, and it's quite a lot easier to use than Blender.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.k-3d.org/wiki/All_Plugins&quot; rel=&quot;nofollow&quot;&gt;http://www.k-3d.org/wiki/All_Plugins&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="791" LastActivityDate="2010-05-19T05:46:32.513" />
  <row Id="2716" PostTypeId="2" ParentId="2708" CreationDate="2010-05-19T15:46:03.373" Score="3" ViewCount="" Body="&lt;p&gt;I would do something super simple, like a contact &quot;switch&quot; and do the &quot;latching&quot; logic in software. That is to say, just use two pieces of metal, one on the door and one on the frame that &quot;touch&quot; when the door is closed and separate when the door is open. Make the input pin have the internal pullup enabled. Attach the metal that is on the frame to your MCU input pin. Attach the metal that is on the door to GND (common to your MCU GND). When the door is closed that input will read &quot;0&quot;, when the door is open that input will read &quot;1&quot;. I think you can then even wake up on a logic level transition on that pin (I think that's how it works anyway). You can also couple this wakeup with a &quot;periodic&quot; wakeup from a timer interrupt as suggested by others.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-05-19T15:46:03.373" CommentCount="1" />
  <row Id="2717" PostTypeId="2" ParentId="2708" CreationDate="2010-05-19T17:38:22.547" Score="4" ViewCount="" Body="&lt;p&gt;Use a Hall Effect sensor and a magnet on the door.  If the sensor picks up a magnetic field, the door is shut.  No magnetic field - not shut.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you can periodically poll the sensor at whatever rate you want (something long...like 250 ms?).  Once you detect no magnetic field, you can start tracking time.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-05-19T17:38:22.547" />
  <row Id="2718" PostTypeId="1" AcceptedAnswerId="2721" CreationDate="2010-05-20T11:50:23.113" Score="9" ViewCount="338" Body="&lt;p&gt;My boss recently asked me how difficult it would be to design a product that could continually record fairly low quality video and store the last few hours in some form of internal memory. I have never done any development with video before. Where would be a good place to start my design?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have any suggestions for an MCU? I have been using Silicon Labs MCUs lately for other designs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be the best camera type to use to keep the project as simple as possible?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What format would be best to store the video in?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would I need a video codec or is that only need for a device that supports playback? This device would probably just need to be able to transfer the video to a PC for playback.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any insight you can offer would be much appreciated!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;ADDED:&lt;/strong&gt;&#xA;I have been looking on digikey at CMOS Image sensors. I see that there are several on there made by a company called OmniVision. These data sheets say that &quot;The captured data can be transferred either by a standard parallel digital video port (DVP) or by a single-land MIPI high-speed serial interface&quot;.&lt;br&gt;&#xA;I have never heard of either of those. How do you go about getting that into an image file? using C?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="1235" LastEditorDisplayName="" LastEditDate="2010-05-20T18:31:26.443" LastActivityDate="2010-05-21T15:18:04.437" Title="Where do I start with embedded video?" Tags="&lt;video&gt;&lt;embedded&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="2719" PostTypeId="2" ParentId="2718" CreationDate="2010-05-20T12:02:39.850" Score="5" ViewCount="" Body="&lt;p&gt;Have you seen CMU cam? &lt;a href=&quot;http://www.cmucam.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.cmucam.org/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this the sort of thing you had in mind? &lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-05-20T12:02:39.850" CommentCount="1" />
  <row Id="2720" PostTypeId="2" ParentId="2718" CreationDate="2010-05-20T12:10:10.507" Score="4" ViewCount="" Body="&lt;p&gt;For really low quality (and cost), you could try hacking a GameBoy Camera.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://sophiateam.undrgnd.free.fr/microcontroller/camera/index.html&quot; rel=&quot;nofollow&quot;&gt;http://sophiateam.undrgnd.free.fr/microcontroller/camera/index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps, just writing raw frames to a big SD card.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-05-20T12:10:10.507" CommentCount="2" />
  <row Id="2721" PostTypeId="2" ParentId="2718" CreationDate="2010-05-20T16:05:25.807" Score="4" ViewCount="" Body="&lt;p&gt;There's a pretty neat UART camera module that you might be able to use for this as well. It's made by &lt;a href=&quot;http://www.comedia.com.hk/&quot; rel=&quot;nofollow&quot;&gt;COmedia&lt;/a&gt;, and the one I've used is called the C328-7640, but I think they've discontinued it (according to SparkFun anyway), with a successor &quot;in the works&quot;. At any rate, you could easily interface with this type of thing directly with something like an Atmel AVR (or Arduino for that matter), and you can also interface with an SD card with that same chip (using the SPI interface)... you'd just need some FAT32 library code to make the card readable in something like Windows. I haven't done that myself, but I've seen AVR and Arduino-based projects that have done it. With a system like this I think you'd end up capturing and storing a sequential JPEG images, and then you could post-process them in windows to create Motion-JPEG file that would give you video.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-05-20T16:05:25.807" CommentCount="3" />
  <row Id="2722" PostTypeId="1" CreationDate="2010-05-20T20:08:26.597" Score="5" ViewCount="1070" Body="&lt;p&gt;I'm reposting this from stackoverflow, as the question is better suited here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a first year Computer Science student looking to get started with development for micro-controllers. I'd like to use the 8051, as it's common as dirt, and is used frequently in the real world.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;During my junior or senior year, I'll be taking a PIC micro-controller based embedded design class, so I'd rather not do PIC now; otherwise, I'll be fairly bored during that course.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most commercial kits I see are for the AVR or PIC series of microprocessors. I'm just looking for something with decent development tools, documentation, and enough add-ons to keep my novice self occupied for the summer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any recommendations for an 8051 family kit? Thanks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should have added, that I'd like to keep the price at $150 or less ideally. I'm pretty much just looking to learn -- not do anything too serious. I'm looking for more of a projects based kit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I ended up going with a SiLabs &lt;a href=&quot;http://www.silabs.com/products/mcu/Pages/MCUniversity.aspx&quot; rel=&quot;nofollow&quot;&gt;MCUNIVERSITY&lt;/a&gt; Kit, on recommendation from svec on stackoverflow. The tools and documentation look superb; there are also a set of exercises and labs. Plus, for less than $50, it's an excellent price. Thanks everyone.&lt;/p&gt;&#xA;" OwnerUserId="800" LastEditorUserId="800" LastEditorDisplayName="" LastEditDate="2010-05-23T23:37:40.510" LastActivityDate="2010-05-23T23:37:40.510" Title="Beginner 8051 microcontroller kit recommendation?" Tags="&lt;8051&gt;&lt;beginner&gt;&lt;kit&gt;&lt;development&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="2723" PostTypeId="2" ParentId="2722" CreationDate="2010-05-20T20:40:40.673" Score="6" ViewCount="" Body="&lt;p&gt;I realize that you're looking for an 8051, but I think that's an antiquated choice. For an old, trusty tool, 8051's are great, but I'd strongly recommend against starting there. They're widely used in industry because they're incumbent, not because they're the best.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The easiest way to start is the &lt;a href=&quot;http://arduino.cc&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt;-- it's cheap and easy to program. You can program it with a subset of C/C++, at least to start with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that seems not hardcore enough, and PICs are ruled out, I'd start with an MSP430 from Texas Instruments. Digikey has &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=296-23006-ND&quot; rel=&quot;nofollow&quot;&gt;an eval board with two different MSP430s for $100&lt;/a&gt;. You also need a JTAG programmer. You can get the TI FET, but I've had success with &lt;a href=&quot;http://www.softbaugh.com/ProductPage.cfm?strPartNo=USBP&quot; rel=&quot;nofollow&quot;&gt;the cheaper Softbaugh programmer&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(But if you really are dying for an 8051, I'd start with &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?mpart=AT89STK-11&quot; rel=&quot;nofollow&quot;&gt;an Atmel chip and the Keil tools&lt;/a&gt;.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-05-23T14:51:22.877" LastActivityDate="2010-05-23T14:51:22.877" CommunityOwnedDate="2010-05-20T20:40:40.673" CommentCount="3" />
  <row Id="2724" PostTypeId="2" ParentId="2722" CreationDate="2010-05-20T20:59:28.007" Score="4" ViewCount="" Body="&lt;p&gt;As has been pointed out, the 8051 is an older 8-bit architecture, but it is still widely used.  If you want to dabble a little in assembly code, it is easier to grasp than the RISC-based microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the cheapest ways to get started is a &quot;Toolstick&quot; from Silicon Labs -- plugs directly into a USB port, includes an evaluation copy of the Keil compiler, and costs only $15.81 from Digi-Key:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=336-1278-ND&quot; rel=&quot;nofollow&quot;&gt;KIT TOOL EVAL SYS IN A USB STICK&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For $99, you can get a prototype board with a connector for add-ons:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=336-1488-ND&quot; rel=&quot;nofollow&quot;&gt;KIT DEV C8051F53XA, C8051F52XA&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-05-20T21:12:28.207" LastActivityDate="2010-05-20T21:12:28.207" CommentCount="1" />
  <row Id="2725" PostTypeId="1" AcceptedAnswerId="2726" CreationDate="2010-05-21T04:56:33.493" Score="3" ViewCount="413" Body="&lt;p&gt;I got given a piece of electronics to take apart that has a magnetic swipe card reader built into it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Upon taking it apart the card reader itself (which appears very much like a tape deck head) seems to have 5 pins, only three of which have wires attached in the current circuit (I'll call these 1 through 3 and will ignore the disconnected pins).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pin 2 is obviously the ground, as it's connected to the outer case (this was also obvious from the circuit board it was attached to).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Resistance from pin 1 to pin 3 is about 65 ohms. 1-2 and 2-3 are OL.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried putting +5V (limited by a 1k ohm resistor) across 1 with 3 hooked up to my oscilloscope, but the voltage was a steady +5V with no change when I swiped a card.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same results for +5V through 3 with 1 hooked up to the scope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oscilloscope does not show any voltage through ground (pin 2) when voltage is applied to 1 or 3.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'm sort of stuck.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried googling around, but so far I haven't really found much information on how the mag stripe readers actually work that gives me a better idea of how I might provoke a reaction from this thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do any of you guys have any thoughts or suggestions?&lt;/p&gt;&#xA;" OwnerUserId="647" LastActivityDate="2010-05-21T23:45:15.697" Title="Pinout of a 3 wire magnetic card reader" Tags="&lt;hack&gt;&lt;magstripe&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="2726" PostTypeId="2" ParentId="2725" CreationDate="2010-05-21T05:56:20.423" Score="5" ViewCount="" Body="&lt;p&gt;Here's a decent summary of how the readers work: &lt;a href=&quot;http://www.eettaiwan.com/ARTICLES/2001OCT/PDF/2001OCT04_AMD_CT_AN2112.PDF&quot; rel=&quot;nofollow&quot;&gt;http://www.eettaiwan.com/ARTICLES/2001OCT/PDF/2001OCT04_AMD_CT_AN2112.PDF&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-21T05:56:20.423" CommunityOwnedDate="2010-05-21T05:56:20.423" CommentCount="6" />
  <row Id="2727" PostTypeId="2" ParentId="2718" CreationDate="2010-05-21T15:18:04.437" Score="0" ViewCount="" Body="&lt;p&gt;The parallel digital video port (DVP) is a SGI thing.  See &lt;a href=&quot;http://techpubs.sgi.com/library/manuals/3000/007-3594-001/pdf/007-3594-001.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; for the spec.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-05-21T15:18:04.437" />
  <row Id="2728" PostTypeId="2" ParentId="726" CreationDate="2010-05-21T15:19:25.030" Score="1" ViewCount="" Body="&lt;p&gt;Some FPGA eval boards can interface to camera daughter boards.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-05-21T15:19:25.030" />
  <row Id="2729" PostTypeId="1" AcceptedAnswerId="2730" CreationDate="2010-05-21T16:39:30.587" Score="5" ViewCount="708" Body="&lt;p&gt;I have a DSC-1555 Alarm system that I am trying to wire up to an Arduino-Mega the problem I've run into is that the DSC uses 12v TTL to the Console and the Arduino uses 5v TTL.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was just guessing to use some resistors but I want to double check before trying.&lt;/p&gt;&#xA;" LastActivityDate="2010-05-30T08:42:21.180" Title="Wiring a Arduino to a 12v TTY" Tags="&lt;arduino&gt;&lt;system&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="2730" PostTypeId="2" ParentId="2729" CreationDate="2010-05-21T16:52:09.567" Score="4" ViewCount="" Body="&lt;p&gt;You'll need to convert the DSC-1555 Alarm systems 12V levels down to something the Arduino can handle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without having prior knowledge of how the DSC-1555's serial hardware works, there's not much I can say. I'd get a hold of the datasheet and get more info.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it RS-232C (or some other revision) compliant?  If so, you should get a 12V RS-232 -&gt; 5V line converter.  You could try &quot;stepping down&quot; the voltage with resistors to something the Arduino can handle, but this is fraught with problems, as the signals will likely be inverted and may be outside the range the CMOS chip can handle, potentially causing damage.  If it's RS-232 compliant, get a converter and your headaches will be far less.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-05-21T16:52:09.567" CommentCount="4" />
  <row Id="2731" PostTypeId="2" ParentId="2729" CreationDate="2010-05-21T22:13:43.107" Score="4" ViewCount="" Body="&lt;p&gt;It's a little unclear what you're interfacing with, exactly, but if it comes down to getting 12V RS-232 levels in &amp;amp; out of an Arduino (or any other 5V logic), it's not all that difficult.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regular RS-232 levels are spec'd at -3V to -12V for the 'marking' state (logic '1') and +3V to +12V for the 'space' state (logic '0'). A typical device isn't going to cover that entire range, for example, a PC serial port might give you a -11.5V mark and a +11.2V space, while another device might give you -9 and +9. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;TTL levels on the other hand are spec'd at logic 0 being less than 0.8V and logic 1 being more than 2.4V, although with CMOS devices logic '1' wants to be as close to the supply rail as you can get it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a number of chips that will change between 5V logic levels and +/-12V RS-232, that are quite cheap, and even work without an extra 12V supply. You could check out parts like the ones &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/2020&quot; rel=&quot;nofollow&quot;&gt;Maxim&lt;/a&gt; makes.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-05-22T00:34:00.490" LastActivityDate="2010-05-22T00:34:00.490" />
  <row Id="2732" PostTypeId="2" ParentId="2725" CreationDate="2010-05-21T22:26:45.497" Score="0" ViewCount="" Body="&lt;p&gt;@kellenjb and @pingswept:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your comments were on the mark.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My eventual setup was to hook the probe up to pin 1 and the scope's ground to pin 3.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found that this produced peaks/valleys of around 10-20mV with about 1-2 ms between &quot;0&quot; peaks (1s are half this width) depending on the card and speed of swipe. It's very obviously data in the format described in @pingswept's PDF.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found setting the scope to trigger in single shot mode at around 7 mV did an excellent job of capturing the data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now all I need to do is transcribe and translate it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks guys.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an additional note, not all hotel swipe cards I tried worked. Only one out of the three I had around produced any data. My AAA and Costco membership cards both worked, though.&lt;/p&gt;&#xA;" OwnerUserId="647" LastEditorUserId="647" LastEditorDisplayName="" LastEditDate="2010-05-21T23:45:15.697" LastActivityDate="2010-05-21T23:45:15.697" CommentCount="2" />
  <row Id="2733" PostTypeId="2" ParentId="2710" CreationDate="2010-05-22T02:22:12.537" Score="2" ViewCount="" Body="&lt;p&gt;Another possibility is that it is a &quot;non-repeating pattern&quot; used to establish register between two cameras.&lt;/p&gt;&#xA;" OwnerUserId="227" LastActivityDate="2010-05-22T02:22:12.537" />
  <row Id="2734" PostTypeId="1" AcceptedAnswerId="2735" CreationDate="2010-05-22T21:13:35.437" Score="5" ViewCount="976" Body="&lt;p&gt;I am working on a simple audio mixer project. The op-amps I am using (LM741) take +9V and -9V inputs. I am currently getting this by wiring two 9V batteries together, connecting + on one to - of the other, and grounding the pair. This seems to work, but I would now like to switch to a power supply. I can find a bunch of 9V power supplies, but they all only have the one polarity. Is there an easy way to get +9V from a center-negative power supply? I figure I probably need an inverter circuit or something, but I don't really understand what I'm doing.&lt;/p&gt;&#xA;" OwnerUserId="678" LastActivityDate="2011-06-04T14:07:15.147" Title="+/- 9V DC Power Supply" Tags="&lt;power-supply&gt;" AnswerCount="6" CommentCount="4" FavoriteCount="1" />
  <row Id="2735" PostTypeId="2" ParentId="2734" CreationDate="2010-05-22T21:57:53.033" Score="6" ViewCount="" Body="&lt;p&gt;Assuming at least one of the power supplies is isolated (which will be true if they are good power supplies, but maybe not if they are cheap), you can make a stack of two supplies, so you have outputs at 0 V, 9 V and 18 V. Then, connect your op-amp circuit like this:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Power supply 18 V -&gt;  9 V op-amp pin&lt;/li&gt;&#xA;&lt;li&gt;Power supply 9 V  -&gt;  0 V op-amp pin&lt;/li&gt;&#xA;&lt;li&gt;Power supply 0 V  -&gt; -9 V op-amp pin&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Another way to think about this is to understand that ground (0 V) is a relative choice; you can change your choice, as long as you're consistent within one circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One other note-- I should explain what I mean by &quot;isolated.&quot; A cheap power supply will have its ground pin connected to the neutral wire of its power cord. Most of the time, that's fine. But if you want to stack supplies, you need an isolated supply, i.e. one where no output pin is connected internally to the power cord.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do try to stack non-isolated supplies, you'll be connecting the positive output to the neutral wire, which is the same as shorting out the supply, so its internal fuse will blow. (If it's a &lt;em&gt;really&lt;/em&gt; cheap supply, this will destroy it.)&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;One other solution&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;If you can't lay your hands on an isolated supply, you could use a &lt;a href=&quot;http://www.national.com/mpf/LM/LM2663.html#Overview&quot; rel=&quot;nofollow&quot;&gt;switched capacitor voltage converter&lt;/a&gt;. This is a chip that charges up a capacitor, and then quickly shifts the pins so what was previously the positive lead is connected to ground, and the old ground becomes a negative output. It does this charge/switch routine at 10-100 kHz, so to humans, it looks like a negative supply.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-05-22T22:09:33.483" LastActivityDate="2010-05-22T22:09:33.483" CommunityOwnedDate="2010-05-22T21:57:53.033" />
  <row Id="2736" PostTypeId="2" ParentId="2734" CreationDate="2010-05-22T22:12:48.477" Score="3" ViewCount="" Body="&lt;p&gt;I usually use an inverting charge pump to supply my negative voltage rails, do pay attention to your noise requirements, some times i use an LC filter on the output to reducing the switching ripple.  In digikey category lingo what you want is an &quot;inverting switched capacitor DC-DC regulator&quot;.  This will turn your +9V input into -9V (more like -8.8V or something close).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your working with audio, choose an IC with a switching frequency well above the audio range, 400khz is a common value but they range from 10khz to 2mhz.  If your circuit also has some digital circuitry on it and is compact, consider a charge pump with switching synchronization input. Keep the switching capacitors as close to the IC as possible to minimize noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you search digikey / mouser there will be tons of choices, just enter your desired parameters/package they come in everything from a SOT-23-5 to a DIP-8.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-05-22T22:32:19.893" LastActivityDate="2010-05-22T22:32:19.893" />
  <row Id="2737" PostTypeId="2" ParentId="2734" CreationDate="2010-05-22T22:15:19.910" Score="5" ViewCount="" Body="&lt;p&gt;One thing you can do when you aren't going to source or sink a lot of current into your 0V, and only have a single supply, is to use a 'virtual ground'. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, suppose you only have an 24V supply - two leads, supply and return. You can get -12V/0V/+12V by dedicating an op-amp to stabilize the half-way point and then use that as a 0V reference. In other words, the 24V supply becomes your +12V line, the 24V supply return becomes your -12V line, and the dedicated op-amp produces the 0V line. All you do is put a 50% voltage divider across the 24V to give you the half-way point, and then buffer it with a voltage follower configuration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically your op-amps are powered from the +V/-V rails anyway, the problem is not having a ground. The half-way point voltage follower effectively 'regulates' the midpoint for you. The limitation is that you can't source or sink more current into the virtual ground than the op-amp delivering it can handle, or you lose the reference.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-22T22:15:19.910" CommentCount="1" />
  <row Id="2738" PostTypeId="2" ParentId="2734" CreationDate="2010-05-23T08:42:29.720" Score="8" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;LM741 is a terrible op-amp for audio.  The NE5532 is something like 15 dB quieter, and still cheap.  &lt;a href=&quot;http://tangentsoft.net/audio/opamps.html&quot; rel=&quot;nofollow&quot;&gt;http://tangentsoft.net/audio/opamps.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;You should be using rails as high as possible for best dynamic range. The mixers I work on are always ±15 V, because that's the highest voltage most op-amps are recommended for.&lt;/li&gt;&#xA;&lt;li&gt;Power supplies with split center-tapped outputs exist, though I can't find any right now.  That's essentially the same thing as stacking two isolated supplies.  Also, you could always build your own with a center-tapped transformer and learn how to build linear supplies.   It's not too complex.  &lt;a href=&quot;http://sound.westhost.com/project30c.htm&quot; rel=&quot;nofollow&quot;&gt;http://sound.westhost.com/project30c.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-05-23T08:42:29.720" CommentCount="2" />
  <row Id="2739" PostTypeId="2" ParentId="2594" CreationDate="2010-05-23T10:09:10.593" Score="2" ViewCount="" Body="&lt;p&gt;I've used &lt;a href=&quot;http://jaycar.com.au/productView.asp?ID=SY4030&quot; rel=&quot;nofollow&quot;&gt;these 5V DIL relays&lt;/a&gt; before, with great results. They are low-current reed relays that can be driven directly from the Arduino. Using these would negate the need to work out whether the terminal goes high or low - just connect the relay pins across the button's contacts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the link is to Jaycar Electronics in Australia, who I can highly recommend.&lt;/p&gt;&#xA;" OwnerUserId="25" LastActivityDate="2010-05-23T10:09:10.593" />
  <row Id="2740" PostTypeId="2" ParentId="2594" CreationDate="2010-05-23T10:20:07.193" Score="2" ViewCount="" Body="&lt;p&gt;Analogue switches like those in the 74HC4066 are often used in situations like that.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-05-24T21:45:43.903" LastActivityDate="2010-05-24T21:45:43.903" />
  <row Id="2742" PostTypeId="2" ParentId="2594" CreationDate="2010-05-24T17:30:19.087" Score="3" ViewCount="" Body="&lt;p&gt;What phone are you using?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I took a look at this over the weekend. It seems (unsurprisingly) that there is more than one button mechanism. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An old Verizon/Samsung phone I pulled apart had separate buttons which looked like discretes. Endolith/Pingswept seem to be on the right track with testing. &lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-05-24T17:30:19.087" />
  <row Id="2743" PostTypeId="1" CreationDate="2010-05-24T17:33:34.097" Score="6" ViewCount="156" Body="&lt;p&gt;I'm designing an altimeter based on a pic microcontroller and a freescale pressure sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to output the altitude from the pic using an analog gauge. I found some useful information [here][1]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I want to know is where to buy analog gauges that allow me to put my own scale (I'm basically looking for the raw ammeter)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[1:] &lt;a href=&quot;http://chiphacker.com/questions/25/analogue-gauge-with-arduino&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/25/analogue-gauge-with-arduino&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1267" LastActivityDate="2010-05-25T08:21:21.363" Title="Analog Gauge provider" Tags="&lt;gauge&gt;&lt;pic&gt;&lt;analog&gt;" AnswerCount="3" />
  <row Id="2744" PostTypeId="2" ParentId="2743" CreationDate="2010-05-24T17:43:01.493" Score="4" ViewCount="" Body="&lt;p&gt;Perhaps try &lt;a href=&quot;http://replacementmeters.com/&quot; rel=&quot;nofollow&quot;&gt;IMS&lt;/a&gt;? I believe they're in southern California.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By the way, A PIC will output a voltage more easily than a current, so you're probably going to want a voltmeter rather than an ammeter (maybe you knew that already). You could always use a handy voltage-to-current converter (a &quot;resistor&quot;) to make a current from a voltage, but it's simpler to just read the voltage directly.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-24T17:43:01.493" />
  <row Id="2746" PostTypeId="2" ParentId="2743" CreationDate="2010-05-24T18:15:33.420" Score="6" ViewCount="" Body="&lt;p&gt;You should be able to buy the 0-5V voltmeter from &lt;a href=&quot;http://futurlec.com/Panel_Meters.shtml&quot; rel=&quot;nofollow&quot;&gt;Futurlec&lt;/a&gt;, then drive it using PWM from your microcontroller. I think using a voltmeter is more efficient than an ammeter, unless it's a very small range ammeter (otherwise, if it's a 0-100mA ammeter, you'll need to waste 100mA just to move the needle to 100%).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The volt meter I linked to can be opened, and you can replace the scale with your own (or just glue your own on top of it).&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-05-24T18:15:33.420" />
  <row Id="2748" PostTypeId="2" ParentId="2743" CreationDate="2010-05-25T08:21:21.363" Score="1" ViewCount="" Body="&lt;p&gt;RS sell a range of meters with blank scales - &lt;a href=&quot;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&amp;amp;R=3488611&quot; rel=&quot;nofollow&quot;&gt;example link&lt;/a&gt;.  You could also use one with a pre-printed scale and calibrate your output signal to give a meaningful reading on the scale.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As with most of these questions, you forgot to say where in the world you are.  If RS do not cover your area then Farnell cover more countries - &lt;a href=&quot;http://uk.farnell.com/anders-electronics/cv15x100ua/meter-moving-coil-0-100ua/dp/7758278&quot; rel=&quot;nofollow&quot;&gt;Example link&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-05-25T08:21:21.363" CommentCount="1" />
  <row Id="2749" PostTypeId="1" AcceptedAnswerId="2750" CreationDate="2010-05-25T14:49:58.877" Score="4" ViewCount="1151" Body="&lt;p&gt;Hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've recently bought some cheap TowerPro SG-50 rc servos from ebay. They seem to work quite well, and despite their small size they are quite strong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But how &quot;strong&quot; are they actually. The datasheet specifies:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Stall Torque: 0.8 kg/cm&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;What does that mean. I guess that stall torque is the amount of torque that needs to be applied  in the reverse direction of the rotation, before the servo stalls. But what does the unit kg/cm mean?&lt;/p&gt;&#xA;" OwnerUserId="718" LastActivityDate="2010-05-25T22:14:02.390" Title="Stall torque for servo, kg/cm?" Tags="&lt;servo&gt;&lt;torque&gt;&lt;rc&gt;&lt;datasheet&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="2750" PostTypeId="2" ParentId="2749" CreationDate="2010-05-25T15:23:36.540" Score="4" ViewCount="" Body="&lt;p&gt;The normal SI units for torque are Newton-metres.  Torque is a force times the distance from the fulcrum/axis.  The units that you are giving do not make sense (although I have seen them in a number of places quoted for this device - puzzling).  I expect that this is a mistyping of the units on a cheap data sheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would expect that the motor will stall when a weight of 0.8kg is hanging from a 1cm long arm attached to the motor spindle.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-05-25T15:23:36.540" CommentCount="6" />
  <row Id="2751" PostTypeId="2" ParentId="2749" CreationDate="2010-05-25T15:50:44.373" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.engineersedge.com/torque_conversion.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.engineersedge.com/torque_conversion.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1 Kg/cm = 9.806x10^-2 N/m&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2010-05-25T15:50:44.373" CommentCount="4" />
  <row Id="2753" PostTypeId="2" ParentId="2749" CreationDate="2010-05-25T22:14:02.390" Score="2" ViewCount="" Body="&lt;p&gt;Stall torque is the maximum torque that the unit can supply when in 'locked shaft' condition. This doesn't mean you actually have to mechanically bolt the shaft or anything, it just means the torque that can be dished out from a dead stop. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Applying a torque that opposed motion, that is less than the stall torque, will cause the rotational speed to slow down and the unit will draw more current. Applying an opposing torque that is &lt;em&gt;greater&lt;/em&gt; than the stall torque will overcome the unit's abilities and will drive it backwards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The value of 0.8 kg-cm means the amount torque you would get if you were to bolt a 1cm long arm to the shaft (set and right angles to the axis of rotation, and positioned dead horizontal), and hang an 0.8kg mass at the end of the arm. This is a product, so it's also the amount of torque you'd get using 0.08kg (i.e., 80g) at the end of a 10cm shaft, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FWIW, the proper SI unit for torque is newton-meters, or possibly even newton-centimeters would be acceptable, as torque is defined as FORCE (Newtons) x MOMENT-ARM (distance). The english units are lbf-ft, pounds-force * feet, often written just ft-lbs, and this probably has influenced the less rigorous spec sheet writers to cast their 'metric' torques in the somewhat mistaken units of kg-cm, kg-m, and g-m.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-25T22:14:02.390" />
  <row Id="2754" PostTypeId="1" CreationDate="2010-05-26T03:23:21.710" Score="1" ViewCount="659" Body="&lt;p&gt;I am working on creating a Hard Drive DJ similar to the &lt;a href=&quot;http://chiphacker.com/questions/16/how-do-you-read-newer-hdd-motors-dc-brushless-into-arduino-like-stepper-motor&quot; rel=&quot;nofollow&quot;&gt;other posting on this website&lt;/a&gt;, except that I want to drive the motor when the user isn't scratching on it. Multiple sources recommended using an ESC for this, but I have two main problems:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I would like to drive the motor forwards and backwards at various speeds. Is this possible with an ESC?&lt;/li&gt;&#xA;&lt;li&gt;I have to have some sort of additional monitoring system for checking when a user starts playing with the spindle so that I can turn off the ESC and switch to monitoring EMF voltage levels with the ADC. Can you think of a good way to do this? &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Also, do you know of a good datasheet or tutorial that describes the protocol for talking with an ESC from a microcontroller?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for the help! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I found an &lt;a href=&quot;http://www.instructables.com/id/BLDC-Motor-Control-with-Arduino-salvaged-HD-motor/&quot; rel=&quot;nofollow&quot;&gt;instructable&lt;/a&gt; that used Hall EMF sensors and an L6234 driver chip. Would the L6234 better fit my needs over an ESC?&lt;/p&gt;&#xA;" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T16:01:01.817" LastActivityDate="2010-10-22T16:01:01.817" Title="Controlling/Reading Hard Drive Brushless Motor w/ uC" Tags="&lt;arduino&gt;&lt;brushless&gt;&lt;esc&gt;&lt;hard-drive&gt;" AnswerCount="1" />
  <row Id="2755" PostTypeId="2" ParentId="2754" CreationDate="2010-05-26T11:23:12.983" Score="2" ViewCount="" Body="&lt;p&gt;An ESC should be ideal basis for what you want. I know that for electric r/c airplanes, you definitely can vary the speed since that's what the throttle control does, although I don't know that you can throw them into reverse. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, an ESC is essentially a device for making three phase AC out of DC, and the old trick for changing direction of a three phase motor would apply, which is that you simply swap any two of the three connections and the direction of rotation changes. A DPDT relay or an H-bridge switching circuit could accomplish that for you. Although there's a very good chance that a ground-vehicle ESC could do reverse without any tinkering. It's worth looking for one that can do reverse before getting tangled in adding circuitry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, they don't have any feedback capability that I'm aware of, it's strictly power into the motor, although again, I'm not familiar with them all. Even if there are expensive models that do what in BLDC controller jargon is referred to as 'sensorless control' - which is almost exactly what you said, every so often you stop driving power and check the voltage being generated to sense speed, it would be doubtful that the ESC would feed this information back to you. Chances are it would only use it to vary the frequency/phase of the AC it produces in order to better sync the fields in the motor. However, nothing says you can't turn off the ESC and directly read the generated voltages directly with the microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing you could do, though, to tell when someone takes control over the platter, is sense the current being pulled by the ESC. You would have to LPF it to mitigate the switching frequency of the AC the ESC produces. As long as the ESC isn't told to accelerate the platter too quickly, with basically no load on it, the current demand should be fairly low. At a constant speed of rotation, the current should also be nearly constant, and low. As soon as someone tries to change the speed/position of the platter, this should be visible as a sudden change in current. The difficulty with this approach is that if you're turning the platter at low speeds, the AC switching frequency required for that is also quite low, so it might be hard to get the signal out of the noise. I'd put the current on a scope and fiddle with it, to see how good (or not) the signal is, before committing to building hardware for it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing is to use those reflective optical sensors, like the lego robotics setups. Or hall sensors as you suggested. Either way, you'd get input that could be changed to speed information, that you could compare against what the controller expects the speed to be. Any change in expected speed, and you momentarily (1/4 second?) disable the ESC and if the platter keeps moving above a certain threshold speed, or doesn't stop for longer than a threshold time, leave it off, otherwise, back on.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-26T11:23:12.983" CommentCount="1" />
  <row Id="2756" PostTypeId="1" CreationDate="2010-05-26T14:19:26.987" Score="7" ViewCount="247" Body="&lt;p&gt;What hobbyist level groups meet to discuss electronics and&#xA;microcontroller applications?  I am interested in groups that have&#xA;free and open meetings and meet on a regular basis (typically&#xA;once per month).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The two I know of in Boston are -- &lt;/p&gt;&#xA;&#xA;&lt;p&gt;dorkbot Boston -- &#xA;&lt;a href=&quot;http://groups.google.com/group/DorkbotBoston?hl=en&amp;amp;pli=1&quot; rel=&quot;nofollow&quot;&gt;http://groups.google.com/group/DorkbotBoston?hl=en&amp;amp;pli=1&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Boston Arduino Users Group &#xA;&lt;a href=&quot;http://www.meetup.com/The-Boston-Arduino-Users-Group&quot; rel=&quot;nofollow&quot;&gt;http://www.meetup.com/The-Boston-Arduino-Users-Group&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:46:41.877" LastActivityDate="2011-05-18T11:46:41.877" CommunityOwnedDate="2010-05-30T12:24:48.803" Title="What hobbyist level groups meet to discuss electronics and microcontroller applications?" Tags="&lt;microcontroller&gt;&lt;electronics&gt;&lt;education&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="2" />
  <row Id="2757" PostTypeId="2" ParentId="2756" CreationDate="2010-05-26T14:45:45.977" Score="3" ViewCount="" Body="&lt;p&gt;Sprout in Davis Square, Somerville, MA, has a lot of people working on microcontroller stuff, and they have open shop nights twice a week. But it's not just dedicated to electronics-- there are people building weird bicycles and the like too. Here's their event calendar: &lt;a href=&quot;http://thesprouts.org/events&quot; rel=&quot;nofollow&quot;&gt;http://thesprouts.org/events&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a while, a young man named &lt;a href=&quot;http://jimmieprodgers.com/&quot; rel=&quot;nofollow&quot;&gt;Jimmie P. Rodgers&lt;/a&gt; was running something called &lt;a href=&quot;http://www.noisenight.com/&quot; rel=&quot;nofollow&quot;&gt;Noise Night&lt;/a&gt; for making noisy electronics, but from the blog, it appears to be idle. His personal blog suggests that he runs soldering workshops; I suspect he would be worth talking to, if you don't know him already. (Update: upon reading your links, it is clear that you do know him already.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-05-26T15:17:52.197" LastActivityDate="2010-05-26T15:17:52.197" CommunityOwnedDate="2011-05-19T00:18:23.010" />
  <row Id="2758" PostTypeId="2" ParentId="2756" CreationDate="2010-05-26T15:38:34.713" Score="11" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://hackerspaces.org/wiki/List_of_Hacker_Spaces&quot; rel=&quot;nofollow&quot;&gt;http://hackerspaces.org/wiki/List_of_Hacker_Spaces&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-05-26T15:38:34.713" CommunityOwnedDate="2011-05-19T00:18:15.273" CommentCount="1" />
  <row Id="2759" PostTypeId="1" AcceptedAnswerId="4212" CreationDate="2010-05-26T18:01:19.517" Score="3" ViewCount="187" Body="&lt;p&gt;First off, I am aware that plugging an UPS into an inverter is a bit redundant.  The only situation I can think of it being useful is in a car when you want full amps for cranking over the motor but still want to run equipment. Anyhow, besides the silliness of why would you plug a UPS into an Inverter, my question is why it will not work. I have been using a motor master 3000 watt modified sine wave inverter with an APC Back-UPS RS 1500VA. When it is plugged in the UPS gives a wiring fault error. I was thinking it may be that the Inverter is not grounded properly so I tied the earth ground pin from the UPS to the buildings ground and still the UPS say’s there is a wiring fault. I heard people say that UPS’s do not like inverters in the past, but the troubling part that I have is that I had the ups working off a Robin Subaru R1700i inverter series generator without any issues. Anyone out there have any thoughts on this matter?  &lt;/p&gt;&#xA;" OwnerUserId="811" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-26T21:51:03.640" LastActivityDate="2010-08-30T17:07:57.130" Title="Plugging a UPS into an inverter." Tags="&lt;inverter&gt;&lt;ups&gt;&lt;power&gt;" AnswerCount="3" />
  <row Id="2760" PostTypeId="2" ParentId="2759" CreationDate="2010-05-27T00:13:53.430" Score="2" ViewCount="" Body="&lt;p&gt;The wiring fault indicator usually means that there is either a bad ground or the pins have a reversed parity. Since you have checked the ground the pins are probably reversed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, this means that the two straight pins on the power jack need to be switched to make the UPC happy. With out knowing more about UPSs myself, I am not sure if this would cause any issues with how the UPS works.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-05-27T00:13:53.430" CommentCount="1" />
  <row Id="2761" PostTypeId="2" ParentId="2759" CreationDate="2010-05-27T00:49:56.517" Score="1" ViewCount="" Body="&lt;p&gt;Could be that high frequency stuff from the inverter gets through into the UPS and confuses it. You could test that theory by putting an EMI filter in line between the two and see what happens.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-27T00:49:56.517" CommentCount="1" />
  <row Id="2762" PostTypeId="2" ParentId="726" CreationDate="2010-05-27T02:02:16.483" Score="0" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://wiki.elphel.com/&quot; rel=&quot;nofollow&quot;&gt;Elphel wiki&lt;/a&gt; discusses the free software and open hardware inside Elphel cameras. That hardware includes a FPGA that helps with the video processing and video compression.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-05-27T02:02:16.483" CommunityOwnedDate="2010-05-27T02:02:16.483" />
  <row Id="2763" PostTypeId="2" ParentId="1609" CreationDate="2010-05-27T02:12:30.270" Score="0" ViewCount="" Body="&lt;p&gt;While Windell Oskay makes a good argument that 104 LEDs is the maximum without adding more transistors,&#xA;&lt;a href=&quot;http://www.tigoe.net/pcomp/code/category/arduinowiring/424&quot; rel=&quot;nofollow&quot;&gt;Tom Igoe&lt;/a&gt;&#xA;has posted photos of a matrix of 128 LEDs directly controlled by a single Arduino Mega -- no extra transistors, discrete or integrated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is Tom Igoe &quot;cheating&quot; by briefly exceeding the &quot;absolute maximum current per pin&quot; listed in the datasheet?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-05-27T02:12:30.270" CommunityOwnedDate="2010-05-27T02:12:30.270" CommentCount="3" />
  <row Id="2764" PostTypeId="1" CreationDate="2010-05-27T12:46:00.563" Score="5" ViewCount="179" Body="&lt;p&gt;I've just finished to solder this little circuit on perfboard and now I realize that the board is bent:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://imgur.com/sQX3t.jpg&quot; alt=&quot;bent perfboard&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am pretty sure that the board was flat when I purchased it. What may cause this bending ?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;excessive heat ?&lt;/li&gt;&#xA;&lt;li&gt;there are some long solder bridges in that part of the board; is it possible that the solder shrinks when getting solid/cold ?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; Those boards are sold as &quot;bakelite&quot; boards at a local shop. I'd say they are low quality boards (eg. the solder pads tend to come off easily)&lt;/p&gt;&#xA;" OwnerUserId="595" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-19T21:10:00.890" LastActivityDate="2011-05-19T21:10:00.890" Title="What may cause a perfboard to bend ?" Tags="&lt;pcb&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="2" />
  <row Id="2765" PostTypeId="2" ParentId="2764" CreationDate="2010-05-27T13:06:23.747" Score="7" ViewCount="" Body="&lt;p&gt;I have noticed that perfboard does all sorts of bad things: corrosion, bending, peeling, etc. It even bends when stacked neatly in a pile and is not in use. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I think the best answer to your question is &quot;it just does&quot;, or perhaps &quot;it uses cheaper, less stable laminate methods, and all laminates are at risk of bending.&quot; (Plywood for example often warps when one side is exposed to air and the other is not.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My recollection is that it is made of &lt;a href=&quot;http://en.wikipedia.org/wiki/FR-2&quot; rel=&quot;nofollow&quot;&gt;FR-2&lt;/a&gt; (synthetic resin) and not FR-4 (bonded epoxy) like commercial circuit boards, and is not as stable a base.&lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-05-27T13:06:23.747" />
  <row Id="2766" PostTypeId="2" ParentId="2764" CreationDate="2010-05-27T13:10:02.513" Score="3" ViewCount="" Body="&lt;p&gt;It's not very stable stuff, because of all those holes. I think it's caused by having all the components on the same side, and all the connections on the other side. I've had large four-layer PCBs warp during manufacture for similar reasons - unbalanced copper areas on the outer layers. Boards made by another supplier were OK, though.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-05-27T13:10:02.513" />
  <row Id="2767" PostTypeId="2" ParentId="2756" CreationDate="2010-05-27T14:59:24.753" Score="3" ViewCount="" Body="&lt;p&gt;In the New York City area there are two excellent resources:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.nycresistor.com/&quot; rel=&quot;nofollow&quot;&gt;NYC Resistor&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Several of the founders of the group are the guys who did the Cupcake CNC 3-D printer&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.buglabs.net/testkitchen&quot; rel=&quot;nofollow&quot;&gt;Bug Lab's Test Kitchen&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="591" LastActivityDate="2010-05-27T14:59:24.753" CommunityOwnedDate="2011-05-19T00:18:31.420" />
  <row Id="2768" PostTypeId="2" ParentId="2764" CreationDate="2010-05-27T17:34:49.727" Score="1" ViewCount="" Body="&lt;p&gt;It could also be the way you had the board clamped when you soldered&#xA;the components. If the board had a bend when it was clamped it&#xA;may not be able to &quot;spring back&quot; after the components are soldered.&#xA;Not clamping the board could also cause the problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What type of board are you using? If you are using epoxy-paper I&#xA;would switch to epoxy-glass. It should spring back a lot&#xA;better. It also is less likely to crack and break. &#xA;I like Vector 169P84WE. The parts I use for breadboarding&#xA;are listed at the bottom of &lt;a href=&quot;http://wiblocks.luciani.org/FAQ/faq-tools.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/FAQ/faq-tools.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:19:34.997" LastActivityDate="2011-05-19T14:19:34.997" CommentCount="2" />
  <row Id="2769" PostTypeId="2" ParentId="2764" CreationDate="2010-05-27T20:01:20.920" Score="2" ViewCount="" Body="&lt;p&gt;These boards are fiberglass and epoxy laminate. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When heated above their glass transistion temperature, the epoxy will become less rigid and more 'rubbery' resulting in warpage and permanent deformation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perf boards which are usually made with cheaper and thinner materials than most other PCB's will warp with heat greater than 140 deg C.&lt;/p&gt;&#xA;" OwnerUserId="591" LastActivityDate="2010-05-27T20:01:20.920" CommentCount="1" />
  <row Id="2770" PostTypeId="2" ParentId="2764" CreationDate="2010-05-27T20:28:23.230" Score="3" ViewCount="" Body="&lt;p&gt;I think you actually hit the nail on the head at the end of your question:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;it possible that the solder shrinks when getting solid/cold&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The coefficient of thermal expansion of solder is around 20 ppm/C, meaning that when you heat it up 200 degrees C to melt it, its length increases by a factor of 200 * 20 * 10^-6 = 0.004. When it cools, it grabs onto the perfboard, and then the length decreases that much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could probably calculate the radius of curvature of the board, knowing the length of contraction and assuming it will bend into a circle.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-27T20:28:23.230" />
  <row Id="2771" PostTypeId="1" AcceptedAnswerId="2774" CreationDate="2010-05-27T20:55:17.677" Score="2" ViewCount="677" Body="&lt;p&gt;Can you run a &lt;a href=&quot;http://en.wikipedia.org/wiki/Brushless_DC_electric_motor&quot; rel=&quot;nofollow&quot;&gt;BLDC motor&lt;/a&gt; backwards without damage?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it OK to drive a model airplane BLDC engine backwards while landing, so it gets a little &quot;reverse thrust&quot; and come to a stop a little quicker on the runway?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it OK to drive a model helicopter BLDC motors backwards so it can hover upside-down?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or do I need to design the hardware so that it never drives the motor backwards, under any circumstances, no matter what the pilot on the ground does at the transmitter?&lt;/p&gt;&#xA;" OwnerUserId="813" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-05-27T21:50:09.063" LastActivityDate="2010-05-28T08:58:36.800" Title="Can you run a BLDC motor backwards without damage?" Tags="&lt;motor&gt;&lt;esc&gt;&lt;autonomous&gt;&lt;brushless&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="2772" PostTypeId="2" ParentId="2041" CreationDate="2010-05-27T21:28:09.857" Score="1" ViewCount="" Body="&lt;p&gt;A (hobby) servo motor &lt;em&gt;is&lt;/em&gt; a DC motor plus a decoder chip and an H bridge all in one convenient package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can't do anything that you couldn't do by taking that same DC motor and adding your own H bridge and your own H bridge driver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main pro of a (hobby) servo motor is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The servo saves time -- it comes in a really convenient package, I can control it with a single pin on my microcontroller, and I don't have to fuss around with wiring up my own H bridge, etc. I can be pretty confident that no matter what the software does, the motor and driver will survive for at least a few seconds -- it's impossible to instantly destroy transistors by accidentally turning on all 4 arms of the H bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since hobby servo motors are made in such huge quantities, it's almost always cheaper to use an off-the-shelf servo if it does what you need, rather than try to re-implement the wheel from parts yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main pro of a DC motor is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have complete control over how I control it, with my own H bridge. I can insert limit switches in the power wires so the software can't drive the motor further past the switch, but it can drive the motor to pull back away from the switch.&#xA;I can build custom solutions that can do things that none of the commonly available servos can do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;p.s.: Have you heard of OpenServo?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-05-27T21:28:09.857" CommunityOwnedDate="2010-05-27T21:28:09.857" CommentCount="1" />
  <row Id="2773" PostTypeId="2" ParentId="565" CreationDate="2010-05-27T21:42:57.970" Score="0" ViewCount="" Body="&lt;p&gt;Another approach is to use &quot;digital&quot; servos, such as &lt;a href=&quot;http://openservo.com/&quot; rel=&quot;nofollow&quot;&gt;OpenServo&lt;/a&gt;. That way you can drive a dozen or so servos using 2 Arduino pins, and a dozen or so more servos using 2 more pins.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-05-27T21:42:57.970" CommunityOwnedDate="2010-05-27T21:42:57.970" />
  <row Id="2774" PostTypeId="2" ParentId="2771" CreationDate="2010-05-27T22:16:27.543" Score="4" ViewCount="" Body="&lt;p&gt;BLDC motors usually just use permanent magnets on the rotor (be it in-runner or out-runner) and use a set of windings on the stator connected in a three-phase delta or wye configuration. The speed controller just generates a variable-frequency, three phase waveform to power the motor. Since the windings are symmetric, electrically there's no reason you can't turn the motor in either direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for whether it's a good idea to run a prop backwards on landing, that's more of an aeronautics problem than anything inherently electronic. Having flown some r/c planes, it seems to make sense to me that if you reverse the prop on landing, you're basically just applying a braking force along the line of the axis of rotation. If that line passes above the center of gravity (not below it), that should torque things so that the tail will stay down, so you should be stable if that's the case. If the prop axis is below the CG, though, you're looking at forward torques that would drive the nose down, which would result in damage.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-27T22:16:27.543" CommentCount="1" />
  <row Id="2775" PostTypeId="2" ParentId="110" CreationDate="2010-05-27T22:28:46.333" Score="2" ViewCount="" Body="&lt;p&gt;Since no one else has said it - you wouldn't be able to practically drive a motor directly from an arduino simply because the AVR chip won't put out enough current to supply any useful amounts of power. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So at the very least, you'd be looking at creating a three-phase H-bridge arrangement (read: three 'half H-bridges') to drive the currents needed, requiring six digital lines just to operate the drive transistors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming you had this drive capability problem solved, and that's not trivial, then you'd have to get into the control code. These motors have permanent magnet rotors, so you can't just blindly spin the stator field and get useful torque. You have to know the orientation of the rotor in order to keep the electrical phase angles adjusted so that you get uniform torque.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So like others have said, unless you want the specific learning experience, there's no dishonor in just buying an ESC.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-27T22:28:46.333" />
  <row Id="2776" PostTypeId="2" ParentId="2771" CreationDate="2010-05-27T22:34:56.303" Score="2" ViewCount="" Body="&lt;p&gt;Yes, you can drive a brushless DC motor in both directions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See, for example, the &lt;a href=&quot;http://www.onsemi.com/PowerSolutions/product.do?id=MC33035PG&quot; rel=&quot;nofollow&quot;&gt;On Semiconductor MC33035&lt;/a&gt; brushless DC motor control chip, which has a pin to control direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a little explanation from p. 9 of &lt;a href=&quot;http://www.onsemi.com/pub/Collateral/MC33035-D.PDF&quot; rel=&quot;nofollow&quot;&gt;the datasheet&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The Forward/Reverse input (Pin 3) is used to change the&#xA;  direction of motor rotation by reversing the voltage across&#xA;  the stator winding. When the input changes state, from high&#xA;  to low with a given sensor input code (for example 100), the&#xA;  enabled top and bottom drive outputs with the same alpha&#xA;  designation are exchanged (AT to AB, BT to BB, CT to CB).&#xA;  In effect, the commutation sequence is reversed and the&#xA;  motor changes directional rotation.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I believe you do have to be careful about &quot;shoot-through&quot;-- if you're trying to switch the direction of current flow in a winding, you have to be sure to turn one set of FETs off completely before you turn on the other set, or you may inadvertently short your power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might google &quot;adaptive gate drive&quot; or &quot;dead time&quot; for more details.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-27T22:34:56.303" CommentCount="1" />
  <row Id="2777" PostTypeId="2" ParentId="2771" CreationDate="2010-05-27T22:37:06.923" Score="1" ViewCount="" Body="&lt;p&gt;What you have to worry about most when you reverse direction of a motor, is that you do not put too much current into either the motor or the electronics/switches that control it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you connect a voltage source across a motor that is at rest and either has a large inertia or a locked rotor, you get a large current flowing through it = V / R where R is the stator winding resistance of the motor. This is called the stall current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are running at full speed with a voltage source across a motor, and you immediately reverse the polarity of the voltage source, you can get up to 2x the stall current, because the voltage source is then at the opposite polarity of the motor's back-emf. This can be too much current, and if that's the case then you have to control the rate at which you reverse voltage across the motor, by using PWM or some other way besides a hard voltage reversal.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-05-27T22:37:06.923" />
  <row Id="2778" PostTypeId="1" CreationDate="2010-05-28T00:43:54.920" Score="1" ViewCount="133" Body="&lt;p&gt;I am looking to build a circuit board that can take a multi segment LCD display signal from a ZIF connector, relay it, and split it to another LCD while having the original and seperate LCD display.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone have experience on this, and are their chipsets that do this already?&lt;/p&gt;&#xA;" LastActivityDate="2011-02-26T03:03:08.790" Title="LCD signal splitter and repeater" Tags="&lt;lcd&gt;&lt;relay&gt;&lt;microcontroller&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="2779" PostTypeId="2" ParentId="2756" CreationDate="2010-05-28T02:13:05.863" Score="1" ViewCount="" Body="&lt;p&gt;Doing a google search of Microcontroller Mondays will yield good results.&lt;/p&gt;&#xA;" LastActivityDate="2010-05-28T02:13:05.863" />
  <row Id="2780" PostTypeId="2" ParentId="2778" CreationDate="2010-05-28T03:45:50.030" Score="1" ViewCount="" Body="&lt;p&gt;I believe you can just run wires in parallel to each LCD. It might draw too much current, but LCDs generally draw very little current, so there's a good chance it will work.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-28T03:45:50.030" CommentCount="1" />
  <row Id="2781" PostTypeId="2" ParentId="2756" CreationDate="2010-05-28T04:13:34.420" Score="2" ViewCount="" Body="&lt;p&gt;Noisebridge in San Francisco is amazing!&lt;/p&gt;&#xA;" LastActivityDate="2010-05-28T04:13:34.420" />
  <row Id="2782" PostTypeId="2" ParentId="2771" CreationDate="2010-05-28T08:58:36.800" Score="1" ViewCount="" Body="&lt;p&gt;Thrust on helycopters is controlled by varying the propeller pitch, not the motor speed/direction. In an helycopter, the main rotor motor turns almost always at the same speed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inverted hovering needs a special designed &lt;a href=&quot;http://en.wikipedia.org/wiki/Swashplate_%28helicopter%29&quot; rel=&quot;nofollow&quot;&gt;swash plate&lt;/a&gt; that allows positive and negative blade pitch.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the original question, yes, you can drive a brushless dc motor in both direction. &#xA;Stopping it quickly (with a propeller connected to it), change direcion to the thrust, and keeping your plane on the track, is another story :-)&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2010-05-28T08:58:36.800" CommentCount="2" />
  <row Id="2783" PostTypeId="1" CreationDate="2010-05-28T13:03:03.080" Score="11" ViewCount="501" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to set up a PCB with an atmega168 and no programming header. I intend to use a serial bootloader (there is a ft232 on the board) to reprogram but I am wondering about the best way to program the bootloader on. Has anyone else tried this before? I am having trouble sourcing a tqfp-32 zif socket.&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-05-28T16:51:30.430" LastActivityDate="2010-10-27T13:50:06.993" Title="Pre-programming surface mount ICs" Tags="&lt;tqfp&gt;&lt;microcontroller&gt;&lt;pcb&gt;&lt;surface-mount&gt;" AnswerCount="7" CommentCount="2" FavoriteCount="1" />
  <row Id="2784" PostTypeId="2" ParentId="2783" CreationDate="2010-05-28T13:17:15.680" Score="4" ViewCount="" Body="&lt;p&gt;What you need is a &lt;a href=&quot;http://www.logicalsys.com/qfp-smt-to-thru-hole-adapters.asp&quot; rel=&quot;nofollow&quot;&gt;surface-mount adapter&lt;/a&gt;. Then a ZIF socket is easy to find.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The QFP ones are kind of expensive, but you can get piles of most footprints pretty cheaply from &lt;a href=&quot;http://www.sparkfun.com/commerce/categories.php?c=20&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt; or &lt;a href=&quot;http://smt-adapter.biz/Main&quot; rel=&quot;nofollow&quot;&gt;other sites&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-28T13:17:15.680" CommentCount="2" />
  <row Id="2785" PostTypeId="2" ParentId="2783" CreationDate="2010-05-28T14:21:50.157" Score="8" ViewCount="" Body="&lt;p&gt;Just put an ISP header on your board as an &quot;alternative&quot; to the serial bootloader. Then use something like the AVRISP MkII to program your hex file and fuses with AVRStudio. Maybe you only use it once to load the bootloader, but it's by far the most cost-effective solution you're going to find.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In case you don't know what I mean by an ISP header, it's a 2x3 male header, with the following pinout:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;2x3 pin    connect to AVR pin&#xA;1          MISO&#xA;2          VCC&#xA;3          SCK&#xA;4          MOSI&#xA;5          RESET&#xA;6          GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Odd numbered pins are on one row, even numbered pins are on the other row, and sequential pins are otherwise adjacent. On a board layout looking down at the top layout the pads are numbered like this (or any consistent rotation):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;2 4 6&#xA;1 3 5&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Wire it like that and you should be able to plug in any programmer that supports ISP (e.g. AVRISP MkII, STK500, etc.)&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-05-28T14:34:36.187" LastActivityDate="2010-05-28T14:34:36.187" CommentCount="1" />
  <row Id="2786" PostTypeId="2" ParentId="2783" CreationDate="2010-05-28T14:44:04.607" Score="14" ViewCount="" Body="&lt;p&gt;It might be easier to bring out the programming pins to some pads then use pogopins to attach your programmer.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-05-28T14:44:04.607" CommentCount="5" />
  <row Id="2787" PostTypeId="2" ParentId="2036" CreationDate="2010-05-28T14:59:14.757" Score="2" ViewCount="" Body="&lt;p&gt;I use a BusBee. The hardware/software is very simple to use and it can log a lot of data. Works on many different protocols, but I typically use it for I2C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.usbee.com/busbee.html&quot; rel=&quot;nofollow&quot;&gt;http://www.usbee.com/busbee.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-05-28T14:59:14.757" />
  <row Id="2788" PostTypeId="2" ParentId="2778" CreationDate="2010-05-28T17:58:42.677" Score="0" ViewCount="" Body="&lt;p&gt;you should be able to just wire them together, however i would include provisions for signal reflection issues.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't split the signal going to them, but rather run the signal to one, then to the other and allow space past the last display to include end termination if needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your limits on the number of displays will be the drive current, length of the signal lines and total bus capacitance.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-05-28T17:58:42.677" />
  <row Id="2789" PostTypeId="2" ParentId="2036" CreationDate="2010-05-28T18:18:44.227" Score="4" ViewCount="" Body="&lt;p&gt;A little more expensive ($389) than the ones mentioned so far, but very capable:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.pctestinstruments.com/&quot; rel=&quot;nofollow&quot;&gt;Logicport by Intronix&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;34 channels&#xA;Adjustable logic threshold (+6V to -6V)&#xA;I2C, SPI, RS232 and CAN interpreters&lt;/p&gt;&#xA;&#xA;&lt;p&gt;plus the software can be run in demo mode before you buy it.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-05-28T18:18:44.227" CommentCount="1" />
  <row Id="2790" PostTypeId="1" AcceptedAnswerId="2792" CreationDate="2010-05-28T18:18:59.423" Score="6" ViewCount="188" Body="&lt;p&gt;I'm building a small, low-power device that will be used inside a standard consumer refrigerator (approximately 2°C).  I've had trouble with Alkaline batteries at low temperatures, and was wondering if anyone has any recommendations for cells to use under these conditions.  How do Lithium coin cells hold up, for instance?  The datasheets I've found for them don't seem to take temperature into account.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update: it looks like I'll have to source ~50mA for short bursts, so the low-end lithium manganese dioxide cells I've been using aren't going to cut it.  Any other suggestions?&lt;/p&gt;&#xA;" OwnerUserId="70" LastEditorUserId="70" LastEditorDisplayName="" LastEditDate="2010-07-15T01:37:58.213" LastActivityDate="2010-07-15T02:57:36.117" Title="Small batteries for use in cold (but not freezing) environments?" Tags="&lt;battery&gt;&lt;temperature&gt;" AnswerCount="2" CommentCount="7" />
  <row Id="2791" PostTypeId="2" ParentId="2783" CreationDate="2010-05-28T18:25:25.940" Score="6" ViewCount="" Body="&lt;p&gt;If you are buying these in large volumes often you can buy chips directly from the vendor pre-programmed with your boot loader. I'm not sure if Atmel offers this service, but I know Microchip does so I would assume they do as well.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-05-28T18:25:25.940" />
  <row Id="2792" PostTypeId="2" ParentId="2790" CreationDate="2010-05-28T19:29:09.150" Score="8" ViewCount="" Body="&lt;p&gt;I would suggest a lithium CR2032 battery. feel free to pick a large package or place a few in parallel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lithium Polymer will have lower capacity at lower temperatures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, to quote battery university, &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://www.batteryuniversity.com/partone-15.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;Lithium-ion  works within the discharge temperature limits of -20°C to 60°C (-4°F to 140°F).&quot;&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;As a side note, they often list 1mA as maximum current on one of these, but they can handle 10mA without much of a battery life loss(this will be worse at lower temps), pass 10mA and you will be killing batteries right and left.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.houseofbatteries.com/pdf/CSO-CR2032&quot; rel=&quot;nofollow&quot;&gt;Here is an example of a discharge curve based on temperature. It is the second page of the data-sheet.&lt;/a&gt; There is a clear decrease in life(~25%), but you should still be very able to use the battery. It looks like -20 degrees C is where you start to have large reductions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please let me know if there is anything I can add to make this more clear or more valuable to you.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-05-28T19:34:12.073" LastActivityDate="2010-05-28T19:34:12.073" CommentCount="4" />
  <row Id="2793" PostTypeId="1" CreationDate="2010-05-29T00:28:45.363" Score="1" ViewCount="326" Body="&lt;p&gt;I'm looking for a low cost adaptor/breakout board for a 64 ball BGA chip (0.8mm pitch) &lt;a href=&quot;http://www.ti.com/lit/gpn/ads1298&quot; rel=&quot;nofollow&quot;&gt;PDF of chip datasheet&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to use the chip with a bread board, any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-05-29T07:08:45.617" CommunityOwnedDate="2010-05-29T00:28:45.363" Title="BGA Adaptor Wanted" Tags="&lt;bga&gt;&lt;breadboard&gt;&lt;breakout&gt;" AnswerCount="3" />
  <row Id="2794" PostTypeId="2" ParentId="2793" CreationDate="2010-05-29T01:13:49.267" Score="0" ViewCount="" Body="&lt;p&gt;See this answer to a sort-of related question: &lt;a href=&quot;http://chiphacker.com/questions/2783/pre-programming-surface-mount-ics/2784#2784&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/2783/pre-programming-surface-mount-ics/2784#2784&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-05-29T01:13:49.267" CommunityOwnedDate="2010-05-29T01:13:49.267" CommentCount="6" />
  <row Id="2795" PostTypeId="2" ParentId="2793" CreationDate="2010-05-29T03:34:08.563" Score="1" ViewCount="" Body="&lt;p&gt;Not sure if this is exactly what you want, but a little bit of googling found me this: &lt;a href=&quot;http://www.adapters.com/Packages/bga_package.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.adapters.com/Packages/bga_package.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-05-29T03:34:08.563" CommunityOwnedDate="2010-05-29T03:34:08.563" CommentCount="1" />
  <row Id="2796" PostTypeId="2" ParentId="2793" CreationDate="2010-05-29T07:08:45.617" Score="3" ViewCount="" Body="&lt;p&gt;BGA chips are very unfriendly for prototyping with directly. Generally if a chip comes in BGA form, you should purchase a pre-made development board with the chip already attached. Even if you made your own PCB, they are very difficult to solder correctly with hobby level tools (Yes there are youtube videos of guys doing it with a candle and a hairdryer or something, but that's not the norm). The only BGA protoboard adapters I've heard of are from &lt;a href=&quot;http://www.schmartboard.com/index.asp?page=products_bga&amp;amp;id=110&quot; rel=&quot;nofollow&quot;&gt;SchmartBoard&lt;/a&gt; -- but a quick look at their site only shows 1.27mm and 1.00mm pitch BGA adaptors, 0.8mm is too small for them. A random google search found these &lt;a href=&quot;http://www.emulation.com/catalog/off-the-shelf_solutions/prototyping_adapters/bga/&quot; rel=&quot;nofollow&quot;&gt;ZIF Sockets&lt;/a&gt;...but I suspect they may be out of their price range. Yes, that's right, pick your jaw up off the floor, that price is for a single piece.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;EDIT: I just looked up the part number, ADS1298 from TI, and it comes in TQFP. Get that instead!! It will be much cheaper, easier, and save you a ton of headache instead of trying to prototype with the BGA part. When you're ready to sell a million of your gadgets, then you can hire a factory to solder on the BGA's for you, but until then, stick to the TQFP.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-05-29T07:08:45.617" CommunityOwnedDate="2010-05-29T07:08:45.617" CommentCount="6" />
  <row Id="2797" PostTypeId="1" CreationDate="2010-05-29T18:56:38.390" Score="2" ViewCount="387" Body="&lt;p&gt;Hey,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was making a breadboard demo for a Microcontroller class. Basically my project is to make a score keeping device. I want to drive 4 seven segment displays using an atmega8. I read about charlie plexing and understand that it will enable me to drive all the 4 displays using a single port. I understood the theory but can't really figure out how to make the charlie plexing circuit on a bread board. Can anyone please help? &lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:38:01.617" LastActivityDate="2011-05-17T12:49:59.660" Title="CharliePlexing on a breadboard" Tags="&lt;charlieplexing&gt;&lt;microcontroller&gt;&lt;avr&gt;&lt;breadboard&gt;" AnswerCount="3" CommentCount="9" FavoriteCount="1" />
  <row Id="2798" PostTypeId="2" ParentId="2797" CreationDate="2010-05-29T19:22:52.673" Score="4" ViewCount="" Body="&lt;p&gt;Take a look at my charlie-plexing schematic at&#xA;&lt;a href=&quot;http://wiblocks.luciani.org/FAQ/faq-charlie-plex.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/FAQ/faq-charlie-plex.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make each row connection the common pin of the seven segment readout.&#xA;Make each column the individual pin connection. For 28 segments&#xA;you need six pins. If you use eight pins instead of six you&#xA;may find it easier to program. With eight pins I would do four&#xA;rows and seven columns.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T12:49:59.660" LastActivityDate="2011-05-17T12:49:59.660" />
  <row Id="2799" PostTypeId="2" ParentId="2797" CreationDate="2010-05-29T20:07:19.357" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Charlieplexing&quot; rel=&quot;nofollow&quot;&gt;Wikipedia article&lt;/a&gt; has simple examples on how to wire charlieplexed LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also a lot of instructables related to charlieplexing. This &lt;a href=&quot;http://www.instructables.com/id/Charlieplexing-7-segment-displays/step4/Charlieplexed-displays/&quot; rel=&quot;nofollow&quot;&gt;particular instructable&lt;/a&gt; explains how to wire 7-segment displays (with additional transistors though).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.josepino.com/microcontroller/charlieplex-7segment-display&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; also explains how to wire 7-segment displays and contains pseudo code on how to drive them. The main difficulty of charlieplexing is to use flickering so that you can switch on arbitrary combinations of segments.&lt;/p&gt;&#xA;" OwnerUserId="595" LastEditorUserId="595" LastEditorDisplayName="" LastEditDate="2010-05-29T20:31:45.313" LastActivityDate="2010-05-29T20:31:45.313" />
  <row Id="2800" PostTypeId="1" CreationDate="2010-05-29T21:45:13.900" Score="3" ViewCount="902" Body="&lt;p&gt;I have an Arduino microcontroller. I wanted to control a few servos for an example project but I soon found out the Arduino can't give it enough power. I don't understand how to power something externally but still use the Arduino to control it. &lt;/p&gt;&#xA;" LastEditorUserId="424" LastEditorDisplayName="" LastEditDate="2010-06-06T01:21:57.107" LastActivityDate="2010-06-06T01:21:57.107" Title="Need help understanding external power on Arduino" Tags="&lt;arduino&gt;" AnswerCount="3" />
  <row Id="2801" PostTypeId="2" ParentId="2800" CreationDate="2010-05-29T23:32:00.300" Score="4" ViewCount="" Body="&lt;p&gt;There are several ways to do this. I suggest you read the following excellent tutorial:&#xA;&lt;a href=&quot;http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads&quot; rel=&quot;nofollow&quot;&gt;http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-05-29T23:32:00.300" />
  <row Id="2802" PostTypeId="2" ParentId="2797" CreationDate="2010-05-29T23:49:08.993" Score="2" ViewCount="" Body="&lt;p&gt;I'm only a beginner at all of this, so take this with a grain of salt, but I'd have a totally different approach.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd use a 7447 decoder instead. This would use 7 pins (4 for the output, and 3 to select the display), but it would be much simpler than having to work out the combinations to charlieplex and would give a brighter output too.&lt;/p&gt;&#xA;" OwnerUserId="776" LastActivityDate="2010-05-29T23:49:08.993" CommentCount="2" />
  <row Id="2803" PostTypeId="2" ParentId="2800" CreationDate="2010-05-30T00:03:01.283" Score="7" ViewCount="" Body="&lt;p&gt;I think you may not fully understand how the servo works. Most servos have a power, ground, and PWM line. The PWM line will pull very little power. This line is what the microcontroller will actually be controlling. The Power and Ground lines are where the servo actually pulls its power from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The power line can be connected to anything as long as the ground lines are at the same potential as the Arduino. If you are using an Arduino board, the voltage regulator that is on the board is limiting your power to the servo and not the microcontroller itself. If you are using an Arduino in an IC form (ie: breadboard) then you will need to make sure what ever you are using as your voltage source (power supply, battery, voltage regulator...) is at the right Voltage level and can handle the current of the servo.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-05-30T00:03:01.283" />
  <row Id="2804" PostTypeId="2" ParentId="2800" CreationDate="2010-05-30T08:14:21.350" Score="1" ViewCount="" Body="&lt;p&gt;As @Kellenjb says, power your servo directly from your main battery/plugpack.   Connect servo ground to same ground as arduino, servo power to your power supply (or a separate regulator if your power supply voltage is too high for the servo) and connect the servo's control line to the arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are powering the arduino over USB, there's only enough power available on the USB interface to drive a small servo, so you should consider a separate power supply.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2010-05-30T08:14:21.350" />
  <row Id="2805" PostTypeId="2" ParentId="2729" CreationDate="2010-05-30T08:42:21.180" Score="0" ViewCount="" Body="&lt;p&gt;&quot;Real&quot; serial ports use the EIA-RS232 standard of +/-12v volts which allows quite long cables.   Lots of embedded gear uses the TTL logic levels of 0/5v, as this is much simpler but can only be run a metre or so.  Sometimes you can cheat and connect TTL outputs to an RS232 input, even though this violates the RS332 spec.   I wouldn't recommend going the other way and connecting 12v to a defenceless uC expecting 5v, though. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason for the use of 12v and -12v is noise immunity---5v serial lines only work over short distances before the noise overwhelms the signal, while RS232 can run up to 10m or more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Traditionally the line drivers/receivers used to convert TTL to RS232 require +/- 12V power.  This is the main reason there is a -12v line on a PC power supply.   For 5v only systems, the Maxim MAX232 is the defacto standard for RS232 interfacing--this chip uses capacitor charge-pumps to generate +/- 12v from a single 5v supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you aren't up to building a MAX232 interfacing circuit you can buy one pre-built from futurlec for about $5: &lt;a href=&quot;http://futurlec.com/Mini_RS232_TTL_5V.shtml&quot; rel=&quot;nofollow&quot;&gt;http://futurlec.com/Mini_RS232_TTL_5V.shtml&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can provide a work-alike single-sided PCB layout for a TTL&amp;lt;-&gt;RS232 converter, if anyone is interested, as I built one a while ago to use when prototyping serial interfaced projects.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2010-05-30T08:42:21.180" />
  <row Id="2807" PostTypeId="1" CreationDate="2010-05-30T08:46:50.070" Score="0" ViewCount="421" Body="&lt;p&gt;Hi, I am a high school student. Please help me, i want shift a 24 volts at the input to 6v on the output!! i need a dc level shifter but i dont know its contents!!&lt;/p&gt;&#xA;" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-05-30T12:06:12.530" LastActivityDate="2010-10-16T08:51:19.397" Title="dc level shifter" Tags="&lt;dc&gt;&lt;voltage-regulator&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="2808" PostTypeId="2" ParentId="2807" CreationDate="2010-05-30T10:04:10.413" Score="7" ViewCount="" Body="&lt;p&gt;just put in a 7806 and you're done&lt;/p&gt;&#xA;" OwnerUserId="348" LastActivityDate="2010-05-30T10:04:10.413" CommentCount="1" />
  <row Id="2809" PostTypeId="2" ParentId="2807" CreationDate="2010-05-30T12:05:01.550" Score="6" ViewCount="" Body="&lt;p&gt;This really depends on what the 6v output is going to be used for. If it is purely an act of showing you can step 24v down to 6v and show on a volt meter that it is actually 6v, you will probably want a simple voltage divider. If this is the case, Google will be your friend.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are needing to power something off of the 6v output, you will need a voltage regulator. As Erik said, a 7806 would do the job. There are many other things that will work also, this is another case that Google will do wonders. Just make sure to use the term &quot;voltage regulator&quot; and not DC level shifter. The advantage of a voltage regulator over a voltage divider is that you can have your load (what your powering) change over time and still have the same voltage output. In the case of a voltage divider, you have to treat your load as a resistor, capacitor, and inductor. All of these will effect the voltage output of a voltage divider. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have some sort of signal at 24v that you want to step down to 6v, then there are a lot more aspects that we would need to know in order to help you out.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-05-30T12:05:01.550" />
  <row Id="2810" PostTypeId="2" ParentId="2778" CreationDate="2010-05-30T12:10:17.343" Score="0" ViewCount="" Body="&lt;p&gt;does the LCD have an onboard controller? probably not, but I figured I would mention that if it does you will have to run individual wires for an enable lines or similar.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-05-30T12:10:17.343" />
  <row Id="2811" PostTypeId="1" AcceptedAnswerId="2817" CreationDate="2010-05-30T15:14:57.473" Score="5" ViewCount="1028" Body="&lt;p&gt;I need to measure the frequency of square-wave that can vary between 0 and 1MHz, and has a resolution of 0.25Hz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I havent decided on which controller yet but It will most likely be one of the 20pin Attiny's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally how I would measure lower frequency signals would be by using two timers one configured in timer capture mode to interrupt on  say the rising edges of the external signal and another timer set up to interrupt every second therefore the former timers counter register value after 1 second would be equal to the frequency of the signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However this method obviously wont work for capturing signals ranging between 0 and 1MHz with a resolution 0.25Hz for this I would need a 22Bit counter (AFAIK 8bit micros only have 8/16bit counters).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One Idea I had was to divide the signal before applying it to the micro but this would be impratical as the signal would have to be divided by 61 therefore the frequency could only be updated every 61 seconds where I would like it to be every few seconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there another method that would allow the frequency to be updated say every 4 seconds?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest solution is to use an use an external interrupt or a timer capture to interrupt on  the rising edge of the signal and have the &lt;code&gt;isr&lt;/code&gt; increment a variable of type &lt;code&gt;long int&lt;/code&gt;. Read the variable every 4 seconds (to allow for frequencies down to 0.25Hz to measured).&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update 2:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As pointed out by JustJeff an 8bit MCU will not be able to keep up with a 1MHz signal so that rules out interrupting on every rising edge and incrementing a &lt;code&gt;long int&lt;/code&gt;...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have chosen the method suggested by timororr. Once I get around to implementing it Ill post back and share the results. Thanks to all for your suggestions. &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Progress Report:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Iv'e started to test some of the ideas presented here. Firstly I tried vicatcu's code. &#xA;There was a obvious problem of TCNT1 not been cleared after the frequency been calculated -not a big deal...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then I noticed when debugging the code that about every  2 to 7 times the frequency was calculated timer 1's (the timer configured to count external events) overflow count would be short by two.&#xA;I put this down to latency of Timer 0 ISR and decided to move the if statement block form the ISR to the main (see snippet below) and just set a flag in the ISR.&#xA;Some debugging showed that the first measurement would be ok but with every subsequent reading Timer 1's overflow count would be over by 2. &#xA;which I can't explain  -I would have expected it to be under not over...&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int main()&#xA;{&#xA;    while(1)&#xA;    {&#xA;        if(global_task_timer_ms &amp;gt; 0 &amp;amp;&amp;amp; (T0_overflow == 1))&#xA;        {&#xA;            global_task_timer_ms--;&#xA;            T0_overflow = 0;&#xA;        }&#xA;&#xA;        .....&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Next I decided I would try to implement timrorrs suggestion. To generate the neccesary interval (of approx 15ms between each timer_isr interrupt) I would have to cascade the two 8-bit timers&#xA;as the only 16-bit timer on the Atmega16 is being utilized to capture the rising edges of the external signal. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I thought this solution would work and be much more efficient as most of the overhead is shifted to the timers and only one short isr left for the cpu to handle.&#xA;However it wasn't as accurate as I had hoped, measurements shifted back and forth by approx 70Hz which I wouldn't mind at high frequencies but its definitely not acceptable at lower frequencies.&#xA;I didnt spend two much time analysing the problem but Im guessing the timer cascading arrangement is not so accurate &#xA;as I have implemented a similar arrangement to timrorrs suggestion on a far slower 8051 controller that had 2 16-bit timers and the results were quite accurate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have now gone back to vicatcu's suggestion,  but I have moved the frequency calculation into the Timer 0 isr &lt;em&gt;(see snippet below&lt;/em&gt;), this code has produced consistent and reasonably accurate measurements.&#xA;With a little calibaration accuracy should be approximatly +/-10Hz.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ISR(TIMER0_OVF_vect)&#xA;{            &#xA;&#xA;    TCNT0 = TIMER0_PRELOAD;         //Reload timer for 1KHz overflow rate&#xA;&#xA;    if(task_timer_ms &amp;gt; 0)&#xA;    {&#xA;        task_timer_ms--;&#xA;    }&#xA;    else&#xA;    {     &#xA;        frequency_hz = 1.0 * TCNT1;&#xA;        TCNT1 = 0;&#xA;        frequency_hz += global_num_overflows * 65536.0;&#xA;        global_num_overflows  = 0;&#xA;        frequency_hz /= (TASK_PERIOD_MS / 1000.0);&#xA;        task_timer_ms = TASK_PERIOD_MS;&#xA;    }                                                 &#xA;}       &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If anybody has any other suggestions Im open to them although but I rather not have to use ranges...&#xA;Im also no longer to intent on getting 0.25% resolution, there  doesnt seem much point with the level of accuracy that I have at the moment.&lt;/p&gt;&#xA;" OwnerUserId="819" LastEditorUserId="819" LastEditorDisplayName="" LastEditDate="2010-06-12T01:34:42.243" LastActivityDate="2010-09-14T18:37:35.240" Title="Measuring 0 - 1MHz ( 0.25Hz resolution) Squarewave using an MCU" Tags="&lt;frequency-measurement&gt;&lt;measurement&gt;&lt;microcontroller&gt;&lt;attiny&gt;&lt;avr&gt;" AnswerCount="7" CommentCount="5" FavoriteCount="0" />
  <row Id="2812" PostTypeId="2" ParentId="2811" CreationDate="2010-05-30T16:01:17.347" Score="2" ViewCount="" Body="&lt;p&gt;Instead of doing a 1 second counter, make it a 0.1 second counter and multiply the count by 10?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's just a matter of storing the counter number, can't you use additional code to keep track of when the counter is about to overflow and write to another memory location to keep the tally?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-05-30T16:01:17.347" CommentCount="2" />
  <row Id="2813" PostTypeId="2" ParentId="966" CreationDate="2010-05-30T17:16:42.050" Score="2" ViewCount="" Body="&lt;p&gt;Decoders such as the 74LS138 for Address Decoding.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;LCD's such as the basic 16x2 character LCD with the HD48770 controller, always nice to have a few of these for projects, they can also come in handy for debugging.&lt;/p&gt;&#xA;" OwnerUserId="819" LastEditorUserId="819" LastEditorDisplayName="" LastEditDate="2010-05-30T17:38:03.270" LastActivityDate="2010-05-30T17:38:03.270" CommunityOwnedDate="2010-05-30T17:16:42.050" />
  <row Id="2814" PostTypeId="2" ParentId="2811" CreationDate="2010-05-30T17:49:26.440" Score="5" ViewCount="" Body="&lt;p&gt;You can mix a hardware and a software counter by counting the overflows of the hardware counter in an ISR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Counting every edge of the signal in an ISR will be too slow for a 1 MHz signal. I think you could do up to about 50kHz that way.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-05-30T17:49:26.440" CommentCount="3" />
  <row Id="2815" PostTypeId="2" ParentId="2811" CreationDate="2010-05-30T20:22:54.393" Score="6" ViewCount="" Body="&lt;p&gt;You might want to consider having two (or more) ranges. The issues with capturing very low frequencies are somewhat different from the issues with the higher ones. As you've already noted, at the high end of your range you have counter overflow problems. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But consider at the low end of your range, your accuracy will suffer from not having &lt;em&gt;enough&lt;/em&gt; counts in the register. Not sure if you really want to discriminate between 0.25Hz and 0.5Hz, but if you do, then you will actually have to count for four seconds to do that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, specifying a flat 0.25Hz resolution, strictly interpreted, means you'd be able to discern 500,000.00Hz from 500,000.25Hz, which is a rather high degree of precision.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For those reasons, designing for distinct ranges could alleviate the counter size problem. Pulling numbers at random for the sake of example, for the low end, say 0 to 100Hz, count for 10 second intervals, and you get 0.1Hz resolution, and you counter only needs to go up to 1000, not even 10 bits. Then from 100Hz to 10kHz, count for 1 second intervals; you only get 1Hz resolution, but your counter only needs to run up to 10,000 still smaller than 16 bits. The upper range of 10kHz to 1MHz could count for just 0.01 sec, and the max count would still only be 10,000 and though your resolution would be 100Hz, this would be reasonable precision.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-05-30T20:22:54.393" CommentCount="1" />
  <row Id="2816" PostTypeId="2" ParentId="2036" CreationDate="2010-05-31T01:51:03.923" Score="3" ViewCount="" Body="&lt;p&gt;What is also interesting is the open sourcing of the software to run the devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bus pirate is on the list and coming along if you look at the commits for SiGrok&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://sigrok.org/wiki/Main_Page&quot; rel=&quot;nofollow&quot;&gt;http://sigrok.org/wiki/Main_Page&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-05-31T01:51:03.923" />
  <row Id="2817" PostTypeId="2" ParentId="2811" CreationDate="2010-05-31T04:36:41.263" Score="4" ViewCount="" Body="&lt;p&gt;If possible I'd suggest selecting a microcontroller that supports a counter operation using the timer inputs; rather than manually incrementing a counter inside an ISR (which at high frequencies quickly ends up saturating the microcontroller activity) you allow the hardware to handle the counting.  At this point your code simply becomes a matter of waiting for your periodic interrupt then calculating the frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To extend the range and make the frequency counter more generalised (removing the need for multiple ranges at the expense of a little more work for the MCU) you could use the following technique.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Select a periodic interrupt rate that allows for measurement accuracy at the highest input frequency; this should take into account your counter size (you need to select the timer period such that the timer counter will not overflow at the maximum input frequency).  For this example I'll assume that the input counter value can be read from the variable &quot;timer_input_ctr&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Include a variable for counting periodic interrupts (should be initialised to 0 at startup); for this example I'll refer to this variable as &quot;isr_count&quot;.  The interrupt period is contained in the constant &quot;isr_period&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your periodic interrupt should be implemented as (C pseudo-code):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void timer_isr()&#xA;{&#xA;  isr_count++;&#xA;  if (timer_input_ctr &amp;gt; 0)&#xA;  {&#xA;    frequency = timer_input_ctr / (isr_count * isr_period).&#xA;    timer_input_ctr = 0;&#xA;    isr_count = 0;&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Obviously this rough example relies on some floating point math that may not be compatible for low-end microcontrollers, there are techniques to overcome this but they are outside of the scope of this answer.&lt;/p&gt;&#xA;" OwnerUserId="820" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-06-01T18:21:45.137" LastActivityDate="2010-06-01T18:21:45.137" CommentCount="2" />
  <row Id="2818" PostTypeId="2" ParentId="1536" CreationDate="2010-05-31T12:13:54.243" Score="1" ViewCount="" Body="&lt;p&gt;The default firmware sends samples to the host once per second. If you need a faster sample rate, you'll need to write custom firmware (and probably some custom USB HID drivers). The MaxSonar rangefinders, available from spaarkfun or littlebird electronics, have an analog output that's perfect for the AVR stick.&lt;/p&gt;&#xA;" LastActivityDate="2010-05-31T12:13:54.243" />
  <row Id="2819" PostTypeId="2" ParentId="2783" CreationDate="2010-05-31T21:06:41.253" Score="4" ViewCount="" Body="&lt;p&gt;In production we use these &lt;a href=&quot;http://cgi.ebay.com/AVR-ATmega8-48-88-168-TQFP32-ISP-Programmer-Adapter-/260609404148?cmd=ViewItem&amp;amp;pt=LH_DefaultDomain_0&amp;amp;hash=item3cad87ecf4&quot; rel=&quot;nofollow&quot;&gt;TQFP32 adapters we bought on ebay&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. We bought several more than we need so if anyone needs them with an EU VAT invoice... ;-)&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-05-31T21:06:41.253" />
  <row Id="2820" PostTypeId="1" CreationDate="2010-06-01T16:26:58.880" Score="3" ViewCount="333" Body="&lt;p&gt;hey i have some chips with the arduino bootloader on it and some chips without. I want to use them using the same circuit. The confusion I have is with the clock the arduino uses 16MHz external and avr has its internal will it cause a problem if I use them in the same circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking, I just add the clock, the arduino chips will use the crystal and the other chips will not. Am I right?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-06-02T20:26:09.480" Title="AVR external clock problem" Tags="&lt;arduino&gt;&lt;bootloader&gt;&lt;avr&gt;" AnswerCount="3" />
  <row Id="2821" PostTypeId="2" ParentId="2820" CreationDate="2010-06-01T17:26:14.853" Score="3" ViewCount="" Body="&lt;p&gt;as long as you have the fuses set to use the internal oscillator and you are not using the XTAL pins for any reason on those chips, you should be A-OK. You should &lt;em&gt;not&lt;/em&gt; set those XTAL pins to outputs however, but rather inputs &lt;em&gt;without&lt;/em&gt; internal pullups enabled (i.e. DDRx = 0; PORTx=0). On a separate note though, I'm not so sure you'll be OK with more than one crystal per chip. The crystals are 'passive' components, and the AVR actually has some circuitry in it for 'driving' the crystal to resonate...&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;&#xA;OK I just wanted to make sure you weren't trying to &quot;share&quot; crystals. As the others have stated, I can't imagine a (sane) reason why you would have to run your chips at the same clock rate. Be mindful however, that some of your register settings (for example timer prescales, baud rate settings, etc) have implicit coupling to your clock rate, and may need adjustment in otherwise identical firmware.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-06-02T20:26:09.480" LastActivityDate="2010-06-02T20:26:09.480" CommentCount="1" />
  <row Id="2822" PostTypeId="2" ParentId="2820" CreationDate="2010-06-01T17:31:08.610" Score="1" ViewCount="" Body="&lt;p&gt;depends on what you mean by &quot;cause problems&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming they communicate with something like SPI or I2C with proper SoC support there will be no communication problem as SPI/I2C are designed to operate without clock syncing between ICs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may have signal integrity and EMI issues with multiple IC's running off independent clocks.  This will be especially evident in hacked together prototype circuits with high resistance to ground for example a breadboard with wired grounds is much more an issue than a PCB with a solid 2oz ground plane.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The out of sync clocks can cause increased jitter and ground bounce in each others circuits.  1 tip is to avoid the ground current return from traveling under other circuits that run from a different clock.  Always remember that high frequency current follows the path of least inductance not the path of least resistance when considering the current return path.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-06-01T17:38:37.283" LastActivityDate="2010-06-01T17:38:37.283" />
  <row Id="2823" PostTypeId="2" ParentId="2820" CreationDate="2010-06-01T17:31:32.977" Score="0" ViewCount="" Body="&lt;p&gt;The clock setting of ATMega*8 chips are defined by the fuses. I'd rather use the same clock settings for the arduino chip and the AVR or you application may not work properly (especially if you use serial communication, etc...).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.micahcarrick.com/05-12-2006/avr-tutorial-clock-source.html&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; contains useful information on the subject as well as links to the relevant parts in the datasheet.&lt;/p&gt;&#xA;" OwnerUserId="595" LastActivityDate="2010-06-01T17:31:32.977" />
  <row Id="2824" PostTypeId="2" ParentId="2811" CreationDate="2010-06-01T18:38:53.760" Score="2" ViewCount="" Body="&lt;p&gt;Can't you just use a 16-bit timer's input capture and overflow interrupts (plus a variable) to do the measurement? Here's how I would do it with the ATTiny24A with AVR-GCC (untested and potentially buggy of course):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;stdint.h&amp;gt;&#xA;#include &amp;lt;avr/io.h&amp;gt;&#xA;#include &amp;lt;avr/interrupt.h&amp;gt;&#xA;&#xA;#define TIMER1_BITS           16    // 16 bit timer&#xA;#define TIMER1_HZ             8.0e6 // 8MHz crystal&#xA;#define TIMER1_OVF_PERIOD_SEC (1.0 * (1 &amp;lt;&amp;lt; TIMER1_BITS) / TIMER1_HZ)&#xA;#define TIMER1_SEC_PER_TICK   (1.0 / TIMER1_HZ)&#xA;&#xA;//global variables for time keeping&#xA;double total_period_sec = 0.0;&#xA;uint16_t  num_overflows = 0;&#xA;&#xA;void setup_timer1_capture(){&#xA;   // set the ICP (input caputure pin) to a floating input&#xA;   DDRA  &amp;amp;= ~_BV(7); // it's A7 on the ATTiny24A...&#xA;   PORTA &amp;amp;= ~_BV(7);&#xA;&#xA;   TIMSK1 =   _BV(ICIE1)  // enable input pin capture interrupt&#xA;            | _BV(TOIE1); // enable overflow interrupt&#xA;&#xA;   TCCR1B =   _BV(ICNC1)  // activate the input noise canceller&#xA;            | _BV(ICES1)  // capture on rising edge of ICP&#xA;            | _BV(CS10);  // run the timer at full speed&#xA;&#xA;}&#xA;&#xA;ISR(TIM1_CAPT_vect, ISR_NOBLOCK){ //pin capture interrupt&#xA;  uint16_t capture_value_ticks = ICR1; // grab the captured value&#xA;  // do some floating point math&#xA;  total_period_sec =   1.0 * num_overflows * TIMER1_OVF_PERIOD_SEC&#xA;                     + 1.0 * capture_value_ticks / TIMER1_SEC_PER_TICK; &#xA;&#xA;  num_overflows = 0; // clear helper variable to be ready for next time&#xA;}&#xA;&#xA;ISR(TIM1_OVF_vect){   //timer overflow interrupt&#xA;    num_overflows++;&#xA;}&#xA;&#xA;int main(int argc, char *argv[]){&#xA;   setup_timer1_capture();&#xA;&#xA;   sei(); // enable interrupts!&#xA;&#xA;   for(;;){ //forever&#xA;      // do whatever you want...&#xA;      // the most recently calculated period is available in the &#xA;      // total_period_sec variable &#xA;      // (obviously 1.0 / total_period_sec is the frequency in Hz)&#xA;   }&#xA;&#xA;   return 0;&#xA;} &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;... at any rate, it compiles :)&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt; I looked at the lss file output from my code, and the generated code has too many instructions to not trip over itself at 1MHz with an 8MHz clock... even the simple increment by one line in the TIM1_OVF_vect generates 19 instructions! So to handle 1MHz events, you would definitely need to optimize, probably register allocate some stuff (probably num_overflows and capture_value_ticks), use inline assembler (steal the important stuff from the lss file), and move processing out of the interrupts and into the main loop wherever possible. &lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-06-02T20:59:45.577" LastActivityDate="2010-06-02T20:59:45.577" CommentCount="2" />
  <row Id="2825" PostTypeId="2" ParentId="966" CreationDate="2010-06-02T02:43:24.277" Score="4" ViewCount="" Body="&lt;p&gt;Don't forget those 10A fast-blow fuses for your DVM&lt;/p&gt;&#xA;&#xA;&lt;p&gt;=P&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-02T02:43:24.277" CommunityOwnedDate="2010-06-02T02:43:24.277" />
  <row Id="2826" PostTypeId="2" ParentId="2539" CreationDate="2010-06-02T03:29:24.810" Score="3" ViewCount="" Body="&lt;p&gt;Does your software poll this input, or do you use an interrupt scheme to process it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're polling, presumably you read the input at a much higher rate than the expected changes in the signal. If the noise is well separated, very high frequency spikes, these would then look like isolated samples of the 'wrong' polarity. You could mitigate this by keeping the most recent N samples and deciding to read the input as whichever polarity is in the majority. I.e., if N=5, then if you have 3, 4 or 5 '1' bits, your input is a '1'; if you have 0, 1, or 2 '1' bits, your input is a '0'. This is really just a sort of low-pass filter in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using the input to trigger interrupts on change (both edges), you can have the interrupt routine (ISR) start a timer to cause a second interrupt a short time later, but longer than the noise spike time. Rather than have the input pin ISR directly accumulate signal bits, you have the timer ISR do it. For example, if the signal is low, and a high spike comes along, the rising edge start the timer, but before the timer count expires, the falling edge of the spike resets it, so when the timer interrupt finally does go off, you're looking at the signal, not the noise. The signal, on the other hand, will kick off the timer just once, and the timer ISR will be able to grab the new signal level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of these two, Polled vs Interrupt, personally I'd go for the polled approach, b/c (1) interrupts are just more complicated, and (2) a pathologically placed pair of spikes could still give you false input.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-02T03:29:24.810" />
  <row Id="2827" PostTypeId="1" CreationDate="2010-06-02T15:05:13.857" Score="9" ViewCount="263" Body="&lt;p&gt;I know of &lt;a href=&quot;http://www.findchips.com/&quot; rel=&quot;nofollow&quot;&gt;findchips.com&lt;/a&gt;, &lt;a href=&quot;http://www.oemstrade.com/&quot; rel=&quot;nofollow&quot;&gt;oemstrade.com&lt;/a&gt;, &lt;a href=&quot;http://octopart.com/&quot; rel=&quot;nofollow&quot;&gt;octopart.com&lt;/a&gt;, and the like. But even the lowest prices on these sites are still higher than the prices on BOMs I get from China.  How do you realistically estimate the cost of an IC purchased at high quantities for manufacturing purposes?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-11-12T16:19:51.173" Title="How do you find high-quantity prices for ICs?" Tags="&lt;manufacturing&gt;&lt;ic&gt;&lt;cost&gt;&lt;development&gt;" AnswerCount="4" FavoriteCount="5" />
  <row Id="2828" PostTypeId="2" ParentId="2827" CreationDate="2010-06-02T15:21:25.263" Score="2" ViewCount="" Body="&lt;p&gt;Starting to have that dilemma myself - trying to price out some kits. Pricing will depend on quantity - contact the manufacturer directly, e.g. Maxim will sell DS1307 real time clock ICs for US$1.36 each for 1000+; retail here is A$3.62 (ex) each for 50+. If China prices are cheaper than the manufacturer you could be getting some ... sub-prime quality components, or &lt;a href=&quot;http://www.sparkfun.com/commerce/news.php?id=350&quot; rel=&quot;nofollow&quot;&gt;slugs&lt;/a&gt;. Would love to hear what anyone else has to say about this as well. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-11-11T05:30:59.117" LastActivityDate="2010-11-11T05:30:59.117" />
  <row Id="2829" PostTypeId="1" AcceptedAnswerId="2833" CreationDate="2010-06-02T15:52:30.517" Score="8" ViewCount="789" Body="&lt;p&gt;Can anyone recommend a good place to go making PCB's? I'm particularly interested in places that also offer assembly, because this makes SMD parts an option. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;GoldPhoenix is an option, but not the cheapest.&lt;/li&gt;&#xA;&lt;li&gt;Anyone used OurPCB?&lt;/li&gt;&#xA;&lt;li&gt;Any order time is OK- there is no particular rush, and the slowboat from China is just fine.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1402" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2010-06-20T19:57:31.390" LastActivityDate="2011-05-03T14:42:48.503" Title="Recommended PCB houses / Assemblers" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;&lt;surface-mount&gt;" AnswerCount="11" CommentCount="3" FavoriteCount="5" />
  <row Id="2830" PostTypeId="2" ParentId="2827" CreationDate="2010-06-02T16:04:41.373" Score="17" ViewCount="" Body="&lt;p&gt;Generally be careful of just getting full BOM pricing from China.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I usually let them handle generic parts, resistors, capacitors, generic diodes, generic transistors.  That type of thing.  Production houses usually buy such parts in the 100k + lot size making them hard to beat.  When your prototypes come back for checking i strongly urge you to test the parts they used.  Its not uncommon for them to slip in 5% parts in place of 1% parts.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there are parts where the exact tolerance or dielectric is critical i would supply these yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a good relationship with the production house, you can let them source some of the IC's as well, common parts like op amps they can usually handle but again, test, test, test to make sure its not some relabeled piece of crap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the rest of the parts, i usually go with a major part supplier.  &lt;a href=&quot;http://www.arrownac.com/&quot; rel=&quot;nofollow&quot;&gt;Arrow&lt;/a&gt; is my favorite so far.  They have a wide array of parts they stock, maintain warehouses and contacts in China to work directly with manufacturing and my local contact is very responsive and happy to dice up the order however I want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What i normally do is get a full BOM price from both arrow and the manufacturer.  Then i sit down and cut up the BOMs based on who is giving the best prices.  Then i move anything that is on the China order that i'm concerned about the quality of over to arrow if the prices are reasonably close.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may find that after a few runs you feel more confident and have a better relationship with your China manufacturer, at this point you may want to move more part sourcing to their end.  There absolutely are some trustworthy and capable production houses over there, there are also some very shady operations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another recommendation for dealing with Chinese manufacturing:  Be very, very methodical with your test procedures.  Use simple, direct language and lots of photos and diagrams.  Remember that the average test technician probably doesn't speak much English.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't expect that they understand what the circuit does or be able to provide much debugging value.  They are very efficient at testing given a solid procedure but generally don't have the time to understand your circuit or put much thought into attempting debug solutions.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-06-02T16:04:41.373" CommentCount="1" />
  <row Id="2831" PostTypeId="1" AcceptedAnswerId="2837" CreationDate="2010-06-02T16:11:34.067" Score="5" ViewCount="164" Body="&lt;p&gt;I currently develop embedded systems using a number of different compilers, the most common coming from IAR systems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My love of hardware is what drives doing embedded systems and firmware. I however seem to lack quite a bit in software engineering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have read many times that a good Lint is invaluable for code. I would like to know if anyone on here uses a Lint, which Lint it is, and how much it helps in detecting errors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for your time.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-04T20:23:02.923" Title="Embedded System LINT use" Tags="&lt;microcontroller&gt;&lt;embedded&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="2832" PostTypeId="2" ParentId="2831" CreationDate="2010-06-02T16:18:37.943" Score="5" ViewCount="" Body="&lt;p&gt;I haven't used lint, but I find that GCC's warnings can detect a lot of programming errors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my preferred CFLAGS&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CFLAGS += -Werror -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align -Wpointer-arith -Wbad-function-cast -Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations -Winline -Wundef -Wnested-externs -Wshadow -Wconversion -Wwrite-strings -Wno-conversion -Wextra -Wstrict-aliasing -Wcast-qual&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also had a go with Linus Torvalds' &lt;a href=&quot;http://en.wikipedia.org/wiki/Sparse&quot; rel=&quot;nofollow&quot;&gt;Sparse&lt;/a&gt; for static analysis. But, I think these kind of tools are more useful for big systems.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-02T16:26:25.427" LastActivityDate="2010-06-02T16:26:25.427" CommentCount="1" />
  <row Id="2833" PostTypeId="2" ParentId="2829" CreationDate="2010-06-02T16:24:53.790" Score="4" ViewCount="" Body="&lt;p&gt;Assembly can get very expensive unless you are making 1K or more pieces. &#xA;At 1K pieces the setup costs start to amortize to reasonable values.&#xA;If you can get to 10K pieces then you could source the parts from&#xA;China too. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have had Gold Phoenix and E-Teknet quote on a job. They both had&#xA;similar quotes. Since I only wanted to do 1K pieces the pricing did&#xA;not work out and I did not do the project. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Neil Munzinger ( sales@e-teknet.com ) at E-Teknet was very responsive&#xA;to my questions and made recommendations about cost saving opportunities.&#xA;Unfortunately the numbers didn't work.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-11T15:05:03.977" LastActivityDate="2010-11-11T15:05:03.977" CommentCount="1" />
  <row Id="2834" PostTypeId="2" ParentId="2829" CreationDate="2010-06-02T16:47:12.023" Score="4" ViewCount="" Body="&lt;p&gt;You can use &lt;a href=&quot;http://batchpcb.com/index.php/Products&quot; rel=&quot;nofollow&quot;&gt;http://batchpcb.com/&lt;/a&gt; from Sparkfun. It's made from small quantity as prototype.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have a bot who check if your pcb is valid. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But they do not the smd assembly, and it take between 20-30 days to receive your pcb.&lt;/p&gt;&#xA;" OwnerUserId="824" LastActivityDate="2010-06-02T16:47:12.023" />
  <row Id="2835" PostTypeId="2" ParentId="2829" CreationDate="2010-06-02T16:51:34.780" Score="3" ViewCount="" Body="&lt;p&gt;Screaming circuits ( &lt;a href=&quot;http://www.screamingcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.screamingcircuits.com/&lt;/a&gt; ) has a proto assembly option and have a tie-up with Sunstone circuits for pcb fab. I've never used it them, so take my advice with a grain of salt!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have a simple proto service where you send them all the parts and they charge you the labor for assembly. They do SMT and thru-hole (no BGA). Expect to pay about $500 for 5 boards.&lt;/p&gt;&#xA;" OwnerUserId="327" LastActivityDate="2010-06-02T16:51:34.780" CommentCount="1" />
  <row Id="2836" PostTypeId="2" ParentId="2829" CreationDate="2010-06-02T17:25:13.393" Score="4" ViewCount="" Body="&lt;p&gt;I usually use &lt;a href=&quot;http://www.protoexpress.com/&quot; rel=&quot;nofollow&quot;&gt;Sierra Proto Express&lt;/a&gt; for quick PCB fab and assembly if its a complicated board like 6 layer with controlled dielectric thickness, non fr-4 dielectric material, small traces, BGAs, blind/buried vias, strange milling, those kinds of things.  They also do a great gob with pick and place assembly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your building something really simple, 4 layers with standard dielectric thickness, no BGAs or ultra fine pitch SMT parts you can use almost anyone for PCB fab. just find the cheapest price.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For SMT parts on small run boards, they really aren't hard to hand solder if you have a decent iron (metcal mx500 or something).  Or you can get a very basic solder paste stencil made for like $30 and bake them yourself, its not hard to do even on the the kitchen stove with a decent skillet and an IR temperature probe.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-06-02T17:25:13.393" CommentCount="2" />
  <row Id="2837" PostTypeId="2" ParentId="2831" CreationDate="2010-06-02T18:18:52.343" Score="2" ViewCount="" Body="&lt;p&gt;I have used lint in the past, and I have found it useful.  However, I had to stop using it as I moved onto a larger project that wasn't using it.  That made it difficult to use lint, because of how interconnected the code was.  The biggest problem with lint is configuring it to remove false positives and don't cares.  It may be better now that they've done another release in the past year.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One company I work with has taken that large project and put it through Coverity's static analzyer. However, that's a big chunk of money to be using, so it's not recommended for small companies.&lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2010-06-02T18:18:52.343" CommentCount="6" />
  <row Id="2838" PostTypeId="2" ParentId="250" CreationDate="2010-06-02T20:12:05.340" Score="1" ViewCount="" Body="&lt;p&gt;A quick googling turned up a useful site&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://how-to.wikia.com/wiki/How_to_identify_integrated_circuit_%28chip%29_manufacturers_by_their_logos&quot; rel=&quot;nofollow&quot;&gt;http://how-to.wikia.com/wiki/How_to_identify_integrated_circuit_%28chip%29_manufacturers_by_their_logos&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;.. but sadly these are indexed by name, so you have to guess the first letter of your logo to narrow things to a reasonable number to look through.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-02T20:12:05.340" />
  <row Id="2839" PostTypeId="2" ParentId="2829" CreationDate="2010-06-02T20:37:29.000" Score="3" ViewCount="" Body="&lt;p&gt;For prototypes, &lt;a href=&quot;http://apcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;APCircuits&lt;/a&gt; in Alberta, Canada, is outstanding. I've been using them for years with great success. They do well with production work too, but they're not quite as competitive on cost for the production stuff. The only competition for prototypes that I know of is &lt;a href=&quot;http://batchpcb.com&quot; rel=&quot;nofollow&quot;&gt;BatchPCB&lt;/a&gt;, but they're slow (which might be worth it if your budget is tight).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For production work, or more finished prototypes, I've had good experiences with &lt;a href=&quot;http://www.protoexpress.com/&quot; rel=&quot;nofollow&quot;&gt;Sierra Circuits&lt;/a&gt; and &lt;a href=&quot;http://pcbexpress.com/&quot; rel=&quot;nofollow&quot;&gt;PCB Express&lt;/a&gt;. I got a tour of Sierra Circuits about 5 years ago, and it was an impressive operation.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-02T20:37:29.000" />
  <row Id="2840" PostTypeId="2" ParentId="2829" CreationDate="2010-06-02T21:04:32.837" Score="3" ViewCount="" Body="&lt;p&gt;I've used Gold Phoenix several times with good results.  It is only $\$$99 per panel, and $\$$20 more if you want electrical testing.  I have always ordered the extra testing, and since there is always a few bad PCBs on the panel, I've always gotten an extra panel.  So this really keeps the per-PCB cost down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BatchPCB is a good way to get a prototype.  They have Gold Phoenix do the fabrication.&lt;/p&gt;&#xA;" OwnerUserId="828" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-03T14:42:48.503" LastActivityDate="2011-05-03T14:42:48.503" />
  <row Id="2841" PostTypeId="1" AcceptedAnswerId="2848" CreationDate="2010-06-03T03:03:42.550" Score="2" ViewCount="383" Body="&lt;p&gt;I realize this is nearly a dupe of &lt;a href=&quot;http://chiphacker.com/questions/2591/sbc-recommendations&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/2591/sbc-recommendations&lt;/a&gt; , but I have slightly different specs in mind.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know of a single-quantity SBC with the following features?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;32 bit CPU, something common e.g., x86, ppc, arm, atom&lt;/li&gt;&#xA;&lt;li&gt;capable of running some fairly modern variant of Linux&lt;/li&gt;&#xA;&lt;li&gt;built-in 100Mbit/s ethernet interface (preferably with RJ-45 jack)&lt;/li&gt;&#xA;&lt;li&gt;built-in RS-232 or RS-232C serial port (DB-9 connector desirable but not critical)&lt;/li&gt;&#xA;&lt;li&gt;capable of booting an arbitrary OS/application from FLASH&lt;/li&gt;&#xA;&lt;li&gt;capable of booting an arbitrary OS/application from ethernet&lt;/li&gt;&#xA;&lt;li&gt;capable of booting over serial port desirable, not critical&lt;/li&gt;&#xA;&lt;li&gt;must have at least one USB 2.0 port. more::=better&lt;/li&gt;&#xA;&lt;li&gt;must operate from a single-voltage DC supply (not more than 28V, not more than 25W)&lt;/li&gt;&#xA;&lt;li&gt;prefer Not to have PS/2 keyboard &amp;amp; mouse interfaces&lt;/li&gt;&#xA;&lt;li&gt;prefer Not to have any graphics capability&lt;/li&gt;&#xA;&lt;li&gt;built-in SPI, I2C, or general-purpose discrete I/O bonus&lt;/li&gt;&#xA;&lt;li&gt;price point under $250&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The mission for this SBC is to sit on my network and operate custom I/O hardware. Heaviest possible use case required would be to support a USB web-cam and serve low-bandwidth (CIF) video through a custom server app. Definitely not required to run databases, web servers, web browsers, middle-ware, ESB, or anything like that. Intended s/w platform C/C++, and maybe, just maybe, J2ME or J2SE.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best match I've found so far is the &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;BeagleBoard&lt;/a&gt; ,  but this falls short by having graphics capability (not needed) in place of ethernet capability (mandatory). I know you can add a USB based ethernet adapter, but ideally there would be a better match that would render this not necessary. There are also some atom-based 'car PCs' that are near misses, mainly for power supply reasons. &lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-03T14:02:32.820" Title="linux sbc recommendations" Tags="&lt;sbc&gt;&lt;subjective&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="2842" PostTypeId="2" ParentId="2841" CreationDate="2010-06-03T03:13:51.487" Score="2" ViewCount="" Body="&lt;p&gt;Not sure if it is quite a sbc, but the &lt;a href=&quot;http://www.globalscaletechnologies.com/p-32-guruplug-server-plus.aspx&quot; rel=&quot;nofollow&quot;&gt;guruplug server plus&lt;/a&gt; has usb, 2x ethernet, uart, i2c, spi, jtag (with an adapter), microsd, no gfx, no ps/2, serial port booting (with an adapter) and runs linux from flash on an arm core. Maybe take a look at it ? With minimal trickery you could run it off a DC supply. They run for US$129.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-06-03T03:13:51.487" CommentCount="2" />
  <row Id="2844" PostTypeId="1" CreationDate="2010-06-03T04:49:01.263" Score="14" ViewCount="855" Body="&lt;p&gt;i have an analogue devices ADXL203 accelerometer on a breadout board and was wanting to use this to measure the inclination of some equipment at a reasonably high frequency (20-30 Hz).  i am hooking it up to a campbells cr3000 logger to do the sensing.  Does anyone have directions on how to interpret the sensor outputs.&#xA;thanks&lt;/p&gt;&#xA;" OwnerUserId="830" LastActivityDate="2010-06-10T20:57:19.400" Title="calculating inclination using accelerometer?" Tags="&lt;accelerometer&gt;&lt;inclination&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="3" />
  <row Id="2845" PostTypeId="2" ParentId="2841" CreationDate="2010-06-03T04:51:23.723" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.armkits.com/&quot; rel=&quot;nofollow&quot;&gt;ArmKits.com&lt;/a&gt; has quite a few boards that meet those specs under $200 without an LCD screen, but has a VGA port.  The &lt;a href=&quot;http://www.armkits.com/Product/SBC9261-I.asp&quot; rel=&quot;nofollow&quot;&gt;SBC9261-I&lt;/a&gt; is one of them. The &lt;a href=&quot;http://www.armkits.com/Product/soc8200.asp&quot; rel=&quot;nofollow&quot;&gt;SOC8200&lt;/a&gt; has a VGA expansion port, but I don't know the price. I would order from their US distributor, &lt;a href=&quot;http://www.iesdistribution.com/&quot; rel=&quot;nofollow&quot;&gt;IESDistribution&lt;/a&gt; to save money on shipping.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.pcengines.ch&quot; rel=&quot;nofollow&quot;&gt;PCEngines&lt;/a&gt; has an &lt;a href=&quot;http://www.pcengines.ch/alix3d3.htm&quot; rel=&quot;nofollow&quot;&gt;Alix3d3&lt;/a&gt; that might meet your needs for $111.  There's an I2Cs bus option for it as well as some enclosures you might buy for it from them.  Also an 18 V power supply can be ordered for it.&lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2010-06-03T04:51:23.723" />
  <row Id="2846" PostTypeId="2" ParentId="2841" CreationDate="2010-06-03T07:05:44.003" Score="1" ViewCount="" Body="&lt;p&gt;How about a &lt;a href=&quot;http://www.gumstix.com/store/catalog/index.php&quot; rel=&quot;nofollow&quot;&gt;Gumstix&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-03T07:05:44.003" CommentCount="2" />
  <row Id="2847" PostTypeId="2" ParentId="2844" CreationDate="2010-06-03T11:44:41.103" Score="2" ViewCount="" Body="&lt;p&gt;I have written and rewritten this answer several times with many crazy mathematical ideas, but I honestly don't think this can be done with any accuracy. You can do some vector maths, but what if:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The object stops moving&lt;/li&gt;&#xA;&lt;li&gt;The object has a constant velocity&lt;/li&gt;&#xA;&lt;li&gt;The object hits a bump/you bump it&lt;/li&gt;&#xA;&lt;li&gt;The force generated moving up the incline is below the resolution of the Z axis&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;While I'm sure there is some crazy workaround for doing this sort of thing, I'm not sure it would be worth it; accelerometers are simply not designed for this task (at least to my knowledge). For what you are trying to achieve, I would suggest a gyroscopic approach using &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8370&quot; rel=&quot;nofollow&quot;&gt;any&lt;/a&gt; &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9058&quot; rel=&quot;nofollow&quot;&gt;of&lt;/a&gt; &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9093&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt;, all of which would be fairly resistant to all of the above problems.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-06-03T11:44:41.103" CommentCount="6" />
  <row Id="2848" PostTypeId="2" ParentId="2841" CreationDate="2010-06-03T14:02:32.820" Score="2" ViewCount="" Body="&lt;p&gt;(Kind of a repeat from my answer to the previous question, but with a new board.) I'd go for the &lt;a href=&quot;http://www.embeddedarm.com/products/board-detail.php?product=TS-7553#&quot; rel=&quot;nofollow&quot;&gt;Technologic Systems TS-7553&lt;/a&gt; for $135-- slightly cheaper than the Beagleboard, and just as good. I haven't actually used the 7553, but I've used its predecessors, the TS-7500 and TS-7550, and they're good. The only requirement it might not meet out of the box is booting over Ethernet, but I know it can be configured to do so (at least via TFTP or NFS).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Maybe this goes without saying, but I have no connection to Technologic Systems at all. I've just used some of their boards.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-03T14:02:32.820" />
  <row Id="2849" PostTypeId="2" ParentId="2844" CreationDate="2010-06-03T14:40:14.820" Score="3" ViewCount="" Body="&lt;p&gt;If I understand the datasheet correctly, the output for each axis will vary between 1.5 V and 3.5 V as you tilt around the axis. When the device is flat (ignoring the ±1 degree package alignment error), both outputs should read 2.5 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you only need to measure the tilt in one direction, you can take the arcsin of the deviation from 2.5 V to get the angle in radians, then convert to degrees. If the device can tilt in any direction, you can calculate the two angles, and then calculate the compound angle from those.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To be explicit: angle around one axis = (180/π) * arcsin (Vout - 2.5)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get good frequency response, you'll need small output capacitors, Cx and Cy. From footnote 6 on p. 3 of the datasheet, it looks like 0.02 uF would give you a bandwidth of 250 Hz, which is probably about right for your sample rate. You could perhaps go as high as 0.1 uF, limiting the bandwidth to 50 Hz, but your signals will start to get attenuated.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-03T14:40:14.820" CommunityOwnedDate="2010-06-03T14:40:14.820" CommentCount="2" />
  <row Id="2850" PostTypeId="2" ParentId="2844" CreationDate="2010-06-03T15:12:27.277" Score="11" ViewCount="" Body="&lt;p&gt;I have a number of things to say here, and some of them do involve agreeing with pingswept and some with penjuin.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;cr3000&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;The cr3000 sampling at 16 bits and 100 Hz is going to be sampling a little slow for you to easily remove noise from your data but at a significantly higher precision then will be usable. I doubt you can get 13 or 14 bits of precision without some pretty good filtering algorithms. Accelerometers have taught me that vibration is the devil, blasted phonons.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Output Capacitor&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;You need to make sure you do as the datasheet says and signal theory dicates. To quote the datasheet:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;blockquote&gt;&#xA;    &lt;p&gt;&lt;a href=&quot;http://www.analog.com/en/sensors/inertial-sensors/adxl203/products/product.html&quot; rel=&quot;nofollow&quot;&gt;The output of the ADXL103/ADXL203 has a typical bandwidth&#xA;    of 2.5 kHz. The user must filter the signal at this point to limit&#xA;    aliasing errors. The analog bandwidth must be no more than half the analog-to-digital sampling frequency to minimize&#xA;    aliasing. The analog bandwidth can be further decreased to reduce noise and improve resolution.&lt;/a&gt;&lt;/p&gt;&#xA;  &lt;/blockquote&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This means you need to pick a capacitor to keep your rate below 50Hz. If you place it above this you can get aliasing, and aliasing makes vibration noise a devil you signed a deal with. They state how to calculate the noise levels from the device, and at a 50Hz bandwidth a peak to peak noise of .006 * Gravity will not even be noticed if you have this on a device with vibrations.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Interpreting Data &lt;/h2&gt;&#xA;&#xA;&lt;p&gt;This is probably what you are most interested in, and is relatively easy to do. You need to tag a time that the device is at neutral, this being when it is flat and you have it relatively still. Give it a second or two at this point, and then you can take the median of this data to determine the no-G voltage. Then you can use this as a point you compare the device to. Now, from this point, I can directly quote the data-sheet:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://www.analog.com/en/sensors/inertial-sensors/adxl203/products/product.html&quot; rel=&quot;nofollow&quot;&gt;When the&#xA;  accelerometer is perpendicular to gravity, its output changes&#xA;  nearly 17.5 mg per degree of tilt&lt;/a&gt;.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So you can just simply use this approximation if you are not going to tilt very much, but you will need to use geometry if you plan to tilt in both direction and in angles that are not extremely small.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are going to be going larger, they even have the equations spelled out as:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://www.analog.com/en/sensors/inertial-sensors/adxl203/products/product.html&quot; rel=&quot;nofollow&quot;&gt;PITCH = ASIN(AX/1 g)&lt;br&gt;&#xA;  ROLL = ASIN(AY/1 g)&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;As far as I can tel your device gives a 1V change per 1G of acceleration placed on it. If you have done the calibrate phase, then you should be able to take measurments, subtract the offset, and you have the number of Gs being experienced.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Stop Reading Here unless you run into issues or you would like more information to improve approach.&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;I added a decent bit more talking about other approaches and methods to improve your approach for fast changing systems or systems where you are going to program the device doing the samples.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Sampling Frequency&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;You need to be sampling significantly faster than the speed at which your device changes the directions in which it is accelerating, as you have to measure orientation 20-30 times per second. you need to be able to measure quickly enough to filter out vibration noise and acceleration due to other affects, which i have found to be quite large when working with an accelerometer.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; 3-axis accelerometer &lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Second, if you have a three axis accelerometer, then you can quite easily recognize when one axis is losing part of the acceleration due to gravity(ie. When the z axis has it's magnitude drop by 2m/s^2, you know that the gain you saw on the other axis is gravity). This will still be messy, but in general there will be an addition of acceleration which gives the velocity needed to change your orientation and then a change in acceleration due to orientation change, often allowing you to recognize orientation.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Problems with 2-axis &lt;/h2&gt;&#xA;&#xA;&lt;p&gt;This is going to be, as penjuin said, almost impossible with a 2 axis accelerometer, and sketchy at best if you have a system that can have 20-30 different orientations a second, or if you need to have an exact measure of orientation at all times. I am sure a master's student could write a pretty nice thesis on this, or a Doctorate could write a dissertation on improving this algorithm.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Vibration Noise &lt;/h2&gt;&#xA;&#xA;&lt;p&gt;To add more, if you can put your device on top of something that will keep it statically locked to the motion of your device, but dampens vibration, you will get much better numbers and not need as much software filtering. Some simple foam type padding can be placed between the accelerometer and your device, and if it is digital this should not increase electrical noise and help absorb some vibration noise. This should only be done if you see problems with the vibration noise.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Digital Accelerometer &lt;/h2&gt;&#xA;&#xA;&lt;p&gt;I would suggest a digital accelerometer that you can use SPI to connect to. Data can be clocked out at a very very high rate and you can work in the back ground as your SPI does the constant work of loading the next set of values. You will need to have a nice microcontroller if it is going to be done digitally. If you can give me better specifics on what you are wanting to do I can give better feedback. If you want a warning based on tilt detection then it should be very easy to do with all analog, but if you want to measure the position and angle of equipment during operation, get ready for some work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please let me know if there is something I can add to make this answer more clear or applicable to what you were looking for.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-03T16:39:08.807" LastActivityDate="2010-06-03T16:39:08.807" CommentCount="4" />
  <row Id="2851" PostTypeId="2" ParentId="2844" CreationDate="2010-06-03T15:58:05.893" Score="3" ViewCount="" Body="&lt;p&gt;I am adding a second answer, because my other one is large, and you may just want simple. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your filter cap needs to be 0.10 uF or larger to keep you below your aliasing rate(50Hz).&#xA;You need to give a calibration phase of a couple seconds with your device sitting level with all Gravity acceleration in the Z direction, this is to determine your zero G point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The voltage you measure for your zero G point, it will probably be different for the X and Y direction, represents nothing. Just take whatever voltage you get and subtract that from it. This voltage, with offset subtracted is the number of Gs that you are getting in that direction. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take the arcsin and you are going to get your angle in that direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This ignores noise and other acceleration. be prepared for NaN to be a result if you have it fully tilted and there is any noise.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-03T15:58:05.893" />
  <row Id="2852" PostTypeId="2" ParentId="2829" CreationDate="2010-06-03T18:28:44.397" Score="5" ViewCount="" Body="&lt;p&gt;I've used Advanced Circuits (www.4pcb.com) before (located in Colorado).  They have a pretty good special I've used a lot.  4 layer boards for $66 each (qty 4+).  They also have a FreeDFM service that checks your gerbers for errors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also do assembly, but I've found that assembly costs are sometimes more expensive than the board itself.  If you're doing this for a hobby, I've heard of folks using toaster ovens for SMD parts.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-06-03T18:28:44.397" CommentCount="3" />
  <row Id="2854" PostTypeId="1" CreationDate="2010-06-03T21:12:49.483" Score="7" ViewCount="499" Body="&lt;p&gt;While reading Linux User's Journal today, I stumbled across &lt;a href=&quot;http://www.linuxjournal.com/article/10785#mpart4&quot; rel=&quot;nofollow&quot;&gt;a little blurb&lt;/a&gt; about &lt;a href=&quot;http://nuttx.sourceforge.net&quot; rel=&quot;nofollow&quot;&gt;NuttX&lt;/a&gt; RTOS.  I checked out their &lt;a href=&quot;http://nuttx.sourceforge.net&quot; rel=&quot;nofollow&quot;&gt;website&lt;/a&gt; and was fairly impressed with it's feature set and it's ability to put it in an 8052! I find it interesting that it supports POSIX which is something I have helped worked on for one of my clients in-house RTOS.  This one seems a little more feature rich than the in-house RTOS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone else heard of NuttX and has given it a try?  If so, how does it compare to other RTOS's such as &lt;a href=&quot;http://www.freertos.org/&quot; rel=&quot;nofollow&quot;&gt;FreeRTOS&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="625" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-18T07:12:28.050" LastActivityDate="2011-01-19T17:56:45.503" Title="Has anyone evaluated NuttX RTOS?" Tags="&lt;embedded&gt;&lt;rtos&gt;" AnswerCount="2" CommentCount="6" FavoriteCount="2" />
  <row Id="2855" PostTypeId="2" ParentId="824" CreationDate="2010-06-03T21:35:03.177" Score="5" ViewCount="" Body="&lt;p&gt;I just found out about &lt;a href=&quot;http://nuttx.sourceforge.net&quot; rel=&quot;nofollow&quot;&gt;NuttX&lt;/a&gt; RTOS, that can even work on an 8052 (8-bit) system.  It's doesn't have a lot of ports, but it looks interesting.  The POSIX can be a plus, because it may make some of your code a little more portable if you move up to a beefier processor and you want to run real-time linux or QNX.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't have any experience with commercial RTOS's myself, but I have used homemade ones for years!  They are great at helping you divide up your code development among many programmers, because they can essentially each get a  &quot;task&quot; or &quot;thread&quot; to work on their part.  You still have to coordinate and someone must oversee the whole project to make sure each task can make it's deadline. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also recommend you research &lt;a href=&quot;http://www.netrino.com/Embedded-Systems/How-To/RMA-Rate-Monotonic-Algorithm&quot; rel=&quot;nofollow&quot;&gt;Rate Monotonic Analysis&lt;/a&gt; or RMA when using an RTOS.  This will help you guarantee that your critical tasks will meet their deadlines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also look into Miro Samek's &lt;a href=&quot;http://www.state-machine.com/index.php&quot; rel=&quot;nofollow&quot;&gt;QP-nano&lt;/a&gt; event-driven programming framework that can work with or without an RTOS and still give you real-time capability.  With it, you're dividing up your design into hierarchical state machines instead of traditional tasks. Jason S mentioned Miro's book in his post.  An excellent read!&lt;/p&gt;&#xA;" OwnerUserId="625" LastEditorUserId="625" LastEditorDisplayName="" LastEditDate="2010-06-04T18:12:59.130" LastActivityDate="2010-06-04T18:12:59.130" CommentCount="1" />
  <row Id="2856" PostTypeId="2" ParentId="824" CreationDate="2010-06-04T02:36:57.050" Score="2" ViewCount="" Body="&lt;p&gt;The CCS compiler for the PIC comes with a simple RTOS. I haven't tried it, but if you have this compiler, it would  be easy to experiment with.&lt;/p&gt;&#xA;" OwnerUserId="222" LastActivityDate="2010-06-04T02:36:57.050" CommentCount="3" />
  <row Id="2857" PostTypeId="1" CreationDate="2010-06-04T04:28:23.513" Score="4" ViewCount="784" Body="&lt;p&gt;I have a color sensor from the original lego mindstorms set. I have had a hard time finding any reliable specs on the thing, but I did find somebody who has reverse engineered it quite a bit &lt;a href=&quot;http://www.extremenxt.com/light.htm&quot; rel=&quot;nofollow&quot;&gt;here.&lt;/a&gt; The thing only has two connectors though. I am not very good at circuits, but I would like to hook this up to my arduino and read values from it. Does this appear possible? If so, do you have any idea which pins to use, or what kind of code I need?&lt;/p&gt;&#xA;" OwnerUserId="678" LastActivityDate="2010-06-04T17:53:11.247" Title="Lego Color Sensor + Arduino" Tags="&lt;arduino&gt;&lt;sensor&gt;" AnswerCount="2" />
  <row Id="2858" PostTypeId="2" ParentId="2857" CreationDate="2010-06-04T12:26:59.700" Score="5" ViewCount="" Body="&lt;p&gt;Most Lego sensors that i have seen use a bridge recifier so that they do only need to have two wires to operate. Also this allows the sensor to be plugged in at any orientation. The circuit for the light sensor is no different.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using an Arduino, you would connect one wire to an output port and the other wire to an input. By reading the additional article at the bottom of the page, i would say that you should be able to turn the sensor on at the Arduino output for 1.2ms then off for 0.1ms. While off, read the value of the sensor at this time on the Arduino input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This article also states that the lego RCX is outputting 8V so as the Arduino will only output 5V, you will need to take multiple values and extrpolate a table of values to determine the reading. The value will correspond to an analogue value of 0 to 127 from a lego sensor.&lt;/p&gt;&#xA;" OwnerUserId="641" LastActivityDate="2010-06-04T12:26:59.700" CommentCount="1" />
  <row Id="2859" PostTypeId="2" ParentId="2857" CreationDate="2010-06-04T17:53:11.247" Score="2" ViewCount="" Body="&lt;p&gt;As for the hardware, you could look at the schematics of the Lego Mindstorms NXT for reference. It is compatible with these old sensors, which can be connected to pins 1 and 2 of the sensor ports:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Go to &lt;a href=&quot;http://mindstorms.lego.com/en-us/support/files/default.aspx&quot; rel=&quot;nofollow&quot;&gt;the support page for the NXT&lt;/a&gt;.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Get the Hardware Developer Kit (no link due to badly designed web page).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Look at the schematics for the main unit in Appendix 1.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The pins 1 of the sensor ports are handled by an ATmega48, take a look at ADC_A0 to ADC_D0 for the inputs and I_ONA to I_OND for power control. Sensor port pin 2 is ground.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The power control circuit contains an extra PNP transistor for current limitation, that may be overkill for you.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;When turned on the sensors are powered by the full battery voltage for most of the time, they are only powered off briefly for doing each measurement (I think the 0.1ms by jme are correct). Standard is to do a measurement every three ms.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-06-04T17:53:11.247" />
  <row Id="2860" PostTypeId="2" ParentId="2811" CreationDate="2010-06-04T18:24:23.410" Score="2" ViewCount="" Body="&lt;p&gt;Posting this code as an alternative per @timrorr's suggestion to my previous post. This compiles for the ATTiny24A using c99 language standard, but I haven't actually tested it in any way beyond that.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;stdint.h&amp;gt;&#xA;#include &amp;lt;avr/io.h&amp;gt;&#xA;#include &amp;lt;avr/interrupt.h&amp;gt;&#xA;#include &amp;lt;util/atomic.h&amp;gt;&#xA;#define TIMER0_PRELOAD   0x83 // for 8MHz crystal and overflow @ 1kHz&#xA;#define TIMER0_PRESCALE 0x03  // divide by 64&#xA;#define TASK_PERIOD_MS 4000   // execute task every 4 seconds&#xA;&#xA;//global variables for time keeping&#xA;volatile uint16_t  global_num_overflows = 0;&#xA;volatile uint16_t  global_task_timer_ms = TASK_PERIOD_MS;&#xA;&#xA;void setup_timers(){&#xA;    // set the T1 pin (PA.4) to a floating input (external event)&#xA;    DDRA  &amp;amp;= ~_BV(4);&#xA;    PORTA &amp;amp;= ~_BV(4);&#xA;&#xA;    // set Timer1 to count external events&#xA;    TIMSK1 = _BV(TOIE1);      // enable overflow interrupt&#xA;    TCCR1B =   _BV(CS10)      // clock on external positive edge of T1 pin&#xA;        | _BV(CS11)&#xA;        | _BV(CS12);&#xA;&#xA;    // set Timer0 for task timing (overflow once per ms)&#xA;    TCCR0B = TIMER0_PRESCALE;&#xA;    TCNT0  = TIMER0_PRELOAD;  // setup appropriate timeout&#xA;    TIMSK0 = _BV(TOIE0);      // enable timer0 overflow interrupt&#xA;}&#xA;&#xA;&#xA;ISR(TIM1_OVF_vect){   //timer1 overflow interrupt&#xA;    global_num_overflows++;&#xA;}&#xA;&#xA;ISR(TIM0_OVF_vect){            //timer0 overflow interrupt @ 1kHz&#xA;    TCNT0 = TIMER0_PRELOAD;   // preload timer for 1kHz overflow rate&#xA;    if(global_task_timer_ms &amp;gt; 0){&#xA;        global_task_timer_ms--;&#xA;    }&#xA;}&#xA;&#xA;int main(int argc, char *argv[]){&#xA;    double frequency_hz = 0;&#xA;    uint16_t num_overflows = 0;&#xA;    uint16_t num_positive_edges  = 0;&#xA;    setup_timers();&#xA;    sei(); // enable interrupts!&#xA;    for(;;){ //forever&#xA;        if(global_task_timer_ms == 0){ // wait for task to be scheduled&#xA;            ATOMIC_BLOCK(ATOMIC_FORCEON){&#xA;                num_overflows        = global_num_overflows; // copy the volatile variable into a local variable&#xA;                global_num_overflows = 0;                    // clear it for next time&#xA;                num_positive_edges   = TCNT1;                // copy num positive edge events to local variable&#xA;            }&#xA;&#xA;            // calculate the 'average' frequency during this task period&#xA;            frequency_hz  = 1.0 * num_positive_edges;  // num edges since last overflow&#xA;            frequency_hz += num_overflows * 65536.0;   // edges per overflow of 16 bit timer&#xA;            frequency_hz /= (TASK_PERIOD_MS / 1000.0); // over the task interval in seconds&#xA;&#xA;            global_task_timer_ms = TASK_PERIOD_MS;     // reschedule task&#xA;        }&#xA;&#xA;        // use frequency_hz for whatever other processing you want to do&#xA;    }&#xA;    return 0;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This is a nice little use of the hardware capabilities of the Timer1 and frees up a ton of processing cycles in comparison to my original post.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-06-05T15:56:21.977" LastActivityDate="2010-06-05T15:56:21.977" />
  <row Id="2861" PostTypeId="2" ParentId="2831" CreationDate="2010-06-04T20:23:02.923" Score="2" ViewCount="" Body="&lt;p&gt;I must admit, I haven't had much use with a lint of some sort on a microcontroller/microprocessor project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On my current embedded project, which uses C++ on a Linux-based PC/104 SBC, we've used &lt;a href=&quot;http://sourceforge.net/apps/mediawiki/cppcheck/index.php?title=Main_Page&quot; rel=&quot;nofollow&quot;&gt;cppcheck&lt;/a&gt; (works with C too!).  It works pretty well, although it has issues with complicated class inheritance trees.  And it has provided some value - it's good for checking for potential locations where memory leaks could occur.  But most of the things it noted were stylistic - use preincrement instead of postincrement in for-loops, that sort of thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also used an &lt;a href=&quot;http://www.jslint.com/&quot; rel=&quot;nofollow&quot;&gt;online lint for Javascript&lt;/a&gt; when developing applications for an enterprise software system.  It was absolutely invaluable there, as there were no debugging tools to check for syntax errors in that setup.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-06-04T20:23:02.923" />
  <row Id="2862" PostTypeId="1" CreationDate="2010-06-05T03:13:13.390" Score="6" ViewCount="399" Body="&lt;p&gt;It occurs to me that, beyond my current problem, I ought to ask, &quot;What should I know when making a library for the Arduino?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;First, what I am doing:&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using Eclipse as my editor and writing code in C++.  I have written a simple Arduino application that includes my header file and am working through errors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;First problem:&lt;/em&gt; how do I do a 'build clean'?  I am seeing errors that I think I've fixed, almost as if the header file were cached.  (Yes, quite likely I am doing something stupid [&lt;em&gt;edit&lt;/em&gt;: I was], but I'd still like to know how to clean the library, and don't know where the object files are).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Secondly:&lt;/em&gt; what conventions should I be aware of?  I haven't used the Arduino as much as I'd like, and it feels so good to be programming in C++, but I know the intent of the libraries is to keep things nice and simple for the users.  Are there conventions for function names?  Creating constants (it looks like the global namespace is polluted with #defines)?  And so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Lastly,&lt;/em&gt; is there anything else I should know?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should mention that I've looked at the &lt;a href=&quot;http://www.arduino.cc/en/Hacking/LibraryTutorial&quot; rel=&quot;nofollow&quot;&gt;Arduino Library Tutorial&lt;/a&gt;, which is good, but doesn't go very far.  I've also peeked at some of the libraries that are installed on my system.&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="625" LastEditorDisplayName="" LastEditDate="2010-06-06T03:47:21.273" LastActivityDate="2010-06-06T03:48:22.380" Title="What should I know when making a library for the Arduino?" Tags="&lt;arduino&gt;&lt;library&gt;&lt;c++&gt;&lt;c&gt;" AnswerCount="1" />
  <row Id="2863" PostTypeId="2" ParentId="2862" CreationDate="2010-06-05T13:59:36.253" Score="2" ViewCount="" Body="&lt;p&gt;I'll take a stab. I haven't written code for Arduino, but I've done a lot of C and C++ programming.  It would help if I actually saw your errors, but nonetheless.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main thing you need to always remember when using C++ with C code is that your C++ code needs functions declared with &quot;extern &quot;C&quot;&quot; if you want C code to be able to link against the C++ code.  The &quot;extern &quot;C&quot;&quot; is what tells the C++ compiler that I'm creating linkable code for C files or I'm using code from C files.  So all your functions in the library API header should correlate with a function in the source file  defined liked &quot;extern &quot;C&quot; void dosomething()&quot;.  If you're trying to use classes in C++, remember that C code can't call it, you'll need to create functions (extern &quot;C&quot;) to access the object.  Now, if your C code is compiled with a C++ compiler, then don't worry about &quot;extern &quot;C&quot;&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to call C code inside your C++ code, then you need to wrap the C header with a construct like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#ifdef ___cplusplus&#xA;extern &quot;C&quot; {&#xA;#endif&#xA;&#xA;///all my C function declarations... yada yada&#xA;&#xA;#ifdef __cplusplus&#xA;}  //end extern &quot;C&quot;&#xA;#endif&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If you working in C++, don't use a lot a #defines unless you're creating compile-time flags like &quot;DEBUG&quot; or &quot;VERSION2&quot; to create special sets of code. Otherwise use &quot;const int/char/float&quot; for number defines for safe type checking. The compilers are usually smart enough to optimize these out, so they wind up in ROM/code space (depends though). Also, don't create MACROS, use inline functions.  Also, don't always follow convention when programming if it's stupid such as using a lot of macros and number defines in C++.  The same thing applies to C99 version of C, it has added things like inline functions and consts from C++.  The industry realizes how much buggy code and hard to maintain code comes from overuse of the preprocessor language.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Eclipse usually stores the obj files in a directory under your project. If you're doing a &quot;Debug&quot; build, then it's located under the &quot;Debug&quot; folder under your project folder.  If you're doing a &quot;Release&quot; build, then look under &quot;Release&quot;, etc.  Normally a clean build just works for me in Eclipse, so I don't know what's going wrong with your setup.  I guess make sure you're not creating precompiled headers.&lt;/p&gt;&#xA;" OwnerUserId="625" LastEditorUserId="625" LastEditorDisplayName="" LastEditDate="2010-06-06T03:48:22.380" LastActivityDate="2010-06-06T03:48:22.380" />
  <row Id="2864" PostTypeId="1" AcceptedAnswerId="2865" CreationDate="2010-06-05T14:26:26.040" Score="4" ViewCount="465" Body="&lt;p&gt;I don't have an explosion chamber so I cannot test critical values.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;If you explode resistors with too high current-voltage combination, does it damage your equipment, such as multimeter and DC-supplier, even in explosion chamber?&lt;/li&gt;&#xA;&lt;li&gt;How to notice when a critical point for resistors is achieved, not touching the hot component?&lt;/li&gt;&#xA;&lt;li&gt;I want to test Zener diode for increasing voltage. I have a great amount of different diodes but no idea which is Zener. Which resistors and zeners should I use and how to find the right ones without exploding them?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-28T09:07:51.930" LastActivityDate="2011-03-10T07:48:44.987" Title="At what current and voltage Typical Resistors explode?" Tags="&lt;resistor&gt;&lt;safety&gt;&lt;zener&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="2865" PostTypeId="2" ParentId="2864" CreationDate="2010-06-05T14:59:32.917" Score="11" ViewCount="" Body="&lt;p&gt;In my experience, resistors and diodes burn, but they don't explode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only components that I've experienced exploding are tantalum capacitors when placed with the wrong polarity and transient voltage suppressors (&quot;tranzorbs&quot;) when exposed to ~2x their rated voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To determine which resistors or diodes to use, you can check their power rating. For example a typical through-hole resistor is rated for 0.25 W. Depending on how you're using the resistor, there are three equations that are useful to calculate the power dissipation:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Watts = volts * amps&lt;/li&gt;&#xA;&lt;li&gt;Watts = volts * volts / ohms&lt;/li&gt;&#xA;&lt;li&gt;Watts = amps * amps * ohms&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;For example, suppose you have a 10k resistor that you're using as a pull-up resistor for a pin on a 5 V microprocessor. The maximum power drawn by the chip through the resistor (by equation #2) will be 5 * 5 / 10000 = 0.0025 W, or 2.5 mW. That's fine even the tiniest surface mount resistors.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-06-05T15:11:22.707" LastActivityDate="2010-06-05T15:11:22.707" CommunityOwnedDate="2010-06-05T15:11:22.707" CommentCount="10" />
  <row Id="2866" PostTypeId="2" ParentId="2864" CreationDate="2010-06-05T15:34:04.537" Score="2" ViewCount="" Body="&lt;p&gt;Manufacturers typically give a maximum voltage for a particular resistor range, such as 200V for a 250 mW resistor. That needs to be taken into account, as well as the power.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-05T15:34:04.537" />
  <row Id="2868" PostTypeId="1" CreationDate="2010-06-05T17:58:16.067" Score="4" ViewCount="182" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm currently troubleshooting a state-variable filter I built. All of the filter types work, but the resonance pot has no effect. Tracing a sine signal through the feedback pathway, I found that it ended at pin 7 of U6 - a LM13700. This is the input to the transistor buffers, and there's no audible signal coming out on pin 8, which is the output from that buffer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.musicfromouterspace.com/analogsynth/STATEVARVCFFEB2006/STATEVARVCFFEB2006.html&quot; rel=&quot;nofollow&quot;&gt;Here's the schematic I'm working from. I'm referring to U6, on the second page of the schematic. It looks like it is hooked up as an emitter follower. DC voltage at pin 7 is -36.7mV and at 8 is -252mV.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I be hearing the signal coming out pin 8?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="835" LastEditorUserId="819" LastEditorDisplayName="" LastEditDate="2010-06-09T19:59:13.583" LastActivityDate="2010-06-09T19:59:13.583" Title="LM13700 Question" Tags="&lt;filter&gt;&lt;signal&gt;&lt;trace&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="2869" PostTypeId="1" AcceptedAnswerId="2871" CreationDate="2010-06-05T18:16:00.747" Score="5" ViewCount="205" Body="&lt;p&gt;I know the values of resistors if they are gold-colored at the end. When both ends are the same, such as brown-o-p-brown and red-x-y-z-red, I am in problems. &lt;strong&gt;How to know which side has the last colour and which side is the starting end?&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T10:05:31.453" LastActivityDate="2011-01-24T12:35:51.557" Title="Resistors with ends of the same colour" Tags="&lt;resistance&gt;&lt;colour-coding&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="2870" PostTypeId="2" ParentId="2869" CreationDate="2010-06-05T18:31:50.967" Score="5" ViewCount="" Body="&lt;p&gt;The starting point should be the band that is closest to one of the ends. The tolerance band is usually at the other end, on its own.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-05T18:31:50.967" />
  <row Id="2871" PostTypeId="2" ParentId="2869" CreationDate="2010-06-05T18:47:23.643" Score="9" ViewCount="" Body="&lt;p&gt;I asked a similar question a long time ago &lt;a href=&quot;http://chiphacker.com/questions/119/6-band-resistors-which-way-should-the-bands-be-read&quot;&gt;here&lt;/a&gt; but the resistor chart which was mentioned there appears to have moved. So from its' new home at &lt;a href=&quot;http://itll.colorado.edu/index.php/electronics_center/resistor_chart/&quot; rel=&quot;nofollow&quot;&gt;itll.colorado.edu&lt;/a&gt; here's the diagram, as far as I can tell one band will be thicker signifying it as the tolerance band (no-one responded when I queried whether this was the case in the previous post above so if I'm wrong please let me know).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://itll.colorado.edu/images/uploads/resistorchart.jpg&quot; alt=&quot;Resistor Chart&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2011-01-23T20:52:49.880" LastActivityDate="2011-01-23T20:52:49.880" CommentCount="6" />
  <row Id="2872" PostTypeId="2" ParentId="1705" CreationDate="2010-06-05T22:16:40.447" Score="0" ViewCount="" Body="&lt;p&gt;My wallet is full of ideas because 3 rules:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;1. Observe&#xA;2. Collect&#xA;3. Act&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;They may become $ but I am not a speculator about the env. If they do not, at least, it is fun easy-to-follow!&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-05T22:21:45.897" LastActivityDate="2010-06-05T22:21:45.897" />
  <row Id="2873" PostTypeId="2" ParentId="2868" CreationDate="2010-06-05T22:18:41.657" Score="4" ViewCount="" Body="&lt;p&gt;If the output transistors are connected as an &lt;a href=&quot;http://en.wikipedia.org/wiki/Common_collector&quot; rel=&quot;nofollow&quot;&gt;emitter follower&lt;/a&gt;, like in this circuit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.idea2ic.com/LM13600/stereovolume.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;then yes, there should be a signal at pin 8.  What's the DC voltage at pins 7 and 8?  What else is connected to pin 8?  Where is the signal at pin 7 coming from?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pins 9 and 10 do the same thing, did you compare with those?  Are they used as the other half of a stereo pair, or for some other function?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://circuits.datasheetdir.com/37/LM13700-pinout.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-06-05T22:18:41.657" CommentCount="1" />
  <row Id="2874" PostTypeId="1" CreationDate="2010-06-05T22:40:39.823" Score="1" ViewCount="475" Body="&lt;p&gt;&lt;em&gt;&lt;strong&gt;WARNING:&lt;/strong&gt; 30V was a mistake -- better to keep voltage down 12V as a beginner! I tested it over a very short time. Got the things hot over a long time with much less voltage -- apparently not enough energy was dissipated to destroy the components.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thermistors are a type of resistors, according to Wikipedia. Two thermistors black-white (18p written on it) and gold-orange-gold-yellow (no text). If the colour coding is the same to &lt;a href=&quot;http://chiphacker.com/questions/2869/resistors-with-ends-of-the-same-colour&quot; rel=&quot;nofollow&quot;&gt;resistors&lt;/a&gt; and reading up-to-bottom, the former is 8 Ohms and the last one is 4k Ohms. I tested both with 30V: the former warm, the last not warm, the current 0,0A (not measurable with my equipment).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Sizes&lt;/strong&gt; are 0.2cm times 0.3cm for both of the components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Accepted Power Estimate by size&lt;a href=&quot;http://chiphacker.com/questions/2864/at-what-current-and-voltage-typical-resistors-explode/2865#2865&quot; rel=&quot;nofollow&quot;&gt;(tip)&lt;/a&gt;:&lt;/strong&gt; &lt;code&gt;3.14*(0.025m)^2 = 0.00196... so P ~=10^-3&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;How to estimate current as it was below &lt;code&gt;10^-2&lt;/code&gt;?&lt;/li&gt;&#xA;&lt;li&gt;How to read thermistors' colour coding and what does 18p mean, 18 pico Ohms or some change?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-07T23:07:42.153" LastActivityDate="2010-06-07T23:07:42.153" Title="Thermistors' colour coding same as the resistors'?" Tags="&lt;beginner&gt;&lt;resistor&gt;&lt;thermistor&gt;&lt;colour-coding&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="2875" PostTypeId="1" CreationDate="2010-06-05T23:11:00.663" Score="4" ViewCount="1055" Body="&lt;p&gt;My school uses HY 3005D-3 but I want to do it myself to save on $. Before opening it, I ask for tips about: not-to-break-it, cheap DC supply and DIY-materials (not that I know them soon). So how to build, to get cheap DC Power supply with such adjusting knobs?&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T06:55:47.260" LastActivityDate="2011-01-29T06:55:47.260" Title="DIY Beginner's DC Power Supply?" Tags="&lt;power-supply&gt;&lt;dc&gt;&lt;safety&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="2876" PostTypeId="2" ParentId="2875" CreationDate="2010-06-05T23:29:22.513" Score="4" ViewCount="" Body="&lt;p&gt;Are you wanting a DC power supply for one specific purpose, or want a generic power supply that will do everything that the one you mention does?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can fairly cheaply buy an AC/DC transformer that will give you something like 12v dc and then you can use a voltage regulator with an adjustable voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want it to do everything, ie have 3 variable voltages each with variable currents along with meters that show what the voltage and current usage are, then I would recommend just buying a power supply. You will find that building your own power supply is much more complicated then you are probably expecting.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-06-05T23:29:22.513" />
  <row Id="2877" PostTypeId="2" ParentId="2875" CreationDate="2010-06-06T01:49:25.353" Score="5" ViewCount="" Body="&lt;p&gt;Why not get one of these kits: &lt;a href=&quot;http://bit.ly/ankadN&quot; rel=&quot;nofollow&quot;&gt;http://bit.ly/ankadN&lt;/a&gt; and use with an old computer power supply? Then spend some time learning about power supply design, linear regulators, smoothing and so on. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-06-06T01:49:25.353" CommentCount="4" />
  <row Id="2878" PostTypeId="1" AcceptedAnswerId="2892" CreationDate="2010-06-06T03:48:24.033" Score="5" ViewCount="174" Body="&lt;p&gt;I have decided to play in the world of GPS modules. I have read the &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=127&quot; rel=&quot;nofollow&quot; title=&quot;GPS Buying Guide&quot;&gt;GPS Buying Guide&lt;/a&gt; from Sparkfun, but still am not sure which unit I want to go with. I am leaning toward the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8975&quot; rel=&quot;nofollow&quot; title=&quot;LS20031&quot;&gt;LS20031&lt;/a&gt;, do any of you have any experience with GPS modules? Any advice you would like to add to the chiphacker community?&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-06-07T12:33:13.057" Title="GPS Suggestions" Tags="&lt;gps&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="2879" PostTypeId="2" ParentId="2875" CreationDate="2010-06-06T08:15:04.177" Score="7" ViewCount="" Body="&lt;p&gt;Before I got a real powersupply I used different kind of AC/DC or AC/AC power adapters, the kind that ship with toys, mobile phones, routers etc etc... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then I just cut the cord and measured the voltage with a multimeter, and if needed added a simple linear regulator like the 7805 (if I wanted a clean 5V).&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-06-06T08:15:04.177" CommentCount="11" />
  <row Id="2880" PostTypeId="2" ParentId="2878" CreationDate="2010-06-06T08:37:18.953" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.u-blox.com/&quot; rel=&quot;nofollow&quot;&gt;u-blox&lt;/a&gt; makes the best ones, but they are expensive. They are used by the military and government agencies because of their performance. I didn't have any problems with one of their modules on a home-made PCB, interfaced to a 16F88 PIC. It works indoors.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-06-06T10:22:55.247" LastActivityDate="2010-06-06T10:22:55.247" />
  <row Id="2881" PostTypeId="2" ParentId="2878" CreationDate="2010-06-06T10:36:22.100" Score="0" ViewCount="" Body="&lt;p&gt;There's lots of detail about building a GPS to SD Card Logger &lt;a href=&quot;http://www.gedanken.demon.co.uk/gps-sd-logger/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. It uses a PIC but you may be able to make alterations as you want.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-06-06T10:36:22.100" />
  <row Id="2882" PostTypeId="1" CreationDate="2010-06-06T17:27:17.370" Score="2" ViewCount="240" Body="&lt;p&gt;Does anyone know if there is a way to cause a interrupt via software?  Right now I am setting up a timer at a very low timeout 1ns and then using that to cause the interrupt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry if this is a dumb question... I think there has to be a better way to do this...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Riley&lt;/p&gt;&#xA;" OwnerUserId="29" LastActivityDate="2010-06-06T19:56:16.373" Title="XMega Software Interrupt?" Tags="&lt;xmega&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="2883" PostTypeId="2" ParentId="2882" CreationDate="2010-06-06T18:52:10.887" Score="2" ViewCount="" Body="&lt;p&gt;I know this may seem odd, but this is true on most microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try just setting the flag that is normally set by an interrupt condition yourself. if the flag that normally triggers from a timer interrupt at ox7857.6, then just try setting this bit yourself, in most microcontrollers you will trigger the interrupt yourself quite easily.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes you need to disable global interrupts, then set it, and then enable global interrupts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Forgive me for not having using an X-Mega, but I know I have seen this work on other controllers.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-06T19:56:16.373" LastActivityDate="2010-06-06T19:56:16.373" />
  <row Id="2884" PostTypeId="2" ParentId="2882" CreationDate="2010-06-06T18:55:43.877" Score="2" ViewCount="" Body="&lt;p&gt;The best way I have found to cause a software interrupt (without using an RTOS)  is to use one of the pinchange interrupts.  Activate the pullup resistor on the pin.  Then when you change the value, it will trigger the interrupt.&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2010-06-06T18:55:43.877" CommentCount="8" />
  <row Id="2885" PostTypeId="2" ParentId="2868" CreationDate="2010-06-06T19:12:32.787" Score="4" ViewCount="" Body="&lt;p&gt;The answer is, yes you should have signal at pin 8.  If you have signal at pin 7 and no signal at pin 8.  I would disconnect the output from everything but R57, to make sure it isn't loaded somewhere else.  If there is still no signal, I would disconnect R56 to leave the 5-7 connection unbiased to ground.  Better yet a trim pot at R56 and a trim pot at R57. Adjust till signal re-appears!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That load value(R57) looks low to me but I have only used LM13700's with single sided supplies appx. 9V so that might be why.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But definitely, signal at 7 should lead to signal at 8.&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2010-06-06T19:12:32.787" CommentCount="3" />
  <row Id="2886" PostTypeId="2" ParentId="2874" CreationDate="2010-06-06T19:22:49.550" Score="1" ViewCount="" Body="&lt;p&gt;Thermistors are only a type of resistor in a limited sense.  Within a given temp. range they behave linearly in current.  The packaging of Thermistors varies quite a lot, Glass beads to plastic packs.  As far as I know there is no color coding that is common.  I did a check on Omega and Honeywell's site.  No mention of a color coding there either.  I would think the 18p is a manufacturing code and not an electrical spec.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, testing with 30V!!  How big are these things!&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2010-06-06T19:22:49.550" CommentCount="2" />
  <row Id="2887" PostTypeId="1" CreationDate="2010-06-06T19:48:32.350" Score="2" ViewCount="924" Body="&lt;p&gt;I've got an &lt;a href=&quot;http://www.petsafe.net/Products/Waste-Removal/Simply-Clean-Litter-Box-System&quot; rel=&quot;nofollow&quot;&gt;automatic litterbox&lt;/a&gt; that 'needs' to be hacked for better control. As it ships, it comes with a 120VAC to 24VAC (300 mA) wall wart that drives the two motors in it. I'm trying not to change out the original power supply, as I don't want to change the motors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'm looking to do is get 5VDC for a microcontroller. My first thought was to simply toss a rectifier circuit and a 7805 and I'd be done. However, it seems that the 7805 wants a max Vin of 20VDC. Next thought was to find a small transformer to step the 24VAC down to around 12VAC and then pass that to the rectifier and 7805.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To that end, I started looking around for a transformer that I could use. Sensibly enough, everything I can find seems designed for a 120VAC primary. I came across &lt;a href=&quot;http://www.allelectronics.com/make-a-store/item/TCTX-280/UNIDENTIFIED-MINI-TRANSFORMER/1.html&quot; rel=&quot;nofollow&quot;&gt;this small tranformer&lt;/a&gt;, which I'm guessing is an audio transformer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I right in presuming that the resistance of each coil is directly proportional to the number of windings? Thus, if I were feed 24VAC into that transformer with a primary of 115 Ohms and a secondary of 69 Ohms, I think I would get 14.4VAC out. Is that correct? Also, can I get away with using what is probably an audio transformer for this purpose?&lt;/p&gt;&#xA;" OwnerUserId="746" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:40:05.140" LastActivityDate="2011-02-09T23:05:06.713" Title="Converting 24VAC to 5VDC - Need transformer demystification" Tags="&lt;transformer&gt;&lt;power-supply&gt;&lt;voltage-regulator&gt;" AnswerCount="6" />
  <row Id="2888" PostTypeId="2" ParentId="2887" CreationDate="2010-06-06T21:48:22.153" Score="5" ViewCount="" Body="&lt;p&gt;You can't rely on using resistance measurements to get turn ratios, because they almost always use different gauge wire for the two windings. The primary winding is usually several hundred turns of some fine gauge stuff, while the secondary is a few dozen turns of something heavier, to carry the necessary current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Probably the easiest solution is to get a 2nd wall-wart that supplies a few hundred mA of regulated 5V, and you're done.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you really want to DIY it, you may be able to find transformers with 24V secondaries that are center-tapped, in which case you may be able to use one leg to the c.t. to get 12V AC for your diode-and-7805 approach.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-06-06T21:56:48.503" LastActivityDate="2010-06-06T21:56:48.503" />
  <row Id="2889" PostTypeId="2" ParentId="2887" CreationDate="2010-06-06T22:46:52.677" Score="0" ViewCount="" Body="&lt;p&gt;you may well end up with close to 20V or less DC after recifiying the 24V AC anyway depending on what rectifier design you use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even failing that there are tons of regulators that will tolerate input voltages higher than 20VDC and i would recommend you look at switching regulators.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a linear regulator to produce a 15V DC drop is going to generate a ton of heat, you'd need a decent heatsink on the regulator.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-06-06T22:46:52.677" CommentCount="7" />
  <row Id="2891" PostTypeId="2" ParentId="2875" CreationDate="2010-06-07T11:41:21.400" Score="2" ViewCount="" Body="&lt;p&gt;You can have a look at &lt;a href=&quot;http://tuxgraphics.org/electronics/201005/bench-power-supply-v3.shtml&quot; rel=&quot;nofollow&quot;&gt;this kit from tuxgraphics&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may not have all the features yon want, but for a DIY power supply, it may be a good start.&lt;/p&gt;&#xA;" OwnerUserId="824" LastActivityDate="2010-06-07T11:41:21.400" />
  <row Id="2892" PostTypeId="2" ParentId="2878" CreationDate="2010-06-07T12:33:13.057" Score="2" ViewCount="" Body="&lt;p&gt;I recently purchased a couple of GPS modules for a project I'm working on.  You didn't specifically mention Arduino, but I bought the &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=17_21&amp;amp;products_id=98&quot; rel=&quot;nofollow&quot;&gt;GPS logger shield&lt;/a&gt; from Adafruit with an EM-406a module.  I'm not using an Arduino, but I figured it was a compact solution that had two things I wanted (GPS and removable storage).  The EM-406a had no problems getting a satellite lock inside my office.  I also got the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8146&quot; rel=&quot;nofollow&quot;&gt;Copernicus DIP Module&lt;/a&gt; from Sparkfun so I could breadboard with it. No problems so far - just read the datasheet and remember to pull XRESET and XSTANDBY high.&lt;/p&gt;&#xA;" OwnerUserId="836" LastActivityDate="2010-06-07T12:33:13.057" CommentCount="1" />
  <row Id="2893" PostTypeId="2" ParentId="2887" CreationDate="2010-06-07T13:58:01.527" Score="3" ViewCount="" Body="&lt;p&gt;If you want to get from 24VAC to 12VAC you need a transformer with a turn ratio of 2:1. Since the input of a power transformer is normally line voltage (120V in your case) such a transformer would be rated for an output of half the line voltage (60V).&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-06-07T13:58:01.527" />
  <row Id="2894" PostTypeId="2" ParentId="1763" CreationDate="2010-06-07T14:09:10.850" Score="7" ViewCount="" Body="&lt;p&gt;Everything by UnwiredBen and Vineeth are great, but dont forget online websites for the freshest hacks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My particular favorite &lt;a href=&quot;http://hackaday.com/&quot; rel=&quot;nofollow&quot;&gt;Hack A Day&lt;/a&gt; is a great resource&lt;/p&gt;&#xA;" OwnerUserId="591" LastActivityDate="2010-06-07T14:09:10.850" />
  <row Id="2895" PostTypeId="2" ParentId="1763" CreationDate="2010-06-07T14:13:11.190" Score="1" ViewCount="" Body="&lt;p&gt;There was a question relating to Blogs and Podcasts that somebody asked 6 months ago in a similar vein, some of the resources there might be of interest: &lt;a href=&quot;http://chiphacker.com/questions/952/electronics-blogs-and-podcasts/&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/952/electronics-blogs-and-podcasts/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-06-07T14:13:11.190" />
  <row Id="2896" PostTypeId="1" AcceptedAnswerId="2900" CreationDate="2010-06-07T18:01:11.113" Score="2" ViewCount="297" Body="&lt;p&gt;This is a AC 220v 60W 0.2A fan I recently bought to replace my old bathroom vent that gave up some time ago. The problem is that the new one doesn't come with a built in speed controller like the old did, so the fan is running really loud. The people at the store tell me to go to another store to buy a speed controller but I have only found dimmers or expensive industrial speed controllers. I studied electronics some years ago and have been looking for a way to build such a speed controller, the question is how. My first guess is to control the speed by reducing the watt or amp. Any help would be welcome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some schematics that came with the unit (The instructions are in German):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://imgur.com/QPKel.jpg&quot; alt=&quot;Schematics&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="837" LastActivityDate="2010-06-08T01:19:57.713" Title="What is used to control AC motor speed?" Tags="&lt;speed&gt;&lt;controller&gt;" AnswerCount="2" />
  <row Id="2897" PostTypeId="2" ParentId="2896" CreationDate="2010-06-07T19:16:30.820" Score="1" ViewCount="" Body="&lt;p&gt;I used a small triac with an integrated diac for triggering many years ago to control an AC motor; the other parts were a potentiometer, a resistor and a capacitor, IIRC. The same technique should work in your case.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-07T19:16:30.820" />
  <row Id="2898" PostTypeId="1" AcceptedAnswerId="2899" CreationDate="2010-06-07T21:54:21.637" Score="3" ViewCount="404" Body="&lt;p&gt;I want to make a case for a PCB using extruded aluminum. (Such as the IPOD nano shown below, and the portable amp under it).&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How do I mount the PCB inside the alumimum extrusion? (I know some come with slots but are there different options?&lt;/li&gt;&#xA;&lt;li&gt;Who are some good suppliers of extruded aluminum? (bonus if they do milling on small quantities too)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kdIGp.jpg&quot; alt=&quot;Example&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-06-07T23:12:42.097" Title="Mounting a PCB in an Extruded Aluminum case" Tags="&lt;cases&gt;&lt;mount&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="2899" PostTypeId="2" ParentId="2898" CreationDate="2010-06-07T23:12:42.097" Score="4" ViewCount="" Body="&lt;p&gt;For extruded aluminum, find the local distributor for aluminum structural framing in your area. Try 8020.net in the US and Bosch-Rexroth in Europe. You might also try &lt;a href=&quot;http://www.frontpanelexpress.com&quot; rel=&quot;nofollow&quot;&gt;frontpanelexpress.com&lt;/a&gt;, though their stuff might be too big.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some options to mount the PCB:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The slots&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.pemnet.com/fastening_products/prod_desc.php3?cat=Fasteners+for+PC+Boards&quot; rel=&quot;nofollow&quot;&gt;PEM studs&lt;/a&gt; (you'd need a fabricator to press these in for you)&lt;/li&gt;&#xA;&lt;li&gt;Bolts and standoffs (try Digikey)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;For the PEM studs, check out the KSSB family-- they're designed specially for mounting PCBs without extra fasteners.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-07T23:12:42.097" CommunityOwnedDate="2010-06-07T23:12:42.097" />
  <row Id="2900" PostTypeId="2" ParentId="2896" CreationDate="2010-06-08T01:19:57.713" Score="1" ViewCount="" Body="&lt;p&gt;For an AC motor, you can reduce the voltage to reduce the speed. As a quick hack, you could try running it off 120 V AC; if that speed is good, you're done.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise, you could try a triac, which chops the voltage for part of each AC cycle, making the average voltage lower, or you could use a variable transformer, like this: &lt;a href=&quot;http://www.electroniccity.com/shopping/pricelist.asp?prid=1147&quot; rel=&quot;nofollow&quot;&gt;http://www.electroniccity.com/shopping/pricelist.asp?prid=1147&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-08T01:19:57.713" />
  <row Id="2901" PostTypeId="1" CreationDate="2010-06-08T03:13:07.633" Score="7" ViewCount="1192" Body="&lt;p&gt;&lt;em&gt;Wikipedia explains the basics about the markings of capacitors, &lt;a href=&quot;http://en.wikipedia.org/wiki/Capacitor#Capacitor_markings&quot; rel=&quot;nofollow&quot;&gt;here.&lt;/a&gt; It lacks many markings most of which confuses me:&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Ceramic brown-yellowish cap&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;104 K5K (small )   --- what is the end &quot;5K&quot;? (Cannot be 5 kelvin as operating temperature!?)&lt;/li&gt;&#xA;&lt;li&gt;10 (box box, perpendicular right upermost corner) 35+  (Tantalum Cap, bigger variant of the last one&lt;/li&gt;&#xA;&lt;li&gt;154 C1K  (what is C1K, some other notation to Wikipedia?)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Orange Ceramic&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;333 K5X   (what is 5X? X roman numeral?)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Brown Circle Slit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;10n (no other marking, what is the op.temp?) (Diameter: 7.5mm)&lt;/li&gt;&#xA;&lt;li&gt;27J 100V (what is 27J?) (Diameter: 4.9mm, blackdot on the head)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Blue Slit Square&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;(triangle) 104K X7R50   (What is triangle? X7R50? Operating V?) (side = 4.9mm)&lt;/li&gt;&#xA;&lt;li&gt;104   (side = 2.6mm, op.V? Tolerance?) &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Questions about the bracketed&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How to know operating V without its explicit marking? &lt;/li&gt;&#xA;&lt;li&gt;What do the symbols, such as squares, plus-sign and triangle, mean?&lt;/li&gt;&#xA;&lt;li&gt;Can you evaluate the operating voltage from the size of the capacitor in the case when no marking or poor marking is given?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T10:27:51.393" LastActivityDate="2011-01-23T10:27:51.393" Title="Various Small capacitors' markings?" Tags="&lt;capacitor&gt;&lt;markings&gt;" AnswerCount="3" />
  <row Id="2902" PostTypeId="2" ParentId="2901" CreationDate="2010-06-08T03:56:32.773" Score="2" ViewCount="" Body="&lt;p&gt;Here's a staring &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/06/04/electronic-components-the-capacitor/&quot; rel=&quot;nofollow&quot;&gt;point&lt;/a&gt;. If you know the type of capacitor that you have, but not what the value is, have a look at (for example) Farnell website and search for that part type. Then you can get a data sheet which usually explains things nicely. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-10-27T15:49:21.613" LastActivityDate="2010-10-27T15:49:21.613" CommentCount="1" />
  <row Id="2903" PostTypeId="1" AcceptedAnswerId="2905" CreationDate="2010-06-08T19:19:46.543" Score="6" ViewCount="143" Body="&lt;p&gt;Can I use a reference design from a data sheet in a commercial product without attribution/licensing of any sort?&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-06-10T16:01:25.210" Title="Are reference designs assumed to be license free?" Tags="&lt;licensing&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="2904" PostTypeId="1" AcceptedAnswerId="2906" CreationDate="2010-06-08T19:29:04.757" Score="3" ViewCount="244" Body="&lt;p&gt;Here's a link to the (crummy) schematic: &lt;a href=&quot;http://it.tinypic.com/r/2v0eveo/6&quot; rel=&quot;nofollow&quot;&gt;http://it.tinypic.com/r/2v0eveo/6&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a filter/phase shift designed by the experimental electronic musician David Tudor, for use in destabilizing audio feedback loops.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit seems unclear to me, and I don't understand the signal flow, or the use of capacitors here. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="835" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:45:53.633" LastActivityDate="2010-08-17T23:45:53.633" Title="Can anyone figure out this (David Tudor) circuit?" Tags="&lt;music&gt;&lt;filter&gt;&lt;schematics&gt;" AnswerCount="1" />
  <row Id="2905" PostTypeId="2" ParentId="2903" CreationDate="2010-06-08T19:59:17.347" Score="6" ViewCount="" Body="&lt;p&gt;In the most general way, yes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The document will normally have some sort of legal disclosure somewhere. Many companies will have a disclosure that you may not use their method unless you are using the part it was designed for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not to get into anything too much legal, if you are doing something small, no worries. If you are doing something very large scale or that you expect to make a large amount of money from, just get a lawyer's opinion, in writing. Then if someone goes wrong you are protected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it is a method they patented, and they are disclosing it with the intention of you licensing it, which I have never seen done without an obvious disclosure, then you do not want to use the technique.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please let me know if there is anything else I can add to make this more clear or more helpful. I am not a lawyer of any sort, please double check with one if there is substantial money at stake.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-08T19:59:17.347" />
  <row Id="2906" PostTypeId="2" ParentId="2904" CreationDate="2010-06-08T20:53:04.773" Score="7" ViewCount="" Body="&lt;p&gt;Take a look at &lt;a href=&quot;http://en.wikipedia.org/wiki/RC_circuit&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/RC_circuit&lt;/a&gt; under the Parallel circuit section.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That circuit allows you to adjust the resistance (with a pot) and adjust the capacitance by opening or closing switches. So, you can have any combination of switches open or closed to get a different effective capacitance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The capacitor between Black and Red is just always added with the switched capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The pot and capacitor at the end is a Snubber, find more info at &lt;a href=&quot;http://en.wikipedia.org/wiki/Snubber&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Snubber&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-06-08T20:53:04.773" CommentCount="3" />
  <row Id="2907" PostTypeId="1" CreationDate="2010-06-08T23:55:02.973" Score="1" ViewCount="226" Body="&lt;p&gt;My diode is:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;VISHAY GENERAL SEMICONDUCTOR 1N4004-E3&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Diode&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Diode Type:Standard Recovery;&#xA;  Repetitive Reverse Voltage Max,&#xA;  Vrrm:400V; Forward Current, If(AV):1A;&#xA;  Forward Voltage Max, VF:1.1V; Forward&#xA;  Surge Current Max, Ifsm:30A; Operating&#xA;  Temperature Ran 78K2120;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://at.farnell.com/jsp/search/browse.jsp;jsessionid=YTEEQOAO1ZSPQCQLCIPJMMQ?N=0&amp;amp;Ntk=gensearch_002&amp;amp;Ntt=1N4004&amp;amp;Ntx=mode+matchallpartial&amp;amp;suggestions=false&amp;amp;ref=globalsearch&amp;amp;_requestid=660188&quot; rel=&quot;nofollow&quot;&gt;Source, please, search for 78K2120.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Questions&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What does &quot;78K2120&quot; mean?&lt;/li&gt;&#xA;&lt;li&gt;According to the new reply, it is an identifier but what does it mean? Why is it chosen? Does it contain some information except being a random identifier?&lt;/li&gt;&#xA;&lt;li&gt;Is there some standard, seen too many manufacturers just throwing similar lines but with different meaning?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-08T01:00:41.530" LastActivityDate="2011-01-08T01:00:41.530" Title="Marking for Operating Tempature Range on Diode's data sheet?" Tags="&lt;diode&gt;&lt;datasheet&gt;&lt;markings&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="2908" PostTypeId="1" AcceptedAnswerId="2912" CreationDate="2010-06-09T01:19:40.387" Score="1" ViewCount="95" Body="&lt;p&gt;My circuit is almost identical to &lt;a href=&quot;http://en.wikipedia.org/wiki/File%3aRC_Filter.png&quot; rel=&quot;nofollow&quot;&gt;the Wikipedia&lt;/a&gt; but with 5V in, 1pF cap, 4 pieces of IN4004 diodes. I am not certain whether it is AC or DC here and there (actually I do but not want to break my multimeter). Is there some safe way to test its type? My multimeter has only separate modes for AC and DC but not a common mode for both of them. &lt;strong&gt;So how to find out unknown voltage type?&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-09T04:26:13.753" LastActivityDate="2010-06-09T04:26:13.753" Title="Measuring Voltage of Unknown Type" Tags="&lt;beginner&gt;&lt;ac&gt;&lt;dc&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="0" />
  <row Id="2909" PostTypeId="2" ParentId="2901" CreationDate="2010-06-09T01:50:06.877" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;2. About &quot;+&quot;-sign&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The plus means &quot;polarised&quot;, the source is &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/06/04/electronic-components-the-capacitor&quot; rel=&quot;nofollow&quot;&gt;tronixstuff's site, point &quot;Tantalum capacitors&quot;&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/2910/what-does-polarization-mean-in-polarized-cap&quot; rel=&quot;nofollow&quot;&gt;More here.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-09T02:18:00.563" LastActivityDate="2010-06-09T02:18:00.563" CommentCount="3" />
  <row Id="2910" PostTypeId="1" AcceptedAnswerId="2913" CreationDate="2010-06-09T01:54:40.440" Score="3" ViewCount="752" Body="&lt;p&gt;&lt;em&gt;Question emerged from my last question about small caps' markings, better to open new question so not become bloated.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Heard term polarization in the context of light but not with caps. Googling revealed the effect: &lt;a href=&quot;http://en.wikipedia.org/wiki/Dipolar_polarization&quot; rel=&quot;nofollow&quot;&gt;Dipolar Polarization&lt;/a&gt;. Not sure whether it is the right effect but at least it mentions cap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;1. What does the term &quot;polarized&quot; mean?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;2. Why should I use &quot;polarized&quot; cap instead of non-polarized cap?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;3. Why does the circuit need a polarized cap? &lt;a href=&quot;http://en.wikipedia.org/wiki/File:RC_Filter.png&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/File:RC_Filter.png&lt;/a&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-09T02:12:25.320" LastActivityDate="2010-06-09T18:49:21.150" Title="What does polarization mean in &quot;polarized cap&quot;?" Tags="&lt;capacitor&gt;" AnswerCount="2" />
  <row Id="2911" PostTypeId="2" ParentId="2910" CreationDate="2010-06-09T03:01:51.237" Score="3" ViewCount="" Body="&lt;p&gt;Check out the section on polarity here, for starters: &lt;a href=&quot;http://en.wikipedia.org/wiki/Electrolytic_capacitor#Polarity&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Electrolytic_capacitor#Polarity&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Polarization is a side-effect of the electrolytic manufacturing process, which allows for large capacitance in small volume.&lt;/p&gt;&#xA;" OwnerUserId="835" LastActivityDate="2010-06-09T03:01:51.237" CommentCount="0" />
  <row Id="2912" PostTypeId="2" ParentId="2908" CreationDate="2010-06-09T04:19:08.073" Score="7" ViewCount="" Body="&lt;p&gt;If you set your multimeter to DC(V) and then measure an AC(V) it will not cause damage, neither will the opposite.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you measure it with both, and one says 5 V, then that is what signal you have. 5V AC wave will not be anything on DC measurement, but will be 5V with AC turned on.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-09T04:19:08.073" CommentCount="1" />
  <row Id="2913" PostTypeId="2" ParentId="2910" CreationDate="2010-06-09T04:36:50.313" Score="9" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Some caps -- such as nearly all electrolytic capacitors and tantalum capacitors -- are polarized. Such caps use some sort of chemical reaction between an anode and a cathode made of two different kinds of materials to form a thin insulating layer. When you hold one of these caps in your hands, you will see a &quot;-&quot; mark by the pin intended to stay more negative, or a &quot;+&quot; mark by the pin intended to stay more positive.&#xA;If a polarized cap is ever &quot;reverse biased&quot; more than 1 V to 1.5 V (typical), it drives that chemical reaction in reverse, eating away at the thin insulating layer, leading to a short between the two pins.&#xA;Not only is that capacitor no longer working,&#xA;after that, any significant voltage -- forward or reverse -- could make that &quot;capacitor&quot; overheat and in some cases explode.&#xA;The person drawing the circuit and connecting the capacitor in a circuit must make sure the &quot;+&quot; end goes towards the more positive voltage, and the &quot;-&quot; end goes towards the more negative voltage, at all times, to prevent catastrophe.&#xA;See the Wikipedia article Greg pointed out for more details.&#xA;Other caps -- such as nearly all ceramic capacitors, paper disk capacitors, and mica capacitors -- are non-polarized.&#xA;Such caps typically use an anode and a cathode made of identical metal, and they work just as well with &quot;reverse biased&quot; voltage as forward biased.&#xA;They don't have either &quot;+&quot; or &quot;-&quot; mark, because they don't need one.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&amp;amp; 3. You never &quot;need&quot; a polarized cap. Practically all physical circuits would work just as well, and perhaps better, if the polarized caps were all replaced with non-polarized caps of the same capacitance and voltage rating.&#xA;The opposite is not true -- you often can't replace non-polarized caps with polarized caps.&#xA;Some circuits require a capacitor that can handle a high positive voltage at some times and a high negative voltage at other times (polarity reversal), which requires a non-polarized capacitor.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The only reason people use polarized caps is because they often cost much less than non-polarized caps of the same capacitance and voltage rating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, when drawing a schematic, you should always draw a &quot;+&quot; sign on one side of a cap whenever you intend that that the cap always has positive voltage applied to it, it never suffers polarity reversal.&#xA;That helps the people reading the schematic understand what you meant.&#xA;That gives people putting together the physical circuit the &lt;em&gt;option&lt;/em&gt; of using polarized capacitors, even though many times it is more convenient to use non-polarized capacitors in the place of the polarized capacitors clearly marked on the schematic.&#xA;It also tells people putting together the physical circuit, should they choose to use a polarized capacitor, which way around the polarized capacitors should go.&#xA;It also communicates to repair people that, if they measure a negative bias voltage, that something has gone horribly wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The schematic you show -- with the clearly marked &quot;+&quot; polarized capacitor -- would work just as well with a non-polarized capacitor.&#xA;The &quot;+&quot; on one end of the capacitor is telling us that that end is expected to never be negative relative to the other end.&#xA;It's also telling us that we have the &lt;em&gt;option&lt;/em&gt; of using a polarized or nonpolarized cap in that location when we build that circuit.&lt;/p&gt;&#xA;" OwnerUserId="813" LastEditorUserId="819" LastEditorDisplayName="" LastEditDate="2010-06-09T18:49:21.150" LastActivityDate="2010-06-09T18:49:21.150" CommunityOwnedDate="2010-06-09T04:36:50.313" CommentCount="4" />
  <row Id="2914" PostTypeId="2" ParentId="2907" CreationDate="2010-06-09T07:36:45.070" Score="3" ViewCount="" Body="&lt;p&gt;78K2120 is the Newark product code for that diode. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.newark.com/vishay-general-semiconductor/1n4004-e3/diode/dp/78K2120?Ntt=78K2120&quot; rel=&quot;nofollow&quot;&gt;http://www.newark.com/vishay-general-semiconductor/1n4004-e3/diode/dp/78K2120?Ntt=78K2120&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Google FTW. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That diode's temperature range is -50~+150 degrees celsius. Data sheet: &lt;a href=&quot;http://www.vishay.com/doc?88503&quot; rel=&quot;nofollow&quot;&gt;http://www.vishay.com/doc?88503&lt;/a&gt;; Farnell Australia (au.farnell.com) part number 1421919. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-06-09T07:36:45.070" CommentCount="4" />
  <row Id="2915" PostTypeId="1" CreationDate="2010-06-09T08:03:46.250" Score="1" ViewCount="294" Body="&lt;p&gt;I've been considering building some LED lights to replace the mains-supplied lights in my house (as a more efficient alternative). For it to be worthwhile though I'd need to build an efficient UK mains converter to supply each cluster of lights.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the most efficient way to turn AC into ~5v to power ~10 luxeon lights?&lt;/p&gt;&#xA;" OwnerUserId="839" LastActivityDate="2010-06-12T16:31:47.923" Title="How do I build a cheap/efficient mains adapter for some LED lighting?" Tags="&lt;led&gt;&lt;light&gt;&lt;transformer&gt;&lt;power-supply&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="2916" PostTypeId="2" ParentId="1262" CreationDate="2010-06-09T14:39:45.777" Score="2" ViewCount="" Body="&lt;p&gt;I was about to change the clock that way... I have a question: are they also programmable by software? if I want to change my clk source whenever I want can I change them according to my needs? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;thank you&lt;/p&gt;&#xA;" LastActivityDate="2010-06-09T14:39:45.777" CommentCount="1" />
  <row Id="2917" PostTypeId="2" ParentId="2915" CreationDate="2010-06-09T14:55:23.060" Score="4" ViewCount="" Body="&lt;h2&gt; Basic Approach&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;The most efficient way would be to rectify the system and use high quality components to get the lowest losses possibly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After you have rectified to DC, I would suggest using a very high efficiency buck converter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, rectify with high grade components to DC(focus is on low leakage here) then buck convert it to the power you need.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Warning: Safety &lt;/h2&gt;&#xA;&#xA;&lt;p&gt;When you build your own system for lighting, that is using 120VAC and has high current output has the possibility for fire in failure modes. If someone is hurt or their property damage, you can probably be found liable, and possibly criminally negligent, depending on your country and their laws. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recognize you said UK, but I will not pretend to know the laws there, I would suggest you spoke to an attorney about it if you are planning to switch your house to this. At minimum use Fuses everywhere they make sense and protect yourself from having a wiring fault and starting a fire. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The filter caps from the rectifier will have a large amount of power stored and a short after that point could easily become a fire if not protected against.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Improving on the Design &lt;/h2&gt;&#xA;&#xA;&lt;p&gt;So, there is still more you can do to improve this, it just gets more complicated and will require control circuitry on your part. This control circuitry will require power, but it should be negligible with a good design compared to what you save. You will do this by having the LEDs blinking at a very high frequency with large off-time and over-current during the on-time.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;LED Heating&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;LEDs have failure brought on by heating effects, this means there are many ways you can trick an LED. An LED Rated for 5A can be vastly overcurrent for a very short period of time without any damage done to the LED. The trick is to hit it with the current very quickly then have an off period where any heat is allowed to dissipate. The average light your eye sees will go up with lower power consumption.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did a quick google search to attempt to give you a good example, but I failed. It seems the words involved in finding these methods are too often used in systems where things like overcurrent are a danger. You should play with it, I think you will find it surprising. I have actually done this myself, multiple times, and with excellent results. One of my professors made the duty cycle to long on purpose once to show me the changing of colors you can get in an LED due to heating also, don't do this, unless to laugh at it, because you have to bury your LED afterward.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;PWM Generation&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;I would suggest using a very simple 555 timer circuit. &lt;a href=&quot;http://www.dprg.org/tutorials/2005-11a/index.html&quot; rel=&quot;nofollow&quot;&gt;This circuit is driving a motor and uses a POT&lt;/a&gt;, but you could easily use 2 resistors of your choice and have it hard set to it's frequency. The motor is an example load and driving an LED is significantly easier(ie. inductance is much lower). This also adds a place to add an on/off switch. By placing a switch on the branch that is used for the &quot;on&quot; cycle and you can disable the system.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Efficiency When Off&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Make sure when you leave a room and switch off all of the lights, or whatever unit it is that you feed from each Buck converter that you are also disconnecting the rectifier and the buck converter. They will continue to drain power when the load is disconnected. This will very quickly remove any power savings you have reaped.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Results &lt;/h2&gt;&#xA;&#xA;&lt;p&gt;You can read about this online, but LEDs really have the highest efficiency in low temperature applications, in room temperature you will probably not save any power over florescent lights at the same cost. You should be able to save a relative amount of power just by upgrading to high end components, but the system will cost you significantly more to implement.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-09T15:43:43.040" LastActivityDate="2010-06-09T15:43:43.040" CommentCount="1" />
  <row Id="2918" PostTypeId="1" AcceptedAnswerId="2996" CreationDate="2010-06-09T15:07:02.867" Score="6" ViewCount="815" Body="&lt;p&gt;Can anyone offer any useful strategies on going from a rat's nest to a routed PCB?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I'm using Eagle and aiming to make single/double sided PCBs at home)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Drawing the schematic is fine, but when it comes to routing the tracks, it feels like unravelling a giant ball of wool.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-12T18:12:00.397" Title="Advice on going from rat's nest to routed PCB" Tags="&lt;pcb&gt;&lt;eagle&gt;" AnswerCount="7" CommentCount="2" FavoriteCount="3" />
  <row Id="2919" PostTypeId="2" ParentId="2918" CreationDate="2010-06-09T15:36:40.747" Score="9" ViewCount="" Body="&lt;p&gt;I like to start by putting my schematic in front of me. You generally want your parts to be arranged in such a way that the traces don't have to go further then they need to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually when people make schematics they try to make their schematics &quot;pretty&quot;. Laying your board out in the same manner as your schematic is usually a very good start. But, before you do that, look at anything that you will need to actually interact with, USB ports, programming ports, buttons, etc and put them where would be best for the end product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have your parts laid out, start by routing the most important traces. These traces are ones that have high speed data on them and you would prefer for them to not be jumping to different sides of the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After you get those traces laid out, route your power traces. By this point you should be able to figure out how to best route anything remaining.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It usually takes me 3 or 4 iterations of laying out a board before I am happy with what I have made. Every time I do it, I learn particular ways that traces need to be routed to make the routing simpler.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a final note, if you have the ability to, be willing to change what pins connect to a peripheral. For example, if you have an LED connected to a microcontroller, you should try to use a pin that is the closest to where you want the LED placed on the board. Many times you don't have this freedom, but it is something to try to do if you can.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-09T15:50:43.853" LastActivityDate="2010-06-09T15:50:43.853" CommentCount="2" />
  <row Id="2920" PostTypeId="2" ParentId="2918" CreationDate="2010-06-09T15:49:51.163" Score="2" ViewCount="" Body="&lt;p&gt;A useful strategy when laying put a board is to place the larger components first, and connectors, then the smaller components like Rs and Cs. Component placement is very important. When routing, start with the critical nets like power, ground and any clocks. Then, start routing the shortest nets, leaving the longest to last.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-09T15:49:51.163" CommentCount="0" />
  <row Id="2921" PostTypeId="2" ParentId="2907" CreationDate="2010-06-09T15:51:00.390" Score="2" ViewCount="" Body="&lt;p&gt;I contacted Newark and their answer is: &quot;Our part# does not mean anything in relation to the specs on the manufacturer part.&quot;. So it is apparently about book-keeping.&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-06-09T20:58:45.353" LastActivityDate="2010-06-09T20:58:45.353" CommentCount="2" />
  <row Id="2922" PostTypeId="2" ParentId="2918" CreationDate="2010-06-09T15:53:25.120" Score="6" ViewCount="" Body="&lt;p&gt;Place the components however you like so that so that your layout &quot;makes sense&quot; from a usability standpoint. Make polarized components always have the same orientation. Place connectors on the perimeter of your board, make IC chips have a consistent orientation. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then let the autorouter do it's magic, setting the DRC to use trace widths that are large initially (I like to start around 20mil). If it fails to get to 100% routed, type &quot;ripup;&quot; in the command line to take you back to a rats nest and change the DRC to progressively lower trace widths until the autorouter is happy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know a lot of &quot;die hard&quot; people have &quot;problems&quot; with the autorouter, but I happen to think it does a pretty great job. Unless you are doing really high bandwidth digital I/O or maybe RF design, the path the signal takes will seldom be a cause of concern for you. I would be a little bit careful about putting things like crystals close to the IC chips pins they are using if you have any, though.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-06-09T16:06:26.747" LastActivityDate="2010-06-09T16:06:26.747" CommentCount="5" />
  <row Id="2923" PostTypeId="2" ParentId="2918" CreationDate="2010-06-09T16:02:27.870" Score="3" ViewCount="" Body="&lt;p&gt;Im no expert, but this is the approach that I follow and it works... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;1.&lt;/strong&gt; Routing the most important tracks first starting with power and ground rails &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;2.&lt;/strong&gt; Run the ground around the edge of the board where possible (but not so close that it is touching the edge)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;3.&lt;/strong&gt; Next step is to divide the circuit into functional building blocks &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;4.&lt;/strong&gt; Arrange the blocks so that connections between them are as simple as possible..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;5.&lt;/strong&gt; I would then use auto routing to check the layout -auto routing should succeed with a few seconds (say less then 60, though this obviously depends on the complexity of your ciruit)if youve your placement is good (please note I use protel 99se, Im not familiar with eagle so auto routing time may vary)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;6.&lt;/strong&gt; Then undo the auto route... and manual route.. routing the tracks within the functional blocks first and then the connections between the blocks. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An old saying is that design is 90% placement and 10% routing, take the time to get the right placement and the rest will fall into place.&lt;/p&gt;&#xA;" OwnerUserId="819" LastEditorUserId="819" LastEditorDisplayName="" LastEditDate="2010-06-09T18:18:10.153" LastActivityDate="2010-06-09T18:18:10.153" CommentCount="8" />
  <row Id="2924" PostTypeId="2" ParentId="2918" CreationDate="2010-06-09T16:11:48.990" Score="3" ViewCount="" Body="&lt;p&gt;I am not going to go into the great detail everyone else has. They have done a great job of discussing a method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.intel.com/design/PentiumII/applnots/243334.htm&quot; rel=&quot;nofollow&quot;&gt;I would like to link you to an app note created by Intel that helped me, when I was starting, to get my mind to think about the things it should first.&lt;/a&gt; If you would like other sources just comment and I can show you where I have gone from there to really improve my technique. This however can show you how to get the quality of a 4 layer board with a ground and a power plane from a well designed 2 layer board.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-09T16:11:48.990" />
  <row Id="2925" PostTypeId="1" CreationDate="2010-06-09T16:52:59.767" Score="2" ViewCount="207" Body="&lt;p&gt;Huge price differences: &lt;a href=&quot;http://fi.farnell.com/tyco-electronics-raychem/fldwc0311-0-25-0/wire-0-25mm-black-100m/dp/797972?Ntt=TYCO+ELECTRONICS+/+RAYCHEM+-+FLDWC0311-0.25-0+-+FLEXLITE+WIRE+0.25MM+BLACK+100M&quot; rel=&quot;nofollow&quot;&gt;Farnell Finland 66.7EUR&lt;/a&gt;, &lt;a href=&quot;http://cpc.farnell.com/tyco-electronics-raychem/fldwc0311-0-25-2/flexlite-wire-0-25mm-red-100m/dp/CB04715?Ntt=WIRE+0.25MM+RED+100M&quot; rel=&quot;nofollow&quot;&gt;Farnell UK CPC 23Pounds&lt;/a&gt;, cannot find in eBay or Dealextreme, nearly out of stock in CPC Farnell. I need it for breadboard, fast prototyping. Where do you get your solid experiment wire? It can apparently be 22AWG or 24AWG, acccording to &lt;a href=&quot;http://chiphacker.com/questions/621/stranded-vs-solid-wire/624#624&quot; rel=&quot;nofollow&quot;&gt;this reply about stranded VS solid wire.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T06:55:00.787" LastActivityDate="2011-01-29T06:55:00.787" Title="Cheap solid equipment wire for breadboard from online shop?" Tags="&lt;prototyping&gt;&lt;wire&gt;&lt;breadboard&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="2926" PostTypeId="2" ParentId="2925" CreationDate="2010-06-09T17:15:24.463" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.bitsbox.co.uk/cable/cable.html&quot; rel=&quot;nofollow&quot;&gt;Bitsbox&lt;/a&gt; sell &lt;em&gt;Single Core 1/06mm&lt;/em&gt; at 12p/metre for up to 100m (Non UK buyers limited to 10m per order)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rapidonline.com/productinfo.aspx?tier1URL=Cables-Connectors&amp;amp;tier2URL=Equipment-Wire&amp;amp;tier3URL=Equipment-Wire&amp;amp;tier4URL=1-0.6mm-Single-core-equipment-wire-on-100m-reels&amp;amp;moduleno=62317&quot; rel=&quot;nofollow&quot;&gt;Rapid Electronics&lt;/a&gt; have &lt;em&gt;Single Core 1/06mm&lt;/em&gt; for £4.05 per 100m roll &#xA;or 11 100m rolls (one of each colour) for £44.59&lt;/p&gt;&#xA;" OwnerUserId="819" LastEditorUserId="819" LastEditorDisplayName="" LastEditDate="2010-06-09T17:51:19.287" LastActivityDate="2010-06-09T17:51:19.287" CommentCount="1" />
  <row Id="2927" PostTypeId="2" ParentId="2925" CreationDate="2010-06-09T17:21:31.067" Score="0" ViewCount="" Body="&lt;p&gt;I think I solved the problem with the tip:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/621/stranded-vs-solid-wire/623#623&quot; rel=&quot;nofollow&quot;&gt;Buy Solid Core Cat 5 or 6 Network&#xA;  cable, a couple of meters goes a long&#xA;  way... &lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Reusable, cheap, have already extra heads and &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.3530&quot; rel=&quot;nofollow&quot;&gt;tools&lt;/a&gt;. There are still different types of RJ45-headed cables, one of mine is stranded copper (cannot cut it with my tools), one is solid wire (soft). I think the last fits to breadboard.&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-09T17:35:34.533" LastActivityDate="2010-06-09T17:35:34.533" />
  <row Id="2928" PostTypeId="2" ParentId="1514" CreationDate="2010-06-09T18:58:11.150" Score="1" ViewCount="" Body="&lt;p&gt;Stabilizing the output voltage is also called &quot;regulating&quot; the output voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect you have at least one of the following problems: failing power adapter, unregulated power adapter, or insufficient bypass capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;failing power adapter&lt;/strong&gt;:&#xA;Some power adapters start to hum more and more loudly just before they fail.&#xA;You may need to replace it soon.&#xA;Are you the kind of person that:&#xA;(a) waits until a light bulb fails, then runs around in a panic trying to find a replacement? Or&#xA;(b) has a replacement light bulb in a closet so when the light bulb fails it can be replaced within minutes? Or&#xA;(c) pre-emptively replaces lightbulbs when they are near the end of their expected lifetime?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, a few kinds of power adapters always hum relatively loudly, even when they are working perfectly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Unregulated power adapter&lt;/strong&gt;:&#xA;AC power in the UK and Europe is held to +-10% steady-state, and often has short-term surges and sags.&#xA;The 74LS132 datasheet only guarantees it will work with a power supply of 5 V +- 5%, so already the +- 10% change in voltage from an unregulated power adapter is out-of-spec.&#xA;Many other Schmitt trigger chips work over a much larger voltage range.&#xA;However, the power supply voltage affects the trip voltage -- so while the chip may technically may be inside spec and &quot;work&quot; in some sense, it may not do what you want.&#xA;The big capacitor helps smooth out short-term surges and sags, so it temporarily masked over your problem, but it does nothing for the longer-term wandering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need a regulated power supply, especially if you are working with audio and radio circuits.&#xA;Either (a) post-regulate your unregulated power adapter with a voltage regulator such as a 7805 and some caps or a LM317 and some caps, or (b) return your unregulated power adapter, and replace it with a regulated power adapter that includes a voltage regulator built in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;insufficient bypass capacitors&lt;/strong&gt;:&#xA;&lt;a href=&quot;http://massmind.org/techref/power/decouple.htm&quot; rel=&quot;nofollow&quot;&gt;Best practice&lt;/a&gt; is to attach a 1 uF cap to the power pins of each chip,&#xA;plus a larger cap somewhere on the board.&#xA;(Before 2001, best practice used 0.1 uF caps).&#xA;Digital chips often pull brief pulses of high current, which are easily supplied by a nearby cap.&#xA;Without caps, the resistance and inductance of the long path between the chip and the voltage regulator often allows the voltage at the power pins of the chip to sag enough (&quot;VCC droop&quot; and &quot;ground bounce&quot;) to reset chips with hysteresis such as Schmitt triggers and flip-flops and microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See chiphacker &lt;a href=&quot;http://chiphacker.com/questions/2272/what-is-a-decoupling-capacitor-and-how-do-i-know-if-i-need-one/2932&quot; rel=&quot;nofollow&quot;&gt;&quot;What is a decoupling capacitor and how do I know if I need one?&quot;&lt;/a&gt; for more details.&lt;/p&gt;&#xA;" OwnerUserId="813" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2010-06-09T20:36:43.713" LastActivityDate="2010-06-09T20:36:43.713" CommunityOwnedDate="2010-06-09T18:58:11.150" />
  <row Id="2929" PostTypeId="2" ParentId="1154" CreationDate="2010-06-09T19:48:40.330" Score="1" ViewCount="" Body="&lt;p&gt;There are &quot;digital BLDC motors&quot; like the ones made by ThinGap that make a motor which is both lightweight, small, and has excellent response at extremely low torque (slow, high power) as well as high speeds (RPM) without the need for any gear.&lt;/p&gt;&#xA;" LastActivityDate="2010-06-09T19:48:40.330" />
  <row Id="2930" PostTypeId="2" ParentId="2915" CreationDate="2010-06-09T19:56:25.280" Score="3" ViewCount="" Body="&lt;p&gt;It's not really efficient to go down to 5V and drive the power LEDs individually.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rather, put several LEDs in series and drive them with a buck converter that regulates current. I think there are special LED driver ICs that do exactly that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are uncomfortable with using line voltage directly (you should be), then you can transform it down to some intermediate voltage and rectify / filter it to drive the LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you just want to have some standard lighting the best way is probably to buy some ready made LED lights that you can just screw in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mikrocontroller.net/topic/147925#1383502&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is an interesting circuit where the LEDs in series can be controlled individually, by shorting them with a FET (in german).&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-06-09T19:56:25.280" CommentCount="3" />
  <row Id="2931" PostTypeId="1" AcceptedAnswerId="2936" CreationDate="2010-06-09T20:25:13.547" Score="4" ViewCount="1309" Body="&lt;p&gt;I am looking at buying a 24V power supply. Two of the options are these:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.automationdirect.com/adc/Shopping/Catalog/Power_Products_%28Electrical%29/DC_Power_Supplies/24VDC,_DIN_Rail_Mount_%28RHINO_PS,_PSB,_PSC,_PSM,_PSP_Series%29/PSP24-060S&quot; rel=&quot;nofollow&quot;&gt;PSP24-060S 24 VDC 2.5A (60W) power supply&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.automationdirect.com/adc/Shopping/Catalog/Power_Products_%28Electrical%29/DC_Power_Supplies/24VDC,_DIN_Rail_Mount_%28RHINO_PS,_PSB,_PSC,_PSM,_PSP_Series%29/PSB24-060-P&quot; rel=&quot;nofollow&quot;&gt;PSB24-060-P 24 VDC 2.5A (60W) power supply&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The first offers &lt;em&gt;&quot;foldback short circuit protection&quot;&lt;/em&gt; and &lt;em&gt;&quot;overvoltage protection,&quot;&lt;/em&gt; but it is $85 dollars. The second is much cheaper but does not mention these.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are these types of protection, and how important are they? Are they worth an extra ~$50? Thanks!&lt;/p&gt;&#xA;" OwnerUserId="842" LastActivityDate="2011-06-03T09:35:36.133" Title="What is &quot;foldback short circuit protection&quot; in a power supply?" Tags="&lt;power-supply&gt;&lt;protection&gt;" AnswerCount="6" CommentCount="2" />
  <row Id="2932" PostTypeId="2" ParentId="2272" CreationDate="2010-06-09T20:34:58.800" Score="0" ViewCount="" Body="&lt;p&gt;Often the datasheet for the chip specifically calls out how many and what size capacitors to use.&#xA;If it doesn't,&#xA;&lt;a href=&quot;http://massmind.org/techref/power/decouple.htm&quot; rel=&quot;nofollow&quot;&gt;best practice&lt;/a&gt; is to attach a 1 uF cap to the power pins of each chip,&#xA;plus a larger cap somewhere on the board.&#xA;(Before 2001, best practice used 0.1 uF caps).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;p.s.: have you considered using a 74HC595 or 74HC166 rather than the 74195?&#xA;I suspect that would work just as well, and free up some pins on your Arduino.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-06-09T20:34:58.800" CommunityOwnedDate="2010-06-09T20:34:58.800" />
  <row Id="2933" PostTypeId="2" ParentId="2931" CreationDate="2010-06-09T20:52:08.813" Score="3" ViewCount="" Body="&lt;p&gt;Foldback is when, under increasing load your maximum supply current is reached, and instead of drawing still more current as the load resistance goes down, the voltage 'folds back' instead. Basically you go from a voltage-source like behavior to a current-source like behavior.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-09T20:52:08.813" />
  <row Id="2934" PostTypeId="2" ParentId="2931" CreationDate="2010-06-09T21:00:46.020" Score="0" ViewCount="" Body="&lt;p&gt;With foldback current limiting both current and voltage are cut back once the psu's maximum rated  current is reached. This reduce's power dissipation and thermal stress on components.&lt;/p&gt;&#xA;" OwnerUserId="819" LastActivityDate="2010-06-09T21:00:46.020" />
  <row Id="2935" PostTypeId="1" AcceptedAnswerId="2939" CreationDate="2010-06-09T21:05:17.563" Score="3" ViewCount="92" Body="&lt;p&gt;I am studying for my digital electronics final and one of the major topics is flip flop counters. I need to know how to get the asynchronous counter to preset to 2 before counting to 10. I know how to make it reset (With some well placed NAND gates), but I cant figure out how to get the counter to preset to 2 after reseting. Any help would be much appreciated. Thanks! &lt;/p&gt;&#xA;" OwnerUserId="92" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-06-10T14:56:14.033" LastActivityDate="2010-06-10T14:56:14.033" Title="Flip flop counters" Tags="&lt;homework&gt;&lt;flipflop&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="2936" PostTypeId="2" ParentId="2931" CreationDate="2010-06-09T21:11:58.337" Score="5" ViewCount="" Body="&lt;p&gt;overvoltage protection: protects the input from exceeding the specifications, this would 'attempt' to protect the device from a voltage surge on the DIN rail.  There may also be some protection on the output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;foldback short circuit protection: is a method used in power supplies to protect them from over current situations such as shorting out the output with a wire or attaching too much equipment to the power supply.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With normal (high side) current limiting there is a hard current cap that the supply is limited to to protect it.  As the load resistance approaches 0 the current is limited to a fixed value and the voltage begins to drop.  This can cause a large amount of power dissipation in the supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With foldback protection, as the voltage drops the current limit also drops fairly linearly.  This provides safer protection from short circuits as a &quot;really bad&quot; short will result in very little current draw so the supply won't be sitting there baking at max current.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;overvoltage is what it is, the response time and current carrying capabilities of basic overvoltage circuits aren't going to save you from lightning strikes but may protect you from small screwy surges from the power company.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A dedicated surge/power smoothing device at the source of the DIN power is a better option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;foldback style over current protection is simply better/safer than only having high side current limiting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In both cases they are reliability/durability features, the question of if its worth it, depends on how critical downtime is for the equipment your connecting to it.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-06-09T21:11:58.337" CommentCount="6" />
  <row Id="2937" PostTypeId="2" ParentId="2829" CreationDate="2010-06-09T21:16:12.430" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://opencircuits.com/PCB_Manufacturers&quot; rel=&quot;nofollow&quot;&gt;list of PCB manufacturers on the Open Circuits wiki&lt;/a&gt; has practically every PCB manufacturer I know; many of them also do assembly now.&#xA;There's another list at &lt;a href=&quot;http://chiphacker.com/questions/1893/cheap-pcb-manufacture&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/1893/cheap-pcb-manufacture&lt;/a&gt; .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you considered one of the many companies that focus entirely on PCB assembly?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-06-09T21:16:12.430" CommunityOwnedDate="2010-06-09T21:16:12.430" />
  <row Id="2938" PostTypeId="2" ParentId="824" CreationDate="2010-06-09T21:28:41.813" Score="2" ViewCount="" Body="&lt;p&gt;Closely related question:&#xA;&lt;a href=&quot;http://stackoverflow.com/questions/1624237/multithreading-using-c-on-pic18&quot;&gt;http://stackoverflow.com/questions/1624237/multithreading-using-c-on-pic18&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-06-09T21:28:41.813" CommunityOwnedDate="2010-06-09T21:28:41.813" CommentCount="3" />
  <row Id="2939" PostTypeId="2" ParentId="2935" CreationDate="2010-06-10T02:02:11.520" Score="3" ViewCount="" Body="&lt;p&gt;Common JK flip flops, such as the 7476 have both preset and clear inputs. These force the state of the FF asynchronously, i.e., without waiting for a clock edge. You can use a simple R-C circuit and a schmitt trigger buffer (or inverter) to give you a short (e.g., 50usec) active-low pulse at circuit power on, and feed this signal to the 'preset' inputs of the FF's that should start at '1', and to the 'clear' inputs of the FF's that need to start at 0. (The unused preset or clear of each FF should be pulled up to prevent erratic operation.) The spec sheet for the particular part will tell you how short this pulse can be made.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-10T02:02:11.520" />
  <row Id="2940" PostTypeId="1" AcceptedAnswerId="2971" CreationDate="2010-06-10T02:18:32.447" Score="0" ViewCount="390" Body="&lt;p&gt;I rectified about 14ACV to about 12DCV but 6 ACV simultaneously with 12DCV at the end! It was verified by two different tests, 2W10 is apparently just an unit jammed with 4 diodes. Rs means large resistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Test 1:&lt;/strong&gt; 2W10 rectifier, Rs  ---&gt; OUT: 12.7 DCV and 6.0 ACV&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/File%3aRC_Filter.png&quot; rel=&quot;nofollow&quot;&gt;TEST 2:&lt;/a&gt;&lt;/strong&gt; 4 pcs of &quot;IN4004 pec616&quot;, Rs --&gt; OUT: 12.0 DCV and 6.0 ACV&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Questions&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Why do I get both ACV and DCV? I expected only DCV. &lt;/li&gt;&#xA;&lt;li&gt;How can I filter ACV out? &lt;/li&gt;&#xA;&lt;li&gt;Can ACV be a problem in circuits that only needs the 12DCV?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-06T16:51:52.670" LastActivityDate="2011-03-06T16:51:52.670" Title="Circuit with ACV and DCV after rectification" Tags="&lt;diode&gt;&lt;rectifier&gt;" AnswerCount="2" />
  <row Id="2941" PostTypeId="2" ParentId="2940" CreationDate="2010-06-10T02:41:07.913" Score="0" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;You miss a cap: it charge and discharges so not allowing ACV, use eg &quot;CK868 X 394K 50V A8722&quot;.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Use the Cap in (1). Then, you will get something like 18 DCV and 0 ACV. The 6 ACV and 12 DCV got to 18 DCV.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Probably.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastActivityDate="2010-06-10T02:41:07.913" CommentCount="4" />
  <row Id="2942" PostTypeId="1" CreationDate="2010-06-10T03:03:41.847" Score="1" ViewCount="368" Body="&lt;p&gt;Small ceramic caps are nasty because their markings, such as ceramic monolithic leaded &quot;104M&quot;(yellow-brownish) and epoxy ceramic monolithic leaded &quot;223&quot;, do not reveal max values. Since I do not know their manufacturers, I cannot google for their max voltages or max currents.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What is a typical maximum I for the smallcap?&lt;/li&gt;&#xA;&lt;li&gt;What is a typical maximum V for the smallcap?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T10:26:59.663" LastActivityDate="2011-01-23T10:26:59.663" Title="Maximum current and voltage of Small Ceramic Capacitors?" Tags="&lt;capacitor&gt;&lt;maximum-ratings&gt;" AnswerCount="3" />
  <row Id="2943" PostTypeId="2" ParentId="2942" CreationDate="2010-06-10T03:16:18.607" Score="2" ViewCount="" Body="&lt;p&gt;This is actually completely based on manufacturer. I hope someone corrects me if I am wrong, but just for the parts store I help keep stocked at my school we have very similar devices with maximum of 5, 15, and 50V. There is no way to know, but you will probably be fine under 5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry, but I do not believe there is a simple answer.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-10T03:16:18.607" CommentCount="5" />
  <row Id="2944" PostTypeId="1" AcceptedAnswerId="2949" CreationDate="2010-06-10T05:10:08.317" Score="4" ViewCount="1044" Body="&lt;p&gt;I can not wrap my head around the fact how I can drive a relay (24V, 160ohm) with an tip32a PNP transistor which has TTL inputs from a controller.&#xA;I can easily calculate my resistors when I use the NPN variant (tip31a), but I cannot conceive how to switch the transistor off with just TTL.&#xA;The relay will be powered from 29.4V and has a resistor in series to give the appropriate 24V for the relay. And of course there is a diode over the relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any tips will be greatly appreciated, but please note that I at the moment can not use any transistor but the tip32a.&lt;/p&gt;&#xA;" OwnerUserId="348" LastEditorUserId="348" LastEditorDisplayName="" LastEditDate="2010-07-18T14:00:36.470" LastActivityDate="2011-06-01T11:31:50.157" Title="Switching relay with a PNP and TTL levels" Tags="&lt;relay&gt;&lt;ttl&gt;&lt;pnp&gt;&lt;transistor&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="2945" PostTypeId="1" CreationDate="2010-06-10T07:33:08.230" Score="14" ViewCount="288" Body="&lt;p&gt;Doing mostly micro-controller work, I have never bothered with grounding myself with a wrist-strap or any other implementation.&lt;br&gt;&#xA;Should I be worried about this?&#xA;How serious is ESD when working at my workbench on projects?&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-06-12T08:11:02.863" Title="Should I be worried about electro-static discharge?" Tags="&lt;esd&gt;" AnswerCount="10" FavoriteCount="2" />
  <row Id="2946" PostTypeId="1" CreationDate="2010-06-10T08:09:57.017" Score="4" ViewCount="622" Body="&lt;p&gt;Hi There,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm pretty new to this and am working it out as I go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been working on a circuit design that would allow me to charge my iPhone/iPod classic 120gb from my Car.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am going to use power from the back of the Cigar lighter sockets and put it into this circuit&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The plan is that it will step the voltage down the a usable charging voltage for the iPod.  I have also had to use a voltage divider to provide power to the D+ and D- pins on the USB plug, apparently the phone will not charge with out it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also an audio out section there that will basically use the GND, L Audio and R Audio and this will be wired into a 3.5mm plug to go to my Car sound system.  There is also a 1M Ohm resistor going from pin 21 on the iPod to GND to tell the iPod to shutdown when power is lost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am unable to breadboard this atm as I don't have the voltage regulator or any rated capacitors.  I have drawn up the breadboard design with Fritzing (see links)&#xA;Now to the question, can anyone see any issues with my design???  I am a little worried about how hot the LM7805 will get and also concerned about the common ground if that going to mess with my audio?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dl.dropbox.com/u/5434831/Ipod/Breadboard.png&quot; rel=&quot;nofollow&quot;&gt;Breadboard&lt;/a&gt;&#xA;&lt;a href=&quot;http://dl.dropbox.com/u/5434831/Ipod/Schematic.png&quot; rel=&quot;nofollow&quot;&gt;Schematic&lt;/a&gt;&#xA;&lt;a href=&quot;http://dl.dropbox.com/u/5434831/Ipod/PCB.png&quot; rel=&quot;nofollow&quot;&gt;PCB&lt;/a&gt;&#xA;&lt;a href=&quot;http://dl.dropbox.com/u/5434831/Ipod/Ipod%20Audio_Charge_bom.txt&quot; rel=&quot;nofollow&quot;&gt;Parts list&lt;/a&gt;&#xA;&lt;a href=&quot;http://pinouts.ru/PortableDevices/ipod_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;iPod Pin out&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&#xA;Ben&lt;/p&gt;&#xA;" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:28:57.027" LastActivityDate="2010-08-17T23:28:57.027" Title="iPod Car Charger w/ Audio Out" Tags="&lt;ipod&gt;&lt;charging&gt;&lt;voltage-regulator&gt;&lt;car&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="2947" PostTypeId="2" ParentId="2945" CreationDate="2010-06-10T08:24:30.007" Score="5" ViewCount="" Body="&lt;p&gt;Yes you should/must be worried about this.  The simple case is where you blow the device completely.  This is easy, it just does not work.  The problem is where you damage the IO driver circuit - quite common as this is the bit that is exposed by the pin.  In this case the driver may appear to work for &lt;em&gt;some&lt;/em&gt; of the time. If it has to operate at high speed for part of the time then it may well fail giving intermittent and hard to diagnose faults. (Been there and got several t-shirts!!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is becoming more and more necessary as device geometries are shrinking and core voltages are dropping.  Microcontroller manufacturing processes have often been slightly behind the bleeding edge but as  oxide layer thicknesses are reducing with the device geometry size the required ESD voltage required to damage the device is reduced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bottom line is that you can get away with ignoring ESD precautions for a while but for how long?  As Clint Eastwood said “You've got to ask yourself one question: 'Do I feel lucky?' Well, do ya punk?”&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-06-10T08:24:30.007" CommentCount="3" />
  <row Id="2948" PostTypeId="2" ParentId="2945" CreationDate="2010-06-10T11:01:55.877" Score="3" ViewCount="" Body="&lt;p&gt;You should only skip ESD measures if you can bear the pain ($$) of replacing whatever it is. If you do go un-grounded, though, be aware that device failure is not all-or-nothing. Complete catastrophic failure is probably the best failure mode, because you won't waste as much time trying to figure out what went wrong. Personally, I won't handle anything bigger than 7400 series stuff without a grounding wrist strap.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-10T11:01:55.877" />
  <row Id="2949" PostTypeId="2" ParentId="2944" CreationDate="2010-06-10T11:10:45.010" Score="4" ViewCount="" Body="&lt;p&gt;If you have an open-collector or open-drain type logic output, you can drive a PNP with it, as long as the device is rated to take your supply voltage. In this configuration, use a pull-up resistor from the supply to the base of the PNP to ensure that the PNP defaults to the OFF state. Now tie the base of the PNP to the open-collector logic output through a second resistor, the value of which should pull just enough current from the base of the PNP to drive it to saturation. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The values aren't too hard to work out. The pull-up usually wants to be something large-ish, like 50K or 100K. The logic resistor will see the supply voltage, less the saturation E-B drop of the PNP, less the Vce sat of the logic output. Basically, the supply voltage minus about a volt. From there, knowing the necessary base current to the PNP will let you work out the exact value. (Be sure that to saturate, the necessary PNP base current isn't actually greater than the current-sink capacity of the logic pin!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do not have an OC/OD output, you can buffer a regular output signal with a small NPN transistor, like a 2n2222 or 2n3904 etc. A typical TTL output, driving the base of a small NPN through about 1K to 2.2K will give you the sort of open collector (the collector of the NPN) that I've assumed above.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-10T11:10:45.010" CommentCount="1" />
  <row Id="2950" PostTypeId="2" ParentId="2944" CreationDate="2010-06-10T11:15:44.023" Score="3" ViewCount="" Body="&lt;p&gt;You can't switch the PNP on and off with TTL levels. Since the emitter will be tied to &#xA;29V the base needs to be at 29V to turn it off. You need to do a level shift using&#xA;a second transistor which is either an NPN or an N-channel MOSFET. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using an NPN transistor the current limiting resistor will then be determined by &lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$R = \frac{(29.4 - V_{be1} - V_{ce2})}{I_{b1}}\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;where \$V_{be1}\$ and \$I_{b1}\$ are for the PNP transistor and \$V_{ce2}\$ is for the NPN transistor.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-01T11:31:50.157" LastActivityDate="2011-06-01T11:31:50.157" />
  <row Id="2951" PostTypeId="2" ParentId="2946" CreationDate="2010-06-10T14:58:53.947" Score="2" ViewCount="" Body="&lt;p&gt;You're on the right track.  You could use a switching regulator for better efficiency and less heat.  Adafruit has the &lt;a href=&quot;http://www.ladyada.net/make/mintyboost/faq.html&quot; rel=&quot;nofollow&quot;&gt;official recharging resistor values&lt;/a&gt; in their FAQ.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your schematic is drawn pretty confusingly, though, so I'm not sure if it's right.  Can you label the pin numbers of the dock connector?  Generally a linear regulator is drawn like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://dawn.singlespoon.org.au/7805.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course the function is the same no matter how you draw it, but &lt;a href=&quot;http://opencircuitdesign.com/xcircuit/goodschem/goodschem.html&quot; rel=&quot;nofollow&quot;&gt;readability counts&lt;/a&gt;.  :)  (Also, in a real AC-to-DC power supply, you need to lay out the PCB in this specific way, or you can have issues with ground current noise getting through to the output.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your car voltage will be varying due to different things using the battery at different times, possibly with a fast enough variation to be in the audible frequencies.  Your regulator will be dumping current to ground in order to keep the output at a stable voltage.  Since the difference between the stable output voltage and the fluctuating input voltage is not constant, the current it shunts to ground will also be fluctuating.  Since copper is not a perfect conductor, this ground current flowing through ground traces back into the battery causes the different points along that trace to be at slightly different voltages, varying at audible frequencies.  If another part of the circuit uses a point along that trace as its ground reference, it will see that slight voltage variance as a signal, and the noise will get into the audio (small buzzes or whines or clicks at low volume).  This is why the layout of PCB traces matters.  The ground traces should be laid out in the same shape as the schematic, and your other circuitry should only be connected &quot;after&quot; the output filter capacitor C2:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.dsaprojects.110mb.com/computers/ps_lpt_expander.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also noise from the iPod.  It draws a lot of current while charging, up to 1 A peak, but like any digital/computer device, the current is intermittent (repetitive spikes from refreshing the screen, moving the hard drive head, etc.)  In your schematic, this isn't a problem, since the audio ground is separate and not touching the charging ground.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-06-11T14:39:47.213" LastActivityDate="2010-06-11T14:39:47.213" CommentCount="4" />
  <row Id="2952" PostTypeId="1" AcceptedAnswerId="2955" CreationDate="2010-06-10T15:43:10.457" Score="7" ViewCount="368" Body="&lt;p&gt;I'm experimenting with PIC microcontrollers and various related circuits both on plugboards and simple homemade PCBS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to use various old AC power adaptors I have lying around to power my circuits instead of relying on batteries all the time. I have several old mobile phone chargers for example that give out 5v with 500-1000mA of available power.  ( I realise they are likely unregulated and I'd need a regulator circuit or similar).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My worry is that that they are very cheaply made so what happens if I accidentally short circuit one or try to draw 1000mA from a 500mA supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are they likely protected against such abuse in any way even if only by an internal fuse? Or are they likely to be severely damaged or worse overheat and catch fire or something? Or will they simply deliver their maximum current and continue working?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;None of this is likely to happen, but I want to be safe?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I doubt this affects the answer but this is the UK with a 240v mains supply.&lt;/p&gt;&#xA;" OwnerUserId="710" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-12-09T12:43:40.920" LastActivityDate="2010-12-09T12:43:40.920" Title="What if I overload a cheap AC adaptor?" Tags="&lt;power&gt;&lt;power-supply&gt;&lt;safety&gt;" AnswerCount="7" CommentCount="2" FavoriteCount="1" />
  <row Id="2953" PostTypeId="2" ParentId="2945" CreationDate="2010-06-10T15:46:58.827" Score="10" ViewCount="" Body="&lt;p&gt;I know most people will yell at me for this. And I do honestly take some ESD precautions day to day, but ESD is a vary rare failure mode in modern electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For my background, I take part in teaching the capstone design class at my university, and they have to build many many things, in 4 phases. Many students(almost all) will not listen to us when we warn of ESD precautions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have seen at-least 10 projects where they blamed ESD, only one that was probably ESD. In that project a board was working and a student walked up and touched it and you could audibly hear the shock as he discharged static electricity. This failed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the other 9, they blamed ESD only to find at a later point that they had a design flaw that was not easy to track down and only reared it's ugly head in very specific conditions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have heard many more than 10 projects blame esd and find a problem within hours, but only 10 have sworn they should be allowed to continue to the next phase because it worked but ESD fried it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On that note, when you are working, you should check datasheets. Most modern devices have ESD protection, rated to some voltage using HBM(Human-body model). If this is below 1kV it is quite susceptible. if it is rated to 2k, it is semi-resilient, for the most part you would have to be dumb to damage it. if it is 4k, it is pretty resilient. if it is 8k you will hear a spark before you hurt it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be wary of those that blame ESD, but wear a wrist strap just in case. you can get a mat and strap for almost nothing.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-10T15:46:58.827" CommentCount="3" />
  <row Id="2954" PostTypeId="2" ParentId="2945" CreationDate="2010-06-10T15:52:37.520" Score="3" ViewCount="" Body="&lt;p&gt;My experience seems to be that you'd probably be ok for months or years (depending on the exact components and how much static charge you build up in your environment) but it's not just a theoretical problem and one day it will bite you. Probably at the most inconvenient time and the most expensive way to fix.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And it's not very difficult to protect against it so just get into the habit of doing it. I've not taken my own advice there, but I really should and do intend to!&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2010-06-10T15:52:37.520" CommentCount="1" />
  <row Id="2955" PostTypeId="2" ParentId="2952" CreationDate="2010-06-10T15:54:13.297" Score="8" ViewCount="" Body="&lt;p&gt;You could try using a resettable fuse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Resettable_fuse&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Resettable_fuse&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tinyurl.com/37reex3&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/37reex3&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-10T15:54:13.297" CommentCount="4" />
  <row Id="2956" PostTypeId="2" ParentId="2903" CreationDate="2010-06-10T16:01:25.210" Score="1" ViewCount="" Body="&lt;p&gt;In many cases, a reference design will show you how to use a manufacturer's own device. So, they only stand to gain if you use the design and buy their devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I am not a lawyer.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-10T16:01:25.210" />
  <row Id="2957" PostTypeId="2" ParentId="2946" CreationDate="2010-06-10T16:10:42.597" Score="2" ViewCount="" Body="&lt;p&gt;This looks proper. If you pull the D+ and D- lines to the proper voltage, as it seems you are, it tells the iPod/iPhone to pull current. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I look at the list of the pins, the ones you linked. It tells me that pin 21 needs to be connected to 68k for the iphone to know how to map out audio. Otherwise I do not think that the iphone will output audio through the connector. Otherwise you will need to use the headphone jack.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-10T16:10:42.597" CommentCount="2" />
  <row Id="2958" PostTypeId="2" ParentId="2952" CreationDate="2010-06-10T16:44:37.483" Score="4" ViewCount="" Body="&lt;p&gt;The transformers are probably made to open circuit internally when they overheat.  It's probably required by UL regulations, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When we do overheat tests on big power amps, the transformers will go open circuit and then you have to let them cool for an hour or more and they'll self-reset.  I don't know what the actual component is since it's presumably buried inside the coils of wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheap wall wart transformers probably don't self-reset, but they are &quot;likely&quot; to at least have some form of internal protection so they don't start on fire.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-07-17T05:36:34.733" LastActivityDate="2010-07-17T05:36:34.733" CommentCount="3" />
  <row Id="2959" PostTypeId="2" ParentId="227" CreationDate="2010-06-10T16:51:23.030" Score="0" ViewCount="" Body="&lt;p&gt;Sparkfun now has a $19 module, the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9913&quot; rel=&quot;nofollow&quot;&gt;BTM-182&lt;/a&gt;, probably similar to the BTM-222 listed in another answer.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-06-10T16:51:23.030" />
  <row Id="2960" PostTypeId="2" ParentId="2942" CreationDate="2010-06-10T17:33:12.357" Score="3" ViewCount="" Body="&lt;p&gt;ceramic through-hole caps are usually rather high in voltage rating, i don't think i've seen one in person under 25V except maybe those with high capacitance, &gt;=1uF and they are usually 16V although i know some with smaller voltage ratings are available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A simple subjective measure is size.  For a given capacitance and type of construction (ceramic in this case) the smaller the package the lower the voltage rating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This rule also means that if you can find a comparable part on digikey to what you have in hand, the voltage rating is probably the same, there aren't too many manufacturers tricks left in the bag when it comes to through-hole ceramics.  Of course the only way to be sure is to try it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for current.  Ceramic capacitors are rarely, if ever, specified with a maximum current.  If the current flowing through the cap is large enough to matter your problem will most likely be the impact of the series resistance of the cap on your circuit or it generating enough heat to push the cap outside its thermal limits. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need assorted capacitors for your lab i'd look at the cap kits on digikey, there are a bunch of them and they usually come in little &quot;fishing box&quot; like containers that keep them all sorted for you.  You also gain the advantage of knowing who made the caps and get actual specs which isn't true of the assortment packs at places like radioshack.  You could also get one of those slide bin storage things from a hardware store and make your own capacitor assortment.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-06-10T17:33:12.357" />
  <row Id="2961" PostTypeId="1" AcceptedAnswerId="2964" CreationDate="2010-06-10T18:37:28.133" Score="1" ViewCount="289" Body="&lt;p&gt;Hey, I came across this Low Volatage Shunt regulator on a Hobby RC forum, I am trying to figure out how the resistor Values are Calculated, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rcgroups.com/forums/attachment.php?attachmentid=210702&quot; rel=&quot;nofollow&quot;&gt;http://www.rcgroups.com/forums/attachment.php?attachmentid=210702&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the one shown here, uses a TL431 regulator and a 2N700 transistor connected with Lithium Polymer batteries of value 11.1v or 7.4v, the circuit trips the alarm at a particular voltage in this case it is 9v when an 11.1v battery is used and 6v when a 7.4v battery is used. If anyone can help this would be super awesome thanks&lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-06T22:24:24.627" LastActivityDate="2011-02-06T22:24:24.627" Title="Low Voltage Shunt Regulator" Tags="&lt;battery&gt;&lt;voltage-regulator&gt;&lt;monitor&gt;" AnswerCount="1" />
  <row Id="2962" PostTypeId="1" AcceptedAnswerId="2963" CreationDate="2010-06-10T18:45:15.863" Score="4" ViewCount="291" Body="&lt;p&gt;I'm trying to pick an op-amp and I'm having trouble figuring out if the op-amp needs a positive and a negative power supply or if I can connect it to ground and the positive supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What do I need to look for in the datasheet?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, where do I find the &quot;drop-out&quot; of the output compared to the rail voltage?&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-06-10T21:26:50.050" Title="OpAmps - Single Supply or Dual?" Tags="&lt;op-amp&gt;&lt;power-supply&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="2" />
  <row Id="2963" PostTypeId="2" ParentId="2962" CreationDate="2010-06-10T19:47:55.780" Score="7" ViewCount="" Body="&lt;p&gt;Most if not all op-amps can be used in either configuration.  Voltage is relative, and &quot;ground&quot; is just an arbitrary potential that you assign the value of 0 volts.  There are op-amps &quot;optimized&quot; for one configuration or the other, but they can be used in either.  &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=LT1006&quot; rel=&quot;nofollow&quot;&gt;This op-amp&lt;/a&gt;, for instance, is &quot;optimized for single supply operation&quot;, and they emphasize features like:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Input Voltage Range Extends to Ground&lt;/li&gt;&#xA;&lt;li&gt;Output Swings to Ground while Sinking&#xA;Current&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;but &quot;Specifications at ±15V are also provided.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Op-amps meant for single-supply often have rail-to-rail outputs, which will usually be featured on the front page of the datasheet.  To find the &quot;drop-out&quot;, look for a graph like &quot;Maximum Output Voltage Swing vs Load Resistance&quot; in &lt;a href=&quot;http://semicon.njr.co.jp/njr/hp/fileDownloadMedia.do?_mediaId=123&quot; rel=&quot;nofollow&quot;&gt;this datasheet&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;All op amps have two power pins. In most cases, they are labeled VCC+ and VCC-, but sometimes&#xA;  they are labeled VCC and GND. This is an attempt on the part of the data sheet author to&#xA;  categorize the part as a split-supply or single-supply part. &lt;strong&gt;However, it does not mean that the op&#xA;  amp has to be operated that way&lt;/strong&gt;— it may or may not be able to operate from different voltage&#xA;  rails. Consult the data sheet for the op amp, especially the absolute maximum ratings and&#xA;  voltage-swing specifications, before operating at anything other than the recommended&#xA;  power-supply voltage(s).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ti.com/sc/docs/psheets/abstract/apps/sloa058.htm&quot; rel=&quot;nofollow&quot;&gt;A Single Supply Op Amp Circuit Collection&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-06-10T19:59:56.737" LastActivityDate="2010-06-10T19:59:56.737" CommentCount="2" />
  <row Id="2964" PostTypeId="2" ParentId="2961" CreationDate="2010-06-10T20:04:52.753" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.fairchildsemi.com/ds/TL%2FTL431.pdf&quot; rel=&quot;nofollow&quot;&gt;Datasheet&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R1 is chosen to set Vref on the TL431 to its nominal value of 2.495V.  The output of the TL431 is dependent on the values of R1 and R2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R4 is chosen to protect the Piezo from seeing more than 7V which is its limit.  To figure out the value of R4 you have to consider the voltage drop of Vds on the FET and the current the piezo draws.  From this calculate R4 to produce enough of a voltage drop to keep the voltage across the piezo to 7V or less.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-06-10T20:04:52.753" />
  <row Id="2965" PostTypeId="2" ParentId="2942" CreationDate="2010-06-10T20:28:24.810" Score="0" ViewCount="" Body="&lt;p&gt;All of my personal small caps in &lt;a href=&quot;http://www.futurlec.com/ValuePacks.shtml&quot; rel=&quot;nofollow&quot;&gt;Futurlec's value packs&lt;/a&gt; are well-labelled between 50V-onwards, btw very price-worthy sets for beginners. The lowest is 1pF with 50V max. My scbool has unlabelled small caps. My teacher said that you can safely test the caps until 5V and even higher because, according to him, ceramic caps do not explode rather burn slowly.&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-11T22:41:10.570" LastActivityDate="2010-06-11T22:41:10.570" CommentCount="4" />
  <row Id="2966" PostTypeId="2" ParentId="2844" CreationDate="2010-06-10T20:57:19.400" Score="0" ViewCount="" Body="&lt;p&gt;To get any angle, you need to measure gravity's acceleration in both X- and Y- directions.  subtract out the middle voltage (2.5V) so that zero is &quot;no acceleration.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you can find the angle with arcsin(y/x).  But that is annoying to use, because of the division, and because the sign is ambiguous, so what you really want the C function atan2(y,x).  atan2() gets the sign right for all 360 degrees.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Off-topic, since you aren't using a micro: If you are looking for atan2() to use on a microcontroller, there is an atan2() generator on my website: &lt;a href=&quot;http://vivara.net/cgi-bin/cordic.cgi&quot; rel=&quot;nofollow&quot;&gt;http://vivara.net/cgi-bin/cordic.cgi&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-06-10T20:57:19.400" CommentCount="1" />
  <row Id="2967" PostTypeId="1" CreationDate="2010-06-10T21:02:17.603" Score="1" ViewCount="142" Body="&lt;p&gt;I desoldered a comp, HY-05 Electro-magnetic sound generator, from a broken motherboard. Its DCV is  3~8V, operating frequency 2400 plus or minus 200 Hz. I can get a small metallic sound with the operating voltage probably because the frequency is wrong. How can I adjust the frequency in the power supply of 50Hz? If the question is bizarre, it may be that the comp is just broken.&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-11T16:33:03.213" LastActivityDate="2010-06-11T16:33:03.213" Title="How to get higher frequency from DC power supply?" Tags="&lt;beginner&gt;&lt;sound&gt;&lt;frequency&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="2968" PostTypeId="2" ParentId="2962" CreationDate="2010-06-10T21:26:50.050" Score="4" ViewCount="" Body="&lt;p&gt;depending on the design of the op amp the drop out of the op amp won't be constant.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example just because the drop is 1.5V with +/- 15V supplies doesn't mean it will be 1.5V with 0/5V supplies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LF347 you mentioned for instance does not have a constant drop out across input voltage options.  Theres a graph in the datasheet showing this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The actual output swing will vary with a few things:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;output current (which can also be presented as output voltage swing vs load resistance)&lt;/li&gt;&#xA;&lt;li&gt;temperature&lt;/li&gt;&#xA;&lt;li&gt;input voltage (this can usually be tied into the output current)&lt;/li&gt;&#xA;&lt;li&gt;frequency and gain&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You have to consider all these in determining your maximum output swing and these numbers are usually defined in the graphs in the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you look for an op amp for a specific purpose you can get away with generic op amps but you will find better performance in parts designed for the task at hand.  The op amp designers usually attempt to mitigate some the variations i've listed above for particular applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance usually rail to rail op amps can drive the output to the rails when the output is open circuit but you will still find they will not drive all the way to the rails when driving a real load and could be substantially under the rails if a large amount of current relative to their rating is sourced/sunk.  Additionally rail to rail op amps usually have low drive capabilities.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-06-10T21:26:50.050" />
  <row Id="2969" PostTypeId="2" ParentId="2967" CreationDate="2010-06-10T22:53:51.110" Score="4" ViewCount="" Body="&lt;p&gt;According to &lt;a href=&quot;http://www.hycomdevice.com.tw/comm/upfile/d_030728_06135.pdf&quot; rel=&quot;nofollow&quot;&gt;the datasheet&lt;/a&gt;, you should give it a square wave with a duty cycle of 50% at a frequency of 2400 Hz with an amplitude of 5 V. You could make that with a 555 timer chip, 2 resistors, and 2 capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More details here: &lt;a href=&quot;http://www.csgnetwork.com/ne555timer2calc.html&quot; rel=&quot;nofollow&quot;&gt;http://www.csgnetwork.com/ne555timer2calc.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-10T22:53:51.110" CommentCount="4" />
  <row Id="2970" PostTypeId="2" ParentId="2967" CreationDate="2010-06-11T00:33:26.727" Score="3" ViewCount="" Body="&lt;p&gt;You could hook it to the output line of a PC serial port, set the port for 4800,n,8,1 and transmit 0x55 bytes at it all day. If you draw out the waveform you'll see that back to back 0x55 bytes will result in a square wave at half the bit rate. Using 8,n,1 settings means it takes 10 bits to send a byte, so at 4800bps, that's 480 chars/second, so each 0x55 that you send would get you a hair more than 2msec of 2400Hz square wave.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it is indeed 'electromagnetic' then it really shouldn't matter about the polarity, but you should use limiting resistors to keep from exceeding the voltage ratings. To keep the peak-to-peak voltage down where it would be with a single-ended 5V square wave, you'd need to trim the +/-12V swings of the serial port down to +/-2.5V .. or if you had an RS-232C port (i.e., already TTL level) you wouldn't have to mess with resistors at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually, if this part is like a tiny dynamic speaker (which the 40ohms suggests), then you should probably worry more about keeping under the &lt;em&gt;current&lt;/em&gt; maximum. It's doubtful that the internal insulation would be remotely close to breakdown at 8V, but it is probable that the fine gauge wire would melt if you push too much current through it. If you have to use resistors, start large and work your way down.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-06-11T00:44:16.517" LastActivityDate="2010-06-11T00:44:16.517" />
  <row Id="2971" PostTypeId="2" ParentId="2940" CreationDate="2010-06-11T00:56:29.020" Score="3" ViewCount="" Body="&lt;p&gt;I'm going to go out on a limb and take a guess that your other question about reading AC and DC relates to this question ..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're feeding regular AC through a full-wave rectifier (the four diodes you mention), the resulting waveform may well give you funny readings on ordinary DVMs. The waveform will resemble the absolute value of a sine wave, and still has enough AC character that a $50 DVM will likely show you a significant reading, albeit an incorrect one. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a DVM to try to figure out a circuit like this gets you into the murky territory of the 'true RMS' problem. DVMs are all over the map with regard to how well they perform at giving correct RMS readings. And even if you have a meter that's dead on, this number may not tell you what you really want to know. In situations like this, an oscilloscope is the preferred instrument, and you can get PC/USB based ones for under $100 that will perform admirably at AC line frequencies.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-11T00:56:29.020" CommentCount="2" />
  <row Id="2972" PostTypeId="1" CreationDate="2010-06-11T04:41:49.847" Score="3" ViewCount="250" Body="&lt;p&gt;How can I configure an xbee pro module in broadcast mode?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are using AT8051 controller..plz help..&lt;/p&gt;&#xA;" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-11T08:41:02.630" LastActivityDate="2010-06-11T08:41:02.630" Title="xbee pro broadcast configuration" Tags="&lt;xbee&gt;&lt;configuration&gt;" AnswerCount="1" />
  <row Id="2973" PostTypeId="2" ParentId="2945" CreationDate="2010-06-11T05:40:54.903" Score="1" ViewCount="" Body="&lt;p&gt;It interesting how people say something to the effect of &quot;I don't follow ESD precautions, but you should&quot; It's OK ... we never live up to our own ideals. I think your question is like &quot;should I get seven to eight hours of sleep every night?&quot; The answer is &quot;yes, getting enough sleep is important ... but sometimes it doesn't happen&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ESD precautions are particularly important in manufacturing settings where you are making a product and you don't want to deal with field repairs. Typically damage from ESD will not be immediately apparent, but might cause a product to fail after months or years of use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a good thing to be in the habit of using basic ESD precautions. That being said, I wouldn't be terribly stringent with yourself about it for most basic work. If you occasionally pick up a chip without a wrist strap on, don't feel like you've committed a sin.&lt;/p&gt;&#xA;" OwnerUserId="227" LastActivityDate="2010-06-11T05:40:54.903" CommentCount="2" />
  <row Id="2974" PostTypeId="2" ParentId="2972" CreationDate="2010-06-11T08:39:54.143" Score="3" ViewCount="" Body="&lt;p&gt;Have you checked the manual? Here's a link from google.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ssdl.stanford.edu/ssdl/images/stories/AA236/0708A/Lab/Rover/Parts/xbeeproproductmanual.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ssdl.stanford.edu/ssdl/images/stories/AA236/0708A/Lab/Rover/Parts/xbeeproproductmanual.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Section 2.4.2 states that to send a broadcast message, set the destination address to 0xFFFF.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-11T08:39:54.143" CommentCount="1" />
  <row Id="2975" PostTypeId="2" ParentId="227" CreationDate="2010-06-11T08:46:35.970" Score="0" ViewCount="" Body="&lt;p&gt;If you're looking for a project, you might consider trying out the new Bluetooth support in the LUFA USB stack for AVRs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This lets you plug a standard HCI-USB bluetooth dongle into a USB enabled AVR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It won't work with Arduino, but it should run on the Teensy boards, which have some support for the Arduino IDE.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://fourwalledcubicle.com/blog/archives/275&quot; rel=&quot;nofollow&quot;&gt;http://fourwalledcubicle.com/blog/archives/275&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's probably more work than you're looking for. But, it is cheap.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-11T08:46:35.970" />
  <row Id="2976" PostTypeId="2" ParentId="2945" CreationDate="2010-06-11T11:36:35.723" Score="3" ViewCount="" Body="&lt;p&gt;If you don't take ESD precautions, you risk damaging things. The probability of damaging something varies all over the place (temperature, humidity and floor surface being important factors), and it's entirely possible that you'll never damage anything (or at least not such that you'd notice).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I HAVE damaged devices before with ESD. Heck, I once killed a serial port (something that's PROTECTED against ESD because the pins are hanging out there) by shocking to the pins. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, that's not to say that you have to have the be-all and end-all of ESD protection. Even if you don't go for the full array with ionizers and wrist straps and conductive tile flooring, try to get an grounded mat for your bench, and try to touch them mat when you sit down. You'll tend to brush the mat with your hands as you are working, and this will keep you mostly at the same potential as the parts on the mat and keep the possibility of problems to a minimum.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2010-06-11T11:36:35.723" CommentCount="3" />
  <row Id="2977" PostTypeId="2" ParentId="2945" CreationDate="2010-06-11T14:21:13.023" Score="1" ViewCount="" Body="&lt;p&gt;We never had any problems with ESD neither in prototyping nor in production and we don't use any wrist-wraps or other stuff. OTOH we don't have any carpets and do not wear wool or synthetic clothing. Because of this we never had a static discharge from you bodies at work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would suggest fighting with static build-up at the source if possible (check you clothes,  furniture and humidity) and after you've done this, you may buy some human grounding equipment for double protection.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-06-11T14:21:13.023" CommentCount="4" />
  <row Id="2978" PostTypeId="1" CreationDate="2010-06-11T19:44:04.560" Score="3" ViewCount="200" Body="&lt;p&gt;I have taken apart a digital weight scale and on the circuit are two pins labelled 'test'. When connecting this to the soundcard of my PC I can see it is a digital signal (high/lows), but I don't know how to read/interoperate it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anybody knows how to do this? I'm pretty sure I once saw a free/open-source program that was able to read different kind of data protocols. Anybody know it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a recording when pressing up/down on the scale, perhaps it helps: &lt;a href=&quot;http://lars.stonerocket.co.uk/images/electronics/weegschaal.wav&quot; rel=&quot;nofollow&quot;&gt;http://lars.stonerocket.co.uk/images/electronics/weegschaal.wav&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="323" LastActivityDate="2010-06-12T03:15:35.693" Title="Bit/data stream unknown. How to figure out?" Tags="&lt;data&gt;&lt;logic&gt;&lt;electronics&gt;&lt;sensor&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="2979" PostTypeId="2" ParentId="2945" CreationDate="2010-06-11T19:53:10.177" Score="0" ViewCount="" Body="&lt;p&gt;I once saw someone touch the (house)radiator to discharge before working inside a PC. Does that really help?&lt;/p&gt;&#xA;" OwnerUserId="323" LastActivityDate="2010-06-11T19:53:10.177" CommunityOwnedDate="2010-06-11T19:53:10.177" CommentCount="3" />
  <row Id="2980" PostTypeId="2" ParentId="2978" CreationDate="2010-06-11T21:07:45.360" Score="3" ViewCount="" Body="&lt;p&gt;You could try, &lt;a href=&quot;http://xoscope.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;xoscope&lt;/a&gt;, &lt;a href=&quot;http://sigrok.org&quot; rel=&quot;nofollow&quot;&gt;sigrok&lt;/a&gt;, &lt;a href=&quot;http://www.sump.org/projects/analyzer/client/&quot; rel=&quot;nofollow&quot;&gt;SUMP&lt;/a&gt; or &lt;a href=&quot;http://gtkwave.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;gtkwave&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-11T21:07:45.360" />
  <row Id="2981" PostTypeId="2" ParentId="2945" CreationDate="2010-06-11T22:27:42.937" Score="0" ViewCount="" Body="&lt;p&gt;If you're a hobbyist, then you don't really need to care about ESD protection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're building prototypes for an actual project, then you &lt;strong&gt;should&lt;/strong&gt; be concerned about ESD protection...but in reality you probably won't bother too much, aside from periodically touching the nearest convenient grounded piece of metal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're building production equipment that will be sold to paying customers, then you &lt;strong&gt;must&lt;/strong&gt; be concerned with ESD protection.  That means a strap &lt;em&gt;and&lt;/em&gt; a mat &lt;strong&gt;at all times&lt;/strong&gt; in an area with no carpet.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-06-11T22:27:42.937" />
  <row Id="2982" PostTypeId="2" ParentId="2978" CreationDate="2010-06-11T23:17:21.933" Score="2" ViewCount="" Body="&lt;p&gt;Just shooting in the dark but a two pin interface for something like a scale is probably a serial signal.  My first try would be 9600 baud with 3.3v levels. If that did not work then I would try different baud rates.&lt;/p&gt;&#xA;" OwnerUserId="540" LastActivityDate="2010-06-11T23:17:21.933" />
  <row Id="2983" PostTypeId="2" ParentId="2978" CreationDate="2010-06-12T02:02:10.193" Score="3" ViewCount="" Body="&lt;p&gt;Looking at it with audacity (thanks, Mark!) you can see that there are definite bit cells of about 3.5msec each. The basic waveform looks like serial data at that rate, but you can see these little spikes superimposed on the basic waveform, which are probably clock signals. This would be what you'd expect if one of the lines is a clock and the other is data, and you measured across them. You could try doing what Mark suggested - find a ground point on the circuit and connect that to the sound card ground, and then feed one signal to the left channel and one to the right. But it's easy enough to separate the clock from the data visually in the sound editor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, it doesn't look like there's a whole lot of data there. There are basically two sequences, these being a simple ..10101010.., and a slightly more complicated one that looks like '01101001' repeated over and over. But these are just the raw bits. It could be something like an NRZ scheme, where '01' means 0 and '10' means 1. Or the other way round. But no matter how you slice it, there just doesn't seem to be much complexity in there.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-12T02:02:10.193" CommentCount="4" />
  <row Id="2984" PostTypeId="2" ParentId="2952" CreationDate="2010-06-12T02:15:39.573" Score="6" ViewCount="" Body="&lt;p&gt;Wall warts are constructed as disposable commodity items, and they're usually 'potted', which means that the case is entirely filled with a solidified epoxy or epoxy-like substance. I think they just count on a fine-gauge wire burning up somewhere in that block of stuff. There's no oxygen available, and as soon as the fault goes open circuit, the show's over. Anyway, I've never seen one of these recover, though they can sometimes provide a bit more current than they're marked for. (..and more often than not, put out more voltage than they're marked for as well)&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-12T02:15:39.573" CommentCount="5" />
  <row Id="2985" PostTypeId="2" ParentId="1887" CreationDate="2010-06-12T02:58:55.133" Score="1" ViewCount="" Body="&lt;p&gt;To make that kind of stepper rotate, you need to produce what amounts to a two-phase (90deg apart) system of currents in the windings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your stepper has legs labeled A and B for one winding, and C and D for the other, you'd want to cycle through the following pattern of currents&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;+A -B  and  +C -D    .. where +A -B means current into A, returned on B, etc.&#xA;+A -B  and  -C +D&#xA;-A +B  and  -C +D&#xA;-A +B  and  +C -D&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Each cycle through those four states will take the motor through one &lt;em&gt;electrical&lt;/em&gt; revolution. Steppers usually have a large number of poles, so it will take some number of cycles before you get one complete mechanical revolution of the motor's shaft.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you have two H-bridges, one for the AB winding, the other for the CD winding. This is four controller bits per winding, eight in all. (It would not be premature to optimize this down to four bits right away, but I'm going to skip doing that for just a moment)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Referring to the high-side drive for leg A as AH, and the low side as AL, and so on, you can produce the above sequence of currents by turning on the drive transistors this way&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;AH AL  BH BL  CH CL  DH DL&#xA; 1  0   0  1   1  0   0  1&#xA; 1  0   0  1   0  1   1  0&#xA; 0  1   1  0   0  1   1  0&#xA; 0  1   1  0   1  0   0  1&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;By now it should be obvious that the H and L controls for a given half-bridge are always the negation of one another. In fact, if you ever drive the high and low sides of the same half-bridge on, you'll smoke the bridge, so it's safer to output just the one control bit per half-bridge, and use a hardware inverter to get the complementary control. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should also notice that the sequence never turns on both high-side drives (or both low-side ones) for a given winding. The B drive is the complement of the A drive. So you could in fact get this down to a mere two bits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think if I had to drive this kind of a motor from a micro-controller, I might use a 7474 dual D flip-flop (D-FF) as a kind of external 2-bit register with dual rail outputs. Each data input of the 7474 would be hooked to its own micro output bit. A third bit from the micro would drive the clock. Then, Q1 would drive AH and BL, Q1* drives AL and BH, and similarly, Q2 feeds CH and DL, while Q2* goes to CL and DH. Each FF bit effectively sets the direction of the current in one of the windings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, in software, you just output the two bits to set the current directions the way you want, and clock them into the FF by driving its clock low and then high again. Then your two-phase motor sequence is&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;clk AB CD&#xA;0   1  0    ; be sure to get D-FF inputs ready with the 0 state of the clock&#xA;1   1  0    ; b/c the 7474 will latch the values on the positive edge.&#xA;0   0  0    ; you want the data lines stable during the clock edge.&#xA;1   0  0&#xA;0   0  1&#xA;1   0  1&#xA;0   1  1&#xA;1   1  1&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;So, at a cost of three bits, you can step the motor, although there's always a current through both coils, so you can't free-wheel the motor.. unless you use a 4th bit to act as a global enable for both sides of both bridges.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-12T02:58:55.133" CommentCount="1" />
  <row Id="2986" PostTypeId="2" ParentId="2978" CreationDate="2010-06-12T03:15:35.693" Score="2" ViewCount="" Body="&lt;p&gt;If it is any kind of standard protocol, it sounds like you might be able to hook up a &lt;a href=&quot;http://code.google.com/p/the-bus-pirate/&quot; rel=&quot;nofollow&quot;&gt;Bus Pirate&lt;/a&gt; to it and try different protocols.&lt;/p&gt;&#xA;" OwnerUserId="836" LastActivityDate="2010-06-12T03:15:35.693" CommentCount="1" />
  <row Id="2987" PostTypeId="2" ParentId="2952" CreationDate="2010-06-12T07:04:45.777" Score="2" ViewCount="" Body="&lt;p&gt;I think endolith and JustJeff are right for most adapters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However I have seen that some drop in voltage when you rise the current to much, &#xA;they seem to have a fix energy that they can deliver. &#xA;Don't how those where designed thou. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you find one of those it will not overheat and burn, but you design will not get the specified voltage and may malfunction. &lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-06-12T07:04:45.777" />
  <row Id="2988" PostTypeId="2" ParentId="2952" CreationDate="2010-06-12T07:26:44.883" Score="4" ViewCount="" Body="&lt;p&gt;Most of the newer ones have switchers in them, with a stabilised output. They are short-circuit protected and almost indestructible. 5V ones are available from most suppliers, and are very useful.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-12T07:26:44.883" />
  <row Id="2989" PostTypeId="1" CreationDate="2010-06-12T08:02:32.757" Score="4" ViewCount="458" Body="&lt;p&gt;How can one build a device that presents itself as a mass storage device to a machine via usb, then whatever files are transfered to it, get sent to a remote location via wifi (can be ad hoc). Something like the eye-fi but that can send any files. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something similar to these devices :&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.infinitec.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.infinitec.com/&lt;/a&gt; (Why can't use : Will be released first of july which is too late for me )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.hsti.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.hsti.com/&lt;/a&gt; (Why can't use : Remote file system is mounted read only)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you&lt;/p&gt;&#xA;" LastActivityDate="2010-06-14T16:08:22.180" Title="Transfer files from mass storage device to other machine via wifi" Tags="&lt;wifi&gt;&lt;usb&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="2990" PostTypeId="2" ParentId="2945" CreationDate="2010-06-12T08:11:02.863" Score="1" ViewCount="" Body="&lt;p&gt;The tricky thing with ESD is that even when it doesn't seem to affect anything, every small discharge &lt;em&gt;does&lt;/em&gt; cause &lt;em&gt;some&lt;/em&gt; damage, whether it's pitting of the silicon, vaporizing a little bit of the bonding wire, removing some of the metalization on one of the semiconductor layers, or some other effect, it will physically alter the product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In most cases, most uses of a given part won't be measurably altered by the change.  Most people overengineer their designs so they aren't using them anywhere near their limit, so there's a huge margin where a pitted part will work just fine for more uses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Over time repeated discharges will change the part enough that it will behave slightly out of spec - but perhaps not enough to notice without thorough testing.  This is really the worst case scenario - since it works most of the time, then it's really difficult to find out why it's not working when it fails.  It's far better for a part to fail completely so it's easy to track down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternately, the one small discharge that happened once damages it enough that when you do use it to full capacity, it then fails. The happens, of course, once you've deployed it in the field and it's a pain to get it back and troubleshoot it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This kind of damage cannot be detected without removing the silicon from the package and inspecting it, or, in cases where the damage is hidden inbetween layers, by slicing the silicon into very thin sheets where the damage is likely to occur.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So yes, everyone here is right when they say, &quot;I rarely follow ESD precautions and I have never seen an issue.&quot;  They will never see it, and when it does fail there will be no reason to believe it was ESD related because there was no recent ESD event.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But that doesn't mean I'm going to trust the products that come from their bench, either.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-06-12T08:11:02.863" CommentCount="1" />
  <row Id="2991" PostTypeId="2" ParentId="2952" CreationDate="2010-06-12T08:20:28.097" Score="4" ViewCount="" Body="&lt;p&gt;Here in the Netherlands you can get used adapters for very cheap in charity shops. From telephone chargers (3V) to printer adapters (18V). Just clean them up and if they work your good to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Overloaded adapters can stink a lot.&lt;/p&gt;&#xA;" OwnerUserId="323" LastActivityDate="2010-06-12T08:20:28.097" />
  <row Id="2992" PostTypeId="1" AcceptedAnswerId="3032" CreationDate="2010-06-12T13:00:41.883" Score="3" ViewCount="630" Body="&lt;p&gt;I need to measure the peak to peak voltage and DC offset of a 1Hz to 1MHz sine/triangle wave. The  signals amplitude varies between 0 and 2Vpp and the offset can vary between -2v and +5v. I will be using an Atmega16 to do the A/D. The Atmega16 has an 8 channel 10-Bit ADC with 50-200KHz sample rate @10-Bit resolution. Taking multiple samples for cycle is obviously out of the question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I was thinking of doing was to sample two different versions of the signal eg connect the signal to both a negative peak detector and a precision rectifier and connect those circuits outputs to two different ADC channels and then from result of these conversions (ie the  negative and positive peaks) calculate the the vpp and DC offset. Obviously the signals will need to scaled and level shifted before being applied to the controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im not really sure if this will work at all, there must be a far simpler and more sophisticated way to do this that I haven't thought of.&lt;/p&gt;&#xA;" OwnerUserId="819" LastActivityDate="2010-06-15T21:41:01.043" Title="Measuring VPP and DC offset of a 1Hz - 1MHz signal using MCU" Tags="&lt;voltage-measurement&gt;&lt;measurement&gt;&lt;microcontroller&gt;&lt;ac&gt;&lt;high-frequency&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="2993" PostTypeId="2" ParentId="2992" CreationDate="2010-06-12T13:29:23.543" Score="4" ViewCount="" Body="&lt;p&gt;I think you're taking the right approach with splitting the signal and measuring each parameter separately.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, you measure the DC offset voltage by low-pass filtering the signal and feeding the output into the A/D. Because the signal swings across such a huge range of frequencies, you'll either need a filter with an adaptive cutoff frequency, or you'll have to put up with a long lag in your readings. You might be able to do something clever by only filtering the signal enough in hardware to get it down to 20 kHz or so; then you could calculate the average value in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I don't think that it speeds up your response, but it might be easier than building a filter with a changing cutoff frequency, which is not trivial.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, you go after the amplitude. You level shift, rectify, and scale the input voltage so that it spans the range of the Atmega16 A/D. You could do this with two fast opamps and a rectifier. I think the order is important, or at least you have to be careful about what voltage your rectifier is referenced to.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-12T13:29:23.543" CommunityOwnedDate="2010-06-12T13:29:23.543" CommentCount="7" />
  <row Id="2995" PostTypeId="2" ParentId="2989" CreationDate="2010-06-12T13:44:12.503" Score="4" ViewCount="" Body="&lt;p&gt;You could buy an embedded Linux board with an SD card, a usb port, and a wifi card. Write a script that uses the &lt;a href=&quot;http://en.wikipedia.org/wiki/Rsync&quot; rel=&quot;nofollow&quot;&gt;rsync&lt;/a&gt; command to synchronize the contents of the SD card with your remote server over an SSH connection. Set the &lt;a href=&quot;http://en.wikipedia.org/wiki/Cron&quot; rel=&quot;nofollow&quot;&gt;cron&lt;/a&gt; daemon to execute the rsync script once per minute (or maybe less frequently, depending on the speed of the connection).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would have to generate an SSH key pair and put the public key on the remote server so that the board could login without a person having to type in a password.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For hardware, I'd try something like one of the following:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.hawkboard.org/&quot; rel=&quot;nofollow&quot;&gt;Hawkboard&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;Beagleboard&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.embeddedarm.com/products/board-detail.php?product=TS-7552&quot; rel=&quot;nofollow&quot;&gt;TS-7552&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-12T13:44:12.503" CommentCount="4" />
  <row Id="2996" PostTypeId="2" ParentId="2918" CreationDate="2010-06-12T15:23:17.427" Score="6" ViewCount="" Body="&lt;p&gt;One resource that I refer people to quite frequently is &lt;a href=&quot;http://www.alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf&quot; rel=&quot;nofollow&quot;&gt;David Jones' PCB Design Tutorial&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lots of good info on component placement, routing, tolerances, layers, etc...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just to reiterate what others have said, and D. Jones says as well, it all starts with component placement.  Be willing to rip up, move components, start over, etc...  Don't get lazy or stubborn and try to force that round peg into a square hole.  If the routing becomes difficult, there is probably a way to move or rotate parts so that suddenly it becomes easier.&lt;/p&gt;&#xA;" OwnerUserId="221" LastActivityDate="2010-06-12T15:23:17.427" CommentCount="1" />
  <row Id="2997" PostTypeId="2" ParentId="1151" CreationDate="2010-06-12T15:27:09.087" Score="4" ViewCount="" Body="&lt;p&gt;Like thisismyrobot, I tend to use a very sharp blade and a straight edge to &quot;score &amp;amp; snap&quot; boards with straight edges.  Generally when I'm doing a board at home, rectangular boards are fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I'm doing a circular or odd shaped board for an enclosure, I'm usually sending it out anyway, at which point I have the board house do it for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As others have said, if you do anything (grinding, sawing) that generates dust, be damn careful, use breathing protection.  Preferably do it outside in an open area.&lt;/p&gt;&#xA;" OwnerUserId="221" LastActivityDate="2010-06-12T15:27:09.087" />
  <row Id="2998" PostTypeId="2" ParentId="2918" CreationDate="2010-06-12T16:08:47.427" Score="2" ViewCount="" Body="&lt;p&gt;Im just going to list some tips here in no particular order:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Determine your power/ground strategy first.  Whenever possible use a power and ground plane.  If sticking to a 2 sided board use a ground pour on the bottom and remember to remove any orphaned copper.  Your goal is to always have the shortest path to ground.  Higher frequency signals will follow the lowest inductance path to ground, not the lowest resistance.  You may need to add additional decoupling capacitors.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Do your layout on a grid, make the grid size a multiple of your smallest trace size.  Make larger traces a multiple of your grid.  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Place components with special attention to any high frequency signals or buses with high capacitance, any which requires you to consider transmission line effects.  Some examples: I2C bus that connects to lots of chips (3-4+), even if its a low speed bus.  SPI buses @ 1MHz or greater especially, I2S buses, clock distribution, crystal oscillators, USB, ethernet, memory buses, etc. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Autorouters suck.  They are useful if you have 25 GPIO signals that are just on-off control and you really really don't care where they go, even then you'll likely scratch your head as you look at what it did.  Never let it route power or signal lines.  I've used altiums, orcads and eagles, they are all pretty bad.  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Never, ever, unless you really really know what you are doing, use a split ground plane, even if the ADC/DAC datasheet says you need separate analog and digital grounds.  Pay attention to the ground return paths but do no split the plane. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If you have to use a split power plane due to areas of multiple supply voltages:  No signal trace can cross the split on an adjacent layer.  Doesn't matter what the trace is or what it does, do not cross that split.  Put keep outs on the effected layers to enforce this.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;When placing components, it can help to layout the component and its closely associated circuitry first, then move them onto the board as a group.  For example with a switching power supply the IC itself is often very small but you need to consider the layout of the external support circuitry as well which often needs to be kept very close together with controlled current paths.  So layout the entire piece of the circuit outside the board dimensions first so you have a good idea of how much space it actually needs.  Do the same for all IC's as even decoupling caps can take up more space than you think they will.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-06-12T18:12:00.397" LastActivityDate="2010-06-12T18:12:00.397" />
  <row Id="2999" PostTypeId="2" ParentId="1151" CreationDate="2010-06-12T16:16:19.467" Score="3" ViewCount="" Body="&lt;p&gt;I prefer a 'nibbler', at least for small jobs it's ideal. I don't know if they all have a square cutting bit, but mine does, and it's fairly easy to cut in a straight line just free-handing it. The downside is that it takes a swath about an 1/8&quot; wide, but for many purposes this is not a problem. Just google 'nibbler tool'. I got mine at a local retailer (RS) ten years ago, it's held up well.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-12T16:16:19.467" />
  <row Id="3000" PostTypeId="2" ParentId="2915" CreationDate="2010-06-12T16:31:47.923" Score="5" ViewCount="" Body="&lt;p&gt;buy one -- for example Digikey sells &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=T977-P6P-ND&quot; rel=&quot;nofollow&quot;&gt;5V regulated power supplies for about US$7&lt;/a&gt; and unregulated ones for less than this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would probably be hard pressed to make something less expensive that is safe.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-06-12T16:31:47.923" CommentCount="4" />
  <row Id="3001" PostTypeId="1" CreationDate="2010-06-12T20:15:44.770" Score="4" ViewCount="222" Body="&lt;p&gt;I have a mac and am looking for some instructions/tutorials on how to start using the Bluetooth Mate with a Lilypad board. If anyone has any experience with this that they would like to share I would appreciate it!&lt;/p&gt;&#xA;" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-13T19:52:36.577" LastActivityDate="2010-06-14T00:06:41.977" Title="BluetoothMate and Lilypad board." Tags="&lt;lilypad&gt;&lt;bluetooth&gt;&lt;mac&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="3002" PostTypeId="2" ParentId="2036" CreationDate="2010-06-12T22:58:09.770" Score="4" ViewCount="" Body="&lt;p&gt;Scanalogic 2 is, well, less expensive than many other logic analyzer, but it's worth the 59€ i think&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ikalogic.com/scanalogic2/&quot; rel=&quot;nofollow&quot;&gt;http://www.ikalogic.com/scanalogic2/&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-06-12T22:58:09.770" CommentCount="1" />
  <row Id="3003" PostTypeId="2" ParentId="2036" CreationDate="2010-06-13T13:12:35.550" Score="2" ViewCount="" Body="&lt;p&gt;Open Workbench Logic Sniffer&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought it and it works great, I'm not sure if they are still preorder but I think it is exactly what you're asking about. :D&lt;/p&gt;&#xA;" OwnerUserId="850" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-08-26T15:29:57.690" LastActivityDate="2010-08-26T15:29:57.690" CommentCount="2" />
  <row Id="3004" PostTypeId="2" ParentId="1869" CreationDate="2010-06-13T15:58:41.193" Score="0" ViewCount="" Body="&lt;p&gt;Simply increasing passive capacitance can only cause the current phase angle to asymptotically approach the limit of leading by 90 degrees. However, in op-amp circuits they can be used to eliminate inductors, but this has more to do with the topology of the feedback circuit than any innate ability to shift phase.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-13T15:58:41.193" />
  <row Id="3005" PostTypeId="2" ParentId="3001" CreationDate="2010-06-13T22:45:53.983" Score="3" ViewCount="" Body="&lt;p&gt;I am having a hard time answering your questions because of a few reasons:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;I don't know your history&lt;/li&gt;&#xA;&lt;li&gt;I don't use a Mac&lt;/li&gt;&#xA;&lt;li&gt;I have never used the BluetoothMate or Lilypads&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;With that said, I am going to take a stab to see if I can help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bluetooth modules like the BluetoothMate tunnel serial just like FTDI USB chips do. This means that you can write serial on one end and it shows up on the other end just like if you had a serial cable connected to your computer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a PC, you would power on the bluetooth module, then from the PC search for the bluetooth module. After connecting, Windows adds a virtual COM port that can be accessed through a terminal such as PuTTY.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On Unix based systems, I believe I remember it being a device such as /dev/ttyUSB0.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully this helps some.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-14T00:06:41.977" LastActivityDate="2010-06-14T00:06:41.977" CommentCount="0" />
  <row Id="3006" PostTypeId="2" ParentId="1262" CreationDate="2010-06-14T04:09:15.140" Score="4" ViewCount="" Body="&lt;p&gt;I see blalor already has an excellent answer for the purpose of Atmel fuses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To answer the follow-on question of &quot;are they physical fuses or are they software programmable&quot;, the answer is neither.&#xA;All modern Atmel and Microchip microcontrollers store the &quot;fuse bits&quot; in nonvolatile memory cells -- physically the same as SLC flash cells.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you use a chip programmer to download a new program into the microcontroller program Flash memory, it also erases and re-programs those fuse bit memory cells.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the software running on a microcontroller cannot change the fuse bits -- not even if you are using a &quot;self-programming&quot; microcontroller -- i.e., a microcontroller that allows bootloader software running on it to re-program its own program flash memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some Atmel processors (especially the low-power ones) allow software running on them to change the clock source on-the-fly by writing to some configuration register -- but whenever they are reset (or the power goes away and then comes back), they go back to using the clock source specified in the fuse bits.&#xA;The only way to change those fuse bits is with a chip programmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Decades ago, those configuration bits (and the program memory as well) were actually stored in fuses -- a bunch of thin strands of metal; appropriate ones were selectively &quot;blown&quot; by applying 12 V until the metal melted and disconnected and the bit became non-conductive.&#xA;As you have probably figured out, that make the microprocessor one-time programmable (OTP) -- the only way to un-blow a fuse was to throw the entire microprocessor away, pull out a fresh new one, and start all over.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We still call those configuration bits &quot;fuse bits&quot; for historical reason -- much like we often call the program memory &quot;ROM&quot; (even though it's not really &quot;read-only&quot; on a self-programming microcontroller), and we have &quot;solid-state relays&quot; that have no moving parts, and &quot;telephone companies&quot; that spend only a small fraction of their time actually dealing with sound, and &quot;computers&quot; that spend most of their time displaying pictures and playing music rather than, you know, computing numbers.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-06-14T04:09:15.140" />
  <row Id="3007" PostTypeId="2" ParentId="2989" CreationDate="2010-06-14T10:51:35.197" Score="1" ViewCount="" Body="&lt;p&gt;If you're looking to just &quot;get the job done&quot;, I'd go with Linux as suggested. It'll work and be fast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're trying to build something with a low bill of materials, you could consider a microcontroller talking USB mass storage, connected to some non-wifi radio. Then, bridge the radio to ethernet/wifi at the other end. Won't be anywhere near as fast as wifi though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One approach could be a couple of &lt;a href=&quot;http://shop.jeelabs.com/products/jeenode&quot; rel=&quot;nofollow&quot;&gt;jeenodes&lt;/a&gt;. One running &lt;a href=&quot;http://www.obdev.at/products/vusb/index.html&quot; rel=&quot;nofollow&quot;&gt;V-USB&lt;/a&gt; to talk mass-storage, the other hooked to &lt;a href=&quot;http://shop.jeelabs.com/products/ether-card&quot; rel=&quot;nofollow&quot;&gt;ethernet&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-14T10:51:35.197" CommentCount="1" />
  <row Id="3008" PostTypeId="1" AcceptedAnswerId="3104" CreationDate="2010-06-14T12:21:50.253" Score="3" ViewCount="615" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recently acquired a number of components including an Arduino Mega microcontroller and a uM-FPU V3.1 Floating Point Coprocessor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a breadboard I have built the circuit shown on Page 2 of the document uMFPU-V3_1 Arduino.pdf from the Micromega website.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Same diagram also here:)&#xA;&lt;a href=&quot;http://www.arduino.cc/playground/uploads/Code/Fpu-connect1.jpg&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/uploads/Code/Fpu-connect1.jpg&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am having some difficulty in getting the circuit to function as expected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PC details: Window Vista 64,&#xA;Microcontroller: Arduino Mega (genuine),&#xA;Arduino IDE: Version 0018&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The documentation (uMFPU-V3_1_Arduino.pdf) says to download the support files (uMFPU-V3_1-Arduino.zip) and place the folders (Fpu, FpuSerial, Spi) in the hardware/libraries subdirectory of the Arduino application directory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems that the directory structure of the Arduino IDE has recently changed?  Earlier versions of the IDE apparently had the libraries located as suggested in the document above, but the current version 0018 of the Arduino IDE seems to have the /libraries subdirectory located directly in the Arduino application directory.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sketches provided in the documentation (sample.pde, graph.pde etc.) seem to only compile in the IDE version 0018 with the FPU libraries placed in the new directory location.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the libraries in the new location, the example sketches (sample.pde, graph.pde etc) can be compiled without error and uploaded to the Arduino.  At the moment, when the sketches run on the microcontroller, the Arduino IDE Serial Monitor only responds with the message 'Sample' or 'Graph' and nothing else.  There is no indication of a connection to the FPU with version details, no display of the results of FP calculations or even the message 'uM-FPU not detected'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also have tried using older versions of the Arduino IDE (0016) (with the libraries placed in the location suggested in the documentation) on another computer with Windows XP (not 64bit) and the result seems to be the same.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully someone may have some ideas or suggestions about where the problem may be?  Could it be a faulty FPU chip or the Arduino board itself?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" LastActivityDate="2010-06-20T04:54:04.227" Title="Arduino Mega/uM-FPU coprocessor" Tags="&lt;arduino&gt;" AnswerCount="1" />
  <row Id="3009" PostTypeId="1" CreationDate="2010-06-14T12:44:24.653" Score="3" ViewCount="443" Body="&lt;p&gt;In my application I have an issue with ground loops and to solve this I require to have devices isolated from their drivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The system operates with a 13.56MHz signal and a wide bandwidth is not of concern.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Capacitive coupling between transformer windings is the greatest concern.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How should I select a transformer 1:1 ratio that will provide the best isolation and allow operation at 13.56MHz?&lt;/p&gt;&#xA;" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-06-29T06:31:06.597" LastActivityDate="2010-06-29T06:31:06.597" Title="Isolation Transformers (Capacitive Coupling)" Tags="&lt;groundloops&gt;&lt;capacitor&gt;&lt;transformer&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="3010" PostTypeId="2" ParentId="3009" CreationDate="2010-06-14T14:48:20.017" Score="3" ViewCount="" Body="&lt;p&gt;The gap they put between the two coils is the most important part. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The larger the gap, the less efficient your transformer will be due to magnetic fields that do not share between the coils. The larger the gap, the larger the isolation. This also stop arcing from high high voltage differences, it both puts a larger dielectric and increases the distance in the epsilon * A / d equation for capacitance. Make sure your coils have some sort of magnetic core to increase efficiency. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are really trying to keep &lt;strong&gt;capacitive coupling&lt;/strong&gt; to a minimum by making sure the two devices have a &lt;strong&gt;shield between the coils&lt;/strong&gt;. A shield grounded will stop them from capacitivly coupling to each other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Secondly, some differential noise can couple through if you are working about differential noise, then you actually need to put a filter on the feed side, this will be a decent bit of work and probably not something you need to deal with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope I helped, let me know if there is anything else I can help with.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-14T16:17:56.063" LastActivityDate="2010-06-14T16:17:56.063" CommentCount="7" />
  <row Id="3011" PostTypeId="2" ParentId="2989" CreationDate="2010-06-14T16:08:22.180" Score="0" ViewCount="" Body="&lt;p&gt;If I may make a twist on @Joby's answer, I think you might be able to use a WiShield on an Arduino to get you the wireless aspect. Then I bet there's someone who's made a MassStorage Shield (if not, that might be a good idea for me to try and pull off someday...)&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-06-14T16:08:22.180" CommentCount="1" />
  <row Id="3012" PostTypeId="1" CreationDate="2010-06-14T21:38:07.960" Score="4" ViewCount="356" Body="&lt;p&gt;My New term is going to start a couple of weeks from now. And as it goes in colleges here the first few months of the semester are easy. I have lots and lots of spare time to learn something new. I like to learn things by myself. But have not done much since a couple of months due to submissions and finals. I would like to dive into something exciting to learn this new semester.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My main interests are into uControllers, intelligence, analog electronics and robotic locomotion. Can you please recommend something which would take a few months to learn and would add to my engineering skills?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;&lt;br&gt;&#xA;My really lazy question has provided the community with a nice list of things to do once you have some knowledge under your belt. The problem is not with starting things, but continuing them. I faced that problem and also many before or after me. I propose we continue adding to this list. Here is a small summary of what I gathered.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Start with BEAM robotics: It has been a very facinating branch of robotics which uses only descreet electronic elements and it also has possiblity of adding intelligence using Nv Nets. But the problem is its still in its research phases and there are not many resources. I had to use the web archive to get to some papers and I dont think thats a very good sign.&lt;/li&gt;&#xA;&lt;li&gt;Making your own PCBs: This is different and you wont get to learn this in class. So if you have to access to cheap PCB manufacturer I propose this to you.&lt;/li&gt;&#xA;&lt;li&gt;Learn C: C is one of the oldest and most widespread languages and still used in industry&lt;/li&gt;&#xA;&lt;li&gt;Learn ARM&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-03T14:05:56.733" LastActivityDate="2011-02-03T14:05:56.733" CommunityOwnedDate="2010-06-14T22:03:25.460" Title="What should I learn?" Tags="&lt;development&gt;" AnswerCount="5" CommentCount="6" FavoriteCount="2" />
  <row Id="3013" PostTypeId="2" ParentId="3012" CreationDate="2010-06-14T21:55:45.617" Score="2" ViewCount="" Body="&lt;p&gt;I vote for BEAM Robotics!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/groups/beam/pool/show/&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; kind of thing.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-14T21:55:45.617" CommunityOwnedDate="2010-06-14T22:03:25.460" CommentCount="2" />
  <row Id="3014" PostTypeId="2" ParentId="3012" CreationDate="2010-06-14T22:01:31.890" Score="3" ViewCount="" Body="&lt;p&gt;Get your Amateur (HAM) Radio License :-). &lt;a href=&quot;http://www.arrl.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.arrl.org/&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a EE who just graduated, I got a 90% on the practice test without any studying. It should be relatively simple to take the test if you have the background, or the drive.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-14T22:13:37.203" LastActivityDate="2010-06-14T22:13:37.203" CommunityOwnedDate="2010-06-14T22:01:31.890" CommentCount="2" />
  <row Id="3015" PostTypeId="2" ParentId="3012" CreationDate="2010-06-14T22:06:22.537" Score="8" ViewCount="" Body="&lt;p&gt;Learn to program seriously in C. Nothing will benefit you more broadly as an electrical/computer engineer.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-15T20:42:11.910" LastActivityDate="2010-06-15T20:42:11.910" CommunityOwnedDate="2010-06-14T22:06:22.537" CommentCount="10" />
  <row Id="3016" PostTypeId="1" CreationDate="2010-06-14T22:49:13.857" Score="3" ViewCount="371" Body="&lt;p&gt;What are some good methods to populate moderate numbers of pcbs (20-100), without the aid of a pick and place machine?&lt;/p&gt;&#xA;" OwnerUserId="582" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-08T00:49:32.340" LastActivityDate="2011-01-08T00:49:32.340" Title="Methods for batch populating PCBs without a pick and place" Tags="&lt;pcb&gt;&lt;pcb-assembly&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="3018" PostTypeId="1" AcceptedAnswerId="3026" CreationDate="2010-06-15T04:04:03.247" Score="3" ViewCount="182" Body="&lt;p&gt;I would like to load TinyOS on CC2420 radio motes to operate on certain communication protocols (e.g. epidemic routing, probabilistic routing, etc.). However, I have no prior experience in programming motes to perform the protocols I want. I'm just wondering about the most applicable resources for reference and how difficult (if not impossible) was implementing such mentioned protocols. It would be great to hear from you. Thanks in advance!&lt;/p&gt;&#xA;" OwnerUserId="854" LastActivityDate="2010-06-15T15:49:16.110" Title="Implementing Communication Protocols on CC2420 motes powered by TinyOS" Tags="&lt;embedded&gt;&lt;radio&gt;&lt;antenna&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="3019" PostTypeId="2" ParentId="2641" CreationDate="2010-06-15T04:23:55.417" Score="6" ViewCount="" Body="&lt;p&gt;How cheap do FPGAs get?&#xA;According to Newark, the cheapest FPGAs are around $10 (the lowest-end Altera Cyclone and lowest-end Xilinx Spartan).&#xA;They might have enough capacity to run a simple 8-bit CPU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you might expect, even simple (i.e., without a MMU) 32-bit CPUs require about 4 times the FPGA resources of an 8 bit CPU.&#xA;FPGAs with barely enough resources to run such a simple 32-bit CPU cost around $14.&#xA;My understanding is that uCLinux has been ported to some of these FPGA soft CPUs (such as the NIOS II/e) -- you might find uClinux adequate for your purposes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Full-fledged Linux requires a CPU with a MMU (such as the NIOS II/f).&#xA;A 32-bit CPU with a MMU requires about 4 times the FPGA resources of a 32-bit CPU without a MMU -- the reasons for this are not so obvious.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I can tell from the &#xA;&lt;a href=&quot;http://www.xilinx.com/tools/microblaze.htm&quot; rel=&quot;nofollow&quot;&gt;Xilinx Microblaze page&lt;/a&gt;,&#xA;the Microblaze soft CPU only runs on Xilinx FPGAs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Linux has already been ported to several other soft CPUs.&#xA;If you want to run Linux on some other company's FPGAs,&#xA;you might want to look at the Linux ports listed at&#xA;&lt;a href=&quot;http://www.1-core.com/library/digital/soft-cpu-cores/&quot; rel=&quot;nofollow&quot;&gt;&quot;Soft CPU Cores for FPGA&quot;&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Several of these soft CPUs -- including a MMU -- will fit on a Xilinx Spartan XC3S400A ( $17 from Avnet ).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've heard that some 32-bit soft CPUs -- including a MMU -- are pretty easy to set up as &quot;dual core&quot; on a $20 FPGA chip.&#xA;Those that follow &quot;Jan's Razor&quot; might attempt to squeeze in a dozen or so 8-bit CPUs on the same chip instead.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-06-15T04:23:55.417" CommunityOwnedDate="2010-06-15T04:23:55.417" CommentCount="3" />
  <row Id="3020" PostTypeId="1" CreationDate="2010-06-15T05:54:26.380" Score="2" ViewCount="342" Body="&lt;p&gt;Hi guys.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have the &lt;a href=&quot;http://www.libelium.com/squidbee/index.php?title=New_GPRS_module_for_Arduino_%28Hilo_-_Sagem%29&quot; rel=&quot;nofollow&quot;&gt;Hilo module&lt;/a&gt; running ok on standalone mode through XP hyper terminal.&#xA;Can send SMS and calls ok. Hilo baud rate is set at 9600.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was reading on a forum that the serial library on the Arduino is only good for 9600 baud. I have dropped the rate down to this but does not make any difference. The serial from the arduino is currently running at 9600. I can't get the arduino to download the code to the libelium shield. The code will download with shield removed. But when i plug the shield in and press the reset button nothing happens with the hilo module.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have the led on pin 13 as a visual cue that the code runs ok and it is. When trying to download from the Ardunio i get the out of sync general error. There are heaps of examples of this error on line but no solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I remove the USB Arduino links on the Hilo shield I can get the download to work without sync errors but will not load into the Hilo of course. There may be a problem with these links, not sure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anybody can give me some advice I would be very grateful. I do not have any power supply current issues as per the libelium notes. I have added the capacitor and the supply is fine. Running version 18 arduino IDE. Using Duemilanove with 328 chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks, Greg&lt;/p&gt;&#xA;" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-24T21:42:12.000" LastActivityDate="2010-08-24T21:42:12.000" Title="Arduino Libelium Hilo Shield Problems" Tags="&lt;arduino&gt;&lt;arduino&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="3021" PostTypeId="2" ParentId="3020" CreationDate="2010-06-15T08:14:18.740" Score="1" ViewCount="" Body="&lt;p&gt;From the documentation, it looks like the Hilo shield is acting like a serial modem. Rather than &quot;download code&quot; to the shield, you should be using the Arduino to send &quot;AT&quot; commands to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's sample code &lt;a href=&quot;http://www.libelium.com/squidbee/index.php?title=New_GPRS_module_for_Arduino_%28Hilo_-_Sagem%29&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-15T08:14:18.740" CommentCount="5" />
  <row Id="3022" PostTypeId="2" ParentId="3018" CreationDate="2010-06-15T08:35:31.887" Score="0" ViewCount="" Body="&lt;p&gt;Usually, routing protocols are developed in &lt;a href=&quot;http://www.cs.berkeley.edu/~pal/research/tossim.html&quot; rel=&quot;nofollow&quot;&gt;simulators&lt;/a&gt; first to test scability and contention issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're interested in jumping straight into hardware hacking, you might like:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.freaklabsstore.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.freaklabsstore.com/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://daveshacks.blogspot.com/2010/01/im-me-hacking.html&quot; rel=&quot;nofollow&quot;&gt;http://daveshacks.blogspot.com/2010/01/im-me-hacking.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-15T08:35:31.887" />
  <row Id="3023" PostTypeId="2" ParentId="3016" CreationDate="2010-06-15T08:39:28.360" Score="3" ViewCount="" Body="&lt;p&gt;Avoid through hole parts. Don't put components on both sides of the PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apply solder paste with a stencil, arrange components, bake/reflow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(update)&#xA;Here's a great video series from a guy who built 100 little dev boards in 10 days.&#xA;&lt;a href=&quot;http://fletchtronics.net/blog/100-bumble-bs-10-days&quot; rel=&quot;nofollow&quot;&gt;http://fletchtronics.net/blog/100-bumble-bs-10-days&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-18T15:37:15.487" LastActivityDate="2010-06-18T15:37:15.487" CommentCount="4" />
  <row Id="3024" PostTypeId="2" ParentId="3020" CreationDate="2010-06-15T13:58:23.167" Score="0" ViewCount="" Body="&lt;p&gt;Your comment about Arduino only being good for 9600 is interesting, and something I haven't heard before. It turns out that for reliable UART communication, you need a timing accuracy of less than +/- 2%. If you look into the datasheet of any AVR with a hardware UART, they have tables in the section detailing the UART Baud Rate Register (UBBR). These tables tell you, for specifical crystal choices, what the timing errorsr are for common baud rates. It is a good idea to pick an operating point in these tables with 0% timing error if at all possible... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now to my knowlege, the Arduino operates at 16MHz and is based on the ATMEGA168 (manual &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2545.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;). You can see that the 16MHz crystal speed is not a &quot;optimal&quot; speed for UART operation, and all the &quot;common&quot; baud rates are within tolerance, but the &quot;odd&quot; crystal speeds like 3.6864MHz and 14.7456are the best. Here's an excerpt from the manual:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;There are two possible sources for the&#xA;  receivers baud rate error. The&#xA;  Receiver’s system clock (XTAL) will&#xA;  always have some minor instability&#xA;  over the supply voltage range and the&#xA;  temperature range. When using a&#xA;  crystal to generate the system clock,&#xA;  this is rarely a problem, but for a&#xA;  resonator the system clock may differ&#xA;  more than 2% depending of the&#xA;  resonators tolerance. The second&#xA;  source for the error is more&#xA;  controllable. The baud rate generator&#xA;  can not always do an exact division of&#xA;  the system frequency to get the baud&#xA;  rate wanted. In this case an UBRRn&#xA;  value that gives an acceptable low&#xA;  error can be used if possible.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I don't know if this is the problem you're running into, but it's a possibility...&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-06-15T13:58:23.167" CommentCount="6" />
  <row Id="3025" PostTypeId="2" ParentId="3012" CreationDate="2010-06-15T14:06:56.033" Score="5" ViewCount="" Body="&lt;p&gt;I'd try to learn things that you won't learn in classes. For me, the biggest target is how to lay out your own PCB with a microcontroller on it. It's not particularly hard to do, but it's intimidating if you haven't done it before. Once you've made a few boards, it's easy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd recommend picking something small, on the scale of an Arduino or a Lilypad, and try making a board. You can start with the free version of Eagle for PCB layout; use batchpcb.com for ultra-cheap (and ultra-slow) PCB manufacture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe an Arduino shield with a cool peripheral on it? Then you could learn to program the Arduino to control it.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-15T14:06:56.033" CommunityOwnedDate="2010-06-15T14:06:56.033" CommentCount="15" />
  <row Id="3026" PostTypeId="2" ParentId="3018" CreationDate="2010-06-15T15:49:16.110" Score="1" ViewCount="" Body="&lt;p&gt;First, I agree with Joby, you should probably start in a simulator. The reason is simple, there is a large cost to program every device on a network with new software and then collecting data about the cause of a failure can be very hard when it just stops working.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; TinyOS&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;On that note, you possibly know this already, or you have accepted routing protocols and you want to test how they function in a real world situation. This is very doable. &lt;a href=&quot;http://docs.tinyos.net/index.php/CC2420&quot; rel=&quot;nofollow&quot;&gt;Lets start by clicking over to all of the information on their wiki about their stack&lt;/a&gt;. This explains what decisions they made when implementing the stack and how it was designed to allow you to easily change out their protocol with your own communications stack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks like they have done a great job of properly implementing a stack and you should be relatively able to replace the protocol with what you need. Now the challenge here is what I have run into when implementing a wireless protocol. If the algorithm is complex, it can be very very hard to find the root of a problem. At my job we implemented a proprietary 900MHz protocol, let me forewarn of two problems we hit.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Possible Problems&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Processing power, try to stay up with how much time you are burning. We found when we started using complicated load equations, and I use the term complicated with reference to how fast an MSP430 runs, the lag on the system and it's response was prohibitive to using a great algorithm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When we did make errors in our implementation we found that a minor error could stay invisible for hours, days or in one case weeks. This should be solved by using a tried and proven algorithm. The problem we had was our algorithm worked well, but in a certain case the load on the microcontroller was so great it caused large problems, which we exacerbated by our systems response.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://docs.tinyos.net/index.php/TOSSIM&quot; rel=&quot;nofollow&quot;&gt;Take the time to play with your code in the simulator that tinyOS has&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me know if there is anything I can add or make more clear. if you put it in a comment I can try to edit in more info.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-15T15:49:16.110" />
  <row Id="3027" PostTypeId="1" CreationDate="2010-06-15T15:55:50.073" Score="22" ViewCount="1177" Body="&lt;p&gt;A common question, here and elsewhere. Is C++ suitable for embedded systems?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microcontrollers? RTOSes? Toasters? Embedded PCs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is OOP useful on microcontrollers?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does C++ remove the programmer too far from the hardware to be efficient?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should Arduino's C++ (with no dynamic memory management, templates, exceptions) be considered as &quot;real C++&quot;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Hopefully, this wiki will serve as a place to contain this potential holy war)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;:-)&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="625" LastEditorDisplayName="" LastEditDate="2010-06-18T20:12:29.430" LastActivityDate="2011-05-13T16:06:01.193" CommunityOwnedDate="2010-06-15T15:55:50.073" Title="Is C++ suitable for embedded systems?" Tags="&lt;c++&gt;&lt;embedded&gt;" AnswerCount="11" CommentCount="7" FavoriteCount="11" />
  <row Id="3028" PostTypeId="2" ParentId="3027" CreationDate="2010-06-15T16:12:11.757" Score="9" ViewCount="" Body="&lt;p&gt;In my experience, C++ is usually ill-suited to small embedded systems. By which I mean, microcontrollers and OS-less devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many C++ OOP techniques rely on dynamic memory allocation. This is often missing in small systems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;STL and Boost really demonstrate the power of C++, both are huge in footprint.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C++ encourages the programmer to abstract away the machine, where in constrained systems it has to be embraced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Last year, I ported a commercial remote desktop product to mobile phones. It was written in C++ and ran on Windows, Linux and OSX. But, it relied heavily on STL, dynamic memory and C++ exceptions. To get it going on WinCE, Symbian and OS-less environments a C rewrite was the sanest option.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-21T00:48:13.640" LastActivityDate="2010-06-21T00:48:13.640" CommunityOwnedDate="2010-06-15T16:12:11.757" CommentCount="9" />
  <row Id="3029" PostTypeId="2" ParentId="3027" CreationDate="2010-06-15T16:18:24.507" Score="4" ViewCount="" Body="&lt;p&gt;Yes, the issue with C++ is the increased footprint of the code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In some systems you are counting bytes, and in that case you are going to have to accept a cost of running that close to the bounds of your systems are increased development cost of C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, even in C, for a well designed system you need to keep everything encapsulated. Well designed systems are hard, and C++ give programmers a place for a very structured and controlled method of development. There is a cost to learn OOP, and if you want to switch to it you much accept it, and in many cases the management would rather continue with C and not pay the cost, as it is hard to measure the results of a switch that increases productivity. You can see an article by &lt;a href=&quot;http://www.ganssle.com/articles/alingo.htm&quot; rel=&quot;nofollow&quot;&gt;embedded systems guru Jack Ganssle here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dynamic memory management is the devil. Not really, the devil is auto-route, dynamic memory management works great on a PC, but you can expect to restart a PC every few weeks at least. &lt;a href=&quot;http://www.ganssle.com/articles/proactive.htm&quot; rel=&quot;nofollow&quot;&gt;You will find that as an embedded system continues to run for 5 years that dynamic memory management can really get screwed up and actually start failing.&lt;/a&gt; Ganssle discusses things like stack and heap in his article.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some things in C++ that are more prone to causing problems and use many resources, removing dynamic memory management and templates are big steps to keep the footprint of C++ closer to the footprint of C. This is still C++, you do not need dynamic memory management or templates to write good C++. I did not realize they removed exceptions, I consider exceptions an important part of my code that I remove in the release, but use until that point. In field testing I can have exceptions generate messages to inform me of an exception being caught.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-16T18:11:56.907" LastActivityDate="2010-06-16T18:11:56.907" CommunityOwnedDate="2010-06-15T16:18:24.507" />
  <row Id="3030" PostTypeId="2" ParentId="3027" CreationDate="2010-06-15T16:52:13.017" Score="3" ViewCount="" Body="&lt;p&gt;I thought &lt;a href=&quot;http://www.realworldtech.com/forums/index.cfm?action=detail&amp;amp;id=110618&amp;amp;threadid=110549&amp;amp;roomid=2&quot; rel=&quot;nofollow&quot;&gt;this anti-C++ rant&lt;/a&gt; by Linus Torvalds was interesting.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;One of the absolute worst features of&#xA;  C++ is how it makes a lot of things so&#xA;  context-dependent - which just means&#xA;  that when you look at the code, a&#xA;  local view simply seldom gives enough&#xA;  context to know what is going on.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;He's not talking about the embedded systems world, but Linux kernel development. To me, the relevance comes from this: C++ requires understanding a larger context, and I can learn to use a set of object templates, I don't trust myself to remember them when I have to update the code in a few months.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(On the other hand, I'm currently working on an embedded device using Python (not C++, but using the same OOP paradigm) that will have exactly that problem. In my defense, it's an embedded system powerful enough to be called a PC 10 years ago.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-15T16:52:13.017" CommunityOwnedDate="2010-06-15T16:52:13.017" CommentCount="11" />
  <row Id="3031" PostTypeId="2" ParentId="3027" CreationDate="2010-06-15T20:21:57.023" Score="-2" ViewCount="" Body="&lt;p&gt;&amp;lt;rant&amp;gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think C++ is a crappy language in the first place. If you want to use OOP, write Java programs. C++ does nothing to enforce OOP paradigms, as direct memory access is fully within your power to (ab)use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have an MCU, you're talking about most likely less than 100kB of flash memory. You want to be programming in a language whose abstraction of memory is: when I declare a variable or an array, it gets memory, period; malloc (aka &quot;new&quot; keyword in C++) should be more or less banned from use in embedded software, except perhaps in rare occasions one call during program startup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hell, there are (frequently) times in embedded programming where C is not quite low-level enough, and you need to do things like allocate variables to registers, and write inline assembly to tighten up your interrupt service routines (ISRs). Keywords like &quot;volatile&quot; become pretty darn important to understand. You spend a lot of your time manipulating memory at the &lt;em&gt;bit&lt;/em&gt; level, not the &lt;em&gt;object&lt;/em&gt; level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why would you want to delude yourself into thinking that things are simpler than they in fact are?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&amp;lt;/rant&amp;gt;&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-06-15T20:21:57.023" CommunityOwnedDate="2010-06-15T20:21:57.023" CommentCount="5" />
  <row Id="3032" PostTypeId="2" ParentId="2992" CreationDate="2010-06-15T21:41:01.043" Score="1" ViewCount="" Body="&lt;p&gt;Several ways to measure peak-to-peak voltage with a MCU:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;undersampling: Directly sample with an ADC, even though you know you are getting less than once sample per cycle of the signal. This requires (a) the signal repeats over and over the same waveform, and any changes to that pattern occur relatively slowly, and (b) the actual sample-and-hold part of the ADC has a high enough bandwidth, even though you only get one sample once every few cycles of the signal, and (c) the exact sampling instant of the sample-and-hold doesn't always hit the same point on the repeating signal, but drifts along it, eventually hitting the highest peak and later the lowest valley of the signal. (Often this drift happens without you having to do anything; but to guarantee it will always work, you may need to &lt;em&gt;lower&lt;/em&gt; your sampling rate with some signals). High-speed digital oscilloscopes often use this undersampling technique to inspect amazingly high frequency signals.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;use maximum peak detector and minimum valley detector to hold the maximum and minimum voltages on sampling capacitors long enough for you to sample them. Either use a resistor on each capacitor with a &quot;long enough&quot; RC time constant that the change in voltage from the actual maximum to your ADC sample is insignificant, or use a transistor on each capacitor to reset the voltage immediately after you sample it. If you can estimate the diode voltage drop in software, the simplest hardware is a diode-capacitor-resistor peak detector and a diode-capacitor-resistor valley detector ... but using an op-amp precision peak detector rather than a single diode may be simpler than trying to estimate the diode voltage drop.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;use a DC blocking capacitor, followed by a diode to ground (to clamp the minimum voltage to 0) and a diode to a peak detect sampling capacitor. The voltage on that capacitor gives you the peak-to-peak voltage directly. Somehow estimate and compensate for the diode voltage drops in software, or else use op-amps to compensate for them in hardware, similar to the peak detector.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;use a frequency mixer (analog multiplier) to shift high-frequency signals down to an easier-to-handle frequency well inside your ADC's capability. (Like undersampling, this assumes the signal repeats over and over the same waveform, and any changes to that pattern occur relatively slowly).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'm not sure why you want a precision rectifier. I assume you really meant &quot;precision peak detector&quot; (which is admittedly almost the same circuit).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A RC filter with a long RC time constant will give you the average voltage of the signal.&#xA;As pingswept says, it's probably best to use a fixed cutoff frequency (for the peak detect, valley detect, and the average detect) to handle the high frequencies with analog circuits, and deal with low frequencies in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As long as the MCU is sampling the highest peak voltage and lowest valley voltage,&#xA;consider also reporting the midway voltage halfway between the two --&#xA;this is not always the same as the true average voltage of the signal.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-06-15T21:41:01.043" CommunityOwnedDate="2010-06-15T21:41:01.043" />
  <row Id="3033" PostTypeId="2" ParentId="2887" CreationDate="2010-06-15T23:33:33.797" Score="0" ViewCount="" Body="&lt;p&gt;I'm going to recommend the easy solution, as JustJeff pointed out -- grab a second wall-wart that gives you an appropriate voltage to feed the 7805 regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you insist on getting your low-current 5 VDC power from 24 VAC, probably the best way to do it is to add a bridge rectifier followed by a switching regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would the &lt;a href=&quot;http://romanblack.com/smps/a04.htm&quot; rel=&quot;nofollow&quot;&gt;3-transistor Black regulator&lt;/a&gt;; or some &lt;a href=&quot;http://romanblack.com/smps/smps.htm&quot; rel=&quot;nofollow&quot;&gt;2-transistor Black regulator&lt;/a&gt;&#xA;work for you?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-06-15T23:33:33.797" CommunityOwnedDate="2010-06-15T23:33:33.797" />
  <row Id="3034" PostTypeId="2" ParentId="785" CreationDate="2010-06-15T23:46:12.290" Score="0" ViewCount="" Body="&lt;p&gt;Yes, if you can run at 2.5 V, and your minimum input is 4.5 V, then a buck regulator should be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Look at the datasheet for your buck regulator.&#xA;The typical &quot;saturation voltage&quot; specification tells you what happens when the input voltage gets too low.&#xA;Typically it's around 1.0 V -- meaning that if the input voltage to a 5 V regulator drops to 5 V, its output voltage is going to drop to about 4 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're willing to spend some time tweaking things,&#xA;Roman Black has some relatively simple buck regulators.&#xA;Would the &lt;a href=&quot;http://romanblack.com/smps/a04.htm&quot; rel=&quot;nofollow&quot;&gt;3-transistor Black regulator&lt;/a&gt;; or some &lt;a href=&quot;http://romanblack.com/smps/smps.htm&quot; rel=&quot;nofollow&quot;&gt;2-transistor Black regulator&lt;/a&gt;&#xA;work for you?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, if you're going to drive power MOSFETs -- they often require 8 V to turn completely on.&#xA;You might as well use a boost or boost-buck converter to generate 8 V or so, and then regulate that down to 5V to power your microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-06-15T23:46:12.290" CommunityOwnedDate="2010-06-15T23:46:12.290" />
  <row Id="3035" PostTypeId="2" ParentId="1024" CreationDate="2010-06-16T00:09:36.330" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Wikipedia%3aElectronics#Drawing_circuits&quot; rel=&quot;nofollow&quot;&gt;same question came up on Wikipedia&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The top recommendation there seems to be Inkscape + a nice collection of public-domain &lt;a href=&quot;http://commons.wikimedia.org/wiki/File%3aElectrical_symbols_library.svg&quot; rel=&quot;nofollow&quot;&gt;electrical symbols&lt;/a&gt; you can download from Wikipedia.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I find that a little surprising, because Inkscape is a general-purpose graphics editor which knows nothing about diagrams or electronics.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-06-16T00:09:36.330" CommunityOwnedDate="2010-06-16T00:09:36.330" CommentCount="3" />
  <row Id="3036" PostTypeId="2" ParentId="3027" CreationDate="2010-06-16T03:10:45.637" Score="14" ViewCount="" Body="&lt;p&gt;Yes, C++ is still useful in embedded systems.  As everyone else has said, that it still depends on the system itself, like 8-bit uC would probably be a no-no in my book even though there is a compiler out there and some people do it(shudder). There's still an advantage to using C++ even when you scale it down to something like &quot;C+&quot; even in a 8-bit micro world.  What I mean by &quot;C+&quot;, I mean don't use new/delete, avoid exceptions, avoid virtual classes with inheritance, possibly avoid inheritance all together, be very careful with templates, use inline functions instead of macros, and use const variables instead of #defines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been working both in C and C++ in embedded systems for well over a decade now, and some of my youthful enthusiasm for C++ has definitely worn off due to some real world problems that shake one's naivete.  I have seen the worst of C++ in an embedded systems which I would like to refer to as &quot;CS programmers gone wild in an EE world.&quot;  In fact, that is something I'm working on with my client to improve this one codebase they have among others.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The danger of C++ is because it's a very very powerful tool much like a two-edged sword that can cut both your arm and leg off if not educated and disciplined properly in it's language and general programming itself.  C is more like a single-edged sword, but still just as sharp.  With C++ it's too easy to get very high-levels of abstraction and create obfuscated interfaces that become meaningless in the long-term, and that's partly due to C++ flexibility in solving the same problem with many different language features(templates, OOP, procedural, RTTI, OOP+templates, overloading, inlining).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I finished a two 4-hour seminars on Embedded Software in C++ by the C++ guru, Scott Meyers.  He pointed out some things about templates that I never considered before and how much more they can help creating safety-critical code.  The jist of it is, you can't have dead code in software that has to meet stringent safety-critical code requirements.  Templates can help you accomplish this, since the compiler only creates the code it needs when instantiating templates.  However, one must become more thoroughly educated in their use to design correctly for this feature which is harder to accomplish in C because linkers don't always optimize dead code. He also demonstrated a feature of templates that could only be accomplished in C++ and would have kept the Mars Climate Observer from crashing had NASA implemented a similar system to protect units of measurement in the calculations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Scott Meyers is very big proponent on templates and judicious use of inlining, and I must say I'm still skeptical on being gung ho about templates.  I tend to shy away from them, even though he says they should only be applied where they become the best tool. He also makes the point that C++ gives you the tools to make really good interfaces that are easy to use right and make it hard to use wrong. Again, that's the hard part.  One must come to a level of mastery in C++ before you can know how to apply these features in most efficient way to be the best design solution.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The same goes for OOP.  In the embedded world, you must familiarize yourself with what kind of code the compiler is going to spit out to know if you can handle the run-time costs of run-time polymorphism.  You need to be willing to make measurements as well to prove your design is going to meet your deadline requirements. Is that new InterruptManager class going to make my interrupt latency too long? There are other forms of polymorphism that may fit your problem better such as link-time polymorphism which C can do as well, but C++ can do through the &lt;a href=&quot;http://en.wikipedia.org/wiki/Opaque_pointer&quot; rel=&quot;nofollow&quot;&gt;Pimpl design pattern (Opaque pointer)&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I say that all to say, that C++ has it's place in the embedded world.  You can hate it all you want, but it's not going away. It can be written in a very efficient manner, but it's harder to learn how to do it correctly than with C.  It can sometimes work better than C at solving a problem and sometimes expressing an better interface, but again, you've got to educate yourself and not be afraid to learn how.&lt;/p&gt;&#xA;" OwnerUserId="625" LastEditorUserId="625" LastEditorDisplayName="" LastEditDate="2010-06-18T20:13:15.920" LastActivityDate="2010-06-18T20:13:15.920" CommunityOwnedDate="2010-06-16T03:10:45.637" CommentCount="15" />
  <row Id="3037" PostTypeId="2" ParentId="1151" CreationDate="2010-06-16T03:14:33.880" Score="3" ViewCount="" Body="&lt;p&gt;How about a sharp hacksaw?  That's what I've always used.   (Although I'll admit that I wasn't aware that the dust was THAT toxic; I'll be more careful next time. )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can cut a small chunk out of a 4x5&quot; piece of protoboard (about 12&quot; of cuts) in less than 5 minutes, and not working that hard!  Are you trying to do a multilayer/thick copper board, or making a great many cuts?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The alternative is to specify a long row of via-size holes (perhaps supplementing with routed cuts) in your PCB, if you're having it manufactured.   Just read up on your board house's rules, put some holes in a row, and you can snap the board with your hands.  Leaves a ragged edge, but not that much worse than a hacksaw.  That's how we do it at work, at least.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-16T03:14:33.880" />
  <row Id="3038" PostTypeId="2" ParentId="3012" CreationDate="2010-06-16T03:35:24.043" Score="2" ViewCount="" Body="&lt;p&gt;AVR and the Arduino are awesome, but all the action (read:jobs) is really turning toward 32-bit micros.  Try to learn an ARM toolchain, get/make a development board.  With many of the larger processors, things like Ethernet and USB are as simple as connecting two traces to the appropriate connector, loading the drivers, and running with it.  You can have hundreds of kB (to multiple MB) of FLASH, dozens of K (to multiple MB) of RAM, memory controllers, color LCDs, 50-600MHz, threaded processes, Linux distros, you name it.  Note that if you've just started with AVRs and electronics, the ARM is probably too complex. But, if you learn it, I guarantee you won't regret it!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dev kits are always expensive (I don't know if your local source can get you one cheaply), but Olimex (among others) has schematics available online, for reference, and they also offer bare bones ARM header boards for as cheap as $20 (20-30McD's, or 1.300R) to full-featured models for $60- Pricey but worth it! A quick search says that they have a distributor &lt;a href=&quot;http://www.logsun.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.logsun.com/&lt;/a&gt; in India (700km away from you, but at least it's not international).&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-16T03:35:24.043" CommunityOwnedDate="2010-06-16T03:35:24.043" CommentCount="8" />
  <row Id="3039" PostTypeId="2" ParentId="2829" CreationDate="2010-06-16T03:39:38.807" Score="2" ViewCount="" Body="&lt;p&gt;Are you a student?  A lot of places (Including Advanced Circuits; not an assembler) give great discounts.&lt;br&gt;&#xA;More lists:&#xA;&lt;a href=&quot;http://claymore.engineer.gvsu.edu/egr326/PCBAssembly&quot; rel=&quot;nofollow&quot;&gt;http://claymore.engineer.gvsu.edu/egr326/PCBAssembly&lt;/a&gt;&#xA;http://claymore.engineer.gvsu.edu/egr326/PCBManufacturing&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-16T03:39:38.807" />
  <row Id="3040" PostTypeId="2" ParentId="3027" CreationDate="2010-06-16T14:43:39.693" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;My background:&lt;/strong&gt;  just out of school training under old Bell Labs programmers; been working for 3 years, 2 on undergrad research project; data acquisition / process control in VB.NET.  Spent 1.5 years doing work on an enterprise database application in VB6.  Currently working on project for &lt;em&gt;embedded&lt;/em&gt; PC with 2GB of storage, 512MB of RAM, 500MHz x86 CPU;  several apps running concurrently written in C++ with an IPC mechanism in between.  Yes, I'm young.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;My opinion:&lt;/strong&gt;  I think C++ can work effectively &lt;em&gt;given the environment I've written above&lt;/em&gt;.  Admittedly, hard real-time performance isn't a requirement for the app I'm on, and in some embedded applications, that can be an issue.  But here are the things I've learned:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;em&gt;C++ is fundamentally different than C&lt;/em&gt; (ie, there is no C/C++).  While everything that is valid C is valid C++, C++ is a very different language and one needs to learn how to program in C++, not C, to effectively use it in &lt;em&gt;any&lt;/em&gt; situation.  In C++, you need to program object-orientedly, not procedurally, and not a hybrid of the two (big classes with lots of functions).  In general, you should focus on making small classes with few functions, and compose all the small classes together into a larger solution.  One of my coworkers explained to me that I used to program procedurally in objects, which is a grand mess and is hard to maintain.  When I started to apply more object-oriented techniques, I found my code's maintainability/readability went up.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;C++ provides additional features in the form of object-oriented development that can provide &lt;em&gt;a way to simplify code to make it easier to read/maintain&lt;/em&gt;.  Honestly, I don't think there's much in the way of a performance/space efficiency improvment in doing OOP.  But I think OOP is a technique that can help split up a complex problem into lots of little pieces.  And that is helpful for the people working on the code, an element of this process that should not be ignored.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Many arguments against C++ have primarily to do with dynamic memory allocation.  C has this same problem too.  You can write an object oriented application without using dynamic memory, although one of the benefits of using objects is that you can allocate these things dynamically in an easy fashion.  Just as in C, you have to be careful about how manage the data to reduce memory leaks, but the &lt;a href=&quot;http://jalf.dk/blog/2010/01/the-meaning-of-raii-or-why-you-never-need-to-worry-about-resource-management-again/&quot; rel=&quot;nofollow&quot;&gt;RAII technique&lt;/a&gt; makes this simpler in C++ (make dynamic memory destruct automatically by encapsulating it in objects).  In some applications, where every memory location counts, this may be too wild &amp;amp; wooly to manage.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;em&gt;WRT the &quot;Arduino C++&quot; question&lt;/em&gt;:  I would argue that C++ without dynamic memory management can &lt;em&gt;still&lt;/em&gt; be useful.  You can organize your code into objects, and then place those objects into various locations within your application, setup callback interfaces, etc.  Now that I have been developing in C++, I can see many ways in which an application with all data allocated on the stack can still be useful with objects.  I will admit though - I never actually written an embedded app like that for the Arduino, so I have no proof behind my claim.  I have some opportunities to do some Arduino development in an upcoming project - hopefully I can test my claim there.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-11-03T17:33:44.733" LastActivityDate="2010-11-03T17:33:44.733" CommunityOwnedDate="2010-06-16T14:43:39.693" CommentCount="4" />
  <row Id="3041" PostTypeId="2" ParentId="3020" CreationDate="2010-06-16T15:07:01.257" Score="0" ViewCount="" Body="&lt;p&gt;Okay, I have two things I see.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have the jumpers to choose between serial and USB set to serial when you connect it to the arduino? Setting the jumpers to USB will stop the arduino from being able to communicate with the shield. This is probably not it, but worth asking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, if you are getting sync errors when you try to program with the hilo connected, is it trying to program over the same UART connection that the hilo will use? I do not know the arduino well, but it sounds like it is. The sharing of connections is not a problem, unless the hilo shield is communicating constantly and corrupting your communication data.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-16T15:47:33.740" LastActivityDate="2010-06-16T15:47:33.740" CommentCount="2" />
  <row Id="3042" PostTypeId="1" AcceptedAnswerId="3043" CreationDate="2010-06-16T16:03:27.750" Score="4" ViewCount="377" Body="&lt;p&gt;Can anyone explain how one would convert one voltage range to another? I'm going to need to convert a range of 0 to +5 volts into a range of -5 to +5 volts. How would this be accomplished? Thanks!&lt;/p&gt;&#xA;" OwnerUserId="835" LastActivityDate="2010-06-17T11:23:20.183" Title="Converting/scaling a voltage range ([0v - 5v] to [-5v - +5v])" Tags="&lt;voltage&gt;&lt;scaling&gt;&lt;negative&gt;" AnswerCount="2" />
  <row Id="3043" PostTypeId="2" ParentId="3042" CreationDate="2010-06-16T16:30:37.713" Score="8" ViewCount="" Body="&lt;p&gt;For working with power conversions rather than signal -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use various integrated circuits for this job, they're commonly referred to as &lt;a href=&quot;http://en.wikipedia.org/wiki/DC-to-DC_converter&quot; rel=&quot;nofollow&quot;&gt;Dc to DC converters&lt;/a&gt;, there's also a range of ways to do the conversion such as &lt;a href=&quot;http://en.wikipedia.org/wiki/Charge_pump&quot; rel=&quot;nofollow&quot;&gt;Charge pumps&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rapidonline.com/Electrical-Power/Power-Supplies/DC-DC-Converter-ICs&quot; rel=&quot;nofollow&quot;&gt;Here's a bunch of different DC to DC converters&lt;/a&gt; they have various different current ratings, some step the voltage up, some step down and others convert between positive and negative values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/1140&quot; rel=&quot;nofollow&quot;&gt;This is a nice charge pump IC&lt;/a&gt; that can double or invert a voltage with the minimum of external components. You could even use a &lt;a href=&quot;http://www.aaroncake.net/circuits/vinvertr.asp&quot; rel=&quot;nofollow&quot;&gt;555 timer to convert a voltage to a negative&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-06-17T11:23:20.183" LastActivityDate="2010-06-17T11:23:20.183" CommentCount="6" />
  <row Id="3044" PostTypeId="2" ParentId="3042" CreationDate="2010-06-16T16:30:44.077" Score="8" ViewCount="" Body="&lt;p&gt;There are many ways to do this, the easiest I think would be a summing op-amp configuration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to try using this ascii system, lets see how it does. This is a circuit that does what you want.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;          -5V&#xA;           |&#xA;          .-.&#xA;          | |&#xA;          | |2K           2K_&#xA;          '-'       .----|___|----.&#xA;           |        |             |&#xA;           |        |             |&#xA;           '--------o             |&#xA;                    |      +Pwr   |&#xA;       ___          |    |\|      |&#xA;input-|___|---------o----|-\      |&#xA;       1K                |  &amp;gt;-----o----Output&#xA;                    .----|+/&#xA;                    |    |/|&#xA;                   GND     -Pwr&#xA;&#xA;(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;So, it takes the input, doubles it and subtracts 5 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will make 2.5V become 0V, 0V becomes -5V, and 5V stays 5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It does it linearly over the range, this can be valuable if it is a signal that needs to be spread over a new range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helped.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-16T16:30:44.077" CommentCount="7" />
  <row Id="3045" PostTypeId="1" CreationDate="2010-06-16T17:03:12.907" Score="3" ViewCount="157" Body="&lt;p&gt;Does anyone sell autosteroscopic displays in non bulk quantities?&lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-06-20T04:48:37.843" Title="Are any autostereoscopic displays readily available? (Nintendo 3DS screen)" Tags="&lt;lcd&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="3046" PostTypeId="1" CreationDate="2010-06-16T18:19:17.853" Score="3" ViewCount="398" Body="&lt;p&gt;I would like to set my AVR's OSCCAL for proper RS-232 communication using the other end's transmission as the calibration clock, without having to solder the RX pin to a timer pin. Is there firmware to do this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wound up writing my own synchronization routine and soldering the RX pin to the ICP (input capture) unit. When the ICP pin changes, TIMER1's value is copied into a register and an interrupt fires.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The code uses an ADCPM-inspired search technique. OSCCAL is incremented or decremented by 1 initially. Each time OSCCAL needs to move in the same direction again it moves twice as far, when it switches direction it starts over at 1. &lt;a href=&quot;http://code.google.com/p/pwmsign/source/browse/synch.c&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/pwmsign/source/browse/synch.c&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All that trouble, and I discovered the perfect OSCCAL was only 1 off from the factory setting.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2010-06-28T12:48:49.500" LastActivityDate="2010-06-28T12:48:49.500" Title="How do I calibrate an AVR's RC oscillator using the UART?" Tags="&lt;avr&gt;&lt;uart&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="3047" PostTypeId="1" CreationDate="2010-06-16T19:37:35.933" Score="4" ViewCount="113" Body="&lt;p&gt;I have come across a Bluetooth legacy product or protocol in a meeting at my employer, but I can't quite recall if its name is called BluetoothLC (Bluetooth Local Connectivity). It would be great to know what kind of legacy Bluetooth classes/protocols are out there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="854" LastActivityDate="2010-11-29T19:32:35.650" Title="Bluetooth legacy products name" Tags="&lt;bluetooth&gt;&lt;wireless&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="3048" PostTypeId="1" AcceptedAnswerId="3049" CreationDate="2010-06-16T20:00:06.140" Score="8" ViewCount="200" Body="&lt;p&gt;Anyone familiar with relays mechanical or otherwise? I would like to be able to switch on/off up to 250W (120V) load using a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will be used to control lighting to an aquarium.&lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2010-07-09T16:45:40.060" Title="Which relay - Mechanical or Solidstate?" Tags="&lt;relay&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="3049" PostTypeId="2" ParentId="3048" CreationDate="2010-06-16T20:56:25.273" Score="7" ViewCount="" Body="&lt;p&gt;Solid-state relays are easier to use than electro-mechanical ones. They can be controlled directly by MCU outputs and you don't have to worry about things like putting diodes across coils. I've used lots of them with an ARM to control motors and valves in a complex piece of medical equipment.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-06-16T22:44:50.127" LastActivityDate="2010-06-16T22:44:50.127" CommentCount="1" />
  <row Id="3050" PostTypeId="2" ParentId="3048" CreationDate="2010-06-16T21:14:39.720" Score="6" ViewCount="" Body="&lt;p&gt;Mechanical relays require gobs of current to keep the coil energized, much more than you can directly get from a microcontroller, and when you want to switch them off, you have to contend with all the flyback energy too (i.e., the diode thing).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Solid state is the way to go.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-16T21:14:39.720" />
  <row Id="3051" PostTypeId="2" ParentId="3027" CreationDate="2010-06-17T00:21:23.680" Score="7" ViewCount="" Body="&lt;p&gt;I always find these debates entertaining to read.  Not so much for the intellectual discussion about the pros and cons of the various available languages but because you can usually peg someones stance on the topic based on their job/experience/area of interest.  Its right up there with the &quot;premature optimization&quot; arguments were the CS majors and maintenance programmers quote Knuth left and right and those who work in the real world where performance matters think they're all crazy (i'm a member of the later group to be fair).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the end of the day, you can develop excellent software in C or C++ or &lt;em&gt;insert language here&lt;/em&gt;.  It comes down to the capabilities of the developer not the language.  Being an expert in a language is usually only required if you've chosen the wrong language to begin with and now need to warp it into solving your problem, in most cases these are the only situations where you need to dive into obscure features or compiler tricks to accomplish the goal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I often hear people start these arguments as &quot;i'm an expert in language X and blah blah&quot; I honestly immediately discredit these people because, in my opinion, they've already approached the problem from the wrong angle and everything after that is tainted by their desire to use their tool to solve the problem and show how 'cool' it is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I so often watch developers choose a tool set first and attempt to bend it to their problem second, which is completely wrong and results in crap solutions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As I mentioned in a comment to another answer, these language wars often devolve into arguing that language X allows the programmer to do more dumb things.  While entertaining to read, all these statements really mean is that you have a problem hiring good developers and need to address that issue directly rather than trying to band aid the situation by continuing to hire bad developers and choosing tools such that they can do as little damage as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my opinion good developers, be it software or hardware development, research the problem, architect a solution and find the tools that allow them to express the solution in the 'best way'.  It shouldn't matter if the required tool is something you've never used before, after you've used 3-4 languages/development tools for projects picking up a new one should have a minimal impact on your development time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, 'best way' is a subjective term and also needs to be defined in the research phase.  One needs to consider a multitude of issues: performance, ease of expression, code density, etc based on the problem at hand.  I didn't include maintainability in that list for a reason, i don't care what language you choose, if you've chosen the proper tool and taken the time to understand the problem this should come 'for free'.  Difficult to maintain code is often the result of choosing the wrong tool or a poor system structure, this results in an ugly hacky mess to make it work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Claiming any language is 'better' than any other is silly without defining a particular problem of interest.  An object oriented approach is not always better than a functional approach.  There are some problems that lend themselves very well to an object oriented design paradigm.  There are many that do not.  The same statement can be made about many language features that people seem to enjoy harping on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your spending more than 20% of your time on a problem actually typing code, your probably producing a very poor system, or have very poor developers(or your still learning).  You should be spending the majority of your time up front diagramming the problem and determining how various pieces of the application interact.  Sticking a group of talented developers in a room with a marker board and a problem to solve and telling them they are not allowed to write any code or choose any tools till they feel comfortable with the entire system will do more to improve the quality of the output and speed development than choosing any hot new tool guaranteed to improve development time.  (look up scrum development as a reference for the polar opposite to my argument)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Often the unfortunate reality is that many businesses can only measure the value of a developer by the number of lines written, or by seeing 'tangible output'.  They view the 3 weeks in a room with a marker board as a loss in productivity.  Developers are often forced to speed through the 'thought' stage of development or are forced into using a tool set by some political issue within the company,  &quot;my boss's brother works for IBM so we can only use their tools&quot;, that kind of rubbish.  Or worse, you get a constantly changing set of requirements from the company because they are not capable of doing proper market research or don't understand the impact of changes on the development cycle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry for being slightly off topic with this rant, I have quite strong opinions on this topic.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-06-17T02:40:13.947" LastActivityDate="2010-06-17T02:40:13.947" CommunityOwnedDate="2010-06-17T00:21:23.680" CommentCount="14" />
  <row Id="3053" PostTypeId="2" ParentId="3045" CreationDate="2010-06-17T04:14:26.347" Score="1" ViewCount="" Body="&lt;p&gt;Once the 3DS is popular repair places will start carrying the LCD.  Until then, since auto-stereoscopic displays are not manufactured in very large mass quantities you'll likely only find them if you're willing to spend quite a bit of money, in which case talking directly to manufacturers for sample units might be workable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While you're waiting, you could experiment with making your own LCD masks to turn regular LCDs into auto-stereoscopic displays.  A bit of math/geometry and a printed transparency might give you a low-end, but usable, solution.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-06-17T04:14:26.347" />
  <row Id="3054" PostTypeId="2" ParentId="1151" CreationDate="2010-06-17T04:27:05.727" Score="5" ViewCount="" Body="&lt;p&gt;I finally settled on a wet tile saw.  Turns out that it's not much different than the PCB saws that many places use to cut PCBs.  A cheap wet tile saw from Harbor Freight costs about $70 (I got &lt;a href=&quot;http://www.harborfreight.com/4-inch-tile-saw-with-wet-tray-3733.html&quot; rel=&quot;nofollow&quot;&gt;mine&lt;/a&gt; for $45 on sale), plus another $12 for the blade.  The blade cuts a little over 1/16th of an inch, and with the saw guides I can cut very accurately.  I also purchased a foot switch so I can cut PCB batches pretty quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The advantage of a wet saw is that the dust is hardly a problem - it's trapped in the water, so while you still should wear protective equipment, you won't end up with fiberglass dust everywhere.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Further it's a &lt;strong&gt;very&lt;/strong&gt; nice, ground cut.  Very smooth - it's no different than the edges that were routed or sawn at the PCB fab house.  I usually use a fine sandpaper to break the edges (which are a bit 'sharp') afterwards if I think people are going to be handling the PCB a lot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The water poses no problem to the PCB itself, and if you already mounted components, most are washable.  If you need to use it immediately a quick blast with the air hose or canned air removes all the water.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-06-17T04:27:05.727" CommentCount="4" />
  <row Id="3055" PostTypeId="2" ParentId="1151" CreationDate="2010-06-17T05:26:59.680" Score="2" ViewCount="" Body="&lt;p&gt;I use a scroll saw for weird cuts on boards I create. It just depends on what design your going for. Sometimes just a box cutter and snapping it over a hard edge is all I need for straight cuts.&lt;/p&gt;&#xA;" LastActivityDate="2010-06-17T05:26:59.680" />
  <row Id="3057" PostTypeId="1" CreationDate="2010-06-17T11:02:09.593" Score="4" ViewCount="329" Body="&lt;p&gt;Hey all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking for an ADC IC and while I could just take the plunge and pick one, I was wondering if anyone had any experience with any particular devices? I need it to:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Connect to an AVR via I2C/SPI (I2C preferred)&lt;/li&gt;&#xA;&lt;li&gt;Have at least 8 bit resolution (10+ would be nice)&lt;/li&gt;&#xA;&lt;li&gt;Have at least 3 inputs&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Currently I am looking at the &lt;a href=&quot;http://au.farnell.com/texas-instruments/ads7830ipwtg4/8bit-adc-8-ch-smd-tssop16-7830/dp/1180129&quot; rel=&quot;nofollow&quot;&gt;ADS7830&lt;/a&gt;. Any recommendations would be fantastic.&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-06-17T13:28:30.717" LastActivityDate="2010-07-17T20:51:23.523" Title="Recommend any ADC ICs ?" Tags="&lt;adc&gt;&lt;i2c&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="3058" PostTypeId="2" ParentId="3046" CreationDate="2010-06-17T12:58:58.090" Score="1" ViewCount="" Body="&lt;p&gt;Clearly I'm looking for the Atmel-provided datasheet, AVR054: Run-time calibration of the internal RC oscillator. I think it could be adapted to PC-to-AVR communication without too much trouble...&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-06-17T12:58:58.090" CommentCount="6" />
  <row Id="3060" PostTypeId="2" ParentId="3057" CreationDate="2010-06-17T14:51:53.633" Score="6" ViewCount="" Body="&lt;p&gt;The Microchip &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010534&quot; rel=&quot;nofollow&quot;&gt;MCP3208&lt;/a&gt; (SPI) is very easy to use.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-17T14:51:53.633" CommentCount="1" />
  <row Id="3061" PostTypeId="2" ParentId="3057" CreationDate="2010-06-17T15:39:56.090" Score="9" ViewCount="" Body="&lt;p&gt;Use the built-in ADC on the AVR microcontroller.  Even if you have to choose an AVR with a slightly higher pin count and slightly higher cost, the total system cost and PCB size will likely be smaller.  Reduced parts count typically results in higher reliability as well.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several AVR choices with 10 and 12 bit A/D converters.  See the &lt;a href=&quot;http://www.atmel.com/dyn/products/param_table_v2.asp?family_id=607&amp;amp;OrderBy=part_no&amp;amp;Direction=ASC&quot; rel=&quot;nofollow&quot;&gt;Parametric Product Table&lt;/a&gt; for more info.&lt;/p&gt;&#xA;" OwnerUserId="529" LastEditorUserId="529" LastEditorDisplayName="" LastEditDate="2010-06-17T16:27:37.100" LastActivityDate="2010-06-17T16:27:37.100" CommentCount="2" />
  <row Id="3062" PostTypeId="1" AcceptedAnswerId="3064" CreationDate="2010-06-17T19:32:22.820" Score="11" ViewCount="722" Body="&lt;p&gt;Usually you either combine capacitors in parallel because you want to increase the total capacitance while fitting the components in a certain shape/position, or you just combine capacitors by buying a single capacitor of a larger value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Combining capacitors in series reduces the total capacitance, and isn't very common, but what are some possible uses for it?  It shouldn't be used to increase the voltage rating, for instance, since you can't guarantee that the middle will be at half the DC voltage of the total, without using bleeder resistors.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-03-04T02:20:06.143" Title="What are some reasons to connect capacitors in series?" Tags="&lt;capacitor&gt;&lt;capacitance&gt;" AnswerCount="8" FavoriteCount="2" />
  <row Id="3063" PostTypeId="2" ParentId="3062" CreationDate="2010-06-17T19:37:31.453" Score="3" ViewCount="" Body="&lt;p&gt;I have only ever done it to increase voltage rating, and we were using large super-capacitors. They were rated to 2.7 V and we wanted 5V, so we connected in series. We purchased a nice charging controller, which did the job of ensuring they both had the same charge, charging them in parallel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It decreased our Capacitance to ~25 Farads I believe, but the ESR was &amp;lt;.1 ohms.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-17T19:37:31.453" />
  <row Id="3064" PostTypeId="2" ParentId="3062" CreationDate="2010-06-17T20:04:40.820" Score="4" ViewCount="" Body="&lt;p&gt;I have only seen it done to increase voltage. On some power supply front-ends (AC/DC conversion) with a voltage doubler the capacitors are in parallel at low voltage&#xA;and in series at high voltage. This works out well since for a constant power out&#xA;the current is double at the lower voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you mention balancing resistors are required. &lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-03-03T19:06:09.937" LastActivityDate="2011-03-03T19:06:09.937" />
  <row Id="3065" PostTypeId="1" CreationDate="2010-06-17T20:18:41.480" Score="4" ViewCount="370" Body="&lt;p&gt;I'm replacing the LED in a car tail-light. Naturally, it will run off 12V (battery) but the circuit I have uses just an LED and a 0.6w (440ohm) resistor. But the existing circuit includes two, larger resistors (the power ratings, that is, I assume are higher) and a diode. Can anyone tell me what functions these play in the circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the diode for protecting from reverse current, as I'd assume? (not for voltage drop or anything like that), if so, why would there be a risk of this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And why are the resistors so much larger, when the LED I put in should easily run from a 0.6 resistor? Would the existing LED be a higher wattage LED; It's just the same looking led, there's no heat-sink or anything.&lt;/p&gt;&#xA;" OwnerUserId="733" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-06-29T06:23:09.140" LastActivityDate="2010-12-12T23:21:42.230" Title="Car Tail light - why the extra components?" Tags="&lt;car&gt;&lt;led&gt;&lt;light&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="1" />
  <row Id="3066" PostTypeId="2" ParentId="3065" CreationDate="2010-06-17T20:59:40.947" Score="7" ViewCount="" Body="&lt;p&gt;The diode is likely a zener diode to short out voltage spikes generated inadvertently by the alternator.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-17T20:59:40.947" CommentCount="3" />
  <row Id="3067" PostTypeId="1" AcceptedAnswerId="3068" CreationDate="2010-06-17T21:39:12.457" Score="20" ViewCount="1407" Body="&lt;p&gt;I understand that a DSP is optimized for digital signal processing, but I'm not sure how that impacts to the task of choosing an IC.  Almost everything I do with a microcontroller involves the processing of digital signals!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, let's compare the popular Microchip dsPIC30 or 33 DSP  and their other 16-bit offering, the PIC24 general purpose microcontroller.  The dsPIC and the PIC can be configured to have the same memory and speed, they have similar peripherial sets, similar A/D capability, pin counts, current draw, etc.  The only major difference that appears on Digikey's listing is the location of the oscillator.  I can't tell the difference by looking at the prices (or any other field, for that matter.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I want to work with a couple of external sensors using various protocols (I2C, SPI, etc.), do some A/D conversions, store some data on some serial flash,  respond to some buttons, and push data out to a character LCD and over an FT232 (a fairly generic embedded system), which chip should I use?  It doesn't appear that the DSP will lag behind the PIC in any way, and it offers this mysterious &quot;DSP Engine.&quot;  My code always does math, and once in a while I need floating point or fractional numbers, but I don't know if I'll benefit from using a DSP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A more general comparison between another vendor's DSPs and microcontrollers would be equally useful; I'm just using these as a starting point for discussion.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-09T20:56:13.407" Title="What is the difference between a DSP and a standard microcontroller?" Tags="&lt;dsp&gt;&lt;microcontroller&gt;&lt;microchip&gt;&lt;dspic&gt;&lt;pic&gt;" AnswerCount="5" FavoriteCount="9" />
  <row Id="3068" PostTypeId="2" ParentId="3067" CreationDate="2010-06-17T22:00:55.603" Score="22" ViewCount="" Body="&lt;p&gt;To be honest the line between the two is almost gone nowadays and there are processors that can be classified as both (AD Blackfin for instance).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally speaking:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microcontrollers are integer math processors with an interrupt sub system.  Some may have hardware multiplication units, some don't, etc.  Point is they are designed for simple math, and mostly to control other devices.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;DSPs are processors optimized for streaming signal processing.  They often have special instructions that speed common tasks such as multiply-accumulate in a single instruction.  They also often have other vector or SIMD instructions.  Historically they weren't interrupt based systems and operated with non-standard memory systems optimized for their purpose making them more difficult to program.  They were usually designed to operate in one big loop processing a data stream.  DSP's can be designed as integer, fixed point or floating point processors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Historically if you wanted to process audio streams, video streams, do fast motor control, anything that required processing a stream of data at high speed you would look to a DSP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you wanted to control some buttons, measure a temperature, run a character LCD, control other ICs which are processing things, you'd use a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Today, you mostly find general purpose microcontroller type processors with either built in DSP-like instructions or with on chip co-processors to deal with streaming data or other DSP operations.  You don't see pure DSP's used much anymore except in specific industries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The processor market is much broader and more blurry than it used to be.  For instance i hardly consider a ARM cortex-A8 SoC a micro-controller but it probably fits the standard definition, especially in a PoP package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; Figured i'd add a bit to explain when/where i've used DSPs even in the days of application processors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A recent product i designed was doing audio processing with X channels of input and X channels of output per 'zone'.  The intended use for the product meant that it would often times sit there doing its thing, processing the audio channels for years without anyone touching it.  The audio processing consisted of various acoustical filters and functions.  The system also was &quot;hot plugable&quot; with the ability to add some number of independent 'zones' all in one box.  It was a total of 3 PCB designs (mainboard, a backplane and a plug in module) and the backplane supported 4 plug in modules.  Quite a fun project as i was doing it solo, i got to do the system design, schematic, PCB layout and firmware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now i could have done the entire thing with an single bulky ARM core, i only needed about 50MIPS of DSP work on 24bit fixed point numbers per zone.  But because i knew this system would operate for an extremely long time and knew it was critical that it never click or pop or anything like that.  I chose to implement it with a low power DSP per zone and a single PIC microcontroller that played the system management role.  This way even if one of the uC functions crashed, maybe a DDOS attack on its Ethernet port, the DSP would happily just keep chugging away and its likely no one would ever know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the microcontroller played the role of running the 2 line character LCD, some buttons, temperature monitoring and fan control (there were also some fairly high power audio amplifiers on each board) and even served an AJAX style web page via ethernet.  It also managed the DSPs via a serial connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So thats a situation where even in the days where i could have used a single ARM core to do everything, the design dictated a dedicated signal processing IC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other areas where i've run into DSPs:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*High End audio - Very high end receivers and concert quality mixing and processing gear&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*Radar Processing - I've also used ARM cores for this in low end apps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*Sonar Processing &lt;/p&gt;&#xA;&#xA;&lt;p&gt;*Real time computer vision&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the most part, the low and mid ends of the audio/video/similar space have been taken over by application processors which combine a general purpose CPU with co-proc offload engines for various applications.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-06-18T23:18:55.350" LastActivityDate="2010-06-18T23:18:55.350" CommentCount="2" />
  <row Id="3069" PostTypeId="2" ParentId="3067" CreationDate="2010-06-17T22:01:55.000" Score="5" ViewCount="" Body="&lt;p&gt;The biggest difference between DSP and the standard uController is the DSP's multiply accumulate feature (MAC) that uC does not have.  This valuable if you want to perform true digital signal processing math such as FFT (one example).  Doing an FFT in a standard microcontroller will take a long time compared to performing it on a MAC of the DSP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Processing I2C and serial signals is not the same as processing waveforms in a DSP.  Totally different kind of processing going on since serial signals are just bit-banging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a similar discussion on a DSP forum: &lt;a href=&quot;http://www.dsprelated.com/showmessage/28154/1.php&quot; rel=&quot;nofollow&quot;&gt;DSP vs. Microprocessor&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="625" LastEditorUserId="625" LastEditorDisplayName="" LastEditDate="2010-06-18T17:49:48.677" LastActivityDate="2010-06-18T17:49:48.677" CommentCount="4" />
  <row Id="3070" PostTypeId="2" ParentId="3065" CreationDate="2010-06-17T22:03:51.827" Score="4" ViewCount="" Body="&lt;p&gt;I don't have an answer to your question about the extra components without a schematic, although I'd agree with Pingswept's guess - Remember that your LED doesn't need a reverse current protector; it is a diode itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I will point out that you want to use 13.8V (The voltage output by the alternator) for your calculations, not 12V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Small difference, but it's always good to remember.  In this circuit, it means you can''t put in a 13V zener, or you'll find yourself sinking the alternator voltage for a short amount of time, and then your zener will release its magic smoke.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-17T22:03:51.827" CommentCount="2" />
  <row Id="3072" PostTypeId="2" ParentId="3065" CreationDate="2010-06-17T22:36:34.150" Score="6" ViewCount="" Body="&lt;p&gt;It is likely a zener to keep the LED at a constant brightness.  Car power is not constant, it's only loosely regulated, and since the LED has a very fast response time changes in vehicle voltage (say when you start your airconditioning) may be percieved as flashing your light.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Filament light bulbs take awhile (100-300mS) to visibly react to a change in voltage, so it's not an issue for them.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-06-17T22:36:34.150" CommentCount="1" />
  <row Id="3073" PostTypeId="2" ParentId="3062" CreationDate="2010-06-17T22:56:42.700" Score="5" ViewCount="" Body="&lt;p&gt;You sometimes see electrolytics connected in series, with opposite polarization directions. In other words, one cap will always be forward biased, no matter what the externally applied voltage. This is, I believe, how one arrives at the situation of having a 'non-polarized electrolytic' capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;follow up -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;turns out that what might LOOK like two ordinary electrolytics are not, in fact, two &lt;em&gt;ordinary&lt;/em&gt; electrolytics. Despite the uncanny resemblance to exactly that, it is highly probable that the devices I saw had other properties as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the moral of the story is, if you see what looks like two electrolytics stuck together back to back, it is high probability an 'NP' electrolytic, but don't try to make one on your own with regular electrolytics. (Kind of like &quot;you can't make a BJT from two diodes&quot;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;live and learn, right? that's why we all love our stackexchanges. thanks out to Kortuk for the eye opener.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-06-18T10:41:33.840" LastActivityDate="2010-06-18T10:41:33.840" CommentCount="8" />
  <row Id="3074" PostTypeId="2" ParentId="3067" CreationDate="2010-06-17T23:05:34.970" Score="3" ViewCount="" Body="&lt;p&gt;What used to set DSPs apart was their optimization for arithmetic operations, especially multiplication, although these days it's not uncommon for microcontrollers to come endowed with multiplication and division instructions. There may still be an edge to doing signal processing with DSP chips, insofar as some of them have hardware support for fixed-point math (e.g., the TI TMS320s 'IQ' lib), whereas micros are more likely to just include integer units.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, when faced with choosing between the two for a design, I'd try to categorize whether the application called for repetitive calculations with only occasional mode change logic, or only needs to perform short sequences of calculations as need arises. The former would be the DSP, the latter a micro.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And then, of course, there are fun things like the OMAP that have both. =P&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-17T23:05:34.970" CommentCount="3" />
  <row Id="3075" PostTypeId="1" CreationDate="2010-06-17T23:46:32.073" Score="5" ViewCount="441" Body="&lt;p&gt;At home, I etch single and double sided PCBs but there are a few of areas I've always had trouble with. Can anyone help?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Tinning&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PCBs I make are useless for hot air rework or skillet reflowing. Once the copper heats up it oxidises, then I'm unable to solder anything else to the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rubbing wet solder wick over the PCB helps, but I usually just end up damaging the tracks.&#xA;Will a tinning solution solve this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any other way?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Vias and plated through hole&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So long as I keep vias big and away from components I can solder short pins or wires through the board. But, these vias are too raised to go under a chip, which is often where they're needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is through hole plating possible/practical at home?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there other ways?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Cutting&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I buy presensitised FR4. It's not cheap, so I like to cut up the sheets to avoid waste. Strong scissors can cut it, but they sometimes curl the edges which makes it hard to get a good contact with the transparency when exposing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's a cheap way to cut PCB?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Coating&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's no soldermask, so I have a lot of exposed copper. Is there something inexpensive I could use for a better finish than hotglue?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-18T00:58:45.640" LastActivityDate="2010-06-18T13:11:12.290" CommunityOwnedDate="2010-06-20T20:32:19.740" Title="Homebrew PCB tips?" Tags="&lt;pcb&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="2" />
  <row Id="3076" PostTypeId="2" ParentId="3075" CreationDate="2010-06-18T00:49:07.503" Score="2" ViewCount="" Body="&lt;p&gt;Regarding the cutting of PCBs, I've found that tin snips do a good job. I haven't had a problem with the remnants curling so far.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-18T00:49:07.503" />
  <row Id="3077" PostTypeId="2" ParentId="3075" CreationDate="2010-06-18T02:49:42.267" Score="5" ViewCount="" Body="&lt;p&gt;For tinning, my cheap home method is to coat the traces with a flux pen as soon as the board is finished etching, then run all over them with the thinnest coat of solder from my iron.&#xA;I've drilled them before and after the flux and or tin process and usually prefer to drill before fluxing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I too use tin snips for cutting my boards, sometimes sanding the edges with 600 grit wet and dry paper with water and a little soap to get a nice smooth edge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Conformal coating is available to coat and protect your board.  I'm planning to give polyurethane varnish a try on my next project.  &lt;/p&gt;&#xA;" LastActivityDate="2010-06-18T02:49:42.267" CommentCount="1" />
  <row Id="3078" PostTypeId="2" ParentId="3062" CreationDate="2010-06-18T06:01:19.327" Score="3" ViewCount="" Body="&lt;p&gt;In an automotive application I've seen two ceramic capacitors in series to increase safety against shorts. In the extreme case a short could start a fire, and I heard that had happened at least once.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-06-18T06:01:19.327" />
  <row Id="3079" PostTypeId="2" ParentId="3062" CreationDate="2010-06-18T06:16:12.493" Score="3" ViewCount="" Body="&lt;p&gt;I've used ten 3.3F supercaps rated at 2.7V in series to build a buffer capacitor for a digitally controlled locomotive of a garden model railroad. This makes it run much better over dirty tracks or switches. The nominal voltage is 24V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the first version I used a schematic proposed by somebody else, which doesn't balance voltage. There is a 3k3 resistor anyway to discharge it over some minutes, to prevent surprises.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second one will use a 1% 330 resistor per capacitor to balance voltage, we'll see if there is a difference in longevity.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-06-18T06:16:12.493" />
  <row Id="3080" PostTypeId="2" ParentId="3067" CreationDate="2010-06-18T06:23:27.753" Score="4" ViewCount="" Body="&lt;p&gt;One thing the others didn't mention is behavior on numeric overflow. In normal processors this usually wraps around from the maximal value to the minimal value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For DSP usage there is often at least an option to use &lt;em&gt;saturation&lt;/em&gt; instead. That is, on overflow the value stays at the maximal value, which produces less distortion and better mimics the behavior of analog circuits.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-06-18T06:23:27.753" />
  <row Id="3081" PostTypeId="2" ParentId="3075" CreationDate="2010-06-18T10:42:15.070" Score="1" ViewCount="" Body="&lt;p&gt;There's a question with 15 answers &lt;a href=&quot;http://chiphacker.com/questions/1151/how-do-you-cut-pcb&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; which discusses cutting PCBs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I may have to dig out my tile cutter (a miniature circular saw with a reservoir for water cooling) and find some PCB to cut as a result of that question.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-06-18T10:42:15.070" CommentCount="2" />
  <row Id="3082" PostTypeId="2" ParentId="3075" CreationDate="2010-06-18T11:41:34.863" Score="2" ViewCount="" Body="&lt;p&gt;I use a room temp &lt;a href=&quot;http://www.rapidonline.com/Tools-Fasteners-Production-Equipment/PCB-Equipment/Etching/Tin-plating-crystals/29475/kw/tin&quot; rel=&quot;nofollow&quot;&gt;tin plating solution&lt;/a&gt; to get an evenly tinned surface, it seems expensive at first, but the solution lasts a long time and can be stored and reused if you make too much up. It comes in the form of crystals that are dissolved in hot water, it smells of eggs really bad! - I really recommend it tho - I use it all the time and it's pretty no-nonsense. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for solder mask, you can get a &lt;a href=&quot;http://www.rapidonline.com/Tools-Fasteners-Production-Equipment/Service-Aids/Sealants-Coatings/Peelable-synthetic-coating-mask/118296/kw/solder+mask&quot; rel=&quot;nofollow&quot;&gt;peelable soldermask&lt;/a&gt; that works well for protecting your board and components, it's not the prettiest of finishes but can be easily removed by hand afterward, it's certainly cheaper and less difficult than working with a DIY &lt;a href=&quot;http://uk.farnell.com/cif/u700001/varnished-welding-kit/dp/1422906&quot; rel=&quot;nofollow&quot;&gt;solder masking kit&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;:)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With regards to DIY vias - have you tried connecting the two sides with just solder, leaving the wire out? Not sure how effective this would be - but it might allow you to make them with a much lower profile so they can fit under a chip. &lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-06-18T13:11:12.290" LastActivityDate="2010-06-18T13:11:12.290" CommentCount="4" />
  <row Id="3083" PostTypeId="1" AcceptedAnswerId="3085" CreationDate="2010-06-18T12:44:01.170" Score="7" ViewCount="460" Body="&lt;p&gt;I'm trying to generate PAL tv signals using a PIC24FJ64GB002 using a similar method to the circuit described half way down &lt;a href=&quot;http://www.micro-examples.com/public/microex-navig/doc/089-pic-pal-tv&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt;. The only difference is that my circuit needs to run at 3v instead of 5v due to using a PIC24 so I've recalculated the necessary resistor values and the closest ones I can find seem to be 220 and 470 ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm connecting to the TV input via a scart lead connecting the video signal to pins 17 and 20 on the diagram on &lt;a href=&quot;http://en.wikipedia.org/wiki/SCART&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I get no picture at all on the TV. It might as well not be connected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking one of three things could be wrong :-&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;My timing is out. I've posted the diagram at the end of this post showing the timing on the two pins for my test and as far as I can tell I'm generating the correct sync timing and the other signal is just some stripes for testing. How accurate does the timing need to be? I'm using the timer interrupt on the PIC to start each line 64uS apart.&lt;/li&gt;&#xA;&lt;li&gt;I'm using the wrong resistors to mix the signal. Can someone check if I calculated the correct values to use at 3volts? How accurate do the voltage levels need to be? I chose the closest standard values, is this accurate enough?&lt;/li&gt;&#xA;&lt;li&gt;I'm connecting to the wrong inputs on my scart lead? Everything I've read shows this as being correct though...&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I am generating what I believe to be the correct frame sync pulses too. Although again, everything I've read seems to indicate that even if I get this wrong I should see &lt;em&gt;something&lt;/em&gt; and as every line is the same loss of vertical sync shouldn't matter for this test?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, any input and suggestions would be welcome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://this.domain.name/wp-content/uploads/2010/06/tv.png&quot; alt=&quot;Signal timing&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit and additional question&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I want to use RGB signals on a scart it looks like I need to have 3 connections for R, G, B and one for the sync on the composite video pin. And then each one has it's own separate GND connection... Is there any reason I can't just connect those 4 together?&lt;/p&gt;&#xA;" OwnerUserId="710" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-06-29T06:22:07.287" LastActivityDate="2010-06-30T21:26:53.647" Title="Generating PAL tv signal using a PIC" Tags="&lt;pic&gt;&lt;tv&gt;&lt;video&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="3084" PostTypeId="2" ParentId="3075" CreationDate="2010-06-18T13:06:25.727" Score="2" ViewCount="" Body="&lt;p&gt;I use the photo-etch technique and find that the small residue of resist remaining on the board after resist removal protects the copper. It's very thin so it doesn't impede soldering. I have some tin-plating compound, but haven't tried it yet.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-18T13:06:25.727" />
  <row Id="3085" PostTypeId="2" ParentId="3083" CreationDate="2010-06-18T13:12:31.773" Score="4" ViewCount="" Body="&lt;p&gt;It could be a SCART switching issue. With SCART, some TVs need a low signal on pin 16 to select RGB rather than composite.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://freespace.virgin.net/matt.waite/resource/av/scart.htm#Note%202%20&quot; rel=&quot;nofollow&quot;&gt;http://freespace.virgin.net/matt.waite/resource/av/scart.htm#Note%202%20&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also try putting your composite signal into one of the RGB channels to see if it's picked up properly.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-18T14:27:48.107" LastActivityDate="2010-06-18T14:27:48.107" CommentCount="6" />
  <row Id="3086" PostTypeId="1" AcceptedAnswerId="3087" CreationDate="2010-06-18T18:09:12.547" Score="5" ViewCount="561" Body="&lt;p&gt;I've just ordered some sample LCD displays. The only model available for now is hot bar solder (instead of a regular connector).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have any experience soldering regular thin wires to this type of connector? It seems like a 25 mil pitch.&lt;/p&gt;&#xA;" OwnerUserId="1267" LastActivityDate="2010-06-19T20:28:08.570" Title="Hot Bar Manual Solder" Tags="&lt;soldering&gt;&lt;lcd&gt;" AnswerCount="2" />
  <row Id="3087" PostTypeId="2" ParentId="3086" CreationDate="2010-06-18T21:09:53.100" Score="7" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.flexdude.com/Back%20Issues/FCN11-00A.PDF&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; pdf has a description of hot bar soldering if you're unfamiliar with it. (It is the top Google result, but it's a popular intro.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;25 mil pitch on a connector isn't too bad; it's the characteristics of the flex cable that will bite you.  If I misinterpreted, and you have the hot bar connector on the PCB they're sending you, then you shouldn't have too much trouble.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If, however, you're soldering off of the flex cable that attaches to the hot bar connector, you left out whether your flex cable has windowed, cantilevered, or unexposed leads.  If you have a choice, cantilevered will give you your best chance of success because the leads will be thicker, and you won't damage the backing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With any of the options, soldering leads onto the 25mm pitch should be alright.  Use 28 gauge wire or finer. I did a 20mil pitch, 10 mil trace cable a few weeks ago, and that went OK.  (I did have the use of a stereo microscope, you'll want a good magnifier at the very least.)  I damaged one practice cable beyond repair - The backing burns like the insulation of a wire, and, and the traces are not copper leads, they're copper foil.  Some form of strain relief will be absolutely mandatory to keep your wires from breaking off. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I would advise that it will be easier if you can solder directly to the connector leads instead.  It's easy to damage the very thin traces on your flex cable, but the connector will be much sturdier. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whatever you end up doing, make sure your wires are as short (and equal length) as possible, you might be dealing with some very high speed stuff! A 500MHz signal (for VGA resolution, using 2-wire differential signals) has a wavelength of just 5cm!&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-18T21:09:53.100" CommentCount="3" />
  <row Id="3088" PostTypeId="1" AcceptedAnswerId="3089" CreationDate="2010-06-18T21:51:07.490" Score="5" ViewCount="500" Body="&lt;h2&gt;Project&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;The system is effectively a sensor network  that connects to a star topology routing network. The Identities of each node's identity must be kept secret from all listeners as the range of the RF transmission and relay may be on the order of tens of miles. Each sensor node has its own Identification number, as required by laws pertaining to our systems target deployment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means that if someone is able to read the identifier on the node then the security has not value, so a side channel attack on our implementation is a waste of time, unless they can implement it from a long distance, but I do not believe our SPI will radiate that well when sandwiched between a power and ground layer.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Security Options&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;This question is asking for solutions to using AES-128. I will explain what I found in an answer that I was lead to directly by Joby Taffey. Thank you Joby. I was looking for off-chip low cost solutions that could speed up our system greatly, it ends up i missed something from my chip supplier.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-20T19:23:33.630" LastActivityDate="2010-06-21T04:06:38.490" Title="AES-128 Chip Solutions" Tags="&lt;encryption&gt;&lt;microcontroller&gt;" AnswerCount="3" CommentCount="0" FavoriteCount="1" />
  <row Id="3089" PostTypeId="2" ParentId="3088" CreationDate="2010-06-18T22:07:58.520" Score="5" ViewCount="" Body="&lt;p&gt;Having a separate encryption co-processor could be risky. Anyone with a Bus Pirate or logic analyser and physical access can sniff the bus and pluck out the plaintext data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can mitigate the risk a bit with BGAs and/or epoxy, but the best solution is likely to be a SoC which combines MCU with AES.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One approach might be to use a SoC ZigBee chip and ignore the radio part, eg. CC2430, or EM250.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, you could go with a Stellaris Cortex-M3 (some have AES tables in ROM)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, do it in software. I've used &lt;a href=&quot;http://gladman.plushost.co.uk/oldsite/AES/&quot; rel=&quot;nofollow&quot;&gt;Brian Gladman's code&lt;/a&gt; before in projects.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-18T22:07:58.520" CommentCount="3" />
  <row Id="3090" PostTypeId="2" ParentId="1199" CreationDate="2010-06-18T22:39:43.063" Score="13" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Atmel AVR&lt;/strong&gt;, perhaps in a &lt;strong&gt;Arduino&lt;/strong&gt;: I'd disagree with Leon, and say that Atmel's AVR line is a great family to start with.  It's pretty diverse, ranging from the ATtiny, through the ATmega, to the Dragon (which I haven't worked with.)  I'd say that the AVR32 and Xmega are different families.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;AVRfreaks is one of the best electronics forums on the web (soon to be surpassed by Chiphacker :), the Arduino community also exists, which is targeted to hobbyists.  Arduino is great for learning microcontroller hardware, although it won't help you with programming (The OP stated that they knew ASM and C). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The WinAVR suite is easy as pie compared to other toolchains.  Just download, push Next a few times, enter some code and hit F5.  It doesn't get any easier than that.  Sure, the AVR Studio editor doesn't have all the features it should have, but a lot of vendor IDEs  are no better, or even worse (*cough*MPLAB*cough*). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure about delivery, but I'd say the 6-pin SOT23 ATtiny is a niche chip, and the SO8 or DIP version is very much available.  On a related note, they also do a great job of sourcing them both in DIP (for prototyping) and compact SMT packages.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2010-06-23T20:31:00.213" LastActivityDate="2010-06-23T20:31:00.213" CommunityOwnedDate="2010-06-18T22:39:43.063" CommentCount="3" />
  <row Id="3091" PostTypeId="2" ParentId="3088" CreationDate="2010-06-18T23:17:16.650" Score="3" ViewCount="" Body="&lt;p&gt;As said before, off-chip is risky as its very hard to control the keys and other important information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are microcontrollers which contain AES accelerators or function tables. The AVR XMEGA has an engine which can do AES fairly quickly (its not super security hardened though, including known power attacks). The aforementioned Stellaris controllers have the large tables in ROM which saves quite a bit of storage space.&lt;/p&gt;&#xA;" OwnerUserId="867" LastActivityDate="2010-06-18T23:17:16.650" CommentCount="3" />
  <row Id="3092" PostTypeId="1" AcceptedAnswerId="3097" CreationDate="2010-06-18T23:48:52.177" Score="6" ViewCount="440" Body="&lt;p&gt;Does anyone have some cool ideas for a use of a scripting language on an embedded system?  I'm thinking about the &lt;a href=&quot;http://www.eluaproject.net/&quot; rel=&quot;nofollow&quot;&gt;eLua&lt;/a&gt; project specifically. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, you need a micro with at least 64k of RAM, 256k of Flash, the Newlib C library, and a gcc compiler, (AVR32, ARM7, Cortex-M3 are all supported right now among others), and you can send it (or program it to load) scripts.  It doesn't need an OS, but it lets you use your micro (which is far too small for embedded Linux) much more like a general purpose computing device, by allowing programs not flashed into the program memory to be run.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current project has a number of example applications, but none of them seem to do anything that you can't do with a program burned into Flash.  The big difference that I can see is that you can send each program separately, and run different programs without resetting.  In addition, you can use it interactively (Change your program flow with your decisions at the keyboard, rather than having to code everything. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would you use such a device?  Would you give it a keyboard and character LCD, and write your own scripts while it sat on your desk?  Would you simply use the scripting language to simplify programming of more complex applications?  (Like the games currently available on the project site?)  Or would you do something completely different?  I'm getting started with it and looking for project ideas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;: You can send it programs over whatever protocol you want to use (UART, SPI/I2C etc., USB, Ethernet), load them from an SD card, whatever your chip supports.  Just wanted to clarify that it didn't have to be in a reprogramming-friendly environment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit2&lt;/strong&gt;: Most of my projects are for my personal use, or for sharing with like-minded friends, not often for sale to the general public.  I expect users of my projects to be interested in and familiar with embedded systems, and able to pick up the rudimentary use of a scripting language without too much trouble.  I might use them around the house or in the car, or more likely in the shop as an aide to designing and debugging more new projects. I also might propose it to my boss at work, where we manufacture and design embedded systems. Or, I might use it on an engineering project for school.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-06-19T01:36:59.853" LastActivityDate="2011-02-22T01:16:42.353" Title="Embedded system scripting" Tags="&lt;projects&gt;&lt;usb&gt;&lt;sd&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="3093" PostTypeId="1" AcceptedAnswerId="3096" CreationDate="2010-06-19T00:04:48.170" Score="3" ViewCount="381" Body="&lt;p&gt;I've found it useful to have a bunch of 2.54mm headers laying around. They fit nicely into breadboards&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://mmccoo.com/clips/2010_06_18_16_002.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I'd like to use a connector to connect to them. Something like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://mmccoo.com/clips/2010_06_18_16_001.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure how to look for these in the catalogs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see these in mouser &lt;a href=&quot;http://www.mouser.com/ProductDetail/Molex/47054-1000/?qs=sGAEpiMZZMtsLRyDR9nM1ym23zbAtOmYHqQplao1K4Q%3d&quot; rel=&quot;nofollow&quot;&gt;mouser part: 538-47054-1000&lt;/a&gt; for $0.06 each. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or these &lt;a href=&quot;http://www.mouser.com/ProductDetail/Tyco-Electronics-AMP/103688-7/?qs=sGAEpiMZZMtsLRyDR9nM1%2fNdx6mvyyyy8sxayqNrIYs%3d&quot; rel=&quot;nofollow&quot;&gt;mouser part: 571-103688-7&lt;/a&gt; for $0.50 each&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;how do I shop for these in the catalogs?&lt;/li&gt;&#xA;&lt;li&gt;how do I know if the crimp terminators (what's the proper term) are included?&lt;/li&gt;&#xA;&lt;li&gt;If they're not included, how do I spec those?&lt;/li&gt;&#xA;&lt;li&gt;How do I actually connect these to my wires?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="550" LastActivityDate="2010-10-01T18:28:19.163" Title="2.54mm connector question" Tags="&lt;connector&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="3094" PostTypeId="2" ParentId="3093" CreationDate="2010-06-19T01:01:57.827" Score="3" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1003651+5254426&amp;amp;Ntk=PLS_MAN_BRAND_NAME&amp;amp;Ntt=harwin&amp;amp;Ntx=&amp;amp;No=0&amp;amp;getResults=true&amp;amp;appliedparametrics=true&amp;amp;locale=en_UK&amp;amp;catalogId=&amp;amp;prevNValues=500006+1003651&amp;amp;filtersHidden=false&amp;amp;appliedHidden=false&amp;amp;originalQueryURL=%2Fjsp%2Fsearch%2Fbrowse.jsp%3FN%3D500006%2B1003651%26Ntk%3DPLS_MAN_BRAND_NAME%26Ntt%3Dharwin%26Ntx%3D%26No%3D0%26getResults%3Dtrue%26appliedparametrics%3Dtrue%26locale%3Den_UK%26catalogId%3D%26prevNValues%3D500006%2B1003651&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; Harwin connectors.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-19T01:01:57.827" CommentCount="2" />
  <row Id="3095" PostTypeId="2" ParentId="3093" CreationDate="2010-06-19T01:09:20.453" Score="6" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;how do I shop for these in the catalogs?&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Search for &quot;receptacle&quot; and narrow down the parameters to Headers, Receptacles, Freehanging, Female Sockets, then further narrow your search by number of rows, positions, pitch, etc.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;how do I know if the crimp terminators (what's the proper term) are included?&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If the catalog doesn't make it clear, call the distributor and find out.  On Digikey, for instance, what you see in the picture is generally what you get.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;If they're not included, how do I spec those?&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Check the data sheet.  Some places make this easy - scroll down on &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?KeyWords=a28356-nd&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; and you'll see a list of header it mates to, as well as terminals that fit it.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;How do I actually connect these to my wires?&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;You'll need a crimping tool.  The manufacturer crimping tools are generally expensive, but some places, such as Radio Shack in the US, have cheap generic crimping tools which work well enough for most uses.  The one I use for prototyping is the &lt;a href=&quot;http://www.radioshack.com/product/index.jsp?productId=2103683&quot; rel=&quot;nofollow&quot;&gt;Radio Shack 276-1595&lt;/a&gt; that I've had forever.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-06-19T01:09:20.453" CommentCount="1" />
  <row Id="3096" PostTypeId="2" ParentId="3093" CreationDate="2010-06-19T01:19:16.063" Score="7" ViewCount="" Body="&lt;p&gt;tl;dr:&lt;br&gt;&#xA;You can get the 36-pin female version of that header, like &lt;a href=&quot;http://parts.digikey.com/1/parts/318656-conn-recept-100-sngl-str-36pos-929850-01-36-10.html&quot; rel=&quot;nofollow&quot;&gt;this one,&lt;/a&gt; and solder it to your perfboard/pcb (not recommended as a long term solution for wires, but it will be fine for breadboarded circuits) or you can do it with connectors like the ones you showed.&lt;br&gt;&#xA;For the special connectors, you probably want to find a like you like (I like &lt;a href=&quot;http://www.jst-mfg.com/product/pdf/eng/eXH.pdf&quot; rel=&quot;nofollow&quot;&gt;mini JST (aka XH)&lt;/a&gt;) and just stock an assortment of those for all your connections.  You will need the 'crimp terminators' (usually called &quot;crimp terminals&quot;) for that, as well as a crimper (which is often expensive, but cheap universal ones/ebay specials can be had).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Extended answer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, it all depends on what you want to do.  For a PCB-PCB connection, the obvious answer is a female header like &lt;a href=&quot;http://parts.digikey.com/1/parts/318656-conn-recept-100-sngl-str-36pos-929850-01-36-10.html&quot; rel=&quot;nofollow&quot;&gt;this one.&lt;/a&gt;  It's the counterpart to the .1&quot; header you showed above.  They are ideal for connecting a PCB; see the Arduino shields for examples.  However, compared to the connector in your second image, they are much weaker, which is OK for two PCBs (you can put some #4 standoffs between them it if you need strength, but there's usually little force acting on them sitting in an enclosure or on a workbench).  Of course, you can always just solder some wires onto the female one.  That's your cheapest, easiest option.  A little heat shrink around the pins and your wires will go a long way towards stopping breakages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you want to plug cables into your breadboard or other project the right way, for long-term stuff from your projects, you're going to need/want something different.  You'll want a connector that is polarized, that has a reasonable insertion force, and some lock or click that verifies the connection is often nice.  The other big difference is that the cables you connect to it have to be able to flex.  The real-world answer to this is crimped connectors (Like the one you showed) and stranded wire (unlike the solid stuff on your breadboard, so it doesn't break at the connection point).&lt;br&gt;&#xA;For this, I like the mini-JST (for 2-10 wires) and AMP-Latch (for 26, 34, 60+ wires) series.  The mini-JST series will fit a breadboard (don't miss that the .098&quot; will also fit in your Digikey searches).  They have &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=455-2270-ND&quot; rel=&quot;nofollow&quot;&gt;vertical&lt;/a&gt; (pulls out of breadboard) and &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=455-2242-ND&quot; rel=&quot;nofollow&quot;&gt;right angle&lt;/a&gt; (works great!) headers to go into the same &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=455-2268-ND&quot; rel=&quot;nofollow&quot;&gt;female cable-side connectors&lt;/a&gt;.  In addition, you'll need a pack of &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=455-1135-1-ND&quot; rel=&quot;nofollow&quot;&gt;these crimp terminals&lt;/a&gt;: &lt;a href=&quot;http://www.tme.eu/katalog_pics/1/0/c/10c65c23c4c4b2899f422cd29ad623ad/svh-21t-p1.1.jpg&quot; rel=&quot;nofollow&quot;&gt;Photo&lt;/a&gt;.  The flying leads on the right go around the insulation, you strip off 3/16&quot; of insulation for the short ones to grab, and the header pin goes in the spring-loaded socket.  They're not bulky, but still easy to handle, quite durable in my experience, have a great assortment, and ... require a &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=455-1136-ND&quot; rel=&quot;nofollow&quot;&gt;$440 crimp tool&lt;/a&gt;.&lt;br&gt;&#xA;You'll find the crimp tool issue to be a problem.  If your school/work has one, you can borrow that and make a bunch of crimped sections one day to bring home, but otherwise you just have to look for what other hobbyists.  Try &lt;a href=&quot;http://shop.ebay.com/i.html?_nkw=%28crimp%2Ccrimping%2Ccrimper%29+tool+%28AMP%2CMOLEX%2CJST%29&amp;amp;_in_kw=1&amp;amp;_ex_kw=&amp;amp;_sacat=See-All-Categories&amp;amp;_okw=%28crimp%2Ccrimping%2Ccrimper%29+tool+%28AMP%2CMOLEX%2CJST%29&amp;amp;_oexkw=&amp;amp;_udlo=&amp;amp;_udhi=&amp;amp;_ftrt=901&amp;amp;_ftrv=1&amp;amp;_sabdlo=&amp;amp;_sabdhi=&amp;amp;_samilow=&amp;amp;_samihi=&amp;amp;_sadis=200&amp;amp;_fpos=Zip+code&amp;amp;_fsct=&amp;amp;LH_SALE_CURRENCY=0&amp;amp;_sop=12&amp;amp;_dmd=1&amp;amp;_ipg=50&quot; rel=&quot;nofollow&quot;&gt;ebay&lt;/a&gt;.  Alternatives like &lt;a href=&quot;http://parts.digikey.com/1/parts/392052-tool-crimp-14-24awg-universal-63811-1000.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; 'universal' one from Molex will work, but if you're going to be in this for a long time, you'll want to find one designed for the connector you're using.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-19T01:19:16.063" CommentCount="2" />
  <row Id="3097" PostTypeId="2" ParentId="3092" CreationDate="2010-06-19T01:20:36.793" Score="5" ViewCount="" Body="&lt;p&gt;I'm planning on embedding a scripting language in my little mom-find-me device (finally progressing again, hope to have a working prototype by the Detroit Maker Faire next month).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a little platform with GPS, compass, SD card, and zigbee that is meant to help my keep track of my younger kids at large parks, and to give them a way to easily find me when they need me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The embedded scripting language will provide a protected sandbox where simple applications, such as games, maps, geocaching programs, or multiplayer games (several kids, each with a unit can play enhanced versions of capture the flag, hide and seek, tag, etc) without affecting the base function of being able to track my kids.  These would go on the SD card as text files so they can easily be edited and updated with no special hardware or software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are lots of other ways and reasons to use a scripting language in embedded systems, but in order to see how or why it might fit into your needs we'd have to understand more about your particular system.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2010-06-19T01:20:36.793" CommentCount="4" />
  <row Id="3098" PostTypeId="2" ParentId="3086" CreationDate="2010-06-19T13:34:38.633" Score="6" ViewCount="" Body="&lt;p&gt;I was worried about it myself, but decided to bite the bullet and try it out.  It's relatively easy and straightforward.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I made the PCB pattern following the LCD data sheet for the cable terminal spacing and pitch.  I made my pads a little longer so I could either solder on top of, or next to the cable if needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PCB came with enough tinning that I simply lined it up, and pressed each terminal down with the tip of my soldering iron.  It melted right into the solder already on the pads.  I added a little more solder to a few terminals that didn't have a nice meniscus from the cable to the PCB.  If the PCB isn't pre tinned, then you might consider adding a &lt;em&gt;little&lt;/em&gt; solder to each pad, then swiping some flux across all the pads.  If you add too much solder you'll find that the terminals will short as the solder squishes under the cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also note that the terminals on the cable have small vias on the terminals themselves - if the solder draws up into them, it's a pretty easy and convenient way to know the connection is made.&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Process&lt;/h1&gt;&#xA;&#xA;&lt;h3&gt;Tin the pads if the PCB doesn't have any solder on the pads already&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/adavis/4715214542/&quot; rel=&quot;nofollow&quot; title=&quot;Hot bar soldering without the hotbar by stienman, on Flickr&quot;&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4068/4715214542_d3f55fec6b.jpg&quot; width=&quot;500&quot; height=&quot;333&quot; alt=&quot;Hot bar soldering without the hotbar&quot; /&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Apply flux to pads, then use the adhesive on the cable, if any, to secure the cable in the right spot.&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/adavis/4715219626/&quot; rel=&quot;nofollow&quot; title=&quot;Hot bar soldering without the hotbar by stienman, on Flickr&quot;&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4028/4715219626_e8fbfc7ecd.jpg&quot; width=&quot;500&quot; height=&quot;333&quot; alt=&quot;Hot bar soldering without the hotbar&quot; /&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Press the soldering iron into the joint so it touches both the contact and the pad, if possible (some cables don't have exposed contacts like this one), then press the soldering iron down on the cable contact itself.  It should pick up a litle of the solder on the board and make a connection.&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/adavis/4714584859/&quot; rel=&quot;nofollow&quot; title=&quot;Hot bar soldering without the hotbar by stienman, on Flickr&quot;&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4020/4714584859_fd491eb956.jpg&quot; width=&quot;500&quot; height=&quot;333&quot; alt=&quot;Hot bar soldering without the hotbar&quot; /&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;For this cable I also added more solder so the connections would be very secure.&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/adavis/4715230416/&quot; rel=&quot;nofollow&quot; title=&quot;Hot bar soldering without the hotbar by stienman, on Flickr&quot;&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4026/4715230416_f1c712d200.jpg&quot; width=&quot;500&quot; height=&quot;333&quot; alt=&quot;Hot bar soldering without the hotbar&quot; /&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The images above link to a page where the full resolution is available.  For reference, the board is 2.5&quot; wide, and the LCD I was attaching is the &lt;a href=&quot;http://www.newhavendisplay.com/index.php?main_page=product_info&amp;amp;cPath=1&amp;amp;products_id=2602&quot; rel=&quot;nofollow&quot;&gt;2.4&quot; TFT LCD&lt;/a&gt; available from Newhaven Display International.&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="161" LastEditorDisplayName="" LastEditDate="2010-06-19T20:28:08.570" LastActivityDate="2010-06-19T20:28:08.570" CommentCount="1" />
  <row Id="3099" PostTypeId="1" AcceptedAnswerId="3100" CreationDate="2010-06-19T20:03:14.487" Score="6" ViewCount="499" Body="&lt;p&gt;They keep me fairly busy at work, and I've got a number of cool projects.  We don't have a &lt;a href=&quot;http://en.wikipedia.org/wiki/Google#Innovation_Time_Off&quot; rel=&quot;nofollow&quot;&gt;Google 20% time&lt;/a&gt; to work on our own ideas, and we have process improvement engineers and R&amp;amp;D engineers who spend their entire careers working on and thinking up new ideas.  I'm not a process engineer, an R&amp;amp;D engineer, or a senior engineer with the freedom to choose or invent my own projects, but I've come up with some projects that I'd like to explore.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How should I pursue this?  I don't want to appear arrogant to my superiors, I don't want to tell R&amp;amp;D what they should be working on, and I definitely can't just put off my assigned projects to work on what I want to work on.  I would like to get payment and/or attribution for the ideas, but that's not as important as seeing it happen.  I'd also like new ideas to happen with the support groups that we already have (I don't want to do someone else's job.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I can tell, my options are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Submit the project to my superiors/R&amp;amp;D.&lt;/li&gt;&#xA;&lt;li&gt;Make time in my schedule or work more hours to do the project at work.&lt;/li&gt;&#xA;&lt;li&gt;Work on the project at home. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;None of these seem to be ideal.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can submit the project to someone higher on the decision chain, but my ideas generally aren't necessary to the business or safe bets, like the ones that they are constantly receiving.  I discuss many of them with my boss, and he generally thinks they're good ideas.  Sometimes I have a solution for a pie-in-the-sky feature request that gets put off as too hard.  I just don't want to go to the gurus and say &quot;Look, why didn't you try this?  You should spend the next couple weeks implementing it.&quot; I'm just an hourly intern.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Working ahead isn't really an option because they keep a list of projects in my queue.  When I get one done, I'm supposed to move onto the next highest priority, and I really can't just ignore that for my ideas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Working on it at home is possible, but then I lack the support chain that the rest of the group provides, have lesser tools, and might get into some issues with not being able to take stuff home.  Additionally, I don't get paid for it this way, and this method also guarantees that it will take more time than if it was implemented at work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone else had similar struggles?  I'm sure that most every engineer has ideas, and I'd like to hear about what you did to submit them to your company.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt;  We have about 5,000 employees at &lt;a href=&quot;http://www.gentex.com/&quot; rel=&quot;nofollow&quot;&gt;my company&lt;/a&gt;.  However, I work in the testing department with about 15 other people; it really doesn't feel very big.  I personally know most of the people who have developed the projects that I want to work on. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit2:&lt;/strong&gt; I've proposed my ideas to my boss, and he's been interested.  I'd rather not just submit them to R&amp;amp;D, as the devices and systems I want to work on would be familiar to myself and my department, but new to the R&amp;amp;D guys. &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T02:50:40.960" LastActivityDate="2011-02-08T02:50:40.960" Title="How to propose/work on a project for work" Tags="&lt;project-management&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="3100" PostTypeId="2" ParentId="3099" CreationDate="2010-06-19T23:00:45.743" Score="4" ViewCount="" Body="&lt;p&gt;I think the fact that you're an hourly intern puts you in a tough spot. While I find your spirit and initiative admirable, and probably a sign of a good engineer in development, I think you're unlikely to find a solution where you will get paid to work on those ideas. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting paid to work on, as you say, &quot;pie-in-the-sky&quot; ideas is one of the hardest qualities to find in a job. You need a trusting boss, an impressive track record of successful implementation of previous work, and a company in a dynamic field. I think it's easier to find jobs that are high-paying, easy, or both.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best strategies I can think of are to impress your boss or inject your ideas into the R&amp;amp;D team. Perhaps you could swing a deal with your boss along the lines of &quot;If I can get this project done well by Monday instead of Tuesday, can I spend Monday working on this new idea? You pay the same amount either way, and this idea is really awesome.&quot;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-19T23:00:45.743" CommentCount="4" />
  <row Id="3101" PostTypeId="1" AcceptedAnswerId="3102" CreationDate="2010-06-19T23:37:25.180" Score="5" ViewCount="179" Body="&lt;p&gt;Does anyone know what's entailed in connecting a computer that has only an 'AUI' network interface into a modern LAN? By AUI port, I'm referring to one of those 15-pin D connector arrangements that used to be popular in the early 1990's. I know that establishing a network protocol will undoubtedly be a challenge in its own right, but that's beyond the scope of this question. At the moment, I just want to &quot;get a link light&quot; from it on one of my ethernet switches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would almost swear I once saw a jury-rigged connector that had just four wires with pins crimped on them jammed into selected points on the 15-pin D, though I don't recall what these wires ran to, but I thought it was an RJ-45. Could easily be mistaken on that. Just b/c someone had something wired with an RJ-45 doesn't necessarily mean it was 10BaseT.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, there are references to the AUI signal set being part of the IEEE 802.11 standard. Could it really be as simple as mapping a certain 4 of the 15 to the 1,2,3, and 6 of 10BaseT? Or could it be done with just a couple of line driver/receiver IC's?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know there are $30 commercial solutions to the problem, but I am loathe to invest even that much on the system in question, as it would already be on its way into the electronics recycling bin but for academic curiosity about the old interface.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-25T16:19:59.613" Title="hacking an AUI network port" Tags="&lt;network-interface&gt;&lt;ethernet&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="3102" PostTypeId="2" ParentId="3101" CreationDate="2010-06-20T01:00:31.943" Score="6" ViewCount="" Body="&lt;p&gt;I believe the AUI interface provides access to the Ethernet MAC directly. You might be able to make it talk to an older 10BASE-T switch, but it definitely won't work with a 100BASE-T or Gigabit Ethernet switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In modern devices, the MAC connects to what's called a PHY chip-- the chip that generates the &lt;a href=&quot;http://en.wikipedia.org/wiki/MLT-3&quot; rel=&quot;nofollow&quot;&gt;MLT-3&lt;/a&gt; waveforms required for higher data rates. Without a PHY chip (which is probably what those $30 adapters contain), it won't work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But with an older switch, you might have a chance. The data might come out Manchester-encoded, which might be comprehensible to a 10BASE-T port. I'd start with the AUI description in Spurgeon's Ethernet book: &lt;a href=&quot;http://books.google.com/books?id=VbTvnxBKzUgC&amp;amp;pg=PA118&quot; rel=&quot;nofollow&quot;&gt;http://books.google.com/books?id=VbTvnxBKzUgC&amp;amp;pg=PA118&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-20T01:00:31.943" CommentCount="3" />
  <row Id="3103" PostTypeId="2" ParentId="3045" CreationDate="2010-06-20T04:48:37.843" Score="0" ViewCount="" Body="&lt;p&gt;Contacting the manufacturers for this topic is a challenge, because the distribution channels do not have answers for samples. Any better idea ?&lt;/p&gt;&#xA;" LastActivityDate="2010-06-20T04:48:37.843" />
  <row Id="3104" PostTypeId="2" ParentId="3008" CreationDate="2010-06-20T04:54:04.227" Score="1" ViewCount="" Body="&lt;p&gt;Arduino Mega hardware SPI pins are not located in the same place as on the ordinary Arduino. You will need to change the library.&lt;/p&gt;&#xA;" OwnerUserId="870" LastActivityDate="2010-06-20T04:54:04.227" CommentCount="1" />
  <row Id="3105" PostTypeId="1" AcceptedAnswerId="3109" CreationDate="2010-06-20T08:58:39.570" Score="13" ViewCount="1569" Body="&lt;p&gt;I am working with a PIC micro-controller with inbuilt 10bit ADC and want to measure a voltage in the range of -1 to -3Volts.&lt;br&gt;&#xA;I thought of using an op-amp in the inverting mode to make voltage positive and then feed it to the adc of the microcontroller however here I would have to power the opamp with a negative power supply, right?. &#xA;I don't want to use a negative power supply at the moment and was wondering whether it was possible to achieve this configuration? &#xA;Can you'll help out?&lt;/p&gt;&#xA;" OwnerUserId="444" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-25T06:28:39.220" LastActivityDate="2011-01-25T06:28:39.220" Title="How do I measure a negative voltage with a ADC?" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;adc&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="4" />
  <row Id="3106" PostTypeId="2" ParentId="3105" CreationDate="2010-06-20T09:21:58.380" Score="9" ViewCount="" Body="&lt;p&gt;You could use a voltage divider, with one end hanging off the positive supply rail. Say you have one with equal resistors and a 5V power supply, this will result in a voltage between +2V and +1V for your -1 to -3V range.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;+5V +&#xA;    |&#xA;    R&#xA;    |&#xA;    +-- OUT&#xA;    |&#xA;    R&#xA;    |&#xA;IN -+&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="401" LastActivityDate="2010-06-20T09:21:58.380" CommentCount="4" />
  <row Id="3107" PostTypeId="1" CreationDate="2010-06-20T10:48:07.973" Score="13" ViewCount="664" Body="&lt;p&gt;Investigated FPGA boards but cannot find open-sourced board and vendor-neutral FPGA development tools:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The ORSoC manufacturer boasts open-sourcing on its &lt;a href=&quot;http://orsoc.se/io_board&quot; rel=&quot;nofollow&quot;&gt;website&lt;/a&gt; but I cannot really find strong evidence except webmastering OpenCores.org. &lt;/li&gt;&#xA;&lt;li&gt;The duo: Xilinx &lt;a href=&quot;http://press.xilinx.com/phoenix.zhtml?c=212763&amp;amp;p=irol-newsArticle&amp;amp;ID=1134271&amp;amp;highlight=&quot; rel=&quot;nofollow&quot;&gt;advertises&lt;/a&gt; its products with &quot;Open Source Hardware Innovation Contest for Mainland China Universities&quot;. Still their products are proprietary, poor support for *ix --. Similarly, Altera has a poor support for *ix, just check their OS support with Quartus or how to have your logic analyser in the synthetic step?&lt;/li&gt;&#xA;&lt;li&gt;Group of small players -- let you point the best.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Is there some manufacturer strong with open-sourcing things such as hw and dev tools?&lt;/p&gt;&#xA;" OwnerUserId="834" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-06-20T13:59:18.773" LastActivityDate="2010-10-01T17:50:23.153" Title="Looking for open source FPGA hardware and dev tools" Tags="&lt;fpga&gt;&lt;open-source&gt;" AnswerCount="5" FavoriteCount="7" />
  <row Id="3108" PostTypeId="2" ParentId="3105" CreationDate="2010-06-20T14:15:50.347" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.leonheller.com/images/Bipolar-unipolar.gif&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is the standard circuit for that sort of conversion. I simulated it to prove to someone that it worked, hence the SPICE schematic. You need to choose appropriate resistor values, it works as long as they are 2R, 2R and R.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-20T14:15:50.347" />
  <row Id="3109" PostTypeId="2" ParentId="3105" CreationDate="2010-06-20T17:50:54.503" Score="21" ViewCount="" Body="&lt;p&gt;I know this has an answer accepted, but I would like to answer the question you asked in your question. You do not need a negative rail to invert the voltage.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;                                   R&#xA;                                   ___&#xA;                           .------|___|----.&#xA;                           |               |&#xA;                           |               |&#xA;                           |               |&#xA;                           |        VCC    |&#xA;                           |         +     |&#xA;              R            |         |     |&#xA;             ___           |       |\|     |&#xA;     Input -|___|----------o-------|-\     |   Output&#xA;                                   |  &amp;gt;----o----&#xA;                            .------|+/&#xA;                            |      |/|&#xA;                            |        |&#xA;                           ===      ===&#xA;                           GND      GND&#xA;(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Try to think of your power rails as what supply your output. If you look at the circuit all op-amp pins are tied to a voltage of 0V or higher. When your range of -1 to -3 comes in, it will show up as the exact opposite of 1 to 3 on the output. This also gives you some advantages as a buffer, as the input impedance of your pin will not affect this circuit very much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I agree that a simple resistor divider does the job, just letting you know that this works also.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-20T17:50:54.503" CommentCount="11" />
  <row Id="3110" PostTypeId="2" ParentId="3107" CreationDate="2010-06-20T19:07:07.120" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.gadgetfactory.net/gf/project/butterfly_main/&quot; rel=&quot;nofollow&quot;&gt;Butterfly Board&lt;/a&gt; looks like a good open source beginners route into FPGAs. They've already ported the AVR8 core so you can run Arduino sketches/AVR object code on the thing, so there's a sane learning curve.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that Xilinx WebPack is needed and it's available for Windows and Linux.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-20T19:07:07.120" CommentCount="5" />
  <row Id="3111" PostTypeId="2" ParentId="3088" CreationDate="2010-06-20T19:31:42.357" Score="2" ViewCount="" Body="&lt;p&gt;Joby pointed me to the CC2430 as a device that can do AES. I went to &lt;a href=&quot;http://www.ti.com/&quot; rel=&quot;nofollow&quot;&gt;TIs site&lt;/a&gt; intrigued by this and did some research. TI also makes our transceiver for our frequency bands(CC1100) and the new &lt;a href=&quot;http://www.ti.com/corp/docs/landing/cc430/index.htm&quot; rel=&quot;nofollow&quot;&gt;CC1100 merged with an MSP430 for a SoC&lt;/a&gt; now has AES-128 built in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This saves us board space and was a planned change already, but this results in full support for AES-128 automatically. Completely internal encryption and decryption, which for our chip without Multiply or divide hardware took more than 10mS to complete on its own.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-06-21T04:06:38.490" LastActivityDate="2010-06-21T04:06:38.490" CommentCount="3" />
  <row Id="3112" PostTypeId="2" ParentId="3027" CreationDate="2010-06-20T19:53:52.610" Score="9" ViewCount="" Body="&lt;p&gt;C++ is absolutely suitable for embedded systems. I now use the presence/absence of good development tools (or lack thereof) as my primary criterion for whether or not to use a particular microprocessor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Areas of C++ that are good to use on embedded systems because they have low resource costs:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;modularity brought by good use of classes/structures&lt;/li&gt;&#xA;&lt;li&gt;templates &lt;strong&gt;if&lt;/strong&gt; the compiler does a good job of compiling them efficiently. Templates are a good tool for bringing reuse of algorithms to different data types.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;OK areas:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;virtual functions -- I used to be against this, but the resource cost is very small (one vtable per &lt;em&gt;class&lt;/em&gt;, not per object; one pointer to the vtable per object; one dereferencing operation per virtual function call) and the big advantage of this is that it allows you to have an array containing several different types of objects w/o having to know what type they are. I used this recently to have an array of objects each representing an I2C device, each with separate methods.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Areas not to use:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;dynamic memory allocation -- others have mentioned this, but another important reason &lt;em&gt;not&lt;/em&gt; to use dynamic memory allocation is that it represents uncertainty in timing; many reasons to use embedded systems are for real-time applications.&lt;/li&gt;&#xA;&lt;li&gt;RTTI (real time type information)&lt;/li&gt;&#xA;&lt;li&gt;exceptions -- a &lt;strong&gt;definite&lt;/strong&gt; no.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-06-20T19:53:52.610" CommunityOwnedDate="2010-06-20T19:53:52.610" CommentCount="1" />
  <row Id="3113" PostTypeId="1" AcceptedAnswerId="3114" CreationDate="2010-06-20T21:30:38.440" Score="2" ViewCount="521" Body="&lt;p&gt;I have been programming an ATMega644PA with avr-gcc and avrdude on linux for a little while with no problems. Well until I decided to change some fuses. I had been using the option for avrdude &lt;code&gt;-p ATMEGA644P&lt;/code&gt; for programming the chip even though the chip is ATMega644P&lt;b&gt;A&lt;/b&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After reading the data sheet (and reading the fuses on the chip) I did the following&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;avrdude -v -c avrispmkII -p ATMEGA644P -P usb -U lfuse:w:0x63:m&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The chip would no longer communicate. I realized after that the problem may have been that I set the bits for external clock rather than crystal oscillator but even with using an ATTiny to generate a 1MHz signal to the proper pin on my Mega644, I still get nothing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas as to why the chip is unresponsive? Could it be that using avrdude's definition for the P version of the chip rather than the PA version is the cause?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And finally, What can I do to rescue my chip? Ive heard that it may be possible with High voltage programming or JTAG. Would I be able to do that with an STK500?&lt;/p&gt;&#xA;" OwnerUserId="872" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-07T06:34:45.103" LastActivityDate="2011-02-07T06:34:45.103" Title="ATMega644PA possibly bricked by setting fuses with avrdude" Tags="&lt;atmega&gt;&lt;linux&gt;&lt;avrdude&gt;&lt;fuse-bits&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="3114" PostTypeId="2" ParentId="3113" CreationDate="2010-06-20T22:36:21.723" Score="5" ViewCount="" Body="&lt;p&gt;Nope, your 0x63 setting on the lfuse byte has selected the internal 128kHz oscillator as the clock source.  (bytes 3..0 are CKSEL, see table 7.1 on p.28 of the &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8272.pdf&quot; rel=&quot;nofollow&quot;&gt;ATmega644 datasheet&lt;/a&gt; where 0011 is 'Internal 128 kHz RC Oscillator').  This is nice and low power, but it means that your programmer likely isn't clocking itself slowly enough to program your device. I'm not familiar with either avrdude or the STK500, but this is where your problem is coming from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, it will be difficult for you to brick your chip, because you've got the STK500, which can do high voltage programming and rescue it from most situations.  As I've never used the device, I'll defer to the &lt;a href=&quot;http://www.google.com/search?q=site%3Aavrfreaks.net+high+voltage+programming+fuses&quot; rel=&quot;nofollow&quot;&gt;many&lt;/a&gt; &lt;a href=&quot;http://www.google.com/search?hl=en&amp;amp;q=site%3Aavrfreaks.net+fuse+settings&quot; rel=&quot;nofollow&quot;&gt;other&lt;/a&gt; &lt;a href=&quot;http://www.google.com/search?hl=en&amp;amp;q=site%3Aavrfreaks.net+fuses+stk500&quot; rel=&quot;nofollow&quot;&gt;threads&lt;/a&gt; where others have posted problems and solutions for AVR fuse settings.  There's also one here on Chiphacker (see my comment.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next time, &lt;a href=&quot;http://www.engbedded.com/fusecalc/&quot; rel=&quot;nofollow&quot;&gt;this fuse setting calculator&lt;/a&gt; is a nice resource.  It's fantastic that you read the datasheet, and tried to calculate what you wanted yourself, but the tool makes it much easier. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, what were the fuses set to before you made the change?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; Looks like the 'A' option just indicates that it's not a member of the &quot;*&lt;em&gt;P&lt;/em&gt;*ico Power&quot; series, so that shouldn't make a difference.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-06-20T23:08:38.667" LastActivityDate="2010-06-20T23:08:38.667" CommentCount="1" />
  <row Id="3115" PostTypeId="1" AcceptedAnswerId="3116" CreationDate="2010-06-21T08:54:51.693" Score="3" ViewCount="144" Body="&lt;p&gt;Hi, I have to choose a tool for production testing of fairly dense PCB's with 4+ FPGAs 10+ DSPs, ethernet controllers and PCI controllers.. Does anyone have any experience with any of the tools available from GOEPEL, XJTAG, Jtag-technologies or if anyone know of any good open source alternatives? That is both the BS hardware controller and/or software.. &lt;/p&gt;&#xA;" LastActivityDate="2010-06-28T19:06:41.317" Title="Boundary scan developer and testing tools" Tags="&lt;jtag&gt;&lt;boundary-scan&gt;&lt;production-testing&gt;" AnswerCount="3" />
  <row Id="3116" PostTypeId="2" ParentId="3115" CreationDate="2010-06-21T09:20:41.517" Score="2" ViewCount="" Body="&lt;p&gt;OpenOCD is an open source JTAG debugger, it supports a good range of &lt;a href=&quot;http://repo.or.cz/w/openocd.git/tree/acee9d1c65bd97bbd5aa2b633e2455e87edbe836:/src/jtag/drivers&quot; rel=&quot;nofollow&quot;&gt;adapters&lt;/a&gt; both open source and proprietary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's worth looking into. But, I have only used it for simple boards with single microcontrollers.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-21T09:20:41.517" CommentCount="1" />
  <row Id="3117" PostTypeId="1" AcceptedAnswerId="3118" CreationDate="2010-06-21T10:01:07.200" Score="4" ViewCount="416" Body="&lt;p&gt;Are there any interesting and graphical videos for learning electronic concepts, like basic principles of capacitor, inductor, resistor, transistor and other advanced concepts like digital electronics?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am mostly looking for animated videos which would teach me concepts and possibly their practical applications. I have been reading books but haven't made much progress.&lt;/p&gt;&#xA;" OwnerUserId="444" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-03T14:07:29.027" LastActivityDate="2011-02-03T14:07:29.027" Title="Learning videos for electronic concepts?" Tags="&lt;electronics&gt;&lt;video&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="3118" PostTypeId="2" ParentId="3117" CreationDate="2010-06-21T10:11:41.143" Score="9" ViewCount="" Body="&lt;p&gt;I really like this interactive circuit simulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.falstad.com/circuit/e-index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.falstad.com/circuit/e-index.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-21T10:11:41.143" CommentCount="2" />
  <row Id="3119" PostTypeId="2" ParentId="3117" CreationDate="2010-06-21T10:47:06.370" Score="4" ViewCount="" Body="&lt;p&gt;Hello Kevin&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from reading books, how are you going with practical examples? Although I don't know about your situation, personally I find actually making basic circuits that relate to sections in a textbook most interesting, and doing so helps no end with learning. &quot;Learn by doing&quot; and all that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't recommend any video sites, but can recommend some very readable books that are easy to read and aren't full of maths. Such as the old ones by Forrest Mims III - still relevant, and easy to read; Practical Electronics Handbook (Ian Sinclair/John Dunton); Digital Electronics: A Practical Approach by William Kleitz, the TTL or CMOS Cookbooks by Don Lancaster, etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;[self-promotion] currently I am working on a series of articles you may find interesting. Please have a look at &lt;a href=&quot;http://tronixstuff.wordpress.com/electronics/&quot; rel=&quot;nofollow&quot;&gt;http://tronixstuff.wordpress.com/electronics/&lt;/a&gt; There is usually a new chapter per week.&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-06-21T10:47:06.370" CommentCount="13" />
  <row Id="3120" PostTypeId="2" ParentId="3115" CreationDate="2010-06-21T13:59:07.267" Score="0" ViewCount="" Body="&lt;p&gt;I can recommend the GOEPEL tools for their extensive set of features and capabilities. Test development is highly automated yet allows me to set constraints easily. The software also comes with great JTAG debug tools. Once you know what you want to do with the tools they can configure a software and hardware configuration that is very price competitive and provides an upgrade path that allows you to add capabilities in the future, if you need to.&lt;/p&gt;&#xA;" LastActivityDate="2010-06-21T13:59:07.267" CommentCount="1" />
  <row Id="3121" PostTypeId="2" ParentId="3117" CreationDate="2010-06-21T14:06:14.923" Score="1" ViewCount="" Body="&lt;p&gt;Not quite what you're looking for, but after you get beyond the introductions that Joby pointed out and on to the practical applications part, you'll want to get comfortable with a simulator so you can try out your own designs and change some of the numbers around.  Most of the web videos don't let you play with the circuits more than flipping switches, and breadboarding all your circuits takes a long time.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Linear Technology's LTspice is an introductory SPICE simulation environment :( for Windows only) which has an easy learning curve and includes a huge number of switching regulator demo circuits (which are one of many applications for caps, inductors, and transistors).  There's a simple video introduction &lt;a href=&quot;http://claymore.engineer.gvsu.edu/~steriana/Videos/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, an active support group &lt;a href=&quot;http://tech.groups.yahoo.com/group/LTspice/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, and the manual is &lt;a href=&quot;http://ltspice.linear.com/software/scad3.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-21T14:06:14.923" />
  <row Id="3122" PostTypeId="2" ParentId="966" CreationDate="2010-06-21T14:24:05.817" Score="3" ViewCount="" Body="&lt;p&gt;Sorry to resurrect this old thread, but it came up in the &quot;Related&quot; box and I felt like I needed to put my $0.02.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.elexp.com/&quot; rel=&quot;nofollow&quot;&gt;Electronix Express&lt;/a&gt; is a great resource for cheap assortments of basic components.  They're tailored towards the education and hobbyist industries, and have a basic group of slightly old-school components.  For example:  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;365 count (5 each of 73 standard 5%&#xA;carbon film resistors from 1 ohm to 1&#xA;meg) 1/4W resistors for &lt;a href=&quot;http://elexp.com/cmp_2501.htm&quot; rel=&quot;nofollow&quot;&gt;$6.95&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;220 count assortment of mylar,&#xA;ceramic, monolithic, and electrolytic&#xA;capacitors from 2.2pF to 1,000uF for &lt;a href=&quot;http://elexp.com/cmp_apki.htm&quot; rel=&quot;nofollow&quot;&gt;$14.95&lt;/a&gt; (Or &lt;a href=&quot;http://elexp.com/cmp_pkit.htm&quot; rel=&quot;nofollow&quot;&gt;$6.95&lt;/a&gt; for a 90-pc kit)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Only complaints are no datasheets and a slightly difficult to navigate web store.  However, it's fun to just browse.  They also have tools, protoyping/breadboarding equipment, and project kits in addition to their components.  I usually spend more than I needed to.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I am not affiliated with them, just a satisfied customer.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-21T14:24:05.817" CommunityOwnedDate="2010-06-21T14:24:05.817" CommentCount="3" />
  <row Id="3123" PostTypeId="2" ParentId="3117" CreationDate="2010-06-21T14:46:07.577" Score="1" ViewCount="" Body="&lt;p&gt;These are for the most part higher level then what you are asking for. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a professor I know whom has put many &lt;a href=&quot;http://www.youtube.com/user/kridnix&quot; rel=&quot;nofollow&quot;&gt;videos on youtube to teach about a range of concepts&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some are about changing education, some are about engineering design, and some are about optics related concepts. Now, none of these may interest you, but he does one of the better explanations of a &lt;a href=&quot;http://www.youtube.com/watch?v=ObklYbQaX24&quot; rel=&quot;nofollow&quot;&gt;Fourier&lt;/a&gt; &lt;a href=&quot;http://www.youtube.com/watch?v=QO3kgwYzpZg&quot; rel=&quot;nofollow&quot;&gt;transform&lt;/a&gt;. Fourier links to the first, transform links to the second part, in case you have a hard time finding it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This professor is big on trying to make engineering education more available to students, and feels with good teaching almost anyone can learn the basics of very complicated subjects, as you see he does some basic maxwell's equations(very basic) and teaching many concepts related to his lasers class. Students build a working laser with a gain medium and mirror by the end of it.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-06-21T14:46:07.577" CommentCount="3" />
  <row Id="3124" PostTypeId="2" ParentId="3092" CreationDate="2010-06-21T15:11:48.927" Score="7" ViewCount="" Body="&lt;p&gt;I've looked into eLua and also an embedded python interpreter for some projects I'm working on in my day job. We're developing a base control system, but these systems go out and are customized extensively in the field. Rather than require the end use to add extra processing modules, we allow them to configure our system, and in some cases, write their own features. Since it is prohibitive to have end users reflash in the field (they could easily brick things), we provide a scripting interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currently, we have a proprietary language that is compiled into bytecode and churned through in order by the kernel, but we are trying to make things more standards compliant and easier to maintain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a comparison of different interpreted languages that can run on 'bare metal': &lt;a href=&quot;http://stackoverflow.com/questions/1082751/what-are-the-available-interactive-languages-that-run-in-tiny-memory&quot;&gt;http://stackoverflow.com/questions/1082751/what-are-the-available-interactive-languages-that-run-in-tiny-memory&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, once the device has been flashed once in the factory, we don't want to have to reflash. It is slow, prone to errors, and difficult for end users. In order to extend functionality after production, some sort of scripting extension is a good solution.&lt;/p&gt;&#xA;" OwnerUserId="875" LastActivityDate="2010-06-21T15:11:48.927" CommentCount="1" />
  <row Id="3125" PostTypeId="2" ParentId="3107" CreationDate="2010-06-21T21:14:47.547" Score="4" ViewCount="" Body="&lt;p&gt;Unfortunately the synthesis tools are all closed source as far as I know. The code contained in them is a big part of their business advantage, so I feel it is unlikely you will seem them open sourced. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Xilinx does have free toolchains for Windows and Linux, and if you don't like their IDE you are free to use their commandline tools with your own editor. I've done this before, it works well for small projects (eg CPLD) where you don't want to fool around with big complex software packages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Altera I believe only offers free tools for Windows, their Linux tools are paid only last time I checked (this may have changed, it's been maybe a year or so since I last looked).&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-06-21T21:14:47.547" />
  <row Id="3126" PostTypeId="1" AcceptedAnswerId="3129" CreationDate="2010-06-22T01:20:32.557" Score="6" ViewCount="688" Body="&lt;p&gt;I just completed a project using the LPC2132 chip, but ran into problems with using up the whole 64kb of RAM. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For my next project, I'd like to use something that can reference an external, much larger memory chip. What sort of ARM can do this and what do I need to do to get the two devices talking?&lt;/p&gt;&#xA;" OwnerUserId="876" LastActivityDate="2010-07-12T17:01:32.807" Title="What is a good choice for an ARM to interface with external memory?" Tags="&lt;arm&gt;&lt;memory&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="3128" PostTypeId="2" ParentId="3126" CreationDate="2010-06-22T02:35:59.620" Score="2" ViewCount="" Body="&lt;p&gt;Maybe an &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=4337&quot; rel=&quot;nofollow&quot;&gt;Atmel AT91SAM9G20&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a bit of a beast (217-pin BGA package), but it's a great chip for the price. If you're looking for something a little more human-friendly, maybe try the &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card_v2.asp?part_id=1988&quot; rel=&quot;nofollow&quot;&gt;Atmel AT91M42800A&lt;/a&gt;. I think that's the smallest MCU that has external memory hardware, at least from Atmel. It's a 144-pin LQFP package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Atmel has a parametric selector: &lt;a href=&quot;http://www.atmel.com/dyn/products/param_table_v2.asp?family_id=605&amp;amp;OrderBy=part_no&amp;amp;Direction=ASC&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/products/param_table_v2.asp?family_id=605&amp;amp;OrderBy=part_no&amp;amp;Direction=ASC&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I guess I should add that I don't work for Atmel; I just happen to be familiar with their stuff.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-22T02:35:59.620" />
  <row Id="3129" PostTypeId="2" ParentId="3126" CreationDate="2010-06-22T04:30:50.787" Score="7" ViewCount="" Body="&lt;p&gt;You don't need an MMU for external RAM memory, the determining factor if you need one is a completely separate issue from simply needing more space.  If you've been coding directly to the metal it may actually make your life easier not having an MMU.  I'd also like to note that an MMU is virtually never an external component but rather on the SoC die.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find ARM SoCs in many families that allow external memory from the ARM7 on up for example the &lt;a href=&quot;http://www.nxp.com/#/pip/pip=%5bpip=LPC2212_2214_4%5d|pp=%5bt=pip,i=LPC2212_2214_4%5d&quot; rel=&quot;nofollow&quot;&gt;NXP LPC2212 Series&lt;/a&gt; not saying its the best, just the first ARM7 SoC that came up in google with an external memory interface, there are lots of options.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd pay more attention to the features of the various cores in the ARM families as you can find almost all of them in SoC's with external memory controllers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now as to what type of memory you need and how to get it working, that depends on the SoC you choose and what memory the external memory controller supports.  For instance the ARM7 SoC i linked supports external SRAM as well as flash's and roms and supports up to 4 16MB banks, so you could hook external flash and SRAM to it at the same time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use separate RAM and flash IC's there are also packages called MCP (Multi Chip Package) that can include both flash and ram in 1 package.  How you choose these devices depends on many factors, you'd need to be more specific about your application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How easy this is to hook up depends on the speed you need.  Most external memory controller have programmable clock rates.  The memory interface clock rates could be very high at least 10MHz and likely much higher.  In short your very likely not breadboarding something like this, you need to design a PCB and pay special attention to signal integrity issues for these lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your best bet is to pick a core you want to play with and a find one of the many development boards out there with external memory on it.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-06-22T04:30:50.787" CommentCount="3" />
  <row Id="3130" PostTypeId="1" AcceptedAnswerId="3131" CreationDate="2010-06-22T13:34:48.660" Score="3" ViewCount="228" Body="&lt;p&gt;Until the 4kb upgrade to the ATtiny2313 is available, which AVRs can I substitute when the ATtiny2313 is too tiny?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-06-23T00:32:44.257" Title="Which AVRs are pin-compatible with the ATtiny2313?" Tags="&lt;avr&gt;" AnswerCount="2" />
  <row Id="3131" PostTypeId="2" ParentId="3130" CreationDate="2010-06-22T15:08:44.833" Score="4" ViewCount="" Body="&lt;p&gt;AFAIK, there isn't one!&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-22T15:08:44.833" CommentCount="2" />
  <row Id="3132" PostTypeId="2" ParentId="3130" CreationDate="2010-06-23T00:32:44.257" Score="4" ViewCount="" Body="&lt;p&gt;You didn't specify if you need the same pin out because of a software issue or a hardware issue...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it is purely not being able to solder a chip to a board because of a different pin out and you have to figure something out, you can &lt;a href=&quot;http://en.wikipedia.org/wiki/Point-to-point_construction#.27Dead_bug.27_construction&quot; rel=&quot;nofollow&quot;&gt;dead bug&lt;/a&gt; the chip.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-06-23T00:32:44.257" />
  <row Id="3133" PostTypeId="1" AcceptedAnswerId="3134" CreationDate="2010-06-23T03:25:10.277" Score="5" ViewCount="225" Body="&lt;p&gt;I'm looking for a (graphic) LCD to get started with. It doesn't need to be color. It doesn't need to be serial (but it should at least be multiplexed so I don't have to connect wires to each individual row/column). I don't care about the resolution as long as it's greater than about 40 pixels in both dimensions. Size should be &gt; 1&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It &lt;em&gt;must&lt;/em&gt; be straightforward to use, have plenty of documentation (preferably even example code, but not necessary), and be easy to connect to (with &amp;lt;30 I/O lines. &amp;lt;18 would be great). And of course, I'd prefer something inexpensive ($20 max) ;-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Feel free to list more than one LCD per post. Try to include resolution, size, I/O lines and approximate cost. Bonus points if you provide a link to a supplier ;-)&lt;/p&gt;&#xA;" OwnerUserId="790" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T06:53:40.273" LastActivityDate="2011-01-29T06:53:40.273" Title="graphic LCD with the greatest ease_of_use:cost ratio" Tags="&lt;lcd&gt;" AnswerCount="2" />
  <row Id="3134" PostTypeId="2" ParentId="3133" CreationDate="2010-06-23T03:41:19.470" Score="3" ViewCount="" Body="&lt;p&gt;128 x 64, buckets of support information, 9 wires. US$15.25.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=37&amp;amp;products_id=250&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=37&amp;amp;products_id=250&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-06-23T03:41:19.470" CommentCount="1" />
  <row Id="3135" PostTypeId="2" ParentId="3133" CreationDate="2010-06-23T08:06:50.733" Score="3" ViewCount="" Body="&lt;p&gt;The LCDs from low end Nokia phones might fit the bill.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=569&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=569&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$15&lt;/p&gt;&#xA;&#xA;&lt;p&gt;128x128 pixels&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4096 colours&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-23T08:06:50.733" CommentCount="2" />
  <row Id="3136" PostTypeId="1" AcceptedAnswerId="3137" CreationDate="2010-06-23T13:07:07.057" Score="3" ViewCount="121" Body="&lt;p&gt;I am looking for some small and cheap stepper motors with &amp;lt;10oz-in torque. Most of the steppers I can find from my regular sources/ebay are 60-1000oz-in which is far too much for my purposes (and will almost certainly push the cost up). Does anyone know of a good source for these types of motors ? Unfortunately I would like 6 (and potentially more) of them, so scrounging from old floppy drives is not really an option.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-06-23T13:15:47.003" Title="Sourcing low torque/small stepper motors" Tags="&lt;stepper&gt;&lt;motor&gt;" AnswerCount="1" />
  <row Id="3137" PostTypeId="2" ParentId="3136" CreationDate="2010-06-23T13:15:47.003" Score="1" ViewCount="" Body="&lt;p&gt;How about this one from Adafruit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;products_id=168&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;products_id=168&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;48 steps per revolution&lt;/li&gt;&#xA;&lt;li&gt;5-12V DC&lt;/li&gt;&#xA;&lt;li&gt;Weight: 77 g.&lt;/li&gt;&#xA;&lt;li&gt;Holding Torque: up to 27 mNm / 3.75 oz-in&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-23T13:15:47.003" CommentCount="1" />
  <row Id="3138" PostTypeId="1" CreationDate="2010-06-23T13:37:34.930" Score="1" ViewCount="146" Body="&lt;p&gt;IR light is the mainstay frequency for optical communication systems.&#xA;How could I experiment with UV frequencies doing the same thing?&#xA;Ideally I want to set up a serial link just as is often done with IR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks you all for your help on this matter.&lt;/p&gt;&#xA;" LastActivityDate="2010-06-23T19:46:03.123" Title="Light Modulation and Detection" Tags="&lt;uv&gt;&lt;ir&gt;&lt;communication&gt;&lt;arduino&gt;&lt;propeller&gt;" AnswerCount="2" />
  <row Id="3139" PostTypeId="1" AcceptedAnswerId="3141" CreationDate="2010-06-23T14:43:18.730" Score="10" ViewCount="780" Body="&lt;p&gt;I've seen Dallas' 1-wire sensors, they look great. But, I'd like to make some custom 1-wire slaves which can be parasitically powered (just ground + data).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone recommend a low power microcontroller which is suitable for this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have a sample circuit for how I would power an MCU from the 1-wire bus?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:39:06.483" LastActivityDate="2010-12-01T05:26:17.520" Title="1-wire parasitically powered microcontroller?" Tags="&lt;one-wire&gt;&lt;microcontroller&gt;" AnswerCount="6" CommentCount="3" FavoriteCount="2" />
  <row Id="3140" PostTypeId="2" ParentId="3138" CreationDate="2010-06-23T15:23:17.960" Score="4" ViewCount="" Body="&lt;p&gt;Surely a UV light bright enough to be of practical use would also be quite dangerous to the naked eye?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, perhaps a UV laser could be dropped into something like this:&#xA;&lt;a href=&quot;http://www.ohmpie.com/laserModem&quot; rel=&quot;nofollow&quot;&gt;http://www.ohmpie.com/laserModem&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-23T15:23:17.960" CommentCount="3" />
  <row Id="3141" PostTypeId="2" ParentId="3139" CreationDate="2010-06-23T15:23:34.527" Score="11" ViewCount="" Body="&lt;p&gt;The one wire bus has the bus passively (i.e. with a resistor) pulled up in the system, and devices communicate on the bus by pulling the bus down. What I would do if I wanted to pull power from the bus is:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Feed the data line right into the&#xA;data input pin of your&#xA;microcontroller. &lt;/li&gt;&#xA;&lt;li&gt;Also feed the data&#xA;line into a Schottky diode. &lt;/li&gt;&#xA;&lt;li&gt;At the output of&#xA;    the diode put a largish (say 10uF)&#xA;    capacitor to ground.  &lt;/li&gt;&#xA;&lt;li&gt;Send the&#xA;        output of the diode to the VCC pin&#xA;        of your microcontroller.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;You should use a Schottky diode, to minimize the voltage drop. The diode/capacitor combination should make it so that communication can take place (i.e. grounding the bus periodically) without shutting down the MCU. Putting the capacitor after the diode will keep the transitions on the bus data sharp, while keeping the decay of power (voltage) to your MCU gradual. The lower power the device you use is the better to minimize drain on your capacitor, but pretty much any MCU will probably work for you. My preference is Atmel's AVRs, but TI MSP430s and Microchip's PICs are also good candidates for low power consumption.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-11-29T18:26:17.700" LastActivityDate="2010-11-29T18:26:17.700" CommentCount="10" />
  <row Id="3142" PostTypeId="2" ParentId="3126" CreationDate="2010-06-23T18:37:58.313" Score="4" ViewCount="" Body="&lt;p&gt;I recently had a similar requirement for a new project, and chose the STMicro STM32F103ZET6 (ARM 32-bit Cortex-M3), with 512K of internal Flash and 64K of internal RAM for around $10 in quantity.  It has a memory controller which can address up to 64MB of external memory (26 address bits).  Available in a 144-pin LQFP package.  (I don't like using BGA for prototypes.)  I will be interfacing it with a 2MB Cypress SRAM, without any other glue required (no multiplexing).&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-07-12T17:01:32.807" LastActivityDate="2010-07-12T17:01:32.807" CommentCount="4" />
  <row Id="3143" PostTypeId="2" ParentId="3138" CreationDate="2010-06-23T19:46:03.123" Score="3" ViewCount="" Body="&lt;p&gt;I actually did some research a couple months ago for a project that involved semiconductors with band gaps in the range needed for UV LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find near UV LEDs commercially available in the 380-400nm range.  This is like a &quot;black light&quot; area, you can even find UV flash lights that operate in this range.  You could use these LEDs, you'd have to build your own receiver as i'm pretty sure there are no commercial options.  You can probably follow a schematic for an IR receiver but will have to make adjustments for the high forward voltage drops of the diodes that produce this type of light, 3-4V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that UV light is easily absorbed by most everyday materials.  I don't think you'll get nearly the range you get from IR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are semiconductors that can produce UV light as low as ~225nm as i recall there are a couple companies working on this tech, &lt;a href=&quot;http://www.crystal-is.com/&quot; rel=&quot;nofollow&quot;&gt;Crystal IS&lt;/a&gt; is the one i remember doing it for use to kill bacteria in water.  I don't think any of the companies working on it are in commercial development yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As to the eye damage issue, UVB and UVC are the real damaging ones to skin, well all DNA, but thats in the &amp;lt; 315nm range for which he probably won't find a commerical source for light in this range.  &lt;strong&gt;EDIT: I'm clearly not a doctor so please don't take this to mean you shouldn't research this more and take proper safety precautions, this is just as i understand it.&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-06-23T19:46:03.123" CommentCount="1" />
  <row Id="3144" PostTypeId="2" ParentId="1199" CreationDate="2010-06-23T19:47:00.423" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Cypress PSoC1&lt;/strong&gt; (CY8C29466) has a simple 8-bit CPU core surrounded by FPGA-like digital and analog blocks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has both analog inputs and analog outputs.&#xA;Many projects that would require a bunch of external parts with any other microcontroller -- op-amps, PGAs, etc. -- can be done with a single PSoC chip.&#xA;Lots of computer mice use a PSoC1.&#xA;For example, it can decode DTMF tones coming in one input pin, and directly generate independent analog DTMF signals on two output pins -- true analog, not PWM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The digital and analog blocks can be set up to do things completely independently of the core -- and therefore with guaranteed fixed response time, even if the CPU is busy handling some interrupt during that time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fairly low power.&#xA;Comes in both DIP and SMT packages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 8-bit, 24 MHz core is roughly equivalent to the PIC16F core, quirky bank-switching and all. Proprietary C compilers are available, but GCC is unlikely to ever be ported to either one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;Gainer.cc&quot; project programs PSoC1-based systems using Processing over a USB cable, very similar to the later &quot;Arduino&quot; project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.psocdeveloper.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.psocdeveloper.com/&lt;/a&gt; forum is friendly.&#xA;There are some utilities available for doing development on Linux: &lt;a href=&quot;http://m8cutils.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;http://m8cutils.sourceforge.net/&lt;/a&gt; .&lt;/p&gt;&#xA;" OwnerUserId="813" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2010-06-23T20:03:21.127" LastActivityDate="2010-06-23T20:03:21.127" CommunityOwnedDate="2010-06-23T19:47:00.423" />
  <row Id="3145" PostTypeId="2" ParentId="1199" CreationDate="2010-06-23T19:55:35.987" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Cypress PSoC5&lt;/strong&gt; has a 32-bit ARM Cortex M3 surrounded by FPGA-like digital and analog blocks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;20-bit resolution analog ADC and DAC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The digital and analog blocks can be set up to do things completely independently of the core -- and therefore with guaranteed fixed response time, even if the CPU is busy handling some interrupt during that time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fairly low power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 32-bit, 80 MHz ARM Cortex-M3 core is roughly equivalent to ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.psocdeveloper.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.psocdeveloper.com/&lt;/a&gt; forum is friendly.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-06-23T19:55:35.987" CommunityOwnedDate="2010-06-23T19:55:35.987" CommentCount="2" />
  <row Id="3146" PostTypeId="1" CreationDate="2010-06-23T22:13:16.367" Score="3" ViewCount="470" Body="&lt;p&gt;Seen hot-air-gunning, super-gluing, epoxy-gluing, plastic-taping, other-taping, --. Super-gluing joints did not look good as you need acetone to remove it!&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;is epoxy gluing better substitute for soldering?&lt;/li&gt;&#xA;&lt;li&gt;when to use such substitutes?&lt;/li&gt;&#xA;&lt;li&gt;are they really substitutes or just bad habit?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-06-23T22:51:30.097" LastActivityDate="2011-05-13T15:06:51.643" CommunityOwnedDate="2010-06-26T10:13:20.943" Title="Soldering substitutes?" Tags="&lt;soldering&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="3147" PostTypeId="2" ParentId="3146" CreationDate="2010-06-23T22:47:45.503" Score="16" ViewCount="" Body="&lt;p&gt;Nothing you listed is a substitute for soldering, they are all things you can use for physical attachment or insulating but are not things to use for making an electrically conductive connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hot-air-gunning, do you mean hot air soldering or maybe given the nature of the other things mentioned heat shrink tubing?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;super glue (cyanoacrylate glue) is a good insulator.  i have heard of people using it to provide extra hold on wire wrap boards.  its not doing the job of solder though, its not providing the electrical connection but rather just keeping it from coming unwrapped.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Every type of epoxy i've used has been an insulator although there appear to be some that are conductive and may be useful in specific situations. (Thanks Michael/Jeanne)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plastic tape is an insulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Duct tape's core is a conductor, but the coating and glue on the tape is an insulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would never use any of these in place of solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do use some of them as insulators though.  For instance if I have soldered wires coming off a pcb i'll plop hot-glue or epoxy over the connection to glue the wire to the PCB and remove stress from the solder connection.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-06-26T19:46:59.760" LastActivityDate="2010-06-26T19:46:59.760" CommentCount="3" />
  <row Id="3148" PostTypeId="2" ParentId="3146" CreationDate="2010-06-23T23:07:13.967" Score="8" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Wire-wrapping is a substitute for soldering but wire-wrap supplies can get very &#xA;expensive unless you buy in very large volumes or happen&#xA;to find a surplus deal.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You could also crimp the wires together. There are terminals called butt splices.&#xA;You could insert multiple wires into the terminal and then crimp. These&#xA;are meant for thinner stranded wires but could work for solid leads.&#xA;Butt splices have two ends but there may be some sort of small ferule you&#xA;could purchase.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:50:10.823" LastActivityDate="2011-05-13T12:50:10.823" CommentCount="1" />
  <row Id="3149" PostTypeId="2" ParentId="3146" CreationDate="2010-06-24T00:33:10.890" Score="6" ViewCount="" Body="&lt;p&gt;Adhesives aren't going to provide any electrical conductivity, and aren't likely to work well with metal surfaces since these don't tend to be very porous.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have two wires that are well twisted together, covering the joint with heat shrink tubing or tape can insulate the otherwise bare metal and prevent shorts (essentially the same job as a 'wire nut'), but has no other advantage. Oxygen and humidity can generally still get into the joint, and these are what eventually will degrade the connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are joining wires, or components with wire leads, then wire nuts, crimp-on splices, or screw-down connections (like barrier strips) will work OK, but aren't really suitable for fiddly little items. These methods are more suited for old-school vacuum tube and relay technology.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For small scale semiconductors and low-wattage passives, you really can't beat solder. It provides a conductive, oxygen-excluding bond between even flat metal surfaces. If the problem is concern about lead, there are lead-free solders that flow at somewhat higher temperatures but are not beyond hobby level tools. &lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-24T00:33:10.890" />
  <row Id="3150" PostTypeId="1" AcceptedAnswerId="3152" CreationDate="2010-06-24T11:50:34.893" Score="1" ViewCount="427" Body="&lt;p&gt;If an AVR's 8-bit timer compare register is 255 and the timer overflows (according to the datasheet, the compare interrupt happens on the next timer clock cycle) then both the overflow interrupt and the compare interrupt should be due at the same time. Which will be serviced first?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-06-29T06:17:42.907" LastActivityDate="2010-06-29T06:17:42.907" Title="On an AVR (ATtiny2313), which is serviced first when TIMER0_OVF and TIMER0_COMPA are due at the same time?" Tags="&lt;avr&gt;&lt;timer&gt;" AnswerCount="2" />
  <row Id="3151" PostTypeId="2" ParentId="3150" CreationDate="2010-06-24T12:43:09.950" Score="2" ViewCount="" Body="&lt;p&gt;I really hope somebody knows this, and that you get a straightforward answer with good reasoning from the docs, examples of how to plan for simultaneous interrupts, etc. but all I can tell you right now is that it's the one that's still running when you do &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ISR(TIMER0_OVF_vect)&#xA;{&#xA;  printf(&quot;OVF ISR Ran First\n&quot;); //or whatever your console output uses&#xA;  fflush(stdout);&#xA;&#xA;  while(1);&#xA;}&#xA;&#xA;ISR(TIMER0_COMPA_vect)&#xA;{&#xA;  printf(&quot;COMPA  ISR Ran First\n&quot;); //or whatever your console output uses&#xA;  fflush(stdout);&#xA;&#xA;  while(1);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-24T12:43:09.950" CommentCount="2" />
  <row Id="3152" PostTypeId="2" ParentId="3150" CreationDate="2010-06-24T13:50:08.350" Score="4" ViewCount="" Body="&lt;p&gt;See the datasheet for the ATtiny2313: &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2543.PDF&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/resources/prod_documents/doc2543.PDF&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The priority of interrupts is determined by the order of the interrupt vectors.  See page 46 for the list.  The lower the number, the higher the priority.  Since Timer/Counter0 Overflow has a lower number (7) than Timer/Counter0 Compare Match A (14), the overflow ISR will run first.&lt;/p&gt;&#xA;" OwnerUserId="828" LastActivityDate="2010-06-24T13:50:08.350" CommentCount="1" />
  <row Id="3153" PostTypeId="2" ParentId="3107" CreationDate="2010-06-24T15:19:54.793" Score="2" ViewCount="" Body="&lt;p&gt;FPGA development tools are all tightly coupled with the FPGA devices themselves and are utterly dependent on proprietary details of the FPGA architecture, particularly at the placement, routing, and bitstream generation levels.  As such, vendor-neutrality is largely non-existent.  Higher-level tools may be vendor-neutral to some degree (e.g., Synplify, ESL tools, verification tools, etc.), but they're certainly not open source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, there are many academic tools that are open source.  As long as you don't want to develop for a real physical device, you can use the &lt;a href=&quot;http://www.eecg.utoronto.ca/vpr/&quot; rel=&quot;nofollow&quot;&gt;VPR 5.0&lt;/a&gt; toolchain.&lt;/p&gt;&#xA;" OwnerUserId="886" LastEditorUserId="886" LastEditorDisplayName="" LastEditDate="2010-06-24T15:29:04.650" LastActivityDate="2010-06-24T15:29:04.650" />
  <row Id="3154" PostTypeId="2" ParentId="3146" CreationDate="2010-06-24T21:55:20.213" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;2: when to use such substitutes?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;When you need to attach things together electrically and you can't solder.  Or your afraid to solder.  Or the device will be local to a person's skin, in which case you shouldn't use solder due to heavy metals which can affect a person's health.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;3: are they really substitutes or just bad habit?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Technical answer:&lt;/strong&gt;  Depends how reliable your connection needs to be and the conditions its going to be in and length of time it needs to work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used black electrical tape to connect resistor leads to wires in a custom Ghostbusters backpack.  The electrical tape was sufficiently sticky and the connections worked well enough that it survived two evenings of my roommate running around begging candy off of people (a fair amount of torture, IMHO), and still worked when it came back to the apartment.  Which was all it needed to do.  So it was a decent substitute, I think.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would you do that in a production unit to sell?  I wouldn't do that even if my job &lt;em&gt;didn't&lt;/em&gt; depend on it.  But for roommate during crazy weekend?  Eh, it works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Real answer:&lt;/strong&gt;  Really, though, its a bad habit used by lazy people who need to improve their soldering techniques...  Don't do what I did.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-06-25T12:50:36.180" LastActivityDate="2010-06-25T12:50:36.180" />
  <row Id="3155" PostTypeId="2" ParentId="966" CreationDate="2010-06-24T23:02:55.683" Score="2" ViewCount="" Body="&lt;p&gt;Definitely add relays to the list, and don't forget &lt;em&gt;flyback protection diodes&lt;/em&gt; for the relay coils so you don't blow up your microcontroller outputs! Some rectifier diodes will work fine, and are good to have around for reverse voltage protection circuits too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure the relay coil voltage and current rating can be met by your microcontroller's outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Very useful for safely driving lamps, solenoids, etc.&lt;/p&gt;&#xA;" OwnerUserId="890" LastActivityDate="2010-06-24T23:02:55.683" CommunityOwnedDate="2010-06-24T23:02:55.683" />
  <row Id="3156" PostTypeId="2" ParentId="3139" CreationDate="2010-06-25T02:00:23.027" Score="5" ViewCount="" Body="&lt;p&gt;Use a capacitor to store the energy, and connect the negative end of the capacitor to ground, and connect a Schottky diode between the data line and the capacitor. Schottky diodes have a low forward drop.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-06-25T02:00:23.027" />
  <row Id="3157" PostTypeId="2" ParentId="966" CreationDate="2010-06-25T06:50:09.347" Score="5" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Solder Wick&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lots of common components can be salvaged from almost anything with a PCB inside.&lt;br&gt;&#xA;(I am &lt;em&gt;not&lt;/em&gt; suggesting that you should ever rely on this though.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And of course, solder wick really helps when you make mistakes too.&lt;/p&gt;&#xA;" OwnerUserId="790" LastActivityDate="2010-06-25T06:50:09.347" CommunityOwnedDate="2010-06-25T06:50:09.347" />
  <row Id="3158" PostTypeId="2" ParentId="966" CreationDate="2010-06-25T11:08:13.423" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Flux, paste and their removal tools&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the pump and the solder wick are not enough...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I like cut in costs so actively looking substitutes on the first item. For the second items, I have been using items meant for car-industry: big bottles, cheap and long-lasting.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;STANNOL® MINI-FLUXER (to manipulate the surface tension)&lt;/li&gt;&#xA;&lt;li&gt;acetone or paint-removal-spray (to remove excess rosin)&lt;/li&gt;&#xA;&lt;li&gt;rosin (like &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.4697&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;) and ethanol (to make your own fluxes)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-25T11:41:46.243" LastActivityDate="2010-06-25T11:41:46.243" CommunityOwnedDate="2010-06-25T11:08:13.423" />
  <row Id="3159" PostTypeId="1" CreationDate="2010-06-25T11:33:37.600" Score="3" ViewCount="220" Body="&lt;p&gt;Got inrested in DIY fluxes by reply &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.4697&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Can you substitute rosin-core wire with DIY flux and non-rosin-core-wire?&lt;/li&gt;&#xA;&lt;li&gt;How and where to actually use DIY fluxes if you have rosin-core wire?&lt;/li&gt;&#xA;&lt;li&gt;Which % of ethanol and rosin should be used with SMD components?&lt;/li&gt;&#xA;&lt;li&gt;Why to use a soldering flux? ( relates part 2)&lt;/li&gt;&#xA;&lt;li&gt;With which substance you can avoid fungi? (relates to part 3)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T06:52:36.733" LastActivityDate="2011-01-29T06:52:36.733" Title="DIY Fluxes with ethanol-propanol-x-nol" Tags="&lt;soldering&gt;&lt;flux&gt;&lt;solder-paste&gt;" AnswerCount="2" />
  <row Id="3160" PostTypeId="2" ParentId="3101" CreationDate="2010-06-25T11:45:04.057" Score="3" ViewCount="" Body="&lt;p&gt;How about putting $9.10 into it? There are AUI to 10-Base-T transceivers on eBay for that price with free shipping. I didn't even look that hard, there are probably cheaper ones yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for connecting to modern commodity network gear, I've never had any problem putting a 10Mb device on a 10/100 Mb switch. Pretty much all switches are store and forward these days, so when there's a speed difference between two ports, the frames are buffered by the switch and sent on at the proper link speed of the destination device.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2010-06-25T11:45:04.057" />
  <row Id="3161" PostTypeId="1" CreationDate="2010-06-25T12:00:00.417" Score="3" ViewCount="257" Body="&lt;p&gt;I am trying to find long-lasting  items -- to buy in bulk. The idea is to order them for a lifetime. What are long-lasting electronic items? Which items are good idea to stock? I have tried to get ideas from this &lt;a href=&quot;http://chiphacker.com/questions/966/which-electronics-components-should-i-always-have-on-hand&quot; rel=&quot;nofollow&quot;&gt;discussion&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;==== YES List ====&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;No staling&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;prototyping tools: breadboards&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Good idea (?)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;1M resistors&lt;/li&gt;&#xA;&lt;li&gt;1k-10k resistors&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;No evaporation but better items may be developed, takes little room&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;ceramic caps&lt;/li&gt;&#xA;&lt;li&gt;op amps: LM741,&lt;/li&gt;&#xA;&lt;li&gt;temperature sensors: DS18B20 &lt;/li&gt;&#xA;&lt;li&gt;transistors such as BC547C&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;==== NO LIST ====&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Moving parts, no lubrication, can get jammed&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;pots&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Modern technology&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;FPGAs&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Absorbs moisture, evaporates&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;rosin (DIY when you need with denatured alcohol+pine cones)&lt;/li&gt;&#xA;&lt;li&gt;electrolytic caps&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;==== HEAVY LIST ====&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Must be ordered as bulk via sea to ge cheaply, long-lasting&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Antistatic mat (55 RMB/1m^2, like &lt;a href=&quot;http://item.taobao.com/item.htm?id=4456406976&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;, but 3kg per pc. In Chinese, 防静电台垫 防静电桌垫 防静电胶皮)&lt;/li&gt;&#xA;&lt;li&gt;solid 1000' 22AWG spools (red and black)&lt;/li&gt;&#xA;&lt;li&gt;stranded 100' 22AWG spools&lt;/li&gt;&#xA;&lt;li&gt;PCB stand&lt;/li&gt;&#xA;&lt;li&gt;Magnifier glass table things such as &lt;a href=&quot;http://item.taobao.com/item.htm?id=5607571788&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; (in Chinese,  20倍放大镜 带灯放大镜 折叠式放大镜 台式放大镜LT-86C 20X)&lt;/li&gt;&#xA;&lt;li&gt;Ultrasonic cleaners (such as &lt;a href=&quot;http://shop33964178.taobao.com/search-cat-33964178-11426586-ob6zrMn5sqjH5c+0xvehvw==.htm?checkedRange=true&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt;. In Chinese, 数码型不锈钢超声波清洗机)&lt;/li&gt;&#xA;&lt;li&gt;Cabinets, lockets -- (like &lt;a href=&quot;http://shop33964178.taobao.com/search-cat-33964178-11426810-ob7Uqrz+utChoqGi1Kq8/rnxoaK5pL7fz+QvsPyhvw==.htm?checkedRange=true&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;li&gt;Soldering stations such as &lt;a href=&quot;http://item.taobao.com/auction/item_detail-db2-36799493db0de7fca9957b6b497e2033.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; (in Chinese, 双数显热风枪带烙铁 热风拆焊台 超)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-26T08:36:49.900" LastActivityDate="2010-06-26T22:25:06.640" CommunityOwnedDate="2010-06-26T07:32:06.737" Title="Long-lasting electronics items" Tags="&lt;components&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="3162" PostTypeId="2" ParentId="3161" CreationDate="2010-06-25T12:29:45.427" Score="3" ViewCount="" Body="&lt;p&gt;Things with moving parts might not be a good idea, I bought some new old stock pots the other week and they're almost impossible to turn. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Umm... why do you want to order for a lifetime? Are you worried through-hole components won't be available in ten or so years?&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-06-25T12:29:45.427" CommentCount="2" />
  <row Id="3163" PostTypeId="2" ParentId="3159" CreationDate="2010-06-25T16:07:07.690" Score="1" ViewCount="" Body="&lt;p&gt;Why have non-rosin core wire? Solder paste is flux with solder granules suspended in it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use it on the surfaces beforehand or a drop on desoldering braid. Keeps things flowing :)  Also, SMT.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've usually seen propanol used as a solvent with resin. As little as possible to keep the active ingredient usably thin.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-25T16:07:07.690" />
  <row Id="3164" PostTypeId="2" ParentId="3161" CreationDate="2010-06-25T16:14:09.563" Score="3" ViewCount="" Body="&lt;p&gt;I'd expect things packed hermetically and/or in reels or such would be better protected than box/tape/strip. SMD parts are easy to store and acquire in bulk because of their small size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anything with exposed conductor may oxidize and that may or may not matter. Ceramic caps are sensitive to moisture, but if the case is intact, I think they should last.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Batteries don't keep well. (Al) electrolytes I think also have a very limited life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Gold is pretty good, of course :)&lt;/p&gt;&#xA;" OwnerUserId="883" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-06-26T22:25:06.640" LastActivityDate="2010-06-26T22:25:06.640" />
  <row Id="3165" PostTypeId="2" ParentId="3101" CreationDate="2010-06-25T16:19:59.613" Score="1" ViewCount="" Body="&lt;p&gt;A transceiver or MAU. Their availability is starting to be a bigger question now, I still have a few from my real computer days.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-25T16:19:59.613" />
  <row Id="3166" PostTypeId="2" ParentId="1763" CreationDate="2010-06-25T16:22:31.093" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://hackaday.com/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-25T16:22:31.093" CommentCount="2" />
  <row Id="3167" PostTypeId="2" ParentId="3159" CreationDate="2010-06-25T16:46:45.457" Score="1" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;Plz, see XTL.&lt;/li&gt;&#xA;&lt;li&gt;The static user commented &lt;a href=&quot;http://www.instructables.com/id/How-to-solder/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;: &quot;There are times when addding additional rosin flux can be beneficial because is allows to solder to flow more readily with the less heating. For example when soldering connectors on coaxial cable.&quot;&lt;/li&gt;&#xA;&lt;li&gt;Probably, it depends on the flux type. You can find instructions to do your own flux &lt;a href=&quot;http://www.instructables.com/id/Make-your-own-Eco-friendly-soldering-flux/step1/Go-Shopping/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;Flux can be &quot;non-corrosive, non-conductive, moisture and fungus resistant&quot;, according to &lt;a href=&quot;http://www.mgchemicals.com/products/835.html&quot; rel=&quot;nofollow&quot;&gt;the marketing of a rosin flux&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-25T18:02:02.343" LastActivityDate="2010-06-25T18:02:02.343" CommentCount="0" />
  <row Id="3168" PostTypeId="2" ParentId="464" CreationDate="2010-06-25T22:57:15.180" Score="0" ViewCount="" Body="&lt;p&gt;I wish I'd known just how easy it is to make a BSD programmer and get started. That would have saved a lot of time tool hunting. Of course I also wish I would have had the Bus Pirate sooner :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And I still wish I knew where to get more chips cheaply (&lt;strong&gt;including delivery&lt;/strong&gt;).&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-25T22:57:15.180" CommunityOwnedDate="2010-06-25T22:57:15.180" />
  <row Id="3169" PostTypeId="1" CreationDate="2010-06-25T23:05:15.740" Score="5" ViewCount="495" Body="&lt;p&gt;How would I press the electrical switch on say an electronic paintball or airsoft gun? Let's say it is just a SPST switch.&lt;/p&gt;&#xA;" LastEditorUserId="3" LastEditorDisplayName="" LastEditDate="2010-06-25T23:56:47.920" LastActivityDate="2010-07-15T09:10:33.590" Title="How to switch something else on with an arduino" Tags="&lt;arduino&gt;" AnswerCount="3" />
  <row Id="3170" PostTypeId="2" ParentId="3169" CreationDate="2010-06-25T23:54:08.043" Score="2" ViewCount="" Body="&lt;p&gt;To press a switch, you'll need some kind of expensive solenoid or &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9065&quot; rel=&quot;nofollow&quot;&gt;servo&lt;/a&gt;, and mechanical linkages, and mounting hardware, and trigger pressure characterizations, and power-loss state characterization, and a 12V power supply, and driver circuitry, and it all adds up to a lot of work to push the physical trigger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I were you, though, and had access to the hardware, I'd characterize the circuit the trigger switch is attached to (is it normally open or normally closed is really all you need to know), and attach a simple &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=524&quot; rel=&quot;nofollow&quot;&gt;relay&lt;/a&gt; or MOSFET to an I/O pin on a microcontroller (I'd suggest the relay, because it's closer to the original circuit, avoids any voltage referencing issues, and has a mechanical spring to ensure that if your circuit goes dead, the trigger won't go off).  Then, remove the switch from the gun, and attach your circuit.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-25T23:54:08.043" CommentCount="4" />
  <row Id="3171" PostTypeId="2" ParentId="3161" CreationDate="2010-06-26T01:21:58.920" Score="4" ViewCount="" Body="&lt;p&gt;I'd avoid three areas:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Depends on chemicals which decay over time: This includes electrolytic (but not ceramic, I think) caps, flux/rosin, solderpaste, hygroscopic chemicals (in some flux removers), and maybe other stuff.  I don't have enough experience to say whether solder (especially with a modern water-based, no-clean flux and lead-free type) fits into this category.&lt;/li&gt;&#xA;&lt;li&gt;Depends on technology which improves at a rapid rate:  This includes microcontrollers, memory, and may or may not include other ICs.  Basic linear regulators of yesteryear may have higher dropout voltage and lower power dissipation, but a 7805 or LM317 still does the job 99% of the time.  The argument could be made that modern switching regulators are light-years ahead (Buck/boost, 0V dropouts, 90+ %efficient, isolated, etc.), and that is true - but some areas don't always need the latest and greatest.  This probably doesn't (but could) include passive semiconductors (diodes might have orders of magnitude higher reverse voltage and lower reverse current, for example, but you might not need that capacity).  Op-amps, transistors, and other ICs are in a fuzzy in-between area (How does 1.8V single-sided opamp operation sound (TLV2761)?  Would you ever be glad you had 100 741s in a box next to those?)  &lt;/li&gt;&#xA;&lt;li&gt;Uses anything proprietary, or is available from only one manufacturer.  This includes communication protocols, ICs, micros, memory/display interfaces, etc.  Will you still be able to use your items (with new products) if one or two semiconductor manufacturers or distributors goes under or out of stock?  If your programmer breaks?  This does not apply to devices which are &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The things which I would not avoid (as long as you're not storing somewhere that the tin coating will oxidize to an unusable level) are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Connectors: Have an assortment always on hand, including some crimp terminals and .1&quot; headers.&lt;/li&gt;&#xA;&lt;li&gt;Wire: 1000' spools will last you forever.  100' will last you a long time. Get 1000' of 22ga solid red and black for your breadboard, then 100' of solid and stranded in a couple &lt;/li&gt;&#xA;&lt;li&gt;Perforated protoboard.  Other non-chemical supplies might be added here.&lt;/li&gt;&#xA;&lt;li&gt;Resistors: Get a kit with 1/4W axial &lt;a href=&quot;http://www.logwell.com/tech/components/resistor_values.html&quot; rel=&quot;nofollow&quot;&gt;E24 (5%) valued resistors&lt;/a&gt; from 10ohm to 1 meg. Stock a couple of the 1 to 10 and 1 meg to 10 meg values, and high-wattage ones as well.  Make sure you get lots of 1k and 10k resistors.&lt;/li&gt;&#xA;&lt;li&gt;Non-electrolytic capacitors: In contrast to what previous posters have said, I would add some tantalum and ceramic caps to my stock.  The decay of ceramic capacitors is logarithmic, and can be reversed by heating (aka soldering).  Some dielectrics do not decay at all.  In addition to small quantities of nF-pF filter caps, I would add a bunch of decoupling caps.  Get 0.1uF ceramics and 10uF tantalums for decoupling.  Electrolytics simply don't work for decoupling logic ICs; they're great in large values but not in small ones. &lt;/li&gt;&#xA;&lt;li&gt;Dependable semiconductors: (Passives and ICs) After thinking critically about what you might be willing to sacrifice in terms of performance in future designs, and making sure that your storage protects them from ESD, get some basic ICs and passive semiconductors. Opamps, logic ICs, Voltage regulators, BJTs, MOSFETs, diodes (Zener in assorted values), Schottky, Silicon rectifier).  &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-26T01:21:58.920" />
  <row Id="3172" PostTypeId="2" ParentId="3139" CreationDate="2010-06-26T01:34:04.387" Score="6" ViewCount="" Body="&lt;p&gt;You might consider adding a request to your custom slave's functions to say &quot;OK, I'm going to need a lot of current for a little while here&quot;, and add a MOSFET pullup to your output.  Then, you could turn this off for a few cycles, and see if the slave is still allowing the line to be resistively pulled up (like on p.3 figure 2 of the &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/DS18S20-PAR.pdf&quot; rel=&quot;nofollow&quot;&gt;DS18S20 datasheet.&lt;/a&gt;)  A lot of 1-wire devices aren't really 1-wire.  If you don't need to interact with actual 1-wire parts and/or you control the master node, you can define your own specs and this should make things much easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your job is made easier because your micro can probably handle between the 5V of the bus and decay all the way to ~2.6.  Therefore, the aforementioned Schottky and capacitor setup should work, or even a silicon diode.  Consider the following diode setups:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Silicon diode: This would be my first choice.  As long as your micro and any peripherials can run at 4.3V, you will minimize your reverse current from tens to hundreds (and even up into mA when warm) on a Schottky down to tens of nano-amps &lt;/li&gt;&#xA;&lt;li&gt;Schottky diode: Use only if the .4V between the standard diode and Schottky is significant for your application, but reverse current on the order of 100uA is acceptable. &lt;/li&gt;&#xA;&lt;li&gt;Ideal diode: Try the LTC4411 or similar if cost is not an issue (Only $1.75, but more than a passive diode) and 20uA reverse current is acceptable.&#xA;Refer to the MSP430 datasheet for power consumption.  At 3V (Using a Li-ion battery rather than a leaky supercap, assuming that you might want to remove this device but retain RAM for lower power code execution), you can have a 100na (nano-amp, .1uA) hibernate mode requiring an external interrupt (like a pin change!)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The other option is to be miserly in power requirements, and use a battery.  See &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/1793&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; app note from Maxim.  If you can keep your MSP430 in sleep mode (i.e., only wake on a pin change, like a 1-wire initialization pulse), you can average less than 1uA and a coin cell will last you for ten years (In theory.) How long do you want the device to last?&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-06-26T01:34:04.387" CommentCount="1" />
  <row Id="3173" PostTypeId="2" ParentId="464" CreationDate="2010-06-26T02:19:49.250" Score="3" ViewCount="" Body="&lt;p&gt;I wish I would have known that I could get &lt;strong&gt;free samples&lt;/strong&gt; from a lot of online stores. Then I wouldn't have been forced to choose which project to get started on based on cost. And I wouldn't have been afraid to buy components that I wasn't 100% sure I could get working.&lt;/p&gt;&#xA;" OwnerUserId="790" LastEditorUserId="790" LastEditorDisplayName="" LastEditDate="2010-06-26T20:22:49.833" LastActivityDate="2010-06-26T20:22:49.833" CommunityOwnedDate="2010-06-26T02:19:49.250" CommentCount="2" />
  <row Id="3174" PostTypeId="2" ParentId="3139" CreationDate="2010-06-26T05:52:17.593" Score="3" ViewCount="" Body="&lt;p&gt;Many of the 1-wire app notes show the standard circuit inside the slave:&#xA;a capacitor between GND and VCC of the internal chip (in your case, between GND and VCC of your CPU).&#xA;Also, a blocking diode from the data line to VCC of the internal chip, to allow the capacitor to fill up when the data line is high, but to block power from draining from the capacitor when the data line is brought low. Check out the schematic in these app notes:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/3754&quot; rel=&quot;nofollow&quot;&gt;http://www.maxim-ic.com/app-notes/index.mvp/id/3754&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/1796&quot; rel=&quot;nofollow&quot;&gt;http://www.maxim-ic.com/app-notes/index.mvp/id/1796&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.1wire.org/index.html?target=p_164.html&amp;amp;lang=en-us&quot; rel=&quot;nofollow&quot;&gt;http://www.1wire.org/index.html?target=p_164.html&amp;amp;lang=en-us&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As long as your capacitor is big enough, you should be able to run most modern microcontrollers.&#xA;The Texas Instruments MSP430 was the lowest-power micro when it was introduced.&#xA;I hear that Atmel claims their PicoPower AVRs use less power than the MSP430.&#xA;Also the Microchip XLP micros use relatively little power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may be surprised to see what the nice people at 1wire.org have to say about building slave 1 wire devices:&#xA;&lt;a href=&quot;http://www.1wire.org/index.html?target=p_142.html&amp;amp;lang=en-us&quot; rel=&quot;nofollow&quot;&gt;http://www.1wire.org/index.html?target=p_142.html&amp;amp;lang=en-us&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="813" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-11T18:13:46.460" LastActivityDate="2010-11-11T18:13:46.460" CommunityOwnedDate="2010-06-26T05:52:17.593" CommentCount="2" />
  <row Id="3175" PostTypeId="1" AcceptedAnswerId="3177" CreationDate="2010-06-26T07:16:16.480" Score="2" ViewCount="518" Body="&lt;p&gt;Hey guys I was referred here from another site and was hoping that someone could help me out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some Background Information:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a 4th year EE student at Georgia Tech.  A research team with the AE department came around to some of our classes and asked for help with their project for some of their more electronic stuff.  I signed up and ended up on the FPGA team which has deteriorated to myself and one other guy, so we're really busy.  My current task is to set up a camera to take and store pictures using the FPGA &amp;amp; DSP on &lt;a href=&quot;http://www.adaptiveflight.com/products_fcs20.html&quot; rel=&quot;nofollow&quot;&gt;this board&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm stuck using firewire due to the limitations of the camera and the restrictions on the number of pins that has been allocated to me, so in the last month or so I've been trying to build a link + host layer for a firewire interface with &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tsb41ab3.html&quot; rel=&quot;nofollow&quot;&gt;this thing arbitrating&lt;/a&gt; for me.  I also have to use system verilog.  Anyways, I've never used the language before and am having a hard time trying to create one from scratch.  The firewire interface seems super complex and I've basically been told &quot;hurry up&quot; by the guys in charge of the project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Originally I had planned to use &lt;a href=&quot;http://opencores.org/websvn,listing?repname=firewire&amp;amp;path=%2Ffirewire%2Ftrunk%2Fbench%2Fverilog%2F#path_firewire_trunk_bench_verilog_&quot; rel=&quot;nofollow&quot;&gt;this project&lt;/a&gt; from opencores.com but it's missing files and I gave up trying to repair it since I don't really know the language all that well, but it looks like I'm probably going to need to either figure out how to fix it or find something else that will work or else I won't be finished in time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the top level file it includes a file called fw_link_defines.vh, which I don't have and doesn't seem to be anywhere else on the internet.  It looks like it defines(?) three things, if that's what the ` is actually doing in statements like &quot;pkt_type = `SELF_ID_PKT;&quot;, which wouldn't be too hard to fix, but there's also some weird thing called phy_ctrl which I thought was a structure or something but after looking on the internet it appears to be an &quot;instantiation&quot;.  I can't figure out what the heck that actually does.  I've looked at a few tutorials but can't seem to find any good ones on them, all I've found is large tutorials with one paragraph that says &quot;this is an instantiation, they are a real pain to work with&quot; and don't really explain much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;(Start here for TL;DR)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically what I'm asking is that if anyone knows any other open FPGA projects that use firewire to talk to a device, or if anyone knows a good source to learn how to use instantiations.  I've been having a real hard time with this and would be very grateful for any help you could give.  Thanks guys.&lt;/p&gt;&#xA;" LastActivityDate="2010-08-10T08:27:13.620" Title="Using FPGA to interface with a camera via 1394/firewire" Tags="&lt;fpga&gt;" AnswerCount="3" />
  <row Id="3176" PostTypeId="2" ParentId="3146" CreationDate="2010-06-26T09:53:40.587" Score="0" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;is epoxy gluing better substitute for soldering?&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;A technique with &lt;a href=&quot;http://en.wikipedia.org/wiki/Ball_grid_array#Disadvantages&quot; rel=&quot;nofollow&quot;&gt;ball grid array&lt;/a&gt; is &quot;under filling&quot; that uses epoxy mixture, the paragrahp is not crystal clear about the mixture. It seems to mean that soldering and epoxy-gluing are used almost simultaneously: you solder first then use epoxy glue to attack mechanical stress issues but &quot;epoxy soldering&quot; would be misleading as the expoxy gluing is no substitute. There may still be cases with epoxy-rosin-lead-mixtures(speculation, plz, attack).&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Mechanical stress issues can be&#xA;  overcome by bonding the devices to the&#xA;  board through a process called &quot;under&#xA;  filling&quot;, which injects an epoxy&#xA;  mixture under the device after it is&#xA;  soldered to the PCB, effectively&#xA;  gluing the BGA device to the PCB.&#xA;  There are several types of under fill&#xA;  materials in use with differing&#xA;  properties relative to workability and&#xA;  thermal transfer.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="834" LastEditorUserId="834" LastEditorDisplayName="" LastEditDate="2010-06-26T09:59:47.523" LastActivityDate="2010-06-26T09:59:47.523" />
  <row Id="3177" PostTypeId="2" ParentId="3175" CreationDate="2010-06-26T20:40:52.453" Score="1" ViewCount="" Body="&lt;p&gt;Ouch, well i've never worked with firewire at this level before but here are some maybe helpful thoughts:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I read through the TI PHY datasheet that you linked, it looks like its designed to work with the TI &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=379&amp;amp;uiTemplateId=NODE_STRY_PGE_T&quot; rel=&quot;nofollow&quot;&gt;Link Layer Controllers&lt;/a&gt;.  Have you considered just using such a part rather than trying to implement its functionality from scratch?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also the PHY &amp;lt;-&gt; LLC link runs at full firewire speed, which for 400mbps and an 8bit link is ~50Mhz, the camera may let you get away with running the link much slower, maybe not.  Point being you can't just take the pins of that PHY, blue wire them into the FPGA pins and expect a remotely functional or stable connection.  You'll very likely have major signal integrity issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks like the LLC's from TI come in various configurations, some with rather simple, generic 8/16 bit microcontroller style interfaces which should be easy to implement.  You can probably find verilog blocks for such an interface freely available.  These links would still need to be fast, ~50Mhz so you'll still have the signal integrity issue.  You could run it slower i guess but if the data feed overruns the FIFO in the LLC your SOL.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once your done with the physical interface you still have an entire firewire driver stack to implement, i guess you'd have to do this in the DSP? Or put a small soft core into the FPGA to handle this work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I would really do is tell them they are crazy for forcing a firewire interface for something of this size/capabilities.  Its going to take a significant amount of resources to build the firewire interface for no gain since you'll never use anywhere near its bandwidth.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that fails, I'd try &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tsb43cb43a.html&quot; rel=&quot;nofollow&quot;&gt;something like this&lt;/a&gt; which is a single part with the firewire PHY.LLC and an ARM7 core in a single chip.  It offers a parallel data bus to get the information into the FPGA.  This way you write the firewire driver to support communications to the camera and plunk it in the ARM7 core and all that has to get transfered to the FPGA are the raw images, no overhead work in the FPGA.  You still need to carefully design a PCB for this, your still dealing with a very high speed firewire bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At 100MBit/s the firewire bus runs at 100MHZ so you have to deal with moving 100MHZ differential signals from the PHY to the firewire connector.  On the PHY&amp;lt;-&gt;LLC&amp;lt;-&gt;FPGA side: I wouldn't personally try to breadboard a 13MHZ parallel data bus, it may be possible if your careful.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The critical issue for signal integrity is the rise/fall time of the signal, not its clock rate.  High clock rate usually means faster rise/fall times but sometimes if you use a transceiver thats designed to run at high frequency at lower frequencies it doesn't actually slow down the rise/fall times.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the wire carrying the signal is longer than: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tr/(2*Td) with&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tr = the signal rise time at the source and &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Td = the propagation delay per unit length of the wire/cable you are using.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you need to consider transmission line effects.  You'll have to deal with reflections in the wire which will cause all sorts of junk on the line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also need to be careful to make sure all the wires of a parallel bus are the same length with the tolerance for variation depending on the clock frequency of the bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this thing really going to end up in an UAV/RC aircraft?  If so you've got to deal with vibrations and G forces as well.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-06-27T17:41:33.433" LastActivityDate="2010-06-27T17:41:33.433" CommentCount="5" />
  <row Id="3178" PostTypeId="2" ParentId="1990" CreationDate="2010-06-26T22:47:26.570" Score="2" ViewCount="" Body="&lt;p&gt;A first step up from breadboard is probably perfboard, stripboard, veroboard or such. The next might be etching copper. Toner transfer is probably least involving (presuming you have other use for a laser printer) followed by photoresists. There's also tape up and pens if you don't mind the handiwork. It all depends on availability. Simple designs on thick material can even be carved with a rotary tool. Having access to a suitable router or a fab place changes the game of course.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Google around for those and maybe also &quot;Manhattan method&quot;. See if any of them is accessible. You may be able to use many of them for different purposes.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-26T22:47:26.570" />
  <row Id="3179" PostTypeId="2" ParentId="2783" CreationDate="2010-06-26T22:53:14.467" Score="2" ViewCount="" Body="&lt;p&gt;In-system programming facility is a good idea. It'll also let you update the firmware if necessary. Other ways probably involve making a needle bed or a substitute for one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a compromise, you could make sure there are test points somewhere on the needed (GND, !RST, SCK, MOSI, MISO, +V) nets and make a needle bed to match those. Then you don't need an actual ISP connector/layout on board. You might extend that to do some automated production testing, too.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-26T22:53:14.467" />
  <row Id="3180" PostTypeId="2" ParentId="1199" CreationDate="2010-06-27T09:03:50.523" Score="5" ViewCount="" Body="&lt;p&gt;The &lt;strong&gt;Parallax Propeller&lt;/strong&gt; is an oddbird 8-core (eight &quot;cogs&quot; plus a hub) microcontroller that can do very interesting/impressive things including SD/VGA video generation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has its own development environment including a language called SPIN that is run as bytecode on the cogs. Assembly is naturally available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is considerable community support and visible projects using the chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There isn't a wide range of models, but the chip appears to be the result of very careful design and long development run done by some extremely talented and competent people. It may be available for around $8.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(In-system) programming hardware apparently consists of TTL-level serial port and reset line. There is a dongle called Prop Plug available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://parallax.com&quot; rel=&quot;nofollow&quot;&gt;http://parallax.com&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Parallax_Propeller&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Parallax_Propeller&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-27T09:03:50.523" CommunityOwnedDate="2010-06-27T09:03:50.523" />
  <row Id="3181" PostTypeId="2" ParentId="1848" CreationDate="2010-06-28T00:15:08.517" Score="1" ViewCount="" Body="&lt;p&gt;If all you want is a led with a built-in series resistor, I believe these are available already.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-28T00:15:08.517" />
  <row Id="3182" PostTypeId="1" AcceptedAnswerId="3187" CreationDate="2010-06-28T15:24:24.337" Score="3" ViewCount="657" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to detect two buttons being pressed together with the Arduino LCD shield. Does anyone have example code of handling multiple button events? I need an event when both the Up and Down buttons are pressed together for 2 seconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LCD Shield is the 16*2 HD44780 compatible LCD with WHITE characters &amp;amp; BLUE backlight that has 6 buttons. I got it from www.hotsolder.co.uk&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Richard.&lt;/p&gt;&#xA;" LastActivityDate="2010-06-28T19:51:32.650" Title="Arduino - Multiple button event with lcd shield" Tags="&lt;arduino&gt;&lt;lcd&gt;" AnswerCount="2" />
  <row Id="3183" PostTypeId="2" ParentId="1848" CreationDate="2010-06-28T15:47:42.990" Score="0" ViewCount="" Body="&lt;p&gt;Here is an example of an OEM I found on globalsources.com: &lt;a href=&quot;http://bit.ly/anXwuR&quot; rel=&quot;nofollow&quot;&gt;http://bit.ly/anXwuR&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-06-28T15:47:42.990" />
  <row Id="3184" PostTypeId="2" ParentId="3182" CreationDate="2010-06-28T16:24:34.510" Score="2" ViewCount="" Body="&lt;p&gt;Depends how the buttons are wired, is it in a matrix, or is each button individually readable? If it's individual, I don't see what the problem is, just read both buttons, wait until they are both pressed, and then wait two seconds making sure they don't get un-pressed during that time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If they're wired in a matrix, it may not be able to read both of them at the same time.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-06-28T16:24:34.510" />
  <row Id="3185" PostTypeId="2" ParentId="3126" CreationDate="2010-06-28T18:56:34.200" Score="4" ViewCount="" Body="&lt;p&gt;The larger series of STM32 processors (32-bit Cortex-M3 core) has a FSMC, which is a Flexible Static Memory Controller.&#xA;With this you is able to connect Flash, RAM, and other memory peripherals like LCD and such.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can recommend the STM32F103ZET6 as tcrosley also said, and you can get a development board including flash and sram on ebay for $68 - &lt;a href=&quot;http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&amp;amp;item=220619908411&quot; rel=&quot;nofollow&quot;&gt;http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&amp;amp;item=220619908411&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-06-28T18:56:34.200" />
  <row Id="3186" PostTypeId="2" ParentId="3115" CreationDate="2010-06-28T19:06:41.317" Score="1" ViewCount="" Body="&lt;p&gt;I work for GOEPEL in the UK, we offer a free trial as well. We normally accompany this with a board setup, so you can get a better feel for what the tools can do. Whereabouts are you based, I can get our local office to get in touch or just register on our website. No real open source alternatives, what you are paying for is automated test generation. The low cost end of the market can normally get you in toggling pins, programming files etc, but if you are looking at production test you need safe quality tests that are going to find your build defects. Depending on your test coverage, you need to consider if Boundary scan alone will cover this or does it need other test strategies or functional test. Be careful on how test coverage is reported, if you start hearing 90-100% quoted then dig deeper into the figures. If it is not too late, check out our design guidelines.&lt;/p&gt;&#xA;" LastActivityDate="2010-06-28T19:06:41.317" />
  <row Id="3187" PostTypeId="2" ParentId="3182" CreationDate="2010-06-28T19:07:37.493" Score="2" ViewCount="" Body="&lt;p&gt;It looks like this shield has 5 buttons attached to different value resistors on a single analogue pin. The sixth button is hardwired to reset. &lt;a href=&quot;http://www.nuelectronics.com/download/projects/LCDshield_v1_1.pdf&quot; rel=&quot;nofollow&quot;&gt;Here's the schematic&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.nuelectronics.com/estore/images/nustore/projects/lcd_schematics.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.nuelectronics.com/download/projects/LCD4Bit_mod.zip&quot; rel=&quot;nofollow&quot;&gt;sample code&lt;/a&gt; has a lookup table to convert the ADC values to keys:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int  adc_key_val[5] ={30, 150, 360, 535, 760 };&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If you're lucky, you might be able to spot two keys being pressed at the same time as a unique ADC reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try writing a short sketch to print the ADC value to the serial port, then experiment. See if you can find unique ranges of ADC values representing the key combinations you're interested in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To detect a press for a length of time, use the Arduino millis() function to record the time then compare. This is very similar to &lt;a href=&quot;http://www.arduino.cc/en/Tutorial/Debounce&quot; rel=&quot;nofollow&quot;&gt;debouncing a button&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-28T19:51:32.650" LastActivityDate="2010-06-28T19:51:32.650" CommentCount="1" />
  <row Id="3188" PostTypeId="1" CreationDate="2010-06-28T20:19:33.253" Score="5" ViewCount="558" Body="&lt;p&gt;I need to build a transistor circuit to go up from 3.3v (output of serial port) to drive some mechanical relays which require 24v input. Thoughts?&lt;/p&gt;&#xA;" LastActivityDate="2010-06-28T21:09:28.887" Title="How to step up from 3.3v to 24v?" Tags="&lt;transistor&gt;&lt;circuit&gt;" AnswerCount="2" />
  <row Id="3189" PostTypeId="2" ParentId="3188" CreationDate="2010-06-28T20:28:01.793" Score="2" ViewCount="" Body="&lt;p&gt;You need a DC-DC boost converter to generate the 24v.  However you didn't say what your current requirements were.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used the following chip to generate a higher voltage for an OLED display: &lt;a href=&quot;http://focus.ti.com/lit/ds/slvs644b/slvs644b.pdf&quot; rel=&quot;nofollow&quot;&gt;TPS61080&lt;/a&gt; -- it can generate at least 24v at 100 ma from a 3.3v input.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-06-28T21:09:28.887" LastActivityDate="2010-06-28T21:09:28.887" CommentCount="1" />
  <row Id="3190" PostTypeId="2" ParentId="3188" CreationDate="2010-06-28T20:51:11.740" Score="7" ViewCount="" Body="&lt;p&gt;I would suggest you find some power source and use an npn transistor to switch your relay.&#xA;Imagine the relay needs 100mA then you would have to provide some 720mA from your source!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Better to switch as following&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;V+ -------------------|&#xA;                      |--------------&#xA;                     |  |           _&#xA;                     |  | Relay     ^  Diode&#xA;                     |  |           |&#xA;                      |             |&#xA;                      |-------------&#xA;                     /&#xA;serial ----- [R1]---| Transistor&#xA;          |          \&#xA;         |R|          |&#xA;         |2|          |&#xA;          |           |&#xA;Gnd ------------------|&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Calulate the resistors according to the Hfe of your transistor&lt;/p&gt;&#xA;" OwnerUserId="348" LastActivityDate="2010-06-28T20:51:11.740" CommentCount="2" />
  <row Id="3191" PostTypeId="2" ParentId="1842" CreationDate="2010-06-28T21:37:42.783" Score="0" ViewCount="" Body="&lt;p&gt;Just regarding the comment about the temperature probe from Analog Devices.   It is still available, see:  www.analog.com/ac2626&lt;/p&gt;&#xA;" LastActivityDate="2010-06-28T21:37:42.783" />
  <row Id="3192" PostTypeId="1" CreationDate="2010-06-29T00:01:20.700" Score="1" ViewCount="620" Body="&lt;p&gt;I am super confused how to hook up this relay&#xA;&lt;a href=&quot;http://www.radioshack.com/product/index.jsp?productId=2062480&quot; rel=&quot;nofollow&quot;&gt;http://www.radioshack.com/product/index.jsp?productId=2062480&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The nerf gun has a  spdt switch for the trigger and runs on 4 AA's .&lt;/p&gt;&#xA;" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-06-29T05:26:30.313" LastActivityDate="2010-06-29T05:26:30.313" Title="5V Relay and Arduino to control a 6v nerf gun" Tags="&lt;relay&gt;&lt;arduino&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="3193" PostTypeId="2" ParentId="3192" CreationDate="2010-06-29T00:17:57.477" Score="2" ViewCount="" Body="&lt;p&gt;You need a transistor to drive the relay from an Arduino pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/Arduino-Expermentation-Kit-How-to-get-Started-wi/step13/Larger-Loads-Relays-CIRC11/&quot; rel=&quot;nofollow&quot;&gt;Here's a tutorial&lt;/a&gt; with some Arduino diagrams.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're driving a motor, you will need a diode also.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-29T00:17:57.477" CommentCount="3" />
  <row Id="3194" PostTypeId="2" ParentId="3192" CreationDate="2010-06-29T00:18:43.573" Score="3" ViewCount="" Body="&lt;p&gt;Relax, it will not be that hard. First of all, work out which pins are for the relay's coil. Then, have a look at this article: &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/04/20/getting-started-with-arduino-chapter-three/&quot; rel=&quot;nofollow&quot;&gt;http://tronixstuff.wordpress.com/2010/04/20/getting-started-with-arduino-chapter-three/&lt;/a&gt;  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[edit] D'oh - Joby beat me by 10 seconds&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-06-29T00:18:43.573" />
  <row Id="3195" PostTypeId="2" ParentId="3175" CreationDate="2010-06-29T01:25:58.713" Score="0" ViewCount="" Body="&lt;p&gt;To be honest, if your goal is to get video/pictures from a camera onto a FPGA-based device, a firewire camera is the wrong starting point. You probably should find a camera more suited to your purpose with an easier interface to use. This probably also has the advantage of being much smaller than an off-the-shelf camcorder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wait, am I misunderstanding something? I just looked a bit at the link describing the board that has your FPGA on it, and it says it already has a camera built into it? (Omnivision OV5610 5.17 megapixel color CMOS image sensor array). Are you saying it's using Firewire for the on-board connection between the FPGA and the built in camera?&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-06-29T01:25:58.713" CommentCount="2" />
  <row Id="3196" PostTypeId="1" AcceptedAnswerId="3197" CreationDate="2010-06-29T13:59:24.940" Score="2" ViewCount="1023" Body="&lt;p&gt;Because I am new to programming on microcontrollers coming from the C++ world, I have been studying on getting code running on a microcontroller board to work with many inputs and outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the first project I am working on an ARM9 chip (STR912FAW44) with Rowley Crossworks for ARM to program my board. I understand that I have to setup port 7.3 to output mode to drive a LED. I also understand that the GPIO port has multiple modes on this pin, defaulting to GP Input. I also know the alternate output 1 configuration is GP Output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now the manual for the chip says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;There are up to 80 GPIO pins available on 10 I/O ports for 128-pin and 144-ball devices, and &#xA;  up to 40 GPIO pins on 5 I/O ports for 80-pin devices. Each and every GPIO pin by default &#xA;  (during and just after a reset condition) is in high-impedance input mode, and some GPIO &#xA;  pins are additionally routed to certain peripheral function inputs. CPU firmware may initialize GPIO pins to have alternate input or output functions as listed in Table 8.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This sounds wonderful. The question is how can I get the port to accept a different function?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have sample code for a similar, but different board where the LED (easiest to test) is on port 9, but this does not work when adjusted to port 7 as I expected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the sample:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void&#xA;ctl_board_init(void)&#xA;{&#xA;  // leds are connected to GPIO9.0-GPIO9.3&#xA;  SCU_PCGR1 |= SCU_PCGR1_GPIO9_MASK; // turn on GPIO9&#xA;  SCU_PRR1 |= SCU_PRR1_RST_GPIO9_MASK;  &#xA;  GPIO9_DIR = 0x01; // select output direction&#xA;}&#xA;&#xA;void &#xA;ctl_board_on_button_pressed(CTL_ISR_FN_t buttonFn)&#xA;{&#xA;}&#xA;&#xA;void&#xA;ctl_board_set_leds(unsigned v)&#xA;{&#xA;  *((&amp;amp;GPIO9_DATA)+(0x01&amp;lt;&amp;lt;2)) = v ? 0x01 : 0;   &#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The macros come from header files, but can anyone help me find reference to which bits I should set to drive GPIO port 7.3 as output?&lt;/p&gt;&#xA;" OwnerUserId="909" LastEditorUserId="909" LastEditorDisplayName="" LastEditDate="2010-06-30T09:35:08.840" LastActivityDate="2011-03-07T15:53:17.843" Title="How to configure an ARM GPIO port (STR9) to an alternate function?" Tags="&lt;arm&gt;&lt;microcontroller&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="3197" PostTypeId="2" ParentId="3196" CreationDate="2010-06-29T15:31:46.063" Score="4" ViewCount="" Body="&lt;p&gt;The STR91x family of microcontrollers has very flexible peripherals.  Unfortunately, this flexibility makes them somewhat complicated to set up.  My suggestion is to start by downloading the &lt;a href=&quot;http://www.st.com/mcu/modules.php?name=mcu&amp;amp;file=familiesdocs&amp;amp;fam=101&amp;amp;doc=76&quot; rel=&quot;nofollow&quot;&gt;STR91xFA Firmware Library&lt;/a&gt; from ST.com.  Once you have the library linked into your project, you need to do something similar to the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void InitGPIO7( void )&#xA;{&#xA;   GPIO_InitTypeDef GPIO_InitStructure;&#xA;&#xA;   /* Enable the GPIO7 clock */&#xA;   SCU_APBPeriphClockConfig(__GPIO7, ENABLE);&#xA;&#xA;   /* Initialize the GPIO port */&#xA;   GPIO_DeInit(GPIO7);&#xA;&#xA;   /* Configure pin GPIO7.3 */&#xA;   GPIO_InitStructure.GPIO_Direction = GPIO_PinOutput;&#xA;   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;&#xA;   GPIO_InitStructure.GPIO_Type = GPIO_Type_PushPull;&#xA;   GPIO_InitStructure.GPIO_IPConnected = GPIO_IPConnected_Disable;&#xA;   GPIO_InitStructure.GPIO_Alternate = GPIO_OutputAlt1;&#xA;   GPIO_Init (GPIO7, &amp;amp;GPIO_InitStructure);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that this is untested but it should be pretty close.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-06-29T15:31:46.063" CommentCount="3" />
  <row Id="3198" PostTypeId="2" ParentId="3196" CreationDate="2010-06-29T15:43:58.130" Score="1" ViewCount="" Body="&lt;p&gt;From looking at the datasheet (&lt;a href=&quot;http://www.st.com/mcu/download2.php?file=13742.pdf&amp;amp;info=STR912FAW44%20Reference%20Manual%20RM0006&amp;amp;url=http://www.st.com/stonline/products/literature/rm/13742.pdf&quot; rel=&quot;nofollow&quot;&gt;13742.pdf&lt;/a&gt;), it looks like for GPIO pins 0-7 you need to set the appropriate bit in the SCU_GPIOTYPE registers and possibly others.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;System control unit GPIO registers GPIO pins on P0&#xA;  thru P7 have multiple input and output&#xA;  alternate functions. You select these&#xA;  using the System Control Unit (SCU)&#xA;  registers. SCU registers are also used&#xA;  to select open collector or Push-Pull&#xA;  operation and to configure Port 4 pins&#xA;  for use as analog inputs. GPIO pins on&#xA;  P8 thru P9 are only multiplexed with&#xA;  EMI and have no SCU output or input&#xA;  control registers. All ports have&#xA;  SCU_GPIOTYPE registers for selecting&#xA;  Open Collector or Push/Pull&#xA;  configuration.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-29T16:33:02.790" LastActivityDate="2010-06-29T16:33:02.790" CommentCount="2" />
  <row Id="3199" PostTypeId="1" CreationDate="2010-06-29T22:40:08.563" Score="4" ViewCount="854" Body="&lt;p&gt;&lt;img src=&quot;http://i46.tinypic.com/2lbfec7.jpg&quot; alt=&quot;http://i46.tinypic.com/2lbfec7.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ok, so this is what my relay looks like. I can't figure out what pins I hook the arduino and transistor to, and what pins to hook the the other device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please help.&lt;/p&gt;&#xA;" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-05T10:48:31.413" LastActivityDate="2010-12-05T10:48:31.413" Title="How do I connect a relay and transistor to an Arduino?" Tags="&lt;arduino&gt;&lt;transistor&gt;&lt;relay&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="3200" PostTypeId="2" ParentId="3199" CreationDate="2010-06-29T23:17:47.923" Score="1" ViewCount="" Body="&lt;p&gt;Connect one end of the relay coil to the 5V rail. Connect the cathode end (the end with the bar) of a diode, such as a 1N4001, to that same end of the relay coil. Hook the other end of the diode to the other side of the relay coil. Connect this side of the relay coil to the collector of an NPN transistor. The emitter of the NPN goes to ground. Hook an output from the Arduino to the base of the NPN through a resistance of about 2.2K ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you set the output HIGH, check the voltage at the collector of the NPN. It shouldn't be more than about 0.2V; if you see 0.25 or more, try a smaller resistor, but don't go below 500 ohms or you'll be pulling more current from the arduino than you really need to.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-29T23:17:47.923" CommentCount="5" />
  <row Id="3201" PostTypeId="1" AcceptedAnswerId="3222" CreationDate="2010-06-29T23:24:43.703" Score="1" ViewCount="56" Body="&lt;p&gt;Knowing that Bluetooth and ANT+ use FH-SS and ZigBee uses DS-SS, I would like to learn of the modulation technique's effects on a wireless point-to-point connection if I am implementing the wireless active sensor prototype (measurement sent from device to terminal, with the terminal sending back infrared LED intensity to the device to adjust the settings. It would be great to hear from you about it. Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="854" LastEditorUserId="854" LastEditorDisplayName="" LastEditDate="2010-06-30T00:31:11.493" LastActivityDate="2010-06-30T13:41:38.577" Title="Modulation technique's effect on Active Sensor" Tags="&lt;wireless&gt;&lt;sensor&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="3202" PostTypeId="2" ParentId="3199" CreationDate="2010-06-29T23:49:54.353" Score="5" ViewCount="" Body="&lt;p&gt;Here's a well illustrated similar answer on a different forum.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://letsmakerobots.com/node/528#comment-15665&quot; rel=&quot;nofollow&quot;&gt;http://letsmakerobots.com/node/528#comment-15665&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(deeplinked images)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A schematic diagram of a relay showing the two coil pins and the three pin switch consisting of normally-open, normally-closed and common (power). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://letsmakerobots.com/files/userpics/u610/relay.jpg&quot; alt=&quot;relay&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A circuit using a transistor to drive the coil and a diode to suppress its back EMF.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://letsmakerobots.com/files/userpics/u610/trans-relay.jpg&quot; alt=&quot;driver&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget to adjust for the different pinout of your relay.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-30T00:00:46.793" LastActivityDate="2010-06-30T00:00:46.793" CommentCount="1" />
  <row Id="3203" PostTypeId="1" AcceptedAnswerId="3209" CreationDate="2010-06-30T00:28:35.583" Score="29" ViewCount="779" Body="&lt;p&gt;What's the cheapest way to link a few microcontrollers wirelessly at low speeds over short distances.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking to keep it ultra-cheap, use common discrete parts and keep it physically small. I don't care about bands and licensing so long as it works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;802.15.4/ZigBee, Bluetooth and WiFi all require an expensive coprocessor, so aren't an option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, are there very cheap radio modules available to hobbyists? The kind of things you find in car keyfobs and wireless thermometers, perhaps?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would building a simple transceiver on a homebrew PCB even be practical, or will I be plagued by tuning, interference and weirdy analogue stuff?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could something like &lt;a href=&quot;http://tacashi.tripod.com/elctrncs/smplfmtr/smplfmtr.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; be driven from a microcontroller?&#xA;What about receive?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-06-30T01:57:43.797" LastActivityDate="2011-06-01T19:47:21.757" Title="What's the cheapest way to link a few microcontrollers wirelessly at low speeds over short distances" Tags="&lt;radio&gt;&lt;rf&gt;" AnswerCount="7" FavoriteCount="13" />
  <row Id="3204" PostTypeId="2" ParentId="3203" CreationDate="2010-06-30T00:35:58.083" Score="6" ViewCount="" Body="&lt;p&gt;I'm not sure if this would count as cheap enough, but the &lt;a href=&quot;http://www.linxtechnologies.com/&quot; rel=&quot;nofollow&quot;&gt;Linx&lt;/a&gt; chips are dead simple. I've made a PCB for these chips and successfully run 16 sets at the same time in a 10 x 20 m room without any special PCB trickery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Future Electronics has the &lt;a href=&quot;http://uk.futureelectronics.com/en/technologies/semiconductors/wireless-rf/rf-modules-solutions/proprietary/Pages/7651854-TRM-315-LT.aspx&quot; rel=&quot;nofollow&quot;&gt;TRM-315-LT modules for £11.33 each&lt;/a&gt; in the UK. There might be other modules that are cheaper, but I think those are the ones I used previously (it was ~6 years ago, so my memory is a little fuzzy).&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-30T00:35:58.083" CommentCount="5" />
  <row Id="3205" PostTypeId="2" ParentId="3203" CreationDate="2010-06-30T01:28:53.917" Score="28" ViewCount="" Body="&lt;p&gt;You pretty much have to buy pre-made modules, you can't expect to wire up your own transmitter/receiver from a few transistors and a crystal, RF circuit design is unforgiving and all but requires a custom PCB (or custom IC) to do. You could probably build your own RF module on a PCB if you did some work, but at that point if you are making your own PCB's, you're not saving much money versus the very cheap modules that are available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SparkFun has &lt;a href=&quot;http://www.sparkfun.com/categories/79?sort_by=price_asc&amp;amp;per_page=50&quot; rel=&quot;nofollow&quot;&gt;RF Transmitters &amp;amp; Receivers&lt;/a&gt; for $4 and $5 respectively. Since they are just basic parts, you will need to do a little extra logic on your microcontroller to compensate for interference, eg sending error control codes so that missing / flipped bits can be detected and recovered.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found SeeeeeedStudio sells almost the exact same thing, but even cheaper. It's $4.90 for a &lt;a href=&quot;http://www.seeedstudio.com/depot/wireless-rfism-c-139_140.html?sort=3a&amp;amp;page=1&quot; rel=&quot;nofollow&quot;&gt;pair of a receiver and transmitter&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="131" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-06-01T19:46:54.927" LastActivityDate="2011-06-01T19:46:54.927" CommentCount="3" />
  <row Id="3206" PostTypeId="1" CreationDate="2010-06-30T01:42:49.443" Score="9" ViewCount="864" Body="&lt;p&gt;Simple question: What is your favorite breadboard, and why? I'm looking to upgrade mine, and am curious to see what other people use.&lt;/p&gt;&#xA;" OwnerUserId="835" LastActivityDate="2011-01-10T10:12:46.500" Title="Best solderless breadboard?" Tags="&lt;breadboard&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="3207" PostTypeId="2" ParentId="3206" CreationDate="2010-06-30T02:36:24.340" Score="8" ViewCount="" Body="&lt;p&gt;I just got &lt;a href=&quot;http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_20812_-1&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; from Jameco a couple of months ago. It's nice to have the room to spare, and in my opinion, nicer than having separate smaller ones, especially considering the general notoriety breadboards have regarding intermittent connections.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-30T02:36:24.340" CommentCount="1" />
  <row Id="3208" PostTypeId="2" ParentId="3203" CreationDate="2010-06-30T02:47:06.017" Score="5" ViewCount="" Body="&lt;p&gt;The Nordic Semi nRF24L01+ is easy to use, SFE sells modules. &lt;a href=&quot;http://www.leonheller.com/MiRF%20V2/&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is some PIC18F4520 hardware of mine with some test software.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-06-30T02:47:06.017" />
  <row Id="3209" PostTypeId="2" ParentId="3203" CreationDate="2010-06-30T03:30:56.047" Score="17" ViewCount="" Body="&lt;p&gt;Infrared emitters and receivers can be used to transmit/receive data. However, interference with other devices like remote controls might be a problem. If the connection needs to be really reliable, this probably wouldn't be that great of an option. However, you might be able to find a really uncommon wavelength emitter and receiver to limit the amount of interference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are pretty common, and very cheap. Packs of 20 emitters for $1 and packs of 100 receivers for $13 can be found on eBay (not including shipping). Lots of electronics stores have them as well.&lt;/p&gt;&#xA;" OwnerUserId="790" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-06-01T19:47:21.757" LastActivityDate="2011-06-01T19:47:21.757" CommentCount="6" />
  <row Id="3210" PostTypeId="2" ParentId="3203" CreationDate="2010-06-30T07:29:14.197" Score="6" ViewCount="" Body="&lt;p&gt;The cheapest radio modules I know are the RFM12 modules, they do frequency shift keying in the 433 or 868 MHz band.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-06-30T07:29:14.197" CommentCount="2" />
  <row Id="3211" PostTypeId="2" ParentId="3206" CreationDate="2010-06-30T08:00:54.320" Score="4" ViewCount="" Body="&lt;p&gt;The breadboards can be helpful in designing, but we have actually stopped using breadboards for the most part. Soldered parts give us a much more reliable indication of how a particular configuration is going to perform when we put it on a print. Especially analog sensoring linked with a microcontroller tends to give interference problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your setup is anything more than basics, I would recommend using something soldered on like this: &lt;a href=&quot;http://www2.conrad-uk.com/goto.php?artikel=528196&quot; rel=&quot;nofollow&quot;&gt;(PCB) Euroboard 160 x 100&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="909" LastEditorUserId="909" LastEditorDisplayName="" LastEditDate="2010-06-30T13:59:38.073" LastActivityDate="2010-06-30T13:59:38.073" CommentCount="4" />
  <row Id="3212" PostTypeId="1" CreationDate="2010-06-30T09:14:40.107" Score="1" ViewCount="238" Body="&lt;p&gt;Hello:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im working on a scale project where i use an INA126 to get my signal, after the filters I need to substract voltaje from it, im using an opamp in the appropiate configuration, it does this operation (signal) - xvoltage, where xvoltage is the output of the same opamp in buffer configuration between a voltage divider, but everytime I add weight to the scale the output of the buffer changes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I dunt know how to explain it.. since its not related by any means.. tnxs&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW the opamp im using its the lm358&lt;/p&gt;&#xA;" LastActivityDate="2010-07-01T04:41:21.433" Title="Can i use an opamp in buffer configuration as a voltage source??" Tags="&lt;op-amp&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="3213" PostTypeId="2" ParentId="2641" CreationDate="2010-06-30T10:47:36.730" Score="11" ViewCount="" Body="&lt;p&gt;I recently attended an online conference on FPGA's with the keynote being &quot;Should your next processor be an FPGA.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The FPGA basically makes sense in any application that requires highly parallelizable work streams, an example being used was analyzing Full HD images to find pedestrians for instance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing you have to remember is that you have to initialize your FPGA every time it powers up, I think the FPGA's Xilinx is coming with (which have an on-chip ARM core) are a good option, but probably expensive. Looking into the Actel ones with on-chip flash may be useful too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for performance, the company BDTI did a benchmark in highly parallel computations where they saw about 40x performance gain switching to an FPGA. The interesting thing is that they compared chips with similar costs (23$ vs 28$ I believe).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are the links that might interest you:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.bdti.com/pocket/pocket.htm&quot; rel=&quot;nofollow&quot;&gt;Pocket guide to processor selection&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://bit.ly/dm1ugx&quot; rel=&quot;nofollow&quot;&gt;FPGA Conference Archives (Free registration, but only available for about 6 months after this answer)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You cannot really compare performance of FPGA based systems based on MIPS or Mhz stats. The way an FPGA is used to process certain tasks is simply too different from a Microcontroller. The design of firmware for an FPGA is something you have to do using VHDL for instance, which is akin to Assembly. A register transfer level (RTL) of abstraction. Some environments are being produced to provide more abstraction, but these are still often vendor specific. Wikipedia has a decent overview of languages available to program FPGA code:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Field-programmable_gate_array#FPGA_design_and_programming&quot; rel=&quot;nofollow&quot;&gt;Wikipedia: Programming FPGA&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Hardware_description_language#Digital_circuit_design&quot; rel=&quot;nofollow&quot;&gt;Wikipedia: Digital Circuit Design&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have money to burn you can use the LabView systems to build FPGA based real time measurement systems for instance. These devices needed for this are in a completely different pricerange (1500$ and up), but open up te FPGA design to a much broader audience with graphic programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More and more vendors are providing boards which combine microcontrollers such as an ARM chip with an FPGA to provide specific additional features and parallel processing power. An example of such products can be found here: &lt;a href=&quot;http://www.embeddedarm.com/products/arm-sbc.php#ts-7300-fpga-series&quot; rel=&quot;nofollow&quot;&gt;EmbeddedARM: FPGA series&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="909" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-06-30T14:36:55.837" LastActivityDate="2010-06-30T14:36:55.837" />
  <row Id="3214" PostTypeId="2" ParentId="3212" CreationDate="2010-06-30T11:45:07.810" Score="2" ViewCount="" Body="&lt;p&gt;If I read you correctly, you have two op-amps in your circuit. One in a summing configuration, to take your signal and subtract off a constant voltage. The other, call it the reference amp, provides the constant voltage to be subtracted? In principle there's nothing wrong with that. You should be able to present a wide range of load impedances to the reference stage without changing its output voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually, op-amps have very high input impedance, so you shouldn't even have to buffer a voltage divider in order to provide the reference voltage to the summing stage. You can add or subtract several signals with a single op-amp, given the correct resistor network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just out of curiosity, what are the resistor values you're using?&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-06-30T11:45:07.810" CommentCount="1" />
  <row Id="3215" PostTypeId="2" ParentId="2641" CreationDate="2010-06-30T12:28:17.803" Score="2" ViewCount="" Body="&lt;p&gt;It depends a lot on your application. The ideal application here would consist of a tiny control part (which fits on a microblaze/NIOS) but a computational part that can benefit from the huge parallelism of custom hardware. In these cases, even a modest-sized FPGA (Spartan or equivalent) can easily outperform any general-purpose CPU. But that's best-case (although very much achievable in a lot of real-world apps), if your app does have a significant control part or doesn't easily map to hardware, spending your money on fixed hardware (i.e. an ARM) is probably better.&lt;/p&gt;&#xA;" OwnerUserId="401" LastActivityDate="2010-06-30T12:28:17.803" />
  <row Id="3216" PostTypeId="1" AcceptedAnswerId="3220" CreationDate="2010-06-30T12:29:30.610" Score="3" ViewCount="127" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Firstly, I am new to ChipHacker as well as arduino.  I just figured out how to write code for the chip in arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, I am connecting a camera on the board, which continuously sends some data. this data could be caught by the sketch that would be flashed on the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question was how could the output from the arduino be received on my computer. Can it be done using a .net based client on the desktop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="913" LastActivityDate="2010-06-30T15:08:43.923" Title="Desktop client for arduino" Tags="&lt;arduino&gt;&lt;wiring&gt;" AnswerCount="2" />
  <row Id="3217" PostTypeId="1" AcceptedAnswerId="3218" CreationDate="2010-06-30T12:36:46.713" Score="1" ViewCount="114" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can connect many resistor in parallel or series to get a final resistance I want in case when I have no necessary nominal out of the box.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wonder is there such trick that will allow me to easily change varistor's nominal. Say, originally I have a varistor that changes its resistance from 0 to 200 kilohm. Can I construct a simple circuit that will map the range to, for example, 0-10 kilohm?&lt;/p&gt;&#xA;" OwnerUserId="914" LastActivityDate="2010-06-30T15:46:58.610" Title="Can I adjust varistor range?" Tags="&lt;resistor&gt;" AnswerCount="2" />
  <row Id="3218" PostTypeId="2" ParentId="3217" CreationDate="2010-06-30T12:48:12.357" Score="4" ViewCount="" Body="&lt;p&gt;An easy trick is to place a fixed resistor, say 10 kOhm, in parallel with the varistor. The total resistance will now vary between 0 and 9.5 kOhm. But the problem here is that the total resistance does not vary linearly with the varistor's resistance, f.i. when the varistor is at one quarter, at 50 kOhm, my circuit will still be at 8.3 kOhm rather than 2.5 kOhm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do need linearity you'll need other, more complicated components (I'm sure that with an opamp you can simulate this).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bigger question is though, in what circuit do you want to use this? Maybe there's an easier way to accomplish this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(You could also place 20 of your 0-200 kOhm varistors in parallel, which also gives you 0-10 kOhm, but that doesn't seem like a very good solution to me either...)&lt;/p&gt;&#xA;" OwnerUserId="401" LastActivityDate="2010-06-30T12:48:12.357" CommentCount="1" />
  <row Id="3219" PostTypeId="2" ParentId="1893" CreationDate="2010-06-30T12:50:21.660" Score="0" ViewCount="" Body="&lt;p&gt;You could try Denis Ferranti &lt;a href=&quot;http://dferrantielectronics.co.uk&quot; rel=&quot;nofollow&quot;&gt;PCB Assembly&lt;/a&gt; - I've worked with them and they are a fantastic PCB manufacturer who could easily handle your needs of through hole and smt assemblies.&lt;/p&gt;&#xA;" LastActivityDate="2010-06-30T12:50:21.660" CommunityOwnedDate="2010-06-30T12:50:21.660" />
  <row Id="3220" PostTypeId="2" ParentId="3216" CreationDate="2010-06-30T13:31:47.193" Score="2" ViewCount="" Body="&lt;p&gt;The easiest way for beginners to do this is to write a program that uses a com port to communicate with the microcontroller. I have never used an arduino, but I know they have the ability to plug in a USB cable to them that then creates a serial port on your computer. This program can be written in any language that can communicate with a serial port (java, c, c++, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, once you have your com port connected, it is just a matter of writing and reading serial on both ends. You have the freedom to use what ever communication protocol you wish. By this I mean you get to determine what is in the data packets being sent. This will very much depend on what format the camera you are using gives as well as what you want to use the video for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, if you have a raw video stream, you could create a communication protocol that gives a header which includes something like frame number and frame length (number of bytes) and then possibly a footer that includes a checksum for the whole image. Or you could scratch the checksum and header and just mark each row. It's all up to you.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-06-30T13:31:47.193" />
  <row Id="3221" PostTypeId="2" ParentId="815" CreationDate="2010-06-30T13:37:09.540" Score="0" ViewCount="" Body="&lt;p&gt;I've been looking at &lt;a href=&quot;http://atomthreads.com/&quot; rel=&quot;nofollow&quot; title=&quot;atomthreads&quot;&gt;atomthreads&lt;/a&gt;. That should run on avr's but I don't know if you can merge any of the fw/sw parts of Arduino into it.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-30T13:37:09.540" />
  <row Id="3222" PostTypeId="2" ParentId="3201" CreationDate="2010-06-30T13:41:38.577" Score="2" ViewCount="" Body="&lt;p&gt;I can't figure out the question here either, but I believe spread spectrum signaling is used to get around (narrow band) noise, increasing link reliability. It will, of course, create a broader spectrum of noise itself compared to sticking to a single channel. There should be a lot of decent material available on the subject and these specific methods.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-30T13:41:38.577" CommentCount="1" />
  <row Id="3223" PostTypeId="2" ParentId="59" CreationDate="2010-06-30T13:48:43.523" Score="0" ViewCount="" Body="&lt;p&gt;Two alternative options might also be worth looking at:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microcontrollers with mixed signal abilities like MSP430. 44k * 2 * 2 is a lot of samples so you might not have a lot of time for processing them on the speeds these run in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Standalone PC, PDA or such. You probably get more or less HI-FI (and upgradeable) AD/DA and audio stuff builtin and will have massive cpu power plus display capability. Good dev software is often free and hardware can be cheap or even free. Latencies might be high, though, and you'd have to work with a big power-hungry ineffective machine.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-06-30T13:48:43.523" CommentCount="1" />
  <row Id="3224" PostTypeId="2" ParentId="3216" CreationDate="2010-06-30T15:08:43.923" Score="2" ViewCount="" Body="&lt;p&gt;It's definitely possible, though it will likely be slower than you'd like at transmitting camera images. Take a look at &lt;a href=&quot;http://arduino.cc/en/Tutorial/Graph&quot; rel=&quot;nofollow&quot;&gt;this tutorial&lt;/a&gt;, which describes how to send data over the serial port. If you can get that working, you just need to swap in the image data instead of the potentiometer reading in the tutorial, and write a .NET client that to render the images.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(You might consider using &lt;a href=&quot;http://processing.org/&quot; rel=&quot;nofollow&quot;&gt;Processing&lt;/a&gt; for the rendering, rather than .NET.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-06-30T15:08:43.923" />
  <row Id="3225" PostTypeId="2" ParentId="3217" CreationDate="2010-06-30T15:46:58.610" Score="3" ViewCount="" Body="&lt;p&gt;Wim is correct with his ideas but I wanted to say that in general placing nonlinear circuit elements in parallel or series will produce undefined behavior.  Unless the two nonlinear elements are precisely matched (ie, their trip points, V-I characteristics, etc are within &amp;lt;1% of each other) then there's no telling what will happen exactly.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, are you using the term varistor here properly?  It's not usually a VARiable ResISTOR (ie, a potentiometer or rheostat) it's a nonlinear voltage protection device that acts like a circuit breaker.  If you're just working with a potentiometer or rheostat then you can add and subtract resistance in parallel or series to your heart's content and you'll get easily calculated behavior since everything combines linearly.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-06-30T15:46:58.610" CommentCount="1" />
  <row Id="3226" PostTypeId="1" AcceptedAnswerId="3238" CreationDate="2010-06-30T15:49:48.270" Score="1" ViewCount="186" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was wondering if it is possible to add my own Bluetooth module (Widcomm or any other chip) to my existing Arduino board? The current board transmits serial data using USB. I know there is a BT version of Arduino available, but it seems to be out of my budget.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it is possible, then;&#xA;1. How do I integrate it to the board?&#xA;2. What changes would I need to do so that my board now transmits data via bluetooth?&#xA;3. Do I need to write any additional firmware for the BT chip?&#xA;4. If the BT chip comes with a built-in firmware, can I modify it? As-In I would like it to have a custom name and so on..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be really appreciable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank You!&lt;/p&gt;&#xA;" OwnerUserId="913" LastActivityDate="2011-05-18T11:41:12.910" Title="Adding BT connectivity to Arduino" Tags="&lt;arduino&gt;&lt;bluetooth&gt;" AnswerCount="2" />
  <row Id="3227" PostTypeId="1" CreationDate="2010-06-30T16:23:37.643" Score="1" ViewCount="158" Body="&lt;p&gt;I'm using an AT91SAM7 chip on the MakingThings board for some custom work. To better understand the peripheral driver, I'm trying to directly call/control an output pin (PA12) to turn on the status LED.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;main()&#xA;{&#xA;    AT91C_BASE_PIOA-&amp;gt;PIO_PER = AT91C_PIO_PA12; //Enable Pin PA12&#xA;    AT91C_BASE_PIOA-&amp;gt;PIO_OER = AT91C_PIO_PA12; // Enable Pin PA12 as 'peripheral manager' controlled pin &#xA;    AT91C_BASE_PIOA-&amp;gt;PIO_PPUDR = AT91C_PIO_PA12; //Disable Pull Up resistors&#xA;    AT91C_BASE_PIOA-&amp;gt;PIO_SODR =  AT91C_PIO_PA12; // Set pin state to 'high'&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;That code builds fine.  When I burn the firmware and test it, that does not turn on the LED on pin A 12. The peripheral controller is a bit complex, so I'm concerned I'm doing something in a wrong order, or that I am missing some other register that must be set. Does anyone have feedback or info on why that might be wrong? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I can run other code, do other examples, run USB data, etc. It's just the simple flicking on an LED that is weird).&lt;/p&gt;&#xA;" OwnerUserId="626" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-07-08T14:27:46.773" LastActivityDate="2010-07-08T14:27:46.773" Title="Problems with peripheral control of a LED on an AT91SAM7X chip" Tags="&lt;arm7&gt;" AnswerCount="2" />
  <row Id="3228" PostTypeId="2" ParentId="3227" CreationDate="2010-06-30T16:29:28.910" Score="1" ViewCount="" Body="&lt;p&gt;Have a look at this blinking LED sample code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.olimex.com/dev/soft/arm/SAM7/Blinking_LED.zip&quot; rel=&quot;nofollow&quot;&gt;http://www.olimex.com/dev/soft/arm/SAM7/Blinking_LED.zip&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you have the LED wired up?&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-06-30T16:29:28.910" />
  <row Id="3229" PostTypeId="2" ParentId="59" CreationDate="2010-06-30T16:56:09.223" Score="1" ViewCount="" Body="&lt;p&gt;you really, really, don't need a DSP to do even advanced audio filtering on a 44.1kHz 16bit stereo signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An ARM core will be just fine for the filtering and running the LCD/buttons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd just grab a &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;beagleboard&lt;/a&gt;, toss RT linux on it and have at it.  If you get really desperate for performance there is a TI 64x+ DSP on board the SoC as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are very few applications for which a DSP is needed today, especially in the audio world.  If you were dealing with 32 channels of 192khz 24bit audio thats latency critical, yea go for the DSP.  But what your working with is well within the capabilities of modern microcontrollers.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-06-30T17:06:55.780" LastActivityDate="2010-06-30T17:06:55.780" />
  <row Id="3230" PostTypeId="1" AcceptedAnswerId="3232" CreationDate="2010-06-30T17:07:55.883" Score="3" ViewCount="118" Body="&lt;p&gt;I have a design that uses an Altera Cyclone FPGA to implement a Physically Unclonable Function (PUF) and an ARM device to do cryptographic work and I/O with the PUF. The PUF is very large, and takes quite a bit of space (only about 1/4th will fit on the Cyclone)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, would I be best served by getting a large enough FPGA to include both the PUF and the ARM core or a smaller FPGA for the PUF and a second, external ARM chip? Can you provide some suggestions?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I used two chips, they would communicate with SPI. There is not a lot of communication between the two, nor does it need to be fast.&lt;/p&gt;&#xA;" OwnerUserId="876" LastActivityDate="2010-07-01T20:13:41.677" Title="What configuration should I use for a system that includes an ARM and an FPGA?" Tags="&lt;fpga&gt;&lt;arm&gt;&lt;interface&gt;" AnswerCount="4" />
  <row Id="3231" PostTypeId="2" ParentId="3230" CreationDate="2010-06-30T17:27:40.880" Score="3" ViewCount="" Body="&lt;p&gt;depends on the size/complexity of the ARM core and the FPGA you need.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only technical concerns are power usage (the single large FPGA is likely higher) and data integrity on the SPI line.  That is, can your system's security be compromised by someone scoping the data being sent on the SPI line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than that, price is the issue.  Don't forget to include PCB space and required external components for each IC when consider the price differences.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-06-30T17:27:40.880" CommentCount="4" />
  <row Id="3232" PostTypeId="2" ParentId="3230" CreationDate="2010-06-30T17:28:54.607" Score="7" ViewCount="" Body="&lt;p&gt;I can't comment on your specific application (not being a cryptography expert), however placing a processor on board with a FPGA is an exceedingly common thing to do. Mostly the reason is that you now free up FPGA space to do what FPGA is good at, while using the less expensive separate processor to do what it is good at, perhaps even faster than could be done with a soft CPU running in the FPGA. In addition, larger FPGA's can get quite expensive, compared to faster ARM's which can be fairly reasonably priced. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically I think you should use the two chips, but it's hard to make a proclamation for sure without knowing details about your specific area.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-06-30T17:28:54.607" />
  <row Id="3233" PostTypeId="2" ParentId="3226" CreationDate="2010-06-30T18:21:37.057" Score="2" ViewCount="" Body="&lt;p&gt;Here's one for £ 26.00:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.droboticsonline.com/index.php/arduino-bluetooth-module.html&quot; rel=&quot;nofollow&quot;&gt;Arduino Bluetooth Module&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-06-30T18:21:37.057" />
  <row Id="3234" PostTypeId="2" ParentId="3083" CreationDate="2010-06-30T21:26:53.647" Score="0" ViewCount="" Body="&lt;p&gt;Did you turn it to channel 3? or do you have a composite input and need to select the correct video source setting on the TV/Monitor?&lt;/p&gt;&#xA;" LastActivityDate="2010-06-30T21:26:53.647" CommentCount="1" />
  <row Id="3235" PostTypeId="2" ParentId="3230" CreationDate="2010-06-30T21:31:24.580" Score="3" ViewCount="" Body="&lt;p&gt;I think the right answer of two chips vs. big FPGA will boil down to what sort of attacks the device will face. That means you need to know something about your possible attack scenarios and security needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the harm if the attacker does probe that SPI communication? Does he get keys? Plaintext? Intermediate stages of the encryption process? If the attacker can parlay that probe into plaintext, what's the harm? Illegal access to a pay satellite tv channel? Financial data? Military secrets? This is the most important thing to understand. It informs all of your other questions (because of course the more sensitive the data, the more it's worth protecting it). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will the device be somewhere that the attacker can mess with it without detection? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, if it's a security system in a blu-ray player, you have to assume that the attacker is going to open the thing up while it's running at some point. On the other hand, if it's a Military communications system used only by the President of the United States, it might be safe to assume that the attacker isn't going to get any alone time with the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How motivated is the attacker? What sort of resources is the attacker likely to have?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you allowed to seal the thing into a special box that can destroy the board if breached?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need a good profile of what you are up against in order to make this decision.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2010-06-30T21:31:24.580" />
  <row Id="3238" PostTypeId="2" ParentId="3226" CreationDate="2010-07-01T01:14:20.283" Score="2" ViewCount="" Body="&lt;p&gt;I have designed a few boards that integrate an Atmel uC (328 and 644) with BlueGiga WT12A.&#xA;The BlueGiga interfaces to the UART so you send and receive ASCII strings. &#xA;If you are using a 328 based board you will need to multiplex the UART or use&#xA;the NewSoftSerial to emulate a UART on the unused pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did the hardware design and the low-level software so I don't know the&#xA;details of the Bluetooth communication. After I could demo that the uC paired&#xA;with the phone my portion of the project was complete ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Changing the name didn't require firmware changes. I sent a &quot;SET BT NAME&quot; command&#xA;to change the name to show the device was pairing.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:41:12.910" LastActivityDate="2011-05-18T11:41:12.910" />
  <row Id="3239" PostTypeId="1" CreationDate="2010-07-01T02:59:12.853" Score="3" ViewCount="193" Body="&lt;p&gt;Hey guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have spent days searching for code on the net there is heaps of code for controlling servos for pan/tilt using a wii nunchuck and arduino. However I want to make it wireless, using:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*2 arduino duemilanove boards&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*Wii nunchuck&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*2x servos&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*433MHZ transmitters / recievers&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know of any code that can be used? OR Can help me be writting some (willing to pay)? OR knows of anyone who can help?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks guys any help would be great&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alex.&lt;/p&gt;&#xA;" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-07-03T22:49:38.497" LastActivityDate="2010-07-03T22:49:38.497" Title="Trouble writting a code for &quot;wii nunchuck controlling pan tilt servo system&quot;" Tags="&lt;nunchuck&gt;&lt;servo&gt;&lt;arduino&gt;&lt;duemilanove&gt;&lt;wireless&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="3240" PostTypeId="2" ParentId="3212" CreationDate="2010-07-01T04:41:21.433" Score="0" ViewCount="" Body="&lt;p&gt;This is my schematic.. im still having the same problem.. guess ill just use an lm317 instead of the buffer&#xA;&lt;/p&gt;&#xA;" LastActivityDate="2010-07-01T04:41:21.433" />
  <row Id="3241" PostTypeId="2" ParentId="984" CreationDate="2010-07-01T05:28:16.997" Score="1" ViewCount="" Body="&lt;p&gt;On unixy systems, &quot;screen /dev/ttyxxx&quot; is pretty handy. I used to use cu a lot but there's a long standing bug in turning off flow control so it's less useful for embedded systems. Then there's Kermit. In all cases, the system's terminal emulation is put to good use instead of trying to reinvent one just for serial communication.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On windos, I second putty or possibly teraterm. Putty makes a good ssh client, too, so it's handy to have around anyway.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-01T05:28:16.997" />
  <row Id="3242" PostTypeId="2" ParentId="1530" CreationDate="2010-07-01T05:35:37.817" Score="0" ViewCount="" Body="&lt;p&gt;I'd recommend having a hot air tool (I have a cheap gas one) if you need to, e.g., desolder bigger components. You can heat a large component or area without touching it pretty easily. On the other hand, there's always some more effort/risk in avoiding burning any adjacent stuff.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-01T05:35:37.817" />
  <row Id="3244" PostTypeId="1" AcceptedAnswerId="3248" CreationDate="2010-07-01T12:46:54.793" Score="3" ViewCount="625" Body="&lt;p&gt;I generally like to solder sockets to my boards, rather than the chip directly, but am now forced to solder the chips directly. I have several DIP and SMD components that this needs to be done with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am concerned that the heat from soldering them might damage the chips so was wondering how I could heat sink them? Is this even necessary?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It doesn't apply to me right now, but how is this done with other packages?&lt;/p&gt;&#xA;" OwnerUserId="876" LastActivityDate="2010-09-01T06:57:49.607" Title="What is the best way to heat sink a chip when soldering it on?" Tags="&lt;heatsink&gt;&lt;soldering&gt;&lt;dip&gt;&lt;surface-mount&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="3245" PostTypeId="2" ParentId="3244" CreationDate="2010-07-01T12:52:44.850" Score="3" ViewCount="" Body="&lt;p&gt;You can buy a &lt;a href=&quot;http://www.jab-tech.com/Clip-On-Heatsink-for-soldering-sensitive-parts-pr-2992.html&quot; rel=&quot;nofollow&quot;&gt;tool&lt;/a&gt; that is a heatsink designed for temporary use while soldering. They look like clumsy pliers. That will work well for the DIP components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For SMD components, you might try putting something cold with large thermal mass and high thermal conductivity (say a chunk of aluminum foil you put in the freezer for a while). I've held stuff like that in place with a rubber band around the PCB, and it makes some difference.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-01T12:52:44.850" />
  <row Id="3246" PostTypeId="1" AcceptedAnswerId="3247" CreationDate="2010-07-01T13:10:03.980" Score="4" ViewCount="1283" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This might be a simple, silly question, but I am wondering why I can't just connect a DC motor to an arduino board to have it running. One pin to the ground and the other to one of the PWM outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just did the sweep tutorial for a servo motor &lt;a href=&quot;http://arduino.cc/en/Tutorial/Sweep&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Tutorial/Sweep&lt;/a&gt; and it works fine. I know that a servo has more electronics in there with pot providing feedback.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I understand to drive even a small DC motor I would need more circuitry (an H bridge?) or another shield dedicated to driving motors. I can understand this if I was driving some relatively big DC motors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I am trying to understand why a small DC motor with a ground and PWM input would not work. Especially for a brushed a motor like this one &lt;a href=&quot;http://music.columbia.edu/~douglas/classes/motor_mania/DC_simple2.jpg&quot; rel=&quot;nofollow&quot;&gt;http://music.columbia.edu/~douglas/classes/motor_mania/DC_simple2.jpg&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Surely its just a matter of DC current passing through the wire. Is it the inductive charge building up in the coils that can cause reverse current back to the board thats the problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, from a conceptual point, given I have a ground and a voltage (albiet a pulsed one), what do I need to do it to make it drive a DC motor.&lt;/p&gt;&#xA;" OwnerUserId="905" LastActivityDate="2010-07-01T18:28:44.220" Title="DC Motor control with an Arduino" Tags="&lt;arduino&gt;&lt;dc-motor&gt;&lt;motor&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="3247" PostTypeId="2" ParentId="3246" CreationDate="2010-07-01T13:17:45.733" Score="6" ViewCount="" Body="&lt;p&gt;It's because of the amount of current you need to drive the motor, the arduino can't supply much.&lt;/p&gt;&#xA;" OwnerUserId="922" LastActivityDate="2010-07-01T13:17:45.733" CommentCount="5" />
  <row Id="3248" PostTypeId="2" ParentId="3244" CreationDate="2010-07-01T13:21:08.757" Score="4" ViewCount="" Body="&lt;p&gt;I have used these tips to get started with SMD soldering. Until now I have not found it necessary to drain heat as long as you mind where you put the soldering iron tip and don't apply heat any longer than needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.infidigm.net/articles/solder/&quot; rel=&quot;nofollow&quot;&gt;http://www.infidigm.net/articles/solder/&lt;/a&gt; - The second article is better, see comments&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS: This article may help as well, it seems to be quite good:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=36&amp;amp;page=1&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=36&amp;amp;page=1&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="909" LastEditorUserId="909" LastEditorDisplayName="" LastEditDate="2010-09-01T06:57:49.607" LastActivityDate="2010-09-01T06:57:49.607" CommentCount="4" />
  <row Id="3250" PostTypeId="2" ParentId="3246" CreationDate="2010-07-01T15:22:02.333" Score="3" ViewCount="" Body="&lt;p&gt;As was stated earlier the Arduino PWM pin can not supply/sink the amount of current required to run even a small DC motor. The best way to do it would be to use an H-Bridge between the Arduino and the motor. A less expensive alternative would be to use a power MOSFET that is capable of supplying the current required by your motor. Microchip has an &lt;a href=&quot;http://ww1.microchip.com/downloads/en/devicedoc/41233A.pdf&quot; rel=&quot;nofollow&quot;&gt;application note&lt;/a&gt; that describes these methods of motor control.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-01T15:33:45.220" LastActivityDate="2010-07-01T15:33:45.220" />
  <row Id="3251" PostTypeId="2" ParentId="3246" CreationDate="2010-07-01T16:05:10.960" Score="5" ViewCount="" Body="&lt;p&gt;In addition to what everyone else said, you need protection circuitry to ensure that inductive kickback from the motor doesn't destroy the pins on your Arduino, which will happen eventually if it's not protected.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-07-01T16:05:10.960" />
  <row Id="3252" PostTypeId="1" AcceptedAnswerId="3285" CreationDate="2010-07-01T16:24:22.653" Score="4" ViewCount="499" Body="&lt;p&gt;As a follow-up to &lt;a href=&quot;http://chiphacker.com/questions/3244/what-is-the-best-way-to-heat-sink-a-chip-when-soldering-it-on&quot; rel=&quot;nofollow&quot;&gt;this question&lt;/a&gt;, what kind of damage could a soldering iron do to an IC or other component if left on it for too long at too high a temperature?  ESD damage can be subtle, for instance.  Is overheating damage usually obvious/complete destruction?  I've desoldered/resoldered things by just globbing on a lot of solder and heating it all up, probably using more heat than is recommended, but I've never noticed any damage.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-03T16:31:25.940" Title="What kind of damage could a soldering iron do to a component?" Tags="&lt;heatsink&gt;&lt;soldering&gt;&lt;dip&gt;&lt;surface-mount&gt;&lt;heat-protection&gt;" AnswerCount="4" />
  <row Id="3253" PostTypeId="2" ParentId="3252" CreationDate="2010-07-01T16:51:49.210" Score="3" ViewCount="" Body="&lt;p&gt;In my experience it is not always obvious that damage has occurred. It isn't until I plug it in and stuff is acting odd that I know I did something bad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have actually found that passive components seem to take a bigger/quicker hit then ICs do. I have seen it mostly with resistors changing their resistance or capacitors acting as shorts and/or opens.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I were to guess, overheating a component would probably lower the life span of the component. ICs just aren't designed to go through very much thermal fatigue. This probably isn't an issue if you are just using the device for a short duration, but could be very bad if it was a fix for a customer.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-07-01T16:51:49.210" />
  <row Id="3254" PostTypeId="2" ParentId="3239" CreationDate="2010-07-01T17:00:36.900" Score="3" ViewCount="" Body="&lt;p&gt;It seems like you are trying to find code that will do everything for you. In the &quot;real&quot; world, it is very unlikely that someone has done the exact same thing as you are wanting to do unless it is something very simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you will need to do is break your project down into very simple blocks. Once you have it broken down you will find it much easier to find code to do what you want it to do for that block. The key for you will be learning how to make all of the blocks interact with each other. If you are not willing to learn how to get these blocks connected, you should look into one of the sites that davr mentioned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Learning how to connect the blocks will require you to learn how to program and design/interact with hardware, but if you want to do any more projects like this in the future, you will need to learn to do it anyways.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-07-01T17:00:36.900" />
  <row Id="3255" PostTypeId="2" ParentId="3244" CreationDate="2010-07-01T17:12:18.373" Score="3" ViewCount="" Body="&lt;p&gt;Most datasheets will list what the max soldering temperature is for the chip, you should look these up and make sure you don't exceed them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For surface mount chips, a reflow profile is usually also included in the datasheet. These profiles show a time versus temperature graph to use when soldering using ovens. Even if you aren't using an oven, it is still good to look at for an idea of how much temperature for how long should be applied.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-07-01T17:12:18.373" />
  <row Id="3256" PostTypeId="2" ParentId="3246" CreationDate="2010-07-01T18:28:44.220" Score="4" ViewCount="" Body="&lt;p&gt;Do you need by-directional control of your DC motor? If that's the case, I would highly recommend the following circuit (even though you will use up one PWM pin for each direction, you will get more than enough current amplification from your power source that the Arduino cannot provide):&#xA;&lt;img src=&quot;http://imagebin.ca/img/CKdfPB6n.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="854" LastActivityDate="2010-07-01T18:28:44.220" CommentCount="1" />
  <row Id="3257" PostTypeId="2" ParentId="3252" CreationDate="2010-07-01T19:32:47.733" Score="2" ViewCount="" Body="&lt;p&gt;Melt it in the very worst case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More likely, you could introduce small defects if you overheat either the board pads or the components leads. Your chip might seem like it is working, except for a few cases it could act erratically.&lt;/p&gt;&#xA;" OwnerUserId="876" LastActivityDate="2010-07-01T19:32:47.733" />
  <row Id="3258" PostTypeId="2" ParentId="3230" CreationDate="2010-07-01T20:13:41.677" Score="0" ViewCount="" Body="&lt;p&gt;From a practical design standpoint, the separate chips are a good idea.  However, security concerns would either required encrypted communications on the bus, careful measures to make sure no important data goes over the bus, or using a single monolithic chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are other issues, too.  FPGA's are usually programmed from Flash memory (except in some rare cases that use things like anti-fuses).  You also have to worry about the application being eavesdropped on during configuration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even after configuration, many FPGA's and other microcontrollers also have JTAG pins that can be used to read the program back out of the device, or inspect other aspects of the programming!&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-07-01T20:13:41.677" />
  <row Id="3259" PostTypeId="2" ParentId="3239" CreationDate="2010-07-01T20:26:54.620" Score="1" ViewCount="" Body="&lt;p&gt;It sounds like the missing piece is the wireless part. Once you have that, it's &quot;just&quot; a software integration problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have a look at &lt;a href=&quot;http://www.open.com.au/mikem/arduino/VirtualWire.pdf&quot; rel=&quot;nofollow&quot;&gt;VirtualWire&lt;/a&gt; for controlling cheap 433MHz devices from Arduino. Another option is the &lt;a href=&quot;http://news.jeelabs.org/2009/02/10/rfm12b-library-for-arduino/&quot; rel=&quot;nofollow&quot;&gt;RFM12B&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-01T20:26:54.620" />
  <row Id="3260" PostTypeId="1" AcceptedAnswerId="3261" CreationDate="2010-07-01T20:28:25.097" Score="1" ViewCount="147" Body="&lt;p&gt;Anyone have any details on how to make a programmable capacitor?  Is it some fancy op amp trick?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I suppose I should be more clear.  The new iPhone 4 is having severe antenna problems, because the antenna is exposed to the user's touch, and some users are bridging two ends of the antenna while holding the phone, altering the capacitance of the antenna so significantly that calls get dropped with even 4 bars.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Allegedly, the iPhone 4 also uses programmable capacitors, and there is some noise about whether the iPhone OS 4 will be able to tune the caps to compensate for the user's hand grip.  When I heard this, I was not sure exactly how one might create a programmable capacitor...&lt;/p&gt;&#xA;" OwnerUserId="1278" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-17T08:03:36.160" LastActivityDate="2011-05-17T10:20:11.080" Title="iPhone programmable caps" Tags="&lt;capacitor&gt;&lt;programming&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="2" />
  <row Id="3261" PostTypeId="2" ParentId="3260" CreationDate="2010-07-01T20:32:34.890" Score="4" ViewCount="" Body="&lt;p&gt;Here's such a device, with some diagrams &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/2450&quot; rel=&quot;nofollow&quot;&gt;MAX1474&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-01T21:53:38.003" LastActivityDate="2010-07-01T21:53:38.003" CommentCount="2" />
  <row Id="3262" PostTypeId="2" ParentId="3260" CreationDate="2010-07-01T20:49:26.837" Score="3" ViewCount="" Body="&lt;p&gt;You can simulate the response of a variable capacitor with an opamp. See this site:&#xA;&lt;a href=&quot;http://www.falstad.com/circuit/e-capmult.html&quot; rel=&quot;nofollow&quot;&gt;http://www.falstad.com/circuit/e-capmult.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-07-01T20:49:26.837" CommentCount="3" />
  <row Id="3263" PostTypeId="1" CreationDate="2010-07-01T23:20:27.760" Score="2" ViewCount="254" Body="&lt;p&gt;I've been working on some digital designs with I2C command &amp;amp; control and need a PC-based tool to test my interfaces. -- In the past, I've used &lt;a href=&quot;http://mcc-us.com/USB_I2C_Adapters.htm&quot; rel=&quot;nofollow&quot;&gt;iPorts (MCC)&lt;/a&gt; to do these tasks but the price tag of approx $500 each has always seemed steep.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have suggestions on similar (hopefully cheaper / more robust) tools?&lt;/p&gt;&#xA;" OwnerUserId="923" LastEditorUserId="923" LastEditorDisplayName="" LastEditDate="2010-07-01T23:40:12.033" LastActivityDate="2010-09-15T00:50:16.117" CommunityOwnedDate="2010-07-01T23:40:12.033" Title="I2C Adapter Recomendations?" Tags="&lt;i2c&gt;&lt;subjective&gt;" AnswerCount="4" />
  <row Id="3264" PostTypeId="2" ParentId="1299" CreationDate="2010-07-01T23:29:20.560" Score="3" ViewCount="" Body="&lt;p&gt;As many have suggested, I2C and SPI are best used for short distances.  While it may be possible to implement a solution with these interfaces, I would higly recommend that you look for a different, &quot;more standard&quot; solution (e.g. Ethernet, RS485, CAN, etc). -- Especially if you're planning to use cables to reach the 6ft distance between microcontrollers.&lt;/p&gt;&#xA;" OwnerUserId="923" LastActivityDate="2010-07-01T23:29:20.560" />
  <row Id="3265" PostTypeId="2" ParentId="991" CreationDate="2010-07-01T23:37:25.577" Score="3" ViewCount="" Body="&lt;p&gt;I've had pretty good success using &lt;a href=&quot;http://www.iar.com/&quot; rel=&quot;nofollow&quot;&gt;IAR&lt;/a&gt; compiler/debug chains for my ARM development. They offer relatively stable development tools complete with an Embedded C++ environment (which seems somewhat rare). -- Depending on your codebase size, they also offer great hardware/software &quot;KickStart Kits&quot; with code-size limited versions of their tools.  &lt;/p&gt;&#xA;" OwnerUserId="923" LastActivityDate="2010-07-01T23:37:25.577" />
  <row Id="3266" PostTypeId="2" ParentId="3263" CreationDate="2010-07-01T23:44:25.243" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.diolan.com/i2c/u2c12.html&quot; rel=&quot;nofollow&quot;&gt;The Diolan U2C-12 is what I use&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Probably not the cheapest, but i've been very happy with it for I2C/SPI and GPIO work, their ready to go linux library was the real reason I chose this part. &lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-07-01T23:44:25.243" CommunityOwnedDate="2010-07-01T23:44:25.243" />
  <row Id="3267" PostTypeId="2" ParentId="2191" CreationDate="2010-07-01T23:47:44.303" Score="1" ViewCount="" Body="&lt;p&gt;Assuming you are looking for a true &quot;plug computer&quot; I think you are certainly on the right track with the &lt;a href=&quot;http://www.plugcomputer.org/&quot; rel=&quot;nofollow&quot;&gt;Sheevaplug&lt;/a&gt;.  The &lt;a href=&quot;http://plugapps.com&quot; rel=&quot;nofollow&quot;&gt;PlugApps Wiki&lt;/a&gt; has a pretty good &lt;a href=&quot;http://www.plugapps.com/index.php5?title=Portal%3aHardware&quot; rel=&quot;nofollow&quot;&gt;summary&lt;/a&gt; of the various Sheevaplug clones.  The &lt;a href=&quot;http://www.globalscaletechnologies.com/t-guruplugdetails.aspx&quot; rel=&quot;nofollow&quot;&gt;GuruPlug&lt;/a&gt; also looks interesting.&lt;/p&gt;&#xA;" OwnerUserId="923" LastActivityDate="2010-07-01T23:47:44.303" />
  <row Id="3268" PostTypeId="2" ParentId="3263" CreationDate="2010-07-01T23:49:46.113" Score="9" ViewCount="" Body="&lt;p&gt;To me, robust means: throwaway price, comes with schematics and software and I could build or fix it at home.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are two favourites, both around the $20 mark, exposing USB serial and PC scriptable:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://code.google.com/p/the-bus-pirate/&quot; rel=&quot;nofollow&quot;&gt;Bus Pirate&lt;/a&gt; is a universal bus interface that talks to most chips from a PC serial terminal. Lots of serial protocols are supported: I2C, SPI, 1-Wire, JTAG etc. as well as a bit of AVR/PIC programming and EEPROM dumping. It has a low speed &lt;a href=&quot;http://www.sump.org/projects/analyzer/client/&quot; rel=&quot;nofollow&quot;&gt;logic analyser&lt;/a&gt; and sniffers for I2C and SPI. There's an &lt;a href=&quot;http://dangerousprototypes.com/forum/index.php?board=4.0&quot; rel=&quot;nofollow&quot;&gt;active forum with good support&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(It's a PIC24 with a USB serial port and some bus switches for open-drain pullup trickery. Windows only MPLAB needed for firmware development. ds30 serial bootloader pre-installed for &quot;field upgrade&quot;.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.tty1.net/userial/&quot; rel=&quot;nofollow&quot;&gt;USerial&lt;/a&gt; is an I2C, SPI and GPIO bridge, using an Atmel AVR. It'll also run on any &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8857&quot; rel=&quot;nofollow&quot;&gt;AT90USBxxx board&lt;/a&gt;, eg. &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=16&amp;amp;products_id=199&quot; rel=&quot;nofollow&quot;&gt;Teensy&lt;/a&gt;, &lt;a href=&quot;http://dorkbotpdx.org/blog/feurig/benito_my_first_at90usb162_project&quot; rel=&quot;nofollow&quot;&gt;Benito&lt;/a&gt;, &lt;a href=&quot;http://www.makestuff.eu/wordpress/?page_id=569&quot; rel=&quot;nofollow&quot;&gt;Nanduino&lt;/a&gt;.&#xA;Compiles with gcc. Well documented.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-02T12:28:08.007" LastActivityDate="2010-07-02T12:28:08.007" CommunityOwnedDate="2010-07-01T23:49:46.113" CommentCount="2" />
  <row Id="3269" PostTypeId="2" ParentId="1738" CreationDate="2010-07-01T23:53:30.650" Score="2" ViewCount="" Body="&lt;p&gt;I agree that it is certainly cheaper/easier to buy one than to build one.  There are a variety of solutions out there...  Here are a few that I'm aware of:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.gumstix.com/&quot; rel=&quot;nofollow&quot;&gt;Gumstix&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;BeagleBoard&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.chumby.com/&quot; rel=&quot;nofollow&quot;&gt;Chumby&lt;/a&gt; (easily hack-able)&lt;/li&gt;&#xA;&lt;li&gt;Plug Computers (&lt;a href=&quot;http://www.plugcomputer.org/&quot; rel=&quot;nofollow&quot;&gt;SheevaPlug&lt;/a&gt;, &lt;a href=&quot;http://www.globalscaletechnologies.com/t-guruplugdetails.aspx&quot; rel=&quot;nofollow&quot;&gt;GuruPlug&lt;/a&gt;, etc -- Check out &lt;a href=&quot;http://www.plugapps.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.plugapps.com/&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="923" LastActivityDate="2010-07-01T23:53:30.650" />
  <row Id="3270" PostTypeId="2" ParentId="991" CreationDate="2010-07-02T00:06:31.760" Score="9" ViewCount="" Body="&lt;p&gt;I use the CodeSourcery (Lite) cross-compilers for Linux to program the &lt;a href=&quot;http://focus.ti.com/general/docs/gencontent.tsp?contentId=54556&quot; rel=&quot;nofollow&quot;&gt;TI Stellaris Microcontrollers&lt;/a&gt;. They work with any Cortex-M3. They're completely free, with binaries for Windows and Linux.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a short recipe (Debian/Ubuntu) to install:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.codesourcery.com/downloads/public/public/gnu_toolchain/arm-none-eabi/arm-2009q3-68-arm-none-eabi.bin&quot; rel=&quot;nofollow&quot;&gt;Download the toolchain&lt;/a&gt; (any version will do, but I use this one)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Install Java Runtime Environment (for the damned installer)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;sudo apt-get install sun-java6-jre ia32-libs&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Install&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;chmod 755 arm-2009q3-68-arm-none-eabi.bin&#xA;./arm-2009q3-68-arm-none-eabi.bin -i console&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Add cross compiler bin directory to your PATH&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;echo 'export PATH=$PATH:~/CodeSourcery/Sourcery_G++_Lite/bin/' &amp;gt;&amp;gt; ~/.bashrc &#xA;. ~/.bashrc &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;To load code and debug, you'll need &lt;a href=&quot;http://openocd.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;OpenOCD&lt;/a&gt; and either gdb or one of the GUIs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll also need a &lt;a href=&quot;http://www.olimex.com/dev/arm-usb-ocd.html&quot; rel=&quot;nofollow&quot;&gt;JTAG adapter&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-02T19:06:08.860" LastActivityDate="2010-07-02T19:06:08.860" CommentCount="1" />
  <row Id="3272" PostTypeId="2" ParentId="1299" CreationDate="2010-07-02T00:36:02.247" Score="1" ViewCount="" Body="&lt;p&gt;Just an FYI, the interface between the wireless Nintendo Wii remote and its Nunchuck companion uses I2C over a cable that is about 3 feet long.  There are also 3-foot extensions cables that extend the total length to about 6 feet.  Not exactly the same as your setup (only two devices connected together), but it is an example of I2C over a cable in a widely-used consumer product.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-07-02T00:36:02.247" />
  <row Id="3273" PostTypeId="1" AcceptedAnswerId="3274" CreationDate="2010-07-02T04:16:34.027" Score="1" ViewCount="988" Body="&lt;p&gt;Hi, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought a WiFly shield ( &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9367&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9367&lt;/a&gt; ) for my Arduino Mega board and am trying to hook it up. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried the wireless talker tutorial which seem to be very popular &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=158&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=158&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried running the first sketch, but it doesn't work. It just gives me a Bridge Locked up message. I tried changing the pin associations in the code as discussed in this post &lt;a href=&quot;http://forum.sparkfun.com/viewtopic.php?f=13&amp;amp;t=22067&amp;amp;p=104343&quot; rel=&quot;nofollow&quot;&gt;http://forum.sparkfun.com/viewtopic.php?f=13&amp;amp;t=22067&amp;amp;p=104343&lt;/a&gt; &#xA;but again no joy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried the standard WiFly library that sparkfun ship from here ( &lt;a href=&quot;http://sparkfun.com/Code/wifly/WiFly-20100519-023939.zip&quot; rel=&quot;nofollow&quot;&gt;http://sparkfun.com/Code/wifly/WiFly-20100519-023939.zip&lt;/a&gt; )&#xA;I extracted the zip files, put them under the libraries directory of the IDE, fired up the IDE, started the example and tried to run it, again no go. I put my credentials in the credentials.h file, changed the pin associations in the Spi.h file (for CS, MOSI, MISO, SCK) as suggested above to 53,51,50,52 respectively. Again, no joy. The terminal window just sits there showing &quot;WiFly Shield Terminal Routine&quot;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What am I doing wrong? Has anyone used the WiFly module by itself or with the Arduino mega board? Do I need to hook up the Mega's 50 - 12 pins to the WiFly shield somehow? There seems to be a similar discussion here with no resolution &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1270926864&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1270926864&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS: I am running this on Windows 7, 64 bit&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be greatly appreciated.&lt;/p&gt;&#xA;" OwnerUserId="905" LastEditorUserId="905" LastEditorDisplayName="" LastEditDate="2010-07-02T04:38:48.703" LastActivityDate="2010-07-02T06:01:28.333" Title="Arduino Mega and Wifly shield" Tags="&lt;arduino&gt;&lt;wifly&gt;&lt;wifi&gt;&lt;arduino&gt;" AnswerCount="1" />
  <row Id="3274" PostTypeId="2" ParentId="3273" CreationDate="2010-07-02T05:26:09.020" Score="1" ViewCount="" Body="&lt;p&gt;Ok, more information here ( &lt;a href=&quot;http://mcukits.com/2009/04/06/arduino-ethernet-shield-mega-hack/&quot; rel=&quot;nofollow&quot;&gt;http://mcukits.com/2009/04/06/arduino-ethernet-shield-mega-hack/&lt;/a&gt; ). Even though this is for Ethernet, I have to do the same thing with the WiFly module and rewire the pins.&lt;/p&gt;&#xA;" OwnerUserId="905" LastEditorUserId="905" LastEditorDisplayName="" LastEditDate="2010-07-02T06:01:28.333" LastActivityDate="2010-07-02T06:01:28.333" />
  <row Id="3275" PostTypeId="2" ParentId="1807" CreationDate="2010-07-02T06:01:38.617" Score="0" ViewCount="" Body="&lt;p&gt;have you found a soution for that ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would be verry interested in something simillar for automating my home :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;any chanches of releasing the design to the community? maybe to the official arduino hardware page ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;alex&lt;/p&gt;&#xA;" LastActivityDate="2010-07-02T06:01:38.617" CommentCount="1" />
  <row Id="3276" PostTypeId="2" ParentId="1807" CreationDate="2010-07-02T06:20:25.610" Score="0" ViewCount="" Body="&lt;p&gt;Maybe you could just get a bulk deal on these:&#xA;&lt;a href=&quot;http://www.freetronics.com/products/etherten&quot; rel=&quot;nofollow&quot;&gt;http://www.freetronics.com/products/etherten&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-07-02T06:20:25.610" />
  <row Id="3277" PostTypeId="2" ParentId="2191" CreationDate="2010-07-02T09:08:21.730" Score="1" ViewCount="" Body="&lt;p&gt;You could also go for an ATOM based motherboard&lt;/p&gt;&#xA;&#xA;&lt;p&gt;eg.  &lt;a href=&quot;http://www.shopbot.com.au/pp-intel-d945gclf2-price-141888-3155510.html&quot; rel=&quot;nofollow&quot;&gt;http://www.shopbot.com.au/pp-intel-d945gclf2-price-141888-3155510.html&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-07-02T09:08:21.730" />
  <row Id="3278" PostTypeId="2" ParentId="3263" CreationDate="2010-07-02T12:26:23.550" Score="3" ViewCount="" Body="&lt;p&gt;If you want to send I2C commands from the PC to an I2C slave device you will need something that will act as a I2C master. In the past when I've wanted to do this I wrote a simple program that converts USART to I2C. Then use a PC terminal program to send data to the I2C master via RS-232. You should be able to do this using a breadboard, PIC, and RS-232 transceiver.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-07-02T14:46:20.413" LastActivityDate="2010-07-02T14:46:20.413" CommunityOwnedDate="2010-07-02T12:26:23.550" CommentCount="2" />
  <row Id="3279" PostTypeId="1" AcceptedAnswerId="3281" CreationDate="2010-07-02T12:40:29.067" Score="4" ViewCount="528" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am very new to embedded world. I had been till now working only on S/W&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone please explain me the use of the Arduino Bootloader? I want arduino to perform some simple mathematics using some additional components that have to be put in to the chip. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I necessarily need a bootloader?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd be really glad if some one can explain me its use. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="913" LastActivityDate="2010-07-02T16:13:02.037" Title="Arduino Bootloader" Tags="&lt;arduino&gt;&lt;bootloader&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="3280" PostTypeId="2" ParentId="3279" CreationDate="2010-07-02T12:44:52.140" Score="4" ViewCount="" Body="&lt;p&gt;The Arduino needs a bootloader in order to program your sketches over serial/USB. Without it you need an AVR In-System-Programmer (ISP) to program the flash memory in the AVR chip directly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you buy an Arduino, it'll come with the bootloader already burnt into the AVR chip. You only need to worry about it if you're building your own board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This should help:&#xA;&lt;a href=&quot;http://chiphacker.com/questions/2603/i-dont-get-the-arduino-concept&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/2603/i-dont-get-the-arduino-concept&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-02T13:00:54.010" LastActivityDate="2010-07-02T13:00:54.010" CommentCount="0" />
  <row Id="3281" PostTypeId="2" ParentId="3279" CreationDate="2010-07-02T13:46:10.807" Score="7" ViewCount="" Body="&lt;p&gt;The Arduino is basically just an Atmel AVR microcontroller, with just enough support electronics to allow it to operate. The AVR has built-in flash to allow it to keep programs with the power off, but to program an AVR chip directly you need a tool like the STK-500 to do the job. The Arduino overcomes this by also having a small USB interface on the board, and the Arduino boot-loader code already on the chip. This allows the PC side application to transfer your programs to the device, and in essence, have it flash itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, bottom line, if you get an Arduino, the boot-loader is already there, and does its job automatically. You code your program on the PC, press the 'upload' button on the IDE, and within a few moments &lt;em&gt;your&lt;/em&gt; program is running on the Arduino. The boot-loader does its job completely transparently.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;fwiw, I personally have an Arduino 2009, &lt;em&gt;and&lt;/em&gt; an STK-500 and can do on-the-metal programming on AVRs, but have found no need to bypass the Arduino's bootloader.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-02T13:46:10.807" CommentCount="2" />
  <row Id="3282" PostTypeId="2" ParentId="3279" CreationDate="2010-07-02T16:13:02.037" Score="3" ViewCount="" Body="&lt;p&gt;I'll give a slightly more theoretical answer; the other answers are quite good from a practical perspective. A bootloader is code that resides in a special segment of flash memory. Code that resides in that segment is allowed to execute Self-Programming Instructions, making it possible to modify flash memory (i.e. where user code resides) without a conventional programmer (i.e. In-System Programming ISP or High-Voltage Programming HVP) like the STK500 or AVRISP mkII.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In principle, the UART Recieve Data Interrupt Service Routine (ISR) makes a function call into the bootloader code that copies the program image being sent serially into the user program space in flash memory. At startup, whatever program is on the chip starts running, but if appropriately formed serial data is received early on, the AVR goes into a sort of self-programming mode. There is some logic in the UART ISR that only defers to the bootloader code for a short period of time during startup. The details are a bit more complicated than that, but that's the basic idea. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The beauty of this is that you can buy an Arduino, and nothing else, download the free Integrated Development Environment (IDE), and start writing Arduino Sketches (programs), and download them onto the AVR just like that, over USB no less thanks to the fancy little FTDI IC chip that's integrated into the Arduino board.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-07-02T16:13:02.037" />
  <row Id="3283" PostTypeId="1" AcceptedAnswerId="3284" CreationDate="2010-07-03T04:43:20.980" Score="7" ViewCount="225" Body="&lt;p&gt;On one board I have a microcontroller with one power supply and on another I have a Flip Flop with a separate power supply. I want to connect a pin of the microcontroller to the reset pin of the flip flop. Can I just put a wire accross or does it need more than that? I was going to do that but now I'm not sure that would work because it wouldn't be a complete circuit and the two boards may not have quite the same ground levels. The two boards have to have separate power supplies because the board with the DSP is premade and the power comes from the mains. Thanks&lt;/p&gt;&#xA;" OwnerUserId="927" LastActivityDate="2010-10-26T21:03:31.457" Title="Communication between microcontroller and separately powered PCB" Tags="&lt;microcontroller&gt;&lt;communication&gt;&lt;pcb&gt;&lt;groundloops&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="3284" PostTypeId="2" ParentId="3283" CreationDate="2010-07-03T04:45:59.253" Score="11" ViewCount="" Body="&lt;p&gt;A single wire may or may not work - check to see if your boards have a common-enough ground.  You may get lucky and it will be just fine (since both boards will be connected to the mains ground, at least in some way).  At the very least, you can probably run two wires - one to tie the two grounds together and another for the data.   If for some reason you can't have a common ground, you can look into &lt;a href=&quot;http://en.wikipedia.org/wiki/Opto-isolator&quot; rel=&quot;nofollow&quot;&gt;optoisolators&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="928" LastActivityDate="2010-07-03T04:45:59.253" CommentCount="2" />
  <row Id="3285" PostTypeId="2" ParentId="3252" CreationDate="2010-07-03T04:58:14.087" Score="7" ViewCount="" Body="&lt;p&gt;My experience is that there are several categories of things that can happen. I think it's easiest to group them by component type. I learned these all the hard way. Note that several of these involve the use of heat and force at the same time. In general this is not a good idea. Most parts can tolerate far more of either, alone, than they can of both combined.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Low temperature plastic components&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;This includes encapsulated DC/DC converters, connectors, switch bodies, etc. These can and will melt with sometimes terrifying ease. The good news is that most of the time the damage is cosmetic. The bad news is that if you care about how the board looks, well...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also you usually can't tell up front what will melt and what won't, without an 'experiment'. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes it's smarter to pull vulnerable parts off the board and then reinstall them later.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Leaded encapsulated components&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Through hole, encapsulated components with through hole leads (DC/DC converters or transformers). Too much heat combined with pulling and the lead comes neatly out. If you are lucky, the lead will fall out or be pulled out during rework. Otherwise it's a debugging problem.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Insulated wire&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;IDC (ribbon) cable is notorious for this. The slang term is &quot;marshmallowing&quot;. If you've ever caught a marshmallow on fire, you know why. The insulation melts, burns, bubbles, etc. This takes skill to avoid, especially with softer insulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course bumping a wire bundle with the barrel of the iron, after everything is soldered in place, is a great trick too.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Printed Circuit Boards&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;I include these for two reasons. First, many breakout boards are used themselves as components. Second, the main PCB is itself an important component in the design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The big things with circuit boards are burning, lifted traces, or gouged solder mask. Burns happen when the iron is too hot. Unmasked boards seem more vulnerable than solder masked boards. Loosened traces/pads and solder mask damage happen when you apply too much force with the soldering iron (trying to get that stubborn lead loose).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Warping of the PCB is possible but you have to try hard. Thin PCB + excess pressure + dwell time = permanent curve.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Integrated Circuits&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;I have never (yet) killed an IC with a soldering iron. I have damaged and destroyed SMT chips with hot air rework tools though (that's another topic). Most chips have a maximum lead temperature/time rating, so I think it's possible.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Passive SMDs&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;These go bad when you are trying to install them, and they stick to the iron. While you're busy trying to get them loose and not lose them, they can cook. Usually one of the terminals comes loose, and usually that happens when the part's half soldered on the board. You can also cook chip resistors this way until they visibly discolor - IMO, that's a throwaway. Of course the smaller they are, the less mass they have and the easier it is to do this. 0201 resistors for instance, take some getting used too (buy many spares).&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2010-07-03T04:58:14.087" CommentCount="4" />
  <row Id="3286" PostTypeId="1" AcceptedAnswerId="3291" CreationDate="2010-07-03T07:41:56.473" Score="3" ViewCount="436" Body="&lt;p&gt;I'm using a TMS320F2812 and want to drive LEDs of some of the pins. I couldn't figure out what the safe levels of current were which could go in or come out of the IO pins from the datasheet. What is the safe range or how could I find out? What are normal values for these levels? Thanks.&lt;/p&gt;&#xA;" OwnerUserId="927" LastActivityDate="2010-07-03T15:06:52.233" Title="How much current can a microcontroller/DSP pin sink/source?" Tags="&lt;microcontroller&gt;&lt;dsp&gt;&lt;led&gt;&lt;pin&gt;&lt;current&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="3287" PostTypeId="2" ParentId="3286" CreationDate="2010-07-03T08:50:17.450" Score="6" ViewCount="" Body="&lt;p&gt;See page 90 of the data sheet. It's 4 mA for some pins, 8 mA for others. You could drive high-brightness LEDs from them, but you might be better off using drivers.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-03T08:50:17.450" CommentCount="1" />
  <row Id="3288" PostTypeId="1" CreationDate="2010-07-03T12:08:09.323" Score="3" ViewCount="201" Body="&lt;p&gt;Been trying to get this to compile but keep getting the following error:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/../lib/gcc/avr/4.3.2/../../../../avr/include/stdlib.h:111: error: expected unqualified-id before 'int'&#xA;&#xA;/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/../lib/gcc/avr/4.3.2/../../../../avr/include/stdlib.h:111: error: expected `)' before 'int'&#xA;&#xA;/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/../lib/gcc/avr/4.3.2/../../../../avr/include/stdlib.h:111: error: expected `)' before 'int'&#xA;&#xA;&#xA;&#xA;    // Receiver Code&#xA;&#xA;#include &amp;lt;ServoTimer2.h&amp;gt;&#xA;&#xA;ServoTimer2 servosteer;  // create servo object to control a servo &#xA;ServoTimer2 servospeed;  // create servo object to control a servo &#xA;//MEGA pin 23 receive pin - displays characters sent by RF&#xA;&#xA;#include &amp;lt;VirtualWire.h&amp;gt;&#xA;#undef int&#xA;#undef abs&#xA;#undef double&#xA;#undef float&#xA;#undef round&#xA;void setup()&#xA;{&#xA;  servosteer.attach(3);  // attaches the servo on pin 25 to the servo object &#xA;  servospeed.attach(4);  // attaches the servo on pin 27 to the servo object &#xA;  // lcd.init();&#xA;  Serial.begin(9600);   // Debugging only&#xA;  Serial.println(&quot;setup&quot;);&#xA;&#xA;  // Initialise the IO and ISR&#xA;  vw_set_ptt_inverted(true); // Required for DR3100&#xA;  vw_setup(4000);    // Bits per sec&#xA;  vw_set_rx_pin(8);&#xA;  vw_rx_start();       // Start the receiver PLL running&#xA;}&#xA;&#xA;void loop()&#xA;{&#xA;  uint8_t buf[VW_MAX_MESSAGE_LEN];&#xA;  uint8_t buflen = VW_MAX_MESSAGE_LEN;&#xA;  if (vw_get_message(buf, &amp;amp;buflen)) // Non-blocking&#xA;  {&#xA;    //invalid message length must be S/B/F/L/R + number (max 3 digits)&#xA;    if (buflen &amp;lt; 3 || buflen &amp;gt; 5)&#xA;      return;&#xA;    digitalWrite(13, true); // Flash a light to show transmitting&#xA;&#xA;    char val[buflen]; //Same as buf, last char will be used for null terminator&#xA;    memset(val, '\0', sizeof(val));&#xA;&#xA;    //Copy value from string i.e. 213 from R213 into separate string&#xA;    strncpy(val, (char *)buf + 1, buflen - 1);&#xA;&#xA;    //convert string containing value to integer e.g. &quot;213&quot; to 213.&#xA;    int VAL = atoi ( val );&#xA;&#xA;    switch (buf[0]) {&#xA;    case 'X': //Deadmans finger stop all&#xA;      Serial.print(&quot;Deadmans finger&quot;);&#xA;      servospeed.write(1500);&#xA;&#xA;      break;&#xA;    case 'P':&#xA;      Serial.print(&quot;Pitch &quot;);&#xA;      Serial.println(VAL);&#xA;      servospeed.write(544+VAL*10);&#xA;&#xA;      break;&#xA;    case 'R':&#xA;      Serial.print(&quot;Roll &quot;);&#xA;      Serial.println(VAL);&#xA;      servosteer.write(544+VAL*10);&#xA;&#xA;      break;&#xA;    default:&#xA;      break;&#xA;    }&#xA;  }&#xA;  digitalWrite(13, false); // Flash a light to show transmitting&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-03T12:12:06.757" LastActivityDate="2010-07-03T15:21:19.887" Title="can't compile code.." Tags="&lt;arduino&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="3289" PostTypeId="2" ParentId="3288" CreationDate="2010-07-03T12:13:12.510" Score="2" ViewCount="" Body="&lt;p&gt;This whole block looks suspect.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#undef int&#xA;#undef abs&#xA;#undef double&#xA;#undef float&#xA;#undef round&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;What error messages do you get if you remove that?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-03T12:29:44.833" LastActivityDate="2010-07-03T12:29:44.833" CommentCount="3" />
  <row Id="3290" PostTypeId="2" ParentId="3288" CreationDate="2010-07-03T12:17:18.977" Score="0" ViewCount="" Body="&lt;p&gt;even when that is taken out it still does not work&lt;/p&gt;&#xA;" LastActivityDate="2010-07-03T12:17:18.977" CommentCount="5" />
  <row Id="3291" PostTypeId="2" ParentId="3286" CreationDate="2010-07-03T14:34:29.960" Score="7" ViewCount="" Body="&lt;p&gt;If you google TMS320F2812, the 2nd link is to a PDF file tms320f2812.pdf; if you look in this document at table 6.2, &quot;Recommended Operating Conditions&quot;, you can find the numbers you need. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you plan to connect the LED from the pin to ground (through a resistor, of course), so that a '1' output lights the LED, the number you want is Ioh, high-level output source current. Whereas if you plan to connect the LED instead to your +V supply, so '0' lights the LED, check Iol, low-level output sink current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at the numbers, you can see values from 4mA to 8mA, but you should also take note that these are in the 'MAX' column, which means these are values you should not exceed. Now, 4mA is not very much current, typical current to light an LED can be 10 or 20mA, to establish useful brightness. Were it me, I would employ some kind of driver between the '2812 and the LEDs, and try to keep the current in/out of the '2812 I/O pins well under 2mA.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-07-03T15:06:52.233" LastActivityDate="2010-07-03T15:06:52.233" />
  <row Id="3292" PostTypeId="2" ParentId="3288" CreationDate="2010-07-03T15:11:49.347" Score="4" ViewCount="" Body="&lt;p&gt;If you look carefully at the error messages, the compiler is complaining about line 111 in the stdlib.h file.  Since you didn't explicitly #include &amp;lt;stdlib.h&amp;gt;, it seems likely that the compiler is implicitly including it at some point &lt;em&gt;after&lt;/em&gt; all those unusual #undef statements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have to keep the #undefs, you could try putting an explicit #include &amp;lt;stdlib.h&amp;gt; at the very top of the file.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-07-03T15:21:19.887" LastActivityDate="2010-07-03T15:21:19.887" />
  <row Id="3293" PostTypeId="2" ParentId="3252" CreationDate="2010-07-03T16:31:25.940" Score="1" ViewCount="" Body="&lt;p&gt;You might not notice anything immediately wrong, but running a component up to molten solder temperatures is likely to short the device's life span. It only takes a couple of seconds to get serious amounts of heat into a part. (Try it with a disc ceramic capacitor some time; by the count of three, you'll see the surface of the cap go all shiny and wet looking as the coating melts!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for protecting parts, this doesn't help for IC's or very small components, but if you want to protect discrete components that have wire leads, it's very easy to clip a small alligator clip on a lead, between the device and the solder point, to sink heat away from the device. This works well for small capacitors, low-wattage resistors, even TO-92 and TO-220 cased semiconductors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Along the same lines as alligator clips, you can use 'medical forceps' if you have those, or even a small pair of needle-nosed pliers with a rubber band wrapped to keep the jaws shut.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-03T16:31:25.940" />
  <row Id="3294" PostTypeId="1" CreationDate="2010-07-03T22:48:00.027" Score="3" ViewCount="143" Body="&lt;p&gt;When did numerous short-range wireless protocols start showing up? I know Bluetooth was first invented by Ericsson in 1994 from reading up resources on the Internet. Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="854" LastActivityDate="2010-07-06T06:07:18.080" Title="Short Range Wireless Protocol History" Tags="&lt;wireless&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="3295" PostTypeId="2" ParentId="3206" CreationDate="2010-07-04T01:09:41.757" Score="6" ViewCount="" Body="&lt;p&gt;3M makes a good quality breadboard. The trick is to use wire and components that are clean and the correct size. Too large of a wire will damage the contacts. If you are careful and route wires cleanly breadboard designs can be reasonably reliable. Just don't expect to make RF or high speed circuits. The parasitics from the contact strips are too high.  &lt;/p&gt;&#xA;" LastActivityDate="2010-07-04T01:09:41.757" CommentCount="1" />
  <row Id="3296" PostTypeId="2" ParentId="1393" CreationDate="2010-07-04T04:28:44.633" Score="1" ViewCount="" Body="&lt;p&gt;I prefer a knife-style tip:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cooperhandtools.com/brands/CF_Files/model_detail.cfm?upc=037103166463&quot; rel=&quot;nofollow&quot;&gt;http://www.cooperhandtools.com/brands/CF_Files/model_detail.cfm?upc=037103166463&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are designed for PLCCs but work really well for SOIC or TSSOP style components. What you do is to bead up a blob of solder, place the edge of the blade at the angle between the toe of the lead and the pad, then drag the iron down the row of pins. The reason for this technique is that it is faster and gives a better result than pin-at-a-time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The solder follows the heat but leaves each lead with a perfect joint and heel fillet. One thing to note is that if you are really good, you can do a whole row of fine pitch pins with no bridging - the solder just walks off the end and onto the iron. Me, I'm not that good and always end up removing the solder bridge on the last two or three pins of fine-pitch SMT parts. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;These tips also work well for discrete SMT components and even through hole leads. By rotating the blade, you can get contact with a larger surface of a through-hole lead for getting extra heat to ground or power pins. By rotating the other way, you can use the tip of the tip for SMT chip components. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I disagree with the advice to use the micro-conical tips. These have never done anything for me except F-up boards and joints. Either they don't melt the solder, or you turn the temperature up so high that you start burning away solder mask and start seeing the tip dissolve away in the solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, consider the boards you'll be working with. Things that work with a little two-layer board or one of those unpopulated, phony &quot;practice&quot; boards the soldering iron vendors give out fail miserably on 4+ layer, fully built, assemblies. &lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2010-07-04T04:28:44.633" CommentCount="1" />
  <row Id="3297" PostTypeId="2" ParentId="3294" CreationDate="2010-07-04T05:14:29.397" Score="3" ViewCount="" Body="&lt;p&gt;The Infrared Data Association (IrDA) was established in 1993, I guess you could call their standards a type of wireless.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-04T05:14:29.397" CommentCount="3" />
  <row Id="3298" PostTypeId="2" ParentId="3294" CreationDate="2010-07-04T08:03:22.047" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.jacksons.net/working%20papers/Dynamic%20Sharing%20%202002%20version.pdf&quot; rel=&quot;nofollow&quot;&gt;This document&lt;/a&gt; may give you some pointers. It discusses the sharing of radio frequencies, which is needed for this kind of radio communication.&lt;/p&gt;&#xA;" OwnerUserId="339" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2010-07-06T06:07:18.080" LastActivityDate="2010-07-06T06:07:18.080" />
  <row Id="3299" PostTypeId="1" AcceptedAnswerId="3307" CreationDate="2010-07-04T09:19:48.127" Score="15" ViewCount="495" Body="&lt;p&gt;SICP(Structure and interpretation of Computer Programes) is regarded as one of the most essential readings for every computer science student/professional as it helps mould their minds to a the art of writing clean and intelligent programs (or something like that, I am not sure how to put this into words).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is, is there any book like SICP for electrical and electronics engineers? By the advent of arduino and books like &quot;Making things talk&quot; we are moving towards more and more abstractions. I would like to read a book (preferably free like SICP) which gives me understanding of how to &quot;think in electronics&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is not a &quot;What are your favourite book?&quot; question. I am looking for a single concise book which would train my mind to think in a electronic systems. The problem with most of the books is they give you principles, rules of thumb and techniques. But they do not give you enable you to think in terms of electronic systems. SICP is just that type of book. It enables the readers to think in the terms of data structures, algorithms and not in terms of the specific language you are using.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also there was one book I had found online that explained the inner workings of computers. Its preface said not enough people knew how computers actually work so they had written this book. Its pdf file was named bookbpdf.pdf. If anyone knows please post the link.(found it here &lt;a href=&quot;http://www.fastchip.net/howcomputerswork/p1.html&quot; rel=&quot;nofollow&quot;&gt;http://www.fastchip.net/howcomputerswork/p1.html&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-13T15:46:19.580" LastActivityDate="2011-05-13T15:46:19.580" CommunityOwnedDate="2011-05-13T20:44:58.630" Title="SICP for Electrical/Electronics Engineers?" Tags="&lt;electronics&gt;&lt;books&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="8" />
  <row Id="3300" PostTypeId="2" ParentId="3299" CreationDate="2010-07-04T11:20:46.043" Score="9" ViewCount="" Body="&lt;p&gt;I would recommend the &lt;em&gt;The Art of Electronics&lt;/em&gt;. Essential reading and is well regarded&#xA;by EE's at a variety of skill levels. A Physics collection I have found very useful&#xA;in EE works are the &lt;em&gt;Feynman Lectures&lt;/em&gt;. A list of my other book recommendations is&#xA;at &lt;a href=&quot;http://wiblocks.luciani.org/FAQ/faq-books-ee.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/FAQ/faq-books-ee.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. SICP is one of my favorites for CS. TAOCP is probably at the top of the list.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Art of Electronics&#xA;Author: Horowitz and Hill&#xA;Publisher: Cambridge University Press; 2nd edition (July 28, 1989)&#xA;ISBN-10: 0521370957&#xA;ISBN-13: 978-0521370950&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Feynman Lectures on Physics (3 Volume Set)&#xA;Author: Richard Phillips Feynman&#xA;Publisher: Addison Wesley Longman (June 1970)&#xA;ISBN-10: 0201021153&#xA;ISBN-13: 978-0201021158&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T12:46:41.447" LastActivityDate="2011-05-13T12:46:41.447" CommunityOwnedDate="2011-05-13T20:44:58.630" />
  <row Id="3301" PostTypeId="2" ParentId="3283" CreationDate="2010-07-04T16:00:00.847" Score="5" ViewCount="" Body="&lt;p&gt;If the supplies on both the boards are isolated, e.g., batteries or most wall-warts, you just need to bridge the grounds together, which provides the return path for the signal you want to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're at all worried that the grounds might not be isolated, you can temporarily connect them through a 100K resistor and measure the voltage drop across the resistor. If the drop across the resistor is nearly zero, then you should not have a problem connecting the two grounds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason for the resistor is that a DVM has high enough input impedance that just measuring between the grounds might show you some voltage that's more electrostatic than actually electromotive; the resistor dissipates the electrostatic aspect. &lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-04T16:00:00.847" />
  <row Id="3302" PostTypeId="1" CreationDate="2010-07-04T16:19:32.967" Score="3" ViewCount="226" Body="&lt;p&gt;I am using a Freescale 3 axis accelerometer to build a model that flies and would like to log and calculate angles during a flight. My model can both hover and move up to 40kph as well as rotate on any axis 360 degrees. I have done some basic calculations on angles using raw data sent back but the data looks kind of weird with spikes.Right now I am just  using Excel to do the calculations until I get the formulas correct for the software I'm developing. I am using:&#xA;X-data = column B&#xA;Y-data = column C&#xA;Z-data = column D&#xA;pitch = ATAN(B3/SQRT(C3^2+D3^2))&#xA;roll = ATAN(C3/SQRT(B3^2+D3^2))&#xA;theta = ATAN(SQRT(B3^2+C3^2)/D3)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The questions I have are:&#xA;Is there a way to calculate speed from the data?&#xA;Can I filter out the spikes using some sort of software filtering without skewing the data?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;JB&lt;/p&gt;&#xA;" LastActivityDate="2010-07-04T18:04:58.977" Title="angle calculations" Tags="&lt;accelerometer&gt;&lt;speed&gt;&lt;filter&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="3303" PostTypeId="2" ParentId="3299" CreationDate="2010-07-04T16:44:45.987" Score="3" ViewCount="" Body="&lt;p&gt;+1 &lt;em&gt;The Art of Electronics&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also recommend these books that I used as an undergrad:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Fundamentals of Applied Electromagnetics&lt;/em&gt; by Ulaby&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Electromagnetics Explained&lt;/em&gt; by Schmitt&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Microelectronic Circuits&lt;/em&gt; by Sedra &amp;amp; Smith&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Analog Electronics with Op Amps&lt;/em&gt; by Peyton and Walsh&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;RF Circuit Design&lt;/em&gt; by Bowick&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Signals and Systems Made Ridiculously Simple&lt;/em&gt; by Karu&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Discrete-Time Signal Processing&lt;/em&gt; by Oppenheim &amp;amp; Schafer&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Digital Image Processing&lt;/em&gt; by Gonzalez &amp;amp; Woods&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a quick intro to VHDL and working with FPGAs, I liked &lt;em&gt;Rapid Prototyping of Digital Systems&lt;/em&gt; by Hamblen and Furman, and I see there's an updated edition available on Amazon that covers SOPC systems. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't have a recommendation for the topics of Circuits, Digital Integrated Circuits, Control Systems, and Digital Design. I mostly relied on course notes from my professors since I &lt;em&gt;did not like&lt;/em&gt; the books we used, i.e. my anti-recommendations: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Basic Engineering Circuit Analysis&lt;/em&gt; by Irwin and Wu&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Digital Integrated Circuits&lt;/em&gt; by Rabaey&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Modern Control Systems&lt;/em&gt; by Dorf &amp;amp; Bishop&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Fundamentals of Digital Logic&lt;/em&gt; by Brown and Vranesic&lt;/p&gt;&#xA;" OwnerUserId="721" LastActivityDate="2010-07-04T16:44:45.987" CommunityOwnedDate="2011-05-13T20:44:58.630" CommentCount="3" />
  <row Id="3304" PostTypeId="2" ParentId="3302" CreationDate="2010-07-04T18:04:58.977" Score="3" ViewCount="" Body="&lt;p&gt;In general, you can integrate acceleration data to obtain rates, and further integrate rates to get position/attitude information. This is known as dead-reckoning. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The model you described has what's known as 6 degrees of freedom. The six degrees are three translational: the north-south axis, east-west axis, up-down axis, and three angular: roll, pitch, and heading (and/or yaw). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Translational accelerations will show up directly as changes in one or more of the three channels. You can get angular orientation by isolating out the 'bias' acceleration due to gravity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for noisy spikes in the data, the easiest approach is to run a low-pass filter (LPF) of some kind on the data. This can be done in software with a moving-window time average of the last N samples. You have to be aware though, that since your speed and position data is an &lt;em&gt;integration&lt;/em&gt; of the raw data, that any errors also get integrated. In other words, your sensor-based estimate of the vehicle's position, speed, orientation all become less accurate as time goes on, so the better you can remove the noise, the better your navigational solution will be.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-04T18:04:58.977" CommentCount="2" />
  <row Id="3305" PostTypeId="2" ParentId="3299" CreationDate="2010-07-04T18:27:47.507" Score="4" ViewCount="" Body="&lt;p&gt;The Art of Electronics, as has already been suggested. It's one book you must have. The third edition should be out some time, but don't wait for it.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-04T18:27:47.507" CommunityOwnedDate="2011-05-13T20:44:58.630" CommentCount="1" />
  <row Id="3306" PostTypeId="2" ParentId="3283" CreationDate="2010-07-05T02:24:28.350" Score="1" ViewCount="" Body="&lt;p&gt;If on separate boards, use a differential signaling approach such as &lt;a href=&quot;http://en.wikipedia.org/wiki/Low-voltage_differential_signaling&quot; rel=&quot;nofollow&quot;&gt;LVDS&lt;/a&gt;, with a driver on one board, and a receiver on the other. (This assumes the two boards have ground voltages that are reasonably close together -- if not then you need an isolation barrier.) Reset signals are an example of something that is sensitive to glitches -- a momentary glitch on a reset line has an effect on the future state of the chip going to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get away with less-careful approaches if the signals in question are stateless inputs.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-07-05T02:24:28.350" />
  <row Id="3307" PostTypeId="2" ParentId="3299" CreationDate="2010-07-05T08:10:08.893" Score="7" ViewCount="" Body="&lt;p&gt;Your not going to find the book you seek, at least not as you have described it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Thinking in Electronics&quot; is an entirely different thing than &quot;Thinking in programming&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Programming is really a rather small, simple field.  Yes there are some complex issues but as you've found, the basics can be described in a single book.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thinking in electronics is entirely different.  To really &quot;Think in electronics&quot; you'd need strong knowledge in at least the following:  (feel free to add more i've missed in comments)&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Linear Algebra&lt;/li&gt;&#xA;&lt;li&gt;Vector Calculus&lt;/li&gt;&#xA;&lt;li&gt;Differential Equations (at least be able to find solutions to wave equations)&lt;/li&gt;&#xA;&lt;li&gt;Chemistry&lt;/li&gt;&#xA;&lt;li&gt;Quantum Mechanics (if you have any interest in semi-conductors)&lt;/li&gt;&#xA;&lt;li&gt;Electro-magnetic Physics&lt;/li&gt;&#xA;&lt;li&gt;Signal Analysis (study of mathematical transforms, Fourier, Laplace, etc.)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;With this background you should be able to characterize and understand the flow of electricity in circuits with resistors, capacitors, diodes, transistors, etc.  Be able to begin to think in electronics.  You can look at the circuit for an op amp and understand how it work and why without mapping out what configuration each transistor is in.  You can analyse how a circuit will react to various input signals.  You can look at a circuit and determine its general properties without anything but in head calculation. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally this learning takes an electrical engineering undergrad between 2-3 years of school and many books.  It was my college's stated goal to get students to have a feeling of how electricity flows in a circuit with non-linear devices (to think in electronics) in this time frame.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If all you want to do is play with arduino's and think up neat ways to use them and connect them to different devices, you don't really need to understand much in terms of electronics at all.  If fact, as far as i can tell, the entire point of that project is to allow people to play with microcontrollers, sensors, buttons, etc without having to think too much in the world of electronics.  Knowing that 2 IC's have 3.3V SPI ports and therefore they can talk is as much a &quot;thinking in computers&quot; as it is a &quot;thinking in electronics&quot;.  If you need to transmit that bus 35ft and don't know how to make it work, then you need to think in electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Art of Electronics is a good intro to electronics if you want to know what its all about at a higher level.  I don't think it teaches you to think in electronics.  It gives you a bunch of formulas to memorize and use with little discussion of why.  I'd equate it to taking high school physics without first taking calculus.  You get to memorize a ton of stuff you wouldn't have to if you understood the origins of where its coming from, which also means you will likely lack the ability to adapt to new situations for which you don't have a handy formula.  Of course this is perfectly fine if your getting into electronics as a hobby, thats why its a hobby and not a career.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-07-05T08:10:08.893" CommunityOwnedDate="2011-05-13T20:44:58.630" CommentCount="2" />
  <row Id="3308" PostTypeId="2" ParentId="3206" CreationDate="2010-07-05T13:56:14.217" Score="3" ViewCount="" Body="&lt;p&gt;Have a look at this &lt;a href=&quot;http://blog.makezine.com/archive/2010/07/if_breadboards_break_thy_brain_buil.html&quot; rel=&quot;nofollow&quot;&gt;Headerboard&lt;/a&gt; design, it's a good looking alternative to the humble breadboard, it looks like the connections would be nice and firm too.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-07-05T13:56:14.217" CommunityOwnedDate="2010-07-05T13:56:14.217" />
  <row Id="3309" PostTypeId="2" ParentId="3299" CreationDate="2010-07-05T18:14:37.563" Score="6" ViewCount="" Body="&lt;p&gt;Even though Mark already gave you the best answer, take a look at this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.allaboutcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.allaboutcircuits.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's much better than most printed books I've seen, even if it's a work in progress. It actually explain things instead of just giving you recipes and formulas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can read it online or download each volume as a pdf.&lt;/p&gt;&#xA;" OwnerUserId="933" LastActivityDate="2010-07-05T18:14:37.563" CommunityOwnedDate="2011-05-13T20:44:58.630" CommentCount="4" />
  <row Id="3310" PostTypeId="1" CreationDate="2010-07-06T04:42:26.370" Score="6" ViewCount="349" Body="&lt;p&gt;I have some routing like this;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://mmccoo.com/clips/2010_07_05_21_002.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like this pad/wire connection to print solid black with a small hole in the middle. After I etch with toner transfer, I'll need to see where to drill.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can use drill-aid.ulp, but the resulting white donut's hole is obscured by the wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Surely this is not a unique problem. What's the trick?&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2010-07-06T16:36:55.500" Title="How can I force drill holes in Eagle" Tags="&lt;eagle&gt;" AnswerCount="2" />
  <row Id="3311" PostTypeId="2" ParentId="3310" CreationDate="2010-07-06T08:21:54.033" Score="3" ViewCount="" Body="&lt;p&gt;When exporting to postscript with the CAM tools, I select &quot;fill pads&quot;. I then have to drill the hole by eye, but I get decent results.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When making two-sided boards, I fill the pads on the bottom and not on the top, then drill from the top.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-06T08:21:54.033" />
  <row Id="3312" PostTypeId="1" AcceptedAnswerId="8232" CreationDate="2010-07-06T12:27:26.950" Score="3" ViewCount="665" Body="&lt;p&gt;How do I connect/use a 3 Wire Digital Scale Strain Gauge Weight Sensor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I took it from an old weight meant for people. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The wires are red, black and white.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this, &lt;a href=&quot;http://www.nerdkits.com/videos/weighscale/&quot; rel=&quot;nofollow&quot;&gt;http://www.nerdkits.com/videos/weighscale/&lt;/a&gt; ,but they use a 4 wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="323" LastActivityDate="2010-12-24T01:45:45.507" Title="3 Wire Digital Scale Strain Gauge Weight Sensor" Tags="&lt;measurement&gt;&lt;wire&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="3313" PostTypeId="2" ParentId="3312" CreationDate="2010-07-06T12:56:25.330" Score="3" ViewCount="" Body="&lt;p&gt;I'd bet that the wires are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Red: power&lt;/li&gt;&#xA;&lt;li&gt;Black: ground&lt;/li&gt;&#xA;&lt;li&gt;White: signal&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;But it's hard to guess what the &quot;power&quot; voltage is. If you knew the power voltage, you could connect that voltage across the red and black wires, and check to see what signal comes out of the white wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't figure out a way to determine the proper voltage, you could use an adjustable power supply. Start with a low voltage (3 V is probably safe), and then slowly raise the voltage while looking for a signal with an oscilloscope. There's a decent chance you'll go too high and burn the sensor, but it may be your only option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any identifying marks on the sensor? Did it come from a battery powered scale?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-06T12:56:25.330" CommentCount="6" />
  <row Id="3314" PostTypeId="1" AcceptedAnswerId="3315" CreationDate="2010-07-06T13:16:52.193" Score="4" ViewCount="475" Body="&lt;p&gt;I have been using 10 mil trace with 10 mil spacing.  The PCB vendors quote that they like traces down to 7 mil.  But then I ran across a PDF showing how to fan out a QFP to get all the signals accessible.  They use millimeters because the QFPs are packaged with 0.4mm or 0.6mm pitches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also make an argument that using a 0.05mm grid approximates mils, but mm allows you to route buses in between the vias and pads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I be using mil or mm when I am routing a PCB?&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-12-16T02:12:39.583" Title="Do you layout in mil or mm?" Tags="&lt;pcb&gt;&lt;layout&gt;&lt;routing&gt;" AnswerCount="7" CommentCount="5" />
  <row Id="3315" PostTypeId="2" ParentId="3314" CreationDate="2010-07-06T13:53:02.317" Score="2" ViewCount="" Body="&lt;p&gt;While the metric system is arguably saner, those that have been doing PCBs for much longer than myself have are pretty adamant about using mils. I think it has something to do with the machines used by manufacturers. That being said, if you have a board house in mind, and they spec their capabilities out mm, then yea you'll probably get a neater routing by picking a grid that is &quot;natural&quot; to your components. Typically though, you're going to have a mix of parts that are mm and mil based, so you'll likely have a &quot;grid mismatch&quot; regardless. I pretty much always use a 25mil grid and things usually turn out &quot;good enough.&quot;&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-07-06T13:53:02.317" CommentCount="1" />
  <row Id="3316" PostTypeId="2" ParentId="3314" CreationDate="2010-07-06T14:00:32.763" Score="5" ViewCount="" Body="&lt;p&gt;Tom at PCB Matrix advocates using metric exclusively, as the majority of high-tech parts are metric. I actually use both, in the same design sometimes, if I have a mixture of metric and Imperial parts. It doesn't really matter all that much with the software I use, as it can make connections off-grid, but I get neater results.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-06T14:00:32.763" />
  <row Id="3317" PostTypeId="2" ParentId="3314" CreationDate="2010-07-06T14:04:06.210" Score="3" ViewCount="" Body="&lt;p&gt;Typically I place parts on a 25mil grid and route on a 5mil grid. For low density boards&#xA;I can usually route on a 10-25mil grid. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I route I have the traces snap to the mid-point of the pad so that traces end&#xA;in the center of the pad for all components.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-16T02:12:39.583" LastActivityDate="2010-12-16T02:12:39.583" />
  <row Id="3318" PostTypeId="2" ParentId="3314" CreationDate="2010-07-06T14:15:45.190" Score="5" ViewCount="" Body="&lt;p&gt;I think the system used by the majority of your active parts is the system to choose. Older parts were all 0.1 inch pitch, but at least some newer parts have ball or pin pitches specified in mm. I'd default to metric because it's the world standard, but if you're manufacturing in the US, you might default to inches.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-06T14:15:45.190" />
  <row Id="3319" PostTypeId="2" ParentId="3310" CreationDate="2010-07-06T16:36:55.500" Score="2" ViewCount="" Body="&lt;p&gt;I have taken the file into photoshop and doctored all of the pads to have guide holes before printing.  Not elegant, but worked well.&lt;/p&gt;&#xA;" OwnerUserId="451" LastActivityDate="2010-07-06T16:36:55.500" />
  <row Id="3320" PostTypeId="1" CreationDate="2010-07-06T16:58:01.473" Score="6" ViewCount="627" Body="&lt;p&gt;I have tried several times, unsuccessfully, to manufacture a PCB at home. A lot of the other questions are about improving PCB performance and such, but I can rarely, if ever, even get the ink to adhere to the copper board. I even bought the special &quot;blue&quot; paper that I saw recommended several places.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are some common gotchas that one might face when making a PCB? Specifically, I am having problems getting the ink to adhere to my board when I iron it. I have heard people briefly mention baking in the oven as an alternative.&lt;/p&gt;&#xA;" OwnerUserId="876" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:36:19.143" LastActivityDate="2010-08-19T00:18:50.260" Title="How can I successfully make a PCB at home?" Tags="&lt;pcb&gt;&lt;manufacturing&gt;" AnswerCount="7" CommentCount="6" FavoriteCount="1" />
  <row Id="3321" PostTypeId="2" ParentId="3320" CreationDate="2010-07-06T17:17:54.763" Score="2" ViewCount="" Body="&lt;p&gt;I use the HP Professional Laser Paper 120 soft gloss ($20-30 for 200 sheets) with a Samsung laser printer and it works great. I iron the board for a couple of minutes and then I soak it in water and remove the paper with my fingers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I forgot to mention that there's no toner left on the paper with this particular kind of sheets (which is the first I've tried for this job, I must have been lucky). The only problem is that, sometimes, if I press too much when ironing, some traces can come out a bit thicker.&lt;/p&gt;&#xA;" OwnerUserId="933" LastEditorUserId="933" LastEditorDisplayName="" LastEditDate="2010-07-07T11:44:58.340" LastActivityDate="2010-07-07T11:44:58.340" />
  <row Id="3322" PostTypeId="2" ParentId="3320" CreationDate="2010-07-06T17:49:54.983" Score="2" ViewCount="" Body="&lt;p&gt;I had the same struggles you did a couple months ago when I first started doing this and for my process two things mattered the most:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;I never got photo paper to work. I tried a couple. I use magazine paper. Any magazine printed on nice glossy paper works. The main thing is that it needs to be thick enough not to jam in the printer.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I use a laminator. I tried the oven technique as well as the iron and neither gave me good results. The GBC laminators sold on ebay are popular in the yahoo homebrew PCB group. I also saw one cheap at the local costco.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="550" LastActivityDate="2010-07-06T17:49:54.983" />
  <row Id="3323" PostTypeId="2" ParentId="3320" CreationDate="2010-07-06T17:54:50.283" Score="1" ViewCount="" Body="&lt;p&gt;I've never had any real sucess with toner transfer. I tried various kinds of paper including magazine paper ands several types of glossy paper and never managed to produce a usable board. They all either had missing traces, or were slightly smeared in places leading to an unusable board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The special press and peel paper worked a lot better but even that it generally took me several attempts to make a usable board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I bought a cheap UV lightbox and used the photoresist method which just seems to work every time with no fuss. &lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2010-07-06T17:54:50.283" />
  <row Id="3324" PostTypeId="2" ParentId="3320" CreationDate="2010-07-06T19:11:03.397" Score="3" ViewCount="" Body="&lt;p&gt;I use a home-made UV exposure unit with transparencies printed on an inkjet printer and pre-coated boards, and get excellent results - 8 mil tracks if necessary. I can make a PCB in 30 minutes or so, not including drilling the holes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.leonheller.com/Photos/UV%20unit.jpg&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;'s a photo of my UV exposure unit, it's made from MDF and strips of wood. A sheet of glass sits on the wood strips at the top, of course. I left space for a third tube. I use an exposure time of 11 minutes.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-07-07T11:15:39.150" LastActivityDate="2010-07-07T11:15:39.150" CommentCount="5" />
  <row Id="3325" PostTypeId="2" ParentId="3312" CreationDate="2010-07-06T21:31:21.630" Score="1" ViewCount="" Body="&lt;p&gt;If the scale had a battery in it, the voltage for that type of battery is probably what you want to put across the red(+) and black(-) leads. A digital scale that I opened up had one of those 2032 'coin' cells in it, which is 3V. The signal will come back on the white wire, referenced to ground (i.e., the black lead), but the protocol may be tricky to sort out.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-06T21:31:21.630" />
  <row Id="3326" PostTypeId="2" ParentId="3320" CreationDate="2010-07-06T23:48:56.707" Score="4" ViewCount="" Body="&lt;p&gt;Get Pulsar's PCB-in-a-box kit: &lt;a href=&quot;http://www.pulsarprofx.com/PCBfx/main_site/pages/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.pulsarprofx.com/PCBfx/main_site/pages/index.html&lt;/a&gt; With a decent laser printer, you'll be in good shape.  It's not perfect, but if you follow his suggestions, you'll be well on your way.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-07-06T23:48:56.707" CommentCount="1" />
  <row Id="3327" PostTypeId="2" ParentId="966" CreationDate="2010-07-07T05:41:56.543" Score="3" ViewCount="" Body="&lt;p&gt;I'll say it: some microcontrollers of your choice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;AVR is extra simple to wire up and breadboard friendly, easy to program (free as in freedom tools and programming hardware you can make in a jiffy), has pretty nice GPIO system and many models have ADC's and PWM generators and decent documentation. They're also more easily available compared to many others. Some attiny2313 (no AD) and attiny26 (fast PWM, AD) are my choices. But don't count out another arch if you know it works!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if you'll want to do something differently eventually, an MCU can easily generate sequences, measure/capture things, switch things, do PWM or frequency generation, logic operations, interface to many devices (see also: Bus Pirate) and/or enable computer control, work as clocks or timers etc. And they are pretty reasonably priced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if you don't want to use microcontrollers at all in a project, they'll be useful for prototyping and instrumentation.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-07T05:41:56.543" CommunityOwnedDate="2010-07-07T05:41:56.543" />
  <row Id="3328" PostTypeId="2" ParentId="3320" CreationDate="2010-07-07T10:35:08.493" Score="4" ViewCount="" Body="&lt;p&gt;I've had a few people asking about the toner transfer method, so we made a &lt;a href=&quot;http://www.youtube.com/watch?v=frsDN7usyCs&quot; rel=&quot;nofollow&quot;&gt;video&lt;/a&gt; to explain. Just ignore the dying part of the process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do have to admit it took a few tries to get the process right, but I can print one in a flash now. Getting the right paper is important, I tried loads of types before finding one I was happy with, also applying enough heat and pressure in order to transfer the toner can be real hard to judge - as long as you don't over-heat the copper clad (It will tarnish initially, then it will start to unclad itself!) you can always just scrub off the toner and try the transfer again.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Paper wise, I use - &lt;a href=&quot;http://www.staples.co.uk/paper-supplies/laser-paper/photo-colour-laser-glossy-paper-a4-180gsm-50-sheets&quot; rel=&quot;nofollow&quot;&gt;Staples Photo Colour Laser, Glossy Paper A4, 180gsm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;common gotchas - &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Spending loads of money on special &quot;Transfer paper&quot; that doesn't seem to perform any better than a good colour laser gloss paper. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Photo &quot;paper&quot; made from plastic that will just melt while ironing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not ironing the edges of the design enough (The edges of the design are the hardest to transfer)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not soaking the paper off for long enough (Soak it, scrub it lightly to permeate the back of the paper, soak it again.....then peel it) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;:)&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-07-07T10:35:08.493" CommentCount="2" />
  <row Id="3329" PostTypeId="1" AcceptedAnswerId="3330" CreationDate="2010-07-07T20:18:16.323" Score="4" ViewCount="470" Body="&lt;p&gt;How to automatically retrieve, given a Digi-Key part number, information such as Manufacturer, Manufacturer Part Number, Description, etc.  Perhaps parsing the GET http respose to:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=DK_PART_NUMBER&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=DK_PART_NUMBER&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(thanks to angryee for the correct parameters) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where DK_PART_NUMBER is the Digikey part number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody know if they have a web service or simply a better interface for this?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;After asking this question I decided to go ahead and write something that did some basic fetching from Digikey:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;dk_pn = '587-1962-1-ND'&#xA;&#xA;from urllib import urlopen&#xA;from sgmllib import SGMLParser&#xA;&#xA;headers = ['Digi-Key Part Number',&#xA;           'Manufacturer',&#xA;           'Manufacturer Part Number',&#xA;           'Description',&#xA;           'Lead Free Status / RoHS Status',&#xA;           'Operating Temperature',&#xA;           'Standard Package',&#xA;           'Price Break',&#xA;           'Unit Price',&#xA;           'Extended Price']&#xA;&#xA;class DK_Parser(SGMLParser):&#xA;    def reset(self):&#xA;&#xA;        SGMLParser.reset(self)&#xA;&#xA;        self.last_td = ''&#xA;        self.inside_th = False&#xA;        self.inside_td = False&#xA;        self.grab_data = False&#xA;        self.part_info = {}&#xA;        self.hdr_index = 0&#xA;        self.row_hdrs = []&#xA;&#xA;    def start_tr(self, attrs): # row&#xA;        self.first_header_in_row = True&#xA;&#xA;    def start_th(self, attrs): # header cell&#xA;        if self.first_header_in_row:&#xA;            self.first_header_in_row = False&#xA;            self.row_hdrs = []&#xA;            self.hdr_index = 0&#xA;        self.inside_th = True&#xA;&#xA;    def end_th(self):&#xA;        self.inside_th = False&#xA;&#xA;    def start_td(self, attrs): # data cell&#xA;        self.inside_td = True&#xA;&#xA;    def end_td(self): &#xA;        self.inside_td = False&#xA;        self.hdr_index = self.hdr_index+1&#xA;&#xA;    def handle_data(self,text):&#xA;        text = text.strip()&#xA;        if self.inside_th:&#xA;            if text in headers:&#xA;                self.row_hdrs.append(text)&#xA;                self.last_td = ''&#xA;                self.grab_data = True&#xA;            else:&#xA;                self.grab_data = False&#xA;        elif self.inside_td and self.grab_data:&#xA;            if self.hdr_index:&#xA;                self.last_td = ''&#xA;            if self.hdr_index &amp;lt; len(self.row_hdrs):&#xA;                self.last_td = self.last_td + text&#xA;                self.part_info[self.row_hdrs[self.hdr_index]] = self.last_td&#xA;&#xA;dk_url = 'http://search.digikey.com/scripts/DkSearch/dksus.dll'&#xA;dk_params = '?Detail&amp;amp;name='&#xA;&#xA;sock = urlopen(dk_url + dk_params + dk_pn)&#xA;&#xA;parser = DK_Parser()&#xA;parser.feed(sock.read())&#xA;sock.close()&#xA;parser.close()&#xA;&#xA;for k,v in parser.part_info.items():&#xA;    print k,&quot;:&quot;,v&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Only the first data line of the the [price break/unit price/extended price] table is captured.&lt;/p&gt;&#xA;" OwnerUserId="688" LastEditorUserId="688" LastEditorDisplayName="" LastEditDate="2010-07-08T02:41:19.080" LastActivityDate="2011-03-07T15:12:53.567" Title="How to retrieve part information from Digi-Key automatically" Tags="&lt;parts&gt;&lt;bom&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="3330" PostTypeId="2" ParentId="3329" CreationDate="2010-07-07T20:40:03.270" Score="3" ViewCount="" Body="&lt;p&gt;You'd want to use the detail option instead of the keyword.  Like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=458-1003-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=458-1003-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That returns an HTML page which is text which can be parsed.  It's all in table format so you can create a list of terms you're interested in and parse out the values.  I can see a parts list script that takes in a list of parts and the values you want to retrieve (ie, Voltage, Max Current, or however Digikey lists it) and then make some Python to read the part number, grab the page, parse out the info and stick it in a CSV, database or HTML file.  I've been thinking of something similar and it doesn't seem too hard.  Well, hard enough to stop me from whipping it out right now anyway :)&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-07-07T20:40:03.270" />
  <row Id="3331" PostTypeId="1" CreationDate="2010-07-07T20:51:05.717" Score="4" ViewCount="784" Body="&lt;p&gt;What are pros and cons using Wiznet W5100 or Microchip EncX24J600?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a bit complicated to explain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is about the performance of Microchip TCP stack vs Wiznet TCP/IP core on the chip. Also about the costs ($$).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example:&#xA;With Wiznet, the microcontroller will have less processing, thereby freeing the microcontroller to do other tasks. But I think that this will depend of which layer you are working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With Microchip TCP stack maybe I have limitations on the peripherals that I can control. Maybe I'll have to use a second microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I hope I've explained better now for you to help me in the best choice.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-22T08:15:34.457" LastActivityDate="2011-02-22T08:15:34.457" Title="Wiznet W5100 vs. Microchip ENCx24J600" Tags="&lt;ethernet&gt;&lt;microchip&gt;&lt;tcp-ip&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="3332" PostTypeId="2" ParentId="2467" CreationDate="2010-07-07T21:03:19.923" Score="3" ViewCount="" Body="&lt;p&gt;With &lt;a href=&quot;http://www.oemstrade.com/&quot; rel=&quot;nofollow&quot;&gt;OEMs Trade&lt;/a&gt;, &lt;a href=&quot;http://www.findchips.com&quot; rel=&quot;nofollow&quot;&gt;Findchips&lt;/a&gt; or &lt;a href=&quot;http://www.octopart.com&quot; rel=&quot;nofollow&quot;&gt;Octopart&lt;/a&gt; you can you can do a search on various distributors and compare prices.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-03T13:21:49.877" LastActivityDate="2010-11-03T13:21:49.877" CommunityOwnedDate="2010-07-07T21:03:19.923" CommentCount="1" />
  <row Id="3333" PostTypeId="2" ParentId="3314" CreationDate="2010-07-07T21:08:04.727" Score="1" ViewCount="" Body="&lt;p&gt;Brazil uses metric system but my layouts are in mils because because it is the most widely used.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-07T21:08:04.727" />
  <row Id="3334" PostTypeId="2" ParentId="3331" CreationDate="2010-07-07T22:35:19.497" Score="3" ViewCount="" Body="&lt;p&gt;The W5100 has a TCP/IP core on the chip. With the Microchip ENC devices the user has to implement a TCP/IP stack themselves, on the MCU that is interfaced to it. This is quite easy with a suitable PIC, as free TCP/IP stacks are available from Microchip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The W5100 has the advantage that it can be used with virtually any MCU, but a fairly powerful device is needed to run a TCP/IP stack if an ENC chip is used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, another option is to use an MCU with a built-in MAC and PHY. Microchip makes some nice ones, and there are ARM variants with them as well.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-07-07T23:26:37.757" LastActivityDate="2010-07-07T23:26:37.757" CommentCount="1" />
  <row Id="3335" PostTypeId="2" ParentId="2467" CreationDate="2010-07-07T22:53:27.593" Score="6" ViewCount="" Body="&lt;p&gt;Believe it or not, but Futurlec have improved their shipping time greatly, using normal postage packages arrive in around ten days... not bad. See www.futurlec.com &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-07-07T22:53:27.593" CommunityOwnedDate="2010-07-07T22:53:27.593" />
  <row Id="3336" PostTypeId="2" ParentId="3329" CreationDate="2010-07-08T00:11:16.940" Score="4" ViewCount="" Body="&lt;p&gt;Perhaps you could do it through &lt;a href=&quot;http://octopart.com/api/overview&quot; rel=&quot;nofollow&quot;&gt;Octopart's API&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-08T00:11:16.940" CommentCount="3" />
  <row Id="3337" PostTypeId="2" ParentId="2467" CreationDate="2010-07-08T00:57:18.443" Score="3" ViewCount="" Body="&lt;p&gt;A little off topic, but &lt;a href=&quot;http://www.elexp.com/&quot; rel=&quot;nofollow&quot;&gt;Electronix Express&lt;/a&gt;, &lt;a href=&quot;http://www.stanleysupplyservices.com/&quot; rel=&quot;nofollow&quot;&gt;Stanley Supply&lt;/a&gt;, and &lt;a href=&quot;http://www.mpja.com/&quot; rel=&quot;nofollow&quot;&gt;Marlin P Jones&lt;/a&gt; (as mentioned by @UnwiredBen) are all great suppliers of tools and test/measurement equipment.&lt;br&gt;&#xA;Of course, Electronix Express also supplies components, although it's more education oriented.  (Lots of kits and generic components - on the cheap!)&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-08T00:57:18.443" CommunityOwnedDate="2010-07-08T00:57:18.443" />
  <row Id="3338" PostTypeId="2" ParentId="2535" CreationDate="2010-07-08T01:31:59.110" Score="1" ViewCount="" Body="&lt;p&gt;Jeff,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I picked up a can of Control/Contact Cleaner and Lubricant at Radio Shack tonight. It was a 4.5 oz. can for around $11.00, a bit pricey, but it should do the trick.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best of luck,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Paul&lt;/p&gt;&#xA;" LastActivityDate="2010-07-08T01:31:59.110" />
  <row Id="3339" PostTypeId="2" ParentId="2535" CreationDate="2010-07-08T02:42:52.353" Score="2" ViewCount="" Body="&lt;p&gt;You can just clean it with WD40 (http://www.wd40.com/) and then, find a hole on the body (usually it has one!), so put some silicone grease inside (http://en.wikipedia.org/wiki/Silicone_grease), it´s a good lubricating and it´s clean.&lt;/p&gt;&#xA;" OwnerUserId="940" LastActivityDate="2010-07-08T02:42:52.353" />
  <row Id="3340" PostTypeId="2" ParentId="3227" CreationDate="2010-07-08T03:16:05.257" Score="0" ViewCount="" Body="&lt;p&gt;If its a hardware thing, there are a couple of different ways to make an LED light using a PIO pin..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you happen to have the LED wired anode to +V, cathode toward the PIO pin (w/a suitable limiting resistor of course), it will be a LOW pin state that would light the LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have the anode of the LED toward the PIO pin, and the cathode toward ground, then a HIGH should light the LED, as you've coded.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A quick googling for ARM91SAM7 turned up an Atmel datasheet for the whole series, Atmel document is filenamed doc6175.pdf .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A rule of thumb for choosing the limiting resistor is to pick a value that will give anywhere from 5 to 20mA, when dropping a voltage about 1.25V less that your supply rail. However, looking at the datasheet, the spec says this chip can 'draw' only 8mA (section 6.6), which is just about enough to get light out of an LED, so choose your resistor accordingly, or use a buffering device if you need more LED current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Figure 27-3 in that pdf shows all the PIO control register settings that set up the pin. Having spent about 15 minutes looking at that and your code, it looks like you've covered the necessaries. The only register you didn't alter was PIO_MDSR, but if I read the diagram right, that comes out of reset in a state compatible with what you are trying to do.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-08T03:16:05.257" />
  <row Id="3341" PostTypeId="1" CreationDate="2010-07-08T08:45:47.660" Score="1" ViewCount="419" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using &lt;a href=&quot;http://www.rovingnetworks.com/rn-41.php&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; in my Arduino board to transfer data via Bluetooth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wanted to know, how is it poosible to receive data sent by this BT on the PC using C#. What sort of a communication would it be? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because Serial data is transmitted by this BT, how am I going to receive this data in a C# application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please help. I'm a newbie &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="913" LastActivityDate="2010-09-13T12:35:23.700" Title="Receive Data From Arduino Bluetooth" Tags="&lt;arduino&gt;&lt;bluetooth&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="3342" PostTypeId="2" ParentId="3341" CreationDate="2010-07-08T09:39:54.200" Score="3" ViewCount="" Body="&lt;p&gt;Here's a tutorial on C# serial comms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.codeproject.com/KB/cs/serialcommunication.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.codeproject.com/KB/cs/serialcommunication.aspx&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-08T09:39:54.200" CommentCount="1" />
  <row Id="3343" PostTypeId="1" AcceptedAnswerId="3361" CreationDate="2010-07-08T13:10:53.647" Score="20" ViewCount="1430" Body="&lt;p&gt;I'd like some tips for those who want to become a good embedded software developer or want to improve in this area.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What should I need learn about hardware, software?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which books are most recommended? Blogs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, how could I go from a beginner hobbyist to an excellent professional?&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T02:42:52.067" LastActivityDate="2011-06-02T14:12:48.413" CommunityOwnedDate="2010-07-08T23:17:42.900" Title="How to become an embedded software developer?" Tags="&lt;embedded&gt;" AnswerCount="8" CommentCount="0" FavoriteCount="19" />
  <row Id="3344" PostTypeId="2" ParentId="3343" CreationDate="2010-07-08T13:23:51.223" Score="16" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;Remember, &lt;a href=&quot;http://en.wikipedia.org/wiki/No_Silver_Bullet&quot; rel=&quot;nofollow&quot;&gt;&quot;There is no silver bullet&quot;&lt;/a&gt;, don't fall into the trap of believing that there is one tool, methodology, language or system that can solve all problems&lt;/li&gt;&#xA;&lt;li&gt;Become an expert in C&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Learn to get by without malloc() and POSIX&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Don't get hung up on one architecture, it's easy to become a PIC or AVR or ARM fanboy by accident&lt;/li&gt;&#xA;&lt;li&gt;Build stuff, debug it, make it work. Practice makes perfect&lt;/li&gt;&#xA;&lt;li&gt;Learn at least one source control system (SVN/git/etc) and use it&lt;/li&gt;&#xA;&lt;li&gt;Always be prepared to test your assumptions. The bug is usually in the thing you are assuming works&lt;/li&gt;&#xA;&lt;li&gt;Don't become too reliant on debuggers, they're different on every system and of varying reliability&lt;/li&gt;&#xA;&lt;li&gt;Think frugally. When problem solving, think about code footprint, RAM footprint and hardware cost&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For books, I'd recommend digging through history. Most of today's embedded software techniques come from the bleeding edge of yesteryear.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like anything, practice daily.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-08T23:18:09.163" LastActivityDate="2010-07-08T23:18:09.163" CommunityOwnedDate="2010-07-08T23:17:42.900" CommentCount="3" />
  <row Id="3345" PostTypeId="1" CreationDate="2010-07-08T13:35:51.750" Score="3" ViewCount="1953" Body="&lt;p&gt;I'd like to buy a Beagleboard, but I'd like to know if there are best alternatives, and what they are.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-03-21T21:50:02.297" ClosedDate="2011-03-22T12:04:11.790" Title="Beagleboard alternatives?" Tags="&lt;beagleboard&gt;&lt;alternatives&gt;&lt;arm&gt;&lt;embedded&gt;" AnswerCount="8" CommentCount="1" FavoriteCount="4" />
  <row Id="3346" PostTypeId="2" ParentId="3345" CreationDate="2010-07-08T13:37:24.470" Score="9" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/2191/options-for-a-small-linux-hw-platform&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/2191/options-for-a-small-linux-hw-platform&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-08T13:37:24.470" />
  <row Id="3347" PostTypeId="2" ParentId="3341" CreationDate="2010-07-08T13:44:05.243" Score="0" ViewCount="" Body="&lt;p&gt;To add onto Joby's answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many bluetooth solutions I have used allow you to have tunneled serial. This means that you will just see a com port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Advanced warning. I have installed drivers for this before and they resulted in about 15 COM ports existing on my computer. They just hang out and annoy me when I am not using bluetooth and am using a different serial port, like an FTDI chip.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-07-08T13:44:05.243" />
  <row Id="3348" PostTypeId="1" AcceptedAnswerId="3354" CreationDate="2010-07-08T13:53:00.077" Score="6" ViewCount="825" Body="&lt;p&gt;There are dedicated &quot;MOSFET driver&quot; IC's available (ICL7667, Max622/626, TD340, IXD*404).&#xA;Some also control IGBTs. What is the practical purpose of these? Is it all about maximizing the switching speed (driving gate capacitance) or are there other motives?&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2011-04-15T12:17:49.807" CommunityOwnedDate="2010-07-08T13:53:00.077" Title="What is the purpose of &quot;MOSFET driver&quot; IC's" Tags="&lt;mosfet&gt;&lt;fet&gt;&lt;driver&gt;&lt;ic&gt;&lt;switch&gt;" AnswerCount="4" />
  <row Id="3349" PostTypeId="2" ParentId="1594" CreationDate="2010-07-08T13:56:25.787" Score="4" ViewCount="" Body="&lt;p&gt;You can use &lt;a href=&quot;http://qucs.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;Qucs&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some tutorials here: &lt;a href=&quot;http://qucs.sourceforge.net/docs.html&quot; rel=&quot;nofollow&quot;&gt;http://qucs.sourceforge.net/docs.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For logics circuits, you can use this great online simulator called &lt;a href=&quot;http://joshblog.net/projects/logic-gate-simulator/Logicly.html&quot; rel=&quot;nofollow&quot;&gt;Logicly&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-08T13:56:25.787" CommentCount="1" />
  <row Id="3350" PostTypeId="2" ParentId="3345" CreationDate="2010-07-08T13:57:18.570" Score="2" ViewCount="" Body="&lt;p&gt;It's not the same, but as a way to get a working OMAP platform, you might look at the Nokia Internet Tablets.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-08T13:57:18.570" CommentCount="2" />
  <row Id="3351" PostTypeId="2" ParentId="3314" CreationDate="2010-07-08T14:02:31.430" Score="1" ViewCount="" Body="&lt;p&gt;I always use the sane international standard unit for distance if distance is involved, although they are functionally equivalent in this case. There are cases where you have to stick to mils because of broken tool support but you can quickly learn to see what 100 (2.54), 50 (1.27), 10 (.25) etc mean and then it all works the same way. The only real reason to use an obscure unit that doesn't mesh with science without a crazy conversion factor is because you have to.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-08T14:02:31.430" />
  <row Id="3352" PostTypeId="1" AcceptedAnswerId="3647" CreationDate="2010-07-08T14:11:26.030" Score="4" ViewCount="791" Body="&lt;p&gt;What are the scenarios where Triacs can not replace a relay or vice-versa?&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-26T16:56:24.540" LastActivityDate="2010-11-26T16:56:24.540" Title="Triac versus Relay" Tags="&lt;electronics&gt;&lt;components&gt;&lt;relay&gt;&lt;triac&gt;" AnswerCount="3" />
  <row Id="3353" PostTypeId="2" ParentId="3348" CreationDate="2010-07-08T14:15:27.240" Score="4" ViewCount="" Body="&lt;p&gt;Yes, it's about maximizing the switching speed by dumping lots of current into the gate, so that the power MOSFET spends the least amount of time possible in the transition state, and therefore wastes less energy and doesn't get as hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It says as much in the datasheets of the parts you listed :)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The ICL7667 is a dual monolithic&#xA;  high-speed driver designed to convert&#xA;  TTL level signals into &lt;strong&gt;high current&#xA;  outputs&lt;/strong&gt; ... Its high speed and current&#xA;  output enable it to drive large&#xA;  capacitive loads with high slew rates&#xA;  and low propagation delays ... The&#xA;  ICL7667’s high current outputs&#xA;  &lt;strong&gt;minimize power losses in the power&#xA;  MOSFETs&lt;/strong&gt; by rapidly charging and&#xA;  discharging the gate capacitance.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-08T14:15:27.240" CommunityOwnedDate="2010-07-08T14:15:27.240" />
  <row Id="3354" PostTypeId="2" ParentId="3348" CreationDate="2010-07-08T14:26:33.077" Score="8" ViewCount="" Body="&lt;p&gt;A MOSFET driver IC (like the ICL7667 you mentioned) translates TTL Or CMOS logical signals, to a higher voltage and higher current, with the goal of rapidly and completely switching the gate of a MOSFET.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An output pin of a microcontroller is usually adequate to drive a small-signal logic level MOSFET, like a 2N7000. However, two issues occur when driving larger MOSFETs: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Higher gate capacitance - Digital&#xA;signals are meant to drive small&#xA;loads (on the order of 10-100pF). &#xA;This is much less than the many&#xA;MOSFETs, which can be in the&#xA;thousands of pF.&lt;/li&gt;&#xA;&lt;li&gt;Higher gate voltage - A 3.3V or 5V&#xA;signal is often not enough.  Usually &#xA;8-12V is required to fully turn on &#xA;the MOSFET.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Finally, many MOSFET drivers are designed explicitly for the purpose of controlling a motor with an H-bridge.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-08T14:26:33.077" CommunityOwnedDate="2010-07-08T14:26:33.077" />
  <row Id="3355" PostTypeId="2" ParentId="3352" CreationDate="2010-07-08T16:17:10.643" Score="2" ViewCount="" Body="&lt;p&gt;If I remember correctly a triac is no good on DC, only AC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But a relay can handle both.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-07-08T16:17:10.643" />
  <row Id="3357" PostTypeId="2" ParentId="83" CreationDate="2010-07-08T17:18:37.143" Score="2" ViewCount="" Body="&lt;p&gt;There is a great article about IR with Arduino on the PragPub Issue 13, July 2010 here: &lt;a href=&quot;http://www.pragprog.com/magazines&quot; rel=&quot;nofollow&quot;&gt;http://www.pragprog.com/magazines&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-08T17:18:37.143" />
  <row Id="3358" PostTypeId="1" CreationDate="2010-07-08T19:48:44.950" Score="4" ViewCount="493" Body="&lt;p&gt;Hi guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wonder if anyone can help me&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am modifying an ROV and thinking of using Arduino Mega&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am new to electronics and robotics and wonder if the Arduino Mega can control 6 DC motors independently as well acquiring data from a few sensors over a tether of about 150 m. I know that some kind of multiplex is needed but I don't understand fully the theory&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks a lot . Appreciate the help&lt;/p&gt;&#xA;" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-07-08T20:10:45.610" LastActivityDate="2010-07-11T21:29:39.340" Title="Can Arduino handle 6 motors independently" Tags="&lt;dc&gt;&lt;motor&gt;&lt;arduino&gt;&lt;arduino&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="3359" PostTypeId="2" ParentId="3358" CreationDate="2010-07-08T20:20:42.930" Score="5" ViewCount="" Body="&lt;p&gt;It's quite possible with the hardware.  You've got a total of 54 accessible pins, of which 14 are PWM outputs for your motors, and 16 are analog-to-digital converter pins (if your sensors output a DC voltage), so you shouldn't have to worry about a hardware multiplexer.  Additionally, many sensors use communication busses which minimize the number of additional pins needed for each device, like SPI or I2C.  I don't predict that you'll have trouble running out of IO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I predict that you'll have more trouble with 'multiplexing' your processor, not its inputs.    When you're trying to switch between 6 motors and a few' sensors, you can get yourself pretty busy trying to keep it all running.   I'm not familiar enough with the Arduino and its sketches to know if it's capable of doing this out of the box, and it also depends on how much processing you're doing (GPS?  Floating point?  Integrating position from an accelerometer?)  but I'll say that your code likely needs to be a whole lot better than a naive polling loop.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, what do you mean by &quot;tether&quot;? If it's just a source of power for the ROV, that's fairly simple, but more thought is required if you've got a 150m communication bus.  I don't think the Arduino has a CAN bus or anything designed to do 150m communication.  You can't just run a USB cable out to the Arduino at those distances, but you knew that...&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-08T20:20:42.930" CommentCount="1" />
  <row Id="3360" PostTypeId="2" ParentId="3343" CreationDate="2010-07-08T22:42:49.217" Score="3" ViewCount="" Body="&lt;p&gt;'Embedded' is a bit of a loaded term.. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In some respects, any system dedicated to running a single application could be called an embedded system, as long as there is some hardware to be controlled. You can arguably call a 400MHz PPC604 with 2GB of RAM running a java application on top of linux an embedded system, if it happens to be controlling a process through local I/O modules. On the other hand, an arduino just running some kind of minimal network application wouldn't be much of an embedded system. But probably 'embedded' makes most people think of flash based controllers with only a few hundred bytes of RAM, no operating system to speak of, and a plethora of on-chip peripherals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, probably the two biggest hurdles non-embedded programmers usually face learning embedded systems are I/O registers and interrupts. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Interrupts may actually be the easier of the two concepts for non-embedded programmers to deal with, since the main issues with these, concurrency and event driven programming, are often encountered in mainstream applications. What makes interrupts a pain is realizing the extreme sensitivity of a system to the quality of its interrupt handling, and the intricacies of dealing with hardware to clear the interrupt condition and set up for the next one. With a GUI, a deadlock kills just the application. With an interrupt handler, a deadlock causes your entire system to lock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I/O devices seem to be the area that cause the most difficulty. For the uninitiated, it can be quite a surprise to discover that reading this register &lt;em&gt;here&lt;/em&gt; has an effect on that register &lt;em&gt;there&lt;/em&gt;. Writing 1's to clear bits. Status bits that clear themselves when you read a data register, etc. There are so many possibilities with I/O hardware that there is no general rule for dealing with it, except to learn how to find and interpret device data sheets. Writing a device driver for a serial port will teach you much about low level I/O programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's really no substitute for learning these things than to roll up one's sleeves, and program some straight C and/or assembly language on the bare metal. Even the aforementioned java based embedded system eventually needs a device driver for the I/O, and this means ultimately dealing with some C. Experience is the best teacher. Pick a microcontroller, be it MSP430, TMS320, AVR, ARM, PIC, 68HC11, whatever, find an eval kit, and build some systems.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-08T22:54:58.167" LastActivityDate="2010-07-08T22:54:58.167" CommunityOwnedDate="2010-07-08T23:17:42.900" />
  <row Id="3361" PostTypeId="2" ParentId="3343" CreationDate="2010-07-08T23:28:29.633" Score="29" ViewCount="" Body="&lt;p&gt;All the answers have been good so far, but I'll throw in my two cents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a repeat of some tips with a twist and some extra:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Learn C: The fundamental language of the hardware that is still portable (too some degree).  Don't just learn it, but become an expert of all it's features like volatile and why it is important for writing device drivers.&lt;/li&gt;&#xA;&lt;li&gt;Start out with a good development kit like Arduino, but as said before learn other architectures once you got a good feel for it.  Luckily there are some Arduino compatible boards built with other processors, that way you can rewrite the same design on a different uC not mess up your whole design while getting a feel for something new.&lt;/li&gt;&#xA;&lt;li&gt;In the learning stage, feel free to re-invent the wheel on device drivers or other pieces of code.  Don't just plop someone else's driver code down in there.  There's value in re-inventing the wheel when you're learning.&lt;/li&gt;&#xA;&lt;li&gt;Challenge yourself to re-write your code more efficiently in terms of speed and memory usage.&lt;/li&gt;&#xA;&lt;li&gt;Becoming familiar with different styles of embedded systems software architectures.  Start with basic interrupt driven/background loop processing, then move up to background schedulers, then real-time operating systems.&lt;/li&gt;&#xA;&lt;li&gt;Get good source control! I prefer &lt;a href=&quot;http://mercurial.selenic.com/&quot; rel=&quot;nofollow&quot;&gt;Mercurial&lt;/a&gt; myself.  &lt;/li&gt;&#xA;&lt;li&gt;Even sign up for some free source control hosting sites like &lt;a href=&quot;http://sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;Sourceforge.net&lt;/a&gt; or &lt;a href=&quot;http://bitbucket.org/&quot; rel=&quot;nofollow&quot;&gt;Bitbucket.org&lt;/a&gt; to host your project even if you're the only one working on it.  They'll back your code up, so you don't have to worry about that occasional hard drive crash destroying everything!  Using a distributed VCS comes in handy, because you can check in changes to your hard drive then upload to the host site when ready.&lt;/li&gt;&#xA;&lt;li&gt;Learn your tools well for whatever chip you're working on!  Knowing how the compiler creates assembly is essential. You need to get a feel for how efficient the code is, because you may need to rewrite in assembly. Knowing how to use the linker file and interpreting the memory map output is also essential! How else are you going to know if that routine you just wrote is the culprit of taking up too much ROM/Flash!&lt;/li&gt;&#xA;&lt;li&gt;Learn new techniques and experiment with them in your designs!&lt;/li&gt;&#xA;&lt;li&gt;Assume nothing when debugging. Verify it!&lt;/li&gt;&#xA;&lt;li&gt;Learn how to program defensively to catch errors and verify assumptions (like using assert)&lt;/li&gt;&#xA;&lt;li&gt;Build a debugging information into your code where you can such as outputting memory consumption or profiling code with timers or using spare pins on the uC to toggle and measure interrupt latency on a O-scope.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Here are some books:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://pragprog.com/titles/tpp/the-pragmatic-programmer&quot; rel=&quot;nofollow&quot;&gt;The Pragmatic Programmer&lt;/a&gt; by Andrew Hunt and David Thomas - more or less required reading for any practical software development&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/Practical-Arduino-Projects-Hardware-Technology/dp/1430224770&quot; rel=&quot;nofollow&quot;&gt;Practical Arduino&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/Programming-Embedded-Systems-Development-Tools/dp/0596009836/ref=sr_1_1?ie=UTF8&amp;amp;s=books&amp;amp;qid=1278630869&amp;amp;sr=1-1&quot; rel=&quot;nofollow&quot;&gt;Programming Embedded Systems&lt;/a&gt; by Michael Barr &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/Embedded-Systems-Building-Blocks-Second/dp/0879306041/ref=sr_1_3?ie=UTF8&amp;amp;s=books&amp;amp;qid=1278630936&amp;amp;sr=1-3&quot; rel=&quot;nofollow&quot;&gt;Embedded Systems Building Blocks&lt;/a&gt; by Jean Labrosse&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/MicroC-OS-II-Kernel-CD-ROM/dp/1578201039/ref=sr_1_1?ie=UTF8&amp;amp;s=books&amp;amp;qid=1278631008&amp;amp;sr=1-1&quot; rel=&quot;nofollow&quot;&gt;MicroC OS II Real Time Kernel&lt;/a&gt; by Jean Labrosse, great intro into RTOS's in general in there along with his OS.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/Embedded-Software-Primer-David-Simon/dp/020161569X/ref=sr_1_1?ie=UTF8&amp;amp;s=books&amp;amp;qid=1278681571&amp;amp;sr=8-1&quot; rel=&quot;nofollow&quot;&gt;Embedded Software Primer&lt;/a&gt; by David Simon - good intro to embedded software&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Here are some websites:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://embeddedgurus.com/&quot; rel=&quot;nofollow&quot;&gt;Embedded Gurus&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ganssle.com/&quot; rel=&quot;nofollow&quot;&gt;Ganssle Group&lt;/a&gt; Jack Ganssle has some wonderful historical stories to tell. Read the articles.  He gets a little preachy about some things though.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://embedded.com&quot; rel=&quot;nofollow&quot;&gt;Embedded.com&lt;/a&gt; Good info for latest techniques and tips from Ganssle, Barr, and other industry experts.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="625" LastEditorUserId="875" LastEditorDisplayName="" LastEditDate="2010-07-09T13:55:53.260" LastActivityDate="2010-07-09T13:55:53.260" CommunityOwnedDate="2010-07-08T23:28:29.633" CommentCount="2" />
  <row Id="3362" PostTypeId="1" AcceptedAnswerId="3387" CreationDate="2010-07-09T00:30:31.560" Score="1" ViewCount="202" Body="&lt;p&gt;I'm having a problem working with the TI/Stellaris EK-LM3S6965 demo board and associated software, specifically the OLED display driver.  My problem is not that it doesn't work, it's that it &lt;em&gt;mostly&lt;/em&gt; works.  Except for this one section:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;//&#xA;// Clear out the buffer used for sending bytes to the display.&#xA;//&#xA;*(unsigned long *)&amp;amp;g_pucBuffer[0] = 0;  //Line 438&#xA;*(unsigned long *)&amp;amp;g_pucBuffer[4] = 0;  //Line 439&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;which causes gcc to complain:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;rit128x96x4.c:438: warning:&#xA;  dereferencing type-punned pointer will&#xA;  break strict-aliasing rules.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The problem occurs because g_pucBuffer is declared as a character array: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;//*****************************************************************************&#xA;//&#xA;// Buffer for storing sequences of command and data for the display.&#xA;//&#xA;//*****************************************************************************&#xA;static unsigned char g_pucBuffer[8];&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;but we're accessing it as a long (32-bit, 4 characters) and so clearing the array in 2 lines of code instead of 8.  The uC is a 32-bit processor, so it should do this in 2 cycles after setup. It actually uses 4 instructions, instead of the possible 1 store-multiple instruction in 2 cycles, but at this point I'm more than happy with the compiler's performance (It's a fairly new architecture, and the compiler's only a few months old). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, when I write each byte sequentially to 0, &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;g_pucBuffer[0] = 0;&#xA;g_pucBuffer[1] = 0;&#xA;g_pucBuffer[2] = 0;&#xA;g_pucBuffer[3] = 0;&#xA;g_pucBuffer[4] = 0;&#xA;g_pucBuffer[5] = 0;&#xA;g_pucBuffer[6] = 0;&#xA;g_pucBuffer[7] = 0;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;it does each write as a single instruction.  I know, it's 4 cycles, but I want to do this right, and I think I have a clever and safe piece of code.  It's more a personal issue now. I've got full optimization turned on, but it can't figure out that I really just want this 64 bits to be 0 as simply as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, what the warning wants me to do is access the variables as characters, because I'm crossing byte boundaries (Writing g_pucBuffer[0, 1, 2, and 3] in a single step).  I know that they're dword aligned, I know that the code works in the original, but I want the warning to go away.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I either cause gcc to ignore this specific cast/aliasing issue, or do it properly?&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-08T00:46:41.737" LastActivityDate="2011-01-08T00:46:41.737" Title="Help fix or ignore aliasing warning in gcc" Tags="&lt;compiler&gt;&lt;arm7&gt;" AnswerCount="5" />
  <row Id="3363" PostTypeId="2" ParentId="3362" CreationDate="2010-07-09T00:45:04.450" Score="1" ViewCount="" Body="&lt;p&gt;Quick answer: remove -Werror from your Makefile. Only with this option enabled will the warning be treated as an error.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-09T00:45:04.450" />
  <row Id="3364" PostTypeId="2" ParentId="3362" CreationDate="2010-07-09T00:47:29.827" Score="3" ViewCount="" Body="&lt;p&gt;An intermediate cast to (void *), then cast to (long *) can get rid of the warning. I verified this earlier today (at least with gcc 3.4.5), that &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;*(long*)(void*)&amp;amp;buffer[0] = 0;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;disabuses the compiler of the notion that the sky will fall if you cast &amp;amp;buffer[0] to (long *). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would contend that this is better than using a -fno-strict-aliasing option, since -fno-strict-aliasing will have global effect, whereas the intermediate cast can be used on a case by case basis, and it's explicitly obvious in your actual source where you have dealt with the problem.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-07-09T21:00:18.627" LastActivityDate="2010-07-09T21:00:18.627" CommentCount="1" />
  <row Id="3365" PostTypeId="2" ParentId="3362" CreationDate="2010-07-09T00:54:29.670" Score="2" ViewCount="" Body="&lt;p&gt;Wouldn't -fno-strict-aliasing do the job?&lt;/p&gt;&#xA;" OwnerUserId="933" LastActivityDate="2010-07-09T00:54:29.670" CommentCount="3" />
  <row Id="3366" PostTypeId="1" AcceptedAnswerId="3404" CreationDate="2010-07-09T03:20:38.597" Score="11" ViewCount="575" Body="&lt;p&gt;I'm a Software Engineer, and I'd like to learn some Electrical Engineering concepts, mostly for robotics applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to know resources (web pages, books) about learning Electrical Engineering for engineers from other specialties, and tips for getting into EE.&lt;/p&gt;&#xA;" OwnerUserId="878" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T22:34:29.947" LastActivityDate="2011-02-09T16:25:28.973" Title="Learning Electrical Engineering" Tags="&lt;electrical-engineering&gt;" AnswerCount="9" FavoriteCount="12" />
  <row Id="3367" PostTypeId="2" ParentId="2704" CreationDate="2010-07-09T07:16:09.853" Score="2" ViewCount="" Body="&lt;p&gt;The imx233 freescale processor costing around 10$ and is available in 128LQFP package&lt;/p&gt;&#xA;" LastActivityDate="2010-07-09T07:16:09.853" />
  <row Id="3368" PostTypeId="2" ParentId="3352" CreationDate="2010-07-09T07:23:43.247" Score="2" ViewCount="" Body="&lt;p&gt;A triac, being a kind of thyristor, will turn off (only) at zero current (zero cross). Its drive requirements are also different.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess the most obvious scenario is where you want to turn something, say a motor, on and off at will. A triac by itself can't cut the power like a relay can so you'll need another pass element that you can turn off and thus turn off the triac.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A triac will probably also be destroyed if you take it outside its limits, so there might be some high voltage or current scenario where you can't find a big enough triac, but can find a relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another might be a very delicate signal that can't keep a triac on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the clearest difference is that a relay is generally completely isolated between drive and switching sides, a triac will require a bit of current between the two circuits, so it won't be appropriate if you need that particular spot to be isolated. You can possibly isolate the gate drive side, though (and often do, when switching 120/230 VAC).&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-09T07:23:43.247" />
  <row Id="3369" PostTypeId="2" ParentId="188" CreationDate="2010-07-09T09:38:27.677" Score="1" ViewCount="" Body="&lt;p&gt;Sorry if it's a bit late for you, but I've just written a &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/07/09/review-maxim-max7219-led-display-driver-ic/&quot; rel=&quot;nofollow&quot;&gt;post about using the MAX7219&lt;/a&gt; with LED matrices and 7-segment LED Displays.&lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-10-07T15:09:41.153" LastActivityDate="2010-10-07T15:09:41.153" />
  <row Id="3370" PostTypeId="2" ParentId="3366" CreationDate="2010-07-09T11:18:24.543" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Linear-Circuit-Analysis-Approaches-Engineering/dp/0195136667&quot; rel=&quot;nofollow&quot;&gt;Linear Circuit Analysis&lt;/a&gt; by DeCarlo is what we used in my classes at school and it worked out pretty well. If you're just learning on the side, look into picking up the answer guide. There is an ebook version of that for around $10.&lt;/p&gt;&#xA;" OwnerUserId="876" LastActivityDate="2010-07-09T11:18:24.543" />
  <row Id="3371" PostTypeId="2" ParentId="3366" CreationDate="2010-07-09T11:27:20.977" Score="10" ViewCount="" Body="&lt;p&gt;For EE concepts:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Lessons in electric circuits is an excellent free resource: &#xA;&lt;a href=&quot;http://www.openbookproject.net/electricCircuits/&quot; rel=&quot;nofollow&quot;&gt;http://www.openbookproject.net/electricCircuits/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;I would also recommend &quot;The Art of Electronics&quot; and the various cookbooks by&#xA;Don Lancaster.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;All of my recommendations are at &lt;a href=&quot;http://wiblocks.luciani.org/FAQ/faq-books-ee.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/FAQ/faq-books-ee.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T22:35:49.367" LastActivityDate="2011-02-08T22:35:49.367" />
  <row Id="3372" PostTypeId="2" ParentId="3366" CreationDate="2010-07-09T12:48:07.427" Score="8" ViewCount="" Body="&lt;p&gt;All the answers have been good so far, but I'll throw in my two cents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find very good free materials here:&#xA;&lt;a href=&quot;http://ocw.mit.edu/courses/audio-video-courses/#electrical-engineering-and-computer-science&quot; rel=&quot;nofollow&quot;&gt;http://ocw.mit.edu/courses/audio-video-courses/#electrical-engineering-and-computer-science&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-09T12:48:07.427" />
  <row Id="3373" PostTypeId="2" ParentId="825" CreationDate="2010-07-09T14:29:28.423" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.silabs.com/products/interface/usbtouart/Pages/default.aspx&quot; rel=&quot;nofollow&quot;&gt;CP210x&lt;/a&gt; from Silabs is a great product. It's difficult to solder, but have lots of tutorials teaching this on Google.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The advantages is that don't need crystal and uses only some capacitors.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-09T14:29:28.423" />
  <row Id="3374" PostTypeId="1" CreationDate="2010-07-09T15:45:05.940" Score="2" ViewCount="439" Body="&lt;p&gt;The problem is designing gain/volume/pan/balance/crossfade/mix controls with a smooth &quot;law&quot; or &quot;taper&quot;; the rate at which the audible volume changes as you turn them.  (Described in &lt;a href=&quot;http://www.geofex.com/article_folders/potsecrets/potscret.htm&quot; rel=&quot;nofollow&quot;&gt;The Secret Life of Pots&lt;/a&gt; and &lt;a href=&quot;http://sound.westhost.com/pots.htm#chg-law&quot; rel=&quot;nofollow&quot;&gt;Changing the Law of a Pot&lt;/a&gt;, for instance.)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's easy to make controls in which the gain changes very little in the middle and then swoops up at the top, for instance, but that's no good.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'd like to &quot;draw&quot; the circuit and then plot the gain/attenuation as a function of pot position, with either log or linear pots, and be able to vary component values and quickly see the effect on the gain function, in order to speed up finding the optimal layout/resistor values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currently I do one of the following:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Simulate the circuit in &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/tina-ti.html&quot; rel=&quot;nofollow&quot;&gt;TINA-TI&lt;/a&gt;.  This sucks because:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The pots only come in linear taper&lt;/li&gt;&#xA;&lt;li&gt;There's no way that I know of to plot something as a function of pot position.  You can set the pot as a control object and vary the position in steps from 0% to 100%, but I don't know of a way to plot the gain.  I just know you can plot the frequency response at each position, read the gains from the frequency response plot, and put them in a spreadsheet, which is very tedious.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Calculate the curve in a mathematics program like &lt;a href=&quot;http://wxmaxima.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;wxMaxima&lt;/a&gt; or Python and plot it.  This sucks because:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;It requires entering the gain equation by hand, which can be tedious and error-prone for certain circuits.  You can't tell by looking at a complex equation whether it's right or not, and modifying it by adding resistors in parallel to existing circuitry is difficult.&lt;/li&gt;&#xA;&lt;li&gt;Again, plotting for a log taper pot is difficult.  You'd have to enter the taper as a separate function which feeds into the gain function, and it still wouldn't match the real world exactly.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Any other ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For illustration, here's a plot I made comparing linear pot, log taper pots, and linear pot with &quot;pull-down resistor&quot; to approximate a log taper.  I'd like something that will plot the yellow curve, for different values of the pull-down resistor, so I can make it behave as closely as possible to the other curves, without having to enter an equation manually.  Of course, my real applications are more complex, but this is an example of what I want to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://flic.kr/p/7eR2DA&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://farm3.static.flickr.com/2761/4094821088_b45ded8fc7.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Copied from &lt;a href=&quot;http://electronics.stackexchange.com/questions/107/is-there-a-way-to-simulate-a-volume-control-pot-taper&quot; rel=&quot;nofollow&quot;&gt;Electronics Exchange&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-07-16T14:57:55.017" LastActivityDate="2010-07-22T21:55:09.013" Title="What's the best way to plot the &quot;taper&quot; of a potentiometer circuit?" Tags="&lt;resistance&gt;&lt;simulation&gt;&lt;potentiometer&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="3375" PostTypeId="1" CreationDate="2010-07-09T15:46:11.680" Score="5" ViewCount="271" Body="&lt;p&gt;Has anyone had good/bad experiences with particular PCB-mount thermocouples?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to design a circuit board with a connector I can plug a standard thermocouple connector into.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(and yes, I am aware that when you connect thermocouple wires to copper traces, you create junctions of dissimilar metals that can cause errors if the junctions are at different temperatures)&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-10-01T18:17:04.450" CommunityOwnedDate="2010-07-09T15:46:11.680" Title="PCB-mount connectors for thermocouples" Tags="&lt;thermocouple&gt;&lt;pcb&gt;&lt;connector&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="3376" PostTypeId="1" CreationDate="2010-07-09T15:59:56.620" Score="6" ViewCount="382" Body="&lt;p&gt;I &lt;em&gt;think&lt;/em&gt; I know how to do this, but you can find a lot of different instructions and calculators online that contradict each other.  I have yet to find a clear, concise procedure for calculating the self-noise of op-amp circuits (thermal noise, shot noise, ...), and one of the sources many people cite apparently has &lt;a href=&quot;http://www.endolith.com/wordpress/2009/11/04/errors-in-op-amps-for-everyone/&quot; rel=&quot;nofollow&quot;&gt;a number of errors&lt;/a&gt;, so I'll ask it here and see who can explain it best.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, how would you calculate the output noise of this circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Op-Amp_Differential_Amplifier.svg/300px-Op-Amp_Differential_Amplifier.svg.png&quot; alt=&quot;A differential op-amp circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess the source would be between V&lt;sub&gt;1&lt;/sub&gt; and V&lt;sub&gt;2&lt;/sub&gt; and would have internal resistance R&lt;sub&gt;S&lt;/sub&gt;.  Which noise sources do you include?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Op-amp internal input voltage noise&lt;/li&gt;&#xA;&lt;li&gt;Op-amp internal input current noise&lt;/li&gt;&#xA;&lt;li&gt;Resistor thermal noise&lt;/li&gt;&#xA;&lt;li&gt;Op-amp output stage noise?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;How do you calculate each component's contribution?  How do you combine the noise components together?  What gain do you use to get the output noise from the input equivalent noise?  How do you calculate the gain?  Is it the same as the signal gain?  What kind of simplifications and shortcuts can be made and how different will the result be from the real world?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;etc. etc. etc.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-04T15:46:57.767" LastActivityDate="2010-10-04T15:46:57.767" Title="How do you calculate the noise of an op-amp circuit?" Tags="&lt;measurement&gt;&lt;impedance&gt;&lt;resistance&gt;&lt;noise&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="3377" PostTypeId="1" CreationDate="2010-07-09T16:06:02.763" Score="5" ViewCount="101" Body="&lt;p&gt;Hey there.  Anyone know of a good book detailing RFID technology, covering theory and hardware?&lt;/p&gt;&#xA;" OwnerUserId="657" LastActivityDate="2010-12-03T03:37:08.303" Title="RFID book suggestions" Tags="&lt;rfid&gt;&lt;books&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="3378" PostTypeId="2" ParentId="3362" CreationDate="2010-07-09T16:12:13.497" Score="3" ViewCount="" Body="&lt;p&gt;Personally I think compiler warnings are there for a reason. Disabling or ignoring them (as some of the other answers seem to advocate) is a bad idea. -fno-strict-aliasing prevents a bunch of other optimizations, in the end, you'll probably lose a lot more performance than the 4 cycles you save by doing the C code hack.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-09T16:12:13.497" />
  <row Id="3379" PostTypeId="1" CreationDate="2010-07-09T16:42:59.873" Score="3" ViewCount="172" Body="&lt;p&gt;Will the WiFly Shield from SparkFun labs be able to connect to a Bluetooth network?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" LastActivityDate="2010-07-09T17:02:55.280" Title="WiFly Shield - Bluetooth?" Tags="&lt;wifly&gt;&lt;bluetooth&gt;" AnswerCount="1" />
  <row Id="3380" PostTypeId="2" ParentId="3048" CreationDate="2010-07-09T16:45:40.060" Score="1" ViewCount="" Body="&lt;p&gt;You can see a list of advantages and disadvantages here: &lt;a href=&quot;http://en.wikipedia.org/wiki/Solid_state_relay#Advantages_over_mechanical_relays&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Solid_state_relay#Advantages_over_mechanical_relays&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your case, whatever. Both solutions work. It will depend on the variable that you take into account, such as price, life cycle, etc.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-09T16:45:40.060" />
  <row Id="3381" PostTypeId="2" ParentId="3379" CreationDate="2010-07-09T16:52:55.813" Score="4" ViewCount="" Body="&lt;p&gt;No, definitely not. It connects to WiFi (802.11a/b/g) networks, not Bluetooth (802.15.1).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think an Arduino Bluetooth shield is available commercially today. Your best bet is to either buy an &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8255&quot; rel=&quot;nofollow&quot;&gt;Arduino with Bluetooth integrated&lt;/a&gt; or figure out how to connect a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8180&quot; rel=&quot;nofollow&quot;&gt;USB&lt;/a&gt; or &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8495&quot; rel=&quot;nofollow&quot;&gt;RS-232 Bluetooth&lt;/a&gt; adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By the way, on behalf of electrical engineers, I apologize for this 802.11.15.1.a.b.g nonsense. Collectively, we're bad at some things, and naming protocols appears to be one of them.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-07-09T17:02:55.280" LastActivityDate="2010-07-09T17:02:55.280" CommentCount="1" />
  <row Id="3382" PostTypeId="1" CreationDate="2010-07-09T16:57:23.640" Score="10" ViewCount="481" Body="&lt;p&gt;This is a supplementary question to the question &lt;a href=&quot;http://chiphacker.com/questions/966/which-electronics-components-should-i-always-have-on-hand&quot; rel=&quot;nofollow&quot;&gt;Which electronics components should I always have on hand?&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T22:37:45.200" LastActivityDate="2011-02-24T17:52:51.120" CommunityOwnedDate="2010-07-09T17:01:04.243" Title="Which equipment for electronics should I always have on hand?" Tags="&lt;equipment&gt;&lt;instruments&gt;" AnswerCount="8" FavoriteCount="5" />
  <row Id="3383" PostTypeId="2" ParentId="952" CreationDate="2010-07-09T17:06:37.930" Score="0" ViewCount="" Body="&lt;p&gt;Here in Brazil we have the Newton C. Braga Blog: &lt;a href=&quot;http://www.newtoncbraga.com.br/&quot; rel=&quot;nofollow&quot;&gt;http://www.newtoncbraga.com.br/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are lots of articles and tutorials.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's in portuguese, but you can try translate it.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-09T17:06:37.930" CommunityOwnedDate="2010-07-09T17:06:37.930" />
  <row Id="3384" PostTypeId="2" ParentId="3382" CreationDate="2010-07-09T17:07:27.143" Score="13" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;Digital multimeter&lt;/li&gt;&#xA;&lt;li&gt;Soldering iron&lt;/li&gt;&#xA;&lt;li&gt;Oscilloscope&lt;/li&gt;&#xA;&lt;li&gt;Power supply&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If you've got those 4, you're in decent shape.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that, I'd add a frequency generator, then a spectrum analyser.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I were starting an EE lab at a company, and I was going to buy those tools, here's what I'd start with:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/Fluke-117-Electricians-True-Multimeter/dp/B000O3LUEI&quot; rel=&quot;nofollow&quot;&gt;Fluke 117 multimeter&lt;/a&gt; ($192)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/Weller-WES51-Analog-Soldering-Station/dp/B000BRC2XU&quot; rel=&quot;nofollow&quot;&gt;Weller WES51&lt;/a&gt; soldering iron ($95)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/Tektronix-Digital-Oscilloscope-MHz-TDS1001B/dp/B000RFPEG8&quot; rel=&quot;nofollow&quot;&gt;Tektronix 1001B&lt;/a&gt; scope ($910)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/Aglient-E3631A-Triple-Output-Supply/dp/B003LZCQLW&quot; rel=&quot;nofollow&quot;&gt;Agilent 3631A&lt;/a&gt; power supply ($900-1000)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If I were a hobbyist just getting into the field, I'd limit myself to the &lt;a href=&quot;http://www.sparkfun.com/commerce/categories.php?c=46&quot; rel=&quot;nofollow&quot;&gt;Tools section of Sparkfun&lt;/a&gt;, plus the Tektronix scope.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-07-09T17:22:03.323" LastActivityDate="2010-07-09T17:22:03.323" CommunityOwnedDate="2010-07-09T17:07:27.143" CommentCount="10" />
  <row Id="3385" PostTypeId="2" ParentId="952" CreationDate="2010-07-09T17:13:48.897" Score="2" ViewCount="" Body="&lt;p&gt;[self-promotion] &lt;a href=&quot;http://tronixstuff.wordpress.com&quot; rel=&quot;nofollow&quot;&gt;http://tronixstuff.wordpress.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-07-09T17:13:48.897" CommunityOwnedDate="2010-07-09T17:13:48.897" CommentCount="1" />
  <row Id="3386" PostTypeId="1" AcceptedAnswerId="3403" CreationDate="2010-07-09T17:32:45.980" Score="3" ViewCount="583" Body="&lt;p&gt;Have people here used the LPC1343 Cortex-M3 chip?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've built a few small circuits with PIC microcontrollers before but now I'm using an LPC1243 Cortex-3/ARM. I've been using an LPCXpresso prototype board which has worked very nicely but I want to build a proper PCB now for my circuit. I'm finding this chip a lot nicer to work with in software than PICs (Which i also like!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the PICs my experience was that it was easy to forget something when building the hardware. For example a pin needed pulling low to disable low voltage programming on some pics or the chip wasn't programmable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My circuit is simply a 18x2 line LCD module connected to the chip which gets its input from a PC connected via a USB HID interface. I have it all working on the prototype board / breadboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the LPC1343 I plan to connect &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The power supply pins to power and decoupling capacitors&lt;/li&gt;&#xA;&lt;li&gt;The 12 MHZ crystal and capacitors.&lt;/li&gt;&#xA;&lt;li&gt;The 6 I/O pins I need to drive my hardware (An LCD module)&lt;/li&gt;&#xA;&lt;li&gt;The USB pins to a USB port via resistors and a pull up resistor&lt;/li&gt;&#xA;&lt;li&gt;Switches on the reset pin and the pin that enables the internal USB bootloader&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;And that's all. &#xA;My question is, are there any other pins I need to connect? It's important that I keep this as simple as possible as it's my first &quot;hobby&quot; project with the chip and frankly it's going to be hard enough to solder it without adding extra complexity (But I'm confident I can do it!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess I should post a schematic really, but have I missed anything obvious?&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2010-07-12T07:34:00.863" Title="Building a circuit with LPC1343" Tags="&lt;arm&gt;&lt;cortex-m3&gt;&lt;microcontroller&gt;" AnswerCount="3" />
  <row Id="3387" PostTypeId="2" ParentId="3362" CreationDate="2010-07-09T17:37:03.310" Score="3" ViewCount="" Body="&lt;p&gt;Can you instead declare your variable as a union of a byte array and a long array?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know if this is any more &quot;legal&quot; than your original code without a careful reading of the spec but it might be worth looking into.&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2010-07-09T17:37:03.310" CommentCount="1" />
  <row Id="3388" PostTypeId="2" ParentId="3377" CreationDate="2010-07-09T18:01:16.270" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/RFID-Dummies-Patrick-J-Sweeney/dp/076457910X&quot; rel=&quot;nofollow&quot;&gt;RFID for Dummies&lt;/a&gt; seemed quite accessible whilst being quite detailed as well when I used it 18 months ago.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-07-10T01:05:22.860" LastActivityDate="2010-07-10T01:05:22.860" />
  <row Id="3389" PostTypeId="2" ParentId="1206" CreationDate="2010-07-09T18:09:32.700" Score="2" ViewCount="" Body="&lt;p&gt;You can use &lt;a href=&quot;http://qucs.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;Qucs&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For logics circuits, you can use this great online simulator called &lt;a href=&quot;http://joshblog.net/projects/logic-gate-simulator/Logicly.html&quot; rel=&quot;nofollow&quot;&gt;Logicly&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-07-10T12:58:06.557" LastActivityDate="2010-07-10T12:58:06.557" CommunityOwnedDate="2011-04-01T14:55:18.717" />
  <row Id="3390" PostTypeId="1" AcceptedAnswerId="3395" CreationDate="2010-07-09T18:46:28.660" Score="3" ViewCount="135" Body="&lt;p&gt;I want to extend the use of a camera. The camera currently uses a special li-ion 3.7V 1000 mAh battery. I could grab a couple of those batteries, wire them up in parallel, and that'd work just fine. But if I didn't want to use those special batteries, would there be any problem using standard batteries? For example, could I wire up three AA 1.2V 2400mAh bats in serial to end up with a 3.6V 2400 mAh battery? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now my real question: Is the voltage difference (3.6V versus 3.7V) a problem, or is it close enough?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="793" LastActivityDate="2010-07-11T08:25:42.197" Title="Close enough for voltages?" Tags="&lt;battery&gt;&lt;batteries&gt;&lt;voltage&gt;&lt;voltage-regulator&gt;" AnswerCount="3" />
  <row Id="3391" PostTypeId="2" ParentId="3386" CreationDate="2010-07-09T18:58:59.760" Score="3" ViewCount="" Body="&lt;p&gt;I would add a debug connector, so that you can use the LPCXpresso for debugging your code. Adding it is quite trivial, but will make the system much easier to use.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-09T18:58:59.760" CommentCount="1" />
  <row Id="3393" PostTypeId="2" ParentId="3390" CreationDate="2010-07-09T19:13:16.423" Score="3" ViewCount="" Body="&lt;p&gt;That will work just fine, but you should measure the voltage of your 1.2 V cells to be sure. As they discharge, their voltage will drop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect that your camera has a 3.3 V low-dropout regulator; I bet you won't get into trouble  until very close to 3.3 V. Even if the voltage sags, I suspect that the worst that will happen is that the camera will turn off sooner than you want.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-09T19:13:16.423" />
  <row Id="3394" PostTypeId="1" CreationDate="2010-07-09T19:38:37.933" Score="3" ViewCount="530" Body="&lt;p&gt;Hi,&#xA;I have a RN 41 (Roving networks) bluetooth module, have no breakout board, want to connect it to Arduino duemilanove, can anyone please help with the circuit diagram and the components required to connect module to arduino&lt;/p&gt;&#xA;" OwnerUserId="947" LastActivityDate="2010-07-10T23:00:37.040" Title="Connecting Bluetooth module to arduino" Tags="&lt;arduino&gt;&lt;bluetooth&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="3395" PostTypeId="2" ParentId="3390" CreationDate="2010-07-09T19:46:27.043" Score="9" ViewCount="" Body="&lt;p&gt;Li-ion batteries range from about 4.3V - 3.3V as they discharge. 3xNiMH batteries would range from about 4.2V - 3V as they discharge. Too low of a voltage is not a problem, the camera already will have circuits to not turn on if the battery drops too low. All it means is you might not get the full use out of the NiMH batteries as compared to the Li-Ion, but there wont be any harm to anything.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-09T19:46:27.043" CommentCount="1" />
  <row Id="3396" PostTypeId="2" ParentId="1206" CreationDate="2010-07-09T21:41:21.617" Score="7" ViewCount="" Body="&lt;p&gt;I use LTSpice&lt;/p&gt;&#xA;&#xA;&lt;p&gt;great info on how to use it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.element-14.com/community/thread/1811&quot; rel=&quot;nofollow&quot;&gt;http://www.element-14.com/community/thread/1811&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In particular this tutorial:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://highered.mcgraw-hill.com/sites/0073106941/student_view0/lt_spice_instructions_and_support_files.html&quot; rel=&quot;nofollow&quot;&gt;http://highered.mcgraw-hill.com/sites/0073106941/student_view0/lt_spice_instructions_and_support_files.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2010-07-09T21:41:21.617" CommunityOwnedDate="2011-04-01T14:55:18.717" />
  <row Id="3397" PostTypeId="2" ParentId="3377" CreationDate="2010-07-10T12:07:08.390" Score="2" ViewCount="" Body="&lt;p&gt;If you want to go deeper I suggest this book that I'm reading now: RFID Essentials (Theory in Practice) &lt;a href=&quot;http://www.amazon.com/RFID-Essentials-Theory-Practice-OReilly/dp/0596009445/ref=sr_1_1?ie=UTF8&amp;amp;s=books&amp;amp;qid=1278763065&amp;amp;sr=1-1&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; and &lt;a href=&quot;http://book.pdfchm.net/rfid-essentials-theory-in-practice/9780596009441/&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-10T12:07:08.390" />
  <row Id="3398" PostTypeId="2" ParentId="632" CreationDate="2010-07-10T13:33:29.160" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Embedded-Software-Primer-David-Simon/dp/020161569X/ref=sr_1_1?ie=UTF8&amp;amp;s=books&amp;amp;qid=1278768782&amp;amp;sr=1-1&quot; rel=&quot;nofollow&quot;&gt;An Embedded Software Primer&lt;/a&gt; and &lt;a href=&quot;http://www.amazon.com/Programming-Embedded-Systems-C/dp/1565923545/ref=sr_1_1?ie=UTF8&amp;amp;s=books&amp;amp;qid=1278768748&amp;amp;sr=1-1&quot; rel=&quot;nofollow&quot;&gt;Programming Embedded Systems in C and C++&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-10T13:33:29.160" />
  <row Id="3399" PostTypeId="2" ParentId="1092" CreationDate="2010-07-10T14:13:57.137" Score="5" ViewCount="" Body="&lt;p&gt;This distinction is one that is much harder to make these days, since a whole spectrum of devices has arisen between the extremes, but if there's one identifier that seems to work, it's to look at the pin-out, and &lt;em&gt;look at what the designers did with the pins&lt;/em&gt;. Are they mostly individual I/O? Or do buses dominate? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my view, a microcontroller has traditionally been something that works as a 1-chip solution; put one on a PCB with a few unavoidable discretes, and some connectors, write a small amount of software, and you have a system. The microcontroller contains all the memory, volatile and not, that the system needs, the price paid for this convenience being that there wouldn't be very much of either at hand. Most of the pins are dedicated to I/O functions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whereas, at the other extreme, the microprocessor is the sort of beast to offload as much as possible to support chips, in order to dedicate silicon to maximizing the throughput of the CPU core. Most of the pins on this kind of device are address and data lines, necessary in order to connect to the memory and I/O devices that the core lacks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's still possible to call some things microprocessors, and other things microcontrollers, when the designers clearly adhered to one philosophy or the other. An Intel Core i7 is clearly a processor, PICs and AVRs are clearly controllers. At this point in time, however, with the amount of logic that can be put in a single chip, you can easily embed an entire 1990 microprocessor &lt;em&gt;system&lt;/em&gt; into a single chip. What do you call a 400MHz PPC604 with an interrupt controller, an SDRAM controller, ethernet support, and a slew of other peripherals, &lt;a href=&quot;http://www.appliedmicro.com/MyAMCC/jsp/public/productDetail/product_detail.jsp?productID=PPC405GP&quot; rel=&quot;nofollow&quot;&gt;all on one chip&lt;/a&gt;? &lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-10T14:13:57.137" />
  <row Id="3400" PostTypeId="2" ParentId="3382" CreationDate="2010-07-10T14:24:38.597" Score="7" ViewCount="" Body="&lt;p&gt;Depending on what kind of components you're using, you'll probably want some kind of magnification. Chip makers just don't make 'em like they used to (DIP, that is). Everything is trending towards smaller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, as part of that, you want a really really really good light source. In fact, you probably want a great light source just for your bench area and then a smaller LED flashlight or something to shine into all the crevices to see part labels, solder bridges, etc. Sometimes you just don't want to pick your board up and move it around to get light into all the places you'll need it.&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-07-10T14:24:38.597" CommunityOwnedDate="2010-07-10T14:24:38.597" CommentCount="1" />
  <row Id="3401" PostTypeId="2" ParentId="3382" CreationDate="2010-07-10T14:36:20.743" Score="2" ViewCount="" Body="&lt;p&gt;Hope nobody takes this the wrong way, but .. how about a fire extinguisher? =P &lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-10T14:36:20.743" CommunityOwnedDate="2010-07-10T14:36:20.743" />
  <row Id="3402" PostTypeId="2" ParentId="3394" CreationDate="2010-07-10T23:00:37.040" Score="3" ViewCount="" Body="&lt;p&gt;Consider using a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=7914&quot; rel=&quot;nofollow&quot;&gt;prototype shield&lt;/a&gt; with the module mounted &quot;dead bug&quot; style (upside down - in this case with the RF cover on the prototype grid). Use hot glue or double sided tape to secure it. Then, solder wires from the Bluetooth module pads to the Arduino shield pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that you can mount the module at the end, to give the required RF keepout clearance the datasheet calls out.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2010-07-10T23:00:37.040" />
  <row Id="3403" PostTypeId="2" ParentId="3386" CreationDate="2010-07-11T01:56:08.713" Score="3" ViewCount="" Body="&lt;p&gt;A debug LED (You can convert it into a watchdog blinky later to verify that your main loop/1ms interrupt or whatever you're using is still running) is something that I would consider pretty mandatory for an exploratory board.  Hello World on your new PCB does not need to be as complex as an LCD.  You could repurpose a backlight controlling MOSFET for this purpose if you don't want to add the real components.    &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm assuming you're giving yourself some form of breakout for your extra pins - An LCD screen is great, and I understand the desire to keep it simple, but there's little that can go wrong simply by adding a trace to nowhere, and nowhere can become somewhere someday.  Even if you don't want to add real headers, some test points (in the form of staggered rows of .05x.1&quot; copper pads) will let you solder and hot glue some wires on later.  This doesn't have to be a big deal.  I'd put some jumpers/resistors on those lines, so you can add some 1k resistors to protect your pins from being shorted or hit with ESD if you decide to do so.   This also gives you the ability to pull any of your other pins high or low if later you find this is necessary!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing that I do on a first board is add a lot of vias.  Vias are your friends when making modifications (assuming you're getting this done at a PCB house and don't have to drill them yourself).  If you've got two vias on every trace, even if you don't change sides with your trace, you can cut the trace later with an Xacto and run 30-ga wire wrap wire between the traces that need to be swapped (Make sure your vias are big enough for this, though).  You can also add 0805 0-ohm jumpers (solder bridges are cheap; you don't need to buy components) and solder wires to the pads later if you don't like the via method.    Probably won't be necessary, but it's cheap/free insurance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh, and connect the LCD/USB setup first, then tack wires on temporarily from your working breadboard to make sure that the externals are working.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-11T01:56:08.713" CommentCount="2" />
  <row Id="3404" PostTypeId="2" ParentId="3366" CreationDate="2010-07-11T05:01:17.473" Score="14" ViewCount="" Body="&lt;p&gt;Find an old electrical engineer, and try and get him to tutor/apprentice you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems a bit anachronistic, but you pick up an enormous amount of incidental information that makes it very easy to hit the ground running once you actually get started in the field. Good practices for design and layout, and practical approaches for problem solving are &lt;strong&gt;far&lt;/strong&gt; more important than knowing all the math. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, it does still work, even in this day and age. It's how I learnt most of what I know.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-07-11T05:01:17.473" CommentCount="1" />
  <row Id="3405" PostTypeId="2" ParentId="3366" CreationDate="2010-07-11T05:21:26.750" Score="5" ViewCount="" Body="&lt;p&gt;If you want to learn EE specifically for robotics, then it would be nice to pick up a book on robotics. These books cover the basic electrical required for robotics anyway. Try &lt;a href=&quot;http://www.societyofrobots.com&quot; rel=&quot;nofollow&quot;&gt;Society of robots&lt;/a&gt;. They have a nice tutorial on hardware.(This was how I got my feet wet). Also try to pick up some knowledge of uControllers and Sensors. Society of Robots is nice to develop an idea for what to do next. Also Try to learn Arduino. It will eliminate the need to learn all of embedded electronics and just concentrate on what to do and not how to do.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-07-11T05:21:26.750" />
  <row Id="3406" PostTypeId="2" ParentId="3390" CreationDate="2010-07-11T08:25:42.197" Score="0" ViewCount="" Body="&lt;p&gt;Lithium batteries are occasionally marked 3.6 or 3.7 volts. More often 3.7 because it looks better. But it's a nominal marking and, as said, the real voltage goes from 4.2 (cutoff to prevent overcharge damage) to somewhere around 3 (cutoff to prevent deep discharge damage). So nickel (or alkaline) and lithium batteries will spend a lot of time in the same range, as it were.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should just work, presuming you take care of charging correctly. There may be a difference in how the battery (and the device!) behaves once the batteries are getting close to empty and how they age. I suppose this is a digital camera that will write to flash memory. That takes a certain voltage at some current. If the battery is too weak and dips when its loaded, the write might get interrupted with undefined results. But it all depends.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the device and its functioning is very important (you're taking the photo of a lifetime...) I wouldn't risk adding random variables like batteries it wasn't designed for. If it's for random use and will work better for you with the new batteries, I'd absolutely go for it.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-11T08:25:42.197" />
  <row Id="3407" PostTypeId="2" ParentId="3366" CreationDate="2010-07-11T13:13:40.390" Score="3" ViewCount="" Body="&lt;p&gt;Although it is amateur radio oriented, the &lt;a href=&quot;http://www.arrl.org/&quot; rel=&quot;nofollow&quot;&gt;ARRL&lt;/a&gt; handbook usually has an extensive section on practical electronics. There is a new edition every year, and beyond the really basic electronics, several actual buildable projects are explored. Some editions have more digital projects than others, apparently at the whim of the editors, so don't think that if you've seen one of these, you've seen them all.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-25T10:20:48.903" LastActivityDate="2010-11-25T10:20:48.903" />
  <row Id="3408" PostTypeId="1" CreationDate="2010-07-11T20:41:28.407" Score="4" ViewCount="494" Body="&lt;p&gt;I am looking for a magnifier tool for an electronics workbench and was wondering what sort of product would be best.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The device must be an all-rounder capable of doing some SMT as well as through hole stuff.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I reckon that something like this &lt;a href=&quot;http://amzn.to/aoqmh6&quot; rel=&quot;nofollow&quot;&gt;http://amzn.to/aoqmh6&lt;/a&gt; would be about right, its a 1.75x 7' ring 28w magnifying lamp.  Is this going to be a usefull addition to the bench?&lt;/p&gt;&#xA;" OwnerUserId="312" LastActivityDate="2011-05-18T11:21:19.690" Title="What is the best Magnifier to use for general electronics duties..." Tags="&lt;electronics&gt;&lt;tools&gt;&lt;surface-mount&gt;&lt;workbench&gt;&lt;light&gt;" AnswerCount="9" CommentCount="1" FavoriteCount="1" />
  <row Id="3409" PostTypeId="2" ParentId="3358" CreationDate="2010-07-11T21:29:39.340" Score="1" ViewCount="" Body="&lt;p&gt;Hi, I´m not familiar with Arduino hardware, but if the information from reemrevnivek is correct, no problem at all in control 6 motor using the PWMs outputs. They will change the speed of your motors with no problem if it´s what you need. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding sensors, depends on what kind and how many sensor you have and where they are connected to Arduino, but, shouldn´t be a problem, again, considering you don´t need a high speed update on these sensors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, you comunication range (150m) can be a problem, consider use RS485 to do this and some CRC or checksum on the comunication.&lt;/p&gt;&#xA;" OwnerUserId="940" LastActivityDate="2010-07-11T21:29:39.340" />
  <row Id="3410" PostTypeId="2" ParentId="3408" CreationDate="2010-07-11T21:40:24.937" Score="2" ViewCount="" Body="&lt;p&gt;I personally prefer the square style magnifiers, &lt;a href=&quot;http://search.digikey.com/scripts/dksearch/dksus.dll?pname&amp;amp;site=us&amp;amp;lang=en&amp;amp;wt.mc_id=Dxn_US_US2010_Catlink&amp;amp;name=243-1027-ND&quot; rel=&quot;nofollow&quot;&gt;something like this&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd also recommend a good &quot;third hand&quot; type of device, i use &lt;a href=&quot;http://search.digikey.com/scripts/dksearch/dksus.dll?Detail&amp;amp;name=324PV-ND&quot; rel=&quot;nofollow&quot;&gt;a panavice unit&lt;/a&gt; they make a ton of different models though with various attachments and arms.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-07-11T21:40:24.937" CommentCount="5" />
  <row Id="3411" PostTypeId="2" ParentId="3408" CreationDate="2010-07-11T21:41:18.817" Score="1" ViewCount="" Body="&lt;p&gt;The techs where I work invariably have something that looks quite like what you linked to, I don't know what the brand would be, but the concept is the same. Large area, illuminated, on an arm so you can position it for hands-free use seem to be the critical requirements.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-11T21:41:18.817" />
  <row Id="3412" PostTypeId="2" ParentId="3408" CreationDate="2010-07-11T22:32:15.140" Score="3" ViewCount="" Body="&lt;p&gt;Get some cheap loupes and learn how to stick em in your eyes so you have both hands free for soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.loupe-magnifier.com/10xBL-CM.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-11T22:32:15.140" CommentCount="7" />
  <row Id="3413" PostTypeId="2" ParentId="3408" CreationDate="2010-07-11T23:32:43.013" Score="3" ViewCount="" Body="&lt;p&gt;I use the Luxo 17113, KRM Series, 3 diopter lense on my bench. The combination of the&#xA;light and magnification is excellent. The Luxo looks similar to the lamp you linked&#xA;to. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also use the Bausch &amp;amp; Lomb 81-42-00 visor. It comes with 3 Lenses 1.8x, 2.2x, 2.6x Magnification Power. These were around $40 or so from Amazon. I have a pair on my bench and a pair in the garage. These work quite well but when I work on the bench I only use the &#xA;lamp + magnifier. The portability of the visor is a major convenience. The multiple&#xA;lenses is also handy. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do primarily SMD soldering. My other tool picks are at &lt;a href=&quot;http://wiblocks.luciani.org/FAQ/faq-tools.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/FAQ/faq-tools.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:21:19.690" LastActivityDate="2011-05-18T11:21:19.690" CommentCount="2" />
  <row Id="3414" PostTypeId="2" ParentId="3408" CreationDate="2010-07-11T23:40:25.620" Score="8" ViewCount="" Body="&lt;p&gt;I've got one of the square ones on my desk at work, and I can't get used to looking through the magnifier.  For me, the magnification benefit is cancelled out by the distortion.  Moving my head moves the view and focus far too much to be useful, and my hands aren't where I see them, and, because I can see my wrists, my arms get confused.  Maybe I'm just dumb, but it doesn't work for me - Some of my coworkers do all of their work under one of those.The light, however, is very nice - The color doesn't make my eyes tired, and I always have it on when soldering.  Sometimes, I tolerate the distortion because placing the light between me and the soldering iron redirects the fumes out of my face.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you asked, the &lt;em&gt;best&lt;/em&gt; magnifier is a stereo boom microscope, and they're priced accordingly (Think $1000-2000 for an industry-grade model).  Think of the question &quot;What is the best power supply.&quot; The answer is the $1500 Agilent, but a modded computer PSU will also work.  That's the contrast between the stereo scope and the boom light.. We have models like &lt;a href=&quot;http://nationaloptical.com/products/stereoscopic/models/400TL-10-2.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; in the labs at my school and work; if you need the best, and can afford it, this is what you want.  Maybe you're starting a business or something, I don't know.  It's got to be stereo, because that's what gives you depth perception.  A ring light around the lens is also a necessity; at high zoom, the ratio of the lens to your pupil diameter divided by the magnification means that a lot less light is going to your eyes. Something in the range of 8-40x zoom is good for soldering, you won't need more unless you're a magician with your soldering iron.  Most of the time, 8 to 10x is adequate, and I just zoom in for inspection.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.scienscope.com/old/elz-binocular-stereo-zoom-microscopes.html&quot; rel=&quot;nofollow&quot;&gt;Scienscope&lt;/a&gt; carries more reasonably priced ones than the name-brand Luxo (Reasonable being $600+light source), and other stereo boom scopes run for around $500 on eBay.  You can also get the traditional microscope style instead of of the boom, like the &lt;a href=&quot;http://nationaloptical.com/products/stereoscopic/models/400TL-10-2.html&quot; rel=&quot;nofollow&quot;&gt;National Optical  400TL&lt;/a&gt; that you used to look at frog livers in high school for as cheap as $175 new, or look on eBay.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-11T23:40:25.620" CommentCount="4" />
  <row Id="3415" PostTypeId="2" ParentId="3408" CreationDate="2010-07-12T02:07:28.710" Score="2" ViewCount="" Body="&lt;p&gt;I use a cheap stereo dissecting microscope (20x) for small surface mount assembly. It's Chinese, and cost about £60. The optical and mechanical quality are surprisingly good for the price.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.lakeland-microscopes.co.uk/stereo.html&quot; rel=&quot;nofollow&quot;&gt;Lakeland Microscopes&lt;/a&gt;. I got the SM20.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The boom version would be better, but costs a lot more. I have thought of making my own boom.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-07-12T08:20:52.217" LastActivityDate="2010-07-12T08:20:52.217" CommentCount="2" />
  <row Id="3416" PostTypeId="2" ParentId="952" CreationDate="2010-07-12T05:18:05.047" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.evilmadscientist.com/&quot; rel=&quot;nofollow&quot;&gt;Evil Mad Scientist Laboratory&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Projects, electronics or otherwise. All very sciency.&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-07-12T05:18:05.047" CommunityOwnedDate="2010-07-12T05:18:05.047" CommentCount="1" />
  <row Id="3417" PostTypeId="2" ParentId="3386" CreationDate="2010-07-12T07:34:00.863" Score="1" ViewCount="" Body="&lt;p&gt;You do have the schematics for your proto/devkit boards? They're of course worth looking at to see what they've connected and where. But they won't tell the full story.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-12T07:34:00.863" />
  <row Id="3419" PostTypeId="1" AcceptedAnswerId="3421" CreationDate="2010-07-12T10:48:55.843" Score="3" ViewCount="286" Body="&lt;p&gt;I'm curious? A watchdog timer could do this, but I would like to do it manually.&lt;/p&gt;&#xA;" OwnerUserId="952" LastActivityDate="2010-07-16T05:48:15.967" Title="Is it possible to reset NXP LPC2100 microcontroller from code" Tags="&lt;arm&gt;&lt;reset&gt;" AnswerCount="3" />
  <row Id="3420" PostTypeId="2" ParentId="3408" CreationDate="2010-07-12T11:45:57.357" Score="1" ViewCount="" Body="&lt;p&gt;I use an &lt;a href=&quot;http://www.chsinteractive.co.uk/electrical-components/tools-service-aids/tools-toolkits/magnifiers-handheld-desktop-head/edsyn-headset-magnifier-ma10-adjustable-headset-feather-weight-optical-grade-acrylic-lenses.htm&quot; rel=&quot;nofollow&quot;&gt;Edsyn MA10 magnifier headset&lt;/a&gt; for SMD work. It comes with 2.5x lenses, and 5x and 7x are available as extra lenses.  5x lenses work best for me.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-07-12T11:45:57.357" />
  <row Id="3421" PostTypeId="2" ParentId="3419" CreationDate="2010-07-12T12:44:12.913" Score="3" ViewCount="" Body="&lt;p&gt;From a quick look at the datasheet, I believe that the watchdog is the only way to reset under software control.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Reset has two sources on the&#xA;  LPC2101/02/03: the RST pin and&#xA;  watchdog reset. The RST pin is a&#xA;  Schmitt trigger input pin with an&#xA;  additional glitch filter. Assertion of&#xA;  chip reset by any source starts the&#xA;  wake-up timer (see wake-up timer&#xA;  description below), causing the&#xA;  internal chip reset to remain asserted&#xA;  until the external reset is&#xA;  de-asserted, the oscillator is&#xA;  running, a fixed number of clocks have&#xA;  passed, and the on-chip flash&#xA;  controller has completed its&#xA;  initialization.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;To do a software reset, start the watchdog with a small timeout value, then go into an infinite loop.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-12T12:44:12.913" CommentCount="4" />
  <row Id="3422" PostTypeId="2" ParentId="3419" CreationDate="2010-07-12T18:28:26.227" Score="2" ViewCount="" Body="&lt;p&gt;Don't run interrupts by starting the timers with a small value - Write directly to the interrupt flag! &#xA;Leon's post wants you to run the interrupt as defined in the &lt;a href=&quot;http://ics.nxp.com/support/documents/microcontrollers/pdf/user.manual.lpc2101.lpc2102.lpc2103.pdf&quot; rel=&quot;nofollow&quot;&gt;user manual&lt;/a&gt;, page 219: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;WDTC = 1024;              // short timeout - WASTEFUL!&#xA;WDMOD = WDEN | WDRESET;   // watchdog resets CPU&#xA;WDFEED = 0xAA;            // start ...&#xA;WDFEED = 0x55;            // ... watchdog.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Instead, do the timer's job for it - Write to the WDINT bit (Which triggers the watchdog interrupt) of the WDMOD register directly, instead of waiting for the timer:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;WDMOD = WDEN;       // Enable interrupt&#xA;WDMOD |= WDINT;     // Trigger interrupt&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The datasheet says that it's read-only, which is a surprise to me, but the TI and Atmel processors I've used usually have writable interrupt triggers.  Give it a try, and see what happens.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The more portable alternative is a software interrupt.  I haven't worked with NXP processors, but the ARM7TDMI family (of which the LPC2100 is a member) can be reset by branching to 0x00000000.  Interestingly, NXP refers to this address as the watchdog interrupt. You should be able to branch to zero with code like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void (*reset)(void); // Declare function to call&#xA;reset = 0x00000000;  // Address in memory of reset ISR &#xA;                     // (See Table 2-4 of ARM7TDMI TRM or &#xA;                     // Table 2 of NXP UM10161)&#xA;reset();             // Call your new function&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Alternatively, use:  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;asm volatile (&quot;mov pc, #0\n&quot;);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;to accomplish the same thing.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There might be a few housekeeping things left to do, but this code will basically do the same thing as the watchdog timer, which is to start your program over from the beginning.  This code will also work across a wide number of microcontrollers.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-12T18:28:26.227" />
  <row Id="3423" PostTypeId="1" CreationDate="2010-07-12T18:32:01.527" Score="10" ViewCount="578" Body="&lt;p&gt;I would like to generate a list of high-level language interpreters and compilers (e.g. something that compiles LISP to C code) for microcontrollers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done a bit of research so far that I will document here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;List of projects for running Python on microcontrollers:&#xA;&lt;a href=&quot;http://web.media.mit.edu/~nvawter/projects/pyMicro/&quot; rel=&quot;nofollow&quot;&gt;http://web.media.mit.edu/~nvawter/projects/pyMicro/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PyMite:&#xA;&lt;a href=&quot;http://wiki.python.org/moin/PyMite&quot; rel=&quot;nofollow&quot;&gt;http://wiki.python.org/moin/PyMite&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;python-on-a-chip:&#xA;&lt;a href=&quot;http://code.google.com/p/python-on-a-chip/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/python-on-a-chip/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Armpit Scheme:&#xA;&lt;a href=&quot;http://armpit.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;http://armpit.sourceforge.net/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TinyScheme:&#xA;&lt;a href=&quot;http://tinyscheme.sourceforge.net/home.html&quot; rel=&quot;nofollow&quot;&gt;http://tinyscheme.sourceforge.net/home.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Minimal LISP Interpreter:&#xA;&lt;a href=&quot;http://www.sonoma.edu/users/l/luvisi/sl5.c&quot; rel=&quot;nofollow&quot;&gt;http://www.sonoma.edu/users/l/luvisi/sl5.c&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Embedded ML:&#xA;&lt;a href=&quot;http://embeddedml.sourceforge.net/Site/Intro.html&quot; rel=&quot;nofollow&quot;&gt;http://embeddedml.sourceforge.net/Site/Intro.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;eLua:&#xA;&lt;a href=&quot;http://www.eluaproject.net/&quot; rel=&quot;nofollow&quot;&gt;http://www.eluaproject.net/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Embedded JAVA:&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Embedded_Java&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Embedded_Java&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;amforth:&#xA;&lt;a href=&quot;http://amforth.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;http://amforth.sourceforge.net/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TinyTCL:&#xA;&lt;a href=&quot;http://tinytcl.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;http://tinytcl.sourceforge.net/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tiny BASIC:&#xA;&lt;a href=&quot;http://www.ittybittycomputers.com/IttyBitty/TinyBasic/index.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.ittybittycomputers.com/IttyBitty/TinyBasic/index.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;AVR shell:&#xA;&lt;a href=&quot;http://www.instructables.com/id/AVRSH-A-Command-Interpreter-Shell-for-ArduinoAVR/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/AVRSH-A-Command-Interpreter-Shell-for-ArduinoAVR/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bitlash shell (AVR): &lt;a href=&quot;http://bitlash.net/wiki/start&quot; rel=&quot;nofollow&quot;&gt;http://bitlash.net/wiki/start&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transterpreter (occam-pi on AVR):&#xA;&lt;a href=&quot;http://www.transterpreter.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.transterpreter.org/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rite (embedded Ruby) (will be released in 2011):&#xA;&lt;a href=&quot;http://www.slideshare.net/yukihiro_matz/rubyconf-2010-keynote-by-matz&quot; rel=&quot;nofollow&quot;&gt;http://www.slideshare.net/yukihiro_matz/rubyconf-2010-keynote-by-matz&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a community wiki – please feel free to add to the list.&lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-17T03:49:52.287" LastActivityDate="2011-05-17T05:33:36.270" CommunityOwnedDate="2010-07-12T18:32:01.527" Title="Survey of High-Level Language Interpreters/Compilers for Microcontrollers" Tags="&lt;microcontroller&gt;&lt;programming&gt;" AnswerCount="5" FavoriteCount="7" />
  <row Id="3424" PostTypeId="2" ParentId="3408" CreationDate="2010-07-12T19:01:40.710" Score="1" ViewCount="" Body="&lt;p&gt;I wanna buy one of these:&lt;br&gt;&#xA;&lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.39047&quot; rel=&quot;nofollow&quot;&gt;http://www.dealextreme.com/details.dx/sku.39047&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.41186&quot; rel=&quot;nofollow&quot;&gt;http://www.dealextreme.com/details.dx/sku.41186&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-12T19:01:40.710" />
  <row Id="3425" PostTypeId="2" ParentId="3423" CreationDate="2010-07-12T19:50:08.537" Score="2" ViewCount="" Body="&lt;p&gt;I would add &lt;a href=&quot;http://zwizwa.be/staapl/&quot; rel=&quot;nofollow&quot;&gt;Staapl&lt;/a&gt; to this list.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Staapl allows you to use Scheme macros as a metaprogramming tool on top of a forth-like stack language. Staapl currently targets the PIC18 chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Forth is definitely not a high level language, but the addition of Scheme on top of it eases the development.&lt;/p&gt;&#xA;" OwnerUserId="595" LastActivityDate="2010-07-12T19:50:08.537" CommunityOwnedDate="2010-07-12T19:50:08.537" />
  <row Id="3426" PostTypeId="2" ParentId="3314" CreationDate="2010-07-12T20:00:59.187" Score="1" ViewCount="" Body="&lt;p&gt;I use mil, because that's what they use at the company I outsource the PCBs to.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-07-12T20:00:59.187" CommentCount="2" />
  <row Id="3427" PostTypeId="1" AcceptedAnswerId="3444" CreationDate="2010-07-12T22:57:40.417" Score="3" ViewCount="1051" Body="&lt;p&gt;Hello everyone, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to use a parallel port from a computer as a form of cheap digital output to do various things (control motors, light LEDs, read limit switches, ect).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to know how to control the 8 data pins on a parallel port using C++, however there's a catch. Since I'm using a modern computer with a modern OS, this presents a few problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First of all, modern windows OS's don't allow direct access to parallel port pins, I must go through a driver. I have been pointed to using Inpout32 to do this, however the sample program compiled and ran properly but my attached hardware didn't respond. Another person has pointed me to using Windows API. I have searched the MSDN and found only mentions of the appropriate function but without some sample code, I'm lost (maybe I'm searching in the wrong places).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second problem is that my new computer doesn't have any parallel ports. I must use USB to parallel ports instead (cheap and direct from China, $5 each, shipping and taxes all included). The ports are recognized by the computer as IEEE-1284 controllers and the appropriate drivers were automatically installed and the computer reports the device as &quot;working properly&quot;. From what i have seen online, there seems to be a wide variety of opinions on the usefulness of these USB to parallel port connectors. One person says it works perfectly fine like any regular parallel port soldered to the motherboard, another says it will work with some hardware hacks, one says it can write but not read, and finally another says it won't work at all because they are not designed to work the same way as &quot;real&quot; parallel ports.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have already done a great deal of research before coming here (sort of as a last resort I guess, StackOverflow didn't yield any answers even after applying a bounty). Pretty much all the information I found on programming parallel ports is outdated and assumes that you have either a parallel port on your motherboard, a pre-Windows-NT OS, or both.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone has any idea how to do this, would you please share it with me?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-Faken&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I'm running Windows 7 x64 OS on a Core i7 860. I'm programming in C++ on Visual Studio 2008 pro. The USB to parallel port connectors are connected via USB 2.0 ports.&lt;/p&gt;&#xA;" OwnerUserId="942" LastActivityDate="2010-11-06T01:14:11.237" Title="Programming a parallel port as digital I/O" Tags="&lt;parallel&gt;&lt;port&gt;&lt;c++&gt;" AnswerCount="7" CommentCount="1" />
  <row Id="3428" PostTypeId="2" ParentId="3427" CreationDate="2010-07-12T23:04:34.153" Score="1" ViewCount="" Body="&lt;p&gt;You might be better off with an Arduino. Then, you can communicate with your PC application over the RS232 link.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not much more expensive than a USB parallel port adapter.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-12T23:04:34.153" />
  <row Id="3429" PostTypeId="2" ParentId="3427" CreationDate="2010-07-12T23:16:38.577" Score="6" ViewCount="" Body="&lt;p&gt;With current technology, if you want to operate on a number of discrete I/O signals, your best bet is to tinker with a dedicated USB microcontroller, or a standard microcontroller coupled with an FTDI USB-to-232 interface. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Old school parallel ports came in a variety of flavors, and not all could do input, since the port was primarily designed to send data to a printer. There were only a couple of handshaking lines that were actually dedicated to input. If you really want to use a USB parallel port, you should look for the EPP or ECP variants, as these were the bi-directional kind.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-12T23:16:38.577" />
  <row Id="3430" PostTypeId="1" AcceptedAnswerId="3431" CreationDate="2010-07-12T23:34:22.440" Score="2" ViewCount="502" Body="&lt;p&gt;Hi, I'm trying to put together a project with some bright LEDs but I'm not sure how to control them.  Ideally I'd like to drive about 64 of these LEDs that have a forward current of 300mA and voltage drop of between 2.2V and 3.4V.  I'm looking for something similar to the MAX7221 I think but one that can support these high currents.  Does anyone have any ideas or experience with driving these kind of LEDs.  I'd like to use arduino to control the driver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&#xA;I came across the &lt;a href=&quot;http://cds.linear.com/docs/Datasheet/3492fa.pdf&quot; rel=&quot;nofollow&quot;&gt;LT3492&lt;/a&gt;, would that work?&lt;/p&gt;&#xA;" OwnerUserId="954" LastEditorUserId="954" LastEditorDisplayName="" LastEditDate="2010-07-12T23:46:24.460" LastActivityDate="2011-05-19T14:19:07.510" Title="LED Driver for 300mA LEDs" Tags="&lt;led&gt;&lt;microcontroller&gt;&lt;controller&gt;&lt;light&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="3431" PostTypeId="2" ParentId="3430" CreationDate="2010-07-13T00:16:59.260" Score="1" ViewCount="" Body="&lt;p&gt;I have controlled the high current LEDs with both current sources and current sinks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am just finishing up the testing on an LT3755 driver circuit (current source) that&#xA;is driving 12 3W Cree XLamps. This driver has excellent performance if you &#xA;are careful with the layout. This device can do almost a 10:1 boost&#xA;at 50W! Being able to simulate in LTSpice was extremely convenient. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want a simpler layout you could look at current sinks. You would need to get&#xA;a supply capable of producing a voltage slightly greater than the sum of the Vf(max)&#xA;of your LEDs. Using a FET and op-amp you would create a voltage controlled current&#xA;sink. You could PWM this by setting the current to zero. I use an analog switch &#xA;on my current-sink.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a picture of my current sink design -- &lt;a href=&quot;http://wiblocks.luciani.org/not-quite-ready/ZB1-ISINK-index.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/not-quite-ready/ZB1-ISINK-index.html&lt;/a&gt;&#xA;The FETs are rated for 40A, the connectors are rated for 10A. For an LED&#xA;application with a reasonable size heatsink you can probably go to 2A. &#xA;The LEDs in the pictures are being driven at 350mA. No heatsinking is&#xA;required if the dissipation in the FETs is kept below 1W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The board in the picture is being controlled by my Arduino compatible NB1&#xA;board.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:19:07.510" LastActivityDate="2011-05-19T14:19:07.510" />
  <row Id="3432" PostTypeId="2" ParentId="3427" CreationDate="2010-07-13T01:10:15.993" Score="2" ViewCount="" Body="&lt;p&gt;The fact that you're trying to do this on Windows further complicates the matter. Direct interaction with hardware, while not impossible, is seriously complicated by the HAL. I have done this under Linux using the parapin library, but that was on an older machine with a real parallel port on the motherboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at the notes for &lt;a href=&quot;http://pyserial.sourceforge.net/pyparallel.html#windows&quot; rel=&quot;nofollow&quot;&gt;pyParallel under windows&lt;/a&gt;, it seems to require the giveio driver, which rules out the use of a USB -&gt; Parallel adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm going to have to agree with Jeff and Joby above. Go get an Arduino or some other microcontroller and tackle the problem that way.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2010-07-13T01:10:15.993" CommentCount="1" />
  <row Id="3433" PostTypeId="1" CreationDate="2010-07-13T02:06:44.553" Score="13" ViewCount="456" Body="&lt;p&gt;Is it still worthwhile to learn, for example, how to tune a 555 timer with resistors and capacitors, when you can write a timer program for a microcontroller in a human-readable programming language?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, to put it another way, are there problems that ICs are good for that microcontrollers are not?&lt;/p&gt;&#xA;" OwnerUserId="955" LastEditorUserId="955" LastEditorDisplayName="" LastEditDate="2010-07-14T05:34:46.790" LastActivityDate="2011-03-23T00:47:33.513" CommunityOwnedDate="2011-03-23T01:08:29.540" Title="Have microcontrollers replaced simpler ICs?" Tags="&lt;learning&gt;&lt;microcontroller&gt;" AnswerCount="10" CommentCount="2" FavoriteCount="4" />
  <row Id="3434" PostTypeId="2" ParentId="3433" CreationDate="2010-07-13T02:15:32.737" Score="2" ViewCount="" Body="&lt;p&gt;High frequency communication applications come to mind. Even though we now have 'software defined radio', it would be very surprising if 100MHz+ signal processing doesn't still have at least some analog stages.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-13T02:15:32.737" CommunityOwnedDate="2011-03-23T01:08:29.540" />
  <row Id="3435" PostTypeId="2" ParentId="3433" CreationDate="2010-07-13T02:25:44.953" Score="3" ViewCount="" Body="&lt;p&gt;I would class learning to tune a 555 timer as &quot;just in case&quot; knowledge. It's the same as people saying &quot;I've lived my whole life just fine without algebra, why are we teaching it to kids?&quot; If you don't know how to use a tool, you will never see a problem it can be applied to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for a specific answer: very fast digital logic is implemented in FPGAs/ASICs nowadays because it would be too slow on a microcontroller/processor (unless it was a specifically designed processor like a DSP).&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-07-13T02:25:44.953" CommunityOwnedDate="2011-03-23T01:08:29.540" />
  <row Id="3436" PostTypeId="2" ParentId="3427" CreationDate="2010-07-13T02:32:22.120" Score="1" ViewCount="" Body="&lt;p&gt;I would like to add that all of the usb to parallel port adapters I have come across do not emulate a parallel port, they emulate a printer over USB and hence cannot be used for their individual IO pins. Perhaps there are some that do this the way you want but surely you would be better off with a USB IO solution with many more IOs such as an &lt;a href=&quot;http://www.codemercs.com/index.php?id=127&amp;amp;L=1&quot; rel=&quot;nofollow&quot;&gt;IO-Warrior&lt;/a&gt; or an Arduino.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-07-13T02:32:22.120" />
  <row Id="3437" PostTypeId="2" ParentId="3433" CreationDate="2010-07-13T03:10:38.117" Score="12" ViewCount="" Body="&lt;p&gt;Strangely enough, I just had one of our Chinese factories trying to add a micro to a project where it was totally overkill, and I told them to use a 555 instead.  A 555 costs maybe 6 cents, vs a cheap microcontroller for 60 cents.  When you're making products in large quantities, that cost difference is important, and you'll definitely want to know how to use the cheaper IC.  So yeah, they're better at costing less. :)&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-13T03:10:38.117" CommunityOwnedDate="2011-03-23T01:08:29.540" CommentCount="1" />
  <row Id="3438" PostTypeId="2" ParentId="3408" CreationDate="2010-07-13T03:25:26.080" Score="1" ViewCount="" Body="&lt;p&gt;Ooh, you can also use a digital camera in macro mode!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4074/4789106122_0fc9437335_z.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just took that with my 8 MP Powershot SD870, and I totally can't see that much detail with a 10x loupe.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-13T03:25:26.080" CommentCount="6" />
  <row Id="3439" PostTypeId="2" ParentId="3433" CreationDate="2010-07-13T03:32:03.643" Score="16" ViewCount="" Body="&lt;p&gt;Mostly, microcontrollers have replaced discrete ICs. I find that even if I could design a circuit with a 555, it's likely that the same circuit will need to be tweaked in a few weeks to do something else, and a micro preserves that flexibility.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But there are a few exceptions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Discrete logic is still faster than most microcontrollers. The propagation delay and switching times for discrete logic are in the 1-10 ns range. To match that with a microcontroller, you have to be able to implement whatever logic you need in 1 instruction, and have a clock in the 100 MHz to 1 GHz range. You can do that, but maybe not on a breadboard in your garage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good example of this is the HCTL2020 quadrature decoder. It takes in two series of pulses and tells you which way your motor is spinning. It's implemented as a nonprogrammable chip for the sake of speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another interesting area where both digital logic and and microcontrollers fail is in signal filtering. If you have an analog signal that you want to filter digitally, you have to sample it at some rate. No matter how fast you sample it, noise in the signal that appears at frequencies more than half your sampling frequency will get aliased down to lower frequencies, where it may interfere with your signal. You can solve this problem with a low-pass filter, made of a cap and a resistor, before your sampling occurs. After the sampling, you're screwed. (Of course, it's frequently the case that the noise won't overlap your signal in frequency, and then a digital filter will work great.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-13T03:32:03.643" CommunityOwnedDate="2011-03-23T01:08:29.540" CommentCount="2" />
  <row Id="3440" PostTypeId="1" CreationDate="2010-07-13T04:51:20.143" Score="4" ViewCount="320" Body="&lt;p&gt;I was just giving my mother's mobile for repair at my local store and saw the owner stocking parts for them. I saw him stocking cheap (I mean really cheap) LCD (coloured and black &amp;amp; white). I was wondering where I can learn to use them in my circuits.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-31T05:24:04.253" LastActivityDate="2011-01-31T05:24:04.253" Title="Using LCD's of mobiles?" Tags="&lt;lcd&gt;&lt;mobile&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="3441" PostTypeId="2" ParentId="3440" CreationDate="2010-07-13T05:33:22.617" Score="4" ViewCount="" Body="&lt;p&gt;Google seems to be the best bet AFAIK. The modules vary wildly. There are types that resemble a TV with horizontal and vertical sync and pixels, ones with smart controllers (even SPI, as in a 3310 IIRC) and probably some had bare segments. Most probably don't have easily published specs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing you'll have to worry about is the connector types. Many cellphone parts have incredibly tight pitch components.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-13T05:33:22.617" CommentCount="1" />
  <row Id="3442" PostTypeId="1" CreationDate="2010-07-13T05:53:23.953" Score="2" ViewCount="218" Body="&lt;p&gt;hey i have just about finished my code but im finding it dificult to get the last bit working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far i have two codes one for taking wii nunchuck data sending through radio then another for picking that up and transfering to two servos.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is does anyone know how to edit the code so when one of the buttons (ie the Z button on the wii nunchuck) is pushed the servos are able to move but when the button is not being pushed they are help in position, like a deadmans finger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the reciever:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// Receiver Code&#xA;&#xA;#include &amp;lt;ServoTimer2.h&amp;gt;&#xA;&#xA;ServoTimer2 servosteer;  // create servo object to control a servo &#xA;ServoTimer2 servospeed;  // create servo object to control a servo &#xA;//MEGA pin 23 receive pin - displays characters sent by RF&#xA;&#xA;#include &amp;lt;VirtualWire.h&amp;gt;&#xA;#undef int&#xA;#undef abs&#xA;#undef double&#xA;#undef float&#xA;#undef round&#xA;void setup()&#xA;{&#xA;servosteer.attach(7);  // attaches the servo on pin 25 to the servo object &#xA;servospeed.attach(8);  // attaches the servo on pin 27 to the servo object &#xA; // lcd.init();&#xA;    Serial.begin(9600); // Debugging only&#xA;    Serial.println(&quot;setup&quot;);&#xA;&#xA;    // Initialise the IO and ISR&#xA;    vw_set_ptt_inverted(true); // Required for DR3100&#xA;    vw_setup(4000);  // Bits per sec&#xA;    vw_set_rx_pin(5);&#xA;    vw_rx_start();       // Start the receiver PLL running&#xA;}&#xA;&#xA;void loop()&#xA;{&#xA;     uint8_t buf[VW_MAX_MESSAGE_LEN];&#xA;    uint8_t buflen = VW_MAX_MESSAGE_LEN;&#xA;  if (vw_get_message(buf, &amp;amp;buflen)) // Non-blocking&#xA;    {&#xA;      //invalid message length must be S/B/F/L/R + number (max 3 digits)&#xA;      if (buflen &amp;lt; 3 || buflen &amp;gt; 5)&#xA;        return;&#xA; digitalWrite(13, true); // Flash a light to show transmitting&#xA;&#xA;      char val[buflen]; //Same as buf, last char will be used for null terminator&#xA;      memset(val, '\0', sizeof(val));&#xA;&#xA;      //Copy value from string i.e. 213 from R213 into separate string&#xA;      strncpy(val, (char *)buf + 1, buflen - 1);&#xA;&#xA;      //convert string containing value to integer e.g. &quot;213&quot; to 213.&#xA;      int VAL = atoi ( val );&#xA;&#xA;      switch (buf[0]) {&#xA;                case 'X': //Deadmans finger stop all&#xA;                    Serial.print(&quot;Deadmans finger&quot;);&#xA;                    servospeed.write(1500);&#xA;&#xA;                    break;&#xA;        case 'P':&#xA;            Serial.print(&quot;Pitch &quot;);&#xA;            Serial.println(VAL);&#xA;                    servospeed.write(544+VAL*10);&#xA;&#xA;            break;&#xA;        case 'R':&#xA;            Serial.print(&quot;Roll &quot;);&#xA;            Serial.println(VAL);&#xA;                    servosteer.write(544+VAL*10);&#xA;&#xA;            break;&#xA;        default:&#xA;            break;&#xA;      }&#xA;    }&#xA;     digitalWrite(13, false); // Flash a light to show transmitting&#xA;} &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Here is the transmit:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// Transmitter Code&#xA;int speedo=96;&#xA;int steero=90; //limit 70-110&#xA;int ii=0;&#xA;int jj=0;&#xA;int roll=0;&#xA;int pitch=0;&#xA;&#xA;#include &quot;Wire.h&quot;&#xA;#include &quot;WiiChuck.h&quot;&#xA;WiiChuck chuck = WiiChuck();&#xA;int zPress = 0;&#xA;int XPress =-130;&#xA;int YPress =-130;&#xA;&#xA;#include &amp;lt;VirtualWire.h&amp;gt; // library for RF RX/TX&#xA;#undef int&#xA;#undef abs&#xA;#undef double&#xA;#undef float&#xA;#undef round&#xA;#undef round&#xA;&#xA;char charnum[10];&#xA;&#xA;int bz=0;&#xA;void setup() {&#xA;  Serial.begin(115200);&#xA;  chuck.begin();&#xA;  chuck.update();&#xA;  chuck.calibrateJoy();&#xA;   // Initialise the IO and ISR&#xA;  vw_set_tx_pin(6);&#xA;  vw_set_ptt_inverted(true); // Required for DR3100&#xA;  vw_setup(4000);    // Bits per sec&#xA;}&#xA;&#xA;void loop() {&#xA; chuck.update();&#xA;&#xA;char bufferP[5];char numP[5];&#xA;char bufferR[5];char numR[5];&#xA;  memset(bufferP, '\0', sizeof(bufferP));&#xA;  memset(numP, '\0', sizeof(numP));&#xA;  memset(bufferR, '\0', sizeof(bufferR));&#xA;  memset(numR, '\0', sizeof(numR));&#xA;  roll= (int)chuck.readRoll();&#xA;  pitch = (int)chuck.readPitch();&#xA;&#xA;   digitalWrite(13, true); // Flash a light to show transmitting&#xA;   XPress=chuck.readJoyX();&#xA;   YPress=chuck.readJoyY();&#xA;&#xA; strcat(bufferR,&quot;R&quot;);&#xA;  //if (chuck.zPressed() == 1) {strcat(bufferR,&quot;R&quot;);} else {strcat(bufferR,&quot;X&quot;);}&#xA;  ii=byte(roll-160); &#xA;  if (ii&amp;lt;70) { ii=70;} if (ii&amp;gt;110) { ii=110;}&#xA;   itoa(ii,numR,10);&#xA;    strcat(bufferR,numR);&#xA;  Serial.println(bufferR);&#xA;  vw_send((uint8_t *)bufferR, strlen(bufferR));&#xA;  vw_wait_tx(); // Wait until the whole message is gone&#xA;  delay(20);&#xA;&#xA;  //strcat(bufferP,&quot;P&quot;);&#xA;  if ((XPress&amp;gt;-127) or (XPress&amp;lt;-133)or (YPress&amp;gt;-127) or (YPress&amp;lt;-133)) { strcat(bufferP,&quot;P&quot;);} else {strcat(bufferP,&quot;X&quot;);}&#xA;&#xA;  jj=byte(pitch); &#xA;   itoa(jj,numP,10);&#xA;    strcat(bufferP,numP);&#xA;  Serial.println(bufferP);&#xA;  vw_send((uint8_t *)bufferP, strlen(bufferP));&#xA;  vw_wait_tx(); // Wait until the whole message is gone&#xA;  delay(20);&#xA;  digitalWrite(13, false);&#xA; }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2010-07-14T06:10:01.860" LastActivityDate="2010-07-28T21:39:39.260" Title="stopping servos" Tags="&lt;arduino&gt;&lt;wii&gt;&lt;nunchuck&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="3443" PostTypeId="1" CreationDate="2010-07-13T06:32:01.830" Score="3" ViewCount="155" Body="&lt;p&gt;I have an electronic load that I want to use to help me with some ATX switch mode power supply repairs.  The instructions that came with the load were rather sparse and I haven't found much for my particular situation on the net.  The electronic load is a CSI3710A sold by Circuit Specialist.  It is a rather inexpensive model and may not have lots of features but I may not need much. I just don't want to damage it or add more damage to the power supplies. I am confused about the Constant Current, Constant Voltage and Constant Resistance Modes and which one to use. When working with a PS that has the +12,+5 and -5 should I tap the +5 or does it matter? Does it matter if the PS is not putting out any voltage or a low voltage would that damage the load?  Anything else to watch out for?&#xA;Thanks&lt;/p&gt;&#xA;" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T00:15:56.433" LastActivityDate="2011-02-15T00:15:56.433" Title="setting up an electronic load" Tags="&lt;power-supply&gt;&lt;electronic-load&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="3444" PostTypeId="2" ParentId="3427" CreationDate="2010-07-13T07:32:18.770" Score="6" ViewCount="" Body="&lt;p&gt;Parallel port is dead, and USB microcontrollers are really the future IMO. If you use the HID or CDC profile you don't even need any driver on your PC. Eg the &lt;a href=&quot;http://pjrc.com/teensy/index.html&quot; rel=&quot;nofollow&quot;&gt;Teensy&lt;/a&gt; for $18, you get 25 I/O, of which all can be used as digital I/O, or up to 12 of them as analog inputs and 7 of them PWM channels. The Teensy is more general purpose, if you want something specifically to provide communication between your PC and electronics, there are other devices targeted more towards that, like the &lt;a href=&quot;http://www.seeedstudio.com/depot/bus-pirate-v3-assembled-p-609.html?cPath=61_68&quot; rel=&quot;nofollow&quot;&gt;Bus Pirate&lt;/a&gt;. Or, if you don't need too many I/O's, you could use the standard, fairly simple &lt;a href=&quot;http://www.sparkfun.com/commerce//news.php?id=386&quot; rel=&quot;nofollow&quot;&gt;FT232R USB chip in 'bit-bang' mode&lt;/a&gt;, and get 8 digitial I/O out of it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you absolutely refuse to listen to reason, then what you need is a PCI card which adds a parallel port, &lt;a href=&quot;http://www.amazon.com/MOSCHIP-Dual-Serial-Parallel-Multi/dp/B000YM7HVY/ref=sr_1_3?tag=robwlas-20&amp;amp;ie=UTF8&amp;amp;s=electronics&amp;amp;qid=1279005891&amp;amp;sr=8-3&quot; rel=&quot;nofollow&quot;&gt;like this one&lt;/a&gt;. You'll need a PCI slot (not PCI-Express), most motherboards still have one these days, but they are starting to get phased out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;USB to Parallel adaptors will have all sorts of problems. The main one is latency...standard parallel port latency is measured in microseconds, whereas USB latency is measured in milliseconds. The other is that many USB to Parallel adaptors are designed only for printers, and lack the extra circuitry needed to individually control the address lines in the way you want.&lt;/p&gt;&#xA;" OwnerUserId="131" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-07-16T19:41:58.353" LastActivityDate="2010-07-16T19:41:58.353" CommentCount="4" />
  <row Id="3446" PostTypeId="2" ParentId="3443" CreationDate="2010-07-13T11:14:03.983" Score="2" ViewCount="" Body="&lt;p&gt;For most testing constant current is the easiest mode to use. You can set&#xA;the current to the appropriate current level and verify the output voltage&#xA;specification. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Constant Current -- the load will try to sink the programmed current&lt;/li&gt;&#xA;&lt;li&gt;Constant Resistance -- the load will try to sink a current to maintain&#xA;a programmed resistance. This is done my multipliers in the control circuit.&lt;/li&gt;&#xA;&lt;li&gt;Constant Voltage -- the load will will increase current to maintain a programmed&#xA;voltage. This is useful when trying to find the current at which&#xA;the power supply folds back (knee current). You set the load to the foldback &#xA;voltage and then measure the current. It is quicker than stepping the current&#xA;but does require a more complex control circuit.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Since most loads are current sinks you shouldn't be able to damage it when the supply&#xA;is putting out low voltages. You could damage the load with too high a voltage&#xA;but for an ATX power supply this is unlikely. The output stage of most loads consists of&#xA;power MOSFETs and these typically have breakdown voltages of 20V and above.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some power supplies have minimum load requirements for the individual outputs.&#xA;A comprehensive test would load all the outputs at various combinations of min and max&#xA;loads but you could probably attach the load to one output at a time. Make&#xA;sure that each of the other outputs has the min load.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-19T01:03:00.917" LastActivityDate="2011-01-19T01:03:00.917" CommentCount="1" />
  <row Id="3447" PostTypeId="2" ParentId="3433" CreationDate="2010-07-13T11:26:42.970" Score="3" ViewCount="" Body="&lt;p&gt;In my current project we are using a Marvell ARM9 chip running at 500Mhz with an FPGA to offer many DIO ports. Still, there are things that are handled in discrete logic. For instance, a stepper motor control is needed for 4 stepper motors controlled individually. There is one oscillator to generate a frequency with a counter that will allow a number of pulses to go through. The counter is set from the microcontroller, but then operates without any further control from the microcontroller, giving it time to work on other tasks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We could have opted for more microcontrollers. But a central controller working with traditional discrete logic can prove to be a powerful and very reliable solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if you have a problem that is clearly defined, the solution should always be as simple as possible, but no simpler (quote hidden in there ;-) ). If a 555 works, why would you not use it? Flexibility might be an argument as someone else opted, but it might not be. It all depends on your problem and your interpretation of what the simplest solution is.&lt;/p&gt;&#xA;" OwnerUserId="909" LastActivityDate="2010-07-13T11:26:42.970" CommunityOwnedDate="2011-03-23T01:08:29.540" />
  <row Id="3448" PostTypeId="2" ParentId="3440" CreationDate="2010-07-13T11:28:39.890" Score="3" ViewCount="" Body="&lt;p&gt;A friend of mine did a teardown of an LCD that he purchased for 0.50USD&#xA;from Electronic Goldmine -- &lt;a href=&quot;http://tim.cexx.org/?page_id=342&quot; rel=&quot;nofollow&quot;&gt;http://tim.cexx.org/?page_id=342&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is quite detailed so even if you don't use that particular screen&#xA;you may be able to follow the steps to interface other screens.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-23T21:04:30.343" LastActivityDate="2010-12-23T21:04:30.343" />
  <row Id="3449" PostTypeId="2" ParentId="1024" CreationDate="2010-07-13T14:14:36.813" Score="5" ViewCount="" Body="&lt;p&gt;Check out this javascript program on google code. It's not ready to be used yet but it's getting close. It doesn't work in IE and it has some glitches. I wouldn't embed it in a web page yet, but you can use it separately. I'm not much of a javascript programmer but with some help we can create our own editor. It won't create waveforms though. It would be awesome if you  could somehow include spice models in the xml .I think that would be a little too much for javascript though. this is just for quick sketches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/webtronics/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/webtronics/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="959" LastActivityDate="2010-07-13T14:14:36.813" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="1" />
  <row Id="3450" PostTypeId="2" ParentId="3423" CreationDate="2010-07-13T14:30:19.557" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://stackoverflow.com/questions/1082751/what-are-the-available-interactive-languages-that-run-in-tiny-memory&quot;&gt;Here&lt;/a&gt; is a good list from SO that lists languages targeted to micros, although I think you got most of them. I've added the ones missing, leaving out the C interpreters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also programs that will compile C++ to C, and I have seen some experimental work to translate c# to c for micro use, but that seems unnecessary.&lt;/p&gt;&#xA;" OwnerUserId="875" LastEditorUserId="875" LastEditorDisplayName="" LastEditDate="2010-07-13T14:44:26.913" LastActivityDate="2010-07-13T14:44:26.913" CommunityOwnedDate="2010-07-13T14:30:19.557" />
  <row Id="3451" PostTypeId="1" AcceptedAnswerId="3453" CreationDate="2010-07-13T15:08:47.033" Score="2" ViewCount="149" Body="&lt;p&gt;I want to save/restore the PIC's carry bit. I'm using the 16F628A.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;SAVE_CARRY&#xA;    btfss STATUS, 0&#xA;    goto CARRY_OFF &#xA;&#xA;CARRY_ON&#xA;    bsf carry, 0&#xA;    return&#xA;&#xA;CARRY_OFF&#xA;   bcf carry, 0&#xA;   return&#xA;&#xA;RESTORE_CARRY&#xA;   btfss carry, 0&#xA;   goto RESTORE_CARRY_OFF&#xA;&#xA;RESTORE_CARRY_ON&#xA;   bsf STATUS, 0&#xA;   return&#xA;&#xA;RESTORE_CARRY_OFF&#xA;   bcf STATUS, 0&#xA;   return&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;There must be a better way. Is there?&lt;/p&gt;&#xA;" OwnerUserId="550" LastEditorUserId="550" LastEditorDisplayName="" LastEditDate="2010-07-13T15:49:54.197" LastActivityDate="2010-10-26T15:01:32.537" Title="What's the most effective way to save/restore a PIC status bit" Tags="&lt;pic&gt;&lt;assembly&gt;" AnswerCount="2" />
  <row Id="3452" PostTypeId="2" ParentId="3451" CreationDate="2010-07-13T16:01:49.687" Score="-1" ViewCount="" Body="&lt;p&gt;Save the Status register in RAM, and restore it?&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-13T16:01:49.687" CommentCount="1" />
  <row Id="3453" PostTypeId="2" ParentId="3451" CreationDate="2010-07-13T16:16:26.507" Score="4" ViewCount="" Body="&lt;p&gt;One way that you can do:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;SAVE_CARRY:&#xA;    bsf    carry, 0&#xA;    btfss  status, c&#xA;    bcf    carry, 0&#xA;    return&#xA;&#xA;RESTORE_CARRY&#xA;    bsf    status, c&#xA;    btfss  carry, 0&#xA;    bcf    status, c&#xA;    return&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If you need to save the registers &quot;W&quot; and &quot;Status&quot;, before execute an interrupt code, there is another way:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Save_Context:&#xA;    movwf w_temp&#xA;    swapf status,w&#xA;    movwf status_temp&#xA;    ;Your interrupt code here. &#xA;&#xA;Restore_Context:&#xA;    swapf status_temp,w&#xA;    movwf status&#xA;    swapf w_temp,f&#xA;    swapf w_temp,w&#xA;    retfie&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-10-26T15:01:32.537" LastActivityDate="2010-10-26T15:01:32.537" />
  <row Id="3454" PostTypeId="2" ParentId="3433" CreationDate="2010-07-13T17:33:20.253" Score="1" ViewCount="" Body="&lt;p&gt;Very few of my recent microcontroller designs have required any discrete logic.  An exception was implementing a Ctrl-Alt-Del type of reset whereby pressing two specific keys on a custom keyboard for two seconds would do a hard reset of the micro.  I used a NOR gate (used as an AND gate with 2 inverted inputs), an AND gate, and a 74HC123.  Was convenient to be able to get the specific gates I needed in single gates in a SMT package, instead of the 4 gates/package in the DIP days.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-07-13T17:33:20.253" CommunityOwnedDate="2011-03-23T01:08:29.540" />
  <row Id="3455" PostTypeId="2" ParentId="3440" CreationDate="2010-07-13T18:30:20.203" Score="2" ViewCount="" Body="&lt;p&gt;Enjoy:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.rancidbacon.com/LearningAboutArduinoNokiaLCD&quot; rel=&quot;nofollow&quot;&gt;http://code.rancidbacon.com/LearningAboutArduinoNokiaLCD&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-13T18:30:20.203" />
  <row Id="3456" PostTypeId="2" ParentId="3433" CreationDate="2010-07-13T19:00:14.653" Score="1" ViewCount="" Body="&lt;p&gt;ICs can be very domain specific.  I'm thinking of a DTMF decoder.  I could program a microcontroller to decode the two frequencies, but it's easier, faster, and cheaper to use an off-the-shelf chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think is it important to have enough knowledge of all the tools to know what tool to use.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-07-13T19:00:14.653" CommunityOwnedDate="2011-03-23T01:08:29.540" CommentCount="2" />
  <row Id="3457" PostTypeId="2" ParentId="3433" CreationDate="2010-07-14T00:55:17.133" Score="3" ViewCount="" Body="&lt;p&gt;One area there discrete logic still beats out micros is long term part stability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this micro going to be available in 10 years? 20? Will the IDE and toolchain still support it in that time?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can pretty much guarantee that discrete logic will still be discrete logic in the future. Micros, not so much. If you're designing a product that you expect to have a long production life, generic logic, and as much as possible, generic parts will reduce the need to redesign the device when parts availability shifts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you're not SOL if your chip manufacturer is backordered. Many people make compatible generic logic, while there is basically no generic micro.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-03-22T23:52:16.787" LastActivityDate="2011-03-22T23:52:16.787" CommunityOwnedDate="2011-03-23T01:08:29.540" />
  <row Id="3458" PostTypeId="2" ParentId="632" CreationDate="2010-07-14T02:00:55.453" Score="2" ViewCount="" Body="&lt;p&gt;I like &quot;Practical UML Statecharts in C/C++, Second Edition: Event-Driven Programming for Embedded Systems&quot; by Miro Samek.  The previous edition was called &quot;Practical Statecharts in C/C++: Quantum Programming for Embedded Systems.&quot;  I read the previous edition of this book cover to cover, and in some ways I prefer that edition because it was more C++ based.  The latest edition is more C based, which makes sense for embedded development because even the smallest micros have a C compiler.  Don't be scared by the UML part.  The important thing to learn is how to use state machines to make your code more robust and reliable.  UML is just one way to express a state machine, and the subset of UML required is very minimal.&lt;/p&gt;&#xA;" LastActivityDate="2010-07-14T02:00:55.453" />
  <row Id="3459" PostTypeId="2" ParentId="3440" CreationDate="2010-07-14T02:13:25.203" Score="3" ViewCount="" Body="&lt;p&gt;It all depends on the controller.  Some are well supported in the embedded world, others have their datasheets hidden away for OEMs only, are  unpublished, or have completely unreadable barely-English text.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd stick with the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=569&quot; rel=&quot;nofollow&quot;&gt;LPC2148&lt;/a&gt; [Sparkfun], which uses the Epson S1D15G10 or Philips PCF8833 controller.  C code for AVRs, PICs, and ARMs, Arduino sketches, Forth implementations, Linux drivers, etc. are all available.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-14T02:13:25.203" />
  <row Id="3460" PostTypeId="2" ParentId="3427" CreationDate="2010-07-14T04:40:28.533" Score="1" ViewCount="" Body="&lt;p&gt;Are you sure you hooked your device up to the parallel port correctly?  Did you get a pinout, hook up to the right ground, etc?  I would get an oscope or a DMM, then toggle all 8 data bits when you press a key on the keyboard, and try to see at least that happen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you using the right address?  The default address for motherboard-soldered parallel ports (0x378, I believe) is probably not going to work.  You should go through Device Manager's Ports (COM and LPT) node, find your USB-&gt;parallel adapter, Resources tab, and find the base address for your adapter.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-07-14T04:40:28.533" />
  <row Id="3461" PostTypeId="2" ParentId="3382" CreationDate="2010-07-14T09:18:24.680" Score="2" ViewCount="" Body="&lt;p&gt;One thing I've found very useful is a large magnifying lens/light combo on a swing arm. Having one clamped to the bench allows me to have good lighting where I need it, and having a lens for checking for solder bridges/cold joints/part numbers... If you want to get pricey, go for a stereo scope which can go to about 40X. These are great for SMT rework. Also on the high end are the Pace soldering stations. I used to have a PRC-2000 (overkill, usually) and some of its features were very handy. Using solder/flux paste with a controlled dispenser, and a hot-air soldering tool (900deg F) will allow for better-than-factory SMT work with a bit of practice.&lt;/p&gt;&#xA;" OwnerUserId="965" LastEditorUserId="965" LastEditorDisplayName="" LastEditDate="2010-07-17T07:00:35.013" LastActivityDate="2010-07-17T07:00:35.013" CommunityOwnedDate="2010-07-14T09:18:24.680" />
  <row Id="3462" PostTypeId="1" AcceptedAnswerId="3466" CreationDate="2010-07-14T11:57:24.920" Score="5" ViewCount="309" Body="&lt;p&gt;I'm designing an embedded device that I would like to make interoperable with third party peripherals through a serial bus. Should I choose SPI, I²C, or some other bus?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The peripherals will be pretty low bandwidth (some sensors that communicate over the bus, polled periodically) and most likely within a metre or less of the controller. The controller's sole task is to collect the sensor data, package it in some way, and then send it off to a wireless module via another bus (although the sensor bus could potentially be reused for this too).&lt;/p&gt;&#xA;" OwnerUserId="536" LastEditorUserId="536" LastEditorDisplayName="" LastEditDate="2010-07-14T13:37:01.840" LastActivityDate="2010-07-14T19:28:08.950" Title="What is the most popular embedded serial bus?" Tags="&lt;spi&gt;&lt;i2c&gt;&lt;bus&gt;&lt;serial&gt;&lt;communication&gt;" AnswerCount="5" CommentCount="5" />
  <row Id="3464" PostTypeId="2" ParentId="632" CreationDate="2010-07-14T12:31:28.250" Score="1" ViewCount="" Body="&lt;p&gt;For ARM chips I have learned a lot from:&#xA;&lt;a href=&quot;http://www.amazon.com/ARM-System-Chip-Architecture-2nd/dp/0201675196&quot; rel=&quot;nofollow&quot;&gt;ARM System-on-chip architecture&lt;/a&gt; by Steve Furber&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a well-written book with a lot of technical background and will probably be useful even if you work on other architectures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had a PIC32 book which is ok and focuses on PIC:&#xA;&lt;a href=&quot;http://www.amazon.co.uk/Programming-32-bit-Microcontrollers-Exploring-Technology/dp/0750687096&quot; rel=&quot;nofollow&quot;&gt;Programming 32 bit Microcontrollers in C&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="909" LastActivityDate="2010-07-14T12:31:28.250" />
  <row Id="3465" PostTypeId="2" ParentId="3462" CreationDate="2010-07-14T12:45:40.463" Score="1" ViewCount="" Body="&lt;p&gt;The question is a bit of a problem because of definition issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Serialized communication is basically what you need if you want to communicate with some external peripherial without using umpteen ports on your controller. Basically every serial communication method needs a clock and a configuration on how to handle data connections.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SPI is a 4 wire bus.&#xA;I2C is a 2 wire bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each has different characteristics. What you need to answer is how fast does your communication need to be, how reliable does it need to be, what options does your microcontroller offer, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This &lt;a href=&quot;http://en.wikipedia.org/wiki/Serial_communications&quot; rel=&quot;nofollow&quot;&gt;wikipedia&lt;/a&gt; article and this &lt;a href=&quot;http://www.epanorama.net/links/serialbus.html&quot; rel=&quot;nofollow&quot;&gt;reference site&lt;/a&gt; explains much more clearly than I can, also follow the references to learn even more!&lt;/p&gt;&#xA;" OwnerUserId="909" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-07-14T12:51:18.493" LastActivityDate="2010-07-14T12:51:18.493" />
  <row Id="3466" PostTypeId="2" ParentId="3462" CreationDate="2010-07-14T13:10:16.100" Score="7" ViewCount="" Body="&lt;p&gt;If you're uncertain, and your requirements are pretty vague, I'd pick I²C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The major difference between SPI and I²C is that SPI requires a chip-select line for every peripheral. I²C broadcasts a peripheral address at the start of communication, so it doesn't need chip-select lines. Chip-select lines get cumbersome after the first few.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, SPI is probably easier to implement and debug. It could be the winner if you just want to connect to a couple of devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd rule out USB unless you need high data rates over relatively long distances (m rather than cm). I'd also rule out RS-232 unless it's still 1976 and your peripherals need a massive signal to distinguish a bit from noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might consider Dallas 1-wire, but I suspect it's not as common as I²C, and a &quot;1-wire&quot; bus that needs 2 wires to operate has always seemed a little fishy to me.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-14T13:10:16.100" CommentCount="4" />
  <row Id="3467" PostTypeId="2" ParentId="3433" CreationDate="2010-07-14T13:26:06.477" Score="1" ViewCount="" Body="&lt;p&gt;Don't forget programmable logic - CPLDs and FPGAs. By replacing discrete logic with a CPLD you aren't affected by parts being discontinued and can get a lot more performance, reduced size and lower cost. If you have an FPGA in the system you can implement a soft core in it, that can easily be upgraded if requirements change, and the whole thing can easily be made &quot;future-proof&quot;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-14T13:26:06.477" CommunityOwnedDate="2011-03-23T01:08:29.540" />
  <row Id="3468" PostTypeId="1" CreationDate="2010-07-14T13:49:59.587" Score="2" ViewCount="155" Body="&lt;p&gt;I need to read a value from a DIP switch. It is connected to ports  P1.16 till P1.21. I use following code:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;to initialize:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define PORT_ADDRESS                    0x003F0000&#xA;#define PORT_ADDRESS_OFFSET             16&#xA;&#xA;IODIR1 &amp;amp;= ~(PORT_ADDRESS);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;to read:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int value = (IOPIN1 &amp;amp; PORT_ADDRESS) &amp;gt;&amp;gt; PORT_ADDRESS_OFFSET;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The problem is that no matter what the DIP switch settings are, the value read is always zero. The code worked earlier, but it stopped, and I have no idea why. &lt;/p&gt;&#xA;" OwnerUserId="952" LastActivityDate="2010-09-28T23:23:07.060" Title="LPC2131 problem reading IO pins" Tags="&lt;arm&gt;&lt;pins&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="3469" PostTypeId="2" ParentId="3462" CreationDate="2010-07-14T13:57:33.040" Score="1" ViewCount="" Body="&lt;p&gt;I would use I2C. Just make sure that you can get a wireless module that can communicate over I2C if you want to have it on the same bus as your sensors. Most communications peripherals I've seen use SPI not I2C.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-07-14T13:57:33.040" />
  <row Id="3471" PostTypeId="2" ParentId="3468" CreationDate="2010-07-14T14:33:32.903" Score="1" ViewCount="" Body="&lt;p&gt;Function of the pins was not correctly selected. When microcontroller reset, value of P1.20 determines how the pins P1.16 till P1.23 will behave. In my case, when P1.20 was set to zero, it didn't work, and when set to one it worked.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fix: manually set pin functions using PINSEL2 register:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    PINSEL2 &amp;amp;= ~(0x8);&#xA;    IODIR1 &amp;amp;= ~(PORT_ADDRESS);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="952" LastActivityDate="2010-07-14T14:33:32.903" CommentCount="1" />
  <row Id="3472" PostTypeId="1" AcceptedAnswerId="3482" CreationDate="2010-07-14T16:53:45.100" Score="13" ViewCount="595" Body="&lt;p&gt;I have a course in Digital Design in this semester and just love it. Now I know that most of the work in embedded system and digital design is done on computer simulators first and then implemented using hardwares. So I was wondering how should I go about learning HDL. I have few questions&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What? I don't know what are the standards but would like to learn which is simple to pick up. I understand that most of the HDLs are designed for use with FPGAs I don't what that. &lt;/li&gt;&#xA;&lt;li&gt;How? Should I follow a text book with independent examples or should I embark upon a project like implementing a small system (may be something like traffic light control).&lt;/li&gt;&#xA;&lt;li&gt;Where? Where would I get the resources?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-03T14:01:40.173" LastActivityDate="2011-03-09T13:20:54.137" Title="How do I learn HDL" Tags="&lt;simulation&gt;&lt;vhdl&gt;&lt;verilog&gt;&lt;hdl&gt;" AnswerCount="7" CommentCount="6" FavoriteCount="6" />
  <row Id="3473" PostTypeId="2" ParentId="3462" CreationDate="2010-07-14T17:04:56.850" Score="2" ViewCount="" Body="&lt;p&gt;Since you said that it would be low bandwidth I would allocate enough IO to handle both SPI and I2C.  I would also if possible have additional CS lines so you can run multiple SPI devices. Also don't forget to look at how you are going to power the peripheral. If you are running off of a battery to get max life you need to put the device in low power mode or remove power when not in use. Also use you controllers serial controller module if possible a lot of controllers will mux SPI, I2C and serial. If you can and split the wireless from the sensor this makes it easier to shut down devices when not in use. Also some sensors have a line that will tell the controller when they need to be serviced so you also want to have an extra IO going into a pin ideally one you can generate an interrupt from.&lt;/p&gt;&#xA;" OwnerUserId="540" LastActivityDate="2010-07-14T17:04:56.850" />
  <row Id="3475" PostTypeId="1" AcceptedAnswerId="3495" CreationDate="2010-07-14T18:34:26.923" Score="5" ViewCount="537" Body="&lt;p&gt;I'm trying to find the best micro controller package for my computer programs to communicate with the real world. I am hoping for a large number of I/O pins (so far 64 digital is all i need, nothing fancy like analog and PWM) which an I can read and write directly by calling functions from my program running on my CPU. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't want to download programs onto the micro controller itself to run, rather i would like something that simply plugs into my USB and gives me a bunch of CPU controlled I/O pins that i can control from my C++ programs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be the best micro controller package for me? I hope for something that is fairly inexpensive but future proof, as in it runs off USB and has 64-bit drivers for modern OS like Windows 7. Being able to interface more than one of these micro controllers with the same computer program would be a great bonus as well (future expansion).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I don't need high sampling rates (maybe 10 Hz for reading inputs, 1 kHz for output signals) and most of the pins are used for output only. I am working with brand new computers (core i7 860) so even if the sampling is a bit inefficient or slow, it should still be ok (just have one thread dedicated to I/O and have the main program communicate with it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also don't need all 64 I/O pins on a single micro controller package. If i can interface many micro controller packages at the same time, that would work too (actually it would be ideal to be able to interface many smaller micro controller packages, that means it's easy to expand).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've looked at this: &lt;a href=&quot;http://www.schmalzhaus.com/UBW32/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.schmalzhaus.com/UBW32/index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone had any experience with something like this? Any idea if it will work or not? The main concern is that it is the micro controller that is running the program, not my CPU.&lt;/p&gt;&#xA;" OwnerUserId="942" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-31T12:59:35.767" LastActivityDate="2011-03-31T12:59:35.767" CommunityOwnedDate="2011-05-15T03:58:52.393" Title="What microcontroller should I use?" Tags="&lt;microcontroller&gt;" AnswerCount="8" CommentCount="3" />
  <row Id="3477" PostTypeId="2" ParentId="3472" CreationDate="2010-07-14T18:57:56.140" Score="8" ViewCount="" Body="&lt;p&gt;I'm almost in the same situation as you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'm doing:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd took a free very basic course of VHDL in the college that I'd studied. I'd played with &lt;a href=&quot;http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,792&amp;amp;Prod=S3EBOARD&quot; rel=&quot;nofollow&quot;&gt;Spartan 3E board&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I bought the board and I will start to play.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A friends of mine have suggested these books:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/Rapid-Prototyping-Digital-Systems-Hamblen/dp/0792374398&quot; rel=&quot;nofollow&quot;&gt;Rapid Prototyping of Digital Systems&lt;/a&gt; , James O. Hamblen,  Michael D. Furman&lt;/li&gt;&#xA;&lt;li&gt;Doone Publications - &lt;a href=&quot;http://www.amazon.com/Hdl-Chip-Design-Synthesizing-Simulating/dp/0965193438&quot; rel=&quot;nofollow&quot;&gt;HDL Chip Design&lt;/a&gt; , Douglas J Smith&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;And he have suggested this doc too:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xilinx.com/itp/xilinx10/books/docs/sim/sim.pdf&quot; rel=&quot;nofollow&quot;&gt;Xilinx Synthesis and Simulation Design Guide&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-07-14T18:57:56.140" CommentCount="1" />
  <row Id="3478" PostTypeId="2" ParentId="3475" CreationDate="2010-07-14T19:01:46.983" Score="3" ViewCount="" Body="&lt;p&gt;I think what you want is not a microcontroller, but something like a &lt;a href=&quot;http://sine.ni.com/nips/cds/view/p/lang/en/nid/12919&quot; rel=&quot;nofollow&quot;&gt;National Instruments PCI-6509 I/O card&lt;/a&gt;. You can get USB versions as well, but they have many fewer I/O than the PCI-6509. National Instruments will sell you C++ drivers as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that looks too expensive, you could try something like the &lt;a href=&quot;http://labjack.com/u3&quot; rel=&quot;nofollow&quot;&gt;Labjack U3&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-14T19:01:46.983" CommunityOwnedDate="2011-05-15T03:58:52.393" CommentCount="1" />
  <row Id="3479" PostTypeId="2" ParentId="3462" CreationDate="2010-07-14T19:28:08.950" Score="2" ViewCount="" Body="&lt;p&gt;Basically, you should choose between I2C and SPI.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regardless of which bus you use, you should consider the voltage level of your sensors and third party peripherials.  You can do this by making your own converter with two MOSFETS (Only goes one way - Pick up/no change or down/no change; only a problem if you need to run your sensors at 3.3 and interface with 1.8 and 5V masters).  See NXP's &lt;a href=&quot;http://www.nxp.com/documents/application_note/AN10441.pdf&quot; rel=&quot;nofollow&quot;&gt;AN10441&lt;/a&gt; [PDF]. This will also work for SPI (Just remove the pullups).  You will need to add a line to your connector to establish a reference voltage (if you're not doing so already.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One downside of I2C is that you're limited to the slowest clock on the bus.  If one sensor is only capable of 100kHz and you want to talk to your memory at 400kHz or 1MHz (both valid speeds), your slower sensor's behavior is unspecified.  If you use SPI, the chip select line means that the slower sensor won't even be listening to what's on the bus, and you can run different speeds for different sensors.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-14T19:28:08.950" />
  <row Id="3480" PostTypeId="2" ParentId="3475" CreationDate="2010-07-14T19:34:47.630" Score="2" ViewCount="" Body="&lt;p&gt;The solution you describe does not exist for lower prices. The problem is that you want to run the control software on a system that's not designed for it. Serializing 64 ports and pushing it through USB at high sampling rates slows down the host computer immensely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are solutions that work for low performance applications like the labjack mentioned. But the real solution you need to handle high IO rates will involve a programmed system. The question is what programming you have to use to implement the system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LabView is highly expensive software (which works great, don't get me wrong). It uses a graphical language to design software and compiles to code running on an FPGA or ARM system. All components are too expensive for a high volume embedded app, but absolutely wonderful in a testing environment because of the quick development, high performance offered.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A less expensive solution is to find a system that runs linux with many I/O. &lt;a href=&quot;http://www.embeddedarm.com/index.php&quot; rel=&quot;nofollow&quot;&gt;EmbeddedARM.com&lt;/a&gt; is a site that offers many types of products for this. The code you can write may be in shell scripts, java, C, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; systems provide microcontrollers that can be developed with a simpler development environment. Their open source nature means there are already &lt;a href=&quot;http://arduino.org&quot; rel=&quot;nofollow&quot;&gt;many projects&lt;/a&gt; to learn from.&lt;/p&gt;&#xA;" OwnerUserId="909" LastEditorUserId="909" LastEditorDisplayName="" LastEditDate="2010-07-14T19:47:55.253" LastActivityDate="2010-07-14T19:47:55.253" CommunityOwnedDate="2011-05-15T03:58:52.393" />
  <row Id="3481" PostTypeId="2" ParentId="3475" CreationDate="2010-07-14T19:37:43.133" Score="2" ViewCount="" Body="&lt;p&gt;i don't know of any with 64 GPIO pins, thats a lot, you may have to build that yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.diolan.com/i2c/u2c12.html&quot; rel=&quot;nofollow&quot;&gt;I use this&lt;/a&gt; for bench testing serial interfaces but it also has 23 GPIO pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you just google for 'USB to GPIO' there a bunch of projects out there that have done this, i didn't see any in the first couple pages with 64 GPIOs &lt;a href=&quot;http://www.xdimax.com/sub20/sub20.html?gclid=CKeUyf7d66ICFVs65QodCy-Xfw#usb_gpio&quot; rel=&quot;nofollow&quot;&gt;this is the closest i found, with 32 pins.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Building one wouldn't be very hard, i'd probably just use a 100pin pic18 with built in USB PHY (depending on your speed requirements a more powerful cpu may be in order) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;you wouldn't have to do too much coding to get it working as long as your uC vendor offers a USB driver skeleton.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would have to build a PCB for it most likely as chips that are large enough to have 64 GPIO pins generally do not come in through-hole packages.  You could also use a smaller microcontroller and use external port expander IC's for your GPIO's but that would be a more complex design and more complex to program.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also look at dev boards that route all I/O pins to headers and have USB.  These will likely be a lot more expensive as they will likely have a bunch of stuff you don't need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One final tip, if you find a board with RS232 but with 64 GPIO pins available, you can use an RS232 to USB adapter, &lt;a href=&quot;http://www.newegg.com/Product/Product.aspx?Item=N82E16812232006&quot; rel=&quot;nofollow&quot;&gt;i have a few of these&lt;/a&gt; that have worked well for me.  This does limit you to the speed of the RS232 interface however.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-07-14T19:48:05.893" LastActivityDate="2010-07-14T19:48:05.893" CommunityOwnedDate="2011-05-15T03:58:52.393" />
  <row Id="3482" PostTypeId="2" ParentId="3472" CreationDate="2010-07-14T19:50:00.500" Score="5" ViewCount="" Body="&lt;p&gt;Can you clarify what HDL you want to use?  The choices are basically Verilog or VHDL, [EDIT], and their relatives, &lt;a href=&quot;http://en.wikipedia.org/wiki/Verilog-AMS&quot; rel=&quot;nofollow&quot;&gt;Verilog-ASM&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/VHDL-AMS&quot; rel=&quot;nofollow&quot;&gt;VHDL-ASM&lt;/a&gt; (Analog mixed-signal).  [/EDIT]Verilog has some C-like syntax, which makes it easier to pick up if you've worked with C before, but this also makes it easy to develop bad habits - You can't program hardware in C, because it's all parallel!  Also like C, it assumes you know what you're doing, and it's easy to shoot yourself in the foot. VHDL forces you to think in a totally different way, which is helpful, but difficult.  It is more verbose, and more likely to warn you if you do something strange.  See this &lt;a href=&quot;http://ask.slashdot.org/article.pl?sid=09/05/31/187208&quot; rel=&quot;nofollow&quot;&gt;Slashdot discussion&lt;/a&gt;, or &lt;a href=&quot;http://www.angelfire.com/in/rajesh52/verilogvhdl.html&quot; rel=&quot;nofollow&quot;&gt;this article&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; The &quot;Netlist languages&quot; are not something I've used for design work (in a text editor), but I suppose that you could.  SPICE, Cadsoft Eagle's format, and EDIF are all examples (with very different purposes) that come to mind.   I've only used netlists to verify that my schematic is correct (does each connection in my Eagle schematic make sense), to tweak the abstraction provided by a simulator (SPICE, similar to the way one uses ASM statements in C), or to do export/import between different programs (EDIF).&lt;br&gt;&#xA;The &lt;a href=&quot;http://www.cadence.com/products/cic/spectre_circuit/pages/default.aspxhttp://www.cadence.com/products/cic/spectre_circuit/pages/default.aspx&quot; rel=&quot;nofollow&quot;&gt;Spectre&lt;/a&gt; netlisting language is related to Verilog-A[nalog] and SPICE, and is designed for design and verification work.  &lt;a href=&quot;http://www.openmast.org/overview/overview.html&quot; rel=&quot;nofollow&quot;&gt;MAST&lt;/a&gt; is a component modeling language which is compatible with Verilog-AMS and VHDL-AMS.  Searching for tutorials on these languages shows that tools which look like schematic capture utilities are often used, rather than programming in the netlisting language itself. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll also second the Xilinx Spartan FPGA, and a &lt;a href=&quot;http://www.digilentinc.com/Products/Catalog.cfm?NavPath=2,400&amp;amp;Cat=10&quot; rel=&quot;nofollow&quot;&gt;Digilent&lt;/a&gt; dev board.   However, I'd go with the Basys ($60) or Nexys ($100) if you don't need the Ethernet on the Starter board ($150) mentioned by O Engenheiro (Prices with education discount).  The Basys and Nexys are cheaper and therefore more popular in schools, so there are more tutorials and labs online.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-07-18T23:35:08.873" LastActivityDate="2010-07-18T23:35:08.873" CommentCount="2" />
  <row Id="3483" PostTypeId="2" ParentId="758" CreationDate="2010-07-14T20:10:34.623" Score="0" ViewCount="" Body="&lt;p&gt;First, for your particular application, you really only need 1 kHz or so sampling rate, assuming you're tuning the fundamental frequency and not &lt;a href=&quot;http://en.wikipedia.org/wiki/Inharmonicity#Guitar&quot; rel=&quot;nofollow&quot;&gt;one of the inharmonic partials&lt;/a&gt;...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, as for the maximum possible sampling rate, the &lt;a href=&quot;http://www.arduino.cc/en/Reference/AnalogRead&quot; rel=&quot;nofollow&quot;&gt;Arduino manual&lt;/a&gt; says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;It takes about 100 microseconds (0.0001 s) to read an analog input, so the maximum reading rate is about 10,000 times a second. &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This would imply 10 kHz sampling frequency is the max.  &lt;strong&gt;However.&lt;/strong&gt;  You can get higher sampling rates by &lt;a href=&quot;http://www.arduino.cc/en/Reference/PortManipulation&quot; rel=&quot;nofollow&quot;&gt;accessing the ADC registers directly&lt;/a&gt;.  The &lt;a href=&quot;http://interface.khm.de/index.php/lab/experiments/arduino-realtime-audio-processing/&quot; rel=&quot;nofollow&quot;&gt;Arduino Realtime Audio Processing&lt;/a&gt; page uses two channels at 15 kHz, for instance.  So the 10 kHz max is only while using the built-in AnalogRead() function, because it has a lot of overhead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ADC is optimized for best operation with a clock speed of between 50 kHz and 200 kHz:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;By default, the successive approximation circuitry requires an input clock frequency [ADC clock] between 50 kHz and 200 kHz to get maximum resolution.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Since an ADC conversion takes 13 clock cycles, this would be a sampling rate of 4 kHz to 15 kHz.  According to &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/DOC2559.PDF&quot; rel=&quot;nofollow&quot;&gt;AVR120: Characterization and Calibration of the ADC on an AVR&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;For optimum performance, the ADC clock should not exceed 200 kHz. However, frequencies up to 1 MHz do not reduce the ADC resolution significantly.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Operating the ADC with frequencies greater than 1 MHz is not characterized.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;1 MHz clock frequency = 77 kHz sampling frequency, so that's the realistic max.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The forum thread &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1208715493/11&quot; rel=&quot;nofollow&quot;&gt;Faster Analog Read?&lt;/a&gt; has more about this.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-14T20:10:34.623" />
  <row Id="3484" PostTypeId="1" CreationDate="2010-07-14T20:12:48.630" Score="2" ViewCount="174" Body="&lt;p&gt;I would like to build my own .100 (2.54mm) cables to mate with standard single and double row headers, but the 'rectangular connectors' section of distributors websites is huge. Which ones do you recommend? Can you recommend an IDC system that works with discrete wires (not ribbon cables)?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-07-15T17:36:35.527" Title="What cable assemblies do you recommend?" Tags="&lt;cable-assemblies&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="3485" PostTypeId="2" ParentId="3475" CreationDate="2010-07-14T20:13:25.370" Score="2" ViewCount="" Body="&lt;p&gt;The NI Labview environment is expensive, but it will do what you need (Over USB, Ethernet, or PCI depending on what you get.) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino Mega has 54 pins, which gets you close, for $60.  However, it's not a logic analyzer out of the box; you'd have to write or find a sketch to do this. There may be one available, I don't know.  This should be fairly simple at low bus rates.  Each instruction on the Mega happens at 16MHz, so you'll have a fairly slow baud rate, you'll be lucky or very clever if you can get a 115200 baud signal.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, this is a very different project if you're sampling at 9600 baud or at 50MHz.  Remember, USB runs at 480 MHz (In theory; your actual data rate will be lower due to latencies and overhead) so you can't do any better than 480/64 = 7.5MHz without buffering.  With buffering and obscene amounts of money (More than your car), logic analyzers can get you 68, 102, or 136 channels at gigahertz data rates. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would suggest that you very seriously try to figure out if you can use a tool that gives you 8 channels or so, and try to analyze them separately.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt;  Aargh, what was I thinking? If you're going at slow rates like that, then working over a serial link is definitely the way to go. I  use the &lt;a href=&quot;http://www.advantech.com/products/RS-485-I-O-Modules-ADAM-4000/sub_1-2MLKHT.aspx&quot; rel=&quot;nofollow&quot;&gt;ADAM 4000&lt;/a&gt; module system from Advantech  all the time at work; they're robust, easy to use (easily interfaced with an ASCII protocol over a COM port, or use the included GUI software), expandable, and well supported.  Get yourself a 4500 (RS-232, use a USB converter or COM port on your computer (if it's still got one)) or 4501 (Ethernet with embedded webserver) controller, link in a bunch of 4053, 4055, and 4056 modules, and you're good to go.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-07-15T01:46:59.010" LastActivityDate="2010-07-15T01:46:59.010" CommunityOwnedDate="2011-05-15T03:58:52.393" CommentCount="3" />
  <row Id="3486" PostTypeId="2" ParentId="3475" CreationDate="2010-07-14T21:19:26.150" Score="5" ViewCount="" Body="&lt;p&gt;I recommend a &lt;a href=&quot;http://www.pjrc.com/teensy/index.html&quot; rel=&quot;nofollow&quot;&gt;Teensy++ 2.0&lt;/a&gt; (or any other AT90USB1286 development board)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;128KB Flash, 8KB RAM, 46 I/O pins, 8 analogue inputs&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;$24&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Teensy boards are USB powered and can provide a virtual COM port (USB Communications Device Class). You could make use of this serial link for your pin control protocol.&#xA;This works without any custom drivers on Windows, OSX and Linux.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To create the pin control firmware, there's &lt;a href=&quot;http://www.pjrc.com/teensy/teensyduino.html&quot; rel=&quot;nofollow&quot;&gt;TeensyDuino&lt;/a&gt; or plain old C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When bit banging, the bottleneck is going to be the microcontroller's USB interface. So you may want to shift protocols such as I2C and SPI down to the microcontroller. For this you could use my &lt;a href=&quot;http://blog.hodgepig.org/busninja/&quot; rel=&quot;nofollow&quot;&gt;Bus Ninja&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adding additional Teensies to your setup is simple, you just need one USB port per device, presenting one virtual COM port per device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Note. This approach will work equally well with a whole range of ARM processors and others, I just don't know of any cheap development boards with available software).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way could be to use an Arduino and a &lt;a href=&quot;http://macetech.com/store/index.php?main_page=product_info&amp;amp;cPath=4&amp;amp;products_id=23&quot; rel=&quot;nofollow&quot;&gt;Caterpillar Shield&lt;/a&gt; to expand the I/O. On a custom board I built around the same I/O expander I was able to update 256 outputs at over 1KHz.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-14T21:24:32.450" LastActivityDate="2010-07-14T21:24:32.450" CommunityOwnedDate="2011-05-15T03:58:52.393" />
  <row Id="3487" PostTypeId="2" ParentId="3484" CreationDate="2010-07-14T22:28:19.503" Score="1" ViewCount="" Body="&lt;p&gt;It's not exactly what you asked for, but check out EMSL's article on &lt;a href=&quot;http://www.evilmadscientist.com/article.php/twistedwire&quot; rel=&quot;nofollow&quot;&gt;Twisted Wire Bundles&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4022/4662284949_6f2980ac07_m.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-14T22:28:19.503" CommentCount="3" />
  <row Id="3488" PostTypeId="1" AcceptedAnswerId="3489" CreationDate="2010-07-14T23:29:17.117" Score="1" ViewCount="159" Body="&lt;p&gt;I'm using an eZdsp board which has a TMS320f2812 chip on it. The board has a parallel port on it which is used to program it. I'm experienced with software but not at using microcontrollers or DSPs and don't know wher to begin with getting a simple program on, like to flash the built in LED on the board. I'm using windows 7 and have downloaded the latest code composer studio and have a parallel to parallel cable to connect from computer to board. So now what to get a program on there? Thanks&lt;/p&gt;&#xA;" OwnerUserId="927" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:17:45.660" LastActivityDate="2010-12-10T22:17:45.660" Title="How do you get a program onto an eZdsp board?" Tags="&lt;dsp&gt;&lt;programming&gt;&lt;ezdsp&gt;" AnswerCount="1" />
  <row Id="3489" PostTypeId="2" ParentId="3488" CreationDate="2010-07-14T23:50:01.373" Score="0" ViewCount="" Body="&lt;p&gt;I used an F2808 based ezDSP board, and it had an integrated USB JTAG programmer on the board. The parallel port interface on yours might also be connected to an integrated JTAG programmer, or if not, the Code Composer IDE is probably equipped to handle the details of the programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry I'm sketchy with the details, it's been a couple of years since I used it .. but look around on the Code Composer menus; somewhere there you should find the option to flash your project into the chip. In CCS 3.2, there was a dialog that could be brought up that listed all the flash banks, let you choose the .out image to flash, PLL multiplier value to use, etc. Device selection was on a nearby menu.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you solve the flashing-the-chip problem, I do recall the biggest pain getting started was dealing with the linker &quot;.cmd&quot; files that set the memory layout for the project. When you write C apps for linux or windows, you don't have to deal with these, but when you get as close to the metal as 28xx's with Code Composer, you have to say exactly what block of physical memory is to be used for what program segment. The easy way to get past the complexities of the .cmd file, initially anyway, was to steal one out of the example projects. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In fact, if your software has them, I'd recommend building and flashing one of the canned examples before setting out to write your own software. A search for 'examples' or 'samples' in the CCS install directory should turn them up.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-14T23:50:01.373" />
  <row Id="3490" PostTypeId="2" ParentId="3484" CreationDate="2010-07-15T00:28:32.940" Score="1" ViewCount="" Body="&lt;p&gt;They aren't IDC, since you do have to strip the wires, but we use &lt;a href=&quot;http://www.mouser.com/ProductDetail/Tyco-Electronics/87124-1/?qs=CPwo8WWixyFgmMyI9mg43g%3d%3d&quot; rel=&quot;nofollow&quot;&gt;these pins&lt;/a&gt; and &lt;a href=&quot;http://www.mouser.com/ProductDetail/Tyco-Electronics/87133-2/?qs=AplfTeSvkkA3LxfIeFJj0w%3d%3d&quot; rel=&quot;nofollow&quot;&gt;these shells&lt;/a&gt; or similar, depending on the number of positions required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We have the correct crimping tool, which is something like &lt;a href=&quot;http://www.mouser.com/ProductDetail/Tyco-Electronics/58448-3/?qs=KBHNWXOs3Q64021l8Po3lA%3d%3d&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;  (but that may not come with the right die for those specific pins).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's expensive, but then it's actually a bit more complicated than a regular pair of pliers. For one thing, it ratchets. When you put the pin in it and start to ratchet it closed, the die will line up and hold the pin while you insert the wire, so you don't feel like you need three hands. And unlike ordinary large automotive/appliance type crimp connectors, it doesn't just crush a tube in which you've inserted the wire. Rather, the die bends the tabs of the connector around and into the stripped wire, and bends the other tabs around the insulation. And it has an adjustable stop, so it will crimp each pin the same regardless of how hard you squeeze it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But that's for production work. For hobbyist use, you could roughly crimp these with small pliers, then carefully solder them.&lt;/p&gt;&#xA;" OwnerUserId="222" LastEditorUserId="222" LastEditorDisplayName="" LastEditDate="2010-07-15T14:46:16.970" LastActivityDate="2010-07-15T14:46:16.970" CommentCount="3" />
  <row Id="3491" PostTypeId="2" ParentId="758" CreationDate="2010-07-15T01:38:30.677" Score="0" ViewCount="" Body="&lt;p&gt;The on-chip converter will work for this application as others have pointed out, but you should really look into using an external ADC.  This will save you a lot of trouble, and free your micro to sample over SPI or I2C at much, mich higher data rates, with less noise from the micro's clock, and with greater precision than using the internal ADC.  If you want more resolution and/or a higher data rate, then use something like the LTC1867 , which will let you sample at up to 175kHz (Although you can clock it however quickly you want to) and then read out the 24-bit data at up to 20MHz over SPI.  See what a real ADC can do?  :)    With that kind of power (And a 24- or 32-bit DSP), you can compress and store your audio, filter it, modulate it, play it back... the possibilities are endless.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-15T01:38:30.677" />
  <row Id="3492" PostTypeId="2" ParentId="3484" CreationDate="2010-07-15T02:06:00.180" Score="2" ViewCount="" Body="&lt;p&gt;well, almost all of them that aren't specifically designed for ribbon cable or other specific cable types will work fine with discrete wires.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most of the easy to use ones aren't true IDC connectors as jeanne mentioned, and generally speaking the crimping tools are really expensive for small scale work ($150 for the tool, which is really just a pair of pliers in the right shape is normal).  You can hack crimp them and solder carefully and be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TBH any of the rectangular connectors in the correct shape/spacing are fine.  Look for the ones that best match your wire and look easy to crimp without the proper tool.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as i can tell in the production world its more or less a battle of who can provide the best automated tools for assembly as it is which shroud/crimp is 'better'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The twisted wire bundle things works OK as long as the signals on the wire don't have integrity issues.  If they do, do not try it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I ran into very much the same problem in the past when having to connect 2 pcb's together with relatively high frequency signals (multiple channels of ~3mhz I2S).  We ended up using the very thin plastic style ribbon cable (FFC or Flat Flexible Cable), the stuff you see on LCD screens or inside cell phones.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't honestly to this day know a good supplier for small quantities of this stuff.  I just asked our factory in china when they normally used and they sent over a bunch of connectors and cables for me to test and match the impedance of ( i think it was 3M's FFC series but not sure).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Worked great but I had a hell of a time attempting to find that stuff myself without it costing a fortune, like $5 for a 3inch cable, but like $0.40 from the factory.  If you can find it cost effectively, it really makes life easier for good controlled impedance interconnects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do find FFC parts for a reasonable price in low quantity let me know how :)&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-07-15T02:12:29.980" LastActivityDate="2010-07-15T02:12:29.980" CommentCount="4" />
  <row Id="3493" PostTypeId="2" ParentId="3484" CreationDate="2010-07-15T02:14:13.817" Score="0" ViewCount="" Body="&lt;p&gt;Why do you want to mate to [EDIT] standard, straight, unpolarized, non-locking [/EDIT] .1&quot; headers?  I'd strongly suggest going with something that's locking and polarized.  The AMP-Latch and mini-JST series both fit the bill [EDIT] and have a 0.1&quot; pitch. [/EDIT]  Mini-JST needs a crimper, AMP-Latch has both crimping options and IDC (designed for ribbon cable, it will work with discrete wires but I don't think you'll find anything marketed as such).  Remember that you can use .098&quot; connectors as well, don't limit yourself to 0.1&quot; for the 2/1000ths of an inch.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-07-15T17:36:35.527" LastActivityDate="2010-07-15T17:36:35.527" CommentCount="7" />
  <row Id="3494" PostTypeId="2" ParentId="2790" CreationDate="2010-07-15T02:57:36.117" Score="3" ViewCount="" Body="&lt;p&gt;I would not recommend the lithium batteries for low temperature applications.  They suffer badly from low temperature, more than either the alkaline or NiMH chemistries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd recommend Nickel-Cadmium (Ni-Cad) batteries, as they have have the best temperature range of any of the typical batteries, They also have very low internal resistance (less than half that of a NiMH) and therefore have very good maximum currents (think of an electric drill). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some things to watch out for are their memory characteristic (Don't recharge it before it's almost dead, or you'll lose the capacity you don't use) and the fact that they contain toxic cadmium.  Use a decent charger or charge IC, and you'll be fine.  You might have some trouble trying to do a dT(emp)/dt(ime) cuttoff, and they don't have a great -dV/dt characteristic either.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another idea (if you own the fridge) - Can you just open up the temperature control panel and light at the back of the fridge, get at the power source, say, for the light (before the switch, if you want it to be running when you close the fridge), and stick in an outlet or a couple (INSULATED! WELL INSULATED!) spade terminals and plug in a wall wart?  That's what I'd do, rather than messing with batteries.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-15T02:57:36.117" />
  <row Id="3495" PostTypeId="2" ParentId="3475" CreationDate="2010-07-15T04:33:00.983" Score="3" ViewCount="" Body="&lt;p&gt;Faken,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The UBW32 is a very good way to go, from what I can tell of your requirements. It will support exactly what you need, as long as you're OK with 3.3V I/O (some are 5V tolerant, but not all.) It is inexpensive ($40) and is very easy to talk to using any language that can support serial ports (which is pretty much all of them - Basic, C, C#, Processing, etc.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use any of the 76 I/O pins as inputs or outputs. The stock firmware as shipped will allow you to do what you want to do, no programming required on the embedded side. Getting that data up to the PC over USB (at only 10Hz) will be no problem. Getting outputs to go at 1KHz will probably work just fine as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have any questions, please let me know. I'm happy to help you out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*Brian Schmalz&#xA;UBW32 creator&lt;/p&gt;&#xA;" LastActivityDate="2010-07-15T04:33:00.983" CommunityOwnedDate="2011-05-15T03:58:52.393" CommentCount="2" />
  <row Id="3496" PostTypeId="1" AcceptedAnswerId="3505" CreationDate="2010-07-15T07:17:07.597" Score="1" ViewCount="214" Body="&lt;p&gt;I'm trying to use a spectrum digital XDS510PP parallel port to jtag emulator to program an ezdsp board. It's not working and I don't see any problem except that it only supports up windows XP. Is it possible that it just can't work with windows 7? thanks&lt;/p&gt;&#xA;" OwnerUserId="927" LastActivityDate="2010-07-15T11:14:48.883" Title="XDS510PP-PLUS JTAG Emulator on windows 7" Tags="&lt;ezdsp&gt;&lt;ccs&gt;&lt;programming&gt;" AnswerCount="1" />
  <row Id="3497" PostTypeId="1" AcceptedAnswerId="3500" CreationDate="2010-07-15T08:49:29.363" Score="1" ViewCount="144" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been trying to get this to work for a few days.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What i have at the moment is TouchOSC installed on my Iphone sending commands to a processing program, which in turn simplify's them and sends them off to my arduino through serial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is where my problem is the commands get there and I can print them out easy enough. They arrive correctly. Format is t11 or t10 (t for toggle control, then # for id of control changed, the last # is on or off (1 or 0)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now when I try and break this down with if statements it never seams to work. I know the data is correct when it gets to the arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to test if the first char is a 't' simple if statement&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if(Serial.read() == 't')&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;before this i test if&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Serial.available()&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;is true&#xA;then through similar if statements i test if next is the number '1' or '2' for the control id, then if number is on or off, '1' or '2'&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When i test this in Serial monitor or with real data off my phone never seam to get into the loops or will get it to one and not the other. Some times i can tweak it to get into all of them to switch the LED on, but then won't turn it off or vica-versa&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone please give me an example of the logic that i need to use, i have also tried using switch statements for the ID doesn't seam to make much difference&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="665" LastActivityDate="2010-07-15T17:36:57.033" Title="Serial nested if statements (Not working)" Tags="&lt;iphone&gt;&lt;serial&gt;&lt;processing&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="3498" PostTypeId="2" ParentId="3169" CreationDate="2010-07-15T09:01:17.693" Score="1" ViewCount="" Body="&lt;p&gt;I would go with the relay personally, quick and easy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Arduino to close the relay, NO connected to the switch. Easy as. Digital pin to run the relay. Sustained fire will work just keep the relay energised. Just make sure your relay can take the current from the switch it's replacing, which should be low anyway, and that the 5v from the arduino is enough to active the relay.&lt;/p&gt;&#xA;" OwnerUserId="665" LastActivityDate="2010-07-15T09:01:17.693" />
  <row Id="3499" PostTypeId="2" ParentId="3169" CreationDate="2010-07-15T09:10:33.590" Score="1" ViewCount="" Body="&lt;p&gt;Here's a bit of a tutorial on relays and Arduino:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tronixstuff.wordpress.com/2010/04/20/getting-started-with-arduino-chapter-three/&quot; rel=&quot;nofollow&quot;&gt;http://tronixstuff.wordpress.com/2010/04/20/getting-started-with-arduino-chapter-three/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-07-15T09:10:33.590" />
  <row Id="3500" PostTypeId="2" ParentId="3497" CreationDate="2010-07-15T09:13:15.360" Score="2" ViewCount="" Body="&lt;p&gt;Without seeing your code I'm taking a guess, but I suspect that you are entering into the code to parse before you have a full serial command available. So sometimes there's only 1 byte available and sometimes all 3 are there, hence the unpredictable behavior.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would change the first test to the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if (Serial.available() &amp;gt;= 3)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Which will wait until you have an entire command present before doing all the tests.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;/y&lt;/p&gt;&#xA;" LastActivityDate="2010-07-15T09:13:15.360" CommentCount="1" />
  <row Id="3501" PostTypeId="1" CreationDate="2010-07-15T09:46:53.467" Score="3" ViewCount="305" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am playing around with a few projects and looking at a few more online. I've had to make some trips to the local electronics shop for a few basic necessities like LEDs, resistors etc. It got me thinking about what would constitute a good set of basic and cheap components. Things that would be useful for random robotic/electronic projects. I have broken the set up into tools and components. I was hoping you guys can add/edit this and provide online links as well for future budding roboticists and electronic hobbyists. The primary requirement being cheap and versatile.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My List so far,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Tools&lt;/strong&gt; &lt;br/&gt;&#xA;Soldering Iron &lt;br/&gt;&#xA;Multimeter &lt;br/&gt;&#xA;A PCB Holder stand for help with soldering &lt;br/&gt;&#xA;Bread board &lt;br/&gt;&#xA;Solder and Solder remover &lt;br/&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Components&lt;/strong&gt; &lt;br/&gt;&#xA;Hobby resistor set (6 of each type for example) &lt;br/&gt;&#xA;Capicitors &lt;br/&gt;&#xA;LEDs &lt;br/&gt;&#xA;L293 motor driver chips &lt;br/&gt;&#xA;555 Timer chips  &lt;br/&gt;&#xA;Potentiometers (Pots)  &lt;br/&gt;&#xA;Transistors &amp;lt;- (What type?)  &lt;br/&gt;&#xA;Voltage Regulators &amp;lt;- (What type?)  &lt;br/&gt;&#xA;Switches &amp;lt;- (What type?)  &lt;br/&gt;&#xA;Relays &amp;lt;- (What type?) &lt;br/&gt;&#xA;Battery Holder case &lt;br/&gt;&#xA;Header for power supply wires &lt;br/&gt;&#xA;DC Motor(s) &lt;br/&gt;&#xA;Servo Motor(s) &lt;br/&gt;&#xA;Veroboard(s) &lt;br/&gt;&#xA;PIC Microcontroller(s) &lt;br/&gt;&lt;/p&gt;&#xA;" OwnerUserId="905" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T02:45:43.437" LastActivityDate="2011-02-08T07:56:29.490" CommunityOwnedDate="2010-07-15T09:46:53.467" Title="What is a general set of components for a robotics hacker?" Tags="&lt;components&gt;&lt;tools&gt;" AnswerCount="4" FavoriteCount="3" />
  <row Id="3502" PostTypeId="2" ParentId="3501" CreationDate="2010-07-15T10:11:17.000" Score="0" ViewCount="" Body="&lt;p&gt;An &lt;a href=&quot;http://en.wikipedia.org/wiki/In-system_programming&quot; rel=&quot;nofollow&quot;&gt;in-system serial programmer&lt;/a&gt; is a good tool if your going to get into micro controllers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also latching &lt;a href=&quot;http://en.wikipedia.org/wiki/Shift_register&quot; rel=&quot;nofollow&quot;&gt;shift registers&lt;/a&gt; are handy to have around should you need to expand the digital pins on your µController - I quite like using the 74HC595.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Micro switches and tactile switches are always handy, small, reliable, minimal bounce and not too expensive either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lastly - if you're not sure what value voltage regulators to get, why not get an adjustable one? The good old &lt;a href=&quot;http://www.national.com/mpf/LM/LM317.html#Overview&quot; rel=&quot;nofollow&quot;&gt;LM317&lt;/a&gt; works well, providing in excess of 1.5A over a 1.2V to 37V output range, it also has a negative voltage counterpart the LM337.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well that's my tuppence!  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;N.B - If you're prototyping robots a bag of &lt;a href=&quot;http://shapelock.com/index.html&quot; rel=&quot;nofollow&quot;&gt;Shape lock&lt;/a&gt; wouldn't go amiss. &lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-07-15T10:23:08.650" LastActivityDate="2010-07-15T10:23:08.650" CommunityOwnedDate="2010-07-15T10:11:17.000" CommentCount="1" />
  <row Id="3503" PostTypeId="2" ParentId="1409" CreationDate="2010-07-15T10:38:08.303" Score="1" ViewCount="" Body="&lt;p&gt;One maintenance shop I worked in had trace repair kits. They had various sections of straight traces and different types of pads. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Carefully remove any conformal coatings from the board, trim the new trace to size (about 5x the width of the trace works well for overlaps on each side,) and carefully solder it to the original trace. Clean it well, then cover it with conformal coating spray or a thin epoxy. I've been able to successfully fix some pretty bad boards (holes burned through) after filling any holes with epoxy, then using this method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, I don't know where to get these, but I would try any of the &quot;usual suspects&quot; such as DigiKey, etc...&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-07-15T10:38:08.303" />
  <row Id="3504" PostTypeId="2" ParentId="216" CreationDate="2010-07-15T11:08:16.090" Score="2" ViewCount="" Body="&lt;p&gt;This is going to sound kind of basic, but it took me a while to figure out that I had to occasionally pull the tip out of the iron, and clean out the socket and the back of the tip. Get enough rust or other junk in there and you'll never get good heat transfer from the iron's heater to the tip itself.&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-07-15T11:08:16.090" />
  <row Id="3505" PostTypeId="2" ParentId="3496" CreationDate="2010-07-15T11:14:48.883" Score="1" ViewCount="" Body="&lt;p&gt;I think it's an old unit, and would need to have a driver written for Windows 7. Very few, if any, systems running Windows 7 will even have a parallel port. The cheapest solution would be to use a Win XP system.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-15T11:14:48.883" />
  <row Id="3506" PostTypeId="1" AcceptedAnswerId="3510" CreationDate="2010-07-15T11:16:14.420" Score="8" ViewCount="463" Body="&lt;p&gt;I've been making a few hobbyist PCBs at home and note that the photoresist developer and ferric chloride etch solutions are both pretty nasty chemicals that come with all kinds of warnings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I've been extremely careful&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Wearing safety goggles while dealing with them.&lt;/li&gt;&#xA;&lt;li&gt;Wearing disposable gloves at all times and throwing them away afterwards.&lt;/li&gt;&#xA;&lt;li&gt;Wearing old heavy clothes so that a splash won't immediately touch skin.&lt;/li&gt;&#xA;&lt;li&gt;Rinsing everything with large amounts of water afterwards.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;My question is just how much of this is needed and how &quot;nasty&quot; are the chemicals?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I shall continue to wear goggles as they are no trouble and there seems no point risking eye damage however unlikely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But what about the rest? If I get a single drop of the photoresist developer or feric chloride on me (and wash it off quickly) is that likely to be a huge problem? If I've rinsed something badly and there is still a trace of diluted chemical on there is that harmful? For example I'm throwing away my disposable gloves every time. I don't believe I get significant amounts of either on there but I'm not taking any risks. I could always wash them and use them again but they are cheap so I don't. But what risk is there that a few drops were on there and didn't get entirely removed by washing and they touched my skin?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm of course not looking for someone to say go ahead, it's fine :) I'm just looking to know what the risks actually are so I can be an appropriate level of careful rather than over the top careful which I am now, which frankly can be a pain.&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2010-08-29T23:20:29.357" Title="Safety of making PCBs" Tags="&lt;pcb&gt;&lt;safety&gt;" AnswerCount="9" CommentCount="1" />
  <row Id="3507" PostTypeId="2" ParentId="3506" CreationDate="2010-07-15T11:19:38.970" Score="4" ViewCount="" Body="&lt;p&gt;Personally, I'm pretty cavalier. But, don't get ferric chloride on your clothes, it never comes out.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-15T11:19:38.970" />
  <row Id="3508" PostTypeId="2" ParentId="3506" CreationDate="2010-07-15T12:03:37.443" Score="7" ViewCount="" Body="&lt;p&gt;For a definitive answer, consult the Material Safety Data Sheets (MSDS) associated with the products you are using. According to USA laws, at least, the manufacturer is required to make MSDSs available on request. Simply doing a Google search with the product name and &quot;msds&quot; will usually get results.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An MSDS is a bit difficult to read, and there is no real standard format, but you should be able to find out what you need for protective clothing, eyewear, and the like. Also included are many other topics, such as fire and explosion data, and HAZMAT transportation information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Going beyond the MSDS; doing a search of the primary ingredients listed should turn up good data if you're interested in long-term effects such as carcinogens and the like.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-07-15T12:03:37.443" CommentCount="2" />
  <row Id="3509" PostTypeId="2" ParentId="3506" CreationDate="2010-07-15T12:45:46.653" Score="6" ViewCount="" Body="&lt;p&gt;I'd agree with Jesse, go to the official government stuff for details - if you're worried.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But.....from purely an experiential standpoint -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To be honest I've had ferric chloride on my skin more times than I'd care to mention, however I do use thick rubber gloves and ventilation whilst etching. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I get it on my skin I'll just stop.....pop my PCB in a sink/bucket of water (if i'm etching caveman stye) remove gloves, then get plenty of water on the area and give it a good wash off. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A while ago - I was alone at home etching and I got a splash of ferric chloride in my eye!....didn't have time to save the board...but got to the kitchen sink and put my eye under the tap whilst blinking franticly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My eye was fine afterward, but it could have been worse (may have tripped and hurt myself!)...so next time I'm etching alone I'll take extra precautions with eye protection!&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-07-16T14:34:41.870" LastActivityDate="2010-07-16T14:34:41.870" />
  <row Id="3510" PostTypeId="2" ParentId="3506" CreationDate="2010-07-15T13:10:07.643" Score="11" ViewCount="" Body="&lt;p&gt;The developer is simply a dilute alkali, I use 12g of NaOH in a litre of water. It's quite safe but don't get it in your eyes and wash it off if you get it on the skin. Ferric chloride is quite safe, just wash it off if it gets on the skin. I always wear rubber gloves, both for protection and so that I can use hot etchant with manual agitation (I put the etchant and board in a small container in an old washing-up bowl with about 1&quot; of just boiled water in it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been making my own PCBs at home for about 40 years, using ferric chloride mostly. The only accident I've had that could have been serious was when I was walking across the room with an open bottle of conc. HCl in my hand, tripped, and a little splashed on my face next to an eye. I thought it might have got in the eye, but the fumes were bad enough. I immediately put my face under a tap and flushed the eye out for several minutes. It was sore for a few hours, but there was no damage.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-07-15T13:16:27.027" LastActivityDate="2010-07-15T13:16:27.027" CommentCount="1" />
  <row Id="3511" PostTypeId="1" AcceptedAnswerId="3515" CreationDate="2010-07-15T13:47:26.410" Score="2" ViewCount="269" Body="&lt;p&gt;What is the best humidity level for an electronic shop? On one end of the scale, you will have problems from corrosion due to high humidity and condensation, but at the other end there will be serious problems from ESD.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've worked in shops at either extreme end of the scale, and would imagine the ideal level being around 50% relative humidity. Thoughts?&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-07-15T15:45:57.677" Title="Best humidity level for electronic shops?" Tags="&lt;esd&gt;&lt;best-practice&gt;&lt;corrosion&gt;" AnswerCount="3" />
  <row Id="3512" PostTypeId="2" ParentId="216" CreationDate="2010-07-15T14:33:57.163" Score="0" ViewCount="" Body="&lt;p&gt;Sometimes when it takes an iron a long time to melt solder, the problem is that oxides have built up in the thermal joint between the heating element and the tip, reducing the ability of the element to keep the tip hot. This is easily remedied by simply loosening and re-tightening the screw or collar the holds the tip in contact with the heating element.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With gun type irons, there are usually two set screws, one for each leg of the tip. In this case, the tip &lt;em&gt;is&lt;/em&gt; the element, so the oxides present electrical resistance, but this accomplishes pretty much the same lack of heating. Just backing the set screws off half a turn and re-tightening is usually enough to restore the heat to this type of iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, it doesn't hurt to periodically take these things apart, and clean them up with a small wire brush, either. I use the same brush for this that I use to shine up component leads and surfaces before soldering them.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-15T14:33:57.163" />
  <row Id="3513" PostTypeId="2" ParentId="3" CreationDate="2010-07-15T14:39:45.517" Score="2" ViewCount="" Body="&lt;p&gt;It's a tricky topic to get good information on, but lead-free solder's supposed to be worse for you, overall.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The transition to lead-free soldering&#xA;  has reduced strain on the environment,&#xA;  but for the operator, the hand&#xA;  soldering process has become more&#xA;  dangerous. The lead in the solder is&#xA;  gone, but to get the solder wire to&#xA;  flow properly, substantially more flux&#xA;  must be used. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The temperature needed to create a&#xA;  good solder joint using lead-free&#xA;  solder is also higher, causing a&#xA;  stronger reaction within the flux and&#xA;  creating more solder smoke with a&#xA;  greater number of particles. Lead-free&#xA;  soldering produces up to 250 % more&#xA;  particles between 0.5 and 1.0 microns&#xA;  in diameter, the size that is the most&#xA;  dangerous to inhale. In addition to&#xA;  particles, solder smoke can contain&#xA;  isocyanates, aldehydes, and other&#xA;  unhealthy substances.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.wellerzerosmog.com/health_risk/&quot; rel=&quot;nofollow&quot;&gt;http://www.wellerzerosmog.com/health_risk/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Recent research has suggested that the fumes and vapours emanating from lead-free solders may be even more dangerous to workers and the environment than those emitted by traditional lead containing solders&#xA;  And it is these fumes that seem to pose the most immediate risk. Many of these lead-free solders use rosin as a fluxing agent. Tin-lead solders melt at around 180°C, whereas lead-free solders melt at temperatures 30-40°C higher. The fear is that that the higher temperatures required for lead-free soldering will significantly increase the amount of fume produced. As solder fume is one of the top eight causes of occupational asthma, Britain's Health and Safety Executive is very concerned about workers breathing in fumes from solders containing rosin-based fluxes, also known as 'colophony fume'. Anyone soldering with rosin-based fluxes is at risk of developing asthma.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dataweek.co.za/article.aspx?pklArticleId=3959&quot; rel=&quot;nofollow&quot;&gt;http://dataweek.co.za/article.aspx?pklArticleId=3959&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yet Wikipedia claims&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The use of lead-free solders and components has provided immediate health benefits to electronics industry workers in prototype and manufacturing operations. Contact with solder paste no longer represents the same health-hazard it did before.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;You also have to worry about &lt;a href=&quot;http://en.wikipedia.org/wiki/Whisker_%28metallurgy%29&quot; rel=&quot;nofollow&quot;&gt;tin whiskers&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-15T14:39:45.517" />
  <row Id="3514" PostTypeId="2" ParentId="3484" CreationDate="2010-07-15T14:44:11.330" Score="2" ViewCount="" Body="&lt;p&gt;We've used ITW PANCON &lt;a href=&quot;http://www.connectorcenteritw.com/mascon.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;MAS-CON&quot;&lt;/a&gt; series connectors. (single row, available in 0.1&quot; or 0.156&quot; spacing) They work pretty nicely, the crimper tool isn't very expensive.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-07-15T14:44:11.330" />
  <row Id="3515" PostTypeId="2" ParentId="3511" CreationDate="2010-07-15T14:56:05.733" Score="2" ViewCount="" Body="&lt;p&gt;Just working with grounded wrist-straps, and keeping major ESD generating clutter to a minimum, you shouldn't have much problem down to about 40% relative humidity. However, below 35% or 40%, you should start being extra vigilant. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, it's always a good idea to keep styrofoam packing material, wool sweaters, polyester fleeces, and rolls of packing tape away from your ESD-safe work area, but when the humidity is very low, even ordinary paper can start to be a problem. An ordinary laminated surface that might be passable at high humidity can start to cause problems when the air gets very dry. The professionals use grounded mats on the workbench surface all the time. When the air is very dry, ionizing fans become necessary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, you can work with almost any R.H., depending on the level of protection measures you have in place.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-15T14:56:05.733" CommentCount="4" />
  <row Id="3516" PostTypeId="2" ParentId="3501" CreationDate="2010-07-15T15:15:57.940" Score="3" ViewCount="" Body="&lt;p&gt;We discussed a few similar questions previously (though never specifically for robotics):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/2320/what-are-the-best-useful-variety-ics-to-have-around-for-pic-microcontrollers&quot; rel=&quot;nofollow&quot;&gt;ICs for microcontrollers?&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/966/which-electronics-components-should-i-always-have-on-hand&quot; rel=&quot;nofollow&quot;&gt;General components&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/3382/what-equipment-for-electronics-should-i-always-have-on-hand&quot; rel=&quot;nofollow&quot;&gt;Equipment&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-15T15:15:57.940" CommunityOwnedDate="2010-07-15T15:15:57.940" />
  <row Id="3517" PostTypeId="2" ParentId="3511" CreationDate="2010-07-15T15:39:41.953" Score="1" ViewCount="" Body="&lt;p&gt;50% seems a bit low. Corrosion of metallic parts has never been an issue in my experience, and condensation is usually not an issue in a climate-controlled building unless you bring metallic parts in from the cold in winter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd probably shoot for something in the 70% range to be safe.&lt;/p&gt;&#xA;" OwnerUserId="875" LastActivityDate="2010-07-15T15:39:41.953" CommentCount="2" />
  <row Id="3518" PostTypeId="1" AcceptedAnswerId="3521" CreationDate="2010-07-15T15:45:30.540" Score="1" ViewCount="896" Body="&lt;p&gt;Does anyone have experience using CCSv4 to program for the MSP430 chips? I know msp-gcc is out there, and I'm sort of kicking myself for not using it, but at this point I'm stuck with CCSv4. I was drawn in by the fact that it was built on Eclipse, but I'm uninspired by the level of library/header file support that exists. I've had very little luck in even getting the UART to work correctly, and I won't even go into my struggles with printf. Does anyone have any advice on making the most of CCSv4 for MSP430 work? Maybe it's just me and I haven't tapped into some awesome resource yet... (I've already seen the MSP code examples provided by TI for my MSP430 family, and I've signed up on TI's e2e community...)&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-07-15T17:42:44.907" Title="Code Composer Studio v4 and MSP430 development" Tags="&lt;msp430&gt;&lt;microcontroller&gt;&lt;ide&gt;&lt;ccs&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="3519" PostTypeId="2" ParentId="3511" CreationDate="2010-07-15T15:45:57.677" Score="4" ViewCount="" Body="&lt;p&gt;There are also ergonomic factors, human beings work best at 40% to 60% RH.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-15T15:45:57.677" />
  <row Id="3520" PostTypeId="2" ParentId="3518" CreationDate="2010-07-15T15:50:07.067" Score="0" ViewCount="" Body="&lt;p&gt;You have to pay for the software ($150 for a personal license) but I can recommend the &lt;a href=&quot;http://www.rowley.co.uk/&quot; rel=&quot;nofollow&quot;&gt;Rowley Associates tools&lt;/a&gt; for the MSP430. I once tried Code Composer, but didn't like it at all.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-15T15:50:07.067" CommentCount="3" />
  <row Id="3521" PostTypeId="2" ParentId="3518" CreationDate="2010-07-15T16:10:57.650" Score="3" ViewCount="" Body="&lt;p&gt;I just got one of those $4.30 MSP-EXP430G2 boards, and, having worked with both Eclipse and CCSv3 (the full license version), I also downloaded CCSv4, thinking that would be the path with the easiest learning curve.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There may be some kind of tutorial on &lt;a href=&quot;http://www.ti.com/launchpadwiki&quot; rel=&quot;nofollow&quot;&gt;the MSP430 launchpad wiki&lt;/a&gt;, but I haven't found it yet. Ideally there should be a how-to that shows, starting from scratch, how to create a project and get it into the device. If I &lt;em&gt;do&lt;/em&gt; find such a thing, I'll edit this post to try to include the correct link.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-07-15T17:42:44.907" LastActivityDate="2010-07-15T17:42:44.907" CommentCount="3" />
  <row Id="3522" PostTypeId="2" ParentId="3497" CreationDate="2010-07-15T17:28:45.550" Score="2" ViewCount="" Body="&lt;p&gt;Although I'm not familiar with Arduino programming, if you have a series of if statements like if(Serial.read() == 't') then I believe the first one probably is gobbling up the character from the serial port, and in then the next test if(Serial.read() == '1') the port will be empty and the character gone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead, you want to save the character in a variable, and then test the variable:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ch = Serial.read();&#xA;if (ch == 't')&#xA;  ...&#xA;else if (ch == '1')&#xA;  ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;etc.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-07-15T17:36:57.033" LastActivityDate="2010-07-15T17:36:57.033" CommentCount="1" />
  <row Id="3523" PostTypeId="2" ParentId="146" CreationDate="2010-07-15T22:50:00.433" Score="3" ViewCount="" Body="&lt;p&gt;At the moment i am doing something similar with a light show.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use TouchOSC on the IPhone to send signals to your computer which can then send them to the arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My set up is IPhone(Touch OSC) -&gt; Processing -&gt; Arduino&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Works a treat I am tidying up my code now will post a link to it if you like. -&lt;/p&gt;&#xA;" OwnerUserId="665" LastActivityDate="2010-07-15T22:50:00.433" />
  <row Id="3524" PostTypeId="2" ParentId="3475" CreationDate="2010-07-15T23:33:14.090" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9931&quot; rel=&quot;nofollow&quot;&gt;This thing&lt;/a&gt;'s got 70 GPIOs and a USB interface for $50.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-15T23:33:14.090" CommunityOwnedDate="2011-05-15T03:58:52.393" CommentCount="3" />
  <row Id="3525" PostTypeId="1" AcceptedAnswerId="3526" CreationDate="2010-07-16T00:22:44.617" Score="6" ViewCount="539" Body="&lt;p&gt;I am a professional software developer who is used to the luxuries of integrated debuggers.  For a while now, I have been experimenting with the Arduino platform.  However, I find that attempting to interface with components like a Dallas DS1820 digital temperature sensor is like fumbling around in the dark.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming a loose budget of $200 or so, what kind of tools are there to help me visualize what's going on?  I have looked at the Link Instruments MSO-19, but I honestly don't know a whole lot about the difference between an oscilloscope and a logic analyzer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I know that the device I buy will be capable of measuring the types of (simple) components I am using?&lt;/p&gt;&#xA;" OwnerUserId="971" LastActivityDate="2010-07-16T19:47:18.317" Title="Best tools to debug simple digital circuits?" Tags="&lt;arduino&gt;&lt;oscilloscope&gt;&lt;logic-analyzer&gt;&lt;beginner&gt;" AnswerCount="8" FavoriteCount="3" />
  <row Id="3526" PostTypeId="2" ParentId="3525" CreationDate="2010-07-16T00:34:38.023" Score="7" ViewCount="" Body="&lt;p&gt;essentially, an oscilloscope gives you a graded reading of the voltage on the line while a logic analyzer will only tell you if it is 0 or &quot;high&quot; (the value of &quot;high&quot; could potentially be 5V, 3.3V or 1.8V depending on your circuit). You will often see that logic analysers have many more channels (lines that can be read simultaneously) than oscilloscopes because of the lower resolution required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for a specific device, I have heard great things about the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8938&quot; rel=&quot;nofollow&quot;&gt;Saleae Logic&lt;/a&gt;. It samples at  24MHz; this means it checks if the voltage on a particular probe is high or low 24 million times a second. The software also appears to have some knowledge of the common embedded protocols to aid debugging. I would imagine that 24MHz would be enough for arduino work as the maximum clock speed of the Atmegaxx8 is 20MHz.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-07-16T00:34:38.023" CommentCount="2" />
  <row Id="3527" PostTypeId="2" ParentId="3525" CreationDate="2010-07-16T00:35:00.600" Score="7" ViewCount="" Body="&lt;p&gt;If you plan to work mainly on digital circuits, the logic analyzer is what you want. Oscilloscopes excel at showing a relatively few (e.g., 2-4) analog signals in fine detail, whereas logic analyzers, since they are concerned mainly with high-vs-low usually have a great many more inputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can certainly use an O-scope as a logic analyzer, but the advantage with the latter is that it's easier to get 'the big picture' by being able to watch dozens of signals simultaneously.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-16T00:35:00.600" />
  <row Id="3528" PostTypeId="2" ParentId="3525" CreationDate="2010-07-16T01:34:13.187" Score="8" ViewCount="" Body="&lt;p&gt;this is just an addition to penjuin's answer as it didn't fit in a comment and his answer is generally correct.  Just want to clarify an implication in his answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be very careful choosing a measurement device based on its bandwidth/sampling rate.  A device with a 25mhz sampling rate can not accurately sample a 25mhz digital clock signal, not even close. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you take a digital clock signal at 25mhz and feed it into an o-scope with a &lt;strong&gt;bandwidth&lt;/strong&gt; of 25mhz you will see something close to a sine wave.  A scope with a 25mhz &lt;strong&gt;sampling rate&lt;/strong&gt; would probably show a DC level since per Nyquist, the highest frequency signal such a scope could sample would be 12.5mhz.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A square wave contains is fundamental frequency which is its clock rate, for this example 25mhz.  It also contains large odd harmonics which give its square shape, to look at a 25mhz digital clock signal with accuracy you would need to not only look at 25mhz but 75, 125, 175, 225, etc.  How far you need to go is up to your desired accuracy or up to the slew rate of the transceiver. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;While this is slightly less important for a logic analyzer is still very important.  The logic analyzer is looking for a 'high' and a 'low' above or under some threshold.  If what is sees coming in is a sine wave you will see artificially short high and low states and artificially long spaces between bits.  This can be somewhat dependent on the architecture of the analyzer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This can make diagnosing issues related to various transmit modes impossible.  For instance SPI has 4 different modes based on data being valid on the rising or falling clock edges and also on data polarity (is high a 1 or a 0?).  Other transmission protocols also have this issue (I2S and related audio formats for example).  If you can't accurately identify when the edge transitions take place its nearly impossible to determine if the bus is acting within specification.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally you need bandwidth/sampling rates much higher than your intended target data rate.  If you want to sample a 40khz I2C bus, a logic analyzer with a sampling rate of 100mhz is more than enough.  If you need to sample a 25mhz SPI bus you need to have a scope/analyzer with a much higher bandwidth, something near 500mhz if you need real accuracy, as well as a sampling rate that allows measurement in that frequency range. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the device penjuin recommended with a sampling rate of 24mhz can likely only provide accurate measurement of digital signals that are less than ~2mhz with a slew rate appreciable to that data rate.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-07-16T16:07:36.523" LastActivityDate="2010-07-16T16:07:36.523" CommentCount="5" />
  <row Id="3529" PostTypeId="2" ParentId="3525" CreationDate="2010-07-16T01:49:26.390" Score="1" ViewCount="" Body="&lt;p&gt;I own an MSO-19 and like it a great deal.  I wish it had more than one analog channel, but it does function as both an oscilloscope and a logic analyzer.  For the price, I think it's a nice piece of equipment (and runs well in VMWare on OS X).  The o'scope's helped me see what's really happening in a part of the circuit, and doesn't show you just the high/low state of a digital line, as a logic analyzer does.  It's a far more accurate (and faster responding) volt meter than your standard multimeter.  It would be really nice if it could decode serial data, however, instead of just I2C and SPI…&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-07-16T01:49:26.390" />
  <row Id="3530" PostTypeId="1" AcceptedAnswerId="3531" CreationDate="2010-07-16T02:31:33.343" Score="1" ViewCount="42" Body="&lt;p&gt;I downloaded a program from texas instruments, PMSM3-2, which is made for code composer studio 3. I only have code composer 4, when attaempting to build it I get the errors:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;'Building target: C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/build/pmsm3_2.out'&#xA;'Invoking: Linker'&#xA;&quot;C:/Program Files/Texas Instruments/ccsv4/tools/compiler/c2000/bin/cl2000&quot; -@ccsLinker.opt -o &quot;C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/build/pmsm3_2.out&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;undefined                   first referenced&lt;br&gt;&#xA;  symbol                         in file&lt;br&gt;&#xA; ---------                   ----------------&lt;br&gt;&#xA; _DLOG_4CH_init              C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _DLOG_4CH_update            C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_EV1_DRIVE_Init       C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_EV1_DRIVE_Update     C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_EV1_PWM_Init         C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_EV1_PWM_Update       C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_EV1_QEP_Calc         C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_EV1_QEP_Init         C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_EV1_QEP_Isr          C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_EV2_PWMDAC_Init      C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_EV2_PWMDAC_Update    C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_ileg2_dcbus_drv_init C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _F281X_ileg2_dcbus_drv_read C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _clarke_calc                C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _ipark_calc                 C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _park_calc                  C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _phase_voltage_calc         C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _pid_reg3_calc              C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _rampgen_calc               C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _rmp_cntl_calc              C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _speed_est_calc             C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _speed_frq_calc             C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _speed_prd_calc             C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&#xA; _svgendq_calc               C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj&lt;/p&gt;&#xA;&#xA;&lt;p&gt;error: unresolved symbols remain&#xA;error: errors encountered during linking;&#xA;   &quot;C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/build/pmsm3_2.out&quot; not&#xA;   built&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;blockquote&gt;&#xA;    &lt;p&gt;Compilation failure&lt;/p&gt;&#xA;  &lt;/blockquote&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Is there something I need to change to make it work with ccs4?&lt;/p&gt;&#xA;" OwnerUserId="927" LastActivityDate="2010-07-16T02:58:40.267" Title="Unresolved symbols building a code composer 3 project in code composer 4" Tags="&lt;ccs&gt;&lt;ccs&gt;&lt;ezdsp&gt;&lt;programming&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="3531" PostTypeId="2" ParentId="3530" CreationDate="2010-07-16T02:58:40.267" Score="1" ViewCount="" Body="&lt;p&gt;There is a device-specific library you have to include that defines the I/O devices as they are on your cpu, and another library that supplies the 'IQ math' routines. I don't have access to the CCSv3/ezDSP setup I worked with a year or two ago (long weekend!), but I think at least the IQ math library was IQmath.lib, or possibly IQmath.out; the F2808 in that project required including a file with a name something like ml28xx.out. Sorry I can't get these file names right until probably Monday evening, but if you search for ml28* and/or IQmath* in the C:\tidcs tree, you might be able to find them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On CCSv3, there was a dialog for compiler/linker options where you could name these libraries as part of your project. Not sure where these would be with the new Eclipse based CCSv4. Perhaps the eclipse way of right clicking the project name, and looking for 'build properties' would reveal the dialog you need.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-16T02:58:40.267" />
  <row Id="3532" PostTypeId="2" ParentId="3419" CreationDate="2010-07-16T05:48:15.967" Score="3" ViewCount="" Body="&lt;p&gt;reemrevnivek has the right idea, but there's a better way.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;WDTC = 1024;              // short timeout; we don't care (won't be using it)&#xA;WDMOD = WDEN | WDRESET;   // watchdog resets CPU&#xA;WDFEED = 0xAA;            // start ...&#xA;WDFEED = 0x55;            // ... watchdog.&#xA;WDFEED = 0xAA;            // start ...&#xA;WDFEED = 0x00;            // ... invalid WDFEED sequence causes instant reset.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;That will give you an immediate reset without the need for waiting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that simply jumping to location 0 isn't the same as a real reset. Jumping to 0 doesn't reset any peripherals nor does it reset the ARM core's state. It may sound like I'm nitpicking here, but you can run into some very unusual and difficult to debug issues if you are expecting a reset and don't actually get one.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-16T05:48:15.967" />
  <row Id="3533" PostTypeId="2" ParentId="3382" CreationDate="2010-07-16T05:58:21.157" Score="2" ViewCount="" Body="&lt;p&gt;I've never bought a bench supply new; I have several second (and third, and worse!) hand bench supplies that have done a superb job. No need for fancy eight decimal point displays... a couple of panel meters and an adjustable current limit are all you really need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd throw into the mix the following&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Aligator clips (both the normal kind and the really tiny &quot;grabber&quot; variety&lt;/li&gt;&#xA;&lt;li&gt;tweezers, and reverse tweezers (they open when you squeeze them)&lt;/li&gt;&#xA;&lt;li&gt;locking &quot;scissors&quot; (they don't cut) - great for clamping&lt;/li&gt;&#xA;&lt;li&gt;light. A couple of gooseneck lamps with &quot;150W&quot; compact fluorescent bulbs&lt;/li&gt;&#xA;&lt;li&gt;collection of banana jacks/sockets and pushbutton and slide/toggle switches&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I also second the magnification. I splurged and found a nice binocular inspection microscope (0.8 - 3x magnification I think). It was about $700 but it's sure handy when trying to solder 0402 components or solder 30AWG on to 0.5mm pitch devices! I don't need a fancier soldering iron than my old Weller WES51 if I've got a decent scope. I get headaches from trying to use loupes or the (much) cheaper magnifier on a swingarm.&lt;/p&gt;&#xA;" OwnerUserId="974" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-24T12:32:57.237" LastActivityDate="2011-02-24T12:32:57.237" CommunityOwnedDate="2010-07-16T05:58:21.157" />
  <row Id="3534" PostTypeId="2" ParentId="3374" CreationDate="2010-07-16T06:10:56.310" Score="0" ViewCount="" Body="&lt;p&gt;It sounds like you want to attach a servo or stepper to a pot and use an ADC to measure your dependent variable, whether it be the response of the system the pot controls (amp, fader, equalizer, etc.) or simply the resistance from the wiper to one of the ends.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-16T06:10:56.310" CommentCount="1" />
  <row Id="3535" PostTypeId="2" ParentId="3525" CreationDate="2010-07-16T09:08:13.133" Score="1" ViewCount="" Body="&lt;p&gt;This answer probably isn't much use to you using ardunio but is an answer to the general question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use the logic analyser functions of my pickit2 a great deal. Clearly it's meant for programming PICs but it also has a 3 channel logic analyser mode which I use all the time for looking at digital signals. I still use it for that even though I'm using Cortex-M3 for my current projects. Clearly its an extremely primitive tool by the standard of proper gear but even so I find it incredibly useful&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used it to debug I2C circuits and TV output signals too for example see my post &lt;a href=&quot;http://chiphacker.com/questions/3083/generating-pal-tv-signal-using-a-pic&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2010-07-16T09:08:13.133" />
  <row Id="3536" PostTypeId="2" ParentId="3506" CreationDate="2010-07-16T11:52:39.467" Score="4" ViewCount="" Body="&lt;p&gt;My worst chemical mishap was probably when I was supergluing some things together and a part slipped and splashed little glue droplets around the desk and me. My first thought was, did I really manage to make drops of flying cyanoacrylate and what if one had hit my eye. I still don't wear goggles while etching or even gloves (I use tweezers, wire, and cotton swabs etc to manipulate the parts), though I do in a lot of other things. I tend towards paranoid carefulness in general otherwise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the important thing in dealing with chemicals is general hygiene. Don't let the chemicals touch anything you haven't intended to contaminate. Always keep a separate spoon/measure/jar/tweezers/spoon for each chemical etc. Store things in appropriate ways, label things and keep foodstuffs well away from toxic things. Know the particular ingredients and their behaviour as well as you can.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-16T11:52:39.467" />
  <row Id="3537" PostTypeId="2" ParentId="3525" CreationDate="2010-07-16T11:55:35.173" Score="2" ViewCount="" Body="&lt;p&gt;There are some good answers to this similar question: &lt;a href=&quot;http://chiphacker.com/questions/2036/beginners-logic-analyzer&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/2036/beginners-logic-analyzer&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-16T11:55:35.173" />
  <row Id="3538" PostTypeId="2" ParentId="3525" CreationDate="2010-07-16T14:03:13.437" Score="0" ViewCount="" Body="&lt;p&gt;This is pretty cool, and really cheap: &lt;a href=&quot;http://www.seeedstudio.com/depot/preorder-open-workbench-logic-sniffer-p-612.html?cPath=75&quot; rel=&quot;nofollow&quot;&gt;http://www.seeedstudio.com/depot/preorder-open-workbench-logic-sniffer-p-612.html?cPath=75&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has decent sampling rate, and you can support a cool open HW project. It looks like it is still in a sort of beta stage, so it might not be the greatest thing if you just want to plug something in and have it work.&lt;/p&gt;&#xA;" OwnerUserId="875" LastActivityDate="2010-07-16T14:03:13.437" CommentCount="1" />
  <row Id="3539" PostTypeId="1" AcceptedAnswerId="3545" CreationDate="2010-07-16T14:08:42.863" Score="8" ViewCount="766" Body="&lt;p&gt;I am building a power supply circuit.  The &lt;a href=&quot;http://www.st.com/stonline/books/pdf/docs/1358.pdf&quot; rel=&quot;nofollow&quot;&gt;Switching Regulator&lt;/a&gt; calls for a low ESR output capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What does &quot;low&quot; mean?  How low?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, how do I find or calculate the ESR for a &lt;a href=&quot;http://nichicon-us.com/english/products/pdf/e-vr.pdf&quot; rel=&quot;nofollow&quot;&gt;capacitor&lt;/a&gt; whose datasheet does not have a parameter called ESR?&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-05-18T11:22:02.217" Title="How to find the ESR of a capacitor" Tags="&lt;capacitor&gt;&lt;power-supply&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="3540" PostTypeId="2" ParentId="3539" CreationDate="2010-07-16T14:22:32.937" Score="3" ViewCount="" Body="&lt;p&gt;How &quot;low&quot; depends on the efficiency and reliability you are trying&#xA;to achieve. For low ESR capacitors the manufacturer will supply&#xA;the values. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Search for Nichicon low ESR capacitors and you will find parts&#xA;that have a low ESR. The VR series is not a low series resistance&#xA;capacitor. The PM Series is and the ESR is specified in the datasheet. &#xA;Nichicon (which makes excellent capacitors) may have some newer series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ESR is critical to the life of the capacitor since as ESR increases&#xA;the temperature of the capacitor will increase which will decrease&#xA;its life.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:22:02.217" LastActivityDate="2011-05-18T11:22:02.217" />
  <row Id="3541" PostTypeId="2" ParentId="3539" CreationDate="2010-07-16T14:24:14.260" Score="4" ViewCount="" Body="&lt;p&gt;It's 'equivalent series resistance', and is somewhat frequency dependent. Basically it's the unavoidable ordinary resistance that comes along with the capacitor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lower ESR means that the capacitor is more like an ideal circuit element. Resistance just dissipates power, which results in heat, which is generally no good for capacitors, especially electrolytics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just speculating now - On that data sheet you linked, the salient parameter looks like 'tangent of loss angle'. If one assumes that 'loss angle' is the angle away from a purely capacitive reactance, then the tangent of that angle would be the series resistance divided by the capacitive reactance, in which case this number being low would imply ESR to be low.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-07-16T14:57:28.557" LastActivityDate="2010-07-16T14:57:28.557" CommentCount="2" />
  <row Id="3542" PostTypeId="2" ParentId="3539" CreationDate="2010-07-16T17:55:07.440" Score="3" ViewCount="" Body="&lt;p&gt;In this case I think the low ESR is needed to get a low ripple on the output voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current through the inductor will have some ripple, and assuming a constant output current the capacitor will have to absorb or supply the difference to the output. Multiply this ripple current with the ESR and you get the ripple voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can measure ESR by charging and discharging the capacitor with a relatively high current switched by a function generator, and then measure the ripple voltage with an oscilloscope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen 170 mOhm in practice for a low ESR SMD electrolytic capacitor. If I remember correctly the voltage difference was 0.5V so the current ripple must have been 3A (limited by the power supply).&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-07-16T17:55:07.440" />
  <row Id="3543" PostTypeId="1" AcceptedAnswerId="3544" CreationDate="2010-07-16T19:05:07.290" Score="1" ViewCount="65" Body="&lt;p&gt;All I can find are adapters and gender changers. Where can I find one with actual leads I can solder?&lt;/p&gt;&#xA;" LastActivityDate="2010-07-16T19:09:26.147" Title="Need to purchase a Serial port that can be soldered to a motherboard" Tags="&lt;serial&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="3544" PostTypeId="2" ParentId="3543" CreationDate="2010-07-16T19:09:26.147" Score="0" ViewCount="" Body="&lt;p&gt;If you're just looking for a connector, how about something like &#xA;&lt;a href=&quot;http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_1952839_-1&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; ?&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-16T19:09:26.147" CommentCount="3" />
  <row Id="3545" PostTypeId="2" ParentId="3539" CreationDate="2010-07-16T19:28:51.653" Score="7" ViewCount="" Body="&lt;p&gt;If a datasheet just says 'low ESR' without specifying a value you are usually fine with any style of capacitor relatively low ESR.  All this really means is that you should avoid cheap unrated aluminum electrolytic caps since their ESR is terribly high, can be several ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this case it wants a 'low ESR' cap for the 1000uF output cap. I don't think i've ever seen a ceramic 1000uF cap and a 1000uF tantalum would probably cost $50 so you are going to have to track down a low ESR aluminum cap for this application.  The output ripple will decrease linearly with the ESR of the cap, so lower is better up to whatever price you want to pay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an aside, that is a ridiculously high required output capacitance for a switching regulator in that voltage range. You may want to take a look around for a regulator that meets your needs but is stable without such a requirement.  Don't get me wrong, usually more capacitance the better but 1000uF is really high for a 1.5A supply.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-07-16T19:28:51.653" CommentCount="2" />
  <row Id="3546" PostTypeId="2" ParentId="3525" CreationDate="2010-07-16T19:47:18.317" Score="2" ViewCount="" Body="&lt;p&gt;As far as logic analyzers go, I wrote a basic comparison of (relatively) inexpensive ones:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.davr.org/2010/03/16/comparison-of-logic-analyzers/&quot; rel=&quot;nofollow&quot;&gt;Comparison of PC-based logic analyzers&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing to note about sampling speed, a rule of thumb is you generally need at least 4x your data rate in order to get an accurate reading, and up to 10x is better. So if you want to monitor a 8MHz signal (which you can easily generate from an inexpensive AVR in SPI for example), you'd want a 32-80MHz sampling rate analyzer. This only applies when capturing in 'async' mode. If you are capturing in 'synchronous' mode (eg with a clock signal), then your sampling rate only needs to match the rate of the clock signal. So for example in that case, 8MHz synchronous sampling would be enough to capture a 8MHz SPI signal (since it has a dedicated clock signal).&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-16T19:47:18.317" />
  <row Id="3547" PostTypeId="2" ParentId="2036" CreationDate="2010-07-16T19:51:29.217" Score="7" ViewCount="" Body="&lt;p&gt;As far as actual logic analyzers go (versus something like the Bus Pirate), I wrote a basic comparison of (relatively) inexpensive ones:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.davr.org/2010/03/16/comparison-of-logic-analyzers/&quot; rel=&quot;nofollow&quot;&gt;Comparison of PC-based logic analyzers&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing to note about sampling speed, a rule of thumb is you generally need at least 4x your data rate in order to get an accurate reading, and up to 10x is better. So if you want to monitor a 8MHz signal (which you can easily generate from an inexpensive AVR in SPI for example), you'd want a 32-80MHz sampling rate analyzer. This only applies when capturing in 'async' mode. If you are capturing in 'synchronous' mode (eg with a clock signal), then your sampling rate only needs to match the rate of the clock signal. So for example in that case, 8MHz synchronous sampling would be enough to capture a 8MHz SPI signal (since it has a dedicated clock signal). &lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-16T19:51:29.217" />
  <row Id="3548" PostTypeId="1" AcceptedAnswerId="3563" CreationDate="2010-07-17T00:43:13.840" Score="1" ViewCount="423" Body="&lt;p&gt;I'm trying to interface an XSens IMU (http://xsens.com) with my computer, and I'm running into interesting difficulties. The IMU has an RS232 connector that just uses the pins VCC, GND, TX, RX, nothing else. The SDK comes with it has a custom RS232-USB adaptor that uses the FT232R and MAX3160, but apart from that it doesn't seem to do anything special.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The manufacturer claims that the IMU uses standard RS232 (and I have no reason to doubt them), so, in order to save space (their converter is quite bulky), I am trying to use a Sparkfun FTDI Basic Breakout 5V (http://www.littlebirdelectronics.com/products/FTDI-Basic-Breakout-%252d-5V.html). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I set all the COM settings the same (baudrate, parity, stop, etc), and I connect to the device, I do get data back, but it just seems like gibberish. I issue commands, the TX LED on the FTDI blink, the RX one too, and I get data, but it's nothing like what I am expecting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone think of any &quot;gotchas&quot; I may be missing? &#xA;Is there a FooBar that needs to be connected to the DingDing to Actuate?&lt;/p&gt;&#xA;" OwnerUserId="978" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:01:47.233" LastActivityDate="2010-12-10T22:01:47.233" Title="Anything special I need to know about RS232 &amp; FT232R?" Tags="&lt;usb&gt;&lt;serial&gt;&lt;uart&gt;&lt;rs232&gt;&lt;imu&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="3549" PostTypeId="1" CreationDate="2010-07-17T00:46:22.197" Score="1" ViewCount="314" Body="&lt;p&gt;Does anyone have any recommendations on an embedded platform that would be able to handle RS232 at 921600 baud and log it to a microSD card or something similar?&lt;/p&gt;&#xA;" OwnerUserId="978" LastActivityDate="2010-07-17T05:08:35.290" Title="High-speed RS232 logging" Tags="&lt;rs232&gt;&lt;microsd&gt;" AnswerCount="3" CommentCount="0" />
  <row Id="3550" PostTypeId="2" ParentId="3549" CreationDate="2010-07-17T01:09:18.150" Score="0" ViewCount="" Body="&lt;p&gt;Sparkfun has the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9530&quot; rel=&quot;nofollow&quot;&gt;OpenLog&lt;/a&gt; which does exactly that albeit at 9600 baud. It has a maximum configurable baud rate of 115200 though, perhaps at such a high speed you are better off using a logic analyser as discussed in &lt;a href=&quot;http://chiphacker.com/questions/2036/beginners-logic-analyzer&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="417" LastEditorDisplayName="" LastEditDate="2010-07-17T01:15:10.107" LastActivityDate="2010-07-17T01:15:10.107" CommentCount="3" />
  <row Id="3551" PostTypeId="2" ParentId="1847" CreationDate="2010-07-17T01:47:02.137" Score="2" ViewCount="" Body="&lt;p&gt;Kapton tape is often used to cover and insulate circuits.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-07-17T01:47:02.137" CommunityOwnedDate="2010-07-17T01:47:02.137" />
  <row Id="3552" PostTypeId="2" ParentId="3548" CreationDate="2010-07-17T01:53:13.117" Score="2" ViewCount="" Body="&lt;p&gt;Looking at the specs for some of the devices on that site, they list the digital interface as being 'max 921600 bps' - so unless you have very good reason to believe the device is operating at that particular baud rate, it would be worth your while to try talking to it at a few other baud rates, especially if you have a good idea what the data is supposed to look like. I'd set my terminal for 115200 and see if the data made any sense at that rate, then, work down the baud rate scale. If you get to 9600 and it still looks like gibberish, go back to 115200 and work up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A rate of 921600 is almost unheard of. It's a standard multiple, but I honestly haven't seen anything push RS232 faster than 115200 before. By the time it becomes necessary to use faster rates than 115200, designers usually switch to some other, more reliable interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Btw, I'm still just assuming that you've connected the device to a PC com port and have some documentation that suggests what the data format is. If it's an &lt;em&gt;option&lt;/em&gt; to select a baud rate, use 115200, it will be much more reliable, assuming it is compatible with your overall data rate needs.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-17T01:53:13.117" CommentCount="4" />
  <row Id="3553" PostTypeId="2" ParentId="795" CreationDate="2010-07-17T01:59:05.293" Score="0" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://opencircuits.com/Multi-touch_display&quot; rel=&quot;nofollow&quot;&gt;open-circuits wiki lists many multi-touch technologies&lt;/a&gt; and techniques:&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-07-17T01:59:05.293" CommunityOwnedDate="2010-07-17T01:59:05.293" />
  <row Id="3554" PostTypeId="2" ParentId="3549" CreationDate="2010-07-17T02:26:40.860" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.parallax.com/tabid/407/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;Parallax Propeller&lt;/a&gt; will do serial full-duplex at 3 &lt;strong&gt;Mbps&lt;/strong&gt; . &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, it will run out of memory in a hurry unless you put the data somewhere. Also, since the serial interface is run in one of the internal processor cores, in software, it is basically infinitely adjustable to any frequency between 0 and ~3 Mbps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://obex.parallax.com/objects/54/&quot; rel=&quot;nofollow&quot;&gt;Here is the serial interface module&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://obex.parallax.com/objects/619/&quot; rel=&quot;nofollow&quot;&gt;Also, there is a SD-Card module that supports FAT16/32 cards&lt;/a&gt;&lt;br&gt;&#xA;I'm not sure if it can keep up with the serial interface though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a lot of other useful pre-written object in the &lt;a href=&quot;http://obex.parallax.com/&quot; rel=&quot;nofollow&quot;&gt;object exchange&lt;/a&gt; too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, the Propeller is awesome.&lt;br&gt;&#xA;For those of you who aren't familiar, it's an 8-Core 32 bit microprocessor, with both a interpreted high level language, and a custom assembly language for speed-critical stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found that it's possible to get away without actually having to use assembly at all, since there are so many available libraries. You mostly just need to write glue-logic to link them together.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-07-17T02:31:46.787" LastActivityDate="2010-07-17T02:31:46.787" />
  <row Id="3555" PostTypeId="1" AcceptedAnswerId="3556" CreationDate="2010-07-17T03:33:58.303" Score="2" ViewCount="109" Body="&lt;p&gt;I have a small PSU board out of a defunct DVD player that I'd like to use as&#xA;a supply for my breadboards. It has two rails, +12 and +5 with two GND&#xA;lines, but there's no current indication. My guess is that it's in the&#xA;500mA-1A range, but I really have no clue.&#xA; &#xA;What's the best way to test it and determine a safe limit?&#xA; &#xA;Also, if it requires a load in order to operate, should I just wire in a big&#xA;resistor across +12 to ground? &lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2010-07-18T18:27:16.187" Title="Power supply amperage" Tags="&lt;power-supply&gt;" AnswerCount="2" />
  <row Id="3556" PostTypeId="2" ParentId="3555" CreationDate="2010-07-17T03:54:54.047" Score="4" ViewCount="" Body="&lt;p&gt;The case for home appliances usually has the power consumption written on it.   That will give you an upper bound if you assume say 80% efficiency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could hook a fat power resistor up chosen to dissipate say 1A and see if the output voltage drops indicating overload.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Really, you could do better with a dual-rail PSU from some obsolete computer equipment (eg Zip drive), available really cheaply at flea markets etc.   If you only want 5v, old mobile phone chargers are good; prefer switchmode (light, efficient, well regulated) over transformer (heavy, inefficient, poor regulation).&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2010-07-17T03:54:54.047" />
  <row Id="3557" PostTypeId="2" ParentId="3549" CreationDate="2010-07-17T05:08:35.290" Score="3" ViewCount="" Body="&lt;p&gt;According to my reading of the datasheet, an Atmel ATmega running at 20MHz (the max) can run its UART at up to 2222222 baud rate (~2.2Mbps), more than double the speed you need.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;(BAUD = Fosc / (8 * UBBRn + 1)) &#xA;   with Fosc = 20000000 (20MHz) &#xA;   and UBBRn = 0 (the minimum)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;So the UART reading part should be no problem. The only question now becomes the writing to the SD card. You can do that over SPI, which is separate from the UART, so you can run them both in parallel with little overhead. &lt;a href=&quot;http://www.dharmanitech.com/2009/01/sd-card-interfacing-with-atmega8-fat32.html&quot; rel=&quot;nofollow&quot;&gt;According to this site&lt;/a&gt;, when running an ATmega at 8MHz (thus 4MHz SPI clock), you can write to a SD card at up to 140kB/sec. You only need ~128kB/sec, and ATmega's can run up to 20MHz (thus 10MHz SPI clock), so there shouldn't be a problem there.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-17T05:08:35.290" CommentCount="3" />
  <row Id="3558" PostTypeId="2" ParentId="184" CreationDate="2010-07-17T05:16:25.457" Score="0" ViewCount="" Body="&lt;p&gt;Yet another alternative to conductive thread: wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;wire-wrap wire (30 AWG) or magnet wire is pretty lightweight and flexible, although constant flexing will eventually make it break.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;stranded wire is a bit thicker and heavier, but it will survive flexing longer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I imagine you would lay it out in a sort of zig-zag or sinewave curve, gluing the midpoints, so that there's a bit of slack between each glue spot to allow the fabric to stretch a little.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-07-17T05:16:25.457" CommunityOwnedDate="2010-07-17T05:16:25.457" />
  <row Id="3559" PostTypeId="2" ParentId="3475" CreationDate="2010-07-17T06:25:08.173" Score="1" ViewCount="" Body="&lt;p&gt;Yes, it looks like the UBW32 would work fine for you, and the default firmware lets you control the I/O pins from your software on your PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to&#xA;&lt;a href=&quot;http://www.sparkfun.com/commerce/news.php?id=386&quot; rel=&quot;nofollow&quot;&gt;&quot;how to bit bang SPI and parallel interfaces on an FT232R&quot;&lt;/a&gt;, you can apparently bit-bang 8 digital pins (possibly more?) on the FT232R controlled by software on your PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=718&quot; rel=&quot;nofollow&quot;&gt;$15 Breakout Board for FT232RL&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It sounds like what you really want is a digital I/O interface; you neither need nor want a programmable microcontroller.&#xA;If you only wanted 16 bits, I would go with a couple of FT232RL boards.&#xA;However, it looks like a single $40 UBW32 looks like it will give you the 64 I/O you want for less cost than 8 of the FT232RL boards it would require to get 64 I/O.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm finding that's becoming increasingly common -- it sometimes costs less to throw an entire microcontroller at a problem, even though it has a million &quot;extra&quot; transistors I'll never use on it, than to use a hard-wired solution.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-07-17T06:25:08.173" CommunityOwnedDate="2010-07-17T06:25:08.173" />
  <row Id="3560" PostTypeId="2" ParentId="3548" CreationDate="2010-07-17T08:54:04.417" Score="2" ViewCount="" Body="&lt;p&gt;Are you sure the voltage levels are compatible?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Standard RS232 has ±12V levels, which are usually converted by some MAX chip to TTL levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your case the Sparkfun FTDI breakout board has TTL levels (0/5V), while the MAX3160 can do RS232 and RS485(!), so there is a mismatch.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-07-17T08:54:04.417" CommentCount="3" />
  <row Id="3561" PostTypeId="2" ParentId="2952" CreationDate="2010-07-17T10:09:32.037" Score="2" ViewCount="" Body="&lt;p&gt;Almost all wall-wart type power supplies have a non-resettable thermal fuse built into the transformer these days. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Overloading them for a short period of time will not do any damage (the voltage output will drop, though). Significant overloading for a period of time will cause the adapter to fail open-circuit, in a manner that is effectively unrepairable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It shouldn't be dangerous, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note - Some chinese dc-dc bricks are &lt;em&gt;so cheap&lt;/em&gt; that they don't even have modicum of protection, though. If they are 60hz transformer-based, you should be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(And that's not even mentioning the issues with &lt;a href=&quot;http://www.electricstuff.co.uk/acadapter.html&quot; rel=&quot;nofollow&quot;&gt;fraudulently-rated power supplies&lt;/a&gt; coming out of china)&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-07-17T10:09:32.037" />
  <row Id="3562" PostTypeId="2" ParentId="1847" CreationDate="2010-07-17T11:33:30.983" Score="4" ViewCount="" Body="&lt;p&gt;I've worked with circuits potted in wax. They were in a housing filled with wax, but you could use something like a milk carton and cut it away when the wax has cooled.  The neat thing about potting with wax is that you can solder right through it.&lt;/p&gt;&#xA;" OwnerUserId="222" LastActivityDate="2010-07-17T11:33:30.983" />
  <row Id="3563" PostTypeId="2" ParentId="3548" CreationDate="2010-07-17T11:59:16.277" Score="4" ViewCount="" Body="&lt;p&gt;Standard rs-232 (like your IMU) and TTL level rs-232 (like the FTDI chip) are different. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Standard rs-232 switches between +V and -V ( where V was originally 12, but now most devices will work on much lower voltages). TTL level rs-232 switches between 0 and 5V. You need an rs-232 transceiver to convert the voltages, such as that MAX3160 chip  (Though that's an unusual one - something like the max2332 is more common).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The USB to TTL level rs-232 converters like the one you linked to are are used to connect to a microcontroller, not to a typical rs-232 device.&lt;/p&gt;&#xA;" OwnerUserId="222" LastEditorUserId="222" LastEditorDisplayName="" LastEditDate="2010-07-18T00:24:04.900" LastActivityDate="2010-07-18T00:24:04.900" CommentCount="1" />
  <row Id="3564" PostTypeId="1" CreationDate="2010-07-17T12:44:20.633" Score="11" ViewCount="859" Body="&lt;p&gt;In my professional life, I sometimes need to create timing diagrams for UART/SPI/etc protocols.  However, I cant find any good programs available.  Do any of you recommend any programs for this that you have tried and liked?&lt;/p&gt;&#xA;" OwnerUserId="107" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-24T21:29:47.163" LastActivityDate="2011-01-25T01:42:54.963" Title="Software to create timing diagrams" Tags="&lt;uart&gt;&lt;spi&gt;&lt;timing&gt;" AnswerCount="7" CommentCount="2" FavoriteCount="9" />
  <row Id="3565" PostTypeId="2" ParentId="1024" CreationDate="2010-07-17T14:02:07.527" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.designspark.com/pcb&quot; rel=&quot;nofollow&quot;&gt;http://www.designspark.com/pcb&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recently started to use it and have found that it works ok for whipping up quick circuits etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's by RS Components and does require registration at their website, however the product appears to be free.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will handle schematics as well as PCB and it is supposed to do Gerber files as well.&#xA;Note I am not affiliated with RS Components in anyway.&lt;/p&gt;&#xA;" LastActivityDate="2010-07-17T14:02:07.527" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="1" />
  <row Id="3566" PostTypeId="2" ParentId="3564" CreationDate="2010-07-17T14:36:59.663" Score="5" ViewCount="" Body="&lt;p&gt;Microsoft Excel is the poor man's 2D CAD program, and has worked well for me. Highlight all cells, then drag the row and column borders until the pixel count matches - this gives you square cells. Then use the Drawing toolbar to add lines and shapes. The snap to grid option should be turned on too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit to add some additional explanation, for the downvoters in comments below:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Blockquote&#xA;  Microsoft Excel is neither a CAD program (It's a spreadsheet)..&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;MS Excel has a lot of features, including a decent drawing package. If you use and explore the software, you'll find things you never thought you would. For instance, would you say that Excel is a programming interface and UI for data acquisition hardware, or a reporting front-end for databases? Answer is that it can be used for these, and I know this from personally implementing these kinds of apps. Just like I've personally implemented Excel to make 2D drawings, of waveforms and more (cables, floorplans, etc).&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;...nor a program for a poor man ... &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This is meant in the sense of a colloquialism: definition &lt;a href=&quot;http://en.wiktionary.org/wiki/poor_man%27s&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. And I'd be astounded if someone who was making waveform drawings in their professional life did not have a copy of Office provided by their employer.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;When drawing as you suggest in Excel, you cannot visualize edge transitions other than vertical lines... &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Sorry to be blunt, but that's flat wrong. Here is a more detailed explanation that you can try yourself. Starting as I described above, consider the square ABCD, with coordinates starting clockwise from the upper left hand corner of the square. If you were to draw a line through points DABC in sequence, you'd have the first half of a square wave. However if you draw a line through DB, you have a 45 degree rising angle. The snap to grid option snaps to the points of the grid, but doesn't enforce angular restrictions. Obviously this can be extended to make other angles by choosing other coordinates - using aa 2x2 grid of cells as your base gives more angular choices, and so on. For example, I've used this to draw trapezoidal waveforms and slope controlled self-clocking Manchester signals - not just 50% duty cycle clock ticks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note also that you aren't limited to straight lines - curves are dirt-simple. Copy-paste (CTRL-C, CTRL-V) and the ability to rotate and group objects make more complex shapes easy. Another example from my experience: If you can draw a single hemisphere you can turn that into the double-helix of a shielded twisted pair on a cable schematic in no time flat (almost literally: I took a hand-wavy concept through to a PDF copy of a drawing, in 45 minutes, including the time spend submitting online requests for quote to cable vendors). For waveforms, the same things could make a sine wave or an amplitude-modulated signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need something really complex, turn the snap to grid option off, draw your thingie, then turn snap back on and drag the thingie into place. Don't forget that you can resize drawn objects too.&lt;/p&gt;&#xA;" OwnerUserId="906" LastEditorUserId="906" LastEditorDisplayName="" LastEditDate="2010-07-22T15:54:24.810" LastActivityDate="2010-07-22T15:54:24.810" CommentCount="4" />
  <row Id="3567" PostTypeId="2" ParentId="1024" CreationDate="2010-07-17T16:38:43.890" Score="-1" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://www.faststone.org/FSCaptureDetail.htm&quot; rel=&quot;nofollow&quot;&gt;FastStone capture&lt;/a&gt; to post screen shots.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are the steps:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;ctrl-printscreen&lt;/li&gt;&#xA;&lt;li&gt;Drag the area I want to capture&lt;/li&gt;&#xA;&lt;li&gt;It pops up the image&lt;/li&gt;&#xA;&lt;li&gt;I click on ftp. it knows my domain and where to put it. It makes up a name based on the date. It copies the url to the clipboard&lt;/li&gt;&#xA;&lt;li&gt;I ctrl-v the url to the insert picture icon&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;That's it. You still have to have a schematic in your computer but this addresses a large part of your question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.mmccoo.com/clips/2010-07-17_093210.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2010-07-17T16:38:43.890" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="4" />
  <row Id="3568" PostTypeId="2" ParentId="3564" CreationDate="2010-07-17T16:54:59.233" Score="9" ViewCount="" Body="&lt;p&gt;The tool that I have bookmarked is -- &#xA;&lt;a href=&quot;http://www.timingtool.com/menu/tour/ttmain.php&quot; rel=&quot;nofollow&quot;&gt;http://www.timingtool.com/menu/tour/ttmain.php&lt;/a&gt;&#xA;I have not tried it or taken a close look.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using TeX and friends there is a timing&#xA;package for the tikz picture environment (check CTAN).&#xA;Sometimes with the TeX tools you can find wrapper&#xA;scripts or GUIs that can create standalone images.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The documentation on the tikz-timing package is at&#xA;&lt;a href=&quot;http://www.tug.org/texmf-dist/doc/latex/tikz-timing/tikz-timing.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.tug.org/texmf-dist/doc/latex/tikz-timing/tikz-timing.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-25T01:42:54.963" LastActivityDate="2011-01-25T01:42:54.963" />
  <row Id="3569" PostTypeId="1" AcceptedAnswerId="3571" CreationDate="2010-07-17T17:10:20.813" Score="1" ViewCount="238" Body="&lt;p&gt;On my 16F628A's I want to iterate of a predefined sequence of values. How do I do this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In C, I would do something like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;char vals = {22, 10, 34, 16};&lt;/p&gt;&#xA;&#xA;&lt;p&gt;char id = 0;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;port = vals[id];&#xA;id++&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's the 'vals[id]' that I haven't figured out.&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2010-07-17T18:43:49.800" Title="How do I do indirect addressing in PIC ASM?" Tags="&lt;pic&gt;&lt;assembly&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="3570" PostTypeId="2" ParentId="3501" CreationDate="2010-07-17T18:42:51.667" Score="0" ViewCount="" Body="&lt;p&gt;There's a nice list of &lt;a href=&quot;http://opencircuits.com/Popular_Parts&quot; rel=&quot;nofollow&quot;&gt;&quot;popular electronics parts&quot;&lt;/a&gt; on the Open Circuits wiki.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-07-17T18:42:51.667" CommunityOwnedDate="2010-07-17T18:42:51.667" />
  <row Id="3571" PostTypeId="2" ParentId="3569" CreationDate="2010-07-17T18:43:49.800" Score="3" ViewCount="" Body="&lt;p&gt;There are no indirect memory access instructions on midrange pics, instead you put the address of the memory location you want to access into the FSR register. And then the value is accessible at the INDF register.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See section 4.4 of the datasheet for your chip.&#xA;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/devicedoc/40044f.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ww1.microchip.com/downloads/en/devicedoc/40044f.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2010-07-17T18:43:49.800" CommentCount="1" />
  <row Id="3572" PostTypeId="2" ParentId="1847" CreationDate="2010-07-17T19:32:34.467" Score="2" ViewCount="" Body="&lt;p&gt;Try some polycaprolactone, its a low temperature melting plastic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.shapelock.com/page2.html&quot; rel=&quot;nofollow&quot;&gt;http://www.shapelock.com/page2.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Never used it before, but from the looks of things you should be able to melt it in an oven and handle it with your hands to mould it into something. &lt;/p&gt;&#xA;" OwnerUserId="942" LastActivityDate="2010-07-17T19:32:34.467" />
  <row Id="3573" PostTypeId="2" ParentId="3057" CreationDate="2010-07-17T20:51:23.523" Score="3" ViewCount="" Body="&lt;p&gt;I know this sounds crazy, but for 8 or 10 bit resolution, a stand-alone ADC costs &lt;em&gt;more&lt;/em&gt; than a chip that includes both a CPU and a ADC.&#xA;(For the reasons Kortuk mentioned, 14 or more bits of precision are usually handled by an external dedicated ADC.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Atmel ATtiny13 is the lowest cost chip I know of with an ADC -- less than the MCP3208 or MCP3204 at my favorite distributor.&#xA;(I think you can program it to emulate a has 3 input 10 bit SPI ADC).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Atmel ATtiny261 is the lowest cost per-analog-input chip I know of (it has 11 input 10 bit ADC).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your analog sensor is far from your CPU, it makes sense to put an ADC right on the analog sensor and pipe noise-resistant digital samples back to the CPU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps that &quot;ADC&quot; should be a second CPU emulating a slave SPI ADC.&#xA;(On the other hand, sometimes it's better to use a hard-wired chip that &quot;just works&quot; -- like the Microchip MCP3208 -- than to spend a bunch of time programming and debugging a microcontroller).&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-07-17T20:51:23.523" CommunityOwnedDate="2010-07-17T20:51:23.523" CommentCount="2" />
  <row Id="3574" PostTypeId="1" AcceptedAnswerId="3636" CreationDate="2010-07-17T21:40:00.740" Score="6" ViewCount="129" Body="&lt;p&gt;What is good stuff to quickly build small hobby robots?&#xA;What sorts of tools do I need to work with those materials?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's assume we already have the electronics parts listed at&#xA;&lt;a href=&quot;http://chiphacker.com/questions/3501/what-is-a-general-set-of-components-for-a-robotics-hacker&quot; rel=&quot;nofollow&quot;&gt;&quot;What is a general set of components for a robotics hacker?&quot;&lt;/a&gt;,&#xA;and focus on all the other parts and tools.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;material for &lt;a href=&quot;http://reprap.org/wiki/Frame_material&quot; rel=&quot;nofollow&quot;&gt;rigid frame&lt;/a&gt; (what type?)&lt;/li&gt;&#xA;&lt;li&gt;material for outer skin (waterproof?) (what type?)&lt;/li&gt;&#xA;&lt;li&gt;wheels (what type?)&lt;/li&gt;&#xA;&lt;li&gt;legs and feet (what type?)&lt;/li&gt;&#xA;&lt;li&gt;gears and belts (what type?)&lt;/li&gt;&#xA;&lt;li&gt;attachment methods: nuts and bolts, glue, zip ties, etc.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'm looking for stuff like &quot;Acrylic is nice, I recommend X thickness, you need Y to cut it to shape and Z to attach the pieces together&quot;&#xA;and &quot;cardboard is nice for quick prototypes; you can make it waterproof using W&quot;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-07-20T20:51:24.493" CommunityOwnedDate="2010-07-17T21:40:00.740" Title="What are good materials and associated tools for a robotics hacker?" Tags="&lt;robotics&gt;&lt;hardware&gt;&lt;tools&gt;&lt;cases&gt;&lt;waterproof&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="2" />
  <row Id="3575" PostTypeId="2" ParentId="3564" CreationDate="2010-07-18T03:11:11.730" Score="3" ViewCount="" Body="&lt;p&gt;Can I suggest you use any form of PERT chart or scheduling program - if it doesn't  support uS or nS just pretend that 'days' are equivalent - this is a great way to find timing problems and worst case paths&lt;/p&gt;&#xA;" OwnerUserId="980" LastActivityDate="2010-07-18T03:11:11.730" />
  <row Id="3576" PostTypeId="1" CreationDate="2010-07-18T05:33:48.430" Score="1" ViewCount="264" Body="&lt;p&gt;Continuing on with my power supply repairs. I hate it when I don't have a component and even with all of the junk parts I have I still have troubles finding things. So I want to buy some Schottky Diodes to have on hand. I am looking at &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.futurlec.com/DiodesGen.shtml#Shottky&quot; rel=&quot;nofollow&quot;&gt;http://www.futurlec.com/DiodesGen.shtml#Shottky&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have some 1N58XX, BAT41-86, SBXXX, Along with lots of others.  My question is: can I just buy the higher voltage and current rated Schottky diode and sub them for the lower rated ones.  Is the main reason for getting the exact match the cost and ability to fit?  Do I only need to match package/voltage/current? Are Schottky and fast recovery the same?  Can I sub an ultra-fast for a fast recovery? And... at the moment I need a Schottky that is in the TO220 package.  Can I use two axial leads and just wire the cathodes together.  I know you can't do this for transistors but is the Schottky just two diodes in one package? Lots of questions and lots of thanks for any help with this.&#xA;Russ&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS: Are those good prices?&lt;/p&gt;&#xA;" LastActivityDate="2010-07-26T15:59:30.777" Title="Schottky Diode substitution" Tags="&lt;diode&gt;" AnswerCount="2" />
  <row Id="3577" PostTypeId="1" AcceptedAnswerId="3593" CreationDate="2010-07-18T06:50:58.960" Score="5" ViewCount="389" Body="&lt;p&gt;I have seen many a toys using just discrete components and IC's to produce songs (with words and everything!). I want to gift someone a piece of electronic art in which I want to use such a circuit. Does anyone know of these? I don't think those toys use uControllers to produce speech so there has to be some cheap alternative. What can it be? Please suggest.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For anyone who reads this question afterwards, I found all the answers very much doable and these are great options. The reason I had marked Leon Heller's answer as my accepted answer is just that it was very very easy to do. And can be implemented using the cute little Attiny uControllers.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="1200" LastEditorDisplayName="" LastEditDate="2010-07-24T06:44:32.153" LastActivityDate="2011-05-04T15:28:35.183" Title="Generating speech using ICs" Tags="&lt;speech&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="2" />
  <row Id="3578" PostTypeId="1" CreationDate="2010-07-18T06:56:16.320" Score="9" ViewCount="1095" Body="&lt;p&gt;I did a big cleanup of my collection of parts today and I now have a big pile of parts on my desk (the majority of which is resistors). My previous method of finding the resistor value I wanted was to look through my little box and read the colour codes. Unfortunately I now have a  &lt;strong&gt;lot&lt;/strong&gt; of resistors, making an individual search almost impossible. Instead of reinventing the wheel, I put it to you my fellow chiphackers: do you know of any efficient (as in fast recall) ways to store and categorise components ? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand you can get lots of small drawers but it seems like such a waste of space to put only a single resistor of an unusual value in its own drawer.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2011-05-18T11:22:19.970" Title="What's the best way to store and categorise resistors/capacitors/ICs/etc?" Tags="&lt;resistor&gt;&lt;components&gt;&lt;storage&gt;" AnswerCount="16" CommentCount="5" FavoriteCount="5" />
  <row Id="3579" PostTypeId="2" ParentId="3578" CreationDate="2010-07-18T07:46:34.873" Score="10" ViewCount="" Body="&lt;p&gt;I keep resistors in drawers organized by the first digits of value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R-1, R-12, R-15, R-18, R-22 and so on. (same for capacitors)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R-1 contains 100ohm, 1k, 10k... &#xA;R-22 contains 22ohm, 220ohm, 2.2k, 22k...&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2010-07-18T07:46:34.873" CommentCount="4" />
  <row Id="3580" PostTypeId="2" ParentId="3577" CreationDate="2010-07-18T11:11:33.510" Score="2" ViewCount="" Body="&lt;p&gt;Sparkfun sells &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9579&quot; rel=&quot;nofollow&quot;&gt;an IC&lt;/a&gt; that can record up to 64 seconds of audio. However, these sort of chips normally work by storing the audio in a bank of capacitors, so it may require a coin cell to keep the audio stored.&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-07-18T11:11:33.510" CommentCount="5" />
  <row Id="3581" PostTypeId="2" ParentId="3576" CreationDate="2010-07-18T11:29:33.767" Score="0" ViewCount="" Body="&lt;p&gt;Depending on your application you may also need to check the forward voltage, as low forward voltage is often the reason to choose a Schottky diode.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-07-18T11:29:33.767" />
  <row Id="3582" PostTypeId="2" ParentId="3578" CreationDate="2010-07-18T12:46:24.010" Score="3" ViewCount="" Body="&lt;p&gt;If really pressed for space, I think I'd lump everything 100 ohms and under in one bin, everything 1M and above in another, then one bin each for 100-1K, 1K-10K, 10k-100k and 100k-1M, but those things with all the little drawers are very cheap and easy to come by.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-18T12:46:24.010" />
  <row Id="3583" PostTypeId="2" ParentId="3578" CreationDate="2010-07-18T14:15:10.957" Score="2" ViewCount="" Body="&lt;p&gt;I've been contemplating a system using labeled envelopes, but I haven't actually done it yet.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-18T14:15:10.957" />
  <row Id="3584" PostTypeId="2" ParentId="3578" CreationDate="2010-07-18T14:53:26.430" Score="7" ViewCount="" Body="&lt;p&gt;I don't do anything but prototype work and 5-10 run prototype assembly here so i don't keep that many parts around but here are my thoughts:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For SMD: &lt;a href=&quot;http://aidetek.com/mm5/merchant.mvc?Screen=PROD&amp;amp;Store_Code=A&amp;amp;Product_Code=BOX-ALL&amp;amp;Category_Code=Encl&quot; rel=&quot;nofollow&quot;&gt;This is about my favorite thing ever created&lt;/a&gt;  I also have &lt;a href=&quot;http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&amp;amp;item=170470907524&amp;amp;rvr_id=&amp;amp;crlp=1_263602_263622&amp;amp;UA=L%2aS%3F&amp;amp;GUID=e5fb63071290a03661e58d25ffac5809&amp;amp;itemid=170470907524&amp;amp;ff4=263602_263622#ht_1477wt_1139&quot; rel=&quot;nofollow&quot;&gt;one of these&lt;/a&gt; for low volume stuff that comes on tape and is useful for testing, ferrite beads and such.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For ICs / connectors: I don't really reuse a lot of this stuff from design to design so they are normally just kept in their digikey/mouser bags and kept in the project box with the PCB's and connectors etc.  I'm fairly good at keep a running inventory of what i have and what project it was for on my workstation so i can usually find this stuff quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For Through Hole: I really don't use this stuff much.  I have a fishing box style assortment of ceramic caps, 1 of 1% 1/4W resistors, 1 of aluminum caps, and 1 full of other stuff, diodes and transistors, etc.  I don't really use this very often with the exception of a resistor or cap here and there if i need to blue wire something onto an early rev design.  This could definitely be better organized.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-07-18T14:53:26.430" CommentCount="1" />
  <row Id="3585" PostTypeId="2" ParentId="3578" CreationDate="2010-07-18T15:13:57.403" Score="3" ViewCount="" Body="&lt;p&gt;For through-hole parts I use something like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/gp/product/B000CRHD6K/ref=oss_product&quot; rel=&quot;nofollow&quot;&gt;http://www.amazon.com/gp/product/B000CRHD6K/ref=oss_product&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find a list of standard resistor values here: &lt;a href=&quot;http://www.rfcafe.com/references/electrical/resistor-values.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.rfcafe.com/references/electrical/resistor-values.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then just start making labels (color-coded labels in excel work great - put the color code on there for your reference).  In fact I have the labels I made with color codes.  I think if everything still works right after uploading to Google Docs that these should print out on mailing labels - maybe two or three to a label?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://spreadsheets.google.com/ccc?key=0AlW3tzPu0DsLdHVtZHBmc1pKajdfSUtoSG8ySjI5dVE&amp;amp;hl=en&amp;amp;authkey=CMS268gM&quot; rel=&quot;nofollow&quot;&gt;http://spreadsheets.google.com/ccc?key=0AlW3tzPu0DsLdHVtZHBmc1pKajdfSUtoSG8ySjI5dVE&amp;amp;hl=en&amp;amp;authkey=CMS268gM&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-07-18T15:13:57.403" />
  <row Id="3586" PostTypeId="2" ParentId="3472" CreationDate="2010-07-18T16:45:05.710" Score="4" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;There are two HDL languages, they're VHDL and Verilog, ask to your professor wich language will you learn and try to see how it works: the syntax and how could you make modules on this and make a big review about ALL digital circuits.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Before making any things do 1, make sure that you really know everything about digital circuits, because that HDL don't create anything new, you only use these things on a different way.&#xA;So you can use one of the two books above, to do some exercises, ask you teacher the books that he recommends and use them or one of the two above.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Ask to you teacher wich FPGA do they use on the classes, if it's Altera, Xilinx, Lattice or other, if Altera make the download of the Quartus Web Edition, if Xilinx, the ISE Webpack, make the free download of one of these and try to learn about one of the softwares and do some of your exercises, simulations on one of them.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;You are right, about 90% of the work on HDL are on simulators, so learn about the Modelsim simulator, and/or the ISIM simulator on xilinx, they commands and how to do testbenches.&lt;/p&gt;&#xA;" OwnerUserId="981" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-09T13:20:54.137" LastActivityDate="2011-03-09T13:20:54.137" CommentCount="1" />
  <row Id="3587" PostTypeId="2" ParentId="3564" CreationDate="2010-07-18T17:01:40.653" Score="4" ViewCount="" Body="&lt;p&gt;Inkscape (&lt;a href=&quot;http://www.inkscape.org/&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;) the first one might be some work but after you've setup some templates it's pretty quick.&lt;/p&gt;&#xA;" OwnerUserId="960" LastActivityDate="2010-07-18T17:01:40.653" />
  <row Id="3588" PostTypeId="2" ParentId="2944" CreationDate="2010-07-18T17:27:13.330" Score="2" ViewCount="" Body="&lt;p&gt;Why don't you use an NPN as TIP31/TIP122 transistors? It will be very simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't use NPN, use the TIP32 on common emitter, and on the base, put an small-signal NPN, as a 2n2222 on common emitter with a resistor (R1) on the 29V (VCC), put these block together with a resistor (R2), then calculate R2 to the same way you do the calculation on NPN (Saturation condition).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then go to Rbase of the NPN, make sure it will be on the saturation condition, to the I2 current flowing into it.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The R1 value it's not so important as the above, so use it to achieve a faster switching condition, as the load is slower, put a value that the power is about 1/5 of the max. IC(NPN), it will work good with this case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have any doubts, make an spice simulation to see if it works or not, if the transistors are on saturation and these things...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good work for you!&lt;/p&gt;&#xA;" OwnerUserId="981" LastActivityDate="2010-07-18T17:27:13.330" />
  <row Id="3589" PostTypeId="2" ParentId="3577" CreationDate="2010-07-18T17:35:14.453" Score="2" ViewCount="" Body="&lt;p&gt;The easiest way to do this is using an ISD17* IC, for example an ISD1730, take a look on the datsheet: &lt;a href=&quot;http://www.alldatasheet.net/datasheet-pdf/pdf/210764/WINBOND/ISD1730.html&quot; rel=&quot;nofollow&quot;&gt;link text&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To buy that, go to ebay, it isn't cheap, but do the work, will work great on your case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An other way is to pick some of these toys and other things that do speech and take the PCB apart and use it on your application.&lt;/p&gt;&#xA;" OwnerUserId="981" LastActivityDate="2010-07-18T17:35:14.453" />
  <row Id="3590" PostTypeId="2" ParentId="3555" CreationDate="2010-07-18T18:27:16.187" Score="1" ViewCount="" Body="&lt;p&gt;Is this an open frame kind of supply? If so, can you make out what kind of regulation it is? Linear supplies tend to have a single rather large transformer, while switchers usually have several, smaller inductors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it happens to be a linear type supply, the capacity would be limited by the regulator devices, e.g., if there were a 7805, you could get a data sheet for the 7805 in the particular case style they used. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's a switching supply (more likely, really) there might be other ways to tell, but I'm not personally familiar enough with switchers to be able to say.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-18T18:27:16.187" />
  <row Id="3591" PostTypeId="2" ParentId="3564" CreationDate="2010-07-18T19:47:35.137" Score="5" ViewCount="" Body="&lt;p&gt;A quick web search turns up &lt;a href=&quot;http://drawtiming.sourceforge.net/samples.html&quot; rel=&quot;nofollow&quot;&gt;Drawtiming&lt;/a&gt;.  Never used it, but it looks like it would work very well for brief examples of a few dozen clock cycles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to do your drawings in an Office-like toolset, try &lt;a href=&quot;http://www.openoffice.org/&quot; rel=&quot;nofollow&quot;&gt;OpenOffice.org&lt;/a&gt;, specifically the &lt;a href=&quot;http://www.openoffice.org/product/draw.html&quot; rel=&quot;nofollow&quot;&gt;Draw&lt;/a&gt; program.  If you want to generate the best graphics (And don't mind if it takes a while), try &lt;a href=&quot;http://www.inkscape.org/&quot; rel=&quot;nofollow&quot;&gt;Inkscape&lt;/a&gt; as suggested by digikata.  Professional datasheets will probably be best served by the &lt;a href=&quot;http://www.texample.net/tikz/examples/tikz-timing/&quot; rel=&quot;nofollow&quot;&gt;tikz-timing package&lt;/a&gt;  an as suggested by jluciani, or the older (but less complex) &lt;a href=&quot;http://www.texample.net/tikz/examples/timing-diagram/&quot; rel=&quot;nofollow&quot;&gt;timing.sty&lt;/a&gt;, both with &lt;a href=&quot;http://www.latex-project.org/&quot; rel=&quot;nofollow&quot;&gt;(La)TeX&lt;/a&gt; (Try &lt;a href=&quot;http://www.lyx.org/&quot; rel=&quot;nofollow&quot;&gt;Lyx&lt;/a&gt; for a shorter learning curve, if you're new to TeX. Be warned that it's a steep curve no matter what, but it's worth it!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also try simulating in GTKWave (or any other circuit simulator with a logic analyzer):&#xA;&lt;img src=&quot;http://bec-systems.com/site/wp-content/uploads/2009/01/spi_sim_small.png&quot; alt=&quot;Example GTK Wave Screenshot&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but that's oriented more towards simulation of Verilog/VHDL/schematics, rather than just drawing waveforms.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-18T19:47:35.137" CommentCount="3" />
  <row Id="3592" PostTypeId="2" ParentId="3577" CreationDate="2010-07-18T20:42:03.013" Score="5" ViewCount="" Body="&lt;p&gt;Atmel's &lt;a href=&quot;http://www.atmel.com/atmel/acrobat/doc1456.pdf&quot; rel=&quot;nofollow&quot;&gt;AVR355 app note&lt;/a&gt; describes how to do this with an 8-bit microcontroller with on-board A/D, an (Optional) external SPI flash chip, an LM324 quad op-amp for the microphone amplification and PWM'd output filtering, amplification, and feedback prevention.  They use an outdated AT90S8535, but you could do this with any 8-bit micro.  You're going to run at about 7,812 (half of your 15,625 PWM frequency) 8-bit samples for every second of sound, so something big like a 644 or 128 would get you, assuming a 8k or less code, 8 seconds on the 64k or 17 with 128, if you can swing the self-flashing code - you'll likely want the external flash.  Less than $\$$3 for a 64MB SST25VF064C will get you 2 1/2 hours of talk time, or $\$$0.68 for a 1MB AT25FS010N will get you just over 2 minutes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the easiest way to do this is to buy a ready-made &lt;strong&gt;recordable&lt;/strong&gt; greeting card, and take it apart.  Some places even will sell just the module, so you can put it in a custom card/enclosure.  Here's one site for &lt;a href=&quot;http://www.vocalgreetings.com/Blanks.html&quot; rel=&quot;nofollow&quot;&gt;cards&lt;/a&gt; and bare &lt;a href=&quot;http://www.vocalgreetings.com/recordablemodule.html&quot; rel=&quot;nofollow&quot;&gt;modules&lt;/a&gt;, and here's another with more &lt;a href=&quot;http://www.soundexpressiongreetings.com/musical-greetings/recordable-greeting-cards.html&quot; rel=&quot;nofollow&quot;&gt;cards&lt;/a&gt; and &lt;a href=&quot;http://www.soundexpressiongreetings.com/musical-greetings/recordable-sound-modules.html&quot; rel=&quot;nofollow&quot;&gt;modules&lt;/a&gt; in bulk (min qty 20).  Looks like they're both using bare dies, but hey, if you can just buy it ready to go, why do you need to make your own?  I know this paragraph wasn't in the spirit of Chiphacker like the first paragraph was, but it is a solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS if you do spring for a premade module, and can figure out what chip is under &lt;a href=&quot;http://www.hjl-tech.com/admin/img/2005132213040.jpg&quot; rel=&quot;nofollow&quot;&gt;that&lt;/a&gt; &lt;a href=&quot;http://images02.olx.com.ph/ui/3/43/02/45354102_1.jpg&quot; rel=&quot;nofollow&quot;&gt;ubiquitous&lt;/a&gt; &lt;a href=&quot;http://www.vtk.com.hk/images/VT2171ST.M.jpg&quot; rel=&quot;nofollow&quot;&gt;black&lt;/a&gt; &lt;a href=&quot;http://image.made-in-china.com/2f0j00wvSEloVRAHcq/Recordable-Sound-Module-ZX007-.jpg&quot; rel=&quot;nofollow&quot;&gt;blob&lt;/a&gt; [Images],  and (optionally, but would be nice) can get a source on it in a hackable package, please let us know!&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-04T15:28:35.183" LastActivityDate="2011-05-04T15:28:35.183" CommentCount="5" />
  <row Id="3593" PostTypeId="2" ParentId="3577" CreationDate="2010-07-18T21:30:53.337" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.romanblack.com/picsound.htm&quot; rel=&quot;nofollow&quot;&gt;Here's&lt;/a&gt; a simple way to do it with a PIC etc.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-18T21:30:53.337" CommentCount="2" />
  <row Id="3594" PostTypeId="2" ParentId="3578" CreationDate="2010-07-18T21:52:40.343" Score="3" ViewCount="" Body="&lt;p&gt;For TH and larger parts I use lots of small drawers. I also use the&#xA;Akro-mils cabinets with dividers. &#xA;&lt;a href=&quot;http://www.amazon.com/gp/product/B00018AR5Y/192-5968131-0652527&quot; rel=&quot;nofollow&quot;&gt;http://www.amazon.com/gp/product/B00018AR5Y/192-5968131-0652527&lt;/a&gt;&#xA;These are nice because you can different draw sizes in a 17&quot;x11&quot;x11&quot;&#xA;cabinet. Very expensive unless you can find them surplus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For SMD components I use a combination of stainless steel tins&#xA;and watchmakers tins. I built some low-profile trays that hold&#xA;the tins. See &#xA;&lt;a href=&quot;http://www.luciani.org/no-place-to-go/comp-storage/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.luciani.org/no-place-to-go/comp-storage/index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One very nice thing about the tins is they are small. For most&#xA;designs you can kit up the different components on your bench.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:22:19.970" LastActivityDate="2011-05-18T11:22:19.970" />
  <row Id="3595" PostTypeId="1" AcceptedAnswerId="3596" CreationDate="2010-07-19T02:41:24.760" Score="3" ViewCount="170" Body="&lt;p&gt;I asked this question over at stack overflow but found this in a few of the comments on some of the microchip questions,&#xA;&lt;a href=&quot;http://stackoverflow.com/questions/3276297/communicating-with-the-pic-16f913&quot;&gt;http://stackoverflow.com/questions/3276297/communicating-with-the-pic-16f913&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is my issue, it appears that all the communication lines for the PIC 16F913 reside on the same set of pins, this is convenient in that I don't have to sacrifice GPIO pins just to do comms, however the problem I'm having now is if I'm using the SPI on the chip, how can I send information to the RS232?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason this issue came up, is that I just bought a CAN bus chip that communicates over SPI, and I would really like to see the data on RS232, so I can see messages. (I really don't know much about CAN yet, so who knows if this even makes sense yet).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are the options I see, and maybe someone else has better ideas that I'm just simply missing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Somehow setup a time scheme that will switch between SPI and RS232 every time I get data,&#xA;-- This doesn't seem hard and should work, but supposing I don't want to miss a message, what if a message is written while I'm writing to RS232, is it possible I'll miss it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2.. I can always use SPI, but then build my own comm bus over 8 of the GPIO lines, to another PIC 16F913, using only the GPIO lines and then since the RS232 lines are free on the second PIC I can simply read the data and spit it out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-- This one is doable but now we're wasting 2 chips, AND all the GPIO lines,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There has to be a better way. Or is there?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help is greatly appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to also clarify, obviously one solution is using a completely different chip (which may in fact be what I end up doing, if I can get the 18F programmed), however, I'm interested in worst case scenario, in which I am limited in resources and only have some 913's, is the way described above the only way to do it with this chip, or is there a better way?&lt;/p&gt;&#xA;" OwnerUserId="982" LastActivityDate="2010-07-19T18:35:57.677" Title="Communicating with the Pic 16F913" Tags="&lt;pic&gt;&lt;microchip&gt;&lt;microcontroller&gt;" AnswerCount="2" />
  <row Id="3596" PostTypeId="2" ParentId="3595" CreationDate="2010-07-19T04:39:11.907" Score="4" ViewCount="" Body="&lt;p&gt;You could use those pins for SPI, and implement a software UART on another pair of pins. I've done that before now when I needed two UARTs on a chip that only had one hardware UART.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to &quot;bit-bang&quot; the software UART. I tried to post some code I've used but it doesn't get formatted properly. &lt;a href=&quot;http://datadog.com/software_uart.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is an example.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-07-19T18:35:57.677" LastActivityDate="2010-07-19T18:35:57.677" CommentCount="3" />
  <row Id="3597" PostTypeId="2" ParentId="3472" CreationDate="2010-07-19T05:17:41.150" Score="3" ViewCount="" Body="&lt;p&gt;wherever you end up working you will have to use the same HDL they already use - so to increase the chances of getting hired try and spend a bit of time with both Verilog and VHDL. It used to be pretty simple: Verilog was used in the US and VHDL in Europe - these days it's not a simple. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Upthread someone mentioned learning to 'think differently' for VHDL - you have to do that for verilog too it looks like C but it's not - a good place to start is to look and see where wires and flops are created during synthesis - once you reach the point where you can see those, and can just 'see' timing hazards in your head you're most of the way there&lt;/p&gt;&#xA;" OwnerUserId="980" LastActivityDate="2010-07-19T05:17:41.150" />
  <row Id="3598" PostTypeId="2" ParentId="1847" CreationDate="2010-07-19T06:27:36.693" Score="2" ViewCount="" Body="&lt;p&gt;I would second some of the epoxy resins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can really easily mix some of the stuff up, and coat your electronics in it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can create a mold to shape the epoxy out of wax. &#xA;Make the final shape out of balsa wood or something (called the pattern), then melt some wax and push the pattern into the wax until the wax solidifies. Then place your electronics in the wax mold, then pour in the epoxy. You may want to brush on the epoxy to make sure you got it in all the right places and then put it with the rest of your epoxy. And since epoxy doesn't stick to wax, you just pull it straight out!&lt;/p&gt;&#xA;" OwnerUserId="978" LastActivityDate="2010-07-19T06:27:36.693" />
  <row Id="3599" PostTypeId="1" AcceptedAnswerId="3604" CreationDate="2010-07-19T09:19:55.187" Score="5" ViewCount="649" Body="&lt;p&gt;With an N type MOSFET you let the current flow from the drain through the source when a high enough voltage is applied to the gate. With a P type MOSFET which direction is the current meant to flow? From the source through the drain or the other way around? thanks&lt;/p&gt;&#xA;" OwnerUserId="927" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T16:16:25.873" LastActivityDate="2010-10-22T16:16:25.873" Title="Basic p type MOSFET question" Tags="&lt;mosfet&gt;" AnswerCount="1" />
  <row Id="3600" PostTypeId="2" ParentId="3578" CreationDate="2010-07-19T11:30:40.120" Score="3" ViewCount="" Body="&lt;p&gt;I keep mine in small labeled envelopes (hand-written), with each decade in a labeled larger envelope, and keep them all in a cardboard box. I have every value from 1R0 to 10M0 (1% metal film) stored that way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I ought to sort the small envelopes before putting them back in the large envelope, to save time finding a particular value, but I don't bother.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-19T11:30:40.120" />
  <row Id="3601" PostTypeId="2" ParentId="3578" CreationDate="2010-07-19T12:06:21.290" Score="2" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://www.clearbags.com/stationery/envelopes/translucent-envelopes/glassine-envelopes/2-1-2-x-4-1-4-glassine-open-end-center-seam-env.html&quot; rel=&quot;nofollow&quot;&gt;glassine envelopes&lt;/a&gt; and keep them organized with little tab dividers.  They're cheap enough to have one for each value and expandable enough to hold all of my SMD and most of my through-hole components.&lt;/p&gt;&#xA;" OwnerUserId="836" LastActivityDate="2010-07-19T12:06:21.290" />
  <row Id="3603" PostTypeId="2" ParentId="1847" CreationDate="2010-07-19T13:11:12.170" Score="1" ViewCount="" Body="&lt;p&gt;The wax, epoxy, and clay answers above might work, but if you want to have something tested with electronics, you want &lt;a href=&quot;http://en.wikipedia.org/wiki/Potting_%28electronics%29&quot; rel=&quot;nofollow&quot;&gt;potting compound&lt;/a&gt;.  3M Scotch-Weld DP270 (&lt;a href=&quot;http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtnxfcOX46EVuQEcuZgVs6EVs6E666666--&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;) and MG Chemicals' 832 series (different datasheets for color, strength, viscosity, hardness, etc.) are both popular examples.  See the MG Chemicals appnote &lt;a href=&quot;http://www.mgchemicals.com/downloads/appguide/appguide0405.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; [pdf] for a description of the potting and conformal coat processes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Conformal_coating&quot; rel=&quot;nofollow&quot;&gt;Conformal coat&lt;/a&gt; is &lt;em&gt;almost&lt;/em&gt; what you want: It insulates, but it doesn't provide the structure you want.  It's a very thin coating (Like paint, but it's usually clear) that provides a high dielectric between the components and the air. Techspray, Humiseal, Loctite, MG Chemicals, and Chemtronics all manufacture it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other option is hot glue.  Every stick I've used is nonconductive. Not sure how well it would work to make a ball, but it's worth a shot.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-19T13:11:12.170" />
  <row Id="3604" PostTypeId="2" ParentId="3599" CreationDate="2010-07-19T14:03:49.307" Score="15" ViewCount="" Body="&lt;p&gt;For an N-Channel MOSFET,  current is switched from drain to source.  But a P-Channel MOSFET works in the opposite way - in a P-channel MOSFET, current is switched from source to drain.  See &lt;a href=&quot;http://www.irf.com/technical-info/appnotes/an-940.pdf&quot; rel=&quot;nofollow&quot;&gt;this appnote&lt;/a&gt; from IRF. Also, the anode of the integral body diode in a power MOSFET is connected to the source of an N-Channel, but the drain of a P-Channel.  See this &lt;a href=&quot;http://www.globalspec.com/reference/10393/121073/chapter-9-2-12-mosfet-rain-to-source-ldquo-body-rdquo-diode&quot; rel=&quot;nofollow&quot;&gt;excerpt&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, when you have a positive voltage connected to a load, and you want to switch it on and off, use an N-Channel MOSFET between the negative terminal and ground.  Allow current to flow by applying a positive voltage that will saturate the transistor (10-12 for power MOSFETs, 3-5V for logic level).  Turn it off by pulling the gate down to the source.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you have a load with the negative terminal grounded (which is usually preferable; don't muck with ground if at all possible!), and want to apply or remove a positive voltage, use a P-channel MOSFET.  Pull its gate up to the source (which is connected to V+) to turn it off, or pull it to ground (through an open collector output if your logic signal is less than V+) to turn it on (So that Vg is 0, and Vs is, say, 12V, therefore Vgs is -12V). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depletion mode mosfets are less common, and usually only available in N-Channel.  For N-Channel depletion mode, the gate must be pulled below the source (which is often ground).  Stick with enhancement mode for most switching applications unless you need something strange.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This schematic shows both (enhancement-mode) configurations:&#xA;&lt;img src=&quot;http://imgur.com/Hgzh9.png&quot; alt=&quot;example circuit&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To identify the source and drain, look at the side which the arrow is connected to.  This is the source.  If you've got a physical component, a diode test on a meter is useful both for finding the switched current direction (Apply positive voltage to the terminal which the diode test identifies as negative) and for a basic test (not a guarantee) that the transistor isn't burned up.  To differentiate between N-Channel and P-Channel, look at the symbol: N-Channel pointing iN. &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-07-20T02:37:17.970" LastActivityDate="2010-07-20T02:37:17.970" CommentCount="3" />
  <row Id="3605" PostTypeId="1" AcceptedAnswerId="3622" CreationDate="2010-07-19T14:08:23.073" Score="3" ViewCount="734" Body="&lt;p&gt;I'm doing an Arduino based project using the PWM hooked up to a 0.5W 8Ω speaker in order to make various sounds, I want to implement a digital volume control and I thought about using another PWM output and an Opto-Isolator....would this be possible?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And....if it is possible - could anyone recommend a suitable candidate? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers Chiphackers -&#xA;Let me know if this is too vague :) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update - I've got the speaker connected directly to the PWM output without amplification&#xA;       - I'm using a couple of tactile switches to turn the volume up and down &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the circuit (In Theory) - &#xA;&lt;img src=&quot;http://i39.servimg.com/u/f39/14/39/80/39/optoi10.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's some code too, I've got the PWM set to high speed and I'm using it to ramp the volume of the tones up and down -&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/////////////////////////////////////////////////////////////////////////////////////&#xA;// Configure PWM on pins 3 and 11 to run at maximum speed, rather than the default //&#xA;/////////////////////////////////////////////////////////////////////////////////////&#xA;&#xA;pinMode(3,OUTPUT); // speaker on pin 3&#xA;&#xA;cli(); // disable interrupts while registers are configured&#xA;&#xA;bitSet(TCCR2A, WGM20);&#xA;bitSet(TCCR2A, WGM21); // set Timer2 to fast PWM mode (doubles PWM frequency)&#xA;bitSet(TCCR2B, CS20);&#xA;bitClear(TCCR2B, CS21);&#xA;bitClear(TCCR2B, CS22);&#xA;&#xA;sei(); // enable interrupts now that registers have been set&#xA;&#xA;&#xA;////////// Function for playing tones -&#xA;&#xA;void playTone(long tone, int duration) &#xA;{&#xA;prevMicros = micros();&#xA;&#xA;  while (micros() - prevMicros &amp;lt; duration) &#xA;  {&#xA;    analogWrite(3, VOLUME);&#xA;    delayMicroseconds(tone);&#xA;    analogWrite(3, 0);&#xA;    delayMicroseconds(tone);&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-07-20T13:55:41.377" LastActivityDate="2010-07-20T22:35:54.163" Title="Opto-Isolator For Volume Control?" Tags="&lt;opto-isolator&gt;&lt;arduino&gt;" AnswerCount="5" CommentCount="3" />
  <row Id="3606" PostTypeId="2" ParentId="3472" CreationDate="2010-07-19T14:56:15.227" Score="1" ViewCount="" Body="&lt;p&gt;I learned Verilog in college in one course. The culmination of that course was the implementation of a 2-way Superscalar MIPS processor (30% of the class got it completely working; I was in the other 70%). I think things in industry are by-and-large moving away from Verilog and towards VHDL. That being said, there are plenty of online tutorials for both languages. Here's &lt;a href=&quot;http://www.seas.upenn.edu/~ese201/vhdl/vhdl_primer.html&quot; rel=&quot;nofollow&quot;&gt;one on VHDL&lt;/a&gt; and here's &lt;a href=&quot;http://www.asic-world.com/verilog/veritut.html&quot; rel=&quot;nofollow&quot;&gt;one on Verilog&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You're going to probably want to use &lt;a href=&quot;http://model.com/content/modelsim-pe-student-edition-hdl-simulation&quot; rel=&quot;nofollow&quot;&gt;ModelSim&lt;/a&gt; and you can probably use the student edition (I think it's free; maybe with restrictions). Incidentally they recommend using &lt;a href=&quot;http://www.thomsonlearning.com/cengage/student.do?product_isbn=9780534384623&amp;amp;codeid=Z933&amp;amp;disciplinenumber=38&amp;amp;courseid=EEG03&amp;amp;sortby=copy&amp;amp;type=all_radio&amp;amp;codeFlag=false&amp;amp;maintab=needit&amp;amp;subtab=empty&quot; rel=&quot;nofollow&quot;&gt;Digital Systems Design Using VHDL 2nd Edition&lt;/a&gt; as a Textbook.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-07-19T14:56:15.227" />
  <row Id="3607" PostTypeId="2" ParentId="3595" CreationDate="2010-07-19T15:00:42.650" Score="2" ViewCount="" Body="&lt;p&gt;To answer the first question I got to. If you have a device on SPI and after reading from it you are writing to UART.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You cannot &quot;miss&quot; a message while writing to UART because if you are master on SPI the other device must wait for you. If it is a device that samples quickly and constantly you just have to ensure that you sample it more often then it will replace it's values. If it is a device that holds data for you in a buffer you should be able to switch back and forth easily.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am quite used to doing this action, at work We have a device with two communication channels. One channel has 5 different devices it can control, 4 on SPI, one on UART. The other channel has two. One on SPI, one on UART. The code is a bit more complex, as the firmware controllers for each device must ask for access to resources and receive them before doing anything, but the system still works perfectly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would suggest you take a quick shot at just switching. You should be able to implement it fast enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other option is to make a software UART. This can be quite doable. It is called &lt;a href=&quot;http://en.wikipedia.org/wiki/Bit-banging&quot; rel=&quot;nofollow&quot;&gt;bit-banging&lt;/a&gt; normally and is very common practice if it is just for debug and not needed for a final product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would suggest bit banging to be lazy. People often overlook bit-banging.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-07-19T15:00:42.650" CommentCount="2" />
  <row Id="3608" PostTypeId="2" ParentId="3605" CreationDate="2010-07-19T15:02:25.467" Score="2" ViewCount="" Body="&lt;p&gt;Wait - You want a digital volume control that is controlled by a PWM &lt;strong&gt;output&lt;/strong&gt;?  As in, you send the Arduino a command over the UART, or flip some switches to a binary value, and tell it to set the &lt;a href=&quot;http://imgs.xkcd.com/comics/spinal_tap_amps.png&quot; rel=&quot;nofollow&quot;&gt;volume to 11&lt;/a&gt;? Then, your optoisolator applies a voltage/current somewhere in your output circuit?  We'd need a lot more info on what kind of output amplifier you're using.  It would probably be much easier to simply modify your PWM.  If you increase the maximum value, or decrease the input value, you can turn the volume down entirely in software.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you must, you can still use the analogWrite() function to control your PWM.  Try something like(pseudocode):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  //File scope variable to set the volume.  &#xA;  static uint8_t volume = 0;   &#xA;&#xA; void set_volume(uint8_t new_volume) {  &#xA;    if (new_volume &amp;lt; 8)   // Would result in a volume of 0 &#xA;       volume = new_volume;  &#xA; } &#xA;&#xA; /** Divide by 2^volume:   &#xA;  *  0 = loudest,  &#xA;  *  1 = half as loud,    &#xA;  *  2 = 1/4 as loud,  &#xA;  *  3 = 1/8 as loud, etc.   &#xA;  */ &#xA; inline uint8_t adjust_volume(uint8_t signal) {  &#xA;    return (uint8_t) signal &amp;gt;&amp;gt; volume;  &#xA; }  &#xA;&#xA; //Identical ISRs for each of the tactile switches  &#xA; ISR(PCINT0_vect) {      &#xA;   setVolume(read(PORTC))  //Or however you get your digital volume signal  &#xA;}  &#xA;&#xA;void main(void)  {  &#xA;   char *sound_buffer;  &#xA;&#xA;   while(*sound_buffer)  &#xA;      analogWrite(adjust_volume(*sound_buffer++));  &#xA;}    &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If you want to do a volume control with an optoisolated input, then yes, that's quite possible.  Assuming your input device is a pot, your options are a logical, frequency (rather than pulse width) modulated signal, which you can get from a voltage to frequency converter like the &lt;a href=&quot;http://www.national.com/ds/LM/LM231.pdf&quot; rel=&quot;nofollow&quot;&gt;LM231&lt;/a&gt; (there are many other options), or from an op-amp circuit with an RC oscillator.  Feed the output into any digital optoisolator, and you should be able to read the frequency on a digital input pin, and modify your speaker output PWM maximum value or modulate your input values accordingly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you can use a photovoltaic output optoisolator, which outputs an analog voltage (or current) based on the input current.  Be careful of linearity issues when working with these circuits.  You don't really want a linear volume control (You want something closer to logarithmic, or you can go all-out and implement an &lt;a href=&quot;http://en.wikipedia.org/wiki/Loudness&quot; rel=&quot;nofollow&quot;&gt;equal loudness contour&lt;/a&gt;,) however, you don't want a digital switch.  The Vishay &lt;a href=&quot;http://www.vishay.com/docs/83622/83622.pdf&quot; rel=&quot;nofollow&quot;&gt;IL300&lt;/a&gt; is an example of a linear phototransistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;: I mentioned the &lt;a href=&quot;http://www.atmel.com/atmel/acrobat/doc1456.pdf&quot; rel=&quot;nofollow&quot;&gt;AVR335 app note&lt;/a&gt; in a recent question about programmable greeting cards with audio.  That would be a good resource for your question as well.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-07-20T01:24:53.917" LastActivityDate="2010-07-20T01:24:53.917" CommentCount="9" />
  <row Id="3609" PostTypeId="2" ParentId="3605" CreationDate="2010-07-19T17:14:36.457" Score="2" ViewCount="" Body="&lt;p&gt;I haven't done a whole lot with audio, but wouldn't a simpler way of reducing the volume be an digitally-controlled potentiometer in-series with the the PWM signal driving the speaker(i.e. you just want to reduce the signal voltage to reduce the volume, right?)&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-07-19T17:14:36.457" CommentCount="3" />
  <row Id="3610" PostTypeId="2" ParentId="3345" CreationDate="2010-07-19T19:04:03.330" Score="3" ViewCount="" Body="&lt;p&gt;If you want a beagleboard, I prefer the embest board it has ethernet and a sane serial port. by the time you get cables and everything the actual beagleboard can double in price to make it useful.  The hawkboard is also omap, also has the dsp on board, half the price not as much other things like dvi video for example.   The open-rd board from the plug computer folks is nice, either form factor depending on what you want/need.  Certainly has the I/O and is double the speed, can put a hard drive on the board directly dont need to go through usb.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It all depends on what you are looking for, what features you need.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-07-19T19:04:03.330" />
  <row Id="3611" PostTypeId="2" ParentId="3472" CreationDate="2010-07-19T19:17:36.520" Score="1" ViewCount="" Body="&lt;p&gt;icarus verilog or verilator are what I would recommend for learning or playing with verilog.  ghdl is what I would use to play with vhdl.  Far from mainstream but I would also recommend cyclicity-cdl.sf.net which has its own sim environment, etc and produces synthesizable verilog.  use and learn gtkwave for examining the .vcd files generated by the simulators.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-07-19T19:17:36.520" />
  <row Id="3612" PostTypeId="2" ParentId="3345" CreationDate="2010-07-19T19:20:53.610" Score="4" ViewCount="" Body="&lt;p&gt;The main alternative to the beagleboard is the hawkboard, &lt;a href=&quot;http://www.hawkboard.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.hawkboard.org/&lt;/a&gt; it has ethernet and is cheaper than the beagleboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option based on similar hardware is the sheevaplug which just has usb and ethernet, it is however a self contained unit and does not require a case and power supply like the other two&lt;/p&gt;&#xA;" OwnerUserId="558" LastActivityDate="2010-07-19T19:20:53.610" CommunityOwnedDate="2010-07-19T19:20:53.610" />
  <row Id="3613" PostTypeId="2" ParentId="3343" CreationDate="2010-07-19T19:36:37.027" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt; has a number of good sub $\$$50 development boards.  Also go to &lt;a href=&quot;http://estore.ti.com&quot; rel=&quot;nofollow&quot;&gt;TI&lt;/a&gt; for the Stellaris family in the $\$$50 to $\$$100, also the &lt;a href=&quot;http://www.hawkboard.org/&quot; rel=&quot;nofollow&quot;&gt;Hawkboard&lt;/a&gt; which for now I would recommend before the &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;Beagleboard&lt;/a&gt; for what you may want/need to learn, also &lt;a href=&quot;http://estore.ti.com&quot; rel=&quot;nofollow&quot;&gt;TI&lt;/a&gt; has the MSP430 family and I would get an EZ430 and a three pack of the add-in boards for $\$$10.  At &lt;a href=&quot;http://www.sparkfun.com&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt; get a &lt;a href=&quot;http://www.sparkfun.com/search/results?term=lilypad&amp;amp;what=products&quot; rel=&quot;nofollow&quot;&gt;Lillypad&lt;/a&gt; with the FTDI USB serial/power board, the &lt;a href=&quot;http://www.sparkfun.com/search/results?term=lilypad&amp;amp;what=products&quot; rel=&quot;nofollow&quot;&gt;Lillypad&lt;/a&gt; is pretty much the same as the &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardProMini&quot; rel=&quot;nofollow&quot;&gt;Arduino pro mini&lt;/a&gt; but you need to solder for the pro mini. I am not a fan of the PIC family but you may want to get something there as a history lesson, same goes for the 8051, both families are still popular and in use, just not very efficient and have been passed over by other architectures.  Absolutely learn ARM and thumb, maybe MIPS (which is a pic-32, not to be confused with the older original PIC architecture).  The ARMmite Pro is a good entry level ARM board, although the Stellaris may be as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you want to learn here is assembler for various platforms. C. C and assembler interaction. Different tools GCC and non-GCC.  How to read a datasheet/programmers reference (and realize they all have some errors or can be misleading, never trust them, the hardware wins over documents) and how to read or use a schematic.  These are not complicated schematics normally.  A number of the boards are good for interfacing in projects meaning they dont have garbage on the board in the way, just direct access to the I/O pins.  But that is not the best for learning. Something like a &lt;a href=&quot;http://www.sparkfun.com/search/results?term=lilypad&amp;amp;what=products&quot; rel=&quot;nofollow&quot;&gt;Stellaris&lt;/a&gt; board which is painful for projects has lots of fun stuff on board for learning embedded and learning to borrow/use drivers or write your own from datasheets. The Atmel AVR butterfly is a good board too if still available, may need to solder on your own serial port to program it or just jam some wires in the holes. What it gives you is a few peripherals you can learn to program.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if you end up doing embedded work that involves writing applications using SDK or API calls on linux or an RTOS (never touching hardware or reading datasheets), the above knowledge will still set you ahead of the rest.&lt;/p&gt;&#xA;" OwnerUserId="985" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-03T14:41:16.023" LastActivityDate="2011-05-03T14:41:16.023" CommunityOwnedDate="2010-07-19T19:36:37.027" />
  <row Id="3614" PostTypeId="2" ParentId="1140" CreationDate="2010-07-19T20:53:36.917" Score="1" ViewCount="" Body="&lt;p&gt;I don't have much experience across multiple programmers, but I have the Pickit 2 and it seems pretty cool, I bought the signal analysis daughter board with the hopes of using it somewhat as a o-scope, but havn't gotten a chance to really play with it yet, I've managed to program the 16F913, and 16F684 I believe using the 100 microcontroller projects for the evil genius as a reference and it's been really helpful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would recommend that one, but until I've used others I won't know if it's the best.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: (I thought I fixed this already....arghhh), I've had pretty good experience with Pickit 1, I don't actually have the pickit 2, I'm sorry, I got confused.&lt;/p&gt;&#xA;" OwnerUserId="982" LastEditorUserId="982" LastEditorDisplayName="" LastEditDate="2010-07-24T16:28:43.850" LastActivityDate="2010-07-24T16:28:43.850" />
  <row Id="3615" PostTypeId="2" ParentId="442" CreationDate="2010-07-19T20:59:55.643" Score="1" ViewCount="" Body="&lt;p&gt;For references to some stuff, I have done a little programming with the PIC using &lt;strike&gt;Pik Kit 2&lt;/strike&gt; Pickit 1, I would recommend the 100 microcontroller projects for the evil genius, &#xA;I also have some blog posts that are dealing with such things&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.onaclovtech.com/2010/01/interrupts.html&quot; rel=&quot;nofollow&quot;&gt;http://blog.onaclovtech.com/2010/01/interrupts.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.onaclovtech.com/2010/01/analog-inputs.html&quot; rel=&quot;nofollow&quot;&gt;http://blog.onaclovtech.com/2010/01/analog-inputs.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.onaclovtech.com/2010/02/pic-16f913-quick-reference-guide.html&quot; rel=&quot;nofollow&quot;&gt;http://blog.onaclovtech.com/2010/02/pic-16f913-quick-reference-guide.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.onaclovtech.com/2010/02/pic-16f913.html&quot; rel=&quot;nofollow&quot;&gt;http://blog.onaclovtech.com/2010/02/pic-16f913.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I plan to post a SPI update as well as when I figure out how to deal with CAN bus traffic using some microchip chips, I'll have updates then too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;onaclov&lt;/p&gt;&#xA;" OwnerUserId="982" LastEditorUserId="982" LastEditorDisplayName="" LastEditDate="2010-07-21T04:19:38.387" LastActivityDate="2010-07-21T04:19:38.387" CommentCount="2" />
  <row Id="3616" PostTypeId="2" ParentId="3345" CreationDate="2010-07-19T21:46:31.153" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.gumstix.com/&quot; rel=&quot;nofollow&quot;&gt;Gumstix&lt;/a&gt; might be an alternative. I got one of the first ones, but never did much with it.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-19T21:46:31.153" />
  <row Id="3617" PostTypeId="2" ParentId="1722" CreationDate="2010-07-19T22:10:10.830" Score="1" ViewCount="" Body="&lt;p&gt;For avr I normally program in assembler using a text editor.  use avra or something like it to assemble and have my own simplified loader to load the programs into the device (command line).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.dwelch.com/arduino&quot; rel=&quot;nofollow&quot;&gt;http://www.dwelch.com/arduino&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-07-19T22:10:10.830" CommentCount="2" />
  <row Id="3618" PostTypeId="1" CreationDate="2010-07-19T22:59:34.610" Score="3" ViewCount="507" Body="&lt;p&gt;I need to buy some IR LED Detectors but I am having a hard time finding anything except for the 940nm.  It seems that there are only three types of IR LED emitters and detectors sold.&#xA;850nm, 880nm &amp;amp; 940nm.  Is this correct?  My main question is can I use a 940nm detector with the 850nm and 880nm?  Will it detect those two?  Can anyone recommend a place to get IR LEDs that has all of these?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use them because I service redemption and other coin-op games.  Many times these things are used in the games but they don't tell you what the part number is. I needed to replace two pairs on a game the other day and they wanted $55.00 for it. That was four LED's mounted on a short wiring harness.  So I want to stock up on all of the likely IR LEDs and then swap them in until I get the game working.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks again&#xA;Russ&lt;/p&gt;&#xA;" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-07-19T23:38:56.650" LastActivityDate="2010-07-21T01:11:34.763" Title="IR LED Detector question" Tags="&lt;ir&gt;&lt;led&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="3619" PostTypeId="2" ParentId="3374" CreationDate="2010-07-19T23:46:47.947" Score="1" ViewCount="" Body="&lt;p&gt;It sounds like the built-in pot model you are using in your circuit simulator only lets you set the pot position once on the schematic, and then the position is constant during the simulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.ecircuitcenter.com/Circuits/pot1/pot1.htm&quot; rel=&quot;nofollow&quot;&gt;Potentiometer Model at eCircuit&lt;/a&gt;&#xA;shows how to build a model that acts like a linear pot that turns during the simulation.&#xA;That's exactly what you need, right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That model has a spice file that uses a piecewise linear source (PWL) that controls the position of the pot vs. time.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;* WIPER POSITION: 0V=CCW, 1V=CW&#xA;VPOS    20  0   PWL(0MS 0V   1000MS 1V)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You could either use the &quot;voltage&quot; of VPOS as the X coordinate on your graph, representing pot position;&#xA;or perhaps it's simpler to plot X as time and pick a PWL that linearly turns the pot proportional to time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you run the simulation, and plot output voltage vs. time.&#xA;Perhaps pipe in a square-wave at some audio frequency, and plot the output voltage vs time; then when viewing several seconds of simulation, you'll see a solid mass (the oscillations are too fast too see, more than 1 cycle per pixel width) that shows the envelope of the output waveform, and you can use either the top or the bottom as an estimate of the gain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To simulate a non-linear pot, you could (a) edit the PWL line to turn the pot at a non-linear rate, but plot X as time, something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;* nonlinear turn&#xA;VPOS    20  0   EXP(TIME)&#xA;VPOS    20  0   LOG10(TIME)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Or you could (b) build a model of a non-linear pot, and keep the PWL turning that pot at a linear rate, using something like&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;EPOS  21 0 TABLE{V(20,0)} = (0 0.7) (1 7.0) (2 700) (3 7k) (4 70k)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Both (a) and (b) give the same resistance-vs-time characteristics, right?&#xA;Hopefully you can find some function or polynomial or a set of points to feed into PWL or TABLE that gives a close-enough approximation to the actual resistance of your real-world nonlinear pot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm assuming you already have software tools that let you draw a circuit schematic and simulate it, that also accept SPICE models.&#xA;If not, I'm pretty sure there is something suitable in the&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/List_of_free_electronics_circuit_simulators&quot; rel=&quot;nofollow&quot;&gt;List of free electronics circuit simulators&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or at the &lt;a href=&quot;http://chiphacker.com/questions/1206/what-are-the-freeware-spice-simulators-available&quot; rel=&quot;nofollow&quot;&gt;Chiphacker list of freeware SPICE simulators&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To plot AC signal gain as a function of pot position,&#xA;first run a transient (time) simulation.&#xA;Then plot the output (the voltage on the wire going to the speaker) vs. time.&#xA;(Or you could plot it vs. the &quot;turn signal&quot;, V(20) in the above code).&#xA;You might have a pull-down menu option to do this; the old-school method is something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;* WARNING: untested code&#xA;* ANALYSIS&#xA;.TRAN   5US  1000MS&#xA;*&#xA;* VIEW RESULTS&#xA;.PRINT  TRAN    V(1) V(2) V(20) V(77)&#xA;*&#xA;.PROBE&#xA;.END&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="813" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2010-07-22T21:55:09.013" LastActivityDate="2010-07-22T21:55:09.013" CommunityOwnedDate="2010-07-19T23:46:47.947" CommentCount="1" />
  <row Id="3620" PostTypeId="2" ParentId="3618" CreationDate="2010-07-19T23:49:25.910" Score="1" ViewCount="" Body="&lt;p&gt;I buy mine from digikey.com &lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-07-19T23:49:25.910" CommentCount="3" />
  <row Id="3621" PostTypeId="2" ParentId="991" CreationDate="2010-07-20T00:32:16.560" Score="6" ViewCount="" Body="&lt;p&gt;code sourcery lite is good, or use emdebian.  or roll your own, it is pretty easy unless you need a full C or gcc library then it is still doable but a little harder.  at first you wont need a thumb2 capable compiler, thumb will do as you search for a toolchain you like.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;llvm is another good one (use clang not llvm-gcc!!), I know the arm side is getting better all the time, version 27 produced faster code than the current gcc for a particular test.  I found a bug in the thumb side when working on my thumb emulator (thumbulator.blogspot.com) which was promptly fixed.  The best part about llvm is it is by default a cross compiler, no extra work or building experience required.  In the next few years I see them cutting deeper into gcc in and passing gcc by for cross compiling/embedded.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried the code-red tool once with the lpcxpresso board, the end result is I am definitely never using code-red and am debating whether to also blacklist lpc.  ymmv.  If you have to use a pay for tool I would go with keil only because they were bought by arm and part of the package is the rvct compiler.  Of course code sourcery is a pay-for house too if you dont meet the lite limitations or choose to get support, being gcc it has the best support by far of all compilers.  Not long ago when I was able to try them metaware and arm's tools blew away gcc as far as quality of the code produced.  gcc is up and down some versions of 3.x produce better code than 4.x, they dont appear to be improving on each release, but they did or perhaps code sourcery added thumb2 support not long ago, which the 3.x versions dont/wont have.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-07-20T00:32:16.560" />
  <row Id="3622" PostTypeId="2" ParentId="3605" CreationDate="2010-07-20T01:03:51.040" Score="2" ViewCount="" Body="&lt;p&gt;Disclaimer: This is in response to the posted circuit, not an answer to the question of control with a PWM.   I just didn't have room in the comment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any special reason you need the optoisolator?  As your circuit currently appears, I don't think that your D5 connection to pin 5 of your optoisolator phototransistor will supply the kind of current you want.  In addition, synchronization between the two PWMs will likely cause you pain (What if the D5 PWM is always off when the D3 PWM is on and vice versa?  No sound!  You need to average your signal, and feed it into a buffer.  You'll also likely want some hefty capacitance on your V+  line to the micro and buffer so that your supply voltage stays smooth..  However, the connection to ground and the connection to D5 totally eliminate the purpose of the optoisolator, which is to allow the speaker circuit to be at a different voltage than the input.  This might be useful if you had the speaker at a remote location from the Arduino, and want to run a low-current differential signal on a twisted pair out to the speaker, which would be powered from a different power supply.  As is, you might as well just connect pin 6 to D3, and just use the transistor, completely ignoring the &quot;Opto&quot; part of the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See the output circuit for the AVR335 appnote linked in my other answer for a circuit which effectively drives a speaker with a PWM.  The filters smooth the output signal to something better approximating the input (With a rolling average), so that you get a smooth wave rather than a rough digital square wave.  You can remove the unary gain amplifier, that's just to remove any feedback from the microphone (Which you don't have).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You really want some filtering and amplification on the output -It'll sound absolutely terrible if you don't.  You know how those talking greeting cards sound?  They have filtered outputs.  Your speaker will sound worse than that if you just connect it to the PWM.  I was previously assuming that you were using the phototransistor to isolate your output and transfer it to an amplifier/filter circuit running on a different power supply, but a straight connection is going to sound really bad.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-20T01:03:51.040" CommentCount="5" />
  <row Id="3623" PostTypeId="1" AcceptedAnswerId="3625" CreationDate="2010-07-20T01:07:56.640" Score="2" ViewCount="421" Body="&lt;p&gt;I want to simulate the load regulation of a power-supply,  Im sure I remember being able to vary the value of a resistor over the course of a simulation in LTspice but I cant remember how. Anyone? &lt;/p&gt;&#xA;" OwnerUserId="819" LastActivityDate="2010-07-20T01:39:01.990" Title="LTspice: Vary a resistors value over time?" Tags="&lt;ltspice&gt;&lt;simulation&gt;" AnswerCount="1" />
  <row Id="3624" PostTypeId="2" ParentId="1107" CreationDate="2010-07-20T01:28:34.193" Score="2" ViewCount="" Body="&lt;p&gt;I agree with the dip package, disagree that arms are harder to configure, lpcs are, but they are not the only kid on the arm block (atmel itself for that matter).  From what I remember and experienced, Atmel was and perhaps still is just more developer friendly.  The AVR butterfly helped them greatly to get more users to their already good sized and happy user base.  The PIC was just painful in a lot of ways, the avr tools were there, programming was a breeze and didnt cost you much more than some wires and a connector from radio shack.  The tools are there and free but not as easy as mainline gcc where you find the arm and thumb solutions.  Long before the arduino came out the AVR was the chip of choice for hobby projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nothing can compete with ARM right now.  For ever other processor you touch in a day you touch a few ARMs at a minimum.  For some almost everything you touch uses an ARM.  It is a natural fit as the 8 bit killer, can get much better performance than an 8 bit for the same size, price, etc.  Tools are much better, instruction set is much cleaner than most of its competition so the same code runs that much faster, etc.  Because anyone and their brother can embed an ARM and it is not locked into a company like pic, avr, msp430 there are a wide variety of solutions, and as many different ways of dealing with the microcontroller rom/ram mixtures and the interrupt vector table.  Sadly the more popular solution is the most painful.  Try a sam7 or something like that or a stellaris.  There is an armmite pro which is an attempt to make an arm based arduino plugin, or something close to that and I actually like that board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It isnt always the processor that is the problem, some chips have known can problems, some have other known problems.  some may not offer a open collector io pin with a weak pull up and you would have to put hardware outside the chip to interface to something, where another may have that available on one or all of the pins.  I recommend sampling the field, trying the different companies and solutions so that when you want low power you can easily use a msp430, you want processing power in a small chip you go with arm or if you want to make an open project that you hope others will build in their garage you base it on an arduino, if you can.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bottom line though for your question is it really depends on your application and how you write it and the performance and resources you are interested in.  In the same way that gcc or firefox will run on many different platforms and processors, you most certainly can write your C application to run on a wide variety of microcontrollers...&lt;em&gt;IF&lt;/em&gt;...you have a microcontroller specific abstraction layer, which has a cost.  if the microcontrollers have similar enough features and have the features you need and you plan ahead and incorporate those.  If the next platform has enough memory/resources.  You are more interested in portability than performance, etc.  Arguably you need to plan for this ahead of time. or at least on the first switch from A to B you re-design the software, if/when there is a third switch from B to C it is less painful.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-07-20T01:28:34.193" CommunityOwnedDate="2011-05-19T14:16:24.430" CommentCount="2" />
  <row Id="3625" PostTypeId="2" ParentId="3623" CreationDate="2010-07-20T01:39:01.990" Score="3" ViewCount="" Body="&lt;p&gt;Use the SpecialFunctions/Varistor.asy component: &lt;a href=&quot;http://imgur.com/Id6nO.png&quot; rel=&quot;nofollow&quot;&gt;Screenshot&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-20T01:39:01.990" CommentCount="5" />
  <row Id="3626" PostTypeId="1" CreationDate="2010-07-20T01:42:50.923" Score="2" ViewCount="334" Body="&lt;p&gt;For my inclinometer application, I use an integrated 3-D accelerometer chip that outputs analog voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Before I deploy my device, I submit it collect a bunch of samples with different temperature and angles for temperature compensation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem I am experiencing is that voltage outputs for each individual axis are not completely independent. For the same temperature, if one axis is kept constant and the other changes, the former will output some change as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, let's say I'm measuring &quot;g&quot; on the pitch axis and the output is zero when the roll axis is zero. If I roll the accelerometer to one side, I get the corresponding roll &quot;g&quot;, but pitch will have a slight change (+/- 2 degrees), even though pitch is still zero.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas on how to achieve better precision out of this?&lt;/p&gt;&#xA;" OwnerUserId="1267" LastActivityDate="2010-07-20T05:34:23.090" Title="Compensating for Accelerometer Cross-Axis Sensitivity" Tags="&lt;accelerometer&gt;&lt;inclination&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="3627" PostTypeId="2" ParentId="3618" CreationDate="2010-07-20T02:15:29.507" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Transmitters&lt;/strong&gt;&lt;br&gt;&#xA;No, there are more than 850, 880, and 940nm transmitters: the IR spectrum ranges from 700nm to 1mm.  A distinct set of values is sold, typically in the 700 to 1400 nm range (IR-A), where 850, 880, and 940 are common values.  &lt;a href=&quot;http://www.mouser.com/Optoelectronics/Infrared-Data-Communications/Infrared-Emitters/_/N-6qrgl?Keyword=Optoelectronics+Infrared+Data+Communications+Infrared+Emitters&amp;amp;FS=True&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;'s a selection of the Mouser listing of IR emitters.  I've used the TSAL series of emitters from Vishay, although I'm not sure that they're in your current, brightness, or bandwidth specs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The parameter you're interested in for transmitters is the &quot;Relative Radiant Power vs. Wavelength&quot;, and for receivers, you want to know the &quot;Relative Spectral Sensitivity vs. Wavelength&quot;.  For instance, the bell curve in Fig. 9 of the datasheet for the TSAL6100 shows that it has a relative intensity of 1 at 940nm, and outputs about 0.125 times this intensity at 890 nm.  That likely means that it's not bright enough to use with an 850 nm detector, and would be iffy at best with an 880nm detector.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Receivers&lt;/strong&gt;&lt;br&gt;&#xA;On the plus side, receivers are usually more generous, for example the TSOP348 detector [picked at random] has a spectral sensitivity of better than 80% for all wavelengths between 850 and 1050nm.  &lt;a href=&quot;http://www.taosinc.com/&quot; rel=&quot;nofollow&quot;&gt;Taos Inc.&lt;/a&gt; also makes some nice digital, analog, and frequency output detectors for many wavelengths; I've used them with good success before.  This will help you if you need to replace a sensor, especially if it's just used as an on/off digital sensor, for instance in a light curtain application, because 80% is pretty close to 100%.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, that sort of receiver will only tell you about the quantity of light.  If you knew that your LEDs were the same brightness (you don't), then you might be able to infer a frequency (i.e. this one is 75% as bright as the 950nm, therefore it's about 820 or 1070nm).  You can also determine that an LED is on with just a digital camera, like the one in your cell phone.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Color Sensors&lt;/strong&gt;&lt;br&gt;&#xA;An &lt;a href=&quot;http://en.wikipedia.org/wiki/Infrared_camera&quot; rel=&quot;nofollow&quot;&gt;infrared camera&lt;/a&gt; could tell you the wavelength after compensating for temperature, but would not fit most budgets. (Note: These are awesome for determining all kinds of things - Night vision, temperature gradients, etc.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you need for that is an color sensor in the infrared range.  A color sensor will have multiple narrow-band and/or filtered detectors, so that you can determine the color of the light.  See Figure 1, Photodiode Spectral Responsivity&quot; of the datasheet for the TAOS &lt;a href=&quot;http://www.taosinc.com/ProductDetails.aspx?id=128&quot; rel=&quot;nofollow&quot;&gt;TCS3200D&lt;/a&gt;[pdf]  for an example (No, it's not going to be a pretty algorithm...). However, you'll notice that the visible light filters stop at about 750nm, and everything goes back to the same curve.  Finding a color sensor that works into the infrared range is left as an exercise to the reader, but this sort of IC is what you're looking for.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative to an IR color sensor (which may not exist) would be to use a broadband sensor with a set of infrared transmitting filters tuned to the region of the spectrum which you need.  A quick Google search turned up &lt;a href=&quot;http://www.hoyaoptics.com/color_filter/ir_transmitting.htm&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt;, you'll probably find something better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Distributors:&lt;/strong&gt;&lt;br&gt;&#xA;As for distributors, I find that Mouser has a better selection and cheaper prices on optoelectronics than Digikey.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-07-20T17:19:34.843" LastActivityDate="2010-07-20T17:19:34.843" CommentCount="3" />
  <row Id="3628" PostTypeId="2" ParentId="3626" CreationDate="2010-07-20T05:34:23.090" Score="5" ViewCount="" Body="&lt;p&gt;If you look at the datasheet for the chip you'll find there is a spec for the cross axis sensitivity. So what you're seeing is just part of the limitations of the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might be able to calibrate it out if you restrict the movement to one axis only. If you are allowing it to move in any axis then I don't think it is possible with only an accelerometer if the second axis is changing because of cross axis sensitivity or because of a change in angle/acceleration on that axis.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you added in some other sensors - gyroscopes or magnetic field - you might be able to combine all the sensor data to work it out.&lt;/p&gt;&#xA;" OwnerUserId="694" LastActivityDate="2010-07-20T05:34:23.090" CommentCount="2" />
  <row Id="3629" PostTypeId="2" ParentId="3578" CreationDate="2010-07-20T15:10:31.633" Score="2" ViewCount="" Body="&lt;p&gt;I've put some of the passives in ziplock type freezer bags. They're transparent and you can write on them easily. Minigrip brand mini bags are about 10x10cm and I could file them in an old floppy disk organizer box. It's not quite ideal, though. Fresh resistors and diodes are kept in those &quot;belts&quot; as long as the glue holds and SMD's are in their tapes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found a source for surplus lot of those plastic boxes (also transparent) with lots of little compartments. I put a piece of tape on each with a number and have kept a small database that tells me what chips to find in which box and how many I have. Those boxes are nice in that they protect parts mechanically. They tend to be horribly expensive, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also have some IC tubes and (Maxim's sweet sweet snappy) sample containers, ESD foam etc that I've gathered over the years that I can store stuff in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And finally there's a few small drawer units from Ikea that I keep tools, batteries and solder/wick/flux/paste etc in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I absolutely hate those &quot;organizers&quot; that shops use with the metal frame and hard plastic drawers that gather dirt, waste space, rattle and every now and then spray all the contents on the floor when you open a drawer quickly and the stop catches and it does that magic slip and flip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's probably no single container to end all containers.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-20T15:10:31.633" CommentCount="1" />
  <row Id="3630" PostTypeId="2" ParentId="3578" CreationDate="2010-07-20T17:09:41.270" Score="2" ViewCount="" Body="&lt;p&gt;We keep our through-hole resistors in small ziplock bags, and keep those bags in baseball card organizer pages (the plastic loose-leaf pages with nine pockets on each side).  All of them fit in a three-ring binder.  Whenever we need a particular value, we just page through the book.  We also add a little card to each pocket with the value that belongs there, so we know what to restock when we're out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The downside is that if you turn the book upside down you're going to make a huge mess, but amazingly enough, in the two years we've been using this system that hasn't happened once.&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2010-07-20T17:09:41.270" CommentCount="1" />
  <row Id="3632" PostTypeId="2" ParentId="1663" CreationDate="2010-07-20T18:31:22.310" Score="1" ViewCount="" Body="&lt;p&gt;Remote serial and jtag access for embedded development.  Instead of paying for pricy networked jtag devices you can get an plug computer, a few usb to serial converters and a few amontec or other ftdi based jtag wigglers and get a lot more bang for your buck.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-07-20T18:31:22.310" />
  <row Id="3633" PostTypeId="2" ParentId="1554" CreationDate="2010-07-20T18:38:07.507" Score="2" ViewCount="" Body="&lt;p&gt;The ez430 is affordable (~ USD 20) and additional microncontroller boards are 3 for USD 10.  Thanks to Travis and others you can now program from Linux without the need for the DLL trick. Travis's motivation to use a different interface chip is right on, because the TI driver does stop working every time the Linux kernel wind blows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sparkfun is another place you might look, msp430 boards and programmers can be had for next to nothing.&lt;/p&gt;&#xA;" OwnerUserId="985" LastEditorUserId="2134" LastEditorDisplayName="" LastEditDate="2011-04-30T23:35:23.293" LastActivityDate="2011-04-30T23:35:23.293" />
  <row Id="3634" PostTypeId="2" ParentId="3578" CreationDate="2010-07-20T19:41:30.347" Score="2" ViewCount="" Body="&lt;p&gt;Personally I use the same thing I've used ever since I was a kid; a little &quot;cabinet&quot; full of plastic drawers. You see them at any hardware store for holding nails and screws and nuts and bolts. Cheap and works pretty well, although if the cabinet tips you're in for a bit of a job.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I organize them numerically; Starting with the smallest capacitors (1-50pf, 51-500pf, 501-999pf, etc.) in whatever &quot;jump&quot; works.  e.g. I only seem to use 4.7pf, 22pf, 47pf and 100pf caps in that range, so they all go in one bin. I have 0402, 0805, 1206 and through-hole caps in the same drawer, unless the TH parts are big.  It's really not that big a chore to pull out a drawer and look for the right package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For &quot;common&quot; values (0.01uF, 0.1uF, 10uF, etc.) they each get a drawer all to themselves, usually with the through-hole variety in their own drawer. I find I buy 500 of the one kind of cap, and just the SMT size takes up most of the drawer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do the same with resistors and inductors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For semiconductor devices, I have all the small-signal diodes in one drawer, all the zeners in another, all the rectifiers in another (again, with TH in their own drawer becuase they're big)... I have a drawer each for red, green, yellow and blue LEDs, and my NPN and PNP transitors get separate drawers too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Solder and angel-hair wire (I actually use &quot;bare&quot; (bus) 30AWG wire and 26 or 28AWG nylon tubing) go on threaded rods which sit in a holder made out of angle-iron. THis lets the spools turn and keeps the spools out of the way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think I'll end up putting all the through-hole devices in a separate cabinet of drawers. ICs I tend to keep in a box, although the smaller and more common devices will end up in drawers as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally I keep the SMT components &lt;em&gt;IN&lt;/em&gt; the plastic DigiKey or Mouser sleeves (the ones with the DigiKey labels on them.)  Helps me with two problems: losing small parts and re-ordering.  Also, if a drawer spills, it's easy to clean up, and it's impossible to mistakenly file the part in the wrong drawer.  (I also take out one drawer at a time when I'm building boards, which helps avoid mixups.)&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-20T19:41:30.347" />
  <row Id="3635" PostTypeId="2" ParentId="3468" CreationDate="2010-07-20T20:12:04.980" Score="0" ViewCount="" Body="&lt;p&gt;Your #defines are very confusing. You're not defining a port address at all; you're giving a bitmask for your switch. Also you do not show whether you are putting these port pins in GPIO mode. The default state of PINSEL1 is to have everything in GPIO mode, but you should never make assumptions.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define SW_MASK 0x3f&#xA;#define SW_OFFSET 16&#xA;&#xA;PINSEL1 &amp;amp;= ~(0x00ffffff);&#xA;IO1DIR = ~(SW_MASK &amp;lt;&amp;lt; SW_OFFSET);&#xA;int sw = (IO1PIN &amp;gt;&amp;gt; SW_OFFSET) &amp;amp; SW_MASK;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This is basically the code you have, although with the PINSEL1 code, and arranged to be a little less confusing (to me).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jobi's right -- you better have a pull-up resistor on P0.20 so that the chip doesn't force these pins into their &quot;trace port&quot; function.  See page 70 of the LPC213x user manual.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take care -- you have put one of the DIP switch switches on P0.20. Either isolate that pin on a reset (a little transistor with an RCD timer on the base which disconnects the switch from P0.20 when you reset the CPU will do the trick), or make sure that you never leave the DIP switch on P0.20 &quot;on&quot; (connected to ground) when resetting. Better yet: just move that switch over to a different I/O and recombine it in code so that your application never knows the difference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e.g. if you move that switch from P0.20 to P0.22, you can get your &quot;clean&quot; value back thusly:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define SW_MASK 0x6f&#xA;#define SW_OFFSET 16&#xA;&#xA;PINSEL1 &amp;amp;= ~(0x03ffffff);&#xA;IO1DIR = ~(SW_MASK &amp;lt;&amp;lt; SW_OFFSET);&#xA;&#xA;int sw;&#xA;sw = (IO1PIN &amp;gt;&amp;gt; SW_OFFSET) &amp;amp; SW_MASK;&#xA;if(sw &amp;amp; (1 &amp;lt;&amp;lt; 6)) sw |= (1 &amp;lt;&amp;lt; 4);&#xA;sw &amp;amp;= ~(1 &amp;lt;&amp;lt; 6);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(there are slicker ways to do this, but I'm trying to show you what's going on, not be slick.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've altered the mask so that you don't read in P0.20 (SW_MASK change), and that you set P0.22 to GPIO as well (PINSEL1 change).  The block that calculates 'sw' will set bit 4 if bit 6 is set (this is P0.20 which was moved to P0.22). It will then &quot;clear out&quot; bit 6, which is now in bit 4's position.  The value of your switch will thus be correct.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(most embedded systems don't care for actual bit positions, but you may, which is why I suggested this.)&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-20T20:12:04.980" />
  <row Id="3636" PostTypeId="2" ParentId="3574" CreationDate="2010-07-20T20:51:24.493" Score="2" ViewCount="" Body="&lt;p&gt;I have seen some really interesting designs made from plastic cutting boards -- yes, cutting boards. They're tough, easy to cut/drill/shape and it's also pretty inexpensive.  There is also polycaprolactone (goes by various names, but I got mine from a vendor selling it as ShapeLock) -- it's cheap, tough and drillable/fileable. It melts in boiling water and becomes tough when it cools, and has a similar feel to nylon. I'd be sure to keep anything that can get hot away from it though, or your 'bot will melt. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(edit: I forgot to mention that you can make sheets of it pretty easily too: &lt;a href=&quot;http://letsmakerobots.com/node/4070&quot; rel=&quot;nofollow&quot;&gt;http://letsmakerobots.com/node/4070&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want metal, you'll probably want some angle iron of various gauges and sizes, at least for prototyping. I don't know if Meccano is still around, but I made some neat stuff out of that (and Lego too, of course). Aluminum flashing, a pop rivet gun, hacksaw and files.  Try to score a small metal brake too for making nice straight folds, and maybe a sheet metal course at the community college to learn how to weld and grind correctly and safely.  Try to make friends with the local panel shops, as they usually have enough scrap to keep a hobbyiest in excellent stock, as well as access to some of the bigger tools that you may want to use on occasion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An assortment of bosses, nuts, bolts, washers, screws and taps is probably going to be high on the list as well, along with your normal assortment of tools for working with these things.  A dremel is very handy, as are various pliers, tweezers and such.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you build a few prototypes you will know what you're after and can get plastic sheeting  or metal stock laser-cut at various places online or if you're fortunate, locally. That really is the ultimate. Maybe take some time to learn how to build up pieces in Blender or a cheap/free 3D CAD package so you can just send the design files off and get back exactly what you're after.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't got any advice on waterproofing. I imagine starting with an already waterproof container of some kind and creating sealed ports would be the quickest method. I'd take a look at electric boat hobbyiest websites and see how they manage.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-20T20:51:24.493" CommunityOwnedDate="2010-07-20T20:51:24.493" CommentCount="1" />
  <row Id="3637" PostTypeId="2" ParentId="3468" CreationDate="2010-07-20T20:53:45.407" Score="1" ViewCount="" Body="&lt;p&gt;You didn't mention where IOPIN1 is declared but make sure its declared &lt;code&gt;volatile&lt;/code&gt; or the compiler can optimize out reading the value if it doesn't think it has changed leading to intermittent functionality.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If its declared in some vendor supplied header file this is probably already done for you.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-07-20T20:53:45.407" CommentCount="1" />
  <row Id="3638" PostTypeId="2" ParentId="1386" CreationDate="2010-07-20T20:58:55.147" Score="0" ViewCount="" Body="&lt;p&gt;It sounds like you're trying to force a watchdog reset, not keep the watchdog from resetting you.  This is accomplished by a misfeed: feeding the watchdog 0xaa followed by a value OTHER than 0x55.  Example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;WDFEED = 0xAA;    /* Correct feed... */&#xA;WDFEED = 0x00;    /* ... Oops, insta-reset! */&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-20T20:58:55.147" />
  <row Id="3639" PostTypeId="2" ParentId="3605" CreationDate="2010-07-20T21:02:14.643" Score="2" ViewCount="" Body="&lt;p&gt;Why don't you just drive the speaker with a normal transistor and alter the PWM to control the volume? You have control over the waveform that the transistor (and thus speaker) gets... no need for additional components to control it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, If you're hell-bent on using the opto, drive the LED with the PWM outputs. Connect the Emitter of the transistor to ground, the collector to the speaker, and the other side of the speaker to your V+ source (more V+ = louder sound).&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-20T21:02:14.643" CommentCount="1" />
  <row Id="3640" PostTypeId="2" ParentId="3605" CreationDate="2010-07-20T22:35:54.163" Score="0" ViewCount="" Body="&lt;p&gt;Ok.....so I've realized that an opto-isolator is not the best approach for this particular application!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And.....as Andrew Kohlsmith and reemrevnivek pointed out - I could pulse width modulate the base of a transistor instead.... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I got some silicon npn epitaxial transistors (BD139) from the electronics store and gave them a go. It actually worked better than i thought - the volume control is nice and fine :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the circuit I used in the end - &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i39.servimg.com/u/f39/14/39/80/39/pictur10.png&quot; alt=&quot;Da Circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for everyones help and suggestions!&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-07-20T22:35:54.163" CommentCount="3" />
  <row Id="3641" PostTypeId="1" CreationDate="2010-07-20T22:40:43.927" Score="7" ViewCount="613" Body="&lt;p&gt;What are some good projects to give to beginners? I want something that involves some soldering, and ideally has some room for creativity. For example, with &lt;a href=&quot;http://www.evilmadscientist.com/article.php/bristlebot&quot; rel=&quot;nofollow&quot;&gt;Bristlebots&lt;/a&gt;, everyone can get their own toothbrush, attach the motor in different orientations, etc, and they will all be a little different. Something where I just solder a bunch of components to a PCB and then everyone's result is exactly the same, feels a little too boring &amp;amp; restrictive to me. I'm looking for things maybe a little more complex than bristlebot, but not so advanced that it requires a microcontroller. Maybe something involving a 555 timer?&lt;/p&gt;&#xA;" OwnerUserId="131" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-05T02:58:54.237" LastActivityDate="2011-03-05T02:58:54.237" Title="Good easy soldering projects like Bristlebots?" Tags="&lt;soldering&gt;&lt;kit&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="3" />
  <row Id="3642" PostTypeId="2" ParentId="3641" CreationDate="2010-07-20T23:00:03.957" Score="2" ViewCount="" Body="&lt;p&gt;Sorry to be a total self promotor and all....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But....It is easy and it also involves 555 timers...and it's a free (open source) design too&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my pocket sized oscillator type thing - &lt;a href=&quot;http://www.sonodrome.co.uk/hardware.html&quot; rel=&quot;nofollow&quot;&gt;The Posc&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://img143.imageshack.us/img143/7898/dsc00214d.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can be easily modified with custom body contacts (massive door knobs would be fun!) &#xA;You could have flashing lights to modulate the LDR controlled oscillator or you could go old school and just pop on some pots n sliders.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most people get creative with a custom case for this project, there's a &lt;a href=&quot;http://forum.sonodrome.co.uk/general-discussion-f1/great-posc-build-on-make-blog-t109.htm&quot; rel=&quot;nofollow&quot;&gt;few&lt;/a&gt; &lt;a href=&quot;http://forum.sonodrome.co.uk/hardware-f6/mike-s-emerson-posc-build-t110.htm&quot; rel=&quot;nofollow&quot;&gt;different&lt;/a&gt; &lt;a href=&quot;http://forum.sonodrome.co.uk/hardware-f6/a-few-kits-we-built-as-demos-t94.htm&quot; rel=&quot;nofollow&quot;&gt;ones&lt;/a&gt; on &lt;a href=&quot;http://forum.sonodrome.co.uk/projects-f2/early-incarnations-of-posc-t96.htm&quot; rel=&quot;nofollow&quot;&gt;our fourm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-07-21T00:06:09.563" LastActivityDate="2010-07-21T00:06:09.563" CommentCount="2" />
  <row Id="3643" PostTypeId="2" ParentId="3641" CreationDate="2010-07-20T23:33:45.670" Score="2" ViewCount="" Body="&lt;p&gt;BEAM bots are cool..... a lot of them are pretty simple circuits - but they're effective. &#xA;I also like how they have tiny little power harvesting solar cells :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also heaps of different types and designs of BEAM bot's to experiment with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check em out on -&gt; &lt;a href=&quot;http://www.solarbotics.net/&quot; rel=&quot;nofollow&quot;&gt;http://www.solarbotics.net/&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://bestiary.solarbotics.net/pix/1230_heads/1230_mckee_biolightseek.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-07-20T23:39:44.787" LastActivityDate="2010-07-20T23:39:44.787" />
  <row Id="3644" PostTypeId="1" CreationDate="2010-07-21T00:06:33.260" Score="6" ViewCount="365" Body="&lt;p&gt;Hey All,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to compile a list of all the best electronics Kits you have come across.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Best&quot;  can be because you &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;learnt something from them&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;found them very satisfying  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;had something very cool at the end&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Personally I loved the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8617&quot; rel=&quot;nofollow&quot;&gt;Lilypad Kit&lt;/a&gt; - cause it gets you started without actually having to make something specific and the &lt;a href=&quot;http://solarbotics.com/products/k_hm/&quot; rel=&quot;nofollow&quot;&gt;Herbie Kit&lt;/a&gt; cause its fun to play with when its done.&lt;/p&gt;&#xA;" OwnerUserId="21" LastActivityDate="2010-11-13T19:39:41.860" CommunityOwnedDate="2010-07-21T00:06:33.260" Title="Best Electronic Kits" Tags="&lt;kit&gt;&lt;electronics&gt;" AnswerCount="5" CommentCount="4" FavoriteCount="4" />
  <row Id="3645" PostTypeId="2" ParentId="3644" CreationDate="2010-07-21T00:44:41.433" Score="1" ViewCount="" Body="&lt;p&gt;I always wanted the 8,753,342,552,124,401 in one electronic kits, but I only ever got this one... &lt;a href=&quot;http://www.apogeekits.com/lab_kit_el301.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.apogeekits.com/lab_kit_el301.htm&lt;/a&gt; (well, the Radio Shack version of it.)  Combined with Forrest M Mims III's book &quot;Getting Started in Electronics,&quot; I was well-equipped to start my journey. My dad was very good about letting me experiment and build and replaced the transistors in that kit at least twice. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought the exact same kit (Radio Shack doesn't exist in the same form now, but I found the exact kit elsewhere) for my own kids, but so far none of them have really shown interest.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-21T00:44:41.433" CommunityOwnedDate="2010-07-21T00:44:41.433" CommentCount="2" />
  <row Id="3646" PostTypeId="2" ParentId="3618" CreationDate="2010-07-21T01:11:34.763" Score="0" ViewCount="" Body="&lt;p&gt;Some IR receivers are more than just a photodiode - they also demodulate the IR carrier. Make sure you also look at the carrier frequency for the IR as there are a few variants with that as well - 38kHz seems to be the most common.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is some info on &lt;a href=&quot;http://en.wikipedia.org/wiki/Consumer_IR&quot; rel=&quot;nofollow&quot;&gt;Wikipedia here&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="694" LastActivityDate="2010-07-21T01:11:34.763" />
  <row Id="3647" PostTypeId="2" ParentId="3352" CreationDate="2010-07-21T03:45:47.600" Score="13" ViewCount="" Body="&lt;p&gt;Triacs are solid-state devices, whereas relays are electromechanical devices.  Triacs can switch both AC and DC, but as XTL said, they will not stop the current flow unless the current between MT1 and MT2 falls below a threshold level, or you forcibly commutate the device off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(note: I spent 13 years in industrial motor control, we designed equipment which switched up to many thousands of Amps and many thousands of Volts through thyristors.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Relays are pretty simple devices to use; you energize the coil and the contacts engage. You de-energize the coil and the contacts open. A simple transistor can drive it, but you'll want some snubbering (a reverse-biased diode across the relay coil at a minimum) to prevent your transistor from dying due to inductive kickback. Your control signal and your controlled signal are completely isolated from one another.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Relay contacts aren't invincible; if you open up the contacts under load you can cause them to  &quot;ice up&quot; (meaning they won't open up). Also, if you use a relay rated for power and try to switch small signals, the contacts can eventually get dirty and you won't get a good connection between the contacts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Triacs (and their unidirectional equivalent, SCRs), being solid-state, are mostly silent. Unless you use a pulse transformer or optoisolator, your control circuit will be at the potential of your controlled circuit (generally the Neutral for your 120/220V circuits). Thyristors can be used to phase-control a load, meaning you can dim lights or (roughly) control the speed of an AC motor. This is pretty much impossible with relays. You can also do neat tricks like allowing only 'x' entire cycles through to do less &quot;noisy&quot; phase control. SCRs are also good for dumping all the energy in a capacitor into a load (flash or railgun type applications). Some power supplies use SCRs as crowbar devices as well; they turn on and short out the supply (blowing the fuse in the process), protecting the load from an overvoltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thyristors don't really enjoy sharp voltage or current spikes when they're turned off; these can cause them to turn on by accident or can destroy the devices. Simple snubbering helps control these failure modes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thyristors also don't completely isolate the load from the source; if you measure the voltage on a load with the thyristor off, you'll measure full voltage. They thyristor is off, but off doesn't mean &quot;open&quot; -- it means &quot;high resistance&quot;.  This can cause trouble with some applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are switching an AC signal, thyristors are pretty painless; they will shut themselves off around the next zero crossing. If you're controlling DC... again... you have more to think about.  DC is also problematic for relays because you will almost always be opening up the relay contacts under load, so you must size your relay for this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Long story short: Yes, triacs can replace SCRs in almost every application. If you don't want to bother with the snubbering and isolation you can always buy solid state relays; they're triacs with the appropriate control circuitry to make them work almost the same as relays.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-21T03:45:47.600" CommentCount="3" />
  <row Id="3648" PostTypeId="2" ParentId="3641" CreationDate="2010-07-21T04:06:37.147" Score="1" ViewCount="" Body="&lt;p&gt;A simple kit that is useful is the &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/03/20/kit-review-seeedstudio-capacitance-meter/&quot; rel=&quot;nofollow&quot;&gt;JYE Capacitance meter&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/MintyBoost-Kit.html&quot; rel=&quot;nofollow&quot;&gt;Adafruit mintyboost&lt;/a&gt; - People go crazy putting it into different types of enclosures&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For more of a fun kit, the &lt;a href=&quot;http://www.littlebirdelectronics.com/products/Meggy-Jr-RGB-Standard-Kit.html&quot; rel=&quot;nofollow&quot;&gt;Meggy jr&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although it isn't the fastest kit to assemble, it isn't difficult; plus you can do many other things with it once finished - you have a game, the opportunity to write your own games, plus get an FTDI cable, then the whole thing is an Arduino development board with a huge RGB LED display, buttons, piezo, etc. Although there is a microcontroller you don't have to program it, but you can later on if you want. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-07-21T05:14:26.240" LastActivityDate="2010-07-21T05:14:26.240" CommentCount="1" />
  <row Id="3649" PostTypeId="1" CreationDate="2010-07-21T04:24:06.177" Score="1" ViewCount="263" Body="&lt;p&gt;When I try to use the PicKit 1 in MPlab for the PIC 16F913, it doesn't allow me to program the chip using my programmer, even though it has ICSP, I currently have to just pick some other programmer, compile my code and then use I think it's called Pic Kit Classic v1.74&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone tell me what I'm doing wrong? I would really like to skip the other step and do everything through MPlab since I have it open already!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The crazy thing is that the Pic Kit 1 is listed as a programmer for the 913, so I would think that MPlab should already know this.&lt;/p&gt;&#xA;" OwnerUserId="982" LastActivityDate="2010-07-21T19:03:46.147" Title="PicKit 1 and mplab" Tags="&lt;mplab&gt;&lt;microcontroller&gt;&lt;pic&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="3650" PostTypeId="2" ParentId="3641" CreationDate="2010-07-21T05:20:55.027" Score="1" ViewCount="" Body="&lt;p&gt;Might I recommend my own &quot;&lt;a href=&quot;http://www.evilmadscientist.com/go/nightlight&quot; rel=&quot;nofollow&quot;&gt;dark detector&lt;/a&gt;&quot; project, or the &lt;a href=&quot;http://www.evilmadscientist.com/go/solar&quot; rel=&quot;nofollow&quot;&gt;simple solar circuits&lt;/a&gt;?  &lt;/p&gt;&#xA;" OwnerUserId="484" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-07-21T15:34:01.573" LastActivityDate="2010-07-21T15:34:01.573" CommentCount="2" />
  <row Id="3651" PostTypeId="2" ParentId="442" CreationDate="2010-07-21T07:17:16.477" Score="1" ViewCount="" Body="&lt;p&gt;If you want to use PICs I would seriously consider the PIC24 series of 16 bit pics or the very similar dsPIC33. They are faster, more powerful, in many ways easier to program, and don't cost any more than the most basic 8 bit ones. The lower end ones are available in breadboard friendly DIP socket packages too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a lot harder to find examples on the internet though, but as far as i can see that's the main disadvantage.&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2010-07-21T07:17:16.477" />
  <row Id="3652" PostTypeId="2" ParentId="3649" CreationDate="2010-07-21T13:34:34.233" Score="0" ViewCount="" Body="&lt;p&gt;I would upgrade to the PicKit2. It's only $35 and it adds some extra features that the PicKit 1 doesn't have. It will work in MPLab or from the command-line.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-07-21T13:34:34.233" CommentCount="3" />
  <row Id="3653" PostTypeId="1" AcceptedAnswerId="3661" CreationDate="2010-07-21T17:14:59.947" Score="6" ViewCount="857" Body="&lt;p&gt;I've read an appnote from TI (SLA0338) that describes a technique for generating &quot;for real&quot; (as opposed to &quot;pseudo&quot;) random numbers. It exploits the somewhat exotic clock subsystem of the MSP430 to achieve this goal. Does anyone know of a technique that can be implemented on an AVR (I'm interested in the XMega's in particular) for generating &quot;for real&quot; random numbers?&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-07-22T23:50:40.797" Title="AVR Random Number Generator" Tags="&lt;avr&gt;&lt;xmega&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="2" />
  <row Id="3654" PostTypeId="2" ParentId="3653" CreationDate="2010-07-21T17:52:08.183" Score="1" ViewCount="" Body="&lt;p&gt;Have you looked at using something like &lt;a href=&quot;http://www.arduino.cc/en/Reference/RandomSeed&quot; rel=&quot;nofollow&quot;&gt;randomSeed()&lt;/a&gt;? - used in the Arduino IDE&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use this function to sample a floating (free) analog pin on the atmel AVR, it then uses the value to create an arbitrary starting point for the &lt;em&gt;pseudo&lt;/em&gt; random number function - random().&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The value created by random() may be a pseudo random number - but the &lt;em&gt;arbitrary starting point&lt;/em&gt; created by randomSeed() should be as real a random number/value as you can get.&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-07-21T17:57:20.860" LastActivityDate="2010-07-21T17:57:20.860" CommentCount="3" />
  <row Id="3655" PostTypeId="2" ParentId="3653" CreationDate="2010-07-21T18:04:36.893" Score="4" ViewCount="" Body="&lt;p&gt;Connect up the ADC to a hardware noise source and use software to &quot;whiten&quot; the random numbers as needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an AVR based project that does this: &lt;a href=&quot;https://mywebspace.wisc.edu/lnmaurer/web/minirng/minirng.html&quot; rel=&quot;nofollow&quot;&gt;Leon's Mini Portable Random Number Generator (mPRNG)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on how cryptographically secure it needs to be, you could use the noise of a floating analog input or the &quot;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1252144888&quot; rel=&quot;nofollow&quot;&gt;internal temperature sensor&lt;/a&gt;&quot; as your randomness seed instead of external hardware.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-07-21T21:45:36.353" LastActivityDate="2010-07-21T21:45:36.353" CommentCount="1" />
  <row Id="3656" PostTypeId="2" ParentId="3653" CreationDate="2010-07-21T18:15:15.147" Score="3" ViewCount="" Body="&lt;p&gt;Another trick for generating a random seed, is to count the number of clock cycles until an external event. For example if this is a device to be used by a person, count the number of clock cycles until he presses the 'go' button, and use that as the random seed.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-21T18:15:15.147" CommentCount="1" />
  <row Id="3657" PostTypeId="1" AcceptedAnswerId="5008" CreationDate="2010-07-21T18:42:21.617" Score="2" ViewCount="277" Body="&lt;p&gt;Does anyone have any directions on what ICEs exist for MSP430s.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I currently use the MSP430F148. I have others in use, and plan to switch to some higher end in the future.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would be interested in ICE or any other solutions people know of. We have some real time systems where power consumption is more important than speed(excluding the deadlines we must hit).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone needs clarity on the question, just pop it in the note and I will try to revise this.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-10T15:51:08.570" Title="MSP430 In Circuit Emulator(ICE)" Tags="&lt;msp430&gt;" AnswerCount="2" />
  <row Id="3659" PostTypeId="2" ParentId="3649" CreationDate="2010-07-21T19:03:46.147" Score="1" ViewCount="" Body="&lt;p&gt;I have a PICKIT2 and there are some devices that it can program if you use the standalone PICKIT2 software but which it can't program from within MPLAB. It looks like the situation is the same for your device with pickit1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you look at the release notes for MPLAB it has a file for supported devices (On my machine it was stored at C:/Program Files (x86)/Microchip/MPLAB IDE/Readmes/Device Support.htm). That file indicates that specific PIC device is NOT supported for programming with a PICKIT1 using MPLAB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And yet the PICKIT1 documentation does indicate that device is supported for programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does the pickit1 come with a standalone programming program like pickit2 does? If so you can probably use that to upload the .hex file to it&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2010-07-21T19:03:46.147" CommentCount="2" />
  <row Id="3660" PostTypeId="2" ParentId="1554" CreationDate="2010-07-21T20:07:55.700" Score="4" ViewCount="" Body="&lt;p&gt;Tried a launchpad? ( &lt;a href=&quot;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_%28MSP-EXP430G2%29&quot; rel=&quot;nofollow&quot;&gt;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_%28MSP-EXP430G2%29&lt;/a&gt;) It's an MSP430 development board for $4.30 US (with free shipping). Only problem is finding one as they were pretty hot when they were announced about a month ago.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2010-07-21T20:07:55.700" />
  <row Id="3661" PostTypeId="2" ParentId="3653" CreationDate="2010-07-22T04:16:28.833" Score="4" ViewCount="" Body="&lt;p&gt;How bad do you to use the XMega?  If the crypto and random number generation are a big part of your project, Atmel's &lt;a href=&quot;http://www.atmel.com/dyn/products/devices.asp?family_id=662&quot; rel=&quot;nofollow&quot;&gt;SecureAVR&lt;/a&gt; series has a hardware random number built in, and is designed for cryptographic applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regardless, I doubt that you'll find a random seed source that has a good distribution.  You'll want to run it through a pseudo random number generator a few times  As long as you start with a different seed every time, this will give you a nice set of random numbers.  An LGC is a quick and easy pseudo random generator:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;static unsigned long Seed; &#xA;&#xA;/* Call before first use of NextVal */&#xA;unsigned long InitSeed()&#xA;{&#xA;   //Your code for random seed here&#xA;&#xA;   // Correct distribution errors in seed&#xA;   NextVal();&#xA;   NextVal();&#xA;   NextVal();&#xA;   return NextVal();&#xA;}&#xA;&#xA; /* Linear Congruential Generator &#xA;  * Constants from  &#xA;  * &quot;Numerical Recipes in C&quot; &#xA;  * by way of &#xA;   * &amp;lt;http://en.wikipedia.org/wiki/Linear_congruential_generator#LCGs_in_common_use&amp;gt;&#xA;   * Note: Secure implementations may want to get uncommon/new LCG values&#xA;  */&#xA;unsigned long NextVal()&#xA;{&#xA;  Seed=Seed*1664525L+1013904223L;&#xA;  return Seed;&#xA;} &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-22T04:16:28.833" CommentCount="3" />
  <row Id="3662" PostTypeId="2" ParentId="3657" CreationDate="2010-07-22T07:13:22.760" Score="1" ViewCount="" Body="&lt;p&gt;I use the TI FET tool.  I started out with the parallel port version but now use the USB FET430UIF.  This has been used successfully with the F149 and the new F5438 and F5418 devices, programming over the full JTAG and Spy-Bi-Wire interfaces.  I use the IAR tools but it is supported by all of the main development tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only problem that I have come across is that when you upgrade your development system to the latest version it can update the FET firmware and driver.  This can break compatibility with the old tool version, and returning to the older version is not easy.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-07-22T07:13:22.760" CommentCount="6" />
  <row Id="3663" PostTypeId="1" CreationDate="2010-07-22T09:12:47.993" Score="2" ViewCount="672" Body="&lt;p&gt;Hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the principles of implementing Ethernet over power lines ?&#xA;Is it reasonable/possible to create an Arduino shield which will provide both power &amp;amp; network ? (properly isolate the &quot;dangerous parts&quot;)&#xA;Mains is 220V 50Hz where I live.&lt;/p&gt;&#xA;" LastActivityDate="2010-07-22T13:06:27.850" Title="Power line communication principles" Tags="&lt;arduino&gt;&lt;power&gt;&lt;communication&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="3664" PostTypeId="2" ParentId="3663" CreationDate="2010-07-22T10:17:10.563" Score="2" ViewCount="" Body="&lt;p&gt;The big question here is what is your objective? If it's to DIY your own powerline ethernet adapters, I'd say don't bother. Working with mains voltages and working out how to make power line carrier work at those speeds is probably not worth it. Additionally, the cost of the whole thing will end up being way more than it would cost you for those DX adapters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If, on the other hand, you've got some other lower data rate application in mind and PLC is your only way to get the signal from point A to point B then you could give it a shot. There might even be some preexisting chipsets/modules you could work with to bootstrap the process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a good general overview of PLC, check out: &lt;a href=&quot;http://en.wikipedia.org/wiki/Power_line_communication&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Power_line_communication&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Standard mains voltage disclaimers applies. Be careful, don't get shocked.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2010-07-22T10:17:10.563" CommentCount="3" />
  <row Id="3665" PostTypeId="2" ParentId="3663" CreationDate="2010-07-22T13:06:27.850" Score="3" ViewCount="" Body="&lt;p&gt;In a nutshell, you add a high-frequency, low amplitude signal to the low-frequency, high amplitude AC signal.  Powered devices don't care about the added noise, and filtering can extract the high frequency signal without the low frequency component.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Probably due to the dangerous nature of mains power, I haven't seen any blogs or tech notes on how to implement it.  However, an &lt;a href=&quot;http://www.amazon.com/gp/search/ref=sr_nr_scat_283155_ln?rh=n%3A283155%2Ck%3Apower+line+communication&amp;amp;keywords=power+line+communication&amp;amp;ie=UTF8&amp;amp;qid=1279802247&amp;amp;scn=283155&amp;amp;h=c74617a312ff4bc1c5962721408e94901301f2ab&quot; rel=&quot;nofollow&quot;&gt;Amazon search&lt;/a&gt; for &quot;Power Line Communication&quot; yields 325 books, of which most appear pertinent to your question, and by much more qualified persons than myself. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is possible.  However, if you're using an Arduino, you likely don't have the expertise to create a well-isolated and well-insulated shield.  No offense intended, I would be hesitant to try it myself, and I've had some training on the topic at a university.  Also, an Arduino is meant to be handled, and, as Joby pointed out, it will definitely need a well-designed enclosure.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;All things considered, you'll have a much more flexible, easier to create, cheaper, and more robust system if you simply use an Ethernet shield and buy a powerline ethernet adapter like the one you linked to.  Do some searching, they're available for less than $30.&#xA;&lt;br&gt;&#xA;&lt;br&gt;&#xA;Slightly off-topic, but I would consider Power over Ethernet to be much more within the reach of an Arduino shield.  National has a decent &lt;a href=&quot;http://www.national.com/an/AN/AN-1474.pdf&quot; rel=&quot;nofollow&quot;&gt;appnote/FAQ&lt;/a&gt; on their &lt;a href=&quot;http://www.national.com/cat/index.cgi?i=i//221&quot; rel=&quot;nofollow&quot;&gt;LM507X&lt;/a&gt; series of powered device controllers.  This is something I'd like to try once I get some free time....&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-22T13:06:27.850" />
  <row Id="3666" PostTypeId="1" CreationDate="2010-07-22T13:25:02.660" Score="2" ViewCount="280" Body="&lt;p&gt;I'd like to multiplex rows of LEDs with a constant current sink driver. Should I just use BJTs to switch current into the rows of anodes, or is it better to use FETs, an array of FETs, or the same packaged into a convenient IC? It's easy to find current sinking ICs but I'm not sure what to search for on the sourcing side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to build something substantially similar to the Rainbowduino, &lt;a href=&quot;http://nkcelectronics.com/rainbowduino-led-driver-platform.html&quot; rel=&quot;nofollow&quot;&gt;http://nkcelectronics.com/rainbowduino-led-driver-platform.html&lt;/a&gt; . The Rainbowduino lights 24 LEDs at once with 24 current sinks and one current source using a Darlington array as the so-called &quot;Super Source Driver&quot;, then it lights the next row of 24 and so on for 8 rows. Very standard. I would like to find a substitute for their unavailable-in-the-USA Darlington array. What do I need search for on digikey/Mouser to find an IC containing an array of current sources?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2010-07-22T17:03:50.967" LastActivityDate="2010-07-22T17:31:33.147" Title="What to use for the high-side (anode) drivers of a common anode LED matrix?" Tags="&lt;led&gt;&lt;multiplexing&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="3667" PostTypeId="2" ParentId="3666" CreationDate="2010-07-22T13:59:03.817" Score="1" ViewCount="" Body="&lt;p&gt;A Maxim &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/1339&quot; rel=&quot;nofollow&quot;&gt;MAX7219&lt;/a&gt; can handle up to 64 LEDs as a current source. I wrote a short review about it &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/07/09/review-maxim-max7219-led-display-driver-ic/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-07-22T13:59:03.817" CommentCount="3" />
  <row Id="3668" PostTypeId="2" ParentId="3666" CreationDate="2010-07-22T15:35:27.530" Score="2" ViewCount="" Body="&lt;p&gt;There isn't anything wrong with using discrete devices (BJTs or FETs). FETs will get you more bang for your buck (lower losses, easier driving) but BJTs are cheaper.  All in one ICs are more convenient and take up less space, but are more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's your call. 750mA across a 1.4V BJT drop is just over a Watt; I understand that you're duty-cycling the drive, but I'd suggest P-channel FETs with small NPN switching transistors driving the gates if I were to do it myself. You're probably going to want to drive those LEDs from a higher (12V?) supply in order to maximize brightness, and the transistor will give you a nice open-collector gate driver (although the pull-up resistor may end up drawing some current.)  Without knowing more about your design it's hard to say what is best.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-22T15:35:27.530" CommentCount="1" />
  <row Id="3669" PostTypeId="2" ParentId="3666" CreationDate="2010-07-22T17:31:33.147" Score="2" ViewCount="" Body="&lt;p&gt;You can build your own common-anode driver out of discretes like this:&#xA;&lt;img src=&quot;http://imgur.com/DgMEn.png&quot; alt=&quot;alt text&quot;&gt;&lt;br&gt;&#xA;A forward-biased diode at the zener (D2) cathode will let you use 1 zener and a bunch of standard silicon diodes for lower cost and easier availability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember that discrete devices are available in arrays, which will greatly simplify breadboard or perfboard construction.  However, this will reduce your available power significantly.   If you're doing it on a PCB, it's perfectly fine to do it with discretes (as long as you have room.)   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With that circuit R1, D2, and Q1 all dissipate minimal power, so can be SOT-23 and 0805/0603, or low power arrays.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-22T17:31:33.147" CommentCount="7" />
  <row Id="3670" PostTypeId="2" ParentId="3644" CreationDate="2010-07-22T17:48:28.403" Score="0" ViewCount="" Body="&lt;p&gt;Kits seem to be nasty expensive at most places that I've shopped.  However, I've found that Electronix Express has a nice set of educational kits.  I've only bought a few prototyping parts kits, which are very well priced.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;See their &lt;a href=&quot;http://www.elexp.com/pro_bppk.htm&quot; rel=&quot;nofollow&quot;&gt;Assortment #1&lt;/a&gt;, &lt;a href=&quot;http://www.elexp.com/pro_bpk2.htm&quot; rel=&quot;nofollow&quot;&gt;supplement&lt;/a&gt; to Assortment #1, and look for their capacitor, inductor, potentiometer, and resistor kits as well.  I haven't used their project directed kits, but they have an &lt;a href=&quot;http://www.elexp.com/kit-all.htm&quot; rel=&quot;nofollow&quot;&gt;incredible selection&lt;/a&gt; if you had something in mind.  Finally, they package custom kits, both as assortments of components (See the &lt;a href=&quot;http://www.elexp.com/ktc_basc.htm&quot; rel=&quot;nofollow&quot;&gt;basic electronics kit&lt;/a&gt; starter) and as build-this-project kits.  I don't know where you're looking to use them, but these would be nice if you're, say, teaching an electronics class.  Of course, minimums apply for the custom kits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I am not affiliated with Electronix Express, just a happy customer.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-22T17:48:28.403" CommunityOwnedDate="2010-07-22T17:48:28.403" />
  <row Id="3671" PostTypeId="2" ParentId="2694" CreationDate="2010-07-22T18:57:54.287" Score="2" ViewCount="" Body="&lt;p&gt;I think the only solid way to monitor a system like that is a kind of watchdog-like arrangement: Have some other, &lt;em&gt;separately powered&lt;/em&gt;, system check it from time to time (or wait for a signal) and if it's not responding, alert.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also use that separate system to check for the battery instead. It won't suffer from the main battery being dead which will kill any monitoring system running off the main battery. If you can arrange a battery monitor that will run on a small battery like a coin cell and guarantee that it will outlast the main battery, that should do the job.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't want or can't have a second power source, the other comments seem to contain very good suggestions for self monitoring.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-22T18:57:54.287" CommentCount="3" />
  <row Id="3672" PostTypeId="2" ParentId="3653" CreationDate="2010-07-22T23:25:14.287" Score="1" ViewCount="" Body="&lt;p&gt;To be sure to not restart with the same sequence, I use somme byte in the eeprom :&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;avr/eeprom.h&amp;gt;&#xA;#include &amp;lt;stdlib.h&amp;gt; // rand&#xA;&#xA;u16  EEMEM randinit; &#xA;&#xA;int main(void) {&#xA;        srand(eeprom_read_word(&amp;amp;randinit));&#xA;        eeprom_write_word(&amp;amp;randinit,rand());&#xA;        [...]&#xA; }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This give quite good random, and does not cost much in programme/memory.&lt;/p&gt;&#xA;" OwnerUserId="824" LastEditorUserId="824" LastEditorDisplayName="" LastEditDate="2010-07-22T23:50:40.797" LastActivityDate="2010-07-22T23:50:40.797" CommentCount="2" />
  <row Id="3673" PostTypeId="2" ParentId="868" CreationDate="2010-07-23T01:52:32.517" Score="1" ViewCount="" Body="&lt;p&gt;The provided answers are incorrect.  Connecting to either the common pin (If there are 4 terminals) or simply shorting all of the cathodes or anodes together (to make a common pin) and using 3 signal lines will let you use a single resistor.  Choose the smallest resistor which can be connected continuously to any one pin without blowing the LED.  The supply voltage must not be too close to the highest voltage, (e.g. a 1.4V red LED and 2.5V blue LED will have manageable current differences at 5V, but 3.3V might make it hard to get a full spectrum over your brightness options.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, the software.  If you PWM each pin at a different time, the current difference in voltage can be compensated for in software.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example:  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Naive White:  &#xA;R --__________  &#xA;G ____--______  &#xA;B ________--__  &#xA;&#xA;More accurate white (V_red &amp;lt; V_green &amp;lt; V_blue, so I_red &amp;gt; I_green &amp;gt; I_blue, and the eye sees some colors brighter):&#xA;R  --____________________&#xA;G ________----___________&#xA;B ________________--------&#xA;&#xA;Bright Red-yellow, whitened:&#xA;R ----___&#xA;G___---_&#xA;B_____-&#xA;&#xA;This causes current drops (probably wouldn't turn on). Don't do this:&#xA;R ___----&#xA;G _----__&#xA;B----____&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Etc.&lt;br&gt;&#xA;The maximum brightness will be the same as PWMing them independently, because you're limited by the power dissipation of the single component.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-23T01:52:32.517" CommentCount="2" />
  <row Id="3674" PostTypeId="2" ParentId="2694" CreationDate="2010-07-23T02:38:30.297" Score="2" ViewCount="" Body="&lt;p&gt;You can get a much more accurate voltage reference with an op amp (use one with an enable pin, so that it can easily be shut off), and just tune your circuit to the voltage range you want to measure: 0V at 0.8V, and 3.3V at 1.1V.  If it's saturated, you know that you've got plenty of charge, and you don't seem to need a monitor, just an alarm.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, make sure that you measure several times (or use a current sense resistor), rather than assuming that a drop in voltage is caused by a dying battery.  It's not - battery voltage is dependent upon both discharge current and remaining charge.  A current spike can cause a big drop in voltage, but the battery will recover when it is removed.   See Figure 9 of &lt;a href=&quot;http://data.energizer.com/PDFs/alkaline_appman.pdf&quot; rel=&quot;nofollow&quot;&gt;Energizer's alkaline datasheet.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-23T02:38:30.297" CommentCount="2" />
  <row Id="3675" PostTypeId="1" AcceptedAnswerId="3717" CreationDate="2010-07-23T18:47:40.147" Score="4" ViewCount="371" Body="&lt;p&gt;What happens to a logic gate (besides magic smoke discharge) seeing a voltage greater than Vcc? Is it just because the gate was not designed to handle a higher voltage than the recommended Vcc, or is it also usually important to limit the voltage to the actual Vcc even if the chip works within a range of voltages?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-07-26T17:36:42.813" Title="Why is it important not to exceed Vcc at the input to a logic gate?" Tags="&lt;voltage&gt;&lt;magic-smoke&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="3677" PostTypeId="2" ParentId="3564" CreationDate="2010-07-23T21:35:41.923" Score="3" ViewCount="" Body="&lt;p&gt;What kind of information do you have to start with?  Or are you creating these from scratch?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do a lot of this stuff using postscript, moveto, lineto, lineto, moveto, etc.  From there you can turn it into just about anything jpeg, png, etc, or embed it directly into a postscript document then that can become a pdf.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Postscript allows for all free tools and is operating system independent so you dont have to buy office this or excel that.  Ghostscript and ghostview are your friends.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;svg is likely another format/language you can use as well, free, open, converts to anything.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-07-23T21:35:41.923" CommentCount="1" />
  <row Id="3678" PostTypeId="2" ParentId="3577" CreationDate="2010-07-23T22:04:36.677" Score="0" ViewCount="" Body="&lt;p&gt;Radio Shack sells a &lt;a href=&quot;http://www.radioshack.com/product/index.jsp?productId=2102855&quot; rel=&quot;nofollow&quot;&gt;9v Recording Module&lt;/a&gt; that stores up to 20 seconds of audio and plays it back at the touch of a button.  Cat # 276-1323, $10.99.  Currently out of stock on-line, but might be available in stores.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-07-23T22:04:36.677" />
  <row Id="3679" PostTypeId="1" AcceptedAnswerId="3680" CreationDate="2010-07-24T02:53:27.607" Score="2" ViewCount="889" Body="&lt;p&gt;I'm new to electronics and was wondering what was the difference between a Mosfet and a voltage regulator?&lt;/p&gt;&#xA;" OwnerUserId="619" LastActivityDate="2010-07-26T14:07:17.437" Title="Difference between Mosfet and Voltage Regulator?" Tags="&lt;beginner&gt;&lt;mosfet&gt;&lt;voltage-regulator&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="3680" PostTypeId="2" ParentId="3679" CreationDate="2010-07-24T05:13:02.233" Score="6" ViewCount="" Body="&lt;p&gt;MOSFETs and voltage regulators often come in similar-looking packages and usually have 3 pins each, but their functions are different.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A voltage regulator takes in a high voltage, like 12 V, and puts out a lower voltage, like 5 V. The canonical example of a voltage regulator is the &lt;a href=&quot;http://www.fairchildsemi.com/pf/LM/LM7805.html&quot; rel=&quot;nofollow&quot;&gt;LM7805&lt;/a&gt;. They tend to be fairly inefficient (some of the power is lost as heat).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A MOSFET is a semiconductor switch. It varies the resistance between two pins in response to a voltage on a third pin. Inside the MOSFET, the voltage on the third pin (the gate) pulls electrons into a narrow path between the other two pins (the source and drain), allowing electricity to flow. Here's &lt;a href=&quot;http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/first11/part9/page4.html&quot; rel=&quot;nofollow&quot;&gt;a decent diagram&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-07-26T14:07:17.437" LastActivityDate="2010-07-26T14:07:17.437" CommentCount="2" />
  <row Id="3681" PostTypeId="2" ParentId="3679" CreationDate="2010-07-24T05:40:28.797" Score="3" ViewCount="" Body="&lt;p&gt;In very basic terms, a voltage regulator is a device for building a power supply, whereas a mosfet is something you use to build an amplifier. A voltage regulator is basically an integrated circuit that has several transistors within it, while a mosfet is exactly a single transistor.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-24T05:40:28.797" CommentCount="2" />
  <row Id="3682" PostTypeId="1" CreationDate="2010-07-24T14:08:54.383" Score="2" ViewCount="129" Body="&lt;p&gt;Hello:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im tryng to place some ultrasound experiments at school and i have this pulser available (&lt;a href=&quot;http://www.olympus-ims.com/en/5800pr/&quot; rel=&quot;nofollow&quot;&gt;Olympus 5800PR&lt;/a&gt;), the problem is that i dont know how to capture the data on my laptop. I know i have to set an adc to do this but maybe there are easier ways to do this, preferable the cheapest ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hearing suggestions.. tnxs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oz!&lt;/p&gt;&#xA;" OwnerUserId="920" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-07-24T18:53:18.657" LastActivityDate="2010-11-17T22:07:19.877" Title="Capture Olympus 5800PR US pulser/receiver data on my laptop" Tags="&lt;ultrasound&gt;&lt;adc&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="3683" PostTypeId="1" AcceptedAnswerId="3725" CreationDate="2010-07-24T15:20:45.247" Score="2" ViewCount="947" Body="&lt;p&gt;Hi all! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to change the PWM output frequency roughly once a millisecond using a dsPIC33FJ256GP710, and I'm having mixed results.  I first tried this: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; #include &amp;lt;p33fxxxx.h&amp;gt; &#xA;&#xA; _FOSCSEL(FNOSC_PRIPLL); &#xA; _FOSC(FCKSM_CSDCMD &amp;amp; OSCIOFNC_OFF &amp;amp; POSCMD_XT); &#xA; _FWDT(FWDTEN_OFF); &#xA;&#xA; static unsigned int PWM_TABLE[7][2] = &#xA; { &#xA;     {132, 66}, {131, 66}, {130, 65}, {129, 65}, {128, 64}, {127, 64}, {126, 63} // Compare, 50% duty &#xA; }; &#xA;&#xA; static int curFreq = 0; &#xA;&#xA; int main(void) &#xA; { &#xA;     int i; &#xA;&#xA;     PLLFBD = 0x009E;                // Set processor clock to 32 MHz (16 MIPS) &#xA;     CLKDIV = 0x0048;  &#xA;&#xA;     LATCbits.LATC1 = 0;             // Make RC1 an output for a debug pin &#xA;     TRISCbits.TRISC1 = 0;     &#xA;&#xA;     LATDbits.LATD6 = 0;             // Make RD6/OC7 an output (the PWM pin) &#xA;     TRISDbits.TRISD6 = 0; &#xA;&#xA;     T2CONbits.TON = 0;              // Disable Timer 2                      &#xA;     OC7CONbits.OCM = 0b000;         // Turn PWM mode off &#xA;     PR2 = PWM_TABLE[curFreq][0];    // Set PWM period &#xA;     OC7RS = PWM_TABLE[curFreq][1];  // Set PWM duty cycle &#xA;     OC7CONbits.OCM = 0b110;         // Turn PWM mode on &#xA;     T2CONbits.TON = 1;              // Enable Timer 2 &#xA;&#xA;     while (1) &#xA;     {                 &#xA;         for (i = 0; i &amp;lt; 3200; i++) {}      // Delay roughly 1 ms         &#xA;         curFreq = (curFreq + 1) % 7;       // Bump to next frequency        &#xA;         PR2 = PWM_TABLE[curFreq][0];       // Set PWM period &#xA;         OC7RS = PWM_TABLE[curFreq][1];     // Set PWM duty cycle &#xA;         LATCbits.LATC1 = !LATCbits.LATC1;  // Toggle debug pin so we know what's happening         &#xA;     } &#xA; } &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The result is that PWM drops out for about 4 ms at what looks to be a repeatable interval, roughly aligned with my debug pin toggle (in other words, when the code is messing with the period and duty cycle registers).  I'll attach a photo of my scope trace.  Channel 1 is PWM and channel 2 is the debug pin that's toggled when the code attempts to adjust the frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, I started thinking about timer rollovers, and I did some searching on a few forums.  I came up with a few ideas based on a few posts I read.  The best idea seemed to be to enable the Timer 2 interrupt, turn PWM mode off inside it, and only change the period and duty cycle registers inside the Timer 2 interrupt.  So, I wrote this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; #include &amp;lt;p33fxxxx.h&amp;gt; &#xA;&#xA; _FOSCSEL(FNOSC_PRIPLL); &#xA; _FOSC(FCKSM_CSDCMD &amp;amp; OSCIOFNC_OFF &amp;amp; POSCMD_XT); &#xA; _FWDT(FWDTEN_OFF); &#xA;&#xA; static int curFreq = 0; &#xA;&#xA; static unsigned int PWM_TABLE[7][2] = &#xA; { &#xA;     {132, 66}, {131, 66}, {130, 65}, {129, 65}, {128, 64}, {127, 64}, {126, 63} // Compare, duty &#xA; }; &#xA;&#xA; int main(void) &#xA; { &#xA;     int i, ipl; &#xA;&#xA;     PLLFBD = 0x009E;                // Set processor clock to 32 MHz (16 MIPS) &#xA;     CLKDIV = 0x0048;  &#xA;&#xA;     LATCbits.LATC1 = 0;             // Make RC1 an output for a debug pin &#xA;     TRISCbits.TRISC1 = 0;     &#xA;&#xA;     LATDbits.LATD6 = 0;             // Make RD6/OC7 an output (the PWM pin) &#xA;     TRISDbits.TRISD6 = 0; &#xA;&#xA;     OC7CONbits.OCM = 0b000;         // Turn PWM mode off     &#xA;     OC7RS = PWM_TABLE[curFreq][1];  // Set PWM duty cycle &#xA;     PR2 = PWM_TABLE[curFreq][0];    // Set PWM period &#xA;     OC7CONbits.OCM = 0b110;         // Turn PWM mode on &#xA;&#xA;     T2CONbits.TON = 0;              // Disable Timer 2 &#xA;     TMR2 = 0;                       // Clear Timer 2 register     &#xA;     IPC1bits.T2IP = 1;              // Set the Timer 2 interrupt priority level &#xA;     IFS0bits.T2IF = 0;              // Clear the Timer 2 interrupt flag &#xA;     IEC0bits.T2IE = 1;              // Enable the Timer 2 interrupt &#xA;     T2CONbits.TON = 1;              // Enable Timer 2 &#xA;&#xA;     while (1) &#xA;     {                 &#xA;         for (i = 0; i &amp;lt; 1600; i++) {}      // Delay roughly 1 ms &#xA;         SET_AND_SAVE_CPU_IPL(ipl, 2);      // Lock out the Timer 2 interrupt &#xA;         curFreq = (curFreq + 1) % 7;       // Bump to next frequency         &#xA;         RESTORE_CPU_IPL(ipl);              // Allow the Timer 2 interrupt &#xA;         LATCbits.LATC1 = !LATCbits.LATC1;  // Toggle debug pin so we know what's happening &#xA;     } &#xA; } &#xA;&#xA; void __attribute__((__interrupt__)) _T2Interrupt(void) &#xA; {     &#xA;     T2CONbits.TON = 0;              // Disable Timer 2 &#xA;     TMR2 = 0;                       // Clear Timer 2 register &#xA;     OC7CONbits.OCM = 0b000;         // Turn PWM mode off &#xA;     OC7RS = PWM_TABLE[curFreq][1];  // Set the new PWM duty cycle &#xA;     PR2 = PWM_TABLE[curFreq][0];    // Set the new PWM period     &#xA;     OC7CONbits.OCM = 0b110;         // Turn PWM mode on &#xA;     IFS0bits.T2IF = 0;              // Clear the Timer 2 interrupt flag &#xA;     T2CONbits.TON = 1;              // Enable Timer 2 &#xA; }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This looks to be more stable as far as I can tell on my ancient scope, but now the waveform is no longer regularly-shaped (the duty cycle seems to be inexplicably inconsistent) and if I try hard enough I can convince myself that I still see a millisecond of PWM dropout when my scope is set to a 5 or 10 millsecond timebase. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's certainly better than it was, and I can continue to mess with it in the hopes of fixing the irregular waveform produced by the second bit of code, but my question is: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a &quot;right&quot; way to do this?  Or at least a better way than the path I'm on? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be thoroughly, thoroughly appreciated. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.freeimagehosting.net/uploads/c132216a28.jpg&quot; alt=&quot;Scope trace&quot;&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-07-26T21:13:38.983" Title="How do I modulate PWM frequency in realtime with a Microchip dsPIC?" Tags="&lt;microchip&gt;&lt;dspic&gt;&lt;pwm&gt;&lt;frequency&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="3684" PostTypeId="2" ParentId="3683" CreationDate="2010-07-24T15:41:17.907" Score="1" ViewCount="" Body="&lt;p&gt;I would try slowing everything down by a factor of 10 so you can see in more detail when exactly the PWM is dying. I'd also try tweaking the values in your table of period and duty cycle. Maybe you're misconfiguring the PWM on 4 of your 7 cycles? I notice that there are 4 PWM period values that are above 128-- maybe that's causing problems?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that didn't help, I would look for a bigger pattern. How often does the 4 ms gap repeat?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Very well-asked question, by the way.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-24T15:41:17.907" CommentCount="4" />
  <row Id="3685" PostTypeId="2" ParentId="3423" CreationDate="2010-07-25T02:28:15.773" Score="0" ViewCount="" Body="&lt;p&gt;I'm in the process of installing the toolchain to use the Transterpreter with the Arduino. It lets you write occam-pi for the ATmega chip (which supports concurrency). There's also an occam-pi library that supports all of the Arduino functions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://projects.cs.kent.ac.uk/projects/kroc/trac/wiki/CrossBuilding&quot; rel=&quot;nofollow&quot;&gt;http://projects.cs.kent.ac.uk/projects/kroc/trac/wiki/CrossBuilding&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Transterpreter is now part of the KRoC (Kent occam-pi system) project. &lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2010-07-25T02:28:15.773" CommunityOwnedDate="2010-07-25T02:28:15.773" />
  <row Id="3686" PostTypeId="1" CreationDate="2010-07-25T09:39:59.030" Score="5" ViewCount="167" Body="&lt;p&gt;I wonder whether anyone here would have actively worked with the Stephen Hobley library for Pixart Sensor &lt;a href=&quot;http://www.stephenhobley.com/blog/2009/03/01/pixartwiimote-sensor-library-for-arduino/comment-page-1/#comment-4173&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. I used the same hardware configuration as mentioned in Stephen's website. However, I run in to this problem:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I read somewhere that the Pixart camera returns a value only when it sees a IR Blob. So, accordingly, the Pixart Library should also return values only when the camera sees any IR blob, right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, in my setup, as soon as I power Arduino, my serial port monitor starts displaying:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Blob 1 detected x=0, y=0, size=0&#xA;Blob 2 detected x=0, y=0, size=0&#xA;Blob 3 detected x=0, y=0, size=0&#xA;Blob 4 detected x=0, y=0, size=0&#xA;...&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I don't show it any IR source, yet I keep getting this. When I give it an IR source, it doesn't track it and still I keep getting the same result!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please help, I dont seem to be getting to the root of problem. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank You&lt;/p&gt;&#xA;" OwnerUserId="913" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-15T22:12:05.760" LastActivityDate="2011-01-15T22:12:05.760" Title="Problem regarding Stephen Hobley's lib for Pixart Sensor" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;ir&gt;" AnswerCount="1" />
  <row Id="3687" PostTypeId="2" ParentId="3430" CreationDate="2010-07-25T16:31:30.703" Score="-1" ViewCount="" Body="&lt;p&gt;Go to YouTube and look up joule thief&lt;/p&gt;&#xA;" LastActivityDate="2010-07-25T16:31:30.703" CommentCount="2" />
  <row Id="3690" PostTypeId="1" AcceptedAnswerId="3692" CreationDate="2010-07-25T20:06:49.573" Score="2" ViewCount="157" Body="&lt;p&gt;What inexpensive or free tools could you recommend to view and control pin states via JTAG boundary-scan?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm aware of full-featured boundary-scan products that cost tens of thousands of dollars and used in manufacturing houses mainly. I want a simple inexpensive tool to occasionally check few suspected pins if they are soldered correctly; to light LEDs on a board without writing any firmware for MCU/CPLD/FPGA; to see if pressing a button on a board changes the appropriate pin state, etc.&lt;/p&gt;&#xA;" OwnerUserId="997" LastActivityDate="2010-10-04T10:47:31.450" Title="JTAG boundary-scan test software to view and control pin states" Tags="&lt;boundary-scan&gt;&lt;jtag&gt;" AnswerCount="3" />
  <row Id="3691" PostTypeId="2" ParentId="622" CreationDate="2010-07-25T20:37:01.013" Score="1" ViewCount="" Body="&lt;p&gt;You're working with an I2C bus, right?&#xA;I'm going to call the lines on the 3.3 V side SDA3 and SCL3; the two lines on the 5.0 V side SDA5 and SCL5.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&quot;mosfet and two resistors&quot;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As todbot and cyphunk already pointed out, the &quot;mosfet and two resistors&quot; circuit described in the &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=65&quot; rel=&quot;nofollow&quot;&gt;Sparkfun &quot;sensor interfacing&quot; tutorial&lt;/a&gt; does what you want:&#xA;The logical data flow is symmetric -- data flows in both directions on the SDA lines, from the low side to the high side and, milliseconds later, from the high side to the low side.&#xA;The &quot;will not work the other direction&quot; note points out the circuit is physically assymetric: your 5.0 V I2C device must be connected to the &quot;high side&quot;, your 3.3 V device must be connected to the &quot;low side&quot;.&#xA;Because the circuit is physically asymmetric, it's certainly not obvious that it is logically symmetric.&#xA;(That tutorial links to a AN97055 app note that shows a &quot;two mosfets and two resistors&quot; circuit that is physically symmetric, and therefore is obviously logically symmetric).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The lines labeled &quot;TX&quot; on the &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8745&quot; rel=&quot;nofollow&quot;&gt;Sparkfun converters&lt;/a&gt; -- that the original poster pointed out -- implement that &quot;mosfet and two resistors&quot; bidirectional circuit.&#xA;So connect SDA3 to TX_LV, SDA5 to TX_HV, SCL3 to TX2_LV, and SCL5 to TX2_HV.&#xA;Then data flows in both directions:&#xA;When your low-side device drives the SDA3 and SCL3 pins, the appropriate voltages are seen on the high-side SDA5 and SCL5 pins.&#xA;Milliseconds later, when the high-side device drives the SDA5 and SCL5 pins, the appropriate voltages are seen on the SDA3 and SCL3 pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Inconsistently, the lines labeled &quot;RX&quot; on that converter board will only transmit data in the high-voltage to low-voltage direction).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;bi-directional optoisolator&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you are using I2C, you might also be interested in a &lt;a href=&quot;http://david.carybros.com/html/schematic.html#isolator&quot; rel=&quot;nofollow&quot;&gt;bi-directional optoisolator for I2C&lt;/a&gt;.&#xA;The two-optoisolator circuit is more expensive and slower than the &quot;mosfet and two resistors&quot; circuit,&#xA;but it works when one side has signals that swing between 0 V and 5.0 V, and the other side has signals that swing between 500.0 V and 505.0 V.&#xA;The two-optoisolator circuit is also completely physically symmetric -- and therefore logically symmetric -- it doesn't matter which side is the high side and which side is the low side.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-07-25T20:37:01.013" CommunityOwnedDate="2010-07-25T20:37:01.013" />
  <row Id="3692" PostTypeId="2" ParentId="3690" CreationDate="2010-07-25T20:55:02.253" Score="3" ViewCount="" Body="&lt;p&gt;Take a look at TopJTAG Probe -- &lt;a href=&quot;http://www.topjtag.com&quot; rel=&quot;nofollow&quot;&gt;http://www.topjtag.com&lt;/a&gt;. It seems intended to what you've described. A good news it works with several popular JTAG pods so you probably don't need to buy additional JTAG pod but use yours existing.&lt;/p&gt;&#xA;" LastActivityDate="2010-07-25T20:55:02.253" CommentCount="1" />
  <row Id="3693" PostTypeId="1" AcceptedAnswerId="3696" CreationDate="2010-07-25T22:52:16.427" Score="6" ViewCount="329" Body="&lt;p&gt;I picked up a 9V switching DC adapter from SparkFun a while back, but I've been hesitant to use it because it doesn't have any of the usual &quot;safety&quot; approvals that you normally see on power adapters (UL listed, CSA approved, etc.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this just unfounded paranoia?  Are there safety issues to think about when using a DC power adapter for a project that will run 24/7?&lt;/p&gt;&#xA;" OwnerUserId="971" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-06T21:20:39.237" LastActivityDate="2011-05-19T14:19:46.323" Title="Is it safe to use a DC power adapter that isn't UL Listed or CSA certified?" Tags="&lt;power-supply&gt;&lt;dc&gt;&lt;adapter&gt;&lt;safety&gt;&lt;ul&gt;" AnswerCount="7" CommentCount="1" />
  <row Id="3694" PostTypeId="2" ParentId="3693" CreationDate="2010-07-26T00:00:24.000" Score="4" ViewCount="" Body="&lt;p&gt;UL listed means that even if the device shorts, you will not get electrocuted when you touch it. Given that it's not expensive to get an UL certified DC adapter (less then $10), why take the chance?&lt;/p&gt;&#xA;" OwnerUserId="327" LastActivityDate="2010-07-26T00:00:24.000" CommentCount="5" />
  <row Id="3695" PostTypeId="2" ParentId="3693" CreationDate="2010-07-26T01:23:15.090" Score="1" ViewCount="" Body="&lt;p&gt;There are a variety of design, manufacturing and qualification requirements&#xA;to meet UL, CSA and TUV. I would not use a line powered supply that does not meet&#xA;these specifications. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also tend to buy these supplies from name brand manufacturers and manufacturers&#xA;that have ISO9000 approval even though it is difficult to know how/where a device was manufactured.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would try to return the supply.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:19:46.323" LastActivityDate="2011-05-19T14:19:46.323" />
  <row Id="3696" PostTypeId="2" ParentId="3693" CreationDate="2010-07-26T02:20:44.027" Score="8" ViewCount="" Body="&lt;p&gt;Safety approvals cost (a LOT) of money. You won't find anything from sites such as SparkFun dispaying these logos. It's not because they're unsafe, it's because it's prohibitively expensive to get the testing done to &lt;em&gt;prove&lt;/em&gt; they're safe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are buying things from sites such as SparkFun, etc. it is also assumed that you are experienced enough to work safely. Personally, I have zero problem using unlisted equipment, but then again I am in the business of designing this kind of equipment and have a pretty good &quot;feel&quot; for circuit safety and design capabilities based on observing the parts and quality of manufacture. I've seen some pretty sketchy stuff in my time, but I haven't gotten the screaming heebie-jeebies from anything from sites like that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said... Use it at your own risk. If something doesn't feel right to you, don't use it.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-26T02:20:44.027" CommentCount="3" />
  <row Id="3697" PostTypeId="2" ParentId="3675" CreationDate="2010-07-26T02:31:35.803" Score="8" ViewCount="" Body="&lt;p&gt;Almost every IC you can buy has a number of &quot;hidden features&quot; that are assumed to be present and thus not discussed in the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Among these are body diodes/ESD suppression diodes. These guys generally hide on every I/O pin on every device, from basic logic gates through memory to high-end microprocessors. They route any voltage that is greater than VDD (supply voltage) or lower than VSS (supply common) to the appropriate rail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you apply a voltage in excess of either of these limits, the body diodes become forward-biased and effectively clamp the level at the pin to either VDD or VSS. This sounds like a good thing and generally is, but they are very small devices and cannot dissipate much power. You can end up damaging this diode (shorting it or blowing it open). In the former case it can lead to &quot;stuck&quot; I/O pins, and in the latter case, the next overvoltage can destroy the input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Open-collector outputs are handy for being able to control some outputs, as pingswept mentioned already. Putting small resistors in series with inputs which may come into contact with nasty voltages, and/or using external diodes (even an 1N914 is HUGE compared to the protection diodes on the IC itself) is a good way to help protect devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, properly designing your input or output circuitry to handle continuous or repeated transient events like these can be a design challenge in and of itself. Generally speaking, if you are worried about blowing an expensive part, buffer the input or output with (much) cheaper and preferably socketed buffer ICs.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-26T02:31:35.803" />
  <row Id="3698" PostTypeId="2" ParentId="3693" CreationDate="2010-07-26T04:06:45.480" Score="2" ViewCount="" Body="&lt;p&gt;Getting a UL stamp means you meet a number of safety tests for your equipment.  In the US a UL stamp is only 'required' on some electrical equipment in some markets, generally items running on main power but there are some exceptions and only when its being sold or placed in some public areas, for instance a school.  Even then a UL stamp is completely optional, however a local inspector may not allow a non-UL device in a building.  Needing to be UL listed is completely a political issue not a technical one. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The documents that cover a UL listing are long and cover many issues from shock prevention, reducing the chance of a fire, RF emissions, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As one example you could use a UL listed power supply to power a low voltage device, something like a laptop brick, but if you place that brick within an enclosure it is no longer UL compliant.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;UL listing is really a hoop you need to jump through for safety compliance for a product your selling as defined by the market your selling that product to.  I wouldn't try to put a non UL listed part in something like a school but for some applications its not needed.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting a UL stamp is expensive.  The European version of the UL stamp is the CE stamp and it actually goes farther in various directions than a UL stamp does.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wouldn't bother worrying or caring about a UL listing unless you know that your market or installation cares about that, the best way to determine this is to call you local electrical inspector and ask him about the issue at hand.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-07-26T04:06:45.480" />
  <row Id="3699" PostTypeId="2" ParentId="3693" CreationDate="2010-07-26T04:53:04.517" Score="1" ViewCount="" Body="&lt;p&gt;Using something like that might invalidate a household insurance policy. It would be a good idea to check the small print.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-26T04:53:04.517" />
  <row Id="3700" PostTypeId="2" ParentId="1468" CreationDate="2010-07-26T05:01:11.187" Score="1" ViewCount="" Body="&lt;p&gt;Best practice is to always drive ADC inputs with an op-amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If, hypothetically, a person were to be the kind of dare-devil hacker as to disregard that rule of thumb and (gasp!) directly connect the ADXL193 +/-250g output to a 10 bit ratiometric ADC, then yes,&#xA;an ADC value of 30 counts above the &quot;resting&quot; value implies an acceleration of&#xA;30 * 5V/2^10 * 1g/8mV = 18 g.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the accelerometer is ratiometric and balances zero g near VCC/2, and assuming your ADC is also ratiometric, then after you drop your power supply voltage to 3.7 V,&#xA;the &quot;resting&quot; value you read on your ADC should be roughly the same as before,&#xA;and an 18 g acceleration will still produce the same 30 counts above the new resting value.&#xA;However, as Lou pointed out, you're likely to get a worse signal/noise ratio with VCC at 3.7 V than with VCC at 5 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you were to follow recommended practice and stick an op-amp between the accelerometer and the ADC, the picture would be slightly different.&#xA;You have to pick some gain for the op-amp.&#xA;I suppose you &lt;em&gt;could&lt;/em&gt; pick a gain of 1, which would give you the same numbers as above, but there are better choices for the gain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would try to spread the entire range of expected g forces, plus some safety margin (&quot;fudge factor&quot;) at the top and bottom of the range, over the ADC input range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lou assumes that you pick a gain such that the full-range output of the accelerometer exactly matches the full-range input of your ADC.&#xA;That's a reasonable choice.&#xA;However, I would probably sacrifice some of that range to get more precision.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The kinds of accelerations I'm interested in are much smaller -- roller coasters and other amusement rides, hand-held tilt and shake and drop sensors, etc.&#xA;I've been told that highly-trained fighter pilots wearing anti-G suits black out around 9 g, so amusement rides will have much lower g forces.&#xA;I'm guessing around roughly +- 20 g is far more than enough.&#xA;To get +-20 g to map to the 0 to 5 V range of the ADC, I need a gain of&#xA;Again = 5 V * 1/40g * 1g/8mV = 16.&#xA;We'll probably round this to some convenient hardware value, and fix up the exact ratio in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With an op amp between the accelerometer an the ADC,&#xA;an ADC value of 30 counts above the &quot;resting&quot; value implies an acceleration of&#xA;30 * 5V/2^10 * 1/Again * 1G/8mV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the gain I've chosen, those 30 counts represent&#xA;30 * 5V/2^10 * 1/16 * 1g/8mV = 1.1 g.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This additional gain gives me an order of magnitude more resolution (I can distinguish between several different small accelerations that would have previously all been lumped into &quot;zero acceleration), at the sacrifice of an order of magnitude of range.&#xA;Using an op-amp will definitely give you a better signal/noise ratio than no op amp at all. Using a gain of 10 or 30 or 100 may also give you a slightly better signal/noise ratio than a 1:1 op-amp.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-07-26T05:01:11.187" CommunityOwnedDate="2010-07-26T05:01:11.187" />
  <row Id="3701" PostTypeId="1" AcceptedAnswerId="3709" CreationDate="2010-07-26T09:30:59.173" Score="3" ViewCount="179" Body="&lt;p&gt;I would like to make a circuit that turns on a power supply to a microcontroller after holding down a button for a period of time (say 2 seconds). To make matters slightly more complicated, if possible, I would like to use this button as an input also. The power off could come from another switch if need be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking of something like a latching RC circuit to an zener that switches a MOSFET on to allow power through.&#xA;Ideally the solution would not consume power until the switch is pressed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for any help&lt;/p&gt;&#xA;" OwnerUserId="641" LastActivityDate="2011-05-18T11:40:42.410" Title="Delayed power supply startup" Tags="&lt;power-supply&gt;&lt;timer&gt;&lt;microcontroller&gt;&lt;delay&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="3702" PostTypeId="2" ParentId="3701" CreationDate="2010-07-26T10:22:15.440" Score="2" ViewCount="" Body="&lt;p&gt;How about using a tiny 6-pin MCU like the PIC10F200? That's the sort of application they were designed for.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-26T10:22:15.440" CommentCount="1" />
  <row Id="3703" PostTypeId="1" AcceptedAnswerId="3718" CreationDate="2010-07-26T10:57:17.863" Score="3" ViewCount="432" Body="&lt;p&gt;Hi all&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I have hooked up a ATtiny88, and am programming it with the Dragon AVR using ISP. I have also set up the build toolchain, using avrdude, and the gnu avr tools. Everything is working great.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I would like to do in-circuit debugging using the advertised debugwire which is also connected to the ISP and which the dragon supports. But which tools do I use? I see there is a avr-gdb, but it seems that I needs some kind of simulator, however I would like to debug in-circuit on the real MCU. Is this possible?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="718" LastActivityDate="2010-07-26T18:19:13.730" Title="AVR debugwire in Linux" Tags="&lt;linux&gt;&lt;avr&gt;&lt;debugwire&gt;&lt;in-circuit&gt;&lt;debug&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="3707" PostTypeId="2" ParentId="3675" CreationDate="2010-07-26T11:45:16.140" Score="3" ViewCount="" Body="&lt;p&gt;Two issues: Protection diodes from an input to GND and VCC will allow large currents if the voltage at the input is above VCC or below GND. Eventually, the diodes might heat up a lot and become low-ohmic, i.e. they will act like a short from the input to VCC or GND. Also, latch-up may occur. This means that a parasitic thyristor hidden inside of the IC's input circuit will turn on and remain turned on as long as the external voltage is present and causes a current to flow into the input. Eventually, the input circuitry might heat up and permanent damage will occur.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are two things to watch in the data sheet: input voltages relative to the actual VCC applied to the chip (they read something like V_in must be less than VCC+0.3V and greater that GND-0.3V) and absolute voltages at the input pins (e.g. V_in must be less than 6V). Exceeding the limits relative to VCC will likely blow the internal diodes. Exceeding the absolute limits will likely blow the gate of the CMOS transistors at the input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some logic gates designed for interfaces between 3.3V logic and 5V logic can handle 5V at the input when the IC itself is supplied with 3.3V, but these are rare. These ICs lack the protection diodes from the input to VCC (and usually have z-diodes from the input to GND and some other tricks to prevent ESD damage).&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-07-26T11:45:16.140" />
  <row Id="3708" PostTypeId="2" ParentId="3679" CreationDate="2010-07-26T11:54:19.180" Score="4" ViewCount="" Body="&lt;p&gt;A MOSFET is a single transistor that will be able to provide a regulated voltage if used inside of a whole voltage regulator circuit (or IC). To build a (linear) voltage regulator, one needs a pass element (regulated &quot;valve&quot;, e.g. MOSFET or biolar transistor), a voltage reference and a circuit that compares the desired, regulated output voltage to the reference voltage and adjusts the pass element such that the output will remain in regulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thus, a MOSFET may act as one part inside of a voltage regulator.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-07-26T11:54:19.180" />
  <row Id="3709" PostTypeId="2" ParentId="3701" CreationDate="2010-07-26T12:12:07.367" Score="2" ViewCount="" Body="&lt;p&gt;You may want to search for &quot;power supply sequencers&quot; and &quot;powerpath controllers&quot; at Linear Technology, Maxim and TI. Those devices integrate a variety of sequencing and control&#xA;functions including on/off, delay start, sequencing of multiple supplies. Some&#xA;have integrated FETs.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:40:42.410" LastActivityDate="2011-05-18T11:40:42.410" />
  <row Id="3711" PostTypeId="2" ParentId="1468" CreationDate="2010-07-26T15:18:39.020" Score="1" ViewCount="" Body="&lt;p&gt;Others have done a good job with the descriptions of how to use the device and calculate your G's, so I'll just focus on your last bullet point.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm assuming that you want to connect the sensor with a micro running at 3.3V.  There are several ways of doing this.  I'll list them from worst to best:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;0&lt;/strong&gt; - Power the sensor off of 3.3V.  This will cause it to run out of spec and possibly behave erratically.  Would not recommend without extensive testing (Compare with one running at 5V) and contacting the manufacturer for possible pitfalls.&lt;br&gt;&#xA;&lt;strong&gt;0.1&lt;/strong&gt; - Power the sensor off of 3.5V and connect directly from the sensor to the micro, without level conversion.  Technically, you're within the maximum pin voltage ratings.  You do loose your upper 200mV of range, so you can only read from -250G to +160G or something like that.&lt;br&gt;&#xA;&lt;strong&gt;1&lt;/strong&gt; - Use a voltage divider.  You need to step down from 5 to 3.3, not the other way, so just stick in one 100k and one 196k resistor.  Your micro now can read the full range of the sensor with its built in ADC.  You are aware of the decreased resolution caused by this change, Also note that your output from the sensor is limited to 100uA, so you'll need large resistors, which makes for noisy signals.  Also, measuring rapidly changing signals will be hard, because pin capacitance will take a long time to charge.  You want an output impedance of less than 10k for most onboard ADCs.&lt;br&gt;&#xA;&lt;strong&gt;1.1&lt;/strong&gt; - Buffer the output of the sensor through an opamp, so that you can use 1k and 1.96k resistors and get less noise and faster conversions.&lt;br&gt;&#xA;&lt;strong&gt;1.2&lt;/strong&gt; - Buffer the output through the opamp, and use it in an amplifier configuration to eliminate the voltage divider as an input, and instead connect the output directly to your ADC.  This just eliminates a little more noise.&lt;br&gt;&#xA;&lt;strong&gt;2&lt;/strong&gt; - Use a separate ADC, powered at 5V, and interface with it over some 1k resistors to protect your 3.3V input pins.  Note that you'll need to do level conversion of some kind to send data from your micro to the ADC if necessary.  This will give you the most accuracy, because you're not limited to the 10-bit ADC on your micro.  This will also free up processor time.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-26T15:18:39.020" />
  <row Id="3712" PostTypeId="2" ParentId="129" CreationDate="2010-07-26T15:45:53.940" Score="1" ViewCount="" Body="&lt;p&gt;I've used the Lantronix XPort Pro (Ethernet) before...very straightforward, and excellent support staff.  If you use the Matchport, call them!  In my research, I also found the &lt;a href=&quot;http://www.digi.com/products/embeddedsolutions/digiconnectwime.jsp&quot; rel=&quot;nofollow&quot;&gt;Digi Connect Wi Me&lt;/a&gt;, but I did not end up selecting it.  It does have a smaller form factor than either of the above, and lower power consumption than the Matchport, but the price was much too high. ($130) Also, it runs on an ARM chip, rather than x86 like the Matchport, so receive/idle/sleep power requirements are lower. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transmit power is similar for both devices.  It's dictated by the antenna power requirements. While you can easily get average current that low (Short, high-density packets and long sleep times), you won't find one that will transmit at the required power with less than a couple hundred mA.  Virtually all of the 650/750mA of current that the Matchport and Wi Me draw during transmit is due to the amplification of the antenna.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The WiFly GSX is an option that I didn't find. Low power due to ceramic antenna, and designed for battery powered applications.  Good and bad things stick out to me about this chip.  Good: It has general purpose digital I/O, analog inputs, and the firmware is upgradeable wirelessly, which are &lt;em&gt;awesome&lt;/em&gt; features.  Bad: it only includes the TCP/IP stack, not an embedded server and included OS like the others.  More configuration will be required to see this module online, I think.  Ask mtrw.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-26T15:45:53.940" CommentCount="2" />
  <row Id="3713" PostTypeId="2" ParentId="3576" CreationDate="2010-07-26T15:59:30.777" Score="4" ViewCount="" Body="&lt;p&gt;Most of your questions can be answered &quot;yes&quot;, but be careful with Schottky vs. (ultra) fast diodes:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&quot;Can I just buy the higher voltage and current rated Schottky diode and sub them for the lower rated ones?&quot;&lt;/em&gt;&#xA;Should Work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&quot;Is the main reason for getting the exact match the cost and ability to fit?&quot;&lt;/em&gt;&#xA;Some issues like the diode's capacitance have an influence on switching speed and, as a consequence, switching losses, i.e. heat generated in the diode. Try to find at least a similar device. Also, pay attention to peak values for current spikes and the like. Average current is one thing, peak current and power handling capabilities are another.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&quot;Do I only need to match package/voltage/current?&quot;&lt;/em&gt;&#xA;This is what designers do when looking for second source parts. In most cases, you will be good to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&quot;Are Schottky and fast recovery the same?&quot;&lt;/em&gt;&#xA;Usually, fast recovery is a label for p-intrinsic-n diodes, i.e. Si diodes, that are trimmed towards blocking fast upon being reverse biased. Schottky diodes are, really, always as fast as can be and should not be replaced with slower Si diodes, even when they're labeled &quot;fast&quot;. The general rule is: Don't replace Schottky with Si diodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&quot;Can I sub an ultra-fast for a fast recovery?&quot;&lt;/em&gt;&#xA;Using an ultra-fast Si diode in place of a fast Si diode should work as far as switching losses go, but the faster switching action might cause worse electro-magnetic emissions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&quot;And... at the moment I need a Schottky that is in the TO220 package. Can I use two axial leads and just wire the cathodes together?&quot;&lt;/em&gt;&#xA;Diodes in three-pin TO220 packages are really just two diodes. They are, however, very similar. When connected in parallel, they will share the load really well. Different packages are also often a hint towards different peak current/power handling capabilities. And, of course, thermal properties will be different. A TO220 has its own little heat sink even when mounted in free air; axial diodes don't have this nice feature.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-07-26T15:59:30.777" CommentCount="2" />
  <row Id="3714" PostTypeId="2" ParentId="3701" CreationDate="2010-07-26T16:02:13.950" Score="0" ViewCount="" Body="&lt;p&gt;Maybe you could use the switch to connect power to the MCU, then have a timing loop there that waits for the two seconds and if it's still running, it'll turn on a FET (or other pass element) in parallel with the button that will keep it on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can't really use a single pole switch as an input button then except maybe by arranging a clever voltage divider...&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-26T16:02:13.950" />
  <row Id="3715" PostTypeId="2" ParentId="3506" CreationDate="2010-07-26T16:19:34.917" Score="3" ViewCount="" Body="&lt;p&gt;An environmental concern is copper ions in the used etching fluid. It's quite likely that down the sink, NaOH and even ferric chloride are not as nasty as copper salts. Care should be taken when disposing of old fluid.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-07-26T16:19:34.917" />
  <row Id="3716" PostTypeId="2" ParentId="3701" CreationDate="2010-07-26T16:39:18.583" Score="0" ViewCount="" Body="&lt;p&gt;You could use a switchable regulator to supply power to the IC, and use an RC circuit to slowly pull the Enable pin into the On position when the button is pressed.  After the regulator turns on, a transistor connected to the output holds the enable pin permanently in the on position?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-26T16:39:18.583" />
  <row Id="3717" PostTypeId="2" ParentId="3675" CreationDate="2010-07-26T17:36:42.813" Score="5" ViewCount="" Body="&lt;p&gt;It's the actual VCC that matters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Logic gates (and microprocessors) have a diode to VCC and a diode to GND at every input and output pin.&#xA;(Except for a few chips that have a few &quot;high-voltage tolerant&quot; open-collector pins, as pingswept mentioned).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you externally drive an input higher than the actual VCC at the time, current will flow through that diode.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;As long as you limit the current through that diode below the maximum current listed in the datasheet, slight over-voltage won't do any permanent damage. However, even when limited to very small amounts of current, this is enough to disrupt analog circuits on the chip -- the digitized value from an ADC reading one analog input pin can be totally wrong when it is upset from a voltage slightly above VCC on some other pin.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;seemingly small currents through that diode can locally over-heat the region on the chip around that pin, destroying functionality associated with that pin. A person can spend days trying to figure out why his software &lt;em&gt;seems&lt;/em&gt; like it mostly works OK, except for stuff connected to that one pin. (Guess how I know this?)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;slightly larger currents through that diode can overheat and destroy the entire chip.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-07-26T17:36:42.813" CommunityOwnedDate="2010-07-26T17:36:42.813" CommentCount="1" />
  <row Id="3718" PostTypeId="2" ParentId="3703" CreationDate="2010-07-26T18:19:13.730" Score="0" ViewCount="" Body="&lt;p&gt;Have a look at &lt;a href=&quot;http://avarice.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;avarice&lt;/a&gt;. It's man page also has something to say about &lt;a href=&quot;http://linux.die.net/man/1/avarice&quot; rel=&quot;nofollow&quot;&gt;debugwire&lt;/a&gt;. I don't know if that'll be good news or bad, though.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-26T18:19:13.730" CommentCount="2" />
  <row Id="3719" PostTypeId="2" ParentId="3690" CreationDate="2010-07-26T18:23:09.390" Score="0" ViewCount="" Body="&lt;p&gt;I wonder if &lt;a href=&quot;http://openocd.berlios.de/web/&quot; rel=&quot;nofollow&quot;&gt;openocd&lt;/a&gt; is of any help.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-07-26T18:23:09.390" CommentCount="1" />
  <row Id="3720" PostTypeId="1" CreationDate="2010-07-26T18:47:23.403" Score="2" ViewCount="264" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm new to hardware field in general. For one of the projects, I'm trying to create a custom keyboard that will have some extra keys, say 20-25 more than the standard keyboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I read about scan codes and scan code sets. I also read about keyboard encoders, controllers etc. I have read pages like:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.beyondlogic.org/keyboard/keybrd.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.beyondlogic.org/keyboard/keybrd.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.computer-engineering.org/ps2keyboard&quot; rel=&quot;nofollow&quot;&gt;http://www.computer-engineering.org/ps2keyboard&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But still I'm not clear which encoder will allow me to generate a custom scan code that is not defined in any standard scan code sets. Also will the standard keyboard controller (8042 compatible) in PC process these non-standard scan codes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can help me that will be great.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks &amp;amp; Regards,&#xA;- Vivek Athalye&lt;/p&gt;&#xA;" OwnerUserId="994" LastActivityDate="2010-08-25T11:23:17.453" Title="how to have custom Scancode set" Tags="&lt;keyboard&gt;&lt;encoder&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="3721" PostTypeId="1" AcceptedAnswerId="3726" CreationDate="2010-07-26T19:01:25.147" Score="1" ViewCount="412" Body="&lt;p&gt;hey friends,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can i programm the atmega48pa with avrdude? I have problems with the signature ...&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;% avrdude -pm48 -cavrisp2 -Pusb -V -U flash:w:main.hex&#xA;&#xA;avrdude: AVR device initialized and ready to accept instructions&#xA;&#xA;Reading | ################################################## | 100% 0.01s&#xA;&#xA;avrdude: Device signature = 0x1e920a&#xA;avrdude: Expected signature for ATMEGA48 is 1E 92 05&#xA;         Double check chip, or use -F to override this check.&#xA;&#xA;avrdude done.  Thank you.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I have add some new lines to the avrdude.conf in /etc -directory&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;[...]&#xA;part&#xA;    id               = &quot;m48pa&quot;;&#xA;    desc             = &quot;ATMEGA48PA&quot;;&#xA;     has_debugwire = yes;&#xA;     flash_instr   = 0xB6, 0x01, 0x11;&#xA;     eeprom_instr  = 0xBD, 0xF2, 0xBD, 0xE1, 0xBB, 0xCF, 0xB4, 0x00,&#xA;                     0xBE, 0x01, 0xB6, 0x01, 0xBC, 0x00, 0xBB, 0xBF,&#xA;                     0x99, 0xF9, 0xBB, 0xAF;&#xA;    stk500_devcode   = 0x59;&#xA;    signature        = 0x1e 0x92 0x0a;&#xA;[...]&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;but now i get a another error&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;avrdude: safemode: Verify error - unable to read lfuse properly. Programmer may not be reliable.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;h3&gt;Edit - 1&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Here some debugging information with &quot;-vvv&quot;:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;% avrdude -pm48pa -cavrisp2 -Pusb -F -vvv -U flash:w:main.hex&#xA;&#xA;avrdude: Version 5.10, compiled on Apr  3 2010 at 18:48:10&#xA;         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/&#xA;         Copyright (c) 2007-2009 Joerg Wunsch&#xA;&#xA;         System wide configuration file is &quot;/etc/avrdude.conf&quot;&#xA;         User configuration file is &quot;/home/silvio/.avrduderc&quot;&#xA;         User configuration file does not exist or is not a regular file, skipping&#xA;&#xA;         Using Port                    : usb&#xA;         Using Programmer              : avrisp2&#xA;avrdude: usbdev_open(): Found AVRISP mkII, serno: 000200030996&#xA;avrdude: usbdev_open(): using read endpoint 0x82&#xA;avrdude: stk500v2_getsync(): found AVRISP mkII programmer&#xA;         AVR Part                      : ATMEGA48PA&#xA;         Chip Erase delay              : 45000 us&#xA;         PAGEL                         : PD7&#xA;         BS2                           : PC2&#xA;         RESET disposition             : dedicated&#xA;         RETRY pulse                   : SCK&#xA;         serial program mode           : yes&#xA;         parallel program mode         : yes&#xA;         Timeout                       : 200&#xA;         StabDelay                     : 100&#xA;         CmdexeDelay                   : 25&#xA;         SyncLoops                     : 32&#xA;         ByteDelay                     : 0&#xA;         PollIndex                     : 3&#xA;         PollValue                     : 0x53&#xA;         Memory Detail                 :&#xA;&#xA;                                  Block Poll               Page                       Polled&#xA;           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack&#xA;           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------&#xA;           eeprom        65     5     4    0 no        256    4      0  3600  3600 0xff 0xff&#xA;                                  Block Poll               Page                       Polled&#xA;           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack&#xA;           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------&#xA;           flash         65     6    64    0 yes      4096   64     64  4500  4500 0x00 0x00&#xA;                                  Block Poll               Page                       Polled&#xA;           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack&#xA;           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------&#xA;           lfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00&#xA;                                  Block Poll               Page                       Polled&#xA;           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack&#xA;           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------&#xA;           hfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00&#xA;                                  Block Poll               Page                       Polled&#xA;           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack&#xA;           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------&#xA;           efuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00&#xA;                                  Block Poll               Page                       Polled&#xA;           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack&#xA;           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------&#xA;           lock           0     0     0    0 no          1    0      0  4500  4500 0x00 0x00&#xA;                                  Block Poll               Page                       Polled&#xA;           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack&#xA;           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------&#xA;           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00&#xA;                                  Block Poll               Page                       Polled&#xA;           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack&#xA;           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------&#xA;           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00&#xA;&#xA;         Programmer Type : STK500V2&#xA;         Description     : Atmel AVR ISP mkII&#xA;         Programmer Model: AVRISP mkII&#xA;         Hardware Version: 1&#xA;         Firmware Version Master : 1.10&#xA;         Vtarget         : 5.0 V&#xA;         SCK period      : 100.37 us&#xA;&#xA;avrdude: AVR device initialized and ready to accept instructions&#xA;&#xA;Reading | ################################################## | 100% 0.02s&#xA;&#xA;avrdude: Device signature = 0x1e920a&#xA;avrdude: safemode read 1, lfuse value: 62&#xA;avrdude: safemode read 2, lfuse value: 62&#xA;avrdude: safemode read 3, lfuse value: 62&#xA;avrdude: safemode: lfuse reads as 62&#xA;avrdude: safemode read 1, hfuse value: df&#xA;avrdude: safemode read 2, hfuse value: df&#xA;avrdude: safemode read 3, hfuse value: df&#xA;avrdude: safemode: hfuse reads as DF&#xA;avrdude: safemode read 1, efuse value: 1&#xA;avrdude: safemode read 2, efuse value: 1&#xA;avrdude: safemode read 3, efuse value: 1&#xA;avrdude: safemode: efuse reads as 1&#xA;avrdude: NOTE: FLASH memory has been specified, an erase cycle will be performed&#xA;         To disable this feature, specify the -D option.&#xA;avrdude: erasing chip&#xA;avrdude: reading input file &quot;main.hex&quot;&#xA;avrdude: input file main.hex auto detected as Intel Hex&#xA;avrdude: writing flash (2336 bytes):&#xA;&#xA;Writing | ################################################## | 100% 8.54s&#xA;&#xA;avrdude: 2336 bytes of flash written&#xA;avrdude: verifying flash memory against main.hex:&#xA;avrdude: load data flash data from input file main.hex:&#xA;avrdude: input file main.hex auto detected as Intel Hex&#xA;avrdude: input file main.hex contains 2336 bytes&#xA;avrdude: reading on-chip flash data:&#xA;&#xA;Reading | ################################################## | 100% 8.26s&#xA;&#xA;avrdude: verifying ...&#xA;avrdude: 2336 bytes of flash verified&#xA;&#xA;avrdude: safemode read 1, lfuse value: 62&#xA;avrdude: safemode read 2, lfuse value: 62&#xA;avrdude: safemode read 3, lfuse value: 62&#xA;avrdude: safemode: lfuse reads as 62&#xA;avrdude: safemode read 1, hfuse value: df&#xA;avrdude: safemode read 2, hfuse value: df&#xA;avrdude: safemode read 3, hfuse value: df&#xA;avrdude: safemode: hfuse reads as DF&#xA;avrdude: safemode read 1, efuse value: 1&#xA;avrdude: safemode read 2, efuse value: 1&#xA;avrdude: safemode read 3, efuse value: 1&#xA;avrdude: safemode: efuse reads as 1&#xA;avrdude: safemode: Fuses OK&#xA;&#xA;avrdude done.  Thank you.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;h3&gt;Question&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Can someone help me to flash a atmega48pa aith a avrispmkii&lt;/p&gt;&#xA;" OwnerUserId="1004" LastEditorUserId="1004" LastEditorDisplayName="" LastEditDate="2010-07-26T19:48:44.270" LastActivityDate="2010-07-26T22:43:09.767" Title="avrdude and atmega48pa" Tags="&lt;atmega&gt;&lt;avrdude&gt;&lt;debug&gt;&lt;embedded&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="3722" PostTypeId="1" CreationDate="2010-07-26T19:43:31.597" Score="1" ViewCount="238" Body="&lt;p&gt;I am a beginner wanting to know how to interface the spartan 3e board with the pickit2- PIC16F887. I have so far connected j2- pin a6(spartan) to port a Pin1 on the PIC, the ground Pins and j2 pin e7 to output port RD 1 on the PIC. I'm trying to configure a code that will run an elevator and I am also having trouble putting the pull-up resistors for the pushbuttons on the spartan board- they seem to be super-sensitive. Any advice would be great or if you know of some tutorials that involve interfacing the two boards. Thanks ahead&lt;/p&gt;&#xA;" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-07-26T20:09:02.507" LastActivityDate="2010-07-26T20:09:02.507" Title="Spartan-3E to PIC16f887" Tags="&lt;pic&gt;&lt;button&gt;&lt;debounce&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="3723" PostTypeId="2" ParentId="3722" CreationDate="2010-07-26T20:08:40.060" Score="2" ViewCount="" Body="&lt;p&gt;There are a number of things that you're battling. I think the best thing to do is take a step back and define what exactly it is you want to do before you start hooking things up. This is much simpler than it may sound, and having something ON PAPER which you can reference will save you endless headaches.  Just draw out two tables: one for inputs and one for outputs.  Now for each output write down what the output is for, and what has to happen for the output to become '1' or '0'.  For the inputs, write down what each one is for and what a change to a '1' or a '0' means to the system.  From that simple document you can start figuring out which physical pins on the FPGA and the microcontroller are best to use for each purpose, and start building a schematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now... super-sensitive pushbuttons? I think what you're describing is known as &quot;contact bounce&quot; -- you cannot hook a mechanical switch up to a high speed digital circuit and expect to get nice clean off-to-on and on-to-off transitions.  Mechanical switches bounce, and that is just how they are.  You need to debounce them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can do it in hardware, in HDL or in software. Where you decide to do it is up to you, and in fact for a beginner it is probably a good exercise to try various methods for each to get a good feel for how they work. Debouncing boils down to either ignoring or &quot;absorbing&quot; extraneous switch transitions until the switch has stopped bouncing.  A really simple way to do it in software is to look for the switch transition you're interested in (1-&gt;0, 0-&gt;1 or maybe both) and if a transition is seen, initialize a counter. Ignore any more switch transitions until the counter is done, then look again at the switch and see what the state is. If the value is the same, you have your new value. If it's not, it was a glitch and should be ignored. The value you initialize the counter to depends on the responsiveness you need and just how &quot;noisy&quot; your switches are, but a good starting value would be 50-100ms.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Very simple software debouncing for button presses:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/* main loop code, executed regularly */&#xA;&#xA;if(debounce1 == 0) {              /* count is 0, we are looking for button presses */&#xA;    if(button1 == 0) {&#xA;        debounce1 = DEBOUNCE_COUNT;&#xA;    }&#xA;} else {                          /* count isn't 0, we are debouncing. */&#xA;    --debounce1;&#xA;    if(debounce1 == 0 &amp;amp;&amp;amp; button1 == 0) {&#xA;        do_something_because_of_button1();&#xA;    }&#xA;}&#xA;&#xA;if(debounce2 == 0) {&#xA;    if(button2 == 0) {&#xA;        debounce2 = DEBOUNCE_COUNT;&#xA;    }&#xA;} else {&#xA;    --debounce2;&#xA;    if(debounce2 == 0 &amp;amp;&amp;amp; button2 == 0) {&#xA;        do_something_because_of_button2();&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Of course here DEBOUNCE_COUNT is some value which represents 50ms. If your main loop executes every 1ms, this value would be 50. Adjust as needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are more elegant ways to do this, but this is probably good enough to get you started, and it's straightforward enough to understand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the concept of button debouncing is new to you I would put the FPGA away for now and focus just on basic interfacing with the PIC for a while.  Once you're comfortable with how the PIC operates and have some experience under your belt, put the PIC away and do the same for the FPGA.  THEN hook the two up. Trying to do too much too soon will just leave you frustrated and hating electronics.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-26T20:08:40.060" CommentCount="1" />
  <row Id="3724" PostTypeId="2" ParentId="3720" CreationDate="2010-07-26T20:22:03.110" Score="0" ViewCount="" Body="&lt;p&gt;It should work fine, isn't that how those &quot;Multimedia&quot; keyboards work? With the play/pause/volume/etc keys on them?&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-26T20:22:03.110" CommentCount="2" />
  <row Id="3725" PostTypeId="2" ParentId="3683" CreationDate="2010-07-26T21:13:38.983" Score="1" ViewCount="" Body="&lt;p&gt;For anyone who's interested, here is the solution I arrived at today:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;p33fxxxx.h&amp;gt;&#xA;&#xA;_FOSCSEL(FNOSC_PRIPLL);&#xA;_FOSC(FCKSM_CSDCMD &amp;amp; OSCIOFNC_OFF &amp;amp; POSCMD_XT);&#xA;_FWDT(FWDTEN_OFF);&#xA;&#xA;static int curFreq = 0;&#xA;static int nextFreq = 0;&#xA;&#xA;static unsigned int PWM_TABLE[7][2] =&#xA;{&#xA;    {132, 66}, {131, 66}, {130, 65}, {129, 65}, {128, 64}, {127, 64}, {126, 63} // Compare, duty&#xA;};&#xA;&#xA;int main(void)&#xA;{&#xA;    int i, ipl;&#xA;&#xA;    PLLFBD = 0x009E;                // Set processor clock to 32 MHz (16 MIPS)&#xA;    CLKDIV = 0x0048; &#xA;&#xA;    LATCbits.LATC1 = 0;             // Make RC1 an output for a debug pin&#xA;    TRISCbits.TRISC1 = 0;&#xA;&#xA;    OC7CONbits.OCM = 0b000;         // Turn PWM mode off    &#xA;    OC7RS = PWM_TABLE[curFreq][1];  // Set PWM duty cycle&#xA;    PR2 = PWM_TABLE[curFreq][0];    // Set PWM period&#xA;    OC7CONbits.OCM = 0b110;         // Turn PWM mode on&#xA;&#xA;    T2CONbits.TON = 0;              // Disable Timer 2&#xA;    TMR2 = 0;                       // Clear Timer 2 register    &#xA;    IPC1bits.T2IP = 1;              // Set the Timer 2 interrupt priority level&#xA;    IFS0bits.T2IF = 0;              // Clear the Timer 2 interrupt flag&#xA;    IEC0bits.T2IE = 1;              // Enable the Timer 2 interrupt&#xA;    T2CONbits.TON = 1;              // Enable Timer 2&#xA;&#xA;    while (1)&#xA;    {                &#xA;        for (i = 0; i &amp;lt; 1600; i++) {}      // Delay roughly 1 ms&#xA;        SET_AND_SAVE_CPU_IPL(ipl, 2);      // Lock out the Timer 2 interrupt&#xA;        curFreq = (curFreq + 1) % 7;       // Bump to next frequency&#xA;        nextFreq = 1;                      // Signal frequency change to ISR&#xA;        RESTORE_CPU_IPL(ipl);              // Allow the Timer 2 interrupt        &#xA;    }&#xA;}&#xA;&#xA;void __attribute__((__interrupt__)) _T2Interrupt(void)&#xA;{   &#xA;    IFS0bits.T2IF = 0;                  // Clear the Timer 2 interrupt flag     &#xA;&#xA;    if (nextFreq)&#xA;    {        &#xA;        nextFreq = 0;                   // Clear the frequency hop flag&#xA;        OC7RS = PWM_TABLE[curFreq][1];  // Set the new PWM duty cycle&#xA;        PR2 = PWM_TABLE[curFreq][0];    // Set the new PWM period         &#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I confirmed with the scope and a debug pin my suspicion: the original code was suffering from a race condition.  The main loop did not bother to synchronize changes to PR2 with the actual state of the TMR2 counter, and so would occasionally set PR2 to a value LESS THAN (or maybe equal to) the current TMR2 value.  This, in turn, would cause TMR2 to count up until it rolled over, then continue counting until it reached PR2 and generated a rising edge.  During the time TMR2 was counting up to 65535 to roll over, no PWM output was being generated.  At 16 MIPS, the rollover time for a 16-bit timer like TMR2 is roughly 4 ms, explaining my 4 ms PWM dropout.  So, the code was doing exactly what I wrote it to do :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the second snippet, the code is correctly synchronizing changes to PR2 and the duty cycle register with the TMR2 rollover event, and so the 4 ms dropout had gone away.  I mentioned a &quot;weird&quot; waveform associated with that example: it was due to the RD6/OC7 pin being configured as an output and having a low value set in the LATD register.  The second snippet actually turns PWM mode off inside the Timer 2 ISR: this lets the GPIO functionality take over and pulls RD6/OC7 down for a few microseconds before reenabling PWM and generating a rising edge, leading to a &quot;hiccup&quot; waveform.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second snippet also has a problem in that it reconfigures PR2 and the duty cycle register on every Timer 2 rollover, regardless of whether the main loop has commanded a frequency change or not.  It seems to me from observation that the timer rolls over and generates a rising edge on the PWM pin and THEN the Timer 2 ISR gets control a few nanoseconds later (owing I'm sure to vector latency, etcetera).  Turning PWM off and rejiggering the registers every time through doesn't get you quite the right frequency and duty cycle in the long run because the hardware has already generated a rising edge and started counting up to the next compare value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What this means is that in the corrected snippet I posted today, the work done in the Timer 2 ISR needs to be minimized!  Because I'm running PWM at such a high frequency, and because there is a small latency between the rising edge generated by the PWM hardware and the invocation of the Timer 2 ISR, by the time I get into the ISR TMR2 has already had time to count up to a fair number.  My code needs to set PR2 and the duty cycle register immediately and directly (i.e. no function calls, and even the table lookup is pushing it), otherwise it runs the risk of missing the compare and causing the 4 ms rollover bug that was my original problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, I &lt;strong&gt;think&lt;/strong&gt; this is an accurate description of things, and I'm running the code in my &quot;real&quot; application with encouraging results so far.  If anything else changes I'll post here, and of course any corrections to the above would be massively appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for your help, pingswept.&lt;/p&gt;&#xA;" LastActivityDate="2010-07-26T21:13:38.983" CommentCount="2" />
  <row Id="3726" PostTypeId="2" ParentId="3721" CreationDate="2010-07-26T22:43:09.767" Score="3" ViewCount="" Body="&lt;p&gt;You are doing:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;% avrdude -pm48 -cavrisp2 -Pusb -V -U flash:w:main.hex&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You should be doing:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;% avrdude -pm48pa -cavrisp2 -Pusb -V -U flash:w:main.hex&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And in your edit 1 you are using the correct -p flag and it also seems to work. :)&lt;/p&gt;&#xA;" OwnerUserId="718" LastActivityDate="2010-07-26T22:43:09.767" CommentCount="3" />
  <row Id="3727" PostTypeId="1" CreationDate="2010-07-26T23:47:02.783" Score="2" ViewCount="462" Body="&lt;p&gt;How does a differential analog to digital converter differ from a regular ADC?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-07-27T00:27:56.320" LastActivityDate="2011-05-18T11:28:14.350" Title="What is a differential ADC?" Tags="&lt;adc&gt;" AnswerCount="5" />
  <row Id="3728" PostTypeId="2" ParentId="3727" CreationDate="2010-07-27T00:14:32.790" Score="3" ViewCount="" Body="&lt;p&gt;A differential ADC will measure the voltage difference between two pins (the plus &#xA;and minus input). A single-ended (&quot;regular&quot;) ADC will measure the voltage difference between&#xA;one pin and ground. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A lot of differential ADCs can be configured to give you twice the channels in&#xA;single-ended mode.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:28:14.350" LastActivityDate="2011-05-18T11:28:14.350" />
  <row Id="3729" PostTypeId="2" ParentId="3727" CreationDate="2010-07-27T00:22:42.943" Score="1" ViewCount="" Body="&lt;p&gt;A regular ADC samples it's inputs in the range 0V to AVcc, where AVcc is often configurable (5V, 2.56V, user input etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A differential ADC shifts the lower reference from 0V to some other value - either a user input on a second analog input, or a internal reference. This is helpful for measuring small signals that have a large DC offset - eg measuring changes of 100mV in the range 2.5-2.6V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Readings for voltages lower than the offset are hardware dependent - can give negative readings, absolute values, or zero.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A typical application is in a load cell which has a small voltage change at some DC offset.&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-07-27T00:22:42.943" />
  <row Id="3730" PostTypeId="2" ParentId="129" CreationDate="2010-07-27T00:26:28.517" Score="2" ViewCount="" Body="&lt;p&gt;If you are using Arduino, the WiShield works very well with a free software stack. SPI interface between the Arduino and the WiShield, but the Arduino could turn that into serial if you want.&lt;/p&gt;&#xA;" LastActivityDate="2010-07-27T00:26:28.517" />
  <row Id="3731" PostTypeId="2" ParentId="3727" CreationDate="2010-07-27T00:27:31.873" Score="2" ViewCount="" Body="&lt;p&gt;It's hard to say exactly what you're talking about without a reference, but I'm guessing that you're talking about an ADC that has a differential pair input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Differential pairs are nifty things that allow you to double the perceived voltage swing without raising the supply and inducing additional noise.  Essentially what goes on is that instead of having a signal referenced to ground, the two wires are total opposites; when one line is at +1.3V, the other is at -1.3V. The voltage of either line to ground is only 1.3V, but since the ADC is converting the difference of the voltage on these signals, you have 2.6V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume you're talking about ADCs which sample differential signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Differential pairs are used where ever you want to limit induced voltages. Ethernet and USB are both differentially signaled. Lots of RF is differentially signaled. If you do some hunting on Google you'll find LOTS of more information.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-27T00:27:31.873" CommentCount="2" />
  <row Id="3732" PostTypeId="2" ParentId="3727" CreationDate="2010-07-27T00:54:17.917" Score="0" ViewCount="" Body="&lt;p&gt;A Differential ADC is a two terminal device. In principle it takes the difference between the voltages on the two terminals and converts that into a 2's complement binary number. I would say it's common to see this type of ADC used for signals that vary around GND, since in principle negative conversions have meaning in this context.  A single-ended ADC is a one-terminal device, where the voltage is converted to a binary number by comparing it to an internal reference (say ground). Typically these are used for sensors that have output a linear voltage in proportion to the phenomenon they are sensing.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-07-27T00:54:17.917" CommentCount="3" />
  <row Id="3733" PostTypeId="2" ParentId="3727" CreationDate="2010-07-27T01:12:48.277" Score="2" ViewCount="" Body="&lt;p&gt;As others said, it has two inputs for each signal, one of which is subtracted from the other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This gives you more signal-to-noise ratio because the maximum input level is 6 dB higher and because it cancels out any common-mode noise.  If the ADC's ground voltage is fluctuating relative to the ground of the thing being measured, for instance, both inputs will move up and down together, and this will be cancelled out.  If the two inputs are both driven from the same op-amp and some of its power supply noise is getting into both outputs, that will be canceled out.  etc.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-27T01:12:48.277" />
  <row Id="3734" PostTypeId="1" AcceptedAnswerId="3739" CreationDate="2010-07-27T06:52:09.723" Score="6" ViewCount="1738" Body="&lt;p&gt;Is it possible to blink an LED using just a capacitor? (and maybe a resistor).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, if I want to LED to blink once every 2 seconds. Is that possible?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know it can be done with a 555 as well as with a capacitor and transistor.&lt;/p&gt;&#xA;" OwnerUserId="1009" LastEditorUserId="1009" LastEditorDisplayName="" LastEditDate="2010-07-27T06:58:47.480" LastActivityDate="2010-07-28T21:50:34.293" Title="Blink an LED with just a capacitor?" Tags="&lt;capacitor&gt;&lt;led&gt;&lt;blink&gt;&lt;electronics&gt;" AnswerCount="8" CommentCount="2" />
  <row Id="3735" PostTypeId="2" ParentId="3442" CreationDate="2010-07-27T06:54:55.813" Score="2" ViewCount="" Body="&lt;p&gt;In the transmitter put in an IF &quot;button address&quot; True then  chuck.update()&lt;/p&gt;&#xA;" LastActivityDate="2010-07-27T06:54:55.813" CommentCount="1" />
  <row Id="3736" PostTypeId="2" ParentId="3734" CreationDate="2010-07-27T09:23:55.877" Score="1" ViewCount="" Body="&lt;p&gt;Some sort of trigger circuit is needed to discharge the capacitor into the LED when it has charged up to a certain level. That can't be achieved with a resistor.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-27T09:23:55.877" />
  <row Id="3737" PostTypeId="2" ParentId="3734" CreationDate="2010-07-27T10:21:57.570" Score="3" ViewCount="" Body="&lt;p&gt;I believe what you are looking for is an astable multivibrator. At it's heart are just two capacitors and two transistors with a couple of resistors. wikipedia has an informative entry about it: &lt;a href=&quot;http://en.wikipedia.org/wiki/Multivibrator&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Multivibrator&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-07-27T10:21:57.570" CommentCount="1" />
  <row Id="3738" PostTypeId="2" ParentId="3734" CreationDate="2010-07-27T10:35:21.957" Score="2" ViewCount="" Body="&lt;p&gt;If you visit &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/04/06/part-review-the-555-precision-timer/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; there are instructions on how to do it with a 555, or &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/06/11/education-the-rc-circuit-2/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; with capacitors and transistors:&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-07-27T10:35:21.957" CommentCount="1" />
  <row Id="3739" PostTypeId="2" ParentId="3734" CreationDate="2010-07-27T11:18:05.643" Score="15" ViewCount="" Body="&lt;p&gt;Blinking an LED can't done with just passive elements. Interestingly, you &lt;em&gt;can&lt;/em&gt; accomplish periodically blinking a light, with a resistor and a capacitor, if your light happens to be a neon discharge lamp. The reason a neon bulb will work and an LED won't has to do with their current-vs-voltage behavior. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the LED's case, no matter what the voltage across it, some current will be passed. This effectively keeps the cap from charging up, as an operating point is established that is determined by the LED and the resistor. You'll just get a constant glow of some intensity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But with the neon bulb, no current is passed until the voltage exceeds some threshold, which is the breakdown voltage of the neon gas. This allows the capacitor to charge up while the bulb remains dark. When the breakdown voltage is reached, the gas ionizes, and the energy stored in the capacitor is dumped through it, producing a short, bright flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically you need some device in the circuit that operates like an active device. To blink an LED, you need a couple of transistors (e.g., multivibrator configuration) or possibly a single SCR (biased to have a suitably low break-over voltage). In the case of a neon bulb, the bulb itself is the active device, having distinct conducting and cutoff behavior.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-27T11:18:05.643" CommentCount="3" />
  <row Id="3740" PostTypeId="2" ParentId="3734" CreationDate="2010-07-27T14:01:32.760" Score="1" ViewCount="" Body="&lt;p&gt;I haven't tried this, but I just thought of it while reading JustJeff's excellent answer.  What if you took a (reverse-biased) zener diode in series with the LED, that pair in parallel with the cap, and a resistor from the (led+zener)-cap node to +V? Is the zener's reverse leakage current low enough to allow this to work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nevermind... I'm an idiot. The resistor to +V would be above the zener breakdown voltage and thus the circuit wouldn't work.  Editing with this instead of deleting the post for posterity. :-)&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-07-27T14:01:32.760" CommentCount="1" />
  <row Id="3741" PostTypeId="1" AcceptedAnswerId="3743" CreationDate="2010-07-27T15:18:16.540" Score="8" ViewCount="1472" Body="&lt;p&gt;I've been messing around with Arduino for a while now, and I'm in the process of moving from beginner to intermediate. I'd like some opinions on the .Net Micro framework, in terms of performance and hardware availability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a .Net programmer, but I've found Processing for Arduino to pretty much zero friction...it's so close to C# that anything I want to do doesn't even require a trip to the docs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyhow, if there's someone out there who has worked with both, and has opinions on which is better, I'd love to hear it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TIA&lt;/p&gt;&#xA;" OwnerUserId="989" LastActivityDate="2011-05-28T09:27:42.253" Title="Arduino / Processing versus .Net Micro Framework? Best language? Best hardware?" Tags="&lt;arduino&gt;&lt;.net-micro-framework&gt;" AnswerCount="8" CommentCount="1" FavoriteCount="3" />
  <row Id="3742" PostTypeId="2" ParentId="3741" CreationDate="2010-07-27T17:33:33.667" Score="5" ViewCount="" Body="&lt;p&gt;I have no experience with the &quot;.NET Micro Framework&quot;, but I am highly suspicious of anything that involves running a virtual machine on low powered embedded platforms. It just seems like a waste to me. You need more power processors, more memory, more power consumption, to achieve the same effect as running a more dedicated platform that compiles down to native machine code. Possibly why my 528MHz Android phone running a virtual machine (similar to JVM) often feels slower than my previous several year old 312MHz Palm Treo which runs applications compiled for native machine code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a quick look, .NET MF requires an ARM processor, which is a step above in power &amp;amp; complexity from the 8-bit ATMega chips used in Arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My suggestion is that if Arduino does what you want it to, stick with that. If not, you can look to the more powerful ATMega or ATXmega chips, and above that work with ARM directly in C/C++, without the extra .NET translation layer on top of it.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-27T17:33:33.667" CommentCount="6" />
  <row Id="3743" PostTypeId="2" ParentId="3741" CreationDate="2010-07-27T17:40:30.153" Score="13" ViewCount="" Body="&lt;p&gt;If you want to move from Beginner to Intermediate, the language you need to learn is C. Even if you put the whole Windows lock-in debate aside, you need to be very good at programming in C before you can do quality work on a microcontroller in a higher level language like .Net Micro or C++.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Embedded systems are composed of a pyramid of knowledge, and you really need to know at least some of each step to be a good designer:&lt;br&gt;&#xA;^User Code&lt;br&gt;&#xA;^^Operating Systems&lt;br&gt;&#xA;^^^The C Language&lt;br&gt;&#xA;^^^^Assembly Language&lt;br&gt;&#xA;^^^^^Microcontroller Architecture&lt;br&gt;&#xA;^^^^^^Digital Design&lt;br&gt;&#xA;^^^^^^^Semiconductors&lt;br&gt;&#xA;^^^^^^^^Basic Electronics (Ohm's law)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino framework provides a convenient hook for hobbyists into the pyramid somewhere between the C language and an operating system. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specific to your the .Net Micro Framework question, the &lt;a href=&quot;http://www.microsoft.com/netmf/about/default.mspx&quot; rel=&quot;nofollow&quot;&gt;About&lt;/a&gt; says: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The typical .NET Micro Framework&#xA;  device has a 32 bit processor with no&#xA;  external memory management unit (MMU)&#xA;  and could have as little as 64K of&#xA;  random-access memory (RAM).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Also, the brochure differentiates it from Windows Mobile, Windows Embedded, CE 6.0, and the .NET Compact Framework, and compares it to Linux, Real-Time, Java, and custom operating systems.  This is a huge jump from the Arduino/Processing framework.&lt;br&gt;&#xA;&lt;br&gt;&#xA;&lt;br&gt;&#xA;Your Arduino has an 8-bit processor with 1k of RAM.  In addition to the 8-bit vs. 32-bit power loss, it also runs less than half as fast as most of the listed processors.  While I wouldn't discourage you from moving to a 32-bit processor, I would recommend it as an intermediate-to-advanced move.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's real easy to use up a lot of time and memory with a few lines in C# or C++, which are insignificant on a dual core processor running at a couple gigahertz with gigabytes of RAM, but which can make a huge difference on an embedded device.  Until you are good in Assembly and/or C, or a guru in C# or C++, I wouldn't recommend using it for embedded programming.&lt;br&gt;&#xA;&lt;br&gt;&#xA;&lt;br&gt;&#xA;So, I'd start with downloading &lt;a href=&quot;http://winavr.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;WinAVR&lt;/a&gt;, and program a simple LED blink routine in C. If C is totally confusing to you, do a little bit of native code (&quot;Hello World&quot;) on your PC, and then move to the microcontroller, but that shouldn't be necessary.  Next, move up to communication over the UART, start using interrupts, and redo some of your Arduino projects in C.  Then, find (or make!) a new dev board with a different microcontroller, maybe a PIC or an ARM, and some goodies like an LCD screen, Ethernet, SD card, or whatever you want, and try to learn a new system.  Once you get there, you'll know better where you want to go. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We'll be here to help you along the way!&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-07-28T12:25:34.497" LastActivityDate="2010-07-28T12:25:34.497" CommentCount="3" />
  <row Id="3744" PostTypeId="1" CreationDate="2010-07-27T17:40:41.643" Score="7" ViewCount="367" Body="&lt;p&gt;I am just getting started out learning electronics and I keep finding myself having to order capacitors and transistors and other parts for simple projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the best starter sets for a beginner? i.e. who sells a good set of capacitors for a newbie? transistors, resistors, LEDs, etc...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im interested in both complete sets (that includes different types), as well as individual sets (say, for just capacitors).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally, the kits are weighted toward pieces that you will use more often.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="1009" LastActivityDate="2010-07-28T11:30:35.793" Title="What are the Best Starter Supply Kits?" Tags="&lt;beginner&gt;&lt;kit&gt;&lt;electronics&gt;" AnswerCount="5" CommentCount="0" FavoriteCount="2" />
  <row Id="3745" PostTypeId="2" ParentId="3744" CreationDate="2010-07-27T18:04:48.567" Score="4" ViewCount="" Body="&lt;p&gt;In answer, I'd try go for the &lt;a href=&quot;http://www.elexp.com/pro_bppk.htm&quot; rel=&quot;nofollow&quot;&gt;Basic Prototyping Parts Kit&lt;/a&gt; from Electronix Express, and possibly the &lt;a href=&quot;http://www.elexp.com/pro_bpk2.htm&quot; rel=&quot;nofollow&quot;&gt;supplement&lt;/a&gt; if it has stuff you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a meta-answer, there are a whole bunch of threads on topics like this one.&#xA;I propose that we set up a FAQ, dedicated tags, or community wiki/sticky for this kind of question on supplies, stocking, and equipment, including:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/3501/what-is-a-general-set-of-components-for-a-robotics-hacker&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/3501/what-is-a-general-set-of-components-for-a-robotics-hacker&lt;/a&gt;  &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/966/which-electronics-components-should-i-always-have-on-hand&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/966/which-electronics-components-should-i-always-have-on-hand&lt;/a&gt;  &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/3161/long-lasting-electronics-items&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/3161/long-lasting-electronics-items&lt;/a&gt;  &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/3578/whats-the-best-way-to-store-and-categorise-resistors-capacitors-ics-etc&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/3578/whats-the-best-way-to-store-and-categorise-resistors-capacitors-ics-etc&lt;/a&gt; &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/869/personal-electronics-tool-kit&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/869/personal-electronics-tool-kit&lt;/a&gt;  &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/3382/what-equipment-for-electronics-should-i-always-have-on-hand&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/3382/what-equipment-for-electronics-should-i-always-have-on-hand&lt;/a&gt;  &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/3644/best-electronic-kits&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/3644/best-electronic-kits&lt;/a&gt;  &lt;/li&gt;&#xA;&lt;li&gt;and this question, &lt;a href=&quot;http://chiphacker.com/questions/3744/what-are-the-best-starter-supply-kits&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/3744/what-are-the-best-starter-supply-kits&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-27T18:04:48.567" CommentCount="4" />
  <row Id="3746" PostTypeId="2" ParentId="3744" CreationDate="2010-07-27T20:02:35.373" Score="1" ViewCount="" Body="&lt;p&gt;SparkFun has a few various types of kits:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9951&quot; rel=&quot;nofollow&quot;&gt;Inventor's Kit&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9466&quot; rel=&quot;nofollow&quot;&gt;Tool Kit&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9952&quot; rel=&quot;nofollow&quot;&gt;Arduino Flex Starter Kit&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9383&quot; rel=&quot;nofollow&quot;&gt;Sensor Kit&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9503&quot; rel=&quot;nofollow&quot;&gt;Robotics Kit - Robo-CIRCLE&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-27T20:02:35.373" />
  <row Id="3747" PostTypeId="2" ParentId="3744" CreationDate="2010-07-27T20:06:00.803" Score="1" ViewCount="" Body="&lt;p&gt;You can get kits of individual components for pretty cheap on eBay. For example:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://cgi.ebay.com/1-4W-Metal-Film-Resistor-Assortmet-kit-set-1000-pcs-/320548786086?cmd=ViewItem&amp;amp;pt=LH_DefaultDomain_0&amp;amp;hash=item4aa2324fa6#ht_3672wt_1036&quot; rel=&quot;nofollow&quot;&gt;1000 resistors (50 values with 20 pieces each)&lt;/a&gt; for $9&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://cgi.ebay.com/21-value-Capacitor-Assortment-Kit-500pcs-0-01-4700uF-/260467530848?cmd=ViewItem&amp;amp;pt=LH_DefaultDomain_0&amp;amp;hash=item3ca5131c60&quot; rel=&quot;nofollow&quot;&gt;500 capacitors for $20&lt;/a&gt; (21 values with different quantities...more of the cheap ones, less of the expensive ones obviously)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-07-27T20:06:00.803" CommentCount="3" />
  <row Id="3748" PostTypeId="2" ParentId="3744" CreationDate="2010-07-27T20:40:49.877" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.rapidonline.com/&quot; rel=&quot;nofollow&quot;&gt;Rapid Electronics&lt;/a&gt; supplies component kits.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-27T20:40:49.877" />
  <row Id="3749" PostTypeId="2" ParentId="3734" CreationDate="2010-07-27T21:02:42.207" Score="3" ViewCount="" Body="&lt;p&gt;You could do it with a high voltage, current-limited supply and a spark gap.  :D&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-07-27T21:02:42.207" />
  <row Id="3750" PostTypeId="2" ParentId="3376" CreationDate="2010-07-27T21:19:41.087" Score="4" ViewCount="" Body="&lt;p&gt;The question which noise sources need to be taken into consideration depends on how severe they are. Your question indicates that you are interested in noise generated at the op amp and not noise generated by interference from neighboring circuits (internal/external noise).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to make things comparable, all noise is referred to the op amp's input (RTI). In theory, I guess any point in your circuit might work as long as you refer all noise sources to that point, but it is common practice to act as if all noise sources were directly at the input pins. Sources include noise in the resistors, noise generated by current flowing into the op amp's input pins and noise that may be considered as a voltage between the inputs pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a very good discussion at &lt;a href=&quot;http://www.analog.com/library/analogDialogue/cd/vol24n2.pdf#page=20&quot; rel=&quot;nofollow&quot;&gt;this Q&amp;amp;A-style source&lt;/a&gt; and also &lt;a href=&quot;http://www.analog.com/library/analogDialogue/cd/vol3n1.pdf#page=1&quot; rel=&quot;nofollow&quot;&gt;in this nice article from 1969 (!)&lt;/a&gt;, both authored by Analog Devices' staff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without re-typing everything in these sources, here are some rules of thumb:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Noise in the resistors becomes bad when the resistor values are high (some 100k or some 1M) and when the circuits are designed for high bandwidth since the noise is proportional to sqrt(4kTBR). You can try to minimize R, you can try to limit the bandwidth B if possible, you can put the circuit in liquid nitrogen (low temperature T), but you can't go for a low Boltzmann constant, because Boltzmann is dead (quote stolen at &lt;a href=&quot;http://www.analog.com/en/amplifiers-and-comparators/operational-amplifiers-op-amps/products/rarely-asked-questions/RAQ_lowNoiseAmp/fca.html&quot; rel=&quot;nofollow&quot;&gt;Analog Devices&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current noise, i.e. noise generated by current flowing into the op amp inputs, will be converted to a noise voltage by the resistors around the input (Rf, Rg) and amplified by the circuit's gain. This is one of the reasons why one prefers op amps with very low input currents especially for high-ohmic circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage noise results from a real op amp's inability to completely null the voltage between the input pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All noise sources can be added up by superposition, which will work only if all sources are RTI.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-07-27T21:19:41.087" />
  <row Id="3751" PostTypeId="2" ParentId="933" CreationDate="2010-07-27T21:54:42.217" Score="1" ViewCount="" Body="&lt;p&gt;I built an EMG amp as my master's thesis. It uses mostly standard parts (no expensive INAs) and has the safety features required for medical electronics. The requirements are similar to EEG amps, I guess. The low-pass filter and the gain stage can be programmed via 2-bit interfaces (00,01,10,11), which is cool if you want to hook it up to a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With an ADC, it might be better to do the isolation on the digital side, but you might be able to use some ideas from the amp anyway. One nice feature is the active shield at the differential input wires which allows wire lengths of &amp;lt; 10 ft (&amp;lt; 3 m) between the electrodes and the preamp, i.e. no little preamp box outside of the the amp's main housing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thesis itself is not available online, but you can find the key chapter in a PhD thesis that is partly based on my work. Feel free to check &lt;a href=&quot;http://deposit.d-nb.de/cgi-bin/dokserv?idn=98510984x&amp;amp;dok_var=d1&amp;amp;dok_ext=pdf&amp;amp;filename=98510984x.pdf&quot; rel=&quot;nofollow&quot;&gt;here (cf. chapter 8)&lt;/a&gt;. Sorry the documentation is in German, but the circuit diagrams are quite international, I guess.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I am not aware of multi-channel InAmps.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-07-27T21:54:42.217" CommentCount="1" />
  <row Id="3752" PostTypeId="2" ParentId="3734" CreationDate="2010-07-27T22:08:36.547" Score="1" ViewCount="" Body="&lt;p&gt;Just a cap and an LED won't do, but you can use a Diac (similar to two anti-parallel Z-diodes with roughly 30 V) with a series resistor and an LED. If you are able to safely work with AC voltages from the mains outlet, you can try to charge a cap from the mains via a diode with a high-ohmic resistor. Once the cap reaches the Diac's (+LED's) breakdown voltage, a part of the stored charge will go into the LED and make it flash. The next flash won't occur before the Diac's breakdown voltage is reached again. (-&gt; relaxation oscillator, kinda similar to what some others suggested, just that spark gaps or neon bulbs are replaced by semiconductors...)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found the idea in the German hackers' magazine Elektor many years ago...&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-07-27T22:08:36.547" />
  <row Id="3753" PostTypeId="2" ParentId="3741" CreationDate="2010-07-28T03:43:21.823" Score="3" ViewCount="" Body="&lt;p&gt;If you want to move to intermediate you should try a platform outside Arduino enviroment.&#xA;There are a lot of them to choose, you can stay at 8 bits, even with an Atmel MCU or move to one from another vendor.&#xA;Use an IDE, write code C language, understand how a MCU works, write your own bootloader code or use an in-circuit programmer and keep moving.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if you really want to try write in C# for microcontrollers, try this:&#xA;&lt;a href=&quot;http://www.trygtech.com/products/sh7619_evb.php&quot; rel=&quot;nofollow&quot;&gt;http://www.trygtech.com/products/sh7619_evb.php&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It uses a much bigger MCU, the typical .NET footprint is about 512K of flash memory and 256k of RAM.&lt;/p&gt;&#xA;" OwnerUserId="940" LastActivityDate="2010-07-28T03:43:21.823" CommentCount="1" />
  <row Id="3754" PostTypeId="2" ParentId="3744" CreationDate="2010-07-28T11:30:35.793" Score="1" ViewCount="" Body="&lt;p&gt;This &lt;a href=&quot;http://www.oomlout.co.uk/arduino-experimentation-kit-ardx-p-183.html&quot; rel=&quot;nofollow&quot;&gt;Arduino starter kit&lt;/a&gt; from .:oomlout:. is fantastic, it's a really good price and you can buy it with or without an &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove&quot; rel=&quot;nofollow&quot;&gt;Arduino Duemilanove&lt;/a&gt; (Programmable &lt;a href=&quot;http://en.wikipedia.org/wiki/Microcontroller&quot; rel=&quot;nofollow&quot;&gt;micro controller&lt;/a&gt;) - plus .:oomlout:. is a groovy company too! &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-07-28T11:30:35.793" CommentCount="2" />
  <row Id="3755" PostTypeId="2" ParentId="1674" CreationDate="2010-07-28T11:58:31.663" Score="4" ViewCount="" Body="&lt;p&gt;EDIF - Electronic Design Interchange Format - is a vendor neutral format in which to store Electronic netlists and schematics. It was one of the first attempts to establish a neutral data exchange format for the electronic design automation (EDA) industry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See &lt;a href=&quot;http://en.wikipedia.org/wiki/EDIF&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/EDIF&lt;/a&gt; for more information and links.&lt;/p&gt;&#xA;" LastActivityDate="2010-07-28T11:58:31.663" CommentCount="3" />
  <row Id="3756" PostTypeId="2" ParentId="1150" CreationDate="2010-07-28T13:52:59.327" Score="0" ViewCount="" Body="&lt;p&gt;Dedicated driver chips with serial interfaces will indeed probably be the best route. Dealing with individual shift registers will probably mean a very complex circuit. At least Maxim and TI make some. I don't remember if either has a model particularly suited for that much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will still take a lot of hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for power, programming, and buses, the datasheet for each driver will probably have most information you'll need.&lt;/p&gt;&#xA;" OwnerUserId="883" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-07-28T13:59:28.910" LastActivityDate="2010-07-28T13:59:28.910" CommunityOwnedDate="2010-07-28T13:53:52.257" />
  <row Id="3759" PostTypeId="2" ParentId="489" CreationDate="2010-07-28T20:39:55.247" Score="1" ViewCount="" Body="&lt;p&gt;Do this:&#xA;NPN trans or two (wired parallel for current)&#xA;Resistor for base (100 ohms or so)&#xA;Pager from 5V to Collector of NPN trans (or whatever max the motor can handle)&#xA;Bring Audio through diode with capacitor to smooth voltage out&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic idea is you use the diode and capacitor to create a variable DC level in the capacitor.  This charge will feed to the resistor to act as the base bias.  This will allow you to use volume control to determine when the pager motor turns on or off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can play with resistor and capacitor sizes with this setup too.  Just be careful not to go too low on the resistor size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use a bridge to rectify audio, but one diode seems to work fine.&lt;/p&gt;&#xA;" LastActivityDate="2010-07-28T20:39:55.247" CommunityOwnedDate="2010-07-28T20:39:55.247" />
  <row Id="3760" PostTypeId="1" CreationDate="2010-07-28T21:04:16.127" Score="8" ViewCount="1032" Body="&lt;p&gt;I have a board I'm working on with a coworker; we are debating whether to go 4-layer or 6-layer board, and would like to use 6-layer but haven't found a reasonably priced fab house.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any reputable PCB fab house out there that has good pricing on small-quantity (3-10 pcs) 6-layer PCBs? (approx 5&quot;x6&quot;, nothing fancy) The best we've been able to do is about US$\$$700, whereas there are specials on 2- or 4-layer PCBs that are in the $\$$200-$\$$300 range.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;clarify background info: the board has 3 widely-used nets = AGND, DGND, +5V, which basically spells 5 layers, and there doesn't seem to be much advantage to 5 vs. 6. We've looked at sharing the AGND and +5V layers, that's an option; we've looked at routing the +5V by hand, that's an option; we've looked at combining AGND and DGND nets and living with the noise. The right thing to do from an engineering standpoint is a 6-layer board, but if it's going to be 2x the price it may be cost prohibitive given our particular situation (further details are beyond the scope of this forum).&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;clarification: (the board was made last year for \$$\$$\$$, but the question is still valid)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I asked about 6 layers and I meant 6 layers. The background info is only for educational purposes. As far as cost tradeoff judgement goes, here's where I was coming from:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a shop that is interested in high-volume ultra-low-cost, you can either spend more time to design a 4-layer board well because of layout constraints, or rush through a 4-layer board design and hope it works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same thing for a hobbyist without much money wanting low quantities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a shop that is interested in time-to-market, you can either spend the money and use a 6-layer board, or rush through a 4-layer board design and hope it works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We were in the middle, and had a coworker who was leaving, so I had to go with something that worked; we didn't have time to respin. Cost turned out to be not as much a barrier as I thought, but in some situations I get flak from management when cost is high, and it's really helpful to have a modest price option so I don't have to deal with that.&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2011-05-20T11:59:13.587" LastActivityDate="2011-05-20T11:59:13.587" CommunityOwnedDate="2011-05-20T11:44:01.827" Title="Moderately priced 6-layer PCB fab?" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;" AnswerCount="12" CommentCount="4" FavoriteCount="3" />
  <row Id="3761" PostTypeId="2" ParentId="3760" CreationDate="2010-07-28T21:29:02.767" Score="1" ViewCount="" Body="&lt;p&gt;I just sent a 4-layer board with some particularly small vias and fine pitch traces out for quote yesterday, and the winner was protoexpress.com. I've previously gotten special discounts from pcbexpress.com, but they don't appear to have any promotions running right now. I suspect you'll have trouble doing better than a 5-day turn for $650 or so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh, one other thought-- try apcircuits.com in Alberta, Canada.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-28T21:29:02.767" CommunityOwnedDate="2011-05-20T11:44:01.827" CommentCount="1" />
  <row Id="3762" PostTypeId="2" ParentId="3442" CreationDate="2010-07-28T21:39:39.260" Score="0" ViewCount="" Body="&lt;p&gt;In conjunction with Denominators answer, depending on the data your'e sending across, you could do the same on the other side, where it reads the data sent to it, and if that variable (or rather bit) isn't set/true, then don't move the motors.&lt;/p&gt;&#xA;" OwnerUserId="982" LastActivityDate="2010-07-28T21:39:39.260" />
  <row Id="3763" PostTypeId="2" ParentId="3760" CreationDate="2010-07-28T21:39:40.273" Score="3" ViewCount="" Body="&lt;p&gt;Interesting problem.  There isn't a &quot;hobbyist&quot; market for 6-layer, so the low-end fabs won't touch this, and high-end fabs charge their usual bucket-of-money NRE.  Most people making 6-layer are at companies with the budget to prototype as needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, you should understand that this is essentially the same things as making three thin 2-layer boards that are then laminated together-- there &lt;em&gt;is&lt;/em&gt; a reason that this is more expensive.  Rather than generating just 1-2 photoplots for the copper there are 6, and three times the processing time for many of the steps... and three times the potential for goofs that require them to redo the whole board.  Because errors are more likely, some fabs include electrical testing with 6-layer, which also contributes to the cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking around, pcbfabexpress can get you started around $500, but my experience is that you probably won't do &lt;em&gt;much&lt;/em&gt; better, for domestic (US) at least.  Overseas fabs should cost considerably less, and may be a better option for this sort of thing.&lt;/p&gt;&#xA;" OwnerUserId="484" LastActivityDate="2010-07-28T21:39:40.273" CommunityOwnedDate="2011-05-20T11:44:01.827" />
  <row Id="3764" PostTypeId="2" ParentId="3734" CreationDate="2010-07-28T21:50:34.293" Score="3" ViewCount="" Body="&lt;p&gt;A completely orthogonal approach, but you could use a thin (read: high-resistance) bimetallic strip, or even a thin enough &quot;muscle wire&quot; to blink an LED, probably with a time scale of a second or two.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This wire or strip heats up due to the current and deforms, breaking the circuit.  It cools, making the circuit again.  This is the standard &quot;blinking christmas light&quot; circuit, and it works fine for LEDs too.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This sort of thing is pretty easy with a high current LED (you didn't say what type you're using!), but if it's a low current LED, you'd probably need a moderately high voltage (maybe 12V) and corresponding resistance to drive the LED properly while heating the wire at the right rate.&lt;/p&gt;&#xA;" OwnerUserId="484" LastActivityDate="2010-07-28T21:50:34.293" />
  <row Id="3765" PostTypeId="1" CreationDate="2010-07-28T21:51:32.607" Score="2" ViewCount="1394" Body="&lt;p&gt;I read this is possible here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/110/how-to-drive-drive-brushless-motor-with-arduino&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/110/how-to-drive-drive-brushless-motor-with-arduino&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm just getting started with Arduino and electronics in general, can anyone recommend a tutorial or guide that could serve as a starting point for how to approach controlling a brushless ESC with an Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't seem to find much information about how a brushless ESC even works, let alone what it will take to use an Arduino to communicate with one (or more).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!&lt;/p&gt;&#xA;" OwnerUserId="1016" LastActivityDate="2010-07-28T23:57:14.983" Title="Controlling a Brushless ESC with Arduino" Tags="&lt;arduino&gt;&lt;brushless&gt;" AnswerCount="2" />
  <row Id="3766" PostTypeId="2" ParentId="3765" CreationDate="2010-07-28T22:37:30.597" Score="1" ViewCount="" Body="&lt;p&gt;If it's the kind of ESC used with R/C planes, the hook-up is pretty straight-forward.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the output side, there will be three wires to connect to the motor. It almost doesn't matter how you connect them, except that if your rotation is opposite to what you expected, you can just swap any two of the three.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For input, the ESC takes a power feed from your DC source, usually a lithium-poly with planes, and a control signal from the R/C receiver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The control signal is the same kind used with servos. There is a pulse of a certain width, and variations in that width cause variations in servo position, or in the case of the ESC, the resulting speed. Point being, that if you can get control an ordinary servo with your Arduino, then you have practically everything in hand for controlling an ESC.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-07-28T22:37:30.597" CommentCount="3" />
  <row Id="3767" PostTypeId="2" ParentId="3760" CreationDate="2010-07-28T23:17:52.993" Score="3" ViewCount="" Body="&lt;p&gt;I recommend Sunstone for this kind of work. I'm not affiliated with them, other than being a very happy customer. I've used a few board houses through the years, but these guys come out on top. Their rates are reasonable, they can accept Eagle board files directly, and every time I've contacted them they've been fast, friendly and efficient. I can't say enough good about them, these guys are on the money.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just got back a set of boards (6 layer, .005 trace/space, .01 vias) -- I don't think you'll find a board like that for under $\$$700 in small volumes.  The trick is to panelize your boards and make an order for 2 panels with 5 boards each.  You'll still be paying $\$$700 but at least you'll have a lower per-board cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just saw this link on hackaday: BatchPCB.com will get you cheaper boards if you're willing to wait a little. I've never used their service, and it's only up to 4-layers, but I'm throwing this out there for others to see as well.&lt;/p&gt;&#xA;" OwnerUserId="974" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-11T01:11:48.013" LastActivityDate="2011-04-11T01:11:48.013" CommunityOwnedDate="2011-05-20T11:44:01.827" CommentCount="7" />
  <row Id="3768" PostTypeId="2" ParentId="3765" CreationDate="2010-07-28T23:21:42.533" Score="2" ViewCount="" Body="&lt;p&gt;Use the Arduino servo library to control your ESC. R/C ESCs are usually driven by the same PWM signals as servos.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/playground/ComponentLib/Servo&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/ComponentLib/Servo&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To calibrate the ESC, I'd measure the rotation speed by painting a pattern on a wheel and tracking it with a light sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't fancy building that, but accuracy is important - try a bicycle speedometer.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-07-28T23:57:14.983" LastActivityDate="2010-07-28T23:57:14.983" CommentCount="1" />
  <row Id="3769" PostTypeId="1" AcceptedAnswerId="3770" CreationDate="2010-07-28T23:39:00.937" Score="1" ViewCount="128" Body="&lt;p&gt;Can anyone identify this gyro?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's from the guts of a (deceased) hovering toy and I'd like to find a datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.hodgepig.org/gyro.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-29T15:02:15.580" Title="Can anyone identify this gyro?" Tags="&lt;gyro&gt;" AnswerCount="1" />
  <row Id="3770" PostTypeId="2" ParentId="3769" CreationDate="2010-07-29T00:22:29.027" Score="2" ViewCount="" Body="&lt;p&gt;Neither the part number nor the logos are familiar to me, and I'm assuming that you've already done the usual Google searches, tried to narrow it down by package size/pin count/axis count on distributor sites, and looked for the repair manual and replacement parts lists.  If no one here recognizes it, the next (and possibly last) step is to try to contact the remnants of the manufacturer.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of info are you looking for?  If it's analog (Plugged into ADC pins or buffers), you should be able to reconstruct what you need just by soldering on some test leads, powering it up, and waving it around. If it's over a digital interface, I wish you all the best of luck in deciphering the init sequence, command set, and data format.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, unless you're trying to upgrade your hover toy, &lt;strong&gt;I think your needs will be better served by purchasing a new one with a known manufacturer, datasheet, and distributors.&lt;/strong&gt;  It's perfectly reasonable to pull off sturdy, easily identifiable parts (switches/buttons, potentiometers, LEDs, and connectors are generally the first things I reach for) but I would generally just leave unknown ICs, ESD/age sensitive, or highly variable parts where they sit.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-07-29T15:02:15.580" LastActivityDate="2010-07-29T15:02:15.580" CommentCount="2" />
  <row Id="3771" PostTypeId="2" ParentId="3760" CreationDate="2010-07-29T00:52:30.570" Score="4" ViewCount="" Body="&lt;p&gt;Others have stepped around the same point, but if you are worried about cost you should really consider going with 4 layers. 4pcb is pretty reasonable for 4 layer boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have found that people tend to think that more layers will result in a better board. This is not always the case. Don't let poor routing be ignored by going with more layers.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-07-29T00:52:30.570" CommunityOwnedDate="2011-05-20T11:44:01.827" CommentCount="4" />
  <row Id="3772" PostTypeId="1" CreationDate="2010-07-29T03:35:04.193" Score="3" ViewCount="154" Body="&lt;p&gt;I'm looking for reputable vendors to purchase phase stable cables for VNA measurements of body area networks. I found Huber + Suhner and Pasternack Enterprizes, but can't find anyone else reputable. Do you know of other reputable vendors that sell high quality RF products? Thanks in advance for the answer.&lt;/p&gt;&#xA;" OwnerUserId="854" LastActivityDate="2010-12-15T03:21:07.370" Title="Phase stable cable vendors" Tags="&lt;rf&gt;&lt;cable-assemblies&gt;" AnswerCount="2" />
  <row Id="3773" PostTypeId="2" ParentId="1150" CreationDate="2010-07-29T06:09:16.883" Score="2" ViewCount="" Body="&lt;p&gt;Mondomatrix makes some serial (rs-485) addressable LED driver boards, and is based on the Arduino platform: &lt;a href=&quot;http://www.displayduino.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.displayduino.com/&lt;/a&gt; You might be able to put together a system using that hardware fairly easily&lt;/p&gt;&#xA;" LastActivityDate="2010-07-29T06:09:16.883" />
  <row Id="3774" PostTypeId="2" ParentId="3741" CreationDate="2010-07-29T06:15:44.410" Score="1" ViewCount="" Body="&lt;p&gt;You could consider doing Arduino-style C development on an STM32 (ARM M3), via one of several open source projects. &lt;a href=&quot;http://leaflabs.com/&quot; rel=&quot;nofollow&quot; title=&quot;LeafLabs&quot;&gt;LeafLabs&lt;/a&gt; and &lt;a href=&quot;http://www.xduino.com/hardware/&quot; rel=&quot;nofollow&quot; title=&quot;xduino&quot;&gt;xduino&lt;/a&gt; both have working hardware and Arduino based toolchains. I've been using the Leaflabs Maple board when I need a 32bit microcontroller, over regular Atmega chips&lt;/p&gt;&#xA;" LastActivityDate="2010-07-29T06:15:44.410" />
  <row Id="3775" PostTypeId="2" ParentId="489" CreationDate="2010-07-29T07:17:40.407" Score="1" ViewCount="" Body="&lt;p&gt;Are you trying to spin the motor at a rate proportional to the &lt;strong&gt;volume&lt;/strong&gt; of the sound, or the &lt;strong&gt;frequency&lt;/strong&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The amplitude is easy, just rectify, integrate, and amplify (diode -&gt; cap -&gt; amplifier).&lt;br&gt;&#xA;Speed proportional to frequency is more involved. &lt;strong&gt;Way&lt;/strong&gt; more involved. All I can think of is trying to implement a &lt;a href=&quot;http://en.wikipedia.org/wiki/Fft&quot; rel=&quot;nofollow&quot;&gt;FFT&lt;/a&gt; in a micro, and using the FFT's output to control the motor via PWM. This would involve a lot of math, and a micro fast enough to do the calculations.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-07-29T07:17:40.407" CommunityOwnedDate="2010-07-29T07:17:40.407" CommentCount="1" />
  <row Id="3776" PostTypeId="1" AcceptedAnswerId="3778" CreationDate="2010-07-29T13:22:51.000" Score="1" ViewCount="432" Body="&lt;p&gt;This &lt;a href=&quot;http://stackoverflow.com/questions/2242817/how-do-i-program-an-avr-raven-with-linux-or-a-mac/2809748#2809748&quot;&gt;post&lt;/a&gt; answers the question of if it possible to program an Atmel AVR Raven board with avrdude or not.  Yes, it is possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is which programmers will work with the Atmel Raven + avrdude?  I'm trying to avoid buying the $300+ AVR JTAGICE mkII.  There are clones available for $50 (for example the &lt;a href=&quot;http://www.olimex.com/dev/avr-isp500.html&quot; rel=&quot;nofollow&quot;&gt;AVR-ISP500&lt;/a&gt; from Olimex).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone confirm having used a clone programmer with avrdude to program the Atmel Raven boards? Which programmer(s)?&lt;/p&gt;&#xA;" OwnerUserId="1020" LastActivityDate="2010-07-30T14:49:04.677" Title="Which programmers work with the Atmel Raven boards?" Tags="&lt;avr&gt;&lt;avrdude&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="3777" PostTypeId="2" ParentId="3776" CreationDate="2010-07-29T14:31:05.387" Score="1" ViewCount="" Body="&lt;p&gt;Any programmer/debugger that supports the AVR controllers on the Raven boards should be suitable, I'd use an AVR Dragon ($50) instead of the specified JTAG ICE Mk II. Clones like that one available from Olimex only support programming, not debugging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The JTAG ICE Mk II might still be available for half-price from Arrow.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-07-29T14:53:25.113" LastActivityDate="2010-07-29T14:53:25.113" CommentCount="1" />
  <row Id="3778" PostTypeId="2" ParentId="3776" CreationDate="2010-07-29T15:08:14.360" Score="1" ViewCount="" Body="&lt;p&gt;I use the &lt;a href=&quot;http://shop.tuxgraphics.org/electronic/index-avr-programmer.html&quot; rel=&quot;nofollow&quot;&gt;TuxGraphics AVRUSB500&lt;/a&gt; to program my Raven-USB (after &lt;a href=&quot;http://ossmann.blogspot.com/2010/01/killerbee-on-budget.html&quot; rel=&quot;nofollow&quot;&gt;wiring on the ISP header&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-29T15:08:14.360" CommentCount="3" />
  <row Id="3779" PostTypeId="1" CreationDate="2010-07-29T17:58:47.947" Score="1" ViewCount="629" Body="&lt;p&gt;I am trying to make an ARM LPC2132 chip and a Altera Cyclone FPGA communicate using the SPI  protocol. Specifically, I have the &lt;a href=&quot;http://www.knjn.com/ShopBoards_USB2.html&quot; rel=&quot;nofollow&quot;&gt;Saxo-L&lt;/a&gt; board from KNJN, which has the signals pre-wired between the two boards, but I cannot get the two chips talking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The documentation supplies code examples, but I am having no luck with these. Can someone share how to get these two chips talking?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the source I am using:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ARM Code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// SPI master using SPI1/SSP&#xA;// (c) KNJN LLC 2007, 2008&#xA;&#xA;// Tested with LPC ARM on Saxo-L (CPOL=0, CPHA=1, MSB first, SSEL controlled through GPIO)&#xA;&#xA;#include &quot;lpc23xx.h&quot;&#xA;&#xA;void SSP_init()&#xA;{&#xA;  SSP0CPSR = 0x02;  // SSP max speed&#xA;  SSP0CR0 = 0x87;  // SSP max speed, 8 bits, CPHA=1&#xA;  SSP0CR1 = 0x02;  // SSP master mode&#xA;&#xA;  PINSEL1 = 0x0A8;  // SPI mode for pins P0.17 to P0.19, while P0.20 (SSEL) stays as GPIO&#xA;  IOSET0 = 0x00100000;  // SSEL inactive (up)&#xA;}&#xA;&#xA;void SSP_send_recv(char* ob, int len_ob, char* ib, int len_ib)&#xA;{&#xA;  // before doing anything, let's make sure the SSP receive FIFO is empty (by reading data out of it if necessary)&#xA;  while(SSP0SR &amp;amp; 0x04) SSP0DR;&#xA;&#xA;  IOCLR0 = 0x00100000;  // SSEL active (down)&#xA;  while(len_ob || len_ib)&#xA;  {&#xA;    if(len_ob &amp;amp;&amp;amp; (SSP0SR &amp;amp; 0x02))&#xA;    {&#xA;        SSP0DR=*ob++;&#xA;        len_ob--;&#xA;    }&#xA;    if(len_ib &amp;amp;&amp;amp; (SSP0SR &amp;amp; 0x04))&#xA;    {&#xA;        *ib++=SSP0DR;&#xA;        len_ib--;&#xA;    }&#xA;  }&#xA;  IOSET0 = 0x00100000;  // SSEL inactive (up)&#xA;}&#xA;&#xA;void SSP_send_only(char* ob, int len)&#xA;{&#xA;  IOCLR0 = 0x00100000;  // SSEL active (down)&#xA;  while(len) if(SSP0SR &amp;amp; 0x02) { SSP0DR=*ob++; len--; }  // transmit&#xA;  while(!(SSP0SR &amp;amp; 0x11));  // wait until transmission is completed&#xA;  while(SSP0SR &amp;amp; 0x04) SSP0DR;  // empty the receive FIFO&#xA;  IOSET0 = 0x00100000;  // SSEL inactive (up)&#xA;}&#xA;&#xA;int main(void)&#xA;{&#xA;  char bufo[2] = {0x55, 0x54};&#xA;  char bufi[2];&#xA;&#xA;  SSP_init();&#xA;  IODIR0 = 0x80100000;  // turn on LED driver (P0.31) and P0.20 (SSEL)&#xA;&#xA;  while(1)&#xA;  {&#xA;    SSP_send_recv(bufo, sizeof(bufo), bufi, sizeof(bufo));&#xA;&#xA;    if(((bufi[0]+bufi[1])&#xA;                    &amp;amp;0xFF)==254)&#xA;      IOSET0 = 0x80000000;&#xA;    else&#xA;      IOCLR0 = 0x80000000;&#xA;  }&#xA;&#xA;  return(0);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;ARM assembly:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/*&#xA; * Some defines for the program status registers&#xA; */&#xA;   ARM_MODE_USER  = 0x10      /* Normal User Mode                             */ &#xA;   ARM_MODE_FIQ   = 0x11      /* FIQ Fast Interrupts Mode                     */&#xA;   ARM_MODE_IRQ   = 0x12      /* IRQ Standard Interrupts Mode                 */&#xA;   ARM_MODE_SVC   = 0x13      /* Supervisor Interrupts Mode                   */&#xA;   ARM_MODE_ABORT = 0x17      /* Abort Processing memory Faults Mode          */&#xA;   ARM_MODE_UNDEF = 0x1B      /* Undefined Instructions Mode                  */&#xA;   ARM_MODE_SYS   = 0x1F      /* System Running in Priviledged Operating Mode */&#xA;   ARM_MODE_MASK  = 0x1F&#xA;&#xA;   I_BIT          = 0x80      /* disable IRQ when I bit is set */&#xA;   F_BIT          = 0x40      /* disable IRQ when I bit is set */&#xA;&#xA;/*&#xA; * Register Base Address&#xA; */&#xA;&#xA;   .section .vectors,&quot;ax&quot;&#xA;   .code 32&#xA;&#xA;/****************************************************************************/&#xA;/*               Vector table and reset entry                               */&#xA;/****************************************************************************/&#xA;_vectors:&#xA;   ldr pc, ResetAddr    /* Reset                 */&#xA;   ldr pc, UndefAddr    /* Undefined instruction */&#xA;   ldr pc, SWIAddr      /* Software interrupt    */&#xA;   ldr pc, PAbortAddr   /* Prefetch abort        */&#xA;   ldr pc, DAbortAddr   /* Data abort            */&#xA;   ldr pc, ReservedAddr /* Reserved              */&#xA;   ldr pc, IRQAddr      /* IRQ interrupt         */&#xA;   ldr pc, FIQAddr      /* FIQ interrupt         */&#xA;&#xA;&#xA;ResetAddr:     .word ResetHandler&#xA;UndefAddr:     .word UndefHandler&#xA;SWIAddr:       .word SWIHandler&#xA;PAbortAddr:    .word PAbortHandler&#xA;DAbortAddr:    .word DAbortHandler&#xA;ReservedAddr:  .word 0&#xA;IRQAddr:       .word IRQHandler&#xA;FIQAddr:       .word FIQHandler&#xA;&#xA;   .ltorg&#xA;&#xA;&#xA;   .section .init, &quot;ax&quot;&#xA;   .code 32&#xA;&#xA;   .global ResetHandler&#xA;   .global ExitFunction&#xA;   .extern main&#xA;/****************************************************************************/&#xA;/*                           Reset handler                                  */&#xA;/****************************************************************************/&#xA;ResetHandler:&#xA;/*&#xA; * Wait for a stable oscillator&#xA; */   &#xA;   nop&#xA;   nop&#xA;   nop&#xA;   nop&#xA;   nop&#xA;   nop&#xA;   nop&#xA;   nop&#xA;&#xA;   /*&#xA;    * Setup a stack for each mode&#xA;    */    &#xA;   msr   CPSR_c, #ARM_MODE_UNDEF | I_BIT | F_BIT   /* Undefined Instruction Mode */     &#xA;   ldr   sp, =__stack_und_end&#xA;&#xA;   msr   CPSR_c, #ARM_MODE_ABORT | I_BIT | F_BIT   /* Abort Mode */&#xA;   ldr   sp, =__stack_abt_end&#xA;&#xA;   msr   CPSR_c, #ARM_MODE_FIQ | I_BIT | F_BIT     /* FIQ Mode */   &#xA;   ldr   sp, =__stack_fiq_end&#xA;&#xA;   msr   CPSR_c, #ARM_MODE_IRQ | I_BIT | F_BIT     /* IRQ Mode */   &#xA;   ldr   sp, =__stack_irq_end&#xA;&#xA;   msr   CPSR_c, #ARM_MODE_SVC | I_BIT | F_BIT     /* Supervisor Mode */&#xA;   ldr   sp, =__stack_svc_end&#xA;&#xA;&#xA;    /* &#xA;     * Copy initialized variables .data section (copy from flash to RAM)&#xA;     */&#xA;   ldr   r1, =etext&#xA;   ldr   r2, =__data_start&#xA;   ldr   r3, =__data_end&#xA;data_copy_loop:&#xA;   cmp   r2, r3&#xA;   ldrlo r0, [r1], #4&#xA;   strlo r0, [r2], #4&#xA;   blo   data_copy_loop&#xA;&#xA;   /*&#xA;    * Clear .bss section&#xA;    */&#xA;   ldr   r1, =__bss_start&#xA;   ldr   r2, =__bss_end&#xA;   ldr   r3, =0&#xA;bss_clear_loop:&#xA;   cmp   r1, r2&#xA;   strlo r3, [r1], #+4&#xA;   blo   bss_clear_loop&#xA;&#xA;&#xA;   /*&#xA;    * Jump to main&#xA;    */&#xA;   mrs   r0, cpsr&#xA;   bic   r0, r0, #I_BIT | F_BIT     /* Enable FIQ and IRQ interrupt */&#xA;   msr   cpsr, r0&#xA;&#xA;   mov   r0, #0 /* No arguments */&#xA;   mov   r1, #0 /* No arguments */&#xA;   ldr   r2, =main&#xA;   mov   lr, pc&#xA;   bx    r2     /* And jump... */&#xA;&#xA;ExitFunction:&#xA;   nop&#xA;   nop&#xA;   nop&#xA;   b ExitFunction   &#xA;&#xA;&#xA;/****************************************************************************/&#xA;/*                         Default interrupt handler                        */&#xA;/****************************************************************************/&#xA;&#xA;UndefHandler:&#xA;   b UndefHandler&#xA;&#xA;SWIHandler:&#xA;   b SWIHandler&#xA;&#xA;PAbortHandler:&#xA;   b PAbortHandler&#xA;&#xA;DAbortHandler:&#xA;   b DAbortHandler&#xA;&#xA;IRQHandler:&#xA;   b IRQHandler&#xA;&#xA;FIQHandler:&#xA;   b FIQHandler&#xA;&#xA;   .weak ExitFunction&#xA;   .weak UndefHandler, PAbortHandler, DAbortHandler&#xA;   .weak IRQHandler, FIQHandler&#xA;&#xA;   .ltorg&#xA;/*** EOF ***/   &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Verilog code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// SPI slave&#xA;// (c) KNJN LLC 2007, 2008&#xA;&#xA;// Configures the LPC ARM with CPOL=0, CPHA=0/1, MSB first&#xA;&#xA;/////////////////////////////////&#xA;module SPI_slave(clk, SCK, MOSI, MISO, SSEL, LED);&#xA;input clk;&#xA;&#xA;input SCK, MOSI, SSEL;&#xA;output MISO;&#xA;&#xA;output LED;&#xA;&#xA;/////////////////////////////////&#xA;reg [2:0] SCKr;  always @(posedge clk) SCKr &amp;lt;= {SCKr[1:0], SCK};&#xA;wire SCK_risingedge = (SCKr[2:1]==2'b01);&#xA;wire SCK_fallingedge = (SCKr[2:1]==2'b10);&#xA;&#xA;reg [2:0] SSELr;  always @(posedge clk) SSELr &amp;lt;= {SSELr[1:0], SSEL};&#xA;wire SSEL_active = ~SSELr[1];  // SSEL is active low&#xA;wire SSEL_startmessage = (SSELr[2:1]==2'b10);  // message starts at falling edge&#xA;wire SSEL_endmessage = (SSELr[2:1]==2'b01);  // message stops at rising edge&#xA;&#xA;reg [1:0] MOSIr;  always @(posedge clk) MOSIr &amp;lt;= {MOSIr[0], MOSI};&#xA;wire MOSI_data = MOSIr[1];&#xA;&#xA;/////////////////////////////////&#xA;reg [2:0] bitcnt;&#xA;reg byte_received;&#xA;reg [7:0] byte_data_received;&#xA;&#xA;always @(posedge clk)&#xA;begin&#xA;    if(~SSEL_active)&#xA;        bitcnt &amp;lt;= 3'b000;&#xA;    else&#xA;    if(SCK_risingedge)&#xA;    begin&#xA;        bitcnt &amp;lt;= bitcnt + 3'b001;&#xA;        byte_data_received &amp;lt;= {byte_data_received[6:0], MOSI_data};&#xA;    end&#xA;end&#xA;&#xA;always @(posedge clk) byte_received &amp;lt;= SSEL_active &amp;amp;&amp;amp; SCK_risingedge &amp;amp;&amp;amp; (bitcnt==3'b111);&#xA;&#xA;/////////////////////////////////&#xA;//assign MISO = 1'b0;&#xA;reg [7:0] byte_data_sent;&#xA;&#xA;reg [7:0] cnt;&#xA;always @(posedge clk) if(SSEL_startmessage) cnt&amp;lt;=cnt+8'h1;  // count the messages&#xA;&#xA;always @(posedge clk)&#xA;if(SSEL_active)&#xA;begin&#xA;    if(SSEL_startmessage)&#xA;        byte_data_sent &amp;lt;= cnt;&#xA;    else&#xA;    if(SCK_fallingedge)&#xA;    begin&#xA;        if(bitcnt==3'b000)&#xA;            byte_data_sent &amp;lt;= ~cnt;&#xA;        else&#xA;            byte_data_sent &amp;lt;= {byte_data_sent[6:0], 1'b0};&#xA;    end&#xA;end&#xA;&#xA;assign MISO = byte_data_sent[7];  // we assume that there is only one slave on the SPI bus, so we don't bother with a tri-state buffer there&#xA;// otherwise we would need to tri-state MISO when SSEL is inactive&#xA;&#xA;/////////////////////////////////&#xA;reg LED;&#xA;always @(posedge clk) if(byte_received) LED &amp;lt;= byte_data_received[0];&#xA;&#xA;endmodule&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="876" LastActivityDate="2010-08-02T00:37:33.823" Title="How can I set up an SPI interface between an LPC2132 ARM and a Cyclone FPGA?" Tags="&lt;spi&gt;&lt;arm&gt;&lt;fpga&gt;&lt;verilog&gt;" AnswerCount="1" CommentCount="9" />
  <row Id="3780" PostTypeId="1" AcceptedAnswerId="3781" CreationDate="2010-07-29T21:26:29.597" Score="5" ViewCount="232" Body="&lt;p&gt;On the one hand, PCB layouts are considered copyrighted information, and copying them verbatim is a bad idea for legal reasons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, the PCB layout of an evaluation board is pretty much a reference design for how to Do It Right.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any issues with copying the eval board as closely as possible?  I would assume that it's &lt;em&gt;meant&lt;/em&gt; to be copied, as their primary goal is for you to keep buying their chips and not have problems with them, but I've never seen this specified anywhere and the datasheets and eval board manuals still have the standard &quot;All Rights Reserved&quot;, etc.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Reproduction of information in TI data&#xA;  books or data sheets is permissible&#xA;  only if reproduction is without&#xA;  alteration and is accompanied by all&#xA;  associated warranties, conditions,&#xA;  limitations, and notices. Reproduction&#xA;  of this information with alteration is&#xA;  an unfair and deceptive business&#xA;  practice. TI is not responsible or&#xA;  liable for such altered documentation.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="142" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-16T18:20:24.387" LastActivityDate="2010-11-16T18:20:24.387" Title="Copying evaluation board PCB layouts" Tags="&lt;pcb&gt;&lt;manufacturing&gt;&lt;legal&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="3781" PostTypeId="2" ParentId="3780" CreationDate="2010-07-29T22:08:26.393" Score="5" ViewCount="" Body="&lt;p&gt;I think that this situation is mostly because chip manufacturers are not particularly savvy about copyright law. You should definitely copy their eval boards as closely as possible and feel good about doing so. The manufacturers make eval boards so that you can use their chips; they're happy to have you follow their examples.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only exception that I can think of would be if you were planning to sell the resulting board as an eval board in competition with the manufacturer. But that seems like approximately the most tedious possible occupation, so I assume that's not your intent.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-29T22:08:26.393" CommentCount="7" />
  <row Id="3782" PostTypeId="2" ParentId="3780" CreationDate="2010-07-30T01:46:41.377" Score="1" ViewCount="" Body="&lt;p&gt;What elements of the PCB layout do you want to copy?  Do you want to use good practices that happen to be implemented on the PCB (as unlikely as that is...)?  In that case, go right ahead!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know that an eval board PCB is a reference for &quot;how to Do It Right&quot; for an application you plan to sell.  Your product will be different - probably more space constrained, more power sensitive, more EMI sensitive, lacking some peripherials and including others. This will change a lot of things in subtle ways.  I think you can feel free to start with their basic layout, and definitely use their recommended ground plane geometry (if they provide one), but tweak it to your needs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The schematic, on the other hand, is often the definitive reference you are looking for.  I'd start with what I needed from the schematic, add my components, and then begin layout.  You could have the board on your desk for reference, but I don't think you should put too much stress on exactly copying the traces.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you say that you want to &quot;copy the eval board as closely as possible.&quot;  I assume you want to just use a few peripherials or the interface so that you can interact with it as if it were the eval board, but if your meaning here is to produce a copy of the eval board, and sell it in competition to the manufacturer, then you're treading on thin ice.   Make your own design from scratch (You must unlearn what you have learned!), and make it better than and more cheaply than the standard eval board, and you'll have something to sell. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, though, there's only so many ways you can do it!  The decoupling caps &lt;em&gt;must&lt;/em&gt;  be placed right next to the chip.  Whether or not a judge would understand this is a whole different story...&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-30T01:46:41.377" CommentCount="3" />
  <row Id="3783" PostTypeId="1" CreationDate="2010-07-30T02:47:10.327" Score="3" ViewCount="386" Body="&lt;p&gt;I am a very novice chiphacker and am asking for ideas on how I might implement something like this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am about to start an RFID project, which is the easy part. RFID readers are cheap, arduinos are cheap, and RFID tags are cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I want the ability to turn the RFID tag &quot;on&quot; or &quot;off&quot;. I want to be able to say &quot;when &lt;em&gt;this&lt;/em&gt; happens, then allow yourself to be 'excited'&quot;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The project I'm working on is testing for the presence of a liquid (which has ions in it.) So one high-level solution would be &quot;separate the RFID chip from its antenna. When the liquid is spilled, it 'shorts' that connection and now the tag may be excited.&quot; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is this: first, is there any mechanism for turning a tag &quot;on&quot;? There are plenty of ways to turn them &quot;off&quot; (basically destroy the tag) but nothing that works in the opposite direction. And how farfetched is the &quot;liquid&quot; idea?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Might there be some resource that could help me understand what possible workarounds would be, or different attributes of different kinds of RFID tags? Or even something that tells me why this &lt;em&gt;won't&lt;/em&gt; work?&lt;/p&gt;&#xA;" OwnerUserId="1021" LastActivityDate="2010-08-31T23:13:55.017" Title="Construct RFID tag to turn on/off?" Tags="&lt;rfid&gt;" AnswerCount="4" CommentCount="5" FavoriteCount="1" />
  <row Id="3784" PostTypeId="1" AcceptedAnswerId="3795" CreationDate="2010-07-30T05:04:42.390" Score="1" ViewCount="682" Body="&lt;p&gt;It's common for a lot of power circuits to bolt to a piece of aluminum flat stock. How large does the stock need to be?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Say that I'm mounting a tip122. The worst case condition is for it to have a 24V drop at 3A and a 50% duty cycle. So it is dissipating  36W.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at the datasheet, at 35W, the max case temp is ~80C. Assume a 25deg ambient temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Temp drop = 35W * Tr = 55 delta or 1.57C/W for the plate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So how much surface area do I need to achieve that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Did I approach it correctly?&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2011-05-18T11:39:48.823" Title="How do I calculate the thermal resistance of aluminum flat stock" Tags="&lt;heatsink&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="3785" PostTypeId="1" CreationDate="2010-07-30T05:52:32.293" Score="3" ViewCount="763" Body="&lt;p&gt;I'm looking for a battery shield for my Arduino Duemilanove. I would be asking &quot;what's the best&quot; but everything I find is out of stock except for this: &lt;a href=&quot;https://www.liquidware.com/shop/show/BP/Lithium+Backpack&quot; rel=&quot;nofollow&quot;&gt;https://www.liquidware.com/shop/show/BP/Lithium+Backpack&lt;/a&gt; which is USD77.86 with the cheapest freight to Australia. So instead I'm asking &quot;is there anything?&quot; I'd prefer a solar-panel capabable shield, but really I'll take anything that's rechargeable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!&lt;/p&gt;&#xA;" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-24T21:41:43.577" LastActivityDate="2010-08-24T21:41:43.577" Title="Arduino Battery Shield" Tags="&lt;arduino&gt;&lt;battery&gt;&lt;arduino&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="3786" PostTypeId="2" ParentId="3780" CreationDate="2010-07-30T08:44:17.193" Score="1" ViewCount="" Body="&lt;p&gt;There is a distinction between evaluation boards and reference designs. Manufacturers even provide Gerber files for the latter, so that they can be copied exactly.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-30T08:44:17.193" />
  <row Id="3787" PostTypeId="1" AcceptedAnswerId="3794" CreationDate="2010-07-30T14:11:10.230" Score="2" ViewCount="89" Body="&lt;p&gt;I have searched high and low on Google for the user manual about the LPC2132 ARM chip. So far, all I have come up with is the ARM7TDMI manual and a short (41 pages) overview of the LPC2132 chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I'm looking for a more detailed description of the various parts of the micro controller, such as register addresses and peripheral information. I have found several promising links, but the PDF documents appear to be broken&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone point me to the full length LPC2132 data sheet?&lt;/p&gt;&#xA;" OwnerUserId="876" LastEditorUserId="876" LastEditorDisplayName="" LastEditDate="2010-07-30T14:22:54.640" LastActivityDate="2010-07-30T18:13:11.520" Title="Where can I find the in-depth LPC2132 datasheet?" Tags="&lt;datasheet&gt;&lt;arm&gt;" AnswerCount="2" />
  <row Id="3789" PostTypeId="2" ParentId="3776" CreationDate="2010-07-30T14:49:04.677" Score="0" ViewCount="" Body="&lt;p&gt;Summary of what I have found:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Raven boards as well as the Raven stick both contain 10-pin, 50-mil JTAG interfaces.  The pins must be soldered on by the user but are also included in the evaluation kit.  A 50-mil to 100-mil adapter allows connecting the JTAG interfaces to programmers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Raven boards but not the Raven stick include 6-pin, 50-mil ISP interfaces.  The pins for these must be soldered on as well but no 6-pin units are shipped with the evaluation set.  However, as they are only header pins, the 10-pin units that ship with the evaluation set can be broken off to create 6-pin units. (See &lt;a href=&quot;http://www.outsidetrains.com/raven/&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;, search for “ISP connectors”).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ISP interfaces on the Raven boards are faulty; VCC and GND are not connected for the 1284p MCU.  Atmel has suggested a workaround by jumping those pins to the VCC and GND pins for the 3290p ISP header. (See &lt;a href=&quot;http://code.rancidbacon.com/LearningAboutAtmelRZRAVEN&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;, search for “7 July 2008”).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Raven stick does not contain an ISP interface at all, however, clever hacking and soldering can change that.  See &lt;a href=&quot;http://www.outsidetrains.com/raven/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; (search for “USB stick”) and &lt;a href=&quot;http://ossmann.blogspot.com/2010/01/killerbee-on-budget.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; for more information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To summarize: it is possible to use a cheap ISP programmer with the Raven boards however it will require some extra soldering on the Raven boards in addition to adding the pins and it will also require quite a hack to the Raven stick.  Nevertheless it is possible and has been done before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which leaves with the recommended JTAG interface to program the Raven boards and stick.  JTAG programmers can be expensive.  The Atmel JTAGICE mkII programmer and debugger goes for around $300.  Clones are cheaper, for example the Olimex AVRISP-500, and while the clones don’t allow debugging more importantly they do not support all AVR chips.  The AVR Dragon goes for around $60 and supports JTAG albeit with its debugging capabilities artificially limited to the first 32kb of an application so as not to cannibalize sales of the higher end JTAG device. Nevertheless, I find the Dragon to be the best choice.&lt;/p&gt;&#xA;" OwnerUserId="1020" LastActivityDate="2010-07-30T14:49:04.677" />
  <row Id="3790" PostTypeId="2" ParentId="3784" CreationDate="2010-07-30T14:50:04.460" Score="2" ViewCount="" Body="&lt;p&gt;You will probably need a &lt;strong&gt;very&lt;/strong&gt; large plate or a fair amount of&#xA;moving air. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the on-time of the TIP122? If the on-time is greater than&#xA;100mS then you are dissipating 72W not 36W. You need to look&#xA;at the transient thermal response curves to determine the derating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to allow some thermal resistance for the interface between the&#xA;case of the transistor and the sink (or plate). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming that your on-time is less than 1mS you are dissipating&#xA;36W. Looking at the On-Semi datasheet --&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rjc = 1.92 degC/W max.&#xA;Absolute maximum junction temperature = 150degC (I would not exceed 125degC)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;T = (Rjc + Rcs + Rsa) * Pd&lt;/p&gt;&#xA;&#xA;&lt;p&gt;125 = (1.92 + 0.5 + Rsa) * 36&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rsa = 1.05degC/W (which agrees with your calculation when you subtract Rcs)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you take a look at the heatsink vendors datasheets you can get an &#xA;idea of sizes. Checkout &lt;a href=&quot;http://www.aavidthermalloy.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.aavidthermalloy.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:39:48.823" LastActivityDate="2011-05-18T11:39:48.823" />
  <row Id="3791" PostTypeId="2" ParentId="2478" CreationDate="2010-07-30T15:29:59.400" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://travisgoodspeed.blogspot.com/2008/09/retargetting-mspgcc-linker.html&quot; rel=&quot;nofollow&quot;&gt;http://travisgoodspeed.blogspot.com/2008/09/retargetting-mspgcc-linker.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-07-30T15:29:59.400" />
  <row Id="3792" PostTypeId="2" ParentId="3787" CreationDate="2010-07-30T16:10:43.737" Score="2" ViewCount="" Body="&lt;p&gt;Here's the 270 page beast: &lt;a href=&quot;http://www.nxp.com/documents/user_manual/UM10120.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.nxp.com/documents/user_manual/UM10120.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-30T16:10:43.737" />
  <row Id="3793" PostTypeId="2" ParentId="3785" CreationDate="2010-07-30T17:04:53.470" Score="4" ViewCount="" Body="&lt;p&gt;Sure: Get &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=71K-ND&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; and &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=BS6I-ND&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; from Digikey (or their equivalents from your favorite distributor), and mount it to some perfboard! &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=1290K-ND&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is another option for an integrated clip/holder.  Do you really need the rechargeable Lithium battery you linked? $70 buys a lot of 9-volts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to go for it, powering your device with a solar panel the size of the Arduino (.004m^2, or 40cm^2) will not be trivial.  In the continental US, the sun puts out about 1kW/m^2 at noon on the brightest day of the year, but a solar panel will only be about 20% efficient, and you'll average about 20% of that peak power, so you'll get about 160mW from your shield, or about 3.2mA at 5V.  Unfortunately, this power is not available at 5V - A solar cell puts out less than 0.5V.  Putting the cells in series is possible, but you can't just draw power from them like a PSU.  You'll need a switching regulator, and you'll probably want to bypass the 7805 on the Arduino for this (or tap into the USB Vbus line).  Linear Technology makes &lt;a href=&quot;http://www.linear.com/pc/viewCategory.jsp?navId=H0,C1,C1003,C1799&quot; rel=&quot;nofollow&quot;&gt;a number of switching regulators for energy harvesting devices&lt;/a&gt;.   I doubt that the components required will be availabe in through-hole configurations.  You'll also need a battery and/or supercap to accumulate the charge from the panel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other mods you'll want to do are to remove indicator LEDs from your board, put the FTDI chip to sleep (pull pin 12 up with a resistor to 5V when you're not programming it), and to make sure any other shields you're using draw as little power as possible. In software, make sure you have no busy waits or polling loops (this may be a big change in programming style), and put the chip to sleep if you're not in an ISR. See &lt;a href=&quot;http://interface.khm.de/index.php/lab/experiments/sleep_watchdog_battery/&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; running an Arduino on low power for years, and &lt;a href=&quot;http://www.arduino.cc/playground/Learning/ArduinoSleepCode&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; for some code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can be done, but it would be tricky!  This would not be a shield for beginners.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-07-30T17:04:53.470" CommentCount="2" />
  <row Id="3794" PostTypeId="2" ParentId="3787" CreationDate="2010-07-30T18:13:11.520" Score="6" ViewCount="" Body="&lt;p&gt;The latest user manual for the LPC213x family can be downloaded &lt;a href=&quot;http://ics.nxp.com/support/documents/microcontrollers/pdf/user.manual.lpc2131.lpc2132.lpc2134.lpc2136.lpc2138.pdf&quot; rel=&quot;nofollow&quot;&gt;here in PDF format&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Note: This is rev 02 -- the URL posted by pingswept above (no fault of his own) is the earlier rev 01 version.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Disclaimer:&lt;/strong&gt; I consulted for NXP and the engineers inside the company are incredibly frustrated with the website organization at NXP.&lt;/p&gt;&#xA;" OwnerUserId="221" LastActivityDate="2010-07-30T18:13:11.520" CommentCount="4" />
  <row Id="3795" PostTypeId="2" ParentId="3784" CreationDate="2010-07-30T18:31:51.577" Score="1" ViewCount="" Body="&lt;p&gt;You can use &lt;a href=&quot;http://www.efunda.com/formulae/heat_transfer/convection_forced/calc_lamflow_isothermalplate.cfm#calc&quot; rel=&quot;nofollow&quot;&gt;this calculator&lt;/a&gt; to run some numbers for a &lt;em&gt;flat plate&lt;/em&gt; (your design should have fins).  Beware that you have a limited number of tries, and that it requires an air velocity parameter.  Plug in your desired case temperature from the derating curves, which I'll go into further later.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you stuck with the TIP122?  How about the TO-220 package?  Both the TIP122 and TO-220 are only designed for medium power applications.  This type of application would be better served by a high power transistor and a metal can package. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The difference between a high power, medium power, or small-signal transistor is not only in their packages-it's in the device's construction as well.  The maximum ratings table for the [TIP122 &lt;a href=&quot;http://www.fairchildsemi.com/ds/TI%2FTIP122.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;] show that it has a maximum collector power dissipation Pc of 2W in 25°C air, or 65W with Tc=25°C.  The second stat assumes that you could have an infinite heat sink, connected with the ultimate heat sink compound to the tab (technically the case, but the tab's all that matters) on the TO-220, such that the heat sink tab is at 25°C.  Even in that case, the transistor junction, which is what you're concerned about, will go over 150°C.  There is thermal resistance between the junction and the tab. (Sidenote: I'd agree with jluciani - I like my silicon 125°C or cooler).  (Sidenote 2: Metal heatsinks on BJTs are usually connected to the collector, so you'll have a 3A source connected the case, at a voltage greater than the emitter/ground, and won't want it to be somewhere that it can short out.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take a look at the derating curves (Figure 5 in the TIP122 datasheet):&lt;br&gt;&#xA;&lt;img src=&quot;http://imgur.com/fZ7sW.png&quot; alt=&quot;TIP122 Derating curve&quot;&gt;&lt;br&gt;&#xA;If you need to dissipate 72W, you simply can't do it.  If you need 36W, you would have to keep your heat sink less than 50°C above ambient (25°C.  It's this 50 degree temperature gradient that gives you power dissipation).  Compare that curve to a high-power transistor such as the &lt;a href=&quot;http://www.onsemi.com/pub_link/Collateral/MJ11021-D.PDF&quot; rel=&quot;nofollow&quot;&gt;MJ11022 [datasheet]&lt;/a&gt;:&lt;br&gt;&#xA;&lt;img src=&quot;http://imgur.com/kPALt.png&quot; alt=&quot;MJ11022 derating curve&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your heatsink can now be a burn hazard long before the transistor is damaged.  72W corresponds to almost 100°C above ambient, and 36W to an absolute operating temperature of almost 150°C.  Beware of thermal cycling if you want to run it really hot.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd strongly suggest that you use a high-power TO-3 or TO-204 transistor instead of your TIP122.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-07-30T20:31:06.797" LastActivityDate="2010-07-30T20:31:06.797" CommentCount="1" />
  <row Id="3796" PostTypeId="1" AcceptedAnswerId="3804" CreationDate="2010-07-30T21:58:59.763" Score="2" ViewCount="671" Body="&lt;p&gt;I've been trying for an embaressing amount of time to figure out how to interpret the wireless accelerometer data from the &lt;a href=&quot;http://processors.wiki.ti.com/index.php/EZ430-Chronos?DCMP=Chronos&amp;amp;HQS=Other+PR+chronoswiki-pr&quot; rel=&quot;nofollow&quot;&gt;TI Chronos&lt;/a&gt;. From my laptop with the usb-radio included, I read it into python basically following &lt;a href=&quot;http://pastebin.com/f71ca7188&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; recepie, then I throw it into a pyglet application to display the 3D acceleration vector. Its read in as unsigned chars, but I can't make any sense of the data. Neither have I find it documented anywhere. Here is an example printout from holding the watch still, while rotating it among 1 axis smoothly.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;[253 245  24 255   6   7   1]&#xA;[  0 241  20 255   6   7 255]&#xA;[255 229  28 255   6   7 255]&#xA;[255 229  25 255   6   7 255]&#xA;[  1 229  19 255   6   7 255]&#xA;[249 224  21 255   6   7 255]&#xA;[254 219  17 255   6   7 255]&#xA;[255 218  11 255   6   7   1]&#xA;[247 211  15 255   6   7 255]&#xA;[251 209  10 255   6   7 255]&#xA;[251 212 255 255   6   7 255]&#xA;[243 194  16 255   6   7 255]&#xA;[243 200   7 255   6   7 255]&#xA;[247 197   3 255   6   7   1]&#xA;[246 190  10 255   6   7 255]&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Obviously the first 3 bytes are the accelerometer data, and also clearly the numbers needs to be signed somehow. But why aren't the force vectors smooth? It's more obvious in the opengl visualization, but even in the small dataset above, one can observe for instance jumping from 255 to 1 in no time. Finally I want to get actual Gs from the data, but for now I'll settle with getting a smooth force vector that seems somewhat coherent with the rotation of the watch. Bonus points if anybody knows what the last 4 bytes means. Hopefully this is a chiphacker type question.&lt;/p&gt;&#xA;" OwnerUserId="941" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-08-01T20:05:37.317" LastActivityDate="2010-08-01T20:45:17.447" Title="How to interpret TI Chronos watch accelerometer data" Tags="&lt;accelerometer&gt;&lt;msp430&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="3797" PostTypeId="1" CreationDate="2010-07-30T22:18:27.587" Score="1" ViewCount="195" Body="&lt;p&gt;What characteristics do I need to look for in an LCD to ensure it is easily readable in the daytime&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adding more info:&#xA;Low power, smaller size &amp;lt; 4&quot; diagonal, either monochrome or color. Bitmap , not character.&lt;/p&gt;&#xA;" OwnerUserId="582" LastEditorUserId="582" LastEditorDisplayName="" LastEditDate="2010-08-02T23:17:53.067" LastActivityDate="2011-05-19T14:20:03.420" Title="Daytime viewable LCDs" Tags="&lt;lcd&gt;&lt;display&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="3798" PostTypeId="2" ParentId="3796" CreationDate="2010-07-30T22:34:20.123" Score="2" ViewCount="" Body="&lt;p&gt;One of the other bytes is indicated if a button is pressed, I did some work on this ages ago ( &lt;a href=&quot;http://chemicaloliver.net/programming/receiving-ti-ez430-chronos-button-presses-in-processing-and-python/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; ) the other two just indicate successful connection and whether you're in ppt or acc mode if I remember correctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also had the same issue with the leaping values: &lt;img src=&quot;http://chemicaloliver.net/images/chronosxyz.png&quot; alt=&quot;alt text&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's almost like they did one direction 0+ and then the other direct subtracted it's value from 255. I thought (but never tried) ploting dx/dy/dz as I think that would give the movement you're looking for and would only require minor smoothing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone has more detailed information I'd be interested to hear too&lt;/p&gt;&#xA;" OwnerUserId="558" LastEditorUserId="558" LastEditorDisplayName="" LastEditDate="2010-07-30T22:39:29.023" LastActivityDate="2010-07-30T22:39:29.023" CommentCount="2" />
  <row Id="3799" PostTypeId="2" ParentId="3797" CreationDate="2010-07-31T00:13:08.653" Score="2" ViewCount="" Body="&lt;p&gt;The only displays that I would consider daytime viewable are organic LEDs. &#xA;Expensive but excellent contrast and saturated colors.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T14:20:03.420" LastActivityDate="2011-05-19T14:20:03.420" CommentCount="3" />
  <row Id="3800" PostTypeId="1" AcceptedAnswerId="3806" CreationDate="2010-07-31T02:12:23.800" Score="-1" ViewCount="721" Body="&lt;p&gt;I am trying to build a simple motor controller for a 3v hobby motor ( &lt;a href=&quot;http://www.radioshack.com/product/index.jsp?productId=2102828&quot; rel=&quot;nofollow&quot;&gt;http://www.radioshack.com/product/index.jsp?productId=2102828&lt;/a&gt; )  that I picked up at Radio Shack. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using the L293NE (Datasheet can be found at: &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/l293.pdf&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/lit/ds/symlink/l293.pdf&lt;/a&gt;) for the H Bridge and have the follow pins laid out&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;pin 1  -&amp;gt; +5v&#xA;pin 2  -&amp;gt; arduino pin 2&#xA;pin 3  -&amp;gt; motor + terminal&#xA;pin 4  -&amp;gt; ground&#xA;pin 5  -&amp;gt; ground&#xA;pin 6  -&amp;gt; Motor - terminal&#xA;pin 7  -&amp;gt; arduino pin 3&#xA;pin 8  -&amp;gt; +5v&#xA;pin 16 -&amp;gt; +5v&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I wrote a small program and when I hook everything up to the +5 and ground on the arduino Duemilanove board, both forward and reverse work great. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Knowing I won't be able to use USB to supply power to the arduino once on my robot, I use a 9v battery and a 7805 Voltage regulator to bring this down to 5v. When I take the +5 from the 7805 to the arduino vin and connect the ground on the arduino to the ground on the breadboard, the motor will only work one way (say forwards) but not the other(say reverse). Any ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've already verified with the multimeter that all the pins, in the pinout above, are still getting +5v &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT: Update #1&lt;/strong&gt; : Grounding pins 9,10,12,13,15 doesn't make a difference. Also, the arduino doesn't freak out at any time while it is getting it's powered by the 7805. Switching the arduino back to usb power after being driven by the 7805, the motor works in both directions. Tells me the L293 is good. Looking into the possible current issues mentioned in the replies. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT: Update #2&lt;/strong&gt; : There was a question how I have the 7805 powering the arduino.&#xA;I have two breadboards as it makes it easier to switch. Breadboard 1 (BB1) has just the 7805 on it where the power rails hook up to the 9v battery. Bread board 2 (BB2) has just the L293 on it. This way I can easily swap out the power supply (either BB1 or the arduino) without having to mess with circuit of the L293. With that said...  From the +5v pin on the 7805, I feed that to the + power rail on BB2. I feed the -rail of the BB2 back to the - rail on BB1. To power the arduino, I just run a wire from the +rail of BB2 to Vin on the arduino board and run Ground on the arduino back to the - rail on BB2. &lt;/p&gt;&#xA;" OwnerUserId="619" LastEditorUserId="619" LastEditorDisplayName="" LastEditDate="2010-07-31T21:48:56.057" LastActivityDate="2010-07-31T21:48:56.057" Title="Arduino Motor Control with L293NE" Tags="&lt;arduino&gt;&lt;motor&gt;" AnswerCount="2" />
  <row Id="3801" PostTypeId="2" ParentId="3800" CreationDate="2010-07-31T03:11:46.583" Score="1" ViewCount="" Body="&lt;p&gt;If it works one direction but not the other, that sounds like one of the control signals into the L293 is stuck. You might want to watch the level on L293 pins 2 and 7 while you toggle the arduino output 2 and output 3, to see if the levels track correctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you mentioned this was on a breadboard, you should always be on the look out for intermittent connections, maybe something got jostled when you changed your power around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, it's good practice not to leave un-used inputs floating, as this can introduce noise into your circuit. In this case, you should probably ground L293 pins 9,10,12,13,15.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One other way this could happen would be if one of the drive transistors on one side of the H-bridge got blown, which is something to worry about if you happened to skip the clamping diodes on the motor. Have you had back to the works-both-ways configuration since getting it into this one-way behavior?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;more ideas ..&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing to think about is the power distribution scheme. You have a 9V feeding a 7805, but from there, how does the wire run? Does it go first to the arduino, and from that point on to the L293? Or did you branch separate runs from the 7805 to the arduino and to the L293? Or maybe you went from the 7805 to the L293 first, then the arduino? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's important because when both devices are sharing a supply path, voltage drops induced in the wiring by one device can affect the other one. This effect is less noticeable with just small digital circuits, which not tend to draw very much current, but when you introduce a motor it can definitely be a factor - especially when using small gauge wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best way to distribute power in a setup like yours is to make separate runs (both the +V and the ground), one from the power supply to the arduino, another from the power supply to the L293. This way, current dumped into the return (ground) line by the L293 won't cause as much drop in the voltage the controller sees.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if you look at the L293 documentation you linked, note that Vcc2 is the supply for the motor, while Vcc1 feeds the logic part of the L293. You could go the dual-battery route with this project. The 7805 could feed the arduino &lt;em&gt;and&lt;/em&gt; the L293's Vcc1 (pin 16), while a second supply connected to the L293 Vcc2 (pin 8) would provide the current that drives the motor. The second supply could be an unregulated battery (or even your existing 9V), since motors don't much care about the flatness of the supply voltage, and you wouldn't be losing any power passing the relatively high motor current through a regulator drop. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One other thing - you're feeding a 3V motor with what theoretically is a 5V supply, which if everything works means your motor will be running a bit hot. It might be better to use a 6V motor and under-volt it than a 3V motor and over drive it.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-07-31T16:35:51.853" LastActivityDate="2010-07-31T16:35:51.853" CommentCount="3" />
  <row Id="3802" PostTypeId="2" ParentId="3797" CreationDate="2010-07-31T03:19:24.760" Score="3" ViewCount="" Body="&lt;p&gt;Reflective LCDs are available, the Palm IIIx PDA I used some years ago had one. It gets more readable with high light levels!&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-07-31T03:19:24.760" CommentCount="2" />
  <row Id="3803" PostTypeId="2" ParentId="3797" CreationDate="2010-07-31T05:03:32.527" Score="2" ViewCount="" Body="&lt;p&gt;Don't forget &lt;a href=&quot;http://en.wikipedia.org/wiki/E_Ink&quot; rel=&quot;nofollow&quot;&gt;e-Ink&lt;/a&gt; the &lt;a href=&quot;http://en.wikipedia.org/wiki/Pixel_Qi&quot; rel=&quot;nofollow&quot;&gt;PixelQi display&lt;/a&gt;, and &lt;a href=&quot;http://en.wikipedia.org/wiki/Cholesteric_liquid_crystal&quot; rel=&quot;nofollow&quot;&gt;Cholesteric LCDs&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MKPQ01&quot; rel=&quot;nofollow&quot;&gt;PixelQi at MakersShed&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9560&quot; rel=&quot;nofollow&quot;&gt;Cholesteric&lt;/a&gt; &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9559&quot; rel=&quot;nofollow&quot;&gt;Displays&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://store.nexternal.com/shared/StoreFront/default.asp?CS=eink&quot; rel=&quot;nofollow&quot;&gt;e-Ink Dev Kits (Expensive)&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-08-03T22:25:42.837" LastActivityDate="2010-08-03T22:25:42.837" CommentCount="4" />
  <row Id="3804" PostTypeId="2" ParentId="3796" CreationDate="2010-07-31T05:05:04.320" Score="6" ViewCount="" Body="&lt;p&gt;It looks like the data is using &lt;a href=&quot;http://en.wikipedia.org/wiki/Signed_integer_representations&quot; rel=&quot;nofollow&quot;&gt;&lt;em&gt;signed&lt;/em&gt; integers&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Therefore, 255 is -1, and 1 is +1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Presumably, the forces are normalized somewhere, probably by taking a reading from the accelerometer when the watch is starting up. Afterwards, any increase in force is positive, and decrease in force is negative. That would seem to exactly match the given data.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-07-31T05:43:00.293" LastActivityDate="2010-07-31T05:43:00.293" CommentCount="0" />
  <row Id="3805" PostTypeId="1" AcceptedAnswerId="3811" CreationDate="2010-07-31T05:36:50.893" Score="5" ViewCount="614" Body="&lt;p&gt;Hey guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just a quick question. I am trying to make an LCD Shield from my Arduino, and am having problems trying to got the solder to stick to the freetronics protoshield PCB. I have cleaned it as best I can. I am using a decent Proxxon soldering bolt with solder that has worked good for me in the past any tips on how I can get it to stick. It wont bond to the PCB only the wires&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any tips will be greatly appreciated&lt;/p&gt;&#xA;" OwnerUserId="665" LastActivityDate="2010-08-02T14:01:23.627" Title="Solder wont stick" Tags="&lt;soldering&gt;&lt;problem&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="3806" PostTypeId="2" ParentId="3800" CreationDate="2010-07-31T14:25:58.183" Score="1" ViewCount="" Body="&lt;p&gt;Since what you changed was the power supply, I'd look at the 5 V rail and the battery voltage and see what they're doing. If they were doing the same thing as the USB-supplied rail, your system would work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a possibility: maybe the motor draws more current in one direction or the other. That makes the 9 V battery sag below the dropout voltage of the 7805 (around 7 V, I think?), which makes the output sag, which makes the Arduino freak out.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-07-31T14:25:58.183" CommentCount="2" />
  <row Id="3808" PostTypeId="2" ParentId="3805" CreationDate="2010-07-31T16:00:38.810" Score="11" ViewCount="" Body="&lt;p&gt;Flux! (One word answer)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[Appendix:]&lt;br&gt;&#xA;Cleaning the board with, say, alcohol or Windex won't be enough-you're not really worried about finger greases here.  What you're worried about is oxidation.  Solder bonds to metal, but not metal oxides.  Gold doesn't oxidize readily, but other compounds found on circuit boards, like copper and nickel, do so readily. I assume that your solder has a flux component, but stubborn joints often need a little more flux than what is embedded in your solder (usually &amp;lt;5%, probably closer to 2%).  A flux pen should be a part of every soldering tool set.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.freetronics.com/products/protoshield-basic&quot; rel=&quot;nofollow&quot;&gt;ProtoShield&lt;/a&gt; product uses a gold-based plating system, and claims features like &quot;The PCB surface is gold-plated for maximum durability&quot; and &quot;Gold plated PCB: solders easily and very resistant to corrosion.&quot; However, that's not the whole story.  Gold is great because it doesn't oxidize readily, but it has the problem that it dissolves in solder, and then reacts to form compounds mainly AuSn4, which weaken the solder joint.&lt;br&gt;&#xA;Joint weakness is a problem primarily for processes which put the gold on in thick layers  - &quot;Immersion gold&quot; - because there's more gold to dissolve and form those intermetallics which weaken the joint.  This would be a concern if you were using surface mount connectors, or something which did not go through the board, but the sheer bulk of your solder joint should make this less problematic.  If you're reworking the joint, make sure you have it quite clean, as the residue is damaging to your joint.&lt;br&gt;&#xA;The dissolving property is a problem for plating processes which put the gold in a very, very thin layer - &quot;ENIG&quot;, or electroless nickel immersion gold - which means that all of the gold dissolves in less than one second, and you're really soldering to the thicker nickel plating below, and using the gold to protect the nickel, like galvanized steel.  This is gaining popularity in big production systems, which rarely need to do rework, and the reduced need for flux from plating with gold makes the process easier.   The gold will be gone if you try to do rework, so you'll need to use flux with your solder on the nickel surface (which isn't that big a deal).   I'm guessing that this is your problem.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-08-02T14:01:23.627" LastActivityDate="2010-08-02T14:01:23.627" CommentCount="5" />
  <row Id="3809" PostTypeId="2" ParentId="3760" CreationDate="2010-07-31T16:53:20.180" Score="2" ViewCount="" Body="&lt;p&gt;PCBfabexpress is fairly cheap for 4 and 6 layer boards.&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2010-07-31T16:53:20.180" CommunityOwnedDate="2011-05-20T11:44:01.827" CommentCount="1" />
  <row Id="3810" PostTypeId="1" AcceptedAnswerId="3827" CreationDate="2010-07-31T17:46:36.673" Score="7" ViewCount="286" Body="&lt;p&gt;I'm asking this in response to &lt;a href=&quot;http://chiphacker.com/questions/3796/&quot;&gt;this question&lt;/a&gt;, which pointed me to a wireless development kit for the MSP430 in a watch form factor.   I had no idea that such a thing existed. and, if I did, I would have bought one long ago.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I'm asking this very open ended question in hopes of discovering the next project to learn on, after the eZ430.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the some dev kits which you're aware of, want to use, or want to buy that are unique, a personal favorite, or, in your opinion, the best dev kits available?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unique might mean that it comes in a unique form factor, or includes a novel set of chips that are hard to come by.  For example, the &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/ez430-chronos.html?DCMP=Chronos&amp;amp;HQS=Tools+PR+chronos-pr&quot; rel=&quot;nofollow&quot;&gt;eZ430&lt;/a&gt;, or the better-known &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9266&quot; rel=&quot;nofollow&quot;&gt;Lilypad&lt;/a&gt; boards.  A favorite might be the kit you turn to for everything involving some GPIO (Bus Pirate), for practicing a certain architecture (FPGA), or it might be one that you've wanted to make but never had the expertise or time(Embedded Linux? TFT display?)  This is pretty broad, I understand.  An example of this would be the &lt;a href=&quot;http://sharism.cc/specs/&quot; rel=&quot;nofollow&quot;&gt;ben nanote&lt;/a&gt;. Not much room for hardware hacking, but it's an awesome, tiny, open hardware Linux system for $99.   I'd also list the &lt;a href=&quot;http://digilentinc.com/Products/Detail.cfm?NavPath=2,400,790&amp;amp;Prod=BASYS2&quot; rel=&quot;nofollow&quot;&gt;Digilent Basys&lt;/a&gt; FPGA board among the kits which everyone should know about.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not really looking for Arduinos.  Everyone's heard of those.  I'm also not looking for the default manufacturer dev kits for a processor, because those are easy to find - unless they fit one of the best/favorite might , like the eZ430.  I'm not looking for answers to &lt;a href=&quot;http://chiphacker.com/questions/3644/best-electronic-kits&quot;&gt;this question&lt;/a&gt; about the &quot;best kits,&quot; which was looking for kits that you solder together and do some minute customization at the end - I'm looking for more open ended development kits, with which to explore the capabilities of a chip and do cool stuff.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What other dev kits should I know about?&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-02-02T01:37:10.040" LastActivityDate="2011-02-02T01:37:10.040" CommunityOwnedDate="2011-02-02T16:42:48.233" Title="Best/Favorite/Unique dev kits" Tags="&lt;dev-kit&gt;" AnswerCount="4" FavoriteCount="4" />
  <row Id="3811" PostTypeId="2" ParentId="3805" CreationDate="2010-07-31T19:58:13.677" Score="5" ViewCount="" Body="&lt;p&gt;Heat! (One word answer)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A classic reason solder won't stick to something is because you're not getting it hot enough. My interns come to me with this problem &lt;em&gt;all the time&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Make sure the tip of the iron is nice and shiny. Touch some solder on it, and it should melt almost instantly.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Put a nice big blob of solder on the tip of the iron.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Press the blob of solder into the metal to be soldered.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Initially the solder won't be too keen, but when the metal reaches the right temperature, the solder will suddenly be attracted to it, and you'll see it move slightly.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Hugo&lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2010-07-31T19:58:13.677" CommentCount="9" />
  <row Id="3812" PostTypeId="2" ParentId="3244" CreationDate="2010-07-31T20:07:29.057" Score="2" ViewCount="" Body="&lt;p&gt;I solder up tons of SMD boards by hand, and I have to say that I don't think I've ever seen a chip damaged by solder heat. This may have been a problem back in the old days, but new chips are made to survive lead-free reflow soldering temperatures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But here's a good tip. Hold your finger on the chip while you solder it. Firstly, this helps to drain heat from it. Secondly, if it gets too hot for your finger, stop soldering for a bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hugo&lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2010-07-31T20:07:29.057" CommentCount="2" />
  <row Id="3813" PostTypeId="2" ParentId="3810" CreationDate="2010-07-31T23:18:54.737" Score="1" ViewCount="" Body="&lt;p&gt;I make a development kit called the NB2AS that has the following features --&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;ATmega644P + RTC + uSD + 2ch/12bit DAC&lt;/li&gt;&#xA;&lt;li&gt;Altoids form factor&lt;/li&gt;&#xA;&lt;li&gt;Single I/O connector that enables you to mount peripherals&#xA;in the same plane, stacked vertically, using a backplane or&#xA;with a ribbon cable. &lt;/li&gt;&#xA;&lt;li&gt;Peripherals include a prototyping board, Li-ion charger,&#xA;and screw terminal board.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;See &lt;a href=&quot;http://wiblocks.luciani.org/NB2/NB2AS-index.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/NB2/NB2AS-index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The board is compatible with the Arduino+Sanguino tools but&#xA;you can use it as an Atmel development board with avr-gcc.&#xA;I usually develop with avr-gcc + Make.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have other boards on the site and in the works but since the&#xA;first specification in your list was form-factor I mentioned&#xA;the NB2AS.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="536" LastEditorDisplayName="" LastEditDate="2011-02-01T20:52:23.013" LastActivityDate="2011-02-01T20:52:23.013" CommunityOwnedDate="2011-02-02T16:42:48.233" CommentCount="3" />
  <row Id="3814" PostTypeId="1" AcceptedAnswerId="3822" CreationDate="2010-07-31T23:29:17.560" Score="1" ViewCount="334" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for some bright LEDs (in the range of 30-50 lumens, which I think means 2-3 W) for use in a piece of scientific equipment. Can anyone recommend an LED manufacturer that has not just powerful LEDs, but also particularly complete datasheets? I'm especially interested in a lumens/current curve.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it helps, I'm mostly interested in LEDs with wavelengths below 560 nm, i.e. green, blue, violet, and UV. If I could get all the LEDs from one manufacturer, that would be good. I'd prefer surface-mount LEDs, but it's not a strict requirement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-08-01T17:39:36.330" Title="Good high-lumen LED suppliers?" Tags="&lt;led&gt;&lt;uv&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="3815" PostTypeId="1" AcceptedAnswerId="3820" CreationDate="2010-08-01T01:19:30.763" Score="1" ViewCount="257" Body="&lt;p&gt;Can the STK500 program the XMEGA as it arrives from Atmel?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-08-01T19:27:40.163" Title="Can the STK500 program an XMEGA?" Tags="&lt;xmega&gt;&lt;avr&gt;" AnswerCount="1" />
  <row Id="3816" PostTypeId="1" AcceptedAnswerId="3819" CreationDate="2010-08-01T01:40:56.390" Score="2" ViewCount="425" Body="&lt;p&gt;Hi, I am working on an arduino project that uses transistor switches to power on high power leds that are powered by a separate 24 volt power supply.  My issue is that I have two different grounds, making it difficult to bias the transistors.  Can I just connect the arduino ground pin to my external power supply's ground or will this damage the board?  How can I end up with just one ground? Thanks.&lt;/p&gt;&#xA;" OwnerUserId="954" LastActivityDate="2011-05-18T11:28:45.063" Title="Connecting arduino and separate power supply grounds" Tags="&lt;arduino&gt;&lt;transistor&gt;&lt;power-supply&gt;&lt;power&gt;&lt;wiring&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="3817" PostTypeId="2" ParentId="3814" CreationDate="2010-08-01T01:50:32.103" Score="1" ViewCount="" Body="&lt;p&gt;The Cree XLamp datasheet looks fairly complete. I just finished a job that used 36 XLamp (3W)&#xA;LEDs and the Cree devices seem to work quite well. IIRC there was a lumen/current&#xA;curve in the datasheet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure about other manufacturers (or part numbers) but the thermal pad of the XLamp is&#xA;electrically neutral making the thermal management a lot easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(* jcl *)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.wiblocks.com&quot; rel=&quot;nofollow&quot;&gt;http://www.wiblocks.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastActivityDate="2010-08-01T01:50:32.103" CommentCount="1" />
  <row Id="3818" PostTypeId="2" ParentId="3816" CreationDate="2010-08-01T01:55:30.080" Score="3" ViewCount="" Body="&lt;p&gt;If the supplies are electrically isolated then the grounds can be connected. &#xA;If you are not sure you have isolated supplies I would not connect them. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to use optical isolators and keep the grounds separate. &#xA;This can be quite a few additional parts but is a very safe way&#xA;to interface circuits.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:28:45.063" LastActivityDate="2011-05-18T11:28:45.063" />
  <row Id="3819" PostTypeId="2" ParentId="3816" CreationDate="2010-08-01T02:17:00.827" Score="5" ViewCount="" Body="&lt;p&gt;You should be able to connect your arduino ground to the 24V ground, unless the power supplies are somehow referenced to one another. If one or the other or both of your supplies happens to be a battery, then you don't have a concern. If both supplies are transformer isolated AC supplies, you shouldn't have a problem. Even if both supplies tie their DC return side to the earth-ground lug of the AC mains, you should be ok.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you bridge the two grounds through a 10K resistor, and a DVM across that resistor shows anything more than a volt or so, your supplies probably aren't isolated enough to just connect the grounds.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-08-01T02:17:00.827" CommentCount="3" />
  <row Id="3820" PostTypeId="2" ParentId="3815" CreationDate="2010-08-01T04:25:35.563" Score="6" ViewCount="" Body="&lt;p&gt;If you look at the device support for the STK500 in the AVR Studio Help you will see that the XMega isn't supported, you need an STK600. I'd use a Dragon, it's a lot cheaper and gives debugging as well as programming.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-08-01T19:27:40.163" LastActivityDate="2010-08-01T19:27:40.163" CommentCount="4" />
  <row Id="3821" PostTypeId="1" AcceptedAnswerId="3824" CreationDate="2010-08-01T17:37:23.100" Score="2" ViewCount="310" Body="&lt;p&gt;Looking at the &lt;a href=&quot;http://www.st.com/stonline/books/pdf/docs/1334.pdf&quot; rel=&quot;nofollow&quot;&gt;L297 datasheet&lt;/a&gt;, it references the use of &quot;fast 2A type diodes&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What does that mean?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would a 1N4001 qualify? Given the application, I'm assuming that it needs to be a higher power part. Not sure about the &quot;fast&quot; part though. The 4001 datasheet doesn't say anything about that.&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2011-04-05T04:15:48.563" Title="What is a &quot;fast 2A type&quot; diode?" Tags="&lt;diode&gt;&lt;stepper&gt;" AnswerCount="4" />
  <row Id="3822" PostTypeId="2" ParentId="3814" CreationDate="2010-08-01T17:39:36.330" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.ledengin.com/led_products.htm&quot; rel=&quot;nofollow&quot;&gt;LedEngin&lt;/a&gt; manufactures a number of high-wattage LEDs and modules, including UV LEDs,  targetting UV adhesive curing applications.  Their primary distributor is &lt;a href=&quot;http://www.mouser.com/LedEngin/&quot; rel=&quot;nofollow&quot;&gt;Mouser&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Their thermal pads are not electrically neutral, and must be isolated from the rest of the PCB. They do this for you if you buy one of their presoldered modules.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Their datasheets contain relative intensity to current curves, rather than lumen to current curves, because lumens are a unit defined by the power of light perceived by the human eye, and UV light is imperceptible.  Especially if you're trying to cure an adhesive, you're interested not in lumens, but rather in watts (of light) per square meter.  This is only a small percentage of the electrical watts dissipated by the device, about 20% for 395nm UV LEDs, and as low as 5% for 365nm LEDs.  For most LEDs, this &quot;curve&quot; is a fairly straight line, corresponding to, say, 20% of the total power dissipated for UV LEDs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Especially when working with high power LEDs, you'll also want to look at the temperature to radiant intensity curve. As the LED warms up, the intensity drops.  A combination of the current and temperature curves into one would be a nice datasheet feature, but I haven't seen one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Safety notice:&lt;br&gt;&#xA;I'm sure you know this, but looking at high-brightness UV or IR LEDs can harm your eyes, and UV LEDs will give you sunburn.  Most UV LEDs will be in the UV-A spectrum from 320-400nm, and, while this spectrum is not as dangerous/cancerous as UV-B, it will still give you a tan or worse.  You'll want sunglasses on your eyes (They don't have to be dark, just rated for UV), and sunscreen on your hands when experimenting with these.  Setting up a webcam to continuously monitor your workbench so that you know for sure when the LED is on would also be a good idea.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-01T17:39:36.330" CommentCount="2" />
  <row Id="3823" PostTypeId="2" ParentId="3821" CreationDate="2010-08-01T18:01:59.797" Score="1" ViewCount="" Body="&lt;p&gt;Try fast recovery diodes like &lt;a href=&quot;http://www.vishay.com/diodes/rectifiers/fast-recovery-superectifier/&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; from Vishay.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-01T18:01:59.797" />
  <row Id="3824" PostTypeId="2" ParentId="3821" CreationDate="2010-08-01T18:02:46.440" Score="6" ViewCount="" Body="&lt;p&gt;The application example (on page 8) which you're looking at shows the diodes connected to an L298N driver, which is distinct from the L297.  &lt;a href=&quot;http://www.st.com/stonline/books/pdf/docs/1773.pdf&quot; rel=&quot;nofollow&quot;&gt;Here's is the datasheet&lt;/a&gt; you want to look at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;...Which shows that the L298N is just a generic motor driver.  The purpose of the diodes is to prevent the inductance from the motor windings from generating voltages which will destroy the motor.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 1N4001 is a standard recovery (not fast) diode rated at 1A of continuous current.  Thus, it does not fit the datasheet recommendations, so very large currents may be shared by the transistors you're trying to protect, and the beginning of every cycle will admit some overvoltage to those same transistors.  However, it may be adequate if you're just driving a low-power motor.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you've got a high powered motor or are concerned about reliability, I'd recommend Schottky diodes like the common 1N5820 series, which will do a great job of protecting the silicon diodes integral to the L298N output transistors.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-01T18:02:46.440" />
  <row Id="3825" PostTypeId="2" ParentId="3796" CreationDate="2010-08-01T20:20:31.073" Score="1" ViewCount="" Body="&lt;p&gt;Check the accelerometer &lt;a href=&quot;http://www.vti.fi/en/products/accelerometers/consumer_electronics/cma3000_series/&quot; rel=&quot;nofollow&quot;&gt;family datasheet&lt;/a&gt; linked in the wiki:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;em&gt;The acceleration data is presented in 2's complement format. At 0 g acceleration the output is ideally 0h.&lt;/em&gt; [sic]&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;You will of course see gravity as a steady roughly 1 G vector in the output. If you have the control center or another working grapher, rotating the watch will show which axes are being pulled and which way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you've installed the &lt;a href=&quot;http://processors.wiki.ti.com/index.php/EZ430-Chronos#Projects&quot; rel=&quot;nofollow&quot;&gt;TI control center&lt;/a&gt;, you should also have the firmware sources for both the watch and the basestation. Reading these should tell you pretty exactly how the data is treated (almost not at all, some IIR filtering and periodical send when ACC is active). The basestation headers also contain info about the protocol between host and the basestation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other programming samples may also be of some practical help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the &quot;four extra bytes&quot;, I think your samples there are off sync. Looks like they are [4 5 6 0 1 2 3] Maybe you forgot to read the response for basestation start command or something. So the first three are from a previous request and the last four are from the current one and since you don't read all seven, the last three will come in at your next read etc. In correct order, the bytes are (IIRC): a start byte (0xff), command/response (0x06 = acc data follows), packet length (0x07 = seven bytes including these three),  &quot;return code&quot; &amp;amp;&amp;amp; button state (0xff = no data), ax, ay, az. But you can find the real constants in one of the headers :)&lt;/p&gt;&#xA;" OwnerUserId="883" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-08-01T20:45:17.447" LastActivityDate="2010-08-01T20:45:17.447" CommentCount="2" />
  <row Id="3826" PostTypeId="2" ParentId="3779" CreationDate="2010-08-02T00:37:33.823" Score="2" ViewCount="" Body="&lt;p&gt;Oh, the joy of debugging.  You need to break this problem down into pieces... first make sure that the SPI master (ARM) is sending the right CS, CLK, &amp;amp; MOSI.  Then check that the Slave(FPGA) got the message from master and replying.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would recommend using a slower SPI clock to rule out signal integrity issues between your connections.  Take it one step at a time, and you'll get it.  Good luck!&lt;/p&gt;&#xA;" OwnerUserId="1026" LastActivityDate="2010-08-02T00:37:33.823" />
  <row Id="3827" PostTypeId="2" ParentId="3810" CreationDate="2010-08-02T01:14:16.320" Score="3" ViewCount="" Body="&lt;p&gt;I'm really intrigued by &lt;a href=&quot;http://focus.ti.com/dlpdmd/docs/dlpdiscovery.tsp?sectionId=60&amp;amp;tabId=2235&quot; rel=&quot;nofollow&quot;&gt;the pico-projector add-on kit for the Beagle Board&lt;/a&gt;; both are from TI. The pico projector is only 7 lumens (not much) and you have to use it with &lt;a href=&quot;http://www.beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;the Beagle Board&lt;/a&gt; as far as I know, but it's still a pretty leading edge product, at least in my opinion. I think we're going to see pico projectors in many phones soon, as LEDs keep getting more powerful and people will crave bigger screens for their phones that keep getting more horsepower.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, I don't know of any others that are targeting this market, so I thought it was pretty unique and cool (if not expensive). Enjoy!&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-08-02T01:14:16.320" CommunityOwnedDate="2011-02-02T16:42:48.233" CommentCount="1" />
  <row Id="3828" PostTypeId="1" CreationDate="2010-08-02T01:57:48.710" Score="0" ViewCount="282" Body="&lt;p&gt;Hello everyone&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone out there got a pair of these APC-220 &lt;a href=&quot;http://www.littlebirdelectronics.com/products/Wireless-RF-Transceiver-431%252d470MHz-GFSK-Data-Transfer-x-2.html&quot; rel=&quot;nofollow&quot;&gt;data transceivers&lt;/a&gt; working with Arduino systems? If so, could you please contact me. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you, john&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-08-02T01:57:48.710" ClosedDate="2010-10-22T04:39:47.947" Title="APC220 Wireless data transceivers" Tags="&lt;apc220&gt;&lt;arduino&gt;&lt;wireless&gt;" FavoriteCount="1" />
  <row Id="3829" PostTypeId="2" ParentId="3805" CreationDate="2010-08-02T13:30:27.753" Score="6" ViewCount="" Body="&lt;p&gt;There has already been some great advice given so I'll provide some extra info about the surface finish on the ProtoShields (and all the other PCBs that Freetronics has done so far) and the reasoning behind the decision. Unfortunately there's no one &quot;best&quot; PCB surface finish and all finishes have both good and bad points, so it's a matter of making a decision based on trade-offs that are most appropriate for the intended use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Our PCBs use an &quot;ENIG&quot; surface finish, as @reemrevnivek guessed. That's &quot;Electroless Nickel Immersion Gold&quot;, and consists of an underlying layer of nickel with a thin layer of gold over the top. The gold layer is very thin and not intended to provide the main structure of the track, it just acts as a protective coating for the nickel to prevent it tarnishing before it's soldered. Gold is extremely resistant to corrosion so ENIG has several upsides: it can be touched with bare fingers without tarnishing, has a very long shelf life, and the pads / tracks are very flat and square-edged (important for fine-pitch SMD). One downside is that it takes a bit more solder to complete a joint because the surface hasn't yet been pre-tinned, and because there isn't an existing layer of solder to melt against the iron and increase the initial contact area (hence increasing the rate of heat transfer) it can take an extra second or so to get the joint hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most common surface finish you see on PCBs is called &quot;HASL&quot;, or &quot;Hot Air Solder Levelling&quot;. HASL boards are dipped in molten solder and then the excess is cleaned off using hot-air knives to leave behind the thinnest possible layer of solder. The solder itself then protects the underlying track from corrosion while making it extremely easy to solder, because the whole pad is pre-tinned. It's generally the cheapest finish available and a great choice for general-purpose boards. One downside to HASL is that even after the hot-air knife has cleaned off as much excess as possible, the meniscus of the solder will still cause the edges of pads to be slightly rounded. That makes surface-mount parts not sit down quite as flat as they would on an ENIG board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you'd expect that for a board like a prototyping shield the obvious solution would be to go for HASL. But there's a catch. We're trying to stick to RoHS-compliance as much as possible, which would mean we couldn't use regular HASL: it would have to be lead-free HASL. Lead-free solder has a higher melting temperature than regular solder so if we went with lead-free HASL it'd be a pain for customers who don't have lead-free equipment. We'd probably end up with lots of complaints from customers using regular solder and soldering irons who have trouble getting the lead-free solder hot enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another possible finish is &quot;immersion silver&quot;, and it provides an amazingly good finish but has a terrible shelf life. For boards intended for machine assembly immediately after manufacture, silver is a great option. The problem is that it tarnishes quickly and is adversely affected by touch, so it's no good for boards that are intended for distribution to hobbyists for (potentially) long storage and hand assembly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end we settled on ENIG because of the benefits of long shelf life, tarnish resistance, RoHS-compliance, and easy soldering compared to other surface finishes. My personal experience with it has been excellent and I haven't come across any particular problems so far, but of course I'm not an expert on PCB manufacturing and I'm very happy to take advice on better ways to do things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Over the last 6 months I've had a little over 2000 ENIG-finished PCBs fabricated, of which just over 1000 were assembled by pick-n-place machines, about 600 were shipped as bare boards to customers, and several hundred of the rest were hand-assembled by me personally using either reflow-soldering in an oven or using a soldering iron. Out of all those boards this is the first time I've ever heard of any problems soldering to them, so it's possible you were just unlucky enough to receive a board with a flawed finish. If there's something wrong with the finishing process from our PCB manufacturer I'd really like to know about it, so if you're still having problems with that board I'd really appreciate it if you could post it to me so I can inspect it. I'll cover the postage and of course I'll send you replacements free of charge. You can contact me personally at jon@freetronics.com to make the arrangements.&lt;/p&gt;&#xA;" OwnerUserId="31" LastActivityDate="2010-08-02T13:30:27.753" />
  <row Id="3830" PostTypeId="1" AcceptedAnswerId="3831" CreationDate="2010-08-02T17:47:15.710" Score="4" ViewCount="182" Body="&lt;p&gt;I'm trying to drive an electromagnet with a 556 timer in a push pull configuration. The magnet has to change polarity rather quickly and sharply about 10 to 20khz. The voltage also has to be variable, between 3 to 15 volts the current draw is in the range of 1amp. What I need is a way to amp the square waves, I was thinking of using a pair of relays driven by the 556 timer in the complimentary configuration that way I can feed through them a varying voltage independently without affecting the 556... Or am I going at this the wrong way? &lt;/p&gt;&#xA;" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-17T14:36:48.503" LastActivityDate="2011-05-17T14:36:48.503" Title="Driving an electromagnet with a 556 timer" Tags="&lt;electromagnetism&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="3831" PostTypeId="2" ParentId="3830" CreationDate="2010-08-02T18:17:34.447" Score="6" ViewCount="" Body="&lt;p&gt;You need to build or buy something called an H-bridge. They are commonly used for motor control.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-08-02T18:17:34.447" CommentCount="3" />
  <row Id="3832" PostTypeId="2" ParentId="3760" CreationDate="2010-08-02T21:16:06.880" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.pcbtrain.com&quot; rel=&quot;nofollow&quot;&gt;http://www.pcbtrain.com&lt;/a&gt; will do 10 boards, 125mm x 150mm for £63.40 each ($101).&lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2010-08-02T21:16:06.880" CommunityOwnedDate="2011-05-20T11:44:01.827" />
  <row Id="3833" PostTypeId="2" ParentId="3821" CreationDate="2010-08-02T21:53:44.183" Score="4" ViewCount="" Body="&lt;p&gt;When you invert the voltage on a diode it will continue to conduct in the reverse direction for a short time, &lt;em&gt;the reverse recovery time&lt;/em&gt; t&lt;sub&gt;rr&lt;/sub&gt;. For fast diodes this time is shorter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This conduction in the reverse direction wastes energy, which heats up the transistors in the H-bridge and the diodes.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-08-02T21:53:44.183" />
  <row Id="3834" PostTypeId="1" AcceptedAnswerId="3837" CreationDate="2010-08-03T04:39:42.693" Score="6" ViewCount="475" Body="&lt;p&gt;I am a novice at electronics hacking. I would like to know how I can make a circuit communicate with a PC. Take for example, a simple circuit, with one LED and a switch. The switch on the circuit however, is not used to control the LED. Pressing it communicates the present state of the LED. I have a program running on my computer, which has for an UI, a button and a graphic object; a black filled circle. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I should be able to turn the LED on and off from my computer by clicking the button on the screen.&lt;/li&gt;&#xA;&lt;li&gt;Pressing the switch on the board, should communicate to the program the state of the LED. If the LED is on, the black circle should turn green, else it should turn black.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This a hypothetical situation I have described to explain the problem. I am not looking for a solution to implement this thing, but want to know how this communication between my circuit and the computer can be achieved, in a simple, inexpensive way, over&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;wire?&lt;/li&gt;&#xA;&lt;li&gt;wireless?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;And if you could suggest where I should look and what I should learn to get started with my electronics project, that would be of great help.&lt;/p&gt;&#xA;" OwnerUserId="1030" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-06T16:53:03.527" LastActivityDate="2011-03-09T10:42:18.970" Title="What are the ways I can make my circuit communicate with a computer?" Tags="&lt;wireless&gt;&lt;communication&gt;" AnswerCount="9" FavoriteCount="2" />
  <row Id="3835" PostTypeId="2" ParentId="3834" CreationDate="2010-08-03T05:23:41.277" Score="0" ViewCount="" Body="&lt;p&gt;Wired or wireless is pretty straightforward these days. You can get bluetooth kits that give you I/O already, and you can also buy very inexpensive USB I/O boards. What you want to use is entirely up to your needs and your budget.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.hexwax.com/Products/expandIO-USB/&quot; rel=&quot;nofollow&quot;&gt;http://www.hexwax.com/Products/expandIO-USB/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something like that (never used it, no affiliation with the company) would probably get you off and running very quickly and with a minimum of fuss. They appear to be available from Digikey and Mouser, and probably others as well.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-08-03T05:23:41.277" />
  <row Id="3836" PostTypeId="2" ParentId="3834" CreationDate="2010-08-03T05:29:28.457" Score="3" ViewCount="" Body="&lt;p&gt;Take a look at the www.ti.com/chronos&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI makes this awesome 16 bit microcontroller family based on the MSP430 chip. One variant of that chip is the CC430, which has wireless embedded in the package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The chronos is a &quot;development board&quot; that they sell for 49 bucks. It comes in a wrist watch form factor (which I use everyday, it's even fashionable outside the geek world :-)) It also comes with two USB dongles, one for the JTAG (programmer) and another one is the wireless counterpart.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the examples in the devboard is controlling the mouse wirelessly using the watch, which is pretty cool. The watch also comes with accelerometer, barometer (altitude) sensor and thermometer.&lt;/p&gt;&#xA;" OwnerUserId="1267" LastActivityDate="2010-08-03T05:29:28.457" CommentCount="2" />
  <row Id="3837" PostTypeId="2" ParentId="3834" CreationDate="2010-08-03T05:49:16.233" Score="12" ViewCount="" Body="&lt;p&gt;There are quite a few different ways you could achieve this. Here are a few:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;You could program a small microcontroller like a &lt;a href=&quot;http://www.microchip.com/wwwproducts/devices.aspx?ddocname=en010230&quot; rel=&quot;nofollow&quot;&gt;Microchip PIC16F84A&lt;/a&gt; to watch the button and the LED. Whenever the button is pressed, the PIC16F84A sends a character through a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9115&quot; rel=&quot;nofollow&quot;&gt;FTDI serial chip&lt;/a&gt; to a USB port on your computer. On your computer, a program written in &lt;a href=&quot;http://processing.org/&quot; rel=&quot;nofollow&quot;&gt;Processing&lt;/a&gt; watches the USB port and updates the pictures on the screen. Total cost: $20 for some chips and a breadboard.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You could buy a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8255&quot; rel=&quot;nofollow&quot;&gt;Bluetooth Arduino&lt;/a&gt; with a prototyping shield. The Arduino talks over a Bluetooth chip to a Bluetooth card in your PC. A program written in &lt;a href=&quot;http://diveintopython.org/&quot; rel=&quot;nofollow&quot;&gt;Python&lt;/a&gt; listens to the Bluetooth card and draws the appropriate picture on the screen with the &lt;a href=&quot;http://www.pygame.org/news.html&quot; rel=&quot;nofollow&quot;&gt;Pygame&lt;/a&gt; library. Total cost: $150 for a Bluetooth Arduino.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You could attach a webcam to your PC that watches your LED and the button. A program written in &lt;a href=&quot;http://www.ruby-lang.org/en/&quot; rel=&quot;nofollow&quot;&gt;Ruby&lt;/a&gt; is analyzing every image coming from the webcam, comparing it to the previous image. When it detects a change in the region of the image near the button, it looks at the color of the pixels in the LED region and updates a value in a &lt;a href=&quot;http://couchdb.apache.org/&quot; rel=&quot;nofollow&quot;&gt;database&lt;/a&gt;. A webpage auto-refreshes using the &lt;a href=&quot;http://plugins.jquery.com/project/timers&quot; rel=&quot;nofollow&quot;&gt;jQuery timer plugin&lt;/a&gt;, and updates an image on the screen based on the value in the database. Total cost: $25 for a crappy webcam.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You could find an old PC with a parallel port and install &lt;a href=&quot;http://www.ubuntu.com/&quot; rel=&quot;nofollow&quot;&gt;Ubuntu Linux&lt;/a&gt; on it. You connect the LED and the button to pins on the parallel port and then write a program in &lt;a href=&quot;http://en.wikipedia.org/wiki/The_C_Programming_Language_%28book%29&quot; rel=&quot;nofollow&quot;&gt;C&lt;/a&gt; that reads address 0x378. Based on the data returned, it makes calls into a &lt;a href=&quot;http://www.friedspace.com/cprogramming/cgraphics.php&quot; rel=&quot;nofollow&quot;&gt;C graphics library&lt;/a&gt; that does the appropriate screen drawing. Total cost: free, if you can find a PC old enough.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9672&quot; rel=&quot;nofollow&quot;&gt;replace the power button&lt;/a&gt; on your computer with the button in question, and the power LED with the LED in question. You replace your BIOS with a version of &lt;a href=&quot;http://www.openfirmware.info/Welcome_to_OpenBIOS&quot; rel=&quot;nofollow&quot;&gt;OpenBIOS&lt;/a&gt; that has been modified to display a green circle on the screen, and never boot any operating system. Total cost: probably the cost of a new PC.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;But in all seriousness&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think I'd recommend an &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; and &lt;a href=&quot;http://processing.org/&quot; rel=&quot;nofollow&quot;&gt;Processing&lt;/a&gt;. They're simple and great for beginners. Total cost: $30 for the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best of luck.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-08-03T05:49:16.233" CommentCount="4" />
  <row Id="3838" PostTypeId="1" CreationDate="2010-08-03T05:55:37.103" Score="1" ViewCount="222" Body="&lt;p&gt;First what is my final goal: to drive 24 RGB LEDS using a microcontroller connected serially to a &lt;a href=&quot;http://www.micrel.com/page.do?page=product-info/products/mm5450.shtml&quot; rel=&quot;nofollow&quot;&gt;Micrel MM5450 LED driver&lt;/a&gt;. It would be nice to be able to drive all of them individually (72 LEDs), but I'll settle (as I did) for multiplexing and only driving one color at time. In the case of the MM5450, I'm using 3 outputs to drive 3 transistors, one for each color.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now here's the problem I'm having.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using the PLCC44 package, which seems to show some differences from the standard text in the datasheet. For example, the datasheet refers to 35 bits of data, but the PLCC only has 34 output pins instead of 35 in the DIP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just to get my feet wet, I've wired 4 LEDs to output pins 1 to 4 and left the rest disconnected. I've wired VDD and VSS (no decoupling capacitors), put a 100K pot on pin 21 (brightness control) and a 1nF on that same pin as the datasheet suggests.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried wiring DATAENABLE to GND, to VCC and to a pulldown resistor, but it didn't work as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The symptoms are that after I send data using the timing as indicated in the datasheet, I get weird results. For example, if I send all bits zero, at power on, only leds 1 3 and 4 will light up. Reset the uc and then led 2 3 and 4 light up.&#xA;If I send just bit one high, then led 1 and 4 light up, and then when I reset the uc leds 3 and 4 light up.&#xA;Just to clarify, when I say reset, it means that I assert the reset line of the microcontroller, which starts my program again (and sent a bitstream to the led driver).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't see a clear pattern of what's happening here. Anybody with more experience on this chip (or a suggestion of a completely different chip that will achieve my goals) to help me?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;b&gt;Edit:&lt;/b&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ok, did some more tests and hooked a storage scope to data and clock. Here are my findings:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Clock and data are doing exactly what I'm telling them to do. As suggested, I placed clock and data on my PORTB and the data enable on my PORTC, if that matters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My data sequence looks like this:&#xA;data: starts low&#xA;data enable: starts high&#xA;data sequence: 0 - [data enable low] - 1 - 34 bits of data - 0 - 0 - [data enable high]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right now I'm working in the 10ms pulses. Since I'm using a breadboard connected to my devboard via long clip wires, I've analyzed the shape of the clock and data signals for any ringing and signal was pretty good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the symptoms, it seems that my bitstream is out of sync with the chip... I'm out of ideas&lt;/p&gt;&#xA;" OwnerUserId="1267" LastEditorUserId="1267" LastEditorDisplayName="" LastEditDate="2010-08-05T18:44:27.150" LastActivityDate="2010-08-05T18:44:27.150" Title="Problems driving leds with the MM5450" Tags="&lt;pic&gt;&lt;led&gt;&lt;driver&gt;&lt;microcontroller&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="3839" PostTypeId="2" ParentId="3834" CreationDate="2010-08-03T07:11:25.353" Score="4" ViewCount="" Body="&lt;p&gt;Go get the book &quot;Making Things Talk&quot; by Tom Igoe: &lt;a href=&quot;http://oreilly.com/catalog/9780596510510&quot; rel=&quot;nofollow&quot;&gt;http://oreilly.com/catalog/9780596510510&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not about speech, it's about all the different methods of making your different devices-- e.g., your computer and your circuit --talk to each other.  In it, you'll find the gory details of all the methods people are outlining in the other answers here, complete with circuit diagrams and source code (where appropriate).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you'd like to learn any or all the different ways to do this, you couldn't have a better starting point.&lt;/p&gt;&#xA;" OwnerUserId="484" LastEditorUserId="484" LastEditorDisplayName="" LastEditDate="2010-08-03T08:24:28.080" LastActivityDate="2010-08-03T08:24:28.080" CommentCount="1" />
  <row Id="3840" PostTypeId="2" ParentId="3838" CreationDate="2010-08-03T12:46:03.077" Score="2" ViewCount="" Body="&lt;p&gt;I suspect the problem is that you need to control the data enable line with the microcontroller. Set it high at reset. Then, set it low right before (more than 100 ns) you start transmitting data. After the 35 bits, bring it high again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the datasheet explains the missing 35th pin you were wondering about in Note 1 on page 1. In the MM5450, it is replaced by the data enable line.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-08-03T12:46:03.077" CommentCount="6" />
  <row Id="3841" PostTypeId="2" ParentId="3834" CreationDate="2010-08-03T12:46:20.597" Score="0" ViewCount="" Body="&lt;p&gt;Assuming that your PC has a serial port you could just use the USART on the chip and an RS-232 transceiver to communicate between the chip and the PC. If your PC doesn't have a serial port you should invest in a USB&amp;lt;-&gt;RS-232 converter.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-08-03T12:46:20.597" />
  <row Id="3842" PostTypeId="2" ParentId="3834" CreationDate="2010-08-03T15:18:56.363" Score="0" ViewCount="" Body="&lt;p&gt;Your quickest and easiest method of doing that would be via Labview and associated USB I/O devices.  Of course, this isn't cheap (thousands of dollars).  What you're describing is not entry level, definitely not 'Hello World'-level.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than spending that much money, you'd probably be best with using an Arduino and communicating with your program via serial and having the Arduino turn the light on and off.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-08-03T15:18:56.363" CommentCount="1" />
  <row Id="3843" PostTypeId="2" ParentId="464" CreationDate="2010-08-03T16:40:33.873" Score="0" ViewCount="" Body="&lt;p&gt;What I wish many of my interns knew is how difficult and demoralising electronics can be. I see many non-engineer types try to add some flashing lights and sensors to a fashion project or something, not realising that they're heading for a debugging nightmare.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I was to write a book on electronics, I'd do my best to scare people away in chapter 1. Anyone who was left would probably be able to put up with debugging.&lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2010-08-03T16:40:33.873" CommunityOwnedDate="2010-08-03T16:40:33.873" CommentCount="4" />
  <row Id="3844" PostTypeId="2" ParentId="3834" CreationDate="2010-08-03T16:49:13.143" Score="1" ViewCount="" Body="&lt;p&gt;There are some nice simple USB devices which can do this, for example the Kadtronics USB Digital I/O Commander:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.kadtronix.com/digio.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.kadtronix.com/digio.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2010-08-03T16:49:13.143" />
  <row Id="3845" PostTypeId="2" ParentId="3783" CreationDate="2010-08-03T17:41:32.367" Score="0" ViewCount="" Body="&lt;p&gt;I've heard of RFID tags that have small amounts of read/write memory in them so it might be possible for you to get a tag containing a microcontroller. You could then 'read' the tag and when the tag is being powered by the reader you could have the microcontroller perform a check of your liquid sensor and return an appropriate value to the tag reader for wet or dry.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-08-03T18:02:14.227" LastActivityDate="2010-08-03T18:02:14.227" />
  <row Id="3846" PostTypeId="1" AcceptedAnswerId="3847" CreationDate="2010-08-03T19:12:16.747" Score="3" ViewCount="319" Body="&lt;p&gt;I finally broke down and bought this board:&#xA;&lt;a href=&quot;http://hackaday.com/2010/02/28/open-source-logic-analyzer-2/&quot; rel=&quot;nofollow&quot; title=&quot;Hackaday.com&quot;&gt;http://hackaday.com/2010/02/28/open-source-logic-analyzer-2/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It &quot;seems&quot; like it would be really helpful, the problem I'm having is getting it setup, I am not finding much of a &quot;how to&quot; anywhere. Here are the problems I'm having.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to get it working on both my windows and linux machines, the problem with the windows machine is that using the logic analyzer software I can't see the &quot;capture&quot; button at the bottom of the screen cause of my netbook resolution, and since I can't change my resolution I can't get it working there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My Ubuntu machine I couldn't find a download for the S/W except in a .exe format, so I had to download and install wine on my machine, but when I plug in my board I'm not sure if it's detected. There appears to be a rxtx module I need to setup and install. But I'm not sure what version I should use. I found links to some of this from the comments (where I in fact commented) here: &lt;a href=&quot;http://dangerousprototypes.com/2010/02/25/prototype-open-logic-sniffer-logic-analyzer-2/&quot; rel=&quot;nofollow&quot; title=&quot;Dangerous Prototypes&quot;&gt;Dangerous Prototypes&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;does anyone have any good suggestions on what to do at this point?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also anyone have/know of a clear step by step guide (with possibly copy paste commands for the command line portion? as the wget calls can get hard to read and I'm not sure what the link is most times)&lt;/p&gt;&#xA;" OwnerUserId="982" LastActivityDate="2010-08-16T21:33:45.607" Title="Openbench Logic Sniffer setup" Tags="&lt;logic-analyzer&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="3847" PostTypeId="2" ParentId="3846" CreationDate="2010-08-03T19:18:36.847" Score="3" ViewCount="" Body="&lt;p&gt;Here's a screencast showing you how to set it up in Windows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.gadgetfactory.net/2010/04/quick-start-video-for-open-bench-logic.html&quot; rel=&quot;nofollow&quot;&gt;http://blog.gadgetfactory.net/2010/04/quick-start-video-for-open-bench-logic.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some instructions I posted to the forum on building and running SUMP in Linux:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dangerousprototypes.com/forum/index.php?topic=549.msg4933#msg4933&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com/forum/index.php?topic=549.msg4933#msg4933&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-08-16T21:33:45.607" LastActivityDate="2010-08-16T21:33:45.607" CommentCount="5" />
  <row Id="3848" PostTypeId="2" ParentId="3846" CreationDate="2010-08-03T20:24:44.647" Score="1" ViewCount="" Body="&lt;p&gt;If you can get your hands on a Windows install disc, you might be better served trying a virtual machine install of Windows on your Ubuntu machine. I know Wine has gotten leaps and bounds better but I've found very few situations where VirtualBox has failed me. &lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-08-03T20:24:44.647" />
  <row Id="3849" PostTypeId="1" AcceptedAnswerId="3854" CreationDate="2010-08-03T23:23:31.283" Score="4" ViewCount="461" Body="&lt;p&gt;Since an 8-bit MCU can't read the whole 16-bit timer in one cycle, this creates a race condition where the low-word can roll over between reads.  Does the community have a preferred method of avoiding these race conditions?  I'm currently considering stopping the timer during reads, but I'd like to know if there's a more elegant solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FYI, this is for a PIC.  EDIT: 16F690&lt;/p&gt;&#xA;" OwnerUserId="1278" LastEditorUserId="1278" LastEditorDisplayName="" LastEditDate="2010-08-04T15:11:28.763" LastActivityDate="2010-08-04T18:36:03.700" Title="Reading a 16-bit timer on an 8-bit MCU" Tags="&lt;microcontroller&gt;&lt;timer&gt;&lt;pic&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="3850" PostTypeId="2" ParentId="3849" CreationDate="2010-08-04T01:31:40.140" Score="8" ViewCount="" Body="&lt;p&gt;Check your datasheet!  It &lt;em&gt;will&lt;/em&gt; talk about this, in gory detail, for your particular chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not certain that this is true for all 16-bit counter/timer registers on all PICs (maybe someone else can answer that!) but at least for the PIC 18F that I use, the datasheet specifically talks about how this is handled.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you read the low byte, it buffers the high byte into a temporary register for the high byte, so that when you read the high byte next, it gives you a full instantaneous snapshot of the timer value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The same basic process is used on AVR (and Arduino of course), and for most other cases where you need to read or write two-byte registers at once on 8-bit MCUs.&lt;/p&gt;&#xA;" OwnerUserId="484" LastActivityDate="2010-08-04T01:31:40.140" CommentCount="3" />
  <row Id="3851" PostTypeId="2" ParentId="3772" CreationDate="2010-08-04T03:45:06.617" Score="2" ViewCount="" Body="&lt;p&gt;Hmmm. First time that I've heard someone call Pasternack &quot;reputable.&quot; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your requirements, you might find cable from Times Microwave or Andrew to be acceptable; these are often good brands for precision, phase stable applications.&lt;/p&gt;&#xA;" OwnerUserId="484" LastActivityDate="2010-08-04T03:45:06.617" />
  <row Id="3852" PostTypeId="1" CreationDate="2010-08-04T06:15:45.093" Score="1" ViewCount="138" Body="&lt;p&gt;This may sound over ambitious and silly but I think I should just ask. Lets assume a college campus (I mean a whole campus with buildings, gardens and workshops and stuff). I am thinking around 17 Acres of land. The signal of cellular phones is full just outside the campus, but just as you cross the first building you lose it totally. And then throughout the core of the campus, you don't have any signal at all. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now how can I do a survey of such a situation for parameters like signal strength, causes of signal drop, places where I get a much better signal etc. There has to be some methodology to do it scientifically. What equipment will I have to use, are there any pre-existing DIY designs for these?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also once I workout the cause of the signal drop, how can I boost it. Are there any signal booster for cellular network? I am thinking DIY type, something I would build myself and learning a lot of things in the process.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-08-04T12:48:11.477" Title="Boost Signals of mobile network" Tags="&lt;signal&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="3853" PostTypeId="2" ParentId="3852" CreationDate="2010-08-04T06:25:13.623" Score="2" ViewCount="" Body="&lt;p&gt;You will need some rather expensive equipment to perform those measurements, it's best left to the professionals. Boosting the signal as you propose isn't feasible and would be illegal, anyway.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-04T06:25:13.623" CommentCount="3" />
  <row Id="3854" PostTypeId="2" ParentId="3849" CreationDate="2010-08-04T06:28:15.277" Score="6" ViewCount="" Body="&lt;p&gt;Windell's right, if you're talking about PICs, the datasheet (and hardware) already handle this for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're not using a PIC, the general method I use is to do this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;byte hi, lo;&#xA;word timer_value;&#xA;&#xA;do {&#xA;    hi = TIMER_HI;&#xA;    lo = TIMER_LO;&#xA;} while(hi != TIMER_HI);&#xA;&#xA;timer_value = (hi &amp;lt;&amp;lt; 8) | lo;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;What this does is to read the upper byte followed by the lower byte, and to continue doing so until the hi byte doesn't change.  This readily handles the case where the low byte of the 16-bit value overflows between reads.  It assumes, of course, that there are no side effects from reading the TIMER_HI register multiple times. If your particular microprocessor doesn't allow that, it's time to throw it out and use one that isn't quite as braindead. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This method ALSO assumes that your timer isn't changing so rapidly that you run the risk of overflowing the low 8 bits within a processor fetch cycle or two.  If you're running a timer so fast (or a microprocessor so slow) then it's time to re-think your implementation.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-08-04T06:28:15.277" CommentCount="17" />
  <row Id="3855" PostTypeId="2" ParentId="3852" CreationDate="2010-08-04T11:03:43.507" Score="2" ViewCount="" Body="&lt;p&gt;As has already been said, transmitting within the mobile phone bands would be illegal and will almost certainly make matters worse with your signal interfering with the legitimate signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of the mobile phone companies (Vodaphone for example) will sell you an internet connected home base station that can allow your mobile phone to &quot;connect&quot; to their network using VOIP if you have no coverage at your home address.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps you should take this up with the mobile network concerned and they could ask the college for permission to place a repeater on site.  On the other hand the college authorities may be quite pleased that there is no coverage over the campus as it prevents all sorts of disruption to lectures from student phones ringing.&lt;/p&gt;&#xA;" OwnerUserId="400" LastEditorUserId="400" LastEditorDisplayName="" LastEditDate="2010-08-04T12:48:11.477" LastActivityDate="2010-08-04T12:48:11.477" CommentCount="2" />
  <row Id="3856" PostTypeId="2" ParentId="3741" CreationDate="2010-08-04T11:59:17.980" Score="4" ViewCount="" Body="&lt;p&gt;I just saw the &lt;a href=&quot;http://blog.makezine.com/archive/2010/08/new_in_the_maker_shed_netduino_a_ne.html&quot; rel=&quot;nofollow&quot;&gt;Netduino&lt;/a&gt; which may be an interesting compromise for you. I have no idea of the system specs or details but it does appear to use .NET Micro so it sounds like a good way to at least try out that framework.&lt;/p&gt;&#xA;" OwnerUserId="1032" LastActivityDate="2010-08-04T11:59:17.980" />
  <row Id="3857" PostTypeId="2" ParentId="3852" CreationDate="2010-08-04T12:13:46.190" Score="3" ViewCount="" Body="&lt;p&gt;What phone do you have? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's a smart phone, chances are there is a free app that can display RSSI (signal strength). You can use this number to make a map. You'll find that buildings and trees pose the most interference, and the higher you are the better the signal. You can even come up with a 3d map if you are ambitious :) Just use a smartphone to map the RSSI or SNR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To boost the signal, the easiest approach is to attach a high gain antenna. A Yagi or even a parabolic dish antenna if you want to get the ladies' attention. :)&lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-08-04T12:13:46.190" CommentCount="9" />
  <row Id="3858" PostTypeId="1" CreationDate="2010-08-04T16:06:35.090" Score="0" ViewCount="172" Body="&lt;p&gt;I am designing a fairly simple board with an 5x8 LED matrix. I plan to drive it with an LED driver I haven't chosen yet, probably on a separate board connected by a ribbon cable. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is: what are the best practices for arranging tightly grouped LEDs on a board? If they're laid out like so:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&lt;br /&gt;&#xA;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&lt;br /&gt;&#xA;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&lt;br /&gt;&#xA;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&lt;br /&gt;&#xA;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;x&lt;br /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;you can see that the channels are going to be pretty tight. Anyhow, this thing just seems like there's got to be a standard solution already worked out (&quot;arranged in a Hofstadter configuration&quot;, or something like that).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, is there a standard ribbon cable with 41 pins?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TIA.&lt;/p&gt;&#xA;" OwnerUserId="989" LastActivityDate="2011-05-20T10:58:19.837" Title="Form factor for a large LED array on a small board" Tags="&lt;board&gt;&lt;matrix&gt;&lt;led&gt;&lt;ribbon-cable&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="3859" PostTypeId="2" ParentId="3858" CreationDate="2010-08-04T16:22:48.603" Score="1" ViewCount="" Body="&lt;p&gt;I'm using a Micrel MM5450... still having some &lt;a href=&quot;http://chiphacker.com/questions/3838/problems-driving-leds-with-the-mm5450&quot; rel=&quot;nofollow&quot;&gt;small problems&lt;/a&gt; with it but bound to have it working on the next few days. It takes only 3 connections to your microcontroller (clock, data enable and data) using serial comm. and it can drive up to 34 LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=Shg0nCd6DRk&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=Shg0nCd6DRk&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1267" LastActivityDate="2010-08-04T16:22:48.603" />
  <row Id="3860" PostTypeId="2" ParentId="3849" CreationDate="2010-08-04T16:29:15.143" Score="3" ViewCount="" Body="&lt;p&gt;The text you referred to in your comment (Section 6.5.1) refers to asynchronous timer operation, where the timer is clocked from a source external to the microcontroller.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The disclaimer is suggesting starting and stopping the timer because Andrew's general method (really any method) won't work because there may be many ticks (More than 256, even) of the external clock and thus the timer in a single cycle of the processor.  I assume you're not running with this edge case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If, instead, you're using the internal oscillator as a reference, you'll be fine.  Even with a prescaler of 1, you've got up to 255 cycles after you read the high byte to read the low byte.  This should be a 2 cycle operation.  You still need the do/while loop in case your high byte changes (What is the difference between 'hi' and 'TIMER_HI' if the value of 'lo' is 0?) between these times.  With a prescaler of 2 or greater, you don't need this test anymore.  It's only with prescalers much less than 1 that it starts to become a problem, and this is impossible without the external clock.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-04T16:29:15.143" CommentCount="1" />
  <row Id="3861" PostTypeId="2" ParentId="3858" CreationDate="2010-08-04T16:55:26.400" Score="0" ViewCount="" Body="&lt;p&gt;What size LEDs? What type of case?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did an 8x8 layout with 5mm LEDs. I equally spaced the LEDs in a 2.1&quot; x 2.1&quot; area.&#xA;I would not space them much tighter than that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can see how the spacing looks if you take a look at the finished&#xA;board and the drill template at&#xA;&lt;a href=&quot;http://wiblocks.luciani.org/PICO/PICO1TR-LED-L-index.html#drill&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/PICO/PICO1TR-LED-L-index.html#drill&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also did a 10x10 layout of 3mm LEDs in the same 2.1&quot; x 2.1&quot; area. &#xA;See &lt;a href=&quot;http://wiblocks.luciani.org/PICO/PICO1TR-LED-S-index.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/PICO/PICO1TR-LED-S-index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pictures of an example wooden case are at &lt;a href=&quot;http://wiblocks.luciani.org/docs/app-notes/pico-led-drill.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/docs/app-notes/pico-led-drill.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do not know of a standard 41 pin ribbon cable. Most ribbon cables crimp on&#xA;dual row headers. I have seen some ribbons for 37 and 50pin D-subs but I would&#xA;stick to a header style. If you could live with 40pins you can use an old IDE&#xA;cable.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T10:58:19.837" LastActivityDate="2011-05-20T10:58:19.837" />
  <row Id="3862" PostTypeId="2" ParentId="3858" CreationDate="2010-08-04T16:55:30.880" Score="0" ViewCount="" Body="&lt;p&gt;There is not a standard ribbon cable with 41 cables.  50 is fairly common, and 40 is also common  (IDE hard drives).  The values (from wikipedia) are usually one of the following: 4, 6, 8, 9, 10, 14, 15, 16, 18, 20, 24, 25, 26, 34, 37, 40, 50, 60, 64 and 80.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd suggest going down to the 13 wires you'd need with a multiplexed array (or 7 you'd need if you were charlieplexing).  You want to drive them with a pulsed wave for maximum brightness and efficiency. If you multiplexed them by rows and columns, you'd have a 20% duty cycle (5 rows) and an 8-output bus (easy even on an 8-bit micro)?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you didn't mention what kind of PCB you were using. With a 2-layer board, assuming you can only fit 1 trace between your LEDs both vertically and horizontally, you can get all but the center 2 just by connecting the outer LEDs and slipping one trace past them to the next row from the top and bottom, and the 3 on each side of your middle row can come in from the sides. Work the last two in some other way, maybe on the ground plane side.  (Note: I'm assuming you're using a ground plane.)  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-04T16:55:30.880" CommentCount="1" />
  <row Id="3863" PostTypeId="1" CreationDate="2010-08-04T17:38:45.487" Score="1" ViewCount="228" Body="&lt;p&gt;Hello,&#xA;  I am building a hot rod and i decided to make a speedometer myself with a 3 digit nixietube display.  I am planning on using a atmel avr microtroller (atmega32 i beleive),  i would like a cmos clock that i can compare time for to keep the speedo as accurate as possibile.&lt;br&gt;&#xA;  What is a good clock chip to use?&#xA;  How to i wire interface it to the avr?&#xA;  How do i properly use it in software?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks, any help is appreaciated.&#xA;  Here is what i have so far&#xA;  Pulse generator for transmission (sign wave, will use the self powered 4069 square wave converter circuit but power it off the ps not the wave)&#xA;  Nixie tubes and sockets&#xA;  atmel microntroller and socket&#xA;  Nixie tube driver chips&#xA;  Programming socket for avr&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to make one order to mouser and get the hardware breadborded asap so any help is appreaciated.&#xA;Thanks&#xA;Ed&lt;/p&gt;&#xA;" LastActivityDate="2010-08-07T19:22:47.180" Title="what is the right clock chip for making a speedometer with an avr" Tags="&lt;avr&gt;&lt;atmel&gt;&lt;clock&gt;" AnswerCount="4" />
  <row Id="3864" PostTypeId="2" ParentId="3863" CreationDate="2010-08-04T18:07:28.487" Score="1" ViewCount="" Body="&lt;p&gt;Your speedometer needs to measure the elapsed time between two pulses, and it doesn't need to know the time of day.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd consider using the AVR's calibrated internal oscillator. Its +-1% deviation from the nominal frequency is probably more precise than the circumference of your vehicle's tires.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that's not good enough for you, spend an extra fifty cents for a crystal oscillator.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2010-08-06T14:18:08.567" LastActivityDate="2010-08-06T14:18:08.567" CommentCount="2" />
  <row Id="3865" PostTypeId="2" ParentId="3849" CreationDate="2010-08-04T18:36:03.700" Score="1" ViewCount="" Body="&lt;p&gt;There is an example in the &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/33023a.pdf&quot; rel=&quot;nofollow&quot;&gt;PIC Mid-Range MCU Family Reference Manual&lt;/a&gt; for Reading and Writing Timer1 in Asynchronous Counter Mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example: Reading a 16-bit Free-Running Timer&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;; All interrupts are disabled&#xA;MOVF TMR1H, W ; Read high byte&#xA;MOVWF TMPH ;&#xA;MOVF TMR1L, W ; Read low byte&#xA;MOVWF TMPL ;&#xA;MOVF TMR1H, W ; Read high byte&#xA;SUBWF TMPH, W ; Sub 1st read with 2nd read&#xA;BTFSC STATUS,Z ; Is result = 0&#xA;GOTO CONTINUE ; Good 16-bit read&#xA;;&#xA;; TMR1L may have rolled over between the read of the high and low bytes.&#xA;; Reading the high and low bytes now will read a good value.&#xA;;&#xA;MOVF TMR1H, W ; Read high byte&#xA;MOVWF TMPH ;&#xA;MOVF TMR1L, W ; Read low byte&#xA;MOVWF TMPL ;&#xA;; Re-enable the Interrupt (if required)&#xA;CONTINUE ; Continue with your code&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-08-04T18:36:03.700" CommentCount="1" />
  <row Id="3866" PostTypeId="2" ParentId="3863" CreationDate="2010-08-04T19:08:26.643" Score="0" ViewCount="" Body="&lt;p&gt;You can probably use the chips oscillator.  I did a similar thing (well I used a two line lcd display) with an old PIC.  The sensor on the transmission sent out so many thousands of pulses per mile, which gives you a fair amount of room to calibrate for tire size and gear ratios, etc.  So you could choose any number of solutions from measuring time between individual pulses to measuring 10 pulses or something like that, with a timeout where you clearly know the car has stopped and the speed is zero.  which you would need for any solution.  if you know or figure out the pulses per mile its not hard to do the math to figure out the time between pulses at different speeds and then add the plus or minus accuracy of the clock on the microcontroller to find out what your speed error is.  My guess is the analog and timing nature of the sensor and wires are themselves going to have as much error as the clock you are using as a reference.  (jitter in the pulses at a fixed rate).  You can also throw in slop in the drivetrain, variation in tire sizes (as you peel out, stress the tire with the brake or acellerator, etc), you are probably fine, I would start with the internal oscillator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using an external oscillator or the internal one you could have a timer count every second or something like that and count speedo ticks per second and update the display (tubes) based on that (instead of measuring between every speedo tick).  The biggest problem I had when I did this was not the sensing or timing of the pulses, I had a heck of a time doing the divide by tens to print the speed in decimal, hex was easy, octal even easier, but decimal when the program space was a kbyte or less and memory was measured in bytes. your avr likely has more resources than I had at the time and a good (and affordable) C compiler.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would love to see pictures when you get it working...&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-08-04T19:08:26.643" />
  <row Id="3867" PostTypeId="2" ParentId="3863" CreationDate="2010-08-04T19:09:59.640" Score="0" ViewCount="" Body="&lt;p&gt;Here are some tips:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://winavr.scienceprog.com/example-avr-projects/measuring-motor-speed-and-display-result-on-lcd.html&quot; rel=&quot;nofollow&quot;&gt;http://winavr.scienceprog.com/example-avr-projects/measuring-motor-speed-and-display-result-on-lcd.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;p=642909&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;p=642909&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As others have said, you don't need a realtime clock unless you care about the date and time, you just need to measure the time between rotations.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-04T19:09:59.640" />
  <row Id="3868" PostTypeId="2" ParentId="3783" CreationDate="2010-08-04T19:29:58.227" Score="0" ViewCount="" Body="&lt;p&gt;There are certainaly RFID tags with sensors coming onto the market soon. I don't know if they exist yet. But batteryless wireless sensor networks are going to be a big thing soon.&lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2010-08-04T19:29:58.227" CommentCount="1" />
  <row Id="3869" PostTypeId="1" AcceptedAnswerId="3870" CreationDate="2010-08-04T22:12:44.487" Score="4" ViewCount="679" Body="&lt;p&gt;I have a need to install an Arduino (actually just the IC) into existing hardware to enhance functionality. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I would like to do is some how connect the Arduino so that is &quot;spys&quot; on the I/O lines between two chips on a board. If the Arduino picks up a specific keyword on that UART connection, it will perform a specific action on a separate set of output pins. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'm uncertain about is, how to connect the Arduino in such a way that it can decode an existing UART connection without participating...? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not possible, I am interested in theories, ideas, etc... I always like a challenge!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-08-05T06:01:52.173" Title="Can the Arduino be used to &quot;spy&quot; on a UART connection between two devices?" Tags="&lt;arduino&gt;&lt;uart&gt;&lt;serial&gt;&lt;data&gt;" AnswerCount="3" />
  <row Id="3870" PostTypeId="2" ParentId="3869" CreationDate="2010-08-04T22:37:13.947" Score="8" ViewCount="" Body="&lt;p&gt;So if I understand correctly, you have 2 devices connected via UART.  I assume just TX, RX and GND lines connected between the devices?  (i.e., no DTS/CTS/DTR/RTS control lines used - this is typical).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this scenario, device 1's TX (transmit) is connected to device 2's RX (receive), and vice-versa.  Their grounds are connected to each other.  Thus, each device can be transmitting and receiving at the same time (each transmits on a separate wire, the communication is full-duplex).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason I mention all this is because it becomes clear that to &quot;sniff&quot; or &quot;listen&quot;, you'll actually need 2 UARTs to listen to both sides of the conversation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, all you'd do is ensure that all 3 devices' UART GNDs are shorted, and connect (really, &quot;tee&quot;, as in a T-fitting, like plumbing) device 1 &amp;amp; device 2's TX lines to the 2 RX lines on 2 UARTs.  Make sure that the baud rates are all configured identically.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a lot of Arduino boards / designs.  The most common one nowadays, the Duemilanove, uses the ATMega328P, which I think has only 1 UART (well, USART).  So you'd either have to wire up a 2nd UART IC, or resort to &quot;bit banging&quot; on the second receiver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Async UART communications is well-defined, with start &amp;amp; stop bits (and sometimes parity bits), so if your processor is fast enough, you can simply connect one of the device's UART TX lines to a GPIO configured as input, and poll the line fast enough with oversampling to detect START &amp;amp; STOP and sample bits.  The article &lt;a href=&quot;http://www.ganssle.com/articles/auart.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;Bit Banging&quot; by Jack Ganssle&lt;/a&gt; will give you plenty to chew on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A decent description of the RS232 waveform can be found at &lt;a href=&quot;http://www.beyondlogic.org/serial/serial1.htm#40&quot; rel=&quot;nofollow&quot;&gt;BeyondLogic&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that there are other issues such as voltage levels (0/+5, -10V/+10V, etc.) that you'll have to take into consideration (see the Beyond Logic section on &quot;RS232 Level Converters&quot;).  I don't have enough information on your system to discuss hardware interfacing besides the &quot;connect the lines&quot; approach discussed above.  Assuming voltage levels are matched, usually it's not a problem to &quot;tee&quot; the TX line into a second receiver (the sniffer), but if the TX doesn't have enough drive, you might need to insert a buffer/driver to prevent the signal from degrading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="221" LastActivityDate="2010-08-04T22:37:13.947" CommentCount="1" />
  <row Id="3871" PostTypeId="2" ParentId="3869" CreationDate="2010-08-04T23:27:54.817" Score="3" ViewCount="" Body="&lt;p&gt;You don't have to hook the AVR's transmit-data pin into your circuit. Just connect the receive line to the half of the the existing link you want to eavesdrop on. If your particular AVR has two serial ports, you should be able to spy on both halves of the existing link simultaneously. You just have to make the port settings match the existing baud rate, stop bits, etc.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-08-04T23:27:54.817" CommentCount="1" />
  <row Id="3872" PostTypeId="2" ParentId="3869" CreationDate="2010-08-05T06:01:52.173" Score="1" ViewCount="" Body="&lt;p&gt;There's a neat trick you can do if the communication is in one direction only at a time (i.e. half-duplex communication). It won't work if both sides talk to each other at the same time (full duplex) but if it's your typical &quot;do this&quot; &quot;ok here's the response&quot; &quot;now do this&quot; &quot;ok here's the new response&quot; type of communications it works quite well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the UART link uses an idle condition of the transmitter at a logic high (1) level you would use a 2-input AND gate and connect the TX from each side to an AND input. The output of the AND gate is your input to your sniffer's UART (it's RX pin). Now take device B's TX line and also bring it to an I/O port on the sniffer. You will configure the sniffer to generate an interrupt when this pin goes from high to low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To recap: device A UART TX -&gt; AND gate input.  Device B UART TX -&gt; other AND gate input AND sniffer GPIO pin.  Output of AND gate -&gt; sniffer UART RX line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UART communications consist of a start bit, some number of data bits, an optional parity bit, and one or more stop bits. Since the idle state is a logic high (1), the start of EVERY byte will be a logic low (0) and the interrupt on the sniffer will fire.  While your sniffer is executing the I/O interrupt the UART hardware will be collecting bits from the AND gate. By the time the UART has received the stop bit, the I/O interrupt will be long done and the UART RX interrupt will fire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The interrupt-on-IO-change routine will set a &quot;direction&quot; variable to indicate that communications are in the &quot;B-&gt;A&quot; direction. The sniffer's UART receive interrupt would look at this &quot;direction&quot; variable and write the just-received byte to the appropriate buffer. The UART RX interrupt would then set the &quot;direction&quot; variable back to the default &quot;A-&gt;B&quot; state:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;volatile int direction = 0;           /* 0 = A -&amp;gt; B */&#xA;&#xA;void io_interrupt(void)&#xA;{&#xA;    direction = 1;                    /* switch direction, now B -&amp;gt; A */&#xA;}&#xA;&#xA;void uart_interrupt(void)&#xA;{&#xA;    unsigned char b;&#xA;&#xA;    b = UART_RX_REG;&#xA;    if(direction) {&#xA;        store_byte_to_device_b_sniff_buffer(b);&#xA;    } else {&#xA;        store_byte_to_device_a_sniff_buffer(b);&#xA;    }&#xA;&#xA;    direction = 0;                   /* reset direction to default A -&amp;gt; B */&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This code is written for clarity and not necessarily what you'd write in a real-world situation. Personally I'd make &quot;direction&quot; a pointer to the appropriate FIFO structure, but that's another exercise entirely. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When device A is talking the I/O line does not move (it remains at a logic '1' since device B's UART transmitter is idle), and the UART RX interrupt will receive a byte, see that the direction is A-&gt;B, and store the data to that buffer.  When device B is talking the I/O line will go low as soon as device B starts shifting data out, and the I/O interrupt routine will set the direction to indicate that device B is talking.  The UART RX interrupt will eventually fire after all the bits have been collected and since I/O interrupt has taken care of setting the direction register appropriately, the received byte will be stored in the correct buffer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Presto: half-duplex communications between two devices captured with a single UART and I/O line on the sniffer, with no bit-banged UART communications.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-08-05T06:01:52.173" CommentCount="3" />
  <row Id="3873" PostTypeId="2" ParentId="464" CreationDate="2010-08-05T10:46:19.090" Score="0" ViewCount="" Body="&lt;p&gt;Everything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Yeah, it's unrealistic)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Also, better).&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-08-05T10:46:19.090" CommunityOwnedDate="2010-08-05T10:46:19.090" />
  <row Id="3874" PostTypeId="2" ParentId="3834" CreationDate="2010-08-05T10:59:27.397" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.python.org/&quot; rel=&quot;nofollow&quot;&gt;Python&lt;/a&gt; + &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=7841&quot; rel=&quot;nofollow&quot;&gt;FT245&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Drop the &lt;a href=&quot;http://bleyer.org/pyusb/&quot; rel=&quot;nofollow&quot;&gt;PyUSB&lt;/a&gt; module, and suddenly it takes only three lines (well, four, if you include the import) of code to get Python talking to meatspace through 8 Parallel IO lines.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;import d2xx&#xA;hardwareHandle = d2xx.open(0)&#xA;#Open the First FTDI device on the computer&#xA;hardwareHandle.setBitMode(0xff, 0x01)      &#xA;#Put the hardware in Async Bit-bang mode, set all pins as outputs&#xA;&#xA;#Finally&#xA;hardwareHandle.write(data)&#xA;#And suddenly&#xA;#`data` shows up on the FT245 pins!&#xA;&#xA;hardwareHandle.setBitMode(0x00, 0x01)&#xA;#set the IO lines to inputs (the first byte is the IO mask)&#xA;input = hardwareHandle.read()&#xA;#and input is equal to the value on the IO lines!&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;It's dead-simple parallel IO from a high-level language.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a bonus, the hardware costs a total of $17.95&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-08-05T10:59:27.397" />
  <row Id="3878" PostTypeId="1" CreationDate="2010-08-05T15:58:38.247" Score="2" ViewCount="201" Body="&lt;p&gt;Sometimes I get unmotivated to finish my personal projects because of a lack of plan on what to do next--should I design a board first, hook up a test circuit, write test code or write design requirements?  Are there any formal design flows maybe specific to embedded hardware that I could follow to make sure I don't miss anything and waste time re-doing things.&lt;/p&gt;&#xA;" OwnerUserId="582" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:40:55.170" LastActivityDate="2010-12-10T22:40:55.170" Title="Embedded design flow" Tags="&lt;design&gt;&lt;project-management&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="3879" PostTypeId="1" CreationDate="2010-08-05T17:05:22.803" Score="4" ViewCount="647" Body="&lt;p&gt;It's said that electrolytic capacitors behave as inductors at high frequencies, which is why we put small ceramic caps in parallel with them:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Electrolytic, paper, or plastic film&#xA;  capacitors are a poor choice for&#xA;  decoupling at high frequencies; they&#xA;  basically consist of two sheets of&#xA;  metal foil separated by sheets of&#xA;  plastic or paper dielectric and formed&#xA;  into a roll. This kind of structure&#xA;  has considerable self inductance and&#xA;  acts more like an inductor than a&#xA;  capacitor at frequencies exceeding&#xA;  just a few MHz.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.analog.com/library/analogdialogue/archives/39-09/layout.html&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://www.analog.com/library/analogdialogue/archives/39-09/3909_01.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Capacitor impedance vs. frequency.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yet I also see a few things like this:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The &quot;inductance problem&quot; associated with electros is another idiotic myth&#xA;  - they have no more inductance than a length of wire the same as the length&#xA;  of the cap.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;What is the exact nature of this effect and in what applications and frequencies do we need to worry about it?  What are the practical implications?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-05T19:28:32.323" LastActivityDate="2010-10-01T22:06:30.923" Title="Frequency dependence of electrolytic capacitors" Tags="&lt;capacitor&gt;&lt;impedance&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="3880" PostTypeId="2" ParentId="3879" CreationDate="2010-08-05T17:39:18.403" Score="0" ViewCount="" Body="&lt;p&gt;cool question - generally speaking a capacitor with capacitance C has an complex impedence with magnitude 1/(2*pi*f*C), fwiw. So at high frequencies a capacitor is supposed look like a short circuit (i.e. 0 ohms). I'm unfamiliar with the argument that they start to act like an inductor (which implies that at some point the impedence increases starts to increase with frequency, since an inductor of size L has a complex impedence with magnitude 2*pi*f*L... I guess I don't really buy it, but I have no basis for that.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-08-05T17:39:18.403" CommentCount="3" />
  <row Id="3881" PostTypeId="1" AcceptedAnswerId="3883" CreationDate="2010-08-05T17:41:27.293" Score="6" ViewCount="633" Body="&lt;p&gt;This is an intentionally very open ended question. What does it mean for an antenna to be a 50-ohm antenna at some  frequency? How do you make a 50-ohm antenna for say 433.92MHz? What are the options? What are the consequences of it being different from 50-ohms?&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-11T18:26:30.127" LastActivityDate="2011-01-11T18:26:30.127" Title="What is a 50-ohm antenna? How would you make one?" Tags="&lt;rf&gt;&lt;antenna&gt;" AnswerCount="6" FavoriteCount="2" />
  <row Id="3882" PostTypeId="1" CreationDate="2010-08-05T18:03:23.150" Score="1" ViewCount="160" Body="&lt;p&gt;To measure (a) rpm and (b) whirling of a drive shaft, I have built a sensor with 3 centripetal accelerometers arranged at 120 degrees separation around the circumference of the housing. The maths indicates that rpm can be calculated from: Arpm = (A1 + A2 + A3)/3  and the whirl speed from the maximum value of: Awhirl = A1 + A2(cos120) + A3(cos240). The rpm calculation works perfectly for any shaft inclination between horizontal and vertical. However, the whirl calculation is only correct when the shaft is horizontal. I have had a second opinion on the maths and the whirl calculation should work at any inclination. So, I wonder if there is something that has been missed with regard to the accelerometers, which are Silicon Designs 1210J-005 (capacitative/analog) and respond to dc and ac accelerations.&lt;/p&gt;&#xA;" LastActivityDate="2010-08-07T13:53:53.777" Title="Vibration sensor, using centripetal accelerometers" Tags="&lt;accelerometer&gt;" AnswerCount="2" />
  <row Id="3883" PostTypeId="2" ParentId="3881" CreationDate="2010-08-05T18:22:57.913" Score="3" ViewCount="" Body="&lt;p&gt;Trying to think what 433 is used for off the top of my head :) Is that the weak signals band? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At any rate, most 2-way radios are made to match up to a 50ohm antenna and the matching is left up to you. You can get an antenna that is already tuned, or you can do impedence matching through a number of techniques (see the referenced article below).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a good match, you reduce standing waves. Standing waves build up when the radio sends out a nicely modulated signal but the antenna isn't resonating at that frequency and causes standing waves, which feed right back into the radio and can blow out the final stage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The higher the output power, the more this becomes important. At very low power, say &amp;lt;1watt, the worst you have to worry about is the antenna not resonating and your signal not going anywhere. At higher powers, say 50+ watts, you can damage your transmitter in less than 1 second. Modern radios have built-in SWR detectors that will cut the power if it detects a problem. Those aren't always guaranteed to work though. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.k0bg.com/match.html&quot; rel=&quot;nofollow&quot;&gt;This page lays out a few key things verey nicely&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-08-05T18:22:57.913" CommentCount="4" />
  <row Id="3884" PostTypeId="2" ParentId="3878" CreationDate="2010-08-05T18:24:12.777" Score="3" ViewCount="" Body="&lt;p&gt;I don't know of a definite design flow, but I'll tell you what works for me:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First you obviously have to do general system design.  Write out something that says what you want your widget to do in general and make a block diagram.  This lets you get on to the next step of selecting a processor and choosing parts.  After that it's time to play around with the parts and see how they work (if you've never used them before).  For analog parts I'll stick them on a breadboard and see how they look on a scope - how much bounce is in the switches, how fast do things change, what voltages will be produced, etc.  Then it's a good idea to hook everything up to your microcontroller in some way.  This will tell you 1) whether hooking it up to the microcontroller changes the characteristics of the part.  Then I'll write up some dummy code on the microcontroller to see how it interacts with the part and what kind of data I can expect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For digital parts I prefer to use a logic analyzer/pattern generator or a bus pirate and get the hang of the device first before attempting to interface it to the microcontroller.  This lets you figure out important things like what buad rate to use as well as what sequence of commands are necessary to make it behave the way you want.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For any complicated algorithms or library functions I always create a unit test and test it on my desktop computer before attempting to put it into the microcontroller.  I've created circular buffers, packet finders, DIO functions etc this way and it's a dream.  Write a function's test a little, write the function a little.  Think up new functions and tests as you go.  Add tests from real-world scenarios you've found (ie, junk at the beginning of a bytestream trying to find a packet, misplaced END, etc).  When you're sure that it works well enough compile it into a library and copy the header and library file to the appropriate places for your microcontroller compiler.  I have a makefile that compiles all of my code to libraries for PSOC and AVR and then copies them to the correct folders so I can use them.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Before you start to bring it all together I find it helpful to write out a test plan.  Start with the most optimistic scenario (&quot;I hook everything up and it works immediately.&quot;) and then go into 'what-ifs'.  What if there's no serial communication?  Have test points to probe, use bus pirate to drive the port to see if it's working, place breakpoints in the UART interrupt handlers, etc.  Always keep asking - What if that doesn't work?  How do I test it?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you start to bring it all together.  You know what analog support hardware you'll need to interface everything and you have all of the background code you want to use.  At this point I'll probably make a board for the project (I hate doing detailed work on a breadboard - one wire goes and you've lost a half hour trying to put it back).  Now you can start on your application code.  When doing this I find it helpful to have a fallback mode.  Sometimes you'll make three changes and everything stops working.  It's useful to have an entirely separate main() function that only drives low-level things - ie, is my UART still working?  Does this button work?  Are all my lights hooked up?  So when you change things and everything stops, you can add one #define in your code and change it to hardware test mode to make sure you didn't destroy everything. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just keep developing and eventually you'll be done.  This is the part I've never actually gotten to, so good luck if you do :) &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-08-05T18:24:12.777" />
  <row Id="3885" PostTypeId="2" ParentId="3878" CreationDate="2010-08-05T18:42:32.013" Score="2" ViewCount="" Body="&lt;p&gt;I like to plan out (achievable) milestones from the beginning. Rather than always aiming for the end, you're just working on a few features for the next milestone.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-05T18:42:32.013" />
  <row Id="3886" PostTypeId="2" ParentId="3881" CreationDate="2010-08-05T18:44:48.357" Score="2" ViewCount="" Body="&lt;p&gt;Here's a good app note for making a Bluetooth PCB antenna (2.4Ghz)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.national.com/appinfo/cp3000/files/SBK/Bluetooth_Antenna_Design.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.national.com/appinfo/cp3000/files/SBK/Bluetooth_Antenna_Design.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-05T18:44:48.357" />
  <row Id="3887" PostTypeId="2" ParentId="3879" CreationDate="2010-08-05T18:51:17.857" Score="8" ViewCount="" Body="&lt;p&gt;This effect is due to the effects of parasitic characteristics of the device.  A capacitor has four basic parasitics:&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Equivalent Series Resistance - ESR:&lt;/h3&gt;  &#xA;&#xA;&lt;p&gt;A capacitor is really a capacitor in series with the resistances of its leads, the foil in the dielectric, and other small resistances. This means that the capacitor cannot truly discharge instantly, and also that it will heat up when repeatedly charged and discharged.  This is an important parameter when designing power systems. &lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Leakage current:&lt;/h3&gt;  &#xA;&#xA;&lt;p&gt;The dielectric is not ideal, so you can add a resistance in parallel with your capacitor.  This is important in backup systems, and the leakage current of an electrolytic can be much greater than the current required to maintain RAM on a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Dielectric Absorption - CDA:&lt;/h3&gt;  &#xA;&#xA;&lt;p&gt;This is usually of less interest than the other parameters, especially for electrolytics, for which leakage current overwhelms the effect.  For large ceramics, you can imagine that there is an RC circuit in parallel with the capacitor.  When the capacitor is charged for a long period of time, the imagined capacitor acquires a charge. If the capacitor is rapidly discharged for a brief period and subsequently returned to an open circuit, the parasitic capacitor begins to recharge the main capacitor.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Equivalent Series Inductance - ESL:&lt;/h3&gt;  &#xA;&#xA;&lt;p&gt;By now, you shouldn't be too surprised that, if everything has capacitance as well as nonzero and non-infinite resistance, everything also has parasitic inductance.  Whether these are significant is a function of frequency, which leads us to the topic of impedance.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We represent impedance by the letter Z.  Impedance can be thought of like resistance, just in the frequency domain.  In the same way that a resistance resists the flow of DC current, so does an impedance impede the flow of AC current.  Just as resistance is V/R, if we integrate into the time domain, impedance is V(t)/ I(t).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll either have to do some calculus, or buy the following assertions about the impedance of a component with an applied sinusoidal voltage with a frequency of w:  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Z[resistor] = R&#xA;Z[capacitor] = 1/(jwC) = 1/(sC)&#xA;Z[inductor] = jwL = sL&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Yes, j is the same as i (the imaginary number, the square root of -1), but in electronics, i usually represents current, so we use j.  Also, w is traditionally the Greek letter omega (which looks like w.)  The letter 's' refers to a complex frequency (not sinusoidal).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yuck, right?  But you get the idea - A resistor doesn't change its impedance when you apply an AC signal.  A capacitor has reduced impedance with higher frequency, and it's nearly infinite at DC, which we expect.  An inductor has increased impedance with higher frequency - think of an RF choke that's designed to remove spikes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We can calculate the impedance of two components in series by adding the impedances.  If we have a capacitor in series with an inductor, we have:  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Z = Z_C + Z_L&#xA;Z = 1/jwC + jwL&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;What happens when we increase the frequency?  A long time ago, our component was an electrolytic capacitor, so we'll assume that C is very much greater than L. At first glance, we'd imagine that the ratios wouldn't change.  But, some trivial (Note: This is a relative term) complex algebra shows a different outcome: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Z = 1/jwC + jwL&#xA;Z = 1/jwC + (jwL * jwC)/jwC   // Get a common denominator&#xA;Z = (1 + jwL * jwC)/jwC &#xA;Z = (1 - (w^2)LC)/jwC         // Simplify, j^2 = -1&#xA;Z = (-j * (1 - (w^2)LC))/jwC  // 1/j = j/j*j = j/ -1 = -j (because j^2 = -1) &#xA;//Send  -j through and then factor out the j for our final impedance:&#xA;Z = ((w^2LC - 1) * j)/wC&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Well, that was fun, right?  This is the kind of thing you do once, remember the answer, and then don't worry about it.  What do we know from the last equation?  Consider first the case where w is small, L is small, and C is large.  We have, approximately,&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  (small * small * large - 1)j / (small * large)  &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;which is a negative number (assuming small * small * large &amp;lt; 1, which it is for practical components). This is familiar as &lt;code&gt;Z_C = -j/wC&lt;/code&gt; - It's a capacitor!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How about, second, your case (High-frequency electrolytic) where w is large, L is small, and C is large.  We have, approximately,&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  (large * small * large - 1)j / (small * large)  &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;which is a positive number (assuming large * small * large &gt; 1). This is familiar as &lt;code&gt;Z_L = jwL&lt;/code&gt; - It's an inductor!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What happens if &lt;code&gt;w^2LC = 1&lt;/code&gt;?  Then the impedance is zero!?!? Yes!  This is called the resonant frequency - It's the point at the bottom of the curve you showed in your question.  Why isn't it &lt;em&gt;actually&lt;/em&gt; zero?  Because of ESR. &#xA;&lt;br&gt;&#xA;&lt;br&gt;&#xA;TL,DR: Weird stuff happens when you increase the frequency a lot.  Always follow the manufacturers' datasheets for decoupling your ICs, and get a good textbook or take a class if you need to do high speed stuff. &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-05T19:25:09.860" LastActivityDate="2010-08-05T19:25:09.860" CommentCount="9" />
  <row Id="3888" PostTypeId="2" ParentId="3881" CreationDate="2010-08-05T18:55:52.540" Score="5" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;What does it mean for an antenna to be&#xA;  a 50-ohm antenna at some frequency?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;It means that if you apply 1 V&lt;sub&gt;RMS&lt;/sub&gt; sine wave of that frequency at the end of the antenna, a 1/50 A&lt;sub&gt;RMS&lt;/sub&gt; current will flow in the antenna at that point.  V = IR&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-06T00:26:11.137" LastActivityDate="2010-08-06T00:26:11.137" CommentCount="6" />
  <row Id="3889" PostTypeId="2" ParentId="3879" CreationDate="2010-08-05T19:00:55.403" Score="1" ViewCount="" Body="&lt;p&gt;The key is that these have the form of a roll, which is similar to a coil, i.e. the current flows in circles.&#xA;This causes a relatively high inductance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other capacitors have the form of sheets (ceramic) or of two surfaces on a porous material (tantal, supercaps), so they don't show this effect.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-08-05T19:00:55.403" CommentCount="3" />
  <row Id="3890" PostTypeId="2" ParentId="3881" CreationDate="2010-08-05T20:11:35.110" Score="2" ViewCount="" Body="&lt;p&gt;A 1/4 wave antenna with four 1/4 wave radials at 45 degrees will give something close to 50 ohms impedance.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-05T20:11:35.110" CommentCount="4" />
  <row Id="3891" PostTypeId="2" ParentId="3882" CreationDate="2010-08-05T21:23:07.987" Score="1" ViewCount="" Body="&lt;p&gt;I'm having a hard time visualizing your setup.  The RPM/centripetal acceleration calculation makes sense, but I can't see what you're trying to measure with the second equation.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you're using a 5g sensor, I'm guessing your rotational rate is slow enough that the acceleration due to gravity is going to be a significant error term in your calculations. The RPM equation will average this out, but the second will not (Although I'm not sure what it will do).  Another characteristic of your sensors is that they're limited to 400Hz signals - How fast is your shaft spinning?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you further explain what the maths you're using are supposed to be doing or how they were derived?&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-05T21:23:07.987" CommentCount="1" />
  <row Id="3892" PostTypeId="2" ParentId="3881" CreationDate="2010-08-05T23:55:31.140" Score="2" ViewCount="" Body="&lt;p&gt;When referring to RF equipment you have to deal with 'characteristic impedance', which is a property of antennas, feed lines, and even transmitter output stages. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The important thing is to make sure that impedances are matched up all the way from the equipment to the antenna. This is more important for transmitters, since more power is involved, but doesn't hurt for receivers either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing you don't want to do is just wire together two items with different impedances. There are RF transformers of various kinds can be used to match up sections that otherwise would be mismatched. Any abrupt change in impedance causes RF energy encountering the mismatch to partially reflect, sort of like what happens when light strikes a piece of glass. When one end of the system is a 100W transmitter, this can result in significant energy being reflected back to the tranmitter's output stage. Basically, it's just inefficient, since the reflected energy just becomes waste heat in the transmitter, and the output from the antenna is diminished. The measure of how much reflection is going on is referred to as the standing wave ratio, often abbreviated SWR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not all RF systems are 50 ohms. There are kinds of coax (e.g. RG-59) that are 75 ohms, and 300 ohm twin lead that are not uncommon.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-08-05T23:55:31.140" />
  <row Id="3893" PostTypeId="1" CreationDate="2010-08-06T01:20:56.137" Score="7" ViewCount="214" Body="&lt;p&gt;My bench is overflowing with stuff ... I have several racks of little drawers, and another bench that has heaps of stuff on it. My label maker works hard. And yet, stuff gets temporarily lost all the time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you keep track of all your parts?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have any ideas on how to keep track of your inventory, please share. This is driving me nuts and spending money to solve the problem is certainly on the table. My latest idea is to have everything ordered by supplier part number, and use a database to look them up. Any better ideas? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(My goal is to optimize findability, not (say) everything being reachable - walking around and collecting stuff is OK).&lt;/p&gt;&#xA;" OwnerUserId="1402" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-16T17:12:40.960" LastActivityDate="2011-05-16T17:12:40.960" Title="Inventory tracking ideas" Tags="&lt;storage&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="3894" PostTypeId="2" ParentId="3893" CreationDate="2010-08-06T01:40:49.103" Score="5" ViewCount="" Body="&lt;p&gt;Hello Dirk&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had exactly the same problem. In the end I gave in to my warehousing instinct and assigned each physical drawer, box, etc a location code. For example, I have ten of those 20-compartment boxes, so they are referenced as 1.1, 10.6 (e.g. box 10, compartment 6). Then everything went into a spreadsheet with tabs for different categories (capacitors, LEDs, relays etc). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each item has a column with part number, type, value, max voltage, RoHS, quantity in stock, min quantity for reorder, etc., plus preferred supplier part number etc. &#xA;Then I can just use 'find' on the spreadsheet to look something up, or run a simple procedure to check for things to reorder. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only thing that isn't given a location is resistors, but each value is in a separate zip-lock bag, in numerical order over three shoe boxes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One day I will port the lot in Access, but couldn't be bothered at this stage. :)&lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-08-06T02:25:17.140" LastActivityDate="2010-08-06T02:25:17.140" CommentCount="1" />
  <row Id="3895" PostTypeId="1" AcceptedAnswerId="3898" CreationDate="2010-08-06T08:46:44.313" Score="1" ViewCount="213" Body="&lt;p&gt;I'm controlling an IGBT inverter with a DSP. I'm pretty sure I turned on two IGBT's at the same time which made a short circuit. The PCB I'm using to step up the PWM signal to drive the IGBT's let the smoke out and I'm trying to figure what my problem is. If the IGBT did get turned on to cause a short then is it possible that the currents going into the IGBT driver got massive? Thanks&lt;/p&gt;&#xA;" OwnerUserId="927" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-08-06T15:27:49.880" LastActivityDate="2010-08-06T15:27:49.880" Title="Was this a high IGBT gate current?" Tags="&lt;inverter&gt;&lt;pwm&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="3896" PostTypeId="2" ParentId="3893" CreationDate="2010-08-06T12:20:07.487" Score="4" ViewCount="" Body="&lt;p&gt;I use a database (Postgres).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wouldn't use the supplier part number. If you change suppliers you will need to&#xA;change your tables. You could use manufacturer/manufacturer part number. If you&#xA;decide to expand your application to do ordering you can create a table &#xA;that maps manufacturer/manufacturer_part_number to supplier/supplier_part_number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Recently I have added an internal part numbering system so that parts with identical&#xA;form/function can be mapped to multiple manufacturer/manufacturer_part_number records.&#xA;For example RES-1K00-0W125 (1K 1/8W resistor) can map to parts made by Xicon, Yageo,&#xA;Stackpole, etc. This is a lot more work to setup but is not difficult to maintain.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:48:14.667" LastActivityDate="2011-05-16T10:48:14.667" CommentCount="2" />
  <row Id="3897" PostTypeId="2" ParentId="3881" CreationDate="2010-08-06T14:19:41.450" Score="4" ViewCount="" Body="&lt;p&gt;A great tutorial: &lt;a href=&quot;http://colinkarpfinger.com/blog/2010/the-%20dropouts-guide-to-antenna-design/&quot; rel=&quot;nofollow&quot;&gt;The Dropout’s Guide to PCB Trace Antenna Design&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-08-06T14:19:41.450" />
  <row Id="3898" PostTypeId="2" ParentId="3895" CreationDate="2010-08-06T15:27:17.663" Score="2" ViewCount="" Body="&lt;p&gt;When you are designing inverters with IGBTs there are a few key things to worry about. You already discovered the big one, which is the timing of the high side and low side IGBTs on the same output leg. If you turn them on at the same time, or turn one on while the other is still in the process of turning off, you get a very high current through the two of them. This is called &quot;shoot-through&quot; and is definitely something you want to avoid.  Remember that IGBTs have resistance measured in tenths of Ohms and your capacitor bank and the traces/wires between it and the IGBTs will be very low impedance by design... That's a lot of energy with an ideal short-circuit path.  On a 208V inverter design you might have a 340V bus and a half an ohm IGBT on-resistance ... you get the idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using a DSP with any kind of motor control enhancements, there will be a few extra settings to play with on the PWM peripheral. You'll see options for tuning how much dead time there is between PWM outputs, tuning the delay before and after the midpoint of the PWM pulse, and there may also be additional inputs to detect things like de-sat or excessive current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my own inverter designs I tended to put the de-sat detection in hardware, as my almost two decades of experience has taught me not to trust software. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another very critical thing, and one that is not quite as critical anymore with the more advanced PWM controllers, is that the high-side driver and the low-side driver must be balanced.  If it takes 500us for a gate fire signal to propagate to the IGBT on the high side, you must add additional delay to the low side (the low side driver is generally a simpler and thus faster circuit). As I said, high-end PWM controllers allow fine-grained control over each PWM output and can unbalance the firing so the hardware side is simpler, but being the old fart that I am, I still think it's good design to have the timing on both sides matched.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When testing, I strongly suggest some kind of fast fusing and even reduced current on the bench. IGBTs can be damned expensive, the magic smoke they let out isn't good for your lungs and the noise they make isn't good for your ears.  Wear proper protection equipment and always be fully aware of the lighting that lurketh in a fully charged capacitor bank. Inverter design mandates that you minimize impedance, which just makes the accidents all that more spectacular and dangerous.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-08-06T15:27:17.663" />
  <row Id="3899" PostTypeId="1" CreationDate="2010-08-06T16:07:48.800" Score="2" ViewCount="431" Body="&lt;p&gt;Hello everyone,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been trying to use my arduino as a thermal anemometer based on the excellent and tiny IST FS5 &quot;thermal mass flow sensor&quot; - there is more information and a datasheet here - &lt;a href=&quot;http://uk.farnell.com/ist/fs5-0-1l-195/sensor-flow-gas/dp/1778049&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/ist/fs5-0-1l-195/sensor-flow-gas/dp/1778049&lt;/a&gt;. I've set up the circuit as recommended in the data sheet, albeit using a different op-amp and transistor (and excluding the calibration resistor) and it seems to work nicely. The only problem is the output is between 5 and 10V, and obviously the arduino likes something in the 0 - 5V range. I've used a simple voltage divider to scale the voltage between 2.5 and 5V, but it would be nice to use the full range... unfortunately my electronics knowledge is far too limited for this! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've read some similar forum posts and tried to use a 5V voltage regulator and another opamp to produce something useful but failed miserably! I'd really appreciate it if anyone could give me some hints on how to use an op-amp to achieve this. I feel like it also must be possible to change the wheatstone bridge arrangment so as to produce this voltage range in the first place, but have no idea how!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks all!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;schematic here - &lt;a href=&quot;http://dl.dropbox.com/u/7549930/aaSchematic1.png&quot; rel=&quot;nofollow&quot;&gt;http://dl.dropbox.com/u/7549930/aaSchematic1.png&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;snap here - &lt;a href=&quot;http://dl.dropbox.com/u/7549930/arduino_anemometer.JPG&quot; rel=&quot;nofollow&quot;&gt;http://dl.dropbox.com/u/7549930/arduino_anemometer.JPG&lt;/a&gt;&lt;/p&gt;&#xA;" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T23:40:49.070" LastActivityDate="2010-08-17T23:40:49.070" Title="arduino thermal anemometer" Tags="&lt;arduino&gt;&lt;output&gt;&lt;scaling&gt;" AnswerCount="3" />
  <row Id="3900" PostTypeId="1" CreationDate="2010-08-06T18:44:21.077" Score="8" ViewCount="299" Body="&lt;p&gt;I've read &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0750682922&quot; rel=&quot;nofollow&quot;&gt;Programming 16-Bit PIC Microcontrollers in C&lt;/a&gt;, and there is this affirmation in the book:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;During the development and debugging&#xA;  phases of a project, though, it is&#xA;  always good practice to disable all&#xA;  optimizations as they might modify the&#xA;  structure of the code being analyzed&#xA;  and render single-stepping and&#xA;  breakpoint placement problematic.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I confess I was a little confused. I didn't understand if the author said that because of the &lt;a href=&quot;http://www.microchip.com/c30/&quot; rel=&quot;nofollow&quot;&gt;C30&lt;/a&gt; evaluation period or if it's really a good practice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to know if you actually use this practice, and why?&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-07T17:15:52.147" LastActivityDate="2011-05-07T17:15:52.147" Title="Is it really a good-practice disable optimizations during the development and debugging phases?" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;books&gt;&lt;best-practice&gt;&lt;optimization&gt;" AnswerCount="9" FavoriteCount="1" />
  <row Id="3901" PostTypeId="2" ParentId="3900" CreationDate="2010-08-06T19:10:53.760" Score="11" ViewCount="" Body="&lt;p&gt;This is pretty standard in software engineering as a whole - when you optimize code, the compiler is allowed to re-arrange things pretty much however it wants, as long as you can't tell any difference in operation. So, for instance, if you initialize a variable inside every iteration of a loop, and never change the variable inside the loop, the optimizer is allowed to move that initialization out of the loop, so that you're not wasting time with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It might also realize that you compute a number which you then don't do anything with before over-writing. In that case, it might eliminate the useless computation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem with optimization is that you'll want to put a breakpoint on some piece of code, which the optimizer has moved or eliminated. In that case, the debugger can't do what you want (generally, it will put the breakpoint somewhere close). So, to make the generated code more closely resemble what you wrote, you turn off optimizations during debug - this insures that the code you want to break on is really there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to be careful with this, however, as depending on your code, optimization can break things! In general code that is broken by a correctly functioning optimizer is really just buggy code that's getting away with something, so you usually want to figure out why the optimizer breaks it.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2010-08-06T19:10:53.760" CommentCount="7" />
  <row Id="3902" PostTypeId="2" ParentId="3900" CreationDate="2010-08-06T19:22:10.237" Score="3" ViewCount="" Body="&lt;p&gt;Depends, and this is generally true of all tools not just C30.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Optimizations often remove and/or restructure the code in various ways.  Your switch statement may get reimplemented with a if/else construct or in some cases may be removed all together.  y = x * 16 may get replaced with a series of left shifts, etc.  although this last type of optimization can usually still be stepped through, its mostly the restructuring of control statement that gets ya.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This can make it impossible to step a debugger through your C code because the structures you defined in C no longer exists, they were replaced or re-ordered by the compiler into something the compiler believes will be faster or use less space.  It can also make breakpoints impossible to set from the C listing since the instruction your breaking on may no longer exist.  For example you may try to set a breakpoint inside an if statement, but the compiler may have removed that if.  You may try to set a breakpoint inside a while or for loop but the compiler decided to unroll that loop so it no longer exists.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For this reason if you can debug with optimizations off, its usually easier.  You should always retest with optimizations on.  This is about the only way you'll find out that you missed an important &lt;code&gt;volatile&lt;/code&gt; and its causing intermittent failures (or some other weirdness).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of embedded development, you have to be careful with optimizations anyway.  Specifically in sections of code that are timing critical, some interrupts for instance.  In these cases you should either code the critical bits in assembly or use compiler directives to make sure these sections are not optimized so you know they have a fixed execution time or a fixed worst case run time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other gotcha can be fitting code into the uC, you may need code density optimizations to simply fit your code into the chip.  This is one reason why its usually a good idea to start with the largest ROM capacity uC in a family and only choose a smaller one for manufacturing, after your code is locked.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-08-06T19:22:10.237" />
  <row Id="3903" PostTypeId="2" ParentId="3899" CreationDate="2010-08-06T19:41:48.873" Score="0" ViewCount="" Body="&lt;p&gt;You could float the grounds between the two. Basically you set the arduino ground to match the minimum output of the sensor (in this case 5V). I'm not sure how reliable the 5V out from the sensor is though. If there's any chance of it dropping below 5V, you want to avoid this method because you could end up sourcing current from the arduino input back to the sensor and damaging it. If you can handle the 2x lower resolution from the scaling, I'd say stick with what you have. That really depends on how accurate the sensor is in the first place though and the resolution of the input to the arduino (not great if I remember correctly).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need more resolution you can put the sensor into an A/D and then isolate it from the arduino (using an optocoupler or something similar) and then do what I said above, measuring at the 5V common mode voltage. Now the arduino would be able to read back (talking SPI, I2C or similar) the full range at a higher precision than if you just put it right into the arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-08-06T19:41:48.873" />
  <row Id="3904" PostTypeId="2" ParentId="3900" CreationDate="2010-08-06T20:18:45.977" Score="4" ViewCount="" Body="&lt;p&gt;Generally, I would debug with whatever settings I planned to release with.  If I was going to release optimized code, I would debug with optimized code.  If I was going to release unoptimized code, I would debug with unoptimized code.  I do this for two reasons.  First, optimizers can make significant enough timing differences to cause the end product to behave differently than unoptimized code.  Second, even though most are pretty good, compiler vendors do make mistakes and optimized code can produce different results from unoptimized code.  As a result, I like to get as much test time as possible with whatever setting I plan to release with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, optimizers can make debugging difficult as noted in the previous answers.  If I find a particular section of code that is hard to debug, I will temporarily turn the optimizer off, do the debugging to get the code working, then turn the optimizer back on and test once more.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-08-06T20:18:45.977" CommentCount="1" />
  <row Id="3905" PostTypeId="2" ParentId="3900" CreationDate="2010-08-06T20:51:21.847" Score="1" ViewCount="" Body="&lt;p&gt;If you are using the debugger then I would disable optimizations and enable debug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally I find that the PIC debugger causes more problems than it helps me fix.&lt;br&gt;&#xA;I just use printf() to USART to debug my programs written in C18.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-08-06T20:51:21.847" />
  <row Id="3906" PostTypeId="2" ParentId="3899" CreationDate="2010-08-06T21:06:42.757" Score="1" ViewCount="" Body="&lt;p&gt;You can use a &lt;a href=&quot;http://en.wikipedia.org/wiki/Operational_amplifier_applications#Differential_amplifier&quot; rel=&quot;nofollow&quot;&gt;differential amplifier&lt;/a&gt; with the negative input V&lt;sub&gt;1&lt;/sub&gt; connected to a fixed voltage (12V or 5V) and V&lt;sub&gt;2&lt;/sub&gt; connected to the output of the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For this to work you need an opamp that can go rail-to-rail (not a 741).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I were you I'd stick with the voltage divider, though, unless there's a definite need for the extra bit of precision.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-08-06T21:06:42.757" CommentCount="1" />
  <row Id="3907" PostTypeId="2" ParentId="354" CreationDate="2010-08-06T21:38:36.500" Score="0" ViewCount="" Body="&lt;p&gt;I Would assume you would have to seal a 4 clear plastic wheels onto your tires with click ties and silicone or just hot glue (I do not know if it would hold on very well to the metal however)&lt;/p&gt;&#xA;" LastActivityDate="2010-08-06T21:38:36.500" />
  <row Id="3908" PostTypeId="2" ParentId="354" CreationDate="2010-08-06T22:32:40.063" Score="0" ViewCount="" Body="&lt;p&gt;There are a few different answers for different variations on this question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Q: Will they survive a rain shower if they're outside and off while I'm inside at school or work?&lt;br&gt;&#xA;A: Sure! Nothing on the PCB isn't waterproof, with the exception (possibly) of the switch, and switches which are sealed are available. Make sure the battery cases don't hold water.  It would probably be best to replace the switch with a jumper in this case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Q: Will they survive a hit from passing a sprinkler while powered on? What about saltwater, which is conductive?&lt;br&gt;&#xA;A: This probably won't cause lasting electrical damage.  I doubt that they'll continue to work while this is happening, but the low voltages everywhere mean that nothing is going to be arcing too badly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Q: I like to ride on the beach, sometimes in the ocean.  I do it every day.  My bike frame crumbles in my hands, but I'm OK with it.  Will my SpokePOV be damaged by this use?&lt;br&gt;&#xA;A: Um, yes.  Components on the PCB will corrode, like other metal objects, when exposed to water. If this is the case, or you'll be riding in the rain often, consider applying a clear conformal coating to your board.  They're available both as aerosol sprays and in pens.  Make sure that you pick a clear one, or your LEDs will be dim!  You might also test a polyurethane clear coat, typically used in wood finishing, if you don't want to order conformal coat.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-06T22:32:40.063" />
  <row Id="3909" PostTypeId="2" ParentId="3900" CreationDate="2010-08-07T03:06:20.010" Score="1" ViewCount="" Body="&lt;p&gt;Use whatever form you are going to release with, debuggers and compiling for debugging hide a lot (A LOT) of bugs that you dont see until you compile for release.  By then it is much harder to find those bugs, vs debugging as you go.  20 something years now and I never had a use for a gdb or other like debugger, no need to watch variables or single step.  Hundreds to thousands of lines per day.  So it is possible, dont be lead to think otherwise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compiling for debug then later compiling for release can and will take twice to more than twice the effort.  If you get into a bind and have to use a tool like a debugger then compile for the debugger to work through the specific problem, then revert back to normal operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other problems are also true like the optimizer makes the code faster so for embedded in particular your timing changes with compiler options and that can affect the functionality of your program, here again use the deliverable compiling choice during the whole phase.   Compilers are programs too and have bugs and optimizers make mistakes and some dont have any faith in that.  If that is the case there is nothing wrong with it compile without optimisation, just do it that way all the time.  The path I prefer is to compile for optimization then if I suspect a compiler problem disable the optimization if that fixes it usually go back and forth sometimes examining the assembler output to figure out why.  &lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-08-07T03:06:20.010" />
  <row Id="3910" PostTypeId="2" ParentId="3900" CreationDate="2010-08-07T03:27:12.627" Score="1" ViewCount="" Body="&lt;p&gt;I always develop code with -O0 (gcc option to turn optimization off). When I feel I'm at the point where I want to start letting things head more toward a release, I will start with -Os (optimize for size) as generally the more code you can keep in cache the better it'll be, even if it's not super-duper optimized.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I find that gdb works far better with -O0 code, and it's a lot easier to follow if you have to step into the assembly. Toggling between -O0 and -Os also lets you see what the compiler's doing to your code. It's quite an interesting education at times, and can also uncover compiler bugs... those nasty things that make you pull your hair out trying to figure out what's wrong with your code!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I really need to, I'll start adding in -fdata-sections and -fcode-sections with --gc-sections, which allow the linker to remove entire functions and data segments that aren't actually used. There are a lot of little things you can tinker with to try to shrink things down further or make things faster, but by and large these are the only tricks I end up using, and anything that has to be smaller or faster I'll hand-assemble.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-08-07T03:27:12.627" />
  <row Id="3911" PostTypeId="1" AcceptedAnswerId="3919" CreationDate="2010-08-07T06:43:08.440" Score="3" ViewCount="323" Body="&lt;p&gt;I'm trying to find a local (nyc) electrical engineer, or electrical engineering company to help me make a small device that involves cell phones and bluetooth - at least I think it will involve bluetooth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are simple:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any sites devoted to contract jobs for electrical engineers?&#xA;How can I find small local EE companies that might be able to help me?&#xA;How can I best judge the quality of an EE?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!  &lt;/p&gt;&#xA;" OwnerUserId="1044" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-08-07T15:35:23.107" LastActivityDate="2011-01-14T11:31:25.837" Title="How can I find a good (local) electrical engineer" Tags="&lt;hire&gt;" AnswerCount="7" CommentCount="3" FavoriteCount="2" />
  <row Id="3912" PostTypeId="2" ParentId="3911" CreationDate="2010-08-07T08:06:03.193" Score="3" ViewCount="" Body="&lt;p&gt;All of these questions are hard, actually.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as judging the quality of an EE when you're not an EE: You will have to be able to communicate well throughout the project, so even if you don't speak that much Electrish, you should try to ask questions in their language. The other way round, EEs who talk so much Electrish that it sounds like they know all and you are dumb, well, they may be bright, but they will not solve your problem. You will have to spend some hours in your first meeting and if you don't even get the least idea about what tricks they are going to use to get your requirements running, you should not sign any contracts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some side-notes: I'm not from NYC and I don't know about an online list, but for jobs as special as this one, It may be the case that no yellow pages (or the like) are available, no matter if you're from Europe or from NYC. My company often arranges contracts with smaller companies for R&amp;amp;D tasks, and it really is very difficult to find good partners. Often, the less shiny and power-pointy ones are the good ones. Once you found a shop who looks like they might be able to help, prepare some good questions concerning your project and try to ask like you're the employer in a job interview without being impolite.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good contract developers are real treasures. Word of mouth might be the only source towards finding them.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-08-07T08:06:03.193" />
  <row Id="3913" PostTypeId="2" ParentId="3911" CreationDate="2010-08-07T12:22:36.007" Score="0" ViewCount="" Body="&lt;p&gt;&quot;Horses for courses&quot;........Different EEs are better for different types of jobs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It all depends on the project in question I suppose....For instance I do commission based work for people that have there own in-house EEs - because I have a different skill set that centers around EEing for audio and sound.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also Zebonaut's point about communication is really important - You need to be able to communicate your ideas well, so it helps if you see eye-to-eye with your EE.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-08-07T12:22:36.007" />
  <row Id="3914" PostTypeId="2" ParentId="3899" CreationDate="2010-08-07T13:09:46.153" Score="0" ViewCount="" Body="&lt;p&gt;Thanks to Chris, starblue and reemrevnivek for your help! And to Tim Williams at the arduino forum. The differential amplifier works nicely, I used an LT1635 that was hanging about with a 7805 as my voltage reference (not sure how accurate / stable this is...). If you're interested in building this circuit you can see the schematic here: &lt;a href=&quot;http://dl.dropbox.com/u/7549930/aaSchematic2-diffAmp.png&quot; rel=&quot;nofollow&quot;&gt;http://dl.dropbox.com/u/7549930/aaSchematic2-diffAmp.png&lt;/a&gt;. I'll also post the calibration data on the arduino playground in the next few weeks should anyone be interested.&lt;/p&gt;&#xA;" LastActivityDate="2010-08-07T13:09:46.153" />
  <row Id="3916" PostTypeId="2" ParentId="3882" CreationDate="2010-08-07T13:53:53.777" Score="0" ViewCount="" Body="&lt;p&gt;Insufficient space in &quot;comments&quot;, so sent as an answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The shaft is rotating (to the right, say) along its longitudinal axis and remains undeflected until it reaches a critical speed (natural harmonic), at which the centre of the shaft deflects away from the original position of the longitudinal axis and orbits to the left, taking on the appearance of a standing wave. This form of lateral vibration is backward whirl, in which condition the accelerometers (located around the shaft circumference at the point of maximum deflection) experience simultaneously the centripetal force from the underlying forward rotation and the centripetal force from the backward orbit. The first equation averages out all external forces (including both whirl &amp;amp; gravity) and gives rpm. The second equation produces a periodic function, the recurring maximum value of which gives the speed of the backward whirl. Unfortunately the second equation only seems to work when the shaft is horizontal. Whether this is due to some assumption in the mathematical derivation or to misapplication of the accelerometers, I do not know. Shaft rotation speed is variable between 50 rpm and 250 rpm and backward whirl speed also lies between these rpm limits. The accelerometers are on a pitch circle radius of 94.15mm. The accelerometers are dc-coupled.&lt;/p&gt;&#xA;" LastActivityDate="2010-08-07T13:53:53.777" CommentCount="2" />
  <row Id="3919" PostTypeId="2" ParentId="3911" CreationDate="2010-08-07T14:50:15.897" Score="5" ViewCount="" Body="&lt;p&gt;I don't know of a good site devoted to contract jobs for EEs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might try talking to folks at &lt;a href=&quot;http://www.nycresistor.com/&quot; rel=&quot;nofollow&quot;&gt;NYC Resistor&lt;/a&gt;. They're a hacker collective, not an EE company, but they're in Brooklyn and might know local EEs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also ask in the &lt;a href=&quot;http://forums.adafruit.com/&quot; rel=&quot;nofollow&quot;&gt;Adafruit forums&lt;/a&gt;. Adafruit is based in New York. While the customers are from all over the place, you might find more New Yorkers than here. (Chiphacker seems to have a lot of folks from Australia and the UK.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are a few examples of folks who could probably do the job (but they're in California): &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://mindtribe.com&quot; rel=&quot;nofollow&quot;&gt;mindtribe.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://219design.com&quot; rel=&quot;nofollow&quot;&gt;219design.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://219design.com&quot; rel=&quot;nofollow&quot;&gt;speckdesign.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://d2m-inc.com&quot; rel=&quot;nofollow&quot;&gt;d2m-inc.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You might also want to think about whether you have the resources to hire an electrical engineer to work for you. Very few individuals do. The going rate for consulting engineers in New York is probably above $100/hour, and developing a real product takes at least hundreds of hours.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-08-07T15:07:47.623" LastActivityDate="2010-08-07T15:07:47.623" CommentCount="2" />
  <row Id="3925" PostTypeId="1" AcceptedAnswerId="3933" CreationDate="2010-08-07T18:49:03.480" Score="3" ViewCount="233" Body="&lt;p&gt;My parents have a cottage which is approximately 1 1/2 hours away from our home.  We're currently in the middle of a major renovation/addition - All of the old wiring (From the 1960s!) has been torn out, and we are preparing the new wiring for inspection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We're in a good neighborhood, but it would be nice to have some remote surveillance of the place.  Our primary adversary is the squirrels that try to stash their pine cones inside.  It would also be good to be able to turn on/off lights around the house occasionally to make the place look occupied (and to scare the squirrels out!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, while we'll keep it at a minimum of, say, 50 deg F (10 deg C) to keep the pipes from freezing if we're gone for just a week or so, we'll drain the pipes and let it get down to the 10 deg F that it gets up here to save on heating bills if we're gone for an extended period.  This means that it's COLD when we come up, and, while the furnace and woodstove will make the air 80 deg F in an hour if we want them to, your tongue will still stick to your spoon if you lick it, and don't even ask about using the bathroom.  A way to ramp the temperature a few hours before we leave would be great. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as remote connectivity, there's not a lot to work with.  We don't want a lot of distraction up here, so we don't get an internet connection.  A number of the neighbors are happy to let us walk over with a laptop and use theirs if we like, and I suppose that a specialized antenna could pull in a signal, but I'd rather not design a system around a borrowed network.  We get decent cell service on a few networks, so we don't have a phone line, so it looks like GSM/GPRS will be the way to go.  I've never worked with cellular networking, but I understand that this requires a SIM card, and I'm not willing to give up my phone. What is the cheapest route here?&#xA;&lt;br&gt;&#xA;&lt;br&gt;&#xA;&lt;br&gt;&#xA;I have my own ideas about how to implement this, but I'm looking for a little brainstorming session. It's going to take a little work to answer.  In summary, my questions are as follows (In order of priority) :&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What are my options for a low-cost remote connection without using the Internet on the system end?  How much will it cost me to use a cellular network?&lt;/li&gt;&#xA;&lt;li&gt;How can I control home lighting with an embedded system? &lt;a href=&quot;http://www.wikipatents.com/US-Patent-6861931/portable-remote-control-circuit-breaker-system&quot; rel=&quot;nofollow&quot;&gt;This patent&lt;/a&gt; is amusing, but not how I'd like to do it.  A system which is transparent to a user with no knowledge of its existence (outside of discovering a module in a switch box) is a must - The switches will be off when we leave. &lt;/li&gt;&#xA;&lt;li&gt;What solutions will pass or fail an electrical inspection?&lt;/li&gt;&#xA;&lt;li&gt;How can I interface with/emulate a thermostat?  I wouldn't mind replacing the original model completely. &lt;/li&gt;&#xA;&lt;li&gt;What kind of security information can be transmitted over a GSM network with low cost?  I'm planning on reed switches in the doors and windows, but any kind of live audio/imaging/video feed seems to be overkill.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;PS For reference, I'd like to use an ARM-Cortex M3 as the main brain, but I'm open to Arduino or AVR implementations as well.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-08-07T18:54:58.523" LastActivityDate="2011-03-02T23:17:31.377" Title="Remote access to Cottage: Surveillance, Heater, Lighting" Tags="&lt;network-interface&gt;&lt;remote&gt;&lt;heating&gt;&lt;light&gt;&lt;monitor&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="2" />
  <row Id="3926" PostTypeId="2" ParentId="3893" CreationDate="2010-08-07T18:49:50.437" Score="4" ViewCount="" Body="&lt;p&gt;I hated having search for datasheets over and over, so I threw together &lt;a href=&quot;http://eparts.jdrnetworking.com/&quot; rel=&quot;nofollow&quot;&gt;a little web app&lt;/a&gt; that keeps track of my inventory and datasheets. ('guest@mailinator.com' and 'guest' if anyone wants to play around with it - be nice).  It's basically a database with a front end so I can get to it from anywhere.  For physical parts storage, I keep most of my SMD stuff in 4 1/4 x 2 1/2 envelopes in plastic bins.  The envelopes are cheap enough that I can use one for each value of small part, and big enough to hold most of my SMD stuff.  Through-hole parts are still in little plastic divided containers, but that's only because I haven't moved them to envelopes yet.&lt;/p&gt;&#xA;" OwnerUserId="836" LastActivityDate="2010-08-07T18:49:50.437" />
  <row Id="3927" PostTypeId="2" ParentId="3925" CreationDate="2010-08-07T19:00:47.673" Score="0" ViewCount="" Body="&lt;p&gt;One option would be to &lt;a href=&quot;http://www.alertme.com/products/home-monitoring&quot; rel=&quot;nofollow&quot;&gt;buy a solution&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I admit, buying isn't very Chiphackery...&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-08-09T20:15:08.240" LastActivityDate="2010-08-09T20:15:08.240" CommentCount="2" />
  <row Id="3928" PostTypeId="2" ParentId="3911" CreationDate="2010-08-07T19:04:32.997" Score="1" ViewCount="" Body="&lt;p&gt;I'm a good (I hope) electrical engineer local to NYC, but that doesn't mean I know anything about Bluetooth.  When judging the quality of the engineer, you need to ask questions related specifically to what you want them to do.  There are lots of different sub-fields, and they can be highly specialized.  Do you want them to develop Bluetooth hardware, or just interface pre-existing Bluetooth hardware to something else?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might just want to try Craigslist (&lt;a href=&quot;http://newyork.craigslist.org/egr/&quot; rel=&quot;nofollow&quot;&gt;Arch / Engineering&lt;/a&gt;).  I think you have to pay to put a job ad on there, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also there are &lt;a href=&quot;http://www.vworker.com/RentACoder/misc/BidRequests/ShowBidRequests.asp?lngBidRequestListType=3&amp;amp;txtMaxNumberOfEntriesPerPage=10&amp;amp;lngBidRequestCategoryId=83&amp;amp;optSortTitle=2&amp;amp;optBidRequestPhase=2&amp;amp;lngSortColumn=-6&amp;amp;blnModeVerbose=True&amp;amp;optBiddingExpiration=1&quot; rel=&quot;nofollow&quot;&gt;hardware sections&lt;/a&gt; on sites like rentacoder (now called vworker?), which seems appropriate for a single small project.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.geekpoint.net/internet-marketing/5886-70-alternatives-rentacoder.html&quot; rel=&quot;nofollow&quot;&gt;70 alternatives to rentacoder.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-08-07T19:04:32.997" />
  <row Id="3929" PostTypeId="2" ParentId="3863" CreationDate="2010-08-07T19:22:47.180" Score="0" ViewCount="" Body="&lt;p&gt;Thanks,&#xA; I reviewed the links and i think we can do it without.  There is a speedo on the market that in order to calibrate you drive on the highway and hit a calibrate button once for 2 mile markers.  this will count how many pulses are in a mile and then we can calculate the speed based on those numbers and use speed buddy's to confirm.  Now all i need is some simple transistor and resistor selection and implementation done and i am ready to order.&lt;br&gt;&#xA;  I want to also have hi voltage turn indicators using neon bulbs so i figured i would use 2 resistors the split the turn lamp voltage and then put that through a transistor.  I have a bunch of mpsa42 transistors i think will work.&#xA;Thanks&#xA;Ed&lt;/p&gt;&#xA;" LastActivityDate="2010-08-07T19:22:47.180" />
  <row Id="3930" PostTypeId="1" CreationDate="2010-08-07T20:58:20.397" Score="2" ViewCount="219" Body="&lt;p&gt;I have a U.S./NTSC LCD HDTV that has a yellow RCA monitor jack on the back.  Would it be possible to monitor this connector on an analog input of a microcontroller to determine when the TV is on or off?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, I don't have scope that will let me look at the signal from the RCA jack.  I think my microcontroller's analog port typically measures from 0 to 5V.  Would I need a scaling circuit, resistor, diode, or something other than just hooking a wire directly to the analog input?  (Yes, I'm fairly inexperienced on the hardware side, thanks!) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What danger do I pose to the TV?&lt;/p&gt;&#xA;" OwnerUserId="971" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-06T16:52:20.407" LastActivityDate="2011-03-06T16:52:20.407" Title="How to determine if TV is on by looking at yellow RCA monitor signal?" Tags="&lt;microcontroller&gt;&lt;ntsc&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="3931" PostTypeId="2" ParentId="3930" CreationDate="2010-08-07T21:37:06.557" Score="2" ViewCount="" Body="&lt;p&gt;First, I'll answer your question about danger to your TV: As long as you connect only high impedance test leads, you pose very little danger to your TV or anything else you want to measure.  This kind of input can be found on a DMM, an oscilloscope, or an analog input pin on an IC - as long as you do not exceed the maximum voltage of the part.  For the Arduino, this means you must be between -0.7 and 5.7V, to avoid turning on the diodes internal to your microcontroller.  As soon as you add discrete components between two digital transceivers, though, you risk a lot.&lt;br&gt;&#xA;Also, make sure that your grounds are the same.  0V according to the TV might be much higher than 0V according to your earth-grounded PC.  Test this with a DMM beforehand, measuring between the shield of a USB cable to the shield of the RCA connector.  Put a 100k  resistor between the two shields.  Anything more than a couple volts on this measurement, and you've got trouble.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To answer your first question, though, the output of an NTSC signal in the US is 1V - source &lt;a href=&quot;http://www.tek.com/Measurement/App_Notes/25_7049/eng/section2.pdf&quot; rel=&quot;nofollow&quot;&gt;this appnote&lt;/a&gt; from &lt;a href=&quot;http://www.tek.com/Measurement/App_Notes/25_7049/eng/&quot; rel=&quot;nofollow&quot;&gt;this page about measuring video signals&lt;/a&gt; by Tektronix.   You'll see frequent references to units of &lt;a href=&quot;http://en.wikipedia.org/wiki/IRE_%28unit%29&quot; rel=&quot;nofollow&quot;&gt;IRE&lt;/a&gt;, which is a unit for measuring composite video signals that (Unlike voltage) is consistent between various formats and countries.  100 IRE is the difference between white and black.  An NTSC signal will never exceed 140 IRE, which is 1V, so 1 IRE is approximately 7mV &lt;em&gt;for your signal&lt;/em&gt;.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If don't trust this random stranger on the Internet (backed by Tektronix, but how credible are they?),  you can connect your DMM instead of your Arduino, which should read the RMS (Root mean squared) value of what it supposes to be a DC input signal, and should be quite safe up to higher voltages than you want to get near enough to measure (600V?).  The AC amplitude likely won't work, as it's optimized for 60Hz household wiring, but check your manual. &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-07T21:37:06.557" CommentCount="6" />
  <row Id="3932" PostTypeId="2" ParentId="3930" CreationDate="2010-08-07T21:38:49.570" Score="1" ViewCount="" Body="&lt;p&gt;Usually TVs are pretty good about protecting outputs like these. Manufactures know that people will accidentally short them and/or hook them up wrong. I would just be sure to not apply any voltage to the port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the simplest form, you will probably find that there is no voltage on the line when the TV is off and some voltage when the TV is on. If you have a DMM, you can check to see if you observe this. Check with the DMM on both the DC mode and AC mode.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-08-07T21:38:49.570" CommentCount="4" />
  <row Id="3933" PostTypeId="2" ParentId="3925" CreationDate="2010-08-07T23:29:07.927" Score="2" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;For the cellular connection, I'd start with the cheapest module from Sparkfun, or something like it: &lt;a href=&quot;http://www.sparkfun.com/commerce/categories.php?c=68&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/categories.php?c=68&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For the lights, I think you'll want to use a relay wired like one of the switches in this clever arrangement: &lt;a href=&quot;http://home.howstuffworks.com/three-way2.htm&quot; rel=&quot;nofollow&quot;&gt;http://home.howstuffworks.com/three-way2.htm&lt;/a&gt; The other option is to wire the relay in parallel, but that breaks your &quot;transparent to a user&quot; rule.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I think this question is approximately &quot;What does the National Electrical Code say?&quot; You can &lt;a href=&quot;http://www.amazon.com/National-Electrical-Code-Protection-Association/dp/0877659141/ref=sr_1_1?ie=UTF8&amp;amp;s=books&amp;amp;qid=1281223238&amp;amp;sr=8-1&quot; rel=&quot;nofollow&quot;&gt;buy that on Amazon&lt;/a&gt;. And, hey, you're in luck! Pre-orders for the 2011 edition just started!&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I've actually done this in my house using an embedded Linux board. There's &lt;a href=&quot;http://pingswept.org/2010/04/12/designing-embedded-systems-with-web-frameworks/&quot; rel=&quot;nofollow&quot;&gt;a short summary on my blog&lt;/a&gt;, in the section labeled &quot;Proof of concept.&quot; I used Python, cron, and Django. &lt;a href=&quot;http://github.com/pingswept/thermopyla&quot; rel=&quot;nofollow&quot;&gt;The code&lt;/a&gt; is on Github if you'd like to use it. (I think this breaks your &quot;no internet&quot; rule, though.)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I know nothing about GSM costs.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Regarding the Cortex M3: that's a good choice. I'd also look at chips from the ARM926EJ/S series. Really, I'd probably just order a Beagleboard and be done with it.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-08-07T23:29:07.927" CommentCount="2" />
  <row Id="3934" PostTypeId="1" AcceptedAnswerId="3951" CreationDate="2010-08-08T03:03:43.547" Score="5" ViewCount="642" Body="&lt;p&gt;A Google search will give you a few billion ideas.  Which is the simplest/easiest/cheapest that you know of?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generating a square wave and then filtering out the harmonics isn't a good solution unless the filter frequency can be varied along with the square.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-05-04T06:50:41.843" Title="What's the easiest/cheapest variable-frequency sine wave oscillator?" Tags="&lt;oscillator&gt;" AnswerCount="6" CommentCount="3" />
  <row Id="3935" PostTypeId="2" ParentId="3934" CreationDate="2010-08-08T03:58:11.150" Score="6" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Wien_bridge_oscillator&quot; rel=&quot;nofollow&quot;&gt;Wien bridge&lt;/a&gt; with a pot to vary the frequency. I bet you could build one for less than one US dollar.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-08-08T15:09:40.750" LastActivityDate="2010-08-08T15:09:40.750" CommentCount="2" />
  <row Id="3937" PostTypeId="2" ParentId="3934" CreationDate="2010-08-09T05:44:19.783" Score="1" ViewCount="" Body="&lt;p&gt;You can still do it with a square wave and filtering out the harmonics.  There are a number of high order filters that can be controlled with a microcontroller easily.  &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/MAX293-MAX297.pdf&quot; rel=&quot;nofollow&quot; title=&quot;This&quot;&gt;This&lt;/a&gt; one allows the user to control the corner frequency with an outside clock (second square wave from the micro).  Because of the large corner frequency to clock frequency ratio you could even do it without the need of another timer/interrupt with a simple software counter...&lt;/p&gt;&#xA;" LastActivityDate="2010-08-09T05:44:19.783" CommentCount="1" />
  <row Id="3939" PostTypeId="1" AcceptedAnswerId="3942" CreationDate="2010-08-09T07:25:01.460" Score="4" ViewCount="185" Body="&lt;p&gt;Is it possible to format an SPI EEPROM (such as AT24C128) to be used as an SD card?&#xA;So format it with FAT 32 and have a 16MB drive appear in windows?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="641" LastActivityDate="2010-09-20T12:58:53.193" Title="Serial EEPROM with FAT" Tags="&lt;serial&gt;&lt;eeprom&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="3941" PostTypeId="1" AcceptedAnswerId="3960" CreationDate="2010-08-09T07:50:04.333" Score="20" ViewCount="465" Body="&lt;p&gt;This is presented as both a resource for the community and a learning experience for myself. I have just enough knowledge of the subject to get myself into trouble, but I don't have the best grasp of the subject's details. Some helpful responses might be:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Explanation of the components of impedance&lt;/li&gt;&#xA;&lt;li&gt;How those components interact&lt;/li&gt;&#xA;&lt;li&gt;How can one transform impedances&lt;/li&gt;&#xA;&lt;li&gt;How this relates to RF filters, power supplies, and anything else...&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Thanks for the help!&lt;/p&gt;&#xA;" OwnerUserId="965" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-02T02:21:06.100" LastActivityDate="2011-04-11T15:24:39.353" CommunityOwnedDate="2010-08-09T07:50:04.333" Title="What is impedance?" Tags="&lt;rf&gt;&lt;filter&gt;&lt;impedance&gt;" AnswerCount="4" CommentCount="7" FavoriteCount="7" />
  <row Id="3942" PostTypeId="2" ParentId="3939" CreationDate="2010-08-09T08:30:17.330" Score="4" ViewCount="" Body="&lt;p&gt;Yes, it is possible, but you'd need some kind of controller, you couldn't just wire the eeprom directly. This is because the EEPROM does not speak SD card protocol. I would probably bypass SD completely, and just use USB. So something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;SPI EEPROM &amp;lt;-SPI-&amp;gt; AVR &amp;lt;-USB-&amp;gt; PC&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Look into the examples provided with the AVR USB library, &lt;a href=&quot;http://www.fourwalledcubicle.com/LUFA.php&quot; rel=&quot;nofollow&quot;&gt;Lufa&lt;/a&gt;, one of the examples shows exactly the above setup...except it's using an Atmel DataFlash instead of a SPI EEPROM. But it's possible, you'd just need to change the code which accesses the Flash to instead access the EEPROM.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-08-09T08:30:17.330" />
  <row Id="3944" PostTypeId="1" AcceptedAnswerId="3947" CreationDate="2010-08-09T12:38:48.500" Score="2" ViewCount="427" Body="&lt;p&gt;I wonder which hardware will be the best for playing with USB because its looks like a lot of projects only use atmega8 (or even attiny). But would it really be easier with an AT90USB which have the built-in USB?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have already looked at some HID libraries (lufa, avr-usb, v-usb…) but they are complex. Does anyone have a link to a specific project or a one-case explanation of the USB implementation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the details : I would like to make a ~25 button joystick and I work on linux.&lt;/p&gt;&#xA;" OwnerUserId="824" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-08-09T13:00:38.027" LastActivityDate="2010-09-14T12:16:12.437" Title="Which AVR hardware for USB?" Tags="&lt;avr&gt;&lt;usb&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="3945" PostTypeId="1" CreationDate="2010-08-09T12:51:32.070" Score="2" ViewCount="196" Body="&lt;p&gt;Hi all,&#xA;I have recently ordered 1 x &lt;a href=&quot;http://www.pololu.com/catalog/product/705&quot; rel=&quot;nofollow&quot;&gt;VNH3SP30 Motor Driver Carrier MD01B&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was just reading the charts and found below saying about the pwm, &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;VNH3SP30 and VNH2SP30 Comparison:   VNH3SP30        VNH2SP30&#xA;Operating supply voltage (Vcc)      5.5 - 36 V*     5.5 - 16 V&#xA;Maximum current rating              30 A            30 A&#xA;MOSFET on-resistance (per leg)      34 mΩ           19 mΩ&#xA;Maximum PWM frequency               10 kHz          20 kHz&#xA;Current sense                       none            approximately 0.13 V/A&#xA;Over-voltage shutoff                36 V*           16 V minimum (19 V typical)&#xA;Time to overheat at 20 A**          8 seconds       35 seconds&#xA;Time to overheat at 15 A**          30 seconds      150 seconds&#xA;Current for infinite run time**     9 A             14 A&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;* Manufacturer specification. &lt;strong&gt;In our experience, shoot-through currents make PWM operation impractical above 16 V.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;** Typical results using Pololu motor driver carrier with 100% duty cycle at room temperature.&#xA;&lt;br&gt;&#xA;&lt;br&gt;&#xA;Does this mean if I want to PWM (vary the speed) of 24v actuators under load, will this work correctly with this VNH3SP30 board? or will it 'jump' voltage and not work &#xA;How/What would you recommend please?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance,&#xA;Galen&lt;/p&gt;&#xA;" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-08-09T13:03:43.767" LastActivityDate="2010-08-12T14:43:12.990" Title="PWM above 16v for speed control? Will it work?" Tags="&lt;pwm&gt;&lt;motor&gt;&lt;speedcontroller&gt;" AnswerCount="3" />
  <row Id="3946" PostTypeId="2" ParentId="3944" CreationDate="2010-08-09T12:53:10.777" Score="4" ViewCount="" Body="&lt;p&gt;The easiest way to interact with an AVR over USB would be to connect an &lt;a href=&quot;http://www.ftdichip.com/Products/FT232BM.htm&quot; rel=&quot;nofollow&quot;&gt;FTDI FT232&lt;/a&gt; to the UART, and then interact with your AVR as a virtual COM port using the &lt;a href=&quot;http://ftdi-usb-sio.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;FTDI drivers&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You've probably heard of or used this chip; it's on a lot of embedded devices (Including the Arduino boards) and it's probably the easiest way to interact with a microcontroller over USB.  However, I'm not sure that it can do what you're trying to do; it creates a virtual COM port.  If you can write a plugin to query the device for button presses, it will be ideal. However, if you want it to show up as an input device, I'm not sure that this is the solution for you.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; This is the plug-in simple solution to get basic communication. Joby's answer does not restrict your project to a virtual COM port as this device does.&lt;br&gt;&#xA;However, the port provided can be made to function in the same way with inputattach. (Source: Joby's comment below) However, it appears that you will have to patch your device driver into the inputattach utility.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-08-09T20:07:41.240" LastActivityDate="2010-08-09T20:07:41.240" CommentCount="2" />
  <row Id="3947" PostTypeId="2" ParentId="3944" CreationDate="2010-08-09T12:58:50.947" Score="4" ViewCount="" Body="&lt;p&gt;Have a look at these questions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/1942/how-to-build-a-usb-controller-having-knobs-sliders-and-switches&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/1942/how-to-build-a-usb-controller-having-knobs-sliders-and-switches&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/276/teensy-development&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/276/teensy-development&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/267/id-like-to-learn-how-to-make-my-own-usb-gadgets&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/267/id-like-to-learn-how-to-make-my-own-usb-gadgets&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would use a Teensy, here are some &lt;a href=&quot;http://www.pjrc.com/teensy/projects.html&quot; rel=&quot;nofollow&quot;&gt;links to projects&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-09T12:58:50.947" />
  <row Id="3948" PostTypeId="2" ParentId="3945" CreationDate="2010-08-09T13:26:08.807" Score="2" ViewCount="" Body="&lt;p&gt;Shoot-through current refers to the condition where both switches/MOSFETs on one side of the H-Bridge are on simultaneously.  Under normal conditions, the H-bridge is under one of the following conditions:&#xA;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/f/f2/H_bridge_operating.svg/310px-H_bridge_operating.svg.png&quot; alt=&quot;From Wikipedia&quot;&gt;&#xA;If, however, both switches on one side are on simultaneously, a huge current can flow (Only 34mΩ per leg, remember?), which is usually destructive.  I'm not sure why both switches would be on - Possibly an issue with gate capacitance and switching time?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.st.com/stonline/products/literature/ds/12688.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; says that the PWM pin is:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Voltage controlled input pin with&#xA;  hysteresis, CMOS compatible. Gates of&#xA;  low side FETs are modulated by the PWM&#xA;  signal during their ON phase allowing&#xA;  speed control of the motor.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;You might get better luck with higher voltages if you modulated the PWM such that it was centered on the ON-pulses:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;Motor on:     ----    ----     --      --&#xA;S-Left-Top__/------\________/------\________  &#xA;S-Rght-Bot___/----\___________/--\__________&#xA;S-Rght-Top__________/------\________/------\&#xA;S-Left-Bot___________/----\___________/--\__  &#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;But you'll definitely want to look very carefully at Figures 4, 5, and 6 of that datasheet.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-09T13:26:08.807" />
  <row Id="3949" PostTypeId="2" ParentId="3934" CreationDate="2010-08-09T13:56:33.720" Score="2" ViewCount="" Body="&lt;p&gt;You could also PWM or otherwise DAC values out of a table to produce sine waves. Then the filtering should be easier. A very cheap MCU could probably do it up to fair frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I might second some RC + opamp design in principle. Whether the output and adjustability suits you depends on the application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also some function generator IC's, ranging from classic &lt;a href=&quot;http://www.mit.edu/~6.331/icl8038info.pdf&quot; rel=&quot;nofollow&quot;&gt;8038&lt;/a&gt; to various complex DDS thingies. They might not come that cheap, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess there's also the option of finding an affordable second hand lab signal/function generator. It might be a long search for a cheap one, but it's all relative. Or you could take a spare AC generator and turn the shaft with variable speed. Amplify for power/impedance/voltage :)&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-08-09T13:56:33.720" CommentCount="3" />
  <row Id="3950" PostTypeId="2" ParentId="3941" CreationDate="2010-08-09T14:19:16.113" Score="10" ViewCount="" Body="&lt;p&gt;Impedance is an extension of the concept of resistance that includes the effects of capacitance and inductance.  Inductors and capacitors have &quot;reactance&quot;, and impedance is the combination of the effects of resistance and reactance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;n00b introduction: Essentially, it lets you think about capacitors and inductors as if they were resistors, making calculations simpler and more intuitive.  For instance, if you know how to calculate the output of a purely resistive voltage divider:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/d/db/Resistive_divider.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;then you can also calculate the magnitude of the output of an RC filter at a given frequency:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/RC_Divider.svg/178px-RC_Divider.svg.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Say R is 1 kΩ and C is 1 uF, for instance, and you want to know the output voltage if you input a sine wave at 160 Hz. The reactance of the capacitor at 160 Hz has a magnitude of about &lt;a href=&quot;http://www.wolframalpha.com/input/?i=1%2F%282%2api%2a160+Hz%2a1+uF%29+to+ohm&quot; rel=&quot;nofollow&quot;&gt;1 kΩ&lt;/a&gt;, so both &quot;resistors&quot; are the same, and the voltage across each will be the same.  Each component has 0.707 of the input voltage across it, though, not 0.5, as in the resistive case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At other frequencies, the magnitude of the reactance of the capacitor would be different, which is why the filter responds differently to different frequencies. You can also work with imaginary numbers to calculate the phase shift in the output, but often the magnitude is the only part you care about.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-19T18:05:08.640" LastActivityDate="2010-08-19T18:05:08.640" CommunityOwnedDate="2010-08-09T14:19:16.113" CommentCount="2" />
  <row Id="3951" PostTypeId="2" ParentId="3934" CreationDate="2010-08-09T14:42:16.830" Score="3" ViewCount="" Body="&lt;p&gt;Making a numerically controlled oscillator (NCO) with  uC + DAC is very easy. &#xA;Could be a fun FPGA project. An advantage to an NCO is that you &#xA;change waveforms. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did a low frequency numerically controller oscillator Arduino sketch &#xA;(see &lt;a href=&quot;http://wiblocks.luciani.org/docs/app-notes/nb1a-nco.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/docs/app-notes/nb1a-nco.html&lt;/a&gt;). At the&#xA;bottom of the webpage are a couple of references to the original&#xA;articles,&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-05-04T05:15:25.317" LastActivityDate="2011-05-04T05:15:25.317" CommentCount="2" />
  <row Id="3952" PostTypeId="2" ParentId="3941" CreationDate="2010-08-09T15:21:55.600" Score="10" ViewCount="" Body="&lt;p&gt;The impedance of a circuit element is the ratio between voltage and current in that element.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Constant voltages and currents&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For constant voltages and currents, impedance is just resistance. A resistor is a device that maintains the same ratio of voltage to current, even as the voltage changes. They're linear-- double the voltage and the current doubles too. If you drew a graph of voltage vs. current, the slope would be the impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A capacitor, which is like two metal plates, acts like an open circuit for constant currents and voltages. An inductor, which means a curly wire, acts like a short circuit for constant currents and voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(In reality, it's not quite this clean. Resistors tend to let through less current then they should when they get hot. Capacitors let a little bit of current leak through, even when they shouldn't. Inductors have a small amount of resistance, like any normal wire.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Voltages and currents that change with time&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's where it gets more interesting. Some circuit elements, like capacitors and inductors, allow more or less current flow depending on the frequency of the voltage they're subjected to. You could think of them as frequency-dependent resistors. The frequency-dependent part of impedance is called reactance. Add reactance and resistance and you get impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Examples of reactance&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Suppose you had a box that generated sine waves of amplitude 120 V. You set the box for 60 cycles per second and connect the box's signal across a 0.1 F capacitor. The current that flows will be a sine wave at the same frequency. The amplitude will be:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I = V * 2 * pi * frequency * C&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I = 120 * 2 * 3.14 * 60 * 0.1 = 4522 amps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(In reality, that much current would make the capacitor explode.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you doubled the frequency of the sine wave, the current would double. This kind of behavior is useful in RC filters-- you can make circuits that have high resistance at one frequency, but low resistance at another, which lets you pick out a signal from amongst noise, for example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An inductor behaves similarly, but as you increase frequency, the impedance increases rather than decreases.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The real world&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In reality, everything has some resistance as well as some reactance (either a little capacitance or inductance, but not both). In addition, all circuits have non-linearities, like temperature dependence or geometrical effects that make them deviate from the ideal model.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the voltages and currents we deal with are never perfect sine waves-- they're a mix of  frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, suppose you're running a solenoid to open a door lock, like the buzzers in apartment buildings. The solenoid is a massive inductor that creates a magnetic field that pulls back a latch against the force of a spring. When you turn off the solenoid, you're making a current change drastically with time. As you try to make the current drop quickly, the inductance of the solenoid makes the voltage rise quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is why you see what's called a &quot;flyback diode&quot; in parallel with big inductors-- to allow the current to drop more slowly, avoiding the voltage spike caused by a high-frequency change.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The next step&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From here, the next step is to learn how to model circuits built of multiple reactive elements (say, a bunch of resistors and capacitors). For that, we have to track not just the amplitudes of voltage and current, but also the phase shift between them-- the peaks of the sine waves don't line up in time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Unfortunately, I have to get some work done here, so I'll have to leave you with this link: &lt;a href=&quot;http://www.usna.edu/MathDept/CDP/ComplexNum/Module_6/ComplexPhasors.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.usna.edu/MathDept/CDP/ComplexNum/Module_6/ComplexPhasors.htm&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-08-09T15:21:55.600" CommunityOwnedDate="2010-08-09T15:21:55.600" />
  <row Id="3957" PostTypeId="1" CreationDate="2010-08-09T18:56:30.937" Score="4" ViewCount="356" Body="&lt;p&gt;I'm looking to get started with Arduino and I wanted to know any good books out there. Any help would be appreciated&lt;/p&gt;&#xA;" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-27T22:51:26.537" LastActivityDate="2011-04-02T16:50:54.497" CommunityOwnedDate="2011-04-02T13:56:39.060" Title="Beginner Hardware development guides" Tags="&lt;arduino&gt;&lt;books&gt;" AnswerCount="6" FavoriteCount="3" />
  <row Id="3958" PostTypeId="2" ParentId="3957" CreationDate="2010-08-09T19:23:04.850" Score="7" ViewCount="" Body="&lt;p&gt;What is your experience level? What types of hardware?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would probably put &quot;Making Things Talk&quot; close to the top of&#xA;the list.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your experience some general electronics books &#xA;like &quot;The Art of Electronics&quot; and &quot;CMOS Cookbook&quot;. An&#xA;excellent free resource is &lt;a href=&quot;http://www.allaboutcircuits.com&quot; rel=&quot;nofollow&quot;&gt;http://www.allaboutcircuits.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-28T03:31:51.517" LastActivityDate="2011-01-28T03:31:51.517" CommunityOwnedDate="2011-04-02T13:56:39.060" CommentCount="1" />
  <row Id="3959" PostTypeId="2" ParentId="3957" CreationDate="2010-08-09T19:31:23.453" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.smileymicros.com/index.php?module=pagemaster&amp;amp;PAGE_user_op=view_page&amp;amp;PAGE_id=82&amp;amp;MMN_position=136:136&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is a very good book for complete beginners:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Joe sent me a copy to see what I thought of it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's also available with a hardware kit.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-09T19:31:23.453" CommunityOwnedDate="2011-04-02T13:56:39.060" />
  <row Id="3960" PostTypeId="2" ParentId="3941" CreationDate="2010-08-09T19:50:31.743" Score="12" ViewCount="" Body="&lt;p&gt;To the question &quot;what is Impedance,&quot; I would note that impedance is a broad concept of physics in general, of which electrical impedance is only one example.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get a grasp of what it means and how it works, it's often easier to consider mechanical impedance instead.  Think of trying to push (slide) a heavy couch across the floor.&lt;br&gt;&#xA;You apply a certain amount of force, and the couch slides at a certain velocity, depending on how hard you push, the weight of the couch, the type of floor surface, the type of feet that the couch has, and so on.  For this situation, it's possible to define a mechanical impedance that gives the ratio between how hard you push and how fast the couch goes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is actually a lot like a dc electrical circuit, where you apply a certain amount of voltage across a circuit, and current flows at a certain corresponding rate through it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the case of both the couch and the circuit, the response to your input may be simple and fairly linear: a resistor that obey's Ohm's Law, where its electrical impedance is just the resistance, and the couch may have friction slider feet that allow it to move with a velocity proportional to your force.*   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Circuits and mechanical systems may also nonlinear. If your circuit consists of a variable voltage placed across a resistor in series with a diode, the current will be near zero until you exceed the forward voltage of the diode, at which point current will begin to flow through the resistor, in accordance with Ohm's law.  Likewise, a couch sitting on the floor will usually have some degree of static friction: it won't begin moving until you push with a certain amount of initial force.   In neither the mechanical nor electrical system is there a single linear impedance that can be defined. Rather, the best that you can do is to separately define impedances under different conditions.  (The real world is much more like this.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even when things are very clear and linear, it's important to note that impedance just describes a ratio-- it doesn't describe the limits to the system, and it's not &quot;bad.&quot; You can definitely get as much current/velocity as you want (in an ideal system) by adding more voltage/pushing harder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mechanical systems also can give a pretty good feel for ac impedance.  Imagine that you're riding a bicycle.  With each half-cycle of the pedals, you push left, push right.  You can also imagine pedaling with just one foot and a toe-clip, such that you push and pull with every cycle of your pedal.  This is a lot like applying an ac voltage to a circuit: you push and pull in turn, cyclicly, at some given frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the frequency is slow enough-- like when you're stopped on the bike, the problem of pushing down on the pedals is just a &quot;dc&quot; problem, like pushing the couch.  When you speed up, though, things can act differently.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, suppose that you're biking along at a certain speed, and your bike is a three-speed with low, medium, and hi gear ratios.  Medium feels natural, hi gear is difficult to apply enough force to make any difference, and at low gear, you just spin the pedals without transferring any energy to the wheels.  This is a matter of &lt;em&gt;impedance matching&lt;/em&gt;, where you can only effectively transfer power to the wheels when they present a certain amount of physical resistance to your foot-- not too much, not too little.  The corresponding electrical phenomenon is very common as well; you need impedance matched lines to transmit RF power effectively from point A to point B, and any time that you connect two transmission lines together, there will be some loss at the interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistance that the pedals provide to your feet is proportional to how hard you press, which relates it most closely to a simple resistance-- particularly at low speeds.  Even in AC circuits, a resistor behaves like a resistor (up to a certain point).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, unlike a resistor, the impedance of a bicycle is dependent on frequency.  Suppose that you put your bike in high gear, starting from a stop.  It can be &lt;em&gt;very&lt;/em&gt; hard to get started.  But, once you do get started, the impedance presented by the pedals goes down as you get going faster, and once you're going very fast, you may find that the pedals present too little impedance to absorb power from your feet.  So there's actually a frequency-dependent impedance (a &lt;em&gt;reactance&lt;/em&gt;) that starts out high and gets lower as you head to higher frequency.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is much like the behavior of a capacitor, and a fairly good model for the mechanical impedance of a bicycle would be a resistor in parallel with a capacitor.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At dc (zero velocity), you just see the high, constant resistance as your impedance.  As the pedaling frequency increases, the capacitor impedance becomes lower than that of the resistor, and allows current to flow that way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are, of course, various other electrical components and their mechanical analogies**, but this discussion should give you some initial intuition on the general concept to stay grounded (pun intended) as you learn about the mathematical aspects of what can at times seem like a very abstract subject.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*A word to the picky:  Ohm's law is never exact for a real device, and real-world friction forces never give velocity exactly proportional to force.  However, &quot;fairly linear&quot; is easy.  I'm trying to be all educational and stuff here. Cut me some slack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;**For example, an inductor is something like a spring-loaded roller on your wheel that adds drag as you get to higher frequency)&lt;/p&gt;&#xA;" OwnerUserId="484" LastEditorUserId="484" LastEditorDisplayName="" LastEditDate="2010-08-12T20:03:11.107" LastActivityDate="2010-08-12T20:03:11.107" CommunityOwnedDate="2010-08-09T19:50:31.743" CommentCount="1" />
  <row Id="3964" PostTypeId="2" ParentId="3720" CreationDate="2010-08-09T22:13:32.550" Score="1" ViewCount="" Body="&lt;p&gt;I was recently educated in &lt;a href=&quot;http://chiphacker.com/questions/3944/&quot; rel=&quot;nofollow&quot;&gt;this question&lt;/a&gt; about two options for USB development: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://pjrc.com/teensy/index.html&quot; rel=&quot;nofollow&quot;&gt;teensy USB development board&lt;/a&gt; (uses ATMEGA32U4 or AT90USB1286 USB enabled AVR microcontroller)  &lt;/li&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://wiki.archlinux.org/index.php/Attaching_serial_input_devices_to_the_kernel_input_system&quot; rel=&quot;nofollow&quot;&gt;inputattach&lt;/a&gt; utility (Linux) for registering serial devices (like an FT232) as input devices&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Would one of these work for you?  Either way, you're going to have to write your own driver for it, because your OS isn't going to like your sending of nonstandard scancodes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The advantage of having standard scancodes is that every keyboard you plug in &quot;just works&quot; (In theory).  If you don't mind some configuration, why bother trying to emulate the scancodes?&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-09T22:13:32.550" />
  <row Id="3965" PostTypeId="2" ParentId="3945" CreationDate="2010-08-09T22:33:04.577" Score="0" ViewCount="" Body="&lt;p&gt;If you have total control of the four transistors comprising the H-bridge, you can mitigate against shoot-through by leaving a dead-band in the control signals. What this means is, for both sides of the bridge, before you turn a high-side driver ON, you turn the low-side driver OFF and allow a small amount of time to elapse. Same goes for turning off the high side and turning on the low side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason you would do this is that turn-on and turn-off times are asymmetric. Usually it takes a device a little longer to turn off than to turn on. If you try to simultaneously change a side of the bridge from high drive to low drive (or the other way), there will be a brief interval of time during which &lt;em&gt;both&lt;/em&gt; devices will be partially conducting, and this allows large currents to flow directly between the supply rails, heating the transistors in the process. For efficiency and longer component lifetimes, you want to keep only one transistor on a side fully conducting, the other completely not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The effect is exacerbated by higher voltages by ohm's law; more voltage means more current, and the heating in the transistors is consequently worse. The effect is also made worse by higher switching frequencies. Every time the polarity is reversed, a little burst of shoot-through current occurs. At a few hundred Hz and under 12V it's not worth worrying about too much. An industrial controller working at 300+ bus volts and 10+ kHz pwm definitely has a concern. Fwiw, dead band times of 1 to 2 microseconds suffice to ensure that shoot through doesn't occur.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-08-09T22:33:04.577" />
  <row Id="3966" PostTypeId="1" CreationDate="2010-08-09T22:48:19.337" Score="5" ViewCount="473" Body="&lt;p&gt;I'm developing a measurement application with the TI MSP430 and I would like to hear some suggestions on what type of memory I can use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea is to use it for logging during a certain time and then download the data to a PC when the device is connected via USB. The estimate is to hold up to 5MB of data, every sample being around 25 bytes of data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would a simple EEPROM chip do or is there something better out there?&lt;/p&gt;&#xA;" OwnerUserId="1267" LastActivityDate="2010-08-12T17:51:58.653" Title="Memory suggestions for MSP430" Tags="&lt;msp430&gt;&lt;embedded&gt;&lt;memory&gt;&lt;eeprom&gt;" AnswerCount="5" />
  <row Id="3970" PostTypeId="2" ParentId="3966" CreationDate="2010-08-10T00:57:57.140" Score="7" ViewCount="" Body="&lt;p&gt;I've used the &lt;a href=&quot;http://www.atmel.com/dyn/products/devices.asp?family_id=616&quot; rel=&quot;nofollow&quot;&gt;AT45D&lt;/a&gt; series of serial flash chips.  They have an internal SRAM buffer to setup a page for erase/programming.  SPI interface to read data in and out.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-08-10T00:57:57.140" />
  <row Id="3971" PostTypeId="2" ParentId="3878" CreationDate="2010-08-10T01:27:54.753" Score="0" ViewCount="" Body="&lt;p&gt;I have tried a lot of different workflow stuff.  It seems like the most helpful parts of any workflow scheme are specifications (what done looks like), Timelines(how to get to done) and Tasklists (what to do right now).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Really the first and last ones are the most important.  You need to know what you want to make as precisely as you can.  You also need to know what to do at a given time.  &lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2010-08-10T01:27:54.753" />
  <row Id="3973" PostTypeId="1" CreationDate="2010-08-10T07:29:07.663" Score="1" ViewCount="571" Body="&lt;p&gt;So I am wanting to make a custom LED scrolling message display. Basically I have a surface I am going to mount 32 LED's to and then have them controlled by an Arduino. What kind of hardware would I need and what would you suggest for a power source, I want to go as light and compact as possible.&lt;/p&gt;&#xA;" LastActivityDate="2010-08-16T14:03:23.567" Title="4x8 LED Scrolling Display with Arduino" Tags="&lt;led&gt;&lt;arduino&gt;" AnswerCount="5" />
  <row Id="3974" PostTypeId="2" ParentId="3966" CreationDate="2010-08-10T07:38:56.847" Score="4" ViewCount="" Body="&lt;p&gt;5MByte is a lot of data to store.  Reading it out over USB implies that you are using one of the new parts with the USB device interface built in.  If not then you are going to be using a USB to serial converter (FTDI or similar) and will be limited to the async serial data rates for reading the data out.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you considered connecting an SD memory card to the MSP, storing the data in that and then moving the card to the pc for reading the stored data.  I have not written an interface to this device but there are plenty that have.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-08-10T07:38:56.847" CommentCount="6" />
  <row Id="3975" PostTypeId="2" ParentId="3175" CreationDate="2010-08-10T08:27:13.620" Score="0" ViewCount="" Body="&lt;p&gt;Hi Guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am involved in a similar project that is mentioned in this post; trying to develop a fully portable system based on a FPGA solution (as one of the possible solutions). In my case, the camera is firewire 800 (1394b).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have any of you come across a single mini interface board that could be used as the firewire 800 interface between the FPGA and the camera. I am trying to look for a solution that require minimum time to setup the interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;@PsychoMedic: I am curious to know how you are dealing with the issues you've mentioned above.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you in advance. &lt;/p&gt;&#xA;" LastActivityDate="2010-08-10T08:27:13.620" />
  <row Id="3976" PostTypeId="2" ParentId="3973" CreationDate="2010-08-10T09:59:00.217" Score="2" ViewCount="" Body="&lt;p&gt;Hey Dave -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess it depends on the rating of your LEDS a bit -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But you will need to look at expanding the Arduinos digital outputs by using some latching &lt;a href=&quot;http://www.arduino.cc/en/Tutorial/ShiftOut&quot; rel=&quot;nofollow&quot;&gt;Shift Registers.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you've worked out what rating LEDs your using you can get a better idea of what power source would be the best. If your just using standard LEDs (around 20mA) there's no reason you couldn't power the whole lot from a 9v PP3 battery, you could even use a smaller equivalent 9v battery to get the size and weight down - but the smaller you get the less it's life span will be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use an Arduino, 3 x 595 Shift Register and one of these &lt;a href=&quot;http://oomlout.co.uk/8-x-8-bicolour-led-matrix-p-233.html&quot; rel=&quot;nofollow&quot;&gt;Bi-colour Red Green LED matrix&lt;/a&gt; - the whole lot is powered by a PP3 9v battery and it'll last around 30 hours of solid LED scrolling fun!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a video link showing my matrix if you're interested -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=EOelyTduz88&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=EOelyTduz88&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-08-10T11:08:59.530" LastActivityDate="2010-08-10T11:08:59.530" />
  <row Id="3977" PostTypeId="2" ParentId="3973" CreationDate="2010-08-10T10:04:21.573" Score="1" ViewCount="" Body="&lt;p&gt;You could also use a Maxim &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/07/09/review-maxim-max7219-led-display-driver-ic/&quot; rel=&quot;nofollow&quot;&gt;MAX7219&lt;/a&gt;, could save some PCB space with it. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-08-10T10:04:21.573" />
  <row Id="3978" PostTypeId="2" ParentId="3973" CreationDate="2010-08-10T10:58:26.680" Score="2" ViewCount="" Body="&lt;p&gt;Here's a similar project:&#xA;&lt;a href=&quot;http://hackaday.com/2009/10/02/smd-led-matrix/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2009/10/02/smd-led-matrix/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-10T10:58:26.680" CommentCount="1" />
  <row Id="3979" PostTypeId="2" ParentId="3966" CreationDate="2010-08-10T12:36:09.103" Score="2" ViewCount="" Body="&lt;p&gt;I would suggest the AT25D series since it appears a little easier to use than the AT45D. Although it's a little slower and does not offer as many data transfer options or the SRAM buffers. It does have the advantage of being less expensive and it is still quick enough for most applications like data logging.&lt;p&gt; If you need 5MB of data it's unlikely that an EEPROM will work since they come in &amp;lt; 1Mbit packages typically. Flash chips from Atmel support up to 64-mbit or 8MB.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-08-10T12:36:09.103" CommentCount="2" />
  <row Id="3980" PostTypeId="2" ParentId="3957" CreationDate="2010-08-10T14:37:09.763" Score="2" ViewCount="" Body="&lt;p&gt;&quot;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Getting-Started-with-Arduino.html&quot; rel=&quot;nofollow&quot;&gt;Getting Started with Arduino&lt;/a&gt;&quot; by Massimo Banzi, then&#xA;&quot;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Practical-Arduino.html&quot; rel=&quot;nofollow&quot;&gt;Practical Arduino&lt;/a&gt;&quot; by Jon Oxer and Hugh Blemings&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-08-10T14:37:09.763" CommunityOwnedDate="2011-04-02T13:56:39.060" />
  <row Id="3981" PostTypeId="2" ParentId="3760" CreationDate="2010-08-10T16:51:03.437" Score="6" ViewCount="" Body="&lt;p&gt;I just received an email from e-Teknet about 2,4,6 and 8 layer promotions they are having.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 6 layer boards are $79.99 each plus shipping, and the proto specials are a 4 board minimum.  The specs are:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maximum board size 35 square inches for 2-layer board, 30 square inches for multilayer boards. Less than 10&quot; in either X or Y direction.  0.062&quot; thick board (FR4 material), 1 oz copper, minimum conductor width/ space &gt;= 7 mil, , minimum annular ring &gt;= 7 mil, minimum hole size &gt;=12 mil (plated through).  Non plated through holes are allowed. Board size&gt;1&quot;x1&quot;. Tin-lead HAL reflow and green LPI,  white silkscreen for both top and bottom sides. For  promotions, the boards should have no countersinks, no cutouts and no panels and V-scores.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have not ordered from e-Teknit but the salesman, Neil Munzinger, has been very&#xA;responsive to my various queries. They also offer assembly services.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Neil Munzinger&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Account Executive&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P: 480-752-7854&lt;/p&gt;&#xA;&#xA;&lt;p&gt;F: 480-752-7855&#xA;E-mail: sales@e-teknet.com&#xA;www.e-teknet.com&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:43:30.753" LastActivityDate="2011-05-16T10:43:30.753" CommunityOwnedDate="2011-05-20T11:44:01.827" CommentCount="2" />
  <row Id="3982" PostTypeId="2" ParentId="3966" CreationDate="2010-08-10T18:07:32.040" Score="3" ViewCount="" Body="&lt;p&gt;Serial flash is superior to EEPROM in this application.  Atmel makes a great &lt;a href=&quot;http://www.atmel.com/products/DataFlash/&quot; rel=&quot;nofollow&quot;&gt;lineup&lt;/a&gt;.  Your choice will depend largely on two things: (1) Your need to edit/sector your logs on the micro and (2) Your RAM availability on the MSP430. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Flash, unlike EEPROM, can only be written from a 1 to a 0.  Changing the data from 0 to 1 requires erasing a section of the part, which is typically only available for pages or blocks of data.  You'll need to buffer this page into RAM, erase the page, make your edit in RAM, and then write it back if you want to change something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The AT45D series, as has been already pointed out, offers a number of parts which have RAM buffers on the chip to facilitate this process without using RAM on the microcontroller.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;In the end, the entire series is pin-compatible, so just put down an 8-SOIC (150mil) footprint, and then you can swap out the parts if you need different options later.&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-10T18:07:32.040" CommentCount="6" />
  <row Id="3983" PostTypeId="2" ParentId="3760" CreationDate="2010-08-10T19:03:18.210" Score="0" ViewCount="" Body="&lt;p&gt;You might want to browse through &lt;a href=&quot;http://opencircuits.com/PCB_Manufacturers&quot; rel=&quot;nofollow&quot;&gt;the list of PCB Manufacturers&lt;/a&gt;.&#xA;Many of them have online calculators that will give you the cost of your board in a few minutes of typing in #layers, minimum trace/space, etc.&#xA;Crank through a few of them and pick the best one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;we've looked at combining AGND and DGND nets and living with the noise.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No matter what you do, you will have to live with &lt;em&gt;some&lt;/em&gt; noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, do you realize that keeping AGND and DGND separate causes &lt;em&gt;more&lt;/em&gt; noise than a single GND plane?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.hottconsultants.com/pdf_files/june2001pcd_mixedsignal.pdf&quot; rel=&quot;nofollow&quot;&gt;Partitioning and Layout of a Mixed Signal PCB&lt;/a&gt;: The importance of single ground plane and partitioning of analog and digital signal traces&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://techref.massmind.org/techref/noises.htm#unsplit_ground&quot; rel=&quot;nofollow&quot;&gt;Massmind Techref: &quot;Unsplit ground&quot;&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-10T19:03:18.210" CommunityOwnedDate="2010-08-10T19:03:18.210" CommentCount="2" />
  <row Id="3984" PostTypeId="2" ParentId="1760" CreationDate="2010-08-10T21:16:04.927" Score="0" ViewCount="" Body="&lt;p&gt;This can be read in the 'debugging' help topic: &quot;All data are stored in little-endian byte order (each word consists of byte 3 followed by byte 2 then 1 then 0). Note that each word can hold 4 characters of a string and those 4 characters will appear in the reverse order from that of the string literal.&quot;&lt;/p&gt;&#xA;" LastActivityDate="2010-08-10T21:16:04.927" />
  <row Id="3985" PostTypeId="2" ParentId="3760" CreationDate="2010-08-10T21:18:12.937" Score="13" ViewCount="" Body="&lt;p&gt;in my experience having truly separate AGND and DGND nets almost never works out well in practice.  90% of the designs i see that try to do this end up with current loops that introduce EMI issues and can generate more noise in the analog portions of the circuit than using a single ground with careful part placement would.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having two GND planes also creates a problem for routing in that signals referenced to a particular ground should only ever be run on layers that are adjacent to this plane or its associate power plane. This can result is a pretty funky stack up that can limit where you can run traces.  Your best answer would be AGND,signal,?GND,POWER,signal,DGND but thats funky to layout, uses lots of vias, only gives 2 signal layers to route on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What i would recommend is a single solid ground plane and careful part placement.  High speed digital signals and noise will follow the path of least &lt;strong&gt;inductance&lt;/strong&gt; to ground not the path of least &lt;strong&gt;resistance&lt;/strong&gt;.  The path of least inductance is the smallest loop area, for signals this is directly under the trace on the adjacent ground plane.  In some cases a ground pour on top, bottom, or both can be helpful in reducing noise pick up as well.  This is dependent on the components and the design layout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Create virtual partitions, keep out areas, where you only run either analog or digital signals, keeping in mind that the return current path for the low frequency analog signals is the path of least resistance, while the return path for the high speed digital signals is the path of least inductance.  As long as your careful to ensure that the return current paths don't cross, especially a digital return running under your analog sections.  You shouldn't get much noise pick up at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your have a particular device that is very sensitive to noise, such as a high resolution ADC, you can use a ground island to increase noise immunity, like this:&#xA;&lt;img src=&quot;http://www.hottconsultants.com/techtips/a-d%20gnd%20plane.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In cases where i have some sensitive analog circuitry i will usually also use a power island that is separated from the digital power supply by an LC filter of some sort, depending on the digital frequencies i'm wishing to block.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-08-10T21:18:12.937" CommunityOwnedDate="2011-05-20T11:44:01.827" CommentCount="2" />
  <row Id="3986" PostTypeId="2" ParentId="3930" CreationDate="2010-08-10T21:57:19.830" Score="0" ViewCount="" Body="&lt;p&gt;The yellow RCA jack should output standard NTSC signals, if it is an Output.  The yellow RCA input should be a high-impedance input, so the level on that won't tell you much about the status of the TV.  On the output jack, NTSC voltage levels vary between 0V and 1.0V practically--some TVs vary on high-white output.  The easiest way would be to check for the line going low for 4.7uS or the horizontal sync pulse.  You could also check for the vertical syncs, but many TVs disagree on the standard for that too.  If the TV is on, the output for video should show 4.7uS h-sync pules, and then color-burst/blanking and then pixel data after that.  The problem with measuring it on a DC meter is the AC nature of the signal, and an AC meter will just average the entire signal.  You might be able to experiment with it a little bit.&lt;/p&gt;&#xA;" LastActivityDate="2010-08-10T21:57:19.830" CommentCount="1" />
  <row Id="3989" PostTypeId="1" CreationDate="2010-08-11T09:37:03.010" Score="3" ViewCount="254" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As requested by &lt;a href=&quot;http://chiphacker.com/users/3/littlebirdceo&quot; rel=&quot;nofollow&quot;&gt;Marcus&lt;/a&gt;, here is a short post about a piece of hardware I bought recently from Little Bird Electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recently bought an &lt;a href=&quot;http://www.littlebirdelectronics.com/products/Arduino-XBee-Shield-Empty.html&quot; rel=&quot;nofollow&quot;&gt;XBee Arduino Shield&lt;/a&gt;, and was a bit curious when I tried to use it the first time. When I connected it to my arduino, it seemed like it wasn't able to be pushed down enough onto the arduino, but now I'm starting to think that it's missing the black plastic bits on the pins on each side. This means that while the shield is connected to the arduino, if you press gently on either side of the shield on top of the either of the two rows of pins, you can actually rock the shield from side to side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a photo of it (sorry it's not a very good photo):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i975.photobucket.com/albums/ae239/dsturmfels/arduino_xbee-shield.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1049" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-24T21:41:50.500" LastActivityDate="2010-08-24T21:41:50.500" Title="Problem with XBee Arduino Shield" Tags="&lt;arduino&gt;&lt;xbee&gt;&lt;arduino&gt;" AnswerCount="2" />
  <row Id="3991" PostTypeId="2" ParentId="3720" CreationDate="2010-08-11T10:56:10.993" Score="1" ViewCount="" Body="&lt;p&gt;Atmel (and Microchip too I think) has a generic HID driver for their MCUs available, with full sourcecode at each end available (Client test software, and embedded HID stack).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Browsing Atmel's offering, they even have a &lt;a href=&quot;http://www.atmel.com/dyn/products/tools_card.asp?tool_id=3879&quot; rel=&quot;nofollow&quot;&gt;full-blown keyboard demo board&lt;/a&gt;, again with source code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not the simplest example (They've written their own task scheduler!), but I think it should be pretty easy to mod to do what you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Look in &lt;code&gt;keyboard_task.c&lt;/code&gt; on the above links keyboard demo (&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/AVR271_USB_Keybord.zip&quot; rel=&quot;nofollow&quot;&gt;or here&lt;/a&gt;). It seems to be exactly what you want. A great big array of scancodes, being used to write a message to the computer by emulating a keyboard into any text editor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The actual HID keystroke values are abstracted away using #define into a file called &lt;code&gt;usb_commun_hid.h&lt;/code&gt;, which seems to be not(!) included in the above download (I guess it comes with the compiler?), but they just map to plain old single byte values, so you should be able to add more all you want. (See the &lt;code&gt;a00102.html&lt;/code&gt; file in the above link.) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would image Microchip has something similar, but I don't feel too much like digging through their implementation right now. If you want, I may be able to do so later.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, this doesn't really do anything about how you're &lt;em&gt;decoding&lt;/em&gt; these scancodes at the computer end, but again, Atmel does have .Net examples of how to talk to their HID devices, so something hackable should be available.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-08-11T10:56:10.993" />
  <row Id="3992" PostTypeId="2" ParentId="3989" CreationDate="2010-08-11T13:17:48.320" Score="4" ViewCount="" Body="&lt;p&gt;That's what it looks like to me as well.  However, this might be a new design - Compare carefully to &lt;a href=&quot;http://www.littlebirdelectronics.com/product_images/s/948/09063-03-L__14101_zoom.jpg&quot; rel=&quot;nofollow&quot;&gt;this picture&lt;/a&gt;, and you'll see that those headers are offset (and therefore have black plastic bits on the male headers), while yours appears to use &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9280&quot; rel=&quot;nofollow&quot;&gt;stackable headers&lt;/a&gt;, which never have black plastic bits on the pins, because then you couldn't put them through the holes! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try moving it just a little to the side, so the shield PCB rests on the female headers (as if you could push it all the way down).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you've got less than the pitch of the connectors between the bottom of the male pins and the Arduino PCB (or the male pins are touching the PCB) then the pins are too long, your female headers are too short, or you need the black plastic bits for spacers.  In this case, I'd probably just cut 4 pins off of a male header strip, pull the black plastic bits off, and then push them onto the corner pins on your XBee. You could also carefully trim the pins to be a little shorter, or you could get back in touch with Marcus for a replacement which matches the picture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you've still got 0.1&quot; between the bottoms of the pins on the XBee and your Arduino PCB, then you're either not pushing hard enough or you've got a piece of something (probably a broken wire) stuck in the bottom of one of your female headers.  In this case, you need to replace the plugged header on your Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does this answer your question?&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-11T13:17:48.320" CommentCount="4" />
  <row Id="3993" PostTypeId="2" ParentId="3989" CreationDate="2010-08-11T14:33:45.290" Score="2" ViewCount="" Body="&lt;p&gt;It might be the plastic bits, but I am not convinced yet. A number of Long pin female connectors don't have these. So long as there is electrical conductivity, you should be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rocking from side to side suggests that the shield is touching something on the Arduino and it's acting as a fulcrum. Check that, as it could cause electrical problems. Also, can you post an oblique view?&lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-08-11T14:33:45.290" CommentCount="2" />
  <row Id="3994" PostTypeId="2" ParentId="3957" CreationDate="2010-08-11T15:02:04.883" Score="2" ViewCount="" Body="&lt;p&gt;The question of how best to get started with Arduino is an important topic. Before recommending books, let me suggest a three step approach:&lt;br/&gt;&lt;br/&gt;&#xA;1) Talk with the community. Since you posted here, you are already doing this step.&lt;br/&gt;&#xA;2) Get your hands dirty as soon as possible, and keep them dirty. Build kits - they allow you to make something cool without understanding all the parts, so you can focus on learning a particular aspect. As you get better, modify kits.&lt;br/&gt;&#xA;3) Read books and blogs. There is a lot out there for free, and you will soon be spending more than you intended on your new hobby :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Books to start with is a very active topic on the Arduino News forum. (arduino.cc) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That discussion suggests &lt;a href=&quot;http://earthshinedesign.co.uk&quot; rel=&quot;nofollow&quot;&gt;http://earthshinedesign.co.uk&lt;/a&gt;, (go to bottom left, External Links, top link, &quot;The complete Beginners Guide ...&quot;) which is a free download. I would suggest trying that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried Getting started with Arduino, and found it OK, but &quot;meh&quot;. There is better stuff nowadays. Making Things Talk is well worth the money and pretty basic, but not for complete beginners.&lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-08-11T15:02:04.883" CommunityOwnedDate="2011-04-02T13:56:39.060" />
  <row Id="3995" PostTypeId="1" AcceptedAnswerId="3997" CreationDate="2010-08-11T17:55:59.723" Score="2" ViewCount="308" Body="&lt;p&gt;What are the hardware and software options for programming an XMEGA from Linux?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-08-11T21:07:06.117" Title="What is the state of XMEGA programming from Linux?" Tags="&lt;atmel&gt;&lt;avr&gt;&lt;xmega&gt;" AnswerCount="2" />
  <row Id="3996" PostTypeId="2" ParentId="3995" CreationDate="2010-08-11T18:50:53.870" Score="1" ViewCount="" Body="&lt;p&gt;Use &lt;a href=&quot;http://www.eclipse.org/downloads/download.php?file=/technology/epp/downloads/release/helios/R/eclipse-cpp-helios-linux-gtk.tar.gz&quot; rel=&quot;nofollow&quot;&gt;Eclipse&lt;/a&gt; + &lt;a href=&quot;http://avr-eclipse.sourceforge.net/wiki/index.php/The_AVR_Eclipse_Plugin&quot; rel=&quot;nofollow&quot;&gt;AVR-GCC plugin&lt;/a&gt; + &lt;a href=&quot;http://www.nongnu.org/avr-libc/&quot; rel=&quot;nofollow&quot;&gt;AVR-GCC Toolchain&lt;/a&gt; and it should all work pretty great. &lt;a href=&quot;http://paul.graysonfamily.org/thoughts/avrlinux/&quot; rel=&quot;nofollow&quot;&gt;This link&lt;/a&gt; has some advice on building and setting up the toolchain. You will (obviously) also need a programmer, and there are lots of options, but I use the AVR-ISP mkII. I will caveat this by admitting I've only developed for AVRs in windows, but using the same set of tools...&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-08-11T18:50:53.870" />
  <row Id="3997" PostTypeId="2" ParentId="3995" CreationDate="2010-08-11T19:18:24.323" Score="3" ViewCount="" Body="&lt;p&gt;I find that command-line avr-gcc and avrdude work great on Mac OS X for programming xmega; Should work equally well under linux.&lt;/p&gt;&#xA;" OwnerUserId="484" LastEditorUserId="484" LastEditorDisplayName="" LastEditDate="2010-08-11T21:07:06.117" LastActivityDate="2010-08-11T21:07:06.117" CommentCount="1" />
  <row Id="3999" PostTypeId="2" ParentId="3957" CreationDate="2010-08-11T20:14:44.447" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.wowebook.com/hardware/make-arduino-bots-and-gadgets.html&quot; rel=&quot;nofollow&quot;&gt;Make: Arduino Bots and Gadgets&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/xT6Ey.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can &lt;a href=&quot;http://www.wowebook.com/download/2536/&quot; rel=&quot;nofollow&quot;&gt;download it for free&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.pragprog.com/titles/msard/arduino&quot; rel=&quot;nofollow&quot;&gt;Arduino: A Quick-Start Guide&lt;/a&gt; by Maik Schmidt&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/AA6q2.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-02T11:07:08.910" LastActivityDate="2011-04-02T11:07:08.910" CommunityOwnedDate="2011-04-02T13:56:39.060" />
  <row Id="4000" PostTypeId="1" AcceptedAnswerId="4003" CreationDate="2010-08-11T22:40:26.670" Score="0" ViewCount="84" Body="&lt;p&gt;hello&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you please tell me how to find part number of the particular chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was trying to find max232 chip locally, and I have been told that I need to provide NTE part number.    I searched google, but could not find proper part number for chip&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you&lt;/p&gt;&#xA;" OwnerUserId="1060" LastActivityDate="2010-08-12T02:05:00.053" Title="how to find NTE part numbers" Tags="&lt;serial&gt;&lt;manufacturing&gt;" AnswerCount="1" />
  <row Id="4001" PostTypeId="2" ParentId="815" CreationDate="2010-08-11T22:50:28.927" Score="2" ViewCount="" Body="&lt;p&gt;Hi, the link to download DuinOS had changed to this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://robotgroup.com.ar/duinos/wiki&quot; rel=&quot;nofollow&quot;&gt;http://robotgroup.com.ar/duinos/wiki&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There you will find (in the downloads section) the v0.1 and the v0.2 versions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards,&#xA;Julián&#xA;&lt;a href=&quot;http://robotgroup.com.ar&quot; rel=&quot;nofollow&quot;&gt;http://robotgroup.com.ar&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-08-11T22:50:28.927" />
  <row Id="4003" PostTypeId="2" ParentId="4000" CreationDate="2010-08-12T02:05:00.053" Score="3" ViewCount="" Body="&lt;p&gt;NTE has &lt;a href=&quot;http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/%24%24Search?OpenForm&quot; rel=&quot;nofollow&quot;&gt;a search engine&lt;/a&gt; for finding part number for their replacement parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the MAX232, it looks like you want NTE7142.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-08-12T02:05:00.053" />
  <row Id="4005" PostTypeId="2" ParentId="3973" CreationDate="2010-08-12T14:36:06.760" Score="0" ViewCount="" Body="&lt;p&gt;I'm working on a similar project for an R2D2 build with Arduino. &lt;br /&gt;&lt;br /&gt;&#xA;I've gone through the following project progression so far:&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Wire eight LEDs (directly) up to Arduino with a breadboard, make them blink randomly. Not too difficult.&lt;/li&gt;&#xA;&lt;li&gt;Charlieplex six LEDs with three lines via Arduino, make them blink randomly. A little more difficult, but not too bad.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;My next project is designing (on paper) the Charlieplexing circuit for the 8x5 LED array. This  will require seven lines, though I will probably use eight to simplify the wiring.&lt;br /&gt;&lt;br /&gt;&#xA;My plan is to wire all this to the Arduino board with an eight pin ribbon cable, making everything all nice and tidy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope all of this helps...if I understand you correctly, the only thing that would be different between our two projects would be software. As far as power, I'm pretty sure that Arduino should be able to drive that many LEDs without too much trouble. Ultimately I'll be relying on Li batteries, but in the meantime, I just use the 5v from the adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;08-13-2010 - I just found this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MKJR3&quot; rel=&quot;nofollow&quot;&gt;http://www.makershed.com/ProductDetails.asp?ProductCode=MKJR3&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks like both of our projects are subsets of this one. I bought one, and I expect that the wiring on the board will give me the education I need.&lt;/p&gt;&#xA;" OwnerUserId="989" LastEditorUserId="989" LastEditorDisplayName="" LastEditDate="2010-08-13T19:03:02.967" LastActivityDate="2010-08-13T19:03:02.967" CommentCount="4" />
  <row Id="4006" PostTypeId="2" ParentId="3945" CreationDate="2010-08-12T14:43:12.990" Score="0" ViewCount="" Body="&lt;p&gt;Is it possible that the author of this data sheet meant to say &quot;flyback current&quot; rather than &quot;shootthrough current&quot;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;During the &quot;on&quot; time of the PWM, two transistors are on and getting warm: current flows from the battery through one high-side transistor through the motor through one low-side transistor to ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;During the dead band, the &lt;em&gt;other&lt;/em&gt; two transistors have current flowing through them and getting warm, even though all four transistors are turned off.&#xA;The parasitic inductance of the motor causes current to flow from ground through the internal protection diode of one low-side transistor through the motor through the internal protection diode of one high-side transistor to the battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So that parasitic inductance indirectly causes the voltage across each of the original two transistors (that were recently turned off) to be a significantly higher voltage than the battery voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The voltage blocking rating of a transistor applies to the actual voltage across the pins of the transistor (which during flyback is significantly &lt;em&gt;more&lt;/em&gt; than the battery voltage).&#xA;So to keep the transistor within its rating -- i.e., in order to keep the transistor from self-destructing -- the battery voltage much be significantly &lt;em&gt;less&lt;/em&gt; than the transistor rating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alas, practically all motor controller driver manufacturers simply copy the voltage blocking rating of a transistor directly to their advertisement.&#xA;It's used as a marketing number because it sounds bigger and more impressive than the &lt;em&gt;actual&lt;/em&gt; battery voltage you can actually use with it.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-12T14:43:12.990" CommunityOwnedDate="2010-08-12T14:43:12.990" />
  <row Id="4007" PostTypeId="2" ParentId="3900" CreationDate="2010-08-12T15:12:48.703" Score="1" ViewCount="" Body="&lt;p&gt;Yes, disabling optimizations during debugging has been best practice for a while now, for three reasons:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;(a) if you're going to single-step the program with a high-level debugger, it's slightly less confusing.&lt;/li&gt;&#xA;&lt;li&gt;(a) (obsolete) if you're going to single-step debug the program with an assembly-language debugger, it's much less confusing. (But why would you bother with this when you could be using a high-level debugger?)&lt;/li&gt;&#xA;&lt;li&gt;(b) (long obsolete) you're probably going to only run this particular executable once, then make some change and recompile. It's a waste of a person's time to wait an extra 10 minutes while the compiler &quot;optimizes&quot; this particular executable, when that's going to save less than 10 minutes of runtime. (This is no longer relevant with modern PCs that can compile a typical microcontroller executable, with full optimization, in less than 2 seconds).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Many people go even further in this direction, and&#xA;&lt;a href=&quot;http://c2.com/cgi/wiki?ShipWithAssertionsOn&quot; rel=&quot;nofollow&quot;&gt;ship with assertions turned on&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-12T15:12:48.703" CommunityOwnedDate="2010-08-12T15:12:48.703" />
  <row Id="4008" PostTypeId="1" CreationDate="2010-08-12T16:12:02.673" Score="3" ViewCount="449" Body="&lt;p&gt;I am driving a digital pin with a 10Mhz signal. At the pin, the signal's rise time is slewed to 35us such that the signal is no longer a pulse but a triangular waveform that does not reach the full output level of 1.8V. I have a source termination resistor on the driving source. However, this source is a couple of feet away and the trace is not a controlled 50Ohms. Would making this trace a controlled 50hms helped with the slewing of the rising time? Does line termination help or is this only to reduce reflections?&#xA;Also,if 50 ohms would help, is it better to have a discontinous 50 ohms or none at all? I have some transitions on the trace that I cannot make 50 ohms.&lt;/p&gt;&#xA;" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-24T21:10:24.910" LastActivityDate="2011-05-20T10:57:36.560" Title="Transmission Line and capacitive effect" Tags="&lt;transmission-line&gt;&lt;capacitance&gt;&lt;impedance&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="4009" PostTypeId="2" ParentId="1316" CreationDate="2010-08-12T16:42:09.880" Score="0" ViewCount="" Body="&lt;p&gt;Yes, two-state &quot;dim&quot; and &quot;bright&quot; is easy.&#xA;Given &lt;em&gt;any&lt;/em&gt; circuit that blinks a LED hard on and off with a transistor, you add one resistor across that transistor. Then when the transistor is fully off, the resistor allows a dim glow. I would start with a resistor of exactly the same value as the current limiting resistor already connected to the LED.&#xA;(Every LED needs a current-limiting resistor).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a few markers, a independent battery and &lt;a href=&quot;http://opencircuits.com/555_Timers&quot; rel=&quot;nofollow&quot;&gt;555 timer&lt;/a&gt; at each one is going to be the simplest marker hardware. (plus a few resistors and capacitors).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The overall system simpler if you can synchronize the LEDs: turn all markers on at the start of the cycle, then turn off one marker at a time until they are all off, then turn them all back on and start the cycle over. The amount of energy needed to keep a bunch of LEDs blinking for a couple of hours typically weighs much less in the form of one or two central batteries rather than one battery per LED.&#xA;(This requires a comparator IC at each LED, or a few shift registers or an Arduino emulating those shift registers at some central location).&#xA;(This requires lots of wires stringing from one marker to the next, or from each marker to some central point -- so that may not be possible for your application.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It makes your vision recognition software much simpler if the PC can control the LEDs directly. Then when the PC is searching for LED_5, it can turn off and on LED_5 and be confident that the one LED that blinked must be LED_5.&#xA;Perhaps using something like a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=7841&quot; rel=&quot;nofollow&quot;&gt;USB to 8 bit parallel port converter&lt;/a&gt;, which (with 8 resistors, one per LED) can directly control 8 LEDs or (with 4 resistors, one per column) a 4x4 matrix of 16 LEDs.&#xA;(This requires yet another wire, a USB cable from the PC to the converter, but it doesn't require &lt;em&gt;any&lt;/em&gt; batteries or transistors or additional chips -- this may be the simplest for a programmer non-electronics guy to get working).&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-12T16:42:09.880" CommunityOwnedDate="2010-08-12T16:42:09.880" />
  <row Id="4010" PostTypeId="2" ParentId="4008" CreationDate="2010-08-12T16:58:02.737" Score="1" ViewCount="" Body="&lt;p&gt;What is the source impedance of the driver? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the source/sink currents?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the impedance of the load?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of cable?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What size is the termination resistor on the driver output and how is it&#xA;connected?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the termination resistor on the driver output goes from the driver output&#xA;to ground you are reducing your output drive current. If this value is small&#xA;enough you will not be able to charge the cable capacitance and you will&#xA;reduce your rise=time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your driver is low-impedance you could add a series termination resistor&#xA;and then use 50Ohm cable. At 10MHz I think your problem is more basic -- not&#xA;enough current drive for the capacitive load.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T10:57:36.560" LastActivityDate="2011-05-20T10:57:36.560" CommentCount="1" />
  <row Id="4011" PostTypeId="2" ParentId="4008" CreationDate="2010-08-12T17:26:03.237" Score="2" ViewCount="" Body="&lt;p&gt;ok, few things:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The source termination resistor value should be equal to the impedance of the transmission line minus the output impedance of the driving IC.  It should be placed as close as possible to the driving IC.  Don't be surprised if you have to try a couple different values to get the signal to be perfect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When using source termination you are actually cutting the signal that goes out in half, it looks full scale because when you match the source termination to the line impedance you get a perfect reflection, hence a doubling and the signal looks full size when scoped.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So yes matching the impedance of the line to the source termination impedance is critical for operation at 10Mhz over several feet.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I have some transitions on the trace that I cannot make 50 ohms.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;What do you mean by transitions?  Cable couplers?  Your not splitting this signal off to more than 1 place i hope?  That will really not work, especially with source termination.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case that your dealing with things that aren't perfectly 50 ohms (or whatever impedance cable your using) you should first avoid them if at all possible.  Use couplers that are closely matched to 50ohm (they'll never be perfect) etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any time the impedance changes in a transmission line there will be reflections, the larger the change in impedance the larger the problem is and they can occur on both sides of the change (secondary reflections on the far side).  If the transitions in the signal patch are just the cable connectors on either end you can minimize their effect by placing the driving and receiving ICs as close as possible to them.  They usually do influence the overall TL impedance some, which is why you may have to tweak the source termination resistor a few ohms either way to get it perfect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT In response to the OP's comment:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There could be excess capacitance due to a faulty cable or connector.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However more likely, you can not, ever, tap off a high frequency signal with a source termination.  You will get nasty reflections.  If you need to tap off a signal like this it needs to be end terminated PAST the final tap, and each tap needs to be as close as possible to the transmission line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume that this interface board is tapping into the signal somehow, if not don't use it and just figure out how to plug the output of the ATE directly into your device board.  If you provide some models for these parts i can probably be of more help with this issue.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-08-12T20:22:33.497" LastActivityDate="2010-08-12T20:22:33.497" />
  <row Id="4012" PostTypeId="1" AcceptedAnswerId="4016" CreationDate="2010-08-12T17:32:40.543" Score="3" ViewCount="268" Body="&lt;p&gt;I've been told that &lt;s&gt;many kinds of batteries work best if they are used until they are completely drained, and then recharged.&lt;/s&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Edit: &lt;em&gt;The &lt;a href=&quot;http://www.repairfaq.org/ELE/F_NiCd_Memory.html&quot; rel=&quot;nofollow&quot;&gt;&quot;memory effect myth&quot;&lt;/a&gt; is quite widespread. Batteries work just as well if they are &quot;topped up&quot; every time.&lt;/em&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right now I design devices the standard way: try to use the battery power as long as possible, and then when there is no power left it doesn't work at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there was some simple way of implementing the following, I might use it from now on:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Two independent batteries (or more)&lt;/li&gt;&#xA;&lt;li&gt;Once you start using one battery, continue to use it until it is &lt;s&gt;completely drained&lt;/s&gt; &lt;em&gt;reaches the manufacturer-recommended minimum voltage&lt;/em&gt;.&lt;/li&gt;&#xA;&lt;li&gt;When the &quot;in use&quot; battery is completely dead, switch to using the next battery. Presumably you use some technique similar to the &lt;a href=&quot;http://chiphacker.com/questions/401/switch-between-5v-power-supplies&quot; rel=&quot;nofollow&quot;&gt;&quot;Switch between 5V power supplies?&quot;&lt;/a&gt; question.&lt;/li&gt;&#xA;&lt;li&gt;Once you switch to the last battery, go into some sort of low-power mode so it can still do the important things in &quot;limp mode&quot;, but the user is notified to plug it into a charger as soon as possible.&lt;/li&gt;&#xA;&lt;li&gt;After plugging into the charger, go back to standard mode -- but if disconnected from the charger before the batteries are fully charged, go back to limp mode.&lt;/li&gt;&#xA;&lt;li&gt;(optional) When plugged into the charger, only charge the drained battery (or batteries) and keep them topped off; leave the one &quot;in use&quot; battery alone.&lt;/li&gt;&#xA;&lt;li&gt;(optional) keep track of precisely how much total energy could be extracted from each particular battery the most recent time it was fully drained. Use that number (perhaps modified using Peukert's law) to give extremely accurate estimates of future run-time.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Why don't all devices do this?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;cell phones: first battery: talk like crazy. last battery: only emergency calls.&lt;/li&gt;&#xA;&lt;li&gt;laptops: last battery: throttle back to a slow speed that is adequate for looking up static documents&lt;/li&gt;&#xA;&lt;li&gt;handheld GPS: last battery: try to reduce energy by updating the screen less often, dimming the backlight, etc.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2010-08-13T12:51:45.443" LastActivityDate="2010-08-13T12:51:45.443" CommunityOwnedDate="2010-08-12T17:32:40.543" Title="How do I design a device to automatically switch to the backup battery?" Tags="&lt;battery&gt;&lt;power-supply&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="4014" PostTypeId="2" ParentId="3966" CreationDate="2010-08-12T17:51:58.653" Score="1" ViewCount="" Body="&lt;p&gt;[This is in response to the comments following Ian's answer].&lt;br&gt;&#xA;An SD card is just an SPI device, so there's no chip/interface necessary.  Other protocols include a 2-wire interface (like I2C) and a 4-wire interface (with a complex CRC), but SPI is the most commonly used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is an SD card application note available for the MSP430 from TI &lt;a href=&quot;http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=slaa281b&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&#xA;It's brief, but it includes sample code.  It handles reading and writing to various sectors on the SD card, which may be all you want if you're not going to plug it into a PC.  Also look at these implementations by &lt;a href=&quot;http://alumni.cs.ucr.edu/~amitra/sdcard/Additional/sdcard_appnote_foust.pdf&quot; rel=&quot;nofollow&quot;&gt;Foust&lt;/a&gt; (recommended) or &lt;a href=&quot;http://www.digitalspirit.org/file/index.php/obj-download/docs/fat/appnote_fat16.pdf&quot; rel=&quot;nofollow&quot;&gt;Evans&lt;/a&gt; from MSU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have the basic functions to read and write a sector, you can either abstract a simple, custom filesystem over USB, or use an existing filesystem library.  &lt;a href=&quot;http://efsl.be/&quot; rel=&quot;nofollow&quot;&gt;FatFS&lt;/a&gt;, &lt;a href=&quot;http://elm-chan.org/fsw/ff/00index_e.html&quot; rel=&quot;nofollow&quot;&gt;EFSL&lt;/a&gt;,  or &lt;a href=&quot;http://www.larwe.com/zws/products/dosfs/index.html&quot; rel=&quot;nofollow&quot;&gt;DOSFs&lt;/a&gt; are all options for the latter.  If implementing all of the required functions seems too hard, remember that all but a few can/will be stubs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the file system will be abstracted through your USB interface to a degree.  This will be easier if you have a real filesystem library and your card is in a readable filesystem, but that takes work.  If you want to write your own &quot;Filesystem&quot; and save work/time/memory for the USB implementation, you can make its definition as simple and inflexible as log 1 starts at 0x0, log 2 starts at 0x10 0000, log 3 at 0x20 0000, and log 4 at 0x30 0000.  Then, you can send this data over USB.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The USB interface can be as complex as you like it to be - from serial interface to mass storage device.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-12T17:51:58.653" />
  <row Id="4015" PostTypeId="1" AcceptedAnswerId="4020" CreationDate="2010-08-12T18:08:49.843" Score="2" ViewCount="101" Body="&lt;p&gt;I'm trying to dig up the &quot;rule of thumb&quot; value for what a telephone company would consider acceptable path loss when they run a new line out to a customer. I spent a lot of time in digital telephony but the number for a regular voice line is eluding me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd always considered 3-4dB to be the number, but some of the articles I'm pulling up are saying 5.5dB to even 8.5dB as within spec.  This seems to be an awful lot of loss which would translate to quiet audio. I know the actual path loss varies with the length of the loop, but there are typical and maximum values that I'm trying to find.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any rules of thumb or experience in this area? What is the typical path loss of a telephone line and at what level of attenuation will a telco actually do something to remedy the situation? &lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-08-12T23:39:32.060" Title="Telephone line acceptable path loss?" Tags="&lt;telephone&gt;&lt;potentiometer&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="4016" PostTypeId="2" ParentId="4012" CreationDate="2010-08-12T18:23:17.297" Score="4" ViewCount="" Body="&lt;p&gt;Why don't all devices use this?  It adds cost and complexity.  Is their any other reason for not doing something?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Seriously, I'd say that there are plenty of options and implementations for this.  Having two equal batteries doesn't make much sense, so often the second is used for emergency or limp-home power.  For instance, your PC has a RAM retaining battery on the motherboard for when you loose power.  A laptop often gives a &quot;Low battery&quot; warning, at which time you're welcome to reduce power however you can.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that your statement that 'batteries work best if they are used until they are completely drained, and then recharged.' is a little broad.  This is more the case for Nickel-based (NiCd and, to a lesser extent, NiMH) chemistries.  Lithium Ion cells don't suffer this memory problem.  In fact, their lifetime improves if you avoid deep discharges.  See &lt;a href=&quot;http://www.batteryuniversity.com/parttwo-34.htm&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; from BatteryUniversity.com for reference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a couple of options for doing more intelligent power management in your own devices.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest is an ORing diode on the power supply.  If all you want is a hot-swappable power supply and you have a bit of leeway for your inputs, you can connect backup battery to the anode of a diode, and connect the cathode to your main battery.  When the voltage of the main battery dips to 0.7V less than your backup (Or is removed), the other battery kicks in.  Be careful of leakage current into the backup battery, it might overcharge it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you can use a power mux IC like the &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tps2110.html&quot; rel=&quot;nofollow&quot;&gt;TPS110&lt;/a&gt;.  This lets you select your input independently (or dependently, if you prefer) of the input voltages, instead of always using the higher supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, Linear Technology incorporates what they call &quot;PowerPath&quot; controllers into their battery charging ICs.  I've used their LTC4011 which seamlessly transitions between battery and external power, and charges the battery while running off of the external power.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-12T18:23:17.297" CommunityOwnedDate="2010-08-12T18:23:17.297" CommentCount="7" />
  <row Id="4017" PostTypeId="2" ParentId="4012" CreationDate="2010-08-12T18:25:33.133" Score="1" ViewCount="" Body="&lt;p&gt;Nickel Cadmium cells were the infamous batteries which could build up a &quot;memory&quot; effect if not periodically cycled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Newer Lithium-Ion rechargeable cells are considered immune from the memory effect. In fact, its best &lt;em&gt;not&lt;/em&gt; to fully discharge them (stored in a fully discharged state can reduce lifetime), hence most electronics enter a &quot;death&quot; state while they can still monitor energy but refuse to enter a high power state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many devices, included laptops, can very accurately monitor battery state via their charger's coloumb counter and voltage of the cell(s). This allows all of the above behavior without the need and cost of duplicate charge circuits and batteries.&lt;/p&gt;&#xA;" OwnerUserId="867" LastActivityDate="2010-08-12T18:25:33.133" CommunityOwnedDate="2010-08-12T18:25:33.133" CommentCount="2" />
  <row Id="4018" PostTypeId="2" ParentId="4008" CreationDate="2010-08-12T19:17:44.550" Score="0" ViewCount="" Body="&lt;p&gt;I was not able to add comments to answer Mark or jluciani so I am replying this way...&#xA;The source driver is from an ATE or Automatic test equipment tester.&#xA;The impedance of driver and termination resistor is 50Ohms.&#xA;The source/sink capability of this driver is +-50mA. The transitions I mentioned are due to the connection from tester to interface board to device board. My device board traces are 50Ohms traces. However, I cannot change the interface board. I don't even know its impedance. Is the slewing that I am observing due to excessive capacitance on the pin or is it due to transmission line effect or are they one and the same?&#xA;How do I determine the source/sink current needed to drive this signal? &lt;/p&gt;&#xA;" LastActivityDate="2010-08-12T19:17:44.550" CommentCount="3" />
  <row Id="4019" PostTypeId="2" ParentId="1316" CreationDate="2010-08-12T22:31:19.393" Score="0" ViewCount="" Body="&lt;p&gt;I think you may run in to trouble on the vision side of things if the frame rate of the camera isn't high enough relative to the rate of motion of the LED's.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;the LED's are going to need to cycle from high to low at some reasonable multiple of the camera's frame rate, at least 2 frames per state change to make sure that some of the frames have light from only one state instead of mixed from two states, which means you need two frames for every bit of data flashed out by the LED's to identify which marker it is.  obviously a shorter code will be best for that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the markers are moving a distance over that  that is on the same order as their distance from each other in the frame, then the vision system may lose confidence in correctly identifying which flashes belong to which marker.&lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2010-08-12T22:31:19.393" />
  <row Id="4020" PostTypeId="2" ParentId="4015" CreationDate="2010-08-12T23:39:32.060" Score="1" ViewCount="" Body="&lt;p&gt;According to &lt;a href=&quot;http://www.sandman.com/loopcur.html#CircuitLoss&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; document, from a company that sells circuit loss testers, telephone companies are required to provide -8.5 dB (relative to a 0 dB 1 KHz test signal).  However it says &quot;generally speaking, anything below a -7.5 gets hard to hear&quot;, and &quot;the ideal db loss to look for is -5.5db.&quot;&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-08-12T23:39:32.060" CommentCount="1" />
  <row Id="4022" PostTypeId="1" AcceptedAnswerId="4024" CreationDate="2010-08-13T04:28:59.140" Score="2" ViewCount="175" Body="&lt;p&gt;Or does that chip require a bunch of weird voltages that can only be generated by a &quot;special&quot; expensive device programmer?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-13T12:18:30.443" CommunityOwnedDate="2010-08-13T04:28:59.140" Title="Can I download a new program to a Silicon Labs C8051F311 with a JTAG programmer?" Tags="&lt;8051&gt;&lt;programmer&gt;&lt;flash&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="4023" PostTypeId="2" ParentId="4012" CreationDate="2010-08-13T10:55:25.467" Score="1" ViewCount="" Body="&lt;p&gt;Completely discharging you battery is bad for &lt;strong&gt;all batteries&lt;/strong&gt; (well, maybe not lithium-hydrogen batteries, but if you have those in your laptop, you know what you're doing anyways).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The practice originates with NiCad batteries, due to a confluence of unfortunate design decisions. The common-knowledge belief that NiCads loose capacity if not fully cycled is &lt;strong&gt;false&lt;/strong&gt;.&lt;br&gt;&#xA;Basically, the shallow-cycling of NiCad batteries results in a depression of the discharge curve, resulting in many electronic devices which use NiCads &lt;em&gt;incorrectly&lt;/em&gt; reporting the battery as being empty. Note that the capacity of the cell is not significantly reduced, the cell voltage is merely depressed by a small amount. The fact that the major portion of the NiCad discharge curve is very flat leads to a small change in overall cell voltage causing a large change in the battery &quot;Charge State&quot; readout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that the memory effect occurs only with NiCads, and was never actually even present in &lt;strong&gt;any&lt;/strong&gt; other cell chemistries. The conflation of battery types, and naive assumption that all batteries are the same is what has lead to the belief about all batteries needing periodic cycling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is probably more accurate to think about batteries as being able to store and release a certain amount of energy, rather than being able to withstand a certain number of cycles. Whether this energy is release in 500 half-cycles or 1000 quarter-cycles is largely not relevant (An increased depth of discharge will actually &lt;em&gt;reduce&lt;/em&gt; the total overall energy capability of batteries, though not significantly unless the batteries is discharged &lt;em&gt;completely&lt;/em&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The manufacturer's that state that you should fully discharge and recharge your devices battery are stating this solely so that the internal battery charge &lt;em&gt;measuring&lt;/em&gt; electronics can properly calibrate themselves. Basically, over time, the charge-state measurement will drift due to slight variance in the efficiency of charging and discharging the battery (basically, it's an integrator). A single full-cycle lets the electronics accurately measure the battery capacity without having to guess about the battery condition. The fact that if not fully cycled, battery measurement electronics will inaccurately &lt;em&gt;report&lt;/em&gt; the battery state has led to the perseverance of the Memory Effect myth. The battery has not actually changed, the electronics are merely reporting an incorrect charge state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I know, the biggest cause of gradually reducing battery life in electronics is time. Lithium batteries actually have a shelf-life rated in a few years, &lt;em&gt;whether they are used or not&lt;/em&gt;. Proper storage practices can extend this shelf life, but they &lt;em&gt;will&lt;/em&gt; decay over time, no matter what use you put them through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Deep cycling lithiums is actually quite bad for them, actually. Don't do it unless you have to (try to stay above 20% SOC).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I am skipping a few things, like the issues with whisker growth in nicads. See the below link on NiCad for further reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See:&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Memory_effect&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Memory_effect&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Nicad&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Nicad&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-08-13T10:55:25.467" CommunityOwnedDate="2010-08-13T10:55:25.467" />
  <row Id="4024" PostTypeId="2" ParentId="4022" CreationDate="2010-08-13T12:18:30.443" Score="1" ViewCount="" Body="&lt;p&gt;From Section 20 of the &lt;a href=&quot;http://www.silabs.com/Support%20Documents/TechnicalDocs/C8051F31x.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;C8051F31x devices include an on-chip&#xA;  Silicon Labs 2-Wire (C2) debug&#xA;  interface to allow Flash program- ming&#xA;  and in-system debugging with the&#xA;  production part installed in the end&#xA;  application. The C2 interface uses a&#xA;  clock signal (C2CK) and a&#xA;  bi-directional C2 data signal (C2D) to&#xA;  transfer information between the&#xA;  device and a host system. See the C2&#xA;  Interface Specification for details on&#xA;  the C2 protocol.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So, yes, sounds like you need a special (non JTAG) programmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.silabs.com/products/mcu/Pages/USBDebug.aspx&quot; rel=&quot;nofollow&quot;&gt;Here's one&lt;/a&gt;, it's $35.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-13T12:18:30.443" CommunityOwnedDate="2010-08-13T12:18:30.443" CommentCount="1" />
  <row Id="4027" PostTypeId="1" AcceptedAnswerId="4028" CreationDate="2010-08-13T19:08:18.943" Score="12" ViewCount="558" Body="&lt;p&gt;I've reviewed the two methods, and multiplexing really only appears to have one advantage, that it would be easier to track down a failed LED than in a Charlieplex array.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone more knowledgeable explain any other trade-offs?&lt;/p&gt;&#xA;" OwnerUserId="989" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-22T10:55:57.257" LastActivityDate="2011-03-22T10:55:57.257" Title="Is Multiplexing ever superior to Charlieplexing?" Tags="&lt;led&gt;&lt;multiplexing&gt;&lt;charlieplexing&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="4028" PostTypeId="2" ParentId="4027" CreationDate="2010-08-13T19:32:32.060" Score="21" ViewCount="" Body="&lt;p&gt;Yes, multiplexing and charlieplexing both have their advantages, and are each best suited for different tasks.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main advantage of charlieplexing is that it can be done on a medium-size microcontroller, driving more LEDs with fewer I/O pins, and potentially no external hardware besides the LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, the advantage of &quot;no external hardware&quot; only applies for relatively small numbers of LEDs, up until you reach the current limit of your microcontroller, and it imposes a brightness limit that multiplexed arrays do not have.  If you choose to use no external hardware, you are generally limited to driving only one LED in the matrix at any given moment-- unlike a multiplexed array where you drive a full row at a time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you add external hardware to drive the LEDs with higher brightness to match that of a multiplexed array, charlieplexing loses its luster.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, a multiplexed array is addressed strictly by row and column; it's very straightforward to do this.  Turn on row 1, turn on all columns for row 1, turn off row 2, turn on all columns for row 2, and so on.   By contrast, a charlieplexed array is much less straightforward.  There's always a diagonal row that's useless, and I personally use look-up tables to relate between my arrays and a rectangular array where I store my data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Secondly, and a killer, is that charlieplexing generally requires tri-state drivers.  Multiplexing, however, is performed with strict on-off binary logic.   If you have a low pin count microcontroller and want to drive a large array of LEDs, it's straightforward to use external logic chips (e.g., shift register and/or LED drivers) to control both the X and Y axes.  Most shift-register type chips don't support the tristating necessary to do the same thing in a charlieplexed array.  Dedicated charlieplexed drivers are available, but are not nearly as versatile.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Third, in a charlieplexed array, every pin that's not actively doing something is still hooked up to the LEDs through a weak (&quot;high impedance&quot;) connection.  And while the connection is weak, it's nonzero.  Suppose that you have 25 I/O pins connected to a grid of LEDs. If you light one LED-- taking one of those 25 lines high and one of those 25 lines low, that leaves 23 high-impedance lines.  Each place that the high I/O line goes through an LED to a neutral line, there's some possibility to leak current. Not much. Maybe a microamp here or there. But with modern, efficient LEDs, that's often enough to create visible ghosting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fourth, it's harder to control LED brightness in a charlieplexed array.  In a multiplexed array, you can use any number of commonly available current-regulating &quot;sinking&quot; LED driver chips that regulate the brightness of each column separately, by using current regulation in combination with a PWM driver.  To the extent that charlieplexed matrix locations are addressed individually and use only a resistor per row or column, it's much harder to perform dot-brightness correction and full grayscale/color animation in a charlieplexed array. &lt;/p&gt;&#xA;" OwnerUserId="484" LastEditorUserId="484" LastEditorDisplayName="" LastEditDate="2010-08-14T21:26:56.417" LastActivityDate="2010-08-14T21:26:56.417" />
  <row Id="4029" PostTypeId="1" CreationDate="2010-08-14T02:48:14.557" Score="2" ViewCount="464" Body="&lt;p&gt;I have very simple loop to read serial port and write to client&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// telnet defaults to port 23&#xA;Server server(23);&#xA;&#xA;void setup() {&#xA;    Serial.begin(9600);// opens serial port, sets data rate to 9600 bps&#xA;&#xA;    // initialize the ethernet device&#xA;    Ethernet.begin(mac, ip, gateway, subnet);&#xA;&#xA;    // start listening for clients&#xA;    server.begin();&#xA;}&#xA;&#xA;void loop() {&#xA;    if (Serial.available() &amp;gt; 0) {&#xA;        char byte = Serial.read();&#xA;        server.write(byte);&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;problem happens if serial port is open (on computer side) after ethernet connection is established, no data is transmitted&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What gives?&#xA;thank you&lt;/p&gt;&#xA;" OwnerUserId="1060" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-08-15T11:59:27.720" LastActivityDate="2010-09-23T21:23:20.130" Title="arduino serial library" Tags="&lt;arduino&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="4030" PostTypeId="1" CreationDate="2010-08-15T23:21:45.657" Score="4" ViewCount="270" Body="&lt;p&gt;ok here goes,&#xA;Iam trying to build a device to test nurse call room controllers, these are basically 8 port boards with rs485 linking (have software for this,&#xA;what i need to do is test these, to do this i need to close a contact (call) for 1 second then 5 seconds later i can cancel that call by closing another contact to do this i need to automate 16 switchable outputs, &#xA;1 to activate it and another to cancel it&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i was hoping an Arduino USB Board might be able to handle this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i used to judt play with 555ic and 4017 ICs untill i got what i needed but i thought i would move into this century and make myself learn something new. . &lt;/p&gt;&#xA;" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-08-16T09:11:23.040" LastActivityDate="2010-08-16T09:11:23.040" Title="How to use Arduino board to automate testing" Tags="&lt;arduino&gt;&lt;rs485&gt;&lt;production-testing&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="4031" PostTypeId="2" ParentId="4030" CreationDate="2010-08-15T23:38:46.800" Score="1" ViewCount="" Body="&lt;p&gt;You can get your 16 outputs by interfacing two 74HC595 shift registers (eight outputs each) to the Arduino using SPI. The SPI function isn't supported by the Arduino, so you will have to write the code yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[Edit]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/playground/Code/Spi&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is some SPI code.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-08-16T05:47:21.970" LastActivityDate="2010-08-16T05:47:21.970" CommentCount="1" />
  <row Id="4033" PostTypeId="2" ParentId="4030" CreationDate="2010-08-16T01:18:56.050" Score="1" ViewCount="" Body="&lt;p&gt;If I was doing this, I'd go for a couple of 74373's. These are latches, which can either pass through a signal, or hold it until needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each one will hold the state of 8 pins, so you need 8 pins for your data, and 2 pins to select each bank. That's a total of 10 pins so will fit on a Duemilanove, and avoids the difficulty of SPI. &lt;/p&gt;&#xA;" OwnerUserId="776" LastActivityDate="2010-08-16T01:18:56.050" />
  <row Id="4034" PostTypeId="2" ParentId="4030" CreationDate="2010-08-16T03:42:42.303" Score="1" ViewCount="" Body="&lt;p&gt;I think arduino has 20 I/O? So you don't need any extra expander chips if all you need is 16 switches. It may still be a good idea to use the expander chips, in case you want to add something in the future, or a LCD display or status LEDs, or input buttons etc.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-08-16T03:42:42.303" CommentCount="1" />
  <row Id="4036" PostTypeId="2" ParentId="4030" CreationDate="2010-08-16T07:42:51.650" Score="1" ViewCount="" Body="&lt;p&gt;Are the inputs of the controller in question compatible with TTL?  If so (and they likely are) then the arduino is a perfect fit.  If they are not, for instance if they want a 12 volt level to switch on, or if the switches use some non-dc signal, then you will need some sort of relay setup.&lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2010-08-16T07:42:51.650" CommentCount="1" />
  <row Id="4040" PostTypeId="2" ParentId="3973" CreationDate="2010-08-16T14:03:23.567" Score="0" ViewCount="" Body="&lt;p&gt;I did this project with 10mm LEDs in a 2 inch grid in a wood frame. I used an ATtiny2313 to drive the cathodes of 8 LEDs at one time, four transistors switch between the columns of anodes, and the chip runs off its internal oscillator at 8MHz. A MAX2313 drives the serial port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://fontstruct.fontshop.com/fontstructions/show/fourwide&quot; rel=&quot;nofollow&quot;&gt;A special 4-pixel wide font&lt;/a&gt; fits on this very low resolution display. An attached computer sends 32-byte frames (8 bits of brightness per LED) over a serial port. Scrolling text at this resolution and size was rather unsatisfying so instead I flash each letter of the message.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The code is at &lt;a href=&quot;http://code.google.com/p/pwmsign/wiki/Home&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/pwmsign/wiki/Home&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-08-16T14:03:23.567" />
  <row Id="4041" PostTypeId="2" ParentId="4029" CreationDate="2010-08-16T15:38:16.997" Score="0" ViewCount="" Body="&lt;p&gt;I haven't really used processing but I have used C and I don't understand how you're getting away with having that&lt;code&gt;char byte = Serial.read();&lt;/code&gt; in the middle of the function.  All variables should be defined at the start of the function and then used.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-08-16T15:38:16.997" CommentCount="1" />
  <row Id="4042" PostTypeId="1" AcceptedAnswerId="4045" CreationDate="2010-08-16T17:13:24.057" Score="5" ViewCount="171" Body="&lt;p&gt;Can someone explain to me / point me to a good explanation of the theory behind an electronic oscillator? The Wikipedia entry explains &lt;em&gt;what&lt;/em&gt;, but not &lt;em&gt;how&lt;/em&gt;, which is what I need to know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TIA.&lt;/p&gt;&#xA;" OwnerUserId="989" LastActivityDate="2010-11-04T01:42:36.657" Title="Grokking oscillators" Tags="&lt;oscillator&gt;&lt;theory&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="3" />
  <row Id="4045" PostTypeId="2" ParentId="4042" CreationDate="2010-08-16T21:58:55.650" Score="3" ViewCount="" Body="&lt;p&gt;Oscillators are just amplifiers with feedback greater than or equal to one, at the frequency of oscillation, so you can generally analyze a given oscillator circuit as an amplifier with a feedback network. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There may be a few components for biasing active element(s), or compensating for the effects of changes in temperature on the circuit elements, but at the heart of it, some active device amplifies, while a certain other components form a feedback path. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The amplifier aspect of an oscillator circuit will generally be capable of over-unity amplification across a relatively broad band of frequencies, and it's mainly the feedback network that will control the frequency of oscillation within that band, so you will almost always find reactive elements in the feedback network, almost always involving capacitors, and sometimes inductors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even the classic two-transistor, two-resistor, two-capacitor multivibrator can be viewed as an amplifier with feedback; you have two stages, each of which has high gain and produces 180 degree phase shift, but with the two stages together, the resulting phase shift is zero.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-08-16T21:58:55.650" CommentCount="1" />
  <row Id="4046" PostTypeId="1" CreationDate="2010-08-16T23:32:20.127" Score="2" ViewCount="329" Body="&lt;p&gt;I'm looking for an easy way to get in between of a HID USB communication.&#xA;Can it work by multiplexing a single usb port on an AVR?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="752" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-08-17T19:08:41.730" LastActivityDate="2010-08-17T19:20:24.657" Title="Any ideas on how to implement a USB man in the middle circuit?" Tags="&lt;usb&gt;&lt;multiplexing&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="4048" PostTypeId="2" ParentId="4046" CreationDate="2010-08-17T01:32:12.270" Score="3" ViewCount="" Body="&lt;p&gt;Sorry, but it's definitely not that easy. USB is pretty timing sensitive, and I'm pretty sure that you can't relay an enumeration request between two USB ports without timing issues killing it off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on what you really are after, there are free usb sniffer tools you can use. sniffusb and usbsnoop come immediately to mind.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-08-17T01:32:12.270" CommentCount="3" />
  <row Id="4049" PostTypeId="2" ParentId="4042" CreationDate="2010-08-17T03:54:33.787" Score="2" ViewCount="" Body="&lt;p&gt;Some people find the description at &lt;a href=&quot;http://en.wikibooks.org/wiki/Circuit_Idea/How_do_We_Create_Sinusoidal_Oscillations%3F&quot; rel=&quot;nofollow&quot;&gt;&quot;Circuit Idea/How do We Create Sinusoidal Oscillations?&quot;&lt;/a&gt; useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Others like &lt;a href=&quot;http://en.wikibooks.org/wiki/Circuit_Idea/ring_oscillators&quot; rel=&quot;nofollow&quot;&gt;Circuit Idea/ring oscillators&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have figured out what is missing from these explanations, &lt;em&gt;please&lt;/em&gt; add a few words about that missing piece -- it's a wiki.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-17T03:54:33.787" CommunityOwnedDate="2010-08-17T03:54:33.787" />
  <row Id="4050" PostTypeId="1" CreationDate="2010-08-17T05:37:28.760" Score="1" ViewCount="958" Body="&lt;p&gt;I have problems with Arduino Mega drivers on Windows 7.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've downloaded  newest driver from &lt;a href=&quot;http://www.ftdichip.com/FTDrivers.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.ftdichip.com/FTDrivers.htm&lt;/a&gt;, but i cant install driver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've installed  USB Serial Converted, but USB Serial Port dosen't work (i tried to reinstal driver, but it don't bring any effect).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used this below instruction:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;In Windows 7 the FTDI driver is plug and play (windows should identify that it has been plugged in and&#xA;can automatically download/install the correct driver)&lt;/li&gt;&#xA;&lt;li&gt;If this doesn't work download the FTDI drivers from: &lt;a href=&quot;http://www.ftdichip.com/Drivers/VCP.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.ftdichip.com/Drivers/VCP.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Make sure you're using the latest JRE in 32-bit (even if you run 64-bit)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;.... and it doesn't bring any effect too. Could you help me?&lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-02T07:44:55.533" LastActivityDate="2011-02-02T07:44:55.533" Title="Arduino and Windows 7" Tags="&lt;arduino&gt;&lt;windows&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="4051" PostTypeId="2" ParentId="4050" CreationDate="2010-08-17T08:51:57.150" Score="1" ViewCount="" Body="&lt;p&gt;I don't have any problems using a Duemilanove with Win7 x64.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try the Arduino forum.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-17T08:51:57.150" />
  <row Id="4052" PostTypeId="2" ParentId="4046" CreationDate="2010-08-17T13:38:05.000" Score="1" ViewCount="" Body="&lt;p&gt;How about implementing a usb host to talk to the usb-device, and implement a usb-client to talk to the usb-host.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then your mcu sits there in the middle and forwards the hight level commands, &#xA;but keeps the low-level stuff locally (things like enumeration).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But it is not a easy thing to do.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-08-17T13:38:05.000" />
  <row Id="4053" PostTypeId="2" ParentId="4046" CreationDate="2010-08-17T16:47:13.423" Score="1" ViewCount="" Body="&lt;p&gt;USB sniffing is hard. There are plenty of commercial tools to do it, or you can dump everything going through the PC end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really want to look at the USB signals have a look at:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.usbmadesimple.co.uk/ums_6.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.usbmadesimple.co.uk/ums_6.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://embeddeddsp.embedded.com/story/OEG20020321S0027&quot; rel=&quot;nofollow&quot;&gt;http://embeddeddsp.embedded.com/story/OEG20020321S0027&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-17T16:47:13.423" />
  <row Id="4054" PostTypeId="2" ParentId="4050" CreationDate="2010-08-17T17:10:48.957" Score="0" ViewCount="" Body="&lt;p&gt;I've used FTDI USB-serial chips on Win 7 x64 before, but not Arduino itself. I didn't need to install any drivers. So don't worry if the driver doesn't install.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does the serial port show up in the list of available ports after you connect the USB cable?&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-08-17T17:10:48.957" />
  <row Id="4055" PostTypeId="2" ParentId="4050" CreationDate="2010-08-17T17:13:38.347" Score="1" ViewCount="" Body="&lt;p&gt;You most likely don't need any drivers at all to use the arduino.  FTDI chips appear as vanilla serial devices on the USB chain, and should appear as a regular COM port after being connected.  Sometimes the numbered port is quite high, and might not be obvious which one it is.  Go to the hardware/device manager and find the FTDI device in the list of USB devices, then check its properties to determine which COM port it landed on.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also need to close and reopen the arduino IDE to see the arduino appear in the list of serial ports.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt; Alternately:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Arduinos have a jumper near the power plug which selects where the arduino receives power, in one position, it receives power over the USB connection, and in the other position it receives power from an external 9volt source.  make sure the jumper is set to receive power from USB.&lt;/p&gt;&#xA;" OwnerUserId="1325" LastEditorUserId="1325" LastEditorDisplayName="" LastEditDate="2010-08-18T06:48:44.350" LastActivityDate="2010-08-18T06:48:44.350" />
  <row Id="4056" PostTypeId="2" ParentId="1886" CreationDate="2010-08-17T17:29:14.273" Score="7" ViewCount="" Body="&lt;p&gt;It is not possible to make an electronic logic gate that functions even when its current is always zero.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, it is possible to arrange CMOS electronic logic gates in such a way that the energy capacitively stored on the transistor gates is later returned to the power supply, so it is using almost zero net power. Once the system is powered up and all the bypass capacitors are fully charged, those logic gates can do an arbitrarily large amount of computation while pulling nearly zero current from the battery. Such arrangements are often called non-destructive computing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, there are many ways to build logically equivalent computational structures without any electronic devices. Such non-electronic logic gates naturally use zero current, although nearly all of them require much more power to operate than their logically equivalent electronic logic gate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;non-electronic computing&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some non-electronic logic gates are listed in the article&#xA;&lt;a href=&quot;http://www.newscientist.com/article/dn13656&quot; rel=&quot;nofollow&quot;&gt;&quot;Ten weirdest computers&quot;&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few more non-electronic logic gates that are apparently not quite weird enough to make that article:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;David Cary has designed a CPU to be built entirely out of spool valves, and is still pondering whether to power the thing with traditional hydraulic oil pressure, water pressure, or air pressure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/fluidic_logic&quot; rel=&quot;nofollow&quot;&gt;fluidic logic&lt;/a&gt; gates have no moving parts, if you don't count the fluid moving through them as a &quot;part&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Is there an article on Wikipedia or some other wiki with a list of ways to implement the abstract concept of a &quot;logic gate&quot; ?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;non-destructive computing&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Non-destructive computing, also called reversible computing, Charge Recovery Logic, or Adiabatic Logic, involves gates that use almost zero power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When a computational system erases a bit of information, it must dissipate a theoretical minimum energy of  kT ln(2) -- the von Neumann-Landauer limit -- where k is Boltzmann's constant and T is the temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most logic gates erase a bit of information for every logic operation.&#xA;However, there are a few logic gates that preserve every bit.&#xA;In theory these non-destructive logic gates could use far less power than the theoretical minimum power of bit-destructive logic gates.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.zyvex.com/nanotech/reversible.html&quot; rel=&quot;nofollow&quot;&gt;&quot;Reversible Logic&quot;&lt;/a&gt; by Ralph C. Merkle at Zyvex&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RevComp - The &lt;a href=&quot;http://www.cise.ufl.edu/research/revcomp/&quot; rel=&quot;nofollow&quot;&gt;Reversible and Quantum Computing Research Group&lt;/a&gt;&#xA;has some nice photos of their reversible CPU.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-17T17:29:14.273" CommentCount="6" />
  <row Id="4057" PostTypeId="2" ParentId="4046" CreationDate="2010-08-17T19:20:24.657" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.totalphase.com/products/beagle_usb12/&quot; rel=&quot;nofollow&quot;&gt;$400 solution&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.linux-usb.org/USBMon/dissertation/USB-dissertation.htm&quot; rel=&quot;nofollow&quot;&gt;Free (Linux) Solution&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-08-17T19:20:24.657" CommentCount="1" />
  <row Id="4058" PostTypeId="2" ParentId="4050" CreationDate="2010-08-17T19:37:41.930" Score="0" ViewCount="" Body="&lt;p&gt;Have just completed a fresh Windows 7 Professional x64 installation last month, Windows took care of everything when I plugged in the FTDI cable for the first time. Follow TokenMacGuy's suggestions as well. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-08-17T19:37:41.930" />
  <row Id="4059" PostTypeId="1" CreationDate="2010-08-17T20:42:51.330" Score="1" ViewCount="258" Body="&lt;p&gt;I have 12 of &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9590&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; LEDs and a 5v Arduino Pro Mini - like &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9218&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; one. This is going to be a very small project I need the smallest power source possible for this. Would I be able to run this with a few coin cell batteries?&lt;/p&gt;&#xA;" LastActivityDate="2010-08-18T02:55:41.987" Title="5V Arduino and 12 led's power options." Tags="&lt;arduino&gt;" AnswerCount="2" />
  <row Id="4060" PostTypeId="1" AcceptedAnswerId="4099" CreationDate="2010-08-17T20:53:07.910" Score="4" ViewCount="806" Body="&lt;p&gt;What are the simplest, cheapest, smallest ways to make a momentary switch control a toggling output or latching momentary switch?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In other words, the output is continuously low, and when you momentarily press the button/tact switch, the output changes to high, and then when you press it again, it switches back to low.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T21:03:04.147" LastActivityDate="2010-09-30T03:09:35.520" Title="Make a momentary switch control a toggle" Tags="&lt;momentary&gt;&lt;logic&gt;&lt;switch&gt;&lt;flipflop&gt;" AnswerCount="7" CommentCount="3" />
  <row Id="4061" PostTypeId="2" ParentId="4060" CreationDate="2010-08-17T20:55:16.033" Score="1" ViewCount="" Body="&lt;p&gt;One possible method:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use an RC to debounce the switch&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.all-electric.com/schematic/debounce.htm&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://www.all-electric.com/schematic/dbounce1.gif&quot; alt=&quot;RC network connected to momentary switch to debounce&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and then feed it into a D flip-flop with the output feeding back to the input to implement a T flip flop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://forum.hackedgadgets.com/viewtopic.php?t=1667&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i220.photobucket.com/albums/dd207/Project_Nightmare/untitled2-1.jpg&quot; alt=&quot;D flip-flop configured as toggle flip-flop&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The D flip-flop needs to be positive edge-triggered only, and needs an inverted output.  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The 8-pin &lt;a href=&quot;http://www.fairchildsemi.com/pf/NC/NC7SZ74.html&quot; rel=&quot;nofollow&quot;&gt;NC7SZ74&lt;/a&gt; should work, is very small, and costs $0.12 in quantity.&lt;/li&gt;&#xA;&lt;li&gt;The 74HC74 is a dual D flip-flop with 14 pins for $0.05.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Are there any issues with this?  The switch would need to be held down for a short period of time for the rise time to trigger the clock input, which is probably good.  If you hold down the button, it will only trigger once, which is good.  Is there a better way to debounce in the feedback loop or something instead?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-17T21:32:32.447" LastActivityDate="2010-08-17T21:32:32.447" CommentCount="2" />
  <row Id="4062" PostTypeId="2" ParentId="4059" CreationDate="2010-08-17T21:08:09.690" Score="1" ViewCount="" Body="&lt;p&gt;With enough coin cells, certainly. But, if you want the batteries to last you may need to save some power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might try a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=341&quot; rel=&quot;nofollow&quot;&gt;small LiPo battery&lt;/a&gt;. But, you'll also need a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=726&quot; rel=&quot;nofollow&quot;&gt;charger&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may want to buy some low power LEDs. That could cut the power budget.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some variants of the &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardProMini&quot; rel=&quot;nofollow&quot;&gt;ArduinoProMini&lt;/a&gt; can run down at 3.3V which would help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could put the Arduino's AVR CPU to sleep to save on batteries while it waits for a button press or it idles &lt;a href=&quot;http://interface.khm.de/index.php/lab/experiments/sleep_watchdog_battery/&quot; rel=&quot;nofollow&quot;&gt;here's a tutorial&lt;/a&gt;. But, with all those LEDs on it'd be slim pickin's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps you don't care how long the battery lasts, but you only want to use one cell?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you could get away with under 100mA, you could use a single 1.5V cell and a DC to DC step up like &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8248&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;. But at 20mA per LED, that will be a problem.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-17T21:08:09.690" CommentCount="2" />
  <row Id="4063" PostTypeId="2" ParentId="4060" CreationDate="2010-08-17T21:14:33.513" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.daycounter.com/Circuits/Latching-Momentary-Switch/Latching-Momentary-Switch.phtml&quot; rel=&quot;nofollow&quot;&gt;This circuit&lt;/a&gt; (also described &lt;a href=&quot;http://www.edn.com/contents/images/102804di.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) is very cheap, but is more complex and takes up some space with all the components.  If transistors are like $0.02 in large quantities, it would be maybe $0.10 total?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.daycounter.com/Circuits/Latching-Momentary-Switch/Latching-Momentary-Switch.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-18T13:52:41.550" LastActivityDate="2010-08-18T13:52:41.550" CommentCount="3" />
  <row Id="4064" PostTypeId="1" CreationDate="2010-08-17T21:16:17.953" Score="3" ViewCount="120" Body="&lt;p&gt;I have a problem: I've got &lt;a href=&quot;http://www.ovt.com/products/sensor.php?id=49&quot; rel=&quot;nofollow&quot;&gt;five tiny CMOS image sensors&lt;/a&gt; (2mm x 2mm), each in a small space (about 10mm x 15mm). They take a clock signal in, and output an analog signal, requiring an 8MSPS ADC each. Somehow I need to get the image data into a PC. This is difficult because of the tight space constraints.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally, I'd like to locally sample the data with a DSP, and video-encode it, at which point, it will be relatively easy to get into the PC via an EtherCAT bus which is close by.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is, how on earth can I get 8MSPS into a tiny DSP in a tiny space?&#xA;I know there are some pretty small DSPs, but:&#xA;Are there any tiny DSPs with 8MSPS ADCs?&#xA;Are there any tiny 8MSPS ADCs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have looked hard, but I cannot find any. Sad&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many thanks&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hugo Elias &lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2010-08-18T05:30:07.193" Title="Tiny 8MSPS DSPs ?" Tags="&lt;dsp&gt;&lt;adc&gt;&lt;cmos&gt;&lt;camera&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="4066" PostTypeId="2" ParentId="4064" CreationDate="2010-08-17T21:38:27.027" Score="1" ViewCount="" Body="&lt;p&gt;How about &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tms320c2812.html&quot; rel=&quot;nofollow&quot;&gt;TI's C2000 microcontrollers&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;80ns sample rate 12.5 MSPS. 1cm^2 BGA package.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-17T21:38:27.027" CommentCount="1" />
  <row Id="4067" PostTypeId="2" ParentId="4064" CreationDate="2010-08-17T22:50:45.723" Score="0" ViewCount="" Body="&lt;p&gt;How about using a dedicated video processor in combination with a small microcontroller? (You might be able to fit a tiny double-sided PCB in there?)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A device like the vsp2582 takes in 12-bit resolution samples at up to 36 MHz and outputs a 12-bit parallel bus. Tiny at 6.3 mm square.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The AD9945 is similar, but 40 MHz and only 5 mm square.  (Both TI and AD have other models as well.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm sure that you can find any number of small microcontrollers that can read 12 input pins at high speed and process them as you see fit.&lt;/p&gt;&#xA;" OwnerUserId="484" LastEditorUserId="484" LastEditorDisplayName="" LastEditDate="2010-08-17T23:03:01.640" LastActivityDate="2010-08-17T23:03:01.640" />
  <row Id="4068" PostTypeId="2" ParentId="4064" CreationDate="2010-08-17T23:26:42.733" Score="1" ViewCount="" Body="&lt;p&gt;your not going to fit that sensor and a DSP in that amount of space no matter what you do, even if you fit the IC's in that space you've not considered any of the required external circuitry.  decoupling caps probably taking the most space, as well as a clock source, regulators, any analog preprocessing needed before ADC conversion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Better options:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transmit the analog signal carefully to an external processing location, as close as possible and with care to maintain signal quality.  I recommend converting the analog signal to differential for transmitting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Identify a CMOS sensor with digital output (on board ADC) and again transmit to a nearby processing location.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your processing location needs to convert to some format to get it to a PC, not to mention the interface circuitry needed for etherCAT or whatever you wish to transmit over.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-08-17T23:26:42.733" CommentCount="1" />
  <row Id="4069" PostTypeId="2" ParentId="1886" CreationDate="2010-08-17T23:47:12.800" Score="1" ViewCount="" Body="&lt;p&gt;If you &lt;a href=&quot;http://www.sciencedaily.com/releases/2006/02/060223084147.htm&quot; rel=&quot;nofollow&quot;&gt;don't have to run the program to get the result&lt;/a&gt;, that would seem like a step in the direction of computing something for nothing, though their apparatus must have been dissipating some power.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-08-17T23:47:12.800" CommentCount="1" />
  <row Id="4070" PostTypeId="2" ParentId="4059" CreationDate="2010-08-18T02:55:41.987" Score="2" ViewCount="" Body="&lt;p&gt;There are a few different calculations you can do that will help figure this out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Energy consumption&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first is how much power you'll need to run the system. Each LED has a voltage drop of 2.0 V. Assuming you run the LEDs at their maximum current (20 mA), they'll each use 2.0 V * 0.020 A = 0.040 W. For 12 LEDs, that's 480 mW, assuming the rest of your system is perfectly efficient. In an hour, you would use 480 mWh, or 0.480 Wh.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a first estimate, let's say your system will be only 50% efficient, so you need 2 * 0.480 Wh (roughly 1 Wh) to run for an hour. (You can probably do better, but we'll get to that.) A &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=337&quot; rel=&quot;nofollow&quot;&gt;CR1225 coin cell&lt;/a&gt; is a 3 V battery rated for 47 mAh. That's the same as 3 V * 0.047 Ah = 0.141 Wh. That's about 1/7th of what you need, so your LEDs will last around 1/7th of an hour, i.e. 8 or 9 minutes, with one CR1225 coin cell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Efficiency&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you do better than just guessing 50% efficiency? Sure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It depends on how you wire the LEDs and what current-limiting resistors you use. You could make 6 strings of 2 LEDs each and run them off of a 6 V pack made from two coin cells in series. Each string would have a 4 V drop, so you'd need to drop the remaining 6 - 4 = 2 V over a resistor. At 20 mA per string, that's a 2 V / 0.020 A = 100 ohm resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this case, 1/3 of your power would be dissipated in the resistors (since 2 V is 1/3 of 6 V), so your efficiency would be 66%.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might try 4 strings of 3 LEDs with no ballast resistors, but I suspect that their brightness would drop off quickly as the battery voltage sagged. Your efficiency would be 100%, but the brightness would suffer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also try running off of the 5 V supply you mentioned; with the right resistor, you could hit 80% efficiency.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-08-18T02:55:41.987" CommentCount="6" />
  <row Id="4071" PostTypeId="2" ParentId="4060" CreationDate="2010-08-18T04:03:01.657" Score="2" ViewCount="" Body="&lt;p&gt;Or you could do it with a single tiny 6-pin microcontroller and no other components. It might cost a tiny bit more, but it's simpler and takes up less space. Debouncing a switch in software is simple, then it's just a manner of storing a boolean if the output should be high or low. The smallest version of this mcu comes in a 2mm x 2mm surface mount package. In large quantities it might be $0.50.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://davr.org/uploads/toggle.png&quot; alt=&quot;toggle schematic&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-08-18T04:03:01.657" CommentCount="5" />
  <row Id="4072" PostTypeId="1" AcceptedAnswerId="4091" CreationDate="2010-08-18T04:45:47.297" Score="3" ViewCount="184" Body="&lt;p&gt;I have a project where my power supplies are giving me a bit of a headache. I have three voltage regulators that I am trying to run from a single bench power supply. There are two 3.3V regulators, and one 12V regulator. The current draw for the 12V regulator is up to 500 mA, and each 3.3V regulator peaks at 150 mA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I hook up about 14V to the inputs of these regulators, the 3.3V regulators start to cook. Doing the math, that's about 1.7W of power dissipation for each of the 3.3V regulators. They're in a TO-220 package pointing straight up, and they got too hot to touch. I was able to throw a random heatsink I found on the tab and cool things down, but the top of the heatsink was about 2.5 inches high - very flimsy and cumbersome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really don't want to sacrifice the single power supply input, and I also really don't want to go to an on-board switching supply for either the 12V or 3.3V supplies. &#xA;What are some passive package+? solutions for dissipating up to 2.0W of heat that are physically secure and low profile (shorter than 1 inch)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&#xA;My reasons for not wanting a switching supply are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;I don't want to deal with switching noise in the analog parts of my design&lt;/li&gt;&#xA;&lt;li&gt;I'm less comfortable with designing a switching regulator than using a linear regulator&lt;/li&gt;&#xA;&lt;li&gt;The PCB that I'm working on is big and expensive. I don't have the time/budget to &quot;try out&quot; a regulator. A linear regulator with enhanced heat dissipation seems a lot safer way to avoid making coasters than a switch mode regulator.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-08-18T16:48:12.277" LastActivityDate="2010-08-18T23:13:46.883" Title="Low Profile Power Dissipation" Tags="&lt;heatsink&gt;&lt;voltage-regulator&gt;&lt;pcb&gt;" AnswerCount="4" />
  <row Id="4073" PostTypeId="2" ParentId="4064" CreationDate="2010-08-18T05:30:07.193" Score="0" ViewCount="" Body="&lt;p&gt;Hearing &quot;tiny&quot; and &quot;adc&quot;, I'd think of &lt;a href=&quot;http://www.linear.com/pc/viewCategory.jsp?navId=C1001&quot; rel=&quot;nofollow&quot;&gt;Linear&lt;/a&gt; first. You might want to look through their stuff.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-08-18T05:30:07.193" />
  <row Id="4074" PostTypeId="2" ParentId="4072" CreationDate="2010-08-18T07:03:30.217" Score="5" ViewCount="" Body="&lt;p&gt;voltage regulators come in two types, linear and switch mode.  linear regulators work well when the voltage in is near the voltage out, but rather poorly if the voltage in is higher than the voltage out.  What you need is a switch mode regulator.  A few minutes on digikey suggests that a LM2574 will do the job.  The down side of using such a regulator is that they require a couple of additional discrete components (a handfull of capacitors, a schottky diode and an inductor, in the case of the lm2574) to work, but they dissipate basically no heat.&lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2010-08-18T07:03:30.217" CommentCount="2" />
  <row Id="4075" PostTypeId="2" ParentId="4060" CreationDate="2010-08-18T11:39:19.287" Score="0" ViewCount="" Body="&lt;p&gt;Could you not just do it in software? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will the button be an input on a programmable device, or do you need to do the toggle in the hardware realm?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By storing a button state in memory it's quite easy to use a momentary switch as a toggle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;boolean buttonState = flase; // store for toggle state, flase = off true = on&#xA;&#xA;if(yourButton == HIGH &amp;amp;&amp;amp; buttonState == false) // if button is pressed and toggled off&#xA;{&#xA;     Serial.println(&quot;Button Toggled On&quot;); // do something while button is on&#xA;&#xA;     buttonState = true // set button state to on&#xA;}&#xA;&#xA;if(yourButton == HIGH &amp;amp;&amp;amp; buttonState == true) // if button is pressed and toggled on&#xA;{&#xA;     Serial.println(&quot;Button Toggled Off&quot;);  // do something else while button is off&#xA;&#xA;     buttonState = false // set button state to off&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Sorry if this is off the mark, obviously this answer depends on you using an MCU or programmable chip.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-08-18T11:39:19.287" CommentCount="1" />
  <row Id="4076" PostTypeId="2" ParentId="4072" CreationDate="2010-08-18T12:42:20.340" Score="4" ViewCount="" Body="&lt;p&gt;As you say that you would rather have a heat dissipation/energy wastage problem than use a switch mode power supply you are left with only one solution - you must bolt your regulators onto a sufficiently large piece of metal.  I used to make folded aluminium boxes for my projects and the usual solution was to bolt the regulators onto the case, with suitable insulation washers and mica sheets, and have flying leads from the PCB to the regulator devices.  For higher dissipation I would add a heatsink externally mounted on the box.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nowadays switch mode regulators are much better understood and characterised.  There are any number of application notes and design guides that will help you to get a good, stable regulator cheaply and without the horrible power wastage that goes with a linear regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Throwing away 3.5W to supply about 1W on the 3.3V rails may be OK for a hobby project but would not be acceptable for a commercial product.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-08-18T12:42:20.340" />
  <row Id="4077" PostTypeId="2" ParentId="614" CreationDate="2010-08-18T13:02:40.710" Score="0" ViewCount="" Body="&lt;p&gt;Texas &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tl852.html&quot; rel=&quot;nofollow&quot;&gt;TL852&lt;/a&gt; and &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tl851.html&quot; rel=&quot;nofollow&quot;&gt;TL851&lt;/a&gt; are two devices that you can use to make an ultrasonic range finder.  See their website for datasheets&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-08-18T13:02:40.710" />
  <row Id="4078" PostTypeId="2" ParentId="4072" CreationDate="2010-08-18T13:26:46.480" Score="1" ViewCount="" Body="&lt;p&gt;You don't mention why you are against a switching supply solution... Is it complexity you're concerned about? There are dozens of very simple switchmode regulators out there. They are inexpensive and much more efficient than the linear regulators.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CUI and Recom both make 3-terminal switchmode regulators which are drop-in replacements for the old 78xx series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're looking for something cheaper (you'll need to supply a diode and inductor though), look at National's LM2575 series of simple switchers, Linear has dozens of varieties, TI... There are tons of app notes to help figure out inductor sizing.  There are very few reasons to need a linear regulator these days.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-08-18T13:26:46.480" CommentCount="1" />
  <row Id="4079" PostTypeId="2" ParentId="4060" CreationDate="2010-08-18T15:38:10.737" Score="0" ViewCount="" Body="&lt;p&gt;I know it's kinda an &quot;indirect&quot; way of doing it, but you can get a hall effect sensor like sparkfun has:&#xA;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9312&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9312&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and just use a magnet, I found out (the hard way) that this particular hall effect is latching, so it won't work for what I need it to, but looks like it could in theory work for what you're looking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just plugged it into a breadboard, I think I may have used a resistor (It's been probably a month so I'm a little fuzzy on the details), and when I move the magnet close (momentary) it closes the sensor and there you go.&lt;/p&gt;&#xA;" OwnerUserId="982" LastActivityDate="2010-08-18T15:38:10.737" CommentCount="2" />
  <row Id="4080" PostTypeId="1" AcceptedAnswerId="4082" CreationDate="2010-08-18T16:57:58.783" Score="7" ViewCount="659" Body="&lt;p&gt;Ok so I have a project I am wanting to create but it would require a bit of processing power. The most powerful thing I've seen yet has been the &lt;a href=&quot;http://www.mouser.com/ProductDetail/Atmel/ATMEGA1284P-PU/?qs=sGAEpiMZZMtVoztFdqDXO3QpeG9FlGm9&quot; rel=&quot;nofollow&quot;&gt;ATMega1284P&lt;/a&gt;. Really by power I mean I need Program Memory and RAM, not raw MIPs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there anything else out there that is hobbyist friendly? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;By hobbyist friendly I mean not having to have any expensive machines to solder it (rework stations etc). Also of course being capable of buying just a couple of them without spending an arm and a leg. And of course having freely available compilers and other software tools. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My project is to build a small (portable) calculator with simple graphing capabilities and possibly some limited programming capabilities. &lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="708" LastEditorDisplayName="" LastEditDate="2010-08-18T22:20:30.440" LastActivityDate="2010-12-14T14:21:04.637" Title="Are there any powerful processors that exist that are hobbyist friendly?" Tags="&lt;microcontroller&gt;" AnswerCount="9" CommentCount="1" FavoriteCount="1" />
  <row Id="4081" PostTypeId="2" ParentId="4080" CreationDate="2010-08-18T17:23:34.630" Score="3" ViewCount="" Body="&lt;p&gt;Depending on the specifics of your project, I might suggest &lt;a href=&quot;http://www.nslu2-linux.org/&quot; rel=&quot;nofollow&quot;&gt;the NSLU2 &quot;Slug&quot;&lt;/a&gt; which is an ARM processor, clocking in at 133 or 266 Mhz. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That gives you a very small (embedded) board and some USB ports and even one or two serial ports (UART plus MAX232). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could write your app to run in Linux, compile it with GCC, etc. &lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-08-18T17:23:34.630" CommentCount="1" />
  <row Id="4082" PostTypeId="2" ParentId="4080" CreationDate="2010-08-18T17:42:37.867" Score="8" ViewCount="" Body="&lt;p&gt;Low-cost ARM boards like the &lt;a href=&quot;http://ics.nxp.com/lpcxpresso/&quot; rel=&quot;nofollow&quot;&gt;LPCXpresso&lt;/a&gt; and &lt;a href=&quot;http://mbed.org/&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt; are easy to use, and will give you a lot more performance.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-18T17:42:37.867" CommentCount="1" />
  <row Id="4083" PostTypeId="2" ParentId="2381" CreationDate="2010-08-18T17:52:31.027" Score="1" ViewCount="" Body="&lt;p&gt;While this is resurrected due to Endolith's retagging, I want to clarify the reason that Pin 2 connects to the shield of the jack, but only when there's no plug inserted.  You can do one of three things to wire this correctly: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Only connect to pin 1.&lt;/li&gt;&#xA;&lt;li&gt;Connect pins 1 and 2 together.&lt;/li&gt;&#xA;&lt;li&gt;Connect pin 1 to your circuit's ground node, and connect pin 2 to another power connector (Black binding post for a banana jack, or battery ground terminal, for example.) Then, you can connect pin 3 to a red binding post or battery positive terminal, and have 2 power supplies without worrying about output contention. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Method 3 is the reason that these plugs are designed the way they are.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-18T17:52:31.027" />
  <row Id="4084" PostTypeId="1" AcceptedAnswerId="4087" CreationDate="2010-08-18T18:58:56.750" Score="3" ViewCount="132" Body="&lt;p&gt;I bought one of these, and forgot to get the connector.&#xA;&lt;a href=&quot;http://www.sparkfun.com/commerce/categories.php?c=139&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/categories.php?c=139&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I need to buy a hall effect sensor and was thinking/looking at mouser, Does anyone know the partnumber of a cable/connector similar to this: &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8733&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=8733&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OR how I would go about figuring out said connector p/n at other places too?&lt;/p&gt;&#xA;" OwnerUserId="982" LastActivityDate="2010-08-18T19:53:53.683" Title="IR Connector for Sharp" Tags="&lt;ir&gt;&lt;connector&gt;" AnswerCount="2" />
  <row Id="4085" PostTypeId="2" ParentId="4080" CreationDate="2010-08-18T19:26:29.937" Score="1" ViewCount="" Body="&lt;p&gt;Depends on your definition of &quot;powerful&quot; of course. Personally I have seen the Propeller processors do some incredible things, and I am partial to most ARM variants, although again, the definition of &quot;powerful&quot; needs to be evaluated. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;32-bit processors are everywhere and come in relatively easy to use packages (leaded PQFP, etc.) What are you trying to do?&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-08-18T19:26:29.937" />
  <row Id="4086" PostTypeId="2" ParentId="4084" CreationDate="2010-08-18T19:52:41.670" Score="0" ViewCount="" Body="&lt;p&gt;I don't know the part number, but I believe those are JST connectors: &lt;a href=&quot;http://www.jst-mfg.com/index_e.php&quot; rel=&quot;nofollow&quot;&gt;http://www.jst-mfg.com/index_e.php&lt;/a&gt; My best guess is the ZH series, but that's really just a guess from the picture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mouser is not a distributor for JST, though they may carry a clone of the connector you're looking for. Digikey does carry JST stuff, including the ZH series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe ask in the Sparkfun IRC channel or forum?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Please post the part number as a comment if you do track it down.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-08-18T19:52:41.670" CommentCount="1" />
  <row Id="4087" PostTypeId="2" ParentId="4084" CreationDate="2010-08-18T19:53:53.683" Score="2" ViewCount="" Body="&lt;p&gt;The connector is made by JST, as the linked page says.  I know from looking at it and using lots of JST connectors that it's PH series connector, but you can also find that by looking at &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9750&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; Sparkfun page, or by (tediously) looking through Digikey and JST catalogs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The plastic part of the connector you linked is called a &quot;housing&quot;, and it holds the crimp terminals that are crimped onto the wire, and which slide over the housing.  That one is part number PHR-3 (PH series, rectangular (1x3), three terminal).  You can get it from Digikey &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=455-1126-ND&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, or from Future Electronics.  &lt;strong&gt;Mouser isn't a JST distributor.&lt;/strong&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you'll definitely need the terminals that go with it.  They're P/N &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=455-1127-1-ND&quot; rel=&quot;nofollow&quot;&gt;SPH-002T-P0.5S&lt;/a&gt; for the 24-30 gauge wire. (You'll also need stranded wire for this.  The picture is nice and big on the Digikey site, but the terminal is TINY.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless you have &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=455-1128-ND&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; $400+ tool, you cannot effectively crimp these terminals.  Note that I've sucessfully crimped these terminals with a PA series crimper, if you happen to have one of those on hand... You need to strip as little insulation as possible (The long tabs grip the insulation and provide strain relief, while the short ones grip the wire), a good hand on your soldering iron, and plenty of flux on both the terminal and the wire.  It can be done.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you need instead is a KR-series connector.  They're IDC style, (Insulation displacement connector) so you don't need to do any crimping.  The datasheet is here:&lt;br&gt;&#xA;&lt;a href=&quot;http://www.jst-mfg.com/product/pdf/eng/eKR.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.jst-mfg.com/product/pdf/eng/eKR.pdf&lt;/a&gt;&lt;br&gt;&#xA;and you'll easily see from the datasheet that what you want has the part number 03KR-6H-P.  Unfortunately, Digikey doesn't keep these on hand.  Finding them is left as an exercise to the reader.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All that being said, I've also used the Sharp IR distance sensors before I had access to the crimp tool at my current place of employment, and simply desoldered the existing connector, soldered on my own wires, and hot-glued the assembly to prevent strain on the wires.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-18T19:53:53.683" CommentCount="5" />
  <row Id="4088" PostTypeId="2" ParentId="4080" CreationDate="2010-08-18T20:02:01.433" Score="4" ViewCount="" Body="&lt;p&gt;Take a look at something in the OMAP family.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://gumstix.com/&quot; rel=&quot;nofollow&quot;&gt;Gumstix&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;Beagleboard&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-08-18T20:02:01.433" CommentCount="7" />
  <row Id="4090" PostTypeId="2" ParentId="4080" CreationDate="2010-08-18T22:26:03.267" Score="1" ViewCount="" Body="&lt;p&gt;Many processors/microcontrollers support external memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, the AVR XMega can support several MiB of external SDRAM for data storage (can't execute from the external bus). (There is a GCC limitation of 16bit pointers for AVR-GCC).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many ARMs have external buses as well: LPC2478, Luminary parts, AT91SAM series.&lt;/p&gt;&#xA;" OwnerUserId="867" LastActivityDate="2010-08-18T22:26:03.267" />
  <row Id="4091" PostTypeId="2" ParentId="4072" CreationDate="2010-08-18T23:01:57.000" Score="4" ViewCount="" Body="&lt;p&gt;If you're stuck using linear regulators, you can put big power resistors in series with the inputs of the regulators to drop the voltage and share some of the heat dissipation.  You're dissipating the same amount of power either way, but it might make it easier to fit on your board or whatever.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're using an LM7833, for instance, and supplying 150 mA, the datasheet says the dropout is 2 V, so the input voltage has to always be above 5.3 V.  From a 14 V supply at 150 mA, this is a &lt;a href=&quot;http://www.wolframalpha.com/input/?i=%2814+V+-+5.3+V%29+%2a+150+mA&quot; rel=&quot;nofollow&quot;&gt;2 W&lt;/a&gt;, &lt;a href=&quot;http://www.wolframalpha.com/input/?i=%2814+V+-+5.3+V%29+%2F+150+mA&quot; rel=&quot;nofollow&quot;&gt;56 Ω&lt;/a&gt; resistor.  The resistor just needs air circulation around it, not a heatsink, and then your regulator only needs a 500 mW heatsink instead.  The highest power dissipated in the regulator will be at the current when resistor and regulator are both dissipating the same power, which in this case is about 95 mA.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-18T23:13:46.883" LastActivityDate="2010-08-18T23:13:46.883" CommentCount="1" />
  <row Id="4092" PostTypeId="2" ParentId="3320" CreationDate="2010-08-19T00:18:50.260" Score="0" ViewCount="" Body="&lt;p&gt;One problem I encountered recently is the varying melting temperature of toner in different brands of laser printers. After some reading, it turns out that recent Brother printers have a much higher melting point (around 400C I think) than other printers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The printer I started out on was a HP LaserJet 1020 and I had problems with getting the toner too hot using an iron, causing the 'smudging' that another post mentions. The solution for me which gave excellent results was to use a hot roll laminator (put the board through 5-10 times) - supposedly the combination of temperature and pressure is the key. Using an iron on a cooler setting should also work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However recently I've switched to using a Brother HL-2142 printer and the laminator was no longer working. Temperature is the problem, so going back to the trusty iron and cranking up the temperature seems to be effective. The blue transfer paper doesn't much like the heat and starts to wrinkle and warp, so I'm going to try the glossy magazine pages that others have mentioned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other tips:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;rub the board until shiny with a plastic scouring pad - the rough surface is supposed to help the toner to adhere. Don't use steel wool as you'll end up contaminating the copper&lt;/li&gt;&#xA;&lt;li&gt;wipe with isopropyl alcohol - avoid finger prints on the board past this point&lt;/li&gt;&#xA;&lt;li&gt;for the laminator method -  affix the paper to the board using a piece of tape at one end only - always feed the board through the laminator tape side first&lt;/li&gt;&#xA;&lt;li&gt;for the iron method, I find that one or two sheets of paper on top of the transfer paper helps (and stops the plastic melting and sticking to the iron in the case of blue transfer paper)&lt;/li&gt;&#xA;&lt;li&gt;cupric chloride is the best etchant as it can be reused again and again after simply bubbling air through the solution - it also etches well at room temperature &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-08-19T00:18:50.260" />
  <row Id="4093" PostTypeId="2" ParentId="952" CreationDate="2010-08-19T09:42:15.747" Score="4" ViewCount="" Body="&lt;p&gt;I'm enjoying The Amp Hour Podcast&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.theamphour.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.theamphour.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From Dave Jones (EEVBlog) and &lt;a href=&quot;http://chiphacker.com/users/404/chris-gammell&quot; rel=&quot;nofollow&quot;&gt;Chris Gammell&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-19T09:42:15.747" CommunityOwnedDate="2010-08-19T09:42:15.747" CommentCount="1" />
  <row Id="4094" PostTypeId="1" CreationDate="2010-08-19T11:44:11.803" Score="4" ViewCount="429" Body="&lt;p&gt;Many times I want my computer to interface old hardware. Such as radio, light switch, etc. This mostly involves pushing pressing and moving various buttons and switches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't want to buy new hardware I want my computer to interface the old hardware I already have.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I thought about it and reached to the conclusion that what I need is a general purpose button-pusher hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need a simple device I can interface by a computer and would be able to push most of the buttons we have in daily accessories, without damaging the button.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any such accessory availible?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(migrated from superuser, where I got no satisfactory answers).&lt;/p&gt;&#xA;" OwnerUserId="1076" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-02T21:39:36.543" LastActivityDate="2010-11-04T15:32:40.110" Title="hardware for pushing buttons" Tags="&lt;button&gt;&lt;mechanical&gt;&lt;actuator&gt;" AnswerCount="8" CommentCount="3" />
  <row Id="4095" PostTypeId="1" CreationDate="2010-08-19T12:42:29.550" Score="0" ViewCount="496" Body="&lt;p&gt;My code is supposed to check a 50Hz signal with AVR ATMEGA32's ADC. It works at 6MHz with an external clock in both real and simulator. But when I use a 12MHz external clock the ADC doesn't work well at all in real and it almost missed the AC signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I use the simulator, it's perfect but in real it's not.. I have set the fuse bit and I turn the ADC on and off before any reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any idea? thx&lt;/p&gt;&#xA;" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-08-19T14:01:08.627" LastActivityDate="2010-08-31T19:48:35.780" Title="ADC problem with ATMEGA32 using external clock more than 8MHz" Tags="&lt;avr&gt;&lt;adc&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="4096" PostTypeId="2" ParentId="4095" CreationDate="2010-08-19T13:15:19.047" Score="3" ViewCount="" Body="&lt;p&gt;You might need to slow down the ADC. The analog to digital converter runs at half the system clock frequency by default so at 6MHz the ADC's input clock is at 3MHz. Setting &lt;code&gt;ADCSRA |= 2&lt;/code&gt; (for the ATmega328, datasheet section 23.9.2, page 265) divides the clock by 4 instead of by 2. 12MHz / 4 = 6MHz / 2 = 3MHz.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-08-19T13:15:19.047" CommentCount="2" />
  <row Id="4097" PostTypeId="2" ParentId="4094" CreationDate="2010-08-19T13:17:34.797" Score="1" ViewCount="" Body="&lt;p&gt;This is an interesting problem. I haven't ever done anything like this, but I too have pondered actuators for physical components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For button pushing, I would probably go with pneumatic (air-powered) actuators; you can easily control the amount of force and you can find them in a wide variety of sizes. Control would be done through solenoid-controlled valves, and all you need is a source of clean and dry compressed air, which is almost never an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Switch flipping is more difficult. My first solution would be to have some kind of a mechanical converter to convert the linear motion of a pair of pneumatic actuators to more of a diagonal motion that switches use, but you'd quickly run into physical size issues. A tiny stepper motor with a similar rotary-to-linear interface over the switch would work and be smaller.  Stepper motors would also work very well for controlling anything that had to be turned (tuning wheels, volume knobs, etc.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a surplus place close to me that had a huge pile of these style of actuators. Now I want to go buy some and play. :-)&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-08-19T13:17:34.797" />
  <row Id="4098" PostTypeId="2" ParentId="4094" CreationDate="2010-08-19T13:28:37.053" Score="0" ViewCount="" Body="&lt;p&gt;For some applications, this might be an easier solution, a relay controlling mains power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=44&amp;amp;products_id=268&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=44&amp;amp;products_id=268&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-19T13:28:37.053" />
  <row Id="4099" PostTypeId="2" ParentId="4060" CreationDate="2010-08-19T14:54:31.373" Score="0" ViewCount="" Body="&lt;p&gt;Here's &lt;a href=&quot;http://forum.allaboutcircuits.com/showthread.php?t=16040&quot; rel=&quot;nofollow&quot;&gt;another alternative&lt;/a&gt; with two inverters and debouncing:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/m4S5p.png&quot; alt=&quot;Two inverters&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For logic output, only the two inverters, RC, and feedback resistor are needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.fairchildsemi.com/pf/NC/NC7WZ14.html&quot; rel=&quot;nofollow&quot;&gt;NC7WZ14&lt;/a&gt; is $0.06 with 2 inverters, small 6-pin package, and Schmitt trigger inputs, though I think this circuit doesn't even need Schmitt inputs because of the RC.  Also it can drive 24 mA, so you could connect the LED directly to it if you're using an LED for whatever reason.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also shown &lt;a href=&quot;http://4.bp.blogspot.com/_Gky8ltNWVFk/ScyB93FOEzI/AAAAAAAAAkA/DUUcJSqP2hA/s1600-h/Relay+Toggle+Circuit+05.gif&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://tech-electronic.blogspot.com/2009/07/all-circuits-and-projects-we-describe.html&quot; rel=&quot;nofollow&quot;&gt;here as a toggle touch switch&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the feedback resistor has to be much smaller than the center resistor to prevent it from oscillating if you hold down the button, because the low-impedance connection to the output will prevent the capacitor from charging to the middle voltage until you let go.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-09-30T03:09:35.520" LastActivityDate="2010-09-30T03:09:35.520" CommentCount="2" />
  <row Id="4100" PostTypeId="2" ParentId="4060" CreationDate="2010-08-19T16:11:20.447" Score="0" ViewCount="" Body="&lt;p&gt;The easiest alternative is to use an alternating pushbutton switch. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you ignore the fact that it latches at different positions, it's almost exactly like a momentary switch. I understand that this isn't the spirit of the question, but it is a simple and compact solution requiring no software and no external hardware.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-19T16:11:20.447" />
  <row Id="4101" PostTypeId="2" ParentId="4094" CreationDate="2010-08-19T16:14:02.250" Score="4" ViewCount="" Body="&lt;p&gt;You could use a variety of actuation devices. First off is the humble solenoid - basically a coil-gun where the slug can't leave the coil. They can exert a lot of force, but can't be controlled in terms of speed and give a nice &quot;whack&quot; sound.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A servo with a rocker arm would work (mechanically more complex). Its capability of pushing buttons would be slower, but more controlled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A stepper motor or a free-running servo could accomplish rotary dials.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A linear actuator (stepper motor on a screw-shaft) could accomplish sliding actions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most custom portion would be the mechanical interface. I suggest hunting around &lt;a href=&quot;http://smallparts.com&quot; rel=&quot;nofollow&quot;&gt;http://smallparts.com&lt;/a&gt; and &lt;a href=&quot;http://mcmaster.com&quot; rel=&quot;nofollow&quot;&gt;http://mcmaster.com&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could probably find ready-made interface electronics (motor controllers over USB even) at Pololu: &lt;a href=&quot;http://www.pololu.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.pololu.com/&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="867" LastActivityDate="2010-08-19T16:14:02.250" CommentCount="1" />
  <row Id="4102" PostTypeId="2" ParentId="4094" CreationDate="2010-08-19T18:06:08.687" Score="6" ViewCount="" Body="&lt;p&gt;Are you completely opposed to making minor modifications to those old devices?  If not, you can probably interface with them by means of placing relays in the circuits the buttons and switches control. &lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2010-08-19T18:06:08.687" CommentCount="2" />
  <row Id="4103" PostTypeId="2" ParentId="4094" CreationDate="2010-08-19T18:32:31.840" Score="1" ViewCount="" Body="&lt;p&gt;Using analogue switches across the actual switches, controlled by a computer or MCU, is a popular technique, and avoids messing about with mechanical actuators. The 74HC4066 is a typical device that can be used.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-19T18:32:31.840" />
  <row Id="4104" PostTypeId="1" AcceptedAnswerId="4105" CreationDate="2010-08-19T21:32:00.610" Score="3" ViewCount="225" Body="&lt;p&gt;I want something that can re-program a PQFP SyncMOS SM5964 chip already soldered to the target circuit board.&#xA;I picture a ribbon cable that I plug between some sort of 2x8 or so header connector soldered on the target circuit board, and a 2x8 or so header connector on a chip programmer, with the chip programmer plugging into a standard PC serial port or USB port.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Is there a standard connector and pinout I should design onto the target board for in-circuit programming a completely blank SM5964 chip soldered to the board? (For older boards, I can temporarily connect such a connector with a bunch of wires from that connector to pins on the chip).&lt;/li&gt;&#xA;&lt;li&gt;Is there such a standard in-circuit programming connector for other 8051 and 8052 chips?&lt;/li&gt;&#xA;&lt;li&gt;Is there a reasonably-priced programmer that can program such a blank SM5964 chip already soldered to the target board?&lt;/li&gt;&#xA;&lt;li&gt;Is there a standard bootloader firmware for this chip?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So far, my web searches have turned up a few chip programmers such as the&#xA;$295 &lt;a href=&quot;http://www.logicaldevices.com/aw1.htm?gclid=COLf1I_3w6MCFQUiawodjG02gw&quot; rel=&quot;nofollow&quot;&gt;XPRO-5000&lt;/a&gt;&#xA;that can program the SyncMOS SM5964&#xA;using a big ZIF socket and a PQFP adapter.&#xA;I suppose I could solder some wires between a DIP socket and a female header, insert the DIP socket into the ZIF socket on such a programmer, and plug the female header into a in-circuit programming header on the target board. But it seems unnecessarily complicated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I expected to find answers to some of these questions at &lt;a href=&quot;http://8052.com/&quot; rel=&quot;nofollow&quot;&gt;http://8052.com/&lt;/a&gt; ; perhaps I am looking in the wrong place.&lt;/p&gt;&#xA;" OwnerUserId="813" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-01T17:13:17.217" LastActivityDate="2010-10-01T17:13:17.217" Title="What is a good way to in-circuit update the program on a SyncMOS 5964?" Tags="&lt;connector&gt;&lt;8051&gt;&lt;in-circuit&gt;" AnswerCount="1" />
  <row Id="4105" PostTypeId="2" ParentId="4104" CreationDate="2010-08-20T04:06:33.187" Score="6" ViewCount="" Body="&lt;p&gt;I can't answer the 8051 specific questions, but I can help with your first problem.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The standard method for doing this in industry (at least as far as I can tell) is to use pogo pins:&#xA;&lt;img src=&quot;http://static.sparkfun.com/images/products/09174-02-L_i_ma.jpg&quot; alt=&quot;image&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The gold part sticks through some protoboard or another PCB.  You connect your programmer to this circuit.  This piece of PCB (or something thicker and sturdier like masonite or acrylic if you're doing hundreds of boards) also has larger pins which go through holes in your target board, to precisely locate your target board above the pogo pins.  Light down pressure on the board makes contact between the spring-loaded pogo pins and the test points on the target PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The company I work at uses this kind of pins to program every one of the millions of circuit boards they make every year, and every trace has a tiny test point which is probed by a tester through these pins. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want a debug header, there are other standard methods.  I'm totally unfamiliar with this chip, so I can't answer that for you.  8, 14, and 20 pin headers are common for other devices.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt;&#xA;I took a quick look at the datasheet, and found on page 10:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;3. In-System Programming (ISP) Function&lt;/strong&gt;&lt;br&gt;&#xA;  The SM5964 can generate&#xA;  flash control signal by internal&#xA;  hardware circuit. User utilize flash&#xA;  control register, flash address&#xA;  register and flash data register to&#xA;  perform the ISP function without&#xA;  removing the SM5964 from the system.&#xA;  The SM5964 provides internal flash&#xA;  control signals which can do flash&#xA;  program/chip erase/page erase/protect&#xA;  functions. User need to design and use&#xA;  any kind of interface which SM5964 can&#xA;  input data. User then utilize ISP&#xA;  service program to perform the flash&#xA;  program/chip erase/page erase/protect&#xA;  functions.&lt;br&gt;&#xA;  &lt;strong&gt;3.1 ISP Service Program&lt;/strong&gt;&lt;br&gt;&#xA;  The ISP service program is a user developed&#xA;  firmware program which resides in the&#xA;  ISP service program space. After user&#xA;  developed the ISP service program,&#xA;  user then determine the size of the&#xA;  ISP service program. User need to&#xA;  program the ISP service program in the&#xA;  SM5964 for the ISP purpose. The ISP&#xA;  service program were developed by user&#xA;  so that it should includes any&#xA;  features which relates to the flash&#xA;  memory programming function as well as&#xA;  communication protocol between SM5964&#xA;  and host device which output data to&#xA;  the SM5964. For example, if user&#xA;  utilize UART interface to&#xA;  receive/transmit data between SM5964&#xA;  and host device, the ISP service&#xA;  program should include baud rate,&#xA;  checksum or parity check or any&#xA;  error-checking mechanism to avoid data&#xA;  transmission error. The ISP service&#xA;  program can be initiated under SM5964&#xA;  active or idle mode. It can not be&#xA;  initiated under power down mode.  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So, it looks like you can provide a bootloader program to read in the data from any interface you like.  This can be some GPIO or the UART that you access with pogo pins, or go to an existing connector on the board. How do you get this program to run?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;3.4 Initiate ISP Service Program&lt;/strong&gt;&lt;br&gt;&#xA;  To initiate the ISP service program is to&#xA;  load the program counter (PC) with&#xA;  start address of ISP service program&#xA;  and execute it. There are two ways to&#xA;  do so:&lt;br&gt;&#xA;  (1) Blank reset. Hardware&#xA;  reset with first flash address blank&#xA;  ($0000=#FFH) will load the PC with&#xA;  start address of ISP service program.&lt;br&gt;&#xA;  (2) Execute jump instruction can load&#xA;  the start address of the ISP service&#xA;  program to PC.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;However, I have no idea how you're supposed to get the ISP program on the blank chip. &lt;a href=&quot;http://www.syncmos.com.tw/technical.php?page_sel=1&amp;amp;pid=3&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; has a few programs and programmers, the MSM9042 looks closer to what you want for in-circuit (not socketed) programming. &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-09-25T16:05:44.650" LastActivityDate="2010-09-25T16:05:44.650" />
  <row Id="4106" PostTypeId="2" ParentId="614" CreationDate="2010-08-20T11:43:30.267" Score="0" ViewCount="" Body="&lt;p&gt;Some information on ultrasonic hardware at &lt;a href=&quot;http://david.carybros.com/html/ultrasonic.html&quot; rel=&quot;nofollow&quot;&gt;http://david.carybros.com/html/ultrasonic.html&lt;/a&gt;&#xA;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-20T11:43:30.267" />
  <row Id="4107" PostTypeId="2" ParentId="2178" CreationDate="2010-08-20T12:32:26.103" Score="0" ViewCount="" Body="&lt;p&gt;I've been researching something similar and came across this paper which might be of help&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.araa.asn.au/acra/acra2006/papers/paper_5_18.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.araa.asn.au/acra/acra2006/papers/paper_5_18.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="52" LastActivityDate="2010-08-20T12:32:26.103" />
  <row Id="4108" PostTypeId="2" ParentId="1313" CreationDate="2010-08-20T13:37:04.827" Score="1" ViewCount="" Body="&lt;p&gt;I see that Newark has some &lt;a href=&quot;http://www.newark.com/jsp/content/printCatalog.jsp?cat=c127&amp;amp;page=0368&amp;amp;display=single&quot; rel=&quot;nofollow&quot;&gt;2mm pitch development boards&lt;/a&gt;.&#xA;They also have a couple of boards (such as the Vector 8018 and &lt;a href=&quot;http://www.newark.com/vector-electronics-technology/8028/pcb-prototyping-board/dp/16J0508&quot; rel=&quot;nofollow&quot;&gt;Vector 8028&lt;/a&gt;) that have a 0.1 inch pitch on the left and 2 mm pitch on the right side.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-20T13:37:04.827" />
  <row Id="4109" PostTypeId="2" ParentId="4080" CreationDate="2010-08-20T14:33:59.017" Score="2" ViewCount="" Body="&lt;p&gt;Cool project!  I suppose that your choice of processor (and reason for needing external memory) will depend on how you define &quot;simple graphing capabilities&quot; and &quot;limited programming ability&quot;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stop and consider that the TI-83 calculator has a 6 MHz processor, uses 8KB of RAM for system functions (24KB is free for user programs), and has 512KB of Flash with an external 2MB Flash chip on the special &quot;Silver&quot; editions.  It runs a proprietary OS, and has support for more mathematical functions than I've ever heard of or used, as well as programming in 4 languages.  Your ATMega1284 has 16KB of RAM and 128KB of Flash.  Do you think you're going to generate enough code to fill those 128KB, given that TI only used about three times that much?  I doubt it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you just want to use a character LCD and a LED array for graphing with basic math functions (Buttons 0-9, variables x and y, +-*/%=, and some kind of storage), then an ATMega or Arduino is more than adequate for your needs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If, on the other hand, you want to run a color TFT with embedded Linux, scripting/programming in bash, lua, or whatever programming language you choose, graph with gnuplot, and enter everything on a mini querty keyboard/numpad, then you should look at more powerful chip.  Definitely go for 32-bit if you want to deal with big numbers, and if you want to address lots of memory.  Most of these chips (I recommend ARM) come in QFP packages - But don't be afraid!  You don't need expensive machines to solder a [LT]QFP or PLCC device - Just a steady hand, a fine tip, and decent technique will be adequate.  Oh, and a well-made board with soldermask.  However, many dev boards will be well suited to this project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy these chips in singles for $2 to $15, depending on the options you want.  Also, many manufacturers will send samples if you just ask, in hopes that you'll buy thousands once everyone is taking the ACT and SAT on an EARLZ-9000 calculator! &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-20T14:33:59.017" CommentCount="4" />
  <row Id="4110" PostTypeId="2" ParentId="3783" CreationDate="2010-08-20T17:46:53.340" Score="1" ViewCount="" Body="&lt;p&gt;It might actually be just a little easier to make your own RFID in this case.  You will need a very low power microcontroller (an attiny or small PIC is typical) with an antenna and a small number of discrete components.  Here's a link to something similar: &lt;a href=&quot;http://micah.navi.cx/2008/09/using-an-avr-as-an-rfid-tag/&quot; rel=&quot;nofollow&quot;&gt;http://micah.navi.cx/2008/09/using-an-avr-as-an-rfid-tag/&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With that, you can arrange for the RFID micro to power on when it gets power from the antenna, perform its sensory operation, and then respond based on the result of the computation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously, the available current from such a setup is pretty small, so unless the sensor works well on very small voltages and currents, you may have a hard time without an external power source.&lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2010-08-20T17:46:53.340" />
  <row Id="4112" PostTypeId="1" AcceptedAnswerId="4114" CreationDate="2010-08-20T19:23:35.543" Score="3" ViewCount="188" Body="&lt;p&gt;Is there a company that will sell me a touch panel similar to the IPhone or IPad surface, in single quantities, complete with a Developer Kit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I get it in a specific form-factor (say, 2x7 inches)?&lt;/p&gt;&#xA;" OwnerUserId="544" LastEditorUserId="327" LastEditorDisplayName="" LastEditDate="2010-08-20T20:10:30.580" LastActivityDate="2010-08-23T23:53:00.367" Title="Source for small Touch-Panels?" Tags="&lt;touch-panel&gt;&lt;touchscreen&gt;&lt;kit&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="4" />
  <row Id="4113" PostTypeId="2" ParentId="3506" CreationDate="2010-08-20T19:53:14.287" Score="1" ViewCount="" Body="&lt;p&gt;From my own experience, the ferric chloride is something you have to be very careful to avoid damaging something near (like furniture). You have to store it very well, preferably in an airtight container inside other airtight container. Its evaporation or spills will stain practically anything it's near of. Be especially careful about aluminium objects, it reacts instantly with them corroding completely and liberating gas (if you drop a piece of aluminium in the ferric chloride solution it'll look like an alka-seltzer tablet).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When in contact to the skin it'll not burn or make damage (provided you wash instantly), but it'll stain (to the point it'll take days to vanish). If you buy it in powder form and dillute yourself, do it in a ventilated place since it'll release gases when dilluted with water.&lt;/p&gt;&#xA;" OwnerUserId="1078" LastEditorUserId="1078" LastEditorDisplayName="" LastEditDate="2010-08-29T23:20:29.357" LastActivityDate="2010-08-29T23:20:29.357" CommentCount="2" />
  <row Id="4114" PostTypeId="2" ParentId="4112" CreationDate="2010-08-20T20:07:49.337" Score="2" ViewCount="" Body="&lt;p&gt;Liquidware sells touchscreen developer kits like: &lt;a href=&quot;http://www.liquidware.com/shop/show/TSL/TouchShield+Slide&quot; rel=&quot;nofollow&quot;&gt;http://www.liquidware.com/shop/show/TSL/TouchShield+Slide&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sparkfun has some also: &lt;a href=&quot;http://www.sparkfun.com/commerce/advanced_search_result.php?keywords=touchscreen&amp;amp;x=0&amp;amp;y=0&amp;amp;search_section=products&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/advanced_search_result.php?keywords=touchscreen&amp;amp;x=0&amp;amp;y=0&amp;amp;search_section=products&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="327" LastActivityDate="2010-08-20T20:07:49.337" />
  <row Id="4115" PostTypeId="2" ParentId="3506" CreationDate="2010-08-20T20:45:15.457" Score="1" ViewCount="" Body="&lt;p&gt;as far as the toxic nature of these chemicals, the only thing you really need to worry about is the resulting copper chloride.  Copper is quite toxic and should definitely not be ingested.  That's not too hard, though, and getting a bit of it on your skin isn't terribly dangerous.  That's about as bad as it gets.  &lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2010-08-20T20:45:15.457" />
  <row Id="4116" PostTypeId="2" ParentId="3506" CreationDate="2010-08-20T21:17:29.177" Score="2" ViewCount="" Body="&lt;p&gt;A year ago, I would have said &quot;Anything that can dissolve copper must be a dangerously strong acid&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, salt and vinegar are generally considered harmless enough to eat and drink,&#xA;and I've recently come across people who claim mixing the two makes an acid strong enough to etch copper-clad circuits:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.kobakant.at/DIY/?p=2575&quot; rel=&quot;nofollow&quot;&gt;Salt and vinegar etching&lt;/a&gt;, also&#xA;&lt;a href=&quot;http://www.flickr.com/photos/jeanbaptisteparis/4831465916/&quot; rel=&quot;nofollow&quot;&gt;etching FabFM radio smt pcb with Salt and Vinegar&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps it would be less hassle to use salt and vinegar, even if it etches boards a little more slowly, rather than spending a lot of time and emotional stress being over-the-top careful and worried.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-20T21:17:29.177" />
  <row Id="4117" PostTypeId="2" ParentId="1024" CreationDate="2010-08-21T01:43:21.690" Score="11" ViewCount="" Body="&lt;p&gt;This &lt;a href=&quot;http://www.falstad.com/circuit/&quot; rel=&quot;nofollow&quot;&gt;Java circuit simulator&lt;/a&gt; is pretty easy to draw schematics in, and it has a way to export them as plain text:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;$ 1 5.0E-6 0.9891409633455756 46 5.0 50&#xA;I 240 256 304 256 0 0.5&#xA;I 352 256 416 256 0 0.5&#xA;w 416 256 416 192 0&#xA;w 240 192 240 256 0&#xA;r 320 272 320 336 0 220000.0&#xA;c 320 352 320 400 0 4.7000000000000004E-8 1.4535908873993098&#xA;g 320 416 320 432 0&#xA;s 224 384 224 320 0 1 true&#xA;w 240 256 224 256 0&#xA;w 224 256 224 320 0&#xA;w 272 384 224 384 0&#xA;w 320 352 320 336 0&#xA;w 320 400 320 416 0&#xA;w 272 384 272 352 0&#xA;w 272 352 320 352 0&#xA;w 304 256 320 272 0&#xA;w 352 256 320 272 0&#xA;r 240 192 416 192 0 5000.0&#xA;o 1 64 0 35 5.0 0.0015625 0 -1&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The above code will produce this circuit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/xpPs2.png&quot; alt=&quot;two-inverter momentary toggle&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe there's a way to integrate it into a site, so that users can draw a circuit, paste the above code into the answer box, surround it with special tags, and it will create a pop-up applet?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even better, a schematic image could be generated from the code, which, when clicked on, opens a simulation applet of that schematic.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe talk to the author about something like this?  He has the applet zipped up for you to use on your own computer, but I don't know about distributing it on other websites.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt; I talked to the author, and he implemented URL data within hours of me proposing it.  There is now an &quot;Export Link&quot; menu option that generates links like this, without requiring a directory or hashtable on the server or anything.  You can use the same URL to display the same circuit while using the java file on your own computer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+0.9891409633455756+46+5.0+50%0AI+240+256+304+256+0+0.5%0AI+352+256+416+256+0+0.5%0Aw+416+256+416+192+0%0Aw+240+192+240+256+0%0Ar+320+272+320+336+0+220000.0%0Ac+320+352+320+400+0+4.7000000000000004E-8+1.4535908873993098%0Ag+320+416+320+432+0%0As+224+384+224+320+0+1+true%0Aw+240+256+224+256+0%0Aw+224+256+224+320+0%0Aw+272+384+224+384+0%0Aw+320+352+320+336+0%0Aw+320+400+320+416+0%0Aw+272+384+272+352+0%0Aw+272+352+320+352+0%0Aw+304+256+320+272+0%0Aw+352+256+320+272+0%0Ar+240+192+416+192+0+5000.0%0Ao+1+64+0+35+5.0+0.0015625+0+-1%0A&quot; rel=&quot;nofollow&quot;&gt;This should display the above circuit&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And he pointed out &lt;a href=&quot;http://www.falstad.com/licensing.html&quot; rel=&quot;nofollow&quot;&gt;the licensing agreement&lt;/a&gt;, which I think permits us to modify it and use it on here to embed schematics, like &lt;a href=&quot;http://www.falstad.com/circuit/e-capseries.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;You have permission to modify the applets and/or copy the applets onto your own web site as long as you credit me (Paul Falstad) and provide a link to my page&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This 4000 character URL should show a &lt;a href=&quot;http://www.falstad.com/circuit/#%24+3+5.0E-6+10.20027730826997+50+5.0+50%0AL+272+32+272+8+2+0+false+5.0+0.0%0AL+320+32+320+8+2+1+false+5.0+0.0%0AL+368+32+368+8+2+0+false+5.0+0.0%0AL+416+32+416+8+2+1+false+5.0+0.0%0AI+272+32+272+80+0+0.5%0AI+320+32+320+80+0+0.5%0AI+368+32+368+80+0+0.5%0AI+416+32+416+80+0+0.5%0Aw+320+32+344+32+0%0Aw+344+32+344+96+0%0A151+72+168+72+216+1+4+5.0%0A151+128+168+128+216+1+3+5.0%0A151+184+168+184+216+1+2+5.0%0A151+240+168+240+216+1+4+5.0%0A151+600+168+600+216+1+3+5.0%0A151+552+168+552+216+1+3+0.0%0A151+504+168+504+216+1+3+5.0%0A151+456+168+456+216+1+3+5.0%0A151+400+168+400+216+1+3+5.0%0A150+304+168+304+216+1+2+0.0%0A152+352+168+352+216+1+2+5.0%0Aw+344+96+120+96+0%0Aw+120+96+120+168+0%0Aw+344+96+512+96+0%0Aw+512+96+560+96+0%0Aw+560+96+608+96+0%0Aw+608+96+608+168+0%0Aw+560+168+560+96+0%0Aw+512+168+512+96+0%0Aw+368+32+392+32+0%0Aw+392+32+392+104+0%0Aw+192+168+192+104+0%0Aw+128+168+128+104+0%0Aw+128+104+192+104+0%0Aw+192+104+392+104+0%0Aw+392+104+456+104+0%0Aw+456+104+456+168+0%0Aw+456+104+600+104+0%0Aw+600+104+600+168+0%0Aw+416+32+440+32+0%0Aw+440+32+440+112+0%0Aw+440+112+552+112+0%0Aw+552+112+552+168+0%0Aw+440+112+408+112+0%0Aw+408+168+408+112+0%0Aw+408+112+256+112+0%0Aw+256+112+256+168+0%0Aw+256+112+136+112+0%0Aw+136+112+136+168+0%0Aw+272+80+272+120+0%0Aw+272+120+248+120+0%0Aw+248+120+248+168+0%0Aw+248+120+56+120+0%0Aw+56+120+56+168+0%0Aw+272+120+360+120+0%0Aw+360+120+360+168+0%0Aw+320+80+320+128+0%0Aw+312+168+312+128+0%0Aw+312+128+320+128+0%0Aw+232+168+232+128+0%0Aw+312+128+232+128+0%0Aw+232+128+176+128+0%0Aw+176+128+176+168+0%0Aw+176+128+64+128+0%0Aw+64+128+64+168+0%0Aw+320+128+392+128+0%0Aw+392+128+392+168+0%0Aw+392+128+464+128+0%0Aw+464+128+464+168+0%0Aw+368+80+368+136+0%0Aw+368+136+400+136+0%0Aw+400+136+400+168+0%0Aw+400+136+504+136+0%0Aw+504+136+504+168+0%0Aw+368+136+296+136+0%0Aw+296+136+296+168+0%0Aw+296+136+224+136+0%0Aw+224+136+224+168+0%0Aw+224+136+80+136+0%0Aw+80+136+80+168+0%0Aw+416+80+416+144+0%0Aw+504+136+544+136+0%0Aw+544+136+544+168+0%0Aw+416+144+448+144+0%0Aw+448+144+448+168+0%0Aw+448+144+496+144+0%0Aw+496+144+496+168+0%0Aw+496+144+592+144+0%0Aw+592+144+592+168+0%0Aw+416+144+272+144+0%0Aw+272+144+88+144+0%0Aw+88+144+88+168+0%0Aw+304+216+328+216+0%0Aw+328+216+328+168+0%0Aw+328+168+344+168+0%0A150+88+280+88+328+1+4+5.0%0A150+264+280+264+328+1+4+5.0%0A150+416+280+416+328+1+4+5.0%0A150+368+280+368+328+1+3+0.0%0A150+320+280+320+328+1+2+5.0%0A150+208+280+208+328+1+3+0.0%0A150+152+280+152+328+1+4+5.0%0Aw+72+216+72+280+0%0Aw+272+144+272+224+0%0Aw+272+224+200+224+0%0Aw+200+224+200+280+0%0Aw+208+280+208+232+0%0Aw+208+232+272+232+0%0Aw+272+232+272+280+0%0Aw+272+232+432+232+0%0Aw+432+232+432+280+0%0Aw+432+232+504+232+0%0Aw+504+232+504+216+0%0Aw+216+280+216+248+0%0Aw+216+248+160+248+0%0Aw+160+248+160+280+0%0Aw+160+248+96+248+0%0Aw+96+248+96+280+0%0Aw+80+280+80+240+0%0Aw+104+280+104+256+0%0Aw+104+256+168+256+0%0Aw+168+256+168+280+0%0Aw+80+240+128+240+0%0Aw+128+240+128+216+0%0Aw+128+240+144+240+0%0Aw+144+240+144+280+0%0Aw+184+216+184+224+0%0Aw+184+224+136+224+0%0Aw+136+224+136+280+0%0Aw+424+280+424+240+0%0Aw+424+240+376+240+0%0Aw+376+240+376+280+0%0Aw+424+240+600+240+0%0Aw+600+240+600+216+0%0Aw+144+240+256+240+0%0Aw+256+240+256+280+0%0Aw+216+248+248+248+0%0Aw+248+248+248+280+0%0Aw+240+216+240+256+0%0Aw+168+256+240+256+0%0Aw+240+256+400+256+0%0Aw+400+256+400+280+0%0Aw+408+280+408+248+0%0Aw+408+248+360+248+0%0Aw+360+248+360+280+0%0Aw+360+248+312+248+0%0Aw+312+248+312+280+0%0Aw+352+216+360+216+0%0Aw+360+216+360+248+0%0Aw+312+248+248+248+0%0Aw+280+280+280+224+0%0Aw+280+224+400+224+0%0Aw+400+224+400+216+0%0Aw+328+280+328+264+0%0Aw+328+264+456+264+0%0Aw+456+264+456+216+0%0Aw+368+280+368+272+0%0Aw+368+272+552+272+0%0Aw+552+272+552+216+0%0A157+464+312+584+312+0%0Aw+464+312+448+312+0%0Aw+448+312+448+328+0%0Aw+448+328+416+328+0%0Aw+464+344+368+344+0%0Aw+368+344+368+328+0%0Aw+464+376+320+376+0%0Aw+320+376+320+328+0%0Aw+464+408+264+408+0%0Aw+264+408+264+328+0%0Aw+528+440+208+440+0%0Aw+208+440+208+328+0%0Aw+560+440+560+448+0%0Aw+560+448+152+448+0%0Aw+152+448+152+328+0%0Aw+592+440+592+456+0%0Aw+592+456+88+456+0%0Aw+88+456+88+328+0%0A&quot; rel=&quot;nofollow&quot;&gt;7-segment decoder&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-27T19:17:21.497" LastActivityDate="2010-10-27T19:17:21.497" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="4" />
  <row Id="4118" PostTypeId="2" ParentId="1024" CreationDate="2010-08-21T06:51:54.993" Score="3" ViewCount="" Body="&lt;p&gt;How about a Quite Universial Circuit Simulator (qucs)? &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://qucs.sourceforge.net/screenshots.html&quot; rel=&quot;nofollow&quot;&gt;http://qucs.sourceforge.net/screenshots.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;(But I'm not sure if it is ready for prime time yet, but so far so good)&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-08-21T06:51:54.993" CommunityOwnedDate="2011-03-22T20:53:31.463" />
  <row Id="4119" PostTypeId="2" ParentId="1696" CreationDate="2010-08-21T17:42:28.817" Score="0" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;You could try converting the file to a plain old binary blob and then edit it with an ordinary &quot;hex editor&quot;. It is suboptimal but since typical hex files contain less than a megabyte of data it should work.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For my simple needs the Vim build in syntax highlighting was sufficient. It colors different parts of the line so you won't mistake the address, type or checksum with data. Maybe it could be enhanced with the new 7.3 &quot;conceal&quot; feature to decode record types on the fly.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;PS. I am really curious why would you need something like this. :)&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-08-21T17:42:28.817" CommunityOwnedDate="2011-02-09T13:48:06.387" CommentCount="2" />
  <row Id="4120" PostTypeId="2" ParentId="1696" CreationDate="2010-08-22T12:40:35.173" Score="1" ViewCount="" Body="&lt;p&gt;For linux systems you have: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;okteta (kde based)&lt;/li&gt;&#xA;&lt;li&gt;ghex / ghex2 (gnome)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="689" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2011-02-01T13:42:37.160" LastActivityDate="2011-02-01T13:42:37.160" CommunityOwnedDate="2011-02-09T13:48:06.387" />
  <row Id="4121" PostTypeId="1" AcceptedAnswerId="4122" CreationDate="2010-08-22T19:41:35.887" Score="7" ViewCount="346" Body="&lt;p&gt;I've always been under the impression that overclocking of any sort of CPU (for a PC, or a microcontroller), its a bad thing.  Your'e essentially operating the unit outside of the manufacturer's specifications, which means that the device may/may not work as intended.  It may go faster, but at the risk of erratic behavior.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand that the answer to overclock/not is a philosophical one depending upon how much risk you wish to take on with your devices.  But,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What kind of permanent damage can be caused by overclocking a CPU?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Note:  I ask this because a number of my friends are gamerz and think overclocking roxors soxors... and for some odd reason after they do this their computers break with bluescreens and then &lt;em&gt;I&lt;/em&gt; get called, and I want some ammunition to use so that I don't have to troubleshoot potentially flaky hardware so often...)&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2011-01-13T22:54:26.303" LastActivityDate="2011-01-13T22:54:26.303" Title="Overclocking: permanent damage?" Tags="&lt;cpu&gt;&lt;overclocking&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="4122" PostTypeId="2" ParentId="4121" CreationDate="2010-08-22T20:12:14.890" Score="12" ViewCount="" Body="&lt;p&gt;I've overclocked almost every computer (excluding laptops) i've ever owned purely for the cost savings and making matlab sims not take all day.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Overclocking, as in raising the clock speed or multiplier shouldn't damage modern CPU's.  The thermal shutdown in the CPU should trigger early enough to prevent damage.  Older CPU's didn't have as robust thermal protection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're raising various voltages in an attempt to run even faster, you can inadvertently cause permanent damage to the CPU.  It's good to stay within the max voltage specifications given by the CPU manufacturer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your usage model, overclocking can cause reduced life span.  This is really just a function of CPU temperature, the hotter it runs the shorter the life span.  If the CPU is running right on the edge of its TDP rating 24/7 i wouldn't expect it to last for 10 years.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You generally are not running the device outside its design specifications as long as you stay within the specified voltage levels.  As a design is fleshed out manufacturing yields get better and better and parts binned to 2.6GHz are very often capable of and tested for much higher speeds, they are just binned to the low end to fill the higher market demand for that segment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currently typing on a core i7 920 @ 4.1ghz with air cooling (granted it's one massive heatsink and 2 140mm fans).  D0 stepping, a newer stepping which is capable of much higher speeds than the older steppings.  I actually ran a 12hour prime95 test at 4.25ghz but anything higher started spewing errors and i didn't want to raise the supply voltages any more so I backed off a bit to get to 4.1 for some headroom.  You also have to make allowances for ambient temperature changes if your space isn't air conditioned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT for sheepsimulator:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The effect on the ram depends on the architecture your talking about and the features offered by the motherboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example in the core i7 architecture:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the Core i7 architecture you have 1 base clock that generates the clocks for the CPU core, the 'uncore', the QPI and the RAM via 4 different multipliers.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In some CPU models these multipliers have limited ranges, but key to your question: when you overclock the system you normally crank the base clock up which does also increase the RAM clock.  But, you can reduce the RAM clock multiplier to get stock or very close to stock ram speeds if you wish.  The core i7 920 by default uses DDR3-1066 ram but DDR3-1600 is almost the same price so most people buy the faster ram and adjust the RAM multiplier to get to the 1600 rating.  You also have control over the ram voltage on good motherboards so you have the options of over volting/clocking the ram should you so wish.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In some older architectures there was limited or no control over the RAM clock multiplier which could mean that you need faster ram to achieve a particular CPU clock.&lt;/p&gt;&#xA;" OwnerUserId="703" LastEditorUserId="703" LastEditorDisplayName="" LastEditDate="2010-08-23T20:11:45.557" LastActivityDate="2010-08-23T20:11:45.557" CommentCount="4" />
  <row Id="4123" PostTypeId="1" AcceptedAnswerId="4124" CreationDate="2010-08-22T22:11:08.533" Score="5" ViewCount="210" Body="&lt;p&gt;Hi there, I have a conceptual question: What means &quot;high&quot; code density? and why is it so important?&lt;/p&gt;&#xA;" OwnerUserId="170" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-07T06:37:02.013" LastActivityDate="2011-02-07T06:37:02.013" Title="About Code Density and its definition." Tags="&lt;microcontroller&gt;&lt;arm&gt;&lt;software&gt;" AnswerCount="2" />
  <row Id="4124" PostTypeId="2" ParentId="4123" CreationDate="2010-08-23T01:24:21.990" Score="15" ViewCount="" Body="&lt;p&gt;Code density refers loosely to how many microprocessor instructions it takes to perform a requested action, and how much space each instruction takes up. Generally speaking, the less space an instruction takes and the more work per instruction that a microprocessor can do, the more dense its code is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I notice that you've tagged your question with the 'arm' tag; I can illustrate code density using ARM instructions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's say you want to copy a block of data from one place in memory to another. Conceptually, your high level code would look something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void memcpy(void *dest, void *source, int count_bytes)&#xA;{&#xA;    char *s, *d;&#xA;&#xA;    s = source; d = dest;&#xA;    while(count_bytes--) { *d++ = *s++; }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Now a simple compiler for a simple microprocessor may convert this to something like the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;movl r0, count_bytes&#xA;movl r1, s&#xA;movl r2, d&#xA;loop: ldrb r3, [r1]&#xA;strb [r2], r3&#xA;movl r3, 1&#xA;add r1, r3&#xA;add r2, r3&#xA;sub r0, r3&#xA;cmp r0, 0&#xA;bne loop&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(my ARM is a little rusty, but you get the idea)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now this would be a very simple compiler and a very simple microprocessor, but you can see from the example that we're looking at 8 instructions per iteration of the loop (7 if we move the '1' to another register and move the load outside the loop). That's not really dense at all. Code density also affects performance; if your loops are longer because the code is not dense, you might need more instruction cache to hold the loop. More cache means a more expensive processor, but then again complex instruction decoding means more transistors to decipher the requested instruction, so it's a classic engineering problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ARM's pretty nice in this respect. Every instruction can be conditional, most instructions can increment or decrement the value of registers, and most instructions can optionally update the processor flags.  On ARM and with a moderately useful compiler, the same loop may look something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;movl r0, count_bytes&#xA;movl r1, s&#xA;movl r2, d&#xA;loop: ldrb r3, [r1++]&#xA;strb [r2++], r3&#xA;subs r0, r0, 1&#xA;bne loop&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;As you can see, the main loop is now 4 instructions. The code is more dense because each instruction in the main loop does more. This generally means that you can do more with a given amount of memory, because less of it is used to describe how to perform the work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now native ARM code often had the complaint that it wasn't super-dense; this is due to two main reasons: first, 32 bits is an awfully &quot;long&quot; instruction, so a lot of bits seem to be wasted for simpler instructions, and second, code got bloated due to ARM's nature: each and every instruction is 32 bits long, without exception. This means that there are a large number of 32-bit literal values that you can't just load into a register. If I wanted to load &quot;0x12345678&quot; into r0, how do I code an instruction that not only has 0x12345678 in it, but also describes &quot;load literal to r0&quot;? There are no bits left over to code the actual operation. The ARM load literal instruction is an interesting little beast, and the ARM assembler must also be a little smarter than normal assemblers, because it has to &quot;catch&quot; these kinds of instructions and code them as a value stored in the object file and an indirect load of that address to the requested register.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, to answer these complaints, ARM came up with Thumb mode. Instead of 32 bits per instruction, the instruction length is now 16 bits for almost all instructions, and 32 bits for branches. There were a few sacrifices with Thumb mode, but by and large these sacrifices were easy to make because Thumb got you something like a 40% improvement in code density just by reducing the instruction length.&lt;/p&gt;&#xA;" OwnerUserId="974" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-08-23T01:30:36.227" LastActivityDate="2010-08-23T01:30:36.227" CommentCount="4" />
  <row Id="4125" PostTypeId="1" AcceptedAnswerId="4126" CreationDate="2010-08-23T06:27:00.850" Score="3" ViewCount="324" Body="&lt;p&gt;Hi,&#xA;me and some friends want to develop a CNC drilling machine for a college project. The idea is to export the hole coordinates and drill size directly from a .brd file on Eagle, which will later be read from a MCU for processing. We're trying to define which format to use: &lt;strong&gt;gcode&lt;/strong&gt; or &lt;strong&gt;gerber&lt;/strong&gt;. Any suggestion for a third option will be gladly welcome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which one is easier to work with or is better documented?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also bare in mind that we want other students to be able to do the exporting from Eagle without much effort.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for your help.&lt;/p&gt;&#xA;" OwnerUserId="1081" LastActivityDate="2010-08-23T19:41:49.810" Title="Which would better suited for a CNC drilling machine: gerber or gcode?" Tags="&lt;eagle&gt;&lt;cnc&gt;&lt;gerber&gt;" AnswerCount="3" />
  <row Id="4126" PostTypeId="2" ParentId="4125" CreationDate="2010-08-23T11:38:47.333" Score="5" ViewCount="" Body="&lt;p&gt;Gerber files are used for making boards, not for CNC drilling. Drilling requires &lt;a href=&quot;http://www.apcircuits.com/resources/information/nc_introduction.html&quot; rel=&quot;nofollow&quot;&gt;Excellon&lt;/a&gt; drill files. Excellon drill files can be generated by Eagle, and would be be more convenient for users than any other format, as no file conversion would be required. They are quite simple.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-23T11:38:47.333" CommentCount="1" />
  <row Id="4127" PostTypeId="2" ParentId="4125" CreationDate="2010-08-23T13:25:41.460" Score="1" ViewCount="" Body="&lt;p&gt;I agree with Leon - I didn't even know where was a choice.  I thought all CNC machines relied on gcode.  I know of gerber to gcode converters: &lt;a href=&quot;http://sourceforge.net/projects/gerbertogcode/&quot; rel=&quot;nofollow&quot;&gt;http://sourceforge.net/projects/gerbertogcode/&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I dont' know about the appropriate drill converter or even if you need one. I think Leon's right about the excellon drill files.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-08-23T13:25:41.460" />
  <row Id="4128" PostTypeId="2" ParentId="4125" CreationDate="2010-08-23T19:41:49.810" Score="1" ViewCount="" Body="&lt;p&gt;Sounds like a cool project.&#xA;The standard format for a drilling machine to accept is &quot;Excellon file&quot; format.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most CNC machines accept&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;a G-code that is a slightly enhanced dialect of RS274D.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Most PCB design software exports information about a file in two formats:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;drill files in &quot;Excellon file&quot; format, a variant of standard RS-274C. (This is the one you want).&lt;/li&gt;&#xA;&lt;li&gt;layer files in Gerber file format, a variant of of RS-274X.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;All three variants of RS-274 are very similar.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-23T19:41:49.810" CommentCount="1" />
  <row Id="4129" PostTypeId="2" ParentId="4123" CreationDate="2010-08-23T19:57:58.193" Score="0" ViewCount="" Body="&lt;p&gt;The &quot;code density&quot; of an instruction set is a measure of how much stuff you can get into a given amount of program memory, or how many bytes of program memory you need to store a given amount of functionality.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As Andrew Kohlsmith pointed out, even on the same MCU, different compilers can get different code density.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might enjoy reading&#xA;&lt;a href=&quot;http://embeddedgurus.com/state-space/2009/03/insects-of-the-computer-world/&quot; rel=&quot;nofollow&quot;&gt;&quot;Insects of the computer world&quot;&lt;/a&gt; by Miro Samek,&#xA;which compares a variety of MCUs.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-08-23T19:57:58.193" />
  <row Id="4130" PostTypeId="1" AcceptedAnswerId="4134" CreationDate="2010-08-23T21:31:19.127" Score="2" ViewCount="258" Body="&lt;p&gt;I'm using the MSP430F5515 variant. I can't figure out any structured reason for it, but the chip clearly resets itself occasionally - i'm logging data and i put a 'known' string that only prints at startup in the code. I'm thinking it has something to do with my manipulation of the Unified Clock System registers, or maybe something to do with the High/Low side Voltage Supervisor functions (which I'm not changing from their system defaults). I'm pretty sure I don't have any kind of stack-overflow (no pun intended) going on, but one can never really rule that out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting to my question here... are there any register settings one needs to assign explicitly in your MSP430 startup code so that the system does not reset? Is there any diagnostics that I can use to determine for what reason (at least &quot;the last&quot;) reset occured. I'm thinking using the MSP430FET-UIF programmer/debugger to halt the processor and look at some register values, though my gut says I can't attach to a running processor without resetting it and loading a new program... Any thoughts / advice would be appreciated...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-Vic&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-08-24T04:13:22.080" Title="MSP430 seems to reset intermittently" Tags="&lt;msp430&gt;&lt;debug&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="4131" PostTypeId="2" ParentId="259" CreationDate="2010-08-23T23:45:12.157" Score="6" ViewCount="" Body="&lt;p&gt;I've also found that capacitive screens are hard to come by if you're not an OEM.  &lt;a href=&quot;http://www.digitimes.com/news/a20090630PD206.html&quot; rel=&quot;nofollow&quot;&gt;This 2009 article&lt;/a&gt; states &lt;em&gt;&quot;With prices of projective capacitive touch panels at about $\$$2.50-3.00 per inch, the average cost for a touch panel module will be about $\$$30 for a mainstream-size netbook&quot;&lt;/em&gt;.  That, of course, is the price for  Asus to buy 100,000 of them, not for you and me to tinker.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fortunately, there are a lot of OEMs who produce products with capacitive screens, and there is a significant market for replacement screens.  I'd recommend that you find a screen (Both LCD and touch panel) which meets your needs on an existing product (whether it's a touchscreen PC, netbook, or PDA) and then try to find a replacement screen for it. While you're looking, take a look at &lt;a href=&quot;http://www.technobuffalo.com/blog/comparisons/not-all-touchscreens-are-created-equal&quot; rel=&quot;nofollow&quot;&gt;this comparison&lt;/a&gt; of the Nexus One, Droid Eris, Motorola Droid, and iPhone touchscreens, to help you decide what to get.  Also look for hardware hacking forums for more help, as the datasheets will be hard to come by.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an example screen, &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9188&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt; sells the replacement iPhone touchscreen and display for $\$$140 - Not bad for the display, but a lot if you just want the sensor.  &lt;a href=&quot;http://www.directfix.com/mm5/merchant.mvc?Screen=PROD&amp;amp;Store_Code=GHT&amp;amp;Product_Code=IP-2342&amp;amp;Category_Code=DIG&quot; rel=&quot;nofollow&quot;&gt;Directfix&lt;/a&gt; (and many others) sell just the digitizer for about $30, some sell the digitizer, glass, and home button for about 50 - you'll have to look around.  (Look &lt;a href=&quot;http://www.directfix.com/mm5/merchant.mvc?Screen=PROD&amp;amp;Store_Code=GHT&amp;amp;Product_Code=IP-2387&amp;amp;Category_Code=DIG&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; - iPAD touchscreen! So long, joystick buttons; hello, 10&quot; glass touchscreen.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/account.php?id=12299&quot; rel=&quot;nofollow&quot;&gt;Calamari&lt;/a&gt; over at Sparkfun said (Concerning the iPhone replacement touchscreen): &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;As you can see in the photos, there&#xA;  are two B2B connectors. On one is for&#xA;  the video. It has a 1v8 SPI bus to&#xA;  configure the controller and a MPL&#xA;  interface for the pixels. You can&#xA;  drive the latter with a LM2506 and&#xA;  that's fairly straightforward to&#xA;  implement although the part is a&#xA;  leadless LLP in its largest&#xA;  incarnation. That interface gives you&#xA;  18bit color.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The second B2B connector is to the&#xA;  touch screen controller. Also 1v8 SPI.&#xA;  During initialization, the touchscreen&#xA;  and host exchange packets of about 80K&#xA;  bytes which tends to rule out using a&#xA;  smaller microcontroller.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;During a touch, the touchscreen will&#xA;  generate an interrupt every 16ms.The&#xA;  host reads 8 bytes which include the&#xA;  length of the payload packet. The&#xA;  payload is 55 bytes for one finger, 83&#xA;  for two, etc, and has a simple&#xA;  checksum. On the iPhone, the host runs&#xA;  it at a bit clock of 12 Mhz, but I&#xA;  imagine slower would be fine.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;As others have said, capacitive touchscreens, while nice, are much harder to work &#xA;with than resistive ones.  Budget some space on your micro (ARM9 or better, probably - Can you handle 1024x768 data at 100Hz?) and PCB accordingly; don't expect to build an iPhone with your Arduino.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-04T15:29:39.973" LastActivityDate="2011-05-04T15:29:39.973" CommentCount="2" />
  <row Id="4132" PostTypeId="2" ParentId="4112" CreationDate="2010-08-23T23:53:00.367" Score="0" ViewCount="" Body="&lt;p&gt;I always see the touchscreen controllers on Atmel's webpage on my way to their microcontrollers, but never stopped to look. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have a 4.3&quot; dev kit for their mXT224 maXTouch touchscreen controller &lt;a href=&quot;http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4621&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll notice that they &lt;strong&gt;really&lt;/strong&gt; want you to register for more information. &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-23T23:53:00.367" />
  <row Id="4133" PostTypeId="2" ParentId="4130" CreationDate="2010-08-23T23:55:43.863" Score="6" ViewCount="" Body="&lt;p&gt;if the watchdog is enabled make sure you don't have some piece of code that can occasionally take a long time to execute (usually blocking IO).  If there is such code make sure you pet the watchdog during such operations.&lt;/p&gt;&#xA;" OwnerUserId="703" LastActivityDate="2010-08-23T23:55:43.863" CommentCount="4" />
  <row Id="4134" PostTypeId="2" ParentId="4130" CreationDate="2010-08-24T04:13:22.080" Score="6" ViewCount="" Body="&lt;p&gt;To see why you are being RESET you need to check the system rest vector (SYSRSTIV) at address 019Eh and you will be able to see the cause of your reset.  There are many things on a MSP430 that will cause a reset &lt;/p&gt;&#xA;" OwnerUserId="540" LastActivityDate="2010-08-24T04:13:22.080" />
  <row Id="4135" PostTypeId="1" CreationDate="2010-08-24T11:39:26.847" Score="1" ViewCount="228" Body="&lt;p&gt;I was about to order Sharp LQ070Y3LG4A 7&quot; TFT LCD from Nu Horizons to find out that they were out of stock when I refreshed the page. Prior to that I had just ordered the Fujitsu N010-0514-T101 4-Wire Resistive Touch Panel to go with it. I am unable to find another LQ070Y3LG4A seller that will distribute to me as I only need 1 and I don't have 16 weeks to wait. So I need to find an alternative screen that will fit the touchscreen. I was wondering if anyone knew any alternatives I could use. The LCD also needs to use an LVDS interface.&lt;/p&gt;&#xA;" OwnerUserId="322" LastActivityDate="2010-10-21T14:02:33.393" Title="7&quot; LCD Panel Supplier" Tags="&lt;lcd&gt;&lt;sharp&gt;" AnswerCount="1" />
  <row Id="4136" PostTypeId="2" ParentId="4135" CreationDate="2010-08-24T12:24:11.623" Score="1" ViewCount="" Body="&lt;p&gt;Not sure if that Sharp panel is touchscreen or not, but you might want to check out mp3car.com. They have a decent selection of touchscreen LCDs at somewhat reasonable prices. None of them seem to be that specific Sharp model you're in search of, but you might find one you can use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://store.mp3car.com/7_inch_Touchscreens_s/27.htm&quot; rel=&quot;nofollow&quot;&gt;http://store.mp3car.com/7_inch_Touchscreens_s/27.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2010-08-24T12:24:11.623" />
  <row Id="4137" PostTypeId="1" AcceptedAnswerId="4138" CreationDate="2010-08-24T13:14:37.043" Score="2" ViewCount="125" Body="&lt;p&gt;How do I lower the clock frequency of a PIC18F2550 and recalculate the peripheral dividers?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to make it run cooler. Currently, it runs at 12MIPs/48mhz (USB-CDC-ACM).&lt;/p&gt;&#xA;" OwnerUserId="1084" LastEditorUserId="1084" LastEditorDisplayName="" LastEditDate="2010-08-24T20:22:55.950" LastActivityDate="2010-08-24T20:22:55.950" Title="Lowering PIC Clock Frequency" Tags="&lt;pic&gt;&lt;clock&gt;&lt;frequency&gt;" AnswerCount="3" />
  <row Id="4138" PostTypeId="2" ParentId="4137" CreationDate="2010-08-24T14:07:53.923" Score="3" ViewCount="" Body="&lt;p&gt;If you're currently running at 48 MHz, you're using an external crystal. You can decrease the frequency by changing bits 2:0 in the PLLDIV register, but we'd need to know the external crystal frequency and what peripherals you want to adjust. Is it just the USB subsystem you need to use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;In response to your comment:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looks like you can get it down to 5 MHz with no hardware changes. Take a look at Table 2-3 the datasheet. Switch clock mode to disable the PLL and set CPUDIV1:0 to 11 and you'll get a 4x divider down to 5 MHZ.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-08-24T15:40:55.833" LastActivityDate="2010-08-24T15:40:55.833" CommentCount="1" />
  <row Id="4139" PostTypeId="1" AcceptedAnswerId="4140" CreationDate="2010-08-24T15:35:00.123" Score="5" ViewCount="163" Body="&lt;p&gt;Why are tristates favored over multiplexers to select the output from RAM? The explanation that I've heard of is that the RAM is too large for using a multiplexer but I need more details.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A theory we've come up with is that using a multiplexer would necessitate a tree of OR-gates to select the output which would dramatically increase the propagation time of the signal to the bus whereas with tristates, no matter the size of the RAM, the propagation delay would be constant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is that correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="1085" LastActivityDate="2011-05-29T23:26:55.603" Title="Use of tristates vs multiplexers in a RAM" Tags="&lt;hardware&gt;&lt;multiplexing&gt;" AnswerCount="3" />
  <row Id="4140" PostTypeId="2" ParentId="4139" CreationDate="2010-08-24T16:48:19.803" Score="4" ViewCount="" Body="&lt;p&gt;It's an issue of &quot;fan-out&quot; or &quot;fan-in&quot;. So your theory is more or less accurate. However there is the additional benefit of using tristate outputs that you can attach them to a bus! If you use a CMOS Multiplexer you cannot share the wires that the output is on, if you use Tri-State devices then you can share the bus with other bussed devices (under the control of an arbiter for example)... in the context of RAM, think &quot;memory bus.&quot;&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-08-26T17:19:02.930" LastActivityDate="2010-08-26T17:19:02.930" CommentCount="3" />
  <row Id="4141" PostTypeId="2" ParentId="4137" CreationDate="2010-08-24T18:30:13.590" Score="0" ViewCount="" Body="&lt;p&gt;Depending on your application, you may want to try putting the PIC to sleep and using an interrupt with an RC circuit to wake it up periodically.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-08-24T18:30:13.590" CommentCount="1" />
  <row Id="4142" PostTypeId="2" ParentId="4137" CreationDate="2010-08-24T19:28:49.723" Score="0" ViewCount="" Body="&lt;p&gt;That's a weird place to have the board get hot.  It could definitely be warm at the other end, near R4, T1, and the TX LED, but there's nothing happening on the end which you say is warm! (&lt;a href=&quot;http://dangerousprototypes.com/docs/images/9/9b/URTiyCctii.png&quot; rel=&quot;nofollow&quot;&gt;Schematic&lt;/a&gt;, &lt;a href=&quot;http://dangerousprototypes.com/docs/images/3/31/UsbirtoyBrd.png&quot; rel=&quot;nofollow&quot;&gt;layout&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to the datasheet (p. 363), the power dissipated in your PIC should be:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;Pdis = VDD x {IDD – Σ IOH} + Σ {(VDD – VOH) x IOH} + Σ(VOL x IOL)&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This uses the &lt;code&gt;Power = Voltage * Current&lt;/code&gt; equation to say that the total power dissipated is the sum of the power consumed by the chip's operation (not including driven outputs) plus any power dissipation on the current sourcing transistors, plus any power dissipation on the current sinking transistors.  See page 375 for data on output voltages and currents.  However, it looks like there should be only minimal power dissipation according to this equation. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Three things I would look at:&lt;br&gt;&#xA; - The next page has a voltage/max frequency graph.  It shows that you're only allowed to operate at 48MHz when you're running above 4.2V.  Is this the case when you're operating off of your ICSP header?  Running out of spec here might cause issues by not switching the transistors fast enough, and developing shoot-through currents.&lt;br&gt;&#xA; - That micro includes an onboard 3.3V LDO for the USB.  If you're drawing any current off of this pin, you will dissipate power in the micro.  If you're not communicating over USB all the time, you can disable this regulator with the VREGEN configuration bit in the CONFIG2L register.&lt;br&gt;&#xA; - You got it hot once, it may now have a weak internal short.  Try a different microcontroller or board.  This is unlikely, but possible.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-24T19:28:49.723" CommentCount="1" />
  <row Id="4143" PostTypeId="1" CreationDate="2010-08-24T21:57:17.183" Score="4" ViewCount="278" Body="&lt;p&gt;I am looking for a USB protocol analyzer and was wondering if anyone had any experience with one.  So far, I am looking at an &lt;a href=&quot;http://www.internationaltestinstruments.com/storefront/Store_Prod1_1480A-USB-20-Protocol-Analyzer.aspx&quot; rel=&quot;nofollow&quot;&gt;Internal Test Instruments&lt;/a&gt; and a &lt;a href=&quot;http://www.totalphase.com/products/beagle_usb12/&quot; rel=&quot;nofollow&quot;&gt;Beagle USB 12&lt;/a&gt;.  I only need to watch the full speed (12 Mbs).  I need some low-level protocol information so I'm looking at hardware solutions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any input is greatly appreciated.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-08-25T17:19:12.953" CommunityOwnedDate="2010-08-24T21:57:17.183" Title="Advice for USB Sniffer" Tags="&lt;usb&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="4144" PostTypeId="2" ParentId="4143" CreationDate="2010-08-24T22:18:52.407" Score="3" ViewCount="" Body="&lt;p&gt;I have been using the Beagle USB 12 over the last year or so and have not run into any problems.  It has been very useful in debugging some protocol problems I was having with an embedded USB chip.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-08-24T22:18:52.407" CommunityOwnedDate="2010-08-24T22:18:52.407" />
  <row Id="4145" PostTypeId="1" AcceptedAnswerId="4149" CreationDate="2010-08-24T23:18:41.073" Score="3" ViewCount="233" Body="&lt;p&gt;Does anyone know of an FPGA soft-core implementation of Donald Knuth's &lt;a href=&quot;http://www-cs-faculty.stanford.edu/~knuth/mmix.html&quot; rel=&quot;nofollow&quot;&gt;MMIX&lt;/a&gt;? My google search only found old discussions of people who knew people who were working on an FPGA implementation.&lt;/p&gt;&#xA;" OwnerUserId="904" LastActivityDate="2010-08-25T14:49:18.870" Title="Is there an FPGA implementation of Donald Knuth's MMIX?" Tags="&lt;fpga&gt;&lt;softcore&gt;" AnswerCount="2" />
  <row Id="4146" PostTypeId="1" CreationDate="2010-08-24T23:27:11.303" Score="2" ViewCount="132" Body="&lt;p&gt;Atmel recommends:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;if the reprogram operations occur in a random fashion in which any number of pages is&lt;br&gt;&#xA;  updated in a random order, then the system must ensure that each page of the Serial DataFlash memory array be updated/rewritten at least once within every 10,000 cumulative page reprogram operations&quot; (http://www.piclist.com/techref/atmel/doc0842.pdf)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;There is an algorithm proposed for rewriting pages, which use page adress pointer (or page reprogram counter). &#xA;My question is what is the right place for this pointer/counter? One of DataFlash pages? &lt;/p&gt;&#xA;" LastActivityDate="2010-09-05T16:20:03.370" Title="Rewriting DataFlash pages" Tags="&lt;flash&gt;&lt;electronics&gt;&lt;memory&gt;&lt;atmel&gt;" AnswerCount="3" />
  <row Id="4147" PostTypeId="2" ParentId="4139" CreationDate="2010-08-25T00:23:48.940" Score="0" ViewCount="" Body="&lt;p&gt;By tri-stating onto a bus, your system scales better. You can just add more tristatable devices, without having to reconfigure both the old devices and the new device to cooperate through a new and larger multiplexer. &lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-08-25T00:23:48.940" />
  <row Id="4148" PostTypeId="2" ParentId="4146" CreationDate="2010-08-25T00:28:55.007" Score="1" ViewCount="" Body="&lt;p&gt;If at all possible, it's nice to keep a number like that in the software (preferably RAM, possibly EEPROM) of the device (e.g., microcontroller) controlling the flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have to do it in that flash device, you might want to take advantage of the extra 8 bytes per 256-byte flash page in that device to store the pointers; that's one of the suggested uses.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;System designers can use all of a&#xA;  page’s 264 bytes for  storing data.&#xA;  Alternatively, the 8 extra bytes per&#xA;  page can  be used for error detection&#xA;  and correction mechanisms  (EDC) or&#xA;  associated control information, such&#xA;  as pointers,  flags, and phone message&#xA;  routing directions.&quot;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="484" LastActivityDate="2010-08-25T00:28:55.007" CommentCount="2" />
  <row Id="4149" PostTypeId="2" ParentId="4145" CreationDate="2010-08-25T08:15:09.793" Score="1" ViewCount="" Body="&lt;p&gt;Google threw this up:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://repo.or.cz/w/fpgammix.git&quot; rel=&quot;nofollow&quot;&gt;http://repo.or.cz/w/fpgammix.git&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-08-25T08:53:32.510" LastActivityDate="2010-08-25T08:53:32.510" />
  <row Id="4150" PostTypeId="1" AcceptedAnswerId="4161" CreationDate="2010-08-25T12:19:26.273" Score="2" ViewCount="591" Body="&lt;p&gt;I wanted to sniff communication between two RS232 devices. &lt;a href=&quot;http://embeddedfreak.wordpress.com/2008/08/17/rs232-serial-sniffermonitoring-circuit/&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; link presents a simple solution but I want to make sure that my 'sniffer' does not load the communication link.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To that effect, I was wondering if I could use a MAX-232 as a 'looping' buffer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RS232 in --&gt;TTL out--&gt;TTL in--&gt;Rs232 out&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The MAX-232 will be powered by an external 5v. Is this a fool proof way of sniffing without loading the line? Does the MAX232 even act as a buffer in this configuration? If not. are there inexpensive RS232 buffer ICs available? All the 74xx range of buffer ICs seem to work only at TTL levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My communication link is only half duplex.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE: I think i was not clear with my description. Please see the image:&#xA;&lt;img src=&quot;http://i33.tinypic.com/2yoribn.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both my devices already are on RS232 levels. I simply wanted to read the data using a COM port of the PC, but thought a MAX-232 in between(the loop buffer that i was talking about) might serve asa buffer. But then again, even the PC's COM port per se might have a MAX-232 inside it...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S:I have not indicated the capacitors etc for the max232 in the above figure.&lt;/p&gt;&#xA;" OwnerUserId="921" LastEditorUserId="921" LastEditorDisplayName="" LastEditDate="2010-08-25T17:28:39.340" LastActivityDate="2010-09-07T08:16:44.570" Title="RS-232 Buffer circuit" Tags="&lt;rs232&gt;&lt;uart&gt;" AnswerCount="5" CommentCount="0" />
  <row Id="4151" PostTypeId="2" ParentId="4146" CreationDate="2010-08-25T12:32:42.283" Score="0" ViewCount="" Body="&lt;p&gt;Here's how I'm doing this to save a circular buffer in flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reserve one page (528 bytes) for the Index.  The first 16 bytes is a bitmask.  The first 0 in the bitmask is the offset position of the latest Index value.  So the first page has 16 bytes for bitmask followed by 128 4-byte values for the Index.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you write to the circular buffer you need to save the new Index value.  Do this by knocking down the next '1' bit in the bitmask to a '0' and writing the Index to this offset position.  You will need to do a &quot;Program without Erase&quot; command to the flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once all the bits in the bitmask are '0', then you have to erase the page and start fresh.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-08-25T12:32:42.283" />
  <row Id="4152" PostTypeId="2" ParentId="4150" CreationDate="2010-08-25T12:36:42.703" Score="3" ViewCount="" Body="&lt;p&gt;If I understand correct, here is your circuit: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;RS232 in --&gt;TTL out--&gt;&lt;code&gt;[Sniffer circuit]&lt;/code&gt;TTL in--&gt;Rs232 out&lt;/p&gt;&#xA;&#xA;&lt;p&gt;in other words: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;[device1] &amp;lt;--&gt; MAX232 &amp;lt;--&gt; [sniffer circruit] &amp;lt;--&gt; MAX232 &amp;lt;--&gt; [device2]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That looks good to me. The fact that each side of the circuit is talking directly with a MAX232 should give you plenty of &quot;isolation&quot;. You may need to cross the lines (or just use a null modem connection on one side) if you're talking CPE-CPE or computer to computer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than that I don't see any issues.&lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-08-25T12:36:42.703" CommentCount="1" />
  <row Id="4153" PostTypeId="2" ParentId="4145" CreationDate="2010-08-25T14:49:18.870" Score="1" ViewCount="" Body="&lt;p&gt;A simulation running on a PC might be more useful than a softcore, especially for testing algorithms.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-25T14:49:18.870" />
  <row Id="4154" PostTypeId="2" ParentId="4150" CreationDate="2010-08-25T14:49:50.867" Score="2" ViewCount="" Body="&lt;p&gt;Hmm, interesting circuit.  You might want to use an actual MAX232 as a buffer between the lines you're reading and your two-diode setup.  It has an input resistance of 5Kohms which means assuming that the receivers have the same you'll see 2.5KOhms of resistance on the bus.  Perhaps a voltage follower with a higher input resistance might be in order - it is possible to break serial ports by trying foolish things (I've done it).  Try testing on something that you don't mind destroying first.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-08-25T14:49:50.867" CommentCount="2" />
  <row Id="4155" PostTypeId="1" AcceptedAnswerId="4159" CreationDate="2010-08-25T15:31:30.503" Score="2" ViewCount="163" Body="&lt;p&gt;I'm sitting here with a pencil and paper trying to arrange a charlieplexed 5x8 LED matrix. I'm trying to arrange this in such a manner that no two lines cross each other. Without a guiding theorem of some sort, I keep isolating lines, that is, the line ends up completely surrounded in a box composed of it's neighbor lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking at this problem and thinking &quot;Some mathematician must have already solved this&quot;. Nodes, matrices, edges...it just feels like a topology problem. Anyhow, I don't have the maths to solve it, at least not conclusively. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anybody have any thoughts on this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To head this off - yes, this would be simple with multiplexing. I need to charlieplex this.&lt;/p&gt;&#xA;" OwnerUserId="989" LastActivityDate="2011-02-25T20:02:02.067" Title="Charlieplexing Topology Question" Tags="&lt;charlieplexing&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="4156" PostTypeId="2" ParentId="4150" CreationDate="2010-08-25T17:03:04.697" Score="1" ViewCount="" Body="&lt;p&gt;Assuming your two devices are talking TTL to each other, a good way to 'isolate' might be something like the following ascii circuit:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;         Tx --------------x------------------------------- Rx&#xA;                          |              &#xA;Device1  Rx --------------------x------------------------- Tx  Device2&#xA;                          |     |                          &#xA;         Gnd -------------------------x------------------ Gnd&#xA;                          |     |     |    &#xA;                          |     |     |&#xA;                         Rx1   Rx2   Gnd&#xA;&#xA;                            Sniffer (say an XMEGA with 3+ UARTS)&#xA;&#xA;                         Tx1&#xA;                          |&#xA;                          x-----TX_IN-[MAX232]-TX_OUT----- Rx Computer Terminal&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;With some creative firmware something like this setup could snoop full-duplex communication between two devices and report the conversation to the user in a 'nice' way. Sorry if this isn't quite what you were asking, but I had to take the ascii art opportunity :).&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-08-25T17:03:04.697" CommentCount="1" />
  <row Id="4157" PostTypeId="2" ParentId="4155" CreationDate="2010-08-25T17:13:51.993" Score="3" ViewCount="" Body="&lt;p&gt;I am unclear what you mean by &quot;no two lines cross each other&quot;. Is this just a problem with the display of the schematic? If so, it's quite common for un-connected lines to cross on a schematic. Often you will see connected lines have a little filled circle 'joint' to indicate the connect, and unconnected lines, one of the lines will make a little unfilled half-circle 'jump' over the other line, to indicate they are crossing but not connected.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-08-25T17:13:51.993" CommentCount="2" />
  <row Id="4158" PostTypeId="2" ParentId="4143" CreationDate="2010-08-25T17:19:12.953" Score="0" ViewCount="" Body="&lt;p&gt;Have you considered doing it in software? Run something on your PC to watch the USB traffic at that level, instead of trying to intercept the actual USB lines in hardware. There are several ways of doing this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you absolutely need hardware, consider the &lt;a href=&quot;http://www.nkcelectronics.com/zeroplus-lap16032u-logic-ana16032.html&quot; rel=&quot;nofollow&quot;&gt;ZeroPlus LogicCube&lt;/a&gt;, it's cheaper, and supports decoding USB 1.1. However the software might not be as nice as your link, since it's more general purpose, and not specifically for USB.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-08-25T17:19:12.953" CommunityOwnedDate="2010-08-25T17:19:12.953" />
  <row Id="4159" PostTypeId="2" ParentId="4155" CreationDate="2010-08-25T18:35:48.337" Score="5" ViewCount="" Body="&lt;p&gt;Since most of the column lines are also row lines I doubt it &#xA;is possible. To avoid crossing lines in a schematic I use&#xA;named nets. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My Charlie-plexing schematics (which use named nets) are at -- &#xA;&lt;a href=&quot;http://wiblocks.luciani.org/FAQ/faq-charlie-plex.html&quot; rel=&quot;nofollow&quot;&gt;http://wiblocks.luciani.org/FAQ/faq-charlie-plex.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-25T20:02:02.067" LastActivityDate="2011-02-25T20:02:02.067" CommentCount="1" />
  <row Id="4160" PostTypeId="2" ParentId="1420" CreationDate="2010-08-25T19:54:57.197" Score="1" ViewCount="" Body="&lt;p&gt;Several people are using mspgcc4 including me. I'm the rare type in that I used it in XP (work machine) and haven't actually tried Linux. I have some 430's and I'm waiting to see if they'll ever ship me a Launchpad so I expect I'll get back to the arch sometime in near future.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Either way, have a look at the non-dead, uncrippled, and not broken_on_half_the_compilers_advertised &lt;a href=&quot;http://github.com/poelzi/OpenChronos&quot; rel=&quot;nofollow&quot;&gt;Openchronos&lt;/a&gt; and #openchronos on freenode. All these people are using GCC4 on the Chronos kit.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-08-25T19:54:57.197" CommentCount="1" />
  <row Id="4161" PostTypeId="2" ParentId="4150" CreationDate="2010-08-25T21:06:47.557" Score="2" ViewCount="" Body="&lt;p&gt;fwiw I've had success with the minimalist two-diode type circuit that you linked to. The only difference being that I used the TX pin of the 'sniffer' device as a handy source of -12V to use through a 47K pull-down to make sure the sniffer's own RX didn't float when neither of the snooped-upon devices was transmitting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless you're driving tens of feet of wire, or are running at faster rates like 115.2kbps, the diode &amp;amp; resistor thing shouldn't affect the circuit too much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really want to buffer the signals to TTL and back, there are of course the MAX chips, and even simple old line-driver/line-receiver type chips like the 1488 quad driver and 1489 quad receiver that would do the job.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-08-25T21:06:47.557" />
  <row Id="4162" PostTypeId="2" ParentId="1420" CreationDate="2010-08-25T22:35:06.617" Score="1" ViewCount="" Body="&lt;p&gt;There is the control panel and sample code software available for Linux for download from TI. I'm not going to look it up but you can. I installed it but was having a problem with it seeing the USB adapter. It does run and like I said it was the adapter driver that was the issue. I'm not a Linux guru but I can I was able to get it going just never bothered to finish up with the USB problem. &lt;/p&gt;&#xA;" OwnerUserId="850" LastActivityDate="2010-08-25T22:35:06.617" />
  <row Id="4163" PostTypeId="1" CreationDate="2010-08-26T13:52:43.240" Score="4" ViewCount="563" Body="&lt;p&gt;I am not a Arduino developer here. However I would like to ask if any developer out there who have experience on the capability of Arduino, is Arduino suitable to develop a humanoid robot? Humanoid robot consists of visual camera, sensors and servos, wireless transceiver, compass, accelerometer and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Correct me if I mentioned anything wrongly. &lt;/p&gt;&#xA;" LastActivityDate="2011-01-13T02:29:33.930" Title="Is Arduino suitable to be a Humanoid Robot controller?" Tags="&lt;arduino&gt;&lt;microcontroller&gt;" AnswerCount="6" />
  <row Id="4164" PostTypeId="2" ParentId="4163" CreationDate="2010-08-26T14:13:16.083" Score="10" ViewCount="" Body="&lt;p&gt;The Arduino Duemilanove only has 14 digital I/Os and six analogue inputs, and 2k SRAM maximum. It doesn't look like it could handle all those peripherals without port expansion, and it hasn't got nearly enough memory for image processing.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-26T14:13:16.083" CommentCount="1" />
  <row Id="4166" PostTypeId="2" ParentId="4163" CreationDate="2010-08-26T15:28:36.913" Score="3" ViewCount="" Body="&lt;p&gt;You might be better off with something beefier than the Arduino. Perhaps an &lt;a href=&quot;http://mbed.org/&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt; (ARM Cortex-M3 based).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although, even it may not have enough lines to control all those peripherals.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-26T15:28:36.913" />
  <row Id="4167" PostTypeId="2" ParentId="4163" CreationDate="2010-08-26T17:22:00.597" Score="0" ViewCount="" Body="&lt;p&gt;Maybe an Arduino plus a whole bunch of Shields, or multiple Arduinos and multiple Shields communicating with one another (wirelessly or otherwise...). Anything is possible :)&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-08-26T17:22:00.597" />
  <row Id="4168" PostTypeId="1" AcceptedAnswerId="4169" CreationDate="2010-08-26T20:19:19.947" Score="6" ViewCount="313" Body="&lt;p&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4119/4930372298_73e5420f5a.jpg&quot; alt=&quot;macro shot of a PCB with a squiggly trace on it&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's on pin 14, which is the master clock input (MCLK) of a &lt;a href=&quot;http://www.wolfsonmicro.com/products/dacs/WM8761/&quot; rel=&quot;nofollow&quot;&gt;WM8761: Low cost stereo DAC&lt;/a&gt;.  I'm guessing it's meant to act as a small inductor?  But why would you want that on a clock input?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-08-26T20:40:29.597" Title="What is this squiggly trace for?" Tags="&lt;pcb&gt;&lt;dac&gt;&lt;inductance&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="4169" PostTypeId="2" ParentId="4168" CreationDate="2010-08-26T20:38:50.690" Score="14" ViewCount="" Body="&lt;p&gt;It's a serpentine track. They are often used where equal track lengths are required with high-speed designs. In this case it is probably used to implement a very short delay.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-26T20:38:50.690" CommentCount="8" />
  <row Id="4171" PostTypeId="1" AcceptedAnswerId="4366" CreationDate="2010-08-27T02:25:51.970" Score="3" ViewCount="274" Body="&lt;p&gt;I'm interested in doing a project to read &lt;a href=&quot;http://en.wikipedia.org/wiki/Radio_Data_System&quot; rel=&quot;nofollow&quot;&gt;FM RDS data&lt;/a&gt;. Can anyone recommend good chips for both the FM receiver and RDS decoder?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an FM receiver, I'd like to be able to control FM frequency (scanning of full range) from a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the RDS decoder, I'm just interested in an IC that's readily available with a simple interface (e.g. I2C or SPI).&lt;/p&gt;&#xA;" OwnerUserId="1025" LastEditorUserId="1025" LastEditorDisplayName="" LastEditDate="2010-08-27T02:32:17.960" LastActivityDate="2010-09-12T13:43:34.813" Title="Good ICs for receiving and decoding FM RDS" Tags="&lt;radio&gt;&lt;fm&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="4172" PostTypeId="1" AcceptedAnswerId="4202" CreationDate="2010-08-27T08:25:44.407" Score="4" ViewCount="454" Body="&lt;p&gt;I'm getting one of these &lt;a href=&quot;http://www.old-computers.com/museum/computer.asp?st=1&amp;amp;c=446&quot; rel=&quot;nofollow&quot;&gt;http://www.old-computers.com/museum/computer.asp?st=1&amp;amp;c=446&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm planning to build a server inside it. And I was thinking of using the built in CGA-monitor as a statusdisplay (LCDInfo style, or whatever the cool geeks use nowadays).&#xA;The screen is monochrome amber so it would probably look a bit like the Planar EL-screens some have been using in their mods. And I want to use an Arduino (or something like it) as a middleware solution... PC -&gt; Arduino -&gt; Screen&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been checking up a bit, and CGA is a RGBI signal using TTL-communications. 4 lines (RGB + Intensity), combined with HSYNC (15.75KHz) and VSYNC (60Hz).&#xA;The 4 &quot;color-inputs&quot; are logic on or off. The combination of these generates up to 16 colors. However, as this is an amber screen, it would probably be easiest to start with &quot;all-high&quot; or &quot;all-low&quot;... White and Black.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the problem is the following... I could probably both wire and code the arduino to flip the TTL-lines on and off, but I'm not sure what I do with the HSYNC and VSYNC inputs. And how to time the TTL-flips to correspond to pixels on the screen. (The standard CGA resolution is 320x200).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not very good at electronics, but I'm very good at following instructions, and taking hints &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone tried this before?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;EDIT&lt;/em&gt;:&#xA;Could I maybe use a modified version of this? &lt;a href=&quot;http://www.eosystems.ro/deogen/deogen_en.html&quot; rel=&quot;nofollow&quot;&gt;http://www.eosystems.ro/deogen/deogen_en.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;EDIT2&lt;/em&gt;:&#xA;I don't &lt;em&gt;need&lt;/em&gt; to use an Arduino. But I want to keep it as simple as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;EDIT3&lt;/em&gt;:&#xA;It might seem that the monitor in question actually is a composite monitor, and not a &quot;real&quot; CGA input monitor. So that probably makes things a bit easier. But I'm still interested in how to generate a pure CGA signal using a microcontroller...&lt;/p&gt;&#xA;" OwnerUserId="1091" LastEditorUserId="1091" LastEditorDisplayName="" LastEditDate="2010-08-31T06:33:07.933" LastActivityDate="2011-05-10T16:55:10.687" Title="How can I control a CGA screen with an Arduino?" Tags="&lt;video&gt;&lt;ttl&gt;&lt;pc&gt;&lt;microcontroller&gt;" AnswerCount="6" CommentCount="0" FavoriteCount="2" />
  <row Id="4173" PostTypeId="1" AcceptedAnswerId="4184" CreationDate="2010-08-27T08:32:18.073" Score="3" ViewCount="359" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an arduino project that is almost finished.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now it controls a series of ShiftBrites(ShiftBrties being 10bit RGB LED's) now they use a simple 4 wire configuration(Data, Logic, Clock, Enable) and +5v and GND. its all done over a wireless setup. ShiftBrites are connected to a Arduino and an xBee module. (My basic setup &lt;a href=&quot;http://ashleyhughesarduino.wordpress.com/2010/08/01/shiftbrites-and-the-arduino/&quot; rel=&quot;nofollow&quot;&gt;http://ashleyhughesarduino.wordpress.com/2010/08/01/shiftbrites-and-the-arduino/&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Problem is that the arduino can only output so much juice(Current) before everything starts smoking, my question is how would I connect it up so that the +5v comes straight off the power pack from the wall?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connect to the Vin point on the arduino? or Connect the +5v before the arduino?&#xA;???&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks Hughesy&lt;/p&gt;&#xA;" OwnerUserId="665" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-08-28T18:55:52.333" LastActivityDate="2011-05-20T10:57:17.700" Title="Arduino how to get more Power" Tags="&lt;arduino&gt;&lt;power&gt;" AnswerCount="2" />
  <row Id="4174" PostTypeId="2" ParentId="4172" CreationDate="2010-08-27T09:41:27.750" Score="0" ViewCount="" Body="&lt;p&gt;I've never used CGA but you may be able to adapt one of the (many) Arduino VGA projects to your purpose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I built a &lt;a href=&quot;http://blog.hodgepig.org/articles/000020-pong/index.html&quot; rel=&quot;nofollow&quot;&gt;VGA pong game&lt;/a&gt; around an ATMega168 which might be a good starting point (links &lt;a href=&quot;http://blog.hodgepig.org/articles/000019-tv3/index.html&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt; &lt;a href=&quot;http://blog.hodgepig.org/articles/000017-tv1/index.html&quot; rel=&quot;nofollow&quot;&gt;2&lt;/a&gt;). I used the &lt;a href=&quot;http://avga.prometheus4.com/&quot; rel=&quot;nofollow&quot;&gt;AVGA library&lt;/a&gt;, which does all of the VGA timing under interrupt so your foreground code only needs to be concerned with moving sprites around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option might be to modify a &lt;a href=&quot;http://www.ladyada.net/make/ybox2/&quot; rel=&quot;nofollow&quot;&gt;YBox&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-08-27T12:24:11.527" LastActivityDate="2010-08-27T12:24:11.527" CommentCount="1" />
  <row Id="4175" PostTypeId="1" CreationDate="2010-08-27T10:42:47.450" Score="3" ViewCount="167" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did not find a place holder for asking questions related to Digital design - Frontend / Backend(Physical) on stackexchange. So i proposed one there on area51. So for time being asking my question here -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1]I am looking for a book on Physical Design/Backend design for beginners. I am basically a software developer,having overview(no hands-on) of Digital design process(both frontend and backend). But now as part of job, I have to start contributing by doing &quot;real work&quot; on Physical design for a SoC. What book would explain in detail, almost all aspects of Physical Design, in a step by step kind of manner. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you point of any other reading material like blogs/IEEE-papers/websites/forums which talk about physical design would also help me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank You.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-AD&lt;/p&gt;&#xA;" OwnerUserId="1092" LastActivityDate="2010-09-02T02:38:43.177" Title="What are good books/reading material for Physical Design" Tags="&lt;physical-design&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="4176" PostTypeId="2" ParentId="4173" CreationDate="2010-08-27T11:04:13.220" Score="1" ViewCount="" Body="&lt;p&gt;The easiest way could be to use two power packs. Plug one into the Arduino and the&#xA;other into your high current load. You just need to tie the output grounds together. &#xA;Since it sounds like the ShiftBrite runs off of 5V you either need a regulated &#xA;output power pack or a voltage regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively you could make a power cable with one input connector &#xA;and two output connectors. I believe you will need a voltage regulator &#xA;on the ShiftBrite side.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T10:57:17.700" LastActivityDate="2011-05-20T10:57:17.700" />
  <row Id="4177" PostTypeId="2" ParentId="4172" CreationDate="2010-08-27T11:39:11.067" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/arduino-tvout/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/arduino-tvout/&lt;/a&gt; is probably what you need. If you are lucky the internal monitor will accept an NTSC signal.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-08-27T11:39:11.067" CommentCount="6" />
  <row Id="4179" PostTypeId="2" ParentId="2036" CreationDate="2010-08-27T14:15:15.377" Score="2" ViewCount="" Body="&lt;p&gt;I use the logic analyser from saleae (http://www.saleae.com/home/).&#xA;It's very good and works fine. It's priced at US$ 149.00.&lt;/p&gt;&#xA;" LastActivityDate="2010-08-27T14:15:15.377" />
  <row Id="4180" PostTypeId="1" CreationDate="2010-08-27T14:31:48.800" Score="2" ViewCount="323" Body="&lt;p&gt;Let's say there is a USB stick that is specifically for storing dates or days or some kind of arbituary data. In order to access the data you must have the software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any way to analyze the USB signals and make your own hardware to read values on flash drive? What methods exist for doing so?&lt;/p&gt;&#xA;" LastActivityDate="2010-09-14T18:00:13.740" Title="Reversing engineering USB signals" Tags="&lt;usb&gt;&lt;engineering&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="4181" PostTypeId="2" ParentId="4180" CreationDate="2010-08-27T14:43:48.150" Score="3" ViewCount="" Body="&lt;p&gt;Yes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been very pleased with the &lt;a href=&quot;http://www.hhdsoftware.com/usb-monitor&quot; rel=&quot;nofollow&quot;&gt;software from HHD&lt;/a&gt;. I used the serial port monitor to do some heavy reverse engineering a few years back and the HHD software was well tailored for the work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I dabbled with their USB sniffer version but never bought the full version. Back in the day there was a free trial version that was somewhat useful. They may still have it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At any rate, I got in over my head with USB because I couldn't figure out how to make the &quot;driver&quot; in Windows. If you're using Linux the project may be quite a bit easier, since all of that low level driver I/O logic is easily accessible in the kernel code. Also, Linux 2.6 offers some devices under /dev which can be used to directly send/receive to the USB device without the need for any special module/drivers. Great for development. &lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-08-27T14:43:48.150" CommentCount="2" />
  <row Id="4182" PostTypeId="1" AcceptedAnswerId="4183" CreationDate="2010-08-27T15:20:09.643" Score="2" ViewCount="43" Body="&lt;p&gt;According to its datasheet, the TD62783AFNG is an 8-channel high-voltage high source-current driver. It is a Darlington arrangement that can source (not sink) up to half an amp through a pin. What similar chips are available?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.semicon.toshiba.co.jp/docs/datasheet/en/LinearIC/TD62783AFNG_en_datasheet_091116.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.semicon.toshiba.co.jp/docs/datasheet/en/LinearIC/TD62783AFNG_en_datasheet_091116.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-08-27T15:41:19.087" Title="What's a good substitute for the TD62783AFNG?" Tags="&lt;led&gt;&lt;driver&gt;" AnswerCount="1" />
  <row Id="4183" PostTypeId="2" ParentId="4182" CreationDate="2010-08-27T15:41:19.087" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tlc59213a.html&quot; rel=&quot;nofollow&quot;&gt;Texas Instruments TLC59213A&lt;/a&gt; is similar, but not as high voltage. Other than that, it looks like a good fit.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-08-27T15:41:19.087" CommentCount="1" />
  <row Id="4184" PostTypeId="2" ParentId="4173" CreationDate="2010-08-27T18:01:59.227" Score="5" ViewCount="" Body="&lt;p&gt;ShiftBrites actually prefer to run on 5.5V to 9V. Most reliable results seem to be with 6 to 7 volts. Regulation is not too crucial, but switching power supplies work well and are smaller and lighter than transformer based supplies. Each ShiftBrite can draw up to 60mA, so multiply that by the number of ShiftBrites you have to determine the current rating of the power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You definitely need to connect the grounds of all your supplies together. Just make sure the ShiftBrite V+ positive supply is not connected to the Arduino 5V supply if you are using different voltages! Actually, if you choose something like 7V you can power the ShiftBrite chain, and connect the same power to the Arduino VIN. The Arduino will regulate the power for itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This simple wiring is all done for you on the ShiftBrite Shield, you attach external power to the screw terminal and plug the ShiftBrite chain into the six pin connector: &lt;a href=&quot;http://macetech.com/store/index.php?main_page=product_info&amp;amp;cPath=4&amp;amp;products_id=7&quot; rel=&quot;nofollow&quot;&gt;http://macetech.com/store/index.php?main_page=product_info&amp;amp;cPath=4&amp;amp;products_id=7&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="870" LastActivityDate="2010-08-27T18:01:59.227" CommentCount="1" />
  <row Id="4185" PostTypeId="1" AcceptedAnswerId="4270" CreationDate="2010-08-27T18:51:50.520" Score="4" ViewCount="496" Body="&lt;p&gt;I am going through the book &quot;Elements of computing systems&quot;. This book teaches how to build a whole computer from scratch. While I was just browsing the chapters on computer architecture, I noticed that it all focused on the Von Neumann architecture. I was just curious as to what are the other architectures and when &amp;amp; where they are used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know about only two, one is Von Neumann and the second is Harvard. Also I know about RISC which is used in uC of AVR.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-09-11T03:32:22.417" Title="What are different types of computer architectures?" Tags="&lt;architecture&gt;&lt;computers&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="4186" PostTypeId="2" ParentId="4185" CreationDate="2010-08-27T18:56:18.177" Score="3" ViewCount="" Body="&lt;p&gt;Both von Neumann and Harvard architectures can be used with RISC processors such as the AVR and ARM. The AVR uses Harvard, whereas some ARM chips use von Neumann and some use Harvard.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-27T18:56:18.177" />
  <row Id="4187" PostTypeId="2" ParentId="4185" CreationDate="2010-08-27T19:25:57.870" Score="5" ViewCount="" Body="&lt;p&gt;CISC is the &quot;opposite&quot; of RISC.  Whereas RISC prefers to have simple instructions that are easy for the compiler to optimize and often the same size, CISC is fond of complex instructions of varying size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, a pop instruction in CISC will modify the stack pointer &lt;em&gt;and&lt;/em&gt; place the data from the stack into another register.  However, a RISC processor would read the data with one instruction and then modify the stack pointer with a second instruction.  (generally; there are some exceptions, like the PowerPC which can update the stack pointer and push data onto the stack, but that's an exception)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since RISC instructions are all the same size, disassemblers are easier to write.  Designing the processor is also easier, because the pipeline doesn't have to account for varying instruction sizes.  However, CISC code density tends to be better, both because the complex instructions require fewer bytes to represent the same number of operations, and because the variable instruction length allows for some &quot;compression&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also other exotic architectures, like VLIW/EPIC.  This sort of architecture was designed with parallel processing in mind.  However, they didn't do very well, because they place a very heavy burden on the compiler to optimize, whereas other architectures have fancy instruction windows that relieve some optimization burden from the compiler.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-08-27T19:25:57.870" CommentCount="2" />
  <row Id="4188" PostTypeId="1" AcceptedAnswerId="4224" CreationDate="2010-08-28T04:30:59.373" Score="3" ViewCount="372" Body="&lt;p&gt;I found this &lt;a href=&quot;http://www.serasidis.gr/circuits/SMSremoteV3/SMSrcV3.htm&quot; rel=&quot;nofollow&quot;&gt;project that uses a GSM module&lt;/a&gt; (scroll down to see Picture 5). It seems the module has to be bought separately. I have old GSM cell phones lying around in the house. Shouldn't these phones contain such a chip? Is it possible to remove the chip and use it on a circuit board as shown in some of the pictures in the project?&lt;/p&gt;&#xA;" OwnerUserId="1030" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-05T02:59:12.537" LastActivityDate="2011-03-05T02:59:12.537" Title="Can I remove a GSM module from an old cell phone?" Tags="&lt;wireless&gt;&lt;gsm&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="4189" PostTypeId="2" ParentId="4188" CreationDate="2010-08-28T05:37:40.087" Score="4" ViewCount="" Body="&lt;p&gt;Unfortunately, no.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In cell phones, the RF components are very tightly integrated with everything else.&lt;br&gt;&#xA;Basically, for size and cost reasons, they design a custom circuit board with the GSM interface devices and the actual phone hardware all assembled together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may be possible to tap the interface between whatever local processor the phone uses, and the RF stage, but it would very likely not provide a simple interface similar to the module used on the linked page. In any event, it would be a &lt;strong&gt;significant&lt;/strong&gt; challenge to even get access to the interface wiring, as most phones use PCBs with many layers (4-10), and all the parts are generally BGA.&lt;br&gt;&#xA;In addition to this, you would also likely have to do a lot of processing to get the RF section of the phone to properly communicate with the cell towers, since it's likely that the phones main processor handles some portion of the wireless interface protocol. This would require a fairly powerful MCU and non-trivial programming effort.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, there is a reason they sell phone modules like that.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-08-28T05:37:40.087" />
  <row Id="4190" PostTypeId="2" ParentId="4172" CreationDate="2010-08-28T05:48:48.583" Score="3" ViewCount="" Body="&lt;p&gt;Are you set on a Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.parallax.com/propeller/&quot; rel=&quot;nofollow&quot;&gt;Parallax Propeller&lt;/a&gt; can generate all sorts of video signals natively. There is code available for Generating VGA and composite video signals, and all the sources are available too, so you can tweak them if you want. Internally, it has a set of specialized video-timing-generation logic. It should be possible to configure the system to drive that screen without too much trouble, though it may require a bit of external SRAM if you want to be able to display full motion in full (well, as full as it gets considering it's a amber display) color.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, it's &lt;strong&gt;way&lt;/strong&gt; more powerful than a arduino.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-08-28T05:48:48.583" CommentCount="2" />
  <row Id="4192" PostTypeId="1" CreationDate="2010-08-28T12:54:37.960" Score="5" ViewCount="217" Body="&lt;p&gt;Has anyone else had instances where an AVR just mysteriously stopped working after several months, but reprogramming it would bring it back?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm running a bunch of atmega328's in wireless sensor network.  I've now had 3 times (in about a year) when one of them has just stopped working.  I'll re-burn the program to it and it'll start working again.  It's not always the same unit, so it doesn't seem like it's a defective chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That seems like it would be a rather disastrous thing that would keep people from using AVRs, so it's obviously something about my particular circumstances.  I was just wondering if anyone else has run into it and might have some pointers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm running at 3.3V off of batteries, so the voltage will sag too low to operate once every couple months and I have to replace the rechargeables.  The modules use sleep mode and the watchdog timer to sleep for 60 seconds, take a reading, radio it back to the base station and then sleep again.  The modules are arduino compatible, so I haven't flipped the &quot;don't let me re-burn this&quot; bit.&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2010-10-16T12:48:40.040" Title="AVR deprogramming itself" Tags="&lt;avr&gt;&lt;flash&gt;&lt;arduino&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="4193" PostTypeId="2" ParentId="4192" CreationDate="2010-08-28T13:27:25.947" Score="3" ViewCount="" Body="&lt;p&gt;Are you using BOD? Nasty things can occasionally happen if a chip browns out.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-28T13:27:25.947" CommentCount="5" />
  <row Id="4194" PostTypeId="1" AcceptedAnswerId="4217" CreationDate="2010-08-28T19:00:31.287" Score="4" ViewCount="402" Body="&lt;p&gt;I was implementing the ALU from the specs given in my The Elements of Computing systems book. I am stuck on only one problem. How do I find if a given number is zero or not. One thing I can do is or every bit in the bus, and then apply a not gate on that. But there has to be some other elegant solution.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-09-02T21:50:13.343" Title="How to find out if a binary number is zero" Tags="&lt;alu&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="4195" PostTypeId="2" ParentId="4194" CreationDate="2010-08-28T19:12:57.960" Score="3" ViewCount="" Body="&lt;p&gt;Some CPUs, MIPS for example, have a register that always contains zero, making testing another register for zero very fast.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-08-28T19:12:57.960" CommentCount="5" />
  <row Id="4196" PostTypeId="2" ParentId="4194" CreationDate="2010-08-28T19:47:29.490" Score="11" ViewCount="" Body="&lt;p&gt;The logic function is the NOR gate. That is the simplest logic function that exists.&lt;/p&gt;&#xA;" OwnerUserId="540" LastActivityDate="2010-08-28T19:47:29.490" />
  <row Id="4197" PostTypeId="2" ParentId="4194" CreationDate="2010-08-28T21:35:45.487" Score="7" ViewCount="" Body="&lt;p&gt;The typical solution with 8 bit machines was that the ALU would produce a number of 'flag' bits that would represent the outcome of the most recent operation. While it would be possible to have any number of flag bits around (i.e., you could have a 'Z' flag for every register in your CPU), it's usually the thing you've just computed that you're most interesting in, so it makes a certain degree of sense to do it that way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of those old CPUs would automatically set flag bits for almost every data move, while others would require you to stick a specific 'compare' instruction in your code if you just suddenly need to know if a certain register was zero. And whether you provide a zero check for every register or just for what's just been computed, there really is no simpler way to check for &quot;is this word zero&quot; than to just OR all the bits together.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-08-28T21:35:45.487" CommentCount="4" />
  <row Id="4198" PostTypeId="2" ParentId="4080" CreationDate="2010-08-28T22:00:06.697" Score="1" ViewCount="" Body="&lt;p&gt;Bifferboard?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://sites.google.com/site/bifferboard/&quot; rel=&quot;nofollow&quot;&gt;http://sites.google.com/site/bifferboard/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;    * 150MHz CPU, Intel 486SX instruction set, MMU.&#xA;    * 1 watt power consumption (200mA @5v)&#xA;    * 68mm x 28mm x 21mm (weight 28g)&#xA;    * 32MB SDRAM/8MB Flash&#xA;    * OHCI/EHCI USB 2.0&#xA;    * 10/100 ethernet&#xA;    * Serial console 115200 baud (can be used as 2 GPIO)&#xA;    * 4-pin JTAG (can be used as GPIO)&#xA;    * 2 permanent GPIO (1 LED, 1 button)&#xA;    * Linux 2.6.32.16&#xA;    * Supplied pre-flashed with OpenWrt&#xA;    * 35 GBP each &#xA;&lt;/pre&gt;&#xA;" OwnerUserId="726" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-10-01T19:46:56.990" LastActivityDate="2010-10-01T19:46:56.990" CommentCount="1" />
  <row Id="4199" PostTypeId="1" CreationDate="2010-08-29T12:07:46.050" Score="2" ViewCount="513" Body="&lt;p&gt;I want to do PIC programming in embedded C. But I don't know the language well. Please help me by suggesting some good sites for getting an idea about C programming.&lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-28T09:06:31.570" LastActivityDate="2011-02-28T09:06:31.570" Title="C language beginner" Tags="&lt;pic&gt;&lt;c&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="2" />
  <row Id="4200" PostTypeId="2" ParentId="4199" CreationDate="2010-08-29T13:34:09.807" Score="4" ViewCount="" Body="&lt;p&gt;Get The C Programming Language by Kernighan and Ritchie. They invented C and it's the best introduction to the language there is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of the low-cost C compilers for the PIC are rather non-standard. Microchip's C18 for the PIC18 and Hi-Tech's C for the smaller PICs would be better; free versions of both compiler are available.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-08-29T15:30:30.110" LastActivityDate="2010-08-29T15:30:30.110" CommentCount="2" />
  <row Id="4201" PostTypeId="2" ParentId="4199" CreationDate="2010-08-29T14:28:14.530" Score="11" ViewCount="" Body="&lt;p&gt;Microcontrollers like the PIC are very unforgiving to the learner. If you're setting out trying to learn C for the first time, practice on a PC first. Test your code as much as you can on your PC where you have a good debugger and protection from memory faults.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you're confident that your logic is working right, then compile your code for the PIC.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-29T14:28:14.530" CommentCount="1" />
  <row Id="4202" PostTypeId="2" ParentId="4172" CreationDate="2010-08-29T16:09:09.320" Score="5" ViewCount="" Body="&lt;p&gt;The hsync and vsync signals are just relatively short, negative pulses that reset the CRT's electron beam to the left and top of the screen respectively.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since CGA was basically just NTSC (AKA RS-170) with separate sync and components, the timing of the pulses should be the same. The hsync would occur about every 63.5 microseconds, and the vsync about every 16.7 milliseconds. The vertical timing should be well within the capabilities of an arduino, but the horizontals might be more challenging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;During the active horizontal scan you'd need to update the luminance according to the horizontal resolution you're designing to. To get 640 pixels, assuming you use about 53 us of the horizontal trace time to allow for HS duration, and margins to make sure your output doesn't run off the edges of the CRT, you need to output a new pixel about every 82 nanos,. Now, 82 ns is (probably) way to fast to get directly from an arduino, but if you employ an external 8-bit shift register, you only have to load that about every 660 ns, i.e., order of half a microsecond. Of course you could opt for 320 pixels and ease the timing further.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If meeting that kind of timing sounds reasonable to you, the exact numbers could easily be had via some light googling. For example, &lt;a href=&quot;http://zone.ni.com/devzone/cda/tut/p/id/3020&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; looks like a pretty good example.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-08-29T16:35:31.903" LastActivityDate="2010-08-29T16:35:31.903" />
  <row Id="4203" PostTypeId="2" ParentId="4199" CreationDate="2010-08-29T19:38:42.673" Score="6" ViewCount="" Body="&lt;p&gt;I'd recommend getting K&amp;amp;R because I like to read a book as I learn a language, but if you're looking for an online resource, Wikibooks' &lt;a href=&quot;http://en.wikibooks.org/wiki/C_Programming&quot; rel=&quot;nofollow&quot;&gt;C Programming&lt;/a&gt; isn't a bad read. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, for a topical resource, look at &lt;a href=&quot;http://www.cprogramming.com&quot; rel=&quot;nofollow&quot;&gt;http://www.cprogramming.com&lt;/a&gt; or &lt;a href=&quot;http://www.cprogramming.com&quot; rel=&quot;nofollow&quot;&gt;http://www.cplusplus.com&lt;/a&gt; - Note that both are C/C++ sites, you must be wary of the differences.  You don't want to use C++ for your PIC projects.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When doing native (PC) programming, follow links to the &lt;a href=&quot;http://www.opengroup.org/onlinepubs/7990989775/&quot; rel=&quot;nofollow&quot;&gt;Opengroup.org Single Unix Specification&lt;/a&gt;.  Also be aware of the cross-referenced and searchable Linux kernel source code at &lt;a href=&quot;http://lxr.linux.no&quot; rel=&quot;nofollow&quot;&gt;http://lxr.linux.no/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://groups.google.com/group/comp.lang.c&quot; rel=&quot;nofollow&quot;&gt;comp.lang.c&lt;/a&gt;  mailing list (Searchable Google Groups page) and its &lt;a href=&quot;http://c-faq.com/&quot; rel=&quot;nofollow&quot;&gt;FAQ&lt;/a&gt; are also useful.  &lt;a href=&quot;http://www.daniweb.com/forums/forum118.html&quot; rel=&quot;nofollow&quot;&gt;Daniweb's C forum&lt;/a&gt; and, of course, &lt;a href=&quot;http://stackoverflow.com/questions/tagged/c&quot;&gt;the &quot;C&quot; tag on Stackoverflow&lt;/a&gt; are also more sources for specific questions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Last, a Google search for &lt;code&gt;&quot;C Language&quot;  + keyword&lt;/code&gt; is a good starting point for many questions, and usually yields better results than just the letter C.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-08-29T19:38:42.673" CommentCount="2" />
  <row Id="4204" PostTypeId="2" ParentId="4199" CreationDate="2010-08-29T21:20:39.997" Score="2" ViewCount="" Body="&lt;p&gt;Once you are ready to apply your C skills to the PIC, I would get a development board, and one of the following books, depending on whether you are dealing with 8-bit (PIC1x), 16-bit (PIC24) or 32-bit (PIC32) devices:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Programming 8-bit PIC Microcontrollers in C: with Interactive Hardware Simulation&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microcontrollers: From Assembly Language to C Using the PIC24 Family&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Programming 32-bit Microcontrollers in C: Exploring the PIC32&lt;/p&gt;&#xA;&#xA;&lt;p&gt;all available on Amazon (along with lots of similar titles covering PICs and C).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I would shy away from 8-bit PICs lower than the PIC18, as they are not as well suited to the C language.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-08-29T21:20:39.997" />
  <row Id="4205" PostTypeId="2" ParentId="4180" CreationDate="2010-08-29T22:14:56.047" Score="1" ViewCount="" Body="&lt;p&gt;Reverse engineering USB can be a challenge; there is a lot of data to sort through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, you have to understand the protocol; I found &lt;a href=&quot;http://www.beyondlogic.org/usbnutshell/usb1.htm&quot; rel=&quot;nofollow&quot;&gt;USB in a Nutshell&lt;/a&gt; to be pretty good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you need some way of collecting the traffic and analyzing it. It requires at least some software, and possibly some hardware. I use a hardware USB analyzer at work, but they are expensive. I know it is possible to use Virtualbox and collect the USB traffic in Linux, but I've never done it. You can start with &lt;a href=&quot;http://vusb-analyzer.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;Virtual USB Analyzer&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="238" LastActivityDate="2010-08-29T22:14:56.047" />
  <row Id="4206" PostTypeId="1" AcceptedAnswerId="4207" CreationDate="2010-08-30T03:51:29.777" Score="3" ViewCount="358" Body="&lt;p&gt;Hi folks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a PIC16F886, I am trying to generate interrupts every 100 milliseconds using TMR0 clocked from the internal oscillator, but I am getting some really strange behaviour.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a battery powered circuit, so I am using the 125KHz internal oscillator, selected via:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;OSCCON = 0b00010000; // select 125 KHz Int. Osc. = IRCF&amp;lt;2:0&amp;gt;=001&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I then assign the prescaler to TMR0 and set a prescaler value of 1:2:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;T0CS = 0;   // TMR0 Clock Source: Internal instruction cycle clock (FOSC/4)&#xA;PSA = 0;    // Prescaler is assigned to TMR0&#xA;PS2 = 0;&#xA;PS1 = 0;    // &amp;gt; TMR0 Rate: 1:2;&#xA;PS0 = 0; &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;So now, according to my calculations each 'tick' should take &lt;code&gt;((1/125 000) / 4) / 2 = 1.0 × 10^-6&lt;/code&gt; seconds, If I preload the timer with 155, it will take 100 'ticks' to overflow, generating an interrupt every 100uS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My interrupt service routine consists of:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if(T0IE)&#xA;{&#xA;    ticks++;&#xA;    if (ticks &amp;gt;= 999){&#xA;        ticks = 0;&#xA;&#xA;        PORTB = ~PORTB;&#xA;    }&#xA;&#xA;    TMR0 = 155; &#xA;    return;     &#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And it does function, but the timing is not exactly right.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I simulate it using the MPLAB SIM, It takes around 85mS and on real hardware it seems take longer than 100mS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The full code listing can be found here: &lt;a href=&quot;http://pastebin.ca/1928766&quot; rel=&quot;nofollow&quot;&gt;http://pastebin.ca/1928766&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is quite possibly I am miscalculating something, so any pointers/corrections would be much appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;br&gt;&#xA;H.&lt;/p&gt;&#xA;" OwnerUserId="1098" LastEditorUserId="1098" LastEditorDisplayName="" LastEditDate="2010-08-30T04:39:25.127" LastActivityDate="2011-05-02T20:25:26.050" Title="PIC16 Timer0 oddity" Tags="&lt;pic&gt;&lt;pic&gt;&lt;c&gt;&lt;mplab&gt;" AnswerCount="4" />
  <row Id="4207" PostTypeId="2" ParentId="4206" CreationDate="2010-08-30T04:42:31.563" Score="5" ViewCount="" Body="&lt;p&gt;I believe your calculations are mixing frequency and time periods.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1 / 125000 Hz equals a period of 8 us.   FOSC/4 divides the frequency further down (or multiplies the period).  You cannot multiply a frequency without special circuitry.  The prescaler also divides the frequency, or multiples the period.  So instead of dividing the 8 us by 4*2, you need to multiply it by 8: 8 * 4 * 2 = a period of 64 us, or 64 times what you thought it was.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, 1000 doesn't divide evenly by 64, so you can't get a exact 1 ms interrupt.  Instead you should probably use a clock frequency of 1 MHz (OSCCON = 0b01000000) for a period of 1 us.  Then 8 * 1 us equals 8 us, and you can use a clock preset of 256-125=134 or 0x86 and get an interrupt every 1 ms.  Count every 100 of those for your 100 ms timing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an alternative, if power consumption is an issue, you could set the clock frequency to 250 KHz (just double what you were using), and get an interrupt every 4 ms.  Then count 25 of those for 100 ms timing.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-08-30T04:50:29.920" LastActivityDate="2010-08-30T04:50:29.920" CommentCount="1" />
  <row Id="4208" PostTypeId="1" AcceptedAnswerId="4213" CreationDate="2010-08-30T06:49:20.737" Score="3" ViewCount="191" Body="&lt;p&gt;I'm looking for some advice on which components to use for this application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem:  We'd like to measure the amount of &quot;noise&quot; in a warehouse and display this on a LCD/monitor/whatever.  When the noise reaches a certain threshold, it will be suggested that employees put on their ear protection headsets.  The sensors (microphones) need to be wireless (RF/Wifi would be preferred!  A wired RS-232/485 solution would be considered as well) and need to send samples at least every second.  Having a dedicated PC to gather and display the samples is also being considered.  For now we're only thinking of one sensor but would like to expand this to many in future.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to know what components you would use to accomplish this.  I'm looking for a very easy way to gauge noise so maybe decibel samples would be good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any hints very welcome!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="561" LastActivityDate="2010-08-30T18:06:38.270" Title="Noise detection data logger - wireless" Tags="&lt;sensor&gt;&lt;microphone&gt;&lt;noise&gt;&lt;detection&gt;&lt;pc&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="4209" PostTypeId="2" ParentId="4199" CreationDate="2010-08-30T13:10:07.227" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://mindview.net/CDs/ThinkingInC/beta3&quot; rel=&quot;nofollow&quot;&gt;Thinking in C&lt;/a&gt;. There are some bugs, but it's a great free ebook from Bruce Eckel.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-09-02T13:07:22.470" LastActivityDate="2010-09-02T13:07:22.470" CommentCount="2" />
  <row Id="4210" PostTypeId="2" ParentId="4208" CreationDate="2010-08-30T13:17:19.207" Score="1" ViewCount="" Body="&lt;p&gt;If there is only one sensor,the easiest way would be to use a simple &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8669&quot; rel=&quot;nofollow&quot;&gt;microphone+Micro controller&lt;/a&gt; interfaced to the PC the via serial port.You can also use the same controller to drive a relay(that switches a hooter) or an LED signage. However if a wireless network is involved (with multiple sensors), you might want to check out &lt;a href=&quot;http://www.thisisant.com/&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If accuracy of measurement is important (especially in a factory setting), you're better off using a professional decibel meter instead of setting up a mesh of nodes. &lt;/p&gt;&#xA;" OwnerUserId="921" LastActivityDate="2010-08-30T13:17:19.207" />
  <row Id="4211" PostTypeId="1" AcceptedAnswerId="4214" CreationDate="2010-08-30T14:25:24.937" Score="6" ViewCount="504" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am thinking about starting a project and was just looking for some general input. Where I work our company currently have remote stations that take data in from a radio link and input the data to a sql database. I am responsible for maintaining the stations and their scripts. Currently they are just running on a desktop pc connected to a radio receiver and an internet connection. I have had some limited experience with working with embedded systems in the past, and would like to explore the possibility of migrating the current setup to an embedded system. The most difficult aspect of the project that I can foresee is gaining internet connectivity to a pic chip and having enough memory for the libraries that would be needed to connect to a sql database.  Can anyone recommend a resource so I can learn how to connect a pic chip to the internet as well as any recommendation on what kind of pic chip to use?  I know this can be quite a daunting task, but I like to think that I am up for the challenge.  &lt;/p&gt;&#xA;" OwnerUserId="811" LastActivityDate="2011-05-16T14:32:09.503" Title="Embedded System that is able to connect to the internet." Tags="&lt;pic&gt;&lt;ethernet&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="4" />
  <row Id="4212" PostTypeId="2" ParentId="2759" CreationDate="2010-08-30T14:33:24.257" Score="2" ViewCount="" Body="&lt;p&gt;I ended up trying a true sine inverter, and that seemed to do the trick. I guess the ups did not like the square wave from the inverter.&lt;/p&gt;&#xA;" OwnerUserId="811" LastEditorUserId="811" LastEditorDisplayName="" LastEditDate="2010-08-30T17:07:57.130" LastActivityDate="2010-08-30T17:07:57.130" />
  <row Id="4213" PostTypeId="2" ParentId="4208" CreationDate="2010-08-30T14:33:30.217" Score="3" ViewCount="" Body="&lt;p&gt;Yep, use an omnidirectional electret with a flat frequency response into the ADC of a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To measure subjective loudness (which I believe is also what you want to measure for hearing protection), you should probably use &lt;a href=&quot;http://en.wikipedia.org/wiki/A-weighting&quot; rel=&quot;nofollow&quot;&gt;A-weighting&lt;/a&gt;, or at least  filter out very low or very high frequencies.  You wouldn't want false positives from ultra low frequencies that encourage them to ignore the warnings, for instance.  (&quot;In almost all countries, the use of A-frequency-weighting is mandated to be used for the protection of workers against noise-induced deafness.&quot;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then do an RMS measurement of the samples over a period of time to get the perceived loudness.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Digital:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a high-level implementation of A-weighting in &lt;a href=&quot;http://www.mathworks.com/matlabcentral/fileexchange/69&quot; rel=&quot;nofollow&quot;&gt;MATLAB&lt;/a&gt; and &lt;a href=&quot;http://gist.github.com/148112&quot; rel=&quot;nofollow&quot;&gt;Python&lt;/a&gt; for reference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suppose micro ADCs don't have any anti-aliasing built-in, so you'd have to add an anti-aliasing filter.  Sampling frequency would have to be pretty high.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Analog:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also do the filtering and RMS measurement in hardware, and just sample the output of that at a much slower rate with the micro.  Here's a &lt;a href=&quot;http://sound.westhost.com/project17.htm&quot; rel=&quot;nofollow&quot;&gt;hardware A-weighting filter&lt;/a&gt; or you could do a simpler band-pass filter for a rough estimate.  It's possible to do true RMS measurements in hardware, but I don't know the circuits.  You can get a similar &quot;VU meter&quot; result by full-wave rectifying and filtering, which is probably good enough for your task.  That's all mixing boards use for their meters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;so maybe decibel samples&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're just using a threshold on the RMS measurement then you don't need to convert to dB or anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;need to send samples at least every second&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd do the RMS processing in the micro in the sensor, and then just send a single measurement of loudness each second.  You don't need to send the actual audio samples.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-30T18:06:38.270" LastActivityDate="2010-08-30T18:06:38.270" CommentCount="1" />
  <row Id="4214" PostTypeId="2" ParentId="4211" CreationDate="2010-08-30T14:40:48.067" Score="5" ViewCount="" Body="&lt;p&gt;Some members of the PIC32 family, such as the &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=PIC32MX675F256H-80I/PT-ND&quot; rel=&quot;nofollow&quot;&gt;PIC32MX675F256H&lt;/a&gt; and &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=PIC32MX795F512L-80I/BG-ND&quot; rel=&quot;nofollow&quot;&gt;    PIC32MX795F512L&lt;/a&gt; include an integrated Ethernet interface.    An evaluation board for the PIC32MX795 is available: &lt;a href=&quot;http://www.mouser.com/ProductDetail/Microchip/DM320004/?qs=kI7nsUnms46D9Q02S%2f9mXA%3d%3d&quot; rel=&quot;nofollow&quot;&gt;DM320004&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also add an &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=ENC28J60/SS-ND&quot; rel=&quot;nofollow&quot;&gt;Ethernet controller&lt;/a&gt; and use Microchip's free &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2505&amp;amp;param=en535724&quot; rel=&quot;nofollow&quot;&gt;TCP/IP stack&lt;/a&gt; with their PIC18, PIC24, dsPIC and PIC32 families.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-08-30T14:54:07.263" LastActivityDate="2010-08-30T14:54:07.263" CommentCount="1" />
  <row Id="4215" PostTypeId="2" ParentId="4211" CreationDate="2010-08-30T14:52:30.403" Score="5" ViewCount="" Body="&lt;p&gt;There are many devices that could fit the bill for you...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're looking for ease of programming, consider an embedded Linux solution. You can find a &lt;a href=&quot;http://chiphacker.com/questions/2191/options-for-a-small-linux-hw-platform&quot; rel=&quot;nofollow&quot;&gt;list of possible boards here&lt;/a&gt;. Most of these have ethernet on board as well as large external flash and RAM chips. Many have USB host, meaning that USB flash drives or GPRS modems can be added.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On Linux, programming your application is easy. You have a choice of languages (C, C++, python, perl, Java, etc) and it should be straightforward to port your existing PC software. &lt;a href=&quot;http://curl.haxx.se/libcurl/&quot; rel=&quot;nofollow&quot;&gt;Curl&lt;/a&gt; is a good library for HTTP and &lt;a href=&quot;http://www.sqlite.org/&quot; rel=&quot;nofollow&quot;&gt;sqlite&lt;/a&gt; is a compact database.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, this ease comes at a hardware cost. In medium volumes, boards are likely to cost around $80-$120 going down to $30-$50 in high (10K+) volumes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're looking to cut costs further, you'll want to target a microcontroller. Your code is going to end up much more hardware dependent and development will take longer...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plenty of hobbyist devices use a low end AVR or PIC along with the &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en022889&quot; rel=&quot;nofollow&quot;&gt;ENC28J60&lt;/a&gt; ethernet MAC/PHY. See &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=7829&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://shop.tuxgraphics.org/electronic/index-eth.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. These systems often use the excellent &lt;a href=&quot;http://www.sics.se/~adam/uip/index.php/Main_Page&quot; rel=&quot;nofollow&quot;&gt;uIP&lt;/a&gt; and sometimes &lt;a href=&quot;http://www.freertos.org/&quot; rel=&quot;nofollow&quot;&gt;FreeRTOS&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an integrated solution, TI/Luminary have a range of &lt;a href=&quot;http://www.luminarymicro.com/products/lm3s6965_ethernet_evaluation_kit.html&quot; rel=&quot;nofollow&quot;&gt;ARM Cortex-M3 devices with on-chip ethernet MAC/PHY&lt;/a&gt;. These devices go up to 512KB flash and 96KB RAM, so are capable of complex tasks. But, you won't fit an SQL database inside.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's lots of choice - it all depends on your requirements.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-30T14:52:30.403" CommentCount="5" />
  <row Id="4216" PostTypeId="2" ParentId="4211" CreationDate="2010-08-30T16:14:36.357" Score="4" ViewCount="" Body="&lt;p&gt;I'll throw in the Arduino option into the mix. An &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; + a &lt;a href=&quot;http://asynclabs.com/&quot; rel=&quot;nofollow&quot;&gt;WiShield&lt;/a&gt; can get you the ability to periodically post data to a webpage (e.g. on an apache server) over an 802.11 network. Your webserver would then handle the job of putting that data in a database (e.g. a PHP script that handles the posted data). This is probably a good place for you to be on the effort to cost curve. Best of luck, this sounds like a fun project!&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-08-30T16:14:36.357" CommentCount="2" />
  <row Id="4217" PostTypeId="2" ParentId="4194" CreationDate="2010-08-30T16:31:20.490" Score="5" ViewCount="" Body="&lt;p&gt;There's simply no way around ORing all the bits, as unsatisfying as that may seem. However, you are not restricted to two input gates in silicon either. You can build a 4-input NOR gate in CMOS logic by putting 4 series p-type transistors in the pullup network and 4 parallel n-type transistors in the pulldown network. That reduces the depth of your tree topology and therefore your propagation delay. You can only take that theory so far though before the cumulative voltage drop across the series transistors makes the pull-up not pull-up enough to be a &quot;1&quot;... four is a good rule of thumb if I remember correctly.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-08-30T16:31:20.490" />
  <row Id="4218" PostTypeId="2" ParentId="4206" CreationDate="2010-08-30T16:52:39.713" Score="1" ViewCount="" Body="&lt;p&gt;I get the same thing with the math as tcrosley - you can't divide the period by 4 for a clock divider.  You multiply the period (divided frequency == multiplied period).  Also, do you need to clear the interrupt flag in the service routine?  I don't see you doing it if you do.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-08-30T16:52:39.713" CommentCount="1" />
  <row Id="4219" PostTypeId="1" AcceptedAnswerId="4220" CreationDate="2010-08-30T21:17:27.840" Score="5" ViewCount="414" Body="&lt;p&gt;I've heard rumors that the power line frequency is kept stable and accurate by syncing it with atomic clocks.  Is this true?  What kind of accuracy does it have?  Is this true everywhere?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-12-13T15:49:46.070" LastActivityDate="2010-12-13T15:49:46.070" Title="Is it true that the power line frequency is kept accurate by atomic clocks?" Tags="&lt;power&gt;&lt;frequency&gt;&lt;clock&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="4220" PostTypeId="2" ParentId="4219" CreationDate="2010-08-30T21:43:20.390" Score="9" ViewCount="" Body="&lt;p&gt;Here's what &lt;a href=&quot;http://en.wikipedia.org/wiki/Utility_frequency#Long-term_stability_and_clock_synchronization&quot; rel=&quot;nofollow&quot;&gt;wikipedia&lt;/a&gt; says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Regulation of power system frequency&#xA;  for timekeeping accuracy was not&#xA;  commonplace until after 1926 and the&#xA;  invention of the electric clock &#xA;  driven by a synchronous motor. Network&#xA;  operators will regulate the daily&#xA;  average frequency so that clocks stay&#xA;  within a few seconds of correct time.&#xA;  In practice the nominal frequency is&#xA;  raised or lowered by a specific&#xA;  percentage to maintain&#xA;  synchronization. Over the course of a&#xA;  day, the average frequency is&#xA;  maintained at the nominal value within&#xA;  a few hundred parts per million.&#xA;  In the synchronous grid of Continental&#xA;  Europe, the deviation between network&#xA;  phase time and UTC is calculated at&#xA;  08:00 each day in a control center in&#xA;  Switzerland, and the target frequency&#xA;  is then adjusted by up to ±0.01 Hz&#xA;  (±0.02%) from 50 Hz as needed, to&#xA;  ensure a long-term frequency average&#xA;  of exactly 24×3600×50 cycles per day&#xA;  is maintained. In North America,&#xA;  whenever the error exceeds 10 seconds&#xA;  for the east, 3 seconds for Texas, or&#xA;  2 seconds for the west, a correction&#xA;  of ±0.02 Hz (0.033%) is applied. Time&#xA;  error corrections start and end either&#xA;  on the hour or on the half&#xA;  hour. A real-time&#xA;  frequency meter for power generation&#xA;  in the United Kingdom is available&#xA;  online. Smaller power systems may not&#xA;  maintain frequency with the same&#xA;  degree of accuracy.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-08-30T21:43:20.390" CommentCount="1" />
  <row Id="4221" PostTypeId="2" ParentId="4219" CreationDate="2010-08-30T21:51:21.790" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://boards.straightdope.com/sdmb/showthread.php?t=446800&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; thread indicates the frequency may vary from 59 to 61 cycles during the day, but midnight to midnight they adjust the frequency to be exactly 5184000 cycles per 24 hour period.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also three (or four, not clear) separate grids in the US that do not maintain a phase relationship between them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So -- short term timing (e.g. a few minutes or a couple of hours), within a fraction of a per cent.  Long term, very accurate.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-08-30T21:51:21.790" />
  <row Id="4222" PostTypeId="1" CreationDate="2010-08-31T06:09:08.287" Score="1" ViewCount="105" Body="&lt;p&gt;I need to configure USB OTG on iMX31 for device mode. We need a raw channel between the host and target and usb seems to be the best suited. However I haven't been able to correctly configure the OTG controller. I dont know what I am missing. I have performed the steps mentioned in section 32.14.1 of iMX31 Reference Manual. I have also configured PORTSC1 register for ULPI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can any one help me out here? any poineters/code/any thing that can help me is welcome.&lt;/p&gt;&#xA;" OwnerUserId="1100" LastActivityDate="2010-12-17T09:00:24.267" Title="how to enable and configure USB OTG for device mode on iMX31 Litekit ?" Tags="&lt;imx31&gt;&lt;arm&gt;&lt;usb&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="4223" PostTypeId="1" CreationDate="2010-08-31T10:55:21.480" Score="4" ViewCount="198" Body="&lt;p&gt;We used an Asian design house to design, program and build our custom MP3 player. The chip we used (Sigmatel) is no longer avaialble and the DH does not do this type of work anymore.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are looking for a reputable company with relevant experience to help us create a new PCB for our existing plastic case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are considering moving to an Atmel chip (UC3) - any suggestions/comments?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are a small company working in a niche market and are looking for a smallish (user friendly) company to work with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are based in Australia.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TIA&lt;/p&gt;&#xA;" LastActivityDate="2010-09-02T01:31:57.973" Title="Help finding a design house to build our MP3 player" Tags="&lt;mp3&gt;&lt;avr&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="2" />
  <row Id="4224" PostTypeId="2" ParentId="4188" CreationDate="2010-08-31T12:10:26.053" Score="5" ViewCount="" Body="&lt;p&gt;Does connection cables exist for your phone ? Or, if it is a Nokia, are there pins behind the battery ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If yes, your old phone is probably able to receive AT or FBUS command, allowing you to easily use the internal modem, for example to send/receive sms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Look at &lt;a href=&quot;http://www.embedtronics.com/nokia/fbus.html&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; for information about the FBUS protocol (for Nokias).&#xA;&lt;a href=&quot;http://wiki.forum.nokia.com/index.php/Using_AT_commands_to_send_and_read_SMS&quot; rel=&quot;nofollow&quot;&gt;This other page&lt;/a&gt; deals with AT commands to send an read SMS (this should work with most phones).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Search about this (for example on chiphacker), many people have done such things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There also exists standalone GSM modules (&lt;a href=&quot;http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9533&quot; rel=&quot;nofollow&quot;&gt;example at SparkFun&lt;/a&gt;).&lt;/p&gt;&#xA;" OwnerUserId="1079" LastActivityDate="2010-08-31T12:10:26.053" CommentCount="3" />
  <row Id="4225" PostTypeId="1" AcceptedAnswerId="4227" CreationDate="2010-08-31T14:40:57.860" Score="5" ViewCount="304" Body="&lt;p&gt;This feels like a dumb question, but I'm going to ask it anyway. If a crystal has a rated load capacitance of 6pF, is the right thing to do to put a 6pF capacitor to GND on either leg of the crystal? I'm using it as the clock source (TOSC) for an XMega and it's got a max ESR of 50kOhm (which is within recommendations).&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-12-13T17:32:20.580" Title="Crystals and Load Capacitance" Tags="&lt;crystal&gt;&lt;capacitance&gt;&lt;microcontroller&gt;&lt;xmega&gt;&lt;avr&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="4226" PostTypeId="2" ParentId="4225" CreationDate="2010-08-31T15:04:59.597" Score="3" ViewCount="" Body="&lt;p&gt;Not a dumb question!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know you need to take into account the capacitance of the pins on the micro and the capacitance of the traces to the crystal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bookmarked this &lt;a href=&quot;http://www.crystek.com/microwave/appnotes/PierceGateLoadCap.pdf&quot; rel=&quot;nofollow&quot;&gt;page&lt;/a&gt; that walked me through the selection.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-08-31T15:04:59.597" />
  <row Id="4227" PostTypeId="2" ParentId="4225" CreationDate="2010-08-31T17:19:14.790" Score="5" ViewCount="" Body="&lt;p&gt;Check out &lt;a href=&quot;http://en.wikipedia.org/wiki/Pierce_oscillator#Load_capacitance&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Pierce_oscillator#Load_capacitance&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The load capacitance is the total capacitance seen from the two pins of the crystal looking into the circuit.  So if you have a 6 pF from each leg to ground, that's 3 pF total (&lt;a href=&quot;http://en.wikipedia.org/wiki/Series_and_parallel_circuits#Capacitors&quot; rel=&quot;nofollow&quot;&gt;capacitors in series halve&lt;/a&gt;, &lt;a href=&quot;http://en.wikipedia.org/wiki/Series_and_parallel_circuits#Capacitors_2&quot; rel=&quot;nofollow&quot;&gt;capacitors in parallel add&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's really rated for 6 pF?  That capacitance could be provided by the traces and PCB layout alone, I would think.  Typically I've seen more like 30 pF.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-08-31T17:24:50.660" LastActivityDate="2010-08-31T17:24:50.660" CommentCount="1" />
  <row Id="4228" PostTypeId="2" ParentId="4225" CreationDate="2010-08-31T18:34:48.040" Score="1" ViewCount="" Body="&lt;p&gt;Are you sure you need a capacitor at all? 6pF and 50KOhms sounds like a watch crystal&#xA;application. As was mentioned usually the IC + traces provide you sufficient capacitance&#xA;(3pF per connection).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The recommendations for some of the Maxim RTC clocks is a 6pF crystal. The 6pF is supplied &#xA;by the IC and traces.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-12-13T17:32:20.580" LastActivityDate="2010-12-13T17:32:20.580" CommentCount="2" />
  <row Id="4229" PostTypeId="2" ParentId="4225" CreationDate="2010-08-31T18:59:34.333" Score="1" ViewCount="" Body="&lt;p&gt;Watch crystal oscillators in some MCUs have the feedback capacitors built-in. The MSP430 is one such family that springs to mind.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-08-31T19:05:37.950" LastActivityDate="2010-08-31T19:05:37.950" CommentCount="1" />
  <row Id="4230" PostTypeId="1" AcceptedAnswerId="4239" CreationDate="2010-08-31T19:47:49.317" Score="3" ViewCount="758" Body="&lt;p&gt;I'm trying to connect an RJ-45 jack with integrated magnetics (&lt;a href=&quot;http://www.belfuse.com/Data/Datasheets/L829-1X1T-91.pdf&quot; rel=&quot;nofollow&quot;&gt;Belfuse L829-1X1T-91 datasheet&lt;/a&gt;) to an Ethernet PHY chip (&lt;a href=&quot;http://www.micrel.com/_PDF/Ethernet/datasheets/ksz8041tl-ftl-mll.pdf&quot; rel=&quot;nofollow&quot;&gt;Micrel KSZ8041TL datasheet&lt;/a&gt;). The TX+/-, RX+/-, and the LED pins are all easy enough to figure out, but I'm not sure what to do with the center taps (TCT and RCT) for the transformers. Should they be connected to 3.3 V power? To the 1.8 V output of the PHY?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for the wisdom.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-09-01T19:58:40.607" Title="Connection of center tap for Ethernet transformer" Tags="&lt;ethernet&gt;&lt;phy&gt;&lt;transformer&gt;" AnswerCount="2" CommentCount="0" FavoriteCount="1" />
  <row Id="4231" PostTypeId="2" ParentId="4095" CreationDate="2010-08-31T19:48:35.780" Score="0" ViewCount="" Body="&lt;p&gt;Make sure the the atmega itself support 12 Mhz&lt;/p&gt;&#xA;" LastActivityDate="2010-08-31T19:48:35.780" />
  <row Id="4232" PostTypeId="2" ParentId="1291" CreationDate="2010-08-31T21:30:56.210" Score="0" ViewCount="" Body="&lt;p&gt;ECLIPSE is working fine on an EeePC with the AVR patch... But it is a little slow.&lt;/p&gt;&#xA;" LastActivityDate="2010-08-31T21:30:56.210" />
  <row Id="4233" PostTypeId="2" ParentId="4230" CreationDate="2010-08-31T21:48:25.360" Score="1" ViewCount="" Body="&lt;p&gt;0.1uF to ground? Just going from &lt;a href=&quot;http://www.circuitcellar.com/library/print/0902/brady/f1.htm&quot; rel=&quot;nofollow&quot;&gt;this circuit&lt;/a&gt; from &lt;a href=&quot;http://www.circuitcellar.com/library/print/0902/brady/2.htm&quot; rel=&quot;nofollow&quot;&gt;this article&lt;/a&gt; on circuit cellar.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-08-31T21:48:25.360" CommentCount="2" />
  <row Id="4234" PostTypeId="2" ParentId="3783" CreationDate="2010-08-31T23:13:55.017" Score="0" ViewCount="" Body="&lt;p&gt;One researcher from Canada is cheaply/easily creating his own RFID tags so he can do something similar; to add other components to them to augment their functionality. Really cool stuff!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.nicolaimarquardt.com/blog/?p=77&quot; rel=&quot;nofollow&quot;&gt;http://www.nicolaimarquardt.com/blog/?p=77&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1021" LastActivityDate="2010-08-31T23:13:55.017" />
  <row Id="4235" PostTypeId="1" CreationDate="2010-09-01T06:24:27.810" Score="2" ViewCount="277" Body="&lt;p&gt;What methods and equipments can I used to measure and record the current variation of CNC servo motor while machining. &lt;/p&gt;&#xA;" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-10-21T17:25:48.093" LastActivityDate="2010-10-21T17:25:48.093" Title="CNC Servo motor current measure" Tags="&lt;motor&gt;&lt;hall-effect&gt;&lt;current-measurement&gt;" AnswerCount="2" />
  <row Id="4236" PostTypeId="2" ParentId="4235" CreationDate="2010-09-01T10:16:42.930" Score="1" ViewCount="" Body="&lt;p&gt;One thing you can do to get an approximate measure, that isn't too complicated, is to measure the DC current going into the switching bridge. If you know the current and voltage of the DC supply, you get at least an upper limit to what the output power can be. This doesn't account for the efficiency of the switching network nor of the motor itself, but has the advantage that it's simpler to implement, and in some cases is sufficient.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise, you're going to have to measure the phase currents into the motor. First you need to know how many current sensors you will need, and how you determine that will depend on the number of phases and their connection. That done, you then need to deal with what amounts to AC current with a boatload of harmonics on it, and possibly under conditions of changing frequency due to changes in the mechanical load on the motor, so this is definitely a more complicated way to go.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-09-01T10:16:42.930" />
  <row Id="4238" PostTypeId="2" ParentId="4172" CreationDate="2010-09-01T16:06:45.490" Score="0" ViewCount="" Body="&lt;p&gt;Would &lt;a href=&quot;http://www.circuitdb.com/show.php?cid=69&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; be good enough?&lt;/p&gt;&#xA;" OwnerUserId="1108" LastActivityDate="2010-09-01T16:06:45.490" CommentCount="2" />
  <row Id="4239" PostTypeId="2" ParentId="4230" CreationDate="2010-09-01T19:58:40.607" Score="3" ViewCount="" Body="&lt;p&gt;Arrrgh, another one of those data sheets that don't tell you what you need... I guess we have to read betweeen the lines: Note 4 on p. 49 says that the transformer draws additional current on the 3.3 V rail, so I guess this is the way to go...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There may be differences among various types of PHYs, and I wasn't able to find better information for the exact type you mentioned, but it is very common to connect the center tap (CT) to the supply rail that is also powering the PHY itself (e.g. 3.3 V). A bypass capacitor from the CT to GND (0.1 uF, ceramic) should be used to provide a low-impedance source for transient currents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Click &lt;a href=&quot;http://www.micrel.com/_PDF/Ethernet/app-notes/an-139.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; for a detailed application note for a similar PHY. It might be worth giving it a try...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See &lt;a href=&quot;http://micrel.com/_PDF/Ethernet/app-notes/an-134.pdf&quot; rel=&quot;nofollow&quot;&gt;this app'note&lt;/a&gt; for some different types of PHYs with more options (cf. Fig. 2) and indeed a connection of the CT to the internal regulator.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-09-01T19:58:40.607" CommentCount="1" />
  <row Id="4240" PostTypeId="2" ParentId="4206" CreationDate="2010-09-01T21:57:27.280" Score="2" ViewCount="" Body="&lt;p&gt;They're right, each T0 tick is 64 us.  In 100 ms, there will be 1,562.5 T0 ticks.  Each T0 overflow takes 256 ticks, so there will be 6 overflows.  Then T0 tick number 26.5 corresponds to your 100'th millisecond.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if (T0IE&amp;amp;&amp;amp;T0IF)&#xA;{&#xA;    // clear interrupt flag&#xA;    T0IF=0;&#xA;    ticks++;&#xA;    if (ticks == 6)&#xA;    {&#xA;        // Prepare fractional overflow of 26 ticks&#xA;        TMR0 = (256 - 26);&#xA;    }&#xA;    else if (ticks == 7)&#xA;    {   &#xA;        ticks = 0;&#xA;        PORTB = ~PORTB;&#xA;    }   &#xA;&#xA;    // don't need return&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-09-01T21:57:27.280" CommentCount="1" />
  <row Id="4241" PostTypeId="2" ParentId="4223" CreationDate="2010-09-02T01:31:57.973" Score="6" ViewCount="" Body="&lt;p&gt;I work at a large automotive supply corporation in the States, and we have a large system in place to deal with this sort of issue.  Here, cars are designed to last for at least 10 years, and an additional problem is that the development, manufacturing, emissions certification etc. takes a lot of time, money, and effort.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Therefore, our ordering department runs every part through a thorough approval process, which attempts to guarantee that a design based on the part will not be negatively impacted by glitch in the supply chain.  For instance, we use a Texas Instruments TLC271 programmable gain op amp in some designs.  We recently had a problem with this part's stocking, so we switched to the ST micro equivalent.  We could also have switched to a number of other parts. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This isn't such a big deal with analog parts - Everyone makes 74XX, 1n4001, 2N700, 2N3904, etc., and finding one at a different supplier isn't too hard.  However, it's more difficult to do this with microcontrollers, because the code isn't usually portable from, say, a PIC to an AVR, without a LOT of work.  If Atmel went out of business, and you used their UC3 chip, you'd be in a bad spot.  Your entire product line would be gone.  A LOT of people would also be in trouble, and it's unlikely, but it could happen, and almost did a while back (Might have been Microchip, can't remember).  This means you want a microcontroller which is produced by several chip manufacturers - in your case, &lt;strong&gt;you want an ARM device&lt;/strong&gt;.  The UC3's peripherals are nice, but have you considered how nice it would be to watch the UC3 go out of stock, and, while your competitors flounder, you simply purchase an ST or TI part instead, solder it on, recompile (you'll probably need to make a few minor adjustments, the system isn't perfect), and continue to ship your products?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're looking for a small DH, make sure that they plan for these possibilities.  Be wary of a design house with a 'favorite' manufacturer.  You'll likely have more sucess in this department with a larger DH that can afford to have one or more people dedicated to selecting parts, rather than depending on the engineers to make a good selection and select components with redundant supply chains, but I won't deny that there are a lot of nice things about a smaller company.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-02T01:31:57.973" CommentCount="1" />
  <row Id="4242" PostTypeId="1" CreationDate="2010-09-02T01:45:18.120" Score="3" ViewCount="223" Body="&lt;p&gt;Hi i bought this data logger a few weeks ago, &lt;a href=&quot;http://www.littlebirdelectronics.com/products/Logomatic-v2-Serial-SD-Datalogger.html&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/Logomatic-v2-Serial-SD-Datalogger.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been having some trouble with it. I read the data sheet and I've powered it up (using a 2Gb Sandisk micro sd card formatted to FAT16 512 allocation size and powered by 2 AA batteries). The data sheet says that on initial startup the leds should blink rapidly and then stop. What I'm having happen is that the usb light will go on and after about 30 seconds the stat1 and stat0 will also light up and they will all stay on. When I turn the unit off and then connect it to the usb, my computer (Windows 7 64bit, also tried 32bit) says that the device has malfunctioned and it cannot install the drivers. I then tried uninstalling the SD card and connecting it to my computer but it shows that the SD card is empty and there are no log files contained on it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really need to get this working in the next week for my uni major project so any help would be greatly appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks heaps,&lt;/p&gt;&#xA;" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-09-02T14:49:43.500" LastActivityDate="2010-12-16T17:48:05.703" Title="Logomatic v2 serial SD Datalogger issues" Tags="&lt;datalogger&gt;&lt;usb&gt;&lt;microsd&gt;" AnswerCount="3" />
  <row Id="4243" PostTypeId="2" ParentId="4175" CreationDate="2010-09-02T02:38:43.177" Score="1" ViewCount="" Body="&lt;p&gt;Any standard academic book on verilog/vhdl should give you an introduction (and more) into the frontend(RTL) design.But in my opinion the backend(VLSI CAD) is too specialized an area (and EDA tool/vendor specific) to study from a book and then go on to do &quot;real work&quot;.&lt;/p&gt;&#xA;" OwnerUserId="921" LastActivityDate="2010-09-02T02:38:43.177" CommentCount="2" />
  <row Id="4244" PostTypeId="1" CreationDate="2010-09-02T07:15:34.940" Score="3" ViewCount="561" Body="&lt;p&gt;Will regular leaded(or non-leaded) solder stick to actual tin or tin foil? Does the tin have a low enough melting point that it'd melt along with the solder? Has anyone actually tried soldering copper to tin using regular solder?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I tried googling, but everything I found seemed to be about tinning a soldering iron)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Note I was talking about the actual metal Tin. I realize that most &quot;tin foil&quot; is actually aluminum and you've given me some useful information about aluminum but what about actual tin?&lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="708" LastEditorDisplayName="" LastEditDate="2010-12-03T23:47:42.287" LastActivityDate="2010-12-04T23:37:09.977" Title="Does solder stick to tin? (not aluminum)" Tags="&lt;soldering&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="4246" PostTypeId="2" ParentId="4244" CreationDate="2010-09-02T10:16:25.737" Score="8" ViewCount="" Body="&lt;p&gt;Regular solder is a mixture of lead and tin, so chances are that, yeah it would stick to actual tin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be aware that most of what is today called 'tin foil' is really made of aluminum. You would have to work at it to find tin foil made of real tin. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Aluminum is notoriously difficult to solder to, almost but not quite impossible, in fact. Basically you have to exclude oxygen from the surface you intend to join, which is easier said than done.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-09-02T16:37:00.050" LastActivityDate="2010-09-02T16:37:00.050" />
  <row Id="4247" PostTypeId="2" ParentId="3641" CreationDate="2010-09-02T13:43:40.170" Score="2" ViewCount="" Body="&lt;p&gt;I found this a very interesting question, really with no satisfactory answer so far. It also seems to be a very important issue if we are to get new folks up to speed. (I'm not even sure there is one single answer). Factors I considered are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;It needs to be fairly cheap. Around $10 - $15 is good. Under $10 is perfect.&lt;/li&gt;&#xA;&lt;li&gt;It's OK to use lot of tech, but the goal is to enable a person to focus on one skill. So I'm OK with a pre-programmed microcontroller.&lt;/li&gt;&#xA;&lt;li&gt;Opinions vary on this, and all are good, but my personal preference is function over form. (Bauhaus rules! :)&lt;/li&gt;&#xA;&lt;li&gt;Should be robust to mistakes. I think it's reasonable to assume that beginners will be spending some time desoldering. &lt;/li&gt;&#xA;&lt;li&gt;Needs to have good support and help.&lt;/li&gt;&#xA;&lt;li&gt;It seems nice if it can be made into something that is not only electronicsy, and includes (an easy) physical build maybe.&lt;/li&gt;&#xA;&lt;li&gt;The level of complexity is hard to pin down. I'm more worried about making it hard to mess up, rather than simple per se, but clearly the two are connected. &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Based on this, I developed one to fulfill the need: The DayCounter. It is available here for $9.95: &lt;a href=&quot;http://wickeddevice.com/index.php?main_page=product_info&amp;amp;cPath=9&amp;amp;products_id=25&quot; rel=&quot;nofollow&quot;&gt;http://wickeddevice.com/index.php?main_page=product_info&amp;amp;cPath=9&amp;amp;products_id=25&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has its own website: &lt;a href=&quot;http://daycounter.wickeddevice.com/&quot; rel=&quot;nofollow&quot;&gt;http://daycounter.wickeddevice.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://daycounter.wickeddevice.com/wp-content/uploads/2010/08/DC-Oblique7SegSm.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;img src=&quot;http://daycounter.wickeddevice.com/wp-content/uploads/2010/08/DCTop-1Sm.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-09-02T13:43:40.170" CommentCount="2" />
  <row Id="4248" PostTypeId="2" ParentId="4244" CreationDate="2010-09-02T14:51:28.667" Score="10" ViewCount="" Body="&lt;p&gt;You might think that aluminum doesn't readily oxidize, because you see shiny aluminum things outdoors, while copper turns green and steel rusts.   To the contrary, aluminum undergoes &lt;a href=&quot;http://en.wikipedia.org/wiki/Passivation&quot; rel=&quot;nofollow&quot;&gt;passivation&lt;/a&gt; almost immediately (100 ps) upon its exposure to air, and coats itself with a thin layer of alumina (aka aluminum oxide) to a depth of about 4nm, more if the aluminum is anodized. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Aluminum is a highly reactive metal, and is fairly easy to solder to.   The problem is, you can't solder to alumina, which coats anything aluminum.   Even if you get a nice, smooth joint, you will not have a good, strong, electrical and/or heat conductive bond. Take a look at &lt;a href=&quot;http://www.aws.org/wj/2004/02/046/&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; from the American Welding Society.  They say,&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;In “normal” soldering of copper,&#xA;  removal of the copper oxide is&#xA;  relatively easy with mild organic and&#xA;  inorganic fluxes. Aluminum oxide is&#xA;  not so easily removed and may require&#xA;  stronger fluxes such as an organic&#xA;  amine-based flux...&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Your solder probably contains about 2-5% RMA flux, which is enough for clean joints between copper or nickel.  Most flux pens are an RMA flux, or a no-clean flux.  Try something stronger, like an an activated rosin flux, and you may be able to get it to work.  If you use a corrosive flux (zinc chloride or other acid), you need to clean it thoroughly (Note: Do not use this for normal electronics soldering!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another problem will be the conduction of heat away from the soldering point, but that can be overcome with more power from your soldering iron.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-02T14:51:28.667" CommentCount="1" />
  <row Id="4249" PostTypeId="2" ParentId="4242" CreationDate="2010-09-02T15:46:36.620" Score="4" ViewCount="" Body="&lt;p&gt;This definitely sounds like a USB issue with the computer.  The device is obviously not recognized and thus its startup can't continue past a certain point.  I'm guessing that the LEDs blinking rapidly is initial USB activity and it sounds like that isn't happening correctly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, have you tried it on several computers?  Do you have any non-windows computers to try it on?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks like the board might incorporate several USB devices - USB mass storage being one.  If the SD card is not formatted correctly for the board then that might stop the startup of the mass storage device.  Try reformatting it again and see what happens.  I doubt it will work but you never know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try a different (smaller if you have it) SD card and see what happens.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have the programming adapter mentioned in the datasheet, attempt to re-flash the firmware or even try the alternate firmware provided.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-02T15:46:36.620" CommentCount="1" />
  <row Id="4252" PostTypeId="2" ParentId="4199" CreationDate="2010-09-02T21:41:04.390" Score="2" ViewCount="" Body="&lt;p&gt;If you're really interested in learning PICs and c, I would say you can check out  &lt;a href=&quot;http://www.amazon.com/123-Microcontroller-Experiments-Evil-Genius/dp/0071451420/ref=sr_1_1?ie=UTF8&amp;amp;s=books&amp;amp;qid=1283463508&amp;amp;sr=8-1&quot; rel=&quot;nofollow&quot;&gt;123 PIC Microcontroller Experiments for the Evil Genius&lt;/a&gt;.  This is how I got started with PICs. However, I would at the minimum recommend purchasing the PIC Kit 2 as the 1 doesn't program nearly as many things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have really enjoyed playing with the PICs, the HI-TECH compiler for the 16 series (and probably other series) is free for the MPLAB environment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck. I'm actually attempting to come up with a RTOS (Real Time Operating System) for a 16F913, just to try it out.&lt;/p&gt;&#xA;" OwnerUserId="982" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-09-03T00:14:53.383" LastActivityDate="2010-09-03T00:14:53.383" CommentCount="1" />
  <row Id="4253" PostTypeId="2" ParentId="4194" CreationDate="2010-09-02T21:50:13.343" Score="-1" ViewCount="" Body="&lt;p&gt;I have to say you can and all the bits with the all 1's case, kinda like or'ing with 0's but now you don't need an or AND a not....just a suggestion.&lt;/p&gt;&#xA;" OwnerUserId="982" LastActivityDate="2010-09-02T21:50:13.343" CommentCount="2" />
  <row Id="4256" PostTypeId="2" ParentId="4199" CreationDate="2010-09-03T22:07:56.020" Score="1" ViewCount="" Body="&lt;p&gt;It all depends on how you learn, but I find its easier to learn with a distinct objective when your'e learning.  If you want to specifically learn C for PICs, here's my recommendations:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ironically, I'd pick up an Arduino and not a PIC setup.  Programming PIC chips in C has a very large learning curve that assumes you know how to read datasheets, burn code into chips, etc.  Arduinos do not have this.  You program Arduinos in C (*).  If you know nothing/vary little about programming or writing in C or with microcontrollers and don't know where to start or what to do, the example code that comes with it is very simple and will allow you to get up and running quickly.  The documentation for the Arduino is easy to read with minimal experience.  A trip to an electronic store and the Arduino board will give you a way to get started.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In conjunction with that, I would read a book or a tutorial on C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In addition, I would find someone else who knows how to program PICs or microcontrollers in C and work with them.  A subject like this has a huge learning curve, but a person who can interact with you and help you fill in the gaps is huge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(*) - It does use a form of avr-gcc in the backend, correct?  I haven't dug into the Arduino IDE source code.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-09-03T22:07:56.020" CommentCount="1" />
  <row Id="4257" PostTypeId="1" AcceptedAnswerId="4258" CreationDate="2010-09-04T16:15:00.787" Score="3" ViewCount="457" Body="&lt;p&gt;I have a device that takes two AA batteries and I want to replace it with my own external power source and regulation circuitry. Instead of clipping or soldering wires to the device contacts, I would rather plug in a dummy battery shell that has the appropriate contacts on the end to make the whole project cleaner and more prototype friendly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does such a thing exist?&lt;/p&gt;&#xA;" OwnerUserId="354" LastActivityDate="2011-01-20T19:40:37.847" Title="Dummy battery shells" Tags="&lt;battery&gt;&lt;power-supply&gt;" AnswerCount="6" />
  <row Id="4258" PostTypeId="2" ParentId="4257" CreationDate="2010-09-04T18:12:04.897" Score="3" ViewCount="" Body="&lt;p&gt;You could almost DIY something out of birch dowel and a couple of small pointy-ended screws, the only thing would be getting the dimensions right. You could even hide the low-tec materials by covering the whole assemblage with heat-shrink tubing.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-09-04T18:12:04.897" CommentCount="6" />
  <row Id="4259" PostTypeId="2" ParentId="4257" CreationDate="2010-09-04T20:45:45.783" Score="0" ViewCount="" Body="&lt;p&gt;Yes. Just connect the power cables of your device to AC adapters by soldering the appropriate leads and heat-shrinking the solder joints.&lt;/p&gt;&#xA;" OwnerUserId="854" LastActivityDate="2010-09-04T20:45:45.783" />
  <row Id="4260" PostTypeId="1" CreationDate="2010-09-05T06:39:19.240" Score="6" ViewCount="355" Body="&lt;p&gt;I am looking for an ARM, preferably with an MMU, that is not in a BGA package so hobbyists reflow it at home.  &lt;/p&gt;&#xA;" OwnerUserId="582" LastActivityDate="2010-09-06T09:53:57.303" Title="Latest ARM processors that are not BGA" Tags="&lt;arm&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="4261" PostTypeId="2" ParentId="4257" CreationDate="2010-09-05T06:52:52.737" Score="4" ViewCount="" Body="&lt;p&gt;There are a few models for 3d printable battery shells up on thingiverse:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dev.thingiverse.com/tag:batteries&quot; rel=&quot;nofollow&quot;&gt;http://dev.thingiverse.com/tag:batteries&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could probably modify these designs to suit your needs.&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2010-09-05T06:52:52.737" />
  <row Id="4262" PostTypeId="2" ParentId="2417" CreationDate="2010-09-05T14:25:42.213" Score="1" ViewCount="" Body="&lt;p&gt;Atmel application note&#xA;&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc3644.pdf&quot; rel=&quot;nofollow&quot;&gt;&quot;Migrating from the B to the New D DataFlash Family&quot;&lt;/a&gt;&#xA;says:&#xA;&quot;The “D” family offers sector lockdown for secure code and data storage. The Lockdown mechanism&#xA;allows each individual sector to be permanently locked so that it becomes read only. Once&#xA;the sector is locked down, it can never be erased or programmed, and it can never be unlocked.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It uses a SPI interface very similar to the SPI interface of a SD/MMC card.&#xA;Alas, I think the details of its protocol are different enough that it can't be directly connected to a standard SD/MMC slot as if it were a standard SD/MMC card.&#xA;And so I don't think you can pop it into a standard off-the-shelf SD/MMC to USB adapter.&#xA;And so it looks like you'll need a custom-programmed microcontroller, as mjh2007 suggests. In which case, you might as well program that microcontroller to enforce &quot;write-once&quot; requirement, and use any random easily-available non-volatile memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Still, practically all software has bugs, and it might be nice to use this relatively easily-available Dataflash (Newark and Digikey have them in stock now) so you don't have to worry about some bug in the microcontroller accidentally overwriting your data.&lt;/p&gt;&#xA;" OwnerUserId="813" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2010-09-05T14:41:33.523" LastActivityDate="2010-09-05T14:41:33.523" />
  <row Id="4263" PostTypeId="2" ParentId="2417" CreationDate="2010-09-05T14:34:57.843" Score="0" ViewCount="" Body="&lt;p&gt;Sandisk normally doesn't sell directly to individuals.&#xA;They sell directly to distributors, who in turn sell directly to individuals such as you and me.&#xA;If you want to buy this or any other Sandisk product, your best bet is to go to the&#xA;&lt;a href=&quot;http://www.sandisk.com/business-solutions/find-a-distributor&quot; rel=&quot;nofollow&quot;&gt;list of Sandisk distributors&lt;/a&gt;&#xA;and call up each one until you find one willing to take your money.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.dpreview.com/news/1006/10062301sandiskwormsd.asp&quot; rel=&quot;nofollow&quot;&gt;press release for the Sandisk WORM cards&lt;/a&gt;&#xA;specifically lists contact information for obtaining these cards.&#xA;If you really want these specific cards mentioned in the press release, perhaps using that contact information might be a possibility?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-05T14:34:57.843" />
  <row Id="4264" PostTypeId="2" ParentId="4260" CreationDate="2010-09-05T15:27:39.317" Score="10" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.caviumnetworks.com/processor_ECONA-ARM.html&quot; rel=&quot;nofollow&quot;&gt;Cavium Networks ECONA family&lt;/a&gt; has several ARM922-based processors with MMUs that run at 200-250 MHz. They have a PQFP 128-pin package. I think they're the most powerful non-BGA ARMs you can get (so far as I know).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PQFP packages are still pretty hairy to solder, so you might also look at the &lt;a href=&quot;http://ics.nxp.com/products/lpc1000/lpc17xx/&quot; rel=&quot;nofollow&quot;&gt;NXP 17xx series&lt;/a&gt; of Cortex M3 chips, which run at 100 MHz. Unfortunately, the M3 core does &lt;em&gt;not&lt;/em&gt; have an MMU. I don't know all the packages used, but at least the LPC1758 comes in a LQFP 80-pin package with 0.5 mm pitch. You could also check the LPC2xxx series, but I'm not familiar with them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that's still too tricky, NXP has announced an ARM Cortex M0 chip, the LPC1114, that will be available in a 44-pin PLCC package in Q4 of 2010 (that is, you can't buy it for a few months yet). It only runs at 50 MHz and it has no MMU, but PLCCs can use through-hole sockets that can be soldered by hand pretty easily.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-09-05T22:01:59.023" LastActivityDate="2010-09-05T22:01:59.023" CommentCount="5" />
  <row Id="4265" PostTypeId="2" ParentId="4146" CreationDate="2010-09-05T16:20:03.370" Score="0" ViewCount="" Body="&lt;p&gt;Another alternative:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reserve a &quot;recently rewritten&quot; bit in each page of that flash chip's memory.&#xA;(Perhaps store that bit in one of the 8 &quot;extra&quot; bytes per page).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the appsheet suggests, every time the application writes to some random page, also re-write some other page that hasn't been re-written in a while.&#xA;To find that other page, scan through all the &quot;recently rewritten&quot; bits searching for a &quot;0&quot; bit. The first &quot;0&quot; bit you find corresponds to the specific page to be rewritten.&#xA;Once you've found it, rewrite the data in page while erasing the &quot;recently rewritten&quot; bit to &quot;1&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you scan in sequential order, the &quot;recently rewritten&quot; bits towards the beginning are all &quot;1&quot;, and the bits towards the end are all &quot;0&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Optionally keep a pointer in RAM pointing to the page with the last page with a &quot;1&quot; &quot;recently rewritten&quot; bit, or first page with a &quot;0&quot; bit, so you can start searching from that point, rather than starting from page 0 every time).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you do the search, and the CPU can't find &lt;em&gt;any&lt;/em&gt; pages that need to be rewritten (every &quot;recently rewritten&quot; bit is a &quot;1&quot;), then program every &quot;recently rewritten&quot; bit to &quot;0&quot;, starting with that bit in flash page 0.&#xA;(You can program just this one bit per page without erasing the entire page).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At boot time, when the power first gets turned on,&#xA;you'll need to check if the flash is in the &quot;normal&quot; state -- all the pages towards the beginning all have a &quot;1&quot; &quot;recently rewritten&quot; bit, and all the pages towards the end all have a &quot;0&quot; bit.&#xA;Anything else indicates the &quot;interrupted&quot; state, in the middle of programming all the &quot;needs to be rewritten&quot; bits to &quot;0&quot;, in which case the CPU should finish programming all those &quot;recently rewritten&quot; bits to &quot;0&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I suppose you could, instead of storing that bit inside its corresponding page,&#xA;pack all those bits together in a bit array and store them in a few pages of flash that you reserve for that use. For example, the 7th bit in that array corresponds to the 7th page of flash.&#xA;In that case, you'll probably want to invert the meaning of the bit, and program the bit to &quot;0&quot; when the corresponding page is erased and rewritten, and once in a long while, whenever you discover that every page has a corresponding &quot;0&quot; bit, erase all those bits to &quot;1&quot;. The result is about the same as what rdeml suggested).&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-05T16:20:03.370" CommentCount="5" />
  <row Id="4266" PostTypeId="1" CreationDate="2010-09-05T22:49:01.840" Score="1" ViewCount="106" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://chiphacker.com/questions/2036/beginners-logic-analyzer&quot; rel=&quot;nofollow&quot;&gt;Beginner&amp;rsquo;s logic analyzer?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Hey guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am wondering if anyone can recommend a logic analyser for a mac environment with similar features as the &lt;a href=&quot;http://www.littlebirdelectronics.com/products/SCANALOGIC-2-PRO.html&quot; rel=&quot;nofollow&quot;&gt;SCANALOGIC 2 PRO&lt;/a&gt; around the same price would be great as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;or some thing that is similar, what type of features am I after for working with SPI and I2C. Fairly new to the Digital electronics&lt;/p&gt;&#xA;" OwnerUserId="665" LastActivityDate="2010-09-05T22:55:57.017" ClosedDate="2010-09-06T06:04:06.650" Title="Tools for MAC Logic analyser" Tags="&lt;digital&gt;&lt;i2c&gt;&lt;spi&gt;&lt;logic&gt;&lt;analyser&gt;" AnswerCount="0" />
  <row Id="4268" PostTypeId="2" ParentId="4257" CreationDate="2010-09-06T01:52:46.163" Score="2" ViewCount="" Body="&lt;p&gt;I agree that wooden dowel is probably your quickest way to success, but if that's too sketch for you I don't think you need to jump to a 3D printer.  Make a silicone mold of two batteries in the configuration you need and use something like Alumilite or ShapeLock (or any modelling material, I've used both of those and you can get some pretty awesome results) to make a plastic part that looks great and fits perfectly.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-09-06T01:52:46.163" />
  <row Id="4269" PostTypeId="2" ParentId="4260" CreationDate="2010-09-06T09:53:57.303" Score="3" ViewCount="" Body="&lt;p&gt;Another to consider is the &lt;a href=&quot;http://www.cirrus.com/en/products/pro/detail/P1066.html&quot; rel=&quot;nofollow&quot;&gt;Cirrus Logic EP9302&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;208 LQFP&lt;/li&gt;&#xA;&lt;li&gt;ARM9&lt;/li&gt;&#xA;&lt;li&gt;USB Host&lt;/li&gt;&#xA;&lt;li&gt;Ethernet MAC&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-06T09:53:57.303" />
  <row Id="4270" PostTypeId="2" ParentId="4185" CreationDate="2010-09-06T13:45:57.237" Score="7" ViewCount="" Body="&lt;p&gt;There are many different kinds of computer architectures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One way of categorizing computer architectures is by number of instructions executed per clock.&#xA;Many computing machines read one instruction at a time and execute it (or they put a lot of effort into acting &lt;em&gt;as if&lt;/em&gt; they do that, even if internally they do fancy superscalar and out-of-order stuff).&#xA;I call such machines &quot;von Neumann&quot; machines, because all of them have a von Neumann bottleneck.&#xA;Such machines include CISC, RISC, MISC, TTA, and DSP architectures.&#xA;Such machines include accumulator machines, register machines, and stack machines.&#xA;Other machines read and execute several instructions at a time (VLIW, super-scalar), which break the one-instruction-per-clock limit, but still hit the von Neumann bottleneck at some slightly larger number of instructions-per-clock.&#xA;Yet other machines are not limited by the von Neumann bottleneck, because they pre-load all their operations once at power-up and then process data with no further instructions.&#xA;Such non-Von-Neumann machines include dataflow architectures, such as systolic architectures and cellular automata, often implemented with FPGAs, and the NON-VON supercomputer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way of categorizing computer architectures is by the connection(s) between the CPU and memory.&#xA;Some machines have a unified memory, such that a single address corresponds to a single place in memory, and when that memory is RAM, one can use that address to read and write data, or load that address into the program counter to execute code. I call these machines Princeton machines.&#xA;Other machines have several separate memory spaces, such that the program counter always refers to &quot;program memory&quot; no matter what address is loaded into it, and normal reads and writes always go to &quot;data memory&quot;, which is a separate location usually containing different information even when the bits of the data address happen to be identical to the bits of the program memory address.&#xA;Those machines are &quot;pure Harvard&quot; or &quot;modified Harvard&quot; machines.&#xA;Most DSPs have 3 separate memory areas -- the X ram, the Y ram, and the program memory.&#xA;The DSP, Princeton, and 2-memory Harvard machines are three different kinds of von Neumann machines.&#xA;A few machines take advantage of the extremely wide connection between memory and computation that is possible when they are both on the same chip -- computational ram or iRAM or CAM RAM -- which can be seen as a kind of non-von Neumann machine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few people use a narrow definition of &quot;von Neumann machine&quot; that does not include Harvard machines. If you are one of those people, then what term would you use for the more general concept of &quot;a machine that has a von Neumann bottleneck&quot;, which includes both Harvard and Princeton machines, and excludes NON-VON?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most embedded systems use Harvard architecture.&#xA;A few CPUs are &quot;pure Harvard&quot;, which is perhaps the simplest arrangement to build in hardware: the address bus to the read-only program memory is exclusively is connected to the program counter, such as many early Microchip PICmicros.&#xA;Some modified Harvard machines, in addition, also put constants in program memory, which can be read with a special &quot;read constant data from program memory&quot; instruction (different from the &quot;read from data memory&quot; instruction).&#xA;The software running in the above kinds of Harvard machines cannot change the program memory, which is effectively ROM to that software.&#xA;Some embedded systems are &quot;self-programmable&quot;, typically with program memory in flash memory and a special &quot;erase block of flash memory&quot; instruction and a special &quot;write block of flash memory&quot; instruction (different from the normal &quot;write to data memory&quot; instruction), in addition to the &quot;read data from program memory&quot; instruction.&#xA;Several more recent Microchip PICmicros and Atmel AVRs are self-programmable modified Harvard machines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to categorize CPUs is by their clock.&#xA;Most computers are synchronous -- they have a single global clock.&#xA;A few CPUs are asynchronous -- they don't have a clock -- including the ILLIAC I and ILLIAC II, which at one time were the fastest supercomputers on earth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please help improve the description of all kinds of computer architectures at&#xA;&lt;a href=&quot;http://en.wikibooks.org/wiki/Microprocessor_Design/Computer_Architecture&quot; rel=&quot;nofollow&quot;&gt;http://en.wikibooks.org/wiki/Microprocessor_Design/Computer_Architecture&lt;/a&gt;&#xA;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-06T13:45:57.237" CommentCount="5" />
  <row Id="4271" PostTypeId="1" AcceptedAnswerId="4272" CreationDate="2010-09-06T14:35:56.233" Score="6" ViewCount="271" Body="&lt;p&gt;Can someone please explain how the &lt;a href=&quot;http://code.google.com/p/arduino/source/browse/tags/0019/hardware/arduino/bootloaders/atmega/ATmegaBOOT_168.c&quot; rel=&quot;nofollow&quot;&gt;Arduino bootloader&lt;/a&gt; works? I'm not looking for a high level answer here, I've read the code and I get the gist of it. I've also read through this &lt;a href=&quot;http://chiphacker.com/questions/347/arduino-bootloader&quot;&gt;other post&lt;/a&gt; (I had even been one of the responders to it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a bunch of protocol interaction that happens between the Arduino IDE and the bootloader code, ultimately resulting in a number of inline assembly instructions that self-program the flash with the program being transmitted over the serial interface. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'm not clear on is on line 270:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void (*app_start)(void) = 0x0000; &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;...which I recognize as the declaration, and initialization to NULL, of a function pointer. There are subsequent calls to app_start in places where the bootloader is intended to delegate to execution of the user-loaded code. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Surely, somehow &lt;code&gt;app_start&lt;/code&gt; needs to get a non-NULL value at some point for this to all come together. I'm not seeing that in the bootloader code... is it magically linked by the program that gets loaded by the bootloader? I presume that main of the bootloader is the entry point into software after a reset of the chip. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wrapped up in the 70 or so lines of assembly must be the secret decoder ring that tells the main program where app_start really is? Or perhaps it's some implicit knowlege being taken advantage of by the Arduino IDE? All I know is that if someone doesn't change app_start to point somewhere other than 0, the bootloader code would just spin on itself forever... so what's the trick?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On a separate note, would it be possible for the bootloader code to rely on interrupts or is that a no-no?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm interested in trying to port the bootloader to an Tiny AVR (specifically the ATTiny44A) that doesn't have separate memory space for boot loader code. As it becomes apparent to me that the bootloader code relies on certain fuse settings and chip support, I guess what I'm really interested in knowing is what does it take to port the bootloader to a chip that doesn't have those fuses and hardware support (but still has self-programming capability)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking I could use the implementation of AVR307 to use the USI as a half-duplex UART (uses Timer0 interrupt, and pin-change interrupt). Can anyone offer guidance on how to go about writing/porting the bootloader code for a chip that doesn't have hardware support for bootloaders?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I presume I would put my bootloader code at the normal location for address main (e.g. 0x029e or wherever the compiler puts main). I would then make it so that 'address' in the bootloader code added an offset that put me just past the end of main, and have 'app_start' set to that address. Am I thinking about this correctly or am I totally missing something? Thanks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT 2&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FWIW, I found a documented process for &lt;a href=&quot;http://blog.wickeddevice.com/?p=117&quot; rel=&quot;nofollow&quot;&gt;how to load Arduino sketches onto a ATTiny85&lt;/a&gt;, which is where I was originally going with this question... pretty neat I think&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-27T18:52:00.683" LastActivityDate="2010-12-27T18:52:00.683" Title="Arduino Bootloader Details" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;bootloader&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="4272" PostTypeId="2" ParentId="4271" CreationDate="2010-09-06T14:56:26.513" Score="5" ViewCount="" Body="&lt;pre&gt;&lt;code&gt;void (*app_start)(void) = 0x0000; &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This isn't a NULL pointer. This really is the address of the start of application code, which the bootloader jumps to. The linker arranges for your application code to start at address 0. See table 26-6 in the ATMEGA168 datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bootloader code starts higher up in flash. Exactly where depends on the bootloader fuses.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-09-06T15:03:06.300" LastActivityDate="2010-09-06T15:03:06.300" CommentCount="6" />
  <row Id="4273" PostTypeId="1" CreationDate="2010-09-06T23:03:22.153" Score="7" ViewCount="321" Body="&lt;p&gt;What projects can be made with an Arduino using a minimum of extra components save what can be found around the house?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T19:08:01.890" LastActivityDate="2011-01-29T19:08:01.890" CommunityOwnedDate="2010-09-06T23:03:36.273" Title="What can you do with an Arduino using no extra components?" Tags="&lt;arduino&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="4274" PostTypeId="2" ParentId="4273" CreationDate="2010-09-06T23:06:30.533" Score="4" ViewCount="" Body="&lt;p&gt;A wide variety of toys and electronics operate on TTL.  For example, you could take an Radio controlled toy car or microav and control it via an Arduino.&lt;/p&gt;&#xA;" OwnerUserId="1325" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-09-06T23:09:42.047" LastActivityDate="2010-09-06T23:09:42.047" CommunityOwnedDate="2010-09-06T23:06:30.533" CommentCount="1" />
  <row Id="4275" PostTypeId="2" ParentId="4273" CreationDate="2010-09-06T23:08:40.957" Score="3" ViewCount="" Body="&lt;p&gt;Using a speaker taken from an old pair of headphones, make &lt;a href=&quot;http://tn42.com/riff&quot; rel=&quot;nofollow&quot;&gt;R.I.F.F&lt;/a&gt; The Randomly Influenced Finger Flute.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You touch floating inputs to trigger a music generator.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-06T23:08:40.957" CommunityOwnedDate="2010-09-06T23:08:40.957" />
  <row Id="4276" PostTypeId="2" ParentId="4235" CreationDate="2010-09-06T23:30:56.543" Score="3" ViewCount="" Body="&lt;p&gt;There are two features of Motor control worth sampling.  The first is the current you mention.  There are two parts of the current path that are going to be interesting, and you probably need to measure them separately.  The first half is the rise current, the part of the commutation when the motor is connected to power.  The natural induction of the motor windings will cause the current to rise gradually, until the control loop shuts it off, either because it is using current limiting (chopper drive), or some other part of the control loop is turning the motor off.  In the case of a normal H-Bridge, this is the only current path.  In the off state, no current can flow in or out of the motor because it is completely disconnected.  More elaborate circuits may also use regeneration, in which the motor is connected to another part of the circuit to assist in deceleration, either a dump resistor or a battery recharging circuit.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For small currents (about 1A or less), the usual way to do this is with a low value current sense resistor, connected in series with the motor windings.  The current passing through the resistor causes a voltage difference on the opposite sides of the resistor, which can be measured quite easily.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Larger currents require fancier tricks, but a good option is a hall effect current sensor.  The result is quite similar, an output voltage in proportion to the instantaneous current.  This type of sensor has a slight propagation delay ( a few microseconds ) because of the multiple stages of amplification needed with the hall effect sensors.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other feature of motor control worth looking at is Back EMF.  This can be useful in some types of (really simple) servo control to determine motor velocity, since back EMF is proportional to motor speed.  This feature can only be measured on windings that are 'off', since the voltage of the power supply will dominate the higher impedance windings.  In the case of a PMDC motor, Back emf would be measured during the off periods of motor control.  The back emf at the moment of switch-off will be equal to the supply voltage, but will decay, due to the natural inductance of the windings until it reaches the level determined by its speed.  &lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2010-09-06T23:30:56.543" CommentCount="2" />
  <row Id="4277" PostTypeId="2" ParentId="4273" CreationDate="2010-09-07T02:13:15.610" Score="3" ViewCount="" Body="&lt;p&gt;If you felt like a challenge, you could try and display different types of data with only the on-board LED. Someone out there made a single-LED voltmeter. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you had an old alarm clock laying around with an LED display, there's a lot of blinky fun. Carefully extract out the LED display, look for a model number and get the data sheet; or probe the pins with 2V to learn how to light up each segment. Plus there would be a buzzer or speaker you could make use of as others have mentioned&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a light-dependent resistor and a speaker or piezo you could make one of those hand-held things that made noise when waved around on an alien surface in the original Star Trek show&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you had a model train set, using a few cheap relays and some resistors you could computer-control track sections just like a real railway&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.practicalarduino.com/projects/appliance-remote-control&quot; rel=&quot;nofollow&quot;&gt;Appliance&lt;/a&gt; remote control could be done for under US$20 &lt;/p&gt;&#xA;&#xA;&lt;p&gt;[self-promo] if you were willing to spend US$25 or so you could follow the first five chapters of my &lt;a href=&quot;http://tronixstuff.com/tutorials&quot; rel=&quot;nofollow&quot;&gt;Arduino tutorials&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-07T02:13:15.610" CommunityOwnedDate="2010-09-07T02:13:15.610" />
  <row Id="4278" PostTypeId="2" ParentId="2346" CreationDate="2010-09-07T04:16:20.427" Score="1" ViewCount="" Body="&lt;p&gt;As far as I know, stamped sheet aluminum is the cheapest way to mass-produce metal cases.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want a pretty wood case, I see 4 options:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;no shielding at all. The electronics in a wood case has almost exactly the same EMI/EMC as if it were sitting out in the open air, or in a glass fish-tank of oil. My understanding is that all PC motherboards emit so much RF that such a case would fail FCC testing, making it illegal to sell in most countries.&lt;/li&gt;&#xA;&lt;li&gt;put a metal box inside the wood case -- perhaps by covering the metal case with veneer.&lt;/li&gt;&#xA;&lt;li&gt;cover the worst RF emitters with tiny metal boxes attached to the PCB. The metal box should be attached to the ground plane of the PCB, preferably at many points all the way around the perimeter. An isolated metal box often makes emitted RF interference worse.&lt;/li&gt;&#xA;&lt;li&gt;spray the inside of the non-metal case with a conductive paint, and somehow attach it to ground.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The last two options (small metal boxes, conductive paint on the case, or often both in combination) are extremely common in many consumer electronic devices that come in a plastic case such as cell phones, televisions, radios, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect that metal roofing tape or aluminum foil would work just as well as or better than the conductive spray paint, but I've never seen it in production.&#xA;(I'm guessing that it has a higher labor cost to install properly than the conductive paint).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A brief google search gives me (in no particular order):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.emdt.co.uk/article/designing-screened-enclosures-part-iii&quot; rel=&quot;nofollow&quot;&gt;Designing Screened Enclosures&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.engineersedge.com/instrumentation/emi_rfi_coatings.htm&quot; rel=&quot;nofollow&quot;&gt;EMI RFI coatings overview&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.thomasnet.com/products/coatings-emi-rfi-shielding-15740350-1.html&quot; rel=&quot;nofollow&quot;&gt;list of EMI/RFI Shielding Coatings Suppliers&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.iqsdirectory.com/emi-shielding/emi-coating/&quot; rel=&quot;nofollow&quot;&gt;list of EMI coating companies&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.macraesbluebook.com/search/product_company_list.cfm?prod_code=1670700&quot; rel=&quot;nofollow&quot;&gt;list of &quot;Emi/Rfi Shielding Coatings&quot; companies&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.objet.com/Misc/_Pages/Application_Notes_Left_Pane/RF_Shielding/&quot; rel=&quot;nofollow&quot;&gt;RF shielding coating&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-07T04:16:20.427" />
  <row Id="4281" PostTypeId="2" ParentId="4150" CreationDate="2010-09-07T08:16:44.570" Score="1" ViewCount="" Body="&lt;p&gt;You can avoid all the 'electronics'completely if you can use two serial ports to do the sniffing. Each of the sniffer ports reads the TX line of one end of the connection. This also gives you extra status input pins to read all status outputs on monitored comms.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  Tx --------------x------------------------------- Rx&#xA;                   |              &#xA;  Rx --------------|-----x------------------------- Tx&#xA;                   |     |                          &#xA;                   |     |         &#xA;                   |     |     &#xA;                   |     x------------ PC COM 1 Rx&#xA;                   |&#xA;                   x-------------------PC COM 2 Rx&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="611" LastActivityDate="2010-09-07T08:16:44.570" CommentCount="2" />
  <row Id="4282" PostTypeId="1" AcceptedAnswerId="4286" CreationDate="2010-09-07T08:29:43.637" Score="4" ViewCount="336" Body="&lt;p&gt;Two parts:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Is it possible to write an&#xA;Arduino Bootloader for a Tiny AVR?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Is it worthwhile to write a&#xA;Arduino Bootloader for an Tiny AVR?&#xA;(more subjective, contingent on 1)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Regards,&#xA;Vic&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-05-23T06:03:56.647" Title="Arduino Bootloader Follow On" Tags="&lt;arduino&gt;&lt;attiny&gt;&lt;avr&gt;&lt;bootloader&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="4283" PostTypeId="2" ParentId="4163" CreationDate="2010-09-07T08:46:30.047" Score="6" ViewCount="" Body="&lt;p&gt;An Arduino on it's own has too little I/O and too little CPU power and memory. You could use multiple Arduinos (as suggested by vicatu) or use something more powerful such as the mbed (as suggested by Joby Taffey). I would suggest a hybrid of both ideas. Use a powerful processor to provide AI and overall control and use simpler microcontrollers as I/O managers. In fact I would suggest a complete hierarchy with as many layers as required with more powerful processors as you rise up through the hierarchy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example I have used the Gameboy Advance as the 'brains'of a robot while the I/O was managed by PIC16F84 microcontrollers. I think an ideal arrangement would be somthing as powerful as a PC (maybe a mini ITX board) or somthing like a Beagle board as the brains, a middle layer with multiple MBEDs or Zilog Z8s as sub-system managers (motion control, sensor management, some sensor preprocessing etc). and lots of small/cheap microcontrollers (Atmel/PIC/TI MSP430 etc) to manage the leg work. The upper layer can use ethernet ot USB, the lower lesvels can use RS232, I2C etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An advantage of this whole approach is the you can modularise your development (good for groups of friends or students). Individual modules can have better defined goals (and easier to achieve) and be complete projects in them selves. At higher levels you can concentrate on AI and overall robot control without having to worry about low level details (for example, if you can issue a command to turn the robot 45 degrees you have effectivly divided your problem in half. The higher level can concentrate on decisions on which way to turn (decision making) while a lower level controller just has to satifsy simple well defined motor comnmands from above. In a way this is modeling our robot on the way our brains work (not at a neurological level). When we decide to reach out and pick up a cup we dont have to conciously think about the mechanics of what we are doing. We could see this action as occuring at three levels:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;1) High level - the decison to pick up the cup.&#xA;&#xA;2) Mid level - co-ordinate motor actions and basic analysis of senory inputs.&#xA;&#xA;3) Low level - perform motor action, collect sensor data.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Hope this is helpful.&lt;/p&gt;&#xA;" OwnerUserId="611" LastEditorUserId="611" LastEditorDisplayName="" LastEditDate="2011-01-12T10:12:34.590" LastActivityDate="2011-01-12T10:12:34.590" CommentCount="2" />
  <row Id="4284" PostTypeId="1" CreationDate="2010-09-07T10:00:30.617" Score="3" ViewCount="225" Body="&lt;p&gt;I am wondering if anyone can recommend a logic analyser for a Apple Mac environment with similar features as the SCANALOGIC 2 PRO around the same price would be great as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;or some thing that is similar, what type of features am I after for working with SPI and I2C. Fairly new to the Digital electronics&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/2036/beginners-logic-analyzer&quot;&gt;http://chiphacker.com/questions/2036/beginners-logic-analyzer&lt;/a&gt; is all PC based.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Was just wondering if anyone knows of any that work with Mac at all. that aren't $199+ dollars&lt;/p&gt;&#xA;" OwnerUserId="665" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-23T19:51:51.083" LastActivityDate="2011-03-23T19:51:51.083" Title="Logic Analyser for Mac environment" Tags="&lt;mac&gt;&lt;logic-analyzer&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="4285" PostTypeId="2" ParentId="4284" CreationDate="2010-09-07T10:13:11.887" Score="8" ViewCount="" Body="&lt;p&gt;I use the &lt;a href=&quot;http://code.google.com/p/the-bus-pirate/&quot; rel=&quot;nofollow&quot;&gt;Bus Pirate&lt;/a&gt; and the &lt;a href=&quot;http://dangerousprototypes.com/docs/Open_Bench_Logic_Sniffer&quot; rel=&quot;nofollow&quot;&gt;Open Logic Sniffer&lt;/a&gt; (both top links in &lt;a href=&quot;http://chiphacker.com/questions/2036/beginners-logic-analyzer&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/2036/beginners-logic-analyzer&lt;/a&gt;) with OSX.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-07T10:13:11.887" />
  <row Id="4286" PostTypeId="2" ParentId="4282" CreationDate="2010-09-07T13:21:29.010" Score="3" ViewCount="" Body="&lt;p&gt;It's not worthwhile to write a new one. There are plenty of &lt;a href=&quot;http://www.ladyada.net/techproj/Atmex/index.html&quot; rel=&quot;nofollow&quot;&gt;existing serial bootloaders&lt;/a&gt; for the Tiny AVR and it would be pretty trivial to port the actual Arduino bootloader. It's not even necessary to speak the same protocol to work with the Arduino environment. The Arduino IDE can be configured to upload to any programmer supported by avrdude.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-09-07T13:21:29.010" />
  <row Id="4287" PostTypeId="1" AcceptedAnswerId="4288" CreationDate="2010-09-07T14:14:19.517" Score="8" ViewCount="521" Body="&lt;p&gt;Alright, I've played around enough with Arduino that I feel pretty comfortable with it. Anything done now is more learning the electronics than it is the Arduino side of it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the next step for my learning? Arduino is a combined programmer / controller, so presumably I need to break that link and start working with a controller chip separate from the controller, I guess? Can somebody point me in the right direction?&lt;/p&gt;&#xA;" OwnerUserId="989" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-05T02:57:53.083" LastActivityDate="2011-03-05T02:57:53.083" Title="I understand Arduino: now what?" Tags="&lt;arduino&gt;" AnswerCount="5" CommentCount="6" FavoriteCount="3" />
  <row Id="4288" PostTypeId="2" ParentId="4287" CreationDate="2010-09-07T14:17:08.807" Score="8" ViewCount="" Body="&lt;p&gt;Here's some tips for working with AVRs and C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/2012/start-off-with-embedded-c-with-atmega32-atmega-avr-series&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/2012/start-off-with-embedded-c-with-atmega32-atmega-avr-series&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-07T14:17:08.807" />
  <row Id="4291" PostTypeId="2" ParentId="4287" CreationDate="2010-09-07T15:10:55.560" Score="9" ViewCount="" Body="&lt;p&gt;I think what to learn next depends on what you want to do that the Arduino can't do. That is, I can't see much point in programming a similar chip to do the same things, but with more difficult means.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some Arduino weaknesses:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Threading, meaning running two sections of code interleaved so that it seems like they're being executed at the same time&lt;/li&gt;&#xA;&lt;li&gt;Medium or high-bandwidth internet stuff, like streaming audio&lt;/li&gt;&#xA;&lt;li&gt;Serious computation, or tasks that require fast computation for fast response&lt;/li&gt;&#xA;&lt;li&gt;Anything that's made easier by having a filesystem around, like datalogging or dealing with images&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I can imagine two directions to go:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;More powerful embedded boards with small operating systems, like the Beagleboard or Gumstix&lt;/li&gt;&#xA;&lt;li&gt;Squeezing more performance out of small Atmega chips using hardware interrupts.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I can add more detail if you comment about which direction is more appealing. (The second one is definitely cheaper.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-09-07T15:29:37.720" LastActivityDate="2010-09-07T15:29:37.720" CommentCount="3" />
  <row Id="4292" PostTypeId="2" ParentId="4287" CreationDate="2010-09-07T15:30:43.180" Score="7" ViewCount="" Body="&lt;p&gt;I agree with Joby - Arduino is great but I always feel stifled by the framework they surround me with.  I'd move on to use straight C on your Arduino and build a lot of the library functionality they provided from scratch.  I generally prefer depth before breadth - don't just start on another microcontroller family by using more provided frameworks.  Learn a bit more about how to implement some of these functions yourself.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Start with a working program and replace the Arduino library calls with your own versions one function at a time.  You'll learn a lot about the control registers, timing, bit operations, etc if you havent' already.  Read the ATMega328 datasheet in depth - everything you need is in there.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try a different IDE like AVR Studio or Code::Blocks.  Learn the GCC toolchain.  Try more advanced coding techniques - unit tests, coverage, profiling, lint/splint checking.  Put an RTOS on the Arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A combined programmer/controller isn't a sign of weakness - it's just a design choice.  The only 'weakness' that could come from it is the lack of in-circuit debugging.  Buy an AVR Dragon and you'll have that licked for $50.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-07T15:30:43.180" />
  <row Id="4293" PostTypeId="1" AcceptedAnswerId="4298" CreationDate="2010-09-07T19:12:46.483" Score="4" ViewCount="425" Body="&lt;p&gt;I am starting work on a project where I want to do some DSP using an embedded solution ideally with very low latency as it will be in a real time environment. In addition I want high quality, preferably 16bit 48khz, but I can settle for 12bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I am wanting to know is if anyone in this community has done this before and has any words of advice. I have read all about it and have a &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en534506&quot; rel=&quot;nofollow&quot;&gt;dsPIC starter kit&lt;/a&gt; to play with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically I want to know if anyone has experience with PCM and how to efficiently apply filters then send back out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also want to know if anyone has any experience with Audio ADC's and DAC's and would have any suggestions for when I get to the point of developing my own board.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-09-07T21:37:42.927" LastActivityDate="2010-09-07T21:37:42.927" Title="High Quality Audio ADC and DAC with Embedded" Tags="&lt;dspic&gt;&lt;adc&gt;&lt;dac&gt;&lt;audio&gt;&lt;dsp&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="4294" PostTypeId="2" ParentId="89" CreationDate="2010-09-07T19:22:40.353" Score="2" ViewCount="" Body="&lt;p&gt;If you still want to go solid-state, they are many &quot;Hall effect switches&quot; which include the Hall effect sensor and Schmitt trigger with hysteresis to provide clean digital output without bounce. They switch whenever some threshold flux density (provided in datasheet) is reached. You can calculate a good combination of magnet and switch or simply experiment. This site will tell you a lot more: &#xA;&lt;a href=&quot;http://www.allegromicro.com/en/Products/Design/hall-effect-sensor-ic-applications-guide/&quot; rel=&quot;nofollow&quot;&gt;http://www.allegromicro.com/en/Products/Design/hall-effect-sensor-ic-applications-guide/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1120" LastActivityDate="2010-09-07T19:22:40.353" />
  <row Id="4295" PostTypeId="2" ParentId="4293" CreationDate="2010-09-07T19:51:51.823" Score="2" ViewCount="" Body="&lt;p&gt;Here's a project using an mbed (ARM Cortex-M3) to do audio delay:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2010/03/28/guitar-echo-pedal-built-with-mbed/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2010/03/28/guitar-echo-pedal-built-with-mbed/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a similar thing using the Maple:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://leaflabs.com/2010/07/audio-and-guitar-effects-on-maple/&quot; rel=&quot;nofollow&quot;&gt;http://leaflabs.com/2010/07/audio-and-guitar-effects-on-maple/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-07T19:51:51.823" />
  <row Id="4296" PostTypeId="2" ParentId="4293" CreationDate="2010-09-07T20:01:11.760" Score="3" ViewCount="" Body="&lt;p&gt;Many dsPICs have an I2S interface for a codec. I interfaced an &lt;a href=&quot;http://www.silabs.com/products/voice/codec/Pages/default.aspx&quot; rel=&quot;nofollow&quot;&gt;Si3000&lt;/a&gt; voice codec to a dsPIC30F4013, using a PCB I designed, for speech processing. Higher quality codecs are available.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-09-07T20:39:06.883" LastActivityDate="2010-09-07T20:39:06.883" />
  <row Id="4297" PostTypeId="2" ParentId="4287" CreationDate="2010-09-07T20:48:47.850" Score="5" ViewCount="" Body="&lt;p&gt;As a start, you may want to move from Arduino as platform to AVR as platform.  Ie, learn how to program/use a virgin AVR microcontroller for your projects instead of the Arduino.  That way, you won't have to buy another Arduino board for each project you do, or for doing projects with friends.  This is a fairly simple step (an Arduino is just a conventional Atmel AVR microcontroller but with a special board and bootloader), but its a big one for selling/giving projects to friends.  The toolchain is similar too: you use avr-gcc or avr-g++ with make in conjunction with a programming utility to install your program.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-09-07T20:48:47.850" CommentCount="1" />
  <row Id="4298" PostTypeId="2" ParentId="4293" CreationDate="2010-09-07T21:33:59.933" Score="3" ViewCount="" Body="&lt;p&gt;ATmega3250P + WM8731 codec: &lt;a href=&quot;http://www.openmusiclabs.com/projects/microdec/&quot; rel=&quot;nofollow&quot;&gt;http://www.openmusiclabs.com/projects/microdec/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other Reprogrammable Audio Platforms: &lt;a href=&quot;http://wiki.openmusiclabs.com/wiki/OtherPlatfroms&quot; rel=&quot;nofollow&quot;&gt;http://wiki.openmusiclabs.com/wiki/OtherPlatfroms&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also see &lt;a href=&quot;http://chiphacker.com/questions/59/dsp-recommendation-for-beginners#432&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/59/dsp-recommendation-for-beginners#432&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-09-07T21:33:59.933" CommentCount="1" />
  <row Id="4299" PostTypeId="2" ParentId="4257" CreationDate="2010-09-08T01:37:19.110" Score="1" ViewCount="" Body="&lt;p&gt;JustJeff's comment gave me an idea:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;@SteveP - you know, you're probably&#xA;  only going to need one wire into each&#xA;  fake battery; if the device takes two,&#xA;  it most likely wants 3V, and two of&#xA;  the contacts in the battery&#xA;  compartment will just be bridged, so&#xA;  you'll need to determine which ends&#xA;  the device takes the power from, and&#xA;  wire to the corresponding battery&#xA;  ends.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;A simple extension of this proposal would be to use two dead (Or fresh, if you like) batteries, put a piece of electrical tape (or otherwise disable) the bridged end of one battery, and then solder/conductive glue your wires onto the caps of the real batteries. This won't work if the batteries are in parallel, or if something is monitoring/drawing off of the middle of the battery pack, but JustJeff is right - most devices are wired in series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative would be to (permanently, sorry) solder a short pair of wires with a connector onto the back side of the device contacts (or PCB), and then remove the batteries and plug into the PSU.  When you want the prototype look to go away (or you want to travel through an airport), you can simply tuck the connector back into the case, and put in normal batteries.  However, I understand the hesitation to touch your (possibly expensive) device with a soldering iron!&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-08T01:37:19.110" CommentCount="1" />
  <row Id="4302" PostTypeId="2" ParentId="146" CreationDate="2010-09-08T11:17:22.967" Score="1" ViewCount="" Body="&lt;p&gt;There's a lot of stuff on controlling things with the iPhone on the Arduino forum. &lt;a href=&quot;http://www.google.com/search?ie=UTF-8&amp;amp;oe=UTF-8&amp;amp;q=iphone&amp;amp;btnG=search&amp;amp;domains=http%3A%2F%2Fwww.arduino.cc&amp;amp;sitesearch=http%3A%2F%2Fwww.arduino.cc%2Fcgi-bin%2Fyabb2%2F&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is what I found with a search.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-09-08T11:17:22.967" />
  <row Id="4303" PostTypeId="1" AcceptedAnswerId="4305" CreationDate="2010-09-08T12:38:13.347" Score="4" ViewCount="238" Body="&lt;p&gt;I'm looking for a document with a description of a method to measure CO and CO2 concentration on a gas. &#xA;I found some information about how to do it with infra red absorption, but not enough information to run a test.&#xA;I also saw something using a wire and a wheatstone bridge, but don't know what king of wire was that. &#xA;Is there another way?&lt;/p&gt;&#xA;" OwnerUserId="940" LastActivityDate="2010-09-09T17:35:25.287" Title="How to measure CO and CO2 concentration on a gas?" Tags="&lt;measurement&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="4304" PostTypeId="2" ParentId="4303" CreationDate="2010-09-08T12:54:23.827" Score="1" ViewCount="" Body="&lt;p&gt;I would take apart a CO detector and look for the sensor. Look up the datasheet, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for CO2 concentration, I'm not sure. &lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-09-08T12:54:23.827" />
  <row Id="4305" PostTypeId="2" ParentId="4303" CreationDate="2010-09-08T15:18:28.600" Score="4" ViewCount="" Body="&lt;p&gt;From my brief Googling, it looks like you'll be better off purchasing an existing CO2 and CO monitor.  If you're trying to measure high concentrations, then you'll have a harder time of it.   You haven't said much about your project, so I don't know if you're trying to go back to the physics of it, design your own circuit board with that feature, or just get the measurements of indoor air.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CO meters are available for wall plug-in for as little as $25.    You could either try to look up the sensor, or just tap the LED display and let it do its own thing.  The LED display shouldn't be too hard to reverse-engineer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;CO2 meters are harder to find and more expensive ($100-250), but they're also available.  They're used in air quality/HVAC monitoring for people and for plants, as well as in taking higher concentration measurements for toxicity analysis (ex. storage of dry ice - you don't want to suffocate by opening the closet door!) or for making carbonated beverages.    &lt;a href=&quot;http://en.wikipedia.org/wiki/Carbon_dioxide_sensor&quot; rel=&quot;nofollow&quot;&gt;Wikipedia has an article&lt;/a&gt; on non-dispersive infrared measurement techniques.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There were also CO2meter.com has sensor systems with I2C interfaces (&lt;a href=&quot;http://sundaecorp.com/co2meters/Documentation/Datasheets/DS22-OC-01%20-%20K22%20OC.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;) available for as little as $99, which looks like a good price. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A silver halide &lt;a href=&quot;http://www.alphasense.com/alphasense_sensors/co2_carbon_dioxide_sensors.html&quot; rel=&quot;nofollow&quot;&gt;system&lt;/a&gt; can be used to make the measurement if the NDIR systems won't work for your application, and a Wheatstone bridge would be required to measure the tiny resistance, but, again, if you're going for accuracy, you'll probably be better off purchasing a commercial solution.  If you're trying to manufacture your own sensor system for sale, you'll need to do your own research.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-08T15:18:28.600" CommentCount="1" />
  <row Id="4306" PostTypeId="1" CreationDate="2010-09-08T23:03:32.900" Score="2" ViewCount="240" Body="&lt;p&gt;I just got &lt;a href=&quot;http://www.elechouse.com/elechouse/index.php?main_page=product_info&amp;amp;products_id=324&quot; rel=&quot;nofollow&quot;&gt;this awesome Bluetooth module&lt;/a&gt; in the mail. I connected power and UART pins, and tied pin 34 to +3.3v with a 1k resistor (that puts the module into AT command mode rather than pass-through bluetooth mode). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the first thing I notice is that it's sending &quot;ERROR:(0)&quot; repeatedly at about 15 messages per second. But if I send a character, it stops. If I have stopped it, then I can send an AT command such as &quot;AT&quot; followed by enter. The module proceeds to then send &quot;OK&quot; repeatedly at 15 messages per second. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm going through all the supported AT commands, and each one works, but it continuously repeats itself until I press the any key.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried connecting the CTS/RTS pins but it acts the same way as when I just use the UART pins alone. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm connected to my PC via USB FTDI UART cable that basically gives me a serial port on my PC (/dev/ttyUSB0) and a uart header on the other end, which I have connected the module to. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I send the AT commands, I am getting valid responses, it's just that I have to press a key to stop it from sending its response over and over, and that key gets thrown away. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Seems really weird, but I bet there's a good explanation out there? &lt;/p&gt;&#xA;" OwnerUserId="1033" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T19:18:04.790" LastActivityDate="2011-05-16T19:18:04.790" Title="What causes a UART device to continuously repeat its last transmission?" Tags="&lt;hardware&gt;&lt;bluetooth&gt;&lt;uart&gt;&lt;ftdi&gt;" AnswerCount="3" CommentCount="0" />
  <row Id="4307" PostTypeId="2" ParentId="259" CreationDate="2010-09-09T07:00:02.437" Score="1" ViewCount="" Body="&lt;p&gt;Microchip Pic16707 with mtouch technology can handle capacitive touch screens easily. Its code is free from microchip site.&lt;/p&gt;&#xA;" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-09-09T17:55:29.613" LastActivityDate="2010-09-09T17:55:29.613" CommentCount="1" />
  <row Id="4308" PostTypeId="2" ParentId="4306" CreationDate="2010-09-09T08:23:34.317" Score="2" ViewCount="" Body="&lt;p&gt;Try connecting your USB serial port to another PC to actually verify that when you send AT, it's only being sent once.My guess is your terminal emulator is sending the same sequence repeatedly. &lt;/p&gt;&#xA;" OwnerUserId="921" LastActivityDate="2010-09-09T08:23:34.317" CommentCount="2" />
  <row Id="4309" PostTypeId="2" ParentId="4306" CreationDate="2010-09-09T08:37:10.510" Score="3" ViewCount="" Body="&lt;p&gt;It sounds like you've connected TX and RX together.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-09T08:37:10.510" CommentCount="2" />
  <row Id="4311" PostTypeId="1" AcceptedAnswerId="4314" CreationDate="2010-09-09T14:28:14.580" Score="2" ViewCount="432" Body="&lt;p&gt;I'm looking at the &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8271.pdf&quot; rel=&quot;nofollow&quot;&gt;ATMega328p data sheet&lt;/a&gt;, and &lt;a href=&quot;http://arduino.cc/en/Hacking/Atmega168Hardware&quot; rel=&quot;nofollow&quot;&gt;an Arduino Pin diagram&lt;/a&gt;, trying to determine if the chip can support three UART connections... I see that PD0 and PD1 are &quot;USART&quot; In and Out... So does that mean the other 10 or so Digital pins can be used for &quot;UART&quot; communications? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a need to connect three UART devices through the ATMega chip. The ATMega will forward traffic between two of the devices at a time, depending on which mode it's in. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&#xA;Brad&lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2011-05-18T11:37:20.430" Title="Three UART connections to an ATMega328?" Tags="&lt;uart&gt;&lt;arduino&gt;&lt;atmega&gt;&lt;atmega328&gt;" AnswerCount="3" />
  <row Id="4312" PostTypeId="2" ParentId="875" CreationDate="2010-09-09T14:32:28.503" Score="1" ViewCount="" Body="&lt;p&gt;Sounds like a cool project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some motor drivers already measure current in order to provide &quot;overload protection&quot;.&#xA;If you can't tap that signal,&#xA;there are &lt;a href=&quot;http://opencircuits.com/current_sense&quot; rel=&quot;nofollow&quot;&gt;several ways to measure current&lt;/a&gt;.&#xA;Start with the simplest and cheapest method, and if that won't work, try the next one.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-09T14:32:28.503" />
  <row Id="4313" PostTypeId="2" ParentId="4311" CreationDate="2010-09-09T14:33:08.693" Score="2" ViewCount="" Body="&lt;p&gt;There is only one UART on the 328P. If your bandwidth is low you can do software emulation&#xA;of a UART with some of the other digital pins. There is an Arduino library called&#xA;NewSoftSerial that enables this functionality.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:37:20.430" LastActivityDate="2011-05-18T11:37:20.430" />
  <row Id="4314" PostTypeId="2" ParentId="4311" CreationDate="2010-09-09T14:34:28.080" Score="1" ViewCount="" Body="&lt;p&gt;If you don't have enough hardware serial ports, you can use other IO pins for serial under software control. But, don't expect to get 115200bps...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://arduiniana.org/libraries/NewSoftSerial/&quot; rel=&quot;nofollow&quot;&gt;http://arduiniana.org/libraries/NewSoftSerial/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-09T14:34:28.080" />
  <row Id="4315" PostTypeId="2" ParentId="4311" CreationDate="2010-09-09T15:50:14.920" Score="2" ViewCount="" Body="&lt;p&gt;It is true - only one serial port on the ATMega 328.  You can do what the others suggested and use software-serial or you can use a multiplexer if you don't need your serial ports to be always on.  Sparkfun has one that can be used for 3.3V here: &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8970&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=8970&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, if there isn't constant traffic, especially if you only need to send messages or you will only receive one response for one command then you can use the multiplexer.  Just switch to the device you want, send commands, wait for response, then switch to another device.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-09T15:50:14.920" />
  <row Id="4316" PostTypeId="2" ParentId="4306" CreationDate="2010-09-09T15:52:11.920" Score="0" ViewCount="" Body="&lt;p&gt;If you can, make sure that it isn't resetting itself repeatedly until you send a character.  It might be something like that.  But check everything that everyone else suggested as well.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-09T15:52:11.920" />
  <row Id="4319" PostTypeId="1" AcceptedAnswerId="4322" CreationDate="2010-09-09T17:58:20.310" Score="3" ViewCount="77" Body="&lt;p&gt;Sometimes I get a notice from a manufacturer that a part has gone obsolete.  I now have to find a new part from a different manufacturer to put on the BOM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a resistor or capacitor, it is pretty easy to look up the value, tolerance, temperature range, etc. of the original part and find a replacement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some ICs are easier than others.  There are lots of OpAmps and RS232 drivers.  But there is still the battle of finding the IC in the correct footprint.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to design in several drop-in-replacement parts for a new design.  I'm stuck on finding some compatible Analog to Digital Converters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know of a site or method for finding this?&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-11-20T00:52:38.650" Title="How to find a drop-in-replacement ADC" Tags="&lt;adc&gt;&lt;bom&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="4320" PostTypeId="2" ParentId="3062" CreationDate="2010-09-09T18:30:05.720" Score="3" ViewCount="" Body="&lt;p&gt;Kortuk's comments here are the first time I've heard that putting two identical electrolytic capacitors back-to-back is &quot;very risky&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The following references seem to contradict Kortuk:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&quot;electrolytic capacitors ... Non-polar (or bi-polar) devices can be made by using two anodes instead of an anode and a cathode, or one could connect the positives or negatives of two identical device together, then the other two terminals would form a non-polar device.&quot; -- &lt;a href=&quot;http://electrochem.cwru.edu/encycl/art-c04-electr-cap.htm&quot; rel=&quot;nofollow&quot;&gt;http://electrochem.cwru.edu/encycl/art-c04-electr-cap.htm&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&quot;you can substitute two regular electrolytics in series ... with their negative ends joined in the middle. ... in fact, that's what you'd find if you opened a real nonpolarized capacitor.&quot; -- Charles Platt. &quot;MAKE: Electronics: Learning Through Discovery&quot;. O'Reilly Media, Inc., 2009. p. 249. (excerpts available on &lt;a href=&quot;http://books.google.com/&quot; rel=&quot;nofollow&quot;&gt;http://books.google.com/&lt;/a&gt; ).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&quot;A common argument is over whether or not you can make a non-polarized capacitor by putting two polarized electrolytics back-to-back.  People have been doing this for years, with no problems to my knowledge.&quot; &lt;a href=&quot;http://my.execpc.com/~endlr/electrolytic.html&quot; rel=&quot;nofollow&quot;&gt;http://my.execpc.com/~endlr/electrolytic.html&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Of course, the capacitor will blow up (or not) no matter which way the majority votes.&#xA;Sometimes the underdog is right.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-09T18:30:05.720" CommentCount="2" />
  <row Id="4321" PostTypeId="2" ParentId="3062" CreationDate="2010-09-09T18:36:31.933" Score="2" ViewCount="" Body="&lt;p&gt;To make a &lt;a href=&quot;http://www.powerlabs.org/railgun.htm&quot; rel=&quot;nofollow&quot;&gt;railgun&lt;/a&gt; =)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connecting them in series increases the voltage capability (add voltage limits of all caps in series). &lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-09-09T18:36:31.933" CommentCount="1" />
  <row Id="4322" PostTypeId="2" ParentId="4319" CreationDate="2010-09-09T19:19:43.747" Score="3" ViewCount="" Body="&lt;p&gt;This is the bane of designers. There really isn't an easy way to get around it; you either design your boards such that they accept similar parts from different vendors, or you try to establish some kind of guarantee of availability with the manufacturers you do use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since most of us are not Apple or Sony or another huge volume company, you're stuck with the multiple vendors route. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There really is no other way around it.  Personally I avoid companies such as Rochester for the very reason that they are a &quot;last resort&quot; type of company, generally with prices that match (i.e. they know they've got you by the short and curlies).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Memories and things like ethernet PHYs are pretty easy to make boards work with multiple vendors or with multiple parts from the same vendor; you usually end up with a few resistor &quot;jumpers&quot; to route the pins that aren't at the same location.  Other devices you usually end up with multiple footprints on the board, sometimes with creative overlapping of the footprints to minimize the amount of space they're taking up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry I don't have better news for you. In my own experience I have gotten such that I will have a spot on the BOM for &quot;alternative part numbers&quot; and some of my device footprints are already set up to accept them. You live and learn. :-)&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-09-09T19:19:43.747" />
  <row Id="4323" PostTypeId="1" CreationDate="2010-09-09T19:20:03.833" Score="4" ViewCount="159" Body="&lt;p&gt;Can anyone suggest an alternative to energy from a battery?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like a system to replace my deep cycle leisure battery, I currently use &lt;a href=&quot;http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_264265_langId_-1_categoryId_165475&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; 110 AH leisure battery with a 1200W inverter. &#xA;I run my computer, lighting and sound system off it while I'm &quot;out in the sticks&quot;, It works just perfect, there's more than enough energy to get a couple of days usage between charges, I just wanted to know if there's a greener way of storing the energy - instead of using ye olde plastic box full of acid and corroding metal.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not interested in using a diesel or petrol generator, I'm looking for something a bit cleaner and greener than that, was thinking about the possibility of running a dynamo off a bottle of pressurized gas or air? - I'd probably need an unfeasibly large tank for this tho!   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers Chiphackers :)&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-09-11T14:37:23.670" CommunityOwnedDate="2010-09-09T19:20:03.833" Title="Alternative Energy Storage" Tags="&lt;energy&gt;&lt;generator&gt;&lt;storage&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="4324" PostTypeId="2" ParentId="4323" CreationDate="2010-09-09T19:42:59.313" Score="9" ViewCount="" Body="&lt;p&gt;You could collect a lot of lumber (like &gt;50kg), tie it all together and throw a long rope over a big tree branch. Then using several winches lift up all the lumber high in the air, and then utilise the energy of the timber slowly descending towards the ground. The winches would convert high torque to low torque but with a very long rope, which would be a good way to drive a dynamo.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just thinking alternatively... :)&lt;/p&gt;&#xA;" OwnerUserId="718" LastActivityDate="2010-09-09T19:42:59.313" CommunityOwnedDate="2010-09-09T19:42:59.313" CommentCount="9" />
  <row Id="4325" PostTypeId="2" ParentId="4323" CreationDate="2010-09-09T21:09:07.393" Score="2" ViewCount="" Body="&lt;p&gt;I don't think there's anything necessarily un-green about a battery, unless you're talking about the production methods of energy required to manufacture it. All of the materials in the battery were in the environment somewhere - all the manufacturing process has done is concentrate it into a small package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there's anything un-green about a battery, I'd say it's the inefficiency of the cycle. While the above idea is very clever, you still have to put some energy into the system in the first place. If that's a hand crank, then that's pretty good...without getting into the question of the green-ness of the food production that put the energy into the food and then into you (the mind boggles). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ultimately, I would look at what local power sources you might have available...wind, solar, hydrothermal, geothermal, hydromechanical. And if you want to take it really seriously, you then have to look into what energy went into refining the materials necessary to harness the energy, transporting it, warehousing it...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is probably more trouble than you asked about, but &quot;energy out in the sticks&quot; is a favorite research topic of mine. If you want to get REALLY serious about it, live underground and don't need 90% of the energy you use in the first place. Then you can run a generator guilt-free in the knowledge that you're light years ahead of the pack.&lt;/p&gt;&#xA;" OwnerUserId="989" LastActivityDate="2010-09-09T21:09:07.393" CommunityOwnedDate="2010-09-09T21:09:07.393" CommentCount="2" />
  <row Id="4326" PostTypeId="2" ParentId="4029" CreationDate="2010-09-09T21:12:41.413" Score="1" ViewCount="" Body="&lt;p&gt;Maybe this is simplistic, but if you open the serial port on the computer, doesn't that make Serial.available() == 0?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could light the LED on the board if that's true. Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="989" LastActivityDate="2010-09-09T21:12:41.413" />
  <row Id="4328" PostTypeId="1" CreationDate="2010-09-09T21:23:28.980" Score="6" ViewCount="438" Body="&lt;p&gt;This is more a physics/chemistry/nanotech question, but what's the theoretical best energy density you could get out of a chemical battery (or fuel cell), if you could arrange atoms in any manner you wanted?  I'm thinking of the nanotech batteries described in &lt;a href=&quot;http://en.wikipedia.org/wiki/The_Diamond_Age&quot; rel=&quot;nofollow&quot;&gt;Diamond Age&lt;/a&gt;.  How does it compare to current technologies?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T10:02:52.690" LastActivityDate="2011-01-23T10:02:52.690" Title="What's the highest theoretical energy density for a chemical battery?" Tags="&lt;battery&gt;&lt;batteries&gt;&lt;energy&gt;&lt;storage&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="2" />
  <row Id="4329" PostTypeId="2" ParentId="4328" CreationDate="2010-09-09T22:36:31.740" Score="4" ViewCount="" Body="&lt;p&gt;I don't know the actual answer to this question, but I know a least upper bound to the answer, and a means of figuring out the real answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Battery scientists have a metric called maximum theoretical specific energy; you can read about the definition in &lt;a href=&quot;http://books.google.com/books?id=atEOtixRHvcC&amp;amp;lpg=PA13&amp;amp;dq=mtse&amp;amp;pg=PA13#v=onepage&amp;amp;q=mtse&amp;amp;f=false&quot; rel=&quot;nofollow&quot;&gt;Advanced Batteries by Robert Huggins&lt;/a&gt;. Right now, the most energy dense batteries you can buy are lithium ion, which are in the 100-200 Wh/kg range. I don't know what the best battery is, but &lt;a href=&quot;http://books.google.com/books?id=atEOtixRHvcC&amp;amp;lpg=PA75&amp;amp;dq=Li/CUCl&amp;amp;pg=PA78#v=onepage&amp;amp;q=Li%2FCUCl&amp;amp;f=false&quot; rel=&quot;nofollow&quot;&gt;later in the book&lt;/a&gt;, Huggins shows calculations that indicate that Li/CuCl&lt;sub&gt;2&lt;/sub&gt; cells have an MTSE of 1166.4 Wh/kg. (5x the capacity of current batteries!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We know that the highest MTSE is at least 1166.4 Wh/kg; you could use his method to calculate the same value for other chemistries, but the search space is pretty large.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also seen references on the internet to Li/O&lt;sub&gt;2&lt;/sub&gt; and Al/O&lt;sub&gt;2&lt;/sub&gt; batteries with MTSE of 2815 and 5200 Wh/kg, respectively. Not sure how credible those references are. Later references, like &lt;a href=&quot;http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&amp;amp;id=JESOAN00015500000600A432000001&amp;amp;idtype=cvips&amp;amp;gifs=yes&amp;amp;ref=no&quot; rel=&quot;nofollow&quot;&gt;this 2008 article&lt;/a&gt; in the Journal of the Electrochemical Society, suggest that the MTSE for a Li/O&lt;sub&gt;2&lt;/sub&gt; cell is around 1400 Wh/kg.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-09-09T22:47:17.760" LastActivityDate="2010-09-09T22:47:17.760" CommentCount="2" />
  <row Id="4330" PostTypeId="1" AcceptedAnswerId="4392" CreationDate="2010-09-10T06:06:26.260" Score="3" ViewCount="144" Body="&lt;p&gt;Here's a good question for the professional electronic engineers of Chiphacker: What is &lt;a href=&quot;http://en.wikipedia.org/wiki/Noise_temperature&quot; rel=&quot;nofollow&quot;&gt;noise temperature&lt;/a&gt;, and how is it used in designing receiving systems as a whole? (I've seen it specified for the Arecibo telescope antenna, for example.) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen this specification used mostly in the UHF and higher bands, but I really don't understand how it's used.&lt;/p&gt;&#xA;" OwnerUserId="965" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-09-10T15:36:50.323" LastActivityDate="2010-09-13T14:34:13.470" Title="What is Noise Temperature?" Tags="&lt;measurement&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="4331" PostTypeId="2" ParentId="4287" CreationDate="2010-09-10T09:17:44.673" Score="6" ViewCount="" Body="&lt;p&gt;Learn I2C, SPI, 1wire and try to interface sensors with such interfaces. Read a lot of datasheets of such sensors and try to understand everything in them. Ask questions when stuck. Learn MODBUS (RTU/ASCII/TCP) or similar protocol that can open your device to the world once you embed it in the device. Learn general electronics and try to interface relays, triacs, what is pull up and pull down, what is sourcing and sinking, how to draw schematics and connect basic drivers to your MCU.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-09-10T09:17:44.673" />
  <row Id="4332" PostTypeId="1" AcceptedAnswerId="5957" CreationDate="2010-09-10T10:35:03.703" Score="6" ViewCount="768" Body="&lt;p&gt;Has anyone managed to get a TI Launchpad doing serial comms via the onboard USB chip (TUSB3410) to OSX?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have mspdebug working for uploading code. But to get serial I'm having to plug an FTDI chip into the serial lines on the MSP430. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody have instructions for making the TUSB3410 work properly in OSX?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They claim to have drivers, but I can't make them work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_Mac_OS_X&quot; rel=&quot;nofollow&quot;&gt;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_Mac_OS_X&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-25T19:29:16.457" LastActivityDate="2010-11-01T02:00:11.133" Title="TI Launchpad USB serial comms in OSX" Tags="&lt;msp430&gt;&lt;osx&gt;&lt;launchpad&gt;" AnswerCount="1" CommentCount="6" FavoriteCount="4" />
  <row Id="4333" PostTypeId="1" CreationDate="2010-09-10T11:58:00.557" Score="27" ViewCount="960" Body="&lt;p&gt;Have you ever looked at a PCB and burst out laughing?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you ever looked at a PCB and said &quot;Wow, that is amazing&quot;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you ever seen a PCB that artistically expressed criticism of society's treatment of the poor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm focusing here on the PCB itself as art -- rather than, say, some large artistic installation that may have light, sound, motion activated by some PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I hope a question focusing on artistic style rather than functionality isn't completely off-topic for chiphacker.&#xA;I was inspired to post this question after seeing the amazing artwork that endolith mentioned in the Chiphacker &lt;a href=&quot;http://chiphacker.com/questions/1128/best-licenses-for-open-hardware&quot;&gt;&quot;Best licenses for Open Hardware&quot;&lt;/a&gt; question ...&#xA;and seeing&#xA;&lt;a href=&quot;http://www.synthgear.com/2009/artists/moldover-theremin-cd-jewel-case/&quot; rel=&quot;nofollow&quot;&gt;The Best CD case insert... ever.&lt;/a&gt;&#xA;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&#xA;Wow, that's a lot of amazing artwork. I wish I could give everyone a prize for telling me about each piece of strange and wonderful artwork.&lt;/p&gt;&#xA;" OwnerUserId="813" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-04-05T15:57:08.800" LastActivityDate="2011-05-07T16:05:53.280" CommunityOwnedDate="2010-09-10T18:02:21.597" Title="What is the most amazing PCB artwork you've ever seen?" Tags="&lt;pcb&gt;&lt;design&gt;&lt;board&gt;&lt;physical-design&gt;" AnswerCount="10" FavoriteCount="9" />
  <row Id="4334" PostTypeId="2" ParentId="4333" CreationDate="2010-09-10T12:28:48.807" Score="3" ViewCount="" Body="&lt;p&gt;I like chip art.  Some examples are shown in &lt;a href=&quot;http://spectrum.ieee.org/semiconductors/design/the-secret-art-of-chip-graffiti/0&quot; rel=&quot;nofollow&quot;&gt;this Spectrum.ieee.org article&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/Chip_art&quot; rel=&quot;nofollow&quot;&gt;this Wikipedia article&lt;/a&gt; has others.&lt;/p&gt;&#xA;" OwnerUserId="921" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-07T16:05:53.280" LastActivityDate="2011-05-07T16:05:53.280" CommunityOwnedDate="2010-09-10T18:02:21.597" />
  <row Id="4335" PostTypeId="1" CreationDate="2010-09-10T12:35:18.093" Score="4" ViewCount="336" Body="&lt;p&gt;What would be the easiest way to read data from a USB glucose meter externally with a microcontroller. Not with the software that is provided. So how could I incercept the digital signals that are being sent out?&lt;/p&gt;&#xA;" LastActivityDate="2010-09-11T00:21:23.230" Title="Reading data from a glucose meter" Tags="&lt;usb&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="4336" PostTypeId="2" ParentId="4335" CreationDate="2010-09-10T12:43:12.233" Score="2" ViewCount="" Body="&lt;p&gt;You'll need an embedded device with USB host to read from your USB device. That implies a certain level of complexity (and cost).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The easiest route is probably to use Linux.&#xA;Have a look at this question for some options: &lt;a href=&quot;http://chiphacker.com/questions/2191/options-for-a-small-linux-hw-platform&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/2191/options-for-a-small-linux-hw-platform&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll also need a linux driver for your device. If one isn't available, you may have to reverse engineer the existing driver (perhaps using usbsnoop or other USB sniffing tools).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, there are smaller/cheaper/more energy efficient devices such as the USB AVRs or various flavours of ARM MCUs which can do USB host.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it wasn't for USB - this would be straightforward with an Arduino. Arduino is only capable of being a USB device and only a serial port over USB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you could find an alternate glucose reader which output a voltage or simple digital signal (I2C/SPI/RS232) then things would be simpler...&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-09-10T14:20:01.447" LastActivityDate="2010-09-10T14:20:01.447" CommentCount="6" />
  <row Id="4337" PostTypeId="2" ParentId="4333" CreationDate="2010-09-10T12:43:19.113" Score="2" ViewCount="" Body="&lt;p&gt;Cool question Davidcary, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I often have a good chuckle when I'm looking at a circuit board, especially if there's something amazing, ridiculous or strange on it. I have to admit to sniggering at a ground plane my friend pointed out only last week - it was, of course, the obligatory and somewhat crude icon - an outline of the male reproductive organ, like the kind seen sprayed on public transport the world over.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyhoo, I'm responding because my girlfriend likes making PCB art and I thought I'd share a &lt;a href=&quot;http://forum.sonodrome.co.uk/general-discussion-f1/pcb-artwork-t43.htm?highlight=artwork&quot; rel=&quot;nofollow&quot;&gt;pic&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I once did a grey-scale print of an angler fish with a rainbow LED for the lure, it was an experiment to see what the different thicknesses of copper would look like - it kinda worked out but it wasn't that consistent...may have to make another angler fish tho, I'm not finished with that idea yet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I forgot to mention my old uni lecturer John, he makes &lt;a href=&quot;http://www.dirtyelectronics.org/shop.html&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; fantastic musical instruments with a kind of, day of the dead theme. &lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-09-10T12:53:06.567" LastActivityDate="2010-09-10T12:53:06.567" CommunityOwnedDate="2010-09-10T18:02:21.597" CommentCount="1" />
  <row Id="4338" PostTypeId="2" ParentId="958" CreationDate="2010-09-10T12:52:07.617" Score="1" ViewCount="" Body="&lt;p&gt;Also noteworthy is that the &lt;a href=&quot;http://lxr.free-electrons.com/source/drivers/usb/serial/ftdi_sio.c&quot; rel=&quot;nofollow&quot;&gt;Linux driver&lt;/a&gt; presently supports speeds (only?) up to 460800 baud. &lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-09-10T12:52:07.617" />
  <row Id="4339" PostTypeId="2" ParentId="4333" CreationDate="2010-09-10T14:26:19.467" Score="7" ViewCount="" Body="&lt;p&gt;I'm partial to the look of EMS's &lt;a href=&quot;http://www.evilmadscientist.com/article.php/diavolino&quot; rel=&quot;nofollow&quot;&gt;Diavolino&lt;/a&gt; PCB; the board color, unusual traces, and goofy silkscreen make it look fantastic.&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2010-09-10T14:26:19.467" CommunityOwnedDate="2010-09-10T18:02:21.597" />
  <row Id="4340" PostTypeId="2" ParentId="4333" CreationDate="2010-09-10T14:30:42.250" Score="9" ViewCount="" Body="&lt;p&gt;Topological Autorouting, because it just looks weird.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://anthonix.resnet.scms.waikato.ac.nz/toporouter/&quot; rel=&quot;nofollow&quot;&gt;http://anthonix.resnet.scms.waikato.ac.nz/toporouter/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-10T14:30:42.250" CommunityOwnedDate="2010-09-10T18:02:21.597" />
  <row Id="4341" PostTypeId="2" ParentId="4333" CreationDate="2010-09-10T14:40:45.210" Score="20" ViewCount="" Body="&lt;p&gt;These are all from the same guy:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://gieskes.nl/undefined/x/files/3trins/3trins-front-angle.jpg&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://gieskes.nl/instruments/files/hard-soft-synth-1/version1/HSS-top-verson1.jpg&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://gieskes.nl/visual-equipment/files/cam_seq_1/Cam-Seq-1/cam_seq_bottomSeq.jpg&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://gieskes.nl/instruments/files/hard-soft-synth-3/HSS3hypnotoad/HSS3-hypnotoad-front.jpg&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://gieskes.nl/visual-equipment/files/pcb_puppet/PCB-Puppet/pcb_puppet2.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen some even cooler freeform drawn ones like this, but I don't remember where.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ecofriend.org/entry/eco-conscious-artist-transforms-trashed-pcbs-into-stunning-sculptures/&quot; rel=&quot;nofollow&quot;&gt;http://www.ecofriend.org/entry/eco-conscious-artist-transforms-trashed-pcbs-into-stunning-sculptures/&lt;/a&gt;&#xA;&lt;img src=&quot;http://www.instablogsimages.com/images/2010/03/25/pcb-sculpture_3_hTkY5_69.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.craftzine.com/archive/2007/09/skull_pcb_bracelet.html&quot; rel=&quot;nofollow&quot;&gt;http://blog.craftzine.com/archive/2007/09/skull_pcb_bracelet.html&lt;/a&gt;&#xA;&lt;img src=&quot;http://blog.craftzine.com/pcbskull1.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/laen/5013353017&quot; rel=&quot;nofollow&quot;&gt;http://www.flickr.com/photos/laen/5013353017&lt;/a&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/6MllH.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-21T15:56:26.380" LastActivityDate="2010-10-21T15:56:26.380" CommunityOwnedDate="2010-09-10T18:02:21.597" CommentCount="1" />
  <row Id="4342" PostTypeId="2" ParentId="952" CreationDate="2010-09-10T14:43:34.457" Score="0" ViewCount="" Body="&lt;p&gt;The site www.newtoncbraga.com.br has a lot of circuits in portuguese, but with the Language Tool box it can be translated into english (or other languages). Try it.&lt;/p&gt;&#xA;" LastActivityDate="2010-09-10T14:43:34.457" CommunityOwnedDate="2010-09-10T14:43:34.457" />
  <row Id="4343" PostTypeId="2" ParentId="4335" CreationDate="2010-09-10T15:07:08.057" Score="3" ViewCount="" Body="&lt;p&gt;If you really want to do USB embedded host you can use PIC24 from Microchip. They provide a good USB stack with some basic device profiles. I have not seen a device profile for a glucose meter, but it's possible they use a HID or CDC profile. If not you may need to get that information from the glucose meter manufacturer.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-09-10T15:07:08.057" />
  <row Id="4344" PostTypeId="2" ParentId="4323" CreationDate="2010-09-10T15:33:07.337" Score="1" ViewCount="" Body="&lt;p&gt;How about solar power?&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-09-10T15:33:07.337" CommunityOwnedDate="2010-09-10T15:33:07.337" CommentCount="2" />
  <row Id="4345" PostTypeId="2" ParentId="4333" CreationDate="2010-09-10T15:49:43.720" Score="10" ViewCount="" Body="&lt;p&gt;Theo Kamecke's sculptures are made of recycled circuit boards. The boards are definitely not functionnal anymore but the result is amazing:&#xA;&lt;img src=&quot;http://www.wired.com/gadgetlab/wp-content/gallery/circuit_board_art/zoroaster.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More pictures can be seen in the &lt;a href=&quot;http://www.wired.com/gadgetlab/2010/08/vintage-circuit-boards-art/?pid=65&amp;amp;viewall=true&quot; rel=&quot;nofollow&quot;&gt;Wired article&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="595" LastActivityDate="2010-09-10T15:49:43.720" CommunityOwnedDate="2010-09-10T18:02:21.597" />
  <row Id="4346" PostTypeId="2" ParentId="4335" CreationDate="2010-09-10T18:24:57.833" Score="4" ViewCount="" Body="&lt;p&gt;If you're still looking for a device, &lt;a href=&quot;http://www.google.com/search?sourceid=chrome&amp;amp;ie=UTF-8&amp;amp;q=glucose+rs232&quot; rel=&quot;nofollow&quot;&gt;this search&lt;/a&gt; suggests that OneTouch UltraMini / UltraEasy have an RS232 interface available, with &lt;a href=&quot;http://www.lifescan.com/pdf/otdms/OneTouchUltraMiniProtocol.pdf&quot; rel=&quot;nofollow&quot;&gt;documentation&lt;/a&gt;- which &lt;em&gt;should&lt;/em&gt; make it easier to interface with. &lt;/p&gt;&#xA;" LastActivityDate="2010-09-10T18:24:57.833" />
  <row Id="4347" PostTypeId="2" ParentId="4335" CreationDate="2010-09-10T21:05:58.063" Score="5" ViewCount="" Body="&lt;p&gt;The native interface to most glucose meters (Abbott, Bayer, J&amp;amp;J and Roche) is a UART output.  There is circuitry at one end of the cable that translates this to USB protocol.  It is possible to read the data with a UART by using a 2.5 mm or 3.5 mm plug to connect directly with the meter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The J&amp;amp;J uses a 3.5 mm plug with Tip being Tx and Ring being Rx (Tx and Rx wrt your UART, not the meter), and communicates at 9600 baud.  Except for the various J&amp;amp;J One-Touch models, the signal levels for the other brands are typically neither regular UART (0 / 3.3) or RS232 (+-5) levels but some weird combination.  Some models also swap Tx/Rx compared to the J&amp;amp;J.  Note: the One Touch Ultra and Ultra 2 use a different (more text based) protocol than the binary protocol used by the Ultra Mini (see CoderTao's answer for a link to the latter).&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-09-11T00:21:23.230" LastActivityDate="2010-09-11T00:21:23.230" />
  <row Id="4348" PostTypeId="1" AcceptedAnswerId="4361" CreationDate="2010-09-10T22:32:15.497" Score="4" ViewCount="243" Body="&lt;p&gt;Is there a practical way to sense 60Hz AC power in a &lt;em&gt;pair&lt;/em&gt; of wires? Measuring the exact power or even current isn't necessary; it would be sufficient to know whether the load is pulling more than, say 5 amps, or not. For example, suppose you have a well pump wired directly into the house distribution panel, and you only want to monitor when it turns on and off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would be a piece of cake if it were possible to separate the conductors and get a regular AC current probe around one of them, but cutting into the romex is unsatisfactory. Finding a place where the conductors are already separate is an obvious angle of attack, but let's leave taking the face off the distribution panel for last resort.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally there are already commercial sensors for this, but it's proving to be an awkward thing to google for. Seems like 8 or 10 amps through two conductors 3/8&quot; or so apart should give off enough stray field to at least tell the difference between on and off.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-09-11T01:52:56.167" LastActivityDate="2010-09-11T15:52:52.790" Title="How to go about sensing AC power in existing wiring" Tags="&lt;power&gt;&lt;sensor&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="4349" PostTypeId="2" ParentId="4348" CreationDate="2010-09-10T22:57:39.413" Score="3" ViewCount="" Body="&lt;p&gt;I don't believe there is a cost efficient wait to sense AC power in a pair, no.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheap home energy monitors use a lump of ferrite and a coil to clamp around a single wire in the fuse box.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of the monitors for single appliances I've seen have to be plugged in between the appliance and the wall.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Eg.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.automatedhome.co.uk/New-Products/AlertMe-Add-More-New-Features.html&quot; rel=&quot;nofollow&quot;&gt;http://www.automatedhome.co.uk/New-Products/AlertMe-Add-More-New-Features.html&lt;/a&gt;&#xA;http://www.vesternet.com/Technologies/Energy-packages/Z-Wave-Energy-Starter-Pack-BASIC&#xA;&lt;a href=&quot;http://www.vesternet.com/Technologies/Energy-packages/Plugwise-9-Piece-Starter-Kit&quot; rel=&quot;nofollow&quot;&gt;http://www.vesternet.com/Technologies/Energy-packages/Plugwise-9-Piece-Starter-Kit&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One possible approach is to take a reading from the main power meter, then try to identify and isolate your target device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.georgehart.com/research/nalm.html&quot; rel=&quot;nofollow&quot;&gt;http://www.georgehart.com/research/nalm.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-10T22:57:39.413" />
  <row Id="4350" PostTypeId="1" AcceptedAnswerId="4367" CreationDate="2010-09-10T23:32:23.733" Score="4" ViewCount="666" Body="&lt;p&gt;I need some sort of Linux powered device capable of running Python (it must have a FPU), and running off portable batteries (No, nothing Lead-Acid based counts.). Ideally it would have onboard USB ports, not on some riser. The cheaper the better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[EDIT]:I would like to keep it under US$100, if possible.&lt;/p&gt;&#xA;" OwnerUserId="1134" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-09-29T22:49:33.183" LastActivityDate="2011-03-05T20:37:51.597" Title="Best embedded linux board for a battery operated device?" Tags="&lt;robotics&gt;&lt;embedded&gt;&lt;linux&gt;" AnswerCount="7" CommentCount="2" FavoriteCount="3" />
  <row Id="4351" PostTypeId="2" ParentId="4282" CreationDate="2010-09-11T02:19:19.573" Score="3" ViewCount="" Body="&lt;p&gt;I would say it worthwhile if for no other reason as an educational experience.  Just because a chip has a default or popular bootloader doesnt make it good or mean you have to use it.  If you have never written one I would highly recommend it, if nothing else modify the existing/popular one.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now saying that, it is best to do this on a platform where you have a recovery path.  So boards/devices where you have a jtag interface and experience using that jtag are preferred.  Or to just get through inventing/using a protocol, have the default bootloader launch your (secondary) bootloader and work through the bootloader/programmer experience (using the original bootloader as your recover path).  But there is another half to the problem that you wont get, and that is the chip initialisation stuff, and that can be difficult to get right and takes many iterations (and most of those iterations result in a nonfunctional bootloader requiring the backdoor recovery path).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The arduino in particular suffered from the transition from 32 to 64 bit (on the host) for a while there so the choice was to change my day to day habits for this board, or step out of the sandbox and do my own thing with this board?  You find this very often in the microcontroller or eval board world, the canned sandboxes are usually windows first then maybe mac and then sometimes linux.  Even today pre-vista or pre windows 7 works but you may not have access to those on your development machine, may not want or be able to buy a copy just to play with a $20 toy.  Linux is usually the last host environment supported, so I often find myself writing a bootloader, using windows or whatever briefly, to load it then I can work in an environment I am more comfortable with to continue to use or evaluate the product.  In the case of the arduino it was easier to write a programmer that worked with the existing bootloader on the current Linux than to write a new or modified bootloader using an older or 32 bit linux or windows.  For the devices that have well designed built in bootloaders either in hardware or in a protected flash, it is often better to replace the programmer than the bootloader.  Which is is part of the bootloader development process anyway, so here again an educational experience as well as sometimes a practical solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The corollary to your question is Am I forced to use the IDE/sandbox provided with an eval or developer board, or can I use other tools or create my own?  Do I have to use such and such library to do something or can I write and use my own?&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-09-11T02:19:19.573" CommentCount="1" />
  <row Id="4352" PostTypeId="2" ParentId="4350" CreationDate="2010-09-11T02:20:58.370" Score="3" ViewCount="" Body="&lt;p&gt;Chumby &lt;a href=&quot;http://www.littlebirdelectronics.com/products/Chumby-Hacker-Board.html&quot; rel=&quot;nofollow&quot;&gt;guts&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-11T02:20:58.370" CommentCount="3" />
  <row Id="4353" PostTypeId="2" ParentId="4185" CreationDate="2010-09-11T03:32:22.417" Score="0" ViewCount="" Body="&lt;p&gt;Well, there is something like the ENIAC, where you have essentially individual ALUs and you &quot;programmed&quot; them by wiring the output of one alu to the input of another alu that was going to perform the next operation on that intermediate variable.  Your &quot;registers&quot; and storage are the wires connecting the alus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recently purchased the book &quot;The First Computers--History and Architectures (History of Computing)&quot;, which in part focuses on this exact topic.  I do not recommend purchasing this book though it is just a collection of academic papers, hard to read and I suspect probably published (for free) elsewhere. (I gave up on it before finishing the introduction)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once memory was invented and became practical, we kinda settled into the two popular ones Von Neumann and Harvard.  Executing from re-wiring, punch cards, paper tape or things like that became less practical.  And there is stack based (the zpu for example), which I suspect probably falls under the Harvard category and not its own.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What about von neumann platforms that boot off of a read-only (in normal use) flash on one memory interface and have read/write data ram in another (that can sometimes operate on both in parallel) but from the programs perspective are in one address space?  Or ones that have several internal and external memories/interfaces all operating in parallel but are von neumann for being in the same address space.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And what good is a harvard platform where the processor cannot access the instruction memory as data in order to change/upgrade the bootloader or for the bootloader to load the next program to run?  Why isnt that a von neumann architecture?  The processor executing from and operating on the same memory on the same interface in likely a sequential (instruction fetches and memory writes not happening at the same time) manner?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The two popular memory based architectures are more close than they are different in current implementations IMO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where do gpu's fall?  Or the business that I work in, network processors (NPUs).  Where you have these relatively small special purpose microengines (processors) that execute from a harvard like program ram (addressable but you just dont want to do that for performance reasons), operate on various data rams each having their own separate address space (separate processor instructions for each space), (the memory spaces operating in parallel) and through those rams hand off intermediate data to have the next computation done by the next microengine in a wired alu (eniac) like fashion?  What would you call that one?  Are npus and gpus just fancy modified harvard architectures?&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-09-11T03:32:22.417" CommentCount="3" />
  <row Id="4354" PostTypeId="2" ParentId="4350" CreationDate="2010-09-11T03:39:27.367" Score="3" ViewCount="" Body="&lt;p&gt;Maybe &lt;a href=&quot;http://www.gumstix.com/store/catalog/index.php?cPath=27&quot; rel=&quot;nofollow&quot;&gt;Gumstix&lt;/a&gt;? I've &lt;a href=&quot;http://pingswept.org/2007/07/22/python-on-the-gumstix-verdex/&quot; rel=&quot;nofollow&quot;&gt;run Python on one of their boards&lt;/a&gt; before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(My usual recommendation would be the TS-7500 from Technologic Systems, but their website is down. Anyway, they might be a bit cheaper.)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-09-11T03:39:27.367" CommentCount="2" />
  <row Id="4355" PostTypeId="1" AcceptedAnswerId="4693" CreationDate="2010-09-11T07:27:20.417" Score="3" ViewCount="376" Body="&lt;p&gt;I was looking for a processor to interface to the DVP port of a 5MP CMOS camera module. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could possibly write the software for doing this but I've heard that many processors have a hardware camera interface port that makes the job much efficient.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would like to do is capture frames from  this camera and store it in external ram for some processing later.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any idea how could I get around doing this? I just a small enough processor about 44pins or 64pins or so that has a camera interface port and external memory interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I think a small enough processor isn't going to be available, I'd be lucky if someone finds some most of the processor pointed out in the answers have 200+ pins. So feel free to point to processors without the &quot;pins&quot; limitation.&lt;/p&gt;&#xA;" OwnerUserId="444" LastEditorUserId="444" LastEditorDisplayName="" LastEditDate="2010-10-01T13:46:36.140" LastActivityDate="2010-10-01T13:46:36.140" Title="Processor with hardware camera interface port?" Tags="&lt;interface&gt;&lt;camera&gt;&lt;processor&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="4356" PostTypeId="1" CreationDate="2010-09-11T10:00:00.063" Score="2" ViewCount="563" Body="&lt;p&gt;Is there anything I can use to replace this circuit? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its a very simple electronic switch circuit, (transistor+zener diode+resistor)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit is connect to a remote control, the remote control is activated via http request via the arduino. which is controlled by an iPhone app.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remote control, when the circuit is closed (ie two wires are connected), it is activated. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Problem, when I unplug the circuit, or when my power goes down, it will set off the remote control and activate it!&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;I need the circuit to be normally open, when no current is applied.&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;USED:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Zener diodle IN4007 &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transistor 2N2222 &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Resistor 1k&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I dont want to use a relay, not for something this simple! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What do I do? &lt;img src=&quot;http://img689.imageshack.us/img689/5518/circuitc.png&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://img688.imageshack.us/img688/1032/201072415pm.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1135" LastEditorUserId="1135" LastEditorDisplayName="" LastEditDate="2010-09-13T03:42:36.763" LastActivityDate="2010-09-13T03:42:36.763" Title="Electronic circuit switch for arduino" Tags="&lt;arduino&gt;&lt;transistor&gt;&lt;zener&gt;&lt;diode&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="4357" PostTypeId="2" ParentId="4323" CreationDate="2010-09-11T10:24:09.467" Score="0" ViewCount="" Body="&lt;p&gt;One alterna-power answer might be fuel cells. A more old-fashioned and commonly available one would be a generator running off some liquid fuel (probably diesel). You might still want a buffer battery for that, of course, but you might be able to get rid of the inverter in some cases.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-09-11T10:24:09.467" CommunityOwnedDate="2010-09-11T10:24:09.467" />
  <row Id="4358" PostTypeId="2" ParentId="4356" CreationDate="2010-09-11T11:55:17.620" Score="2" ViewCount="" Body="&lt;p&gt;I cannot ascertain much from the photograph and your description. Could you please sketch out your circuit schematic and post that instead? &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-11T11:55:17.620" CommentCount="2" />
  <row Id="4359" PostTypeId="2" ParentId="4356" CreationDate="2010-09-11T14:11:41.060" Score="2" ViewCount="" Body="&lt;p&gt;It's hard to tell from that picture, but it looks like you have maybe two wires from the arduino going to the breadboard, and two wires going from the breadboard to that thing on the left. Assuming the thing on the left is the remote control, and that, from what you said shorting its two wires together turns it on, then it's very possible to have, as you say, a transistor that's normally open.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The usual thing would be to use a cheap NPN transistor like a 2n2222 or 2n3904. The collector of the NPN would go to the more positive of the two leads from the remote. The emitter would go to the other remote lead. (Use a DVM to be sure which is which, you can't always count on insulation color!) To ensure that the NPN passes no current when no input is connected, you can put a 50K or 100K resistor across the NPN's emitter and base leads. Then, to get input from the arduino, connect the arduino's ground to the NPN's emitter, and connect the arduino control signal you want to use to the NPN's base through a resistor in the range of 1K to 2K ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A circuit like that should not activate the remote when you disconnect the arduino.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-09-11T14:11:41.060" CommentCount="1" />
  <row Id="4361" PostTypeId="2" ParentId="4348" CreationDate="2010-09-11T15:52:52.790" Score="3" ViewCount="" Body="&lt;p&gt;I agree that the stray magnetic field from your power cables seems like it would be enough to at least discriminate between &quot;at least 5 amps on&quot; or &quot;0 amps off&quot;.&#xA;Perhaps you could build up a system based on one of the &lt;a href=&quot;http://opencircuits.com/Current_sense#magnetic_field_sense&quot; rel=&quot;nofollow&quot;&gt;magnetic field sensors listed at Open Circuits&lt;/a&gt; and press it against the power cord at some convenient point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As Joby Taffey pointed out, most equipment plugs into an electric socket, and so inserting a meter between the equipment and the electric socket is common:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.newark.com/extech-instruments/480172/test-equipment-ac-line-seperator/dp/27K9937&quot; rel=&quot;nofollow&quot;&gt;AC Line Seperator for Current Clamps&lt;/a&gt; solves the &quot;cutting into the power cord&quot; problem, and assumes you already have some &lt;a href=&quot;http://www.newark.com/tenma/72-7222/digital-clamp-amp-meter/dp/01N4891&quot; rel=&quot;nofollow&quot;&gt;clamp meter&lt;/a&gt; or another &lt;a href=&quot;http://www.newark.com/extech-instruments/38387/ac-clamp-meter/dp/27K9683&quot; rel=&quot;nofollow&quot;&gt;clamp meter&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://www.thinkgeek.com/brain/whereisit.cgi?t=watt+usage&quot; rel=&quot;nofollow&quot;&gt;&quot;watt usage&quot; meters at ThinkGeek&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;These things are generally calibrated to linearly measure current, so they are total overkill for merely discriminating between &quot;on&quot; and &quot;off&quot;.&#xA;And they won't work as-is for your application, since there is no socket between your well pump and the distribution panel.&#xA;But perhaps using one of these off-the-shelf devices, hacking it open and pressing the magnetic sensor against the weak magnetic field that leaks out of your romex cable, will be able to discriminate between &quot;on&quot; and &quot;off&quot; and take much less time and effort than building up something from scratch.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-11T15:52:52.790" />
  <row Id="4362" PostTypeId="2" ParentId="4350" CreationDate="2010-09-11T15:58:18.607" Score="3" ViewCount="" Body="&lt;p&gt;Most of the devices listed at&#xA;&lt;a href=&quot;http://opencircuits.com/Motherboards_that_run_Linux&quot; rel=&quot;nofollow&quot;&gt;&quot;Open Circuits: Motherboards that run Linux&quot;&lt;/a&gt;&#xA;have USB ports.&#xA;I suspect several of them would work adequately for your project, and you could choose based on price and energy consumption.&lt;/p&gt;&#xA;" OwnerUserId="813" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2010-09-11T20:08:39.837" LastActivityDate="2010-09-11T20:08:39.837" />
  <row Id="4363" PostTypeId="1" CreationDate="2010-09-11T19:26:25.210" Score="4" ViewCount="549" Body="&lt;p&gt;I see a few questions here casually mention that image sensor modules have a&#xA;&quot;standard parallel digital video port (DVP) or ... MIPI high-speed serial interface&quot;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/2718/where-do-i-start-with-embedded-video&quot; rel=&quot;nofollow&quot;&gt;&quot;Where do I start with embedded video?&quot;&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://chiphacker.com/questions/4355/processor-with-hardware-camera-interface-port&quot; rel=&quot;nofollow&quot;&gt;&quot;Processor with hardware camera interface port?&quot;&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://darling-china.en.made-in-china.com/product/YerQzwRFgUpM/China-Chip-CMOS-Camera-Module-Omnivision-Sensor.html&quot; rel=&quot;nofollow&quot;&gt;&quot;digital video port (DVP) parallel output interface MIPI serial input and output interface&quot;&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Is there a specific digital video port (DVP) interface standard?&#xA;Is there a specific MIPI standard?&#xA;If so, where can I get the details on the signals, standard connectors, etc.?&#xA;Or is &quot;DVP&quot; merely a generic term that includes a variety of interfaces such as DVI, DMP, HDMI, SDI, UDI, DVB-ASI, FireWire, i.LINK, DisplayPort, etc.?&#xA;Is there maybe more than one interface standard that (confusingly) has the same &quot;DVP&quot; initialism?&#xA;In particular, some people seem to think that it's possible to directly connect a 44 pin processor a DVP interface, so apparently they are &lt;em&gt;not&lt;/em&gt; talking about the 100 wire &lt;a href=&quot;http://techpubs.sgi.com/library/manuals/3000/007-3594-001/pdf/007-3594-001.pdf&quot; rel=&quot;nofollow&quot;&gt;SGI DVP&lt;/a&gt; interface -- are they perhaps some other DVP interface, or is this merely a typo for one of the above specific interfaces?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-18T18:34:32.187" Title="What is a digital video port?" Tags="&lt;video&gt;&lt;interface&gt;&lt;standard&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="4366" PostTypeId="2" ParentId="4171" CreationDate="2010-09-12T13:43:34.813" Score="1" ViewCount="" Body="&lt;p&gt;My apologies for the lateness in my reply, but there is a project in the &lt;a href=&quot;http://www.elektor.com/magazines/2010/july-047-august/the-elektor-dsp-radio.1391200.lynkx&quot; rel=&quot;nofollow&quot;&gt;July/August 2010&lt;/a&gt; [just arrived yesterday...] edition of Elektor that may be of interest. It uses the Si4735 DSP receiver IC that can decode RDS. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Farnell part number for the IC is 1835849&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-12T13:43:34.813" CommentCount="2" />
  <row Id="4367" PostTypeId="2" ParentId="4350" CreationDate="2010-09-12T16:06:49.723" Score="3" ViewCount="" Body="&lt;p&gt;There's the &lt;a href=&quot;http://www.hawkboard.org/&quot; rel=&quot;nofollow&quot;&gt;hawkboard&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It runs about $90-$110 depending on where you buy it from. 375MHz ARM board, 128MB RAM, 128MB flash storage on board, ethernet, usb, etc.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-09-12T16:06:49.723" CommentCount="2" />
  <row Id="4368" PostTypeId="2" ParentId="4350" CreationDate="2010-09-12T16:15:29.687" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://designsomething.org/leopardboard/default.aspx&quot; rel=&quot;nofollow&quot;&gt;Leopardboard&lt;/a&gt; has a 216MHz ARM with 128MB RAM, 256MB flash storage, ethernet, usb, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It costs &lt;a href=&quot;http://shop.leopardimaging.com/product.sc;jsessionid=F187FD0C8E5D8FC7E349A481132BE7B2.qscstrfrnt01?productId=18&amp;amp;categoryId=7&quot; rel=&quot;nofollow&quot;&gt;$84&lt;/a&gt; for the board alone.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-09-12T16:15:29.687" />
  <row Id="4369" PostTypeId="1" CreationDate="2010-09-12T16:25:22.970" Score="3" ViewCount="571" Body="&lt;p&gt;I'm trying to convert the frequency of a 0-5V square wave, which ranges from 0-20kHz, to a voltage using a simple LM2907 (8 pin) circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using R1 as 100k, I've calculated C1 to be 416pF for a maximum output of 12V @ 20kHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, when I do a transient simulation, all I get is an exponentially shrinking output voltage starting at ~2mV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What simulation settings should I use in LTSpice to verify the linearity of my frequency-to-voltage converter? Transient, DC operating point? Some kind of sweep?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is my circuit:&#xA;&lt;img src=&quot;http://img840.imageshack.us/img840/6758/lm2907ftovtest.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1027" LastEditorUserId="1027" LastEditorDisplayName="" LastEditDate="2010-09-13T20:08:00.127" LastActivityDate="2010-10-01T21:56:22.253" Title="How to correctly simulate a simple LM2907 circuit in LTSpice?" Tags="&lt;spice&gt;&lt;ltspice&gt;&lt;frequency-measurement&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="4370" PostTypeId="2" ParentId="4330" CreationDate="2010-09-12T16:52:16.207" Score="1" ViewCount="" Body="&lt;p&gt;Noise temperature is another way to measure Noise Figure, the amount of Additive Noise added by a Receiver. Good receivers can have noise figures in the 1 dB range, which translates to a noise temperature of 75degrees. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;NF = 10*log10(NoiseTemp/290 +1)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dave&lt;/p&gt;&#xA;" LastActivityDate="2010-09-12T16:52:16.207" />
  <row Id="4371" PostTypeId="1" AcceptedAnswerId="4372" CreationDate="2010-09-12T19:09:15.517" Score="2" ViewCount="212" Body="&lt;p&gt;I'm trying to learn about SPI and I have a old bluetooth headset with SPI solder points on it. I've already soldered the corresponding [MISO,MOSI,CS,CLK] pins and connected them to the buspirate correctly. The chip on the headset is a CSR-31315 (9A11U-717AT) which I've found a PDF for &lt;a href=&quot;http://datasheetz.com/data/RF%20and%20RFID/RF%20Transceiver%20ICs%20and%20Modules/BC413159A11-IQA-E4CT-datasheetz.html&quot; rel=&quot;nofollow&quot;&gt;HERE&lt;/a&gt; (SPI on pg74). The PDF says to perform a read operation all that needs to happen is the CS needs to go from high to low, then a 8bit read command of 0b00000011 needs to be sent then the 16bit address to read needs to be sent. After that it will output on MISO a check word which is composed of {command, address [15:8]} (what is the [15:8] for?) and then finally the contents of the address. Then last take CS high again so it doesn't continue on to print the Address+1 on MISO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The command I'm feeding to my buspirate is &lt;code&gt;[ 0b11 0x00 0x00 r:16 r:16 ]&lt;/code&gt; which I believe should take CS from high to low (it idles high), output 0b00000011 the read command, write the 16bit address of 0x00 0x00, read the 16bit checkword, read the 16bit address data, and finally take CS high again. I think that should work but it doesn't :/&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas for a beginner?&lt;/p&gt;&#xA;" LastActivityDate="2010-09-12T19:22:50.270" Title="BusPirate and SPI Reading Memory" Tags="&lt;spi&gt;&lt;bluetooth&gt;&lt;problem&gt;" AnswerCount="1" />
  <row Id="4372" PostTypeId="2" ParentId="4371" CreationDate="2010-09-12T19:22:50.270" Score="2" ViewCount="" Body="&lt;p&gt;The 'r' command for bus pirate reads a single byte, so r:16 is attempting to read 16 bytes, not 16 bits. I'd guess you want &quot;r:2 r:2&quot; (or just &quot;r:4&quot;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, I doubt that's the problem. If it had worked, you'd have seen the 4 bytes then some FFs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think it's more likely that your chip is not ready to accept commands over SPI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did some work with the CSR BC04 a few years ago. They can be configured to accept commands over the UART, SPI or USB. It's possible that yours isn't accepting commands over SPI. Fixing this may involve reflashing the firmware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might give the Bus Pirate SPI sniffer a go and see if you can intercept some valid looking signals when your device is running normally. That would give some confidence that it really is using SPI. Another way to do this would be to use a 2 channel oscilloscope, trigger on CS and look for the SPI clock ticking while CS is asserted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To be honest, if you're just trying to get SPI going on the Bus Pirate - choose something easier. &lt;a href=&quot;http://blog.hodgepig.org/articles/000033-buspirate/index.html&quot; rel=&quot;nofollow&quot;&gt;The first device I used mine on was an RGB LED matrix from Sparkfun&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-12T19:22:50.270" CommentCount="1" />
  <row Id="4373" PostTypeId="1" CreationDate="2010-09-12T23:56:08.323" Score="4" ViewCount="711" Body="&lt;p&gt;I'm working on a computer-controlled indoor waterfall. One of the requirements is to be able to change the water pressure via computer interface. I've googled all day long and can't seem to find a valve that can be controlled via computer. Anybody happen to know of such a device and where I could find one?&lt;/p&gt;&#xA;" OwnerUserId="1140" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-09-13T15:59:37.807" LastActivityDate="2010-11-27T23:50:44.630" Title="Computer controlled water valve." Tags="&lt;servo&gt;&lt;motor&gt;&lt;microcontroller&gt;&lt;computers&gt;" AnswerCount="6" FavoriteCount="2" />
  <row Id="4374" PostTypeId="1" AcceptedAnswerId="4419" CreationDate="2010-09-13T01:12:53.050" Score="5" ViewCount="388" Body="&lt;p&gt;I'm trying to find an efficient way of calculating an inverse on an AVR (or approximating it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to calculate the pulse period for a stepper motor so that I can vary the speed linearly. The period is proportional to the inverse of the speed (&lt;code&gt;p = K/v&lt;/code&gt;), but I can't think of a good way of calculating this on the fly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My formula is&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;p = 202/v + 298; // p in us; v varies from 1-&amp;gt;100&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Testing on the Arduino, the division seems to be ignored completely leaving &lt;code&gt;p&lt;/code&gt; fixed at &lt;code&gt;298&lt;/code&gt; (though perhaps this would be different in avr-gcc). I've also tried summing &lt;code&gt;v&lt;/code&gt; in a loop until it exceeds &lt;code&gt;202&lt;/code&gt;, and counting the loops, but this is quite slow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could generate a lookup table and store it in flash, but I was wondering if there was another way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;: Maybe the title should be &quot;efficient divide&quot;...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;: As pingswept points out, my formula for mapping period to velocity is incorrect. But the main problem is the divide operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit 2&lt;/strong&gt;: On further investigation, divide is working on the arduino, the problem was due to both the incorrect formula above and an int overflow elsewhere.&lt;/p&gt;&#xA;" OwnerUserId="554" LastEditorUserId="554" LastEditorDisplayName="" LastEditDate="2010-09-14T04:18:42.880" LastActivityDate="2010-09-15T14:07:35.967" Title="Efficient inverse (1/x) for AVR" Tags="&lt;avr&gt;&lt;divide&gt;" AnswerCount="8" CommentCount="2" FavoriteCount="1" />
  <row Id="4375" PostTypeId="2" ParentId="4374" CreationDate="2010-09-13T01:31:16.203" Score="3" ViewCount="" Body="&lt;p&gt;There are some very good techniques mentioned in the book &lt;a href=&quot;http://www.amazon.com/Hackers-Delight-Henry-S-Warren/dp/0201914654&quot; rel=&quot;nofollow&quot; title=&quot;Hacker's Delight&quot;&gt;&quot;Hackers Delight&lt;/a&gt; by Henry Warren and on his website &lt;a href=&quot;http://www.hackersdelight.org/&quot; rel=&quot;nofollow&quot; title=&quot;Hackers Delight&quot;&gt;hackersdelight.org&lt;/a&gt;.  For a technique that works well with smaller microcontrollers when dividing by constants have a look at &lt;a href=&quot;http://www.hackersdelight.org/divcMore.pdf&quot; rel=&quot;nofollow&quot;&gt;this file&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="820" LastActivityDate="2010-09-13T01:31:16.203" CommentCount="2" />
  <row Id="4376" PostTypeId="2" ParentId="4373" CreationDate="2010-09-13T02:39:41.380" Score="0" ViewCount="" Body="&lt;p&gt;This Australian organisation may be able to help you - &lt;a href=&quot;http://www.valvesonline.com.au/products/index_solenoid_valves01.asp&quot; rel=&quot;nofollow&quot;&gt;Valves Online&lt;/a&gt; or perhaps point you in the right direction. You can control solenoid valves easily enough. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-13T02:39:41.380" />
  <row Id="4377" PostTypeId="1" CreationDate="2010-09-13T02:58:27.930" Score="2" ViewCount="138" Body="&lt;p&gt;Hey there,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been using a Freetronics 100% Arduino Compatible board to run switches that trigger sound file players in MaxMSP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only sketch and patch I could use to get the board and Max communicating was Arduino2Max. I am able to get 1's and 0's out of the board using the Arduino2Max patch to trigger the sound file players on and off but the signal is extremely ambiguous. When the switch is open it should be sending a 0, when it is closed a 1 but it is flickering between the two. It also can take up to 4 secs to switch back to a 0 to close the switch. When the sample rate is slowed it just means that the signal flickers at a slower rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried using a prototyping board as well as plugging directly into the digital pins. Can someone please give me any advice? Could this be a signal issue to do with the quality of the wires I am using or could there be a problem with the board or the way the signal is converted through usb?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!!&lt;/p&gt;&#xA;" LastActivityDate="2010-09-16T01:47:41.493" Title="Signal strength on Freetronics 100% Arduino Compatible Board" Tags="&lt;arduino&gt;&lt;maxmsp&gt;&lt;switch&gt;&lt;signal&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="4378" PostTypeId="2" ParentId="1629" CreationDate="2010-09-13T04:13:35.063" Score="0" ViewCount="" Body="&lt;p&gt;To add to this list. my manufacturer of choice has been International Circuits (http://www.internationalcircuits.com). They have similar services as both GP and PCBI, but I find their customer service to be exceptional. $95 for 100 square inch is a great deal anyway you look at it. &lt;/p&gt;&#xA;" LastActivityDate="2010-09-13T04:13:35.063" />
  <row Id="4379" PostTypeId="2" ParentId="1629" CreationDate="2010-09-13T04:59:13.493" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.completepcbsolutions.com/&quot; rel=&quot;nofollow&quot;&gt;Complete PCB&lt;/a&gt; down at Burleigh Heads. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-13T04:59:13.493" />
  <row Id="4380" PostTypeId="2" ParentId="4374" CreationDate="2010-09-13T05:30:00.487" Score="3" ViewCount="" Body="&lt;p&gt;Your function doesn't seem like it would give the result you want. For example, the value 50 returns roughly 302, while 100 returns roughly 300. Those two results will cause almost no change in the speed of the motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I understand you correctly, you're really looking for a fast way to map the numbers 1-100 to the range 300-500 (approximately), such that 1 maps to 500 and 100 maps to 300.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps try: &#xA;p = 500 - (2 * v)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I might be misunderstanding-- are you trying to calculate the on-time of a constant frequency square wave? What's the 298?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-09-13T05:30:00.487" CommentCount="3" />
  <row Id="4381" PostTypeId="2" ParentId="4373" CreationDate="2010-09-13T05:37:11.577" Score="3" ViewCount="" Body="&lt;p&gt;If you're in the US, try a 24 V DC solenoid valve from McMaster-Carr: &lt;a href=&quot;http://www.mcmaster.com/#solenoid-valves/=8to0so&quot; rel=&quot;nofollow&quot;&gt;http://www.mcmaster.com/#solenoid-valves/=8to0so&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To control it from a computer, you'll also need a 5 V relay that can be controlled by something like an &lt;a href=&quot;http://arduino.cc&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; and a 24 V power supply. You might be able to find a solenoid valve with a low-voltage relay built in, but I've not seen one before.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-09-13T05:37:11.577" CommentCount="5" />
  <row Id="4382" PostTypeId="1" AcceptedAnswerId="4393" CreationDate="2010-09-13T06:36:01.327" Score="6" ViewCount="911" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've worked on the Arduino family (specifically the Sanguino), built a few simple devices and a simple phototrope. I am thus pretty comfortable with microcontrollers - specifically Atmel's. I'm curious to know how do FPGA's differ from standard microcontrollers. I am from a technical background (C/C++ programming) and thus would love technical answers. Just keep in mind that I am a newbie (relative to my s/w experience) in the electronics domain. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did go through &lt;a href=&quot;http://chiphacker.com/questions/1060/what-is-an-fpga&quot; rel=&quot;nofollow&quot;&gt;this query&lt;/a&gt; and it was good but I'm looking for further deeper details.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&#xA;Sushrut.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastActivityDate="2010-09-27T05:59:39.283" Title="FPGA's vs Microcontrollers" Tags="&lt;fpga&gt;&lt;microcontroller&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="2" />
  <row Id="4383" PostTypeId="2" ParentId="4382" CreationDate="2010-09-13T11:22:50.037" Score="1" ViewCount="" Body="&lt;p&gt;There isn't really any difference between an MCU like an AVR, and one programmed into an FPGA. The OpenCores site has &lt;a href=&quot;http://opencores.org/project,avr_core&quot; rel=&quot;nofollow&quot;&gt;VHDL code for an AVR&lt;/a&gt; that can be used in an FPGA. You can study it and see how it works, and even try it for yourself in a simulator without buying a suitable FPGA board.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-09-13T11:22:50.037" CommentCount="2" />
  <row Id="4384" PostTypeId="1" CreationDate="2010-09-13T11:23:40.083" Score="5" ViewCount="175" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a hobby project that's been on the backburner for about 3 years now. It's very simple - just a solar-powered oscillator hooked up to a speaker, that changes frequency in response to the level of sunlight.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the circuit I'm using right now. It's mostly designed by Wilf Rigter from the BEAM circuits mailing list:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://frey.co.nz/content/images/solarchorus/solar_sounder_wilfs_improved_1_small.jpg&quot; alt=&quot;schematic&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing is I'd like to invert the frequency/sunlight response. At the moment in dark light it's a quiet tone with low frequency, and in bright light it's a loud tone with high frequency. Instead, I'd like to have a high-frequency tone in low light and a low-frequency tone/pulse train in bright light.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm really up against my knowledge limit in understanding this circuit as it is. What I do understand is that the 10nF capacitor charges through the 22k resistor until its voltage reaches the Vbe threshold for the NPN transistor on the bottom left, at which point the transistor opens and the capacitor discharges through the speaker, making a click. Then something happens to reset the system and it starts again. With more light the capacitor charges faster and so the tone has a higher pitch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inverting the frequency/light level response, though, is beyond me. I think I'd need to somehow slow down the charging of the timing capacitor here as the light increases by diverting the current somehow, and I suspect that I'd want to be storing this diverted current in another storage capacitor to be discharged through the speaker, instead of discharging the timing capacitor through the speaker. Actually building this into a schematic, though, is too difficult for me right now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help much appreciated!&lt;/p&gt;&#xA;" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-06T20:23:05.090" LastActivityDate="2010-10-06T20:23:05.090" Title="How can I invert a solar-powered oscillator's frequency?" Tags="&lt;analog&gt;&lt;oscillator&gt;&lt;solar-cell&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="4385" PostTypeId="2" ParentId="3341" CreationDate="2010-09-13T12:35:23.700" Score="0" ViewCount="" Body="&lt;p&gt;You have a few options. I'll start by saying that to spy on a Bluetooth connection already in progress is very difficult unless you have access to one of the connected peers. By access, I mean the ability to start up a Bluetooth stack sniffer. I don't know of one for Windows, so we're left with Linux. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Option 1: &quot;Linux option&quot;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Sniff&quot; the traffic on the Bluetooth connection in Linux, simply run this command: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;hcidump -X&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Which will dump all Bluetooth I/O to and from your PC to the screen. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Option 2: &quot;Electronics option&quot;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another, more electronics oriented solution is to &lt;a href=&quot;http://chiphacker.com/questions/3869/can-the-arduino-be-used-to-spy-on-a-uart-connection-between-two-devices&quot; rel=&quot;nofollow&quot;&gt;spy on the I/O communications&lt;/a&gt; on one of the peers.&lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-09-13T12:35:23.700" />
  <row Id="4386" PostTypeId="2" ParentId="4374" CreationDate="2010-09-13T12:42:42.627" Score="3" ViewCount="" Body="&lt;p&gt;An efficient way to approximate divides is by shifts.  e.g. if x = y / 103;&#xA;dividing by 103 is the same as multiplying by 0.0097087, so to approximate this first select a 'good' shift number (i.e. a base-2 number, 2,4,8,16,32 and so on)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For this example 1024 is a good fit as we can say that 10 / 1024 = 0.009765&#xA;Its then possible to code:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;x = (y * 10) &gt;&gt; 10; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remembering of course to ensure the variable y does not overflow its type when multiplied.  Its not exact, but its quick.&lt;/p&gt;&#xA;" LastActivityDate="2010-09-13T12:42:42.627" CommentCount="1" />
  <row Id="4387" PostTypeId="1" AcceptedAnswerId="4388" CreationDate="2010-09-13T13:02:22.360" Score="3" ViewCount="81" Body="&lt;p&gt;I would like to build a board for an LPC1* processor. Are there published Eagle layouts for these?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-09-13T14:05:07.743" Title="Are there any open design files for an NXP LPC1* breakout board?" Tags="&lt;lpc&gt;" AnswerCount="1" />
  <row Id="4388" PostTypeId="2" ParentId="4387" CreationDate="2010-09-13T13:15:43.867" Score="3" ViewCount="" Body="&lt;p&gt;MicroBuilder.eu have an Eagle format reference design for the LPC1114.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microbuilder.eu/Projects/LPC1114ReferenceDesign.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.microbuilder.eu/Projects/LPC1114ReferenceDesign.aspx&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microbuilder.eu/Projects/LPC1114ReferenceDesign/LPC1114CodeBase.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.microbuilder.eu/Projects/LPC1114ReferenceDesign/LPC1114CodeBase.aspx&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-09-13T14:05:07.743" LastActivityDate="2010-09-13T14:05:07.743" />
  <row Id="4389" PostTypeId="1" AcceptedAnswerId="4404" CreationDate="2010-09-13T13:55:33.790" Score="4" ViewCount="392" Body="&lt;p&gt;I want to try programming a PIC chip and just see, how much different it is compared to an AVR, what are the differences and so on. I've got an &lt;a href=&quot;http://www.ladyada.net/make/usbtinyisp/&quot; rel=&quot;nofollow&quot;&gt;AVRtinyISP&lt;/a&gt; and would like to know, if it would be possible to use that to program a PIC chip at all? What would limit me from doing that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both today's AVR and PIC chips have ICSP interfaces for program uploading and use apparently compatible pinouts for programming (PIC used to require a higher voltage supplied to program it, but newer chips don't require that anymore). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is: &lt;strong&gt;is it even remotely possible to program a PIC chip with an AVR ISP programmer, such as AVRtinyISP or AVR ISP MkII&lt;/strong&gt;? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone ever tried that? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's not possible or is too hard, then what are the limitations -- it is the protocols used, pinouts not matching exactly, voltages/current ratings, anything else? Is it possible to do that vice versa, i.e. using a PICKit clone to program an AVR chip? What would be the modifications needed to make anything of that possible at all? &lt;/p&gt;&#xA;" OwnerUserId="1036" LastEditorUserId="1036" LastEditorDisplayName="" LastEditDate="2010-09-14T08:25:42.740" LastActivityDate="2010-09-14T08:25:42.740" Title="Is it possible to use AVR ISP programmer to program a PIC chip?" Tags="&lt;avr&gt;&lt;pic&gt;&lt;programmer&gt;&lt;isp&gt;&lt;pickit&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="4390" PostTypeId="2" ParentId="4389" CreationDate="2010-09-13T14:03:31.787" Score="2" ViewCount="" Body="&lt;p&gt;The protocol is different.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a good thread from dangerousprototypes.com detailing their development of a PIC programmer for Bus Pirate. Lots of juicy technical detail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dangerousprototypes.com/forum/index.php?topic=550.0&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com/forum/index.php?topic=550.0&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-13T14:03:31.787" />
  <row Id="4391" PostTypeId="2" ParentId="4389" CreationDate="2010-09-13T14:32:23.473" Score="1" ViewCount="" Body="&lt;p&gt;A PICkit 2 can be used to program an AVR, &lt;a href=&quot;http://pickit2.isgreat.org/&quot; rel=&quot;nofollow&quot;&gt;with the right software&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-09-13T14:32:23.473" CommentCount="1" />
  <row Id="4392" PostTypeId="2" ParentId="4330" CreationDate="2010-09-13T14:34:13.470" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Little bit of background&lt;/strong&gt;&lt;br /&gt;&#xA;Everything in the world creates noise. Sometimes a little, sometimes a lot. In general, the hotter something is, the more noise it creates. This comes down to the fact that the hotter something is, the faster things move at the very lowest level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a resistor, there is a fairly linear amount of noise added to a system as the temperature goes up. The function of temperature to noise in a resistor is commonly used to identify the amount of noise added.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What's this actually mean?&lt;/strong&gt;&lt;br /&gt;&#xA;In Antenna systems it is useful to be able to identify how much noise is introduced into a system. This is done with the Noise Temperature. A particular system will have a Noise Temperature associated with it. This is just saying that if your system were to be a perfect noiseless system, you could add a resistor in series at the temperature given and that is how much noise is being added.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many times the temperature is way above what a resistor would ever be at, but it is just a very easy way to model and convey the noise in a system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Going a little bit more in-depth&lt;/strong&gt;&lt;br /&gt;&#xA;Thermal noise is generally modeled as white noise (noise that is equal at all frequencies) within what ever frequency range will make it through a system. In order to actually use noise temperature it is helpful to know the bandwidth that is being talked about. This is what the wiki page is calling the noise bandwidth.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-09-13T14:34:13.470" />
  <row Id="4393" PostTypeId="2" ParentId="4382" CreationDate="2010-09-13T17:49:50.953" Score="14" ViewCount="" Body="&lt;p&gt;Designing for an FPGA requires a Hardware Description Language (HDL).  HDLs are absolutely nothing at all like C.  Whereas a C program is a sequential series of instructions and must contort itself to achieve parallel execution, an HDL describes a concurrent circuit and must contort itself to achieve sequential execution.  It is a very different world and if you try to build a circuit in an FPGA while thinking like a software developer it will hurt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An MCU is time-limited.  In order to accomplish more work, you need more processor cycles.  Clocks have very real limits to their frequencies, so it's easy to hit a computational wall.  However, an FPGA is space-limited.  In order to accomplish more work, you merely add more circuits.  If your FPGA isn't big enough, you can buy a bigger one.  It's very hard to build a circuit that can't fit in the largest FPGA, and even if you do there are app notes describing how to daisy chain FPGAs together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FPGAs focus way more on parallel execution.  Sometimes you have to worry about how long your MCU's ISR takes to service the interrupt, and whether you'll be able to achieve your hard-real-time limits.  However, an in FPGA there are lots of Finite State Machines (FSM) running all the time.  They are like &quot;femto-controllers&quot;, like little clouds of control logic.  They are all running simultaneously, so there's no worrying about missing an interrupt.  You might have an FSM to interface to an ADC, another FSM to interface to a microcontroller's address/data bus, another FSM to stream data to a stereo codec, yet another FSM to buffer the dataflow from the ADC to the codec...You need to use a simulator to make sure that all the FSMs sing in harmony.  If any control logic is off by even a single clock cycle (and such mistakes are easy to make) then you will get a cacophony of failure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FPGAs are a PCB layout designer's wet dream.  They are extremely configurable.  You can have many different logic interfaces (LVTTL, LVCMOS, LVDS, etc), of varying voltages and even drive strengths (so you don't need series-termination resistors).  The pins are swappable; have you ever seen an MCU address bus where the pins were scattered around the chip?  Your PCB designer probably has to drop a bunch of vias just to tie all the signals together correctly.  With an FPGA, the PCB designer can then run the signals into the chip in pretty much any order that is convenient, and then the design can be back-annotated to the FPGA toolchain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FPGAs also have lots of nice, fancy toys.  One of my favorites is the Digital Clock Manager in Xilinx chips.  You feed it one clock signal, and it can derive four more from it using a wide variety of frequency multipliers and dividers, all with pristine 50% duty cycle and 100% in phase...and it can even account for the clock skew that arises from propagation delays external to the chip!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT (reply to addendum):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can place a &quot;soft core&quot; into an FPGA.  You're literally wiring together a microcontroller circuit, or rather you're probably dropping someone else's circuit into your design, like Xilinx's PicoBlaze or MicroBlaze or Altera's Nios.  But like the C-&gt;VHDL compilers, these cores tend to be a little bloated and slow compared to using an FSM and datapath, or an actual microcontroller.  The development tools can also add significant complexity to the design process, which can be a bad thing when FPGAs are already extremely complex chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also some FPGAs that have &quot;hard cores&quot; embedded in them, like Xilinx's Virtex4 series that have a real, dedicated IBM PowerPC with FPGA fabric around it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT2 (reply to comment):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think I see now...you're asking about connecting a discrete MCU to an FPGA; i.e. two separate chips.  There are good reasons to do this; the FPGA's that have hard cores and the ones that are big enough to support decent soft cores are usually monsters with many hundreds of pins that end up requiring a BGA package, which easily increases the difficulty of designing a PCB by a factor of 10.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C is a lot easier, though, so MCUs definitely have their place working in tandem with an FPGA.  Since it's easier to write C, you might write the &quot;brains&quot; or the central algorithm in the MCU, while the FPGA can implement sub-algorithms that might need accelerated.  Try to put things that change into the C code, because it's easier to change, and leave the FPGA to be more dedicated type stuff that won't change often.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MCU design tools are also easier to use.  It takes several minutes for the design tools to build the FPGA bit file, even for somewhat simple designs, but complex MCU programs usually take a few seconds.  There's much, much less to go wrong with the MCU, so they're also easier to debug...I cannot understate how complex FPGAs can be.  You really need to get the datasheet for the one you have, and you should try to read every page of it.  I know, it's a few hundred pages...do it anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best way to connect them is to use an MCU with an external address and data bus.  Then you can simply memory map the FPGA circuits into the MCU, and add your own &quot;registers&quot; that each have their own address.  Now the FPGA can add custom peripherals, like a 32-bit timer that can latch all 4 bytes at once when the first byte is read to prevent overflows between 8-bit reads.  You can also use it as glue logic to memory map more peripherals from other chips, like a separate ADC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, some MCUs are designed for use with an &quot;external master&quot; like an FPGA.  Cypress makes a few USB MCUs that have an 8051 inside, but the intent is for the USB data to be produced/consumed by e.g. an FPGA.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastEditorUserId="1278" LastEditorDisplayName="" LastEditDate="2010-09-22T16:55:18.367" LastActivityDate="2010-09-22T16:55:18.367" CommentCount="5" />
  <row Id="4394" PostTypeId="1" AcceptedAnswerId="10807" CreationDate="2010-09-13T17:52:05.630" Score="4" ViewCount="186" Body="&lt;p&gt;Some micros have all bits of a port nicely lined up, while others' bits seem to have been scattered by the winds to all four points of the compass. Why?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-27T19:54:11.457" LastActivityDate="2011-02-28T09:49:49.833" Title="Why put the bits of a port on non-adjacent pins?" Tags="&lt;microcontroller&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="4395" PostTypeId="2" ParentId="4374" CreationDate="2010-09-13T18:06:37.333" Score="1" ViewCount="" Body="&lt;p&gt;This process &lt;a href=&quot;http://www.bearcave.com/software/divide.htm&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; looks mcu-friendly, though it might need a bit of porting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though it seems as if the LUT would be easier.  You would only need 100 bytes, less if you used some interpolation, and since the LUT is filled with constants then the compiler might even locate it in the code area instead of the data area.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-09-13T18:06:37.333" CommentCount="1" />
  <row Id="4396" PostTypeId="2" ParentId="4374" CreationDate="2010-09-13T18:51:37.603" Score="1" ViewCount="" Body="&lt;p&gt;Check to make sure that the division is being performed as floating point. I use Microchip not AVR, but when using C18 you need to force your literals to be treated as floating point. Eg. Try changing your formula to:&lt;p&gt;&lt;code&gt;p = 202.0/v + 298.0;&lt;/code&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-09-13T18:51:37.603" />
  <row Id="4397" PostTypeId="2" ParentId="4394" CreationDate="2010-09-13T19:38:01.953" Score="6" ViewCount="" Body="&lt;p&gt;Often this has alot to do with lead inductance. You need to keep your grounds spread out, and based on layout decisions in the chip internal to the package it may need to spread out the I/O pins. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would you rather have ground problems or spread out pins. In general, I use #define to handle which pin I am using and all but forget which actual pin it is. Since most people do this also, chip manufacturers know this and focus on electrical parameters.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-09-13T19:38:01.953" CommentCount="3" />
  <row Id="4398" PostTypeId="2" ParentId="4394" CreationDate="2010-09-13T20:02:53.293" Score="2" ViewCount="" Body="&lt;p&gt;Might have something to do with the alternate uses for a pin.  If you have an oscillator connection then it would be a good idea to have it kept away from high-noise paths for instance.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-13T20:02:53.293" />
  <row Id="4399" PostTypeId="2" ParentId="4389" CreationDate="2010-09-13T20:05:39.330" Score="0" ViewCount="" Body="&lt;p&gt;Programming a chip is basically a serial communications operation.  From what I've looked at it's basically a lot of 'put this data here' routines with some startup commands.  Essentially, the chip is programming itself (or at least one part programs another).  PICs and AVRs don't use the same command-set so one programmer can't program the other.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-13T20:05:39.330" />
  <row Id="4400" PostTypeId="2" ParentId="4333" CreationDate="2010-09-13T20:50:09.247" Score="4" ViewCount="" Body="&lt;p&gt;I'm not sure if it qualifies as art, but FR-4 makes a good, strong building material that can be cut, drilled, plated, and colored (silk and soldermask =  2 colors), and some people use it as such.  For example, the &lt;a href=&quot;http://www.evilmadscientist.com/article.php/eggbot&quot; rel=&quot;nofollow&quot;&gt;eggbot&lt;/a&gt;:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4108/4970935346_123ee543f2.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-07T16:01:42.813" LastActivityDate="2011-05-07T16:01:42.813" CommunityOwnedDate="2010-09-13T20:50:09.247" />
  <row Id="4401" PostTypeId="2" ParentId="4389" CreationDate="2010-09-13T23:44:38.570" Score="0" ViewCount="" Body="&lt;p&gt;I have recently seen this article on Xeltek's website:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xeltek.com/Atmel-AVR-pages-282&quot; rel=&quot;nofollow&quot;&gt;http://www.xeltek.com/Atmel-AVR-pages-282&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe, you can use their ISP programmer; IS01. But it won't be a low cost solution just like PICkit. as far as i know, IS01 even supports ATE...&lt;/p&gt;&#xA;" LastActivityDate="2010-09-13T23:44:38.570" CommentCount="2" />
  <row Id="4402" PostTypeId="2" ParentId="4363" CreationDate="2010-09-14T00:14:28.817" Score="1" ViewCount="" Body="&lt;p&gt;MIPI (Mobile Industry Processor Interface) is a standard.  &lt;a href=&quot;http://www2.electronicproducts.com/MIPI_display_standards_for_mobile_Internet_devices-article-FAJH_CMD_May2009-html.aspx&quot; rel=&quot;nofollow&quot;&gt;more info here&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DVP is just a parallel bus interface.  They are meant to interface with a MCU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, if you're interested in using their product, contact them for a datasheet.&lt;/p&gt;&#xA;" OwnerUserId="1026" LastActivityDate="2010-09-14T00:14:28.817" CommentCount="1" />
  <row Id="4403" PostTypeId="1" CreationDate="2010-09-14T01:34:40.893" Score="3" ViewCount="193" Body="&lt;p&gt;I kinda already asked the question in title, but I will reiterate --  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;In the case of audio, would it be accurate to think of a potentiometer with, for example, three lugs, as a fader between two inputs?&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please tell me why thats dumb or not dumb or something!&lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-27T04:10:56.267" LastActivityDate="2011-02-27T04:10:56.267" Title="In the case of audio, would it be accurate to think of a potentiometer as a fader between two inputs?" Tags="&lt;audio&gt;&lt;potentiometer&gt;" AnswerCount="4" />
  <row Id="4404" PostTypeId="2" ParentId="4389" CreationDate="2010-09-14T02:24:24.877" Score="1" ViewCount="" Body="&lt;p&gt;This page has the circuit diagrams, C code, and compiled windows executable for using ISP to program a PIC.  The (windows) software is different form the AVR software, so maybe it is just a cheap way to program PICs.  Certainly cheaper than $1200.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://elm-chan.org/works/avrx/report_e.html&quot; rel=&quot;nofollow&quot;&gt;http://elm-chan.org/works/avrx/report_e.html&lt;/a&gt; (near the bottom)&lt;/p&gt;&#xA;" OwnerUserId="1271" LastActivityDate="2010-09-14T02:24:24.877" CommentCount="1" />
  <row Id="4405" PostTypeId="2" ParentId="4403" CreationDate="2010-09-14T02:48:07.073" Score="4" ViewCount="" Body="&lt;p&gt;You could use it that way, as a blend or balance control, by connecting each leg to an input and the wiper to a high input impedance amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.gearslutz.com/board/attachments/geekslutz-forum/171764d1273264645-wet-dry-mix-knob-will-schematic-work-mix_buffer_emitfollower.jpg&quot; alt=&quot;linear pot used as a balance control&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More commonly, you have two 3-terminal pots, and each acts as a volume control (one leg to the input, the other to ground), and are then fed to a &lt;a href=&quot;http://en.wikipedia.org/wiki/Operational_amplifier_applications#Summing_amplifier&quot; rel=&quot;nofollow&quot;&gt;summing amplifier&lt;/a&gt; to mix them. That way you can control the level of each instead of just their relative difference, and you can use &lt;a href=&quot;http://sound.westhost.com/pots.htm#taper&quot; rel=&quot;nofollow&quot;&gt;log-taper pots&lt;/a&gt; so that the change in loudness is proportional to the change in angle of the knob.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.circuitdb.com/downloadimg.php?fileID=130&quot; alt=&quot;simple mixer circuit with two volume controls&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.aaroncake.net/circuits/mixer2.gif&quot; alt=&quot;simple inverting op-amp mixer circuit with 3 volume controls&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-09-14T16:45:29.490" LastActivityDate="2010-09-14T16:45:29.490" CommentCount="5" />
  <row Id="4407" PostTypeId="2" ParentId="4373" CreationDate="2010-09-14T11:07:00.320" Score="3" ViewCount="" Body="&lt;p&gt;I don't think that ON/OFF valves are the way to go for your project since that will hardly give you precise and fast control of water jets amplitude for your fountain. DC water pumps like Attwood V500 can be easily controlled via PWM, and 0-100% can define the height of each independent fountain water jet amplitude. Interfacing these 16 water pumps can be seen here: &lt;a href=&quot;http://www.ece.gatech.edu/academic/courses/spring2004/ece4006d/g08/files.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.ece.gatech.edu/academic/courses/spring2004/ece4006d/g08/files.htm&lt;/a&gt; and especially here: &lt;a href=&quot;http://www.ece.gatech.edu/academic/courses/spring2004/ece4006d/g08/files/4006D-FP.ppt&quot; rel=&quot;nofollow&quot;&gt;http://www.ece.gatech.edu/academic/courses/spring2004/ece4006d/g08/files/4006D-FP.ppt&lt;/a&gt;. Of course, you don't have to complicate and use FPGA. You can just use some simple microcontroller board like Arduino. It can run fountain on it's own (like changing some predefined patterns), or it can be controlled by some PC application (like audio spectrum analysis via custom WinAmp plugin). Slightly different principle but with similar effect (although less controllable and less powerful) can be made using these micro valves: &lt;a href=&quot;http://www.theleeco.com/EFSWEB2.NSF/CVG!OpenView&quot; rel=&quot;nofollow&quot;&gt;http://www.theleeco.com/EFSWEB2.NSF/CVG!OpenView&lt;/a&gt;. Which one to choose depends on your specific application.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastEditorUserId="1129" LastEditorDisplayName="" LastEditDate="2010-09-14T11:13:38.897" LastActivityDate="2010-09-14T11:13:38.897" />
  <row Id="4408" PostTypeId="2" ParentId="267" CreationDate="2010-09-14T11:26:17.267" Score="2" ViewCount="" Body="&lt;p&gt;Object Development has made a library for AVR microcontrollers that enables you to make very cheap USB devices on your own (starting at just 2-3$). GCC for AVR is linux friendly. There are hudreds of devices already made. Take a look here: &lt;a href=&quot;http://www.obdev.at/products/vusb/projects.html&quot; rel=&quot;nofollow&quot;&gt;http://www.obdev.at/products/vusb/projects.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-09-14T11:26:17.267" />
  <row Id="4409" PostTypeId="2" ParentId="4180" CreationDate="2010-09-14T11:59:50.277" Score="1" ViewCount="" Body="&lt;p&gt;I think that you are refering to USB dongles used for software protection. They don't use standard USB HID or MASS STORAGE device classes, and usually implement their own protocol and provide their own PC side driver for communication with them. PC application usually asks them to correctly reply to sent crypted message, or they provide some critical info not existing in PC application, needed by application to work correctly. These messages can be sniffed, like anything else over USB, but beware since you might be walking on the edge. Educating yourself about USB is one thing, but publishing work that breaks software protection is not legal and will be prosecuted. Don't do it. I apologize if I misunderstood the question.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastEditorUserId="1129" LastEditorDisplayName="" LastEditDate="2010-09-14T18:00:13.740" LastActivityDate="2010-09-14T18:00:13.740" CommentCount="1" />
  <row Id="4410" PostTypeId="2" ParentId="1942" CreationDate="2010-09-14T12:05:46.937" Score="0" ViewCount="" Body="&lt;p&gt;Take a look at ObDev V-USB AVR based projects: &lt;a href=&quot;http://www.obdev.at/products/vusb/prjhid.html&quot; rel=&quot;nofollow&quot;&gt;http://www.obdev.at/products/vusb/prjhid.html&lt;/a&gt;. I think that this one might be just what you are looking for: &lt;a href=&quot;http://www.fredrikolofsson.com/pages/hardware.html&quot; rel=&quot;nofollow&quot;&gt;http://www.fredrikolofsson.com/pages/hardware.html&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-09-14T12:05:46.937" />
  <row Id="4411" PostTypeId="2" ParentId="4094" CreationDate="2010-09-14T12:08:20.710" Score="0" ViewCount="" Body="&lt;p&gt;You can find many very cheap USB DIY projects that could be used to interface your old equipment here: &lt;a href=&quot;http://www.obdev.at/products/vusb/prjhid.html&quot; rel=&quot;nofollow&quot;&gt;http://www.obdev.at/products/vusb/prjhid.html&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-09-14T12:08:20.710" />
  <row Id="4412" PostTypeId="2" ParentId="3944" CreationDate="2010-09-14T12:16:12.437" Score="1" ViewCount="" Body="&lt;p&gt;AVR based 25 buttons joystick programmable from linux can be one of those projects: &lt;a href=&quot;http://www.obdev.at/products/vusb/prjhid.html&quot; rel=&quot;nofollow&quot;&gt;http://www.obdev.at/products/vusb/prjhid.html&lt;/a&gt;. USB has many standard device classes, and HID is one of them, convenient for keyboards, mices and joysticks, especially since all operating systems support it, which means that you don't have to provide driver for your device. You don't need to know the low level side of USB/HID if you use such example projects, but you can find a lot of info at USB official site and documentation.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-09-14T12:16:12.437" />
  <row Id="4413" PostTypeId="1" AcceptedAnswerId="4416" CreationDate="2010-09-14T12:28:46.067" Score="3" ViewCount="571" Body="&lt;p&gt;Is there an open source solution to interface any profibus slave or master chips?&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-09-15T13:59:56.133" Title="AVR or Arduino Profibus interface project?" Tags="&lt;avr&gt;&lt;arduino&gt;&lt;slave&gt;" AnswerCount="2" />
  <row Id="4414" PostTypeId="2" ParentId="4403" CreationDate="2010-09-14T13:59:18.903" Score="3" ViewCount="" Body="&lt;p&gt;A pot can be used as a fader between two inputs, but not at constant power, so it's probably not a particularly useful way to think of it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the problem: suppose you have a 10k pot with an input attached to each end and the output coming out the wiper. When the wiper is moved to either end of its range, you get full volume out of one channel and a severely attenuated contribution from the other. When the pot is set to the middle of the range, both inputs are attenuated equally, but they're not at half-volume-- they're much quieter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of audio, I think it would be better to think of a pot as a single-channel fader that has an extra lug on the end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I don't actually know whether in real audio equipment the extra lug has some use that I haven't thought of. Anyone know?)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-09-14T13:59:18.903" CommentCount="4" />
  <row Id="4415" PostTypeId="2" ParentId="4374" CreationDate="2010-09-14T17:53:54.293" Score="1" ViewCount="" Body="&lt;p&gt;On another note if you are trying to do a divide on a CPU that doesn't support divide there's a really cool way to do it in this Wiki article.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Multiplicative_inverse&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Multiplicative_inverse&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;To approximate the reciprocal of x,&#xA;  using only multiplication and&#xA;  subtraction, one can guess a number y,&#xA;  and then repeatedly replace y with 2y&#xA;  − xy2. Once the change in y becomes&#xA;  (and stays) sufficiently small, y is&#xA;  an approximation of the reciprocal of&#xA;  x.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-09-14T17:53:54.293" CommentCount="1" />
  <row Id="4416" PostTypeId="2" ParentId="4413" CreationDate="2010-09-14T18:18:41.717" Score="2" ViewCount="" Body="&lt;p&gt;No idea, but since I googled, I might just paste this:&#xA;&lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;p=692535&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;p=692535&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-09-14T18:18:41.717" CommentCount="2" />
  <row Id="4417" PostTypeId="2" ParentId="2811" CreationDate="2010-09-14T18:37:35.240" Score="2" ViewCount="" Body="&lt;p&gt;Using prescalers even GHz measurement can be achieved. This is simple 40MHz frequency meter with ATMEL AVR AT90S2313: &lt;a href=&quot;http://www.myplace.nu/avr/countermeasures/index.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.myplace.nu/avr/countermeasures/index.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some other similar projects:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ikalogic.com/freq_meter_2.php&quot; rel=&quot;nofollow&quot;&gt;http://www.ikalogic.com/freq_meter_2.php&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.saturn.dti.ne.jp/~khr3887/lfcd_e.html&quot; rel=&quot;nofollow&quot;&gt;http://www.saturn.dti.ne.jp/~khr3887/lfcd_e.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.circuitlake.com/rs232-frequency-meter-and-pulse-generator.html&quot; rel=&quot;nofollow&quot;&gt;http://www.circuitlake.com/rs232-frequency-meter-and-pulse-generator.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ulrichradig.de/home/index.php/avr/frequenzcounter&quot; rel=&quot;nofollow&quot;&gt;http://www.ulrichradig.de/home/index.php/avr/frequenzcounter&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.triplespark.net/elec/analysis/FreqCnt/&quot; rel=&quot;nofollow&quot;&gt;http://www.triplespark.net/elec/analysis/FreqCnt/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cappels.org/dproj/30MHzfmeter/30MhzFmtr.html&quot; rel=&quot;nofollow&quot;&gt;http://www.cappels.org/dproj/30MHzfmeter/30MhzFmtr.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.qsl.net/pa3ckr/bascom%20and%20avr/rfcounter/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.qsl.net/pa3ckr/bascom%20and%20avr/rfcounter/index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sump.org/projects/counter&quot; rel=&quot;nofollow&quot;&gt;http://www.sump.org/projects/counter&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://digilander.libero.it/alfred73/eprojects.htm#1300%20Mhz%20Frequencymeter%20with%20prescaler&quot; rel=&quot;nofollow&quot;&gt;http://digilander.libero.it/alfred73/eprojects.htm#1300%20Mhz%20Frequencymeter%20with%20prescaler&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-09-14T18:37:35.240" />
  <row Id="4418" PostTypeId="2" ParentId="4403" CreationDate="2010-09-14T19:16:48.137" Score="2" ViewCount="" Body="&lt;p&gt;Maybe it will help some of you guys to see a simulation of this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4104/4991010642_eedf1d4c21_o.jpg&quot; alt=&quot;Mixer&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Full size can be found at &lt;a href=&quot;http://www.flickr.com/photos/kellenjb/4991010642/lightbox/&quot; rel=&quot;nofollow&quot;&gt;http://www.flickr.com/photos/kellenjb/4991010642/lightbox/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason I wouldn't do it this way is because you might have sources with different resistance. Or be driving something with a much lower resistance. Or... well lots of things. It is just much cleaner to use an op-amp adder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ADDITION:&#xA;1) If you make the 50K pot larger, lets say 500K, you get a much smaller signal out when you are at 50% on the pot and the same signal out as the 50K when you change it to the 0% and 100%.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) If you keep the 50K pot but change R2 and R3 to be bigger, you aren't able to get purely just the signal from 1 source over the other and the effect of the percentage that the pot is at becomes less and less important.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) If you keep the pot and the source resistances the same but change the output to be 8ohms (such as a speaker might be) you get an effect similar to #1.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-09-14T20:12:57.467" LastActivityDate="2010-09-14T20:12:57.467" CommentCount="1" />
  <row Id="4419" PostTypeId="2" ParentId="4374" CreationDate="2010-09-14T19:43:35.063" Score="5" ViewCount="" Body="&lt;p&gt;One nice thing about division is that more or less everyone is doing it.  It is a pretty core feature of the C language, and compilers like AVR-GCC (called by the Arduino IDE) will choose the best division algorithm available, even when the microcontroller does not have a hardware division instruction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In other words, you don't need to worry about how division is implemented unless you have a very strange special case.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;If you do worry, then you might enjoy reading Atmel's official suggested division algorithms (one optimized for code size, and one optimized for execution speed; neither take any data memory).  They are in:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc0936.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/resources/prod_documents/doc0936.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;which is the Application Note &quot;AVR200: Multiply and Divide Routines&quot; listed on the Atmel page for its (reasonably big) Atmega processors like the Atmega 168 and Atmega 328 used in the standard Arduinos.  The list of data-sheets and application notes is at:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=4720&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/products/product_card.asp?part_id=4720&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1271" LastActivityDate="2010-09-14T19:43:35.063" />
  <row Id="4420" PostTypeId="2" ParentId="4403" CreationDate="2010-09-14T21:56:58.380" Score="1" ViewCount="" Body="&lt;p&gt;It's better to think of a potentiometer as a volume control(*) for a single audio channel.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your &lt;strong&gt;+&lt;/strong&gt; and &lt;strong&gt;-&lt;/strong&gt; audio input signal connect to the non-wiper pins of the potentiometer. The attenuated output &lt;strong&gt;+&lt;/strong&gt; signal connects to the wiper pin, while the attenuated output &lt;strong&gt;-&lt;/strong&gt; signal connects to the same pin you connected the - audio input signal to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;That application actually works, and is how you actually make volume controls.&lt;/strong&gt;  To think of a single, unaided pot as a fader really stretches the analogy into inaccuracy land.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(*) - For pots that have a audio/log taper, or a &lt;a href=&quot;http://sound.westhost.com/project01.htm&quot; rel=&quot;nofollow&quot;&gt;simulated log taper&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-09-14T22:02:17.280" LastActivityDate="2010-09-14T22:02:17.280" />
  <row Id="4421" PostTypeId="2" ParentId="3263" CreationDate="2010-09-15T00:50:16.117" Score="0" ViewCount="" Body="&lt;p&gt;Another alternative I've heard good things about but haven't worked with myself (yet) is the &lt;a href=&quot;http://www.robotfuzz.com/OSIF&quot; rel=&quot;nofollow&quot;&gt;Open Source Interface (OSIF)&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="923" LastActivityDate="2010-09-15T00:50:16.117" CommunityOwnedDate="2010-09-15T00:50:16.117" />
  <row Id="4422" PostTypeId="2" ParentId="4374" CreationDate="2010-09-15T02:51:57.487" Score="1" ViewCount="" Body="&lt;p&gt;looks to me like all you need is a 100-entry lookup table. Doesn't get much faster than that.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define VALUE_FOR_V_EQUALS_ZERO 0&#xA;uint16_t formula_lookup[100] = {VALUE_FOR_V_EQUALS_ZERO, 500, 399, 365, 348, ..., 300};&#xA;&#xA;...&#xA;&#xA;//&quot;calculate&quot; formula&#xA;p = formula_lookup[v &amp;gt; 67 ? 67 : v];&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt; you actually only a 68 value lookup table since values of v greater than 67 always evaluate to 300. &lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-09-15T14:07:35.967" LastActivityDate="2010-09-15T14:07:35.967" CommentCount="1" />
  <row Id="4423" PostTypeId="1" CreationDate="2010-09-15T09:58:50.660" Score="5" ViewCount="356" Body="&lt;p&gt;I've seen in a lot of projects a cool presentation of byte such as :&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;      Fuse high byte:  &#xA;      0xc9 = 1 1 0 0   1 0 0 1 -- BOOTRST (boot reset vector at 0x0000)  &#xA;             ^ ^ ^ ^   ^ ^ ^------ BOOTSZ0  &#xA;             | | | |   | +-------- BOOTSZ1  &#xA;             | | | |   + --------- EESAVE (don't preserve EEPROM over chip erase)  &#xA;             | | | +-------------- CKOPT (full output swing)  &#xA;             | | +---------------- SPIEN (allow serial programming)  &#xA;             | +------------------ WDTON (WDT not always on)  &#xA;            +-------------------- RSTDISBL (reset pin is enabled)  &#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;or&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;    Fuse low byte:&#xA;     0x9f = 1 0 0 1   1 1 1 1&#xA;            ^ ^ \ /   \--+--/&#xA;            | |  |       +------- CKSEL 3..0 (external &gt;8M crystal)&#xA;            | |  +--------------- SUT 1..0 (crystal osc, BOD enabled)&#xA;            | +------------------ BODEN (BrownOut Detector enabled)&#xA;            +-------------------- BODLEVEL (2.7V)&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I wonder if anyone can tell me how, or where, I can make some of these ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit : I mean, I often see those type of presentation in texte format, so I suppose it isen't made by hand. I was hopping to find the software/url to generate the samme.&lt;/p&gt;&#xA;" OwnerUserId="824" LastEditorUserId="824" LastEditorDisplayName="" LastEditDate="2010-09-15T16:38:12.360" LastActivityDate="2010-12-10T17:13:13.020" Title="Text presentation of a byte" Tags="&lt;documentation&gt;" AnswerCount="6" CommentCount="2" FavoriteCount="5" />
  <row Id="4424" PostTypeId="2" ParentId="4423" CreationDate="2010-09-15T10:18:39.330" Score="5" ViewCount="" Body="&lt;p&gt;In your favourite text editor. I can recommend &lt;a href=&quot;http://vim.org&quot; rel=&quot;nofollow&quot;&gt;vim&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-15T10:18:39.330" CommentCount="2" />
  <row Id="4425" PostTypeId="2" ParentId="4423" CreationDate="2010-09-15T10:57:23.963" Score="2" ViewCount="" Body="&lt;p&gt;You could use &lt;a href=&quot;http://www.gliffy.com&quot; rel=&quot;nofollow&quot;&gt;Gliffy&lt;/a&gt;, an online package similar to Visio. I knocked out some of your diagram in about two minutes:&#xA;&lt;a href=&quot;http://www.gliffy.com/pubdoc/2237997/L.png&quot; rel=&quot;nofollow&quot;&gt;http://www.gliffy.com/pubdoc/2237997/L.png&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-15T10:57:23.963" />
  <row Id="4426" PostTypeId="2" ParentId="4423" CreationDate="2010-09-15T13:54:22.550" Score="1" ViewCount="" Body="&lt;p&gt;I could potentially whip something up with XML that could transcode to PDF or some other graphic format&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-15T13:54:22.550" CommentCount="2" />
  <row Id="4427" PostTypeId="2" ParentId="4413" CreationDate="2010-09-15T13:59:56.133" Score="1" ViewCount="" Body="&lt;p&gt;ProfiBus-DP is just RS-485; electrically this is not a challenge. If you're going after PA it's a little trickier, as you might have some trouble sourcing onesie-twosie quantities, but I can't imagine an Arduino talking on the PA network anyway, so let's not worry about it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think your biggest challenge will be in finding or developing an protocol stack. I wrote a CIP (DeviceNet and Ethernet/IP) protocol stack for a project several years ago and that was quite a challenge. Designing to industrial specifications isn't easy. I swear that they develop the specifications in order to give consultants work. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy networking stacks from various suppliers, but they aren't cheap, and you will likely have to do a lot of porting (and thus compliance testing) work to get it to work on something like Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck! It will be a challenging project!&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-09-15T13:59:56.133" />
  <row Id="4428" PostTypeId="1" CreationDate="2010-09-15T14:03:28.883" Score="4" ViewCount="316" Body="&lt;p&gt;Hello all, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just bought a pic 32 starter kit, and since I did little reading before I picked up the product I found that it came with no simple way of accessing the pic32's input and output. I know there is a pic32 expansion board but I am feeling a little bit burnt by microchip for even suggesting that I need to get an expansion board for my starter kit... anyways before I start ranting, What options do I have to getting simple access the pins? there is a connector on the bottom of the starter kit, I was wondering if there was a standard cable that would fit into that? I just don't see the need buying a 72 dollar board when a bit of wire should do the trick? anyways I would greatly appreciate any advice that can be given  &lt;/p&gt;&#xA;" OwnerUserId="811" LastActivityDate="2010-09-15T17:21:09.553" Title="pic 32 starterkit i/o" Tags="&lt;pic&gt;&lt;microprocessor&gt;&lt;programming&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="4429" PostTypeId="2" ParentId="4428" CreationDate="2010-09-15T14:28:31.207" Score="1" ViewCount="" Body="&lt;p&gt;The mating connector is a Hirose 132-pin FX10. Digikey sells the mating connector, but I haven't seen a version that attaches to a cable. Sparkfun doesn't have an expansion board that I can find.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe try asking in the Adafruit or Sparkfun forums? It's pretty likely that someone has made a breakout board that will be cheaper than $72.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-09-15T14:28:31.207" />
  <row Id="4431" PostTypeId="2" ParentId="4428" CreationDate="2010-09-15T15:26:03.150" Score="4" ViewCount="" Body="&lt;p&gt;According to page 48 of the &lt;a href=&quot;http://www.microchip.com/Microchip.WWW.SecureSoftwareList/secsoftwaredownload.aspx?device=en532453&amp;amp;lang=en&amp;amp;ReturnURL=http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2615&amp;amp;dDocName=en532453#&quot; rel=&quot;nofollow&quot;&gt;user manual&lt;/a&gt; &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2615&amp;amp;dDocName=en532453&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, it's actually a &lt;strong&gt;120&lt;/strong&gt; pin connector.  According to the schematic on page 57 (and according to Pingswept) it's a 132 pin connector. Digikey has the 120-pin plug which would be on the expansion board &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=H11238-ND&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; for $7.22.   This is probably a discrepancy between different revs of the datasheet, you should call Microchip on this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Eagle part layout is &lt;a href=&quot;ftp://ftp.cadsoft.de/eagle/userfiles/libraries/conn-hirose.lbr&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; if you want to make the board. It seems that Adafruit or Sparkfun would want to sell such a board, and, if they don't do so now, this is your opportunity!  I'd go with batchPCB for this application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've previously made a few conversion boards for stuff like this (yes, 0.5mm pitch can be done!) by placing the connector onto some kapton tape on a piece of perfboard (make the tape just short enough so that you can solder the mounting posts on the end of your connector to the perfboard for a secure mount), and then running 30-gauge jumpers to whatever connector your heart desires.  I only needed 28 connections on my biggest job (had to do it twice), but the process is doable.  A few words of advice: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Flux is your friend. Lots and lots of flux!  Get a jug of liquid flux (a quart should last you just about forever) and a bottle with a small tip that will dispense it one drop at a time, so that you don't bend the leads of your connector or break previous joints with the tip of your flux pen.  Clean excess, dried up, and sticky flux off occasionally with some isopropyl alcohol and blot dry, then reapply clean flux.&#xA;&lt;li&gt;Using two or three colors (depending on the number of rows you're breaking this out to) will make organization much easier. &#xA;&lt;li&gt;A good stereo microscope and fume extractor will make this job a lot more pleasant.  Not necessary, but nice to have.&#xA;&lt;li&gt;Be careful to avoid heating the connector pins to much: You'll soften the plastic, which will then stop holding the pins parallel.  &#xA;&lt;li&gt;Cut your 30-guage wires to a constant length, and just bunch them with loops of bus wire through holes in the perfboard.  Don't do too much until they're secured, which brings me to:&#xA;&lt;li&gt;Secure your delicate connections and wires from shorts and provide strain relief by coating the whole thing with hot glue once you're done.   Don't use so much that you can't see which wires go to which pins, or at least determine that from your color coding.&#xA;&lt;li&gt;When connecting to a nice, big post on a nice, big .1&quot; header :), just give the wire a 270 degree bend, pull it reasonably tight (hold the other side!) coat it with flux, and burn the insulation off.  Pick any remnants off with tweezers, and then apply more flux and solder.  Don't try to strip it and endanger your delicate connections.&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So, your process is: Put flux on the wire.  Put solder on the wire, trim it if you burned the insulation too far back. Flux the tinned wire and connector.  Hold the wire on the connector lead. Tin soldering iron, clean the tip, and apply heat to flow the joint. Repeat x 120. &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-15T15:26:03.150" CommentCount="6" />
  <row Id="4432" PostTypeId="2" ParentId="4428" CreationDate="2010-09-15T17:12:51.880" Score="2" ViewCount="" Body="&lt;p&gt;It would seem that digikey has a breakout board for $33.66. &#xA;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?FullDetail&amp;amp;name=876-1000-ND#usewithchildren&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?FullDetail&amp;amp;name=876-1000-ND#usewithchildren&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="811" LastEditorUserId="811" LastEditorDisplayName="" LastEditDate="2010-09-15T17:21:09.553" LastActivityDate="2010-09-15T17:21:09.553" CommentCount="1" />
  <row Id="4434" PostTypeId="2" ParentId="4242" CreationDate="2010-09-15T21:11:00.033" Score="2" ViewCount="" Body="&lt;p&gt;You said TWO AA batteries -- try THREE. It needs 3.6 - 7.5v power. &lt;/p&gt;&#xA;" LastActivityDate="2010-09-15T21:11:00.033" CommentCount="1" />
  <row Id="4436" PostTypeId="2" ParentId="4377" CreationDate="2010-09-16T01:47:41.493" Score="5" ViewCount="" Body="&lt;p&gt;When my digital signals fluctuate when I expect them to be a constant 1 or 0,&#xA;it's usually something about the pull-up resistors -- I haven't connected them properly, or they've somehow gotten disconnected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once I've ruled out that problem, my next most common problem is contact bounce.&#xA;&lt;a href=&quot;http://www.ganssle.com/debouncing.htm&quot; rel=&quot;nofollow&quot;&gt;Jack Ganssle ran some experiments and has some debounce recommendations&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-16T01:47:41.493" CommentCount="1" />
  <row Id="4437" PostTypeId="1" CreationDate="2010-09-16T09:53:19.660" Score="3" ViewCount="255" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I must admit, I don't know too much about analog electronics but I am keen to know if it possible to construct an equivalent time sampler (ETS) using the A/D's on a micro. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this question isn't too vague. Basically my understanding is that ETS is used to sample very high freqeuncy signals and is a trick that is used for digital oscilliscopes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wondering if anyone has tried this before or knows of a good reference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nathan &lt;/p&gt;&#xA;" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-09-16T14:53:03.640" LastActivityDate="2010-09-16T14:53:03.640" Title="Equivalent time sampling on microcontrolers." Tags="&lt;adc&gt;&lt;sampling&gt;&lt;high-frequency&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="4438" PostTypeId="2" ParentId="4437" CreationDate="2010-09-16T14:07:39.083" Score="1" ViewCount="" Body="&lt;p&gt;I believe that the answer is yes, but the performance would be limited. So far as I know, the highest sampling rates on A/Ds built into microcontrollers is in the 10-100 kHz range. You're also limited by the settling time of the A/D. With a dedicated, high speed, successive-approximation register A/D, you can get above 1 MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For repetitive signals, you could approximate faster signals by using multiple channels, but I suspect that you'd have trouble accurately reconstructing even 1 MHz signals, which is worse than even the cheapest oscilloscope on the market.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Might be fun to try anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this description useful: &lt;a href=&quot;http://www2.tek.com/cmswpt/tidetails.lotr?ct=TI&amp;amp;cs=Application+Note&amp;amp;ci=14295&amp;amp;lc=EN&quot; rel=&quot;nofollow&quot;&gt;http://www2.tek.com/cmswpt/tidetails.lotr?ct=TI&amp;amp;cs=Application+Note&amp;amp;ci=14295&amp;amp;lc=EN&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-09-16T14:07:39.083" />
  <row Id="4439" PostTypeId="2" ParentId="4437" CreationDate="2010-09-16T14:41:37.843" Score="4" ViewCount="" Body="&lt;p&gt;Equivalent Time Sampling (ETS) is a trick to measure high frequency signals when you can make an assumption about the signal that you are measuring. The assumption is that the signal you are sampling is a repetitive signal (i.e. a sine wave or other &quot;time-constant&quot; signal).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to do this in a homebrew fashion you need a means to accurately and repetitively trigger at some fixed location (your trigger point), delay for a variable amount of time and then start and ADC acquisition at fixed intervals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Triggering can be done with a fast comparator and an accurate reference. If your accurate reference is a filtered or otherwise stable DAC output then you have a nifty (albeit simplistic) software-controlled trigger point. Feed the output of the comparator into a &quot;start timer&quot; capture input on your microcontroller. The idea is to have your microcontroller's timer start counting the instant the comparator fires. When the timer overflows, it starts an ADC capture and stops (until you tell it to watch for the event again).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using a tight loop or interrupt routine (i.e. software) to detect when the timer expires in order to start your ADC capture you may experience some jitter as it will take a variable amount of time to detect that the timer is done. If you can, set the timer interrupt to start the ADC transfer automatically. This is possible on numerous microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you haven't already guessed, you will be adjusting the timer's starting value in order to give you a variable &quot;pause&quot; before starting the sampling loop. In essence, you'll be &quot;walking across&quot; the repetitive waveform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now for the ADC. For simplicity, let's say you will be sampling as fast as you can at all times. (I'll talk about alternatives below.)  What this means is that as soon as the ADC finishes, you will tell it to start again.  Now some microcontrollers are better at this than others; if you can DMA your ADC results and automatically restart, this is your best option. Otherwise you will have ANOTHER source of jitter in your ETS: the delay between an ADC complete interrupt (or polling detecting the completion), storing the sample, and starting another capture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is your basic system. pseudocode:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;volatile int adc_count;&#xA;&#xA;/* assumes you can't use DMA to drive the ADC */&#xA;void adc_interrupt(void)&#xA;{&#xA;    store_value();&#xA;&#xA;    if(--adc_count) {&#xA;        start_adc();&#xA;    }&#xA;}&#xA;&#xA;do {&#xA;    int offset;&#xA;    offset = 0;               /* offset from trigger to first ADC sample */&#xA;&#xA;    do {&#xA;        adc_count = 256;      /* arbitrary, how many samples per trigger */&#xA;&#xA;        load_timer(offset);   /* set timer value */&#xA;        arm_timer();          /* timer will now start when the trigger occurs */&#xA;    } while(adc_count);&#xA;&#xA;    offset += 10;             /* arbitrary, how much to &quot;move over&quot; each trigger */&#xA;} while(offset &amp;lt; 100);        /* arbitrary, how many triggers to use for an ETS capture */&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Pretty straightforward stuff, but as I mentioned, you need to design the code and select a microcontroller that allows you to have the lowest jitter possible. This means that you want a microcontroller that can be set up such that a timer interrupt can start and ADC capture and that an ADC complete event can DMA results (and restart the ADC). If your microcontroller can't do this then you will have some jitter in your sampling and the captured waveform may look a little &quot;off&quot; as the sample points won't be at evenly spaced intervals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now what if you don't want to sample as quickly as possible? You'd want the ADC interrupt to start a second timer that waits the amount of time you want to have between samples, and have that second timer's interrupt start the ADC again.  If you're doing this, you have to be aware that this is yet another source of jitter if you have to use an interrupt routine or polling (i.e. software) to detect and start the peripherals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a nutshell, that's ETS.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-09-16T14:41:37.843" CommentCount="4" />
  <row Id="4441" PostTypeId="1" AcceptedAnswerId="4442" CreationDate="2010-09-17T00:37:32.300" Score="3" ViewCount="202" Body="&lt;p&gt;This is probably a very easy question, but I've been trying for several weeks now to create a simple circuit that &quot;fades in&quot; some LEDs using only discrete components like resistors, capacitors, inductors, (photo) diodes, transistors, and a voltage source.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Using only discrete parts (no ICs), how do I &quot;fade in&quot; a few LEDs over the course of a second or two?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;I've managed to create the &lt;strong&gt;opposite&lt;/strong&gt;, the &quot;fade away&quot;:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;+Volts connected to &quot;RC&quot; and then to &quot;PL&quot; and then to ground in series&lt;/li&gt;&#xA;&lt;li&gt;RC is a resistor and capacitor in parallel&lt;/li&gt;&#xA;&lt;li&gt;PL is roughly some leds in parallel: PL1 and PL2 in parallel&lt;/li&gt;&#xA;&lt;li&gt;PL1 is a LED and resistor in series&lt;/li&gt;&#xA;&lt;li&gt;PL2 is three LEDs and resistor, all in series&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;When powered up (at +6V with the RC using 1K ohm and 2200uF) all LEDs immediately light (no fade in at all), but over 2 seconds the triple LED (PL2) fades to black.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;I can of course make this using an Arduino and the PWM output pins to make intricate fade in and fade out patterns, but the circuit is to demonstrate using a simple transistor to switch a system on, and if I'm using a microcontroller to drive that system, I might as well have the transistor trigger my laptop to play a youtube video.&lt;/p&gt;&#xA;" OwnerUserId="1271" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T22:16:12.443" LastActivityDate="2011-04-28T14:49:33.100" Title="Analog, discrete component fade-in" Tags="&lt;led&gt;&lt;audio&gt;&lt;analog&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="4442" PostTypeId="2" ParentId="4441" CreationDate="2010-09-17T01:35:55.180" Score="4" ViewCount="" Body="&lt;p&gt;Put the capacitor in parallel with the LEDs and leave the resistor where it is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you power up, the voltage across the cap is 0 V. It will slowly charge up to match the voltage at the top of the LEDs.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-09-17T01:35:55.180" CommentCount="3" />
  <row Id="4443" PostTypeId="2" ParentId="4441" CreationDate="2010-09-17T08:15:03.570" Score="2" ViewCount="" Body="&lt;p&gt;Here's an instructable on making a fade in and out circuit without an MCU&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/No-CPU-MCU-led-pulse-fade/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/No-CPU-MCU-led-pulse-fade/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-17T08:15:03.570" CommentCount="1" />
  <row Id="4444" PostTypeId="2" ParentId="4094" CreationDate="2010-09-17T10:32:37.680" Score="1" ViewCount="" Body="&lt;p&gt;Interesting problem. I am assuming that the types of buttons/switches you would want to push/move in will have a variety of 'resistances'. By resistances I mean that you may need a small nudge for one button but a forceful whack for another. Also, this may ask for a configurable position (horizontal + vertical) of your actuator that does the actual work of pushing or moving on the accessory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though, I've personally never tried this, I think a mini servo motor that gives a fine grained degree of control in its movement can be used (similar to Andrew's answer in this thread). The servo motor in turn can be connected to your actuator through a spring loaded trigger mechanism. The spring tension will vary as per the 'resistance' of the button or switch. This whole mechanism in turn should sit on a platform that itself is movable horizontally and vertically (a set of couple of mini servo motors again).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Admittedly, my option looks elaborate but I feel if it is designed well, it has endless applicability on all kinds of accessories and may be cheaper than custom devices. The platform can be omitted initially to make it even cheaper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rgds,&#xA;Sushrut.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastActivityDate="2010-09-17T10:32:37.680" />
  <row Id="4445" PostTypeId="2" ParentId="1942" CreationDate="2010-09-17T10:35:22.607" Score="2" ViewCount="" Body="&lt;p&gt;I would go with an Arduino or a Sanguino as most folks suggested. Just google for them. They are extremely easy to use and you can be up and running in a few hours once you have all the necessary components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rgds,&#xA;Sushrut.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastActivityDate="2010-09-17T10:35:22.607" />
  <row Id="4446" PostTypeId="2" ParentId="4373" CreationDate="2010-09-17T10:40:38.070" Score="0" ViewCount="" Body="&lt;p&gt;How about building your own?! If you have the time and inclination. It may be cheaper and you could learn a lot of useful stuff in the process. Take a mini servo motor, couple it with your inlet pipe and you have a rudimentary but workable valve! Of course you may need to extend the servo motors fins with custom cut PVC portions that match your pipe, but that is not really difficult. You'll need a micro controller or something like an Arduino for precise control of the servo.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rgds,&#xA;Sushrut.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastActivityDate="2010-09-17T10:40:38.070" />
  <row Id="4447" PostTypeId="1" CreationDate="2010-09-17T22:23:06.247" Score="3" ViewCount="153" Body="&lt;p&gt;I have a smart card that is used with a Respironics CPAP machine.  I need to read the data off of the card.  I have the Windows software for the card but I don't have a card reader just yet.  Many people say you need a specific MAKO DT3500 card reader which costs 60-160.00.   In the manual it says that you don't need a driver if you use a serial smart card reader.  My question is: Are serial smart card readers able to access data on most any/every smart card out there?  Is it like a SD memory card reader where pretty much anyone I buy will be able to read the card?  Is that the same for the USB versions?  If I buy a newer USB reader and load the drivers that came with it, will the Respironics software be able to see it.  I know this might be hard to answer but in the experience of the smart card users out there do you generally need a specific card reader for a specific card?&lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-04T03:55:13.873" LastActivityDate="2011-02-04T03:55:13.873" Title="Serial Smart Card Readers" Tags="&lt;reader&gt;&lt;smart-card&gt;" AnswerCount="1" />
  <row Id="4448" PostTypeId="1" CreationDate="2010-09-18T08:01:04.803" Score="3" ViewCount="411" Body="&lt;p&gt;I have purchased a pair of APC220 modules.&#xA;I also purchased a USB TTL module to programme these.&#xA;I down loaded the drivers from Silabs and the RF-magic 4.2 software which is supposed to be able to programme thee modules.&#xA;The RF-Magic programme is proving less than magical as it does not see the device.&#xA;Tried 3 different computers&#xA;While trolling the web for suggestions option I came across the APC220 software which finds my device but does not allow me to change the settings that I need to change as it is for a different type of device using the same chip. &#xA;I tried a FTDI cable but this does not help.&#xA;Any suggestions?&#xA;Warren &lt;/p&gt;&#xA;" LastActivityDate="2011-03-13T14:00:21.837" Title="APC220 and the not so magical RF-Magic" Tags="&lt;apc220&gt;" AnswerCount="3" />
  <row Id="4449" PostTypeId="2" ParentId="4448" CreationDate="2010-09-18T10:22:16.430" Score="2" ViewCount="" Body="&lt;p&gt;Hello Warren&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry to have to say this, but I also had the same issues to the point of frustration. Unfortunately they were a complete failure to me. Much better off with XBees, which worked almost instantly. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-18T10:22:16.430" />
  <row Id="4450" PostTypeId="1" AcceptedAnswerId="4455" CreationDate="2010-09-18T12:33:10.150" Score="2" ViewCount="600" Body="&lt;p&gt;I want to do a project where the temperature of a device is controlled by toggling on/off a heating element (120VAC),presumeably by using a relay.  I would like a board that has an input for a temperature sensor of some sort and some form of a display and buttons to allow me to create a user interface.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whether the board itself has the relay or not does not matter (I can use 5V to trigger a 'powerswitch tail' if I need to).  The board would definitely need a display of some sort (nothing fancy needed), some buttons, and the ability to measure temperature accurately (+/0 0.5 °F worst case).  Does anybody know of anything that fits the bill?&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2010-09-20T00:15:53.910" Title="Good board for DIY temperature control/readout" Tags="&lt;temperature&gt;&lt;microcontroller&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="4451" PostTypeId="2" ParentId="4450" CreationDate="2010-09-18T13:53:32.233" Score="1" ViewCount="" Body="&lt;p&gt;All the parts would be relatively easy to get and put together: LCD module, any simple MCU, some suitable digital temperature sensor, buttons... and the relay should indeed be easy to control. I think this complete DIY approach would seem most obvious and you won't &quot;waste&quot; a kit doing it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to look for a ready board, something with enough PIO, ISP, some sync serial bus for the sensor and ready buttons and displays would probably be. Maybe some available memory for logging and/or UART in case you want to attach it to a computer at some point. Which particular one probably depends on which one you can get and from where.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd probably pick an ATTiny series AVR and a separate LCD module, some stripboard, and pin headers and work from there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Either way, I don't think trying to fit the sensor and/or relay (that needs to have one half well isolated) on the same board is a good idea unless you have a really good reason for it.&lt;/p&gt;&#xA;" OwnerUserId="883" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-09-18T14:00:10.337" LastActivityDate="2010-09-18T14:00:10.337" />
  <row Id="4452" PostTypeId="2" ParentId="4363" CreationDate="2010-09-18T18:34:32.187" Score="0" ViewCount="" Body="&lt;p&gt;For video, DVI and HDMI are very similar, you can convert one video to another just be rearranging lines. HDMI also adds audio though...&lt;/p&gt;&#xA;" OwnerUserId="960" LastActivityDate="2010-09-18T18:34:32.187" CommentCount="1" />
  <row Id="4453" PostTypeId="2" ParentId="4373" CreationDate="2010-09-18T21:18:44.617" Score="0" ViewCount="" Body="&lt;p&gt;Excuse me – I didn't see that you needed variable water flow. Perhaps you could pulse this, but I do not believe it is what you want. Anyway:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just bought a bunch of &quot;Electric Solenoid Water Valves&quot; from Seeedstudio Depot: &lt;a href=&quot;http://www.seeedstudio.com/depot/electric-solenoid-valve-p-636.html?cPath=119_121&quot; rel=&quot;nofollow&quot;&gt;http://www.seeedstudio.com/depot/electric-solenoid-valve-p-636.html?cPath=119_121&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They work well.&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2010-09-18T21:18:44.617" CommentCount="2" />
  <row Id="4454" PostTypeId="2" ParentId="4450" CreationDate="2010-09-19T01:28:05.770" Score="2" ViewCount="" Body="&lt;p&gt;Those who know me realise I am biased towards the Arduino way of doing things, so if you had an &#xA;Arduino, HD44780-compatible LCD, Analog Devices TMP36, that powerswitch tail from Adafruit, the job could be done very easily. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might find &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/04/15/getting-started-with-arduino-chapter-two/&quot; rel=&quot;nofollow&quot;&gt;this article&lt;/a&gt; of interest, it discusses how to use that temperature sensor, LCDs and making decisions based on temperature. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-19T01:28:05.770" />
  <row Id="4455" PostTypeId="2" ParentId="4450" CreationDate="2010-09-19T01:47:17.050" Score="3" ViewCount="" Body="&lt;p&gt;I've seen a couple of &quot;buttons and LCD and thermocouple&quot; kits.&#xA;If none of them are adequate for what you are working on, I suspect you could pick almost any &quot;buttons and LCD&quot; kit and almost any &quot;thermocouple interface kit&quot; and connect them.&#xA;(in no particular order):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;== buttons and LCD and thermocouple ==&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.adafruit.com/blog/2010/09/07/a-thermocouple-datalogger-based-on-the-arduino-platform/&quot; rel=&quot;nofollow&quot;&gt;Adafruit: &quot;A thermocouple datalogger based on the Arduino platform&quot;&lt;/a&gt; and at &lt;a href=&quot;http://lukemiller.org/index.php/2010/08/a-thermocouple-datalogger-based-on-the-arduino-platform/&quot; rel=&quot;nofollow&quot;&gt;Luke Miller's blog&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=81&quot; rel=&quot;nofollow&quot;&gt;Sparkfun Reflow Toaster Controller&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;(The &lt;a href=&quot;http://hackaday.com/2007/12/26/arduino-controlled-espresso-machine/&quot; rel=&quot;nofollow&quot;&gt;Arduino controlled Espresso Machine&lt;/a&gt; sounds similar to what you want, but alas, it's apparently not for sale).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;== buttons and LCD ==&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Arduino shield LCD+buttons &lt;a href=&quot;http://www.liquidware.com/shop/show/PMP/Portable+MegaPalm&quot; rel=&quot;nofollow&quot;&gt;Portable MegaPalm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9363&quot; rel=&quot;nofollow&quot;&gt;Arduino shield LCD+buttons&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Parallax Propeller &lt;a href=&quot;http://gadgetgangster.com/find-a-project/56?projectnum=175&quot; rel=&quot;nofollow&quot;&gt;LCD UI Module&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Microchip PIC LCD+buttons &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=26&quot; rel=&quot;nofollow&quot;&gt;28 Pin PIC Terminal Development Board&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;TI MSP430 LCD+buttons &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=60&quot; rel=&quot;nofollow&quot;&gt;MSP430F449 Evaluation Board&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;ARM MCU LCD+buttons &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=260&quot; rel=&quot;nofollow&quot;&gt;LPC2106 Terminal Development Board&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=41&quot; rel=&quot;nofollow&quot;&gt;EasyWEB2 Internet Development Board&lt;/a&gt; has LCD+buttons&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Orangutan-LV%252d168-Robot-Controller.html&quot; rel=&quot;nofollow&quot;&gt;Orangutan LV-168 Robot Controller&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Orangutan-SV%252d328-Robot-Controller.html&quot; rel=&quot;nofollow&quot;&gt;Orangutan SV-328 Robot Controller&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;== thermocouple interfaces ==&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you ever need to measure temperatures above 125 C (257 F), you'll need to use a thermocouple and a thermocouple interface chip.&#xA;(Thermistors and IC sensors such as the Analog Devices AD592 and the Maxim DS18B20 cost less, but generally can't handle temperatures above 125 C).&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://ryanjmclaughlin.com/shop/quad-thermocouple-shield/&quot; rel=&quot;nofollow&quot;&gt;Arduino Thermocouple Shield&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://reprap.org/wiki/Thermocouple_Sensor_1.0&quot; rel=&quot;nofollow&quot;&gt;RepRap thermocouple sensor&lt;/a&gt; (controls the heater head for the right temperature for melting and extruding plastic)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://code.google.com/p/multidisplay/&quot; rel=&quot;nofollow&quot;&gt;Multidisplay project&lt;/a&gt; and &lt;a href=&quot;http://www.youtube.com/watch?v=U49XVXNET9Q&quot; rel=&quot;nofollow&quot;&gt;Multidisplay video&lt;/a&gt; (measures various temperatures in an automobile engine)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://hearth.com/econtent/index.php/forums/viewthread/48781/&quot; rel=&quot;nofollow&quot;&gt;flue temperature sensor&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.mlgp-llc.com/arduino/public/arduino-pcb.html&quot; rel=&quot;nofollow&quot;&gt;4-Channel Thermocouple Input Arduino Shield&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;(I've made this &quot;community wiki&quot; so others can add really good/cheap examples and trim out obsolete items).&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-19T01:47:17.050" CommunityOwnedDate="2010-09-19T01:47:17.050" />
  <row Id="4456" PostTypeId="1" CreationDate="2010-09-19T15:51:13.410" Score="2" ViewCount="235" Body="&lt;p&gt;Can enyone help to make it for 650kHz (600-700kHz) for BBC reception from Poland ?&#xA;After making it does not receive any station.&#xA;What`s wrong ?&#xA;&lt;a href=&quot;http://www.next.gr/inside-circuits/Simple-Coil-less-AM-receiver-l6022.html&quot; rel=&quot;nofollow&quot;&gt;http://www.next.gr/inside-circuits/Simple-Coil-less-AM-receiver-l6022.html&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-09-19T17:43:42.153" Title="Simple-Coil-less-AM-receiver- how to make for 650kHz (BBC from Poland)" Tags="&lt;signal&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="4457" PostTypeId="2" ParentId="4456" CreationDate="2010-09-19T16:09:26.320" Score="5" ViewCount="" Body="&lt;p&gt;Any number of things could be wrong, but there are some very basic things to check on, if you feel the circuit is assembled correctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1- are you sure the battery you're using isn't dead? Often times batteries can show a fair voltage when checked open-circuit with a DVM, but then when put under load they have almost no voltage. If you have a new battery, this shouldn't be a concern.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2- any time you have a radio circuit, you have to make sure you have an adequate antenna. For low frequency AM you shouldn't need much, a meter or two of wire should do it, but not necessarily if you are in a basement or inside a metal sided building.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3- with a circuit like that, you probably aren't going to be able to drive a regular speaker low-impedance. Headphones are more likely to work.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-09-19T17:43:42.153" LastActivityDate="2010-09-19T17:43:42.153" CommentCount="1" />
  <row Id="4458" PostTypeId="1" AcceptedAnswerId="4460" CreationDate="2010-09-19T16:53:38.290" Score="7" ViewCount="802" Body="&lt;p&gt;Why is it that the produced clock frequency is 6.144 MHz, but internally it (8085 processor) uses only 3.072 MHz. Also what leads to the specific value of 6.144 in a clock. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found an answer at yahoo.... &lt;a href=&quot;http://answers.yahoo.com/question/index?qid=20080810090119AAurr2i&quot; rel=&quot;nofollow&quot;&gt;http://answers.yahoo.com/question/index?qid=20080810090119AAurr2i&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but I must admit I didn't still get it it well. Could any of you guys throw out a few lines on this, please? &lt;/p&gt;&#xA;" OwnerUserId="1163" LastActivityDate="2011-02-02T21:53:27.793" Title="Why in 8085 microprocessor, the clock frequency is divided by two?" Tags="&lt;8085&gt;&lt;microprocessor&gt;&lt;clock&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="4460" PostTypeId="2" ParentId="4458" CreationDate="2010-09-19T17:25:22.830" Score="9" ViewCount="" Body="&lt;p&gt;One reason to divide a clock by two is to obtain an even 50% duty cycle square wave. It may be that the 8085 internally uses both clock edges, and wouldn't function if one half of the cycle happened to be much shorter than the other. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the days when the 8085 was new, those nice canned oscillators weren't common, and people often cobbled together clock circuits out of discrete crystals, capacitors, and logic gates. Dividing by two ensures that you have equally spaced rising and falling edges.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for 6.144MHz, you will find that it can be divided by an integer to get common baud rate values, at least up to 38400. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;follow up ...&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at an Intel data sheet for the 8085, there are three interesting statements&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(1) &quot;The 8085 incorporates all of the features that the 8224 clock generator and 8228 system controller provided for the 8080A&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(2) &quot;X1 and X2: Are connected to a crystal, LC or RC network to drive the internal clock generator. The input frequency is divided by 2 to give the processor's internal operating frequency&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(3) &quot;CLK: Clock output for use as a system clock. The period of CLK is twice the X1, X2 input period&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, speculations about using the odd edges of the clock to move stuff around internally aside, it becomes apparent that when they designed the 8085, Intel was replacing the need for a special clock controller by integrating that feature into the chip. Dividing the X1-X2 timebase in half before outputting it as CLK ensures that the &lt;em&gt;system&lt;/em&gt; gets a nice even duty cycle, if nothing else.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-09-20T23:13:11.347" LastActivityDate="2010-09-20T23:13:11.347" CommentCount="3" />
  <row Id="4462" PostTypeId="1" CreationDate="2010-09-19T23:08:27.777" Score="3" ViewCount="605" Body="&lt;p&gt;I'm trying to send data to an SD card from a PIC18f4580, but the PIC is not sending what it should be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;related global variables:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;unsigned char TXBuffer[128]; //tx buffer&#xA;unsigned char TXCurrentPos = 0x00; //tracks the next byte to be sent&#xA;unsigned char TXEndPos = 0x00; //tracks where new data should be put into the array&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I am adding data to a buffer using the following function:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void addToBuffer(char data){&#xA;&#xA;    TXBuffer[TXEndPos] = data;&#xA;    TXEndPos++;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And putting the data from the TXBuffer into TXREG with the following interrupt:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;else if (PIR1bits.TXIF == 1){&#xA;&#xA;    if((TXEndPos - TXCurrentPos) &amp;gt; 0){         // if there is data in the buffer&#xA;        TXREG = TXBuffer[TXCurrentPos];           // send next byte&#xA;        TXCurrentPos++;               // update to the new position&#xA;    }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Using an oscilloscope I am able to see that the PIC is sending 0x98, regardless of what I put into the buffer. In fact I never put 0x98 into the buffer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if I replace&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TXREG = TXBuffer[TXCurrentPos];&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;with&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TXREG = 0x55;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;or&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TXREG = TXCurrentPos;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;then I get the expected results, that is the PIC will send 0x55 repeatedly, or count up from 0 respectively.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So why does the PIC have trouble sending data from the array, but any other time it is fine? I'll emphasize that transferring is handled in an interrupt, because I feel like that's the root of my issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: It is a circular buffer in the sense that TXEndPos and TXCurrentPos return to 0 when they reach 127.&#xA;I also disable the transmit interrupt when TXEndPos - TXCurrentPos == 0, and re-enable it when adding data to the buffer. Really, my code works completely as expected in that if I add 13 characters to TXBuffer in main, my PIC will transmit 13 characters and then stop. The problem is that they are always the same (wrong) character - 0x98.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT2: more complete functions are here: &lt;a href=&quot;http://pastebin.com/MyYz1Qzq&quot; rel=&quot;nofollow&quot;&gt;http://pastebin.com/MyYz1Qzq&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT3: By changing our linker script and appropriately using pragmas we're able to get some of our data into our buffer. We statically placed variables related to the buffer into the same memory bank, and that has certainly helped but not all of our data is getting into our buffer. Strangest of all, running the program multiple times yields different data in the buffer, even though all of the data to be placed in the buffer is defined in our code. Also, we get drastically different results when the pic automatically runs after programming it, when we cut the power and restart power with the pickit3 still plugged in, and when we reset the power with the pickit3 disconnected. Also, simulating in MPLAB results in the buffer being filled perfectly, however when actually running the code on the PIC and viewing it's memory, it is not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Our code as of 5:38 9/22/10 is here: &lt;a href=&quot;http://pastebin.com/yvdC73jS&quot; rel=&quot;nofollow&quot;&gt;http://pastebin.com/yvdC73jS&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Our modified linker file is here: &lt;a href=&quot;http://pastebin.com/np3DE3KC&quot; rel=&quot;nofollow&quot;&gt;http://pastebin.com/np3DE3KC&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-09-27T15:49:00.133" Title="USART transmit problems on a PIC" Tags="&lt;pic&gt;&lt;microcontroller&gt;&lt;c&gt;&lt;interrupts&gt;&lt;serial&gt;" AnswerCount="5" CommentCount="6" FavoriteCount="1" />
  <row Id="4463" PostTypeId="2" ParentId="4450" CreationDate="2010-09-20T00:15:53.910" Score="1" ViewCount="" Body="&lt;p&gt;My design (Eagle files and Arduino sketch) is on the web: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dorkbotpdx.org/blog/scott_d/temperature_controller_board_final_design&quot; rel=&quot;nofollow&quot;&gt;http://dorkbotpdx.org/blog/scott_d/temperature_controller_board_final_design&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The design includes an Arduino compatible and has provision for a MAX6675 thermocouple chip and an IR temperature sensor based on a modified IR thermometer from Harbor Freight Tools.  It also has a built in interface for a common 16x2 (or similar) LCD, inputs which could be used for buttons (although I'm currently using an encoder instead) and a digital output for controlling an SSR or other relay.  A number of local hobbyists are using this board for temperature control of various projects including reflow hotplates.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I note that you require +/- 0.5°F temperature accuracy, which is better than most thermocouples can provide, so you might have to find some other type of temperature sensor for your project.  It depends on the temperature range you need to measure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to use my Eagle files to make a PCB, I can recommend the Portland DorkBot group PCB order:  &lt;a href=&quot;http://dorkbotpdx.org/wiki/pcb_order&quot; rel=&quot;nofollow&quot;&gt;http://dorkbotpdx.org/wiki/pcb_order&lt;/a&gt;.  It is inexpensive and designed for hobbyists.&lt;/p&gt;&#xA;" LastActivityDate="2010-09-20T00:15:53.910" />
  <row Id="4465" PostTypeId="2" ParentId="4462" CreationDate="2010-09-20T06:48:54.847" Score="4" ViewCount="" Body="&lt;p&gt;It's a little confusing that the code in the question differs to the code in pastebin - but assuming that the pastebin code is correct, I'd say that the problem is that you're sending uninitialised data from the array instead of the characters that you put in it.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TXREG = TXBuffer[TXEndPos];           // send next byte&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;should be&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TXREG = TXBuffer[TXCurrentPos];           // send next byte&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;It's important to copy/paste the code directly (using pastebin is great!) because you've actually corrected this yourself in the question - making it hard for people to spot the problem :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This may have been easier to spot yourself if you initialised the buffer to a known value on startup (eg 0x5A).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also mention that you reset the &lt;code&gt;TxCurrentPos&lt;/code&gt; &amp;amp; &lt;code&gt;TxEndPos&lt;/code&gt; variables to zero at some point, but I can't see that in your code. It's best to do this whenever you increment those values. Eg&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TxCurrentPos++;&#xA;TxCurrentPos %= TX_BUFFER_SIZE;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Aside: I like that you've removed the redundant TxBufferSize variable in the question - this follows the &lt;a href=&quot;http://en.wikipedia.org/wiki/Don%27t_repeat_yourself&quot; rel=&quot;nofollow&quot;&gt;DRY Principle&lt;/a&gt; and eliminates the source for an error. Having data duplicated in two spots is asking for trouble.&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-09-20T06:48:54.847" CommentCount="2" />
  <row Id="4466" PostTypeId="2" ParentId="4462" CreationDate="2010-09-20T12:49:07.953" Score="2" ViewCount="" Body="&lt;p&gt;A few things to try:&lt;br&gt;&#xA;1) Make sure your buffer is initialized this will tell you if 0x98 is coming from the buffer or somewhere else.&lt;br&gt;&#xA;2) Disable interrupts when you are adding items to the buffer&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-09-20T12:49:07.953" CommentCount="2" />
  <row Id="4467" PostTypeId="2" ParentId="3939" CreationDate="2010-09-20T12:58:53.193" Score="0" ViewCount="" Body="&lt;p&gt;Microchip also has an example of how to implement a USB mass storage device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en536602&quot; rel=&quot;nofollow&quot;&gt;AN1189 - Implementing a Mass Storage Device&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-09-20T12:58:53.193" />
  <row Id="4468" PostTypeId="2" ParentId="4458" CreationDate="2010-09-20T18:10:32.887" Score="1" ViewCount="" Body="&lt;p&gt;There are lots of reasons to split the instruction cycle into multiple clock cycles.  A good example is accessing the main memory bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most modern processors are Von-Neumann architectures; that is, their code and data both exist in the same memory chip.  Well, if you want to read an instruction, and that instruction is going to load a variable from memory...that's two memory accesses.  But most memory is only single-port (that is, it can only do one read or write per cycle).  So how do you read the instruction &lt;em&gt;and&lt;/em&gt; read your variable?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The solution is to use a two-stage instruction cycle.  The first stage will fetch the instruction from memory, and the second stage can then read (or write!) the variable from main memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some older chips went even further.  Back in the day, if your chip had 16-bits of addressable memory, but the external address bus is only 8-bits, then you would be familiar with the Address Latch Enable.  One clock cycle sends the upper 8-bits of the 16-bit address, and the next clock cycle sends the lower 8-bits.  A third cycle could then read/write the variable from/to memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are other, better reasons to have an instruction cycle that is multiple clock cycles in length.  One of the best reasons is pipelining.  This is a trick that modern processors use to more fully exploit all the execution units available in a chip; for example, while one instruction is being executed, the next is being fetched at the same time.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-09-20T18:10:32.887" CommentCount="2" />
  <row Id="4469" PostTypeId="2" ParentId="4462" CreationDate="2010-09-20T18:21:11.087" Score="1" ViewCount="" Body="&lt;p&gt;I see nothing that makes your buffer circular.  I think you're relying on an overflow to get you from 127 to 0...but an unsigned char can represent the values from 0 to 255.  So your TXCurrentPos is going to walk right off the end of your array.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also seen the PIC C compilers do some weird stuff before for no good reason.  Most compilers can also output the assembled version of the program; it might be worth some time to peruse the assembly listing and see how the C being compiled.  Depending on the data type TXREG is declared as, the compiler might be trying to do a cast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, in your receive code in the interrupt, you &lt;strong&gt;MUST&lt;/strong&gt; check the receiver for an overrun condition and clear it.  Every.  Single.  Time.  The RS232 receiver will refuse to receive additional data while the overrun error bit is set.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void ClearRXOverRun()&#xA;{&#xA;    // If there's a frame overrun, RS232 will refuse to receive&#xA;    if (OERR == 1)&#xA;    {&#xA;        // Clear overrun condition by turning RX off and back on&#xA;        CREN = 0;&#xA;        CREN = 1;   &#xA;    }   &#xA;}   &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1278" LastEditorUserId="1278" LastEditorDisplayName="" LastEditDate="2010-09-22T16:35:14.900" LastActivityDate="2010-09-22T16:35:14.900" CommentCount="6" />
  <row Id="4470" PostTypeId="1" CreationDate="2010-09-20T21:03:03.290" Score="7" ViewCount="260" Body="&lt;p&gt;I seem to be going through soldering tips at a breakneck pace. Four or five hourly sessions, and it's corroded all to hell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does this sound about right, or is there something I should be doing differently? It's a standard 40 watt cheapo iron.&lt;/p&gt;&#xA;" OwnerUserId="989" LastActivityDate="2010-09-24T16:34:19.717" Title="Going through Soldering tips quickly" Tags="&lt;soldering&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="3" />
  <row Id="4471" PostTypeId="2" ParentId="4470" CreationDate="2010-09-20T21:12:53.120" Score="3" ViewCount="" Body="&lt;p&gt;Here are some tips for maintaining your tip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chiphacker.com/questions/216/soldering-iron-maintenance&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/216/soldering-iron-maintenance&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-20T21:12:53.120" />
  <row Id="4472" PostTypeId="2" ParentId="4470" CreationDate="2010-09-20T21:32:10.443" Score="3" ViewCount="" Body="&lt;p&gt;Plated tips last longer ( much longer ) than unplated.  Also a thermostatically regulated tip does not overheat and eat the tip.  Just a couple of tips.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-09-20T21:32:10.443" CommentCount="2" />
  <row Id="4473" PostTypeId="2" ParentId="4470" CreationDate="2010-09-20T22:01:08.080" Score="2" ViewCount="" Body="&lt;p&gt;Tell us more specifically what kind it is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Our Wellers were burning up from the temperature sensor malfunctioning.  They use a magnetic sensor, which we think were ruined by soldering next to the big magnets of loudspeakers, so they were permanently magnetized and stayed on perpetually.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The WTCPx models use a magnet and a bit of iron allow which has its&#xA;  Curie point at the set temp. When the Curie temp is exceeded the&#xA;  magnet is no longer attracted to the alloy piece and the magnet is&#xA;  pulled back by a spring. This motion opens a mechanical switch. These&#xA;  irons will only regulate at the temp labeled on the back of the tip.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.electronicspoint.com/weller-soldering-iron-sensor-t49505.html&quot; rel=&quot;nofollow&quot;&gt;http://www.electronicspoint.com/weller-soldering-iron-sensor-t49505.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-09-20T22:01:08.080" />
  <row Id="4474" PostTypeId="2" ParentId="4462" CreationDate="2010-09-21T04:29:14.830" Score="0" ViewCount="" Body="&lt;p&gt;I'm sorry this might sound really simple, but have you tried writing your data to EEPROM, and then reading later, to verify you are in fact actually assigning the right data to the array? &#xA;If the data that is getting assigned to the buffer isn't valid data then that might be your problem?&lt;/p&gt;&#xA;" OwnerUserId="982" LastActivityDate="2010-09-21T04:29:14.830" />
  <row Id="4475" PostTypeId="1" CreationDate="2010-09-21T04:42:41.413" Score="7" ViewCount="806" Body="&lt;p&gt;I know that lots of people out there feel that autoroute results are not useable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I find that the autorouter is a good way to get a good placement. I use eagle. I do a basic placement, autoroute everything and look where my wire crossings are. Where I can reduce wire length.  ripup, repeat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing is, the eagle router really isn't that good. I often get routes that should be doable with a straight shot, yet eagle insists on adding jogs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I feel that given a good placement, many routes should be obvious. I don't want to click them all by hand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'm looking for something better. &lt;a href=&quot;http://www.toporouter.com/&quot; rel=&quot;nofollow&quot;&gt;toporouter&lt;/a&gt; is intriguing. The problem there is I don't know how to write an output from eagle that it reads.&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2010-10-27T04:43:00.360" CommunityOwnedDate="2010-09-21T12:15:54.840" Title="Which PCB software has the best autorouter?" Tags="&lt;eagle&gt;&lt;pcb&gt;" AnswerCount="6" CommentCount="4" FavoriteCount="3" />
  <row Id="4476" PostTypeId="2" ParentId="1942" CreationDate="2010-09-21T04:43:41.280" Score="0" ViewCount="" Body="&lt;p&gt;I always liked this concept&gt;&#xA;&lt;a href=&quot;http://www.create.ucsb.edu/~dano/CUI/&quot; rel=&quot;nofollow&quot; title=&quot;Create USB&quot;&gt;http://www.create.ucsb.edu/~dano/CUI/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This uses the Pic family to do what you're looking for. You'll probably need a PicKit 2 though (at a minimum) to program it, as I've recently discovered my limitations to the PicKit 1.&lt;/p&gt;&#xA;" OwnerUserId="982" LastActivityDate="2010-09-21T04:43:41.280" />
  <row Id="4477" PostTypeId="2" ParentId="4447" CreationDate="2010-09-21T05:43:12.167" Score="2" ViewCount="" Body="&lt;p&gt;It all depends on what type of smart card that you are trying to read.&#xA;Is it a  mifare card iso 14443 or ISO 7816 iso.  It should confrm to a standard of the card type (the beauty of standards)  The card is made up of different sectors that you can read and write to and a card identity number.  Some sectors are private and need an access code.  So if you have a card writer you can set these sectors as you wish and add your own access code.  A serial read of the card should send back the card number binary which then needs to be converted into hex or decimal.&#xA;If I have a 26bit card reader for a 32bit card then it will not read all of the bits of the card id.  Then also you will need to mask if the reader starts reading at the second bit and where it finishes. Does that make it a bit clearer.  Find what sort of card it is first then go from there. Good luck&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Warren&lt;/p&gt;&#xA;" LastActivityDate="2010-09-21T05:43:12.167" CommentCount="1" />
  <row Id="4478" PostTypeId="2" ParentId="4475" CreationDate="2010-09-21T07:28:11.770" Score="3" ViewCount="" Body="&lt;p&gt;Pulsonix uses the &lt;a href=&quot;http://www.konekt.com/&quot; rel=&quot;nofollow&quot;&gt;Electra&lt;/a&gt; autorouter, as do several other packages; it's very good. It can be used with Eagle.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-09-21T12:32:27.430" LastActivityDate="2010-09-21T12:32:27.430" CommunityOwnedDate="2010-09-21T12:15:54.840" CommentCount="2" />
  <row Id="4479" PostTypeId="2" ParentId="4475" CreationDate="2010-09-21T08:27:43.880" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.altium.com/na/&quot; rel=&quot;nofollow&quot;&gt;Altium&lt;/a&gt; ostensibly now uses &lt;a href=&quot;http://wiki.altium.com/display/ADOH/Topological+Autorouting+-+Mapping+the+Changing+Space&quot; rel=&quot;nofollow&quot;&gt;topological routing&lt;/a&gt;, though I haven't had much of a chance to play with it yet.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-09-21T08:27:43.880" CommunityOwnedDate="2010-09-21T12:15:54.840" CommentCount="3" />
  <row Id="4480" PostTypeId="2" ParentId="4475" CreationDate="2010-09-21T09:41:38.837" Score="7" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.freerouting.net/index.php?page=eagle&quot; rel=&quot;nofollow&quot;&gt;Freerouting&lt;/a&gt; has an improved autorouter for Eagle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://jeelabs.org/2009/05/17/better-pcb-auto-routing/&quot; rel=&quot;nofollow&quot;&gt;http://jeelabs.org/2009/05/17/better-pcb-auto-routing/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-21T09:41:38.837" CommunityOwnedDate="2010-09-21T12:15:54.840" />
  <row Id="4481" PostTypeId="2" ParentId="4475" CreationDate="2010-09-21T12:52:17.013" Score="2" ViewCount="" Body="&lt;p&gt;Well, I'm one of those people that don't use autorouter, but, if you want to use it, I would recommend &lt;a href=&quot;http://www.freerouting.net/index.php?page=home&quot; rel=&quot;nofollow&quot;&gt;FreeROUTE&lt;/a&gt; and, to keep everything free, use &lt;a href=&quot;http://www.lis.inpg.fr/realise_au_lis/kicad/&quot; rel=&quot;nofollow&quot;&gt;KiCAD&lt;/a&gt; for schematics and everything else!&lt;/p&gt;&#xA;" OwnerUserId="940" LastActivityDate="2010-09-21T12:52:17.013" CommunityOwnedDate="2010-09-21T12:52:17.013" />
  <row Id="4482" PostTypeId="1" CreationDate="2010-09-21T12:57:23.710" Score="4" ViewCount="468" Body="&lt;p&gt;I built a mod-16 counter, and the output result is a INTEGER (all the examples I saw used INTEGER).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I built a hex-to-7-segment-display decoder, and its input is a STD_LOGIC_VECTOR (wrote it that way because it was easy to map out the truth table).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to connect the output of the counter to the input of the decoder, but I get 'type mismatch' errors when trying to compile in QuartusII.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Is there a way to convert from a INTEGER type to a STD_LOGIC_VECTOR type in a VHDL listing?&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2011-06-05T16:03:03.267" Title="VHDL: Converting from an INTEGER type to a STD_LOGIC_VECTOR" Tags="&lt;vhdl&gt;" AnswerCount="4" />
  <row Id="4483" PostTypeId="2" ParentId="4470" CreationDate="2010-09-21T16:20:15.053" Score="0" ViewCount="" Body="&lt;p&gt;Okay, basics:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You have a sponge and you're using it&#xA;in an OCD-like fashion right? &lt;/li&gt;&#xA;&lt;li&gt;Do you&#xA;have temperature control?  Lower the&#xA;temperature. &lt;/li&gt;&#xA;&lt;li&gt;You tin the tip a little&#xA;before applying it to the pad,&#xA;correct? &lt;/li&gt;&#xA;&lt;li&gt;Do you have a tip tinner&#xA;and/or brass sponge?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-21T16:20:15.053" />
  <row Id="4484" PostTypeId="2" ParentId="4482" CreationDate="2010-09-21T17:35:41.183" Score="2" ViewCount="" Body="&lt;p&gt;Let's say that your 4-bit counter had an INTEGER output SOME_INTEGER, and you wanted to convert it to a 4-bit STD_LOGIC_VECTOR&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;SOME_VECTOR &amp;lt;= conv_std_logic_vector(SOME_INTEGER, 4);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You can also use this to initialize vectors with meaningful numbers&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;SOME_VECTOR &amp;lt;= conv_std_logic_vector(9, 4); -- instead of &quot;1001&quot;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I think you may need to add &quot;use IEEE.STD_LOGIC_ARITH.ALL;&quot; and/or STD_LOGIC_UNSIGNED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The complementary operation is conv_integer(vector).  I like to use this when I do comparisons.  So I might declare&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;constant SOME_CONSTANT : integer := 999;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And then, later, I can use this in an if statement&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if (conv_integer(SOME_VECTOR)=SOME_CONSTANT)&#xA;  then OTHER_VECTOR &amp;lt;= (others =&amp;gt; '0');&#xA;end if;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;EDIT: You shouldn't need to declare the variable as an Integer.  Try changing the declaration to std_logic_vector instead.  The + and - operators work on std_logic_vectors.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastEditorUserId="1278" LastEditorDisplayName="" LastEditDate="2010-09-21T17:45:10.463" LastActivityDate="2010-09-21T17:45:10.463" CommentCount="3" />
  <row Id="4486" PostTypeId="2" ParentId="4470" CreationDate="2010-09-22T04:00:39.900" Score="0" ViewCount="" Body="&lt;p&gt;Two things I have experienced:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The tip is dirty (like: caked-on vulcanized whatever that refuses to come off). Thermal shock (loading the tip with solder, aggressive scrubbing against a wet sponge, repeat) will help break this up, although you may also need a tip tinner (again, aggressive scrubbing). Prevent this by always cleaning and tinning the tip before turning the iron off.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Pieces of the tip going away - chunks missing. The temperature of the iron is (way) too hot.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="906" LastActivityDate="2010-09-22T04:00:39.900" />
  <row Id="4493" PostTypeId="2" ParentId="1893" CreationDate="2010-09-22T17:37:13.103" Score="1" ViewCount="" Body="&lt;p&gt;If you are looking to FAB more complex boards, you can try International Circuits &lt;a href=&quot;http://www.internationalcircuits.com&quot; rel=&quot;nofollow&quot;&gt;http://www.internationalcircuits.com&lt;/a&gt;. Overall they look to be a little more expensive that GP for 2 layer bare boards, but once you need extra features i.e. 5/5 trace and space, 10-12 mil drill holes, 4 layer and up they become a much better value.&lt;/p&gt;&#xA;" LastActivityDate="2010-09-22T17:37:13.103" CommunityOwnedDate="2010-09-22T17:37:13.103" />
  <row Id="4495" PostTypeId="1" CreationDate="2010-09-22T19:33:47.730" Score="3" ViewCount="195" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://chiphacker.com/questions/3760/moderately-priced-6-layer-pcb-fab&quot;&gt;moderately priced 6-layer PCB fab?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I'm sure this topic has been done to death, but I really have no experience ordering multi layer boards (most complex ones I've done is 1 and 2 layers from Gold Phoenix). For this specific design (8&quot; x 9&quot;, 5/5 trace and space, ENIG finish, black solder, yellow silkscreen) GP would charge about $700+, which is really out of my price range. Based on some postings on chiphacker, I found the following companies and their pricing:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;International Circuits - &lt;a href=&quot;http://www.internationalcircuits.com&quot; rel=&quot;nofollow&quot;&gt;http://www.internationalcircuits.com&lt;/a&gt; ($365.00)&lt;br&gt;&#xA;PCB Universe  - &lt;a href=&quot;http://www.pcbuniverse.com&quot; rel=&quot;nofollow&quot;&gt;http://www.pcbuniverse.com&lt;/a&gt; ($461.00) &lt;br&gt; &#xA;PCB wing - &lt;a href=&quot;http://www.pcbwing.com&quot; rel=&quot;nofollow&quot;&gt;http://www.pcbwing.com&lt;/a&gt; ($596.25)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looks like these companies besides pcb wing have US based customer service (which is a real positive for me). International Circuits obviously looks good, but I guess the main question I'm trying to ask is if anyone has tried them before and if there are other recommendations out there. Just trying to finish up a grad project, so every penny counts for me. &lt;/p&gt;&#xA;" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-09T01:30:03.647" LastActivityDate="2011-02-09T01:30:03.647" ClosedDate="2010-09-23T22:55:53.203" Title="Cheap 6 Layer PCB Manufacturers" Tags="&lt;pcb-fabrication&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="4496" PostTypeId="2" ParentId="4495" CreationDate="2010-09-22T19:41:36.900" Score="1" ViewCount="" Body="&lt;p&gt;See &lt;a href=&quot;http://chiphacker.com/questions/3760/moderately-priced-6-layer-pcb-fab&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/3760/moderately-priced-6-layer-pcb-fab&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-22T19:41:36.900" />
  <row Id="4497" PostTypeId="1" CreationDate="2010-09-23T02:37:41.857" Score="3" ViewCount="420" Body="&lt;p&gt;How can you control the speed of an AC water pump? In particular, this one: &lt;a href=&quot;http://www.watergarden.org/s.nl/it.A/id.70/.f?sc=2&amp;amp;category=44&quot; rel=&quot;nofollow&quot;&gt;http://www.watergarden.org/s.nl/it.A/id.70/.f?sc=2&amp;amp;category=44&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My guess is that PWM won't work on an AC motor? I've heard that controlling the voltage will change it's speed...is this true? If so, how can I control the voltage via microcontroller (arduino probably)?&lt;/p&gt;&#xA;" OwnerUserId="1140" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-09-23T04:18:11.880" LastActivityDate="2010-09-25T13:46:28.623" Title="Controlling water pump speed" Tags="&lt;ac&gt;&lt;motor&gt;&lt;control&gt;&lt;triac&gt;&lt;speedcontroller&gt;" AnswerCount="2" />
  <row Id="4498" PostTypeId="2" ParentId="4497" CreationDate="2010-09-23T04:17:46.607" Score="7" ViewCount="" Body="&lt;p&gt;AC motors are not as easy to speed control as DC motors; their torque is related to both the applied voltage and the applied frequency. This is known as the Volts:Hz ratio.  In order to maintain torque at a speed other than its rated speed, you need to adjust the frequency in proportion to the voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to do it right, you rectify the AC into a DC bus and then use IGBTs to chop up the bus (using PWM) to generate an AC waveform at the frequency and average voltage you need. This is not quite as simple as it sounds, and single-phase AC motors have capacitors which are the sworn enemies of active devices such as IGBTs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All is not lost, though: If you can live with the torque drop-off you can simply phase back the voltage applied to the motor using a triac. Use an optocoupler to detect when the AC wave crosses zero and then use that as a reference point to drive a timer which controls where in the AC wave that you turn on the triac. This is classic phase angle firing or phase angle control and works for general dimmer applications for lighting and heating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have something in your favour: most water pumps are a cube-log load; the torque requirements drop off drastically as the speed of the pump drops. If you have a positive-displacement type of water pump (piston pumps) you will not be so lucky, but centrifugal and impeller type pumps are fairly easy to slow down.  You should be able to get close to a 2:1 speed reduction and still move water, but no more.  Also remember that you may not be able to meet the static head requirements of your system if you slow down too much; the pump simply will not be able to make the head pressure required.  You won't break anything, but it may not work as well as you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of this should be VERY doable with an arduino or other small microcontroller. I used to design three phase motor controllers using the PIC microcontrollers available in the late 90s. Just keep in mind that you will be playing with line voltage; use optical isolation both for detecting zero crossings and for driving the thyristor, and work slowly and deliberately when you're testing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that if you just want a knob to turn down the pump you can do it without any microcontroller at all using a diac and a triac. Do some web searches for resistive heater controllers or soldering iron temperature control, or &quot;phase angle&quot; triac controllers. Tons of examples online.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-09-23T04:17:46.607" CommentCount="4" />
  <row Id="4502" PostTypeId="1" AcceptedAnswerId="4504" CreationDate="2010-09-23T15:13:22.883" Score="3" ViewCount="391" Body="&lt;p&gt;I need to buffer an audio signal (feeding into a variable input impedance), and make it mutable with a digital control.  The best thing I can think of is an op-amp (maybe &lt;a href=&quot;http://www.st.com/stonline/products/literature/ds/6031/ts971.htm&quot; rel=&quot;nofollow&quot;&gt;TS971&lt;/a&gt;? 3×2 mm SOT23) feeding into an analog switch, like &lt;a href=&quot;http://www.onsemi.com/PowerSolutions/product.do?id=NLAS4599&quot; rel=&quot;nofollow&quot;&gt;NLAS4599&lt;/a&gt; (3×3 mm TSOP-6), but this requires several external components (&lt;a href=&quot;http://www.geofex.com/article_folders/cd4053/cd4053.htm&quot; rel=&quot;nofollow&quot;&gt;example circuits&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone know of anything better?  A tiny IC that acts as both a unity-gain buffer and a digitally-controlled mute?  Supplies are 4.5 V and ground, signal is biased to half that, and the mute and unmute transitions should be pop-free.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-09-24T20:41:31.420" LastActivityDate="2011-01-04T22:22:22.400" Title="Tiny, cheap audio buffer with mute?" Tags="&lt;audio&gt;&lt;op-amp&gt;&lt;buffer&gt;" AnswerCount="3" />
  <row Id="4504" PostTypeId="2" ParentId="4502" CreationDate="2010-09-23T17:43:22.307" Score="2" ViewCount="" Body="&lt;p&gt;Would any old op-amp/buffer with a shutdown signal be sufficient? Digikey has TONS of options if this is acceptable. &lt;s&gt;MAX9812 is a SC70-6 package, for example.&lt;/s&gt; (Not a buffer.  &lt;a href=&quot;http://www.national.com/pf/LM/LMV341.html&quot; rel=&quot;nofollow&quot;&gt;LMV341&lt;/a&gt; is a single op-amp with shutdown in an SC70-6 package.)&lt;/p&gt;&#xA;" OwnerUserId="974" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-23T19:40:45.173" LastActivityDate="2010-11-23T19:40:45.173" CommentCount="5" />
  <row Id="4508" PostTypeId="1" CreationDate="2010-09-24T14:35:41.403" Score="2" ViewCount="218" Body="&lt;p&gt;I want to send a signal through the DC power lines used in railway compartments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you please help me to do that, or provide some documents or links?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-09-24T14:42:33.450" LastActivityDate="2010-09-24T19:35:57.717" Title="DC power line communications" Tags="&lt;dc&gt;&lt;signal&gt;&lt;power&gt;&lt;line&gt;&lt;communication&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="4509" PostTypeId="2" ParentId="4508" CreationDate="2010-09-24T15:01:31.277" Score="1" ViewCount="" Body="&lt;p&gt;Take a look at &lt;a href=&quot;http://chiphacker.com/questions/3663/power-line-communication-principles&quot; rel=&quot;nofollow&quot;&gt;http://chiphacker.com/questions/3663/power-line-communication-principles&lt;/a&gt; to start.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-09-24T15:01:31.277" CommentCount="2" />
  <row Id="4510" PostTypeId="2" ParentId="4470" CreationDate="2010-09-24T16:34:19.717" Score="2" ViewCount="" Body="&lt;p&gt;One thing I haven't seen mentioned yet is this: Whenever you are planning on not using the iron for more than about a minute, load the tip with solder. This way, the solder oxidizes in the air, instead of your tip. An unprotected tip will start to oxidize pretty quickly in air, and the longer it is allowed to do so, the worse it gets. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you are ready to use the iron, do the following:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;knock the solder off into a jar&lt;/li&gt;&#xA;&lt;li&gt;flash the tip on a sponge (cover the sponge with a paper towel so your sponge stays clean) &lt;/li&gt;&#xA;&lt;li&gt;and get to work.&lt;/li&gt;&#xA;&lt;li&gt;As soon as you're done, recoat the whole working surface with solder.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Tips oxidize dramatically faster when they're too hot, so check your temperature if you can.&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-09-24T16:34:19.717" />
  <row Id="4511" PostTypeId="1" AcceptedAnswerId="4513" CreationDate="2010-09-24T16:47:55.683" Score="3" ViewCount="162" Body="&lt;p&gt;Some cell phones are TTY/TDD (telecommunications device for the deaf) compatible, meaning a terminal can be plugged into the headset jack for text communications. Is it just a hidden RS-232 interface?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-09-24T17:43:32.357" Title="What protocol does a TDD/TTY use to communicate with a cell phone's headset jack?" Tags="&lt;cellphone&gt;" AnswerCount="1" />
  <row Id="4513" PostTypeId="2" ParentId="4511" CreationDate="2010-09-24T17:43:32.357" Score="6" ViewCount="" Body="&lt;p&gt;TTY/TDD uses tones in the audio band (similar but not compatible with the old Hayes modems) to communicate over telephone lines.  The original protocol uses Baudot code at 45.5 or 50 baud.  In 1994 the ITU  approved a newer V.18 standard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I would presume the headset jack would just pass these tones back and forth to a TTY/TDD modem.  It would not be a hidden RS-232 interface -- i.e. the cellphone is not acting as the modem.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-09-24T17:43:32.357" CommentCount="2" />
  <row Id="4514" PostTypeId="2" ParentId="4508" CreationDate="2010-09-24T19:35:57.717" Score="2" ViewCount="" Body="&lt;p&gt;For model railways the predominant standard is &lt;a href=&quot;http://en.wikipedia.org/wiki/Digital_Command_Control&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Digital_Command_Control&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-09-24T19:35:57.717" />
  <row Id="4515" PostTypeId="1" AcceptedAnswerId="4517" CreationDate="2010-09-24T20:08:35.073" Score="9" ViewCount="1265" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How should I route USB Connector shield on PCB? Should it be connected to GND plane right where USB is placed, or should  the shield be isolated from GND, or should it be connected to ground through ESD protection chip, high resistance resistor or fuse?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. Should I put the shield connections on schematic, or just route it on PCB?&lt;/p&gt;&#xA;" OwnerUserId="1177" LastActivityDate="2011-02-27T17:22:33.803" Title="How to connect USB Connector shield?" Tags="&lt;usb&gt;&lt;shield&gt;&lt;connector&gt;&lt;layout&gt;&lt;pcb&gt;" AnswerCount="7" CommentCount="2" FavoriteCount="2" />
  <row Id="4516" PostTypeId="2" ParentId="4515" CreationDate="2010-09-24T21:49:58.987" Score="-2" ViewCount="" Body="&lt;p&gt;The shield shouldn't be grounded. It is grounded at the host end, of course.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-09-24T21:49:58.987" CommentCount="5" />
  <row Id="4517" PostTypeId="2" ParentId="4515" CreationDate="2010-09-24T21:50:19.223" Score="3" ViewCount="" Body="&lt;p&gt;Check to see if the manufacturer of your USB chip specs out what you should use.  I'm pretty sure Cypress recommends a 1M resistor and 4.7nf cap connecting the shield to ground.  The two shield holes should be connected with a very large trace (I believe they suggested 100 mils?)&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-09-24T21:50:19.223" />
  <row Id="4518" PostTypeId="2" ParentId="4515" CreationDate="2010-09-24T23:16:34.917" Score="1" ViewCount="" Body="&lt;p&gt;Well, since it appears we need another answer, I'll put in my vote for grounding it through an ESD protection chip, like the &lt;a href=&quot;http://www.st.com/stonline/products/literature/ds/11265.pdf&quot; rel=&quot;nofollow&quot;&gt;USBLC6&lt;/a&gt;.  It's worked well for me on several projects - No apparent destruction of components through ESD, and no issues with data integrity.  I feel that it would be at least a little suspicious if STmicroelectronics manufactures such a chip, and is aware that a resistor, capacitor, or short to ground would be just as good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know if this success is because it's the right thing to do, or just dumb luck.  Given the wide variety of responses, I'd be tempted to say that no one does.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At work, we tie Ethernet jacks straight to ground. AFAIK, this is the same as the issue at hand, even though the Ethernet cable carries no ground signal. It seems to work, and was decided by someone with more experience than myself.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-24T23:16:34.917" />
  <row Id="4519" PostTypeId="2" ParentId="4515" CreationDate="2010-09-25T03:59:13.950" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;4 Connect the SHIELD connection to&#xA;  GND through a resistor. This helps &#xA;  isolate it and reduces EMI and RFI &#xA;  emissions. Keep this resistor close &#xA;  to the USB connector. Some &#xA;  experimentation may be necessary to &#xA;  obtain the correct value.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;5 Provide a plane for the USB shield&#xA;  on the signal layer adjacent to the&#xA;  VCC plane that is no larger than the&#xA;  USB header.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cypress.com/?docID=4398&quot; rel=&quot;nofollow&quot;&gt;http://www.cypress.com/?docID=4398&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The principal challenge of full speed&#xA;  device EMI compliance is preventing&#xA;  high frequency energy from coupling to&#xA;  the shield.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Full speed devices use a shielded&#xA;  cable which requires that the&#xA;  connector shell be tied to the ground&#xA;  plane. It is important to note that a&#xA;  ground plane does not behave like an&#xA;  equipotential surface at high&#xA;  frequencies. The location of the&#xA;  connector shell’s termination to the&#xA;  Gnd plane is critical. The connection&#xA;  needs to be made to the quietest area&#xA;  of the ground plane to prevent noise&#xA;  from the ground plane from coupling to&#xA;  the shield...&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ti.com/sc/docs/apps/msp/intrface/usb/emitest.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.ti.com/sc/docs/apps/msp/intrface/usb/emitest.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;etc.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Google for &quot;USB guidelines&quot;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-09-25T03:59:13.950" />
  <row Id="4520" PostTypeId="2" ParentId="4497" CreationDate="2010-09-25T13:46:28.623" Score="2" ViewCount="" Body="&lt;p&gt;Assuming that the reason for varying the speed of a pump motor is to do flow control, why not just place a valve on the output and regulate the flow by adjusting the valve?  &lt;/p&gt;&#xA;" LastActivityDate="2010-09-25T13:46:28.623" CommentCount="1" />
  <row Id="4521" PostTypeId="1" AcceptedAnswerId="4522" CreationDate="2010-09-25T20:25:54.260" Score="3" ViewCount="274" Body="&lt;p&gt;We all share a common interest in electronics and there as some articles, essays, papers, books, podcasts, videocasts, or any other things that just &lt;em&gt;blow our minds&lt;/em&gt;. Please share something of that sort so others can also take part in the joy.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-19T18:05:35.187" LastActivityDate="2010-12-19T18:05:35.187" CommunityOwnedDate="2010-09-25T20:39:51.180" Title="Share your favourite reads." Tags="&lt;books&gt;&lt;education&gt;&lt;website&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="3" />
  <row Id="4522" PostTypeId="2" ParentId="4521" CreationDate="2010-09-25T20:39:42.350" Score="3" ViewCount="" Body="&lt;p&gt;Here's an OPML dump of all the tech blogs I read. Enjoy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.hodgepig.org/tech-subs.opml&quot; rel=&quot;nofollow&quot;&gt;http://www.hodgepig.org/tech-subs.opml&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-25T20:39:42.350" CommunityOwnedDate="2010-09-25T20:39:51.180" CommentCount="3" />
  <row Id="4523" PostTypeId="2" ParentId="4521" CreationDate="2010-09-25T21:49:31.437" Score="1" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.adafruit.com/blog&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/blog&lt;/a&gt; - reposts a LOT of stuff, hard to keep up with&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.electronics-lab.com/blog&quot; rel=&quot;nofollow&quot;&gt;http://www.electronics-lab.com/blog&lt;/a&gt; - lots of projects and stuff.  They'll pay you $80 for an original project that you publish on their site&lt;/li&gt;&#xA;&lt;li&gt;Engadget - feeds from tags that might show stuff I've designed, or competitors&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://amasci.com/ele-edu.html&quot; rel=&quot;nofollow&quot;&gt;http://amasci.com/ele-edu.html&lt;/a&gt; - Intuitive descriptions of things that are not intuitive, electronics mythbusting&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://blog.screamingcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;http://blog.screamingcircuits.com/&lt;/a&gt; - PCB layout tips&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.swharden.com/blog&quot; rel=&quot;nofollow&quot;&gt;http://www.swharden.com/blog&lt;/a&gt; - Python + microcontrollers, sending signals across the ocean with a few mW&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://prometheusfusionperfection.com/&quot; rel=&quot;nofollow&quot;&gt;http://prometheusfusionperfection.com/&lt;/a&gt; - trying to build Bussard's Polywell fusion reactor&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://linuxhaters.blogspot.com/&quot; rel=&quot;nofollow&quot;&gt;http://linuxhaters.blogspot.com/&lt;/a&gt; - :D&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://ericarcher.net/devices/&quot; rel=&quot;nofollow&quot;&gt;http://ericarcher.net/devices/&lt;/a&gt; - cool/weird audio projects&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://gieskes.nl/circuitbending&quot; rel=&quot;nofollow&quot;&gt;http://gieskes.nl/circuitbending&lt;/a&gt; - cool/weird audio projects&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Also I subscribe to the RSS feed for this weird site called Chiphacker.  Not sure what that's all about...&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-09-25T21:49:31.437" CommunityOwnedDate="2010-09-25T21:49:31.437" />
  <row Id="4524" PostTypeId="2" ParentId="4521" CreationDate="2010-09-25T23:22:03.640" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.graffe.com/forums/forum.php&quot; rel=&quot;nofollow&quot;&gt;http://www.graffe.com/forums/forum.php&lt;/a&gt; - Lots of things of general interest, gaming discussion, political and news.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2010-09-25T23:22:03.640" CommunityOwnedDate="2010-09-25T23:22:03.640" />
  <row Id="4525" PostTypeId="1" CreationDate="2010-09-26T00:13:29.300" Score="10" ViewCount="248" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm getting ready to hire an electrical engineer for a small contract job - creating a prototype.  What I'd like to know is, what should I have him deliver to me when the project is complete?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I imagine schematics, the prototype, parts list would be standard, but what am I missing?  Should I ask for an auto-cad file - not sure what this is yet...  Are there other things that I would need in the future for a different engineer to take over the project?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simply, what should I be asking for?&lt;/p&gt;&#xA;" OwnerUserId="1044" LastActivityDate="2011-05-18T11:37:44.847" Title="What should a contract Electrical Engineer Deliver once a project is complete?" Tags="&lt;electronics&gt;&lt;hire&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="4526" PostTypeId="2" ParentId="4525" CreationDate="2010-09-26T02:49:43.857" Score="3" ViewCount="" Body="&lt;p&gt;If they're in your hire, you should expect any designs they made while working for you, notes regarding their designs, any reports made during the process (incluing the final one), and pretty much anything else that related to the contract.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2010-09-26T02:49:43.857" CommentCount="4" />
  <row Id="4527" PostTypeId="2" ParentId="4525" CreationDate="2010-09-26T06:50:32.923" Score="6" ViewCount="" Body="&lt;p&gt;Assuming the engineer will be creating a printed circuit board (PCB), they will be using some sort of schematic capture and PCB layout program.  You want to get a copy of his design files (not just the final output, such as a PDF of the schematic), so that they can be turned over to another engineer in the future if needed.  Otherwise the second engineer would have to recreate the design files from the drawings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, I use &lt;a href=&quot;http://www.cadsoftusa.com/&quot; rel=&quot;nofollow&quot;&gt;Eagle PCB&lt;/a&gt;, so the relevant files would be the schematic (.sch) and layout (.brd) files, along with any custom parts that I have added to a library (.lbr files).  Also any unique design rule checks (.dru) and tooling files (.cam).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although the Gerber files, which are sent to a board house to make the PCB, can be recreated from the design files, it would be a good idea to get a copy of those also.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is no standard for the part-list (a.k.a a Bill of Materials, or BOM), but they are usually created using a spreadsheet such as Excel (.xls file).  Make sure the engineer provides a source for each part, such as a &lt;a href=&quot;http://www.digikey.com/&quot; rel=&quot;nofollow&quot;&gt;Digi-Key&lt;/a&gt; part number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a prototype case is being made, for example with SolidWorks or other CAD software then you will want to get the relevant files for that as well.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-09-26T06:50:32.923" CommentCount="2" />
  <row Id="4528" PostTypeId="1" AcceptedAnswerId="4532" CreationDate="2010-09-26T10:19:24.457" Score="2" ViewCount="484" Body="&lt;p&gt;Hi, I'm looking to a simple solution to keep the position of a robot. It has two DC motor and one wheel encoder for each. The encoder are incremental type.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to be able to get the current count of increment from an atmega.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found some chip like the LM628/629 who will do great job, too great in fact, because it cost ~50$. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you know a dedicated IC that has only the count (in both direction) features for a wheel encoder, Or is it possible to make à simple one with an attiny ?&lt;/p&gt;&#xA;" OwnerUserId="824" LastActivityDate="2011-03-02T23:22:00.193" Title="how to count 2 wheel encoder signal?" Tags="&lt;robotics&gt;&lt;wheel&gt;&lt;encoder&gt;&lt;motor&gt;" AnswerCount="3" />
  <row Id="4529" PostTypeId="2" ParentId="4528" CreationDate="2010-09-26T11:32:02.950" Score="2" ViewCount="" Body="&lt;p&gt;Wheel encoders are very easy to use for dead-reckoning systems. If you have just a slotted wheel and two detectors it'll be a quadrature encoder; you call one of the signals your clock and the other one your direction. Get both signals into your microcontroller and either set it up so that it counts clock pulses (i.e. an event counting algorithm). Whenever you get a clock pulse, check the direction line. It will always be '1' for one direction and '0' for the other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fancier (more expensive) encoders are usually Grey code encoders and are less suitable for dead reckoning, although they will give you better dead reckoning position due to their higher accuracy. You could feed the output of one of them into your microcontroller and have an interrupt or timer that reads the position of the wheels and determines how far and in which direction the robot moved.  This is a more complicated solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be aware that dead reckoning systems &lt;em&gt;do&lt;/em&gt; drift over time and unless you have some means of resetting the dead reckoning system your robot's idea of where it is in space will become more and more inaccurate.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-09-26T11:32:02.950" CommentCount="4" />
  <row Id="4530" PostTypeId="2" ParentId="4382" CreationDate="2010-09-27T03:09:39.377" Score="2" ViewCount="" Body="&lt;p&gt;Often FPGAs get used specifically to do tasks a microcontroller cannot do efficiently, such as highly parallel or low latency operations, operating in multiple clock domains, or doing custom logic at hardware speeds. As such, they'll do the heavy lifting, and you rarely need an MCU to be central to the design - they may be moved to management positions, such as loading the configuration bitstream. An example of this is the PIC or ARM in the &lt;a href=&quot;http://en.wikipedia.org/wiki/Minimig&quot; rel=&quot;nofollow&quot;&gt;Minimig&lt;/a&gt;, which implements the storage interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few products blur the lines, however. Some examples:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Larger FPGAs tend to have hard CPUs built in (larger projects often need them anyhow), just as they have RAM and multiplier blocks&lt;/li&gt;&#xA;&lt;li&gt;Some microcontrollers aim at parallel operations (XMOS XS1, Atmel Xmega, GreenArray, Parallax Propeller)&lt;/li&gt;&#xA;&lt;li&gt;Some chips are designed as hybrids (Cypress PSoC, Atmel FPSLIC)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Coming from an imperative programming background, it is quite an adjustment to design in hardware as you need to gain the advantages of FPGAs. You'll find the experience useful elsewhere too, however.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-09-27T03:09:39.377" />
  <row Id="4531" PostTypeId="1" AcceptedAnswerId="4533" CreationDate="2010-09-27T04:05:16.467" Score="6" ViewCount="645" Body="&lt;p&gt;I'm trying to transmit from an ATtiny85 to a PC using Arduino-esque code over a USB-Serial converter without understanding very much of anything.  I was shocked and appalled that it did not work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I confirmed that the tiny is flickering the voltage on one of its pins, but when I connect that pin to transmit or receive on the USB-serial cable and try to listen using a terminal program, I get nothing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure how to tell which part is broken.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Do I need more than VCC, GND, and TXD to transmit serial?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Details:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The code for the tiny is written in the Arduino environment and similar code successfully blinks all 4 &quot;PORTB&quot; pins, at least according to the LEDs.  I use the &lt;a href=&quot;http://hlt.media.mit.edu/wiki/pmwiki.php?n=Main.ArduinoATtiny4585&quot; rel=&quot;nofollow&quot;&gt;code from HLT and Saporetti&lt;/a&gt; to let me use the Arduino dialect of C++ to program it.  The program still comes in under a K.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;SoftwareSerial.h&amp;gt;&#xA;&#xA;SoftwareSerial s(0,1); //receive on &quot;0&quot;, and transmit on &quot;1&quot; aka &quot;PB1&quot; aka pin 6&#xA;&#xA;void setup() { s.begin(4800); } // assuming 1Mhz, 4800 baud&#xA;void loop() { s.println(millis()); } // transmit something at every opportunity&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;There's a lot of translation involved, but the code is pretty basic.  The code that sets the baud rate seems to assume 1MHz, but luckily my attiny has factory default fuses and runs at 1MHz.  At any rate, pin 6 is flickering its voltage according to the LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I use the little wires to connect the &quot;ftdi&quot; end of the &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=33&amp;amp;products_id=70&quot; rel=&quot;nofollow&quot;&gt;FTDI USB-serial converter&lt;/a&gt; to the tiny: black to GND, red to VCC, orange to 6.  I open the program &quot;minicom&quot; on the PC, set the baud rate to 4800 and wait, for nothing.  When talking to my &lt;a href=&quot;http://www.ladyada.net/make/boarduino/&quot; rel=&quot;nofollow&quot;&gt;Boarduino&lt;/a&gt;, it has no trouble.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The FTDI converter cable has the following pinout: black is GND, brown is &quot;CTS&quot;, red is VCC (+4.98V), orange is &quot;TXD&quot;, yellow is &quot;RXD&quot;, green is &quot;RTS&quot;.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If I want to transmit from the tiny to the PC, should I be flickering the voltage on &quot;TXD&quot; or &quot;RXD&quot;?  In other words is the transmit wire to transmit from the slave to the host, or the host to the slave?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I actually tried both, neither worked.  I've fried less than a dollar's worth of equipment so far, and I'm getting cocky, so I just plug wires into the cable.  Maybe I'm not supposed to ignore the &quot;CTS&quot; and &quot;RTS&quot; wires?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Do I need to use any other wires?  Do RTS and CTS do anything?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The hardware is an ATTiny85-PU (DIP-8 package, running at 1MHz, rated to 20MHz) powered by USB at 4.98V.  The host PC is a MacBook, and it successfully does all things arduino, including using ArduinoISP to program the ATtiny to blink its little heart out.&lt;/p&gt;&#xA;" OwnerUserId="1271" LastEditorUserId="1271" LastEditorDisplayName="" LastEditDate="2010-09-27T18:56:23.890" LastActivityDate="2010-09-30T04:21:44.823" Title="Serial newbie: why can't I just hook the wires up?" Tags="&lt;attiny&gt;&lt;arduino&gt;&lt;serial&gt;&lt;ftdi&gt;&lt;usb&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="4532" PostTypeId="2" ParentId="4528" CreationDate="2010-09-27T04:50:55.090" Score="4" ViewCount="" Body="&lt;p&gt;&lt;em&gt;&quot;Do you know a dedicated IC that has only the count (in both direction) features&quot;&lt;/em&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may be surprised to learn that a few simple, cheap, generic logic chips are sufficient to decode a rotary encoder -- it doesn't require some special chip specifically customized for rotary decoders.&#xA;The &lt;a href=&quot;http://www.mindspring.com/~tom2000/Delphi/Codewheel.html&quot; rel=&quot;nofollow&quot;&gt;Codewheel Generator Page&lt;/a&gt;&#xA;has a few relatively simple circuits that decode the 2 rotary quadrature outputs into a &quot;direction&quot; and &quot;count&quot; outputs.&#xA;Those outputs can be wired into the &quot;direction&quot; and &quot;clock&quot; inputs of any up/down counter -- such as, for example, the CD4029, the CD4516, the CD40193, 74HC193, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&quot;is it possible to make à simple one with an attiny&quot;&lt;/em&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, you can make a simple quadrature encoder with an ATtiny.&#xA;Some tips for connecting a quadrature encoder to a Atmel chip and decoding it in software are at:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://abrobotics.tripod.com/Ebot/using_encoder.htm&quot; rel=&quot;nofollow&quot;&gt;Alex Brown's Robotics Page: Using Encoders&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/playground/Main/RotaryEncoders&quot; rel=&quot;nofollow&quot;&gt;Arduino Playground wiki: Reading Rotary Encoders&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.neufeld.newton.ks.us/electronics/?p=248&quot; rel=&quot;nofollow&quot;&gt;Keith's Electronics Blog: LED Calculator with Rotary Quadrature Encoder&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you have relatively few pulses-per-second, you might be able to run the 2 signals from each encoder directly into your main ATmega and use the above techniques to do it all in software, without any external conversion hardware.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-27T04:50:55.090" />
  <row Id="4533" PostTypeId="2" ParentId="4531" CreationDate="2010-09-27T05:02:48.810" Score="3" ViewCount="" Body="&lt;p&gt;You can definitely transmit data using just TX &amp;amp; GND.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Firstly, you want to hook up the ATtiny85 TX line to the FTDI RX line (yellow on the TTL-232R). Make sure that the USB adapter can handle 5V - I'm fairly sure even the 3.3V TTL-232R is 5V tolerant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to the example page for &lt;a href=&quot;http://arduino.cc/en/Reference/SoftwareSerialExample&quot; rel=&quot;nofollow&quot;&gt;SoftwareSerial&lt;/a&gt;, you need to set the direction of the TX &amp;amp; RX lines in your setup function:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// include the SoftwareSerial library so you can use its functions:&#xA;#include &amp;lt;SoftwareSerial.h&amp;gt;&#xA;&#xA;#define rxPin 2&#xA;#define txPin 3&#xA;#define ledPin 13&#xA;&#xA;// set up a new serial port&#xA;SoftwareSerial mySerial =  SoftwareSerial(rxPin, txPin);&#xA;byte pinState = 0;&#xA;&#xA;void setup()  {&#xA;  // define pin modes for tx, rx, led pins:&#xA;  pinMode(rxPin, INPUT);&#xA;  pinMode(txPin, OUTPUT);&#xA;  pinMode(ledPin, OUTPUT);&#xA;  // set the data rate for the SoftwareSerial port&#xA;  mySerial.begin(9600);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The baudrate will be 4800 in your case. The SoftwareSerial library doesn't seem to support CTS &amp;amp; RTS, so just make sure you aren't using them on the host software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out the &lt;a href=&quot;http://www.arduino.cc/en/Reference/SoftwareSerial&quot; rel=&quot;nofollow&quot;&gt;reference&lt;/a&gt; page for more details, where they talk about some potential timing issues which may be exacerbated if you're running at 1MHz using the internal oscillator on the tiny.&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-09-27T05:02:48.810" CommentCount="8" />
  <row Id="4534" PostTypeId="2" ParentId="4382" CreationDate="2010-09-27T05:59:39.283" Score="4" ViewCount="" Body="&lt;p&gt;&lt;em&gt;&quot;examples in the real world ... combining FPGAs with microcontrollers?&quot;&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In principle, a sufficiently large FPGA alone can do anything that a FPGA plus a microcontroller can do -- perhaps by implementing a soft CPU inside the FPGA.&#xA;In practice, a given level of performance often has lower parts costs and requires lower power when implemented with a FPGA plus a separate microcontroller than with FPGAs alone (or MCUs alone).&#xA;Here are a few of the more famous devices with both FPGAs and microcontrollers onboard:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://opencircuits.com/Elphel_camera&quot; rel=&quot;nofollow&quot;&gt;Elphel camera&lt;/a&gt;; &lt;a href=&quot;http://wiki.elphel.com/&quot; rel=&quot;nofollow&quot;&gt;Elphel Project Wiki&lt;/a&gt; has a Xilinx (R) Spartan 3e 1200K gates FPGA and a ETRAX FS processor running GNU/Linux.&lt;/li&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://www.embeddedarm.com/products/board-detail.php?product=TS-7500&quot; rel=&quot;nofollow&quot;&gt;TS-7500&lt;/a&gt; has a 5000 LUT Lattice FPGA and a 250MHz Cavium ARM9 CPU that can run Linux.&lt;/li&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://balloonboard.org/&quot; rel=&quot;nofollow&quot;&gt;Balloon board&lt;/a&gt; has a Xilinx Spartan FPGA and a ARM CPU&lt;/li&gt;&#xA;&lt;li&gt;several &lt;a href=&quot;http://www.linuxfordevices.com/c/a/Linux-For-Devices-Articles/Teeny-weeny-Linux-SBCs/&quot; rel=&quot;nofollow&quot;&gt;Teeny weeny Linux SBCs&lt;/a&gt; include both a FPGA and a CPU&lt;/li&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://www.armadeus.com/wiki/&quot; rel=&quot;nofollow&quot;&gt;Armadeus Project wiki&lt;/a&gt; documents a few boards board with both a Xilinx Spartan-3 FPGA and a 400 MHz ARM9 CPU.&lt;/li&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://www.cs.uml.edu/blackfin/&quot; rel=&quot;nofollow&quot;&gt;Blackfin Handy Board&lt;/a&gt; includes both a Xilinx Spartan 3e FPGA and a 600 MHz Analog Devices Blackfin® ADSP-BF537 processor. (It doesn't have a MMU, so it can't run full Linux, but it can run uClinux).&lt;/li&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://opencircuits.com/Minimig&quot; rel=&quot;nofollow&quot;&gt;&quot;Minimig&quot; (mini Amiga)&lt;/a&gt; includes a Xilinx Spartan-3 FPGA, a M68000 CPU, and a small PIC MCU as acting disc controller.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-09-27T05:59:39.283" />
  <row Id="4535" PostTypeId="2" ParentId="4525" CreationDate="2010-09-27T09:58:28.190" Score="2" ViewCount="" Body="&lt;p&gt;To add to the other descriptions, If your engineer uses Altium Designer, the file types are as follows:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;.PcbDoc - PCB File&lt;br&gt;&#xA;.SchDoc - Schematic File&lt;br&gt;&#xA;.PrjPcb - Logical project Grouping file. Not absolutely necessary, but nice to have.&lt;br&gt;&#xA;.PcbLib, .SchLib, .IntLib - PCB Library, Schematic library, and a baked-together library with both pcb and schematic primitives.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All the DFM and DRC rules are packaged into the .pdbdoc file, which is nice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting the design files from your engineer is &lt;strong&gt;critical&lt;/strong&gt;. I've recently been working on a project where the electrical design was farmed out, and no one knew what files they needed to get from the design house. Fast-forward a few years, and the design-house went out of business. and I'm stuck having to recreate the boards from the gerbers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maintenance is a nightmare without the proper files.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-09-27T09:58:28.190" />
  <row Id="4536" PostTypeId="2" ParentId="4525" CreationDate="2010-09-27T14:38:09.647" Score="2" ViewCount="" Body="&lt;p&gt;Here is what I have typically delivered --&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Initial Prototypes &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two functional prototypes.&#xA;  These boards may contain minor engineering changes&#xA;  but will be sufficient to verify functionality.&#xA;  It is expected that one revision of the design&#xA;  will be required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Final Report&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A design summary report that includes schematics, BOMs and component&#xA;  datasheets. All major design decisions are documented. Recommendations&#xA;  for future improvements are included. When I create the report I&#xA;  structure the BOM so that each line item in the BOM is a hyperlink to&#xA;  an embedded datasheet for the component.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Software Files&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All application and library files. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDA files&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All EDA files for the first revision of the design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Production PCB Files&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If required, CAD files and manufacturing drawings to &#xA;  produce PCB panels will be provided.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cost Estimates&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Provide cost estimates for building multiple units.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:37:44.847" LastActivityDate="2011-05-18T11:37:44.847" CommentCount="1" />
  <row Id="4537" PostTypeId="2" ParentId="4515" CreationDate="2010-09-27T14:42:57.157" Score="1" ViewCount="" Body="&lt;p&gt;I use a resistor between 10K and 50K. IIRC I saw a value of 33K in an FTDI application note.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would put all connections on the schematic. &lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-27T17:22:33.803" LastActivityDate="2011-02-27T17:22:33.803" />
  <row Id="4538" PostTypeId="2" ParentId="4462" CreationDate="2010-09-27T15:49:00.133" Score="0" ViewCount="" Body="&lt;p&gt;For this type of problem I divide the problem even further then I usually look at the assembly.  Also I have seen problems where the RX could corrupt or overflow a buffer so I would disable the RX until you have the TX working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first thing I would do is move &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if(waitingForACK == 0){&#xA;    PIE1bits.TXIE = 1; //Enable the TX interrupt&#xA;} &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;out of addToBuffer to is own function.  Then call it when the buffer is full not as you go. It could be some timing problem where you are not able to add while the interrupt is sending out the data.  When I transmit a packet I usually disable TX interrupt, fill up TX buffer and then enable the TX interrupt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then test the circular buffer outside of the interrupt. In you main function fill up the buffer then read out the data out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then next change your interrupt code to go through an intermediate volatile. So you can put a break point in your interrupt and see what is happing. The volatile is so that the complier does not remove the temp variable.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;volatile unsigned char temp;&#xA;if((TXEndPos - TXCurrentPos) &amp;gt; 0)            // if there is data in the buffer&#xA;{                                              &#xA;    temp  = TXBuffer[TXCurrentPos]; &#xA;    Nop();                                   // for adding breakpoints&#xA;    Nop();&#xA;    Nop();&#xA;    // add error checking to make sure TXREG is empty.&#xA;    TXREG = temp;                            // send next byte&#xA;    TXCurrentPos = TXCurrentPos + 0x01;      // update to the new position&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Another small thing is that I would also look into changing &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;else if (PIR1bits.TXIF == 1){&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;to &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if (PIR1bits.TXIF == 1){&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;to insure that the other interrupts are not starving the TX interrupt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then if you still have the problem look at the assembly code I have seen where the complier does something weird and it is usually obvious if you look at the assembly.&lt;/p&gt;&#xA;" OwnerUserId="540" LastActivityDate="2010-09-27T15:49:00.133" />
  <row Id="4539" PostTypeId="1" CreationDate="2010-09-27T19:11:01.193" Score="9" ViewCount="1024" Body="&lt;p&gt;The next Arduinos have been &lt;a href=&quot;http://arduino.cc/blog/2010/09/24/dinner-is-ready/&quot; rel=&quot;nofollow&quot;&gt;announced&lt;/a&gt;, the &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardUno&quot; rel=&quot;nofollow&quot;&gt;Arduino Uno&lt;/a&gt; &amp;amp; Arduino Mega 2560. The major difference is that it's equipped with a USB chip which can be reprogrammed to act like different USB devices like a keyboard, mouse or similar, and the Mega has twice as much memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would you like to do with the new boards?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My plans are to make a keyboard/mouse replacement for playing certain games. Press a button to quickly &amp;amp; repeatedly click the left mouse button type thing. &lt;/p&gt;&#xA;" OwnerUserId="776" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-09-27T23:26:50.377" LastActivityDate="2010-10-05T01:22:02.010" CommunityOwnedDate="2010-09-27T19:11:01.193" Title="What are you going to do with the Arduino Uno?" Tags="&lt;arduino&gt;&lt;uno&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="4541" PostTypeId="2" ParentId="4539" CreationDate="2010-09-27T22:10:43.117" Score="2" ViewCount="" Body="&lt;p&gt;Re: Arduino Uno&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a huge fan of the USB-AVRs. Last year I built an &lt;a href=&quot;http://blog.hodgepig.org/2009/07/07/488/&quot; rel=&quot;nofollow&quot;&gt;AT90USB162 board&lt;/a&gt;. Since then, I've been working on a &lt;a href=&quot;http://blog.hodgepig.org/busninja/&quot; rel=&quot;nofollow&quot;&gt;single chip Bus Pirate&lt;/a&gt; clone on one and using them to build USB connected test jigs for our production line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also love Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had hoped that the Arduino Uno would combine the two chips. But, I'm disappointed. My advice - wait for v1.1 (Uno punto uno?) (see @reemrevnivek below).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at the &lt;a href=&quot;http://arduino.cc/en/uploads/Main/arduino-uno-schematic.pdf&quot; rel=&quot;nofollow&quot;&gt;Uno schematic&lt;/a&gt;, they haven't connected up most of the pins from the ATmegaU8 (not even out to pads). So, lots of interesting LUFA stuff won't work without big changes (JTAG, AVR programming, SD cards as mass storage, etc)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are two lines connecting the ATmegaU8 to the ATmega328 - meant for a serial link.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My advice, buy a Teensy. If the Arduino users start coding for ATmegaU8 it'll run better on Teensy's ATmegaU4 and have acres of flash and RAM left. With the DFU/HID bootloader in the ATmega8, things must be very tight indeed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. ATmegaU8 as FTDI replacement for Arduino - see &lt;a href=&quot;http://dorkbotpdx.org/blog/feurig/benito_my_first_at90usb162_project&quot; rel=&quot;nofollow&quot;&gt;Benito&lt;/a&gt; and &lt;a href=&quot;http://dorkbotpdx.org/blog/feurig/usually_it_only_takes_6_months_for_people_to_understand_what_i_said&quot; rel=&quot;nofollow&quot;&gt;Uno response&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PPS. Here's the &lt;a href=&quot;http://www.ladyada.net/library/arduino/unofaq.html&quot; rel=&quot;nofollow&quot;&gt;FAQ&lt;/a&gt;. The U8 is a cost down.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-04T23:34:45.937" LastActivityDate="2010-10-04T23:34:45.937" CommunityOwnedDate="2010-09-27T22:10:43.117" CommentCount="4" />
  <row Id="4542" PostTypeId="1" AcceptedAnswerId="4545" CreationDate="2010-09-27T22:57:21.827" Score="6" ViewCount="595" Body="&lt;p&gt;I have an analog audio project I'm playing around with designs for and it will need about 150 solid-state variable resistors. I plan to control these from a micro controller so a digitally controlled pot would work but all the ones I've found are way too expensive ($1.00-$1.50).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My original plan was to use something like a MOSFET with a small capacitor and another transistor to hold a voltage on the gate. I would then update the voltages of each in turn via a DAC and some GPIO. However I haven't found any transistors suitable for my application (i.e. something that behaves enough like an ideal resistor).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;FWIW: the project is a variant on this (discontinued) EQ design: &lt;a href=&quot;http://www.national.com/an/AN/AN-435.pdf&quot; rel=&quot;nofollow&quot;&gt;Designing with the LMC835 Digital-Controlled Graphic Equalizer&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1182" LastEditorUserId="1182" LastEditorDisplayName="" LastEditDate="2010-09-28T03:23:30.580" LastActivityDate="2010-10-21T23:26:03.373" Title="Inexpensive solid-state variable resistor" Tags="&lt;transistor&gt;&lt;components&gt;&lt;analog&gt;&lt;audio&gt;" AnswerCount="5" CommentCount="8" FavoriteCount="3" />
  <row Id="4543" PostTypeId="1" CreationDate="2010-09-28T00:33:21.103" Score="4" ViewCount="207" Body="&lt;p&gt;What are the cheapest (&amp;lt;$5 in large quantities) reverb implementations you can think of for interfacing with analog audio circuitry?  It can be crappy but, of course, better is better.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-12-02T17:27:53.043" LastActivityDate="2010-12-02T17:35:22.743" Title="Cheapest reverb to stick in analog audio circuitry?" Tags="&lt;audio&gt;&lt;analog&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="4544" PostTypeId="2" ParentId="4542" CreationDate="2010-09-28T00:33:58.857" Score="2" ViewCount="" Body="&lt;p&gt;I'd agree with endolith that you should seriously look at other ways to solve the problem. As you haven't described the circuit you're trying to add this component to, much less posted the schematic or the transfer function you're trying to achieve, I can only guess that there are more efficient ways to solve the problem.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is one terminal of your variable resistor connected to a supply?  This will make many approaches much more feasible.  In the case of a connection to ground, for example, an N-type MOSFET, a capacitor, a resistor, and a PWM will probably suffice for a (relatively) slow-changing pot.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The key to designing a solid-state variable resistor is operating in your transistor in the active region, rather than allowing it to become saturated.  Your audio application likely requires a logarithmic or frequency weighting scale anyways, so why not build in some feedback or monitoring, and not worry about the slight  nonlinearity?&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-28T00:33:58.857" CommentCount="4" />
  <row Id="4545" PostTypeId="2" ParentId="4542" CreationDate="2010-09-28T00:51:06.730" Score="9" ViewCount="" Body="&lt;p&gt;If you want something that behaves more like a resistor, you can use a &lt;a href=&quot;http://www.silonex.com/audiohm/index.html&quot; rel=&quot;nofollow&quot;&gt;photocell and light it with an LED&lt;/a&gt; from a filtered PWM.  That's acting as a 2-terminal variable resistor rather than a 3-terminal pot, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could control all the LEDs from a single microcontroller using something like the &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tlc5940.html&quot; rel=&quot;nofollow&quot;&gt;TLC5940&lt;/a&gt;, which has 16 PWM LED driver outputs, with brightness of each programmable over a serial connection.  You'd need 10 of these at &lt;a href=&quot;http://avnetexpress.avnet.com/store/em/EMController/LED-Driver/Texas-Instruments/TLC5940NTG4/_/R-4216263/A-4216263/An-0?action=part&amp;amp;catalogId=500201&amp;amp;langId=-1&amp;amp;storeId=500201&quot; rel=&quot;nofollow&quot;&gt;$1.84 each&lt;/a&gt; to control 150 channels, though twice that if you need two resistors per channel (to simulate an actual pot).&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Also, have you looked at ICs with lots of pots inside?  $0.33 per pot is better than $1, for instance: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/3829&quot; rel=&quot;nofollow&quot;&gt;DS3930 Hex Nonvolatile Potentiometer with I/O and Memory&lt;/a&gt; ($1.95 @1k)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.analog.com/en/digital-to-analog-converters/digital-potentiometers/ad5206/products/product.html&quot; rel=&quot;nofollow&quot;&gt;AD5206:  6-Channel, 256-Position Digital Potentiometer&lt;/a&gt; (Price 1000 pcs. $1.94)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You could also look into voltage-controlled or programmable gain amplifier ICs, which might take the place of both an op-amp and a pot:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.analog.com/en/amplifiers-and-comparators/variable-gain-amplifiers/ssm2164/products/product.html&quot; rel=&quot;nofollow&quot;&gt;SSM2164: Low Cost Quad Voltage Controlled Amplifier&lt;/a&gt; - 4 channels for $3.12&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010482&quot; rel=&quot;nofollow&quot;&gt;MCP6S28: Single-Ended, Rail-to-Rail I/O, Low Gain PGA&lt;/a&gt; - 8 channels for $1.85&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As for a computer-controlled many-channel graphic EQ, a DSP is a cheaper option.  For instance, &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=929&amp;amp;uiTemplateId=NODE_STRY_PGE_T&quot; rel=&quot;nofollow&quot;&gt;TI&lt;/a&gt;, &lt;a href=&quot;http://akm.com/prod-dsp.asp&quot; rel=&quot;nofollow&quot;&gt;AKM&lt;/a&gt;, and &lt;a href=&quot;http://www.analog.com/en/embedded-processing-dsp/sigmadsp/processors/index.html&quot; rel=&quot;nofollow&quot;&gt;Analog&lt;/a&gt; have audio signal processors with ADCs and DACs built-in, and easy to use GUIs for making the EQ, though you need to buy the development board. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you seen &lt;a href=&quot;http://www.thatcorp.com/datashts/AES13-031_Digitally_Controllable_Audio_Filters.pdf&quot; rel=&quot;nofollow&quot;&gt;Digitally-Controllable Audio Filters and Equalizers&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-21T21:35:51.190" LastActivityDate="2010-10-21T21:35:51.190" CommentCount="9" />
  <row Id="4546" PostTypeId="1" CreationDate="2010-09-28T03:42:11.940" Score="2" ViewCount="116" Body="&lt;p&gt;I am specifically talking about the circuit found &lt;a href=&quot;http://www.kpsec.freeuk.com/projects/trafficlight.htm&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. I am waning to make this same circuit but make it run on much less, preferably a coin cell or two. Longevity of life is not important.&lt;/p&gt;&#xA;" LastActivityDate="2010-09-28T04:19:57.353" Title="Optimizing a &quot;stop light&quot; circuit to run on lower voltage" Tags="&lt;timer&gt;" AnswerCount="1" />
  <row Id="4547" PostTypeId="2" ParentId="4546" CreationDate="2010-09-28T04:19:57.353" Score="2" ViewCount="" Body="&lt;p&gt;You could run it from 6 volts - just stick two CR2032 coin cells together. Make sure your 4017 and 555 ICs are the CMOS versions, as they can run on lower voltages (see your data sheets). You also may want to reduce the value of the 470 ohm current-limiting resistors that are before the LEDs, perhaps 330 ohm if you're on 6 volts. &#xA;That looks like fun, I'm going to build it myself tonight. Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-28T04:19:57.353" CommentCount="2" />
  <row Id="4548" PostTypeId="2" ParentId="4542" CreationDate="2010-09-28T12:12:20.693" Score="4" ViewCount="" Body="&lt;p&gt;How about this?&#xA;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=MCP4014T-503E/OTCT-ND&quot; rel=&quot;nofollow&quot;&gt;MCP4011-4014&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is $0.39 each for 100QTY.  So for 150 QTY, it would be $58.50 + shipping.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-09-28T12:12:20.693" CommentCount="1" />
  <row Id="4549" PostTypeId="2" ParentId="4543" CreationDate="2010-09-28T14:44:55.293" Score="1" ViewCount="" Body="&lt;p&gt;There's always the option of a plate or spring reverb - it's not pretty but it's certainly low cost. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can be built for cheap using a couple of piezoelectric transducers and a lump of material with a nice resonance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can drive the signal into a small metal plate with one of the piezo disks, the other is used as a contact microphone - it picks up the signal after it's been transmitted through the metal. (I've done it with my wooden workbench before, it sounds quite good) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's the same sort of thing that's used in the back of old-school guitar amps, like this spring reverb - &lt;a href=&quot;http://www.amplifiedparts.com/products/amp_parts/P-R4AB3C1B&quot; rel=&quot;nofollow&quot;&gt;http://www.amplifiedparts.com/products/amp_parts/P-R4AB3C1B&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can beef them up easily too - &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sageelectronics.com/bovasound/emt.html&quot; rel=&quot;nofollow&quot;&gt;http://www.sageelectronics.com/bovasound/emt.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That EMT one may have cost a few bucks!, but if your just making a small one with a couple of piezo disks, you should be able to make one for less than 10 US$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, despite the limitations you can get some really fantastic results with a plate or spring style reverb.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;:)&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-09-28T14:57:34.720" LastActivityDate="2010-09-28T14:57:34.720" CommentCount="2" />
  <row Id="4550" PostTypeId="2" ParentId="4543" CreationDate="2010-09-28T19:29:18.790" Score="0" ViewCount="" Body="&lt;p&gt;What about the &lt;a href=&quot;http://www.profusionplc.com/pro/gex/pcatdtl0?ipartno=SPN1001-FV1&quot; rel=&quot;nofollow&quot;&gt;FV-1 from Spin Semiconductor&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to &lt;a href=&quot;http://www.profusionplc.com/pro/gex/pcatdtl0?ipartno=SPN1001-FV1&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt;, they can be had for about $12, in individual quantities.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a &lt;a href=&quot;http://www.spinsemi.com/Products/datasheets/spn1001/FV-1.pdf&quot; rel=&quot;nofollow&quot;&gt;spec sheet.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See also &lt;a href=&quot;http://www.echotapper.nl/dev/index.php?option=com_content&amp;amp;view=article&amp;amp;id=41&amp;amp;Itemid=45&quot; rel=&quot;nofollow&quot;&gt;http://www.echotapper.nl/dev/index.php?option=com_content&amp;amp;view=article&amp;amp;id=41&amp;amp;Itemid=45&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="544" LastEditorUserId="544" LastEditorDisplayName="" LastEditDate="2010-09-28T23:04:41.520" LastActivityDate="2010-09-28T23:04:41.520" />
  <row Id="4551" PostTypeId="2" ParentId="4543" CreationDate="2010-09-28T19:43:13.743" Score="4" ViewCount="" Body="&lt;p&gt;Another option is a Microchip &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en548414&quot; rel=&quot;nofollow&quot;&gt;Microstick&lt;/a&gt;. It comes with a 40 MIPS dsPIC chip that is suitable for implementing a reverb algorithm. Audio could be sampled with the on-chip ADC and output using PWM; very few external parts would be needed. The dsPIC chip on its own is about $5, it's a lot less in large quantities.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-02T17:35:22.743" LastActivityDate="2010-12-02T17:35:22.743" CommentCount="2" />
  <row Id="4552" PostTypeId="1" AcceptedAnswerId="4563" CreationDate="2010-09-29T01:55:35.453" Score="5" ViewCount="215" Body="&lt;p&gt;I would like to trigger a [7]555 timer when a phototransistor stops receiving light from an IR led, more precisely when the (expected to be smallish) signal from the light-sensitive voltage divider, consisting of a phototransistor and a resistor, changes quickly. How should I wire the timer? I expect if I decouple the light sensor from the timer with a capacitor I might be able to get a sufficient voltage swing to trigger the timer from a small but quick change in the signal?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to implement a version of the &lt;a href=&quot;http://alan-parekh.com/projects/stair-lights/&quot; rel=&quot;nofollow&quot;&gt;LED staircase&lt;/a&gt;. The project idea is to build a number of as-cheap-as-possible photodetector-triggered lamps on one side of a 3-foot gap opposite IR LED throwies on the other. When someone passes by they break the beam and trigger an entertaining trail of lights that slowly turn off, one by one, a couple of seconds later.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was overthinking the problem. After some experimentation it appears all I need is a photodarlington (a phototransistor by itself is not sensitive enough) in series with a resistor. This forms a voltage divider with a usable signal. If a potentially long low pulse is a problem then merely decouple the photodarlington from the logic with a capacitor differentiator.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2010-10-01T02:24:40.717" LastActivityDate="2010-10-01T02:24:40.717" Title="How can I generate a logic pulse from a broken IR beam?" Tags="&lt;ir&gt;&lt;555&gt;&lt;phototransistor&gt;" AnswerCount="3" />
  <row Id="4553" PostTypeId="2" ParentId="4373" CreationDate="2010-09-29T04:45:36.087" Score="0" ViewCount="" Body="&lt;p&gt;Hi,&#xA;I am doing something similar, except connecting tanks at different levels together. Whilst I could have used a solenoid valve to control the valve, I do not want to consume power the whole time the valve is open, which could be days or weeks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am fabricating a small DC motor to drive the valve for on to off, and it will use optical sensors to close the feedback loop. If you were to use a flow sensor and an arduino, you could open and close the valve to any point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I am finished, I could send you a photo, and instructions on doing your own.&lt;/p&gt;&#xA;" LastActivityDate="2010-09-29T04:45:36.087" />
  <row Id="4554" PostTypeId="2" ParentId="4521" CreationDate="2010-09-29T05:03:44.003" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Books&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Beginners-Reading-Schematics-Robert-Traister/dp/0830676325&quot; rel=&quot;nofollow&quot;&gt;Beginner's Guide To Reading Schematics&lt;/a&gt; - I find myself returning to this over and over again to figure out circuits on various devices that I tend to disassemble.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Embedded-Software-Primer-David-Simon/dp/020161569X/ref=sr_1_11?s=books&amp;amp;ie=UTF8&amp;amp;qid=1285736181&amp;amp;sr=1-11&quot; rel=&quot;nofollow&quot;&gt;Embedded Software Primer&lt;/a&gt; - A good intro for beginners&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Practical-Electronics-Inventors-Paul-Scherz/dp/0070580782&quot; rel=&quot;nofollow&quot;&gt;Practical Electronics for Inventors&lt;/a&gt; - Awaiting shipment - seen mostly good reviews on this. There are some typos that are supposed to plague this edition - however if you aren't a greenhorn, I guess it would not pose a big problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Websites&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.roboticsindia.com&quot; rel=&quot;nofollow&quot;&gt;Robotics India&lt;/a&gt; - A good resource for beginners and pro's alike&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/&quot; rel=&quot;nofollow&quot;&gt;Hack-a-day&lt;/a&gt; - no intro needed, I guess.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://letsmakerobots.com/&quot; rel=&quot;nofollow&quot;&gt;Lets make Robots&lt;/a&gt; - another great robotics site.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rgds,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sushrut.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastActivityDate="2010-09-29T05:03:44.003" CommunityOwnedDate="2010-09-29T05:03:44.003" CommentCount="2" />
  <row Id="4555" PostTypeId="1" AcceptedAnswerId="4568" CreationDate="2010-09-29T05:18:34.047" Score="4" ViewCount="141" Body="&lt;p&gt;Assume that you have a couple of ideas that you think are good enough to prototype into demonstrable devices. What option would you take and why?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Option 1 - Build everything from scratch including designing and soldering the circuit, embedded software and finishing / packaging touches. Basically in this option, you do everything and don't source ready-made circuits from elsewhere. For e.g., you can easily get ready-to-use PCB's for power supplies, motor drivers and so on. Instead you build your own. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Option 2 - Figure out the common or readily available blocks in your schematics and source them from third parties. You work on only the parts that you think add value / novelty to your prototype (or one's that aren't readily available). These may include the electronics and/or the software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are obvious costing implications but I am asking to ignore those since they are easy to arrive at and analyze against. I am also not touching on obvious IP implications on getting stuff from 3rd parties - again assuming that these are taken care of legally. Also, please sensitize your answers to commercialization of these prototypes - that is, assume that these will be available as custom or off-the-shelf products in the future.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rgds,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sushrut.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-26T17:33:54.023" LastActivityDate="2010-10-26T17:33:54.023" Title="Prototype building route" Tags="&lt;prototyping&gt;&lt;sourcing&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="4556" PostTypeId="2" ParentId="4555" CreationDate="2010-09-29T07:17:31.107" Score="2" ViewCount="" Body="&lt;p&gt;Option 1. I am a pedantic masochist who wants to control everything and either own all the IP or give the whole design away freely under creative commons licensing. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-29T07:17:31.107" CommentCount="3" />
  <row Id="4558" PostTypeId="2" ParentId="4555" CreationDate="2010-09-29T08:33:08.597" Score="4" ViewCount="" Body="&lt;p&gt;It would depend on the goal, maturity, and duration of the project.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Putting together building blocks for a final design is:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Fast.&lt;/li&gt;&#xA;&lt;li&gt;Easy.&lt;/li&gt;&#xA;&lt;li&gt;Dependable.&lt;/li&gt;&#xA;&lt;li&gt;Expensive (in volume).&lt;/li&gt;&#xA;&lt;li&gt;Hobbyist-oriented.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In contrast, a final design from scratch is:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Time intensive.&lt;/li&gt;&#xA;&lt;li&gt;Difficult.&lt;/li&gt;&#xA;&lt;li&gt;Vulnerable to failure of concept.&lt;/li&gt;&#xA;&lt;li&gt;Cheap (in volume).&lt;/li&gt;&#xA;&lt;li&gt;Professional quality.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In general, I'd start with blocks for a prototype.  Sometimes, I'll substitue something I have on hand for a given block (i.e., lab PSU for a power supply circuit, or a PC/overpowered dev board for a smaller micro).  Then, I'll use that working prototype for a reference as I seek to find cheaper parts, simpler circuits, and implement the design on a custom PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When designing a custom solution, however, remember not to reinvent the wheel.  This is an especially potent doctrine when it comes to software.  If a library or circuit is available, tested, refined, and proven, don't fix what ain't broke! &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-29T08:33:08.597" />
  <row Id="4559" PostTypeId="2" ParentId="4555" CreationDate="2010-09-29T12:40:07.270" Score="2" ViewCount="" Body="&lt;p&gt;I build from scratch. modules are more expensive and you have to deal with third parties who change designs, go out of business or may have licensing issues you'll have to contend with. Boards aren't difficult or expensive to design and fab out (although I hand-assemble most prototypes and low-volume production boards) and the resultant design is often much smaller than something built out of modules.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there's an overly complicated piece, I may use a module. For example, I use Gumstix COMs for a design, but only for the prototype and first 50 or so; I'll incorporate the OMAP3530 on my board for production. They're expensive and support is poor but they are very nice in the sense that I don't have to worry about the OMAP/SDRAM/support circuitry and can focus on verifying that the other bits of the design work properly.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-09-29T12:40:07.270" CommentCount="1" />
  <row Id="4560" PostTypeId="1" AcceptedAnswerId="4561" CreationDate="2010-09-29T13:22:57.983" Score="3" ViewCount="153" Body="&lt;p&gt;I'm having trouble understanding how much current flows through the base of a BJT. With a MOSFET the answer is easy: 0. How do I calculate the amount of base current in a BJT and am I doing it wrong if my circuit cares?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-09-29T13:46:03.510" LastActivityDate="2010-09-29T16:00:54.143" Title="How should I understand the amount of base current in BJT transistors?" Tags="&lt;bjt&gt;&lt;transistor&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="4561" PostTypeId="2" ParentId="4560" CreationDate="2010-09-29T13:59:13.743" Score="5" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/en/thumb/4/46/BJT_Switch.jpg/400px-BJT_Switch.jpg&quot; alt=&quot;http://upload.wikimedia.org/wikipedia/en/thumb/4/46/BJT_Switch.jpg/800px-BJT_Switch.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this circuit, the base current would be approximately (Vs - 0.7) / R2.  The BE junction (with the arrow) behaves like a diode, so as long as Vs is greater than 0.7 V, then current will flow through the diode and there will be a drop of about 0.7 V (depending on the part) and then the current is just limited by the resistor according to Ohm's law.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-09-29T16:00:54.143" LastActivityDate="2010-09-29T16:00:54.143" CommentCount="4" />
  <row Id="4562" PostTypeId="1" CreationDate="2010-09-29T14:31:04.187" Score="2" ViewCount="160" Body="&lt;p&gt;Would it be possible (if the traces can be identified) to use a blutooth card from a laptop to transmit data from an arduino to say a phone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know the arduino to phone part will work, I am just unsure if I can use a laptop bluetooth card in  such a manner&lt;/p&gt;&#xA;" LastActivityDate="2010-09-29T16:14:59.097" Title="Utilizing mini-pci bluetooth card from laptop as a transmitter" Tags="&lt;bluetooth&gt;" AnswerCount="2" />
  <row Id="4563" PostTypeId="2" ParentId="4552" CreationDate="2010-09-29T14:33:58.150" Score="5" ViewCount="" Body="&lt;p&gt;I would start it using a &lt;a href=&quot;http://www.national.com/ds/LM/LM567.pdf&quot; rel=&quot;nofollow&quot;&gt;LM567&lt;/a&gt; to detect the presence of someone on the stair. I recommend this circuit: &lt;a href=&quot;http://www.mondotronics.com/PDFs/3-337_Mod_IR_v22.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.mondotronics.com/PDFs/3-337_Mod_IR_v22.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using the output of this circuit, you should trigger your &lt;a href=&quot;http://www.national.com/ds/LM/LM555.pdf&quot; rel=&quot;nofollow&quot;&gt;LM555&lt;/a&gt; to keep the light on as much time as you want, but not using a large capacitor as you mentioned, but just a LM555 in monostable operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output from LM555 can drive a transistor to control as many LEDs as you want!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some level or signal inversion maybe required.&lt;/p&gt;&#xA;" OwnerUserId="940" LastActivityDate="2010-09-29T14:33:58.150" CommentCount="1" />
  <row Id="4564" PostTypeId="2" ParentId="4562" CreationDate="2010-09-29T14:44:21.157" Score="2" ViewCount="" Body="&lt;p&gt;Without knowing which laptop bluetooth card, we can't answer. Chances are if it's a Dell that they use the BC4 (BlueCore IV) chipset, which is very well documented and hacker friendly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative is to use a breakout board such as &lt;a href=&quot;http://www.elechouse.com/elechouse/index.php?main_page=product_info&amp;amp;products_id=324&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-09-29T14:44:21.157" />
  <row Id="4565" PostTypeId="2" ParentId="4552" CreationDate="2010-09-29T14:50:57.703" Score="2" ViewCount="" Body="&lt;p&gt;This may seem like a challenge, but I can give you a link to a &lt;a href=&quot;http://claymore.engineer.gvsu.edu/~moelkern/Book555.jpg&quot; rel=&quot;nofollow&quot;&gt;relatively common circuit&lt;/a&gt;. You can then use the photo-transistor as a discharge from the capacitor. when the transistor has light, it will keep the capacitor discharged, you just need to use the potentiometer to tune the circuit to have a low enough resistance to charge the capacitor when the transistor has no signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is another easy way to do this with two 555 timers, but I need to draw it. Let me know if you need it, another answer popped up. I am still posting this as another option. I was going to use a 555 to detect the change, and then have it trigger a 555 to stay on as long as you want, as andre says.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-09-29T14:50:57.703" />
  <row Id="4566" PostTypeId="1" CreationDate="2010-09-29T15:02:41.623" Score="4" ViewCount="320" Body="&lt;p&gt;I didn't jump on Netduino when I should have now it looks like they are in a very limited supply. Does any one know if there is going to be any more manufactured or possibly the beta Netduino? &lt;/p&gt;&#xA;" OwnerUserId="850" LastActivityDate="2010-09-30T23:04:30.313" Title="Is Netduino awaiting a second run?" Tags="&lt;netduino&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="4567" PostTypeId="2" ParentId="4566" CreationDate="2010-09-29T15:06:05.463" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/netduino.html&quot; rel=&quot;nofollow&quot;&gt;Little Bird&lt;/a&gt; are still taking orders for the &lt;a href=&quot;http://www.littlebirdelectronics.com/products/netduino.html&quot; rel=&quot;nofollow&quot;&gt;original&lt;/a&gt;. Might a while for the new one (November?)&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-09-29T15:06:05.463" CommentCount="1" />
  <row Id="4568" PostTypeId="2" ParentId="4555" CreationDate="2010-09-29T15:26:24.067" Score="2" ViewCount="" Body="&lt;p&gt;I think it's a combination of both.  When starting out, you have a core idea that differentiates your product from others on the market.  You'll start out breadboarding the idea to see if it works, how well, etc.  During this phase you should buy ready-made components - I'm thinking mainly of something like a breadboard power adapter.  There's no sense in making EVERYTHING from scratch to test one idea; get the idea down in code/circuit, make sure it works and is feasible.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, after this point if you want to make a standalone product you'll have some work to do.  The breadboard power supply may not be useful because it only does 5V, and you want to use 3.3V to lower power consumption, etc.  So you pick a regulator IC, design the circuit, test that, etc.  Once everything is pretty well set in stone I would make a PCB and solder up the prototype myself and create a testing scenario to make sure everything works.  You'll find problems, fix them, respin the boards, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, I wouldn't put a module sold from Sparkfun or some other place in my finished product.  You could and I don't think there's any major legal hurdles - my hesitance is mainly cost and usefulness-related.  If this is going to be sold in any major numbers you don't want to have to buy headers to plug the modules in, pay the markup on the boards, or have to figure out workarounds for the drawbacks of the modules.  For instance, I used an Arduino Mega in a serial bus tester.  However, not all of the pins on the uC are brought out to headers, so I had to have a tech solder a magwire to the right pin so we could use it.  If I had been making more than two of these then I would have just soldered the uC onto the PCB for the device instead of connecting the Arduino to the PCB via headers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general I don't think that much of the functionality of the modules you see in places is that hard to reproduce.  Some of them are just straight implementations of reference designs for the chips they integrate.  These are easy enough to reproduce on your own and very legal as far as I know.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-29T15:26:24.067" />
  <row Id="4569" PostTypeId="2" ParentId="4552" CreationDate="2010-09-29T15:33:03.337" Score="1" ViewCount="" Body="&lt;p&gt;I'm sure there's some way to create an analog solution to this but nowadays I wouldn't even bother.  If a small microcontroller can handle it, use that.  I'm not sure if I'll ever use 555 timers anymore because a microcontroller can do it and so much more in the same package.  True, the ATTiny45 costs about 4x the LM555, but if your application requires a microcontroller it might as well do one more job.  Using the 555 has always been a lot more difficult for me than figuring out some C code to do the same thing.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-29T15:33:03.337" CommentCount="7" />
  <row Id="4570" PostTypeId="2" ParentId="4562" CreationDate="2010-09-29T16:14:59.097" Score="1" ViewCount="" Body="&lt;p&gt;I would guess it's wired to the USB, which would make it difficult.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try to identify the chip(set) and/or how it's wired on the laptop. If it's not a dead laptop, you should be able to look at the buses and see where it appears and as what type.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-09-29T16:14:59.097" />
  <row Id="4571" PostTypeId="1" CreationDate="2010-09-29T16:48:41.453" Score="16" ViewCount="736" Body="&lt;p&gt;I am looking for a free (as in freedom) tool chain for Linux (Ubuntu) that allows me to develop for an ARM cortex-m3 (lpc1343) microcontroller. Where do I find such a toolchain? Are there any tutorials?&lt;/p&gt;&#xA;" OwnerUserId="936" LastActivityDate="2011-04-11T17:07:40.277" Title="Cortex-m3 toolchain" Tags="&lt;cortex-m3&gt;&lt;arm&gt;&lt;linux&gt;" AnswerCount="5" FavoriteCount="8" />
  <row Id="4572" PostTypeId="2" ParentId="4566" CreationDate="2010-09-29T16:55:50.513" Score="1" ViewCount="" Body="&lt;p&gt;New stock is arriving at dealers in the next few days.&#xA;October 1st is the slated delivery date for US dealers, not sure about AU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I still have &lt;a href=&quot;http://stores.ebay.com.au/Microcontrollers-and-More&quot; rel=&quot;nofollow&quot;&gt;one left&lt;/a&gt; in stock in AU&lt;/p&gt;&#xA;" LastActivityDate="2010-09-29T16:55:50.513" />
  <row Id="4573" PostTypeId="2" ParentId="4571" CreationDate="2010-09-29T16:57:26.733" Score="3" ViewCount="" Body="&lt;p&gt;The Maple development board is an Arm Cortex M3 and although it has its own IDE and such you can certainly use the GCC ARM toolchain as described here: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://leaflabs.com/docs/libmaple/unix-toolchain/&quot; rel=&quot;nofollow&quot;&gt;http://leaflabs.com/docs/libmaple/unix-toolchain/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This guide uses Code::Blocks as its IDE, which I use and find very useful.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-09-29T16:57:26.733" />
  <row Id="4574" PostTypeId="2" ParentId="4571" CreationDate="2010-09-29T18:23:14.193" Score="13" ViewCount="" Body="&lt;p&gt;CodeSourcery has a free gcc-based toolchain for the Cortex M3.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are instructions on configuring the toolchain for the Luminary LM3s6965 for a Windows, Mac, and Linux host here: &lt;a href=&quot;http://claymore.engineer.gvsu.edu/egr326/LM3S6965&quot; rel=&quot;nofollow&quot;&gt;http://claymore.engineer.gvsu.edu/egr326/LM3S6965&lt;/a&gt;.  It should also work with your LPC processor with minor tweaks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See also this question:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/991/arm-cortex-m3-development-tools&quot;&gt;http://electronics.stackexchange.com/questions/991/arm-cortex-m3-development-tools&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-29T18:23:14.193" CommentCount="3" />
  <row Id="4575" PostTypeId="1" AcceptedAnswerId="4588" CreationDate="2010-09-29T19:15:24.167" Score="4" ViewCount="303" Body="&lt;p&gt;Does anyone know how to build a push/pull oscillator or a similar square wave oscillator?&lt;/p&gt;&#xA;" OwnerUserId="1203" LastActivityDate="2010-10-01T04:43:42.017" Title="Push Pull Oscillator" Tags="&lt;oscillator&gt;" AnswerCount="4" CommentCount="4" />
  <row Id="4576" PostTypeId="1" AcceptedAnswerId="4581" CreationDate="2010-09-29T19:26:05.710" Score="5" ViewCount="171" Body="&lt;p&gt;I'm a student living in the UK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have this great idea for a product that fills a niche market and it interests me. It's a powerful on screen display module with datalogging capabilities, and it's open source hardware and software. See &lt;a href=&quot;http://code.google.com/p/super-osd/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/super-osd/&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to start selling these modules. I have PCB designs and I'm ready to order the components, but what route should I take for manufacturing the modules? I see three main possibilities:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Etch my own PCBs and solder components on - pretty much a no go as I'm dealing with double sided surface mount boards.&lt;/li&gt;&#xA;&lt;li&gt;Order PCBs cheap from China and solder all 40 odd (0603, TQFP44 etc.) components on myself. (Probably the cheapest option but lots of manual labour.)&lt;/li&gt;&#xA;&lt;li&gt;Get a quote for PCB+assembly.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-09-30T08:13:36.767" Title="Launching a new product as a student" Tags="&lt;electronics&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="5" />
  <row Id="4578" PostTypeId="1" CreationDate="2010-09-29T19:29:14.237" Score="3" ViewCount="245" Body="&lt;p&gt;Last year, I entered into the Robocup Junior Soccer competition using a robot built from the &lt;a href=&quot;http://area51.stackexchange.com/proposals/4105/lego-mindstorms-robotics?referrer=xdbfIk67GZl3hJ0vc5L2Fg2&quot;&gt;Lego Mindstorms&lt;/a&gt; NXT kit. It worked well, but we were thrashed at the international level, mainly because of the sheer speed and strength of the opposition.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This year, I'm intending to build the robot from scratch, as interfacing non-lego motors and sensors with the NXT is troublesome at best. However, I have absolutely no experience with any other microprocessor, and am wondering what to get.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The microprocessor needs I&lt;sup&gt;2&lt;/sup&gt;C and PWM outputs (to drive 3-5 motors), and preferably should be cheapish, and programmable in some object-oriented programming language.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would an arduino be suited to this purpose, or this that insuffient/overkill?&lt;/p&gt;&#xA;" OwnerUserId="1217" LastEditorUserId="1217" LastEditorDisplayName="" LastEditDate="2010-09-29T19:56:48.287" LastActivityDate="2010-09-29T20:12:05.943" Title="Suitable processor for a Robocup Junior Soccer robot?" Tags="&lt;microcontroller&gt;&lt;robotics&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="2" />
  <row Id="4579" PostTypeId="1" AcceptedAnswerId="4595" CreationDate="2010-09-29T19:30:38.680" Score="3" ViewCount="189" Body="&lt;p&gt;I designing a circuit will store log data to an SD card. The information will be coming form a parent circuit that this one plugs into. The parent circuit will supply 5V to my daughter card. The daughter card uses an MCU that operates at 3.3V so I am just using a couple of diodes to step down the voltage from 5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MY CHALLENGE IS: In the event of a power failure, I want the MCU on my daughter card to be able to sense the main power loss and then immediately flush the data from it's RAM to the SD card and then go idle before it shuts down. When writing to an SD card you can cause corruption if you lose power in the middle of a write procedure. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am thinking about using a big capacitor to just buffer the power for a bit. I know there are some MCU Supervisor IC's out there that would do a really nice job but they are intended for cases where you need to maintain power for days. I just need a second or two at the most. But I do have to be careful about not letting the MCU &quot;flicker&quot; on and off as the capacitor power decreases below the IC's threshold. Does anyone have a schematic or can offer any suggestions of how I should go about this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is what I have so far... (the .5F cap is my power back-up capacitor)&#xA;&lt;img src=&quot;http://i.imgur.com/9mHGs.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2010-09-29T20:50:19.283" Title="Help with power-loss protection using capacitor." Tags="&lt;circuit&gt;&lt;power-supply&gt;&lt;capacitor&gt;&lt;buffer&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="4580" PostTypeId="2" ParentId="4542" CreationDate="2010-09-29T19:36:32.857" Score="4" ViewCount="" Body="&lt;p&gt;A JFET can be configured as a variable resistor, operating in its ohmic region. It works in many cases.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my über-crude design:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Vdd -----------+&#xA;               |&#xA;       R1     _|&#xA;  G -\/\/\-+-|_&#xA;           |   |&#xA;           \   v  put &#xA;        R2 /   v  load&#xA;           \   |  here&#xA;           +---|&#xA;               |&#xA;GND -----------+&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(We need a schematics editor: that would be awesome.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a bit tricky to get it biased (if that's even the right word) in the right position. I made a variable oscillator circuit with one before. I also designed a variable PWM+frequency circuit (variable frequency-variable speed drive) for driving a motor using a dual op-amp and JFET.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-09-29T19:36:32.857" CommentCount="4" />
  <row Id="4581" PostTypeId="2" ParentId="4576" CreationDate="2010-09-29T19:43:53.600" Score="3" ViewCount="" Body="&lt;p&gt;I would say there are three major factors that would need to be considered before making a decision. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) How many products are you planning on selling yearly? If it is a lot, say more than a hundred, you probably don't want to be doing much assembly. You need to save your time for future product development!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) How many surface mount components &#xA;are on the board and can you reduce that number more. Yes you can solder surface mount chips in your house and there are tons of cool methods for simplifying that process but still, nothing beats the speed and precision of a machine. (If you want some tips on how to solder surface mount chips ask that in another question. I have found some very good techniques) Anyways, thru-hole components are obviously way easier to solder by hand and if you are going to be doing more than a few boards and actually selling them to customers they are a lot easier do not screw up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Do you enjoy circuit assembly. You need to consider what you like doing. If soldering boards all day gives you jollies and you have the time then maybe you should go for it. But if you are also interested in design and development of new stuff than you may not want to be tied down with your soldering iron all day. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whatever you end up with, Good luck!&lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-09-29T23:57:21.880" LastActivityDate="2010-09-29T23:57:21.880" CommentCount="3" />
  <row Id="4582" PostTypeId="2" ParentId="4579" CreationDate="2010-09-29T19:48:40.970" Score="0" ViewCount="" Body="&lt;p&gt;A solution to this is to use your microcontroller's comparators.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You did not mention what microcontroller you are using, so we can only guess if it actually has comparators on the chip. If your micro has a voltage reference, even better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But assuming it does, you can set up an interrupt to jump to an ISR. The ISR could switch the clock (if possible) to a low power routine and then shut down. If you're running at a low frequency you may have much longer to perform the save - the tradeoff is however that the save takes more cycles.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-09-29T19:48:40.970" CommentCount="10" />
  <row Id="4583" PostTypeId="1" AcceptedAnswerId="4590" CreationDate="2010-09-29T19:59:08.663" Score="3" ViewCount="214" Body="&lt;p&gt;I'd like to build a &lt;em&gt;cheap and easy&lt;/em&gt; op-amp to use with my electric guitar.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The op-amp should input from the guitar's &lt;em&gt;jack&lt;/em&gt; and output to a standard &quot;earphone's cable&quot; jack ( not sure about the jargon here ). So that I can plug it into my Hi-Fi's aux channel, or my PC, or just listen on my earphones. A &lt;em&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Nine-volt_battery&quot; rel=&quot;nofollow&quot;&gt;9v battery&lt;/a&gt;&lt;/em&gt; would be the preffered power source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where can I find schematics for a projet like this? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, If I wanted to extend the op-amp to handle basic effects, ( Distortion, Feedback, etc. ) How would I achieve that?&lt;/p&gt;&#xA;" OwnerUserId="1258" LastActivityDate="2010-11-05T15:06:17.297" Title="Building a intermediate op-amp" Tags="&lt;op-amp&gt;&lt;schematics&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="4584" PostTypeId="2" ParentId="4578" CreationDate="2010-09-29T20:12:05.943" Score="1" ViewCount="" Body="&lt;p&gt;Consider using the Parallax Propeller and dedicated motor controllers such as the DMC-1. The Propeller has 8 32 bit cores which can run up to 8 processes simultaneously. You can program it using its native OO language SPIN, or for more performance, its own assembly language. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DMC-1 is a low cost I2C dual motor controller which can drive loads of up to 2.6A at 15V continuously. It's very easy to control. You can find out about it here: &lt;a href=&quot;http://web4robot.com&quot; rel=&quot;nofollow&quot;&gt;http://web4robot.com&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if you decide to use the Arduino, I would recommend using the DMC-1.&lt;/p&gt;&#xA;" OwnerUserId="1265" LastActivityDate="2010-09-29T20:12:05.943" CommentCount="1" />
  <row Id="4585" PostTypeId="2" ParentId="4583" CreationDate="2010-09-29T20:19:01.660" Score="5" ViewCount="" Body="&lt;p&gt;I don't think you want to build an op-amp.  An op-amp is an electronic component that you usually buy already-made and build other things with.  A typical op-amp IC looks like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kpRZb.jpg&quot; alt=&quot;This is an op-amp&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think what you want is to build a headphone/line amplifier &lt;em&gt;with&lt;/em&gt; an op-amp.  There's a popular guide here:  &lt;a href=&quot;http://tangentsoft.net/audio/cmoy-tutorial/&quot; rel=&quot;nofollow&quot;&gt;http://tangentsoft.net/audio/cmoy-tutorial/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-09-29T20:19:01.660" CommentCount="1" />
  <row Id="4586" PostTypeId="2" ParentId="4583" CreationDate="2010-09-29T20:22:42.707" Score="1" ViewCount="" Body="&lt;p&gt;There is a project about a &lt;a href=&quot;http://www.generalguitargadgets.com/projects/28-other-projects/145-practice-board&quot; rel=&quot;nofollow&quot;&gt;practice board&lt;/a&gt; in the General Guitar Gadgets website.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-05T15:06:17.297" LastActivityDate="2010-11-05T15:06:17.297" />
  <row Id="4587" PostTypeId="2" ParentId="4583" CreationDate="2010-09-29T20:23:00.837" Score="3" ViewCount="" Body="&lt;p&gt;I'm guessing from the description, you are not looking to build an op-amp but rather an amp (ie without the op part)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;you might start with something like the cmoy headphone amp. google for cmoy kit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of the kits you find may or may not have a volume knob but once you have a gain that works, the stereo could adjust from there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would be a good starting project that is nice to have and it will also teach some of the basics.... like what an op-amp is.&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2010-09-29T20:23:00.837" CommentCount="1" />
  <row Id="4588" PostTypeId="2" ParentId="4575" CreationDate="2010-09-29T20:23:42.287" Score="1" ViewCount="" Body="&lt;p&gt;One Schmitt-trigger inverter (74LS14) together with an RC circuit feeding it will do a pretty good job of creating a simple oscillator. Adjust the RC time constant to adjust the frequency.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-09-30T12:44:20.767" LastActivityDate="2010-09-30T12:44:20.767" CommentCount="3" />
  <row Id="4589" PostTypeId="2" ParentId="3741" CreationDate="2010-09-29T20:23:47.217" Score="1" ViewCount="" Body="&lt;p&gt;You might want to check out the &lt;a href=&quot;http://netduino.com&quot; rel=&quot;nofollow&quot;&gt;Netduino&lt;/a&gt;.  It is built to be compatible with the arduino layout and pins, and runs the .NET Micro Framework.  So you can code in C# and even debug inside Visual Studio!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far I have found it to be very good and easy to work with.  While I haven't found a lot of tutorials, I think that you can just port a lot of the Arduino stuff.  Me being a newb, I was able to easily port a photoresistor/photocell setup and code from an Arduino tutorial.&lt;/p&gt;&#xA;" OwnerUserId="1252" LastActivityDate="2010-09-29T20:23:47.217" />
  <row Id="4590" PostTypeId="2" ParentId="4583" CreationDate="2010-09-29T20:26:16.920" Score="6" ViewCount="" Body="&lt;p&gt;Wow....there's so many choices out there, it can be hard to pick one!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good place to start is with the &lt;a href=&quot;http://sound.westhost.com/&quot; rel=&quot;nofollow&quot;&gt;Elliott Sound Products&lt;/a&gt; website, there's a heap of different amplifier designs for all manner of applications, and there's also different levels of difficulty too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A great way to get started is to get a &lt;a href=&quot;http://en.wikipedia.org/wiki/Breadboard&quot; rel=&quot;nofollow&quot;&gt;breadboard&lt;/a&gt;, buy all the stuff you need to make a simple looking amp, (there's a few single chip circuits on that link also) and just have a good experiment with it :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can do stuff with a 9v battery quite safely, just get some audio jacks soldered to some wires and you can hook up your guitar and stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Distortion and feedback are a natural progression from amp design, you'll get into that quite quickly I'd imagine, it's not a big leap in complexity - it's normally just changing a few component values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;this site is also great, lots of great stuff for guitarists -&gt; &lt;a href=&quot;http://www.beavisaudio.com/projects/&quot; rel=&quot;nofollow&quot;&gt;Beavis Audio&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck dude!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just pop back if you need any more help.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-09-29T20:26:16.920" CommentCount="2" />
  <row Id="4591" PostTypeId="2" ParentId="4350" CreationDate="2010-09-29T20:31:15.120" Score="0" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.pcengines.ch/alix1d.htm&quot; rel=&quot;nofollow&quot;&gt;Alix1.D&lt;/a&gt; is a great board. They retail for about $130 and consume about 4W. It can run of a car 12v lead battery, but obviously is not really &quot;portable&quot;.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;500 MHz AMD Geod &lt;/li&gt;&#xA;&lt;li&gt;256 MB of RAM&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1279" LastActivityDate="2010-09-29T20:31:15.120" />
  <row Id="4593" PostTypeId="1" CreationDate="2010-09-29T20:37:44.257" Score="4" ViewCount="148" Body="&lt;p&gt;I was toying around with an idea for a digital musical instrument with breath control. I've successfully experimented with pressure sensors and they are probably the right way to go, but my first idea was just using a plastic sealed microphone. I never got very far with it, but I think it still has potential for the kind of response I want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea was that a stream of air directed to the hit the microphone would generate white'ish noise (just thinking blowing on a mic) and I could use the loudness of this noise to create the ADSR envelope for my sound. Covering the mic with plastic sheeting still allows this to work and protects it from the moisture in your breath.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, most of my electronics experience is digital (from discrete digital in college to microcontrollers now) and I'm more of a programmer. I got as far as looking at the noise signal on my 'scope and verifying that it had the characteristics I wanted (to use the smoothed, positive magnitude of the noise as the loudness of the synthesized tones) and I know that if I can get it to a wide enough analog range I can use an ADC to get a digital magnitude. What I lack is the analog knowledge to take the noise waveform and transform it to a varying analog signal representing the average positive magnitude at a fairly high sampling rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas or links to get me started?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;P.S.&lt;/strong&gt;&lt;br&gt;&#xA;I won't really know which answer is totally correct until I get do some experimentation, but the responses have been great so far. The VU meter is pretty close that what I need and the reminder that loudness is logarithmic is useful as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may have been easier to state my problem this way: I want to control a digital tone (either generated or via MIDI) where the &quot;loudness&quot; of the tone is proportional to the intensity of the sound generated by blowing on the mic if that makes any more sense.&lt;/p&gt;&#xA;" OwnerUserId="152" LastEditorUserId="152" LastEditorDisplayName="" LastEditDate="2010-09-30T03:57:16.933" LastActivityDate="2010-09-30T03:57:16.933" Title="How do I measure loudness?" Tags="&lt;microcontroller&gt;&lt;analog&gt;&lt;sound&gt;&lt;music&gt;&lt;wave&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="4594" PostTypeId="2" ParentId="4593" CreationDate="2010-09-29T20:43:00.983" Score="1" ViewCount="" Body="&lt;p&gt;I recommend you amplify the signal to some level in the range of 0V to 3.3V, and feed this into your microcontroller's ADC. A fairly fast digital signal processor will need to be used. I recommend something like a dsPIC33F. Once you have the analog signal working, the digital side shouldn't be too hard, given your digital knowledge.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-09-29T20:43:00.983" CommentCount="2" />
  <row Id="4595" PostTypeId="2" ParentId="4579" CreationDate="2010-09-29T20:50:19.283" Score="1" ViewCount="" Body="&lt;p&gt;Using diodes to drop voltage?  Yuck.  Use a 3.3V regulator.  It's just the right thing to do.  You and/or your customers will be glad you did it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have the right idea, generally.  Use a huge cap, although .5F might be a bit &lt;em&gt;too&lt;/em&gt; huge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead of using a comparator, you could use a voltage divider and run the output into one of the Interrupt-On-Change pins of the PIC.  Set up the divider so that the input is a bit above the max Vih when the 5V is active.  This has the added bonus of also pulling the 5V down faster once the source is removed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also try using a battery and a power mux.  When the 5V goes away, the mux will switch to battery power.  &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=422&amp;amp;uiTemplateId=NODE_STRY_PGE_T&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=422&amp;amp;uiTemplateId=NODE_STRY_PGE_T&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-09-29T20:50:19.283" CommentCount="2" />
  <row Id="4596" PostTypeId="1" AcceptedAnswerId="4597" CreationDate="2010-09-29T20:59:41.340" Score="2" ViewCount="198" Body="&lt;p&gt;I'm building a small circuit with an arduino bootloaded ATMega328 chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The project will be housed in a small box, and is intended to be stuck to the side of a fridge using a magnet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Everything in my brain tells me that magnets and chips do not mix well. What is the likelihood that the sketch loaded onto the chip will become corrupted, or that something else will happen as a direct result of the magnetic forces, causing the chip to cease operation/ operate incorrectly?&lt;/p&gt;&#xA;" OwnerUserId="623" LastActivityDate="2010-09-29T21:25:11.423" Title="How do magnets affect the ATMega328?" Tags="&lt;atmega&gt;&lt;atmega328&gt;" AnswerCount="3" CommentCount="0" />
  <row Id="4597" PostTypeId="2" ParentId="4596" CreationDate="2010-09-29T21:06:54.027" Score="8" ViewCount="" Body="&lt;p&gt;Magnets cause problems with magnetic storage (hard disks, tapes, etc). The AVR chips use flash, so won't be a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Recently, I did some &lt;a href=&quot;http://blog.hodgepig.org/2010/04/04/541/&quot; rel=&quot;nofollow&quot;&gt;experiments&lt;/a&gt; with AVRs and hall effect sensors. I never saw problems from being near magnets.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-29T21:06:54.027" CommentCount="1" />
  <row Id="4598" PostTypeId="2" ParentId="4596" CreationDate="2010-09-29T21:16:58.153" Score="2" ViewCount="" Body="&lt;p&gt;Magnets will not usually affect the chip. Magnets cause damaged to hard disks and floppy disks (remember those?) because they misalign the domains and destroy the data. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you happen to have long traces on your PCB and strong (especially pulsating) magnetic fields, you could get induced voltage in these traces. This could range from a tiny bit of additional noise causing no harm to damaging the microcontroller from a voltage spike. This is only theoretical. You'd probably need MRI-level magnetic fields to induce any significant voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you are using a fridge magnet I do not see any of the above being a problem.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-09-29T21:16:58.153" CommentCount="4" />
  <row Id="4599" PostTypeId="2" ParentId="4596" CreationDate="2010-09-29T21:25:11.423" Score="3" ViewCount="" Body="&lt;p&gt;Joby hit it on the head as far as storage goes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would caution people experimenting with magnets and electronics (like reed switches) to be very wary of the filings that collect on powerful magnets.  You'll get nearly invisible shorts when an iron filing that collected on the magnet falls onto your chip, embeds itself in some leftover flux, and takes down your system.  Industry is worried about tin whiskers 10um in diameter and less than 1mm long - iron filings are just as dangerous.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-29T21:25:11.423" />
  <row Id="4600" PostTypeId="2" ParentId="4593" CreationDate="2010-09-29T21:28:13.750" Score="4" ViewCount="" Body="&lt;p&gt;Loudness is roughly correlated to &lt;a href=&quot;http://en.wikipedia.org/wiki/Root_mean_square&quot; rel=&quot;nofollow&quot;&gt;RMS amplitude&lt;/a&gt;, not to peak amplitude, so you need to&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;sample the input regularly, recording the samples to memory &lt;/li&gt;&#xA;&lt;li&gt;take a chunk of samples and square each&lt;/li&gt;&#xA;&lt;li&gt;take the average of all the resulting values &lt;/li&gt;&#xA;&lt;li&gt;square root&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;You can probably simplify this depending on how much accuracy you need.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Oh wait, you want analog output.  You can put the wave through a &lt;a href=&quot;http://en.wikipedia.org/wiki/Precision_rectifier&quot; rel=&quot;nofollow&quot;&gt;precision rectifier&lt;/a&gt; (&lt;a href=&quot;http://sound.westhost.com/appnotes/an001.htm&quot; rel=&quot;nofollow&quot;&gt;schematics&lt;/a&gt;) to get the absolute value, and then filter with an RC filter to get its envelope, as in the circuitry leading to pin 5 of &lt;a href=&quot;http://freecircuitdiagram.net/wp-content/uploads/2009/09/10-led-VU-Meter-using-LM3915.gif&quot; rel=&quot;nofollow&quot;&gt;this schematic&lt;/a&gt;.  Instead of that IC, pin 5 would be your micro's ADC.  It's not RMS, but it will show you approximate loudness.  This is how most &lt;a href=&quot;http://en.wikipedia.org/wiki/VU_meter&quot; rel=&quot;nofollow&quot;&gt;VU meters&lt;/a&gt; work.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-09-29T23:54:41.853" LastActivityDate="2010-09-29T23:54:41.853" CommentCount="2" />
  <row Id="4601" PostTypeId="1" CreationDate="2010-09-29T21:37:07.583" Score="2" ViewCount="150" Body="&lt;p&gt;I'm building a simple circuit based on a relay and transistor to switch a fan for use on my boat. A digital pin from an arduino is connected to base of an NPN transistor, the emitter to ground and the collector to the ground pin of the relay. The circuit does not properly switch. However, if I short the emitter to the collector, the circuit functions fine (although not triggered by the pin). I took out a multimeter and the voltage from collector to emitter reads 0.02v. Is this enough to throw off the pin? Why is there any voltage at all?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Extra info. 5V relay, 2N3904, pin from micro &gt; 1k &gt; base&#xA;                                                        |&#xA;                                                       10k Pull down&#xA;I do have a protection diode across the coil.&lt;/p&gt;&#xA;" OwnerUserId="446" LastEditorUserId="446" LastEditorDisplayName="" LastEditDate="2010-09-29T22:35:30.657" LastActivityDate="2010-09-29T22:35:30.657" Title="How close to ground is close enough for a relay?" Tags="&lt;arduino&gt;&lt;motor&gt;&lt;relay&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="4602" PostTypeId="2" ParentId="4601" CreationDate="2010-09-29T21:49:05.637" Score="1" ViewCount="" Body="&lt;p&gt;First, the voltage from collector to emitter for a BJT will be about 0.2V minimum in saturation mode.  Your DMM was making an inaccurate reading for some reason.  This limit can be overcome by using a MOSFET, which will simply provide a tiny resistance (5ohms to 10s of milliohms) and, consequently, a tiny voltage drop. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You didn't post any information about your relay, either.  Are you operating it within the specified voltages?  Some relays will work at 5V, and some will not.  Whether it's referenced to ground or not is gloriously irrelevant - Just provide it with the datasheet specified voltage/current, and don't worry about your ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All that being said, however, I would guess that you've simply blown up your transistor.  The coil in the relay has a lot of inductance and a lot of current, and switching it can generate damaging voltage spikes.  If you're using a 5V relay, just hook a 5.1V zener across the coil (cathode to 5V, anode to the collector of your transistor).  This should help protect your electronics.  With the zener in place, give it another try.  (Note that there are more sophisticated protection methods if you need it, but I've always found a zener sufficient for reasonably rugged transistors with the small signal relays I work with - How big is the relay?).&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-09-29T21:49:05.637" CommentCount="11" />
  <row Id="4603" PostTypeId="2" ParentId="4576" CreationDate="2010-09-29T23:25:06.273" Score="2" ViewCount="" Body="&lt;p&gt;In terms of quality and reliability, you cannot beat machine placement on professionally manufactured PCBs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will most likely find that option #2 + #3 will work best - get the PCBs made offshore by a reputable low-cost shop that deals in prototype volumes (which may or may not be easy) and shop around for contract assembly places.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you considered sourcing the parts yourself (i.e. issuing a complete parts + boards kit to prospective builders) or are you looking for someone to supply parts as part of the service?&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-09-29T23:25:06.273" CommentCount="1" />
  <row Id="4604" PostTypeId="1" AcceptedAnswerId="4610" CreationDate="2010-09-29T23:57:42.580" Score="11" ViewCount="591" Body="&lt;p&gt;Once I heard of &lt;a href=&quot;http://netduino.com/&quot; rel=&quot;nofollow&quot;&gt;Netduino&lt;/a&gt; I began to wonder which other systems would provide the same features:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Processor and Memory Micro .NET Framework ready&lt;/li&gt;&#xA;&lt;li&gt;USB interface&lt;/li&gt;&#xA;&lt;li&gt;Cheap&lt;/li&gt;&#xA;&lt;li&gt;Portable&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1298" LastActivityDate="2010-11-12T00:12:21.103" Title="What are the .NET Micro Framework ready systems available?" Tags="&lt;system&gt;&lt;.net-micro-framework&gt;&lt;netduino&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="6" />
  <row Id="4605" PostTypeId="2" ParentId="4593" CreationDate="2010-09-30T00:09:27.913" Score="1" ViewCount="" Body="&lt;p&gt;You'll want a &lt;a href=&quot;http://en.wikipedia.org/wiki/Log_amplifier&quot; rel=&quot;nofollow&quot;&gt;logarithmic amplifier&lt;/a&gt; or log amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Loudness is measured in decibels; what sounds like a linearly increasing/decreasing loudness to a human being, actually corresponds to exponential changes in acoustic energy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can do this by buying off the shelf ICs (e.g. Linear Tech's &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1011,C1743,P12432&quot; rel=&quot;nofollow&quot;&gt;LT5537&lt;/a&gt;). Or you can do it yourself with op-amps, resistors, diodes, and transistors. Transistors have a very nice logarithmic relationship between collector current and base voltage over 5 or 6 decades of current (usually from 10s - 100s of nA to 1-10mA) and can be combined with op-amps to turn a current or voltage in, into a logarithmic voltage out (see &lt;a href=&quot;http://www.falstad.com/circuit/e-logconvert.html&quot; rel=&quot;nofollow&quot;&gt;this website&lt;/a&gt; for a circuit along w/ spiffy waveform graphics). You'll need to have your own waveform-to-RMS detector first, then feed the result into a log amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't use a log-amp, you're limited in dynamic range by the resolution + linearity + zero offset of the ADC you use, which may only be 20-30dB.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-09-30T00:09:27.913" CommentCount="1" />
  <row Id="4606" PostTypeId="1" AcceptedAnswerId="4630" CreationDate="2010-09-30T02:04:56.610" Score="3" ViewCount="159" Body="&lt;p&gt;Our house has 4 heat/cool zones, controlling two separate furnace units.   I'd like to build a system to log on/off times for each of the zones and the burners/compressors.   This makes a total of 10 inputs.    Is arduino a good platform for this type of application?  I have plenty of software experience, but limited hardware design knowledge (but I am comfortable with a soldering iron if I know the required design).    I would probably ship the data (input#, new state) to a nearby server using TCP or UDP to be logged.&lt;/p&gt;&#xA;" OwnerUserId="1295" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-28T09:08:31.990" LastActivityDate="2011-02-28T09:08:31.990" Title="Is Arduino a good platform for monitoring 24VAC thermostat circuits?" Tags="&lt;arduino&gt;&lt;hardware&gt;" AnswerCount="1" />
  <row Id="4607" PostTypeId="1" AcceptedAnswerId="4622" CreationDate="2010-09-30T02:16:06.930" Score="3" ViewCount="129" Body="&lt;p&gt;I'm looking for a embedded controller for a project. I don't really know what's out there so I don't know where to start looking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My requirements are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Support for significant amounts of I/O&#xA;&lt;ul&gt;&#xA;&lt;li&gt;~150 GPIO (directly or via expanders)&lt;/li&gt;&#xA;&lt;li&gt;Several SPI (or  I2C) interfaces&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Reasonably powerful, able to simultaneously do&#xA;&lt;ul&gt;&#xA;&lt;li&gt;~3MIPS&lt;/li&gt;&#xA;&lt;li&gt;~1MB/s I/O (via SPI/I2C) &lt;/li&gt;&#xA;&lt;li&gt;&amp;lt;1MB/s of eathernet traffic&lt;/li&gt;&#xA;&lt;li&gt;And enough room left over for the parts I'm forgetting&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Can be used from a standard environment (c, gcc, etc. Not a custom language and IDE)&lt;/li&gt;&#xA;&lt;li&gt;Simple to use (one, maybe two chips, etc.)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;My wants are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A &quot;standard&quot; architecture that has many implementations (to minimize the effort if I need to switch chips, for some reason I'm leaning towards ARM)&lt;/li&gt;&#xA;&lt;li&gt;Available on low cost dev boards.&lt;/li&gt;&#xA;&lt;li&gt;Available as chips (mounting a board on a custom PCB seems silly to me)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1182" LastActivityDate="2010-09-30T08:28:51.307" Title="Help selecting an embedded controller." Tags="&lt;embedded&gt;" AnswerCount="2" />
  <row Id="4608" PostTypeId="2" ParentId="4607" CreationDate="2010-09-30T02:41:43.460" Score="1" ViewCount="" Body="&lt;p&gt;I think that one of Atmel middle-class ARM controllers would satisfy almost all of your needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example: &lt;a href=&quot;http://atmel.com/dyn/products/product_card.asp?part_id=3754&quot; rel=&quot;nofollow&quot;&gt;AT90SAM7X128&lt;/a&gt; has:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;2 SPI (with 4 hardware chip select lines) and 1 I2C interface&lt;/li&gt;&#xA;&lt;li&gt;Ethernet controller&lt;/li&gt;&#xA;&lt;li&gt;DMA channels for all of the peripherals&lt;/li&gt;&#xA;&lt;li&gt;55Mhz of processing power&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Moreover, it is not very costly, and if you want to make some boards by yourself, the LQFP package allows you to do so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only drawback is that you need a lot of GPIOs, but AFAIK, it would be cheaper to add a (cheap and stupid) CPLD which only purpose would be GPIO handling. Then you can control it via hardware SPI or just by bit-banging already existing GPIOs.&lt;/p&gt;&#xA;" OwnerUserId="1311" LastActivityDate="2010-09-30T02:41:43.460" CommentCount="4" />
  <row Id="4610" PostTypeId="2" ParentId="4604" CreationDate="2010-09-30T03:09:43.880" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.tinyclr.com/&quot; rel=&quot;nofollow&quot;&gt;TinyCLR&lt;/a&gt; produces several different boards that support the .Net Micro Framework, the most popular being the &lt;a href=&quot;http://www.tinyclr.com/hardware/1/fez-domino/&quot; rel=&quot;nofollow&quot;&gt;Fez Domino&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://i.imgur.com/6fyvw.jpg&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/6fyvw.jpg&quot; width=&quot;500&quot; /&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;FEZ (Freakin' Easy!) is a tiny open-source board running Microsoft .NET Micro Framework. This means, you can write code with much more efficiency using C# programming language under free Microsoft Visual C# express. Build your next projects in minutes by connecting FEZ Domino to one of the shields or the many available components. Includes USB cable.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Many libraries are already included like FAT file system, threading, USB Client, USB Host, UART, SPI, I2C, GPIO, PWM, ADC, DAC and many more. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;FEZ offers many features not found in Arduino, BASIC STAMP and others:&lt;/p&gt;&#xA;  &#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;Based on Microsoft''s .NET Micro Framework.&lt;/li&gt;&#xA;  &lt;li&gt;Runs on 72Mhz NXP ARM processors.&lt;/li&gt;&#xA;  &lt;li&gt;Supports runtime debugging (breakpoints, variable inspection, stepping, etc.)&lt;/li&gt;&#xA;  &lt;li&gt;Use &lt;a href=&quot;http://www.microsoft.com/express/Downloads/#2010-Visual-CS&quot; rel=&quot;nofollow&quot;&gt;Visual C# 2010 Express Edition&lt;/a&gt; for development.&lt;/li&gt;&#xA;  &lt;li&gt;Advanced capabilities like FAT, USB device and USB host.&lt;/li&gt;&#xA;  &lt;li&gt;Easily upgrades to hardware such as &lt;a href=&quot;http://www.ghielectronics.com/product/128&quot; rel=&quot;nofollow&quot;&gt;EMX&lt;/a&gt;.&lt;/li&gt;&#xA;  &lt;li&gt;Open source hardware design files.&lt;/li&gt;&#xA;  &lt;li&gt;Use existing shields and holder boards.&lt;/li&gt;&#xA;  &lt;li&gt;Based on the &lt;a href=&quot;http://www.ghielectronics.com/product/116&quot; rel=&quot;nofollow&quot;&gt;USBizi chipset&lt;/a&gt; (ideal for commercial use).&lt;/li&gt;&#xA;  &lt;li&gt;&lt;a href=&quot;http://www.tinyclr.com/hardware/2/fez-mini/&quot; rel=&quot;nofollow&quot;&gt;FEZ Mini&lt;/a&gt; is &lt;a href=&quot;http://www.parallax.com/&quot; rel=&quot;nofollow&quot;&gt;BS2&lt;/a&gt; pin-out compatible with extra I/Os.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;a href=&quot;http://www.tinyclr.com/hardware/1/fez-domino/&quot; rel=&quot;nofollow&quot;&gt;FEZ Domino&lt;/a&gt; is &lt;a href=&quot;http://arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; pin-out compatible with extra I/Os.&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="693" LastActivityDate="2010-09-30T03:09:43.880" CommentCount="3" />
  <row Id="4611" PostTypeId="1" AcceptedAnswerId="4612" CreationDate="2010-09-30T03:57:47.580" Score="8" ViewCount="384" Body="&lt;p&gt;Pardon me, I'm a total newb to electronics. My question is, when a device is measured in watts, such as a 60-watt light bulb, is this ALWAYS supposed to be assumed to be watt-hours, i.e. 60 watts per hour?&lt;/p&gt;&#xA;" OwnerUserId="1314" LastActivityDate="2011-04-27T12:50:48.200" Title="Are watts usually measured in watt-hours?" Tags="&lt;power&gt;" AnswerCount="5" FavoriteCount="3" />
  <row Id="4612" PostTypeId="2" ParentId="4611" CreationDate="2010-09-30T04:16:39.317" Score="26" ViewCount="" Body="&lt;p&gt;&lt;em&gt;Energy&lt;/em&gt; is an amount, while &lt;em&gt;power&lt;/em&gt; is a rate at which energy is used.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Energy is measured in watt-hours (W·h) or joules (J).  &lt;/li&gt;&#xA;&lt;li&gt;Power is measured in watts (W) or joules per second (J/s).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Watt-hours are like buckets, and watts are like buckets per hour.  If you have 5 buckets of energy and you pour one bucket per hour, you'll be able to pour for 5 hours before you run out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you turn on a 60-watt light bulb for 1 hour, you have used 60 watt-hours of energy.  If you use it for 2 hours, you have used 120 watt-hours of energy.  If you turn it on for only 1 minute, you have used 1 watt-hour.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a little confusing since the &quot;per hour&quot; is inside the term &quot;watt&quot;, so to make the rate into an amount, you need to multiply by a time unit to cancel it out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be a lot more intuitive if we worked in kilojoules and kilojoules per hour.   :)&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-26T21:59:08.140" LastActivityDate="2011-04-26T21:59:08.140" CommentCount="4" />
  <row Id="4613" PostTypeId="2" ParentId="4611" CreationDate="2010-09-30T04:18:20.387" Score="2" ViewCount="" Body="&lt;p&gt;Stimpy, the power rating tells you the &lt;em&gt;rate&lt;/em&gt; at which the device consumes energy. So yes, a 60-Watt bulb will consume 60W*h or 0.06kWh of electricity in one hour. Watt-hours measure energy consumption. There is a simple little page &lt;a href=&quot;http://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci795904,00.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; that shows some calculations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also strongly recommend reading the &lt;strong&gt;HyperPhysics&lt;/strong&gt; &lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/work.html&quot; rel=&quot;nofollow&quot;&gt;box on Work, Energy, and Power&lt;/a&gt;, and especially the links on the &lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/powcon.html&quot; rel=&quot;nofollow&quot;&gt;Power Concepts page&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="690" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-09-30T12:12:27.190" LastActivityDate="2010-09-30T12:12:27.190" CommentCount="1" />
  <row Id="4614" PostTypeId="2" ParentId="4531" CreationDate="2010-09-30T04:21:44.823" Score="4" ViewCount="" Body="&lt;p&gt;So the answer does appear to be: you &lt;strong&gt;can&lt;/strong&gt; just hook up the wires, indeed just GND (black) and RXD (yellow), and everything works as long as the software is good.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Things that did not matter:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Internal oscillator works just fine.  It appears relatively stable to my limiting testing.  At 9600 baud whatever problems it has are negligible.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Using USB power on the signals works just fine.  You can use a separate voltage source (sharing a common ground), but the FTDI cable reads both 3V and 5V signals perfectly.  I connected a battery pack, - to GND of both the FTDI and the tiny, + to the tiny's VCC, and this worked just fine.  However just using the VCC (red) of the FTDI (USB power 5V) is much simpler and just as effective.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Things I did wrong:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;The Yellow FTDI &quot;RXD&quot; line receives bits from the microcontroller, so it connects to the transmit in on the microcontroller.  I could have figured this out myself by connecting the transmit and receive lines (orange and yellow) to LEDs or an Arduino and checking which voltage flickered when I transmitted from the PC.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Neither SoftwareSerial nor NewSoftSerial works out of the box with an ATtiny.  While the ATmega328p and the ATtiny85 share a lot of similarities, there are enough differences that just getting the old software to compile for the new chip is not sufficient.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Slower baud rates do not cure things. 300 baud requires more complicated delay routines since the number of cycles between bits is significantly more than an 8bit counter. 9600 baud works just fine, and higher baud rates are doable.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Be careful of writing timing critical code in C, especially in inline functions.  The time it takes to execute will depend on how the compiler optimizes it.  In particular, when calibrating the delay by just changing it up and down, you will get a different answer than when using a (compile time detectable) constant delay, because the assembly generated can be fairly different.  It's not that C is &quot;slow&quot;, but rather that it was too fast.  At one point I was sending 1s faster than 0s (presumably they are more aerodynamic).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;To start a transmission, you bring the line LOW (the start bit) and then you need to make sure the line is at the right voltage at each of the next 8 sample points, and then make sure the voltage is HIGH at the 9th sample.  NewSoftSerial mentions doing a half-length delay on the start bit, but this did not work well for me.  I used a 75% delay on the start and a 125% delay on the end.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The real concern about voltage might be that some &quot;serial&quot; (especially RS232) is ±12V, not 0V/5V.  I spent a lot of time trying to understand how I could adjust the voltage from 5V to 3.3V, but I think that was completely irrelevant.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;At any rate, transmitting serial is easy, but getting the timing &quot;perfect&quot; appears pretty important.  For me, this was just a matter of coding the transmit in assembly so that I could count the cycles.&lt;/p&gt;&#xA;" OwnerUserId="1271" LastActivityDate="2010-09-30T04:21:44.823" CommentCount="3" />
  <row Id="4615" PostTypeId="2" ParentId="1011" CreationDate="2010-09-30T04:37:29.077" Score="0" ViewCount="" Body="&lt;p&gt;I try to take as little work home as possible, but if you really enjoy what you do, it's inevitable to try to hash out solutions.  As others said, some of your best insights might come from when you're not actively pursuing a solution, but when it is on the back-burner.  Also, right before sleep is a great time to think.&lt;/p&gt;&#xA;" OwnerUserId="1297" LastActivityDate="2010-09-30T04:37:29.077" CommunityOwnedDate="2010-09-30T04:37:29.077" />
  <row Id="4616" PostTypeId="2" ParentId="4611" CreationDate="2010-09-30T04:40:21.333" Score="0" ViewCount="" Body="&lt;p&gt;You are correct in assuming a 60 watt device will consume 60 watt-hours in one hour, but the former (power) is a rate, the latter is an amount (energy).&lt;/p&gt;&#xA;" OwnerUserId="1297" LastEditorUserId="1297" LastEditorDisplayName="" LastEditDate="2010-09-30T20:50:55.257" LastActivityDate="2010-09-30T20:50:55.257" CommentCount="1" />
  <row Id="4618" PostTypeId="1" AcceptedAnswerId="4625" CreationDate="2010-09-30T04:54:57.253" Score="10" ViewCount="395" Body="&lt;p&gt;I use a &lt;a href=&quot;http://www.ladyada.net/make/boarduino/&quot; rel=&quot;nofollow&quot;&gt;Boarduino&lt;/a&gt; and a 30-row bread board to program my ATtiny.  I load a not too complicated sketch called &lt;a href=&quot;http://arduino.cc/en/Tutorial/ArduinoISP&quot; rel=&quot;nofollow&quot;&gt;ArduinoISP&lt;/a&gt; (included by default now in the Arduino IDE), and suddenly I have a working programmer.  Atmel sells a &lt;a href=&quot;http://www.atmel.com/dyn/products/tools_card.asp?tool_id=2726&quot; rel=&quot;nofollow&quot;&gt;nice programmer&lt;/a&gt; for between $30 and $40, and there are lots of kits for making cheaper ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was very happy once I got my working programmer and made the tiny blink some leds.  However, now my poor boarduino is stuck on programmer duty.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I can tell this programmer holds down the reset button, and then transmits and receives on the MOSI and MISO pins.  &lt;s&gt;I think the SCK is unused or at least unneeded.&lt;/s&gt; &lt;sup&gt;(SCK is needed according to the ATtiny datasheet, my programmer doesn't work without it, and I can't find the place I thought I read it was not needed.)&lt;/sup&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why do I need a hardware programmer to just transmit serial? I mean, let's suppose I am willing to hold down the reset button with my finger instead of using an IC.  All that's left is serial send and receive, so all I need are three wires GND, RXD, and TXD.  Heck, if I have the &quot;DTR&quot; line or whatever, you can even hold down the reset button with the serial cable.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Why are there all these hardware solutions that &lt;em&gt;also&lt;/em&gt; require fancy software (like AVRdude, or AVR studio, or whatever)?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I mean I could understand a little USB cable that presented the microcontroller as a mass storage device and let you drag binary files over for programming (like &lt;a href=&quot;http://www.microbuilder.eu/Projects/LPC1343ReferenceDesign.aspx&quot; rel=&quot;nofollow&quot;&gt;this ARM dev board&lt;/a&gt;).  Hardware only, using standard software drivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could also understand a software only solution (modulo hooking wires from the USB to the chip, using something like the FTDI chip to simplify what goes down the wires).  All of the fancy programming protocol would be handled by software on the computer, and the hardware would just be some wires.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why do we have both (complicated) software and hardware involved?  I mean, as far as I can tell, programming microcontrollers is pretty easy, but when I was just getting into this I was really worried about how I was going to ever buy a chip from mouser or digikey without paying some guru to program a bootloader for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm sure there is a good reason (it's not like I've written the software or started manufacturing the drag-n-drop USB programmer), but as a newcomer, I have no idea what it is.&lt;/p&gt;&#xA;" OwnerUserId="1271" LastEditorUserId="1271" LastEditorDisplayName="" LastEditDate="2010-10-01T00:41:22.060" LastActivityDate="2010-10-01T00:56:43.710" Title="Why do we need hardware programmers?" Tags="&lt;arduino&gt;&lt;microcontroller&gt;&lt;avrdude&gt;&lt;isp&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="3" />
  <row Id="4619" PostTypeId="1" AcceptedAnswerId="4620" CreationDate="2010-09-30T05:09:10.720" Score="6" ViewCount="207" Body="&lt;p&gt;Hello everyone, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need a number of digital outputs to connect my computer to the real world, however it seems that this job is not nearly as easy as I had hoped.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've looked into a number of different methods, ranging from dedicated digital I/O cards, micro controllers with USB interfaces, serial ports, parallel ports, ect. However all of the solutions seem to be either too expensive, too much work, or the technology is too dated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope to have 64+ digital outputs running at approximately 1khz each, individually controllable. So far the best idea I can come up with is sticking the outputs of a serial port to an 8-bit serial to parallel shift register and sending chars down the serial connection whenever I wish to change and output (run from a USB to serial port adaptor). I haven't tested this yet so i don't know if it will work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any other quick and dirty method of getting a fairly large number of inexpensive digital outputs from the computer of which I can easy control with very basic C++ commands?&lt;/p&gt;&#xA;" OwnerUserId="1319" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-09-30T12:56:20.803" LastActivityDate="2011-05-18T11:32:26.503" Title="Easiest and cheapest way to get digital outputs from a computer to the real world" Tags="&lt;stepper&gt;&lt;output&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="2" />
  <row Id="4620" PostTypeId="2" ParentId="4619" CreationDate="2010-09-30T06:21:26.097" Score="7" ViewCount="" Body="&lt;p&gt;Sounds like you intend to flash some christmas lights. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anything wrong with using an arduino or similar?&#xA;It would be fairly easy to expand the number of IO ports if the number of ports say on the mega 1280/2560 aren't enough. You can drive it via serial/USB terminal. You could use shift registers on the output pins of the arduino or you could use the i2c port expander and drive through that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using standard components like that will give you the shortest amount of prototyping time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note, my way may not be the cheapest. But it's effective and will actually get you rolling quickly.&lt;/p&gt;&#xA;" OwnerUserId="1304" LastActivityDate="2010-09-30T06:21:26.097" CommentCount="4" />
  <row Id="4621" PostTypeId="1" CreationDate="2010-09-30T06:27:24.383" Score="2" ViewCount="162" Body="&lt;p&gt;I need to get beagle board XM in India? Any useful information on vendors?&lt;/p&gt;&#xA;" OwnerUserId="1323" LastActivityDate="2010-11-13T12:11:31.103" ClosedDate="2010-11-18T13:37:56.300" Title="Getting Beagle Board in India" Tags="&lt;beagleboard&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="4622" PostTypeId="2" ParentId="4607" CreationDate="2010-09-30T07:11:29.453" Score="3" ViewCount="" Body="&lt;p&gt;Check out the Digikey website&#xA;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556109&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556109&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have an online configurator where you can spec out your micro piece by piece... there are several that meet your spec.  If you load the above page, be sure to scroll to the right, as there are tons and tons of options including package, memory peripherals etc...&lt;/p&gt;&#xA;" OwnerUserId="991" LastActivityDate="2010-09-30T07:11:29.453" />
  <row Id="4624" PostTypeId="2" ParentId="4576" CreationDate="2010-09-30T08:13:36.767" Score="0" ViewCount="" Body="&lt;p&gt;&lt;em&gt;&lt;strong&gt;Don't forget the marketing!&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from the hardware assembly and manufacturing side of your project, you may also wish to consider how to market your product earlier in the piece.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it really turns out to be as good as you expect, having one of the review forums like hackaday or hacked gadets review the product will help you achieve critical mass a lot faster and move the product out the door.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you are a student and investing in 50-100 built units is going to cost you a serious chunk of change. Once they are built and have them sitting on the shelf isn't going to get you a good return on investment. So you need to be just a bit clever about the way you intend to sell your product. Blogging the process, twittering, tumblr'ing will hopefully get you a bit of a following and make it just that much easier to sell some product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think about what support or other options you might also provide purchasers with. Building a logging device is probably one of those things which would probably benefit from regular firmware updates to improve or add features to the logging. (Bug fixes even!)  Make it easier for purchasers to access this info and update their product.&lt;/p&gt;&#xA;" OwnerUserId="1304" LastActivityDate="2010-09-30T08:13:36.767" CommentCount="2" />
  <row Id="4625" PostTypeId="2" ParentId="4618" CreationDate="2010-09-30T08:27:08.767" Score="10" ViewCount="" Body="&lt;p&gt;You are right, programming AVRs is pretty easy. It's just a custom protocol implemented on top of SPI, running at low voltage. SCK is needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, programming older PICs (and non ISP AVR programming) requires high voltages and a different custom protocol. This necessitates a special hardware programmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other devices are more complex. Most ARM microcontrollers must be programmed via JTAG, here memory is being written directly and the processor is instructed to write to the flash. Again, every device is different.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-09-30T14:45:49.173" LastActivityDate="2010-09-30T14:45:49.173" CommentCount="5" />
  <row Id="4627" PostTypeId="2" ParentId="4618" CreationDate="2010-09-30T08:45:03.553" Score="3" ViewCount="" Body="&lt;p&gt;I did a lot of research and am preparing to start playing with AVRs, but I never actually used one, so this may be wrong, but:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most cheap programmers will not support AVR high voltage programming. It is needed if the controller is set to be nonprogrammable using fuse bits or if you somehow made some serious bugs and need to reset it to defaults and so on.  &lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-09-30T10:19:16.037" LastActivityDate="2010-09-30T10:19:16.037" CommentCount="4" />
  <row Id="4629" PostTypeId="1" AcceptedAnswerId="4672" CreationDate="2010-09-30T09:58:56.777" Score="3" ViewCount="134" Body="&lt;p&gt;In datacenters it's common to use &lt;a href=&quot;http://en.wikipedia.org/wiki/Uninterruptible_power_supply&quot; rel=&quot;nofollow&quot;&gt;Uninterruptible power supply (UPS)&lt;/a&gt; to protect the computers. They are used for several reasons, but one is that electronics possibly can suffer from the power grid if the power isn't &quot;filtered&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it only the power supply unit of the computer that can suffer or can the computer parts also suffer? And how can they suffer? Does an &lt;a href=&quot;http://en.wikipedia.org/wiki/Uninterruptible_power_supply&quot; rel=&quot;nofollow&quot;&gt;Uninterruptible power supply&lt;/a&gt; work differently to an &lt;a href=&quot;http://en.wikipedia.org/wiki/Power_supply_unit_%28computer%29&quot; rel=&quot;nofollow&quot;&gt;Power supply unit (PSU)&lt;/a&gt; or is the PSU already protecting the computer parts from the power grid?&lt;/p&gt;&#xA;" OwnerUserId="1330" LastActivityDate="2010-10-01T02:01:26.813" Title="How can computer parts suffer if the computer isn't protected by an UPS?" Tags="&lt;power-supply&gt;&lt;ups&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="4630" PostTypeId="2" ParentId="4606" CreationDate="2010-09-30T10:23:17.933" Score="3" ViewCount="" Body="&lt;p&gt;It's perfect.  I did this exact thing in my house.  I used an MID400 optocoupler to turn the 24VAC present across the terminals of the thermostat (at the furnace end) when the thermostat is NOT calling for heat into a digital high at the Arduino.  I'm using an XBee network, but Ethernet (or even a tethered computer) would work just fine, too.  It'll work for higher voltages, too.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-09-30T10:23:17.933" CommentCount="1" />
  <row Id="4631" PostTypeId="1" AcceptedAnswerId="4638" CreationDate="2010-09-30T11:37:15.727" Score="2" ViewCount="1152" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking to get a spi serial port running on a pic32 (pic32mx360f). can anyone point me to some good resources on how to do this so that a newb can figure it out? I am using the pic32 starter kit and have a pic32 breakout board from digi-key&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the code that I have been using... I found it in the pic32 family manual.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;p32xxxx.h&amp;gt;&#xA;    int main(void){&#xA;    int rData;&#xA;    IEC0CLR=0x03800000; // disable all interrupts&#xA;    SPI1CON = 0; // Stops and resets the SPI1.&#xA;    rData=SPI1BUF; // clears the receive buffer&#xA;    IFS0CLR=0x03800000; // clear any existing event&#xA;    IPC5CLR=0x1f000000; // clear the priority&#xA;    IPC5SET=0x0d000000; // Set IPL=3, Subpriority 1&#xA;    IEC0SET=0x03800000; // Enable RX, TX and Error interrupts&#xA;    SPI1BRG=207; // use FPB/4 clock frequency&#xA;    SPI1STATCLR=0x40; // clear the Overflow&#xA;    SPI1CON=0x8220; // SPI ON, 8 bits transfer, SMP=1, Master mode&#xA;    // from now on, the device is ready to transmit and receive data&#xA;    SPI1BUF='A'; // transmit an A character&#xA;&#xA;    while(1){&#xA;        SPI1BUF= 'A'; // transmit an A character&#xA;        while(i &amp;lt; 10000){i++;}&#xA;        i = 0;&#xA;    }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;}&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I set the baudrate? I am guessing it got something to do with SPI1BRG&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks to tcrosley I feel that I am getting closer to being able to communicate with my pic32. I changed SPI1BRG to 207. By my calculations this will set the baudrate to around 9600.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fsck = Fpb/(2(SPIxBRG +1)) = 4MHZ/(2*(207+1))= 9615&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to view the output on the picchip with HyperTerminal. The settings I am using are: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Baud: 9600&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Data bits: 8&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Parity: None&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stop bits: 1&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Flow Control: None&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The pins I am using are:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;93 - connected to db9 3&lt;/p&gt;&#xA;&#xA;&lt;p&gt;95 - connected to db9 2&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and db9 5 is connected to the boards ground...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am now getting an output, which is nice, but unfortunately it is garbage. my output on HyperTerminal comes out as a bunch of hearts :S now I just feel like my pic32 is mocking me&lt;/p&gt;&#xA;" OwnerUserId="1337" LastEditorUserId="1337" LastEditorDisplayName="" LastEditDate="2010-10-07T12:58:15.560" LastActivityDate="2010-10-09T05:17:38.437" Title="how to get a pic32 spi port working for transmitting data." Tags="&lt;pic&gt;&lt;spi&gt;&lt;pickit&gt;" AnswerCount="5" CommentCount="6" />
  <row Id="4632" PostTypeId="2" ParentId="4621" CreationDate="2010-09-30T12:12:35.433" Score="1" ViewCount="" Body="&lt;p&gt;Try these guys - &lt;a href=&quot;http://www.idasystems.net/beagle_board&quot; rel=&quot;nofollow&quot;&gt;idasystems&lt;/a&gt;. If you are looking for a 50% cheaper option to Beagleboard (with lesser features) try the &lt;a href=&quot;http://www.innovatesolutions.net/products/hawkboard&quot; rel=&quot;nofollow&quot;&gt;Hawkboard&lt;/a&gt;. I think both of them are in based in bangalore / hyderabad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Disclaimer: I havent bought from either of these vendors nor have I tried either of these boards.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastActivityDate="2010-09-30T12:12:35.433" CommentCount="1" />
  <row Id="4633" PostTypeId="2" ParentId="3107" CreationDate="2010-09-30T12:21:55.133" Score="1" ViewCount="" Body="&lt;p&gt;Neither open-source nor still supported but Xilinx offers a free, cross-platform (Java) API called Jbits which allows directly programming (and on-the-fly reprogramming) of FPGAs. I believe only CPLDs and up to Virtex-II are supported, but it's the closest thing to allowing devs to produce their own custom synthesis tools.  Planning to play around with this quite a bit in the near future.&lt;/p&gt;&#xA;" LastActivityDate="2010-09-30T12:21:55.133" />
  <row Id="4634" PostTypeId="2" ParentId="1011" CreationDate="2010-09-30T12:25:47.277" Score="0" ViewCount="" Body="&lt;p&gt;To be happy in life I believe you have to do what you love at home, AND at work. A complete separation of work and home suggests a person's career isn't in a field they love, and it's is a combination for an unhappy life (find a job doing something you love, something you would do at home for fun). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cue rhetoric and disgruntled employee comments in 1.. 2.. 2...&lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-09-30T12:25:47.277" CommunityOwnedDate="2010-09-30T12:25:47.277" />
  <row Id="4635" PostTypeId="2" ParentId="4629" CreationDate="2010-09-30T12:36:37.233" Score="2" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Is it only the power supply unit of the computer that can suffer or can the computer parts also suffer?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The power supply is the area that can be damaged by surges in the AC mains. But if the power supply is really damaged, and it delivers overvoltages in its output, the CPU and other parts can be damaged as well. It's all about failure propagation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a lightning strike, there's no telling what can happen. &lt;em&gt;For what it's worth&lt;/em&gt;: if you protect your power supply with a surge protector or other power conditioning device, make sure that &lt;em&gt;all&lt;/em&gt; connections to your computer (telephone line for modem / ethernet connection) are protected, so that in a lightning storm the surge currents can't find a back-door into damaging your computer. &lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-09-30T12:36:37.233" />
  <row Id="4636" PostTypeId="2" ParentId="4629" CreationDate="2010-09-30T12:47:32.087" Score="2" ViewCount="" Body="&lt;p&gt;Take into account that the output of the PSU under load never changes instantly, due to the inductance of the transformer, the output inductors and the caps. The MOSFET &lt;em&gt;should&lt;/em&gt; go pop before anything bad happens. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's more like that the power supply will fail before delivering increased voltage, but if you want to be extra-safe, use a surge protector. I opened up a scope power supply (from a HP 54501A) to find it has spark gaps on the input mains. Don't see that quality much more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember: most UPSes are not line interactive, and continue to supply voltage to your devices unless a complete power failure occurs. A cheapy UPS will not do anything. It might have some MOVs on the inputs, at best.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-09-30T12:47:32.087" />
  <row Id="4637" PostTypeId="2" ParentId="4631" CreationDate="2010-09-30T12:52:30.703" Score="0" ViewCount="" Body="&lt;p&gt;For starters: &lt;p&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Make sure you have your TRIS registers setup properly&lt;/li&gt;&#xA;&lt;li&gt;Use a bus monitor or oscilloscope to see if the SPI signal timing is correct for the device you are trying to communicate with&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-09-30T12:52:30.703" />
  <row Id="4638" PostTypeId="2" ParentId="4631" CreationDate="2010-09-30T13:22:54.190" Score="3" ViewCount="" Body="&lt;p&gt;This application note &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en542689&quot; rel=&quot;nofollow&quot;&gt;AN1277&lt;/a&gt; describes how to interface a serial SRAM to a PIC32 microcontroller using the C32 Compiler.  The page has a link to a zip file containing source code, which should have low level routines for reading and writing data via the SPI interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;How do I set the baudrate? I am&#xA;  guessing it got something to do with&#xA;  SPI1BRG&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I see that you have downloaded the &quot;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/PIC32MX_Datasheet_v3_61143C.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;&quot; for your processor (datasheet is a bit of a misnomer, it is 632 pages long), so I will be using page references from that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The equation (on page 397) for the SPI clock frequency is&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fsck = Fpb / (2 * (SPI1BRG+1))&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe the PIC32MX360F starts out with a internal FRC oscillator of 8 MHz, divided by 2 (due to the FRCDIV default value of 1 in OSCCON register, page 56), and since you are not making a changes in your code to OSCCON, the SYSCLK value will be 4 MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fpb is the Peripheral Bus Clock frequency.  It is set up in PBDIV field of the OSCCON register, which in turn is initialized to the value of the FPBDIV field in the DEVCFG1 (boot configuration register), depicted on page 63.  Assuming you haven't changed this, the default POR (power-on reset) value is binary 11, which means the Fpb is SYSCLK divided by 8.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Therefore Fpb = 4 MHz / 8 or 500 KHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If SPI1BRG = 1, as in your example, Fsck = Fpb / (2 * (1+1)) = Fpb / 4 = 500 KHz / 4 or 125 KHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your SYSCLK differs from 4 MHz, then scale the Fpb accordingly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Aren't embedded processors fun?  &lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-10-06T06:17:28.807" LastActivityDate="2010-10-06T06:17:28.807" CommentCount="3" />
  <row Id="4639" PostTypeId="1" CreationDate="2010-09-30T13:38:53.987" Score="4" ViewCount="314" Body="&lt;p&gt;I'm looking to power several small, Wi-Fi enabled sensors, in a domestic home or office environment. As such I'm interested in keeping them powered as long as possible between charges.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously an expensive Li-xx battery would be simple solution, but I've also been looking for more 'inspired' alternatives, such as &lt;a href=&quot;http://www.micropelt.com/applications/energy_harvesting.php&quot; rel=&quot;nofollow&quot;&gt;Micropelt thermogenerators&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What &lt;strong&gt;other alternatives&lt;/strong&gt; are there that would provide a &lt;em&gt;decent amount&lt;/em&gt; of power, in a small size? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternative wireless networking ideas are welcome, but I'm keen to use WiFi - most homes have a WiFi network and enabled computer - I'd like to keep the extra equipment needed to an absolute minimum.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[There is a &lt;a href=&quot;http://electronics.stackexchange.com/questions/4323/alternative-energy-storage&quot;&gt;related question&lt;/a&gt;, about energy &lt;em&gt;storage&lt;/em&gt;. My question is about generation and my needs are fairly specific (size, high power etc.]&lt;/p&gt;&#xA;" OwnerUserId="1329" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-23T21:16:06.210" LastActivityDate="2010-12-23T21:16:06.210" Title="What are some alternative power sources for wireless sensors?" Tags="&lt;power-supply&gt;&lt;wireless&gt;&lt;hardware&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="3" />
  <row Id="4640" PostTypeId="1" AcceptedAnswerId="4647" CreationDate="2010-09-30T13:42:09.260" Score="5" ViewCount="229" Body="&lt;p&gt;Every RC car I've cannibalized has had a small ceramic capacitor soldered on to the contacts of the motors. What is the purpose of having this? What happens to the performance of the motor with out this?&lt;/p&gt;&#xA;" OwnerUserId="1308" LastActivityDate="2010-09-30T14:38:31.960" Title="Capacitors and motors" Tags="&lt;motor&gt;&lt;capacitor&gt;&lt;rc&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="3" />
  <row Id="4641" PostTypeId="2" ParentId="4640" CreationDate="2010-09-30T13:55:39.903" Score="1" ViewCount="" Body="&lt;p&gt;A capacitor across leads is always a filter, filtering out high frequency (noise) signals. It also can be charged up, and discharged, so it acts like a very small and short lived battery, smoothing out the signal that doesn't get filtered out.&lt;/p&gt;&#xA;" OwnerUserId="1266" LastActivityDate="2010-09-30T13:55:39.903" />
  <row Id="4642" PostTypeId="2" ParentId="4631" CreationDate="2010-09-30T14:01:34.033" Score="1" ViewCount="" Body="&lt;p&gt;What are you interfacing the SPI to? Whatever that is will have a datasheet that gives you the requirements for your SPI channel. &#xA;So, &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;set up your TRIS register correctly, &lt;/li&gt;&#xA;&lt;li&gt;properly enable the SPI channel, &lt;/li&gt;&#xA;&lt;li&gt;set the levels of SI and SO and how they're phased with the SCLK. And you might need an enable (slave select).  The datasheet of what your interfacing to will tell you that. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Use an oscope to double check that you're doing it correctly.&lt;/p&gt;&#xA;" OwnerUserId="1266" LastEditorUserId="1266" LastEditorDisplayName="" LastEditDate="2010-09-30T18:51:34.133" LastActivityDate="2010-09-30T18:51:34.133" />
  <row Id="4643" PostTypeId="2" ParentId="4640" CreationDate="2010-09-30T14:03:34.427" Score="2" ViewCount="" Body="&lt;p&gt;Low value capacitors are used to reduce the RF noise caused by brushed motors. RF noise can interfere with your control signal which is obviously a particular problem in RC vehicles because of the proximity to the receiver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a brushed motor the brush contacts are constantly making and breaking contact with the power, which produces high frequency electrical noise. &lt;strike&gt;The capacitor acts to reduce this high frequency signal by holding charge and smoothing over any changes so rather than fast spikes and dips in the power supply you just get a gentle wave.&lt;/strike&gt; [See &lt;a href=&quot;http://electronics.stackexchange.com/questions/4640/capacitors-and-motors/4647#4647&quot;&gt;Andrew's answer&lt;/a&gt; for the details on how this works.]&lt;/p&gt;&#xA;" OwnerUserId="898" LastEditorUserId="898" LastEditorDisplayName="" LastEditDate="2010-09-30T14:38:31.960" LastActivityDate="2010-09-30T14:38:31.960" CommentCount="2" />
  <row Id="4644" PostTypeId="2" ParentId="4629" CreationDate="2010-09-30T14:10:08.190" Score="3" ViewCount="" Body="&lt;p&gt;An UPS is generally used to keep power to your system during a power outage. On the most basic level, it is just a battery bank connected with a relay and an inverter. When the power goes out the relay switches to the inverter(often just a modified square wave with off the shelf UPS). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't assume that the ups has any filtering without reading the spec's. Cheaper UPS's only give a direct feed from your outlet until there is an outage, so if you have dirty power from your outlet, it is likely you will have dirty power entering your electronics. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A PSU is different in the sense that it may not have a battery backup. A PSU on a computer generally just takes AC power and converts it to DC. There will be some filtering effects in this process but I would suggest still using a surge protector for any valuable electronics. The cost of a surge protector vs replacing is minuscule. &lt;/p&gt;&#xA;" OwnerUserId="1337" LastActivityDate="2010-09-30T14:10:08.190" />
  <row Id="4645" PostTypeId="2" ParentId="4639" CreationDate="2010-09-30T14:11:08.430" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.rachelselectronics.com&quot; rel=&quot;nofollow&quot;&gt;Rachel's Electronics&lt;/a&gt; has been posting about a solar-powered Arduino solution for remote sensors lately.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/lXwaj.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure if that provides enough power for Wi-Fi, though.  I'd look at less power-hungry wireless if I were you.  Are you really sending 10 Mbit/s?  Or do you just need a few kbit per hour?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-09-30T14:11:08.430" CommentCount="8" />
  <row Id="4646" PostTypeId="2" ParentId="4619" CreationDate="2010-09-30T14:22:41.320" Score="3" ViewCount="" Body="&lt;p&gt;The serial to parallel shift register will work. Using the SPI port you will&#xA;have no problem with the 1KHz update rate. IIRC on an ATmega328 with an 8MHz crystal (or higher) you should be able to get 1Mbits per second. A lot of other microcontrollers&#xA;will work as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to use multiple microcontrollers. For example -- using an ATmega328 (which is around $5 with the passives) would give you 18 lines while keeping the TXD and RXD lines free. Parallel up the RXD lines and then all the uCs will receive the same command strings.&#xA;You would need to parse the command strings on the uC. Use an FTDI cable to get to&#xA;USB. Add an Arduino bootloader to the uC and you could use the Arduino tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The serial to parallel conversion is more straight forward. If your application can&#xA;use open-drain outputs you could use a 16 channel LED driver. This would mean adding&#xA;four chips.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:32:26.503" LastActivityDate="2011-05-18T11:32:26.503" />
  <row Id="4647" PostTypeId="2" ParentId="4640" CreationDate="2010-09-30T14:24:18.883" Score="14" ViewCount="" Body="&lt;p&gt;The other two people who have answered have the first part right: the small-value ceramic capacitor acts as a high frequency filter. The brushes create insane amounts of broad-spectrum high frequency noise and this can interfere with the electronics (especially the radio receiver).  The capacitor acts as a short-circuit at high frequencies (Xc = 1/(2*pi*fC)) and it is soldered as close as possible to the commutator (i.e. right at the motor leads) to minimize the &quot;antenna&quot; these frequencies see. If the capacitor was not there the noise would &quot;see&quot; several inches of motor lead which would act as a great little antenna for broadcasting this noise into anything nearby, especially the sensitive radio receiver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has nothing to do with smoothing over anything -- the capacitor is far too small to be effective as a temporary storage device. It's being used as a frequency-selective low-impedance shunt, a low-pass filter, if you will.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-09-30T14:24:18.883" CommentCount="3" />
  <row Id="4648" PostTypeId="2" ParentId="1011" CreationDate="2010-09-30T14:39:51.083" Score="0" ViewCount="" Body="&lt;p&gt;Not much, but happens sometimes - say a couple of times a month. I try to minimize it and what that means is that I stay back late in the office. I tend to attend meetings that are later in the day from home too sometimes...&lt;/p&gt;&#xA;" OwnerUserId="1143" LastActivityDate="2010-09-30T14:39:51.083" CommunityOwnedDate="2010-09-30T14:39:51.083" />
  <row Id="4649" PostTypeId="2" ParentId="4639" CreationDate="2010-09-30T14:42:10.270" Score="2" ViewCount="" Body="&lt;p&gt;You should specify what sort of environment you're talking about.  Most of the methods I've heard of also use batteries to store the energy, but you could also use an array of supercapacitors.  However, that's getting expensive as well.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideas I've seen used successfully to some degree:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Solar is the first one, but it does require light.  Any light will do of course, even fluorescents.  Will it keep your circuit powered for a significant amount of time?  Depends on where it's put.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vibration/Piezoelectric generation has been used successfully to power sensors placed under busy stairs.  The key is busy stairs - imagine the New York subway or the main stairs at a university between classes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EM capturing - If there's a lot of ambient EM then you can put out an antenna, rectify the results and regulate it - boom, power.  However, it's usually illegal to do this with significant sources.  For example, you can power a light bulb if you're with a quarter mile of a large radio antenna, but harvesting that power is illegal in most countries.  It WILL be noticed too. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As Endolith said, you'll probably want a less power-hungry module.  Consider Zigbee instead of WiFi - it was designed to be used in low-power devices that transmit for short bursts then stop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[EDIT] Ok, office/home/domestic is the application.  If you control it significantly, maybe you can alter it. Say by adding inductive chargers?  I don't think there's that many source of power in a standard office other than solar. &lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="249" LastEditorDisplayName="" LastEditDate="2010-10-01T23:56:49.340" LastActivityDate="2010-10-01T23:56:49.340" CommentCount="6" />
  <row Id="4650" PostTypeId="2" ParentId="1011" CreationDate="2010-09-30T14:56:10.517" Score="0" ViewCount="" Body="&lt;p&gt;I just started a few months ago working as a software engineer (although I was trained as an electrical engineer) I try my best to keep work at work, But that being said the type of work we do as engineers makes it hard to do this. I often find myself drifting off thinking about ways to optimize code or what have you. I also find that I continuously researching different subject matter relating to what I do at work online while I am home. Further more, I also find myself checking scripts and making sure systems that I had help to put in place at work are still running properly remotely from my PC at home. So while I do not actively take work home with me, I am often doing work related activities at home.  &lt;/p&gt;&#xA;" OwnerUserId="1337" LastActivityDate="2010-09-30T14:56:10.517" CommunityOwnedDate="2010-09-30T14:56:10.517" />
  <row Id="4651" PostTypeId="1" AcceptedAnswerId="4669" CreationDate="2010-09-30T15:01:34.597" Score="4" ViewCount="623" Body="&lt;p&gt;Well, the question is the title: Is it worth really buying a Fluke for hobbyist use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a cheap meter at the moment. Is it worth spending a 3 figure sum on a nice, shiny, new Fluke? I honestly don't think so, but I'm curious what other's opinions are.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-08T03:51:47.240" LastActivityDate="2011-05-18T11:32:40.357" Title="Is it worth really buying a Fluke for hobbyist use?" Tags="&lt;equipment&gt;&lt;multimeter&gt;&lt;multimeter&gt;" AnswerCount="8" CommentCount="1" FavoriteCount="1" />
  <row Id="4652" PostTypeId="1" AcceptedAnswerId="4653" CreationDate="2010-09-30T15:55:24.177" Score="2" ViewCount="130" Body="&lt;p&gt;I am a total newbie for electronics and hardware programming, but I would really like to start practicing it. As a first achievement, I would like to find a simple step motor and drive it through a simple USB connection. The easiest (less HW/less SW) is the way to achieve this, the better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of hardware and software do I need ? How can I achieve this first step? Please consider as you are explaining it to a child. I really know nothing about this activity.&lt;/p&gt;&#xA;" OwnerUserId="1272" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-09-30T16:07:57.867" LastActivityDate="2010-09-30T16:07:57.867" Title="Driving a stepper motor via USB and OSX" Tags="&lt;usb&gt;&lt;stepper&gt;" AnswerCount="1" />
  <row Id="4653" PostTypeId="2" ParentId="4652" CreationDate="2010-09-30T16:04:07.923" Score="3" ViewCount="" Body="&lt;p&gt;I'd buy an Arduino and the Adafruit stepper shield.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;products_id=81&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;products_id=81&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have some great documentation:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ladyada.net/make/mshield/&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/make/mshield/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-30T16:04:07.923" CommentCount="2" />
  <row Id="4654" PostTypeId="2" ParentId="4651" CreationDate="2010-09-30T16:07:41.753" Score="3" ViewCount="" Body="&lt;p&gt;Like everything, it depends on what your are doing... For must applications a cheap meter will do the job. One of the advantages of Fluke multimeter is that they give true RMS readings for ac readings. Most of the readings you will be taking will likely be sinusoidal anyways, so this shouldn't be an issue. Other meter's have different capabilities like measuring power. for example a cheap meter will not be able to give an accurate measure of ac power because you will not know the power coefficient, but you would be able to measure its VA's...   &lt;/p&gt;&#xA;" OwnerUserId="1337" LastActivityDate="2010-09-30T16:07:41.753" CommentCount="3" />
  <row Id="4655" PostTypeId="2" ParentId="4651" CreationDate="2010-09-30T16:09:30.220" Score="6" ViewCount="" Body="&lt;p&gt;Depends on how important it is to you to have high-quality good accuracy gear. I bought two Fluke 73 and a Fluke 87-III off ebay YEARS ago. Calibrated them once (a shop I know people at had their calibration people in so I got mine thrown into their calibration run) and they've never, ever let me down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally I try to never buy equipment new. My oscilloscope, logic analyzer, meters, soldering equipment... all used. The only items I purchased new were a Usbee SX, Bus Pirate and my inspection microscope.  Sure, the equipment's not latest-tech but generally speaking you don't need it. It's like buying a new car vs buying one a few years old, except that test equipment generally does not die, and Fluke equipment (getting back to your question) is built rugged as hell.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-09-30T16:09:30.220" CommentCount="1" />
  <row Id="4656" PostTypeId="2" ParentId="4651" CreationDate="2010-09-30T16:31:56.157" Score="3" ViewCount="" Body="&lt;p&gt;I have had the same Fluke 8060A for over 20 years. It is well designed, well built and documentation&#xA;is available. Since I use it professional I would buy another one. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Extech meters seem to have good specifications and appear&#xA;to be popular among hobbyists who are looking for something between a $10 meter and a &#xA;professional grade instrument.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:32:40.357" LastActivityDate="2011-05-18T11:32:40.357" CommentCount="5" />
  <row Id="4657" PostTypeId="2" ParentId="4651" CreationDate="2010-09-30T18:43:31.227" Score="4" ViewCount="" Body="&lt;p&gt;Even if you are only a digital hobbyist, a reasonable meter for about £20-£40 is worth it, a second-hand fluke will fit, and so might an Extech. I have a really nice one of dubious brand name, it's works like a fluke, but eats battery - my Fluke (at work) never did that to me. You will need a backup instrument of some sort anyway, as a beginner so if you have not got something else that gives rough measurements as a reference point it's not so much fun. I go with Andrew K (but I'm still unable to vote here for some reason)&lt;/p&gt;&#xA;" OwnerUserId="1357" LastActivityDate="2010-09-30T18:43:31.227" CommentCount="1" />
  <row Id="4658" PostTypeId="1" CreationDate="2010-09-30T19:29:50.687" Score="6" ViewCount="265" Body="&lt;p&gt;I am a total zero in electronics. I just know what is a resistor and what is a capacitor. I also know what is a 555 just because I've been told what it does, 15 years ago. Apart from this and a bunch of other names, nothing more. However, I do have advanced knowledge of math and physics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to learn electronics. The quicker the better, but without wacky stuff and practical exercises. I am not going to implement the circuits practically. I don't want to make my own blinking led or my own crystal radio. I'd like instead to know what are the characteristics of the many components (transistor, zener diode, FET, MOSFET, whatever), when it's appropriate to use them and why, how to design a circuit and balance the components etc. In other words, I want to &lt;em&gt;understand&lt;/em&gt;. I don't want to &lt;em&gt;do&lt;/em&gt; (I'd like to, but I can't for lack of space).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where can I find resources (either books or online tutorials) to achieve this goal?&lt;/p&gt;&#xA;" OwnerUserId="1272" LastActivityDate="2010-10-02T06:48:11.693" Title="From zero to &quot;almost pro&quot;: Newbie trying to learn. Good, quick resources ?" Tags="&lt;learning&gt;" AnswerCount="7" CommentCount="3" FavoriteCount="6" />
  <row Id="4659" PostTypeId="2" ParentId="4658" CreationDate="2010-09-30T19:32:44.043" Score="2" ViewCount="" Body="&lt;p&gt;Simulators are a great help. Have a look at &lt;a href=&quot;http://www.falstad.com/circuit/&quot; rel=&quot;nofollow&quot;&gt;http://www.falstad.com/circuit/&lt;/a&gt;&#xA;You could also try one of the SPICE versions.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-09-30T19:32:44.043" CommentCount="1" />
  <row Id="4660" PostTypeId="2" ParentId="4575" CreationDate="2010-09-30T19:36:37.617" Score="1" ViewCount="" Body="&lt;p&gt;I'd use a 555 Timer in an astable configuration feeding a D-type falling edge triggered flip-flop.&lt;/p&gt;&#xA;" LastActivityDate="2010-09-30T19:36:37.617" />
  <row Id="4661" PostTypeId="2" ParentId="4575" CreationDate="2010-09-30T19:43:58.123" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.vk6fh.com/vk6fh/kalitron.htm&quot; rel=&quot;nofollow&quot;&gt;Kalitron&lt;/a&gt; is the classic push-pull oscillator. They aren't used much these days, but were quite popular at one time in the valve era, often using a double-triode valve.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-09-30T19:43:58.123" />
  <row Id="4662" PostTypeId="1" CreationDate="2010-09-30T19:57:17.217" Score="3" ViewCount="68" Body="&lt;p&gt;I saw a post today on the Make blog about a challenge to create an extremely cheap FM/SW radio kit for developing nations. The organization sponsoring the challenge distributes donated wind-up powered Grundig radios, but they're relatively expensive, get stolen, can't be repaired, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The specs they are looking for are certainly challenging, but may all be reasonable except for the power. They are asking that the radio be powered by a single AA battery (it may also have a solar cell) and contain a LED bright enough to use as a small lamp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can read the specs here: &lt;a href=&quot;http://blog.makezine.com/archive/2010/09/maker_challenge_fm_radio_kit_for_th.html&quot; rel=&quot;nofollow&quot;&gt;FM Radio Challenge&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is whether this community thinks that these specs are just written by non-experts. Is a practical device do-able with that power? Assume the price requirement could be met (the solar cell may be the priciest part). If a single AA was chosen due to its ubiquity, would a high quality rechargeable battery still meet the needs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And yes, I did really want to put this challenge in front of the readers here by putting it in the form of a real question. Note that it is tagged community wiki.&lt;/p&gt;&#xA;" OwnerUserId="152" LastActivityDate="2010-09-30T20:15:50.643" CommunityOwnedDate="2010-09-30T19:57:17.217" Title="Are the specs for the &quot;Ears of the World&quot; challenge reasonable?" Tags="&lt;power&gt;&lt;battery&gt;&lt;kit&gt;&lt;radio&gt;&lt;design&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="4663" PostTypeId="2" ParentId="4662" CreationDate="2010-09-30T20:15:50.643" Score="1" ViewCount="" Body="&lt;p&gt;Sure it's practical, the specs sound reasonable - there's &lt;a href=&quot;http://gizmodo.com/5456687/motz-mini-fm-radio-is-a-serious-choking-hazard&quot; rel=&quot;nofollow&quot;&gt;tiny FM receivers&lt;/a&gt; available on the market that run off small 3v button batteries. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the hardest part will be designing a radio that is cost effective and can be built without a soldering iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It sounds like a great challenge tho, will be really interesting to see what ideas people come up with :)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;@ Cmpalmer - Do you intend to enter the competition yourself?&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-09-30T20:15:50.643" CommunityOwnedDate="2010-09-30T20:15:50.643" CommentCount="1" />
  <row Id="4664" PostTypeId="1" CreationDate="2010-09-30T20:55:55.320" Score="8" ViewCount="523" Body="&lt;p&gt;From &lt;a href=&quot;http://electronics.stackexchange.com/questions/4639/alternative-power-sources/4649#4649&quot;&gt;this answer&lt;/a&gt;: How much energy can be harvested from nearby radio towers or power lines?  What circuits would you use?  How much would you have to absorb for it to be noticeable by the producers or by other consumers?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see a lot of stories, rumors and anecdotes online, but I'd like facts and references better.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-23T15:22:40.837" LastActivityDate="2010-10-23T15:22:40.837" Title="Stealing energy from radio towers or power lines" Tags="&lt;radio&gt;&lt;electromagnetism&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="2" />
  <row Id="4665" PostTypeId="2" ParentId="4658" CreationDate="2010-09-30T20:56:47.947" Score="5" ViewCount="" Body="&lt;p&gt;I think you've made a good start already, forums like this are great for learning, general help and advice, one of the nice things about this forum in particular is the fact that you can ask the simplest or most basic of questions and still get good responses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to look into the theory, maths and nitty gritty of it all, you can have a look at &lt;a href=&quot;http://www.youtube.com/user/nptelhrd&quot; rel=&quot;nofollow&quot;&gt;The National Program On Technology Enhanced Learning&lt;/a&gt; Youtube channel. It's a great resource for lectures on electronics and semiconductors, it's got pretty much entire university courses on there. To be honest you can get quite a lot from just using Youtube and Wikipedia, the &lt;a href=&quot;http://www.electronics-wiki.com/&quot; rel=&quot;nofollow&quot;&gt;electronics specific wiki&lt;/a&gt; is pretty darn good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a heap of good books on electronics too, just have a look through some of the previous questions and answers on the Electronics Exchange - there's plenty of talk about it, I guess it kinda depends on what kind of things you want to make, but there's also good general reference books available too. Just search for &quot;book&quot; on the Electronics exchange search.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And finally my favourite technique, I know you said you didn't want to do practical stuff - but..........pull stuff apart! do it often, every day if possible! - I pulled apart an old compressor today, it was dumped by a beauty salon, they used to use it for spray tans, I got tanning gunk all over my hands! was great tho, I love pulling things apart :)&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-09-30T20:56:47.947" CommentCount="3" />
  <row Id="4666" PostTypeId="2" ParentId="4658" CreationDate="2010-09-30T22:45:38.593" Score="5" ViewCount="" Body="&lt;p&gt;Let me make one thing clear: without actually making the blinking LED and the transistor amplifier and the diode steering circuit and the bistable miltivibrator you &lt;strong&gt;WILL NOT&lt;/strong&gt; understand. You can't book learn this stuff, you need to get hands-on. You need to get a visceral understanding of what's going on; you need to identify when something's going wrong by touch and by smell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Grab practically everything from Forrest M. Mims III; &quot;Getting Started in Electronics&quot; was my bible when I was learning this stuff. His Engineer's Mini-Notebooks were also gold. Robert Grossblatt was another author I frequently checked out from the local library.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Get a little breadboard, a resistor kit, a small capacitor kit and some diodes and transistors and start playing. It's the only way to learn. Spice is nice, but I have only found it useful once you have a half an idea of what's going on. Spice has a nasty nasty habit of lying to you and unless you have a decently-tuned bs detector when it comes to electronics, spice can really throw you for a loop. You mention a lack of space, but really this won't take up anything more than a small kitchen table when it's all out, and it'll pack away into a small box or briefcase when it's put away.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that I'd start looking at an Arduino or Propeller chip to start your journey into microcontrollers. I've never used either but they're pretty much the de-facto standard when it comes to beginner microcontrollers. After that, jump right in to small ARM processors. Skip the PICs and AVRs; nothing beats using REAL gcc and REAL debuggers. If you really find yourself needing a small microcontroller for space or power reasons, THEN look to the PIC/AVR stuff, but not before looking at low power beauties like the MSP430.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've developed industrial control equipment using the PICs and I've done my share of time on 68xx/z80/80186/80196 microcontrollers and even more with various DSPs and microprocessors. For a hobbyiest or someone trying to learn there really isn't any need to stray from what I'd mentioned above. Not unless you either want to learn a particular processor or need the specific features of one of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Above all, enjoy learning. Electronics is a lot of fun.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-09-30T22:45:38.593" CommentCount="2" />
  <row Id="4667" PostTypeId="2" ParentId="4566" CreationDate="2010-09-30T23:04:30.313" Score="1" ViewCount="" Body="&lt;p&gt;There are others available in UK&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.coolcomponents.co.uk/catalog/product_info.php?products_id=559&quot; rel=&quot;nofollow&quot;&gt;http://www.coolcomponents.co.uk/catalog/product_info.php?products_id=559&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1298" LastActivityDate="2010-09-30T23:04:30.313" />
  <row Id="4668" PostTypeId="2" ParentId="4651" CreationDate="2010-09-30T23:34:51.550" Score="1" ViewCount="" Body="&lt;p&gt;As always it depends on your exact requirements, but I would prefer a cheap multimeter and a digital oscilloscope, than a great multimeter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've heard good things about the &lt;a href=&quot;http://www.rigolna.com/products/digital-oscilloscopes/ds1000e/&quot; rel=&quot;nofollow&quot;&gt;Rigol DS1000E&lt;/a&gt; (2ch 50MHz) and they retail for around USD400.&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-09-30T23:34:51.550" CommentCount="1" />
  <row Id="4669" PostTypeId="2" ParentId="4651" CreationDate="2010-10-01T00:27:42.330" Score="11" ViewCount="" Body="&lt;p&gt;I think you should make sure you select a multimeter &lt;strong&gt;that answers the questions you need answered&lt;/strong&gt;.  Or start with a cheap one, and if you need more features / better accuracy, get a better one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most folks working on digital electronics need to know if:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Is this signal high or low?&lt;/li&gt;&#xA;&lt;li&gt;Is this signal switching?&lt;/li&gt;&#xA;&lt;li&gt;Is this wire continuous?&lt;/li&gt;&#xA;&lt;li&gt;Is my transistor PNP or NPN, and is the Radioshack package correct? (it wasn't, once, for me)&lt;/li&gt;&#xA;&lt;li&gt;How much current is running through this section of the circuit?&lt;/li&gt;&#xA;&lt;li&gt;What is the duty cycle of the PWM signal?  (This is easily found by doing a little bit of math based on the voltage)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Really, to solve all those problems, a $5USD digital multimeter does all that and more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to measure capacitors, inductors, are panicky about your duty cycle, or need tight accuracy, or you need the thing to survive falling down a waterfall or being inside crazy EMF fields or your'e gonna beat the thing up, I'd look for a Fluke or something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to watch really fast signals, you should be doing that with a logic analyzer or an oscilloscope anyway.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-10-01T00:27:42.330" CommentCount="3" />
  <row Id="4670" PostTypeId="2" ParentId="4618" CreationDate="2010-10-01T00:56:43.710" Score="2" ViewCount="" Body="&lt;p&gt;Most cheap AVR programmers are just sync serial interfaces with a reset line. You can you an FT232 to bitbang out Serial Peripheral Interface(SPI). The FT232 is designed for async serial not sync so its all done in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could just upload a bootloader like arduino which would allow you to upload code via the async serial interface using the ft232 in normal mode or any async serial interface using level converters as needed. Just don't forget to use the right bootloader for your clock speed and to set the fuse bytes correctly.&lt;/p&gt;&#xA;" OwnerUserId="1369" LastActivityDate="2010-10-01T00:56:43.710" />
  <row Id="4671" PostTypeId="2" ParentId="4629" CreationDate="2010-10-01T01:10:51.990" Score="1" ViewCount="" Body="&lt;p&gt;UPS are used in data centers to prevent data loss and maintain services during power outages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In alot of cases UPS's are just used to give the computer enough time to save the contents of RAM to the harddrive and properly shutdown. For an example if a computer was in the middle of a harddrive write during a power outage the file system might get corrupted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a data center application the UPS systems provide power long enough for backup generators to startup and usually allow for a few hours of operations if the generator fails to start. In telecom downtime is expensive so great lengths are taken to make sure power is never lost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Interesting random fact: Data centers and telco central offices must have disconnects for all power sources in case there is a fire(to make it safe for firefighters to work). These are often big red buttons mounted on the wall for easy access. These often get hit by new guys and sales people wondering what they do and cause huge business losses. &lt;/p&gt;&#xA;" OwnerUserId="1369" LastActivityDate="2010-10-01T01:10:51.990" CommentCount="1" />
  <row Id="4672" PostTypeId="2" ParentId="4629" CreationDate="2010-10-01T02:01:26.813" Score="3" ViewCount="" Body="&lt;p&gt;I'm not an expert on this, but I think there's a device here you haven't mentioned:  a &lt;strong&gt;power conditioner&lt;/strong&gt;.  These devices take power from the wall and pass it through filters to make a (fairly clean) output power signal.  In some cases they also have automatic voltage regulation, and can boost/cut the power from the wall.  In certain cases, they are also tailored to the applications they are used in.  For example, APC makes a seperate lines of power conditioners and UPSes for home theater and computing, as they have different power usage profiles (home theaters tend to have high peak usage).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't have any hard numbers on this, but if the power signal is out of spec or the PSU you are providing with that power signal is poorly designed, damage may occur to the device.  Specifically what, I don't know, and others that know more will have to chime in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some UPSes perform a power conditioning function, but most don't.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-10-01T02:01:26.813" CommentCount="2" />
  <row Id="4673" PostTypeId="1" AcceptedAnswerId="4680" CreationDate="2010-10-01T02:31:33.503" Score="2" ViewCount="98" Body="&lt;p&gt;A number &gt; 0 of 555 timer tutorials warn against holding the trigger of a 555 timer in monostable configuration low for longer than the duration of the output pulse. Why not?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-10-01T05:34:17.170" Title="What's wrong with giving a really long low pulse to a 555 timer?" Tags="&lt;555&gt;" AnswerCount="1" />
  <row Id="4674" PostTypeId="2" ParentId="4651" CreationDate="2010-10-01T03:51:32.477" Score="6" ViewCount="" Body="&lt;p&gt;A brand-name multimeter is absolutely worth it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fluke multimeters are some of the most reliable out there. They respond faster than most cheap DMMs, and most of them have a analog bar-graph that tries to bridge the graph between analog and digital meters, and is better than a pure digital readout. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, one thing that I do not see mentioned, and is very convenient about them is that they run &lt;strong&gt;forever&lt;/strong&gt; on a single 9v battery. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may seem a trivial thing, but I've used a lot of no-name DMMs, and they all go through batteries every few weeks, particularly if you forget to turn them off.&lt;br&gt;&#xA;Flukes, on the other hand, turn themselves off automatically, and I think I have had the same battery in mine for 3+ years.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's extremely nice to know that your battery powered equipment will just work when you turn it on, rather than having to try and track down the proper batteries so you can take a measurement.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-01T03:51:32.477" CommentCount="2" />
  <row Id="4675" PostTypeId="2" ParentId="4658" CreationDate="2010-10-01T04:21:17.577" Score="0" ViewCount="" Body="&lt;p&gt;Well, in my opinion, you need to get down and dirty if you have to understand what component goes where and optimal placements in a given circuit. Just a dry theoretical knowledge will not get you anywhere especially in electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the best ways to get up and running quickly is buy yourself something like an Arduino or a clone of it with a starter kit and have fun. Using such a platform ensures that you have a validated and functional microprocessor platform and provides you with an easy programming interface. You are then free to spend the majority of your time in understanding electronics, which is what, I gather, you want. Such platforms (most of the popular ones) come with a very vibrant community forum who will help you out a lot.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastActivityDate="2010-10-01T04:21:17.577" />
  <row Id="4676" PostTypeId="2" ParentId="4575" CreationDate="2010-10-01T04:43:42.017" Score="0" ViewCount="" Body="&lt;p&gt;Going more basic, a positive feedback OP-AMP circuit can be used to build a square wave oscillator. &lt;/p&gt;&#xA;" LastActivityDate="2010-10-01T04:43:42.017" />
  <row Id="4677" PostTypeId="1" AcceptedAnswerId="4682" CreationDate="2010-10-01T04:43:49.987" Score="2" ViewCount="261" Body="&lt;p&gt;I need to speed control small ( 0.25 HP ) 3 phase 2800 rpm motor to achieve speed in the range of 6000-7000 rpm. I know basic stuffs. ( have created soft starter etc ... which is good enough for achieving slower speed than rated speed...) but How would I increase speed ? another problem is, I have 1 phase input. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can work out the micro controller ( mostly AVR and ARM ) stuff but have no idea about power electronics &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have read to use pwm to create sine wave form which in turn can be smooth out by motor coil itself. I can generate the frequency and wave forms in microcontroller. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) How do I create DC from 1 phase AC that can be good enough for 0.25 HP 3 phase motor. ( for at least 10 hour continuous running. )&#xA;2) What do I need to convert my pwm waveform to actual ac using dc source. I know theory, but I am concerned about chip selection and detail circuitry. &lt;/p&gt;&#xA;" OwnerUserId="1312" LastEditorUserId="1312" LastEditorDisplayName="" LastEditDate="2010-10-01T04:56:42.690" LastActivityDate="2010-10-01T06:45:56.963" Title="3 phase ac induction motor speed control" Tags="&lt;power&gt;&lt;motor&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="4678" PostTypeId="1" AcceptedAnswerId="4728" CreationDate="2010-10-01T04:52:46.573" Score="22" ViewCount="684" Body="&lt;p&gt;Possibly many questions have been asked on soldering smd parts, but I haven't found specific answers, Like:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Do you use a watchmakers lens or some other type of magnifying glass while soldering these miniature components? What would be most optimum to see a larger picture?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;How do you solder components where pads lie beneath the package, I don't own a reflow oven and have tried to ignore these packages but can't do that anymore. &#xA;Are there any techniques to manually solder BGA, iLCC, CSP amongst others.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;What tools do you use, apart from tweezers, soldering iron, solder wire, and a bright/ illuminated workplace. Any suitable &quot;third hand&quot; that you have found that makes a monster of a difference?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Is there a specific tip thickness to use for the soldering iron, what about the solder wire guage?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For prototyping if would not always be feasible to make a pcb, do you solder these components on a veroboard or do you buy a breakout board?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;You could add more to these based on your experience and wisdom...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your turn.&lt;/p&gt;&#xA;" OwnerUserId="444" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-13T14:34:03.550" LastActivityDate="2011-01-21T16:24:44.283" Title="What tools, equipment, and techniques do you use to solder fine-pitch SMT parts?" Tags="&lt;soldering&gt;&lt;surface-mount&gt;&lt;components&gt;&lt;tools&gt;" AnswerCount="8" FavoriteCount="12" />
  <row Id="4679" PostTypeId="1" AcceptedAnswerId="4694" CreationDate="2010-10-01T04:54:42.150" Score="3" ViewCount="223" Body="&lt;p&gt;I need to detect zero crossing for a soft starter. A long while ago, I have done it using a 1 Mega ohm resistor directly connected to micro controller at one side and live power at another side. I was successful but is it advisable ? what other way I can do it cheaply and reliably ?&lt;/p&gt;&#xA;" OwnerUserId="1312" LastEditorUserId="1312" LastEditorDisplayName="" LastEditDate="2010-10-01T05:02:11.247" LastActivityDate="2011-06-05T08:56:06.787" Title="detecting zero cross in ac ?" Tags="&lt;power&gt;&lt;ac&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="4680" PostTypeId="2" ParentId="4673" CreationDate="2010-10-01T05:23:54.853" Score="5" ViewCount="" Body="&lt;p&gt;As I understand it, the output simply will not go high until the trigger goes high. If the timer times out before the trigger goes high, you will no longer have a uniform pulse-width.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This datasheet has a good description of the behavior: &lt;a href=&quot;http://www.datasheetarchive.com/pdf-datasheets/Datasheets-25/DSA-494116.html&quot; rel=&quot;nofollow&quot;&gt;http://www.datasheetarchive.com/pdf-datasheets/Datasheets-25/DSA-494116.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-10-01T05:34:17.170" LastActivityDate="2010-10-01T05:34:17.170" />
  <row Id="4681" PostTypeId="2" ParentId="4679" CreationDate="2010-10-01T05:49:18.187" Score="0" ViewCount="" Body="&lt;p&gt;There are probably a LOT of ways to do this... but if I was doing it I would use a little isolation transformer just in case. It's never advisable to connect mains to a microcontroller directly, even through a large resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess your options are to use a large resistor divider in to a micro, or a small transformer that pushing the mains level voltages down to the range of your micro. Of course, you can also use a combination of them both.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you dont want to use a microcontroller, you can always use a comparitor and have the voltage tested against 0v. The pulse from the comparitor will be short, but there are ways to deal with that too.&lt;/p&gt;&#xA;" OwnerUserId="1376" LastActivityDate="2010-10-01T05:49:18.187" CommentCount="5" />
  <row Id="4682" PostTypeId="2" ParentId="4677" CreationDate="2010-10-01T06:45:56.963" Score="1" ViewCount="" Body="&lt;p&gt;So you want to rotate a motor at nearly three times its rated speed. Depending on how well the motor is built, it will fail immediately or later. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you build a 200W recitifier. This is the standard Diode Bridge, condensator setup. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And a 200W Pulse width sine generator. The tools for that are listed on Atmels AVR site. They have example code to do just that. You should be able to glean the code from some of the examples on &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/dyn/products/app_notes.asp?family_id=607#Application_Example_and_Algorithms&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/products/app_notes.asp?family_id=607#Application_Example_and_Algorithms&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wouldnt it be cheaper to get a faster motor in the first place?&lt;/p&gt;&#xA;" OwnerUserId="1381" LastActivityDate="2010-10-01T06:45:56.963" CommentCount="4" />
  <row Id="4683" PostTypeId="2" ParentId="4658" CreationDate="2010-10-01T08:06:34.583" Score="2" ViewCount="" Body="&lt;p&gt;Learning electronics is like driving a car. You can understand everything about a motor vehicle, the theory behind internal combustion, emissions, suspension geometry, road camber, interior ergonomics, types of fuel, etc. But you will still need to start driving to put it all together. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same for electronics :) Build a 555 timer circuit; an oscillator; etc. Plus it's much more fun that way. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are short of space, that is quite understandable. No matter how much space you have - it isn't enough! I manage to run tronixstuff.com with a 100 x 80cm desk that holds a PC, CRO, test equipment, tea, etc (and small ikea boxes underneath) and have one bookshelf 2m wide by about 2m tall. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;[edit] Forgot to mention this website - &lt;a href=&quot;http://www.talkingelectronics.com&quot; rel=&quot;nofollow&quot;&gt;Talking Electronics&lt;/a&gt;, run by an Australian man who is devoutly passionate about many things. The layout is a little 1995, but the information is there. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-10-02T06:48:11.693" LastActivityDate="2010-10-02T06:48:11.693" CommentCount="1" />
  <row Id="4685" PostTypeId="2" ParentId="4678" CreationDate="2010-10-01T08:54:34.320" Score="10" ViewCount="" Body="&lt;p&gt;I use:  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Stereo microscope (with a focal-distance increasing add-on lens) and fiber-optic microscope illuminator.&lt;/li&gt;&#xA;&lt;li&gt;Hot-air soldering station (cheap chinese crap, significantly modified).  &lt;/li&gt;&#xA;&lt;li&gt;Good-quality soldering iron. (I have an OKI-Metcal RF Heated soldering station).  &lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;A syringe of solder paste&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;and most importantly good tweezers&lt;/strong&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'd say the most important things to success are a good pair of tweezers, and solder paste. You do not need a solder-stencil. A simple syringe with a fine dispensing tip gives you much better control over solder volume than using wire solder. I can even get away without using solder-wik most of the time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BGA packages and other package types with lots of leads on the underside of the device are pretty much our of reach of simple hand assembly, since checking your soldering job requires a x-ray inspection station. Also, mask registration becomes progressively more important as the parts get smaller, and hand-dispensing the solderpaste is no longer effective. It may be possible to manage with a solder stenciling jig and a reflow oven, but I don't have much experience there, and fixing a botched solder job is likely to be very difficult.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-01T08:54:34.320" CommentCount="3" />
  <row Id="4687" PostTypeId="2" ParentId="4678" CreationDate="2010-10-01T09:53:03.963" Score="5" ViewCount="" Body="&lt;p&gt;I use a &lt;a href=&quot;http://www.veho-uk.com/main/shop.aspx?category=usbmicroscope&quot; rel=&quot;nofollow&quot;&gt;Veho USB microscope&lt;/a&gt; (about £40 on eBay) or a x15 loupe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I sometimes use a tiny spot of blu-tack to hold a component in place.&#xA;Flux is essential, as is solder wick for cleaning up errors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tend to etch my own breakout boards, they are shockingly expensive to buy.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-01T09:53:03.963" CommentCount="3" />
  <row Id="4689" PostTypeId="2" ParentId="4604" CreationDate="2010-10-01T11:11:15.173" Score="2" ViewCount="" Body="&lt;p&gt;I'll also post about &lt;a href=&quot;http://netduino.com/netduino/&quot; rel=&quot;nofollow&quot;&gt;Netduino US$ 34.95&lt;/a&gt;, a open source platform&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/dFHcH.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Processor and memory&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Atmel 32-bit microcontroller&lt;/li&gt;&#xA;&lt;li&gt;Speed: 48MHz, ARM7&lt;/li&gt;&#xA;&lt;li&gt;Code Storage: 128 KB&lt;/li&gt;&#xA;&lt;li&gt;RAM: 60 KB&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;digital i/o features&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;all 20 digital and analog pins: GPIO&lt;/li&gt;&#xA;&lt;li&gt;digital pins 0-1: UART 1 RX, TX&lt;/li&gt;&#xA;&lt;li&gt;digital pins 2-3: UART 2 RX, TX&lt;/li&gt;&#xA;&lt;li&gt;digital pins 5-6: PWM, PWM&lt;/li&gt;&#xA;&lt;li&gt;digital pins 7-8: UART 2 RTS, CTS&lt;/li&gt;&#xA;&lt;li&gt;digital pins 9-10: PWM, PWM&lt;/li&gt;&#xA;&lt;li&gt;digital pins 11-13: SPI MOSI, MISO, SPCK&lt;/li&gt;&#xA;&lt;li&gt;analog pins 4-5: I2C SDA, SCL&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-11-06T00:00:47.520" LastActivityDate="2010-11-06T00:00:47.520" CommentCount="2" />
  <row Id="4690" PostTypeId="2" ParentId="4679" CreationDate="2010-10-01T11:41:03.107" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/40171a.pdf&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; Microchip's Application Note on page 3 suggest a 20 MOhms resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you can use the &lt;a href=&quot;http://www.fairchildsemi.com/pf/MO/MOC3061-M.html&quot; rel=&quot;nofollow&quot;&gt;Mock 3061&lt;/a&gt; that has a zero crossing detector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But there are a lot of devices models as you can see &lt;a href=&quot;http://www.fairchildsemi.com/sitesearch/fsc.jsp?text=Zero+Crossing&amp;amp;as=1&amp;amp;render=1&amp;amp;w=&amp;amp;command=text&amp;amp;attr1=&amp;amp;attr2=&amp;amp;t=0&amp;amp;i=sitemap+id&amp;amp;ia=1&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-01T11:41:03.107" CommentCount="1" />
  <row Id="4691" PostTypeId="2" ParentId="4355" CreationDate="2010-10-01T11:43:02.947" Score="1" ViewCount="" Body="&lt;p&gt;The COTS chip-scale cameras I've worked with have either used discrete GPIO, Address-data-busses, and/or I2C to create closed-circuit-tv-quality output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Potential camera vendor:  &lt;a href=&quot;http://www.ovt.com/&quot; rel=&quot;nofollow&quot;&gt;OmniVision&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="923" LastActivityDate="2010-10-01T11:43:02.947" CommentCount="1" />
  <row Id="4692" PostTypeId="2" ParentId="4678" CreationDate="2010-10-01T12:01:32.467" Score="3" ViewCount="" Body="&lt;p&gt;I use one of &lt;a href=&quot;http://www.lakeland-microscopes.co.uk/stereo.html&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; SM-20 stereo dissecting microscopes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For soldering I use a Metcal system. They are expensive if bought new, but an old STSS power unit can often be picked up cheap on Ebay, and used with the later MX-500 handpieces and cartridges. I think it can also be used with the latest MX-5000 accessories, as well, but I haven't tried them.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-01T12:01:32.467" CommentCount="2" />
  <row Id="4693" PostTypeId="2" ParentId="4355" CreationDate="2010-10-01T12:30:57.107" Score="1" ViewCount="" Body="&lt;p&gt;Have you looked at the Gumstix Overo COMs? COM = Computer On Module. They have a dedicated camera interface (J5). Beagleboard may have this as well, as it is the same OMAP35xx series processor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to roll your own, there are many, many microprocessors with camera interfaces. Freescales i.MX series of devices (i.MX31, i.MX51, etc.), the OMAP processors I mentioned above, Atmel has the AT91SAM series... What other features do you need? &lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-01T12:30:57.107" CommentCount="5" />
  <row Id="4694" PostTypeId="2" ParentId="4679" CreationDate="2010-10-01T12:44:35.693" Score="5" ViewCount="" Body="&lt;p&gt;I have designed soft starters using the PIC16C74A/F77 processors. Zero crossing can be tricky if you also have to work in noisy environments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't need the processor to be isolated from the line, there's nothing wrong with a couple high-value resistors feeding a CPU pin. I would use a couple shottky diodes to augment the internal protection diodes just as a matter of robustness, but it'll work fine. If you need isolation, use a transistor output optoisolator. Pay attention to the switching speed of the opto and minimize the transistor collector current to maximize switching speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having said that, let's move on to noise. If you're phase-controlling anything other than resistive heating you'll have noise to contend with which means it's very likely you will have zero-crossing noise to deal with. Don't do the rookie mistake of feeding the zero crossing input to an interrupt pin; that will turn your software into a smoking mass of nastiness when the processor tries to deal with a gazillion interrupts.  (I speak from experience.)  Throwing an RC or more advanced low-pass filter on the line will just introduce phase shift. If you can work with that, great. If not (I had to deal with 50/60 and 400Hz systems) then you have to try other means.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On my own design I took care of it in software by polling the line and essentially making a voting routine that ignored transients. The phase shift was within what I could handle, it was fast and it wouldn't crap out even in heavy noise. (Tested in a facility where they removed the filter caps from an induction furnace, I've never seen such a noisy line before!)  If I were to redesign it I think I might try an external solution involving a one-shot that would &quot;latch&quot; the zero cross and then the microcontroller would acknowledge it before the next interrupt could be set.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All said, I think that reliably finding the real zero crossing in any practical situation was one of the trickier bits of the soft starter design. Closing the control loop was secondary, but it was mostly just tuning. It seems like a dead-simple thing to do but I learned quite a bit about the difference between theory and practice during that time. :-)&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-01T12:44:35.693" CommentCount="1" />
  <row Id="4695" PostTypeId="2" ParentId="4658" CreationDate="2010-10-01T12:48:25.107" Score="1" ViewCount="" Body="&lt;p&gt;Here in Brazil we have a web site of a man that has more than 2600 articles about electronics, and everyday has a new article. His name is Newton C. Braga and his site is this: &lt;a href=&quot;http://www.newtoncbraga.com.br/&quot; rel=&quot;nofollow&quot;&gt;http://www.newtoncbraga.com.br&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's in Portuguese, but you can try to use a translator tool.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;He has some books in English too: &lt;a href=&quot;http://www.amazon.com/Newton-C.../e/B001H9U1U2&quot; rel=&quot;nofollow&quot;&gt;www.amazon.com/Newton-C.../e/B001H9U1U2&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-01T12:48:25.107" />
  <row Id="4696" PostTypeId="1" AcceptedAnswerId="4697" CreationDate="2010-10-01T12:55:32.560" Score="4" ViewCount="178" Body="&lt;p&gt;I am very new to electronics so please go easy on me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whilst I have read a couple of electronics fundementals books so far, one of the things that confuses me the most about electronics is how voltage and current is managed based on the fact that current affects the whole circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a very simple explanation of a situation that would confuse me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Say I had an LED which had a 330R resistor on a 5V DC supply and I decided to connect 4 more in parallel.  According to the laws of electronics, this should increase the current going into each LED (as according to my calculations, each LED now has a resistance of 66R - raising the current to &lt;em&gt;pop&lt;/em&gt; levels).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be the best way to solve this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A more complex example would be where I had a PIC driven circuit for detecting voltage and checking for a specific combination of keys (an electronic keypad).  I then decide to add in a power LED, in parallel, to determine if the circuit is even on.  I assume this would affect the voltage and current delivered in my original circuit and potentially break things, would it not?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If so, again, what would be the best way to solve this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;I think, to sum it up, I am confused as to how circuits of any complexity are managed when adding a component can completely upset the balance of voltage and current.&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-10-01T13:04:10.187" LastActivityDate="2010-10-01T22:52:58.497" Title="Managing circuits beyond a basic level" Tags="&lt;circuit&gt;&lt;design&gt;&lt;parallel&gt;" AnswerCount="5" CommentCount="4" FavoriteCount="1" />
  <row Id="4697" PostTypeId="2" ParentId="4696" CreationDate="2010-10-01T13:06:44.423" Score="11" ViewCount="" Body="&lt;p&gt;The current through each LED would not change.  Each one would draw 5/330 or 15mA (I=V/R).  The power supply would have to supply 4*15mA or 60mA.  You didn't change the amount of current through any of the LEDs, all you did is add more of them in parallel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's use a classic water analogy: you have a bucket of water with a single hole drilled in the bottom.  The amount of water flowing out of that hole  will not change if you drilled three more holes in the bottom.  The amount of water flowing out of the bucket, however, would quadruple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember that in any circuit the current flowing through components in series will be the same, and the voltage across components in parallel will be the same. I think this is where your confusion lies.  Adding an LED across a power supply doesn't affect the voltage or current for the already-existing circuit just the same as plugging a radio into the outlet that a lamp is already plugged in to does not make the lamp get dimmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are still confused please comment and I will clarify. There's nothing wrong with wanting to learn. :-)&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-01T13:06:44.423" CommentCount="4" />
  <row Id="4698" PostTypeId="1" CreationDate="2010-10-01T13:14:09.767" Score="3" ViewCount="193" Body="&lt;p&gt;I can successfully burn programs using my USB connected STK600 through Eclipse/AVRDude.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the command line, I can read fuses (using: &lt;code&gt;avrdude -px128a1 -Pusb -cstk600 -v&lt;/code&gt;), but when I click &quot;Read Fuses&quot; from within AVREclipse/AVRDude I get the following error:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Programmer &quot;stk600&quot; could not initialize the target hardware.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Please Check that the target hardware is connected correctly&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Reason:&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;avrdude: initialization failed, rc=-1&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Is this a bug or a setup problem?&lt;/p&gt;&#xA;" OwnerUserId="1236" LastActivityDate="2010-10-31T17:45:33.737" Title="AVRDude not reading fuses in Eclipse with USB attached STK600" Tags="&lt;avr&gt;&lt;avrdude&gt;" AnswerCount="1" />
  <row Id="4699" PostTypeId="2" ParentId="3331" CreationDate="2010-10-01T13:33:42.013" Score="2" ViewCount="" Body="&lt;p&gt;You might want to consider other chips too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/297/good-microcontroller-for-ethernet&quot;&gt;http://electronics.stackexchange.com/questions/297/good-microcontroller-for-ethernet&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-01T13:33:42.013" CommentCount="1" />
  <row Id="4700" PostTypeId="2" ParentId="4696" CreationDate="2010-10-01T13:38:42.917" Score="2" ViewCount="" Body="&lt;p&gt;Ohm's law: V = R x I&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see, voltage is directly proportional to resistence and current. The current through an ideal voltage source is completely determined by the external circuit. The ideal voltage source does not change its voltage. So, when the resistance value decreases, the current value must increase to maintain the same voltage value. The lower the resistance value, the greater is the current value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Every load has an equivalent resistence. In your example, when you had only a LED with a 330R resistor (load), you had an Req = R1 (any value). When you put more LEDs and resistors, you changed the Req to R2. If R2 &amp;lt; R1, then the current will increase.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the real world, the source voltage has a current limit that it can provide. If the current value increase a lot, you have to change the voltage source.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-01T13:38:42.917" CommentCount="1" />
  <row Id="4701" PostTypeId="2" ParentId="4696" CreationDate="2010-10-01T14:01:43.180" Score="3" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;and I decided to connect 4 more in&#xA;  parallel. According to the laws of&#xA;  electronics, this should increase the&#xA;  current going into each LED&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;No, each LED would still have the same current through it, but the &lt;em&gt;total&lt;/em&gt; current being used by all the LEDs together would be 4x as much.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;to add in a power LED, in parallel, to&#xA;  determine if the circuit is even on. I&#xA;  assume this would affect the voltage&#xA;  and current delivered in my original&#xA;  circuit and potentially break things,&#xA;  would it not?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;It could.  It depends on the output impedance (or &lt;a href=&quot;http://en.wikipedia.org/wiki/Internal_resistance&quot; rel=&quot;nofollow&quot;&gt;internal resistance&lt;/a&gt;) of the power supply.  If the power supply has a low output impedance (as most do), then the droop in voltage by adding another load will not be very much.  A low impedance power supply is described as &quot;stiff&quot; because the voltage will not change very much as you change the loading.  A &lt;a href=&quot;http://www.fairchildsemi.com/ds/LM/LM7805.pdf&quot; rel=&quot;nofollow&quot;&gt;LM7805&lt;/a&gt; has an output impedance of 15 mΩ (thousandths of an ohm), for instance, which is very low.  It's designed to supply current to changing loads while not varying in voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it has a high output impedance, then increasing the load will cause the supply voltage to droop, which may affect the other loads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Every component has some internal resistance.  Sometimes it matters, sometimes it doesn't.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-01T14:08:23.183" LastActivityDate="2010-10-01T14:08:23.183" CommentCount="1" />
  <row Id="4702" PostTypeId="2" ParentId="4678" CreationDate="2010-10-01T14:05:51.640" Score="3" ViewCount="" Body="&lt;p&gt;You might find this &lt;a href=&quot;http://www.freetronics.com/pages/surface-mount-soldering-with-a-toaster-oven&quot; rel=&quot;nofollow&quot;&gt;tutorial&lt;/a&gt; interesting, by Jon Oxer from Freetronics. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-01T14:05:51.640" CommentCount="1" />
  <row Id="4703" PostTypeId="2" ParentId="3331" CreationDate="2010-10-01T14:14:02.727" Score="1" ViewCount="" Body="&lt;p&gt;The company I work for uses the PIC18F97J60. It's an 8-bit microprocessor with a built-in MAC and PHY that is very similar to the ENC24J60. If you are planning on using a PIC microprocessor then you can use the Microchip TCP/IP stack. This stack provides everything right up to the application layer. If you are using a non-Microchip processor I think you can only use the ENC24J60 drivers. That said it looks like the Wiznet integrates the transport layers into the hardware not just the MAC and PHY. However they leave it to the developer to implement the application layers like Telnet, FTP, and HTTP.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-01T14:14:02.727" CommentCount="3" />
  <row Id="4704" PostTypeId="1" CreationDate="2010-10-01T14:17:56.767" Score="3" ViewCount="71" Body="&lt;p&gt;I want to create something like ambilight that can work based on a composite tv input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically I need to work out the average colour and brightness at 3 or 4 points along each edge which can then be used to control strips of RGB leds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no problem with the LED control part but where do I start with dealing with the TV signal?  Can anyone point me in the right direction of what component I could use or where to learn how to do this with a PIC?&lt;/p&gt;&#xA;" OwnerUserId="1334" LastActivityDate="2010-10-01T15:19:09.257" Title="How to compute average colours of the edges of a composite tv signal" Tags="&lt;avr&gt;&lt;pic&gt;&lt;video&gt;" AnswerCount="2" />
  <row Id="4705" PostTypeId="2" ParentId="4696" CreationDate="2010-10-01T14:27:34.120" Score="3" ViewCount="" Body="&lt;p&gt;I suggest that you review your Kirchhoff's circuit laws:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As O Engenheiro has stated if the voltage source is considered to be ideal, its voltage source will not change. If you have read a few electronics books you will also know that a diode does not follow ohm's law. IE there is not a direct relationship between its current and voltage, however for quick and dirty calculations it can be assumed that its voltage drop would be .7V(assuming it is silicon, which it is likely the case)  seeing that your source is greater than this value(otherwise the diode could be treated as an open circuit) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using KVL we know that VS - VResistor - VDiode = 0 =&gt; VResistor = 4.3V&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and now since resistors do follow ohm's law:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I = VResistor/Resistance = 4.3V/330 = 13mA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the total current being drawn from the source will be 4X13mA = 52mA&lt;/p&gt;&#xA;" OwnerUserId="1337" LastEditorUserId="1337" LastEditorDisplayName="" LastEditDate="2010-10-01T14:39:18.970" LastActivityDate="2010-10-01T14:39:18.970" CommentCount="2" />
  <row Id="4706" PostTypeId="2" ParentId="1011" CreationDate="2010-10-01T14:30:13.240" Score="0" ViewCount="" Body="&lt;p&gt;I spend a great deal of the time at my company writing specifications, checking BOMs, reviewing circuit diagrams and concepts on a block-diagram level or completing design and test reports. &lt;em&gt;Real&lt;/em&gt; work at the bench, with oscilloscopes and soldering irons, is only a tiny fraction. It happens that I want to have some concepts or design ideas in a new product that have not yet been implemented before and this is when I build and tweak breadboards at home. The reason for this is that I don't want to put concepts into my specs that I haven't tried and tested as real circuits on the bench and observed their (mis-)behaviour with an oscilloscope. Usually, while I'm at my company writing specs, I lack the time to try stuff out. Often, I run simulations at work and build the first proof-of-concept at home.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To answer the question: This happens every 2 months, on average, and may take some evenings or week-ends in my home lab.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't mind doing this type of r&amp;amp;d at home because that's the part of my job I enjoy so much that I would even do it without being paid. However, I am pretty careful about not working any extra hours, especially if they don't get paid, because hey, my company expects me to do my part of my contract, and I expect them to do what they agreed to in the same contract. And I know from experience that continued periods of 50+ hour weeks wear me out and become inefficient. A 40 hour week is called full time for a reason.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-10-01T14:30:13.240" CommunityOwnedDate="2010-10-01T14:30:13.240" />
  <row Id="4707" PostTypeId="2" ParentId="4704" CreationDate="2010-10-01T14:43:42.510" Score="1" ViewCount="" Body="&lt;p&gt;I think an analog solution is the best. A hybrid digital-analog solution will be tricky, but not impossible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have a look at the chips used in a CRT TV. You may be able to hack one to get R, G, B outputs. To take the edge colours only might require storing the frame and grabbing pixels. It could be tricky, in other words.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-01T14:43:42.510" />
  <row Id="4708" PostTypeId="1" AcceptedAnswerId="4723" CreationDate="2010-10-01T14:49:05.420" Score="7" ViewCount="634" Body="&lt;p&gt;I am planning on using CAN bus in an industrial automation application, however I'm having a hard time deciding how to implement the network layer. Does anyone here have any recommendations for a higher layer protocol to use over CAN that provides guidelines for how to assign message IDs and how to format data packets? Should I develop my own proprietary network layer or implement an existing standard like CANopen?&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-10-06T14:01:29.530" LastActivityDate="2010-10-06T14:01:29.530" Title="Selecting a network layer over CAN bus" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;communication&gt;&lt;can&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="4709" PostTypeId="2" ParentId="4704" CreationDate="2010-10-01T14:50:02.350" Score="1" ViewCount="" Body="&lt;p&gt;This might be easier with an RGB signal (as found in VGA and sometimes carried by SCART). With that, you could probably watch VSYNC with an interrupt, then sample the R/G/B lines and produce your colour.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, for composite you're going to have to pick apart the &lt;a href=&quot;http://en.wikipedia.org/wiki/Colorburst&quot; rel=&quot;nofollow&quot;&gt;colourburst&lt;/a&gt;. To do this, you'll need a fast clock. It won't be easy with a PIC.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-01T15:19:09.257" LastActivityDate="2010-10-01T15:19:09.257" CommentCount="1" />
  <row Id="4710" PostTypeId="2" ParentId="4658" CreationDate="2010-10-01T14:51:57.900" Score="1" ViewCount="" Body="&lt;p&gt;I highly recommend the allaboutcircuits.com textbooks. They are free, open source textbooks. I'm an active member of the All About Circuits forums as well. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, there is only so much simulations can teach you. I manage to fit a PC+LCD, oscilloscope, laptop and electronics lab (including breadboards and a multimeter...) on an entire desk about 1.5m long. The only problem is storing components: at the moment, I keep everything in small boxes and organisation is tricky.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-01T14:51:57.900" />
  <row Id="4711" PostTypeId="2" ParentId="4664" CreationDate="2010-10-01T14:58:53.203" Score="3" ViewCount="" Body="&lt;p&gt;With out trying to attempt to do any mind numbing number crunching I am just going to suggest that harvesting energy from radio towers would not be very cost effective. It would be much cheaper and more realistic to look at other sources in the environment for energy harvesting. EM signals transmits minuscule amounts of energy to an antenna that is amplified by another power source....&lt;/p&gt;&#xA;" OwnerUserId="1337" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-23T14:49:11.603" LastActivityDate="2010-10-23T14:49:11.603" />
  <row Id="4712" PostTypeId="1" AcceptedAnswerId="4717" CreationDate="2010-10-01T15:10:08.453" Score="9" ViewCount="243" Body="&lt;p&gt;I do low-speed circuit design for microcontrollers and such (usually &amp;lt;20MHz) and now I'm getting started on some more high-speed circuits.  What I want to know is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What considerations need to be made for traces in high-speed circuits?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I have to impedance-match each line between two high speed devices?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do all the traces need to be the same length?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a good reference for these rules?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;AND&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can this be done using open-source circuit design tools (gEDA and company)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&#xA;~Alex&lt;/p&gt;&#xA;" OwnerUserId="1390" LastActivityDate="2011-01-01T17:38:41.063" Title="When laying out circuit board traces, what impedances do i need to consider?" Tags="&lt;layout&gt;&lt;impedance&gt;&lt;trace&gt;&lt;high-frequency&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="4" />
  <row Id="4713" PostTypeId="2" ParentId="4708" CreationDate="2010-10-01T15:12:38.793" Score="6" ViewCount="" Body="&lt;p&gt;I write code to access the CAN bus on GM cars, which uses a mostly proprietary network layer. Have you looked into OpenCAN? I would choose an open standard such as CANOpen or even OpenCAN. It really depends on the level of control and flexibility you want in your automation environment. &lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-10-01T15:12:38.793" CommentCount="2" />
  <row Id="4714" PostTypeId="2" ParentId="4664" CreationDate="2010-10-01T15:43:41.133" Score="2" ViewCount="" Body="&lt;p&gt;In &lt;a href=&quot;http://www.youtube.com/watch?v=P8s3Xjeg0sk&quot; rel=&quot;nofollow&quot;&gt;EEVBlog #55&lt;/a&gt; Dave Jones dissects the (bogus) claims of a gadget which can harvest energy from Wi-Fi signals. Most of the mathematics should be applicable to radio towers.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-01T15:43:41.133" CommentCount="7" />
  <row Id="4715" PostTypeId="2" ParentId="4712" CreationDate="2010-10-01T16:05:35.557" Score="5" ViewCount="" Body="&lt;p&gt;For high speed digital signals, you'll want to match the impedance of the trace to the output impedance of the signal's output driver.  Many signal transmission lines also require termination.  This reduces reflections and inter-symbol interference. The trace's impedance is determined primarily by it's width and the PCB stack-up, but the signal return path also plays a role.  Switching layers or routing a signal across a split ground plane will create impedance discontinuities and will degrade the maximum speed at which the link can operate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Trace length matching requirements will be driven by the timing requirements of the bus protocol used by the signals.  E.b., a DDR memory interface will require that the DQ (data) signals arrive within so many pico-seconds of the DQS (strobe) signal.  A rough estimate of the mismatch can be calculated from the trace length mismatch and the propagation delay of the transmission line.  Signal integrity engineers create more precise analyses of timing skew by running simulations of the routing topology and models of the I/O drivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A great reference on the subject is Dr. Howard Johnson's book &quot;High Speed Digital Design: A Handbook of Black Magic&quot;  (http://www.amazon.com/High-Speed-Digital-Design-Handbook/dp/0133957241)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jason&lt;/p&gt;&#xA;" OwnerUserId="1391" LastActivityDate="2010-10-01T16:05:35.557" />
  <row Id="4716" PostTypeId="2" ParentId="4080" CreationDate="2010-10-01T16:17:25.050" Score="2" ViewCount="" Body="&lt;p&gt;Parallax Propeller. 8-32 bit parallel cores and built in VGA support.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be very easy to build a programmable graphing calculator using this processor. The chip is in 40 pin DIP configuration and there are a number of prototyping boards available, several of which have video, keyboard and mouse support hardware built in.&lt;/p&gt;&#xA;" OwnerUserId="1265" LastActivityDate="2010-10-01T16:17:25.050" />
  <row Id="4717" PostTypeId="2" ParentId="4712" CreationDate="2010-10-01T16:43:20.860" Score="7" ViewCount="" Body="&lt;p&gt;(I should say at the outset that I have some experience with boards in the 100 MHz range, but I'm far from an expert.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The canonical reference is High-Speed Digital Design by Johnson and Graham. Johnson also wrote a more advanced sequel, High-Speed Signal Propagation, in 2003.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can lay out any board with gEDA and company, but it can become arbitrarily difficult to the extent that I would seek a better tool if you can get it. Matching the lengths of many traces by hand gets tedious quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for what you actually need to do with traces, here are the things I watch out for:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The length of traces starts mattering once your traces are longer than 1/6 of the rising edge of a digital signal. For a rise time of 1 ns on a typical PCB, the rising edge spans around 6 inches, so you want your traces to be less than 1 inch in length.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You want to match the termination of your traces to their characteristic impedance to prevent reflected signals. In practice, this means either putting a resistor to ground right before the trace reaches its destination or putting a resistor in series at the start of the trace. I've found the diagrams in chapter 12 of Analog Electronics by Crecraft and Gergely to be worth staring at for extended durations: &lt;a href=&quot;http://books.google.com/books?id=lS7qN6iHyBYC&amp;amp;lpg=PP1&amp;amp;ots=cg6ZMM2GI1&amp;amp;dq=analog%20electronics%20crecraft&amp;amp;pg=PA296#v=snippet&amp;amp;q=propagation%20of%20a%20pulse&amp;amp;f=false&quot; rel=&quot;nofollow&quot;&gt;http://books.google.com/books?id=lS7qN6iHyBYC&amp;amp;lpg=PP1&amp;amp;ots=cg6ZMM2GI1&amp;amp;dq=analog%20electronics%20crecraft&amp;amp;pg=PA296#v=snippet&amp;amp;q=propagation%20of%20a%20pulse&amp;amp;f=false&lt;/a&gt; Manufacturer's datasheets will sometimes have recommended termination schemes.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;As your signal speed increases, you have to start worrying about voltages induced in neighboring traces due to mutual inductance and rapidly changing currents (V = L * di/dt). People call this &quot;crosstalk.&quot; This means that you need to spaces traces away from each other, use a ground plane under all your traces, and/or put ground traces (&quot;guard traces&quot;) between the traces you're trying to isolate.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;That's all that I actually worry about in practice.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-01T16:43:20.860" />
  <row Id="4718" PostTypeId="2" ParentId="4696" CreationDate="2010-10-01T17:01:45.553" Score="2" ViewCount="" Body="&lt;p&gt;You bring up the point of a PIC.  The PIC's pins will either source or sink the current necessary to drive the output pin to 5V or 0V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's say you have an LED's anode connected to a PIC output pin.  The cathode is then connected to ground through your current limiting resistor.  If you tell the PIC to output a 0, then we have 0V across the LED, so no current will flow through it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, let's say you switch the output to a 1.  Now there's 5V across the LED and resistor; the output begins to &lt;em&gt;source&lt;/em&gt; current.  The &quot;1&quot; connects the output pin to the VDD rail of the PIC, so that's where the current is coming from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So now there's this burst of current where there was no current before.  The PIC is demanding more power.  Unfortunately, the power supply is &quot;far away&quot;, and it takes some time for the PIC's demands to propagate across the board, and more time for the regulator to respond, and more time for the regulator's response to propagate back to the PIC's VDD pin.  During this time, there could be a catastrophic droop in the power supply at the VDD pin of the PIC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To compensate for this, we use &lt;em&gt;bypass capacitors&lt;/em&gt;.  Think of them as little puddles of charge.  When the output pin switches, the PIC will demand more current, and the capacitor will be able to provide some of it until the regulator can react.  This is why bypass caps must be placed as close as possible to the VDD/GND pins...they need to be able to react as fast as possible when the current gets switched on.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-01T17:01:45.553" />
  <row Id="4719" PostTypeId="2" ParentId="4712" CreationDate="2010-10-01T17:12:49.153" Score="3" ViewCount="" Body="&lt;p&gt;This all really depends on what you mean by &quot;high speed&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most important factor in determining whether you need termination is the amount of time it takes for a rising edge to propagate.  If your rise time is 100 ps, then it doesn't matter if you're 100 MHz or 10 MHz, reflections will still hurt you.  But reflections are only a problem when you reach &quot;transmission line&quot; lengths.  I think that's something like...for every 300 ps of rise time you can go about an inch without termination.  So for a rise time of .9 ns, you can go about three inches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as the impedance of traces, you should google &quot;microstrip&quot;.  You will need a solid ground plane underneath the trace.  Then, the distance of the trace from the plane (determined by board stackup), and the width of the trace, should largely determine trace impedance.  Many PCB design tools will automatically calculate the trace impedance for you.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-01T17:12:49.153" CommentCount="1" />
  <row Id="4721" PostTypeId="2" ParentId="4698" CreationDate="2010-10-01T17:21:54.157" Score="1" ViewCount="" Body="&lt;p&gt;Have you tried reading the fuses in AVRStudio?&lt;/p&gt;&#xA;" OwnerUserId="1256" LastActivityDate="2010-10-01T17:21:54.157" CommentCount="2" />
  <row Id="4723" PostTypeId="2" ParentId="4708" CreationDate="2010-10-01T17:31:02.827" Score="4" ViewCount="" Body="&lt;p&gt;You will definitely want to choose a standard network layer.  I've seen some cases where people have rolled their own, and frequently the protocol is inefficient, and in the end its a waste of time.  A proven network layer provides basic functionality to solve most of the problems you'll likely face in networking with an embedded device, and that will save you precious time and money in the end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have familiarity with CANopen, so I'll put a bit of an explanation in here and it might help you decide if that's the way you want to go.  If it doesn't fit what you need to do, I'd look at something else.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CANopen is very data centric.  All CANopen slave nodes (things you control from a master node, like sensors or motor drivers) provide a dictionary that contains all configuration, control and data-acquisition data you need to read/write to get your job done.  You can then read/write these objects individually via the SDO (service data object) mechanism, or read/write these objects periodically in timed CAN message trasmissions via the PDO (producer data object) mechanism.  Startup, shutdown, and reset, and heartbeat/node-malfunction detection are provided from NMT services, as well as a node ID assignment service (if you wish to use it).  To implement a device using an embedded CANOpen libary, you basically setup an object dictionary, setup PDOs to periodically send/receive data updates, and write user code that behaves based on those data entries.  There are other things CANopen provides, but that is the bulk of it.  &lt;a href=&quot;http://www.canopenbook.com/&quot; rel=&quot;nofollow&quot;&gt;Read this book for more info.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-10-01T17:36:43.550" LastActivityDate="2010-10-01T17:36:43.550" CommentCount="2" />
  <row Id="4724" PostTypeId="1" CreationDate="2010-10-01T17:49:28.033" Score="1" ViewCount="118" Body="&lt;p&gt;Good Morning,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am a scripting programmer (PHP) and do a lot of backend development with web servers.  I am very interested in learning VHDL, but the tutorials I have tried seem very antiquated and difficult to follow without some previous coding experience directly in that language.  I am considering buying a Xilinx FPGA, but would like to learn more before I make an out-of-pocket purchase.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I especially interested in online or downloadable testing environments where I can prove out a theory before I move forward.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any advise here is appreciated! &lt;/p&gt;&#xA;" OwnerUserId="1396" LastActivityDate="2011-05-24T13:21:08.793" Title="Resources to learn and test VHDL" Tags="&lt;fpga&gt;&lt;prototyping&gt;&lt;vhdl&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="4725" PostTypeId="2" ParentId="3107" CreationDate="2010-10-01T17:50:23.153" Score="2" ViewCount="" Body="&lt;p&gt;Sadly, there isn't much free software for programmable hardware. There are a few synthesis tools, such as &lt;a href=&quot;http://raintown.org/lava/&quot; rel=&quot;nofollow&quot;&gt;Lava&lt;/a&gt; (which expects largely manual placing), &lt;a href=&quot;http://www.tomahawkins.org/&quot; rel=&quot;nofollow&quot;&gt;Confluence, HDCaml and Atom&lt;/a&gt;, and &lt;a href=&quot;http://www.icarus.com/eda/verilog/&quot; rel=&quot;nofollow&quot;&gt;Icarus Verilog&lt;/a&gt;, but next to no fitter, mapper or place and route tools (I would absolutely love to be proven wrong in this). &lt;a href=&quot;http://opencircuitdesign.com/verilog/index.html&quot; rel=&quot;nofollow&quot;&gt;Opencircuitdesign.com&lt;/a&gt; has collected some tools, but it probably requires some documentation and a bitstream generator. Simulation, on the other hand, is fairly well covered.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the non-free side, Xilinx' non-free but gratis tools have seen some improvement recently, by adding libusb support and dropping Wind/U (a horrible non-free winelib analog) in favor of Qt (but they won't be updating for retired chips). Most other tools seem sabotaged using a package called flexlm, to such a degree that it's hard to get them running even &lt;em&gt;with&lt;/em&gt; the aid of the vendor. I have also been able to run Lattice Diamond software under Linux, but that lacked simulation. For Atmel AT40KAL, the place and route tool could be run in Wine, but the library demands non-standard components (it uses LPM, but refuses 2-input gates), so a sort of mapper would be needed.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-10-01T17:50:23.153" CommunityOwnedDate="2010-10-01T17:50:23.153" />
  <row Id="4726" PostTypeId="2" ParentId="4724" CreationDate="2010-10-01T18:08:03.607" Score="2" ViewCount="" Body="&lt;p&gt;My advice is to borrow a book at the library. Most of the books on VHDL will cover the basics well but not teach all the nuances, and you really do need the basics because logic design is fundamentally different from imperative programming. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many simulation tools available to test your theories, including Xilinx WebPack (gratis) which you'll be using if you do get a Xilinx based board later, or GHDL for a free software example. Several books already come with an analysis/simulation tool. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have a fair knowledge of the structure of the language, dig around for examples. Opencores.org is one place to look, and fpga4fun.com has basic examples. You may even want to head there first for links to tutorials, explanations and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most projects won't be very interesting in simulation alone, so you'll quickly want to get some hardware to play with as well. These will have a bunch of concerns, such as purchase price, tool flexibility, and included peripherals. Kits like Spartan 3[AE] Starter have a fair range, from expansion ports through switches and LEDs to video and audio ports. Simpler ones like Papilio One may have nothing at all but what you add. Make sure you get the software side working, though, because there's little more frustrating than a limited time license to use what you paid for while it doesn't work.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="1181" LastEditorDisplayName="" LastEditDate="2010-10-01T19:29:38.053" LastActivityDate="2010-10-01T19:29:38.053" CommentCount="2" />
  <row Id="4727" PostTypeId="2" ParentId="3375" CreationDate="2010-10-01T18:11:57.097" Score="3" ViewCount="" Body="&lt;p&gt;The most important part of how/where/when for connecting a thermocouple is to measure the temperature as close as possible to the bimetalic joint.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From here feed that temperature into your uP and then you can use software to perform the CJC compensation and use the known polynomials (or simplified linearised equation for smaller ranges) for converting your ADC value into temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the past we have got a big chunk of aluminium and performed wire to wire terminations around it and installed a LM35 for temperature measurement.  This was performed off the PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having said that you can freely do it with connections n stuff on the PCB as long as for are able to measure the temperature as close as possible to the bimetalic junction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So to keep the distance as short as possible consider using screw terminals and mount the LM35 right near the screw terminals themselves for the most accurate reading.  If you really want to use a connector try DB9 with the metal back shell - cheap as chips and being metal will conduct heat well for accurate measurement of the back shell temperature.  Use male pins on the PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assumed you are using a uP and software, if not you can do the CJC in hardware but thats a bit trickier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastEditorUserId="1397" LastEditorDisplayName="" LastEditDate="2010-10-01T18:17:04.450" LastActivityDate="2010-10-01T18:17:04.450" CommunityOwnedDate="2010-10-01T18:11:57.097" />
  <row Id="4728" PostTypeId="2" ParentId="4678" CreationDate="2010-10-01T18:17:52.093" Score="14" ViewCount="" Body="&lt;p&gt;Before I start, this is a lot of questions in one question.  Please try to break it up a little more next time.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;One: Do you use a watchmakers lens or some other type of magnifying glass&#xA;  while soldering these miniature&#xA;  components? What would be most optimum&#xA;  to see a larger picture?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/3408&quot;&gt;This question&lt;/a&gt; discussed optics in further detail.  I have a 10x loupe that I use to inspect solder joints when I'm not at the microscope workstation at school or work, but there is no doubt that the stereo microscope is the best tool.  Stereo gives you depth perception.&lt;br&gt;&#xA;As far as seeing the larger picture, zooming out (microscopes I've used go from ~3x to 40x) gives you plenty of room to find your place if you're concerned about that.  Zooming in, however, is when a scope shines.  You will burn tall plastic parts (like connector shrouds) for a while, but eventually you get a feel for where your iron is outside of the field of view.  A good microscope will give you about a 3&quot; focal length (contrast with a cheap loupe, mine is probably about 1.5&quot; for 1/4 the magnification), so you can wave your soldering iron halfway between the two until you see a fuzzy brown cloud moving through your field of view. Move the iron back until you see the tip, and only then lower it to the pad you're soldering.&#xA;A lighted diopter lens doesn't provide enough magnification, in my opinion, to justify the obtrusiveness of having the lens in the way.  Same with the magnifiers on helping hands.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Two: How do you solder components where pads lie beneath the package, I&#xA;  don't own a reflow oven and have tried&#xA;  to ignore these packages but can't do&#xA;  that anymore. Are there any techniques&#xA;  to manually solder BGA, iLCC, CSP&#xA;  amongst others.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If at all possible, stay away from BGA type packages for hand soldering. In a pinch, iLCC (and the more common QFN) packages can be done by placing small domes of solder on the pad (which must extend outside of the chip boundaries), fluxing the bottom of the component, and heating the solder.  If all goes well, the solder will melt, heat the contact on the chip, and the surface tension will pull the joint together.  For low pin count devices, this works quite well, including &lt;a href=&quot;http://img-asia.electrocomponents.com/largeimages/R6720599-01.jpg&quot; rel=&quot;nofollow&quot;&gt;crystal oscillators&lt;/a&gt;. If the contacts extend up the side of the chip, just heat those.&#xA;Another option is hot air guns or hot air soldering stations.  Steinel makes good air guns, and many soldering stations have air attachments.  I've found that air guns are more effective than solder stations for applying/reflowing chips, they just seem to apply the heat more evenly and sustainably.  Pay attention to the reflow profiles: You want to start heating it up slowly, over a period of a minute or two, and only then actually apply the real heat. Thermal stress is a real concern here.  Note that I've only ever used this method for rework; I haven't tried it for assembly runs.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Three: What tools do you use, apart&#xA;  from tweezers, soldering iron, solder&#xA;  wire, and a bright/ illuminated&#xA;  workplace. Any suitable &quot;third hand&quot;&#xA;  that you have found that makes a&#xA;  monster of a difference?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Solder wick.  Miles and miles of the stuff.  For most work, even fine pitches, normal .11&quot; stuff is fine, but the smaller stuff (.05&quot; or .03&quot;) is helpful.  Most tutorials will have you apply it rather indiscriminately.  For fine work, you want to lay it parallel to the edge of the chip, poke the edge nearest the pad with the tip of your soldering iron, and slide it over the PCB until it contacts the edge of the chip.  Be wary of allowing little shreds to break off and cause shorts.&lt;br&gt;&#xA;For helping hands, I've used a &lt;a href=&quot;http://www.panavise.com/index.html?pageID=1&amp;amp;page=full&amp;amp;--eqskudatarq=2&quot; rel=&quot;nofollow&quot;&gt;Panavise 301&lt;/a&gt; with the &lt;a href=&quot;http://www.panavise.com/index.html?pageID=1&amp;amp;page=full&amp;amp;--eqskudatarq=20&quot; rel=&quot;nofollow&quot;&gt;312 tray base&lt;/a&gt;.  It holds the work 10&quot; off the table, which lets you steady your elbows.   However, some people like to put the work on the table (on an antistatic pad, of course), so you can steady the heel of your hand instead.&lt;br&gt;&#xA;Last, and probably most importantly, you'll want flux.  Flux pens are cheap and easy to find, but I have a little dropper bottle that I like better - You don't have to worry about damaging anything if you drip the flux onto the PCB.  This, of course, mandates keeping some isopropyl alcohol and cotton blotters on hand to remove the residue intermittently.&#xA;Oh, and you'll also want a spool of 30-gauge wire-wrap wire to fix mistakes.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Four: Is there a specific tip thickness to use for the soldering&#xA;  iron, what about the solder wire&#xA;  guage?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This depends completely on what you're doing.  I have a 1/32&quot; cone that I use for most everything, and I use standard .031&quot; solder for connectors, through-hole, and wiring work, and .01&quot; Kester 44 for fine work.  You'll just have to experiment.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Five:  For prototyping if would not&#xA;  always be feasible to make a pcb, do&#xA;  you solder these components on a&#xA;  veroboard or do you buy a breakout&#xA;  board?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I usually dead-bug tiny components: Superglue the top, attach to protoboard (like Twin Industries 8200-45-LF), and then run 30-gauge wire to each of the pads, like &lt;a href=&quot;http://macetech.com/blog/files/images/deadbug4.jpg&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;, and connect to headers or whatever you need to do. (Note: Pic of someone else's work, not mine).  Then, after verifying that everything's in the right places, put a blob of hot glue over the whole thing to give the wires some strain relief.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-01T18:17:52.093" CommentCount="5" />
  <row Id="4729" PostTypeId="2" ParentId="3093" CreationDate="2010-10-01T18:28:19.163" Score="1" ViewCount="" Body="&lt;p&gt;For the Molex 47054-1000 connector pictured above, if you follow the &lt;a href=&quot;http://www.molex.com/customer.html?supplierPN=0470541000&quot; rel=&quot;nofollow&quot;&gt;&quot;Data Sheet&quot;&lt;/a&gt; link, it'll take you to the detail page for the part on the Molex site.  On that page on the right, you'll see a couple of info boxes that say &quot;mates with&quot; (for the male/PCB side) and &quot;use with&quot; (for the terminals).  From the links in those sections you'll get actual part numbers, but it appears that you have to strip off the leading 0 in order to successfully search Mouser for them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The cheapest 2759 Series terminals I see &lt;a href=&quot;http://www.mouser.com/ProductDetail/Molex/08-50-0113/?qs=3%2fy1uQ6JZnnRcF05F9zelA%3d%3d&quot; rel=&quot;nofollow&quot;&gt;on Mouser&lt;/a&gt; are $3 for 100.  A 4-pin mate for your connector is &lt;a href=&quot;http://www.mouser.com/ProductDetail/Molex/47053-1000/?qs=ph4zPCVRuvqoDX7hrEhxNA%3d%3d&quot; rel=&quot;nofollow&quot;&gt;this 47053-1000 header&lt;/a&gt;.  It might be easiest to search the Molex site and then find the actual part on Mouser's site…&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-10-01T18:28:19.163" />
  <row Id="4730" PostTypeId="1" AcceptedAnswerId="4732" CreationDate="2010-10-01T19:41:13.173" Score="2" ViewCount="222" Body="&lt;p&gt;I am developing an OSD project which also manipulates audio signals. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The aim is to add a 'mux' system, which allows a microcontroller to select between the input audio and an internally generated audio signal as the output. This allows it to add a voice to the signal or transmit data in the right audio channel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any solutions for this? I would like to avoid something like a 4066 which takes up valuable space. Also, since line level is alternating current, it needs to somehow work well with this.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-06T15:13:09.193" Title="Line level audio and muxing" Tags="&lt;microcontroller&gt;&lt;audio&gt;&lt;dac&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="4732" PostTypeId="2" ParentId="4730" CreationDate="2010-10-01T20:30:23.313" Score="2" ViewCount="" Body="&lt;p&gt;You need something like the 4066.  Luckily, there are smaller versions with only one switch inside, like a tiny 6-pin SPDT, with 1/3 the circuitry of a 4053.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.onsemi.com/PowerSolutions/product.do?id=NLAS4599DFT2G&quot; rel=&quot;nofollow&quot;&gt;NLAS4599: Single SPDT Analog Switch Single Supply&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.onsemi.com/PowerSolutions/product.do?id=NLASB3157DFT2&quot; rel=&quot;nofollow&quot;&gt;NLASB3157: Single SPDT Analog Switch&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.fairchildsemi.com/pf/FS/FSA4157.html&quot; rel=&quot;nofollow&quot;&gt;FSA4157 Low Voltage 1 Ohm SPDT Analog Switch&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;(I was just looking at these parts for &lt;a href=&quot;http://electronics.stackexchange.com/questions/4502/tiny-cheap-audio-buffer-with-mute&quot;&gt;this question&lt;/a&gt;.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find examples of how to bias and interface with these kinds of parts here:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.geofex.com/article_folders/cd4053/cd4053.htm&quot; rel=&quot;nofollow&quot;&gt;Bypassing and Switching with the CD4053 CMOS Analog MUX&lt;/a&gt;  &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://neatcircuits.com/audiosw/index.html&quot; rel=&quot;nofollow&quot;&gt;Audio Switch Notes&lt;/a&gt; (also shows a JFET switch)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.geofex.com/article_folders/juggler/juggler.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;The Juggler 4 is a CMOS based effects order switcher&quot;&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-06T15:13:09.193" LastActivityDate="2010-10-06T15:13:09.193" CommentCount="6" />
  <row Id="4733" PostTypeId="2" ParentId="4369" CreationDate="2010-10-01T21:56:22.253" Score="2" ViewCount="" Body="&lt;p&gt;A time domain transient sweep is what you would use in OrCAD PSpice - LTSpice should have something similar. A DC bias point analysis is of no help with a dynamic signal (pulsed source). An AC analysis is for things like gain and phase analysis of filters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the results look a little funky, see if there's an option to skip the initial bias point calculation - it may cause the simulation to take longer but you often get better (i.e. more realistic) results when dealing with dynamic circuitry.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-01T21:56:22.253" />
  <row Id="4734" PostTypeId="1" CreationDate="2010-10-01T21:59:23.323" Score="4" ViewCount="210" Body="&lt;p&gt;Howdy,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know enough to be dangerous, i can build circuits and make minor changes but i am not an expert.  I put this together after looking at schematics i have found online and i need some help getting the right components.  The individual components i cant take credit for but i think the idea and final unit will be unique.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a speedometer for my 1950 Studebaker.  It is a modern charging/ battery system.  Should give between 11 and 14 volts.  Both power supplies i have, the avr i am familiar with and have, i used it to control a skeeball machine.  It uses a pulse generator on the transmission (new Dakota digital sen-01-1), i then modified the self powered sine to square wave circuit to run off of available power.  I am hoping this will make it more sensitive.  I am using the Russian equivalent to the Nixie drivers 74141.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1: i would like to control 2 of the elements without the need for a chip what should i do here? (mpsa42 and a 33k resistor? I have!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2: Between the at mega avr and the 74141 (K155ID1)? do i need anything?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3: Do i need to do something special on the input voltage for these 74141 s?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4 and 5: I would also like to use ne2 lamps to replace my hi beam and left and right turn indicators.  These are roughly a 12v signal i have 5v and 170v what circuit should i use?  Hi beam may be on for long times.  (tip 102?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;6: (not numbered on schematic) Is my use of the sine to square appropriate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MY hand drawn schematic: &lt;a href=&quot;http://i871.photobucket.com/albums/ab280/FortyTwo-edo/nispedov1.jpg&quot; rel=&quot;nofollow&quot;&gt;http://i871.photobucket.com/albums/ab280/FortyTwo-edo/nispedov1.jpg&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry this is long but i have been looking at this for awhile and finally need to get it prototyped before snow so i can test it before i build the case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&#xA;Ed Owens&lt;/p&gt;&#xA;" OwnerUserId="1400" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-02T15:32:00.613" LastActivityDate="2010-10-02T15:32:00.613" Title="I need some component selection help with a nixie tube AVR speedometer" Tags="&lt;avr&gt;&lt;atmega&gt;&lt;nixie&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="4735" PostTypeId="2" ParentId="3693" CreationDate="2010-10-01T21:59:39.797" Score="2" ViewCount="" Body="&lt;p&gt;Bear in mind also that there are other companies doing safety approvals for North America these days. Just because there isn't a UL or CSA mark doesn't mean that there are no approvals whatsoever on the product. (ETL and MET are examples).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there aren't any recognizable marks &lt;em&gt;at all&lt;/em&gt; on the product, well, your mileage may vary.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-01T21:59:39.797" />
  <row Id="4736" PostTypeId="2" ParentId="3879" CreationDate="2010-10-01T22:06:30.923" Score="1" ViewCount="" Body="&lt;p&gt;Anyone with access to an impedance meter (HP / Venable) can easily tell you that electrolytic capacitors certainly do become inductive at high frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is part of the reason why you see a lot of ceramic capacitors used in high-frequency DC-DC converters - electrolytics simply aren't that good up in the hundreds of kilohertz / megahertz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is also why ceramic capacitors from 100nF - 1uF are commonly used as IC decouplers - an electrolytic cannot beat a small ceramic can because of its high-frequency impedance.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-01T22:06:30.923" />
  <row Id="4737" PostTypeId="2" ParentId="2864" CreationDate="2010-10-01T22:22:32.100" Score="1" ViewCount="" Body="&lt;p&gt;The maximum voltage has more to do with the package dimensions than blow-up issues - if the maximum voltage across the device is exceeded it may arc across the terminals effectively bypassing the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Resistors can fail both open and short depending on the nature of the stress exposed to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A typical multimeter in voltage mode is tens of megohms. Blowing a resistor while measuring its voltage will likely only damage the probes. If you're measuring current, it will depend on the meter. Is it fused? If so, the fuse should protect the meter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;critical point&quot; for a resistor is solely based on its temperature. If it gets too hot, the internal structure breaks down and the part dies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have some sort of current-limited DC source, set it to 5mA or so and use it directly to test for the zener effect in your unlabelled diodes. Otherwise, use the highest resistor you can find to keep the current to a minimum (recognize that the zener voltage varies with load current) and test away, reducing gradually once you get an idea of the approximate voltage. Keep the total power in the zener below a few hundred milliwatts for safety's sake (if you don't know what power they can handle).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-01T22:22:32.100" CommentCount="2" />
  <row Id="4738" PostTypeId="2" ParentId="1849" CreationDate="2010-10-01T22:27:07.553" Score="2" ViewCount="" Body="&lt;p&gt;Low pull-up values (lower resistance) can improve the edges of the signal transitions but can sometimes be too stiff - if the devices on the bus cannot sink the pull-up current you get logic 'low' which isn't really that low, which can cause communication errors (and much pain.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would go with the highest pull-up resistance that gives you reliable communications.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-01T22:27:07.553" />
  <row Id="4740" PostTypeId="2" ParentId="4734" CreationDate="2010-10-02T02:01:55.603" Score="1" ViewCount="" Body="&lt;p&gt;1) I used MPSA42 transistors as low side switches in my Nixie tube clock. A 10K current limit resistor on the anode of the tube and (as I recall - schematics not at hand) a 68K resistor on the base of the transistor. The MPSA42 components are cheap enough that you can experiment with them.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2010-10-02T02:01:55.603" CommentCount="2" />
  <row Id="4741" PostTypeId="2" ParentId="4639" CreationDate="2010-10-02T02:07:00.910" Score="2" ViewCount="" Body="&lt;p&gt;How often/how much data do you need to send?  If it's fairly intermittent (on the order of a minute or so), some AA batteries could last you a very long time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For sensor applications, the &lt;strong&gt;most important thing to optimize is the sleep-mode power consumption&lt;/strong&gt;.  You can wake up and send data using several hundred mA (seemingly typical for a 802.11* module) for a few seconds, but if you can then sleep for a few minutes using less than 1 mA, plain ol' alkalines will work just fine.  NiMH might be an alternative, but in an optimized wireless sensor design their internal discharge rate will limit their life more than capacity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use some complex energy-harvesting thing, you will need to spend a great deal on supercaps, as using a solar cell, peltier junction, or RF harvester will give you nowhere near enough &lt;em&gt;power&lt;/em&gt;.  Batteries can happily deliver a watt each with no added cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A much more tried-and-true method for RF sensors all about is using, as mentioned before, ZigBee (well, 802.15.4--very few people use true ZigBee).  They will run for years with a very modest battery, and you can easily bridge them to an 802.11 network with some &lt;a href=&quot;http://www.digi.com/products/wirelessdropinnetworking/connectportxgateways.jsp#overview&quot; rel=&quot;nofollow&quot;&gt;Digi ConnectPort X2&lt;/a&gt;'s.  802.15.4 modules can wake up and send data in milliseconds using several times less power with a much greater range.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-02T02:07:00.910" CommentCount="1" />
  <row Id="4742" PostTypeId="1" AcceptedAnswerId="4823" CreationDate="2010-10-02T02:34:27.330" Score="3" ViewCount="306" Body="&lt;p&gt;I need a circuit that fires a relay when it detects audio pulses from one channel of an mp3 player.  I'm going to record audio pulses in sync with the music to control a motor for mouth movement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its been 20 years since I've done this kind of stuff, so I need some help with this design.&lt;br&gt;&#xA;This is what I'm thinking so far:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.excellerate.com/images/acr.jpg&quot; alt=&quot;audio controlled relay circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea is to convert the AC audio to a DC level with D1 , use C1 to smooth it out.  Set R1 so the transistor is just below switching on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does this look like it will work?  If so, what would be a reasonable value for C1?  Does it have to be electrolytic, or can it be ceramic?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Clarification - I'm mostly interested in knowing:&#xA;- will my design work?&#xA;- suggestions for improvement?&lt;/p&gt;&#xA;" OwnerUserId="1406" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T22:16:00.853" LastActivityDate="2011-04-27T22:16:00.853" Title="audio controlled relay circuit" Tags="&lt;audio&gt;&lt;transistor&gt;&lt;relay&gt;" AnswerCount="4" CommentCount="5" />
  <row Id="4743" PostTypeId="2" ParentId="4678" CreationDate="2010-10-02T02:55:33.413" Score="1" ViewCount="" Body="&lt;h3&gt;Tools&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Hakko 936's are cheap (at work it was ~$85 from a supplier) but perform great.  They don't heat up as fast as some of the newer irons (ones where the &quot;tip&quot; includes the heating element), but in easily under a minute.  The standard tip that they come with I've used for soldering everything down to 0.50 mm QFNs.  They even make &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9672&quot; rel=&quot;nofollow&quot;&gt;knockoffs&lt;/a&gt; of them if you're trying to save a buck.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And yes, tweezers.  Get a few different styles and if they get bent much, throw them away.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Materials&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;For moderately fine-pitch work, 0.015&quot; is common, but have some 0.025 or 0.031 for thru-hole so you're not using an inch of solder per connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found using tacky flux instead of flux pens works quite well.  I got a 30 g tube of some Kester tacky no-clean RMA flux (forgot number) from my rep for free (out of expiration date) when I bought some flux cleaner and it's proven to perform much better, if being &lt;em&gt;slightly&lt;/em&gt; less convenient.  A fine-point Luer-lock tip and I can put a dot right where I want.  It also can hold fine parts down fairly well and sort of dampen some hand vibration when nudging parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;30 AWG Kynar (wire-wrap) wire is great when that connection somehow slips through your layout package's DRC or you FUBAR the pinout and have to rotate the part and have half of it hanging up in the air&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Techniques&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;As far as techniques for some leadless/bottom pad parts, I usually go with reemrevnivek's dead-bug approach if I can't get the same part in a more convenient leaded package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to put them down onto a board, bottom pads can occasionally be hand-soldered with a sufficiently large via under the pad, even &lt;a href=&quot;http://www.youtube.com/watch?v=D3PTpaB4kro&quot; rel=&quot;nofollow&quot;&gt;large-pitch BGAs&lt;/a&gt; (have not personally done BGAs).  Alternatively, you could attach the leadless components with solder paste and hot-plate reflow before hand-working the leaded components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I work around the third-hand problem for SMT placement by putting a minimal amount of solder onto one pad (be it for a TQFP-64 or 2512) then tacking the part down.  For ICs, you might have to nudge it just-so to align it properly, then tack down an opposite corner then go to work.  Be sure to hit the tacked locations again to get a proper joint.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-02T02:55:33.413" CommentCount="1" />
  <row Id="4744" PostTypeId="2" ParentId="3472" CreationDate="2010-10-02T02:59:11.277" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.latticesemi.com/products/developmenthardware/developmentkits/xp2breviadevelopmentkit.cfm&quot; rel=&quot;nofollow&quot;&gt;Here's&lt;/a&gt; a cheap FPGA development kit that may be right for you. However, I am not sure about the level of Open source tools that work with it. The vendor's toolkit chains are available for free download. I have heard that at the price point this kit is available for, it is worth going and getting it.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastActivityDate="2010-10-02T02:59:11.277" />
  <row Id="4745" PostTypeId="2" ParentId="4333" CreationDate="2010-10-02T03:36:08.663" Score="6" ViewCount="" Body="&lt;p&gt;From &lt;a href=&quot;http://dementeddiode.org/blog/2010/09/adventures-with-silkscreen/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/szFpI.jpg&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/Z6dy9.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-10-02T03:36:08.663" CommunityOwnedDate="2010-10-02T03:36:08.663" />
  <row Id="4746" PostTypeId="1" CreationDate="2010-10-02T06:00:10.620" Score="5" ViewCount="240" Body="&lt;p&gt;When I copy a binary that works on a lpc1343 to the mounted usb-device representing the lpc1343 flash, the binary file is changed and does not work. Doing the same with the flash mounted via usb on Windows or Mac OS does not have the same problem. What could be the problem, and how can it be fixed?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: The problem seems to be the vfat implementation in Linux which seems to prefix 0s before the file to be transferred. &lt;/p&gt;&#xA;" OwnerUserId="936" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-20T16:27:51.290" LastActivityDate="2011-01-20T16:27:51.290" Title="Problems programming LPC1343 microcontroller in Ubuntu" Tags="&lt;microcontroller&gt;&lt;usb&gt;&lt;linux&gt;&lt;programmer&gt;&lt;cortex-m3&gt;" AnswerCount="1" CommentCount="7" FavoriteCount="2" />
  <row Id="4747" PostTypeId="1" CreationDate="2010-10-02T06:03:44.060" Score="3" ViewCount="296" Body="&lt;p&gt;In Eagle, I've dealt with a couple of parts that have pads that don't seem to be accessible from the schematic: HTSSOP packages with a thermal pad that should be connected to a ground pin; a battery holder which is a metal can soldered to pads 1 and 3 but Eagle only knows about pad 1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I tell Eagle to put copper between the thermal pad and the ground pin? How do I tell Eagle that the metal can electrically connects pads 1 and 3, even though Eagle must not put any copper between them?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-10-02T10:58:01.170" Title="How do I connect a pin that is not included on the main symbol or any of the gates of an Eagle part?" Tags="&lt;eagle&gt;&lt;routing&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="4748" PostTypeId="2" ParentId="4571" CreationDate="2010-10-02T07:22:43.213" Score="6" ViewCount="" Body="&lt;p&gt;There's a build script here: &lt;a href=&quot;http://github.com/esden/summon-arm-toolchain&quot; rel=&quot;nofollow&quot;&gt;http://github.com/esden/summon-arm-toolchain&lt;/a&gt; to build a gcc based toolchain which targets ARM from Debian based computers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It states that it is tested and confirmed working for:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;STM32F10x (Olimex STM32-H103 eval board, Open-BLDC v0.1, v0.2, v0.3)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;which appears to be Cortex-M3 based.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-10-02T07:22:43.213" CommentCount="1" />
  <row Id="4749" PostTypeId="1" AcceptedAnswerId="4751" CreationDate="2010-10-02T10:38:25.983" Score="3" ViewCount="432" Body="&lt;p&gt;I'm working on a low power application. With a PIC24F (3.3V) I want to control the power to an SD card, turning it on and off. Typical current draw is 50mA, but can go as high as 200mA. I already have a 3.3V supply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking of something using a 2N7000 MOSFET. What gate-source voltage would saturate these? Is it possible to do this on the high side or will it have to be on the low side?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-02T12:01:02.780" Title="Controlling power to an SD card" Tags="&lt;pic&gt;&lt;mosfet&gt;" AnswerCount="1" FavoriteCount="0" />
  <row Id="4750" PostTypeId="2" ParentId="4747" CreationDate="2010-10-02T10:58:01.170" Score="1" ViewCount="" Body="&lt;p&gt;Sounds like the parts are not defined exactly as you would like them in the Eagle library.  I would make new versions of the parts in the library (I don't suggest directly editing the existing ones) by copying the parts and adding the missing pins.  In the case of the HTSSOP package you will also want to add the thermal pad for the layout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several tutorials on the web re creating and copying parts in the Eagle library, such as &lt;a href=&quot;http://myhome.spu.edu/bolding/EE4211/EagleTutorial4.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; one.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-02T10:58:01.170" CommentCount="2" />
  <row Id="4751" PostTypeId="2" ParentId="4749" CreationDate="2010-10-02T11:40:08.527" Score="3" ViewCount="" Body="&lt;p&gt;Low-side configuration are fine for simple loads like relays or lights, but you don't want to use a low-side configuration in this case, since it would place the ground of the SD card at a different level than the ground for the PIC24, which would interfere with the logical levels used to drive the data interface.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I like to use P-channel MOSFET's in a high-side configuration for this purpose, with the gate tied to the source lead through a 499K resistor to keep the device off when starting up.   You can then turn the MOSFET on by configuring the pin on the PIC24 in an open-drain configuration and driving it low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You want a P-channel MOSFET with a very low Rds (below 1 ohm) and low Vgs, such as &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=NDS352APCT-ND&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;.  (I couldn't find any that met your criteria in a thru-hole package.)  The MOSFET you chose (2N7000) has an Rds of 5 ohms, which means there would be a 1 volt voltage drop at 200 ma.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet/vishay/70611.pdf&quot; rel=&quot;nofollow&quot;&gt;document&lt;/a&gt; that explains why it is best to use P-channel MOSFET's in a high-side configuration.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-10-02T12:01:02.780" LastActivityDate="2010-10-02T12:01:02.780" CommentCount="1" />
  <row Id="4752" PostTypeId="1" AcceptedAnswerId="4770" CreationDate="2010-10-02T11:54:00.293" Score="4" ViewCount="663" Body="&lt;p&gt;Hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm attempting to draw the following two circuits up in NI Multisim 10, to attempt simulation and confirm my calculations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I'm not sure how to represent the Vin and Vout sources. Also, multisim only seems to have amplifiers with power supplies, but all theory I read seems to draw the amplifiers without. Does that matter for a eventual simulation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, ff there's any better software for the purpose than Multisim, then please tell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WDWcg.png&quot; alt=&quot;Circuits&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1412" LastActivityDate="2010-10-02T20:35:20.223" Title="Drawing a comparator op-amp in Multisim" Tags="&lt;op-amp&gt;&lt;simulation&gt;" AnswerCount="3" />
  <row Id="4753" PostTypeId="2" ParentId="4742" CreationDate="2010-10-02T11:57:04.813" Score="0" ViewCount="" Body="&lt;p&gt;R.E Caps Electrolytic or ceramic? - &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It depends on what value is required (sorry I can't help you with that, I'm not familiar with the circuit in question) If you need a large value you'll probably want an electrolytic, the larger the value the more expensive and harder it is to find in a ceramic package. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ceramics in general have a longer life span than the electrolytics, but they're quite brittle and don't like being bashed about excessively.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope that helps. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;your project sounds like fun, I'm super curious to see what the mouth-face bit looks like! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck :)&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-10-02T11:57:04.813" CommentCount="2" />
  <row Id="4754" PostTypeId="2" ParentId="4752" CreationDate="2010-10-02T12:14:11.343" Score="3" ViewCount="" Body="&lt;p&gt;I'm pretty sure it's quite common to omit an op-amps power connections when doing a circuit schematic, it's just for clarity I think - it's presumed you know they're supposed to be there, it keeps diagram complexity down and makes other connections easier to visualise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not familiar with Multisim, but I'd imagine - If the option to connect the power rails is there, you should probably hook them up, in theory the op-amps will not function correctly if they don't have the power hooked up, but this may not be the case in the sim-world. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can always test both - if the simulation still works without the power connection - it may be that it assumes the nominal power supply is connected. The connection may be more applicable for testing power supplies outside the nominal range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also - The de-facto circuit simulator that most people seem to use is &lt;a href=&quot;http://bwrc.eecs.berkeley.edu/classes/icbook/spice/&quot; rel=&quot;nofollow&quot;&gt;SPICE&lt;/a&gt;, as it's quite common, it has a good community base and there's loads of help and tutorials available for it.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just my thoughts on the matter, some of it may be helpful :)&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-10-02T12:47:31.607" LastActivityDate="2010-10-02T12:47:31.607" CommentCount="1" />
  <row Id="4755" PostTypeId="1" AcceptedAnswerId="4761" CreationDate="2010-10-02T12:42:17.263" Score="5" ViewCount="440" Body="&lt;p&gt;What are the differences and where would your use each?&lt;/p&gt;&#xA;" OwnerUserId="1411" LastActivityDate="2010-10-02T14:19:12.940" Title="What are the differences between NAND and NOR flash?" Tags="&lt;flash&gt;" AnswerCount="3" />
  <row Id="4756" PostTypeId="1" CreationDate="2010-10-02T13:33:28.050" Score="3" ViewCount="269" Body="&lt;p&gt;Hi, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an application in mind in which I need to communicate via SPI with an FPGA. Both the FPGA and microcontroller are in our control, and so I have the flexibility to define the protocol as I see fit. However, I was wondering if there are any good example uses out there that work well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is what I was thinking. (byte oriented)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Master: &amp;lt;REG&amp;gt;&amp;lt;WR+LEN&amp;gt;&amp;lt;MSTR_DATA&amp;gt;&amp;lt;CHK&amp;gt;&#xA;Slave : &amp;lt; 0 &amp;gt;&amp;lt;  0   &amp;gt;&amp;lt;SLAV_DATA&amp;gt;&amp;lt;CHK&amp;gt;&#xA;&#xA;REG : register within FPGA to read or write&#xA;WR  : read / write bit&#xA;LEN : 7 bit payload length (not including REG,WR+LEN or CHK)&#xA;MSTR: master data if write mode.&#xA;SLAV: slave data if read mode.&#xA;MCHK: 8 bit checksum of MSTR_DATA (by master), (CRC8, XOR, mod 256 etc)&#xA;SCHK: 8 bit checksum of SLAV_DATA (by slave ), (CRC8, XOR, mod 256 etc)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Is this workable? Are there any better examples out there?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT1:&#xA;Some clarification on requirements:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The microcontroller is to read and&#xA;write small blocks of data to/from&#xA;the FPGA. &lt;/li&gt;&#xA;&lt;li&gt;The FPGA will support&#xA;read/write operations to registers.&lt;/li&gt;&#xA;&lt;li&gt;The registers can be many bytes deep&#xA;(like a fifo) or autoincrementing&#xA;(next read or write byte comes from&#xA;the next register).&lt;/li&gt;&#xA;&lt;li&gt;I would like the&#xA;operation including the checksum /&#xA;ack to occur in a single&#xA;transmission.&lt;/li&gt;&#xA;&lt;li&gt;I would like this have a low overhead, some operations will be fetching or posting 5-10 bytes. The largest could be 127 or 64.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1411" LastEditorUserId="1411" LastEditorDisplayName="" LastEditDate="2010-10-03T10:24:44.363" LastActivityDate="2010-10-03T10:24:44.363" Title="Any examples of an SPI based protocol with a checksum?" Tags="&lt;microcontroller&gt;&lt;fpga&gt;&lt;spi&gt;" AnswerCount="2" />
  <row Id="4757" PostTypeId="2" ParentId="4755" CreationDate="2010-10-02T13:35:39.230" Score="1" ViewCount="" Body="&lt;p&gt;NOR allows for random access, but NAND does not (page access only.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From Wikipedia: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;NOR and NAND flash get their names from the structure of the &#xA;interconnections between memory cells. In NOR flash, cells &#xA;are connected in parallel to the bitlines, allowing cells to &#xA;be read and programmed individually. The parallel connection &#xA;of cells resembles the parallel connection of transistors in &#xA;a CMOS NOR gate. In NAND flash, cells are connected in series, &#xA;resembling a NAND gate. The series connections consume less &#xA;space than parallel ones, reducing the cost of NAND flash. It &#xA;does not, by itself, prevent NAND cells from being read and &#xA;programmed individually.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-02T13:35:39.230" />
  <row Id="4758" PostTypeId="2" ParentId="4756" CreationDate="2010-10-02T13:39:31.080" Score="1" ViewCount="" Body="&lt;p&gt;I believe SD card SPI mode has a checksum.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-02T13:39:31.080" CommentCount="2" />
  <row Id="4759" PostTypeId="2" ParentId="4752" CreationDate="2010-10-02T14:04:08.573" Score="2" ViewCount="" Body="&lt;p&gt;Your issue is which op amp you are using from their library. You are using an ideal op-amp. Almost always students in class will show me a simulation where they use an ideal op amp and it does not work, or it works too well. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try selecting a different op amp from the master database that has connections for power. I just opened my library and I have many many options. You need to determine which one fits your applications. They will have power connections, non-infinite gain, not be able to completely hit the rail, so forth so on.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-02T14:04:08.573" CommentCount="1" />
  <row Id="4760" PostTypeId="2" ParentId="4755" CreationDate="2010-10-02T14:12:42.213" Score="3" ViewCount="" Body="&lt;p&gt;NAND flash is cheaper, so you want to use it if you can. The drawback is that it's not as reliable. NAND flash is faster at most operations, with the notable exception being small random access reads. If you want to read a couple bytes from a random address in memory, NOR is faster. For large memory reads, NAND does reasonably well, and actually beats NOR for large enough chunks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most embedded operating systems include code to correct the errors in NAND Flash. There are also microcontrollers with hardware error correction. The real problem happens at boot time-- first-level bootloaders don't have error-correcting code, and they haven't configured the memory controller to run hardware ECC yet. It's a bit of a chicken-and-egg problem-- you can't load the ECC code without errors because you haven't loaded the ECC code yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get around this problem, some memory manufacturers will specify a certain region of the chip that is guaranteed to be error free (the first 4 kB, or something like that). You put a bootloader with software ECC there (like &lt;a href=&quot;http://www.denx.de/wiki/U-Boot/WebHome&quot; rel=&quot;nofollow&quot;&gt;U-boot&lt;/a&gt;), read it out with no errors, and then use it to read out your OS kernel, correcting errors as you go. You can also store a bootloader in a serial flash, and just use NAND flash for large stuff like an OS kernel or filesystem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found this Atmel application note useful: &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc6255.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/resources/prod_documents/doc6255.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-02T14:12:42.213" CommentCount="1" />
  <row Id="4761" PostTypeId="2" ParentId="4755" CreationDate="2010-10-02T14:19:12.940" Score="4" ViewCount="" Body="&lt;p&gt;There is a lot of trade-off to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wikipedia also:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Despite the additional transistors,&#xA;  the reduction in ground wires and bit&#xA;  lines allows a denser layout and&#xA;  greater storage capacity per chip. In&#xA;  addition, NAND flash is typically&#xA;  permitted to contain a certain number&#xA;  of faults (NOR flash, as is used for a&#xA;  BIOS  ROM, is expected to be&#xA;  fault-free). Manufacturers try to&#xA;  maximize the amount of usable storage&#xA;  by shrinking the size of the&#xA;  transistor below the size where they&#xA;  can be made reliably, to the size&#xA;  where further reductions would&#xA;  increase the number of faults faster&#xA;  than it would increase the total&#xA;  storage available.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So, NOR flash can address easier, but is not even close to as dense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you take at a look at a &lt;a href=&quot;http://maltiel-consulting.com/NAND_vs_NOR_Flash_Memory_Technology_Overview_Read_Write_Erase_speed_for_SLC_MLC_semiconductor_consulting_expert.pdf&quot; rel=&quot;nofollow&quot;&gt;pretty decent comparison PDF.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NOR has lower standyby power, is easy for code execution and has a high read speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NAND has much lower active power(writing bits is faster and lower cost), higher write speed(by a lot), much higher capacity, much much lower cost per bit and is very easy for file storage use. due to it's lower read speed when using it for code execution you really need to ghost it to ram.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To quote a small section with a great table above it...&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://maltiel-consulting.com/NAND_vs_NOR_Flash_Memory_Technology_Overview_Read_Write_Erase_speed_for_SLC_MLC_semiconductor_consulting_expert.pdf&quot; rel=&quot;nofollow&quot;&gt;The characteristics of NAND Flash are:&#xA;  high density, medium read speed, high&#xA;  write speed, high erase speed, and an&#xA;  indirect or I/O like access. The&#xA;  characteristics of NOR Flash are lower&#xA;  density, high read speed, slow write&#xA;  speed, slow erase speed, and a random&#xA;  access interface.&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-02T14:19:12.940" />
  <row Id="4762" PostTypeId="2" ParentId="4756" CreationDate="2010-10-02T14:54:06.157" Score="2" ViewCount="" Body="&lt;p&gt;I would have a look at &lt;a href=&quot;http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf&quot; rel=&quot;nofollow&quot;&gt;Modbus&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/HDLC&quot; rel=&quot;nofollow&quot;&gt;HDLC&lt;/a&gt; &lt;a href=&quot;http://en.wikipedia.org/wiki/High-Level_Data_Link_Control#Asynchronous%5Fframing&quot; rel=&quot;nofollow&quot;&gt;Asynchronous framing&lt;/a&gt; for examples of how to transfer packets over a serial bus. I would also have a look at this question &lt;a href=&quot;http://stackoverflow.com/q/815758/32598&quot;&gt;Simple serial point-to-point communication protocol&lt;/a&gt; over on &lt;a href=&quot;http://stackoverflow.com&quot;&gt;Stack Overflow&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you are in need of low overhead I would just do what you are doing. Use Chip select to gate the packet and include length and checksum.  I would probably stay away from CRC8 as your data is byte based not bit based. I checked several SPI memory devices and none of the ones I looked at included a checksum. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One example of a check sum is the &lt;a href=&quot;http://www.netfor2.com/udpsum.htm&quot; rel=&quot;nofollow&quot;&gt;UDP checksum&lt;/a&gt;. For your example that would translate to the ones complement of the sum mod 256.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For ack or status back from slave you can take advantage of the fact that SPI is full duplex and instead of just sending nothing back the slave can just send a status byte and in that byte you can use one bit to flag checksum errors. The status can also include a busy bit so you can use this to poll the slave to see when it is done and ready for another command.&lt;/p&gt;&#xA;" OwnerUserId="540" LastEditorUserId="540" LastEditorDisplayName="" LastEditDate="2010-10-02T22:11:46.843" LastActivityDate="2010-10-02T22:11:46.843" CommentCount="2" />
  <row Id="4763" PostTypeId="2" ParentId="4708" CreationDate="2010-10-02T15:07:58.667" Score="2" ViewCount="" Body="&lt;p&gt;There have been great answers. I do not know what micro you use, but here are links to some info from microchip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en020237&quot; rel=&quot;nofollow&quot;&gt;J1939 library&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en012120&quot; rel=&quot;nofollow&quot;&gt;DeviceNet™ Group 2 Slave Firmware for PIC18 with CAN&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en020605&quot; rel=&quot;nofollow&quot;&gt;CANopen&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They each have code and a basic datasheet letting you know what you need to implement them.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-02T15:07:58.667" CommentCount="4" />
  <row Id="4764" PostTypeId="1" AcceptedAnswerId="4768" CreationDate="2010-10-02T18:03:35.537" Score="1" ViewCount="178" Body="&lt;p&gt;I want to use a 0.1F 5.5V supercap to keep time with a PIC24FJ64GA004 device. Does anyone have any idea on how to implement this? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking of using the supercap on the +3.3V supply line and monitoring the battery input. When the main supply drops below say 5V I would put the micro into ultra low power sleep mode (~400-500nA with RTCC.) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know how long a 0.1F cap lasts with &amp;lt;1µA current draw? It'll be charged up to 3.3V and 2.0V is the terminal voltage, though it would probably work down even lower.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-04T13:12:47.790" Title="Using a super-cap with a PIC24F to keep time in case of supply failure" Tags="&lt;capacitor&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="4765" PostTypeId="1" AcceptedAnswerId="4779" CreationDate="2010-10-02T19:13:04.740" Score="3" ViewCount="475" Body="&lt;p&gt;Hey guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've bought that famous Receiver/Transmitter RWS-375 and TWS 375. I want to clone the remote control of my  garage door.&lt;br&gt;&#xA;So I connected the RWS-375 in my Arduino, and build a program to receive the sinal that the remote control send.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However every time I press the button the program writes differente sequence of characters. I mean, I never get the same sequence of characters from the remote control. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've already tried changing the bits per seconds rate, but I think the correct is 9600, right?&lt;br&gt;&#xA;Also is there anything else I should verify in that I'm missing?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that I've already check that they operate at the same frequency...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks guys&lt;/p&gt;&#xA;" OwnerUserId="1416" LastActivityDate="2010-10-03T10:53:25.007" Title="Cloning a 433Mhz Transmitter using RWS-375 Receiver" Tags="&lt;arduino&gt;&lt;remote&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="4766" PostTypeId="1" AcceptedAnswerId="4769" CreationDate="2010-10-02T19:23:49.133" Score="3" ViewCount="259" Body="&lt;p&gt;I don't have any experience with electronics really but I do have experience in programming.  I'm interested in writing a program to control my stereo, TV etc.  To achieve this I'll need a piece of hardware which is WiFi capable and can generate a range of infrared signals to control my TV, stereo and other infrared capable devices.  Given my lack of experience with microcontrollers etc, I'd probably find it easier if I could minimize the amount of work the hardware had to do and focussed it on converting data it receives via WiFi into infrared.  What components would I require and are there any relatively inexpensive out-of-the-box solutions which will have the majority of what I need without requiring too much additional soldering?  Also, at a high level, what way should the operation of such a device be architected?&lt;/p&gt;&#xA;" OwnerUserId="1415" LastEditorUserId="1415" LastEditorDisplayName="" LastEditDate="2010-10-02T20:12:18.573" LastActivityDate="2010-10-02T21:02:08.850" Title="Components for a WiFi enabled IR controller" Tags="&lt;hardware&gt;&lt;remote&gt;&lt;infrared&gt;&lt;wifi&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="4767" PostTypeId="2" ParentId="4766" CreationDate="2010-10-02T19:34:36.530" Score="2" ViewCount="" Body="&lt;p&gt;Check out the &lt;a href=&quot;http://dangerousprototypes.com/docs/USB_Infrared_Toy&quot; rel=&quot;nofollow&quot;&gt;USB Infrared Toy&lt;/a&gt; (from the people who brought us Bus Pirate).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, you'll still need the wifi part. A linux based router running OpenWRT could be a good choice.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-02T19:34:36.530" />
  <row Id="4768" PostTypeId="2" ParentId="4764" CreationDate="2010-10-02T19:36:47.610" Score="1" ViewCount="" Body="&lt;p&gt;According to page 4 this &lt;a href=&quot;http://industrial.panasonic.com/www-data/pdf/ABC0000/ABC0000TE5.pdf&quot; rel=&quot;nofollow&quot;&gt;document&lt;/a&gt;, a 0.047F 5.5V supercap will drop from 3.3v to 2.0v in about 18 hours with a 3.75M load (&amp;lt;1µA).  So I would expect your 0.1F cap to do about twice that.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-02T19:36:47.610" CommentCount="1" />
  <row Id="4769" PostTypeId="2" ParentId="4766" CreationDate="2010-10-02T20:27:07.017" Score="2" ViewCount="" Body="&lt;p&gt;You could hook up a RF/Bluetooth (cheap) module to your IR receiver, which usually requires a UART header (USB IR Toy's UART header is not supported in the firmware, only UART-to-USB bridge), or you can use some kind of USB-to-Wireless converter (USB IR Toy uses USB CDC/ACM).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you need to check the connections in your IR receiver and wireless module (signal levels, host/slave configuration, etc). Probably your best bet is to get a USB-to-Wireless bridge module.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: If you want to make your IR receiver truly wireless, you probably should look for a way to power it and the wireless bridge module. Take a look at these links (can't post more than one link, so check second link as a comment below  ^.^):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dangerousprototypes.com/forum/index.php?topic=759.0&quot; rel=&quot;nofollow&quot;&gt;Parts for Solar/Bluetooth Hot-Swappable Unit&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1084" LastEditorUserId="1084" LastEditorDisplayName="" LastEditDate="2010-10-02T21:02:08.850" LastActivityDate="2010-10-02T21:02:08.850" CommentCount="2" />
  <row Id="4770" PostTypeId="2" ParentId="4752" CreationDate="2010-10-02T20:35:20.223" Score="2" ViewCount="" Body="&lt;p&gt;Multisim does have ideal opamps, they can be found in the master database under Analog&gt;Analog_Virtual_OPAMP_3T_VIRTUAL, but as Kortuk said, you should strongly consider using an opamp that forces you to include a power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a particular opamp that you know you will be using in a lab, you should see if you can find it in the multisim database. Multisim has very good models for how the opamps will actually act even more then just how you are powering them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for your question about Vin and Vout, in Multisim you can go to Simulate&gt;Instruments and select what ever instrument you want to place. So you could put a function generator in for Vin and a Oscope for Vout.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-02T20:35:20.223" />
  <row Id="4771" PostTypeId="2" ParentId="4765" CreationDate="2010-10-02T23:08:59.007" Score="1" ViewCount="" Body="&lt;p&gt;It may be doing this on purpose, and you are receiving the bytes correctly.  They may be using randomized encryption for security -- this way no one can snoop on your receiver, and play back the data later to open your garage.  The same concept is used for &lt;a href=&quot;http://en.wikipedia.org/wiki/KeeLoq&quot; rel=&quot;nofollow&quot;&gt;keyless remote entry&lt;/a&gt; systems for automobiles.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-02T23:08:59.007" />
  <row Id="4772" PostTypeId="1" AcceptedAnswerId="4774" CreationDate="2010-10-03T00:35:38.737" Score="0" ViewCount="62" Body="&lt;p&gt;How does a motion detector work?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-10-03T01:11:53.163" Title="What's the circuit for a PIR sensor?" Tags="&lt;sensor&gt;&lt;motion&gt;" AnswerCount="1" />
  <row Id="4773" PostTypeId="2" ParentId="3693" CreationDate="2010-10-03T01:02:52.937" Score="1" ViewCount="" Body="&lt;p&gt;The problem is with certification marks, like anything else  - they can be faked. Go to globalsources.com, find a cheap manufacturer, they will most likely say &quot;email us the artwork and we'll add it to the transformer!&quot;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In defence of Sparkfun, I wouldn't think they would risk their reputation over such a thing. But it couldn't hurt to ask them about it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally I spend a lot more and get the certified ones with the half-insulated pins as specified by the Australian standards (being in Australia). As after this &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/06/16/seriously-dont-buy-a-cheap-plugpack/&quot; rel=&quot;nofollow&quot;&gt;experience&lt;/a&gt;, I don't like to take any chances. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-03T01:02:52.937" />
  <row Id="4774" PostTypeId="2" ParentId="4772" CreationDate="2010-10-03T01:11:53.163" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.logosfoundation.org/ii/infrared_sensing.html&quot; rel=&quot;nofollow&quot;&gt;http://www.logosfoundation.org/ii/infrared_sensing.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Passive_infrared_sensor&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Passive_infrared_sensor&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-03T01:11:53.163" CommunityOwnedDate="2010-10-03T01:11:53.163" />
  <row Id="4775" PostTypeId="2" ParentId="2407" CreationDate="2010-10-03T08:32:02.887" Score="2" ViewCount="" Body="&lt;p&gt;For higher current ranges, such as the one you're looking at, it is probably better to use an inductive pickup. This allows you to measure high currents accurately, without having to dissipate lots of heat from shunt resistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An example would be the &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=398-1081-ND&quot; rel=&quot;nofollow&quot;&gt;Digi-Key 398-1081-ND&lt;/a&gt;, which gives a DC voltage out proportional to the AC current in the system. &lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-10-03T08:32:02.887" />
  <row Id="4776" PostTypeId="2" ParentId="4765" CreationDate="2010-10-03T08:32:03.883" Score="1" ViewCount="" Body="&lt;p&gt;Right, it makes sense. The algorithm used is called &lt;a href=&quot;http://en.wikipedia.org/wiki/KeeLoq&quot; rel=&quot;nofollow&quot;&gt;keyloq&lt;/a&gt;. There is a kind of counter that is incremented everytime you press your garage key. I let you read the Wiki page for more detail.&lt;/p&gt;&#xA;" LastActivityDate="2010-10-03T08:32:03.883" />
  <row Id="4777" PostTypeId="1" CreationDate="2010-10-03T09:00:11.187" Score="0" ViewCount="781" Body="&lt;p&gt;I am very new to Electronics. I am Programmer and I've never done anything with electronics. &#xA;However Started Using Simulators now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to Make Simple a Quiz Buzzer Circuit With LED. e.g. I need LED instead of Buzzer. I don't need any reset Switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to maximize the Use of Logic Gates in this Circuit.&#xA;and Obviously no Capacitors are Allowed.and obviously no microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to do this for 2 days. But Cannot Make it Out.&#xA;I think The Basic Idea should be this:&#xA;&lt;img src=&quot;http://www.freeimagehosting.net/uploads/92da05b218.png&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done a Lot of things on the top of this but non of them seemed to work.&lt;/p&gt;&#xA;" OwnerUserId="1424" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-03T09:29:22.060" LastActivityDate="2010-10-16T19:57:36.417" Title="LED Quiz Buzzer Circuit With Logic Gates" Tags="&lt;circuit&gt;&lt;logic&gt;" AnswerCount="3" CommentCount="7" FavoriteCount="2" />
  <row Id="4778" PostTypeId="2" ParentId="4777" CreationDate="2010-10-03T09:23:18.747" Score="1" ViewCount="" Body="&lt;p&gt;The trick you're missing is feedback from your outputs back into the circuit.  A is disabled when B or C or D or E is already active.  B is disabled when A or C or D or E is active.  See the pattern?  You'll need 4 input NOR gates where all your inverters are now.&lt;/p&gt;&#xA;" OwnerUserId="1425" LastActivityDate="2010-10-03T09:23:18.747" CommentCount="4" />
  <row Id="4779" PostTypeId="2" ParentId="4765" CreationDate="2010-10-03T10:53:25.007" Score="1" ViewCount="" Body="&lt;p&gt;I did a project like this a while back:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2009/10/03/garage-door-packet-sniffer/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2009/10/03/garage-door-packet-sniffer/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from the protocol being based on rolling code or some encryption scheme like Keeloq, some of the cheaper rf modules have bad response time, you have to have some data on the line for a couple of ms before your receiver starts putting out the correct stream.&lt;/p&gt;&#xA;" OwnerUserId="1427" LastActivityDate="2010-10-03T10:53:25.007" />
  <row Id="4780" PostTypeId="1" AcceptedAnswerId="4783" CreationDate="2010-10-03T14:03:01.043" Score="3" ViewCount="499" Body="&lt;p&gt;Hi all, I have an idea for a project but need some help on achieving what I want to do.  I want to create a device which will insert into the audio jack of my iPhone which will emit IR signals to control my TV.  Most IR devices use signals in the 35-45K range and the audio out has a max frequency of around 20K.  So, since I cant directly tell the IR LED what frequency to emit, I'm thinking this device will need to have a microcontroller in the middle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what I'm thinking of doing is, having my iPhone app send a signal via the headphone jack to the device, have the device interpret it and then generate the appropriate IR signal to control the TV.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions on how I might achieve this at a high level?&lt;br&gt;&#xA;Any suggestions for kits which might allow me to easily prototype this kind of thing?&lt;br&gt;&#xA;Any alternatives to my suggested solution which might work better?&lt;/p&gt;&#xA;" OwnerUserId="1415" LastActivityDate="2011-01-09T04:48:56.703" Title="How to use an audio output to generate IR frequencies" Tags="&lt;microcontroller&gt;&lt;infrared&gt;&lt;iphone&gt;" AnswerCount="2" />
  <row Id="4782" PostTypeId="2" ParentId="2407" CreationDate="2010-10-03T18:38:18.557" Score="1" ViewCount="" Body="&lt;p&gt;If you're just measuring AC, use a current-sensing transformer, such as &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=495-4042-1-ND&quot; rel=&quot;nofollow&quot;&gt;this EPCOS one from Digikey&lt;/a&gt; (or flip through &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=786724&quot; rel=&quot;nofollow&quot;&gt;some others&lt;/a&gt;).  It offers much lower resistance than a shunt resistor (0.8 mΩ nominally) and provides the added benefit of isolating your sensing circuitry from the mains line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hall-effect current sensors also offer similar performance, such as &lt;a href=&quot;http://www.allegromicro.com/en/Products/Categories/Sensors/currentsensor.asp&quot; rel=&quot;nofollow&quot;&gt;these from Allegro&lt;/a&gt;, but work with DC as well as AC.  Digi-Key carries most of their product offering as well.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-03T18:38:18.557" />
  <row Id="4783" PostTypeId="2" ParentId="4780" CreationDate="2010-10-03T19:18:29.763" Score="3" ViewCount="" Body="&lt;p&gt;This problem is really not that bad at all. You do not need to send the carrier frequency over the headphone jack. Instead, you should build the oscillator into your device a-la &lt;a href=&quot;http://jap.hu/electronic/infrared.html&quot; rel=&quot;nofollow&quot;&gt;http://jap.hu/electronic/infrared.html&lt;/a&gt; (or just use a micro) and then you just need to switch it on and off based on a much slower signal from the headphone jack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to the internets, almost all remote control receivers expect a 38kHz carrier wave. You will need to turn it on and off at 2-4kHz. See also &lt;a href=&quot;http://en.wikipedia.org/wiki/RC-5&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/RC-5&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are as clever as off-the-shelf iPhone headphone jack infrared transmitters then you can get your power from the audio signal, but if I were you I'd just use batteries.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2010-10-03T22:21:02.950" LastActivityDate="2010-10-03T22:21:02.950" CommentCount="1" />
  <row Id="4784" PostTypeId="1" CreationDate="2010-10-03T19:36:18.107" Score="6" ViewCount="557" Body="&lt;p&gt;I am complete virgin in Electronics. Though I am very experienced in Programming. I've never played anything with electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing I cannot Understand is. In most circuits I see its live. e.g. You power it On and it works. and power it off and it stops. Show Why do you need to store the voltage for some time in a capacitor ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why can't the whole circuit be drawn capacitor free ? If its meant for storage isn't Flip flop the right thing for the purpose ?&lt;/p&gt;&#xA;" OwnerUserId="1424" LastActivityDate="2011-01-09T12:36:55.313" CommunityOwnedDate="2010-10-04T05:22:04.580" Title="Why Use Capacitors" Tags="&lt;circuit&gt;&lt;capacitor&gt;" AnswerCount="7" CommentCount="6" FavoriteCount="2" />
  <row Id="4785" PostTypeId="2" ParentId="4784" CreationDate="2010-10-03T19:53:05.023" Score="13" ViewCount="" Body="&lt;p&gt;If all you wanted to build was digital circuitry, and your voltage sources really held constant voltage no matter how much current was drawn from them, and nothing produced electrical noise, you wouldn't need capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But voltage sources sag when you draw current from them. Motor brushes (and lots of other components) produce horrendous voltage spikes that you want to filter out of your digital circuitry. Some people also deal with analog circuitry, where voltage and current signals vary continuously across a wide range. For that kind of time-varying circuitry, capacitors are needed.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-03T19:53:05.023" CommentCount="4" />
  <row Id="4786" PostTypeId="2" ParentId="4784" CreationDate="2010-10-03T19:56:08.623" Score="17" ViewCount="" Body="&lt;p&gt;Digital circuits can be especially bad, but in general you are attempting to make the power rail stay a source of DC power. most circuits when they suddenly draw power from the power rail would not be too happy if the power rail reacted by dipping.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you go to higher speed, inductance causes a bigger problem than resistance. The capacitor acts as a very close source of power. You pull your high speed power from the capacitor and the power source slowly charges the capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When done properly, everything works to spec. When making a commercial product and done improperly you get a product that has very odd bugs, normally tied to high load as the voltage really sags(sags= goes below what it needs to be). In the worst case high speed signals traverse your power lines and the FCC does not approve your product as it is radiating high frequency energy.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-03T19:56:08.623" CommentCount="5" />
  <row Id="4787" PostTypeId="2" ParentId="4784" CreationDate="2010-10-03T21:32:04.663" Score="8" ViewCount="" Body="&lt;p&gt;Capacitors are also widely used in &lt;a href=&quot;http://electronics.howstuffworks.com/oscillator2.htm&quot; rel=&quot;nofollow&quot;&gt;oscillator&lt;/a&gt;, &lt;a href=&quot;http://en.wikipedia.org/wiki/Electronic_filter&quot; rel=&quot;nofollow&quot;&gt;filter&lt;/a&gt; and &lt;a href=&quot;http://www.kpsec.freeuk.com/555timer.htm&quot; rel=&quot;nofollow&quot;&gt;timing&lt;/a&gt; circuits, because their charging rate and discharging rate can be accurately calculated.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In an &lt;a href=&quot;http://webphysics.davidson.edu/physlet_resources/gustavus_physlets/RCCircuit.html&quot; rel=&quot;nofollow&quot;&gt;RC&lt;/a&gt; circuit, the value of the time constant (in seconds) is equal to the product of the circuit resistance (in ohms) and the circuit capacitance (in farads), i.e. R × C. It is the time required to charge the capacitor, through the resistor, to 63.2% of full charge; or to discharge it to 36.8% of its initial voltage.  These odd looking percentages are derived from the mathematical constant e (2.71828, the base for natural logarithms), specifically 1 − 1/e and 1/e respectively.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oscillator and timing circuits are commonly used in digital systems to provide frequency generators and timing.  Oscillators and filters are typically found in analog circuits, i.e. audio or radio-frequency (RF).&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-10-03T23:19:42.210" LastActivityDate="2010-10-03T23:19:42.210" CommentCount="3" />
  <row Id="4788" PostTypeId="1" AcceptedAnswerId="4790" CreationDate="2010-10-03T22:03:03.123" Score="5" ViewCount="160" Body="&lt;p&gt;Could you explain how a quartz crystal works, maybe with a simple schematics with the essential things ? I know it acts like a kind of stabilizer for an oscillator, but nothing more than that.&lt;/p&gt;&#xA;" OwnerUserId="1272" LastActivityDate="2010-10-04T17:17:06.957" Title="How does a quartz crystal work ?" Tags="&lt;crystal&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="4789" PostTypeId="2" ParentId="4788" CreationDate="2010-10-03T22:21:26.680" Score="3" ViewCount="" Body="&lt;p&gt;From &lt;a href=&quot;http://en.wikipedia.org/wiki/Crystal_oscillator&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;An oscillator crystal has two electrically conductive plates, with a slice or tuning fork of quartz crystal sandwiched between them. During startup, the circuit around the crystal applies a random noise AC signal to it, and purely by chance, a tiny fraction of the noise will be at the resonant frequency of the crystal. The crystal will therefore start oscillating in synchrony with that signal. As the oscillator amplifies the signals coming out of the crystal, the signals in the crystal's frequency band will become stronger, eventually dominating the output of the oscillator. The narrow resonance band of the quartz crystal filters out all the unwanted frequencies.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1415" LastActivityDate="2010-10-03T22:21:26.680" />
  <row Id="4790" PostTypeId="2" ParentId="4788" CreationDate="2010-10-03T22:50:54.483" Score="6" ViewCount="" Body="&lt;p&gt;Quartz is a piezoelectric material, which means that if you mechanically deform it, it develops charges on its surface. Similarly, if you place charges on its surface, it causes mechanical stress in the crystal. The way a quartz crystal benefits a circuit is that mechanically the crystal acts much like a tuning fork, with a natural resonant frequency, and the piezoelectric property allows that to be coupled into an electronic circuit. Since the resonant frequency is mainly determined by the physical size and shape of the quartz, you get a frequency reference that is much less sensitive to temperature than you would get using just LC circuits.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-03T22:50:54.483" CommentCount="1" />
  <row Id="4791" PostTypeId="2" ParentId="1748" CreationDate="2010-10-03T23:54:49.570" Score="1" ViewCount="" Body="&lt;p&gt;The Linistepper generates 6 microsteps in hardware, using the diodes and resistors to make the correct voltage levels for the 6 microsteps. This gives 200 x6 = 1200 steps/rotation which is one of the Linistepper microstep modes that you can select.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make 3600 steps/rotation the Linistepper alternates very fast in software between 2 of the microsteps. So it either does AAA or AAB or ABB (where A and B are 2 sequential microsteps) and at a high frequency around 333 kHz if you are using the 16MHz xtal. The overall effect is to provide 3600 microsteps from the 1200 hardware microsteps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Interesting note; the Linistepper is the only stepper driver that produces 3600 steps/rotation, making it ideal for things that work in degrees as it makes 10 microsteps per degree, also the smoothing caps C5 and C6 can be tuned (by choosing their value) to give very smooth transition from one microstep to the next when running at the &quot;tuned&quot; motor speed. Both those factors make it ideal for telescope movement (astronomy etc) and pan/tilt setups etc.&lt;/p&gt;&#xA;" LastActivityDate="2010-10-03T23:54:49.570" CommentCount="4" />
  <row Id="4792" PostTypeId="1" CreationDate="2010-10-04T05:41:42.510" Score="1" ViewCount="249" Body="&lt;p&gt;I am complete virgin in Electronics. Though I am very experienced in Programming. I've never played anything with electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the Specifications of Microcontrollers ?  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;No. of digital Pins:&lt;br&gt;&#xA;  No. of Analog Pins:&lt;br&gt;&#xA;  SRAM:&lt;br&gt;&#xA;  EEPROM:&lt;br&gt;&#xA;  Flash:&lt;br&gt;&#xA;  Operatng Voltage:  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If only these few are the characteristics of microcontroler. Why the come with long pdf Datasheet ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now a days they can all be programmed in C. and while coding only the first 5 informations are needed all others can easily be found in headers.  So why don't the manufacturer companies just give out these few infos only and with some links of here and there ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and If all vendors(Atmel/Motorola/Philips etc..) makes the same thing why professional people don't use AVR much. rather hobbyist people uses AVR.(got this info from another thread &lt;a href=&quot;http://electronics.stackexchange.com/questions/2324/why-are-atmel-avrs-so-popular&quot;&gt;http://electronics.stackexchange.com/questions/2324/why-are-atmel-avrs-so-popular&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="1424" LastActivityDate="2010-11-27T17:32:27.927" Title="Specifications of Microcontrollers Is it all same ?" Tags="&lt;avr&gt;&lt;microprocessor&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="4793" PostTypeId="2" ParentId="4784" CreationDate="2010-10-04T05:51:15.830" Score="2" ViewCount="" Body="&lt;p&gt;Hello user1424&#xA;You seem to be asking a lot of questions about many things electronic. May I recommend you find a good book such as &quot;The Art of Electronics&quot; by Horowitz and Hill, and have a good read through that. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-04T05:51:15.830" CommunityOwnedDate="2010-10-04T05:51:15.830" CommentCount="3" />
  <row Id="4794" PostTypeId="2" ParentId="4742" CreationDate="2010-10-04T05:53:49.200" Score="1" ViewCount="" Body="&lt;p&gt;If I understand you correctly, you are essentially using an audio output to create a digital signal. You have a pulse of some constant voltage for about 250ms and then 0 voltage for the rest of the time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the placement of C1 and R1, the rate at which the voltage can go high is a function of the size of R1 and the rate at which the voltage can go low is a function of the size of C1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both of these are completely dependent on how you are wanting your circuit to act. If you are wanting the mouth motor to be activated for longer then the pulse then you will want a larger capacitor (uF or larger range). If you are wanting the mouth motor to only be activated for the exact length of your pulse, you will want a smaller capacitor (nF) or maybe not even one at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for type of capacitor. I believe you will always have a positive voltage across your capacitor so the type of capacitor used is not a big factor. If you need a larger capacitor you will find that an electrolytic will be cheaper while other sizes you might want to look at ceramic for some of their performance benefits.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-04T05:53:49.200" CommentCount="1" />
  <row Id="4795" PostTypeId="1" CreationDate="2010-10-04T06:06:06.333" Score="2" ViewCount="182" Body="&lt;p&gt;I've started from Here &lt;a href=&quot;http://stackoverflow.com/questions/3794665/interested-in-device-programming-where-to-start&quot;&gt;http://stackoverflow.com/questions/3794665/interested-in-device-programming-where-to-start&lt;/a&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now though I'vent got my Arduino Board yet. I've got enough confidence that I can code a microcontroller in C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I think I should know little things like Capacitors, Registers, Transistors etc.. Once (5 years ago) I was very good in physics but now I've forgotten everything.&#xA;Now Where to start ?&#xA;Which book would be good to start for a Software programmer. Who want to read less and Do more.&lt;/p&gt;&#xA;" OwnerUserId="1424" LastActivityDate="2010-10-04T10:53:27.570" CommunityOwnedDate="2010-10-04T06:51:58.867" Title="books for basic electronics." Tags="&lt;electronics&gt;&lt;books&gt;&lt;basic&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="6" />
  <row Id="4796" PostTypeId="2" ParentId="4730" CreationDate="2010-10-04T06:34:55.330" Score="0" ViewCount="" Body="&lt;p&gt;I have come up with my own solution to this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As I'm not worried about distortion I simply use a passive adder circuit which adds 3V to a ±2V signal. This can be switched using conventional, ground referenced circuits. Then, when I want to output it, I pass it through a capacitor + emitter follower amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kA3Xb.png&quot; alt=&quot;The biasing adds some DC to the AC, muxes it appropriately (not shown), then amplifies it and converts it back to AC&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-04T06:44:05.257" LastActivityDate="2010-10-04T06:44:05.257" CommentCount="3" />
  <row Id="4797" PostTypeId="2" ParentId="4795" CreationDate="2010-10-04T07:33:45.790" Score="2" ViewCount="" Body="&lt;p&gt;First,  &quot;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Make%3a-Electronics.html&quot; rel=&quot;nofollow&quot;&gt;Make: Electronics&lt;/a&gt;&quot; then &quot;The Art of Electronics&quot; (2nd ed.) by Horowitz and Hill.&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-04T07:33:45.790" CommunityOwnedDate="2010-10-04T07:33:45.790" />
  <row Id="4798" PostTypeId="2" ParentId="4792" CreationDate="2010-10-04T08:04:20.950" Score="0" ViewCount="" Body="&lt;p&gt;I too don't have much experience, but here are some thoughts of this matter:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some reasons of different vendors of chips: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They often use different architectures and such things can be important when programming. Some instructions take longer to execute and some take shorter amounts of time. RISC designs solve that to some level, but there are still few instructions which take more than one cycle. Of course, this is more important if you are programming directly in assembly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not all C compilers are that good. I've heard people complaining about behavior of C compilers for various embedded platforms and the large number of quirks which are often present.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also social factor. In my country PIC became generic name for microcontroller. PICs became everyone's default choice when deciding which microcontroller to use. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another point are physical differences among chips themselves. Some have different operating temperatures, different power consumption, fail in different ways and so on. All this things are very important when making a serious product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now for information: The closest thing to datasheet in programming world would be language specification. There simply needs to be one authoritative source for all information about that chip and that is its datasheet. All those things in those long long PDF files are very important to some users. For example while it is enough to know few basic libraries to make C++ programs, there are users who need to read the whole ISO/IEC 14882:2003 standard. So how would you make a compiler for a chip if you don't know what a chip actually does? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also important electrical characteristics of the chip which affect entire circuit in which the chip is used. There are lowest and highest voltages for each pin and they can on some chips change with change of frequency and temperature. There is time needed for one cycle to execute (while it may not be important from programming point of view, it is important of you need to synchronize the rest of the circuit with the chip). All these things are important when choosing microcontroller for a project. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-10-04T08:04:20.950" />
  <row Id="4799" PostTypeId="1" AcceptedAnswerId="4815" CreationDate="2010-10-04T08:24:11.173" Score="2" ViewCount="103" Body="&lt;p&gt;I'm looking for tutorials/explained examples on circuit design in general, but specifically on using various sensors.&lt;/p&gt;&#xA;" OwnerUserId="1443" LastActivityDate="2010-10-06T17:16:25.657" Title="Where can I find good tutorials on sensor circuit design?" Tags="&lt;sensor&gt;&lt;circuit&gt;&lt;tutorial&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="4800" PostTypeId="2" ParentId="4792" CreationDate="2010-10-04T08:30:37.813" Score="3" ViewCount="" Body="&lt;p&gt;One of the main reasons for the very long (sometimes hundreds of pages) &lt;em&gt;datasheets&lt;/em&gt; is that each microcontroller family tends to have unique ways of controlling such things as serial ports (UART, I2C, SPI, USB), ADCs and DACs, timers/PWM, clock generators, parallel ports, interrupts, and flash memory programming.  Each of these peripherals is configured and controlled by several internal registers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even though the registers can be programmed in C, each bit in each register still has to be documented.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The number of pins and the amount of memory is just a small part of the specification.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-04T08:30:37.813" />
  <row Id="4801" PostTypeId="2" ParentId="4792" CreationDate="2010-10-04T08:33:26.580" Score="7" ViewCount="" Body="&lt;p&gt;The list of parameters that you have quoted is just the beginning.  The important things (for me) are the number and type of peripherals built in to the processor silicon, which pins are they available from and how they are driven by the software.  The different processor families, even different ranges within the same family from a single manufacturer, have very different peripheral sets and operating modes.  Providing the level of support that is available through a major operating system, such as you would get on a desktop system is just not possible within the processor memory resources.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of the peripheral devices have their own set of control registers, all of which will be different to those found on other processor families.  This has to be documented to allow the device to be used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;A simple example&lt;/em&gt;.&lt;br&gt;&#xA;On the AVR32 most modules have separate registers to set and clear the interrupt enable bits for a peripheral.  To enable an interrupt you write a 1 to the bit in the enable register.  To disable it you write a 1 to the bit in the disable register.  To find out if it is enabled you read the bit state from a third register.&#xA;On the MSP430 to enable the interrupt you write a 1 to the single interrupt enable register, to disable it you write a 0 to this bit, to find out whether it is enabled you read the state of the bit in this one register.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without all of the detail in the datasheet you would never manage to work this out.  This is then repeated for each of the registers available for every peripheral within the device and you can see why the datasheet gets so big so quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used a number of ARM, AVR32 and MSP variants and, while each comes with a number of header files and device libraries to allow the use of the on chip peripherals, these libraries are, to be quite honest, of variable quality (the LINT errors from some of the code have to be seen to be believed) and often do not cover the interrupt mode of operation that is needed for my application.  The information in the datasheet allows me to write and debug the software to get the optimum performance &lt;strong&gt;for my application&lt;/strong&gt;.  My requirements, normally extremely low power dissipation, will mean that my code has to be written using the device in a different way to that where the priority is data throughput.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your final point about AVR not being used much in professional systems - there are many processors in the market and each has its strengths and weaknesses.  I tend to use MSP430 because of its very low power requirements.  I have used AVR32 in preference to the ARM-M3 for the same reason.  Price is very important.  On chip peripheral mix and their fit to my application will make one processor a killer and another very similar device a dud.  For me the AVR and AVR mega did not have the right mix of processing power, peripherals and power consumption and were discounted very early in the processor selection process.&lt;/p&gt;&#xA;" OwnerUserId="400" LastEditorUserId="400" LastEditorDisplayName="" LastEditDate="2010-10-04T08:42:26.850" LastActivityDate="2010-10-04T08:42:26.850" />
  <row Id="4802" PostTypeId="2" ParentId="4795" CreationDate="2010-10-04T08:40:48.033" Score="0" ViewCount="" Body="&lt;p&gt;One of my favorite electronics books is &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0071452818&quot; rel=&quot;nofollow&quot;&gt;&quot;Practical Electronics for Inventors&quot;&lt;/a&gt;.  Ignore the title, it has nothing to do with inventions and patents.  It starts out with a basic intro to electronics, various electronics components, semiconductors, optoelectronics, ICs and op-amps, filters, oscillators and timers, voltage regulators and power supplies, audio electronics, digital electronics, motors, and ends up with constructing circuits, multimeters, and oscilloscopes.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-04T08:40:48.033" CommunityOwnedDate="2010-10-04T08:40:48.033" />
  <row Id="4803" PostTypeId="1" AcceptedAnswerId="4804" CreationDate="2010-10-04T09:29:02.300" Score="2" ViewCount="205" Body="&lt;p&gt;I salvaged a 1kΩ potentiometer from a broken circuit. Is there any way to determine how much power can it take without destroying it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt; Picture of the potentiometer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/bjUUt.jpg&quot; alt=&quot;potentiometer&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The distance between left-most and right-most connector is about 2cm.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-10-04T15:44:49.570" LastActivityDate="2010-10-04T19:25:19.190" Title="Is there any way to determine power rating of a potentiometer?" Tags="&lt;power&gt;&lt;components&gt;&lt;potentiometer&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="4804" PostTypeId="2" ParentId="4803" CreationDate="2010-10-04T09:49:03.797" Score="4" ViewCount="" Body="&lt;p&gt;Hmm... how big is it? Most potentiometers I have found are rated for 1/2W or 1W. A general rule of thumb though is that you shouldn't be putting much power through it anyway - it should only be controlling a small signal.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-04T09:49:03.797" CommentCount="5" />
  <row Id="4805" PostTypeId="2" ParentId="3690" CreationDate="2010-10-04T10:47:31.450" Score="1" ViewCount="" Body="&lt;p&gt;Another option might be the free Buzz utility offered at &lt;a href=&quot;http://www.jtaglive.com&quot; rel=&quot;nofollow&quot;&gt;Jtag Live&lt;/a&gt;&#xA;That also works with Xilinx and Alter cables and possibly FTDI chip based&#xA;cables. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It allows you to 'watch'a signal using SAMPLE mode and buzz out mutiple connection between JTAG devices - pretty neat really.&lt;/p&gt;&#xA;" LastActivityDate="2010-10-04T10:47:31.450" />
  <row Id="4806" PostTypeId="2" ParentId="4795" CreationDate="2010-10-04T10:53:27.570" Score="4" ViewCount="" Body="&lt;p&gt;tronixstuff recommended &quot;The Art of Electronics&quot;. I think the associated student manual would also be helpful. It has 23 labs, 20 worked examples, extra notes and associated reading assignments out of the main text. Here's an informal YouTube review of the student manual: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=yCk56XPKw9g&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=yCk56XPKw9g&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;I know you're not looking to read a whole lot, but I figure it can't hurt to include some links that you may find useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lectures:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;LearnersTV: &lt;a href=&quot;http://www.learnerstv.com&quot; rel=&quot;nofollow&quot;&gt;http://www.learnerstv.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;EE Times Courses: &lt;a href=&quot;http://www.eetimes.com/electrical-engineers/education-training/courses&quot; rel=&quot;nofollow&quot;&gt;http://www.eetimes.com/electrical-engineers/education-training/courses&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Books:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Simple Nature (physics with calculus): &lt;a href=&quot;http://www.lightandmatter.com/area1sn.html&quot; rel=&quot;nofollow&quot;&gt;http://www.lightandmatter.com/area1sn.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;HyperPhysics: &lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html&quot; rel=&quot;nofollow&quot;&gt;http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Free Books by Topic: &lt;a href=&quot;http://www.freebookcentre.net&quot; rel=&quot;nofollow&quot;&gt;http://www.freebookcentre.net&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;Lessons in Electric Circuits: &lt;a href=&quot;http://www.openbookproject.net/electricCircuits&quot; rel=&quot;nofollow&quot;&gt;http://www.openbookproject.net/electricCircuits&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;DSP for Scientists and Engineers: &lt;a href=&quot;http://www.dspguide.com&quot; rel=&quot;nofollow&quot;&gt;http://www.dspguide.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Software Design: &lt;a href=&quot;http://www.htdp.org/2003-09-26/Book&quot; rel=&quot;nofollow&quot;&gt;http://www.htdp.org/2003-09-26/Book&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Articles &amp;amp; Tutorials:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Review of Electronics: &lt;a href=&quot;http://mysite.du.edu/~etuttle/electron/elecindx.htm&quot; rel=&quot;nofollow&quot;&gt;http://mysite.du.edu/~etuttle/electron/elecindx.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Electronics Links &amp;amp; Tutorials: &lt;a href=&quot;http://www.101science.com/eleclinks.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.101science.com/eleclinks.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Capacitors: &lt;a href=&quot;http://my.execpc.com/~endlr/index.html&quot; rel=&quot;nofollow&quot;&gt;http://my.execpc.com/~endlr/index.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Sensors: &lt;a href=&quot;http://www.sensorsportal.com/HTML/Sensor.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.sensorsportal.com/HTML/Sensor.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;FPGAs: &lt;a href=&quot;http://www.fpga4fun.com/FPGAinfo1.html&quot; rel=&quot;nofollow&quot;&gt;http://www.fpga4fun.com/FPGAinfo1.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;PSpice: &lt;a href=&quot;http://denethor.wlu.ca/PSpice/pspice_tutorial.html&quot; rel=&quot;nofollow&quot;&gt;http://denethor.wlu.ca/PSpice/pspice_tutorial.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;VHDL: &lt;a href=&quot;http://esd.cs.ucr.edu/labs/tutorial&quot; rel=&quot;nofollow&quot;&gt;http://esd.cs.ucr.edu/labs/tutorial&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Applets &amp;amp; Simulations:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Physics &amp;amp; Mathematics: &lt;a href=&quot;http://www.falstad.com/mathphysics.html&quot; rel=&quot;nofollow&quot;&gt;http://www.falstad.com/mathphysics.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Electronics: &lt;a href=&quot;http://www.falstad.com/circuit/e-index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.falstad.com/circuit/e-index.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Karnaugh Maps: &lt;a href=&quot;http://courseware.ee.calpoly.edu/~rsandige/KarnaughExplorer.html&quot; rel=&quot;nofollow&quot;&gt;http://courseware.ee.calpoly.edu/~rsandige/KarnaughExplorer.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="721" LastActivityDate="2010-10-04T10:53:27.570" CommunityOwnedDate="2010-10-04T10:53:27.570" />
  <row Id="4807" PostTypeId="1" AcceptedAnswerId="4811" CreationDate="2010-10-04T11:17:33.600" Score="10" ViewCount="360" Body="&lt;p&gt;Is there any kit or board on which I can test out customized android os?&lt;/p&gt;&#xA;" OwnerUserId="1446" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-10-04T16:35:22.440" LastActivityDate="2010-11-17T23:15:01.133" Title="Is there any kit for android development?" Tags="&lt;kit&gt;&lt;android&gt;" AnswerCount="7" FavoriteCount="4" />
  <row Id="4808" PostTypeId="1" AcceptedAnswerId="4809" CreationDate="2010-10-04T11:38:19.307" Score="5" ViewCount="336" Body="&lt;p&gt;I've been researching pullup and pulldown resistors after seeing them used in many digital circuits and while I understand what their purpose is, I haven't found any resource on how to determine the resistance values to use in such circuits and how these values affect the circuit's behaviour.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the examples I have is...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/DIC0I.jpg&quot; alt=&quot;ADC Keypad Circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;...which is an A/D converter circuit for a keypad input.  I have implemented this and it actually works very well but I can't quite pinpoint why a 1Mohm resistor was picked as the pullup and what exactly happens to it when one of the buttons are pressed - does it affect the voltage of the ADC input in such a small amount that it doesn't register or is it overridden somehow or...?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this is probably a very basic question but I can't seem to apply the thoery I have learned to this one.&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-25T06:31:54.270" LastActivityDate="2011-01-25T06:31:54.270" Title="Using Pullup and Pulldown Resistors" Tags="&lt;resistor&gt;&lt;adc&gt;&lt;parallel&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="4809" PostTypeId="2" ParentId="4808" CreationDate="2010-10-04T11:50:08.783" Score="14" ViewCount="" Body="&lt;p&gt;That 1M is there just to make sure that the ADC input pin isn't totally free-floating, and also gives a known voltage (+5) when no switches are pressed. This keeps the ADC from picking up ambient noise from the rest of the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason for the value of 1M is a compromise between a value low enough to keep the ADC input from acting like an antenna, and a value high enough to not overly skew the result you get when a switch is pressed. When a switch is pressed, that 1M is in parallel with the 'top half' of a voltage divider formed by the 1K resistors either side of the switch.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-04T11:50:08.783" CommentCount="8" />
  <row Id="4810" PostTypeId="2" ParentId="4807" CreationDate="2010-10-04T12:16:30.227" Score="7" ViewCount="" Body="&lt;p&gt;You can use a Beagle Board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://beagleboard.org/project/android/&quot; rel=&quot;nofollow&quot;&gt;http://beagleboard.org/project/android/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://antipastohw.blogspot.com/2010/10/introducing-diy-android-gadget-starter.html&quot; rel=&quot;nofollow&quot;&gt;http://antipastohw.blogspot.com/2010/10/introducing-diy-android-gadget-starter.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://3.bp.blogspot.com/_pGsJFsc5Buc/TLv_gwQaGTI/AAAAAAAAA0g/QoeDJsYSGDg/s400/Android+DIY+Starter+Fading.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-19T16:37:22.590" LastActivityDate="2010-10-19T16:37:22.590" />
  <row Id="4811" PostTypeId="2" ParentId="4807" CreationDate="2010-10-04T12:17:10.107" Score="10" ViewCount="" Body="&lt;p&gt;There are various, but I'll suggest the &lt;a href=&quot;http://www.friendlyarm.net/products/mini2440&quot; rel=&quot;nofollow&quot;&gt;FriendlyArm&lt;/a&gt; Mini2440 with 3.5&quot; Display and Touch Panel. See images bellow of the &lt;a href=&quot;http://www.sergioprado.org/2010/09/12/mini2440-instalando-o-android/&quot; rel=&quot;nofollow&quot;&gt;Sergio Prado's blog&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/EjA9y.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-10-04T18:28:41.300" LastActivityDate="2010-10-04T18:28:41.300" />
  <row Id="4812" PostTypeId="2" ParentId="4764" CreationDate="2010-10-04T13:12:47.790" Score="0" ViewCount="" Body="&lt;p&gt;I've used a super-cap to power an external real-time clock before. The super-cap works quite well and it will power a DS1306 for almost two weeks.&lt;p&gt;I've never tried implementing a super-cap backed up real-time clock implemented using a PIC24. The problem is how will you isolate the super-cap from the rest of your circuit when you lose primary power? If you just connect the super-cap between your primary power and ground when you lose power the super-cap will be trying to supply power to the whole circuit and it will drain it very quickly.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-04T13:12:47.790" CommentCount="4" />
  <row Id="4813" PostTypeId="2" ParentId="4807" CreationDate="2010-10-04T13:13:45.073" Score="3" ViewCount="" Body="&lt;p&gt;I am not sure of the cost of the other options, but it may make most sense to just buy an unlocked phone from google as a developer. You can then do what ever you want to the phone including flashing a new OS.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-04T13:13:45.073" CommentCount="1" />
  <row Id="4814" PostTypeId="1" AcceptedAnswerId="4820" CreationDate="2010-10-04T13:26:00.233" Score="3" ViewCount="374" Body="&lt;p&gt;I'm using an Atmega328 chip with the arduino bootloader in a very small circuit. The sketch simply plays a tune using the tone() function to play a melody through a piezo speaker on a single pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Clearly using this chip is overkill, but the programming environment is so simple for arduino, and easy for me to use. &#xA;Can I use a Attiny with the arduino bootloader or something similar? What would be the right way to miniaturise this project, so I don't feel like I'm wasting components. If it's a case of using a different chip/environment entirely, where do I start?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(for clarity, I am not using an arduino in the circuit, just the Atmega328 chip)&lt;/p&gt;&#xA;" OwnerUserId="623" LastActivityDate="2010-10-04T14:14:53.560" Title="My Atmega328 seems to be overkill, what should I use instead?" Tags="&lt;arduino&gt;&lt;audio&gt;&lt;atmega&gt;&lt;sound&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="4815" PostTypeId="2" ParentId="4799" CreationDate="2010-10-04T13:35:54.770" Score="1" ViewCount="" Body="&lt;p&gt;You can find a few &lt;a href=&quot;http://extremeelectronics.co.in/category/avr-tutorials/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. Mostly on ultrasonic rangefinders, rfid sensors, accelerometers, temp sensors etc. There are a few good beginner tutorials that teach about basics of working with microcontrollers, if you need.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastActivityDate="2010-10-04T13:35:54.770" CommentCount="1" />
  <row Id="4816" PostTypeId="1" AcceptedAnswerId="4818" CreationDate="2010-10-04T13:42:18.310" Score="1" ViewCount="200" Body="&lt;p&gt;How do I calculate the peak output voltage of a capacitor differentiator?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-10-04T14:21:19.430" Title="How do I calculate the peak output voltage of a capacitor differentiator?" Tags="&lt;capacitor&gt;" AnswerCount="1" />
  <row Id="4817" PostTypeId="2" ParentId="4814" CreationDate="2010-10-04T13:49:43.127" Score="2" ViewCount="" Body="&lt;p&gt;The Arduino libraries &lt;a href=&quot;http://arduino.cc/en/Main/Programmer&quot; rel=&quot;nofollow&quot;&gt;don't actually depend on the bootloader&lt;/a&gt; - it's merely a convenient delivery method, if you have the serial connection. In theory you could use most any AVR that has some RAM built in, though I never tried (I tend to write directly with avr-libc). Given the task, however, you'll probably want to pay attention to the fuse settings for clock options as Arduinos tend to run at 8 or 16MHz while the chips often default to roughly 1MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1236434254&quot; rel=&quot;nofollow&quot;&gt;LumiNet&lt;/a&gt; uses the Arduino environment ported to the ATtiny84 chip, as an example.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-10-04T13:49:43.127" />
  <row Id="4818" PostTypeId="2" ParentId="4816" CreationDate="2010-10-04T14:06:51.353" Score="3" ViewCount="" Body="&lt;p&gt;You mean like this? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/G0mYv.gif&quot; alt=&quot;alt text&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The peak output voltage would just be the peak input voltage.  If it changes fast enough, the output will track it almost exactly, and then decay to smaller values:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/e6owD.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh wait.  That doesn't take into account a repeating waveform, like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/l4llM.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After the wave has decayed, when you switch the input again, the output will jump to a lower voltage than the input:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/99K1Y.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I think the worst case would be square waves of low frequency, so that they decay completely to zero before switching, and the peak-to-peak output voltage would then be 2× the input peak-to-peak voltage.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-04T14:21:19.430" LastActivityDate="2010-10-04T14:21:19.430" CommentCount="1" />
  <row Id="4819" PostTypeId="2" ParentId="4814" CreationDate="2010-10-04T14:12:01.703" Score="1" ViewCount="" Body="&lt;p&gt;There are plenty of options for another chip entirely. One to consider are TI's MSP430 value line devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI sell a complete dev kit (programmer + 2 DIP MCUs) called the Launchpad for $4.30.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like AVR, there's a gcc port. So, it's not a huge leap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_%28MSP-EXP430G2%29?DCMP=launchpad&amp;amp;HQS=Other+OT+launchpadwiki&quot; rel=&quot;nofollow&quot;&gt;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_%28MSP-EXP430G2%29?DCMP=launchpad&amp;amp;HQS=Other+OT+launchpadwiki&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2010/06/22/ti-makes-a-big-bid-for-the-hobby-market/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2010/06/22/ti-makes-a-big-bid-for-the-hobby-market/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.43oh.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.43oh.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-04T14:12:01.703" CommentCount="4" />
  <row Id="4820" PostTypeId="2" ParentId="4814" CreationDate="2010-10-04T14:14:53.560" Score="5" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Using Atmel chips in the Arduino IDE&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the ATtiny45 and ATtiny85 you can use &lt;a href=&quot;http://hlt.media.mit.edu/wiki/pmwiki.php?n=Main.ArduinoATtiny4585&quot; rel=&quot;nofollow&quot;&gt;this library&lt;/a&gt; that you put in the same directory as your sketches (make a &quot;hardware&quot; directory, then unzip this in there).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found lots of things just work, but not everything.  These chips are pretty tiny.  You only get 4 input/outputs (or 5 if you have a high voltage programming device), and you have to be careful which ones can produce the type of output needed by tone (probably only 2 of the pins).  These guys are in the $1.25 to $2.25 range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also use ATtiny2313's, but I've not tried using the Arduino IDE with them.  I switched to using AVR style GCC, as its not much harder and if something breaks I know its my fault.  The 2313 has a ton more pins (not as many as the ATmega), hardware serial support, etc.  It is in the $1.50 to $2.50 range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ATmega328p is more in the $3.00 to $4.50 range (and currently is often out of stock).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can think of the Arduino IDE as consisting of 3 main parts:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;a nice, reduced programming language for AVR style chips (mostly by providing you with simple to use functions like tone)&lt;/li&gt;&#xA;&lt;li&gt;a nice, easy to use upload mechanism for ATmega and larger ATtiny chips (the bootloader)&lt;/li&gt;&#xA;&lt;li&gt;a nice GUI interface that makes it easy to use the right part when you need it&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;When you work with the ATtinyX5 chips, the bootloader doesn't work, but you can use an Arduino to program the ATtiny's very easily.  The library I linked to makes the first and third parts of the IDE available to you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want something cheaper, but mostly the same as the ATmega328p, I would go with the ATtiny2313.  If you want something smaller, then the 8-pin ATtiny85 is nice, but it is not too much cheaper and lacks a lot of the nice features of the ATtiny2313 and the ATmega328p.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't tried the other Atmel AVR product lines, but they definitely have others.  Luminet (mentioned in another answer) uses the ATtinyX4 line and has a modified IDE to work with them.  They appear to be in the $1.80 to $3.00 range.&lt;/p&gt;&#xA;" OwnerUserId="1271" LastActivityDate="2010-10-04T14:14:53.560" CommentCount="1" />
  <row Id="4821" PostTypeId="2" ParentId="4792" CreationDate="2010-10-04T14:18:57.683" Score="3" ViewCount="" Body="&lt;p&gt;I'm attempting to answer a few points in your question more directly, to give examples of where this data does not suffice. The basic specifications you list aren't complete, but only an overview. Each can be divided into more related questions, which &lt;em&gt;should&lt;/em&gt; be answered in the datasheets:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;No. of digital Pins:&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;How many are 5V tolerant? Higher voltages? Open collector or emitter? Available for higher level peripherals (timers, bit shifters, etc)? How many can be read or updated simultaneously?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;No. of Analog Pins:&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Input or output? How many bits of precision? Technology (delta-sigma, PWM, R2R..)? How often can they be measured? It's not unusual at all that they can't be measured at the same time.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;SRAM:&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Does the stack go in the RAM, or separate? How wide is it? Can parts be powered down for lower current draw? Can code be run from RAM?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;EEPROM:&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Again, width? How long does it take to read or write? What are the power requirements (often a higher voltage is needed to complete a write here)?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Flash:&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Self programmable (so one might have a bootloader)? Can data be read out of Flash? Can all those bits be used for data? How many operations (and of what scale) can I fit into this size?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Operatng Voltage:&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;For which frequency ranges? Do the I/Os tolerate higher voltages than the power supply? Do we need separate supply rails for analog and digital, core and I/O?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Now a days they can all be programmed in C. and while coding only the first 5 informations are needed all others can easily be found in headers.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Actually, a few can be programmed in something only resembling C, and much information will not be present in the headers, such as what port maps to which pin. Often this will vary depending on the package. This is also only scraping the surface, as you'll find some controllers implement hardware for very different purposes, such as threads, IPC, event systems, DMA and so on that may be critical for one use and irrelevant for another. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So within a family an overview of the type you show can be enough, but usually there will be many more parameters to compare (number of timers, for instance). It depends very much on the task. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;FWIW, the AVRs are popular in industry too, but sometimes avoided for specific reasons - such as single supplier, availability and resilience.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-10-04T14:18:57.683" />
  <row Id="4822" PostTypeId="2" ParentId="4808" CreationDate="2010-10-04T14:32:39.590" Score="2" ViewCount="" Body="&lt;p&gt;Suppose we label the first switch &lt;code&gt;num=1&lt;/code&gt;, the last switch &lt;code&gt;num=16&lt;/code&gt;, &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;R_hi = (1M * num * 10k) / (1M + num * 10k)&#xA;R_lo = (17 - num) * 10k&#xA;Vout = 5V * R_lo / (R_hi + R_lo)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1450" LastActivityDate="2010-10-04T14:32:39.590" />
  <row Id="4823" PostTypeId="2" ParentId="4742" CreationDate="2010-10-04T15:04:17.137" Score="2" ViewCount="" Body="&lt;p&gt;Okay, I have some feedback, and mine is mostly directed at your circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, I see two discrete stages.  &lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Stage 1: Averaging&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Your first stage is the capacitor/diode circuit. This is your averaging circuit. This is missing a very important component, a resistor. right now, if you ignore the loading from the rest of the circuit, this will effectively be a peak detector. as the input is connected with a current independent .7V drop to the capacitor. With addition of a series resistor with the diode you will find that you can make this system have a time constant to get an averaged value out of your system. You will need to tweak this value to give you a resistance in the range of what you are wanting.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Stage 2: Gain&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Your second stage is the amplifier circuit, or driving circuit. This is made up of a basic biasing resistor and the BJT. This gives the bias you need to then superimpose a small signal(welcome back to school, it is small signal model all over again). The issue I see is that you have your capacitor directly tied into the BJT gate. This BJT looks like a diode when you look into the base. A diode to ground. This means that it will really pull current when you try to pass .7 V but that your capacitor has almost no load below this voltage. This means that your input in the current circuit drives it directly in your current circuit. This is bad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you place a resistance between the averaging circuit and the driving circuit you can control how much the voltage change on the capacitor affects the driving current. This will give a more controlled load on the RC averaging circuit, and allow it to just impose a small increase in current through the base so that your averaging circuit helps drive without over-driving the input and allowing the averaged signal to slowly affect your system. Make sure the isolation is large enough compared to your averaging resistance to not affect load your averaging circuit to the point it is just showing the peak.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Schematic&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2KIL3.png&quot; alt=&quot;I will draw this new schematic up if it will help.&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Choosing Resitance&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Editing this in because it seems I did not give good feedback on how to pick values.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Averaging Resistance&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;First, Vin from the audio minus .7 volts(diode drop) divided by R needs to be less than the maximum current your audio device can supply. This is worst case where the capacitor is charged to 0V.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Averaging Capacitance &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Now, your &lt;a href=&quot;http://en.wikipedia.org/wiki/RC_circuit&quot; rel=&quot;nofollow&quot;&gt;averaging resistance times your capacitance needs to equal 1 over the frequency&lt;/a&gt; you want to have as a maximum. This means, if you want it to &quot;update&quot; 20 times a second you need RC to equal 1/20.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Isolation Resistance &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;This is a more complex choice. If you would like 5 V to be your full drive from audio, and this relates to needing 10mA from the BJT then you need to pick an isolation resistance that will give you 100uA(hfe=100) when you have 5V-.7V/Isolation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This gets messy if you end up loading your circuit too much and then will need a preamp stage that reduces the load that your averaging circuit sees.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Extra Information&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Second, if you find you are discharging the capacitor too quickly, use a &lt;a href=&quot;http://en.wikipedia.org/wiki/Darlington_transistor&quot; rel=&quot;nofollow&quot;&gt;darlington pair as your transistor instead&lt;/a&gt;. Easy to take care of by just hooking up two of those transistors together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Third, if you are having problems where your averaged current is staying a bit too low and you come back and post it here I can draw a schematic of how to level shift your input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me know if there is anything I was not clear on.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-10-04T16:08:03.057" LastActivityDate="2010-10-04T16:08:03.057" CommentCount="4" />
  <row Id="4824" PostTypeId="2" ParentId="4784" CreationDate="2010-10-04T15:06:42.283" Score="1" ViewCount="" Body="&lt;p&gt;See this question:&lt;br&gt;&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/2272/what-is-a-decoupling-capacitor-and-how-do-i-know-if-i-need-one&quot;&gt;What is a decoupling capacitor and how do I know if I need one?&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-04T15:06:42.283" CommunityOwnedDate="2010-10-04T15:06:42.283" />
  <row Id="4825" PostTypeId="2" ParentId="4742" CreationDate="2010-10-04T15:16:15.187" Score="0" ViewCount="" Body="&lt;p&gt;A completely different approach could be to feed your audio signal into the PWM input of a servo. You could then use one of the audio channels to do some fairly sophisticated motion.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-04T16:13:34.380" LastActivityDate="2010-10-04T16:13:34.380" />
  <row Id="4826" PostTypeId="2" ParentId="1199" CreationDate="2010-10-04T15:31:39.777" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Freescale HCS08&lt;/strong&gt; micros are direct competitors to PIC10-18s and AVRs, generally of lower-cost but still with a fairly rich peripheral set.  Their library of app notes and reference material is quite good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Their CodeWarrior IDE (free compiler for up to 32k code) includes some useful &quot;Device Initialization&quot; libraries for a GUI-driven approach to flipping bits, and a more advanced &quot;Processor Expert&quot; which can generate higher level drivers for peripherals.  You are not obligated to use either, and can simply do everything in straight C code if desired.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-15T12:20:30.813" LastActivityDate="2010-12-15T12:20:30.813" CommunityOwnedDate="2010-10-04T15:31:39.777" />
  <row Id="4827" PostTypeId="2" ParentId="4784" CreationDate="2010-10-04T15:40:40.420" Score="2" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Why can't the whole circuit be drawn&#xA;  capacitor free?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Circuits are occasionally drawn without capacitors, as it is &lt;em&gt;implicit&lt;/em&gt; that they will be included on every logic power pin.  Obviously if using an EDA tool, they must be on the schematic somewhere (usually disembodied in some corner), but it is implied that there will be at least one on each pin (multiple caps can cover a wider range of frequencies), and as close as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For prototypes--&lt;em&gt;especially&lt;/em&gt; for prototypes--bypass capacitors are even more important.  There will often be much more inductance in the ball of wires than normal.  Even if your switch frequency is low, the spectral content of edges can be extremely high.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-04T15:40:40.420" CommunityOwnedDate="2010-10-04T15:40:40.420" />
  <row Id="4828" PostTypeId="1" AcceptedAnswerId="4830" CreationDate="2010-10-04T15:56:48.757" Score="2" ViewCount="177" Body="&lt;p&gt;I decided to start working with hobby electronics, but I'm having a problem finding a local source of solid wires. As far as I know solid wires are often recommended for use with protoboards because inner wires of stranded wire can get jammed inside protoboards wire holding mechanism.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for tips on how to modify stranded wires to work with protoboards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The obvious solution which comes to my mind is to use solder on the exposed part of the wire and make it solid.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any other ideas?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-10-04T16:06:11.297" Title="How to modify stranded wire for use in protoboards?" Tags="&lt;wire&gt;&lt;breadboard&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="1" />
  <row Id="4829" PostTypeId="2" ParentId="4828" CreationDate="2010-10-04T16:01:19.047" Score="4" ViewCount="" Body="&lt;p&gt;You can also solder pins (from breakaway pin strips) onto the ends.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-04T16:01:19.047" CommentCount="3" />
  <row Id="4830" PostTypeId="2" ParentId="4828" CreationDate="2010-10-04T16:06:11.297" Score="3" ViewCount="" Body="&lt;p&gt;I have always used a dab of solder on stranded wire when needing to use it in a breadboard. It has always worked perfectly for me. Just be careful to make sure that you do not have any excess solder at the end as the wire tends to get stuck in the breadboard if there is anything sticking out that can get caught on it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know you asked for local, but here are a few links to items similar to what I have used before:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mouser.com/ProductDetail/Twin-Industries/TW-E012-000/?qs=sGAEpiMZZMvJBlHRSOGUxOhvehuk8u4qJwTh7IUsHNU%3d&quot; rel=&quot;nofollow&quot;&gt;http://www.mouser.com/ProductDetail/Twin-Industries/TW-E012-000/?qs=sGAEpiMZZMvJBlHRSOGUxOhvehuk8u4qJwTh7IUsHNU%3d&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mouser.com/ProductDetail/SchmartBoard/920-0067-01/?qs=sGAEpiMZZMvJBlHRSOGUxIxWMAp5GnPY3nX1cMlAHE0%3d&quot; rel=&quot;nofollow&quot;&gt;http://www.mouser.com/ProductDetail/SchmartBoard/920-0067-01/?qs=sGAEpiMZZMvJBlHRSOGUxIxWMAp5GnPY3nX1cMlAHE0%3d&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also use these: &lt;a href=&quot;http://www.mouser.com/ProductDetail/3M/2340-6111TG/?qs=R%252bzptqw7cJImGeX9bGiQLA%3d%3d&quot; rel=&quot;nofollow&quot;&gt;http://www.mouser.com/ProductDetail/3M/2340-6111TG/?qs=R%252bzptqw7cJImGeX9bGiQLA%3d%3d&lt;/a&gt;&#xA;&lt;br /&gt; They break away into any number you want and are the same spacing as common bread boards.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-04T16:06:11.297" CommentCount="1" />
  <row Id="4831" PostTypeId="2" ParentId="4807" CreationDate="2010-10-04T16:30:11.527" Score="2" ViewCount="" Body="&lt;p&gt;Unless you are going to do &lt;em&gt;hardware&lt;/em&gt; development, an existing device (phone) will likely be much more convenient and common in the community.  A &quot;customized Android OS&quot; sounds like pure software.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-04T16:30:11.527" />
  <row Id="4834" PostTypeId="2" ParentId="4788" CreationDate="2010-10-04T17:10:13.250" Score="5" ViewCount="" Body="&lt;p&gt;Both people have already given great answers, I am just going to try to give a different explanation of the same thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;H2&gt; Background&lt;/h2&gt;&#xA;So, in a &lt;a href=&quot;http://en.wikipedia.org/wiki/Pierce_oscillator&quot; rel=&quot;nofollow&quot;&gt;pierce oscillator&lt;/a&gt; you have a digital system connected to a crystal oscillator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you have probably seen how logic gates switch state, with a specified rise time. If you put any time into learning about &lt;a href=&quot;http://en.wikipedia.org/wiki/Electromagnetic_compatibility&quot; rel=&quot;nofollow&quot;&gt;Electromagnetic Compatibility&lt;/a&gt; or just &lt;a href=&quot;http://www.google.com/search?q=high+speed+digital+desing&amp;amp;ie=utf-8&amp;amp;oe=utf-8&amp;amp;aq=t&amp;amp;rls=org.mozilla%3aen-US%3aofficial&amp;amp;client=firefox-a#hl=en&amp;amp;client=firefox-a&amp;amp;hs=51o&amp;amp;rls=org.mozilla%3aen-US%3aofficial&amp;amp;&amp;amp;sa=X&amp;amp;ei=vQaqTL7JM86NnQfC35ShDA&amp;amp;ved=0CBwQvwUoAQ&amp;amp;q=high+speed+digital+design&amp;amp;spell=1&amp;amp;fp=84f34ab5383c7ee9&quot; rel=&quot;nofollow&quot;&gt;high speed digital design&lt;/a&gt;(&lt;a href=&quot;http://books.google.com/books?id=yTyGKJHvfDQC&amp;amp;dq=high+speed+digital+design&amp;amp;source=bl&amp;amp;ots=LwA8PqmxLO&amp;amp;sig=gNFK-L78oMFR9ilxeU_T6z-B7ds&amp;amp;hl=en&amp;amp;ei=wQaqTK7cA8T4nAfFmIWiDA&amp;amp;sa=X&amp;amp;oi=book_result&amp;amp;ct=result&amp;amp;resnum=12&amp;amp;ved=0CEYQ6AEwCw&quot; rel=&quot;nofollow&quot;&gt;the book by Johnson being the best book in existence&lt;/a&gt;), you will learn that this can be looked at as a wide range of frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;H2&gt; What the crystal&lt;/h2&gt;&#xA;There are two ways from this point, from the frequency domain, or from the time domain. I will start with the frequency domain due to personal preference. For every EE I work with I push them to become at home with the frequency domain, many problems become simple here, and complicated responses have meaning. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;H3&gt; Frequency Domain&lt;/h3&gt;&#xA;From the frequency domain, a crystal is a filter at a very specific frequency with a very high Q(quality) factor. This means that of all of those frequencies you generate, you only allow the specific one the crystal allows through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;H3&gt; Time Domain&lt;/h3&gt;&#xA;The other method is to think of a gate tied back on itself. if there was nothing there, it would create a square wave with a frequency equal to the delay, but this frequency is not extremely reliable, and also will vary based on many manufacturing parameters. This is where the crystal affects it. If the crystal has a rising edge placed on it, it will only &quot;pass through&quot; the signal at the frequency it has selected for. Suddenly, the 100MHz square wave becomes a 20MHz sin wave due to the crystal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;H2&gt; A little extra thought&lt;/h2&gt;&#xA;Wonder why oscillators pull so much current, you are charging and discharging the capacitance in the oscillator circuit 20 million times per second. Also, for all the clock cycles many transistors in your circuit do the same. if you do not need speed, a 32KHz oscillator costs very little in power on microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me know if I can be more clear.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-10-04T17:17:06.957" LastActivityDate="2010-10-04T17:17:06.957" />
  <row Id="4837" PostTypeId="2" ParentId="4807" CreationDate="2010-10-04T18:38:29.160" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://armkits.com/Product/devkit8000.asp&quot; rel=&quot;nofollow&quot;&gt;Embest DevKit8000&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="625" LastActivityDate="2010-10-04T18:38:29.160" />
  <row Id="4839" PostTypeId="1" AcceptedAnswerId="4841" CreationDate="2010-10-04T18:44:39.630" Score="1" ViewCount="111" Body="&lt;p&gt;I recently purchased this item to use with an arduino:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9105&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9105&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My problem is that I realized after the fact that this wasn't attached to the breakout board. Are these connections too small to be soldered by hand? What is the smallest distance between connections that can realistically be soldered by hand?&lt;/p&gt;&#xA;" OwnerUserId="1308" LastActivityDate="2010-10-04T18:54:50.970" Title="Soldering tiny connectors" Tags="&lt;soldering&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="4840" PostTypeId="2" ParentId="1849" CreationDate="2010-10-04T18:48:32.147" Score="2" ViewCount="" Body="&lt;p&gt;There is a correct range of values, however it is difficult to describe exactly what that range is.  Generally, 10k works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digital outputs have a specified ability to source or sink current.  If your output could sink 5 mA and the output was connected through a pull-up to 5 V and then set to 0, you would need a minimum of 1k resistance.  If you use less than 1k, the output will not be able to sink enough current to pull the pin all the way down to 0V.  If you use a bigger value, like 10k, then the pin only has to sink 0.5 mA, which is much less than it's rating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digital inputs have a specified leakage current.  This is kinda like the amount of current it takes to &quot;maintain&quot; a 0 or 1 at an input.  If your pull-up resistor is too large, then it won't be able to overcome the leakage current.  If it just barely overcomes the leakage current, then any noise in the circuit could be enough to change the input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When using digital outputs that can sink and source current (&quot;totem pole driver&quot;, &quot;push-pull driver&quot;), you might be tempted to not use pull-up or pull-down resistors.  However, it is very important that CMOS inputs not be allowed to float or they can pull excessive current...and it's very easy to forget that bidirectional MCU pins usually come up as inputs!&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;I2C and other protocols like it use &quot;open drain&quot; (or &quot;open collector&quot;) outputs.  Instead of having outputs that can pull up and down, and open drain outputs can only pull down.  That is why the external pull-up resistor is required.  There are now additional restrictions on the range of pull-up resistors; the pull-up value will form an RC circuit with the bus capacitance.  Too small of a value will once again prevent the output drivers from sinking enough current to pull the pin all the way down to 0.  However, too large a value will take too long to charge the bus capacitance up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there are setup/hold times that you are not allowed to violate, those will help you determine an RC time constant.  The bus capacitance is largely determined by PCB layout, so you can then pick an R value that combines with the C to provide a value that is comfortably within the setup/hold time for your digital input.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-04T18:48:32.147" />
  <row Id="4841" PostTypeId="2" ParentId="4839" CreationDate="2010-10-04T18:54:50.970" Score="2" ViewCount="" Body="&lt;p&gt;I don't have any problems hand-soldering connectors like that. I use a Metcal soldering station with a mini-hoof cartridge. I tack the connector down at two opposite corners, making sure it is positioned properly using a stereo microscope, apply plenty of jelly flux, and drag-solder each row.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-04T18:54:50.970" />
  <row Id="4842" PostTypeId="1" AcceptedAnswerId="4902" CreationDate="2010-10-04T19:11:45.227" Score="3" ViewCount="234" Body="&lt;p&gt;I have a PAL or NTSC video signal and I want to extract the CSYNC information. Preferably, I would like to avoid using an LM1881, because I am short on space and I'm optimising for cost.  Also, the LM1881 is limited to an operating range of 0°C to +70°C and I want a full industrial range of -40°C to +85°C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I set up a little divider network like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;3.3V --------------+&#xA;                   |&#xA;                   /&#xA;                   \ 4.7k&#xA;                   /&#xA;       4.7u   1k   |&#xA;Inp  --| |--/\/\/\-+--- to PIC comparator&#xA;                   |&#xA;                   /&#xA;                   \ 4.7k&#xA;                   /&#xA;              1k   | &#xA;                  ---&#xA;                   -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This produces a signal with ranging from 1.27V to 1.5V, but the signal moves up and down when the brightness in the scene changes! I think this is happening because the DC offset is changing. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any idea on how to eliminate this offset? I guess I could add some other components, but I'd rather not - I'm trying to keep this as simple as possible.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-04T19:18:04.750" LastActivityDate="2010-10-19T11:27:58.967" Title="Best way to do sync separation without an LM1881 or equivalent" Tags="&lt;pic&gt;&lt;video&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="4845" PostTypeId="2" ParentId="4333" CreationDate="2010-10-04T19:23:38.507" Score="0" ViewCount="" Body="&lt;p&gt;Long time ago, I've seen a photograph of a digital clock with no board at all. All resistors, capacitors, transistors, LED displays were soldered in a nice sculpture artwork.&lt;/p&gt;&#xA;" OwnerUserId="1350" LastActivityDate="2010-10-04T19:23:38.507" CommunityOwnedDate="2010-10-04T19:23:38.507" CommentCount="3" />
  <row Id="4847" PostTypeId="1" CreationDate="2010-10-04T19:25:12.480" Score="4" ViewCount="157" Body="&lt;p&gt;Hello,&#xA;I have to replace this kind of button : &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/nFW9j.jpg&quot; alt=&quot;button&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the left side I need to put  the same switch than in the right side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please, could you tell me &lt;strong&gt;where to buy it&lt;/strong&gt; and how to name it !&lt;/p&gt;&#xA;" OwnerUserId="1454" LastEditorUserId="1454" LastEditorDisplayName="" LastEditDate="2010-10-05T08:59:26.247" LastActivityDate="2010-10-05T11:51:25.483" ClosedDate="2011-03-20T17:03:18.070" Title="where to buy this kind of button" Tags="&lt;button&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="1" />
  <row Id="4848" PostTypeId="2" ParentId="4803" CreationDate="2010-10-04T19:25:19.190" Score="3" ViewCount="" Body="&lt;p&gt;Please note that the power rating of a potentiometer is for the entire end-to-end resistance. If you use (as is typical) a fraction of the potentiometer's end-to-end resistance, the power is reduced accordingly. The easiest way to think about it is that there is a maximum current through the pot. If you have a 1W 100 ohm potentiometer, the max. current is 100mA (full voltage = 10V); if you are using only 27 ohms of the potentiometer then the max. current is still 100mA and your effective max. power is 0.27W.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-10-04T19:25:19.190" CommentCount="4" />
  <row Id="4851" PostTypeId="1" AcceptedAnswerId="4853" CreationDate="2010-10-04T20:32:26.840" Score="3" ViewCount="198" Body="&lt;p&gt;I'd like to decode some IR signals from a TV remote control. I scavenged a 3 pin IR receiver from some old junk and hooked it up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I've read about RC-5, I was expecting to see a start bit indicating the bit time, which I could synchronize to. But, I'm seeing lots of transitions per bit time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this a sign that I'm mixing 38kHz and 56kHz devices? Or am I expecting the wrong thing?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://oi53.tinypic.com/9hrwc9.jpg&quot;&gt;&#xA;&lt;img src=&quot;http://oi52.tinypic.com/2zhp5vt.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was concerned that the weirdness I was seeing was the IR receiver being odd. So, I wired up a plain old 2 pin IR LED receiver to compare (bottom trace). With the LED, I see the 32kHz carrier wave and the modulated signal, the &quot;smart&quot; receiver filters out the carrier perfectly leaving just the pulse widths.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ladyada tutorial explained it all.&#xA;Ta.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://oi52.tinypic.com/2rcord0.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-04T23:21:36.327" LastActivityDate="2010-10-07T13:23:14.730" Title="Confused by IR pulses" Tags="&lt;ir&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="4852" PostTypeId="1" CreationDate="2010-10-04T21:07:37.773" Score="1" ViewCount="135" Body="&lt;p&gt;Howdy,&#xA;  I have some ne2 lamps i want to controll with a signal from my car.  Signal voltage is about 11 to 14 volts and isnt very clean.  I also have 170vdc avalible to power the ne2's.  I plan on using these for turn signals and high beam indicator.  Componets must be able to be on for long periods of time.  I would like to be efficiant with power due to limitation of my 170v powersupply.  I do have some TIP102's laying around but fear the input voltage is too low.  Is there a 12v version of these.  What resistors should i use to nock it down to the appropriate voltage.  I cant find much data on these lamps and use.&#xA;  Thanks for your help.  I hope to order from mouser here to get needed parts.&#xA;Ed Owens&lt;/p&gt;&#xA;" OwnerUserId="1400" LastActivityDate="2010-10-05T01:15:28.890" Title="controlling a ne2 lamp with a 12v signal." Tags="&lt;transistor&gt;&lt;control&gt;&lt;nixie&gt;&lt;car&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="4853" PostTypeId="2" ParentId="4851" CreationDate="2010-10-04T22:31:00.197" Score="6" ViewCount="" Body="&lt;p&gt;ladyada has a discussion about ir pulses over on her page detailing the design of the &lt;a href=&quot;http://www.ladyada.net/make/tvbgone/design.html&quot; rel=&quot;nofollow&quot;&gt;TV-B-Gone Kit&lt;/a&gt; she sells. It might be of some use to you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: There's a brand new tutorial on ladyada's site discussing how to build an IR decoder in even more detail, which has just been posted today: &lt;a href=&quot;http://www.ladyada.net/learn/sensors/ir.html&quot; rel=&quot;nofollow&quot;&gt;IR Detector&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-06T18:05:41.673" LastActivityDate="2010-10-06T18:05:41.673" CommentCount="2" />
  <row Id="4854" PostTypeId="2" ParentId="4847" CreationDate="2010-10-04T22:41:55.567" Score="3" ViewCount="" Body="&lt;p&gt;That looks, a little bit, like those touch buttons they used to (maybe still do) put in handheld video games.    I remember taking them apart when I was younger.  You have a small graphite(?) (or some other conductive material) pad beneath the flexible rubbery outer shell that, when pressed down, closes the circuit between two contact points on the PCB.  Because the outer shell is flexible and rubbery, when you let go, the circuit opens due to rubber-spring-back-action -- what's the technical term for that?  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(EDIT:  &lt;a href=&quot;http://en.wikipedia.org/wiki/Keyboard_technology#Dome-switch_keyboard&quot; rel=&quot;nofollow&quot;&gt;Wikipedia states that the technical term for these are dome switches&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most of the time, I believe, they were specifically designed for a particular device, and you'll have a hard time finding a replacement unless you can get a hold of another one of those devices.  In other words, you probably won't find this switch in an electronics catalog.  You could maybe fabricate another, if you know how / know a person who can make the rubber part and can find a graphite pad to put inside it.  &lt;strong&gt;Really, though, your best bet, in my opinion, is to find another non-working example of this unit with the switch you need, and cannibalize the two to make a working one.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might be able to wire another momentary switch in its place, although that's rather hackish.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-10-05T11:51:25.483" LastActivityDate="2010-10-05T11:51:25.483" CommentCount="2" />
  <row Id="4856" PostTypeId="2" ParentId="4852" CreationDate="2010-10-05T01:06:07.087" Score="3" ViewCount="" Body="&lt;p&gt;To custom design a circuit to switch an NE-2 bulb directly from a 170V DC supply, you would need a transistor that can withstand the 170V supply voltage when off, and pass the 0.5 (or so) mA of current when on. The TIP102 you mention would have no problem with the on-current, but can only take 100V in the off state. To get some margin over that 170V you probably would want to use a transistor with a Vceo rated 200V (or better). This would be a relatively high-voltage, low-current kind of part, compared to the majority of parts that you'll find listed in Mouser or Jameco.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an alternative, you might investigate using a solid-state relay to switch the high voltage under control of the typical 12V automotive signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if you obtained bare NE-2 bulbs, be sure to put a limiting resistor in series with the bulbs. Ionized neon has very low resistance, so you need a resistor to keep the current under control. From 170V, using a 220K ohm resistor would give you roughly 0.75mA through the bulb, which would be a typical current for an NE-2.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-10-05T01:15:28.890" LastActivityDate="2010-10-05T01:15:28.890" CommentCount="4" />
  <row Id="4857" PostTypeId="1" AcceptedAnswerId="5210" CreationDate="2010-10-05T01:07:31.183" Score="3" ViewCount="341" Body="&lt;p&gt;What are some good RFID readers to look at for a keyless residential entry system? Are there any on the market that can read a key fob or similar RFID token from a range of 3 feet or more?  This would be a DIY project for a new home, so price is less of an issue than reliability and ease of integration.&lt;/p&gt;&#xA;" OwnerUserId="1317" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T19:07:25.807" LastActivityDate="2011-01-29T19:07:25.807" Title="RFID reader for a keyless residential entry system?" Tags="&lt;rfid&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="4858" PostTypeId="2" ParentId="4539" CreationDate="2010-10-05T01:22:02.010" Score="1" ViewCount="" Body="&lt;p&gt;It seems there are issues with the quality of the Arduino Uno's ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dangerousprototypes.com/2010/10/04/arduino-uno-quality-control/&quot; rel=&quot;nofollow&quot;&gt;Arduino Uno Quality Control&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://wtfmoogle.com/?p=1528&quot; rel=&quot;nofollow&quot;&gt;to: The Arduino Opensource Community&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and a hardware bug in the Arduino design ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://forum.pololu.com/viewtopic.php?f=3&amp;amp;t=3083#p14193&quot; rel=&quot;nofollow&quot;&gt;Arduino Hardware Bug&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;After looking into the design, it seems to us that the circuit is just fundamentally flawed, and there is little reason to expect it to work well regardless of which MOSFET is used. The newer MOSFET makes the problem more evident, so it is easily verifiable in all kinds of tests. (These were not just contrived tests: on the one laptop we tried, we measured almost 200mA flowing into the USB port after powering it off. We verified that this occurred across the entire recommended operating range of 7-12V on VIN.) The new Arduino Uno looks like it will have the same basic problem, but we have not tried one yet.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1084" LastActivityDate="2010-10-05T01:22:02.010" CommunityOwnedDate="2010-10-05T01:22:02.010" />
  <row Id="4859" PostTypeId="1" CreationDate="2010-10-05T01:40:21.537" Score="3" ViewCount="612" Body="&lt;p&gt;Let's see some bad examples of circuit design. If you've seen one, post the circuit and please say why it's a bad design.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-05-04T20:47:10.860" CommunityOwnedDate="2010-10-05T01:40:21.537" Title="examples of bad circuit design" Tags="&lt;circuit-design&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="1" />
  <row Id="4860" PostTypeId="2" ParentId="4859" CreationDate="2010-10-05T01:51:42.773" Score="4" ViewCount="" Body="&lt;p&gt;Lack of &lt;a href=&quot;http://en.wikipedia.org/wiki/Flyback_diode&quot; rel=&quot;nofollow&quot;&gt;freewheeling diodes&lt;/a&gt; is a common mistake.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.edn.com/file/25586-Control_a_dc_motor_with_your_PC_figure_1.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.edn.com/file/25586-Control_a_dc_motor_with_your_PC_figure_1.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The circuit in this Design Idea controls the speed of a 5V permanent-magnet dc motor through the PC’s parallel port &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Motors / relays / etc. are inductive loads, which when switched off rapidly generate high voltages to oppose being switched off rapidly, and you need to provide a path for that current to flow and the inductive energy to dissipate. The typical route is to put a freewheeling diode for current to flow when the load is being turned off. The authors use a ULN2003 which has freewheeling diodes. But they do not provide one for the most important load in this circuit, namely the DC motor, which is turned on and off with a strange series combination of a 2N2222 and a relay... in any case when the motor turns off it will provide an inductive surge that will damage Q1, unless you put a diode across the motor. (cathode to positive terminal, anode to negative terminal)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(There's a typo in the magazine, where pins R8 and the 1N4148 do nothing as they connect between two nodes in the circuit that are shorted together. Figure 1 has this correct. Unfortunately EDN / Electronics Design / etc. are notorious for publishing circuits w/o much effort into checking for mistakes.)&lt;/p&gt;&#xA;" OwnerUserId="330" LastEditorUserId="330" LastEditorDisplayName="" LastEditDate="2010-10-05T11:33:20.007" LastActivityDate="2010-10-05T11:33:20.007" CommunityOwnedDate="2010-10-05T01:51:42.773" CommentCount="4" />
  <row Id="4861" PostTypeId="2" ParentId="4859" CreationDate="2010-10-05T02:16:13.720" Score="17" ViewCount="" Body="&lt;p&gt;My all-time favorite bad design, &lt;a href=&quot;http://electronicdesign.com/article/analog-and-mixed-signal/simple-ac-stop-dc-pass-circuit-uses-four-op-amps61.aspx&quot; rel=&quot;nofollow&quot;&gt;from a 1999 issue of Electronic Design&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://archive.electronicdesign.com/files/29/6190/figure_01.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's see, they're buffering a signal (U1), then using an RC high-pass filter, then buffering that (U2), then inverting that signal (R2+R3+U3), then adding it to the original buffered signal (R6 + R7 + R4 + R5 + U4).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is called a LOW PASS FILTER, and a better and simpler equivalent circuit can be made by just swapping R1 with C1, and deleting R7 and all components to the right of R2. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the original circuit, U3+R2+R3 is unnecessary: you can make a 1-opamp differential amplifier to subtract two signals using U4 + R6 + R7 + R4 + R5, rather than inverting and then adding. And when you take a signal and go to all that trouble to subtract out the high-pass components, instead of just use a low-pass filter, the performance is poorer for two main reasons:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) an RC low-pass filter will use a passive element (capacitor) to shunt high-frequency signal content out of the signal path. In order for the circuit in Fig. 1 to work, the high frequency components in the original signal must be canceled out by using active circuits to create an equal and opposite signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) This circuit is prone to several component tolerance issues: R2/R3 must be matched, as do R4/R5/R6/R7. (The authors say &quot;Its accuracy depends on the matching of resistors and the performance of the op amps.&quot; Well, if you design a simple low pass filter, you don't need to depend on matching resistors.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally it is a bad idea to put a large capacitor (C2) directly on the output of an op-amp. The op-amp is unable to keep stable feedback in such a configuration. A small series resistor between Vout and C2 might do the trick; there are other circuits that will combine the passive high-frequency low impedance of C2, and the active low-frequency low impedance of an op-amp. (See Horowitz &amp;amp; Hill.)&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-10-05T02:16:13.720" CommunityOwnedDate="2010-10-05T02:16:13.720" CommentCount="6" />
  <row Id="4862" PostTypeId="2" ParentId="4857" CreationDate="2010-10-05T03:02:06.927" Score="3" ViewCount="" Body="&lt;p&gt;Sparkfun has some RFID devices that are fairly DIY ready. Here is a link to one:&#xA;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8419&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=8419&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is if you are wanting to actually build your own device to do keyless entry. If you are wanting a pre-built key-less entry you might need to look else where.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt;&#xA;After answering I did realize you mentioned that you wanted reliability and ease of integration. My solution probably isn't the best for this requirement.&#xA;Look at this site: &lt;a href=&quot;http://www.househacker.com/permanent/DIY-RFID-Access-to-your-Front-Door&quot; rel=&quot;nofollow&quot;&gt;http://www.househacker.com/permanent/DIY-RFID-Access-to-your-Front-Door&lt;/a&gt; or &lt;a href=&quot;http://lmgtfy.com/?q=diy+rfid+keyless+entry&quot; rel=&quot;nofollow&quot;&gt;http://lmgtfy.com/?q=diy+rfid+keyless+entry&lt;/a&gt; (sorry couldn't help myself)&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-10-05T03:14:20.563" LastActivityDate="2010-10-05T03:14:20.563" CommentCount="1" />
  <row Id="4863" PostTypeId="2" ParentId="4859" CreationDate="2010-10-05T04:30:13.157" Score="3" ViewCount="" Body="&lt;p&gt;Don't have a circuit, but: lack of reverse power protection on DC devices and lack of power-rail tolerance on pins adjacent to power. Because of course &lt;em&gt;everyone&lt;/em&gt; field-wires everything right the first time.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2010-10-05T04:30:13.157" CommunityOwnedDate="2010-10-05T04:30:13.157" CommentCount="2" />
  <row Id="4864" PostTypeId="2" ParentId="4859" CreationDate="2010-10-05T07:12:09.733" Score="5" ViewCount="" Body="&lt;p&gt;I was, a long, long time ago, given a circuit to debug.  There were many things wrong with it but the &quot;best&quot; mistake was that the /WR and /CS lines to the memory chips were tied together, turning each of the HM6116 devices into a 2Kx8 WOM or Write only memory.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-10-05T07:12:09.733" CommunityOwnedDate="2010-10-05T07:12:09.733" />
  <row Id="4865" PostTypeId="1" CreationDate="2010-10-05T09:17:55.197" Score="2" ViewCount="129" Body="&lt;p&gt;hi fellows,&#xA;im a beginner at electronics.&#xA;im trying make an drawdio circuit with the instructions in the link below:&#xA;&lt;a href=&quot;http://www.ladyada.net/make/drawdio/drawdio2schem.png&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/make/drawdio/drawdio2schem.png&lt;/a&gt;&#xA;i have following components on the circuit.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;NE555N 555 timer&lt;/li&gt;&#xA;&lt;li&gt;PN2907 transistor&lt;/li&gt;&#xA;&lt;li&gt;100uF 25V capacitor &lt;strong&gt;(instead of 6.3v one on the ladyada's page)&lt;/strong&gt;&lt;/li&gt;&#xA;&lt;li&gt;680pF ceramic capacitor &lt;/li&gt;&#xA;&lt;li&gt;0.1uF non-ceramic capacitor &lt;strong&gt;( instead of ceramic one on ladyada's page)&lt;/strong&gt;&lt;/li&gt;&#xA;&lt;li&gt;1/4W 5% 10 MEGAohm resistor&lt;/li&gt;&#xA;&lt;li&gt;1/4W 5% 10 ohm resistor&lt;/li&gt;&#xA;&lt;li&gt;1/4W 5% 300K resistor&lt;/li&gt;&#xA;&lt;li&gt;Small 8ohm speaker 0.5w&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;do you think any of those changes i made might be causing low sound problem??&#xA;please help :/&lt;/p&gt;&#xA;" OwnerUserId="1461" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-05T12:03:21.613" LastActivityDate="2011-05-18T11:34:49.043" Title="Drawdio the sound is very very low :S ?" Tags="&lt;circuit&gt;&lt;capacitor&gt;&lt;sound&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="4866" PostTypeId="1" AcceptedAnswerId="4867" CreationDate="2010-10-05T10:14:15.057" Score="6" ViewCount="318" Body="&lt;p&gt;Is there software out there that will take a schematic as input and simulate its functioning?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't have a lot of cash for components and tools, so this would be a cheap and easy way for me to learn more about electronics.&lt;/p&gt;&#xA;" OwnerUserId="1258" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-10-06T13:54:46.530" LastActivityDate="2010-10-06T13:54:46.530" Title="Can you simulate a schematic?" Tags="&lt;software&gt;&lt;simulation&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="3" />
  <row Id="4867" PostTypeId="2" ParentId="4866" CreationDate="2010-10-05T10:56:17.373" Score="10" ViewCount="" Body="&lt;p&gt;We usually call that simulation, not emulation. If we were to emulate the board, that means having another device perform similarly. There are plenty of circuit simulators, most famous of which is Spice (ltspice is one popular version). Qucs, ktechlab, klogic (limited to digital), and gnucap are a few others; for those without a graphical interface, there typically is one separately, such as oregano or gspiceui.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-10-05T10:56:17.373" CommentCount="1" />
  <row Id="4868" PostTypeId="1" CreationDate="2010-10-05T10:59:30.003" Score="1" ViewCount="157" Body="&lt;p&gt;Hi all, This will be my first try at USB intefacing !&lt;/p&gt;&#xA;&#xA;&lt;p&gt;May I know how to transfer the data from pins : 11-15 of KT3170 IC to USB ? Data sheet : &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet/SamsungElectronic/mXuusvq.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.datasheetcatalog.org/datasheet/SamsungElectronic/mXuusvq.pdf&lt;/a&gt; I guess I will need to configure a Microprocessor for making the OS uderstand what profile of device is this , In that Case what will be my device profile ? Mine is an RF remote control receiver using DTMF which I want to connect to the PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also have a doubt on fast can The KT3170 can interpret the DTMF tone. That is if I press a button (say 1) and immediately within the same second if I press key 2 Will it be able to recieve and decode the DTMF correctly with proper time synchronization ? What will be the latency if I transmit this signal through Frequency Modulation (FM) ?&lt;/p&gt;&#xA;" OwnerUserId="1462" LastActivityDate="2011-04-09T17:17:47.250" Title="How can I connect the KT3170 (The DTMF reciever) to USB (4bit data) ?" Tags="&lt;electronics&gt;&lt;usb&gt;&lt;circuit&gt;" AnswerCount="4" />
  <row Id="4869" PostTypeId="2" ParentId="4859" CreationDate="2010-10-05T11:08:03.663" Score="2" ViewCount="" Body="&lt;p&gt;Most of the really poor connections stem from momentary lapses in attention. For instance, EEVblog had a problem with a Microchip device that was supposed to have several programming ports, only the one chosen never worked. And a friend of mine was going to build a controller with a PIC until I noticed a pin he planned to switch a low side transistor with was in fact open collector - it couldn't drive high at all. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of the truly horrifying designs, on the other hand, are just overly clever workarounds. I'll submit the example of the MIT Handyboard, where the RAM interface has to be turned off to update the display. It therefore needs to page out the internal RAM to make space for the display driver. I suppose, at the time, there weren't many cheap options.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-10-05T11:08:03.663" CommunityOwnedDate="2010-10-05T11:08:03.663" CommentCount="1" />
  <row Id="4870" PostTypeId="2" ParentId="4866" CreationDate="2010-10-05T11:14:57.180" Score="6" ViewCount="" Body="&lt;p&gt;As @LoneTech said, there are plenty of circuit simulators. My two cents:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Proteus - You can simulate some microcontrollers, but isn't free.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.falstad.com/circuit/&quot; rel=&quot;nofollow&quot;&gt;http://www.falstad.com/circuit/&lt;/a&gt; - java applet that allows you to simulate your circuits&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://logic.ly/&quot; rel=&quot;nofollow&quot;&gt;http://logic.ly/&lt;/a&gt; - An online tool limited to digital&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-05T11:14:57.180" CommentCount="1" />
  <row Id="4871" PostTypeId="2" ParentId="4859" CreationDate="2010-10-05T11:38:14.107" Score="8" ViewCount="" Body="&lt;p&gt;It's not a circuit, but it's funny.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that the worst of the history is the WOM (Write Only Memory) 25120 from Signetics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/KBvGp.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;The origin of the WOM - the &quot;Write Only Memory&quot;&lt;/strong&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;An engineer at Signetics, frustrated&#xA;  by the long and useless sequence of&#xA;  approvals for data sheets (during&#xA;  which no actual checking occurred),&#xA;  once made up a spec for a &quot;Write Only&#xA;  Memory&quot; (a &quot;WOM&quot;) and sent it along&#xA;  with a batch of other data sheets to&#xA;  be approved. After all, if you are&#xA;  selling &quot;Read Only Memories&quot;, why not&#xA;  have a &quot;Write Only Memory&quot;? It's&#xA;  perfectly logical - - which is why the&#xA;  managers saw nothing wrong with the&#xA;  data sheet.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The WOM data sheet went through the&#xA;  approval chain, just fine, and wound&#xA;  up in Signetics' new products catalog.&#xA;  This came to the attention of the&#xA;  managers at Signetics, only after&#xA;  customers began asking for price and&#xA;  delivery. Signetics shortly printed up&#xA;  new &quot;corrected&quot; databooks, without any&#xA;  WOMs, and asked for the &quot;erroneous&quot;&#xA;  ones to be returned. But customers&#xA;  soon got word of why they asked for&#xA;  returns, and hid them properly.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;About 1974, Signetics bought a&#xA;  two-page, full-color spread in the&#xA;  April issue of ELECTRONICS Magazine,&#xA;  and published the WOM data sheet, as a&#xA;  (rather expensive) April Fool's Joke.&#xA;  This version of the WOM data sheet&#xA;  shows the various features of&#xA;  Signetics' Model 25120 &quot;fully-encoded,&#xA;  9046 x N Random Access, Write Only&#xA;  Memory&quot;. This advertisement has been&#xA;  saved, and greatly prized by&#xA;  engineers, for many years. We recently&#xA;  found a copy of this data sheet, in&#xA;  very good shape except for where it&#xA;  had been punched for a 3-ring binder.&#xA;  See the next pages.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;This was not the end of the WOM.&#xA;  Signetics also brought out a&#xA;  promotional pamphlet, &quot; Be Famous!!&#xA;  Have a WOM named after you.&quot;&#xA;  Unfortunately, not many of these&#xA;  survive. If anybody can loan us a good&#xA;  photocopy, we would love to add it to&#xA;  these pages.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;At many companies, managers are&#xA;  accused of not having any sense of&#xA;  humor. But in this case, the Signetics&#xA;  guys did it right! Even if it did cost&#xA;  them a lot of money!! And our managers&#xA;  here at National approved my posting&#xA;  of this Data Sheet on my web site - to&#xA;  show that we have a good sense of&#xA;  humor, too!&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Further, as we pointed out in a recent&#xA;  web-cast, XILINX makes FPGA's such as&#xA;  the XC4V LX15-10 SF363 - - which can&#xA;  be used in conjunction with our&#xA;  3-Giga-samples-per-second ADC's, at&#xA;  such high data rates, that they are&#xA;  faster than most WOMs. The FPGA's can&#xA;  then give you back your data at a&#xA;  slower, controlled rate - - whereas&#xA;  WOMs never give you your bits back!&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;a href=&quot;http://www.national.com/rap/files/datasheet.pdf&quot; rel=&quot;nofollow&quot;&gt;Download datasheet&lt;/a&gt; (pdf 2.4MB)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Source: &lt;a href=&quot;http://www.national.com/rap/Story/WOMorigin.html&quot; rel=&quot;nofollow&quot;&gt;http://www.national.com/rap/Story/WOMorigin.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can see more here:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.swtpc.com/mholley/RadioElectronics/Apr1973/RE_Apr_1973_pg53.jpg&quot; rel=&quot;nofollow&quot;&gt;http://www.swtpc.com/mholley/RadioElectronics/Apr1973/RE_Apr_1973_pg53.jpg&lt;/a&gt; (Radio-Electronics announce)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Write-only_memory&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Write-only_memory&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="938" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-04T16:12:21.150" LastActivityDate="2011-05-04T16:12:21.150" CommunityOwnedDate="2010-10-05T11:38:14.107" CommentCount="3" />
  <row Id="4873" PostTypeId="2" ParentId="4866" CreationDate="2010-10-05T11:54:56.970" Score="1" ViewCount="" Body="&lt;p&gt;The Altera Quartus II software for their FPGAs and CPLDs supports schematic entry, for digital simulation and synthesis. Most people use VHDL or Verilog, though. There is a free version.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-05T11:54:56.970" />
  <row Id="4874" PostTypeId="1" AcceptedAnswerId="6278" CreationDate="2010-10-05T12:52:29.323" Score="6" ViewCount="323" Body="&lt;p&gt;I am considering building an RFID reader system that can monitor runners times in a foot race. I have read that there are three different types of RFID systems. LF, HF, and UHF. Which one would be best for this application? Has anyone had success building an antenna that can read RFID tags from a distance of a meter or more?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:  Active or Passive? My current thought is to use passive technology. I want to be able to get the tags for as cheap as possible and I don't want there to be a chance of the internal batteries failing. &lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="1235" LastEditorDisplayName="" LastEditDate="2010-10-06T02:15:00.870" LastActivityDate="2010-11-05T18:48:17.400" Title="Best RFID Technology for long range detection?" Tags="&lt;rfid&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="4875" PostTypeId="2" ParentId="765" CreationDate="2010-10-05T13:49:49.543" Score="1" ViewCount="" Body="&lt;p&gt;My two cents: &lt;a href=&quot;http://www.circuitstoday.com/simple-water-level-idicator&quot; rel=&quot;nofollow&quot;&gt;http://www.circuitstoday.com/simple-water-level-idicator&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-05T13:49:49.543" />
  <row Id="4876" PostTypeId="2" ParentId="4866" CreationDate="2010-10-05T15:39:46.907" Score="3" ViewCount="" Body="&lt;p&gt;Some of the higher-level programs for general analog simulation are Multisim and OrCad's suite (including PSpice). Other programs which offer limited capabilities are Simulink in MATLAB and National Instruments LabView. If you are in higher education, you may find that these are available in a computer lab.&lt;/p&gt;&#xA;" OwnerUserId="1468" LastActivityDate="2010-10-05T15:39:46.907" />
  <row Id="4877" PostTypeId="2" ParentId="4868" CreationDate="2010-10-05T15:54:53.217" Score="3" ViewCount="" Body="&lt;p&gt;I'd suggest a microprocessor with built-in USB, such as the PIC 18F2455 (or one of its variants). The USB interface to your PC is very simple and ends up looking like an RS-232 serial port to the PC. The driver is probably already in your OS if you're using recent Windows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way I interpret the data sheet, I would connect Q1 - Q4 to digital inputs on the microcontroller. Then connect the DSO (pin 15) to a digital input with an interrupt-on-change and process when it goes high. When you get the interrupt, read the Q1 - Q4 data, do whatever pre-processing you may want and send it out the USB port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't definitively tell by the data sheet if the KT3170 output would change if you pressed a second key while the first one is still pressed, but I'd guess that the fist output would stay latched unless you fully released the first key prior to the second press. You might have to just try and see.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you press one key and then quickly press the next, you should be okay and get the second keypress as the maximum interdigit pause time is 40 ms. As long as you aren't faster than 40 ms between presses, you'll get the second press.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know what your transmit latency will be. You'll have to look for that in the transmitter/receiver pair documentation.&lt;/p&gt;&#xA;" OwnerUserId="1467" LastEditorUserId="1467" LastEditorDisplayName="" LastEditDate="2010-11-01T22:12:30.153" LastActivityDate="2010-11-01T22:12:30.153" CommentCount="2" />
  <row Id="4878" PostTypeId="2" ParentId="4868" CreationDate="2010-10-05T16:17:28.670" Score="1" ViewCount="" Body="&lt;p&gt;I'd have a look at the AVR USB chips and the Teensy dev boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/1942/how-to-build-a-usb-controller-having-knobs-sliders-and-switches&quot;&gt;http://electronics.stackexchange.com/questions/1942/how-to-build-a-usb-controller-having-knobs-sliders-and-switches&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-05T16:17:28.670" CommentCount="1" />
  <row Id="4879" PostTypeId="2" ParentId="4631" CreationDate="2010-10-05T17:35:37.797" Score="1" ViewCount="" Body="&lt;p&gt;Buy this book: &lt;a href=&quot;http://www.exploringpic32.com/index.html&quot; rel=&quot;nofollow&quot;&gt;Programming 32-bit microcontrollers in C. Learning to fly the PIC32&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has a chapter called Synchronous Communication Using the SPI Modules and much more.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-05T17:35:37.797" CommentCount="1" />
  <row Id="4880" PostTypeId="1" CreationDate="2010-10-05T18:26:13.733" Score="1" ViewCount="195" Body="&lt;p&gt;Hi am currently looking at creating an IR remote control for a robot but i need something that i can use to monitor the signal so i was think that a wii remote has a IR cam in it so i can use that to report back to my pc the signal that my remote is generating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;anyone know if this is possible?&lt;/p&gt;&#xA;" OwnerUserId="1473" LastActivityDate="2010-10-08T10:42:06.097" Title="Wii remote as ir signal detector" Tags="&lt;ir&gt;&lt;wii&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="4881" PostTypeId="1" AcceptedAnswerId="4885" CreationDate="2010-10-05T18:57:21.273" Score="3" ViewCount="326" Body="&lt;p&gt;I would like to build DIY linear bench power supply, with adjustable, regulated output voltage and current limiting functions. The voltage and current regulation will be implemented using analog feedback loops. The functionality of the device requires sensing of the output current in order to:   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Use it in feedback loop to limit current&lt;br&gt;&#xA;2) Measure output current  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since whole this is to be controlled by microcontroller (voltage and current limit setting, measurment) it means that I need to generate voltage with respect to ground proportional to the current (or not?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the possible solution is to implement high side current sensing using resistor (it is preferable solution due to protection against accidental shorts compering to low side sensing). Examples of the high (and low) sensing circuits can be found in nice &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en551198&quot; rel=&quot;nofollow&quot;&gt;app note&lt;/a&gt; from microchip. I am hesitating to use any  of the provided solution as that would mean placing two opamps in cascade (opamp for control + current sensing) which may be an issue for circuit stability. Do you have other ideas how high side current sensing could be implemented and be suitable for both analog control and measurement? (do not have to be the same circuit)&lt;/p&gt;&#xA;" OwnerUserId="1471" LastActivityDate="2010-10-05T20:04:13.363" Title="High side currents sensing in DIY bench supply" Tags="&lt;power-supply&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="2" />
  <row Id="4882" PostTypeId="2" ParentId="4880" CreationDate="2010-10-05T19:02:39.970" Score="1" ViewCount="" Body="&lt;p&gt;Unfortunately it's not a good idea to do that with a $40 Wii remote, designed to track the position of IR emitters, not data signals. You could do it with a &amp;lt; $10. part such as &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8554&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=8554&lt;/a&gt; . See also &lt;a href=&quot;http://www.gumbolabs.org/2010/05/29/radioshack-infrared-receiver-arduino/&quot; rel=&quot;nofollow&quot;&gt;http://www.gumbolabs.org/2010/05/29/radioshack-infrared-receiver-arduino/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-10-05T19:02:39.970" CommentCount="2" />
  <row Id="4884" PostTypeId="2" ParentId="4859" CreationDate="2010-10-05T19:53:51.157" Score="2" ViewCount="" Body="&lt;p&gt;The adventures of poor Kur Killapot are not only the single best application note ever written, they are also real examples of what some circuit hackers are up to. It's great that Bourns has made &lt;a href=&quot;http://www.bourns.com/data/global/pdfs/OnlinePotentiometerHandbook.pdf&quot; rel=&quot;nofollow&quot;&gt;the pdf of their nice Potentiometer Handbook available online&lt;/a&gt;. Be sure to check chapter 9.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-10-05T19:53:51.157" CommunityOwnedDate="2010-10-05T19:53:51.157" CommentCount="1" />
  <row Id="4885" PostTypeId="2" ParentId="4881" CreationDate="2010-10-05T20:03:44.920" Score="2" ViewCount="" Body="&lt;p&gt;For a linear supply i would recommend using a foldback current limiting scheme, especially on something that has a tendency to be shorted/over driven as often as a bench supply.  Theres lots of ways to do this and how you do it will be based on the linear regulator design.  That being said googling for 'foldback current limiting' especially on google books should give you all the information you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For current measurement, you can go high side or low side, whatever you want.  The reason to avoid low side is generally to avoid increasing resistance to ground.  The small sense resistor you use probably wouldn't matter much in a bench supply.  The easiest way to implement this is to use a custom made IC.  Such as the &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/1971&quot; rel=&quot;nofollow&quot;&gt;MAX4173&lt;/a&gt; there are lots of manufacturers for these though, look around for the one that best fits your needs/cost/package.  There are also some that output PWM which can be more accurate to work with than the ADC on most cheap microcontrollers.  You just measure the pulse width using a timer and usually either a pin with external interrupt or a comparator input.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-05T20:03:44.920" />
  <row Id="4886" PostTypeId="2" ParentId="4881" CreationDate="2010-10-05T20:04:13.363" Score="2" ViewCount="" Body="&lt;p&gt;The most simple solution is to use a differential amplifier stage across your high side resistor to measure the current, and measure that value with your microcontroller. You could much more easily add a second stage, probably, to your power supply to make a current limit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you already have a regulating transistor in place, you can probably make a little comperator that compares your set current (a reference voltage) against the measured voltage (representing your current). If you include that in the feedback loop of your power supply, it should regulate rather easily.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wouldn't do low-side sensing because that makes your ground not fixed (i.e. if you draw 2A, the ground potential shifts when the current drops). Also, if the ground terminal is shorted with a low-side resistor in place, the power supply has not current limit set. This could unbalance your load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also stay with an analog regulation; analog electronics are much easier to set up (it's a few resistors and opamps, maybe a few caps required) instead of a proccesor + some kind of PI regulator.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-10-05T20:04:13.363" CommentCount="2" />
  <row Id="4887" PostTypeId="2" ParentId="1099" CreationDate="2010-10-05T20:13:22.620" Score="0" ViewCount="" Body="&lt;p&gt;I found a shield that uses a virtual serial port to communicate to the modem. I think the store is from Chile.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;here is the link &lt;a href=&quot;http://www.olimex.cl/product_info.php?products_id=733&quot; rel=&quot;nofollow&quot;&gt;http://www.olimex.cl/product_info.php?products_id=733&lt;/a&gt;&#xA;[img]http://www.olimex.cl/images/MCI-TDD-00733.JPG[/img]&lt;/p&gt;&#xA;" LastActivityDate="2010-10-05T20:13:22.620" />
  <row Id="4888" PostTypeId="1" AcceptedAnswerId="4922" CreationDate="2010-10-06T01:34:13.210" Score="5" ViewCount="194" Body="&lt;p&gt;We have a device that runs off of a AC adapter, or a pack of 8 AA batteries. Since in normal use we use both, it would seem to make sense to have the battery pack recharge while using the AC adapter - instead of throwing the rechargeable batteries into a separate charge each time they're depleted.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the basics of designing/modifying the existing battery pack and AC adapter to implement that kind of charging?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A quick observation shows that the battery pack looks to be just the cells in series, with a capacitor (perhaps for protection from voltage spikes, it's powering a motor). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My thoughts are that I'll need to make sure the AC adapter can provide enough current to power the device and charge the batteries. The pack will have to somehow be modified to charge the cells in parallel (right?) while powering the device in series. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than those vague ideas, I don't know where to start/how possible this is. So what are the basics I need to know when it comes to building this kind of charger?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Slight Update:&lt;/em&gt; I know I need a circuit to control the recharge, I'm not just looking for a circuit to build, but the basic purposes of that kind of circuit. How does it monitor the charge (and determine when charging is needed)? What are the basic components involved and their purposes? &lt;/p&gt;&#xA;" OwnerUserId="1479" LastEditorUserId="1479" LastEditorDisplayName="" LastEditDate="2010-10-06T18:38:51.783" LastActivityDate="2010-10-07T09:16:02.520" Title="What are the basics of making a rechargeable battery pack?" Tags="&lt;power-supply&gt;&lt;battery&gt;&lt;batteries&gt;&lt;charging&gt;" AnswerCount="4" CommentCount="0" FavoriteCount="1" />
  <row Id="4889" PostTypeId="2" ParentId="4888" CreationDate="2010-10-06T02:04:10.210" Score="4" ViewCount="" Body="&lt;p&gt;You can't just connect an AC adapter to a bunch of rechargeable batteries directly.  Instead you need to have some sort of supervisory circuit to shut off (or taper) the charge when the batteries are fully charged.  These days that is usually done with a specialized IC doing most of the work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a charging &lt;a href=&quot;http://www.talkingelectronics.com/projects/AutoAACharger/AutoAACharger.html&quot; rel=&quot;nofollow&quot;&gt;circuit&lt;/a&gt; that supposedly works with up to 8 AA NiCad cells.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-06T02:04:10.210" CommentCount="1" />
  <row Id="4890" PostTypeId="1" AcceptedAnswerId="4892" CreationDate="2010-10-06T02:20:37.107" Score="3" ViewCount="330" Body="&lt;p&gt;I would like to universal stepper motor driver circuit. Is it possible for one circuit to be able to drive unipolar and bipolar motors with only a firmware change or do they require much different circuits? I know that bipolar motors use 4 wires and unipolar uses 6 so if i use a connector with 6 pins would it be possible?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2010-10-06T09:42:17.720" Title="Unipolar and Bipolar Stepper motors" Tags="&lt;stepper&gt;&lt;driver&gt;" AnswerCount="2" />
  <row Id="4892" PostTypeId="2" ParentId="4890" CreationDate="2010-10-06T03:20:19.783" Score="2" ViewCount="" Body="&lt;p&gt;You can drive a unipolar stepper with a bipolar stepper circuit-- just ignore the center taps.  In fact, it should be more efficient to drive a unipolar stepper this way.  The only reason (that I know of) to drive a unipolar stepper in the traditional way is to simplify the hardware; if you've already got a pair of H-bridges, you may as well use them.&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2010-10-06T03:20:19.783" CommentCount="2" />
  <row Id="4893" PostTypeId="2" ParentId="2226" CreationDate="2010-10-06T03:47:46.840" Score="0" ViewCount="" Body="&lt;p&gt;You could try a JNIB from Ajile Systems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A couple of serial ports, ethernet, USB, runs Java.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ajile.com/index.php?option=com_content&amp;amp;task=view&amp;amp;id=23&amp;amp;Itemid=53&quot; rel=&quot;nofollow&quot;&gt;http://www.ajile.com/index.php?option=com_content&amp;amp;task=view&amp;amp;id=23&amp;amp;Itemid=53&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used their processors and they are very effective to develop on.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-10-06T03:47:46.840" />
  <row Id="4895" PostTypeId="1" AcceptedAnswerId="4903" CreationDate="2010-10-06T08:28:35.457" Score="5" ViewCount="273" Body="&lt;p&gt;I was wondering if anybody was using PLL (Phase Locked Loop) in DIY hobby project? If yes what was the application? Did you made it from discrete components (as opposed from one placed in uController or FPGA) ?&lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T19:06:46.837" LastActivityDate="2011-01-30T13:39:29.267" Title="PLL usage in DIY hobby project" Tags="&lt;clock&gt;&lt;pll&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="2" />
  <row Id="4896" PostTypeId="2" ParentId="2226" CreationDate="2010-10-06T09:06:37.940" Score="0" ViewCount="" Body="&lt;p&gt;I don't see why is it hard for you to find hardware to run existing DOS system? Some ARM Linux SBC could be found for less then 100$ (plus external modem), but why going through all the platform change trouble if current solution runs well? Find some x86 SBC board as a temporary solution, and then only make platform change if you need new features hardly achievable with DOS. Platform change and rewriting all from scratch is very, very time consuming, and can eat all the budget if you don't have a backup plan. And I think you have one. Just googling with words &quot;smallest&quot; &quot;dos&quot; &quot;sbc&quot; gives enough hits for you to start.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-10-06T09:06:37.940" />
  <row Id="4897" PostTypeId="2" ParentId="4890" CreationDate="2010-10-06T09:42:17.720" Score="2" ViewCount="" Body="&lt;p&gt;Sometimes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are actually three stepper motor topologies. &quot;Bipolar&quot;, &quot;Unipolar&quot;, and &quot;Universal&quot; (the parlance I have always heard, anyways).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bipolar motors are 4-leaded, and have two field separate field coils.&lt;br&gt;&#xA;Unipolar motors are 5 leaded, and effectively have 4 field coils, with one end of each connected together (The &quot;Common&quot; lead) See &lt;a href=&quot;http://www.electronics-project-design.com/StepperMotorControl.html&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;.&lt;br&gt;&#xA;Universal motors have 6 leads, and are effectively a center-tapped bipolar motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 5-leaded unipolar motor &lt;strong&gt;cannot&lt;/strong&gt; be driven with a bipolar stepper motor driver. A bipolar driver can only drive a universal or bipolar motor.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-06T09:42:17.720" CommentCount="3" />
  <row Id="4899" PostTypeId="2" ParentId="4866" CreationDate="2010-10-06T10:55:42.797" Score="2" ViewCount="" Body="&lt;p&gt;If you are a student I would HIGHLY recommend National Instruments Multisim. With a valid student ID, or student email, or even a offical transcript you can pick up a copy for $40 dollars. It also comes packaged with Utilboard which is a perfboard layout program. &lt;/p&gt;&#xA;" OwnerUserId="1480" LastActivityDate="2010-10-06T10:55:42.797" CommentCount="2" />
  <row Id="4900" PostTypeId="2" ParentId="4874" CreationDate="2010-10-06T11:20:43.370" Score="1" ViewCount="" Body="&lt;p&gt;RFID for runners times? Do you think that all tags will trigger at exactly the same distance from tag reader? I don't think so, and that will ruin accuracy a lot. For simplicity, imagine that you have single reader located exactly on the finish line. How will you know if runner is 2m from crossing the line in front of the reader, or just crossing the finish line 2m to the left or right? Do you plan to have more then one reader? I don't think that you have chosen the right technology to solve this problem...&lt;/p&gt;&#xA;" OwnerUserId="1129" LastEditorUserId="1129" LastEditorDisplayName="" LastEditDate="2010-10-06T11:41:00.973" LastActivityDate="2010-10-06T11:41:00.973" CommentCount="4" />
  <row Id="4901" PostTypeId="2" ParentId="765" CreationDate="2010-10-06T11:27:45.900" Score="0" ViewCount="" Body="&lt;p&gt;One more clever approach:&#xA;Make use of the bigger thermal conductivity of the water (fluid). The idea is to have temperature sensor and measure difference of its self heating when submerged and when in free air.&lt;/p&gt;&#xA;" OwnerUserId="1471" LastActivityDate="2010-10-06T11:27:45.900" />
  <row Id="4902" PostTypeId="2" ParentId="4842" CreationDate="2010-10-06T11:36:59.377" Score="1" ViewCount="" Body="&lt;p&gt;If you already have AD sampling with PIC, then you might consider software only detection of CSYNC.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-10-06T11:36:59.377" CommentCount="1" />
  <row Id="4903" PostTypeId="2" ParentId="4895" CreationDate="2010-10-06T13:09:23.933" Score="3" ViewCount="" Body="&lt;p&gt;I used a PLL made of a Signetics NE565 PLL chip plus a few discrete components in a walkie-talkie. It was used for FM demodulation at 300 kHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From Google, it looks like Signetics has been bought by NXP; I can't find a product page for the chip.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-06T13:09:23.933" CommentCount="1" />
  <row Id="4904" PostTypeId="1" AcceptedAnswerId="4912" CreationDate="2010-10-06T13:13:56.433" Score="4" ViewCount="326" Body="&lt;p&gt;I'm looking for a small, 32KB or so SRAM device that two MCUs can read or write (at two different times; I don't need simultaneous reading/writing.) It would be good if it used a serial interface as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem I'm trying to solve is sending data between two devices without the other device having to pause to receive this. I would transfer an audio sample into the buffer, then the other chip, as required, would read the audio out, and do something with it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found serial SRAM's like Microchip's 23A256/23K256, however, they seem to have a single serial interface. Is there any way to have two chips accessing this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally, the receiving device only has 2KB data memory free (maximum) so it looks like using DMA or some similar transfer mechanism through I2C or other interface will not work.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-10-06T15:58:44.440" LastActivityDate="2011-01-02T05:24:05.393" Title="SRAM which two chips can read/write" Tags="&lt;pic&gt;&lt;memory&gt;&lt;sharedbus&gt;" AnswerCount="4" FavoriteCount="3" />
  <row Id="4905" PostTypeId="1" AcceptedAnswerId="4911" CreationDate="2010-10-06T13:26:03.423" Score="7" ViewCount="395" Body="&lt;p&gt;I am currently working on Super OSD - an on screen display project. &lt;a href=&quot;http://code.google.com/p/super-osd&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/super-osd&lt;/a&gt; has all the details.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the moment I'm using a dsPIC MCU to do the job. This is a very powerful DSP (40 MIPS @ 80 MHz, three-register single-cycle operations and a MAC unit) and, importantly, it comes in a DIP package (because I'm using a breadboard to prototype it.) I'm really getting every last bit of performance out of it running the OSD - the chip has about 200ns or 10 cycles per pixel on the output stage so the code has to be very optimised in this part (for this reason it will always be written in assembly.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I was considering using an FPGA for this because due to the parallel architecture of such a chip it is possible to have a simple logic program running the OSD. Things like drawing lines and algorithmic code would be handled by an MCU, but the actual output would be done with an FPGA. And some simple things like setting pixels or drawing horizontal and vertical lines I would like to integrate onto the FPGA, to improve speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have some questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Will it cost significantly more? The cheapest FPGA's I found were ~£5 each and the dsPIC is £3 each. So it will cost more, but by how much?&lt;/li&gt;&#xA;&lt;li&gt;The dsPIC fits in a SO28 package. I would not like to go bigger than SO28 or TQFP44. Most FPGA's I've seen come in BGA or TQFP&gt;100 packages, which aren't an option at the moment, due to the shear size, and the difficulty of soldering them myself.&lt;/li&gt;&#xA;&lt;li&gt;How much current is used by an FPGA? The dsPIC solution currently consumes about 55mA +/- 10mA, which is okay at the moment. Would an FPGA consume more or less? Is it variable, or is it pretty much static, like the dsPIC?&lt;/li&gt;&#xA;&lt;li&gt;I need at least 12KB of graphics memory to store the OSD graphics. Do FPGA's have this kind of memory available on the chip or is this only available with external chips?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-25T20:23:21.763" Title="Is an FPGA viable for such a project?" Tags="&lt;fpga&gt;&lt;dspic&gt;&lt;microcontroller&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="4906" PostTypeId="2" ParentId="4895" CreationDate="2010-10-06T13:29:10.203" Score="2" ViewCount="" Body="&lt;p&gt;I use the onboard PLL on dsPIC processors. Normally designed to operate at 40 MHz output (80 MHz internally) it will go up to 65 MHz with no sign of problems. This was on a breadboard, but the only part connected to the breadboard was the chip's pin, connected to a scope probe. The PLL is only designed for internal use by the chip as the CPU clock. But it can be used to synthesise frequencies.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-06T13:29:10.203" />
  <row Id="4907" PostTypeId="2" ParentId="4904" CreationDate="2010-10-06T13:42:27.097" Score="2" ViewCount="" Body="&lt;p&gt;The easiest way would be to implement a multi-master SPI bus. You could use two additional I/O lines between the masters for arbitration using a handshaking mechanism.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-06T13:42:27.097" />
  <row Id="4908" PostTypeId="2" ParentId="4904" CreationDate="2010-10-06T13:43:36.580" Score="2" ViewCount="" Body="&lt;p&gt;I see two possible solutions for your problem: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Find FIFO chip that is suitable for your needs (one &lt;a href=&quot;http://www.datasheetcatalog.org/datasheets/700/373887_DS.pdf&quot; rel=&quot;nofollow&quot;&gt;example&lt;/a&gt;). It may be not be simple/possible to use as I do not know if  FIFO chip with simple interface (such as SPI) exist. The FIFOs I know have parallel interface.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Share the mentioned SRAM from Microchip with two SPI masters (in two uControllers). When first is in use, the SPI ports in other uController have to be in high impedance and opposite when second uController will use the SRAM. You will need some simple handshake interface between uControllers (something like read request/read done/busy lines). This can be implemented using 2 or 3 unidirectional connections between uControllers. Your imagination is the limit.&lt;/p&gt;&#xA;" OwnerUserId="1471" LastActivityDate="2010-10-06T13:43:36.580" />
  <row Id="4909" PostTypeId="2" ParentId="4895" CreationDate="2010-10-06T13:45:50.990" Score="1" ViewCount="" Body="&lt;p&gt;I use the on-chip PLL’s in Microchip PIC parts to increase the clock frequency. They work fine for me. The only problem I've had with them is when I’ve set them up incorrectly. This causes you to get a clock frequency different from what you are expecting. I’ve found that outputting the clock to an I/O pin then taking a mesasurement with an oscilloscope can easily detect this issue.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-06T13:45:50.990" />
  <row Id="4910" PostTypeId="2" ParentId="4905" CreationDate="2010-10-06T14:24:53.993" Score="4" ViewCount="" Body="&lt;p&gt;You could use a CPLD rather than an FPGA, such as one of the Altera MAX II parts. They are available in QFP44 packages, unlike FPGAs. They are actually small FPGAs, but Altera plays down that aspect. CPLDs have an advantage over most FPGAs in that they have on-chip configuration memory, FPGAs generally require an external flash chip. There are other CPLDs, of course, but I like the MAX II.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's impossible to say what the current consumption will be, as it depends on clock speeds and the amount of logic that is actually in use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FPGAs usually have a limited amount of on-chip memory you can use, but you will need external memory with a CPLD.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option would be an &lt;a href=&quot;http://www.xmos.com/&quot; rel=&quot;nofollow&quot;&gt;XMOS&lt;/a&gt; chip, but the smallest one (the XS1-L1) is in a QFP64 package. It has plenty of on-chip RAM - 64k.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-10-06T15:00:08.870" LastActivityDate="2010-10-06T15:00:08.870" />
  <row Id="4911" PostTypeId="2" ParentId="4905" CreationDate="2010-10-06T15:01:27.270" Score="6" ViewCount="" Body="&lt;p&gt;In principle this is good candidate for FPGA based design. Regarding your requirements:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;ad 1. The FPGA most likely will be more expensive, by how much that depends on the device you choose. At first glance smallest Spartan 3 from Xilinx (XC3S50AN) will be more then enough for this task (~10£ from Farnell). I think you can assume this is upper boundary for the cost (it has 56kB RAM inside, so it is more then you need). You may find cheaper device either from Xilinx offering or their competitors Altera and Lattice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ad 2. The package is the tough issue, I did not saw FPGA with smaller footprint either. However maybe you can use CPLD device (for sake of argument the CPLDs are small FPGAs) which may be in smaller package (PLCC or QFN). On plus side they will be cheaper (even single $) on negative side most likely will not have RAM inside. With CPLD probably you would need external SRAM chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ad 3. FPGAs and CPLD current consumption is highly dependent on the programmed design. However there is good chance that FPGA and especially CPLD design would consume less than your current solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ad 4. FPGA do have that kind of memory inside, CPLD most certainly not. This may be solved by external sram chip (or two). For example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;|SRAM 1| &amp;lt;--&gt; |CPLD| &amp;lt;--&gt; |uC|&lt;br&gt;&#xA;|SRAM 2| &amp;lt;--&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In such arrangement while the uC is writing to SRAM 1, the CPLD will be displaying data from SRAM 2. The CPLD should be able to handle both task simultaneously.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course you can solve this in other ways too:&lt;br&gt;&#xA;1) use faster uController (ARM for example)&lt;br&gt;&#xA;2) use device with some programmable fabric and uC inside (for example FPSLIC from Atmel, however I have never used such devices and I know very little about those)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Standard disclaimer -&gt; as designs are open problems, with many constrains and possible solutions whatever I wrote above may not be true for your case. I believe it is worth checking those option, though.&lt;/p&gt;&#xA;" OwnerUserId="1471" LastActivityDate="2010-10-06T15:01:27.270" />
  <row Id="4912" PostTypeId="2" ParentId="4904" CreationDate="2010-10-06T15:57:51.673" Score="8" ViewCount="" Body="&lt;p&gt;You don't need dual-port RAM or even a serial RAM with two interfaces; For SPI it's a little trickier, but I2C allows multiple masters &quot;out of the box.&quot;  Either way, your software will have to monitor the bus conditions to see if it lost the bus and if so, wait for another opportunity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For SPI, the MOSI, CS and CLK lines must be tri-stated (or open-collector) with pull-up resistors to keep the lines from floating. You will also need some kind of bus arbitration. This can be as simple as a single GPIO between the two masters so that the one with higher priority signals the lower-priority master that the bus is unavailable, but a more elegant solution would be a single open-collector line between the masters.  When the bus is idle, neither master is yanking the line down so it floats high with a pull-up. The logic is that if the line is high, the bus is available.  The master that wants to use the memory would look at the &quot;bus available&quot; line and if it's high, drive the line low and wait a few ms to make sure the other master didn't grab the bus at the same time. If the RAM SPI CS line is still inactive, it can be safe to assume that the bus is yours. Do the transfer, tri-state your MOSI/CLK lines and let go of the &quot;bus active&quot; signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;wait a few ms after yanking the bus request line low&quot; is necessary since it is possible for both masters to grab the line at the same time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are only ever using one shared device and that device does not require multiple transfers, you could use its CS line as the &quot;bus available&quot; signal, but this isn't quite as robust.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-06T15:57:51.673" CommentCount="4" />
  <row Id="4913" PostTypeId="2" ParentId="4799" CreationDate="2010-10-06T17:07:42.513" Score="0" ViewCount="" Body="&lt;p&gt;if there are any specific sensors you need to interface to, ask away :)&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-06T17:07:42.513" />
  <row Id="4914" PostTypeId="2" ParentId="4384" CreationDate="2010-10-06T17:12:22.560" Score="1" ViewCount="" Body="&lt;p&gt;I was able to simulate this circuit and play around with it a bit. The relationship between the voltage of the solar cell, the 330k resistor and the 10nF cap sets the operating frequency of the circuit. The difficulty in inverting this relationship is that the condition in which you want highest frequency (low light) also corresponds to the condition where VCC is lowest. Unless you can introduce an additional voltage supply independent of the solar cell, I don't see how you can achieve what you want. Sorry...&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-06T17:12:22.560" />
  <row Id="4915" PostTypeId="2" ParentId="4799" CreationDate="2010-10-06T17:16:25.657" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/1441918388&quot; rel=&quot;nofollow&quot;&gt;Handbook of Modern Sensors [3rd Edition] by Jacob Fraden&lt;/a&gt;&lt;br&gt;&#xA;ISBN: 1441918388&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This reference book covers a number of different types of sensors and the circuits that can be used to read them.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-06T17:16:25.657" />
  <row Id="4916" PostTypeId="1" CreationDate="2010-10-06T18:43:45.643" Score="2" ViewCount="267" Body="&lt;p&gt;Hi,&#xA;I am looking for a PIC which has a webserver builtin or has the ability to install one(with) . I want to experiment connecting  in reasonable price please)two PIC/PICAXE boards or different type and send data from one to another. I will be running a server program in the webserver where I want to capture the data sent from 2nd PIC board. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1491" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:01:09.683" LastActivityDate="2011-03-04T16:32:07.157" Title="Looking for a PIC board with webserver" Tags="&lt;pic&gt;&lt;programming&gt;&lt;picaxe&gt;&lt;tcp-ip&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="4917" PostTypeId="2" ParentId="4916" CreationDate="2010-10-06T18:54:36.503" Score="3" ViewCount="" Body="&lt;p&gt;Any PIC18+ can run the Microchip TCP/IP stack which includes a web server and is a free download from their website.  All you need is a PIC based dev board with ethernet circuitry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2807&amp;amp;devicefamilyid=2231&amp;amp;page=wwwdevWiredConnectivity&quot; rel=&quot;nofollow&quot;&gt;Microchip sells a few such dev boards directly&lt;/a&gt;, they also have some wifi boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There may also be some third party dev boards that are cheaper, I have no experience with those however, I've only works with the ones straight from uC.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-06T18:54:36.503" />
  <row Id="4918" PostTypeId="2" ParentId="4916" CreationDate="2010-10-06T18:55:38.627" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en028217&quot; rel=&quot;nofollow&quot;&gt;DM163024  - PICDEM.NET 2&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-06T18:55:38.627" />
  <row Id="4919" PostTypeId="2" ParentId="4905" CreationDate="2010-10-06T18:58:38.590" Score="2" ViewCount="" Body="&lt;p&gt;1) Yes, the FPGA will be more expensive.  Not only is the chip itself more expensive, but you will also need Flash memory to store the programming.  FPGA + Flash is probably 3x the cost of just the dsPIC...about $10 for a small FPGA and $3 for small Flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) They may exist, but I'm not really aware of any FPGA that's not surface mount.  Most of them are probably QFP or BGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) The FPGA will probably pull about 3x the current that the dsPIC does, but that can go up or down depending on what features you use.  FPGAs have many features that can increase power draw.  But expect at least 150 mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) FPGAs usually have block RAM inside them.  All but the smallest FPGAs should have that much memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Others mention CPLDs.  If you carefully partition your design, you could probably move some small but expensive operations into the CPLD.  It would be like a mini co-processor.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-06T18:58:38.590" />
  <row Id="4920" PostTypeId="2" ParentId="4905" CreationDate="2010-10-06T19:15:03.897" Score="2" ViewCount="" Body="&lt;p&gt;Cheapest solution with the lowest learning curve would be to move to a higher powered processor, ARM most likely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Programming a FPGA/CPLD in VHDL/Verilog is a pretty steep learning curve coming from C for many people.  They also aren't overly cheap parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a decently capable ARM maybe a LPC1769? (cortex-M3) you would also likely be able to replace the PIC18 in your design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the through hole issue, as long as you can get the SoC in an exposed pin QFP type package, &lt;a href=&quot;http://www.futurlec.com/SMD_Adapters.shtml&quot; rel=&quot;nofollow&quot;&gt;just grab some of these adapters&lt;/a&gt; for the needed pin out for your prototyping.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-06T19:15:03.897" CommentCount="2" />
  <row Id="4921" PostTypeId="2" ParentId="4916" CreationDate="2010-10-06T19:32:33.093" Score="1" ViewCount="" Body="&lt;p&gt;I think the simplest and cheapest solution for you is this product:  &lt;a href=&quot;http://www.ezweblynx.com/&quot; rel=&quot;nofollow&quot;&gt;EZ Web Lynx&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-06T19:32:33.093" />
  <row Id="4922" PostTypeId="2" ParentId="4888" CreationDate="2010-10-06T19:57:02.677" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;The pack will have to somehow be&#xA;  modified to charge the cells in&#xA;  parallel (right?) while powering the&#xA;  device in series.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yep.  A relay is an easy way to do this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See &lt;a href=&quot;http://www.batteryuniversity.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.batteryuniversity.com/&lt;/a&gt; for the specific type of battery you're using.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To recharge &lt;a href=&quot;http://www.batteryuniversity.com/partone-13.htm&quot; rel=&quot;nofollow&quot;&gt;lead-acid batteries, for instance&lt;/a&gt;, you start out with a trickle charge to make sure the battery doesn't have any shorted cells, etc.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When it's up to a certain threshold, you do a constant-current charge.  The maximum current is specified by the battery manufacturer.  (You measure the current with a small current-sensing resistor in series with the battery.  A 0.1 ohm resistor with 100 mV across it has a current of 1 A going through it, for instance.)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After the constant current stage, you apply a large constant voltage, and then when that stops taking current, you drop back down to a float charge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are &lt;a href=&quot;http://www.batteryuniversity.com/partone-11.htm&quot; rel=&quot;nofollow&quot;&gt;instructions for nickel batteries&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-06T19:57:02.677" />
  <row Id="4923" PostTypeId="1" AcceptedAnswerId="4924" CreationDate="2010-10-06T20:00:38.080" Score="4" ViewCount="234" Body="&lt;p&gt;I want to measure how much power my PIC is using. At the output of my 3.3V regulator I put a 1 ohm resistor in series with the rest of the circuit. I was going to measure the voltage drop across that resistor to get the current and so on. With the 1 ohm resistor installed the circuit works just fine but when I put the probe of my o'scope across it it my 3.3V goes to zero. It seems as though the scope is creating a short to ground or something. Does anyone know why this happens or how to make it stop?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2010-10-06T20:59:55.060" Title="Why does Oscilloscope cause short?" Tags="&lt;power&gt;&lt;circuit&gt;&lt;current&gt;&lt;oscilloscope&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="4924" PostTypeId="2" ParentId="4923" CreationDate="2010-10-06T20:02:39.397" Score="12" ViewCount="" Body="&lt;p&gt;The ground clip on your o-scope is actually tied to ground. it is a hard short and rather low resistance. This means that you are shorting the 3.3 rail to ground with your ground probe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To fix this there are two options, &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Put the resistor in the return path&#xA;so that one side of it is ground.&#xA;That way the ground probe does not&#xA;hurt it. &lt;/li&gt;&#xA;&lt;li&gt;Use two probes, one for&#xA;each side of the resistor and use&#xA;the math function on your O-Scope.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Let me know if this is not clear. I can add more information.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-06T20:02:39.397" CommentCount="11" />
  <row Id="4925" PostTypeId="2" ParentId="4923" CreationDate="2010-10-06T20:14:29.157" Score="1" ViewCount="" Body="&lt;p&gt;Maybe another channel is already tied up to the real ground of the system, of the scope is sharing the same real ground in another way. It's not like the normal probes on your scope are + and - , they are actually Voltage and Ground (single-ended).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really would like to measure + and - , you would need a differential probe. But I guess you haven't got those lying around, so using 2 probes on both sides, or moving your resistor to the low-side of your device could work more practical.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-10-06T20:14:29.157" CommentCount="0" />
  <row Id="4926" PostTypeId="2" ParentId="4916" CreationDate="2010-10-06T20:21:25.453" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://dangerousprototypes.com/docs/Web_Platform&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com/docs/Web_Platform&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.seeedstudio.com/depot/web-platform-assembled-p-582.html&quot; rel=&quot;nofollow&quot;&gt;http://www.seeedstudio.com/depot/web-platform-assembled-p-582.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://dangerousprototypes.com/docs/images/thumb/8/86/Webpbrd.png/490px-Webpbrd.png&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://dangerousprototypes.com/docs/images/thumb/e/ef/Webpcct.png/490px-Webpcct.png&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-04T16:32:07.157" LastActivityDate="2011-03-04T16:32:07.157" />
  <row Id="4927" PostTypeId="2" ParentId="4923" CreationDate="2010-10-06T20:59:55.060" Score="5" ViewCount="" Body="&lt;p&gt;Does the circuit need to be grounded?  If you can supply it from a battery or double-insulated power brick, you should be able to connect any single point to the scope probe's Earth ground without affecting the functionality.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-06T20:59:55.060" />
  <row Id="4928" PostTypeId="1" CreationDate="2010-10-06T21:14:26.903" Score="2" ViewCount="141" Body="&lt;p&gt;I'm Looking at using one of the TI ARM chips (see list below) and I'm wondering what I should be looking for to do experiments with, the computer equivalent of breadboarding. I've seen Development boards, Evaluation Kit and a few others. I've also seen price ranges from $50-$5000 (clearly I'm more interested in the $50 end) so I' guessing some of these are WAY more than what I'm looking for. Mostly what I want is a board that wires the chip to power and IO connectors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The chips I'm look at are TI's Stellaris serise:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;LM3S{6618, 6753, 6911, 6918, 6938, 6950&#xA;     6965, 8730, 8733, 8738, 8930, 8933&#xA;     8938, 8962, 8970, 8971, 9781, 9790&#xA;     9792, 9997, 9b81, 9b90, 9b92, 9b95}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1182" LastEditorUserId="1182" LastEditorDisplayName="" LastEditDate="2010-10-07T02:50:19.907" LastActivityDate="2010-10-07T02:50:19.907" Title="Where can I get a microcontroller board for TI Stellaris?" Tags="&lt;arm&gt;&lt;kit&gt;&lt;development&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="4929" PostTypeId="2" ParentId="4928" CreationDate="2010-10-06T21:38:48.117" Score="6" ViewCount="" Body="&lt;p&gt;I have one of the Stellaris EKT-LM3S6965 boards. It has an LCD, ethernet and other goodies. All of the pins are broken out to pads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;JTAG is provided by an FTDI chip onboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Very easy to work with. See this question for dev tools:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/991/arm-cortex-m3-development-tools/3621&quot;&gt;http://electronics.stackexchange.com/questions/991/arm-cortex-m3-development-tools/3621&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://media.digikey.com/photos/Luminary%20Micro%20Photos/EKT-LM3S6965.JPG&quot; width=&quot;200&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-06T23:22:49.383" LastActivityDate="2010-10-06T23:22:49.383" CommentCount="2" />
  <row Id="4930" PostTypeId="2" ParentId="4928" CreationDate="2010-10-06T21:48:22.610" Score="-2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_%28MSP-EXP430G2%29?DCMP=launchpad&amp;amp;HQS=Other+OT+launchpadwiki/&quot; rel=&quot;nofollow&quot; title=&quot;MSP430&quot;&gt;The Launchpad&lt;/a&gt; by Texas Instruments, is a simple development board, with a usb programmer. It may be more simple than you are searching for but you can't beat a $4.30 price tag. &lt;/p&gt;&#xA;" OwnerUserId="92" LastActivityDate="2010-10-06T21:48:22.610" CommentCount="1" />
  <row Id="4933" PostTypeId="1" CreationDate="2010-10-06T23:39:39.353" Score="1" ViewCount="235" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a binary of the form &quot;.out&quot;, from a project that was generated by an IAR development suite. The release directory does not have an ELF or HEX file. This is for the STM32F103 ARM based micro controller. I need to program the binary onto a board off site an so I will not have an IAR development suite.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I use a JTAG debugger like the Segger J-Link or Atollic's ST-Link to program the board with the .out file? I know I can program .ELF file in this way. Is it possible with .out files? Can I convert it to an ELF file?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1411" LastActivityDate="2010-10-07T10:06:02.473" Title="Can I load program a micro with a .out file like I can with an ELF or HEX?" Tags="&lt;jtag&gt;" AnswerCount="2" />
  <row Id="4934" PostTypeId="2" ParentId="4933" CreationDate="2010-10-07T00:06:21.550" Score="1" ViewCount="" Body="&lt;p&gt;Yes.  The .out file is actually and ELF file.  Set the debugger in your IAR project options to be J-Link/J-Trace.  In the download tab, check &quot;Verify download&quot; and &quot;Use flash loader(s)&quot;.  When you debug the project, the microcontroller is programmed as part of the debugging process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you would like, you can also choose the &quot;Output Converter&quot; category on the project options dialog and generate an output file in addition to the .out file.  You probably have choices of Motorola S-record, Intel-Hex, or straight binary.&lt;/p&gt;&#xA;" OwnerUserId="529" LastEditorUserId="529" LastEditorDisplayName="" LastEditDate="2010-10-07T00:14:01.377" LastActivityDate="2010-10-07T00:14:01.377" CommentCount="2" />
  <row Id="4935" PostTypeId="2" ParentId="4933" CreationDate="2010-10-07T00:07:25.307" Score="1" ViewCount="" Body="&lt;p&gt;I use OpenOCD to program Cortex-M3 microcontrollers over JTAG. It works with many JTAG adapters including Olimex ARM-OCD-USB, Segger J-Link and Bus Pirate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd guess that the .out is the raw binary to be copied to flash.&#xA;When JTAG loading, you need this binary as you're writing direct to the flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the .out is in fact an ELF file. Use objdump to convert it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;file&quot; on a linux system can identify ELF files:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;$ jrt@linux: file myfile.elf&#xA;ELF 32-bit LSB executable, ARM, version 1 (SYSV), statically linked, not stripped&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;But, not raw ARM binaries&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;$ jrt@linux: file myfile.bin &#xA;myfile.out: data&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;To see if your .out is an ARM binary, you could disassemble it. Or, just hexdump the start and look for what you expect at location 0 (likely the interrupt vectors).&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;$ xxd myfile.out | head&#xA;&#xA;0000000: 7037 0020 fd52 0300 6553 0300 6d53 0300  p7. .R..eS..mS..&#xA;0000010: 8553 0300 7953 0300 8553 0300 0000 0000  .S..yS...S......&#xA;0000020: 0000 0000 0000 0000 0000 0000 8553 0300  .............S..&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The ELF cannot be recreated from this. The &lt;a href=&quot;http://en.wikipedia.org/wiki/Intel_HEX&quot; rel=&quot;nofollow&quot;&gt;Intel Hex&lt;/a&gt; file is another version of the binary. It's a list of addresses and chunks of data to write to the flash, but may contain holes.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-07T10:06:02.473" LastActivityDate="2010-10-07T10:06:02.473" CommentCount="3" />
  <row Id="4936" PostTypeId="2" ParentId="4888" CreationDate="2010-10-07T02:05:02.013" Score="1" ViewCount="" Body="&lt;p&gt;Batteries can be very temperamental, depending on chemistry, which you don't mention. If you get the voltages wrong even by a little bit it can mean the difference between long life and short life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lithium-ion is really several different types of chemistries but all are rather fickle for charging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This isn't perhaps the best answer but if you really depend on having your batteries last longer, don't do it yourself -- use the manufacturer's charger.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2010-10-07T02:05:02.013" CommentCount="1" />
  <row Id="4937" PostTypeId="1" CreationDate="2010-10-07T04:19:57.907" Score="2" ViewCount="363" Body="&lt;p&gt;I'm having trouble talking to an Arduino Mega using serial port commands on Windows. Identical code works fine to connect to an Arduino Duemilanove but doesn't allow connection to the serial port with the Mega. Also, I can access both cards from the Arduino IDE software, on both Linux and Windows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have serial port code that works fine on Linux for both Duemilanove and Mega. But I can't write code that works for the Mega on Windows, even though it works fine with the Duemilanove at this stage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My only thought is that perhaps something is different in the way that the Mega's USB-to-serial hardware is set up, and perhaps, at least on Windows, I need to add some additional command (maybe on the Arduino, or maybe in my C code) to enable the interface to be correctly visible/accessible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any thoughts anyone? Anyone else had this problem?&lt;/p&gt;&#xA;" OwnerUserId="1495" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-24T03:45:20.973" LastActivityDate="2011-02-24T03:45:20.973" Title="Connect to Arduino Mega serial interface by C code" Tags="&lt;arduino&gt;&lt;serial&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="4938" PostTypeId="1" AcceptedAnswerId="4946" CreationDate="2010-10-07T05:28:28.323" Score="1" ViewCount="109" Body="&lt;p&gt;Someone pointed me at the freeware version of Eagle as a good starter dev tool. So I start playing around and I can't seem to find a part library for the chips I want to use. I found a library (the works) on the eagle site but it doesn't have the right parts and I found a library on the TI/Luminary Mico site (that I think has the right part) but it wont load (it has .src files and I seem to need .lbr) despite the fact it has files tagged specifically as for eagle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know where I can get files that will work? (Or how to make the files I have work?)&lt;/p&gt;&#xA;" OwnerUserId="1182" LastActivityDate="2010-10-07T10:15:22.200" Title="Stellaris 6/8/9000 part libraries for Eagle?" Tags="&lt;pcb&gt;&lt;software&gt;&lt;library&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="4939" PostTypeId="1" AcceptedAnswerId="4940" CreationDate="2010-10-07T05:39:41.587" Score="1" ViewCount="192" Body="&lt;p&gt;Ipad doesn't charge while in use and connected to the usb port. It definitely charges when connected to the supplied 10 watt power adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The USB port, as far as I know, supplies 5 watts. Can we modify it by simply adding an extra usb adapter to the cable of ipad to draw the extra 5 watt? something which the older external hard-drives used to do?&lt;/p&gt;&#xA;" OwnerUserId="1446" LastActivityDate="2010-10-07T10:43:29.057" Title="Ipad charging via usb port." Tags="&lt;power-supply&gt;&lt;battery&gt;&lt;ipad&gt;" AnswerCount="3" />
  <row Id="4940" PostTypeId="2" ParentId="4939" CreationDate="2010-10-07T06:25:32.393" Score="3" ViewCount="" Body="&lt;p&gt;You may find this &lt;a href=&quot;http://forums.adafruit.com/viewtopic.php?f=15&amp;amp;t=16729&amp;amp;hilit=ipad&quot; rel=&quot;nofollow&quot;&gt;thread&lt;/a&gt; over at adafruit of interest. Some people have stripped down various chargers for the iPad (including the Apple one) and published the schematics for everyone to analyse. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-07T06:25:32.393" />
  <row Id="4941" PostTypeId="2" ParentId="4939" CreationDate="2010-10-07T06:37:42.920" Score="1" ViewCount="" Body="&lt;p&gt;USB supplies per specification only 5V * 0.5A = 2.5 Watt maximum. Even my mobile phone (Sony, not Apple though) does not charge to 100% on an USB port.&lt;/p&gt;&#xA;" OwnerUserId="1472" LastActivityDate="2010-10-07T06:37:42.920" CommentCount="1" />
  <row Id="4942" PostTypeId="1" AcceptedAnswerId="5963" CreationDate="2010-10-07T08:28:13.687" Score="4" ViewCount="314" Body="&lt;p&gt;A project has finally reached the point where prototypes are operational and ducks are lining up in rows for the first pre-production lot of boards. It uses a SOC device that boots its ARM core from an external NAND FLASH chip, which normally contains a boot loader, the embedded application, and other data resources. With a minimal boot loader and application in FLASH, it is easy to field upgrade. The prototypes got boot loaders installed with a JTAG cable, but that seems more than a little unwieldy for production lots larger than a dozen or so boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this were a NOR FLASH or OTP PROM I would expect a vendor to be happy to take an Intel HEX or Motorola SRecord file and deliver devices that just work when soldered down. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given the different nature of NAND FLASH devices, what issues should we be watching for? &#xA;What questions should we be asking vendors? &#xA;What form of image should we be expecting to be able to supply?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In short, what is the usual practice for pre-programming a NAND FLASH device before assembly?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it were to make a difference, it is an STM (numonyx or micron, why can't the chip companies stop selling each other their product lines mid design cycle?) NAND512xxx 512 Mb SLC family device that wants programming.&lt;/p&gt;&#xA;" OwnerUserId="1494" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-08T00:43:42.677" LastActivityDate="2011-03-02T18:41:49.173" Title="Best practices for production programming of data/NAND flash devices" Tags="&lt;programming&gt;&lt;flash&gt;&lt;pcb-assembly&gt;" AnswerCount="5" />
  <row Id="4943" PostTypeId="2" ParentId="4895" CreationDate="2010-10-07T09:08:14.297" Score="0" ViewCount="" Body="&lt;p&gt;I've also only used PLL's in clock systems for AVR (tiny26) and FPGA (NIOS) applications.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-10-07T09:08:14.297" />
  <row Id="4944" PostTypeId="2" ParentId="4888" CreationDate="2010-10-07T09:16:02.520" Score="1" ViewCount="" Body="&lt;p&gt;This Maxim appnote talks about similar setups (especially Li).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/3241&quot; rel=&quot;nofollow&quot;&gt;http://www.maxim-ic.com/app-notes/index.mvp/id/3241&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also see whether you can do constant voltage charging, but it's usually not ideal. It all does depend on the batteries and usage patterns.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-10-07T09:16:02.520" />
  <row Id="4945" PostTypeId="2" ParentId="4942" CreationDate="2010-10-07T10:05:26.967" Score="1" ViewCount="" Body="&lt;p&gt;When I've done similar things, I've always programmed the SoC with JTAG (or a gang programmer) then had the ARM core format and program the NAND flash (being fed data over serial or ethernet).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This way, the software can map out any bad blocks in the NAND.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-07T10:05:26.967" CommentCount="2" />
  <row Id="4946" PostTypeId="2" ParentId="4938" CreationDate="2010-10-07T10:15:22.200" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;ftp://ftp.cadsoft.de/eagle/userfiles/libraries/luminary-arm.lbr&quot; rel=&quot;nofollow&quot;&gt;ftp://ftp.cadsoft.de/eagle/userfiles/libraries/luminary-arm.lbr&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Symbols and footprints for: &#xA;LM3S101&#xA;LM3S102&#xA;LM3S301&#xA;LM3S310&#xA;LM3S315&#xA;LM3S316&#xA;LM3S328&#xA;LM3S601&#xA;LM3S610&#xA;LM3S613&#xA;LM3S615&#xA;LM3S628&#xA;LM3S6911&#xA;LM3S6918&#xA;LM3S6938&#xA;LM3S6950&#xA;LM3S6952&#xA;LM3S6965&#xA;LM3S801&#xA;LM3S811&#xA;LM3S812&#xA;LM3S815&#xA;LM3S828&#xA;LM3S8962&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-07T10:15:22.200" CommentCount="1" />
  <row Id="4947" PostTypeId="2" ParentId="4939" CreationDate="2010-10-07T10:43:29.057" Score="0" ViewCount="" Body="&lt;p&gt;No. The ability to use the USB interface for data while charging requires some negotiation WRT current capabilities when the USB device is connected to the computer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, the computer has to tell the iPad that it can source 2A once it is connected. The charger does this by pulling some of the USB data lines high or low. However, this precludes data transfer.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-07T10:43:29.057" CommentCount="2" />
  <row Id="4948" PostTypeId="2" ParentId="4942" CreationDate="2010-10-07T10:48:45.037" Score="2" ViewCount="" Body="&lt;p&gt;The trick here is &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8870&quot; rel=&quot;nofollow&quot;&gt;PogoPins&lt;/a&gt; (&lt;a href=&quot;http://en.wikipedia.org/wiki/Pogo_pin&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically you make a jig where you drop the board in  often descriped as a Bed-Of-Nails &lt;a href=&quot;http://en.wikipedia.org/wiki/In-circuit_test&quot; rel=&quot;nofollow&quot;&gt;In-Circuit Tester&lt;/a&gt;/programmer, and it's then flashed without having to deal with the connector-mating aspect of the jtag interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LadyAda did a &lt;a href=&quot;http://ladyada.net/make/pogojig/&quot; rel=&quot;nofollow&quot;&gt;tutorial&lt;/a&gt;, and so did &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=138&quot; rel=&quot;nofollow&quot;&gt;SparkFun&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-07T10:48:45.037" CommentCount="2" />
  <row Id="4949" PostTypeId="2" ParentId="4865" CreationDate="2010-10-07T10:56:49.070" Score="2" ViewCount="" Body="&lt;p&gt;Does ladyada recommend the 2N2907? I did not see a label on the schematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the transistor is being used as a switch a better choice would be a 2N3906&#xA;which has much lower Vbe(sat) and Vce(sat) specifications.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T11:34:49.043" LastActivityDate="2011-05-18T11:34:49.043" />
  <row Id="4951" PostTypeId="1" AcceptedAnswerId="4953" CreationDate="2010-10-07T11:51:13.317" Score="6" ViewCount="371" Body="&lt;p&gt;Say I have a 1F capacitor that is charged up to 5V. Then say I connect the cap to a circuit that draws 10 mA of current when operating between 3 and 5 V. What equation would I use to calculate the voltage across the capacitor, with respect to time, as it is discharging and powering the circuit?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2010-10-07T12:13:34.463" Title="How do I calculate how fast a capacitor will discharge?" Tags="&lt;capacitor&gt;&lt;discharge&gt;" AnswerCount="2" FavoriteCount="3" />
  <row Id="4952" PostTypeId="2" ParentId="4951" CreationDate="2010-10-07T11:53:54.073" Score="0" ViewCount="" Body="&lt;p&gt;delta U = I*T/C for DC current only! (I - current, T - time, C - capacitance).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;in general:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;u(t) = (1/C)  * integration(i(t))&lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="1471" LastEditorDisplayName="" LastEditDate="2010-10-07T12:05:59.210" LastActivityDate="2010-10-07T12:05:59.210" CommentCount="5" />
  <row Id="4953" PostTypeId="2" ParentId="4951" CreationDate="2010-10-07T12:04:46.060" Score="15" ViewCount="" Body="&lt;p&gt;charge on a cap is a linear product of capacitance and voltage, Q=CV. If you plan to drop from 5V to 3V, the charge you remove is 5V*1F - 3V*1F = 2V*1F = 2 Coulombs of charge. One Amp is one Coulomb per second, so 2C can provide 0.01A for 2C / (0.01 C/sec) or 200 seconds. If you actually withdraw charge from the cap at a &lt;em&gt;constant current&lt;/em&gt;, the voltage on the cap will decrease from 5V to 3V linearly with time, given by Vcap(t) = 5 - 2*(t/200).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, this assumes you have a load that draws a constant 10mA even while the voltage supplied to it changes. Common simple loads tend to have relatively constant impedance, which means that the current they draw will decrease as the cap voltage decreases, leading to the usual non-linear, decaying exponential voltage on the cap. That equation has the form of V(t) = V0 * exp(-t/RC).&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-10-07T12:13:34.463" LastActivityDate="2010-10-07T12:13:34.463" CommentCount="2" />
  <row Id="4954" PostTypeId="1" AcceptedAnswerId="5250" CreationDate="2010-10-07T12:16:04.223" Score="4" ViewCount="290" Body="&lt;p&gt;I am thinking to go in for a FPGA starter kit, I browsed the Xilinx website and found that the Spartan 3 series were quite economical - Spartan3AN, Spartan3A and Spartan3E. The Spartan 3AN seems to be a new board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can the Spartan FPGA handle processing of a 5MegaPixel camera, interface would be 8bit parallel data in raw rgb, and do some edge detection 15 times a second?&lt;/p&gt;&#xA;" OwnerUserId="444" LastActivityDate="2010-10-19T11:12:27.840" Title="Can a Spartan-3A / AN / E implement edge detection for a 5MP camera." Tags="&lt;fpga&gt;&lt;interface&gt;&lt;camera&gt;&lt;xilinx&gt;" AnswerCount="2" CommentCount="10" FavoriteCount="2" />
  <row Id="4955" PostTypeId="2" ParentId="4851" CreationDate="2010-10-07T13:23:14.730" Score="2" ViewCount="" Body="&lt;p&gt;Take a look at &lt;a href=&quot;http://www.opencircuits.com/Experimenting_with_IR_Remotes_using_a_PIC_running_BoostC_Project&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/Experimenting_with_IR_Remotes_using_a_PIC_running_BoostC_Project&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-10-07T13:23:14.730" />
  <row Id="4956" PostTypeId="1" AcceptedAnswerId="4957" CreationDate="2010-10-07T13:28:28.537" Score="4" ViewCount="391" Body="&lt;p&gt;I am working on a project which uses a PIC24FJ64GA002 mcu. &#xA;I am working on a bit-banged serial communication function that will use one wire to send data and then switch to receive mode to receive data on the same pin. A separate pin will be used for clocking which will always be controlled by a different board (always an input). I am wondering is there a way to configure the pin for open-collector operation that that it can be used as an input and and output or do I have to change the pin configuration every time i go from reading to writing?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2011-05-11T13:07:03.017" Title="Configure a PIC pin for Input and Output" Tags="&lt;pic&gt;&lt;output&gt;&lt;port&gt;&lt;input&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="4957" PostTypeId="2" ParentId="4956" CreationDate="2010-10-07T14:10:49.837" Score="5" ViewCount="" Body="&lt;p&gt;Change the pin configuration every time.  It's the TRIS register that controls if it's an input (1) or output (0).  And, when you change direction, you have to wait a moment (check the datasheet) like a cycle or two before you use that pin.  a couple Nop(); will do fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And, make sure you write to the LAT register, and read from the R register.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e.g.&#xA;for port D, pin 0.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;//output&#xA;_TRISD0 = 0;&#xA;Nop();&#xA;Nop();&#xA;_LATD0 = 1;&#xA;_LATD0 = 0;&#xA;&#xA;&#xA;//input&#xA;_TRISD0 = 1;&#xA;Nop();&#xA;Nop();&#xA;int i = _RD0;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1266" LastActivityDate="2010-10-07T14:10:49.837" CommentCount="0" />
  <row Id="4958" PostTypeId="2" ParentId="4777" CreationDate="2010-10-07T14:19:37.517" Score="2" ViewCount="" Body="&lt;p&gt;A few notes on your current design:&lt;br&gt;&#xA; 1. You cannot have floating inputs on logic gates (Your inverter inputs are floating)&lt;br&gt;&#xA; 2. You cannot have multiple outputs connected together (outputs from your AND gates)&#xA;&lt;p&gt;&#xA;First you need to clearly define what it is you are trying to do. My guess is you want a circuit where when someone hits a button their light comes on. Once one light turns on everyone else's button is disabled. My guess is you will also need some way to reset this. This will probably require a latch.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-07T14:19:37.517" CommentCount="1" />
  <row Id="4959" PostTypeId="2" ParentId="4956" CreationDate="2010-10-07T14:19:47.797" Score="3" ViewCount="" Body="&lt;p&gt;If you want to simulate an open collector write a zero to the latch register.  Then you do the rest with the TRIS register. When a zero goes to the TRIS bit this will turn the bit to an output and the line will be driven low. Then if you write a one to the TRIS bit the line will become an input and the pull up will cause the line to go high unless an external device is driving it low.  The line will also be in an input state at that time.  You can read the port at any time and it will show the proper bus state because when TRIS bit is 0 the bus will be low and that is what will be read and if TRIS bit is high it will be an input and then what ever is on the bus will be read as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some pins also have the ability to enable a weak pullup on them and you can also enable the pin change interrupt on some of the pins.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;//init&#xA;_LATA0 = 0;&#xA;&#xA;&#xA;//drive low&#xA;_TRISA0 = 0;&#xA;&#xA;// let pull up bring pin high.&#xA;_TRISA0 = 1;&#xA;&#xA;// read bit&#xA;in = _RA0;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="540" LastEditorUserId="540" LastEditorDisplayName="" LastEditDate="2010-10-07T14:28:23.013" LastActivityDate="2010-10-07T14:28:23.013" />
  <row Id="4960" PostTypeId="1" AcceptedAnswerId="4963" CreationDate="2010-10-07T14:51:27.887" Score="3" ViewCount="163" Body="&lt;p&gt;I am working on a project that uses a PIC24F mcu.&#xA;The power to my pic is backed by a very large capacitor (1F).&#xA;When there is a main power loss, I can sense that immediately via a port pin but the PIC itself stays powered for several minutes via the capacitor as the charge in the cap slowly dissipates. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once I detect that the main power is cut, I want to perform some actions (several micro seconds only) and then stop the PIC from doing anything else (sleep or hibernate i guess). But as the caps charge slowly dissipates the power to the pic will VERY slowly decrease below 3.3V down to zero.  At any point, if the main power is re-applied, the pic should detect it at the Port Pin, and restart normal operation. I am wondering what would be the best way to handle this in software? I know that the PIC has  Brownout detection and some kind of Low Voltage Tracking but I don't quite understand how to use them.&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2010-10-07T18:01:19.117" Title="How can I handle a low power condition with PIC?" Tags="&lt;pic&gt;&lt;power&gt;&lt;capacitor&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="4961" PostTypeId="2" ParentId="4960" CreationDate="2010-10-07T15:04:59.030" Score="1" ViewCount="" Body="&lt;p&gt;Use the instruction &quot;PWRSAV #SLEEP_MODE&quot;. This puts the chip into a power save sleep condition where it draws a few microamps. Remember to turn off peripherals before doing this, or they will draw current in sleep. This is a single cycle instruction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can set up pin change interrupts to wake the CPU from sleep.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-07T15:04:59.030" CommentCount="2" />
  <row Id="4962" PostTypeId="1" CreationDate="2010-10-07T15:05:04.973" Score="5" ViewCount="632" Body="&lt;p&gt;I'm looking for something that I can play around with but not spend too much on. I'm not eligible for an academic discount so take that into account when making suggestions. Thanks for the input in advance!!! :D&lt;/p&gt;&#xA;" OwnerUserId="1352" LastActivityDate="2011-05-16T13:23:24.110" Title="Most affordable FPGA dev kit for learning VHDL and FPGA theory?" Tags="&lt;fpga&gt;&lt;vhdl&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="6" />
  <row Id="4963" PostTypeId="2" ParentId="4960" CreationDate="2010-10-07T15:24:16.603" Score="1" ViewCount="" Body="&lt;p&gt;The easiest way to handle this is to add a pull-down to a pin that can be set up to interrupt on a change.  Then put a diode from this pin to VIN and another diode from VIN to VCC. Then you will receive an interrupt when the VIN is removed where you can gracefully shut down and then goto PWRSAV #SLEEP_MODE.  When power comes back the system will then get an interrupt which will take the part out of sleep mode. The diodes should be Schottky diode like a bat54c.  The capacitor is use to filter out quick changes in VIN.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;&#xA;    PIN --o---|&amp;lt;|----- VIN  ------|&amp;gt;|----- VCC&#xA;          |&#xA;          o-----&#xA;          \    |&#xA;          /   ---&#xA;          \   ---&#xA;          /    |&#xA;          o-----&#xA;          |&#xA;         GND&#xA;&#xA;&lt;/pre&gt;&#xA;" OwnerUserId="540" LastActivityDate="2010-10-07T15:24:16.603" />
  <row Id="4964" PostTypeId="2" ParentId="4962" CreationDate="2010-10-07T15:27:54.967" Score="5" ViewCount="" Body="&lt;p&gt;One of the &lt;a href=&quot;http://www.digilentinc.com/&quot; rel=&quot;nofollow&quot;&gt;Digilent kits&lt;/a&gt; would be ideal; I've got one of their &lt;a href=&quot;http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,799&amp;amp;Prod=S3BOARD&quot; rel=&quot;nofollow&quot;&gt;Spartan-3 kits&lt;/a&gt;. It's an older chip but the board probably has most things on it that you are likely to need, and lots of pins are brought out to connectors for other stuff that you might want to interface to it. They start at $109. Mine has one of the 400k gate chips on it, they don't seem to sell that option any more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I formed &lt;a href=&quot;http://tech.groups.yahoo.com/group/s3_kit/&quot; rel=&quot;nofollow&quot;&gt;this support group&lt;/a&gt; for users. Xilinx has their own forums, as well.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-10-07T16:02:09.903" LastActivityDate="2010-10-07T16:02:09.903" CommentCount="1" />
  <row Id="4965" PostTypeId="2" ParentId="4962" CreationDate="2010-10-07T16:42:16.947" Score="2" ViewCount="" Body="&lt;p&gt;This page is probably worth a look even if you won't end up rolling your own :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.eix.co.uk/Articles/FPGA/Welcome.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.eix.co.uk/Articles/FPGA/Welcome.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-10-07T16:42:16.947" />
  <row Id="4966" PostTypeId="2" ParentId="684" CreationDate="2010-10-07T16:56:43.807" Score="1" ViewCount="" Body="&lt;p&gt;200 ohms between Vcc and Vss: are you sure the MCU is to blame? You would have to remove it completely from the circuit just in case there is something else connected to the Vcc rail that is actually faulty.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you apply power, do you see any of the I/O lines changing state?&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-07T16:56:43.807" />
  <row Id="4967" PostTypeId="1" AcceptedAnswerId="4969" CreationDate="2010-10-07T17:57:57.510" Score="8" ViewCount="217" Body="&lt;p&gt;What is the simplest way to regulate the min DC voltage in a circuit?&#xA;Is it possible to do with zener diodes?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Desired performance:&#xA;&#xA;Input &amp;gt; 3.3 VDC     Output = Input&#xA;Input = 3.3 VDC     Output = Input&#xA;Input &amp;lt; 3.3 VDC     Output = 0.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-03T04:44:38.850" LastActivityDate="2010-11-03T04:44:38.850" Title="Circuit to protect against undervoltage?" Tags="&lt;protection&gt;&lt;undervoltage&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="3" />
  <row Id="4968" PostTypeId="2" ParentId="4960" CreationDate="2010-10-07T18:01:19.117" Score="1" ViewCount="" Body="&lt;p&gt;When your devices power gets too low, your PIC will reset itself. If you have a certain state that you want your pic to be in when it comes back on, you could save settings to eeprom just before putting it to sleep. Then, every time your pic starts you can have it check eeprom for your state settings and act accordingly.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-07T18:01:19.117" />
  <row Id="4969" PostTypeId="2" ParentId="4967" CreationDate="2010-10-07T19:04:02.817" Score="3" ViewCount="" Body="&lt;p&gt;According to your description, something like this should work:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/8GIHN.png&quot; alt=&quot;undervoltage cutoff&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tlv3012.html&quot; rel=&quot;nofollow&quot;&gt;TLV3012&lt;/a&gt; has the reference voltage built-in, so that's 1 6-pin IC, 1 FET, and 2 resistors.  Not sure if you consider that &quot;simple&quot;.  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/juL1n.jpg&quot; alt=&quot;TLV3012 pinout&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Similar:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/shFcj.gif&quot; alt=&quot;Similar circuit based on this IC&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a pMOS to switch a load is summarized &lt;a href=&quot;http://www.physics.udel.edu/~watson/scen103/mos5.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could probably use a Zener as the reference for the comparator, too, or maybe rig something up to drive the MOSFET from the Zener more directly, but I don't know how precise that would be.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-07T21:07:48.953" LastActivityDate="2010-10-07T21:07:48.953" CommentCount="9" />
  <row Id="4970" PostTypeId="1" AcceptedAnswerId="4974" CreationDate="2010-10-07T19:26:15.163" Score="12" ViewCount="475" Body="&lt;p&gt;I'm hoping to power an ATtiny85V for a nice long time on some small battery, probably a coin cell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've looked into the software side, and my code is watchdog timer driven, has unused analog and digital converters turned off, the chip is running at 1MHz etc.  Of course being both busy and new at this, I'm not sure exactly how much current it is drawing, but I'm hoping I have basically minimized it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Every few seconds it wakes up, does its voltage level checks on the ADCs, records it to ram, and goes back to sleep.  If it detects a serial line is connected, it spews the data out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, now I'm looking at the circuit as a whole and wondering if there are things I should do to make the circuit as a whole more battery friendly?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;What are the basic dos and don'ts when it comes to designing a long lasting (simple) circuit where one component (the microcontroller) has a repetitive but variable current draw?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;For instance:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Is an indicator LED a big deal?  Is it using up the battery when it is bright?  Should I put a giant resistor on it to make it dim, or does that just make the resistor use the battery?&lt;/li&gt;&#xA;&lt;li&gt;Should I use bypass/decoupling capacitors to even out the current draw from the battery, or will the capacitor just waste the battery's power?&lt;/li&gt;&#xA;&lt;li&gt;The microcontroller only needs 1.8V, but I don't have any 1.8V batteries.  Should I use two 1.x batteries and send it too much voltage?  Can I prolong the battery life by &quot;not using as many volts&quot;?  How do I do that?&lt;/li&gt;&#xA;&lt;li&gt;Does it take extra power to check if a pin is HIGH or LOW?  Like compared to a no-op or some arithmetic, is there much additional power usage in checking one of the GP I/O pins for its state?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I vaguely know how to compute (and more vaguely how to measure) current, voltage, power, but I'm not really sure which of those things equates to battery life.  Is the important measurement of battery life in Coulombs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have this vague idea that batteries are full of stuff like:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;charge, as in amp-hours&lt;/li&gt;&#xA;&lt;li&gt;energy, as in watt-hours&lt;/li&gt;&#xA;&lt;li&gt;power, as in watts&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;but I am not really clear on what my circuit &quot;eats&quot; when it runs.  I've read a fair amount of EE101 and physics textbooks, but I don't really have any lab experience.  In other words, I've read a ton about batteries, but I'm not really sure what most of it means in practice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do resistors use up battery life?  Do capacitors? Do diodes?  I suspect they all do, but which of the numbers are the ones that matter?  Impedance? Power dissipation? Current?  Voltage?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a way to lower voltage without wasting battery?  Is there a way to lower voltage while increasing battery life?&lt;/p&gt;&#xA;" OwnerUserId="1271" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-24T06:14:33.750" LastActivityDate="2011-01-24T06:14:33.750" Title="Making a battery last a long time in a microcontroller circuit" Tags="&lt;microcontroller&gt;&lt;battery&gt;&lt;design&gt;&lt;attiny&gt;&lt;low-power&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="6" />
  <row Id="4971" PostTypeId="2" ParentId="4962" CreationDate="2010-10-07T20:05:02.020" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.gadgetfactory.net/index.php?main_page=product_info&amp;amp;cPath=1&amp;amp;products_id=18&quot; rel=&quot;nofollow&quot;&gt;Papilio One&lt;/a&gt; is fairly cheap, but it doesn't have &lt;em&gt;any&lt;/em&gt; I/O devices on it, such as switches, LEDs, displays and whatnot. On the plus side, they have some thorough examples - including a usable Arduino and a logic analyzer. Digilent's &lt;a href=&quot;http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,790&amp;amp;Prod=BASYS2&quot; rel=&quot;nofollow&quot;&gt;Basys2&lt;/a&gt; costs considerably more but has lots of switches, lights, connectors and direct Xilinx WebPack support. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lattice has a smaller &lt;a href=&quot;http://www.latticesemi.com/products/developmenthardware/developmentkits/xp2breviadevelopmentkit.cfm&quot; rel=&quot;nofollow&quot;&gt;Lattice XP2 Brevia&lt;/a&gt; development kit for an apparent sale price (Oct 2010) of only $\$$29! That's with no-cost software, switches, LEDs and expansion ports. The downsides are (as far as I know): no simulation, and requires a real parallel port to program - or the USB cable which costs over twice as much. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&amp;amp;CategoryNo=13&amp;amp;List=Simplehttp://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&amp;amp;CategoryNo=13&amp;amp;List=Simple&quot; rel=&quot;nofollow&quot;&gt;Terasic&lt;/a&gt; offer a bunch of Altera based development boards, with prices ranging from $\$$79 (academic) or $\$$119. Not quite as low budget, but look like good deals, with plenty of easily accessible I/O as well as useful ports, switches and LEDs. &lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-03T19:17:54.767" LastActivityDate="2011-05-03T19:17:54.767" CommunityOwnedDate="2010-10-22T18:26:19.517" CommentCount="3" />
  <row Id="4972" PostTypeId="1" CreationDate="2010-10-07T20:55:20.897" Score="4" ViewCount="224" Body="&lt;p&gt;First I apologize if this is the wrong place for this question. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Recently my sub-woofer/amplifier stopped working, and I would like to know what is broken. I opened the case and didn't find any physical damage, and was wonder how I should proceed to discover what the defect is. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am electronics novice, but would like to use this as an opportunity to learn more. What is the general procedure in a case like this? Should I use multimeter to find where the current is blocked? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be greatly appreciated.&lt;/p&gt;&#xA;" OwnerUserId="1503" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-12-09T16:34:28.647" LastActivityDate="2011-03-19T02:31:53.630" Title="Troubleshooting a broken speaker system" Tags="&lt;amplifier&gt;&lt;troubleshooting&gt;" AnswerCount="5" />
  <row Id="4973" PostTypeId="2" ParentId="4972" CreationDate="2010-10-07T21:07:17.970" Score="2" ViewCount="" Body="&lt;p&gt;In general when troubleshooting, you need to isolate the problem by proving whether parts work or don't work.  Does the power supply work if it's disconnected from anything else?  Does the preamp work if it's disconnected from the amp?  Does the speaker work if connected to another amplifier?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have only a multimeter?  A scope would be more useful.  With a meter you can still test for signal by measuring AC voltage, though.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-07T21:07:17.970" />
  <row Id="4974" PostTypeId="2" ParentId="4970" CreationDate="2010-10-07T21:42:05.710" Score="11" ViewCount="" Body="&lt;p&gt;Just a random list, if you post your schematic it would probably be easier:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1.8V lithium Coin cells are very easy to find, but more likely your serial interface needs 3.3v?  Unless your receiving end will deal with 1.8V.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Leakage current does generally go up as your voltage increases, so lower is better usually.  Also consider the brown-out point for the system vs the battery characteristics.  The 'death' characteristics of the battery will be determines by the battery chemistry you use.  For instance if your uC browns out at 1.7V you may actually want to use a higher voltage battery as with some batteries the output voltage will lower slowly as the battery dies.  You'd get more life out of a 3.3V battery as when it begins to die its output will slowly drop and you can operate all the way down to 1.8V.  If you use a 1.8V battery your going to shut down fairly quickly as the battery dies.  This all assumes your serial interface or other components can deal with a wide voltage range (I know the AVR can).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;LED's use a lot of power, unless you use a very low power LED and are controlling its current draw it's probably drawing a lot more current than the AVR is.  If its just there for debug, don't populate it for production or only have it blink once in a while or something to minimize its on time, and definitely control its current draw.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can, pick the polarity / rest state of your serial interface to draw as little power as possible, it's rest state should not be drawing power.  If pull ups are required use the largest resistor possible to maintain signal integrity but minimize current usage.  If power is a huge concern use a signally scheme that favor's bits that don't draw power.  For instance if you have pull ups, using a protocol that results in lots of 1's in the signal will leave the serial interface in a state that isn't drawing as much power most of the time.  Such optimizations are only worthwhile if your making heavy use of the serial bus.  If its very lightly used just make sure its rest state isn't drawing power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally speaking you can assume all instructions (reading GPIO, etc) require the same amount of power.  Its not really true but the power difference is minimal.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Power usage is much more dependent on the number/type of peripherals you have powered on, and the amount of time the micro spends active vs sleeping.  So the ADC uses more power, EEPROM writes use a fair amount of power.  Specifically something like the EEPROM writes are usually done in fairly large 'chunks' so you should accumulate as much information as you can before doing the write to the EEPROM (if your even using it of course).  For the ADC that micro supports doing the ADC read during 2 of its sleep states, as ADC conversion takes a relatively long time this is a good time to sleep.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should probably just read the sections on power management, sleep states and minimizing power using in the microcontroller's data sheet: &lt;a href=&quot;http://www.avrfreaks.net/index.php?module=Freaks%20Files&amp;amp;func=viewFile&amp;amp;id=1500&amp;amp;showinfo=1&quot; rel=&quot;nofollow&quot;&gt;linky&lt;/a&gt; page 35 on.  Keep the AVR in the deepest sleep state possible as long as possible.  The only exception to this is that you have to consider the start up and shutdown time.  Its not worth it to sleep for 10 cycles if waking back up takes 25, etc. &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Do resistors use up battery life? Do capacitors? Do diodes?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;They all do to some extent.  Resistors dissipate the most in most applications: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;P = V*I&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P = V^2 / R or P = I^2 * R  (where V is the voltage drop across the resistor)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Diode's have a (relatively) fixed voltage drop, so power dissipation is almost exclusively tied to current passing through the diode.  For instance a diode with a 0.7V forward voltage drop, P = 0.7 * I if current is moving forward through the diode.  This is a simplification of course and you should check out the operating mode based on the diode's I-V characteristics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Capacitors theoretically shouldn't dissipate any power, but in reality they have a finite series resistance and non-zero leakage current which means they do dissipate some power, generally not something you should worry about with such low voltages though.  That being said choosing capacitors with minimal leakage current and ESR is a power win.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as using them to smooth out battery draw, this doesn't really help for power usage, its more for filtering.  Also battery chemistry comes into play here, some chemistries will be happier with a constant draw, some deal better with spiky current draws.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-07T21:47:12.613" LastActivityDate="2010-10-07T21:47:12.613" CommentCount="6" />
  <row Id="4975" PostTypeId="2" ParentId="4972" CreationDate="2010-10-07T21:44:12.120" Score="3" ViewCount="" Body="&lt;p&gt;First checks are the obvious ones; things like the fuse and the wiring require little experience to verify. Make sure the speakers are actually okay, by testing them on another system, if possible, or by testing another set of speakers with the amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then use your multimeter to test the power supply. Use it on DC volts and measure the output. A failure in the power supply will likely take out the whole amp. Be careful - mains voltages are present in some parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other things to test would really come down to the exact model and specifications. Consulting the service manual, which is usually only a google away, may be very useful. Often lower end brands don't have service manuals, because they intend for the models to be replaced anyway. But higher end gear will have some.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Test equipment of at least a multimeter will be required, but a scope is invaluable, even if it's just a 10 MHz single channel model (though I'd recommend a 50-100 MHz dual channel.) A scope is a serious bit of kit and the price reflects that - around $\$$200 is about what you'll pay for an second hand one and you can pick up a nice new 50 MHz digital storage scope for ~$\$$400. With a scope, you can compare the reference waveforms often given in a service manual with what you see on the screen.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1802" LastEditorDisplayName="" LastEditDate="2011-03-16T20:16:31.653" LastActivityDate="2011-03-16T20:16:31.653" />
  <row Id="4976" PostTypeId="2" ParentId="4970" CreationDate="2010-10-07T21:54:46.317" Score="2" ViewCount="" Body="&lt;p&gt;With your circuit, I'd recommend using a multimeter on the microamps range to measure current consumption. Then, given the battery characteristics you can calculate the longevity. It's not necessarily amp-hours / current, as the battery will have different discharge characteristics for different loads. But, it can be useful as an approximation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At 1 MHz I think you will be sucking a bit of power - at least 100µA, if PIC micros are anything to compare with. But this is going to be overwhelmed by the 5mA to 20mA going through your LED, so you should get rid of that first.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-07T21:54:46.317" CommentCount="1" />
  <row Id="4977" PostTypeId="2" ParentId="4972" CreationDate="2010-10-07T22:03:14.753" Score="5" ViewCount="" Body="&lt;p&gt;well, to be honest you'd have to have a decent understanding of the circuit to really track down a component failure.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said i've fixed a few of my own internally amplifier speakers, it was almost always a solder joint that cracked or came free from its pad, probably as a result of thermal stress.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So one thing you can do is look over all the solder joints carefully and re-solder any that look like they are possibly cracked.  All you should need is a soldering iron, some flux and some solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: One additional common point of failure in such electronics: electrolytic capacitors.  They are used a ton in audio electronics and have limited life spans, look for any bulging or exploded cans.  They are pretty easy to replace if this is the issue.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-07T22:42:49.827" LastActivityDate="2010-10-07T22:42:49.827" />
  <row Id="4978" PostTypeId="2" ParentId="4970" CreationDate="2010-10-07T23:34:20.200" Score="5" ViewCount="" Body="&lt;p&gt;Mark gave a most excellent answer and hit on many of the points I was going to make. There are a few that I'd like to contribute as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use an oscilloscope with a low-ohm resistor in series with the return to battery common to make current measurements. Current draw with a microcontroller is not straightforward and as a general rule, meters are FAR too slow to give you a good idea of what's going on. What &quot;low-ohm&quot; means depends on the expected current draw. a 1 ohm resistor will develop 100mV for every 100mA drawn, and that is probably too much for you. I'd try a 10 ohm 1% or 0.5% resistor; you'll see 100mV for every 10mA of current draw. 18 ohms would give you 100mV for every 5.5mA. If you're REALLY going for low power you might be able to get away with 1k; I=V/R: you'll see 100mV for every 100uA of current drawn.  Careful though; if you draw enough current you'll end up dropping too much across the shunt and your measurements will be off, not to mention the circuit probably won't work. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the 'scope connected, try a few different operating frequencies for the microcontroller. You may be surprised to learn that you consume less power with a higher clock speed because you spend much less time &quot;awake.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Eliminate pull-ups/downs as much as possible. You shouldn't have any on any output, since you can drive them to an idle state in most cases. Inputs should be tied to what makes sense, using as high a value as possible, as Mark said.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure that your microcontroller has as much shut off as possible. Turn unused pins into outputs and drive them to a state (high or low, doesn't matter). Don't leave LEDs on. If you can power down other components or stop their clocks, do it.  SPI Flash memories, for example, often have a 'power down' command that will take the already low power draw and drive it even lower.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Others have touched on the voltage aspect, and I'd like to comment on it as well. You will likely end up with MUCH better battery use if you use a high-efficiency buck/boost regulator between the battery and your circuit. The regulator will be in buck mode (voltage reduction) when the battery level is higher than the 1.8V you need, and switch to boost mode (voltage increasing) when the battery level drops below 1.8V. This will allow you to run the circuit until the battery is well and truly dead, which is well worth the few percent efficiency loss you'll get when using them.  Make sure to select the regulator based on its efficiency over the entire range you want to use, and size the regulator appropriately; a regulator that can deliver 1A at 98% efficiency is probably at 60% efficiency delivering 50mA. Read the datasheets carefully. &lt;/p&gt;&#xA;" OwnerUserId="974" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-10-07T23:41:23.590" LastActivityDate="2010-10-07T23:41:23.590" CommentCount="3" />
  <row Id="4979" PostTypeId="1" AcceptedAnswerId="4980" CreationDate="2010-10-07T23:35:19.883" Score="6" ViewCount="358" Body="&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; Here is a much brief version, the meandering motivated version is probably subsumed in &lt;a href=&quot;http://electronics.stackexchange.com/questions/4970/making-a-battery-last-a-long-time-in-a-microcontroller-circuit&quot;&gt;the parent question on general battery life optimizations&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;How can I lower the current into a LED without wasting battery?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I think using a resistor to lower the current will use up battery life.  Is this true?  How does it use up the battery if the current is kept small?  Is it the power dissipation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think using a diode (and smaller resistor) will still use up the battery (LadyAda said something like &quot;any linear device to lower the voltage uses the same amount of power&quot;).  Is this true?  Is it the same amount?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I lower the voltage &quot;for free&quot;, that is, without wasting too much power?  How can a regulator IC do what a resistor or diode cannot?&lt;/p&gt;&#xA;" OwnerUserId="1271" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-24T06:12:42.067" LastActivityDate="2011-01-24T06:12:42.067" Title="LEDs on a (battery) budget! – How can I lower the current through a LED without using up the battery?" Tags="&lt;led&gt;&lt;battery&gt;&lt;design&gt;&lt;pwm&gt;&lt;low-power&gt;" AnswerCount="6" CommentCount="5" FavoriteCount="1" />
  <row Id="4980" PostTypeId="2" ParentId="4979" CreationDate="2010-10-07T23:45:31.197" Score="10" ViewCount="" Body="&lt;p&gt;Use a low current LED. For example, &lt;a href=&quot;http://parts.digikey.com/1/parts/1315383-led-ss-3mm-568nm-grn-diff-wp7104lgd.html&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; consumes 2mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use Pulse Width Modulation (PWM) to drive the LED. During the off period, it's not consuming power. 50% brightness might be acceptable.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-08T13:34:48.383" LastActivityDate="2010-10-08T13:34:48.383" CommentCount="7" />
  <row Id="4981" PostTypeId="1" AcceptedAnswerId="4996" CreationDate="2010-10-08T00:25:36.423" Score="3" ViewCount="156" Body="&lt;p&gt;I help maintain an old beaten down LED sign on the side of a highway. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right it has a program running on Win98 to generate the image that should be on the sign (FLASH animation, temperature, etc), and drive a PCI IO card which in turn drives the sign logic. I'd like to (be able to) replace the control package of the sign with something less painful. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A different sign we're working on has a DVI input to a control board. The control board takes a specific portion of the video and sends it off to the sign. I like this scheme because it makes it easier to change out the computer if it breaks, and allows a lot of freedom in terms of what software/hardware can be used- so long as a PC has a DVI port, it can drive the sign.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Core Question: How can I go from 'video input' to a copy of what is on the screen for consumption by digital logic? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The one thing I've come up with so far is using a &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tfp401a.html&quot; rel=&quot;nofollow&quot;&gt;TFP401A&lt;/a&gt;, and feeding that into an FPGA where a lot of accompanying logic would sit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does that seem reasonable? Is there a better way? At least one concern is that I don't have any experience with high frequency design- I'm not certain how much care needs to be taken on the traces between DVI connector and receiver, as well as from receiver to FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Few added details: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The sign is low resolution (47x127 image, 24x64 sign)&lt;/li&gt;&#xA;&lt;li&gt;It displays animation (refresh rate &gt; 10Hz)&lt;/li&gt;&#xA;&lt;li&gt;I'd prefer something without dependence on software on the PC (suggests taking a video signal of some format)&lt;/li&gt;&#xA;&lt;li&gt;This is 80% learning experience- while the goal is a practical replacement system, I would like to end with the knowledge of how this can be done.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1507" LastEditorUserId="1507" LastEditorDisplayName="" LastEditDate="2010-10-08T13:53:58.670" LastActivityDate="2010-10-08T16:02:52.457" Title="How to get Video Input" Tags="&lt;fpga&gt;&lt;video&gt;&lt;display&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="4982" PostTypeId="2" ParentId="4857" CreationDate="2010-10-08T00:46:24.483" Score="1" ViewCount="" Body="&lt;p&gt;Jon Oxer (the co-author of &quot;Practical Arduino&quot;) has documented home-access RFID systems on his &lt;a href=&quot;http://www.practicalarduino.com/projects/rfid-access-control-system&quot; rel=&quot;nofollow&quot;&gt;website&lt;/a&gt;. He is also the first Australian to have an RFID implant. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-08T00:46:24.483" CommentCount="1" />
  <row Id="4983" PostTypeId="1" CreationDate="2010-10-08T02:44:47.640" Score="6" ViewCount="761" Body="&lt;p&gt;I have a 3-axis accelerometer and a 2-axis gyroscope. I intend to measure something that only moves in the X and Z axis. I've heard of using Kalman filters to smooth out the acceleration vectors, but I can't find a good tutorial for a complete beginner to the topic. Also, I know I can double integrate acceleration to get position, but how do I do this with a finite number of sampled acceleration vectors? I would appreciate links to good tutorials for beginners on both these topics.&lt;/p&gt;&#xA;" OwnerUserId="1510" LastActivityDate="2010-10-08T09:49:46.200" Title="How to determine position from gyroscope and accelerometer input?" Tags="&lt;sensor&gt;&lt;accelerometer&gt;&lt;math&gt;&lt;imu&gt;&lt;gyro&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="2" />
  <row Id="4984" PostTypeId="2" ParentId="684" CreationDate="2010-10-08T02:52:12.813" Score="0" ViewCount="" Body="&lt;p&gt;Not really sure what your question is but the &lt;a href=&quot;http://www.national.com/ds/CO/COP87L84BC.pdf&quot; rel=&quot;nofollow&quot;&gt;data sheet is here&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Theres a section covering development tools near the end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its a one time programmable unit so don't expect an in circuit programming connection of any sort nor debug support.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its very doubtful you'd be able to read the program out of the chip at all, at least not without some very specialized hardware.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-08T02:52:12.813" />
  <row Id="4986" PostTypeId="2" ParentId="4983" CreationDate="2010-10-08T07:21:26.090" Score="5" ViewCount="" Body="&lt;p&gt;Here's a tutorial on implementing a direction cosine matrix for an IMU:&#xA;&lt;a href=&quot;http://gentlenav.googlecode.com/files/DCMDraft2.pdf&quot; rel=&quot;nofollow&quot;&gt;http://gentlenav.googlecode.com/files/DCMDraft2.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take a look at the ArduIMU pages:&#xA;&lt;a href=&quot;http://code.google.com/p/ardu-imu/wiki/Theory&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/ardu-imu/wiki/Theory&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are a couple of open source projects which do this. Reading the code should give some clues:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/gluonpilot/source/browse/trunk/Firmware/#Firmware/rtos_pilot%3Fstate%3Dclosed&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/gluonpilot/source/browse/trunk/Firmware/#Firmware/rtos_pilot%3Fstate%3Dclosed&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/sf9domahrs/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/sf9domahrs/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-08T09:49:46.200" LastActivityDate="2010-10-08T09:49:46.200" />
  <row Id="4988" PostTypeId="2" ParentId="4981" CreationDate="2010-10-08T08:18:16.783" Score="0" ViewCount="" Body="&lt;p&gt;Decoding DVI is going to be tricky - some cards provide digital+analog, while some only provide digital outputs. And resolution can of course vary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you'd be better off with a simple serial interface that you could connect to the computer to and send commands, e.g. &quot;turn LED 3,4 on red&quot;, &quot;draw this sprite&quot;, &quot;clear screen&quot;...&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-08T08:18:16.783" />
  <row Id="4989" PostTypeId="1" AcceptedAnswerId="5007" CreationDate="2010-10-08T09:07:24.957" Score="3" ViewCount="226" Body="&lt;p&gt;I'd like to connect my landline tellephone to my computer's soudcard, and I was about to do this when somebody warned me that the voltages are all wrong and that I will blow my soundcard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To what voltages must I change the line, and how do I do that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the telephone line has two wires. How to I split them into input &amp;amp; output for my soundcards's ports?&lt;/p&gt;&#xA;" OwnerUserId="1258" LastEditorUserId="1397" LastEditorDisplayName="" LastEditDate="2010-10-22T22:48:28.130" LastActivityDate="2010-10-29T20:46:00.173" Title="Connecting landline to soundcard" Tags="&lt;computers&gt;&lt;telephone&gt;" AnswerCount="6" CommentCount="2" FavoriteCount="1" />
  <row Id="4990" PostTypeId="1" AcceptedAnswerId="4991" CreationDate="2010-10-08T10:01:12.923" Score="1" ViewCount="673" Body="&lt;p&gt;FOllowing on from &lt;a href=&quot;http://electronics.stackexchange.com/questions/4814/my-atmega328-seems-to-be-overkill-what-should-i-use-instead&quot;&gt;this question&lt;/a&gt;, I'm following the tutorial for &lt;a href=&quot;http://hlt.media.mit.edu/wiki/pmwiki.php?n=Main.ArduinoATtiny4585&quot; rel=&quot;nofollow&quot;&gt;programming an ATtiny45 using an arduino&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using v0021 of the Arduino IDE, with a Duemilanove which i've replaced the 168 chip with a 328, I'm able to upload the ArduinoISP sketch correctly. However, trying to upload the blink sketch to the Attiny results in the following error:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ArduinoISP.cpp: In function 'void setup()':&#xA;ArduinoISP.cpp:79: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void loop()':&#xA;ArduinoISP.cpp:136: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'uint8_t getch()':&#xA;ArduinoISP.cpp:142: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp:143: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void readbytes(int)':&#xA;ArduinoISP.cpp:147: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void spi_init()':&#xA;ArduinoISP.cpp:164: error: 'SPCR' was not declared in this scope&#xA;ArduinoISP.cpp:165: error: 'SPSR' was not declared in this scope&#xA;ArduinoISP.cpp:166: error: 'SPDR' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void spi_wait()':&#xA;ArduinoISP.cpp:172: error: 'SPSR' was not declared in this scope&#xA;ArduinoISP.cpp:172: error: 'SPIF' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'uint8_t spi_send(uint8_t)':&#xA;ArduinoISP.cpp:177: error: 'SPDR' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void empty_reply()':&#xA;ArduinoISP.cpp:194: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp:198: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void breply(uint8_t)':&#xA;ArduinoISP.cpp:204: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp:209: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void start_pmode()':&#xA;ArduinoISP.cpp:263: error: 'SS' was not declared in this scope&#xA;ArduinoISP.cpp:265: error: 'SCK' was not declared in this scope&#xA;ArduinoISP.cpp:270: error: 'MISO' was not declared in this scope&#xA;ArduinoISP.cpp:271: error: 'MOSI' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void end_pmode()':&#xA;ArduinoISP.cpp:277: error: 'MISO' was not declared in this scope&#xA;ArduinoISP.cpp:278: error: 'MOSI' was not declared in this scope&#xA;ArduinoISP.cpp:279: error: 'SCK' was not declared in this scope&#xA;ArduinoISP.cpp:280: error: 'SS' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void program_page()':&#xA;ArduinoISP.cpp:348: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp:356: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp:362: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'char flash_read_page(int)':&#xA;ArduinoISP.cpp:375: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'char eeprom_read_page(int)':&#xA;ArduinoISP.cpp:387: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void read_page()':&#xA;ArduinoISP.cpp:397: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp:400: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'void read_signature()':&#xA;ArduinoISP.cpp:409: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp:412: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp: In function 'int avrisp()':&#xA;ArduinoISP.cpp:436: error: 'Serial' was not declared in this scope&#xA;ArduinoISP.cpp:497: error: 'Serial' was not declared in this scope&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;How can I fix this please? Or does anyone know if it works with a previous version of the IDE?&lt;/p&gt;&#xA;" OwnerUserId="623" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-07T20:53:16.733" LastActivityDate="2010-12-07T20:53:16.733" Title="Why am I receiving &quot;error 'Serial' was not declared in this scope&quot; when building my Arduino sketch?" Tags="&lt;arduino&gt;" AnswerCount="1" />
  <row Id="4991" PostTypeId="2" ParentId="4990" CreationDate="2010-10-08T10:10:30.200" Score="1" ViewCount="" Body="&lt;p&gt;Doh fixed it myself.&#xA;Needed to include the SoftwareSerial library in the updated blink sketch. That piece of info is missing from the tutorial linked above.&lt;/p&gt;&#xA;" OwnerUserId="623" LastActivityDate="2010-10-08T10:10:30.200" CommentCount="3" />
  <row Id="4993" PostTypeId="1" AcceptedAnswerId="4997" CreationDate="2010-10-08T10:20:02.157" Score="7" ViewCount="259" Body="&lt;p&gt;Inspired by &lt;a href=&quot;http://electronics.stackexchange.com/questions/4905/is-an-fpga-viable-for-such-a-project&quot;&gt;question&lt;/a&gt; I would like to ask what microcontrollers with CPLD or FPGA-like functions build in are available? The most interesting would be low-cost ones in friendly packages (non-BGA). The CPLD/FPGA portion should be big enough to allow implementing fairly complicated state machine (10+ states), fairly big logic function (10+ inputs), fairly big counters and shift registers (8+ bits) and be able to run at tens of MHz frequencies. Preferable method of design input for programmable logic function should be HDL based (Verilog or VHDL).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far I have found two examples:&lt;br&gt;&#xA;1) FPSLIC from Atmel&lt;br&gt;&#xA;2) PSOC3 and PSOC5 from Cypress (those are not available yet, except in samples volume)&lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-10-08T14:38:34.003" LastActivityDate="2010-10-09T17:13:41.563" Title="What microcontrollers with programmable logic built in (FPGA/CPLD like) are available on the market?" Tags="&lt;microcontroller&gt;&lt;fpga&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="4994" PostTypeId="2" ParentId="4989" CreationDate="2010-10-08T10:23:41.533" Score="8" ViewCount="" Body="&lt;p&gt;If the goal of this action to record the call or to use computer headset for telephoning, it is more safe solution to buy a voice modem. Costs 10-20 USD and there are plenty of software to record sound,  make answering machine, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is right that you cannot connect the phone line directly to your sound card. There is around 80-100 V AC in the phone line when it is ringing! And for legal reasons you cannot connect any device to the line which is not approved by local agencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you can use an audio transformer to isolate the sound component from the dc voltage, but you have to make some protection circuit in case of ringing.&lt;/p&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2010-10-08T10:23:41.533" CommentCount="6" />
  <row Id="4995" PostTypeId="2" ParentId="4880" CreationDate="2010-10-08T10:42:06.097" Score="0" ViewCount="" Body="&lt;p&gt;There is a .net based SDK for the wiimote: &lt;a href=&quot;http://wiimotelib.codeplex.com/&quot; rel=&quot;nofollow&quot;&gt;http://wiimotelib.codeplex.com/&lt;/a&gt;&#xA;You can use the test program in the SDK to &quot;see&quot; the IR lights.&#xA;You will need a bluetooth adapter to communicate with the mote.&lt;/p&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2010-10-08T10:42:06.097" />
  <row Id="4996" PostTypeId="2" ParentId="4981" CreationDate="2010-10-08T10:54:26.223" Score="2" ViewCount="" Body="&lt;p&gt;The fundamental question here is how fast you need to update the sign's image.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't need to update it more often than once every few seconds, DVI is WAAAAAY overkill. (And placing something that shows video next to a highway seems like a very bad idea)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You're probably best off using a frame-buffer in your hardware, and using something like a &lt;a href=&quot;http://www.ftdichip.com/Products/ICs/FT232R.htm&quot; rel=&quot;nofollow&quot;&gt;FT232&lt;/a&gt; or &lt;a href=&quot;http://www.ftdichip.com/Products/ICs/FT245R.htm&quot; rel=&quot;nofollow&quot;&gt;FT245&lt;/a&gt; to dump images to it.  The FT2** IC Gives you ~8 MBps of interface bandwith over USB, and a dead-easy software driver you can talk to. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, depending on your sign's resolution, you could use a simple serial interface. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would assume you would be sending raw bitmaps to the sign (it makes the software end easier). Then you just cache them in the hardware, and then serve them up to whatever interface the sign implements from your hardware.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-08T10:54:26.223" CommentCount="4" />
  <row Id="4997" PostTypeId="2" ParentId="4993" CreationDate="2010-10-08T10:55:11.913" Score="6" ViewCount="" Body="&lt;p&gt;Xilinx has FPGAs with PowerPC 440 and 405 hard processors. Actel has FPGAs with ARM Cortex-M3 cores.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both Xilinx and Altera have IP for soft processors - the MicroBlaze and NIOS II - and there are several similar free processors available on the Open Cores web site.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-10-08T11:00:56.037" LastActivityDate="2010-10-08T11:00:56.037" />
  <row Id="4998" PostTypeId="2" ParentId="4993" CreationDate="2010-10-08T11:46:44.370" Score="4" ViewCount="" Body="&lt;p&gt;Check out Atmel - they make an AVR + FPGA...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/products/fpslic/default.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/products/fpslic/default.asp&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-=mike=-&lt;/p&gt;&#xA;" LastActivityDate="2010-10-08T11:46:44.370" />
  <row Id="4999" PostTypeId="2" ParentId="4989" CreationDate="2010-10-08T12:40:10.763" Score="0" ViewCount="" Body="&lt;p&gt;This may be oldschool, but how about a (small) balancing inductor (transformer)...&lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-10-08T12:40:10.763" CommentCount="4" />
  <row Id="5000" PostTypeId="2" ParentId="4979" CreationDate="2010-10-08T12:46:43.647" Score="3" ViewCount="" Body="&lt;p&gt;If you increase the resistance of your current limiting resistor I would think your battery life would be extended. With a voltage source (such as a battery) using a larger resistor means less current will flow through the resistor and the diode. The only downside is you have a dimmer diode. However since the current through the whole circuit has been reduced your battery life rated in mAh will be increased. &lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-08T12:46:43.647" />
  <row Id="5001" PostTypeId="2" ParentId="4989" CreationDate="2010-10-08T14:17:33.080" Score="0" ViewCount="" Body="&lt;p&gt;If you want to record the telephone line, here's  a cable on &lt;a href=&quot;http://cgi.ebay.com.au/RJ11-BT-CABLE-PLUG-TELEPHONE-PHONE-RECORD-RECORDER-LEAD-/280456864618?pt=UK_Gadgets&amp;amp;hash=item414c88236a#ht_2343wt_911&quot; rel=&quot;nofollow&quot;&gt;eBay&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-08T14:17:33.080" />
  <row Id="5002" PostTypeId="2" ParentId="4979" CreationDate="2010-10-08T14:28:21.500" Score="2" ViewCount="" Body="&lt;p&gt;What you want is a current control circuit. These are commonly found in better LED flashlights (&lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.26110&quot; rel=&quot;nofollow&quot;&gt;example&lt;/a&gt;), and devices like &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/4809&quot; rel=&quot;nofollow&quot;&gt;MAX6969&lt;/a&gt; can help you control a bunch of LEDs from a microcontroller. That particular chip won't save you power unless you combine it with a lower voltage (perhaps supplied by a constant voltage buck regulator) to power the LEDs or PWM. Increasing a series resistor will indeed draw less current, and thus give you longer battery life, but the light will be reduced as well. With the constant current supplies you can eliminate the power converted to heat in the series resistors.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-10-08T14:28:21.500" />
  <row Id="5003" PostTypeId="2" ParentId="4979" CreationDate="2010-10-08T14:40:34.550" Score="6" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;I think using a resistor to lower the&#xA;  current will use up battery life. Is&#xA;  this true? &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The first statement is hard to give a yes/no answer to. Technically it uses up some of the power on itself, but as the resistance goes up the power goes down (the current also decreases, which is what matters in a battery).&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;How does it use up the&#xA;  battery if the current is kept small?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This is a very very messy statement. &quot;Small&quot;, that means something different to every person. If you mean small, as in negligible, then it can be ignored, but I doubt this is true with a circuit counting uA. For it to be negligible a good rule can be that it's average current is less then 1/10 of your overall system current (I am fields, 1/10 is enough for 1/infinity).&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Is it the power dissipation?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes, in the shortest answer. A battery has a voltage associated with it, which you normally know up front. Most devices have a current that varies as the voltage is varied, but since you know the voltage you can tell its current draw. Since the battery's capacity is measured in AH or mAH then you are set. take capacity, in AH, and divide by how many A your device pulls and you have your lifetime in hours.  Number big enough? you are set. Gonna die 3 weeks early? now you have to find a way to reduce your average current draw, or get bigger batteries.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I think using a diode (and smaller&#xA;  resistor) will still use up the&#xA;  battery (LadyAda said something like&#xA;  &quot;any linear device to lower the&#xA;  voltage uses the same amount of&#xA;  power&quot;). Is this true? Is it the same&#xA;  amount?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;As stated before you effectively have a current budget. if your average current draw is increased then you have lost battery life.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Can I lower the voltage &quot;for free&quot;,&#xA;  that is, without wasting too much&#xA;  power? How can a regulator IC do what&#xA;  a resistor or diode cannot?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes, if you use a device like an LED Driver then it can do the trick. Most of these are &lt;a href=&quot;http://en.wikipedia.org/wiki/Switched-mode_power_supply&quot; rel=&quot;nofollow&quot;&gt;Switching mode power supplies&lt;/a&gt;. These are a relatively advanced concept in electronics, do not beat yourself up trying to understand it. Just understand that it cheats. It will have an efficiency in the 80 or 90% range. You can calculate the power consumption of your device and then factor in efficiency to get the real power draw. This can then be divided by voltage and should correlate to your average current draw.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;My advice&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;There is an easier way. As Joby was talking about, PWM. But i would not suggest using a 10% PWM, or even a 1%. Instead, blink your LED for short periods to let you know of important events.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to check your device is sleeping, blink it every 1 second wakeup. If you are transmitting when rs232 is connected, blink it every time you TX a &quot;packet&quot;. This can give you &quot;on&quot; times of milliseconds every few seconds. If you think of this as a basic PWM, then you are getting less than a .1%. if you are pulling 20mA to blink(quite bright) then you are pulling an average of 20uA. Go to a 2mA diode, and you are doing 2uA average current. if you blink every minute, you get to divide by 60 on that: 1/30uA.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-08T14:40:34.550" CommentCount="4" />
  <row Id="5004" PostTypeId="2" ParentId="4981" CreationDate="2010-10-08T16:02:52.457" Score="1" ViewCount="" Body="&lt;p&gt;How about something simpler?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps a compact flash card with a bitmap image file or GIF89a on it?&#xA;A microcontroller could read the card and drive the display.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-08T16:02:52.457" CommentCount="1" />
  <row Id="5005" PostTypeId="2" ParentId="4989" CreationDate="2010-10-08T16:13:15.243" Score="1" ViewCount="" Body="&lt;p&gt;It's a little bit tricky. Indeed, there's a DC voltage present when the phone is on the hook (usually 48V) and the ringing signal is high-voltage AC, as in old times it used to physically drive a motor to ring a bell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The two wires you refer to are commonly referred to as 'tip' and 'ring', which again dates to olden times when operators used to manually switch calls by moving plugs around - one wire was to the tip of the plug, the other was behind the insulating ring (look at a headphone plug if you need a visual aid). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe both incoming and outgoing voice are mixed and sent on one wire with reference to the other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A &quot;safer&quot; way (but also most likely illegal) to do this would be to simply hook the sound card line input to the earpiece of an old handset that you don't mind butchering. You'll have to take that phone off the hook to make the speaker active, but you'll hear both what's being said on your end plus the remote end (since there's a small amount of audio feedback from the talker sent to the talker's earpiece). You'll also (hopefully) not be exposed to the -48V and the ringer voltage - you may wish to put a small capacitor in series with the soundcard connection to isolate any DC on the speaker side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-08T16:13:15.243" />
  <row Id="5006" PostTypeId="2" ParentId="4989" CreationDate="2010-10-08T16:59:04.530" Score="4" ViewCount="" Body="&lt;p&gt;Basically sounds me to like you need a way to make your computer pretend it behaves the way a conventional POTS phone does.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Traditionally, you interface with the phone line via a modem on the PC.  Some modems allow for voice calls via PC, sometimes called a voice modem.  If your'e cool with writing software or using a Hyperterm window, you can try &lt;a href=&quot;http://en.wikipedia.org/wiki/Voice_modem_command_set&quot; rel=&quot;nofollow&quot;&gt;controlling the modem in voice mode&lt;/a&gt; using AT commands and a software package.  You can do pretty much anything to a phoneline by sending the right combination of AT commands to the modem.  This assumes your'e cool with experimenting with the software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For this use, I'd use a modem rather than implementing a hardware-based solution.  One, because it is cheaper, and two, because your'e likely to get significantly better results with the debugged PC&amp;lt;-&gt;PhoneLine interface that the modem provides.  You can make a hardware solution, too, but it may take a while, be expensive to figure out, and may not work reliably - but you'll learn a whole lot more.  Depends on what you want to do.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-10-08T16:59:04.530" />
  <row Id="5007" PostTypeId="2" ParentId="4989" CreationDate="2010-10-08T17:11:40.120" Score="4" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ALiZk.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get a transformer from an damaged modem, like that:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wtVo9.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reminder: In my country (Brazil) it is forbidden to record a phone conversation without the consent of another person on the phone.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-10-29T20:46:00.173" LastActivityDate="2010-10-29T20:46:00.173" />
  <row Id="5008" PostTypeId="2" ParentId="3657" CreationDate="2010-10-08T17:19:09.137" Score="1" ViewCount="" Body="&lt;p&gt;It seems there are not any major ICEs available for the MSP430. I thought I had seen one, but cannot find it and find other places where people state there are not ICEs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is incorrect, please post. Tomorrow I am going to accept my answer if there is not one. I will always go back and switch to an answer that has a real solution to what I need.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-10-10T15:51:08.570" LastActivityDate="2010-10-10T15:51:08.570" />
  <row Id="5009" PostTypeId="1" AcceptedAnswerId="5022" CreationDate="2010-10-08T19:13:48.700" Score="2" ViewCount="265" Body="&lt;p&gt;So I have four computers all using these little &lt;a href=&quot;http://www.mini-box.com/picoPSU-160-XT&quot; rel=&quot;nofollow&quot;&gt;pico itx power supplies&lt;/a&gt; and was wondering rather than have 4 power bricks attached to these power supplies could I just use an &lt;a href=&quot;http://www.amazon.com/Power-Bright-PW900-12-Inverter-Watt/dp/B000NM4DVW&quot; rel=&quot;nofollow&quot;&gt;Power-Bright-PW900-12-Inverter&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To me it seems like a better and more power efficient solution unless I am missing something. Also if I were to do this what is the best way to slap DC wires from four different power supplies into this thing?&lt;/p&gt;&#xA;" OwnerUserId="1518" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-08T23:01:14.737" LastActivityDate="2010-10-08T23:34:34.773" Title="Pico ITX Power Supply and AC-DC Inverter" Tags="&lt;power-supply&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="5010" PostTypeId="1" CreationDate="2010-10-08T20:39:30.147" Score="3" ViewCount="424" Body="&lt;p&gt;&lt;strong&gt;Some background info first:&lt;/strong&gt;&lt;br&gt;&#xA;In my country, price of electricity depends among other things on the time of the day when energy is used. Because of that, many people tend to turn on big energy consumers after midnight, when electricity is cheaper. One of my friends needs a new laundry washing machine, so I went browsing with her. We noticed that many new machines have a delayed start option which would be very useful because it would be possible to fill the machine and program it and it would start working by itself during cheaper time. I don't think that it would be too complicated to make a circuit which will start a washing machine after X amount of time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;More relevant part:&lt;/strong&gt;&lt;br&gt;&#xA;After examining my washing machine, I noticed that machine itself is started by a normally off pushbutton. I'm thinking that the button could be replaced by a transistor or some sort of normally off relay. Anyway that's not (yet) the problematic part for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The question itself:&lt;/strong&gt;&lt;br&gt;&#xA;How would I design a circuit which would wait for several hours and then &quot;push&quot; a button without using microcontrollers? I know that a microcontroller is the most elegant solution, but I'd rather skip collecting necessary gear for working with them at this time. Discrete logic gates, flip-flops or anything else which doesn't need a programmer is acceptable for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first idea is to create or find prefabricated some sort of counter which would be connected to a slow oscillator. The oscillator would have very low frequency (say 2Hz if possible) and the counter would send signals to a device which would respond when counter reaches a certain number (say after 18 000 seconds).   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking about using 74LS162/3 counters. In 74LS162's datasheet under minimum frequency it says 25MHz if I'm reading it right, so I guess that it doesn't fit my needs, but 74LS163 has 0 as minimal frequency so it looks like a logical choice to me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the oscillator, the slowest crystal I could find is 32 768 KHz which is too fast for me. I thought about using capacitor and coil to make my own oscillator. Some (maybe too) basic calculations tell me that L*C needs to be 1.989*10^-2. What capacitor/coil combination would be good for that? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I didn't think too much about power supply, but I'd either use &quot;wall-wart&quot; adapter or check the insides of the washing machine for any available power sources. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The last part of my question are vibrations. Are there any special considerations for circuits which are going to vibrate? I was thinking of using one of those solderable  protoboards for basic circuit board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that a book can be written for every point, but at this moment I'm just looking for some rough ideas.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-10-09T02:39:53.527" LastActivityDate="2011-05-22T18:27:02.787" Title="General directions for a timer circuit which will not use microcontroller and which can measure several hours needed." Tags="&lt;timer&gt;" AnswerCount="6" CommentCount="5" FavoriteCount="1" />
  <row Id="5011" PostTypeId="1" AcceptedAnswerId="5017" CreationDate="2010-10-08T20:46:07.843" Score="6" ViewCount="284" Body="&lt;p&gt;For my Super OSD project, I need a +3.3V supply at 250mA from a variable input of 5.5V to 20V. Cost is a concern, as is size. Originally, I considered an LM317 in a SOT-223 package, due to the small size. Unfortunately, it's difficult to get a heatsink for SOT-223 packages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then I did some calculations; the LM317 would be dissipating up to 4.175W with 20V input and 250mA of load and with a θJA of 140°C/W, the LM317 would cook along nicely at 584°C above ambient. So not practical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The next solution would be a little buck converter, but I'm looking to get a small design and a cost of &amp;lt;$3. Does anyone know of an ideal chip for the job? Or is it still possible to use a linear regulator? I'd prefer to do so, but getting rid of the wasted heat is really a problem. Power efficiency is not critical for this application, as an electric motor will be drawing 10's of amps, compared to the few hundred mA for this module. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-08T22:46:41.637" LastActivityDate="2010-10-08T22:46:41.637" Title="Best solution to get 3.3V from 5V-20V @ 250mA" Tags="&lt;voltage&gt;&lt;3.3v&gt;&lt;buck&gt;&lt;linear&gt;&lt;ldo&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="5012" PostTypeId="2" ParentId="5010" CreationDate="2010-10-08T20:56:04.513" Score="4" ViewCount="" Body="&lt;p&gt;CMOS 555 timers can be used to achieve delays of hours. A C of 4,700µF and R of 15 Mohm would time for 7550 seconds, or 2.09 hours (2 hours, 5 minutes, 50 seconds.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Due to the input current on bipolar 555 timers, they cannot be used with such large resistors, similar to how you cannot use high valued resistors with bipolar op-amps.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-08T20:56:04.513" />
  <row Id="5013" PostTypeId="1" AcceptedAnswerId="5015" CreationDate="2010-10-08T20:57:52.893" Score="3" ViewCount="218" Body="&lt;p&gt;I know the X-10 protocol. X-10 is a good choice or is there better?&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-08T21:25:10.857" Title="What is the best wired protocol choice for home automation?" Tags="&lt;wire&gt;&lt;home-automation&gt;&lt;protocol&gt;&lt;x-10&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="5014" PostTypeId="2" ParentId="5013" CreationDate="2010-10-08T21:01:40.183" Score="2" ViewCount="" Body="&lt;p&gt;I know this is far too short of an answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wireless.&#xA;Zigbee makes a great option and tinkerers do great with the XBEE units(handles the protocol for you, just basic configuration commands and acts like uart.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-08T21:01:40.183" />
  <row Id="5015" PostTypeId="2" ParentId="5013" CreationDate="2010-10-08T21:02:56.180" Score="1" ViewCount="" Body="&lt;p&gt;It depends on what you want. X-10 is very limited. You can only send command messages to devices, and the bit rate is limited to 50 or 60 bits per second. But it is enough for turning things like lights on and off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For large-scale automation, ethernet over power may be a good idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, you could try one of the newer protocols. &lt;a href=&quot;http://en.wikipedia.org/wiki/Domotics&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Domotics&lt;/a&gt; lists many of them.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-08T21:09:45.540" LastActivityDate="2010-10-08T21:09:45.540" />
  <row Id="5016" PostTypeId="2" ParentId="5011" CreationDate="2010-10-08T21:04:48.037" Score="1" ViewCount="" Body="&lt;p&gt;You could use a mc34063 chip as a step-down converter. There is a calculator  &lt;a href=&quot;http://dics.voicecontrol.ro/tutorials/mc34063/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; which you can fill in and get the right parts out of it. Note that you need a good diode, i.e. one that is fast enough to switch your operation frequency, and is able to handle the peaks (Schottky). So is for the inductor. Those will probably be the 2 major expenses, as with any switching supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you should be able to design such a circuit for under $3. It's possible to get that chip for under $0.30 at digikey (at quantity)&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-10-08T21:04:48.037" CommentCount="1" />
  <row Id="5017" PostTypeId="2" ParentId="5011" CreationDate="2010-10-08T21:12:03.410" Score="6" ViewCount="" Body="&lt;p&gt;There are number of companies that offer drop in switching regulators that might meet your needs.  I'd look at some of the electronics distributors out there with good parametric search capabilies like Digikey, Newark, or Mouser that might have something already designed that will work for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although it's a little more expensive than your $3 cost target.  Look at &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=102-1708-ND&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; drop-in switching regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It handles the output current and input voltage range you've specified.  It's $5.10 in quantities of 100.  Take into consideration the time saving cost benefit of not having to design one yourself.&lt;/p&gt;&#xA;" OwnerUserId="1520" LastEditorUserId="1520" LastEditorDisplayName="" LastEditDate="2010-10-08T22:01:11.417" LastActivityDate="2010-10-08T22:01:11.417" CommentCount="1" />
  <row Id="5018" PostTypeId="2" ParentId="5013" CreationDate="2010-10-08T21:25:10.857" Score="0" ViewCount="" Body="&lt;p&gt;In my system, I've used a CAN bus, at 125kbit/s, using Microchip CAN controller and transceiver. X10 is a really simple and limited protocol, even with bidirectional modules, and it's SLOW!&#xA;In my old house I had an X10 system with computer control... and there was a 3 seconds delay from the push of a button on the radio remote to the action (RADIO REMOTE -&gt; RADIO RECEIVER -&gt; X10 CODE ON POWERLINE -&gt; COMPUTER RECEIVER -&gt; COMPUTER PROCESS -&gt; COMPUTER TRANSMITTER -&gt; X10 CODE ON POWERLINE -&gt; APPLIANCE/LAMP MODULE)&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2010-10-08T21:25:10.857" />
  <row Id="5019" PostTypeId="2" ParentId="5011" CreationDate="2010-10-08T21:47:52.253" Score="4" ViewCount="" Body="&lt;p&gt;This &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=LM2574MX-ADJTR-ND&quot; rel=&quot;nofollow&quot;&gt;buck converter&lt;/a&gt; is $1.19 in 1000 unit quantities.  Input 4-40v, output fixed at 3.3v or three other voltages or adjustable from 1.3 to 37v, @500 ma.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-08T21:47:52.253" CommentCount="1" />
  <row Id="5020" PostTypeId="2" ParentId="4979" CreationDate="2010-10-08T22:35:07.380" Score="4" ViewCount="" Body="&lt;p&gt;Here's a fancy app note from Microchip about high-efficiency LED driving.  &lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/91060b.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ww1.microchip.com/downloads/en/AppNotes/91060b.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The gist is that they use an inductor to drive the LED with no current limiting resistor.  The inductor automagically drives the LEDs at the appropriate voltage.  I don't know how practical it is, but it may be worth investigating.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-08T22:35:07.380" />
  <row Id="5022" PostTypeId="2" ParentId="5009" CreationDate="2010-10-08T23:34:34.773" Score="3" ViewCount="" Body="&lt;p&gt;There are two components to powering a computer: The rectification from AC to DC, and the regulation from one DC voltage to another, like 3.3 or 5.5V.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PICOPSU-160-XT is a tiny form-factor device that regulates 12V DC down to the +3.3, +5.5, -12V, and other voltages required by the &lt;a href=&quot;http://www.formfactors.org/developer%5Cspecs%5Catx2_2.pdf&quot; rel=&quot;nofollow&quot;&gt;ATX Power Supply Specification&lt;/a&gt;.  It requires a 12V input from a male plug into a &quot;Female, panel mount, 2.5*5.5*10 mm&quot; jack according to Page 4 of the (brief) &lt;a href=&quot;http://resources.mini-box.com/online/PWR-PICOPSU-160-XT/PWR-PICOPSU-160-XT-manual.pdf&quot; rel=&quot;nofollow&quot;&gt;manual&lt;/a&gt;.  This jack would presumably be attached to your computer case.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The easiest solution would be to buy four AC-to-DC desktop wall warts, like the kind used to charge laptop batteries. However, &lt;a href=&quot;http://www.mini-box.com/110w-12v-8-5A-AC-DC-Power-Adapter&quot; rel=&quot;nofollow&quot;&gt;the biggest one on the store you used&lt;/a&gt; only delivered about 8.5A, which is just over half of the 16A maximum (13A continuous) that the PICOPSU supports.  You would need to know how much current your computers will be drawing, but this may be OK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another alternative would be to purchase a desktop ATX power supply of sufficient amperage (600-1000W), and run ATX power supply cabling into your four computers.  Similarly, four small PSUs could be used to the same effect.  Visit &lt;a href=&quot;http://www.newegg.com/Store/Category.aspx?Category=32&amp;amp;name=Power-Supplies&quot; rel=&quot;nofollow&quot;&gt;newegg&lt;/a&gt; for a good selection of power supplies.   We'd have to know more about your setup to determine whether this is a viable solution. - Would bulky, short cables going into your computers be OK?  Would they be located within a few feet of each other? Would a (relatively) bulky ATX power supply fit into the case?&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-08T23:34:34.773" CommentCount="5" />
  <row Id="5024" PostTypeId="1" CreationDate="2010-10-09T01:44:01.143" Score="2" ViewCount="340" Body="&lt;p&gt;I am experimenting with the Parallax Propeller chip but don't have any ideas for projects to learn with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are some good strategies on how to learn this chip? Are there any techniques or projects I should try?&lt;/p&gt;&#xA;" OwnerUserId="876" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:23:54.733" LastActivityDate="2010-12-11T11:51:25.093" Title="What is a good way to learn the Parallax Propeller chip?" Tags="&lt;propeller&gt;&lt;parallax&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="5025" PostTypeId="2" ParentId="5010" CreationDate="2010-10-09T02:46:19.737" Score="4" ViewCount="" Body="&lt;p&gt;I know you specifically said that you did not want to use a microcontroller, but I think you should consider taking the plunge into the microcontroller world. Doing a timer like this is very easy to do on a very cheap micro since you don't need it to do anything special.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general I have found that using a &quot;complex&quot; circuit of discrete components is usually plagued with minor errors in both design and construction that cause them to take a lot of time and money.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-09T02:46:19.737" CommentCount="2" />
  <row Id="5026" PostTypeId="2" ParentId="5024" CreationDate="2010-10-09T02:48:29.013" Score="3" ViewCount="" Body="&lt;p&gt;Whenever I start with a new microcontroller I always go back to a few of my standard projects. The things I enjoy playing with most are RGB LED's, 7 Segment Displays and i2c real time clocks like the DS1307+&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first projects almost always revolve around something I am familiar with like these components.  I might start off with just lighting up the RGB leds. Then I'll get more adventurous and work out PWM on the chip and start making lots of different colours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This gives me some time with the development tools and I can start to learn my way around the chip. This is just as important as what to make or how to learn about the micrcontroller you are using.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most controllers these days have a reasonable library so it should be relatively easy to get i2c going. So that instantly opens up a world of add on components to play with. The RTC chips are pretty easy to get going and they teach you a few programming techniques like BCD conversion. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Seven segment displays are also easy and fun. You can play around with single displays or even use the microcontroller to multiplex additional displays. Not hard to get going and the projects are semi useful and fun right off the bat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So by learning i2c, seven segment and driving leds. You can now build a very simple clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I realise these aren't propeller specific, but for anyone starting off it might just give you an idea about what to try!&lt;/p&gt;&#xA;" OwnerUserId="1304" LastActivityDate="2010-10-09T02:48:29.013" CommentCount="1" />
  <row Id="5027" PostTypeId="2" ParentId="4631" CreationDate="2010-10-09T05:17:38.437" Score="0" ViewCount="" Body="&lt;p&gt;It is likely that your problem is that after sending the first &quot;A&quot; you are not reading SPI1BUF back to clear whatever the SPI &quot;read&quot; back. Recall that SPI works like a shift register; for every bit you push out you get a bit in. If you do not read the contents of SPI1BUF then likely you get an overun, and per section 17.2.6 of the data sheet, the device stops working until you clear SPIROV&lt;/p&gt;&#xA;" OwnerUserId="1526" LastActivityDate="2010-10-09T05:17:38.437" CommentCount="1" />
  <row Id="5028" PostTypeId="2" ParentId="4211" CreationDate="2010-10-09T05:30:24.053" Score="0" ViewCount="" Body="&lt;p&gt;I've been working with Microchip microcontrollers for a long time and I know that family quite well, but I think you would be better served by the solution proposed by the &lt;a href=&quot;http://mbed.org&quot; rel=&quot;nofollow&quot;&gt;Mbed dev board&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will give you without doubt the fastest route to have Ethernet running on a microcontroller. Take a look at them, the price isn't too bad either. Also, take a look at the forum, there's already a driver for MySQL, although I don't know the reliability of such driver. I suppose it could be a starting point for your particular SQL database (in case it is not MySQL).&lt;/p&gt;&#xA;" OwnerUserId="1526" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T14:08:13.860" LastActivityDate="2011-05-16T14:08:13.860" />
  <row Id="5030" PostTypeId="2" ParentId="5024" CreationDate="2010-10-09T08:15:57.543" Score="1" ViewCount="" Body="&lt;p&gt;the &lt;a href=&quot;http://www.parallax.com/Portals/0/Downloads/docs/prod/prop/PELabsFunBook-v1.1.pdf&quot; rel=&quot;nofollow&quot;&gt;education kit book&lt;/a&gt; is a must read to learn the propeller. It contains a gentle introduction to the SPIN langage and a bunch of exercices for every concept introduced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you don't have to actually purchase the kit if you already have a propeller chip. You'll only need very common components to follow the book (a bunch of LEDs, resistors, push buttons, etc...). It's also good to know that you don't need to purchase a PropPlug to program the microcontroller, most FTDI adapters will do the job (I use the much cheaper USB BUB from modern device myself).&lt;/p&gt;&#xA;" OwnerUserId="595" LastActivityDate="2010-10-09T08:15:57.543" CommentCount="6" />
  <row Id="5031" PostTypeId="1" AcceptedAnswerId="5394" CreationDate="2010-10-09T08:37:12.453" Score="4" ViewCount="187" Body="&lt;p&gt;I would like to use Control Register controlled pins of LPT (1, 14, 16, 17) as inputs. These are said to be normally used as open collector outputs, but have the ability to operate as inputs too. &lt;a href=&quot;http://www.beyondlogic.org/spp/parallel.htm&quot; rel=&quot;nofollow&quot;&gt;This site&lt;/a&gt; describes the use of this pins as inputs, but I'm a bit confused and don't really understand what I'm supposed to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://i.imgur.com/dvqve.png&quot; rel=&quot;nofollow&quot;&gt;Here's what the circuit looks so far.&lt;/a&gt; This fails for Control Register pins, but &lt;strong&gt;works&lt;/strong&gt; for Status Register pins (10, 11, 12, 15). How do I need to change my schematic to make it work for with the other ones?&lt;/p&gt;&#xA;" OwnerUserId="1528" LastEditorUserId="1528" LastEditorDisplayName="" LastEditDate="2010-10-09T13:14:11.400" LastActivityDate="2010-10-20T11:04:59.670" Title="How to use Control Register inputs of LPT port?" Tags="&lt;parallel&gt;&lt;port&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="5032" PostTypeId="1" CreationDate="2010-10-09T11:15:53.150" Score="3" ViewCount="401" Body="&lt;p&gt;Does anyone know of any (foss) application to create karnaugh maps. I don't need a K-map solver, just to be able create them so I can export them to ms-word.&lt;/p&gt;&#xA;" OwnerUserId="819" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-01T21:30:37.097" LastActivityDate="2010-12-01T21:30:37.097" Title="Software To Create Karnaugh Maps" Tags="&lt;software&gt;&lt;karnaugh-map&gt;" AnswerCount="2" />
  <row Id="5033" PostTypeId="2" ParentId="5032" CreationDate="2010-10-09T11:27:29.643" Score="4" ViewCount="" Body="&lt;p&gt;There is at least a &lt;a href=&quot;http://www.ctan.org/tex-archive/macros/latex/contrib/karnaugh/&quot; rel=&quot;nofollow&quot;&gt;LaTeX package for Karnaugh maps and Veitch charts&lt;/a&gt;. &lt;a href=&quot;http://k-map.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;K-map&lt;/a&gt; on sourceforge looks promising too (though the source included no Makefile). I hope we'll see others listed here!&lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="1181" LastEditorDisplayName="" LastEditDate="2010-10-09T11:39:05.140" LastActivityDate="2010-10-09T11:39:05.140" CommentCount="2" />
  <row Id="5034" PostTypeId="1" AcceptedAnswerId="5042" CreationDate="2010-10-09T12:23:07.213" Score="3" ViewCount="315" Body="&lt;p&gt;I am trying to swap dead capacitors in my motherboard. Removing them was relatively easy, but I can not insert the new ones. The solder melted into the vias and the desoldering wire does not suck it out of the hole.&#xA;Is there any safe method to remove the blocking solder from the vias?&lt;/p&gt;&#xA;" OwnerUserId="1514" LastEditorUserId="1514" LastEditorDisplayName="" LastEditDate="2010-10-12T22:52:34.643" LastActivityDate="2010-10-12T22:52:34.643" Title="How to remove solder from via?" Tags="&lt;soldering&gt;&lt;soldering&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="1" />
  <row Id="5035" PostTypeId="2" ParentId="5034" CreationDate="2010-10-09T12:31:30.250" Score="2" ViewCount="" Body="&lt;p&gt;Try melting the solder and blowing it out. You might find that desoldering braid works better if you add some more solder to the pad, first.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-09T12:31:30.250" />
  <row Id="5036" PostTypeId="2" ParentId="5024" CreationDate="2010-10-09T12:37:29.863" Score="2" ViewCount="" Body="&lt;p&gt;You will find lots of projects on the Parallax Propeller forum.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-09T12:37:29.863" />
  <row Id="5037" PostTypeId="2" ParentId="5034" CreationDate="2010-10-09T12:42:19.480" Score="5" ViewCount="" Body="&lt;p&gt;Have you tried a &lt;a href=&quot;http://en.wikipedia.org/wiki/Desoldering#Desoldering_pump&quot; rel=&quot;nofollow&quot;&gt;desoldering pump&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/LNj0r.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="819" LastActivityDate="2010-10-09T12:42:19.480" CommentCount="4" />
  <row Id="5038" PostTypeId="2" ParentId="5031" CreationDate="2010-10-09T12:55:20.447" Score="2" ViewCount="" Body="&lt;p&gt;With those bi-directional LPT pins, if the open-collector output is active, it will prevent you from reading anything but a 0 from the pin. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With your circuit, if you ground that input that goes to pin 1 of your opto isolator, and pin 5 of the opto doesn't float up to +5 (while connected to the LPT port), it means the output driver of the LPT port is active, in which case you should be able to modify your software to turn it off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'm getting at is mentioned on the &lt;a href=&quot;http://www.beyondlogic.org/spp/parallel.htm&quot; rel=&quot;nofollow&quot;&gt;beyond logic web page&lt;/a&gt; you mentioned: &quot;the Control Port must be set to xxxx0100 to be able to read data, that is all pins to be +5v at the port so that you can pull it down to GND (logic 0).&quot;&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-10-09T13:03:34.903" LastActivityDate="2010-10-09T13:03:34.903" />
  <row Id="5039" PostTypeId="2" ParentId="5034" CreationDate="2010-10-09T13:49:46.110" Score="4" ViewCount="" Body="&lt;p&gt;Beyond what has already been answered, you can try to use wick solder remove.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/q2fP4.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a great article at wikipedia: &lt;a href=&quot;http://en.wikipedia.org/wiki/Desoldering&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Desoldering&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And Youtube has many videos about: &lt;a href=&quot;http://www.youtube.com/results?search_query=desoldering&amp;amp;aq=f&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/results?search_query=desoldering&amp;amp;aq=f&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-09T13:49:46.110" CommentCount="3" />
  <row Id="5040" PostTypeId="1" AcceptedAnswerId="5048" CreationDate="2010-10-09T13:55:55.487" Score="2" ViewCount="138" Body="&lt;p&gt;So I have 4 systems with &lt;a href=&quot;http://www.mini-box.com/picoPSU-160-XT&quot; rel=&quot;nofollow&quot;&gt;mini itx power supplies&lt;/a&gt; and am looking to purchase power bricks from the manufacturer. What confuses me is the &lt;a href=&quot;http://www.mini-box.com/110w-12v-8-5A-AC-DC-Power-Adapter&quot; rel=&quot;nofollow&quot;&gt;power bricks are 102 Watts&lt;/a&gt; while the PSU can do 160W with a max of 200W. This is probably obvious question but since the power brick can only do 102 watts that means the PSU can only provide 102W, and if this is the case why would the manufacturer bundle the two together?&lt;/p&gt;&#xA;" OwnerUserId="1518" LastActivityDate="2010-10-09T18:02:28.590" Title="Mini ITX PSU and Power Brick Wattages" Tags="&lt;power-supply&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="5042" PostTypeId="2" ParentId="5034" CreationDate="2010-10-09T15:13:31.813" Score="4" ViewCount="" Body="&lt;p&gt;Sometimes you can just push the majority of the stuff out, by quickly pushing a couple inches of un-heated solid wire through the hole while the solder is melted. If you do it fast enough, you end up with the solder frozen on the wire sticking out the other side of the board, and you can break the solder off and then just pull the wire back through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing that sometimes works is to heat the via and then quickly tap the board against the edge of a bench, moving the board in a short swing in the direction of the via. The inertia of the molten solder will cause it to keep going forward (and probably onto the floor) when the rest of the board stops. And (obviously, I had thought) &lt;strong&gt;you don't want use this technique on any but the sturdiest of boards&lt;/strong&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like the blowing technique, the down-side of these is that they can produce tiny, loose bits of conductive material to watch out for, which can cause shorts if you don't get them all. Suction is really the way to go.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-10-09T23:44:02.087" LastActivityDate="2010-10-09T23:44:02.087" CommentCount="5" />
  <row Id="5043" PostTypeId="1" AcceptedAnswerId="5046" CreationDate="2010-10-09T17:05:59.940" Score="1" ViewCount="519" Body="&lt;p&gt;hi fellows, &#xA;i just made a motor driver circuit on a veroboard to use with my arduino&#xA;but the problem is l298 spinning motor only one way.&#xA;here is the code&#xA;it was supposed to spin motor forth and backwards every 2 seconds right?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int mot1ana=5;&#xA;int mot1a=6;&#xA;int mot1b=7;&#xA;&#xA;void setup() {&#xA;pinMode(mot1ana,OUTPUT);&#xA;pinMode(mot1a,OUTPUT);&#xA;pinMode(mot1b,OUTPUT);&#xA;}&#xA;&#xA;void loop() {&#xA;  analogWrite(mot1ana,200);&#xA;  digitalWrite(mot1a,HIGH);&#xA;  digitalWrite(mot1b,LOW);&#xA;  delay(2000);&#xA;  analogWrite(mot1ana,200);&#xA;  digitalWrite(mot1a,LOW);&#xA;  digitalWrite(mot1b,HIGH);&#xA;  delay(2000);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/dSdaS.jpg&quot; alt=&quot;http://farm5.static.flickr.com/4124/5065468848_a210d091aa.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1461" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-10-09T17:36:12.753" LastActivityDate="2010-10-09T20:42:23.663" Title="L298 Motor Driver spinning motor only one way :/" Tags="&lt;arduino&gt;&lt;motor&gt;&lt;driver&gt;" AnswerCount="3" />
  <row Id="5044" PostTypeId="2" ParentId="4993" CreationDate="2010-10-09T17:13:41.563" Score="3" ViewCount="" Body="&lt;p&gt;Check out &lt;a href=&quot;http://www.actel.com/products/smartfusion/default.aspx&quot; rel=&quot;nofollow&quot;&gt;Actel's SmartFusion&lt;/a&gt; - they combine a FPGA with an ARM Cortex-M3 microcontroller, as well as some pretty nifty analog circuitry. This &lt;a href=&quot;http://www.actel.com/products/hardware/devkits_boards/smartfusion_eval.aspx&quot; rel=&quot;nofollow&quot;&gt;evaluation kit&lt;/a&gt; is pretty reasonably priced for what it does.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-10-09T17:13:41.563" />
  <row Id="5045" PostTypeId="2" ParentId="5043" CreationDate="2010-10-09T17:16:52.170" Score="0" ViewCount="" Body="&lt;p&gt;The first thing would be to check your motor driver actually works. It could be damaged, or perhaps is not designed to run motors in reverse. I'd check it by connecting the appropriate control pins to its V+ input.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-09T17:16:52.170" />
  <row Id="5046" PostTypeId="2" ParentId="5043" CreationDate="2010-10-09T17:17:00.133" Score="1" ViewCount="" Body="&lt;p&gt;It looks like you have chosen to use arduino pin numbers that are very similar to the necessary pin numbers on the L298. Nothing wrong with that, you can use whichever arduino pins are convenient. But it seems like it would be an easy mistake (with the given code) just to wire pin N from the arduino to pin N of the L298 under such circumstances. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the L298, you want the analog PWM going into pin 6, and your arduino is producing that at pin 5. So you'd want 5 from the arduino going to 6 on the L298, and 6 on the arduino going to 5 on the L298. Arduino pin 7 would still go to L298 pin 7.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;OR&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;if want to go with the 5-5, 6-6, 7-7 wiring, you could fix it in software, just by changing&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int mot1ana=5;&#xA;int mot1a=6;&#xA;int mot1b=7;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;to&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int mot1ana=6;&#xA;int mot1a=5;&#xA;int mot1b=7;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-10-09T20:42:23.663" LastActivityDate="2010-10-09T20:42:23.663" CommentCount="6" />
  <row Id="5047" PostTypeId="2" ParentId="5043" CreationDate="2010-10-09T17:32:44.870" Score="0" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/dSdaS.jpg&quot; alt=&quot;http://farm5.static.flickr.com/4124/5065468848_a210d091aa.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1461" LastActivityDate="2010-10-09T17:32:44.870" CommentCount="0" />
  <row Id="5048" PostTypeId="2" ParentId="5040" CreationDate="2010-10-09T17:42:05.113" Score="1" ViewCount="" Body="&lt;p&gt;It's like the weakest point in the system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example on a car the tires may only be good up to 130 mph but the engine can go up to 140 mph. Or something like that, I'm not a car person.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Really it's being a bit cheap to only stock the 102W supply. If you want a decent 12V supply you should look at an ATX power supply. In fact the pico PSU could be replaced by one of these entirely. Only go for that brick if size is a problem. Even then, you can find a 150W ATX PSU in a small form factor nowadays anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally I would find it very difficult to believe that the pico PSU can provide 150W without cooking itself. Looking at it, the inductors are small surface mount types, probably not greater than 4-5 amps continuous. And I can't see a power transistor; if there is one, it would need some serious heatsinking. (Think about your computer power supply: 300-400W, about 2x as much as the pico PSU but with a large heatsink, plus it has a fan. Yes, one operates off 12V and one off mains, but the mains PSU's FET will actually have less current flowing through it and probably run cooler.) I would like to be wrong, but I can't see it.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-09T18:02:28.590" LastActivityDate="2010-10-09T18:02:28.590" />
  <row Id="5049" PostTypeId="2" ParentId="5034" CreationDate="2010-10-09T17:56:25.977" Score="0" ViewCount="" Body="&lt;p&gt;What soldering Iron are you using?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This sound suspiciously like the pad's your having a problem with are tied directly to the ground plane and your iron isn't transferring enough heat effectively.  Or more specifically the ground plane is sinking enough heat to not get the solder up to the proper temperature. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use a metcal MX500 and when i have this issue stepping up to a larger tip usually transfers enough heat to solve the problem.  As a last step you can try a hotter tip, or if your using an adjustable iron, turn the heat up, just be careful not to go too high, if it gets too hot the pad will separate from the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Failing that, hold the board on edge, apply heat to the back side of the pad while pushing the cap in the top side, move the cap in as you move the iron out.  This usually works for me. &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-09T17:56:25.977" />
  <row Id="5050" PostTypeId="2" ParentId="5010" CreationDate="2010-10-09T18:11:32.287" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Intermatic-TN311C-Heavy-Grounded-Timer/dp/B00002N5FO/ref=pd_sim_dbs_k_14&quot; rel=&quot;nofollow&quot;&gt;buy one of these&lt;/a&gt; that fits your countries power system, they make digital ones too that aren't much more expensive if you need greater control.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plug your devices and an AC relay rated for your countries power into it.  Use the relay's output to &quot;push your button&quot; however that needs to be done for the particular device.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-09T18:11:32.287" CommentCount="1" />
  <row Id="5051" PostTypeId="1" CreationDate="2010-10-09T19:30:17.300" Score="2" ViewCount="209" Body="&lt;p&gt;Maybe a bit of a homework question, but I've done my homework and just can't seem to find the (an) answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for a small microcontroller that can accept high speed serial data. NXP calls it an SSP peripheral -- it works with a SPI, Microwire or SSI bus, and I'm using it in a 32-bit SSI application. By small I mean both physically (under 50 pins) and in terms of RAM/Flash (the 8k RAM and 32k Flash is more than enough). High speed means working as an SSI slave with clocks up to about 50MHz or so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm currently using an LPC2103 and it performs pretty well up to about 2-3MHz as an SSI slave, but I can only see the first 16 bits of the 32-bit word. I'm using both the SSP and SSI peripheral to grab all 32-bits, but that's a real kludge and for the next version I'm hoping to do away with the speed limitation and word length barrier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as architecture goes... it's really open. The LPC's ARM7TDMI of course, but PIC or AVR would work just fine, I'm not tied to any particular architecture and have worked with practically all of them at one point or another. Hell, I'd even looked at a small FPGA but it's also damn near impossible to find a low pin-count FPGA with a large number of programmable logic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's been a few days and all my searching's come up short, which is why I'm asking the broader stackexchange community for some fresh ideas and maybe a new direction. &lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-09T22:04:15.363" Title="small, inexpensive microcontroller capable of high speed SSP?" Tags="&lt;microcontroller&gt;&lt;slave&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="5052" PostTypeId="2" ParentId="5034" CreationDate="2010-10-09T19:45:45.007" Score="2" ViewCount="" Body="&lt;p&gt;If you can justify it, look into a desoldering iron, such as the &lt;a href=&quot;http://www.pacedirect.com/product.php?id=762&quot; rel=&quot;nofollow&quot;&gt;Pace SX-90&lt;/a&gt;. I've found them very useful because you don't have to remove your heat source to suck out solder, they're temperature-controlled, and they also can pull vacuum indefinitely. (They use a vacuum pump, instead of a spring piston.) Granted, the Pace iron requires a controller, but that controller can also control a temp-regulated iron as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/HXgaD.jpg&quot; alt=&quot;SX-90&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-10-09T19:45:45.007" CommentCount="2" />
  <row Id="5053" PostTypeId="2" ParentId="5051" CreationDate="2010-10-09T20:18:00.663" Score="1" ViewCount="" Body="&lt;p&gt;You're not going to find a 50MHz serial port on a PIC or an AVR as far as I know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My guess is you'd need to look at something on the order of a cortex-A8 SoC to get peripherals that fast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why not slow down the baud rate generator on the master when talking to this slow device?&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-09T21:56:34.680" LastActivityDate="2010-10-09T21:56:34.680" CommentCount="4" />
  <row Id="5054" PostTypeId="2" ParentId="5051" CreationDate="2010-10-09T20:24:20.697" Score="3" ViewCount="" Body="&lt;p&gt;An &lt;a href=&quot;http://www.xmos.com/&quot; rel=&quot;nofollow&quot;&gt;XMOS chip&lt;/a&gt; can easily manage 50 MHz SPI in software, the I/Os can handle 100 MHz events. A CPLD such as the Altera MAX II could also be used with a PIC or AVR. They are available in small 44-lead packages but development would be harder.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-10-09T20:30:53.973" LastActivityDate="2010-10-09T20:30:53.973" CommentCount="1" />
  <row Id="5055" PostTypeId="2" ParentId="5051" CreationDate="2010-10-09T22:04:15.363" Score="0" ViewCount="" Body="&lt;p&gt;Why does it need to be so fast? Are you pushing a constant stream of data at 50MHz? Or just occasional blips of data with idle periods in between? Because if it's a large stream of data, your MCU will need to be fast enough to handle the data as well.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-10-09T22:04:15.363" CommentCount="1" />
  <row Id="5057" PostTypeId="2" ParentId="1337" CreationDate="2010-10-10T04:36:30.140" Score="1" ViewCount="" Body="&lt;p&gt;@vicatcu: Your answer helped to clarify something similar which I was having problems with - thanks. Just a point (for anyone reading this long after the original thread):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void setup_timer(double p_ms, double duty){&#xA;  TCCR0A = _BV(COM0A0); // toggle OC0A on Compare Match&#xA;  TCCR0B = _BV(WGM02); // set CTC mode WGM0[2,1,0] = 0b100&#xA;&#xA;  // ... do some stuff based on your CPU frequency&#xA;  // to define the csxx_bits of TCCR0B when the timer is running&#xA;  // and consequently, to set on_time_ticks and off_time_ticks&#xA;  OCR0A = on_time_ticks;&#xA;  TCCR0B |= your_settings_here;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Your choice of 0b100 for WGM0[2,1,0] won't set CTC mode. (In fact it'll set a mode that's reserved by Atmel.) The ATtiny13 datasheet says CTC mode needs &lt;em&gt;value&lt;/em&gt; 2; you've accidentally given it _bit_number_ 2 instead (i.e. value 4). Because of that it's also necessary not only to change (i.e. clear) WGM02 in TCCR0B but also to set bits WGM01 and WGM00 to 1 and 0 respectively. Those bits are in TCCR0A, so it's not sufficient to set TCCR0A with only the COM0A bits.&lt;/p&gt;&#xA;" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-10T07:33:53.617" LastActivityDate="2010-10-10T07:33:53.617" CommentCount="1" />
  <row Id="5058" PostTypeId="1" CreationDate="2010-10-10T10:02:59.073" Score="2" ViewCount="395" Body="&lt;p&gt;I have followed the tutorial here &lt;a href=&quot;http://www.arduino.cc/playground/Main/MAX72XXHardware&quot; rel=&quot;nofollow&quot;&gt;MAX7219&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now when i wire it up to a 4 Digit 7 Segment display, and run any code changing the display I get all the segments on all digits lit up&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &quot;LedControl.h&quot; //  need the library&#xA;LedControl lc=LedControl(12,11,10,1); // lc is our object&#xA;// pin 12 is connected to the MAX7219 pin 1&#xA;// pin 11 is connected to the CLK pin 13&#xA;// pin 10 is connected to LOAD pin 12&#xA;// 1 as we are only using 1 MAX7219&#xA;void setup()&#xA;{&#xA;  // the zero refers to the MAX7219 number, it is zero for 1 chip&#xA;  lc.shutdown(0,false);// turn off power saving, enables display&#xA;  lc.setIntensity(0,8);// sets brightness (0~15 possible values)&#xA;  lc.clearDisplay(0);// clear screen&#xA;}&#xA;void loop()&#xA;{&#xA;  lc.setDigit(0,0,'0',false);&#xA;  delay(1000);&#xA;  lc.setDigit(0,0,'7',false);&#xA;  delay(1000);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The above code should clear the display so that all segments are off and change the 1st digit to a '0' then a '7' and loop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No matter how I change the code this does not happen they just all stay lit up, I have even rewired a few times and tried a different IC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone had any experience with this setup or these chips. I have read that 2 capacitors between the +5v and GND help so added them 10uF (Electrolytic) and 100nF. No yet still no change.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help or ideas would be great, I don't have a logic analyser to debug (Getting one at christmas!).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Thanks, Hughesy&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="665" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-10-10T12:09:41.393" LastActivityDate="2010-10-10T13:29:12.037" Title="MAX7219 Arduino Issue with 7 Segment display" Tags="&lt;arduino&gt;&lt;7segmentdisplay&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="5059" PostTypeId="1" CreationDate="2010-10-10T10:05:20.103" Score="2" ViewCount="191" Body="&lt;p&gt;We were doing an experiment on how to get the battery reading. we will be using a resistive voltage divider with a LM741 op-amp and we were wondering what resistor values is the best to use for the r1 and r2 given that our battery source is around 8v.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thank you.&lt;/p&gt;&#xA;" LastActivityDate="2010-10-10T16:16:33.917" Title="Voltage Divider Circuit" Tags="&lt;voltage-measurement&gt;" AnswerCount="1" CommentCount="7" FavoriteCount="1" />
  <row Id="5060" PostTypeId="2" ParentId="5010" CreationDate="2010-10-10T10:31:19.240" Score="3" ViewCount="" Body="&lt;p&gt;Have a look at basing your circuit around a CMOS 4060 14-stage ripple counter and oscillator. I have used these in the past for long interval timer projects - before PICs came along :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-=mike=-&lt;/p&gt;&#xA;" LastActivityDate="2010-10-10T10:31:19.240" CommentCount="1" />
  <row Id="5063" PostTypeId="2" ParentId="5058" CreationDate="2010-10-10T13:29:12.037" Score="1" ViewCount="" Body="&lt;p&gt;+1 - you need a common-cathode display; and you don't need the apostrophes around the 7 or 0, for example you just use:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;lc.setDigit(0,0,0,false);&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have written up a fair bit about the MAX7219 &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/07/09/review-maxim-max7219-led-display-driver-ic/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-10T13:29:12.037" CommentCount="3" />
  <row Id="5064" PostTypeId="1" AcceptedAnswerId="5067" CreationDate="2010-10-10T13:41:14.620" Score="3" ViewCount="244" Body="&lt;p&gt;Hi all&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm starting with electronics and I don't have a lot of resistors.&#xA;Every new project I try to do, I have to buy new resistors, but they take a long time to arrive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the solution?&#xA;What variable resistors should I buy?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="1539" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T22:15:48.890" LastActivityDate="2011-04-27T22:15:48.890" Title="Variable resistor" Tags="&lt;resistor&gt;&lt;breadboard&gt;" AnswerCount="5" CommentCount="1" />
  <row Id="5065" PostTypeId="2" ParentId="5010" CreationDate="2010-10-10T13:51:03.910" Score="2" ViewCount="" Body="&lt;p&gt;For what its worth...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I implemented a circuit on my dryer for programmed start with an Omron PLC. There is a button for ARM and a button 4hr / 8hr setting. The PLC has 6 inputs and 4 outputs. The outputs go to the buttons and one is paralleled with the dryer start switch as you mentioned. (might be a relay in there too for the dryer switch)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PLC was a cheap one I bought second hand on ebay (Omron CPM1A). IT takes 120v AC as an input and provides a 24v DC output for driving relays (or switch lights in this case).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Works well. It was interesting to program with ladder logic too. &lt;/p&gt;&#xA;" OwnerUserId="1411" LastActivityDate="2010-10-10T13:51:03.910" CommentCount="2" />
  <row Id="5066" PostTypeId="2" ParentId="5034" CreationDate="2010-10-10T13:55:36.757" Score="2" ViewCount="" Body="&lt;p&gt;Thanks for your tips. Here are my observations:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;em&gt;desoldering pump&lt;/em&gt; - After cleaning and oiling my pump I had still no luck with it. Maybe I have to practice more :)&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;desoldering braid&lt;/em&gt; - Adding some fresh solder before using this definitely improves the cleaning effect, but it leaves the solder inside the hole. I've tried three different types of solder wick without success.&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;tap-tap method&lt;/em&gt; - It seems usable for smaller boards but not for a computer motherboard so I have not tried it.&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;Pushing out&lt;/em&gt; - I had no thin solid wire here, so I added a little extra solder and heated the via while pushing in the new capacitor from the opposite side. Sometimes worked but this thing has two legs and I have only 1 soldering iron :)&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;Blowing out&lt;/em&gt; - I tried to blow with my mouth without any effect. Then I tried a dust blower, but I cannot aim it precisely into the hole.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Then I found something in my drawer:&#xA;&lt;img src=&quot;http://i.imgur.com/hLwfQ.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a plastic bottle with metal needle head, 1 USD from &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.5068&quot; rel=&quot;nofollow&quot;&gt;DX&lt;/a&gt;. I inserted it to the hole from the opposite side then I heated the hole. After removing the soldering iron I quickly squeezed the bottle. It cleaned out the via! 8 of 10 times I was able to insert the new component to the hole without problem. For the remaining two holes I used a sewing needle to broaden the hole.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Still not the best method, but it worked for me better than any others mentioned here. However I am considering to buy a vacuum desoldering tool to save a whole day next time :)&lt;/p&gt;&#xA;" OwnerUserId="1514" LastEditorUserId="1514" LastEditorDisplayName="" LastEditDate="2010-10-10T22:31:32.003" LastActivityDate="2010-10-10T22:31:32.003" />
  <row Id="5067" PostTypeId="2" ParentId="5064" CreationDate="2010-10-10T14:51:30.160" Score="8" ViewCount="" Body="&lt;p&gt;There is a thing named &lt;strong&gt;resistance decade&lt;/strong&gt;. It is like a programmable resistor, you can set the value and it precisely holds it. Costs about 100 to 1000 USD depending on precision and wattage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other cheaper solution is to buy a &lt;strong&gt;Resistor Assortment Kit&lt;/strong&gt;. It includes 20-50 pcs of every value of resistors. You can find it on &lt;a href=&quot;http://shop.ebay.com/?_kw=resistor%20assortment%20kit&quot; rel=&quot;nofollow&quot;&gt;ebay&lt;/a&gt; from 10 USD&#xA;&lt;img src=&quot;http://i.imgur.com/xU51I.jpg&quot; alt=&quot;resistance decade&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2010-10-10T14:51:30.160" CommentCount="4" />
  <row Id="5068" PostTypeId="2" ParentId="5059" CreationDate="2010-10-10T16:16:33.917" Score="4" ViewCount="" Body="&lt;p&gt;Choose what precision you want. Lets say .1V(100mV).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you look up your op-amps leakage current. Lets say it is 1.5uA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a voltage drop of .01(10mV) from 1.5 uA(.0015mA) you need a resistance of 10kOhms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I stay below 10kOhms I cannot get more than a 10mV voltage drop from it. You now know what you upper limit is for the resistance of your divider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need higher precision, use an op-amp with lower leakage current or use a lower resistance. In all reality with a 1.5uA leakage you will probably not know the difference with a 100K resistance, but I always plan for worst case and then test it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me know if there is anything I can do to make this more clear.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-10T16:16:33.917" />
  <row Id="5069" PostTypeId="1" AcceptedAnswerId="5076" CreationDate="2010-10-10T17:58:51.517" Score="7" ViewCount="352" Body="&lt;p&gt;I've been making my way through &quot;MAKE: Electronics: Learning Through Discovery&quot;, but have gotten stuck on Experiment 11, where I am making an oscillating circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The book calls for a 2.2uF capacitor, but I only have a 1000uF capacitor. I decided it would be fun to try to create a circuit that functions similarly with the parts I have (or at least to understand why doing so would be impossible)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit specified by the book is this:&#xA;&lt;img src=&quot;http://i.imgur.com/amoQZ.jpg&quot; alt=&quot;Figure 2.98&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R1: 470K Resistor, R2: 15K Resistor, R3: 27K Resistor, C1: 2.2uF electrolytic capacitor, D1: LED, Q1: 2N6027 PUT&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first thing I did was replace R1 with a 6.7K resistor so it wouldn't take so damn long to charge the capacitor. Next I replaced R2 with a 26K resistor and R3 with a 96K resistor so that the PUT would only let charge through when the capacitor was near the peak of its voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was expecting the LED to turn on once the capacitor charged to ~5v, and turn off once the capacitor discharged to less than ~5v. Instead, the capacitor charges for a few seconds, and the LED remains dimly lit while the capacitor's voltage remains steady at ~2.7v.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With my very limited knowledge of electronics, I am stumped by this behavior. Am I misunderstanding how a capacitor works? Thanks in advance for your expertise!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UPDATE:&lt;/strong&gt; I still don't exactly understand the relationship between the resistor values and the LED/capacitor getting &quot;stuck&quot; (where getting stuck means the LED will stay lit and the capacitor voltage will stay constant around 2.5v). After some more testing it appears that:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The larger R2 and R3 are (keeping the R2:R3 ratio approximately constant), the more likely it is the LED/cap will get stuck&lt;/li&gt;&#xA;&lt;li&gt;The smaller R1 is the more likely the LED cap will get stuck.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;For example, with R2 at 15K, R3 at 21K, and R1 at 66K, the LED/cap will oscillate properly (although slowly). If I change R1 to 46K the LED/cap gets &quot;stuck&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know of an explanation for this behavior?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;I believe Mark has the right answer (based on some testing) so I've accepted it. If R1 has much less resistance than R2 and R3, the cap charges much faster than it discharges so that it oscillates quickly while it appears to the multimeter that it is &quot;stuck&quot; at one voltage.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;However, I would appreciate if Mark (or anyone else) can explain how to come up with that insight about Rg from the &lt;a href=&quot;http://www.onsemi.com/pub/Collateral/2N6027-D.PDF&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="1540" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-27T19:55:56.510" LastActivityDate="2011-02-27T19:55:56.510" Title="Capacitor behavior in oscillating circuit" Tags="&lt;capacitor&gt;&lt;transistor&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="5070" PostTypeId="1" AcceptedAnswerId="5072" CreationDate="2010-10-10T18:00:18.660" Score="4" ViewCount="124" Body="&lt;p&gt;This question is very basic, but I'd like to ask it anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to drive a &lt;a href=&quot;http://www.velleman.eu/distributor/products/view/?id=375874&quot; rel=&quot;nofollow&quot;&gt;small motor&lt;/a&gt;. I'm thinking about connecting it directly to 4 AA batteries and using a simple switch. Is there anything else needed?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, it its datasheet unit gcm is mentioned. What is it? I thought that torque is measured in N*m or similar units.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-10-10T18:10:49.980" Title="Driving a small motor: What's needed?" Tags="&lt;motor&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="5072" PostTypeId="2" ParentId="5070" CreationDate="2010-10-10T18:10:49.980" Score="6" ViewCount="" Body="&lt;p&gt;gcm is gram * centimeters. The stall torque is listed as 340 gcm. This means that if you stuck a pulley with a radius of 1 cm on the shaft, wrapped a string around it, and tied it to some weights, it would fail to lift more than 340 grams.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your strategy of 4 AA batteries and a switch will probably work. If the system involved digital electronics, you'd want to add a diode in parallel with the motor to prevent voltage spikes when you opened the switch. (Google &quot;flyback diode.&quot;) You'd also want a capacitor in parallel with the motor to filter out high-frequency electrical noise, which would scramble the rest of your circuitry. But for a small motor and a mechanical switch, you'll be fine.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-10T18:10:49.980" />
  <row Id="5073" PostTypeId="2" ParentId="5069" CreationDate="2010-10-10T18:54:42.777" Score="3" ViewCount="" Body="&lt;p&gt;You're probably not misunderstanding how a capacitor works. It's probably the programmable unijunction transistor that's acting weird.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My understanding is that a PUT stays on as long as the current through it is greater than a certain threshold. Since you decreased R1, I bet the current when the cap is discharged is higher than that threshold, so the PUT never quite turns off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try changing R1 back to 470k and see if it works. (It will be a little tedious to test.) Then you can decrease R1 and see how far you can go while still having the PUT turn off.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-10T18:54:42.777" CommentCount="3" />
  <row Id="5074" PostTypeId="2" ParentId="5069" CreationDate="2010-10-10T19:24:56.930" Score="3" ViewCount="" Body="&lt;p&gt;Why don't you try a spice simulator like ltspice?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.linear.com/designtools/software/#Spice&quot; rel=&quot;nofollow&quot;&gt;http://www.linear.com/designtools/software/#Spice&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can change values and quickly see the differences.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-=mike=-&lt;/p&gt;&#xA;" LastActivityDate="2010-10-10T19:24:56.930" />
  <row Id="5075" PostTypeId="2" ParentId="5064" CreationDate="2010-10-10T19:39:10.873" Score="3" ViewCount="" Body="&lt;p&gt;I would recommend getting an assortment of some kind from your electronics dealer, they should have some. You'll probably get them cheaper that way, too. If you do SMD, you might need separate sets for different sizes plus a pth kit. But the price still isn't bad and usually those kits are so big you won't have to worry about it after you buy one set. If you find yourself running out of one size (220Ω, 10kΩ), you can get a strip/tape of 100(0) and be set for a long while again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In many cases you can get away with rounding the values a lot, so you'll probably only need a few per magnitude. You can combine values and a few pots/trimmers can help test values quickly (while prototyping).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That decade box (or such) can be made if you can find the switches. There should be ready schematics for various types.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Either way, I'd say stock up on a wide set of values. If you're doing anything more than putting together a ready kit now and then, you can probably use the selection. There's also a couple of other questions here about how to keep those parts in order, what parts to keep in stock, and what belongs into a &quot;basic electronics kit&quot;.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-10-10T19:39:10.873" />
  <row Id="5076" PostTypeId="2" ParentId="5069" CreationDate="2010-10-10T20:42:45.393" Score="2" ViewCount="" Body="&lt;p&gt;never really played with a PUT before (actually never heard of em) but i was interested and read the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks like the current through the PUT is dependent on the resistance between gate and ground, which explains why when the cap is feeding the LED it doesn't get really mad about the LED not having a current limiting resistor.  In this case the Rg gate resistance is your R3.  My guess is that when you moved R3 up to 96k your limiting the current so much that your LED isn't getting to full brightness.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally the low limit of this current combined with a really big cap means your capacitor discharges much slower.  Combine this with the very small R1, which charges the cap quickly, and i'm betting you are getting some oscillation, but its happening very, very fast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try a larger R1, smaller R3 and whatever sized R2 you need to keep the divider ratio the same.  Ideally track down a smaller cap, it would make finding the resistor sizes needed easier.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-11T04:35:36.273" LastActivityDate="2010-10-11T04:35:36.273" CommentCount="3" />
  <row Id="5077" PostTypeId="1" CreationDate="2010-10-10T21:32:20.080" Score="4" ViewCount="253" Body="&lt;p&gt;I have a digital cable box that lives in a wooden cabinet under my tv.  I would like to use the remote with the doors to the cabinet closed.  It looks like an IR Repeater runs about $30+.  Can one be built easily for less?  &lt;/p&gt;&#xA;" OwnerUserId="1544" LastActivityDate="2010-10-11T04:35:54.633" Title="How to build an IR Repeater?" Tags="&lt;ir&gt;" AnswerCount="2" />
  <row Id="5078" PostTypeId="1" AcceptedAnswerId="5079" CreationDate="2010-10-10T21:55:32.847" Score="1" ViewCount="154" Body="&lt;p&gt;I have zeroed it down to these two phones &lt;a href=&quot;http://www.gsmarena.com/compare.php3?idPhone1=2922&amp;amp;idPhone2=3229&quot; rel=&quot;nofollow&quot;&gt;Nokia X6 and Nokia C6&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from others, one difference is the presence of capacitive touchscreen in one and resistive in the other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I were to decide only on the basis of these touchscreen technologies, which one should I go for?&lt;/p&gt;&#xA;" OwnerUserId="1546" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-10T22:16:37.617" LastActivityDate="2010-10-10T22:31:24.670" Title="What are the pros and cons of resistive and capacitive touchscreen mobile devices?" Tags="&lt;mobile&gt;&lt;touchscreen&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="5079" PostTypeId="2" ParentId="5078" CreationDate="2010-10-10T22:31:24.670" Score="5" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Capacitive:&lt;/strong&gt; Generally more expensive, can support &quot;multi-touch&quot;, rely on skin contact because the persons electrical field is what causes changes.  This means they don't work well, or at all with gloves on.  Doesn't rely on touch pressure, so are generally more responsive to finger use/light taps, etc.  Requires a fairly complicated controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Resistive:&lt;/strong&gt; Cheap, only a single touch point can be detected.  Rely on pressure to achieve detection (u may have to push hard on them).  Any object touching the screen can create a &quot;press&quot; event, so gloves, non-conductive pens, etc work fine.  Controller is very simple, just measures a few resistances.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-10T22:31:24.670" />
  <row Id="5080" PostTypeId="1" AcceptedAnswerId="5098" CreationDate="2010-10-10T22:48:00.987" Score="3" ViewCount="179" Body="&lt;p&gt;My building recently installed a CCTV camera system. Anyone with cable TV is able to tune into channel XX and watch the CCTV stream live.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to get a cheap and small LCD (≤7&quot;) and build a dedicated &quot;television&quot; that would be tuned to channel XX. Eventually, the plan is to hook this up to a caller-id circuit and have the &quot;TV&quot; turn on when I get a call from downstairs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a programmer by trade and don't have much experience with building circuits.&#xA;I'd just like a ballpark figure of what I'll need and how difficult it would be to make a primitive TV these days.&lt;/p&gt;&#xA;" LastActivityDate="2010-10-14T06:31:04.637" Title="DIY Single-Channel Television" Tags="&lt;circuit&gt;&lt;lcd&gt;&lt;tv&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="5081" PostTypeId="2" ParentId="5077" CreationDate="2010-10-10T23:12:43.170" Score="3" ViewCount="" Body="&lt;p&gt;Should be fairly simple. I'd imagine a IR (infrared) phototransistor (receiver) driving a IR led (transmitter) would work. There are a range of different infrared frequencies used in devices, from around 800nm to 940nm. 940nm is fairly common* though and I would start with that, but it may take some experimenting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IR remotes are modulated at a certain frequency so that they are less prone to interference from other light sources. This modulation is in the order of 38KHz, but the phototransistor should just copy that modulation to the led without any problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit would be something like a &lt;a href=&quot;http://en.wikipedia.org/wiki/Darlington_transistor&quot; rel=&quot;nofollow&quot;&gt;darlington&lt;/a&gt; with the left transistor as your IR phototransistor, the right hand transistor should just be an NPN capable of handling 100mA or so. Your led sits above the right hand transistor with a current limiting resistor and gets pulled to ground (and turned on) when light hits the phototransistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CAUTION: Bad ascii art schematic follows:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;        --- VCC&#xA;         |&#xA;         R  RESISTOR&#xA;         |&#xA;         V  LED&#xA;         |&#xA;   ------|&#xA; |/      |&#xA;-|       |&#xA; |\    |/&#xA;   ----|    NPN&#xA;       |\&#xA;         |&#xA;        --- GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;There is a chance though that this would be too sensitive to ambient light, leaving your led turned on for the majority of the time. If that is the case then something more complicated with a 38KHz (or your specific frequency) receiver and modulator may be necessary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[*] - I suspect this is due to the H2O absorption band in the atmosphere &lt;a href=&quot;http://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water&quot; rel=&quot;nofollow&quot;&gt;filtering&lt;/a&gt; out sunlight at this frequency. The &lt;a href=&quot;http://www.ladyada.net/make/tvbgone/index.html&quot; rel=&quot;nofollow&quot;&gt;TV-B-Gone&lt;/a&gt; uses 940nm, so this is probably what you want.&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-10-10T23:12:43.170" CommentCount="2" />
  <row Id="5082" PostTypeId="1" AcceptedAnswerId="5086" CreationDate="2010-10-11T02:36:36.817" Score="6" ViewCount="610" Body="&lt;p&gt;I'm going to buy some things for back to the electronic world.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Starting with an Resistor Assorted Kit.&#xA;Need to buy some kits containing the most common capacitors and transistors... what to buy???&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[I want to buy to create a lot of things that there is schematic on the web without having to buy new components]&lt;/p&gt;&#xA;" OwnerUserId="1539" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-29T12:30:08.547" LastActivityDate="2011-05-18T11:35:42.523" CommunityOwnedDate="2011-03-28T11:23:46.830" Title="&quot;Starter Kit&quot; - What to buy? transistors/capacitors" Tags="&lt;capacitor&gt;&lt;transistor&gt;&lt;kit&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="2" />
  <row Id="5083" PostTypeId="2" ParentId="5077" CreationDate="2010-10-11T04:35:54.633" Score="0" ViewCount="" Body="&lt;p&gt;There was a &lt;a href=&quot;http://www.jaycar.com.au/productView.asp?ID=KC5432&quot; rel=&quot;nofollow&quot;&gt;kit made&lt;/a&gt; a few years ago, still on the market. The plans would be in Silicon Chip &lt;a href=&quot;http://www.siliconchip.com.au/cms/A_107822/article.html&quot; rel=&quot;nofollow&quot;&gt;magazine&lt;/a&gt; (Australia) October 2006. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-11T04:35:54.633" CommentCount="2" />
  <row Id="5084" PostTypeId="2" ParentId="5082" CreationDate="2010-10-11T05:44:02.177" Score="7" ViewCount="" Body="&lt;p&gt;SparkFun has a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=10003&quot; rel=&quot;nofollow&quot;&gt;Beginner Parts Kit&lt;/a&gt; for $25 which contains the following:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;1 - Parts Box&lt;/li&gt;&#xA;&lt;li&gt;10 - 0.1uF cap&lt;/li&gt;&#xA;&lt;li&gt;5 - 100uF cap&lt;/li&gt;&#xA;&lt;li&gt;5 - 10uF cap&lt;/li&gt;&#xA;&lt;li&gt;5 - 1uF cap&lt;/li&gt;&#xA;&lt;li&gt;5 - 10nF cap&lt;/li&gt;&#xA;&lt;li&gt;5 - 1nF cap&lt;/li&gt;&#xA;&lt;li&gt;5 - 100pF cap&lt;/li&gt;&#xA;&lt;li&gt;5 - 10pF cap&lt;/li&gt;&#xA;&lt;li&gt;5 - 1N4148 Diode&lt;/li&gt;&#xA;&lt;li&gt;5 - 1N4001 Diode&lt;/li&gt;&#xA;&lt;li&gt;5 - 2N3906 PNP Transistor&lt;/li&gt;&#xA;&lt;li&gt;5 - 2N3904 NPN Transistor&lt;/li&gt;&#xA;&lt;li&gt;3 - 20 pin female header&lt;/li&gt;&#xA;&lt;li&gt;3 - 20 pin male header&lt;/li&gt;&#xA;&lt;li&gt;3 - Mini power switch&lt;/li&gt;&#xA;&lt;li&gt;2 - Push buttons&lt;/li&gt;&#xA;&lt;li&gt;2 - 10k trimpot&lt;/li&gt;&#xA;&lt;li&gt;2 - LM358 OpAmp&lt;/li&gt;&#xA;&lt;li&gt;2 - 3.3V regulator&lt;/li&gt;&#xA;&lt;li&gt;2 - 5V regulator&lt;/li&gt;&#xA;&lt;li&gt;1 - 555 Timer&lt;/li&gt;&#xA;&lt;li&gt;1 - Green LED&lt;/li&gt;&#xA;&lt;li&gt;1 - Yellow LED&lt;/li&gt;&#xA;&lt;li&gt;1 - Red LED&lt;/li&gt;&#xA;&lt;li&gt;1 - 7 segment Red LED&lt;/li&gt;&#xA;&lt;li&gt;1 - mini Photocell&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;It is intended for those starting out in embedded electronics but looks like a pretty good general selection.  Unfortunately it is out of stock right now, but it is a pretty good list to go by.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-11T05:44:02.177" CommunityOwnedDate="2011-03-28T11:23:46.830" CommentCount="6" />
  <row Id="5085" PostTypeId="1" CreationDate="2010-10-11T06:30:57.077" Score="1" ViewCount="292" Body="&lt;p&gt;How can I disable the JTAG in the ATmega32 using a serial programmer?&lt;/p&gt;&#xA;" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-10-19T12:58:14.523" LastActivityDate="2010-10-19T12:58:14.523" Title="How can I disable the jtag in atmega 32 using serial programmer ?" Tags="&lt;microcontroller&gt;&lt;atmega&gt;&lt;jtag&gt;" AnswerCount="2" />
  <row Id="5086" PostTypeId="2" ParentId="5082" CreationDate="2010-10-11T08:21:41.563" Score="7" ViewCount="" Body="&lt;p&gt;I'm still a beginner but here are some things I have bought and found useful:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tools wise - most important are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Multimeter&lt;/li&gt;&#xA;&lt;li&gt;Storage Unit&lt;/li&gt;&#xA;&lt;li&gt;Side Cutters&lt;/li&gt;&#xA;&lt;li&gt;Long Nose Pliers&lt;/li&gt;&#xA;&lt;li&gt;Solderless Breadboards&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Less important are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Good Lighting&lt;/li&gt;&#xA;&lt;li&gt;Soldering Iron&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Components wise, get kits wherever possible to ensure you have a good selection of components:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Capacitor Kit&lt;/li&gt;&#xA;&lt;li&gt;Trimmer Kit&lt;/li&gt;&#xA;&lt;li&gt;Resistor Kit&lt;/li&gt;&#xA;&lt;li&gt;Zener Diode Kit&lt;/li&gt;&#xA;&lt;li&gt;Diode Kit&lt;/li&gt;&#xA;&lt;li&gt;Transistor Kit&lt;/li&gt;&#xA;&lt;li&gt;5mm LEDs&lt;/li&gt;&#xA;&lt;li&gt;555 Timers (get 2) &lt;/li&gt;&#xA;&lt;li&gt;Logic ICs (These will let you perform logic on circuits - not so important but if you want to be prepared for the future get at least one of each AND, OR, NAND, NOR, XOR (2 input versions) and a 4069 inverter.)&lt;/li&gt;&#xA;&lt;li&gt;Power and Power Clips (At the very least get a 9v PP3 battery and PP3 clip)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;After that, get the rest of your stuff in bulk from eBay (works out nice and cheap).&lt;/p&gt;&#xA;" OwnerUserId="1333" LastActivityDate="2010-10-11T08:21:41.563" CommunityOwnedDate="2011-03-28T11:23:46.830" CommentCount="2" />
  <row Id="5087" PostTypeId="2" ParentId="5085" CreationDate="2010-10-11T11:17:20.303" Score="1" ViewCount="" Body="&lt;p&gt;You disable the JTag by setting the fuses. You can use the &lt;a href=&quot;http://palmavr.sourceforge.net/cgi-bin/fc.cgi&quot; rel=&quot;nofollow&quot;&gt;AVR Fuse Calculator&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-11T11:17:20.303" />
  <row Id="5088" PostTypeId="2" ParentId="5064" CreationDate="2010-10-11T11:29:30.350" Score="1" ViewCount="" Body="&lt;p&gt;Sometimes you can use a good emulator like &lt;a href=&quot;http://qucs.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;qucs&lt;/a&gt;, that is free.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/6lkmm.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-11T11:29:30.350" CommentCount="1" />
  <row Id="5090" PostTypeId="2" ParentId="5064" CreationDate="2010-10-11T11:49:00.087" Score="2" ViewCount="" Body="&lt;p&gt;One option is to combine resistors in series and parallel to produce the resistance you need.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-11T11:49:00.087" />
  <row Id="5091" PostTypeId="2" ParentId="5064" CreationDate="2010-10-11T12:41:46.683" Score="4" ViewCount="" Body="&lt;p&gt;Another idea is to just buy resistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I buy resistors in packs of 100 for about 50p each; packs of 1,000 are also available for £2.88 each. They are 1/4W, 5%, carbon film. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, I'd recommend you stock up on the most common values: 10, 47, 100, 470, 1k, 4.7k, 10k, 47k and 100k provide a good range. Then get the in-between values. You'll rarely find a use for 1M+ resistors, so I don't have any of them.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-11T12:41:46.683" CommentCount="2" />
  <row Id="5092" PostTypeId="2" ParentId="5032" CreationDate="2010-10-11T13:04:30.740" Score="2" ViewCount="" Body="&lt;p&gt;If you are looking for software to simplify logic equations or create logic diagrams from truth tables I would recommend &lt;a href=&quot;http://sontrak.com/downloads.aspx&quot; rel=&quot;nofollow&quot;&gt;Logic Friday&lt;/a&gt;. I think there is an export feature as well.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-11T13:04:30.740" CommentCount="3" />
  <row Id="5093" PostTypeId="2" ParentId="5085" CreationDate="2010-10-11T13:09:44.687" Score="2" ViewCount="" Body="&lt;p&gt;(from &lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=printview&amp;amp;t=53097&amp;amp;start=0&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=printview&amp;amp;t=53097&amp;amp;start=0&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;avrdude -U hfuse:w:0xD9:m&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Or:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ldi   temp,0x80&#xA;out   mcucsr,temp      ;JTAG&#xA;out   mcucsr,temp      ;disabled&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(I have not tested either of these as I have no ATmega32. Messing with AVR fuses can potentially brick your chip unless you  have a high voltage/parallel programmer, caveat emptor...)&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-11T13:09:44.687" />
  <row Id="5094" PostTypeId="1" AcceptedAnswerId="5122" CreationDate="2010-10-11T13:25:52.223" Score="3" ViewCount="147" Body="&lt;p&gt;Are there some general resources (other than spec sheets of boards) to compare the differences between computing formats like VPX, VME, IBM bladecenter-h, etc?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am tasked with doing some legwork what form-factor we should be looking at when buying our processing equipment for a high performance semi-rugged system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've read specs on size, connectors, bandwidth density, power usage, etc. Is there anything more I am missing?  I'm having trouble comparing the overall possible bandwidth to each server in each architecture.  Particularly VPX and all of its dot level specifications.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;These would run custom software and FPGAs, DACs, ADCs, a linux machine, etc.&lt;/p&gt;&#xA;" OwnerUserId="1297" LastEditorUserId="1297" LastEditorDisplayName="" LastEditDate="2010-10-12T21:48:57.947" LastActivityDate="2010-10-14T03:00:28.847" Title="Pros/Cons of different backplane architectures ?" Tags="&lt;computers&gt;&lt;processing&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="5095" PostTypeId="1" AcceptedAnswerId="5101" CreationDate="2010-10-11T14:32:49.210" Score="8" ViewCount="345" Body="&lt;p&gt;Some of my projects need to live outside for long periods.  Sometimes, moisture gets into the enclosures.  That means that a circuit board might be sitting around in contact with water for hours on end at upwards of 100F.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've noticed that solder joints can start to corrode, and recently moisture made it under the solder mask on a board and actually ate through one of the traces, breaking the circuit.  I know the ideal answer is to make a perfectly sealed enclosure, but I'd like to toughen the boards up a bit as a second level of defense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone suggest some tips and tricks for making PCBs more corrosion resistant?  Does scrubbing off excess flux help?  What about spray acrylic sealant?  Special solder?&lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2010-11-05T09:44:19.513" Title="What's the best way to protect a board from corrosion in a hot/moist environment?" Tags="&lt;pcb&gt;&lt;corrosion&gt;&lt;moisture&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="5096" PostTypeId="1" AcceptedAnswerId="5099" CreationDate="2010-10-11T14:40:26.117" Score="6" ViewCount="262" Body="&lt;p&gt;I want to connect multiple I2C slave devices to a micro controller all on the same set of pins but the I2C devices all share the same address. The addresses are fixed in the hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any way to connect multiple devices with the same address?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps some kind of I2C address translation module with each device with an configurable address so I can assign my own addresses to each one.&lt;/p&gt;&#xA;" OwnerUserId="898" LastActivityDate="2010-10-11T14:56:21.817" Title="How to resolve I2C address clashes?" Tags="&lt;serial&gt;&lt;i2c&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="5097" PostTypeId="1" CreationDate="2010-10-11T14:49:14.347" Score="2" ViewCount="167" Body="&lt;p&gt;Could anyone recommend a high speed PCI-bus SSP capable of 10Mbps supplied with suitable drivers to interface to a dotNET application?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Data is sent via RS422 type drivers with differential twisted screened pairs terminated at both ends. &lt;/li&gt;&#xA;&lt;li&gt;Data is accompanied by a clock with +ve transitions mid-bit. &lt;/li&gt;&#xA;&lt;li&gt;Every 5 msec the data stream transmits 2000 bytes &lt;/li&gt;&#xA;&lt;li&gt;Each byte will have one start bit, eight data bits and one stop bit (no parity). &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" LastActivityDate="2010-10-15T02:10:44.537" Title="Requirement for a High Speed (10Mbps) PCI -bus Synchronous Serial Port" Tags="&lt;serial&gt;" AnswerCount="1" CommentCount="6" FavoriteCount="0" />
  <row Id="5098" PostTypeId="2" ParentId="5080" CreationDate="2010-10-11T14:49:57.120" Score="1" ViewCount="" Body="&lt;p&gt;This probably isn't the best first electronics project.  Decoding a cable TV feed isn't all that that complicated but its not overly easy either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One approach is to use something like: &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/sn761678b.html&quot; rel=&quot;nofollow&quot;&gt;This for getting from baseband to the IF signal&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That part is designed to be tuned over I2C with a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sounds like you can ignore audio in your case which eases post processing, actually the IF signal can probably just go right into your little LCD screen, assuming it accepts an NTSC input.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-11T14:49:57.120" CommentCount="1" />
  <row Id="5099" PostTypeId="2" ParentId="5096" CreationDate="2010-10-11T14:56:21.817" Score="11" ViewCount="" Body="&lt;p&gt;There is nothing built into I2C to do this, normally slave devices will have some externals pins that can be set to 0 or 1 to toggle a couple of the address bits to avoid this issue.  Alternatively I've dealt with a few manufacturers that have 4 or 5 part numbers for a part, the only difference being its I2C address.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most devices have specific hardware that handles the I2C communication, that is the slave ACK is in hardware so you really can't hack around it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the translation module, you could buy some $0.50 PIC's with 2 I2C buses and write some quick code to make them act as address translators i guess.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-11T14:56:21.817" CommentCount="3" />
  <row Id="5100" PostTypeId="2" ParentId="5095" CreationDate="2010-10-11T15:02:47.257" Score="2" ViewCount="" Body="&lt;p&gt;I used to &quot;paint&quot; the ready PCB with rosin soluted in alcohol. When the alcohol evaporates, it leaves a air-sealing rosin coating on the PCB. However I don't know how it behaves in outdoor conditions maybe it melts in hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively there are special PCB protecting sprays, here is an overview &lt;a href=&quot;http://www.acc-silicones.com/products/coatings.ashx&quot; rel=&quot;nofollow&quot;&gt;http://www.acc-silicones.com/products/coatings.ashx&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1514" LastEditorUserId="1514" LastEditorDisplayName="" LastEditDate="2010-10-11T15:09:29.443" LastActivityDate="2010-10-11T15:09:29.443" />
  <row Id="5101" PostTypeId="2" ParentId="5095" CreationDate="2010-10-11T15:03:24.690" Score="10" ViewCount="" Body="&lt;p&gt;Sounds like your boards are in a very tough environment, but anyway, it is common practise (and an accepted industry standard) to use so-called &lt;a href=&quot;http://en.wikipedia.org/wiki/Conformal_coating&quot; rel=&quot;nofollow&quot;&gt;Conformal Coating&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know from experience at one of my previous companies that it does help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Material varies, but the article in the above link explains a lot and internet searches for &quot;Conformal Coating&quot; will yield many products. I have used brushes to apply the coating after reworking PCBs, but in volume production, spray or dipping are used.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2010-11-05T09:44:19.513" LastActivityDate="2010-11-05T09:44:19.513" CommentCount="4" />
  <row Id="5102" PostTypeId="2" ParentId="5095" CreationDate="2010-10-11T15:17:00.550" Score="4" ViewCount="" Body="&lt;p&gt;The coating zebonaut mentioned is the best solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing to pay attention to is avoiding DC voltage gradients wherever possible.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I mean is that when your choosing which pins to use on parts, don't choose 2 adjacent pins such that one is almost always say, +5V, and the other is always 0v (GND).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The constant voltage gradient between the two pins will drive electro-chemical reactions, corrosion and the like.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try to separate pins when possible, use the lowest voltage possible, and as a last option if the signal levels can be modulated, even if it serves no purpose but to modulate them, such as pulsing an LED or a switch you don't really need to, do it to avoid the constant gradient. &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-11T15:17:00.550" />
  <row Id="5103" PostTypeId="2" ParentId="5080" CreationDate="2010-10-11T15:53:39.593" Score="2" ViewCount="" Body="&lt;p&gt;It might be easier to buy a small handheld TV/ display that accepts NTSC, tune it to the channel (or hook it to a cable box / tuner tuned to the right channel), and then simply turn the power to it (or the video feed) on and off by some controller that handles the caller-id condition.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your'e a programmer by trade, this is likely the easiest way to solve the problem, maximizing use of off-the-shelf parts.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-10-11T15:53:39.593" CommentCount="1" />
  <row Id="5104" PostTypeId="1" CreationDate="2010-10-11T16:17:03.950" Score="5" ViewCount="232" Body="&lt;p&gt;I'm looking at a situation where I'd want to connect a number of devices together to pass line level analog audio signals around. For the connections in question, there will always be small groups of channels (I've been assuming groups of 4) that go together. So rather than require a big mess of patch cables, I'm wondering what existing off the shelf items would work. 1m Cat-5/6 patch cords are easy to get and would have the correct number of conductors and meets the mechanical requirements but how would it do for signal quality?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Edit 1&lt;/em&gt;: I'm not sure that I didn't introduce some confusion here. I haven't settled on what kind of signaling I'm going to be using other than that it doesn't inherently need to deliver any power (the component at the other end will have whatever amps are needed to avoid that).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Edit 2&lt;/em&gt;: In the case I'm considering, I would be building the devices at each end and one of the advantages I'm seeing to using Cat5 is that I can use a single RJ-45 jack rather than four 1/4in TRS or XLR jacks (one of the devices could easily be limited by panel space for  jacks).&lt;/p&gt;&#xA;" OwnerUserId="1182" LastEditorUserId="1182" LastEditorDisplayName="" LastEditDate="2010-10-12T15:33:29.523" LastActivityDate="2010-10-12T15:33:29.523" Title="How well would cat-5/6 work as a multi pair audio cable?" Tags="&lt;analog&gt;&lt;wiring&gt;" AnswerCount="3" CommentCount="8" FavoriteCount="2" />
  <row Id="5105" PostTypeId="2" ParentId="3578" CreationDate="2010-10-11T16:38:41.150" Score="1" ViewCount="" Body="&lt;p&gt;For small components I recommend &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.4727~r.18353065&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; mini storage boxes. The resistors, diodes, &#xA;LEDs are easily fit in it. The best advantage of this versus a divided box with one lid, that it opens invidually. It is very useful when you accidentally knock off the box from your table...&#xA;&lt;img src=&quot;http://i.imgur.com/7WKiF.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1514" LastEditorUserId="1514" LastEditorDisplayName="" LastEditDate="2010-10-11T18:22:14.733" LastActivityDate="2010-10-11T18:22:14.733" CommentCount="1" />
  <row Id="5106" PostTypeId="2" ParentId="5104" CreationDate="2010-10-11T16:42:29.560" Score="6" ViewCount="" Body="&lt;p&gt;Should be fine over short distances.  If the cable is going to be in a noisy environment (lots of 50/60hz EM especially) go with shielded CAT5 and make sure the shield is grounded properly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your looking at longer distances, consider differential signaling, which again the twisted pairs of a cat5 cable are just fine for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As always when dealing with patching devices together like this be careful of creating ground loops.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-11T16:42:29.560" CommentCount="17" />
  <row Id="5107" PostTypeId="2" ParentId="5104" CreationDate="2010-10-11T16:50:11.237" Score="1" ViewCount="" Body="&lt;p&gt;From what I've seen in radio stations, they work well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The audio is differential and the twisted pair removes common mode noise.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-10-11T16:50:11.237" CommentCount="9" />
  <row Id="5108" PostTypeId="2" ParentId="5104" CreationDate="2010-10-11T16:56:47.007" Score="2" ViewCount="" Body="&lt;p&gt;I have found that the gauge of cat5 seems to be too small of diameter for line level audio. It may work just fine but you might want to consider something like this: &lt;a href=&quot;http://www.parts-express.com/pe/showdetl.cfm?Partnumber=240-286&quot; rel=&quot;nofollow&quot;&gt;http://www.parts-express.com/pe/showdetl.cfm?Partnumber=240-286&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-11T16:56:47.007" CommentCount="4" />
  <row Id="5111" PostTypeId="1" AcceptedAnswerId="5118" CreationDate="2010-10-11T20:08:00.787" Score="11" ViewCount="577" Body="&lt;p&gt;I want to learn PID (Proportional–Integral–Derivative) control mainly for temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to learn preferably through an easy project to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you please recommend something which would take a few weeks to learn?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; I want to control the temperature of a water tank. The heating is done by a resistor.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-23T19:07:02.217" LastActivityDate="2011-02-24T07:04:25.393" Title="How to learn PID Control?" Tags="&lt;microcontroller&gt;&lt;controller&gt;&lt;control&gt;&lt;pid-controller&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="9" />
  <row Id="5112" PostTypeId="2" ParentId="5095" CreationDate="2010-10-11T20:40:35.330" Score="1" ViewCount="" Body="&lt;p&gt;Conformal coating (something silicone-based) is the less extreme solution, but if your part is small enough (or environment harsh enough) you might consider &lt;a href=&quot;http://en.wikipedia.org/wiki/Potting_%28electronics%29&quot; rel=&quot;nofollow&quot;&gt;potting&lt;/a&gt; it.  However, when potted, boards will be &lt;strong&gt;extremely&lt;/strong&gt; difficult to rework if needed, while conformal coat is somewhat easy (if annoying) to scrape off.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-11T20:40:35.330" />
  <row Id="5113" PostTypeId="1" AcceptedAnswerId="5115" CreationDate="2010-10-11T20:45:34.457" Score="3" ViewCount="119" Body="&lt;p&gt;I am looking for suggestions of a low bandwidth (&amp;lt;1 kbps) mesh network which can be implemented between RC model planes. It should be able to communicate over distances of 500m or more, preferably 1km+, and it should gracefully handle the loss of nodes in the network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should be legal worldwide to operate; at least Europe and the USA if that is not possible. And, it must be relatively cheap to implement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is for an RC plane game I am developing. Real world model aircraft in dogfights. Or racing each other. It will be part of Super OSD.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-11T20:53:02.863" Title="A low bandwidth mesh network for RC planes" Tags="&lt;communication&gt;&lt;radio&gt;&lt;wifi&gt;" AnswerCount="1" CommentCount="7" FavoriteCount="2" />
  <row Id="5114" PostTypeId="2" ParentId="5111" CreationDate="2010-10-11T20:49:57.050" Score="3" ViewCount="" Body="&lt;p&gt;Yes. Get a thermistor and a resistor. Pick a resistance that can pull a decently large current (&gt;100mA).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use thermal paste between them and tape them together with tape. Hook the thermistor circuit to a microcontroller through ADC. Use a transistor to control the resistor and control this with a PWM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Develop a PID that allows you to control temp with a dial and practice making a PID that overshoots and rings the temperature. Make it over-damped and take forever to reach temp, and try to get it critically damped and get to the temp at max speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me know if more detail would help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After you get this done reduce their thermal conductance, try adding a stage that will delay the temperature propagation and try to get it to control well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This can also be done with an LED and a photo-transistor.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-23T14:17:07.750" LastActivityDate="2011-02-23T14:17:07.750" CommentCount="1" />
  <row Id="5115" PostTypeId="2" ParentId="5113" CreationDate="2010-10-11T20:53:02.863" Score="5" ViewCount="" Body="&lt;p&gt;Take a look at the 900MHz band XBEE modules. They can get great range. They are relatively easy to operate and you can sleep them when not being used.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-11T20:53:02.863" CommentCount="7" />
  <row Id="5116" PostTypeId="1" AcceptedAnswerId="5117" CreationDate="2010-10-11T20:58:23.880" Score="2" ViewCount="162" Body="&lt;p&gt;I need some help in figuring out what size capacitor I need, and if my idea will even work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a &lt;a href=&quot;http://www.xheli.com/newsy3chs1mi.html&quot; rel=&quot;nofollow&quot;&gt;small remotely-controlled helicopter&lt;/a&gt;, and a &lt;a href=&quot;http://www.chucklohr.com/808/&quot; rel=&quot;nofollow&quot;&gt;very small camera&lt;/a&gt;.  I am trying to record video while flying the helicopter around.  So far, cutting down the body of the helicopter and taking the PCB out of the camera and mounting it to the helicopter has worked well.  However, the usable flight time is reduced from 10 minutes or so to 1 minute.  I noticed that the battery on the camera and the battery on the helicopter are the same type and voltage.  What I would like to do is power the helicopter and the camera from the same battery to save on weight.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My original plan was to simply cut the camera battery out of the picture and tie the camera directly do the helicopter.  However, I thought this would cause problems, as the voltage while charging would likely fry the camera.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, I noticed the decorative LED on the front of the helicopter.  The voltage (3.7V or so, depending on battery charge) is exactly what is needed to power the camera.  The LED is also off while the helicopter is turned off and/or charging.  Now, this helicopter alternates the polarity going to the LED twice a second, as it is a bi-color LED.  My current plan is to cut out the LED, rectify the voltage with 4 diodes so I have straight DC, and use this to power the camera.  (Barring any current issues of course.  I plan to measure the current load of the LED vs. the camera before doing this, but I expect they will be similar, given the amount of time the camera can run off of its own battery [1 hour+] of similar capacity to that of the helicopter.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am going to experiment with this plan tonight, but I just realized that there is probably a very short time where the LED driver outputs 0V in between its polarity switch.  I'm thinking that sticking a capacitor in there will help with the problem, but I have no idea how to calculate what size I need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you tell me what I need to do to calculate the size cap that would likely keep things running smoothly?  Again, the voltage output of the LED driver and the voltage requirement of the camera is 3.7V, but I'm guessing will be anywhere from 4.2 to 3.6 during operation.  I don't yet know the current requirements, but plan to figure those out tonight.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you for your time.&lt;/p&gt;&#xA;" OwnerUserId="1554" LastActivityDate="2010-10-13T21:46:58.153" Title="Capacitor to provide power to a circuit during a very small interruption" Tags="&lt;power-supply&gt;&lt;capacitor&gt;" AnswerCount="2" />
  <row Id="5117" PostTypeId="2" ParentId="5116" CreationDate="2010-10-11T21:32:37.917" Score="2" ViewCount="" Body="&lt;p&gt;I would guess the camera takes 100-150 mA (180 mAh 3.7V battery, ~1 h runtime), and your LED will only be driven with about 20 mA, plus there should be a resistor in series with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd just power them both off the same battery if weight is a major issue, and if you're concerned about the charging voltage damaging the camera, add some cutoff switch (or just unplug it) while charging.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-11T21:32:37.917" CommentCount="2" />
  <row Id="5118" PostTypeId="2" ParentId="5111" CreationDate="2010-10-11T22:18:45.563" Score="12" ViewCount="" Body="&lt;p&gt;Controlling temperature (it depends upon your medium) isn't terribly hard.  That was my first project when I started.  Pardon me, if I repeat things you already know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume you already have a way of controlling the system (ie, a heater or cooler unit), and a way of getting feedback from the system (a temperature sensor like a thermistor or something).  You'll need both to implement a PID loop, which is a type of closed loop control.  All you really need to do after that is write a bit of software to send control commands, read feedback, and make decisions upon that feedback.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd start out by reading &lt;a href=&quot;http://igor.chudov.com/manuals/Servo-Tuning/PID-without-a-PhD.pdf&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;PID without a PhD&lt;/strong&gt;&lt;/a&gt;.  It's the article I used when I first had to regulate temperature in a science experiment.  It provides some easy-to-understand pictures, and nice sample code (a basic loop that you can tweak only needs 30 lines) that explains how to control your 'plant' - in this case, the thing you want to control the temperature of.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The gist of PID - Proportional-Integral-Differential - control is to use instantaneous, past, and predicted future performance (respectively) of the system to determine how to control a system at a given point in time to reach a specified set point.  In many cases, you'll have to tune the algorithm's gain factors to get the desired performance you need - how quickly the temperature will rise, how much you want to avoid overshoot, etc.  You might even find you don't need the differential or even integral control to get where you want to be!&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-10-11T22:18:45.563" CommentCount="1" />
  <row Id="5119" PostTypeId="2" ParentId="3578" CreationDate="2010-10-11T22:41:26.780" Score="1" ViewCount="" Body="&lt;p&gt;For passives (resistors/caps) I use little coin envelopes, one value per envelope, with the envelopes kept in a shoebox that's subdivided so they can stay upright and in order. I segregate by types, of course.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I previously used a hole punch to put a hole in each envelope, and then strung them on a keyring, but as the number of values increased, that got a bit unwieldy. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For ICs and the like, I have so few hanging around that I just keep them in little ESD bags in a box. With so few to look through it's not worth better organizing yet.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2010-10-11T22:41:26.780" />
  <row Id="5120" PostTypeId="1" AcceptedAnswerId="5128" CreationDate="2010-10-11T23:39:18.660" Score="1" ViewCount="273" Body="&lt;p&gt;Since MW is actually the rate of energy is being used, why would we use MWh/h as in &lt;a href=&quot;http://www.fingrid.fi/portal/in_english/electricity_market/load_and_generation/&quot; rel=&quot;nofollow&quot;&gt;this URL&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wouldn't MWh/h be the same as MW???&lt;/p&gt;&#xA;" OwnerUserId="1556" LastActivityDate="2010-10-12T12:48:39.923" Title="Does it make sense to use MWh/h as unit of measure?" Tags="&lt;power&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="5121" PostTypeId="2" ParentId="5095" CreationDate="2010-10-12T02:02:31.870" Score="2" ViewCount="" Body="&lt;p&gt;In re conformal coating: a garage shop I talked to once admitted that for conformally coating boards, they just dipped them in urethane deck varnish. They claimed this worked well enough that they used it for PCBs for salt-water marine installs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I actually got them to do a dead board for me. Cosmetically it wasn't nice (ever seen an epoxy-coated board? Like that, big drips and all) but coverage was 100%. I chickened out of trusting them with the real thing though. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a hobby project or a garage shop, I think it's worth trying. The big problem with any conformal coating is masking - keeping coating out of where it shouldn't be. Given that most coatings are transparent and thus noninspectable (my experience is that UV dyes don't homogenize and so are worse than useless), process is everything. Do it wrong and you're dead. Dipping has the advantage that you can keep connectors clear if they are all on one side. If not, you can use an acid brush to paint around them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In summary: haven't tried it myself, but &quot;Home Depot Brand&quot; coating is what I'll try if I ever do my own outdoors project.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2010-10-12T02:02:31.870" CommentCount="1" />
  <row Id="5122" PostTypeId="2" ParentId="5094" CreationDate="2010-10-12T02:04:56.657" Score="2" ViewCount="" Body="&lt;p&gt;If this is professional interest, the VITA standards documents are available for $300 or so for a CD of all of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit to add: what are you looking for? Performance, price, ubiquity, etc?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: some additional thoughts. Will add to these as I think of them.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;COTS Journal, Embedded Computing Design, and similar trade magazines have high level technical articles on these interfaces. Caveat emptor, since the articles are written by vendors.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For ADC/DAC applications, how much bandwith do you really need? If this is a control/sensing application (LVDT, etc), you may not need more than a few tens of KHz/channel. Which might imply that you don't need a x16 PCIe interface. My experience is that a lot of folks tend to spec as much CPU, RAM, Flash, and IO bandwidth as they can get. Even if they need to move a few dozen bytes every 50 mSec.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If you're looking at commercial cards or chassis, you should also consider IO card availability. Don't forget the possibility of using PMC/XMC cards on carriers.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I would stay away from anything that doesn't have a decent ecosystem yet. VME and cPCI are safe. RapidIO? StarFabric? Maybe not there in 5 years.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I think VPX's costs will kill it. $140 per board connector, x3 for a 3U IO card? Really?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="906" LastEditorUserId="906" LastEditorDisplayName="" LastEditDate="2010-10-14T03:00:28.847" LastActivityDate="2010-10-14T03:00:28.847" CommentCount="2" />
  <row Id="5123" PostTypeId="1" CreationDate="2010-10-12T02:11:41.397" Score="6" ViewCount="175" Body="&lt;p&gt;I have implemented a PID function using the formula,&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;correction = Kp * error + Kd * (error - prevError) + kI * (sum of errors)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;What should I do to keep my output between a certain range? say 0-255 If I disregard any value not between 0 to 255 it produces a jiggly behavior?&lt;/p&gt;&#xA;" OwnerUserId="496" LastActivityDate="2010-10-12T21:26:58.110" Title="Scaling PID (Proportional Integral Derivative) Output" Tags="&lt;controller&gt;&lt;control&gt;&lt;pid-controller&gt;" AnswerCount="2" FavoriteCount="3" />
  <row Id="5124" PostTypeId="2" ParentId="952" CreationDate="2010-10-12T02:42:37.173" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://revision3.com/tbhs&quot; rel=&quot;nofollow&quot;&gt;Ben Heck show&lt;/a&gt; has turned out to be a really great show about hacking electronics. He digs into existing electronics and mods them for different purposes. &lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-10-12T02:42:37.173" CommunityOwnedDate="2010-10-12T02:42:37.173" />
  <row Id="5125" PostTypeId="2" ParentId="5123" CreationDate="2010-10-12T04:53:56.820" Score="4" ViewCount="" Body="&lt;p&gt;I usually just limit the integral term (sum of errors) and if you cannot handle ringing you need to drop the gain to make the system over damped.  Also make sure your variables for error, prevError and (sum of error ) are larger variables that do not clip or overflow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you just clip the correction and then feed that back into the next error term it will cause a non-linearity and the control loop will be getting a step response into it each time you clip which will cause your jiggly behavior.&lt;/p&gt;&#xA;" OwnerUserId="540" LastActivityDate="2010-10-12T04:53:56.820" />
  <row Id="5126" PostTypeId="2" ParentId="5120" CreationDate="2010-10-12T09:42:12.230" Score="1" ViewCount="" Body="&lt;p&gt;No, it doesn't. h/h = 1, so it's MW. But power companies never made sense anyway :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe they think the target audience doesn't understand watts but have a vagues idea about what MWh is and know how to think of magnitudes per hour.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(And fingrid? What shame. ;)&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-10-12T09:42:12.230" />
  <row Id="5127" PostTypeId="2" ParentId="5111" CreationDate="2010-10-12T12:03:28.010" Score="1" ViewCount="" Body="&lt;p&gt;A nice &lt;a href=&quot;http://wiki.scilab.org/Xcos/Examples/PID&quot; rel=&quot;nofollow&quot;&gt;PID simulator&lt;/a&gt; is available for Scilab.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-12T12:03:28.010" />
  <row Id="5128" PostTypeId="2" ParentId="5120" CreationDate="2010-10-12T12:48:39.923" Score="1" ViewCount="" Body="&lt;p&gt;agreed, it is power companies trying to keep their end simple consistent.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As people are generally billed in kWh or (MWh for big business?) it is simpler to indicate the a unit of power per time period.&lt;br&gt;&#xA;* kWh and MWh are alternatives to joules for representing an amount of energy, &#xA;* kWh/h and MWh/h are alternatives to kW and MW for representing power (or energy production/consumption).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As appliances as generally rated in W (or kW) telling people they have been charged for 100MJ of electricity might be confusing to the end user, so instead they have opted for kWh as the unit for energy.  The kWh/h and MWh/h is just an extension of that, to provide end users with units that have meaning to them.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example Fingrid is now generating enough power to supply a 1,000,000 fridges (assuming 1kW fridge).  So it does make sense, in weird non scientific kind of way&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-12T12:48:39.923" />
  <row Id="5129" PostTypeId="1" AcceptedAnswerId="5131" CreationDate="2010-10-12T13:19:57.430" Score="5" ViewCount="214" Body="&lt;p&gt;I'm using an LM2734 buck regulator to get +3.3V at 400mA. The datasheet is unclear on how to lay out the supply, so I tried to follow some common sense, keeping all power traces short where possible. The power supply has to be very small, which is why it uses ceramic caps and the LM2734, which operates at 3 MHz and thus requires a smaller inductor (it's still pretty massive!)&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;L1: 3.3uH 2A inductor&lt;/li&gt;&#xA;&lt;li&gt;C1: 4.7uF 50V ceramic cap&lt;/li&gt;&#xA;&lt;li&gt;C2: 4.7uF 50V ceramic cap&lt;/li&gt;&#xA;&lt;li&gt;C3: 0.01uF 16V ceramic cap&lt;/li&gt;&#xA;&lt;li&gt;C4: 22uF 10V ceramic cap&lt;/li&gt;&#xA;&lt;li&gt;D1: RB160M (input protection)&lt;/li&gt;&#xA;&lt;li&gt;D2: RB160M&lt;/li&gt;&#xA;&lt;li&gt;D3: (mislabeled D1, the SOT-23) any small signal silicon diode&lt;/li&gt;&#xA;&lt;li&gt;R1: 10k&lt;/li&gt;&#xA;&lt;li&gt;R2: 31.6k&lt;/li&gt;&#xA;&lt;li&gt;R3: 1k&lt;/li&gt;&#xA;&lt;li&gt;LED1: any small LED&lt;/li&gt;&#xA;&lt;li&gt;U1: LM2734, SOT-23-6&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'm generating the boost voltage from the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/VLcuX.png&quot; alt=&quot;my PSU&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-12T23:07:45.477" Title="Critique my SMPS buck design" Tags="&lt;buck&gt;&lt;smps&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="2" />
  <row Id="5130" PostTypeId="1" CreationDate="2010-10-12T13:24:46.530" Score="5" ViewCount="302" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking for any information that would help me reduce the power rail noise and EMI of DC brush motors. I am building a robot that is powered by 2 x 250 W 24V DC motors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you in advance&lt;/p&gt;&#xA;" OwnerUserId="1562" LastActivityDate="2011-02-22T05:17:34.790" Title="Methods of filtering noise caused by DC brush motors" Tags="&lt;motor&gt;&lt;robotics&gt;&lt;dc&gt;&lt;filter&gt;&lt;dc-motor&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="5131" PostTypeId="2" ParentId="5129" CreationDate="2010-10-12T13:28:20.937" Score="2" ViewCount="" Body="&lt;p&gt;From the details below:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At 400mA and 20V in, you're running in continuous mode with a duty cycle of around 18%, with a peak inductor current of around 0.7A. At 4.8V, it's also CCM with a duty cycle near 70% and a peak inductor current of around 0.5A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may want to consider having a footprint on the PCB for the feed-forward capacitor Cff, just in case the internal compensation needs a speed-up. (You could also add a resistor in series with Cff, making what's referred to as type-3 compensation when combined with the ICs internal feedback). Bucks can be tricky to stabilize, especially with ceramic output capacitors (and with most of the compensation inside the chip!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can afford some copper, add some around the SW and/or Vin pins. Copper here can pull some of the heat out of the internal MOSFET and improve reliability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 2% reference may cause a setpoint error of up to +/- 66mV, not including the tolerance of the resistors used in the feedback divider. You may want to add another footprint in parallel with the bottom resistor in the divider or add a trim pot if the setpoint is critical for your application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't expect great efficiency at 20V in - the duty cycle is very small. It'll be much better than a linear regulator of course, but not great.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2010-10-12T16:35:24.833" LastActivityDate="2010-10-12T16:35:24.833" CommentCount="9" />
  <row Id="5132" PostTypeId="2" ParentId="5130" CreationDate="2010-10-12T13:39:05.550" Score="6" ViewCount="" Body="&lt;p&gt;The noise could be generated by either the brushes (commutation) or the driver if its PWM.  Easiest fix for brush noise (which would be random or 'static') is a capacitor right across the PMDC motor leads, something like a 1 µF, 100 V ceramic capacitor might be a good starting point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the PWM supply is causing problems (something with narrow spectral content), you would need a choke between the PWM power rail and your main supply.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-12T13:39:05.550" CommentCount="1" />
  <row Id="5133" PostTypeId="2" ParentId="5129" CreationDate="2010-10-12T14:20:13.487" Score="1" ViewCount="" Body="&lt;p&gt;Looks good to me. The trace running through C3 is really tight-- maybe switch to a cap in a larger package? I might also flip C4 180 degrees so the trace to the small signal diode and R1 is shorter.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-12T14:20:13.487" />
  <row Id="5134" PostTypeId="1" CreationDate="2010-10-12T14:28:48.057" Score="5" ViewCount="485" Body="&lt;p&gt;I need to design a timing circuit. After a duration of 6 months a  LED must come on. The LED can then be turned off at the press of a button and the 6 month count-down must begin again. Anyone have any idea where I would start? Is a 555 timer capable of doing something for a time of this duration or would I need somthing else? Any help would be greatly appreciated..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[added] it will be used as a reminder to change a water filter so it should be powered off a small battery..something small, easy to setup and with a low current consumption would also be handy..any help appreciated..thanks for the previous input..&lt;/p&gt;&#xA;" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-10-22T16:26:50.837" LastActivityDate="2010-10-23T18:18:34.840" Title="6 Month Countdown Timer Circuit" Tags="&lt;led&gt;&lt;timer&gt;&lt;555&gt;" AnswerCount="6" CommentCount="4" />
  <row Id="5135" PostTypeId="2" ParentId="5134" CreationDate="2010-10-12T14:52:32.587" Score="6" ViewCount="" Body="&lt;p&gt;Based on &lt;a href=&quot;http://electronics.stackexchange.com/questions/5010/general-directions-for-a-timer-circuit-which-will-not-use-microcontroller-and-whi/5012#5012&quot;&gt;this answer&lt;/a&gt;, I think a 555 won't work. You'd need a massive capacitor and a huge resistor, and the accuracy would be terrible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd recommend using the simplest of 8-bit microcontrollers. You'd have to handle the numbers carefully, but a PIC16F84A (or an Arduino, or lots of other similar devices) could do it. I might set up a 1 second timer, and then count 15778463 timer expirations, storing the count in a 32-bit variable. (For Arduino 32-bit variables, see &lt;a href=&quot;http://www.arduino.cc/en/Reference/Double&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Reference/Double&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-12T14:52:32.587" CommentCount="5" />
  <row Id="5136" PostTypeId="2" ParentId="5134" CreationDate="2010-10-12T15:07:57.730" Score="3" ViewCount="" Body="&lt;p&gt;The tricky part would be precision over such a large time interval.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may want to consider a crystal oscillator combined with a cascade of binary counters. See &lt;a href=&quot;http://www.fairchildsemi.com/ds/CD/CD4060BC.pdf&quot; rel=&quot;nofollow&quot;&gt;4060 datasheet&lt;/a&gt; for examples.&lt;/p&gt;&#xA;" OwnerUserId="1350" LastActivityDate="2010-10-12T15:07:57.730" />
  <row Id="5137" PostTypeId="2" ParentId="5134" CreationDate="2010-10-12T15:30:50.950" Score="5" ViewCount="" Body="&lt;p&gt;Like pingswept, I'd recommend a cheap microcontroller. The TI Launchpad MSP430 comes with a 32.768KHz crystal and supports very low power operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This project is not far off what you want:&#xA;&lt;a href=&quot;http://kennethfinnegan.blogspot.com/2010/08/msp430-bicolor-led-clock.html&quot; rel=&quot;nofollow&quot;&gt;http://kennethfinnegan.blogspot.com/2010/08/msp430-bicolor-led-clock.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-12T15:30:50.950" />
  <row Id="5138" PostTypeId="2" ParentId="5129" CreationDate="2010-10-12T16:05:55.047" Score="4" ViewCount="" Body="&lt;p&gt;Good first stab, just some thoughts:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) The R1 / R2 feedback voltage divider has some really long traces and paths to ground.  Anything you can do to keep the FB traces short will improve regulation stability and the ground used should be tightly coupled to the IC ground.  I'd put R1 and R2 directly next to each other and put em where the small signal diode is, moving the diode over to where R1 is now.  Ground R2 to the IC ground via (its low current).  The LED can go pretty much anywhere and trace length doesn't matter so just move it to fit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) The input caps, C1/C2 and the catch diode D2 should be very tightly coupled, their ground references need to be very very close to each other.  I'd flip D2 90 degrees and move it over next to C2, ground them all right there, you should use more than 1 via for this ground.  What i normally do for this is a little copper pour on the surface that connects to all 3 pads (D2/C1/C2) and extends out enough to plop 3 decently sized vias in it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) the output filter cap C4 is in a really odd place It should also be quite tightly coupled to the ground of D2/C1/C2, move L1 over and you can probably put it right next to D2 and included it in the little ground pour I was talking about in 2).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) With the above re-organization you can move C3 over just above/to the right a touch of the IC which will get rid of the problem you have with the input supply trace having to fit between C3's pads, as drawn right now that will short out, the trace is way too close to the pads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that your critical path in this circuit, that is the loop where there will be high current AC and DC spike is from the input -&gt; D1 -&gt; C1+ -&gt; C2+ -&gt; ICin -&gt; ICsw -&gt; D2+ -&gt; L1 -&gt; C4+ -&gt; C4- -&gt; through other grounds back to C1- &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your goal is to minimize the loop area and the resistance in that loop, which moving C1,C2,D2,C4 as close as possible to each other and the IC will help with as well as tightly coupling their grounds through a small pour on the surface with multiple vias to the ground plane.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-12T23:07:45.477" LastActivityDate="2010-10-12T23:07:45.477" CommentCount="1" />
  <row Id="5139" PostTypeId="1" AcceptedAnswerId="5143" CreationDate="2010-10-12T18:02:03.820" Score="12" ViewCount="801" Body="&lt;p&gt;Hey, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So recently when i was routing a PCB , I came across the option to either fill/pour my ground plane with either solid or hatched copper. I've also noticed that the old arduino duemilanove also had a hatched ground plane. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what benefits does a hatched ground plane have over solid ground plane and vice versa.&lt;/p&gt;&#xA;" OwnerUserId="1568" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-10-12T18:22:04.887" LastActivityDate="2011-04-18T09:03:22.027" Title="Solid ground-plane vs Hatched ground-plane" Tags="&lt;pcb&gt;&lt;routing&gt;" AnswerCount="7" CommentCount="4" FavoriteCount="4" />
  <row Id="5140" PostTypeId="2" ParentId="5139" CreationDate="2010-10-12T18:15:00.267" Score="4" ViewCount="" Body="&lt;p&gt;I believe hatched ground planes are easier to solder on to due to their thermal properties. The counter to this is to use a solid plane but put solder reliefs around each pin/pad that you need to solder to on the ground plane.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other then that I am not sure of other reasons, maybe others have an idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For me, I always use solid planes. It is easier to etch since there isn't a bunch of little things you have to etch off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I did some Google searching and found this page: &lt;a href=&quot;http://www.diyaudio.com/forums/parts/89354-ground-planes-solid-vs-hatched.html&quot; rel=&quot;nofollow&quot;&gt;http://www.diyaudio.com/forums/parts/89354-ground-planes-solid-vs-hatched.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-10-13T01:35:40.543" LastActivityDate="2010-10-13T01:35:40.543" CommentCount="6" />
  <row Id="5141" PostTypeId="2" ParentId="5134" CreationDate="2010-10-12T18:47:25.847" Score="3" ViewCount="" Body="&lt;p&gt;I think you should use a 555 timer to time for 16 minute intervals, and then feed that into a counter circuit of some sort to divide it. A 14-bit counter would make the interval about 6.06 months.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-12T18:47:25.847" CommentCount="3" />
  <row Id="5142" PostTypeId="2" ParentId="5139" CreationDate="2010-10-12T19:08:22.853" Score="4" ViewCount="" Body="&lt;p&gt;Cross-hatching avoids problems with large copper areas when using the toner transfer technique, or if a laser printer is used to generate photo-etch artwork. Now I use an inkjet printer to produce transparencies I don't usually bother with it. I use thermal reliefs if I need to make soldering easier on copper areas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not so good from an environmental point of view, perhaps, as more copper has to be removed. OTOH, the copper can be reclaimed by commercial board makers, and doesn't end up in landfill, when the equipment containing the board is disposed of.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-12T19:08:22.853" />
  <row Id="5143" PostTypeId="2" ParentId="5139" CreationDate="2010-10-12T19:17:05.230" Score="10" ViewCount="" Body="&lt;p&gt;As others said its mostly because it was easier to manufacture than solid layers for various reasons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also can be used in certain situations where you need controlled impedance on a very thin board.  The traces width needed to get 'normal' impedances on such a thin board would be ridiculously narrow but the cross hatching changes the impedance characteristics on adjacent layers to allow wider traces for a given impedance.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If for some reason you need to do this, you can only route controlled impedance traces at 45 deg to the hatch pattern.  This approach greatly increases mutual inductance between signals and consequently, cross-talk.  Also note that this only works when the size of the hatch is much less than the length of the signal's rise time, this normally correlates to the frequency of the digital signals in question.  As such, as frequency increases you reach a point where the hatch pattern would have to be so tightly spaced that you lose any benefit vs a solid plane.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In Summary: Never use a cross hatched ground plane, unless your stuck in some really weird situation.  Modern PCB construction and assembly techniques no longer require it. &lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-12T22:41:56.830" LastActivityDate="2010-10-12T22:41:56.830" CommentCount="5" />
  <row Id="5144" PostTypeId="1" AcceptedAnswerId="5401" CreationDate="2010-10-12T20:23:09.247" Score="5" ViewCount="367" Body="&lt;p&gt;First, I've read though questions &lt;a href=&quot;http://electronics.stackexchange.com/q/216/1240&quot;&gt;Soldering Iron Maintenance&lt;/a&gt; and &lt;a href=&quot;http://electronics.stackexchange.com/q/4470/1240&quot;&gt;Going through Soldering tips quickly&lt;/a&gt; and was unable to solve my problem. I have recently (as in less then a month ago) obtained &lt;a href=&quot;http://www.ersa.com/index.php?modul=entry&amp;amp;id=359&amp;amp;entry_id=1890&quot; rel=&quot;nofollow&quot;&gt;Multitip 25 ERSA Microsoldering iron&lt;/a&gt; with &lt;a href=&quot;http://www.ersa.com/index.php?modul=entry&amp;amp;id=403&amp;amp;entry_id=1675&quot; rel=&quot;nofollow&quot;&gt;0172BD/10&lt;/a&gt; tip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the start I had problems wetting the tip. I tried everything but solder just wouldn't flow over the whole tip. I later found information in one of manufacturer's catalogs that I should wrap solder with flux around the tip and then turn on the iron. After few tries, I managed to get a big part of the tip wet (and it was working great), but one small part wouldn't wet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After some soldering I decided to try to get whole tip wet and obtained &lt;a href=&quot;http://www.ersa.com/index.php?modul=entry&amp;amp;id=386&amp;amp;entry_id=2019&quot; rel=&quot;nofollow&quot;&gt;0TR01/SB&lt;/a&gt; tip refresher. After using it according to the manual, the whole tip was covered in black substance which should be easily removable, but it isn't.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now about half of the tip is contaminated and about half seems to be working (I managed to clean the working part).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is: Is there any other way to clean the tip? Two things from questions I linked I didn't use were dedicated tip cleaning mesh (couldn't find a source of them in my country) and flux outside the wire (because I don't have any at the moment) and how to decide when a tip is dead and needs replacing?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, how do the tip refreshers feel (I'm assuming that they are more or less all alike)? I often find them described as paste, while the one I got is solid (but melts when in contact with hot tip).&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T19:46:47.900" LastActivityDate="2011-02-08T19:46:47.900" Title="How to clean my soldering iron tip or how to determine that it's beyond repair?" Tags="&lt;soldering&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="5145" PostTypeId="2" ParentId="5144" CreationDate="2010-10-12T20:40:51.573" Score="1" ViewCount="" Body="&lt;p&gt;I've always used this stuff:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://cgi.ebay.com/Multicore-MM01921-SOLDER-TIP-CLEANER-LEAD-FREE-5-OZ-CA-/390192006668?pt=LH_DefaultDomain_0&amp;amp;hash=item5ad941860c&quot; rel=&quot;nofollow&quot;&gt;http://cgi.ebay.com/Multicore-MM01921-SOLDER-TIP-CLEANER-LEAD-FREE-5-OZ-CA-/390192006668?pt=LH_DefaultDomain_0&amp;amp;hash=item5ad941860c&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It doesn't work forever, and of course you must take good care of your tips. It can't repair all tips, but it does a pretty good job on ones which are slightly oxidised. I haven't found it gets stuck on the tip; just melt some solder on it after wiping the iron through the stuff to tin it again.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-12T20:40:51.573" CommentCount="3" />
  <row Id="5146" PostTypeId="2" ParentId="5144" CreationDate="2010-10-12T20:45:17.287" Score="7" ViewCount="" Body="&lt;p&gt;(Solid) tip &quot;tinners&quot; are almost always ammonium phosphate with some tin (or tin-lead) bits mixed in. They are moderately aggressive at cleaning oxides off, so shouldn't be used constantly, but only when needed.  The &lt;em&gt;best&lt;/em&gt; tip tinner is your solder--tips should always be coated with a small amount of solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If some of the oxides are just sticking really well, you could try to mildly abrade them on some copper braid or similar, but you can't be too hard or you will damage the iron plating (good tips are typically copper core, plated with iron, then chromium everywhere but the working area).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.hakkousa.com/kb/attachments/How%20to%20maximize%20soldering%20iron%20tip%20life-GUIDe088627954984a4986039711460ec36a.pdf&quot; rel=&quot;nofollow&quot;&gt;Practice good tip care.&lt;/a&gt; (PDF, 4 pages)  I use a Hakko iron and tips at work and mine has lasted about a year (moderately light use, maybe 5-6 projects).  Put a good amount of solder on the tip when storing it or leaving it idle for any length of time; &lt;strong&gt;don't&lt;/strong&gt;, for instance, wipe it off, put it in the holder, then leave it on over lunch.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-10-12T21:23:15.957" LastActivityDate="2010-10-12T21:23:15.957" CommentCount="7" />
  <row Id="5147" PostTypeId="2" ParentId="5123" CreationDate="2010-10-12T21:26:58.110" Score="2" ViewCount="" Body="&lt;p&gt;A couple of refinements you might want to consider:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;generate proper I and D terms using suitable filters rather than just using sums and differences (otherwise you will be very prone to noise, accuracy problems and various other errors). NB: make sure your I term has sufficient resolution.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;define a &lt;em&gt;prop band&lt;/em&gt; outside which D and I terms are disabled (i.e. proportional-only control outside prop band, PID control inside prop band)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1489" LastActivityDate="2010-10-12T21:26:58.110" />
  <row Id="5148" PostTypeId="1" CreationDate="2010-10-12T21:53:22.727" Score="3" ViewCount="476" Body="&lt;p&gt;Hi , I just learnt of TopoR routing software. It routes PCB traces without grids, with curves and arcs for reduced trace length and vias.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.toporouter.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.toporouter.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But its not a complete PCB routing solution , they have examples on how to use it with DipTrace.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At work we all use and are comfortable with EagleCad . Has anybody used TopoR with Eaglecad? or know of EagleCad plugin/user script that kinda does the same.&lt;/p&gt;&#xA;" OwnerUserId="1568" LastActivityDate="2010-11-30T22:54:38.390" Title="Using TopoR with EagleCad" Tags="&lt;pcb&gt;&lt;routing&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="3" />
  <row Id="5150" PostTypeId="2" ParentId="5148" CreationDate="2010-10-12T23:01:53.330" Score="3" ViewCount="" Body="&lt;p&gt;Pretty interesting.  Every auto router i've ever used has been terrible with anything but the simplest boards, including OrCad and Altium (tho i love Altium for a lot of other reasons).  This looks like it may be worth playing with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, according to their website:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;TopoR supports standard Specctra DSN/SES interface that most CAD systems have. Also TopoR can import/export P-CAD and PADS ASCII formats.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think eagle supports Specctra DSN/SES, at least last i knew, so you may be out of luck.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-12T23:01:53.330" />
  <row Id="5151" PostTypeId="2" ParentId="5134" CreationDate="2010-10-13T01:59:27.813" Score="3" ViewCount="" Body="&lt;p&gt;Arduino (or other microcontroller) with a &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=42&amp;amp;products_id=255&quot; rel=&quot;nofollow&quot;&gt;DS3231 super accurate real-time clock IC&lt;/a&gt;. When the button is pressed, the time and date is stored in memory - the MCU can loop around checking the date and time and turn off when ready; or when button pressed it restarts etc.&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-13T01:59:27.813" />
  <row Id="5152" PostTypeId="1" CreationDate="2010-10-13T02:17:20.527" Score="1" ViewCount="399" Body="&lt;p&gt;Hi Marcus, I'm a student from QUT doing interaction design this semester (you've probably heard from a few of us over the past few months). Anyway I just order the 25 diffused RGB Leds if that rings a bell for you. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now onto my project, Im basically building a 450mm3 white perspex cube that changes colour based on sound. On the inside of the cube I intend to build a smaller 5 sided cube structure from circuit borad and attach 4 RGB leds to each side of the inner cube at the corners to maximise the dispersion. I am using Arduino to attach a microphone to read the audio, and i then intend to connect the RGB leds to the pwm. However from what i have found out from my lecturer Gavin Sade, the leds will draw too much power as there will be 20 all up. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;His solution was to use the BlinkM MaxM controller chip and connect my own circuit of 20 RGB leds and power according with something like a 5Volt 2am p power supply. I have little money to spend on this project unfortunately and from the looks of it this would be the cheapest way to go as I have already got my Arduino, RGB leds and microphone ready to go.. just need to work out a circuit to control that many leds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.littlebirdelectronics.com/products/Triple-Output-LED-RGB-Diffused-25pcs.html&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/Triple-Output-LED-RGB-Diffused-25pcs.html&lt;/a&gt; that is the rgb leds that im using. Ill be using 20 of them in my cube, utilising each colour it that makes any difference. I need to work out the power supply also to maximise the brightness potential of these lights. Also need to know how to set up correct resistors for this setup.&lt;/p&gt;&#xA;" OwnerUserId="1572" LastEditorUserId="1572" LastEditorDisplayName="" LastEditDate="2010-10-13T02:39:55.207" LastActivityDate="2010-10-13T14:34:35.653" Title="Arduino, RGB LED, BlinkM MaxM controller." Tags="&lt;arduino&gt;&lt;led&gt;&lt;rgb&gt;&lt;blinkm&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="5153" PostTypeId="2" ParentId="5024" CreationDate="2010-10-13T07:23:31.383" Score="0" ViewCount="" Body="&lt;p&gt;I tried a few basic LED blinkenlightz experiments with the Propeller and found I liked it a lot. So I plunged ahead and bought a Stingray… I have to admit it has mostly languished on my workbench since then — but that has more to do with my day job than with the kit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The cool part about the Stingray is that it's a very bare-bones chassis. It's sort of a blank page as far as fun robotics experiments go. And the Parallax forums are simply awesome!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're a Mac user, there's even a tool called bst (Brad's [?] Spin Tool) that lets you develop code on your Mac natively rather than forcing you to run a toolchain under Windows.&lt;/p&gt;&#xA;" OwnerUserId="1317" LastActivityDate="2010-10-13T07:23:31.383" CommentCount="2" />
  <row Id="5154" PostTypeId="1" AcceptedAnswerId="5163" CreationDate="2010-10-13T08:08:19.027" Score="3" ViewCount="235" Body="&lt;p&gt;I have multiple stationary baby items for my son Oliver that require a serious supply of batteries each month. I would like to hook a few of these stationary items up to wall warts to conserve the constant expense of alkaline purchase/recharging of batteries. I currently have two spare wall warts laying around the house: first at 9V/1A and the second at 12V/1A. I am located 15km from a Mouser warehouse in case the garage will not suffice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two items I would like to wire up right now include a baby rocker which requires one D battery and a crib which includes a mobile electronic toy rotation device requiring 3 AA batteries. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was lucky enough to get these from a baby shower and due to my current job situation, I can't upgrade. I would like to build a circuit for both but will discuss the baby rocker at this point. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This circuit would need to accept either voltage from the wall warts and drop it to 1.5V to run the baby rocker's vibrator. I have been looking at the 780x type linear regulators at this point but am not sure if this is the way to go. I wanted to see what you might recommend. I need advice that will not only eliminate batteries, hopefully save electricity, and also be easy to solder as I do not have the skills and equipment for SMD applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thx in advance for your help! &lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="1575" LastEditorDisplayName="" LastEditDate="2010-10-13T09:38:07.673" LastActivityDate="2010-10-15T17:29:13.890" Title="Best Circuit Design for a 12VDC Wall-Wart &gt; Ouput Voltage of 1.5V (Replacing Alkaline Batteries)" Tags="&lt;battery&gt;&lt;dc&gt;&lt;batteries&gt;&lt;voltage-regulator&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="5155" PostTypeId="2" ParentId="5154" CreationDate="2010-10-13T09:28:13.367" Score="2" ViewCount="" Body="&lt;p&gt;The easy solution is to get a couple of rechargeable batteries and a charger, that will solve your problem... but it is a boring answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second is to use a switched regulator, but I don't know any good one that can be soldered by hand so...&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-10-13T09:28:13.367" CommentCount="1" />
  <row Id="5156" PostTypeId="2" ParentId="5148" CreationDate="2010-10-13T11:42:48.593" Score="2" ViewCount="" Body="&lt;p&gt;I'm guessing &lt;a href=&quot;http://www.eremex.com/products/topor/competitiveadvantages/compatibility.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; is their parent company's site? &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;This allows to use TopoR with many other PCB CAD Systems which support SPECCTRA DSN format, such as Elektra, Altium, Pulsonix, &lt;strong&gt;Eagle&lt;/strong&gt;, DipTrace, etc.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-10-13T11:42:48.593" />
  <row Id="5157" PostTypeId="1" AcceptedAnswerId="5159" CreationDate="2010-10-13T12:35:57.500" Score="4" ViewCount="192" Body="&lt;p&gt;I'm trying to reverse engineer the SPI communications between two chips. But, it's not clear who's master and who's slave.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found the chip select. Without lifting any pins or cutting traces is there a way to detect which end is asserting it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The chips are:&#xA;CC1110 (SoC radio) and CY7C63803 (USB MCU). The chip select comes off of the SSEL (slave select) line on the CY7C63803 and into a GPIO pin on the CC1110.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The CY7C63803 is an SOIC, so I could lift a leg, but I don't want to break it.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-13T13:13:00.030" LastActivityDate="2010-10-13T16:16:25.023" Title="Identifying the SPI master" Tags="&lt;spi&gt;&lt;reverse-engineering&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="5158" PostTypeId="2" ParentId="5157" CreationDate="2010-10-13T13:15:02.717" Score="1" ViewCount="" Body="&lt;p&gt;You'd need to figure out which way the current is flowing-- the upstream chip on the chip select line is the driver. That's hard without cutting traces. My best idea would be to place a coil of magnet wire connected to a large resistor next to the trace. Measure the voltage induced in the resistor through the mutual inductance when the chip select line changes state. The polarity of the voltage should correspond to the direction of current flow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But honestly, that's just a theoretical answer. Given that you're probably trying to detect uA, which would induce nV potentials in the coil, I think the chances of it actually working are very close to zero. Maybe try it with a wire and a signal generator first, to see how small a change you can detect?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-13T13:15:02.717" />
  <row Id="5159" PostTypeId="2" ParentId="5157" CreationDate="2010-10-13T13:35:09.477" Score="7" ViewCount="" Body="&lt;p&gt;It's difficult to use a GPIO pin on a slave device as a chip select. If the chip select signal is not detected soon enough at the slave device after it is asserted you can miss the data that the master is clocking out. Since the CY7C63803 has its SSEL pin connected to the chip select line my guess is that it is the slave. The CC1110 is probably the master. You will probably need to lift a pin on one of the devices to know for sure.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-13T13:35:09.477" CommentCount="2" />
  <row Id="5160" PostTypeId="2" ParentId="5152" CreationDate="2010-10-13T14:00:09.317" Score="1" ViewCount="" Body="&lt;p&gt;If you are on a budget you can use discrete NPN transistors or ICs with open collector (or open drain outputs) that can be scraped from old transistor radios, television sets, old printers, and other outdated electronic devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Discrete NPN transistors&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The maximum emitter current, Ie, must be observed&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Small signal transistors, like BC 547B or 2N2222 can be used, but can only drive &lt;strong&gt;one&lt;/strong&gt; of the RGB LEDs as the emitter current, Ie, will be 60 mA in your circuit and their limit is typically 100 mA. I have shown a transistor driving &lt;strong&gt;two&lt;/strong&gt; in the diagram below.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Power/driver transistors, like BD 135 (1.0 A), with their much higher maximum emitter current can drive many more RGB LEDs, 16 (1.0 A/0.06 A) for BD 135.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Ntk9e.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I far as I can tell the RGB LEDs you are using are common cathode (where the &quot;arrow&quot; is pointing), hence the diagram above. The operating current is 20 mA and the forward voltage drops at this current are 2.0 V, 3.2 V and 3.2 for red, green and blue, respectively.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other values: R4 is in the kiloohm range, e.g. 3.3 kohm. One resistor is used for each internal LED as this makes for more uniform light and also accounts for the difference in forward voltage drop for red and blue/green. &lt;code&gt;Vcca&lt;/code&gt; is the supply voltage to the CPU and can be different from the 5 V for LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Computing the current limiting resistors&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For green and blue (R2 and R3): as the current is 20 mA through the diode the same current flows through the resistor. If the voltage drop over the driver (transistor) is assumed to be 0 V then the voltage drop over the resistor is 5 V - 3.2 V = 1.8 V. We now know the current and voltage for the resistor and can use Ohm's low to find the value of resistor:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;U = R3 * I   =&amp;gt;  R3 = U / I = 1.8 V / 0.02 A = 90 ohm&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;For red (R1):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;R1 = U / I = (5.0 V - 2.0 V) / 0.02 A = 3.0 V / 0.02 A =  150 ohm&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Standard values of resistors (&lt;a href=&quot;http://en.wikipedia.org/wiki/Preferred_number#E_series%3a_Capacitors_and_resistors&quot; rel=&quot;nofollow&quot;&gt;E24&lt;/a&gt;, 5%) close to these two values happens to exist (91 ohm and 150 ohm).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;ICs with open collector (or open drain outputs)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The principle is the same as for the discrete transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An example is the &lt;a href=&quot;http://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logic&quot; rel=&quot;nofollow&quot;&gt;TTL&lt;/a&gt; 7405 (variations: 74LS05, 74HC05). The maximum current can be found in the datasheet, but most likely it can only drive one RGB LED per output. On the other hand it is more compact as there are 6 inverters in one IC. Some others in the TTL family (some with fewer outputs) are 7401, 74LS03, 7405, 7406, 7409, 74LS12, 74LS15, 7416, 7417, 74LS22, 74LS33, 74LS38, 74LS136, and 74LS266.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think bus buffer/line drivers, like the 74LS244 (8 outputs) can also be used, but I have to look into it further.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;A good background article is &quot;&lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/2198&quot; rel=&quot;nofollow&quot;&gt;Driving LEDs with Open Drain Port Expander Outputs&lt;/a&gt;&quot;.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="804" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2010-10-13T14:34:35.653" LastActivityDate="2010-10-13T14:34:35.653" />
  <row Id="5161" PostTypeId="2" ParentId="5157" CreationDate="2010-10-13T14:35:41.650" Score="2" ViewCount="" Body="&lt;p&gt;How fast is it toggling the line?  If it is slow enough, you could you measure the voltage between the pins with a good multimeter to determine which side is trying to sink the current.  From pullup values/drive strength/trace resistance that I'd guess it might be possible with my 187 for instance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Short of absolute proof though, mjh2007 is probably right; if one side is using the SS pin shared by the SPI hardware peripheral while the other uses some random GPIO, that's all but conclusive.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-13T14:35:41.650" />
  <row Id="5162" PostTypeId="2" ParentId="5157" CreationDate="2010-10-13T14:40:58.657" Score="7" ViewCount="" Body="&lt;p&gt;How about holding each of the chips in reset (in turn) and observing the CS line?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The theory being that the line will tristate while the chip's in reset.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-13T14:40:58.657" CommentCount="2" />
  <row Id="5163" PostTypeId="2" ParentId="5154" CreationDate="2010-10-13T15:21:20.933" Score="5" ViewCount="" Body="&lt;p&gt;I'm surprised the rocker doesn't have a DC inlet already.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could connect the 9 V supply to a linear 1.5 V regulator, and it would be easy, but you'd be wasting a lot of energy.  It would be better to just go to a thrift store and try to find wall warts that are close (more appropriate transformer turns ratio) to the voltage you need.  Regulating a 3.3 V or 5 V supply down to 1.5 V would be more efficient.  The voltage might not even need regulating, or could be anywhere within a large range and still work, but you'd have to take the products apart and see what they feed into.  I ruined a digital camera by accidentally using a higher voltage adapter, but many things don't care.  &lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-15T17:29:13.890" LastActivityDate="2010-10-15T17:29:13.890" CommentCount="6" />
  <row Id="5164" PostTypeId="2" ParentId="5157" CreationDate="2010-10-13T16:16:25.023" Score="2" ViewCount="" Body="&lt;p&gt;Try zooming waaaaaaaaaaaaay in with a really high resolution o-scope.  Maybe you can see the reflection on the trace?  The ringing at the load should be worse than the ringing at the source.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-13T16:16:25.023" />
  <row Id="5165" PostTypeId="2" ParentId="5148" CreationDate="2010-10-13T16:36:40.060" Score="2" ViewCount="" Body="&lt;p&gt;I haven't tried TopoR from Eagle but I have used freerouting.net which also requires a dsn file as input.  The freerouting.net site instructions pointed to the ULP script brd_to_dsn.ulp, which can create a dsn file from an Eagle brd file.  I would guess that process would also work with TopoR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;freerouting.net is also worth looking at as an alternative autorouter for Eagle.  One thing to note, which might be relevant to TopoR as well, is tha brd_to_dsn.ulp doesn't do the right thing with ground planes (copper filled polygons) from Eagle so I've ended up putting those in after freerouting.net has done the routing.  The same might be true with TopoR.&lt;/p&gt;&#xA;" OwnerUserId="1579" LastActivityDate="2010-10-13T16:36:40.060" CommentCount="5" />
  <row Id="5166" PostTypeId="2" ParentId="4423" CreationDate="2010-10-13T17:06:25.217" Score="1" ViewCount="" Body="&lt;p&gt;In the editor of &lt;a href=&quot;http://www.dnosp.com/e_index.php&quot; rel=&quot;nofollow&quot; title=&quot;Dos Navigator&quot;&gt;Dos Navigator&lt;/a&gt; there is a special draw mode. You can enable double line drawing by pressing F4, then F4 again for single line, and again to disable. You can easily draw lines with the cursor keys while holding the shift key.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;1 1 0 0   1 1 0 0 ───────┬┐&#xA;│ │   ║       ║ │        │├───────┐&#xA;│ │   ║       ║ └────────┴┘       │&#xA;│ │   ║       ║                   │&#xA;│ │   ║       ║                   │&#xA;│ │   ║       ║                   │&#xA;│ │   ║       ╚═════════════╗     │&#xA;│ │   ╚═════════════════════╝     │&#xA;│ │                               │&#xA;│ │                               │&#xA;│ └───────────────────────┬┐     ┌┘&#xA;│                 ┌┬┐┌┐  ┌┘└┐   ┌┘&#xA;└───────────────┐┌┤│││└┐┌┘  └┐ ┌┘&#xA;                └┘└┘└┘ └┘    └─┘&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2010-10-13T17:06:25.217" CommentCount="1" />
  <row Id="5167" PostTypeId="1" CreationDate="2010-10-13T17:15:46.363" Score="3" ViewCount="459" Body="&lt;p&gt;Does anybody know the magic command to set baud rate, parity, flow control, etc. for an RS-232 port on the MacOS X CLI?&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-10-13T21:46:02.393" Title="Set RS232 port options from MacOS X CLI" Tags="&lt;serial&gt;&lt;mac&gt;&lt;rs232&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="5168" PostTypeId="2" ParentId="5167" CreationDate="2010-10-13T17:27:34.773" Score="2" ViewCount="" Body="&lt;p&gt;I don't know in bash (or whatever shell OS X uses), but it's probably achievable in Python with the pyserial library.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt; How about this answer on StackOverflow: &lt;a href=&quot;http://stackoverflow.com/questions/3918032/bash-serial-i-o-and-arduino/3926278#3926278&quot;&gt;http://stackoverflow.com/questions/3918032/bash-serial-i-o-and-arduino/3926278#3926278&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh, wait, you wrote that. Does it work?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-13T17:27:34.773" CommentCount="3" />
  <row Id="5169" PostTypeId="1" AcceptedAnswerId="5170" CreationDate="2010-10-13T17:34:27.233" Score="1" ViewCount="149" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/922/how-does-an-lm7805-voltage-regulator-work&quot;&gt;How does an LM7805 voltage regulator work?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;How exactly does a voltage regulator like  LM138 work? what is the function of V-adjust?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a Datasheet: &lt;a href=&quot;http://www.jaycar.com.au/images_uploaded/LM138.PDF&quot; rel=&quot;nofollow&quot;&gt;http://www.jaycar.com.au/images_uploaded/LM138.PDF&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1581" LastActivityDate="2010-10-13T22:57:45.603" ClosedDate="2011-02-23T14:12:07.343" Title="Voltage Regulator" Tags="&lt;voltage-regulator&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="5170" PostTypeId="2" ParentId="5169" CreationDate="2010-10-13T18:45:17.797" Score="5" ViewCount="" Body="&lt;p&gt;The LM138 is a linear regulator, similar to devices like the 7805. It uses a series-pass transistor acting like a variable impedance to keep the output side regulated to a certain voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Vadj pin is used to program the desired output voltage. You connect a voltage divider from the output to ground, with the midpoint going to Vadj.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The formula Vout = Vref (1 + (R2 / R1)) + Iadj*R2 defines the output of the device. (Iadj is typically 50 microamps).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-13T18:45:17.797" CommentCount="2" />
  <row Id="5171" PostTypeId="1" CreationDate="2010-10-13T20:11:50.453" Score="2" ViewCount="131" Body="&lt;p&gt;We have a solution for graphic color LCD's (resolution up to 800x600) right now that we are not very happy with: Our ARM Cortex M3 drives the LCD over a 8080 bus and the LCD module must provide the LCD driver (currently SSD1963). This solution was recommended to us by consultants who's priority was optimizing the cost of the processor module. The problem with this is that it pretty much ties us up to one LCD vendor and even only a subset of that vendors displays. The 8080 bus is standard but the cabling (tail) to the LCD module seems to vary slightly from vendor to vendor. The signals is not always on the same pins etc. Another problem is that LCD displays seems to have a very limited market lifetime, I heard less than a year in some cases. &#xA;Now, we have chance to redesign the processor module and I want to do this RIGHT this time. I'm looking for a solution that is:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Cheap both on the processor board and the LCD module&lt;/li&gt;&#xA;&lt;li&gt;Vendor agnostic&lt;/li&gt;&#xA;&lt;li&gt;Somewhat future proof&lt;/li&gt; &#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Various solutions have been suggested:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Integrate the LCD driver on the processor board: Would this really help us become more vendior agnostic?&lt;/li&gt;&#xA;&lt;li&gt;Integrate an FPGA (programmed as a display driver) on the processor board and reprogram it when we need to switch LCD vendor: Sounds cool but somewhat backwards, surely there is a standard solution to the problem?&lt;/li&gt;&#xA;&lt;li&gt;Integrate an LCD driver on the processor that speaks DVI or HDMI to the LCD module: I like this because of the standards, but it sounds like both processor board and display module becomes MUCH more expensive&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;What do you guys think? Is there a standard way to do this that I have missed?&lt;/p&gt;&#xA;" OwnerUserId="1321" LastActivityDate="2010-10-13T21:52:24.443" Title="Recommended LCD interface solution?" Tags="&lt;lcd&gt;&lt;interface&gt;" AnswerCount="1" />
  <row Id="5172" PostTypeId="2" ParentId="4423" CreationDate="2010-10-13T20:53:07.487" Score="5" ViewCount="" Body="&lt;p&gt;You can play with something with &lt;a href=&quot;http://www.graphviz.org/&quot; rel=&quot;nofollow&quot;&gt;graphviz&lt;/a&gt; and dot. Those are the tools doxygen uses to create the diagrams. It is not exactly what you are searching for, but it is fast and easy to script and the output is kind of nice looking (even thou it is a little hard to follow some lines...)&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;This example will generate something like this&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/8dV1t.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To do this you first create a file called byte.dot&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;digraph structs { &#xA;node [shape=plaintext] &#xA;&#xA;struct1 [label=&amp;lt; &#xA;&amp;lt;TABLE BORDER=&quot;0&quot; CELLBORDER=&quot;1&quot; CELLSPACING=&quot;0&quot; ALIGN=&quot;left&quot;&amp;gt;  &#xA;    &amp;lt;TR&amp;gt;&#xA;        &amp;lt;TD&amp;gt;0xc9&amp;lt;/TD&amp;gt;&#xA;        &amp;lt;TD PORT=&quot;f0&quot;&amp;gt; 1 &amp;lt;/TD&amp;gt;&#xA;        &amp;lt;TD PORT=&quot;f1&quot;&amp;gt; 1 &amp;lt;/TD&amp;gt;&#xA;        &amp;lt;TD PORT=&quot;f2&quot;&amp;gt; 0 &amp;lt;/TD&amp;gt;&#xA;        &amp;lt;TD PORT=&quot;f3&quot;&amp;gt; 0 &amp;lt;/TD&amp;gt;&#xA;&#xA;        &amp;lt;TD PORT=&quot;f4&quot;&amp;gt; 1 &amp;lt;/TD&amp;gt;&#xA;        &amp;lt;TD PORT=&quot;f5&quot;&amp;gt; 0 &amp;lt;/TD&amp;gt;&#xA;        &amp;lt;TD PORT=&quot;f6&quot;&amp;gt; 0 &amp;lt;/TD&amp;gt;&#xA;        &amp;lt;TD PORT=&quot;f7&quot;&amp;gt; 1 &amp;lt;/TD&amp;gt;&#xA;    &amp;lt;/TR&amp;gt; &#xA;&amp;lt;/TABLE&amp;gt;&amp;gt;]; &#xA;&#xA;struct2 [label=&amp;lt; &#xA;&amp;lt;TABLE BORDER=&quot;0&quot; CELLBORDER=&quot;1&quot; CELLSPACING=&quot;0&quot; &amp;gt;  &#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f0&quot;&amp;gt; RSTDISBL (reset pin is enabled) &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f1&quot;&amp;gt; WDTON (WDT not always on) &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f2&quot;&amp;gt; SPIEN (allow serial programming)  &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f3&quot;&amp;gt; CKOPT (full output swing) &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f4&quot;&amp;gt; EESAVE (don't preserve EEPROM over chip erase)  &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f5&quot;&amp;gt; BOOTSZ1 &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f6&quot;&amp;gt; BOOTSZ0 &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f7&quot;&amp;gt; BOOTRST (boot reset vector at 0x0000) &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;&amp;lt;/TABLE&amp;gt;&amp;gt;]; &#xA;&#xA;struct1:f0:s -&amp;gt; struct2:f0:w;&#xA;struct1:f1:s -&amp;gt; struct2:f1:w;&#xA;struct1:f2:s -&amp;gt; struct2:f2:w; &#xA;struct1:f3:s -&amp;gt; struct2:f3:w;&#xA;&#xA;struct1:f4:s -&amp;gt; struct2:f4:w;&#xA;struct1:f5:s -&amp;gt; struct2:f5:w;&#xA;struct1:f6:s -&amp;gt; struct2:f6:w; &#xA;struct1:f7:s -&amp;gt; struct2:f7:w;&#xA;} &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then run one of those commands.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;dot -Tpng byte.dot -o byte.png &#xA;dot -Tps  byte.dot -o byte.ps&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Maybe it will be nicer if we do not cross all the lines in the middle?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/GtMn3.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just switched the named in the second table from f0..f7 into f7..f0.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;&amp;lt;TABLE BORDER=&quot;0&quot; CELLBORDER=&quot;1&quot; CELLSPACING=&quot;0&quot; &amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f7&quot;&amp;gt; RSTDISBL (reset pin is enabled) &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f6&quot;&amp;gt; WDTON (WDT not always on) &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f5&quot;&amp;gt; SPIEN (allow serial programming)  &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f4&quot;&amp;gt; CKOPT (full output swing) &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f3&quot;&amp;gt; EESAVE (don't preserve EEPROM over chip erase)  &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f2&quot;&amp;gt; BOOTSZ1 &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f1&quot;&amp;gt; BOOTSZ0 &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;    &amp;lt;TR&amp;gt; &amp;lt;TD ALIGN=&quot;left&quot; PORT=&quot;f0&quot;&amp;gt; BOOTRST (boot reset vector at 0x0000) &amp;lt;/TD&amp;gt; &amp;lt;/TR&amp;gt;&#xA;&amp;lt;/TABLE&amp;gt;&amp;gt;];&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="689" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2010-10-14T17:10:48.373" LastActivityDate="2010-10-14T17:10:48.373" />
  <row Id="5173" PostTypeId="1" AcceptedAnswerId="5178" CreationDate="2010-10-13T20:58:02.233" Score="3" ViewCount="183" Body="&lt;p&gt;I have a project for a small remote control in which I'll use a magnet instead of screws/etc. to close the case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically it is a two-piece plastic case in which one of the pieces has a magnet glued to it, and the other has a matching metal band at the corresponding spot. When the two are put together, the magnet holds them closed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking if I could also use that same metal band as the antenna for the remote. I'd connect the magnet to the circuit, and since when the case is closed the band is tightly attached to the magnet, it'd be electrically connected to the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would the magnetic field in the magnet prevent this from working? If yes, is there a workaround?&lt;/p&gt;&#xA;" OwnerUserId="1078" LastActivityDate="2010-10-13T22:15:31.950" Title="Can a magnet be an antenna?" Tags="&lt;antenna&gt;&lt;electromagnetism&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="5174" PostTypeId="1" AcceptedAnswerId="5180" CreationDate="2010-10-13T21:06:39.983" Score="3" ViewCount="153" Body="&lt;p&gt;I'm using the Microchip 16-bit 28-pin starter board and the USB communication with the PC keeps breaking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are two microprocessors on the board. The application processor communicates to the USB processor via UART. The USB processor is configured as a CDC class USB device and shows up in device manager as a serial port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The device enumerates ok and the data being transmitted from the PC to the application processor ok. The application processor is responding to the USB processor, but the response never gets to the PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know the UART communications between the two processors is working ok because I'm using a BusBee to monitor the UART. I did not write the code for the USB processor (that came from Microchip). It's worked before, but I can't seem to get it working again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a tool or anything I can use to debug the USB end points on the PC?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something like wireshark, but for USB?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone else used the 16-bit starter kit from Microchip and had similar problems?&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-14T12:13:50.150" LastActivityDate="2010-10-14T16:07:55.537" Title="Problems with CDC Device Class" Tags="&lt;pic&gt;&lt;usb&gt;&lt;serial&gt;&lt;uart&gt;" AnswerCount="2" />
  <row Id="5175" PostTypeId="2" ParentId="5167" CreationDate="2010-10-13T21:46:02.393" Score="4" ViewCount="" Body="&lt;p&gt;To read from my arduino or attiny, I use this simple program:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;unistd.h&amp;gt;&#xA;#include &amp;lt;fcntl.h&amp;gt;&#xA;#include &amp;lt;termios.h&amp;gt;&#xA;&#xA;int main(int argc, char **argv) {&#xA;&#xA;    int fd;&#xA;    ssize_t len;&#xA;    unsigned char buf[8192];&#xA;    struct termios tio;&#xA;&#xA;    fd = open( argv[1], O_RDONLY | O_NOCTTY | O_NONBLOCK );&#xA;    cfmakeraw(&amp;amp;tio);&#xA;    cfsetispeed(&amp;amp;tio,B9600);&#xA;    cfsetospeed(&amp;amp;tio,B9600);&#xA;    tcsetattr(fd,TCSANOW,&amp;amp;tio);&#xA;&#xA;    for(;;) {&#xA;        len = read( fd, &amp;amp;buf[0], 8192 );&#xA;        if( len &amp;gt; 0 ) write(1,buf,len);&#xA;        sleep(1);&#xA;    }&#xA;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;On the mac, using the FTDI chip (Arduino Duemilanove) for serial means that the stty command has no lasting effect.  Once the port is closed, it reverts to default parameters.  While this program is running, you can use stty to alter parameters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the default:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;$ stty -f /dev/tty.usbserial-* -a&#xA;speed 9600 baud;&#xA;lflags: -icanon -isig -iexten -echo&#xA;iflags: -icrnl -ixon -ixany -imaxbel -brkint&#xA;oflags: -opost -onlcr -oxtabs&#xA;cflags: cs8 -parenb&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then if the C program is running:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;$ stty -f /dev/tty.usbserial-A6003SHf -a&#xA;speed 9600 baud;&#xA;lflags: -icanon -isig -iexten -echo&#xA;iflags: -icrnl -ixon -ixany -imaxbel ignbrk -brkint&#xA;oflags: -opost -onlcr -oxtabs&#xA;cflags: cs8 -parenb -hupcl&#xA;discard dsusp   eof     eol     eol2    erase   intr    kill    lnext   &#xA;^@      ^@      ^@      ^@      ^@      ^@      ^@      ^@      ^@      &#xA;quit    reprint start   status  stop    susp    werase  &#xA;^@      ^@      ^@      ^@      ^@      ^@      ^@      &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You can change the baud rate if for instance the Arduino is using Serial.begin(19200) for faster transmission.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;$ stty -f /dev/tty.usbserial-* 19200&#xA;$ stty -f /dev/tty.usbserial-*&#xA;speed 19200 baud;&#xA;lflags: -icanon -isig -iexten -echo&#xA;iflags: -icrnl -ixon -ixany -imaxbel ignbrk -brkint&#xA;oflags: -opost -onlcr -oxtabs&#xA;cflags: cs8 -parenb -hupcl&#xA;discard dsusp   eof     eol     eol2    erase   intr    kill    lnext   &#xA;^@      ^@      ^@      ^@      ^@      ^@      ^@      ^@      ^@      &#xA;quit    reprint start   status  stop    susp    werase  &#xA;^@      ^@      ^@      ^@      ^@      ^@      ^@      &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Once the C program is closed, the serial port reverts back to its default.&lt;/p&gt;&#xA;" OwnerUserId="1271" LastActivityDate="2010-10-13T21:46:02.393" CommentCount="4" />
  <row Id="5176" PostTypeId="2" ParentId="5116" CreationDate="2010-10-13T21:46:58.153" Score="0" ViewCount="" Body="&lt;p&gt;I think that just putting a 2.2mF capacitor across the battery terminals will work well enough to smooth voltage. I presume the voltage dips when the ESC draws large current pulses for the motor.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-13T21:46:58.153" />
  <row Id="5177" PostTypeId="2" ParentId="5171" CreationDate="2010-10-13T21:52:24.443" Score="3" ViewCount="" Body="&lt;p&gt;There are several different interfaces, but I recommend you implement the same solution as is used in laptops; LVDS, if I recall correctly. The interface is fairly standard, but the pin-out may vary. In theory, any GPU can interface with any panel, with a few exceptions. There's also the cost benefit; if you stick with the same panels laptop manufacturers use you can also benefit from economies of scale. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-13T21:52:24.443" />
  <row Id="5178" PostTypeId="2" ParentId="5173" CreationDate="2010-10-13T21:59:04.997" Score="7" ViewCount="" Body="&lt;p&gt;The field from a permanent magnet is the magnetic equivalent of DC; zero frequency. It shouldn't bother a bit, in terms of receiving. Now if you were &lt;em&gt;transmitting&lt;/em&gt; through it, you might degauss it, but the power levels in receiving are so low as to not be a concern.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-13T21:59:04.997" CommentCount="4" />
  <row Id="5179" PostTypeId="2" ParentId="5173" CreationDate="2010-10-13T22:07:48.247" Score="4" ViewCount="" Body="&lt;p&gt;For the metal band to act as an antenna, it needs to be the correct length for 2.4 GHz operation and matched to the transmitter with a suitable network. The field from the magnet is irrelevant, but it might have a detuning effect on the antenna because of its size and position, which will need to be checked. It should be insulated from the antenna, of course.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-10-13T22:15:31.950" LastActivityDate="2010-10-13T22:15:31.950" CommentCount="4" />
  <row Id="5180" PostTypeId="2" ParentId="5174" CreationDate="2010-10-13T22:29:42.250" Score="4" ViewCount="" Body="&lt;p&gt;The PIC UART can be picky.  Did you remember to check the Frame Overrun (OERR) bit?  The PIC will be unable to receive UART communications until the OERR is cleared.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I was also thinking...perhaps you could try a sort of loopback?  That is, cut the UART out of the loop, and when the PC sends anything over USB, just send it straight back.  This would tell you whether the issue is with the UART or the USB side of the PIC.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-13T22:29:42.250" CommentCount="2" />
  <row Id="5181" PostTypeId="2" ParentId="5169" CreationDate="2010-10-13T22:57:45.603" Score="3" ViewCount="" Body="&lt;p&gt;Please look at &lt;a href=&quot;http://electronics.stackexchange.com/questions/922/how-does-an-lm7805-voltage-regulator-work&quot;&gt;http://electronics.stackexchange.com/questions/922/how-does-an-lm7805-voltage-regulator-work&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-13T22:57:45.603" />
  <row Id="5182" PostTypeId="1" CreationDate="2010-10-14T00:12:53.037" Score="3" ViewCount="639" Body="&lt;p&gt;I have Lego Mindstorms RCX 1.0, and would like to program it with a modern computer, preferably running MacOS (Snow Leopard) or Windows XP.  I have the software CD that came with the set, and a serial/usb cable (Prolific, PL2303) to use with the serial IR tower.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I successfully installed the software on Windows XP, and am able to watch the tutorials and write programs.  The software seems to recognize the cable as a COM port, but fails to download programs to the RCX.  I have tried two different towers, and two different RCXs, so I don't think it's a simple hardware failure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I installed the software on Snow Leopard with wine, but had less success.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Can I use my old hardware with a new computer?  If not, what is the minimum that I must replace?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1255" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-15T02:37:44.943" LastActivityDate="2011-02-11T21:12:29.687" Title="Can I program old Lego Mindstorms with a new computer?" Tags="&lt;serial&gt;&lt;ir&gt;&lt;lego-mindstorms&gt;" AnswerCount="3" />
  <row Id="5183" PostTypeId="2" ParentId="5174" CreationDate="2010-10-14T00:15:39.303" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;USB Sniffing&lt;/strong&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Windows:&#xA;&lt;a href=&quot;http://sourceforge.net/projects/usbsnoop/&quot; rel=&quot;nofollow&quot;&gt;http://sourceforge.net/projects/usbsnoop/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Linux:&#xA;&lt;a href=&quot;http://www.linux-usb.org/tools.html&quot; rel=&quot;nofollow&quot;&gt;http://www.linux-usb.org/tools.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Microchip CDC&lt;/strong&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm afraid that I know nothing about their official stack, but...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Over at &lt;a href=&quot;http://dangerousprototypes.com&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com&lt;/a&gt; they've been building a new &lt;a href=&quot;http://dangerousprototypes.com/2010/09/02/open-source-pic-usb-demoed/&quot; rel=&quot;nofollow&quot;&gt;Open Source PIC USB&lt;/a&gt; stack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They're using it in the new &lt;a href=&quot;http://dangerousprototypes.com/docs/Bus_Pirate_v4&quot; rel=&quot;nofollow&quot;&gt;single chip Bus Pirate&lt;/a&gt;. The Bus Pirate &lt;a href=&quot;http://code.google.com/p/the-bus-pirate/source/browse/#svn/trunk/HonkenUSBStack&quot; rel=&quot;nofollow&quot;&gt;CDC driver is here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, you can &lt;a href=&quot;http://dangerousprototypes.com/forum/index.php?topic=937.0&quot; rel=&quot;nofollow&quot;&gt;pick up the original alternative stack version here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-14T16:07:55.537" LastActivityDate="2010-10-14T16:07:55.537" CommentCount="2" />
  <row Id="5184" PostTypeId="2" ParentId="5144" CreationDate="2010-10-14T00:39:20.683" Score="2" ViewCount="" Body="&lt;p&gt;Cheap soldering irons (the unregulated kind that run at 10-25W and the power cord goes straight into the handle) have a lot more problems with corrosion than the nicer regulated irons.  It doesn't matter too much if it's ugly, as long as you can get a nice shiny bit right at the tip.  Dedicated tip cleaning mesh is the best thing I've found for that, but the traditional damp sponge works fairly well.  Just try to wipe it off after every 4-5 solder joints.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't worry too much if the whole tip isn't nicely covered in solder.  You only need the last 5 mm or so - the part that comes in contact with the parts you are soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a last ditch kind of thing, I've been known to go after a badly corroded tip using a metal file.  I'd only do this on a really cheap iron, but I had one where the tip had been eaten away in an irregular pattern and I was able to reshape it and get some more use out of it with the metal file.  &lt;strong&gt;Do not try this with a fancy iron like a Weller or Hakko that has a ceramic tip.&lt;/strong&gt; &lt;/p&gt;&#xA;" OwnerUserId="213" LastActivityDate="2010-10-14T00:39:20.683" CommentCount="1" />
  <row Id="5185" PostTypeId="2" ParentId="4962" CreationDate="2010-10-14T01:09:52.387" Score="0" ViewCount="" Body="&lt;p&gt;Avnet express has a great one for either $\$$50 or $\$$60, I forget. Spartan-3A based.&lt;/p&gt;&#xA;" OwnerUserId="1584" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-03T15:00:05.030" LastActivityDate="2011-05-03T15:00:05.030" CommentCount="1" />
  <row Id="5186" PostTypeId="1" AcceptedAnswerId="5410" CreationDate="2010-10-14T01:23:34.027" Score="13" ViewCount="577" Body="&lt;p&gt;I find very difficult to read part numbers. I haven't figured out how which kind the ideal amount of light and inclination would help me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also wonder why chipmakers don't paint the numbers in white for a better contrast.&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T19:46:10.600" LastActivityDate="2011-02-08T19:46:10.600" Title="How to read the text printed on top of every IC?" Tags="&lt;components&gt;" AnswerCount="6" CommentCount="5" FavoriteCount="4" />
  <row Id="5187" PostTypeId="2" ParentId="5186" CreationDate="2010-10-14T01:42:40.200" Score="5" ViewCount="" Body="&lt;p&gt;It sounds obvious, but have you tried a magnifying glass? I always use one when trying to read part numbers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once I've done that, I usually print out a sticky label with the same information and stick it to the part.&lt;/p&gt;&#xA;" OwnerUserId="776" LastActivityDate="2010-10-14T01:42:40.200" />
  <row Id="5188" PostTypeId="1" CreationDate="2010-10-14T02:46:03.187" Score="5" ViewCount="155" Body="&lt;p&gt;So I'm working on a new project where I'm trying to identify devices on a closed protocol &quot;network&quot; of sorts. I'm trying to determine how many devices are out there and unique id's of each device. I'll probably have an eprom or something similar to store the unique identifier. The question I would have for the forum would be: is a daisy chain the best way to identify the devices? (as shown below)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/e4kxr.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking I could try to also route individual control lines to the devices but I won't necessarily know how many total devices are out there. I &lt;i&gt;will&lt;/i&gt; be able to connect the final device back to a return line (physically using a jumper and identified here by the blue dot). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So again, my question is: is there a better way to do this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2011-02-22T03:19:34.050" Title="Help with device identification in a chain" Tags="&lt;protocol&gt;&lt;identification&gt;" AnswerCount="6" CommentCount="4" FavoriteCount="1" />
  <row Id="5189" PostTypeId="2" ParentId="5186" CreationDate="2010-10-14T04:52:19.690" Score="12" ViewCount="" Body="&lt;p&gt;Use a 10x loupe, very handy.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Occasionally some markings might be illegible after soldering and splattering some flux on them, so flux cleaner can help there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes you can change the contrast by wiping the markings with your fingers; the skin oils can change the reflectivity to make it easier (or more difficult) to read.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-14T04:52:19.690" CommentCount="3" />
  <row Id="5190" PostTypeId="2" ParentId="5148" CreationDate="2010-10-14T05:49:10.900" Score="1" ViewCount="" Body="&lt;p&gt;According to &lt;a href=&quot;http://www.element-14.com/community/message/15753&quot; rel=&quot;nofollow&quot;&gt;this forum post&lt;/a&gt;, you can export DXF from Topor, and then use dxf2scr to convert the DXF to a SCR file, then load the SCR file into Eagle. There are 3 different apps that convert DXF to SCR listed on &lt;a href=&quot;http://www.cadsoftusa.com/cgi-bin/download.pl?page=/home/cadsoft/html_public/download.htm.en&amp;amp;dir=eagle/userfiles/misc&quot; rel=&quot;nofollow&quot;&gt;cadsoft's website&lt;/a&gt;, try them and report back which one works best.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-10-14T05:49:10.900" CommentCount="3" />
  <row Id="5191" PostTypeId="2" ParentId="5080" CreationDate="2010-10-14T06:31:04.637" Score="0" ViewCount="" Body="&lt;p&gt;Your camera probably has composite output which goes into some modulator box that encodes the signal to some specific TV channel. Intercept this signal before the box, and buy some cheap baby monitoring wireless camera system (actually you just need some home range CBSV to TV via air system). Every TV in the range will receive camera picture via air (including small 7&quot; LCD if it is capable of receiving air TV signal). It can hardly get simpler then this.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-10-14T06:31:04.637" />
  <row Id="5192" PostTypeId="2" ParentId="5186" CreationDate="2010-10-14T07:04:23.277" Score="4" ViewCount="" Body="&lt;p&gt;I use a USB microscope with built in LED lights.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is very useful for reading part numbers, but also comes in handy when reading values of resistors and small caps. I'm not sure on the magnification range, but I think it's from 5x to 50x. Around 10x-15x works well for reading part numbers.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-14T07:04:23.277" CommentCount="1" />
  <row Id="5193" PostTypeId="2" ParentId="5188" CreationDate="2010-10-14T08:31:39.583" Score="4" ViewCount="" Body="&lt;p&gt;It would help to know what phy layer you're using. But, here's some general information:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're using I2C, your bus should look something like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(taken from societyofrobots.com)&#xA;&lt;img src=&quot;http://www.societyofrobots.com/member_tutorials/files/SoR_tut1_html_649df559.gif&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At runtime, you can detect the I2C addresses by &lt;a href=&quot;http://dangerousprototypes.com/forum/index.php?topic=1079.msg11159#msg11159&quot; rel=&quot;nofollow&quot;&gt;scanning the bus&lt;/a&gt; by sending a START condition to every address and checking for an ACK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're using SPI, you'll need a chip select line per device. If you run out of pins, you could use some kind of multiplexer. You may be able to scan the bus by asserting each chip select line in turn and attempting to communicate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://kkamagui.springnote.com/pages/422905/attachments/177111&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-14T08:31:39.583" CommentCount="3" />
  <row Id="5194" PostTypeId="2" ParentId="5186" CreationDate="2010-10-14T10:19:08.940" Score="5" ViewCount="" Body="&lt;p&gt;Get an LED torch with blue or clear/blueish LEDs, it works well for highlighting the text on chips - and it's handy to have while rummaging through the dark depths of the parts cupboard!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I rarely have to break out a magnifying glass, unless the print has started to rub off - bad design if you ask me, I've got a load of old 555 timers and 386 amps that are hard to tell apart as there's barely enough print visible to distinguish them.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-10-14T10:19:08.940" CommentCount="1" />
  <row Id="5195" PostTypeId="2" ParentId="5188" CreationDate="2010-10-14T12:58:35.820" Score="2" ViewCount="" Body="&lt;p&gt;Send a command to the first device to send its address, followed by a counter (zero to start)&#xA;Each device will read in the command and output the command.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then read in the counter, increment it, and output the counter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then read in any previous addresses and send them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then send its address.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As each device gets the command, it appends its address to the response.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the devices are numbered 1, 2, 3, then the resulting response will be:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;DISCOVER CMD&#xA;COUNT = 3&#xA;ADDRESS 1&#xA;ADDRESS 2&#xA;ADDRESS 3&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-10-14T12:58:35.820" />
  <row Id="5196" PostTypeId="1" AcceptedAnswerId="5205" CreationDate="2010-10-14T13:39:18.543" Score="17" ViewCount="677" Body="&lt;p&gt;I'm aware that nobody actually does this at the hobbyist level, that successful commercial products have been launched without certification, and it's probably something I can't afford if I have to ask. However, I've always wondered about the ballpark cost. About how much does it cost to receive FCC certification?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2011-05-23T20:17:43.923" Title="Which products should have FCC certification and about how much does that cost?" Tags="&lt;fcc&gt;&lt;certification&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="7" />
  <row Id="5197" PostTypeId="2" ParentId="5182" CreationDate="2010-10-14T14:26:40.090" Score="1" ViewCount="" Body="&lt;p&gt;Zemkat...I am not 100% familiar with the RCX 1.0 setup, but according to Google, it should run fine on Windows XP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you checked the device manager on Windows XP to see if that system is currently using the COM port and/or IRQ for something else? If so, this can cause issues for sure. If you go into your BIOS of the computer, you will see which COM port and IRQ are being used for the serial connection. Once you have that information, you can go into the Device Manager in windows and go to Ports (COM &amp;amp; LPT) then right click and do Properties on COM1 or whatever it is using. You can then go to the resource tab to see if it has a conflict.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a conflict exists, check your other hardware devices to determine which device is using the COM port or IRQ. You can use the resource tab of the other hardware device to reassign it to a different port or IRQ.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know you said it recognizes it, but I would still check up on this as a device on the same hardware resource can cause communication problems over serial. I hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastActivityDate="2010-10-14T14:26:40.090" />
  <row Id="5198" PostTypeId="2" ParentId="5188" CreationDate="2010-10-14T14:46:59.997" Score="2" ViewCount="" Body="&lt;p&gt;You might want to look at LIN ( &lt;a href=&quot;http://en.wikipedia.org/wiki/Local_Interconnect_Network&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Local_Interconnect_Network&lt;/a&gt; ) which can use something called SNPD to detect and assign addresses to nodes at run-time. There are three methods presented in the Wikipedia article, and any would work, but some are apparently patented, so be careful. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LIN protocol itself is a fairly simple SCI-based protocol with some added reliability features, but the SNPD techniques could be applied to any serial data transfer.&lt;/p&gt;&#xA;" OwnerUserId="875" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-14T14:53:52.603" LastActivityDate="2010-10-14T14:53:52.603" />
  <row Id="5199" PostTypeId="1" AcceptedAnswerId="5208" CreationDate="2010-10-14T15:31:36.883" Score="4" ViewCount="201" Body="&lt;p&gt;I don't mean the colored bands, but the colors of the bodies themselves.  They come in brown, blue, green, etc.  Is there a standard?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, &lt;a href=&quot;http://www.epanorama.net/documents/markings/resistor_colorcodes.html&quot; rel=&quot;nofollow&quot;&gt;epanorama says&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;But there are two resistor body colors which you should know what they need if youre fixing some electronics circuit. Resistor body colors white and blue are used to mark non-flammable resistors and fusible resistors. If you encounter tjis type of resistor in the circuit do not replace it with normal reistor because this would cause fire danger is something goes wring in the circuit.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Is this always true?  Only with certain manufacturers?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-15T16:10:45.903" LastActivityDate="2010-10-15T16:36:59.740" Title="What do the colors of resistors mean?" Tags="&lt;resistor&gt;&lt;colour&gt;&lt;colour-coding&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="5200" PostTypeId="2" ParentId="1842" CreationDate="2010-10-14T15:34:17.700" Score="0" ViewCount="" Body="&lt;p&gt;Additional thoughts about encapsulating your thermocouple in oil, potting compound or anything else, is thermal capacitance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The amount of thermal capacitance is proportional to the amount and type of compound used.  This will slow down the temperature response of the thermocouple due to the heat retained, or lost by the encapsulant.  As long as you use substances with less thermal capacitance than the water it is surrounded by you can be sure that the temperature you are measuring is the actual water temperature, and not the delay of the thermocouple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the issue of joining thermocouple to copper wires.  This is ideally performed in a bit more of controlled manner, and most importantly that the temperature is measured and recorded &lt;em&gt;where&lt;/em&gt; this takes place.  A simple LM35 sensor will do fine, and feed this into your ADC alongside the filtered and amplified thermocouple signals.  From here use the known thermocouple polynomials and some software to calculate the temperature or use look up tables for the range you are interested in.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-14T15:34:17.700" />
  <row Id="5201" PostTypeId="1" CreationDate="2010-10-14T15:54:06.340" Score="-6" ViewCount="63" Body="&lt;p&gt;It is unclear to me if Google TV provides DVR functionality. Does anyone know?&lt;/p&gt;&#xA;" OwnerUserId="1595" LastActivityDate="2010-10-14T16:10:47.423" ClosedDate="2010-10-14T19:22:06.957" Title="Google TV: Does it do DVR?" Tags="&lt;tv&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="5202" PostTypeId="2" ParentId="5201" CreationDate="2010-10-14T15:56:38.003" Score="1" ViewCount="" Body="&lt;p&gt;So far as I know, it's all streamed. Trickplay (fast forward/rewind) is all done at the head end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No internet, no tv.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-14T16:10:47.423" LastActivityDate="2010-10-14T16:10:47.423" />
  <row Id="5204" PostTypeId="2" ParentId="5199" CreationDate="2010-10-14T16:13:36.610" Score="3" ViewCount="" Body="&lt;p&gt;It's up to the manufacturer, it doesn't have any relevance to the properties of the device.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-14T16:13:36.610" />
  <row Id="5205" PostTypeId="2" ParentId="5196" CreationDate="2010-10-14T16:15:07.960" Score="13" ViewCount="" Body="&lt;p&gt;As a rough estimate, the cost is $10k-20k, plus your labor cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the US, all products containing electronics that oscillate above 9 kHz must be certified. The law that governs this is FCC Part 15. The lawyers call this &quot;Title 47 CFR Part 15,&quot; meaning that it is the 15th subsection of the 47th section of the Code of Federal Regulations. In Europe, there is a similar regulation called CISPR 22. The requirements are almost the same, but slightly stricter about emissions at certain frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can read &lt;a href=&quot;http://www.access.gpo.gov/nara/cfr/waisidx_05/47cfr15_05.html&quot; rel=&quot;nofollow&quot;&gt;47 CFR 15&lt;/a&gt; online. It's not as incomprehensible as you might expect. It seems overwhelming, but if you read the first few PDF's, you'll realize that most of it irrelevant for any single product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Within 47 CFR 15, there are two classes of testing: Class A and Class B. Class A is an easier test to pass, intended for devices that are used in industrial settings. Class B is stricter, intended for devices that are targeted at consumers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is additional testing for &quot;intentional radiators,&quot; meaning radios, Wi-fi, Bluetooth and such. There may be an exception if your device is intended for use as a component in a larger system (like a microprocessor or memory card in a PC), but I'm not sure of the legal details there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The major expense is renting the test chamber. This is what's called an &quot;anechoic chamber,&quot; instrumented with a pile of sensors for detecting electromagnetic radiation. To my knowledge, these cost around $1000/hour, and each testing session takes 2 or 3 hours. It's unlikely, but not impossible, that you will pass on the first try.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a &lt;a href=&quot;http://en.wikipedia.org/wiki/File%3aRadio-frequency-anechoic-chamber-HDR-0a.jpg&quot; rel=&quot;nofollow&quot;&gt;decent picture&lt;/a&gt; of a test chamber. The one I've been in was actually much larger, like a squash court. I think it was an &lt;a href=&quot;http://www.intertek.com/&quot; rel=&quot;nofollow&quot;&gt;Intertek&lt;/a&gt; facility in Menlo Park, CA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless you're experienced with emissions testing, it is worth hiring an expert, which costs around $500/hour. They can tell you things like, &quot;Put a ferrite bead on that power cable, and that will reduce the emissions at this frequency.&quot; The folks I've worked with arrive with a bunch of ferrite beads and inductors (and maybe caps?) of various sizes that you can use in the chamber to hack your device into compliance. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Perhaps it goes without saying, but I'm an engineer, not a lawyer. I have taken a few products through Part 15, but not in the last couple of years.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're thinking about doing this, start by reading &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0750681705&quot; rel=&quot;nofollow&quot;&gt;EMC for Product Designers&lt;/a&gt; by Tim Williams. I'd avoid the books by Mark I. Montrose; I found them less helpful and more expensive.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-10-14T16:52:39.450" LastActivityDate="2010-10-14T16:52:39.450" />
  <row Id="5206" PostTypeId="2" ParentId="5196" CreationDate="2010-10-14T16:26:50.930" Score="2" ViewCount="" Body="&lt;p&gt;Where I used to work we saved a lot of money on CE testing by hiring the facility for half a day and doing our own preliminary testing. We fixed any problems, they were usually quite minor, and the equipment always then passed first time. You do need to have someone who knows how to drive the test instruments, of course.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-14T16:26:50.930" CommentCount="1" />
  <row Id="5207" PostTypeId="2" ParentId="5182" CreationDate="2010-10-14T16:46:35.390" Score="3" ViewCount="" Body="&lt;p&gt;Yes, you can, but the included software may not work. Many developers still using the RCX and its relatives use alternative software such as &lt;a href=&quot;http://bricxcc.sourceforge.net/nqc/&quot; rel=&quot;nofollow&quot;&gt;NQC&lt;/a&gt; (possibly with &lt;a href=&quot;http://bricxcc.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;BricxCC&lt;/a&gt;) or &lt;a href=&quot;http://brickos.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;brickOS&lt;/a&gt; - more on &lt;a href=&quot;http://en.wikipedia.org/wiki/Lego_Mindstorms#Programming_languages_2&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;. These two do not have the graphical control flow interface, however. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your problem description is a little worrying, as any of the software options needs the same IR tower. The IR towers are simply electric to infrared adaptors for serial ports (on newer ones, with a serial to USB converter). Did you check the tower's battery? Sometimes the near/far switch on the front also needs to be toggled.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-10-14T16:46:35.390" CommentCount="1" />
  <row Id="5208" PostTypeId="2" ParentId="5199" CreationDate="2010-10-14T17:39:15.523" Score="7" ViewCount="" Body="&lt;p&gt;I've seen a few manufacturers that make their high precision metal film resistors blue and their generic paper/carbon ones pale brown, but I'd guess it's not a universal thing...it's like when Walkers (Lays) crisps messed around with the colour flavour combos, everyone had to relearn cheese &amp;amp; onion and salt &amp;amp; vinegar grrrr!   &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-10-14T17:39:15.523" CommentCount="1" />
  <row Id="5210" PostTypeId="2" ParentId="4857" CreationDate="2010-10-14T18:54:35.447" Score="0" ViewCount="" Body="&lt;p&gt;Doing some more Googling on this topic (armed with some hints provided by Kellenjb, tronixstuff and avra), I have turned up an example of the kind of reader I'm interested in:&#xA;&lt;a href=&quot;http://www.iautomate.com/products/Home-Automation-RFID-Reader.html&quot; rel=&quot;nofollow&quot;&gt;Home Automation RFID Reader&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will be trying to find a tear-down of this or a similar unit that describes the components it uses. I'll try to keep this answer updated with what I learn.&lt;/p&gt;&#xA;" OwnerUserId="1317" LastActivityDate="2010-10-14T18:54:35.447" />
  <row Id="5211" PostTypeId="2" ParentId="4962" CreationDate="2010-10-14T20:49:36.770" Score="1" ViewCount="" Body="&lt;p&gt;Not the easiest to access I/O but a cool form factor: &lt;a href=&quot;http://www.altera.com/b/nios-bemicro-evaluation-kit.html&quot; rel=&quot;nofollow&quot;&gt;The BeMicro Altera Cyclone 3&lt;/a&gt;. I am partial to Altera over Xilinx. I know Xilinx has a free web tool kit but Altera is free-er for longer (into the development cycle) if I remember it correctly. Plus I like their SOPC system builder, it's pretty simple to compile an on-board soft-core processor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bonus: labs included on the site to get you started.&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-10-14T20:49:36.770" CommentCount="1" />
  <row Id="5212" PostTypeId="2" ParentId="5188" CreationDate="2010-10-14T21:48:20.690" Score="2" ViewCount="" Body="&lt;p&gt;If you don't have to do too much fast talking look at Dallas One-Wire for your bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1 wire ( and an implicit ground)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;addressable, 250 off per bus, routeable, and the interface devices are very cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Really useful as a system management bus because it is so expendable.&#xA;I've got a family of systems that use 1-wire for system management and device discovery, then something else (like) jindi for communications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wholeheartedly recommend something with a meta-protocol so you can change things later.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-10-14T21:48:20.690" />
  <row Id="5213" PostTypeId="1" AcceptedAnswerId="5219" CreationDate="2010-10-14T22:18:08.623" Score="4" ViewCount="333" Body="&lt;p&gt;I want to get a stable 3V reference from a +3.3V ±5% supply (so it can go as low as 3.135V and as high as 3.465V.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know the TL431 is a shunt/zener regulator, so doesn't really have a dropout voltage, but there probably is some point above 3V at which it cannot maintain the 3V output. What I want to know is will a typical TL431 be able to handle this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My circuit configuration is below:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;         115R&#xA;+3.3V-+-/\/\/\---+----------+-------+-- 3V out&#xA;      |          |          |       |&#xA;     --- 100n    /          |      --- 4.7u&#xA;     --- 16V     \ 634R     |      --- 10V&#xA;      |          /       ___|__|    |&#xA;     ---         |       | / \     ---&#xA;      -          +--------/___\     -&#xA;                 |          |&#xA;                 /          |&#xA;                 \ 3.16k    |&#xA;                 /          |&#xA;                 |          |&#xA;                ---        ---&#xA;                 -          -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-15T22:58:00.833" Title="Does the TL431 have a &quot;dropout voltage&quot; per se?" Tags="&lt;zener&gt;&lt;tl431&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="5214" PostTypeId="2" ParentId="5196" CreationDate="2010-10-14T22:43:42.493" Score="8" ViewCount="" Body="&lt;p&gt;About five years ago I got a product CE tested for $7500.  The testing house provided advice, and they retested until it passed as part of the upfront cost.  It passed on the second attempt (barely).  Since, I've read &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0133957241&quot; rel=&quot;nofollow&quot;&gt;High-Speed Digital Design: A handbook of black magic&lt;/a&gt; several times until I mostly got it and I probably won't have nearly as much trouble in the future.  I highly recommend the book.&lt;/p&gt;&#xA;" OwnerUserId="1270" LastEditorUserId="3441" LastEditorDisplayName="" LastEditDate="2011-05-23T20:17:43.923" LastActivityDate="2011-05-23T20:17:43.923" CommentCount="1" />
  <row Id="5215" PostTypeId="2" ParentId="5188" CreationDate="2010-10-15T01:19:49.583" Score="2" ViewCount="" Body="&lt;p&gt;You really can't even make a choice here without determining the PHY layer but some ideas:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the system really is daisy chained as drawn then bring up each device in order.  Factory program to the &quot;broadcast address&quot; if the PHY has one (like I2C does).  Then just have each device pick an address and send that address to the next device as it moves down the chain.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If use 8bit UIDs, you get bonus points, at least from me, if you spell something comical in ASCII with the addresses:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Master: &quot;Hey device 1, choose an address&quot;&#xA;Device 1: &quot;M&quot;, hey device 2 choose an address&#xA;Device 2: &quot;y&quot;&#xA;Device 3: &quot;B&quot;&#xA;Device 4: &quot;o&quot;&#xA;Device 5: &quot;s&quot;&#xA;Device 6: &quot;s&quot;&#xA;Device 7: &quot;S&quot;&#xA;Device 8: &quot;u&quot;&#xA;Device 9: &quot;c&quot;&#xA;Device 10: &quot;k&quot;&#xA;Device 11: &quot;s&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively if your design has a fixed number of devices: I had a design that used a backplane that allowed up to 4 cards to be plugged in.  What i ended up doing what placing a I2C based GPIO expander on the backplane (actually it was a fan control IC i needed anyway, i just picked one with and I2C interface and some GPIOs on it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I routed a GPIO through each card edge connector to the reset pin of the DSP on each plug in card.  All DSPs were factory programmed to 1 address.  The system controller brought the slots out of reset 1 at a time, an I2C command was sent, if something ACKed it was assumed the slot was populated and a command was sent for it to change its I2C address to a UID for that slot.  This was done for each slot with a reasonable reply time out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If its a shared bus that capable of slave initiating transfers, aka multi-master.  Just have the slave device assert control of the bus and ask the master for an address, master just gives it the next address in line, think DHCP. Same bonus points as above.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the PHY is single master and you have a completely unknown number of devices....daisy chain a GPIO through them and use that to control if they respond to a factory programmed address?  Then when the slave gets its address, it de-asserts the next device in line?  This way you only need 2 GPIO pins per device and 1 for the master and you can bring devices up one at a time.  Should work i think.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, honestly all speculation till you choose a PHY and can tell us more about how the overall system is connected.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-15T01:19:49.583" />
  <row Id="5216" PostTypeId="2" ParentId="5097" CreationDate="2010-10-15T02:10:44.537" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.sealevel.com/store/serial/synchronous-serial/pci/5104s-pci-rs-232-rs-422-rs-485-rs-530-rs-530a-v-35-synchronous-serial-interface-uses-z16c32.html&quot; rel=&quot;nofollow&quot;&gt;SeaLevel Systems&lt;/a&gt; makes a synchronous board that does 10 Mbit. Have not used their products but they have been in business for at least a few years. Even if they don't have a native .NET interface, keep in mind that you can call 'unsafe' code from .NET environments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.generalstandards.com/view-products.php?product=PCI-SIO8BXS&quot; rel=&quot;nofollow&quot;&gt;General Standards&lt;/a&gt; also makes a board. They are pricey.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing to consider is using a PMC card on a PCI carrier. Note that this is at least a $1500 solution.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2010-10-15T02:10:44.537" CommentCount="2" />
  <row Id="5217" PostTypeId="1" CreationDate="2010-10-15T04:20:57.460" Score="4" ViewCount="135" Body="&lt;p&gt;Im trying to design a maximum strength electromagnet. I have a soft iron core that is 1.3&quot; (33mm) round by 1.9&quot; (50mm) long and I'm using 12 volts of input and my wire gauge is 18awg. Unfortunately I don't have the proper program to achieve this task. I was wondering if there was anyone with the know how that could help.&#xA;Thanks Warren. &lt;/p&gt;&#xA;" OwnerUserId="1600" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-15T04:58:43.683" LastActivityDate="2010-10-15T11:05:51.840" Title="Electromagnet design" Tags="&lt;electromagnetism&gt;&lt;optimization&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="2" />
  <row Id="5218" PostTypeId="1" AcceptedAnswerId="5220" CreationDate="2010-10-15T04:43:40.870" Score="2" ViewCount="216" Body="&lt;p&gt;I am currently interested in determining how a home thermostat controls a home HVAC unit. I have run into plenty of schematics that can control a HVAC window unit, walk in freezer, water temperature, etc. However, using a circuit like those on a unit as expensive as a HVAC unit is just nuts as far as I am concerned...plus it doesn't take care of all possible operations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The question I seek an answer for: How do you build a complete home thermostat. A device that protects and is built to ensure no damage is done to the HVAC unit. I am planning on buying a cheap $10-20 thermostat just to tear it apart and study the board in detailin a few weeks if I cannot find any other answers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My current home HVAC unit uses a 4 Wire Heat/Cool setup which is referenced on page 17 (10 on adobe reader) of this thermostat installation manual: &lt;a href=&quot;http://www.ritetemp-thermostats.com/60XX/images/6022_installation_guide.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.ritetemp-thermostats.com/60XX/images/6022_installation_guide.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Connections are as follows:&#xA;W - Heater Control Line&#xA;Y - Cooler Compressor&#xA;RH - Heater/Cooler Power&#xA;G - Fan Control&#xA;C - Optional Thermostat Power (which I have)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;What kind of control does this device use? Is it 1-wire? Where is the GND connection? In addition to this wire diagram, the unit also provides C which powers the thermostat itself ensuring no batteries are required. I wish I could tear this unit apart but do not have another thermostat to put in its place until I get paid.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can help me/point me in the right direction; I would be much appreciative.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="1575" LastEditorDisplayName="" LastEditDate="2010-10-15T05:17:13.793" LastActivityDate="2010-10-15T06:55:35.037" Title="ISO Example Home HVAC Control Schematics and Circuit Design Info" Tags="&lt;microcontroller&gt;&lt;circuit&gt;&lt;embedded&gt;&lt;temperature&gt;&lt;home-automation&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="5219" PostTypeId="2" ParentId="5213" CreationDate="2010-10-15T06:41:17.717" Score="3" ViewCount="" Body="&lt;p&gt;There is no dropout voltage as such. The reference voltage is 2.5V and it will run happily at 2.5V if you short circuit the ref pin to the cathode. The important spec to consider is the shunt current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You must ensure that there is at least 1 mA biasing the device. (Based on the TI data sheet.) From your circuit, with 115R and a minimum voltage drop of 3.135 - 3 = 0.135 you will end up with a shunt current of 0.135/115 = 1.1 mA. However the voltage divider which has a total resistor of about 3.7 kR is going to use almost 1 mA itself, not leaving enough for the TL431. You also have to add in the current that you load will used, but if it is a high impendence - say into an op-amp - it shouldn't be a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can fix that by increasing the value of the voltage divider resistors. Say we multiply them by ten, to get 6.34k and 31.6k. The max input current to the ref pin is stated as 4 uA, which might start to give you some errors in the set point (depending on how accurate you expect the Vout to be). The worst case error will be about 4uA * 6.34k or 25 mV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The last thing you need to consider will be the maxiumum shunt current. When the input voltage is at its max value the 115R resistor will have 0.465 V across it. This means the shunt current (including the voltage divider and load) will be 0.465 / 115 = 40 mA. Fortunately that is well within the 100 mA maximum of the 431. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because we're still far below the maximum shunt current you could consider reducing the series resistor - too say 56R. That will help satify the minimum shunt current without changing the voltage divider and still stay under the maximum shunt current rating with the input voltage is at its maxiumum. At higher current you will also need to check the power dissipation. 100 mA * 3V gives a maximum power off 300mW. For some small smd packages that is getting a bit too high.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic problem trying to optimise the circuit as it is, comes from the fact that the voltage across the series resistor is too low and any variation in the supply voltage represents a big variation across the series resistor.    &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't (as suggested in the comments) afford to waste the current you might need to consider a difference approach. Either a series regulator (will be tough with only 100mV dropout voltage), reduce your reference voltage or increase the supply voltage to the series resistor.&lt;/p&gt;&#xA;" OwnerUserId="328" LastEditorUserId="328" LastEditorDisplayName="" LastEditDate="2010-10-15T22:58:00.833" LastActivityDate="2010-10-15T22:58:00.833" CommentCount="3" />
  <row Id="5220" PostTypeId="2" ParentId="5218" CreationDate="2010-10-15T06:41:50.587" Score="1" ViewCount="" Body="&lt;p&gt;After reading a few posts and doing a little testing with a DMM, I believe I have solved my questions concerning how a home thermostat works. First the posts/info that led to the conclusion:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ritetemp-thermostats.com/60XX/images/6022_installation_guide.pdf&quot; rel=&quot;nofollow&quot;&gt;RiteTemp Installation Guide (pg 17 - 4 Wire Heat/Cool No Pump)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.eevblog.com/forum/index.php?topic=1528.msg20345#msg20345&quot; rel=&quot;nofollow&quot;&gt;JohnSAZ from EEVBlog&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Of course your thermostat may be&#xA;  different but every one that I've ever&#xA;  looked at worked the same (and your&#xA;  color codes pretty much indicate an&#xA;  industry standard setup).&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Think of the thermostat as nothing&#xA;  more than three switches. The &quot;RH&quot; is&#xA;  your common. If you short &quot;RH&quot; to &quot;G&quot;,&#xA;  your blower fan will turn on. If you&#xA;  short &quot;RH&quot; to &quot;Y&quot;, the air&#xA;  conditioning compressor will turn on.&#xA;  If you short &quot;RH&quot; to &quot;W&quot;, the heater&#xA;  system will turn on. This could be a&#xA;  gas burner solenoid, or relays to&#xA;  energize resistive electric heaters.&#xA;  If the unit is a heat pump, it will&#xA;  turn on the air conditioning&#xA;  compressor, but it will also energize&#xA;  a reversing valve that will make the&#xA;  freon run the other way around&#xA;  (kinda).&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Obviously you need to ensure that the&#xA;  &quot;G&quot; and &quot;Y&quot; leads are NEVER turned on&#xA;  at the same time. You also need to&#xA;  make sure that the eater system can&#xA;  not be turned on with the blower off.&#xA;  Also, you need to make sure that when&#xA;  the compressor turns off, it is not&#xA;  allowed to turn back on for some time&#xA;  (10 minutes? don't know the time limit&#xA;  for sure). Also, higher quality&#xA;  thermostats keep the blower running&#xA;  for some time after the compressor (or&#xA;  heater) has turned off to suck every&#xA;  last Btu out of the system before&#xA;  shutting down.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I grabbed my trusty DMM and confirmed that W, Y, G, and C all measure 30VAC+ when tested against RH (or R) - GND. When the system is running, G drops to 0.05 for both heat and cold (meaning the fan is running). W drops to 0.05 if the heater is running. Y drops to 0.05 if the Cooler is running.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I still need to research the appropriate timing for cooler/heater shutdown etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone can think of any additional circuit protection outside of what JohnSAZ noted, please let me know. I am interested in adding a fail safe to the circuit design in case the unit fails. Not sure if relays in off positions during power outage would take care of business or not. Either way, I do plan on providing battery backup to the project just in case (IE. detect power failure, disable all controls).&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="1575" LastEditorDisplayName="" LastEditDate="2010-10-15T06:55:35.037" LastActivityDate="2010-10-15T06:55:35.037" CommentCount="5" />
  <row Id="5221" PostTypeId="1" AcceptedAnswerId="5226" CreationDate="2010-10-15T07:46:09.720" Score="1" ViewCount="162" Body="&lt;p&gt;I've lost touch with electronics. I used to be an electronics hobbyist in my childhood.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have some old small hobby project circuits, which I want to repair. One of which is a remote-operated garage gate. It has many (8) old electro-mechanical relays which are dead. What should I replace them with? I just read on wikipedia about the new solid-state relays, are they costly? Are they available?&lt;/p&gt;&#xA;" OwnerUserId="1446" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-06T22:23:20.383" LastActivityDate="2011-02-06T22:23:20.383" Title="What to replace a relay with?" Tags="&lt;relay&gt;&lt;solid-state-relay&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="5222" PostTypeId="2" ParentId="2024" CreationDate="2010-10-15T08:57:36.873" Score="0" ViewCount="" Body="&lt;p&gt;I have tried accessing the page:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://scratchconnections.wik.is/User:Chalkmarrow/Catenary&quot; rel=&quot;nofollow&quot;&gt;http://scratchconnections.wik.is/User:Chalkmarrow/Catenary&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but it is asking for a login and there does not appear to be a way to sign up for an account. Can anyone help?&lt;/p&gt;&#xA;" LastActivityDate="2010-10-15T08:57:36.873" CommentCount="1" />
  <row Id="5223" PostTypeId="1" AcceptedAnswerId="5224" CreationDate="2010-10-15T09:54:40.767" Score="5" ViewCount="191" Body="&lt;p&gt;I am currently designing a small PCB in Eagle Cad that has a GPS 1PPS signal (one short pulse per second) as input. The pulsetime for the 1pss is something like 1us. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ok, I know thats not super HF but still.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are good design practises when designing PCB's for HF?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Are curved corners of routes better then perpendicular?&lt;/li&gt;&#xA;&lt;li&gt;Is thicker routes better than thin or opposite?&lt;/li&gt;&#xA;&lt;li&gt;Groundplane = good?&lt;/li&gt;&#xA;&lt;li&gt;etc..&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1605" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-01T21:13:33.117" LastActivityDate="2011-01-01T21:13:33.117" Title="What to think about when designing HF PCB's?" Tags="&lt;pcb&gt;&lt;design&gt;&lt;high-frequency&gt;" AnswerCount="4" FavoriteCount="4" />
  <row Id="5224" PostTypeId="2" ParentId="5223" CreationDate="2010-10-15T10:06:38.227" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf&quot; rel=&quot;nofollow&quot;&gt;Dave Jones' PCB design tutorial&lt;/a&gt; has lots of useful information.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-15T10:06:38.227" />
  <row Id="5225" PostTypeId="2" ParentId="5221" CreationDate="2010-10-15T10:14:16.820" Score="1" ViewCount="" Body="&lt;p&gt;Here's an article about EMR vs SSR:&#xA;&lt;a href=&quot;http://electronicdesign.com/article/components/electromechanical-relays-versus-solid-state-each-h.aspx&quot; rel=&quot;nofollow&quot;&gt;http://electronicdesign.com/article/components/electromechanical-relays-versus-solid-state-each-h.aspx&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SSR are widely available and 'cheap', but why change something that 's guaranteed to work with something... less certain? I don't know the details of the board you want to repair, but I'd say: replace EMR with EMR.&lt;/p&gt;&#xA;" OwnerUserId="1124" LastActivityDate="2010-10-15T10:14:16.820" />
  <row Id="5226" PostTypeId="2" ParentId="5221" CreationDate="2010-10-15T10:45:14.603" Score="6" ViewCount="" Body="&lt;p&gt;There are a few problems with replacing electromechanical relays with solid state relays.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Most SSR's cannot control an AC signal. They are only rated for DC. They will usually conduct all the time with a reverse biased drain-source current, due to the body diode of the MOSFETs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) SSR's can be damaged by exceeding the maximum current through the photodiode, which is usually no more than 10-20mA. A relay will take 100's of mA through its coil. So they aren't a drop in replacement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) They are faster than electromechanical relays, which can cause problems for some circuits (the circuit may be designed to reset in the time the relay is transitioning between the two states, for example.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) They are sensitive to ESD, electromechanical relays are not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5) And finally, most importantly, they do not click when they change, which makes them kind of boring. I love hearing my scopes' relays click when you change the attenuation. Don't underestimate how awesome this is.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-15T10:59:49.553" LastActivityDate="2010-10-15T10:59:49.553" CommentCount="4" />
  <row Id="5227" PostTypeId="2" ParentId="5223" CreationDate="2010-10-15T10:47:48.110" Score="2" ViewCount="" Body="&lt;p&gt;Probably best to keep the high frequency signals as direct as possible. Place the IC/components you are going to feed the signal into right next to the input where possible.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-15T10:47:48.110" />
  <row Id="5228" PostTypeId="2" ParentId="5217" CreationDate="2010-10-15T11:05:51.840" Score="4" ViewCount="" Body="&lt;p&gt;Assuming this is a DC application, wind as many turns as you have room for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason being, magnetization is the product of the number of turns and the current through them. If you double the number of turns, however, while keeping the wire gauge constant, you double the resistance and thereby get half the current from your fixed voltage source; the turns*current product comes out being the same. What's different, though, if you double the number of turns, is that the &lt;em&gt;power&lt;/em&gt; that the coil will draw will be half. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if you keep adding turns, the magnetization doesn't change, but the current drawn goes down, and consequently the power required to run the coil decrease, too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(If you're intending to use AC though, even 50Hz or 60Hz, the above argument doesn't apply since it disregards inductance issues.)&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-15T11:05:51.840" CommentCount="7" />
  <row Id="5229" PostTypeId="1" AcceptedAnswerId="5231" CreationDate="2010-10-15T11:49:41.117" Score="6" ViewCount="116" Body="&lt;p&gt;I'm using the LM2734Z, which operates at 3 MHz. I'm using it to step down 4.8V-20V down to 3.3V +/-5%.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know if is better to use ceramic capacitors or electrolytic capacitors in this circuit? They seem to show ceramic caps in the datasheet, but would electrolytics be smaller and better at filtering ripple and handling load transients? Size is critical for this product. Cost is a minor issue. I would like the operational temp range to be -40C to +85C, if not that then -20C to +70C.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-15T17:12:03.673" Title="Ceramic or Electrolytic caps for a switching buck regulator?" Tags="&lt;capacitor&gt;" AnswerCount="3" />
  <row Id="5230" PostTypeId="2" ParentId="2024" CreationDate="2010-10-15T12:08:32.180" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Modkit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Modkit is an in-browser graphical&#xA;  programming environment for little&#xA;  devices called embedded systems.&#xA;  Modkit can currently program &lt;strong&gt;Arduino&lt;/strong&gt;&#xA;  and Arduino compatible hardware using&#xA;  simple graphical blocks similar to and&#xA;  heavily inspired by the &lt;strong&gt;Scratch&lt;/strong&gt;&#xA;  programming environment developed by&#xA;  the Lifelong Kindergarten Group at the&#xA;  MIT Media Lab.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.modk.it/&quot; rel=&quot;nofollow&quot;&gt;Modkit&lt;/a&gt; &lt;br&gt;&#xA;&lt;a href=&quot;http://4.bp.blogspot.com/_edUeWfBB4Kg/TI8NoUehCFI/AAAAAAAAAGU/XccnX6QRwbQ/s1600/modkit_danger_expanded_screenshot-755x600.png&quot; rel=&quot;nofollow&quot;&gt;Screenshot 1&lt;/a&gt; &lt;br&gt;&#xA;&lt;a href=&quot;http://2.bp.blogspot.com/_edUeWfBB4Kg/TI8L_EsE2iI/AAAAAAAAAGE/bzXKJtE3WO4/s1600/modkit_danger_screenshot-755x600.png&quot; rel=&quot;nofollow&quot;&gt;Screenshot 2&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1084" LastActivityDate="2010-10-15T12:08:32.180" />
  <row Id="5231" PostTypeId="2" ParentId="5229" CreationDate="2010-10-15T12:31:08.367" Score="7" ViewCount="" Body="&lt;p&gt;With chips like that it's best to follow the manufacturer's design closely, unless you really know what you are doing. Ceramics are generally preferred in that sort of application, they are smaller and more reliable than electrolytics, handle high temperatures better, and often have a lower ESR.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-15T12:31:08.367" CommentCount="1" />
  <row Id="5232" PostTypeId="2" ParentId="5229" CreationDate="2010-10-15T13:03:57.910" Score="5" ViewCount="" Body="&lt;p&gt;If size really is critical, you're going to have to go with ceramic. 5-10 years ago, this wasn't even possible with the values you might need (100uF) but it is today. I think you've got it figure out about the ESR, the resistance with the capacitance will change the frequency response of the circuit, so that's the only thing to watch for. &lt;a href=&quot;http://chrisgammell.com/2008/12/05/best-free-spice-program/&quot; rel=&quot;nofollow&quot;&gt;I usually use LTSpice to simulate similar switching type circuits&lt;/a&gt;, as you can start playing with the detailed specs on the capacitors and see how the circuit responds (just choose one of the similar LT 1A buck switchers).&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-10-15T13:03:57.910" />
  <row Id="5233" PostTypeId="1" AcceptedAnswerId="5238" CreationDate="2010-10-15T13:32:11.707" Score="3" ViewCount="150" Body="&lt;p&gt;I'm thinking of using two of &lt;a href=&quot;http://www.pololu.com/catalog/product/1092&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; motors with &lt;a href=&quot;http://www.pololu.com/catalog/product/713&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; motor driver. However, one thing concerns me: the stall current of the motor is 3.3A, and the motor driver has a peak current output of 3A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The motor would be used in a robotics situation involving rapid changes of direction, and potential stalling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could this cause an issue, and do I need to get a lower power motor / better driver, or will it still work?&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;EDIT:&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;What will happen if I DO exceed that thing's current rating, given that it has temperature protection? Will it blow the microcontroller, the motor chip, or the motors?&lt;/p&gt;&#xA;" OwnerUserId="1217" LastEditorUserId="1217" LastEditorDisplayName="" LastEditDate="2010-11-23T19:58:25.290" LastActivityDate="2010-11-23T19:58:25.290" Title="How lenient can I be about motor stall current?" Tags="&lt;robotics&gt;&lt;dc-motor&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="5234" PostTypeId="1" AcceptedAnswerId="5237" CreationDate="2010-10-15T13:57:04.940" Score="2" ViewCount="91" Body="&lt;p&gt;I am trying to find a hex inverter which has as high output current as 74AC04E (50mA) but surface mounted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't had any luck so far...&lt;/p&gt;&#xA;" OwnerUserId="1605" LastActivityDate="2011-05-20T10:57:51.600" Title="High output current hex inverter in SMD capsule" Tags="&lt;components&gt;&lt;inverter&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="5235" PostTypeId="2" ParentId="5233" CreationDate="2010-10-15T14:06:07.173" Score="1" ViewCount="" Body="&lt;p&gt;first things first.  what load does your motor have to move?  at what speeds?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;knowing the above two pieces of information is most important in being able to correctly work out the rest problem.  The load will tell you peak torque, which is directly proportional to current, and later will tell you two things.  The first is power output, which is equal to torque by speed (with a bit of a constant), and the second is inertia (with a bit of modelling of your actual load)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inertia can be a bit of a gotcha is these situations.  If you think that the motor has enough torque and power handle the load, you may find you have problems in trying to &quot;control&quot; the load.  With more inertia on the load, it will take the motor sometime to ramp up, and the load will continue to drive the motor, on the other hand, having too much inertia in the motors rotor will mean the motor responds slower than needed for the given load.  Ideally these need to be matched by circa 10:1 in the motors favour.  dont forget that inertia scales by the square of the gearbox ratio!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;back to your problem, if you are not interested in precise control, consider, but do not worry about the inertia issues. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you do need to answer is the questions about your load, speed and gearbox being used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the extra information, it will be possible to answer your question about matching the amplifier to the motor!&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-15T14:06:07.173" />
  <row Id="5236" PostTypeId="2" ParentId="5223" CreationDate="2010-10-15T14:12:11.093" Score="3" ViewCount="" Body="&lt;p&gt;Yeah, that's not really HF.  Still...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ground plane, definitely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The one big thing about noise if you remember anything is to think in terms of current loops.  All signals must have return current going back to complete a loop.  All else being equal... the larger the area formed by the path of the signal and it's return current, the more noise you'll emit and receive. So, if you've got a signal with a ground wire half a foot away, you're going to be spitting out a lot of noise and coupling a lot of external noise onto your signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One major reason for ground planes is that they provide a very very close return path for the signal.  Strangely, the HF components of return current tend to follow underneath the path of the signal trace and not just the straight path across a ground plane to the battery/input voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you think of minimizing noise in terms of minimizing return loops...  then most other noise-reducing steps become self-explanatory if not self-evident.  Like, you don't want to have a signal trace going across a big slot on ground plane if you can help it...  since the return current will have to divert around the slot and create a larger return loop area.  Putting traces on your ground plane can also cause problems for the same reason.  You can do these things, you just need to try your best to route other signals in ways that don't cross them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vias are tricky.  If you have a typical signal-ground-power-signal 4 layer board, then when you transition to the bottom layer through a via, then the HF components of the return current may have to detour to the closest decoupling capacitor in order to follow underneath the bottom layer signal trace on the power plane.  So, put decoupling caps relatively near to any vias.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On cabling, twist the signal wires together with a ground wire.  If you've got ribbon cable, alternate ground and signal.  (Or ground-signal-signal-ground-signal-signal-ground-... so that a signal is always next to a ground)&lt;/p&gt;&#xA;" OwnerUserId="1270" LastActivityDate="2010-10-15T14:12:11.093" />
  <row Id="5237" PostTypeId="2" ParentId="5234" CreationDate="2010-10-15T14:12:12.027" Score="1" ViewCount="" Body="&lt;p&gt;You'll have better luck searching for what your after as a &quot;inverting buffer&quot; or &quot;inverting line driver&quot; or simply a &quot;buffer&quot; as many have an invert option.  They often come with 4,8,16,32 I/Os.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?&amp;amp;familyId=280&amp;amp;uiTemplateId=SZVI_T&amp;amp;techFamId=null&amp;amp;rootFamilyId=null&amp;amp;sectionId=null&amp;amp;tabId=null&amp;amp;appId=null&amp;amp;viewDeviceCallingPage=null&amp;amp;totalCount=387&amp;amp;showAdditionalParameters=no&amp;amp;parameter=2475604390&amp;amp;lc=3000199&amp;amp;lc=3000214&amp;amp;lc=3000202&amp;amp;lc=2000437&amp;amp;lc=2000438&amp;amp;lc=2000440&amp;amp;lc=2000441&amp;amp;lc=2000444&amp;amp;lc=2000454&amp;amp;lc=2000469&amp;amp;lc=2001498&amp;amp;lc=2000460&amp;amp;lc=2000470&amp;amp;lc=2000564&amp;amp;lc=2001512&amp;amp;compare=yes&amp;amp;download=yes&amp;amp;sort=yes&amp;amp;customize=yes&amp;amp;paramResults=yes&amp;amp;paramCriteria=yes&amp;amp;familyTree=yes&amp;amp;military=no&amp;amp;baSystem=yes&amp;amp;paramTable=no&amp;amp;sortOption=PA_SUB_FAMILY_NAME&amp;amp;sortMode=ASC&amp;amp;searchPaths=1000280&amp;amp;pageId=280&amp;amp;templateId=0&amp;amp;navigationId=0&amp;amp;family=logic&amp;amp;paramTable=no&amp;amp;military=no&amp;amp;&amp;amp;uiTemplateId=SZVI_T&amp;amp;techFamId=null&amp;amp;rootFamilyId=null&amp;amp;sectionId=null&amp;amp;tabId=null&amp;amp;appId=null&amp;amp;viewDeviceCallingPage=null&amp;amp;resetCompare=true#sdp&quot; rel=&quot;nofollow&quot;&gt;Texas Instruments&lt;/a&gt; has a few, I chose them at random though, there are plenty of companies that make such parts.  likely at whatever voltage/current/propagation delay you could want.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-15T14:12:12.027" />
  <row Id="5238" PostTypeId="2" ParentId="5233" CreationDate="2010-10-15T14:15:30.353" Score="6" ViewCount="" Body="&lt;p&gt;You should not use that driver if you think you'll be pulling that much current.  For one, it's rated for 3A for a maximum of 10ms per the datasheet and you'll certainly try to draw for longer than 10ms in a stalled condition.  And that is the maximum rating for the device which the datasheet says is not to be exceeded under any circumstance.  It sounds to me like you'll be abusing the poor thing.  Find a beefier driver, or if you're feeling really adventurous, parallel two of them.  Is that a good idea?  I've never done it, never heard of it being done, and wouldn't do it myself, but you could certainly try :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would just find another motor driver on pololu's site.  It looks like there's plenty of them.  Make sure their maximum CONTINUOUS current is greater than your stall current. &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-10-15T14:15:30.353" CommentCount="2" />
  <row Id="5239" PostTypeId="2" ParentId="5234" CreationDate="2010-10-15T16:05:44.857" Score="1" ViewCount="" Body="&lt;p&gt;You might want to use a Darlington driver chip with six or more channels. Some come with built in inverters, and some come in versions with inverters and without. These can output up to 500mA per channel, depending on thermal dissipation and the output current for all other channels.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-15T16:05:44.857" />
  <row Id="5241" PostTypeId="2" ParentId="4979" CreationDate="2010-10-15T16:33:21.100" Score="3" ViewCount="" Body="&lt;p&gt;A resistor wastes power, as you observe.  Any other analog device like a transistor in a regulator circuit, any kind of IC, a diode, or whatever, if it's conveying current from a voltage source to the LED, is going to waste power.  There's a voltage drop across it, from the supply voltage to the forward voltage drop across the LED, with whatever LED current is flowing through.  Multiply to find the power wasted as heat.  No fancy regulator IC can escape this basic physics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are only two electrical elements that don't waste power: empty air and wire.  Empty air, that is to say, any non-connection such as an open switch or turned-off transistor, has zero current.  Wire, or any conductor such as a turned-on transistor (ignoring the small saturation voltage) has zero voltage drop.   Low power circuits must avoid resistors, and use transistors as switches, always either on or off.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the LED, needing some particular amount of current, you can drive a transistor with a rectangular wave.  Very little power is wasted in the transistor, whether &quot;on&quot; or &quot;off&quot;.  Charge is efficiently transferred to the LED.  Of course, you don't want to let too much current flow during the &quot;on&quot; phase, and toast the LED or cause it to age, so smooth the voltage at the load with a capacitor. (This is optional, depending on the LED's max current rating, frequency of switching, etc)   The LED brightness can be varied by altering the rectangular wave's duty cycle, though you'd want to hold back from using a 100% on wave - then the full voltage supply is given to the LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a basic switched-mode power supply, a vital technology of recent and coming decades.  &lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-10-15T16:33:21.100" CommentCount="1" />
  <row Id="5242" PostTypeId="2" ParentId="5199" CreationDate="2010-10-15T16:36:59.740" Score="1" ViewCount="" Body="&lt;p&gt;You haven't seen different colors until you've seen inside a scope, or at least an old one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OxhTp.jpg&quot; alt=&quot;HP 54501A&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a HP 54501A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can take a guess at what the colors mean, but without knowing the manufacturers it is difficult, nigh impossible. In this example suspect the green ones are precision (probably ±0.1%), while the pink and blue ones have larger tolerance, due to the relative quantities of them.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-15T16:36:59.740" CommentCount="3" />
  <row Id="5243" PostTypeId="1" AcceptedAnswerId="5245" CreationDate="2010-10-15T17:05:13.943" Score="2" ViewCount="110" Body="&lt;p&gt;For a project, I need a 500mV reference. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some requirements:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Relatively low cost.&lt;/li&gt;&#xA;&lt;li&gt;Small size. Preferably surface mount.&lt;/li&gt;&#xA;&lt;li&gt;Supply from 4.8V to 25V.&lt;/li&gt;&#xA;&lt;li&gt;Accuracy ±5% or better&lt;/li&gt;&#xA;&lt;li&gt;Stable over voltage (that is, it doesn't change that much with a different supply.)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I could use a diode drop but it does not satisfy condition 5, being stable over voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions appreciated!&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-15T17:11:32.270" LastActivityDate="2010-10-15T17:16:02.903" Title="Cheap 500mV reference" Tags="&lt;voltage&gt;&lt;voltage-regulator&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="2" />
  <row Id="5244" PostTypeId="2" ParentId="5229" CreationDate="2010-10-15T17:12:03.673" Score="4" ViewCount="" Body="&lt;p&gt;At 3 MHz, most electrolytics are useless due to ESL. (Some ceramics, too. Check the datasheets carefully!) They're OK on the input side, but stick with ceramic on the output side.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-15T17:12:03.673" CommentCount="1" />
  <row Id="5245" PostTypeId="2" ParentId="5243" CreationDate="2010-10-15T17:16:02.903" Score="2" ViewCount="" Body="&lt;p&gt;what about this &#xA;&lt;a href=&quot;http://www.analog.com/static/imported-files/Data_Sheets/ADR130.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.analog.com/static/imported-files/Data_Sheets/ADR130.pdf&lt;/a&gt;&#xA;cheap from digikey circa $2 for single units, wide input voltage range (2-18 V) stable output over temperature a wide temperature range of 50 ppm per degree C, and +/- 0.7% initial accuracy, and small size TSOT package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use a voltage divider on the input side to drop your 4.8 V - 25 V to 2.4 to 12.5V which is suitable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that is a tick in every box :)&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-15T17:16:02.903" CommentCount="1" />
  <row Id="5246" PostTypeId="2" ParentId="4192" CreationDate="2010-10-15T17:20:15.473" Score="1" ViewCount="" Body="&lt;p&gt;I've also seen insufficient / poorly placed / missing Vcc decoupling capacitors cause similar effects. Do you have local decoupling as close as possible to the IC? (100nF - 1uF ceramic type is preferred)&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-15T17:20:15.473" />
  <row Id="5247" PostTypeId="2" ParentId="5213" CreationDate="2010-10-15T17:30:55.743" Score="2" ViewCount="" Body="&lt;p&gt;Also bear in mind that the TL431 has a maximum sinking current, beyond which the voltage will no longer be regulated (and the device could be damaged). With 3.3V and 115R you'll not be anywhere close to that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is also generally recommended to have a small capacitor from the cathode to the anode, for stability reasons. (431s can and do oscillate). The 'safe' range of capacitor depends on the setpoint and is usually specified in the datasheet. I'd recommend something from 1nF to 10nF, and check to make sure the output isn't a sawtooth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that not all manufactures have the stability region curves, but it's been my experience that the curves in the National Instruments LM431 datasheet hold true for other vendors' 431 regulators (TI, ON Semi, Fairchild, etc. etc. and so on)&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-15T17:30:55.743" />
  <row Id="5248" PostTypeId="2" ParentId="5223" CreationDate="2010-10-15T17:33:12.340" Score="1" ViewCount="" Body="&lt;p&gt;Howard Johnson has a massive collection of high-speed digital design newsletters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sigcon.com/pubsAlpha.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.sigcon.com/pubsAlpha.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of my favorites visibly demonstrates the return currents that darron mentioned.  DC will flow in a straight line (the path of least &lt;em&gt;resistance&lt;/em&gt;; a straight line on the ground plane), while AC will flow underneath the signal conductor (the path of least &lt;em&gt;inductance&lt;/em&gt;; a mirror image of the signal path on the ground plane)  So avoid having that return path cross a split plane, avoid having it cross too many other high-speed return paths, etc.  Also, power planes can act like ground planes for a return path, and the return path can jump planes through a capacitor (remember, cap is a short to high frequencies); the return path always chooses the plane closest to the signal.  &lt;a href=&quot;http://www.sigcon.com/Pubs/news/8_08.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.sigcon.com/Pubs/news/8_08.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe there are other newsletters.  For instance, 90 degree angles aren't really that bad; they merely add excess capacitance to the trace.  At &quot;regular&quot; high speed frequencies, this is no big deal.  But when you hit microwave, the parasitic capacitance can do you in.  &lt;a href=&quot;http://www.sigcon.com/Pubs/edn/bigbadbend.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.sigcon.com/Pubs/edn/bigbadbend.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding trace size, this largely depends on your stackup.  If you use a solid reference plane (ground or power!), then your trace impedance is a function of trace width and distance from the plane.  If you don't care about the impedance, then trace size largely doesn't matter, as long as it's not too small.  Unless you're trying to carry obscene amounts of current (amps?), in which case you need traces big enough that they won't melt!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try to keep signal planes adjacent to reference planes.  i.e. for an 6 layer board, signal layers 1 and 3 reference ground plane 2, and signal layers 4 and 6 reference power plane 4.  If signal planes are adjacent, be careful that there are no long parallel runs that could induce cross-talk.  This is less of a concern if there's a reference plane (although the return currents can still cross-talk, it's not as bad)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep clock traces and other strong sources of noise as far away from other traces as you can (I think the rule of thumb is 5x the trace width away for clocks and 3x for other switching signals).&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-15T17:33:12.340" />
  <row Id="5249" PostTypeId="2" ParentId="4192" CreationDate="2010-10-15T17:37:11.237" Score="3" ViewCount="" Body="&lt;p&gt;Probably the Brown-Out-Detection is the right way to do, but...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had a &lt;strong&gt;software only&lt;/strong&gt; problem that caused very similar symptoms, though much more quickly.  I believe some bad C++ (compiling?) resulted in stack corruption, and the function returned outside of the real program, executing random instructions.  I'm not sure exactly what happened next, but the only way to fix it was to reburn the program (apparently some of those random instructions included writing to program memory).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bug was just a destructor being called at the wrong time.  Making the variable global (so it was never destroyed) fixed the problem.  The problem was very easily reproducible (took about one minute to trigger), and on very steady power.  The particular setup was Arduino+WaveShield using the WaveHC library, but I think this could happen to anyone using C++.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you prefer low level languages, I accidentally did about the same thing in assembly, but miraculously this never caused anything but sporadic timing problems: most instructions are 2 bytes long, but some are longer, and I foolishly calculated the jump distance myself and jumped into the middle of a 4 byte instruction.  It got realigned fairly quickly, but it is not hard to imagine something like this on a rarely used code path causing insanity.&lt;/p&gt;&#xA;" OwnerUserId="1271" LastActivityDate="2010-10-15T17:37:11.237" CommentCount="1" />
  <row Id="5250" PostTypeId="2" ParentId="4954" CreationDate="2010-10-15T17:37:18.117" Score="7" ViewCount="" Body="&lt;p&gt;In terms of interfacing to the camera and clocking data in, that will be fine it can handle it.  It may not handle the speeds you are interested in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5MP * 3 (colours, RGB) * 15 (times per second) = 225*e6.  (assuming 24 bit colour depth)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So that means you will need a clock speed of at least 225 MHz assuming you can move data on every clock signal, which you may not, depending on the sensor, so you may need to double this figure to circa 450-500 MHz&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Spartan you are looking at has a clock signal of 50MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the short answer is no, not at those speeds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other consideration you need to apply is how many logic blocks does your logic require?  to work this out, write out your implementation in VHDL/verilog, simulate and then synthese.  Read the outputs from the tool and it will tell you how many logic blocks you need, then select an appropriate FPGA which has 50% more logic blocks to allow for unuseable blocks due to routing constraints and gives you some room to grow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also you need to consider RAM or some other sort of memory and how your will store these bursts.  If you are shooting at 15 fps for 1 second then you need 225 MB which is a lot or RAM for an embedded system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After storing in RAM you will need to flush into ROM of some sort (for example compact flash).&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-15T17:37:18.117" CommentCount="11" />
  <row Id="5251" PostTypeId="2" ParentId="1024" CreationDate="2010-10-15T17:48:24.000" Score="4" ViewCount="" Body="&lt;p&gt;There's also this web-based thing, meant to have screenshots taken of it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.qsl.net/wd9eyb/klunky/framed.html&quot; rel=&quot;nofollow&quot;&gt;http://www.qsl.net/wd9eyb/klunky/framed.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But it could be modified to generate code that could be copied and pasted into this site?  Something that generates a single image would be preferable, of course.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.qsl.net/wd9eyb/klunky/0.jpg&quot; alt=&quot; &quot;&gt;&lt;img src=&quot;http://www.qsl.net/wd9eyb/klunky/r24.jpg&quot; alt=&quot;R&quot;&gt;&lt;br/&gt;&#xA;&lt;img src=&quot;http://www.qsl.net/wd9eyb/klunky/r13.jpg&quot; alt=&quot;R&quot;&gt;&lt;img src=&quot;http://www.qsl.net/wd9eyb/klunky/npn.jpg&quot; alt=&quot;npn&quot;&gt;&lt;br/&gt;&#xA;&lt;img src=&quot;http://www.qsl.net/wd9eyb/klunky/0.jpg&quot; alt=&quot; &quot;&gt;&lt;img src=&quot;http://www.qsl.net/wd9eyb/klunky/r24.jpg&quot; alt=&quot;R&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a real need for a quick web-based schematic drawing tool, not just here, but everywhere.  I would code it if I knew how, but my skills are weak.  Could we somehow commission someone at Stack Overflow to write something in exchange for rep?  In exchange for money?  Kickstarter?  A simple javascript editor could allow for blocks to be put next to each other, like this Klunky editor, then it could generate a URL with a bunch of gibberish at the end, which then causes the server to generate a single PNG, for instance.  The image could be linked directly from forums or copied to imgur automatically by the Stackexchange software.  The URL of the image could be plugged back into the editor to allow modifications, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The text labels in Klunky could use some work, too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or if stackexchange accepted data: URLs, it could generate an image that could be copied and pasted into the URL box without requiring a server at all. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or SVG.  Or Flash.  Or something.  But I think a simple block-based editor would be sufficient for the vast majority of online schematic examples, rather than a full-fledged schematic capture program that allows you to draw wires manually and move components one pixel at a time and change all their parameters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an HTML 5 image editor that generates images as data: URLs, for instance:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://mugtug.com/sketchpad/&quot; rel=&quot;nofollow&quot;&gt;http://mugtug.com/sketchpad/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://softwareas.com/ajaxjavascript-8-ways-to-create-graphics-on-the-fly&quot; rel=&quot;nofollow&quot;&gt;http://softwareas.com/ajaxjavascript-8-ways-to-create-graphics-on-the-fly&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;data urls can be converted into tinyurls!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://preview.tinyurl.com/smallreddot&quot; rel=&quot;nofollow&quot;&gt;http://preview.tinyurl.com/smallreddot&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-19T19:38:56.470" LastActivityDate="2010-10-19T19:38:56.470" CommunityOwnedDate="2011-03-22T20:53:31.463" CommentCount="1" />
  <row Id="5252" PostTypeId="1" AcceptedAnswerId="5254" CreationDate="2010-10-15T19:08:31.093" Score="0" ViewCount="200" Body="&lt;p&gt;Let me start off by saying that I know just enough about electronics to be dangerous (how to solder, follow a simple schematic, and check for connectivity problems and usually figure out what each wire is for).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've installed a cruise control kit in my car, and I want to use a set of Honda steering wheel controls instead of the stock controls from the kit.  The cruise kit controls are expecting 12 volts, but I'm not comfortable running any more than 5 volts through the small steering wheel wires next to the airbag wiring.  I'd prefer even less, like 2-3 volts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I need to build a switching circuit that will provide the 12 volt signals to the cruise kit.  I was thinking of keeping it solid-state, since I don't know of any relays that will switch on 2-3 volts.  However, if there's a good reason to use relays then I can.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a rough drawing of what I need:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2uh9t.png&quot; alt=&quot;schematic&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I get started with this project?&lt;/p&gt;&#xA;" OwnerUserId="1610" LastActivityDate="2010-10-16T19:46:46.790" Title="How can I build a switching circuit that scales several 12v signals down to &lt;5v?" Tags="&lt;switch&gt;&lt;automotive&gt;" AnswerCount="4" />
  <row Id="5253" PostTypeId="2" ParentId="5252" CreationDate="2010-10-15T19:31:00.163" Score="1" ViewCount="" Body="&lt;p&gt;The potential safety issue is the current, not the voltage. You can use a resistor to limit the current so a short won't cause irritating fires. The control switches may not be expected to pass a significant amount of current but you can measure that with a multimeter.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2010-10-15T19:36:57.727" LastActivityDate="2010-10-15T19:36:57.727" CommentCount="2" />
  <row Id="5254" PostTypeId="2" ParentId="5252" CreationDate="2010-10-15T19:31:10.587" Score="1" ViewCount="" Body="&lt;p&gt;I assume by switching, you mean logic level translation. That is, you want to step 5V up to 12V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest solution would be a set of 5V SPST relays, connecting the coil to the switches and the NO (normally open) to the 12V and the output to the cruise control system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want a cheaper and better solution you could consider using a transistor wired as a switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And be careful with auto electronics, if that doesn't go without saying.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Possible transistor circuit:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/M4ulU.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-15T19:54:14.773" LastActivityDate="2010-10-15T19:54:14.773" CommentCount="13" />
  <row Id="5255" PostTypeId="1" AcceptedAnswerId="5296" CreationDate="2010-10-15T19:40:20.450" Score="5" ViewCount="169" Body="&lt;p&gt;Software developers have TopCoder...is there anything analogous for electronics geeks to exercise their wit, test their cleverness or quickness, that is done online?&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-11-04T20:21:40.633" Title="What online competitions are there to show off electronics skills?" Tags="&lt;electronics&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="5256" PostTypeId="2" ParentId="3105" CreationDate="2010-10-15T20:38:19.310" Score="2" ViewCount="" Body="&lt;p&gt;I'm at (non-electronics) work right now, w/o handy electronics sw or books, so this will be just a rough idea.  Maybe someone else can fill in the details...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try a current mirror using a pair of PNP transistors hanging on the Vcc rail.  Feed the negative voltage signal to the input side of the mirror through an appropriate resistor.  The same current should then flow through the output transistor of the mirror.  With a well-chosen resistor you create a voltage range within 0V to Vcc.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT - NEW:  Here is the current mirror schematic.  Whatever current passes through transistor T1, T2 will try to make the same current flow.  The negative voltage to be measured, relative to the power supply which I randomly chose to be 15v, creates some trickle of current through R1 (measured in simulation as &quot;inputcurrent&quot;).  If R2 were the same as R1, you'd find the same voltage across it, if it were allowed to.  But it's connect to 0V (gnd) - our circuit is based purely on a positive supply.  It won't work unless we make R2 smaller, say 1/2 of R1 then the voltage across it will be 1/2 of whatever's across R1.  Measure it, do math (whoo, multiply by 2, hard!) and there you are.   The schematic has different values, a different ratio&lt;img src=&quot;http://i.imgur.com/gHp2q.png&quot; alt=&quot;alt text&quot;&gt;, but I think we all can handle the math for this.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The advantage of this over a simple voltage divider is that 1) it looks more complicated, 2) it's a common trick in analog IC design.  Since I wrote another answer using a Zener diode, I'm not sure now why this is better, but it is an alternative to a voltage divider and may allow getting at different ranges of voltages or something.  Now I let others comment on the wisdom or foolishness of this idea...&#xA;&lt;img src=&quot;http://i.imgur.com/bku0E.png&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/uCzG2.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1609" LastEditorUserId="1609" LastEditorDisplayName="" LastEditDate="2010-10-19T04:29:26.390" LastActivityDate="2010-10-19T04:29:26.390" CommentCount="3" />
  <row Id="5257" PostTypeId="1" CreationDate="2010-10-15T22:00:46.430" Score="2" ViewCount="133" Body="&lt;p&gt;I have an old external battery for Apple devices (has 30 pin Apple Dock Connector), and I want to repurpose it to be an external battery for all my USB devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, I don't have much experience with this kind of thing, so if someone could give me some good advice on how to accomplish this, it'd be great! I only really need to convert it to any kind of USB cable, since I can just get converters from there.&lt;/p&gt;&#xA;" OwnerUserId="1611" LastEditorUserId="92" LastEditorDisplayName="" LastEditDate="2010-10-16T03:19:00.963" LastActivityDate="2010-10-17T16:40:34.980" Title="Male Apple Dock Connector =&gt; USB (power only)" Tags="&lt;power&gt;&lt;usb&gt;&lt;convert&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="5258" PostTypeId="2" ParentId="5257" CreationDate="2010-10-15T22:23:51.347" Score="0" ViewCount="" Body="&lt;p&gt;You'd be better off trying something like the &lt;a href=&quot;http://www.ladyada.net/make/mintyboost/&quot; rel=&quot;nofollow&quot;&gt;MintyBoost&lt;/a&gt; which you can make for a few bucks, compared to the time/effort put into repurposing the dock battery thingy.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-15T22:23:51.347" />
  <row Id="5259" PostTypeId="2" ParentId="5257" CreationDate="2010-10-15T23:28:39.233" Score="1" ViewCount="" Body="&lt;p&gt;If your external battery was designed to plug into a iPod or iPhone, then you need a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8035&quot; rel=&quot;nofollow&quot;&gt;female 30-pin connector&lt;/a&gt; to mate with it, like this one from SparkFun.  Be warned however, that this is designed to mount as a SMD to a PCB board, and the pins are tiny.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like others have said, it's probably not worth the effort.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-15T23:28:39.233" />
  <row Id="5260" PostTypeId="1" AcceptedAnswerId="5271" CreationDate="2010-10-16T07:21:06.163" Score="5" ViewCount="232" Body="&lt;p&gt;I wish to expose a usb flash drive and read it as raw binary data, particularly read each byte &amp;amp; simultaneously writing it to another flash drive. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given that I am working with an 8085 microprocessor, &amp;amp; I am in a position to program it &amp;amp; read data from secondary memory device, how can I start working with the usb.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried to understand USB from this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.beyondlogic.org/usbnutshell/usb1.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.beyondlogic.org/usbnutshell/usb1.shtml&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I still have no idea how I would be writing my program to host flash drives.&lt;/p&gt;&#xA;" OwnerUserId="1432" LastActivityDate="2010-10-16T15:54:16.797" Title="Reading/Writing a usb flash drive." Tags="&lt;microcontroller&gt;&lt;usb&gt;&lt;microprocessor&gt;&lt;8085&gt;" AnswerCount="2" FavoriteCount="3" />
  <row Id="5261" PostTypeId="2" ParentId="2807" CreationDate="2010-10-16T08:51:19.397" Score="1" ViewCount="" Body="&lt;p&gt;There is another aspect to consider, and that is how much current you need at 6V.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As already correctly answered, to demonstrate 6 V, a voltage divider will work fine, for small amounts of current a linear regulator will be ok.  For larger currents a switching regulator will be more efficient and not require a heatsink.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example using a linear regulator: 100 mA * 18 V (24 - 6) = 1.8 W of thermal energy that you need to dissipate. Using a 10 K/W heatsink will result in a temperature raise of 18 K over ambient.  That will be ok for room temperature through to hot areas, circa 80 deg C.  Above this temperature you will need to check the thermal resistance of the regulator and add that to the equation to find the junction temperature and keep it below the maximum, normally 125 deg C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternative using a switching regulator will increase the efficiency and not require a heatsink.  An example of one is here:&#xA;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=PT78ST106V-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=PT78ST106V-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This one is expensive, but there will be similar products out there that are cheaper.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-16T08:51:19.397" />
  <row Id="5262" PostTypeId="2" ParentId="5260" CreationDate="2010-10-16T09:10:53.890" Score="2" ViewCount="" Body="&lt;p&gt;I would look for a reference design for both the hardware and software to get you going.  The website you have linked to is good night time reading and background, but actually implementing have a search for some code examples.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check this site from Atmel, it has some software examples for the various 8051 subsystems and should help you get going for USB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/dyn/products/tools.asp?family_id=604#1535&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/products/tools.asp?family_id=604#1535&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1397" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-16T13:01:22.707" LastActivityDate="2010-10-16T13:01:22.707" />
  <row Id="5263" PostTypeId="2" ParentId="5234" CreationDate="2010-10-16T09:16:53.953" Score="0" ViewCount="" Body="&lt;p&gt;You could try using a p channel mosfet.  Pull up the gate to your logic level, say 5 V, and connect a series resistor from your logic source to the gate.  This will invert a logic level of 0 and turn the p-channel mosfet on, and a logic input of 1, will turn the p-channel mosfet off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you have inversion, and current is only limited by your choice of mosfet.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-16T09:16:53.953" />
  <row Id="5264" PostTypeId="2" ParentId="5234" CreationDate="2010-10-16T12:12:47.360" Score="0" ViewCount="" Body="&lt;p&gt;The 74AC04E has a rated operating of current of +-24mA. The 50mA is the absolute&#xA;maximum rating which you should not be operating at. There is also an absolute maximum&#xA;rated current of 100mA into Vcc or GND for the package. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;IIRC LVC family form TI has the same +-24mA output currents. TI also has some power logic&#xA;devices. Not sure is they have a hex inverter or just a shift register. You could also&#xA;try Allegro.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For CMOS devices you can parallel the input and outputs of gates within the same package&#xA;to increase the current drive. Do not parallel gates from different packages.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T10:57:51.600" LastActivityDate="2011-05-20T10:57:51.600" />
  <row Id="5265" PostTypeId="2" ParentId="2176" CreationDate="2010-10-16T12:21:53.703" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/MATLAB&quot; rel=&quot;nofollow&quot;&gt;MATLAB&lt;/a&gt; is a pretty good place to start for filter simulation and design.  There is a filter design toolbox that is pretty useful. However it does come at a cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For sensor applications &lt;a href=&quot;http://en.wikipedia.org/wiki/Butterworth_filter&quot; rel=&quot;nofollow&quot;&gt;Butterworth&lt;/a&gt; filters are generally better as they have a maximum flat passband (at the expense of phase response and roll off).  That means that your signal amplitude will be flat throughout the frequency range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stay away from implementing a &lt;a href=&quot;http://en.wikipedia.org/wiki/Sallen%E2%80%93Key_topology&quot; rel=&quot;nofollow&quot;&gt;Sallen-Key&lt;/a&gt; topology active filter, it is very difficult to get all the components to be matched and maintain good accuracy, try doing a &lt;a href=&quot;http://en.wikipedia.org/wiki/Monte_Carlo_method&quot; rel=&quot;nofollow&quot;&gt;Monte Carlo simulation&lt;/a&gt; on a Sallen-Key circuit to get a better understanding.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Switched capacitor filters are good for steep roll-off and these are available in Butterworth filters.  These do need a single pole before and after them to remove an aliasing due to the clock signal of the switching which occurs anywhere from 50 - 100 times greater than your cut-off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively use a simple single pole RC filter (active or passive) and feed into a higher speed ADC and then you can use digital signal processing on an embedded platform or PC to perform decimation and analysis.  This shifts cost and complexity from analog components to software and processing requirements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most importantly - ensure you comply with the &lt;a href=&quot;http://en.wikipedia.org/wiki/Nyquist_stability_criterion&quot; rel=&quot;nofollow&quot;&gt;Nyquist criteria&lt;/a&gt; and that you are sampling at at least twice the highest frequency, in practice, this means sample at four - 10 times your highest frequency, to allow for filter roll off well below your ADC resolution level at the Nyquist rate.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2011-02-09T11:22:37.917" LastActivityDate="2011-02-09T11:22:37.917" CommunityOwnedDate="2010-10-16T12:21:53.703" CommentCount="4" />
  <row Id="5266" PostTypeId="2" ParentId="250" CreationDate="2010-10-16T12:25:54.417" Score="2" ViewCount="" Body="&lt;p&gt;is it this group?&#xA;&lt;a href=&quot;http://www.hli.com.my/Corp_Info/Semiconductor/semiconductor.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.hli.com.my/Corp_Info/Semiconductor/semiconductor.asp&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-16T12:25:54.417" CommentCount="1" />
  <row Id="5267" PostTypeId="2" ParentId="1964" CreationDate="2010-10-16T12:38:18.047" Score="0" ViewCount="" Body="&lt;p&gt;No radio station amplifiers and transmitters work at the speed of sounds, hence you hear the radio at the other end, whereas television amplifiers and transmitters work at the speed of light, as you can see the pictures at the other end .....  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(sorry couldn't help but add my dry humor as the question has already been answered correctly)&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-16T12:38:18.047" />
  <row Id="5268" PostTypeId="2" ParentId="4192" CreationDate="2010-10-16T12:48:40.040" Score="1" ViewCount="" Body="&lt;p&gt;Another factor that can cause devices to loss their memory is electro static discharges (ESD).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Placing a few varistors on all the external facing connectors that are subject to exposure can alleviate this issue.  I have seen it before in some commercial products based on Microchip PIC microcontrollers, so it is not unheard of.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some handy varistors that double as filter capacitors also (in the order of 10-150 pF).  Check these out &lt;a href=&quot;http://www.tdk.co.jp/tefe02/e9c11_avr.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.tdk.co.jp/tefe02/e9c11_avr.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are small, cheap, and will protect your device.  Place them as close as possible to the connectors bringing external signals onto the board, and route all traces immediately away from the connector pins.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-16T12:48:40.040" CommentCount="3" />
  <row Id="5269" PostTypeId="1" AcceptedAnswerId="5270" CreationDate="2010-10-16T15:30:58.537" Score="3" ViewCount="339" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to know about the workings of mobile phone battery chargers. I know the basic principle, you take a transformer to bring it down to 9/6/3.7 volts then a bridge rectifier circuit and a capacitor input filter to rectify it into DC. Then you apply it to the battery. But I know this should not be enough, I need at least two things,&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Protection against back current flow&lt;/li&gt;&#xA;&lt;li&gt;Switch off power when the battery is fully charged.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Can someone point me to something simple (apart from this &lt;a href=&quot;http://www.extremecircuits.net/2009/07/mobile-phone-battery-charger-circuit.html&quot; rel=&quot;nofollow&quot;&gt;http://www.extremecircuits.net/2009/07/mobile-phone-battery-charger-circuit.html&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="906" LastEditorDisplayName="" LastEditDate="2010-10-19T02:44:47.657" LastActivityDate="2011-05-16T10:48:04.247" Title="Mobile phone battery charger" Tags="&lt;battery&gt;&lt;safety&gt;&lt;charger&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="5270" PostTypeId="2" ParentId="5269" CreationDate="2010-10-16T15:39:37.207" Score="5" ViewCount="" Body="&lt;p&gt;You are taking an AC signal from the wall and then as you say, the transformer, recitifier and capacitors are bringing it down to a lower DC voltage. From there, most charging circuits are either &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1037,C1078,C1088,P90562&quot; rel=&quot;nofollow&quot;&gt;linear regulator type chargers&lt;/a&gt; or &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1037,C1078,C1089,P2493&quot; rel=&quot;nofollow&quot;&gt;switch mode power supply type regulators&lt;/a&gt; (both of those are advanced type links, but just there to see they both exist). They are basically normal DC/DC power converters with some kind of monitoring circuit inside. These two components fulfill the needs you list in number 1 and 2. To learn more about how they work, I'd check out &lt;a href=&quot;http://www.eevblog.com/2010/05/29/eevblog-90-linear-and-ldo-regulators-and-switch-mode-power-supply-tutorial/&quot; rel=&quot;nofollow&quot;&gt;Dave's explanation of linear and switch mode power supplies&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're looking to build your own eventually, you'll need to figure out how to do the monitoring with a micro or otherwise and then control some kind of DC/DC power converter. Good luck! &lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-10-16T15:39:37.207" CommentCount="1" />
  <row Id="5271" PostTypeId="2" ParentId="5260" CreationDate="2010-10-16T15:54:16.797" Score="2" ViewCount="" Body="&lt;p&gt;FTDI's &lt;a href=&quot;http://www.ftdichip.com/Products/ICs/VNC1L.htm&quot; rel=&quot;nofollow&quot;&gt;Vinculum&lt;/a&gt; embedded USB host may be of interest to you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It handles most of the protocol details, and gives you SPI/FIFO access to the USB Device.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-16T15:54:16.797" CommentCount="1" />
  <row Id="5272" PostTypeId="2" ParentId="5269" CreationDate="2010-10-16T16:23:19.580" Score="5" ViewCount="" Body="&lt;p&gt;The battery charging for Li-ion is a little more involved. IIRC The Li-ion chargers typically&#xA;apply a constant voltage until the battery is charged to a certain level and then&#xA;apply constant current until the battery is charged. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a number of Li-ion charger ICs that handle the various charging cycles and&#xA;also have the safeties built in. One of the popular ones is the Maxim MAX1555. &#xA;The application notes on the Maxim site will provide the details about Li-ion&#xA;charging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you decide to build your own charger I would suggest purchasing a UL approved wall transformer that provides you an isolated DC output. Add your charging circuit to the&#xA;output of the safe DC voltage.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T10:48:04.247" LastActivityDate="2011-05-16T10:48:04.247" CommentCount="5" />
  <row Id="5273" PostTypeId="2" ParentId="5269" CreationDate="2010-10-16T17:45:02.097" Score="3" ViewCount="" Body="&lt;p&gt;For a cell phone, the wall adapter just supplies a constant voltage, like any other wall wart, and the phone has all the current regulation and charge monitoring circuitry internally.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the charger is small, light-weight, and cool to the touch during operation, it probably has a switching regulator inside.  If it's heavy, bulky, cheap, and warm to the touch during operation, it's probably a linear regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5 V micro USB chargers &lt;a href=&quot;http://www.maximumpc.com/article/news/microusb_way_becoming_cell_phone_charging_standard&quot; rel=&quot;nofollow&quot;&gt;will be the standard in the future.&lt;/a&gt;  With any charger, the voltage applied to the phone is fixed, but the phone can adjust the amount of current it draws.  Some supplies can provide a lot, but some (like plugging into a laptop's USB) can only supply a little.  There are a few different ways to tell the phone how much current it's allowed to draw.  The USB-IF &lt;a href=&quot;http://www.usb.org/developers/devclass_docs/batt_charging_1_1.zip&quot; rel=&quot;nofollow&quot;&gt;battery charging standard&lt;/a&gt; has the charger short the D+ and D- pins together.  iPhones, on the other hand, &lt;a href=&quot;http://www.adafruit.com/blog/2010/08/03/the-mysteries-of-apple-device-charging-video/&quot; rel=&quot;nofollow&quot;&gt;require certain voltages&lt;/a&gt; applied to the D+ and D- pins.  &lt;a href=&quot;http://wiki.openmoko.org/wiki/USB_charger&quot; rel=&quot;nofollow&quot;&gt;Others use the 5th ID pin&lt;/a&gt; to indicate a dedicated charger.  Otherwise, without some kind of identification of the charger, a USB-charged phone should only draw 100 mA, in case it's connected to a low-power computer port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for &quot;Protection against back current flow&quot;, a simple Schottky diode will do.  The charger circuitry drives current into the battery by applying a larger voltage than the battery's voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And the phone's internal circuitry takes care of this, as well as switching off power (or applying a float charge?) when the battery is fully charged.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-16T17:45:02.097" />
  <row Id="5274" PostTypeId="1" AcceptedAnswerId="5275" CreationDate="2010-10-16T18:04:06.297" Score="4" ViewCount="318" Body="&lt;p&gt;Now I know when it comes to electrolytic capacitors it's usually good practice to use a voltage rating 1.5x - 2.5x the maximum rating you ever expect the capacitor to be exposed to, as the lifetime can be significantly reduced by running it near its limits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But does the same protocol apply to ceramic capacitors? For example, assume a 25V ceramic capacitor - will running it at 24V reduce its lifespan significantly?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm currently designing a PSU which needs to be reliable, so at the moment I'm using 50V caps for a maximum 20V input (35V caps aren't available), but I'd like to switch to 25V caps if possible.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-05T03:29:26.993" Title="Voltage ratings of capacitors: ceramic vs electrolytic" Tags="&lt;capacitor&gt;" AnswerCount="3" />
  <row Id="5275" PostTypeId="2" ParentId="5274" CreationDate="2010-10-16T18:41:04.763" Score="5" ViewCount="" Body="&lt;p&gt;You do not have the same lifespan issues with ceramic caps. You will lose &#xA;capacitance as the voltage increases. The amount you lose is dependant&#xA;on the dielectric.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When choosing the electrolytics you also need to look at the ESR, temperature&#xA;rating and the maximum operating temperature. Since the lifetime is predicted&#xA;using the Arrhenius activation energy law running using a 105degC rated&#xA;cap will give you a significant increase over running a 85degC cap (assuming&#xA;all other conditions are the same). There are some 5000 hour rated electrolytics.&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-05T03:29:26.993" LastActivityDate="2010-11-05T03:29:26.993" CommentCount="5" />
  <row Id="5276" PostTypeId="2" ParentId="5274" CreationDate="2010-10-16T18:45:03.040" Score="3" ViewCount="" Body="&lt;p&gt;ceramic caps are really durable, MLCC's are often tested at rated to 200% rated voltage for ~1000 hours before failure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, I often find that higher voltage MLCC's can actually be cheaper than the lower voltage for a given capacitance due to higher industry volume for the higher voltage ratings.  For instance finding 16v 0.1uf MLCC is never a problem, but something like 100pF may be cheaper at 50V than it is at 16V&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-16T18:45:03.040" CommentCount="1" />
  <row Id="5277" PostTypeId="2" ParentId="5274" CreationDate="2010-10-16T19:02:58.437" Score="1" ViewCount="" Body="&lt;p&gt;You should actually not be comparing ceramics to electrolytics in terms of lifespan at all, they are actually intended for totally different purposes. Most beginners (I did untill recently) think they are just higher values, but they are as different as inductors are to resistors. Mainly because electrolytic values are more approximate, and their value much more temperature dependant than ceramic, polycarbonates or tantalum. Note: Tantalum are very voltage sensitive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You answer is that I would also use a 50V cap for a 20V supply, in fact if you glance at the charge curve for electrolytics you will notice that they work better (more farads) at about 1/3 of their rating anyway. As for being for different purpose, you will get heating in an electrolytic if you allow it to completely charge and discharge on a cycle, for instance using a 220uF to service a 10 amp load on a rectifier will tax the cap and cause heating in the leads, and as the other answers alread indicate, heating equals less farads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm just an amateur, so no clever math, sorry.&lt;/p&gt;&#xA;" OwnerUserId="1357" LastActivityDate="2010-10-16T19:02:58.437" CommentCount="4" />
  <row Id="5279" PostTypeId="2" ParentId="5252" CreationDate="2010-10-16T19:41:54.157" Score="0" ViewCount="" Body="&lt;p&gt;Airbag requires about 6V only to set it off, so setting 5V as your ceiling is probably pushing it, I think I remember it needed less than 200mA, so a fuse is actually a waste of time, if not a bad placebo. I only know this because I once helped build an airbag tester to be used for Volkswagen and BMW on the Uitenhage plant in South Africa, AND had to wait patiently while everyone still messed about with antistatic gear (which I thought was overkill, but I may be wrong). The trouble with relays or switches, is that they need to have a good bit of juice running through the contacts, else they do not make good contact (they are designed to actually arc, and in low current applications, a small ceramic is used to sometimes make a tiny spark to weld the contacts together). DC is also not that great, since the arc carries metal with it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So a transistor switching (boosting) circuit (which you have designed) is also getting my vote, you can use the transistors to drive a 12V relay (small one), ro regulators needed, and since car battery is 13.5V and the darlington-style circuit (which you drew) often looses just over a volt anyway. The voltage (and needed current) for the BASE of the darlington is going to be low enough to be safe. Just remember to place a diode across the relay coil for back EMF taking your transistors out.&lt;/p&gt;&#xA;" OwnerUserId="1357" LastActivityDate="2010-10-16T19:41:54.157" CommentCount="1" />
  <row Id="5280" PostTypeId="2" ParentId="5252" CreationDate="2010-10-16T19:46:46.790" Score="0" ViewCount="" Body="&lt;p&gt;Why exactly are you concerned about 12V on those wires?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its perfectly fine and doesn't represent any more or less danger than 5V would, or even GND honestly.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-16T19:46:46.790" CommentCount="2" />
  <row Id="5281" PostTypeId="2" ParentId="5255" CreationDate="2010-10-16T19:47:16.883" Score="0" ViewCount="" Body="&lt;p&gt;google up &quot;Maker&quot;, &quot;hack-a-day&quot;, and probably a good few forums once you start there. But to really show your metal, build something, and just sell it on ebay.&lt;/p&gt;&#xA;" OwnerUserId="1357" LastActivityDate="2010-10-16T19:47:16.883" />
  <row Id="5282" PostTypeId="2" ParentId="4777" CreationDate="2010-10-16T19:57:36.417" Score="1" ViewCount="" Body="&lt;p&gt;Start with just 2 buttons, and build an RS-flip flow (RS= Reset Set), which requires 2 gates. (http://en.wikipedia.org/wiki/Flip-flop_%28electronics%29). The flip-flop comes in 2 flavours, RS (sometimes called SR), and JK, I believe you want the RS variety. One extra button (for quizzmaster) ties all the reset lines together, and each contestant's button pulls a &quot;set&quot; input to their flip-flop high when pressed. Lastly, the tricky part, is to ensure the first button (winner) disables all the other contestant's buttons. I think this requires the feedback (as in Karl's answer) to take away the ability to pull the set line high on ALL of the flip-flops. (that bit is for your to figure out I suspect). Lastly, the quizmaster has a button that pull the reset line high on all flip-flops, this will clear all the outputs :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need 4 contestants, it's a bigger duplication job.&lt;/p&gt;&#xA;" OwnerUserId="1357" LastActivityDate="2010-10-16T19:57:36.417" CommentCount="1" />
  <row Id="5283" PostTypeId="2" ParentId="5255" CreationDate="2010-10-16T20:49:34.320" Score="1" ViewCount="" Body="&lt;p&gt;Electronics is not software, and sitting down to design something, or a part of circuit often takes time to consider all aspects.  For example power supply issues, noise issues, temperature variation, monte carlo analysis for mass production, reliability, testability, maintainability, and other design for manufacture issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sure there could be site that tests various op amp circuits: for instance design a non inverting, below one gain, bipolar amplifier with an input of 2.5 V +/- 2.5 V using a only a OPA211 op amp and a 3.3 V rail.  Acceptable solution must have a CMRR of 100 dB, PSRR &gt; 80 dB over 0 - 100 MHz, stable for -40 deg C through to 80 deg C and so on. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see the tests would be need to define a lot of real world constraints around this circuit, to make it &quot;real&quot; in the sense of something that can be used for a product to go into production.  However, defining and calculating these constraint is all part of the engineering process. Going back up one level, you would need to define a bigger problem, and defining the bigger problem is easy enough, but designing a solution would take some time to do.  Not something that could be done in an hour or two of online tests.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically I do not think it is testable in the same sense as an improved sorting algorithm with memory constraints is with software land (ok it is a simple example, but it is only an example).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only other &quot;testing&quot; that could be done in a timely manner, is purely theoretical, similar to second electronic engineering exams!  Perhaps there is a market opportunity for that :)  From my experience as a professional electronic/hardware engineer, is that it is the real world design process that is more important to get right, than knowing everything about the theory.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-16T20:49:34.320" />
  <row Id="5284" PostTypeId="1" AcceptedAnswerId="5290" CreationDate="2010-10-16T23:45:26.743" Score="5" ViewCount="308" Body="&lt;p&gt;I'm wondering at the moment with my Super OSD project whether to go to a 4 layer board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the moment, it consists of two micros and some additional circuitry such as a discrete audio amp and switch logic, and a serial EEPROM plus a temperature sensor. There are probably around 40 resistors, 10-15 caps and a few other components (all surface mount 0805 or 0603.) It might get tricky to route it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it worth paying the extra bucks to get 4 layer boards for a relatively simple project?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm on the fence, I like 2 layer because it's cheap and if you've got the right equipment you can even do it at home, 4 layer is more expensive, but allows me to squash more stuff into each square millimeter. I've seen a couple of open source projects (Super OSD is open source) using 4 layers but many more using 2 layer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, opinions?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-18T11:08:40.807" Title="How much more does it cost to fab a 4 layer board compared to a 2 layer board and is it worth it?" Tags="&lt;pcb&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="5285" PostTypeId="1" AcceptedAnswerId="5292" CreationDate="2010-10-17T00:05:29.940" Score="8" ViewCount="343" Body="&lt;p&gt;Often 100n to 1µF decoupling caps are placed across IC supply lines for digital logic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For analog circuitry, are decoupling caps necessary when the environment is also shared by microcontrollers and digital logic?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have never placed them and haven't had any troubles, but I haven't made production stuff yet, so wouldn't have much experience.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-19T11:59:04.103" Title="Are decoupling caps necessary for analog ICs (e.g. LM339, LM324...)?" Tags="&lt;capacitor&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="5286" PostTypeId="1" AcceptedAnswerId="5287" CreationDate="2010-10-17T00:07:25.590" Score="5" ViewCount="232" Body="&lt;p&gt;I just bought my first analog oscilloscope (GoldStar OS-7020A) and noticed it has a port on the front labeled &quot;ground&quot;. What exactly is this port for?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I thought it might be for plugging in a ground clip for probes that don't have one included, but there are two channels and only one ground port, so I'm not sure. Is it simply for providing a convenient ground connection for other devices?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could I, for example, attach my anti-static wrist strap to it? Would the oscilloscope have to be on for that to work? (Electronics newbie here, so please forgive me if this is a stupid question.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/T2wdB.png&quot; alt=&quot;GoldStar OS-7020A&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1616" LastEditorUserId="1616" LastEditorDisplayName="" LastEditDate="2010-10-17T00:21:16.180" LastActivityDate="2010-10-17T00:21:16.180" Title="What is the ground port on an analog oscilloscope for?" Tags="&lt;oscilloscope&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="2" />
  <row Id="5287" PostTypeId="2" ParentId="5286" CreationDate="2010-10-17T00:14:34.183" Score="4" ViewCount="" Body="&lt;p&gt;Most oscilloscopes have a safety ground. This connects to the earth ground on the plug and also to the case. The thinking is if you wire it up wrong worst case you trip the GFI/RCD instead of shocking yourself or damaging the instrument.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an oscilloscope is usually a bench instrument it is not isolated from the mains. You can use an isolation transformer, but this is not recommended, as it removes this protection leaving the earth ground floating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tektronix sells an oscilloscope which has fully isolated inputs, I don't know of any other models. It is significantly more expensive to add high speed isolation circuitry. Usually it means the whole analog and acquisition side must be isolated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ground should always be connected to your circuit's ground or you will get strange behaviour. Trust me. I've spent hours looking at a trace wondering where the noise was coming from, just to find I haven't properly connected the ground.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-17T00:14:34.183" CommentCount="11" />
  <row Id="5288" PostTypeId="2" ParentId="5285" CreationDate="2010-10-17T00:14:43.243" Score="2" ViewCount="" Body="&lt;p&gt;Usually I'd &lt;em&gt;have gone&lt;/em&gt; with no. The reason decoupling capacitors are critical for digital circuitry is that they can use high currents when switching states; the capacitor will then reduce the size of that current loop, and even out the draw from the source. For analog circuitry this may be less of an issue, although some of the time the reason it's an issue is because analog circuitry will produce poor results because of the supply noise. Sensitive analog circuitry is therefore separated to its own supply, possibly with capacitors and inductors to smooth things out. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm also fairly inexperienced, however, so expect better answers soon.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Indeed there were better answers. Do decouple opamps, and particularly comparators. Glad I learned something!&lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="1181" LastEditorDisplayName="" LastEditDate="2010-10-19T11:26:59.530" LastActivityDate="2010-10-19T11:26:59.530" CommentCount="2" />
  <row Id="5290" PostTypeId="2" ParentId="5284" CreationDate="2010-10-17T00:45:52.903" Score="8" ViewCount="" Body="&lt;p&gt;Some reasons to move to 4+ layer:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Need additional routing space&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Need power and ground supply planes due to current draw&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Need to control trace impedance.  You can only control the impedance of a trace if it has a consistent reference on the adjacent layer(s).  This is critical for signal integrity of many signals but mostly associated with medium-high speed digital and/or long traces.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Need low noise performance, either analog or digital.  Its almost impossible to pull this off without at least a ground plane in the stack up.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;EMI: Unless you're able to devote the bottom to a full ground pour you have to be very vigilant with your ground return paths to avoid current loops.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'm sure there are more, that's just what popped into my head.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've personally never had a board fabbed that wasn't at least 4 layers so I can't say too much about the cost of 2 layer.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The move to 6 or 8 layers is usually what I have to fight with and most of the time the same rules I listed above are the driving forces, with the addition of needing to route very high speed signals between plane layers to reduce EMI.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-18T11:08:40.807" LastActivityDate="2010-10-18T11:08:40.807" />
  <row Id="5291" PostTypeId="2" ParentId="5284" CreationDate="2010-10-17T00:58:27.593" Score="1" ViewCount="" Body="&lt;p&gt;Put it this way, the cost of the time you save by being able to route on 4 layers (or having internal power planes to ease routing) will pretty much always outweigh the cost difference between a 2 and 4 layer board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So its very worth it in my opinion&lt;/p&gt;&#xA;" OwnerUserId="1376" LastActivityDate="2010-10-17T00:58:27.593" CommentCount="4" />
  <row Id="5292" PostTypeId="2" ParentId="5285" CreationDate="2010-10-17T00:59:01.680" Score="10" ViewCount="" Body="&lt;p&gt;In a mixed signal environment for production that has to pass FCC, yes absolutely.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;More specifically, what you need to do is look at your current usage, the frequencies that will be present, and determine what your overall power supply capacitance needs to be to minimize those frequencies on the supplies.  Otherwise you'll get ringing on the supply planes that can be a huge EMI issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll get some capacitance from the PCB stack up, assuming you have power and ground planes.  You'll then usually come up with a needed capacitance and size of capacitors to achieve your goal.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance you can come up with something like:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;30   0.1uF 0603 max&lt;/li&gt;&#xA;&lt;li&gt;30   10nF 0402 to avoid lead inductance&lt;/li&gt;&#xA;&lt;li&gt;5   10uF tantalum&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Then sprinkle these around in a logical manner.  1 0.1uF and 1 10nF per power pin.  One tant per major IC or near a section of smaller current/analog ICs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With mixed signal design you always have to remember that just because a signal is low frequency analog you still have to treat it as an EMI threat.  There will be transients from the rest of your system on that signal no matter how amazing your isolation is.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not only talking about high speed here either.  A system with a 25Mhz clock and easily have these issues and fail FCC pretty miserably (trust me :0)&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-17T00:59:01.680" CommentCount="5" />
  <row Id="5293" PostTypeId="2" ParentId="5285" CreationDate="2010-10-17T01:37:53.867" Score="5" ViewCount="" Body="&lt;p&gt;This really depends on the ICs you are using. Generally the higher bandwidth an analogue device has the more important power supply decoupling becomes. Most of the time the data sheet for different devices will give you an indication of what is required. Any high speed amplifier or comparators may be susceptible to oscillation if not correctly bypassed.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2010-10-17T01:37:53.867" />
  <row Id="5294" PostTypeId="1" CreationDate="2010-10-17T04:19:39.930" Score="7" ViewCount="438" Body="&lt;p&gt;Being a green-oriented treehugger, I've put in all CFL lights in my house.  Just as much light for about 1/4 or 1/3 the power.   Nice, but flourescent lights put out a lot of EMI.  Does this cause trouble for anyone?  What are your experiences of CFL or other flourescents versus incandescent bulbs  in the room or house where you do sensitive electronics work?   Does anyone stick with ol' tungsten just to keep EMI down? &lt;/p&gt;&#xA;" OwnerUserId="1609" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-30T20:53:01.927" LastActivityDate="2011-03-29T08:15:26.857" CommunityOwnedDate="2010-11-30T23:44:02.540" Title="EMI: CFLs vs Incandescent Lights in Your Lab?" Tags="&lt;light&gt;&lt;interference&gt;&lt;workbench&gt;&lt;emi&gt;" AnswerCount="9" CommentCount="5" />
  <row Id="5295" PostTypeId="2" ParentId="2170" CreationDate="2010-10-17T06:04:40.883" Score="3" ViewCount="" Body="&lt;p&gt;Try exploring some ham radio DIY sites.  I was looking for DIY receiver designs last month, and varactors (as we call 'em over here) are used commonly.  Sorry, I took no detailed notes on this.  Sites with varactor-based projects will probably have information on suppliers, or at least have a forum for asking.&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-10-17T06:04:40.883" />
  <row Id="5296" PostTypeId="2" ParentId="5255" CreationDate="2010-10-17T06:23:16.763" Score="4" ViewCount="" Body="&lt;p&gt;The only competitions I've heard of required submitting physical samples. The American Radio Relay League &lt;a href=&quot;http://www.arrl.org/&quot; rel=&quot;nofollow&quot;&gt;(arrl.org)&lt;/a&gt; occasionally has contests for designing and building &lt;a href=&quot;http://www.hello-radio.com/whatis.html&quot; rel=&quot;nofollow&quot;&gt;amateur radio&lt;/a&gt; transceivers and amplifiers. Each year they do something a little different. The details can be found &lt;a href=&quot;http://www.arrl.org/news/get-ready-for-the-arrl-homebrew-challenge-iii&quot; rel=&quot;nofollow&quot;&gt;here.&lt;/a&gt; (If it's not password protected. I hope not!) &lt;a href=&quot;http://www.arrl.org/news/the-arrl-second-homebrew-challenge-and-the-winners-are&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; are the results from the last competition they held.&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-10-17T06:23:16.763" CommentCount="1" />
  <row Id="5297" PostTypeId="2" ParentId="5294" CreationDate="2010-10-17T08:41:44.680" Score="3" ViewCount="" Body="&lt;p&gt;I have CFL bulbs in both of my lights and in fact around most of the home. No particular reason other than they were giving them away at 20p each and they do save energy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My test equipment seems sufficiently isolated that this causes no problems whatsoever. But... in order for the manufacturer to sell these, they have to already meet EMI standards.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-17T08:41:44.680" CommunityOwnedDate="2010-11-30T23:44:02.540" />
  <row Id="5298" PostTypeId="2" ParentId="2170" CreationDate="2010-10-17T10:14:52.230" Score="2" ViewCount="" Body="&lt;p&gt;Farnell show 40 lines, including a D0-35 package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.farnell.com/jsp/search/browse.jsp;jsessionid=CD0B05RZM3J02CQLCIQZMMQ?N=0&amp;amp;Ntk=gensearch_001&amp;amp;Ntt=varicap&amp;amp;Ntx=mode+matchallpartial&amp;amp;suggestions=false&amp;amp;ref=globalsearch&amp;amp;_requestid=545325&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/jsp/search/browse.jsp;jsessionid=CD0B05RZM3J02CQLCIQZMMQ?N=0&amp;amp;Ntk=gensearch_001&amp;amp;Ntt=varicap&amp;amp;Ntx=mode+matchallpartial&amp;amp;suggestions=false&amp;amp;ref=globalsearch&amp;amp;_requestid=545325&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think reports of their death are greatly exaggerated :-)&lt;/p&gt;&#xA;" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-05T14:23:45.087" LastActivityDate="2011-05-05T14:23:45.087" />
  <row Id="5299" PostTypeId="2" ParentId="5294" CreationDate="2010-10-17T10:27:12.607" Score="4" ViewCount="" Body="&lt;p&gt;The only time I have experienced the type of trouble you mention was in a room where we did measurements with radiated EMI up to some 100 MHz. Electronic (&quot;green&quot;) ballasts were installed for the fluorescent lamps in there, and we could clearly see them (and not our DUT) on the spectrum analyzer. We went back to simple mains frequency chokes and things were a lot better again. I guess the same reasoning goes for compact fluorescent lamps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than EMI measurements with test receivers or spectrum analyzers, I wouldn't expect trouble. Hacking radios with dimmed incandescent bulbs on in the same room usually is worse than interference from CFLs.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-10-17T10:27:12.607" CommunityOwnedDate="2010-11-30T23:44:02.540" />
  <row Id="5300" PostTypeId="1" AcceptedAnswerId="5304" CreationDate="2010-10-17T10:42:35.520" Score="5" ViewCount="131" Body="&lt;p&gt;As in the title. What limits most integrated circuits to 150°C junction temperature?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know it's not good practice to run chips very hot (as it shows you are wasting a lot of energy) but I'm curious as to what actually limits them to around 150°C.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-17T12:19:34.073" Title="What limits most integrated circuits to 150°C junction temperature?" Tags="&lt;temperature&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="5301" PostTypeId="2" ParentId="5255" CreationDate="2010-10-17T11:34:04.413" Score="2" ViewCount="" Body="&lt;p&gt;Although not &quot;competitions&quot; as such, a lot of magazines accept circuits as readers' submissions, and offer prizes if they are published. Then you can show it off to friends, potential employers, etc. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-17T11:34:04.413" CommentCount="3" />
  <row Id="5302" PostTypeId="1" CreationDate="2010-10-17T11:41:46.727" Score="3" ViewCount="981" Body="&lt;p&gt;Hi guys!&#xA;I'm new to this stuff... So, what do i have to do to read a digital input (pushbutton) on ATmega16? Do I have to enable pullup-resistors or can I use a 10KOhm one? Some simple code would be awesome, thanks. Just a simple 'turn the led on when its pressed thing'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you give me a link to a beginner's tutorial? I have tried google and AVR freaks but everything just evolves into a fight there and i don't get my answer. I really haven't found any tutorials about this stuff. Tons of specific things but nothing simple about my avr...&lt;/p&gt;&#xA;" OwnerUserId="1619" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-14T05:37:07.957" LastActivityDate="2011-03-07T19:23:52.627" Title="How do I read digital input on ATmega16?" Tags="&lt;avr&gt;&lt;atmega&gt;" AnswerCount="5" CommentCount="4" FavoriteCount="1" />
  <row Id="5303" PostTypeId="2" ParentId="5294" CreationDate="2010-10-17T11:49:17.133" Score="6" ViewCount="" Body="&lt;p&gt;CFLs are not very green at all, there's enough components inside them to make a &lt;a href=&quot;http://blog.makezine.com/archive/2008/12/das_derelicht_ham_radio_transmitter.html&quot; rel=&quot;nofollow&quot;&gt;ham radio transmitter!&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They use so many different third party components - the cost in resources and transportation of CFLs and their constituent parts far outweigh the environmental impact of using a regular incandescent bulb. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a fallacy that CFLs are greener, and I've not seen any evidence to suggest they are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However -&#xA;What they are good at is reducing power consumption and running cost, so from the users point of view they're great for reducing the energy bill, just not so great at reducing the impact of electrical lighting on the planet and it's resources.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;More efficient != More environmentally friendly&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With regard to EMI - I work with audio, it's quite common to get interference on audio or signal lines that run close to a large lighting ballast or power transformer. My advice is to keep power and signal lines separate when possible, but they'd have to be pretty close in order to have an effect. The only time where I'd get anal about it is when fitting lighting in a sound recording studio, I've used so many badly wired studios over the years that I'd insist on having the lighting ballasts in a separate room.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;REVISION: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should be corrected - my reason for believing CFLs are bad looks like &lt;a href=&quot;http://www.consumerreports.org/cro/home-garden/home-improvement/hardware-building-supplies/lightbulbs/cfls/overview/cfl-ov-.htm&quot; rel=&quot;nofollow&quot;&gt;misinformation&lt;/a&gt; - a commonly held misconception - doh! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I retract my earlier comment that:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;the cost in resources and&#xA;  transportation of CFLs and their&#xA;  constituent parts far outweigh the&#xA;  environmental impact of using a&#xA;  regular incandescent bulb.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I'd like to replace it with:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;the environmental impact of using a&#xA;  CFL far outweighs the environmental&#xA;  impact of using a regular incandescent&#xA;  bulb.....probably :)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I do still have an issue with CFL mercury content, &lt;a href=&quot;http://en.wikipedia.org/wiki/Mercury_in_fish&quot; rel=&quot;nofollow&quot;&gt;it's really bad for the environment&lt;/a&gt;, but... as things are currently - I admit CFLs are the lesser of two evils when you consider &lt;a href=&quot;http://en.wikipedia.org/wiki/World_energy_resources_and_consumption&quot; rel=&quot;nofollow&quot;&gt;how the majority of electricity is generated&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I guess it's not so easy to say which is better, maybe we need more data to make an informed decision, I remain unconvinced with CFLs green credentials.&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-10-17T19:39:53.357" LastActivityDate="2010-10-17T19:39:53.357" CommunityOwnedDate="2010-10-17T11:49:17.133" CommentCount="11" />
  <row Id="5304" PostTypeId="2" ParentId="5300" CreationDate="2010-10-17T12:19:34.073" Score="4" ViewCount="" Body="&lt;p&gt;The materials that the transistor is made out of primarily defines this.  Germanium junctions will actually be much lower, more like 70C.  Silicon and Gallium-Arsenide can handle 150-200C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Someone with more semiconductor manufacturing experience can probably give a better answer but I believe that most of these junction limits are imposed due to the transistor crossing a thermal runaway point.  Both BJTs and FETs, although for different reasons, have the characteristic that as temperature increases so does power dissipation, which of course creates more heat.  As such once you break a threshold, the junction temperature will will rise very fast to the thermal breakdown point of the materials that make up the junction.  Which if this occurs for very long results in smoke, and lots of fun smells.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would venture a guess that 150C in the junction is roughly where normal packaging materials / the junction materials themselves can no longer pull enough heat out of the junction to keep it out of runaway and that the semiconductor materials themselves start to incur physical damage shortly after this temperature.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't exactly know what this process is, but it may simply be the point at which the crystalline structure begins to break down.  A silicon transistor is normally made with a silicon crystal thats doped with boron (p type) or phosphorus(n type).  You may get a more exact answer if you look into the chemistry of those structures.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-17T12:19:34.073" />
  <row Id="5306" PostTypeId="1" CreationDate="2010-10-17T14:35:53.150" Score="7" ViewCount="325" Body="&lt;p&gt;I want to design a product that uses a small LCD screen like those used in digital picture frames. Is it possible to get those very cheap? I've seen those picture frames for sale for 50 dollars but I have never seen LCD screens that cheap. Where is a good place to purchase LCD screens like that for use with embedded devices?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2010-10-20T13:31:44.590" ClosedDate="2011-05-26T16:11:33.857" Title="Cheap LCD displays available?" Tags="&lt;lcd&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="4" />
  <row Id="5307" PostTypeId="2" ParentId="5306" CreationDate="2010-10-17T14:39:35.087" Score="1" ViewCount="" Body="&lt;p&gt;Have a search for replacement Nokia LCD screens. The 3310 is monochrome, and there are various colour ones available too. All of them  are quite cheap.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-10-17T14:39:35.087" />
  <row Id="5308" PostTypeId="2" ParentId="5306" CreationDate="2010-10-17T14:40:06.703" Score="3" ViewCount="" Body="&lt;p&gt;Volume. The manufacturer will produce thousands and get a deal with the LCD manufacturer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you can still get graphical QVGA LCD displays for around $80 / £50 each, for example here is a list of &lt;a href=&quot;http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1004364+5446812+5446815+5446818+5446817+5446819+5446820+5446821&amp;amp;Ns=PRICE_PLS_006_PRICE1|0&amp;amp;Ntk=gensearch_001&amp;amp;Ntt=lcd&amp;amp;Ntx=mode+matchallpartial&amp;amp;locale=en_UK&amp;amp;appliedparametrics=true&amp;amp;getResults=true&amp;amp;originalQueryURL=/jsp/search/browse.jsp%3FN%3D500006%2B1004364%26Ntk%3Dgensearch_001%26Ntt%3Dlcd%26Ntx%3Dmode%2Bmatchallpartial%26No%3D0%26getResults%3Dtrue%26appliedparametrics%3Dtrue%26locale%3Den_UK%26catalogId%3D%26prevNValues%3D500006%2B1004364&quot; rel=&quot;nofollow&quot;&gt;Farnell&lt;/a&gt; offerings.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-17T14:40:06.703" />
  <row Id="5310" PostTypeId="2" ParentId="250" CreationDate="2010-10-17T16:18:41.497" Score="1" ViewCount="" Body="&lt;p&gt;Here's another page full of IC logos:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.advanced-tech.com/ic_logos/ic_logos.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.advanced-tech.com/ic_logos/ic_logos.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However I didn't see your logo (but maybe I didn't look hard enough)&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-10-17T16:18:41.497" />
  <row Id="5311" PostTypeId="2" ParentId="5257" CreationDate="2010-10-17T16:23:43.307" Score="1" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;Buy a cheap USB cable, cut it in half.&lt;/li&gt;&#xA;&lt;li&gt;Determine which of the &lt;a href=&quot;http://pinouts.ws/usb-pinout.html&quot; rel=&quot;nofollow&quot;&gt;wires in the USB cable&lt;/a&gt; are power (aka +5V) and ground&lt;/li&gt;&#xA;&lt;li&gt;Determine which of the &lt;a href=&quot;http://pinouts.ru/Devices/ipod_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;pins in the battery&lt;/a&gt; are power and ground&lt;/li&gt;&#xA;&lt;li&gt;Connect the respective USB wires to the pins on the battery&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;It's a fairly simple hack, only requires you to connect two wires.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;WARNING: Do not plug this into your computer! It will now have a USB connection, but plugging it into your computer will be putting power on lines that the PC does not expect! Things might explode.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-10-17T16:23:43.307" />
  <row Id="5312" PostTypeId="2" ParentId="5257" CreationDate="2010-10-17T16:33:37.230" Score="1" ViewCount="" Body="&lt;p&gt;You can google around a bit but its likely that your not just dealing with a battery wired to the dock, but rather theres probably some logic and control in the battery pack that doesn't deliver power until activated properly or limits current to 100ma until requested, per USB spec.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apple is a real pain in this regard.  &lt;a href=&quot;http://gizmodo.com/5029844/simple-hack-turns-usb-charger-units-into-iphone-chargers&quot; rel=&quot;nofollow&quot;&gt;Heres an example&lt;/a&gt; of what it takes to get a generic charger to provide power to the iphone.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course your talking about doing basically the opposite, but i wouldn't be at all surprised to see similar handicapping of the device.    &lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-17T16:40:34.980" LastActivityDate="2010-10-17T16:40:34.980" />
  <row Id="5313" PostTypeId="1" AcceptedAnswerId="5320" CreationDate="2010-10-17T22:49:06.980" Score="2" ViewCount="360" Body="&lt;p&gt;What is the difference between a TSOT-23-6 and a SOT-23-6?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know one is thinner. But in what dimension? I have looked in my PCB editor and they both have the same footprint.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any clarity appreciated!&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-18T20:25:30.283" Title="TSOT-23-6 vs SOT-23-6" Tags="&lt;surface-mount&gt;" AnswerCount="3" />
  <row Id="5314" PostTypeId="1" AcceptedAnswerId="5324" CreationDate="2010-10-17T23:10:24.893" Score="7" ViewCount="854" Body="&lt;p&gt;It's easy to get an introductory explanation of Zigbee.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/ZigBee&quot; rel=&quot;nofollow&quot;&gt;Zigbee on Wikipedia&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.eetimes.com/design/communications-design/4006430/Home-networking-with-Zigbee&quot; rel=&quot;nofollow&quot;&gt;Home networking with Zigbee&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.zigbee.org/&quot; rel=&quot;nofollow&quot;&gt;Zigbee alliance&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;But technical information on XBee seems harder to find. It's unclear to me what its similarities and differences to Zigbee are.&lt;/p&gt;&#xA;" OwnerUserId="1025" LastActivityDate="2010-10-18T03:23:10.943" Title="What is XBee and how is it different from Zigbee?" Tags="&lt;wireless&gt;&lt;xbee&gt;&lt;zigbee&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="5315" PostTypeId="1" AcceptedAnswerId="5423" CreationDate="2010-10-17T23:13:19.413" Score="4" ViewCount="588" Body="&lt;p&gt;I was trying to use the ATMega328 ADC port A0 to read a signal. The hardware I used was:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.seeedstudio.com/depot/seeeduino-stalker-atmega-328-p-600.html&quot; rel=&quot;nofollow&quot;&gt;Seeeduino Stalker&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.seeedstudio.com/depot/electronic-brick-shield-v4-p-458.html?cPath=48_49&quot; rel=&quot;nofollow&quot;&gt;Electronic Brick Shield&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.seeedstudio.com/depot/electronic-brick-microphone-with-amplifier-analog-p-481.html?cPath=48_54&quot; rel=&quot;nofollow&quot;&gt;Microphone Electronic Brick&lt;/a&gt; (I found a &lt;a href=&quot;http://item.taobao.com/item.htm?id=1694977260&quot; rel=&quot;nofollow&quot;&gt;link to the original developer store&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The signal I got seems to be only the positive part of a sine wave. Is it possible that this setup isn't suited for audio recording? What I have to change?&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-10-26T00:46:16.900" LastActivityDate="2010-10-26T00:46:16.900" Title="How to read an audio signal using ATMega328?" Tags="&lt;arduino&gt;&lt;audio&gt;&lt;adc&gt;&lt;arduino&gt;" AnswerCount="3" CommentCount="7" FavoriteCount="1" />
  <row Id="5316" PostTypeId="2" ParentId="5313" CreationDate="2010-10-17T23:28:39.863" Score="5" ViewCount="" Body="&lt;p&gt;Check the datasheet for the part you are using. There is usually a dimensioned drawing in the back, although some manufactures put them in a separate documents buried somewhere on their website. There can be small differences in package dimensions (of the same designation) from different manufactures. So if it is import in your design, it is best to refer to the specific documentation for that part.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2010-10-17T23:28:39.863" />
  <row Id="5317" PostTypeId="2" ParentId="5315" CreationDate="2010-10-17T23:38:32.163" Score="2" ViewCount="" Body="&lt;p&gt;Without having ever used any of those parts, let me see if I can take a stab. Do you happen to have access to an oscope? If so you might want to check your signal before you start building anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most likely your microphone/amp is outputting a wave that is centered around 0v, meaning you have + and - voltages. Think of a sin wave that fluctuates between -1v and 1v. In order for your micro to use this, you will need to add a DC offset such that you most negative voltage becomes slightly above 0v and your most positive voltage is slightly below the max that your micro can read (probably around 5v).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With out looking into your components in more, it is hard to tell you specifically what you need to do in order to get your DC offset, but maybe this will put you in the right direction.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-10-18T00:08:35.177" LastActivityDate="2010-10-18T00:08:35.177" CommentCount="2" />
  <row Id="5318" PostTypeId="2" ParentId="5306" CreationDate="2010-10-17T23:39:07.743" Score="7" ViewCount="" Body="&lt;p&gt;Ran into this the other day...may help you out. ITeadStudio is Chinese based so it might cost a bit extra depending on your government. Also check their shipping page if you live far away.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$27.50 – 3.2” LCD w/Touch &amp;amp; SD - &lt;a href=&quot;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=3&amp;amp;products_id=54&quot; rel=&quot;nofollow&quot;&gt;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=3&amp;amp;products_id=54&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$20.50 – 2.4” LCD w/Touch &amp;amp; SD - &lt;a href=&quot;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=3&amp;amp;products_id=55&quot; rel=&quot;nofollow&quot;&gt;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=3&amp;amp;products_id=55&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$29.80 – 3.2” Wide LCD w/Touch &amp;amp; SD - &lt;a href=&quot;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=3&amp;amp;products_id=263&quot; rel=&quot;nofollow&quot;&gt;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=3&amp;amp;products_id=263&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$4.80 – Arduino Shield for LCD screens - &lt;a href=&quot;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=18&amp;amp;products_id=149&quot; rel=&quot;nofollow&quot;&gt;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=18&amp;amp;products_id=149&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LCD screens are complete with controller. All you have to do is plug it in and code your micro!&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="1575" LastEditorDisplayName="" LastEditDate="2010-10-20T13:31:44.590" LastActivityDate="2010-10-20T13:31:44.590" CommentCount="2" />
  <row Id="5320" PostTypeId="2" ParentId="5313" CreationDate="2010-10-18T00:05:20.650" Score="6" ViewCount="" Body="&lt;p&gt;I've successfully used a SOT footprint for TSOT parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I can tell, what differences there are are only in part height, which is not important from the board layout perspective.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-18T00:05:20.650" CommentCount="3" />
  <row Id="5321" PostTypeId="2" ParentId="5315" CreationDate="2010-10-18T00:13:35.987" Score="3" ViewCount="" Body="&lt;p&gt;Do you have a DC-blocking/biasing capacitor at the input?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kS3kb.png&quot; alt=&quot;Analog input with DC-blocking capacitor&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The combination of the C with the R sets the lowest frequency that can pass through to the ADC.  DC (the ultimate low frequency) is blocked, while AC passes through.  In this case, the cutoff frequency would &lt;a href=&quot;http://www.wolframalpha.com/input/?i=1%2F%282+pi+100+kohm+1+uF%29&quot; rel=&quot;nofollow&quot;&gt;be 1 Hz&lt;/a&gt;, which is plenty low for audio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DC bias is provided by something in the middle of the ADC range, with low noise.  For example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/yIERi.png&quot; alt=&quot;DC bias source&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would produce 2.5 V at DC, but the AC is closely coupled to ground by the capacitor, so it filters out any fluctuations in the supply.  A larger capacitor would improve the noise at lower frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Originally I linked to &lt;a href=&quot;http://sites.google.com/site/ki4mcw/_/rsrc/1270799838828/Home/arduino-tnc/voltage_divider_simple.png&quot; rel=&quot;nofollow&quot;&gt;this image&lt;/a&gt;, but that would only work if your 5 V supply is noise-free.)&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-19T16:01:23.860" LastActivityDate="2010-10-19T16:01:23.860" CommentCount="13" />
  <row Id="5322" PostTypeId="2" ParentId="5284" CreationDate="2010-10-18T02:41:10.007" Score="1" ViewCount="" Body="&lt;p&gt;I agree Mark, but would like to add some info about cost. If you are looking purely at prototyping in low quantities you can get a 4 layer board from &lt;a href=&quot;http://www.4pcb.com/index.php?load=content&amp;amp;page_id=131&quot; rel=&quot;nofollow&quot;&gt;Advanced Circuits&lt;/a&gt; for $66  and $33 for a 2 layer board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are looking further into the future and want to think about large quantity fab you will need to consider that PCB fab houses will look at everything, more then just number of layers, when they give you a cost. Some items include size, number of vias, special cuts, number of holes... So in this sense, if you are able to get a board to be half of the size and with half of the vias by going to a 4 layer board it may be well worth it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, when you get to higher quantities you will probably need to be looking at FCC testing. Many times in order to pass FCC testing you would need to get a 4 layer board in order to get your unintentional radiators down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So hopefully by now you can tell that there are many many factors that factor into which way is the smarter choice. It is hard to tell which way to go, but at some point you have to make it.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-18T02:41:10.007" />
  <row Id="5323" PostTypeId="2" ParentId="5294" CreationDate="2010-10-18T02:58:20.997" Score="2" ViewCount="" Body="&lt;p&gt;I used to work for a group that had dimmers on their light circuits, which worked fine until they switched to dim-able CFLs. I am not sure what it is about them, but they caused tons and tons of noise in our audio system when ever they weren't fully on or fully off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, to answer you, the way I look at it is we should deal with any noise from the environment so that we know that the electronics we design can handle the noise.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-18T02:58:20.997" CommunityOwnedDate="2010-11-30T23:44:02.540" CommentCount="1" />
  <row Id="5324" PostTypeId="2" ParentId="5314" CreationDate="2010-10-18T03:23:10.943" Score="11" ViewCount="" Body="&lt;p&gt;ZigBee / ZigBee Pro are mesh communication protocols that sits on top of IEEE 802.15.4 PHY.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;XBee / XBee Pro are product names for a radio communication modules made by Digi.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The modules can be loaded with various firmwares to support ZigBee / ZigBee Pro / DigiMesh and come in several frequency bands.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DigiMesh is an alternative to ZigBee that changes a few things, and adds some features to make it generally better to work with.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, you sacrifice compatibility with ZigBee devices.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example DigiMesh allows routers to sleep, has lower overhead, has 1 node type vs zigbee's 3 leading to a more robust mesh, can run at higher data rates, etc.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Frankly its a better protocol all around, in my opinion.  I wouldn't use ZigBee unless i needed interoperability with other vendor's nodes.  Not that DigiMesh is the only answer, there are other mesh protocols that sit on IEEE 802.15.4 as well.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-18T03:23:10.943" CommentCount="3" />
  <row Id="5325" PostTypeId="1" AcceptedAnswerId="5546" CreationDate="2010-10-18T04:34:52.390" Score="2" ViewCount="85" Body="&lt;p&gt;I am interested in experimenting with PoE for a variety of small embedded controller projects. Is there a hobbiest's source for any of the Akros Silicon PoE evaluation boards? Or is there another bit of kit I should be looking into?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My ideal prototyping board would be something like an Ethernut powered by PoE…&lt;/p&gt;&#xA;" OwnerUserId="1317" LastActivityDate="2010-10-24T17:13:26.813" Title="Is there a hobbiest's source for Akros Silicon PoE evaluation boards?" Tags="&lt;microcontroller&gt;&lt;power&gt;&lt;port&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5326" PostTypeId="2" ParentId="22" CreationDate="2010-10-18T07:26:08.663" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://linusakesson.net/scene/craft/index.php&quot; rel=&quot;nofollow&quot;&gt;lft's Craft&lt;/a&gt; is another example of an AVR doing VGA output. &lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-10-18T07:26:08.663" />
  <row Id="5327" PostTypeId="1" CreationDate="2010-10-18T11:48:22.260" Score="13" ViewCount="170" Body="&lt;p&gt;Which sites do you use for electronics equipment reviews?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for sites which make reviews of products which are of interest to electronics hobbyists and(or) professionals. Some examples of what I'm looking for would be multimeter reviews, oscilloscope reviews, logic analyzer reviews, soldering iron reviews, reviews of pin compatible components from various manufacturers and similar.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that this question may have common points with &lt;a href=&quot;http://electronics.stackexchange.com/q/952&quot;&gt;this&lt;/a&gt; question, but here I'm only looking for reviews of products and not electronics blogs and sites in general.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, should this be community-wiki?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-10-18T15:53:52.367" LastActivityDate="2010-11-01T06:54:25.820" Title="Which sites do you use for electronics equipment reviews?" Tags="&lt;website&gt;&lt;equipment&gt;&lt;instruments&gt;" AnswerCount="3" FavoriteCount="7" />
  <row Id="5328" PostTypeId="2" ParentId="5327" CreationDate="2010-10-18T12:27:10.683" Score="9" ViewCount="" Body="&lt;p&gt;Dave Jones' &lt;a href=&quot;http://www.eevblog.com&quot; rel=&quot;nofollow&quot;&gt;eevblog&lt;/a&gt; - he tests, and tests, and tests various items of test equipment. And sometimes destroys them. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-18T12:27:10.683" CommentCount="3" />
  <row Id="5329" PostTypeId="2" ParentId="5325" CreationDate="2010-10-18T13:34:59.833" Score="2" ViewCount="" Body="&lt;p&gt;I'm not sure about the specific chip you talk about but &lt;a href=&quot;http://www.freetronics.com/products/ethernet-shield-with-poe&quot; rel=&quot;nofollow&quot;&gt;Freetronics has a Ethernet+POE Arduino shield&lt;/a&gt;. It's not cheap, but it gets the job done. There's also a &lt;a href=&quot;http://www.freetronics.com/products/poe-injector-4ch&quot; rel=&quot;nofollow&quot;&gt;mid-span injector board&lt;/a&gt; to power more than one device from a central point. I like that the freetronics boards often have prototyping built right into the board without requiring an extra shield. Could be a good starting point for an embedded project.&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2010-10-18T13:34:59.833" CommentCount="3" />
  <row Id="5330" PostTypeId="1" AcceptedAnswerId="5332" CreationDate="2010-10-18T15:27:48.093" Score="7" ViewCount="218" Body="&lt;p&gt;We're nearing the exhaustion of IPv4. What should be my concern about it for embedded devices?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know about others manufacturers but until today, Microchip TCP stack doesn't implement the IPV6.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-12-01T10:07:01.550" LastActivityDate="2010-12-01T14:48:33.723" Title="Do I have to worry about the depletion of IPv4 addresses in embedded applications?" Tags="&lt;microcontroller&gt;&lt;embedded&gt;&lt;ethernet&gt;&lt;ipv6&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="5331" PostTypeId="2" ParentId="5327" CreationDate="2010-10-18T15:33:56.317" Score="5" ViewCount="" Body="&lt;p&gt;My 2 cents: &lt;a href=&quot;http://www.engineeringtv.com/&quot; rel=&quot;nofollow&quot;&gt;Engineering TV&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-18T15:33:56.317" />
  <row Id="5332" PostTypeId="2" ParentId="5330" CreationDate="2010-10-18T15:36:00.463" Score="9" ViewCount="" Body="&lt;p&gt;No.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IPv4 isn't going away any time soon.&#xA;If you are concerned about IPv6 compatability, have a look at &lt;a href=&quot;http://www.sics.se/~adam/contiki/docs-uipv6/a01110.html/&quot; rel=&quot;nofollow&quot;&gt;uIP&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.embeddedrelated.com/usenet/embedded/show/99338-1.php&quot; rel=&quot;nofollow&quot;&gt;Here's&lt;/a&gt; a thread from comp.arch.embedded about embedded IPv6 stacks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my experience, most embedded devices which are not explicitly for networking (routers, gateways, switches) are behind NAT. So, running out of IPv4 addresses is not an issue.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-18T15:36:00.463" />
  <row Id="5333" PostTypeId="1" AcceptedAnswerId="5334" CreationDate="2010-10-18T15:43:03.207" Score="2" ViewCount="240" Body="&lt;p&gt;I'm trying to use an RC oscillator on a PIC 16F84A-20 that I have on a breadboard. The code is supposed to (at this point) simply flip an output back and forth every so often.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't need it to run very fast, so I figured I'd try using the RC network on CLKIN instead of a crystal. My problem is that my code doesn't seem to be running consistently (I get some LED flashes for a few seconds, then nothing, then perhaps more flashes, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm working on a plug-in breadboard. I've got +5 provided by a PIC dev board I had handy.&#xA;+5 is reading 4.94 volts via my DMM.&#xA;I used a 4.7K resistor from CLKIN to +5, and a 33pf cap to GND. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I put an o-scope on CLKIN, and I see a sawtooth-ish wave of about 2.5Mhz, but I also see some other, longer waveform in the background, if you will (it's far fainter than the sawtooth). it's a much wider, slowly decaying pulse. The sawtooth wave is, unfortunately, only about .2-.3 volt high, and centered between +5 and GND.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I put the scope on CLKOUT, and in the instances where I'm seeing my LEDs blink, I've got a nice squarewave on CLKOUT. Other times it's just flat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My assumption is that I've made some basic error with the RC circuit that's causing it to not generate a sufficient waveform, and thus not work. I'd like pointers to what I should be checking next.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2010-10-18T15:47:43.350" Title="PIC 16F84A RC oscillator problems" Tags="&lt;pic&gt;&lt;rc&gt;" AnswerCount="1" />
  <row Id="5334" PostTypeId="2" ParentId="5333" CreationDate="2010-10-18T15:47:43.350" Score="5" ViewCount="" Body="&lt;p&gt;Is MCLR pulled up? Leaving it floating can cause intermittent operation like that.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-18T15:47:43.350" CommentCount="1" />
  <row Id="5335" PostTypeId="2" ParentId="5285" CreationDate="2010-10-18T16:51:24.950" Score="3" ViewCount="" Body="&lt;p&gt;Analog ICs like comparators and op-amps most certainly DO need decoupling, especially if they're used as hysteretic switches. You can see very strange behaviour (bouncing between states being quite common) if there isn't good decoupling and there's some HF noise on the supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Coming from an analog switching power background - if I suspect an op-amp or comparator isn't doing what I think it should be, the first two things I always check are: (1) is there a decoupling capacitor, and (2) if there is, is it in a good electrical position in the layout?&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-18T16:51:24.950" />
  <row Id="5336" PostTypeId="1" AcceptedAnswerId="5337" CreationDate="2010-10-18T16:57:23.867" Score="9" ViewCount="554" Body="&lt;p&gt;Every reference I can find on transistors immediately launches into theory-heavy alphabet soup. The above seems also to be assumed knowledge for reading a datasheet. I don't care; I just want to get one to work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand there's some relationship between the current/voltage applied to the base to get a particular current to flow from the collector to the emitter. Which numbers on the datasheet relate to that? If I'm only trying to operate the transistor in &quot;switch&quot; mode, do I really need to care what current I apply to the base or will I be fine just whacking a 1k resistor in between my logic level output and the transistor base?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the only difference between an NPN and a PNP transistor which way the current flows when a current is applied to the base?&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2010-10-20T03:55:35.997" Title="I don't care how a transistor works, how do I get one to work?" Tags="&lt;transistor&gt;" AnswerCount="4" CommentCount="8" FavoriteCount="4" />
  <row Id="5337" PostTypeId="2" ParentId="5336" CreationDate="2010-10-18T17:14:12.193" Score="15" ViewCount="" Body="&lt;p&gt;The base-emitter junction is like a diode. When the voltage across it (Vbe) exceeds approximately 0.65V (can be as low as 0.55V and as high as 0.9V, check the datasheet for your transistor) it begins conducting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current (not voltage!) through the base emitter junction is amplified by the gain of the transistor, which is known as HFE. Ic(collector current) = Ib(base current) * HFE. Remember HFE is not constant for transistors, it varies from transistor to transistor and depending on temperature, previous usage, etc., so don't rely on it for controlled amplification. For the 2N2222 it is around 160, plus or minus 30.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By applying a base-emitter voltage exceeding 0.65V to the transistor you can use it as a switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a simple circuit in TomCAD.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; 3V --+--------+&#xA;      |        |&#xA;      /      __|__   .&#xA;      \ 1k   \   /  /.  blue&#xA;      /      _\_/_  /   LED&#xA;      |+       |&#xA;Switch |       | collector&#xA;      |+     |/&#xA;      +------|&#xA;        base |\  emitter&#xA;               |&#xA;              ---&#xA;               -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(Sorry I couldn't draw the arrow on the emitter. It is an NPN transistor you want. 2N3904 or 2N2222 will do.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to use an LED which is not blue or white then use a 47 ohm resistor in series with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you press the switch the LED will come on.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-18T22:41:13.037" LastActivityDate="2010-10-18T22:41:13.037" CommentCount="9" />
  <row Id="5338" PostTypeId="1" AcceptedAnswerId="5343" CreationDate="2010-10-18T17:21:56.647" Score="6" ViewCount="280" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm working with two chips on a board, a dsPIC33F and a PIC24F as well as a serial EEPROM (24FC1025.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen these little ESD protection devices in 0603 packages:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.farnell.com/panasonic/ezaeg3a50av/esd-suppressor-0603-15v-0-1pf/dp/1292692RL&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/panasonic/ezaeg3a50av/esd-suppressor-0603-15v-0-1pf/dp/1292692RL&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For MCUs like I'm using, is this necessary? The boards may be constantly handled and the external interfaces (I2C, UART) may be exposed to ESD. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would the internal diodes protect the chip anyway and make these pointless?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-18T20:08:24.140" Title="ESD protection devices - necessary for MCUs?" Tags="&lt;esd&gt;&lt;microcontroller&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="5339" PostTypeId="2" ParentId="5338" CreationDate="2010-10-18T17:31:06.620" Score="4" ViewCount="" Body="&lt;p&gt;I put similar parts on the signals that leave the board, such as UART, Ethernet, digital I/O.  For intra-board signals, don't worry about it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;About the internal diodes: There's a limit of what the diode will take.  The internal diodes will be OK with normal handling.  The external diodes will protect against larger &quot;shag carpet in the dead of winter&quot; static shocks.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-10-18T17:31:06.620" CommentCount="1" />
  <row Id="5340" PostTypeId="2" ParentId="5327" CreationDate="2010-10-18T18:18:28.670" Score="5" ViewCount="" Body="&lt;p&gt;For RF related stuff (all ham radio related) try &lt;a href=&quot;http://www.eham.net/reviews/&quot; rel=&quot;nofollow&quot;&gt;eham.net&lt;/a&gt;. They cover everything from vacuum tubes (yes, they're still used... a lot) to RF and audio filters, to GPS receivers.&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-10-18T18:18:28.670" />
  <row Id="5341" PostTypeId="1" AcceptedAnswerId="5349" CreationDate="2010-10-18T18:20:49.693" Score="3" ViewCount="151" Body="&lt;p&gt;I'm building an iPod adaptor for my car.  It's something of a clone of some similar devices, such as the Dension ice&gt;Link: Plus and DICE adapter for some MINI and BMW vehicles.  I've got the firmware sorted, but I'm sort of stuck for what to do for a cable between the adapter and the iPod.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a Podgizmo iPod dock connector breakout board/adapter (similar to &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8295&quot; rel=&quot;nofollow&quot;&gt;this one, but smaller&lt;/a&gt;).  I need to run 9 wires from the adaptor to the dock connector.  I could somehow bundle 9 individual wires from the adaptor to the connector, but I think that would be neither neat nor particularly durable.  I've been hoping that I could use a mini-DIN 9pin cable, as &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=CP-2290-ND&quot; rel=&quot;nofollow&quot;&gt;this part&lt;/a&gt; could be easily integrated into my board, but I'm not able to find a source for cables that carry all 9 wires and include a molded 9-pin male mini-DIN connector. I have found 100' spools of 9-conductor cable at Mouser and DigiKey, but those are between 75¢ and $1 per foot and aren't available in smaller quantities. I found &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8743&quot; rel=&quot;nofollow&quot;&gt;an extension cable at SparkFun&lt;/a&gt; that would probably do the trick, but $32 seems expensive when I need to cut one end off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the questions I put before my esteemed Chiphackers are:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;• is there a better alternative for getting 9 signal wires between my board and the dock connector that I haven't considered?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;• if not, is there another vendor who would carry a (preferably black) cable with 9 individual stranded wires in lengths of 6-12 feet?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;• is there another cable I could repurpose for this task, and if so, where would I find it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 9-wire count is firm.  If I can reduce that number, it would probably be to 6, but I would have to design a board that would live in the dock connector housing (perhaps inside of &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=704&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;), and if I could get it down to 6 I would probably just try to find some nice cat5.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&#xA;Brian &lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-01-17T05:42:42.047" Title="Source for multi-conductor cable?" Tags="&lt;components&gt;&lt;wire&gt;&lt;sourcing&gt;&lt;cable-assemblies&gt;&lt;ipod&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="5342" PostTypeId="2" ParentId="5341" CreationDate="2010-10-18T19:23:06.277" Score="0" ViewCount="" Body="&lt;p&gt;Also check with NKC electronics.   I bought nice connectors from them to hook my CBM 1541 to modern PC, and it was reasonably priced and good quality.  I also bought a bunch of Arduino stuff from them.   &lt;/p&gt;&#xA;" OwnerUserId="1222" LastActivityDate="2010-10-18T19:23:06.277" CommentCount="1" />
  <row Id="5343" PostTypeId="2" ParentId="5338" CreationDate="2010-10-18T20:08:24.140" Score="2" ViewCount="" Body="&lt;p&gt;You can certainly use such devices.  They are usually a poor choice for anything that has lower power usage requirements as they have high leakage current.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also have to be careful of the clamping voltage, ESD of ~200V can damage a micro-controller, the device you linked is specced at 500V max.  Make sure whatever your trying to protect is actually be protected to the extent it needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For digital lines also pay attention to the capacitance of these device/package, they can screw up your signal integrity.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I usually do if the input is likely to get hit with ESD, like an input that is often connected in the field is use a 2 pronged approach.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First Use a ESD device, or diodes closer to the circuit to protect, which type I would use depends on the signal/circuit in question.  This is to protect against lower spikes, say 8kV.  More and more you see this type of protection inside devices, especially boundary devices like RS232 drives and line drivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, when you build the PCB use spark gaps, which is really nothing more than putting 2 pads on the surface of the PCB, 1 being the signal, the other being a good ground and spacing them very close to each other, like 6 thou apart.  This will protect against higher voltage hits, like 25kV.  Pretty simple concept, the high voltage jumps the gap and goes straight to ground.  Just be careful how you place these, as close to the connector as possible with the best possible ground connection.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also pay attention to the manufacturing process your using, you don't want solder to accidental bridge the gap. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Gaps can be tough to do on digital traces and avoid changing the impedance, usually requires tweaking the signal termination after the prototype run.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is some argument over the proper shape of the pad, some use half moons, some use pointed triangles with the tips near each other and some use square pads.  I've always used square pads, the more area that is close to the other pad the more repeated strikes the gap will survive.  The trade off is that the square pads will take the most effort to ensure there is no solder bridging.  Best answer is to get your CM to not apply solder to these pads at all, but that can require special effort on their part.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-18T20:08:24.140" CommentCount="11" />
  <row Id="5344" PostTypeId="2" ParentId="5313" CreationDate="2010-10-18T20:18:44.723" Score="3" ViewCount="" Body="&lt;p&gt;The difference between a TSOT-23-6 and a SOT-23-6 is the height, apparent from the two PDF files below. The exact dimensions varies between manufacturers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From &lt;a href=&quot;http://www.intersil.com/design/packages/plastic.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.intersil.com/design/packages/plastic.asp&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;SOT-23-6. &lt;a href=&quot;http://www.intersil.com/data/pk/P6.064.pdf&quot; rel=&quot;nofollow&quot;&gt;6 Lead Small Outline Transistor Plastic Package (SOT)&lt;/a&gt; (PDF, 103 KB). 2.8 x 1.6 x &lt;strong&gt;1.15&lt;/strong&gt; mm (body)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;TSOT-23-6. &lt;a href=&quot;http://www.intersil.com/data/pk/P6.064B.pdf&quot; rel=&quot;nofollow&quot;&gt;6 Lead &lt;strong&gt;Thin&lt;/strong&gt; Small Outline Transistor Plastic Package (TSOT)&lt;/a&gt; (PDF, 52 KB). 2.8 x 1.6 x &lt;strong&gt;0.87&lt;/strong&gt; mm (body)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="804" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2010-10-18T20:25:30.283" LastActivityDate="2010-10-18T20:25:30.283" />
  <row Id="5345" PostTypeId="1" AcceptedAnswerId="5346" CreationDate="2010-10-18T21:32:27.603" Score="2" ViewCount="86" Body="&lt;p&gt;What is the difference between these parts? The datasheet shows completely different pinnings, but both are specified over the same range and both have the A, B and ungraded specifications for tolerance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just curious.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-18T21:43:41.657" Title="Difference between TL431 and TL432" Tags="&lt;tl431&gt;" AnswerCount="1" FavoriteCount="0" />
  <row Id="5346" PostTypeId="2" ParentId="5345" CreationDate="2010-10-18T21:43:41.657" Score="2" ViewCount="" Body="&lt;p&gt;From &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/tl431a.pdf&quot; rel=&quot;nofollow&quot;&gt;the datasheet&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The TL432 has exactly the same&#xA;  functionality and electrical&#xA;  specifications as the TL431, but has&#xA;  different pinouts for the DBV, DBZ,&#xA;  and PK packages.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-18T21:43:41.657" CommentCount="6" />
  <row Id="5347" PostTypeId="1" AcceptedAnswerId="5348" CreationDate="2010-10-18T22:39:53.747" Score="1" ViewCount="90" Body="&lt;p&gt;Got an old 12V UPS battery, a sealed lead acid 17.2Ah battery. Quite a nice YUASA battery. Unfortunately it reads 9.92V so has been discharged badly. Is there any chance of salvaging it?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-18T23:51:07.577" Title="Resurrecting a 12V SLA from a UPS" Tags="&lt;battery&gt;" AnswerCount="1" />
  <row Id="5348" PostTypeId="2" ParentId="5347" CreationDate="2010-10-18T23:51:07.577" Score="4" ViewCount="" Body="&lt;p&gt;Does it have a bunch of specs printed on the side? Check for a manufacture date. If it's more than 3 or 4 years old, it may not be such a prize. Smaller ones (e.g. 1.5A-Hr) can become completely unable to take a charge in that amount of time. On the other hand I've seen 7A-Hr ones last more than 5 years.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd put it on a 12V trickle charger for a couple of days, then once the open-circuit voltage (off the charger) is 12.5 or 12.6V, put a load on it and see if the voltage sags. Use something that pulls an amp or so, and if the voltage sags more than a couple of tenths, it means the internal resistance has gone up, and the battery is just plain old.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-18T23:51:07.577" CommentCount="4" />
  <row Id="5349" PostTypeId="2" ParentId="5341" CreationDate="2010-10-19T01:48:47.323" Score="3" ViewCount="" Body="&lt;p&gt;CAT5 is so cheap, can you get away with 2 runs? This has the advantage of being already in twisted pair format.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not, this &lt;a href=&quot;http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_644412_-1&quot; rel=&quot;nofollow&quot;&gt;Jameco cable&lt;/a&gt; is ~$0.50/foot for 25 feet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mpja.com/&quot; rel=&quot;nofollow&quot;&gt;Marlin P. Jones&lt;/a&gt; has 15 foot 25 pin extender cables for $5, if this is a one-off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also don't forget your local thrift store - $1 for a parallel port printer cable.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2010-10-19T01:48:47.323" CommentCount="1" />
  <row Id="5350" PostTypeId="2" ParentId="3105" CreationDate="2010-10-19T03:49:48.443" Score="3" ViewCount="" Body="&lt;p&gt;The voltage divider idea is nice, cheap, but gives you the problem of a change of the voltage to be measured will be seen as 1/2 the change at the ADC input.   If accurate measurements are of interest, the solution is a zener diode as the bottom half of the divider.  If the thing being measured can tolerate losing a teeny bit of current, this will work great.  Zeners aren't absolutely flat in their reverse breakdown voltage, especially for very small currents, so don't make R1 too big.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now to see if this stackexchange site allows me to add images...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/20nCY.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/HfnHr.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-10-19T03:49:48.443" CommentCount="1" />
  <row Id="5351" PostTypeId="2" ParentId="5336" CreationDate="2010-10-19T05:46:47.117" Score="2" ViewCount="" Body="&lt;p&gt;I'd propose starting step by step with something tangible. Chew on one case at a time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might start with the simple case of a switch and I'm sure you can find very simple examples by looking. Don't dive into an old book with CE bipolar amplifier biasing with half a dozen resistors, compensation and h parameters flown through on the first page written by someone who doesn't remember what it was like not to know all that stuff first. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you look around, it should be easy to find &lt;a href=&quot;http://www.allaboutcircuits.com/vol_3/chpt_4/2.html&quot; rel=&quot;nofollow&quot;&gt;some tutorials&lt;/a&gt; with &lt;a href=&quot;http://www.rason.org/Projects/transwit/transwit.htm&quot; rel=&quot;nofollow&quot;&gt;BJT&lt;/a&gt;, &lt;a href=&quot;http://www.allaboutcircuits.com/vol_3/chpt_5/2.html&quot; rel=&quot;nofollow&quot;&gt;JFET&lt;/a&gt;, &lt;a href=&quot;http://brunningsoftware.co.uk/FET.htm&quot; rel=&quot;nofollow&quot;&gt;MOSFET&lt;/a&gt;... Maybe skip P and depletion devices first as well. Mostly P (PNP) does look like a mirror image, once you have an idea how the N part works, it should be easy to relate to the P part. That way you won't get so much chance to be confused by negative voltages and currents and circuits drawn upside down (they really do all that).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you really need to look at the datasheet parameters like just how much current and voltage it can take safely, what's the ratio of base current (gate voltage) needed/taken for a given collector current, total power dissipation (voltage loss * current) etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you're done with switches, you might look at turning on/off only partially (amplifier, current control). All three types behave a bit differently. Then maybe see different typical circuits: regulators, current sources and mirrors, timers, logic gates, B and AB power amplifiers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A bit of theory (multiplication, Ohm's law, diode...) is necessary, more will help you understand what's going on and predict things. But you should be able to jump in with ballpark values first. Use some cheap parts (with the datasheet, at least for the pinouts and type) and perhaps a simulator to try things out.&lt;/p&gt;&#xA;" OwnerUserId="883" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-10-19T05:53:11.213" LastActivityDate="2010-10-19T05:53:11.213" />
  <row Id="5352" PostTypeId="1" AcceptedAnswerId="5354" CreationDate="2010-10-19T07:41:24.873" Score="5" ViewCount="398" Body="&lt;p&gt;As I mentioned, I have just beginned programming pic16f877a. I can now work with 7 segment displays. At present I am using ccs compiler. Nothing wrong with that. But i prefer to be a compiler independent programmer. So i simultaneously want to work in other compilers like IAR or Hitechc. I want to know whether the &quot;program statement declaration in compilers&quot; other than ccs will be different? Please guide me how to approach this thing. I would welcome all forms of suggestions. Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="1484" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-24T03:44:32.363" LastActivityDate="2011-02-24T03:44:32.363" Title="PIC 16F beginner.. difference in program-syntax when using different compilers.." Tags="&lt;pic&gt;&lt;compiler&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="5353" PostTypeId="2" ParentId="5352" CreationDate="2010-10-19T09:53:32.863" Score="2" ViewCount="" Body="&lt;p&gt;Unfortunately you will find it is very difficult to find a compiler independent program for a microcontroller. There are several problems, here are just two:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Differences in peripherals, SFR naming, etc (especially over other processors, but even with compilers from the same family), and;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Non-standard features on some compilers like setting bits individually or different structures for invoking assembly code.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The 16F series is very limited in terms of architecture and not really designed to support a C compiler. That is why there is no GCC for it.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-19T09:53:32.863" />
  <row Id="5354" PostTypeId="2" ParentId="5352" CreationDate="2010-10-19T09:55:53.447" Score="6" ViewCount="" Body="&lt;p&gt;That great that you want to be compiler independent!  Unfortunately hitech and CCS compilers for the low end PICs use a lot of compiler specific preprocessor declarations, compiler specific pin access routines, and in the case of CCS compiler specific routines for access core functions such as SPI, I2C, ADC and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is not possible to write your code to be non-compiler specific without a lot of preprocessor #define, #ifdef, #ifndef and so on to get access to specific parts of what each compiler has on offer. This would make your code unreadable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best thing you could aim for is to be IDE independent and use something like eclipse, so at least you are using the same IDE.  This will result in losing CCS wizards for setting up core functions, but will give you greater flexibility in using the same IDE.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing to consider is that both hitech and CCS do not have (at least in the past) a true c compiler linker and required you to use &quot;#include myfile.c&quot; which I personally despise ... but that is another story.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have not commented on the IAR compiler as I have only used CCS and hitech.  Both worked ok, but I was never really happy with either after migrating across from the Motorola (now freescale) platform and using the metroworks compiler which was more advanced at the time.  The IAR compiler looks good but I have never used it.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastEditorUserId="1397" LastEditorDisplayName="" LastEditDate="2010-10-19T10:53:11.777" LastActivityDate="2010-10-19T10:53:11.777" CommentCount="1" />
  <row Id="5355" PostTypeId="1" AcceptedAnswerId="5360" CreationDate="2010-10-19T10:15:31.557" Score="6" ViewCount="382" Body="&lt;p&gt;On several circuit simulators I have seen capacitors with a &quot;Power&quot; figure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I have wondered how capacitive power supplies work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does an ideal, zero resistance, zero leakage, zero inductance capacitor dissipate any power?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See image:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/sLONK.png&quot; alt=&quot;cap power&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.falstad.com/circuit/#%24%201%205.0E-6%2010.20027730826997%2050%205.0%2043%0Av%20288%20192%20288%20272%200%201%2040.0%205.0%200.0%200.0%200.5%0Ar%20288%20192%20384%20192%200%20100.0%0Ac%20384%20192%20384%20272%200%201.0E-5%201.6020737594995769%0Aw%20288%20272%20384%20272%200%0Ag%20288%20272%20288%20288%200%0Ao%202%2064%200%2035%205.0%200.0125%200%20-1%0Ao%202%2064%201%2035%200.3125%209.765625E-5%201%20-1%0A&quot; rel=&quot;nofollow&quot;&gt;Link to simulation of this schematic&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1397" LastEditorDisplayName="" LastEditDate="2010-10-22T22:34:56.383" LastActivityDate="2010-10-22T22:34:56.383" Title="Does an ideal capacitor dissipate power?" Tags="&lt;capacitor&gt;&lt;simulation&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="5356" PostTypeId="2" ParentId="5355" CreationDate="2010-10-19T10:50:50.470" Score="8" ViewCount="" Body="&lt;p&gt;An ideal capacitor would not dissipate any power. Real capacitors dissipate a small amount of power whenever current flows through them, due to ohmic losses. Also, when operated under continuous AC there are dielectric losses, which are minor at power line frequencies but can get significant at higher frequencies, depending on the type of cap.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-10-19T16:26:50.607" LastActivityDate="2010-10-19T16:26:50.607" CommentCount="3" />
  <row Id="5357" PostTypeId="2" ParentId="4954" CreationDate="2010-10-19T11:12:27.840" Score="3" ViewCount="" Body="&lt;p&gt;We simply don't know enough from the question and comments (as yet). Internally a Spartan 3 family chip could probably do the edge detection, but reading the image sensor at that speed is more of an open question - it depends more on the sensor interface and board layout. Then there's the question of what to do with all the data - it's doable to just feed it out again, possibly using wider connections, but the FPGA itself certainly can't store it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately this question is turning into more of a discussion, which this site wasn't designed for. We keep having to dig to find the new comments. To give a verifiably correct answer, we would have to do half the design work - all the way to component selection and algorithm data flow. &lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-10-19T11:12:27.840" CommentCount="3" />
  <row Id="5358" PostTypeId="2" ParentId="4842" CreationDate="2010-10-19T11:27:58.967" Score="0" ViewCount="" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had the same problem with varying DC offset based on light level. I got around this by making the PIC code track the level and so the reference for the comparator would always be within the signal deflection range. It works well but now have another problem. I am trying to detect the vertical sync so I know when to switch a video multiplexer and stop any flicker or rolling. I can detect the vertical sync but cannot currently discriminate between even and odd fields. I am still getting a flicker as the two camera feeds and not genlocked. Does anyone know at what point I should switch the multiplexer, do I do it at the start of the odd field only? Or could the problem be due to the camera seeing different light levels and as they change the DC blocking cap need to charge/discharge to a different level? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&#xA;Jose&lt;/p&gt;&#xA;" LastActivityDate="2010-10-19T11:27:58.967" CommentCount="1" />
  <row Id="5359" PostTypeId="2" ParentId="5285" CreationDate="2010-10-19T11:59:04.103" Score="1" ViewCount="" Body="&lt;p&gt;Another point to consider with decoupling capacitors on op-amps is they need to go from rail to ground, not rail to rail.  For example an op amp with +/-5 V rails needs to capacitors one from each rail to ground.  This will ensure the op amp has properly decoupled power supplies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also need to have them on signal paths also, for example a small capacitor across the feedback resistor will help your op amp circuit transition from a simulator to a real PCB with out noise and oscillations.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-19T11:59:04.103" CommentCount="2" />
  <row Id="5360" PostTypeId="2" ParentId="5355" CreationDate="2010-10-19T12:15:16.017" Score="8" ViewCount="" Body="&lt;p&gt;No, they don't dissipate energy, but they do store it.  So energy can flow into a capacitor, and remain there, and then flow back out.  Since power is the rate at which energy is used or moved, the power will be non-zero whenever energy is moving.  But it's not being dissipated (converted into heat).  It's just being moved around and stored.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's important to remember the difference between instantaneous power and average power.  A 1 ohm resistor with 1 V&lt;sub&gt;RMS&lt;/sub&gt; AC across it will dissipate an &lt;em&gt;average&lt;/em&gt; power of &lt;a href=&quot;http://www.wolframalpha.com/input/?i=%281+V%29%5E2%2F1+ohm&quot; rel=&quot;nofollow&quot;&gt;1 W&lt;/a&gt;, for instance, but the instantaneous power will vary with the waveform:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Power_factor&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/d/db/Power_factor_1.svg/500px-Power_factor_1.svg.png&quot; alt=&quot;average vs instant power for a resistive load&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a reactive element (capacitor or inductor) as the load, the power will fluctuate between positive and negative as energy flows in and out, but the average will be zero:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Power_factor&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/2/23/Power_factor_0.svg/500px-Power_factor_0.svg.png&quot; alt=&quot;average vs instant power for an inductive (i think) load&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-19T15:31:10.657" LastActivityDate="2010-10-19T15:31:10.657" CommentCount="4" />
  <row Id="5361" PostTypeId="2" ParentId="5352" CreationDate="2010-10-19T12:50:35.460" Score="5" ViewCount="" Body="&lt;p&gt;If you were using PIC18 parts I would recommend C18 compiler from Microchip. It conforms much more closely to ANSI C than the CCS compiler. I'm not sure about the Hi-Tech compiler since I have not used it. As was said earlier if you really need to make compiler independent code you will need to use lots of pre-compiler directives. I'd recommend taking a look at some of the Microchip example programs that support multiple compilers to get an idea of how it is done.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-19T12:50:35.460" CommentCount="4" />
  <row Id="5362" PostTypeId="2" ParentId="4155" CreationDate="2010-10-19T15:03:58.253" Score="0" ViewCount="" Body="&lt;p&gt;I think a better formulation of this question is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can the schematic of an n-channel charlieplexed circuit be drawn as a finite, connected planar graph?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Euler's formula could probably be used in some way (it's a planar graph if vertices − edges + faces = 2), but you'd need a nice clean formula (well, maybe a messy one would work too) for determining the number of faces in the graph.&lt;/p&gt;&#xA;" OwnerUserId="1643" LastActivityDate="2010-10-19T15:03:58.253" />
  <row Id="5363" PostTypeId="2" ParentId="5352" CreationDate="2010-10-19T15:21:18.193" Score="3" ViewCount="" Body="&lt;p&gt;Take a look at &lt;a href=&quot;http://sdcc.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;SDCC&lt;/a&gt;. It supports many of the PIC16 and PIC18 devices. GCC supports PIC24 and dsPIC.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-19T15:21:18.193" CommentCount="1" />
  <row Id="5364" PostTypeId="2" ParentId="5336" CreationDate="2010-10-19T15:23:59.110" Score="5" ViewCount="" Body="&lt;p&gt;Watch &lt;a href=&quot;http://blog.makezine.com/archive/2009/03/make_presents_the_transistor.html&quot; rel=&quot;nofollow&quot;&gt;this cool video about transistors&lt;/a&gt;. It'll trick you into being interested about the alphabet soup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should really learn about the basic chemistry of p-type materials, n-type materials and doping. You can then visualize the potential differences and where the electrons are going to go without having to really memorize anything. Don't be lazy here. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then &lt;a href=&quot;http://en.wikipedia.org/wiki/P-n_junction&quot; rel=&quot;nofollow&quot;&gt;an article like this&lt;/a&gt; will fill in the gaps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Learn about the concepts behind a basic transistor/diode. Then all of the other acronyms will fall into place without any real effort on your part.&lt;/p&gt;&#xA;" OwnerUserId="1643" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2010-10-20T03:55:35.997" LastActivityDate="2010-10-20T03:55:35.997" />
  <row Id="5365" PostTypeId="1" AcceptedAnswerId="5366" CreationDate="2010-10-19T17:45:57.607" Score="4" ViewCount="254" Body="&lt;p&gt;I'm using the LM2734Z, a 3 MHz buck regulator. It's really fast which means it has a small inductor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the things I'm wondering is how important is the self-resonant frequency of the inductor? I'm using it to step 4.8V to 20V down to 3.3V ±5%.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found a 3.3µH 2A inductor (as recommended by the datasheet for 3.3V @ 1A, I'm rating the output to 400mA maximum) &quot;SDR0604-3R3ML.&quot; Its self-resonant frequency is 60 MHz, which seems to be well clear of 3 MHz, but it is a multiple and I'm wondering if harmonics come into it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if this case is okay, is there a rule of thumb for avoiding certain resonant frequencies (i.e. if they match?)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-19T23:32:44.817" Title="How important is self-resonant frequency for an inductor when used in a fast (~3MHz) buck SMPS?" Tags="&lt;buck&gt;&lt;smps&gt;&lt;inductor&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="5366" PostTypeId="2" ParentId="5365" CreationDate="2010-10-19T18:29:05.673" Score="6" ViewCount="" Body="&lt;p&gt;I wouldn't worry about it for 2 reasons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First it is a multiple but, 60Mhz is an even harmonic of 3Mhz.  The output of the regulator should be basically a square wave and square waves have content at their fundamental and only odd harmonics.  So 3, 9, 15, 21, 27, 33, 39, 45, 51, 57, 63.  Of course a non-perfect wave will have some even harmonic content but it should be well below any odd harmonics, if its a good square wave, it'll be in the noise floor.  If in question set up your scope to do an FFT on the regulator output and see what its output looks like at 60Mhz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, as the list above shows, you're at a very high harmonic at 60mhz.  The switching supply would have to be outputing a square wave with really fast rise/fall times to have much if any content up that high.  Usually only the first 3-6 odd harmonics are what you need to worry about with a square wave, depending on rise/fall times.  That would work out to a theoretical rule of thumb that as long as the SRF is 5-10 times your switching speed you should be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Decided to model this so some degree...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Test Circuit, I used the parameters from the inductor you linked for the inductance, stray capacitance, ESR and shunt resistance.  Shunt resistance changes based on frequency and is defined in Eqn.  I modeled a generic 10uF ceramic cap for the output filter cap including ESR and ESL and arbitrarily chose 1k for the load.  Doing an AC sweep with a 1V source from 0 to 250Mhz then later to 1Ghz to peek at the frequency response.  The output resistance of the switcher is a shot in the dark but probably about right.&#xA;&lt;img src=&quot;http://i.imgur.com/m5V8N.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here we are doing a sweep without the output filter cap attached to see the SRF of the inductor model, as expected at 60Mhz.&#xA;&lt;img src=&quot;http://i.imgur.com/9EWMo.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here we sweep with the cap in place:&#xA;&lt;img src=&quot;http://i.imgur.com/PVcX0.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This one is actually interesting.  Whats happening is that even though the inductor loses its filtering properties at SRF there is still an RC filter formed by Rout,the inductors resistance and the output cap.  This filter is capable of blocking the high frequencies somewhat, which is why we don't see as sharp a change is we saw with the inductor only.  However at these frequencies the ESL of the cap is really starting to come into play so we see a rising output level as frequency increases.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally lets see how it increases:&#xA;&lt;img src=&quot;http://i.imgur.com/fdGlU.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At 1 ghz the inductor is completely dominated by the stray capacitance and the filter cap in dominated by the ESL, at 10Ghz (not shown) it levels right off.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course there are a bunch of stray inductances,capacitances and variations (especially at the really high frequencies) not included in this simple model but maybe it will aid as a pictorial representation of whats happening.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most interesting thing that came out of this for me is that SRF isn't a brick wall.  The inherent RC filter can mitigate some of the effect of hitting the SRF.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT2: One more edit, mostly because i'm using this as an opportunity to play with Qucs circuit sim for the first time.  Cool program.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This shows 2 things.  First its displaying the frequency response of the circuit in magnitude (in dB, Blue) and phase (red) this shows more clearly where the component's parasitic capacitance / inductance takes over.  It also shows a secondary sweep of the ESL of the output capacitor showing how important it is to minimize this through component selection and PCB layout.  Its sweep from 1nH to 101nH in steps of 10nH.  You can see if the total inductance on the PCB gets very high you lose almost all of your filtering capability.  This will result in EMI issues and/or noise problems.&#xA;&lt;img src=&quot;http://i.imgur.com/SBfAf.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-19T23:32:44.817" LastActivityDate="2010-10-19T23:32:44.817" CommentCount="4" />
  <row Id="5367" PostTypeId="2" ParentId="5336" CreationDate="2010-10-19T18:31:29.420" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/NPN_transistor#NPN&quot; rel=&quot;nofollow&quot;&gt;NPN&lt;/a&gt; (and PNP) implies &lt;a href=&quot;http://en.wikipedia.org/wiki/Bipolar_junction_transistor&quot; rel=&quot;nofollow&quot;&gt;BJT&lt;/a&gt;s. No, you do not need to understand the bipolar transistor to great depth (is an advantage, of course). Just know and use standard circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Easy to follow explanations and calculations for finding resistor values (or checking that the 1 kohm resistor is OK) for the switch you have are in &quot;&lt;a href=&quot;http://webpages.ursinus.edu/lriley/ref/circuits/node4.html#SECTION00042000000000000000&quot; rel=&quot;nofollow&quot;&gt;Transistor Switch&lt;/a&gt;&quot;. Standard small signal amplifier circuits are also listed on the same page.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/JVAN2.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A more detailed explanation can be found in &quot;&lt;a href=&quot;http://www.zen22142.zen.co.uk/Design/bjtsw.htm&quot; rel=&quot;nofollow&quot;&gt;Transistor as a Switch&lt;/a&gt;&quot;.&lt;/p&gt;&#xA;" OwnerUserId="804" LastActivityDate="2010-10-19T18:31:29.420" />
  <row Id="5368" PostTypeId="2" ParentId="3366" CreationDate="2010-10-19T19:31:43.853" Score="1" ViewCount="" Body="&lt;p&gt;Since you already a software engineer, you will probably be getting into embedded firmware/hardware pretty quick.  SparkFun has a number of &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorials.php&quot; rel=&quot;nofollow&quot;&gt;tutorials&lt;/a&gt; on embedded electronics, and also a lot of &lt;a href=&quot;http://www.sparkfun.com/commerce/categories.php?c=31&quot; rel=&quot;nofollow&quot;&gt;robotics&lt;/a&gt; stuff.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-19T19:31:43.853" />
  <row Id="5369" PostTypeId="1" AcceptedAnswerId="5383" CreationDate="2010-10-19T19:48:42.680" Score="7" ViewCount="322" Body="&lt;p&gt;This zero ohm resistor,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.farnell.com/multicomp/mc0603wg00000t5e-tr/resistor-0603-0-063w-0r/dp/1692453?Ntt=MC+0.063W+0603+1%25+0R&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/multicomp/mc0603wg00000t5e-tr/resistor-0603-0-063w-0r/dp/1692453?Ntt=MC+0.063W+0603+1%25+0R&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;has a tolerance of ±1%.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well it would only be +1% at best because you can't have a negative resistance* but still 1% of zero is still zero?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Shouldn't it be something like zero ohms + 0.001R?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*&lt;em&gt;except in very special cases with certain devices but never over the full operating range.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-20T00:13:48.273" Title="Zero ohm resistor tolerance??" Tags="&lt;resistor&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="5370" PostTypeId="1" AcceptedAnswerId="5372" CreationDate="2010-10-19T19:58:44.420" Score="3" ViewCount="101" Body="&lt;p&gt;I'm using a TL431B (±0.5%) shunt regulator to get 3V ±1% (max.) from a 3.3V ±5% supply, so from 3.135V to 3.465V. The 3.3V supply is a switcher, so has a decent amount of high frequency (~3 MHz) noise on it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is related to my previous question;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/5213/does-the-tl431-have-a-dropout-voltage-per-se&quot;&gt;http://electronics.stackexchange.com/questions/5213/does-the-tl431-have-a-dropout-voltage-per-se&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In fact the circuit configuration is very similar but I adjusted the values of the resistors, so I'll use the same diagram drawn in my TomCAD style:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;        560R 5%&#xA;+3.3V-+-/\/\/\---+----------+-------+-- 3V out&#xA;      |          |          |       |&#xA;     --- 100n    /          |      --- 4.7u&#xA;     --- 16V     \ 6.34k    |      --- 6.3V&#xA;      |          / 0.1%  ___|__|    |&#xA;     ---         |       | / \     ---&#xA;      -          +--------/___\     -&#xA;                 |          |&#xA;                 /          |&#xA;                 \ 31.6k    |&#xA;                 / 0.1%     |&#xA;                 |          |&#xA;                ---        ---&#xA;                 -          -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Two questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Will it work?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;What is the accuracy given the precision ±0.1% resistors and 2.495V ±0.5% reference? Is it the sum, so ±0.7%, or something complicated?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-19T21:51:32.263" Title="TL431, take two" Tags="&lt;tl431&gt;" AnswerCount="1" />
  <row Id="5371" PostTypeId="2" ParentId="5369" CreationDate="2010-10-19T20:13:20.090" Score="8" ViewCount="" Body="&lt;p&gt;Yeah, that doesn't make sense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Zero-ohm_link&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Zero-ohm_link&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The resistance is only approximately zero; only a maximum (typically 10–50 mΩ) is specified. Thus, a fractional tolerance (as a percentage of the zero-ohm ideal value) would be infinite and is not specified.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-19T20:13:20.090" CommentCount="2" />
  <row Id="5372" PostTypeId="2" ParentId="5370" CreationDate="2010-10-19T21:17:52.483" Score="2" ViewCount="" Body="&lt;p&gt;It will work, but it will not be very stiff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(3.135V - 3V) / 560R gives 241 microamps. If the load is higher than that, the voltage drop across the 560 ohm resistor will lower the input voltage to below the setpoint you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Typically you should allow the 431 to eat 1 mA to keep all of the datasheet assumptions in check. You should go with a lower series resistor - 51R allows 2.65mA at minimum input. The 431 can safely eat a few milliamps so don't worry about power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A quick analysis shows the lowest voltage = 2.980V, the highest 3.012V (nominal 2.996V) so we're looking at +/- 0.53%. Worst-case setpoints are when the two resistors are at opposite ends of the tolerance spectrum (one large, one small).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2010-10-19T21:51:32.263" LastActivityDate="2010-10-19T21:51:32.263" CommentCount="2" />
  <row Id="5373" PostTypeId="1" AcceptedAnswerId="5381" CreationDate="2010-10-19T21:18:19.457" Score="4" ViewCount="255" Body="&lt;p&gt;I'm looking for a cheap source of broken/outdated TQFP-44 and SO-28 ICs or packages which I can test my soldering skills with. The chips I'm using are £3 each and this is money I'd rather not throw away if I damage them. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions will be appreciated! Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1397" LastEditorDisplayName="" LastEditDate="2010-10-22T22:42:02.000" LastActivityDate="2010-10-22T22:42:02.000" Title="Cheapest TQFP-44's &amp; SO-28's to practice SMD soldering?" Tags="&lt;soldering&gt;&lt;surface-mount&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="5374" PostTypeId="1" AcceptedAnswerId="5376" CreationDate="2010-10-19T21:28:17.263" Score="3" ViewCount="204" Body="&lt;p&gt;I'm considering doing DIY SMT Reflow for production of my Super OSD project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An overview of the component count:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Resistors: ~50 x 0603; precision 0.1% resistors as well as 1% and 5% components&lt;/li&gt;&#xA;&lt;li&gt;Capacitors: 17 x 0603, 2 x 0805, 1 x 1206 (all ceramics), 2 x EIA-3216 (tantalums.)&lt;/li&gt;&#xA;&lt;li&gt;Inductors: 1 SDR-0604 package&lt;/li&gt;&#xA;&lt;li&gt;Chips: SOIC-8 (EEPROM), SOIC-28, TQFP-44, some SOT-23 (temp sensor + TL431.)&lt;/li&gt;&#xA;&lt;li&gt;Transistors: 3 x SOT-23 (2 x N-ch mosfet, 1 x NPN)&lt;/li&gt;&#xA;&lt;li&gt;Diodes: 2 x SOT-23, 2 x SOD-323&lt;/li&gt;&#xA;&lt;li&gt;Misc: polyfuse 0805 x 1, LED 0603 x 1&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As can be seen this going to be a monster to solder manually so I was thinking of doing DIY toaster oven reflow. Would this be suitable? Are there any pitfalls I need to be aware of?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise I'm going to have to solder them up myself but I see it being a real problem with almost 80 tiny components per board.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-20T07:41:05.890" Title="Reflow at home or solder manually?" Tags="&lt;soldering&gt;&lt;surface-mount&gt;&lt;reflow&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="5375" PostTypeId="2" ParentId="5369" CreationDate="2010-10-19T21:42:02.347" Score="5" ViewCount="" Body="&lt;p&gt;Apparently someone got carried away and thought that just because it looks like a resistor, it should have a tolerance like one. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, it's really just a resistor shaped piece of wire, so the only thing that would make much sense would be to spec 'not more than X amount of resistance', where X would presumably be a few milli-ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it was absolutely necessary to state it as a tolerance, it wouldn't be incorrect to say X/2 +/- 50%, but who has ever heard of a 50% tolerance part?&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-19T21:42:02.347" CommentCount="3" />
  <row Id="5376" PostTypeId="2" ParentId="5374" CreationDate="2010-10-19T22:13:51.857" Score="5" ViewCount="" Body="&lt;p&gt;If you can get hold of a dissecting scope and some decent tweezers, you could probably solder all those parts in about 2 hours. I've done a similar board with around 125 components in about 3 hours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my setup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/UcBwU.jpg&quot; alt=&quot;microscope on dining room table&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This isn't to say that you shouldn't use an oven-- I haven't tried that; it might be better. Seems a little bit like all your eggs in one basket, but I guess you could always rework parts in either case.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-19T22:13:51.857" CommentCount="7" />
  <row Id="5377" PostTypeId="2" ParentId="5374" CreationDate="2010-10-19T22:37:16.750" Score="0" ViewCount="" Body="&lt;p&gt;You could always buy this...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.reflow-kit.com/rkuk/index.html?PHPSESSID=d55897733554ef27e3d1f29bff7727cc&quot; rel=&quot;nofollow&quot;&gt;http://www.reflow-kit.com/rkuk/index.html?PHPSESSID=d55897733554ef27e3d1f29bff7727cc&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-=mike=-&lt;/p&gt;&#xA;" LastActivityDate="2010-10-19T22:37:16.750" />
  <row Id="5378" PostTypeId="2" ParentId="5373" CreationDate="2010-10-19T23:05:20.540" Score="3" ViewCount="" Body="&lt;p&gt;Sparkfun had a reel of &lt;a href=&quot;http://www.sparkfun.com/commerce/news.php?id=350&quot; rel=&quot;nofollow&quot;&gt;fake ATmega328s&lt;/a&gt; which would have been perfect for this.&#xA;Sadly, they're now seem to be sold out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9831&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9831&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It might be worth contacting them to see if they have any more...&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-19T23:05:20.540" CommentCount="1" />
  <row Id="5379" PostTypeId="2" ParentId="5374" CreationDate="2010-10-19T23:13:44.277" Score="1" ViewCount="" Body="&lt;p&gt;Related question: &lt;a href=&quot;http://electronics.stackexchange.com/questions/1184/diy-smt-reflow-toaster-oven-skillet-or&quot;&gt;http://electronics.stackexchange.com/questions/1184/diy-smt-reflow-toaster-oven-skillet-or&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-19T23:13:44.277" />
  <row Id="5380" PostTypeId="1" AcceptedAnswerId="5395" CreationDate="2010-10-19T23:22:22.547" Score="4" ViewCount="159" Body="&lt;p&gt;As a simple and cheap way of protecting my MCU against higher than 3.3V logic inputs, can I use for low speed data transfers some resistors on the data lines? In theory, these should act in tandem with the pin diodes inside the MCU to clamp the voltage. But will it work in practice? Logic shifter chips aren't an option due to space and cost constraints.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-10-20T12:58:19.493" LastActivityDate="2010-10-20T12:58:19.493" Title="MCU clamping diodes" Tags="&lt;microcontroller&gt;&lt;diode&gt;&lt;microcontroller&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="5381" PostTypeId="2" ParentId="5373" CreationDate="2010-10-19T23:52:49.470" Score="5" ViewCount="" Body="&lt;p&gt;Unless you're soldering with a blow torch I highly doubt you will damage a SO-28 as long as you have some soldering experience.  Just tag 2 corners, use plenty of no-clean flux both on the board before you place and on the rest of the pins after you tag and you really can't go wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The TQFP is pretty much the same process.  Don't try to solder a pin at a time.  Tag opposing corners (takes a bit more care to get all the pins lined up).  Apply plenty of flux, again to the board before you place and then to the pins after its tagged and soldering the sides only takes a couple seconds.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In both cases don't try to be cheeky and solder 1 pin at a time, if you've fluxed properly you can use a chisel tip the size of the entire side of the IC and solder without bridging while only heating the IC for a few seconds, although i'd recommend starting with a smaller chisel.  The only special thing you need is thin solder to avoid getting way too much on there, 0.4mm is what i use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really doubt you'll kill many, if any, ICs learning unless you try to solder with no flux and go 1 pin at a time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll save way more IC's by using decent soldering equipment than anything else. &lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-20T00:06:25.577" LastActivityDate="2010-10-20T00:06:25.577" CommentCount="3" />
  <row Id="5382" PostTypeId="2" ParentId="5380" CreationDate="2010-10-20T00:09:04.370" Score="5" ViewCount="" Body="&lt;p&gt;Sparkfun have a good summary of &lt;a href=&quot;http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=65&quot; rel=&quot;nofollow&quot;&gt;ways to connect 5V and 3.3V devices&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As well as using diodes, you could consider MOSFETs or inline resistors.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-20T00:09:04.370" />
  <row Id="5383" PostTypeId="2" ParentId="5369" CreationDate="2010-10-20T00:13:48.273" Score="8" ViewCount="" Body="&lt;p&gt;If you look at a &quot;proper&quot; data sheet (example: &lt;a href=&quot;http://www.yageo.com/documents/recent/PYu-RC0603_51_RoHS_L_4.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.yageo.com/documents/recent/PYu-RC0603_51_RoHS_L_4.pdf&lt;/a&gt;) you'll usually find that the zero ohm resistor is defined separately using something like &amp;lt; 0.05R.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this case, you're looking at a more or less automatically generated set of data which is probably more relevant to the other resistors in the range.  Multicomp in this case refers to multiple sources so the parts could be coming from anywhere; the data in this case is fairly general and is most likely the lowest common denominator for a variety of alternative devices.&lt;/p&gt;&#xA;" OwnerUserId="820" LastActivityDate="2010-10-20T00:13:48.273" />
  <row Id="5384" PostTypeId="2" ParentId="3366" CreationDate="2010-10-20T01:42:08.160" Score="0" ViewCount="" Body="&lt;p&gt;I found a book called Electrical Engineering 101 to be useful for rule-of-thumb and general engineering design type information. I'd only recommend it because it's reasonably cheap - &lt;a href=&quot;http://books.google.com.au/books?id=XdFP6LYoB4sC&quot; rel=&quot;nofollow&quot;&gt;http://books.google.com.au/books?id=XdFP6LYoB4sC&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise, my EE course recommended &lt;a href=&quot;http://www.prenhall.com/hambley/&quot; rel=&quot;nofollow&quot;&gt;Hambley's Electrical Engineering: Principles and Applications&lt;/a&gt;. It's fairly expensive but it's pretty well in-depth and has had sufficient content to cover about 40 - 50% of the EE subjects that I've completed in my 3 years to date. I'd link you directly to this book on google books but apparently I can't post more than one hyperlink - so the book id to locate it on google books is MtpIHCEVKacC :]&lt;/p&gt;&#xA;" OwnerUserId="1647" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-25T10:12:49.240" LastActivityDate="2010-11-25T10:12:49.240" />
  <row Id="5385" PostTypeId="2" ParentId="5374" CreationDate="2010-10-20T03:05:45.613" Score="1" ViewCount="" Body="&lt;p&gt;How many do you intend to build? Have you considered getting a quote from some contract manufactures? If you are building enough of them, a robot is going to make it cheaper than placing by hand. Although you will have up front tooling to produce a solder paste stencil and engineering or setup costs to consider.&lt;/p&gt;&#xA;" OwnerUserId="328" LastEditorUserId="328" LastEditorDisplayName="" LastEditDate="2010-10-20T06:45:48.150" LastActivityDate="2010-10-20T06:45:48.150" CommentCount="3" />
  <row Id="5386" PostTypeId="1" AcceptedAnswerId="5392" CreationDate="2010-10-20T03:07:52.150" Score="6" ViewCount="440" Body="&lt;p&gt;One of my projects would greatly benefit from being able to run a program that isn't stored in the microcontroller (but is instead stored in a SD card).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I'm looking for a device that will allow me to load the code from the SD card into RAM and then execute the code from RAM. Currently, I only have the programmer that comes with the PicKit2, so I'd prefer to stay with PICs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know which, if any, PICs can do this? If no PICs are capable of this, then what are some different micro controllers that would work for this? Preferably ones that are available in a breadboard compatible package.&lt;/p&gt;&#xA;" OwnerUserId="790" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-20T11:01:05.717" LastActivityDate="2011-02-23T21:04:43.320" Title="Execute instructions from RAM in a hobbyist-friendy microcontroller" Tags="&lt;microcontroller&gt;&lt;pic&gt;" AnswerCount="9" CommentCount="3" FavoriteCount="2" />
  <row Id="5387" PostTypeId="2" ParentId="5306" CreationDate="2010-10-20T04:05:09.207" Score="2" ViewCount="" Body="&lt;p&gt;Here's a &lt;a href=&quot;http://www.mdfly.com/index.php?main_page=product_info&amp;amp;cPath=40_85&amp;amp;products_id=352&amp;amp;zenid=r7dfrifb235jcj1lsrhbmvqi85&quot; rel=&quot;nofollow&quot;&gt;cheap OLED display&lt;/a&gt;, but it's only 1&quot;. Here's &lt;a href=&quot;http://www.goldmine-elec-products.com/prodinfo.asp?number=G16239&quot; rel=&quot;nofollow&quot;&gt;a cheap LCD&lt;/a&gt;, it's about 6&quot;, but low resolution. &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.18438&quot; rel=&quot;nofollow&quot;&gt;Here's a higher resolution cheap one&lt;/a&gt;, but it's 3.8&quot;. You can get &lt;a href=&quot;http://cgi.ebay.com/UXGA-LCD-Replacement-screen-15-LTM15c162-1600x1200-HiR-/330478085422?pt=LH_DefaultDomain_0&amp;amp;hash=item4cf207652e&quot; rel=&quot;nofollow&quot;&gt;15&quot; LCD panels for pretty cheap&lt;/a&gt; as well -- but you will need a pretty powerful processor to interface with it. Most likely either a FPGA or a high end ARM board with a built in LCD driver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Give us more exact details of what you want, and we can find something that meets your interests better.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-10-20T04:05:09.207" />
  <row Id="5388" PostTypeId="2" ParentId="5302" CreationDate="2010-10-20T06:28:52.290" Score="0" ViewCount="" Body="&lt;p&gt;Well this is for the AT90Usb1287, a ATMega, but the basic button stuff should be more or less the same. Just change the IO names. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.avrfreaks.net/wiki/index.php/Documentation%3aTutorials_gcc_AT90UsbKey#Push_the_Button&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/wiki/index.php/Documentation:Tutorials_gcc_AT90UsbKey#Push_the_Button&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="689" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2010-10-20T06:35:36.090" LastActivityDate="2010-10-20T06:35:36.090" />
  <row Id="5389" PostTypeId="2" ParentId="5386" CreationDate="2010-10-20T06:55:45.447" Score="3" ViewCount="" Body="&lt;p&gt;None of the low and mid range PIC can execute from RAM because of their memory architecture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ARM based CPU should execute from RAM. Although they tend to be in smd packages, there are quite a few 'DIP' size module that have the microcontroller already loaded. Have a look at the &lt;a href=&quot;http://mbed.org/&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt; or &lt;a href=&quot;http://ics.nxp.com/lpcxpresso/&quot; rel=&quot;nofollow&quot;&gt;LPCXpresso&lt;/a&gt; for example. These both come with either a bootloader or, in the case of the LPCXpresso, a debug interface along with free compilers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you would prefer to stay with simple 8 bit micros, perhaps consider something from the freescale HCS08 Family. These can execute from RAM and there is a code limited version of the  codewarrior IDE and C compiler available for free.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm fairly sure the MPS430 should also be able to do this, but I've not ever done it myself.&lt;/p&gt;&#xA;" OwnerUserId="328" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-20T19:07:22.337" LastActivityDate="2010-10-20T19:07:22.337" CommentCount="1" />
  <row Id="5390" PostTypeId="2" ParentId="5374" CreationDate="2010-10-20T07:41:05.890" Score="1" ViewCount="" Body="&lt;p&gt;At my previous work place, the guys would kit all the SMT components into little trays and then do small batches using solder paste and place all the passive resistors and capacitors, then using a handheld hot air soldering iron go over each component briefly until it &quot;wiggled&quot; into place and the solder reflows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next phase was for the semiconductors (transistors and mosfets and the like) followed by integrated circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Final stage was handsoldering the larger connectors and through hole components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Spending the time to kit and prepare good assembly drawings (hand colour coded to match the bins of the parts) it meant placing all the passives went quickly as did the soldering.  This method will help speed up small one man batch production, at the expense of setup time.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-20T07:41:05.890" />
  <row Id="5391" PostTypeId="2" ParentId="5386" CreationDate="2010-10-20T07:45:55.460" Score="3" ViewCount="" Body="&lt;p&gt;As has already been said, PICs (other than the PIC32) cannot do this.  You will probably have to go to the larger processors in any family or to a processor with an external memory bus as most microcontrollers have very limited RAM resources.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The MSP430 processors can run code from their RAM space but you will need something like the F5438 with 16k RAM space - running code in 128 bytes is not really an option!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a processor has an external bus then you can put RAM into the code space.  You may have to add some extra logic to map the RAM into two memory regions if the processor architecture does not allow data to be written into execution memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have run code from RAM in an 8051 based system but that meant that the RAM had to be mapped into the EXTERN memory space for programming and then back into the CODE space for execution.  The loader/monitor program handled the memory bank switching and loading.  Please don't ask for the code - I did this about 30 years ago and it is long since lost (and written in PL/M-51)&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-10-20T07:45:55.460" />
  <row Id="5392" PostTypeId="2" ParentId="5386" CreationDate="2010-10-20T10:34:48.413" Score="2" ViewCount="" Body="&lt;p&gt;There are a few PIC's that allow you to add external program memory. I've never done this but Application Notes &lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/00869b.pdf&quot; rel=&quot;nofollow&quot;&gt;AN869&lt;/a&gt; and &lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/00778a.pdf&quot; rel=&quot;nofollow&quot;&gt;AN778&lt;/a&gt; has more information of how to implement the external memory.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-20T10:34:48.413" />
  <row Id="5393" PostTypeId="2" ParentId="5386" CreationDate="2010-10-20T11:00:03.130" Score="7" ViewCount="" Body="&lt;p&gt;Another option to consider is using an interpreted language for your programs stored on the SD card. This way, the processor isn't executing the machine code read from the card, it's just treating it as data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This approach gives you flexibility at the cost of speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are plenty of options to choose from:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/3423/survey-of-high-level-language-interpreters-compilers-for-microcontrollers&quot;&gt;http://electronics.stackexchange.com/questions/3423/survey-of-high-level-language-interpreters-compilers-for-microcontrollers&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-20T11:00:03.130" CommentCount="1" />
  <row Id="5394" PostTypeId="2" ParentId="5031" CreationDate="2010-10-20T11:04:59.670" Score="0" ViewCount="" Body="&lt;p&gt;I switched my LPT to Normal mode (from ECP + EPP) in BIOS and now everything works.&lt;/p&gt;&#xA;" OwnerUserId="1528" LastActivityDate="2010-10-20T11:04:59.670" CommentCount="1" />
  <row Id="5395" PostTypeId="2" ParentId="5380" CreationDate="2010-10-20T11:10:08.463" Score="2" ViewCount="" Body="&lt;p&gt;If the pins have clamp diodes, you need only a series resistor to limit the current. You can see in the application note &lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/00521c.pdf&quot; rel=&quot;nofollow&quot;&gt;AN521&lt;/a&gt; from microchip that it connect the pin of the microcontroller directly in the AC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used a voltage divider to connect a PIC to a GPRS module with a speed higher than 19,200 and had no problem.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-20T11:13:08.120" LastActivityDate="2010-10-20T11:13:08.120" />
  <row Id="5396" PostTypeId="2" ParentId="5302" CreationDate="2010-10-20T11:10:58.697" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;https://www.mainframe.cx/~ckuethe/avr-c-tutorial/&quot; rel=&quot;nofollow&quot;&gt;https://www.mainframe.cx/~ckuethe/avr-c-tutorial/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;https://www.mainframe.cx/~ckuethe/avr-c-tutorial/#digital-in&quot; rel=&quot;nofollow&quot;&gt;https://www.mainframe.cx/~ckuethe/avr-c-tutorial/#digital-in&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;avr/io.h&amp;gt;&#xA;&#xA;/*&#xA; * Assumptions:&#xA; *  - LED connected to PORTB.2&#xA; *  - Switch connected to PORTD.2&#xA; */&#xA;&#xA;int main (void)&#xA;{&#xA;    /* set PORTB for output*/&#xA;    DDRB = 0xFF;&#xA;    /* set PORTD for input*/&#xA;    DDRD &amp;amp;= 0xFB;&#xA;    PORTD |= 0x04;&#xA;&#xA;    while (1) {&#xA;        if (PIND &amp;amp; 0x04)&#xA;            PORTB &amp;amp;= ~0x20;&#xA;        else&#xA;            PORTB |= 0x20;&#xA;    }&#xA;    return 0;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-20T11:10:58.697" />
  <row Id="5397" PostTypeId="2" ParentId="5386" CreationDate="2010-10-20T12:39:41.560" Score="1" ViewCount="" Body="&lt;p&gt;I remember reading about a bootloader for AVRs that would re-flash the chip with a .hex file (presumably) from an SD card.  I can't find the original source, but &lt;a href=&quot;http://www.google.com/search?client=safari&amp;amp;rls=en&amp;amp;q=avr+sd+card+bootloader&amp;amp;ie=UTF-8&amp;amp;oe=UTF-8&quot; rel=&quot;nofollow&quot;&gt;this Google search&lt;/a&gt; turns up a couple of interesting hits.  Yes, I know this is AVR and not PIC, but you might find it useful if the PIC thing doesn't work out.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-10-20T12:39:41.560" />
  <row Id="5398" PostTypeId="2" ParentId="2004" CreationDate="2010-10-20T12:41:21.137" Score="2" ViewCount="" Body="&lt;p&gt;Hi Natan. Here in Brazil we have a web site of a man that has more than 2600 articles about electronics, and everyday has a new article. His name is Newton C. Braga and his site is this: &lt;a href=&quot;http://www.newtoncbraga.com.br&quot; rel=&quot;nofollow&quot;&gt;http://www.newtoncbraga.com.br&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's in Portuguese.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-20T12:41:21.137" />
  <row Id="5399" PostTypeId="1" AcceptedAnswerId="5400" CreationDate="2010-10-20T14:14:55.043" Score="3" ViewCount="115" Body="&lt;p&gt;Is it possible to place components on both sides of the board if I'm doing DIY toaster-oven style reflow soldering? I would think that doing the reflow twice (for the other side) might overheat the components already soldered on.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-20T14:40:28.950" Title="Components on both sides of the board with reflow" Tags="&lt;soldering&gt;&lt;reflow&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="2" />
  <row Id="5400" PostTypeId="2" ParentId="5399" CreationDate="2010-10-20T14:40:28.950" Score="2" ViewCount="" Body="&lt;p&gt;I have seen this done with a two step method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most professional way I have been taken part in involved all of the components have a bit of glue sticking them down(technically epoxy). The oven then would heat the top side to the correct temp, then the board was flipped and the board had the top heated. This was being used by a firm that created products exclusively for the military and I believe had strict requirements on reliability and I believe their oven method was very reliable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have also seen methods where people use high temp epoxy and then just bake the whole thing at once. You need things lined up carefully because the epoxy will stop things from moving around and normally during reflow parts move into their proper position on the board almost automatically.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-20T14:40:28.950" CommentCount="5" />
  <row Id="5401" PostTypeId="2" ParentId="5144" CreationDate="2010-10-20T15:22:09.203" Score="1" ViewCount="" Body="&lt;p&gt;Well, the solution to my problem turned out to be both very simple and very unexpected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I decided to buy a real stand for my soldering iron and the one I got came with it's own sponge. It did a great job cleaning the tip and the tip looks like brand new now! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sponge itself as a spare part is just about 2.5€, so the moral of my story is don't try to save money on the sponge! Buy a high quality sponge and save yourself lots of headache!&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-10-20T15:37:57.620" LastActivityDate="2010-10-20T15:37:57.620" />
  <row Id="5402" PostTypeId="2" ParentId="3382" CreationDate="2010-10-20T16:10:28.380" Score="3" ViewCount="" Body="&lt;p&gt;I have on my workbench and around my room:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Digitising oscilloscope. Essential for debugging circuits, especially as I work on video a lot. I picked up mine for £150 a few years back. &lt;/li&gt;&#xA;&lt;li&gt;Personal laptop (my main computer.)&lt;/li&gt;&#xA;&lt;li&gt;Desktop computer+LCD (also a stable 12V, 5V &amp;amp; 3.3V power supply and a video monitor.)&lt;/li&gt;&#xA;&lt;li&gt;Cheap multimeter (about £20.)&lt;/li&gt;&#xA;&lt;li&gt;Temperature controlled soldering iron.&lt;/li&gt;&#xA;&lt;li&gt;Cheap soldering iron (backup.)&lt;/li&gt;&#xA;&lt;li&gt;Solder, solder sucker and wick.&lt;/li&gt;&#xA;&lt;li&gt;Breadboards x 10.&lt;/li&gt;&#xA;&lt;li&gt;Various stripboards and completed projects.&lt;/li&gt;&#xA;&lt;li&gt;PICkit 2 + demo board, AVR programmer and Launchpad (MSP 430) board.&lt;/li&gt;&#xA;&lt;li&gt;Components (all E12 resistors up to 1M ohm, various electrolytics and various ceramics.)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;At a minimum I would recommend a multimeter, scope and power supply. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-20T16:10:28.380" CommunityOwnedDate="2010-10-20T16:10:28.380" CommentCount="2" />
  <row Id="5403" PostTypeId="1" AcceptedAnswerId="5406" CreationDate="2010-10-20T16:54:23.273" Score="10" ViewCount="529" Body="&lt;p&gt;Is there a standard for the sizes of PCB traces?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That is are some 25 mil and others 10 mil or is can you choose your own?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I plan to run 400mA through some thicker traces, but less than 30mA for all other traces. About what size would I need?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1397" LastEditorDisplayName="" LastEditDate="2010-10-22T22:37:34.870" LastActivityDate="2011-04-20T10:58:24.047" Title="Standard PCB trace widths?" Tags="&lt;pcb&gt;&lt;layout&gt;" AnswerCount="2" FavoriteCount="6" />
  <row Id="5404" PostTypeId="1" AcceptedAnswerId="5460" CreationDate="2010-10-20T16:56:01.557" Score="7" ViewCount="340" Body="&lt;p&gt;What is the input impedance of a typical MCU ADC? In this case I'm working with a PIC24FJ64GA004. I don't need high speed sampling - a maximum of 100 samples per second.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wish to connect a resistive divider with a 100k resistor and a 10k resistor, so the impedance should be higher than 1M or else the impedance will start skewing the readings.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1397" LastEditorDisplayName="" LastEditDate="2010-10-22T22:35:43.797" LastActivityDate="2010-10-22T22:35:43.797" Title="ADC input impedance on MCUs" Tags="&lt;microcontroller&gt;&lt;adc&gt;&lt;impedance&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="2" />
  <row Id="5405" PostTypeId="2" ParentId="5403" CreationDate="2010-10-20T17:10:23.123" Score="10" ViewCount="" Body="&lt;p&gt;You can use this nomograph to determine the width according with current:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2doGi.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Using the nomograph&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Locate the width of the conductor on the left side of the bottom chart.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Move right horizontally, until you intersect the line of the appropriate conductor thickness. Move down vertically to the bottom of the chart to determine the cross-sectional area of the conductor.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Move up vertically, until you intersect the line of the appropriate allowable temperature rise. This is the increase in temperature of the current-carrying conductor. Conductor temperature should not exceed 105°C. For example, if the ambient temperature might reach 80°C, the temperature rise above ambient of the conductor should be less than 25°C (105°C - 80°C). In this case use the 20°C curve.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Move left horizontally, to the left side if the chart to determine the maximum allowable current.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Reverse the order of these steps to calculate required conductor width for a given current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More informations at this site: &lt;a href=&quot;http://www.minco.com/products/flex.aspx?id=1124&quot; rel=&quot;nofollow&quot;&gt;http://www.minco.com/products/flex.aspx?id=1124&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This graph is from IPC, but I cannot find it there.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-20T10:58:24.047" LastActivityDate="2011-04-20T10:58:24.047" CommentCount="2" />
  <row Id="5406" PostTypeId="2" ParentId="5403" CreationDate="2010-10-20T17:25:36.310" Score="12" ViewCount="" Body="&lt;p&gt;Your traces can be any size you want as long as you stay within the minimum feature size and spacing that your PCB fab supports for your particular price point. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;These will cover basic needs, the trace width one is a best fit calculation to the chart Engen posted:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://circuitcalculator.com/wordpress/?p=25/&quot; rel=&quot;nofollow&quot;&gt;PCB Trace Width Calculator&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://circuitcalculator.com/wordpress/2006/03/12/pcb-via-calculator/&quot; rel=&quot;nofollow&quot;&gt;PCB Via Calculator&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Neither of those cover controlled impedance calculations, if you need those look elsewhere.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-20T20:24:06.880" LastActivityDate="2010-10-20T20:24:06.880" CommentCount="1" />
  <row Id="5407" PostTypeId="2" ParentId="5404" CreationDate="2010-10-20T17:27:01.923" Score="5" ViewCount="" Body="&lt;p&gt;Take a look at page 198 of the &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/39881D.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;.  There's 6-11pF at the pin and 4.4pF on the holding cap.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-10-20T17:27:01.923" CommentCount="3" />
  <row Id="5408" PostTypeId="2" ParentId="5386" CreationDate="2010-10-20T18:09:01.390" Score="2" ViewCount="" Body="&lt;p&gt;As other posters have noted, you can't execute from RAM on an 8 or 16-bit PIC, because they use a Harvard architecture (separate code and data spaces).  Whether or not it is practical to load a program off an SD card and flash it to code memory depends on how often you are going to be doing this.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are trying to create dynamic environment like an OS which is overlaying programs constantly, then no.  But in my case, I have a program that loads drivers as needed off of a 2 GB SD card.  The PIC24FJ256GB110 has a 10,000 erase/write cycle minimum.  Even if this was done five times per day, the flash would last a minimum of 5 1/2 years.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Note: the 10,000 figure is a minimum.  Typical erase/write cycles endurance might be five times that -- so if you are doing development, you can probably re-flash a processor 140 times a day -- every 3 1/2 minutes for eight hours -- and it might still last a year.)&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-10-20T21:03:23.090" LastActivityDate="2010-10-20T21:03:23.090" />
  <row Id="5409" PostTypeId="2" ParentId="5404" CreationDate="2010-10-20T18:24:32.737" Score="10" ViewCount="" Body="&lt;p&gt;MCU ADC inputs can experience variable input impedance depending on whether the sample-and-hold cap is connected to the pin or not.  It might be worth the trouble to use an op amp to buffer the signal.  The op amp would have the added benefit of allowing you to filter out frequencies above Nyquist, which is also good practice.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-20T18:24:32.737" CommentCount="3" />
  <row Id="5410" PostTypeId="2" ParentId="5186" CreationDate="2010-10-20T19:00:23.590" Score="23" ViewCount="" Body="&lt;p&gt;1.&amp;nbsp;Clean up the text with a cotton swab dipped in rubbing alcohol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/mz64F.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2.&amp;nbsp;Wait for the alcohol to evaporate and rub yellow or white chalk on markings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/vQ4tF.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3.&amp;nbsp;Wipe gently with a cotton swab and bingo!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/RhWBb.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Source (in Portuguese): &lt;a href=&quot;http://www.piclistbr.org/paginas.php?fname=%20dicas.htm%20&amp;amp;autor=%2009/2010%20-%20Luciano%20Sturaro&quot; rel=&quot;nofollow&quot;&gt;http://www.piclistbr.org/paginas.php?fname=%20dicas.htm%20&amp;amp;autor=%2009/2010%20-%20Luciano%20Sturaro&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-26T21:19:20.777" LastActivityDate="2010-10-26T21:19:20.777" CommentCount="2" />
  <row Id="5411" PostTypeId="1" AcceptedAnswerId="5432" CreationDate="2010-10-20T20:23:50.313" Score="1" ViewCount="122" Body="&lt;p&gt;After getting some helpful critiques from my original post;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/5129/critique-my-smps-buck-design&quot;&gt;http://electronics.stackexchange.com/questions/5129/critique-my-smps-buck-design&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I worked on my design and made a few major changes.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;L1: 3.3uH 2A inductor&lt;/li&gt;&#xA;&lt;li&gt;C1: 10uF 25V ceramic cap&lt;/li&gt;&#xA;&lt;li&gt;C2: 0.01uF 16V ceramic cap&lt;/li&gt;&#xA;&lt;li&gt;C3: 22uF 6.3V ceramic cap&lt;/li&gt;&#xA;&lt;li&gt;D1: RB160M (input protection)&lt;/li&gt;&#xA;&lt;li&gt;D2: RB160M (catch diode)&lt;/li&gt;&#xA;&lt;li&gt;D3: BAV99W (dual diode)&lt;/li&gt;&#xA;&lt;li&gt;R1: 10k 0.1%&lt;/li&gt;&#xA;&lt;li&gt;R2: 31.6k 0.1%&lt;/li&gt;&#xA;&lt;li&gt;R3: 56R&lt;/li&gt;&#xA;&lt;li&gt;LED1: blue LED, 2.85V, 5mA&lt;/li&gt;&#xA;&lt;li&gt;U1: LM2734Z (3 MHz variant), SOT-23-6&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I have added some copper around the pins in an effort to remove heat from the IC. The only thing I'm presently worried about is if the trace for the feedback voltage is too long. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/NKlT8.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-21T02:51:01.490" Title="Critique my SMPS buck design, take 2" Tags="&lt;buck&gt;&lt;smps&gt;" AnswerCount="1" />
  <row Id="5412" PostTypeId="1" AcceptedAnswerId="5426" CreationDate="2010-10-20T20:49:41.343" Score="3" ViewCount="392" Body="&lt;p&gt;I am looking for a PoE Ethernet chip that I can incorporate in a design I plan on using along with some of the Arduino features. I would prefer to implement a standalone mcu for the Ethernet device capable of providing Ethernet. All possible solutions must support PoE to power the Micro. I do not plan on buying an Arduino nor do I want any shields per se. I am looking for a PoE Ethernet chip that would work well with the Arduino firmware and micro controller. A chip that I can incorporate into my own custom Arduino board. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also be interested in any AVR chips which provide the same capabilities (pin wise) as the Arduino ATMega168/etc that has Ethernet built on board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My devel platform would be AVRStudio or something like it with a Jtag ICE MKII. I do not have the ability to use PIC as I do not have a programmer, the software, nor the cash to invest in another platform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thx in advance for your help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;: Andrew noted that I should post more info. First of all Andrew: I have not looked at the MFGs you mentioned. I will do so now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to place a few Freeduino type setups around the house to do various home automation tasks. My home is already wired with Cat6 and I plan on plugging certain network drops into a 10/100 8 port Linksys POE switch. I would like to provide network and power to each device without having to hack the network cables. I have verified that the switch conforms to the 802.3af standard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to create each board to solely pull power off of the PoE lines to provide sensor and relay capability (relays would be SSR - GA8-6D05 from Crouzet which requires 3-32VDC for the relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would expect the PoE chip to deliver either full PoE voltage or be nice enough to drop it down to 7-12VDC. If needed, I can add a 7805 or appropriate chip to ensure voltage regulation. In the end, my micro would need 5V + 3V DC regulated @ 1A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this answers anything my original post left out.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-10-21T12:48:28.070" LastActivityDate="2010-10-21T12:56:33.210" Title="Easiest and Best PoE Ethernet Chip/Micro/Design for DIY Interface with Custom Arduino Board (AVR Solution)" Tags="&lt;avr&gt;&lt;power-supply&gt;&lt;poe&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="5413" PostTypeId="1" AcceptedAnswerId="5422" CreationDate="2010-10-20T20:51:02.887" Score="3" ViewCount="371" Body="&lt;p&gt;I'm using an HD44780 clone LCD module a KS0066U. Everything works ok on the module except when I rapidly power cycle the device (on-&gt;off-&gt;on). For some reason a very short interruption in the power causes the display module to improperly initialize as a 1-line LCD instead of a 2-line LCD display. What would cause this behavior? Is there any way to prevent it in software?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I'm using the display controller in 4-bit mode not 8-bit mode.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-10-20T21:42:18.737" LastActivityDate="2011-02-23T21:37:53.733" Title="Power-up Initialization of HD44780 LCD Module" Tags="&lt;lcd&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="5414" PostTypeId="2" ParentId="5413" CreationDate="2010-10-20T20:55:37.397" Score="0" ViewCount="" Body="&lt;p&gt;Inserting a delay in your code so when it switches on it gives the LCD long enough to initialize when it starts up. A maximum of a few hundred milliseconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also try connecting the LCD power to the microcontroller and powering off the LCD for a second after start up.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-20T20:55:37.397" CommentCount="5" />
  <row Id="5415" PostTypeId="1" AcceptedAnswerId="5442" CreationDate="2010-10-20T21:00:13.217" Score="4" ViewCount="204" Body="&lt;p&gt;My &lt;a href=&quot;http://en.wiktionary.org/wiki/Google-fu&quot; rel=&quot;nofollow&quot;&gt;Google-fu&lt;/a&gt; is letting me down today.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What do &lt;code&gt;PA&lt;/code&gt; and &lt;code&gt;PU&lt;/code&gt; mean in ATmega88PA and ATmega8-16PU?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If &lt;code&gt;P&lt;/code&gt; for &lt;a href=&quot;http://en.wikipedia.org/wiki/Dual_in-line_package#Variants&quot; rel=&quot;nofollow&quot;&gt;PDIP&lt;/a&gt; what is &lt;code&gt;A&lt;/code&gt; and &lt;code&gt;U&lt;/code&gt;, then?&lt;/p&gt;&#xA;" OwnerUserId="804" LastActivityDate="2010-10-21T16:49:03.697" Title="What do PA and PU mean in AVR lingo?" Tags="&lt;avr&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="5416" PostTypeId="2" ParentId="5386" CreationDate="2010-10-20T21:07:28.080" Score="3" ViewCount="" Body="&lt;p&gt;The Propeller loads its program from external storage.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-10-20T21:07:28.080" CommentCount="1" />
  <row Id="5417" PostTypeId="2" ParentId="5415" CreationDate="2010-10-20T21:19:23.737" Score="2" ViewCount="" Body="&lt;p&gt;This link might help,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.zmitac.aei.polsl.pl/Electronics_Firm_Docs/ATMEL/Atmel/acrobat/doc0538.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.zmitac.aei.polsl.pl/Electronics_Firm_Docs/ATMEL/Atmel/acrobat/doc0538.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but it's a little outdated and doesn't seem to mention A and U.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-20T21:19:23.737" />
  <row Id="5418" PostTypeId="2" ParentId="5412" CreationDate="2010-10-20T21:27:14.810" Score="1" ViewCount="" Body="&lt;p&gt;The Olimex PIC Micro Web board seems to support POE with a BD9001F switching regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.olimex.com/dev/images/PIC/PIC-MICRO-WEB-sch.gif&quot; rel=&quot;nofollow&quot;&gt;http://www.olimex.com/dev/images/PIC/PIC-MICRO-WEB-sch.gif&lt;/a&gt;&#xA;&lt;img src=&quot;http://www.olimex.com/dev/images/PIC/PIC-MICRO-WEB-sch.gif&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This looks like a low cost way of adding PoE to a device.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-20T21:27:14.810" CommentCount="2" />
  <row Id="5419" PostTypeId="2" ParentId="5415" CreationDate="2010-10-20T21:31:09.173" Score="1" ViewCount="" Body="&lt;p&gt;I believe that the AVR codes mean:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;AU - TQFP&lt;/li&gt;&#xA;&lt;li&gt;MU - QFN&lt;/li&gt;&#xA;&lt;li&gt;PU - DIP&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-20T21:31:09.173" />
  <row Id="5420" PostTypeId="2" ParentId="952" CreationDate="2010-10-20T21:45:59.547" Score="0" ViewCount="" Body="&lt;p&gt;Here's a very nice electronics blog: &lt;a href=&quot;http://blog.tkjelectronics.dk/&quot; rel=&quot;nofollow&quot;&gt;http://blog.tkjelectronics.dk/&lt;/a&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-10-20T21:45:59.547" CommunityOwnedDate="2010-10-20T21:45:59.547" />
  <row Id="5422" PostTypeId="2" ParentId="5413" CreationDate="2010-10-20T21:56:48.093" Score="2" ViewCount="" Body="&lt;p&gt;I changed my initialization code so that it sent the upper 4-bit nibble of the function set command twice. Following which I resent the upper 4-bit nibble followed by the lower 4-bit nibble. This does not match the datasheet which seems to indicate that you can send the upper 4-bit nibble then send the function set command upper 4-bit followed by lower 4-bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;// Works sometimes pseudo-code&lt;br&gt;&#xA;port=0x20;&lt;br&gt;&#xA;e=1; e=0;&lt;br&gt;&#xA;port=0x20;&lt;br&gt;&#xA;e=1; e=0;&lt;br&gt;&#xA;port=0xC0;&lt;br&gt;&#xA;e=1; e=0;&lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;// Works all the time pseudo-code&lt;br&gt;&#xA;port=0x20;&lt;br&gt;&#xA;e=1; e=0;&lt;br&gt;&#xA;e=1; e=0;&lt;br&gt;&#xA;port=0x20;&lt;br&gt;&#xA;e=1; e=0;&lt;br&gt;&#xA;port=0xC0;&lt;br&gt;&#xA;e=1; e=0;&lt;br&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-20T21:56:48.093" />
  <row Id="5423" PostTypeId="2" ParentId="5315" CreationDate="2010-10-20T22:20:23.323" Score="1" ViewCount="" Body="&lt;p&gt;The solution is to use an Amp-Op&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/DtBDg.gif&quot; alt=&quot;Pins&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a circuit like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/I33Vp.gif&quot; alt=&quot;Circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can simulate it using the &lt;a href=&quot;http://www.falstad.com/circuit/&quot; rel=&quot;nofollow&quot;&gt;Java Circuit Simulator&lt;/a&gt; where you can import the following code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;$ 1 5.0E-6 10.20027730826997 57 5.0 50&#xA;g 240 240 240 288 0&#xA;r 240 112 240 160 0 47000.0&#xA;r 240 192 240 240 0 47000.0&#xA;R 240 112 240 80 0 0 40.0 5.0 0.0 0.0 0.5&#xA;r 272 384 336 384 0 1000.0&#xA;R 176 384 144 384 0 1 40.0 0.5 0.0 0.0 0.5&#xA;w 176 384 192 384 0&#xA;c 192 384 256 384 0 1.0000000000000001E-7 -2.9572014071857935&#xA;c 192 176 192 240 0 1.0000000000000001E-7 2.5000000000001608&#xA;w 192 240 240 240 0&#xA;w 256 384 272 384 0&#xA;w 336 384 336 192 0&#xA;r 416 240 512 240 0 100000.0&#xA;w 512 240 512 176 0&#xA;w 192 176 240 192 0&#xA;w 416 240 416 192 0&#xA;w 240 192 240 160 0&#xA;a 416 176 512 176 1 5.0 0.0 1000000.0&#xA;w 416 160 240 160 0&#xA;w 336 192 416 192 0&#xA;o 13 64 0 35 20.0 9.765625E-5 0 -1&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The gain will be proportional to the ratio between the resistance of the 100k resistor and the 1k one.&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-10-20T22:51:13.780" LastActivityDate="2010-10-20T22:51:13.780" />
  <row Id="5424" PostTypeId="1" AcceptedAnswerId="5450" CreationDate="2010-10-20T23:18:59.593" Score="5" ViewCount="211" Body="&lt;p&gt;I would like to print a fairly common circuit. But I don't want to design the PCB myself. Where should I look when searching for PCB layouts?&lt;/p&gt;&#xA;" OwnerUserId="1298" LastActivityDate="2011-03-16T20:53:56.160" Title="Is there a directory of open source hardware projects?" Tags="&lt;pcb&gt;&lt;open-source&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="4" />
  <row Id="5425" PostTypeId="2" ParentId="5424" CreationDate="2010-10-20T23:34:58.310" Score="3" ViewCount="" Body="&lt;p&gt;I found some open source hardware at&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/hosting/search?q=hardware&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/hosting/search?q=hardware&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but there are many software projects in these results also.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only way I found of getting hardware only results is searching for PCB files:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/codesearch?as_q=file%3A%5C.(grb%7Cpcb%7Cpcbdoc%7Cbrd%7Cgto%7C057%7Cgbl%7Cgto%7Cgbo%7Cgts)%24&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/codesearch?as_q=file%3A%5C.(grb%7Cpcb%7Cpcbdoc%7Cbrd%7Cgto%7C057%7Cgbl%7Cgto%7Cgbo%7Cgts)%24&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-10-21T10:32:45.303" LastActivityDate="2010-10-21T10:32:45.303" CommentCount="3" />
  <row Id="5426" PostTypeId="2" ParentId="5412" CreationDate="2010-10-21T00:00:02.523" Score="1" ViewCount="" Body="&lt;p&gt;You really haven't given us any actual information to help you with other than you don't want an Arduino shield solution. What kind of power supply do you need? How many voltages, and at what current levels? Are you just powering the AVR? Do you need galvanic isolation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have successfully used National's LM5071 PoE PD controller in one of my designs. Depending on how you want to hook it up, it'll give you full galvanic isolation and multiple output voltages. My particular setup gives me 3.3V at 2A and a separately-isolated 5V at 1A. I &quot;slave&quot; an LTC3523 off the 3.3V to give me 1.8V and 5V supplies that aren't isolated from the main 3.3V supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many companies offer PoE PD controllers. National, Maxim, Linear Tech, TI... Have you done any poking through their websites to see what's out there so you can narrow down your search?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT now that I have more information from the edited question. :-)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI's TPS2370 looks like a perfect fit. It's an 8-pin SOIC device that takes care of the 802.3af spec part and you can drive pretty much ANY regulator off of that. So a really simple supply would consist of the TPS2370 and something like the BD9001 (personally I like Linear's LT1676 but I don't think it has a high enough input voltage spec for PoE) from the previous answer. Two 8 pin SOIC devices, a handful of passives and a small inductor would get you what you're after.&lt;/p&gt;&#xA;" OwnerUserId="974" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2010-10-21T12:47:11.650" LastActivityDate="2010-10-21T12:47:11.650" CommentCount="2" />
  <row Id="5427" PostTypeId="1" CreationDate="2010-10-21T00:55:37.377" Score="5" ViewCount="186" Body="&lt;p&gt;I am looking for photos of MCUs / Arduinos and the like which have been used in difficult/dirty/challenging environments but still work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone can point me towards any pics like this, I'd appreciate it.&lt;/p&gt;&#xA;" OwnerUserId="1402" LastActivityDate="2010-10-21T19:14:46.123" Title="Photos of abused MCU's" Tags="&lt;arduino&gt;" AnswerCount="2" CommentCount="7" FavoriteCount="2" />
  <row Id="5428" PostTypeId="2" ParentId="5427" CreationDate="2010-10-21T02:20:16.777" Score="2" ViewCount="" Body="&lt;p&gt;I'll see if I can get some good pictures of the inside of my Roomba, but I did just clean it out.  Trust me, it's filthy in there.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-10-21T02:20:16.777" />
  <row Id="5429" PostTypeId="1" AcceptedAnswerId="5431" CreationDate="2010-10-21T02:26:21.427" Score="4" ViewCount="350" Body="&lt;p&gt;I'm in the market for an oscilloscope.  My previous approach was to get a used Tektronix on eBay.  There are plenty of good ones - even 100MHz 4 channel digital scopes for about $1100.  However, I started looking at Rigol - specifically the DS1102D (http://www.rigol.com/templates/T_Product_en/index.aspx?nodeid=765).  It's two channel, 100MHz BW and it has a 16 channel logic analyzer as well as USB interface and color screen.  I know better than to just compare bullet points because Tektronix is a very well respected brand and Rigol as far as I can tell is of Chinese design and manufacture.  Has anyone used it?  Are there any gotchas?  Anything I should watch out for?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm liking the answers so far and I just realized Rigol is the scope that had the bandwidth hack, so I'll extend the question to include the BW hack - who has used it and how did it treat you? And has anyone tried it on anything other than the DS1052E?&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-21T19:27:25.790" LastActivityDate="2011-01-08T22:01:25.343" Title="Has anyone used Rigol and its BW hack?" Tags="&lt;oscilloscope&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="5430" PostTypeId="2" ParentId="5373" CreationDate="2010-10-21T02:33:17.557" Score="2" ViewCount="" Body="&lt;p&gt;Rework and soldering equipment vendors (Pace, etc) have little kits with a PCB, fake ICs, chip components, etc that they use as sales tools. You may want to contact some of these vendors to see if they'll sample you one. In my experience they are pretty free with them, in a professional environment at least. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that since these are sales tools, the PCB is designed for soldering success (no ground planes, big spacings between parts, etc).&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2010-10-21T02:33:17.557" />
  <row Id="5431" PostTypeId="2" ParentId="5429" CreationDate="2010-10-21T02:34:16.587" Score="2" ViewCount="" Body="&lt;p&gt;You can see some reviews at EEVBlog: &lt;a href=&quot;http://www.eevblog.com/tag/rigol/&quot; rel=&quot;nofollow&quot;&gt;http://www.eevblog.com/tag/rigol/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-21T02:34:16.587" CommentCount="1" />
  <row Id="5432" PostTypeId="2" ParentId="5411" CreationDate="2010-10-21T02:51:01.490" Score="4" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/84Amm.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yellow is the critical current flow out, not sure where it goes from the output cap, C3.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pink is the ground return, kinda sorta, theres a few critical loops in a circuit like this, some follow the path of least resistance, some follow the path of least impedance (follow their supply trace).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind your goal is to minimize the size of this loop and minimize the resistance between yellow/pink at high frequency, (minimize impedance to ground).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lets just quote the datasheet since it covers all of this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;When planning layout there are a few things to consider when&#xA;trying to achieve a clean, regulated output. The most impor-&#xA;tant consideration when completing the layout is the close&#xA;coupling of the GND connections of the CIN capacitor and the&#xA;catch diode D1.  These ground ends should be close to one&#xA;another and be connected to the GND plane with at &lt;strong&gt;least&lt;/strong&gt; two&#xA;through-holes. Place these components as close to the IC as&#xA;possible. &quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C1 and D2 in this case.  C1 has a really, really, long path to ground for a power supply decoupling cap.  Its also on the other side of the circuit from D2's ground. When your talking about high frequency PCB design when it says &quot;tightly coupled&quot; that doesn't mean just both tied to a ground plane.  It means both ground pins are right next to each other, with a surface polygon pour connecting them and multiple via's to a ground plane right next to the pads. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incidentally aren't your diode silkscreen's backwards?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Next in importance is the location of the GND con-&#xA;nection of the COUT capacitor, which should be near the GND&#xA;connections of CIN and D1.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C3 is the output cap and its ground is roughly as far away from the other 2 as you can get.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;The FB pin is a high impedance node and care should be&#xA;taken to make the FB trace short to avoid noise pickup and&#xA;inaccurate regulation. The feedback resistors should be&#xA;placed as close as possible to the IC, with the GND of R2&#xA;placed as close as possible to the GND of the IC. The VOUT&#xA;trace to R1 should be routed away from the inductor and any&#xA;other traces that are switching.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think your ok with this one, your probably better off running the trace from C3 further away from the inductor but its probably ok.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;High AC currents flow through the VIN, SW and VOUT traces,&#xA;so they should be as short and wide as possible. However,&#xA;making the traces wide increases radiated noise, so the de-&#xA;signer must make this trade-off. Radiated noise can be de-&#xA;creased by choosing a shielded inductor.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If were you i'd just use polygon pours for most of these connections, just make sure you have appropriate filtering in place and a shielded inductor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;The remaining components should also be placed as close&#xA;as possible to the IC. Please see Application Note AN-1229&#xA;for further considerations and the LM2734 demo board as an&#xA;example of a four-layer layout.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If using 4 layer why not reference &lt;a href=&quot;http://www.national.com/an/AN/AN-1229.pdf#page=1&quot; rel=&quot;nofollow&quot;&gt;that app note?&lt;/a&gt; pretty much covers using a big ol' ground pour for the critical ground return and a pour for the SW output.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-21T02:51:01.490" CommentCount="5" />
  <row Id="5433" PostTypeId="2" ParentId="5429" CreationDate="2010-10-21T03:14:40.190" Score="2" ViewCount="" Body="&lt;p&gt;I bought a Rigol DS1052E (50Mhz @ $330.00 US; hackable to 100Mhz) after doing some research and bumping into EEVBlog info. It is not a bad scope. Have not hacked it yet, but I have run tests on SPI, IC2, and Serial. It returned great results. My only gripe so far is that the PC (Windows 7 here) interface will not install. Other than that, great readings and great data retrieved using a USB stick.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mine did not come with the logic analyzer. Not sure about that part of it.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-08T22:01:25.343" LastActivityDate="2011-01-08T22:01:25.343" CommentCount="2" />
  <row Id="5434" PostTypeId="2" ParentId="5413" CreationDate="2010-10-21T03:33:59.503" Score="0" ViewCount="" Body="&lt;p&gt;Not sure if this helps AT ALL, but I messed with the KS0066U on an Arduino project. Here is the &lt;a href=&quot;http://www.tekcrack.com/interfacing-arduino-with-a-purdy-lcd-4x40-modified-lcd4bit-library.html&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastActivityDate="2010-10-21T03:33:59.503" />
  <row Id="5435" PostTypeId="1" AcceptedAnswerId="5437" CreationDate="2010-10-21T05:55:31.797" Score="10" ViewCount="1541" Body="&lt;p&gt;I intend to purchase an FPGA, development kit and I have looked at both the Xilinx and Digilent website. Both seem to have good development kits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have never worked with FPGA's before but have some experience working with microcontrollers.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see that the entry level Spartan 6 boards are on a par in terms of price with the Spartan 3A/AN boards. I've not compared the features.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;From your experience what development kit would you suggest Spartan3A/AN or Spartan6?&lt;/p&gt;&#xA;" OwnerUserId="444" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-23T14:07:33.643" LastActivityDate="2011-03-31T18:18:28.337" Title="FPGA development kit for beginners , Spartan6 or Spartan3 ?" Tags="&lt;fpga&gt;&lt;kit&gt;&lt;development&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="3" />
  <row Id="5436" PostTypeId="2" ParentId="5373" CreationDate="2010-10-21T07:04:47.707" Score="1" ViewCount="" Body="&lt;p&gt;If you can do it, you might find suitable chips in an old switch or motherboard or some other junk, desolder (hot air/gas/oven) them and use those for practice. Recycle and save the planet. :)&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-10-21T07:04:47.707" CommentCount="1" />
  <row Id="5437" PostTypeId="2" ParentId="5435" CreationDate="2010-10-21T07:35:07.813" Score="8" ViewCount="" Body="&lt;p&gt;It looks to me like you still get a lot more to play with at a lower price point with Spartan-3. I found three different Spartan-6 options:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Avnet Spartan-6 LX16 evaluation kit, $225&lt;/li&gt;&#xA;&lt;li&gt;Spartan-6 SP601 evaluation kit, $249 (limited time offer)&lt;/li&gt;&#xA;&lt;li&gt;Digilent Atlys, \$199 academic or $349&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Of note here is that only the Atlys has a lot of on-board common I/O connectors, such as audio, video and keyboard. The LX16 kit has most of the interesting details on a Cypress PSoC instead, though it features a battery that may be interesting. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It boils down to what your intended projects are. With the lower budget Spartan-6 boards, you get an FMC-LPC connector that you can attach your own builds to; the LX16 kit also has a pin header, which is easier to get connectors for. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the Spartan-3 kits, such as I have, we have a quite varied set of connections of more limited quality, and for major expansion there's the Hirose FX2 connector (again, somewhat unusual). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your plan is to do video processing, I'd be very tempted to save up the extra money for the Atlys. It doesn't have very many expansion pins, but it has multiple on-board HDMI ports.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-31T18:18:28.337" LastActivityDate="2011-03-31T18:18:28.337" CommentCount="5" />
  <row Id="5438" PostTypeId="1" AcceptedAnswerId="5439" CreationDate="2010-10-21T07:42:10.253" Score="2" ViewCount="396" Body="&lt;p&gt;If I attach a USB cable to a USB port, and then strip the wire at the end, then how do I connect a multimeter to it to measure the voltage?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2010-10-21T09:27:15.810" Title="How to measure the voltage coming out of a USB port" Tags="&lt;usb&gt;&lt;voltage&gt;&lt;multimeter&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="5439" PostTypeId="2" ParentId="5438" CreationDate="2010-10-21T07:58:13.417" Score="11" ViewCount="" Body="&lt;p&gt;The standard pin numbers and colours in a USB cable are shown below.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Pin Number   Cable Colour   Function&#xA;     1          Red         VBUS (5 volts)&#xA;     2          White       D-&#xA;     3          Green       D+&#xA;     4          Black       Ground&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If there is no device connected to the USB port then the maximum current that the port can support may be quite low.  Once a device has enumerated itself on the port then it can negotiate for up to 500mA from the host controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To measure the voltage then you either touch the meter probes onto the stripped ends of the wires or, if your cable end is a large connector, then touch the probes (without shorting them together) onto pins 1 and 4 of the connector.  The power pins on the USB connector are easy to identify as they are longer than the data pins.  This is so that they mate first and ensures that the power is connected before the data.&lt;/p&gt;&#xA;" OwnerUserId="400" LastEditorUserId="400" LastEditorDisplayName="" LastEditDate="2010-10-21T09:27:15.810" LastActivityDate="2010-10-21T09:27:15.810" CommentCount="2" />
  <row Id="5440" PostTypeId="2" ParentId="5412" CreationDate="2010-10-21T12:56:33.210" Score="0" ViewCount="" Body="&lt;p&gt;Looks like you've got a good answer already, but I thought I'd point out this shield (yes, a shield!) from Freetronics: &lt;a href=&quot;http://www.freetronics.com/products/ethernet-shield-with-poe&quot; rel=&quot;nofollow&quot;&gt;Freetronics — Ethernet Shield with PoE&lt;/a&gt;.  His design files are linked to at the bottom of the page.  Those might provide some insight into making your own design.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-10-21T12:56:33.210" CommentCount="2" />
  <row Id="5441" PostTypeId="2" ParentId="5429" CreationDate="2010-10-21T15:28:40.217" Score="1" ViewCount="" Body="&lt;p&gt;If you cannot see videos at work, I think that it's better you see reviews from &lt;a href=&quot;http://www.amazon.com/Rigol-DS1052E-50MHz-Digital-Oscilloscope/dp/B001P63VOA&quot; rel=&quot;nofollow&quot;&gt;Amazon&lt;/a&gt; or &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.30573&quot; rel=&quot;nofollow&quot;&gt;Deal Extreme&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also have a friend here in Brazil who bought a Rigol and he is very satisfied with it.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-22T14:13:39.303" LastActivityDate="2010-10-22T14:13:39.303" CommentCount="1" />
  <row Id="5442" PostTypeId="2" ParentId="5415" CreationDate="2010-10-21T15:51:29.383" Score="2" ViewCount="" Body="&lt;p&gt;I think the confusion here is that ATmega88PA is an actual chip. As you can see from the way it's written, &quot;PA&quot; is not a tag-on package code after a dash but a part of the model number. And yes, the information for the package types and codes is in the datasheet under &quot;ordering information&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, the ATmega8-16PU is an &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=2004&quot; rel=&quot;nofollow&quot;&gt;ATmega8&lt;/a&gt;, and the ATmega88PA-* are &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=4446&quot; rel=&quot;nofollow&quot;&gt;ATmega88PA&lt;/a&gt;. I might guess A's are somehow improved (from non-A) devices and P means picopower line.&lt;/p&gt;&#xA;" OwnerUserId="883" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-10-21T16:49:03.697" LastActivityDate="2010-10-21T16:49:03.697" CommentCount="2" />
  <row Id="5443" PostTypeId="1" AcceptedAnswerId="5449" CreationDate="2010-10-21T15:56:40.103" Score="4" ViewCount="131" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to know how could I know the current consumed from a battery using this &lt;a href=&quot;http://flytron.com/osd-headtrackers/30-50a-current-sensor-for-simpleosd.html&quot; rel=&quot;nofollow&quot;&gt;sensor&lt;/a&gt;, or other similar, using a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I would like to know is shown in &lt;a href=&quot;http://www.youtube.com/watch?v=ZslcHqyIc38&quot; rel=&quot;nofollow&quot;&gt;this video&lt;/a&gt;, where you can see the current consumption.&lt;/p&gt;&#xA;" OwnerUserId="1660" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-21T19:51:55.677" LastActivityDate="2010-10-21T19:58:35.233" Title="Total current consumed from a battery" Tags="&lt;current&gt;&lt;current-measurement&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="5445" PostTypeId="2" ParentId="5443" CreationDate="2010-10-21T16:56:49.537" Score="0" ViewCount="" Body="&lt;p&gt;I didn't see a datasheet for this sensor via the supplied link, but from the photo see that the sensing element is a hall-effect device, p/n ACS754.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to the manufacturer's website, this is a discontinued part:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;DISCONTINUED PRODUCT. These parts are no longer in production. The device should not be purchased for new design applications. Samples are no longer available. Date of status change: May 3, 2010.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, according to the ACS754 datasheet, the output offset voltage at zero current and 25C is +/- 10mV, which (at 40mV/A) means that any readings less than 250mA could be suspect. What current range do you intend to sense?&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-21T16:56:49.537" CommentCount="2" />
  <row Id="5446" PostTypeId="1" CreationDate="2010-10-21T17:44:06.023" Score="7" ViewCount="225" Body="&lt;p&gt;I'm considering buying a &quot;helping hand&quot; and &lt;a href=&quot;http://www.velleman.eu/distributor/products/view/?id=18736&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; one looks interesting to me. Since I'm pretty new to hobby electronics, my question is what are important things to look for when purchasing such device?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-10-21T21:01:55.323" Title="What to look for when buying a &quot;helping hand&quot; device?" Tags="&lt;equipment&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="5447" PostTypeId="2" ParentId="5446" CreationDate="2010-10-21T18:09:22.253" Score="10" ViewCount="" Body="&lt;p&gt;I would say that the most useful part is a strong, heavy base along with interchangeable grips.  I have had really good luck with the Panavise series before.  They are expensive, but worth every penny.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most places that I've worked have had these on pretty much any bench that soldering or electronics work would get done.  I especially like the circuit board holder vice grip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find a list of their products here: &lt;a href=&quot;http://www.panavise.com/index.html?pageID=1&amp;amp;id1=1&amp;amp;startat=1&amp;amp;--woSECTIONSdatarq=1&amp;amp;--SECTIONSword=ww&quot; rel=&quot;nofollow&quot; title=&quot;here&quot;&gt;Panavise Products, Inc.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-10-21T18:09:22.253" CommentCount="3" />
  <row Id="5448" PostTypeId="2" ParentId="5446" CreationDate="2010-10-21T18:17:02.727" Score="7" ViewCount="" Body="&lt;p&gt;As an owner of the exact device you've linked to (frequently referred to as a Helping Hand), &lt;strong&gt;I would recommend you not get that device, especially if you plan to do soldering with it&lt;/strong&gt;.  I had issues with using it to hold the Protoshield for the Arduino. There isn't much weight in the base, and its designed for holding items that are far smaller than most circuit boards.  In the end, I found it useless for holding anything but maybe cables for soldering.  I think it was originally designed for doing intricate work on very small items, like jewlery.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;mjcarroll's recommendations, while they cost far more than a Helping Hand, work far better.  So I'd recommend looking at those.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-10-21T18:17:02.727" CommentCount="2" />
  <row Id="5449" PostTypeId="2" ParentId="5443" CreationDate="2010-10-21T18:57:09.293" Score="2" ViewCount="" Body="&lt;p&gt;In order to measure the current consumption or the battery's state of charge, you need to integrate current over time.  The most basic method is to sample a current sensor (be it a hall-effect, shunt resistor, whatever) at a fixed rate fast enough to capture your current signal (10-100 Hz might be fine for a RC plane), and multiply it by the sample time to obtain charge (A·h, mA·h, coulombs, whatever).  The Allegro sensors have an adjustable bandwidth, so you could get away with &lt;code&gt;fs = 2*BW&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have the current consumed, you could subtract that from your battery's capacity to obtain the 'fuel level', preferably padded with a good margin of safety.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This method will not be terribly accurate, because the battery's useful charge is not exact, and will fluctuate wildly depending on discharge rate and temperature, among other variables, but it should be good enough to provide a rough 'gas gauge'.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-21T18:57:09.293" />
  <row Id="5450" PostTypeId="2" ParentId="5424" CreationDate="2010-10-21T19:13:23.023" Score="7" ViewCount="" Body="&lt;p&gt;If you're interested in arduino, there is &lt;a href=&quot;http://shieldlist.org&quot; rel=&quot;nofollow&quot;&gt;http://shieldlist.org&lt;/a&gt;. It's a wiki listing of all of the boards that can interface to the arduino board. All should be licensed as open hardware.&lt;/p&gt;&#xA;" OwnerUserId="404" LastEditorUserId="404" LastEditorDisplayName="" LastEditDate="2010-10-21T19:23:09.390" LastActivityDate="2010-10-21T19:23:09.390" CommentCount="2" />
  <row Id="5451" PostTypeId="2" ParentId="5427" CreationDate="2010-10-21T19:14:46.123" Score="5" ViewCount="" Body="&lt;p&gt;Any &quot;harsh environment&quot; will destroy a stock Arduino.  They utterly lack any sort of protection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A company I used to work for would get warranty returns for vehicle data computers that were half filled with water but still fine electrically as the board was conformal coated with a silicone resin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In any case, outside of temperature swings (and occasionally, &lt;a href=&quot;http://www.atmel.com/products/radhard/default.asp&quot; rel=&quot;nofollow&quot;&gt;radiation&lt;/a&gt;), the MCU does not, nor is expected to, survive.  It is the job of enclosures and coatings to protect it from everything else, such as moisture, chemicals, and thermal shock.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-21T19:14:46.123" />
  <row Id="5452" PostTypeId="2" ParentId="5446" CreationDate="2010-10-21T19:32:53.817" Score="4" ViewCount="" Body="&lt;p&gt;I had one just like the one you linked to, and I would recommend against it.  I remember the joints not holding very well, slipping around, flopping, etc. and the base being too small to counterweight pretty much anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some cool projects on &lt;a href=&quot;http://www.instructables.com/id/Third-Hand-A-multi-use-helping-hand-for-electro/&quot; rel=&quot;nofollow&quot;&gt;Intructables made of coolant hose&lt;/a&gt; or wire that look more promising.  You can build actual PCB holders with slots, scope probe holders, etc:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/k1bUz.jpg&quot; alt=&quot;helping hand made of coolant hose&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/kckZ1.jpg&quot; alt=&quot;PCB holder&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I wouldn't be surprised if someone is selling these in small quantities somewhere, too.)&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-21T19:32:53.817" />
  <row Id="5453" PostTypeId="2" ParentId="5386" CreationDate="2010-10-21T19:39:46.797" Score="2" ViewCount="" Body="&lt;p&gt;At my school we used HC11 or HC12 processors with external RAM to load and execute programs on...but I forgot the name of the boards/kit :(   In any case, Freescale HC(S)-line MCUs address RAM and ROM identically, so you can load code into RAM and execute it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Taking a queue from &lt;code&gt;blalor&lt;/code&gt;, the best solution might be to just add a button on your board that can reflash the PIC from data stored on an SD card that you insert with a bootloader.  I can't imagine what wouldn't sort of code wouldn't fit on the larger PICs; if you have some static data (graphics, text, sound), keep that on external storage.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-10-21T19:39:46.797" />
  <row Id="5454" PostTypeId="2" ParentId="5443" CreationDate="2010-10-21T19:58:35.233" Score="2" ViewCount="" Body="&lt;p&gt;I've used a small high-side &lt;a href=&quot;http://www.eetimes.com/design/automotive-design/4010355/Understand-low-side-vs-high-side-current-sensing&quot; rel=&quot;nofollow&quot;&gt;current-sensing resistor&lt;/a&gt; and connected an Arduino ADC to each side to measure the voltage on each side (--&gt; voltage difference --&gt; current).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not very accurate because of the limited resolution of the converters, and because the important quantity is a small difference between two similar voltages.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could improve on this by using an op-amp &lt;a href=&quot;http://en.wikipedia.org/wiki/Operational_amplifier_applications#Differential_amplifier&quot; rel=&quot;nofollow&quot;&gt;to amplify the difference&lt;/a&gt; in voltage, and then output a single DC voltage corresponding to the current.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.eetimes.com/design/automotive-design/4010355/Understand-low-side-vs-high-side-current-sensing&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/NE3Rb.gif&quot; alt=&quot;high and low side current sensing resistors&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-21T19:58:35.233" />
  <row Id="5455" PostTypeId="2" ParentId="5446" CreationDate="2010-10-21T21:01:55.323" Score="4" ViewCount="" Body="&lt;p&gt;I've never used helping hands devices for soldering. Ever. I've always found them to be useless. I've used all kinds of them, including expensive Panavises.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I went a different route. I work on a metal table and have bought some small (1&quot;? 1.5&quot;) square rare-earth magnets. I tack the boards down to the table with the magnets and then I'm free to solder away.  I primarily work with surface mount devices and find this is perfect for me. When I flip the board over to solder the bottom side, I have some tall rare earth magnets that I use.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-21T21:01:55.323" />
  <row Id="5456" PostTypeId="2" ParentId="4542" CreationDate="2010-10-21T23:26:03.373" Score="3" ViewCount="" Body="&lt;p&gt;this is less an answer and more a word of caution when using digital pots or similar devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure you look carefully at their actual mode of operation and not just the theory or equivalent circuit in the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had a design a few years ago that had several analog inputs that were designed to operate at both line and microphone level.  As such there was a differential pre amp stage using an IC designed for that purpose with adjustable gain from 0 to 60dB.  We needed to control the gain set digitally with a micro controller which was set with a single external resistor.  The resistor was in the signal path and AC coupled (swung +/- around ground).  This wasn't mentioned in the pre-amp datasheet and wasn't expected as the output of the pre amp was referenced to the ADC input of a DSP.  The output swung around 1.65V and always stayed above ground.  Through feedback from the DSP the system automatically adjusted the pre-amp gain to get very close to full range input on the ADC to improve resolution.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At first i just used an AD digital potentiometer that appeared in all regards to be a regular old pot, everything indicated it was a resistor with a digitally controlled wiper position.  Well it wasn't.  Internally it was implemented with a cascade of transistors setup to present a constant resistance.  This doesn't sound bad at first but what it does mean is that the resistor couldn't pass voltage outside the bounds of the pot's supplies.  I implemented it with 3.3V and GND for the 2 rails as thats what we used for digital I/O.  But in that configuration the resistor couldn't pass current with a negative voltage and it just chopped the bottom off any AC coupled signal going through it.  We ended up having to replace it in the next rev with a digital pot that allowed +/- rails wide enough to support the signal going through the resistor.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That was a bit of a pain as it meant that it needed to run off the analog supplies but still have serial signals from the digital portions of the circuit attached to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, point is make sure you do your diligence and know exactly what the signal that needs to pass through the variable resistor looks like and that it will work given the topology of the resistor's design. &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-21T23:26:03.373" CommentCount="1" />
  <row Id="5457" PostTypeId="2" ParentId="5424" CreationDate="2010-10-22T01:57:44.397" Score="2" ViewCount="" Body="&lt;p&gt;Maybe you find something interesting in the Arduino board at Dangerous Prototypes forum:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dangerousprototypes.com/forum/index.php?board=34.0&quot; rel=&quot;nofollow&quot;&gt;Project development, ideas, and suggestions &gt;&gt; Arduino&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1084" LastEditorUserId="1084" LastEditorDisplayName="" LastEditDate="2010-10-22T17:57:36.167" LastActivityDate="2010-10-22T17:57:36.167" CommentCount="3" />
  <row Id="5458" PostTypeId="1" AcceptedAnswerId="5462" CreationDate="2010-10-22T02:12:59.773" Score="7" ViewCount="330" Body="&lt;p&gt;I would like to make a circuit that causes an audio delay using discrete components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know I can do small phase shifts using an opamp, but I am looking for something in the millisecond or second range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any way, at least easily, to do this with discrete components?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I would like to know this for both the purposes of synchronization as well as reverb and such. This may take two completely different paths, but both paths are applicable to work I will be doing.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-22T13:36:19.917" LastActivityDate="2010-10-22T14:54:40.063" Title="Audio delay using discrete components" Tags="&lt;audio&gt;&lt;op-amp&gt;&lt;delay&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="2" />
  <row Id="5459" PostTypeId="1" AcceptedAnswerId="5467" CreationDate="2010-10-22T02:58:25.203" Score="3" ViewCount="174" Body="&lt;p&gt;I am looking to build a 5 DSLR camera triggering system using arduinos over our network. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currently we have physical trigger cables so that we can trigger each DLSR camera without delay. Even though all the cameras are on the network and running Nikon capture pro, there is a small delay from hitting the &quot;shoot button&quot; in the software, and the camera actually capturing the image. The physical trigger is instantaneous.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically I'd like to eliminate the need to run dedicated triggering cable to the cameras, as all I want to run is power, and a couple of ethernet to each camera. I want to have the ability to trigger, and intelligently change camera timings through an arduino or similar ip connectible device, sometimes we may have a single trigger, but slight delays to each shot, like, take one immediately, then two slightly later....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The triggering needs to be done physically, but may be done via sensor, so having an arduino with each camera will give us lots of options.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the control room we want to be able to trigger any of the cameras with physical buttons, much like you'd see in industrial applications, something that can really take a beating. So from these buttons I would expect to run them all into an arduino, and then that arduino communicates with the others to trigger them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Signal flow is like this&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Button in control room &gt; arduino &gt; internet &gt; arduino &gt; Nikon external trigger cable &gt; Nikon Camera.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some cameras will trigger at the same time, others with delays.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my key question is: What is the latency of one ip connected arduino, triggering another?&lt;/p&gt;&#xA;" OwnerUserId="1665" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-22T13:43:54.207" LastActivityDate="2010-10-22T14:25:13.470" Title="Using IP connected arduinos to trigger cameras" Tags="&lt;arduino&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="5460" PostTypeId="2" ParentId="5404" CreationDate="2010-10-22T03:26:08.100" Score="5" ViewCount="" Body="&lt;h3&gt; Input Leakage Current &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;To determine your resistors voltage drop from the gate you need to use the leakage current from the datasheet. Microchip specifies an &quot;Input Leakage Current&quot; on their datasheets. The &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/39881D.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet that I have looked up&lt;/a&gt; specifies an input leakage current of 1uA. This could cause a .1V or 100mV, which is only double what robert calculated, probably not a problem on your signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now remember, if you are dividing a 30V signal down  to 30/11(2.7v) volts full read then the 100mV is added to this, causing up to 3% error on your 30V signal. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need a resolution of 1V, divide that by 11 and then add the 100mV. This 100mV could be larger then the 1V signal.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Input Capacitance &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Robert is correct, there will be a capacitance, but this really specifies an amount of time that is needed to take the ADC measurement. This also, combined with your input resistance you chose, creates a low pass filter, if you ware wanting to measure signals with a higher frequency, you are not going to be able to capture them.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Reducing the error&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;The easiest way is to either reduce your resistance on your divider, or to buffer your signal. When you buffer the signal you will replace the PICs leakage current with your op-amps leakage current which you can get quite low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This 1uA is a worst case, unless it costs you a large amount to make minor changes to the design, fab your design and test how bad it is for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please let me know if there is anything I can do to make this easier to read.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-10-22T14:34:46.803" LastActivityDate="2010-10-22T14:34:46.803" CommentCount="3" />
  <row Id="5461" PostTypeId="2" ParentId="5459" CreationDate="2010-10-22T05:27:20.760" Score="2" ViewCount="" Body="&lt;p&gt;To answer your key question, the latency of one IP connected arduino to another is almost completely dependent on your computer network. The arduino hardware and trigger will add some latency, but it can be treated as 0 compared to the amount of latency that a computer network and physical trigger hardware will add.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Typically in medium to large size corporate networks I have seen a latency of anywhere between 3ms and 50ms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are wanting all of your cameras to trigger at the exact same time you might want to consider a more sophisticated approach to deal with unpredicted delays on the network. Every so often you can send timing information to your trigger arduino. Over time you can start to average out the jitter on the network. Jitter being the difference between the latency of one packet to the latency of other packets at different times. You should be able to get &quot;ok&quot; time with this method, then when you want your cameras to trigger, you send a packet saying what time stamp you want them to trigger at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also add a return packet which the user control side ardunio would receive. With a bit of work you can use the round trip time to perfect your timing even more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't care about having them all go at the exact same time, you will just need to keep your trigger packet, and any associated overhead, as small as possible.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-22T05:27:20.760" CommentCount="1" />
  <row Id="5462" PostTypeId="2" ParentId="5458" CreationDate="2010-10-22T06:03:42.160" Score="7" ViewCount="" Body="&lt;p&gt;One common method is to use a circuit know as a bucket brigade.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These circuits consist of a chain of capacitors. Connecting the capacitors are switches. By driving the control signal for the switches the signal is transferred from one capacitor to the next each time the control (or clock) signal transitions. The time delay you can achieve is limited by the number of stages you have and the slowest sampling rate you can tolerate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because you need many stages to create a longer delay it is not really practical to implement this with discrete components. There are a few ICs that implement the function varying from 512 to 4096 stages. With 4096 stages a 20kHz sampling rate will give you 100 ms of delay. You could cascade a number of delay lines together, but you will be losing signal quality with each section.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If signal quality and the length of the delay is important, then digital sampling techniques will be very hard to pass up.&lt;/p&gt;&#xA;" OwnerUserId="328" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-22T13:38:23.797" LastActivityDate="2010-10-22T13:38:23.797" CommentCount="4" />
  <row Id="5463" PostTypeId="2" ParentId="5435" CreationDate="2010-10-22T07:19:44.723" Score="5" ViewCount="" Body="&lt;p&gt;If you have never worked on FPGAs before, have you considered Altera FPGAs? Terasic makes some great ones with nice reference materials. You can check out www.terasic.com. Also I hear that Altera's Quartus environment is a lot more user-friendly than Xilinx's.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;budget -&gt; Altera DE1&lt;/li&gt;&#xA;&lt;li&gt;suggested -&gt; Altera DE2 or DE2-115 (because there's SO much resources online at college websites which include their source codes)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Also, the Altera university program is a great place for beginner tutorials. They start from the very beginning of &quot;Hello World&quot; type programs.&lt;/p&gt;&#xA;" OwnerUserId="1666" LastActivityDate="2010-10-22T07:19:44.723" CommentCount="5" />
  <row Id="5464" PostTypeId="2" ParentId="5134" CreationDate="2010-10-22T10:55:51.920" Score="0" ViewCount="" Body="&lt;p&gt;it will be used as a reminder to change a water filter so it should be powered off a small battery..something small, easy to setup and with a low current consumption would also be handy..any help appreciated..thanks for the previous input..&lt;/p&gt;&#xA;" LastActivityDate="2010-10-22T10:55:51.920" CommentCount="1" />
  <row Id="5466" PostTypeId="1" AcceptedAnswerId="5474" CreationDate="2010-10-22T14:08:01.640" Score="5" ViewCount="404" Body="&lt;p&gt;So I have spent the past two days going through various budget oscilloscopes and checking their specs VS price.  Most of the information I have gathered has been from here and I am almost sold on an MSO-19.  The only reason I haven't bought it already is that it's a single channel oscilloscope and before I spend £180 on it, I want to make sure it's going to cover 95% of my electronics needs.  I think my major problem is that I don't know what area of electronics I will be going into in the future and so can't predict exactly what I am going to need.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currently I work as a software engineer and so am already playing around with PICs, AVRs and MSP430s.  I think, in the short term, I will be looking into making small intelligent robots (not bump and turn stuff you see on most hobbyist sites but something with 'character'). I have been in AI for a number of years and whilst I'm no Marvin Minsky, I do know a thing or two about what makes something seem intelligent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other thing I have been looking at is this 32-channel logic analyser (&lt;a href=&quot;http://www.seeedstudio.com/depot/open-workbench-logic-sniffer-p-612.html&quot; rel=&quot;nofollow&quot;&gt;Open Workbench Logic Sniffer&lt;/a&gt;) which is only £30 and is a more powerful logic analyser than comes with the MSO-19.  Would it be a better idea just to buy that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm open to other suggestions too but I don't want to spend over £250 in total if I can help it.&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-03T08:37:37.033" LastActivityDate="2011-02-03T08:37:37.033" Title="Is a single channel oscilloscope enough for most purposes?" Tags="&lt;oscilloscope&gt;&lt;logic-analyzer&gt;" AnswerCount="8" CommentCount="1" FavoriteCount="1" />
  <row Id="5467" PostTypeId="2" ParentId="5459" CreationDate="2010-10-22T14:18:29.780" Score="1" ViewCount="" Body="&lt;p&gt;TCP/IP on Arduinos isn't exactly the best choice for anything real-time.  Ethernet timing isn't deterministic, so regardless of any method that attempts to remove jitter or compensate for latency, it will never be spot on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You mention &quot;Arduino -&gt; network -&gt; Arduino&quot; as your desired topology, in which case I would throw away the idea of using the (very expensive) Ethernet boards and use something designed for embedded systems, like RS-485.  As you have total network control, your master module could send a 'shutter' message for every slave to pick up and act upon after message completion.  They would all receive it at the exact same time (+/- 1 ns/foot), so jitter and lag would be negligible for any camera application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's &lt;a href=&quot;http://www.robotshop.com/dfrobot-i-o-expansion-board-arduino-v5-1.html&quot; rel=&quot;nofollow&quot;&gt;a shield that has RS-485 on it&lt;/a&gt;, but it's just a single chip (e.g. &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/1111&quot; rel=&quot;nofollow&quot;&gt;MAX485 &amp;amp; friends&lt;/a&gt;) that you could breadboard.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How far apart are these cameras?  If they're only ~10 meters apart and you want a (light?) sensor that goes to each one, just wire up a sensor+shutter+power cable and run them to the same Arduino.  It should only be 4-6 wires; buy some good connectors and it should be painless to tear-down and set-up.  You might be able to get away with &lt;em&gt;significantly&lt;/em&gt; longer cables even, depending on the sensor, etc.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-10-22T14:25:13.470" LastActivityDate="2010-10-22T14:25:13.470" CommentCount="2" />
  <row Id="5468" PostTypeId="2" ParentId="5466" CreationDate="2010-10-22T14:23:34.863" Score="4" ViewCount="" Body="&lt;p&gt;As soon as you get a single-channel, you will want the double-channel. Heck, I have a double and am shopping for a four-channel. You will get to the stage where you need to compare signals, for education, troubleshooting or fun. With your budget of 250 quid you should be able to scrape in with the perennial favourite, the &lt;a href=&quot;http://www.rigolna.com/products/digital-oscilloscopes/ds1000e/ds1052e/&quot; rel=&quot;nofollow&quot;&gt;Rigol DS-1052E&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T15:36:15.677" LastActivityDate="2010-10-22T15:36:15.677" CommentCount="3" />
  <row Id="5469" PostTypeId="2" ParentId="5458" CreationDate="2010-10-22T14:28:39.090" Score="2" ViewCount="" Body="&lt;p&gt;There are a lot of ways to get a delay, but I don't know of any that just use &quot;discrete components&quot;.  The best way to do reverb in the modern world is to use a DSP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only way I know of to do this &quot;analog&quot; is to use physical objects like &lt;a href=&quot;http://en.wikipedia.org/wiki/Delay_%28audio_effect%29#Analog_delay&quot; rel=&quot;nofollow&quot;&gt;rooms or metal plates, or magnetic tape&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;In the millisecond or second range&quot; is a pretty huge range, you know.  If you have a circuit that produces 1 ms of delay, you would need 1,000 of them to get to 1 second.  Older reverbs created long tails using feedback, rather than long delay elements.    &lt;a href=&quot;http://valhalladsp.wordpress.com/2009/05/30/schroeder-reverbs-the-forgotten-algorithm/&quot; rel=&quot;nofollow&quot;&gt;Schroeder reverb&lt;/a&gt;, &lt;a href=&quot;http://www.bagger288.com/temp/aboutThisReverberationBusiness.pdf&quot; rel=&quot;nofollow&quot;&gt;enhanced version&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use &lt;a href=&quot;http://en.wikipedia.org/wiki/All-pass_filter&quot; rel=&quot;nofollow&quot;&gt;all-pass filters&lt;/a&gt; to add short delays, but they delay different frequencies by different amounts, resulting in &lt;a href=&quot;http://www.audioholics.com/education/acoustics-principles/human-hearing-phase-distortion-audibility-part-2&quot; rel=&quot;nofollow&quot;&gt;phase distortion&lt;/a&gt;.  &lt;a href=&quot;http://www.linkwitzlab.com/filters.htm#4&quot; rel=&quot;nofollow&quot;&gt;4 -  Delay correction&lt;/a&gt;,  &lt;a href=&quot;http://www.linkwitzlab.com/page_index.htm#Projects&quot; rel=&quot;nofollow&quot;&gt;Projects&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/uYudN.gif&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/vQMk6.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise you need to use &lt;a href=&quot;http://en.wikipedia.org/wiki/Bucket-brigade_device&quot; rel=&quot;nofollow&quot;&gt;bucket brigade devices&lt;/a&gt;, which emulate a slow transmission line.  But they aren't &quot;really&quot; analog (&lt;a href=&quot;http://en.wikipedia.org/wiki/Switched_capacitor&quot; rel=&quot;nofollow&quot;&gt;switched capacitor&lt;/a&gt; = &lt;a href=&quot;http://en.wikipedia.org/wiki/Discrete_signal&quot; rel=&quot;nofollow&quot;&gt;discrete time&lt;/a&gt; device) and aren't feasible to make from discrete components anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/x5QpO.jpg&quot; alt=&quot;bucket brigade circuit&quot;&gt;&#xA;&lt;a href=&quot;http://www.soundonsound.com/sos/apr04/articles/synthsecrets.htm&quot; rel=&quot;nofollow&quot;&gt;Figure 1: A simple eight-stage bucket-brigade device (or BBD) delay line.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-22T14:54:40.063" LastActivityDate="2010-10-22T14:54:40.063" CommentCount="4" />
  <row Id="5471" PostTypeId="2" ParentId="2829" CreationDate="2010-10-22T15:41:31.187" Score="2" ViewCount="" Body="&lt;p&gt;For prototypes or personal projects, I just found this group buy thing the other day:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dorkbotpdx.org/wiki/pcb_order&quot; rel=&quot;nofollow&quot;&gt;http://dorkbotpdx.org/wiki/pcb_order&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Two layer: $5 per square inch for three copies of your board. &lt;/li&gt;&#xA;&lt;li&gt;Four layer: $10 per square inch for three copies of your board.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Shipping within the US is included, and there are no setup fees. Your boards will be mailed within 9 days of the [monthly] order deadline.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-12-01T14:35:15.307" LastActivityDate="2010-12-01T14:35:15.307" />
  <row Id="5472" PostTypeId="2" ParentId="5435" CreationDate="2010-10-22T16:26:40.147" Score="1" ViewCount="" Body="&lt;p&gt;I have used a Spartan 3 in college, and the board had a vast array of connectors (of that age): PS2, VGA, DB9, and the classic pinheaders, plus some leds, 7segments displays, push-buttons and switches. That was more than enough for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PD: the simulator was SO huge that was better to &quot;compile&quot; the gates and test them on board.&lt;/p&gt;&#xA;" OwnerUserId="1673" LastActivityDate="2010-10-22T16:26:40.147" CommentCount="2" />
  <row Id="5473" PostTypeId="2" ParentId="5466" CreationDate="2010-10-22T17:18:04.520" Score="2" ViewCount="" Body="&lt;p&gt;If you are only going to deal with low speed digital signals then a logic sniffer will get the job done.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you get higher speed you may need an o-scope to check for signal integrity issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do analog, you are going to want an analog o-scope.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-22T17:18:04.520" />
  <row Id="5474" PostTypeId="2" ParentId="5466" CreationDate="2010-10-22T17:35:24.547" Score="6" ViewCount="" Body="&lt;p&gt;I agree with the others that two-channels is very convenient at times.  Particularly if there is a separate trigger input (almost like a third channel).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are your minimum bandwidth requirements?  Do you really need something as fast as the MSO-19?  The &lt;a href=&quot;http://www.audon.co.uk/dso2090.html&quot; rel=&quot;nofollow&quot;&gt;DSO-2090&lt;/a&gt; is a 100MS/s, 40 MHz dual channel (plus external trigger) PC-based scope for £139.  You would then have money left over to buy the standalone £30 logic analyzer.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-22T17:35:24.547" CommentCount="8" />
  <row Id="5475" PostTypeId="2" ParentId="1629" CreationDate="2010-10-22T18:12:15.487" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Futurlec&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2 / 136 Broadmeadow Rd, Broadmeadow, NSW 2292 Australia&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fax: +61 2 94 754 051&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Printed Circuit Board Manufacturing Service&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Futurlec can supply custom designed printed circuit boards to your design or from our design department. We can deliver single sided or double sided boards at reasonable prices, with fast turnaround times delivered to your door. In single quantities for a pcb prototype or in large manufacturing runs.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://futurlec.com/PCBService.shtml&quot; rel=&quot;nofollow&quot;&gt;Quotation Form&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1084" LastActivityDate="2010-10-22T18:12:15.487" CommentCount="1" />
  <row Id="5476" PostTypeId="1" AcceptedAnswerId="5479" CreationDate="2010-10-22T18:18:20.130" Score="3" ViewCount="287" Body="&lt;p&gt;The title pretty much sums up my question: Are there any native Mac OS X environments for getting started with VHDL / FPGAs?&lt;/p&gt;&#xA;" OwnerUserId="1317" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-27T04:10:31.277" LastActivityDate="2011-02-28T10:41:44.593" Title="Any native Mac OS X environments for getting started with VHDL / FPGAs?" Tags="&lt;fpga&gt;&lt;vhdl&gt;&lt;mac&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5477" PostTypeId="2" ParentId="535" CreationDate="2010-10-22T18:21:17.973" Score="0" ViewCount="" Body="&lt;p&gt;I tried an evaluation version of &lt;a href=&quot;http://www.mccad.com/&quot; rel=&quot;nofollow&quot;&gt;McCAD&lt;/a&gt; and was quite pleased with it. I found it significantly more Mac-user-friendly than Eagle (which I also tried). YMMV, of course…&lt;/p&gt;&#xA;" OwnerUserId="1317" LastActivityDate="2010-10-22T18:21:17.973" />
  <row Id="5478" PostTypeId="1" CreationDate="2010-10-22T18:25:20.693" Score="3" ViewCount="430" Body="&lt;p&gt;Mainly, I want to persist data onto the onboard Netduino memory (if there is any?) without hooking anything else up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea is that I either read the data back in the next time the Netduino is plugged in (for settings), or read the data when it's plugged into a computer (for analytical data). Specifically data from sensors like temperature, ambient light, GPS Position, xyz orientation, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know there is the Netduino Plus, which has a MicroSD slot to store data via &lt;code&gt;System.IO&lt;/code&gt;, but I have a regular Netduino :(&lt;/p&gt;&#xA;" OwnerUserId="1252" LastEditorUserId="1252" LastEditorDisplayName="" LastEditDate="2010-10-22T20:49:59.993" LastActivityDate="2010-11-01T22:37:32.523" Title="How can I persist data onto the Netduino?" Tags="&lt;.net-micro-framework&gt;&lt;netduino&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="5479" PostTypeId="2" ParentId="5476" CreationDate="2010-10-22T18:30:23.383" Score="2" ViewCount="" Body="&lt;p&gt;Short Answer Nope!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have investigated this in the past, and sure you can use a text editor to write the code, but none of the major (xilinx and altera) have any design flows for the mac os x platform, so synthesizing and place and route are out.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the simulation front, I did find a program that claims to perform simulation for the mac platform, but I had my doubts on the quality of said program. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best option is to dual boot (parallels or fusion) into windows or linux.  Having said Linux, I am not sure if you can get the free webpacks to support Linux, they may only be windows based for the free tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So either dual boot or use remote desktop type thing to access a windows PC.  It is a bugger, I know but such is life on a mac :)&lt;/p&gt;&#xA;" OwnerUserId="1397" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-02-27T08:23:56.673" LastActivityDate="2011-02-27T08:23:56.673" CommentCount="5" />
  <row Id="5480" PostTypeId="2" ParentId="5478" CreationDate="2010-10-22T18:35:26.517" Score="2" ViewCount="" Body="&lt;p&gt;SkippyFire, you can add an SD card using the v4.1.1 firmware and an expansion shield.  The Adafruit MicroSD expansion card also works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a feature within .NET Micro Framework called &quot;ExtendedWeakReferences&quot; which can be used if you recompile the firmware and enable it--but I'd highly recommend using MicroSD instead.  Simpler, standard, and powerful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Chris&lt;/p&gt;&#xA;" LastActivityDate="2010-10-22T18:35:26.517" CommentCount="1" />
  <row Id="5481" PostTypeId="2" ParentId="5466" CreationDate="2010-10-22T18:58:00.967" Score="1" ViewCount="" Body="&lt;p&gt;I have the MSO-19 and I like it.  It works well under VMWare on my Mac.  I do often find myself wanting a 2nd channel, however.  &lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-10-22T18:58:00.967" />
  <row Id="5482" PostTypeId="2" ParentId="5466" CreationDate="2010-10-22T19:37:12.367" Score="2" ViewCount="" Body="&lt;p&gt;It is virtually impossible to use a single channel oscilloscope other than for basic measurements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dual channel allows you to debug most serial protocols. It is also crucial for the analysis of complex signals, like video (for example, with my OSD project I need to compare the video signal and Csync.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Heck, I have a quad channel scope and I say if you can get one second hand for a little extra I say it's well worth it.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-22T19:37:12.367" />
  <row Id="5483" PostTypeId="2" ParentId="535" CreationDate="2010-10-22T19:38:47.907" Score="1" ViewCount="" Body="&lt;p&gt;I think the gEDA package will compile under Mac OS X.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-22T19:38:47.907" CommentCount="1" />
  <row Id="5484" PostTypeId="1" AcceptedAnswerId="5491" CreationDate="2010-10-22T20:01:14.463" Score="3" ViewCount="153" Body="&lt;p&gt;In my spare time I've decided to create something on my own. I've never designed difficult things, but I'm very curious, moreover experience would never be useless ;) I decided to create a robot, but I want to do this from 0: schematic, programming to do this the way I want. And the important one: I want it to be autonomous as more as possible (self charging, path finding - some kind of intellectual robot).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have experience with MCUs and simple logic devices, so I can imagine, which way should robot move, which way I could control it etc. But to achieve desired autonomy at first I should create a way to interact with it (autonomy dictates - radio transmitter-receiver) and some kind of navigation system. Well, this is my way of thinking and I think so.&#xA;So for now my question is: which ways is it possible to track movements of a robot, current position and what accuracy is achievable?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Broadly used radio-location is useless here because I have no intentions to measure distances about km (really centimetres and meters - in my room). GPS is useless too as signal is lost in-door.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking about to use servomotors and count ticks(!), but it is not so reliable as wants to be (robot could rotate wheels, but not move).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking about GPS in miniature: putting several antennae and measure distances (this is just an idea, which may be either nonsense or unrealisable).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Recently I found inertial navigation system (INS) article on wikipedia, but I'm confused with integral error rate. Wiki states error level expected is to be approximately 650m, which is no good at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Did anyone deal with similar problems? If someone could tell me practically obtained accuracy values for different navigation systems or some concepts, ideas or even papers concerning that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I repeat once again - no industrial realisations, I  want to do this on my own with available elements, costing reasonable money. &lt;/p&gt;&#xA;" OwnerUserId="1651" LastEditorUserId="1397" LastEditorDisplayName="" LastEditDate="2010-10-22T22:32:44.293" LastActivityDate="2010-10-22T22:36:26.557" Title="Primitive navigation system" Tags="&lt;robotics&gt;&lt;navigation&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="5485" PostTypeId="2" ParentId="5466" CreationDate="2010-10-22T20:14:21.767" Score="3" ViewCount="" Body="&lt;p&gt;It's worth scouring eBay for a second hand DSO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I got my Tektronix TDS-210 for £180:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;2 channel + separate trigger&lt;/li&gt;&#xA;&lt;li&gt;60MHz&lt;/li&gt;&#xA;&lt;li&gt;1 GS/s&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I bought an Open Logic Sniffer too. It's a great device for the price, but given the tiny amount of RAM it has, it feels a bit like keyhole surgery.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-22T22:09:43.060" LastActivityDate="2010-10-22T22:09:43.060" />
  <row Id="5486" PostTypeId="2" ParentId="5484" CreationDate="2010-10-22T20:26:24.383" Score="0" ViewCount="" Body="&lt;p&gt;The cheapest, simplest approach &lt;a href=&quot;http://en.wikipedia.org/wiki/Dead_reckoning&quot; rel=&quot;nofollow&quot;&gt;dead reckoning&lt;/a&gt;. This is where you use knowledge about your heading and speed to calculate your position.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two popular methods are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://psurobotics.org/wiki/index.php?title=Wheel_Encoders&quot; rel=&quot;nofollow&quot;&gt;Wheel encoders&lt;/a&gt; - measuring the rotation of wheels to calculate distance travelled&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1257038219&quot; rel=&quot;nofollow&quot;&gt;Homemade encoders&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.bot-thoughts.com/2010/10/wheel-encoder-generator-testers-wanted.html?utm_source=feedburner&amp;amp;utm_medium=feed&amp;amp;utm_campaign=Feed%3A+BotThoughts+%28Bot+Thoughts%29&quot; rel=&quot;nofollow&quot;&gt;Encoder generator&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Inertial Measurement - using accelerometers to calculate position&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://code.google.com/p/ardu-imu/&quot; rel=&quot;nofollow&quot;&gt;Arduimu&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-22T20:52:36.917" LastActivityDate="2010-10-22T20:52:36.917" />
  <row Id="5487" PostTypeId="2" ParentId="5478" CreationDate="2010-10-22T20:56:49.570" Score="0" ViewCount="" Body="&lt;p&gt;I'm not familiar with the Netduino, but most PIC microprocessors have self-writeable flash memory. Some of them even have a small amount of on board EEPROM ~1kB. Both types of memory are non-volatile and will provide you with a way to store data between power-ups.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-22T20:56:49.570" />
  <row Id="5488" PostTypeId="2" ParentId="5484" CreationDate="2010-10-22T21:50:42.890" Score="0" ViewCount="" Body="&lt;p&gt;If you try to determine your position from on-board sensors that integrate the movement that can be measured, you have a dead reckoning system. The major weakness with dead reckoning is that the errors in your measurements accumulate and as time goes by your estimate of where you are becomes less and less accurate. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could mitigate this somewhat by placing things in the robot's environment that represent known positions. For example, if your dead reckoning system works well enough to get your robot through a mission and back to a charging station, you can reset your position information to the known position of the charging station when you get there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for alternatives to dead reckoning, (&lt;em&gt;and this is purely speculation as I've never tried it or seen it done&lt;/em&gt;) it seems like it ought to be possible to have a stationary system set up in the room that does with the robot the same thing that head-tracking software does. In other words, an off-board computer with a couple of cameras could triangulate on your robot, derive its position, and relay this information to your robot over your wireless link. With this kind of setup, position error wouldn't accumulate, it would just be whatever you get from the tracking system.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-22T21:50:42.890" CommentCount="1" />
  <row Id="5489" PostTypeId="2" ParentId="5484" CreationDate="2010-10-22T22:03:18.070" Score="1" ViewCount="" Body="&lt;p&gt;You could use some kind of beacons in the room. For example, IR beacons, radio beacons or maybe even sonic beacons. If you can estimate the distance to your robot from three beacons (and you only need to estimate, you don't need to know the exact position) you can apply simple trigonometry to figure out your position. This has the advantage that errors do not accumulate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;INS systems are not very useful except for short runs. For example, assume you have an accelerometer has an offset of +0.1%, that is, its measurements are all 0.1% greater than they should be (which would be a top spec accelerometer) and your robot runs for 30 minutes taking five samples per second, it would lead to an overall position error of +8066%.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-22T22:03:18.070" />
  <row Id="5490" PostTypeId="2" ParentId="5466" CreationDate="2010-10-22T22:06:46.507" Score="3" ViewCount="" Body="&lt;p&gt;You need two channels for most tasks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason that two channels is import is you often interested in the relationship between different signals. Here are some examples of when two channels can be very important:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A clock signal and a data signal where you need to check the setup and hold timing.&lt;/li&gt;&#xA;&lt;li&gt;An enable signal to an analogue circuit, where you need to see how fast the analogue circuit stabilises after being enabled. This might be the case in a low power system where an sensor is only powered up when it needs to be sampled.&lt;/li&gt;&#xA;&lt;li&gt;To examine the relative timing of some tasks on a microcontroller, where you set each task to toggle a different IO pin upon entry and exit.&lt;/li&gt;&#xA;&lt;li&gt;Where you have a PWM output with a complementary drive and you need to confirm the dead time between the top and bottom switches.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="328" LastActivityDate="2010-10-22T22:06:46.507" />
  <row Id="5491" PostTypeId="2" ParentId="5484" CreationDate="2010-10-22T22:21:57.147" Score="2" ViewCount="" Body="&lt;p&gt;An INS will suffer from errors due to accelerometer drift.  Using a Kalman filter along with better and more accurate Giros will help this situation greatly. Basically doing the maths means better accuracy giros can compensate for not so great accelerometers.  You can always add some extra sensors such as magentometer and this will give you another input into your system, once again it will help reduce drift errors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wheel encoders are great, provided you do not suffer from slippage.  As soon as a wheel slips you will get innaccurate readings. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another method (as used on mars pathfinders!) is to use optical systems.  Two cameras, one processor, and some algorithms and you will be able to accurately and reliably calculate distance travelled! This is easier to implement if you have lots of easily identified static items around the room for the algorithm to pickup on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also instrument your room! this means you could place RF, magnetic, or white lines around the room and use an appropriate sensor and use them for navigation!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another method is to use simple ultrasonic sensors (reverse parking sensors anyone?) these will aide collision avoidance!  fuse them with INS sensors and magnetometer and you will far more accurate position tracking system.  Or use them on their own and avoid hitting stuff!!!! &lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-22T22:21:57.147" CommentCount="2" />
  <row Id="5492" PostTypeId="2" ParentId="5484" CreationDate="2010-10-22T22:36:26.557" Score="1" ViewCount="" Body="&lt;p&gt;Don't forget about simple methods: ultrasound distance measuring.  You can build up a map of the room or area and then fine-tune it as you move around.  Also consider using angular rate sensors to measure turning as well as accelerometers to measure linear movement.  Do look up Kalman filters as mentioned before.  You can combine all of these measurements into one reading with kalman filters and improve your consistency (not necessarily accuracy).&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-10-22T22:36:26.557" CommentCount="1" />
  <row Id="5493" PostTypeId="1" AcceptedAnswerId="5497" CreationDate="2010-10-22T23:26:40.720" Score="1" ViewCount="131" Body="&lt;p&gt;I'm looking for a high density (&gt;512Mbyte) FLASH or other memory device in a small package with a serial interface. I'm hopeful but I can only find sizes up to around 16 MB with serial interfaces.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any suggestions on where to look?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-24T09:00:09.427" Title="High density serial interface nonvolatile memory" Tags="&lt;memory&gt;" AnswerCount="4" />
  <row Id="5494" PostTypeId="1" AcceptedAnswerId="5495" CreationDate="2010-10-22T23:28:27.793" Score="4" ViewCount="171" Body="&lt;p&gt;So far the most RAM laden MCU I have found in a hobbyist friendly DIP package is a dsPIC33FJ128GP802, which has 16KB, and the Parallax Propeller, which has 32KB. But does anyone know of chips with more memory in said packages? This is only for prototyping, I also need surface mount chips for production.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-23T18:42:15.750" Title="Most RAM for an MCU in a DIP package" Tags="&lt;microcontroller&gt;&lt;ram&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="5495" PostTypeId="2" ParentId="5494" CreationDate="2010-10-22T23:42:48.607" Score="6" ViewCount="" Body="&lt;p&gt;If you only need the DIP format for prototyping, use some adapter boards and prototype with those. With a steady hand you should be able to solder SOIC and TQFP parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This kind of thing:&#xA;&lt;a href=&quot;http://microcontrollershop.com/product_info.php?cPath=301_52&amp;amp;products_id=3721&quot; rel=&quot;nofollow&quot;&gt;http://microcontrollershop.com/product_info.php?cPath=301_52&amp;amp;products_id=3721&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://microcontrollershop.com/Images/1B2.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-22T23:42:48.607" CommentCount="6" />
  <row Id="5496" PostTypeId="2" ParentId="5493" CreationDate="2010-10-22T23:48:20.500" Score="1" ViewCount="" Body="&lt;p&gt;I've seen serial flash up to about 512mbit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For bigger, I've only seen parallel NAND flash and possibly NOR flash.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-23T00:02:34.263" LastActivityDate="2010-10-23T00:02:34.263" />
  <row Id="5497" PostTypeId="2" ParentId="5493" CreationDate="2010-10-23T01:28:45.270" Score="6" ViewCount="" Body="&lt;p&gt;I'm guessing the way you can satisfy this request is by letting &quot;serial&quot; include microSD in SPI mode. Unfortunately it's very costly to sell anything with SD support, though. USB flash wouldn't be as compact.&#xA;Edit: As Mark says, there are cards that do not have SPI mode.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="1181" LastEditorDisplayName="" LastEditDate="2010-10-24T09:00:09.427" LastActivityDate="2010-10-24T09:00:09.427" CommentCount="9" />
  <row Id="5498" PostTypeId="1" CreationDate="2010-10-23T09:26:39.547" Score="12" ViewCount="905" Body="&lt;p&gt;I heard that the current limit for a USB port is 100mA. However, I also heard that some devices can get up to 1.8A from a port. How do you get past the 100mA limit?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-03-31T11:23:57.467" Title="How to get more than 100mA from a USB port" Tags="&lt;usb&gt;&lt;current&gt;&lt;port&gt;&lt;current-source&gt;&lt;usb-device&gt;" AnswerCount="6" CommentCount="3" FavoriteCount="5" />
  <row Id="5499" PostTypeId="2" ParentId="2829" CreationDate="2010-10-23T09:54:22.117" Score="1" ViewCount="" Body="&lt;p&gt;For UK I'd recommend &lt;a href=&quot;http://www.screenbond.co.uk&quot; rel=&quot;nofollow&quot;&gt;Screenbond&lt;/a&gt;. Not as cheap as PCBCart but usually comparable to Eurocircuits on price. Unusually low tooling coists, usually £40 for DS/PTH.&#xA;They can do down to 24hr turnround if you have deep pockets.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-23T09:54:22.117" />
  <row Id="5500" PostTypeId="2" ParentId="5466" CreationDate="2010-10-23T09:57:25.463" Score="3" ViewCount="" Body="&lt;p&gt;A single channel scope is a complete waste of time. Maybe worth a fifth of a 2-channel one. &#xA;You almost always want to look at the relationship between signals.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-23T09:57:25.463" />
  <row Id="5501" PostTypeId="2" ParentId="5493" CreationDate="2010-10-23T10:11:30.293" Score="1" ViewCount="" Body="&lt;p&gt;ST/Numonyx and possibly others do some serial NAND flash devices, and parallel NAND doesn't need a ridiculous number of pins as they used a command-based protocol. Remember however that with NAND you need to do error correction and bad-block management. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-23T10:11:30.293" />
  <row Id="5502" PostTypeId="1" CreationDate="2010-10-23T10:34:18.117" Score="1" ViewCount="150" Body="&lt;p&gt;How do I connect my mbed NXP LPC1768 to my computer. I have a USB cable and a breadboard. What else do I need? What connections do I need to make?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2010-10-23T13:32:46.843" Title="How to connect mbed to computer" Tags="&lt;usb&gt;&lt;mbed&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="5503" PostTypeId="1" CreationDate="2010-10-23T11:34:34.377" Score="3" ViewCount="149" Body="&lt;p&gt;Yesterday, I read about TEM waves on wikipedia. Those are waves that have no electric or magnetic field vectors pointing into propagation direction of the wave. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But on any picture illustrating EM waves, they &lt;em&gt;are&lt;/em&gt; showing TEM waves instead of the (normal?) non-TEM waves. Before reading about TEM waves, I thought that there exist &lt;em&gt;only&lt;/em&gt; TEM waves (i.e that the characteristic about EM waves is that they &lt;em&gt;are&lt;/em&gt; transversal).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When do non-TEM waves get created and what factors do influence the angle of oscillation of the electric and/or magnetic fields of an EM wave? How do these waves behave different in practice?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for any insight!&lt;/p&gt;&#xA;" LastActivityDate="2010-10-27T19:07:10.710" Title="When do non-TEM waves occur?" Tags="&lt;electromagnetism&gt;&lt;wave&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="5504" PostTypeId="2" ParentId="5498" CreationDate="2010-10-23T12:06:35.687" Score="3" ViewCount="" Body="&lt;p&gt;The theoretical current limit on a bus-powered USB port (the kind in your computer) is 100mA, negotiable up to 500mA. In practice, you probably won't  get as much from the ports on your computer. If you use a &lt;strong&gt;self-powered&lt;/strong&gt; USB hub however, you should be able to get 500mA from every port on the HUB. So if your HUB has 4 ports, you can get 4 * 500mA = 2A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Beware: make sure your HUB comes with a decent power adapter. Some hubs come with a 1A adapter, because manufacturers think it's an unrealistic scenario for users to draw 500mA from EVERY port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out this wiki article:&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/USB_hub#Power&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/USB_hub#Power&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1124" LastActivityDate="2010-10-23T12:06:35.687" CommentCount="2" />
  <row Id="5505" PostTypeId="2" ParentId="5502" CreationDate="2010-10-23T12:07:33.517" Score="2" ViewCount="" Body="&lt;p&gt;You will also need internet access (unless you have local tools installed) to compile and upload programs to the mbed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once plugged in check your computer and you should see the MBED as a USB drive/device. This will then have the necessary website access info you need to start working with the mbed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See this pdf from Philips for further info.. &#xA;&lt;a href=&quot;http://ics.nxp.com/literature/presentations/microcontrollers/pdf/mbed.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ics.nxp.com/literature/presentations/microcontrollers/pdf/mbed.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1304" LastEditorUserId="1304" LastEditorDisplayName="" LastEditDate="2010-10-23T12:28:32.843" LastActivityDate="2010-10-23T12:28:32.843" />
  <row Id="5506" PostTypeId="2" ParentId="5503" CreationDate="2010-10-23T12:38:52.933" Score="-2" ViewCount="" Body="&lt;p&gt;Waveguides propagate TE or TM modes.&lt;/p&gt;&#xA;" OwnerUserId="1644" LastActivityDate="2010-10-23T12:38:52.933" CommentCount="1" />
  <row Id="5507" PostTypeId="1" AcceptedAnswerId="5512" CreationDate="2010-10-23T13:04:15.680" Score="6" ViewCount="245" Body="&lt;p&gt;Without buying an expensive calibration tool, how can I accurately calibrate my multimeters?&lt;/p&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2010-10-24T23:08:56.637" Title="How to calibrate multimeters?" Tags="&lt;multimeter&gt;&lt;multimeter&gt;&lt;calibration&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="3" />
  <row Id="5508" PostTypeId="2" ParentId="4664" CreationDate="2010-10-23T13:13:38.743" Score="3" ViewCount="" Body="&lt;p&gt;Wireless power distribution is a load of bollocks! Pardon my directness, however it is not realistic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nikola Tesla was determined to do this along with General electric as his main sponsor.  He proposed a network of towers emitting power for people to use, the major downfall was that there was no way to bill people.  So GE pulled the plug.  The other issues are to do with interference from such a high voltage electric field, it caused all sorts of problems where it was trialed, so it's not a realistic option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;High voltage transmission lines, and radio towers, do emit energy, it is spherical and goes out in three dimensions, so for a larger radio tower, of for example, 100 kW transmitter, for each meter you are away from it, the amount of power that you can possibly receive is calculated by the inverse square relationship.  At 100 m away, the amount of energy is 100 kW/(4·pi·r&lt;sup&gt;2&lt;/sup&gt;), where r = 100 m.  This equates to 79.58 W/m&lt;sup&gt;2&lt;/sup&gt;.  So if your antenna dish is one square meter in area, and you stand at 100 m from the 100 kW transmitter, at best, you have enough power to run a incandescent light bulb.  not much really.  move away another 100 m, and you are down to 40 W.  This is a large antenna, and for not a great return, and you will most definitely be questioned.  I doubt, however, it would really have an effect on people receiving a signal, you will only create a tiny blind spot in the transmitters path.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand high voltage transmission lines conduct most of their energy, to there is far less radiated out.  Similar maths can be performed to work out the radiated energy and potential recieved energy.  In doing this, you are not &quot;stealing&quot; energy, just collecting waste, and recycling it, so it should not pose a problem to anyone, it may raise some eyebrows with your neighbors, depending on where you live.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of these forms are far field radiation, near field radiation does work for transmission of energy quite effectively, but in this situation, you are transmitting and receiving, so it is not free!!!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are of course, RFID devices, which do not consume much energy, so do work quite well using far field radiation, but not much energy is available, just enough to power some small microprocessors.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-23T14:33:43.217" LastActivityDate="2010-10-23T14:33:43.217" CommentCount="6" />
  <row Id="5509" PostTypeId="2" ParentId="4651" CreationDate="2010-10-23T13:14:11.707" Score="3" ViewCount="" Body="&lt;p&gt;The big thing is whether or not you're ever likely to be using mains voltages - quality gear like Fluke has significant safety features to prevent injury when things go bad. &#xA;For hobbyist use, issues like accuracy, robustness and lost time when it breaks are much less important than for professional use, so the benefits of an expensive unit are much lower. &#xA;If the decision is between cheap DMM plus a cheap scope, or an expensive DMM, the former would usually be more useful to you. &#xA;Also consider a used name-brand over a new cheapie. You will usually get a better bit of kit for your money, albeit maybe a bit bigger and less shiny.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-23T21:25:14.880" LastActivityDate="2010-10-23T21:25:14.880" CommentCount="3" />
  <row Id="5510" PostTypeId="2" ParentId="5435" CreationDate="2010-10-23T13:21:12.957" Score="2" ViewCount="" Body="&lt;p&gt;S3 has been around a while so you'll probably find more options, and cheaper ones as used boards may be an option. &#xA;If you're doing it with a view to making a product in the forseeable future stick with S3 until Xilinx get their act together on availability of newer parts.&#xA;I also hear that the ISE software is getting flakier in later versions, so with S3 you can use an older. more stable version. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-23T13:21:12.957" CommentCount="1" />
  <row Id="5511" PostTypeId="2" ParentId="5502" CreationDate="2010-10-23T13:32:46.843" Score="4" ViewCount="" Body="&lt;p&gt;To expand on my answer in the comment above. Take your mbed out of the packaging and insert it into its' new semi-permanent home on your breadboard. Turn on your computer and connect your mbed using the USB cable which came in the box (or any other similar cable). As Rob says it'll show up as a flash drive called MBED,  I've not used one on a Windows computer but I don't think you have to install any drivers (on Linux it's all ready to go out of the box).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the mbed drive is a single html file,  open this using your browser of choice and it'll take you to the mbed.org site and ask you to register (you have to register to gain access to the online compiler). The good thing about this process is it automagically attaches your mbed serial number to your registered  user (you can't register without having a valid serial number at the moment).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The getting started instructions on the mbed.org site (and on the leaflet that came in the box)  will walk you through downloading the compiled binary example to make LED1 flash on and off. Once you've downloaded it, copy it to the mbed drive, and press the reset button on the mbed (it's in the middle of the board) you should now have a fully functioning blinking LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next have a look at the program in the online compiler and change it. Once you've got it going then you can start hooking it up to various external things. There are various instructions in the Cookbook and Notebook pages at mbed.org (including how to hook it up to a dual digit 7 segment display by me).&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-10-23T13:32:46.843" CommentCount="2" />
  <row Id="5512" PostTypeId="2" ParentId="5507" CreationDate="2010-10-23T13:35:17.123" Score="8" ViewCount="" Body="&lt;p&gt;You can buy a few 0.1% resistors to calculate resistance ranges cheaply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage is tricker - if you have access to several meters you can 'calibrate by consensus', as it is improbable that they will all go out in the same direction. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is buy a precision voltage reference IC - e.g. AD581 is 10V with 0.1% accuracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current can also be done using voltage across a known, accurate resistance.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-23T13:57:11.507" LastActivityDate="2010-10-23T13:57:11.507" />
  <row Id="5513" PostTypeId="1" AcceptedAnswerId="5525" CreationDate="2010-10-23T14:10:33.707" Score="3" ViewCount="214" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;My electronics teacher asked me the other day to research the SAA 1027 to drive stepper motors however whats happened to them? In some newer textbooks they talk about using a PIC and then using a ULN2803 to drive it. Is this the new way as SAA 1027 are now obsolete?&lt;br&gt;&#xA;Thanks in Advance,&lt;br&gt;&#xA;Dean &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-10-23T21:00:29.560" Title="What happened to the SAA1027?" Tags="&lt;stepper&gt;" AnswerCount="1" />
  <row Id="5514" PostTypeId="2" ParentId="5498" CreationDate="2010-10-23T14:22:53.290" Score="2" ViewCount="" Body="&lt;p&gt;As far as I know, no one actually bothers to include current limiting in the USB host, so devices are really on the honor system not to draw more than they are allowed.  I've seen a lot of devices that claim one power but actually draw a lot more, and I've never seen them shut down or anything.  On a desktop, at least, I assume the ports are capable of more than 500 mA.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if you're making a product that will be used by others, read the USB spec and learn how to negotiate with the computer to draw up to 500 mA.  If you're just doing a one-off and you know for some reason that the port is capable of 1.8A, then just draw it.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-23T14:22:53.290" CommentCount="9" />
  <row Id="5515" PostTypeId="2" ParentId="4664" CreationDate="2010-10-23T15:00:00.453" Score="1" ViewCount="" Body="&lt;p&gt;There are stories about farmers winding wire around old engine blocks, and placing these under low-hanging sections of high-power transmission lines that cross their fields, and obtaining usable amounts of energy from them. If you were going to try to capture energy wirelessly as you suggest, this is probably the only practical setup that would amount to anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, it should be pointed out that the same people with the stories about the farmers also frequently have stories about the same farmers being caught. I.e., while it may be fun to talk about in a hypothetical kind of way, it's not advisable to try it, because the power companies and indeed the law tend to view it as a kind of theft.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-23T15:00:00.453" />
  <row Id="5516" PostTypeId="1" AcceptedAnswerId="5543" CreationDate="2010-10-23T16:43:18.130" Score="7" ViewCount="504" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have read bits and pieces of computer organization from the web and off some books. I have also taken a stab at making my own computer architecture while reading the book &quot;The elements of computing systems&quot;. So now I am looking for books which offer me something more than an introduction. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I am looking for something which is more systems design oriented. Thus I have a large amount of theory but also a small amount of system designing of my own (like I did with tecs).&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-06T12:02:11.460" LastActivityDate="2011-01-06T12:02:11.460" Title="A fun book to learn computer architecture (for not-exactly-beginners)." Tags="&lt;computers&gt;&lt;architecture&gt;&lt;risc&gt;" AnswerCount="5" FavoriteCount="6" />
  <row Id="5517" PostTypeId="2" ParentId="5498" CreationDate="2010-10-23T17:03:35.457" Score="2" ViewCount="" Body="&lt;p&gt;I  that it differs from motherboard supplier how good the power supply for the USB is. Some cheap B-brand manufacturers may just link the +5V of the power supply down to the USB port.  Some better ones may actually include the whole package for overcurrent protection etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I got a sweex 4-port (el-cheapo, costed me like 10 euro's) USB hub so I don't have to get under the desk all the time for an USB connection. This sweex port clearly doesn't have any protection. I have smoked shorted MOSFET with it once, which its rated current was 3A. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, my point I want to make is that no matter what your project is, you probably will not want to get over 500mA of current drawn from a USB port. As a one off, maybe.. if you want to risk blowing it up on your own behalf. Certainly not for anyone else.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to think that the power provided by USB is mainly to make it possible to have communication with the real device. You might feature an isolation circuit to give better protection for USB hosts. I'd certainly not take USB as a universal 5V power supply, because adapters can do that much better (and in the long-term probably cheaper).&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-10-23T17:03:35.457" />
  <row Id="5519" PostTypeId="2" ParentId="5494" CreationDate="2010-10-23T18:36:32.163" Score="2" ViewCount="" Body="&lt;p&gt;If you just need extra RAM, and you don't need to address it directly as a memory address (i.e. okay to go through a function call), Microchip makes a &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=23K256-I/P-ND&quot; rel=&quot;nofollow&quot;&gt;32KB SRAM&lt;/a&gt; with a 20 MHz SPI interface in an 8-pin DIP (also available as a SMD) for $1.66 in singles, $1 in quantity.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-10-23T18:42:15.750" LastActivityDate="2010-10-23T18:42:15.750" CommentCount="6" />
  <row Id="5520" PostTypeId="2" ParentId="5493" CreationDate="2010-10-23T18:39:30.913" Score="2" ViewCount="" Body="&lt;p&gt;A quick digikey search with your parameters (&gt;512 MB, serial) reveals these digikey parts:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=TH58100FT-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=TH58100FT-ND&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;TC58DVG02A1FT-ND&lt;/li&gt;&#xA;&lt;li&gt;TC58DVM92A1FT-ND&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;(I would have posted 3 hyperlinks but I don't have enough reputation.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, from brief reading of the data sheet, it looks like their &quot;serial&quot; interface requires you to use a lot more than 2 pins.  Also, they're non-stock items and there is no price listed.&lt;/p&gt;&#xA;" OwnerUserId="1545" LastActivityDate="2010-10-23T18:39:30.913" CommentCount="1" />
  <row Id="5521" PostTypeId="2" ParentId="5516" CreationDate="2010-10-23T18:41:52.863" Score="8" ViewCount="" Body="&lt;p&gt;See the &lt;a href=&quot;http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-823-computer-system-architecture-fall-2005/readings/&quot; rel=&quot;nofollow&quot;&gt;reading list&lt;/a&gt; for MIT's &lt;a href=&quot;http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-823-computer-system-architecture-fall-2005/lecture-notes/&quot; rel=&quot;nofollow&quot;&gt;6.823 Computer System Architecture&lt;/a&gt; course.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-27T13:49:00.757" LastActivityDate="2010-10-27T13:49:00.757" CommentCount="2" />
  <row Id="5522" PostTypeId="1" CreationDate="2010-10-23T20:04:41.853" Score="2" ViewCount="205" Body="&lt;p&gt;How can I check the level of charge left in a battery?&lt;/p&gt;&#xA;" OwnerUserId="1392" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-23T21:11:55.353" LastActivityDate="2010-10-24T17:15:45.317" Title="Battery level - how to check" Tags="&lt;battery&gt;&lt;power-meter&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="2" />
  <row Id="5523" PostTypeId="2" ParentId="5522" CreationDate="2010-10-23T20:46:23.150" Score="0" ViewCount="" Body="&lt;p&gt;If you have a multimeter, set it to &quot;voltage&quot; mode by turning the knob until it says something like &quot;V&quot; for voltage.  (If you have more than one mode with &quot;V&quot; in the name, just try all of them.)  Then connect the black wire of the multimeter to the negative terminal of the battery and connect the red write of the multimeter to the positive terminal of the battery.  The multimeter should tell you the voltage.  You can then compare this to the expected voltage level of a fully charged battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a microcontroller with an ADC, you should make a simple voltage divider circuit using a few resistors that in the 10-100kOhm range, and connect the output of the voltage divide to an ADC pin on your microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The point of the voltage divider is to divide your battery's voltage down to a level that your microcontroller can read (typically 0-3.3V or 0-5V).  If you are using a battery whose voltage is always in that range already, you don't need to use a voltage divide.  Here's an explanation of voltage divider circuits:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage_divider&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Voltage_divider&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1545" LastActivityDate="2010-10-23T20:46:23.150" CommentCount="4" />
  <row Id="5524" PostTypeId="1" AcceptedAnswerId="5578" CreationDate="2010-10-23T20:52:56.590" Score="7" ViewCount="994" Body="&lt;p&gt;So I have just finished learning the basics of Eagle (Lite) and I really like it.  As I don't have the full kit to start home PCB etching yet (something I am looking into now) I would like a tool that could help me design a layout for a veroboard/stripboard.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I had an Eagle schematic, how would I go about designing an equivilent veroboard/stripboard layout either within Eagle itself or possibly even through an export/import into another tool.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-10-23T21:07:30.693" LastActivityDate="2010-11-15T00:12:41.127" Title="Design a veroboard/stripboard layout from an Eagle schematic." Tags="&lt;schematics&gt;&lt;eagle&gt;&lt;stripboard&gt;&lt;stripboard&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="5525" PostTypeId="2" ParentId="5513" CreationDate="2010-10-23T21:00:29.560" Score="3" ViewCount="" Body="&lt;p&gt;I looked for the SAA1027 using findchips.com and it looks like no one has it.  According to this &lt;a href=&quot;http://www.sfu.ca/phys/430/datasheets/saa1027.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet from 13 years ago&lt;/a&gt;, The SAA 1027 can only provide 0.5 A output current and its inputs require inconvenient voltages: you have to provide it a voltage abpve 7.5 V for it to read as high!  This means it would be difficult to interface it with a modern microcontroller running at 3.3 or 5 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One modern, popular way of driving stepper motors is to use the A4983 IC.  It can provide up to 2 A of current per coil, perform microsteps, and it can easily interface with a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pololu sells a convenient &lt;a href=&quot;http://www.pololu.com/catalog/product/1201&quot; rel=&quot;nofollow&quot;&gt;carrier board&lt;/a&gt; for it so you don't have to do SMT soldering yourself.  The reprap community uses this board a lot (&lt;a href=&quot;http://reprap.org/wiki/Pololu_Electronics&quot; rel=&quot;nofollow&quot;&gt;see here&lt;/a&gt;).&lt;/p&gt;&#xA;" OwnerUserId="1545" LastActivityDate="2010-10-23T21:00:29.560" />
  <row Id="5526" PostTypeId="1" AcceptedAnswerId="5528" CreationDate="2010-10-23T21:08:55.570" Score="4" ViewCount="94" Body="&lt;p&gt;At the moment I'm working on a system which will use a 400KHz I2C bus. The bus wires (SCL, SDA) are different lengths by a few cm, so the delay between them will be in picosecond to nanosecond range - I don't think I need to worry about this but am I misguided?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-23T21:11:50.087" Title="Is it worth worrying about propagation delay differences when dealing with relatively slow protocols like I2C @ 400kHz?" Tags="&lt;i2c&gt;&lt;delay&gt;&lt;timing&gt;" AnswerCount="1" FavoriteCount="0" />
  <row Id="5527" PostTypeId="2" ParentId="5522" CreationDate="2010-10-23T21:09:26.490" Score="4" ViewCount="" Body="&lt;p&gt;Two things happens to batteries as they discharge. The open-circuit (unloaded) voltage goes down, but there is also internal resistance in the battery that goes up with increasing states of discharge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the battery technology, the voltage may gradually slope off over time, or it may only dip a couple of tenths before suddenly giving out all at once. So generally you can tell the difference between a fully charged battery and a nearly dead one by measuring voltage, but it can be difficult to tell with partially discharged batteries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The internal resistance is what really matters anyway. You can't measure it by sticking an ohm-meter on a battery, but you can infer it by measuring the battery voltage while it's under a load. You need a load appropriate for the battery voltage and current capability, so you might use an automotive incandescent bulb for a small 12V lead-acid battery, or an LED for a coin cell. Just something you'd typically expect the battery to be able to power. If you measure the voltage while the battery is powering the load, you get a much better indication of how charged it is.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-23T21:09:26.490" CommentCount="0" />
  <row Id="5528" PostTypeId="2" ParentId="5526" CreationDate="2010-10-23T21:11:50.087" Score="6" ViewCount="" Body="&lt;p&gt;For anything under 50MHz, difference in trace lengths like that wouldn't be a concern.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-23T21:11:50.087" CommentCount="2" />
  <row Id="5529" PostTypeId="2" ParentId="2190" CreationDate="2010-10-23T21:24:02.217" Score="4" ViewCount="" Body="&lt;p&gt;You might not need a MOSFET.  You should measure how much current your servo uses when you are not sending any pulses on the signal line.  I imagine that a well-designed servo would go in to a deep sleep mode and only use a few hundred micro-amps, but I've never tried this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do need a MOSFET, I recommend using a P-channel MOSFET on the power line of the servo (the middle wire).  You can connect the gate of of the MOSFET to the power supply through a 10-100kOhm pull-up resistor to guarantee that it is off by default.  Then use a microcontroller IO line to pull the gate low when you want the servo to be powered, and then make the IO line be a high impedance input when you want to cut servo power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your circuit diagram should look like the right-hand side of this &lt;a href=&quot;http://electronics.stackexchange.com/questions/3599/basic-p-type-mosfet-question/3604#3604&quot;&gt;diagram from reemrevnivek&lt;/a&gt; (just look at Q2)&#xA;&lt;img src=&quot;http://i.imgur.com/iewyp.png&quot; alt=&quot;Diagram of how to use MOSFETs from reemrevnivek&quot;&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this case, the &quot;load&quot; on the right-hand side is your servo.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll want to look at your MOSFETs datasheet to make sure that the leakage currents are not too bad.&lt;/p&gt;&#xA;" OwnerUserId="1545" LastActivityDate="2010-10-23T21:24:02.217" CommentCount="4" />
  <row Id="5530" PostTypeId="2" ParentId="5524" CreationDate="2010-10-23T22:02:13.630" Score="5" ViewCount="" Body="&lt;p&gt;I've never tried Eagle for stripboard layout, but here's a tutorial I found:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://home.roadrunner.com/~perks/micros/Projects/Stripboard_EAGLE/Stripboard_EAGLE.htm&quot; rel=&quot;nofollow&quot;&gt;http://home.roadrunner.com/~perks/micros/Projects/Stripboard_EAGLE/Stripboard_EAGLE.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-23T22:02:13.630" />
  <row Id="5531" PostTypeId="1" AcceptedAnswerId="5535" CreationDate="2010-10-24T04:21:32.023" Score="6" ViewCount="412" Body="&lt;p&gt;I just obtained an old rotary phone at a garage sale. I am working on hooking it up to an arduino project, and I was able to get the dial and hook switches figured out pretty easily. I cannot really figure out how the ringer works, or how to wire it up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is an old western electric C4A ringer. It has two bells and a striker arm between them. There is a coil, and some magnetic plates that move the ringer, with four wires going into the coil. I have found schematics online for how the thing connects to the other phone components for normal operation, but I really just wanna figure out how to make the thing ring on its own. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I read that most phone lines run in the vicinity of 90 volts ac. Is there any possibility I can make this thing ring with a 12 volt wall wart, or am I gonna need a full 120 line and a relay or something? &lt;/p&gt;&#xA;" OwnerUserId="1686" LastEditorUserId="1686" LastEditorDisplayName="" LastEditDate="2010-10-24T05:53:10.977" LastActivityDate="2010-10-24T12:48:05.950" Title="Wiring up old phone ringer to arduino" Tags="&lt;arduino&gt;&lt;telephone&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="5532" PostTypeId="1" CreationDate="2010-10-24T04:31:21.687" Score="3" ViewCount="496" Body="&lt;p&gt;The specific kit I am talking about is this one&#xA;&lt;a href=&quot;http://www.oreillynet.com/pub/a/network/2000/01/31/mindstorms/&quot; rel=&quot;nofollow&quot;&gt;http://www.oreillynet.com/pub/a/network/2000/01/31/mindstorms/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I integrate these motors with an arduino. &lt;/p&gt;&#xA;" OwnerUserId="1687" LastActivityDate="2010-10-24T23:23:03.140" Title="Using Lego Mindstorms Inventions motors with arduino" Tags="&lt;arduino&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5533" PostTypeId="2" ParentId="5531" CreationDate="2010-10-24T04:59:31.650" Score="4" ViewCount="" Body="&lt;p&gt;Phone lines normally run on -48v DC (referenced to ground) when the line is idle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;During the ringing cycle (in the US, 2 seconds on, 4 seconds off), a ringing voltage of 75-90v AC (typically 20 Hz in the US) is superimposed on top of the -48v DC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you take your phone off-hook, the line card at the central office (CO) senses the current and disconnects the ringing voltage.  Meanwhile the voltage at the phone drops down to -12v or so, mostly due to the voltage drop across the line from the CO to your house.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you cannot ring an older style phone with a voltage lower than 75v AC or so.  Also, do not use 60 Hz AC from your house outlet -- that won't work either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need some sort of circuit that will create a 20 Hz sine wave (square wave would probably also work), that is amplified to 90v.  There is a circuit on &lt;a href=&quot;http://www.techlib.com/electronics/telephone.html&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt;, under &quot;Telephone Ringer&quot;.  (Note: I haven't built it, but it looks like it could work.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would need a relay connected to the Arduino to turn it on and off.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-24T04:59:31.650" CommentCount="4" />
  <row Id="5534" PostTypeId="2" ParentId="5532" CreationDate="2010-10-24T06:43:31.903" Score="4" ViewCount="" Body="&lt;p&gt;I have done this quite easily with &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=17_21&amp;amp;products_id=81&amp;amp;zenid=23551fb15568be2dffcb6d248a1f116e&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; shield. That may be a little overkill, but if you are like me and don't know much about voltages and stuff, it is a good safe way to get some good motor drivers. I power that off of my arduino with a 9-12v wall adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to actually connect to the motors you have a couple of options. I split one of the lego wires in the middle and wired it into the motor shield directly. Another, less destructive way would be to solder two wires to one of the metal lined lego plated and connect those wires to the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The motors are really just simple dc motors, so nothing special is required. Just use the example code on the instruction page for that shield.&lt;/p&gt;&#xA;" OwnerUserId="1686" LastActivityDate="2010-10-24T06:43:31.903" />
  <row Id="5535" PostTypeId="2" ParentId="5531" CreationDate="2010-10-24T07:25:21.483" Score="5" ViewCount="" Body="&lt;p&gt;Look at page 2 and 3 of the schematic .pdf from this &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8929&quot; rel=&quot;nofollow&quot;&gt;page&lt;/a&gt;. Sparkfun have done it using an H-bridge and voltage booster circuit. Quite nifty really. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-24T07:25:21.483" CommentCount="1" />
  <row Id="5537" PostTypeId="1" AcceptedAnswerId="5538" CreationDate="2010-10-24T10:52:48.277" Score="3" ViewCount="125" Body="&lt;p&gt;When it comes down to having PCBs produced is solder paste applied to the pads so I can stick the IC's down or do I have to add paste myself?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-24T22:00:57.540" Title="Solder paste, is it standard?" Tags="&lt;pcb&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="5538" PostTypeId="2" ParentId="5537" CreationDate="2010-10-24T10:57:38.793" Score="6" ViewCount="" Body="&lt;p&gt;You need to apply paste yourself. Once applied it deteriorates quite quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Conventional soldering equipment can be used with surface-mount devices; I do it all the time.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-24T10:57:38.793" CommentCount="2" />
  <row Id="5539" PostTypeId="2" ParentId="5531" CreationDate="2010-10-24T12:48:05.950" Score="1" ViewCount="" Body="&lt;p&gt;You could take a small one of those 120V to 6.3V step-down transformers (like RS sells), and 'use it backwards' to step up a low voltage signal from some drive transistors to nearly the right voltage for the phone ringer mechanism.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you run 5V AC into the 6.3V secondary, you should get about 5 * (120/6.3) = 95.2V out on the primary side, which is a little high, but not terribly so. You could probably get away with using a single switching transistor to drive the secondary from your 5VDC supply, but be sure to put a fly-back diode across the coil to keep the transistor from getting killed. Then it's just a matter of turning the drive transistor on/off at about 20Hz for the desired length of time.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-24T12:48:05.950" />
  <row Id="5540" PostTypeId="1" AcceptedAnswerId="5561" CreationDate="2010-10-24T13:28:22.447" Score="7" ViewCount="586" Body="&lt;p&gt;Currently purchasing the required kit to start etching my own boards and have gotten to the etching solution stage.  Ferric Chloride seems to be the standard for etching but I have also read about &lt;a href=&quot;http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/#step1&quot; rel=&quot;nofollow&quot;&gt;Muriatic Acid + Hydrogen Peroxide ecthing&lt;/a&gt;, which apparently is better all round (both for the environment and my pocket).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone had any experience with this method of etching?&lt;/p&gt;&#xA;" OwnerUserId="1333" LastActivityDate="2011-03-17T12:27:59.673" Title="Ferric Chloride or Muriatic Acid + Hydrogen Peroxide for etching?" Tags="&lt;pcb&gt;&lt;etching&gt;" AnswerCount="6" FavoriteCount="2" />
  <row Id="5541" PostTypeId="2" ParentId="5540" CreationDate="2010-10-24T14:10:44.967" Score="4" ViewCount="" Body="&lt;p&gt;Can't comment on that specific combo but I know that some alternatives have poor shelf life of made-up solution. &#xA;FeCl solution lasts indefinitely. The  biggest downside of FeCl is that it stains.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-24T14:10:44.967" />
  <row Id="5542" PostTypeId="2" ParentId="5540" CreationDate="2010-10-24T15:15:02.690" Score="4" ViewCount="" Body="&lt;p&gt;I always use Natrium Persulfate for etching. I quite like it because it is results in a clear liquid so you can see the progress of your etching. It turns blue after a while but with a sufficient concentration you can reuse it multiple times. It will stain your clothes if you're not careful but it's doesn't stain your skin, like Ferric Chloride does. The advantage over  Muriatic Acid + Hydrogen Peroxide is that it won't hurt you (as much) if it comes in contact with your skin. If you get Natrium Persulfate on your hands you can just rinse it off. &lt;a href=&quot;http://www.roxlu.com/blog/entry/66/womby-0.1/?page=4&amp;amp;tag=&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;'s some of my etching being performed using Natrium Persulfate. (photo's in reversed order)&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2010-10-24T15:15:02.690" CommentCount="2" />
  <row Id="5543" PostTypeId="2" ParentId="5516" CreationDate="2010-10-24T15:54:21.803" Score="10" ViewCount="" Body="&lt;p&gt;Hennessy and Patterson Computer Organization and Design is a great intro.  James L. Patterson, Computer Architecture is at a higher level.&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2010-10-24T15:54:21.803" CommentCount="1" />
  <row Id="5544" PostTypeId="1" AcceptedAnswerId="5611" CreationDate="2010-10-24T16:36:23.790" Score="4" ViewCount="173" Body="&lt;p&gt;Hi, I am a PHP programmer with basic knowledge of c/c++ and electronics. But i have keen interest in robotics and AI. &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What are the basic things that i&#xA;need to learn before switching to&#xA;the robotics ?&lt;/li&gt;&#xA;&lt;li&gt;What languages are&#xA;used to write the code and how is&#xA;that code transferred to the chips ? &lt;/li&gt;&#xA;&lt;li&gt;What are the basic components that i&#xA;need to know ?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I would like to learn about the both hardware components and the programming part. (Are these different streams?)&lt;/p&gt;&#xA;" OwnerUserId="1525" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-27T04:09:33.820" LastActivityDate="2011-02-27T04:09:33.820" Title="How can a PHP programmer go to robotics" Tags="&lt;robotics&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="5545" PostTypeId="1" AcceptedAnswerId="5559" CreationDate="2010-10-24T17:08:29.847" Score="3" ViewCount="206" Body="&lt;p&gt;Is there a Arduino-like hardware platform that allows for wireless connectivity (think remote control) and for connection of a webcam (with streaming that wireless video over the wireless connection)? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really like the idea of a prebuilt hardware platform and would be interested in getting into robotics. Since I am already a proficient programmer, it would be great to take this into the physical world as well.&lt;/p&gt;&#xA;" OwnerUserId="1692" LastActivityDate="2010-10-26T01:12:18.570" Title="Arduino-like Platform With Wireless and Video?" Tags="&lt;arduino&gt;&lt;wireless&gt;&lt;hardware&gt;&lt;video&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5546" PostTypeId="2" ParentId="5325" CreationDate="2010-10-24T17:13:26.813" Score="0" ViewCount="" Body="&lt;p&gt;As I am looking to deploy on a &quot;real&quot; PoE network, the Freetronics stuff is not going to work for me. I've contacted the folks at Akros and arranged to get a protoboard after signing an NDA… But at present Akros does not have a US distributor, so parts availability for homebrew projects is likely to be problematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm still interested if anyone has suggestions for a similar SoC solution for standards-compliant PoE.&lt;/p&gt;&#xA;" OwnerUserId="1317" LastActivityDate="2010-10-24T17:13:26.813" />
  <row Id="5547" PostTypeId="2" ParentId="5522" CreationDate="2010-10-24T17:15:45.317" Score="3" ViewCount="" Body="&lt;p&gt;I think the way a lot of commercial devices do it is with measuring the current coming out of the battery over time, known as &quot;Coulomb Counting&quot;. If your battery holds 1000 mAh, and you measure 300mA being used for an hour, then you know there is 700mAh left in the battery, or 70%. Here's a page &lt;a href=&quot;http://www.mpoweruk.com/soc.htm&quot; rel=&quot;nofollow&quot;&gt;that talks about this method&lt;/a&gt; (along with the less accurate voltage-based method)&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-10-24T17:15:45.317" CommentCount="1" />
  <row Id="5548" PostTypeId="2" ParentId="5498" CreationDate="2010-10-24T17:20:40.467" Score="6" ViewCount="" Body="&lt;p&gt;You can negotiate for 500mA with one of the FTDI USB chips, here's a &lt;a href=&quot;http://forums.adafruit.com/viewtopic.php?f=25&amp;amp;t=16108&quot; rel=&quot;nofollow&quot;&gt;forum post&lt;/a&gt; that talks about it. If you use some other chip, you still need something that can speak the USB protocol and tell the PC that it wants 500mA. Please don't violate the USB spec, your device might work fine for some people, but then it wont work for others, and you risk causing damage to poorly designed PC's.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-10-24T17:20:40.467" />
  <row Id="5549" PostTypeId="1" AcceptedAnswerId="5553" CreationDate="2010-10-24T17:21:02.677" Score="3" ViewCount="283" Body="&lt;p&gt;Are these traces too close for conventional PCB manufacture? DRC check advises against it, but I haven't filled out all the settings for it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/BljK6.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For scale, the resistors are all 0603.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-30T21:26:20.607" LastActivityDate="2010-11-30T22:00:51.207" Title="How close is too close for traces on a PCB?" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;&lt;layout&gt;&lt;dfm&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="3" />
  <row Id="5550" PostTypeId="2" ParentId="5544" CreationDate="2010-10-24T17:24:02.433" Score="2" ViewCount="" Body="&lt;p&gt;You should learn by experimentation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To your questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;You should learn basic electronics theory, and the basics of microcontrollers.&lt;/li&gt;&#xA;&lt;li&gt;Code is often written in C, but sometimes it can be written in other languages like Basic, and some processors support .NET.&lt;/li&gt;&#xA;&lt;li&gt;Resistors, capacitors, diodes and transistors are probably the most common devices you will encounter, in that order. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I would recommend you try with a board already available, like an Arduino or PICAXE.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-24T17:24:02.433" CommentCount="3" />
  <row Id="5551" PostTypeId="2" ParentId="5544" CreationDate="2010-10-24T17:26:30.297" Score="4" ViewCount="" Body="&lt;p&gt;I would suggest starting with an Arduino board and one of the many &quot;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596155514&quot; rel=&quot;nofollow&quot;&gt;Getting Started with Arduino&lt;/a&gt;&quot;-style books out on the market. This is a very beginner-friendly way to get introduced to the world of embedded processors, device programming and simple circuit hacking. A few hours with an Arduino will also help you decide where your interests are really focused. (E.g. if you hate having to wire up an LED circuit just to see your program work, you probably want to focus on a more ready-made platform for robotics exploration. Whereas if you find the hardware tinkering appealing, you might want to move on to a very basic, bare-bones kit like the &lt;a href=&quot;http://www.parallax.com/Store/Robots/AllRobots/tabid/128/ProductID/601/List/0/Default.aspx?SortField=ProductName,ProductName&quot; rel=&quot;nofollow&quot;&gt;Parallax Stingray&lt;/a&gt;.)&lt;/p&gt;&#xA;" OwnerUserId="1317" LastActivityDate="2010-10-24T17:26:30.297" />
  <row Id="5552" PostTypeId="2" ParentId="5503" CreationDate="2010-10-24T17:28:15.350" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://redshift.vif.com/JournalFiles/Pre2001/V07NO1PDF/V07N1MGU.pdf&quot; rel=&quot;nofollow&quot;&gt;http://redshift.vif.com/JournalFiles/Pre2001/V07NO1PDF/V07N1MGU.pdf&lt;/a&gt; &#xA;That PDF has a nice writeup on non-planar EM waves which all have longitudinal components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at my non-linear optics literature I see that one cause of non-transverse behavior is when the EM field generated alters the dielectric properties of the propagation material.  This alteration travels with the wave (thus in the propagation direction).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What a cool question!&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2010-10-24T17:28:15.350" />
  <row Id="5553" PostTypeId="2" ParentId="5549" CreationDate="2010-10-24T17:36:55.200" Score="11" ViewCount="" Body="&lt;p&gt;It really depends entirely on what the signals are carrying and what the manufacturer says they are capable of.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The general rule of thumb is that you should maintain a minimum of the width of the trace. If you are using 10mil traces, then you should also have 10 mil of space between them. If your traces are carrying sharp-edged waveforms (i.e. square waves, digital signals, data buses) or sensitive networks (A/D, sensor or op-amp inputs) then you want to maintain more of a distance and perhaps add a guard ring (ground traces) on either side of the trace in question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am a (very) happy customer of Sunstone; their manufacturing process allows me to use 5 mil trace with 5 mil space without any trouble, and they can do 3/3 if you're willing to pay extra. A 5 mil trace is a damned thin trace and pretty much at the level of most commercial boards these days, so there is little reason to go thinner unless you have some specialized application. For most of my boards I try to stick to 8, 12 or even 16 mil traces since they're much more rugged and easier to work with should you have to modify the board. If you're carrying high current or routing supplies I will make the traces as wide as I can afford to, from a board real-estate perspective. Wide traces are good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see from your picture that you're running traces between the pads of 0603 components. This isn't verboten, but it's also generally something you will want to avoid. It's too easy to end up either bridging some solder to the trace underneath (soldermask failure) or damaging the trace if you have to lift the component off (e.g. a bit of flux sticking under the part and effectively &quot;gluing&quot; the trace to the bottom of the component. The trace from R15 also goes &lt;strong&gt;awfully&lt;/strong&gt; close to the pad for R8, and the trace that goes around the top right-hand side of the board seems to come awfully close to the via. It would be wise of you to find out what the board manufacturer is capable of doing, and what the recommend (these are not the same thing) and programming that into your layout's DRC. If the DRC flags something, fix it. This is Design For Manufacture (DFM) 101. If you violate the DRC you end up with higher manufacture wastage and in the end, more expensive boards.  Sunstone is really nice here; they provide eagle-format DRC rule files. You simply download it and use them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DRC can be a real pain in the ass, but it's like eating your veggies; your project will be better off for it in the end.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-24T17:36:55.200" CommentCount="4" />
  <row Id="5556" PostTypeId="1" AcceptedAnswerId="5560" CreationDate="2010-10-24T18:27:18.980" Score="8" ViewCount="226" Body="&lt;p&gt;I am going to be selling my project, Super OSD. It has a 3 MHz SMPS PSU and an 8 MHz crystal oscillator, but is not intended to emit radio signals. Will it be necessary to get it FCC tested to sell it in the USA? What about other countries? I am selling from Europe, the UK to be specific.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-24T23:55:38.880" Title="Is FCC testing necessary for all devices?" Tags="&lt;fcc&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="5557" PostTypeId="1" AcceptedAnswerId="5564" CreationDate="2010-10-24T18:30:13.140" Score="3" ViewCount="173" Body="&lt;p&gt;Why are polyfuses so big? I was looking at a 500mA polyfuse, it is in an 0805 package, but there was only one of them - the rest were 1206. I have two questions.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Why so big?&lt;/li&gt;&#xA;&lt;li&gt;Does anyone make 0603 polyfuses?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-03T17:02:33.673" LastActivityDate="2011-01-03T17:02:33.673" Title="Why are polyfuses so big?" Tags="&lt;fuses&gt;&lt;pptc&gt;&lt;pptc&gt;" AnswerCount="2" />
  <row Id="5559" PostTypeId="2" ParentId="5545" CreationDate="2010-10-24T18:36:23.197" Score="3" ViewCount="" Body="&lt;p&gt;I think that your best bet would be a Linux based system. Something like Beagle Board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Arduinos and their ilk tend to target low cost microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to stream video over a wireless connection, you're going to need a fast processor and a fast wireless link. I'd pick an ARM based system, running Linux with WiFi.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an example of what can be done with a BeagleBoard:&#xA;&lt;a href=&quot;http://mechomaniac.com/OpenCVBallTracking&quot; rel=&quot;nofollow&quot;&gt;http://mechomaniac.com/OpenCVBallTracking&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-24T18:49:50.877" LastActivityDate="2010-10-24T18:49:50.877" CommentCount="3" />
  <row Id="5560" PostTypeId="2" ParentId="5556" CreationDate="2010-10-24T18:38:41.960" Score="6" ViewCount="" Body="&lt;p&gt;To sell in the EU, you will need a CE mark, wheelie bin logo and RoHS statement.  You do not need to use an EU test house, but do need to be able to provide evidence to the authorities upon request for all of these. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are manufacturing in China, they will generally provide you with a RoHS statement.  If buying from China they will also provide the CE Mark (remember to ask for documentation).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure about what is required to get an FCC mark.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-24T18:38:41.960" />
  <row Id="5561" PostTypeId="2" ParentId="5540" CreationDate="2010-10-24T18:49:36.150" Score="5" ViewCount="" Body="&lt;p&gt;I've used the muriatic acid/hydrogen peroxide solution.  It works great when it's fresh, but it does NOT keep for me.  If I go back and use it a couple of weeks later, it just doesn't work.  I haven't pursued proper disposal, yet, so I've accrued a bit of the stuff in mason jars (whose lids are rusting from the acid, by the way).  Once I figure out how to get rid of the acid/peroxide mixture, I think I'm going to try FeCl.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-10-24T18:49:36.150" CommentCount="3" />
  <row Id="5562" PostTypeId="2" ParentId="5516" CreationDate="2010-10-24T18:58:09.843" Score="3" ViewCount="" Body="&lt;p&gt;Computer System Architecture - M. Morris Mano&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will teach you every basics in a &lt;em&gt;very right way&lt;/em&gt;&lt;/p&gt;&#xA;" LastActivityDate="2010-10-24T19:04:50.300" CommentCount="1" />
  <row Id="5563" PostTypeId="2" ParentId="5549" CreationDate="2010-10-24T20:16:08.033" Score="2" ViewCount="" Body="&lt;p&gt;Andrew's answer is spot on for general routing.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some other aspects that are worth knowing even if they are not relevant for this application, is clearance for higher voltages and low pressure (high altitude).  EN60065 is a good starting place for higher voltages and mains voltages as it gives minimum clearances required for commercial equipment. In one of my previous roles, we did designs for avionics systems and the clearance required become much larger due to the reduced air pressure, hence reduced insulation between traces.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One method of increasing insulation is to use conformal coating.  This has the added advantage that the insulation will not change over time, compared to an uncoated board that has dust and dirt settle on it.  Dust and dirt will reduce the resistance, and may lead to  short circuits between higher voltages traces.  Hence the requirements of EN60065.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-24T20:16:08.033" />
  <row Id="5564" PostTypeId="2" ParentId="5557" CreationDate="2010-10-24T20:32:24.813" Score="7" ViewCount="" Body="&lt;p&gt;As I can see from wikipedia, a polyfuse works as that it is a thermistor where the resistance changes non-linear with it's temperature. It's designed to heat up much faster when the current goes after a certain point. That's why there is a tripping time, because the fuse has to heat up. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can see why they aren't in 0603 because you would blow them up too quickly. Polyfuses aren't indestructible , for sure they will go bang if you trip them with too much current. I think to make them a lot more durable, because they need some room to have enough material in place. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also I can imagine that the series resistance can't be very low  (it needs to heat up), and it might be difficult to produce a polyfuse with very low series resistance for it's size and current.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-10-24T20:32:24.813" CommentCount="2" />
  <row Id="5565" PostTypeId="1" AcceptedAnswerId="5570" CreationDate="2010-10-24T20:47:37.237" Score="3" ViewCount="74" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I got given a Cirrus Logic EDB7209-2B.0 with LCD Display. It powers up(the power LED lights up and there is power on the board accessing the ARM CPU) but i'm unsure on what to do with it has anyone got any experience with one of these development boards? I know when it left the factory it was running some basic MP3 player. It has some NAND Flash, Flash and DRAM memory. But i have no programming cable for it. Is there a jtag cable i can make? The main processsor is a Cirrus Logic EP7209-CV-C. I would quite like the board to be able to program to play with software development for the ARM processors.&lt;br&gt;&#xA;Thanks in Advance,&lt;br&gt;&#xA;Dean &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-10-24T22:37:27.487" Title="Any ideas on what to do with a board that condition is unknown?" Tags="&lt;arm&gt;&lt;embedded&gt;" AnswerCount="1" />
  <row Id="5566" PostTypeId="1" AcceptedAnswerId="5567" CreationDate="2010-10-24T20:49:05.547" Score="4" ViewCount="220" Body="&lt;p&gt;In one of the answers on this site, I found link to &lt;a href=&quot;http://www.evilmadscientist.com/article.php/nightlight&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; project. That article mentions internal resistance of batteries and cells. Where can I find data about common ranges of internal resistances for batteries? I've always heard that it's low, but I couldn't find anywhere how low is low and common resistances for common battery types.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-24T21:44:13.993" LastActivityDate="2010-10-24T21:44:13.993" Title="Internal resistance of batteries?" Tags="&lt;battery&gt;&lt;batteries&gt;&lt;resistance&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="5567" PostTypeId="2" ParentId="5566" CreationDate="2010-10-24T21:19:53.417" Score="5" ViewCount="" Body="&lt;p&gt;The datasheets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, here is the datasheet for Duracell Plus AA (retail) batteries: &lt;a href=&quot;http://www.farnell.com/datasheets/97133.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.farnell.com/datasheets/97133.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do some searching around on the websites of Duracell, Energizer and the like you can often find these datasheets, though they are hidden away. I found this on Farnell's website.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First page, table 1: &quot;Nominal Internal Impedence&quot; - 181mohm @ 1kHz. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-24T21:19:53.417" CommentCount="1" />
  <row Id="5568" PostTypeId="2" ParentId="5566" CreationDate="2010-10-24T21:19:57.740" Score="-2" ViewCount="" Body="&lt;p&gt;I found &lt;a href=&quot;http://en.wikipedia.org/wiki/Internal_resistance&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; with Google.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-24T21:19:57.740" CommentCount="1" />
  <row Id="5569" PostTypeId="2" ParentId="5566" CreationDate="2010-10-24T21:26:53.910" Score="4" ViewCount="" Body="&lt;p&gt;You wouldn't know it by purchasing from a department store, but battery manufacturers (like &lt;a href=&quot;http://data.energizer.com/&quot; rel=&quot;nofollow&quot;&gt;Energizer&lt;/a&gt;, &lt;a href=&quot;http://www1.duracell.com/procell/productdata/&quot; rel=&quot;nofollow&quot;&gt;Duracell&lt;/a&gt;, etc.) publish datasheets.  Look for their industrial/OEM sections. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A standard alkaline Energizer AA battery has an internal series resistance of 150 to 300 milliohms, from the datasheet &lt;a href=&quot;http://data.energizer.com/PDFs/E91.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  The asterisk by that number will refer you to Energizer's &lt;a href=&quot;http://data.energizer.com/PDFs/BatteryIR.pdf&quot; rel=&quot;nofollow&quot;&gt;whitepaper on battery internal resistance&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take some time to look around &lt;a href=&quot;http://data.energizer.com/&quot; rel=&quot;nofollow&quot;&gt;data.energizer.com&lt;/a&gt;, it's really a very good resource.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-24T21:26:53.910" />
  <row Id="5570" PostTypeId="2" ParentId="5565" CreationDate="2010-10-24T21:36:28.593" Score="4" ViewCount="" Body="&lt;p&gt;Getting the power light to work is step 0.  Once you know it might be in working condition (You might also want to see if you can poke around with an oscilloscope and see if anything appears to be working).  After that, step 1 is finding the datasheets/manuals.  You want the quick start manual and/or one-page advertisement for the basic specs, then the datasheet for the board, the manufacturer's datasheet for the processor, and the ARM datasheet(s) for the processor.  Here's what I found with some brief Googling: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.cirrus.com/en/pubs/manual/EP7209QS-1.pdf&quot; rel=&quot;nofollow&quot;&gt;Quick Start User's Guide&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://ecos.sourceware.org/ecos/boards/edb7209.html&quot; rel=&quot;nofollow&quot;&gt;eCos page&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://infocenter.arm.com/help/topic/com.arm.doc.ddi0192a/DDI0192A.pdf&quot; rel=&quot;nofollow&quot;&gt;ARM 720T Technical Reference Manual&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Step 2 is to blink an LED, and Step 3 is to start up some kind of communication between the device and a development PC.  Step 4 is completely up to you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you can load the device with whatever OS you want to play with (this platform appears to have good OS support in spite of its age), and work from there.  I'd advise more knowledge about the inner workings of the processor before going too far here, but it's your choice.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be aware that the board has been &lt;a href=&quot;http://www.cirrus.com/en/products/eol/detail/EOL60.html&quot; rel=&quot;nofollow&quot;&gt;discontinued since around 2003&lt;/a&gt;.  You might have some luck bugging Cirrus for support, and seeing if you can convince them to send you a newer version :)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that &lt;a href=&quot;http://www.cirrus.com/en/products/eol/index.html&quot; rel=&quot;nofollow&quot;&gt;they do say&lt;/a&gt; that they can't provide applications engineering support for discontinued products.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, I'd recommend against using this board if your real goal is to learn to develop software for the ARM processors.  This is using a v4 architecture from the early 2000s, they're on v7 now.  From the &quot;Classic Processors&quot; section of arm.com: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;While the ARM7 processor family&#xA;  continues to be used today for simple&#xA;  32-bit devices, newer embedded designs&#xA;  are increasingly making use of latest&#xA;  ARM processors such as the Cortex™-M0&#xA;  and Cortex-M3 processors, both of&#xA;  which offer significant technical&#xA;  enhancements over the ARM7* family.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This is more for the continuingly and overwhelmingly popular ARTM7TDMI than any other processor in this lineup.  I'd strongly suggest, if you want to learn software development for ARM processors as a marketable skill, that you learn on a newer processor like a Cortex-M0 or -M3 (or a Cortex-A9 if the better embedded OS support and MMU on the 720T is important to you).  If you just want to have fun with some donated hardware, then you're going to need some serious Google-fu in your fingertips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*The ARM7 family and ARMv7 architecture version are very different things. ARM7 is [mostly] related to ARMv4, but also ARMv3 and v5, and ARMv4 is related to ARM7, 8, and 9.  The Cortex family and v7 architecture are mostly equivalent.  See the &lt;a href=&quot;http://en.wikipedia.org/wiki/ARM_architecture&quot; rel=&quot;nofollow&quot;&gt;Wikipedia article&lt;/a&gt; for more information.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-24T22:37:27.487" LastActivityDate="2010-10-24T22:37:27.487" CommentCount="3" />
  <row Id="5571" PostTypeId="2" ParentId="5557" CreationDate="2010-10-24T21:46:57.660" Score="4" ViewCount="" Body="&lt;p&gt;Littelfuse make &lt;a href=&quot;http://www.littelfuse.com/data/en/Data_Sheets/Littelfuse_PTC_0603L.pdf&quot; rel=&quot;nofollow&quot;&gt;0603 polyfuses&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-24T21:46:57.660" />
  <row Id="5572" PostTypeId="1" AcceptedAnswerId="5589" CreationDate="2010-10-24T21:50:19.650" Score="3" ViewCount="381" Body="&lt;p&gt;Something like this&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/oFLOK.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://falstad.com/circuit/#%24+1+5.0E-6+10.20027730826997+50+5.0+50%0Av+144+208+144+288+0+1+50.0+320.0+0.0+0.0+0.5%0Ar+144+192+208+192+0+47.0%0Ac+208+192+272+192+0+3.3000000000000004E-8+145.0041552541953%0Ar+208+144+272+144+0+2200000.0%0Aw+272+144+272+192+0%0Aw+208+192+208+144+0%0Ad+304+192+368+192+1+0.805904783%0Ad+304+224+368+224+1+0.805904783%0Ad+368+256+304+256+1+0.805904783%0Ad+368+288+304+288+1+0.805904783%0Aw+144+208+144+192+0%0Aw+304+224+288+224+0%0Aw+288+224+288+288+0%0Aw+288+288+144+288+0%0Aw+304+256+272+256+0%0Aw+272+256+272+192+0%0Aw+272+192+304+192+0%0Aw+304+288+288+288+0%0Aw+368+224+368+192+0%0Aw+368+256+368+288+0%0Aw+368+192+400+192+0%0Aw+368+288+400+288+0%0Ar+512+192+512+288+0+10000.0%0Ac+448+192+448+288+2+4.7E-5+3.2183512965471346%0Az+400+288+400+192+1+0.805904783+3.3%0Aw+448+288+400+288+0%0Aw+448+192+400+192+0%0Aw+512+192+448+192+0%0Aw+512+288+448+288+0%0Ag+400+288+400+304+0%0Ao+22+64+0+35+5.0+0.003125+0+-1%0Ao+0+64+1+291+3.57986298980937+9.765625000000002E-255+1+-1%0Ao+23+64+0+33+1.789931494904685+0.008949657474523427+2+-1%0A&quot; rel=&quot;nofollow&quot;&gt;Falstad sim version of it&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I'm tired, I keep making mistakes, so please excuse me for the second time.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now these are not very safe PSU's, due to the lack of isolation. But in sealed units, they can be a cheap way of getting the supply voltage for a microcontroller without an SMPS or transformer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are not 100% efficient due to the zener and resistors. But, I have several questions.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How does the capacitor step down the voltage, anyway? Does it waste power as heat? &lt;/li&gt;&#xA;&lt;li&gt;If the zener were gone and the output was let to float around 50V, would it approach 100% efficiency?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-25T00:34:52.560" LastActivityDate="2011-02-07T19:10:31.187" Title="How efficient is a capacitive power supply?" Tags="&lt;psu&gt;" AnswerCount="5" CommentCount="7" FavoriteCount="1" />
  <row Id="5573" PostTypeId="2" ParentId="5572" CreationDate="2010-10-24T21:54:44.933" Score="4" ViewCount="" Body="&lt;p&gt;The zener is what gives you the 3.3V output. The capacitor doesn't 'step down' the voltage, it just soaks up a charge whenever the rectified AC happens to exceed the zener voltage, and feeds the load during the times when the rectified AC is less than that. Since your load is only 10K and the cap is 47uF, the 0.47 second RC constant means that the capacitor doesn't discharge much while the zener is off, meaning the load voltage doesn't sag significantly while operating on capacitor power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The major power waster would be the series dropping resistor, as it takes all of the load (and zener) current and drops practically all of the line voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you left off the zener and tried to use this as an unregulated supply, the efficiency depends on the load. More current means more dissipation in that series resistor, means less efficiency. You could get near 100% efficiency only if you were only drawing incredibly minute amounts of current, in which case the voltage would also ride up to about 1.4 times the line RMS voltage.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-10-25T02:33:48.343" LastActivityDate="2010-10-25T02:33:48.343" CommentCount="3" />
  <row Id="5575" PostTypeId="2" ParentId="5537" CreationDate="2010-10-24T22:00:57.540" Score="3" ViewCount="" Body="&lt;p&gt;No. You get bare, dry boards.  Solder paste should be used as soon as possible after application, because the flux contained in the paste will deteriorate when exposed to oxygen. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're doing mass manufacture yourself, consider getting a stencil made for your board.  I've heard good things about &lt;a href=&quot;http://www.stencilsunlimited.com&quot; rel=&quot;nofollow&quot;&gt;Stencils Unlimited&lt;/a&gt; for small-volume work.  Then, you just squirt out a little solder paste at one end, run a (sharp steel) squeegee over the stencil, and lift - Perfect solder paste application in seconds!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're doing just a few/small boards and the $125 investment in a prototype stencil feels steep, I'd just use standard solder wire. Put a small dome on the PCB pad, position the part, heat the pin until it drops to the PCB, and you're off to the races.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-24T22:00:57.540" />
  <row Id="5576" PostTypeId="2" ParentId="5507" CreationDate="2010-10-24T23:08:56.637" Score="2" ViewCount="" Body="&lt;p&gt;Bring them to your university or employer, and see if you can get them to calibrate them for you the next time they do their calibration run. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;No, I'm serious.  I expect that most schools and employers will be happy to see that their students and employees are developing their skills outside of the school/work environment, and when you've got a production line set up for a hundred meters already, the addition of one (or a few) more meters isn't that big of a deal.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-24T23:08:56.637" />
  <row Id="5577" PostTypeId="1" AcceptedAnswerId="5583" CreationDate="2010-10-24T23:10:39.433" Score="4" ViewCount="161" Body="&lt;p&gt;I have an 800W ATX power supply given to me by a friend because it doesn't work any more. It's quite a beast and would set me back a considerable amount new, so I'd like to see if I can fix it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, here's the story. It has standby power at 5.15V. The power indicator on the back lights up (on the mains switch - it's an LED not a neon apparently, because when you turn off the unit it fades slowly, making me think it's not directly connected to the mains.) Anyway, when you turn it on (by grounding the PS_ON pin) it makes a faint clicking sound but does nothing else. With my scope I have found three short pulses of ~11.8V on the 12V rail for about 500 ms to 1.5 seconds before the supply goes dead, which makes me think some kind of protection system is being activated, as the power supply does work - it is producing the required output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it doesn't work it is going in the trash, so no loss there.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-24T23:36:19.247" LastActivityDate="2010-10-25T22:36:45.453" Title="Fixing an ATX PSU." Tags="&lt;psu&gt;&lt;atx&gt;&lt;repair&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="5578" PostTypeId="2" ParentId="5524" CreationDate="2010-10-24T23:18:54.533" Score="7" ViewCount="" Body="&lt;p&gt;First, you don't need to do &lt;em&gt;home&lt;/em&gt; PCB etching to get real circuit boards made.  BatchPCB and other prototype services can get you real, quality PCBs for (sometimes much) less than $50.   If it's just for a temporary project, solderless breadboards are also a great tool.  I will admit, however, that some projects fall into the middle of these categories.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually, I just poke the components through .2&quot; graph paper for checking that an imagined layout will work.  This seems to work well enough for most of the simple circuits that I make on perfboard.  If you want to use Eagle PCB, configure the layout editor for 0.1&quot; grid spacing, and display the lines:&#xA;&lt;img src=&quot;http://i.imgur.com/jpX6v.png&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;br&gt;&#xA;Now you can lay it out on a model of your stripboard.  You might even want to diagram the strips.  Use the &quot;Draw Lines&quot; tool on a non-copper layer (like Documents) to avoid confusing Eagle with respect to electrical connections.  Record where the strips should be left intact on one layer, and make wire jumpers on (an) other layer(s).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that, it's up to you to create an intelligent layout. Since these kinds of boards are usually for development purposes, make it spacious and easy to understand. I try to organize power busses with higher voltages at the top and ground at the bottom, route signals from left to right, color-code connecting wires (esp. if you're not using stripboard), and provide lots of room for edits to fix the mistakes I know I will make.  I also like to keep my components on one side and route wires on the other even when using double-sided board.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-24T23:18:54.533" CommentCount="1" />
  <row Id="5579" PostTypeId="2" ParentId="5532" CreationDate="2010-10-24T23:23:03.140" Score="3" ViewCount="" Body="&lt;p&gt;You can do it captncraig's way - or if you want to learn while your building I have another suggestion. What you can do instead of purchasing an already configured motor sheield you can learn how to interface a dc motor on your own. Trust me, this will come in handy later down the road. You do this with an H-Bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first thing you need to do is to figure out the specs of your motor. You would want to know the amperage and voltage it runs on and also all the stall specs. You could do this manually with a multimeter but lucky for you someone did it already.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are all the specs for the mindstorms motors: &lt;a href=&quot;http://www.philohome.com/motors/motorcomp.htm&quot; rel=&quot;nofollow&quot;&gt;your welcome ;)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the next thing you have to do is find an H-Bridge that will meet those requirements. That should be too hard. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have a good idea what you are doing you can put it all together. This is a wonderful tutorial that will show you how to use an H-Bridge with an arduino. It even has a sketch you can download! &#xA;&lt;strong&gt;(because of my reputation I can't post more than one link, this link will be in a comment below)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck and happy hacking!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;logickills&lt;/p&gt;&#xA;" OwnerUserId="1480" LastActivityDate="2010-10-24T23:23:03.140" CommentCount="1" />
  <row Id="5580" PostTypeId="2" ParentId="1990" CreationDate="2010-10-24T23:48:18.647" Score="2" ViewCount="" Body="&lt;p&gt;I'd been producing my own boards for nearly 10 years. But for me at least, it is no longer the most cost effective solution. With the prevalence of PCB manufacturers in Asia -- I just find it so much inexpensive for someone to do it for you. If you are looking for good English customer service, these are a few of tried during the past year (for low volume quantities): &lt;/p&gt;&#xA;&#xA;&lt;p&gt;internationalcircuits.com&lt;br&gt;&#xA;pcbexpress.com&lt;br&gt;&#xA;jetpcb.com&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards&lt;/p&gt;&#xA;" LastActivityDate="2010-10-24T23:48:18.647" CommentCount="1" />
  <row Id="5581" PostTypeId="2" ParentId="5498" CreationDate="2010-10-24T23:51:51.817" Score="19" ViewCount="" Body="&lt;p&gt;I think I can attempt to clear this up.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;USB-100mA&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;USB by default will deliver 100mA of power(it is power because we know it is 5v, right?) to a device. This is the most you can pull from a USB hub that does not have its own power supply, as they never offer more than 4 ports and keep a greedy 100mA for themselves.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some computers that are cheaply built will use an bus powered hub internally to increase the number of USB ports and to save a small amount of money. This can be frustrating, but you can always be guaranteed 100mA.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;USB-500mA&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;When a device is connected it goes through enumeration. This is not a trivial process and can be seen in detail on &lt;a href=&quot;http://www.lvr.com/usbcenum.htm&quot; rel=&quot;nofollow&quot;&gt;Jan Axelson's site&lt;/a&gt;. As you can see this is a long process, but a chip from a company like FTDI will handle the hard part for you. They discuss enumeration in one of &lt;a href=&quot;http://www.ftdichip.com/Support/Documents/TechnicalNotes/TN_113_Simplified%20Description%20of%20USB%20Device%20Enumeration.pdf&quot; rel=&quot;nofollow&quot;&gt;their app notes&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Near the end of enumeration you setup device parameters. Very specifically the configuration descriptors. If you look on &lt;a href=&quot;http://www.beyondlogic.org/usbnutshell/usb5.shtml&quot; rel=&quot;nofollow&quot;&gt;this website they will show you all of the different pieces that can be set&lt;/a&gt;. It shows that you can get right up to 500mA of power requested. This is what you can expect from a computer. You can get FTDI chips to handle this for you, which is nice, as you only have to treat the chip as a serial line.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;USB-1.8A&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;This is where things get interesting. You can purchase a charger that does outlet to USB at the store. This is a USB charging port. your computer does not supply these, and your device must be able to recognize it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, to get the best information about USB, you sometimes have to bite the bullet and go to the people whom write the spec. I found &lt;a href=&quot;http://www.usb.org/developers/devclass_docs&quot; rel=&quot;nofollow&quot;&gt;great information about the USB charging spec here&lt;/a&gt;. The link on the page that is useful is the &lt;a href=&quot;http://www.usb.org/developers/devclass_docs/batt_charging_1_1.zip&quot; rel=&quot;nofollow&quot;&gt;link for battery charging&lt;/a&gt;. This link seems to be tied to revision number, so I have linked both in case the revision is updated people can still access the information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, what does this mean. if you open up the batt_charging PDF and jump to chapter three they go into charging ports. Specifically 3.2.1 explains how this is gone about. Now they keep it very technical, but the key point is simple. A usb charging port places a termination resistance between D+ and D-. I would like to copy out the chapter that explains it, but it is a secured PDF and I cannot copy it out without retyping it.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Summing it up&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;You may pull 100mA from a computer port. You may pull 500mA after enumeration and setting the correct configuration. Computers vary their enforcement, as many others have said, but most I have had experience with will try to stop you. If you violate this, you may also damage a poorly design computer (Davr is spot on there, this is poor practice). You may pull up to 1.8A from a charging port, but this is a rare case where the port tells you something. You have to check for this and when it is verified you may do it. This is the same as buying a wall adapter, but you get to use a USB cable and USB port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why use the charging spec? So that when my phone dies, my charger charges it quickly, but if I do not have my charger I may pull power from a computer, while using the same hardware port to communicate files and information with my computer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please let me know if there is anything I can add.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-20T02:52:23.933" LastActivityDate="2011-02-20T02:52:23.933" CommentCount="6" />
  <row Id="5582" PostTypeId="2" ParentId="5556" CreationDate="2010-10-24T23:55:38.880" Score="5" ViewCount="" Body="&lt;p&gt;Here is a question that answers the FCC part of your question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/5196/which-products-should-have-fcc-certification-and-about-how-much-does-that-cost&quot;&gt;http://electronics.stackexchange.com/questions/5196/which-products-should-have-fcc-certification-and-about-how-much-does-that-cost&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-24T23:55:38.880" />
  <row Id="5583" PostTypeId="2" ParentId="5577" CreationDate="2010-10-25T00:02:25.137" Score="12" ViewCount="" Body="&lt;p&gt;Bad capacitors. It's always bad capacitors ( and it's never Lupus)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They've dried out and become resistive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the process they sometimes make life ugly for power transistors and diodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're not safe with some mains voltage ( there may be &lt;em&gt;some&lt;/em&gt; in the hot side of the supply) please don't open the box.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Look for swollen electrolytic capacitors  (metal cans)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Replace with reputable parts^H^H^H^H^H^H^H^H^H same value parts (no consumer components supplier will sell parts as nasty as a cheap manufacturer can buy wholesale).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check diodes and transistors on output side for blowage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Main high voltage mains side capacitor might be dried out. Shows up as overload in feedback paths and shutdown. Replace it. Must be same voltage rating!!!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Go see the sci.electronics.repair FAQ.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-10-25T00:02:25.137" CommentCount="7" />
  <row Id="5584" PostTypeId="2" ParentId="3760" CreationDate="2010-10-25T00:04:36.420" Score="1" ViewCount="" Body="&lt;p&gt;Here are a couple of low priced options I've used before (though not for 6 layers).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PCB Universe (pcbuniverse.com) offers a deal similar to E-teknet - 4 pcs/99.99 each (but they provide the option of ordering more than 4 pcs at a discounted cost). Min cost = $400.00.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;International Circuits (internationalcircuits.com) they provide a more unique service (fit as many pcs into preset panel sizes): &lt;/p&gt;&#xA;&#xA;&lt;p&gt;100 square inches for $350.00 &lt;br&gt;&#xA;200 square inches for $400.00&lt;/p&gt;&#xA;" LastActivityDate="2010-10-25T00:04:36.420" CommunityOwnedDate="2011-05-20T11:44:01.827" CommentCount="1" />
  <row Id="5585" PostTypeId="1" AcceptedAnswerId="5610" CreationDate="2010-10-25T00:30:14.780" Score="4" ViewCount="363" Body="&lt;p&gt;See image below;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/MI84B.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My suspicions would say that part of the silkscreen would disappear over a via, does this happen in production?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-25T16:50:40.280" Title="What happens when you get silkscreen over a via?" Tags="&lt;pcb&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="5586" PostTypeId="2" ParentId="5585" CreationDate="2010-10-25T00:36:23.743" Score="1" ViewCount="" Body="&lt;p&gt;This really depends on the fab house. I have found at the fab houses that I use they don't even attempt to put silkscreen over a via. It is possible though that when they put the solder mask down it covers the entire hole allowing for the silkscreen to attach to something.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-25T00:36:23.743" />
  <row Id="5587" PostTypeId="2" ParentId="5572" CreationDate="2010-10-25T01:26:24.397" Score="2" ViewCount="" Body="&lt;p&gt;Here is the simulation I am looking at. Don't pay too much attention to the instantaneous readings on the AC side as they are of course fluctuating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I adjust the 10k load to a 1k load I am only able to get 782mV out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/O1XId.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-25T01:26:24.397" CommentCount="4" />
  <row Id="5588" PostTypeId="2" ParentId="5585" CreationDate="2010-10-25T01:57:55.273" Score="6" ViewCount="" Body="&lt;p&gt;It depends on what's already been done with the via.  Vias can be:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Filled - A silver-based epoxy inserted so that the via can be...&lt;/li&gt;&#xA;&lt;li&gt;Capped - Copper layers cover the filler.  The via can now be used as a pad.&lt;/li&gt;&#xA;&lt;li&gt;Plugged - A blob of soldermask is applied to the via. Creates a slight bump.&lt;/li&gt;&#xA;&lt;li&gt;Tented - Just plain soldermask film covers the via, often slightly concave.  Limited to small-diameter vias.&lt;/li&gt;&#xA;&lt;li&gt;Plain.  Nothing is done, this is your ordinary via.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If a via (or other metal surface) has not had any of these treatments, the silkscreen will not stick to the via.  No big deal. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recommend plugging all vias in non-development boards to maintain insulation for the trace.   Then, silkscreen might be distorted, but it will be visible.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, the answer is &quot;Ask your fab house.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, the better option is to re-arrange of your silk. Keep all silk  aligned in the same direction, for the sake of your neck.  Be consistent locally with respect to what side of the component the silk is located on.  If an area is a little bit too tight, move the silk away and draw a line (in silk) pointing to the component.  If everything is too tight, or you want a less busy looking board, leave off components that are never going to change or be looked at (decoupling caps, pullup/pulldown resistors, protection diodes) in favor of clarity for components which are going to be looked at (CONNECTORS, integrated circuits, power components).   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The image you've provided is nearly indecipherable to me.  Either of the large components could be U6, and the two-pad device at the bottom could be R22, 27, or 18. Also, if that is an 0603, then it looks like that text will be painfully small.  &lt;strong&gt;All silk should have a width of at least 6 mils&lt;/strong&gt; for most fab houses (and easier reading).  In Eagle, this means that size x ratio &gt; 0.006.  0.08&quot; text at a 10% ratio will produce 8 mils, which is workable, and 0.05&quot; text at a 12% ratio just makes it.  Bigger/bolder fonts for important stuff are nice.  Also, &lt;strong&gt;use vector fonts, not proportional fonts.&lt;/strong&gt;  This is based on my experience with Eagle, but the font you use isn't encoded in the Gerbers, unless you use a vector font.  Otherwise, your fab may substitute some other font, which will cause all your careful alignment to be screwed up.  It appears that you're doing the latter, but not the former.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-25T01:57:55.273" />
  <row Id="5589" PostTypeId="2" ParentId="5572" CreationDate="2010-10-25T02:23:22.503" Score="10" ViewCount="" Body="&lt;p&gt;I'd suggest either implementing a standard power supply configuration, or (preferably) purchasing one.  If you're not capable of calculating the efficiency of this circuit, you're likely not capable of implementing a new power supply design connected to mains power safely.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't mean to be harsh, but the cost of an isolated, safe, ready-made, efficient, nicely packaged wall wart is absolutely negligible compared with the medical bills associated with electrocution, which is itself negligible compared to the costs associated with being sued for causing electrocution if you're selling/distributing this thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh, and in answer to your questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;it's using all linear, passive&#xA;components, so the efficiency is&#xA;&lt;code&gt;vout/vin[peak]&lt;/code&gt;.  This turns out to be pretty bad; you'll need a huge resistor and zener.  &lt;/li&gt;&#xA;&lt;li&gt;The capacitor doesn't step down the voltage, the 47 ohm resistor and zener diode do that.  The capacitor just smooths it out a little.  Note that using your original half-wave rectifier, you'd have a ripple of I/(fC) = 1.6V. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-25T02:23:22.503" CommentCount="1" />
  <row Id="5591" PostTypeId="2" ParentId="5572" CreationDate="2010-10-25T06:10:08.813" Score="4" ViewCount="" Body="&lt;p&gt;Don't do it, these circuits are really quite dangerous.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have pretty bad efficiency, but it doesn't really matter as a circuit like this can only operate with a steady current thats very low.  You lose power in all the resistors, the diodes and some in the caps due to ESR.  The ESR of a ceramic cap can be quite high at 50hz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can't open circuit these circuits, at least not without a bulky zener, remove the load resistor and look at the current through the zener.  You basically have to operate them at a constant load current, something in the range of 10-15mA usually to get reasonable regulation.  As your current goes up your ripple will increase a lot and the voltage output will begin to sag heavily.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As to your questions:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;How does the capacitor step down the&#xA;  voltage, anyway? Does it waste power&#xA;  as heat?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;basically, you've built a low pass filter set such that with a load resistance in the operational range your after it's attenuation at 50hz is whatever was needed.  As the load resistance drops (current increases) this attenuation increases to the point where your regulated voltage drops. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit will make a lot more sense if you look at in the frequency domain instead of time.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If the zener were gone and the output&#xA;  was let to float around 50V, would it&#xA;  approach 100% efficiency?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;No, you lose power in all the diodes and all the resistors.  If you remove the zener you lose basically all regulation, the voltage and level of ripple would vary heavily with load resistance.  &lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-25T06:34:09.203" LastActivityDate="2010-10-25T06:34:09.203" />
  <row Id="5592" PostTypeId="1" CreationDate="2010-10-25T10:04:19.670" Score="6" ViewCount="352" Body="&lt;p&gt;According to Wikipedia, processing power is strongly linked with Moore's law:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Moore%27s_law&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Moore's_law&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The number of transistors that can be&#xA;  placed inexpensively on an integrated&#xA;  circuit has doubled approximately&#xA;  every two years. The trend has&#xA;  continued for more than half a century&#xA;  and is not expected to stop until 2015&#xA;  or later. The capabilities of many&#xA;  digital electronic devices are&#xA;  strongly linked to Moore's law:&#xA;  processing speed, memory capacity,&#xA;  sensors and even the number and size&#xA;  of pixels in digital cameras. All&#xA;  of these are improving at (roughly)&#xA;  exponential rates as well.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;As someone who has some background in computer architecture, I don't understand why throwing in more transistors in a CPU would boost a its power since ultimately, instructions are roughly read/executed sequentially. Could anyone explain which part I'm missing?&lt;/p&gt;&#xA;" OwnerUserId="1702" LastActivityDate="2010-10-25T12:55:21.357" Title="Why does more transistors = more processing power?" Tags="&lt;microprocessor&gt;&lt;cpu&gt;&lt;architecture&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="5593" PostTypeId="2" ParentId="5592" CreationDate="2010-10-25T10:31:29.187" Score="8" ViewCount="" Body="&lt;p&gt;The number of transistors does not necessarily correlate to more processing power, however, with more transistors, the processor can perform increasingly more complicated instructions than before. For example, a processor with SSE will use additional transistors to implement these complex instructions (adding many numbers in one cycle, for example.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-25T10:31:29.187" CommentCount="1" />
  <row Id="5594" PostTypeId="2" ParentId="5540" CreationDate="2010-10-25T10:40:13.573" Score="5" ViewCount="" Body="&lt;p&gt;I've switched from FeCl to acid/hydrogen peroxide exclusively, in my experience it has an extremely short shelf life but considering how cheap it is that hardly matters, the main benefits are etching speed and results, FeCl takes 3 to 4 times longer than a new batch of acid/hydrogen peroxide and with the latter I've done tracks down to 0.2mm with no problems.&lt;/p&gt;&#xA;" OwnerUserId="1427" LastActivityDate="2010-10-25T10:40:13.573" CommentCount="1" />
  <row Id="5595" PostTypeId="2" ParentId="5592" CreationDate="2010-10-25T11:18:35.527" Score="3" ViewCount="" Body="&lt;p&gt;Another factor: as you cram more transistors into a given area they get smaller, making them faster.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-25T11:18:35.527" CommentCount="1" />
  <row Id="5596" PostTypeId="2" ParentId="5592" CreationDate="2010-10-25T11:29:00.057" Score="8" ViewCount="" Body="&lt;p&gt;A lot of things that give you more power just require more transistors to build them. Wider buses scale the transistor count up in almost all processor components. High speed caches add transistors according to cache size. If you lengthen a pipeline you need to add stages and more complex control units. If you add execution units to help mitigate a bottleneck in the pipeline, each of those requires more transistors, and then the controls to keep the execution units allocated adds still more transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing is, in an electronic circuit, &lt;em&gt;everything&lt;/em&gt; happens in parallel. In the software world, the default is for things to be sequential, and software designers go to great pains to get parallelism built into the software so that it can take advantage of the parallel nature of hardware. Parallelism just means more stuff happening at the same time, so roughly equates to speed; the more things that can be done in parallel, the faster you can get things done. The only &lt;em&gt;real&lt;/em&gt; parallelism is what you get when you have more transistors on the job.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-25T11:29:00.057" />
  <row Id="5597" PostTypeId="1" AcceptedAnswerId="5599" CreationDate="2010-10-25T11:58:15.270" Score="4" ViewCount="500" Body="&lt;p&gt;The HC-49 xtal is an 8 MHz crystal, and the radial crystal is an RTC 32.768 kHz crystal. C11, C12 are 22pF, and C13, C14 are 18pF.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/nxOuK.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The traces go directly into a micro (a PIC24F.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried to follow Microchip's guidelines on this, but they advised using surface mount xtals and talked about &quot;guard rings&quot; which are alien to me.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-25T16:20:32.300" Title="How's my crystal oscillator layout?" Tags="&lt;pcb&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="5598" PostTypeId="1" AcceptedAnswerId="5607" CreationDate="2010-10-25T12:16:41.047" Score="5" ViewCount="305" Body="&lt;p&gt;I'm designing an auto-ranging voltmeter using the on-board ADC of my micro for A to D and a digital potentiometer as a programmable resistive divider to control the range. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My concern is the possibility of the ADC input being momentarily shorted to the measured input voltage before the micro-controller has adjusted the pot for the appropriate range. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How is over-voltage protection usually implemented in this type of scenario?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also if there are resources for digital multimeter design, e.g schematics etc, that would also be very useful for ideas (as I'm sure there are probably better ways to approach this than mine), Ive have searched but haven't found much.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks to everyone for the informative answers. &#xA;Here is the over-voltage protection circuit that Iv decided on. &#xA;I plan to use schottky diodes for greater precision.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;During a negative voltage transient,&#xA;  the bottom diode will conduct, thereby&#xA;  clamping the voltage to one diode drop&#xA;  below ground. During a positive&#xA;  voltage transient, the top diode will&#xA;  be forward biased, thus conducting the&#xA;  surge to the power rail.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;From: &lt;a href=&quot;http://www.conformity.com/artman/publish/printer_116.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.conformity.com/artman/publish/printer_116.shtml&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/PkEV8.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="819" LastEditorUserId="819" LastEditorDisplayName="" LastEditDate="2010-10-29T18:22:13.110" LastActivityDate="2010-10-29T18:22:13.110" Title="Auto-Ranging Meter Design" Tags="&lt;microcontroller&gt;&lt;adc&gt;&lt;voltage-measurement&gt;&lt;protection&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="4" />
  <row Id="5599" PostTypeId="2" ParentId="5597" CreationDate="2010-10-25T12:22:22.430" Score="4" ViewCount="" Body="&lt;p&gt;It's a good idea to return the ground for the feedback capacitors directly to the nearest ground pin on the MCU, to reduce emissions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A guard ring is simply a track connected to ground. It shouldn't have any other connections made to it, as it shouldn't carry any current.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-10-25T12:29:33.767" LastActivityDate="2010-10-25T12:29:33.767" />
  <row Id="5600" PostTypeId="2" ParentId="5597" CreationDate="2010-10-25T12:24:21.220" Score="2" ViewCount="" Body="&lt;p&gt;Guard rings are a term used to describe low-impedance traces that surround or &quot;guard&quot; a high-impedance or sensitive signal. Usually the guard ring is a ground connection, but it can be any low-impedance signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A quick google search for &quot;guard ring&quot; with a few other terms (layout, crystal, oscillator) brought up several useful links such as &lt;a href=&quot;http://this&quot; rel=&quot;nofollow&quot;&gt;http://www.emesystems.com/pdfs/parts/DS1307_xtal.pdf&lt;/a&gt;, &lt;a href=&quot;http://this&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/resources/prod_documents/doc8128.pdf&lt;/a&gt; and &lt;a href=&quot;http://this&quot; rel=&quot;nofollow&quot;&gt;www.national.com/an/AN/AN-1372.pdf&lt;/a&gt;, among others.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-25T12:24:21.220" CommentCount="1" />
  <row Id="5601" PostTypeId="2" ParentId="5598" CreationDate="2010-10-25T12:46:32.123" Score="2" ViewCount="" Body="&lt;p&gt;In this scenario you would usually use a combination of zeners and diodes to protect the ADC input from excessive voltages. You would also avoid letting even the overload voltage approach the maximum input voltage (e.g. have your meter measure 0-2V and set the overload at 3V for a 3.3V supply.) &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-25T12:46:32.123" CommentCount="1" />
  <row Id="5602" PostTypeId="2" ParentId="5592" CreationDate="2010-10-25T12:55:21.357" Score="2" ViewCount="" Body="&lt;p&gt;Microprocessors have advanced significantly in recent years, things like longer pipelines, predicative branching and on chip cache have all added to the complexities associated with a processor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sure the basics of CPU processing, fetch, decode, ALU, write is still the same, but to speed things up, longer pipelines are used. Longer pipelnes increase performance for continous code executiion, but also incur bigger hit times when the code branches damage performance. Remedy, predictive branching.  Predictive branching is a trade secret, that intel do not normally disclose the full workings of, just simply use it to keep the performance as high as possible on their CPUs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cache memory is much faster than RAM, but what to move from RAM into cache and from cache back to RAM??? That is again, proprietary stuff, but it again takes transistors to implement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the extra transistors go into things like the longer pipeline, predictive branch algorithms, cache memory, and memory algorithms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is without mentioning multi core processors, and shared memory/resource access controllers.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-25T12:55:21.357" />
  <row Id="5603" PostTypeId="1" CreationDate="2010-10-25T13:26:38.723" Score="7" ViewCount="236" Body="&lt;p&gt;What would be the simplest way without using a microcontroller to make a stop light circuit. All it must do is go from Green -&gt; Yellow -&gt; Red.&lt;/p&gt;&#xA;" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-26T17:27:03.200" LastActivityDate="2010-10-26T17:27:03.200" Title="Most Simple Stoplight circuit" Tags="&lt;homework&gt;&lt;logic&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="2" />
  <row Id="5604" PostTypeId="2" ParentId="5603" CreationDate="2010-10-25T13:29:14.847" Score="6" ViewCount="" Body="&lt;p&gt;You could do it with a 555 timer and a counter:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.kpsec.freeuk.com/projects/trafficlight.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.kpsec.freeuk.com/projects/trafficlight.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-25T13:29:14.847" CommentCount="4" />
  <row Id="5605" PostTypeId="2" ParentId="5585" CreationDate="2010-10-25T13:34:34.853" Score="1" ViewCount="" Body="&lt;p&gt;Just as an example this is a silkscreen gone wrong, it's all over the pads. Luckily I just made 2 boards. (9 mil for spaces, 16 mils for traces).&#xA;&lt;img src=&quot;http://i.imgur.com/SfqkA.jpg&quot; alt=&quot;Silkscreen gone wrong&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1673" LastActivityDate="2010-10-25T13:34:34.853" CommentCount="2" />
  <row Id="5606" PostTypeId="2" ParentId="5597" CreationDate="2010-10-25T13:41:51.240" Score="1" ViewCount="" Body="&lt;p&gt;General uC layout guidelines can be found in Atmel's AVR042 application note.  I like it a lot and it has some good basic advice.  Specifically it has guidelines on laying out the board with crystals in mind: &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2521.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/resources/prod_documents/doc2521.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-10-25T13:41:51.240" />
  <row Id="5607" PostTypeId="2" ParentId="5598" CreationDate="2010-10-25T14:19:46.370" Score="4" ViewCount="" Body="&lt;p&gt;OpenCircuits input protection discussion: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.opencircuits.com/Input_protection&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/Input_protection&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It basically boils down to some resistors to limit current and a zener to limit voltage with a couple of capacitors thrown in.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-10-25T14:19:46.370" CommentCount="1" />
  <row Id="5608" PostTypeId="2" ParentId="5597" CreationDate="2010-10-25T14:36:03.470" Score="4" ViewCount="" Body="&lt;p&gt;I realize you are using a through hole crystal, but the idea is the same.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/3XYS0.jpg&quot; alt=&quot;ground&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a professionally fabricated board I would have smaller vias allowing me to place more along my shield as well as some under my pic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a note, only 1 of the pins on the PIC is ground, but I went ahead and connected an IO pin to ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And as another note, it is not shown here, but I a full ground plane that my vias are connecting to.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-10-25T15:05:46.133" LastActivityDate="2010-10-25T15:05:46.133" CommentCount="1" />
  <row Id="5609" PostTypeId="2" ParentId="5603" CreationDate="2010-10-25T14:55:51.997" Score="0" ViewCount="" Body="&lt;p&gt;You are going to want a very slow clock source, but this should be relatively easy to do with next state logic and 3 flip-flops (clearly you only need two, but one hot encoding makes it easy for 1 extra flip-flop)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;just feed the flip flops to each other in a loop, have it reset so that one goes to green, and you have it.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-25T14:55:51.997" CommentCount="1" />
  <row Id="5610" PostTypeId="2" ParentId="5585" CreationDate="2010-10-25T15:17:18.877" Score="2" ViewCount="" Body="&lt;p&gt;By default gEDA PCB Designer will just cover all the vias with the solder mask, to change this you can hover over the via with your cursor and press &amp;lt;&lt;em&gt;key&lt;/em&gt;&gt; k to uncover the vias, use &amp;lt;&lt;em&gt;key&lt;/em&gt;&gt; &lt;em&gt;shift&lt;/em&gt; k to go back to tented.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out PCB's manual entry on vias for more info-&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://pcb.gpleda.org/pcb-cvs/pcb.html#Via-Objects&quot; rel=&quot;nofollow&quot;&gt;http://pcb.gpleda.org/pcb-cvs/pcb.html#Via-Objects&lt;/a&gt;   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plus- &lt;a href=&quot;http://www.delorie.com/pcb/docs/gs/gs.html&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; by DJ Delorie describes how Geda PCB handles solder masking, it also has some great illustrations of the different masked vias. &lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-10-25T16:50:40.280" LastActivityDate="2010-10-25T16:50:40.280" CommentCount="7" />
  <row Id="5611" PostTypeId="2" ParentId="5544" CreationDate="2010-10-25T15:28:58.023" Score="3" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;1) What are the basic things that i&#xA;  need to learn before switching to the&#xA;  robotics ?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Really, all you need to know is what your goals and interests are.  Often, you can't find this out until you try a few things. Without this knowledge, there's a huge amount to learn.  Motion, size, code volume, and interfaces are all very different in various systems.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;2) What languages are used to write&#xA;  the code and how is that code&#xA;  transferred to the chips ?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The vast majority of the time, code is written in C, possibly with a little bit of assembler to do some hardware operations that can't be done in C.  Sometimes, C is used to build up an operating system, and then code is written for that operating system (again, still using C) or a virtual machine is created, which runs a higher-level language like Java, Lua, or C#.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually, this is done on a PC with a cross-compiler, which creates a hex or  which cannot run on the machine that the compiler runs on, but can run on the micro.  Then, a programmer is used to interface with the microcontroller using USB, serial, or even Ethernet.  Sometimes, this 'programmer' is located on the same PCB as the microcontroller, such as on the Arduino board.  Communication protocols like JTAG, ISP, and other various standard methods can be used, although some chips require specialized programmers.  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;3) What are the basic components that&#xA;  i need to know ?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Again, this depends on what your end goal is.  You should have a basic understanding of electricity (Ohms' law can probably get you by in most cases, as well as an understanding of diodes and transistors/MOSFETs).   Blinking an LED is an easy first step (off a tall cliff).  If you're serious about robotics, you should learn about motor drivers, servos, and stepper motors. &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I would like to learn about the both&#xA;  hardware components and the&#xA;  programming part. Are these different&#xA;  streams?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Only slightly so.  It is possible to use hardware components without having to write a program, and it is possible to buy premade hardware modules and then just do the programming part, but eventually the two go hand in hand.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-25T15:28:58.023" CommentCount="4" />
  <row Id="5613" PostTypeId="1" AcceptedAnswerId="5667" CreationDate="2010-10-25T15:37:45.873" Score="4" ViewCount="474" Body="&lt;p&gt;I am interested to know if there is a good audiobook on electronics for a beginner.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have searched about the web, but haven't found anything yet.&lt;/p&gt;&#xA;" OwnerUserId="1706" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-04T16:10:15.597" LastActivityDate="2011-05-04T16:10:15.597" Title="Audio Book for beginners in Electronics Design" Tags="&lt;audio&gt;&lt;books&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="5614" PostTypeId="2" ParentId="5613" CreationDate="2010-10-25T15:58:45.207" Score="3" ViewCount="" Body="&lt;p&gt;I'm haven't heard of any in particular, but don't let that stop you in your search.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I will say that I imagine it would be hard to learn electronics using only audio.  The mathematical, graphical, and technical nature of the subject combine to make learning the subject with limited control over the pace of the speaker and a complete lack of graphics nearly impossible in my mind.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-25T15:58:45.207" />
  <row Id="5615" PostTypeId="2" ParentId="5597" CreationDate="2010-10-25T16:20:32.300" Score="2" ViewCount="" Body="&lt;p&gt;I would move C13 and C14 to the right of the crystal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also put more space between the oscillator signals and the RTC signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On C14, you have the trace going right through it.  I've seen recommendations against this for thermal reasons.  That pad will leak more heat and cause the solder to solidify differently.  The recommended way is to put a small stub from the main trace to the pad.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-10-25T16:20:32.300" CommentCount="1" />
  <row Id="5616" PostTypeId="2" ParentId="5516" CreationDate="2010-10-25T17:15:38.240" Score="4" ViewCount="" Body="&lt;p&gt;The classic CS book for this is Andrew Tanenbaum's &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0131485210&quot; rel=&quot;nofollow&quot;&gt;Structured Computer Organization&lt;/a&gt;.  Tanenbaum is rather accessible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It assumes you wish to work with other architectures, though, and not build your own.  It might be too basic for you at this point...&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-10-25T17:15:38.240" />
  <row Id="5618" PostTypeId="2" ParentId="5598" CreationDate="2010-10-25T17:35:01.843" Score="2" ViewCount="" Body="&lt;p&gt;Here is another solution that may be more expensive and take more space, but it is something to consider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use an opamp and set the rails of the opamp to be the same rails as the microcontroller. This will prevent the opamp from ever outputting more then what the microcontroller can handle. Then you can use the pot to control the gain of the opamp.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-25T17:35:01.843" CommentCount="6" />
  <row Id="5619" PostTypeId="2" ParentId="5603" CreationDate="2010-10-25T17:38:24.507" Score="4" ViewCount="" Body="&lt;p&gt;The minimal autonomous circuit, I think, involves at least a 555 (or another astable multivibrator, some TRC circuit perhaps) and a counter (or some opamps or diode-diode logic).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried a circuit right now, it includes a astable mv (you can also use a 555) and one op-amp: &lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+8.281975887399955+50+5.0+50%0Aw+416+64+496+64+0%0Aw+496+64+576+64+0%0Aw+576+64+656+64+0%0Ar+416+64+416+192+0+330.0%0Ar+496+64+496+192+0+1020.0%0Ar+576+64+576+192+0+1020.0%0Ar+656+64+656+192+0+320.0%0Ac+416+192+496+192+0+3.9E-5+1.1627034765993394%0Ac+576+192+656+192+0+3.9E-5+-2.7160378785169366%0Aw+656+192+656+256+0%0At+576+272+656+272+0+1+-4.526395369314887+-1.142915884195429+100.0%0Aw+496+192+576+272+0%0Aw+576+192+496+272+0%0At+496+272+416+272+0+1+0.6476540141986116+0.6674416066025219+100.0%0Aw+416+192+416+256+0%0Ag+416+288+416+320+0%0Ag+656+288+656+320+0%0Ax+447+228+468+232+0+16+C1%0Ax+605+229+626+233+0+16+C2%0Ax+384+276+405+280+0+16+Q1%0Ax+670+278+691+282+0+16+Q2%0A162+784+432+704+432+1+2.1024259+1.0+0.0+0.0%0A162+704+560+784+560+1+2.1024259+0.0+1.0+0.0%0Ag+864+640+864+688+0%0Aw+784+464+784+496+0%0Aw+864+528+864+560+0%0Aw+784+432+864+432+0%0Aa+576+496+656+496+0+15.0+-15.0+1000000.0%0Aw+704+464+704+496+0%0Aw+576+272+576+480+0%0Aw+496+272+496+512+0%0Aw+784+560+864+560+0%0Ar+704+496+656+496+0+1000.0%0Aw+576+512+496+512+0%0Ar+704+560+656+560+0+1000.0%0Aw+656+496+656+560+0%0Aw+864+560+864+640+0%0Aw+704+432+704+464+0%0Ac+784+496+864+496+0+1.0E-5+10.644673612572733%0Aw+864+432+864+496+0%0Aw+864+496+864+528+0%0A162+784+496+704+496+1+2.1024259+1.0+1.0+0.0%0Ad+704+464+784+464+1+0.805904783%0AR+656+64+736+64+0+0+40.0+5.0+0.0+0.0+0.5%0Aw+656+560+656+592+0%0Aw+656+592+416+592+0%0A162+288+496+224+496+1+2.1024259+1.0+0.0+0.0%0A162+288+560+224+560+1+2.1024259+1.0+0.0+0.0%0A162+224+624+288+624+1+2.1024259+0.0+1.0+0.0%0Ad+224+528+288+528+1+0.805904783%0Ac+224+560+160+560+0+1.0E-5+0.3192659353350115%0Aw+224+528+224+560+0%0Aw+224+496+160+496+0%0Aw+160+496+160+560+0%0Aw+160+560+160+624+0%0Aw+160+624+224+624+0%0Aw+288+496+288+528+0%0Aw+288+528+288+560+0%0Ar+288+560+352+560+0+1000.0%0Ar+288+624+352+624+0+1000.0%0Aw+352+560+352+592+0%0Aw+352+592+352+624+0%0Aw+416+592+352+592+0%0Ag+160+624+160+688+0%0A&quot; rel=&quot;nofollow&quot;&gt;circuit simulator&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1673" LastEditorUserId="1673" LastEditorDisplayName="" LastEditDate="2010-10-26T14:43:03.797" LastActivityDate="2010-10-26T14:43:03.797" CommentCount="1" />
  <row Id="5620" PostTypeId="1" AcceptedAnswerId="5626" CreationDate="2010-10-25T17:41:56.907" Score="2" ViewCount="377" Body="&lt;p&gt;Does anyone have a good solution for a mechanical connector for flexible printed PCB, like those used for strips of common-cathode RGB LEDs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/FzpQc.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(You can cut the strip across any of the solder pads and scrape back the silicon insulation)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Just solder&quot; isn't the answer I want to hear (neither is &quot;get better at soldering&quot;) as a) I need to do &lt;em&gt;lots&lt;/em&gt; of these joins which need to be b) mechanically sound and ideally c) field-repairable, in quite a tough field (on the playa at Burning Man.) The joints need to be mechanically sound as I plan to sew about 30 x 50cm strips into a garment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally I'd like some kind of screw-terminal. But I don't know what to ask for and can't find one on my own.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another idea I've come up with is taking 90° header pins and pushing/piercing/drilling little holes for them through the printed track and soldering those in (a much easier task—I've found component-through-hole soldering orders of magnitude easier than wire-to-pad soldering; tracks lift and it's hard to get everything to bloody stay still.) Anyone think this might work and/or tried it?   &lt;/p&gt;&#xA;" OwnerUserId="1633" LastEditorUserId="1633" LastEditorDisplayName="" LastEditDate="2010-10-27T16:33:45.507" LastActivityDate="2010-10-27T16:33:45.507" Title="Mechanical connectors for flexible PCBs?" Tags="&lt;connector&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="5621" PostTypeId="1" AcceptedAnswerId="5627" CreationDate="2010-10-25T17:58:15.170" Score="12" ViewCount="489" Body="&lt;p&gt;If you overclock a microcontroller, it gets hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you overclock a microcontroller, it needs more voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In some abstract way it makes sense: it is doing more computation, so it needs more energy (and being less than perfect, some of that energy dissipates as heat).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, from a just plain old Ohm's law level electricity and magnetism, what is going on?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Why does the clock frequency have anything to do with power dissipation or voltage?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;As far as I know, the frequency of AC has nothing to do with its voltage or power, and a clock is just a super-position of a DC and a (square) AC.  Frequency doesn't affect the DC.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Is there some equation relating clock frequency and voltage or clock frequency and power?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I mean does a high speed oscillator need more voltage or power than a low speed one?&lt;/p&gt;&#xA;" OwnerUserId="1271" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-24T06:11:20.087" LastActivityDate="2011-01-28T19:17:10.527" Title="Why does a faster clock require more power?" Tags="&lt;frequency&gt;&lt;oscillator&gt;&lt;low-power&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="2" />
  <row Id="5622" PostTypeId="2" ParentId="5621" CreationDate="2010-10-25T18:45:47.360" Score="1" ViewCount="" Body="&lt;p&gt;I think you may have a slight confusion between voltage and power. Power seems to be what you are talking about in your question. Power=voltage*current&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is one approach that you may want to think about this: How much power does it take per instruction? If it takes x seconds to compute an instruction and y amount of power, you could expect that if you speed it up such that it took x/4 seconds to compute the same instruction it would take the same amount of power for the single instruction. But since you are able to get 4 more instructions per second you would expect it to take 4 times as much power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a very simplistic view on it, and with out knowing more about you knowledge level I hope this can help. There are many other factors that I have completely ignored that cause my description to not be accurate, but at least this should give you an idea.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-25T18:45:47.360" CommentCount="1" />
  <row Id="5623" PostTypeId="2" ParentId="5621" CreationDate="2010-10-25T18:51:23.493" Score="3" ViewCount="" Body="&lt;p&gt;Think of a basic RC circuit where the R and C are in parallel.  Our goal is to have a clock at the output of this circuit - a 0-5V 1KHz square wave.  So when we want the clock to be high we turn on our voltage source and it charges up the capacitor until the output is at 5V, and when we want 0V we turn it off and let it discharge.  The charge/discharge time is determined by the RC constant of the circuit.  There's a problem - the circuit doesn't charge up quick enough for a 1KHz clock.  What do I do?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We can't change the RC constant of the circuit - it's fixed.  So we have to charge the capacitor up quicker somehow, but still have the same charged voltage.  To do this we need an active circuit that monitors the output voltage of the RC circuit and varies the current going into the capacitor to charge it up quicker.  More current means more power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you want a faster clock, you need to charge up the capacitor faster.  You charge up a capacitor by pushing current into it. Current * voltage = power.  You need more power!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Everything in a digital system is tied to the clock and everything has capacitance.  If you have 100 TTL chips on one clock it has to drive a lot of current to charge all of them, then draw a lot of current to pull them down.  &lt;strong&gt;The fundamental reason ohms law isn't holding is because these are active devices, not passive.&lt;/strong&gt;  They do electrical work to force the clock to be as close to a perfect square wave as possible.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If you overclock a microcontroller it gets hot&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes - quicker change means more current flowing and power is voltage * current.  Even if voltage stays the same, current used increases, so more power dissipation, more heat.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If you overclock a microcontroller it needs more voltage&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Partially true - it needs more power, not necessarily more voltage.  The microcontroller is in some way converting the extra voltage to more current to achieve its needs.  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;As far as I know, the frequency of AC has nothing to do with its voltage or power, and a clock is just a super-position of a DC and a (square) AC. Frequency doesn't affect the DC.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Only for a purely resistive load.  There's a lot of trickery happening with AC power.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Is there some equation relating clock frequency and voltage or clock frequency and power?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Probably not a consistent one, but it's related to the simple equations Q=CV, V=I*R, P=I*V&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just remember: Higher frequency =&gt; faster rise time =&gt; must fill up capacitors quicker =&gt; more charge =&gt; more current =&gt; &lt;strong&gt;more power&lt;/strong&gt;.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-10-25T18:51:23.493" CommentCount="3" />
  <row Id="5624" PostTypeId="2" ParentId="5621" CreationDate="2010-10-25T18:53:19.610" Score="13" ViewCount="" Body="&lt;p&gt;In general, CMOS gates only use current when they switch states.  So the faster the clock speed is, the more often gates are switching, thus more current is switched, and more power is consumed.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-25T18:53:19.610" />
  <row Id="5625" PostTypeId="2" ParentId="5621" CreationDate="2010-10-25T18:53:40.143" Score="6" ViewCount="" Body="&lt;p&gt;Well, it's all about logic level transitions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When any single bit of an output changes...  the electrical value must slew from high to low, or low to high.  This pulls power from the power supply, or dumps some power back onto the ground plane.  It also generates a little waste heat due to inefficiencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you increase the clock rate, you increase the number of these transitions per unit time, therefore you use more power to feed these logic level transitions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Increased voltage requirements are a little different.  The time it takes a signal to transition from low to high is called the rise time.  To safely operate at any given frequency the logic must be able to consistently make this transition before the next clock samples the new value.  At a certain point, the logic will not be able to meet the rise time requirements of a particular frequency.  This is where upping the voltage will help, as it decreases rise time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Heat is fairly simple.  The chip is designed to handle a certain amount of heat generated by a certain clock rate.  Increase the number of transitions by increasing the clock rate, and you're going to get more waste heat.  When overclocking, you can easily outpace the cooling system's ability to remove that heat.&lt;/p&gt;&#xA;" OwnerUserId="1270" LastActivityDate="2010-10-25T18:53:40.143" />
  <row Id="5626" PostTypeId="2" ParentId="5620" CreationDate="2010-10-25T18:54:25.120" Score="2" ViewCount="" Body="&lt;p&gt;How thick is the flexible PCB that you are using? Could you put a flat flex connector on your board and design your flexible pcb to socket into it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hmm... As I type this I wonder if this will actually work. I would be interested in what someone who has used flex pcb has to say.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-25T18:54:25.120" CommentCount="7" />
  <row Id="5627" PostTypeId="2" ParentId="5621" CreationDate="2010-10-25T18:57:52.383" Score="19" ViewCount="" Body="&lt;p&gt;Voltage required is affect by significantly more than clock speed, but you are correct, for higher speeds you will need higher voltages in general.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Why does power consumption increase?&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;This is a lot messier than a simple circuit, but you can think about it being similar to an RC circuit.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; RC circuit equivilent &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;At DC an RC circuit consumes no power. At a frequency of infinity, which is not attainable, but you can always solve this theoretically, the capacitor acts as a short and you are left with a resistor. This means you have a simple load. As frequency decreases the capacitor stores and discharges power causing a smaller amount of power dissipated overall.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; What is a microcontroller?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Inside it is made up of many many &lt;a href=&quot;http://en.wikipedia.org/wiki/MOSFET&quot; rel=&quot;nofollow&quot;&gt;MOSFETs&lt;/a&gt; in a configuration we call &lt;a href=&quot;http://en.wikipedia.org/wiki/CMOS&quot; rel=&quot;nofollow&quot;&gt;CMOS&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you try to change the value of the gate of a MOSFET you are just charging or discharging a capacitor. This is a concept I have a hard time explaining to students. The transistor does a lot, but to us it just looks like a capacitor from the gate. This means in a model the CMOS will always have a load of a capacitance. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wikipedia has an image of a CMOS inverter I will reference.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/pVc7l.png&quot; alt=&quot;CMOS Inverter Schematic&quot;&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The CMOS inverter has an output labeled Q. Inside a microcontroller your output will be driving other CMOS logic gates. When your input A changes from high to low the capacitance on Q must be discharged through the transistor on bottom. Every time you charge a capacitor you see power use. You can see this on &lt;a href=&quot;http://en.wikipedia.org/wiki/CMOS&quot; rel=&quot;nofollow&quot;&gt;wikipedia under power switching and leakage&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Why does voltage have to go up?&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;As you voltage increases it makes it easier to drive the capacitance to the threshold of your logic. I know this seems like a simplistic answer, but it is that simple. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I say it is easier to drive the the capacitance I mean that it will be driven between the thresholds faster, as mazurnification put it:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;With increased supply drive capability of the MOS transistor also increases (bigger Vgs). That means that actual R from RC decreases and that is why gate is faster.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;In relation to power consumption, due to how small transistors are there is a large leakage through the gate capacitance, Mark had a bit to add about this:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;higher voltage results in higher leakage current. In high transistor count devices like a modern desktop CPU leakage current can account for the majority of power dissipation. as process size gets smaller and transistor counts rise, leakage current becomes more and more the critical power usage statistic.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-01-28T19:17:10.527" LastActivityDate="2011-01-28T19:17:10.527" CommentCount="5" />
  <row Id="5628" PostTypeId="1" AcceptedAnswerId="5632" CreationDate="2010-10-25T19:49:39.047" Score="14" ViewCount="653" Body="&lt;p&gt;I'm designing something which will use an SD card. The device will be able to read and write the cards, using publicly available specifications. Do I need to pay the SD card people?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-22T14:35:52.143" Title="Do I need to pay royalties to the SD card people if my device &quot;just happens&quot; to be compatible with SD cards?" Tags="&lt;sd&gt;" AnswerCount="4" CommentCount="7" FavoriteCount="3" />
  <row Id="5629" PostTypeId="1" AcceptedAnswerId="5695" CreationDate="2010-10-25T19:54:45.190" Score="3" ViewCount="184" Body="&lt;p&gt;I'm attempting to interface a PIC18F4520 to a 25LC640 via SPI protocol. I'm using the built in MSSP hardware of the PIC. The PIC18F4520 is the only master on the bus. I'm reading 16 bytes of data from the EEPROM 32 times per second. I've double-checked the following items:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;TRIS Registers for SDI, SDO, SCK, and CS&lt;/li&gt;&#xA;&lt;li&gt;Baud Rate ~ 1 Mhz&lt;/li&gt;&#xA;&lt;li&gt;SPI Mode 0,0&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I've checked the signals on an oscilloscope and everything looks fine. I've tried using a BusBee to log the data coming from the EEPROM and 99% of the time it's correct. Every once in a while there are a string of requests where the MOSI (SDO) line does not seem to contain the correct EEPROM read instruction causing the data being clocked into the micro to be invalid. This happens even though I'm writing the same read instruction in the SSPBUF each time. What else can go wrong with a SPI bus?&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-10-26T23:05:01.300" Title="Intermittent SPI bus" Tags="&lt;pic&gt;&lt;spi&gt;&lt;eeprom&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="5630" PostTypeId="1" AcceptedAnswerId="5644" CreationDate="2010-10-25T19:57:19.957" Score="1" ViewCount="135" Body="&lt;p&gt;See this image, it's a composite video signal on my scope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/rGfCW.jpg&quot; alt=&quot;Scope shot&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As can be seen the dc offset of the signal is varying with time; it also varies with brightness in the scene. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am plugging the signal from a composite video signal directly into my scope, however the cable is also spliced and goes to my computer's TV card. Without the TV card attached I do not see this. Now I would like to be able to debug my signal using the TV card, but it seems to be interfering (maybe it's loading the signal too much) - what could be causing this? I have another card I'm going to try but I'm not hopeful. Apart from buffering the signal using expensive video buffer amps, what can I try?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-26T00:04:38.177" Title="What's causing this ramp on a video signal?" Tags="&lt;video&gt;&lt;oscilloscope&gt;" AnswerCount="1" CommentCount="6" />
  <row Id="5631" PostTypeId="2" ParentId="5629" CreationDate="2010-10-25T20:00:38.737" Score="0" ViewCount="" Body="&lt;p&gt;I've had similar intermittent bugs and found that it was a bug in the code. It wasn't to do with SPI, but every so often the chip would reset and this would cause garbage to be written to on-chip memory; make certain your code is stable. One way to do this would be on reset to have you press a button so it does not restart automatically.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-25T20:00:38.737" CommentCount="3" />
  <row Id="5632" PostTypeId="2" ParentId="5628" CreationDate="2010-10-25T20:06:33.040" Score="14" ViewCount="" Body="&lt;p&gt;I had the same concern just a few days ago.  I am planning on using a microSD card internally inside a device for extra storage.  I will only be accessing it via the SPI interface and not using any proprietary features.  The end user will not even be aware there is a microSD card buried inside the device, so there is no need (or desire) to put a SD logo on the product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I sent an inquiry to helpdesk@sd.org.  Their reply was &quot;If your client's product will be interoperable with SD cards, they will need to sign the Host Ancillary Product License Agreement.  SD Association membership is required in order to sign the HALA.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it looks like we have to pay the piper to be completely legal.  My understanding it is $\$$3000 a year ($\$$2000 for the membership, and $\$$1000 for the HALA).&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-22T14:35:52.143" LastActivityDate="2011-03-22T14:35:52.143" CommentCount="10" />
  <row Id="5633" PostTypeId="2" ParentId="5629" CreationDate="2010-10-25T20:48:34.027" Score="3" ViewCount="" Body="&lt;p&gt;If you have a schematic, post it, also any information regarding how your treating the signal lines.  At 1Mhz transmission line effects can come into play, you mentioned you scoped the signal and everything looked fine but did you verify rise/fall times, reflections and ringing?  Are your signal line terminated and impedance controlled?  How long are they?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other random things it could be:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;bug in code, create a minimal program that does nothing but read from the EEPROM to test&lt;/li&gt;&#xA;&lt;li&gt;Check for proper CS setup and hold times before transfers begin&lt;/li&gt;&#xA;&lt;li&gt;are you writing to the EEPROM as well? if so are you checking the status register to ensure the write is complete before you attempt a read?&lt;/li&gt;&#xA;&lt;li&gt;Are you using slew rate control in the MSSP? Either way check that your min/max rise/fall times are within the EEPROMS limits.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-25T21:33:38.760" LastActivityDate="2010-10-25T21:33:38.760" CommentCount="4" />
  <row Id="5634" PostTypeId="1" AcceptedAnswerId="5652" CreationDate="2010-10-25T20:57:36.120" Score="13" ViewCount="331" Body="&lt;p&gt;What is the current state of things when it comes to super capacitors and batteries? Are super caps anywhere near rivalling LiPo's in capacity? I've often heard people talking about super caps as being a viable replacement for batteries, in that you can charge virtually instantly and recharge millions of times, but is this just a pipe dream?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-26T08:14:20.170" Title="Supercap compared to a battery" Tags="&lt;capacitor&gt;&lt;battery&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="5635" PostTypeId="1" AcceptedAnswerId="5637" CreationDate="2010-10-25T21:04:09.077" Score="7" ViewCount="172" Body="&lt;p&gt;I'm looking for some freeware that will do (as much as possible) of what Matlab does DSP-wise...&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Filtering tools&lt;/li&gt;&#xA;&lt;li&gt;Modulation&lt;/li&gt;&#xA;&lt;li&gt;File I/O (as I need these to compare vhdl simulation results to software computed results)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I've used both Scilab and Octave.  I'm wondering which one (or another unmentioned option) would be the best freeware DSP design replacement.&lt;/p&gt;&#xA;" OwnerUserId="1571" LastActivityDate="2010-11-14T23:05:55.580" Title="Which freeware analysis software most closely resembles the functionality of Matlab DSP toolbox" Tags="&lt;dsp&gt;" AnswerCount="3" CommentCount="0" FavoriteCount="1" />
  <row Id="5636" PostTypeId="2" ParentId="5634" CreationDate="2010-10-25T21:07:46.530" Score="7" ViewCount="" Body="&lt;p&gt;I would say, anything that you would consider a coin cell battery for you can &quot;start&quot; to consider a supercap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other aspect is that in devices that need current in spurts (like a wireless transmitter), you can use a supercap to provide the short bursts of power needed and then slowly charge them back up from your battery. This method extends the life of your battery.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-25T21:07:46.530" CommentCount="1" />
  <row Id="5637" PostTypeId="2" ParentId="5635" CreationDate="2010-10-25T21:15:06.477" Score="9" ViewCount="" Body="&lt;p&gt;Try SciPy/NumPy and Matplotlib if you're into Python.  It doesn't have all of the functionality of the Matlab toolboxes but lots of the basic functionality.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I actually doubt you'll find a complete freeware replacement for the DSP toolbox.   The toolboxes are the hard part and where Mathworks puts most of its effort.  The general functionality is easier to find for free.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-10-25T21:15:06.477" CommentCount="2" />
  <row Id="5638" PostTypeId="2" ParentId="5634" CreationDate="2010-10-25T21:20:18.707" Score="6" ViewCount="" Body="&lt;p&gt;Supercaps can be worthwhile if you'll be doing energy harvesting.  They're much easier to charge/discharge than batteries.  If you have lots of incidental power coming in short bursts it makes sense to store it in a capacitor instead of a battery immediately.  They don't match batteries for energy density yet (and they're certainly not as cheap joule for joule).  If you plan on having this sit around a long time without any power coming in to charge it and expect it not to have lost any charge I don't think you'll be happy.  You're better off with a high-resistance battery if it has to sit a long time and not source a large amount of current. The exact determination depends on what you're doing but I think you'll be happier with batteries.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-10-25T21:20:18.707" />
  <row Id="5639" PostTypeId="2" ParentId="5613" CreationDate="2010-10-25T22:07:25.410" Score="0" ViewCount="" Body="&lt;p&gt;The same here, you'll have to learn at least:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The AC models for the elementals (eg: for decoupling, modeling speakers)&lt;/li&gt;&#xA;&lt;li&gt;The DC models for the elementals (eg: for supply)&lt;/li&gt;&#xA;&lt;li&gt;Active elements&lt;/li&gt;&#xA;&lt;li&gt;Filters (both passive and active)&lt;/li&gt;&#xA;&lt;li&gt;maybe DSP&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Everyone is talking about &quot;The art of electronics&quot;, I haven't read it yet.&lt;/p&gt;&#xA;" OwnerUserId="1673" LastEditorUserId="1673" LastEditorDisplayName="" LastEditDate="2010-10-25T22:13:11.690" LastActivityDate="2010-10-25T22:13:11.690" />
  <row Id="5640" PostTypeId="2" ParentId="5577" CreationDate="2010-10-25T22:36:45.453" Score="1" ViewCount="" Body="&lt;p&gt;I'm going to go with Tim's answer.  The caps are my first suspect.  I once checked out a DVD player whose 5V line would pulse, much like your 12V line.  Turned out to be a bad cap in the rectifier.  I almost missed it, until I started touching the tops of all the caps with my finger (this is a good time to remind you to avoid getting yourself a Darwin award!).  It was then immediately apparent which cap was bulging.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-25T22:36:45.453" CommentCount="3" />
  <row Id="5641" PostTypeId="2" ParentId="5549" CreationDate="2010-10-25T22:39:33.703" Score="0" ViewCount="" Body="&lt;p&gt;My own personal rule-of-thumb is 3x trace width between generic traces and 5x trace width for &quot;noisy&quot; traces (clocks, etc)&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-25T22:39:33.703" />
  <row Id="5642" PostTypeId="2" ParentId="5628" CreationDate="2010-10-25T22:47:51.853" Score="6" ViewCount="" Body="&lt;p&gt;No license is needed if you use SPI mode (as this doesn't involve any patented protocols) and you don't use the SD logo. &#xA;They probably have some lame-ass patent on the multi-bit faster modes for which  a license is needed&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-25T22:47:51.853" CommentCount="10" />
  <row Id="5643" PostTypeId="7" CreationDate="2010-10-25T23:56:36.383" Score="0" ViewCount="0" Body="&lt;p&gt;This site is for electronics professionals and serious hardware hacking enthusiasts. We ask and answer questions about electronics engineering topics, which include electronics, physical computing, and those working with microcontrollers, Arduinos and embedded systems. We feel the best Electronics Design questions have a schematic or some C code in them, but if your question generally covers …&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;a specific electronics design problem&lt;/li&gt;&#xA;&lt;li&gt;the theory and simulation of electromagnetic forces&lt;/li&gt;&#xA;&lt;li&gt;a communication scheme&lt;/li&gt;&#xA;&lt;li&gt;the writing of firmware for bare-metal or RTOS applications&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;and it is not about …&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;a shopping or buying recommendation&lt;/li&gt;&#xA;&lt;li&gt;consumer electronics such as media players, cell phones or smart phones, except when designing these products or hacking their electronics for other uses&lt;/li&gt;&#xA;&lt;li&gt;Programming software for a PC&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;… then you’re in the right place to ask your question!&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-02T13:25:03.820" LastActivityDate="2011-04-02T13:25:03.820" />
  <row Id="5644" PostTypeId="2" ParentId="5630" CreationDate="2010-10-26T00:04:38.177" Score="5" ViewCount="" Body="&lt;p&gt;I'm guessing that the source is AC coupled ( and shouldn't be)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;you've got dc offset shifting with picture brightness. Video should be DC coupled and terminated into 75ohms. If that sounds like something that your wouldn't string across a room, congratulations; it was never designed to. I remember reading that in-studio distribution was never raw analog video. So check the source path for a cap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless it's just a really bad ground connection (high resistance) ;and the ground is elevating with brightness, which is consistent with that. So check the return path resistance too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Analog video; it's frustrating because it was never intended to go very far as a baseband signal.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-10-26T00:04:38.177" CommentCount="1" />
  <row Id="5645" PostTypeId="2" ParentId="5545" CreationDate="2010-10-26T01:12:18.570" Score="2" ViewCount="" Body="&lt;p&gt;Take a look at the Bug Labs gear - they've got some modules for Wifi, video, 3G and such. &lt;a href=&quot;http://www.buglabs.net/products&quot; rel=&quot;nofollow&quot;&gt;http://www.buglabs.net/products&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1712" LastActivityDate="2010-10-26T01:12:18.570" />
  <row Id="5646" PostTypeId="2" ParentId="5613" CreationDate="2010-10-26T01:31:24.190" Score="1" ViewCount="" Body="&lt;p&gt;Have you looked at &lt;a href=&quot;http://www.amazon.com/s/ref=nb_sb_noss?url=node%3D368395011&amp;amp;field-keywords=electronics&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;Amazon&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-26T01:31:24.190" CommentCount="2" />
  <row Id="5647" PostTypeId="1" CreationDate="2010-10-26T02:23:38.010" Score="5" ViewCount="158" Body="&lt;p&gt;What would be a sensor that I could use to detect if my desktop's CD tray has opened?  There are so many sensors to choose from in the Digikey catalog.  Should I use a mechanical component?  A light beam interference component? Which one would allow me to detect if my CD tray is open such that the information can be fed into a PIC MCU?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know I can do a system call for this sort of question, but I would prefer some sort of external sensor.&lt;/p&gt;&#xA;" OwnerUserId="1708" LastActivityDate="2010-11-23T18:06:29.950" Title="What external sensor could detect if a cd-tray had opened?" Tags="&lt;pic&gt;&lt;sensor&gt;&lt;microcontroller&gt;" AnswerCount="3" CommentCount="0" FavoriteCount="1" />
  <row Id="5648" PostTypeId="2" ParentId="5647" CreationDate="2010-10-26T03:27:22.703" Score="9" ViewCount="" Body="&lt;p&gt;Use a permanent magnet and a &lt;a href=&quot;http://en.wikipedia.org/wiki/Reed_switch&quot; rel=&quot;nofollow&quot;&gt;reed switch&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fix the magnet on the moving part and put the &lt;a href=&quot;http://en.wikipedia.org/wiki/Reed_switch&quot; rel=&quot;nofollow&quot;&gt;reed switch&lt;/a&gt; on the fixed part. Then monitor the reed switch with the microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-23T16:57:18.840" LastActivityDate="2010-11-23T16:57:18.840" />
  <row Id="5649" PostTypeId="1" AcceptedAnswerId="5690" CreationDate="2010-10-26T05:50:15.637" Score="2" ViewCount="294" Body="&lt;p&gt;I have learned that the maximum 'delay' possible in pic16f877a running with a source of 11.0592MHz (11059200 / 4 actually) is 23 ms.. without using software delays (delay_ms( ))..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the calculation was max_delay = ((FF-00)xPrescalarxTimeperiod) = (255x256x3.62xe-7) = ~23ms..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is how to 'increase this delay to 1 second' without using software delay?&lt;/p&gt;&#xA;" OwnerUserId="1484" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-14T05:38:06.710" LastActivityDate="2011-02-14T05:38:06.710" Title="Increasing the delay using 'option' register in Pic16f877a" Tags="&lt;pic&gt;&lt;timer&gt;&lt;interrupts&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="5650" PostTypeId="1" CreationDate="2010-10-26T06:09:19.453" Score="7" ViewCount="308" Body="&lt;p&gt;Suppose I have a standard credit card with a magnetic stripe, lying (a)right on top of a cellphone, or (b)in a regular leather wallet that's lying right on top of a cellphone. The cellphone is on (but not in a call), uses a 3G network, and is in a good reception area.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will the credit card be demagnetized (to the point where it can't be read) in the above 2 scenarios? If so, how long will it typically take? An answer that shows all assumptions and calculations used would be especially useful!&lt;/p&gt;&#xA;" OwnerUserId="1715" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-04T03:54:16.810" LastActivityDate="2011-02-04T03:54:16.810" Title="Can a credit card be demagnetized with a nearby cellphone?" Tags="&lt;electromagnetism&gt;&lt;cellphone&gt;&lt;magstripe&gt;" AnswerCount="2" />
  <row Id="5651" PostTypeId="2" ParentId="5634" CreationDate="2010-10-26T06:32:29.983" Score="3" ViewCount="" Body="&lt;p&gt;Super caps are lower voltage (1.2V or so each), so need to be wired in series and parallel combinations to be able to get accessible voltage from them.  You will generally need a buck boost converter on the output side to adjust the voltage dependent on the charge left in the super capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compared to a Lion battery where you can get a much linear voltage over a smaller range in relation to charge, so generally a buck converter will suffice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So as a replacement for battery not really, there are too many issues with them.  As a complement to a battery use.  Do you want to the device to remain powered after power lose? for a reasonable time to change batteries and the like?  then super caps may be the answer.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-26T06:32:29.983" CommentCount="1" />
  <row Id="5652" PostTypeId="2" ParentId="5634" CreationDate="2010-10-26T08:14:20.170" Score="5" ViewCount="" Body="&lt;p&gt;Some ballpark figures I remember from a year or two ago:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Batteries have 10 times the energy density of supercaps.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Supercaps have 10 times the power density of batteries.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So for the same size you can store a lot more energy in batteries, but draw much more power from supercaps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's why some &lt;a href=&quot;http://www.bombardier.com/en/transportation/sustainability/technology/mitrac-energy-saver?docID=0901260d80048697&quot; rel=&quot;nofollow&quot;&gt;trams&lt;/a&gt; use supercaps and not lithium batteries.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-10-26T08:14:20.170" />
  <row Id="5653" PostTypeId="2" ParentId="5650" CreationDate="2010-10-26T08:23:46.983" Score="8" ViewCount="" Body="&lt;p&gt;Mythbusters did this: &lt;a href=&quot;http://en.wikipedia.org/wiki/MythBusters_%28season_1%29#Eelskin_Wallet&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/MythBusters_%28season_1%29#Eelskin_Wallet&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I recall correctly, they tried rubbing cards with magnets and cellphones, but failed to cause any damage.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-26T08:23:46.983" CommentCount="2" />
  <row Id="5654" PostTypeId="1" AcceptedAnswerId="5677" CreationDate="2010-10-26T09:47:09.690" Score="3" ViewCount="166" Body="&lt;p&gt;Many integrated circuits I have seen have the specification of maximum junction temperature (150°C) but storage temperature is invariably higher (165°C) and often lower, e.g. -55°C. Why the discrepancy? Surely the junction will be damaged whether or not it has current flowing through it...?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-26T17:09:56.367" Title="Why the difference between maximum junction temp (150°C) and storage temp (165°C)?" Tags="&lt;temperature&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="5655" PostTypeId="2" ParentId="5650" CreationDate="2010-10-26T10:08:11.363" Score="4" ViewCount="" Body="&lt;p&gt;No, you're fine. &#xA;However a GSM phone could knock out a 3.5&quot; floppy disk - I learned that lesson the hard way a long time ago. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-26T10:08:11.363" />
  <row Id="5656" PostTypeId="2" ParentId="3539" CreationDate="2010-10-26T10:21:39.090" Score="3" ViewCount="" Body="&lt;p&gt;ESR is frequency and temperature dependant.  Most data sheets will list the ESR for a number of discrete frequencies,  which may or may not be your switching frequency.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have an LCR meter you can connect up the capacitor and set the frequency and measure the ESR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is important for calculating the thermal loss inside your capacitor.  It comes back to ohms law, for your switching frequency, there is an ESR, which is R, and you have current flowing into and out of the capacitor, which is I, square it and multiply by R and you have power loss inside the capacitor.  The capacitor data sheet will also state its thermal resistance, so you can estimate the temperature you will be running your capacitor at, and select a suitable temperature rating for your application.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-26T10:21:39.090" CommentCount="2" />
  <row Id="5657" PostTypeId="2" ParentId="1404" CreationDate="2010-10-26T11:00:21.547" Score="0" ViewCount="" Body="&lt;p&gt;You said you're using the CC2500 for other projects, the CC2540 might appeal (if BLE is an option).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, BTStack looks like it can drive cheap HCI USB dongles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/btstack/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/btstack/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-26T11:00:21.547" />
  <row Id="5658" PostTypeId="1" AcceptedAnswerId="5661" CreationDate="2010-10-26T11:34:52.957" Score="5" ViewCount="406" Body="&lt;p&gt;I would like to play around with an Atmel ARM MCU that is breadboard friendly. I require it to be based on an open source C programming language and use something like AVRStudio + GCC or whatever (aka I will not pay for an IDE/devel platform). I am not concerned about the size as long as it will fit onto a breadboard. If it was similar to the Arduino Nano which has all built on chips for usb, crystal, etc...that would be a big plus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would be using an AVR JTAG ICE MK II for development along with the AVR tool chain and either Eclipse-AVR or AVRStudio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If no such product exists, I would be open to suggestions on how to make such a DIP compatible ARM MCU that is breadboard friendly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I realize that there are a ton of Ateml ARM processors out there. I would prefer a finished product that would allow USB, Ethernet, JTAG (either true JTAG or JTAG over USB OSC), and as many IO Ports as possible. One chip that comes to mind is the AT91SAM7X256. I would still prefer more memory and a lot more pins. I plan to drive this &lt;a href=&quot;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=3&amp;amp;products_id=263&quot; rel=&quot;nofollow&quot;&gt;lcd (3.2&quot; TFT + touch + sd card socket)&lt;/a&gt; and still have a little room for sensors and things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you in advance for your help.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-26T12:58:04.863" LastActivityDate="2010-11-29T09:24:51.680" Title="Searching for Atmel ARM MCU in a Breadboard Setup ... Like Arduino Nano but Obviously Longer" Tags="&lt;avr&gt;&lt;arm&gt;&lt;atmel&gt;&lt;breadboard&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="5659" PostTypeId="1" AcceptedAnswerId="5664" CreationDate="2010-10-26T11:42:07.663" Score="2" ViewCount="206" Body="&lt;p&gt;I have a problem with a relatively simple board which consists of an ENC28J60 Ethernet controller and an ATmega168.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit around the ENC28J60 is straight out of the datasheet and I have the same circuit built up in a prototype with DIP parts where it works, but in my SMD version the ENC sucks down 40 mA @ 3.3V and it gets pretty hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet mentions that a relatively high current is sunk by the two TPOUT pins and that the total current is around 180 mA, but there is no mention of how much current the ENC itself will pull out of VDD.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The oscillator runs perfectly and CLKOUT is 6.25 MHz, so the chip is not completely dead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've measured the voltage at every pin and:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Every VSS pin is 0V&lt;/li&gt;&#xA;&lt;li&gt;Every VDD pin is 3.3V&lt;/li&gt;&#xA;&lt;li&gt;The oscillator and CLKOUT out are good.&lt;/li&gt;&#xA;&lt;li&gt;VCAP is 2.65V&lt;/li&gt;&#xA;&lt;li&gt;RBIAS is at 1.2V.&lt;/li&gt;&#xA;&lt;li&gt;!RESET is 3.3V.&lt;/li&gt;&#xA;&lt;li&gt;SPI looks ok.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Yet, I can't seem to raise the chip over SPI from the AVR and it gets pretty damn hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried yanking !RESET low and that doesn't affect the power usage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any clues?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice that the pin numbers for OSC1, OSC2, VDDOSC and VSSOSC are wrong in the schematic, I fixed that bug after exporting that version of the PDF.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.hackaarhus.dk/forum/download/file.php?id=19&quot; rel=&quot;nofollow&quot;&gt;Full schematic in pdf&lt;/a&gt;&#xA;Ok, here's the real list of problems with my design that led to my problem:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;My 3.3V regulator is dumping waaay too much power, so it gets too hot.&lt;/li&gt;&#xA;&lt;li&gt;The ENC28J60 eats lots of power, even when working normally, so that gets hot too.&lt;/li&gt;&#xA;&lt;li&gt;I fucked up and forgot to double check the Eagle library pinout, so I had to do some board hacking to fix that.&lt;/li&gt;&#xA;&lt;li&gt;The RX center tap should not be connected.&lt;/li&gt;&#xA;&lt;li&gt;I forgot to update my Makefile to build for the Mega168 part.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Problem number 5 was the real source of my problem, #1 &amp;amp; #2 kept me looking at the hardware for far too long, which is doubly embarrassing because I make my living writing software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for the help debugging the board, now I just need to do another PCB spin, then I'm &quot;done&quot;.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastEditorUserId="1675" LastEditorDisplayName="" LastEditDate="2010-11-01T18:05:34.113" LastActivityDate="2010-11-01T18:05:34.113" Title="Hot ENC28J60 @ 132 mW" Tags="&lt;avr&gt;&lt;ethernet&gt;&lt;current&gt;&lt;debug&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="5660" PostTypeId="2" ParentId="5654" CreationDate="2010-10-26T11:51:12.933" Score="5" ViewCount="" Body="&lt;p&gt;Max junction temp guarantees it will still work within spec, storage temp is damage threshold. &#xA;Semiconductor characteristics vary with temp, so there will be areas where it may not work within spec but won't suffer damage.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-26T11:51:12.933" />
  <row Id="5661" PostTypeId="2" ParentId="5658" CreationDate="2010-10-26T11:54:51.947" Score="8" ViewCount="" Body="&lt;p&gt;To JTAG program an ARM, you will need a different adapter. The AVR JTAG ICE doesn't support ARM (so far as I know)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See &lt;a href=&quot;http://electronics.stackexchange.com/questions/2209/jtag-cable-and-device-interchangeability/2213&quot;&gt;http://electronics.stackexchange.com/questions/2209/jtag-cable-and-device-interchangeability/2213&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GCC has a mature ARM backend. Here's a question dealing with development for ARM Cortex-M3&#xA; &lt;a href=&quot;http://electronics.stackexchange.com/questions/991/arm-cortex-m3-devolpment-tools/1091&quot;&gt;http://electronics.stackexchange.com/questions/991/arm-cortex-m3-devolpment-tools/1091&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From your requirements, it sounds like an &lt;a href=&quot;http://mbed.org&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt; or &lt;a href=&quot;http://ics.nxp.com/lpcxpresso/&quot; rel=&quot;nofollow&quot;&gt;lpcxpresso&lt;/a&gt; could be a good choice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The mbed is very breadboard friendly:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://mbed.org/media/img/mbedMicrocontroller.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Others to consider (google for ARM DIP):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.audon.co.uk/armexp.html&quot; rel=&quot;nofollow&quot;&gt;http://www.audon.co.uk/armexp.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.audon.co.uk/images/armexp.jpg&quot; width=&quot;150&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.burntec.com/tinyarm40.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.burntec.com/tinyarm40.asp&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.burntec.com/images/tinyarm.jpg&quot; width=&quot;150&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://microcontrollershop.com/product_info.php?products_id=1747&quot; rel=&quot;nofollow&quot;&gt;http://microcontrollershop.com/product_info.php?products_id=1747&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://microcontrollershop.com/Images/ADuC-H7020.jpg&quot; width=&quot;150&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-26T15:08:43.517" LastActivityDate="2010-10-26T15:08:43.517" CommentCount="1" />
  <row Id="5662" PostTypeId="2" ParentId="5659" CreationDate="2010-10-26T12:19:40.560" Score="1" ViewCount="" Body="&lt;p&gt;You have some pins wrong.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet has pin 23 as Vssosc.  The SCH has is as OSC2.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet has pin 24 as OSC2.  The SCH has is as pin 22.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pin 25 in the datasheet is Vddosc.  The SCH has Vssosc.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-10-26T12:19:40.560" CommentCount="1" />
  <row Id="5663" PostTypeId="2" ParentId="5658" CreationDate="2010-10-26T12:20:52.257" Score="5" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Maple Native&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://leaflabs.com/devices/&quot; rel=&quot;nofollow&quot;&gt;http://leaflabs.com/devices/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Maple Native is identical to the Maple, but we’ve diverged from Arduino form factor and pin layout. The STM32 is an amazing chip and it deserves a layout that was designed just for it... With Maple Native, you wont have to dig through schematics or pin mapping charts again. To make things even easier, the pins are arranged to keep peripheral ports together wherever possible. Our extended library makes using any of the STM32’s advanced peripherals as easy as blinking an LED.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;STM32F103ZE: a 32-bit ARM Cortex-M3 microprocessor at 72Mhz&lt;/li&gt;&#xA;&lt;li&gt;64KB RAM and 512KB Flash&lt;/li&gt;&#xA;&lt;li&gt;21 Analog inputs at 12-bit resolution&lt;/li&gt;&#xA;&lt;li&gt;Many PWM pins at 16-bit resolution&lt;/li&gt;&#xA;&lt;li&gt;45-pin FSMC connected to an optional external RAM chip, but also run out to headers with chip select&lt;/li&gt;&#xA;&lt;li&gt;Low power and sleep modes&lt;/li&gt;&#xA;&lt;li&gt;Integrated LiPo battery charging&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/moqsc.png&quot; alt=&quot;Maple Native&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/37hOp.png&quot; alt=&quot;Maple IDE&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1084" LastEditorUserId="1084" LastEditorDisplayName="" LastEditDate="2010-10-26T13:54:15.497" LastActivityDate="2010-10-26T13:54:15.497" CommentCount="3" />
  <row Id="5664" PostTypeId="2" ParentId="5659" CreationDate="2010-10-26T12:50:23.970" Score="2" ViewCount="" Body="&lt;p&gt;The Center Tap of the receive magnetics should not be connected to R5 and R6.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-10-26T12:50:23.970" CommentCount="3" />
  <row Id="5666" PostTypeId="1" AcceptedAnswerId="5686" CreationDate="2010-10-26T13:07:59.830" Score="15" ViewCount="302" Body="&lt;p&gt;I am currently using AA batteries in my projects but would like to look at cell batteries for my next project, due to their compactness.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from the physical appearance, how do cell batteries differ from the more chunky AA batteries? (I am guessing the mAH would suffer for example?)&lt;/p&gt;&#xA;" OwnerUserId="1333" LastActivityDate="2011-03-31T17:44:42.060" Title="Are coin cells a suitable replacement for AA batteries?" Tags="&lt;battery&gt;&lt;cell-battery&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="5667" PostTypeId="2" ParentId="5613" CreationDate="2010-10-26T13:22:00.000" Score="3" ViewCount="" Body="&lt;p&gt;MIT has several Electrical Engineering courses online.&#xA;Here's a &lt;a href=&quot;http://ocw.mit.edu/courses/audio-video-courses/#electrical-engineering-and-computer-science&quot; rel=&quot;nofollow&quot;&gt;page&lt;/a&gt; that lists all of their electronics/computer audio-video courses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="1720" LastActivityDate="2010-10-26T13:22:00.000" CommentCount="2" />
  <row Id="5668" PostTypeId="2" ParentId="5666" CreationDate="2010-10-26T13:32:54.010" Score="11" ViewCount="" Body="&lt;p&gt;I'll compare against alkaline AA's and lithium CR2032's as these are the most likely candidates to replace each other. However, they have several differences:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Coin cells are usually 3V, instead of 1.5V.&lt;/li&gt;&#xA;&lt;li&gt;Coin cells can only deliver a few mA before the voltage drops too low - you can power an LED with them at most.&lt;/li&gt;&#xA;&lt;li&gt;Coin cells have significantly less capacity, you'd be lucky to get 100mAh out of a coin cell whereas 2000mAh isn't unusual for a good AA and even the cheapies will do &gt;1000mAh.&lt;/li&gt;&#xA;&lt;li&gt;Coin cells are usually more expensive per cell compared to an AA cell.&lt;/li&gt;&#xA;&lt;li&gt;Their terminal voltage characteristic is to keep a stable voltage (&gt;2.7V) for a long time before dropping very quickly, whereas alkalines generally fall to ~0.9V before dropping out completely. This can create difficulties for low battery warning circuits. Here's an image that shows what I mean: &lt;img src=&quot;http://i.imgur.com/wMmBJ.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-26T14:27:10.667" LastActivityDate="2010-10-26T14:27:10.667" CommentCount="10" />
  <row Id="5669" PostTypeId="2" ParentId="4475" CreationDate="2010-10-26T14:05:20.507" Score="0" ViewCount="" Body="&lt;p&gt;I've used &lt;a href=&quot;http://www.sunstone.com/pcb123.aspx&quot; rel=&quot;nofollow&quot;&gt;Sunstone Circuits PCB123 V3&lt;/a&gt;'s auto-router with great success.  The previous version of their software were pretty buggy, but as of version 3 it seems stable.  For a point of reference, I had a 6&quot;x4&quot; board with about 1000 nets and it was able to successfully route all but 40 of them.  Their auto-router even has options to fanout traces, relax routing, or set the desired trace tolerances.  The software itself is a pretty full feature (for being free) PCB design too, boasting 3D modeling, the ability to read in netlists in a variety of formats, as well as output mechanical drawings.  I'm not sure of it's ability to inter-operate with Eagle, but it might be worth a try.&lt;/p&gt;&#xA;" OwnerUserId="1571" LastActivityDate="2010-10-26T14:05:20.507" CommunityOwnedDate="2010-10-26T14:05:20.507" />
  <row Id="5670" PostTypeId="1" AcceptedAnswerId="5673" CreationDate="2010-10-26T15:04:46.500" Score="1" ViewCount="239" Body="&lt;p&gt;How is a diode damaged by exceeding its Vrrm (maximum peak repetitive reverse voltage)? At this point it conducts more current than usual, so is it the current flow that damages it? Why would that be any different from being forward biased when it conducts almost unlimited current? Or is there some other factor?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-26T16:33:22.507" Title="Damage to diodes by exceeding Vrrm" Tags="&lt;diode&gt;&lt;maximum-ratings&gt;" AnswerCount="1" />
  <row Id="5671" PostTypeId="1" AcceptedAnswerId="5676" CreationDate="2010-10-26T15:34:07.820" Score="6" ViewCount="425" Body="&lt;p&gt;Is a function generator necessary for every day lab use, or is it special purpose equipment? That is, does it have similar utility to an oscilloscope, or multimeter - would you use it regularly enough to justify it's cost?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-04T20:15:06.750" Title="Is it worth getting a function generator?" Tags="&lt;equipment&gt;" AnswerCount="8" CommentCount="1" FavoriteCount="1" />
  <row Id="5672" PostTypeId="2" ParentId="5671" CreationDate="2010-10-26T15:44:08.137" Score="5" ViewCount="" Body="&lt;p&gt;I found a fairly cheap one for $153: &lt;a href=&quot;http://www.bellnw.com/products/0762/&quot; rel=&quot;nofollow&quot;&gt;http://www.bellnw.com/products/0762/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's pretty much no-name but it will certainly be quicker for me to use as the PWM input to a breadboarded switch-mode power supply than rigging up something with an Arduino and op-amps.  Plus, only $153.  That's an expensive dinner for four, or a couple of outfits.  If you'd buy a $1k plus scope, buy this, no question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: It may be worth it to get the SFG-1013.  It has a voltage display.&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="249" LastEditorDisplayName="" LastEditDate="2010-10-27T01:21:14.390" LastActivityDate="2010-10-27T01:21:14.390" CommentCount="1" />
  <row Id="5673" PostTypeId="2" ParentId="5670" CreationDate="2010-10-26T15:47:53.893" Score="4" ViewCount="" Body="&lt;p&gt;From looking at a diode curve you can see that its reverse current sharply rises at Vr much like the forward current does. From this I would imagine that repetitively hitting the diode with reverse voltage in excess of Vrrm would cause the diode to conduct significant current and the resultant power dissipation to either melt the silicon and fail open, or, if the supply is limited, fail shorted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A diode will certainly not &quot;conduct almost unlimited current&quot; -- the device has a designed power dissipation and will not conduct more than this amount for very much time. When reverse-biased you are essentially damaging the thin junction and it is for this reason that it's not the same as simply forward-biasing the diode.  Avalanche and Zener diodes are designed to operate reverse-biased and have differently-formed junctions which are designed to withstand this mode of operation. Zener diodes especially have a much more heavily doped junction than normal diodes.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-26T15:47:53.893" CommentCount="5" />
  <row Id="5675" PostTypeId="2" ParentId="5671" CreationDate="2010-10-26T15:59:39.467" Score="5" ViewCount="" Body="&lt;p&gt;This all depends on what work you are doing. Some people don't even need a scope or a dmm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More generally, some people will say its not worth getting a computer (even some EE's), yet I am sure most of us would argue it is worth it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what work do you do that you wish you had a function generator? If you can't think of anything then it's not worth it.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-26T15:59:39.467" CommentCount="4" />
  <row Id="5676" PostTypeId="2" ParentId="5671" CreationDate="2010-10-26T17:05:43.813" Score="17" ViewCount="" Body="&lt;p&gt;If you're working with digital systems and square waves/pulse trains only, then it's probably not necessary.  However, for analog amplifier design (ex. audio), it's an imperative.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you haven't been stymied on a project because you lacked this tool, you probably don't need it.  Spend your money on an oscilloscope and logic analyzer instead.  Conversely, if you can't imagine why you would need a logic analyzer, you should spend your money on a function generator.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-26T17:05:43.813" CommentCount="4" />
  <row Id="5677" PostTypeId="2" ParentId="5654" CreationDate="2010-10-26T17:09:56.367" Score="1" ViewCount="" Body="&lt;p&gt;Temperature extremes will damage the physical package itself and interconnecting wires. It is the different expansion rates or silicon, metal wires (gold??), and plastic housing that will effectively destroy the part. The silicon itself will normally survive to a limit.  That is why earlier on in electronic development there was a difference between plastic dip and ceramic dip packages which had different temperature ranges.  The silicon was the same, just the packaging was different.  It was this difference in packaging that allowed the 'military' ceramic packages to have a greater usable temperature range than commercial plastic package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With SMD packages, this has changed slightly and they all tend to have greater temperature range, but you can still get commercial, industrial and military temperature ranges of 0 to 85, -40 to 125, and -55 to 125 as a general rule. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That is why devices have lower limits and medium range upper limits, due to packages constraints.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also phsyics limits for the upper end where the silicon itself may become damaged and the dopants might defuse?  I am not sure of the exact function here or temperature limit.  &lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-26T17:09:56.367" />
  <row Id="5678" PostTypeId="2" ParentId="5671" CreationDate="2010-10-26T17:22:54.653" Score="6" ViewCount="" Body="&lt;p&gt;Depends on what waveforms would be useful in everyday work.  I like to play with waveshaping and signal processing, so a good versatile function generator is one of my favorite instruments.  It's likely to be useful for almost anyone into electronics who's gone beyond building crystal radios and blinking LEDs.  A more important question is: which waveforms will you need, and at what quality?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sines are good for testing linear filters, taking measurements at specific frequencies. For accuracy, the sines have to be low distortion.  Less expensive generators have poor sine waves (look at the THD).   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Triangles and squares are good for testing amplifiers - our eyes aren't sensitive to small deviations from a sine, but are very good at seeing problems with straight lines and square corners.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ramp waves are good to sweep oscillators over a frequency range, which is also good for testing linear filters, and also circuits like mixers, modulators/demodulators, and audio testing.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're into experimental physics, pulses that you control in fine detail can be useful in controlling equipment, data acquistion, strobing to observe fast repetitive phenomena.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In most cases, for serious accurate work there are specialized instruments for the job, but even with a budget for such things, a function generator is useful for quick and dirty experiments of all kinds.&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-10-26T17:22:54.653" />
  <row Id="5679" PostTypeId="2" ParentId="5658" CreationDate="2010-10-26T17:25:27.273" Score="4" ViewCount="" Body="&lt;p&gt;I doubt you'll find a DIP-style board with an Ethernet jack.  As you mentioned that you want Ethernet, the AT91SAM7X256 would be a poor choice, as many other processors have an integrated MAC (just add magnetics).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.luminarymicro.com/index.php?option=com_remository&amp;amp;func=download&amp;amp;id=448&amp;amp;chk=7545df079d4f2150213509a18f8f8166&amp;amp;Itemid=591&quot; rel=&quot;nofollow&quot;&gt;LM3s6965&lt;/a&gt; is a $70 development board with USB, USB-to-JTAG (No programmer required), true JTAG, Ethernet, a (small, grayscale) OLED display, and SD peripherials, among others.  In addition, one 26-pin header and one 34-pin header (0.1&quot; spacing, 2 rows, separated by 1.8&quot; on the inside - not quite breadboard friendly, but easy to work with) break out all the IO on the chip.  All of the onboard peripherials can be bypassed simply by desoldering a jumper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It comes with the CodeSourcery GCC compiler, and a couple of crippled IDEs if you want them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is that more in the vein of you were looking for?  You mentioned &quot;breadboard-friendly&quot; in your title, but then said &quot;I would prefer a finished product that would allow...&quot;.  Development boards, not DIP breakouts, seem to fit that bill a little better.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-26T17:25:27.273" CommentCount="1" />
  <row Id="5680" PostTypeId="1" AcceptedAnswerId="5687" CreationDate="2010-10-26T17:30:27.127" Score="1" ViewCount="174" Body="&lt;p&gt;I have some powerline networking adapters which can transfer at a peak rate of 200 Mbps (I get around 60 Mbps typical, but I am sharing the network with many other devices and many pieces of equipment are running on the line.) How do they do it? I always thought that it was during the zero crossing, but packing so many bits into such a space must be very difficult, nigh impossible. HowStuffWorks has an article on it, but it's only relevant to adapters which go at 14 Mbps.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-10-26T18:00:16.620" LastActivityDate="2010-10-27T00:45:37.400" Title="How do these powerline networking adapters work?" Tags="&lt;communication&gt;&lt;powerline&gt;" AnswerCount="3" CommentCount="0" />
  <row Id="5681" PostTypeId="1" AcceptedAnswerId="5699" CreationDate="2010-10-26T17:32:01.603" Score="1" ViewCount="247" Body="&lt;p&gt;Hi everyone:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm designing a regulator/converter that can generate -120/-108/+60Vdc for a current of 180mA each from a supply of 12Vdc or 24Vdc (5A like it's nothing, 15A tops) and I was choosing a MC34063 but the absolute maximum rating for Vout is 40Vdc:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;strong&gt;Is it sane to overspec for 300%?&lt;/strong&gt; In the datasheet there is a circuit for use with external transistors, but I really know little of supply design.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Is there another ubiquitous IC for doing this?&lt;/strong&gt; (I googled it and all that I can find are car inverters)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT: the three separate rails can be independently regulated&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;: for the record there is a circuit called the &lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage_multiplier&quot; rel=&quot;nofollow&quot;&gt;Villard cascade&lt;/a&gt; that works for very low currents (like the CRT screens), but it was too dangerous to prototype (by me).&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Final Update&lt;/strong&gt;&#xA;I found a full LED replacement for the screen I was planning to supply and for the old ones we salvaged supplies from older equipment.&lt;/p&gt;&#xA;" OwnerUserId="1673" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T21:45:09.773" LastActivityDate="2010-12-10T21:45:09.773" Title="High voltage/Mid current boost converter" Tags="&lt;power-supply&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="5682" PostTypeId="2" ParentId="5681" CreationDate="2010-10-26T17:36:26.593" Score="2" ViewCount="" Body="&lt;p&gt;First question. No. It is not a good idea to exceed the rating of the converter's output switch, because it may break down. The switch is like a diode, it can only handle so many volts across it in the off state without being damaged. The converter's switch may become uncontrollable at high voltages due to the breakdown state. In fact, you would be pushing it for 40V output, because it's more than likely your output will have ripple on it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second question. I think the best solution for this would either be three boost/boost-buck converters, or you could use an SMPS controller chip (like would be used in a computer power supply) with a custom wound transformer. The problem with solution #2 is it depends on the loading of individual rails - the voltage varies if you load one rail more than another, but it doesn't matter too much for low current levels. It depends on what you want: the most expensive and reliable solution or the cheapest and slightly less reliable.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-26T17:41:48.910" LastActivityDate="2010-10-26T17:41:48.910" CommentCount="1" />
  <row Id="5683" PostTypeId="2" ParentId="5680" CreationDate="2010-10-26T17:47:47.173" Score="4" ViewCount="" Body="&lt;p&gt;Your power line only has significant frequency content at 50-60hz and the first few harmonics which means there is a massive chunk of the cable in the frequency domain that is being unused.  So use it to transmit digital data. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thats pretty much it, if your interested in encoding techniques you may want to just look at those directly.  The encoding system is really the only interesting thing about it, you don't get controlled impedance twisted pair cable for power line networking, you get busted romex with screw terminals all over the place so the encoding system has to be robust and deal well with poorly controlled transmission line impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IEEE 1901 is the standard that covers power line networking and allows for &lt;a href=&quot;http://en.wikipedia.org/wiki/OFDM&quot; rel=&quot;nofollow&quot;&gt;OFDM&lt;/a&gt; or Wavelet modulation for the PHY.  New versions are getting up to 500mbps -&gt; 1gbps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As to the many devices, ODFM splits the available bandwidth into a lot of different channels, multiple channels can be used for different things at 1 time.  Device A and B are talking on channel 1 while device A and C are talking on channel 2, etc.  I don't know the negotiation protocol for what channels get used and when within IEEE 1901.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;OFDM is also the basis for 4G LTE, WiMAX, and other multiple access systems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can insert/remove high frequency information from the power line with a simple isolation transformer specced for your frequency (look in the pulse transformer section) and a high pass filter on the receiver side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example from one of Maxim's datasheets:&#xA;&lt;img src=&quot;http://i.imgur.com/7EFe8.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-27T00:45:37.400" LastActivityDate="2010-10-27T00:45:37.400" CommentCount="3" />
  <row Id="5684" PostTypeId="2" ParentId="5671" CreationDate="2010-10-26T17:59:34.660" Score="2" ViewCount="" Body="&lt;p&gt;If you check ebay, you can quite a few between cheap and $50.  Frankly, I'd do that and put your extra money into oscilloscope.&lt;/p&gt;&#xA;" OwnerUserId="1720" LastActivityDate="2010-10-26T17:59:34.660" />
  <row Id="5685" PostTypeId="2" ParentId="1404" CreationDate="2010-10-26T18:27:25.750" Score="3" ViewCount="" Body="&lt;p&gt;Bluetooth products appear to be hampered by their licensing fees for low cost low volume use. These folks: &lt;a href=&quot;http://www.mdfly.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.mdfly.com/&lt;/a&gt; have a USD 9.95 bluetooth module that does simple bluetooth serial, nothing else [even though the chip has much more ability, but would need different firmware with higher licensing costs]. This chip interfaces with the Android bluetooth stack for serial comm just fine. the nordic RF24 hardware is lower cost and lower license issues mean more abilities for experimenters. But you will need a dongle Android [some day the native hardware on some Android devices may be opened up] and other platforms, iPhone, PC...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good hunting!&lt;/p&gt;&#xA;" LastActivityDate="2010-10-26T18:27:25.750" />
  <row Id="5686" PostTypeId="2" ParentId="5666" CreationDate="2010-10-26T19:57:43.203" Score="13" ViewCount="" Body="&lt;p&gt;Let me sum up your limitations of a CR2032:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;10mA is about the max current you&#xA;want to pull from a single, it is&#xA;easy to put them in parallel, but a&#xA;large amount of testing(more than&#xA;2000 batteries worth) has confirmed&#xA;this.*&lt;/li&gt;&#xA;&lt;li&gt;They can be purchased to have&#xA;400mAh, the less current you pull&#xA;the closer to this it will be,&#xA;pulling more then 1mA decreases this a decent&#xA;bit.**&lt;/li&gt;&#xA;&lt;li&gt;Under a 1mA load they will&#xA;decay all the way to 1.5V before&#xA;they fail, they will be at 2.7V&#xA;almost right away.&lt;/li&gt;&#xA;&lt;li&gt;You can measure an almost full voltage on them with a multimeter when they are dead. This is solved by placing a load on them.***&lt;/li&gt;&#xA;&lt;li&gt;If you are lazy, it is very easy to tell how much charge they have left by how much they make your tongue tingle. Your tongue acts as the load and measures. This is probably by far the easiest way to test them, although it does pull a decent bit of current.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;I think Thomas wrote a good answer, I just thought it might be helpful to give some details of the coin cells since it seems you have used AA quite a bit.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*&lt;a href=&quot;http://en.wikipedia.org/wiki/List_of_battery_sizes&quot; rel=&quot;nofollow&quot;&gt;Wiki says up to 15mA pulsed&lt;/a&gt;, but we confirmed that up to 1mA shows a nearly consistent capacity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;**&lt;a href=&quot;http://en.wikipedia.org/wiki/CR2032_battery&quot; rel=&quot;nofollow&quot;&gt;Wiki&lt;/a&gt; shows a standard that is a bit lower, but my company would always purchase 400mAh or 450mAh CR2032. When you buy a &quot;standard battery&quot; you can expect 200mAh it seems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*** People often will measure batteries without load, when someone tells you on a project that ran out of power early, ensure their original battery measurement was under load, very easy mistake.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-31T04:50:36.017" LastActivityDate="2011-03-31T04:50:36.017" CommentCount="2" />
  <row Id="5687" PostTypeId="2" ParentId="5680" CreationDate="2010-10-26T20:46:06.900" Score="3" ViewCount="" Body="&lt;p&gt;If you want a simplistic answer. Here it is&lt;br&gt;&#xA;You have the power source. It gives you 220 Volts at rather low frequency (as noted: 50-60 Hz). You connect a capacitor with a low value and an inductance of a low value to this line this way: low inductance doesn't allow 50-60 Hz to pass in - it shorts such currents to the ground (being placed after capacitor! not to short everything at all), on the other hand capacitor in it's place again doesn't allow low frequency in and passes through high frequency, which we send or receive. The other party does the same - we have a working transfer line.&lt;br&gt;&#xA;But, ofcourse we connect different devices to our power socket. What happens in such a situation is simple too: mostly they are - ac/dc convertors, which use either transformer, or impulse scheme. This schematic doesn't allow high frequencies, eg they provide huge resistance to it. But we remember the capacitor in both our devices - it provides low resistance, so our-generated high frequency signal takes the easiest way: our receiver.&#xA;Ofcource there will be noise and leakage, our coding system and filters will deal with it.&lt;br&gt;&#xA;That's the picture in it's simplest form. &lt;br&gt;Hope this is what you were asking ;)&lt;/p&gt;&#xA;" OwnerUserId="1651" LastActivityDate="2010-10-26T20:46:06.900" />
  <row Id="5688" PostTypeId="2" ParentId="5186" CreationDate="2010-10-26T20:47:29.163" Score="3" ViewCount="" Body="&lt;p&gt;I usually keep my digital camera with me when I'm working on stuff for this exact purpose. Put it in Macro mode, play with the flash settings as required and take the photo at an angle between 30 and 45 degrees from board level. Not only will the part numbers be plain as day - and you can zoom in for more detail - but the photos tend to look pretty awesome as well.&lt;/p&gt;&#xA;" OwnerUserId="1712" LastActivityDate="2010-10-26T20:47:29.163" CommentCount="1" />
  <row Id="5689" PostTypeId="2" ParentId="3283" CreationDate="2010-10-26T21:03:31.457" Score="0" ViewCount="" Body="&lt;p&gt;Thinking out of the box:&lt;br&gt;&#xA;You could place a simple motor or a relay near controller, connect a usual thread to it and lay it to the second board, where you place a switch, connected to it's ground or it's VCC. (it could be a real wire -&gt; single-wire signal transfer :D )&lt;br&gt;&#xA;If those two boards are in optical visibility you could put IR transmitter-receiver.&lt;br&gt;&#xA;...something else...&lt;/p&gt;&#xA;" OwnerUserId="1651" LastActivityDate="2010-10-26T21:03:31.457" />
  <row Id="5690" PostTypeId="2" ParentId="5649" CreationDate="2010-10-26T21:06:33.553" Score="2" ViewCount="" Body="&lt;h2&gt; Why is it hard?&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;This is not the easiest thing to do. you have picked a crystal oscillator that is specifically chosen to give easy division to common baud rates.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;11.0592MHz/9600 is 1152&lt;/p&gt;&#xA;&#xA;&lt;p&gt;11.0592MHz/115200 is 96&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That means you can hit some standard baud rates perfectly with a certain divider. Gives very consistent UART. Now you want to count time.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Counting 1 Second&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;If you take a 11.0592MHZ then divide by 256 and 64 you get a value of 675. This means if you want an accurate count of seconds you need to have that interrupt every 256 * 64 clock cycles and count with a variable in your interrupt you can hit it.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;How to make it easier&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;You have two options, accepting error. First, your equation you divided by 255 since you are counting from 0 to 255, but since the interrupt is on overflow it is actually as you count to 256, so you should be dividing by 256.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;My clock has error?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Decide how much precision you need. Often you do not need spot on precision, if this is the case, accept that it is almost a second and use what Thomas said in comment. Count to as close as you can get and cope. Timer 1 will allow you to divide by 65536 and spend more time doing things other than handling interrupts.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;I need precision in my clock!&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;You need to pick an &lt;a href=&quot;http://en.wikipedia.org/wiki/Crystal_oscillator_frequencies&quot; rel=&quot;nofollow&quot;&gt;oscillator value that is a multiple of 32768 Hz&lt;/a&gt;. What you want is something that can be reduced to 1Hz from division by a power of 2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need the nice baud rate and a nice counter, the wiki page has a mark for RTC(good for real time clock). 4.608 MHz is a great thing, it divides to 1Hz pretty easy and is good for 115200 baud also.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-10-27T01:13:35.727" LastActivityDate="2010-10-27T01:13:35.727" CommentCount="3" />
  <row Id="5691" PostTypeId="1" CreationDate="2010-10-26T21:22:43.857" Score="10" ViewCount="403" Body="&lt;p&gt;Does anyone know of a good basic Cortex-A9 design? Something with just enough to run with power and ethernet? I'm looking for something as a starting point and maybe with eagle files.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: While this isn't my first time designing something. I do think I'm in way over my head still. I'm looking for something with a lot of horsepower, +1GHz. I really like the Panda board, and this would be my first choice. The only problem with it is the extras, the video, sound just use extra power and won't be used. The M3 is close in design, ie loadable via USB (SD card would be nice too). I really just looking for horsepower. I also didn't have a chip picked out, I wanted to leave that open, but was looking at the OMAP4430. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for all the input. I will likely just use a panda board unless some knows of a better design. I think the cost of eagle (full version) will put this project out of my range to prototype.&lt;/p&gt;&#xA;" OwnerUserId="1726" LastEditorUserId="1726" LastEditorDisplayName="" LastEditDate="2010-10-27T01:05:57.257" LastActivityDate="2011-02-01T07:44:14.450" Title="Minimalist Cortex-A9 design" Tags="&lt;arm&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="3" />
  <row Id="5692" PostTypeId="2" ParentId="5680" CreationDate="2010-10-26T21:37:12.207" Score="1" ViewCount="" Body="&lt;p&gt;I think it would be helpful to consider power line modems as radio devices since they use  traditional radio techniques (modulation) to achieve data transfer. If you take two radio modems and plug a cable between them instead of an antenna they will still be able to communicate (impedance matching aside).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic idea is not to encode the data as high-low voltage levels (which can be prone to interference) but as frequency/phase of (a set of) sinusoids. The second thing to do is to eliminate low-frequency components by clever encoding and/or frequency conversion. This makes it possible to separate different users by frequency filtering (in addition to being critical in radio since electromagnetic waves won't happen from a DC signal).&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-10-26T21:37:12.207" />
  <row Id="5693" PostTypeId="2" ParentId="5691" CreationDate="2010-10-26T22:18:21.623" Score="8" ViewCount="" Body="&lt;p&gt;Are you sure you need an A9?  These are not &quot;minimalist&quot; or &quot;basic&quot; chips in any way.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://pandaboard.org/&quot; rel=&quot;nofollow&quot;&gt;PandaBoard&lt;/a&gt; uses an OMAP4430 Cortex-A9 chip from TI, which has 547 balls and 216 pads on a 0.4mm pitch.  Can you solder this chip, and/or create a layout for it?  No, the 2-layer freeware version of Eagle won't cut it, no matter how hard you try.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't want to discourage you on your first question, but it looks like you've jumped in over your head.  I'd suggest that you do one of the following:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Look at using a simpler chip, like an M0 or M3.  The &lt;a href=&quot;http://electronics.stackexchange.com/questions/tagged/arm&quot;&gt;ARM tag&lt;/a&gt; is a great place to start.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://dkc1.digikey.com/us/en/ph/ti/pandaboard.html&quot; rel=&quot;nofollow&quot;&gt;Purchase a PandaBoard&lt;/a&gt; (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?site=us&amp;amp;keywords=UEVM4430F-01-00-00-ND&quot; rel=&quot;nofollow&quot;&gt;$174 US&lt;/a&gt;) or similar dev board if you really want the A9.&lt;/li&gt;&#xA;&lt;li&gt;Let us know that you're familiar with the challenges of using complex chips like this, and give us a part number you were considering. In this case, I'll shut up.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-26T22:25:52.440" LastActivityDate="2010-10-26T22:25:52.440" CommentCount="1" />
  <row Id="5694" PostTypeId="2" ParentId="5691" CreationDate="2010-10-26T22:23:47.143" Score="2" ViewCount="" Body="&lt;p&gt;If you just want an ARM with Ethernet, get an &lt;a href=&quot;http://mbed.org/&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-10-26T22:23:47.143" CommentCount="4" />
  <row Id="5695" PostTypeId="2" ParentId="5629" CreationDate="2010-10-26T23:05:01.300" Score="3" ViewCount="" Body="&lt;p&gt;In the past I have noticed that some of the PIC datasheets do not correctly show the SPI CPOL and CPHA registers, there was some issues that when looking at the output on a scope, two of the four combinations were back to front from what was expected.  So double check you are actually getting the expected waveform out of your PIC and that the waveform matches what is needed on the EEPROM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have also come across some A/D converters that worked intermittently when I had incorrect SPI settings on a HC12, drove me banana's trying to work it out, was one of my first projects as a professional engineer, eventually I worked it out.  But I digress.  So it is possible to get intermittent problems using SPI bus due to incorrectly set CPOL/CPHA.  As it is a shift register after all, and the last bit on one character may be being read of the first of the next character.  This type of problem  may not be noticed straight away either.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So ensure you have the correct settings on a scope, and do not relay on just setting the registers of the PIC. &lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-26T23:05:01.300" CommentCount="1" />
  <row Id="5696" PostTypeId="1" CreationDate="2010-10-26T23:07:54.843" Score="17" ViewCount="436" Body="&lt;p&gt;Does anyone know of any (reasonably low-cost) SoC which combines &lt;strong&gt;all&lt;/strong&gt; of:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Microcontroller (any architecture, at least 4KB RAM/8KB flash)&lt;/li&gt;&#xA;&lt;li&gt;Radio transceiver (433MHz - 915MHz or 2.4GHz)&lt;/li&gt;&#xA;&lt;li&gt;Ethernet MAC + PHY&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;(For a wireless sensor application - connecting to low power sensor nodes)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can find examples of micros with either peripheral, but not both:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Eg.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Micro + ethernet:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.luminarymicro.com/products/lm3s9b96.html&quot; rel=&quot;nofollow&quot;&gt;LM3S9B9x&lt;/a&gt; = ARM Cortex-M3 + Ethernet MAC and PHY&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en026447&quot; rel=&quot;nofollow&quot;&gt;PIC18F66J6x&lt;/a&gt; = PIC18 + Ethernet MAC and PHY&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Micro + radio:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/cc430f6137.html&quot; rel=&quot;nofollow&quot;&gt;CC430&lt;/a&gt; = MSP430 + Sub-1GHz radio&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ember.com/products_zigbee_chips_e250.html&quot; rel=&quot;nofollow&quot;&gt;EM250&lt;/a&gt; = XAP2b + 802.15.4/ZigBee&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please only answer this question if you can name a chip.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-01T14:59:54.237" LastActivityDate="2010-11-04T16:58:06.777" Title="Microcontroller with both ethernet and radio onboard?" Tags="&lt;microcontroller&gt;&lt;ethernet&gt;&lt;radio&gt;&lt;soc&gt;" AnswerCount="3" CommentCount="15" FavoriteCount="8" />
  <row Id="5697" PostTypeId="1" AcceptedAnswerId="5724" CreationDate="2010-10-27T01:24:17.367" Score="4" ViewCount="233" Body="&lt;p&gt;Is it possible to increase the resolution of an ADC by supersampling on a PIC24F ADC, which has 10 bits of resolution and is implemented using a successive approximation engine? Speed is not critical - greater than 1 kHz or so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My initial thought was no, as it is not a Delta-Sigma ADC and results are not cumulative, so I thought I could add noise to the voltage reference (3V nominal) using a pin of the MCU and a high valued resistor. Would this work? The additional noise should improve the resolution, but I'm unsure if this applies for all types of ADC's.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-27T05:09:50.233" LastActivityDate="2010-10-27T09:30:33.077" Title="Increasing ADC resolution by supersampling on a successive approximation ADC" Tags="&lt;adc&gt;&lt;microcontroller&gt;&lt;sampling&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="5698" PostTypeId="1" CreationDate="2010-10-27T01:27:03.753" Score="1" ViewCount="99" Body="&lt;p&gt;I'm considering the possibility of using an ethernet-connected (SNMP would be a bonus) microcontroller board of some sort to monitor a RAID card inside a server that doesn't have OS support; the card has LED headers and an I2C header. So:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Which board? Arduino or &lt;a href=&quot;http://electronics.stackexchange.com/q/297/1696&quot;&gt;something more specialised&lt;/a&gt;? I'd be OK with a through-hole kit but would prefer pre-assembled to save time; SMT or etching a board are right out.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Where should I mount the board? should I run wires through ventilation holes and have the board outside, or make up some sort of expansion slot mounting bracket and have the board physically inside? Being inside the server does give me access to +5V/+12V for power.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1696" LastActivityDate="2010-10-27T05:27:05.427" Title="Microcontroller board with ethernet for computer sensors" Tags="&lt;microcontroller&gt;&lt;sensor&gt;&lt;ethernet&gt;&lt;computers&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="5699" PostTypeId="2" ParentId="5681" CreationDate="2010-10-27T01:31:11.133" Score="3" ViewCount="" Body="&lt;p&gt;frankly if your not familiar with power supply design you shouldn't be starting with generating dangerous voltages.  Additionally i assume your listed outputs are DC given that the part you listed is a DC-DC converter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;+60V DC will penetrate your skin (not to speak of -108 or -120).  It takes &amp;lt;100mA of current through your heart to send it into fibrillation.  Which you could easily do with +60V, dry skin and getting +vdd on one hand and GND on the other, wet skin is far worse. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;All that aside what you need is a DC to DC boost converter controller with invert for the negative voltages and external switching transistors that can handle the voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should build a few low voltage designs using this topology so you fully understand it before you attempt to create what your asking for.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-27T01:31:11.133" CommentCount="1" />
  <row Id="5700" PostTypeId="1" AcceptedAnswerId="5707" CreationDate="2010-10-27T01:33:22.847" Score="3" ViewCount="227" Body="&lt;p&gt;If I have two 1k resistors rated at 1% fed by a perfect 10V source then what is the otuput guaranteed to be? 5V ±1% or 5V ±2% or some other value?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can work out this case easily, assume that R1 is at the minimum, R2 is at the maximum, then the output is 4.95V; for the reverse case it is 5.05V, which is ±1%.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But is there a general rule for differing values? What about differing tolerances - what if one resistor were ±0.1% and one ±1%. While you can work it out by plugging values into the voltage divider formula, I'm looking for some general rule of thumb.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-17T08:03:33.087" LastActivityDate="2011-05-17T08:03:33.087" Title="Tolerance of voltage dividers with different values for R1 and R2." Tags="&lt;resistor&gt;&lt;voltage&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="5701" PostTypeId="1" CreationDate="2010-10-27T01:56:33.873" Score="0" ViewCount="163" Body="&lt;p&gt;We're trying to build a rudimentary Balance Board using four force sensitive resistors and an Arduino unit, but are not sure how to wire up the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do we connect the sensors to the Arduino?&lt;/p&gt;&#xA;" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-10-27T02:49:10.020" LastActivityDate="2010-10-27T02:49:10.020" Title="Balance board with Arduino" Tags="&lt;voltage-measurement&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="5702" PostTypeId="2" ParentId="5701" CreationDate="2010-10-27T02:02:04.217" Score="4" ViewCount="" Body="&lt;p&gt;You have given very little detail which means my answer is going to have to have very little detail as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a resistance that changes based off of force being applied to it, I would recommend creating a voltage divider with the resistor. I would then have the microcontroller compute an A/D. This analog voltage will be related to the pressure that is being applied.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-27T02:02:04.217" />
  <row Id="5703" PostTypeId="2" ParentId="5701" CreationDate="2010-10-27T02:21:45.087" Score="5" ViewCount="" Body="&lt;p&gt;Lady Ada has a tutorial on using force sensitive resistors with the Arduino:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ladyada.net/learn/sensors/fsr.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/learn/sensors/fsr.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;She also has quite a few other useful tutorials to get you started on many things Arduino and electronic.&lt;/p&gt;&#xA;" OwnerUserId="1271" LastActivityDate="2010-10-27T02:21:45.087" />
  <row Id="5704" PostTypeId="2" ParentId="5700" CreationDate="2010-10-27T02:47:00.910" Score="1" ViewCount="" Body="&lt;p&gt;no rule of thumb for different tolerances.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assume R2 between Vout and GND.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your math above only holds for R1=R2.  That is When R1=R2 both with equal tolerance your output has tolerance equal to the resistor tolerance.  When R1 != R2 and the tolerances of each resistor are equal the total error logarithmically approaches 200% of the tolerance of an indicidual resistor as the ratio of R1 to R2 increases.  If R1 is 100 times bigger than R2 then the output tolerance is roughly twice the tolerance of a single resistor.  I'll leave the inverse up to you for calculation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now if the output tolerances are not equal, you've added an additional variable into the equation.  You'd be looking at a multidimensional equation and attempting to locate maxima and minima to determine Vout tolerance, which is not trivial.  So use the same tolerance for both resistors.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-27T02:47:00.910" />
  <row Id="5705" PostTypeId="2" ParentId="5697" CreationDate="2010-10-27T02:51:12.730" Score="4" ViewCount="" Body="&lt;p&gt;oversampling allows higher ADC resolution, if you oversample at 4x nyquist you can gain 1 bit of resolution via spreading quantization noise and decimation.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-10-27T03:32:53.660" LastActivityDate="2010-10-27T03:32:53.660" />
  <row Id="5706" PostTypeId="2" ParentId="5700" CreationDate="2010-10-27T03:17:58.337" Score="2" ViewCount="" Body="&lt;p&gt;Any two tolerances differ by a factor of at least 5 (as in 5% vs. 1%), so as a rough approximation, you can ignore the effect of the smaller one. This means that at the edge of the tolerance range, the voltage at the middle of the divider will be off by a percentage equal to roughly half of the larger tolerance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that this is only true if the two resistors have similar magnitudes, as in your 1k example. If the divider consists of a 1k and a 100k resistor, error in the larger resistor could dwarf the smaller resistor.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-27T03:17:58.337" CommentCount="4" />
  <row Id="5707" PostTypeId="2" ParentId="5700" CreationDate="2010-10-27T03:34:46.093" Score="9" ViewCount="" Body="&lt;p&gt;I think you asking for sensitivity analysis of f(x,y) = x/(x+y).  Since there are two variables, I do a general analysis first, then look at the dependence on each variable separately.  Since you might not care for the algebra, I tried to sum up each case after the bold heading.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The bad news is that the tolerance on the measured voltage can be very far from the predicted voltage, 1000000% or more relative error.  The good news is that in reasonable cases it can only be a tad more than twice as bad as the resistor tolerances, and often you can do much better.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;If X is supposed to be x, then the signed relative error is (X-x)/x = dx and X = x*(1+dx).  If dx is 1% = 0.01, then X is x*101%, and if dx is -1%, then X is x*99%.  In other words, we care about X = x*(1+dx).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If X is the resistance of R1, and Y is the resistance of R2, with R1 and R2 in series connected +10V to ground, then the measured voltage with one probe between R1 and R2 and the other probe at ground is f(X,Y) = X/(X+Y), but it was supposed to be f(x,y) = x/(x+y).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If x changes to X=x*(1+dx) and y changes to Y=y*(1+dy) then f(x,y) changes to f(X,Y):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;x*(1+dx)/( x*(1+dx) + y*(1+dy) )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The relative error is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;E(x,y,dx,dy) = | f(x,y) - f(X,Y) | / f(x,y) = ( x/(x+y) - x*(1+dx)/( x*(1+dx) + y*(1+dy) ) ) / ( x/(x+y) )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;which simplifies to the:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Exact relative error&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;E(x,y,dx,dy) = y*|dy-dx| / ( X + Y )&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This formula is not too bad to plug values into, and it is not too bad to analyze in specific cases.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Quick symmetric bound&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming |dx| and |dy| are bounded by 0 ≤ e &amp;lt; 100%, this is bounded by:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;E  ≤  2*y*e / ((x+y)*(1-e))  =  y/(x+y) * 2 * ( e + e*e + e*e*e + … )&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;For instance when x = R1 = 1K and y = R2 = 1K and dx = 1% = 0.01 and dy = -1% = -0.01 you get the relative error E = 1% = 0.01.  The bound I gave is a little loose since it predicts 1.0101...% but probably this is not too big a deal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Large R1&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;When R1 is very large compared to R2, then the relative error goes down considerably.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If x → ∞, then E(x,y,dx,dy) → 0.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It goes to zero about as fast 1/x: x*E(x,y,dx,dy) → y*(dx-dy)/(1+dx).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is not too surprising: if you have an open circuit with +10V attached to your probe and the other other probe attached to R2 attached to ground, then the current is 0 and both terminals of R2 remain at +0V, so you measure +10V no matter what the value of R2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Large R2&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;When R2 is very large compared to R1, then the relative error can be very large, but for reasonable tolerances on R1 and R2, E is only a little more than twice as bad.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If y → ∞, then r(x,y,dx,dy) → |dx-dy|/(1+dx).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If dy = -dx = 0.10 = 10%, then you get 22% error (a little more tan twice as bad).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If dy = -dx = 0.50 = 50%, then r = 2 = 200% relative error (four times as bad).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As dx → 1 = 100%, r → ∞ (infinitely worse).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If |dx| and |dy| are bounded by e &amp;lt; 1 = 100%, then for large y, r is bounded by 2e/(1-e), which is a little bigger than twice as big as e.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If dy = -dx = 0.01 = 1%, then you get E = 2*1%/(99%) = 2.0202…% relative error on the measured voltage (a little more than twice as bad).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If dy = -dx = 0.001 = 0.1%, then you get 2*0.1%/(99.9%) = 0.2002002…% relative error (a very little more than twice as bad).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Asymmetric tolerances&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If R2 is very accurate and R1 ≈ R2, then the error is at most a little more than half as bad.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If dy = 0, then E = dx*y / ( X + y ) and if x = y, then E = dx/(2+dx).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If -dx = 0.01%, then E = 0.01 / 1.99 = 0.005025… = 0.5025…% (a little more than half as bad).&lt;/p&gt;&#xA;" OwnerUserId="1271" LastActivityDate="2010-10-27T03:34:46.093" CommentCount="3" />
  <row Id="5708" PostTypeId="2" ParentId="5697" CreationDate="2010-10-27T03:48:32.107" Score="3" ViewCount="" Body="&lt;p&gt;If when you say adding noise to your reference, you are adding a known offset to your offset in order to determine when a signal shifts to reading a different value and then interpolating, then yes, I think that should work. (wow, long sentence)&#xA;I think this is probably very difficult to code compared to the method that Mark mentioned where you over-sample. What I would worry about in the method is the error caused by adding more non-ideal components to a system where you are looking for very high precision.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are concerned about noise, you can over-sample, and then in code filter and then down-sample. This method will actually give you less noise then to just sample at your desired rate, but costs more in the since of processing time.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-27T03:48:32.107" />
  <row Id="5709" PostTypeId="2" ParentId="4475" CreationDate="2010-10-27T04:43:00.360" Score="2" ViewCount="" Body="&lt;p&gt;The one between your ears.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Seriously, PCB software autorouters leave a lot to be desired, especially the cheap ones.&lt;/p&gt;&#xA;" OwnerUserId="1728" LastActivityDate="2010-10-27T04:43:00.360" CommunityOwnedDate="2010-10-27T04:43:00.360" CommentCount="2" />
  <row Id="5710" PostTypeId="1" CreationDate="2010-10-27T04:49:22.510" Score="7" ViewCount="262" Body="&lt;p&gt;I'm looking to implement a phase lock in an FPGA without using any external components (other than the ADC). For simplicity locking to a simple binary pulse is adequate. The frequency of the signals is ~0.1-1% of the clock. I can't use the onboard clock PLL's because they are typically&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Not configurable (set during synthesis) &lt;/li&gt;&#xA;&lt;li&gt;Jittery &lt;/li&gt;&#xA;&lt;li&gt;Don't support the frequency I need.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I've been sorting through the literature and found a few binary phase locked loops. Most notable a &quot;pulse steal&quot; design that I can post a link to if desired. Which I have implemented and synthesized with some success, but its jitter and lock range was not as good as advertised. I've also had success using a external DVCO, but I would prefer it if I can implement everything on chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A digital circuit design or even a hint in the right direction would be helpful (I've been banging my head against this for a while), a proven FPGA implementation would be wonderful but not expected. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;ADDED 10-27-2010&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The actual DPLL design that I used has a &quot;Random Walk Filter&quot; as the loop filter (Not the &quot;pulse steal&quot; described earlier, going through my notes that didn't work to well), which then drives the clock pulses to the DCO. The lock-in range is set via divider in the DCO. The sensitivity of the Loop is established by varying the length of the random walk. The paper in which this is found is cited at the end of this post. After implementing parts of it myself, I found that it was actually already implemented on open-cores, however it turns out that in the last few months the project was deleted so here is a &lt;a href=&quot;http://webcache.googleusercontent.com/search?q=cache:OS38UXKGLkEJ:opencores.org/project,dpll_rwf,overview+Open+cores+Random+Walk+filter&amp;amp;cd=1&amp;amp;hl=en&amp;amp;ct=clnk&amp;amp;gl=us&quot; rel=&quot;nofollow&quot;&gt; link &lt;/a&gt; to the google cache of the page (I have the verilog files saved if anyone wants them) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yamamoto, H.; Mori, S.; , &quot;Performance of Binary Quantized All Digital Phase-Locked Loop with a New Class of Sequential Filter,&quot; Communications, IEEE Transactions on , vol.26, no.1, pp. 35- 45, Jan 1978&lt;/p&gt;&#xA;&#xA;&lt;p&gt;doi: 10.1109/TCOM.1978.1093972&lt;/p&gt;&#xA;&#xA;&lt;p&gt;URL: &lt;a href=&quot;http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&amp;amp;arnumber=1093972&amp;amp;isnumber=23895&quot; rel=&quot;nofollow&quot;&gt;http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&amp;amp;arnumber=1093972&amp;amp;isnumber=23895&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1729" LastEditorUserId="1729" LastEditorDisplayName="" LastEditDate="2010-10-27T22:57:37.990" LastActivityDate="2010-11-08T19:54:21.320" Title="All Digital Phase Lock Loop" Tags="&lt;fpga&gt;&lt;dsp&gt;&lt;pll&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="5711" PostTypeId="2" ParentId="5698" CreationDate="2010-10-27T05:27:05.427" Score="1" ViewCount="" Body="&lt;p&gt;For a one time board, I think an Arduino with a ethernet shield is going to be your easiest path for you. If you are wanting to produce and market you should look into a more specialized/customized solution for the aspect of cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Placing the board inside is good because you will be keeping your SPI lines short and have power close by, but putting your board outside will give you less of a concern of shorting to other electronics in the server.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-27T05:27:05.427" />
  <row Id="5712" PostTypeId="1" CreationDate="2010-10-27T05:38:11.093" Score="1" ViewCount="427" Body="&lt;p&gt;I have two recorded audio voice WAV files I have recorded by saying &quot;Good Morning&quot; twice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to compare the two audio files and say both are identical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can i do that?&#xA;What is the right approach to achieve this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1730" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-27T11:05:55.843" LastActivityDate="2010-10-27T11:15:28.527" Title="How to compare two audio files?" Tags="&lt;audio&gt;&lt;dsp&gt;" AnswerCount="4" CommentCount="9" />
  <row Id="5713" PostTypeId="1" AcceptedAnswerId="5716" CreationDate="2010-10-27T05:44:54.833" Score="6" ViewCount="532" Body="&lt;p&gt;I have a microcontroller with one available digital pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I control 25 LEDs?&lt;/p&gt;&#xA;" OwnerUserId="1725" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-27T15:41:51.067" LastActivityDate="2010-11-26T11:46:07.623" Title="Serial control of 25 LEDs from a single pin" Tags="&lt;microcontroller&gt;&lt;led&gt;&lt;multiplexing&gt;" AnswerCount="9" CommentCount="2" FavoriteCount="3" />
  <row Id="5714" PostTypeId="2" ParentId="5713" CreationDate="2010-10-27T05:56:08.507" Score="1" ViewCount="" Body="&lt;p&gt;I'd just chain a few shift registers together.  (This reduces the frequency with which you can toggle the LEDs, of course..)&lt;/p&gt;&#xA;" OwnerUserId="504" LastActivityDate="2010-10-27T05:56:08.507" />
  <row Id="5715" PostTypeId="2" ParentId="5713" CreationDate="2010-10-27T05:56:30.240" Score="0" ViewCount="" Body="&lt;p&gt;The answer is probably &quot;a series of shift registers,&quot; but can you be more specific in your question? What microcontroller? What do you mean by &quot;digital port&quot;? A single pin?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-27T05:56:30.240" CommentCount="1" />
  <row Id="5716" PostTypeId="2" ParentId="5713" CreationDate="2010-10-27T06:00:07.980" Score="9" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=8130&quot; rel=&quot;nofollow&quot;&gt;I2C IO Expander&lt;/a&gt;: - Some protocol overhead, but it should be expandable to a very large (thousands) number of LEDs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=733&quot; rel=&quot;nofollow&quot;&gt;Simple shift register&lt;/a&gt; - Dead Simple interface, the LEDs may flicker when updating if the shift register clock is not fairly fast. Using a double buffered shift register will fix this.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-27T06:00:07.980" CommentCount="5" />
  <row Id="5717" PostTypeId="2" ParentId="5713" CreationDate="2010-10-27T06:11:43.560" Score="1" ViewCount="" Body="&lt;p&gt;25 LED's depending on size can draw a lot of power for a single digital IO pin on a micro-controller. Rather than driving them directly, you should probably use a simple FET switch (so the IO is tied to gate) to control the power to the LED chain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your application, there are other more robust ways to accomplish this. But throwing in a fet will probably get you working the fastest. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, if you want to gate a variable signal, there more complicated devices, sometimes called digital relays, that give you a way to digitally switch it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for &lt;em&gt;individually&lt;/em&gt; controlling 25 LED's with a single IO port. As others suggested, you can use a few shift registers. There are more complicated solutions involving communicating with another IC using a serial protocol (I2C for example).&lt;/p&gt;&#xA;" OwnerUserId="1729" LastActivityDate="2010-10-27T06:11:43.560" />
  <row Id="5718" PostTypeId="2" ParentId="5712" CreationDate="2010-10-27T06:27:29.607" Score="1" ViewCount="" Body="&lt;p&gt;I do agree with the comments about how this question is very difficult to answer in this community, but I would like to provide a few of the more simple methods for you to look into. Ultimately a good and robust system will require the use of many different techniques and many many hours. This is why there is tons and tons of money put into voice recognition, and as you may know, still isn't great.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, people will speak within about the same frequency range every time they say a command word. If you look at the frequency domain of your signal, you can record what range was used when the person recorded their command word and then look for that in the future. You can get to the frequency domain using the FFT, wikipedia and some google search can help you with what this means and how to do it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can expand the frequency method to determine what the frequency is for each part of the word. For example, some people will raise the pitch of their voice as they finish a word. This could be another &quot;signature&quot; to look at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also people will generally speak the same speed for the same command word. For this you can look at amplitude of your signal to determine how long it took them to say each word and even the pause between two words. Then you can compare these pauses to your future signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again, these are just a few basic methods, but should get you a sense of the type of things that can be done.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-27T06:27:29.607" />
  <row Id="5719" PostTypeId="2" ParentId="5620" CreationDate="2010-10-27T06:32:34.733" Score="0" ViewCount="" Body="&lt;p&gt;i'd probably solder some 18-20awg stranded wire to the ends of the flex, after you solder, coat the joint with some decent strength insulating epoxy such that there is a firm physical attachment between the wire and the flex material to remove any stress from the solder joint.  The stranded wire should be strong but flexible enough to not break and run back to your controlling box which i assume will be on your belt or something.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The wire shouldn't be too bad on the weight of the clothing if you use some light stuff with thin insulation and loosly stitch it into the cloth so it can slide back and forth a bit.  The wire attachment into the control box could be screw terminals, although i'd recommend some sort of quick disconnect with a tension relieving mechanism for the wire, 3m makes a lot of connectors that would work.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally leave enough slack in the wire that the slack doesn't get into the way but there isn't a tension issue on the connection to the box.  You can probably stitch a sliding loop of wire into the back of the top of the 'clothing' such that tension on the wire that results from crazy dancing around fires just contracts the loop rather than putting much strain on the wire connectors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know if that picture you posted is of the actual strips you plan to use but if so i'd go over all the exposed solder joints with epoxy or some other sealing insulator.  Between the heat and the shenanigans at Burning Man i wouldn't count on those strips staying dry. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for field repair, bring a tube of epoxy (an environmentally friendly type highly recommended for Burning Man) and a &lt;a href=&quot;http://www.amazon.com/Weller-Battery-Powered-Soldering-Iron/dp/B000S63P9E/ref=pd_sim_sbs_hi_1&quot; rel=&quot;nofollow&quot;&gt;battery powered solder iron&lt;/a&gt;.  I imagine you'll have a solar battery charger of some sort with you anyway so that should cover it, maybe a bit of solder.  Worst case you can be the town soldering helper, i'm sure you'll find someone in need.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-27T06:32:34.733" CommentCount="7" />
  <row Id="5720" PostTypeId="2" ParentId="5712" CreationDate="2010-10-27T07:10:14.733" Score="1" ViewCount="" Body="&lt;p&gt;Try search for AI methods on Audio processing, and possibly wavelets.  Also use Matlab to develop your algorithms first before try to code it within an application.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-27T07:10:14.733" />
  <row Id="5721" PostTypeId="1" AcceptedAnswerId="5736" CreationDate="2010-10-27T07:32:59.980" Score="3" ViewCount="466" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am planning to create a robot arm using the MicroController.&#xA;The robot arm should move from the angle of 0 degrees to 60 degrees.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am going to use this robot arm in my application to stop and allow the small small toy vehicles on a dummy road. This is for demonstration of my project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the specifications that I need to keep in mind while choosing the Stepper Motor and MicroController.&lt;/p&gt;&#xA;" OwnerUserId="1731" LastActivityDate="2010-10-28T15:35:45.393" Title="Create a robot arm using microcontroller" Tags="&lt;microcontroller&gt;&lt;motor&gt;&lt;stepper&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5722" PostTypeId="1" AcceptedAnswerId="5728" CreationDate="2010-10-27T08:29:42.593" Score="7" ViewCount="302" Body="&lt;p&gt;Are there any good resources for learning the intricacies of PCB layout when dealing with BGA packages?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm very familiar with layout for almost every SMT part that has leads on the edge (QFP, TSSOP, QFN, etc...) However, I have not ever had a chance to work with BGA parts because of the difficulties involved in their assembly, as the shop where I work does not have the facilities to do so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyways, I've been looking into farming assembly out, and am hoping for some reference material for dealing with BGA devices. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm interested in both general and specifics. Escape routing, blind vias, vias in pad, SMD pads vs NSMD pads, filled and open vias, etc... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done a lot of sporadic reading (blogs, mainly), but am missing the bigger picture, namely how different techniques interact and a lot of basic common sense knowledge that likely comes through actual experience, even if only by proxy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far, I have spent some time studying any open-source project that uses BGA I can find (the BeagleBoard, Mainly) but most open source projects are not at the level of complexity that requires a BGA device, and the ones that do are rather rare.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-27T12:28:19.013" Title="Getting started with PCB Layout for BGA Packages" Tags="&lt;pcb&gt;&lt;design&gt;&lt;bga&gt;&lt;pcb-design&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="5723" PostTypeId="2" ParentId="5503" CreationDate="2010-10-27T09:01:01.700" Score="5" ViewCount="" Body="&lt;p&gt;If you check out the wikipedia page:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Transverse_mode&quot; rel=&quot;nofollow&quot; title=&quot;Transverse Mode&quot;&gt;Transverse Mode&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll see at the start of the second paragraph they say &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Transverse modes occur because of boundary conditions imposed on the wave by the waveguide&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This accounts for the discrepancy you have observed. Most diagrams of electromagnetic waves depict waves in free space, far away from any objects, and in that situation, you will have no electric or magnetic component in the propagation direction. Waveguides are (metal or fiber) tubes that confine an electromagnetic wave and force it in a particular direction. Since you have now introduced materials into the picture, things get more complicated, and you can have a non-zero electric and magnetic fields in the propagation direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most E+M textbooks will have a section on waveguides, and these concepts figure heavily into fiber optics engineering. &lt;/p&gt;&#xA;" OwnerUserId="1725" LastEditorUserId="1725" LastEditorDisplayName="" LastEditDate="2010-10-27T19:07:10.710" LastActivityDate="2010-10-27T19:07:10.710" CommentCount="1" />
  <row Id="5724" PostTypeId="2" ParentId="5697" CreationDate="2010-10-27T09:30:33.077" Score="6" ViewCount="" Body="&lt;p&gt;Atmel has very clear application note about increasing ADC resolution by oversampling with sources in C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Description in PDF is &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8003.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, sources are on Atmel website.&lt;/p&gt;&#xA;" OwnerUserId="1736" LastActivityDate="2010-10-27T09:30:33.077" />
  <row Id="5725" PostTypeId="2" ParentId="5713" CreationDate="2010-10-27T09:56:49.157" Score="14" ViewCount="" Body="&lt;p&gt;Shift Register and I2C is good, but only if there are at least 2 pins free. I suggest Dallas 1-wire port extender &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/DS2408.pdf&quot; rel=&quot;nofollow&quot;&gt;DS2408&lt;/a&gt; will be an optimal solution. Code for Dallas 1-wire device access is not so complicated and there are plenty of examles on the web.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may use several DS2408 connected to one pin or implement more logic after single DS2408 whichever you'd like.&lt;/p&gt;&#xA;" OwnerUserId="1736" LastActivityDate="2010-10-27T09:56:49.157" CommentCount="2" />
  <row Id="5726" PostTypeId="2" ParentId="5712" CreationDate="2010-10-27T10:17:13.500" Score="0" ViewCount="" Body="&lt;p&gt;Read about audio fingerprinting:&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Acoustic_fingerprint&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Acoustic_fingerprint&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See some example open source code: &lt;a href=&quot;http://wiki.musicbrainz.org/AudioFingerprint&quot; rel=&quot;nofollow&quot;&gt;http://wiki.musicbrainz.org/AudioFingerprint&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a non-trivial problem.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-27T11:11:34.760" LastActivityDate="2010-10-27T11:11:34.760" />
  <row Id="5727" PostTypeId="2" ParentId="3539" CreationDate="2010-10-27T10:38:39.900" Score="3" ViewCount="" Body="&lt;p&gt;As far as numbers would go: A low ESR cap for a switcher should usually have not more than a few 10 mOhm.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-10-27T10:38:39.900" />
  <row Id="5728" PostTypeId="2" ParentId="5722" CreationDate="2010-10-27T10:51:55.440" Score="6" ViewCount="" Body="&lt;p&gt;If you want affordable boards, forget about blind vias, via in pad, and filled vias. &lt;a href=&quot;http://mentor1.na5.acrobat.com/p24156661/&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is a good presentation on BGA routing, albeit for very high-density boards, but the basic principles will be the same for less demanding layouts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SMD pads vs NSMD pads is something you need to ask the company doing your BGA assembly about. The latter seems to be preferred. Some chip manufacturers have recommendations, as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have questions, &lt;a href=&quot;http://communities.mentor.com/mgcx/community/pcb/land_patterns_libraries&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; forum is very useful. You can also learn a lot by reading the various posts.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-10-27T10:58:04.577" LastActivityDate="2010-10-27T10:58:04.577" CommentCount="4" />
  <row Id="5729" PostTypeId="2" ParentId="5722" CreationDate="2010-10-27T10:55:21.630" Score="3" ViewCount="" Body="&lt;p&gt;They're a nightmare to use, most manufacturers use an x ray to check the connections properly! - not sure if I've got one lying around in the tool shed :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this &lt;a href=&quot;http://www.google.co.uk/url?sa=t&amp;amp;source=web&amp;amp;cd=25&amp;amp;ved=0CCsQxQEwDjgK&amp;amp;url=http%3A%2F%2Fdocs.google.com%2Fviewer%3Fa%3Dv%26q%3Dcache%3AR-kkMyxNzvkJ%3Awww.onboard-technology.com%2Fpdf_ottobre2007%2F100701.pdf%2Bbga%2Bdesign%2Btips%26hl%3Den%26gl%3Duk%26pid%3Dbl%26srcid%3DADGEESh4gg6tty_azI5y4sxBS__87YLmJctvvoQvJgl2WuG285JwL32XK3jPIfYfH2g1RXlQYGvgqdH6Orrgtyjl0J6RjiOzsng5nm97Wk7xu_GHdNAe2DpgJ0ZHSjQODpNlk_A713-i%26sig%3DAHIEtbR0MaafsEGlvzUHwaBtml_Udoz89A&amp;amp;ei=7ADITIi8JIuRjAfm5sVS&amp;amp;usg=AFQjCNH9BR56SiIDy_ZBkcH-ujGHybtbMg&amp;amp;sig2=w10d0G9wIkcrPyPdu5Hjew&quot; rel=&quot;nofollow&quot;&gt;BGA design tips PDF&lt;/a&gt; helpful, it has a pretty no nonsense look at BGA design and should give you a few pointers on PCB layout.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a side point - there's issues with heat and mechanical stress affecting the BGA's connections, although they dissipate heat well, they hate movement and flex in the PCB. The &lt;a href=&quot;http://en.wikipedia.org/wiki/Xbox_360_technical_problems&quot; rel=&quot;nofollow&quot;&gt;Xbox 360 technical problems&lt;/a&gt; are a good example of this - much of the problems are based around insufficient heat dissipation warping the PCB and effecting delicate BGA connections such as the one's on the graphics chip, a flat pack SMD has a certain amount of flexibility in the leads and they stand up better to expansion and movement caused by heat even if they don't dissipate the heat into the PCB as efficiently.  &lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-10-27T10:55:21.630" CommentCount="1" />
  <row Id="5730" PostTypeId="2" ParentId="5712" CreationDate="2010-10-27T11:15:28.527" Score="1" ViewCount="" Body="&lt;p&gt;You could look at integrating a voice recognition module into your project. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.robotshop.ca/vrbot-voice-recognition-module-for-robonova-and-other-robots.html&quot; rel=&quot;nofollow&quot;&gt;Tigal voice recognition module&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I guess it depends on what results your after, IMO speech recognition is still pretty basic, one of the first issues is differentiating ambient sound from vocal commands - the best current solution is when the person issuing commands has been close mic'ed with a kinda Madonna style headset. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ah....it brings back memories of my first Macbook, I spent the first week or so shouting &quot;Mac.......What time is it!&quot; just for it to turn around and reply &quot;.....opening safari&quot; - or some other unrelated operation.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-10-27T11:15:28.527" CommentCount="2" />
  <row Id="5731" PostTypeId="2" ParentId="5722" CreationDate="2010-10-27T12:28:19.013" Score="2" ViewCount="" Body="&lt;p&gt;Here's a &lt;a href=&quot;http://www.altera.com/literature/an/an114.pdf&quot; rel=&quot;nofollow&quot;&gt;PDF&lt;/a&gt; from Altera.  I've usually seen the diagonal via location because this gives the most space between the via and ball.  You can also Google &quot;BGA fan out&quot; to get more help.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-10-27T12:28:19.013" />
  <row Id="5733" PostTypeId="2" ParentId="5700" CreationDate="2010-10-27T12:47:42.660" Score="1" ViewCount="" Body="&lt;p&gt;If you have a bunch of components, all with different tolerances, you do a &lt;a href=&quot;http://en.wikipedia.org/wiki/Monte_Carlo_method&quot; rel=&quot;nofollow&quot;&gt;Monte Carlo analysis&lt;/a&gt; to see what kind of risk the worst case is, but also what a probable case is, since it's not likely that every component is at it's worst. This gets as detailed as you want to make it.&lt;/p&gt;&#xA;" OwnerUserId="1266" LastActivityDate="2010-10-27T12:47:42.660" />
  <row Id="5734" PostTypeId="2" ParentId="5671" CreationDate="2010-10-27T12:53:55.067" Score="6" ViewCount="" Body="&lt;p&gt;In the audio frequency range you can use your soundcard.  Use google to find the software.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-10-27T12:53:55.067" />
  <row Id="5735" PostTypeId="1" AcceptedAnswerId="5738" CreationDate="2010-10-27T13:17:50.200" Score="5" ViewCount="164" Body="&lt;p&gt;I've seen several microcontrollers rated to operate from 2.97V to 3.63V. Others I've seen rated from 3V to 3.6V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's with the extra 30mV on either end of the scale? It doesn't seem like it would make any difference, but maybe I'm missing something.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-27T14:14:00.473" Title="What a weird operating range, 2.97V to 3.63V." Tags="&lt;microcontroller&gt;&lt;ratings&gt;" AnswerCount="2" />
  <row Id="5736" PostTypeId="2" ParentId="5721" CreationDate="2010-10-27T13:19:17.773" Score="6" ViewCount="" Body="&lt;p&gt;You might get more mileage out of a high torque servo at first.  Servos have their own control circuitry so all you need to do is give them a command.  Stepper motors are good, but perhaps you should save them for future development as you'll probably have a lot of effort just making the mechanics of the arm and handling anything unforeseen that comes up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Servos are either controlled digitally or via a pulse width.  The pulse width control is easy - the length of the pulse determines what angle the servo sets itself to.  I haven't yet worked with them but from what my project partners tell me it's between 1ms and 2ms pulse width for the full range of motion and the pulses need to come every 16ms This makes choosing a microcontroller easy - it just needs to have a timer/counter module with output compare.  You won't have to worry about powering the motor through the microcontroller because the control pulse doesn't power the motor.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll need to judge the amount of torque necessary for the servo depending on the weight of what it's moving, and the amount of time it takes to travel a full 180 degrees (or whatever its full range is) is also important.  The servos seem to operate at 4.8V or 6V so that's a consideration.  Here's a page with some hobby servos to buy: &lt;a href=&quot;http://www.servocity.com/html/hitec_servos.html&quot; rel=&quot;nofollow&quot;&gt;http://www.servocity.com/html/hitec_servos.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may or may not need high-torque, but that should at least get you started and send you in the right direction.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-10-27T13:19:17.773" CommentCount="2" />
  <row Id="5737" PostTypeId="2" ParentId="5735" CreationDate="2010-10-27T13:35:08.340" Score="4" ViewCount="" Body="&lt;p&gt;I am assuming that is just a precaution or tolerance.  Stating that if you run it at 3V its not the bottom of the scale, and you are safe there.&lt;/p&gt;&#xA;" OwnerUserId="1414" LastEditorUserId="1414" LastEditorDisplayName="" LastEditDate="2010-10-27T13:52:18.020" LastActivityDate="2010-10-27T13:52:18.020" CommentCount="1" />
  <row Id="5738" PostTypeId="2" ParentId="5735" CreationDate="2010-10-27T13:38:40.503" Score="10" ViewCount="" Body="&lt;p&gt;So that is 3V (with a 1% tolerance) to 3.6V (again with approx 1% tolerance)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OR&lt;/p&gt;&#xA;&#xA;&lt;p&gt;as Thomas O commented 3.3V +/- 10%&lt;/p&gt;&#xA;" OwnerUserId="400" LastEditorUserId="400" LastEditorDisplayName="" LastEditDate="2010-10-27T14:14:00.473" LastActivityDate="2010-10-27T14:14:00.473" CommentCount="3" />
  <row Id="5739" PostTypeId="2" ParentId="2783" CreationDate="2010-10-27T13:50:06.993" Score="3" ViewCount="" Body="&lt;p&gt;I have had huge success with this setup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An &lt;a href=&quot;http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4254&quot; rel=&quot;nofollow&quot;&gt;STK600&lt;/a&gt; with &lt;a href=&quot;http://media.digikey.com/photos/Atmel%20Photos/ATSTK600-TQFP32.JPG&quot; rel=&quot;nofollow&quot;&gt;TQFP32 Zif&lt;/a&gt;.  This will allow you to program your chips via USB before putting them on the board.&lt;/p&gt;&#xA;" OwnerUserId="1414" LastActivityDate="2010-10-27T13:50:06.993" />
  <row Id="5740" PostTypeId="2" ParentId="5516" CreationDate="2010-10-27T15:12:19.700" Score="0" ViewCount="" Body="&lt;p&gt;Not quite sure if this fits your needs but you might browse the free online UC Berkley computer courses &lt;a href=&quot;http://webcast.berkeley.edu/courses.php?semesterid=27&quot; rel=&quot;nofollow&quot;&gt;here.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1720" LastActivityDate="2010-10-27T15:12:19.700" />
  <row Id="5741" PostTypeId="2" ParentId="5628" CreationDate="2010-10-27T15:35:38.407" Score="1" ViewCount="" Body="&lt;p&gt;Another issue to be aware of - having support for Microsoft's FAT filing system (on SD cards) in your device may infringe patents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.swpat.org/wiki/Microsoft%27s_FAT_patents&quot; rel=&quot;nofollow&quot;&gt;http://en.swpat.org/wiki/Microsoft%27s_FAT_patents&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I am not a lawyer) My understanding is that there's only a problem when using long filename support.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-27T15:35:38.407" CommentCount="1" />
  <row Id="5743" PostTypeId="1" AcceptedAnswerId="5745" CreationDate="2010-10-27T16:09:00.443" Score="8" ViewCount="266" Body="&lt;p&gt;I have an embedded Linux system with a single Ethernet port, but I need to go to many ports. It is obvious I need to add magnetics and ports. The trickier parts follow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My processor has an on-board MAC and I'm using a single-driver PHY. Do I only need a new PHY with more drivers? Is it possible to use multiple PHYs on the same MAC? Do I need a MAC for each port?&lt;/p&gt;&#xA;" OwnerUserId="1199" LastActivityDate="2010-10-28T08:02:27.673" Title="What is needed to go from single Ethernet to many?" Tags="&lt;embedded&gt;&lt;ethernet&gt;&lt;linux&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="5744" PostTypeId="2" ParentId="5743" CreationDate="2010-10-27T16:13:00.933" Score="5" ViewCount="" Body="&lt;p&gt;If each port is going on a completely separate network you can get away with a single MAC address, but this really doesn't work if you are going to have it on the same network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would highly recommend having separate drivers with separate MAC address per port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My answer is focused on if you were creating a device like an embedded firewall where you were wanting traffic to come in on one port, filtered, and then be sent back out on a different port going to a different network.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-10-27T16:46:06.073" LastActivityDate="2010-10-27T16:46:06.073" />
  <row Id="5745" PostTypeId="2" ParentId="5743" CreationDate="2010-10-27T16:13:58.140" Score="13" ViewCount="" Body="&lt;p&gt;If this is for a prototype - consider adding a USB ethernet adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're building a product, I'd consider an onboard ethernet switch chip. Like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.micrel.com/page.do?page=product-info/fastether_sw.jsp&quot; rel=&quot;nofollow&quot;&gt;http://www.micrel.com/page.do?page=product-info/fastether_sw.jsp&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.micrel.com/images/SwitchesApps.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.bettina-attack.de/jonny/view.php/projects/linksys_befsx41_stuff/adm6996_driver/&quot; rel=&quot;nofollow&quot;&gt;ADM6996&lt;/a&gt; may also be an option, if you can find it.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-27T16:36:05.273" LastActivityDate="2010-10-27T16:36:05.273" CommentCount="7" />
  <row Id="5746" PostTypeId="2" ParentId="5713" CreationDate="2010-10-27T17:32:59.837" Score="5" ViewCount="" Body="&lt;p&gt;With only 1 IO pin, you can use a 1-wire expander/shift register or add another device to your I2C bus, as already pointed out.  The only thing that hasn't been mentioned yet is the possibility of adding another slave to your SPI port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SPI is called a 4-wire protocol - You have two data lines, a clock line, and a select line (as well as a common ground, but that doesn't usually count).  However, the first three are shared among all the devices on the bus, so each device after the first one takes only one more trace/wire. SPI also increases your bus to full duplex, but that won't matter for this application.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-27T17:32:59.837" />
  <row Id="5747" PostTypeId="1" AcceptedAnswerId="5753" CreationDate="2010-10-27T17:45:19.330" Score="4" ViewCount="362" Body="&lt;p&gt;I know that this question may be off-topic here, but I'll ask it anyway since they do have electronics inside.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've noticed that my fluorescent lamps keep dying after only couple of months of use. When they die, they die in groups of 2-3 and as far as I can see, both new and old lamps may die during such events. As far as I can see, electronics inside dead lamps look normal to me, but then again, I don't have much experience in electronics, so I could be wrong. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'm asking you people what could be the cause and how can I prevent it? I'm thinking about bad electricity supply, because I have frequent brown-outs, but as far as I can see, deaths of lamps aren't more frequent during times when I have brown-outs. I'm thinking about connecting lamps over a UPS or &quot;power conditioner&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UPDATE:&lt;/strong&gt;&lt;br&gt;&#xA;I did some investigating and I think that I've found source for my problem. As I mentioned, I had brownouts. I noticed that nobody in my area had brownouts, so I the problem was probably with my installation. Then I noticed that voltage for two phases was between 220 V and 230 V, as expected, but one was between 190 V and 200 V. The main cause for that seems to be a 35 A DIAZED DIII fuse which is connected to the phase which powers my lamps. It turned out that the tip of the cartridge and fitting element of the fuse case were corroded and were sparking and overheating (the cartridge was so hot that I had difficulties removing it). It also turned out that when power company replaced my electromechanical meter with solid state meter, they installed new circuit breakers in such way that fuses are serially connected to breakers and are &quot;downstream&quot; from them. I talked to few electrical engineers and electricians and they all believe that since circuit breakers are installed, fuses should be removed. I'll get an electrician to remove them will report back how that effected lifetime of my lamps.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-12-09T09:45:46.453" LastActivityDate="2010-12-09T09:45:46.453" Title="Why do my compact fluorescent lamps keep dying?" Tags="&lt;light&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="1" />
  <row Id="5748" PostTypeId="2" ParentId="5747" CreationDate="2010-10-27T17:49:59.817" Score="2" ViewCount="" Body="&lt;p&gt;As you said, it's going to be tricky to figure out the cause of why these bulbs die - but it could be affecting other appliances too. Have you noticed any other devices malfunctioning or breaking?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most CFL's and the ballasts are designed to be cheaply produced; the ballast is based off a simple self-resonant circuit and thus has little protection against problems on the line.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-27T17:49:59.817" CommentCount="4" />
  <row Id="5749" PostTypeId="2" ParentId="5743" CreationDate="2010-10-27T18:13:14.373" Score="6" ViewCount="" Body="&lt;p&gt;If your processor only has one PHY, you're not going to get a lot more speed by embedding the switch on your board.  It will be much easier to just add a switch:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/COWZ8.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the text on this example indicates, any halfway decent switch will autonegotiate  10/100/1000 Mbps, cable crossover.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Switches are available in anywhere from 4 to 48 ports, with 5 ports being a common number for simple desktop switches.  They can sit on your desk or be rack-mounted.  You can chain them together for ridiculous numbers of ports, if you feel so compelled.  You can get them for less than $10 (visit &lt;a href=&quot;http://www.newegg.com/Store/SubCategory.aspx?SubCategory=30&amp;amp;name=Switches&amp;amp;Order=PRICE&quot; rel=&quot;nofollow&quot;&gt;Newegg&lt;/a&gt;), or as much as 10,000.  One important thing to consider is whether you want a managed or unmanaged switch, but we'd need more information to make this decision, and this is swiftly turning into a question for ServerFault.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An external switch is probably the most flexible, simple, and cheap way to do what you want.  It will be physically larger than putting the contents of a switch on your PCB, but I wouldn't do that unless it was absolutely necessary.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-27T18:13:14.373" CommentCount="3" />
  <row Id="5750" PostTypeId="2" ParentId="5148" CreationDate="2010-10-27T19:06:32.053" Score="0" ViewCount="" Body="&lt;p&gt;This will be much more feasible when &lt;a href=&quot;http://www.element-14.com/community/message/15751#15751&quot; rel=&quot;nofollow&quot;&gt;Eagle switches to a text-based file format&lt;/a&gt;.  Converters should show up once this happens, and you can then use another piece of software to do the routing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I remember correctly, gEDA also has some support for topological autorouting.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-27T19:06:32.053" />
  <row Id="5751" PostTypeId="2" ParentId="5747" CreationDate="2010-10-27T19:26:35.993" Score="2" ViewCount="" Body="&lt;p&gt;Off the top of my head: Vibration from ceiling fans, many on/off cycles, heat, bad power format, cheap CFL.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-10-27T19:26:35.993" CommentCount="1" />
  <row Id="5752" PostTypeId="1" AcceptedAnswerId="5755" CreationDate="2010-10-27T20:10:01.870" Score="4" ViewCount="312" Body="&lt;p&gt;I'm using an LM317T to regulate 5V to 3.38V for a microcontroller. R1 is 330 ohms and R2 is 560 ohms. There is no input capacitor and the output capacitor is a 470µF 25V, because I had that value in a pack of 50. The microcontroller is drawing at least 50mA, so I'm fairly sure I'm meeting the minimum load specs. The regulator is being powered from a computer SMPS, but I had a very similar configuration set up last time running off an SMPS with no problems. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a scope trace of an IO pin to show you what I mean:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/xdRpD.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ripple is about 60mVp-p, but as you can see also happens when the pin is low. I'm &#xA;worried it might affect the microcontroller itself (e.g. make it unstable.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'm more worried about are these large bursts of noise which occur seemingly randomly about 100 times per second:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/pZA1A.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Turns out this noise is coming from my power line network adapters&lt;/strong&gt;; it's leaking through from the power line into the computer SMPS and to the 5V output. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-28T17:22:25.327" LastActivityDate="2010-10-28T23:18:33.333" Title="What's causing this high frequency ripple on the output of my LM317?" Tags="&lt;voltage-regulator&gt;&lt;noise&gt;&lt;lm317&gt;" AnswerCount="5" CommentCount="13" />
  <row Id="5753" PostTypeId="2" ParentId="5747" CreationDate="2010-10-27T20:20:42.593" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.pavouk.org/hw/lamp/en_index.html&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;Schematics &amp;amp; Photos for 17 CFLs&lt;/strong&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Failures&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Common failure is broken capacitor C3. it is possible mainly at cheap lamps, where are used cheaper components for lower voltage. Whet the pipe doesn't lights up on time, there are risk of destroying transistors Q1 and Q2 and next resistors R1, R2, R3 and R5. When lamp starts, changer is very overloaded and transistors usually doesn't survive longer temperature overloading. When the pipe serve out, electronics is usually destroyed too. When the pipe is old, there can be overburned one of filaments and lamp doesn't lights up anymore. Electronics usually survives. Sometimes can be pipe broken due to internal tension and temperature difference. Most frequently lamp fails, when power on.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Reviewing&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Most of these compact fluorescent lamps use same or very similar wiring. More expensive lamps use a little complicated wiring with electrode preheating and thanks to it they have longer lifetime.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/r70HA.png&quot; alt=&quot;LUXAR 11W&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1084" LastEditorUserId="1084" LastEditorDisplayName="" LastEditDate="2010-10-27T21:51:18.873" LastActivityDate="2010-10-27T21:51:18.873" />
  <row Id="5754" PostTypeId="2" ParentId="5752" CreationDate="2010-10-27T20:47:46.323" Score="3" ViewCount="" Body="&lt;p&gt;The ripple could come from a number of sources.&#xA;It's a little hard to tell from the photo, but it looks like the ripple is at 100 kHz. Is there anything in you circuit that operates at that frequency? If anything is getting switched at that frequency it is most likely the source and you will have to find some way to isolate it from the power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But first, check that the oscilloscope ground isn't picking up the noise. It could be picking up the noise it two ways. Make sure it is connected to a sensible reference point so that there is no common impedance that could be coupling the noise. Secondly, remove the ground wire and use a spring ground clip to ensure that no mutual inductance it coupling into the probe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there is no 100kHz frequency in your circuit and you have a bench supply, try running the circuit off that to remove any influence of the switch mode supply. You could also double check the bypassing on your LM317. These will often require input decoupling. (The data sheet suggests input decoupling if it is more that 6 inches from the power source)&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2010-10-27T20:47:46.323" CommentCount="3" />
  <row Id="5755" PostTypeId="2" ParentId="5752" CreationDate="2010-10-27T20:56:07.967" Score="4" ViewCount="" Body="&lt;p&gt;Make sure that there is a small ceramic decoupling capacitor at the supply pin(s) of the microcontroller. Something 100nF - 1uF should be OK. (The 470uF cannot deal very well with HF noise).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How is the grounding on the microcontroller side? Is there a large ground plane?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the circuit return earth-referenced? Is the scope connected to the same earth reference?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't have a spring-clip for the ground, and don't mind abusing a probe, you can solder short pieces of solid wire from the supply rail to the probe tip and ground ring (under the probe tip) which will cut down on CM noise pickup dramatically.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, most ripple measurements in the switching power world are done with short probes (or direct coax) with 100nF and 10uF ceramic / tantalum caps shunting the probe and the scope set @ 20MHz bandwidth limit. (CM noise &amp;lt;&gt; PARD)&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-27T20:56:07.967" CommentCount="2" />
  <row Id="5756" PostTypeId="2" ParentId="5681" CreationDate="2010-10-27T21:14:56.060" Score="2" ViewCount="" Body="&lt;p&gt;This isn't exactly a hobbyist project by any stretch of the imagination, but:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're into transformers (or need isolation) you could design a flyback converter. The -120V rail would be your regulated output, and the -108V and +60V rails would be slave windings (loosely regulated simply based on the turns ratio). There are many integrated devices on the market which contain a HV MOSFET and simple controller for flybacks. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't care about isolation, you could design a boost for the +60 and something exotic like a Cuk for the -108/-120V rails. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-27T21:14:56.060" />
  <row Id="5757" PostTypeId="1" AcceptedAnswerId="5762" CreationDate="2010-10-27T22:40:07.030" Score="1" ViewCount="481" Body="&lt;p&gt;I bought&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.seeedstudio.com/depot/uartsbee-v31-p-688.html?cPath=104_109&amp;amp;zenid=0c4f29549324dc90d977325a5ca19eea&quot; rel=&quot;nofollow&quot;&gt;Seeeduino Stalker&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.seeedstudio.com/depot/uartsbee-v31-p-688.html?cPath=104_109&amp;amp;zenid=0c4f29549324dc90d977325a5ca19eea&quot; rel=&quot;nofollow&quot;&gt;UartsBee&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Two &lt;a href=&quot;http://www.seeedstudio.com/depot/xbee%C3%82%C2%AE-rf-modules-znet-25-1-mw-chip-antenna-p-226.html?cPath=2&quot; rel=&quot;nofollow&quot;&gt;XBees&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;When I physically connect (1), (2) and the computer USB, I can receive on my computer data sent by (1) at 115200 Kbps. But when I physically  disconnect (1) and to (2), and link them again using the XBees the computer receives no data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I noticed that in (1) the UART Tx and Rx are directly connected to XBee's Dout and Dint. But in (2) there are 1k resistors in each of those connections. Can such resistance be the cause of the problem?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The UartsBee is configured to use 3V, and I tested both connecting and disconnecting the DTR interrupt from the XBee to the ATMega328 (there is a jumper slot for it on (1)). The board is supplied with a 9V 200mA wall adapter. Both XBees were installed pointing the closest edges of the respective boards.&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-10-27T22:52:08.700" LastActivityDate="2010-10-29T02:14:49.447" Title="How to send data through XBee using ATMega328?" Tags="&lt;arduino&gt;&lt;atmega&gt;&lt;atmega328&gt;&lt;xbee&gt;&lt;zigbee&gt;" AnswerCount="1" />
  <row Id="5758" PostTypeId="2" ParentId="5752" CreationDate="2010-10-27T22:59:55.250" Score="2" ViewCount="" Body="&lt;p&gt;The 317 has a rather big voltage drop (Vin-Vout). At room temperature, it is at least 1.5 V at light loads (20 mA), increasing to as much as 2.5 V for larger loads (roughly two diode drops). What may happen is that the uC draws a larger current every once in a while, the regulator can't maintain 3.3 V with as little as 5 V at its input and goes out of regulation, causing what looks like noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try using a low dropout-regulator (Vin-Vout &amp;lt; 0.7 V) instead of the 317, or try increasing the input voltage.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-10-27T22:59:55.250" CommentCount="1" />
  <row Id="5759" PostTypeId="1" AcceptedAnswerId="5760" CreationDate="2010-10-27T23:14:06.160" Score="5" ViewCount="242" Body="&lt;p&gt;When I measure a 9V DC wall adapter power supply with a multimeter it shows 11.8V. When connected to my board this voltage lowers to 10V. Is this normal? Should I be afraid of toasting my &lt;a href=&quot;http://www.alldatasheet.com/datasheet-pdf/pdf/205686/ADMOS/AMS1117CD-5.0.html&quot; rel=&quot;nofollow&quot;&gt;1117CD-5.0&lt;/a&gt; supplied board when using this adapter?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;: This regulator accepts up to 12V inputs. So that will be no problem. A second &quot;9V&quot; adapter yields 15V to the multimeter. Will this one burn my circuit?&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-10-27T23:19:41.897" LastActivityDate="2011-02-16T21:11:30.287" Title="Is it normal for DC wall adapter power supplies to provide voltages above the nominal ones?" Tags="&lt;power-supply&gt;&lt;voltage&gt;&lt;voltage-regulator&gt;&lt;voltage-measurement&gt;&lt;adapter&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="5760" PostTypeId="2" ParentId="5759" CreationDate="2010-10-27T23:25:38.367" Score="11" ViewCount="" Body="&lt;p&gt;Yes, this can be normal.  There are two kinds of wall-warts -- regulated and unregulated (the latter are usually cheaper).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have two of the unregulated ones.  These provide their rated voltage (e.g. 9v) under the load specified on their label, but the no-load voltage can be &lt;em&gt;much&lt;/em&gt; higher as you have discovered.  It &lt;em&gt;probably&lt;/em&gt; won't hurt to use the one outputting 15v, since under the load of the board it will be closer to its rated voltage.  But frankly, I wouldn't chance it.  Use the other one instead.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-02-16T21:11:30.287" LastActivityDate="2011-02-16T21:11:30.287" CommentCount="2" />
  <row Id="5761" PostTypeId="2" ParentId="2901" CreationDate="2010-10-28T00:36:17.417" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Generally there are two labels on most caps.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first is the value, which is written:&lt;br&gt;&#xA;&lt;code&gt;&amp;lt;Digit&amp;gt;&amp;lt;Digit&amp;gt;&amp;lt;Exponential Notation&amp;gt;&lt;/code&gt;&lt;br&gt;&#xA;It's generally in picofarads. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second is the TempCo, or Temperature Coefficient. There are two common specification systems, namely &lt;a href=&quot;http://en.wikipedia.org/wiki/EIA_Class_1_dielectric&quot; rel=&quot;nofollow&quot;&gt;EIA Class 1&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/EIA_Class_2_dielectric&quot; rel=&quot;nofollow&quot;&gt;Class 2&lt;/a&gt;. This is the mysterious second label in most cases. It's generally written:&lt;br&gt;&#xA;&lt;code&gt;&amp;lt;Letter&amp;gt;&amp;lt;Number&amp;gt;&amp;lt;Letter&amp;gt;&lt;/code&gt; (though there are a few variations)&lt;br&gt;&#xA;There are a few common tempcos - NP0/C0G, X7R, X5R, Y5V, Z5U  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tantalums, and bigger ceramics often also have the voltages:&lt;br&gt;&#xA;&lt;code&gt;&amp;lt;voltage number&amp;gt;&amp;lt;+ or v&amp;gt;&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Therefore:  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;104 K5K (small )&lt;br&gt;&#xA;The value is 10e4, or 100,000 pf / 0.1 uF. The tempco is not standard, may be manufacturer specific/extended range.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;10 (box box, perpendicular right upermost corner) 35+ (Tantalum Cap, bigger variant of the last one)&lt;br&gt;&#xA;Need a picture to be more specific, it's very likely a 35v rated cap, from the 35+.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;154 C1K (what is C1K, some other notation to Wikipedia?)&lt;br&gt;&#xA;Capacitance is 15e4, or 150,000 pf / 0.15 uF. Looks to be a Class 1 dielectric from the C1K. Is this a large cap? the tempco is &lt;em&gt;very&lt;/em&gt; good.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Orange Ceramic 333 K5X (what is 5X? X roman numeral?)&lt;br&gt;&#xA;33e3, or 33,000 pf / 33 nF. Tempco is either manufacturer specific, or incorrectly read.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Brown Circle Slit 10n (no other marking, what is the op.temp?) (Diameter: 7.5mm)&lt;br&gt;&#xA;10n very likely means 10 nf, or 10,000 pf. If it's ceramic, it's &lt;em&gt;probably&lt;/em&gt; 50v. Likely a cheap part, if the voltage is not marked.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;27J 100V (what is 27J?) (Diameter: 4.9mm, blackdot on the head)&lt;br&gt;&#xA;Voltage rating is self evident. J is the multiplier, and I &lt;em&gt;think&lt;/em&gt; there is a standard for letter multipliers, but I do not remember where to find it.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Blue Slit Square (triangle) 104K X7R50 (What is triangle? X7R50? Operating V?) (side = 4.9mm)&lt;br&gt;&#xA;10e4 is the value - 100,000 pf / 0.1uF Tempco is X7R. the 50 is likely the voltage rating.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;104 (side = 2.6mm, op.V? Tolerance?)&lt;br&gt;&#xA;10e4 - 100,000 pf / 0.1uF. Voltage is not known&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This is kind of a guess. Anyways, it should show how this sort of thing works. Older parts may vary wildly, and it's always just a guideline. The best thing to do is find the cap's actual datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A lot of the parts have unusual tempcos. Is this a automotive/extreme duty part which contains these components?&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-24T06:57:41.300" LastActivityDate="2010-12-24T06:57:41.300" />
  <row Id="5762" PostTypeId="2" ParentId="5757" CreationDate="2010-10-28T00:55:34.650" Score="1" ViewCount="" Body="&lt;p&gt;I think what I am missing is that the XBee's modules must be programmed both to send and to receive data. In the following thread there is someone claiming that acomplished that and posting some code which will run in a ATMega processor:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1223492621/all&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1223492621/all&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also found a tutorial of how to configure the XBee module using a graphical environment:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://forums.trossenrobotics.com/tutorials/how-to-diy-128/xbee-basics-3259/&quot; rel=&quot;nofollow&quot;&gt;http://forums.trossenrobotics.com/tutorials/how-to-diy-128/xbee-basics-3259/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I read above, I tested it, and I finally established a connection, then I wrote a tutorial showing how I did it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://arduinolessons.blogspot.com/2010/10/how-to-use-xbee-module.html&quot; rel=&quot;nofollow&quot;&gt;http://arduinolessons.blogspot.com/2010/10/how-to-use-xbee-module.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately not all data gets through though...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since I'm using a XB24-B the following blog gave me some light:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://lizard43.blogspot.com/2009/04/xbee-series-2-jv-channel-verification.html&quot; rel=&quot;nofollow&quot;&gt;http://lizard43.blogspot.com/2009/04/xbee-series-2-jv-channel-verification.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-10-29T02:14:49.447" LastActivityDate="2010-10-29T02:14:49.447" />
  <row Id="5763" PostTypeId="2" ParentId="5747" CreationDate="2010-10-28T02:47:29.580" Score="1" ViewCount="" Body="&lt;p&gt;Funny you mention that your CFLs have a short life. In this month's &lt;a href=&quot;http://www.siliconchip.com.au&quot; rel=&quot;nofollow&quot;&gt;Silicon Chip&lt;/a&gt; magazine, page 7, a reader wrote in with the same complaint. It turns out that Philips would not offer a warranty on their CFLs if used in an enclosed fixture. However no explanation to why was offered by Philips or discussed in the article. I would scan the page to show you the letter but I don't need Leo Simpson getting cranky with me. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-10-28T02:47:29.580" CommentCount="4" />
  <row Id="5764" PostTypeId="1" CreationDate="2010-10-28T02:59:18.063" Score="5" ViewCount="314" Body="&lt;p&gt;I am hacking some old phones into my arduino project. I am currently controlling all of the ringers, dials, and hooks through my board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At a certain point, I would like to connect the two handsets and let them function kind of like a basic intercom. There are four wires into each handset, two for the microphone, and two for the speaker. As I understand it they function much like any cheap microphone or headphones you could plug into your computer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My initial thought is that I could just connect the mic of one to the speaker of the other, but I don't know audio circuits very well and am not sure if additional circuitry or op-amps would be required. What is the simplest way to do this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, what would be the best way to toggle this connection, so I can control if the lines are open or closed?&lt;/p&gt;&#xA;" OwnerUserId="1686" LastActivityDate="2011-03-01T00:19:59.637" Title="Connecting two phone handsets to talk" Tags="&lt;arduino&gt;&lt;communication&gt;&lt;telephone&gt;" AnswerCount="3" />
  <row Id="5765" PostTypeId="2" ParentId="5764" CreationDate="2010-10-28T03:20:00.903" Score="3" ViewCount="" Body="&lt;p&gt;Your microphone will need to have a simple amplifier in order to power the speaker. This might depend a little bit on what speaker is actually being used in the headset but an op-amp circuit should work for you. You will just have to make sure that the op-amp can output enough power to power the headset. If standard op-amps are not powerful enough to power to speaker you will need to go with a more complicated amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the toggling the connection, are you wanting to just have a dedicated 1-1 connection that can either be on or off? If so, you could do this by powering off the amps with a simple switch. If you are wanting some switch capabilities, such as 1 phone can be routed to 2 different locations, you should look into analog multiplexers.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-28T03:20:00.903" CommentCount="2" />
  <row Id="5766" PostTypeId="2" ParentId="5752" CreationDate="2010-10-28T07:35:47.950" Score="1" ViewCount="" Body="&lt;p&gt;I just looked at your oscillograms again, and there is one detail that may hint towards your problem: The ripple seems to be just as bad when the uC's output is low. If it was the 317, I would expect the problem to be worse at a high output voltage, and maybe even almost invisible with an output at the low state. Try tracing back the problem from there, by considering both the VCC and the GND rail.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-10-28T07:35:47.950" />
  <row Id="5767" PostTypeId="2" ParentId="5743" CreationDate="2010-10-28T08:02:27.673" Score="0" ViewCount="" Body="&lt;p&gt;I second the switch suggestion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to separate different networks then configure the switch chip to split the ports into different VLANs and trunk all VLANs to the port that the Linux box is on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Linux will be able to access all VLANs as though the system had individual network interfaces to the different networks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most, if not all, switch chips can be configured via a serial EEPROM, so modifying an off-the-shelf switch for a POC or a one-off hack ought to be easy enough.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-10-28T08:02:27.673" />
  <row Id="5768" PostTypeId="2" ParentId="5764" CreationDate="2010-10-28T11:15:30.330" Score="1" ViewCount="" Body="&lt;p&gt;If those are truly old fashioned phones, (e.g., like 1950's phones) there is probably a way to interconnect things without needing any active elements. After all, at the time when they were designed (1920's?), there were no active elements that would fit inside the phone case and which also would not require bulky power supplies. Basically, the whole phone was passive elements and ran off batteries in the local office, the voltages being surprisingly low. I don't know the exact levels off the top of my head (google is your friend here) but want to say that while off-the-hook, the voltage is somewhere around 7 volts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only significant part you find inside an old phone, other than the mic and the speaker, (and disregarding the mechanical ringer and dialer) is some kind of a multi-tap transformer. Not sure what the transformer accomplished. The microphones used a finely divided carbon powder, under a diaphragm, and were basically variable power resistors that respond to sound. I know, from fooling around with them as a kid, that you can put a 6V lantern battery, a carbon mic, and an 8 ohm speaker in series, and you can get a signal through. If you put two such microphones in series with two speakers, and of course, the battery, you should get at least some signal back and forth. The transformer in the phone was (speculation!) probably there to get a better signal into the ear piece by doing an impedance match.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At some point (1960's maybe, or 70's?), they stopped using those carbon microphone elements in favor of more modern microphone technology, at which point there would have to have been an amplifier involved. The carbon mics I've referred to can be recognized by the fact that when you unscrewed the mouthpiece cover, this nearly 2 inch diameter mic element would fall out in your hand. If your old phones are newer than that, just disregard everything I said.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-28T11:15:30.330" CommentCount="3" />
  <row Id="5769" PostTypeId="1" AcceptedAnswerId="5812" CreationDate="2010-10-28T11:33:58.847" Score="5" ViewCount="549" Body="&lt;p&gt;I have been given an audio file (sine wave) 1000Hz as an input to my FFT algorithm.&#xA;I have got 8192 power spectrum samples in a array.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the best and easiest way to check whether my output is right or wrong?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I give a silent audio file then the output is zero for all samples.&#xA;In a sine wav the o/p increases from 20 (0th sample) to 26059811 (743rd sample) and decreases gradually to 40.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I get an idea of the output range then I can prove technically whether the FFT is working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas would be helpful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Refer to &lt;a href=&quot;http://stackoverflow.com/questions/4040918/how-to-check-the-fft-results-in-iphone&quot;&gt;this link&lt;/a&gt; for any technical doubts.&lt;/p&gt;&#xA;" OwnerUserId="1730" LastEditorUserId="1730" LastEditorDisplayName="" LastEditDate="2010-10-29T06:37:10.313" LastActivityDate="2010-10-29T06:37:10.313" Title="How to check the FFT results of a sine wave?" Tags="&lt;dsp&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="5771" PostTypeId="2" ParentId="5769" CreationDate="2010-10-28T13:25:43.430" Score="0" ViewCount="" Body="&lt;p&gt;I have used the Fourier analysis tool within the Excel Analysis Toolpak to do a quick check on the data and results.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-10-28T13:25:43.430" CommentCount="2" />
  <row Id="5772" PostTypeId="2" ParentId="5769" CreationDate="2010-10-28T13:57:34.167" Score="5" ViewCount="" Body="&lt;p&gt;You need to plot the magnitude of the output of the FFT.  I'm not familiar with your programming language, but in Python you would use something like &lt;code&gt;plot(abs(fft(a)))&lt;/code&gt;.  For a silent input, the output should be all zeros.  For a sine wave input, you should see two spikes:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/zNMf1.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a real signal, the spikes will be symmetrical from left to right.  If you're doing a &lt;a href=&quot;http://en.wikipedia.org/wiki/Fast_Fourier_transform#FFT_algorithms_specialized_for_real_and.2For_symmetric_data&quot; rel=&quot;nofollow&quot;&gt;real FFT&lt;/a&gt;, though (which is more computationally efficient) you'll only get the left half of the plot as your output, since it ignores the redundant mirror image.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the frequency is higher, the spikes will be closer to the center.  If &lt;a href=&quot;http://gist.github.com/236567&quot; rel=&quot;nofollow&quot;&gt;the frequency is perfectly in sync with the chunk size&lt;/a&gt;, the spike will only be one point wide and everything else will be exactly 0.  Otherwise it will have a tapering &quot;skirt&quot; like above.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-28T16:23:06.173" LastActivityDate="2010-10-28T16:23:06.173" CommentCount="5" />
  <row Id="5773" PostTypeId="1" CreationDate="2010-10-28T14:11:53.107" Score="9" ViewCount="1542" Body="&lt;p&gt;Hi All,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking at buying a NetDuino for some fun home hobby projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have any of you used it and how was your experience?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should i look at the Arduino or FreeDuino range instead(or something totally different)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I decided to stick to the NetDuino due to my C# knowledge, but that is not a requirement. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. I am not sure if this belongs to the community wiki or not (guidance appreciated).&lt;/p&gt;&#xA;" OwnerUserId="1706" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-29T01:35:56.703" LastActivityDate="2011-02-27T05:33:43.340" CommunityOwnedDate="2011-02-27T07:33:15.000" Title="Should I buy a Netduino or Arduino?" Tags="&lt;arduino&gt;&lt;microcontroller&gt;&lt;netduino&gt;" AnswerCount="10" CommentCount="8" FavoriteCount="4" />
  <row Id="5774" PostTypeId="1" AcceptedAnswerId="5777" CreationDate="2010-10-28T14:58:58.593" Score="5" ViewCount="126" Body="&lt;p&gt;A batch of questions here really (if it helps I'm operating at 433.92MHz):&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How should I orient a helical antenna with respect to my board (i.e. my &quot;ground plane&quot;) to get the best range performance? &lt;/li&gt;&#xA;&lt;li&gt;What should the dimensions of my ground plane have to be in order to get good performance / how much does this matter compared to orientation?&lt;/li&gt;&#xA;&lt;li&gt;I'm also wondering what effect (if any) the relative orientation of these types of antennas between the transmitter and receiver has on link quality (due to polarization?). &lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Is the antenna pattern directional for these types of antennas (related to 3), and if so how narrowly?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry if this question is a little bit all over the place - I've got an EE background, but RF can be kind of mysterious (if you know what I mean)...&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Regards,&#xA;Vic&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;[Edit]&lt;/strong&gt; 3-d visuals would be really helpful in helping me get my head around this as well &lt;strong&gt;[/Edit]&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;[Edit2]&lt;/strong&gt;&#xA;5. Going to attempt some ASCII art here - what's the best way to mount my antennas? slashes (/) are the helix orientation, underbars (_) are the ground plane, and vertical bar (is the feed point):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    Transmitter                             Receiver&#xA;**A**&#xA;         /                                     /&#xA;         /                                     /&#xA;         /                                     /&#xA;         /                                     /&#xA;     ____|____                             ____|____&#xA;&#xA;**B**&#xA;      ////////                              ////////&#xA;     _|_________                           _|_________&#xA;&#xA;&#xA;**C**&#xA;      ////////                              ////////&#xA;     _|_________                           ________|__&#xA;&#xA;&#xA;**D**&#xA;         /                                     &#xA;         /                                     &#xA;         /                                     &#xA;         /                                  ////////   &#xA;     ____|____                             _|_________&#xA;&#xA;&#xA;**E**&#xA;         /                                     &#xA;         /                                     &#xA;         /                                     &#xA;         /                                  ////////   &#xA;     ____|____                             ________|__&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;[/Edit2]&lt;/strong&gt;         &lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-10-28T16:44:56.683" LastActivityDate="2010-10-28T16:47:58.507" Title="Helical antennas and orientation" Tags="&lt;rf&gt;&lt;antenna&gt;" AnswerCount="1" CommentCount="6" FavoriteCount="1" />
  <row Id="5775" PostTypeId="1" CreationDate="2010-10-28T15:28:23.427" Score="6" ViewCount="257" Body="&lt;p&gt;I've seen microcontrollers which claim to drive LCD segments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, the &lt;a href=&quot;http://www.ti.com/corp/docs/landing/cc430/index.htm?DCMP=CC430&amp;amp;HQS=Other+BA+cc430-bhp&quot; rel=&quot;nofollow&quot;&gt;CC430&lt;/a&gt; can drive 96 segments. But, it's a 64 pin chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, it must be providing signals for some kind of mux, what is this interface called?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For dot matrix LCDs, could a microcontroller like this drive more than 96 segments by scanning? I want to drive a small (eg. 32x32 pixel display).&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-28T15:44:40.240" LastActivityDate="2010-11-19T16:21:18.690" Title="How are dot matrix LCDs controlled?" Tags="&lt;lcd&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="5776" PostTypeId="2" ParentId="5721" CreationDate="2010-10-28T15:35:45.393" Score="4" ViewCount="" Body="&lt;p&gt;Here's a suggestion:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out &lt;a href=&quot;http://www.cs.uiowa.edu/~jones/step/index.html&quot; rel=&quot;nofollow&quot;&gt;Jones on Stepper Motors&lt;/a&gt;, with links to manufacturers, controllers, distributors, etc. and a ton of information on how to control them. The control signals will come from your microcontroller. The control power will likely come from a Driver.  If you use AVR or PIC, the manufacturer will have tutorials and white papers, with code, on motor control.  Read about the different types of stepper motors, and how they're driven with a pulse train.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, pick your motor. Shop around on google to see what's available. Have an idea of what kind of stepper motor you want (bipolar and unipolar are popular).  You are looking at what the holding torque is, and what the rated voltage and current are. I'm assuming your positioning can be quite coarse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To decide what kind of holding torque you need:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Measure the amount of torque the motor has to have, either with a torque wrench or by estimation. To estimate: you probably the know the length of the arm that needs to move (say, 6&quot; or 15cm), and the amount of weight that needs to be moved (say, 0.1lb or 45 grams). &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Multiply those numbers together to get 6&quot; * 0.1lb = 0.6 ft*lb or 15 * 45 = 675 cm*g = 0.675 kg*cm) &lt;/li&gt;&#xA;&lt;li&gt;Multiply by some safety factor to give you some margin (anywhere from 1.3 to 3, 1.3 is probably fine for you, so 0.675 * 1.3 = 0.8775 kg*cm) &lt;/li&gt;&#xA;&lt;li&gt;Then you look for a stepper motor rated with a hold torque of at least that 0.88 kg*cm.  That's its maximum torque if you feed its rated voltage and current.  Now look at that motor's rated voltage and current, can you supply that? (As in, if it asks for 120VDC at 1mA, you probably don't want that motor.) If you don't like it, look for a different motor, or look more carefully at what you're trying to move.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1266" LastActivityDate="2010-10-28T15:35:45.393" CommentCount="1" />
  <row Id="5777" PostTypeId="2" ParentId="5774" CreationDate="2010-10-28T16:23:52.507" Score="3" ViewCount="" Body="&lt;p&gt;First, a caveat - I'm primarily a CE, so this is just my understanding of the matter:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1.&amp;nbsp;Generally, the worst reception is when the antenna is upside-down, or nearly so, and the best is when it is vertical.  However, horizontal orientations are nearly as good as vertical; the radiation pattern is usually something like this, with &quot;up&quot; in the picture corresponding to the positive Z axis (defects overemphasized): &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/D43K4.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2.&amp;nbsp;Again, your antenna manufacturer will likely have a reference design for this.  Sarantel publishes sample gerbers for many of its antennas.  If the antenna is not directly coupled with a ground plane, near-field radiation will still be helpful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3.&amp;nbsp;No idea.  I doubt that it would matter as long as both antennas had decent signal strength.  Back-to-back might not be ideal, but everywhere else should work fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4.&amp;nbsp;No, it's hardly directional at all.The reason you use a helical antenna is because you want near-omnidirectional performance.  If orientation is controllable, use a different antenna.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-28T16:47:58.507" LastActivityDate="2010-10-28T16:47:58.507" CommentCount="4" />
  <row Id="5778" PostTypeId="1" AcceptedAnswerId="5781" CreationDate="2010-10-28T16:43:47.903" Score="2" ViewCount="140" Body="&lt;p&gt;I'm trying design a video transmitter around an 5.8GHz Airwave module. The documentation says the trace to the antenna must have a characteristic impedance of 50 ohms. How do I calculate the characteristic impedance of my trace?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-10-28T18:31:55.743" LastActivityDate="2010-10-28T19:13:10.067" Title="Characteristic impedance of a trace" Tags="&lt;rf&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5779" PostTypeId="2" ParentId="5775" CreationDate="2010-10-28T17:00:23.407" Score="3" ViewCount="" Body="&lt;p&gt;Microcontrollers that drive LCDs are typically for driving segmented LCD with very few segments. They are typically made of custom LCD glass and how the display is multiplexed is built into the LCD glass itself. You will need to check with the display vendor to determine how many common and segment lines there are for your LCD and how they are wired. For a dot matrix LCD you will probably need an external LCD controller. The LCD display vendor can probably recommend one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For some background in how a on-chip LCD module works.&lt;br&gt;&#xA;&lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CBUQFjAA&amp;amp;url=http%3A%2F%2Fwww.microchip.com%2Fstellent%2Fidcplg%3FIdcService%3DSS_GET_PAGE%26nodeId%3D1824%26appnote%3Den011075&amp;amp;ei=LMDKTN75EIS0lQeXzrT_AQ&amp;amp;usg=AFQjCNG0NcKZa6LHyJVchEq-XUqXheeHcg&quot; rel=&quot;nofollow&quot;&gt;Microchip application note AN658&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: NXP Has a number of LCD segment drivers available and application notes explaining how to use them. I have not seen a microcontroller that has a built in LCD driver for more than a few segments and certainly not 1024. I'd recommend something like the PCF8576C. You can cascade multiple chips together to drive more segments.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-11-19T16:21:18.690" LastActivityDate="2010-11-19T16:21:18.690" />
  <row Id="5780" PostTypeId="1" AcceptedAnswerId="5787" CreationDate="2010-10-28T17:12:10.307" Score="4" ViewCount="161" Body="&lt;p&gt;I have a Blackberry Torch that needs to send 10 bytes per second to a serial device.  The serial device will probably be a basic stamp 2 or other microcontroller.  The Blackberry does not need to receive any data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there an interface that will let me do this for less than $50?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using the Wifi or Bluetooth connections are the obvious choices but those options look more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also thought about using the headphone jack to send out different frequencies and an intermediate circuit could convert the sound into bytes, but I'm not sure where to start with that cicuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1345" LastActivityDate="2010-10-29T00:17:27.467" Title="How to interface a Blackberry Torch with a serial device?" Tags="&lt;serial&gt;&lt;cellphone&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5781" PostTypeId="2" ParentId="5778" CreationDate="2010-10-28T17:22:41.167" Score="3" ViewCount="" Body="&lt;p&gt;As a quick rule of thumb for 50 ohms, you want the ratio of the trace width to the height above the ground plane (probably your board thickness) to be around 1.8 with 2-oz copper. With a standard 0.063&quot; thick PCB, that means a trace width around 120 mil. (Fat!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Formulas for calculating this can be found in various places. If you access to an engineering library, try chapter 4 of High Speed Digital Design by Johnson and Graham. (Equation 4.90 on p. 187 is the key one.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an online calculator: &lt;a href=&quot;http://referencedesigner.com/tutorials/si/si_06.php&quot; rel=&quot;nofollow&quot;&gt;http://referencedesigner.com/tutorials/si/si_06.php&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-10-28T18:31:39.207" LastActivityDate="2010-10-28T18:31:39.207" CommentCount="11" />
  <row Id="5782" PostTypeId="2" ParentId="5773" CreationDate="2010-10-28T17:50:16.510" Score="10" ViewCount="" Body="&lt;p&gt;Your C# knowledge is close to useless on an embedded platform anyway, so don't put too much weight on that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd go with an Arduino or one of the clones, not because .Net is the devil, but because that's what everybody else is using, so you will have a much easier time getting help and mooching off of people's code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have gotten your feet wet, by all means branch out and try different stuff.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-28T19:35:55.897" LastActivityDate="2010-10-28T19:35:55.897" CommunityOwnedDate="2011-02-27T07:33:15.000" CommentCount="4" />
  <row Id="5783" PostTypeId="2" ParentId="5775" CreationDate="2010-10-28T18:20:19.110" Score="2" ViewCount="" Body="&lt;p&gt;&lt;em&gt;First, there are many types of dot matrix displays, some even receive ASCII data via parallel or serial buses, the following answer covers the pixel-addressable ones.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The dot matrix displays that I've analysed (various LED, LCD and a pair of fluorescent ones, all grey-scale) use two lines (for v-clock and h-clock) and one line for pixel value, internally they integrate a mux for one dimension and a shift-register for the other (used as a counter). Sometimes, for adding shades of gray, the MCU holds the clock for the shift-register and refreshes the same line several times.&lt;/p&gt;&#xA;" OwnerUserId="1673" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-10-28T19:57:43.807" LastActivityDate="2010-10-28T19:57:43.807" />
  <row Id="5784" PostTypeId="2" ParentId="5778" CreationDate="2010-10-28T19:13:10.067" Score="2" ViewCount="" Body="&lt;p&gt;See the section titled &quot;Sizing the feedline&quot; in &lt;a href=&quot;http://colinkarpfinger.com/blog/2010/the-dropouts-guide-to-antenna-design/&quot; rel=&quot;nofollow&quot;&gt;this article&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-28T19:13:10.067" />
  <row Id="5785" PostTypeId="2" ParentId="5773" CreationDate="2010-10-28T19:31:38.257" Score="2" ViewCount="" Body="&lt;p&gt;Personally, I'm not a fan of C# or .NET. I'm a C luddite. So, my choice of platform comes down to which has the hardware features I want (flash, RAM, clock speed, number of ADCs, number of timers, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, I can imagine C#/.NET being useful for rapid prototyping:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;String handling will likely be much simpler&lt;/li&gt;&#xA;&lt;li&gt;RPC and object serialization is probably easy. I suspect that you can just push C# objects over a serial link. RPC likely &quot;just works&quot;&lt;/li&gt;&#xA;&lt;li&gt;Portability - .NET is a virtual machine, so code should run on other boards or even on PCs&lt;/li&gt;&#xA;&lt;li&gt;Garbage collection makes many algorithms simpler to implement&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Of course, this all comes at a cost:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Code footprint is bigger (especially when you factor in the standard libraries)&lt;/li&gt;&#xA;&lt;li&gt;RAM usage is higher (everything's an object, is everything typed?)&lt;/li&gt;&#xA;&lt;li&gt;The garbage collector likely meddles with real-time performance&lt;/li&gt;&#xA;&lt;li&gt;If a hardware feature isn't supported by the .NET libraries, you can't use it (unless you implement the features yourself, for which you'll need C/C++, see comments)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;And, most of all, by using your C# skills on an embedded platform you're not really learning anything about embedded devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, it'll get the job done - but, where's the fun in that?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-29T08:40:04.033" LastActivityDate="2010-10-29T08:40:04.033" CommunityOwnedDate="2011-02-27T07:33:15.000" CommentCount="6" />
  <row Id="5786" PostTypeId="2" ParentId="5775" CreationDate="2010-10-28T19:38:11.680" Score="2" ViewCount="" Body="&lt;p&gt;mjh2007 hit the nail on the head when he said that they're typically used with custom LCD glass.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You used the CC430 as an example; it's integrated into the TI Chronos watch, with a watch LCD on the face.  See pages 75 (Schematic) and 83-84 (LCD information) of the &lt;a href=&quot;http://focus.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=slau292b&amp;amp;fileType=pdf&quot; rel=&quot;nofollow&quot;&gt;watch manual&lt;/a&gt; for a description of this implementation. It uses its 24 segment pins and 4 'com' pins to drive those 24*4 = 96 LCD segments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's probably easier, though, to just get a dot-matrix display with an integrated controller.  Do you have a source on a display without a controller?&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-28T21:54:10.950" LastActivityDate="2010-10-28T21:54:10.950" CommentCount="6" />
  <row Id="5787" PostTypeId="2" ParentId="5780" CreationDate="2010-10-28T20:22:04.000" Score="2" ViewCount="" Body="&lt;p&gt;For under $50, you could buy an SPP &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9913&quot; rel=&quot;nofollow&quot;&gt;bluetooth module&lt;/a&gt; (and a microcontroller dev board if you need one)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For $50 you can buy a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=10004&quot; rel=&quot;nofollow&quot;&gt;complete WiFi module&lt;/a&gt; with a serial interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use the headphone jack, investigate &lt;a href=&quot;http://en.wikipedia.org/wiki/Frequency-shift_keying&quot; rel=&quot;nofollow&quot;&gt;Frequency Shift Keying&lt;/a&gt;. FSK is a modulation scheme used in audio modems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a couple of relevant projects for pointers:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://sree.cc/electronics/arduino/arduino-as-an-fsk-modem&quot; rel=&quot;nofollow&quot;&gt;http://sree.cc/electronics/arduino/arduino-as-an-fsk-modem&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://code.google.com/p/arduino-iphone-shield/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/arduino-iphone-shield/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;On the Blackberry side, you could either do the same thing, or play back pre-canned .wav files.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-28T21:20:07.227" LastActivityDate="2010-10-28T21:20:07.227" CommentCount="1" />
  <row Id="5788" PostTypeId="1" AcceptedAnswerId="5789" CreationDate="2010-10-28T22:58:36.767" Score="2" ViewCount="179" Body="&lt;p&gt;Many IC's I've seen suggest decoupling capacitors across Vdd to Vss - this is sensible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However some IC's for example the dsPIC33FJ128GP802 has THREE Vss pins and only two Vdd pins (AVdd and Vdd.) So would I put a decoupling capacitor on each Vdd pin, or from each Vdd pin to each Vss pin? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-29T00:04:17.990" Title="Decoupling capacitors" Tags="&lt;capacitor&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="5789" PostTypeId="2" ParentId="5788" CreationDate="2010-10-28T23:04:13.470" Score="7" ViewCount="" Body="&lt;p&gt;I believe the general rule is 1 cap per Vdd pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you using a ground plane?  If so, don't bother attaching the caps to Vss pins.  However, if you are using a ground bus instead, then yeah you should attach the cathode of the caps directly to Vss.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-28T23:04:13.470" CommentCount="10" />
  <row Id="5790" PostTypeId="1" AcceptedAnswerId="5795" CreationDate="2010-10-28T23:08:47.353" Score="2" ViewCount="189" Body="&lt;p&gt;I'm looking for a microcontroller in a TQFP-44 package with 30 KB or more of RAM and, if possible 40 MIPS instruction cycle speed or faster. I can find dsPIC33F's with 30 KB of RAM, but they come in TQFP-100 packages, and I'm only going to be using maybe 15-20 pins of those so it seems like a massive waste of space and money. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'm looking for some reasonably sized package with lots of RAM. I've given up on the SO28's but if anyone finds one it would be excellent as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current candidates are the Parallax Propeller, but that only has 20 MIPS instruction cycle, and the dsPIC's in TQFP-100's. One parameter but not both!!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is for my Super OSD project.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-30T09:43:08.000" Title="Microcontroller with &gt;30KB RAM and high performance in a TQFP-44 or similar package" Tags="&lt;microcontroller&gt;" AnswerCount="5" CommentCount="4" />
  <row Id="5791" PostTypeId="2" ParentId="5752" CreationDate="2010-10-28T23:18:33.333" Score="1" ViewCount="" Body="&lt;p&gt;Noise when the output is low...to me, that implies ground bounce.  But nothing in your statement implies anything that could cause that kind of ground bounce.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you drawing enough load from the ATX supply?  They have minimum load requirements.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-10-28T23:18:33.333" CommentCount="1" />
  <row Id="5792" PostTypeId="2" ParentId="5790" CreationDate="2010-10-28T23:29:53.043" Score="2" ViewCount="" Body="&lt;p&gt;Consider an ARM microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To find exactly what you want, I recommend that you search manufacturer websites (TI/Luminary, Atmel, ST Micro, NXP, etc). They all have product search systems.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-28T23:54:01.743" LastActivityDate="2010-10-28T23:54:01.743" CommentCount="1" />
  <row Id="5793" PostTypeId="2" ParentId="5790" CreationDate="2010-10-28T23:32:52.277" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/products/at91/sam3s.asp?family_id=605&quot; rel=&quot;nofollow&quot;&gt;Atmel&lt;/a&gt; makes some Cortex-M3 parts that come in LQFP-48 (or QFN-48) packages.  There are three different RAM sizes available...16, 32, and 48 KB.  ARM claims the Cortex-M3 executes 1.25 MIPS/MHz and these parts have a maximum clock speed of 64 MHz so figure 1.25*64 = 80 MIPS.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-10-28T23:32:52.277" CommentCount="2" />
  <row Id="5794" PostTypeId="2" ParentId="5790" CreationDate="2010-10-28T23:33:13.913" Score="1" ViewCount="" Body="&lt;p&gt;Running your requirements through Digikey's interface (In stock, then 32kB+ of RAM, then 40MHz+, then &gt;48-pin packages) results in:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=P8X32A-M44-ND&quot; rel=&quot;nofollow&quot;&gt;P8X32A-XXX&lt;/a&gt;: $8, 80MHz Parallax Propeller, in DIP, QFP, and LQFN packages, 32kB RAM&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=AT32UC3B1256-Z1UT-ND&quot; rel=&quot;nofollow&quot;&gt;AT32UC3B1128&lt;/a&gt;: $10, 60MHz Atmel AVR32 in QFN Exposed Pad, 32kB RAM (&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=568-4368-ND&quot; rel=&quot;nofollow&quot;&gt;LPC2105&lt;/a&gt;: $15, 60MHz NXP ARM7 chip in 48-LQFP, 64kB RAM&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I feel bad just throwing Digikey pages at you, but it's pretty easy.  I started to do Mouser, but they can't seem to figure out how to sort their values.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the cost will probably be determined as much by the volume in which the part is produced as by the number of pins.  Don't sweat 40 vs. 64 pins.  Oh, and &lt;em&gt;please&lt;/em&gt; break out the other pins to through holes or at least test points for future hackers!&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-10-28T23:49:25.170" LastActivityDate="2010-10-28T23:49:25.170" CommentCount="6" />
  <row Id="5795" PostTypeId="2" ParentId="5790" CreationDate="2010-10-28T23:33:25.660" Score="4" ViewCount="" Body="&lt;p&gt;Atmel makes a 32-bit 60 MHz &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/32059S.pdf&quot; rel=&quot;nofollow&quot;&gt;AT32UC3B1256&lt;/a&gt; AVR microcontroller with 256K of flash, 32KB of RAM in a 48-pin TQFP package.  That's as close as I could find to your specs.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-10-28T23:56:40.633" LastActivityDate="2010-10-28T23:56:40.633" CommentCount="5" />
  <row Id="5796" PostTypeId="1" AcceptedAnswerId="5798" CreationDate="2010-10-29T00:00:38.110" Score="4" ViewCount="339" Body="&lt;p&gt;I'd like to know how a 'hand clap' switch works. You know, the kind where you *clap-clap* and the light turns on, *clap-clap* again and the light turns off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How is the clapping sound detected? How can it be differentiated from whistling, people talking, a barking dog, ... ? Can it be another kind of sound?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of components would I need to build such a sensor/switch, assuming everything works on DC?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Note: I am &lt;strong&gt;not&lt;/strong&gt; interested in just buying a Velleman kit :-)&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="1124" LastActivityDate="2011-02-07T15:28:14.190" Title="How do 'hand clap' switches work?" Tags="&lt;switch&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="5797" PostTypeId="2" ParentId="5788" CreationDate="2010-10-29T00:04:17.990" Score="3" ViewCount="" Body="&lt;p&gt;In the case of that chip, yes, you would.  They actually allocate quite a bit of space (pages 21 and 22 in &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/70292D.pdf&quot; rel=&quot;nofollow&quot;&gt;the datasheet&lt;/a&gt;) to describing the capacitors required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, as a general rule, you do want 1 cap per Vdd pin.  A ground plane negates the need for decoupling on Vss, if you don't have one you're going to have problems.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of the dsPIC linked (and many other chips), each Vdd pin is adjacent to a Vss pin, so just put it right there.  There are actually four Vdd pins, and four Vss pins, so they match up: 2xVdd (IO supply), 1xAVdd (ADC supply), and 1xVcap/Vddcore (internal regulator capacitance), along with 3xVss and 1xAVss.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-29T00:04:17.990" CommentCount="4" />
  <row Id="5798" PostTypeId="2" ParentId="5796" CreationDate="2010-10-29T00:09:50.107" Score="3" ViewCount="" Body="&lt;p&gt;The most famous example of this was &lt;a href=&quot;http://en.wikipedia.org/wiki/The_Clapper&quot; rel=&quot;nofollow&quot;&gt;&quot;The Clapper&quot;&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See the patents for the details:&#xA;&lt;a href=&quot;http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&amp;amp;Sect2=HITOFF&amp;amp;d=PALL&amp;amp;p=1&amp;amp;u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&amp;amp;r=1&amp;amp;f=G&amp;amp;l=50&amp;amp;s1=5493618.PN.&amp;amp;OS=PN/5493618&amp;amp;RS=PN/5493618&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt; and &lt;a href=&quot;http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&amp;amp;Sect2=HITOFF&amp;amp;d=PALL&amp;amp;p=1&amp;amp;u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&amp;amp;r=1&amp;amp;f=G&amp;amp;l=50&amp;amp;s1=5615271.PN.&amp;amp;OS=PN/5615271&amp;amp;RS=PN/5615271&quot; rel=&quot;nofollow&quot;&gt;2&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/how-773/step1/Clapper-Circuit-Diagram/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/how-773/step1/Clapper-Circuit-Diagram/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.instructables.com/image/FEQY8PO721EP27V2CO/Clapper-Circuit-Diagram.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a recent hackaday post on achieving the same thing:&#xA;&lt;a href=&quot;http://hackaday.com/2011/02/07/diy-clapper/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2011/02/07/diy-clapper/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-02-07T15:28:14.190" LastActivityDate="2011-02-07T15:28:14.190" CommentCount="10" />
  <row Id="5799" PostTypeId="2" ParentId="5780" CreationDate="2010-10-29T00:17:27.467" Score="1" ViewCount="" Body="&lt;p&gt;The USB port will provide wired serial (or did you mean UART/SPI/I2C?) communication cheaply.  I doubt (but I don't know positively) that the Torch can act as a USB host, so you'll have to find a device capable of doing that to interface with the Torch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another alternative is to remove the microSD card (assuming that you don't need it), and use those connections for this purpose.  There's probably an SPI port (or at least a few GPIO with which to bit-bang a serial connection) in that slot.  A PCB with a right-angle connector should make this connection possible, if not pretty.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-10-29T00:17:27.467" CommentCount="5" />
  <row Id="5800" PostTypeId="1" AcceptedAnswerId="5815" CreationDate="2010-10-29T00:41:12.873" Score="0" ViewCount="154" Body="&lt;p&gt;I'm looking for a programmable comparator which has a digital or open-drain output and a voltage reference which can be programmed over I2C. My searches at my favourite sites of Microchip and Farnell haven't brought up anything interesting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this isn't possible I'd be looking at making an external R-2R (or R = 2^n) divider (precision not critical) from 4-5 IO pins to get 16 or 32 levels granularity. The setpoint needs to be adjusted to compensate for varying video levels. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: such comparator should also have &amp;lt;1µs response time. Most comparators satisfy this, but there are a few cheap ones that don't.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1609" LastEditorDisplayName="" LastEditDate="2010-12-02T16:15:02.400" LastActivityDate="2010-12-03T01:32:32.150" Title="Comparator over I2C with programmable reference" Tags="&lt;analog&gt;&lt;i2c&gt;&lt;comparator&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="5801" PostTypeId="1" AcceptedAnswerId="5802" CreationDate="2010-10-29T00:43:53.977" Score="1" ViewCount="382" Body="&lt;p&gt;I have a GPS device which I need to pull data from (the NMEA strings.) However, many times per second my MCU will be busy processing something else. Is there any way to &quot;pause&quot; an UART/RS232 TTL signal or buffer it while my MCU does stuff? I'm looking at either a dsPIC33FJ128GP802 or an AT32UC38x.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The processing of my OSD cannot be interrupted, so interrupts are out.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-29T01:05:03.387" LastActivityDate="2011-02-25T17:49:34.637" Title="How to poll UART while processing lots of other stuff." Tags="&lt;microcontroller&gt;&lt;rs232&gt;" AnswerCount="7" CommentCount="3" />
  <row Id="5802" PostTypeId="2" ParentId="5801" CreationDate="2010-10-29T00:48:19.263" Score="3" ViewCount="" Body="&lt;p&gt;Two things. &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Make it so you have a buffer and the&#xA;interrupts just queues up the data&#xA;into it until you have time. Make it&#xA;so parsing the GPS string is&#xA;interrupt driven. &lt;/li&gt;&#xA;&lt;li&gt;I have helped 5&#xA;different people do this. This is&#xA;especially simple when you only need&#xA;a small part of the string, like&#xA;position.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I can go into more detail on either method if more clarity is required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Side note for microchip. I think their wizard for the c18 compiler(have not used the c30 much yet) will give you a library to handle queuing the data from UART for you.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;You have other interrupts that cannot ever be delayed?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;If your screen controller is all done in interrupts, can you not just put it in a higher level interrupt?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means that whenever you leave your interrupt the RX data interrupt has time to put the data in a queue. This also means that whenever your other interrupts are triggered they will get the priority you expect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then place in your main control loop that is not interrupt driven the processing for your GPS data. This keeps things nicely compartmentalized. Remember at most GPS baud rates you have a long time to pull chars from the character string as 4800 or 9600 baud is slow...&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-10-29T02:50:49.803" LastActivityDate="2010-10-29T02:50:49.803" CommentCount="5" />
  <row Id="5804" PostTypeId="2" ParentId="5801" CreationDate="2010-10-29T01:13:43.980" Score="4" ViewCount="" Body="&lt;p&gt;It sounds like you really need to have your PIC dedicated to the display, 80-90% CPU usage is a lot. I see some similarities between a computer and its video card. I think you should strongly consider splitting your project into 2 PICs, 1 will handle all of the video (like a video card) and the other will handle any other processing. This second PIC can have some flow control setup between your video PIC such that the video PIC lets you know when it has some free CPU time. As soon as your 2nd PIC sees that there is extra time it will dump data to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Addition:&#xA;The GPS packet probably includes lot more information then what your display needs, your separate PIC can &quot;clean up&quot; the data to get you exactly what you want/need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if your second PIC isn't doing much, you can probably get away with a very cheap PIC (sub $3). This cost is probably well worth the time you will save in coding and debugging on a single PIC.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-10-29T01:27:26.803" LastActivityDate="2010-10-29T01:27:26.803" CommentCount="4" />
  <row Id="5805" PostTypeId="2" ParentId="5801" CreationDate="2010-10-29T01:16:46.813" Score="2" ViewCount="" Body="&lt;p&gt;Assuming that your GPS unit is outputting NMEA strings at 4800bps - you should be able to find a few spare cycles in your video generator to decode a serial bitstream.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Failing that:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;If your GPS unit supports hardware flow control, you might be able to service it between frames or when your device is idle&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Another option would be an external SPI/I2C to UART bridge. Some of these devices have reasonable sized FIFOs, allowing it to buffer up outside of your PIC. Again, service it during your idle time&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-29T08:41:49.913" LastActivityDate="2010-10-29T08:41:49.913" CommentCount="1" />
  <row Id="5806" PostTypeId="2" ParentId="5773" CreationDate="2010-10-29T01:43:01.747" Score="2" ViewCount="" Body="&lt;p&gt;I'm primarily a C# developer. I bought an Arduino instead of a Netduino because of the availability of source code. It wouldn't be easy to integrate Netduino with Arduino electronic bricks because you'll have to rewrite some of the samples from scratch.&lt;/p&gt;&#xA;" OwnerUserId="1298" LastActivityDate="2010-10-29T01:43:01.747" CommunityOwnedDate="2011-02-27T07:33:15.000" />
  <row Id="5807" PostTypeId="2" ParentId="5801" CreationDate="2010-10-29T03:48:36.323" Score="3" ViewCount="" Body="&lt;p&gt;Another possible reason to go with the Propeller chip that was discussed in the &lt;a href=&quot;http://electronics.stackexchange.com/questions/5790/microcontroller-with-30kb-ram-and-high-performance-in-a-tqfp-44-or-similar-packa&quot;&gt;other&lt;/a&gt; thread -- built-in timing for the video, and you can use a separate cog for RS232 without impacting the video.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It appears the AT32UC3B1256 also has a peripheral DMA capability, so you can receive data from the GPS without using interrupts.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-10-29T04:02:04.080" LastActivityDate="2010-10-29T04:02:04.080" />
  <row Id="5808" PostTypeId="2" ParentId="5801" CreationDate="2010-10-29T03:51:40.097" Score="4" ViewCount="" Body="&lt;p&gt;I believe some of the dsPIC family have DMA support in the MSSP peripheral, that will allow buffering of the input stream without cpu intervention up to a point, limited by available memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use an interrupt for processing the GPS data in chunks, just make sure the interrupt for your video processing work is set to a higher priority so it can bump the GPS handling interrupt.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-10-29T03:51:40.097" />
  <row Id="5809" PostTypeId="2" ParentId="5800" CreationDate="2010-10-29T04:33:57.337" Score="2" ViewCount="" Body="&lt;p&gt;Have you considered using a fixed voltage reference in conjunction with a I2C digital pot, for example the Analog Devices &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=AD5258BRMZ100-ND&quot; rel=&quot;nofollow&quot;&gt;ADC5258&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As mikeselectricstuff has pointed out, this functionality is actually built into many PICs.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-10-29T08:49:54.603" LastActivityDate="2010-10-29T08:49:54.603" CommentCount="1" />
  <row Id="5810" PostTypeId="1" CreationDate="2010-10-29T05:23:16.760" Score="2" ViewCount="98" Body="&lt;p&gt;I am building a pole camera, normally you would have someone on the other end to move the pole, but we want to be able to operate it remotely. As the movement needs to be very smooth, with a soft start and soft finish, some sort of dampening needs to be added into the pole motor movement. The pole itself will be about 2.8 meters long, with a lightweight HD PTZ camera at the end. I'd like to be able to have control over the current position of of the pole, no need for tilt, only for pan, as well as setting presets, and auto move. Auto move would be something like setting limits to the pan, and having the pole move in a sin wave side to side. I'm thinking something like an arduino for the control, but uncertain of what would be good mechanically to move the pole not only with precision, but also be very strong, as we often get very high winds.&lt;/p&gt;&#xA;" OwnerUserId="1665" LastActivityDate="2010-10-29T05:38:35.553" Title="Remote pan a 2.7m carbon fibre camera pole" Tags="&lt;arduino&gt;&lt;motor&gt;&lt;camera&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="5811" PostTypeId="2" ParentId="5810" CreationDate="2010-10-29T05:38:35.553" Score="1" ViewCount="" Body="&lt;p&gt;A PID controller may be more then what you need, but a PID controller can control the damping and overshoot of your motor. There is more on PID controllers at &lt;a href=&quot;http://electronics.stackexchange.com/questions/5111/how-to-learn-pid-control&quot;&gt;http://electronics.stackexchange.com/questions/5111/how-to-learn-pid-control&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for your motors, I think using a stepper motor will probably be your best option. There is some information about stepper motors at &lt;a href=&quot;http://electronics.stackexchange.com/questions/1/arduino-stepper-motor&quot;&gt;http://electronics.stackexchange.com/questions/1/arduino-stepper-motor&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using an Arduino or any other micro-controller should work just fine for you. &lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-29T05:38:35.553" CommentCount="2" />
  <row Id="5812" PostTypeId="2" ParentId="5769" CreationDate="2010-10-29T05:55:56.097" Score="3" ViewCount="" Body="&lt;p&gt;It seems you're calculating the spectrum by averaging 10 windows (non-overlapping?) to get the magnitude squared at 8192 or 8193 frequencies (from 0 to Nyquist, but some algorithms might drop the Nyquist frequency at bin 8192).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first thing to check is that the peak is in the right bin. You didn't say what the sampling rate is, but bin 743 would be 743/16384 times the sampling rate. If the signal really is at 800 Hz, that puts Fs at approximately 17640 samples/second. That seems wrong. Your test signal would probably be at a standard rate such as 8000, 16000, 22050, 32000, 44100, or 48000. For Fs = 22050, the peak would be sharply in bin 800/22050*16384 = 594.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another criteria to check is that the total energy in the signal is approximately the same in both the time and frequency domains. Here's an example in Python:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;In [1]: NFFT = 2048; N = 10*NFFT; n = arange(N); Fs = 22050&#xA;In [2]: x = 0.4*cos(2*pi*400/Fs*n) + 0.6*cos(2*pi*800/Fs*n)&#xA;&#xA;In [3]: y,freqs = psd(x, NFFT=NFFT, Fs=Fs, pad_to=16384)  # PSD by Welch's Method&#xA;&#xA;In [4]: sum(x**2)/Fs           # time-domain energy&#xA;Out[4]: 0.24149869319296949&#xA;In [5]: sum(y) * N/16384       # frequency-domain energy&#xA;Out[5]: 0.24148752834391252&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The input signal x, which consists of two sinusoids sampled at Fs = 22050 samples/second, is segmented into 10 non-overlapping windows of size NFFT = 2048 samples. The call to psd (power spectral density) computes the spectrum y as the average of the magnitude squared of ten 16384-point DFTs (actually it's 8193 points since x is real-valued). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The computed frequency-domain energy has a scaling factor of N/16384 because the psd function scaled y to the DFT size instead of to the total signal length. Whether or not this is an issue depends on how your system handles normalizing the PSD. Another optional normalization is scaling by 1/Fs. This matches the energy to the original analog signal. The default normalizations should be well documented in the library.&lt;/p&gt;&#xA;" OwnerUserId="721" LastActivityDate="2010-10-29T05:55:56.097" CommentCount="1" />
  <row Id="5813" PostTypeId="1" CreationDate="2010-10-29T07:04:47.807" Score="9" ViewCount="795" Body="&lt;p&gt;I have to do cross correlation of two audio file to prove they are similar.&#xA;I have done FFT of two audio files and have the power spectrum value of both the audio file in a separate array.how should i proceed further to do cross correlation  to prove they are similar.Is there any other best way to do it.If i come to know how to do it ,then i will try to implement technically.Any basic ideas will be helpful for me to learn and apply it.Thanks for your support.&lt;/p&gt;&#xA;" OwnerUserId="1730" LastActivityDate="2010-10-30T05:31:45.807" Title="How to implement cross correlation to prove two audio files are similar" Tags="&lt;dsp&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="4" />
  <row Id="5814" PostTypeId="2" ParentId="5813" CreationDate="2010-10-29T08:12:01.010" Score="0" ViewCount="" Body="&lt;p&gt;if you are using matlab try the cross correlate function c= xcorr(x,y)&#xA;more details here:http://www.mathworks.com/help/toolbox/signal/xcorr.html&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-29T08:12:01.010" />
  <row Id="5815" PostTypeId="2" ParentId="5800" CreationDate="2010-10-29T08:18:02.127" Score="2" ViewCount="" Body="&lt;p&gt;Many PICs would be able to do this. Any part  with I2C Slave, comparator and voltage reference module.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-29T08:18:02.127" CommentCount="3" />
  <row Id="5816" PostTypeId="2" ParentId="5813" CreationDate="2010-10-29T08:27:28.250" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Correlation_and_dependence&quot; rel=&quot;nofollow&quot;&gt;Correlation&lt;/a&gt; is a way to express the similarity of two timeseries (audio samples in your case) in one number. It is an adaptation of &lt;a href=&quot;http://en.wikipedia.org/wiki/Covariance&quot; rel=&quot;nofollow&quot;&gt;covariance&lt;/a&gt; which is implemented as follows:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;period = 1/sampleFrequency;&#xA;covariance=0;&#xA;&#xA;for (iSample = 0; iSample&amp;lt;nSamples; iSample++)&#xA;    covariance += (timeSeries_1(iSample)*timeSeries_2(iSample))/period;&#xA;    //Dividing by `period` might not even be necessary&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The correlation is the normalized version of covariance, which is the covariance divided by the product of the standard deviations of both the time series. The correlation will yield a 0 when there is no correlation (totally not similar) and a 1 for total correlation (totally similar). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can imagine that two sound samples might be similar but are not synchronized. That's where &lt;a href=&quot;http://en.wikipedia.org/wiki/Cross_correlation&quot; rel=&quot;nofollow&quot;&gt;cross correlation&lt;/a&gt; comes in. You calculate the correlation between the time series where you have one of them shifted by one sample:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;for (iShift=0; iShift&amp;lt;nSamples; iShift++)&#xA;    xcorr(iShift) = corr(timeSeries_1, timeSeries_2_shifted_one_sample);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then seek out the maximum value in the &lt;code&gt;corr&lt;/code&gt; series and you're done. (or stop if you've found a sufficient correlation) There's slightly more to it of course. You must implement the standard deviation and you must do some memory management and implement the time shifting stuff. If all your audio samples are equal in length, you might do without normalizing the covariance and go ahead and calculate the cross-covariance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A cool relation to &lt;a href=&quot;http://electronics.stackexchange.com/questions/5769/how-to-check-the-fft-results-of-a-sine-wave&quot;&gt;your earlier question&lt;/a&gt;: Fourier analysis is just an adaptation of the cross covariance. Rather than shifting one time series and calculating the covariances with the other signal, you calculate the covariances between one signal and a number of (co)sine waves with different frequencies. It's all based on the same principle.&lt;/p&gt;&#xA;" OwnerUserId="10" LastEditorUserId="10" LastEditorDisplayName="" LastEditDate="2010-10-29T10:58:36.730" LastActivityDate="2010-10-29T10:58:36.730" CommentCount="2" />
  <row Id="5817" PostTypeId="2" ParentId="5658" CreationDate="2010-10-29T09:05:14.460" Score="4" ViewCount="" Body="&lt;p&gt;I've been tempted by some modules at futurlec (decent shipping AFAIK).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://futurlec.com/ET-STM32_Stamp.shtml&quot; rel=&quot;nofollow&quot;&gt;http://futurlec.com/ET-STM32_Stamp.shtml&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://futurlec.com/Pictures/ET_ARM_STAMP_II_600.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://futurlec.com/ET-ARM_Stamp.shtml&quot; rel=&quot;nofollow&quot;&gt;http://futurlec.com/ET-ARM_Stamp.shtml&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://futurlec.com/Pictures/ET-ARM%20Stamp1_600.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Supposedly serial loading and looks quite friendly. Not much in the way of peripherals and smaller types, but priced under $30. They also sell loose ARM chips of various types.&lt;/p&gt;&#xA;" OwnerUserId="883" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-11-28T12:09:05.857" LastActivityDate="2010-11-28T12:09:05.857" CommunityOwnedDate="2010-10-29T09:05:14.460" CommentCount="2" />
  <row Id="5819" PostTypeId="1" AcceptedAnswerId="6738" CreationDate="2010-10-29T09:51:00.770" Score="1" ViewCount="200" Body="&lt;p&gt;I'm looking for a buck converter in a SOIC-8 package which requires a small inductor (preferably ≤10µH) which can convert 6V-16V to 5V @ 1A. Unfortunately the package &lt;em&gt;must&lt;/em&gt; be a SOIC package, because the person I'm designing for requires the SOIC package to be easy to place and solder. At the moment I've drawn a blank: all the high speed buck converters I have found only have a 6V or so maximum input voltage or they come in strange packages which are difficult to hand solder.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-29T10:09:41.740" LastActivityDate="2010-11-29T16:02:56.263" Title="Looking for a small inductor buck converter in a SOIC-8 package" Tags="&lt;buck&gt;" AnswerCount="6" CommentCount="4" />
  <row Id="5820" PostTypeId="2" ParentId="5819" CreationDate="2010-10-29T10:31:56.393" Score="2" ViewCount="" Body="&lt;p&gt;Allegro A4447. Wide supply range and also pretty cheap. It has a thermal pad, but at low outputs you may not need to solder it, so can treat it as a normal SO8.&#xA;Only possible issue is input voltage range at the low end - won't quite go down to 6v&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-29T10:31:56.393" CommentCount="1" />
  <row Id="5821" PostTypeId="1" AcceptedAnswerId="5822" CreationDate="2010-10-29T11:28:39.277" Score="1" ViewCount="128" Body="&lt;p&gt;I want to read 8 PWM inputs (standard servo PWM, 1ms to 2ms) without an input capture module (my module only has 7 channels.) Could I use a capacitor and the ADC on my MCU? Does anyone know of any successful implementation of this, or have any references for this?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-29T14:49:19.990" Title="Reading up to 8 PWM's" Tags="&lt;adc&gt;&lt;pwm&gt;" AnswerCount="3" />
  <row Id="5822" PostTypeId="2" ParentId="5821" CreationDate="2010-10-29T12:25:53.143" Score="2" ViewCount="" Body="&lt;p&gt;What MCU are you on?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where are you getting all those PWM signals from?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's from an RC receiver, then a much better solution would be to get at the multiplexed signal in stead, see:&#xA;&lt;a href=&quot;http://paparazzi.enac.fr/wiki/RC_Receivers_and_Radios#R.2FC_Receiver_Interface&quot; rel=&quot;nofollow&quot;&gt;http://paparazzi.enac.fr/wiki/RC_Receivers_and_Radios#R.2FC_Receiver_Interface&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the receiver demultiplexes using a 4017, then the different servo signals will be staggered and you can re-multiplex them, simply by OR'ing the signals using diodes and a pull-down resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... bottom line is that it's much easier to decode one multiplexed signal than it is to mess about with 8 inputs.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-10-29T12:25:53.143" CommentCount="6" />
  <row Id="5823" PostTypeId="2" ParentId="5821" CreationDate="2010-10-29T13:16:08.703" Score="2" ViewCount="" Body="&lt;p&gt;I would suggest that you put all of the PWM lines on port B. You can then setup an interrupt that is triggered on any change on that port. (I believe port B is the correct port for dsPIC33f, not sure about AVR32 though) When ever you are interrupted you can check all of your inputs and see what has changed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a separate timer/counter running you can count the on time for each servo.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-29T13:16:08.703" CommentCount="1" />
  <row Id="5824" PostTypeId="2" ParentId="5773" CreationDate="2010-10-29T13:32:21.543" Score="5" ViewCount="" Body="&lt;p&gt;As a BasicStamp user for almost 20 years and a NetDuino user for only 2 weeks (I've never used a Arduino), I'd say that the NetDuino is a great platform.  The two main features that I am enjoying: ease of programming (and breakpoints!) in VisualStudio and the hi-resolution ADC on the board are key reasons.  The few Arduino shields that I have tried from SparkFun have worked perfectly with the NetDuino.&lt;/p&gt;&#xA;" OwnerUserId="1758" LastActivityDate="2010-10-29T13:32:21.543" CommunityOwnedDate="2011-02-27T07:33:15.000" CommentCount="1" />
  <row Id="5825" PostTypeId="1" AcceptedAnswerId="5827" CreationDate="2010-10-29T13:55:17.513" Score="3" ViewCount="476" Body="&lt;p&gt;I'm finding it hard to understand. Can somebody please provide a link or explanation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance&lt;/p&gt;&#xA;" OwnerUserId="1760" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-29T14:00:24.917" LastActivityDate="2010-10-29T22:26:36.927" Title="What is the difference between PLA and ROM?" Tags="&lt;logic&gt;&lt;rom&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="5826" PostTypeId="1" AcceptedAnswerId="5829" CreationDate="2010-10-29T14:08:03.493" Score="1" ViewCount="221" Body="&lt;p&gt;I have a choice between a CD4017 and a CD4017B.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also seen CD4026 and CD4026B. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the difference between these - is it a silicon revision or do they have different functionality?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-29T15:15:20.987" Title="Difference between CD4017 and CD4017B" Tags="&lt;cmos&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="5827" PostTypeId="2" ParentId="5825" CreationDate="2010-10-29T14:23:04.727" Score="3" ViewCount="" Body="&lt;p&gt;They are quite different devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;PLA&lt;/strong&gt; = Programmable Logic Array.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A PLA or PAL (programmable array logic) device is like a baby FPGA which can be programmed to perform basic logic functions. Tens to hundreds of gates on a PAL can be connected to perform simple logic functions. A PAL is often read only, in that after programming you have to perform a complete erase to update it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;ROM&lt;/strong&gt; = Read Only Memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A ROM does not perform logic functions, but stores data. A type of ROM might be EPROM, eraseable programmable read only memory. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use a ROM as a logic device, by implementing a simple logic table lookup. Like a truth table. However, it is somewhat wasteful and expensive to do this compared to actually using a PAL or even a CPLD/FPGA.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-29T14:36:55.903" LastActivityDate="2010-10-29T14:36:55.903" CommentCount="14" />
  <row Id="5828" PostTypeId="2" ParentId="5821" CreationDate="2010-10-29T14:49:19.990" Score="1" ViewCount="" Body="&lt;p&gt;As a side note, I see you already accepted an answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use an RC circuit with a cutoff frequency below the frequency of your PWM to average the PWM. You need it to have a cut-off of a low enough frequency to stop you having a varying output based on the phase of the PWM going by, but you must also pick a PWM that will react to a change in duty cycle fast enough for you to see it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope that makes sense. This is a very easy way to do it, and with some external comparators you could use it to easily tell if a certain threshold value is violated.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-29T14:49:19.990" />
  <row Id="5829" PostTypeId="2" ParentId="5826" CreationDate="2010-10-29T15:02:37.070" Score="7" ViewCount="" Body="&lt;p&gt;Quoting Wikipedia: &quot;The original 4000 series was available in two versions: The A series was unbuffered, while the B series featured buffered inputs and outputs (in the form of additional, simple logic gates). The buffered outputs are able to source or sink more current than the unbuffered outputs, thus eliminating the need for discrete switching transistors in some designs.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think it's pretty safe to say that the CD4000 number is the generic number, not caring about specific properties like buffered outputs, just the basic logic function. The suffix letter, according to wikipedia, will tell you about the output buffer. Further suffix letters (2nd, 3rd, ... letter) will tell you about packaging options and the like; this may differ from one manufacturer to another and is noted in the data sheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Today, only the B versions of the 4000 logic ICs seem to be available. At least that's what the manufacturers' websites tell me. Do you have a link for the 4000 (without B) series data sheet? Is there a manufacturer's logo on the chip?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It might be the case that some manufacturers produce the buffered version (-B), but mark the actual devices without the B. To be sure, you would need a data sheet that tells you the specifics about device marking code.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2010-10-29T15:15:20.987" LastActivityDate="2010-10-29T15:15:20.987" CommentCount="2" />
  <row Id="5830" PostTypeId="1" AcceptedAnswerId="5831" CreationDate="2010-10-29T15:27:09.537" Score="14" ViewCount="594" Body="&lt;p&gt;Currently I run all my gadgets from batteries and don't use decoupling capacitors.  Are they generally needed/useful when drawing energy from a battery?&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-10-30T19:03:51.457" LastActivityDate="2010-11-01T22:08:22.410" Title="Are decoupling capacitors needed with battery power?" Tags="&lt;battery&gt;&lt;decoupling-capacitor&gt;" AnswerCount="5" FavoriteCount="3" />
  <row Id="5831" PostTypeId="2" ParentId="5830" CreationDate="2010-10-29T15:28:38.927" Score="19" ViewCount="" Body="&lt;p&gt;In broad terms, you should always use them. It is simply something that cannot hurt you to do, but could cause serious problems to ignore.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have probably not seen any major problems with your batteries because they are placed relatively close to your chips and because they have an internal resistance to snub higher frequency signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This could still cause power concerns in higher frequency signals. If a Microcontroller runs at 20MHz then you are having 20e6 pulses of current pulled per second. This may not seem like a big issues, but when enough inputs change at once you may cause &lt;a href=&quot;http://en.wikipedia.org/wiki/Ground_bounce&quot; rel=&quot;nofollow&quot;&gt;ground bounce&lt;/a&gt; or many similar problems that come with high inductance paths to ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Decoupling_capacitor&quot; rel=&quot;nofollow&quot;&gt;wikipedia&lt;/a&gt; article has some background if it helps.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Little extra on decoupling capacitor terminology&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;The job of a decoupling capacitor is to &quot;decouple&quot; your devices power draw from the rest of the circuit. If a decoupling capacitor does its job you will only measure a DC power draw. They remove the AC wave.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are different terms for decoupling capacitors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;strong&gt;bulk capacitors&lt;/strong&gt; act as large power sources that can supply power for periods of time, these are required for functionality. Without a bulk filter cap you will have to have time dependent current as your chip pulls power on it's cycle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Bypass capacitors&lt;/strong&gt; are often of lower value and are designed to terminate higher frequencies. As frequency reduces your impedance decreases for capacitors. A smaller value capacitor has a higher impedance. These small capacitors are the backbone of terminating higher frequency waves.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Decade capacitors&lt;/strong&gt; are another term for bypass caps but the name implies more. If your bulk filter cap is .1uF then your decade caps will be .01uF and .001 and even .0001uF depending on what you are doing. Normally I only see 1 decade cap, but I have had to use 2 or 3 before.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-10-29T21:00:40.097" LastActivityDate="2010-10-29T21:00:40.097" CommentCount="5" />
  <row Id="5832" PostTypeId="2" ParentId="5813" CreationDate="2010-10-29T15:49:57.497" Score="3" ViewCount="" Body="&lt;p&gt;In short, you &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;zero-pad the input signals (add zeros to the end so that at least half of the wave is &quot;blank&quot;)&lt;/li&gt;&#xA;&lt;li&gt;take the FFT of both signals&lt;/li&gt;&#xA;&lt;li&gt;multiply the results together (sample-by-sample)&lt;/li&gt;&#xA;&lt;li&gt;do the inverse FFT&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;corr = ifft(fft(a and zeroes)*fft(b and zeroes))&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will give you the cross-correlation function, which is a measure of similarity vs offset.  For the offset at which the waves are &quot;lined up&quot; with each other, there will be a peak in the correlation function:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/dzOuV.png&quot; alt=&quot;peak in correlation function&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://jfk-records.com/NRC_Science/science.htm&quot; rel=&quot;nofollow&quot;&gt;http://jfk-records.com/NRC_Science/science.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've only seen this used to find the offset between two waves.  You can get a more precise estimate of the offset (less than one sample) by using &lt;a href=&quot;https://ccrma.stanford.edu/~jos/sasp/Quadratic_Interpolation_Spectral_Peaks.html&quot; rel=&quot;nofollow&quot;&gt;parabolic/quadratic interpolation&lt;/a&gt; on the peak.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get a similarity value between 0 and 1 you'd need to scale the amplitude according to the length of the inputs, length of the FFT, your particular FFT implementation's scaling, etc.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that this will only work on waves that have the same shape.  If they've been sampled on different hardware or have some noise added, but still have the same shape, it will work, but if they've been filtered or the wave shape has been changed by phase shifts, they may sound the same, but won't correlate as well.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-29T15:49:57.497" CommentCount="1" />
  <row Id="5833" PostTypeId="2" ParentId="5830" CreationDate="2010-10-29T16:46:25.393" Score="10" ViewCount="" Body="&lt;p&gt;They're useful because devices drawing power can also cause ripples - not just the regulator.  For instance a microcontroller will draw more current on a clock rising edge and less otherwise.  This draw causes the supply voltage to be drawn down ever so slightly.  If everything is running off of the same clock it gets worse.  With a capacitor on the power pins there's a reserve available to minimize this ripple.  It's a good idea.&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-30T13:50:16.440" LastActivityDate="2010-10-30T13:50:16.440" />
  <row Id="5834" PostTypeId="2" ParentId="5830" CreationDate="2010-10-29T17:39:39.263" Score="7" ViewCount="" Body="&lt;p&gt;A battery has an internal resistance. The pulses of current drawn by microcontrollers and other digital logic can cause dips in the battery voltage. A bulk decoupling cap (10µF or so) across the power rails is necessary to prevent big dips causing problems. Don't forget small 100nF caps are also necessary on the Vdds of all digital logic ICs to provide a local current source. The inductance of traces on your PCB will make these necessary, or you may discover strange and unusual bugs are affecting your circuit.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-29T17:39:39.263" CommentCount="6" />
  <row Id="5835" PostTypeId="1" AcceptedAnswerId="5836" CreationDate="2010-10-29T17:45:50.903" Score="2" ViewCount="167" Body="&lt;p&gt;For my Super OSD Pro project (Super OSD is divided into two versions: Lite and Pro) I'm going to be using a 4-layer board. Are there any gotchas to be aware of when using 4 layer boards? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking of having the most widely used nets (+3.3V and GND) on layers 1 and 2, and having layers 3 and 4 for carrying signals. I could also occasionally use layers 1 and 2 for carrying signals where 3 and 4 are full up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One other thing I'm also concerned about is how to connect pins to the right layers? Say I want to connect a pin on the top to layer 2. I've always routed a trace from the pin to a via, then dropped the via to that layer, but is there a better way? I've heard of via on pad but I've also heard that can produce bad results and is only really for BGA's, not the TQFP's I'll be working with.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-30T09:37:39.637" Title="General tips for 4 layer boards" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;" AnswerCount="3" />
  <row Id="5836" PostTypeId="2" ParentId="5835" CreationDate="2010-10-29T18:26:39.210" Score="10" ViewCount="" Body="&lt;p&gt;It's more usual to have the ground and power planes on the inner layers. It's best to keep them free of tracks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just use a short track and a via to connect leads to the other layers.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-10-29T18:45:30.917" LastActivityDate="2010-10-29T18:45:30.917" CommentCount="1" />
  <row Id="5837" PostTypeId="1" CreationDate="2010-10-29T19:05:53.077" Score="1" ViewCount="93" Body="&lt;p&gt;I'm building a system for a small manufacturing business that requires a mobile barcode scanner (at minimum) and would be great if it could be an RFID reader too. I would really like this to be a powerful device that runs Android and could have custom applications written in Java on it. However, I'm a software guy and I'm not sure where to start on the hardware side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a good hardware option for this?&lt;/p&gt;&#xA;" OwnerUserId="1763" LastActivityDate="2010-10-29T19:31:41.400" Title="Is there a good and reasonably priced way to make a custom RFID reader and barcode scanner that runs Android?" Tags="&lt;rfid&gt;&lt;android&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="5838" PostTypeId="2" ParentId="5837" CreationDate="2010-10-29T19:09:38.333" Score="1" ViewCount="" Body="&lt;p&gt;Have a look in &lt;a href=&quot;http://www.touchatag.com/&quot; rel=&quot;nofollow&quot;&gt;TouchATag&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-29T19:09:38.333" />
  <row Id="5839" PostTypeId="2" ParentId="5835" CreationDate="2010-10-29T19:26:01.763" Score="4" ViewCount="" Body="&lt;p&gt;Ground and power planes are best to put on the inner layers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You do not want vias in your pads except when you need them there for a specific reason, such as leading away heat or excessive solder paste from the middle ground pad on a BGA.&lt;/p&gt;&#xA;" OwnerUserId="1764" LastActivityDate="2010-10-29T19:26:01.763" />
  <row Id="5840" PostTypeId="2" ParentId="5837" CreationDate="2010-10-29T19:31:41.400" Score="1" ViewCount="" Body="&lt;p&gt;You can run Android on the BeagleBoard:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/4807/is-there-any-kit-for-android-development&quot;&gt;http://electronics.stackexchange.com/questions/4807/is-there-any-kit-for-android-development&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could plug a ready made USB RFID reader into that.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-29T19:31:41.400" CommentCount="1" />
  <row Id="5841" PostTypeId="1" AcceptedAnswerId="5843" CreationDate="2010-10-29T19:32:34.970" Score="1" ViewCount="129" Body="&lt;p&gt;The headphones work fine in other devices.  If I push or pull the connector a little bit I can get sound from both.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is apparently an issue in the mechanical connection of the jack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone had this issue and fixed it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is out of warranty but well take care of.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://support.apple.com/kb/ht1353#ipodfifth&quot; rel=&quot;nofollow&quot;&gt;This is the version&lt;/a&gt; 5th gen video/color ipod&lt;/p&gt;&#xA;" OwnerUserId="209" LastEditorUserId="209" LastEditorDisplayName="" LastEditDate="2010-10-29T20:08:34.327" LastActivityDate="2010-11-02T05:26:36.393" Title="ipod headphone jack only driving one side - is there an easy way to fix this?" Tags="&lt;ipod&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="5842" PostTypeId="2" ParentId="5819" CreationDate="2010-10-29T19:35:35.327" Score="2" ViewCount="" Body="&lt;p&gt;Texas Instruments TPS 5410, although 68 uH inductor is recommended.&lt;/p&gt;&#xA;" OwnerUserId="1764" LastActivityDate="2010-10-29T19:35:35.327" CommentCount="2" />
  <row Id="5843" PostTypeId="2" ParentId="5841" CreationDate="2010-10-29T19:41:57.500" Score="3" ViewCount="" Body="&lt;p&gt;Have a look in &lt;a href=&quot;http://www.ifixit.com/&quot; rel=&quot;nofollow&quot;&gt;IFixIt&lt;/a&gt;. It's a great site about repairs.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-29T19:41:57.500" CommentCount="1" />
  <row Id="5844" PostTypeId="2" ParentId="5841" CreationDate="2010-10-29T19:46:35.850" Score="2" ViewCount="" Body="&lt;p&gt;It's probably a solder joint that is loose, but it is more likely you will damage some other component in fixing it. Take it to someone who can solder/rework really small components - don't even think about using that $10 RadioShack iron.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-29T19:46:35.850" CommentCount="2" />
  <row Id="5845" PostTypeId="1" AcceptedAnswerId="5846" CreationDate="2010-10-29T20:10:19.433" Score="5" ViewCount="217" Body="&lt;p&gt;Y5V capacitors are much more temperature dependent, but is that really critical for decoupling capacitors and a product operating over a -40°C to +85°C range maximum (typical -20°C to +55°C)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason I ask this is the cost is much lower, compare 0.8p with 8p per capacitor.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-01T16:36:58.137" Title="Is Y5V okay for decoupling capacitors?" Tags="&lt;ceramic&gt;" AnswerCount="4" />
  <row Id="5846" PostTypeId="2" ParentId="5845" CreationDate="2010-10-29T20:44:12.777" Score="4" ViewCount="" Body="&lt;p&gt;If the application must operate over a wide temperature range Y5V is not recommended.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-10-29T20:44:12.777" />
  <row Id="5847" PostTypeId="2" ParentId="5830" CreationDate="2010-10-29T21:16:28.643" Score="11" ViewCount="" Body="&lt;p&gt;Decoupling isn't about smoothing out power, decoupling is about suppressing the high frequency noise generated by circuits that generate high slew rate signals, especially logic circuits. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When a node changes through several volts in a matter of nanoseconds, it takes a brief slug of current to charge/discharge the capacitance at that node. If you have a bunch of IC's sharing supply wiring, the inductance in the supply lines means that those slugs of current going into one IC translate into supply voltage dips for the other IC's, and this can glitch things into unintended states. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason you stick a good high-frequency cap on every IC is to provide individually for these gulps of current, thereby 'decoupling' the supply demands of the ICs from one another.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-29T21:16:28.643" CommentCount="2" />
  <row Id="5848" PostTypeId="1" CreationDate="2010-10-29T22:13:40.963" Score="2" ViewCount="137" Body="&lt;p&gt;Can anyone identify this mobile phone?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.adafruit.com/blog/2010/10/29/what-is-that-electronic-thing-from-yemen/&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/blog/2010/10/29/what-is-that-electronic-thing-from-yemen/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/ladyada/5126516011/&quot; rel=&quot;nofollow&quot;&gt;http://www.flickr.com/photos/ladyada/5126516011/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm2.static.flickr.com/1312/5126516011_afc928eac1_o.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.bunniestudios.com/blog/?p=1351&quot; rel=&quot;nofollow&quot;&gt;http://www.bunniestudios.com/blog/?p=1351&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-30T08:36:00.707" LastActivityDate="2010-10-30T23:54:36.143" CommunityOwnedDate="2010-10-29T22:15:22.820" Title="Can anyone identify this phone PCB?" Tags="&lt;pcb&gt;&lt;phone&gt;" AnswerCount="3" />
  <row Id="5849" PostTypeId="2" ParentId="5825" CreationDate="2010-10-29T22:26:36.927" Score="2" ViewCount="" Body="&lt;p&gt;For the sake of example, suppose you have a PLA device and a ROM, both with 12 inputs and 8 outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ROM will have 8 bit cells for each of 2^12 = 4096 addresses. This ROM would therefore have 32768 individual bit cells. The logic on the chip would (in larger parts at least) include a demultiplexer for the high order input bits, which would select a bank of, for example, 1024 cells, and a multiplexor for the low order inputs to select the 8 actual output bits from the bank. This would give on the order of four gate delays for the muxing, plus whatever the technology for the bit cells required. Old UV EPROMs might take 120ns to cough up a result, but there were (are there still?) one-time-programmable ROMS that could do the same job in a few tens of nanoseconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A PLA on the other hand, will have an array of programmable 'fuses', usually much smaller than the 32768 bit cells in the equivalent ROM. Internally a PLA provides a bank of AND gates, followed by a bank of OR gates, and optionally a flip-flop per output. A PLA of this size might have 16 AND gates, each with anywhere from 8 to 16 inputs. In the erased state, the 'fuses' are short-circuits, so each input of each AND is connectable to (usually) any of the chip inputs or outputs, or their inversions. When you program the PLA, the programmer blows the fuses to leave only the connections you want. Then, the OR array similarly can be programmed to OR together various combinations of the AND outputs. The fuse technology incurs minimal delay, so propagation delay from input pin to output pin can be as small as two gate delays or up to four, depending on how many inverted signals are needed, which automatically beats the usual ROM topology for speed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the same numbers of inputs and outputs, a ROM is capable of more general logic, in that you can burn any truth table you like into the ROM. However, as a logic device, the ROM is not optimal. If you attempt to burn several independent little functions into a ROM, you'll find you have a lot of 'don't care' cases that must nonetheless be programmed into the ROM to get the desired output. The PLA is better for logic because you don't have to deal with the don't-cares, but the trade-off is that you can't program completely arbitrary functions of the bits. However, they are nonetheless sufficiently flexible to be useful for many common 'glue-logic' tasks, and they are generally faster at producing output.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-29T22:26:36.927" CommentCount="1" />
  <row Id="5850" PostTypeId="1" AcceptedAnswerId="5851" CreationDate="2010-10-29T22:27:23.043" Score="1" ViewCount="208" Body="&lt;p&gt;I'm going to be using an 8 MHz crystal to run my microcontroller at 16 MIPS (PLL 4x, 2 cycle instructions.) However, 8 MHz doesn't divide into any UART frequencies AFAIK... so how critical are these frequencies? I plan to use 115,200 baud.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can UART run within ±1%? If this doesn't work, what frequency should I use? (I would like to get as near to 16 MIPS as possible, for maximum processing speed.) If it matters, I'm using a PIC24FJ64GA004.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-30T00:06:57.327" Title="How critical are UART frequencies?" Tags="&lt;microcontroller&gt;&lt;uart&gt;&lt;frequency&gt;" AnswerCount="1" />
  <row Id="5851" PostTypeId="2" ParentId="5850" CreationDate="2010-10-29T22:38:10.803" Score="3" ViewCount="" Body="&lt;p&gt;If you are within 1%, you should be OK. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Suppose your UART uses a 16x oversampling clock, for example, you can set it to 1,843,200 Hz to 16x oversample 115,200 bps. (oversampling like this is fairly common) This lets the UART count off 8 over-clocks from the falling edge of the start bit, so it can locate the center of the bit cells to within +/- one period of the over clock, after which it counts off 16 periods of the over-clock to determine when to sample data. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you assume it can hit the center of the start bit, then in order to keep sampling serial data in the correct bit cells across 8 data bits, the clock frequency has to stay between (8-0.5)/8 and (8+0.5)/8, or +/-6.25% of the intended bit rate. Higher overclocking gets closer to the ideal condition of hitting the center of the start bit, but 8x or 16x is usually close enough that you can assume a 5% mismatch will work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you can't count on the other side being perfectly on frequency. If you connect a device that's 4% fast to a device that's 4% slow, you'll have a problem. I've run into at least one case were a PC was running a little slow, and a device a little fast, and the two could only marginally communicate, though the same device was fine with other PCs, and the PC was fine with other devices. (O-scoped these at about 112kbps and 119kbps) For that reason it's good to try to hit the nominal frequency as closely as possible. I've never seen anything within 2% of nominal have a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The usual thing to do is use a master clock rate that provides a whole number multiple of the intended UART over-sampling rate times the baud rate. For example, if you wanted a CPU running at about 8MHz, you might use a 7.3728MHz oscillator, which can be divided by 4 to get 1.8432MHz, which happens to be exactly 16 times 115200.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-10-30T00:06:57.327" LastActivityDate="2010-10-30T00:06:57.327" CommentCount="5" />
  <row Id="5852" PostTypeId="2" ParentId="5848" CreationDate="2010-10-29T22:38:40.677" Score="1" ViewCount="" Body="&lt;p&gt;It looks like it's missing a board. The two connectors on the board probably connect to something of more importance like a processor board. Hidden under the shielded components is probably a chipset for running the GSM portion, but of course without seeing the components it's a blind guess. Maybe someone will recognise it, but it's not going to be easy to deduct.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My guess would be a low cost payphone. Certainly not a smartphone; sub £30 range.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-29T22:38:40.677" CommunityOwnedDate="2010-10-29T22:38:40.677" CommentCount="1" />
  <row Id="5853" PostTypeId="1" AcceptedAnswerId="5885" CreationDate="2010-10-30T00:03:16.970" Score="3" ViewCount="109" Body="&lt;p&gt;Headers like these:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.farnell.com/harwin/m20-8760342/header-smt-vertical-2x3way/dp/1517388&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/harwin/m20-8760342/header-smt-vertical-2x3way/dp/1517388&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for cables that connect to these, with female headers on either end. Any length more than ~5cm is ideal. But I can't seem to find any results on my favourite websites. I'd rather not spend time crimping them myself as I have to produce a lot of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For this application I need 4 way connections, but it would be nice if many different way counts were available, so I know what to buy in future.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-30T00:44:21.397" LastActivityDate="2010-10-30T12:01:30.990" Title="Where to find pre-made wires for plugging into headers?" Tags="&lt;connector&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="5854" PostTypeId="1" AcceptedAnswerId="5859" CreationDate="2010-10-30T00:11:02.033" Score="1" ViewCount="56" Body="&lt;p&gt;I want to buy components from places like Farnell, Mouser, etc. But I then want to distribute them in kits, each kit would have maybe 10 of each component; the components are tiny 0603 types. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is, there are nearly 50 bags in each kit, and removing the required components from the right bag and rebagging them sounds like it will take a long time, and it seems wasteful as many distributors already have these bagging facilities. It's also not an option to make an order for each kit, because that's looking to be £50 each.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So do any distributors offer the option of splitting each order into little bags? I've already shot off an email to Farnell about this possibility, but I'm not hopeful - I'm wondering if any distributors just offer it as an option on their website somewhere.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-30T02:25:36.863" Title="Do any distributors pack in bags of 10 or so?" Tags="&lt;distributors&gt;" AnswerCount="1" />
  <row Id="5855" PostTypeId="1" AcceptedAnswerId="5857" CreationDate="2010-10-30T01:20:57.523" Score="2" ViewCount="157" Body="&lt;p&gt;My usual method of reprogramming AVRs (so-far limited to ATtiny13 and ATtiny2313) is to disconnect the chip from the host circuit, plug it into another breadboard with all of the ICSP hookups in place, program, then replace.  However, I keep hearing that one can program the chip in place (which is, I understand, the whole point of ICSP).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any special hardware considerations one has to take into account before programming the chip in situ?  For instance, I worry that the ICSP process may damage circuit components connected to the same AVR pins which are used for ICSP.  Does one occasionally need to add diodes or some other kind of buffering to protect these components?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this question sounds kind of vague, and I guess it is - but I've not provided details of my particular circuit because I'm interested in more general rules of thumb. I.e. does one never have to worry about this, or does the answer really depend on the particular circuit the MCU is a part of?&lt;/p&gt;&#xA;" OwnerUserId="504" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-13T04:23:28.267" LastActivityDate="2011-02-13T04:23:28.267" Title="How do I plan for in circuit programming of an AVR ?" Tags="&lt;avr&gt;&lt;isp&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5856" PostTypeId="2" ParentId="5855" CreationDate="2010-10-30T01:24:43.280" Score="-1" ViewCount="" Body="&lt;p&gt;Unfortunately, you cannot do in circuit programming for your AVR's if the pins are shared by other functions, for example lighting LEDs. While it might work, it's not guaranteed as it may cause the programmer's or µC's outputs to drop too low for it to work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One other alternative is to order your chips pre-programmed. I know Microchip offers this for some of their chips, but I'm not sure about Atmel.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-30T01:24:43.280" CommentCount="3" />
  <row Id="5857" PostTypeId="2" ParentId="5855" CreationDate="2010-10-30T02:05:42.747" Score="7" ViewCount="" Body="&lt;p&gt;I've used ISP for just about every AVR board I've done; it's nothing to be afraid of.  The &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/AVRISPmkII_UG.pdf&quot; rel=&quot;nofollow&quot;&gt;AVR ISP mkII manual&lt;/a&gt; gives a pretty good summary of the limitations you need to look out for in the &quot;Target Interface&quot; section.  Basically, if you run the MISO/MOSI/SCK pins directly to the programmer and have about 820 ohms between them and the rest of the circuit (and aren't doing anything funky with the reset pin) you're okay.  I wouldn't worry about the ISP damaging other components; it's not a high voltage programmer.  The signals all run at 5V, so if it can damage an external component, so can your microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're really stuck with a board that doesn't permit ISP programming, I'd at least try to use a ZIF socket for your programming board.  They're pricey, but it will greatly improve your quality of life.&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2010-10-30T02:05:42.747" CommentCount="1" />
  <row Id="5858" PostTypeId="1" AcceptedAnswerId="5958" CreationDate="2010-10-30T02:08:56.440" Score="4" ViewCount="139" Body="&lt;p&gt;I can either use an R-2R divider or a R = 2^N divider to get a 5-bit DAC.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Which will be more accurate? R = 2^N I suspect, but;&lt;/li&gt;&#xA;&lt;li&gt;Which will be cheaper? I think R-2R because it can use standard values, but...&lt;/li&gt;&#xA;&lt;li&gt;I've heard R-2R have issues with monotonicity, when the output doesn't change for the same amount with each count. Would this be an isuse with 5-bit DAC - would any such monotonicity simply be overwhelmed by divider error?&lt;/li&gt;&#xA;&lt;li&gt;There's also the trade off of size, R = 2^N will be larger.&lt;/li&gt;&#xA;&lt;li&gt;Also there's the possibility of using an IC to do this. I'd be open to doing this as well, if it wasn't very big and could be interfaced over I2C.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The DAC is going to be used to feed a comparator. The comparator will use this reference to compare against an incoming video signal.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-30T02:14:12.083" LastActivityDate="2010-11-01T07:23:25.677" Title="Best/cheapest way to cheaply get a 5-bit DAC: R-2R, or R = 2^N." Tags="&lt;resistor&gt;&lt;dac&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5859" PostTypeId="2" ParentId="5854" CreationDate="2010-10-30T02:25:36.863" Score="2" ViewCount="" Body="&lt;p&gt;I think Digi-Key does this; check &lt;a href=&quot;https://ordering.digikey.com/Help.aspx?WT.z_homepage_link=hp_BOM&amp;amp;id=New%20BOM%20Wizard&amp;amp;site=US&amp;amp;lang=en&quot; rel=&quot;nofollow&quot;&gt;their BOM manager&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2010-10-30T02:25:36.863" CommentCount="2" />
  <row Id="5860" PostTypeId="1" CreationDate="2010-10-30T03:14:17.517" Score="2" ViewCount="86" Body="&lt;p&gt;I attached split the end of a USB  wire and attached a switch. When I press the switch, I measure 5V from the port, but am only measuring 33mA. Why am I getting only 33mA instead of 100mA?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2010-10-30T20:20:04.227" Title="Only getting 33mA from a USB port" Tags="&lt;usb&gt;&lt;current&gt;&lt;current-measurement&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="5861" PostTypeId="1" CreationDate="2010-10-30T03:17:53.810" Score="4" ViewCount="376" Body="&lt;p&gt;What's the best PIC to start learning with?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an 16F628A, but I think that the 16F684 could be better. What is the difference between PIC16F648 and 684A?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want a PIC with 8 pins and with analog inputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which would be best?&lt;/p&gt;&#xA;" OwnerUserId="1539" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-31T01:17:55.057" LastActivityDate="2011-03-18T13:39:06.250" CommunityOwnedDate="2011-05-15T04:20:58.030" Title="What PIC should I use?" Tags="&lt;pic&gt;" AnswerCount="7" CommentCount="1" />
  <row Id="5862" PostTypeId="2" ParentId="5861" CreationDate="2010-10-30T04:13:07.823" Score="2" ViewCount="" Body="&lt;p&gt;I'd recommend &lt;strong&gt;PIC16F877A&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This has 5 ports for I/O operations. With this, you can learn PIC programming step by step, starting with LED's, switches, 7segment displays, external interrupts, hardware interrupts (timer0,1,2), USART, CCP, EEPROM and so on...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This powerful (200 nanosecond instruction execution) yet easy-to-program (only 35 single word instructions) CMOS FLASH-based 8-bit microcontroller packs Microchip's powerful PIC® architecture into an 40- or 44-pin package and is upwards compatible with the PIC16C5X, PIC12CXXX and PIC16C7X devices. The PIC16F877A features 256 bytes of EEPROM data memory, self programming, an ICD, 2 Comparators, 8 channels of 10-bit Analog-to-Digital (A/D) converter, 2 capture/compare/PWM functions, the synchronous serial port can be configured as either 3-wire Serial Peripheral Interface (SPI™) or the 2-wire Inter-Integrated Circuit (I²C™) bus and a Universal Asynchronous Receiver Transmitter (USART). All of these features make it ideal for more advanced level A/D applications in automotive, industrial, appliances and consumer applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can be programmed over a serial link.&lt;/p&gt;&#xA;" OwnerUserId="1484" LastEditorUserId="1484" LastEditorDisplayName="" LastEditDate="2010-11-10T04:21:31.747" LastActivityDate="2010-11-10T04:21:31.747" CommunityOwnedDate="2011-05-15T04:20:58.030" CommentCount="3" />
  <row Id="5863" PostTypeId="2" ParentId="1147" CreationDate="2010-10-30T04:38:38.260" Score="0" ViewCount="" Body="&lt;p&gt;I've got a Hakko FX888. Great iron to use everyday. I've got a cheapo Chinese eBay hot air station to go with it, and it does the job fine - soldered a fair few QFN and LGA packages with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't be afraid to go for the cheap tools from brands such as Aoyue if you're on a budget! They're not that bad!&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-10-30T04:38:38.260" />
  <row Id="5864" PostTypeId="2" ParentId="5813" CreationDate="2010-10-30T05:12:15.817" Score="1" ViewCount="" Body="&lt;p&gt;In signal processing the cross-correlation (xcorr in MATLAB) is a convolution operation with one of the two sequences reversed. Since time reversal corresponds to complex conjugation in the frequency domain, you can use the DFT to compute the cross-correlation as follows: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;R_xy = ifft(fft(x,N) * conj(fft(y,N)))&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;where N = size(x) + size(y) - 1 (preferably rounded up to a power of 2) is the length of the DFT. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Multiplication of DFTs is equivalent to &lt;em&gt;circular&lt;/em&gt; convolution in time. Zero padding both vectors to length N keeps the circularly shifted components of y from overlapping with x, which makes the result identical to the linear convolution of x and time reversed y.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A lag of 1 is a right circular shift of y, while a lag of -1 is a left circular shift. The cross-correlation is simply the sequence of dot products for all lags. Based on standard fft ordering, these will be in an array that can be accessed as follows. Indices 0 through size(x)-1 are the positive lags. Indices N-size(y)+1 to N-1 are the negative lags in reverse order. (In Python the negative lags can be accessed conveniently with negative indices such as R_xy[-1].) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can think of the zero-padded x and y as N-dimensional vectors. The dot product of x and y for a given lag is &lt;code&gt;|x|*|y|*cos(theta)&lt;/code&gt;. The norms of x and y are constant for circular shifts, so dividing them out leaves just the varying cosine of the angle theta. If x and y (for a given lag) are orthogonal in N-space, the correlation is 0 (i.e. theta = 90 degrees). If they're co-linear, the value is either 1 (positively correlated) or -1 (negatively correlated, i.e. theta = 180 degrees). This leads to the cross-correlation normalized to unity:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;R_xy = ifft(fft(x,N) * conj(fft(y,N))) / (norm(x) * norm(y))&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This can be made unbiased by recomputing the norms for just the overlapping parts, but then you may as well do the entire computation in the time domain. Also, you'll see different versions of normalization. Instead of being normalized to unity, sometimes the cross-correlation is normalized by M (biased), where M = max(size(x), size(y)), or M-|m| (an unbiased estimate of the mth lag).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For maximum statistical significance the mean (DC bias) should be removed before computing the correlation. This is called the cross-covariance (xcov in MATLAB):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;x2 = x - mean(x)&#xA;y2 = y - mean(y)&#xA;phi_xy = ifft(fft(x2,N) * conj(fft(y2,N))) / (norm(x2) * norm(y2))&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="721" LastEditorUserId="721" LastEditorDisplayName="" LastEditDate="2010-10-30T05:31:45.807" LastActivityDate="2010-10-30T05:31:45.807" />
  <row Id="5865" PostTypeId="2" ParentId="5853" CreationDate="2010-10-30T05:19:28.580" Score="1" ViewCount="" Body="&lt;p&gt;Couple of ideas --&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9389&quot; rel=&quot;nofollow&quot;&gt;SparkFun&lt;/a&gt; sells individual wires with a female connector at both ends, designed to plug into pins spaced 0.1&quot; (2.54 mm) apart.  Wires are 12&quot; (4.75 cm) long.  Sold in packs of 10 or 100.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.samtec.com/ftppub/pdf/hcmd.pdf&quot; rel=&quot;nofollow&quot;&gt;Samtec&lt;/a&gt; has ribbon cables with single-row 0.1&quot; sockets (HCSS series), but only has options for 5, 8, 10, 12 or higher count wires.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-10-30T05:36:04.933" LastActivityDate="2010-10-30T05:36:04.933" />
  <row Id="5866" PostTypeId="2" ParentId="5860" CreationDate="2010-10-30T05:23:21.777" Score="2" ViewCount="" Body="&lt;p&gt;There is a decent chance that the computer is detecting a short and limiting the current back.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As pingswept said, &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;try a 50 ohm resistor&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This will stop the computer from thinking there is broken hardware connected.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-10-30T20:20:04.227" LastActivityDate="2010-10-30T20:20:04.227" CommentCount="1" />
  <row Id="5867" PostTypeId="1" CreationDate="2010-10-30T05:40:24.173" Score="2" ViewCount="268" Body="&lt;p&gt;&lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+0.26073472713092677+50+5.0+43%0Aw+160+224+160+64+0%0Aw+160+64+480+64+0%0At+336+272+368+272+0+1+-9.572668024803502+-0.704666154791141+100.0%0Aw+368+288+368+400+0%0Aw+368+400+160+400+0%0Aw+336+272+272+272+0%0Aw+368+256+368+192+0%0Aw+480+176+480+64+0%0Aw+272+272+272+224+0%0Aw+272+272+272+352+0%0Aw+416+192+368+192+0%0Aw+416+192+448+192+0%0Ac+272+352+416+352+0+1.0E-7+-0.7054745605126409%0Aw+416+352+480+352+0%0Aw+480+208+480+240+0%0Aw+480+240+480+352+0%0Aw+480+240+512+240+0%0Aw+512+400+368+400+0%0Ar+512+400+512+304+0+10.0%0Aw+512+304+512+240+0%0Ar+160+224+272+224+0+120000.0%0Ar+160+224+160+304+0+47.0%0Av+160+400+160+304+0+0+40.0+9.0+0.0+0.0+0.5%0At+448+192+480+192+0+-1+8.86719346429086+-0.12819862309348018+100.0%0Ao+19+64+0+35+2.5+0.2+0+-1%0A&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is one of the circuits in the Electronics 9/10 class. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/8lOpC.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The package did not explain how transistor combination worked and why the capacitor will reverse its current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you explain this circuit? Why I can't make a transistor combination with only two NPNs?&lt;/p&gt;&#xA;" OwnerUserId="1769" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-25T10:16:09.673" LastActivityDate="2010-11-25T10:16:09.673" Title="Explain this circuit?" Tags="&lt;capacitor&gt;&lt;transistor&gt;&lt;oscillator&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="5868" PostTypeId="2" ParentId="5853" CreationDate="2010-10-30T05:57:05.993" Score="1" ViewCount="" Body="&lt;p&gt;Digikey sells something along those lines.  They are flex cables with headers mounted on either end.  Keep in mind that they are pretty pricey versus building your own.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are on page 74 and 75 of the 2010 catalog:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dkc3.digikey.com/PDF/US2010/P0074.pdf&quot; rel=&quot;nofollow&quot;&gt;http://dkc3.digikey.com/PDF/US2010/P0074.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dkc3.digikey.com/PDF/US2010/P0075.pdf&quot; rel=&quot;nofollow&quot;&gt;http://dkc3.digikey.com/PDF/US2010/P0075.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adafruit sells them as well, but only in 6-conductor, 6&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=33&amp;amp;products_id=206&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=33&amp;amp;products_id=206&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1477" LastEditorUserId="1477" LastEditorDisplayName="" LastEditDate="2010-10-30T06:07:26.867" LastActivityDate="2010-10-30T06:07:26.867" />
  <row Id="5871" PostTypeId="1" AcceptedAnswerId="5896" CreationDate="2010-10-30T07:37:00.657" Score="7" ViewCount="275" Body="&lt;p&gt;This is about how micro controllers work in general.. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The programming that we do is converted into 1's and 0's by the compiler and these machine understandable code are then loaded to the microcontroller.. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How does the microcontroller respond to this.. I mean are these 1's and 0's converted into corresponding logic voltage (5v and 0) by DAC? If its like that, how does this small piece of silicon decide what to do with these various combinations of 5v and 0v?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand that every single IC is made of logic gates and these gates are composed of transistors.. So how does these transistors respond to various combinations of 5v and 0v?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What makes them look for these logics.. I mean how they monitor these instructions when they are powered on?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So certainly there got to be an Operating System loaded into the mcu that tells it to process and how to process these instructions, isn't?..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next thing is.. consider a timer.. it is simply a register that increments by one after each clock cycle.. Isn't the OS again that instructs the mcu to increment after each clock? Am I right? In that case, in what language, all the code for a operating system is written? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can just proceed my work with programming the mcu for different tasks but today I was interested to know how my code is understood by this machine..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry that my question is lengthy to read.. please help me learn these basic things..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance..  &lt;/p&gt;&#xA;" OwnerUserId="1484" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-13T04:25:07.827" LastActivityDate="2011-02-13T04:25:07.827" Title="Fundamentals of Embedded Systems" Tags="&lt;microcontroller&gt;" AnswerCount="7" CommentCount="2" FavoriteCount="4" />
  <row Id="5872" PostTypeId="2" ParentId="5848" CreationDate="2010-10-30T07:50:44.743" Score="0" ViewCount="" Body="&lt;p&gt;Not sure of make, but based on current news stories, it came from Yemen.&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2010-10-30T07:50:44.743" CommunityOwnedDate="2010-10-30T07:50:44.743" />
  <row Id="5873" PostTypeId="2" ParentId="5848" CreationDate="2010-10-30T08:37:36.197" Score="4" ViewCount="" Body="&lt;p&gt;Nokia 6120c&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ownta.com/compatible-nokia-6120c-cell-phone-mainboard-with-power-ic-and-used-flash-ic-no-software.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ownta.com/compatible-nokia-6120c-cell-phone-mainboard-with-power-ic-and-used-flash-ic-no-software.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Answer from here:&#xA;&lt;a href=&quot;http://www.bunniestudios.com/blog/?p=1351&quot; rel=&quot;nofollow&quot;&gt;http://www.bunniestudios.com/blog/?p=1351&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Commentary:&#xA;&lt;a href=&quot;http://www.bunniestudios.com/blog/?p=1359&quot; rel=&quot;nofollow&quot;&gt;http://www.bunniestudios.com/blog/?p=1359&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-30T23:54:36.143" LastActivityDate="2010-10-30T23:54:36.143" CommunityOwnedDate="2010-10-30T08:37:36.197" />
  <row Id="5874" PostTypeId="2" ParentId="5845" CreationDate="2010-10-30T09:30:27.980" Score="4" ViewCount="" Body="&lt;p&gt;You may also want to use more caps or higher capacitance and/or voltage rating than with X5R or X7R, as Y5V capacitance has a dependence on applied voltage as well as temperature.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-30T09:30:27.980" />
  <row Id="5875" PostTypeId="2" ParentId="5835" CreationDate="2010-10-30T09:37:39.637" Score="4" ViewCount="" Body="&lt;p&gt;You'd normally put power/gnd planes on inner layers, mostly as these are the least likely to need track-hacking to fix errors or aid debugging. Almost all 4L PCBs you'll see do it like this. You will often have space available on the power plane to route a few signals. &#xA;There can sometimes be some marginal benefits in EMC and track density (due to via size) by putting them on outer layers but you'd only do this if you'really struggling to avoid going to 6 layers, or need a little extra EMC performance due to the shielding effect of outer planes.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-30T09:37:39.637" CommentCount="1" />
  <row Id="5876" PostTypeId="2" ParentId="5867" CreationDate="2010-10-30T09:39:40.777" Score="1" ViewCount="" Body="&lt;p&gt;It looks to me (with quite limited electronic circuit analysis skills) like the 100nF capacitor charges until it reaches a voltage high enough to forward bias the BE junction of the NPN transistor. When this happens, it discharges its energy through the BE junction to ground until its voltage drops below the minimum BE voltage, thus switching off the NPN. The capacitor reverses its current because that's what they do when faced with a falling DC voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally, because the -ve leg of the capacitor is tied to the Collector of the PNP, the capacitor voltage receives a positive offset equal to the voltage at the Collector / the voltage across the 10 ohm resistor. This is also why there is no current flowing from the voltage source through the Base of the NPN.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately I'm not really sure where to start for your second question so I'll have to defer to someone more experienced (and hope they don't have too many corrections to make about my original circuit analysis). :]&lt;/p&gt;&#xA;" OwnerUserId="1647" LastEditorUserId="1647" LastEditorDisplayName="" LastEditDate="2010-10-30T09:47:12.370" LastActivityDate="2010-10-30T09:47:12.370" />
  <row Id="5877" PostTypeId="2" ParentId="5790" CreationDate="2010-10-30T09:43:08.000" Score="1" ViewCount="" Body="&lt;p&gt;Check the PIC24 range - there are some 44 pin parts, some with USB host, which may have more than normal RAM to support the USB functions. &#xA;You don't often see large RAM or flash in low pin counts due to the size of the die - the large pin count isn't a major factor in cost, it's the die size for the RAM etc.&#xA;Similarly you don't see large pin counts on low-end devices as the size of the pad ring dictates the die size, so it would be a waste of silicon to not use it for functionality.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-30T09:43:08.000" />
  <row Id="5878" PostTypeId="2" ParentId="5871" CreationDate="2010-10-30T10:21:25.273" Score="2" ViewCount="" Body="&lt;p&gt;You don't really need to know these things unless you are about to design CPUs yourself, but it all comes down to a huge &lt;a href=&quot;http://en.wikipedia.org/wiki/Finite-state_machine&quot; rel=&quot;nofollow&quot;&gt;state-machine&lt;/a&gt; implemented in hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The biggest problem with this sort of question is that the answer is &lt;em&gt;huge&lt;/em&gt; and takes up several years of University courses, so any answer you get here is only going to scratch the surface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really want to know what goes into a CPU take a look at the vhdl/verilog source code on: &lt;a href=&quot;http://opencores.org/projects&quot; rel=&quot;nofollow&quot;&gt;http://opencores.org/projects&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just learning vhdl and verilog is going to be a large'ish task on it's own, so you are in for a long read:)&lt;/p&gt;&#xA;" OwnerUserId="1675" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-30T13:26:25.327" LastActivityDate="2010-10-30T13:26:25.327" CommentCount="2" />
  <row Id="5879" PostTypeId="1" AcceptedAnswerId="5880" CreationDate="2010-10-30T10:33:02.210" Score="-4" ViewCount="150" Body="&lt;p&gt;I've just read that if I want to implement gate OR with two entries I can't use function like &lt;code&gt;f(A,B) = A + B, f(A,B) = max(A,B)&lt;/code&gt; cause I have &lt;code&gt;noise margin&lt;/code&gt; and &lt;code&gt;forbidden area&lt;/code&gt; but I can use function &lt;code&gt;f(A,B) = 2*max(A,B)&lt;/code&gt; can somebody explain me why? if my gate receive two logic '0' I can pass noise margin if I multiply by 2, am I wrong? thanks in advance&lt;/p&gt;&#xA;" OwnerUserId="1760" LastActivityDate="2010-11-03T00:47:51.987" Title="implementation of the gate OR" Tags="&lt;logic&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="5880" PostTypeId="2" ParentId="5879" CreationDate="2010-10-30T10:43:29.037" Score="0" ViewCount="" Body="&lt;p&gt;max(A,B) would find the maximum of the two inputs. Let's write out a little truth table and compare it to the OR function.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;+-----+-----+-----------+-------+&#xA;|  A  |  B  | max(A, B) | A + B |&#xA;+-----+-----+-----------+-------+&#xA;|  0  |  0  |     0     |   0   |&#xA;|  0  |  1  |     1     |   1   |&#xA;|  1  |  0  |     1     |   1   |&#xA;|  1  |  1  |     1     |   1   |&#xA;+-----+-----+-----------+-------+&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;As can be seen this is the equivalent of A + B. As an aside, min(A,B) is also equivalent to A and B.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't see why you'd use f(A,B) = 2*max(A,B) though - that would give you outputs of 0 or 2. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-30T10:43:29.037" CommentCount="4" />
  <row Id="5881" PostTypeId="1" CreationDate="2010-10-30T10:55:59.240" Score="2" ViewCount="201" Body="&lt;p&gt;A system that I'm developing will use XBee modules for a point to point connection between a micro-controller and a PC. Data will only be sent only in one direction -Micro to PC and  at 10-20fps. The data portion of each frame will be 4 Bytes. XBee modules will be run in transparent mode(to begin with at least). On the PC side I'm using python to grab the data from the serial port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Initially I wrote a very simple python program to grab data 4 Bytes at a time from the serial Port, which worked fine when tested with a virtual com connection (I haven't run any real world tests yet though), but I decided to experiment and ended up implementing a simple frame structure like this.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;sync_flag | Payload_length | frame_number | payload&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;After some research I discovered &lt;a href=&quot;http://en.wikipedia.org/wiki/High-Level_Data_Link_Control&quot; rel=&quot;nofollow&quot;&gt;HDLC&lt;/a&gt; and now I'm considering implementing something similar albeit simpler. Before I endeavor to do so Id like to hear what others have to say. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When is such a protocol merited? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What have you done when you implemented your XBee networks? &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Being somewhat new to this area I'm sure there's some relevant specifics Iv left out, but at the same time I didn't want to make the question too narrow / system specific, but if necessary Ill update the question. &lt;/p&gt;&#xA;" OwnerUserId="819" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-10-30T13:51:57.237" LastActivityDate="2010-10-31T00:45:23.510" Title="Doubts on Implementing a Simple Protocol for XBee Comms" Tags="&lt;serial&gt;&lt;communication&gt;&lt;xbee&gt;&lt;rs232&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="5882" PostTypeId="1" AcceptedAnswerId="5934" CreationDate="2010-10-30T11:08:41.017" Score="2" ViewCount="580" Body="&lt;p&gt;Two weeks ago, I pulled out my AVR JTAG ICE MKII and successfully burned a few C programs to my Arduino through AVRStudio 4 SP3. Everything was working very well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Life caught up to me and I did not touch the Arduino or JTAG until yesterday. I decided that I wanted to play with a few XBees. Downloaded XCTU to update firmware and what not. I realized I needed to reinstall Arduino firmware back on the Diecimila to use the Arduino-XBee shield to update the firmware. I attempted to load the original Arduino boot loader hex file via the JTAGICE2 with AVRProg in AVRStudio and ran into a problem that I have been unsuccessful in solving for the past 9 hours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I switched over to AVRDude so I could see verbose output. Every time I use AVRDude to program the ATMEGA168, I get the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;avrdude: AVR device initialized and ready to accept instructions&#xA;&#xA;Reading |                                                    | 0% 0.00savrdude:&#xA;Send: u [75]   [20]&#xA;avrdude: Recv:&#xA;Reading | ################################################## | 100% 0.05s&#xA;&#xA;avrdude: Device signature = 0xffffff&#xA;avrdude: Yikes!  Invalid device signature.&#xA;         Double check connections and try again, or use -F to override&#xA;         this check.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I also received:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;avrdude: jtagmkII_setparm()&#xA;avrdude: jtagmkII_setparm(): Sending set parameter command (parm 0x03, 1 bytes): 0xa0 (1 bytes msg)&#xA;avrdude: jtagmkII_setparm(): bad response to set parameter command: RSP_FAILED&#xA;avrdude: jtagmkII_getsync(): ISP activation failed, trying debugWire&#xA;avrdude: jtagmkII_setparm()&#xA;avrdude: jtagmkII_setparm(): Sending set parameter command (parm 0x03, 1 bytes): 0xac (1 bytes msg)&#xA;avrdude: jtagmkII_setparm(): bad response to set parameter command: RSP_DEBUGWIRE_SYNC_FAILED&#xA;avrdude: failed to sync with the JTAG ICE mkII in ISP mode&#xA;avrdude: jtagmkII_close()&#xA;avrdude: jtagmkII_close(): Sending sign-off command: avrdude: usb_fill_buf(): usb_bulk_read() error error reaping URB: No such device&#xA;avrdude: jtagmkII_recv(): Timeout receiving packet&#xA;&#xA;avrdude: jtagmkII_close(): timeout/error communicating with programmer (status -1) &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;While using the JTAGICE2, I was connecting its 6 pin header to the ICSP header on the Arduino. I would plug in my 12VDC wall wart first to the Arduino, then turn on the USB connected JTAGICE2, and then open AVRStudio or use AVRDude in DOS to attempt programming. Both programs never had a problem with the jtag itself...just the target. During the JTAGICE2 issue, I would use the following command:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;arduino-0021...\avr\bin&amp;gt;.\avrdude -C .\avrdude.conf -p m168 -c jtag2isp -P usb:64:b0 -vvvv -b 19200 -t&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;or&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;arduino-0021...\avr\bin&amp;gt;.\avrdude -C .\avrdude.conf -p m168 -c jtagmkII -P usb:64:b0 -vvvv -b 19200 -t&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;After quite a few hours without success, I finally pulled out a Arduino Nano v3.0 (ATMEGA328P) and blasted ArduinoISP on it via the latest Arduino Wiring. Connected wires correctly according to the &lt;a href=&quot;http://arduino.cc/en/Tutorial/ArduinoISP&quot; rel=&quot;nofollow&quot;&gt;Arduino.cc (First 'Schematic')&lt;/a&gt; website and attempted to upload the bootloader to the Diecimila again. This time I tried the following avrdude command:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;arduino-0021\..\avr\bin&amp;gt;.\avrdude -C .\avrdude.conf -p m168 -c avrisp -P com4 -b 19200 -vvvv -t&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I continue to receive the same error. The weird thing is that the last program I loaded 2 weeks ago on the Diecimila works perfectly fine. I just cannot get the darn thing off of there!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fact that the error mentioned that the Device Signature of the ATMEGA168 chip is 0xffffff worries me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I believe this problem may be occurring for a few different reasons:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;While programming the Arduino two weeks ago with AVRProg &amp;amp; JTAGICEMK2, maybe fuses were set. I can however tell you that they were in whatever default state AVRProg uses as I NEVER screwed with the fuses tab at all. My most plausible explanation however, is that ISP has been disabled via fuse.&lt;/li&gt;&#xA;&lt;li&gt;Somehow hardware may have been damaged causing the programming capability to not work. I do not know of any damage I did but cannot rule that out.&lt;/li&gt;&#xA;&lt;li&gt;The JTAGICEMKII may be damaged...although receiving the same error using ArduinoISP should disprove that possibility&lt;/li&gt;&#xA;&lt;li&gt;During Google research, I read that the JTAG ribbon cable has major touchy issues. Not sure if this is a serious problem or not.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Well I am officially at a loss. I hope I included all necessary information. I am running this setup off of a stable Windows 7 64bit PC using the latest Arduino, AVR ToolChain, and AVRStudio software available as of two weeks ago. In case it was my desktop computer, I also downloaded Arduino D/L and libusb-win32 on my Vista laptop, attempted AVRDude query using first DOS command and received the first error listed above. Do I just need to buy a new chip? I know they cost nothing but I would prefer to save it and learn from my mistake so I can fix it next time or avoid the problem all together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have any suggestions that might help? Thanks in advance for your reply.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="1575" LastEditorDisplayName="" LastEditDate="2010-10-30T11:28:51.163" LastActivityDate="2010-10-31T15:17:13.323" Title="Arduino Diecimila (ATMEGA168) + JTAG ICE MKII Hell..Did I Fry the Chip?" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;avrdude&gt;&lt;jtag&gt;&lt;isp&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="5883" PostTypeId="2" ParentId="5871" CreationDate="2010-10-30T11:19:04.997" Score="5" ViewCount="" Body="&lt;p&gt;Consider an NPN BJT; a transistor. One of the first discovered.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you wire it up such that the collector is connected to a variable logic input, and the emitter is connected to another logic input, with a resistor in series. Then, a resistor from the emitter to ground.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;               logic&#xA;                 |&#xA;         10k   |/&#xA;logic --/\/\/--|  NPN&#xA;               |&amp;gt;&#xA;                 +-- output&#xA;                 |&#xA;                 /&#xA;                 \ 10k&#xA;                 /&#xA;                 |&#xA;                ---&#xA;                 -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You have just constructed an AND gate. The output is only high when both inputs are high. It's not perfect by any means as it depends on the input to the collector, and because it doesn't fan out well, but it gives you an idea on how transistors can be used to compute a function.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, you can also construct a NOT gate;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;                5V&#xA;                 |&#xA;                 /&#xA;                 \  10k&#xA;                 /&#xA;                 +-- output&#xA;                 |&#xA;         10k   |/&#xA;logic --/\/\/--|  NPN&#xA;               |&amp;gt;&#xA;                 |&#xA;                ---&#xA;                 -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Adding this on to the output of the AND gate just built gives us a NAND gate, and you might know that with a NAND gate you can construct any form of logic. It also has the advantage that the signal is buffered, increasing the fan out and chaining capability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Real processors rarely use BJT's, but instead CMOS logic, but the same principles apply.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-30T11:19:04.997" CommentCount="3" />
  <row Id="5884" PostTypeId="1" AcceptedAnswerId="5889" CreationDate="2010-10-30T11:45:41.730" Score="6" ViewCount="304" Body="&lt;p&gt;Let's say I have a 1 million gate FPGA. I've found a few processors on OpenCores which only require 50k gates. So would it be possible to make, say, an 8 core processor with such an FPGA? Or are there limits to FPGAs when it comes to implementing massively parallel things? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry if it sounds newbish, but I am a newb to FPGAs.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-15T20:22:51.833" Title="Are FPGA's as powerful as the number of gates they have?" Tags="&lt;fpga&gt;" AnswerCount="6" FavoriteCount="2" />
  <row Id="5885" PostTypeId="2" ParentId="5853" CreationDate="2010-10-30T11:53:07.943" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;4P/F to 1P/F Jumper Wire&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mdfly.com/index.php?main_page=product_info&amp;amp;cPath=65_69&amp;amp;products_id=74&amp;amp;zenid=035ga7ae4fmop7s4bmpi424h65&quot; rel=&quot;nofollow&quot;&gt;MDFLY&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jumper wire with one 4-pin female connector on one end and four 1-pin female connectors on the other end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/T4IQ9.jpg&quot; alt=&quot;4P/F to 1P/F Jumper Wire&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;'x'P/F to 'x'P/F Jumper Wire Combination&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mdfly.com/index.php?main_page=product_info&amp;amp;cPath=65_69&amp;amp;products_id=79&amp;amp;zenid=035ga7ae4fmop7s4bmpi424h65&quot; rel=&quot;nofollow&quot;&gt;MDFLY&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Select a jumper wire with 1-pin to 8-pin female connector on each end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WUpLn.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1084" LastEditorUserId="1084" LastEditorDisplayName="" LastEditDate="2010-10-30T12:01:30.990" LastActivityDate="2010-10-30T12:01:30.990" CommentCount="1" />
  <row Id="5886" PostTypeId="2" ParentId="5881" CreationDate="2010-10-30T11:56:13.140" Score="1" ViewCount="" Body="&lt;p&gt;I'm going to be using Xbee modules. I'll be trying to use a point to multipoint network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the moment, I plan to have a transmitter identifier, payload type, payload length, payload and checksum - it would look something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Field            Type    Description   &#xA;transmitter_id   uint8   Identifies the transmitting module (0-255)&#xA;type             uint8   Type of data (GPS coordinates, hit status, etc.)&#xA;length           uint8   Length of payload in bytes&#xA;payload          -       Actual payload&#xA;checksum         uint16  CRC16 of everything before&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;That's how I imagine it, the format might change but this will be the basic protocol in use.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-30T12:18:22.013" LastActivityDate="2010-10-30T12:18:22.013" CommentCount="2" />
  <row Id="5887" PostTypeId="2" ParentId="5871" CreationDate="2010-10-30T11:57:43.797" Score="2" ViewCount="" Body="&lt;p&gt;Maybe you should look up some digital systems references or look into stuff like VHDL. An MCU is basically designed with building blocks, which can be a variety of logic gates and (smaller) building blocks. Ultimately it all goes down to logic gates which are indeed composed with transistors. A typical simple MCU like a PIC18F or something doesn't run an operating system. The program you load into it are a bunch of machine instructions that the PIC runs continuously. All of the proccesing is done by hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A general proccesor usually has an ALU (computes the result of a certain instruction) and a more blocks around it that loads instructions, manages stack and manages the memory. The proccesor has a few registers to work with it itself, mainly to load inputs and store results in. You might not see much of this in C or another language but a lot of it in assembly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ALU handles instructions with certain operation codes and inputs. For example, a typical instruction could be ADD 12 1 , which means 12+1 = 13. The result is stored in a register on the proccesor itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the architecture, the ALU is for example 8 bits wide. A simple 8 bit adder can be made of 8x 1-bit adders tied together (using blocks to build a bigger block). A 1-bit adder can be easily written down to logic gates using boolean algebra. Writing down a whole 8-bit adder manually with only using logic gates would be an insane amount of work. That's like writing a program without having the ability to use any function or subroutines at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make the digital systems work correctly , most blocks are designed to clock based. Every digital system has a certain amount of time required to reach it's end state. This is due to switching delays in transistors and states influencing other states. The clock signal is something you should be familiar with, the speed the proccesor runs on. A timer could be a really simple device that has a little adder block and increments by 1 every time it gets a clock tick. &lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-10-30T11:57:43.797" />
  <row Id="5888" PostTypeId="2" ParentId="5867" CreationDate="2010-10-30T12:05:43.710" Score="4" ViewCount="" Body="&lt;p&gt;The cap charges through all three resistors, until it reaches a voltage where the NPN base-emitter junction starts to conduct. At that point, the NPN allows current to flow into its collector, which means it begins to draw current from the base of the PNP, turning it on, too. Now, the base of the NPN will be somewhere in the range of 0.6 to 0.8 volts while that transistor is on, and that's one leg of the cap. The other leg of the cap experiences the I-R drop that occurs on the 10 ohm resistor. The closer the PNP gets to saturation, the closer the top of that 10 ohm will get to being a voltage divider formed with the 47 ohm resistor. Now I don't see the battery voltage here, but I'd bet its at least 5V. At 5V, the voltage at the top of the 10 ohm will &lt;em&gt;approach&lt;/em&gt; 5*(10/(10+47)) = 0.88 V (discounting Vce-sat of the PNP). This means that the capacitor now sees a voltage higher on the right side, so current begins to flow the other direction. While charging up, the cap built up a charge with (+) on the left and (-) on the right, so the capacitor now looks like a tiny battery in series with the 0.88V on the 10 ohm, so it basically discharges into the base of the NPN, helping keep that transistor on. Once the cap has charged up in this opposite direction, it ceases to conduct, and behaves again like a DC open circuit, leaving the NPN biased only by the 120K, which isn't enough to keep the transistor active. So the NPN shuts off, this kills the PNP, and we're back to the start .. only you can see that the capacitor not only has to charge 'up', it has to actually discharge the reverse-polarity charge first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for trying to use just NPN - you might be able to do it with &lt;em&gt;three&lt;/em&gt; NPN's, but two seems unlikely. Essentially, the second transistor needs to be something that passes current under control of a node that is either very high impedance or connected to the negative rail, which just shouts PNP. To go NPN-only, you'd need to move the 2nd transistor (call it Q3) to between the 10 ohm and the negative rail, and you'd need an intermediate stage (call it Q2) to act like an inverter, delivering current into the base of Q3 only when the original NPN (call it Q1) is conducting. There would have to be a pull-up resistor on the collector of Q1, to supply current to the base of Q2 when Q1 is off. You'd need another pull up resistor on the collector of Q2, which would feed current into the base of Q3 when Q2 is off.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-10-30T13:00:15.083" LastActivityDate="2010-10-30T13:00:15.083" CommentCount="2" />
  <row Id="5889" PostTypeId="2" ParentId="5884" CreationDate="2010-10-30T12:10:21.570" Score="5" ViewCount="" Body="&lt;p&gt;Yes in principle. Although if you want them to talk to each other, it may use quite a lot more logic for arbitration, bus switching etc. and when running busses around the FPGA a lot of gates and connection capacity may get used up for routing.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-10-30T12:10:21.570" />
  <row Id="5890" PostTypeId="2" ParentId="5845" CreationDate="2010-10-30T12:11:39.900" Score="4" ViewCount="" Body="&lt;p&gt;I looked some Y5V caps up last week. The money is what you get, they are very cheap, and very bad. They might lose about 80% or their capacity over temperature or voltage. Depending if you need the capacity, you might be better of spending a bit more on X5R.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastEditorUserId="1476" LastEditorDisplayName="" LastEditDate="2010-10-30T14:47:26.830" LastActivityDate="2010-10-30T14:47:26.830" />
  <row Id="5891" PostTypeId="1" AcceptedAnswerId="5897" CreationDate="2010-10-30T13:17:21.067" Score="1" ViewCount="142" Body="&lt;p&gt;What is the failure mode of flash memory? I've got some chips rated for 10,000 cycles - what happens after 10k cycles? Do the chips stop writing properly, do you get read errors, etc.? Does it also happen to EEPROMs?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-30T16:51:46.073" Title="Failure mode of FLASH memory" Tags="&lt;flash&gt;&lt;eeprom&gt;&lt;durability&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="5892" PostTypeId="2" ParentId="5871" CreationDate="2010-10-30T13:47:25.627" Score="2" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;I mean are these 1's and 0's converted into corresponding logic voltage (5v and 0) by DAC?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;No, not a DAC.  The 1s and 0s never really exist.  They're just a mathematical abstraction we use to make programming easier.  The actual digital voltages might be 5 V, or 3.3 V, or 1 V, depending on the hardware.  Ultimately a computer is just digital logic.  The memory stores the 1s and 0s as digital logic, a digital logic circuit transfers them from memory to the processor, the processor is a digital logic circuit that can add, subtract, or compare binary numbers, etc.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;how does this small piece of silica&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Silic&lt;b&gt;a&lt;/b&gt; is glass, a mixture of silicon and oxygen.  Chips are made from pure silic&lt;b&gt;on&lt;/b&gt;, with impurities added in specific places to make all the transistors.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I understand that every single IC is made of logic gates&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Digital ICs are made from logic gates, not analog ICs.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;So how does these transistors respond to various combinations of 5v and 0v?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Read up on the simplest example, the &lt;a href=&quot;http://bwrc.eecs.berkeley.edu/classes/icdesign/ee141_f99/notes/chapter5.pdf&quot; rel=&quot;nofollow&quot;&gt;CMOS inverter&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-30T13:47:25.627" CommentCount="3" />
  <row Id="5893" PostTypeId="2" ParentId="5871" CreationDate="2010-10-30T14:06:21.930" Score="2" ViewCount="" Body="&lt;p&gt;This is a big topic and I can't give a simple answer but...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get a little closer to this answer by doing some divided and conquer, &#xA;and since the other answer tries to attack this problem from a hw point of view&#xA;I will try from a high level SW view.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you write some software in let's say c code (a very high level of abstraction), &#xA;you do not really see what is happening not really understand all of the lover stuff that you are asking about.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But let's begin there anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A simple program that just inc a variable.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int main(void)&#xA;{&#xA;    int i=0;&#xA;    while(1) {&#xA;        i++;&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then we need to get the assembler code so we can understand what is going on.&#xA;This step can be done on what ever platform you use, &#xA;but to keep it simple I use gcc on a pc (but it does not matter...)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;gcc -O0 -S main.c -o main.lst&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then we end up with something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    .file   &quot;main.c&quot;&#xA;    .text&#xA;.globl main&#xA;    .type   main, @function&#xA;main:&#xA;    pushl   %ebp&#xA;    movl    %esp, %ebp&#xA;    subl    $16, %esp&#xA;    movl    $0, -4(%ebp)&#xA;.L2:&#xA;    addl    $1, -4(%ebp)&#xA;    jmp .L2&#xA;    .size   main, .-main&#xA;    .ident  &quot;GCC: (Ubuntu 4.4.3-4ubuntu5) 4.4.3&quot;&#xA;    .section    .note.GNU-stack,&quot;&quot;,@progbits&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then you try to understand every line of code and what it does.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And then you start to look into how every instruction is implemented...&#xA;For example the subl&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    subl    $16, %esp&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;At this point it is different on different architectures and x86, arm, pic is kind of different...&#xA;But since my example was x86.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/X86_assembly_language&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/X86_assembly_language&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;subl    $4,%esp    /* allocate 4 bytes of stack space for this function's local variables */&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;And at this level when you read the copy most of actions will look like you are just moving numbers around, and in some sense this is what is happening.&#xA;We have a predefine program that we step trough, this program is store in a some kind of flash memory that is usually some kind of electronic logic that will trap one logic level. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you see some kind of &quot;&lt;a href=&quot;http://www.electronics-tutorials.ws/sequential/seq_1.html&quot; rel=&quot;nofollow&quot;&gt;Flip-flop&lt;/a&gt;&quot; for every bit then you are kind of close, and then we needs a lot of those. Here we start to find your ones and zeros.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then in order for some action to occur we add some cool logic that can transform one number into another number (the CPU it self).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And then we follow the program one step at a time, and to know where we are we have a program counter (PC). And move numbers back and fourth and storing those in another memory that is also kind of a grid with flip-flops.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But let's go back into some specific example again, &#xA;in order to understand the CPU a little better we can have a look at the &lt;a href=&quot;http://en.wikipedia.org/wiki/Arithmetic_logic_unit&quot; rel=&quot;nofollow&quot;&gt;ALU&lt;/a&gt; and this &lt;a href=&quot;http://en.wikipedia.org/wiki/File:2-bit_ALU.png&quot; rel=&quot;nofollow&quot;&gt;simplified picture&lt;/a&gt;.&#xA;Where you can see that when we move data into this logic block and do select some operation with the OP pins, we will get a new result at the output.&#xA;That we in turn can move back into some place in memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And of curse your ALU in your CPU part of your MCU is way more complex that this one, but it operates with the same basic principle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At this point we kind of can see some logic circuit that does the &quot;work&quot; on one side, and some storage on the other side. And the storage has two parts, one for the program and one for the data.&#xA;But how does we actually &quot;move&quot; then, those must be connected in some way...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And this is where we connect those parts with some a bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A bus is just some wires that connects the different parts together, and then the control logic tells the memory what data to send onto this bus, and what part of the CPU that should listen to this data that was sent. And this is done with some parallel control lines that will enable/disable the different parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;...&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;So if you take your mcu of choice and dissect a very small program, &#xA;and as long as you do not understand what is happening you dissect it even more until you have a nice little puzzle that can be used to create a &quot;mcu&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And don't forget to read the datasheet for your mcu and look into what kind of parts it was made with, like what kind of memory, alu, busses etc etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps a little ???&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck&lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2010-11-01T07:22:15.263" LastActivityDate="2010-11-01T07:22:15.263" CommentCount="1" />
  <row Id="5894" PostTypeId="2" ParentId="5871" CreationDate="2010-10-30T14:07:48.153" Score="6" ViewCount="" Body="&lt;p&gt;Get the book &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/073560505X&quot; rel=&quot;nofollow&quot;&gt;&quot;Code: The Hidden Language of Computer Hardware and Software&quot; by Charles Petzold&lt;/a&gt;. It is awesome, easy to read, and will answser many of those questions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't afford Petzold's book, then check out &lt;a href=&quot;http://www.fastchip.net/howcomputerswork/p1.html&quot; rel=&quot;nofollow&quot;&gt;&quot;How Computers Work&quot; by Roger Young&lt;/a&gt;. It covers much of the same stuff, and the HTML and PDF versions are free.&lt;/p&gt;&#xA;" OwnerUserId="1199" LastEditorUserId="1199" LastEditorDisplayName="" LastEditDate="2010-10-30T19:13:56.377" LastActivityDate="2010-10-30T19:13:56.377" CommentCount="1" />
  <row Id="5895" PostTypeId="2" ParentId="5891" CreationDate="2010-10-30T14:37:11.710" Score="4" ViewCount="" Body="&lt;p&gt;Here's a project designed to destroy an EEPROM by writing to it repeatedly:  &lt;a href=&quot;http://dangerousprototypes.com/2010/05/25/prototype-flash_destroyer/&quot; rel=&quot;nofollow&quot;&gt;Flash Destroyer&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to the comments, though, it's not a particularly good demonstration:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I am guessing that this test will actually not show the real problem very obviously, or should I say early. Since I think the real issue is that the data retention time will drop with number of writes. I.e. after 1 million writes it will store the data for a number of hours specified in the datasheet.&#xA;  Eventually the data retention time will be so short you will see problems, but in real-life, problems with lost data would occur much earlier.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I also asked a similar question on SuperUser: &lt;a href=&quot;http://superuser.com/questions/102228/what-happens-when-a-flash-drive-wears-out&quot;&gt;What happens when a flash drive wears out?&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-10-30T14:37:11.710" />
  <row Id="5896" PostTypeId="2" ParentId="5871" CreationDate="2010-10-30T16:12:51.913" Score="5" ViewCount="" Body="&lt;p&gt;There is no need to use a DAC. Voltages are used to represent 1's and 0's by the convention that anything under 0.8V (AKA 'low') is a zero, and anything over 2.4V (AKA 'high') is a one. It's relatively simple to construct circuits that perform logic on these representative voltages. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, a circuit can output something in the 2.4V to 5V range to represent '1' if either input is over 2.4V, or something less than 0.8V otherwise, and you have an OR gate. If it requires &lt;em&gt;both&lt;/em&gt; inputs representing 1 in order to output 2.4V, you have an AND gate. An inverter just outputs a high when the input is low, and vice-versa. You can build simple gates like these with just a very few transistors, and perform combinatorial boolean logic. By using groups of bits to represent numbers, you can even build circuits to add numbers with combinatorial logic, no software required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you are working with gates, you can construct flip flops, and from them, registers and counters. Flip-flops allow you to store 1's and 0's from one point in time and use them later on. Registers and counters are circuits that perform functions on groups of bits that represent numbers. A register holds a number until you load a new number into it. A counter is like a register, but has another input that causes the stored number to increment. (Decrement is possible too). This puts you in the realm of state machines and sequential logic, still, no software required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Memory systems are a way to store massive numbers of bits. At a component level, some memory is built like a huge collection of flip-flops, but more commonly there is another technology (DRAM) that, while not exactly a flip flop, does the same thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a further step, you can build a system of sequential and combinatorial logic that can carry out operations depending on the bits stored in a memory system, including writing back new values to that memory system. Now you've arrived at the level of the processor, and everything the processor does, is just hardware carrying out lots of simple tasks. (microprogrammed cores notwithstanding). At this point, the particular combinations of bits that you put in the memory system can be considered machine language software.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-30T16:12:51.913" CommentCount="2" />
  <row Id="5897" PostTypeId="2" ParentId="5891" CreationDate="2010-10-30T16:38:30.457" Score="4" ViewCount="" Body="&lt;p&gt;Flash memory degrades as a function of the number of write-erase cycles it is subjected to. Essentially the dielectric structure of the memory cell degrades and becomes unable to maintain a 'low' state. (Think of a N-channel MOSFET - a high on the gate turns the device on, which makes the drain-source resistance low. If the gate is damaged, the drain-source channel can never be established.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is often a mechanism to 'mask' these bad blocks once they're identified (usually by a verify operation failing after a write) preventing them from being used - a bad block table, essentially.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See &lt;a href=&quot;http://www.linfo.org/flash_memory.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/Flash_memory&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; for more details on the physics of it all.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-10-30T16:38:30.457" />
  <row Id="5898" PostTypeId="2" ParentId="5891" CreationDate="2010-10-30T16:51:46.073" Score="3" ViewCount="" Body="&lt;p&gt;I suppose if your flash is broken, you can write a value to it but i doesn't take it correctly. For example, some bits are maybe unable to go low anymore which yields a different value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some flash drives in PC's like SSDs have controllers that monitor the broken parts of the flash chips and saves the data to different spots and reports a decrease in capacity. It's just like a normal hard drive has about 0,5% of extra sectors when some turn out to be bad sectors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are speaking in normal EEPROM chips or memories that are embedded into MCU's or external, I am not sure if they got any error correction system built in. It might just write the value and not know it fails in doring so correctly.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-10-30T16:51:46.073" />
  <row Id="5899" PostTypeId="1" AcceptedAnswerId="5901" CreationDate="2010-10-30T16:59:28.210" Score="3" ViewCount="245" Body="&lt;p&gt;I've done 5 or so Arduino projects now and am at the point where I think I'm outgrowing the whole pre-packaged platform/shield arrangement.  It was great for lowering the barrier to entry of getting into microcontroller projects, and for quickly getting projects off the ground, but I'm really seeing the cost and implementation tradeoffs impacting me more and more these days.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One question that has been bugging me is, why do shield designers and manufacturers leave so little room for other circuit elements in their design?  Who really does a project that is literally just an arduino and a shield?  Doesn't everyone hook up other inputs and outputs to fully realize the vision behind their project?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a shield only needs and uses 5 or so pins, why not omit the headers for the other ones, or better yet provide some blank through holes/pads connected to the unused underlying arduino pins for the user to utilize as they see fit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know some shields do this to some extent.  The Speakjet/voice shield from Sparkfun for example has a relatively large open prototyping section.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems like shield designers almost go out of their way to make it more difficult than it needs to be to tap into the pins their design doesn't use, by calling for headers that seem to only serve as a mechanical connection to the arduino, surfacing with a tiny soldered nub you can tack a wire onto but can't make a solid mechanical connection?  Or am I missing something basic in my soldering/construction skills?  Is there a better way to utilize pins a shield doesn't need?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know about stackable headers...but wouldn't it be better to provide a more directly solder-friendly set of through holes for tapping into the unused pins?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again, maybe this is just reflective of where I'm at with my relationship with arduino right now...ready to get off the yellow brick road of arduino + shield = solution and into using the arduino strictly as a dev and prototype platform.&lt;/p&gt;&#xA;" OwnerUserId="707" LastActivityDate="2010-10-31T12:41:54.483" Title="Why do Arduino shield kit designers &quot;consume&quot; pins they don't use?" Tags="&lt;arduino&gt;&lt;arduino&gt;&lt;subjective&gt;&lt;shield&gt;" AnswerCount="2" />
  <row Id="5901" PostTypeId="2" ParentId="5899" CreationDate="2010-10-30T17:52:01.253" Score="2" ViewCount="" Body="&lt;p&gt;I suspect that most shield designers either don't think of it or run out of time. When I've made shields (for personal projects), I've had intentions at the start of adding other features, but by the time everything is laid out, I just think, &quot;OK, this will work. Maybe I'll add that other stuff on the next rev.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adding blank holes for hacking on extra stuff is a great idea. Given that most (all?) of the shields on Sparkfun are open hardware, why don't you make an improved version? I suspect that the Sparkfun folks would be delighted to accept your improvements.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-30T17:52:01.253" />
  <row Id="5902" PostTypeId="2" ParentId="5801" CreationDate="2010-10-30T18:50:01.740" Score="2" ViewCount="" Body="&lt;p&gt;4800 baud is one character every 2ms. This is a dog's-age to most microcontrollers (PICs included) and you shouldn't have ANY problem collecting the data from the UART's holding register. Remember that even the most simple UART has a built-in 2 character FIFO (the holding register and the shift register). If you can't find a few cycles every 2ms to pick up a character then you need to find a beefier processor, one with a FIFO or split the job up as other people have mentioned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The dsPIC you mentioned has 4-byte FIFOs on the UART and also has DMA capability. While 90% is a high system load for OSD (are you sure you're doing your OSD in the most efficient manner possible?) I don't know why you'd have trouble pulling in a 4800 byte NMEA stream at this system load. Missing the odd GPS update probably won't affect your application all that much, either.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-30T18:50:01.740" />
  <row Id="5903" PostTypeId="1" CreationDate="2010-10-30T19:13:22.070" Score="2" ViewCount="449" Body="&lt;p&gt;I'm building out a circuit with an ATmega 1281 MCU, some switches for input and a Nokia 5110 LCD (SPI interface) for display. I can load code on it just fine with my USBtinyISP programmer. With the programmer connected, the code runs great. It sits there and will chug away for hours. When I remove the programmer and reset the MCU, things either freeze up or the display gets really hinky and displays garbage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both the LCD and the ICSP are SPI interfaces. In attempts to get it run without the ISP connected, I've tried pulling both up and down with a 10K resistor on MISO, MOSI, SCK and RST. Nothing makes a difference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone else ever seen this happen? What did you do to fix it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(edit: image added to question)&#xA;&lt;img src=&quot;http://duksta.org/images/ProtoBreakout.png&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="746" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-30T22:24:41.023" LastActivityDate="2010-11-01T11:20:39.207" Title="atmega1281 + Nokia 5110 LCD circuit works with USBtinyISP plugged in. Hangs without?" Tags="&lt;avr&gt;&lt;atmega&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="5904" PostTypeId="1" AcceptedAnswerId="5911" CreationDate="2010-10-30T20:19:39.363" Score="3" ViewCount="233" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Why is my transistor only driving 5V instead of 6V?  How can I fix it?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I have a 6V, 25mA circuit running some LEDs.  I can control them by connecting and disconnecting the positive terminal of the battery pack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to control them with an Arduino.  So I added an NPN bipolar junction transistor with the base attached to the arduino's digital output pin and the collector-emitter acting like a wire from the positive terminal of the battery to the LED circuit.  I also connected the Arduino's ground to the battery's negative terminal, but the Arduino is powered off a separate power supply.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;          o---------o&#xA; #####    |         |&#xA; #   #  |/         /+\&#xA; # A #--|         (   )&#xA; # R #  |&amp;gt;         \-/&#xA; # D #    | ####### |&#xA; # U #    | #     # |&#xA; # I #    o-# LED #-o&#xA; # N #      #     # |&#xA; # O #      ####### |&#xA; #   #              |&#xA; #####--------------o&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The problem is that the LED circuit really needs 6V to run, while the Arduino's digital pins only output 5V.  I don't quite understand why, but even though the collector is attached to 6V, the emitter is not really driving 6V, even when the base is on at 5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a little hard for me to debug, since the circuit is all diode-y, so if it doesn't get enough voltage that part just turns off in a non-ohmic way.  Part of the circuit only needs 5V to function, and it works, but the longer series of LEDs only works when I connect the base to a 6V source.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;What is going wrong, and just as importantly, how do I fix it?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1271" LastEditorUserId="1271" LastEditorDisplayName="" LastEditDate="2010-10-30T20:42:05.093" LastActivityDate="2010-10-30T23:47:42.047" Title="Transistor with two voltage levels, Vb ≠ Vcc" Tags="&lt;voltage&gt;&lt;transistor&gt;&lt;basic&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="5905" PostTypeId="2" ParentId="5903" CreationDate="2010-10-30T20:26:38.933" Score="0" ViewCount="" Body="&lt;p&gt;There are lots of things it could be, here are some ideas:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You definitely need to tie RST high with a resistor&lt;/li&gt;&#xA;&lt;li&gt;Is your power source good enough? Are you powering your circuit from USB?&lt;/li&gt;&#xA;&lt;li&gt;What settings do you have for the brownout detection fuses in the AVR?&lt;/li&gt;&#xA;&lt;li&gt;Do you have a decoupling capacitor placed near the power pin of the AVR?&lt;/li&gt;&#xA;&lt;li&gt;Does the AVR circuit work ok without the display connected (can it blink an LED reliably)?&lt;/li&gt;&#xA;&lt;li&gt;What are the power supply requirements of the display? Are you powering it from the same source as the AVR?&lt;/li&gt;&#xA;&lt;li&gt;Does it work if you turn the LCD backlight off?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-30T20:26:38.933" CommentCount="5" />
  <row Id="5906" PostTypeId="2" ParentId="5904" CreationDate="2010-10-30T20:57:42.650" Score="1" ViewCount="" Body="&lt;p&gt;For something like an LED, put the transistor on the low side (that is, emitter connected to ground.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: It seems I should have expanded, as I have got -1 perhaps due to my vague asnwer. If you put it on the low side, then any signal above 0.7V will usually saturate it (turn it completely on.) &lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-30T23:47:42.047" LastActivityDate="2010-10-30T23:47:42.047" />
  <row Id="5907" PostTypeId="2" ParentId="5884" CreationDate="2010-10-30T21:10:05.913" Score="3" ViewCount="" Body="&lt;p&gt;You'll find gate counts are barely estimations, rather than simple facts about the FPGAs. Looking more closely, the gate counts advertised will include things like using portions of block RAM for logic, and the logic you synthesize will not be reduced to a single standard gate type as if you were building with nothing but 2-input NAND gates, since the logic blocks are a fair bit more complex - typically featuring LUTs with 4 or more inputs for each register. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the real question is how efficiently the synthesis software can map your specific design to your specific chip. You probably can do an 8 core processor easily - if the cores, and just as importantly their interconnects, suit the chip well enough. It's quite possible a design fails for lack of signal routing rather than lack of logic. &lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-10-30T21:10:05.913" />
  <row Id="5908" PostTypeId="2" ParentId="5899" CreationDate="2010-10-30T21:40:31.817" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=17_21&amp;amp;products_id=94&quot; rel=&quot;nofollow&quot;&gt;Adafruit audio shield&lt;/a&gt; has a row of vias next to the headers so you can solder a connection directly on, I think it's a good approach for a shield with unused pins, but your right - a lot of shield designs just offer the headers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For my own shield designs I try to use stackable headers and I rarely bother with a prototyping area (normally out of laziness) - I guess you can always jam a &lt;a href=&quot;http://www.ladyada.net/make/pshield/&quot; rel=&quot;nofollow&quot;&gt;proto board&lt;/a&gt; right on top. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think shields are good tools for prototyping, but I agree they should probably add more prototyping areas, I also agree with Pingswept that designers probably over look this or can't be bothered.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the great thing is...they're open source and you can change them to suit, this probably won't make it any cheaper tho (unless it's a supper minimal design) but it will probably help to reduce the project's size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe, if you don't have the opportunity to make the changes yourself, you could make some suggestions to the &lt;a href=&quot;http://www.sparkfun.com/commerce/static.php?name=customer_service&quot; rel=&quot;nofollow&quot;&gt;chaps and chapettes at Sparkfun&lt;/a&gt; - they're a friendly bunch.    &lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-10-31T12:41:54.483" LastActivityDate="2010-10-31T12:41:54.483" />
  <row Id="5909" PostTypeId="2" ParentId="984" CreationDate="2010-10-30T22:18:56.567" Score="1" ViewCount="" Body="&lt;p&gt;You can use &lt;a href=&quot;http://www.digi.com/support/productdetl.jsp?pid=3352&amp;amp;osvid=57&amp;amp;s=316&amp;amp;tp=5&amp;amp;tp2=0&quot; rel=&quot;nofollow&quot;&gt;X-CTU&lt;/a&gt;, which is a lightweight XBee programmer that has a very good serial terminal in one of its 4 tabs. It features&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Hexadecimal view&lt;/li&gt;&#xA;&lt;li&gt;Text view&lt;/li&gt;&#xA;&lt;li&gt;CTS, CD and DSR line statuses&lt;/li&gt;&#xA;&lt;li&gt;DTR, RTS and Break assertions&lt;/li&gt;&#xA;&lt;li&gt;1-click port opening and closing&lt;/li&gt;&#xA;&lt;li&gt;Text editor for sending data in packets&lt;/li&gt;&#xA;&lt;li&gt;Clear screen button&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-10-30T22:24:18.597" LastActivityDate="2010-10-30T22:24:18.597" />
  <row Id="5910" PostTypeId="2" ParentId="5904" CreationDate="2010-10-30T22:32:52.177" Score="3" ViewCount="" Body="&lt;p&gt;Sounds like the load you're driving is floating the emitter voltage up to where the signal from the arduino can't really completely saturate the transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could move the load up so that it's between the transistor's collector and the battery, and wire the transistor's emitter to ground. This will ensure that the signal from the arduino will be high enough relative to the base-emitter junction to get the transistor on and saturated. In fact, you would probably want to put a current limiting resistor between the arduino output and the base of the transistor, something in the 500 to 2000 ohms ballpark.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-30T22:32:52.177" />
  <row Id="5911" PostTypeId="2" ParentId="5904" CreationDate="2010-10-30T23:15:48.520" Score="4" ViewCount="" Body="&lt;p&gt;You can do this a number of ways. I usually drive transistors in common-emitter mode when using them as switches. The emitter of the NPN transistor goes to the common (ground) rail, the collector to the cathode of the LED and then a current limiting resistor to B+. The transistor will turn on when the base voltage is approximately 0.7V above the emitter voltage. Use a resistor on the base of the transistor (to the I/O pin) since BJTs are current controlled devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the I/O line goes high (say +5V), you will have 5V across the resistor and the B-E junction of the transistor. The transistor B-E junction will drop 0.7V with the remainder (4.3V) across the resistor. Say you use 1k for the base resistor. This will give you 4.3/1000 or 4.3mA of base drive current. This is TONS of current, and since the B-E junction is forward-biased it will amplify the base current by the gain of the transistor (usually between 50 and 200) and limit the C-E current to this level. (When using transistors as switches you usually don't care about the actual collector current, you just want to make sure the transistor is allowing much more current than you will actually draw.) The end result is that the transistor is fully on and your LED will light, limited by the series resistor you chose to limit the LED current to something like 10-20mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the I/O line is low, the B-E junction has no appreciable voltage across it and the transistor is considered &quot;off.&quot;  I like to include a 4.7k-ish resistor between the base and emitter to make sure that the transistor doesn't accidentally switch on due to noise or a floating I/O pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This basic NPN switch circuit works well as long as your C-E voltage is under about 30V and your load is mainly resistive and relatively low current (under a few Amps). When you're trying to control higher voltages you have to start looking at either more specialized (high voltage) transistors or more complex drive circuits. When driving inductive loads (relays, motors, etc.) you need to protect the transistor from the inductive kickback that occurs when current stops flowing through an inductor.  When driving high current loads you may have to again look at specialized transistors or more complex drivers to ensure the transistor remains fully switched-on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your load must be connected to common (instead of the transistor emitter) then you can use a PNP transistor. Emitter to B+, collector to the LED anode, LED cathode to a current limit resistor and the other end of the resistor to common. Now a logic '1' should turn the LED off and a logic '0' should turn it on, but you've got a problem. The problem is that your I/O line cannot turn the transistor off, because the highest voltage it can reach is 5V (in our example). This would maintain 1V across the B-E junction and the transistor would remain on, even only if partially on.  In this case I like to &quot;cheat&quot;. You can turn the I/O line into an input to turn the transistor off (remember I like to have a 4.7kish resistor between the base and emitter). This is not ideal because it slows down your turn-off (which may or may not be a problem) but also because you now have (in this example) 6V going to an I/O line. It may not be able to withstand this kind of voltage and you can damage the line or the internal protection circuitry on the input.  What I do to mitigate the problem is to use an NPN transistor to turn on the PNP transistor. This doesn't solve the turn-off problem but for most general cases it's nothing to worry about.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-30T23:15:48.520" />
  <row Id="5912" PostTypeId="1" AcceptedAnswerId="5918" CreationDate="2010-10-30T23:50:27.347" Score="3" ViewCount="271" Body="&lt;p&gt;I want to use a linear regulator for some application, it's in a SOT-223 (not SOT-89) package. How do I keep it cool, preferably without a bulky heatsink? The regulator may be dissipating 2-3W of heat. I've heard that you can use copper traces under the regulator on the PCB to keep the regulator cool; does anyone have any references on this? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-10-31T00:31:40.993" LastActivityDate="2010-11-01T20:01:31.017" Title="How to keep a linear regulator cool without an actual heatsink?" Tags="&lt;heatsink&gt;&lt;linear&gt;&lt;regulator&gt;" AnswerCount="6" />
  <row Id="5913" PostTypeId="2" ParentId="5628" CreationDate="2010-10-30T23:56:29.183" Score="5" ViewCount="" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please, please: don't build a SD host: build a MMC Host! that way, you can read SD cards, using MMC mode!  off course, in order to use microSD, you will need the microSD -&gt; SD (MMC) adapter.  I believe that in this way, you don't need to pay the royalties, but if I'm wrong, somebody tell me!&lt;/p&gt;&#xA;" OwnerUserId="1777" LastActivityDate="2010-10-30T23:56:29.183" CommentCount="3" />
  <row Id="5914" PostTypeId="1" AcceptedAnswerId="5921" CreationDate="2010-10-31T00:02:22.743" Score="3" ViewCount="261" Body="&lt;p&gt;Hi All!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I create an device running Linux (Android OS) with video output?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. I don't want to use an existing very sophisticated dev board, I want to create one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1539" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-31T00:55:24.780" LastActivityDate="2010-10-31T01:47:45.537" Title="MCU + Linux + Video?" Tags="&lt;pic&gt;&lt;video&gt;&lt;android&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="2" />
  <row Id="5915" PostTypeId="2" ParentId="5914" CreationDate="2010-10-31T00:13:40.173" Score="1" ViewCount="" Body="&lt;p&gt;Not possible. PIC microcontrollers are not 32-bit, nor do they have anything even close to the requirements of even the smallest Linux kernel, let alone userspace.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even PIC32s still do not have the resources that even a tiny Linux kernel requires.&lt;/p&gt;&#xA;" OwnerUserId="974" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-31T00:59:31.657" LastActivityDate="2010-10-31T00:59:31.657" CommentCount="3" />
  <row Id="5916" PostTypeId="2" ParentId="5914" CreationDate="2010-10-31T00:14:49.433" Score="1" ViewCount="" Body="&lt;p&gt;I hate to put a downer on your idea, but I don't think you could get a PIC running Linux and certainly not Android. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may just about be able to get a PIC32 running a basic RTOS, but not Linux - as the PIC32's don't have enough memory (128KB maximum.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-31T00:14:49.433" CommentCount="6" />
  <row Id="5917" PostTypeId="2" ParentId="5914" CreationDate="2010-10-31T00:20:51.300" Score="1" ViewCount="" Body="&lt;p&gt;Microcontrollers are complete computers (RAM + CPU + storage + I/O) all on a single chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far as I know there are no Linux ports to microcontrollers which can run without extra external RAM - so Linux needs 2 or more chips (except in FPGAs, perhaps).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are looking for a well supported Linux dev board with video output, the &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;beagleboard&lt;/a&gt; is a popular choice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, you can &lt;a href=&quot;http://electronics.stackexchange.com/questions/1738/whats-the-simplest-linux-capable-board-i-could-make-at-home&quot;&gt;build your own&lt;/a&gt;. But, you'll also need some kind of video processor and video RAM to produce anything more than basic graphics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On top of all that, Android is big - really big.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some relevant tags:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/tagged/android&quot;&gt;android&lt;/a&gt;,&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/tagged/pic&quot;&gt;pic&lt;/a&gt;,&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/tagged/microcontroller&quot;&gt;microcontroller&lt;/a&gt;,&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/tagged/linux&quot;&gt;linux&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-10-31T01:14:03.563" LastActivityDate="2010-10-31T01:14:03.563" />
  <row Id="5918" PostTypeId="2" ParentId="5912" CreationDate="2010-10-31T00:27:19.477" Score="9" ViewCount="" Body="&lt;p&gt;You won't be able to dissipate that much heat with only copper traces to wick away the heat. (A SOT-89 is also a very small package, are you sure that specific part in that specific package is rated for 3W?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use D-Pak sized packages with lots of copper on the four layers and arrays of vias to try to give the device a lot of copper for a heat sink.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/9QEPi.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This works reasonably well for low duty cycle loads but doesn't work well for continuous load applications (there is high thermal resistance to the air). For high dissipation requirements you need fins and air moving over them, and unless you're building circuit boards differently than I know how to, you're going to need a heat sink to get those fins.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-10-31T00:27:19.477" CommentCount="3" />
  <row Id="5919" PostTypeId="2" ParentId="5881" CreationDate="2010-10-31T00:45:23.510" Score="1" ViewCount="" Body="&lt;p&gt;When you come out of transparent mode, I assume that the XBee exposes the payload of &lt;a href=&quot;http://freaklabs.org/index.php/Articles/Zigbee/IEEE-802.15.4-in-the-Context-of-Zigbee-Part-2-MAC-Layer.html&quot; rel=&quot;nofollow&quot;&gt;802.15.4&lt;/a&gt; frames to your application. However, it's possible that your data will be packed into a ZigBee APS/NWK frame too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://freaklabs.org/images/stories/802_15_4_Zigbee/general_frame_format.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Data is sent in packets - so there is no need for a sync header&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is already a 2 byte checksum field (FCS) - so there is no need to add your own&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The maximum allowed payload size will be less than 128 bytes&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Frame delivery and reception are unreliable&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The XBee API may allow you to read the sequence numbers from the underlying packets. If not, you will need an incrementing sequence number and a retry mechanism.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-31T00:45:23.510" CommentCount="1" />
  <row Id="5920" PostTypeId="2" ParentId="5914" CreationDate="2010-10-31T01:07:46.007" Score="1" ViewCount="" Body="&lt;p&gt;TI has several video processors in their &lt;a href=&quot;http://focus.ti.com/dsp/docs/dspplatformscontenttp.tsp?sectionId=2&amp;amp;familyId=1300&amp;amp;tabId=1854&quot; rel=&quot;nofollow&quot;&gt;DaVinci series&lt;/a&gt;, some of which combine a microprocessor with a video system, with or without DSP, that will run Linux.  For example, the &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tms320dm365.html?lid=Alternative_Devices&amp;amp;lpos=See_Also_Container&quot; rel=&quot;nofollow&quot;&gt;TMS320DM365&lt;/a&gt; includes an ARM9, and an H.264/MPEG4/MJPEG video accelerator.   It can output 720p H.264 and MPEG4 at 30 fps. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know you aren't interested in a development board, but just FYI, the &lt;a href=&quot;http://designsomething.org/leopardboard/default.aspx&quot; rel=&quot;nofollow&quot;&gt;Leopardboard 365&lt;/a&gt;, which uses this chip, costs only $129, and the schematics are available on-line so you would be able to adapt them for your own project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The two varieties of Linux that have support for the DM365 are Ubuntu and MontaVista.  Don't know anything about Android.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-10-31T01:15:53.467" LastActivityDate="2010-10-31T01:15:53.467" />
  <row Id="5921" PostTypeId="2" ParentId="5914" CreationDate="2010-10-31T01:47:45.537" Score="4" ViewCount="" Body="&lt;p&gt;I've been doing something like this over the course of about 4 of the last 6 months (I worked on some other stuff in between). Building my own Linux board has been a tremendous learning experience, but it's also been quite challenging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some things I wish I knew before I started:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Generally, BGA packages mean you have to use fine-pitch traces and vias, and you it's difficult to assemble the boards yourself. Even if you were to succeed in soldering a BGA yourself, if you had a problem, you wouldn't know if it was due to bad soldering or bad design. The worst problem, though, is that this makes iterating on your design expensive-- around $1000 and 15 business days per rev if you live in the US.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For the love of William Shockley, start with a reference design with Android support (well, just Linux in my case). My board is based off the Atmel AT91SAM9G20 eval kit; that's saved me a great deal of headache.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Use the U-boot bootloader. It's the dominant one, which means that you can get support in more places.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Before you start laying out a board, think very carefully about how to position the components to minimize trace length. I did this to some extent, but not as much as I should have.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Buy the dev kit that is most similar to what you're planning to build, and build the bootloader and kernel from source. That will teach you a lot. If you're serious about video, I would probably try to validate whatever hardware platform I chose before laying out a board.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Good luck.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-10-31T01:47:45.537" CommentCount="7" />
  <row Id="5922" PostTypeId="2" ParentId="5912" CreationDate="2010-10-31T02:04:37.487" Score="2" ViewCount="" Body="&lt;p&gt;As described in &lt;a href=&quot;http://electronics.stackexchange.com/questions/4072/low-profile-power-dissipation/4091#4091&quot;&gt;Low Profile Power Dissipation&lt;/a&gt;, you might be able to waste some heat in another component (upstream resistor or second regulator), so your regulator doesn't have to dissipate as much.  You'll have to do the calculations for the min and max voltages and min and max loads you expect to see.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-01T20:01:31.017" LastActivityDate="2010-11-01T20:01:31.017" CommentCount="2" />
  <row Id="5923" PostTypeId="2" ParentId="5884" CreationDate="2010-10-31T07:03:15.360" Score="1" ViewCount="" Body="&lt;p&gt;Yes, sort of.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In addition to the differences in on-die peripherals (RAM, IO buffers, etc...) You also need to consider the fact that different FPGAs are rated for different clock-speeds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may have two 500k gate FPGAs, but if one has a maximum clock of 50 MHz, and the other goes up to 1 GHz, one is clearly more powerful than the other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, it's generally not that simple in the real world, as FPGAs are more limited by propagation delays than pure clock speed, but different devices have faster or slower logic units, which change how complex your logic can be without having to use synchronous buffering or encounter metastability issues.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-31T07:03:15.360" />
  <row Id="5924" PostTypeId="2" ParentId="5912" CreationDate="2010-10-31T08:55:33.487" Score="3" ViewCount="" Body="&lt;p&gt;Its the laws of physics.  You need to dissipate 3W through devices with large thermal resistance there will be a temperature rise. Using copper traces can take the heat away from surface mount devices into the printed circuit board.  But that heat still needs to be sunk.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at a SOT223 device, they have a Rj-a of 91 K/W which means at two to three watts a temperature of rise of 273 K can be expected.  This will cook your device.  The Rj-s (junction to solder point resistance) is 10 K/W so provided your board can dissipate the heat the device will be 30 K above ambient.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your board is mounted in metal enclosure, you can with a bit of design effort, align the large thermal pads on the circuit board with islands on the metal enclosure.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;        /---\                        hot device    &#xA;==================================   PCB&#xA;_______/     \______/    \______     Metal enclosure&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Using large copper pads on each layer with lots of via will aid in transferring the heat.  The only other issue is to clamp the circuit board to the metal enclosure and apply sufficient pressure and thermal compound so the board can conduct heat into the enclosure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doing this effectively transfers the heat from the component to the board and into the enclosure.  So the enclosure effectively becomes the heatsink.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without a heatsink on the board, you will reduce the Rj-a from 91 K/W to a lower value.  What this value is, you will need to determine experimentally. Make a simple circuit board with the device in question on it, and thermal pads on each layer with vias, then ramp up the amount of power you are running through the device from less than one watt gently to two/three watts and using a thermocouople, record the temperature on the board and device.  This will enable you to calculate the Rj-a of the device on your circuit board.  &lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-10-31T08:55:33.487" />
  <row Id="5925" PostTypeId="2" ParentId="5912" CreationDate="2010-10-31T09:26:16.007" Score="2" ViewCount="" Body="&lt;p&gt;This can be a big brutal and I haven't done any thermal guesstimates on your requirements but one option if the physical size of a heatsink is a problem is to pot the board or device area with a compound that has a low thermal resistance. I have seen this done with plain old Araldite to spread the thermal load. If the potting is done inside a metal case then you have the benefit of the metalwork too. Mind you - this makes reworking a tad difficult!&lt;/p&gt;&#xA;" OwnerUserId="1750" LastEditorUserId="1750" LastEditorDisplayName="" LastEditDate="2010-10-31T11:07:30.297" LastActivityDate="2010-10-31T11:07:30.297" />
  <row Id="5926" PostTypeId="2" ParentId="5861" CreationDate="2010-10-31T09:51:23.960" Score="2" ViewCount="" Body="&lt;p&gt;Eight pins and analogue inputs means something like the PIC12F675. It has a 10-bit ADC with four channels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd forget about the 16F628A unless you can't find anything else, it's obsolete. The modern equivalent is the 16F88. The latter has on-chip debug hardware that you don't get with many of the smaller devices (they need a special debug header).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The A after a part denotes that it's a newer, improved version.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-10-31T13:39:25.773" LastActivityDate="2010-10-31T13:39:25.773" CommunityOwnedDate="2011-05-15T04:20:58.030" CommentCount="0" />
  <row Id="5927" PostTypeId="2" ParentId="5861" CreationDate="2010-10-31T10:01:41.703" Score="1" ViewCount="" Body="&lt;p&gt;I'd recommend the PIC16F690.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a great starter chip: it's got 256 bytes EEPROM, 7K program memory, 256 bytes RAM, 3 timers (1 x 16-bit), MSSP, UART, 8ch 10-bit ADC, comparators - everything you should need. Microchip used ship the chip with their PICkit 2 demo boards. They now ship the PIC16F887, which is also a very powerful chip (similar to the PIC16F690.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-31T10:01:41.703" CommunityOwnedDate="2011-05-15T04:20:58.030" CommentCount="1" />
  <row Id="5928" PostTypeId="2" ParentId="5861" CreationDate="2010-10-31T11:49:05.003" Score="3" ViewCount="" Body="&lt;p&gt;If you are after 8-pin I'd give the PIC12F683 a go. It has the same pinout as the PIC12F675 and PIC12F629 but double the memory and all the features of the lesser models. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;8-pin PICs are a great way to start as they are simple enough that you can quickly use them them without having to keep too much new information in your head. Just remember that lots of tutorials will expect you to be using &lt;code&gt;PORTA&lt;/code&gt; or &lt;code&gt;PORTB&lt;/code&gt; which are 8-pin binary inputs or outputs.  As these chips only have 6 input/output pins you'll be using &lt;code&gt;GPIO&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/41211D_.pdf&quot; rel=&quot;nofollow&quot;&gt;Read the datasheet&lt;/a&gt; before you use it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Following these, I would just move on to a PIC18F or PIC24F (select one that matches the features and memory you want - you'll be able to better judge this after fiddling with a PIC12F).&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-10-31T11:54:14.963" LastActivityDate="2010-10-31T11:54:14.963" CommunityOwnedDate="2011-05-15T04:20:58.030" />
  <row Id="5929" PostTypeId="1" CreationDate="2010-10-31T12:07:28.133" Score="1" ViewCount="158" Body="&lt;p&gt;How can I use my computer to control the frequency of a variable oscillator?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;THANK YOU.&lt;/p&gt;&#xA;" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-10-31T12:33:35.943" LastActivityDate="2010-10-31T13:28:32.070" Title="create oscillator with variable frequency by computer" Tags="&lt;microcontroller&gt;&lt;oscillator&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="5930" PostTypeId="2" ParentId="5929" CreationDate="2010-10-31T13:28:32.070" Score="4" ViewCount="" Body="&lt;p&gt;Specify a frequency range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you only want 20 Hz to 20 kHz you can use the sound card built into most computers. It usually has at least 2 channels, sometimes more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specify a type of waveform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A sound card can output almost any waveform but the output is ac coupled, so you can't offset it with a dc level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specify the amplitude.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output from a sound card is in the range of 1Vp-p to 2Vp-p, this may be okay for some situations but not all.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-31T13:28:32.070" CommentCount="9" />
  <row Id="5931" PostTypeId="1" AcceptedAnswerId="5933" CreationDate="2010-10-31T13:45:09.480" Score="3" ViewCount="161" Body="&lt;p&gt;In a recent question on &lt;a href=&quot;http://electronics.stackexchange.com/questions/5861/what-pic-should-i-use&quot;&gt;which PIC to use&lt;/a&gt;, one answer mentioned that a particular PIC had the feature that of debug hardware being built in, so that a special debug header was not needed.  What is a debug header?&lt;/p&gt;&#xA;" OwnerUserId="1780" LastActivityDate="2010-10-31T14:08:42.130" Title="In relation to a PIC, what is a debug header?" Tags="&lt;pic&gt;&lt;debug&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5932" PostTypeId="2" ParentId="5931" CreationDate="2010-10-31T13:54:44.280" Score="1" ViewCount="" Body="&lt;p&gt;I think it's the same as an ICD header.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because on some low pin count chips the extra wires needed for debugging (two of them) can be significant compared to the total pin count of the chip, a bigger chip with more or less the same CPU core is produced for debugging alone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example here is a PIC header for a PIC16F648A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/VP1BF.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's bigger than the actual chip and has extra pins for debugging support. Note the -ICD suffix on the part number.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-31T13:54:44.280" CommentCount="3" />
  <row Id="5933" PostTypeId="2" ParentId="5931" CreationDate="2010-10-31T14:08:42.130" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en537580&amp;amp;redirects=icd3&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;MPLAB ICD 3 In-Circuit Debugger&lt;/strong&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/51292S.pdf&quot; rel=&quot;nofollow&quot;&gt;Header Specification&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;WHY DO I NEED A HEADER TO DEBUG?&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Some PIC® microcontrollers, particularly low pin count devices (with 20 pins or less), &#xA;  generally must use a header for debugging. This is done to free up I/O lines for your &#xA;  application and to make production parts more affordable. Optional headers are also &#xA;  available for high pin count devices (with 64 pins or higher).&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Debugging requires a two-line connection (plus VDD, VSS and VPP) to communicate with the device. In a high pin count device, losing a few I/O lines is generally not a problem for most designs. But in a low pin count device, it can be a critical problem.  Imagine having to do an 8-pin design where there are only 5 I/Os, having used up 2 I/Os just for debugging!&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Notes about Headers&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Some 8-, 14- and 18-pin devices use &lt;strong&gt;small header boards&lt;/strong&gt; with a special MCU for debugging. This special MCU has extra pins for MPLAB ICD 3 communication and therefore allows the use of all pins on the part for the application. The header board is not used or needed for programming. However, when debugging these devices the header must be used.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/3SmFm.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/jr8Nd.png&quot; alt=&quot;Figure 1&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/A8lcp.png&quot; alt=&quot;Figure 2&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1084" LastActivityDate="2010-10-31T14:08:42.130" />
  <row Id="5934" PostTypeId="2" ParentId="5882" CreationDate="2010-10-31T15:17:13.323" Score="1" ViewCount="" Body="&lt;p&gt;I believe I may have found a two part solution for my particular problem. I currently own an Arduino Diecimila (which has the ATMEGA168 with the problem) and also a new Arduino Nano 3.0. I went ahead and flashed the Arduino Nano with the &lt;a href=&quot;http://arduino.cc/en/Tutorial/ArduinoToBreadboard&quot; rel=&quot;nofollow&quot;&gt;ArduinoISP&lt;/a&gt; firmware. I then picked up 3 28 Pin ATMEGA328P DIP chips for $5.00 each at the local electronics store.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used the ArduinoISP to flash one of the virgin chips with the Arduino Firmware using the above link with a crystal. I plan to now flash one of the other ATMEGA328Ps with the &lt;a href=&quot;http://mightyohm.com/blog/2008/09/arduino-based-avr-high-voltage-programmer/&quot; rel=&quot;nofollow&quot;&gt;High Voltage Programmer&lt;/a&gt; firmware. This chip along with a bit of wiring on a breadboard should allow me to reset all of the fuses on the original ATMEGA168. Once that is done, I will be able to use the Arduino Nano to reprogram the chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the ATMEGA328Ps only cost $5 each, my end goal is to setup one 328 as an Arduino ISP programmer, setup the 168 as a HV Programmer, keep one 328 chip in my current Arduino Diecimila (upgrade!!), and I'll have one left over for whatever. I can then either switch chips on the Diecimila or build out a real board for the ISP and HV Programmer boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I still have not tested the JTAG ICE MKII yet with a logic/oscilloscope. Not sure if it is the root of the problem or not. I will address this issue after I build the HV Programmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will report back on the success/failure of the HV Programmer. I just need to go get a few more 1K resistors to pull it off. Anyone ever tried the HV Programmer? Any other suggestions? If nothing else, hope this helps someone.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastActivityDate="2010-10-31T15:17:13.323" CommentCount="2" />
  <row Id="5935" PostTypeId="1" AcceptedAnswerId="5942" CreationDate="2010-10-31T15:47:30.113" Score="4" ViewCount="169" Body="&lt;p&gt;By rubbing a cotton cloth along a PVC pole, static electricity is generated. How can this be used to charge a capacitor?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://home.earthlink.net/~lenyr/stat-gen.htm&quot; rel=&quot;nofollow&quot;&gt;http://home.earthlink.net/~lenyr/stat-gen.htm&lt;/a&gt; is what I'd like to do, but it doesn't explain how it should be wired up.&lt;/p&gt;&#xA;" OwnerUserId="1781" LastActivityDate="2010-11-01T13:47:12.377" Title="Electrostatically charging a capacitor" Tags="&lt;capacitor&gt;" AnswerCount="4" />
  <row Id="5936" PostTypeId="2" ParentId="5935" CreationDate="2010-10-31T16:14:07.683" Score="3" ViewCount="" Body="&lt;p&gt;Sounds like you want a &lt;a href=&quot;http://en.wikipedia.org/wiki/Leyden_jar&quot; rel=&quot;nofollow&quot;&gt;Leyden Jar&lt;/a&gt; (an early type of capacitor), here's a tutorial:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_p049.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_p049.shtml&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-10-31T16:14:07.683" CommentCount="1" />
  <row Id="5937" PostTypeId="2" ParentId="5912" CreationDate="2010-10-31T17:05:33.593" Score="2" ViewCount="" Body="&lt;p&gt;Yes you can cool the device using the board. Note that this takes a reasonably amount of surface area to do so. Don't expect that the whole of your board will give the component a cooling effect, for example if it's tab is on the ground plane. The only effective area is within 6cm's to 8cm's I believe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The via's or small holes you usually see in those planes are thermal via's. On the other side of the board there probably is a copper plane as well. It increases the thermal cooling, but might be hard to make when you prototype your own boards inhouse. The holes can't be that big (in the order of a few tenth's of mm). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've made a switching regulator the other day that needed some cooling as well. It was in a TO-263 casing, which is a little bit bigger. But anyway, the &lt;a href=&quot;http://www.national.com/ds/LM/LM2678.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet of national&lt;/a&gt; at page 4 and 5 specified that with 1 sq inch of copper area I had a cooling resistance of 26C/W. That's J-A, which isn't too bad. If you disspiate 3W that would add 75C above ambient, which is good enough. In this particular case I was making the PCB on an amateur etching machine, so I made the area twice as big because the soldering connection to the pab is harder to make.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-10-31T17:05:33.593" CommentCount="2" />
  <row Id="5938" PostTypeId="2" ParentId="5861" CreationDate="2010-10-31T17:08:39.003" Score="9" ViewCount="" Body="&lt;p&gt;Might as well put my 2 cents in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip has a part selector here: &lt;a href=&quot;http://www.microchip.com/maps/microcontroller.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/maps/microcontroller.aspx&lt;/a&gt; You can input all of the required items that you have and it will show you what will meet your requirements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are wanting a PIC that is easier to learn with you shouldn't be worried about low pin count. Instead you should be looking at things like what compiler you will be using and what the package type is of the chip. If you are wanting to bread board, you should get a PIC in a through hole version. You can also get a development board with all of the required hardware built in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I brought up considering you compiler because not all PIC series have good free or cheap C compilers. The PIC16F series has a very different architecture then the PIC18F. Because of this, several of the C compilers do not support the 16F series, leaving you to program in assembly or forking over some money. Also, since the architecture is different, it is harder to do something in assembly on them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, long story short, I would recommend going with a PIC18F series unless you have some strict requirements for 8 pins. The class that I help instruct has switched over to using 18F series only because of the reasons I listed.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-31T17:08:39.003" CommunityOwnedDate="2011-05-15T04:20:58.030" CommentCount="4" />
  <row Id="5939" PostTypeId="2" ParentId="5912" CreationDate="2010-10-31T17:34:08.677" Score="5" ViewCount="" Body="&lt;p&gt;I do realize this isn't answering your question directly, but something you might want to consider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead of dissipating so much energy, you can put a buck converter before your linear regulator. Get the buck to output at a voltage just above what is required by your linear regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will not only decrease the amount of heat you have to dissipate, but also improve the efficiency of your design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as heat sinking goes, I tend to put several vias directly to my ground plane. The ground plane seems to be very good at dissipating heat. If you go to a 4+ layer board and have the ground plane internal then heat dissipation wont be nearly as good.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-10-31T17:34:08.677" CommentCount="2" />
  <row Id="5940" PostTypeId="2" ParentId="5935" CreationDate="2010-10-31T17:52:46.983" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://vimeo.com/3386456&quot; rel=&quot;nofollow&quot;&gt;My favorite demo of charging a Leyden jar&lt;/a&gt; is by Makezine's Collin Cunningham, it's a very basic video that looks at capacitors in general, but it does show how to charge a simple Leyden using the PVC pipe and cloth method.&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-10-31T17:52:46.983" />
  <row Id="5941" PostTypeId="2" ParentId="5935" CreationDate="2010-10-31T18:00:24.133" Score="3" ViewCount="" Body="&lt;p&gt;This is a good way to explain the behavior of capacitors, actually.  People talk about &quot;charging up&quot; a capacitor, but they don't actually store charge.  They store energy in the form of a displacement of charge.  The electric charge of an empty capacitor and a full capacitor are both 0.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you charge up a piece of PVC and touch it to a floating capacitor, it won't accept any more charge than any other piece of metal of the same size.  The reason capacitors can store so &quot;much&quot; is because you're removing charge from one plate and depositing it on the other.  If you connect one terminal to ground, you should be able to add more charge to the other terminal, since an equal amount can &quot;escape&quot; to the earth from the other side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://amasci.com/emotor/cap1.html&quot; rel=&quot;nofollow&quot;&gt;http://amasci.com/emotor/cap1.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-01T13:47:12.377" LastActivityDate="2010-11-01T13:47:12.377" CommentCount="2" />
  <row Id="5942" PostTypeId="2" ParentId="5935" CreationDate="2010-10-31T18:59:16.003" Score="5" ViewCount="" Body="&lt;p&gt;To get the charge from the PVC into a capacitor, you could ground one side of the cap, and attach a wire to the other side of the cap. The end of the wire should preferably end in a fine point or collection of fine points, and you sweep this over the charged surface of the PVC to collect what charge you can. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use a smaller capacitor you will tend to get more voltage, but even a small capactior (e.g., 100pF) is probably only going to get as far as a couple of volts, even off a PVC surface charged to 10's of kV, because the capacitance of the PVC surface probably isn't even 0.1pF.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-10-31T18:59:16.003" CommentCount="2" />
  <row Id="5943" PostTypeId="1" AcceptedAnswerId="5945" CreationDate="2010-10-31T19:48:12.393" Score="3" ViewCount="291" Body="&lt;p&gt;Following &lt;a href=&quot;http://electronics.stackexchange.com/questions/5466/is-a-single-channel-oscilloscope-enough-for-most-purposes&quot;&gt;this question&lt;/a&gt;, I purchased a &lt;a href=&quot;http://www.audon.co.uk/dso2090.html&quot; rel=&quot;nofollow&quot;&gt;DSO-2090 USB oscilloscope&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I power it up, I see lots of small fluctuations in the waveform, whether connected to nothing, a battery source, itself (small waveform generator on the back) or by shorting the ground clip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/k8BaK.png&quot; alt=&quot;Oscilloscope Noise&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(&lt;a href=&quot;http://i.imgur.com/k8BaK.png&quot; rel=&quot;nofollow&quot;&gt;See the large version&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the screenshot above, the CH1 is connected to a small, battery powered circuit of mine. CH2 does not have the probe connected at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have spoken to a colleague about this and was told that I should see a flat line so I am worried I have purchased a faulty unit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is whether or not background noise like this is normal in an oscilloscope?&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Edit 1&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;Added 1kHz waveform example as per comment:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/mbhpI.png&quot; alt=&quot;1kHz&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(&lt;a href=&quot;http://i.imgur.com/mbhpI.png&quot; rel=&quot;nofollow&quot;&gt;See the large version&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-10-31T21:16:22.767" LastActivityDate="2010-10-31T23:01:55.000" Title="How much background &quot;noise&quot; is normal on an oscilloscope" Tags="&lt;oscilloscope&gt;&lt;noise&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="5944" PostTypeId="2" ParentId="5943" CreationDate="2010-10-31T20:16:23.627" Score="3" ViewCount="" Body="&lt;p&gt;I would have to touch the oscope to confirm something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This amount of noise is common. There are many sources of noise, but with a noise magnitude that small, it is probably not a concern.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me list off a couple things.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Sources of Noise &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;The loop of your ground clip creates has an inductance with everything on your board. any electrical signal nearby can induce a wave on your ground loop. This ground loop also acts as a low pass filter, albeit the frequency that it cuts off is normally in the high MHz range, not normally any issues for a 40Mhz scope. I have drawn a red line around what I am referring to in the following image.&#xA;&lt;img src=&quot;http://i.imgur.com/YnSuu.gif&quot; alt=&quot;oscope probe image with red line around the ground clip. In this image there is a 6 inch ground clip&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fact that you have a ground reference in one circuit, and another ground reference in the other circuit plus your ground line connecting them can create &lt;a href=&quot;http://en.wikipedia.org/wiki/Ground_loop_%28electricity%29&quot; rel=&quot;nofollow&quot;&gt;ground loops&lt;/a&gt;(not to be confused with the ground clip issue I mentioned above, have to love similar terminology). This can actually create quite a problem, and is also no fun to fix. One method is to wrap the probe almost the the extreme tip with aluminum foil and ground it at the o'scope. This shields the interior ground connection and greatly decreases ground loop problems. It also looks awesome(not at all).&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Testing for issues&lt;/h3&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;To see if it is just a 1bit bounce,&#xA;try changing your resolution and&#xA;watching if the noise changes in the&#xA;amount it is jumping by.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;To check if the ground loop is your&#xA;issue, try using an sharp blade and&#xA;touching between the ground at the&#xA;very tip of your probe to the ground&#xA;on your board. This gives more than&#xA;an order of magnitude drop in&#xA;inductance. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;To check for ground loops, you get&#xA;to wrap your probe in foil. Do not&#xA;enjoy this too much.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;If your noise disappears just from connecting to the waveform generator on your scope then your circuit is probably the cause.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-10-31T22:33:46.770" LastActivityDate="2010-10-31T22:33:46.770" CommentCount="1" />
  <row Id="5945" PostTypeId="2" ParentId="5943" CreationDate="2010-10-31T22:15:30.643" Score="3" ViewCount="" Body="&lt;p&gt;As an indicator that the second capture you displayed looks normal, here's one I just made of a 1 KHz square wave, from my ELAB-080 combination instrument (dual channel DSO, 16-channel logic analyzer, arbitrary waveform generator (AWG), and dual channel power supply) which also has a vertical 8-bit resolution in its DSO section.  (Note: at $495, the ELAB-080 was over your budget in your other question where I recommended the DSO-2090).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can see the noise at the top and bottom of each square wave, which looks almost identical to your trace.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/GgEQz.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-10-31T22:15:30.643" CommentCount="11" />
  <row Id="5946" PostTypeId="2" ParentId="5943" CreationDate="2010-10-31T22:36:38.683" Score="4" ViewCount="" Body="&lt;p&gt;I have one of these scopes (a DSO-2250, so a slightly faster model).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can confirm that there is approximately ~1-2 bits worth of noise at all input settings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, these scopes are worthless for anything but digital work, which is what I bought it for anyways.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the few uses I have found for the thing is to use it with a laptop, which gives you a simple battery-scope, which can be useful when you have ground-loop issues.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-10-31T22:36:38.683" CommentCount="1" />
  <row Id="5947" PostTypeId="2" ParentId="5943" CreationDate="2010-10-31T23:01:55.000" Score="1" ViewCount="" Body="&lt;p&gt;I don't have a PC scope but a real bench oscilloscope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When running normally I see around 500µV noise on all settings about 5mV/div, and about 1mV noise on the 5mV/div setting. The noise is uniform across all channels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This noise is not significant for any of my uses so far. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's also not unusual for the scope to read ±1mV dc offset when there is zero input; some scopes have this calibrated out but expect a slight drift over time. Mine's quite old (manufactured '93), so I get around -3mV offset.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-10-31T23:01:55.000" />
  <row Id="5948" PostTypeId="1" AcceptedAnswerId="6532" CreationDate="2010-10-31T23:16:49.217" Score="2" ViewCount="99" Body="&lt;p&gt;Which board is better overall for .net mf development, the Tahoe 2 or the GHI EMX module?&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://devicesolutions.net/Products/TahoeII.aspx&quot; rel=&quot;nofollow&quot;&gt;Tahoe 2&lt;/a&gt;  &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ghielectronics.com/product/129&quot; rel=&quot;nofollow&quot;&gt;GHI EMX&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I'm looking at a general purpose board for plugging in different types of sensors (at once) and using functions like the NIC and SD file io.&lt;/p&gt;&#xA;" OwnerUserId="1457" LastEditorUserId="1457" LastEditorDisplayName="" LastEditDate="2010-11-01T00:37:07.603" LastActivityDate="2010-11-10T15:48:58.980" Title="Which board is better overall for .net mf development, the Tahoe 2 or the GHI EMX module?" Tags="&lt;.net-micro-framework&gt;&lt;arm7&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="5949" PostTypeId="1" CreationDate="2010-10-31T23:18:20.913" Score="5" ViewCount="334" Body="&lt;p&gt;Could someone please explain why computers are built to run on DC power instead of AC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to make a computer that runs on AC, even theoretically?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I understand that it wouldn't be possible to use diodes)&lt;/p&gt;&#xA;" OwnerUserId="1732" LastActivityDate="2011-03-10T12:16:31.610" Title="Is it possible for a computer to use AC power?" Tags="&lt;power-supply&gt;" AnswerCount="6" FavoriteCount="0" />
  <row Id="5950" PostTypeId="2" ParentId="5949" CreationDate="2010-10-31T23:28:40.120" Score="5" ViewCount="" Body="&lt;p&gt;Computers save state by saving what voltage some input(often internally generated) is at the last rising edge. With DC voltage, in the simplest terms, they save gnd as a logic 0(false) and pwr as a logic 1(true).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If we ignore the complexities of getting the transistors to work with an AC input power. whenever you saved the state, you would have to know what pwr was at that instance. Lets say you clock it when the pwr is -2V, on the next clock it might be 4 V, now you need more than a simple comparator to determine if the -2V was ground with noise, or logic true at the time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, the physics of transistors would not like this. I see your statement, it would not be possible to use diodes, Transistors are diodes, just pointed at each other with an enable to allow a much higher leakage current through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please let me know if there is something I need to add to make more sense of this.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-31T23:28:40.120" CommentCount="7" />
  <row Id="5951" PostTypeId="1" AcceptedAnswerId="5952" CreationDate="2010-10-31T23:29:00.687" Score="4" ViewCount="411" Body="&lt;p&gt;Is there a standard for via sizes, or can you make them any size you want?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I'm going to be using traditional PCB houses to manufacture my PCB's.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-06T18:09:15.400" Title="Standard via sizes?" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;&lt;via&gt;" AnswerCount="3" />
  <row Id="5952" PostTypeId="2" ParentId="5951" CreationDate="2010-10-31T23:31:15.873" Score="3" ViewCount="" Body="&lt;p&gt;PCB houses will give you acceptable sizes for their process. They have a tolerance and a cost associated with different sizes, but unless you are making the next batch of Iphones you will probably just be given a cost per via, if even that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally they just give me a cost/square inch and tell me my minimum size.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-10-31T23:31:15.873" CommentCount="10" />
  <row Id="5953" PostTypeId="1" AcceptedAnswerId="5975" CreationDate="2010-10-31T23:43:45.297" Score="1" ViewCount="120" Body="&lt;p&gt;assuming I have already purchased a .net mf board such as a tahoe II, what other items are required?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously sensors will vary on the projects I'm doing, but what stuff will I need for every project?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Okay so maybe I got excited and didn't provide enough detail. Assuming I have a board such as the Tahoe 2 and a computer and a cable to hook it up and copy programs across. What other items do I need (examples circuit boards, transistors, soldering iron, etc) what are the required items that each project is likely to need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update:&lt;br&gt;&#xA;&lt;strong&gt;Basic Hardware Parts list&lt;/strong&gt;&lt;br&gt;&#xA;•Leds&lt;br&gt;&#xA;•Resistors&lt;br&gt;&#xA;•Caps&lt;br&gt;&#xA;•Transistors&lt;br&gt;&#xA;•Solderless breadboard&lt;br&gt;&#xA;•Solid core wire&lt;br&gt;&#xA;•Crocodile clamps&lt;br&gt;&#xA;•External power supply (5V for Meridan boards)&lt;br&gt;&#xA;•Multimeter&lt;br&gt;&#xA;•Some sensors&lt;br&gt;&#xA;•Network Cable  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;GPIO, I2C,SPI and UART all supported.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Software&lt;/strong&gt;&lt;br&gt;&#xA;Visual Studio 2010 (express or a retail edition)&lt;/p&gt;&#xA;" OwnerUserId="1457" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:23:35.873" LastActivityDate="2010-12-10T22:23:35.873" Title="Can someone give me a basic parts list of required items for .net micro framework development?" Tags="&lt;.net-micro-framework&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="5954" PostTypeId="1" AcceptedAnswerId="5959" CreationDate="2010-11-01T00:19:43.277" Score="2" ViewCount="166" Body="&lt;p&gt;I have a 6V to 20V input I want to convert to 12V at 1 amp maximum continuous current. The output must be the same polarity as the input, so that pretty much means a SEPIC is the only way to go... However, I've been looking around and all solutions I've seen thus far require many components and a lot of surface area; I'm looking to minimise surface area as far as possible, and to do this I don't mind sacrificing a bit of efficiency. Does anyone have any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-01T08:44:47.143" Title="12V @ 1A from a 6V to 20V input" Tags="&lt;power-supply&gt;&lt;sepic&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="5955" PostTypeId="2" ParentId="5949" CreationDate="2010-11-01T00:26:37.140" Score="9" ViewCount="" Body="&lt;p&gt;Computers represent everything with bits, and ordinarily this means one voltage range for a 0 and another voltage range for a 1. If you really wanted to use AC to in some way directly represent bits, you wouldn't be able to rely on voltage in the usual way, since by definition AC voltage is always changing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could play games with phase or frequency though. Consider using phase. You could define a 'reference' phase with some oscillator, and then a 0 could be AC with phase matching the reference, and 1 would be AC that's 180 degrees out of phase. (or vice versa) But right away you should see the problem even with this: while you can tell what the state of a DC bit is practically instantly, with these hypothetical AC bits, you'd have to wait a significant portion of a cycle to tell what sort of bit you had. So you'd have to run your reference phase at a very high frequency to get even mediocre performance. If you tried to use different frequencies for bits, the situation would be as bad or worse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be interesting to try to get a couple of logic gates implemented this way, but only as an academic curiosity.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-01T00:26:37.140" CommentCount="1" />
  <row Id="5956" PostTypeId="2" ParentId="5949" CreationDate="2010-11-01T01:07:53.703" Score="2" ViewCount="" Body="&lt;p&gt;You could use AC with some number of discrete phases to represent numbers.&#xA;(Take a look a CQAM modulation on analog modems) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would let you use transformers to implement logic gates. ( magnetic amplifiers!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;AC at high frequency woudn't be efficient in CMOS so it wouldn't scale to awesome numbers of gates. ( and what you'd use for a gate in a semicondicutor ??)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but a similar principle can be used with light.&#xA;you can use laser light, and a discrete set of phases to represent numbers. It's an interesting technique. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not so great in AC electricity.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-11-01T01:07:53.703" />
  <row Id="5957" PostTypeId="2" ParentId="4332" CreationDate="2010-11-01T02:00:11.133" Score="1" ViewCount="" Body="&lt;p&gt;The drivers for the TUSB3410 for Mac OS X are still in beta. You should consider contact TI about this and maybe they can try to fix your problem. Even if they aren't currently interested in pushing the Mac side, the more interest they get from Mac users the more likely they are to do something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also found a few comments about how there are open source version of the driver, but was unable to find any of them. Maybe you will have better luck looking for them.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-01T02:00:11.133" />
  <row Id="5958" PostTypeId="2" ParentId="5858" CreationDate="2010-11-01T03:03:07.810" Score="4" ViewCount="" Body="&lt;p&gt;If it were me I would use an IC to do the DAC for me. The manufactures of the ICs take a lot of time and consideration for getting matched components and put them in the best configuration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010546&quot; rel=&quot;nofollow&quot;&gt;TC1320EOA&lt;/a&gt; is probably a good solution for what you want. It has I2C and in an 8pin SOIC configuration. I bet you will be hard pressed to get a design this small if you take into account the traces from your micro as well as the resistors and possibly smoothing caps and such. It has 8 bits of resolution, which is more then you need, but I wouldn't think this would be an issue. I also think the cost of it will be fairly equal if you account for the more pins needed on your micro for a home brewed solution and the PCB space required.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-01T03:03:07.810" />
  <row Id="5959" PostTypeId="2" ParentId="5954" CreationDate="2010-11-01T03:58:20.113" Score="2" ViewCount="" Body="&lt;p&gt;Page 31 of &lt;a href=&quot;http://cds.linear.com/docs/Datasheet/3757fb.pdf&quot; rel=&quot;nofollow&quot;&gt;this datasheet&lt;/a&gt; for the Linear Technology LT3757 has an application circuit using a SEPIC converter for a 5.5v to 36v input and 12v 2A output.  The biggest part appears to be the &lt;a href=&quot;http://parts.digikey.com/1/parts/667954-inductor-shield-dual-3-3uh-smd-drq127-3r3-r.html&quot; rel=&quot;nofollow&quot;&gt;dual inductor&lt;/a&gt;, which is 12.5 mm square.  Since you only need a 1A output, you might get by with a smaller inductor in the &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=513-1263-1-ND&quot; rel=&quot;nofollow&quot;&gt;DRQ74&lt;/a&gt; series, which is 7.6 mm square.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-11-01T04:41:16.507" LastActivityDate="2010-11-01T04:41:16.507" />
  <row Id="5960" PostTypeId="1" AcceptedAnswerId="5981" CreationDate="2010-11-01T05:38:19.313" Score="4" ViewCount="167" Body="&lt;p&gt;I'm trying to debug a friend's &lt;a href=&quot;http://shop.41hz.com/shop/item.asp?itemid=8&amp;amp;catid=&quot; rel=&quot;nofollow&quot;&gt;AMP6 audio amp kit&lt;/a&gt;. It seems that an electrolytic smoothing cap on the output of a 5 V regulator has been soldered in backwards. This seems bad, but the component is going to be a little tricky to desolder because of its physical location. Because of this, I'm trying to be certain that this is the problem before attempting the job.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Before it explodes, how does a backwards cap behave? Like a 100 ohm resistor?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-01T15:01:22.477" Title="What's the resistance of an electrolytic cap soldered in backwards?" Tags="&lt;capacitor&gt;" AnswerCount="5" />
  <row Id="5962" PostTypeId="2" ParentId="5858" CreationDate="2010-11-01T07:23:25.677" Score="3" ViewCount="" Body="&lt;p&gt;If you have a spare PWM output on your micro, driving it into an RC filter will be the cheapest way to do this, and will take up very little space. This will be slower than the resistor arrays though. &lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2010-11-01T07:23:25.677" />
  <row Id="5963" PostTypeId="2" ParentId="4942" CreationDate="2010-11-01T07:54:51.143" Score="2" ViewCount="" Body="&lt;p&gt;It turns out that the distributor has figured out that they can perform this service on loose parts before delivery to the assembly house. I'm personally not involved in the purchasing process, and can't begin to guess how much (if anything) this increased the cost of the parts. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We had to produce a file containing a copy of every bit to be programmed including the 16 extra bytes per page, with the extra bytes properly formatted with the ECC and bad block information structure that matches the assumptions of the NAND driver, and with all unused blocks (and their extra bytes) left blank. The file was as large as the device, but ZIP had lots of leverage for compression.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Along side that, we had to produce a table of base addresses and expected sizes of the partitions in use in the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apparently the Data I/O FLASH programmer will verify each page during programming, mark pages that fail as bad, and automatically retry on the next page. This requires that the partitions have enough spare space to allow for some bad pages. The part will be rejected if a specified number of pages are bad, or if a partition won't fit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Our first batch are in process based on an image dump of the live chip in a prototype unit. Our plan is to improve on that by writing a tool that can produce the necessary image on demand or as a final build step.&lt;/p&gt;&#xA;" OwnerUserId="1494" LastActivityDate="2010-11-01T07:54:51.143" CommentCount="1" />
  <row Id="5964" PostTypeId="2" ParentId="5954" CreationDate="2010-11-01T08:44:47.143" Score="2" ViewCount="" Body="&lt;p&gt;I've built a SEPIC and published this page about it, there's even a description of how to build a the inductor without unobtainium:&#xA;&lt;a href=&quot;http://dren.dk/carpower.html&quot; rel=&quot;nofollow&quot;&gt;http://dren.dk/carpower.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... but the inductor design is pretty hackish, so it's not going to win any medals for production use.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-01T08:44:47.143" />
  <row Id="5965" PostTypeId="2" ParentId="4942" CreationDate="2010-11-01T09:45:34.660" Score="1" ViewCount="" Body="&lt;p&gt;One possible way to avoid the bad block issue may be to have just a minimal bootloader in the initial guaranteed error-free area of the NAND, and have this program the main content via whatever interface the product has available during test. e.g. temporarily connect a SD card or something. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option if you have plenty of space in the NAND is to preprogram multiple images, and have the processor derive a good image from these images the first time it powers up. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be worth talking to companies who already offer programming services, as they may have already found solutions to this. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-01T09:45:34.660" CommentCount="3" />
  <row Id="5967" PostTypeId="1" AcceptedAnswerId="5983" CreationDate="2010-11-01T10:11:43.450" Score="2" ViewCount="131" Body="&lt;p&gt;I'm using an Airwave 663 module. It's a 5.8GHz FM video + stereo audio transmitter module. Here is the datasheet: &lt;a href=&quot;http://www.airwave.com.tw/specification/RF%20modules/AWM663TX.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.airwave.com.tw/specification/RF%20modules/AWM663TX.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is apparent that the module requires a 470uF 16V capacitor on the BYPASS pin. Compared to the other components on my board, this is absolutely massive. But I can't find any specification anywhere about what this capacitor does and whether or not this capacitor can be made smaller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone here has dealt with similar modules, what was your expereience?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2010-11-01T20:06:08.333" LastActivityDate="2010-11-01T20:06:08.333" Title="Airwave TX &quot;BYPASS&quot; capacitor" Tags="&lt;capacitor&gt;&lt;video-transmitter&gt;" AnswerCount="1" CommentCount="0" FavoriteCount="0" />
  <row Id="5968" PostTypeId="1" CreationDate="2010-11-01T10:41:43.577" Score="2" ViewCount="168" Body="&lt;p&gt;I am planning to compare two audio files. I have recorded two voices and compared them using cross correlation. Since the presence on background noise while recording the resulting correlation value is always near 0.5. If i give any recorded waves from internet, i am able to get the correct value. So how can i reduce the background noise from the recorded .wav file. If i come to know how to do it, then i will try to implement technically. Any basic ideas will be helpful for me to learn and apply it. Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1730" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-01T10:46:49.277" LastActivityDate="2010-11-01T19:37:07.763" Title="Reduce background noise from a .wav file?" Tags="&lt;dsp&gt;&lt;noise&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="5969" PostTypeId="2" ParentId="5968" CreationDate="2010-11-01T10:44:25.600" Score="0" ViewCount="" Body="&lt;p&gt;I recommend you look at the software package Audacity. It's free open-source software, and it has a noise reducing algorithm/plugin. I wouldn't expect you could copy it straight from the source, but it might give you some ideas on how it's done. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-01T10:44:25.600" />
  <row Id="5970" PostTypeId="1" AcceptedAnswerId="5971" CreationDate="2010-11-01T10:55:08.303" Score="4" ViewCount="117" Body="&lt;p&gt;Is it possible to put SMT components on both sides of the board with the pads touching? I don't want the pads to be electrically connected, but my PCB program (gEDA PCB) warns that they are shorted. Is there any way to avoid this?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T20:35:00.137" LastActivityDate="2011-04-27T20:35:00.137" Title="SMT pads on both sides of the board" Tags="&lt;surface-mount&gt;&lt;pads&gt;" AnswerCount="3" />
  <row Id="5971" PostTypeId="2" ParentId="5970" CreationDate="2010-11-01T11:18:23.107" Score="3" ViewCount="" Body="&lt;p&gt;It's done all the time, the software I use doesn't give a warning. Contact the support people for your PCB software, they should tell you how to avoid the problem. Or, just ignore the warnings, the boards should come out OK. You could check the Gerbers with a program like GC-Prevue to make sure.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-01T13:19:37.417" LastActivityDate="2010-11-01T13:19:37.417" CommentCount="2" />
  <row Id="5972" PostTypeId="2" ParentId="5903" CreationDate="2010-11-01T11:20:39.207" Score="1" ViewCount="" Body="&lt;p&gt;Seems that it was a power supply issue. I switched from the 9v regulated wall wart (that came with my Arduino from Adafruit) I was using to a 9v regulated supply that came with a piece of network gear. The wall wart put out 9v @ 2/3A. The other supply puts out 9v @ 1A. The other supply also has a proper ground plug to (it uses a IEC power cable).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, it was either an issue of not enough amperage or unclean grounding.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2010-11-01T11:20:39.207" />
  <row Id="5973" PostTypeId="2" ParentId="5970" CreationDate="2010-11-01T11:48:35.957" Score="3" ViewCount="" Body="&lt;p&gt;Are you sure the pad definitions are OK, and the parts are actually placed on different sides? - it shouldn't give a warning about pads on different layers touching.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-01T11:48:35.957" />
  <row Id="5974" PostTypeId="2" ParentId="5960" CreationDate="2010-11-01T12:40:50.370" Score="2" ViewCount="" Body="&lt;p&gt;That would depend upon the type/construction/driver characteristics for this particular instance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have had a number of instances of faulty manufacture resulting in reversed electrolytic capacitors.  The results were &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Aluminium foil - A roomfull of shredded aluminium confetti.  Very pretty but a pain to clear up as it got everywhere.&lt;/li&gt;&#xA;&lt;li&gt;Solid Tantalum (cylindrical) - a molten blob like a very large lump of solder between the component leads.  In this case the short circuit current was limited by a series resistance in the supply line.&lt;/li&gt;&#xA;&lt;li&gt;Chip Tantalum - Smoke and flame from the burning plastic body of the components.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In all cases accompanied by the &quot;lovely&quot; aroma of burning plastic. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I never had a chance to find out what they looked like as a circuit element in the few seconds before the catastrophic failure.&lt;/p&gt;&#xA;" OwnerUserId="400" LastEditorUserId="400" LastEditorDisplayName="" LastEditDate="2010-11-01T15:01:22.477" LastActivityDate="2010-11-01T15:01:22.477" CommentCount="2" />
  <row Id="5975" PostTypeId="2" ParentId="5953" CreationDate="2010-11-01T12:56:56.330" Score="3" ViewCount="" Body="&lt;p&gt;There is no such thing as 'required items'. You can stock up on some basic parts, however. You're very likely to need:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Leds&lt;/li&gt;&#xA;&lt;li&gt;Resistors&lt;/li&gt;&#xA;&lt;li&gt;Caps&lt;/li&gt;&#xA;&lt;li&gt;Transistors&lt;/li&gt;&#xA;&lt;li&gt;Solderless breadboard&lt;/li&gt;&#xA;&lt;li&gt;Solid core wire&lt;/li&gt;&#xA;&lt;li&gt;Crocodile clamps&lt;/li&gt;&#xA;&lt;li&gt;External power supply (5-12V?)&lt;/li&gt;&#xA;&lt;li&gt;Multimeter&lt;/li&gt;&#xA;&lt;li&gt;Some sensors&lt;/li&gt;&#xA;&lt;li&gt;...&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;And if you're planning to actually build something: there are loads of questions about soldering irons/solder/... on this site; check those out.&lt;/p&gt;&#xA;" OwnerUserId="1124" LastEditorUserId="1124" LastEditorDisplayName="" LastEditDate="2010-11-01T15:05:33.537" LastActivityDate="2010-11-01T15:05:33.537" CommentCount="2" />
  <row Id="5976" PostTypeId="2" ParentId="5960" CreationDate="2010-11-01T13:13:28.377" Score="6" ViewCount="" Body="&lt;p&gt;I would be more concerned with the risk of explosion/destruction of the capacitor, than I would with the resistance.&lt;/p&gt;&#xA;" OwnerUserId="1413" LastActivityDate="2010-11-01T13:13:28.377" />
  <row Id="5977" PostTypeId="2" ParentId="5960" CreationDate="2010-11-01T13:16:32.290" Score="6" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Most electrolytic capacitors are&#xA;  polarized and require one of the&#xA;  electrodes to be positive relative to&#xA;  the other; they may &lt;strong&gt;catastrophically&#xA;  fail&lt;/strong&gt; if voltage is reversed. This is&#xA;  because a reverse-bias voltage above 1&#xA;  to 1.5 V[1][2][3] will destroy the&#xA;  center layer of dielectric material&#xA;  via electrochemical reduction (see&#xA;  redox reactions). Following the loss&#xA;  of the dielectric material, the&#xA;  capacitor will short circuit, and with&#xA;  sufficient short circuit current, the&#xA;  electrolyte will rapidly heat up and&#xA;  either leak or cause the capacitor to&#xA;  burst. This is because, if the&#xA;  aluminium foil with a layer of&#xA;  aluminium oxide on it is made negative&#xA;  the oxide ion will get reduced and&#xA;  will convert into oxygen gas&#xA;  generating a high pressure and hence&#xA;  may burst open the capacitor.[citation&#xA;  needed] This is same as the&#xA;  electrochemical principle in an&#xA;  electrolyte with 2 electrodes.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Electrolytic_capacitor&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Electrolytic_capacitor&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1737" LastActivityDate="2010-11-01T13:16:32.290" />
  <row Id="5978" PostTypeId="2" ParentId="5970" CreationDate="2010-11-01T13:31:45.110" Score="3" ViewCount="" Body="&lt;p&gt;Make sure the pads don't have any vias in them. I have seen some component footprints that have vias on their pads and I don't realize it until it comes to fab. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have also seen footprints in our corporate database that have been made with keep out markers that go to all layers causing DRC errors when I put components top to bottom.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Probably unlikely any of these are your issue, but at least something to check.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-01T13:31:45.110" />
  <row Id="5979" PostTypeId="2" ParentId="5968" CreationDate="2010-11-01T13:41:40.417" Score="1" ViewCount="" Body="&lt;p&gt;Noise usually creeps up at various specific frequencies in audio, these frequencies change depending on the environment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Option 1&lt;/strong&gt;&lt;br/&gt;&#xA;The easiest way to get rid of noise is the put a band pass filter right around where the frequency of your voice is at. There may still be noise at the same frequency of your voice, but this will be much harder to deal with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Option 2&lt;/strong&gt;&lt;br/&gt;&#xA;I am not sure what Audacity does, but I have seen many programs that require a sample of &quot;silence&quot; and use that to determine the noise. In other words, you record your voice but leave a gap of dead air at the end or beginning. Then you can go analyze what frequency components are around in your dead air. From this you can know how much of each frequency to remove from your voice signal.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-01T13:41:40.417" />
  <row Id="5980" PostTypeId="1" CreationDate="2010-11-01T13:42:09.637" Score="5" ViewCount="189" Body="&lt;p&gt;Are there any microcontrollers which are able to act as a USB host for audio devices?&#xA;Basically I'd like to create an interface which allows my to connect my USB headset to the analog microphone/headphone jacks of my PC (so it doesn't appear as a separate sound device to the OS).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I have no idea if cheap microcontrollers are powerful for that or if there are any microcontrollers which support usb-audio.&#xA;Googling wasn't very helpful; most controllers supporting usb-host only support mass storage devices...&lt;/p&gt;&#xA;" OwnerUserId="1790" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-01T13:52:30.857" LastActivityDate="2010-11-01T14:51:54.590" Title="Microcontroller acting as USB host for an audio device" Tags="&lt;audio&gt;&lt;usb-host&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="3" />
  <row Id="5981" PostTypeId="2" ParentId="5960" CreationDate="2010-11-01T13:49:46.837" Score="5" ViewCount="" Body="&lt;p&gt;I have actually intentionally blown up an electrolytic capacitor in order to demonstrate to students the concern of putting them in properly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I applied 5v to it, my power supply was current limiting at over 5amps. Clearly the effective resistance is much lower then 1 ohm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, when using a DMM to measure resistance, the DMM will only be applying a very small amount of current, small enough that you wont hurt the capacitor. As for the actual resistance shown, I am not sure of this and expect it will depend on many aspects including how the DMM is measuring and the fab process of the cap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a DMM with a diode tester, I would try to use this to determine the polarity. This will put more current through the capacitor, but it shouldn't be large enough to cause it to go pop.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-01T13:49:46.837" />
  <row Id="5982" PostTypeId="2" ParentId="5980" CreationDate="2010-11-01T13:52:27.377" Score="1" ViewCount="" Body="&lt;p&gt;Unless you really like hacking USB, I'd recommend that you either buy an analogue headset or wire some audio jacks onto your existing one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.fourwalledcubicle.com/files/LUFA/Doc/090810/html/page_libraryapps.html&quot; rel=&quot;nofollow&quot;&gt;LUFA supports USB audio&lt;/a&gt; device mode on the USB AVR microcontrollers. With some work, host audio mode may also be possible.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-01T14:51:54.590" LastActivityDate="2010-11-01T14:51:54.590" />
  <row Id="5983" PostTypeId="2" ParentId="5967" CreationDate="2010-11-01T13:57:39.883" Score="2" ViewCount="" Body="&lt;p&gt;Bypass capacitor is just another name for a decoupling or smoothing capacitor. This probably means that the board has a voltage regulator on board and decided to have you be the one to provide the capacitor for it instead of on its own board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a RF module that can output a good amount of power, I would expect for a cap this large to be a necessity.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-01T13:57:39.883" CommentCount="6" />
  <row Id="5984" PostTypeId="2" ParentId="5980" CreationDate="2010-11-01T14:01:32.593" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;https://www.xmos.com/applications/usb-audio&quot; rel=&quot;nofollow&quot;&gt;XMOS devices&lt;/a&gt; support USB Audio 2.0 for really high audio quality, you could dispense with the PC. They are quite cheap. &lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-01T14:01:32.593" />
  <row Id="5985" PostTypeId="2" ParentId="5949" CreationDate="2010-11-01T14:06:02.713" Score="1" ViewCount="" Body="&lt;p&gt;Reversible Energy Recovery Logic uses AC power, but I think that's mostly theoretical at this point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Fsa1r.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chipdesignmag.com/lpd/blog/2009/07/16/existing-circuit-styles-shed-light-on-low-power-design/&quot; rel=&quot;nofollow&quot;&gt;http://chipdesignmag.com/lpd/blog/2009/07/16/existing-circuit-styles-shed-light-on-low-power-design/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-01T14:17:11.700" LastActivityDate="2010-11-01T14:17:11.700" CommentCount="1" />
  <row Id="5986" PostTypeId="2" ParentId="5960" CreationDate="2010-11-01T14:34:52.693" Score="2" ViewCount="" Body="&lt;p&gt;We had a couple .1uF electrolytic go on backwards on a PCB due to the solderer not realizing they were polarized caps(we did not mean to order them).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This caused very odd problems only solved by adding large decoupling capacitors to power(10uF). It was very odd but only had around 20 extra mA being pulled at 5V. We found out we had put them on backwards, swapped them and there was no need for the extra caps on power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My long and short of it, I am not sure how I would have told in the same situation that this happened.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-01T14:34:52.693" />
  <row Id="5987" PostTypeId="2" ParentId="5953" CreationDate="2010-11-01T14:37:18.803" Score="2" ViewCount="" Body="&lt;p&gt;Since you have decided to go with a development platform that is all inclusive the number of require components will be rather small.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the software side, I believe you will need Visual Studio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the hardware side, this will depend mostly on what sensors you will want to integrate with and through what interface. In almost all circumstances I would suggest getting &quot;Expansion connectors that expose GPIO, I2C, SPI and UART signals&quot;&#xA;These are different protocols that you will be using to interface with your sensors.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-01T14:37:18.803" CommentCount="3" />
  <row Id="5988" PostTypeId="2" ParentId="5980" CreationDate="2010-11-01T14:43:11.577" Score="2" ViewCount="" Body="&lt;p&gt;The two cheapest USB host devices I kmow of are Vinculum VNC2L (not sure if available yet) and Microchip PIC24FJ64GB0004. &#xA;You'll need to look through their USB libraries to see how much work would be needed for audio support.&#xA;However for this application I can't help thinking a more analogue solution may be a lot easier, i.e. rip out the digital stuff from the headset.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-01T14:43:11.577" CommentCount="4" />
  <row Id="5989" PostTypeId="2" ParentId="5696" CreationDate="2010-11-01T14:56:29.830" Score="4" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.ralinktech.com/product.php?s=30&quot; rel=&quot;nofollow&quot;&gt;Ralink RT3050&lt;/a&gt; has what you need.&lt;/p&gt;&#xA;" OwnerUserId="1199" LastActivityDate="2010-11-01T14:56:29.830" CommentCount="2" />
  <row Id="5990" PostTypeId="1" AcceptedAnswerId="5992" CreationDate="2010-11-01T15:22:21.307" Score="7" ViewCount="301" Body="&lt;p&gt;From Wikipedia:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;To create the anti-static effect, the black or silver bags are slightly conductive&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;and&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;A device should not be powered while in an antistatic bag, because the conductivity of the bag could cause damaging short-circuits between parts of the device.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So I deduce that those bags are conductive in the interior surface. What about the exterior surface?&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-11-01T15:33:23.417" LastActivityDate="2010-11-03T19:04:02.127" Title="Do antistatic bags have conductive interior, exterior or both?" Tags="&lt;antistatic&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="5991" PostTypeId="2" ParentId="5990" CreationDate="2010-11-01T15:26:39.243" Score="4" ViewCount="" Body="&lt;p&gt;I tested with a multimeter and from the samples I have on my home, that look like this:&#xA;&lt;img src=&quot;http://i.imgur.com/IRIvK.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have both internal and external resistances above 2 MOhms for small sections.&#xA;I even perforated them to see if their interior was conductive, but I don't know if my test reached the inner layer of the plastic (if there is one). Anyhow, the result was the same as for the exterior layers.&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-11-01T15:48:08.367" LastActivityDate="2010-11-01T15:48:08.367" CommentCount="3" />
  <row Id="5992" PostTypeId="2" ParentId="5990" CreationDate="2010-11-01T15:39:23.480" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.packagingknowledge.com/Anti_Static_Bags.asp&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;Antistatic Bags &amp;amp; Conductive Bags&lt;/strong&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;These plastic bags normally have a distinctive color according to its properties:&lt;/p&gt;&#xA;  &#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;Silver for metalized PET film and other similar plastics&lt;/li&gt;&#xA;  &lt;li&gt;Pink or black for polyethylene&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;  &#xA;  &lt;p&gt;(*) The polyethylene model can also be made as foam or bubble wrap, either as sheets or bags.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;To create the anti-static effect, the black bags or silver bags are &lt;strong&gt;slightly conductive&lt;/strong&gt;, forming what is known as a &lt;strong&gt;Faraday Cage&lt;/strong&gt; around the item to be protected avoiding any discharges from being deposited onto the protected devices as the bags are handled.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;“METALIZED SHIELDING” BAGS (Silver in color).&lt;/p&gt;&#xA;  &#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;DO NOT &lt;strong&gt;CREASE&lt;/strong&gt; the bag, as this can breakdown the integrity of the metalized shield!&lt;/li&gt;&#xA;  &lt;li&gt;You should not use any bags damaged with &lt;strong&gt;TEARS&lt;/strong&gt; AND / OR &lt;strong&gt;PUNCTURES&lt;/strong&gt;, as these can DESTROY THE FUNCTION OF THE FARADAY CAGE!&lt;/li&gt;&#xA;  &lt;li&gt;Metalized Shielding bags CAN &lt;strong&gt;DETERIORATE&lt;/strong&gt; with use, MONITORING them for effectiveness is VERY IMPORTANT!&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.esdjournal.com/techpapr/ryne/esdbags.htm&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;ESD Bags: To Shield Or Not To Shield&lt;/strong&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Antistatic Bags&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Antistatic bags are typically coated with a &lt;strong&gt;topical&lt;/strong&gt; antistatic agent that helps minimize the generation of a static imbalance ... Some antistatic bags are made with an antistat &lt;strong&gt;built into&lt;/strong&gt; the films layers and tend to be more reliable and cleaner then the topically treated ones. A good bag has &lt;strong&gt;antistatic properties on both the inside and outside&lt;/strong&gt; of the bag’s film construction.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Dissipative Bags&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Bags with the films surface resistance in the dissipative range are preferred because &lt;strong&gt;charge dissipates across the surface&lt;/strong&gt; at a controlled rate. Most dissipative bags also have the property of being antistatic. These are good general bags to be used in non-critical environments.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Metalized Shielding Bags&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Metalized shielding bags have either a metal film &lt;strong&gt;embedded&lt;/strong&gt; into the bag film construction or &lt;strong&gt;coated&lt;/strong&gt; onto an existing layer. This metal film acts as an electrical shield against electrical discharges from the &lt;strong&gt;outside&lt;/strong&gt; of the bag. Depending on the energy and duration of the discharge and the thickness of the metal film, an ESD event is typically spread out over the outer surface of the metal film and if fully enclosed, i.e. the bag is sealed, then the charges current from the &lt;strong&gt;ESD event is contained to the outside (outer surface) of the metal film&lt;/strong&gt;, i.e., providing a region of no electrostatic fields within the bag, thereby protecting the contents within. This effect is known as the &lt;strong&gt;Faraday Cage Effect&lt;/strong&gt; and is commonly used in controlling ESD via metalized shielding bags, conductive bags and the conductive tote box with a cover.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1084" LastEditorUserId="1084" LastEditorDisplayName="" LastEditDate="2010-11-01T15:55:47.323" LastActivityDate="2010-11-01T15:55:47.323" />
  <row Id="5993" PostTypeId="1" AcceptedAnswerId="5994" CreationDate="2010-11-01T15:40:55.503" Score="2" ViewCount="365" Body="&lt;p&gt;I have an &lt;a href=&quot;http://www.eztronics.nl/webshop/catalog/product_info.php/cPath/33_39/products_id/281&quot; rel=&quot;nofollow&quot;&gt;i-Snail-VC-50&lt;/a&gt; sensor with an output of 0-5V. I'd like to connect this output to the base of a &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet/philips/BC546_547_3.pdf&quot; rel=&quot;nofollow&quot;&gt;BC547&lt;/a&gt; transistor, which powers an LED with an external 5V power source. What I want to achieve, is that the LED lights up as soon as the sensor output voltage rises above 0V (most of the time, the output will be either 0V or within the 0-1V range).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How could I achieve this, making sure that no components get damaged if the sensors output is at its maximum (6.5V)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know transistors are current driven, so perhaps a voltage driven mosfet (I have some IRFZ48N's at my disposal) would be better suited for this task?&lt;/p&gt;&#xA;" OwnerUserId="1124" LastActivityDate="2010-11-01T16:14:15.783" Title="How to drive a BC547 using a 0-5V sensor output?" Tags="&lt;transistor&gt;&lt;hall-effect&gt;" AnswerCount="1" />
  <row Id="5994" PostTypeId="2" ParentId="5993" CreationDate="2010-11-01T16:05:06.763" Score="2" ViewCount="" Body="&lt;p&gt;You can do this with a BC547 transistor, but you'll need an op-amp or comparator to amplify the sensor signal first. The transistor won't turn on until you raise the base 0.6 V above the emitter, so for your 0-1 V range, it would be off most of the time. Even above the 0.6 V threshold, the current drive capability of the sensor is very low, so the LED would only weakly turn on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you amplify the sensor signal, you can use the transistor as a digital switch. On this linked page, see the diagram under example #2, labeled &lt;a href=&quot;http://www.electronics-tutorials.ws/transistor/tran_4.html&quot; rel=&quot;nofollow&quot;&gt;Digital Logic Transistor Switch&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-11-01T16:14:15.783" LastActivityDate="2010-11-01T16:14:15.783" CommentCount="3" />
  <row Id="5995" PostTypeId="2" ParentId="5845" CreationDate="2010-11-01T16:36:58.137" Score="3" ViewCount="" Body="&lt;p&gt;Decoupling would be about the only thing I would consider using Y5V for (and only if I didn't have X7R or X5R available). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;8p seems expensive. In large volumes, MLCCs in surface-mount should be a fraction of that price.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-01T16:36:58.137" />
  <row Id="5996" PostTypeId="1" AcceptedAnswerId="6001" CreationDate="2010-11-01T16:38:49.580" Score="3" ViewCount="389" Body="&lt;p&gt;suppose I want to keep an Arduino powered during the night, and recharge it during the day with a solar cell. What kind of circuit do I have to make, how many and which type of batteries, and what size of solar panel do I need to keep it going?&lt;/p&gt;&#xA;" OwnerUserId="1272" LastActivityDate="2010-11-01T17:44:16.747" Title="powering arduino via solar cells" Tags="&lt;arduino&gt;&lt;solar-cell&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="5997" PostTypeId="2" ParentId="5996" CreationDate="2010-11-01T16:57:42.613" Score="2" ViewCount="" Body="&lt;p&gt;I'd start by measuring the power consumption of the Arduino and figure out how to put it to sleep when possible. From what I've &lt;a href=&quot;http://fightpc.blogspot.com/2008/10/low-power-arduino.html&quot; rel=&quot;nofollow&quot;&gt;read&lt;/a&gt;, the Arduino Pro Mini consumes something like 5 mA at 3.3 V, which is around 15 mW. With a solar panel, your capacity factor is likely to be around 10 percent, meaning that it will produce an average power of around 10% of its peak power. This suggests that you need a panel that can produce 150 mW, but I'd probably go for a 1 W panel unless size is an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For batteries, you want to get as low a voltage as you can, while still being above 3.3 V. I might try a 6 V lantern battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For wiring, put all three devices (Arduino, battery, and solar panel) in parallel. Example (minus the battery) &lt;a href=&quot;http://little-scale.blogspot.com/2008/03/connecting-solar-panel-to-arduino.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-01T16:57:42.613" CommentCount="3" />
  <row Id="5998" PostTypeId="1" AcceptedAnswerId="6002" CreationDate="2010-11-01T17:05:39.150" Score="13" ViewCount="339" Body="&lt;p&gt;This is more of a opinion question than a information question. I am designing some boards that will be working near decent sized actuators, so I ask you, what is more resistant a 0805 SMD or a 7mm thru-hole resistor?&lt;/p&gt;&#xA;" OwnerUserId="1673" LastActivityDate="2010-11-02T15:52:36.553" Title="SMD vs. Through-hole components in high vibration environments" Tags="&lt;pcb&gt;&lt;design&gt;&lt;physical-design&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="2" />
  <row Id="5999" PostTypeId="2" ParentId="5998" CreationDate="2010-11-01T17:31:59.660" Score="7" ViewCount="" Body="&lt;p&gt;Less mass has to be better, and an SMD resistor has a lot less mass than thru-hole.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-01T17:31:59.660" CommentCount="2" />
  <row Id="6000" PostTypeId="2" ParentId="5998" CreationDate="2010-11-01T17:39:46.267" Score="3" ViewCount="" Body="&lt;p&gt;Are you up against twisting forces at all? Or just vibration? SMD component has a bit less mass, so for a given amount of vibration it'll put less stress on it's joints. On the other hand, the through-hole component won't care nearly as much if the board is flexing because it's got wire leads that should let it move around a bit.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2010-11-01T17:39:46.267" />
  <row Id="6001" PostTypeId="2" ParentId="5996" CreationDate="2010-11-01T17:44:16.747" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.rachelselectronics.com/categories/open-source-hardware/&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;SolArduino v1&lt;/strong&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/hswgu.png&quot; alt=&quot;Board&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/g3F3u.jpg&quot; alt=&quot;PCB&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rachelselectronics.com/2010/09/solar-piston-v1/&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;Solar Piston v1&lt;/strong&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/NVco0.png&quot; alt=&quot;Schematic&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1084" LastActivityDate="2010-11-01T17:44:16.747" />
  <row Id="6002" PostTypeId="2" ParentId="5998" CreationDate="2010-11-01T18:12:07.523" Score="8" ViewCount="" Body="&lt;p&gt;The only vibration (SAE J1455) SMT problems I've ever seen for common components are failures for large Al-electrolytics.  The solution there is just to anchor them down with a gob of silicone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An 0805 resistor will not fall off from pure vibration unless there is a tremendous amount of board warping going on (then it may fracture), or unless you are going to expose it to several thousand &lt;em&gt;g&lt;/em&gt; routinely (in which case you have bigger things to worry about).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An 0805 resistor weighs about 4 mg, and the pound of force or so I just put on it with my fingernail did nothing, so that's &lt;a href=&quot;http://www.google.com/#sclient=psy&amp;amp;hl=en&amp;amp;safe=active&amp;amp;q=1+pounds+force+%2F+4+milligrams+%2F+earth%27s+gravity&quot; rel=&quot;nofollow&quot;&gt;equivalent to about 113,000 times earth's gravity&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-01T18:12:07.523" CommentCount="1" />
  <row Id="6003" PostTypeId="2" ParentId="5998" CreationDate="2010-11-01T18:41:07.800" Score="4" ViewCount="" Body="&lt;p&gt;I've had problems with microphonic (converting vibration into signal) surface mount capacitors that were resolved by switching them to through-hole&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-11-01T18:41:07.800" CommentCount="1" />
  <row Id="6004" PostTypeId="2" ParentId="3345" CreationDate="2010-11-01T19:17:02.353" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://pandaboard.org/&quot; rel=&quot;nofollow&quot;&gt;PandaBoard&lt;/a&gt; is a good alternative too.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-01T19:17:02.353" />
  <row Id="6005" PostTypeId="2" ParentId="5998" CreationDate="2010-11-01T19:17:44.677" Score="2" ViewCount="" Body="&lt;p&gt;A friend of mine who does control boards for windturbines (read: high-vibration, high-reliability) swears by SMD, specifically BGA, even QFP have too long pins and will suffer from fatigue too soon in that application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The shorter the pins, the stiffer the mount and the higher the reliability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You must protect the board from warping, though, because there is no give in those stiff connections and BGAs will crack before jumping off the board. &lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-01T19:17:44.677" />
  <row Id="6006" PostTypeId="2" ParentId="5968" CreationDate="2010-11-01T19:37:07.763" Score="1" ViewCount="" Body="&lt;p&gt;If by &quot;background noise&quot;, you mean noise that has a wide bandwidth and is relatively stationary, then spectral subtraction should work quite well for you.  This is the general technique that Audacity/Cool Edit use when they say &quot;Noise Reduction&quot;.  Spectral subtraction is a very google-friendly term if you're interested in more research.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You take a sample of sound where there is no signal, and you create an FFT noise template from that.  Then, you subtract that FFT noise template from the FFT of your signal + noise.  Some algorithms get fancy and smooth the resulting frequency domain waveform before doing the inverse FFT.  You have to be careful about how &quot;strong&quot; the reduction is, or you get these &quot;underwater musical echoes&quot;.  Sometimes it's better to do two &quot;weak&quot; passes than one &quot;strong&quot; pass.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However if there's e.g. cars moving in the background this won't work.  In such a case, you might want to look at crazier stuff like Wiener filters.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-11-01T19:37:07.763" />
  <row Id="6007" PostTypeId="2" ParentId="5884" CreationDate="2010-11-01T19:46:16.943" Score="2" ViewCount="" Body="&lt;p&gt;In addition to on-die peripherals (which can make quite a large difference in &quot;power&quot; with things like Block RAM, embedded multipliers, etc), and clock speed/&quot;timing closure&quot;, another limiting factor of FPGAs is quite often the pin count.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sure, you can put 8 cores into an FPGA, but then you have to get those 8 cores to talk to the outside world.  To make matters worse, once you get beyond a few hundred pins you have to use a BGA package, which is much more difficult to design a PCB for.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-11-01T19:46:16.943" />
  <row Id="6008" PostTypeId="1" CreationDate="2010-11-01T20:10:52.520" Score="3" ViewCount="283" Body="&lt;p&gt;I am building a digital voltage gauge for my motorcycle for fun.  I am buying a nice little display which has common ground, so that I can provide 5 and 12 volts from the same source.  I was hoping to use a &quot;7805&quot; regulator to control the 5v, but do not want to provide the varying 12+- volts directly to the 7805.  I would like to drop about 7 volts before I apply the power to the 7805.  I looked at &lt;a href=&quot;http://electronics.stackexchange.com/questions/263/using-diodes-to-limit-current-to-leds&quot;&gt;http://electronics.stackexchange.com/questions/263/using-diodes-to-limit-current-to-leds&lt;/a&gt; which seems to indicate that using diodes forward voltage drop is not a good idea for leds, and maybe using a zener diode is not either.  If I just use a series resistor, I would have to guestimate and experiment to get in the ballpark (as I don't know the current draw), and, as I understand it, the voltage dropped over the resistor would vary with the applied voltage.  Here are my questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is using a diode(s) to drop the voltage independent of current a bad idea here? (Is it always a bad idea?)&lt;/li&gt;&#xA;&lt;li&gt;Do I still get he same IIR loss for the voltage dropped whether it is a resistor or diode?&lt;/li&gt;&#xA;&lt;li&gt;Is there a conventional &quot;best practices&quot; approach I should be using?&lt;/li&gt;&#xA;&lt;li&gt;Lets go out into left field for a minute: other than heat-sinking the 7805, can I pot the whole mess with RTV silicon to vibration and moisture resist?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Always nice to know if the alternator is working OK.  Not an electronics guy, just a tinkerer.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;==================================&lt;br&gt;&#xA;Thank you Nick and Thomas.  I agree that a motorcycle is about the harshest environment one can choose-greater vibration, direct exposure to rainwater, probably greater variations in regulated voltage due to greater variations in engine (and so alternator) speeds. I had hoped to fuse and put the dropping resistor at the battery connection to provide the greatest protection for anticipated faults in the wiring run and/or the digital readout itself.  Based on your comments, I will fuse at the battery connection, run fine (#28?) wire to a MIC2945 and let it do all the voltage dropping.  I anticipate a mounting plate fastened directly to the 2945 heat sink, with the entire remainder of the assembly &quot;glued&quot; to the mounting plate with RTV silicon.  Waterproofing is a concern, for which I will rely on the RTV silicon. &lt;/p&gt;&#xA;" OwnerUserId="1796" LastEditorUserId="1796" LastEditorDisplayName="" LastEditDate="2010-11-02T15:17:00.097" LastActivityDate="2010-11-02T15:17:00.097" Title="Use diodes to obtain lowered DC voltage?" Tags="&lt;diode&gt;&lt;voltage-regulator&gt;" AnswerCount="2" />
  <row Id="6009" PostTypeId="1" AcceptedAnswerId="6012" CreationDate="2010-11-01T20:23:11.170" Score="4" ViewCount="366" Body="&lt;p&gt;I've seen some PCB's with components mounted at multiples of 45 degrees (45, 135, etc.) I recently discovered my PCB program (gEDA PCB) supports these, though it isn't a GUI function and you have to run a command. When is it appropriate to mount at these angles? And what about angles of 30 degrees and 60 degrees, or arbitrary angles? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-06-03T16:32:18.450" Title="When is it appropriate to mount components at a 45 degree angle?" Tags="&lt;pcb&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="6010" PostTypeId="2" ParentId="6008" CreationDate="2010-11-01T20:29:29.170" Score="4" ViewCount="" Body="&lt;p&gt;First, why would you do this? The 7805 will be perfectly fine with 12V. If you're passing a lot of current, use a heatsink. The diodes will only move power loss from the regulator to the diodes themselves.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;In this case it should be fine, but diodes do not drop a fixed voltage; the voltage drop varies depending on current in a non-linear fashion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So for example getting 5V from a 12V source using 10 diodes in series would be bad, and the voltage could range from as much as 7V to as little as 2V, depending on the current draw. The 7805 has a minimum voltage of 7V to output 5V at 1 amp, so as long as you can guarantee this 7V you should be okay. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that the output of the 7805 will vary depending on input voltage by a few millivolts - it will be slightly higher at 12V than at 7V.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The same loss happens no matter if you use resistors or diodes. The energy must go somewhere and it is converted into heat by either resistors or diodes.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The best practice here is just to feed 12V into the 7805. Introducing more components into the circuit will make for more chance of failure. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Why is a heatsink not practical? Here, I'm unsure if potting would work. Best to ask someone else.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;You should be cautious when using the 7805 in an automotive circuit. The battery line is a harsh place. When you turn the headlamp(s) on your car/bike off, for example, the excess energy in the alternator has to go somewhere and it does - it appears as up to a 60V spike on the 12V line. And in some rare circumstances you can get a negative voltage on the battery line. Both of these situations will destroy a 7805, and the output could short, connecting the battery line to the 5V output, giving your load 12V instead of 5V. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-01T20:38:26.417" LastActivityDate="2010-11-01T20:38:26.417" />
  <row Id="6011" PostTypeId="2" ParentId="6009" CreationDate="2010-11-01T20:33:39.387" Score="4" ViewCount="" Body="&lt;p&gt;Placing a QFP chip at 45 degrees can make it easier to connect the leads to pins on a DIL board. Try it for yourself. Other angles aren't helpful.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-01T20:33:39.387" CommentCount="2" />
  <row Id="6012" PostTypeId="2" ParentId="6009" CreationDate="2010-11-01T20:50:57.010" Score="5" ViewCount="" Body="&lt;p&gt;Another reason would be for indicator or display components. It's not terribly uncommon to see chip LEDs at varying angle to fit the aesthetics of a particular device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whatever the reasoning, most SMT machines can places parts at angles without issue.&lt;/p&gt;&#xA;" OwnerUserId="1467" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-01T21:49:26.630" LastActivityDate="2010-11-01T21:49:26.630" CommentCount="2" />
  <row Id="6013" PostTypeId="2" ParentId="6008" CreationDate="2010-11-01T21:19:51.763" Score="3" ViewCount="" Body="&lt;p&gt;&lt;code&gt;1.&lt;/code&gt; Usually. &#xA;&lt;code&gt;2.&lt;/code&gt; The energy will go somewhere&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How much current are you drawing?  A conservative junction-to-ambient &lt;code&gt;Td&lt;/code&gt; for a TO-220 is 65°C/W, so much above 1 W or drawing 100 mA you will need some form of a heat sink.  It doesn't have to be anything glorious, e.g. a screw, if you get really high you could screw the regulator directly to some plate of aluminum and have that be exposed in your enclosure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Echoing Thomas's fear of vehicle DC power, I think motorcycles are worse than the typical car due to a much smaller battery and the more variable output from the dynamo.  The standard operating voltage range (SAE J1455) is 9-16 V, faults of +24 V (double battery), -12 V (reverse battery), and some spooky transients.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;3.&lt;/code&gt; Nevertheless, a stock 7805 should be just fine with a reverse blocking diode, and preferably a &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=SA30CA-TPMSCT-ND&quot; rel=&quot;nofollow&quot;&gt;TVS&lt;/a&gt; to chop off any high (&gt;30 V) transients.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally, &lt;strong&gt;always remember to fuse vehicle electronics&lt;/strong&gt;.  Currents can be ridiculously high, and if you drag the bus down for very long, you might cause problems or even damage everything else like the ECU and ABS (not really standard on most motorcycles, but on cars).  Even if you splice into a fused line, it can still be nice to only blow your fuse instead of one that will take other things with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;4.&lt;/code&gt; I would think your environmental protection selection will depend a little more on the mechanical considerations of your other parts (gauges...) in addition to the regulator's power dissipation.  RTV isn't the best heat conductor, so if you end up needing a good heatsink, you'll need to expose that to the air in some way.  It was used fairly commonly at my previous company to protect the more vibration-sensitive parts (SMT electrolytics, large TH parts) in small blobs, but never to fully pot assemblies as it's fairly spendy (but for hobby projects, whatever &lt;code&gt;:P&lt;/code&gt;).&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-01T21:28:49.223" LastActivityDate="2010-11-01T21:28:49.223" CommentCount="4" />
  <row Id="6014" PostTypeId="2" ParentId="6009" CreationDate="2010-11-01T21:38:26.700" Score="6" ViewCount="" Body="&lt;p&gt;Parts can be at whatever angle they need to be to help layout or fit into some bizarre package.  Your manufacturing engineer may not like it, but if it's required, then oh well.  As Duane mentions, this is rarely a problem nowadays, but be sure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Conversely, your manufacturing engineer will pretty much demand 45° rotation of QFPs if they are to be wave soldered.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-01T21:38:26.700" CommentCount="4" />
  <row Id="6015" PostTypeId="2" ParentId="5861" CreationDate="2010-11-01T21:42:31.343" Score="1" ViewCount="" Body="&lt;p&gt;In terms of C compilers and related software, Microchip gives away their standard MPLAB IDE for free. With that, you can always program in assembly language. However, if you want C, they also have a version of their Hi_Tech C compiler free of charge. They offer it for the 18F series and then a different one for the 10/12/16F series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I started with MPLAB and the CC5X C compiler (bknd.com) and have also used HI-Tech C.&lt;/p&gt;&#xA;" OwnerUserId="1467" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-01T21:51:50.937" LastActivityDate="2010-11-01T21:51:50.937" CommunityOwnedDate="2011-05-15T04:20:58.030" />
  <row Id="6016" PostTypeId="1" CreationDate="2010-11-01T21:47:33.353" Score="5" ViewCount="190" Body="&lt;p&gt;Disclaimer: I am a beginner.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am reading a knol book on electronics, and I am faced with &lt;a href=&quot;http://knol.google.com/k/-/-/1f4zs8p9zgq0e/lxzei8/rectif-split-1.jpg&quot; rel=&quot;nofollow&quot;&gt;this schematics&lt;/a&gt;. I don't know if I am allowed to put the actual image, so I just make a link.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I read a circuit to understand what it does ? Do I have to imagine the electrons flowing, or is there a better strategy ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another example I found, this time more complex:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/A41ik.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While I do understand the left part, how do I make sense to the remaining mess ?&lt;/p&gt;&#xA;" OwnerUserId="1272" LastEditorUserId="1272" LastEditorDisplayName="" LastEditDate="2010-11-01T22:43:51.967" LastActivityDate="2011-04-08T21:32:33.783" Title="Reading a circuit" Tags="&lt;circuit&gt;" AnswerCount="5" CommentCount="5" FavoriteCount="1" />
  <row Id="6017" PostTypeId="1" AcceptedAnswerId="6036" CreationDate="2010-11-01T21:49:57.270" Score="4" ViewCount="220" Body="&lt;p&gt;&lt;strong&gt;The Background&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My main background is embedded software but I have had to debug the analog circuitry myself so I've picked up a little bit here and there, enough so to describe the problem in a coherent way to someone who could give me a solution. At my work, I was on a project where we were developing a hand-held radar transceiver that operated in the single Ghz frequency range. One particularly thorny issue that we never resolved was the antenna connectors we used introduced ringing artifacts in the receive signal. To prove this as a source we would put 50ohm terminators instead of the antennas and would observe a significant decrease in the noise in the signal. We also observed decreasing noise as we introduced progressively longer lengths of cable between the Tx/Rx connector and their respective antennas. So the initial conclusion was to introduce delay between the connectors and their antennas to dissipate the ringing and make our lives easier on the Rx side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The Problem&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the real problem is how do we implement that delay, preferable 15-20ns worth, where space is our main constraint (the last board we built was two dual-side 10cm x 10cm boards, one for the electronics and the other for the antennas with the aforementioned connectors between the two boards)? I had once suggested drawing out trace paths between the connectors and antennas in the same manner as illustrated in &lt;a href=&quot;http://electronics.stackexchange.com/questions/4168/what-is-this-squiggly-trace-for&quot;&gt;this question&lt;/a&gt; except that's for digital signals and my limited experience with analog signals has taught me that analog RF signals are a lot more pickier than digital signals. Never did get to try out my idea and now the project is on hold for lack of funding.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The Question&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if nothing else I'd like an answer to whether using PCB traces for large analog RF delay is a feasible idea and what pitfalls would need to be considered. Is this even a common practice or does the RF world rely on special circuits to do that function? Another project which I was involved in had the same problem and used a gated switch as a solution which worked but added quite a bit more components (guesstimate of 25% extra space required). I'm mostly looking for a general argument about how this problem could be approached but references would also be appreciated (even if its way above my head!). Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1614" LastActivityDate="2010-11-02T03:52:24.530" Title="Feasibility of introducing RF delay via PCB trace?" Tags="&lt;pcb&gt;&lt;analog&gt;&lt;radio&gt;" AnswerCount="4" CommentCount="5" />
  <row Id="6018" PostTypeId="2" ParentId="5747" CreationDate="2010-11-01T21:54:53.700" Score="1" ViewCount="" Body="&lt;p&gt;If your CFLs are in enclosed fixtures and are not specifically rated for such, I'd say that's the problem. Most are designed to be used in open fixtures with the base down so the heat can rise away from the electronics. To keep costs down, they have electronics designed on the hairy edge. The heat can easily dramatically shorten their life&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I started recording lifespans and found that in an enclosed fixture, my CFLs had a typical life of one to three months. Used as designed, open, vertical and base down, they tend to not die.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd suggest either going back to incandescent in your closed fixtures or paying extra and purchasing CFLs specifically rated for enclosed fixtures.&lt;/p&gt;&#xA;" OwnerUserId="1467" LastEditorUserId="1467" LastEditorDisplayName="" LastEditDate="2010-11-01T22:11:53.647" LastActivityDate="2010-11-01T22:11:53.647" CommentCount="1" />
  <row Id="6019" PostTypeId="2" ParentId="6016" CreationDate="2010-11-01T21:56:03.700" Score="3" ViewCount="" Body="&lt;p&gt;To understand electronics, you first need to understand what the individual components do.  There are two parts in that circuit:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The transformer&lt;/li&gt;&#xA;&lt;li&gt;Diodes (rectifiers)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Transformer&quot; rel=&quot;nofollow&quot;&gt;transformer&lt;/a&gt; can change the voltage of AC (&lt;a href=&quot;http://en.wikipedia.org/wiki/Alternating_current&quot; rel=&quot;nofollow&quot;&gt;alternating current&lt;/a&gt;) power from what you're supplied with (here 120 V, household current) to something closer to what you require (here 12 V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Diode&quot; rel=&quot;nofollow&quot;&gt;diodes&lt;/a&gt; (here in a &lt;a href=&quot;http://en.wikipedia.org/wiki/Diode_bridge&quot; rel=&quot;nofollow&quot;&gt;&quot;full-bridge&quot; configuration&lt;/a&gt;) convert the AC to DC (&lt;a href=&quot;http://en.wikipedia.org/wiki/Direct_current&quot; rel=&quot;nofollow&quot;&gt;direct current&lt;/a&gt;) by only allowing current to flow in one direction.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-01T21:56:03.700" CommentCount="6" />
  <row Id="6020" PostTypeId="2" ParentId="5691" CreationDate="2010-11-01T21:59:59.107" Score="2" ViewCount="" Body="&lt;p&gt;Is it the 1GHz  you are looking for or the Cortex-A9 specifically (ethernet, etc.)?  Have you looked at the &lt;a href=&quot;http://open-rd.org/&quot; rel=&quot;nofollow&quot;&gt;open-rd.org&lt;/a&gt; boards or plug computers from Marvell?  They are in the 1.2GHz range but are not Cortex-A9, I don't think.  Hawkboard and Beagleboard have ethernet.  All so far are similar price range of the Pandaboard.  I like the &lt;strong&gt;&lt;em&gt;open-rd&lt;/em&gt;&lt;/strong&gt; because you can plug a laptop SATA hard drive right into it and not have to deal with flash based media (except for the initial boot).&lt;/p&gt;&#xA;" OwnerUserId="985" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-01T07:44:14.450" LastActivityDate="2011-02-01T07:44:14.450" CommentCount="1" />
  <row Id="6021" PostTypeId="2" ParentId="5830" CreationDate="2010-11-01T22:08:22.410" Score="2" ViewCount="" Body="&lt;p&gt;Every time a transistor changes state in a digital system, it takes a tiny bit of current to switch. Tons of the transistors in a logic chip or microcontroller are changing at nearly the same instant. When that happens, the power consumed by the chip spikes briefly. Bypass (or decoupling) capacitors help supply that power so that those brief load spikes don't cause the supply voltage on other chips to drop. (Especially since the other chips might be briefly needing their own surge of current at the same time.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's why you want very fast (small, low ESR) caps located near each IC, as close to the power pins as practical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The big caps near the power supply provide the current to carry the load while the AC supply goes through 0V, and the small/medium caps near the supply help refill the bypass caps scattered all over the board.&lt;/p&gt;&#xA;" OwnerUserId="1292" LastActivityDate="2010-11-01T22:08:22.410" />
  <row Id="6022" PostTypeId="2" ParentId="6017" CreationDate="2010-11-01T22:24:21.853" Score="1" ViewCount="" Body="&lt;p&gt;What you're proposing is a common practice. People use serpentine traces to delay signals, though I don't personally know of a case in the 1 GHz range. I've seen estimates before of delays using approximate 1 in^2 for a 7 ns delay, so you'd need to dedicate 2-3 in^2 of board per signal.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-01T22:24:21.853" />
  <row Id="6023" PostTypeId="2" ParentId="6017" CreationDate="2010-11-01T22:27:18.610" Score="1" ViewCount="" Body="&lt;p&gt;The general idea (theoretically) is to put in a stub some distance away from the antenna feed. The length of that stub and how far back it should go is somewhat in the realm of black magic. The tool used to figure this stuff out is called a Smith Chart...&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-11-01T22:27:18.610" CommentCount="3" />
  <row Id="6024" PostTypeId="2" ParentId="5478" CreationDate="2010-11-01T22:37:32.523" Score="0" ViewCount="" Body="&lt;p&gt;MSDN provides a &lt;a href=&quot;http://msdn.microsoft.com/en-us/library/cc561925.aspx&quot; rel=&quot;nofollow&quot;&gt;extendedweakreferences sample&lt;/a&gt;&lt;br&gt;&#xA;and I believe this requires to write and read to flash memory, which I guess the Netduino has.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So essentially the extendedweakreferences class is just a way of letting you use flash memory.&lt;br&gt;&#xA;In relation to your question is it safe? Yes it provides a way of encapsulating the read/write process, although it may not be safe for whatever data was already on the flash memory in the same location.&lt;/p&gt;&#xA;" OwnerUserId="1457" LastActivityDate="2010-11-01T22:37:32.523" />
  <row Id="6025" PostTypeId="2" ParentId="6016" CreationDate="2010-11-01T22:39:13.567" Score="8" ViewCount="" Body="&lt;p&gt;In electronics engineering there are a lot of common circuits, electronic building blocks. After you learn how the basic components work, the next step is to analyze, measure, and learn these buliding blocks. For example there are several well working solutions for AC-DC conversion, and if know these, you can recognize this kind of circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is no easy way to do this. In the university the teaching begins with the electrons and low level physical laws. Then come the passive electronic components, then the active ones, after that the basic circuits, etc. Each of them has a characteristic (what output it gives for what input) which you have to learn and memorize. So next time you will be able to imagine what that type of circuit does.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are manual methods and calculations to analyze the current flows in the circuit, but I think the simplest solution is to measure the circuit in an electronic simulator program. &#xA;Of course there are a lot of information on the net, for example about the recifier circuit you linked, see &lt;a href=&quot;http://www.allaboutcircuits.com/vol_3/chpt_3/4.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1514" LastEditorUserId="1514" LastEditorDisplayName="" LastEditDate="2010-11-01T22:47:37.160" LastActivityDate="2010-11-01T22:47:37.160" CommentCount="1" />
  <row Id="6026" PostTypeId="2" ParentId="6017" CreationDate="2010-11-01T22:44:24.293" Score="2" ViewCount="" Body="&lt;p&gt;the reflections and ringing your seeing are a result of impedance mismatches caused by the connectors and stray elements in the design.  Running something in the multi Ghz range through connectors and the like isn't overly simple, especially analog stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the Ghz range stray inductances and capacitances in the PCB make up and trace routing become very significant.  There are tools to analyze these situations but they are not cheap, your best bet is to get a book on microwave design that covers designing matching circuits.  (sorry i don't have a good recommendation for you)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use serpentine traces to delay these types of signals but you have to include any structure you create in your matching analysis as serpentine patterns will create additional stray inductance.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-01T22:44:24.293" />
  <row Id="6027" PostTypeId="1" AcceptedAnswerId="6030" CreationDate="2010-11-01T23:02:47.010" Score="4" ViewCount="204" Body="&lt;p&gt;I have a 15µH 1.6A inductor: &lt;a href=&quot;http://uk.farnell.com/bourns/sdr0604-150yl/inductor-smd-15uh-1-6a/dp/1828004&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/bourns/sdr0604-150yl/inductor-smd-15uh-1-6a/dp/1828004&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;em&gt;operating current&lt;/em&gt; is 1.3A, but the &lt;em&gt;saturation current&lt;/em&gt; is 1.6A. What is the difference between these? Will the inductor work properly at less than 1.3A or less than 1.6A? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-01T23:38:51.003" Title="How important is saturation current for an inductor?" Tags="&lt;inductor&gt;" AnswerCount="1" />
  <row Id="6028" PostTypeId="1" AcceptedAnswerId="6046" CreationDate="2010-11-01T23:05:36.413" Score="0" ViewCount="255" Body="&lt;p&gt;I'm building a 3.3V 400mA power supply around an ultra fast buck reg (3 MHz or 1.6 MHz, LM2734Z/X.) According to simulations, the ripple will be &amp;lt;2mVp-p. The noise floor of my scope is about 500µVp-p on 5mV/div (the minimum setting), so how do I measure such a small signal? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking I'm going to need an amplified probe of some kind, but I suspect these will be very expensive. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking of fine tuning the trigger and using the averaging function to remove the noise from the signal, but would this be adequate for power supply ripple? Scope is a HP 54501A, 100 MHz -3dB b/w, 10 MS/a digitising, quite an old scope but only cost £150.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-02T11:54:36.707" Title="Measuring low ripple on a power supply with an oscilloscope" Tags="&lt;oscilloscope&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="6029" PostTypeId="1" AcceptedAnswerId="6031" CreationDate="2010-11-01T23:19:14.577" Score="3" ViewCount="231" Body="&lt;p&gt;I am curious about a resonant LC circuit. Assuming a perfect inductor and capacitor, would it be possible to tap off the energy in the oscillations to use it as a battery? Literally, it would be an AC battery. With a bridge rectifier and filter cap would this act as a DC battery?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(This is just theoretical stuff - I doubt you could get useful energy from an LC circuit as it would dissipate too quickly due to losses in the inductor and capacitor, plus to store any reasonable amount of energy would probably require a massive inductor and capacitor.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-04T14:55:17.833" Title="LC circuit: can it act as an &quot;AC battery&quot;?" Tags="&lt;capacitor&gt;&lt;inductor&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="6030" PostTypeId="2" ParentId="6027" CreationDate="2010-11-01T23:25:56.910" Score="6" ViewCount="" Body="&lt;p&gt;What they're telling you with the saturation current is that above 1.6A, the core can't take any more magnetic flux, and this translates into a change in the effective inductance when the current gets into that realm. You can put more current through the winding, and you do get more flux as a result, but the effective permeability of the core drops off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The effect won't be a sharp break, either; you would start to see some of the effects as you get near the saturation point. If you apply a pure sine wave voltage across the coil that would result in less than 1.3A peaks, the current will also be sinusoidal, but if you run the voltage up to where the peak currents would reach saturation, the current waveform will have a significant harmonic component.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-11-01T23:38:51.003" LastActivityDate="2010-11-01T23:38:51.003" CommentCount="1" />
  <row Id="6031" PostTypeId="2" ParentId="6029" CreationDate="2010-11-02T00:06:49.463" Score="10" ViewCount="" Body="&lt;p&gt;This actually exists in RF transmitters like walkie-talkies. People call them &quot;LC tanks.&quot; You're right that the amount of energy that can be stored is quite small. The reason people use them is to store energy that can be withdrawn as oscillations at a certain frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might Google &quot;Colpitts oscillator&quot; or &quot;Hartley oscillator&quot; for more information.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-02T00:06:49.463" CommentCount="4" />
  <row Id="6032" PostTypeId="2" ParentId="6009" CreationDate="2010-11-02T00:40:30.653" Score="0" ViewCount="" Body="&lt;p&gt;Ha!  The layout program specified (gEDA PCB) doesn't support rotating a square to 45 degrees.  The thermal pad of a QFN is usually a square.  Rotating it at 45 degrees doesn't work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One workaround is to make it a not-quite-square.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will also encounter another problem with gEDA PCB:&#xA;text cannot be rotated to arbitrary angles.  Only 0,90,180,270 degrees.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't recommend PCB for anything other than simple rectilinear designs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: I have been using pcb for increasingly geometrically complex designs, and it gets harder and harder.  Finally, I made a script to convert DXF to pcb's format, such as it is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The script is here: &lt;a href=&quot;http://vivara.net/software/dxftopy.tar.gz&quot; rel=&quot;nofollow&quot;&gt;http://vivara.net/software/dxftopy.tar.gz&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It goes from qcad:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/RTDeX.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To pcb:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/4lXvW.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Resulting file (ben-mode render):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/cBzir.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But this process is an unspeakable pain in the hindquarters.  pcb is terrible at editing anything that is not on a grid.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-11-02T15:23:42.933" LastActivityDate="2010-11-02T15:23:42.933" CommentCount="11" />
  <row Id="6033" PostTypeId="2" ParentId="6028" CreationDate="2010-11-02T00:45:03.610" Score="2" ViewCount="" Body="&lt;p&gt;I have a similar scope. Not a bad little unit but I have to take the front panel off and clean all the buttons. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You've already figured out that accumulate mode will give you a good idea of the &quot;envelope&quot; of the ripple over time. In order to get a clearer picture than that you'll need either a better scope or amplified probes, but I'm not sure why you'd need to worry so much about that ripple. Is this merely academic or are you trying to do something unusual?&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-11-02T00:45:03.610" CommentCount="4" />
  <row Id="6034" PostTypeId="1" AcceptedAnswerId="6035" CreationDate="2010-11-02T02:33:00.693" Score="5" ViewCount="293" Body="&lt;p&gt;When I solve questions, I usually get confused between when to use the Kirchhoff's Voltage Law (KVL) and when Kirchhoff's Circuit Law (KCL). Please help.&lt;/p&gt;&#xA;" OwnerUserId="1799" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-28T11:27:56.440" LastActivityDate="2011-04-28T11:27:56.440" Title="How do I decide whether to use Kirchhoff's Voltage Law or Kirchhoff's Circuit Law?" Tags="&lt;theory&gt;&lt;kirchhoffs-laws&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="6035" PostTypeId="2" ParentId="6034" CreationDate="2010-11-02T03:25:24.490" Score="6" ViewCount="" Body="&lt;p&gt;Whichever gives an easy set of equations. If you are doing resistor networks, count if there are more loops or more nodes. KVL if there are more loops, KCL if there are more nodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In more advanced circuits, like transistors, there is normally a very specific mode that lends itself to your problem space.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-02T03:25:24.490" CommentCount="1" />
  <row Id="6036" PostTypeId="2" ParentId="6017" CreationDate="2010-11-02T03:52:24.530" Score="5" ViewCount="" Body="&lt;h2&gt;Creating Delay&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;To create a delay you want to pick a filter with a large &lt;a href=&quot;http://www.microwaves101.com/encyclopedia/groupdelay.cfm&quot; rel=&quot;nofollow&quot;&gt;group delay&lt;/a&gt; at your frequency range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microwaves101.com/encyclopedia/groupdelayfilters.cfm&quot; rel=&quot;nofollow&quot;&gt;Microwaves101 explains it to some extent&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Why a longer line helps &lt;/h2&gt;&#xA;&#xA;&lt;p&gt;If you are using a longer line and dropping your noise floor you are actually creating a very basic &lt;a href=&quot;http://www.microwaves101.com/encyclopedia/isolators.cfm&quot; rel=&quot;nofollow&quot;&gt;isolator&lt;/a&gt;. Now the microwaves101 explanation of an isolator is a tied to an easy to implement microwaves component, the &lt;a href=&quot;http://www.microwaves101.com/encyclopedia/circulators.cfm&quot; rel=&quot;nofollow&quot;&gt;circulator&lt;/a&gt;. Now this is a relativly complicated device to think about implementing if you are used to frequencies that Microwave engineers consider DC(like 500kHz). The device that approximates an isolator for you is a diode. If you connect power to a line with a diode that is idea, any reflections/ringing/feedback will be blocked and dissipated by the diode.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; What the Cable Does. &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;As you increase the cable length, you increase cable loss. Lets say you have a number like 1dB loss (which is a gain of -1dB). If reflections are your primary source of noise then a reflection off of your load will travel back to antenna and then back to the load again. This means just from the cable you have caused a 3dB loss(half power). This neglects the fact that the reflection is a rather large loss on both interfaces also. This &quot;isolates&quot; in the respect that as the line gets longer your reflected signals have a larger and larger loss, at-least 3 times what your signal feels.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; How Do I Fix It?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;This is probably a sign that your load, whatever you are measuring with, is miss-matched, A decent match, giving a reflection of around -20dB coupled with the loss hitting the antenna again should leave your reflections relatively small.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can fix this with a tuning network, which adds discrete components nearby to attempt to create the correct impedance. You can correct this by fixing any flaws in your layout also. Probably both (based on experience with my own boards).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to approach this is to really cheat with your line connecting the boards. If you are operating over a small frequency range(ie. Able to treat the signal as a single frequency), then you can use stub tuners(which have been mentioned in this thread, just not by name) where the length of the stub acts as a capacitor or inductor(this is very frequency and fab dependent). You can also have a lot of fun by using a length of cable that is a quater-wavelength long. This means that when a signal is reflected, it will return to the antenna with a 90 degree phase shift, then return to the load completing a 180 degree phase shift. This cancels itself out in stead state(not perfectly, but it gets the job done).&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Summing it Up&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;At least you jumped in head first. There are a number of other things that can cause a miss-match, with more application specifics they can be looked into also. For example, a COAX cable causes a missmatch due to its shield having currents on the outside and inside that do not sum to the inner conductors current. I hope this has helped some, and I hope microwaves101 can be of some help. It is by far not the perfect learning resource, but someone is trying.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-02T03:52:24.530" CommentCount="4" />
  <row Id="6037" PostTypeId="1" AcceptedAnswerId="6041" CreationDate="2010-11-02T05:19:11.073" Score="5" ViewCount="254" Body="&lt;p&gt;I've been working in software for way too long, dislike it for a number of reasons, and would like to shift completely into electronics engineering work.  I'd prefer analog, microwave, optoelectronics or maybe some specialty yet to be invented, but any electronics is better than any software.    I have more talent and interest in electronics, and my love of herding electrons goes back to when I was a kid.  I read IEEE publications and understand them far better than anything coming out of the software development or computer science world.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately I have no formal degree in EE, only in Physics, a fine subject but apparently not sufficient to land an EE job, so I've found over the past several years.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The question is whether it's best to somehow get into a full time job first, with my existing experience, enthusiasm and education, and then perhaps earn a Master's to further my career, or to go full blast studying for a Master's in EE while continuing work in software, and only then try to land a job.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm currently employed, live next to a reputable tech school, and my employer depends heavily on electronics although there aren't any opening right now.   &lt;/p&gt;&#xA;" OwnerUserId="1609" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T19:39:34.303" LastActivityDate="2011-02-08T19:39:34.303" Title="Shifting into an EE Career - with or without Master's first?" Tags="&lt;education&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="6038" PostTypeId="2" ParentId="5841" CreationDate="2010-11-02T05:26:36.393" Score="1" ViewCount="" Body="&lt;p&gt;Most likely cracked solder joint. Open it, find the cracked joint, solder it down. Maybe give it some hot glue or something to strengthen it. I've repaired a portable minidisc (sidenote: man did those things really fail the market) player in this exact way -- headphones only worked if you wiggled it around in the jack, it was cracked solder joint inside.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2010-11-02T05:26:36.393" CommentCount="1" />
  <row Id="6039" PostTypeId="2" ParentId="6037" CreationDate="2010-11-02T05:52:23.110" Score="7" ViewCount="" Body="&lt;p&gt;If you can manage to get a job doing what you want to do without a degree, do it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the longer term, a Master's is a good investment, but you'll get more out of it if you have a year or two of experience first.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-02T05:52:23.110" CommentCount="1" />
  <row Id="6040" PostTypeId="2" ParentId="6037" CreationDate="2010-11-02T06:36:24.077" Score="4" ViewCount="" Body="&lt;p&gt;I agree with pingswept, that if you can get a nice job without that extra education so go for it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the jobs you get with formal education tend to be more advanced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And don't forget that formal education makes it easier to get to the job interview, but to land then job is up to you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But to stop working and go back to school is a huge investment, in both time and money, but if you feel that it is right then go for it since you would probably regret it if you did not do it...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck.&lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2010-11-03T07:16:23.383" LastActivityDate="2010-11-03T07:16:23.383" CommentCount="3" />
  <row Id="6041" PostTypeId="2" ParentId="6037" CreationDate="2010-11-02T08:20:43.333" Score="5" ViewCount="" Body="&lt;p&gt;In my experience the usefulness of the person decreases with the level of degree above Bachelors.  The problem is that to get the higher degrees the candidate has to specialise in a narrower and narrower field and as a result loses their general spread of skills that will always be required in a real work environment.  Having a Masters degree specialising in the dielectric properties of PCB materials really does not help when trying to debug the memory interface on the processor or designing the switch mode power regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would try to get some hardware practice with a processor, or design yourself an audio amp, anything that you could point to to show your enthusiasm.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-11-02T08:20:43.333" CommentCount="5" />
  <row Id="6042" PostTypeId="2" ParentId="6016" CreationDate="2010-11-02T09:00:34.617" Score="3" ViewCount="" Body="&lt;p&gt;The &quot;electrons go from A to B&quot; statement prevalent in many well known electronics books is what confused me most about electronics.  That and the fact that they didn't explain properly (or I didn't grasp properly) that every &quot;loop&quot; of a circuit would have the same voltage over it meaning you can isolate individual &quot;loops&quot; and discover what they do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found a resource (I think the link was from here somewhere) that really helped clear up the mechanics for me:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://amasci.com/ele-edu.html&quot; rel=&quot;nofollow&quot;&gt;http://amasci.com/ele-edu.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This guy takes a unique and clear way to explain the fundementals and covers things that you won't usually see in an equation heavy textbook, such as:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;Charge&quot; is the stuff inside wires, but usually nobody tells us that all metals are always full of movable charge. Always. A hunk of metal is like a tank full of water.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Another thing you'll notice is that many circuits you'll see schematics for will have components that may not be necessary for it to work but are there to stabalise or improve the operation of a circuit.  Such an example would be &lt;a href=&quot;http://electronics.stackexchange.com/questions/2272/what-is-a-decoupling-capacitor-and-how-do-i-know-if-i-need-one&quot;&gt;decoupling capacitors&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than that, search some of the articles on here and ask some questions - the guys and girls here are friendly and helpful and have so far been a fantastic help to me.&lt;/p&gt;&#xA;" OwnerUserId="1333" LastActivityDate="2010-11-02T09:00:34.617" />
  <row Id="6043" PostTypeId="1" AcceptedAnswerId="6044" CreationDate="2010-11-02T10:40:59.140" Score="2" ViewCount="106" Body="&lt;p&gt;I know applying kcl but I dont know how to consider the directions of the current.What I do is I make a general current direction for the whole loop,then with the help of that I see the currents entrying the node or leaving it but I usually go wrong with this logic..Here's an example which includes my try an the real directions&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/zNhEd.gif&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/OLB0R.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1799" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2010-11-02T21:14:27.403" LastActivityDate="2010-11-02T21:14:27.403" Title="How to suppose the current directions for KCL?" Tags="&lt;electronics&gt;&lt;kirchhoffs-laws&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="6044" PostTypeId="2" ParentId="6043" CreationDate="2010-11-02T11:14:05.680" Score="4" ViewCount="" Body="&lt;p&gt;Question statement is a little hazy, but the general idea is, current entering a node gets a positive sign, current leaving a node gets a negative sign, and the sum of all of them comes to zero.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One way to assign currents is to recognize that current flows around the loops. So for each loop, you name a variable for the current. Then it should be straightforward to enumerate the currents entering and leaving a node.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-02T11:14:05.680" />
  <row Id="6045" PostTypeId="2" ParentId="6034" CreationDate="2010-11-02T11:19:44.083" Score="3" ViewCount="" Body="&lt;p&gt;Do you want to solve for currents first, or voltages? Certainly once you have all the currents you can work out the voltages, and vice versa, but sometimes you're really after one or the other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you apply KVL, you end up getting currents first. This is because, to write the voltage drops around the loops, you use ohms law with the loop current, which is your unknown. So you write a system of loop equations and the solution gives you currents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Conversely, with KCL, you can write the expressions for current into a node using ohms law to find the current contribution of a component in terms of the voltage differences between the node in question and the other node the component is attached to. Solve this system and you arrive at voltages.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-02T11:19:44.083" CommentCount="2" />
  <row Id="6046" PostTypeId="2" ParentId="6028" CreationDate="2010-11-02T11:54:36.707" Score="1" ViewCount="" Body="&lt;p&gt;Just an idea... Measure with two probes and use the add function for the two channels :)&lt;/p&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2010-11-02T11:54:36.707" CommentCount="1" />
  <row Id="6047" PostTypeId="1" AcceptedAnswerId="14114" CreationDate="2010-11-02T12:44:48.783" Score="2" ViewCount="404" Body="&lt;p&gt;I am transmitting continuously at 9600 bps using the default configurations for both my XBees XB24-B. &#xA;The communication is one way only, the transmitter is connected to the ATMega328 UART and the receiver is connected to the PC via USB (FTDI).&#xA;Here is the actual data rate for a given program:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Wired connection (no XBee) : 7694 bps&lt;/li&gt;&#xA;&lt;li&gt;from the ZNET 2.5 Router/End Device AT to ZNET 2.5 Coordinator AT: 6800 bps (some lost packets)&lt;/li&gt;&#xA;&lt;li&gt;from the ZNET 2.5 Coordinator AT to ZNET 2.5 Router/End Device AT: 0356 bps (many lost packets)&lt;/li&gt;&#xA;&lt;li&gt;from the Zigbee Router/End Device AT to Zigbee Coordinator AT : 0000 bps (doesn't work)&lt;/li&gt;&#xA;&lt;li&gt;from the Zigbee Coordinator AT to Zigbee Router/End Device AT : 0328 bps (many lost packets)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Why is that? Is there anything I can do to improve these rates?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt; For higher baud rates (115200) I get even worse packet drop rates:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Wired connection (no XBee) : 94200 bps&lt;/li&gt;&#xA;&lt;li&gt;using XBee XB24-B ZNet 2.5 : 27900 bps&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt; If I make the Coordinator address the End device, then the packet drop rate falls to the normal levels (6800 bps), which is not ideal but better than the previous scenario&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-11-06T20:49:41.477" LastActivityDate="2011-05-10T08:02:06.690" Title="XBee dropping packets and actual data rate lower than expected" Tags="&lt;serial&gt;&lt;wireless&gt;&lt;xbee&gt;&lt;zigbee&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="6048" PostTypeId="2" ParentId="6043" CreationDate="2010-11-02T12:57:48.693" Score="3" ViewCount="" Body="&lt;p&gt;It doesn't particularly matter which direction you assign to each loop, it's just your best guess, so long as once you pick it, you keep it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, on Node A,  you have blue arrows i1 + i2 - i3 - i4 = 0.  That's fine.  If you keep that, then when you solve for what the currents actually are, you may find that i2 comes out negative.  Which is okay, it just means that the current is flowing in the opposite direction of what you guessed. &lt;/p&gt;&#xA;" OwnerUserId="1266" LastActivityDate="2010-11-02T12:57:48.693" />
  <row Id="6049" PostTypeId="2" ParentId="6037" CreationDate="2010-11-02T13:02:47.270" Score="1" ViewCount="" Body="&lt;p&gt;I think getting my Masters was a great idea, and I studied with several students coming from a physics undergrad degree. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It gives you a foot in the door to any EE job, takes only about 18 months, and will often be paid for by the school if your grades are decent.  It's true I don't end up using what I learned for my degree for my day-to-day, but it's a fun party trick to explain exactly how heterojunction bipolar transistors work.&lt;/p&gt;&#xA;" OwnerUserId="1266" LastActivityDate="2010-11-02T13:02:47.270" CommentCount="3" />
  <row Id="6050" PostTypeId="1" AcceptedAnswerId="6051" CreationDate="2010-11-02T14:50:23.403" Score="2" ViewCount="168" Body="&lt;p&gt;How do I find the thevinin voltage in this diagram?In parallel the voltage remains the same,so it should be 10 volts across ab ?&lt;img src=&quot;http://i.imgur.com/94HqI.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1799" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-02T15:31:26.960" LastActivityDate="2010-11-02T16:38:23.007" Title="How to find the Vth?" Tags="&lt;electronics&gt;&lt;homework&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="6051" PostTypeId="2" ParentId="6050" CreationDate="2010-11-02T15:35:52.393" Score="3" ViewCount="" Body="&lt;p&gt;R3 and R4 have no voltage drop, when open they do not receive current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are then measuring the voltage on R2, with R1 and R5 giving a voltage drop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this is clear.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-02T15:35:52.393" CommentCount="1" />
  <row Id="6052" PostTypeId="2" ParentId="5998" CreationDate="2010-11-02T15:52:36.553" Score="2" ViewCount="" Body="&lt;p&gt;for design in previous role for defence and aerospace, we would subject our boards and enclosures to large amounts of shock and vibration in order to comply with the required standards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a construction perspective, any boards with larger components (or where possible) would be fitted with anti vibration (AV) mounts of some sort.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally we never had issues with surface mount components.  Large electrolytic capacitors, inductors, transformer and so on would normally need some extra adhesive.  Poly-sulphide was used for this, not a pleasant chemical to work with, but it would meet the stringent environmental requirements of the defence and aerospace industries, and stop the large components from vibrating off.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-02T15:52:36.553" />
  <row Id="6053" PostTypeId="1" AcceptedAnswerId="6054" CreationDate="2010-11-02T15:56:30.607" Score="3" ViewCount="282" Body="&lt;p&gt;I want to read a voltage from 0-30V with an MCU ADC which has a maximum input of 3V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Initially I thought of using a 100k-10k divider (so 33V translates to 3V) but according to these answers, &lt;a href=&quot;http://electronics.stackexchange.com/questions/5404/adc-input-impedance-on-mcus&quot;&gt;http://electronics.stackexchange.com/questions/5404/adc-input-impedance-on-mcus&lt;/a&gt;, it will add a 3% error, I'm looking for 0.5% error maximum. However, at lower values for the divider, I risk damaging the MCU's inputs because of overvoltage (the resistors act in tandem with the clamping diodes on the input.) I also increase power dissipation in my resistors, which are tiny 0603 devices, rated for 0.063W maximum. How can I avoid this? n.b. input impedence is not critical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not worried about sampling speed, a maximum of 100 Hz.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-02T20:34:24.267" LastActivityDate="2010-11-02T20:34:24.267" Title="Voltage dividers and ADC's" Tags="&lt;adc&gt;" AnswerCount="2" CommentCount="7" FavoriteCount="0" />
  <row Id="6054" PostTypeId="2" ParentId="6053" CreationDate="2010-11-02T16:17:48.547" Score="5" ViewCount="" Body="&lt;p&gt;Use the voltage divider with resistors, and an opamp follower afterwards.  Alternative use an opamp circuit to reduce the voltage and you can perform anti alias filtering in one stage!&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-02T16:17:48.547" CommentCount="7" />
  <row Id="6055" PostTypeId="1" AcceptedAnswerId="6059" CreationDate="2010-11-02T16:19:03.090" Score="4" ViewCount="124" Body="&lt;p&gt;I'd like to understand this simple schematic to see if I get things clearly&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/vGqHl.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I understand things correctly:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;when the switch is open, the current at the right black point is zero, the voltage is 12V.&lt;/li&gt;&#xA;&lt;li&gt;when the switch is closed, the current at the right black point is 20 mA, the voltage is 0V&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If this is correct, suppose now a similar schema with the following difference: between the switch and ground I have another 600 ohm resistor.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;the potential at the black dot with the closed switch is now 6 V ?&lt;/li&gt;&#xA;&lt;li&gt;any point along the horizontal connection between the T junction and the black dot are at the same potential. I guess they also enjoy the same current. If two points in a circuit experience the same potential and they are directly connected, do they always experience the same current as well ?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1272" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-11-02T17:20:16.103" LastActivityDate="2010-11-02T17:20:16.103" Title="Voltage and current in this schematic" Tags="&lt;circuit&gt;&lt;voltage&gt;&lt;current&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="6057" PostTypeId="2" ParentId="6055" CreationDate="2010-11-02T16:34:56.270" Score="1" ViewCount="" Body="&lt;p&gt;I see where you are coming from, but you have 1 concept wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what you show, it is unknown what happens at vout. If you just have it connecting to something that is measuring the voltage, say a dmm or a microcontroller, then you can assume you have a very large resistor from vout to ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So case that the switch is open, you have 600ohms in series with a very large resistance. V/R=I, but since R is 600+verylarge, I is almost 0.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now in the case the switch is closed, you have a wire (0ohms) in parallel with with very large, which results in an effective resistance of 0. So now you have V/R=I &gt; 12/(600+0)=.02V&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you can step back and look at voltages:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the case that the switch is open, you have little current through the 600ohm resistor so V=0*600ohm=0v drop across the 600 ohm resistor, so Vout is 12v.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-02T16:42:11.050" LastActivityDate="2010-11-02T16:42:11.050" CommentCount="3" />
  <row Id="6058" PostTypeId="2" ParentId="6050" CreationDate="2010-11-02T16:38:23.007" Score="2" ViewCount="" Body="&lt;p&gt;Wikipedia has very nice article about &lt;a href=&quot;http://en.wikipedia.org/wiki/Th%C3%A9venin%27s_theorem&quot; rel=&quot;nofollow&quot;&gt;Thévenin's theorem&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1471" LastActivityDate="2010-11-02T16:38:23.007" CommentCount="1" />
  <row Id="6059" PostTypeId="2" ParentId="6055" CreationDate="2010-11-02T17:01:02.527" Score="2" ViewCount="" Body="&lt;p&gt;(In ideal conditions)&#xA;You're correct in your understanding of the first case. When you close the switch, you short one end of the resistor to ground, so there's a 12V drop across it and I=0.02A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your second case, with the switch closed, you are creating a voltage divider so the point between the resistors is at 6V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't have a load connected along Vout (between the black dot and ground), then I=0 there since there isn't a voltage drop along the horizontal connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Measuring along the path connecting the resistors/switch, you'll see your 0.01A, and since there is no other path for the current to take, both resistors will see the full 0.01A.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2010-11-02T17:01:02.527" />
  <row Id="6060" PostTypeId="2" ParentId="6047" CreationDate="2010-11-02T17:17:50.080" Score="1" ViewCount="" Body="&lt;p&gt;whats the signal strength and speed of the wireless link look like?  Check the XBee API docs you should be able to access this information.  What antennas are you using? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Zigbee's raw data rate is only 250kbit/sec in the 2.4Ghz band and it is a very high overhead protocol.  With near perfect signal strength and encryption enabled you should only expect ~20-25kbit/sec max data throughput without customizing the stack, a bit more without encryption.  Zigbee's protocol really only supports sending data that fits in a single packet, which off the top of my head is something like 100 bytes.  If your sending a stream of data the application layer has to break that data into packets, and include additional information in the data space of the packet so that it can be reassembled.  This process can be quite slow and cut further into the data throughput.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digi's digimesh stack is a bit faster as it cuts overhead and allows larger packets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure what your intended final application is here, but Zigbee is not at all designed for streaming data.  Its for sending small bits of information, sensor readings, instructions, etc that fit into a single packet.  You very well may have just chosen the wrong protocol for your application.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-02T17:17:50.080" CommentCount="5" />
  <row Id="6061" PostTypeId="2" ParentId="6047" CreationDate="2010-11-02T17:31:07.657" Score="0" ViewCount="" Body="&lt;p&gt;UPDATE: With the recent revalation that the Zigbee isn't made for streaming data, I would suggest throwing it in the trash and purchasing &lt;a href=&quot;http://www.elechouse.com/elechouse/index.php?main_page=product_info&amp;amp;products_id=324&quot; rel=&quot;nofollow&quot;&gt;a better transceiver with more functionality, more throughput, and about 1/4 the pric&lt;/a&gt;e&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I highly recommend utilizing flow control if possible to address the lost packets. Chances are, small but significant periods of time when one device is processing, it is not looking at its UART pins and thus misses bits/bytes and can hang things up. By implementing hardware flow control (RTS &amp;amp; CTS pins), each device can tell the other when it is ready or not for more data. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you hook up flow control, I think you'll achieve the higher throughput you're looking for =) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I work with Bluetooth OBD devices that link my Android app to vehicle networks, so I work with wireless/Bluetooth quite a bit.&lt;/p&gt;&#xA;" OwnerUserId="1033" LastEditorUserId="1033" LastEditorDisplayName="" LastEditDate="2010-11-03T12:32:47.890" LastActivityDate="2010-11-03T12:32:47.890" CommentCount="4" />
  <row Id="6062" PostTypeId="2" ParentId="6037" CreationDate="2010-11-02T18:15:31.940" Score="1" ViewCount="" Body="&lt;p&gt;If you're not quite sure what you want to get into as far as electronics goes you should start working on a hobbyist level and see where it takes you.  It will give you actual experience and help you refine your goals, plus it looks good to employers.  It's one thing to say you love electronics and are very interested in it, but another thing to end the sentence with '...and this is what I did with it.'  A masters' degree can make you seem too expensive and unless a company is looking for candidates with a masters' they are more likely to see it as a liability than a benefit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Watch job openings and see the words they use, then try to figure out what they mean.  You may already have experience with 'mixed-signal board-level design' and not know it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I honestly don't know what employers are looking for.  I got my first job because of my masters degree in controls.  Nowadays it seems to be buzzword bingo with HR and otherwise soft skills like 'working well with others', 'self-motivated','good at solving complex problems'.  And it's not easy to get feedback from them either - the last employer I tried to apply with flatly said 'No inquiries' when I called to ensure they got my application email.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good cover letter tends to work wonders when applying for jobs.  It certainly doesn't hurt to address your lack of EE degree - in fact hit it head on and say something like 'Despite the fact that my degree is in physics I'm a good electrical engineer because...'  Then you have to practice the heck out of interview questions.  A fairly good (and free) interview guide from a blog I like is here: &lt;a href=&quot;http://www.askamanager.org/2010/08/ask-manager-guide-to-preparing-for-job.html&quot; rel=&quot;nofollow&quot;&gt;http://www.askamanager.org/2010/08/ask-manager-guide-to-preparing-for-job.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="249" LastEditorDisplayName="" LastEditDate="2010-11-02T18:29:27.653" LastActivityDate="2010-11-02T18:29:27.653" />
  <row Id="6063" PostTypeId="1" CreationDate="2010-11-02T18:21:26.450" Score="1" ViewCount="77" Body="&lt;p&gt;I am designing a package in eaglecad and I got the pin width incorrect. I don't want to change all 100 pads manually. Is there a way to select a group and change the dimensions on all the pads?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" LastActivityDate="2010-11-02T19:42:21.997" Title="Change group pin width with eaglecad?" Tags="&lt;cad&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="6064" PostTypeId="2" ParentId="3345" CreationDate="2010-11-02T18:33:29.637" Score="3" ViewCount="" Body="&lt;p&gt;Chumby hacker board seems appropriate: &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;products_id=278&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;products_id=278&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But it's a beta right now.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-02T18:33:29.637" />
  <row Id="6065" PostTypeId="2" ParentId="6053" CreationDate="2010-11-02T19:01:27.973" Score="5" ViewCount="" Body="&lt;p&gt;Okay, from your response to my comment I think I can be more help with a full answer.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Build it!&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Build your simple Resistive divider. This has many advantages, for one size, another is cost.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Characterize it!&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Now, you are going to use a microcontroller also, this is where you need to characterize your error. use a voltage generator that is very accurate, now check voltages and see what error the uC actually measures.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Analyze it!&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Now is when it gets fun. There are a number of things you could measure. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Accuracy_and_precision&quot; rel=&quot;nofollow&quot;&gt;&lt;h3&gt; Accuracy and Precision &lt;/h3&gt;&lt;/a&gt;&#xA;The biggest thing to measure here is if the error at the points is repeatable. IF every time you sweep you get a different error, or if your sweep following a different path gives a different error at the same point, this is not an option. This often happens with leakage currents. The important part here is that &lt;strong&gt;you do not need high accuracy, just a high degree of precision.&lt;/strong&gt; If you can characterize your error, your uC can correct for it. If you have a large variance you need to change your solution.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; What is an X point calibration?&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Now, if you have a high precision, as discussed before, you can move on to correcting the accuracy. Now, if when you graph your input voltage versus your output voltage you are going to have to decide the number of &quot;reference points&quot; you need. Nice devices allow a 1 point(or zero point, no need for calibration). Many temperature probes.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; One point calibration &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Both lines have the same slope, but an offset, so you just need to find the value you must add to a data-point to correct it. This is an ideal situation, as any new calibration only needs a single data-point to calibrate again.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Two Point calibration &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;both linear curves, possibly an offset and there is a slop difference, you only need two reference points and linear interpolation to extract your offset. This is still relatively easy, you just take any point, multiply it by a scalar and add an offset.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see, it gets messier the more points you need. At some point it is easier to just take every datapoint and correlate it to the actual value. For example, finding that 0000 is 1V, 0001 is 2V, 0002 is 1.5V. This is messy, and this still only works if the offsets are repeatable. This can happen though.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Summing it up&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;I hope this helps, tell me if you need more clarity. If you end up with a varying leakage current that is not dependable, it is time to just deal with needing a buffer, or something of the like.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can see a possibility of high error from leakage, but I would bet that the error is relatively small over most of the range, and when it is there can be easily corrected.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-02T19:01:27.973" CommentCount="3" />
  <row Id="6066" PostTypeId="1" AcceptedAnswerId="6067" CreationDate="2010-11-02T19:25:25.343" Score="3" ViewCount="406" Body="&lt;p&gt;How can I make a device that will make the power connected as long as the voltage of the power-supply keeps over 12.4 V (adjustable) and disconnect it if it falls below?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It also must connect the power back, but only if it rises above 13.5 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This has to sustain at least 70 A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a simple way to build such device?&lt;/p&gt;&#xA;" OwnerUserId="1691" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-03T04:44:25.777" LastActivityDate="2011-03-23T09:15:32.160" Title="how to build a low-voltage disconnect switch for DC 12.4V 70A?" Tags="&lt;power-supply&gt;&lt;voltage&gt;&lt;switch&gt;&lt;low-battery&gt;&lt;undervoltage&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="6067" PostTypeId="2" ParentId="6066" CreationDate="2010-11-02T19:31:53.230" Score="1" ViewCount="" Body="&lt;p&gt;70A power relay and voltage comparator with a transistor to run the relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a schematic:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/FU1zw.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use &lt;a href=&quot;http://falstad.com/circuit/#%24+1+5.0E-6+10.20027730826997+46+5.0+50%0Aa+272+256+384+256+0+15.0+0.0+1000000.0%0Aw+384+256+384+320+0%0Ar+384+320+240+320+0+220000.0%0Aw+240+272+272+272+0%0Aw+240+272+240+320+0%0Aw+240+272+240+192+0%0Ar+240+192+240+128+0+10000.0%0Ar+240+320+240+384+0+10000.0%0Ag+240+384+240+416+0%0Aw+208+384+240+384+0%0Ap+208+272+208+384+0%0Aw+208+272+240+272+0%0Aw+272+240+160+240+0%0Ar+160+240+160+384+0+3300.0%0Ag+160+384+160+416+0%0Ar+160+240+160+128+0+10000.0%0A172+160+80+160+48+0+6+11.1+15.0+0.0+0.0+0.5+Voltage%0At+448+256+480+256+0+1+-9.59773452744542+0.6691315836845756+100.0%0Ar+448+256+384+256+0+10000.0%0A178+480+144+544+144+0+1+0.2+0.041656694441668134+0.05+1000000.0+0.02+20.0%0Aw+160+80+160+128+0%0Aw+480+80+480+144+0%0Aw+480+80+160+80+0%0Aw+480+192+480+240+0%0Ag+480+272+480+288+0%0Ar+576+128+576+192+0+0.16%0Ag+576+192+576+208+0%0Aw+576+128+544+128+0%0Aw+480+176+480+144+0%0Aw+240+128+96+128+0%0Az+96+192+96+128+1+0.805904783+5.6%0Ag+96+192+96+208+0%0Ar+96+128+96+80+0+10000.0%0Aw+96+80+160+80+0%0AO+240+128+288+128+1%0Ao+10+64+0+34+5.144485763404778+9.765625E-55+0+-1+threshold%0Ao+12+64+0+35+5.0+9.765625E-5+1+-1%0A&quot; rel=&quot;nofollow&quot;&gt;this link to simulate it&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll need to tweak the values to get it how you want, I didn't perfect it.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-02T19:52:20.980" LastActivityDate="2010-11-02T19:52:20.980" CommentCount="5" />
  <row Id="6068" PostTypeId="2" ParentId="6063" CreationDate="2010-11-02T19:42:21.997" Score="1" ViewCount="" Body="&lt;p&gt;You should be able to script this up in eagle's scripting language without too much problem. Something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if(library(L)) {&#xA;    L.packages(P) {&#xA;        P.contacts(C) {&#xA;            if(C.smd) {&#xA;                C.smd.dx = 10; C.smd.dy = 30; /* or whatever */&#xA;            }&#xA;        }&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-11-02T19:42:21.997" />
  <row Id="6069" PostTypeId="1" AcceptedAnswerId="6071" CreationDate="2010-11-02T20:12:59.357" Score="2" ViewCount="217" Body="&lt;p&gt;I'm trying to understand &lt;a href=&quot;http://www.farnell.com/datasheets/359827.pdf&quot; rel=&quot;nofollow&quot;&gt;this mechanical drawing&lt;/a&gt; so I can create a layout for it in gEDA PCB. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically on page 4. I've already managed to place GND 1 and GND 2; those were fairly simple to work out. But GND 3 confuses me, because it's apparent from close inspection of the drawing that it doesn't quite line up with GND 1 and the offset doesn't appear to be given. The same is true for GND 4 which doesn't quite line up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also on a semi-related note it is unclear whether the pins are in the order as they are on the SD card or if they are numbered arbitrarily - that is, does pin 1 correspond to pin 1 on the SD card?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While this isn't strictly electronics, I think it passes as an appropriate question because it is an electronic connector and it requires a PCB layout.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-03T14:16:15.400" Title="Help me decode this mechanical drawing of an SD card PCB layout" Tags="&lt;pcb&gt;&lt;mechanical&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="6070" PostTypeId="2" ParentId="6066" CreationDate="2010-11-02T20:33:44.223" Score="4" ViewCount="" Body="&lt;p&gt;70 A is a lot of current. Make sure your relay is rated for the full amount plus a generous safety factor. I would also add both a set of fuses and circuit breakers. The fuses to protect against shorts and the circuit breaker to protect against over loads. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-11-02T20:33:44.223" CommentCount="4" />
  <row Id="6071" PostTypeId="2" ParentId="6069" CreationDate="2010-11-02T20:39:52.190" Score="4" ViewCount="" Body="&lt;p&gt;If an offset isn't given from the center-line or some other point, it should be symmetrical about the c.l. (always has been in my experience).  So 4.7 mm between the inside of GND3/GND4 would mean they are each 2.35 mm away from the c.l., likewise with the 8.3 mm outer to outer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The pins appear to correspond to the SD card pinout I looked up.  It appears backwards on the footprint because the actual SD terminals would be on the right side, but the contacts lead to the left to connect to the board.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-02T20:39:52.190" CommentCount="1" />
  <row Id="6072" PostTypeId="2" ParentId="6069" CreationDate="2010-11-02T20:46:13.090" Score="3" ViewCount="" Body="&lt;p&gt;Converting drawings to actual library packages is always fun. You have to think like a mechanical engineer. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have a centerline and dimensions from the center line; you have to work all the math from that point. Specifically, GND3/4 start 2.35mm from the center line and are (8.3-4.7)/2=1.8mm wide. You can see that they are 13.55mm center-to-center to GND1/2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there is no mapping given, it's relatively safe to assume that the pins line up with the SD card. I would ohm it out myself or contact the manufacturer though to be sure.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-11-02T20:46:13.090" CommentCount="1" />
  <row Id="6073" PostTypeId="1" CreationDate="2010-11-02T21:23:30.060" Score="3" ViewCount="193" Body="&lt;p&gt;I just received my ArduinoBT in the mail, and was a little confused about how to get code onto it. Typically, you can upload it via USB through the Arduino IDE.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a vague understanding of what a bootloader is - which comes pre-installed on the ArduinoBT, but I don't understand how I can get the code to the bootloader.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The docs suggest that you can still connect via the IDE and they provide the default name of the device, along with a default password. However, wouldn't I need some sort of BlueTooth receiver on my PC to achieve communication with the ArduinoBT?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I have to have an AVR ISP Programmer? Is there another way to get code on the device?&lt;/p&gt;&#xA;" OwnerUserId="1811" LastActivityDate="2010-11-02T21:46:17.877" Title="Getting Code onto Arduino Bluetooth" Tags="&lt;arduino&gt;" AnswerCount="2" />
  <row Id="6074" PostTypeId="1" AcceptedAnswerId="6082" CreationDate="2010-11-02T21:34:22.687" Score="3" ViewCount="129" Body="&lt;p&gt;I've been looking for a 3V ±0.1% reference in a SOT-23 package to replace my current ±0.5% solution of a TL431 and about 5 passive 0603 components. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the moment I've found LM4040A30 which is $1 at 1ku, and comes in a SOT-23 package. It also requires a 0603 resistor, but is stable without a capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wondering if anyone has any better solutions. Even more awesome would be something like an ultra stable precise zener diode in 0603 or 0805 size. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-02T22:19:19.923" Title="3V ±0.1% reference" Tags="&lt;reference&gt;" AnswerCount="1" />
  <row Id="6075" PostTypeId="2" ParentId="6073" CreationDate="2010-11-02T21:40:02.200" Score="3" ViewCount="" Body="&lt;p&gt;The ArduinoBT, &lt;a href=&quot;http://www.arduino.cc/en/Guide/ArduinoBT&quot; rel=&quot;nofollow&quot;&gt;after pairing&lt;/a&gt;, exposes a virtual serial port that you can use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that, you connect to it using the Arduino IDE over that virtual serial port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So &lt;strong&gt;yes, you need a Bluetooth receiver on your PC for this to work&lt;/strong&gt;, as the virtual serial port used for programming (typically provided by a virtual serial port over USB on a conventional Arduino), is now provided via the Bluetooth connection.  You'll definitely want to use that instead of a ICSP programmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't have Bluetooth on your PC, there are addon USB adapters that provide it.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-11-02T21:45:55.853" LastActivityDate="2010-11-02T21:45:55.853" />
  <row Id="6076" PostTypeId="1" AcceptedAnswerId="6080" CreationDate="2010-11-02T21:40:18.097" Score="2" ViewCount="270" Body="&lt;p&gt;I'm considering putting a small lithium battery on my Super OSD Pro boards. The battery would provide power to the RTC. I am wondering how small can you get a battery? I don't really care about capacity, I expect current draw to be less than 1µA, so it's really only size I'm looking for. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best solution would be one that is removable, because I'd like people to be able to replace the battery when it does go flat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And I'm open to suggestions on how to control the power to the main bus which has some heavier current draw devices which would overwhelm the 1µA for the RTC (the RTC is provided by a PIC24F in deep sleep mode.) I'm thinking of a power monitor, but it needs to be able to switch at least 100mA for the MCU when it's running full speed.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-02T21:45:37.187" LastActivityDate="2010-11-03T15:11:25.243" Title="Smallest lithium battery backup?" Tags="&lt;coin-cell&gt;&lt;lithium&gt;&lt;rtc&gt;" AnswerCount="2" />
  <row Id="6077" PostTypeId="1" AcceptedAnswerId="6085" CreationDate="2010-11-02T21:41:36.660" Score="5" ViewCount="148" Body="&lt;p&gt;I've got an extensive music background and have been infatuated with synthesizers since I was young. I had dreamed of going into an EE program to make my dream a reality, but I couldn't afford school (long story).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, I'd like to build a 3 oscillator analog synthesizer, but I have zero experience building boards. I know basic signal flow and process and have a strong design sense, but I really lack the knowledge otherwise to get started. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think starting simple with a 1 oscillator and building upwards would be an awesome learning experience, and I would love to get to the level that some of you are at and actually make a fully usable synthesizer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, for audio-oriented electronics, where can I get started for this full analog synthesizer? Am I reaching too far? What will I need to make this happen?&lt;/p&gt;&#xA;" OwnerUserId="1812" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-13T04:24:35.393" LastActivityDate="2011-02-13T04:24:35.393" Title="Building a synthesizer with no prior experience" Tags="&lt;audio&gt;&lt;synthesizer&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="6078" PostTypeId="1" AcceptedAnswerId="6081" CreationDate="2010-11-02T21:43:42.943" Score="5" ViewCount="302" Body="&lt;p&gt;Here's the current design for Super OSD Lite, an open hardware project to bring a low cost on screen display to the masses. The price target is $71 to $90.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/x7ZIB.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://i.imgur.com/x7ZIB.png&quot; rel=&quot;nofollow&quot;&gt;bigger image&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are components on the bottom, but most components are on the top.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's one of my first PCB designs involving such a complex circuit, so I expect I've made a few mistakes. Constructive criticism appreciated!&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-03T18:55:01.797" Title="Have a look at my PCB design and tell me how I can improve" Tags="&lt;pcb&gt;" AnswerCount="7" CommentCount="4" FavoriteCount="2" />
  <row Id="6079" PostTypeId="2" ParentId="6073" CreationDate="2010-11-02T21:46:17.877" Score="1" ViewCount="" Body="&lt;p&gt;To use the bootloader, yes, you would have to connect to it over BlueTooth (wiring a TTL converter in between the BT module and AVR would be tricky).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have an ISP, you can skip over everything and directly program the AVR without any bootloaders.  BlueTooth transceivers for computers nowadays are extremely cheap, so I would pick one up to use your ArduinoBT to the fullest, but ISPs are also very handy when things go wrong or you want to graduate from Arduinos.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-02T21:46:17.877" />
  <row Id="6080" PostTypeId="2" ParentId="6076" CreationDate="2010-11-02T22:00:43.943" Score="4" ViewCount="" Body="&lt;p&gt;CR2032 (20mm x 3.2mm) is the cheap standard for coin cells, if you want smaller there are several other CRxxyy type cells (e.g. &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=P033-ND&quot; rel=&quot;nofollow&quot;&gt;CR1220&lt;/a&gt;) that are meant for this sort of thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The crudest design could just be a diode-OR with the power supply, before or after the regulator depending on the voltages/regulator type, otherwise you could implement something like in &lt;a href=&quot;http://electronicdesign.com/article/power/battery-backup-uses-delay-to-avoid-glitches12547.aspx&quot; rel=&quot;nofollow&quot;&gt;this article&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-02T22:00:43.943" CommentCount="3" />
  <row Id="6081" PostTypeId="2" ParentId="6078" CreationDate="2010-11-02T22:04:51.507" Score="8" ViewCount="" Body="&lt;p&gt;Looks great!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few thoughts:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Make all your designators readable from one direction (or at least within 90 degrees of each other).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Where you have space, label the pins on your connectors.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Add a pair of vias to ground that you can solder a little loop of wire to. Then you can clip your scope ground to it.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Make sure your CONN2 and CONN3 connector bodies don't overlap in the real world.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The orientation dot for U6 is almost hidden by a via.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Add vias so you can easily probe your EEPROM data lines.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Make sure your mounting holes are sensibly spaced (not 2.718282 inches apart).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-02T22:04:51.507" CommentCount="12" />
  <row Id="6082" PostTypeId="2" ParentId="6074" CreationDate="2010-11-02T22:19:19.923" Score="1" ViewCount="" Body="&lt;p&gt;I think the LM4040 is the way to go.  I don't know of any &quot;pre-biased&quot; shunt diodes, and if there were they would likely cost more and you would have to weigh that against the scant space savings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can ease up on the 0.1% to 0.2 (B-grade) or 0.5 (C), the prices seem to drop quite dramatically.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-02T22:19:19.923" CommentCount="1" />
  <row Id="6083" PostTypeId="2" ParentId="6069" CreationDate="2010-11-02T22:30:10.453" Score="2" ViewCount="" Body="&lt;p&gt;I think it might be easier to put down the numbered pins before GND3 and GND4, then justify GND3 and GND4 to them instead of trying to justify them to the GND1 and GND2 pins. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if I give it a shot....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can determine the distance between the horizontal centers of GND1 and GND3 - it's all the way at the bottom and has a value of 13.55 +/- .05 mm.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good helper is the dotted center line that runs through the middle of the footprint.  If we assume GND3 and GND4 are symmetric about that line and they're the same size then we can use two measurements (8.3mm and 4.7mm) give us a height for each of 1.8mm. This means they should be the same height as GND1 and GND2.  We can use this information to determine the vertical center of GND3 with respect to GND1.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The top of GND3 is 4.7mm/2 from the center line which is 2.35mm.  Its center is .9mm from the edge, so it's 3.15mm from the center line.  The center of GND1 is 2.4+.9mm = 3.3mm from the center line, so the vertical center of GND3 is .15mm higher than GND1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tada!&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-02T22:30:10.453" />
  <row Id="6084" PostTypeId="1" CreationDate="2010-11-02T22:54:39.170" Score="5" ViewCount="170" Body="&lt;p&gt;I've found a number of &quot;starter pack&quot; suggestions for generic packs of items, but my ask is a little more specific.  I am a (reasonably) experienced through-hole kit assembler, and can see some time in my future a desire to hand-build some items that I expect I'll want to &quot;shrink&quot; by using SMDs, so my first thought was to get a &quot;starter&quot; pack of resistors/capacitors that had a mix of values, so I'm looking for suggestions on where you'd suggest I look for these.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there &quot;concerns&quot; over different suppliers, for instance I've noticed some significant price deltas on ebay for what should be similar kits (mixed 5% 1/4w resistors + capacitors)?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One more consideration, I'm in Australia, so my &quot;retail&quot; options are limited, and places like Farnell I mean Element 14 or Mouser are options but often will incur freight above what a directed buy somewhere like ebay can get.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks in advance for suggestions!&lt;/p&gt;&#xA;" OwnerUserId="1784" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-11-03T08:46:23.813" LastActivityDate="2010-11-03T12:13:42.353" Title="SMT &quot;starter&quot; packs" Tags="&lt;kit&gt;&lt;components&gt;&lt;surface-mount&gt;&lt;distributors&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="6085" PostTypeId="2" ParentId="6077" CreationDate="2010-11-02T23:31:42.253" Score="4" ViewCount="" Body="&lt;p&gt;There is plenty of interesting info at the &lt;a href=&quot;http://www.musicfromouterspace.com/index_oldsite.php&quot; rel=&quot;nofollow&quot;&gt;Music From Outer Space&lt;/a&gt; website. Including circuit schematics accompanied by detailed explanations of the designs. As well as a range of advice and links relevant to building synthesizers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'd be better off first gaining experience with some simpler audio electronics projects, and building up the skills and equipment that a major project like this would require. Then you'd be in a better position to evaluate how/whether to proceed further.&lt;/p&gt;&#xA;" OwnerUserId="1380" LastEditorUserId="1380" LastEditorDisplayName="" LastEditDate="2010-11-02T23:53:11.310" LastActivityDate="2010-11-02T23:53:11.310" />
  <row Id="6086" PostTypeId="2" ParentId="6078" CreationDate="2010-11-03T00:11:21.347" Score="4" ViewCount="" Body="&lt;p&gt;Make a prettier png!  Use my &quot;pcbrender&quot; script.  pcbrender input.pcb output.png&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#/bin/sh&#xA;&#xA;INFILE=$1&#xA;OUTFILE=$2&#xA;&#xA;DPI=300&#xA;OVERSAMPLE=3&#xA;&#xA;PCB=pcb #/home/markrages/src/pcb/src/pcb&#xA;&#xA;PCBOPTS=&quot;-x png --photo-mode --dpi $(( $OVERSAMPLE*$DPI )) --use-alpha --only-visible&quot;&#xA;&#xA;$PCB $PCBOPTS --outfile /tmp/$INFILE.front.png $INFILE &amp;amp;&amp;amp; \&#xA;$PCB $PCBOPTS --outfile /tmp/$INFILE.back.png --photo-flip-x --photo-flip-y $INFILE &amp;amp;&amp;amp; \&#xA;montage /tmp/$INFILE.front.png /tmp/$INFILE.back.png -tile x1 -shadow -geometry &quot;+50+50&quot; -resize $(( 100 / $OVERSAMPLE))% -background lightblue $OUTFILE &#xA;&#xA;rm -f /tmp/$INFILE.front.png /tmp/$INFILE.back.png&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Here's the output:&#xA;&lt;img src=&quot;http://i.imgur.com/pw6xm.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-11-03T00:18:32.200" LastActivityDate="2010-11-03T00:18:32.200" CommentCount="4" />
  <row Id="6087" PostTypeId="2" ParentId="6078" CreationDate="2010-11-03T00:18:01.653" Score="6" ViewCount="" Body="&lt;p&gt;I checked out the .pcb file from the git repository.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://super-osd.googlecode.com/hg/hardware/V3%20Lite/pcb-v3-lite.pcb&quot; rel=&quot;nofollow&quot;&gt;http://super-osd.googlecode.com/hg/hardware/V3%20Lite/pcb-v3-lite.pcb&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I loaded it into pcb and ran DRC on it, with the following results:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Rules are minspace 10.01, minoverlap 10.0 minwidth 10.00, minsilk 10.00&#xA;min drill 15.00, min annular ring 10.00&#xA;Found 251 design rule errors.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Some traces are too close.  For example, the via under D1 is 2.5 mils away from shorting out against the pad.  It will be very hard for you to find a fab with 2.5 mil spacing capability, and will be extremely expensive if you do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to have a board that can be manufactured easily, I suggest you adjust the sizes and move traces until DRC passes.  Dave of EEVblog fame wrote a good pcb design guide: &lt;a href=&quot;http://www.alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-03T00:18:01.653" CommentCount="3" />
  <row Id="6088" PostTypeId="1" AcceptedAnswerId="6092" CreationDate="2010-11-03T00:28:14.840" Score="1" ViewCount="136" Body="&lt;p&gt;I have a 0.1% 3V reference with a temperature coefficient of 100ppm/°C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does this mean it will be off by 8500ppm (0.085%) on top of my 0.1% when operating in an environment at 85°C?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does something similar apply to resistors?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-03T00:34:35.270" LastActivityDate="2010-11-03T00:38:34.193" Title="How does temperature affect voltage references, resistors etc.?" Tags="&lt;temperature&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="6089" PostTypeId="2" ParentId="6078" CreationDate="2010-11-03T00:28:53.050" Score="6" ViewCount="" Body="&lt;p&gt;I don't know what PCB houses require for board production. But stencil printer and pick-and place lines always need 3-4 fiducials on corners of panel. Panel can contain single pattern of board or multiples of patterns if you will go with mass production. The distance from panel edge to center of fiducial is 5-7.5mm. Fiducial is a copper circle 1-1.5 mm diameter. It is surrounded by circle 3-4mm large of bare substrate, so no solder mask is covering fiducial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same fiducials should be created on stencil (solder paste mask made of steel) &lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-03T00:28:53.050" />
  <row Id="6090" PostTypeId="1" AcceptedAnswerId="6097" CreationDate="2010-11-03T00:31:00.797" Score="2" ViewCount="89" Body="&lt;p&gt;Something interesting I've noticed with cheap devices from China (such as iPhone clones and digital cameras and the like) is that the manuals always specify they are &quot;T-flash&quot; (TransFlash) compatible, instead of &quot;microSD&quot; or &quot;SD&quot; compatible. Is this to get around paying the $3k/yr license fee, or is it something else entirely? The devices seem compatible with microSD as well as TransFlash cards.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-03T02:45:34.980" Title="Micro SD cards &amp; T-flash?" Tags="&lt;sd&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="6091" PostTypeId="1" AcceptedAnswerId="6105" CreationDate="2010-11-03T00:36:55.673" Score="4" ViewCount="333" Body="&lt;p&gt;I already have a 4 channel oscilloscope but it's quite old and I might have some money soon to upgrade with. The price for a 4 channel is almost 2-3x that of a 2 channel, but is the cost justified by the increased utility? I find I mostly use 2 channels on my scope currently, occasionally using a third but so far no use for all four. I'm dealing with serial protocols and video signals most of the time.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-27T19:47:54.657" Title="4 channel scope vs 2 channel scope" Tags="&lt;oscilloscope&gt;" AnswerCount="6" CommentCount="4" />
  <row Id="6092" PostTypeId="2" ParentId="6088" CreationDate="2010-11-03T00:38:34.193" Score="1" ViewCount="" Body="&lt;p&gt;The tempco can be specced from any part of chart. Its better to look at datasheet and see what do they mean by this coefficient. 85C looks too high for normal operating point. On the other hand if there is no access to datasheet, then its safest to treat the 100ppm number as worst case at the end of temperature range. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Say normal t=20C, then at 85C the error will be Unom*65*100/1000000 = +/-0.0195v and +/-0.1% initial error&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-03T00:38:34.193" />
  <row Id="6093" PostTypeId="1" AcceptedAnswerId="6103" CreationDate="2010-11-03T00:46:23.180" Score="4" ViewCount="446" Body="&lt;p&gt;I'm going to be driving a bank of 20-25 LEDs from a single output of a PIC micro. Obviously, I need a transistor, because that's going to be somewhere in the vicinity of 400 mA (the LEDs are speced at 20 mA with 3.2V of drop, which I'll get close to by using a 100 ohm resistor and a 5V power supply). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I get into trouble when I try to figure out what sort of transistor I should use for this, because I don't understand how transistors are rated. In discussions of general transistors, the 2N3904G &amp;amp; 2N3906G come up as good, all-around NPN &amp;amp; PNP transistors. How do I look at the transistor data sheet and understand that these transistors will work? What parameters do I need to pay attention to? I want to be sure the transistor can handle the load, and I want to be sure that my PIC's output can force the transistor all the way on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got some familiarity with digital electronics, but when we get into the analog world I just don't have enough of a frame of reference yet.&lt;/p&gt;&#xA;" OwnerUserId="259" LastEditorUserId="259" LastEditorDisplayName="" LastEditDate="2010-11-05T00:55:56.903" LastActivityDate="2010-11-05T00:55:56.903" Title="How to pick a switching transistor to drive LEDs? Or, how to read a transistor data sheet?" Tags="&lt;microcontroller&gt;&lt;led&gt;&lt;transistor&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="6094" PostTypeId="2" ParentId="5879" CreationDate="2010-11-03T00:47:51.987" Score="0" ViewCount="" Body="&lt;p&gt;Is it electical circuit or different matter ?&#xA;It looks like you are operating with terms of some modeling environment for logic circuits. I dont know if will help. So generally you are asking: &quot;I understand boolean OR gate function, but is it possible to improve noise immunity ? or improve signal to noise ratio ?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are allowed to use non-linear building blocks, then yes, you can improve immunity. Just look at schmitt trigger or saturated amplifier or diode clipper cicuit.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-03T00:47:51.987" />
  <row Id="6095" PostTypeId="2" ParentId="6093" CreationDate="2010-11-03T00:53:01.327" Score="1" ViewCount="" Body="&lt;p&gt;For bipolar transistors if you are in ballpark of voltage, current, frequency, then the only critical part is power. And for switching circuit the power is even not that important. So, any part with matching V, I, f and P will do.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-03T00:53:01.327" />
  <row Id="6096" PostTypeId="2" ParentId="6037" CreationDate="2010-11-03T01:02:39.807" Score="0" ViewCount="" Body="&lt;p&gt;If you are are bachelor in software, then its OK to have associate or bachelor level in electronics. Don't overspend your time on master degree, unless your current education was poorly sourced and you are questioning it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had 3.5 years in electronics, then switched to computer sicence. Stayed in boring financial industry doing software for 20 years, then returned to robotics and industrial automation with some luck in job search. &lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-03T01:02:39.807" CommentCount="2" />
  <row Id="6097" PostTypeId="2" ParentId="6090" CreationDate="2010-11-03T02:45:34.980" Score="5" ViewCount="" Body="&lt;p&gt;I think that T-flash and TransFlash are just the name of the microSD spec before it was adopted by the Secure Digital standards body.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-03T02:45:34.980" CommentCount="1" />
  <row Id="6098" PostTypeId="2" ParentId="6091" CreationDate="2010-11-03T03:05:16.313" Score="3" ViewCount="" Body="&lt;p&gt;Your question is similar to the thought process when purchasing a new computer, only buy one when you actually /need/ it, instead of buying one as you 'might need the extra...'. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-11-03T03:05:16.313" />
  <row Id="6099" PostTypeId="1" AcceptedAnswerId="6102" CreationDate="2010-11-03T03:23:04.630" Score="4" ViewCount="175" Body="&lt;p&gt;I am attempting to connect and control a device which only accepts RS-485 input. I wish to communicate to this device via my existing UC3A1512. Does anyone have any existing source code or examples that may help me to create this interface?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need a method of outputting date via RS-485 format.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do not need to establish round trip communication, I simply need the ability to send commands to the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have looked at Atmel's website and also on AVRFreaks and I see nothing of value to my project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help is welcomed and appreciated!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I originally posted this question on &lt;a href=&quot;http://stackoverflow.com/questions/4033256/does-anyone-have-any-sample-code-or-suggestions-to-help-me-to-interface-my-100-pi&quot;&gt;StackOverflow&lt;/a&gt; before I knew of &lt;a href=&quot;http://electronics.stackexchange.com&quot;&gt;electronics.stackexchange.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1413" LastEditorUserId="1413" LastEditorDisplayName="" LastEditDate="2010-11-12T10:25:52.893" LastActivityDate="2011-02-09T16:00:49.733" Title="Does anyone have any sample code or suggestions to help me to interface my 100 pin uc3a1512to a device via RS-485?" Tags="&lt;atmel&gt;&lt;rs485&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="6100" PostTypeId="2" ParentId="1904" CreationDate="2010-11-03T03:48:13.123" Score="2" ViewCount="" Body="&lt;p&gt;My first reaction to your question was, yes the fumes are going to harm you.  My second was to conduct some quick research.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Amazingly, as I quote next, Lead-Free Solder inhalation can lead to pneumonia and a 24-48H flu.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&quot;INHALATION: Inhalation of dusts and fumes may cause irritation of the upper respiratory tract.&#xA;Inhalation of freshly formed metal oxides may cause metal fume fever, a brief (24-48 H) flu-like illness.&#xA;Inhalation of tin oxide may cause pneumonia.&quot;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to the &lt;a href=&quot;http://www.cooperhandtools.com/MSDS/weller/LeadFreeSolderMSDSEnglish.pdf&quot; rel=&quot;nofollow&quot;&gt;MSDS&lt;/a&gt; from Weller on some of their non-lead solder&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can guarantee this must be a frequent event or the company wold not be disclosing this in such a cavalier manner.&lt;/p&gt;&#xA;" OwnerUserId="1413" LastEditorUserId="1413" LastEditorDisplayName="" LastEditDate="2010-11-03T20:50:57.813" LastActivityDate="2010-11-03T20:50:57.813" CommentCount="2" />
  <row Id="6101" PostTypeId="2" ParentId="3027" CreationDate="2010-11-03T04:48:37.037" Score="2" ViewCount="" Body="&lt;p&gt;My background, embedded (mcu, pc, unix, other), realtime. Safety critical.&#xA;I introduced a previous employer to STL.&#xA;I don't do that anymore.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some Flame content&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is C++ suitable for embedded systems?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Meh. C++ is a pain to write and a pain to maintain. C+ is sort-of okay ( don't use some features) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;C++ in Microcontrollers? RTOSes? Toasters? Embedded PCs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again I say Meh. C+ is not too bad, but ADA is less painful (and that's really saying something) . If you're lucky like me, you get to do embedded Java. Checked array access and no pointer arithmetic makes for very reliable code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is OOP useful on microcontrollers?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sure is. &#xA;The UART is an object.....&#xA;The DMAC is an object...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Object State machines are very easy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does C++ remove the programmer too far from the hardware to be efficient?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless it's a PDP-11, C ain't your CPU. &#xA;C++ was originally a preprocessor ontop of C so Bjarne Strotrup would stop getting laughed at for having slow Simula simulations while at AT&amp;amp;T.&#xA;C++ ain't your CPU. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Go get an MCU that runs java bytecodes. Program in Java. Laugh at the C guys.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should Arduino's C++ (with no dynamic memory management, templates, exceptions) be considered as &quot;real C++&quot;? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nope. just like all the bastardised C compilers out there for MCU's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Forth, Embedded Java or Embedded ADA are standardised(ish); all else is sorrow.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-11-03T04:48:37.037" CommunityOwnedDate="2010-11-03T04:48:37.037" CommentCount="3" />
  <row Id="6102" PostTypeId="2" ParentId="6099" CreationDate="2010-11-03T04:54:09.653" Score="5" ViewCount="" Body="&lt;p&gt;You need to put a RS-485 transceiver on your USART. Maybe a TI SN65HVD11, looks like it works with 3.3V IO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you you need to transmit, any sample that writes out the USART in asynchronous  mode will do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you don't mention having to share a RS-485 bus, tie the TX enable on on the transceiver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That way RS-232 example code will work for you.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-11-03T04:54:09.653" CommentCount="3" />
  <row Id="6103" PostTypeId="2" ParentId="6093" CreationDate="2010-11-03T05:59:09.887" Score="2" ViewCount="" Body="&lt;p&gt;The 2N2222 might be a better choice - inexpensive, commonly available, handles the current, and overall a good choice for switching.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The spec you want to look at most Icmax, or sometimes just Ic  (The 'C' being a subscript) which is the maximum current you'd normally be able to put through a fully turned on (saturated) transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 2N2222 apparently is popular enough to get its own web domain &lt;a href=&quot;http://2n2222datasheet.com/&quot; rel=&quot;nofollow&quot;&gt;http://2n2222datasheet.com/&lt;/a&gt;  where I found several PDF spec sheets.  I see (pun not intended) that Ic is 600mA  - you could use one transistor to drive all your LEDs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another spec to pay attention to is beta - the current gain.  If you're switching 400mA and the transistor has a beta of, say , 100 then you'll need to supply 400mA/100 = 4mA to the base from your digital output.  Beta isn't very consistent from transistor to transistor, even of the same type. Just make sure the math works out for the lower end of the beta range when choosing a resistor for the base.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Practically all the other specs aren't of as much importance, not a your low 5V supply, unless you're going to drive the LEDs very fast, e.g. a few MHz.    &lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-11-03T05:59:09.887" CommentCount="3" />
  <row Id="6104" PostTypeId="2" ParentId="6093" CreationDate="2010-11-03T07:11:10.657" Score="2" ViewCount="" Body="&lt;p&gt;You might be better off with a pchannel mosfet (inverted logic out) or low side n-channel mosfet as they will perform will as switches for this type of application, and reduce the voltage drop across the device to be directly proportional to the LED current.  With the bipolar transistor the LED current will be proportional to the PIC output current, and you will always lose 0.7 V across the emitter.   A mosfet will have a low Rdson which can result in much less losses across the switching device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For selection purposes you need to know your maximum bus voltage, then double it, to give you margin of error, next look a device with the smallest Rdson for a given voltage and package and cost.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-03T07:11:10.657" CommentCount="2" />
  <row Id="6105" PostTypeId="2" ParentId="6091" CreationDate="2010-11-03T07:15:05.530" Score="6" ViewCount="" Body="&lt;p&gt;The times when I have needed a four channel scope, are few, but when I do there is no replacement for it.  You mentioned serial protocols, using four channels can really help debug  SPI communications, especially if the scope is fitted with a analyser to conver the SPI waveform into actual characters!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having said that, buying a two channel scope, and then hiring a high end four channel with analysers (fft/spi and so on) might be a worthy alternative.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The saving you make up front, can go towards the hire cost of when you actually need it!  Might be worth investigating the hire cost upfront so you know what you might be in for.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-03T07:15:05.530" CommentCount="1" />
  <row Id="6106" PostTypeId="2" ParentId="1904" CreationDate="2010-11-03T07:23:12.643" Score="5" ViewCount="" Body="&lt;p&gt;Yes, but it all about exposure time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you solder 8h per day and 5 days per week your exposure is quite high and the odds of side effect if you don't ventilate it away is quite high.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, if you solder a couple of prototype boards now and then, and you don't directly inhale the fumes the amount of chemicals is probably not that high.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-11-03T07:23:12.643" />
  <row Id="6107" PostTypeId="2" ParentId="6077" CreationDate="2010-11-03T07:27:53.420" Score="2" ViewCount="" Body="&lt;p&gt;Another place to start is the TB303 schematics!  the machine that started it all :)  &lt;a href=&quot;http://machines.hyperreal.org/manufacturers/Roland/TB-303/schematics/&quot; rel=&quot;nofollow&quot;&gt;http://machines.hyperreal.org/manufacturers/Roland/TB-303/schematics/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Start off by understanding a portion of the circuit and go ahead and design something based on it on small piece of breadboard, and build up from there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have a few of the elements working, try designing your own pcb with ground planes (this will improve the noise levels) or check out some kits as Rob has already linked to.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-03T07:27:53.420" />
  <row Id="6108" PostTypeId="1" AcceptedAnswerId="6109" CreationDate="2010-11-03T07:40:06.913" Score="4" ViewCount="416" Body="&lt;p&gt;I've got a SOT-23 transistor (I think, but it could also be an IC) marked with 1E. Another one is marked with A7W. Then I can also see WR5. How are you supposed to decode these?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-11-03T08:38:13.613" LastActivityDate="2010-11-03T12:15:33.607" Title="Small SOT-23 transistor markings" Tags="&lt;components&gt;&lt;surface-mount&gt;&lt;markings&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="3" />
  <row Id="6109" PostTypeId="2" ParentId="6108" CreationDate="2010-11-03T08:34:04.850" Score="3" ViewCount="" Body="&lt;p&gt;You could try the &quot;&lt;a href=&quot;http://www.marsport.org.uk/smd/mainframe.htm&quot; rel=&quot;nofollow&quot;&gt;SMD code book&lt;/a&gt;&quot; or get the actual schematic or package for the device, but there may not really be a clear way to identify many SMD parts from the surface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1E for example might be a plain BC847A according to the list.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-11-03T08:34:04.850" />
  <row Id="6110" PostTypeId="2" ParentId="6099" CreationDate="2010-11-03T08:36:04.880" Score="2" ViewCount="" Body="&lt;p&gt;Are you asking about the RS-485 physical connection or the data protocol that you have to use?  From the phrasing of the question I will assume that it is the former.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RS-485 specifies the signal levels and number of wires used to send the data together with the maximum transmission distances for the various data rates used, in much the same way as RS-232.  All that you need to do, from a physical point of view, is to replace any RS-232 driver with an RS-485 transceiver.  These are available from many suppliers (Maxim, TI, ON-semi...)  As you say you only have to transmit to the remote device, you can just leave the receive side open and use 3 wires to connect to the remote device (TxA, TxB and Gnd).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The commands sent to the remote device are defined in its protocol spec and will be sent in exactly the same way as on any other async serial interface.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-11-03T08:36:04.880" />
  <row Id="6111" PostTypeId="2" ParentId="6091" CreationDate="2010-11-03T09:30:38.247" Score="3" ViewCount="" Body="&lt;p&gt;My view is that two channels is usually enough for analog usage, but four channels is not enough for digital use. I have an Agilent scope with two analog channels and 16 digital channels. As long as you don't need to probe very high frequency signals an oscilloscope like that should not be too expensive.&lt;/p&gt;&#xA;" OwnerUserId="1627" LastActivityDate="2010-11-03T09:30:38.247" CommentCount="2" />
  <row Id="6112" PostTypeId="2" ParentId="739" CreationDate="2010-11-03T09:52:58.893" Score="5" ViewCount="" Body="&lt;p&gt;So many questions; let's try try to answer them in order:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;strong&gt;Resource requirement for signal processing:&lt;/strong&gt; In order to determine what hardware you need to use/build you need an idea of the amount of processing you want to do on the signals in question. 8 channels @ 10 kHz is not a very high data rate, so unless your requirements are very special most FPGAs and DSPs should be able to process the data.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;How do I choose the right device?&lt;/strong&gt; Based on the requirements of your signal processing you should be able to figure out which device is required for your application. Key points are memory requirement, are hard multipliers required, special IO considerations, etc. Most FPGA vendors have tools (web based) that let you search their portfolio based on such factors.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;How do I get started with DPSs?&lt;/strong&gt; DPSs are just ordinary computers that usually have SIMD[Single Instruction, Multiple Data] instructions relevant for signal processing. To get started you just need to understand the limitations of &quot;embedded&quot; hardware and a C compiler so that you can test your code on an ordinary PC.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;How do I get started with FPGAs?&lt;/strong&gt; FPGAs are programmed in a Hardware Description Language. These are significantly different from sequential languages such as C or Java. In order to develop for FPGA you need to understand the concurrent nature of real hardware. The tools you need to get started is a HDL simulator such as Simili (free for small designs) or Modelsim. This lets you simulate your code on PC. After that you need a vendor specific synthesis tool which compiles you HDL-code into a bit-file which is used to configure the FPGA. If you get a starter kit from Altera, Actel or Xilinx all the tools you need is part of the kit.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Linux support:&lt;/strong&gt; FPGA tools from most vendors run on Linux, but in the DSP field you are usually forced to use Windows-only compiles unless your DSP is supported by GCC (Blackfin from Analog and several models from Texas Instruments are).&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1627" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-11-03T15:18:18.520" LastActivityDate="2010-11-03T15:18:18.520" CommentCount="3" />
  <row Id="6113" PostTypeId="2" ParentId="6076" CreationDate="2010-11-03T10:15:42.913" Score="3" ViewCount="" Body="&lt;p&gt;Check out &lt;a href=&quot;http://nl.wikipedia.org/wiki/Knoopcel#Uitvoeringen&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; table with button cell battery specs. There is one 1.55V battery sized 11,6 x 5,4mm @ 190mAh.&#xA;If you're trying to save space 'horizontally' on the board, just stack 2 of these vertically: that gives you 3.1V and 190mAh. That's about what you'd get from an almost twice as wide CR2032.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I haven't checked battery type, availability or cost, you'll have to check those yourself.&lt;/p&gt;&#xA;" OwnerUserId="1124" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-11-03T15:11:25.243" LastActivityDate="2010-11-03T15:11:25.243" CommentCount="3" />
  <row Id="6114" PostTypeId="2" ParentId="6084" CreationDate="2010-11-03T11:18:14.893" Score="3" ViewCount="" Body="&lt;p&gt;Manufacturers will often supply free sample books of components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, you can buy these. In the UK, one supplier I found is &lt;a href=&quot;http://www.fastcomponents.co.uk/&quot; rel=&quot;nofollow&quot;&gt;http://www.fastcomponents.co.uk/&lt;/a&gt; who sell mixed packs of SMT resistors and capacitors.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-03T11:18:14.893" CommentCount="0" />
  <row Id="6115" PostTypeId="2" ParentId="6084" CreationDate="2010-11-03T11:20:27.637" Score="1" ViewCount="" Body="&lt;p&gt;Not a direct answer to  your question, but Element14 in Australia has free shipping on all orders ($10 minimum for credit card)! Very handy!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've ordered single quantity resistors and capacitors from them when i need it, and haven't had the need to buy a whole resistor/capacitor pack yet. Prices are reasonable for prototyping quantities!&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-03T11:20:27.637" />
  <row Id="6116" PostTypeId="2" ParentId="6078" CreationDate="2010-11-03T11:24:22.407" Score="1" ViewCount="" Body="&lt;p&gt;R6 is damn close to the QFP packaged IC. I would move it away slightly for easy hand-assembly. Also - U4 (your crystal), is your through hole crystal really that small?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-03T11:24:22.407" CommentCount="1" />
  <row Id="6118" PostTypeId="2" ParentId="6084" CreationDate="2010-11-03T11:47:18.603" Score="1" ViewCount="" Body="&lt;p&gt;You can get very cheap &lt;a href=&quot;http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&amp;amp;item=160441673158&quot; rel=&quot;nofollow&quot;&gt;500x reels of resistors&lt;/a&gt; from eBay.  Would probably be a good idea to get a set of your most common resistor values in these reels to save you some money in the long run.&lt;/p&gt;&#xA;" OwnerUserId="1333" LastActivityDate="2010-11-03T11:47:18.603" />
  <row Id="6119" PostTypeId="2" ParentId="6084" CreationDate="2010-11-03T12:13:42.353" Score="2" ViewCount="" Body="&lt;p&gt;Where I work we use the &lt;a href=&quot;http://www.murata-northamerica.com/kits&quot; rel=&quot;nofollow&quot;&gt;Murata's design kit&lt;/a&gt;. It's great for prototypes and there is several configurations to chose.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-03T12:13:42.353" />
  <row Id="6120" PostTypeId="2" ParentId="6108" CreationDate="2010-11-03T12:15:33.607" Score="2" ViewCount="" Body="&lt;p&gt;The A7W is a &lt;a href=&quot;http://www.s-manuals.com/smd-files/pdf/b/bav99_p.pdf&quot; rel=&quot;nofollow&quot;&gt;double diode&lt;/a&gt;.  I took a guess and googled &quot;transistor marking A7W&quot;.  Good luck on the rest.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://matthieu.benoit.free.fr/cross/competitive/philips/SMD-PHILIPS.pdf&quot; rel=&quot;nofollow&quot;&gt;Here's a PDF that shows the markings for SMD Philips chips&lt;/a&gt;.  Most are standard parts, so then you can look up a real datasheet.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-11-03T12:15:33.607" />
  <row Id="6122" PostTypeId="2" ParentId="6091" CreationDate="2010-11-03T13:53:45.783" Score="2" ViewCount="" Body="&lt;p&gt;2 channels analogue is fine, then get a USB logic analyser for serial protocols (I like the &lt;a href=&quot;http://www.saleae.com/logic/&quot; rel=&quot;nofollow&quot;&gt;Salea&lt;/a&gt; ones)&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2010-11-03T13:53:45.783" />
  <row Id="6123" PostTypeId="1" AcceptedAnswerId="6129" CreationDate="2010-11-03T14:07:45.230" Score="12" ViewCount="404" Body="&lt;p&gt;The title pretty much sums it up... Hyperbole aside, how much actual power is consumed by a typical wall wart when the device it's attached to isn't powered on? And are there designs for wall warts that minimize or eliminate this sort of parasitic load?&lt;/p&gt;&#xA;" OwnerUserId="1317" LastActivityDate="2010-11-03T16:31:36.967" Title="How much power is really wasted by a wall wart?" Tags="&lt;power&gt;&lt;wall-wart&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="6124" PostTypeId="2" ParentId="6069" CreationDate="2010-11-03T14:16:15.400" Score="1" ViewCount="" Body="&lt;p&gt;Consider this approach: &lt;a href=&quot;http://www.penguin.cz/~utx/pstoedit-pcb&quot; rel=&quot;nofollow&quot;&gt;http://www.penguin.cz/~utx/pstoedit-pcb&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-03T14:16:15.400" CommentCount="4" />
  <row Id="6125" PostTypeId="2" ParentId="6123" CreationDate="2010-11-03T14:48:46.957" Score="10" ViewCount="" Body="&lt;p&gt;How much gas is wasted by a car?  It depends on the manufacturer and particular model.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Old AC/DC converters just had a large transformer, some diodes, and a capacitor, but nowadays many are switching converters that offer better regulation, improved efficiency, and smaller size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the couple transformers I've looked at on Digi-Key, all the Energy Star level IV and V transformers have a maximum of 0.5 W usage at no-load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Energy Star has &lt;a href=&quot;http://www.energystar.gov/ia/partners/prod_development/downloads/power_supplies/powersupplyreport.pdf&quot; rel=&quot;nofollow&quot;&gt;a whole report on this&lt;/a&gt;, and fancy graph (on page 5):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2n4Xl.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-03T15:44:41.647" LastActivityDate="2010-11-03T15:44:41.647" />
  <row Id="6126" PostTypeId="2" ParentId="6123" CreationDate="2010-11-03T14:59:36.337" Score="3" ViewCount="" Body="&lt;p&gt;Numbers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best ones will waste &amp;lt; 0.5 W when no load is connected, but the no-load-losses can be as high as &gt; 10 W, depending on the design, and even for switch-mode wall warts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My guess is that most typical wall warts used today consume about 1...3 W when no load is connected.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-11-03T14:59:36.337" CommentCount="3" />
  <row Id="6127" PostTypeId="2" ParentId="6123" CreationDate="2010-11-03T15:10:37.007" Score="1" ViewCount="" Body="&lt;p&gt;Depends on the wall wart.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example some cheaper ones may use higher leakage capacitors which might waste a tiny bit of current. And the diodes might drop some voltage and waste this as heat when charging up this leakage. And then you've got other losses, like those of the transformer, or in some cases of the surge protection devices (MOV's) across the input. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-03T15:10:37.007" />
  <row Id="6128" PostTypeId="2" ParentId="739" CreationDate="2010-11-03T15:14:33.493" Score="2" ViewCount="" Body="&lt;p&gt;Just about any FPGA vendor will do.  It's like Intel vs AMD...there are differences between Xilinx and Altera, but they're remarkably similar in terms of functionality.  Buy whatever development kit is in your price range - I personally liked Spartan 3's from Xilinx - and run with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding gate count, the dev kit will typically be very large, hopefully much larger than you need.  When you get ready to move to your own PCB, the synthesis tools will estimate for you how many gates your design requires.  You can use this to select a smaller FPGA, though you may find out that package constraints (QFP vs BGA) play an important role too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With proper design techniques, the clock speed won't be an issue.  In fact, you can typically use a relatively low speed crystal, like 12 MHz, and the FPGA can synthesize a much faster clock (or many faster clocks!)  If you're really worried about multiply-adds, I know the Virtex4 series has dedicated DSP slices that can accelerate those calculations.  But FPGAs are massively parallel, so you don't need too many MHz to do a ton of work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would definitely stick with fixed point if you can.  It's possible to do floating point, and Xilinx even has a Core Generator that will provide you with a floating point core, but fixed point will be way, way faster, and will require far fewer gates.  Another advantage is that you can do some odd fixed point; you can use as many bits as you want, it doesn't have to be a power-of-2 bit count, and/or you can use larger fixed points for intermediate stages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best way to get started with FPGAs?  Find a class or a seminar or something.  If you are unfamiliar with the technology, the development tools will be very confusing, because there is a lot that can go wrong.  Tools for MCUs are much more forgiving and require less intimacy with the underlying architecture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh, and you should read the FPGA's datasheet, front to back.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-11-03T15:14:33.493" />
  <row Id="6129" PostTypeId="2" ParentId="6123" CreationDate="2010-11-03T15:46:44.693" Score="9" ViewCount="" Body="&lt;p&gt;About 1 billion percent.  No useful work is being done except to heat your house, and energy is being dissipated which would not be dissipated if the wall wart was not plugged in.  The actual quantity is small, so I wouldn't worry about it too much if you're concerned about your electricity bill - A few cell phone chargers left in the wall 24-7 won't make a dent. &#xA;For some math, if a device is just barely CEC certified (0.5W no-load dissipation) and left in the wall unused all month, you have 730 hours (in one month) * 0.5W * 0.001 W/kW = 0.365kWh [kilowatt hours] and electricity costs of, say, $0.20/kWh, and you have a cost of $0.07 Find a dime, pay the bill.  Compare that to, say, your 73W fridge, which will be around $10/month.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If, however, you have a lot of wall warts, or the small losses are significant to you, look at switch-mode power supplies.  They're more expensive, but more efficient both at no-load conditions and during use, and switch-mode supplies will actually regulate, as opposed to transformer-based designs which require further regulation circuitry.  You can tell what kind a converter is just by the weight - A switch-mode supply will have just a lightweight circuit board with some electronics inside, while a traditional wall wart has a big, heavy transformer.   I've used CUI switch-mode PSUs before, they're  a good company with a nice line-up: See &lt;a href=&quot;http://products.cui.com/catfeatures.asp?brand=v-infinity&amp;amp;catky=764537&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; for some of their AC-DC converter products.  See their &lt;a href=&quot;http://www.cui.com/Resources/Compliance&quot; rel=&quot;nofollow&quot;&gt;Compliance page&lt;/a&gt; for more information on efficiency ratings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: Some people use the term &quot;wall-wart&quot; for the transformer-based devices only, while others use it for both switch-mode and transformer-based wall plug-in AC-DC converters.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-03T15:46:44.693" CommentCount="3" />
  <row Id="6130" PostTypeId="2" ParentId="6123" CreationDate="2010-11-03T16:21:31.143" Score="2" ViewCount="" Body="&lt;p&gt;Not enough to worry about.  If a bad one wastes 10 W (according to zebonaut), that will be a total energy waste of 7 kWh per month.  This &lt;a href=&quot;http://blog.lastinfirstout.net/2008/09/unplug-your-wall-warts-and-save-planet.html&quot; rel=&quot;nofollow&quot;&gt;actual test&lt;/a&gt; of real wall warts measured 2 W max (1.5 kWh/month)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By comparison:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A single hour of running an electric oven uses 2 kWh&lt;/li&gt;&#xA;&lt;li&gt;A single load of laundry in a hot clothes washer uses 4.5 kWh&lt;/li&gt;&#xA;&lt;li&gt;A single load in an electric dryer uses 3.2 kWh&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If the wall wart is warm to the touch when unloaded, it's wasting energy and you could try to unplug it when not in use.  If it's cool to the touch, then don't worry about it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SMPS supplies and AC supplies shouldn't draw too much (an unloaded transformer is just an inductor, and only the residual resistance is wasting energy).  DC supplies with linear regulators inside would be the worst.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, don't worry about it.  It's straining out gnats while swallowing camels.  :D&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And in winter, definitely don't worry about it.  The &quot;wasted&quot; energy is heating your home and making your heater work less.  All household appliances magically become 100% efficient in the winter.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-03T16:31:36.967" LastActivityDate="2010-11-03T16:31:36.967" CommentCount="3" />
  <row Id="6131" PostTypeId="2" ParentId="6078" CreationDate="2010-11-03T17:46:00.430" Score="4" ViewCount="" Body="&lt;p&gt;Put a part number and revision number on the silkscreen.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-11-03T17:46:00.430" CommentCount="2" />
  <row Id="6132" PostTypeId="2" ParentId="6091" CreationDate="2010-11-03T17:50:55.927" Score="4" ViewCount="" Body="&lt;p&gt;Personally I use 4 channels all the time for analog work but if your not doing something that involves multiple stage audio filters or something of that nature it may be overkill.  As long as you can verify signal integrity you shouldn't need very many analog channels for what your describing.  Your better off having a scope with a higher bandwidth so you can see EMI issues than your are a 4 channel scope.  For instance in your application i would get a 2 channel 500mhz scope over a 4 channel 100mhz scope.  I would make sure the scope has good math and FFT functions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also consider any differential measurement issues, unless your scope support differential probes your 2 channel scope can only measure a single signal differentially.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only caveat I would add to the number of channels is if your doing design for mass production.  The first time you run into some weird intermittent error that only occurs on some boards your going to want to be able to scope as many signals as possible in the analog domain while you try to induce the error.  This is much more common than it sounds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For digital work, as long as you can verify signal integrity issues i don't find having the scope be able to decode serial data to be all that important.  Using a USB to serial converter for the appropriate serial bus type i find much easier to work with.  The amount of data i can store on my computer and how quickly i can navigate it with a mouse/keyboard massively surpasses every scope i've ever worked with, unless your talking very high speed, like PCI-express or something.  Also being able to act as a master on an I2C/SPI bus is very useful for testing slave functionality.  I can right up a python script to test all functions of a slave device much much faster than i could trying to do that from the board's true master. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your working with higher speeds or parallel buses, a logic analyzer may be very useful.  The one i work with a lot that doesn't operate within the USB&amp;lt;-&gt;serial realm well is I2S and i don't bother with the logic analyzer, i check the signal integrity with a scope then feed it through a little converter board I made that converts I2S &amp;lt;-&gt; S/PDIF and feed it right into my computer to analyze in matlab. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some scopes will do video triggering on NTSC/PAL/HDMI which you may find useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no idea what your budget is, the scope I use most is a tektronics MSO3014 which is a 4 analog + 16 digital @ 100mhz scope, which i find takes care of 95% of what i need, only failing to meet my needs when the bandwidth isn't high enough.  But at ~$8,000 it may not be what your after.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-03T17:50:55.927" />
  <row Id="6133" PostTypeId="2" ParentId="3900" CreationDate="2010-11-03T18:04:24.493" Score="3" ViewCount="" Body="&lt;p&gt;I've sent this question to Jack Ganssle and this is what he answered me:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Daniel,&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;I prefer to debug using whatever optimizations will be in the released code. NASA says &quot;test what you fly, fly what you test.&quot; In other words, don't do testing and then change the code!&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;However, sometimes one has to turn off optimizations so that the debugger will work. I try to turn them off just in the modules I'm working on. For that reason I believe in keep files small, say a few hundred lines of code or so.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;All the best,&#xA;  Jack&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-03T18:04:24.493" CommentCount="4" />
  <row Id="6134" PostTypeId="1" AcceptedAnswerId="6138" CreationDate="2010-11-03T18:23:35.610" Score="2" ViewCount="141" Body="&lt;p&gt;In class today our physics teacher was demonstrating how ionic fluids move when a high voltage exists between them. A USB microscope was placed above the test rig, and the image was projected onto the virtual board. He used a 500V-5kV supply, limited to 60µA. The demonstration was interesting, but more interesting was what happened when he turned the supply voltage up: the image on the board began to flicker, then broke up completely and eventually &quot;no signal&quot; popped up. It also caused the USB microscope to reset.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking it was interference, but how could a high voltage but low current supply cause such problems for the projector? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think it might be related to my digital clock having difficulties (resetting, alarm going off randomly, time skipping several seconds at a time) when it is within about 10 cm of my plasma ball, because both use high voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-17T14:36:44.713" LastActivityDate="2011-05-17T14:36:44.713" Title="Interference from high voltage power supply (EHT power supply)" Tags="&lt;high-voltage&gt;&lt;interference&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="6135" PostTypeId="2" ParentId="6029" CreationDate="2010-11-03T18:36:07.653" Score="1" ViewCount="" Body="&lt;p&gt;You aren't talking about a battery, but an RF receiver.  When you add the antenna and ground connections, you are receiving energy that is broadcast by a transmitter.  The resonant frequency of your tank should match the frequency of the transmitter.  If you're going to harvest energy, I guess you would target 60/50 Hz, unless you have a stronger source nearby.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Wardenclyffe_Tower#Theory_of_wireless_transmission&quot; rel=&quot;nofollow&quot;&gt;Nikola Tesla started to build such a transmitter&lt;/a&gt; for communications and experiments on power distribution, but his financing was coming from people who had a vested interest in the power generation systems of the day.  When he mentioned the possibility of broadcasting power that anyone could pick up for free, then his funding dried up.  So, it took another forty years to lay a transatlantic cable to make reliable communications with England happen.&lt;/p&gt;&#xA;" OwnerUserId="1824" LastEditorUserId="1824" LastEditorDisplayName="" LastEditDate="2010-11-04T14:55:17.833" LastActivityDate="2010-11-04T14:55:17.833" />
  <row Id="6136" PostTypeId="2" ParentId="2601" CreationDate="2010-11-03T18:47:44.770" Score="0" ViewCount="" Body="&lt;p&gt;The big problem is that the output voltage stays fairly flat for most of the time.  So, unless you have a really good A/D, you can't monitor it directly.  That is why laptops and such tend to use clocks to measure the remaining power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's pretty easy to find the graphs if you search for &quot;battery discharge curve&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://shdesigns.org/batts/battcyc.html&quot; rel=&quot;nofollow&quot;&gt;http://shdesigns.org/batts/battcyc.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1824" LastActivityDate="2010-11-03T18:47:44.770" />
  <row Id="6137" PostTypeId="2" ParentId="6078" CreationDate="2010-11-03T18:55:01.797" Score="1" ViewCount="" Body="&lt;p&gt;On the bottom, north of R36, is a GND fill that is isolated from the main GND fill.  It looks like this is CONN6-4.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-11-03T18:55:01.797" />
  <row Id="6138" PostTypeId="2" ParentId="6134" CreationDate="2010-11-03T19:00:28.173" Score="4" ViewCount="" Body="&lt;p&gt;Its not a result of the high voltage but rather a by product of how that high voltage is generated.  Very high frequency switching is used, such devices often emit a ton of RF around 25Mhz depending on the design.  This is what throws off the USB scope and other digital electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the whining your heard, plasma can actually transfer energy to the air very effectively.  If fact you can even build a &lt;a href=&quot;http://www.youtube.com/watch?v=cEeWtBAE5LY&quot; rel=&quot;nofollow&quot;&gt;tweeter from plasma generation&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incidently be careful with that stuff, ionizing the air into plasma generates a fair amount of ozone which isn't good for the lungs.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-03T19:00:28.173" CommentCount="9" />
  <row Id="6139" PostTypeId="2" ParentId="5990" CreationDate="2010-11-03T19:04:02.127" Score="0" ViewCount="" Body="&lt;p&gt;If your parts distributor drops the coin cells you ordered into antistatic bags for shipping, then just send them back.  Yeah, it happens some times.&lt;/p&gt;&#xA;" OwnerUserId="1824" LastActivityDate="2010-11-03T19:04:02.127" CommentCount="5" />
  <row Id="6140" PostTypeId="1" AcceptedAnswerId="6141" CreationDate="2010-11-03T19:39:07.590" Score="0" ViewCount="159" Body="&lt;p&gt;I'm looking for a device which monitors a 3.3V line. When the line drops below, say, 2.7V, I would like it to switch power over to a battery backup (3V lithium coin cell.) It would also be good if it provided a logic signal to alert of the supply failure so the MCU in my project can switch over to a low power mode. It needs to be able to switch up to 120mA when the supply is high. What is the name of this device? I have a feeling it's quite common in applications like laptop computers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally it would have 5 pins: Vin main, Vin backup, GND, Vout, Logic out.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2010-11-04T14:07:24.223" LastActivityDate="2010-11-04T14:07:24.223" Title="What's the name of the device I'm looking for..." Tags="&lt;power-supply&gt;&lt;battery&gt;" AnswerCount="4" />
  <row Id="6141" PostTypeId="2" ParentId="6140" CreationDate="2010-11-03T19:47:22.533" Score="3" ViewCount="" Body="&lt;p&gt;Power Management Controller / Power Management IC&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The functionality your after would normally be part of a full system power management IC or a battery charging/management IC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If all you need to implement is exactly what you asked for, a single FET with a low Drain &amp;lt;-&gt; Source voltage drop and maybe a couple resistor to set the trip point are all thats required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to smoothly handle bounce, such as the bounce that occurs when you plug in a DC barrel jack, you can use a supervisor/reset controller designed to deal with bounce and use the reset output to trigger the FET.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-03T20:17:15.143" LastActivityDate="2010-11-03T20:17:15.143" CommentCount="8" />
  <row Id="6142" PostTypeId="2" ParentId="6140" CreationDate="2010-11-03T19:58:32.243" Score="3" ViewCount="" Body="&lt;p&gt;Power Supervisor IC&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-03T19:58:32.243" />
  <row Id="6143" PostTypeId="2" ParentId="6140" CreationDate="2010-11-03T19:59:53.150" Score="2" ViewCount="" Body="&lt;p&gt;It sounds like a Diode-OR'd power with the line voltage also going to a digital input pin to read the line voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But there's probably a chip for that.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-11-03T19:59:53.150" CommentCount="8" />
  <row Id="6144" PostTypeId="2" ParentId="6140" CreationDate="2010-11-03T20:01:47.920" Score="1" ViewCount="" Body="&lt;p&gt;Trying to replace &lt;a href=&quot;http://electronics.stackexchange.com/questions/6076/smallest-lithium-battery-backup/6080#6080&quot;&gt;OR-ing diodes&lt;/a&gt;?  How about an &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=1644&amp;amp;uiTemplateId=NODE_STRY_PGE_T&quot; rel=&quot;nofollow&quot;&gt;OR-ing controller&lt;/a&gt;?  Such devices are generally designed for much more current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maxim has some interesting &lt;a href=&quot;http://www.maxim-ic.com/products/supervisors/battery_backup/&quot; rel=&quot;nofollow&quot;&gt;battery backup supervisors&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-03T20:08:11.517" LastActivityDate="2010-11-03T20:08:11.517" CommentCount="2" />
  <row Id="6145" PostTypeId="1" AcceptedAnswerId="6146" CreationDate="2010-11-03T20:23:56.673" Score="0" ViewCount="333" Body="&lt;p&gt;I want to be able to switch on a device that requires 5v and 100mA from a Netduino. From looking on the web, I believe I need to use a Darlington array in order to meet the current requirements (since the Netduino pins are only at 8mA max).  Is a ULN2803 the right component to use?  Can it generate what I need with the 3.3v of the Netduino?&lt;/p&gt;&#xA;" OwnerUserId="1206" LastActivityDate="2010-11-03T20:48:50.030" Title="Using an ULN2803 with Netduino" Tags="&lt;microcontroller&gt;&lt;netduino&gt;" AnswerCount="2" />
  <row Id="6146" PostTypeId="2" ParentId="6145" CreationDate="2010-11-03T20:48:30.593" Score="1" ViewCount="" Body="&lt;p&gt;The ULN2803 is generally meant to work with 5 V it seems, but based on some of the datasheets it might be able to supply 100 mA with 3.3 V in.  The related ULN2805 appears to function better at lower voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're looking for a &lt;em&gt;single&lt;/em&gt; low-side driver (where the device is always connected to the positive supply while you switch the ground), you can use a logic-level N-channel MOSFET (&lt;a href=&quot;http://www.electronics-tutorials.ws/transistor/tran_7.html&quot; rel=&quot;nofollow&quot;&gt;tutorial&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're looking to switch several loads, a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=734&quot; rel=&quot;nofollow&quot;&gt;high current shift register&lt;/a&gt; might be of use to you, and it also can save some I/O pins at the expense of some more complicated driving logic&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-03T20:48:30.593" CommentCount="2" />
  <row Id="6147" PostTypeId="2" ParentId="6145" CreationDate="2010-11-03T20:48:50.030" Score="1" ViewCount="" Body="&lt;p&gt;The 100mA current requirement is easily met. On page 2 of the &lt;a href=&quot;http://www.datasheetcatalog.org/datasheets/90/366828_DS.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;, you can see that 3V will provide for up to 300mA sink current.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-03T20:48:50.030" />
  <row Id="6148" PostTypeId="1" AcceptedAnswerId="7253" CreationDate="2010-11-03T21:29:31.840" Score="0" ViewCount="131" Body="&lt;p&gt;Is it possible to buy Pre-Made cables &amp;amp; headers to suit GLCD's, the model Im using has a 20-Pin interface like the model in the image below.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If as I fear such a convience does not exist what do you use/have you found to be the neatest way to connect these?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/aPurB.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="819" LastActivityDate="2010-11-28T17:29:46.523" Title="Pre-Made Cables &amp; Headers for (Parallel Interface) GLCD's" Tags="&lt;distributors&gt;&lt;cable-assemblies&gt;&lt;ribbon-cable&gt;&lt;glcd&gt;" AnswerCount="2" />
  <row Id="6149" PostTypeId="2" ParentId="6066" CreationDate="2010-11-03T21:36:48.833" Score="3" ViewCount="" Body="&lt;p&gt;To switch that much DC current I would use a contactor, as an example:&#xA;&lt;a href=&quot;http://www.albrightinternational.com/lang/en/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.albrightinternational.com/lang/en/index.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2010-11-03T21:36:48.833" CommentCount="1" />
  <row Id="6150" PostTypeId="2" ParentId="6148" CreationDate="2010-11-03T21:43:27.793" Score="1" ViewCount="" Body="&lt;p&gt;A place I used to work at connected a graphic LCD to the main board with what looked like a bunch of tinned strips sandwiched between Tyvek-type (non-woven polymer cloth) material.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nevertheless, is something like &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=WM10-04A-ND&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; (in &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=WM10-04A-ND&quot; rel=&quot;nofollow&quot;&gt;this category&lt;/a&gt;, but &lt;em&gt;not&lt;/em&gt; FFCs) what you're looking for?  Digi-Key doesn't seem to have 20-pin cables in-stock. &lt;a href=&quot;http://www.molex.com/molex/products/family?key=ribbon_cable_jumpers&amp;amp;channel=products&amp;amp;chanName=family&amp;amp;pageTitle=Introduction&quot; rel=&quot;nofollow&quot;&gt;Manufacturer (Molex) link&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt;&#xA;If you want to go the rigid route, headers come in all shapes and sizes.  Ones explicitly for this application I've heard them called double-level, mezzanine, but Digi-Key has them filed under &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1442852&quot; rel=&quot;nofollow&quot;&gt;board spacers/stackers&lt;/a&gt;, though of the 4900 they &quot;carry&quot;, 4 are in-stock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For prototyping male/female 0.100&quot; headers can be nice.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-03T21:57:36.467" LastActivityDate="2010-11-03T21:57:36.467" CommentCount="5" />
  <row Id="6151" PostTypeId="1" AcceptedAnswerId="6157" CreationDate="2010-11-03T23:43:28.923" Score="9" ViewCount="403" Body="&lt;p&gt;I'm trying to repair an 800W power supply (see my previous question on this.) One thing that gets me is that the design has two schottky diode packages (in TO-220) in parallel. I was always told this was A Bad Idea, but since they are thermally coupled to the same heatsink, does it present a problem in this instance? I've also noticed the same for the input bridge rectifier, two are used in parallel.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-02T18:51:14.113" LastActivityDate="2010-12-02T18:51:14.113" Title="Is paralleling diodes a bad idea?" Tags="&lt;diode&gt;&lt;parallel&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="6152" PostTypeId="2" ParentId="6151" CreationDate="2010-11-03T23:50:19.697" Score="7" ViewCount="" Body="&lt;p&gt;It's not ideal but in practice you can usually get away with it, especially if they are thermally coupled. If they aren't the potential problem is that silicon's -ve temperature coefficient could make one 'hog' more of the current, however in practice they will tend to both heat up at the same rate, and the slope resistance is never zero, so you will still get current sharing even when one is hotter.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-03T23:50:19.697" />
  <row Id="6153" PostTypeId="2" ParentId="1904" CreationDate="2010-11-03T23:53:22.490" Score="2" ViewCount="" Body="&lt;p&gt;I've been soldering daily for 35-odd years and the only time I do anything about fumes is if I'm doing a production batch, when I stick a 4&quot; fan at the side of the bench to blow air across, which is as effective as extraction, and doesn't get in the way. Unless you are allergic or find it annoying I wouldn't worry too much unless you're doing it continuously all day. &#xA;I do find the flux in LF solder significantly more irritating, which is another reason I rarely use it.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-03T23:53:22.490" />
  <row Id="6154" PostTypeId="2" ParentId="6134" CreationDate="2010-11-03T23:57:15.050" Score="1" ViewCount="" Body="&lt;p&gt;Most likely partial HV discharges (corona)  - these have an extremely fast risetime (sub nS) and therefore have a very wide spectral content. The high voltage also means the instantaneous current can be extremely high, so it gets everywhere.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-03T23:57:15.050" CommentCount="1" />
  <row Id="6155" PostTypeId="2" ParentId="3900" CreationDate="2010-11-04T00:02:54.753" Score="2" ViewCount="" Body="&lt;p&gt;My normal strategy is to develop with the final optimisation ( max for size or speed as appropriate), but flip the optimisation off temporarily if I need to debug ot trace something. &#xA;This reduces the risk of bugs surfacing as a result of changing optimisation levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A typical failure mode is when increasing optimisation causes previously unseen bugs to surface due to you not having declared variables as being volatile where necessary - this is essential to tell the compiler which things should not be 'optimised'.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-04T00:02:54.753" />
  <row Id="6156" PostTypeId="2" ParentId="126" CreationDate="2010-11-04T00:30:13.343" Score="1" ViewCount="" Body="&lt;p&gt;I found a great article on &lt;a href=&quot;http://hackaday.com/2010/09/02/using-an-nes-controller-on-an-android-phone/&quot; rel=&quot;nofollow&quot;&gt;Hack-A-Day&lt;/a&gt; regaring your quest.  This article is on interfacing the SNES controller with an Android utilizing an Arduino.  To save you some of the trouble of sifting through the article, I found the linked code they cited:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;This code uses an old-school 1980's&#xA;  NES controller to control a servo and&#xA;  an LED with the Arduino.   With this&#xA;  code, the 'up' pad turns a servo to&#xA;  180 degrees, 'right' turns it to 90,&#xA;  and 'down' turns it to 0 degrees. &#xA;  Also, the A and B buttons turn a LED&#xA;  on and off.   You can get a NES&#xA;  controller from ebay for less than&#xA;  $10.00 Here is a crude drawing of the&#xA;  controller plug, four holes on one&#xA;  side, three holes on the other.&lt;/p&gt;&#xA;  &#xA;  &lt;hr&gt;&#xA;&#xA;&lt;pre&gt;&#xA;                       0     --  0v (ground)&#xA;      +5V  ---  0      0     --CLOCK   &#xA;  nothing  ---  0      0     --LATCH  &#xA;  nothing  ---  0      0     --SERIAL OUT &lt;/pre&gt;&#xA;  &#xA;  &lt;hr&gt;&#xA;  &#xA;  &lt;p&gt;You can just stick wires into the&#xA;  controller plug holes for prototyping.&#xA;  The +5 is connected to the Arduino +5&#xA;  Ground to Arduino Ground Latch goes to&#xA;  Pin 2 (with this code) Clock to Pin 3&#xA;  Serial Out to Pin 4&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The servo data line is connected to&#xA;  Pin 10, and the LED is on Pin 11.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;If you want to see the controller&#xA;  input on the serial monitor then just&#xA;  open up the serial monitor.  It will&#xA;  show you the binary numbers that are&#xA;  coming in from the controller.   Each&#xA;  button has its own binary number. &#xA;  'Up' is 11110111, for example.   I&#xA;  included a //hidden Serial.println&#xA;  code that will display &quot;Button has&#xA;  been pressed&quot; if you press down the&#xA;  start button.  Just erase the '//' if&#xA;  you want to use that.   The SNES plug&#xA;  is different, you're interested in&#xA;  that you will have to look elsewhere&#xA;  for the clock,latch,serial out info.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Quote:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/* INITIALIZATION */&#xA;#include &amp;lt;ServoTimer1.h&amp;gt;&#xA;ServoTimer1 servo1;&#xA;&#xA;int latch = 2; // set the latch pin&#xA;int clock = 3; // set the clock pin&#xA;int datin = 4;// set the data in pin&#xA;byte controller_data = 0;&#xA;int ledpin = 11;&#xA;&#xA;&#xA;/* SETUP */&#xA;void setup() {&#xA;Serial.begin(57600);&#xA;pinMode(latch,OUTPUT);&#xA;pinMode(clock,OUTPUT);&#xA;pinMode(datin,INPUT);&#xA;pinMode(ledpin, OUTPUT);&#xA;&#xA;digitalWrite(latch,HIGH);&#xA;digitalWrite(clock,HIGH);&#xA;&#xA;servo1.attach(10);&#xA;&#xA;}&#xA;&#xA;/* THIS READS DATA FROM THE CONTROLLER */&#xA;void controllerRead() {&#xA;controller_data = 0;&#xA;digitalWrite(latch,LOW);&#xA;digitalWrite(clock,LOW);&#xA;&#xA;digitalWrite(latch,HIGH);&#xA;delayMicroseconds(2);&#xA;digitalWrite(latch,LOW);&#xA;&#xA;controller_data = digitalRead(datin);&#xA;&#xA;for (int i = 1; i &amp;lt;= 7; i ++) {&#xA;digitalWrite(clock,HIGH);&#xA;delayMicroseconds(2);&#xA;controller_data = controller_data &amp;lt;&amp;lt; 1;&#xA;controller_data = controller_data + digitalRead(datin) ;&#xA;delayMicroseconds(4);&#xA;digitalWrite(clock,LOW);&#xA;}&#xA;&#xA;}&#xA;&#xA;/* THE LED, SERVO, AND SERIAL MONITOR PROGRAM */&#xA;void loop() {&#xA;controllerRead();&#xA;Serial.println(controller_data, BIN);&#xA;&#xA;// if (controller_data==B11101111){&#xA;  // Serial.println(&quot;Button has been Pressed&quot;);   &#xA;   //}  else {&#xA;   //Serial.println(&quot;Button not pressed&quot;);&#xA;   //}&#xA;&#xA;//for REFERENCE:  &#xA;//UP = 11110111&#xA;//DOWN=11111011&#xA;//LEFT=11111101&#xA;//RIGHT=11111110&#xA;//SELECT=11011111&#xA;//START=11101111&#xA;//A=01111111&#xA;//B=10111111&#xA;&#xA;if (controller_data==B01111111){&#xA; digitalWrite(ledpin, HIGH);   &#xA; }&#xA;&#xA;if (controller_data==B10111111){&#xA; digitalWrite(ledpin, LOW);&#xA;}&#xA;&#xA;if (controller_data==B11110111){&#xA; servo1.write(180);&#xA;}  &#xA;&#xA;if (controller_data==B11111011){&#xA; servo1.write(0);&#xA;}&#xA;&#xA;if (controller_data==B11111110){&#xA; servo1.write(90);&#xA;}&#xA;&#xA;delay(100);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1254964306/0#0&quot; rel=&quot;nofollow&quot;&gt;Arduino SNES Instructable&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1413" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-11-04T00:57:48.957" LastActivityDate="2010-11-04T00:57:48.957" />
  <row Id="6157" PostTypeId="2" ParentId="6151" CreationDate="2010-11-04T00:36:59.280" Score="10" ViewCount="" Body="&lt;p&gt;The issue with putting diodes in parallel is that as they heat up their resistance decreases. As a result, that diode ends up taking on more current then the other diode, resulting it in heating up even more. As you can probably see this cycle will cause thermal run away causing the diode to eventually burn if you give it enough current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now the fact that you couple them to the same heatsink will reduce this effect some, but I still would not recommend it. There are far too many unknowns that will effect this to not ever trust it, especially in a commercial product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now for the case of this power supply you are looking at, it may very well be that they spent the time to get the diodes matched as closely as possible and allow the heatsink to keep them at about the same temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may also be that they are running the diodes far under their capacity and they put the second one in parallel so that they aren't always running them near max capacity, but I find this unlikely.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-04T00:36:59.280" CommentCount="6" />
  <row Id="6158" PostTypeId="2" ParentId="6151" CreationDate="2010-11-04T00:42:56.180" Score="13" ViewCount="" Body="&lt;p&gt;If you put a low value resistor, for example 1 ohm or 1/2 ohm, something like that, in series with each diode, and then parallel those assemblies, the resistors help to keep the load even between the two diodes. If one diode starts to take more of the load current (as it would with thermal run-away), the IR drop on the resistor lowers the voltage for that diode, tending to push the current back down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistors need to be rated for whatever I^2*R loss they incur, and this usually means multi-watt ratings. Fortunately this sort of thing is typically only encountered in power supplies, where the inductance associated with wire-wound resistors isn't a bad thing. It's generally not a problem to find 0.1 ohm, 0.25 ohm, etc, in 5W, on up.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-04T00:42:56.180" CommentCount="1" />
  <row Id="6159" PostTypeId="2" ParentId="4042" CreationDate="2010-11-04T01:42:36.657" Score="0" ViewCount="" Body="&lt;p&gt;The oscillator is an amplifier with filter and loop back connection. In theory with no noise it will never work. In practice there is always some thermal/mechanical/electromagnetic noise. So noise is amplified, filtered and fed back.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For this reason some modeling software fails to model oscillation. For the same reason oscillators with very high quality of signal (narrow band) have difficulty to startup (slow startup time). &lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-04T01:42:36.657" />
  <row Id="6160" PostTypeId="1" AcceptedAnswerId="6601" CreationDate="2010-11-04T01:52:42.313" Score="2" ViewCount="236" Body="&lt;p&gt;For small batch production I am looking for small low cost product. Need it to be network controlled (Ethernet TCP/IP) with open documentation. The current is about 1..2..3 Ampere, voltage 24..48V. Also nice to have just 1..4 axes and DIN rail mount. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Problem is, that everything I can find is serial port controlled or modular blocks with 2-3 accessories with proprietary software and lot of unnecessary features, making software part complicated and requiring for host PC to be equipped with extra $100 I/O ports.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you&lt;/p&gt;&#xA;" OwnerUserId="924" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T21:59:18.500" LastActivityDate="2010-12-10T21:59:18.500" Title="Sourcing for low power stepper motor driver assembly. Which is best cost and host software wise ?" Tags="&lt;ethernet&gt;&lt;stepper&gt;&lt;tcp-ip&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="6161" PostTypeId="2" ParentId="3348" CreationDate="2010-11-04T02:03:11.210" Score="1" ViewCount="" Body="&lt;p&gt;Yes. And another reason is to drive &quot;high side&quot; of the bridge. For this those ICs have an external capacitor and internal oscillator with diode voltage multiplier, so the gate driving output is providing voltage few volts higher than bridge and/or bus voltage. &lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-04T02:03:11.210" CommunityOwnedDate="2010-11-04T02:03:11.210" />
  <row Id="6162" PostTypeId="2" ParentId="739" CreationDate="2010-11-04T02:32:49.193" Score="0" ViewCount="" Body="&lt;p&gt;If you like very easy to use software, then Actel is best in usability. They have mixed analog/digital FPGA brand Fusion. It also contains ADCs on-chip.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-04T02:32:49.193" />
  <row Id="6163" PostTypeId="1" AcceptedAnswerId="6165" CreationDate="2010-11-04T02:36:05.407" Score="2" ViewCount="258" Body="&lt;p&gt;I'm building a project where I will be lighting up 2 RGB LEDs using PWM. Since the Netduino only has 4 PWM pins (of which I will only use 3 - one pin each for the R, G, and B values respectively), I need a way to be able send the signal to either LED or both. Something like the following: &lt;img src=&quot;http://i.imgur.com/CcP8L.png&quot; alt=&quot;Netduino PWM&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What component(s) do I need for that black box?  I considered something like a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=10136&quot; rel=&quot;nofollow&quot;&gt;TLC 5940 PWM Driver&lt;/a&gt;, but I want to be able to power this off of the Netduino itself (i.e. no external power source). Do I just use a bunch of AND gates?&lt;/p&gt;&#xA;" OwnerUserId="1206" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-12T06:43:02.007" LastActivityDate="2011-02-12T06:43:02.007" Title="How to switch control between 2 RGB LEDs with PWM from a Netduino" Tags="&lt;microcontroller&gt;&lt;netduino&gt;&lt;pwm&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="6164" PostTypeId="2" ParentId="6163" CreationDate="2010-11-04T03:11:25.667" Score="1" ViewCount="" Body="&lt;p&gt;If both LEDs are on are they going to be the same?  You could control the common pin with a transistor to totally shut off either or both LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use the TLC5940, you wouldn't even need to use the PWM pins from your micro as it will run all by it self after you send it a command.  As far as powering it, it should easily be powered off any sort of dev board, your LEDs are going to be far more power hungry than it.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-04T03:11:25.667" />
  <row Id="6165" PostTypeId="2" ParentId="6163" CreationDate="2010-11-04T03:17:58.643" Score="3" ViewCount="" Body="&lt;p&gt;Assuming your PWM output can supply enough current for both LED's then put a FET between the cathode and ground for each LED.  Control each FET's gate with an I/O line from the microcontroller.  This way you can turn either on, both off, or both on by controlling the I/O lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just make sure the PWM pins on the uC can actually provide enough current to drive the LED and that the current is properly limited.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-04T03:53:06.680" LastActivityDate="2010-11-04T03:53:06.680" CommentCount="2" />
  <row Id="6166" PostTypeId="2" ParentId="6160" CreationDate="2010-11-04T03:28:30.507" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.amci.com/stepper-motor-control/nexus-stepper-motor-controller.asp&quot; rel=&quot;nofollow&quot;&gt;This work?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The command/control layout is right in the data sheet, looks like it just responds to any packets sent to it.  Driver is a separate piece.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-04T03:28:30.507" CommentCount="2" />
  <row Id="6167" PostTypeId="1" CreationDate="2010-11-04T03:40:40.480" Score="4" ViewCount="197" Body="&lt;p&gt;The limited stack size of budget PICs is a problem area and I have adjusted my code to accommodate this reality. I currently adopt a rough paradigm of grouping closely related functions into a module and declaring all variables global static in the module (to reduce the amount of variables stored in the auto psect, and issues of mutability are only relevant in ISRs, which I account for.) I don't do this because it is good practice, but the reality is you have a finite amount of space to allocate all local function vars that exist in an entire project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the embedded world of 8/16 bit chips, is this an appropriate method, provided I'm sure to take necessary precautions? I also do things like allocate &gt; 256 bytes of RAM for Ethernet buffers and have to access that memory via pointers so I can avoid the semantics of memory banking. Am I doing it wrong? My app works, but I am 100% open to suggestions for improvement.&lt;/p&gt;&#xA;" OwnerUserId="1830" LastEditorUserId="1830" LastEditorDisplayName="" LastEditDate="2010-11-04T14:17:48.707" LastActivityDate="2010-11-04T14:17:48.707" Title="PIC18 Memory Management" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;memory&gt;&lt;c&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="6168" PostTypeId="1" AcceptedAnswerId="7001" CreationDate="2010-11-04T03:51:30.757" Score="7" ViewCount="258" Body="&lt;p&gt;In my application, the device is going to be placed on top of a metal disc, less than a centimeter away from the pcb!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I have prototyped up the device using a nRF24L01+ breakout board with only a chip antenna, and I can communicate with the device from a few meters away (obviously from a receiver with line of sight to the PCB, not from underneath the disc). However, if I want to enhance my design and enhance the reliability of the wireless link what kind of antenna should I use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I switch to a lower RF frequency band?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I have read around the internet, a patch antenna with a ground plane underneath might be a good antenna to use, because the effects of the metal disc underneath the whole pcb will be reduced since our design involves a ground plane underneath the antenna anyway. This seems to take up a lot of space as opposed to a IFA antenna etched directly on a pcb.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, being quite new to all this RF theory, I basically don't really have a clue. Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-20T16:25:49.357" Title="Which antenna to use if close proximity to metal objects is unavoidable?" Tags="&lt;rf&gt;&lt;antenna&gt;" AnswerCount="2" FavoriteCount="4" />
  <row Id="6169" PostTypeId="2" ParentId="6168" CreationDate="2010-11-04T04:45:45.107" Score="5" ViewCount="" Body="&lt;h2&gt;How to cope with IFA&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;So, if you place a large ground plan below an antenna you create an image of the antenna and equal distance from the ground plane but on the other side, as if the ground plane is not there. The only important part being any solution exists above the ground plane, and there is 0 below it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not getting caught up in the solution, try placing the ground plane plate one half wavelength below your IFA radiator. This should cause the radiation up to be doubled. You can test this, move it around, measure your RSSI with different distances, pick the one that you like the most.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope that is clear, let me know If i can do more.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Your solution&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;From a general perspective, you will be happy at about 2.4GHz, it has a lot developed at it, this reduces cost. An IFA antenna seems to get you a nice form factor, it is actually a type of patch antenna, and if the ground piece causes a problem just look into other patch. These are commonly used because of low cost and low form factor.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Other options&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;If you need to radiate up from the disk(ie. The direction that passes through the disk) then the patch antenna is a very easy method. There are also chip antennas designed to have a ground plane. Both these will radiate very well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to radiate in the place of the disk, to its sides, this is where you cannot go wrong with a &lt;a href=&quot;http://en.wikipedia.org/wiki/Dipole_antenna&quot; rel=&quot;nofollow&quot;&gt;half wavelength dipole&lt;/a&gt;. Specifically the &lt;a href=&quot;http://en.wikipedia.org/wiki/Monopole_antenna&quot; rel=&quot;nofollow&quot;&gt;quarter wavelength monopole&lt;/a&gt;, using the ground disk as a conductor. This can be a very effective configuration.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-04T04:45:45.107" CommentCount="6" />
  <row Id="6170" PostTypeId="2" ParentId="6167" CreationDate="2010-11-04T04:49:22.560" Score="1" ViewCount="" Body="&lt;p&gt;Maybe i'm missing something here (paragraphs would help) but with the C18 compiler local variables within a function are generally allocated on the software stack so i have no idea what the following means:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;but the reality is you have a finite&#xA;  amount of space to allocate all local&#xA;  function vars that exist in an entire&#xA;  project&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;By moving all your variables to globals within a module you are requiring there is space for all of them at the same time.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;buffers and have to access that memory&#xA;  via pointers so I can avoid the&#xA;  semantics of memory banking.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;What compiler are you using?  &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-04T04:49:22.560" CommentCount="7" />
  <row Id="6171" PostTypeId="1" AcceptedAnswerId="6195" CreationDate="2010-11-04T05:34:07.220" Score="3" ViewCount="196" Body="&lt;p&gt;Just what is special about the resist pens used to draw directly on PCBs before etching?   Would a permanent marker work as well, or some other kind pen or marker?  Naturally I have in mind something cheaper but good enough.   This is for one-off handmade projects, single or double sided boards only.&lt;/p&gt;&#xA;" OwnerUserId="1609" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-07T15:35:49.703" LastActivityDate="2011-02-07T15:35:49.703" Title="What's Special about Resist Pens?" Tags="&lt;prototyping&gt;&lt;pcb-fabrication&gt;&lt;etching&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="6172" PostTypeId="1" AcceptedAnswerId="6185" CreationDate="2010-11-04T05:46:43.433" Score="13" ViewCount="243" Body="&lt;p&gt;What was your worst electronics workbench accident involving equipment, voltage, soldering irons, chemicals, or whatever else, and what changes have you made to prevent that type of accident from happening again?&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-11-05T04:31:43.047" CommunityOwnedDate="2010-11-04T15:52:06.790" Title="What Workbench Safety Improvements Have You Made?" Tags="&lt;safety&gt;&lt;workbench&gt;" AnswerCount="9" CommentCount="3" />
  <row Id="6173" PostTypeId="1" AcceptedAnswerId="6471" CreationDate="2010-11-04T06:35:40.660" Score="0" ViewCount="346" Body="&lt;p&gt;The title says it.&lt;/p&gt;&#xA;" OwnerUserId="1731" LastEditorUserId="1731" LastEditorDisplayName="" LastEditDate="2010-11-08T10:26:22.400" LastActivityDate="2010-11-09T12:44:06.617" Title="How to find the resistor value using the color codes ?" Tags="&lt;resistor&gt;&lt;colour-coding&gt;" AnswerCount="5" CommentCount="15" FavoriteCount="1" />
  <row Id="6174" PostTypeId="1" AcceptedAnswerId="6178" CreationDate="2010-11-04T06:36:56.007" Score="8" ViewCount="231" Body="&lt;p&gt;For all the other stupid things I often do, I've found ways to boobytrap myself.  For example keeping my wallet on the floor where the door opens - I can't help but stumble on it when I leave the house.  But here's an electronics parts problem that has me stumped.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I sometimes accidently throw out IR LEDs as &quot;nonworking&quot; since they don't visibly glow when tested.   How can I prevent myself from doing that, at least to force myself to reconsider and remember there's such a thing as IR?&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-11-05T03:23:20.210" Title="Keeping those IR LEDs" Tags="&lt;led&gt;&lt;ir&gt;&lt;parts&gt;" AnswerCount="5" />
  <row Id="6175" PostTypeId="2" ParentId="6172" CreationDate="2010-11-04T06:48:48.057" Score="9" ViewCount="" Body="&lt;p&gt;Only a switch that cut the power to everything, so that I don't forget something turned on (like the soldering iron...)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/iPhj0.jpg&quot; alt=&quot;http://thumbs.dreamstime.com/thumblarge_519/12784118163hDBbE.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-11-04T06:48:48.057" CommunityOwnedDate="2010-11-04T15:52:06.790" CommentCount="6" />
  <row Id="6176" PostTypeId="2" ParentId="6173" CreationDate="2010-11-04T06:55:43.937" Score="7" ViewCount="" Body="&lt;p&gt;There are a zillion websites that cover this.  Some have online interactive tools you can use to read one resistor or learn the art of doing so.  Google &quot;resistor color code&quot;  and maybe add -&quot;free software&quot; to avoid spammy sites.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a basic chart: &lt;a href=&quot;http://www.azega.com/how-to-read-a-resistor-color-code/&quot; rel=&quot;nofollow&quot;&gt;http://www.azega.com/how-to-read-a-resistor-color-code/&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an online tool for practicing, once you think you've got the basics. Comes with sound effects to keep you awake and/or remind you of 1980s style arcade games:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.wisc-online.com/Objects/ViewObject.aspx?ID=DCE1002&quot; rel=&quot;nofollow&quot;&gt;http://www.wisc-online.com/Objects/ViewObject.aspx?ID=DCE1002&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These sites could vanish, but others appear.  Quality varies wildly but seek and after perusing several, you'll know what you need to know.&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-11-04T06:55:43.937" />
  <row Id="6178" PostTypeId="2" ParentId="6174" CreationDate="2010-11-04T07:21:59.013" Score="16" ViewCount="" Body="&lt;p&gt;Tape your trash can shut, and instead of throwing the LED away, put it in a 'TO TEST' container :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a way to test them visually:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;get your digital camera&lt;/li&gt;&#xA;&lt;li&gt;turn camera on&lt;/li&gt;&#xA;&lt;li&gt;power the IR LED&lt;/li&gt;&#xA;&lt;li&gt;point camera at LED&lt;/li&gt;&#xA;&lt;li&gt;look at camera screen, you should see the LED lit up (if it still works)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You can find video's on Youtube about this.&lt;/p&gt;&#xA;" OwnerUserId="1124" LastEditorUserId="1124" LastEditorDisplayName="" LastEditDate="2010-11-04T13:37:48.413" LastActivityDate="2010-11-04T13:37:48.413" CommentCount="3" />
  <row Id="6179" PostTypeId="2" ParentId="6172" CreationDate="2010-11-04T07:27:23.857" Score="4" ViewCount="" Body="&lt;p&gt;Common accident: burnt fingers and/or wires.&lt;br&gt;&#xA;Safety improvement: make note to self to be more careful with the soldering iron next time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rinse and repeat.&lt;/p&gt;&#xA;" OwnerUserId="1124" LastActivityDate="2010-11-04T07:27:23.857" CommunityOwnedDate="2010-11-04T15:52:06.790" CommentCount="2" />
  <row Id="6180" PostTypeId="2" ParentId="6174" CreationDate="2010-11-04T08:00:04.427" Score="0" ViewCount="" Body="&lt;p&gt;You could also try using an IR filter as you would find in a camera store. Under such filter they should glow, just about enough to be visible.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-04T08:48:46.800" LastActivityDate="2010-11-04T08:48:46.800" CommentCount="3" />
  <row Id="6181" PostTypeId="2" ParentId="6172" CreationDate="2010-11-04T08:53:03.537" Score="4" ViewCount="" Body="&lt;p&gt;Many, many years ago when I was around 5-10 I burnt my fingers a lot on soldering irons, but hey, kids heal fast, so no biggie, I still have one faint scar from that time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many years ago when I lived at home and had a 6 year old little brother, I left my soldering iron on when I left my room, my brother knocked the iron on the floor and picked it up, using the wrong end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My parents were not impressed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... so, yeah, I second the big red rocker switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More recently I was digging around a digital camera and I accidentally grabbed the flash capacitor, it burnt a black mark in my finger while delivering the worst shock I've had since I cut a live 230 V line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Recovering from the shock took a couple of minutes of cursing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I then proceeded to take my multimeter to measure the voltage on the capacitor, but I fat-fingered it and the probe slipped to short out the cap, enough energy was released to leave a blackened area in my eyes for 10 minutes afterwards and the PCB around the HV traces basically exploded.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... but other than that I've been pretty safe, so there hasn't been many improvements, other than to add &quot;the big red rocker switch&quot; to power down everything on my workbench at once.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastEditorUserId="1675" LastEditorDisplayName="" LastEditDate="2010-11-04T09:06:19.140" LastActivityDate="2010-11-04T09:06:19.140" CommunityOwnedDate="2010-11-04T15:52:06.790" />
  <row Id="6182" PostTypeId="2" ParentId="6171" CreationDate="2010-11-04T08:58:02.193" Score="2" ViewCount="" Body="&lt;p&gt;It's mostly about how much ink they put down - certainly worth testing some standard permanent markers on some scrap material. Many shops that sell markers have testers you can try so maybe take a bit of copperclad with you &amp;amp; try a few.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-04T08:58:02.193" CommentCount="1" />
  <row Id="6183" PostTypeId="2" ParentId="1904" CreationDate="2010-11-04T08:59:50.560" Score="2" ViewCount="" Body="&lt;p&gt;Fume extractors are worth every penny in my opinion. Smoke goes in - no smoke comes out - and the best bit is that the air smells clean. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're in the UK, get the cheap Maplins one for £15.&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-11-04T10:17:27.173" LastActivityDate="2010-11-04T10:17:27.173" />
  <row Id="6184" PostTypeId="2" ParentId="739" CreationDate="2010-11-04T09:04:05.910" Score="0" ViewCount="" Body="&lt;p&gt;If you want to estimate gate count you don't need to buy hardware yet - the main FPGA makers have free software, and many will have appnotes on doing dsp. &#xA;You can design and simulate stuff without hardware, and the software will tell you what resources are used.&#xA;However for signal processing, a dsp would normally be the first step, and FPGA only if you run out of processing power. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-04T09:04:05.910" />
  <row Id="6185" PostTypeId="2" ParentId="6172" CreationDate="2010-11-04T10:12:42.763" Score="10" ViewCount="" Body="&lt;p&gt;Here are some precautions I take... they might be a little excessive but I'd rather play it safe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Soldering:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Cheap solder extractor.&lt;/li&gt;&#xA;&lt;li&gt;Simple, clear glasses to protect my eyes against bits of metal flying away from my side-cutters.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;PCB Manufacture:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;All-round protection goggles to try and keep my eyes as dust/chemical free as possible (and to protect from a shattering drill bit).&lt;/li&gt;&#xA;&lt;li&gt;Wet-wipes for cleaning the area after drilling (wet to help pick up the loose particles).&lt;/li&gt;&#xA;&lt;li&gt;A fine-dust mask is important when drilling due to the toxic effects of FR2 and FR4.&lt;/li&gt;&#xA;&lt;li&gt;Good ventilation (either a fine-dust extractor or lots of open doors and windows).&lt;/li&gt;&#xA;&lt;li&gt;Plenty of clean water and rags/kitchen roll for chemical spills.&lt;/li&gt;&#xA;&lt;li&gt;A neutralising agent for the chemicals (such as baking soda).&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;Disposable&lt;/em&gt; but thin gloves (you don't want nasty chemicals lying around on them for too long).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="965" LastEditorDisplayName="" LastEditDate="2010-11-05T04:31:43.047" LastActivityDate="2010-11-05T04:31:43.047" CommunityOwnedDate="2010-11-04T15:52:06.790" CommentCount="2" />
  <row Id="6186" PostTypeId="2" ParentId="6174" CreationDate="2010-11-04T10:58:00.527" Score="4" ViewCount="" Body="&lt;p&gt;After LEDs fail, they rarely electrically resemble diodes any more. If you have a DVM that has a diode test mode, use that. Mine shows a representative forward drop of 1.2 to 1.5V for various sorts visible LEDs (just talking reds, yellows, greens here), and 0.9 to 1.1V for IR ones.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-11-04T22:57:50.527" LastActivityDate="2010-11-04T22:57:50.527" />
  <row Id="6187" PostTypeId="2" ParentId="6172" CreationDate="2010-11-04T11:10:41.763" Score="4" ViewCount="" Body="&lt;p&gt;I admit that I don't have much experience, but the thing which isn't mentioned here and helped me the most was thinking steps through before doing anything.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've burned myself several times and I noticed that each time that happens, it's because I want to just do something without thinking how I'm going to do it. So I have a circuit board and want to desolder something. No problem, right? I'll just desolder it and that's it. Well, that kind of thinking got me burned. Instead I found it better to separate &quot;complex&quot; operation into simple steps and plan on what I'm going to do if it doesn't work correctly and stop if I get into area I did think of. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So for my desoldering example I'll first examine the board and decide where I'm going to apply the soldering iron, if I'm going to use vacuum pump or desoldering braid, what am I going to do if solder melts and part is still stuck, what am I going to do braid sticks to the part and so on. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thinking part does take a couple of seconds, but I think it's better to wait a few seconds than to burn yourself.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-11-04T14:45:22.323" LastActivityDate="2010-11-04T14:45:22.323" CommunityOwnedDate="2010-11-04T15:52:06.790" CommentCount="1" />
  <row Id="6188" PostTypeId="2" ParentId="6171" CreationDate="2010-11-04T12:38:38.147" Score="2" ViewCount="" Body="&lt;p&gt;I used to get very good results with ordinary cellulose paint, applied with a fine paint brush. Thinning the paint a little with cellulose thinners helped if I needed narrow tracks. It worked better than the resist pens and was much cheaper.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-04T12:38:38.147" CommentCount="2" />
  <row Id="6189" PostTypeId="2" ParentId="6171" CreationDate="2010-11-04T12:46:42.333" Score="0" ViewCount="" Body="&lt;p&gt;I've had success with &lt;em&gt;some&lt;/em&gt; overhead-projector-transparency pens (remember OHPs? :).  The dark blue and brown Staedtlers worked best IIRC, the purple one not very well at all - remember to use the &quot;permanent&quot; ones, not the water-based ones.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A bit of trial and error is the order of the day!&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2010-11-04T12:46:42.333" />
  <row Id="6191" PostTypeId="1" AcceptedAnswerId="6194" CreationDate="2010-11-04T13:47:40.407" Score="3" ViewCount="573" Body="&lt;p&gt;In my PCB editor, both LQFP and TQFP have the same footprints, except the TQFP has shorter leads than the LQFP. Is that the only difference?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-04T18:12:54.093" Title="LQFP package vs. TQFP package?" Tags="&lt;pcb&gt;&lt;tqfp&gt;" AnswerCount="3" />
  <row Id="6192" PostTypeId="2" ParentId="6174" CreationDate="2010-11-04T14:22:13.263" Score="2" ViewCount="" Body="&lt;p&gt;Almost all digital cameras like the one in an iPhone has enough bandwidth to pick up IR.  To prove this to yourself get your digital camera and look at an IR remote with it and you will see the IR LEDs. As pointed out by others expensive digital cameras sometimes put optical filters to allow only the visible range in.  A fun thing to do is to use your phone camera to look at things like atms and other security devices that use the IR range to operate in. &lt;/p&gt;&#xA;" OwnerUserId="540" LastEditorUserId="540" LastEditorDisplayName="" LastEditDate="2010-11-05T03:23:20.210" LastActivityDate="2010-11-05T03:23:20.210" CommentCount="6" />
  <row Id="6193" PostTypeId="2" ParentId="6174" CreationDate="2010-11-04T14:37:37.337" Score="2" ViewCount="" Body="&lt;p&gt;What Vincent mentioned above is the method I'v been using so far, and is the easiest :)&#xA;just take any cam (mobile or point n shoot) and when you see the IR LED through it you should be able to see a purple color light I guess (Unless I am color blind ;) )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;JUST AS A NOTE DON'T FORGET TO KEEP A RESISTOR(lower value like 220-470E) IN SERIES TO THE IR LED WHILE YOU POWER IT UP AS YOU DON'T WANT IT TO BURN UR LED :)&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2010-11-04T14:37:37.337" CommentCount="2" />
  <row Id="6194" PostTypeId="2" ParentId="6191" CreationDate="2010-11-04T15:00:15.563" Score="7" ViewCount="" Body="&lt;p&gt;L is for Low-profile (1.4 mm) and T is for thin(er, 1.0 mm), so I think the only definitive difference between them is height.  The pitch and package size can vary within each.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-04T15:00:15.563" />
  <row Id="6195" PostTypeId="2" ParentId="6171" CreationDate="2010-11-04T15:05:50.573" Score="1" ViewCount="" Body="&lt;p&gt;A permanent marker will work but the finishing may not be that very great and you might want to give it a solder coat later. A resist pen just forms a thicker layer than a marker would do, giving it more isolation from etching chemical and a better finish.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used it couple of time If I am lazy for other long method where I get the circuit done on a PCB designer and get it printed on photo-paper etc. But for a good finish and a complex circuit I would suggest this method of etching is the best and reliable. I have been using it since years and never had a problem.&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2010-11-04T15:05:50.573" />
  <row Id="6196" PostTypeId="1" CreationDate="2010-11-04T15:15:38.770" Score="7" ViewCount="306" Body="&lt;p&gt;What type, what could the potential effects be, and why would this happen?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; Yes, I am talking about physics not the supernatural. I figured this would be obvious unless people thought I was joking around, the tides are effected I know that much so obviously there is something physical going on here and I know some electronics can be very sensitive at very 'small' levels (not sure if 'small' is there word I am looking for here).&lt;/p&gt;&#xA;" OwnerUserId="1840" LastEditorUserId="1840" LastEditorDisplayName="" LastEditDate="2010-11-04T15:54:44.323" LastActivityDate="2010-11-07T10:34:42.003" Title="Is it possible that the phases of the moon could have an effect on the operation of certain types of electronics?" Tags="&lt;electronics&gt;&lt;interference&gt;" AnswerCount="9" CommentCount="10" FavoriteCount="1" />
  <row Id="6197" PostTypeId="2" ParentId="6196" CreationDate="2010-11-04T15:21:38.067" Score="3" ViewCount="" Body="&lt;p&gt;Yes:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1.) In case a design is so sensitive the miniscule influence of the moon (capacitance, inductance, luminosity, gravity, shielding from cosmic rays etc) leads to a change of results, it is reasonable to assume the moon might have an influence. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But this means a design mistake has been made in the first place. The influence of a person with an electric wristwatch will be way bigger probably. It means the electronics design is unreliable in the first place. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;2.) It is darker in moonless nights, so with optical sensors feedback will be different. (or other types of sensors, for that matter)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3.) If your electronics are right on the waterfront of tidal waters, because tides are of a different height depending on the phase of moon, the effects of saltwater on the electronics might differ. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;4.) Since there seems to be an influence of moon phase on people (even if only they believe there is), the interpretation of electronics results might be psychologically attributed to the moon (poor thing). Or maybe the users just use the stuff wrong. &lt;/p&gt;&#xA;" OwnerUserId="1381" LastEditorUserId="1381" LastEditorDisplayName="" LastEditDate="2010-11-05T09:58:14.957" LastActivityDate="2010-11-05T09:58:14.957" CommentCount="1" />
  <row Id="6198" PostTypeId="2" ParentId="6173" CreationDate="2010-11-04T15:22:02.967" Score="1" ViewCount="" Body="&lt;p&gt;There is an answer to another question that answers this also: &lt;a href=&quot;http://electronics.stackexchange.com/questions/2869/resistors-with-ends-of-the-same-colour/2871#2871&quot;&gt;http://electronics.stackexchange.com/questions/2869/resistors-with-ends-of-the-same-colour/2871#2871&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-04T15:22:02.967" />
  <row Id="6200" PostTypeId="2" ParentId="6196" CreationDate="2010-11-04T15:28:50.520" Score="4" ViewCount="" Body="&lt;p&gt;There is no evidence whatsoever that the phases of the moon have any effect on electronic equipment, unless it is light-sensitive. It used to be thought that they affected human behaviour, which is where the word lunacy comes from, but &lt;a href=&quot;http://en.wikipedia.org/wiki/Lunar_effect&quot; rel=&quot;nofollow&quot;&gt;studies&lt;/a&gt; have failed to show any associations.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-04T15:28:50.520" CommentCount="4" />
  <row Id="6201" PostTypeId="2" ParentId="6196" CreationDate="2010-11-04T15:28:54.810" Score="1" ViewCount="" Body="&lt;p&gt;Yes: &lt;a href=&quot;http://www.outpost9.com/reference/jargon/jargon_31.html#TAG1361&quot; rel=&quot;nofollow&quot;&gt;http://www.outpost9.com/reference/jargon/jargon_31.html#TAG1361&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;iow: If someone tries to print out the phase of the moon to aid in debugging and fails to do that in some situations.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-04T15:28:54.810" />
  <row Id="6202" PostTypeId="2" ParentId="6191" CreationDate="2010-11-04T15:29:10.460" Score="7" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.practicalcomponents.com/amkor/amkor-pq-lqfp.htm&quot; rel=&quot;nofollow&quot;&gt;LQFP Dimensions and Characteristics&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.practicalcomponents.com/amkor/amkor-tqfp.htm&quot; rel=&quot;nofollow&quot;&gt;TQFP Dimensions and Characteristics&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1414" LastActivityDate="2010-11-04T15:29:10.460" />
  <row Id="6203" PostTypeId="2" ParentId="6196" CreationDate="2010-11-04T15:32:09.053" Score="4" ViewCount="" Body="&lt;p&gt;Maybe:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The moon can have a slight effect on perceived gravity; look at tides. If you had ultra precise accelerometers or devices for measuring this, then you might notice an effect due to the rotation or position of the moon. I am not sure though if just the phases would have an effect.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-04T15:32:09.053" CommentCount="1" />
  <row Id="6204" PostTypeId="2" ParentId="4094" CreationDate="2010-11-04T15:32:40.110" Score="0" ViewCount="" Body="&lt;p&gt;Interface to Lego Mindstorms, build fake fingers with the rubber-tip part, have Mindstorms motor press the button. I did this once. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, use a Microcontroller to interface to RC servos. &lt;/p&gt;&#xA;" OwnerUserId="1381" LastActivityDate="2010-11-04T15:32:40.110" />
  <row Id="6205" PostTypeId="2" ParentId="1635" CreationDate="2010-11-04T15:43:23.490" Score="1" ViewCount="" Body="&lt;p&gt;No, I wouldn't advise it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Main reasons:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;While it has a 1 MHz bandwidth, its sample rate is only 1 MS/s. Practically this means you can only measure up to 100 KHz square waves. It is only suitable for audio signals in my opinion.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You spend $90 on the DSO Nano but you could spend $200 on a second hand oscilloscope with at least 60 MHz. I spend £150 (around $200 at the time) on my HP 54501A which was a pretty good deal. It has everything a hobbyist should need: 100 MHz bandwidth (will measure up to 300 MHz clock signals), excellent trigger facilities, including video, pattern and state (&lt;em&gt;very&lt;/em&gt; useful for what I'm doing), it's digitising and it has HP-IB. If you can find a similar deal, go for it. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Trigger: it only mentions auto and single. Out of luck for complex triggers like I mentioned. You don't think you need them, but you often will.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Input protection: or lack of it. Most good scopes can take at least 100V on the inputs. This one only goes to 80Vp-p (so 40V amplitude maximum.) Don't worry, I've done this one or two times to be thankful that my scope has 250V maximum inputs.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;It's not earthed. Don't even touch equipment plugged into the mains or you won't be protected like a normal scope is.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-04T15:43:23.490" />
  <row Id="6206" PostTypeId="1" AcceptedAnswerId="6207" CreationDate="2010-11-04T15:45:37.543" Score="4" ViewCount="225" Body="&lt;p&gt;My oscilloscope's inputs are rated &quot;250V DC + AC peak (10 KHz).&quot; Does this mean it would withstand mains voltage (325V peak) or only 250V DC? I have &lt;strong&gt;no&lt;/strong&gt; plans on doing this any time soon, I am only curious.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-20T20:07:37.100" LastActivityDate="2011-03-20T20:07:37.100" Title="What does 250V DC + AC peak mean?" Tags="&lt;oscilloscope&gt;&lt;ratings&gt;" AnswerCount="2" />
  <row Id="6207" PostTypeId="2" ParentId="6206" CreationDate="2010-11-04T15:47:06.717" Score="5" ViewCount="" Body="&lt;p&gt;if you add peak voltage to your dc offset, it must be less than 250V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;this was verified with dc and a 10kHz ac wave.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-04T15:47:06.717" CommentCount="8" />
  <row Id="6208" PostTypeId="2" ParentId="6196" CreationDate="2010-11-04T15:47:39.277" Score="4" ViewCount="" Body="&lt;p&gt;I actually think the phase of the moon could have an effect on the noise level on an antenna.&#xA;In satellite applications there is usually planned outages where the satellite you are talking to is in line with the sun. The noise from the sun is so great your system fails.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now the moon would have much much much less noise, but I could see it still adding a bit of noise.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-04T15:53:07.063" LastActivityDate="2010-11-04T15:53:07.063" CommentCount="3" />
  <row Id="6209" PostTypeId="2" ParentId="6172" CreationDate="2010-11-04T15:52:28.607" Score="5" ViewCount="" Body="&lt;p&gt;How about a soldering iron with automatic turnoff?  Don't want to leave that thing on all the time...&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-04T15:52:28.607" CommunityOwnedDate="2010-11-04T15:52:28.607" />
  <row Id="6210" PostTypeId="2" ParentId="5696" CreationDate="2010-11-04T15:55:52.277" Score="2" ViewCount="" Body="&lt;p&gt;Both together I've never seen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ST has &lt;a href=&quot;http://www.st.com/mcu/inchtml-pages-stm32w.html&quot; rel=&quot;nofollow&quot;&gt;STM32W&lt;/a&gt; that integrates a 2.4GHz transceiver and Freescale has &lt;a href=&quot;http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MC13224V&amp;amp;fsrch=1&amp;amp;sr=1&quot; rel=&quot;nofollow&quot;&gt;MC1322x&lt;/a&gt; that integrates ARM7/Coldfire with 2.4GHz transceivers, but both don't have the ethernet PHY.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-04T15:55:52.277" CommentCount="1" />
  <row Id="6211" PostTypeId="1" AcceptedAnswerId="6216" CreationDate="2010-11-04T16:05:23.160" Score="6" ViewCount="223" Body="&lt;p&gt;I've had this question for a while.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assume you have an otherwise perfect op-amp with a gain-bandwidth product of 5 MHz. You input a signal of 50mVp-p and amplify it by 10x. This limits your bandwidth to 500 kHz. Now, say you stack another op-amp on the output and configure that as a 10x amplifier. Your overall bandwidth is 500 kHz but you have amplified by 100x, so your GBWP is 50 MHz. Where is the flaw in this logic?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-06-03T13:04:14.350" Title="Op-amp gain bandwidth product" Tags="&lt;op-amp&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="6212" PostTypeId="1" AcceptedAnswerId="6214" CreationDate="2010-11-04T16:11:08.413" Score="9" ViewCount="155" Body="&lt;p&gt;I'm trying to design my project, Super OSD, to be as reliable as possible. I want it to work good as new when 5 years old. I hate unreliable products, environmentally it's a waste, and economically it's expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To that end, I'm avoiding electrolytic capacitors, and I've spec'd everything at least 1.5x, most 2x where size/cost permits. However, I am still having to use tantalum bead caps for the on-board regulators of the microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any other things I should be aware of?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-07T04:25:29.547" Title="Component reliability" Tags="&lt;reliability&gt;" AnswerCount="3" FavoriteCount="4" />
  <row Id="6214" PostTypeId="2" ParentId="6212" CreationDate="2010-11-04T16:27:53.780" Score="7" ViewCount="" Body="&lt;p&gt;If you use appropriate derating guidelines for electrolytic capacitors (keeping the ripple current in check, ensuring they stay well below their maximum temperature rating) they can last a very long time and still provide adequate performance. I've seen capacitors come out of 15 year-old equipment and still 'work' to some degree.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fans have a limited lifespan depending on how fast you operate them. They tend to gradually fail over time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a primarily surface-mount design, consider conformal coating to help limit exposure to the elements and mitigate oxidation, etc. Products in the field for years which have some air exposure can very easily get several millimeters of dust, which makes a very effective thermal blanket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure that, if you're using RoHS parts, that you're not using parts prone to tin whiskering. (This is another area where conformal coating can be helpful). &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-04T16:27:53.780" CommentCount="5" />
  <row Id="6215" PostTypeId="2" ParentId="6172" CreationDate="2010-11-04T16:36:19.327" Score="7" ViewCount="" Body="&lt;p&gt;Never, EVER use a chair with open armrests (non-closed loops) at a workbench with soldering irons. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's just a matter of time before a hot soldering iron is grabbed by its cord (courtesy of your chair) and introduced to your groin area. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, I'm still fully functional. I did burn a pair of pants, though. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-04T16:36:19.327" CommunityOwnedDate="2010-11-04T16:36:19.327" CommentCount="1" />
  <row Id="6216" PostTypeId="2" ParentId="6211" CreationDate="2010-11-04T16:46:09.007" Score="2" ViewCount="" Body="&lt;p&gt;Your logic is sound.  More opamps means more gain for a given bandwidth.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compensated op-amps are made with a single dominant pole so the gain/bandwidth product is constant.  If this isn't working for your application, use a decompensated amp and do the compensation network yourself.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-04T16:46:09.007" />
  <row Id="6217" PostTypeId="2" ParentId="5696" CreationDate="2010-11-04T16:58:06.777" Score="0" ViewCount="" Body="&lt;p&gt;Not really a chip, but would a &lt;a href=&quot;http://www.digi.com/products/wirelessdropinnetworking/connectportxgateways.jsp#overview&quot; rel=&quot;nofollow&quot;&gt;Digi ConnectPort&lt;/a&gt; be a turnkey solution for what you have in mind?  You can run custom software (Python) on them to manage your wireless devices and communicate over Ethernet.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-04T16:58:06.777" CommentCount="1" />
  <row Id="6218" PostTypeId="2" ParentId="6211" CreationDate="2010-11-04T17:24:57.023" Score="0" ViewCount="" Body="&lt;p&gt;Your logic is perfect correct! so is the output. Only thing you got to remember is that when cascaded the gain multiplies but not the frequency response. So in your case the gain-bandwidth of both the op-amps cascaded would be  gain1 * gain2 *frequency(the smallest of the two)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;so the answer would be 10 * 10 * 500khz = 50MHz which is perfectly correct.&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2010-11-04T17:24:57.023" />
  <row Id="6219" PostTypeId="2" ParentId="6191" CreationDate="2010-11-04T18:12:54.093" Score="2" ViewCount="" Body="&lt;p&gt;My advice would be to never, ever, use those sort of names to actually match a PCB footprint to a device.  Always, always check the dimensions.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-04T18:12:54.093" />
  <row Id="6220" PostTypeId="1" AcceptedAnswerId="6222" CreationDate="2010-11-04T18:52:08.100" Score="3" ViewCount="131" Body="&lt;p&gt;My dsPIC33F does not seem to support routing the comparator to the input capture module. Would it be okay to run a wire from the comparator output to the input capture input?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using a &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en532298&quot; rel=&quot;nofollow&quot;&gt;dsPIC33FJ128GP802&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-04T19:00:26.093" LastActivityDate="2010-11-04T22:54:44.617" Title="Is it okay to wire an MCU output to an MCU input on the same chip?" Tags="&lt;microcontroller&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="6221" PostTypeId="2" ParentId="6172" CreationDate="2010-11-04T19:22:20.417" Score="6" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Regularly clean/organize my bench.&lt;/strong&gt;  Fewer knives hiding, waiting to stab me.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-04T19:22:20.417" CommunityOwnedDate="2010-11-04T19:22:20.417" />
  <row Id="6222" PostTypeId="2" ParentId="6220" CreationDate="2010-11-04T20:06:10.457" Score="3" ViewCount="" Body="&lt;p&gt;I did something quite similar for a PIC16F690 with no problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For that PIC, it could use the comparator output internally to trigger an interrupt, but there was a note indicating that there's a small window where the comparator can miss the interrupt.  In the end, I connected the comparator's output to an Interrupt-On-Change pin to make sure that I would always get an interrupt.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-11-04T20:06:10.457" CommentCount="4" />
  <row Id="6223" PostTypeId="2" ParentId="5255" CreationDate="2010-11-04T20:21:40.633" Score="2" ViewCount="" Body="&lt;p&gt;There are a couple of microcontroller related contests started recently:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ebv.com/en/products/stm32-design-contest.html&quot; rel=&quot;nofollow&quot;&gt;STM32 Design Contest&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.renesasrulz.com/community/rx-contest&quot; rel=&quot;nofollow&quot;&gt;Renesas RX Design Contest&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;And there are already completed ones worth checking:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.lpc1100challenge.com/&quot; rel=&quot;nofollow&quot;&gt;NXP LPC1100 Design Challenge&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.mypic32.com/web/guest/projects&quot; rel=&quot;nofollow&quot;&gt;PIC32 Design contest&lt;/a&gt;  (many open source projects with full docs available)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2010-11-04T20:21:40.633" />
  <row Id="6224" PostTypeId="2" ParentId="6220" CreationDate="2010-11-04T20:39:52.850" Score="1" ViewCount="" Body="&lt;p&gt;Provided the processor doesn't set them both as outputs during reset (most unlikely, and probably not very harmful in real life anyway), then you'll be fine.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-04T20:39:52.850" CommentCount="3" />
  <row Id="6225" PostTypeId="1" AcceptedAnswerId="6226" CreationDate="2010-11-04T20:49:13.547" Score="2" ViewCount="240" Body="&lt;p&gt;I'm looking for a microcontroller in a TQFP-44 package with a reasonable amount of RAM which can run code from RAM. I've considered the PIC32 but it's only available in 64 pin versions. Any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-05T15:52:41.770" Title="Small microcontroller which can execute from RAM" Tags="&lt;microcontroller&gt;" AnswerCount="7" CommentCount="6" />
  <row Id="6226" PostTypeId="2" ParentId="6225" CreationDate="2010-11-04T20:58:18.660" Score="2" ViewCount="" Body="&lt;p&gt;SAM7S?  (Atmel ARM7) - &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=4502&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/products/product_card.asp?part_id=4502&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though that's 48 pin actually, not 44 - don't know if that's a show-stopper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does it have to be LQFP-44, or can it be something smaller?   (QFN, for example)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As 48-pin is fine, there are a number of ARM7 or Cortex parts from Atmel and NXP which can run code from RAM as well as being useful micros in their own right.  You probably have a rather longer list of criteria than the two you've revealed so far...&lt;/p&gt;&#xA;" OwnerUserId="1844" LastEditorUserId="1844" LastEditorDisplayName="" LastEditDate="2010-11-04T21:34:46.620" LastActivityDate="2010-11-04T21:34:46.620" CommentCount="1" />
  <row Id="6227" PostTypeId="1" AcceptedAnswerId="6267" CreationDate="2010-11-04T22:05:02.537" Score="3" ViewCount="198" Body="&lt;p&gt;I'm looking for a sensor that can detect large magnetic fields.  Basically, I want a 1 when the field is greater than 75 Gauss, and a 0 when it's less than 75 Gauss.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believed (EDIT: Wrongly!) Hall Effect sensors rely on moving through a magnetic field.  &lt;s&gt;Unfortunately, my application does not permit me to move through the field, and the field is not changing.&lt;/s&gt;  It's since been pointed out that the Hall Effect does not rely on a change in the magnetic field.  However, I still do not have any control over the orientation of the field.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any suggestions on how to detect such a magnetic field?&lt;/p&gt;&#xA;" OwnerUserId="1278" LastEditorUserId="1278" LastEditorDisplayName="" LastEditDate="2010-11-05T15:59:18.810" LastActivityDate="2010-11-07T03:26:44.227" Title="Magnetic Field Sensor?" Tags="&lt;sensor&gt;" AnswerCount="5" CommentCount="1" />
  <row Id="6228" PostTypeId="1" AcceptedAnswerId="6238" CreationDate="2010-11-04T22:05:38.717" Score="4" ViewCount="233" Body="&lt;p&gt;GAL chips seem expensive to get started with, since programmers cost hundreds of dollars and even ISP cables aren't cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a cheaper way?&lt;/p&gt;&#xA;" OwnerUserId="876" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-16T17:12:24.390" LastActivityDate="2011-05-16T17:12:24.390" Title="Is there an inexpensive way to get started with GAL (Generic Array Logic) chips?" Tags="&lt;shopping&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="2" />
  <row Id="6229" PostTypeId="1" AcceptedAnswerId="6240" CreationDate="2010-11-04T22:07:57.083" Score="2" ViewCount="85" Body="&lt;p&gt;For my senior design project, we have various sensors (Thermocouples, Heat flux sensors, load cell) plugged into our DAQ. We are using LabView and some National Instruments devices (ugh) and discovering that our loaned equipment doesn't have the resolution necessary to read accurate values from our heat flux and load cell sensors. The DAQ can read around a 100 mV range effectively. The heat flux sensor provides values in the microvolt range (0-100uV IIRC) and the load cell is in the milivolt range (0-5mV). We're looking into getting a better DAQ, but I was wondering if there is a way to easily amplify these signals into the volt range? Our grad student we have working for us is very concerned about impedance and other factors that can throw off our readings and is very against any sort of amplification circuits. Is amplification a viable route, and how would we go about amplifying the signal?&lt;/p&gt;&#xA;" OwnerUserId="1846" LastActivityDate="2010-11-04T23:13:17.313" Title="What should I be using to amplify a heat flux and load cell signal?" Tags="&lt;sensor&gt;&lt;amplifier&gt;&lt;sampling&gt;" AnswerCount="1" />
  <row Id="6230" PostTypeId="1" AcceptedAnswerId="6233" CreationDate="2010-11-04T22:19:10.530" Score="3" ViewCount="163" Body="&lt;p&gt;I'm considering a future product. A high definition (720p) video transmitter. Ideally a compressed MPEG link would be used but this would still require at least 80 Mbit/s. I'm not looking at a simple solution, and I don't even think it's possible without high cost and big transmitting gear, but what is everyone's opinions? What about sending component video over long distances? I'm talking about 10km or so and the link must be wireless. The nodes may move, one would likely be an RC plane.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-04T22:45:42.120" LastActivityDate="2010-11-05T18:39:58.870" Title="What kind of options are there for very high bandwidth long distance data links?" Tags="&lt;radio&gt;&lt;data&gt;&lt;hd&gt;" AnswerCount="6" CommentCount="7" FavoriteCount="2" />
  <row Id="6231" PostTypeId="2" ParentId="6227" CreationDate="2010-11-04T22:33:09.033" Score="5" ViewCount="" Body="&lt;p&gt;The Hall effect doesn't depend on variations in the magnetic field (i.e., motion relative to the field or time-varying field), as far as I know, it only depends on the strength of the field, and the orientation relative to the sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternately you could look into 'magnetic reed switches'.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-11-04T22:56:49.483" LastActivityDate="2010-11-04T22:56:49.483" CommentCount="1" />
  <row Id="6232" PostTypeId="2" ParentId="6225" CreationDate="2010-11-04T22:48:49.037" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/5386/execute-instructions-from-ram-in-a-hobbyist-friendy-microcontroller&quot;&gt;http://electronics.stackexchange.com/questions/5386/execute-instructions-from-ram-in-a-hobbyist-friendy-microcontroller&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-04T22:48:49.037" CommentCount="3" />
  <row Id="6233" PostTypeId="2" ParentId="6230" CreationDate="2010-11-04T22:51:31.017" Score="5" ViewCount="" Body="&lt;p&gt;We use Microhard Systems 1.5 Mbps radios that send data over 100km.&#xA;They run at 900Mhz www.microhardcorp.com&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They make 54Mbps broadband wireless gear too, quoted range is 16km.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We've used their 900Mhz gear for years, and it's only gotten better, from 1200bps to 1.5Mbps.&#xA;Works great in cluttered environments (urban or forest)&lt;/p&gt;&#xA;" OwnerUserId="1481" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-11-05T18:39:58.870" LastActivityDate="2010-11-05T18:39:58.870" CommentCount="2" />
  <row Id="6234" PostTypeId="2" ParentId="6230" CreationDate="2010-11-04T22:54:20.910" Score="4" ViewCount="" Body="&lt;p&gt;A 10km link for 80Mbit/sec? Not going to happen. You're going to have a hell of a problem getting consumer gear to do 10km with one endpoint mobile, let alone 80Mbps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why not encode that stream with an FPGA or encoder chip to get it down to a more manageable bit rate? Now you can start looking for high-power commercial gear, but I'm guessing that you won't find anything you can use without a license.  The gear that Tim is talking about is all for fixed point to point links. I've set up some long range 2.4GHz stuff but again, fixed points where you can use a big antenna and jack up the EIRP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry for the letdown of an answer, but there isn't consumer gear which can do this yet, and the commercial gear will either be pricey or simply unavailable. &lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-11-04T22:54:20.910" CommentCount="2" />
  <row Id="6235" PostTypeId="2" ParentId="6220" CreationDate="2010-11-04T22:54:44.617" Score="4" ViewCount="" Body="&lt;p&gt;It's not just possible, it's darn useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All pins are inputs on power up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Commonly used by embedded software guys like me to give a interrupt from a GPIO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Who says there's no software interrupt instruction ?&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-11-04T22:54:44.617" CommentCount="2" />
  <row Id="6236" PostTypeId="2" ParentId="6230" CreationDate="2010-11-04T22:55:09.723" Score="-4" ViewCount="" Body="&lt;p&gt;Such technology already exists.  Digital, Hi-Def TV transmissions are either 720p or 720i and broadcast over miles.  Do some research into what they use. &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-04T22:55:09.723" CommentCount="2" />
  <row Id="6237" PostTypeId="2" ParentId="6230" CreationDate="2010-11-04T22:57:48.877" Score="2" ViewCount="" Body="&lt;p&gt;There are a few things you need to consider in a project like this:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What are the wireless regulations for the markets you are planning on selling to? Typically the wireless spectrum is very limited on what frequencies you can use, how much power, and for how long you can broadcast. Of course you can usually pay a licensing fee to go above it, but you would have to look into the rules for the area you would be selling to see if the license is something you can afford for your project. &lt;/li&gt;&#xA;&lt;li&gt;What is the free space and obstacle loss that are associated with the range and environment that you want it to work in? Now how much power will you need in order to go that far?&lt;/li&gt;&#xA;&lt;li&gt;Portable or fixed? How high (elevation wise) will it be? Because of the curvature of the earth, the longer distances you want to go the higher you have to be.&lt;/li&gt;&#xA;&lt;li&gt;Do you want the user to have to aim their antenna or is it going to be omni-directional. How tight of range are you going to have? The tighter the range the higher your effective gain will be on your antenna.&lt;/li&gt;&#xA;&lt;li&gt;Are you going digital or analog? This will effect how you will encode your data, acceptable error amounts and acceptable signal to noise ratio.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I think once you consider these items you will probably realize it isn't practical for a consumer application.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-04T22:57:48.877" />
  <row Id="6238" PostTypeId="2" ParentId="6228" CreationDate="2010-11-04T23:00:30.060" Score="4" ViewCount="" Body="&lt;p&gt;I'm not even sure GALs are still around today. CPLDs and FPGAs are preferred I believe, though I'm no expert.  You can dig up development kits from digilentinc.com.  There's a CPLD kit for $18 and the USB JTAG programming cable is $50.  Those parts are Digilent C-Mod and JTAG-USB Cable.  I believe the software (at least starter software) is free.  Good luck! &lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="1197" LastEditorDisplayName="" LastEditDate="2011-03-10T23:41:33.193" LastActivityDate="2011-03-10T23:41:33.193" CommentCount="3" />
  <row Id="6239" PostTypeId="2" ParentId="6172" CreationDate="2010-11-04T23:01:00.743" Score="3" ViewCount="" Body="&lt;p&gt;The jumbo version of the big red rocker is to get a contactor installed in your lab&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then there can be an off switch (Big E-STOP button) at the door.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So somebody trying to save you doesn't get electrocuted either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The training from my aluminum smelter days won't go away.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The real reason is to get a second off switch repeater put somewhere you actually live.&#xA;then you can say &quot;hey I left the lab on!&quot; and turn it off without havng to go too far ;-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, if your workbench is only little, you can probably hook up an E-Stop loop pretty easily with a consumer grade power control switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Consider an E-Stop loop. The life it saves will probably be yours.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastEditorUserId="965" LastEditorDisplayName="" LastEditDate="2010-11-05T04:29:59.367" LastActivityDate="2010-11-05T04:29:59.367" CommunityOwnedDate="2010-11-04T23:01:00.743" CommentCount="1" />
  <row Id="6240" PostTypeId="2" ParentId="6229" CreationDate="2010-11-04T23:13:17.313" Score="3" ViewCount="" Body="&lt;p&gt;Your DAQ probably looks pretty similar to an opamp from the sensors perspective. I can't imagine your DAQ having anything overly special about its input impedance. Even if it did, you would need to be concerned about the input impedance of a new DAQ.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I would be concerned about is the noise floor associated with your sensors and circuitry. You are needing to look at voltage ranges that most oscopes can't even see. You will need to put time into every aspect of your signal acquisition including board layout and shielding from noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may be able to to use just a simple op-amp to provide your gain, but be cautious of the noise as opamps can be very noisy if you aren't careful on what you buy. There are other methods of providing a gain, but I suspect that will all have issues with noise.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-04T23:13:17.313" CommentCount="5" />
  <row Id="6241" PostTypeId="1" CreationDate="2010-11-04T23:25:08.413" Score="4" ViewCount="285" Body="&lt;p&gt;I have this component called a breadboard friend. It has a 9V battery that is lowered to 5v so we can power most AOI logic chips. It has a built in 555 timer and a potentiometer. It  has 4 leds to link outputs from our logic circuits to - and it has 4 spst switches that are used to simulate binary values:  0000 or 1000 etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I want to do is make another part of this circuit that can simulate counting in binary for me up to X values. This way I can plug in the switches to the digital output and maybe press a switch to increment through the truth table.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking I could use the onboard 555 timer and use that somehow but I am lost.&lt;/p&gt;&#xA;" OwnerUserId="1687" LastActivityDate="2010-11-05T02:41:33.397" Title="Making a binary counter for my breadboard." Tags="&lt;breadboard&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="6242" PostTypeId="2" ParentId="6228" CreationDate="2010-11-05T00:12:36.613" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.leonheller.com/XC9536/XC9536.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is the schematic for a simple home-made PCB for experimenting with Xilinx XC9536 CPLDs. It has a connector for a Xilinx programming cable, a socket for a crystal oscillator and an LED, as well as a small prototyping area. The artwork file is available.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-05T00:12:36.613" />
  <row Id="6243" PostTypeId="2" ParentId="6227" CreationDate="2010-11-05T00:47:46.977" Score="2" ViewCount="" Body="&lt;p&gt;A hall effect sensor can detect large magnetic fields relatively easily. This is done by measuring the variance in resistance. You allow a DC current to pass, the Magnetic field will deflect electrons, increasing the DC resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This gives you a magnetic field dependent resistor. These will be able to measure the current in 2 planes, the path of the current will be unaffected by a magnetic field in it's direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to measure in 3 directions, I would suggest 2 to detect magnitude of field, and a general idea of direction. With 3 you can get a rather precise idea of direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is no motion of the sensor required.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-05T00:47:46.977" CommentCount="1" />
  <row Id="6244" PostTypeId="2" ParentId="6241" CreationDate="2010-11-05T01:54:47.673" Score="2" ViewCount="" Body="&lt;p&gt;Take flip-flops for the state of the counter. Use logic tied from output to input(called next state logic) to give the counting. Use the square wave from the 555 timer to give your clock signal.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-05T01:54:47.673" />
  <row Id="6245" PostTypeId="2" ParentId="6241" CreationDate="2010-11-05T02:41:33.397" Score="3" ViewCount="" Body="&lt;p&gt;Wire the 555 as a one-shot to make a clock signal for a binary counter IC (eg. 74LS93) that single-steps every time the 555 is fired.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-05T02:41:33.397" CommentCount="1" />
  <row Id="6246" PostTypeId="2" ParentId="6151" CreationDate="2010-11-05T02:48:48.530" Score="1" ViewCount="" Body="&lt;p&gt;From the switching power world, I have seen paralleled diodes and bridges as you've described. The hope is that with matched heatsinking and small part-to-part variation, the devices will share load without any sort of external balancing. There are no guarantees, of course, so each of the devices has to be rated to handle the full load current else there can be &quot;issues&quot; (to put it mildly)...&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-05T02:48:48.530" />
  <row Id="6247" PostTypeId="2" ParentId="6225" CreationDate="2010-11-05T04:44:53.510" Score="3" ViewCount="" Body="&lt;p&gt;How often do you need to load the program?  Have you considered downloading from the SD card using some sort of boot loader, programming the flash and executing from there?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are trying to create dynamic environment like an OS which is overlaying programs constantly, then this would not work. But in my case, I have a program that loads dirvers and overlays as needed off of a 2 GB SD card. The PIC24FJ256GB110 has a 10,000 erase/write cycle minimum.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But since the 10,000 figure is a minimum, and typical erase/write endurance might be five times that, so if you are doing development, you can probably re-flash a processor 100 times a day -- every 5 minutes for eight hours -- and it might still last a year and a half.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-11-05T04:44:53.510" CommentCount="1" />
  <row Id="6248" PostTypeId="1" AcceptedAnswerId="6255" CreationDate="2010-11-05T06:24:19.230" Score="8" ViewCount="117" Body="&lt;p&gt;I think I've found a solution for &lt;a href=&quot;http://electronics.stackexchange.com/questions/5620/mechanical-connectors-for-flexible-pcbs&quot;&gt;my previous question&lt;/a&gt; and I'm now going to order some &lt;a href=&quot;http://portal.fciconnect.com/res/en/pdffiles/datasheets/950500-025_FPC-Clincher2.pdf&quot; rel=&quot;nofollow&quot;&gt;FCI &quot;Clincher&quot;&lt;/a&gt; connectors from a local supplier to try them out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, should I terminate the ends of the &lt;a href=&quot;http://electronics.stackexchange.com/questions/5620/mechanical-connectors-for-flexible-pcbs&quot;&gt;flexible LED strips&lt;/a&gt; with &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=609-2160-ND&quot; rel=&quot;nofollow&quot;&gt;sockets&lt;/a&gt; or &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=609-2178-ND&quot; rel=&quot;nofollow&quot;&gt;pins&lt;/a&gt;? And why?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(In practice I'm going to be using sockets for this prototype because that's what &lt;a href=&quot;http://sg.element14.com/&quot; rel=&quot;nofollow&quot;&gt;Element14&lt;/a&gt; have in stock, but if there's a strong reason to do it the other way 'round its worth me waiting for the stock to come in for the &quot;real&quot; (much bigger, more expensive) project.)&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2010-11-05T10:31:42.640" Title="Sockets or pins, and why?" Tags="&lt;connector&gt;&lt;pins&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="6249" PostTypeId="2" ParentId="6225" CreationDate="2010-11-05T07:59:15.593" Score="1" ViewCount="" Body="&lt;p&gt;You have not specified what exactly &quot;reasonable amount of RAM&quot; means, but you can take a look at ATMEL devices parametric table:&#xA;&lt;a href=&quot;http://atmel.com/dyn/products/param_table.asp?family_id=607&amp;amp;OrderBy=part_no&amp;amp;Direction=ASC&quot; rel=&quot;nofollow&quot;&gt;http://atmel.com/dyn/products/param_table.asp?family_id=607&amp;amp;OrderBy=part_no&amp;amp;Direction=ASC&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-11-05T07:59:15.593" CommentCount="1" />
  <row Id="6250" PostTypeId="1" CreationDate="2010-11-05T08:05:05.253" Score="5" ViewCount="290" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recently dug out of my box o' stuff a pair of seemingly decent 2.5ohm bookshelf speakers. I wired them to an old mp3 player I have and while they sound good at low volumes, I get lots of distortion at high volume. Given that they are only 2.5ohm, I'm assuming that this is because they are trying to draw more current than the poor mp3 player can produce.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rather than buying one (or new speakers for that matter), I'd like to try and build an amplifier for these speakers. I was looking at using an IC such as the &lt;a href=&quot;http://au.element14.com/stmicroelectronics/tda7294v/amp-audio-100v-100w/dp/1366583?Ntt=tda7294&quot; rel=&quot;nofollow&quot;&gt;TDA7924&lt;/a&gt; but like all of these chips, the advised load impedance is 4 ohms. It doesn't specifically state anywhere that the absolute minimum is 4-8 ohms, but has anyone had any experience with this sort of thing? Will it still work at a lower load impedance if I just make sure that the volume is limited? If not, will I be able to use this IC if I chuck a big 2 ohm power resistor in series (as much of a waste of electricity as that is)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll probably get some anyway to play with but I am a poor student and I would prefer not to blow up several $12 chips. thanks!&lt;/p&gt;&#xA;" OwnerUserId="417" LastEditorUserId="417" LastEditorDisplayName="" LastEditDate="2010-11-05T08:13:52.950" LastActivityDate="2010-11-05T22:10:02.577" Title="building an audio amplifier for 2.5 ohm speakers" Tags="&lt;amplifier&gt;&lt;speakers&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="6251" PostTypeId="2" ParentId="6230" CreationDate="2010-11-05T08:26:00.127" Score="1" ViewCount="" Body="&lt;p&gt;What about using a TCP/IP data link established with some modern mobile phone or modem? I guess GPRS is too slow but 3G might do the job. Mobile phone might even use it's camera and compress the picture for sending, or you can just put it in an automatic answer mode and use it as a simple 3G video phone. This solution might also spare you wireless licensing problems.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-11-05T08:26:00.127" />
  <row Id="6252" PostTypeId="2" ParentId="6230" CreationDate="2010-11-05T09:37:39.177" Score="0" ViewCount="" Body="&lt;p&gt;First of all compress the data to get the bandwidth down to less than 20 Mb/s, then get long range 5GHz 802.11n radios with directional antennae like these:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ubnt.com/&quot; rel=&quot;nofollow&quot;&gt;http://ubnt.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If one end is mobile, then you will need to steer the antennas to keep them pointing in the right direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd find some low-bandwith + long-range radios that can be used to transmit the GPS position of the rover back to the base to allow the base-antenna to be aimed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative solution would be to have two radios at either end and scan the second radio around to optimize the aim of the main radio, but mechanically that's quite complicated and heavy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might get away with an omnidirectional antenna on the rover and only use a directional antenna on the station, but range will suffer a lot.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-05T09:37:39.177" />
  <row Id="6253" PostTypeId="2" ParentId="6212" CreationDate="2010-11-05T09:44:30.980" Score="2" ViewCount="" Body="&lt;p&gt;How big do you need your caps to be?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get ceramic 100uF/6.3V low-ESR caps in 1210 packages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IOW: You can solve most power supply problems with ceramic SMD caps that are superior to electrolytics in just about every way.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-05T09:44:30.980" CommentCount="2" />
  <row Id="6254" PostTypeId="2" ParentId="6225" CreationDate="2010-11-05T10:30:34.497" Score="1" ViewCount="" Body="&lt;p&gt;NXP ARM Cortex-M0 and -M3 parts are available in small packages down to 32 pins, but probably QFN rather than QFP&#xA;I think sopem of the ex-Motorola parts like HC11 may be able to do this but not sure if any are still in production&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-05T10:30:34.497" />
  <row Id="6255" PostTypeId="2" ParentId="6248" CreationDate="2010-11-05T10:31:42.640" Score="8" ViewCount="" Body="&lt;p&gt;The general convention is sockets for power sources, pins for loads. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-05T10:31:42.640" CommentCount="4" />
  <row Id="6256" PostTypeId="2" ParentId="6228" CreationDate="2010-11-05T10:33:23.653" Score="4" ViewCount="" Body="&lt;p&gt;Standard GALs need funky voltages and waveforms for programming. Lattice do some 'ispGAL' products which added an IS interface, but unless you want to stick to DILs and/or 5V, low-end CPLDs are more capable and easier to program.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-11-09T19:06:46.173" LastActivityDate="2010-11-09T19:06:46.173" />
  <row Id="6257" PostTypeId="2" ParentId="6250" CreationDate="2010-11-05T10:35:47.517" Score="3" ViewCount="" Body="&lt;p&gt;If you don´t mind to lose stereo sound, you can wire up the speakers in series resulting in one load of 5 ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that a 2 ohm resistor is not a good solution because a common output voltage will be arround 10 volts and with current of 5 amp you´ll need a resistor of 50 Watts, which is pretty expensive. Maybe buying an cheap tweeter will be better and improve high frequency sound quality.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking in the datasheet I found that this IC specifically (TDA7924) have an short-circuit and overload protection. Using a load of 2.5 ohms may not be a problem if you don´t exagerated in the volume.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Some other thoughts, how did you measured the speaker impedance? If it was only using an DC multimeter the number you got (2.5 ohms) is only the resistance of the speaker. The impedance also needs to consider the inductor. If the DC resistance is 2.5 ohms probably the total impedance is alredy 4 ohms, so you don´t need any modifications on the circuit. The speakers whose impedance are not 4 or 8 ohms are rarelly manufactured.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-05T19:19:00.130" LastActivityDate="2010-11-05T19:19:00.130" CommentCount="1" />
  <row Id="6258" PostTypeId="2" ParentId="6250" CreationDate="2010-11-05T10:50:26.843" Score="1" ViewCount="" Body="&lt;p&gt;I would suggest you do some research into &lt;a href=&quot;http://www.pic101.com/op_amp.htm&quot; rel=&quot;nofollow&quot;&gt;Op Amps&lt;/a&gt;, as they will allow you to manipulate the output of the mp3 player into a more suitable input for your 2.5Ω speakers.  You can in essence create a pre-amplifier for your speakers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;More information on Op Amps can be found at &lt;a href=&quot;http://en.wikipedia.org/wiki/Operational_amplifier&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While your amp does not emphatically state itself to be an op amp, have you metered the impedance of the speakers?  I found a link at &lt;a href=&quot;http://www.prestonelectronics.com/audio/Impedance.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.prestonelectronics.com/audio/Impedance.htm&lt;/a&gt;, which states&#xA;&quot;&lt;strong&gt;a 4 ohm speaker will typically measure about 2.5 - 3 ohms, and an 8 ohm speaker will typically read about 5-6 ohms, while a 16 ohm speaker will measure around 12 ohms.&lt;/strong&gt;&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you speakers actually meter to 2.5Ω and the typical speaker meters 2.5Ω also, then your speakers should work fine on the &quot;op amp&quot; you have selected then you may find you are able to utilize your amp.&lt;/p&gt;&#xA;" OwnerUserId="1413" LastEditorUserId="1413" LastEditorDisplayName="" LastEditDate="2010-11-05T11:28:48.230" LastActivityDate="2010-11-05T11:28:48.230" CommentCount="1" />
  <row Id="6259" PostTypeId="1" AcceptedAnswerId="6264" CreationDate="2010-11-05T11:02:20.647" Score="5" ViewCount="370" Body="&lt;p&gt;How do devices which measure energy consumed work? For example the ones in solar regulators/chargers which display how many Ah went into the battery and how many went out?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do they just measure the current for example every second and a microprocessor constantly adds up the measurements, assuming that the current 0.5s before and after each measurement is the same as while they take the current measurement, or do they have a way of really measuring how much energy went through, without referring to such, possibly inaccurate approximation?&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-06-01T14:50:42.140" Title="how do energy consumption (Ah, kWh) meters work?" Tags="&lt;measurement&gt;&lt;energy&gt;&lt;current-measurement&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="3" />
  <row Id="6260" PostTypeId="2" ParentId="6259" CreationDate="2010-11-05T11:33:02.750" Score="4" ViewCount="" Body="&lt;p&gt;Ah would be measured with a coulomb counter - basically what you said, measuring current and numerically integrating this over time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for kWh, you could measure current and voltage, multiply them together to get power, then again, numerically integrate this over time to get kWh&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-05T11:33:02.750" />
  <row Id="6261" PostTypeId="2" ParentId="4604" CreationDate="2010-11-05T11:36:08.853" Score="2" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://devicesolutions.net/Products/TahoeII.aspx&quot; rel=&quot;nofollow&quot;&gt;Tahoe 2&lt;/a&gt;  &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ghielectronics.com/product/129&quot; rel=&quot;nofollow&quot;&gt;GHI EMX&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-05T11:36:08.853" />
  <row Id="6262" PostTypeId="2" ParentId="6259" CreationDate="2010-11-05T11:53:06.033" Score="2" ViewCount="" Body="&lt;p&gt;In practice, yes an MCU will be doing individual measurements of current and voltage and assuming an average over the time period.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the frequency of the measurements and how the voltages are filtered before digitizing you will get something that's very, very close to the truth.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-05T11:53:06.033" CommentCount="1" />
  <row Id="6263" PostTypeId="1" CreationDate="2010-11-05T12:01:29.233" Score="12" ViewCount="398" Body="&lt;p&gt;Ok This may be a little out of the usual questions we get here but I am willing to risk some reputation points to find out if you all are willing to answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yesterday I was sitting with a friend of mine who has graduated as a CS major. All of his work is in J2EE and he is quite good at it. He went on and on about how easy it is to look for work with his profile online. He goes to websites like elance or freelancer and bids on projects. He gets some and that makes some extra cash for him. But the beauty is, the work is almost menial work just with better pay. Setup a wordpress blog or make one or two servelets in java. I found this quite fascinating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This got me wondering if there equivalent skills in things related to EE. Here are some things which got into my mind&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;C programs for uControllers&lt;/li&gt;&#xA;&lt;li&gt;Small circuit design&lt;/li&gt;&#xA;&lt;li&gt;Writing HDL for different systems&lt;/li&gt;&#xA;&lt;li&gt;Linux Drivers&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;But all this is quite high level stuff. Can you think of things which smart people can learn in a few weeks and then use the knowledge to make some money from outsourced online.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-16T17:12:57.730" LastActivityDate="2011-05-16T17:12:57.730" CommunityOwnedDate="2011-05-16T17:13:11.787" Title="What kind of skills as electronics engineer are marketable for small freelance works online?" Tags="&lt;career&gt;" AnswerCount="4" FavoriteCount="7" />
  <row Id="6264" PostTypeId="2" ParentId="6259" CreationDate="2010-11-05T12:08:15.130" Score="3" ViewCount="" Body="&lt;p&gt;An MCU is not required to perform this sort of measurement.  The &lt;a href=&quot;http://www.st.com/internet/analog/product/214267.jsp&quot; rel=&quot;nofollow&quot;&gt;STC3100&lt;/a&gt; is a simple I2C interfaced coulomb counter that measures the charge state of a battery.  It works by integrating the measured current into/out of the battery over time and providing the result in a form that can be read by the processor.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used this device on a couple of products and find the results better than I would have thought bearing in mind the large variations in the load current that can be seen, in my case the load current varies over at least 4 orders of magnitude.  The errors due to the sampling of the varying current seem to cancel out over time. &lt;/p&gt;&#xA;" OwnerUserId="400" LastEditorUserId="3028" LastEditorDisplayName="" LastEditDate="2011-06-01T14:50:42.140" LastActivityDate="2011-06-01T14:50:42.140" />
  <row Id="6265" PostTypeId="2" ParentId="6263" CreationDate="2010-11-05T12:11:49.800" Score="4" ViewCount="" Body="&lt;p&gt;Checkout &lt;a href=&quot;http://www.adafruit.com/jobs/&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/jobs/&lt;/a&gt; to see the kinds of things which are in demand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would expect that the most useful skills for small freelance work would be the specialised things which companies contract out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;EMC design/test&lt;/li&gt;&#xA;&lt;li&gt;RF design/testing&lt;/li&gt;&#xA;&lt;li&gt;Production test jigs&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-05T12:33:57.727" LastActivityDate="2010-11-05T12:33:57.727" CommunityOwnedDate="2011-05-16T17:13:11.787" CommentCount="4" />
  <row Id="6266" PostTypeId="2" ParentId="6225" CreationDate="2010-11-05T12:22:11.113" Score="3" ViewCount="" Body="&lt;p&gt;(copied from &lt;a href=&quot;http://electronics.stackexchange.com/questions/5386/execute-instructions-from-ram-in-a-hobbyist-friendy-microcontroller&quot;&gt;Execute instructions from RAM in a hobbyist-friendy microcontroller&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option to consider is using an interpreted language for your programs stored on the SD card. This way, the processor isn't executing the machine code read from the card, it's just treating it as data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This approach gives you flexibility at the cost of speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are plenty of options to choose from:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/3423/survey-of-high-level-language-interpreters-compilers-for-microcontrollers&quot;&gt;Survey of High-Level Language Interpreters/Compilers for Microcontrollers&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-05T12:22:11.113" />
  <row Id="6267" PostTypeId="2" ParentId="6227" CreationDate="2010-11-05T12:27:49.670" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.allegromicro.com/en/Products/Part_Numbers/1301/&quot; rel=&quot;nofollow&quot;&gt;Allegro A1301&lt;/a&gt; is a cheap analogue hall effect sensor. It's a 3 pin device: 5V GND and OUT. It outputs 2.5mV per Gauss detected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's very easy to use, &lt;a href=&quot;http://blog.hodgepig.org/2010/04/04/541/&quot; rel=&quot;nofollow&quot;&gt;here's a project I used it in&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-05T12:27:49.670" CommentCount="2" />
  <row Id="6268" PostTypeId="1" AcceptedAnswerId="6271" CreationDate="2010-11-05T12:42:28.843" Score="2" ViewCount="150" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/4678/what-tools-equipments-and-techniques-do-you-use-to-solder-microminiature-smd-par&quot;&gt;What tools, equipments and techniques do you use to solder microminiature smd parts?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;A very small button component has broken of from a friends MP3 player, and I will need to re-&lt;strong&gt;solder&lt;/strong&gt; it back.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See image: ( standard ball point pen included for size refference ) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/F0kKb.jpg&quot; alt=&quot;referrence image&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will need to touch up the soldering at the &lt;em&gt;green&lt;/em&gt; arrows, and re-attach the button according to the &lt;em&gt;red line and dots&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is much more fine and precise than any soldering I've done before, and before I mess up a MP3, I was hoping to get a few pointers. Also, what gear would I need for this job? &lt;/p&gt;&#xA;" OwnerUserId="1258" LastActivityDate="2010-11-05T13:39:00.033" ClosedDate="2010-11-05T14:47:25.073" Title="What gear is required to do fine soldering?" Tags="&lt;soldering&gt;" AnswerCount="4" CommentCount="6" />
  <row Id="6269" PostTypeId="2" ParentId="6268" CreationDate="2010-11-05T12:44:41.770" Score="3" ViewCount="" Body="&lt;p&gt;You'll need a soldering iron with a fine tip - similar to your pen.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-05T12:44:41.770" />
  <row Id="6270" PostTypeId="2" ParentId="6263" CreationDate="2010-11-05T12:46:39.823" Score="3" ViewCount="" Body="&lt;p&gt;I suggest you visit sites like &lt;a href=&quot;http://www.rentacoder.com&quot; rel=&quot;nofollow&quot;&gt;RentACode&lt;/a&gt;, &lt;a href=&quot;http://www.odesk.com&quot; rel=&quot;nofollow&quot;&gt;ODesk&lt;/a&gt; etc. to see the needs of hirers.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-05T12:46:39.823" CommunityOwnedDate="2011-05-16T17:13:11.787" CommentCount="3" />
  <row Id="6271" PostTypeId="2" ParentId="6268" CreationDate="2010-11-05T12:51:47.597" Score="5" ViewCount="" Body="&lt;p&gt;Have a look at this very similar question:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/4678/what-tools-equipments-and-techniques-do-you-use-to-solder-microminiature-smd-par&quot;&gt;What tools, equipments and techniques do you use to solder microminiature smd parts?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also: after you soldered it, you might want to use a little hot glue, so the button has more support.&lt;/p&gt;&#xA;" OwnerUserId="1124" LastActivityDate="2010-11-05T12:51:47.597" />
  <row Id="6272" PostTypeId="2" ParentId="6268" CreationDate="2010-11-05T13:03:25.947" Score="4" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;Apply a very low melting point solder and lift the button;&lt;/li&gt;&#xA;&lt;li&gt;Clean the pads with a &lt;a href=&quot;http://electronics.stackexchange.com/questions/5034/how-to-remove-solder-from-via/5039#5039&quot;&gt;wick solder&lt;/a&gt;;&lt;/li&gt;&#xA;&lt;li&gt;Use a soldering iron with a fine tip to put the new button.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-05T13:03:25.947" />
  <row Id="6273" PostTypeId="2" ParentId="6263" CreationDate="2010-11-05T13:25:41.970" Score="3" ViewCount="" Body="&lt;p&gt;&quot;Will solder for money&quot; or in a more serious light, paid kit assembly. There are a lot of people out there who would like a kit but cannot solder for the life of them. E.g. those adafruit &quot;ice tube&quot; clocks are an example of something that would sell very well as a finished product (although shipping them assembled might be an issue). You could advertise on etsy or eBay, or in the classifieds sections of electronics magazines. There are a few people here in Australia that make good money doing this. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-11-06T08:58:00.043" LastActivityDate="2010-11-06T08:58:00.043" CommunityOwnedDate="2011-05-16T17:13:11.787" CommentCount="4" />
  <row Id="6274" PostTypeId="2" ParentId="6268" CreationDate="2010-11-05T13:39:00.033" Score="4" ViewCount="" Body="&lt;p&gt;You can never have too much flux. It always helps!&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-05T13:39:00.033" />
  <row Id="6275" PostTypeId="2" ParentId="6250" CreationDate="2010-11-05T13:46:57.730" Score="3" ViewCount="" Body="&lt;p&gt;Ahh!!! I remember doing one in my school days. I have few tips for you where you can still have these speakers work perfectly fine with the least risk ;) coz I tested them on mine.&#xA;For reference I have used the datasheet from this site &#xA;&lt;a href=&quot;http://www.st.com/stonline/books/pdf/docs/1057.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.st.com/stonline/books/pdf/docs/1057.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The logic here is the lower the resistance of speaker the higher current it will end up drawing from the amplifier, so what you have to take care is to make sure the current your speaker are drawing to keep it within safe operating range of the amplifier. Some tips you can use are&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Keep the input voltage much less that the MAX SOURCE VOLTAGE of the amplifier, in this case its 40V. You can use a 12V supply with 1AMP current.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Make sure you have good HEAT SINK, a big one. preferably use the &quot;heat sink paste&quot; and screw it up tight and arrange it properly in the board such that it gets a good AIR CIRCULATION.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;And since the speaker are just 2.5 ohms from my experience they are going to be real loud and noisy at higher volumes (I &lt;em&gt;re-winded&lt;/em&gt; the coils for higher ohms in my case and used custom &lt;em&gt;cloth spider and cone&lt;/em&gt; to get the best out of my speakers ) So keep the volume low :)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2010-11-05T13:46:57.730" />
  <row Id="6276" PostTypeId="2" ParentId="6227" CreationDate="2010-11-05T14:27:39.427" Score="2" ViewCount="" Body="&lt;p&gt;Are you sure that you want it to both turn off and on at 75 Gauss?  Magnetic fields are variable, and you might get a lot of noise at that edge.  Most Hall effect switches are designed with Hysteresis, or a &lt;a href=&quot;http://en.wikipedia.org/wiki/Schmitt_trigger&quot; rel=&quot;nofollow&quot;&gt;Schmitt Trigger&lt;/a&gt;, for this reason.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With this knowledge, you can start looking at &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1967232&quot; rel=&quot;nofollow&quot;&gt;Digikey's selection of magnetic sensors&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.allegromicro.com/en/Products/Part_Numbers/3295/&quot; rel=&quot;nofollow&quot;&gt;Allegro A3295&lt;/a&gt; is an example of such a device.  It turns on at 75 Gauss, and turns off once the field decays to 5 Gauss.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-05T14:27:39.427" CommentCount="1" />
  <row Id="6277" PostTypeId="2" ParentId="6196" CreationDate="2010-11-05T14:36:18.877" Score="2" ViewCount="" Body="&lt;p&gt;In theory the gravity of the moon would cause small changes in very precise accelerometers and gyros. As a practical matter there are gravity deviations due to mountains, ore deposits and so on that would be larger. As these don't normally effect equipment, I doubt the moon does.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-11-05T14:36:18.877" />
  <row Id="6278" PostTypeId="2" ParentId="4874" CreationDate="2010-11-05T14:45:22.547" Score="3" ViewCount="" Body="&lt;p&gt;Can you make it compatible with &lt;a href=&quot;http://en.wikipedia.org/wiki/ChampionChip&quot; rel=&quot;nofollow&quot;&gt;ChampionChip&lt;/a&gt; (now merged with &lt;a href=&quot;http://www.mylaps.com/index.php/us_eng/Websites/B2B/run/home&quot; rel=&quot;nofollow&quot;&gt;MyLaps&lt;/a&gt;)?  Many runners have their own chips, and that would be a good standard to work from.   You can pick up &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In response to the comments and answers about the applicability of this technology to racing, I can say that I've run at least two dozen races with RFID tags, and have never had a problem with tag collisions, misses, or accuracy/finish order.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For redundancy, use two mats, and program in the rate at which runners are crossing. Then, if the first mat has a problem, you can use the second and extrapolate the time to cross the line. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Find a race that uses disposable chips, or just keep a pair from your next race, and see what you can come up with.  Alternatively, &lt;a href=&quot;http://www.score-this.com/championchip.html&quot; rel=&quot;nofollow&quot;&gt;this site&lt;/a&gt; sells personalized tags.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-05T14:45:22.547" CommentCount="1" />
  <row Id="6279" PostTypeId="2" ParentId="6225" CreationDate="2010-11-05T15:52:41.770" Score="1" ViewCount="" Body="&lt;p&gt;I would recommend TI's MSP430 (16-bit) or a Cortex-M3 (32-bit). The good sources for the latter are NXP (LPC17xx/LPC13xx), ST (STM32 series) or TI (Stellaris LM3S). All(?) of them are available in QFP packages (usually LQFP-48).&lt;/p&gt;&#xA;" OwnerUserId="1082" LastActivityDate="2010-11-05T15:52:41.770" />
  <row Id="6280" PostTypeId="1" CreationDate="2010-11-05T16:13:46.867" Score="3" ViewCount="183" Body="&lt;p&gt;It is said that in frequency modulation the normal wave represents a '0' (False) and a more frequent wave represents a '1' (True).&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is there any particular rule that the normal wave's frequency should continuously be the same? How actually is this &quot;normal frequency&quot; found out?&lt;/li&gt;&#xA;&lt;li&gt;Consider an example of a wave that has first 3 waves in a time period, then 2 waves and finally one wave. How would it frequency modulate it?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1799" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-17T16:50:57.493" LastActivityDate="2010-11-17T16:50:57.493" Title="How does frequency modulation takes place?" Tags="&lt;modulation&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="2" />
  <row Id="6281" PostTypeId="2" ParentId="6280" CreationDate="2010-11-05T16:46:45.650" Score="4" ViewCount="" Body="&lt;p&gt;This is not a perfect explanation, but I hope it helps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When something is frequency modulated there are 2 frequencies, I would not define one as &quot;normal&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a frequency that is a digital 1, there is a frequency that is a digital 0.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, when you are receiving, lets look at a conceptually simple detector. You have a bandpass for each frequency, and on the output of these, you have a rectifier which measures your relative power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you are receiving, you need to know the bitrate, or you need a shared clock (which requires a second connection to clock the data, or a second communication channel that cycles between its two frequencies to send the data). Often you read off of the two rectified signals as if you were reading a UART line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally your data rate is significantly slower than your modulation frequency. Normally by a factor of infinity, which in engineering we can get by as approximating as 10.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please let me know if there is something I can expand on to make this make more sense.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-05T16:51:25.797" LastActivityDate="2010-11-05T16:51:25.797" CommentCount="12" />
  <row Id="6283" PostTypeId="1" CreationDate="2010-11-05T17:23:28.963" Score="5" ViewCount="219" Body="&lt;p&gt;Hello all - I'm a computer scientist with zero exposure to things directly related to hardware (barring what I learned from my undergrad computer org class.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been very attracted to the field of embedded software and computer engineering, and I've been trying to find a class/lab where I can learn and practice the fundamentals of circuits and electronics. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding the theory, I can learn that from books, and I have a few. Or I can take some undergrad courses from a local university (offered both within brick walls and in distance learning format.) &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;h2&gt;The problem: Labs&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;However, the problem is the practicum, &lt;strong&gt;&lt;em&gt;the labs&lt;/em&gt;&lt;/strong&gt;. The closest university has the labs during the day. The other local university has lab classes at night, but they are too far to drive. As a working software developer, then I really have no options to sign up for a lab class to get my hands dirty.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be the value of learning from books (or from classes) if I don't get to a lab? The stuff they do at EE labs (the typical electronics lab I class), is that something I can learn on my own? If so, how? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to close this skills gap I have in front of me and get more into Computer Engineering. The last thing I want to be is a &lt;em&gt;paper tiger&lt;/em&gt; with all theory and no practice. But the labs are always during times of the day that conflict with my work schedule.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any advice?&lt;/p&gt;&#xA;" OwnerUserId="1598" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-12T06:42:23.597" LastActivityDate="2011-02-12T06:42:23.597" Title="learning about electronics stuff" Tags="&lt;electronics&gt;&lt;electrical-engineering&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="6284" PostTypeId="2" ParentId="6283" CreationDate="2010-11-05T17:41:01.397" Score="4" ViewCount="" Body="&lt;p&gt;My thoughts:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;What would be the value of learning from books (or from classes) if I don't get to a lab? &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The lab is fundamental for electronics. There are several things that you can't learn from books.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The stuff they do at EE labs (the typical electronics lab I class), is that something I can learn on my own? If so, how?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes, you can learn for your own. Nowadays it's easier because you have a lot of books, Google, YouTube, &lt;a href=&quot;http://ocw.mit.edu/courses/audio-video-courses/#electrical-engineering-and-computer-science&quot; rel=&quot;nofollow&quot;&gt;MIT&lt;/a&gt;, etc. And you can solve your doubts here or others foruns.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Any advice?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You can invest the money you would spend on college and build your own lab.&lt;/li&gt;&#xA;&lt;li&gt;Look for a &lt;a href=&quot;http://hackerspaces.org/wiki/&quot; rel=&quot;nofollow&quot;&gt;hackerspace&lt;/a&gt; near from you. It's a nice place to learn electronics.&lt;/li&gt;&#xA;&lt;li&gt;Take a look at the &lt;a href=&quot;http://electronics.stackexchange.com/questions/tagged/beginner&quot;&gt;begginer tag&lt;/a&gt; for more tips.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-05T17:51:26.813" LastActivityDate="2010-11-05T17:51:26.813" CommentCount="4" />
  <row Id="6285" PostTypeId="2" ParentId="6283" CreationDate="2010-11-05T18:12:32.773" Score="2" ViewCount="" Body="&lt;p&gt;Personally speaking - I've gotten a lot out of taking old stuff apart and trying to figure the circuit out (&lt;a href=&quot;http://en.wikipedia.org/wiki/Capacitor#Hazards_and_safety&quot; rel=&quot;nofollow&quot;&gt;just stay away from those massive capacitors!!&lt;/a&gt;) I find stuff dumped in the street all the time and I like to take something apart almost every day (My house has become like a hostel for homeless electronics, people bring junk round all the time, I took apart in infra red remote control for a helicopter today, had a poke around the circuit and modified the accelerator so it's no longer springy) You'll probably need some basic test equipment, a soldering iron and some kind of prototyping board (Stripboard, Veroboard, breadboards...whatever) then you can just harvest components and circuits to experiment with, it shouldn't cost much. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could get a little way with just a multimeter or two, if you can get a hold of an oscilloscope, then your sorted! - but they're expensive... I guess that's why labs are great, it's always good to try and get access to one when possible, even if it's just to talk to other engineers/students and use the nice expensive test equipment :)   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember tho - BE SAFE, don't listen to me, don't mess about with the mains...bla bla bla...if you're not sure about something - don't bother! &#xA;You can start with small electronic devices with batteries (I don't mean massive 12v car batteries!), then there's not so many dangers to worry about, except the sharp bits and the massive caps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With regards to paper tigers - The only way to become an electrical engineer is to start building circuits! books and world wide webs are fine, but eventually you have to get your hands dirty.&lt;/p&gt;&#xA;" OwnerUserId="399" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-11-05T18:30:37.557" LastActivityDate="2010-11-05T18:30:37.557" CommentCount="2" />
  <row Id="6286" PostTypeId="2" ParentId="4874" CreationDate="2010-11-05T18:48:17.400" Score="1" ViewCount="" Body="&lt;p&gt;I don't think you need long range (at least not how I categorize long range, like 15-30ft like a highway toll sensor).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the Boston Marathon this year all the runners got a very small plastic cased passive RFID tag which was designed to be tied into their shoe laces.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the 11 check points there was a large thin mat across the race track which detected the tag as they ran over it.  I don't know the nature of the mat but i imagine it had multiple antennas so the detection distance was maybe 1 foot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also seen some races where the RFID tag was in the bib but i believe there were still using mats for the antennas, the range would just need to be a few feet longer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In terms of the final results accuracy, long distance races hardly ever end in a &quot;photo finish&quot; situation.  If they were to end in that manner I image the judges would have a photo back up of the finish.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-05T18:48:17.400" />
  <row Id="6287" PostTypeId="2" ParentId="6206" CreationDate="2010-11-05T18:49:33.943" Score="1" ViewCount="" Body="&lt;p&gt;AC signals sometimes ride on a DC voltage level. On the scope you may see a sin wave of +60 to - 40 VDC. This is 100 V Ac signal riding on a 10 V DC voltage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I once worked with a 10 V peak to peak sin and cos signal from a resolver. The reference signal had a 0 V, 400 mV or 800 mV DC level applied to it. A multiplexer would switch between 3 different resolvers based on DC level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your scope could handle anything from 250 V peak AC signal to a peak 125 VAC on top of 125 V DC to a pure 250 V DC or any mix as long as the AC Peak signal + the DC level is less then 250 V&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For dealing with High voltage signals, use high voltage probes. These typically reduce the signal by a factor of 10 or more. So a 250 VAC signal become a 25 V signal.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-11-05T18:49:33.943" />
  <row Id="6288" PostTypeId="1" AcceptedAnswerId="6289" CreationDate="2010-11-05T19:16:24.210" Score="0" ViewCount="67" Body="&lt;p&gt;I'm looking for a replacement MOSFET for the SI7460DP. It's a 60V 11A 0.0096 ohm MOSFET.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think I can solder the PPAK, but a design I am using requires this fet. So I'd be okay with SOT-89, SOT-223, DPAK, SOIC-8 - anything with exposed leads - if it fits the requirements I'd be happy with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-05T20:52:32.613" Title="Replacement MOSFET (in a different package)" Tags="&lt;mosfet&gt;" AnswerCount="2" />
  <row Id="6289" PostTypeId="2" ParentId="6288" CreationDate="2010-11-05T19:49:08.160" Score="0" ViewCount="" Body="&lt;p&gt;SO8 is rare, but DPAK might work. Infineon, for example, has plenty. The IPD088N06N3 (DPAK=TO-252) with 60.0 V and 8.8 mOhm seems to be closest, but there are many more with even smaller Rds,on. To get a good comparison, I suggest relying rather on Rds,on and not on the current rating, because the latter is used differently by various manufactureres.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-11-05T19:49:08.160" CommentCount="4" />
  <row Id="6290" PostTypeId="1" CreationDate="2010-11-05T20:15:44.670" Score="2" ViewCount="67" Body="&lt;p&gt;In industry, when purchasing sensors from an external manufacturers, are those sensors tested, and if so, how thoroughly? For example, I buy some accelerometers from Sparkfun and do some minimal testing using gravity. Is this a waste of time? What are the chances of getting a defective sensor?&lt;/p&gt;&#xA;" OwnerUserId="1510" LastActivityDate="2010-11-06T10:06:42.633" Title="Testing sensors?" Tags="&lt;sensor&gt;&lt;best-practice&gt;" AnswerCount="3" />
  <row Id="6291" PostTypeId="2" ParentId="6288" CreationDate="2010-11-05T20:52:32.613" Score="0" ViewCount="" Body="&lt;p&gt;Consider the Renesas HAT2266H - 60V, 9.2 milliohm. It's in a SM package that's a little easier to solder than the Vishay PowerPAK (especially as a rework - trust me, I work with those PowerPAKs and without a hot air tool, forget it)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://documentation.renesas.com/jpn/products/transistor/rej03g1370_hat2266hds.pdf&quot; rel=&quot;nofollow&quot;&gt;Link to datasheet&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-05T20:52:32.613" />
  <row Id="6292" PostTypeId="2" ParentId="6290" CreationDate="2010-11-05T21:00:41.610" Score="1" ViewCount="" Body="&lt;p&gt;It really depends on the manufacturers quality standards. Some more expensive components/chips are 100% tested. Some cheaper devices are tested through sampling, 1 to 10, 1 to 1000. In this case they try to sample at least one unity from each package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should also consider storage and transportation. Accelerometers can be more sensitive to vibration than other circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find the ratio of defective/working items/sensors from the history of that specific vendor/manufacturer. This is done in bigger manufacturers when planning new products or building costs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, if the quantity is low, I'd advice you to test all of them. Extra care is never enough, nothing is worst then build the whole board and try to find the defective component.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-05T21:00:41.610" />
  <row Id="6293" PostTypeId="2" ParentId="6283" CreationDate="2010-11-05T21:07:58.060" Score="1" ViewCount="" Body="&lt;p&gt;You could make the lab experiences with a simulator. Being a computer scientist, it will be easier to you in order to learn how to use them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are lots of good free simulators ex: &lt;a href=&quot;http://embedded.eecs.berkeley.edu/pubs/downloads/spice/&quot; rel=&quot;nofollow&quot;&gt;spice&lt;/a&gt; or &lt;a href=&quot;http://sourceforge.net/projects/ktechlab/&quot; rel=&quot;nofollow&quot;&gt;KTechlab&lt;/a&gt; (a complete IDE for simulator, even microcontrolers).&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-05T21:07:58.060" />
  <row Id="6294" PostTypeId="2" ParentId="6290" CreationDate="2010-11-05T21:36:43.487" Score="2" ViewCount="" Body="&lt;p&gt;The chances of a bad sensor (if you're buying 1-10 units) is probably acceptably low.  I think you'll notice if you do any testing of your device when the sensor is installed.  But a dedicated method for testing just the sensor might be a little onerous.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-05T21:36:43.487" />
  <row Id="6295" PostTypeId="1" AcceptedAnswerId="6299" CreationDate="2010-11-05T22:08:57.870" Score="3" ViewCount="194" Body="&lt;p&gt;I have to make a filter with DSPIC33 and I want a program that design the filter (there are a lot), yet export code to DSPIC (in c, any compiler or assembly).&lt;/p&gt;&#xA;" OwnerUserId="1613" LastActivityDate="2010-11-06T21:23:07.673" Title="Does somebody know about a tool to design filters for DSPIC?" Tags="&lt;filter&gt;&lt;dspic&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="6296" PostTypeId="2" ParentId="6250" CreationDate="2010-11-05T22:10:02.577" Score="3" ViewCount="" Body="&lt;p&gt;You could try using an audio transformer to get a better match between the output impedance of the amp and your low-impedance speakers. Transformers match impedance by the square of their turns ratio, so if your device has an 8 ohm output, to match a 2.5 ohm load you'd want a ratio of sqrt(8/2.5), or about 1.8:1. Using a 2:1 transformer would make a 2.5 ohm load look like 4*2.5=10 ohms, which would still be a closer match to 8 than 2.5 is. &lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-05T22:10:02.577" />
  <row Id="6297" PostTypeId="1" CreationDate="2010-11-05T22:53:08.710" Score="6" ViewCount="297" Body="&lt;p&gt;Does anyone have any references/examples for detailed circuitry for time-of-flight laser distance measurements - schematics, appnotes etc.?&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-22T18:34:38.137" Title="Any published designs for time-of-flight laser distance measurement" Tags="&lt;laser&gt;&lt;distance&gt;" AnswerCount="3" CommentCount="7" FavoriteCount="1" />
  <row Id="6298" PostTypeId="2" ParentId="6259" CreationDate="2010-11-05T23:08:27.410" Score="1" ViewCount="" Body="&lt;p&gt;Mechanical wattmeter is essentially a motor with voltage and current sense windings. The velocity of motor is proportional to multiplication of voltage by current. In case if the multiplication gives negative result, the motor will rotate backwards.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-05T23:08:27.410" />
  <row Id="6299" PostTypeId="2" ParentId="6295" CreationDate="2010-11-05T23:17:06.903" Score="3" ViewCount="" Body="&lt;p&gt;Microchip sells such software: &lt;a href=&quot;http://www.microchipdirect.com/productsearch.aspx?Keywords=SW300001&quot; rel=&quot;nofollow&quot;&gt;http://www.microchipdirect.com/productsearch.aspx?Keywords=SW300001&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively if you don't want to pay, you can use any FIR or IIR filter design software you want to come up with your coefficients, implementing the filter on the dsPIC is really easy with microchip's DSP library which is included in the C30 compiler, which I assume your using.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-05T23:17:06.903" CommentCount="3" />
  <row Id="6300" PostTypeId="2" ParentId="6297" CreationDate="2010-11-05T23:18:16.513" Score="0" ViewCount="" Body="&lt;p&gt;You can look at current state of the art for Lunar Distance measurement &lt;a href=&quot;http://en.wikipedia.org/wiki/Apache_Point_Observatory_Lunar_Laser-ranging_Operation&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Apache_Point_Observatory_Lunar_Laser-ranging_Operation&lt;/a&gt;&#xA;I think that this materials are public property. There is another link there to Single Photon Avalanche Photodiodes &lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-05T23:18:16.513" CommentCount="1" />
  <row Id="6301" PostTypeId="1" AcceptedAnswerId="6302" CreationDate="2010-11-05T23:28:35.297" Score="2" ViewCount="217" Body="&lt;p&gt;What is the difference between a ceramic capacitor of the same dielectric, but different voltage rating?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would the lower voltage one have lower ESR or ESL?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;X7R 10uF 4V &lt;/p&gt;&#xA;&#xA;&lt;p&gt;as compared to a&lt;/p&gt;&#xA;&#xA;&lt;p&gt;X7R 10uF 10V&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-03-16T17:31:21.900" Title="What is the difference between a ceramic capacitor of the same dielectric, but different voltage rating?" Tags="&lt;capacitor&gt;&lt;ceramic&gt;" AnswerCount="5" />
  <row Id="6302" PostTypeId="2" ParentId="6301" CreationDate="2010-11-05T23:40:40.020" Score="7" ViewCount="" Body="&lt;p&gt;ESL is almost entirely determined by lead inductance, so the size and type of the package determine this value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ESR is a function of many things, but one of them is dielectric thickness, as thickness increases so does ESR.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage rating is a function of dielectric strength and thickness.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, if a package size is fixed, say both 0805, you should expect the same or extremely close ESL, while the dielectric strength or thickness would need to have increased to increase the voltage rating, so ESR would be higher.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This isn't a firm rule, remember that ESR varies with frequency.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-06T01:18:10.060" LastActivityDate="2010-11-06T01:18:10.060" />
  <row Id="6303" PostTypeId="1" AcceptedAnswerId="6309" CreationDate="2010-11-05T23:45:08.083" Score="3" ViewCount="136" Body="&lt;p&gt;I have 9V Li-ion battery. If I apply regulated 9V to it, will it recharge?&#xA;What about other kinds of rechargeable batteries?&lt;/p&gt;&#xA;" OwnerUserId="1298" LastActivityDate="2010-11-06T23:08:02.877" Title="Is it safe to recharge a battery without a specific device?" Tags="&lt;battery&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="6304" PostTypeId="2" ParentId="4604" CreationDate="2010-11-05T23:50:38.280" Score="3" ViewCount="" Body="&lt;p&gt;Complementing &quot;O Engenheiro&quot; answer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ghielectronics.com/product/129&quot; rel=&quot;nofollow&quot;&gt;GHI EMX US$ 299.95&lt;/a&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/Zhtad.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;72 MHz 32-bit ARM 7 Processor&lt;/li&gt;&#xA;&lt;li&gt;16MB RAM and 4.5MB FLASH&lt;/li&gt;&#xA;&lt;li&gt;320 x 240 3.5&quot; TFT Display with touch screen.&lt;/li&gt;&#xA;&lt;li&gt;RJ-45 Ethernet connector.&lt;/li&gt;&#xA;&lt;li&gt;GHI WiFi-Expansion compatible.&lt;/li&gt;&#xA;&lt;li&gt;Standard JTAG connector (only available for GHI partners).&lt;/li&gt;&#xA;&lt;li&gt;TFT signals exposed.&lt;/li&gt;&#xA;&lt;li&gt;GPIO signals with interrupts exposed on 0.1&quot; header pins with on-board pin descriptions.&lt;/li&gt;&#xA;&lt;li&gt;2 SPI Master bus (8/16bit).&lt;/li&gt;&#xA;&lt;li&gt;I2C interface.&lt;/li&gt;&#xA;&lt;li&gt;4 exposed UART (serial ports), one RS232 interface with hardware handshaking.&lt;/li&gt;&#xA;&lt;li&gt;7 analog inputs (ADC), 2 are used with touch screen.&lt;/li&gt;&#xA;&lt;li&gt;1 analog output (DAC).&lt;/li&gt;&#xA;&lt;li&gt;2 CAN interfaces, CAN 1 is connected to CAN PHY with 9-DSUB interface.&lt;/li&gt;&#xA;&lt;li&gt;6 PWM signals.&lt;/li&gt;&#xA;&lt;li&gt;One-wire interface support&lt;/li&gt;&#xA;&lt;li&gt;SD/MMC card connector with spring.&lt;/li&gt;&#xA;&lt;li&gt;USB Device port&lt;/li&gt;&#xA;&lt;li&gt;USB Host port&lt;/li&gt;&#xA;&lt;li&gt;XBee module socket.&lt;/li&gt;&#xA;&lt;li&gt;UEXT interface for easy expansions such as GPS, MP3 decoder or 3-axis accelerometer.&lt;/li&gt;&#xA;&lt;li&gt;Real Time Clock backup battery.&lt;/li&gt;&#xA;&lt;li&gt;LEDs and push buttons.&lt;/li&gt;&#xA;&lt;li&gt;On-board Piezo.&lt;/li&gt;&#xA;&lt;li&gt;Powered by USB or DC power (input 6 volts through 2.1mm power connector).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://devicesolutions.net/Products/TahoeII.aspx&quot; rel=&quot;nofollow&quot;&gt;Tahoe-II&lt;/a&gt; &lt;a href=&quot;http://app.arrownac.com/aws/pg_webc?s=P&quot; rel=&quot;nofollow&quot;&gt;US$ 399.00&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/1lrZy.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Meridian CPU (ARM920 @ 100MHz)&lt;/li&gt;&#xA;&lt;li&gt;8Mbytes SDRAM and 4Mbytes Flash&lt;/li&gt;&#xA;&lt;li&gt;3.5” Landscape TFT LCD with touch-screen&lt;/li&gt;&#xA;&lt;li&gt;9 user input buttons&lt;/li&gt;&#xA;&lt;li&gt;RS232 serial (DB9)&lt;/li&gt;&#xA;&lt;li&gt;USB Function&lt;/li&gt;&#xA;&lt;li&gt;Ethernet&lt;/li&gt;&#xA;&lt;li&gt;Accelerometer, with support for event notification including free-fall detection&lt;/li&gt;&#xA;&lt;li&gt;SD Card interface&lt;/li&gt;&#xA;&lt;li&gt;Temperature sensor and 2x ADC channels&lt;/li&gt;&#xA;&lt;li&gt;Interface for XBee wireless module (and additional ADC channels if fitted)&lt;/li&gt;&#xA;&lt;li&gt;PWM output&lt;/li&gt;&#xA;&lt;li&gt;Expansion connectors that expose GPIO, I2C, SPI and UART signals&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="1298" LastEditorDisplayName="" LastEditDate="2010-11-05T23:57:50.987" LastActivityDate="2010-11-05T23:57:50.987" />
  <row Id="6305" PostTypeId="1" AcceptedAnswerId="6311" CreationDate="2010-11-06T00:36:20.097" Score="0" ViewCount="96" Body="&lt;p&gt;I'm looking for a high side current monitor which can measure 0-3A on a 12V rail with either a built in sense resistor or with a hall effect current sensor. I'm also space constrained, to SOT-23 or so in size. Does anyone have any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-06T03:32:55.573" Title="Measuring current drawn on a 12V rail" Tags="&lt;current-measurement&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="6306" PostTypeId="2" ParentId="6283" CreationDate="2010-11-06T00:47:29.757" Score="1" ViewCount="" Body="&lt;p&gt;Parallax has a series of education kits that combine learning electronics with their embedded processors.  The &lt;a href=&quot;http://www.parallax.com/Products/Microcontrollers/BASICStampProgrammingKits/tabid/136/CategoryID/11/List/0/SortField/0/Level/a/ProductID/313/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;BASIC Stamp Activity Kit&lt;/a&gt; is specifically designed for beginners learning about electronics in conjunction with a microcontroller.  The &lt;a href=&quot;http://www.parallax.com/Store/Microcontrollers/PropellerProgrammingKits/tabid/144/ProductID/415/List/0/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;Propeller Education Kit - 40 pin DIP Version&lt;/a&gt; is a somewhat more advanced kit which includes one of their Propeller microcontrollers with 8 cores (which they call cogs).  Both sell for $100.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also have a number of other analog and digital kits &lt;a href=&quot;http://www.parallax.com/Store/Education/KitsandBoards/tabid/182/List/0/CategoryID/67/Level/a/SortField/0/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-11-06T00:47:29.757" />
  <row Id="6307" PostTypeId="2" ParentId="3427" CreationDate="2010-11-06T01:14:11.237" Score="0" ViewCount="" Body="&lt;p&gt;USB devices have no base address, they are not part of the address space of the CPU, much like a server on the internet is not part of your address space.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And everything about USB to parallel adapters has been said in this tread already, they usually do not work for anything but printing.&lt;/p&gt;&#xA;" LastActivityDate="2010-11-06T01:14:11.237" />
  <row Id="6308" PostTypeId="2" ParentId="6303" CreationDate="2010-11-06T01:25:38.557" Score="1" ViewCount="" Body="&lt;p&gt;Yeah. It'll recharge for a few seconds. But then it explodes, bummer. Battery chargers exist for good reason. &lt;/p&gt;&#xA;" OwnerUserId="1829" LastActivityDate="2010-11-06T01:25:38.557" CommentCount="1" />
  <row Id="6309" PostTypeId="2" ParentId="6303" CreationDate="2010-11-06T02:28:06.193" Score="3" ViewCount="" Body="&lt;p&gt;See the graph at endolith's link: &lt;a href=&quot;http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries&quot; rel=&quot;nofollow&quot;&gt;http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't need an official charger, but a constant voltage isn't what you need either.  You need a constant current, followed by a constant voltage, followed by switching off the charging circuit.  I have used a standard adjustable-current bench supply for this.  It works fine if the current and voltage limits are set appropriately.  (For safety's sake, don't charge the battery all the way.  If it starts to feel warm, shut off the charger.)&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-06T02:28:06.193" CommentCount="1" />
  <row Id="6310" PostTypeId="2" ParentId="6259" CreationDate="2010-11-06T03:18:26.510" Score="1" ViewCount="" Body="&lt;p&gt;DC Energy consumption is fairly simple, as others have stated. You sample the voltage and current at regular intervals, interpolate, and integrate for total power consumption.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;AC power meters like the Kill-A-Watt have to do a bit more, because with AC systems&lt;br&gt;&#xA; &lt;code&gt;current * voltage != power&lt;/code&gt; for reactive loads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, what the device has to do is sample at a frequency much higher than the AC carrier for a short period of time, and integrate the product of the &lt;code&gt;voltage * current&lt;/code&gt; for that period. This enables the device to account for any phase difference between the current and voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.ladyada.net/make/tweetawatt/software.html&quot; rel=&quot;nofollow&quot;&gt;Tweet-a-Watt project&lt;/a&gt; has more info, though it is not a great example, as they are sampling at too slow a frequency to get highly accurate results.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-11-06T03:18:26.510" />
  <row Id="6311" PostTypeId="2" ParentId="6305" CreationDate="2010-11-06T03:32:55.573" Score="0" ViewCount="" Body="&lt;p&gt;Maybe use an Allegro linear hall sensor, and lay out a current loop under the SOT-23 package? I haven't done the math. Use Ampère's Law and the sensor datasheet to see how likely this is to work.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-06T03:32:55.573" CommentCount="1" />
  <row Id="6312" PostTypeId="1" AcceptedAnswerId="6314" CreationDate="2010-11-06T04:38:21.930" Score="5" ViewCount="154" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand that this is a really basic question, but, I've been unable to really understand electrical terminology for some reason. What exactly is an amp? How does it correspond to a watt?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And:&#xA;How does a watt correspond to a volt?&#xA;What does the frequency of electricity refer to? (Hz, 50/60)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please be as specific, and laymeny as possible :).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&#xA;Since I didn't get anyone yelling at me for talking about adding a few more questions, here goes:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is a volt? My understanding of it is the difference between the neutral and phase, but, this doesn't make it any clearer. If anyone can help out with more information, with an analogy or two, plus some technical information, I'd appreciate it very much!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What does the &quot;earth&quot;/ground portion of the circuit do? How does it help safety? If it helps safety, why aren't all plugs 3-pin instead of 2-pin?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hypothetical:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I plugged in two wires to a socket, and put the other end into something conductive (for instance, a bucket of water), assuming the breaker doesn't go off (if it would, why would it?) after I remove said wires(or turn off the socket), does the water &quot;hold&quot; the charge? Is it in any way unsafe?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For what it's worth, I'm assuming no. The current flows from phase-neutral, the water simply facilitates this. Right? If I'm right, I assume this means that I am in some way &quot;using&quot; the electricity? How does this differ if I for instance put the wires up against a block of wood? How does it differ if I stick the wires on myself?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I apologize if some of these questions show a fundamental mis-understanding of electricity. If they do, smack me across the head and point me to a resource that will educate me and help me answer such questions myself. These questions have plagued the back of my mind for a while, but I've never found the right place to ask.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have more such questions, both hypothetical, and real (how does a stabilizer work, why is it required? Why do motors require 2x as much electricity to start up vs to run? Why can't this be optimized/why hasn't it been fixed yet?). I'm hoping I'll be able to answer the hypothetical ones myself once I gain more of an understanding, with your help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope questions at these level (and their answers) are useful to at least one other person!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again, Thanks to whoever helps me out!&lt;/p&gt;&#xA;" LastActivityDate="2010-11-06T15:17:22.047" Title="What is an amp (and other such basic questions) in the simplest possible terms?" Tags="&lt;voltage&gt;&lt;basic&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="6313" PostTypeId="1" CreationDate="2010-11-06T05:32:05.893" Score="1" ViewCount="116" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/6241/making-a-binary-counter-for-my-breadboard&quot;&gt;Making a binary counter for my breadboard.&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;How would I get this chip hooked up so I could just get it to output binary count sequence?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WVMnn.png&quot; alt=&quot;image of the chip that is going to be used.&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1687" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-24T22:55:30.307" LastActivityDate="2010-11-24T22:55:30.307" ClosedDate="2010-11-29T01:32:01.233" Title="Simulating 74LS93D in NI Multisim." Tags="&lt;prototyping&gt;&lt;homework&gt;" CommentCount="2" />
  <row Id="6314" PostTypeId="2" ParentId="6312" CreationDate="2010-11-06T06:32:46.627" Score="6" ViewCount="" Body="&lt;p&gt;An ampere is a measure of how many electrons move past a point every second.  1 ampere = 6,241,510,000,000,000,000 electrons per second.  A pipe with water moving through it could be measured in gallons per second.  Same idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Watts are not just used in electronics.  They're a measure of the rate at which energy is used or transferred.  A firecracker uses up chemical energy faster than a candle, even if the total energy is the same for both, so the firecracker has a higher power output for a shorter time.  Likewise you could use two identical batteries in different ways.  If one way uses more power, the battery will not last as long.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1 horsepower is about 750 watts, if you're familiar with cars.  Just different ways to measure the same thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;watts = volts * amps.  So a 60 W bulb plugged into a 120 V socket will be drawing 1/2 an amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;60 W = 120 V * 0.5 A&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In AC circuits, the electrons are vibrating back and forth instead of going in a continuous loop.  The frequency is just the number of vibrations per second.  50 Hz means they move back and forth 50 times per second.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's important to understand the difference between current flow and energy flow, though.  The actual electrons in a wire don't move very fast.  In a DC circuit, the actual electron flow around the loop might be at the speed of molasses.  The reason flipping a switch causes the light to turn on very quickly is because the &lt;em&gt;energy&lt;/em&gt; flow is very fast.  The energy is carried by waves in the electrons, not the electrons themselves.  They repel each other, so when you push some extra electrons onto a wire, the others nearby jump away, which causes more near them to jump away, and so on down the wire.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-06T15:17:22.047" LastActivityDate="2010-11-06T15:17:22.047" CommentCount="2" />
  <row Id="6315" PostTypeId="1" AcceptedAnswerId="6371" CreationDate="2010-11-06T09:02:06.530" Score="4" ViewCount="238" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was planning on learn an HDL (preferably verilog as I have to take a course in it in subsequent semesters). My initial plan was to first learn the syntax and then implement all the digital systems I studied in my digital electronics course using HDL. But just out of curiosity, is there a book which would combine teaching computer architecture with HDL implementation? I think that would be much more fun.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-11-07T15:40:32.197" LastActivityDate="2010-11-08T13:25:12.090" Title="Exercise based book to learn Verilog/vhdl?" Tags="&lt;vhdl&gt;&lt;verilog&gt;&lt;hdl&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="2" />
  <row Id="6316" PostTypeId="1" AcceptedAnswerId="6337" CreationDate="2010-11-06T09:13:18.467" Score="2" ViewCount="375" Body="&lt;p&gt;What is the difference between a coupled inductor and an actual transformer? The LT3757 datasheet mentions that I need a coupled inductor for the SEPIC to work&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-07T03:58:01.037" Title="Coupled inductor vs an actual transformer?" Tags="&lt;inductor&gt;" AnswerCount="4" />
  <row Id="6317" PostTypeId="2" ParentId="6301" CreationDate="2010-11-06T09:21:26.817" Score="0" ViewCount="" Body="&lt;p&gt;What does the datasheet for the capacitors say?&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-06T09:21:26.817" CommentCount="0" />
  <row Id="6318" PostTypeId="2" ParentId="6312" CreationDate="2010-11-06T10:03:32.227" Score="3" ViewCount="" Body="&lt;p&gt;You'll find an excellent and clear explanation of the physics behind electricity in the article: &lt;a href=&quot;http://amasci.com/elect/vwatt1.html&quot; rel=&quot;nofollow&quot;&gt;How are Watts, Ohms, Amps and Volts related?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;He doesn't explain it like convertional textbooks. He is a physicist, not a mathematician, and explains it as such. When I was learning, that small article cleared up a lot of confusion I had and I refer back to it frequently for a refresher on the basics. &lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-11-06T10:49:44.010" LastActivityDate="2010-11-06T10:49:44.010" CommentCount="3" />
  <row Id="6319" PostTypeId="2" ParentId="6290" CreationDate="2010-11-06T10:06:42.633" Score="1" ViewCount="" Body="&lt;p&gt;Many accelerometers have internal test hardware, which apply known forces electrostatically to the sensing element- this would be what manufacturers use for production test. You would not normally expect any device like this to be faulty on arrival - a significant part of the price you pay for any semiconductor device is testing. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-06T10:06:42.633" />
  <row Id="6320" PostTypeId="2" ParentId="6316" CreationDate="2010-11-06T10:34:29.427" Score="0" ViewCount="" Body="&lt;p&gt;The inductor stores energy as magnetic flux, the transformer just transfers energy magnetically.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;.. as far as I know anyway:)&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-06T10:34:29.427" CommentCount="2" />
  <row Id="6321" PostTypeId="1" AcceptedAnswerId="6327" CreationDate="2010-11-06T12:25:50.533" Score="4" ViewCount="119" Body="&lt;p&gt;Is it possible to create a coupled inductor (with high coupling coefficient) by just placing two inductors very close to each other on the PCB? (Even as far as placing them on top of each other.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-07T23:48:01.207" Title="Creating a coupled inductor with two discrete inductors" Tags="&lt;inductor&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="6322" PostTypeId="2" ParentId="6321" CreationDate="2010-11-06T12:41:49.237" Score="4" ViewCount="" Body="&lt;p&gt;In short: No. For a good coupling coefficient, it even takes a lot of consideration to arrange the windings on one bobbin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For power inductors (isolated flyback/buck), don't even try. For measurement or signal applications, it might work, but will be very hard.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-11-06T12:41:49.237" CommentCount="1" />
  <row Id="6323" PostTypeId="1" AcceptedAnswerId="6326" CreationDate="2010-11-06T12:48:57.980" Score="5" ViewCount="226" Body="&lt;p&gt;I am dealing with a 0.01R 500mW resistor. It is a current sense resistor and measures the current flowing through a MOSFET and inductor. According to simulations, when the supply starts up, the RMS current is very high (~3A) for about 1 millisecond, and the resistor will be exposed to pulses of ~1.2W. The pulses then drop down to 200mW, and the RMS is around 125mW. Is it okay to briefly exceed the ratings of any resistor? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I have to pick a 2W resistor it will be much bigger, so I'd like to use a smaller resistor, but reliability is a high priority for this product.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-06T13:07:09.873" LastActivityDate="2010-11-07T03:57:43.170" Title="Is it okay to briefly exceed a resistor's power rating in a high-reliability product?" Tags="&lt;power&gt;&lt;resistor&gt;&lt;reliability&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="6324" PostTypeId="2" ParentId="6323" CreationDate="2010-11-06T12:54:37.253" Score="0" ViewCount="" Body="&lt;p&gt;3A through 0.01R is 90mW, not 1.2W. 1.2W would be about 11 amps.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-06T12:54:37.253" CommentCount="1" />
  <row Id="6325" PostTypeId="2" ParentId="6316" CreationDate="2010-11-06T13:14:10.287" Score="1" ViewCount="" Body="&lt;p&gt;I am no absolute expert on SEPIC converters, but as far as I can tell from the data sheet, individual inductors should work: &quot;As shown in Figure 1, the SEPIC converter contains two inductors: L1 and L2. L1 and L2 can be independent, but can also be wound on the same core, since identical voltages are applied to L1 and L2 throughout the switching cycle.&quot; A coupled inductor may have been suggested because it uses less board space: &quot;By making L1 = L2, and winding them on the same core, the value of inductance in the preceding equation is replaced by 2L...&quot;&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-11-06T13:14:10.287" />
  <row Id="6326" PostTypeId="2" ParentId="6323" CreationDate="2010-11-06T13:23:44.910" Score="8" ViewCount="" Body="&lt;p&gt;The data sheet should mention the peak power or current capabilities of the resistor. It is usually much higher than the mean power rating, but if it is not specified anywhere, I would rather not rely on it.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-11-06T13:23:44.910" />
  <row Id="6327" PostTypeId="2" ParentId="6321" CreationDate="2010-11-06T13:27:39.443" Score="3" ViewCount="" Body="&lt;p&gt;Normally you put a magnetic material between them. It becomes a &lt;a href=&quot;http://en.wikipedia.org/wiki/Magnetostatics&quot; rel=&quot;nofollow&quot;&gt;magnetostatics&lt;/a&gt; problem instead of an electrostatics. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This core of magnetic material directs all of their magnetic field to be shared, minus a small leakage. You need this core for high coupling coefficient. What you want is called a &lt;a href=&quot;http://en.wikipedia.org/wiki/Transformer&quot; rel=&quot;nofollow&quot;&gt;transformer&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is an image of what you need:&#xA;&lt;img src=&quot;http://i.imgur.com/XgVfL.png&quot; alt=&quot;image of an Ideal transformer.&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-06T13:27:39.443" />
  <row Id="6328" PostTypeId="2" ParentId="6312" CreationDate="2010-11-06T13:37:39.963" Score="1" ViewCount="" Body="&lt;p&gt;Endolith explained the current very succinctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Volage is a measure of how much potential energy the current has. You are probably used to potential energy from other subjects. mgh is a common equation for potential energy when you have a gravitational field and you raise a mass into the air. when you let the mass go it will have an amount of potential relational to its height and its mass.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have water, the higher you pump it into the air the more potential energy the water will have. If you then bring the pipe all the way back down to the bottom where there is a turbine that resists the flow of current(current of water) then it will do work on that turbine. The turbine will receive power relative to the amount of water that is moving(the current) and the height the water was(its potential).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope that helps.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-06T13:37:39.963" CommentCount="1" />
  <row Id="6329" PostTypeId="2" ParentId="6295" CreationDate="2010-11-06T13:40:16.467" Score="1" ViewCount="" Body="&lt;p&gt;I thought that matlab had a solution for filter design where you could export to dsPICs. I saw a lot about it, I can look into it later.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; After Research&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Take a look at the &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/MATLAB_Device_Blocks_51771b.pdf&quot; rel=&quot;nofollow&quot;&gt;application note that Microchip about it&lt;/a&gt;. I also found that there are a few notes at &lt;a href=&quot;http://www.kerhuel.eu/RTWdsPIC/download.html&quot; rel=&quot;nofollow&quot;&gt;http://www.kerhuel.eu/RTWdsPIC/download.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I cannot guarantee that this will get the job done for you, just trying to show you rapid prototyping options.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-06T16:50:54.843" LastActivityDate="2010-11-06T16:50:54.843" CommentCount="4" />
  <row Id="6330" PostTypeId="2" ParentId="5294" CreationDate="2010-11-06T13:56:16.863" Score="2" ViewCount="" Body="&lt;p&gt;Have you considered using LEDs? It can take a bit of work to get the spectrum right, but they dont produce any EMI, and in my experience, they tend to be more energy efficient than CFLs.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Edit:&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;The other main problem for LEDs is their higher cost. LEDs last even longer than CFLs, so it evens out in the long run, but it does put some prohibitive front-loading on LEDs. OTOH, people who worry about front-loading more than long-term efficiency probably wouldn't switch away from incandescents in the first place. (As far as I know, CFLs are still more expensive (initially) than incandescents.)&lt;/p&gt;&#xA;" OwnerUserId="1859" LastEditorUserId="1859" LastEditorDisplayName="" LastEditDate="2010-11-11T01:19:03.863" LastActivityDate="2010-11-11T01:19:03.863" CommunityOwnedDate="2010-11-30T23:44:02.540" CommentCount="4" />
  <row Id="6331" PostTypeId="1" AcceptedAnswerId="6332" CreationDate="2010-11-06T14:01:11.663" Score="3" ViewCount="215" Body="&lt;p&gt;I want to step down 5V to 3.3V at around 250mA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I see it, there are two options to consider:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Buck: more space, higher cost&lt;/li&gt;&#xA;&lt;li&gt;LDO: less space, lower cost, more difficult to remove heat(?), less efficient(?)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;What I am wondering is will the LDO be more efficient and better at doing this job? I've heard things like 6V to 5V solutions usually use LDO's instead of buck regulators because they are more efficient, but I'm wondering if this works for 5V to 3.3V?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-06T21:27:13.817" Title="For a small Vin-Vout difference, is it worth using an LDO vs a buck regulator?" Tags="&lt;buck&gt;&lt;ldo&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="6332" PostTypeId="2" ParentId="6331" CreationDate="2010-11-06T14:25:29.950" Score="3" ViewCount="" Body="&lt;p&gt;Dropping 5 to 3.3 V at 250 mA will mean having to lose 0.425 Watt in the LDO, you will need a massive heat sink to make that work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An LDO will never be more efficient than a buck converter, unless you need so little current that the power used by the regulator itself becomes an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a mis-designed PCB right now where I tried doing exactly what you are proposing to turn 5 V into 3.3V at 200 mA and even though I have a large'ish copper plane as a heatsink the LDO still reaches 80 deg C in a few seconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm currently redesigning my power supply to use a MC34063A converter in stead.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-06T14:25:29.950" CommentCount="6" />
  <row Id="6333" PostTypeId="2" ParentId="6331" CreationDate="2010-11-06T14:31:18.210" Score="4" ViewCount="" Body="&lt;p&gt;LDOs will not be more efficient: (5V-3.3V)*250mA = 0.425W. Already quite a lot for smallish (SOT-23) LDOs, at least a DPAK is likely necessary. The design (not the efficiency) could be improved with series resistors at the LDO's input to take heat away from the IC and into the resistors, but make sure the voltage drop doesn't get too big for the highest current that is required. Might well be worth using a buck.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-11-06T14:31:18.210" />
  <row Id="6334" PostTypeId="1" AcceptedAnswerId="6335" CreationDate="2010-11-06T15:18:40.600" Score="3" ViewCount="281" Body="&lt;p&gt;0402 packages - absolutely tiny. I'm wondering if it's possible to reflow solder them using a hotplate/skillet or toaster oven. Does anyone have any experience with doing this?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-19T01:08:15.293" LastActivityDate="2011-01-19T01:08:15.293" Title="Boundary of DIY soldering: is it possible to reflow 0402?" Tags="&lt;soldering&gt;&lt;surface-mount&gt;" AnswerCount="4" />
  <row Id="6335" PostTypeId="2" ParentId="6334" CreationDate="2010-11-06T15:36:25.710" Score="4" ViewCount="" Body="&lt;p&gt;Not a big problem, although rather more fussy about the right amount of paste and more prone to tombstoning than 0603's. Much more viable with a stencil than with dispensed paste.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-06T15:36:25.710" CommentCount="4" />
  <row Id="6336" PostTypeId="2" ParentId="6331" CreationDate="2010-11-06T15:39:32.077" Score="1" ViewCount="" Body="&lt;p&gt;Not quite true than an LDO will never be more efficient, as at some point the switching losses and supply current for the switcher will outweigh the benefits. &#xA;On, and 34063A is a pretty lousy converter as swictehrs go - for 5v to 3v3 it wouldn't surprise me if the benefit is minimal. There are much better converters for this voltage range. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-06T15:39:32.077" />
  <row Id="6337" PostTypeId="2" ParentId="6316" CreationDate="2010-11-06T15:42:20.190" Score="4" ViewCount="" Body="&lt;p&gt;You don't have to use coupled inductors in a SEPIC configuration.  The main advantage is that you can get by with lower inductance windings.  If the two inductors are closely coupled, the ripple current is divided between them and the required inductance is halved.  So if you want to replace a coupled inductor which has two 3.3 uH windings, you would need two individual inductors of 6.6 uH each at the same current rating.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-11-06T15:42:20.190" CommentCount="1" />
  <row Id="6338" PostTypeId="2" ParentId="6323" CreationDate="2010-11-06T15:47:27.133" Score="0" ViewCount="" Body="&lt;p&gt;If there are any circuit failures possible that would result in the peak current becoming the steady-state current, then you need to allow for the larger power rating.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-11-06T15:47:27.133" CommentCount="1" />
  <row Id="6339" PostTypeId="1" AcceptedAnswerId="6340" CreationDate="2010-11-06T15:57:00.070" Score="3" ViewCount="183" Body="&lt;p&gt;What I need is: when I turn on a IR led, a receiver circuit in the other side would have 5V or 0V depending on the state of the transmitter. Simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a IR transmitter and a photo-diode for receive, those used on every IR control and receiver. I don't know how the photo-diode works so how should the circuit be? Should I use a transistor configured in saturation / cut-off working with the receiver?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Feel free to recommend me. Thanks&lt;/p&gt;&#xA;" OwnerUserId="1613" LastActivityDate="2010-11-08T17:00:42.567" Title="Simplest remote IR?" Tags="&lt;wireless&gt;&lt;infrared&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="6340" PostTypeId="2" ParentId="6339" CreationDate="2010-11-06T16:06:46.157" Score="1" ViewCount="" Body="&lt;p&gt;Phototransistor configured as an inverter:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;5V ----+&#xA;       |&#xA;       /&#xA;       \  47k&#xA;       / &#xA;       |&#xA;       +----- Logic output (inverted)&#xA;       |&#xA;  \   /&#xA;  \  |    NPN&#xA;      \&amp;gt;  Phototransistor&#xA;       |&#xA;      ---&#xA;       -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;A phototransistor is like a photodiode, but has a significantly increased gain. So when light shines on it (or IR, if it has an IR filter) it will pull down the output, conducting a few mA. A photodiode could do the same job, but you'd need a much greater (x100-1000) resistor, and this might be overwhelmed by the any load impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could put another inverter on the output to get a logic signal of the correct polarity (or to buffer it, as it won't take much load current.) Here is one possible inverter circuit:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;          5V ----+&#xA;                 |&#xA;                 /&#xA;                 \  10k&#xA;                 / &#xA;                 |&#xA;                 +--- output&#xA;                 |&#xA;          10k   /&#xA;Input ---/\/\/--|   NPN&#xA;                \&amp;gt;  2N3904&#xA;                 |&#xA;                ---&#xA;                 -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-06T16:42:29.123" LastActivityDate="2010-11-06T16:42:29.123" CommentCount="9" />
  <row Id="6341" PostTypeId="2" ParentId="6331" CreationDate="2010-11-06T16:07:56.107" Score="1" ViewCount="" Body="&lt;p&gt;Well I think I know of a simpler solution. You can use &lt;strong&gt;LM117/LM317&lt;/strong&gt; IC to do your job and since your current limit is &lt;strong&gt;250mA&lt;/strong&gt; this should be the best option and you don't have to worry about the heat as these can go up to 1.5A. The requirement here is the input voltage should be at least 1.5V more than the output voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used these even without any heat sink for such small currents and they go perfectly fine. Here's the data sheet hope this helps you and the circuit is is not that complex. For a safer side you can find out if you need the heat sink or not by using the formula provided in the data sheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.national.com/ds/LM/LM117.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.national.com/ds/LM/LM117.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2010-11-06T16:07:56.107" CommentCount="3" />
  <row Id="6342" PostTypeId="2" ParentId="6323" CreationDate="2010-11-06T16:22:30.010" Score="2" ViewCount="" Body="&lt;p&gt;sounds like you need to include inrush current limiting in your circuit.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-06T16:22:30.010" />
  <row Id="6343" PostTypeId="2" ParentId="6331" CreationDate="2010-11-06T17:19:43.830" Score="1" ViewCount="" Body="&lt;p&gt;Many have already given you an opinion on the power efficiency, I would just like to bring up some of the reasons I have seen others do this.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Noise immunity.  buck/bost regulators, more broadly [SMPS][1], have very poor noise characteristics. They almost guarantee harmonics at the switching frequency. LDOs do not, they create very smooth power.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Simplicity, you are only dropping a small voltage, keep your circuit clean and your components count low.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;This noise immunity is normally one of the main reasons I see this. LDOs cannot be beat on this note, you pay power to get clean output power. The specific reason LDOs are so popular is related to the fact that you can use a buck/boost to get your voltage just barely above the operating voltage of your LDO. I have seen this often in 5V circuits, they boost power to 5.5V and then LDO it to the 5V rail. This gives very low noise high quality power while only suffering a 1/11 power loss, still getting about 90% power efficiency off of the LDO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, from this perspective, you could always drop the voltage to 4V with a buck and LDO it, but I would just LDO it and make sure you have it connected to a low resistance thermal path so that the heat is easily dissipated. &lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-06T17:19:43.830" CommentCount="4" />
  <row Id="6344" PostTypeId="1" AcceptedAnswerId="6353" CreationDate="2010-11-06T20:49:25.740" Score="3" ViewCount="663" Body="&lt;p&gt;I have a &lt;a href=&quot;http://www.newegg.com/Product/Product.aspx?Item=N82E16889259013&quot; rel=&quot;nofollow&quot;&gt;Magnavox 42MF438B/27 42&quot; LCD TV&lt;/a&gt;.  The IR sensor (or something related) quit working after awhile, so we have been unable to use the remote.  Today, I was digging around behind the TV and noticed a &quot;Serv U.&quot; port on the back with what looks to be a standard 1/8&quot; jack.  I figured this was a serial port for firmware upgrades and what not.  Some quick googling revealed this assumption was correct... the manual calls it &quot;Service UART&quot;.  So I am assuming it is a standard 1/8&quot; TRS plug, one ground, one send, one receive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My hope is that I can send it commands... volume up/down, power on/off, etc. over this port.  Trouble is, I can't find any specs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know what the voltage this serial port runs at?  I'd rather not fry it with RS232 levels if it is just 3.3V.  Then, any thoughts on what the pinout might be?  Or, any safe way to find out?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, any thoughts on where I can find protocol spec?  I certainly have no problems poking around, but I'm hoping perhaps a Philips tech can help me out here a bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks a ton!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; I found &lt;a href=&quot;http://answers.yahoo.com/question/index?qid=20080127142336AA3gAmN&quot; rel=&quot;nofollow&quot;&gt;another message board post&lt;/a&gt; where someone's manual says, &quot;For use by authorized service personnel, for installers, integrators, do not connect RS232 without level shifter&quot;, so I think I am on the right track.  3.3V then I am guessing?  I think I have an old USB-&gt;cell phone cable around with the appropriate adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit #2:&lt;/strong&gt; &lt;a href=&quot;http://www.scribd.com/doc/26366292/Philips-q528e-Service-Training-Manual-Part2&quot; rel=&quot;nofollow&quot;&gt;I found a service manual&lt;/a&gt;!  It says their techs can connect with HyperTerminal... 38400 bps, 8/N/1.  It also says I can access &quot;Customer Service Mode (CSM)&quot; by keying in the code &lt;code&gt;123654&lt;/code&gt;.  For &quot;Service Default Mode (SDM)&quot;, &lt;code&gt;062596menu&lt;/code&gt; or for DVB-T Service Mode, &lt;code&gt;062593menu&lt;/code&gt;.  For &quot;Service Alignment Mode (SAM)&quot;, &lt;code&gt;0625961+&lt;/code&gt; (osd/status).  That last character may be an &quot;i&quot;, not sure.  Program display option code, &lt;code&gt;062598menu&lt;/code&gt;.  No specs on the port itself though, or what is in those modes.  Still digging...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit #3:&lt;/strong&gt; Seems the service cable adapter kit is called ComPair, or possibly ComPair II.&lt;/p&gt;&#xA;" OwnerUserId="1554" LastEditorUserId="1554" LastEditorDisplayName="" LastEditDate="2010-11-06T21:28:18.933" LastActivityDate="2010-11-07T02:16:42.470" Title="Philips/Magnavox LCD TV Service UART / ComPair" Tags="&lt;serial&gt;&lt;uart&gt;&lt;tv&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="6345" PostTypeId="2" ParentId="6295" CreationDate="2010-11-06T21:23:07.673" Score="3" ViewCount="" Body="&lt;p&gt;Best way is to design and simulate your filters and algorithms in matlab and then implement the functions by writing your own C code.  By using matlab you can tune your filters on real data for optimum results and then write your c code based on the initial values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At some point you will need to consider rounding and errors (for example real filter coefficents are floats in matlab) and you will probably want to implement them as integers on the pic to reduce the overhead of floating point arithmetic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have written your code and tested it, transfer it back to matlab to see the effects of the rounding errors, and optimise your filter coefficients there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This may sounds difficult, but in the long term it will give you a few things. Better understanding of the filters, better understanding of the dsPIC architecture and built in hardware (integer multiplier), understanding of rounding errors on the filter coefficents, and most importantly highly optimised code!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is the optimised code that you really want running on your dsPIC.  You will only be able to acheieve this by iterating between matlab and your c code (perhaps even assembly if you want to getter maximum performance out of the pic).&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-06T21:23:07.673" />
  <row Id="6346" PostTypeId="2" ParentId="6331" CreationDate="2010-11-06T21:27:13.817" Score="3" ViewCount="" Body="&lt;p&gt;depends on your requirements, for high efficiency digital circuit: buck.  For precision, low noise analog circuits, LDO!&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-06T21:27:13.817" CommentCount="1" />
  <row Id="6347" PostTypeId="2" ParentId="6344" CreationDate="2010-11-06T21:50:06.127" Score="1" ViewCount="" Body="&lt;p&gt;Here is one circuit that will clamp ±15V RS-232 levels to 0-3.3V (or so) logic levels.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;      1N4148&#xA;        |\     4.7k&#xA;Input --| &amp;gt;|--/\/\/\--+-------- Output&#xA;        |/            |&#xA;                      |  |&#xA;                   +-----+&#xA;                   | / \   3V zener diode&#xA;                    /___\  500mW&#xA;                      |&#xA;                     ---&#xA;                      -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This only handles the transmit voltages though, and won't amplify the logic levels for the receive (to the computer.) If you're lucky, your computer will recognise 3.3V as a logic high and 0V as a logic low. If not, you'll have to use a chip like a MAX232.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be very careful with this. Make certain it works as required, use a multimeter and 12V supply before plugging it in to verify it. The worst thing you could do is damage the UART processor, which could be the main processor, which would brick your TV.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-06T21:50:06.127" CommentCount="1" />
  <row Id="6348" PostTypeId="2" ParentId="6339" CreationDate="2010-11-06T23:01:15.927" Score="1" ViewCount="" Body="&lt;p&gt;Look at 3-pin 38 KHz IR receiver. Its best possible receiver part with very low cost.&#xA;If your signal channel can comply to return to zero requirement (no information bit=1 state of signal is longer than milliseconds) then you can use standard parts like this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry for radioshack reference, but its first link on google: &lt;a href=&quot;http://www.radioshack.com/product/index.jsp?productId=2049727&quot; rel=&quot;nofollow&quot;&gt;http://www.radioshack.com/product/index.jsp?productId=2049727&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-06T23:01:15.927" CommentCount="5" />
  <row Id="6349" PostTypeId="2" ParentId="6303" CreationDate="2010-11-06T23:08:02.877" Score="2" ViewCount="" Body="&lt;p&gt;No, it is definitely not safe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Li batteries and compatible chargers usually mate with more than just 2 wires. The battery must include termoswitch or thermometer circuit which is servo feedback to charger controller. The constant parameter of control loop is not a voltage or current, but top temperature over time figure to avoid fire damage.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-06T23:08:02.877" CommentCount="2" />
  <row Id="6350" PostTypeId="2" ParentId="6323" CreationDate="2010-11-06T23:15:02.497" Score="2" ViewCount="" Body="&lt;p&gt;It is OK if you are in I^2T window. This figure is typically applied to motors, not resistors, but still applicable for large resistors. Say if you know that 5W over 10Sec is a limit, then 50W over 1 sec is same limit. But for very small parts with very low thermal mass, its better to use equivalence 10 or 100 times shorter in time. Say 0.5W over 1sec is 5W over 0.1 sec.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So answer is yes. For your example in ms range it is ok if part is heavier than say 0.2..0.5 gram. This kind of parts is designed for precision, so the specs are about staying accurate within working currents. If you exceed the current 10 times for ms you only loose precision, but part is far from being destroyed or self desoldering.&lt;/p&gt;&#xA;" OwnerUserId="924" LastEditorUserId="924" LastEditorDisplayName="" LastEditDate="2010-11-07T03:01:44.843" LastActivityDate="2010-11-07T03:01:44.843" />
  <row Id="6351" PostTypeId="2" ParentId="6334" CreationDate="2010-11-06T23:23:30.150" Score="3" ViewCount="" Body="&lt;p&gt;While it is entirely possible to reflow them, hand soldering 0402s is not too hard with practice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Use a fine tipped iron, a magnifying glass and plenty of flux).&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-06T23:23:30.150" CommentCount="1" />
  <row Id="6352" PostTypeId="2" ParentId="6334" CreationDate="2010-11-06T23:30:16.893" Score="2" ViewCount="" Body="&lt;p&gt;There's nothing wrong with hand-soldering 0402 or even 0201 with practice. 0402 I can do without an inspection microscope, but 0201 is getting too small to do without one. Then again, I also solder 0.5mm TSSOP and TQFP packages without a magnifier or microscope. Just need to take your time, use flux and relax.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-11-06T23:30:16.893" />
  <row Id="6353" PostTypeId="2" ParentId="6344" CreationDate="2010-11-07T02:16:42.470" Score="3" ViewCount="" Body="&lt;p&gt;If you just need to shift the voltage levels, use a &lt;a href=&quot;http://en.wikipedia.org/wiki/MAX232&quot; rel=&quot;nofollow&quot;&gt;max232&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These chips are very dependable and resilient. I would suggest against building a logic shifting circuit.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-07T02:16:42.470" />
  <row Id="6354" PostTypeId="2" ParentId="6334" CreationDate="2010-11-07T02:57:08.560" Score="0" ViewCount="" Body="&lt;p&gt;I have no expirience in manual dispense, but I know the automatic and semiautomatic paste printing. Talking of how much manual effort is involved, consider this. When you are using oven for reflow step, then there are no hands involved. So the limit is defined only by 2 factors. Proper amount and type of solder and thermal profile.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Component placement is not critical, because reflow is automatically aligning components with wet forces. The geometry of footprints and solder masks is not manual either, just follow the specified footprint for each component. Thermal profile is easy to achieve with measurement, timing etc. For simple components (not a bga or 100 pin) the geometry of paste is not critical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So limit is in accuracy of amount of paste dispensed on a pad. &#xA;For manual dispense, I'd recommend create a syringe with some screw pusher and calibrate the amount of paste per angle of screw rotation. This must work for any sizes.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-07T02:57:08.560" />
  <row Id="6355" PostTypeId="2" ParentId="765" CreationDate="2010-11-07T02:59:02.960" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Simplest approach&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Place a small tube in a corner of the tank that is slightly larger in diameter than a ping pong ball.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Place an infrared LED on one side of the tube and a photoresistor opposite of the LED (by drilling a hole in the tube of it's opaque or placing on the outside if its transparent). Hot glue the electrical parts to waterproof them and drop the ping pong ball into the tube. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the water level raises or lowers to the point that the ping pong ball breaks the infrared beam you'll know it hit the desired level. This works if you just need a discrete (on/off) level indicator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This system is also used in paintball guns designed to prevent you from chopping balls by assuring that the whole ball is in the firing chamber before allowing the electronic trigger to arm the firing solenoid.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's simple, effective, and requires little or no calibration.&lt;/p&gt;&#xA;" OwnerUserId="1866" LastActivityDate="2010-11-07T02:59:02.960" />
  <row Id="6356" PostTypeId="2" ParentId="5294" CreationDate="2010-11-07T03:21:54.680" Score="1" ViewCount="" Body="&lt;p&gt;I have seen signal of 3x CFL on input of 19-22 bit stereo DAC as a single very narrow peak more than 10Db above noise floor. Distance in air was about 5-10 feet. The signal was puzzling me, until I spotted CFLs and turned them off.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-07T03:21:54.680" CommunityOwnedDate="2010-11-30T23:44:02.540" />
  <row Id="6357" PostTypeId="2" ParentId="6227" CreationDate="2010-11-07T03:26:44.227" Score="0" ViewCount="" Body="&lt;p&gt;If you dont need high speed, look at reed contacts.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-07T03:26:44.227" />
  <row Id="6358" PostTypeId="2" ParentId="6196" CreationDate="2010-11-07T03:36:08.837" Score="0" ViewCount="" Body="&lt;p&gt;There is a list of relativistic effects of gravity and speed on clocks, including GPS clocks. &#xA;Tidal potentials of the Moon is namely known. Amplitude of periodic effect is on the order of 1 ps. I dont know if its over the range of 1 day.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;so yes.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-07T03:36:08.837" />
  <row Id="6359" PostTypeId="2" ParentId="6301" CreationDate="2010-11-07T03:55:13.800" Score="2" ViewCount="" Body="&lt;p&gt;I respectfully disagree with Mark on point, that ESR will vary for the same material when thickness is different. If capacitance is the same and ESR is mainly defined by properites if dielectric, then with doubling of dielectric thickness, the area will be also doubled to maintain same capacitance. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd also guess that ESR is mostly function of conductor plate material, its surface and geometry. Why I am so certain, is because ESR is highly frequency dependent. Capacitance is much less dependent on frequency. So ESR on higher frequencies can be blamed on skin effect. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Answer is no. Can not expect change in ESR, ESL&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-07T03:55:13.800" CommentCount="2" />
  <row Id="6360" PostTypeId="2" ParentId="6323" CreationDate="2010-11-07T03:57:43.170" Score="4" ViewCount="" Body="&lt;p&gt;Be careful of film resistors, where the film can be easily vaporized during power surges, EVEN IF the temperature of the entire package remains within safe limits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wire wound and resistive pellet resistors have much more thermal inertia than film resistors.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-07T03:57:43.170" />
  <row Id="6361" PostTypeId="2" ParentId="6316" CreationDate="2010-11-07T03:58:01.037" Score="1" ViewCount="" Body="&lt;p&gt;I think coupled inductor is marketing techno-term. I fail to see difference between 100% coupled inductors and perfect transformer. and.. Look, you can buy whole 2 inductors for price of one transformer.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-07T03:58:01.037" CommentCount="4" />
  <row Id="6362" PostTypeId="1" CreationDate="2010-11-07T04:02:58.250" Score="3" ViewCount="100" Body="&lt;p&gt;I'm reading a datasheet for an accelerometer (specifically &lt;a href=&quot;http://www.bosch-sensortec.com/content/language1/downloads/BMA145_DataSheet_Rev.1.1_02APR2008.pdf&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;) and it lists the max supply current as 290 uA. Does this mean that the power supply I use should never output more than 290 uA? Or does this just mean the device only consumes 290 uA max? In standby mode, the max supply current decreases. Does this mean I have to dynamically reduce the output current from the power supply?&lt;/p&gt;&#xA;" OwnerUserId="1510" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-11-08T13:23:32.480" LastActivityDate="2010-11-08T13:23:32.480" Title="Sensor supply current?" Tags="&lt;sensor&gt;&lt;power-supply&gt;&lt;current&gt;&lt;datasheet&gt;" AnswerCount="2" />
  <row Id="6363" PostTypeId="2" ParentId="6362" CreationDate="2010-11-07T04:14:21.147" Score="4" ViewCount="" Body="&lt;p&gt;No.Yes.No. If it was opposite, then there would be 10 extra pages in datasheet with description of power supply and manufacturer would never be able to sell a single device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only power critical device (voltage wise) I know is laser diode&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-07T04:14:21.147" CommentCount="2" />
  <row Id="6364" PostTypeId="2" ParentId="6212" CreationDate="2010-11-07T04:25:29.547" Score="2" ViewCount="" Body="&lt;p&gt;People already named ceramic SMD as alternative. But there are even better things. Look at stacked film SMD caps which are even more reliable, can stand mechanical stress, self heal and acoustically immune.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-07T04:25:29.547" />
  <row Id="6365" PostTypeId="2" ParentId="6196" CreationDate="2010-11-07T07:31:50.320" Score="2" ViewCount="" Body="&lt;p&gt;Not the answer you were looking for but if you're designing electronics which will run ON the moon you'll have to take into account the big (~ 290 degrees C) temperature differences between the light and the dark phase.&lt;/p&gt;&#xA;" OwnerUserId="1867" LastActivityDate="2010-11-07T07:31:50.320" CommentCount="1" />
  <row Id="6366" PostTypeId="2" ParentId="6196" CreationDate="2010-11-07T10:34:42.003" Score="4" ViewCount="" Body="&lt;p&gt;A long time ago I encountered a network (thin Ethernet) issue that turned out to be due to tide height in a river next to the building - to cut a long story short, the tide height affected the height of the ground water table below the building which, in turn, affected the ground/earth voltage level in different parts of the building, giving rise to changes in noise levels and earth loop currents. The fix was to arrange for better, common ground points.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the moon's phase affects tidal flow, I would suggest that you could therefore say 'yes' to your question.&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2010-11-07T10:34:42.003" CommentCount="1" />
  <row Id="6367" PostTypeId="2" ParentId="6362" CreationDate="2010-11-07T13:14:22.250" Score="10" ViewCount="" Body="&lt;p&gt;You seem to be suffering from a fairly common misconception about current. Typical power supplies do not &lt;em&gt;push&lt;/em&gt; current into loads. Instead, they provide a constant voltage. Under a given voltage, an intrinsic property of the device (AKA resistance or impedance) determines how much current will flow. In other words, the supply sets the voltage, and the device decides what the current will be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your case, the data sheet tells you the device will need 290 uA, presumably at some voltage which you didn't mention. This means your supply needs to be &lt;em&gt;capable&lt;/em&gt; of at least that much current. Extra capability in the supply doesn't hurt the device, in fact, it's desirable, because when a device tries to draw more current than a supply is capable of, undesirable things happen. Better supplies will reduce their output voltage to keep the current down to what they can handle, but lower voltage may make the device operate erratically, or not at all. In a cheaper supply, you'll pop a fuse. Very poorly designed supplies may even burn out.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-11-07T13:22:19.530" LastActivityDate="2010-11-07T13:22:19.530" />
  <row Id="6368" PostTypeId="1" CreationDate="2010-11-07T16:46:47.300" Score="0" ViewCount="293" Body="&lt;p&gt;Arduino is a microcontroller, so it won't help if you need complex tasks potentially involving standard hardware, like reading from an sd-card, or accessing ethernet/wifi. Is there a system-on-chip with the same amount of openness/documentation available ?&lt;/p&gt;&#xA;" OwnerUserId="1272" LastActivityDate="2010-11-08T07:54:06.230" Title="Arduino-like system-on-chip ?" Tags="&lt;system-on-chip&gt;" AnswerCount="4" CommentCount="4" />
  <row Id="6369" PostTypeId="2" ParentId="6368" CreationDate="2010-11-07T17:50:11.967" Score="3" ViewCount="" Body="&lt;p&gt;Well, an Ardunio can access ethernet and can read from an SD card.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said check out the &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;BeagleBoard&lt;/a&gt; for a more powerful development board.  The current version doesn't have ethernet on board but works fine with several USB ethernet/wifi adapters, the new beagleboard-xM has ethernet on board.  They are both cortex-A8 based boards, with the xM being a bit faster and having more ram (600mhz vs 1ghz and 256MB vs 512MB).  Theres are also some other differences.  Both run linux among other operating system choices. &lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-07T18:19:04.937" LastActivityDate="2010-11-07T18:19:04.937" CommentCount="5" />
  <row Id="6370" PostTypeId="1" AcceptedAnswerId="6405" CreationDate="2010-11-07T18:04:36.943" Score="3" ViewCount="169" Body="&lt;p&gt;I know that getting a perfect tuning network for an antenna and transceiver requires some rather expensive equipment plus human knowledge to operate the equipment. I have never done any antenna tuning, but I would like to know if there is any way a DIYer can perform at least a semi-decently good match.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any way I can use an oscope to do this? Is there any difference between tuning a PCB antenna versus a wire antenna?&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-08T09:53:18.827" Title="DIY Antenna Tuning" Tags="&lt;antenna&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="6371" PostTypeId="2" ParentId="6315" CreationDate="2010-11-07T18:12:05.177" Score="2" ViewCount="" Body="&lt;p&gt;My two recommendations, only read the later but I like the author so i'll plug the other one as well:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/1439811245&quot; rel=&quot;nofollow&quot;&gt;Computer Arithmetic and Verilog HDL Fundamentals&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/1420074156&quot; rel=&quot;nofollow&quot;&gt;Digital Design and Verilog HDL Fundamentals&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digital Design and Verilog HDL Fundamentals is probably more what your looking for, the first is more focused on implementing mathematical operations.  It may depend on what your after though, if your EE classes walk you through the entire design of a microprocessor as mine did you may find both useful eventually.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-07T18:12:05.177" />
  <row Id="6372" PostTypeId="1" CreationDate="2010-11-07T20:15:03.667" Score="5" ViewCount="226" Body="&lt;p&gt;I've noticed that when soldering small PCBs can get very hot. Since I haven't yet been able to find a good vise in which to hold PCBs, I mostly hold them in my hand and after several minutes of soldering, they tend to get uncomfortably hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't seen many information on Internet about this, so I'm asking for tips here.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-11-08T16:49:37.090" Title="How do I keep PCBs cool when soldering?" Tags="&lt;pcb&gt;&lt;soldering&gt;&lt;heatsink&gt;&lt;heat&gt;" AnswerCount="5" CommentCount="1" />
  <row Id="6373" PostTypeId="2" ParentId="6297" CreationDate="2010-11-07T20:18:33.267" Score="5" ViewCount="" Body="&lt;p&gt;I also wondered how these affordable devices work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Searching for 'laser distance measurement patent' I came across: &lt;a href=&quot;http://www.freepatentsonline.com/3733129.html&quot; rel=&quot;nofollow&quot;&gt;http://www.freepatentsonline.com/3733129.html&lt;/a&gt; . Note that this patent was filed already in 1973 so I could imagine that today's laser distance measurement devices use some other method. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I understood is this using the target as one of the reflectors of the laser cavity and then modulates the laser trying to find a resonance frequency which seems related to be related to the wavelength of an electromagnetic wave with this frequency (e.g. 1 meter seems to correspond to 150 MHz, bringing this down to a more 'manageable' frequency range). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have to admit that I did not fully understand the details in the patent abstract though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not convinced though how well this actually works with 'real world surfaces'...I would think that e.g. a wall surface &lt;strong&gt;alone&lt;/strong&gt; is not reflective enough to keep the system lasing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; I found another page here: &lt;a href=&quot;http://www.acuitylaser.com/resources/principles-measurement.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.acuitylaser.com/resources/principles-measurement.shtml&lt;/a&gt; . Looking at the 'Time of flight' section, they are a bit more specific: the reflected laser light is focused onto a light diode whose (inverted) signal is then used to modulate the laser. This will form an oscillator. The phase shift is determined by the distance to be measured (apart from fixed delays inside the device), so the frequency of this 'oscillator' is determined by the distance and can be measured.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(again, the time it takes to travel to a object at e.g. 1.5 m distance and back is 3m / 3E8 m/s = 10ns which corresponds to an oscillation frequency of 100 MHz).&lt;/p&gt;&#xA;" OwnerUserId="1867" LastEditorUserId="1867" LastEditorDisplayName="" LastEditDate="2010-11-07T20:35:03.187" LastActivityDate="2010-11-07T20:35:03.187" CommentCount="5" />
  <row Id="6374" PostTypeId="2" ParentId="6372" CreationDate="2010-11-07T20:34:00.577" Score="1" ViewCount="" Body="&lt;p&gt;Try holding your PCB in a vise. Special &lt;a href=&quot;http://www.panavise.com/index.html?pageID=1&amp;amp;page=full&amp;amp;--eqskudatarq=1&quot; rel=&quot;nofollow&quot;&gt;PCB vises&lt;/a&gt; are available.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-08T16:49:37.090" LastActivityDate="2010-11-08T16:49:37.090" CommentCount="2" />
  <row Id="6375" PostTypeId="2" ParentId="6372" CreationDate="2010-11-07T20:34:25.487" Score="7" ViewCount="" Body="&lt;p&gt;Shouldn't need to cool them while hand soldering. In fact, cooling them whilst soldering would induce a lot of thermal stress with cool areas of the PCB and really hot areas in other bits of the PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may be overheating the PCB with incorrect soldering technique or maybe your PCB has big ground polygons/planes and you're soldering on joints connecting to these ground polygons/planes without a thermal relief.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-07T20:34:25.487" />
  <row Id="6376" PostTypeId="2" ParentId="6372" CreationDate="2010-11-07T20:54:14.877" Score="3" ViewCount="" Body="&lt;p&gt;Having a vise is critical, especially for small chips, but since you are holding out of the right one, here are some suggestions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having the right size soldering iron and power will reduce the amount that your PCB heats up. Ideally you want a soldering iron that can quickly transfer heat to your pad so that you can get your solder on and take the heat off fast. To do this you will want to use the largest tip that you can find that still gives you the precision needed for what you are soldering. Adjustable temperature soldering irons are nice, but you need to also make sure that your iron is able to output enough power to keep your iron at the temperature you want it at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a large ground plane, you will most likely have to heat it up in order to get good soldering. You can added extra space at the edge of your PCB with no copper for you to be able to hold on to. If you aren't holding it where there is metal then you are more then likely over heating your board and should look at my prior suggestion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, with that said, you should really consider getting yourself a nice vise that lets you put your board at any angle that you want, this will really help with getting a great soldering job. The next investment you should consider getting is either a better soldering iron and/or nice lighting.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-07T20:54:14.877" />
  <row Id="6377" PostTypeId="2" ParentId="6370" CreationDate="2010-11-07T21:24:42.183" Score="0" ViewCount="" Body="&lt;p&gt;You should get a second opinion on this, but if you don't need a super wide-band analyzer, check out &lt;a href=&quot;http://www.metageek.net/products/wi-spy&quot; rel=&quot;nofollow&quot;&gt;Wi-Spy&lt;/a&gt;.  The $99 variety claims to let you &quot;see interference&quot;, and that interference would be whatever you are firing up at 2.4GHz.  It's a simple spectrum analyzer, but might be enough for what you are doing.&lt;/p&gt;&#xA;" OwnerUserId="1554" LastActivityDate="2010-11-07T21:24:42.183" CommentCount="1" />
  <row Id="6378" PostTypeId="2" ParentId="6368" CreationDate="2010-11-07T21:46:22.800" Score="1" ViewCount="" Body="&lt;p&gt;Arduino is not a microcontroller. Arduino is a piece of hardware which contains a microcontroller, which happens to be an Atmega328 (I believe - not very experienced in Arduino's). They use a simplified language to make it easy for beginners to get into it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But that doesn't mean you can't read from a SD card. A SD card just has a SPI interface, so not much truoble there if you get it hooked up correctly and find/write a library for it. There are also &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoEthernetShield&quot; rel=&quot;nofollow&quot;&gt;ethernet&lt;/a&gt; and &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardBluetooth&quot; rel=&quot;nofollow&quot;&gt;bluetooth&lt;/a&gt; modules/editions available for Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Althuogh shields are available, I think you're going to discover that such small proccesors lack any power for such operatings. Especially when computing &gt;8 bit data it becomes tedious. Beagleboard is a much more expanded board with a very different architecture, and I think something that integrates into hardware it self less easily. The arduino is so simple that it doesn't take that much work to transfer the programmed code into a 'real' embedded environment.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-11-07T21:46:22.800" CommentCount="1" />
  <row Id="6379" PostTypeId="1" AcceptedAnswerId="6382" CreationDate="2010-11-07T22:11:08.353" Score="5" ViewCount="284" Body="&lt;p&gt;For a fan, should air be sucked in, or should it blow air out?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm talking about an enclosure mounted fan.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-07T22:30:58.033" LastActivityDate="2010-11-08T02:38:26.893" Title="Fans: suck or blow?" Tags="&lt;cooling&gt;&lt;fan&gt;" AnswerCount="5" />
  <row Id="6380" PostTypeId="2" ParentId="6379" CreationDate="2010-11-07T22:19:19.890" Score="3" ViewCount="" Body="&lt;p&gt;If you are talking about a fan on an enclosure, then the whole point of this fan is to cycle hot air out of the enclosure &lt;em&gt;and&lt;/em&gt; pull cool air in.  You have to have the appropriate vent on the other side of the enclosure to allow this to happen.  Some enclosures have fans blowing both directions to help the process along.  If you only have one, make it blow out, and near the biggest source of heat.&lt;/p&gt;&#xA;" OwnerUserId="1554" LastActivityDate="2010-11-07T22:19:19.890" CommentCount="8" />
  <row Id="6381" PostTypeId="1" AcceptedAnswerId="6385" CreationDate="2010-11-07T22:35:02.630" Score="2" ViewCount="91" Body="&lt;p&gt;I'm using a breadboard to prototype my projects. On one pin of an MCU, which is an output, I'm getting a 0-3.3V signal, as expected. However, another pin has a 20mVp-p signal almost matching the other one, but lower in amplitude. Where is this coming from? Has my board got a weak short or something like that?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-08T00:21:32.500" Title="Is my breadboard faulty?" Tags="&lt;breadboard&gt;" AnswerCount="1" CommentCount="8" />
  <row Id="6382" PostTypeId="2" ParentId="6379" CreationDate="2010-11-07T22:54:38.517" Score="8" ViewCount="" Body="&lt;p&gt;Airflow is the key. Any direction will do. Just keep in mind where the hot components inside your enclosure is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you blow into the enclosure, you have the option of putting a dust filter on your fan. Whereas if you have your fan blowing out, air will enter your enclosure through all sorts of holes, and lots of dust may eventually accumulate.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-07T22:54:38.517" CommentCount="2" />
  <row Id="6383" PostTypeId="2" ParentId="6379" CreationDate="2010-11-07T23:04:02.347" Score="7" ViewCount="" Body="&lt;p&gt;In my experience, the choice of direction determines where the inevitable dust build-up will occur. Dust seems to accumulate wherever the air enters the case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With fans blowing in, you tend to get the most dust build up right in front of the fan. You wouldn't want this happening on the heat sink of your CPU, as the dust acts like an insulating blanket. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, with fans blowing out, you get dust in the case near every possible way for air to get in. One place this can be a problem in a PC is when the air comes in through the openings for removable drives.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Probably the best design I've seen involves having two fans, one blowing in and the other out. The exhaust fan sits near the heat sink of the CPU to ensure good air flow there, w/o the dust problem, and the other fan pulls air into the case to keep the pressure in the case high enough to prevent sucking air (and dust) in through all the other openings.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-07T23:04:02.347" />
  <row Id="6384" PostTypeId="2" ParentId="6370" CreationDate="2010-11-07T23:30:30.377" Score="0" ViewCount="" Body="&lt;p&gt;Could make use of the RSSI (Received Signal Strength Indicator) on many RF transcievers to give you a rough indication.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-07T23:30:30.377" CommentCount="1" />
  <row Id="6385" PostTypeId="2" ParentId="6381" CreationDate="2010-11-08T00:21:32.500" Score="3" ViewCount="" Body="&lt;p&gt;The spikes you are seeing are just an effect of your breadboard allowing coupling. This is expected with any breadboard.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-08T00:21:32.500" CommentCount="2" />
  <row Id="6386" PostTypeId="2" ParentId="6379" CreationDate="2010-11-08T00:48:32.743" Score="1" ViewCount="" Body="&lt;p&gt;When I design something like airflow, there are a few important points.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What components generate heat, and how distributed my heat sources are.&lt;/li&gt;&#xA;&lt;li&gt;Where I can expect the user to be in reference to the device.&lt;/li&gt;&#xA;&lt;li&gt;Dust buildup.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In order. If you have single units that generate a bulk of your heat, they need something near them. You have options, a fan on them in extreme cases similar to a high end processor or a fan on the enclosure next to them. If you have generally generated heat, you just need to focus on getting general air flow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After you know where fans are needed, you need to think about the user. Why would your o-scope have a fan on the front that blows in? It is generating a lot of heat there, but if it blew forward and blew warm air in the user's eyes all the time I doubt they would thank you. Design air to exhaust in a direction the user can be expected not to be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, on dust buildup, you want to limit this. I have two directions for this.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Fan with filter blowing air in. Without a filter the high speed air will pull in dust with the air, but as air slows down it will act like a river slowing down and drop silt.&lt;/li&gt;&#xA;&lt;li&gt;Exhaust in a few key locations you can pull in over a large area and expect significantly less dust to enter the enclosure due to low air speed entering the device, but you will still have dust issues. I would prefer everyone used filters, but I do not mind blowing out devices once in a while with an air compressor(just kidding).&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-08T00:48:32.743" />
  <row Id="6387" PostTypeId="2" ParentId="6372" CreationDate="2010-11-08T01:29:47.997" Score="1" ViewCount="" Body="&lt;p&gt;This is one of the places where proper equipment helps loads. If its a particularly small PCB a third hand type device is invaluble, in more ways than one (it also serves to hold leads in place), though i suppose you can use a small clamp as a temporary improvised holder.&lt;/p&gt;&#xA;" OwnerUserId="1870" LastActivityDate="2010-11-08T01:29:47.997" />
  <row Id="6388" PostTypeId="1" AcceptedAnswerId="6390" CreationDate="2010-11-08T01:44:11.770" Score="5" ViewCount="348" Body="&lt;p&gt;I'm building a small audio amp (&lt;a href=&quot;http://diyaudioprojects.com/Solid/IRF610-Class-A-Headphone-Amp/&quot; rel=&quot;nofollow&quot;&gt;a current controlled varient of the szekeres design&lt;/a&gt;) and it apparently needs a very clean, regulated power source. Due to minimum parts order requirements, i'm going to end up with, amongst other things, a spare lm317 and others. As i understand, both the standard transformer-&gt; wheatstone bridge and switching power supplies are relatively noisy, so since i have parts spare, i'm wondering if following the reference design to build a voltage regulator would make a difference, or if i should just use a switching power supply to power it - i should be able to find a 15-20 v one which i'm planning on using anyway, and not using the voltage regulator at all for power supply&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For that matter &lt;em&gt;does&lt;/em&gt; using a voltage regulator reduce rippling and noise, or is it just a complicated voltage divider?&lt;/p&gt;&#xA;" OwnerUserId="1870" LastActivityDate="2010-11-10T07:43:29.233" Title="Regulated power supplies - how do they work?" Tags="&lt;power-supply&gt;" AnswerCount="5" CommentCount="5" FavoriteCount="1" />
  <row Id="6389" PostTypeId="2" ParentId="6368" CreationDate="2010-11-08T02:01:23.043" Score="2" ViewCount="" Body="&lt;p&gt;Most microcontrollers are as open as the AVR.  Granted Atmel does a better job than other companies, that doesnt make the others closed, their documents are just not done as well.  As far as that goes you can go with any of the Atmel ARM series and stick with atmel.  The sam7 series for example.  Olimex sells a nice little header board (sparkfun.com).  Also look for the armmite pro while at sparkfun. It is arduino like but arm based.  ARM based, microchip pic, mips, ti msp430, 8051, avr, etc.  All offer similar levels of open documentation.  ARM and the 8051 you are going to find a wider selection of in the sense that many vendors use these cores. (mips is open but not really found in this market other than the pic32)  The pic, msp430, avr are locked to one vendor.  If you want to try boards with sd, ethernet, usb, etc on board you can look at the ti stellaris eval boards, in the $50 to $100 range.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2010-11-08T02:01:23.043" CommentCount="2" />
  <row Id="6390" PostTypeId="2" ParentId="6388" CreationDate="2010-11-08T02:26:49.947" Score="4" ViewCount="" Body="&lt;p&gt;Switching power is noisy, there's no doubt about it - typically anywhere from kilohertz up to the megahertz range, both CM and DM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also think you're getting your terms mixed up. I presume you meant to say transformer and bridge rectifier, not Wheatstone bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use a switcher to feed a 317 regulator and get the benefit of cleaner output and less efficiency loss than a fully linear solution (mains frequency transformer et al)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 317 is active and will reject ripple as a function of the voltage feedback network controlling the series-pass transistor in the device. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-08T02:26:49.947" />
  <row Id="6391" PostTypeId="2" ParentId="6379" CreationDate="2010-11-08T02:38:26.893" Score="1" ViewCount="" Body="&lt;p&gt;Generally, airflow isn't reversible in electronics without ramifications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Complex software like Flowtherm is used to pattern airflow and heat patterns for a specific air direction. Usually parts are placed to maximize cooling with specific direction and speed of air.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Going against this could potentially lead to hot spots and bad things like thermal runaway.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-08T02:38:26.893" />
  <row Id="6392" PostTypeId="1" AcceptedAnswerId="6394" CreationDate="2010-11-08T03:32:44.240" Score="8" ViewCount="337" Body="&lt;p&gt;I have worked on developing a feature on a particular product of ours. There has been a request to port the same feature to another product.&#xA;This product is based on a M16C microcontroller, which traditionally has 64K Flash and 2k of RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a mature product, and therefore, only has 132 Bytes of Flash and 2 Bytes of RAM left.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To port the feature requested (the feature itself has been optimised), I need 1400 bytes of Flash and ~200 Bytes of RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any suggestions on how to retrieve these Bytes by code compaction?&#xA;What specific things do I look for when I am trying to compact already existing working code?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas will really be appreciated. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1785" LastActivityDate="2010-11-09T15:23:54.657" Title="How to squeeze code for more Flash and RAM?" Tags="&lt;embedded&gt;" AnswerCount="14" CommentCount="3" FavoriteCount="3" />
  <row Id="6393" PostTypeId="2" ParentId="6388" CreationDate="2010-11-08T03:40:35.290" Score="1" ViewCount="" Body="&lt;p&gt;A linear regulator is a voltage regulator based on an active device such as a bipolar junction transistor (BJT) or field effect transistor (FET) operating in its linear region.  It is very inefficient compared to a switched-mode power supply, since the difference between the input and output voltage is dissipated as heat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LM317 has three terminals: input, output, and adjust.  The regulator develops a nominal 1.25V reference voltage between the output and adjust terminals. This constant voltage is applied across a resistor, causing a constant current to flow. This constant current flows through a second resistor tied to ground. By varying the value of the second resistor, the voltage across it will vary and hence the output voltage can be set.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although the LM317 can be used without capacitors, adding a 1 uF capacitor on both the input and output will give a cleaner output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.k7mem.150m.com/Electronic_Notebook/power_supplies/lm317.html&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; is useful for calculating the values of the resistors.  &lt;a href=&quot;http://www.reuk.co.uk/print.php?article=LM317-Voltage-Calculator.htm&quot; rel=&quot;nofollow&quot;&gt;Here is&lt;/a&gt; another one.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-11-08T03:45:51.610" LastActivityDate="2010-11-08T03:45:51.610" />
  <row Id="6394" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T03:55:17.133" Score="12" ViewCount="" Body="&lt;p&gt;You have a couple of options first is to look for redundant code and move it to a single call to get rid of the duplication.  The second is to remove functionality. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take a good look at your map file and see if there are function that you can get rid of or rewrite.  Also make sure that library call are being used are really needed. Also certain things like division and multiplications can bring in a lot of code but using shifts and a better use of constants can make the code smaller.  Also have a look at things like string constants and printf.  For example each printf will eat up your rom but you might be able to have a couple of shared format strings instead of repeating that string constant over and over again.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For memory see if you can get rid of globals and use autos in a function instead.  Also avoid as many variable in the main function as possible these eat up memory just like globals do.&lt;/p&gt;&#xA;" OwnerUserId="540" LastActivityDate="2010-11-08T03:55:17.133" CommentCount="7" />
  <row Id="6395" PostTypeId="1" AcceptedAnswerId="6396" CreationDate="2010-11-08T05:49:30.813" Score="10" ViewCount="260" Body="&lt;p&gt;I hope many people might feel little awkward to see this question. But I feel this is important. Because in my place where I am living I can get a radio (Audio Receiver) very cheaply. I don't know till what extent they allow the audio frequency ranges. I guess they use  ICs for Frequency Demodulators, Frequency Clippers, etc. If the Frequency demodulator doesn't work properly and allows all the frequencies that comes through air then its going to be a big problem to the humans. Can somebody answer which are all the frequency ranges that are available and which causes human hazards?&lt;/p&gt;&#xA;" OwnerUserId="1731" LastEditorUserId="1731" LastEditorDisplayName="" LastEditDate="2010-11-09T03:41:00.543" LastActivityDate="2010-11-09T03:41:00.543" Title="Frequency ranges that causes a hazard to humans" Tags="&lt;radio&gt;&lt;frequency&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="6396" PostTypeId="2" ParentId="6395" CreationDate="2010-11-08T06:55:24.000" Score="23" ViewCount="" Body="&lt;p&gt;The short answer is that unless you are dealing with professional power levels in the several watts range, RF is very difficult to cause injury with.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Long answer&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RF doesn't affect humans directly unless there is a &lt;em&gt;tremendous&lt;/em&gt; amount of power.  Effects are typically thermal, when a particular chemical bond is struck just-so, it will absorb a photon, moving it slightly.  Enough heating will damage cells by denaturing or &quot;cooking&quot; proteins.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Particular wavelengths (2.4 GHz) are well absorbed by water and fat, but absorption is still very diffuse so it would take a tremendous dose to cause enough heating in any one area to cause damage.  The FCC safe exposure limit is 1.6 W absorbed per kilogram (as per one source), and 4 W/kg (in following link) for the entire body.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;More&lt;/strong&gt;: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.fcc.gov/oet/rfsafety/rf-faqs.html&quot; rel=&quot;nofollow&quot;&gt;FCC RF Safety FAQ&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Specifically &lt;a href=&quot;http://www.fcc.gov/oet/rfsafety/rf-faqs.html#Q28&quot; rel=&quot;nofollow&quot;&gt;this question&lt;/a&gt; which has links to &#xA;&lt;ul&gt;&#xA;&lt;li&gt;the &lt;a href=&quot;http://www.fda.gov/cdrh/radhealth/&quot; rel=&quot;nofollow&quot;&gt;Center for Devices and Radiological Health (CDRH)&lt;/a&gt;, Food and Drug Administration.&lt;/li&gt;&#xA;&lt;li&gt;the &lt;a href=&quot;http://radiation.custhelp.com/cgi-bin/radiation.cfg/php/enduser/std_alp.php?p_sid=zNOYeSej&amp;amp;p_lva=&amp;amp;p_li=&amp;amp;p_accessibility=0&amp;amp;p_redirect=&amp;amp;p_page=1&amp;amp;p_cv=&amp;amp;p_pv=2.176&amp;amp;p_prods=139%2C176&amp;amp;p_cats=&amp;amp;p_hidden_prods=&amp;amp;prod_lvl1=139&amp;amp;prod_lvl2=176&amp;amp;p_search_text=&amp;amp;srch_btn_su&quot; rel=&quot;nofollow&quot;&gt;Environmental Protection Agency's Office of Radiation Programs&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.osha.gov/SLTC/radiofrequencyradiation/index.html&quot; rel=&quot;nofollow&quot;&gt;OSHA guidelines and studies&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Atomic nuclei can also also respond to RF, allowing for nuclear magnetic resonance spectroscopy (or MRIs), but this is a strictly nuclear effect and has no influence on chemical bonds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IR and light obviously can cause burns, but only at sufficient power.  IR lasers can be particularly hazardous to eyes, as it invisible it will not trigger a blink or aversion reflex, allowing a large, damaging dose to be absorbed before noticing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Higher energy photons, UV, X-ray, and gamma, are able to ionize atoms when they strike them, causing unexpected chemical reactions to occur which can destroy, damage, or mutate cells.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are all forms of &quot;radiation&quot;, but the layperson couldn't tell what the implications of non-ionizing versus ionizing radiation are, which causes all sorts of unfounded fears of these invisible phantoms that carry our cell phone calls and webpages.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-08T06:55:24.000" CommentCount="2" />
  <row Id="6397" PostTypeId="2" ParentId="6368" CreationDate="2010-11-08T07:54:06.230" Score="0" ViewCount="" Body="&lt;p&gt;If you need more power, but want to save your investment in Arduino shields, then take a look at FEZ Domino &lt;a href=&quot;http://www.tinyclr.com/hardware/1/fez-domino&quot; rel=&quot;nofollow&quot;&gt;http://www.tinyclr.com/hardware/1/fez-domino&lt;/a&gt;. It is affordable ARM board with .NET Micro Framework programmable in C# with free Visual Studio, and compatible with Arduino shields. There is even simpler and cheaper version called FEZ Mini, but it doesn't take Arduino shields from the box. Beware that .NET Micro Framework keeps developer a little away from the bare metal and abstracts it sometimes too much. You will hardly have real time analysis and generation of composite TV signal with that like you can have with just AVR, but after all that is not what it's made for.&#xA;Btw. There are plenty Arduino shields for SD and Eth/Wifi. Just google around.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-11-08T07:54:06.230" />
  <row Id="6398" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T08:03:41.823" Score="4" ViewCount="" Body="&lt;p&gt;It's always worth checking your compiler manual for options to optimise space.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For gcc &lt;code&gt;-ffunction-sections&lt;/code&gt; and &lt;code&gt;-fdata-sections&lt;/code&gt; with the &lt;code&gt;--gc-sections&lt;/code&gt; linker flag are good for stripping dead code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some other &lt;a href=&quot;http://www.tty1.net/blog/2008-04-29-avr-gcc-optimisations_en.html&quot; rel=&quot;nofollow&quot;&gt;excellent tips&lt;/a&gt; (geared towards AVR)&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-08T18:47:20.077" LastActivityDate="2010-11-08T18:47:20.077" CommentCount="4" />
  <row Id="6399" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T08:28:22.907" Score="6" ViewCount="" Body="&lt;p&gt;It's always worth looking at listing file (assembler) output to look for things which your particular compiler is particularly bad at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, you may find that local variables are very expensive, and if the application is simple enough to be worth the risk, moving a few loop counters into static variables might save a lot of code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or array indexing might be very expensive but pointer operations much cheaper.  Or vice versa.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But looking at the assembly language is the first step.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-08T08:28:22.907" CommentCount="1" />
  <row Id="6401" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T09:22:26.620" Score="6" ViewCount="" Body="&lt;p&gt;Compiler optimisations, for example, &lt;code&gt;-Os&lt;/code&gt; in GCC gives the best balance between speed and code size. Avoid &lt;code&gt;-O3&lt;/code&gt;, as it may increase code size. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-08T09:22:26.620" CommentCount="6" />
  <row Id="6402" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T09:23:08.227" Score="6" ViewCount="" Body="&lt;p&gt;For RAM, check the range of all of your variables - are you using ints where you could use a char? Are buffers bigger than they need to be?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Code squeezing is very application and coding-style dependent. Your amounts left suggest that maybe the code has already gone though some squeezing, which may mean there's little left to be had. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also take a hard look at the overall functionality - is there something that's not really used and can be jettisoned?&lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-08T09:49:06.273" LastActivityDate="2010-11-08T09:49:06.273" />
  <row Id="6403" PostTypeId="1" AcceptedAnswerId="6408" CreationDate="2010-11-08T09:38:38.480" Score="5" ViewCount="492" Body="&lt;p&gt;Integrated circuits seem to have standard voltages of 5V, 3.3V, 2.5V. 1.8V... &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Who decides these voltages?&lt;/li&gt;&#xA;&lt;li&gt;Why do smaller devices require lower voltages?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:29:24.813" LastActivityDate="2011-03-05T16:29:24.813" Title="What's with the operating voltages: 5V, 3.3V, 2.5V, 1.8V, etc..." Tags="&lt;ic&gt;" AnswerCount="8" CommentCount="3" />
  <row Id="6405" PostTypeId="2" ParentId="6370" CreationDate="2010-11-08T09:53:18.827" Score="3" ViewCount="" Body="&lt;p&gt;Here's the &quot;Dropout's guide to antenna design&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://colinkarpfinger.com/blog/2010/the-dropouts-guide-to-antenna-design/&quot; rel=&quot;nofollow&quot;&gt;http://colinkarpfinger.com/blog/2010/the-dropouts-guide-to-antenna-design/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-08T09:53:18.827" CommentCount="3" />
  <row Id="6406" PostTypeId="2" ParentId="6403" CreationDate="2010-11-08T10:04:42.497" Score="2" ViewCount="" Body="&lt;p&gt;Whoever makes an IC decides on the voltages it needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the olden days someone started using 5V for digital logic and that stuck for a long time, mainly because it's much harder to sell a chip that needs 4V when everybody is designing with a lot of chips that run on 5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;iow: The reason that everybody tends to use the same voltage is not so much a matter of them all choosing the same process as it's a matter of them not wanting to be cursed for using &quot;unusual&quot; voltages by the designers who use their chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Switching a signal at a certain speed takes more power if the voltage is higher, so with higher speeds you need lower voltages to keep the current down, that's why the faster, denser, modern circuits tend to use lower voltages than the old chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many chips even use 3.3V for i/o and a lower voltage, like 1.8V for the internal core.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Chip designers know that 1.8V is an oddball voltage and will often have an internal regulator to provide the core voltage for the chip itself, sparing the designer from having to generate the core voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an example of the dual-voltage situation take a look at the ENC28J60 which runs on  3.3V, but has an internal 2.5V regulator.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-08T10:04:42.497" CommentCount="4" />
  <row Id="6407" PostTypeId="2" ParentId="6403" CreationDate="2010-11-08T11:39:30.377" Score="4" ViewCount="" Body="&lt;p&gt;&quot;&lt;em&gt;Why do smaller devices require lower voltages&lt;/em&gt;?&quot; Smaller ICs have less surface to get rid of the heat. Whenever a bit toggles somewhere in an IC, a capacitor has to be charged or discharged (i.e. the gate capacitance of a CMOS transistor). Although the transisotrs in a digital IC are usually very very tiny, there are a lot of them, so the issue is still important. The energy stored in a capacitor is equal to 0.5*C*U^2. Twice the voltage will cause 2^2=4 times the energy that has to be used for every MOSFET's gate. Therefore, even a small step down from, say, 2.5V to 1.8V will bring a considerabe improvement. That's why IC designers didn't just stick to 5V for decades and waited until the technology was ready to use 1.2V, but used all the other funny voltage levels in between.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2010-11-08T16:10:03.753" LastActivityDate="2010-11-08T16:10:03.753" CommentCount="0" />
  <row Id="6408" PostTypeId="2" ParentId="6403" CreationDate="2010-11-08T11:56:08.517" Score="4" ViewCount="" Body="&lt;p&gt;New voltages have often been chosen to give some degree of compatibility with what came before them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3V3 CMOS output levels were compatible with 5V TTL inputs, for example.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-08T11:56:08.517" CommentCount="0" />
  <row Id="6409" PostTypeId="1" AcceptedAnswerId="6413" CreationDate="2010-11-08T12:19:39.717" Score="2" ViewCount="154" Body="&lt;p&gt;I have an old computer, an &lt;a href=&quot;http://en.wikipedia.org/wiki/ABC_80&quot; rel=&quot;nofollow&quot;&gt;ABC80&lt;/a&gt; from the late seventies or early eighties, in which I have reason to believe one or more of the voltage regulators are broken.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/BkUd2.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ub1e2.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I wonder, what may be suitable replacement parts?  I know that similarly named parts are still produced, but I am not sure about the details.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What about &lt;a href=&quot;http://shop.conrad.se/websale7/?shopid=conrad%2dswe&amp;amp;act=product&amp;amp;prod_index=179205&amp;amp;cat_index=SHOP%5fAREA%5f17336%5f0204453&amp;amp;Ctx=%7Bver%2F7%2Fver%7D%7Bst%2F3ec%2Fst%7D%7Bcmd%2F0%2Fcmd%7D%7Bm%2Fwebsale%2Fm%7D%7Bs%2Fconrad-swe%2Fs%7D%7Bl%2F01-aa%2Fl%7D%7Bsf%2F%3Cs1%3E7805%3C%2Fs1%3E%3Cs5%3E2%3C%2Fs5%3E%2Fsf%7D%7Bp1%2Fb1288725c4222b966991d7bc317fb8ae%2Fp1%7D%7Bmd5%2F78386f0c816881a98a1d5c0a5270a784%2Fmd5%7D&quot; rel=&quot;nofollow&quot;&gt;this for a 7805 replacement&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="1877" LastEditorUserId="1877" LastEditorDisplayName="" LastEditDate="2011-02-04T09:31:04.510" LastActivityDate="2011-02-04T09:31:04.510" Title="Replace broken 79M12 and 7805 voltage regulators?" Tags="&lt;voltage-regulator&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="6410" PostTypeId="2" ParentId="6388" CreationDate="2010-11-08T12:24:11.393" Score="0" ViewCount="" Body="&lt;h3&gt;Regulated power (voltage) supply operation:&lt;/h3&gt;  &#xA;&#xA;&lt;p&gt;To start from the big, more simplistic perspective, the job of the voltage regulators, both switching and linear is to act as ideal voltage source. That is to provide constant voltage even in case of varying load and/or its own supply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually it is being achieved by using feedback loop. In such setting output voltage is being sensed and in case it drops below set value, something is done to provide more current to output which should result in output voltage going back to set value (and reverse if voltage is above set value). This &quot;something&quot; in linear regulators is to make pass element *1) to conduct more current from input to output by adjusting base current or gate voltage. In switching regulator usually &quot;something&quot; is to adjust frequency and/ or duty cycle to achieve the same goal. So in sum both linear and switching regulators main job is to reduce output voltage variations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, nothing in life is perfect, and both realizations of the same goal have (severe) limitations. There is a lot of factors to to take into account (line, load regulation, regulation speed, stability, output noise, operating input/output voltage/current range and many many more) but for sake of (over)simplification linear regulators are better at providing ripple-less output then switched at the cost of the efficiency (this is beacouse switched regulator introduce its own ripple, but in turn are more efficient and can do things that linear regulators cannot do - such as stepping up voltage).&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;For the case from question:&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;A) In this application one really need good, regulated power source, as 50Hz/60Hz (100Hz/120Hz) ripple from mains are audible (so called power line hum). Also beacouse linked amplifiers trade supply variation immunity for simplicity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;B) LM317, from its DS, has 80dB *2) typical ripple rejection at 120Hz (power line x2). That is if you have 1V pk-pk ripple at the input your output ripple should be 0.1mV (10k times attenuation). Do not quote me on that (as there are a lot of factors to take care of) but it look like this should be more then enough for this application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C) The switching regulator/power supply may be good enough providing that it does reject 100Hz/120Hz very well (80dB as in case of LM317 would be nice). Even as it produce more ripple (finding one with less then 5mV output self-ripple is difficult), if those are above 20kHz (and for most of the switching supply it is the case) you do not have to worry about it as those ripple would be outside frequency range that human ear can hear. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW you can look at linear regulators as &quot;complicated voltage dividers&quot;), which in fact is quite good analogy (as the pass element could be treated as &quot;adjustable&quot; resistance). Note, however, this &quot;complication&quot; gives you 80dB of ripple rejection :)&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;*1) pass element - usually it is transistor, BJT or MOSFET, connected between regulator input and output. The feedback loop will adjust it towards more &quot;open&quot; or &quot;close&quot; state such this element will pass more or less current in order to maintain output voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*2) you need to design it in correctly, that is provide sufficient decoupling caps, make sure that it will work with appropriate drop to maintain regulation etc. Documentation is your friend.&lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="1471" LastEditorDisplayName="" LastEditDate="2010-11-10T07:43:29.233" LastActivityDate="2010-11-10T07:43:29.233" CommentCount="1" />
  <row Id="6411" PostTypeId="2" ParentId="6403" CreationDate="2010-11-08T12:47:42.563" Score="4" ViewCount="" Body="&lt;p&gt;The voltages appear to follow a pattern:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;3.3v = 2/3 of 5v&lt;/li&gt;&#xA;&lt;li&gt;2.5v = 1/2 of 5v&lt;/li&gt;&#xA;&lt;li&gt;1.8v = ~1/3 of 5v (1.7 would be closer to 1/3, this seems to be the only oddball)&lt;/li&gt;&#xA;&lt;li&gt;1.2v = 1/4 of 5v&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-11-08T12:47:42.563" CommentCount="1" />
  <row Id="6412" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T12:57:10.240" Score="2" ViewCount="" Body="&lt;p&gt;You can try to rearrange to code a lot, to a more compact style. It depends a lot on what the code is doing. The key is to find similar things and re-implement them in terms of each other. An extreme would be to use a higher level language, like Forth, with which it can be easier to achieve a higher code density than in C or assembler.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is &lt;a href=&quot;ftp://80.100.243.19/pub/ciforth/&quot; rel=&quot;nofollow&quot;&gt;Forth for M16C&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1877" LastActivityDate="2010-11-08T12:57:10.240" />
  <row Id="6413" PostTypeId="2" ParentId="6409" CreationDate="2010-11-08T13:21:15.010" Score="4" ViewCount="" Body="&lt;p&gt;You can replace them with any equivalent regulator, so long as it is better in terms of current rating and in the same package. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, don't replace a 79M12 with a 79L12, because the &lt;em&gt;M&lt;/em&gt; indicates a MEDIUM current level and is about 500mA-1A, while the &lt;em&gt;L&lt;/em&gt; indicates a LOW current level which is usually ~100mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could replace the 7805 with 7805 in a TO-220 package. The 79M12 could be replaced by any 7912 rated for ~1A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Back in the day when that computer was produced, it was more expensive to produce a regulator which could do 1A vs. one which could do 500mA. It's still the same, but as manufacturing methods have improved, the price gap has shrunk.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-08T13:21:15.010" CommentCount="10" />
  <row Id="6414" PostTypeId="2" ParentId="6315" CreationDate="2010-11-08T13:25:12.090" Score="4" ViewCount="" Body="&lt;p&gt;Peter Ashenden's &quot;&lt;a href=&quot;http://www.ashenden.com.au/designers-guide/DG.html&quot; rel=&quot;nofollow&quot;&gt;The Designer's Guide to VHDL&lt;/a&gt;&quot; uses a DLX CPU design to illustrate many topics. However, if you're only interested in Verilog HDL then this might not be the book for you.&lt;/p&gt;&#xA;" OwnerUserId="1815" LastActivityDate="2010-11-08T13:25:12.090" CommentCount="3" />
  <row Id="6415" PostTypeId="2" ParentId="6339" CreationDate="2010-11-08T13:41:07.383" Score="0" ViewCount="" Body="&lt;p&gt;The modulated route is the way to go.  But try the other untill you are sufficiently frustrated with it.  Use a 555 timer in the transmitter.  This is still very simple and cheap.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-11-08T13:41:07.383" />
  <row Id="6416" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T13:41:42.567" Score="2" ViewCount="" Body="&lt;p&gt;Set the optimization level of the compiler.  Many IDE's have settings that allow for code-size optimizations at the expense of compile-time (or maybe even processing time in some cases).  They can accomplish code compacting by rerunning their optimizer a couple of times, searching for less-common optimize-able patterns, and a whole other host of tricks that may not be necessary for the casual/debug compilation.  Usually, by default, compilers are set to a medium level of optimization.  Dig around in the settings an you should be able to find some integer-based optimization scale.&lt;/p&gt;&#xA;" OwnerUserId="1571" LastActivityDate="2010-11-08T13:41:42.567" CommentCount="1" />
  <row Id="6417" PostTypeId="2" ParentId="6388" CreationDate="2010-11-08T13:51:57.590" Score="0" ViewCount="" Body="&lt;p&gt;The voltage regulator isn't a glorified voltage divider - it has internal references and feedback circuitry that allow it to actively maintain the power level.  It's not perfect (so you still get ripple) but it is much better than a voltage divider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Power supplies are generally rated by two criteria: line regulation and load regulation.  Line regulation is the ability of the supply to compensate for changes in the input voltage.  This helps to reduce ripple - if you're using a transformer and wheatstone bridge you'll still have some ripple after low-pass filtering.  Good line regulation (low delta Vout / delta Vin) means that the output voltage resists these ripples and is cleaner.  Load regulation deals with how well the supply can deliver current while maintaining voltage.  If you were to draw no current from the supply, chances are you'd get the correct output voltage.  But as you draw more and more current, most supplies lose voltage.  A good load regulation characteristic (low delta Vout / delta I load) means your power supply maintains the correct voltage despite changes in the load.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage dividers have terrible line or load regulation - they're just feed forward devices that don't compensate their outputs at all.  Any regulated supply will be better than that.  Look at the regulators data sheets and see what numbers they provide for line and load regulation. Also important will be bandwidth.  The regulator has a little control loop inside that can only account for ripple that it sees.  Any ripple that falls outside of its bandwidth is invisible and it can't fix.  If you see a particular problem frequency you may need to switch regulators.  There are also some application notes from some manufacturers that contain information on how to extend the bandwidth of regulators sometimes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-08T13:51:57.590" />
  <row Id="6418" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T13:54:18.370" Score="0" ViewCount="" Body="&lt;p&gt;If you can, use inline functions or compiler macros instead of small functions.  There's size and speed overhead with passing arguments and such that can be remedied by making the function inline. &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-08T13:54:18.370" CommentCount="2" />
  <row Id="6419" PostTypeId="2" ParentId="6403" CreationDate="2010-11-08T13:58:30.540" Score="6" ViewCount="" Body="&lt;p&gt;A lower VDD is required as the gate geometry shrinks. This prevents damage to the CMOS gate oxide and minimizes leakage. When the fabs switched from 0.5um to 0.35um, the thinner gates could only handle potentials up to 3.6V. That led to supplies at 3.3V +/- 10%. With the switch to 0.18um the voltage was reduced further to 1.8V +/- 10%. In the latest processes (e.g. 45nm), the gates are made of high-k dielectrics such as halfnium to reduce leakage.&lt;/p&gt;&#xA;" OwnerUserId="721" LastActivityDate="2010-11-08T13:58:30.540" />
  <row Id="6420" PostTypeId="2" ParentId="6403" CreationDate="2010-11-08T13:59:30.273" Score="3" ViewCount="" Body="&lt;p&gt;The voltages are dictated by the physics of the materials (semiconductor materials anyhow) and the processes used in the making of the chip.  (I hope I'm using the right terms here...) Different types of semiconductors have different gap voltages - essentially the voltage that 'activates' them.  They can also optimize the structure of the chip to allow lower voltages to work more reliably when they do layouts (I believe).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not so much that smaller devices require lower voltages, it's that they've designed them to use smaller voltages because less voltage means less heat dissipation and potentially faster operation.  It's easier to have a 10MHz clock signal if it only has to go between 0V and 1.8V.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-08T13:59:30.273" CommentCount="1" />
  <row Id="6421" PostTypeId="1" AcceptedAnswerId="6423" CreationDate="2010-11-08T14:37:05.467" Score="2" ViewCount="105" Body="&lt;p&gt;For a project, I am connecting the output ports of a 74AC04E hex inverter to bnc ports.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something could be (but not necessarily) be plugged in at one or more ports at a given time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should the ports have pull-up:s / pull-down:s or could they be left floating?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/YLnwU.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1605" LastEditorUserId="1605" LastEditorDisplayName="" LastEditDate="2010-11-08T14:43:32.487" LastActivityDate="2010-11-08T15:55:02.960" Title="Hex inverter floating outputs" Tags="&lt;output&gt;&lt;inverter&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="6422" PostTypeId="2" ParentId="6421" CreationDate="2010-11-08T15:08:51.443" Score="1" ViewCount="" Body="&lt;p&gt;If you just connect an output of your 7404 chip to a BNC connector you don't have to worry about pull-ups or pull-downs on the output side.  It looks like outputs of this chip cannot be tristated so you should always have a known output of the BNC connector.  The output will be determined by the input of the NOT gate.  You may  need to put a pull-up or a pull-down on the input, but that depends on that portion of the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These mating BNC connectors (that would be inputs) however should probably have a pull-up or a pull-down.  Which direction you pull depends on your circuit that mates to this circuit.  Just think of the situation where you would have your BNC unconnected, resulting in an input that is not actively driven, do you want it to be GND or VCC?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope I'm helping and not confusing the situation more.&lt;/p&gt;&#xA;" OwnerUserId="1819" LastActivityDate="2010-11-08T15:08:51.443" />
  <row Id="6423" PostTypeId="2" ParentId="6421" CreationDate="2010-11-08T15:09:05.233" Score="2" ViewCount="" Body="&lt;p&gt;There is no problem in left the ports floating. If you want to insert a resistor (avoiding some high frequency noise problems) its better a pull down, as the IC has greater capacity to load a low level (8mA) than a high level (-0.4mA).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a 5v a 47k ohms resistor would be ok (from datasheet min output resistance is 2k).&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-08T15:09:05.233" />
  <row Id="6424" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T15:40:13.147" Score="4" ViewCount="" Body="&lt;p&gt;If it's an old project but the compiler has been developed since, it could  be that a more recent compiler may produce smaller code&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-08T15:40:13.147" CommentCount="2" />
  <row Id="6425" PostTypeId="2" ParentId="6421" CreationDate="2010-11-08T15:55:02.960" Score="0" ViewCount="" Body="&lt;p&gt;The outputs will never be 'floating', they'll always be driven by your IC, so you don't need to add pull-ups/downs.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-08T15:55:02.960" CommentCount="2" />
  <row Id="6426" PostTypeId="2" ParentId="6173" CreationDate="2010-11-08T16:09:21.367" Score="3" ViewCount="" Body="&lt;p&gt;I learned 'em the old-fashioned way:  By having a stack of assorted resistors on my desk and having to look up the code each time I needed one.  Pretty soon, I could recognize a 470 or 10K by sight. (This is what you want, rather than reading digits individually.  Or do you read words one letter at a time?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now it is 2010, and color codes are obsolete.  Do not spend time learning them.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-08T16:09:21.367" CommentCount="3" />
  <row Id="6427" PostTypeId="1" CreationDate="2010-11-08T16:17:01.037" Score="0" ViewCount="150" Body="&lt;p&gt;I read about Looxcie - &lt;a href=&quot;http://www.looxcie.com/how-looxcie-works.html&quot; rel=&quot;nofollow&quot;&gt;http://www.looxcie.com/how-looxcie-works.html&lt;/a&gt; and it looks great, but I'm trying to get a better idea of the alternative products out there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In case ppl dont wanna follow the link - its a &quot;wearable camcorder&quot; that fits over your ear and records things at eye level.&lt;/p&gt;&#xA;" LastActivityDate="2010-11-08T16:17:01.037" ClosedDate="2010-11-09T10:19:47.877" Title="Alternatives to Looxcie - wearable camcorder" Tags="&lt;hardware&gt;&lt;video&gt;" />
  <row Id="6428" PostTypeId="2" ParentId="6403" CreationDate="2010-11-08T16:25:30.847" Score="4" ViewCount="" Body="&lt;p&gt;That's a combination of several factors:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;conventions - it's easier to design a system when the chips are supplied with the same voltage. Even more important is that the supply voltage determines voltage levels of CMOS digital outputs and voltage thresholds of inputs. The standard for chip-to-chip communication used to be 5V, nowadays it is 3.3V, although recently there was an explosion of low voltage swing serial communication interfaces. You could say that here &quot;the industry&quot; decides the supply voltage.&lt;/li&gt;&#xA;&lt;li&gt;CMOS manufacturing process limitations - as the MOS transistors shrink, so does the thickness of the gate insulation material and the channel length. As the result the supply voltage has to be lowered to avoid reliability issues or damage. To maintain a &quot;convenient&quot; supply voltage at I/O interfaces (like 3.3V - see above), these cells are made using different (bigger and slower) transistors than the core of the chip. Here the &quot;fab&quot; (whoever designed the manufacturing process there) decides the voltage.&lt;/li&gt;&#xA;&lt;li&gt;Power consumption - at each process generation a chip can accommodate 2x more transistors, running at x2 higher frequency (at least that was true until recently) - if nothing is done that gives 2*2=4 times increase in power consumption per unit area. To reduce it the supply voltage is (or was) scaling down proportionally to transistor sizes, leaving 2x increase in power/unit area. Here the chip designer's voice is important.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Recently the picture got more complicated - the supply voltage can't easily scale down because of limited intrinsic transistor gain. This gain presents a tradeoff (at a given supply voltage) between the &quot;on&quot; resistance of the transistor channel, which limits switching speed, and &quot;off&quot; resistance that causes current leakage through it. That's why core supply voltage settled at around 1V causing the speed of new digital IC chips to grows more slowly and their power consumption to grows faster than it used to be. Things are getting worse if you consider manufacturing process variability - if you can't position transistor switching threshold voltage accurately enough (and as transistors are getting smaller it becomes very difficult) the margin between &quot;on&quot;/&quot;off&quot; resistances disappears. The variability is an engineering problem so, at least in theory, it is fixable, but limited gain of MOS transistors is something we have to live with until we get better devices.&lt;/p&gt;&#xA;" OwnerUserId="1880" LastActivityDate="2010-11-08T16:25:30.847" CommentCount="5" />
  <row Id="6429" PostTypeId="2" ParentId="6403" CreationDate="2010-11-08T16:29:20.890" Score="2" ViewCount="" Body="&lt;p&gt;Short answer:  The geeks at TI said so, and everyone else followed suit by making compatible or competing products.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5 Volts was chosen for &lt;a href=&quot;http://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logic#Interfacing_considerations&quot; rel=&quot;nofollow&quot;&gt;noise immunity&lt;/a&gt;.  Early chips were power hogs, causing ripple in the power supply every time something switched that designers would try to overcome by putting a capacitor on the supply pins of every chip.  Even so, an extra 2.4 volts of headroom gave them a cushion against going into the forbidden area between 0.8V and 2.2V.  Also, the transistors caused ~0.4 V voltage drop just by their operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The supply voltages have been dropping to extend battery life, and because the chip dies have been shrinking to make your portable devices smaller and lighter.  The closer spacing of the components on the chip demands lower voltages to prevent excessive heating and because the higher voltage could cross through the thinner insulation.&lt;/p&gt;&#xA;" OwnerUserId="1824" LastActivityDate="2010-11-08T16:29:20.890" CommentCount="1" />
  <row Id="6430" PostTypeId="2" ParentId="6372" CreationDate="2010-11-08T16:30:58.373" Score="1" ViewCount="" Body="&lt;p&gt;A vise is an essential tool for soldering.  If you're still looking, I'd recommend the &lt;a href=&quot;http://www.panavise.com/index.html?pageID=1&amp;amp;id1=1&amp;amp;startat=1&amp;amp;--woSECTIONSdatarq=1&amp;amp;--SECTIONSword=ww&quot; rel=&quot;nofollow&quot;&gt;Panavise tools&lt;/a&gt;.  The pads for the 203 and 303 heads often have (or can be made to have) grooves which hold PCBs well, or you can use a vise specifically designed for holding PCBs, like the 315.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you're burning your hands because you don't want to spend the money on a vise, or you're just looking for a more economical alternative, a set of &lt;a href=&quot;http://www.pandawill.com/images/l/201007/12803024420.jpg&quot; rel=&quot;nofollow&quot;&gt;'helping hands'&lt;/a&gt; is a perfectly fine for holding small PCBs.  These can often be found for less than $10, and usually include a magnifier and heavy base.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need it right now, you can probably save your fingertips from being burned with just a heavy piece of wire affixed to your workstation and a pair of alligator clips screwed to each end of the wire.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-08T16:30:58.373" CommentCount="2" />
  <row Id="6431" PostTypeId="2" ParentId="6388" CreationDate="2010-11-08T16:50:30.130" Score="0" ViewCount="" Body="&lt;p&gt;The voltage regulator compares the output voltage against a reference voltage (often built into the regulator itself), so &lt;strong&gt;if&lt;/strong&gt; there were no any imperfections, the output voltage would be totally independent from the input voltage, output current, temperature etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A switching regulator may not necessarily be a bad idea, if you can make sure the switching noise is always out of frequency band of your signal of interest (here 20Hz~20kHz) - then it is just as good as a linear voltage regulator. In practice that might not be so easy to verify (the noise is modulated by the loop response etc.)&lt;/p&gt;&#xA;" OwnerUserId="1880" LastActivityDate="2010-11-08T16:50:30.130" />
  <row Id="6432" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T16:55:39.017" Score="4" ViewCount="" Body="&lt;p&gt;You can examine the amount of stack space and heap space that are allocated.  You may be able to get a substantial amount of RAM back if either or both of these are over allocated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My guess is for a project that fits into 2k of RAM to start with there is no dynamic memory allocation (use of &lt;code&gt;malloc&lt;/code&gt;, &lt;code&gt;calloc&lt;/code&gt;, etc.).  If this is the case you can get rid of you heap altogether assuming the original author left some RAM allocated for the heap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have to be very careful reducing the stack size as this can cause bugs that are very difficult to find.  It may be helpful to start by initializing the entire stack space to a known value (something other than 0x00 or 0xff as these values occur commonly already) then run the system for a while to see how much stack space is unused.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-11-08T16:55:39.017" CommentCount="4" />
  <row Id="6433" PostTypeId="2" ParentId="6339" CreationDate="2010-11-08T17:00:42.567" Score="1" ViewCount="" Body="&lt;p&gt;You'll find that without modulation the circuit (like one posted by Thomas O) will be extremely sensitive to ambient illumination. When the lightning conditions change the output will stick to either 0 or 5V. In theory you could work it around by adding a biasing circuit driven by a very low bandwidth feedback loop (so that slow illumination changes are cancelled and your signal is not) but it's much easier to modulate the signal driving your IR LED - that's what most (all?) commercial circuits do.&lt;/p&gt;&#xA;" OwnerUserId="1880" LastActivityDate="2010-11-08T17:00:42.567" />
  <row Id="6434" PostTypeId="2" ParentId="6280" CreationDate="2010-11-08T17:49:20.057" Score="0" ViewCount="" Body="&lt;p&gt;As for (1): before modulating a carrier, data are usually encoded - one reason is to guarantee that there are no long trains of zeros or ones. Other reason is to add some data redundancy, so that the receiver can decode original data even if some of them were demodulated incorrectly due to channel noise or interferers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for (2): the transition time is (should be) negligible comparing to the data rate. Transition times may in fact be further extended by some filtering (band-pass or low-pass) often required to remove interferences.&lt;/p&gt;&#xA;" OwnerUserId="1880" LastActivityDate="2010-11-08T17:49:20.057" />
  <row Id="6435" PostTypeId="2" ParentId="5773" CreationDate="2010-11-08T18:18:49.317" Score="10" ViewCount="" Body="&lt;p&gt;I love C# and find the productivity benefits of developing in C# with Visual Studio to be a very strong factor in favor of the Netduino.  I would not pooh-pooh Netduino because &quot;C# isn't for microcontroller/embedded environments&quot; as other answers here indicate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can make great fun projects and learn a lot about connecting different physical inputs and output devices using Netduino just as you can with Arduino or going &quot;bare metal&quot; and doing the direct MCU management of the AVR, PIC, or other microcontrollers.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With that said I am sticking with Arduino for the following reasons:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Better community support.  Arduino just has way more samples, examples, and a bigger community you can draw upon.&lt;/li&gt;&#xA;&lt;li&gt;Netduino doesn't have a story for going beyond the expensive kit/prototyping approach.  Going to implement an interactive art exhibit requiring dozens of microcontrollers running your code?  Get ready to shell out $35 each for the Netduinos.  With Arduino you can prototype on the Arduino and then implement on a bare-bones MCU-only solution with the AVR microcontroller for under $10 each.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So I would say if your C skills are dusty or nonexistant,  you love C# and Visual Studio, and just want to tinker on a few hobby projects that won't need to scale out to where cost becomes a bigger issue, go Netduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are comfortable in C, or comfortable in getting by in it with the help of code samples and the community, and want to be closer to the metal and look at eventually getting away from the &quot;prototype&quot; approach of Netduino and Arduino, go Arduino to get started.&lt;/p&gt;&#xA;" OwnerUserId="707" LastActivityDate="2010-11-08T18:18:49.317" CommunityOwnedDate="2011-02-27T07:33:15.000" />
  <row Id="6436" PostTypeId="1" AcceptedAnswerId="6449" CreationDate="2010-11-08T19:04:48.203" Score="13" ViewCount="501" Body="&lt;p&gt;Hi there,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a software guy who wants to get into the hardware side of things so I can enjoy the same creativity from software design in the physical world. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found plenty of posts here regarding how to get &quot;up and running&quot; in the electronics world, but I would like to know if there are any gotchas when embarking on this journey if your goal is to potentially have a device manufactured in the future. (probably robotics-centric solutions, boards that would control servos, sensors, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to make sure that wherever I aim my focus, I won't be &quot;learning myself into a corner&quot;, so to speak.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have read good things about the flexibility and easy to learn nature of Arduino devices, but have trouble finding anything about getting them manufactured. Are there manufacturers that can produce an arduino-based solution? What kind of production volume is available for something using Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What realms/devices of programmable electronics are best for having manufactured? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any tips or info regarding learning and designing with manufacturing in mind? Any general tips for a newbie?&lt;/p&gt;&#xA;" OwnerUserId="1886" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-30T21:25:48.717" LastActivityDate="2011-01-26T16:42:03.900" Title="How to go from newbie to manufactured?" Tags="&lt;manufacturing&gt;&lt;learning&gt;&lt;dfm&gt;" AnswerCount="10" CommentCount="1" FavoriteCount="10" />
  <row Id="6437" PostTypeId="2" ParentId="6436" CreationDate="2010-11-08T19:15:26.200" Score="1" ViewCount="" Body="&lt;p&gt;I'm not clear if it's technical corners you're worried about or business corners?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I may be a bit jaundiced about 'hobbyists', but I seriously doubt the world needs more not-really-industrial-quality robotic subsystems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sub-contract production facilities exist for every volume from 1-off to millions-off, and things like PCBs can be made at every timescale from next-day to weeks.  My experience of electronic production is that component supply is one of the biggest problem unless you're at sufficient volumes to have component manufacturers run around for you.  Nowadays for low-ish value parts, that will be seriously, seriously high volumes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps you should clarify your question slightly - are you planning to speculatively design devices and have them manufactured, then place them on the open market?&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-08T19:15:26.200" CommentCount="2" />
  <row Id="6438" PostTypeId="2" ParentId="5710" CreationDate="2010-11-08T19:54:21.320" Score="2" ViewCount="" Body="&lt;p&gt;Can you post more details regarding the target frequency, jitter and loop bandwidth (required settling time)? Also, what kind of oscillator do you want to use (external with a DAC, with/without dithering?, an on chip digital counter/accumulator)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're happy with a digital &quot;oscillator&quot; (i.e. an overflowing accumulator) and its jitter then the rest of the circuit can be fairly simple:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;a counter (PFD) counting number of cycles between the reference and the (optionally divided) PLL output,&lt;/li&gt;&#xA;&lt;li&gt;a digital filter - anything will do assuming it does the integration (an accumulator) and it has a zero (minus (or plus?) a scaled PFD output) to stabilize the loop, optionally one or more poles above the loop bandwidth to reduce the control value &quot;ripple&quot; at reference frequency (only matters if fref&#xA;&lt;li&gt;most significant bits of the digital filter output (DVCO control value) are given as an input to the overflowing accumulator (DVCO).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As for the loop bandwidth, if not enforced by settling time, decide it based on the noise contributions of all components.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;If the jitter comes mainly from the reference or from PFD - use a smaller bandwidth,&lt;/li&gt;&#xA;&lt;li&gt;If the noise comes from the oscillator - increase it.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In case if the reference signal is phase or frequency modulated - use a loop bandwidth lower than the smallest frequency of the signal modulating the reference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Trickier techniques are used if the output frequency is close or equal to clock frequency and/or if the low jitter or very fast locking range is required. Maybe in your case they are not needed, besides they may not be well suited to an FPGA implementation.&lt;/p&gt;&#xA;" OwnerUserId="1880" LastActivityDate="2010-11-08T19:54:21.320" />
  <row Id="6439" PostTypeId="1" CreationDate="2010-11-08T19:55:36.193" Score="1" ViewCount="201" Body="&lt;p&gt;Hello folks, I have a couple of questions regarding using a precision voltage reference on a DAC - AD7545A. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to fix an existing circuit that uses AD584  to provide a 5V DAC (AD745A) to provide an Analog Output between 0 to 5V using a circuit design similar to this figure 4 on the &lt;a href=&quot;http://www.analog.com/static/imported-files/data_sheets/AD7545A.pdf&quot; rel=&quot;nofollow&quot;&gt;AD7545A&lt;/a&gt; datasheet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And then it is stepped up (amplified to 0 - 12V) with a high current opamp OPA548 to drive a load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, my question is can I use AD7545A to provide the 0 - 12 V output without going through an extra space? I will have to replace the AD711 in the figure with OPA548 to drive the load, and also I will need a precision voltage reference that can provide a 12 V reference to the DAC. AD584 has only 4 programmable outputs - 10,7.5,5 and 2.5. What would be a good replacement. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, and the second question is, that in case I have to use the existing circuit, the application notes I found on the AD584 datasheet shows it giving a -10V reference to DAC using the configuration of figure 16.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to give it a +ve 5 V reference instead. Is it as easy as as just connecting the +5V pin to the Vdd of the DAC, providing the 15V Vin to 584 and grounding the common?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry, I tried posting the figures here, but as a new user I cannot post pictures yet.&lt;/p&gt;&#xA;" OwnerUserId="1581" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:30:37.107" LastActivityDate="2011-03-05T16:30:37.107" Title="Precision Voltage Reference" Tags="&lt;dac&gt;&lt;voltage-reference&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="6440" PostTypeId="2" ParentId="6436" CreationDate="2010-11-08T20:03:17.967" Score="1" ViewCount="" Body="&lt;p&gt;If you are looking for a easy and cheap start for microcontroller programming, one good place to start would be using the TI's new Launchpad development toolkit. &#xA;&lt;a href=&quot;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_%28MSP-EXP430G2%29?DCMP=launchpad&amp;amp;HQS=Other+OT+launchpadwiki&quot; rel=&quot;nofollow&quot;&gt;Launchpad&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This thing costs only $5 and is quite easy to learn in my opinion. &lt;/p&gt;&#xA;" OwnerUserId="1581" LastActivityDate="2010-11-08T20:03:17.967" CommentCount="1" />
  <row Id="6441" PostTypeId="2" ParentId="5773" CreationDate="2010-11-08T20:09:34.123" Score="1" ViewCount="" Body="&lt;p&gt;When reading 'C# isn't suitable for embedded platforms', remember that people older than a certain age have already heard that said at least once about 'C' and then again about C++ in their lifetimes...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course it's monumentally 'wasteful' of the underlying capabilities of the processor, but the ability to run your idle loop 1000x faster than you need rather than 10x faster than you need never made anyone rich.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-08T20:09:34.123" CommunityOwnedDate="2011-02-27T07:33:15.000" CommentCount="2" />
  <row Id="6442" PostTypeId="1" AcceptedAnswerId="6445" CreationDate="2010-11-08T20:35:08.227" Score="2" ViewCount="128" Body="&lt;p&gt;As seen on &lt;a href=&quot;http://meta.electronics.stackexchange.com/questions/146/is-er-the-place-to-ask-about-questions-of-programming-but-related-to-microcontr/147#147&quot;&gt;Meta&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm asking for the ISR name for the comparator interrupt for a dsPIC33F. I've tried _CompInterrupt, _CMInterrupt and _CMPInterrupt. All three bring up warnings about non-existent ISR names. I can't find it anywhere in the datasheets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-08T23:47:16.197" Title="What is the ISR for the comparator change interrupt on a dsPIC33F?" Tags="&lt;dspic&gt;&lt;interrupt&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="6443" PostTypeId="2" ParentId="6439" CreationDate="2010-11-08T20:35:48.587" Score="1" ViewCount="" Body="&lt;p&gt;As for supplying AD7545A with higher voltage, that should be alright. Don't forget level shifters for your digital inputs, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the reference voltage - you need an independent 12V voltage source to set the required output voltage range of the DAC. Not sure how to do this with AD584 - I don't see any obvious way. You could perhaps use two of them but they have to refer to ground (not Vdd).&lt;/p&gt;&#xA;" OwnerUserId="1880" LastActivityDate="2010-11-08T20:35:48.587" CommentCount="2" />
  <row Id="6444" PostTypeId="2" ParentId="6442" CreationDate="2010-11-08T22:04:00.623" Score="1" ViewCount="" Body="&lt;p&gt;The data sheet should give a table of interrupt vectors. For the dsPIC33FJ06GS101 it's on page 99, and shows the analogue comparator interrupt (CMP1) at Vector Number 26.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Questions about Microchip devices will probably get a better response on the &lt;a href=&quot;http://www.microchip.com/forums/Default.aspx?&quot; rel=&quot;nofollow&quot;&gt;Microchip forums&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-08T23:47:16.197" LastActivityDate="2010-11-08T23:47:16.197" CommentCount="2" />
  <row Id="6445" PostTypeId="2" ParentId="6442" CreationDate="2010-11-08T23:12:57.833" Score="2" ViewCount="" Body="&lt;p&gt;Looks like this might be what you want &lt;a href=&quot;http://www.microchip.com/forums/tm.aspx?m=427159&amp;amp;mpage=1&amp;amp;print=true&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/forums/tm.aspx?m=427159&amp;amp;mpage=1&amp;amp;print=true&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="820" LastActivityDate="2010-11-08T23:12:57.833" CommentCount="1" />
  <row Id="6446" PostTypeId="2" ParentId="6436" CreationDate="2010-11-08T23:19:03.407" Score="6" ViewCount="" Body="&lt;p&gt;Watch this video which highlights the differences between software and hardware :&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.adafruit.com/blog/2010/10/28/hardware-will-cut-you-video/&quot; rel=&quot;nofollow&quot;&gt;Hardware will cut you&lt;/a&gt;&#xA;(contans NSFW language)  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-08T23:19:03.407" CommentCount="1" />
  <row Id="6447" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T23:27:00.990" Score="1" ViewCount="" Body="&lt;p&gt;If you're already using a professional-level compiler like IAR, I think you're going to struggle to get any serious savings by minor low-level code-tweaking - you'll need to be looking more towards removing functionality or doing major rewrites of parts in a more efficient way. You'll need to be a smarter coder than whoever wrote the original version... &#xA;As for RAM you need to take a very hard look at how it is currently used, and see if there is scope for overlaying usage of the same RAM for different things at different times (unions are handy for this).&#xA;IAR's default heap and stack sizes in the ARM/AVR ones I've have tended to be over-generous, so these would be the first thing to look at.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-08T23:27:00.990" CommentCount="2" />
  <row Id="6448" PostTypeId="2" ParentId="6392" CreationDate="2010-11-08T23:44:53.100" Score="2" ViewCount="" Body="&lt;p&gt;Does your code use floating point math? You may be able to re-implement your algorithms using integer math only, and eliminate the overheads of using the C floating point library. E.g. in some applications, such functions as sine, log, exp can be replaced by integer polynomial approximations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does your code use large look-up tables for any algorithms, such as CRC calculations? You can try substituting a different version of the algorithm that calculates values on-the-fly, instead of using the look-up tables. The caveat is that the smaller algorithm is most likely slower, so make sure you have enough CPU cycles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does your code have large amounts of constant data, such as string tables, HTML pages, or pixel graphics (icons)? If it's large enough (say 10 kB), it could be worth implementing a very simple compression scheme to shrink the data and decompress it on-the-fly when needed.&lt;/p&gt;&#xA;" OwnerUserId="1025" LastEditorUserId="1025" LastEditorDisplayName="" LastEditDate="2010-11-08T23:52:34.400" LastActivityDate="2010-11-08T23:52:34.400" CommentCount="1" />
  <row Id="6449" PostTypeId="2" ParentId="6436" CreationDate="2010-11-09T00:00:04.987" Score="17" ViewCount="" Body="&lt;p&gt;Just to let you know what lies ahead....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to go from making a hand-built breadboard or prototype to actual PCB's, you have a lot of hours and anywhere from several hundred to a few thousand dollars cost in front of you, depending on how much you are willing to do yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Schematic capture and PCB layout&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First of all you need to capture your design using some sort of schematic capture program, and then design a PCB.  One of the more popular programs is &lt;a href=&quot;https://www.cadsoft.de/index.htm&quot; rel=&quot;nofollow&quot;&gt;EAGLE&lt;/a&gt;, which I use.  They have a EAGLE Light version ($49), but it can only be used for schematics with one sheet (any size), two signal layers, and 100x80mm (approx 4&quot;x3&quot;) routing area.  For any serious work, you need at least the EAGLE Standard version, which costs $747.  There are probably other less costly (even free) alternatives.  There are lots of others that cost thousands or tens of thousands of dollars.  In any case you will have to spend considerable time learning how to use the program.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or you can pay someone like me to do it for you ($$/hour).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;PCB Fabrication&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting boards made is the next step by a &lt;a href=&quot;http://www.4pcb.com/&quot; rel=&quot;nofollow&quot;&gt;PCB fabricator&lt;/a&gt;.  The problem here is the NRE (non-recurring engineering) costs.  Some board houses treat this as a separate figure, and others built it into their per-board quote.  In any case, it is almost never economical to have just a few boards made.  You might spend $100 for two boards, and $500 for 25.  You need to have really large quantities to get down to just a few dollars per board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The gotcha is, if you make 25 boards, populate just a couple of them for testing and find they don't work (and there is not an easy fix -- e.g. because you laid out a connector backwards), you might end up throwing away the other 23 blank boards away and you would have been better off just getting two.  I have stacks of blank PCB's as evidence of this phenomena.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;PCB Assembly&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless you are willing to build the boards by hand, you will need to have them assembled.  Surface mount packages are difficult to deal with.  If the board has BGA or QFN packages, you probably won't be able to build them yourself unless you have your own reflow oven.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting your first two boards built by an &lt;a href=&quot;http://www.screamingcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;assembly house&lt;/a&gt; might cost $500.  Whereas getting 25 built might cost $1200.  (Once again, the problem here is the NRE costs.)  Getting down to just a few dollars per board requires (again) large quantities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And someone else has already discussed the problem of getting parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure you use parts that are readily available -- if both DigiKey and Mouser have hundreds of the part available you should be okay.  If instead, they have it in their catalog, but it is currently out-of-stock, try to find something else.  If you need some special parts that aren't carried by DigiKey or Mouser, make sure you have a reliable source before incorporating it in your product.  (Note: the more unusual parts you use, the more likely you will have to add the part manually to your PCB parts library.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Custom Cases&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you want to put your board into a case?  If you need to have a custom case designed, that will be a couple thou for the designer using a program like &lt;a href=&quot;http://www.solidworks.com/&quot; rel=&quot;nofollow&quot;&gt;SolidWorks&lt;/a&gt; (I don't do that, but can recommend someone who can).  If you are going to make just a few cases to begin with, you will probably need to go with rapid prototyping, such as &lt;a href=&quot;http://www.padtinc.com/rm/sls/default.htm&quot; rel=&quot;nofollow&quot;&gt;Selective Laser Sintering&lt;/a&gt; (SLS).  Figure at least $100 per case in small quantities.  To get down to a few dollars per case cost, you need to have a custom mold made.  NRE time again!  Plan on spending $10,000 or more for the mold.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And I won't even start on EMC or EMI testing, since I don't know if it applies to your product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see from all of this, until you get into production, the cost of the electronic parts is usually not the biggest item on a per board basis.  Doing your own assembly for small volumes will save you a lot of money.  So it is important to design with that in mind -- no impossible to solder-by-hand parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get really low prices for high-volume, generally you need to go offshore -- China etc.  But I would avoid doing so in the beginning.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-11-09T12:02:07.983" LastActivityDate="2010-11-09T12:02:07.983" CommentCount="5" />
  <row Id="6450" PostTypeId="2" ParentId="6436" CreationDate="2010-11-09T01:57:48.963" Score="4" ViewCount="" Body="&lt;p&gt;Premature optimization is the root of all evil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino is a fine place to start.  Don't worry about mass production yet.  Once you have a couple designs under your belt you'll have a much better idea of what you need to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Learning new hardware is part of the game here.  Don't try to avoid it.  The more you are familiar with, the better an engineer you'll be.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-09T01:57:48.963" />
  <row Id="6451" PostTypeId="1" AcceptedAnswerId="6459" CreationDate="2010-11-09T03:12:40.157" Score="2" ViewCount="117" Body="&lt;p&gt;Any idea where I can get parts for Roland synthesizers?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a Roland Fantom (FA-76, the original without sequencers and what not) and its pitch bender seems to be a bit worn out, or possibly dusty. (As I pitch up/down, sometimes the pitching skips around a bit, especially near center.)  I'd like to get a replacement for the pitch bender, but can't figure out where to order parts.  E-mails to Roland never get replied.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any thoughts?&lt;/p&gt;&#xA;" OwnerUserId="1554" LastActivityDate="2010-11-09T07:30:23.587" Title="Pitch Bender for Roland Fantom FA-76" Tags="&lt;parts&gt;" AnswerCount="1" />
  <row Id="6452" PostTypeId="1" AcceptedAnswerId="6456" CreationDate="2010-11-09T03:18:24.253" Score="2" ViewCount="110" Body="&lt;p&gt;&lt;a href=&quot;http://www.kemet.com/kemet/web/homepage/kechome.nsf/weben/500731829C9D2F51852572EC006DFE40/%24file/F3281_X7R_FlexCap.pdf&quot; rel=&quot;nofollow&quot;&gt;These capacitors from Kemet&lt;/a&gt; have flexible termination.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet says it caters for applications where the board flexes and normal ceramic caps can fail. However, I fail to see a situation where PCB's flex? If PCB's had the potential to flex, wouldn't you just get a tougher enclosure?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-11-09T06:14:00.100" LastActivityDate="2010-11-16T01:24:26.123" Title="What situation would you use flexible termination ceramic capacitors?" Tags="&lt;pcb&gt;&lt;capacitor&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="6453" PostTypeId="2" ParentId="6452" CreationDate="2010-11-09T03:29:11.853" Score="1" ViewCount="" Body="&lt;p&gt;Data sheet says shear stress and thermal cycling. Good points. Furthermore, a PCB may flex in use if it had a socket for something that was inserted and removed more than occasionally. Or perhaps in high-vibration environments such as a data logger in an off-road vehicle? &lt;/p&gt;&#xA;" OwnerUserId="1307" LastEditorUserId="1307" LastEditorDisplayName="" LastEditDate="2010-11-09T03:41:41.823" LastActivityDate="2010-11-09T03:41:41.823" />
  <row Id="6454" PostTypeId="1" AcceptedAnswerId="6455" CreationDate="2010-11-09T03:30:00.153" Score="6" ViewCount="242" Body="&lt;p&gt;I always see the option for E-testing when sending PCB's off to a fab house. I gather it is an eletrical test to test all the connections. But how do they do it? They don't have my schematic! Only gerbers? And surely it is done by machine?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-13T21:04:47.577" LastActivityDate="2010-12-13T21:04:47.577" Title="How does E-Test at a PCB Fab work?" Tags="&lt;pcb&gt;&lt;manufacturing&gt;&lt;gerber&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="6455" PostTypeId="2" ParentId="6454" CreationDate="2010-11-09T04:02:30.467" Score="10" ViewCount="" Body="&lt;p&gt;As I understand it, they extract a pad-list and netlist from the gerbers, and then have a machine with robotic arms carrying test-probes (Termed &quot;Flying Probes&quot;) to manually ohm-out all the connected nets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See:&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Flying_probe&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Flying_probe&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.spea.com/ElectronicsIndustryTestAutomation/FlyingProbeTesters/tabid/108/language/en-US/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.spea.com/ElectronicsIndustryTestAutomation/FlyingProbeTesters/tabid/108/language/en-US/Default.aspx&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.youtube.com/user/speamovies&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/user/speamovies&lt;/a&gt; (Really cool videos)  &lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="399" LastEditorDisplayName="" LastEditDate="2010-11-09T15:00:33.133" LastActivityDate="2010-11-09T15:00:33.133" />
  <row Id="6456" PostTypeId="2" ParentId="6452" CreationDate="2010-11-09T04:09:34.947" Score="2" ViewCount="" Body="&lt;p&gt;Flexible-termination caps are commonly used in automotive applications, where vibration causes the board to flex back-and forth a small amount repeatedly. Normal components in this application can sprout fatigue stress-fractures that gradually enlarge over time until they fail, which in some automotive applications can have catastrophic effects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is very hard to completely remove vibration-caused flex without massively supporting a PCB, and that is very expensive, even compared to fancy caps like the Kemet ones linked.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As tronixstuff mentioned, they are also commonly used in situation where the environment is fairly extreme, as there is no way to completely prevent thermal stresses, since the different aspects of a PCB have different coefficients of expansion as the temperature changes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, they're for high-reliability/extreme-environment applications.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-11-16T01:24:26.123" LastActivityDate="2010-11-16T01:24:26.123" CommentCount="1" />
  <row Id="6457" PostTypeId="2" ParentId="6452" CreationDate="2010-11-09T04:30:48.020" Score="1" ViewCount="" Body="&lt;p&gt;Here is an example of an interesting case where flexible PCB is used:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/5620/mechanical-connectors-for-flexible-pcbs&quot;&gt;Mechanical connectors for flexible PCBs?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like other have said though, the biggest focus is applications where you have vibrations.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-09T04:30:48.020" />
  <row Id="6458" PostTypeId="1" CreationDate="2010-11-09T07:28:52.007" Score="2" ViewCount="449" Body="&lt;h3&gt;DESCRIPTION:&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;It will play &lt;strong&gt;.wav&lt;/strong&gt; and &lt;strong&gt;.mp3&lt;/strong&gt; files from a Micro SD Card. The memory card can be written through USB (its an in-board unit). It will have a LCD screen to show the contents and functions like next, pause, previous, volume control and so on. Obviously, these functions can be remotely operated too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am familiar with PIC MCUs but being a beginner I have difficulties in deciding which MCU is enough for the job.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;Should I go for a PIC32 or dsPIC?&lt;/em&gt;&lt;/strong&gt; I'd appreciate all suggestions regarding this project.&lt;/p&gt;&#xA;" OwnerUserId="1484" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-12T06:40:51.507" LastActivityDate="2011-02-12T06:40:51.507" Title="Which PIC MCU for an Audio player?" Tags="&lt;pic&gt;&lt;usb&gt;&lt;audio&gt;&lt;dspic&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="6459" PostTypeId="2" ParentId="6451" CreationDate="2010-11-09T07:30:23.587" Score="2" ViewCount="" Body="&lt;p&gt;It's not exactly what you are looking for, but potentiometers' resistive elements often get a bit oxidised as they get older.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, potentiometers are designed to be &lt;em&gt;self-wiping&lt;/em&gt;, meaning that cycling the pot back and forth will often break through the oxide layer and restore some of the functionality.&lt;br&gt;&#xA;Alternatively, any electronics &lt;a href=&quot;http://www.google.com/search?q=contact+cleaner&quot; rel=&quot;nofollow&quot;&gt;contact cleaner&lt;/a&gt; may be very effective. Just squirt a bit down the sides into the pitch-bend controller, and work it back and forth repeatedly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a last ditch attempt, if the above does not work, the wiper may have relaxed a bit, and therefore may not be making good contact with the resistive element in the pot (see the &lt;a href=&quot;http://en.wikipedia.org/wiki/Potentiometer&quot; rel=&quot;nofollow&quot;&gt;wikipedia article&lt;/a&gt; for info on how the internals fit together). It may be possible to disassemble the pitch-bend assembly and manually bend the wiper to help it make better contact.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I realize it may not be information on how to obtain replacement parts, but many companies are a nightmare to deal with regarding obtaining any information about the internals of their products, let-alone parts. It may be worth the time to try and fix the issue yourself before simply trying to replace the defective assembly en-masse.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-11-09T07:30:23.587" CommentCount="1" />
  <row Id="6460" PostTypeId="1" CreationDate="2010-11-09T08:03:25.273" Score="1" ViewCount="102" Body="&lt;p&gt;I need to recover my data from my Memory Stick Pro Duo. It is not detectable by anything, not my PC, not my PSP, nor camera, nothing. But i need the data. It is very important. I have tried all recovery software but none of them function as it is not detectable. I dont even have enough budget to sent to a recovery lab. Is there any way I can do this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please....................&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Appreciation in Advance&lt;/p&gt;&#xA;" OwnerUserId="1895" LastActivityDate="2010-11-09T08:03:25.273" ClosedDate="2010-11-10T00:57:55.997" Title="Recover data from Memory Stick Pro Duo" Tags="&lt;memory&gt;" CommentCount="5" />
  <row Id="6461" PostTypeId="2" ParentId="5773" CreationDate="2010-11-09T08:04:13.437" Score="1" ViewCount="" Body="&lt;p&gt;If you want to feel the bare metal and for example be able to generate or capture video signal directly, that's where every cycle matters and AVR/Arduino will let you do that. If you want higher level of abstraction, higher level programming and debugging comfort, garbage collector and can live with the fact that like in Windows you don't control everything, then choose NetDuino or FEZ Domino. Since both have ARM in their hearth, I bet that if needed you can kill .NET MF on the board and flash bare metal ARM GCC code directly from some Eclipse like IDE with help of a small JTAG debugger. Investigate a little. The problem might be that if JTAG header is missing, you'll need to do some soldering.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastEditorUserId="1129" LastEditorDisplayName="" LastEditDate="2010-11-09T08:10:07.563" LastActivityDate="2010-11-09T08:10:07.563" CommunityOwnedDate="2011-02-27T07:33:15.000" CommentCount="2" />
  <row Id="6462" PostTypeId="2" ParentId="6173" CreationDate="2010-11-09T10:11:07.903" Score="0" ViewCount="" Body="&lt;p&gt;I like this &lt;a href=&quot;http://samengstrom.com/nxl/10116/5_band_resistor_color_code_page.en.html&quot; rel=&quot;nofollow&quot;&gt;site&lt;/a&gt; because it converts 4, 5 and 6 band resistors. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-11-09T10:11:07.903" />
  <row Id="6463" PostTypeId="2" ParentId="6458" CreationDate="2010-11-09T10:24:06.277" Score="5" ViewCount="" Body="&lt;p&gt;The dsPIC seems to be not powerful enought to play an mp3, although you can use a dedicated chip to decode and the dsPIC to play the music and read the file on the SD card. A tutorial on a similar project can be seen at &lt;a href=&quot;http://www.uchobby.com/index.php/2008/07/21/dspic-wav-player/&quot; rel=&quot;nofollow&quot;&gt;http://www.uchobby.com/index.php/2008/07/21/dspic-wav-player/&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip themselves have an application note on how to port Helix MP3 decoder to PIC32, (AN1367: &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en551513&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en551513&lt;/a&gt;) so that may be the natural choice.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-11-09T18:55:38.527" LastActivityDate="2010-11-09T18:55:38.527" CommentCount="7" />
  <row Id="6464" PostTypeId="2" ParentId="6436" CreationDate="2010-11-09T10:25:36.693" Score="4" ViewCount="" Body="&lt;p&gt;I've gone down this route over the past few years and am now selling small quantities of my designs. I chose Microchip microcontrollers early on and have stuck with them, but Arduinos and the AVR microcontrollers seem an equally good solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For PCB design I can recommend Eagle - I've never gone past the Light version since I'm only building quite small boards. It allows you to add your own parts, which you are going to need at some stage. It does auto-routing of PCB tracks, although I find I'm using this less as time goes by - partly because I'm making boards with very tight space constraints and am constantly fiddling with both part placement and routing to get everything packed in. It provides checking against design rules, which helps to catch blunders in your layout. There is a lot to learn but you will get proficient with it over time and boards can be manufactured from your digital files.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PCB fabrication: I build my own prototype boards then get them made professionally once I've got past the initial prototyping. I prototype double-sided boards using the Press-n-Peel transfer film and a laser printer. I routinely make boards with the little QFN surface mount packages with 0.5 mm pad spacing - it is fiddly but can be done with care. The costs for professionally made boards has been between $3 and $10 for quantities around 100.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PCB assembly: I quite successfully do reflow soldering using an electric frypan. Takes a little bit of care but is reasonably reliable and quite quick. The slowest part is getting the solder paste onto the board, although if you go to the bother of making a solder mask that can be made easier too. I frequently use leadless packages like QFN because they are small and don't have too much trouble with them. Packages with leads can be hand-soldered if you want, but I think it is quicker to use solder paste and reflow in the pan.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you get into significant volume you will want to move to paying someone else to do the assembly for you. I've not done this yet, but have been quoted on the order of $6500 for 30 boards, for which the parts cost around $80. So the added cost is not insignificant but it depends on how you cost your time to do the assembly yourself :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from the (large) time investment, my biggest single investment has probably been a USB digital oscilloscope and logic analyser from Bitscope - invaluable for working out what is actually going on, as opposed to what you think should happen!&lt;/p&gt;&#xA;" OwnerUserId="1897" LastActivityDate="2010-11-09T10:25:36.693" />
  <row Id="6465" PostTypeId="2" ParentId="6436" CreationDate="2010-11-09T10:36:37.060" Score="2" ViewCount="" Body="&lt;p&gt;For PCB manufacturing you can do a lot of prototyping on strip-board and bread-board and jump directly to professional PCBs for the &quot;production&quot; units, I use these guys and I've been very happy:&#xA;&lt;a href=&quot;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=19_20&amp;amp;products_id=175&quot; rel=&quot;nofollow&quot;&gt;http://iteadstudio.com/store/index.php?main_page=product_info&amp;amp;cPath=19_20&amp;amp;products_id=175&lt;/a&gt;&#xA;Seeed uses the same factory as itead at about the same price.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For PCB layout do not invest too much time in EAGLE as it has several limitations in the free version and it's rather clunky and hard to use, in stead take a good look at kicad and geda, both are free software and more capable than EAGLE.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-09T10:36:37.060" />
  <row Id="6467" PostTypeId="2" ParentId="6436" CreationDate="2010-11-09T11:16:07.473" Score="6" ViewCount="" Body="&lt;p&gt;Mitch Altman, designer of the TV-B-Gone gave a talk at The Next Hope on taking your project from idea to reality.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://c2047862.cdn.cloudfiles.rackspacecloud.com/tnha16.mp3&quot; rel=&quot;nofollow&quot;&gt;Here's the MP3&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Mitch has brought his personal pet&#xA;  projects (including TV-B-Gone&#xA;  universal remote controls) from idea&#xA;  to reality, and is fortunate to make a&#xA;  living doing what he loves. Mitch will&#xA;  outline the practical steps he took to&#xA;  bring his projects from a mere idea,&#xA;  through the steps of research,&#xA;  development, manufacture, sales and&#xA;  distribution, leading, finally, to&#xA;  collecting checks while in the comfort&#xA;  of his home (and while traveling the&#xA;  world). This talk will also show some&#xA;  of the pitfalls of running one’s own&#xA;  business.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-09T11:16:07.473" CommentCount="1" />
  <row Id="6468" PostTypeId="1" AcceptedAnswerId="7067" CreationDate="2010-11-09T11:16:53.060" Score="2" ViewCount="506" Body="&lt;p&gt;I'm developing a gyro+accelerometer data logging device using the Invensense ITG3200 gyro device and I'm having a real struggle getting it to talk to me. I have tried 5 of them and none of them are responding to I2C commands. Has anyone had experience using these and had to overcome hurdles to make them work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have two other sensors on the same I2C bus and they are behaving as expected, so my I2C comms is working fine. The sole bus master is a PIC microcontroller. I have wired the chip up exactly as shown in the specs, and use a common 3.3V supply for Vdd and Vlogic. Pullup resistors are 4k7, but have tried reducing them to 1k5 with no effect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The gyro chip is a bit odd electrically too - it is behaving as if it has a pullup on the SDA line to a voltage at 2/3 the supply voltage, but that ceases to supply current when the SDA voltage drops below about 0.6V. That behaviour kind of makes sense but is not documented in the spec sheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am wondering if I have managed to damage all 5 chips in exactly the same way, but that seems unlikely. One of them I purchased on a breakout board and it behaves exactly the same as the others: 2 of those are reflow soldered onto a PCB, the other 2 I glued upside down and hand soldered fine wires to the pads (getting desperate there!).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be good to hear from anyone who has used this chip successfully - seems like a great device but I am getting a tad frustrated ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did send a query to Invensense but haven't heard anything back from them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for any clues.&lt;/p&gt;&#xA;" OwnerUserId="1897" LastActivityDate="2010-12-23T22:52:54.797" Title="Any tips on using the Invensense ITG-3200 gyro?" Tags="&lt;i2c&gt;&lt;gyro&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="6469" PostTypeId="2" ParentId="6468" CreationDate="2010-11-09T11:36:40.470" Score="2" ViewCount="" Body="&lt;p&gt;I have one of these:&#xA;&lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9801&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/commerce/product_info.php?products_id=9801&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... and I've talked to it using one of these:&#xA;&lt;a href=&quot;http://dangerousprototypes.com/bus-pirate-manual/&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com/bus-pirate-manual/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... with these commands, ignore blank lines and lines starting with #, those aren't used by the BP, refer to the BP manual for info about the notation, but rest assured that all the I2C commands were found by reading the datasheet:&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;I2C mode&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;M&#xA;4&#xA;2&#xA;1&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;pull ups on&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;p&#xA;2&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Power on&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;W&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Read address:&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;[ 0b11010010 0x00 [ 0b11010011 r ]&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Configure for high bandwidth:&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;[ 0b11010010 0x15 15 24 ]&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Configure to use Z gyro as oscilator:&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;[ 0b11010010 0x3e 3 ]&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Read data:&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;[ 0b11010010 0x1b [ 0b11010011 rr rr rr rr ]&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-09T11:36:40.470" CommentCount="3" />
  <row Id="6470" PostTypeId="2" ParentId="6468" CreationDate="2010-11-09T11:55:14.697" Score="1" ViewCount="" Body="&lt;p&gt;Without seeing something more specific about your design, I'm only guessing here but looking at the datasheet for the Gyro I would suspect that your problem may have something to do with the power on sequence required (Section 4.4).  With a common supply it may be possible that due to local capacitance or signal routing that Vlogic is coming up too soon, or it may be that you haven't met the specified voltage ramp required to startup the device cleanly.&lt;/p&gt;&#xA;" OwnerUserId="820" LastActivityDate="2010-11-09T11:55:14.697" CommentCount="1" />
  <row Id="6471" PostTypeId="2" ParentId="6173" CreationDate="2010-11-09T12:44:06.617" Score="3" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WLemG.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2010-11-09T12:44:06.617" CommentCount="2" />
  <row Id="6473" PostTypeId="2" ParentId="6392" CreationDate="2010-11-09T13:09:04.493" Score="0" ViewCount="" Body="&lt;p&gt;Change the local variables to be the same size of your CPU registers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the CPU is 32-bit, use 32-bit variables even if the max value will never get above 255.  I you used an 8-bit variable, the compiler will add code to mask off the upper 24 bits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first place I would look is at the for-loop variables.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;for( i = 0; i &amp;lt; 100; i++ )&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This might seem like a good place for an 8-bit variable, but a 32-bit variable might produce less code.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-11-09T13:09:04.493" CommentCount="3" />
  <row Id="6474" PostTypeId="2" ParentId="606" CreationDate="2010-11-09T13:18:32.063" Score="1" ViewCount="" Body="&lt;p&gt;We have had a lot of luck subsituting regular white paper stock for the transparency.  We have found that the process ends up with less broken tracees and &quot;blob&quot; spots.  You have to increase the exposure time for the time under the UV light.  This only works for photo-etching.  &lt;/p&gt;&#xA;" OwnerUserId="1413" LastActivityDate="2010-11-09T13:18:32.063" />
  <row Id="6475" PostTypeId="1" AcceptedAnswerId="6477" CreationDate="2010-11-09T13:18:50.243" Score="3" ViewCount="179" Body="&lt;p&gt;Is there a special name for a potentiometer whose A-W or B-W resistance can drop to zero? I have a 1k +/-10% pot and I can only vary A-W or B-W resistance from 118 ohms to 1.2k. Note A, B refer to the outer pins and W the wiper pin.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-11T04:01:02.497" Title="Potentiometer that goes to zero" Tags="&lt;potentiometer&gt;" AnswerCount="5" CommentCount="4" FavoriteCount="1" />
  <row Id="6476" PostTypeId="2" ParentId="6475" CreationDate="2010-11-09T13:48:35.503" Score="0" ViewCount="" Body="&lt;p&gt;The way to achieve what you are asking is probably either really expensive or impossible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good engineering practice is to design a circuit allowing for 10% tolerances, anyway.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-11-09T13:48:35.503" CommentCount="2" />
  <row Id="6477" PostTypeId="2" ParentId="6475" CreationDate="2010-11-09T14:02:00.280" Score="6" ViewCount="" Body="&lt;p&gt;I suspect that what you're seeing is a combination of a poorly-manufactured pot and the resistance of the connections to the pot. There's always a couple ohms of resistance in anything you measure, just because you can't attach your multimeter to anything with infinitely low resistance wires. But beyond that, you just have a lousy pot.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-09T14:02:00.280" CommentCount="1" />
  <row Id="6478" PostTypeId="2" ParentId="606" CreationDate="2010-11-09T14:49:08.517" Score="1" ViewCount="" Body="&lt;p&gt;Tracing paper in a laser printer is better than film you get better toner adhesion. Use the thick stuff &gt;=90gsm to avoid crinkling in the fuser. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-11-09T19:16:10.310" LastActivityDate="2010-11-09T19:16:10.310" />
  <row Id="6479" PostTypeId="2" ParentId="6475" CreationDate="2010-11-09T14:56:53.550" Score="1" ViewCount="" Body="&lt;p&gt;You could easily have one made where the wiper goes onto a straight conductive surface at the ends, but I don't know what they're called.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For low-volume/prototype, you might be able to use a rotary switch with a pot (some seem to stack) to accomplish the same thing by using the switch to short the wiper at the tail end.  May be similar to volume/power knobs.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-09T14:56:53.550" />
  <row Id="6480" PostTypeId="2" ParentId="6475" CreationDate="2010-11-09T14:57:55.327" Score="2" ViewCount="" Body="&lt;p&gt;Do you mean &quot;silvered ends&quot;?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Top Silver End Terminations (CP Only)&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;A type of tap used for excitation, wherein the connection is placed on the conductive film. This is the most common connection which is used, and has an end resistance below 0.5Q. For certain applications requiring a smooth transition from end to function, this tap may not be suitable. See Fig. 1A.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.vsensors.com/potentiometer_tutorial.htm&quot; rel=&quot;nofollow&quot;&gt;Precision Potentiometer Tutorial&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;End resistance on pots is pretty normal.  Audio controls at their minimum often still bleed through a little, like -60 dB.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-11-09T14:57:55.327" />
  <row Id="6481" PostTypeId="2" ParentId="6392" CreationDate="2010-11-09T15:23:54.657" Score="2" ViewCount="" Body="&lt;p&gt;Something else to check - some compilers on some architectures copy constants to RAM - typically used when access to flash constants is slow/difficult (e.g. AVR) &#xA;e.g. IAR's AVR compiler requires a _ _flash qualifer to &lt;strong&gt;not&lt;/strong&gt; copy  a  constant to RAM)  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-09T15:23:54.657" CommentCount="1" />
  <row Id="6482" PostTypeId="2" ParentId="6228" CreationDate="2010-11-09T15:31:21.693" Score="3" ViewCount="" Body="&lt;p&gt;A simple GAL programmer: &lt;a href=&quot;http://elm-chan.org/works/pgal/report_e.html&quot; rel=&quot;nofollow&quot;&gt;http://elm-chan.org/works/pgal/report_e.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And if you want to know how to program: &lt;a href=&quot;http://www.rexfisher.com/Downloads/CUPL%20Tutorial.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.rexfisher.com/Downloads/CUPL%20Tutorial.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-16T16:15:12.047" LastActivityDate="2010-11-16T16:15:12.047" />
  <row Id="6483" PostTypeId="1" AcceptedAnswerId="6487" CreationDate="2010-11-09T16:03:53.183" Score="0" ViewCount="103" Body="&lt;p&gt;Every optical computer mouse I have ever owned has had 4 pads or &lt;em&gt;feet&lt;/em&gt; on the bottom to help it glide across surfaces.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These all seem to be glued on very cheaply/poorly because after about a year or so they start to come loose. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When they become loose they shift a little and the glue that is revealed collects lent (or fuzz or whatever that stuff is) over time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This drives me crazy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also I have once removed the loose feet. This was a terrible mistake because then the sticky glue would stick to the surface making it very difficulty to glide gently.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it just me? Am I using the wrong/cheap mice? Is there something I can do to remedy this? (besides buying a new mouse every year.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;P.S. I would add the tag &quot;computer-mouse&quot; but I don't have enough rep.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="1822" LastActivityDate="2010-11-09T16:29:05.650" ClosedDate="2010-11-09T16:42:03.667" Title="How to keep your mouse feet from becoming fuzzy/sticky?" Tags="&lt;hardware&gt;&lt;computers&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="6484" PostTypeId="1" CreationDate="2010-11-09T16:09:40.383" Score="5" ViewCount="357" Body="&lt;p&gt;I need to find a safe and reliable way to power a DC hobby motor off mains supply. The motor is large (i.e. 500W) 14.4V. Therefore, the current requirements are large i.e. 35A for a 14.4V supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't find such a power supply to purchase and my budget is small. Therefore, I thought I could use an ATX power supply from a computer. They typically have a high current 12V line that can deliver the required current, 42A in this case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will be using a power MOSFET to regulate the power going to the motor by switching it on and off using pulse width modulation PWM. There should be some huge inductive spikes created. I need a way to protect the power supply from these. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking of using several layers of protection just to be safe as long as they are compatible with each other. There location in the order that I mention them is arranged starting closest to the motor and moving towards the supply. The first line of defense is a freewheeling diode put in parallel with the motor forward biased from 0 to the positive supply direction. In addition, perhaps an RC snubber also in parallel. Then a 12V standoff TVS also in parallel in case the other two fail. However, this will short the power supply if it is triggered. If the supply doesn't have over current protection it will kill the supply. I need some sort of fast acting fuse or polyswtich to at as a current limiter in series with the supply. I've noticed that a the polyswitches are very slow. like 9 seconds to &quot;disconnect&quot; the line and I don't want to use a fuse that I have to replace when this happens. Is there a good solution to this problem, or is this all too much? That is, should I just leave the TVS and polyswitch out of the design?&lt;/p&gt;&#xA;" OwnerUserId="1900" LastActivityDate="2010-11-11T03:12:02.163" Title="How do I safely drive a 500W inductive load with a computer power supply and suppress voltage spikes from switching?" Tags="&lt;protection&gt;&lt;dc-motor&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="6485" PostTypeId="2" ParentId="6484" CreationDate="2010-11-09T16:16:21.977" Score="3" ViewCount="" Body="&lt;p&gt;You've considered protecting the supply, but not the FET. The FET will also be hit by spikes when switched off. In fact, as it is gating the supply, it should be the only device subject to the spikes. If you have it on the low side then that might not be true.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, have you considered using the PS_ON pin to do duty cycle modulation instead of an external FET? I'm not sure how fast the supply will work with this though - it might take 100ms to switch on and this might limit your modulation rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'd also have to be aware of the supplies' spikes as well as the motor. The supply could get very large spikes on it if lots of load is dumped suddenly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The TVS will cook itself long before the supply overheats from the overcurrent situation. 500W into a TVS will toast it if continued for more than a few seconds.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-09T16:16:21.977" CommentCount="5" />
  <row Id="6486" PostTypeId="2" ParentId="6484" CreationDate="2010-11-09T16:28:34.003" Score="4" ViewCount="" Body="&lt;p&gt;A PC supply may well have a problem with the startup current surge of a large motor. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-09T16:28:34.003" CommentCount="2" />
  <row Id="6487" PostTypeId="2" ParentId="6483" CreationDate="2010-11-09T16:29:05.650" Score="0" ViewCount="" Body="&lt;p&gt;I have used Logitech mice for ages and never noticed the problem of loose feet occuring in them.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes dirt does tend to stick around the feet regularly and when it does I just take a small screwdriver that is eternally lying on my desk and gently scrape it off and the mouse is good to go again.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To find more about the problem I just browsed around and found &lt;a href=&quot;http://labnol.blogspot.com/2006/06/how-to-clean-optical-mouse.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; link. Would possibly give you more hints.&lt;/p&gt;&#xA;" OwnerUserId="444" LastActivityDate="2010-11-09T16:29:05.650" />
  <row Id="6488" PostTypeId="1" AcceptedAnswerId="6538" CreationDate="2010-11-09T16:55:35.147" Score="2" ViewCount="112" Body="&lt;p&gt;Anybody has reference of the what chemicals photoresist for PCB patterning are made of?&#xA;I would like something as specific as possible. No brand names please. Peer reviewed papers would be awesome.&lt;/p&gt;&#xA;" OwnerUserId="1901" LastEditorUserId="1901" LastEditorDisplayName="" LastEditDate="2010-11-11T11:43:33.103" LastActivityDate="2010-11-11T11:43:33.103" Title="Photoresist for PCB patterning" Tags="&lt;pcb-fabrication&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="6489" PostTypeId="1" AcceptedAnswerId="6491" CreationDate="2010-11-09T17:59:43.563" Score="4" ViewCount="161" Body="&lt;p&gt;What is the best way to measure the maximum power generated by a solar panel? &lt;/p&gt;&#xA;" OwnerUserId="245" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-11-09T19:02:20.780" LastActivityDate="2010-11-09T19:02:20.780" Title="How to measure the maximum power of a solar panel" Tags="&lt;power&gt;&lt;solar-cell&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="6490" PostTypeId="2" ParentId="6489" CreationDate="2010-11-09T18:02:44.733" Score="-1" ViewCount="" Body="&lt;p&gt;I would measure it the same way you measure power.&lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;P = I*V&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-11-09T18:02:44.733" CommentCount="2" />
  <row Id="6491" PostTypeId="2" ParentId="6489" CreationDate="2010-11-09T18:31:15.017" Score="4" ViewCount="" Body="&lt;p&gt;Assuming the current/voltage relationship is linear (it's not, but this gives you a crude lower bound), you could measure the short-circuit current and the open-cell voltage and do &lt;code&gt;1/4 * I * V&lt;/code&gt; to obtain the maximum theoretical power given a worst-case 0.25 fill factor.  However a more reasonable value might be obtained by using a different factor&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Typical fill factors range from 0.5 to 0.82. (&lt;a href=&quot;http://zone.ni.com/devzone/cda/tut/p/id/7230#_Ref194827281&quot; rel=&quot;nofollow&quot;&gt;source&lt;/a&gt;)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Because the I-V curve is non-linear you either need to find the parameters of your cell and apply equations (such as found &lt;a href=&quot;http://zone.ni.com/devzone/cda/tut/p/id/7230&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;), or simply do it numerically by taking measurements at various I/V and finding the largest &lt;code&gt;I*V&lt;/code&gt; coordinate.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-09T18:31:15.017" />
  <row Id="6492" PostTypeId="1" AcceptedAnswerId="6495" CreationDate="2010-11-09T18:33:56.633" Score="2" ViewCount="254" Body="&lt;p&gt;What is the best way to break out a Flat Flexible Cable (FFC)? Specifically I've got a sensor which uses the 0.5mm pitch FFC that I would like to break out onto a breadboard. As you might already know these cables are extremely small and thin and soldering wires directly to them is almost impossible. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note I DO NOT have access to the inside of the sensor so solder/connecting to the board directly is not an option.&lt;/p&gt;&#xA;" OwnerUserId="245" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-11-09T18:42:41.757" LastActivityDate="2010-11-09T20:18:18.500" Title="Breakout for FFC cables?" Tags="&lt;connector&gt;&lt;ffc&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="6493" PostTypeId="1" AcceptedAnswerId="6496" CreationDate="2010-11-09T19:18:26.813" Score="2" ViewCount="314" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/1147/choosing-a-new-soldering-iron&quot;&gt;Choosing a new soldering iron&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I have an unexpected £100 or thereabouts available to spend on a new soldering iron. I'm looking for one which would be ideal for doing small 0402 to relatively large 1206 SMD work. It must be temperature controlled (thermostatically, and not duty cycle only, like the one I bought was.) Does anyone have any suggestions? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;High reliability is very important to me. I recently bought a £49 Xytronic LF-369D iron. It failed within a few hours - it wouldn't switch on. The supplier (Rapid Electronics) sent me another one, only for that one to fail now, a few weeks later, exactly the same - not switching on, no display indication, iron not heating up. Rapid have refunded my money, so I have some extra to spend on a really good iron.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-11-09T19:31:00.370" LastActivityDate="2010-11-10T09:10:15.617" ClosedDate="2010-11-09T23:06:05.487" Title="Temperature controlled soldering iron for SMD work, costing less than £100?" Tags="&lt;soldering&gt;&lt;surface-mount&gt;&lt;soldering&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="6494" PostTypeId="1" CreationDate="2010-11-09T19:19:55.257" Score="0" ViewCount="107" Body="&lt;p&gt;Are there any AV receivers that support multiple streams concurrently?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have 2 HDTVs and many different output devices. Are there any AV receivers that are capable of taking many inputs, and directing them to 2 outputs at the same time? So that I could have my PC running on 1 HDTV with cable on the other HDTV and then that I could switch it on the receiver to run my PC and PS3 etc.&lt;/p&gt;&#xA;" OwnerUserId="1903" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-20T20:06:36.337" LastActivityDate="2011-03-20T20:06:36.337" ClosedDate="2010-11-10T00:48:31.077" Title="Are there any AV receivers that support multiple streams concurrently?" Tags="&lt;consumer-electronics&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="6495" PostTypeId="2" ParentId="6492" CreationDate="2010-11-09T20:07:07.263" Score="2" ViewCount="" Body="&lt;p&gt;You can get free-hanging terminal blocks for FFC, but a quick check on &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1442840&quot; rel=&quot;nofollow&quot;&gt;Digikey&lt;/a&gt; revealed that these are only available for 1mm and larger pitches, which I imagine to be about the lower bound on the pitch of crimp housings for real wires.  You might inquire with Tyco or Hirose about smaller pitches.  If you can find these in 0.5mm pitch, this is the way to go for sure!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't find a free-hanging terminal block, the best way to do this dependably, repeatably, and professionally is to build a breakout PCB.  It doesn't need to be anything more than a connector and a couple of headers, but that will add some time and cost to your project.  If you go to all that work, you might as well move the rest of your breadboard circuit to the PCB!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connectors for FFC are almost always locking, so you should be able to buy a connector, put it on a protoboard/breakout board, and then solder to the connector pins.  The pins will be small, but should be made of more durable stuff (Like solid brass or nickel, and likely gold plated) than the FFC.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/zbfne.jpg&quot; alt=&quot;Right-angle SMD FFC Connector&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've soldered to these (Mounted on a circuit board, but otherwise similar) before, and I'll warn you that you want to do it with a cable clamped into the connector for heatsinking and stabilization.  Otherwise, when you heat the pins and the plastic softens, the slightest twitch will push the hot pin through the soft plastic, and you'll get solder bridges and mangled plastic all over the place.  I moved misbehaving pins back into place with tweezers and superglued everything after I was done, but, it might be helpful to let some glue harden in the bottom of the housing before you start.  I couldn't get at the bottom of mine because it was already on the PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, you &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1442690&quot; rel=&quot;nofollow&quot;&gt;can get&lt;/a&gt; crimp/solder terminals for free-hanging terminal blocks individually.  They look like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/RSxQZ.jpg&quot; alt=&quot;crimp terminal for FFC&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While you may have found it impossible to solder wires to the FFC, it's possible that a sturdier crimp terminal with a flat end will be easier to solder.  Just make sure you crimp the wire in place first or heat sink your soldering job on the FFC when attaching the wire to make sure you don't mess that up after you get it working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whatever you end up doing, don't forget to the strain relief!&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-09T20:07:07.263" CommentCount="1" />
  <row Id="6496" PostTypeId="2" ParentId="6493" CreationDate="2010-11-09T20:09:14.780" Score="4" ViewCount="" Body="&lt;p&gt;Asked and answered:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/q/1147/411&quot;&gt;Choosing a new soldering iron&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-09T20:09:14.780" />
  <row Id="6497" PostTypeId="2" ParentId="6492" CreationDate="2010-11-09T20:18:18.500" Score="1" ViewCount="" Body="&lt;p&gt;If you can get the right surface mount connector, then you might be able to use a board like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.farnell.com/roth-elektronik/re900-02/adaptor-smd-0-5mm-28-48pin/dp/1426156&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/roth-elektronik/re900-02/adaptor-smd-0-5mm-28-48pin/dp/1426156&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;as a breakout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you were brave, you might even be able to reflow the flexy directly onto the 0.5mm pads, though personally I would use a connector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a lot of Roth Elektronik boards of various kinds - there may be something else more suitable for you specific connector.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-09T20:18:18.500" CommentCount="2" />
  <row Id="6498" PostTypeId="2" ParentId="5773" CreationDate="2010-11-09T20:21:03.850" Score="3" ViewCount="" Body="&lt;p&gt;I found the &lt;a href=&quot;http://mbed.org&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt; to be a marvellous substitute for the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The software library is more C++ oriented, complete with all the syntactic sugar of assignment operator overloading. Additionally, a system is set up such that users can publish and document code libraries, which can then easily be searched and imported into projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another good feature is the ability to treat the device as a USB stick, and just put the &lt;code&gt;.bin&lt;/code&gt; files straight onto the drive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, the IDE is comparable to that of the arduino. Also, &lt;em&gt;it's online&lt;/em&gt;. This is both really good (can be used on any PC, no installation required), and really bad (can't easily be reprogrammed without an internet connection).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The cost of the board is $60, but they have a sponsorship scheme, where they will donate boards to interesting projects provided progress is documented and source code made public.&lt;/p&gt;&#xA;" OwnerUserId="1217" LastActivityDate="2010-11-09T20:21:03.850" CommunityOwnedDate="2011-02-27T07:33:15.000" CommentCount="1" />
  <row Id="6499" PostTypeId="1" AcceptedAnswerId="6502" CreationDate="2010-11-09T20:50:56.620" Score="2" ViewCount="149" Body="&lt;p&gt;The comparators on my MCU, a dsPIC33FJ128GP802, give the common-mode input range as AVdd-1.15V. AVdd is 3.3V, so does this mean the comparators can't compare voltages in the range of 2.15V to 3.3V?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-09T21:21:45.980" Title="Common mode input voltage range and comparators on an MCU" Tags="&lt;microcontroller&gt;&lt;comparator&gt;&lt;common-mode&gt;" AnswerCount="1" />
  <row Id="6500" PostTypeId="1" AcceptedAnswerId="6516" CreationDate="2010-11-09T21:16:14.467" Score="3" ViewCount="507" Body="&lt;p&gt;Hi all!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a 4 KHz piezo buzzer and a microcontroller (arduino) that outputs that 4 KHz from one of it's pins. All is fine if I connect the buzzer to the output with one pin and to the ground with another. Also all works as expected if I try to control it with MOSFET: +5V to the drain, buzzer between source and ground, and the output pin to the gate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However if I replace MOSFET with BJT, something goes wrong and the buzzer emits just a very-very-very quiet sound. Here's what I have:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Buzzer between +5 V and the collector&lt;/li&gt;&#xA;&lt;li&gt;Output pin connected to the base through 2K2 resistor&lt;/li&gt;&#xA;&lt;li&gt;Emitter connected to the ground&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I have tried few other configurations with BJT, but result is the same. I use BC337 as a transistor (AFAIK it is analogue of 2N2222).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could anybody clarify why this happens?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UPD&lt;/strong&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've measured voltage levels. I have 2.51 V between the microcontroller output and the ground. I get 5 V / 2 because it generates square waves, isn't it? Then I have 2.1 V around the base resistor. And, surprisingly I've got 5 V around the buzzer! Shouldn't I get 2.5 V?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also I noticed that once I measure voltage across the buzzer the sound become a bit louder. So I've tried to add a resistor in parallel to it. Aaaand… now it works!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/nl1Ld.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The question left open: why it doesn't work as expected if I remove &lt;em&gt;R2&lt;/em&gt;?&lt;/p&gt;&#xA;" OwnerUserId="914" LastEditorUserId="914" LastEditorDisplayName="" LastEditDate="2010-11-10T07:22:54.700" LastActivityDate="2010-11-10T08:57:56.363" Title="Connecting piezo buzzer with BJT" Tags="&lt;frequency&gt;&lt;sound&gt;&lt;bjt&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="6501" PostTypeId="2" ParentId="6494" CreationDate="2010-11-09T21:20:00.640" Score="0" ViewCount="" Body="&lt;p&gt;My best advice is to look into a multi zone receiver.  Or a simpler approach is to look at the specs on 7.1 or 7.2 recievers,  Alot of these receiver's usually let you set up to be 2 zones.  What it does is you configure zone A to be 5.1, and you get 2.0 for zone B,  Means you can have your tv going with 5.1, and your pc with 2.0 (or possibly 2.1 if you have a 7.2 receiver).  I have a pioneer that does 2 zones, I run Zone A for my tv, and Zone B for a stereo downstairs.&lt;/p&gt;&#xA;" OwnerUserId="1902" LastActivityDate="2010-11-09T21:20:00.640" />
  <row Id="6502" PostTypeId="2" ParentId="6499" CreationDate="2010-11-09T21:21:45.980" Score="3" ViewCount="" Body="&lt;p&gt;Yes, that is what it means.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-09T21:21:45.980" CommentCount="6" />
  <row Id="6503" PostTypeId="1" AcceptedAnswerId="6504" CreationDate="2010-11-09T21:29:02.047" Score="2" ViewCount="144" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I know this is like my other question on the SAA1027 but i can't find the UCN5804 anywhere. Are they obsolete now?&lt;br&gt;&#xA;Thanks in Advance,&lt;br&gt;&#xA;Dean &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-11-09T21:32:34.680" Title="What has happened to the UCN5804?" Tags="&lt;stepper&gt;" AnswerCount="1" />
  <row Id="6504" PostTypeId="2" ParentId="6503" CreationDate="2010-11-09T21:32:34.680" Score="7" ViewCount="" Body="&lt;p&gt;From &lt;a href=&quot;http://www.allegromicro.com/en/Products/Part_Numbers/Archive/index.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.allegromicro.com/en/Products/Part_Numbers/Archive/index.asp&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;5804: BiMOS II Unipolar Stepper-Motor&#xA;  Translator/Driver&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;a href=&quot;http://www.allegromicro.com/en/Products/Part_Numbers/Archive/5804.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.allegromicro.com/en/Products/Part_Numbers/Archive/5804.pdf&lt;/a&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;discontinued October 2004; replaced by&#xA;  A3967 and A3977&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-11-09T21:32:34.680" CommentCount="0" />
  <row Id="6505" PostTypeId="2" ParentId="6500" CreationDate="2010-11-09T22:07:06.550" Score="1" ViewCount="" Body="&lt;p&gt;Are you definitely sure you're using an output pin which can source current properly? (for example, it's not just got some weak internal pull-up turned on?)   What voltage does each end of the 2k2 resistor rise to during the cycle?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know it sounds as though you have this OK if you can source current into the buzzer directly, but it might be worth checking that nothing changed between tests.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-09T22:07:06.550" />
  <row Id="6506" PostTypeId="2" ParentId="1393" CreationDate="2010-11-09T22:11:31.997" Score="2" ViewCount="" Body="&lt;p&gt;Mini-wave tip:&lt;br&gt;&#xA;&lt;a href=&quot;http://www.sterntech.com/soldering.php&quot; rel=&quot;nofollow&quot;&gt;http://www.sterntech.com/soldering.php&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My two cents worth. I recently had to solder on of our prototype boards, which had only SMD components. I agree with most of the comments above for general SMD parts. &#xA;The toughest part I found (only when I did this for the first time), was to solder the microcontroller on the board. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is extremely critical to get this part aligned on the pads. &#xA;There are a few tricks that make this the easiest part to solder in the end:&lt;br&gt;&#xA;1) Lots of FLUX on the pads where the part will be placed!&lt;br&gt;&#xA;2) And then this magical tip called the mini-wave tip. &#xA;After tacking on the corner pins to ensure proper alignment, you fill the tip with solder and just slightly drag it along the pins of the microcontroller.  Once all the pins are tacked on, you can use this tip to drag/suck away the excess solder off the pins!   Works much better than tacking each pin on and using wick to dab away the excess solder.&lt;/p&gt;&#xA;" OwnerUserId="1785" LastActivityDate="2010-11-09T22:11:31.997" />
  <row Id="6507" PostTypeId="2" ParentId="6493" CreationDate="2010-11-09T22:41:14.283" Score="0" ViewCount="" Body="&lt;p&gt;You might also be interested in soldering iron tips:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/1393/which-soldering-iron-tip-should-i-use&quot;&gt;Which soldering iron tip should I use?&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1785" LastActivityDate="2010-11-09T22:41:14.283" />
  <row Id="6508" PostTypeId="2" ParentId="6493" CreationDate="2010-11-09T22:46:18.177" Score="1" ViewCount="" Body="&lt;p&gt;I recently bought &lt;a href=&quot;http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=1737234&quot; rel=&quot;nofollow&quot;&gt;one of these&lt;/a&gt; for £30 + VAT. Absolute bargain for what it is and the solder that comes with it for free, nearly costs as much as the iron, when bought separately.&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-11-10T09:10:15.617" LastActivityDate="2010-11-10T09:10:15.617" />
  <row Id="6509" PostTypeId="2" ParentId="6500" CreationDate="2010-11-10T00:01:38.700" Score="0" ViewCount="" Body="&lt;p&gt;A MOSFET is controlled by voltage, a BJT is controlled by current.  You left out a critical parameter in your description - The base resistor. Your drive circuit to test whether your transistor is working or not will look like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/G9G47.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can assume that the base-to-emitter voltage is 0.7V (a diode drop), so a 5V supply would produce a base current of: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;IB = (5-0.7)/100k = 43uA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Find &amp;beta; or hFE for your transistor (usually around 100), and you have the collector current:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IC = IB * &amp;beta; = 4.3mA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to increase the collector current, you need to decrease RB.  Once the collector-to-emitter voltage (5V - RC * IC, or about 4.5V in our example) decreases to 0.2V, the transistor goes into saturation and you can't get any more current.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With RB = 0, you're going to cause problems with your drive circut - Think of the base like a diode, not like a capacitor as in a MOSFET.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Short answer: Put a 10k resistor from the base to your drive pin.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-10T00:01:38.700" CommentCount="2" />
  <row Id="6510" PostTypeId="1" AcceptedAnswerId="6511" CreationDate="2010-11-10T00:28:59.173" Score="0" ViewCount="189" Body="&lt;p&gt;Is it possible to use a digital potentiometer with an SMPS, to adjust the voltage? I'm looking at one with a 2 MHz -3dB bandwidth. What does this mean for a 300 kHz switcher?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-10T09:33:35.353" Title="Using a digital potentiometer with a SMPS?" Tags="&lt;resistor&gt;&lt;potentiometer&gt;&lt;smps&gt;&lt;digital&gt;" AnswerCount="3" />
  <row Id="6511" PostTypeId="2" ParentId="6510" CreationDate="2010-11-10T01:02:21.533" Score="2" ViewCount="" Body="&lt;p&gt;Thomas, This question may be a bit too broad. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are normally SMPS that will have a set resistance. This can be controlled by a digital pot, very effective at that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are wanting to change components inside the control loop of the SMPS, I would suggest against it.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-10T01:02:21.533" CommentCount="4" />
  <row Id="6512" PostTypeId="2" ParentId="6510" CreationDate="2010-11-10T03:01:22.737" Score="2" ViewCount="" Body="&lt;p&gt;Bandwidth is usually not relevant when it comes to a power supply adjustment pot. The value is generally set at a single calibration point and isn't varied. Even if the pot were being varied (by a micro, for example) the adjustment speed has to be significantly lower than the switching frequency to maintain Nyquist stability criteria.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bottom resistor of the feedback voltage divider isn't really part of the compensation formulae, so generally this is where adjustment is made. If you tweak this value, you can end up with lower (or higher) voltage, but there are many things that have to be considered with a change of output voltage (duty cycle, rectifier and switching device stress, capacitor voltage, etc.) so tread carefully.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-10T03:01:22.737" CommentCount="1" />
  <row Id="6513" PostTypeId="1" CreationDate="2010-11-10T03:11:33.023" Score="0" ViewCount="166" Body="&lt;p&gt;I've got an arduino board that I'm trying to program via ISP with an AVRDragon.  I think I've got it all cabled up right (I made my own ISP cable by cutting up an old floppy ribbon cable) but when I attempt to connect avrdude I get the following errors&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;sudo /usr/bin/avrdude -pm328p -c dragon_isp -v -v -v -v -P usb -B 1 -t&#xA;&#xA;avrdude: Version 5.10, compiled on Jun 29 2010 at 03:44:14&#xA;     Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/&#xA;     Copyright (c) 2007-2009 Joerg Wunsch&#xA;&#xA;     System wide configuration file is &quot;/etc/avrdude.conf&quot;&#xA;&#xA;     Using Port                    : usb&#xA;     Using Programmer              : dragon_isp&#xA;     Setting bit clk period        : 1.0&#xA;avrdude: stk500v2_dragon_isp_open()&#xA;avrdude: usbdev_open(): Found AVRBLDR, serno: 00A200007E77&#xA;avrdude: usbdev_open(): using read endpoint 0x82&#xA;avrdude: jtagmkII_getsync()&#xA;avrdude: jtagmkII_getsync(): Sending sign-on command: &#xA;avrdude: jtagmkII_send(): sending 1 bytes&#xA;avrdude: Sent: . [1b] . [00] . [00] . [01] . [00] . [00] . [00] . [0e] . [01] . [f3] . [97] &#xA;avrdude: jtagmkII_recv():&#xA;avrdude: usb_fill_buf(): usb_bulk_read() error No error&#xA;avrdude: jtagmkII_recv(): Timeout receiving packet&#xA;avrdude: jtagmkII_getsync(): sign-on command: status -1&#xA;avrdude: jtagmkII_getsync(): Sending sign-on command: &#xA;avrdude: jtagmkII_send(): sending 1 bytes&#xA;avrdude: usbdev_send(): wrote -19 out of 11 bytes, err = error submitting URB: No such device&#xA;avrdude: jtagmkII_send(): failed to send command to serial port&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I've hooked the dragon to two different arduinos and they both have the same issue.&lt;/p&gt;&#xA;" OwnerUserId="1906" LastActivityDate="2010-11-10T14:13:52.140" Title="avrdude throws errors when attempting ISP with AVRDragon" Tags="&lt;arduino&gt;&lt;avrdude&gt;&lt;isp&gt;" AnswerCount="1" />
  <row Id="6514" PostTypeId="1" AcceptedAnswerId="6515" CreationDate="2010-11-10T03:38:50.400" Score="2" ViewCount="127" Body="&lt;p&gt;I found 12 solar panels, but they are very thin and fragile. They put out approximately .5V under an incandescent bulb. What would be the best way to turn these 12 panels into a 12V car battery charger? I am looking at bumping up the voltage to ~13V, possibly by using a Maxim converter. Has anyone else done this? Thanks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Kyle&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; Schematics would be very helpful. And tips on how to mount very fragile solar panels.&lt;/p&gt;&#xA;" OwnerUserId="1907" LastEditorUserId="1907" LastEditorDisplayName="" LastEditDate="2010-11-10T04:05:01.717" LastActivityDate="2010-11-10T07:24:03.877" Title="How can I build a solar powered car charger?" Tags="&lt;battery&gt;&lt;solar-cell&gt;&lt;charger&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="6515" PostTypeId="2" ParentId="6514" CreationDate="2010-11-10T07:24:03.877" Score="2" ViewCount="" Body="&lt;p&gt;If they are just bare cells, you probably don't have much chance in salvaging all of them.  In my experience of building panels (only a few), I usually end up using 10-20% more panels than actually end up in the panel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as actually building the panel, just solder all of the tabs together in some order (whatever size/shape you are going for), and then mount them between sheets of acrylic. Use some spacers so that the acrylic sheets don't put pressure on the cells.  You can also use some sort of silicone adhesive to hold the cells down to one of the sheets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as charging a battery, you probably want a boost converter to get the panel voltage to a battery charging voltage.  Past that, it should just be a normal lead-acid charge circuit, there are several of these floating around the internet as schematics or off-the-shelf solutions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your cells, you may not have enough power to really charge a big battery in any sort of reasonable timeframe, so that's something you may want to consider.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-11-10T07:24:03.877" CommentCount="1" />
  <row Id="6516" PostTypeId="2" ParentId="6500" CreationDate="2010-11-10T08:08:49.687" Score="4" ViewCount="" Body="&lt;p&gt;The piezo buzzer use &lt;a href=&quot;http://en.wikipedia.org/wiki/Piezoelectric_effect&quot; rel=&quot;nofollow&quot;&gt;piezoelectric effect&lt;/a&gt; to emit sound (the material in the buzzer deform itself due to voltage, deformation will be &quot;proportional&quot; to the voltage applied). Since sound is pressure wave one have to provide oscillating voltage to the buzzer in order to produce oscillating deformations. And most important:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;From the electrical perspective piezo buzzer act like capacitor!&lt;/em&gt; &lt;/p&gt;&#xA;&#xA;&lt;h3&gt;So why circuit with BJT and without R2 did not work?&lt;/h3&gt;  &#xA;&#xA;&lt;p&gt;With BJT in the configuration that you use, BJT can only &quot;sink&quot; current. That is it can only lower voltage at its collector. So after first &quot;turn on&quot; the voltage at the collector dropped to ground (or close) level. Next turn on cycle will not change voltage across buzzer as the voltage at the collector was already at ground level. (That is why you have measured 5V across the buzzer). Since voltage across buzzer do not change buzzer will not vibrate and thus will not produce sound.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adding R2 solved the issue. When BJT is conducting, it lowers voltage at collector (C). When BJT is NOT conducting, R2 pull voltage up. This crates oscillation and produce sound.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Now, more interesting question is why MOSFET seemed to work (and BJT did not)?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;I am not sure but here is my thory:&#xA;My guess is that you have used one of this big power mosfets. They tend to have big parasitic gate to source/drain capacitance, at the same order of magnitude as a capacitance of the piezo buzzer(hundreds of pF). This parasitic capacitance created AC coupling between your input signal and buzzer which was enough to produce sound.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now BJT of the type you have used have much smaller capacitance (single pF) that was not enough to provide enough AC coupling (it did provide some that is why you did hear some barely audable sound)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Note: The whole issue is little more complicated then simple AC coupling, but I believe is good enough first order explanation of the phenomena.&lt;/em&gt; &lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="1471" LastEditorDisplayName="" LastEditDate="2010-11-10T08:57:56.363" LastActivityDate="2010-11-10T08:57:56.363" CommentCount="2" />
  <row Id="6517" PostTypeId="2" ParentId="6500" CreationDate="2010-11-10T08:16:33.140" Score="3" ViewCount="" Body="&lt;p&gt;I think this is because a piezo device is essentially like a capacitor. The output of your microcontroller both charges and discharges the capacitor because it actively drives its output both high and low. The transistor circuit you show can charge the capacitor when it turns on, but it cannot discharge the capacitor. Your piezo will charge up to 5V but when the transistor turns off the charge stays at 5V. No change in voltage = no sound out of the peizo.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adding the resistor in parallel provides a path for the piezo capacitance to discharge, so then you get the varying voltage you need to produce sound.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That doesn't explain why it works with a MOSFET though, unless there is an internal diode in the MOSFET that discharges the piezo capacitance through the gate?&lt;/p&gt;&#xA;" OwnerUserId="1897" LastActivityDate="2010-11-10T08:16:33.140" />
  <row Id="6518" PostTypeId="2" ParentId="6500" CreationDate="2010-11-10T08:54:54.437" Score="0" ViewCount="" Body="&lt;p&gt;I have experienced this with a bjt before as well .A piezo crystal is a very high impedance part. You'll want some other lower impedance load in parallel with the piezo. Maybe start with a 47K? Then work up and down from there for the required volume.&lt;/p&gt;&#xA;" OwnerUserId="1891" LastActivityDate="2010-11-10T08:54:54.437" />
  <row Id="6519" PostTypeId="2" ParentId="6510" CreationDate="2010-11-10T09:33:35.353" Score="0" ViewCount="" Body="&lt;p&gt;Bear in mind you will only be able to adjust output voltage over a limited range, maybe +/-25% before stability or other issues like popping output caps cause problems&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-10T09:33:35.353" CommentCount="1" />
  <row Id="6520" PostTypeId="1" AcceptedAnswerId="6521" CreationDate="2010-11-10T11:26:34.053" Score="2" ViewCount="291" Body="&lt;p&gt;This one should be obvious, but I'd rather ask here then get some unexpected surprises.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of my friends fried a proprietary USB cable which has male USB A connector at one end and TRS connector at the other end. As far as we can see, only the USB A connector seems to be damaged (one of the pins melted). I'm thinking of removing damaged connector and replacing it with something like &lt;a href=&quot;http://mikroprinc.com/proizvodi.aspx?sub=pp&amp;amp;pg=F3550&amp;amp;pid=15702&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;. How would I assemble that connector? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;: Results for future users with same problem: Step one was to cut off burnt connector in such way that there is a bit of cable remaining connected to it. Then I removed metal shield from old connector and found relation between pins on connector and colors of internal cables. In retrospective, I think it would have been better to remove shield and to see which pin is connected to which ring before cutting off the connector. Maybe some crazy product uses internal wires of same color?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that I removed piece of insulation from the healthy part of the cable, placed heatshrink and removed pieces of insulation from individual wires. To me it looked like the black part of the connector was there to facilitate cold welding, but it turned out that I had to solder wires to white plastic part. After that I placed black part on the white part. I was surprised with big metal part as it turned out that the protruding metal part should go next to the black plastic part. To me opposite it looked logical, but plastic parts would go in in only one orientation. In the end, small metal part is just placed on the exposed area of big metal part and small metal jaws are tightened. After that I moved heatshrink so that it covers the jaws and applied heat.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-08T15:45:37.197" LastActivityDate="2011-01-08T15:45:37.197" Title="How to assemble male USB A connector?" Tags="&lt;usb&gt;&lt;connector&gt;&lt;cable-assemblies&gt;&lt;mechanical-assembly&gt;" AnswerCount="2" CommentCount="7" />
  <row Id="6521" PostTypeId="2" ParentId="6520" CreationDate="2010-11-10T11:39:42.687" Score="1" ViewCount="" Body="&lt;p&gt;I think you'll find assembling it pretty straightforward when you have the bits in your hand.  It's the 'now injection-mould the body' stage which comes next that you'll struggle with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a one off repair like this, you can probably do something useful with heatshrink to keep it all together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, cut an existing USB cable in half, and use the 'A' end with some of its attached cable.  Then you'll only have to join the cables - another heatshrink job.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-10T11:39:42.687" CommentCount="4" />
  <row Id="6522" PostTypeId="2" ParentId="6520" CreationDate="2010-11-10T11:40:37.393" Score="3" ViewCount="" Body="&lt;p&gt;No need to buy a connector, pick up another male USB cable then:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Cut the head off the broken one.&lt;/li&gt;&#xA;&lt;li&gt;Cut the tail off the replacement (leaving some excess wire underneath the connector).&lt;/li&gt;&#xA;&lt;li&gt;Strip about 1/2&quot; both sides of insulation (including the 4 wires).&lt;/li&gt;&#xA;&lt;li&gt;(Optional) Add heatshrink to one side of the wire (but don't heat).&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=BLfXXRfRIzY&quot; rel=&quot;nofollow&quot;&gt;Solder them together&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;Wrap each wire in electrical tape or position and heat the heatshrink.&lt;/li&gt;&#xA;&lt;li&gt;Wrap the whole join in electrical tape to reinforce.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1333" LastActivityDate="2010-11-10T11:40:37.393" CommentCount="5" />
  <row Id="6523" PostTypeId="1" CreationDate="2010-11-10T12:10:39.227" Score="6" ViewCount="426" Body="&lt;p&gt;I started a robotics club at my high school and I wanted to come up with some projects that would be easy, cheap but rewarding experience wise. Do you have any good ideas? &lt;/p&gt;&#xA;" OwnerUserId="1687" LastActivityDate="2010-11-12T13:38:32.793" CommunityOwnedDate="2010-11-10T12:36:42.857" Title="Project ideas for a high school robotics club." Tags="&lt;learning&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="2" />
  <row Id="6524" PostTypeId="2" ParentId="6454" CreationDate="2010-11-10T13:10:25.840" Score="2" ViewCount="" Body="&lt;p&gt;Some manufacturers also use a &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/In-circuit_test#Bed_of_nails_tester&quot; rel=&quot;nofollow&quot;&gt;bed of nails&lt;/a&gt;&quot; tester. This measures the resistance / conductance from locations on the PCB board surface to other points on the surface. From the Gerber files they know where there should be conductance and where there should be opens. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-11-10T13:10:25.840" CommentCount="1" />
  <row Id="6525" PostTypeId="2" ParentId="6523" CreationDate="2010-11-10T13:28:12.467" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://imagineering.org.uk/&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is a UK based organisation that I used to work with when I ran an Engineering club at my local primary school.  They have a number of general engineering type projects that the kids can build using simple tools - hammer, screwdriver, etc.  While not really robotics the morse code key and buzzer, Telescope and rubber band powered helicopter were always popular.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have two sets of projects one for primary school years 5/6 (I used this set) and a second set for early years secondary school (years 7/8).&lt;/p&gt;&#xA;" OwnerUserId="400" LastEditorUserId="400" LastEditorDisplayName="" LastEditDate="2010-11-10T14:43:09.867" LastActivityDate="2010-11-10T14:43:09.867" CommunityOwnedDate="2010-11-10T13:28:12.467" />
  <row Id="6526" PostTypeId="2" ParentId="6454" CreationDate="2010-11-10T13:41:23.927" Score="1" ViewCount="" Body="&lt;p&gt;E-testing is primarily used to detect bad plated holes, as this is the most common failure as it's more process-sensitive.&#xA;Bear in mind that a flying-probe e-test rarely checks for shorts as it requires a huge amount more checks (therefore test time) than a continuity test - each node to each other possible node. Probably easier on a bed-of-nails tester which has connectivity to all nodes at the same time.&#xA;I've certainy had a few supposedly e-tested boards with shorts. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-10T13:41:23.927" />
  <row Id="6527" PostTypeId="2" ParentId="6523" CreationDate="2010-11-10T14:01:04.810" Score="3" ViewCount="" Body="&lt;p&gt;I think that a good start can be with Arduino. Having an already assembled hardware can help initiate in electronics area.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have a pretty good tutorial and lots of projects for the begginers: &lt;a href=&quot;http://arduino.cc/en/Tutorial/HomePage&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Tutorial/HomePage&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-10T14:01:04.810" CommunityOwnedDate="2010-11-10T14:01:04.810" CommentCount="2" />
  <row Id="6528" PostTypeId="2" ParentId="6513" CreationDate="2010-11-10T14:13:52.140" Score="1" ViewCount="" Body="&lt;p&gt;The Dragons have always had some problems - not that they're not great.  Start by making sure the firmware is up to date.  It can be updated in AVR Studio.  Then I'd make sure that your cable is correct (verify pin 1 goes to pin 1, pin 2 to pin 2, etc with a DMM) and after that ensure that you have pin 1 of the ISP headers hooked together.  Those things are easy to get the wrong orientation on. &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-10T14:13:52.140" />
  <row Id="6529" PostTypeId="1" AcceptedAnswerId="6531" CreationDate="2010-11-10T15:00:20.767" Score="2" ViewCount="709" Body="&lt;p&gt;I was told that i could make a simple battery charger from a LM317 and a resistor to charge some Ni-MH Batteries. Can someone just expand on this a little such as how it works as I don't really understand it. Some more information is that there are 12 AAA batteries that hold a charge of 1000mAh and 1.2v per cell.  &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-05-26T18:49:11.300" LastActivityDate="2011-05-26T18:49:11.300" Title="Building a Battery Charger with an LM317" Tags="&lt;battery&gt;&lt;battery-charging&gt;&lt;lm317&gt;" AnswerCount="4" />
  <row Id="6530" PostTypeId="2" ParentId="6529" CreationDate="2010-11-10T15:02:46.027" Score="5" ViewCount="" Body="&lt;p&gt;A good tutorial using a microcontroler to automatically disconnect the charger when the battery is full is available on &lt;a href=&quot;http://www.angelfire.com/electronic/hayles/charge1.html&quot; rel=&quot;nofollow&quot;&gt;http://www.angelfire.com/electronic/hayles/charge1.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-10T15:02:46.027" />
  <row Id="6531" PostTypeId="2" ParentId="6529" CreationDate="2010-11-10T15:45:29.720" Score="7" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.electronicsforu.com/EFYLinux/circuit/feb2005/Circ01-Feb05.pdf&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; apparently describes a LM317-based charger with auto-shutoff, though it has a few more parts than a resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the &lt;em&gt;most crude&lt;/em&gt;, you can use an LM317 and resistor to form a regulated current source, which is how NiMH/NiCd's should be charged.  See &quot;Precision Current Limiter&quot; (p. 19) on the &lt;a href=&quot;http://www.national.com/ds/LM/LM117.pdf&quot; rel=&quot;nofollow&quot;&gt;LM317 datasheet&lt;/a&gt;.  The regulator functions as a current source by attempting to supply as much current as possible to have &lt;code&gt;Vout - Vadj&lt;/code&gt; be 1.25 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that there is nothing inherent in the LM317 to shut off a charge, so if the batteries are fast-charged (~C/2 or higher), they will fail if you do not terminate the charge at the appropriate time.  With a trickle-charge (C/20), you &quot;can&quot; leave them alone with no ill-effect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So in your specific case, the 2-part charger would be a LM317 and a resistor to charge the pack at C/20.  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Charge rate: &lt;code&gt;1000 mA·h @ C/20 =&amp;gt; 50 mA&lt;/code&gt;&lt;/li&gt;&#xA;&lt;li&gt;Resistor value: &lt;code&gt;1.25 V / 50 mA = 25 Ω&lt;/code&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You need to provide a voltage to &lt;code&gt;Vin&lt;/code&gt; at least 2.0 V (dropout voltage) + 1.25 V (reference voltage) = 3.25 V greater than the maximum charging voltage.  The resistor would be connected between &lt;code&gt;Vout&lt;/code&gt; and &lt;code&gt;Adj&lt;/code&gt;, and your load is connected to &lt;code&gt;Adj&lt;/code&gt; (&lt;strong&gt;&lt;em&gt;not Vout&lt;/em&gt;&lt;/strong&gt;)&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-10T15:53:32.330" LastActivityDate="2010-11-10T15:53:32.330" CommentCount="3" />
  <row Id="6532" PostTypeId="2" ParentId="5948" CreationDate="2010-11-10T15:48:58.980" Score="2" ViewCount="" Body="&lt;p&gt;GHI EMX seems to have a bigger number of peripherals and IO ports. If you're looking for using lots of sensor at the same time its the better choice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although I like the built in accelerometer in Tahoe 2.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-10T15:48:58.980" CommentCount="1" />
  <row Id="6533" PostTypeId="2" ParentId="6529" CreationDate="2010-11-10T15:50:38.450" Score="5" ViewCount="" Body="&lt;p&gt;You can use this for simple trickle charge. Use the resistor to ensure that the charge delivered to the &lt;a href=&quot;http://www.greenbatteries.com/bachfa.html&quot; rel=&quot;nofollow&quot;&gt;battery is less then C/10&lt;/a&gt; (capacity of battery divided by ten, ie. 1200mAH batter gets 120mA or less). &lt;a href=&quot;http://www.powerstream.com/NiMH.htm&quot; rel=&quot;nofollow&quot;&gt;Most NiMH batteries can handle this&lt;/a&gt; for quite a while. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.8051projects.info/blogs.asp?view=plink&amp;amp;id=130&quot; rel=&quot;nofollow&quot;&gt;There are some&lt;/a&gt; &lt;a href=&quot;http://www.electro-tech-online.com/general-electronics-chat/28204-regarding-nimh-battery-charger-using-lm317.html&quot; rel=&quot;nofollow&quot;&gt;pretty cool&lt;/a&gt; designs out there for this. As long as you keep your charge current low you can accidentally leave the battery on the charger for many hours past the point of full charge without having to worry about overcharge damage, the downside being that they will take 12 or 15 hours to charge in general.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.electro-tech-online.com/general-electronics-chat/28204-regarding-nimh-battery-charger-using-lm317.html&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/voaHn.gif&quot; alt=&quot;NiMH charger&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NiMH have very interesting charge characteristics. They need to be changed very intelligently to stop from possibly shortening their life. If you want something that charges in a time like 4 or 5 hours from fully dead you need an intelligent controller.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-10T15:50:38.450" CommentCount="3" />
  <row Id="6534" PostTypeId="1" AcceptedAnswerId="6535" CreationDate="2010-11-10T16:18:21.123" Score="3" ViewCount="212" Body="&lt;p&gt;Any ideas on how to get 3.3V from 5V - 35V at a low 10mA current level? 3.3V need not be precise. It can be 3.5V or 3V, it is powering a small microcontroller. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for a small and cost effective solution. That pretty much rules out through hole stuff.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-02-28T13:59:57.907" LastActivityDate="2011-02-28T21:31:49.783" Title="3.3V @ 10mA from 5V - 35V." Tags="&lt;voltage-regulator&gt;&lt;ldo&gt;" AnswerCount="4" />
  <row Id="6535" PostTypeId="2" ParentId="6534" CreationDate="2010-11-10T16:22:34.370" Score="4" ViewCount="" Body="&lt;p&gt;Use a linear regulator that can handle 5V to 35V input. It outputs 3.3V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is that simple. You can use a buck regulator, if efficiency is an issue. but 10mA at a 35V drop is still only a 350mW dissipation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suggest the linear, keep components/complexity/noise down.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-10T16:32:05.993" LastActivityDate="2010-11-10T16:32:05.993" CommentCount="8" />
  <row Id="6536" PostTypeId="2" ParentId="6523" CreationDate="2010-11-10T17:20:02.103" Score="2" ViewCount="" Body="&lt;p&gt;You should look at registering for the &lt;a href=&quot;http://www.usfirst.org/roboticsprograms/ftc/default.aspx?id=968&quot; rel=&quot;nofollow&quot;&gt;FTC - First Tech Challenge&lt;/a&gt; :&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Design, build and program robots&lt;/li&gt;&#xA;&lt;li&gt;Apply real-world math and science concepts&lt;/li&gt;&#xA;&lt;li&gt;Develop problem-solving, organizational, and team-building skills&lt;/li&gt;&#xA;&lt;li&gt;Compete and cooperate in alliances and tournaments&lt;/li&gt;&#xA;&lt;li&gt;Earn a place in the World Championship&lt;/li&gt;&#xA;&lt;li&gt;Qualify for close to $7 million in college scholarships&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="245" LastActivityDate="2010-11-10T17:20:02.103" CommunityOwnedDate="2010-11-10T17:20:02.103" CommentCount="0" />
  <row Id="6537" PostTypeId="2" ParentId="6534" CreationDate="2010-11-10T17:31:09.593" Score="0" ViewCount="" Body="&lt;p&gt;You'd struggle to find a buck reg with 35v input range that didn't draw 10mA quiescent before you got any power out. &#xA;35V is a bit on the high side for many linear regs so you need to look carefully at specs. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-10T17:31:09.593" CommentCount="3" />
  <row Id="6538" PostTypeId="2" ParentId="6488" CreationDate="2010-11-10T17:33:08.523" Score="1" ViewCount="" Body="&lt;p&gt;Study on thermal crosslinking reaction of &lt;strong&gt;o-naphthoquinone diazides&lt;/strong&gt; and application to electrodeposition positive photoresist.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Authors: Kenji Miyagawa, Keisuke Naruse, Shinsuke Ohnishi, Koji Yamaguchi, Kenji Seko, Nobushige Numa and Naozumi Iwasawa&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-10T17:33:08.523" CommentCount="2" />
  <row Id="6539" PostTypeId="2" ParentId="6534" CreationDate="2010-11-10T17:37:48.577" Score="3" ViewCount="" Body="&lt;p&gt;This &lt;a href=&quot;http://cds.linear.com/docs/Datasheet/3631fc.pdf&quot; rel=&quot;nofollow&quot;&gt;LTC3631&lt;/a&gt; handles 4.5 to 45V in, 3.3v out, and comes in either a 3x3 mm or MSOP-8 package.  81% efficiency at 36v in and 10 ma out (page 4).  You should be able to get a suitable inductor in an 0805 (2 x 1.3 mm) or smaller package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.st.com/stonline/products/literature/ds/5257/mc34063ab.pdf&quot; rel=&quot;nofollow&quot;&gt;MC34063&lt;/a&gt; might also work but it is a larger package (SOIC-8), uses more quiescent current (2.5 ma) and would require more external components.  But it is 1/4 the cost of the LTC3631.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-11-10T21:41:37.290" LastActivityDate="2010-11-10T21:41:37.290" />
  <row Id="6540" PostTypeId="2" ParentId="6529" CreationDate="2010-11-10T17:42:09.253" Score="1" ViewCount="" Body="&lt;p&gt;Quoting Russell from the PIClist: &quot;AA cells of over 2000 or so mAh from reputable manufacturers recommend NO trickle charge or low AND extremely short duration trickle charge.&quot; Low capacity cells (e.g, 800 mAh AA) are OK with trickle charge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are definitely into high-capacity cells with 1000 mAh AAAs.  Check the manufacturer's datasheet before charging them with the indefinite-trickle method. However reputable manufacturers place a catalyst that will handle small amounts of excess trickle charging and will be able to handle a few extra hours of C/40 or less charge rate after charged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most dependable smart chargers(in relation to ensuring full charge) must use overcharge heating to detect overheating. It is almost unavoidable.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-11-10T18:03:26.110" LastActivityDate="2010-11-10T18:03:26.110" CommunityOwnedDate="2010-11-10T17:42:09.253" />
  <row Id="6541" PostTypeId="1" AcceptedAnswerId="6542" CreationDate="2010-11-10T18:21:42.080" Score="2" ViewCount="83" Body="&lt;p&gt;In the intrinsic semi-conductors,the electrons are bonded by covalent bonds to the nearby electron,when we do doping the electrons make bond with the atom we doped,so the covalent bonds between the semi-conductor electron is broken?How are they still connected to each other?&lt;/p&gt;&#xA;" OwnerUserId="1799" LastActivityDate="2010-11-10T18:55:22.707" Title="Bonding in intrinsic semi-conductors" Tags="&lt;electronics&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="6542" PostTypeId="2" ParentId="6541" CreationDate="2010-11-10T18:55:22.707" Score="1" ViewCount="" Body="&lt;p&gt;A simple explanation, not what 'really' goes on but good enough for introduction:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Covalent bonds exist between atoms, basically 2 atoms 'share' an electron.  In a pure semi-conductor crystal used for electronics, for example, silicon, all atoms are bound to 4 neighboring atoms via covalent bonds.  This should make sense given that silicon has 4 valence electrons and therefore 'wants' to bind with 4 additional electrons to fill its valence orbital.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you dope a semiconductor you blast out some of the silicon atoms and replace them with atoms that have either 3 or 5 valence electrons.  This means that you will either have 1 extra electron or be missing an election to fill the doped atom's valence orbital.  The bonds in the crystalline structure are very strong and the dopant percentage of the structure is low so the crystalline structure in maintained despite these impurities imparting a &quot;desire to change&quot; the structure. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The presence of the free electron or electron hole is what changes the nature of the material to be a donor (n-type) or acceptor (p-type).&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-10T18:55:22.707" CommentCount="1" />
  <row Id="6543" PostTypeId="1" AcceptedAnswerId="6546" CreationDate="2010-11-10T18:57:10.963" Score="2" ViewCount="375" Body="&lt;p&gt;Hello everyone&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I started a project with my students to build a full open source PIC IDE in windows. My first try was to port &lt;a href=&quot;http://piklab.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;Piklab&lt;/a&gt; to windows but it is dependent on Qt and KDE. We decide then to use &lt;a href=&quot;http://www.eclipse.org/cdt/&quot; rel=&quot;nofollow&quot;&gt;Eclipse CDT&lt;/a&gt; as IDE, SDCC as compiler and GPUtils as linker and assembler. We managed to make the compiler-chain plugin so we can build the whole project in eclipse and generate the binary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem now is how to use eclipse to program the PIC (we are targeting specifically on ICD2 because it is what we have available on our lab). Does anyone knows an open-source programmer that can run on command line on windows?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="1757" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-16T16:13:57.647" LastActivityDate="2010-11-16T16:13:57.647" Title="Open source pic programmer in windows" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;programming&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="6544" PostTypeId="2" ParentId="6543" CreationDate="2010-11-10T19:18:58.190" Score="1" ViewCount="" Body="&lt;p&gt;What about using the &lt;a href=&quot;http://hyvatti.iki.fi/~jaakko/pic/picprog.html&quot; rel=&quot;nofollow&quot;&gt;PicProg&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use commands like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;picprog [/h] [/log] [/info] [/list] [/init2] [/standby] [/read] [/continue] [/compare] [/noF84] [lpt1|lpt2] [/w:FILENAME]&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Parameter definition:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;/h&lt;/strong&gt;    help&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/log&lt;/strong&gt;  write output to picprog.log, forces /info&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/info&lt;/strong&gt; show full programming information&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/list&lt;/strong&gt; list of supported PIC&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/init2&lt;/strong&gt;    use /MCLR before Vpp power-up mode&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/standby&lt;/strong&gt;  loop program&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/continue&lt;/strong&gt; continue programming also while errors occur&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/noF84&lt;/strong&gt;    blocks PIC16F84 mode&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/lptX&lt;/strong&gt; definition of parallel port&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/read&lt;/strong&gt; data transfer from pic to file, reverses /w: command&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/compare&lt;/strong&gt;  data comparison of pic and file, overrides /w: command&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;/w:&lt;/strong&gt;   erase and write PIC, uses hex-file, extension will be ignored and set to .hex&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;You can find more information about open source tools (in portuguese) at this site: &lt;a href=&quot;http://www.sergioprado.org/2010/06/17/ferramentas-open-source-para-pic/&quot; rel=&quot;nofollow&quot;&gt;http://www.sergioprado.org/2010/06/17/ferramentas-open-source-para-pic/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-10T19:18:58.190" />
  <row Id="6545" PostTypeId="1" AcceptedAnswerId="6547" CreationDate="2010-11-10T19:19:09.717" Score="2" ViewCount="165" Body="&lt;p&gt;I am going to use a 400 kHz I2C bus, but I want to talk to a slave MCU, a PIC16F690 (&lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/41262C.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;), running at 32 kHz. Is it possible to do this? I think so, because the master does the clocking, but are there any unforeseen problems that might occur? (e.g. MCU can't load data into RAM quick enough.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-11-10T21:24:58.703" LastActivityDate="2010-11-10T21:24:58.703" Title="Is it possible to use 400 kHz I2C buses with a 32 kHz slave?" Tags="&lt;microcontroller&gt;&lt;i2c&gt;" AnswerCount="3" />
  <row Id="6546" PostTypeId="2" ParentId="6543" CreationDate="2010-11-10T19:20:06.537" Score="2" ViewCount="" Body="&lt;p&gt;Have you looked at &lt;a href=&quot;http://sourceforge.net/apps/mediawiki/piklab/index.php?title=Command-line_Utility&quot; rel=&quot;nofollow&quot;&gt;piklab-prog.exe&lt;/a&gt; in the piklab package?  Its a CLI tool for programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively the PicKit 2 has a stand alone CLI tool direct from microchip.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-10T19:25:28.003" LastActivityDate="2010-11-10T19:25:28.003" CommentCount="2" />
  <row Id="6547" PostTypeId="2" ParentId="6545" CreationDate="2010-11-10T19:23:21.543" Score="2" ViewCount="" Body="&lt;p&gt;read the data sheet to determine if the slave's MSSP can support the speed your interested in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need extra time to copy the data out of the receiving register use clock stretching, again read the data sheet for the slave for proper usage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: from the datasheet for that part, 400khz requires minimum device speed of 10Mhz, 100khz requires 1.5Mhz.  &lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-10T19:52:11.690" LastActivityDate="2010-11-10T19:52:11.690" CommentCount="1" />
  <row Id="6548" PostTypeId="2" ParentId="6543" CreationDate="2010-11-10T19:27:30.760" Score="0" ViewCount="" Body="&lt;p&gt;The PICkit 2 has source-available firmware and host application.  The firmware is not true OSI-approved Open Source as its use is restricted to Microchip's products.  There are alternative command-line tools that are Free software.  Many PICkit 2 clones are available. &lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-11-10T19:38:03.107" LastActivityDate="2010-11-10T19:38:03.107" />
  <row Id="6549" PostTypeId="2" ParentId="6545" CreationDate="2010-11-10T20:14:04.043" Score="0" ViewCount="" Body="&lt;p&gt;Mark's &quot;look at the datasheet&quot; is the right answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You tend to find that a synchronous digital part like a microcontroller samples all its inputs via registers which are clocked from the main clock (or a clock divided from the main clock).    So even things which feel like they are 'clocks' in their own right often have upper frequency limits which are imposed by the CPU's clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, even if the I2C slave logic does have a clock domain of its own, truly clocked by SCL, then the way that domain is connected to the CPU's clock domain will impose some restrictions on the relative frequencies of the two sections of logic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is just unfortunate stuff which comes up in synchronous logic design.  If you ever do FPGA design, you have to deal with it endlessly.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-10T20:14:04.043" />
  <row Id="6550" PostTypeId="2" ParentId="6545" CreationDate="2010-11-10T20:42:29.503" Score="1" ViewCount="" Body="&lt;p&gt;The datasheet makes it sound like the I2C operates asynchronously, as it apparently can run while sleeping (no clock to peripheral).  Though it might take a few cycles to determine if it was addressed and if it should send an ACK.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;h3&gt;13.6 Slave Mode&lt;/h3&gt;&#xA;  &#xA;  &lt;p&gt;While in Slave mode, the external clock is supplied by the external clock source on the SCK pin. This external clock must meet the minimum high and low times as specified in the electrical specifications.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;While in Sleep mode, the slave can transmit/receive data. When a byte is received, the device will wake-up from Sleep.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The electrical specifications don't mention if they are for just master or both it and slave modes; the 10 MHz for 400 kHz and 1.5 MHz for 100 kHz are comments on the bit-hold time parameter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to run with wildly disparate clocks, SPI might be a better bet, as you generally have direct control of the shift register clock.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-10T20:42:29.503" CommentCount="1" />
  <row Id="6551" PostTypeId="1" AcceptedAnswerId="6554" CreationDate="2010-11-10T20:46:59.500" Score="4" ViewCount="344" Body="&lt;p&gt;I'm designing an Open Hardware door-lock-controller for our hackerspace, to these basic requirements:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Be made exclusively from available and inexpensive parts.&lt;/li&gt;&#xA;&lt;li&gt;Read external Wiegand keyboard&lt;/li&gt;&#xA;&lt;li&gt;Read external Wiegand RFID reader&lt;/li&gt;&#xA;&lt;li&gt;Control various door-locks and other actuators.&lt;/li&gt;&#xA;&lt;li&gt;Read 125 kHz EM4100 RFID directly with an onboard reader.&lt;/li&gt;&#xA;&lt;li&gt;Passive POE powered, to make cabling easier.&lt;/li&gt;&#xA;&lt;li&gt;Run off unregulated 15-30V DC (cheap and easy high-capacity UPS via SLA)&lt;/li&gt;&#xA;&lt;li&gt;Provide a regulated 12V DC out @ 300 mA to 1.5A peak for external gear.&lt;/li&gt;&#xA;&lt;li&gt;Talk Ethernet to the server.&lt;/li&gt;&#xA;&lt;li&gt;Keep a local list of allowable keys, so only power is needed to let us in.&lt;/li&gt;&#xA;&lt;li&gt;Control external 230V gear using two relays.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This is the second spin of the PCB with a few changes to fix the problems I've found, the biggest change I've made is to throw away the LDO that regulated the 3.3V rail, in exchange for a simple MC34063 based switcher.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm pretty sure it's going to work, but I'd like some comments to check if I've overlooked something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compromises I've had to make in the design are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The primary (35V) capacitor is stacked on top of the Ethernet transformer to save space.&lt;/li&gt;&#xA;&lt;li&gt;The Ethernet transformer is huge, but I have a bunch of them and they were cheap, so I'm going to use them, even if they are huge.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;h1&gt;Main questions&lt;/h1&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Is there a cheaper and better way to implement the two power supplies (I need around 200mA@3.3V and 300mA@12V with peaks to 1.5A) ?&lt;/li&gt;&#xA;&lt;li&gt;Does the MC34063 switcher circuit/layout look sane?&lt;/li&gt;&#xA;&lt;li&gt;I have no idea how inefficient the MC34063 is so I've tried to heat sink it as well as possible using the copper I have available, any hints for improvements?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.hackaarhus.dk/forum/download/file.php?id=33&quot; rel=&quot;nofollow&quot;&gt;Schematic in pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.hackaarhus.dk/forum/download/file.php?id=32&quot; rel=&quot;nofollow&quot;&gt;Click to embiggen PCB image&lt;/a&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/LSTpR.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-10T21:44:13.700" Title="(Why) does this design suck?" Tags="&lt;avr&gt;&lt;pcb&gt;&lt;ethernet&gt;&lt;rfid&gt;&lt;pcb-design&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="6552" PostTypeId="1" AcceptedAnswerId="6572" CreationDate="2010-11-10T21:24:57.113" Score="3" ViewCount="208" Body="&lt;p&gt;I have boards that through a mistake of my own have a bunch of vias that &lt;strong&gt;should&lt;/strong&gt; connect to the ground plane, but are actually isolated. See all of the holes that are isolated:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/oldZK.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I need to bridge all of them to the ground plane. Since there is no solder mask I figured I could just use solder to bridge the connections. Here is what my solution looks like:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/7iV0c.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not so pretty. I am wondering if there are any suggestion of what I can do to short these in a better manner. I will have it fixed in my next board revision, but it is a few weeks before I will have the boards and need to solder a few of these up now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ADDITION: The biggest problem I was having was the ground plane heated up very slow and It didn't seem to want to stick to both the pad and the ground plane at the same time.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-10T21:46:11.297" LastActivityDate="2010-11-11T17:28:02.040" Title="How do I neatly bridge to a ground plane?" Tags="&lt;soldering&gt;" AnswerCount="4" CommentCount="6" FavoriteCount="1" />
  <row Id="6553" PostTypeId="2" ParentId="6543" CreationDate="2010-11-10T21:31:14.027" Score="0" ViewCount="" Body="&lt;p&gt;I'm not sure what devices you want to program, but Travis Goodspeed's GoodFET (Open hardware, open source) tool has some support for PICs (even though it's focused on the MSP430 line).   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out &lt;a href=&quot;http://goodfet.sourceforge.net/apps/pic/&quot; rel=&quot;nofollow&quot;&gt;http://goodfet.sourceforge.net/apps/pic/&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-10T21:31:14.027" />
  <row Id="6554" PostTypeId="2" ParentId="6551" CreationDate="2010-11-10T21:44:13.700" Score="6" ViewCount="" Body="&lt;p&gt;I'd be really surprised if this operates, at least with any reliability.  You desperately need a power plane and a ground plane with components like these.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance the ENC28J60SS is a current mode driver, those traces from it to the pulse transformer to the jack are going to be carrying high currents switching at high speeds with no reasonable supply or ground path for them.  I'd also be concerned with the crystal as its tuning capacitors have a very long high inductance path to ground.  I would guess that this design will emit a ton of EMI, possibly enough to interfere with any nearby electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The layout for the switcher is also huge, i would expect you to have serious amounts of noise and supply ringing throughout this design coming from the switcher and the ethernet components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also mentioned POE but there is no POE controller on this board.  If your planning to just plug into a POE switch there is a negotiation procedure to request power (in various levels).  The only way you could power this off the ethernet port as is would be to find a mid run injector that just dumped voltage on the unused pairs in 10/100 Base-T.  If you plugged this into a gigabit switch that could cause major problems.  Those pairs also aren't center tapped as they should be for POE.  Dumping pins 7/8 directly to ground could cause major problems for both this device and the switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a lot i could go into but 90% of it is a result of not having power/ground planes, clear that up first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also the mid point of R5 and R6 should not be connected to the center tap of the pulse transformer and the jack side of the Output transformer should have a small, high voltage cap to chassis ground at its center tap&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-10T21:44:13.700" CommentCount="12" />
  <row Id="6555" PostTypeId="2" ParentId="6543" CreationDate="2010-11-10T21:46:12.327" Score="2" ViewCount="" Body="&lt;p&gt;Microchip is developing a new version of MPLAB based on netbeans called &lt;a href=&quot;http://microchip.wikidot.com/mplab%3a_start&quot; rel=&quot;nofollow&quot;&gt;MPLAB X&lt;/a&gt;. This will be their cross-platform open source IDE going forward. &lt;/p&gt;&#xA;" OwnerUserId="245" LastActivityDate="2010-11-10T21:46:12.327" CommentCount="2" />
  <row Id="6556" PostTypeId="2" ParentId="6552" CreationDate="2010-11-10T21:52:05.673" Score="1" ViewCount="" Body="&lt;p&gt;you'll have a very hard time heating up that ground plane.  You could put the PCB in a board heater then maybe solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively you can use conductive epoxy, that should work as long as the impedance to ground isn't super critical for the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, isn't that pad underneath that TO-220ish looking package shorting to the ground plan? &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-10T21:52:05.673" CommentCount="2" />
  <row Id="6557" PostTypeId="2" ParentId="6523" CreationDate="2010-11-10T22:03:55.593" Score="1" ViewCount="" Body="&lt;p&gt;Depending on where your high school is, you have a couple options:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;BEST Robotics - A middle school/high school robotics challenge.  Mainly in the Southeastern and Central united states, with a few branches into the Northeast.  I particularly enjoy this competition, because all of the teams are given the same components to solve a given engineering challenge.  The competition is free to enter, and all of the building supplies are given to you at the beginning of the season.  Unfortunately, the season is almost at a close, and the next season won't begin until next Fall.  One of the better aspects of BEST is that you also have to create a project engineering notebook and a set of drafts for your robot.  I found that this is much closer to &quot;real life&quot; engineering.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;FIRST Robotics - This is the expensive one.  You want some serious company sponsors and a legitimate team if you want to attempt this one.  It's pretty awesome.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;VEX Robotics - I don't know much about this one, because it started after my time.  It's supposed to be a good middle ground between BEST and FIRST in terms of cost.  The BEST competition is now using VEX hardware for controls.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I would encourage you to try and do competitions, as they give your club some focus and deadlines.  They are also take place in a single school year so that student turnover (due to graduation) won't affect any single year of the club too much.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-11-10T22:03:55.593" CommunityOwnedDate="2010-11-10T22:03:55.593" />
  <row Id="6558" PostTypeId="2" ParentId="2827" CreationDate="2010-11-11T01:25:57.937" Score="2" ViewCount="" Body="&lt;p&gt;From franchised distributors:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arrownac.com/%22Arrow%22&quot; rel=&quot;nofollow&quot;&gt;Arrow&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://avnetexpress.avnet.com%22Avnet%22&quot; rel=&quot;nofollow&quot;&gt;Avnet&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.digikey.com/%22Digikey%22&quot; rel=&quot;nofollow&quot;&gt;Digikey&lt;/a&gt;, pricier but quick to ship&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You will need to get quotes; they don't put this stuff online for &quot;real&quot; (&gt;1 k) quantities.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-12T16:19:51.173" LastActivityDate="2010-11-12T16:19:51.173" />
  <row Id="6559" PostTypeId="2" ParentId="6523" CreationDate="2010-11-11T01:49:42.017" Score="0" ViewCount="" Body="&lt;p&gt;This can be super challenging for any level of robotics engineering, but.&#xA;No much machined parts required. the challenge is pure physics, motion and software. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Imagine a tall construction crane scaled like 1:100 which runs on wheels on narrow rails with no other attachment to ground. All you have for balance is a weight block at bottom and small block on back arrow. The crane operates an electro magnet or hook or lock and performs task of picking blocks from ground and putting them as fast as possible to higher spot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Technically its a robot with 3 or 4 axises: X-axis is rails, Theta-axis is rotational and Z-axis is a cable. Optionally there can be an extra R-axis for point of cable block on the arrow, or Phi-axis for yaw movement of arrow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The challenge is, that, when properly scaled, it will be very interesting to perfect the motion with swinging loads. If you have 2-3 cranes in class, the team designed fastest safe motion sequence wins. Or team, which builds taller tower. Also, teams can be free to pick as many extra parts to make crane taller, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And no hard bolted attachments to the ground.&lt;/p&gt;&#xA;" OwnerUserId="924" LastEditorUserId="924" LastEditorDisplayName="" LastEditDate="2010-11-11T02:05:36.683" LastActivityDate="2010-11-11T02:05:36.683" CommunityOwnedDate="2010-11-11T01:49:42.017" />
  <row Id="6560" PostTypeId="2" ParentId="6484" CreationDate="2010-11-11T02:37:08.200" Score="1" ViewCount="" Body="&lt;p&gt;I have bad experience of similar attempt. The cause is that contemporary switching supplies are too smart for dynamic inductive load with regenerative an other switching spikes.&#xA;The only workaround is to use raw power supply (transformer, bridge, zero active components).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you will possibly see if you try direct connection:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Motor will accelerate OK on low torgue&lt;/li&gt;&#xA;&lt;li&gt;Motor will trip supply when acceleration is high on start from zero velocity&lt;/li&gt;&#xA;&lt;li&gt;Motor will accelerate OK with high acceleration but will trip supply protection when decelerated&lt;/li&gt;&#xA;&lt;li&gt;Motor will never burn, but supply very likely will&lt;/li&gt;&#xA;&lt;li&gt;Nothing will will break and will work ok, but you will trip mains 20A breaker once in a while.&lt;/li&gt;&#xA;&lt;li&gt;Trying to put ferrite chokes on positive wire will make no difference, supply will keep tripping&lt;/li&gt;&#xA;&lt;li&gt;Overall currents will never be near 50% of rated by supply, but peak values will keep protection tripping even if the motion is smooth&lt;/li&gt;&#xA;&lt;li&gt;The protection diode (overvoltage 50V surge diode in parallel to 48V supply) can help for 90% of motions, but supply will be ever tripping unpredictably over long run&lt;/li&gt;&#xA;&lt;li&gt;etc.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So answer is probably the thing we did not try, but which can help:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Calculate the energy budget for motions and double it and put super large capacitor at the output. With surge diode with voltage rating 1-2V greater than nominal voltage and a bit lower than overvoltage protection of supply.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Other aspects involved:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The breakdown of high power semiconductors is caused not by voltage, but by speed of voltage increase (about 5000V/microsecond typically). Rule of thumb &quot;Everything is thyristor&quot;&lt;/li&gt;&#xA;&lt;li&gt;The TVS is a must. They survive at 49..50V 400W loads with no sweat.&lt;/li&gt;&#xA;&lt;li&gt;The regenerative energy absorbtion (large capacitor and/or power resistor with few diodes) is a must if voltage is over 100V. Can be skipped for low voltage setup unless you need 24/7 run in hard conditions.&lt;/li&gt;&#xA;&lt;li&gt;Custom FET switching is cause of trouble, simply because you cause mechanical shock with infinite torgue on start, unless you use PWM with clever S-curve acceleration.&lt;/li&gt;&#xA;&lt;li&gt;Safety is also not last aspect if you deal with near horsepower motion.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="924" LastEditorUserId="924" LastEditorDisplayName="" LastEditDate="2010-11-11T03:12:02.163" LastActivityDate="2010-11-11T03:12:02.163" />
  <row Id="6561" PostTypeId="1" CreationDate="2010-11-11T02:58:37.590" Score="4" ViewCount="218" Body="&lt;p&gt;I'm working with an 8051 (Cypress FX2LP) that doesn't have jtag/bdm capability. Typically, developers on this project have been using ad-hoc serial printfs for debugging. I'm looking into options for serial debug monitors such as Keil's Mon51, Isd51 or IAR's generic ROM-monitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll need to modify/configure this debug monitor to write to code RAM (to set software breakpoints). I'd guess that most 8051 debug monitors offer the ability for such modifications in order to support Harvard architecture or bank switching.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Keil tools come with Mon51 and Isd51. The Isd51 is very small and comes as source that can optionally be embedded in the application. C:/Keil/C51/ISD51/Examples/Generic_8052 works as-is on the Cypress eval board. This can all be done with the free Keil eval (subject to the eval size limitations).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This pdf &lt;a href=&quot;ftp://www-s.ti.com/pub/data_acquisition/MSC_CD-ROM/Application_Notes/sbaa078_MSC1210_Debugging_Strategies.pdf&quot; rel=&quot;nofollow&quot;&gt;'MSC1210 Debugging Strategies'&lt;/a&gt;  from TI, explains some strategies for serial debugging on an 8051.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this Cypress part had jtag/bdm - it would be a no-brainer - I'd use that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody have recommendations for serial debuggers for 8051 or similar processors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you had to modify it to write to Harvard code RAM or flash etc?&lt;/p&gt;&#xA;" OwnerUserId="1912" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-01-07T14:45:38.837" LastActivityDate="2011-01-07T14:45:38.837" Title="8051 serial debug monitors" Tags="&lt;debug&gt;&lt;8051&gt;" AnswerCount="1" />
  <row Id="6562" PostTypeId="2" ParentId="6475" CreationDate="2010-11-11T04:01:02.497" Score="1" ViewCount="" Body="&lt;p&gt;Can &quot;potentiometer with switch&quot; be the name ? You need just wire the switch to A and W. So it will guarantee a very good zero (when turned counter clock wise all way until click).&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-11T04:01:02.497" CommentCount="1" />
  <row Id="6563" PostTypeId="1" AcceptedAnswerId="6564" CreationDate="2010-11-11T05:16:28.920" Score="4" ViewCount="174" Body="&lt;p&gt;Say I've got a peltier block that is rated at 15.2V and 6A, providing 90W of cooling power to one side. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will I be able to operate it at 5V, and will it draw 2A, providing 30W of cooling power?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: sorry, error above. :P brain was not working. 5V and 2A would indeed be 10W instead of 30W above.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="1688" LastEditorDisplayName="" LastEditDate="2010-11-11T06:04:45.947" LastActivityDate="2010-11-11T09:48:52.240" Title="Are peltier devices linear?" Tags="&lt;peltier&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="6564" PostTypeId="2" ParentId="6563" CreationDate="2010-11-11T05:27:39.320" Score="4" ViewCount="" Body="&lt;p&gt;No, because power is a product of the voltage and current:&lt;br&gt;&#xA;15.2V * 6A = 91.2W&lt;br&gt;&#xA;5V * 2A = 10W&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would need approximately 9V @ 3.6A, which would give you ~32W&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember, peltier devices are not very efficient, so 30W of input will not give you 30W of cooling power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wikipedia &lt;a href=&quot;http://en.wikipedia.org/wiki/Thermoelectric_cooling&quot; rel=&quot;nofollow&quot;&gt;cites Peltier devices&lt;/a&gt; at an efficiency of approximately 5-10%, which means that for a best-case application cooling a 10W heat load, you will need a 100W peltier with a heatsink that can handle the aggregate power, or 110W of dissipation to maintain the 10W heat load at ambient temperature (this is assuming a 0° C/W heatsink on the hot side of the peltier).&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-11-11T05:33:21.927" LastActivityDate="2010-11-11T05:33:21.927" CommentCount="3" />
  <row Id="6565" PostTypeId="1" CreationDate="2010-11-11T06:07:55.677" Score="3" ViewCount="233" Body="&lt;p&gt;I still haven't found a really good solution for grabbing tiny surface mount stuff.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Crocodile_clip&quot; rel=&quot;nofollow&quot;&gt;Alligator clips&lt;/a&gt; are definitely way too big.&lt;/li&gt;&#xA;&lt;li&gt;Mini-grabbers like this with the spring-loaded hook are an ok solution for bigger stuff, but no good for little surface mount components.  I can solder on little bits of wire and then mini-grab those, but it's tedious and time-consuming. And in my experience they tend to be broken more often than not:&#xA;&lt;img src=&quot;http://i.imgur.com/u1sjA.jpg&quot; alt=&quot;minigrabbers&quot;&gt;&lt;/li&gt;&#xA;&lt;li&gt;I got some Tektronix KlipChips and some HP 5090-4356 clips on eBay.  &lt;img src=&quot;http://i.imgur.com/YjmDy.jpg&quot; alt=&quot;Tektronix KlipChips and HP 5090-4356&quot;&gt;  The Tektronix clips are hard to open, because the plastic head tips to the side and jams instead of sliding down when you try to squeeze it. The HPs don't have that problem. The Tek pincers are made of wire, so they splay out sideways instead of grabbing well (and get permanently bent, making them jam on each other and not close completely, so connections to thin wires are intermittent).  &lt;img src=&quot;http://i.imgur.com/VKH8N.jpg&quot; alt=&quot;alt text&quot;&gt;  The HP pincers are made of thin strips of metal, so they are more rigid in that direction. The wire pincers depend on the bendiness of the wire to overlap each other side-by-side (which doesn't work very well) while the HP pincers fold inside each other, with one a little shorter than the other. This seems to work better, but they get bent outward, and the tubes are plastic, so they get bent outwards by any angular stress and no longer close well.  &lt;img src=&quot;http://i.imgur.com/WllQz.jpg&quot; alt=&quot;alt text&quot;&gt;  The orientation of the pincers on the HP relative to your fingers is more natural.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;These work on SOICs or bigger, but after they've become worn they don't stay on as well. They don't work for surface mount resistors (they just pop off if disturbed even a little) or smaller-pitch ICs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And I've broken the retractable hook tip for oscilloscope probes by attaching it to a circuit and then letting go, and the weight of the bulky probe and wire put too much stress on the plastic tip and bend it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally I'd like something that can grip one side of a surface mount resistor, or a pin on a smaller pitch IC, not fall off, not produce any stress on anything, and not break easily.  Any advice, ideas, tips, tricks, ingenious alternatives, cheap Chinese knock-offs of better clips?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Previously asked on &lt;a href=&quot;http://forums.xkcd.com/viewtopic.php?f=18&amp;amp;t=20673&quot; rel=&quot;nofollow&quot;&gt;xkcd forums&lt;/a&gt; and &lt;a href=&quot;http://forums.adafruit.com/viewtopic.php?f=8&amp;amp;t=5659&quot; rel=&quot;nofollow&quot;&gt;adafruit forums&lt;/a&gt;.)&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-11-11T22:33:09.533" Title="What do you use to probe circuits?" Tags="&lt;prototyping&gt;&lt;oscilloscope&gt;&lt;probe&gt;" AnswerCount="7" FavoriteCount="1" />
  <row Id="6566" PostTypeId="2" ParentId="6565" CreationDate="2010-11-11T06:29:27.563" Score="8" ViewCount="" Body="&lt;p&gt;If you're designing your own boards, add test points. Aside from that, soldering on short bits of wire is the best solution I've found so far.  I find that the amount of time it takes to strip and solder a wire is far less than what I'd otherwise waste futzing with clips or trying to hold a probe just so while also keeping an eye on a scope.&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2010-11-11T06:29:27.563" CommentCount="3" />
  <row Id="6567" PostTypeId="2" ParentId="6565" CreationDate="2010-11-11T08:43:02.733" Score="2" ViewCount="" Body="&lt;p&gt;I haven't tried it myself, but I've seen &lt;a href=&quot;http://travisgoodspeed.blogspot.com/2008/05/syringe-logic-probe.html&quot; rel=&quot;nofollow&quot;&gt;insulin syringes used&lt;/a&gt;. I think the idea is that they're sharp enough to catch on pads and components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://travis.frob.us/~travis/public/blog/images/syringe/probe_un.jpg&quot; width=&quot;200&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-11T08:43:02.733" CommentCount="5" />
  <row Id="6568" PostTypeId="2" ParentId="105" CreationDate="2010-11-11T09:10:51.477" Score="1" ViewCount="" Body="&lt;p&gt;To read EM4100 tags (the cheap, 125 kHz kind) you need to get a good coupling between the tags coil and the reader coil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bigger the tag coil, the better and more reliable the signal will be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First of all you'd need to wrap the reader coil all the way around the portal to ensure that the animal is going to be within the magnetic field.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second of all you need to make sure that the tag coil is parallel to the reader coil, I think the easiest way to do that is to build collar where the coil is built into the collar and connected via a connector where the chip is located.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The entire trick is to build the RFID collar to be both durable and removable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit for the reader is very simple and can be built for under $2 provided you have an AVR such as the one found in an Arduino to connect it to, take a look at the bottom of this schematic: &lt;a href=&quot;http://www.hackaarhus.dk/forum/download/file.php?id=33&quot; rel=&quot;nofollow&quot;&gt;http://www.hackaarhus.dk/forum/download/file.php?id=33&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-11T09:10:51.477" />
  <row Id="6569" PostTypeId="2" ParentId="105" CreationDate="2010-11-11T09:17:37.967" Score="0" ViewCount="" Body="&lt;p&gt;Have also done some work with &lt;a href=&quot;http://tronixstuff.wordpress.com/2010/08/18/moving-forward-with-arduino-%e2%80%93-chapter-15-%e2%80%93%c2%a0rfid-introduction/&quot; rel=&quot;nofollow&quot;&gt;RFID and Arduino&lt;/a&gt; if anyone is interested. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-11-11T09:17:37.967" />
  <row Id="6570" PostTypeId="2" ParentId="2827" CreationDate="2010-11-11T09:43:21.453" Score="3" ViewCount="" Body="&lt;p&gt;You need to talk (and I mean talk - some still don't answer emails!) to franchised distributors, and if necessary play them off against each other.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-11T09:43:21.453" />
  <row Id="6571" PostTypeId="2" ParentId="6563" CreationDate="2010-11-11T09:48:52.240" Score="1" ViewCount="" Body="&lt;p&gt;Peltiers are almost always a disappointment.  You will find that the fantastic headline figures they quote are always for when there is no temperature gradient across the device.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In reality that's rarely what you want (particularly if when you're trying to get something cold, rather than merely stop it getting hot).   The device itself acts as a thermal short-circuit, busily conducting heat back from the hot site to the cool side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not saying they're useless, but ultimately your question is unlikely to be 'how much can I under-drive this device' and much more likely to be 'how much can I squeeze out of this (and the poor PSU) by running it at 120%'.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-11T09:48:52.240" />
  <row Id="6572" PostTypeId="2" ParentId="6552" CreationDate="2010-11-11T11:09:32.400" Score="1" ViewCount="" Body="&lt;p&gt;Get a better soldering iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not the easiest solution, but in the long term (having a better iron improves &lt;em&gt;everything&lt;/em&gt;), I think it is the best.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an &lt;a href=&quot;http://octopart.com/ps-800-metcal-9130&quot; rel=&quot;nofollow&quot;&gt;OKI-Metcal soldering station&lt;/a&gt;, and I can easily solder D2PAK devices down to a solid copper plane with no thermal relieving at all. Any similar &quot;Serious&quot; iron should be able to do similar. (They generally run ~$200. It's an investment)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, what tip do you have on your iron? For something like that, a &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=0054470299-ND&quot; rel=&quot;nofollow&quot;&gt;chisel tip&lt;/a&gt; (pick one for your iron, link is just an examle) is really essential to get good thermal contact between your iron and the copper plane.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-11-11T11:09:32.400" CommentCount="3" />
  <row Id="6573" PostTypeId="2" ParentId="6565" CreationDate="2010-11-11T12:48:03.943" Score="2" ViewCount="" Body="&lt;p&gt;For passive components there are &lt;a href=&quot;http://www.conrad.de/ce/de/product/121305/&quot; rel=&quot;nofollow&quot;&gt;small spring-loaded plier-like probes&lt;/a&gt; with two 0.6mm contacts from Hirschmann.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For IC pins there are some really small ones from &lt;a href=&quot;http://www.pomonaelectronics.com/index.php?i=prodmain&amp;amp;page=2&amp;amp;getDetails=1&amp;amp;parent=GRABCLIP&quot; rel=&quot;nofollow&quot;&gt;Pomona 6351/6352/6353&lt;/a&gt;, though the price is inversely related to the size (or maybe the square of the size?), so these are really expensive. I've used two of these on adjacent pins with 0.5mm pitch (unfortunately they weren't mine).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good search term is &quot;grabber&quot;.&lt;/p&gt;&#xA;" OwnerUserId="339" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2010-11-11T22:33:09.533" LastActivityDate="2010-11-11T22:33:09.533" />
  <row Id="6574" PostTypeId="1" AcceptedAnswerId="6578" CreationDate="2010-11-11T13:40:23.460" Score="2" ViewCount="119" Body="&lt;p&gt;Related to my &lt;a href=&quot;http://electronics.stackexchange.com/questions/6534/3-3v-10ma-from-5v-35v&quot;&gt;last question&lt;/a&gt;, I decided to go with a step-down charge pump to convert 5V to 35V down to 3.3V at 10mA, due to the smaller required component size. However, I can't find a single charge pump IC rated to go up to 35V. Does anyone have any suggestions? If there are no ICs to do this, woudl there be any way of dropping 35V down to 18V with minimal loss and a small surface area?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd also be open to using a buck regulator, but it seems like a waste for only 10mA.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-11T17:34:53.643" Title="High input voltage charge pump" Tags="&lt;charge&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="6575" PostTypeId="2" ParentId="6565" CreationDate="2010-11-11T14:14:03.027" Score="1" ViewCount="" Body="&lt;p&gt;Those Pomona grabbers starblue posted are great and work very well but they break very easily and you would have to support most of the weight of the grabber or it will come of the pin.  I'd say they are not worth it for home use unless you are extremely careful and use them sparingly.  They do work very well once you get one on properly.  Unfortunately I don't know of anything else except for soldering or holding a probe on the pin as an alternative.&lt;/p&gt;&#xA;" OwnerUserId="1819" LastActivityDate="2010-11-11T14:14:03.027" CommentCount="1" />
  <row Id="6576" PostTypeId="2" ParentId="6552" CreationDate="2010-11-11T15:47:15.630" Score="0" ViewCount="" Body="&lt;p&gt;Maybe a heat gun or hot air rework station would improve things. But you are still going to have the problem of the ground plane transferring heat away from the area you want to heat up moreso than the vias.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For everyone else: I'm envisioning something that would fix this problem perfectly - sort of a mesh (like a solder wick, but small and circular) that would be coated in solder which you could then place over the via and heat up with a hot air gun.  When the solder starts to melt, it would adhere to the ground plane and via.  Then just remove the heat and let it solidify.  Like a drywall patch for PCBs.  Does anything like THAT exist?&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-11T15:47:15.630" CommentCount="2" />
  <row Id="6577" PostTypeId="2" ParentId="6565" CreationDate="2010-11-11T16:39:27.557" Score="2" ViewCount="" Body="&lt;p&gt;I've found &lt;a href=&quot;http://www.testpath.com/Categories/Cal-Test-Micro-Test-Clips-24550.htm&quot; rel=&quot;nofollow&quot;&gt;these SMD test clips&lt;/a&gt; quite effective. They look similar to the Pomona clips. I haven't broken any yet.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-11T16:39:27.557" CommentCount="2" />
  <row Id="6578" PostTypeId="2" ParentId="6574" CreationDate="2010-11-11T17:06:02.993" Score="2" ViewCount="" Body="&lt;p&gt;Charge pumps tend to be oriented towards fixed ratios, so your wide input range means they are probably not a good option. For 10mA I think linear is the best bet cost-wise - may be worth seeing if you can afford to slow down the clock on the micro to reduce this by a few mA. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-11T17:06:02.993" />
  <row Id="6579" PostTypeId="2" ParentId="4604" CreationDate="2010-11-11T17:22:16.773" Score="3" ViewCount="" Body="&lt;p&gt;Here's a recently announced system. &lt;strong&gt;It may not be available for purchase yet&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://research.microsoft.com/en-us/projects/gadgeteer/default.aspx&quot; rel=&quot;nofollow&quot;&gt;The .NET Gadgeteer&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://research.microsoft.com/en-us/projects/gadgeteer/gadgeer_modules.png&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://research.microsoft.com/en-us/projects/gadgeteer/gadgeteer_example.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-12T00:12:21.103" LastActivityDate="2010-11-12T00:12:21.103" CommunityOwnedDate="2010-11-12T00:12:52.647" CommentCount="3" />
  <row Id="6580" PostTypeId="2" ParentId="6552" CreationDate="2010-11-11T17:28:02.040" Score="1" ViewCount="" Body="&lt;p&gt;Is soldering a requirement? Because if it's only a prototype or something, you can use conductive copper foil tape to &quot;patch&quot; the holes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/v0JNE.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2010-11-11T17:28:02.040" CommentCount="1" />
  <row Id="6581" PostTypeId="2" ParentId="6574" CreationDate="2010-11-11T17:34:53.643" Score="2" ViewCount="" Body="&lt;p&gt;this isn't what charge pumps are really designed for, they aren't variable input regulators but supply multipliers/dividers/inverters.  They're not really designed to be fed an unregulated voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just use a &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1042,P88521&quot; rel=&quot;nofollow&quot;&gt;buck converter&lt;/a&gt; or a &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1040,P86928&quot; rel=&quot;nofollow&quot;&gt;linear regulator&lt;/a&gt;, examples linked.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-11T17:34:53.643" />
  <row Id="6582" PostTypeId="2" ParentId="6565" CreationDate="2010-11-11T17:54:05.313" Score="2" ViewCount="" Body="&lt;p&gt;The options i've seen are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Solder a blue wire onto the pin you need to look at (what i usually do)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Both agilent and tektronics make probes with solder-able, replaceable tips, expensive&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Use a 'third arm' device, tektronics and agilent make ones specific for scope probes but &#xA;they are expensive.  However you can get ones designed for chemistry work that are just as effective in my opinion and are much cheaper.  Examples &lt;a href=&quot;http://www.coleparmer.com/catalog/product_view.asp?sku=6352860&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://www.opticsforyou.com/control-company-vwr-ph-electrode-arm-3090.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  This holds an advantage for testing signals in potentially noisy areas of the circuit by limiting both the length of wire from test point to probe and keeping the probe/probe wire as far from the circuit as reasonably possible.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The best solution is to include test points, or at least a via big enough for a blue wire on a signal you know you'll need to test.  Some times this obviously isn't possible.  I always at least include a spot where i can hook to a decent ground.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-11T17:54:05.313" />
  <row Id="6583" PostTypeId="1" AcceptedAnswerId="6586" CreationDate="2010-11-11T18:07:38.520" Score="2" ViewCount="116" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an Intel D975XBX2KR motherboard that has a few of the on-board heat sinks that have come loose because of improper shipping.  I'm trying to salvage the motherboard because it is quite an expensive board and this is the only issue I see with the motherboard and expect it to still function correctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is an image reference of what it looks like: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/43540779@N07/5167389178/&quot; rel=&quot;nofollow&quot;&gt;http://www.flickr.com/photos/43540779@N07/5167389178/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found some thermal adhesive paste that I think may work but would like to get some community suggestions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, what would you recommend for removing the old thermal paste on the heat sink/mobo components?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1919" LastActivityDate="2010-11-11T18:32:36.730" ClosedDate="2010-11-16T16:46:17.323" Title="Re-secure a motherboard heat sink.. what to use?" Tags="&lt;heatsink&gt;" AnswerCount="1" CommentCount="5" FavoriteCount="1" />
  <row Id="6584" PostTypeId="1" AcceptedAnswerId="6592" CreationDate="2010-11-11T18:09:41.140" Score="0" ViewCount="235" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On almost every remote controller the buttons stop reacting after a while, and you end up squeezing the remote out of his life while trying to switch the channel...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found some &lt;a href=&quot;http://www.wikihow.com/Repair-a-Remote-Control&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt; where it explains how to &quot;refresh&quot; the contact-making surface on the backside of the buttons, but that kit is not something I can find around. Could you suggest what would be a good replacement?&lt;/p&gt;&#xA;" OwnerUserId="1921" LastActivityDate="2011-03-24T20:29:26.613" Title="Fix remote controller button contacts" Tags="&lt;remote&gt;&lt;button&gt;&lt;repair&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="6585" PostTypeId="2" ParentId="6584" CreationDate="2010-11-11T18:20:25.027" Score="1" ViewCount="" Body="&lt;p&gt;That guide says the key repair kit costs $23. Can't you buy a nice new remote for that price? It looks like the main thing that kit has is conductive paint, which you can buy separately:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/search?q=conductive+paint&amp;amp;hl=en&amp;amp;prmd=ivs&amp;amp;source=univ&amp;amp;tbs=shop:1&amp;amp;tbo=u&amp;amp;ei=sjPcTKXeMIPGlQeVn9jaDQ&amp;amp;sa=X&amp;amp;oi=product_result_group&amp;amp;ct=title&amp;amp;resnum=1&amp;amp;ved=0CC0QrQQwAA#q=conductive+paint&amp;amp;hl=en&amp;amp;sa=X&amp;amp;tbs=shop:1,p_ord:p&amp;amp;prmd=ivs&amp;amp;fp=7e54633210c96bac&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/search?q=conductive+paint&amp;amp;hl=en&amp;amp;prmd=ivs&amp;amp;source=univ&amp;amp;tbs=shop:1&amp;amp;tbo=u&amp;amp;ei=sjPcTKXeMIPGlQeVn9jaDQ&amp;amp;sa=X&amp;amp;oi=product_result_group&amp;amp;ct=title&amp;amp;resnum=1&amp;amp;ved=0CC0QrQQwAA#q=conductive+paint&amp;amp;hl=en&amp;amp;sa=X&amp;amp;tbs=shop:1,p_ord:p&amp;amp;prmd=ivs&amp;amp;fp=7e54633210c96bac&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1256" LastActivityDate="2010-11-11T18:20:25.027" CommentCount="1" />
  <row Id="6586" PostTypeId="2" ParentId="6583" CreationDate="2010-11-11T18:24:57.563" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm&quot; rel=&quot;nofollow&quot;&gt;Arctic Silver Thermal Adhesive&lt;/a&gt; is what I use.  Should be able to find it at many online computer stores, newegg probably, or microcenter if you have one locally.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They make &lt;a href=&quot;http://www.arcticsilver.com/arcticlean.htm&quot; rel=&quot;nofollow&quot;&gt;some cleaner&lt;/a&gt; also, you should carefully and thoroughly clean the IC's and the heatsink before reattaching.  Q-tips work well for the ICs. &lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-11T18:32:36.730" LastActivityDate="2010-11-11T18:32:36.730" CommentCount="6" />
  <row Id="6587" PostTypeId="2" ParentId="6584" CreationDate="2010-11-11T18:27:07.533" Score="1" ViewCount="" Body="&lt;p&gt;If we want to go the &lt;em&gt;really&lt;/em&gt; hack route, you could use gum wrappers as a handy source of adhesive backed foil.  Cover the membrane pads with that and you might get another 1-1000 button cycles out of your remote.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-11T18:27:07.533" />
  <row Id="6588" PostTypeId="1" AcceptedAnswerId="6589" CreationDate="2010-11-11T18:48:18.000" Score="4" ViewCount="188" Body="&lt;p&gt;I was looking for an equivalent MOSFET and haven't had any success.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to know if are there any websites or software which gives a list of alternative equivalent components?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The purpose of this question is not only for MOSFET's, but for any type of component. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to learn how to find equivalents (or similar) components without having the need to ask about specific components here.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="400" LastEditorDisplayName="" LastEditDate="2010-11-12T08:52:22.243" LastActivityDate="2010-11-12T16:22:05.650" Title="How does one find an equivalent component?" Tags="&lt;components&gt;&lt;prototyping&gt;&lt;development&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="2" />
  <row Id="6589" PostTypeId="2" ParentId="6588" CreationDate="2010-11-11T18:53:15.433" Score="5" ViewCount="" Body="&lt;p&gt;many distributors offer a cross reference search.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For something as simple as a mosfet i would probably just go to digikey, head to the mosfet section and enter the parameters in the digikey search options from the datasheet of the part you have.  Then compare datasheets for the results.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-11T18:53:15.433" CommentCount="1" />
  <row Id="6590" PostTypeId="2" ParentId="6565" CreationDate="2010-11-11T18:58:07.583" Score="2" ViewCount="" Body="&lt;p&gt;Are you asking about debugging others' boards or your own?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have the ability to control the PCB, some test pads are an easy thing to add.  Just a little rectangle of copper makes a world of difference in avoiding shorts, damaged traces, and the like.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even a small pad can be poked reliably with pogo pins or an oscilloscope probe.  However, if you want to be able to clip to the connection, either solder a little loop of wire onto the point, or get some of &lt;a href=&quot;http://www.keyelco.com/pdfs/M55p51.pdf&quot; rel=&quot;nofollow&quot;&gt;Keystone's test points&lt;/a&gt;[pdf].  They have SMT ones as small as .1&quot;x.04&quot; which are easy to put down and then remove for later use, and the through-hole versions clip and unclip in a .04&quot; or .063&quot; diameter hole.  Just enlarging a few vias on your main communication busses in case you need to plug one of these in is an easy way to protect yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're working with boards over which you have no control, a Chip Clip is often helpful.  The plastic jaws grip the underside of the chip (between and below the leads), and there are contacts for the chip.  It looks like this (8-pin SOIC clip shown):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/CEzDw.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It breaks the contacts out to .1&quot; headers.  They're available for PLCC and SOIC packages, and I think TSSOP as well.  They require a chip with exposed leads and a grippable body, so that rules out QFPs, BGAs, and rectangular passive devices, but those are nearly impossible to clip even with other methods. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recently had to reprogram several hundred SPI flash chips and didn't want to take the time or money to solder the required computer interfaces onto all those sparsely populated boards.  So, I removed the chip from one board (which had the interface), ran wires from the empty pads pads to chip clips, held the micro on the new board in reset (It was the only thing connected to the SPI bus), and went to work.  I went through a few clips in the process, but it was nowhere near the cost of the magnetics.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-11T18:58:07.583" CommentCount="1" />
  <row Id="6591" PostTypeId="1" AcceptedAnswerId="6879" CreationDate="2010-11-11T19:19:59.607" Score="4" ViewCount="388" Body="&lt;p&gt;I'm planning on building some dimmable lighting controller for Christmas lights, but with LEDs being all the rage nowadays, I was thinking that instead of using triacs and dimming at 60/120 Hz, rectify the AC to DC and use MOSFETs to reduce the strobing that is more evident in LEDs.  This might allow the controller to be smaller and/or cheaper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would depend on how the LED strings are actually wired up.  I don't currently have any to look at, and I could imagine a few different ways they might be connected, such as diodes that only conduct for half the cycle, which would axe the DC idea if true.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-17T11:38:45.637" Title="How are LED Christmas Lights Wired?" Tags="&lt;led&gt;&lt;ac&gt;&lt;dimming&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="6592" PostTypeId="2" ParentId="6584" CreationDate="2010-11-11T19:29:12.107" Score="1" ViewCount="" Body="&lt;p&gt;I've used aluminum foil with great success before.  You can get it from a gum wrapper like Nick T suggested.  Just make sure you don't use super glue, it'll dry out the rubber in the buttons and cause even more problems.&lt;/p&gt;&#xA;" OwnerUserId="1819" LastActivityDate="2010-11-11T19:29:12.107" CommentCount="2" />
  <row Id="6593" PostTypeId="1" AcceptedAnswerId="6598" CreationDate="2010-11-11T19:30:54.377" Score="3" ViewCount="399" Body="&lt;p&gt;Hi, I need to send 800 bytes of data from a computer to an arduino board every 20ms (approximately).  I began with the serial library which works nicely but it is too slow even at its highest rate (115200 baud) for interfacing with a computer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What other interfaces are available that can send at a faster rate?  Can I use usb or spi?  I can't seem to find libraries for these.  I need something with about a 320 kBaud rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any shields that might be able to do this?  Bluetooth or wifi?&lt;/p&gt;&#xA;" OwnerUserId="954" LastEditorUserId="954" LastEditorDisplayName="" LastEditDate="2010-11-11T19:52:30.327" LastActivityDate="2010-11-12T11:49:49.437" Title="Computer to Arduino Interface Options" Tags="&lt;arduino&gt;&lt;usb&gt;&lt;serial&gt;&lt;spi&gt;&lt;interface&gt;" AnswerCount="5" CommentCount="5" />
  <row Id="6594" PostTypeId="1" AcceptedAnswerId="6595" CreationDate="2010-11-11T20:03:46.277" Score="2" ViewCount="99" Body="&lt;p&gt;I've got a Chinese pot datasheet, and the rotational torque is listed as &quot;20~200gf.cm&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.bourns.com/data/global/pdfs/PDB182-GTRB.pdf&quot; rel=&quot;nofollow&quot;&gt;This Bourns datasheet&lt;/a&gt; lists &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Rotational Torque ............. 10 to 150 gf-cm&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Why such a wide range?  Is this a tolerance issue, or is it something like the difference between slip and stick friction?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-11-12T00:46:10.543" Title="Meaning of potentiometer torque measurements" Tags="&lt;potentiometer&gt;" AnswerCount="2" />
  <row Id="6595" PostTypeId="2" ParentId="6594" CreationDate="2010-11-11T20:23:47.670" Score="6" ViewCount="" Body="&lt;p&gt;The tolerance stackup for the torque is probably quite large, including bearing friction (2+), wiper friction, and misalignment, all of which will drift and change with age, (cycle) life, and temperature.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-11T20:23:47.670" CommentCount="9" />
  <row Id="6596" PostTypeId="2" ParentId="6593" CreationDate="2010-11-11T20:38:41.473" Score="2" ViewCount="" Body="&lt;p&gt;The limiting factor is likely your computer's serial port, drivers and/or the Arduino library.  If I recall correctly, the AVR UART can go up to its clock rate divided by 8 or 16, and an FTDI chip can be at arbitrary baud rates equally high (3 Mbaud for this FT232RL on my desk).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most shields are going to communicate over the AVR UART, so if the Arduino library is limiting you then they won't help.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-11T20:38:41.473" />
  <row Id="6597" PostTypeId="2" ParentId="6593" CreationDate="2010-11-11T20:57:43.563" Score="1" ViewCount="" Body="&lt;p&gt;I do not know what shields are available, I am only a microcontroller guy in general.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As your baud rate goes higher a synchronous protocol makes a very large amount of sense. SPI is very simple and will allow baud rates in excess of 1Mbps very easily. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you just need to get to 300kBaud or even 1MBaud and are okay with UART the &lt;a href=&quot;http://www.ftdichip.com/Products/ICs.htm&quot; rel=&quot;nofollow&quot;&gt;FTDI chip line is the real deal&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the chips that can do this specifically is the &lt;a href=&quot;http://www.ftdichip.com/Products/ICs/FT2232H.htm&quot; rel=&quot;nofollow&quot;&gt;FT2232H&lt;/a&gt;. These do not support SPI, but can handle very fast UART. From their specs:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;RS232/RS422/RS485 UART Transfer Data&#xA;  Rate up to 12Mbaud. (RS232 Data Rate&#xA;  limited by external level shifter).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-11T21:48:06.140" LastActivityDate="2010-11-11T21:48:06.140" CommentCount="8" />
  <row Id="6598" PostTypeId="2" ParentId="6593" CreationDate="2010-11-11T22:43:26.807" Score="2" ViewCount="" Body="&lt;p&gt;How about only sending changed bytes each 20 ms? You'd need an additional 9 bits for addressing, but if you stuffed that bit in the empty bit in your 15-bit color data, you could do it with just one extra byte per LED. Depending on how fast your display is changing colors, that might work well. You could make a threshold, so if the color changes by less than X, you wait for the next round to send that data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or maybe try interlacing the data? Send even rows and odd rows in alternating sequence?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or use 4 Arduinos in parallel?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or control the LEDs through a shift register, and then send 15 bits to 15 Arduino pins via a parallel port (assuming you can find a PC with a parallel port)?&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-11T22:43:26.807" />
  <row Id="6599" PostTypeId="1" CreationDate="2010-11-11T23:41:18.353" Score="3" ViewCount="260" Body="&lt;p&gt;I am wanting to make a small handheld circuit that could flash anywhere between 4-6 leds in a programmed order. It has to be as small as possible and use very little energy. I am trying to make these cheap enough that I can make a lot. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking about using one of the AVR series mcu. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Size wise I was thinking of having it run on triple A'S.  I am open to suggestions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt; I am looking for DIP MCUs not smd.&lt;/p&gt;&#xA;" OwnerUserId="1687" LastEditorUserId="1687" LastEditorDisplayName="" LastEditDate="2010-11-12T00:03:35.243" LastActivityDate="2010-11-18T20:55:58.810" Title="What is the simplest way to make a small low power and low price circuit that flashes LED's." Tags="&lt;microcontroller&gt;&lt;avr&gt;&lt;electronics&gt;&lt;prototyping&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="6600" PostTypeId="2" ParentId="6599" CreationDate="2010-11-12T00:00:34.530" Score="3" ViewCount="" Body="&lt;p&gt;Depending on how programmable/complex your flashing is - you may be able to do it without software. In which case:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/5603/most-simple-stoplight-circuit&quot;&gt;Most Simple Stoplight circuit&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/3734/blink-an-led-with-just-a-capacitor&quot;&gt;Blink an LED with just a capacitor?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do need to use a microcontroller - with 6 I/O pins which is low power and small then I'd look at:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ti.com/ww/en/mcu/valueline/index.shtml?DCMP=Value_Line&amp;amp;HQS=Other+BA+430value-promo&quot; rel=&quot;nofollow&quot;&gt;MSP430 (Value Line)&lt;/a&gt;. Here's an app note on &lt;A href=&quot;http://focus.ti.com/lit/an/slaa398/slaa398.pdf&quot; rel=&quot;nofollow&quot;&gt;powering an MSP430 from a single cell (using a charge pump)&lt;/a&gt;. There's also now an &lt;a href=&quot;http://processors.wiki.ti.com/index.php/Msp430l092?DCMP=MSP430&amp;#153;16-BITULTRA-LOWPOW+Other&amp;amp;HQS=Other+OT+lowvoltagewiki&quot; rel=&quot;nofollow&quot;&gt;MSP430 which runs at 0.9V&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/products/AVR/default_picopower.asp&quot; rel=&quot;nofollow&quot;&gt;AVR PicoPower&lt;/a&gt; is also worth a look. Even the ATMega168/328 used in Arduino though can be put into quite low power modes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a couple of Arduino libs to do it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/narcoleptic/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/narcoleptic/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/playground/Code/Enerlib&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/Code/Enerlib&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-12T00:00:34.530" CommentCount="6" />
  <row Id="6601" PostTypeId="2" ParentId="6160" CreationDate="2010-11-12T00:15:33.363" Score="3" ViewCount="" Body="&lt;p&gt;It looks like the &lt;a href=&quot;http://ultimachine.com/ramps&quot; rel=&quot;nofollow&quot;&gt;Arduino Mega RepRap Pololu Carrier&lt;/a&gt;  (RAMPS) is compatible with the &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoEthernetShield&quot; rel=&quot;nofollow&quot;&gt;Arduino Ethernet shield&lt;/a&gt;. The RAMPS board doesn't seem to use mega pins 50, 51, 52 and 10, which is what the shield page says it uses. I've never actually tried this myself though. The Pololu drivers can do about 1A and up to 35V. &lt;/p&gt;&#xA;" OwnerUserId="1256" LastActivityDate="2010-11-12T00:15:33.363" CommentCount="1" />
  <row Id="6602" PostTypeId="2" ParentId="6599" CreationDate="2010-11-12T00:17:18.273" Score="1" ViewCount="" Body="&lt;p&gt;Have you looked at the &lt;a href=&quot;http://www.mouser.com/ProductDetail/Texas-Instruments/MSP430G2231IN14/?qs=sGAEpiMZZMvu0Nwh4cA1wRJeGVHRRTIMb5J5dZL4y5Q%3d&quot; rel=&quot;nofollow&quot;&gt;MSP430G2231&lt;/a&gt;?&#xA;It's really low power and is pretty cheap too. Plus it isn't a SMD MCU.&lt;/p&gt;&#xA;" OwnerUserId="1480" LastEditorUserId="1480" LastEditorDisplayName="" LastEditDate="2010-11-12T00:32:07.543" LastActivityDate="2010-11-12T00:32:07.543" CommentCount="1" />
  <row Id="6603" PostTypeId="2" ParentId="6599" CreationDate="2010-11-12T00:41:00.843" Score="1" ViewCount="" Body="&lt;p&gt;if you want cheap you dont even need a micro controller for simple on/off. Infact i would avoid them alltogether. a Simple sequence of leds that repeat you could use a simple 555 timer and a counter module, i cant think off which ones off the top of my head but there are lots of option and would take some time to plow through data sheets.&lt;/p&gt;&#xA;" OwnerUserId="1929" LastActivityDate="2010-11-12T00:41:00.843" CommentCount="1" />
  <row Id="6604" PostTypeId="2" ParentId="6594" CreationDate="2010-11-12T00:46:10.543" Score="0" ViewCount="" Body="&lt;p&gt;Nick has it pretty much dead on. Whenever modeling a Sensor, motor etc you will find that you end up with a very broad range that often makes it difficult to fine tune things. Adding to what Nick said there is also the difference between static and dynamic friction the means you will have different frictions and oppoing forces depending on how the arm i moving or if it is stopped. The best solution is to design it for the worst problem X 2 then your covered.&lt;/p&gt;&#xA;" OwnerUserId="1929" LastActivityDate="2010-11-12T00:46:10.543" />
  <row Id="6605" PostTypeId="2" ParentId="6593" CreationDate="2010-11-12T00:51:38.183" Score="0" ViewCount="" Body="&lt;p&gt;Arduinos are awesome, but they have their limitations. Unless you are programing In C and just making use of the arduino bootloader they will tend to run a lot slower. Im not a big guru on data rates etc but i would expect that at 50hz you would be hitting the wall for the arduinos capabilities. I would suggest looking at programing in C (hackaday.com has just done a great set of tutorials on this) or trying another microcontroller, my favorite for projects like this is the parallax propellor essentially 8 microcontrollers in one.&lt;/p&gt;&#xA;" OwnerUserId="1929" LastActivityDate="2010-11-12T00:51:38.183" />
  <row Id="6606" PostTypeId="2" ParentId="6584" CreationDate="2010-11-12T01:05:20.213" Score="5" ViewCount="" Body="&lt;p&gt;Use a pencil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the buttons are one of those silicone membranes with little black rubber disks on the back that are responsible for actually making the button-contact, the black rubber disks are just graphite-loaded rubber/silicone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Taking a (preferably soft-leaded) pencil and rubbing it on the contact surface of the disks to get a nice fresh coating of graphite will typically bring it back to life for a while.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, if you're after a longer-lived solution, a conductive-ink pen would probably also work nicely.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-11-12T01:05:20.213" />
  <row Id="6607" PostTypeId="1" AcceptedAnswerId="6619" CreationDate="2010-11-12T01:59:11.143" Score="1" ViewCount="601" Body="&lt;p&gt;A &lt;a href=&quot;http://forums.netduino.com/index.php?/topic/366-netduino-serial-port-code-review/&quot; rel=&quot;nofollow&quot;&gt;serial port demo&lt;/a&gt; shows how to use GPIOs to communicate through a second USB connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But as a Arduino developer I'm used to use the same USB for both programming and runtime communication.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I do the same with Netduino?&lt;/p&gt;&#xA;" OwnerUserId="1298" LastActivityDate="2010-11-12T10:20:43.993" Title="Can I use the Netduino USB as a serial port?" Tags="&lt;arduino&gt;&lt;netduino&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="6608" PostTypeId="2" ParentId="984" CreationDate="2010-11-12T02:05:39.823" Score="0" ViewCount="" Body="&lt;p&gt;I also found this excelent option: HTerm by Der-Hammer&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.der-hammer.info/terminal/&quot; rel=&quot;nofollow&quot;&gt;http://www.der-hammer.info/terminal/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1298" LastActivityDate="2010-11-12T02:05:39.823" />
  <row Id="6609" PostTypeId="1" CreationDate="2010-11-12T02:27:56.673" Score="0" ViewCount="173" Body="&lt;p&gt;Hello&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am thinking to use arduino to generate square wave of various duty cycle and frequency.&#xA;the square wave is going to be fed into transistor amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What options do I have for programmatically controlling the output of transistor?&lt;/p&gt;&#xA;" OwnerUserId="1930" LastActivityDate="2010-11-12T03:41:56.207" Title="Arduino limit PWM voltage" Tags="&lt;arduino&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="6610" PostTypeId="2" ParentId="6609" CreationDate="2010-11-12T03:20:29.423" Score="0" ViewCount="" Body="&lt;p&gt;If you use a low pass filter (Resistor to capacitor) you can filter the higher frequency PWM to be an average value of your PWM. So, if you are at 50% duty cycle and your voltage range is 0-5V you will get 2.5 V. This can be used to easily generate analog voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The analog voltage can then be used to control the mosfet.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-12T03:20:29.423" />
  <row Id="6611" PostTypeId="2" ParentId="6609" CreationDate="2010-11-12T03:41:56.207" Score="2" ViewCount="" Body="&lt;p&gt;The arduino has an analogWrite(pin, level) function that takes care of the details of the on-chip PWM hardware. Programmatically, you just give analogWrite the pin number you're writing to, and a value 0 to 255 to control the duty cycle. If the hardware is such that the transistor saturates at one logic level from the PWM pin, and cuts off at the other, it should deliver proper PWM controlled power to your load. Be aware that the RMS value of PWM goes by the square of the duty cycle; 70% on 30% off equates to half power.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-12T03:41:56.207" />
  <row Id="6612" PostTypeId="1" CreationDate="2010-11-12T04:42:34.230" Score="3" ViewCount="99" Body="&lt;p&gt;I have an odd sized PCB (about 0.8&quot; x 14&quot; x 5&quot; ) that needs to be housed in data centers (rack mount.)  It's a fairly expensive device so even though we won't have too many of them we're considering having a custom case designed, and style will matter. We're also therefore thinking aluminum or some other nice material. Further, the device has a PCIe finger. While we don't plan on using it in the near future, we'd eventually like to link up several to communicate with one another over a PCIe bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The optimal design would therefore have a case for the cards that left the fingers exposed, but could be mounted as is in a rack, or be placed in a very spacious computer (it's over-sized for PCIe), but also that in the future would allow us to insert the same card into a case with a PCIe bus (&lt;a href=&quot;http://www.magma.com/oemboard.asp&quot; rel=&quot;nofollow&quot;&gt;magma&lt;/a&gt; has a nice kit, but it seems expensive for what it is and it doesn't allow for too many slots.) That plus the low quantity and need for high quality, plus my general inexperience with enclosures has led me here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So where do I start? What design firms could pull this off? Could laser sintering give us the quality we want?&lt;/p&gt;&#xA;" OwnerUserId="1913" LastActivityDate="2010-11-12T05:03:10.010" Title="Custom Enclosure Design?" Tags="&lt;enclosure&gt;" AnswerCount="1" CommentCount="6" FavoriteCount="1" />
  <row Id="6613" PostTypeId="2" ParentId="6612" CreationDate="2010-11-12T05:03:10.010" Score="3" ViewCount="" Body="&lt;p&gt;A few similar questions with good answers:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/2145/plastic-enclosure-for-small-product&quot;&gt;Plastic enclosure for small product&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/2388/custom-enclosures&quot;&gt;Custom enclosures&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Regarding laser sintering, the answer is probably yes, but the price might be higher than you want. A good model maker can make stuff that looks indistinguishable from the final product, but for many k$.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-12T05:03:10.010" CommentCount="2" />
  <row Id="6614" PostTypeId="1" AcceptedAnswerId="6616" CreationDate="2010-11-12T05:11:37.330" Score="2" ViewCount="95" Body="&lt;p&gt;My idea is to implement &lt;code&gt;Automatic and Dynamic Traffic Control System&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to get the Vehicles density that were stopped along in all the roads in a particular junction. I want to get the binary information. &#xA;For ex:&#xA; If I get 1111s that means it has the highest traffic. &#xA; If I get 0001s that means it has very less traffic. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something like this. I am Ok if I get the information in any other format. I can redesign my implementation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Based on the information I will change the timings for each road to clear.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have implemented the logic using a simple flash software. But I need to implement this on board for the demo purpose. The sensor should cost low. Or any other circuit from which I can get information is also very helpful. &lt;/p&gt;&#xA;" OwnerUserId="1731" LastEditorUserId="1731" LastEditorDisplayName="" LastEditDate="2010-11-12T05:17:40.850" LastActivityDate="2010-11-12T07:06:39.823" Title="Is there any Low cost sensor or sensory circuit which can figure out the Traffic density in a Junction ?" Tags="&lt;electronics&gt;&lt;sensor&gt;&lt;circuit&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="6615" PostTypeId="1" AcceptedAnswerId="6729" CreationDate="2010-11-12T05:47:32.443" Score="7" ViewCount="652" Body="&lt;p&gt;I do have a physics degree and graduate school experience.  But without a BSEE or MSEE, is it fair to put &quot;Electronics Engineer&quot; as the headline on my resume?  I do have the knowledge, more or less, and have designed and worked on electronics projects, doing about as well as many BSEE holders.  I have not officially been employed with the job title &quot;Electronics Engineer&quot; though I would like that in the future.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not, what are good alternative titles to put on the resume, assuming it's written for electronics R&amp;amp;D work?   (I have other resumes for Digital Artist, Software Developer, etc.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, I am already employed otherwise now, not job hunting, but always keep at least one type of resume on hand for snagging interesting side work, involvement in startups, background for reporters (um yeah that happens a lot, right) or whatever other reasons come up. &lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-11-15T22:41:42.293" Title="Title my resume &quot;Electronics Engineer&quot; w/o an EE degree?" Tags="&lt;career&gt;" AnswerCount="5" CommentCount="4" FavoriteCount="2" />
  <row Id="6616" PostTypeId="2" ParentId="6614" CreationDate="2010-11-12T06:47:35.017" Score="4" ViewCount="" Body="&lt;p&gt;Existing systems use inductive proximity sensors buried in the road. Using this and integrating the output you could get overall traffic volume, but it would not give you instantaneous traffic density.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since it sounds like you're doing some sort of model, I think installing wires embedded in the road-surface isn't to viable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your best bet, I would think, since it seems you need something that does not take significant installation is a webcam and &lt;a href=&quot;http://opencv.willowgarage.com/wiki/&quot; rel=&quot;nofollow&quot;&gt;OpenCV&lt;/a&gt;. I bet you could put together a system that counts the approximate numbers of cars at an intersection using a computer-vision system without too much trouble.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-11-12T06:47:35.017" />
  <row Id="6617" PostTypeId="2" ParentId="6614" CreationDate="2010-11-12T07:06:39.823" Score="1" ViewCount="" Body="&lt;p&gt;One solution I see in use a lot is having rubber hoses stretched across the road surface. They are sealed at one end, and have a pressure sensor at the other end. By having one at the end of an intersection (counting the outflow) and having one as far back as plausible (counting the inflow) you can get a count of how many axles are waiting at that intersection. It could also be done with IR beams, similar to the entryway chimes at some stores.&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-11-12T07:06:39.823" CommentCount="2" />
  <row Id="6618" PostTypeId="2" ParentId="6615" CreationDate="2010-11-12T08:20:13.487" Score="13" ViewCount="" Body="&lt;p&gt;I suppose to some extent it depends upon the legal position in your particular jurisdiction.  In some parts of the world the title Engineer is legally protected and you must have certain qualifications/registration before you can use the title.  In other countries the use of the term is much looser and I would say that as long as you are working as an engineer then it would be perfectly acceptable to describe yourself as one. &lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-11-12T08:20:13.487" CommentCount="13" />
  <row Id="6619" PostTypeId="2" ParentId="6607" CreationDate="2010-11-12T10:20:43.993" Score="2" ViewCount="" Body="&lt;p&gt;The problem is that the Netduino uses the USB port for communicating the debugging information required so you can live debug through visual studio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is possible to switch the Netduino and use an FTDI serial cable to do the programming/debugging which will leave the USB port free for communications. There is a thread about this &lt;a href=&quot;http://forums.netduino.com/index.php?/topic/178-serial-communication-between-the-computer-and-the-netduino/&quot; rel=&quot;nofollow&quot;&gt;on the Netduino forums&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also discussions &lt;a href=&quot;http://forums.netduino.com/index.php?/topic/449-serial-comms-via-usb-in-the-cards/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://forums.netduino.com/index.php?/topic/481-serialread-via-usb-yu-know-like-on-the-good-ol-arduino/page__p__3549__hl__serial__fromsearch__1#entry3549&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; that confirm they are working on the problem.&lt;/p&gt;&#xA;" OwnerUserId="898" LastActivityDate="2010-11-12T10:20:43.993" />
  <row Id="6620" PostTypeId="2" ParentId="6593" CreationDate="2010-11-12T11:44:13.980" Score="1" ViewCount="" Body="&lt;p&gt;With proper hardware, Windows can handle serial communication up to 921600bps (115200 x2, x4, x8). There are PCI communication cards that support this baudrate, but more popular are USB&amp;lt;&gt;RS232 convertors. If I remember well, all FTDI based convertors can handle it. The bigger problem is AVR side, where you will not be able to do anything else while data is received. RX should be the only interrupt allowed on AVR side. You will also probably have to clock your AVR as high as you can (16 or 20MHz depending on the model, 14.746 Mhz if you want to have &lt;a href=&quot;http://www.wormfood.net/avrbaudcalc.php?postbitrate=921600&amp;amp;clock_speed_table=on&amp;amp;postclock=20&quot; rel=&quot;nofollow&quot;&gt;921600 exactly&lt;/a&gt;). Then you will send from PC the whole communication packet, AVR does the job after receiving it, and sends acknowledge byte that it is ready for next packet. When PC gets acknowledge then it can send another packet. And so on... Simple timers on PC side are (because of multitasking in windows) very bad at handling 10ms like resolution and they are not accurate at all (except multimedia timers when handled properly), so using simple acknowledge byte already described is a much better option.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastEditorUserId="1129" LastEditorDisplayName="" LastEditDate="2010-11-12T11:49:49.437" LastActivityDate="2010-11-12T11:49:49.437" />
  <row Id="6621" PostTypeId="1" AcceptedAnswerId="6628" CreationDate="2010-11-12T13:10:04.950" Score="4" ViewCount="194" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recently purchased piezoresistive &lt;a href=&quot;http://www.tekscan.com/flexible-force-sensors&quot; rel=&quot;nofollow&quot;&gt;Flexiforce pressure sensors&lt;/a&gt; but I´m having some problems connecting it to an A/D converter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On their website &lt;a href=&quot;http://www.tekscan.com/flexiforce-sample-circuit&quot; rel=&quot;nofollow&quot;&gt;they show an example of an excitation circuit&lt;/a&gt; but it is using negative voltage which is something I don´t have access to. I need to make a circuit that does pretty much the same thing but with only positive voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the circuit they recomend:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/KQH0O.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1637" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-12T14:53:42.973" LastActivityDate="2010-11-12T15:07:32.790" Title="Flexiforce pressure sensor with positive voltage" Tags="&lt;sensor&gt;&lt;adc&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="6622" PostTypeId="1" CreationDate="2010-11-12T13:14:40.500" Score="2" ViewCount="166" Body="&lt;p&gt;Time to trip of most of PTCs is about 0.1 seconds. In case of short between VCC and GND the current will be very high (maximum a power supply can provide) for at least 0.1s. Isn't it enough to burn out one of the components usually present in series with PTC: voltage regulators, power FETs, ferrite beads, etc?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To be specific: I have a device which is powered from USB bus via 500mA hold current PTC, 5V-&gt;3.3V LDO and ferrite bead. In case of short the current will be about 20-25A (this is what PC power supply can provide) for a period of 0.1s, afterwards a PTC of PC side or PTC on USB device will trip off power. Does LDO and ferrite bead survive 0.1 s of high current (and also does PC survive)?&lt;/p&gt;&#xA;" OwnerUserId="1932" LastActivityDate="2010-11-12T21:45:21.030" Title="Are PTC resettable fuses fast enough to protect from shorts?" Tags="&lt;protection&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="6623" PostTypeId="2" ParentId="6622" CreationDate="2010-11-12T13:21:38.713" Score="2" ViewCount="" Body="&lt;p&gt;I believe at 20-25A time for a PTC to trip is significantly less than 0.1s.  From what I recall, 0.1s is generally the time to trip at 7A or less.  In either case, voltage regulators usually have over current protection, and for the most part, a ferrite bead is just a wire.  You should be fine for the most part unless you have some real sensitive components.&lt;/p&gt;&#xA;" OwnerUserId="1819" LastActivityDate="2010-11-12T13:21:38.713" />
  <row Id="6624" PostTypeId="2" ParentId="6523" CreationDate="2010-11-12T13:38:32.793" Score="0" ViewCount="" Body="&lt;p&gt;Check out &quot;mbed.org&quot;. They provide an easily programmed controller (all tools are online) and they have in the past visted schools (UK) and run workshops getting kids to connect simple sensors etc. There are many robotics projects in their projects section and a very active forum.&lt;/p&gt;&#xA;" OwnerUserId="611" LastActivityDate="2010-11-12T13:38:32.793" CommunityOwnedDate="2010-11-12T13:38:32.793" />
  <row Id="6625" PostTypeId="1" AcceptedAnswerId="6626" CreationDate="2010-11-12T13:48:11.863" Score="4" ViewCount="149" Body="&lt;p&gt;I'm currently trying to lay out my first from scratch project on veroboard. While I get connecting things in series and parallel I'm trying to work out if a + shaped connection and a pair of + shapes would be equivalent. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/O3bfV.png&quot; alt=&quot;T shaped connections&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would they?&lt;/p&gt;&#xA;" OwnerUserId="1870" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-10T05:51:26.290" LastActivityDate="2011-02-10T05:51:26.290" Title="Layouts - would a joint at 1 point, or 2 be the same?" Tags="&lt;layout&gt;&lt;stripboard&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="6626" PostTypeId="2" ParentId="6625" CreationDate="2010-11-12T13:50:56.150" Score="8" ViewCount="" Body="&lt;p&gt;Yes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For simple circuits, so long as all the same electrical connections exist then the circuit is equivalent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Only for high speed or some analogue circuits do wire length and shape start to have effects)&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-12T13:50:56.150" CommentCount="4" />
  <row Id="6627" PostTypeId="2" ParentId="6615" CreationDate="2010-11-12T14:45:48.757" Score="9" ViewCount="" Body="&lt;h1&gt;NO!&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;&lt;br&gt;&#xA;&lt;strong&gt;Absolutely do not do it, you will be in several thousand dollars worth of legal trouble, have your name on a publicly available list of malpractice incidences, and it will be much harder for you to become an engineer in the future if you so desire.&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can say you're a Digital Artist and no one will be hurt if all you can do is MS Paint.  However, other careers are professional and require certification - Like doctors, airline pilots, and engineers.  People's lives are often at stake, and an entrance exam and/or degree requirement allows the public to place trust in your ability to do the job correctly and safely.  Take a look at Wikipedia's &lt;a href=&quot;http://en.wikipedia.org/wiki/Professional_Engineer&quot; rel=&quot;nofollow&quot;&gt;Professional Engineer&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/Fundamentals_of_Engineering_exam&quot; rel=&quot;nofollow&quot;&gt;Fundamentals of Engineering Exam&lt;/a&gt; pages for more general info.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically, your profile says that you live in New Mexico.  &lt;a href=&quot;http://www.sblpes.state.nm.us/complaint.html&quot; rel=&quot;nofollow&quot;&gt;Here's a link&lt;/a&gt; to a page of the 'New Mexico Board of Licensure for Professional Engineers &amp;amp; Professional Surveyors' which reads, in part, &quot;Persons that offer to practice engineering when they are not licensed commit a criminal offense.&quot;  Don't do it!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sblpes.state.nm.us/act.html&quot; rel=&quot;nofollow&quot;&gt;Elsewhere on that site&lt;/a&gt;, the requirements are given.  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;61-23-14.1. LICENSURE AS A&#xA;  PROFESSIONAL ENGINEER--&#xA;  REQUIREMENTS.--&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;A. Licensure as a professional&#xA;  engineer may be either through&#xA;  examination or through endorsement or&#xA;  comity. In either case, an applicant&#xA;  shall file the appropriate application&#xA;  in which it shall be demonstrated that&#xA;  the applicant:&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;(1) is of good moral character and&#xA;  reputation;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;(2) has five references, three of whom&#xA;  shall be licensees practicing in the&#xA;  branch of engineering for which the&#xA;  applicant is applying and who have&#xA;  personal knowledge of the applicant's&#xA;  engineering experience and reputation.&#xA;  The use of nonlicensed engineer&#xA;  references having personal knowledge&#xA;  of the applicant's engineering&#xA;  experience and reputation other than&#xA;  professional engineers may be accepted&#xA;  by the board provided a satisfactory&#xA;  written explanation is given; and the&#xA;  applicant meets one of the following&#xA;  requirements:&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;(a) is certified as an engineer intern&#xA;  and has at least four years of&#xA;  board-approved engineering experience&#xA;  after graduation from a board-&#xA;  approved engineering curriculum;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;(b) is certified as an engineer&#xA;  intern, and has, including the two&#xA;  years for engineer intern&#xA;  certification, at least six years of&#xA;  board-approved engineering experience&#xA;  after graduation from a&#xA;  board-approved, four-year engineering&#xA;  technology curriculum accredited by&#xA;  the technical accreditation commission&#xA;  of the accreditation board for&#xA;  engineering and technology;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;(c) has obtained a doctorate degree in&#xA;  an engineering discipline recognized&#xA;  by the board and has a minimum of four&#xA;  years of board-approved engineering&#xA;  experience subsequent to the awarding&#xA;  of the degree;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;(d) has obtained a master's degree in&#xA;  an engineering discipline recognized&#xA;  by the board from a board-approved&#xA;  program and has a minimum of six years&#xA;  of engineering experience subsequent&#xA;  to the awarding of the degree; or&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;(e) has graduated from a&#xA;  board-approved, four-year engineering&#xA;  curriculum and has a minimum of twelve&#xA;  years of engineering experience&#xA;  subsequent to the awarding of the&#xA;  degree .&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;B. An applicant shall be allowed to&#xA;  take the appropriate examination for&#xA;  licensure as a professional engineer&#xA;  as approved by the Board.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;C. Upon successfully completing the&#xA;  examination, required experience, and&#xA;  all the requirements as noted in this&#xA;  section, the applicant shall be&#xA;  eligible to be licensed as a&#xA;  professional engineer upon action of&#xA;  the board.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;You may be able to become certified as a technician with less schooling and examinations.  Some states and countries have fewer requirements (for example, in my state of Michigan, you only need a 4-year degree from an accredited university), so moving might help you.&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Don't do it.&lt;/h1&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-12T14:45:48.757" CommentCount="14" />
  <row Id="6628" PostTypeId="2" ParentId="6621" CreationDate="2010-11-12T14:59:22.287" Score="4" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Piezoresistive_effect&quot; rel=&quot;nofollow&quot;&gt;piezoresistive effect&lt;/a&gt; just means the resistance of the sensor changes with pressure.  With their circuit, the -5 V supply will be inverted and amplified with the gain varying with the sensor resistance.  The output voltage will vary from 0 to 5 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead of using a -5 V supply, you could just connect the bottom of the sensor to ground, and connect the positive input of the op-amp to a 2.5 V bias voltage.  Then the voltage at the output would vary from 2.5 to 5 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on what you're using it for, you could just &lt;a href=&quot;http://www.doctronics.co.uk/voltage.htm&quot; rel=&quot;nofollow&quot;&gt;connect it as a voltage divider&lt;/a&gt;, and then follow that by an inverting amplifier with an adjustable gain and DC bias so that you can get 0 to 5 V for whatever pressure range you want.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-12T15:07:32.790" LastActivityDate="2010-11-12T15:07:32.790" CommentCount="1" />
  <row Id="6629" PostTypeId="1" AcceptedAnswerId="6638" CreationDate="2010-11-12T15:07:32.197" Score="4" ViewCount="270" Body="&lt;p&gt;I'm thinking about making a simple LED flashlight.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After doing some research, I think I'm going to use some 5 mm 12 Cd white LEDs with 3.6 V drop which can pass 20 mA. I'm not yet sure how much LEDs I'd need, but for now, I'm thinking about 5 or 10.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For power supply, I was thinking about single 6LR61 battery or 4 serially connected LR6 batteries or maybe even two serially connected 6LR61 batteries (but I'd like to avoid that as 6LR61 are pretty expensive here).   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 6LR61 batteries popular here according to data sheet have capacity 550 mAh while LR6 have capacity of 2600 mAh.  Minimal voltage for 6LR61 is 4.8 V and 0.8 V for LR6. Since LR6 batteries have considerably higher capacity, I'm most likely going to use them, unless you provide a reason why to go with 9V battery. Also, if I serially connect batteries, would pack's capacity increase?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for circuit itself, I was thinking something like battery pack with a switch serially connected to it. I'd the use parallel connection to connect a number of branches consisting of a resistor and LED to the switch on one end and battery pack on the other end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/6MBVz.png&quot; alt=&quot;circuit sketch&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However I'm concerned about energy usage. I'll have lots of resistors and each one will consume some energy. If I go for 9 V option or even 18 V option, I'd reduce amount of energy wasted by resistors, since I could connect several LEDs serially with a single resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another point which bothers me is what type of resistors to choose. I'd like to use up as much of the batteries as possible and have device work as long as possible. I've been experimenting with results form &lt;a href=&quot;http://ledcalc.com/&quot; rel=&quot;nofollow&quot;&gt;http://ledcalc.com/&lt;/a&gt;, but I'm still not certain what to choose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT 1&lt;/strong&gt;&lt;br&gt;&#xA;Another idea: Would a 555 timer plus a transistor as a switch be a good choice for making device PWM controlled?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-03T08:35:47.707" LastActivityDate="2011-02-03T08:35:47.707" Title="Need comments and ideas for LED flashlight project." Tags="&lt;led&gt;&lt;power&gt;&lt;light&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="1" />
  <row Id="6630" PostTypeId="2" ParentId="6629" CreationDate="2010-11-12T15:35:13.040" Score="3" ViewCount="" Body="&lt;p&gt;One idea is use a microcontroler, so you can drive the leds via a PWM output. This way you can adjust the luminosity while increasing battery life.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-12T15:35:13.040" CommentCount="2" />
  <row Id="6631" PostTypeId="1" AcceptedAnswerId="6632" CreationDate="2010-11-12T15:37:23.833" Score="2" ViewCount="336" Body="&lt;p&gt;I am trying to design an analog direction driver circuit for an H-bridge configuration on a small DC motor. I have a pretty tight space constraint, and a simple requirement for my design, hence why I am trying to avoid microcontrollers. What I want to happen is for the motor to travel in one direction for 2.5 seconds, then to switch directions and travel for another 2.5 seconds. That's it for right now. In my design so far I have a 555 timer driving the timing side of things, and it is giving the desired output (HI for 2.5, OFF for 2.5 seconds). I also have the motor driver circuit built and functioning such that:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Input A = LO, Input B = HI - Output=Clockwise&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Input A = HI, Input B = LO - Output=Counter-Clockwise&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If In A = In B, Output = Stopped&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is: How can I use the output of the 555 timer to drive the inputs of the H-bridge in the manner mentioned above? I am missing the link between the two sides of the circuit, and was wondering what suggestions you might have.&lt;/p&gt;&#xA;" OwnerUserId="1935" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-10T05:49:06.040" LastActivityDate="2011-02-10T05:49:06.040" Title="555 timer as Dual Direction H-bridge driver" Tags="&lt;analog&gt;&lt;dc-motor&gt;&lt;555&gt;" AnswerCount="1" />
  <row Id="6632" PostTypeId="2" ParentId="6631" CreationDate="2010-11-12T15:47:22.027" Score="4" ViewCount="" Body="&lt;p&gt;You can use an inverter chip connected to your 555 timer output.  That way you will get two signals, your normal 555 timer output and an inverted version.  It sounds like you can use these two signals for your H-bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;555 timer output connected to H-bridge input A and inverter input,&#xA;inverter output connected to H-bridge input B.&lt;/p&gt;&#xA;" OwnerUserId="1819" LastActivityDate="2010-11-12T15:47:22.027" CommentCount="2" />
  <row Id="6633" PostTypeId="2" ParentId="6625" CreationDate="2010-11-12T15:48:36.627" Score="1" ViewCount="" Body="&lt;p&gt;For simple projects on Veroboard, they're exactly equivalent electrically.  However, there are other things you need to consider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I think that a better question is to ask whether they're equivalent to you.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's been some research (I can't remember where at the moment - Can anybody help?) that there's an inverse correlation between the number of wires coming from a single node and the readability of a schematic.  For some circuits it makes sense, but for others it makes more sense to treat one wire as a bus and have the others coming off of it at different points instead of one crowded location on the schematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On a more physical sense, consider the ease of reworking the above wires.  If you wanted to remove or replace a component, would it be easier to work on a joint which branches in three directions or just connects to a single wire?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They're electrically equivalent, but there are differences in their perceived meaning in a schematic and their physical construction.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-12T15:48:36.627" CommentCount="1" />
  <row Id="6634" PostTypeId="2" ParentId="6588" CreationDate="2010-11-12T16:22:05.650" Score="1" ViewCount="" Body="&lt;p&gt;Go to a vendor that might sell it, then check their cross reference.  For example for a National analog part I would go to TI, Linear and Analog Devices.  Also their FAE or the distributor's FAE.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-11-12T16:22:05.650" />
  <row Id="6635" PostTypeId="1" AcceptedAnswerId="6642" CreationDate="2010-11-12T16:32:41.640" Score="0" ViewCount="201" Body="&lt;p&gt;Hi, I have a readynas NV+ power supply which I recently bought, thinking it would be compatible with a normal PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I have discovered that the wiring is slightly different, namely pin 12 which should be -12V (ATX) is +12 (ReadyNas) and pin 18 which should be -5v (atx) is +12V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there some way that I can adjust the unit so that it will work as a normal atx unit?&lt;/p&gt;&#xA;" OwnerUserId="1937" LastActivityDate="2010-11-12T17:36:32.180" ClosedDate="2010-12-01T17:06:28.107" Title="Modify a Readynas NV+ to work as a normal atx power supply" Tags="&lt;power-supply&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="6636" PostTypeId="2" ParentId="6629" CreationDate="2010-11-12T16:35:11.193" Score="1" ViewCount="" Body="&lt;p&gt;You need a buck DC-DC converter for highest efficiency.  It has to be designed to produce the desired average current rather than a fixed average voltage.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ideal is to design the product to have zero resistors - then you know that the power wasted as heat in resistors is zero.   After that, efficiency is a matter of LED semiconductor physics - good luck with improving that!&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-11-12T16:35:11.193" CommentCount="1" />
  <row Id="6637" PostTypeId="1" CreationDate="2010-11-12T16:36:15.460" Score="1" ViewCount="288" Body="&lt;p&gt;I've been experimenting with oscillators, and am particularly fond of &lt;a href=&quot;http://www.discovercircuits.com/DJ-Circuits/astable.htm&quot; rel=&quot;nofollow&quot;&gt;a very low-current MOSFET design&lt;/a&gt; that uses ceramic capacitors and oscillates at about 1 to 10 Hz.  However, I am having trouble adjusting its frequency and duty cycle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistors involved are the largest I've got, so to slow it down a little I decided to use larger capacitors, like a 1μF electrolytic instead of 0.01μF ceramic.  Instead of slowing it down by a factor of 100, it just had some weird smoothing effect on the square wave, depending on which side was connected to the load.  In fact, 100μF and 1000μF had the same frequency, just more smoothing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I figured I just had the capacitor in backwards, and flipped it around, but this often made no difference, and it never made the frequency &quot;correct&quot;.  Also, even with 100μF on one side and 0.01μF on the other, the duty cycle was as close to 50% as I could measure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used a multi-meter to check which way the capacitor should really go, and was shocked to find it was always backwards.  Eventually I discovered that the voltage was swinging from -130mV to +130mV, and if the capacitors weren't balanced or the phase of the moon was wrong, it would sort of get stuck on one side, and the other capacitor would handle all the oscillating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Through many hours of simulating oscillators in spice and the falstad.com simulator, I have found that some of my oscillators maintain 0 to +V across the capacitors over the entire wave, but some configurations are more like -0.5V to 3V across the capacitors.  I have no idea what controls this.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;How does one design an astable multi-vibrator to have a specified voltage range across the capacitors? (Ideally, given a fixed frequency and duty cycle, and maintaining low current.)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If it matters, I substituted ON 2N7000's for the depletion mosfets, and this works with ceramic capacitors, just not polarized capacitors.&lt;/p&gt;&#xA;" OwnerUserId="1271" LastActivityDate="2010-11-12T17:35:35.873" Title="How to avoid ±voltage on capacitors in astable multivibrator" Tags="&lt;capacitor&gt;&lt;oscillator&gt;&lt;circuit-design&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="6638" PostTypeId="2" ParentId="6629" CreationDate="2010-11-12T16:46:25.557" Score="6" ViewCount="" Body="&lt;p&gt;Well, let's analyze the circuit. We know that the power required in a DC circuit is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P =  Vsrc * Iout&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We know that &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I = (Vout - Vled)/R&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and the power delivered to the LEDs is all that matters, so we want to maximize&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pr = (Vout - Vled) * I = (Vout - Vled)^2/R&lt;br&gt;&#xA;Pled = Vled * I = Vled * (Vout - Vled)/R &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Clearly, we want to minimize Pr and maximize Pled.  We can do this without decreasing the current by reducing R and making Vled close to Vsrc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is accomplished by putting the LEDs in series. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, your battery (isn't the 6LR61 a 9V battery?) will go from some nominal voltage (ex 9V) to a lower voltage - 9Vs are spec'd to be dead at 4.8V.  This means that a passive solution will go dim while there's still charge left in the battery.  For your original schematic, that might mean that you'd end up below the minimum current to turn the LED on, or for the series version, the voltage might go below the diode forward voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A simple way to extract more brightness with the same power is to pulse the LEDs - Human eyes percieve blinking light to be brighter than continuous light, even if the average power is the same.  A 555 timer or other oscillator/switch combination will be able to do this, no microcontroller required. Try playing with the duty cycle and frequency of your LEDs to see where it looks the brightest - You may be surprised!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, a switching power supply can increase the efficiency of your regulation circuit to 80, 90, or even 95%.  However, that will drive up the cost and complexity of the design, and may not be necessary.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-12T16:46:25.557" CommentCount="1" />
  <row Id="6639" PostTypeId="2" ParentId="6637" CreationDate="2010-11-12T16:50:21.797" Score="3" ViewCount="" Body="&lt;p&gt;Have you considered bipolar electrolytics? Normal electrolytics only have one plate doped (if that's the right word), so they can only withstand a unipolar signal (in reverse they act as a short, if I recall correctly, which is what causes them to bulge and eventually vent/explode.) Bipolar electrolytics usually internally have two capacitors connected in inverse series, or, in some cases, both plates equally doped. You can create the same effect in a pinch by wiring two electrolytics in inverse series, like this. &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  |  / +  + \  |&#xA;--| |--------| |--&#xA;  |  \      /  |&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You can also get axial ceramics in values up to around 1µF, and bigger in surface mount sizes (I use 22µF 6.3V 0805 capacitors.) For example here is a &lt;a href=&quot;http://uk.farnell.com/multicomp/mcmlr50v105kx7r/capacitor-ceramic-1uf-50v-x7r-radial/dp/1600878&quot; rel=&quot;nofollow&quot;&gt;1µF cap rated for 50V&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-12T17:33:16.770" LastActivityDate="2010-11-12T17:33:16.770" CommentCount="2" />
  <row Id="6640" PostTypeId="2" ParentId="6635" CreationDate="2010-11-12T16:58:35.660" Score="0" ViewCount="" Body="&lt;p&gt;From pictures I found online, that looks like a standard molex-type plug.  If it indeed is the same plug as an ATX supply, you can try snipping the wires to the two offending pins.  It is quite possible that your motherboard doesn't use the negative voltages for anything, except maybe  RS-232 ports.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-12T16:58:35.660" CommentCount="1" />
  <row Id="6641" PostTypeId="2" ParentId="6637" CreationDate="2010-11-12T17:35:35.873" Score="3" ViewCount="" Body="&lt;p&gt;That is a high-impedance circuit.  The capacitor is in series with a 22 megohm resistor.  Any capacitor leakage at all is going to cause problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Electrolytic caps are known for their high leakage.  They are not a good choice for this circuit.   You will be better off to use a series of flip flops (also knows as a divider) to get a lower frequency output from a higher frequency oscillator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a datasheet for a low-leakage electrolytic: &lt;a href=&quot;http://products.nichicon.co.jp/en/pdf/XJA043/e-kl.pdf&quot; rel=&quot;nofollow&quot;&gt;http://products.nichicon.co.jp/en/pdf/XJA043/e-kl.pdf&lt;/a&gt;  Notice it has a leakage spec of 0.2uA, and this is only after settling for a minute.  0.2uA through the 22 megohm resistor will drop 4.4 volts.  Since the circuit is only powered by 1.5V, the capacitor will simply not charge through 22 megohms.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-12T17:35:35.873" CommentCount="6" />
  <row Id="6642" PostTypeId="2" ParentId="6635" CreationDate="2010-11-12T17:36:32.180" Score="1" ViewCount="" Body="&lt;p&gt;You can ignore the -5V rail as it is a legacy rail and no new power supplies provide it. If I recall correctly, it is only required for ISA slots - remember those? Remember to disconnect it though just in case it is connected to something. The -12V rail is used for RS232 and PCI requires this, so if your ReadyNAS doesn't have this, you might be out of luck.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-12T17:36:32.180" CommentCount="3" />
  <row Id="6643" PostTypeId="2" ParentId="6629" CreationDate="2010-11-12T17:41:42.753" Score="1" ViewCount="" Body="&lt;p&gt;Series connected batteries add voltage but the capacity stays the same, more or less. Parallel connected batteries add capacity, if they are of the same voltage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could consider a boost circuit to suck the last joules out of your battery. Something like a MCP1640T would let you run the 3.6V LED's from a 1.5V battery. If you're clever and set the output voltage of the MCP1640T at the same voltage as the LED's you'll only need a small resistor, say around 1 to 10 ohms (to help with balancing the current between the LED's.) Unfortunately, the MCP1640T is a surface mount only part, which could pose problems for a one-time project.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-12T17:41:42.753" CommentCount="2" />
  <row Id="6644" PostTypeId="1" AcceptedAnswerId="6645" CreationDate="2010-11-12T17:59:36.880" Score="7" ViewCount="443" Body="&lt;p&gt;I'm looking for a good schematic capture checklist to use when reviewing schematics.  This is for the usual issues such as check that you don't have similar but different nets (e.g. GND and GROUND) that are separate and style/readability issues (e.g. no 4-way ties).  Either your list or a link to an external one would help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For what it's worth, I'm using DX Designer, so if you have specific checks you run, let me know about that too.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-12T23:47:33.187" LastActivityDate="2011-05-20T21:15:20.737" Title="Good schematic checklist" Tags="&lt;schematics&gt;&lt;checklist&gt;&lt;dxdesigner&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="5" />
  <row Id="6645" PostTypeId="2" ParentId="6644" CreationDate="2010-11-12T18:00:29.877" Score="8" ViewCount="" Body="&lt;p&gt;One I found online was from &lt;a href=&quot;http://www.avanthon.com/schematic_checklist.php&quot; rel=&quot;nofollow&quot;&gt;Avanthon Engineering, Inc&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-12T18:03:23.947" LastActivityDate="2010-11-12T18:03:23.947" CommentCount="1" />
  <row Id="6646" PostTypeId="2" ParentId="3382" CreationDate="2010-11-12T18:19:54.327" Score="2" ViewCount="" Body="&lt;p&gt;A logic analyzer if you or doing digital or certain microcontroller work.  Many more channels than a scope, better triggering, e.g. on patterns. But you still need the scope to check signal levels, signal integrity.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-11-12T18:19:54.327" CommunityOwnedDate="2010-11-12T18:19:54.327" CommentCount="1" />
  <row Id="6647" PostTypeId="1" AcceptedAnswerId="6650" CreationDate="2010-11-12T18:33:52.693" Score="5" ViewCount="341" Body="&lt;p&gt;I have a negative LDO (-5V from -5.5V to -10V) which requires a tantalum or aluminum capacitor. I'm wondering why it can't use a ceramic capacitor? Is there any specific reason for this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regulator is a TC59 (&lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/21438b.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Correction: the regulator I originally gave was stable with ceramics, this one is not.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-12T18:49:20.433" LastActivityDate="2010-11-13T21:27:21.233" Title="Tantalum capacitors vs. ceramic capacitors" Tags="&lt;capacitor&gt;&lt;ldo&gt;&lt;ceramic&gt;&lt;tantalum&gt;&lt;aluminum&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="6648" PostTypeId="2" ParentId="6644" CreationDate="2010-11-12T18:36:03.957" Score="5" ViewCount="" Body="&lt;p&gt;Functionality:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Check symbol pinouts, especially for new symbols and parts with multiple packages.&lt;/li&gt;&#xA;&lt;li&gt;Review vendors' latest data sheets and errata to see if anything has changed since you downloaded it.&lt;/li&gt;&#xA;&lt;li&gt;Have the vendor's FAE review the part of the schematic that uses their part(s)&lt;/li&gt;&#xA;&lt;li&gt;Label all power nets consistently.  Makes it easier to find them during the PCB design.&lt;/li&gt;&#xA;&lt;li&gt;Check for on- and off-page connections, using the tool's DRC.&lt;/li&gt;&#xA;&lt;li&gt;Check for same net on different pages without on/off page, using DRC.&lt;/li&gt;&#xA;&lt;li&gt;Avoid strange symbols (e.g. #) that other tools may not handle well.&lt;/li&gt;&#xA;&lt;li&gt;All upper case.&lt;/li&gt;&#xA;&lt;li&gt;Show revisions.  Show when drawn, whom by.&lt;/li&gt;&#xA;&lt;li&gt;Think about EMI/EMC/FCC/UL/CE, etc.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Ease of use:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;No 4-way ties.&lt;/li&gt;&#xA;&lt;li&gt;Label all important nets, e.g. clocks, power even if only going between 2 chips.  Makes checking if the clock's serial termination resistor is near the clock driver.  Also good for high-current signals that aren't the main power rails, e.g. around the FET or inductor in a DC/DC switcher.&lt;/li&gt;&#xA;&lt;li&gt;Table of contents on an early page; block diagram on an early page.&lt;/li&gt;&#xA;&lt;li&gt;Show power and ground on schematic symbols.&lt;/li&gt;&#xA;&lt;li&gt;Show unused gates/resistors from multi-gate/resistor packages.&lt;/li&gt;&#xA;&lt;li&gt;Show active low pins on symbol; show active low nets consistently.&lt;/li&gt;&#xA;&lt;li&gt;No extra connection dots where there isn't a connection.&lt;/li&gt;&#xA;&lt;li&gt;Not larger than B-sized (11x17) or metric equivalent.&lt;/li&gt;&#xA;&lt;li&gt;Bus common signals.&lt;/li&gt;&#xA;&lt;li&gt;Connect by name on-page if it makes it more readable.  Similarly don't wire power/ground all over the page, use multiple power/ground symbols.&lt;/li&gt;&#xA;&lt;li&gt;Inputs on the left, outputs on the right.&lt;/li&gt;&#xA;&lt;li&gt;Everything on a grid.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-30T18:15:40.733" LastActivityDate="2010-11-30T18:15:40.733" CommentCount="5" />
  <row Id="6649" PostTypeId="2" ParentId="6647" CreationDate="2010-11-12T18:59:27.580" Score="1" ViewCount="" Body="&lt;p&gt;Ceramic capacitors with those properties should be OK.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-12T18:59:27.580" CommentCount="6" />
  <row Id="6650" PostTypeId="2" ParentId="6647" CreationDate="2010-11-12T19:09:06.990" Score="9" ViewCount="" Body="&lt;p&gt;ceramic should work as long as you meet the requirements in the datasheet: 0.1ohm &amp;lt; esr &amp;lt; 5ohm and srf &gt; 1mhz.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its probably easier to find those properties in a tantalum cap, especially back in 2002 when that datasheet was released.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Some more info about LDO stability and why the ESR has to fall in a particular range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A generic LDO works by comparing the output voltage to an internal voltage reference with an error amplifier and driving a PNP transistor to correct for this error.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem comes in when you look at the phase shift and loop gain of this feedback path.  The error amplifier and the load being driven both contribute poles to the frequency response of the feedback loop.  These poles act as a low pass filter resulting in loop gain decreasing as frequency increases.  As we know a pole also introduces a negative phase shift.  If this phase shift is allowed to reach -180deg the feedback loop becomes unstable and the LDO will oscillate.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What this means is that every time the error amp tries to compensate for an error the result of its correction is 180deg out of phase, or inverted, consequently the error amp is basically thrown for a loop and begins making the opposite correction that it should be making, resulting in wild instability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To avoid this situation we need to prevent the phase shift in the feedback loop from ever getting to -180deg, actually we only need to keep it from reaching -180deg within the region that the LDO can generate gain &gt; 1 as the damped response of the system past this point will prevent oscillation.  This frequency is defined by the unity-gain point of PNP pass transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way we prevent this phase shift is by using a capacitor with a ESR in a certain region.  The capacitance will shift the pole created by the load but more importantly the ESR will contribute a higher frequency zero.  Basically you've added a high pass filter to the feedback loop.  The phase shift introduced by the ESR will work to counteract the phase shift introduced at lower frequencies by the poles from the error amp and the load.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason that the ESR has to be in a particular range is that if its too low, the zero contributed to the frequency response will be located very high in frequency, above the unity-gain point of the pass transistor.  As a result its not effective in making sure the phase shift of the feedback loop doesn't reach -180deg before the unity-gain frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the ESR is too high, the zero will be very low in frequency.  There is another pole in the frequency response created by the parasitics of the pass transistor, if the zero from the capacitor ESR is too low in frequency, this pole will be reached while we still have gain &gt; 1, this will cancel out the effect of the ESR zero and we will likely reach -180deg phase shift before we reach unity gain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All that said, these problems are indicative of older LDO designs.  Many/Most/All new designs include additional internal compensation in the feedback loop which uncouples LDO stability from the ESR specification of the output capacitors.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-13T21:27:21.233" LastActivityDate="2010-11-13T21:27:21.233" CommentCount="2" />
  <row Id="6651" PostTypeId="1" AcceptedAnswerId="6654" CreationDate="2010-11-12T19:29:26.830" Score="1" ViewCount="208" Body="&lt;p&gt;I have a MSOP10 package with an exposed pad. How do I solder this, if at all possible, with just my temperature controlled iron?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-12T21:43:01.533" Title="How to solder MSOP-EP package with just an iron?" Tags="&lt;soldering&gt;&lt;surface-mount&gt;&lt;surface-mount&gt;" AnswerCount="4" />
  <row Id="6652" PostTypeId="2" ParentId="6651" CreationDate="2010-11-12T19:48:43.343" Score="0" ViewCount="" Body="&lt;p&gt;Ideally you put a via in the center of the pad, so you can do it from the back.  If one isn't there and you can drill a hole, that may work as well, possibly using some wire to couple the heat to the pad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the pad has a plane (or very large trace) leading outside of the package, you may be able to get heat into the joint via that (possibly after scraping off solder resist).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a few parts to do like that, it may be worth it to do it on a hot plate.  Tin the part and pad (preferably use paste), then heat it up to 240-250°C for a brief time (non-contact IR thermometers are handy for this).&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-12T19:48:43.343" CommentCount="2" />
  <row Id="6653" PostTypeId="1" AcceptedAnswerId="6658" CreationDate="2010-11-12T19:48:50.703" Score="1" ViewCount="126" Body="&lt;p&gt;I am designing a SEPIC supply around an LT3757. The MOSFET will have ~6.5A pulses with a strange ramping pattern (see image), but the RMS current is only 3.38A and the average current is 2.60A. Assuming 50% over-rating, which rating should I be looking for in a suitable FET? Also, does this apply for resistors, inductors and capacitors, or are there other specifications to look out for?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/lX1wt.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-12T23:40:13.910" Title="Should I select components based on peak current, RMS current, or average current?" Tags="&lt;smps&gt;&lt;ratings&gt;&lt;component&gt;" AnswerCount="1" />
  <row Id="6654" PostTypeId="2" ParentId="6651" CreationDate="2010-11-12T19:51:57.333" Score="3" ViewCount="" Body="&lt;p&gt;Have not tried myself but here is video of soldering QFN (I believe exposed pad technique should be identical with MSOP):&#xA;&lt;a href=&quot;http://www.youtube.com/watch?v=d-f-SBC0GrU&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=d-f-SBC0GrU&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For general SMD soldering I found this helpful:&#xA;&lt;a href=&quot;http://www.youtube.com/watch?v=3NN7UGWYmBY&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=3NN7UGWYmBY&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW: Kudos for makers of this two videos.&lt;/p&gt;&#xA;" OwnerUserId="1471" LastActivityDate="2010-11-12T19:51:57.333" />
  <row Id="6655" PostTypeId="2" ParentId="6651" CreationDate="2010-11-12T19:57:10.863" Score="0" ViewCount="" Body="&lt;p&gt;An MSOP10 package doesn't have an exposed pad according to any datasheet I can find.  &lt;a href=&quot;http://www.fairchildsemi.com/dwg/MU/MUA10A.pdf&quot; rel=&quot;nofollow&quot;&gt;Here's a link&lt;/a&gt;[PDF] to Fairchild's description - It's just a smaller SOIC.  What are you working on?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, though, if you've got a package with an exposed pad, the general method for soldering pads underneath a package is one two large vias (large enough to push a soldering iron tip and solder through), which should allow you to heat up that ground pad and the solder will wick around to the whole thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may be able to expose some of the pad on the circuit board and heat that up (use a big chisel tip!).  However, be aware that this is difficult to do right sometimes. Especially if you can't see the wicking action, it's really hard to get the bottom of the package to heat up enough to get solder to pull up to it.  Often, all you get is a dome of solder on the pad and a cold joint at best to the underside of the chip.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-12T19:57:10.863" CommentCount="1" />
  <row Id="6656" PostTypeId="2" ParentId="6615" CreationDate="2010-11-12T20:29:09.453" Score="3" ViewCount="" Body="&lt;p&gt;This doesn't seem like the place to debate the legalities, jurisdictions and merits of professional licensing organizations, but I'd say you shouldn't do it regardless of the law. I assume you want your resume to stand out. Titling your resume like you're a cog to be fit into a machine doesn't seem like the best you can do.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-12T20:29:09.453" />
  <row Id="6657" PostTypeId="1" AcceptedAnswerId="6659" CreationDate="2010-11-12T20:55:26.203" Score="2" ViewCount="224" Body="&lt;p&gt;I have a SEPIC supply with coupled inductors. The inductors have phase dots. What do these &quot;phase dots&quot; mean? Is it important to have the phase dot in the same place?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-13T22:55:33.793" Title="What do phase dots on an inductor mean?" Tags="&lt;inductor&gt;&lt;sepic&gt;" AnswerCount="4" />
  <row Id="6658" PostTypeId="2" ParentId="6653" CreationDate="2010-11-12T21:10:49.040" Score="2" ViewCount="" Body="&lt;p&gt;In short you need to choose the part to survive the peak current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Longer Answer: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd work your way through the SEPIC topology's design calculations again, your current ripple is really high, the difference between average and peak current should be much smaller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet says that ΔIsw should be 20-40% of Isw(average max).  Or to use the datasheet's terminology χ should be between 0.2 and 0.4.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your case (estimating by looking at the simulation output graph):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Isw(average max) = ~2.75A&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ΔIsw = ~5.5A&lt;/p&gt;&#xA;&#xA;&lt;p&gt;χ = ~2.0&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try rerunning your simulation with larger L1/L2 inductors, this should reduce the ripple currents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: try a larger cap for C3 also (try 10uf or a second 4.7uf in parrellel), the ESR / ESL of this part is also critical, check what the values of these are for your simulation model. &lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-12T23:40:13.910" LastActivityDate="2010-11-12T23:40:13.910" CommentCount="8" />
  <row Id="6659" PostTypeId="2" ParentId="6657" CreationDate="2010-11-12T21:38:33.723" Score="3" ViewCount="" Body="&lt;p&gt;If we're thinking about same thing, then dots show relation between coils. &lt;a href=&quot;http://www.allaboutcircuits.com/vol_2/chpt_9/4.html&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;'s an article about that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I get the dot relation correctly (and I'm not sure that I do), if current is going into the dot on one side of the inductor and the other dot is on the same side of the inductor, that means that current is going into the dot on the other side too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How important it is to have dots in the same place is up to design of the circuit. In some cases it may not be relevant, but often it is important to take it into account.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-11-12T21:57:21.513" LastActivityDate="2010-11-12T21:57:21.513" CommentCount="2" />
  <row Id="6660" PostTypeId="2" ParentId="6651" CreationDate="2010-11-12T21:43:01.533" Score="0" ViewCount="" Body="&lt;p&gt;Put several small vias underneath ( better than fewer lare ones for themal conduction, leave a hole in the bottom solder resist, or scrape of resist. Apply some paste to the pad,place the part, and apply heat &amp;amp; a little solder for thermal contact to the underside and wait til the paste reflows. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-12T21:43:01.533" />
  <row Id="6661" PostTypeId="2" ParentId="6622" CreationDate="2010-11-12T21:45:21.030" Score="0" ViewCount="" Body="&lt;p&gt;USB ports should be protected, so 25A even for short periods is unlikely.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-12T21:45:21.030" />
  <row Id="6662" PostTypeId="2" ParentId="6644" CreationDate="2010-11-12T22:08:35.437" Score="4" ViewCount="" Body="&lt;p&gt;Here is another one from &lt;a href=&quot;http://www.aqdi.com/check.htm&quot; rel=&quot;nofollow&quot;&gt;Atlantic Quality Design&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Added 11/16/10: And one from &lt;a href=&quot;http://archive.chipcenter.com/eexpert/hwallace/hwallace001.html&quot; rel=&quot;nofollow&quot;&gt;chipcenter.com&lt;/a&gt; that was updated by &lt;a href=&quot;http://volersystems.com/v-2010-issue-1/pcb-layout-checklist&quot; rel=&quot;nofollow&quot;&gt;Voler Systems&lt;/a&gt;.&#xA;Both cover more than just schematics.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-05-20T21:15:20.737" LastActivityDate="2011-05-20T21:15:20.737" />
  <row Id="6663" PostTypeId="2" ParentId="6657" CreationDate="2010-11-12T23:11:46.480" Score="5" ViewCount="" Body="&lt;p&gt;The dots just indicate the polarity of the windings on the schematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currents entering on the dotted ends of the windings will produce magnetic flux in the same direction, whereas if you have current entering one dotted end, and leaving another dotted end, the currents will produce opposing flux.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're looking at something like a power supply schematic, the dots show you the ends of the coils that have the same phase angle.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-12T23:11:46.480" />
  <row Id="6664" PostTypeId="1" AcceptedAnswerId="6667" CreationDate="2010-11-12T23:19:18.847" Score="6" ViewCount="319" Body="&lt;p&gt;I'm looking at some capacitors, namely ceramic, 10µF 50V caps. &lt;a href=&quot;http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1000225&amp;amp;Ntk=gensearch_001&amp;amp;Ntt=10u+50V&amp;amp;Ntx=mode+matchallpartial&quot; rel=&quot;nofollow&quot;&gt;Here are the search results&lt;/a&gt; on Farnell UK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most are in big packages, 2220 or some form of stacked capacitor. But then there are the occasional X7R and X5R caps in 1206 and 1210 packages, like this one: &lt;a href=&quot;http://uk.farnell.com/murata/grm31cr61h106ka12l/capacitor-1206-10uf-50v/dp/1845762&quot; rel=&quot;nofollow&quot;&gt;GRM31CR61H106KA12L&lt;/a&gt;. It seems too good to be true, it's half the size of others and very low cost. It's not available yet, otherwise I would have bought some and tested them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any opinions? Has anyone tried these?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-24T20:35:38.483" LastActivityDate="2011-02-24T20:35:38.483" Title="Large-value ceramic caps  in small packages?" Tags="&lt;capacitor&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="6665" PostTypeId="2" ParentId="6664" CreationDate="2010-11-12T23:27:33.587" Score="1" ViewCount="" Body="&lt;p&gt;The part you listed is apparently X5R, not X7R, and yes, ceramic caps have become incredible in the last few years.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-12T23:27:33.587" CommentCount="1" />
  <row Id="6666" PostTypeId="2" ParentId="6664" CreationDate="2010-11-12T23:30:22.170" Score="0" ViewCount="" Body="&lt;p&gt;Look at them all its to do with the tolerances the cheap ones have a much higher tolerance than the more expensive ones. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-11-12T23:30:22.170" CommentCount="1" />
  <row Id="6667" PostTypeId="2" ParentId="6664" CreationDate="2010-11-13T00:32:32.613" Score="10" ViewCount="" Body="&lt;p&gt;It is very likely that the 1206 ceramic cap and the large stacked ceramic cap differ greatly in one very important characteristic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ESR&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The larger cap can probably handle much larger surge and RMS currents, and likely has significantly lower ESR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember, there is more to a cap than voltage and number of uF. If you're putting the cap in a big DC-DC that dumps 10A into the cap every switching cycle, and the 1206 cap has an ESR of .05 Ω, it'll get really hot and fail in a hurry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The big stacked ceramics are typically used in extreme-duty power supplies, where a tantalum or electrolytic cannot handle the conditions.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-11-13T10:31:01.910" LastActivityDate="2010-11-13T10:31:01.910" CommentCount="2" />
  <row Id="6668" PostTypeId="1" AcceptedAnswerId="6672" CreationDate="2010-11-13T00:54:53.197" Score="4" ViewCount="92" Body="&lt;p&gt;On page 7 of the &lt;a href=&quot;http://cds.linear.com/docs/Datasheet/3631fc.pdf&quot; rel=&quot;nofollow&quot;&gt;LTC3631 datasheet&lt;/a&gt;, the diagram shows a comparator with two noninverting inputs. What does such a comparator do?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-13T01:37:44.573" Title="Comparator with two noninverting inputs??" Tags="&lt;comparator&gt;" AnswerCount="1" />
  <row Id="6669" PostTypeId="1" AcceptedAnswerId="6677" CreationDate="2010-11-13T01:07:26.853" Score="3" ViewCount="88" Body="&lt;p&gt;I read the following in the datasheet of &lt;a href=&quot;http://www.hestore.hu/files/uln2803.pdf&quot; rel=&quot;nofollow&quot; title=&quot;ULN2803&quot;&gt;ULN2803&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Utmost care is necessary in the design&#xA;  of the output line, COMMON and GND&#xA;  line since IC may be destroyed due to&#xA;  short−circuit between outputs, &lt;strong&gt;air&#xA;  contamination fault&lt;/strong&gt;, or fault by&#xA;  improper grounding.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I understand what short-circuit is, but what does &quot;air contamination fault&quot; mean?&lt;/p&gt;&#xA;" OwnerUserId="1514" LastEditorUserId="1514" LastEditorDisplayName="" LastEditDate="2010-11-13T01:24:28.080" LastActivityDate="2010-11-13T08:39:47.730" Title="What is air contamination fault?" Tags="&lt;datasheet&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="6670" PostTypeId="1" CreationDate="2010-11-13T01:12:54.727" Score="1" ViewCount="154" Body="&lt;p&gt;Hey guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 500W inductive load question got me thinking.  Cars have large radiator fans that often draw more than 15A and are pretty inductive.  Do automotive relays have any sort of protection from inductive kick back?  Also, in a situation where a physical switch does the switching of power does the switch take the grunt of damaging kick back or does the damaging effect propagate to the source as well?  The physical act of breaking the circuit does generate a spark when a simple switch is used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&#xA;Andrey&lt;/p&gt;&#xA;" OwnerUserId="1819" LastActivityDate="2010-11-13T03:04:24.647" Title="Do automotive relays come with TVS diodes?" Tags="&lt;relay&gt;&lt;diode&gt;&lt;inductive&gt;&lt;fan&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="6671" PostTypeId="2" ParentId="6669" CreationDate="2010-11-13T01:20:32.907" Score="1" ViewCount="" Body="&lt;p&gt;Perhaps poorly translated from excessive humidity?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-13T01:20:32.907" CommentCount="2" />
  <row Id="6672" PostTypeId="2" ParentId="6668" CreationDate="2010-11-13T01:32:21.020" Score="6" ViewCount="" Body="&lt;p&gt;In this context, it means that the comparator can be triggered by comparison of the inverting input against both of the two non-inverting inputs. My impression (though I'm not 100% certain on this) is that the inverting input needs to exceed &lt;em&gt;both&lt;/em&gt; of the non-inverting inputs to switch the output. The input hooked to the soft-start pin is dominant at start up, but during normal operation, the 800 mV reference is dominant. This means that at start-up, the inductor current cycles more slowly than during normal operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the description from the datasheet of the what the comparator does during normal operation:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The inductor current &#xA;  increases until either the current exceeds the peak current &#xA;  comparator threshold or the voltage on the VFB pin &#xA;  exceeds 800mV, at which time the high side power switch &#xA;  is turned off, and the low side power switch (N-channel &#xA;  MOSFET) turns on. The inductor current ramps down until &#xA;  the reverse current comparator trips, signaling that the &#xA;  current is close to zero. If the voltage on the VFB pin is &#xA;  still less than the 800mV reference, the high side power &#xA;  switch is turned on again and another cycle commences.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-11-13T01:37:44.573" LastActivityDate="2010-11-13T01:37:44.573" />
  <row Id="6673" PostTypeId="2" ParentId="6670" CreationDate="2010-11-13T02:23:37.063" Score="1" ViewCount="" Body="&lt;p&gt;No.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I checked google images for &quot;Automotive Relay&quot; and found picture of what is inside. There is no diode there.  The reason can be that everything made for auto is massively produced, designed for low cost. It evolved over multiple generations into perfectly cheap,  reliable and very low part count things.&lt;/p&gt;&#xA;" OwnerUserId="924" LastEditorUserId="924" LastEditorDisplayName="" LastEditDate="2010-11-13T03:04:24.647" LastActivityDate="2010-11-13T03:04:24.647" CommentCount="1" />
  <row Id="6674" PostTypeId="1" AcceptedAnswerId="6675" CreationDate="2010-11-13T03:18:41.080" Score="2" ViewCount="482" Body="&lt;p&gt;Will the 3rd edition be published ?&lt;/p&gt;&#xA;" OwnerUserId="924" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-02-09T23:56:47.130" LastActivityDate="2011-02-09T23:56:47.130" Title="When will the 3rd edition of &quot;Art of Electronics&quot; by Horowitz and Hill finally be published?" Tags="&lt;books&gt;" AnswerCount="1" />
  <row Id="6675" PostTypeId="2" ParentId="6674" CreationDate="2010-11-13T03:24:57.047" Score="8" ViewCount="" Body="&lt;p&gt;Next year is my guess. Win Hill has said that the problem with finalising the book is the pace of change in electronics, it's something of a moving target.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-13T03:24:57.047" CommentCount="1" />
  <row Id="6676" PostTypeId="1" AcceptedAnswerId="6755" CreationDate="2010-11-13T06:23:02.763" Score="3" ViewCount="479" Body="&lt;p&gt;I want to drive lots of LEDs in a spinning persistence-of-vision (POV) device.&#xA;I need one output pin per LED, because matrix techniques don't work right in spinning POV devices.&#xA;A serial-input, parallel-output (SIPO) chip is the best way to independently control lots of output pins using only a few pins on my microcontroller, right?&#xA;Which SIPO chip should I choose?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;74HC4094 used in &lt;a href=&quot;http://reprap.org/wiki/Doboz&quot; rel=&quot;nofollow&quot;&gt;Doboz&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;74HC595 used in &lt;a href=&quot;http://code.google.com/p/bicycleledpov/&quot; rel=&quot;nofollow&quot;&gt;bicycleledpov&lt;/a&gt; aka &lt;a href=&quot;http://electronics.stackexchange.com/search?q=spokepov&quot;&gt;spokepov&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;TPIC6595 used in ... (a POV device I can't find the link to right now)&lt;/li&gt;&#xA;&lt;li&gt;... or perhaps something I'm overlooking?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Does one SIPO chip clearly have more capabilities or easier to use than another, or are they all more-or-less equivalent functionality?&#xA;They all can be connected in the &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus#Daisy_chain_SPI_configuration&quot; rel=&quot;nofollow&quot;&gt;daisy-chain SPI&lt;/a&gt;&quot; configuration, right?&#xA;If I only have room for one kind of SIPO chip in my box of&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/966/which-electronics-components-should-i-always-have-on-hand&quot;&gt;&quot;electronics components I always have on hand&quot;&lt;/a&gt;,&#xA;which one should it be?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-05T02:34:12.750" Title="Which SIPO chip is better, 74HC4094 or 74HC595 or something else?" Tags="&lt;led&gt;&lt;components&gt;&lt;spi&gt;&lt;74hc595&gt;&lt;pov&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="6677" PostTypeId="2" ParentId="6669" CreationDate="2010-11-13T06:46:45.510" Score="3" ViewCount="" Body="&lt;p&gt;I'm fairly certain it means crap from the air being deposited on the board and/or chip. Think dust/little metal fibers/similar things. They're often a problem in places where you need to drive big magnetics or coils, which this driver could be used for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think factory equipment, etc...&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-11-13T06:46:45.510" />
  <row Id="6678" PostTypeId="2" ParentId="6669" CreationDate="2010-11-13T08:39:47.730" Score="2" ViewCount="" Body="&lt;p&gt;Dust or other crud accumulating on the device, acting as insulation keeping it from cooling off as well as it needs to.  &lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2010-11-13T08:39:47.730" />
  <row Id="6679" PostTypeId="2" ParentId="6676" CreationDate="2010-11-13T10:03:14.660" Score="1" ViewCount="" Body="&lt;p&gt;Read the datasheets.  TPIC6595 is for when you need more output current. HC595 is very cheap &amp;amp; widely available, and would be the 'default' choice - I think the HC4094 similar but may be some small differences - I've only used the old CMOS 4094 ages ago.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-13T10:03:14.660" CommentCount="1" />
  <row Id="6680" PostTypeId="2" ParentId="6664" CreationDate="2010-11-13T10:07:59.960" Score="3" ViewCount="" Body="&lt;p&gt;Unfortunately there are  some major leadtime issues on the denser ceramics at the moment, so the latest dielectrics seem to include some unobtanium.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-13T10:07:59.960" />
  <row Id="6681" PostTypeId="1" AcceptedAnswerId="6754" CreationDate="2010-11-13T11:22:20.080" Score="2" ViewCount="180" Body="&lt;p&gt;I've been looking for a 3.3V compatible shift register (SIPO) with latched open-drain outputs. I've settled on a 74xx596 (not a '595!), but of all the 74xx CMOS series I've been looking at omit this one. Any idea on why? and if it's possible to get CMOS variants of these, because of the open-drain outputs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Correction: I was getting confused between 595 and 596. 595 has tri-state outputs, 596 has open collector outputs.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-13T12:32:45.483" LastActivityDate="2010-11-15T06:44:50.463" Title="CMOS (or CMOS compatible) shift register with latched open-drain outputs" Tags="&lt;logic&gt;&lt;cmos&gt;&lt;74xx&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="6682" PostTypeId="2" ParentId="6681" CreationDate="2010-11-13T12:01:44.723" Score="0" ViewCount="" Body="&lt;p&gt;595 does not have OD outputs - 74HC595 is very common. Ti do a high-power open-drain one &lt;a href=&quot;http://focus.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=tpic6595&amp;amp;fileType=pdf&amp;amp;track=no&quot; rel=&quot;nofollow&quot;&gt;TPIC6595&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-13T12:01:44.723" CommentCount="1" />
  <row Id="6684" PostTypeId="1" AcceptedAnswerId="6685" CreationDate="2010-11-13T12:24:48.733" Score="1" ViewCount="197" Body="&lt;p&gt;What should be DC resistance of the external WiFi antenna?  (when measured between center and shield of the SMA connector).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In case of:&lt;br&gt;&#xA;a) DIY &quot;pringles&quot; antenna&lt;br&gt;&#xA;b) Consumer grade antenna, connected to external USB WiFi adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe there should be no difference between a) and b). Right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thx.&lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="1471" LastEditorDisplayName="" LastEditDate="2010-11-13T12:30:28.573" LastActivityDate="2011-01-04T03:57:06.027" Title="What is DC resistance of the WiFi antenna?" Tags="&lt;antenna&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="6685" PostTypeId="2" ParentId="6684" CreationDate="2010-11-13T12:29:20.760" Score="5" ViewCount="" Body="&lt;p&gt;Do you mean the resistance across the coaxial connector, from the center pin to the ground?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the type of antenna, it should either be infinite (Most antennas, including pringles cantenna, which uses a simple 1/4 wave antenna), or a dead short (Some odd types, like a folded dipole).&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-11-13T12:41:09.277" LastActivityDate="2010-11-13T12:41:09.277" CommentCount="2" />
  <row Id="6686" PostTypeId="1" CreationDate="2010-11-13T12:44:17.700" Score="15" ViewCount="300" Body="&lt;p&gt;I would like to have a list on things a parent could build with his or her child? The things should be considered 'cool', fun and not be too advanced (the child should be able to help out and be able to understand what we are doing). A child would be anything from a 3-4 year old kid up to (say) 12. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know there are tons of science kits (and lego kits such as lego mindstorms and lego technic) out there so please try to avoid mentioning them. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example: &#xA;One can build a laser from an old DVD burner [insert guide here].&lt;/p&gt;&#xA;" OwnerUserId="1942" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-09T08:18:39.660" LastActivityDate="2011-02-09T08:18:39.660" CommunityOwnedDate="2011-02-09T13:31:09.723" Title="What 'cool' things can you build as a parent and child activity?" Tags="&lt;kit&gt;" AnswerCount="6" CommentCount="2" FavoriteCount="7" />
  <row Id="6687" PostTypeId="1" AcceptedAnswerId="6690" CreationDate="2010-11-13T13:24:52.507" Score="0" ViewCount="146" Body="&lt;p&gt;I am looking to upgrade my iron for SMT components and recon it's probably worth skipping the middle ground and getting myself a Metcal (as almost everyone I have asked has mentioned that they are close to as good as they get).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was looking on Farnell and &lt;a href=&quot;http://uk.farnell.com/oki-metcal/mfr-1110/soldering-station-cartridge-style/dp/1629771&quot; rel=&quot;nofollow&quot;&gt;found one&lt;/a&gt; at a reasonable price but it seems it has no temperature control. Is this something I need or would this iron still be an excellent investment?&lt;/p&gt;&#xA;" OwnerUserId="1333" LastActivityDate="2010-11-13T17:02:07.837" Title="Metcal but no temperature control?" Tags="&lt;soldering&gt;&lt;soldering&gt;&lt;buying&gt;" AnswerCount="3" />
  <row Id="6688" PostTypeId="2" ParentId="6687" CreationDate="2010-11-13T14:11:45.493" Score="0" ViewCount="" Body="&lt;p&gt;You don't need it, as Metcal has enough power and responsiveness to dump  the right amount of power into the joint without overshooting. The primary reason for needing temp control on conventional irons is to overcome the thermal resitance between the heater and the tip surface.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-13T14:11:45.493" CommentCount="6" />
  <row Id="6689" PostTypeId="2" ParentId="6686" CreationDate="2010-11-13T15:14:42.143" Score="4" ViewCount="" Body="&lt;p&gt;Well one thing I remember now which I did with my father when I was maybe 10 or so was to make a miniature airplane (he teaches aerodynamic constructions at local university, so we didn't have to do a lot of research). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We made body of the plane out of a fountain pen, main surface of monoplane out of folded lightweight cardboard, hobby motor to drive the propeller and cardboard to make the tail. We got wheels form toy cars and used small paper clips as axles. Propeller was made out of a piece of 0.5 mm aluminium sheet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then we connected it to a base of a vise via rotating joint and a lever. A counterweight was attached at the other side so that the plane side of the lever was just a little bit heavier than the weight side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We run a cable form the base of the vise to the plane and connected it on the other side with a potentiometer, analogue voltmeter, amperemeter and a wall wart.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yeah, I know it isn't very electronics related, but it did show relation between current and voltage. It was also very visible that changing voltage could make plane start moving on the table and that changing it even more could make it lift off and control its altitude.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the time I thought it was pretty cool.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of the other things I did was to make electromagnets form pieces of iron and thin cables. They were very simple and not very cool to me at the time, but they could lift small nails and similar objects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two things that are simple and could be cool are &lt;a href=&quot;http://www.instructables.com/id/LED-Throwies/&quot; rel=&quot;nofollow&quot;&gt;LED Throwies&lt;/a&gt; and &lt;a href=&quot;http://www.instructables.com/id/LED-Floaties-That-float-away/&quot; rel=&quot;nofollow&quot;&gt;LED Floaties&lt;/a&gt;. There are also &lt;a href=&quot;http://www.evilmadscientist.com/article.php/nightlight&quot; rel=&quot;nofollow&quot;&gt;improved LED Throwies&lt;/a&gt; which only work in dark, so they save battery energy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't think of anything else interesting at the moment.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-11-13T17:06:41.183" LastActivityDate="2010-11-13T17:06:41.183" CommunityOwnedDate="2011-02-09T13:31:09.723" />
  <row Id="6690" PostTypeId="2" ParentId="6687" CreationDate="2010-11-13T15:49:44.573" Score="3" ViewCount="" Body="&lt;p&gt;The temperature control is in the tip cartridge.  This is one of the biggest advantages of a system like this, you never need to calibrate it.  If the temp is &quot;off&quot; you throw out the tip cartridge and get a new one.  The temperature regulation is also extremely good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy tips for different temperatures, for the MX-500 (What i use) there are 4 different temperature control ranges.  For the part you linked there are 3 temp ranges:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;F = FR4 / Fiber Glass for most standard applications. Two other series also available, just replace F with either T or C. T = Temperature Sensitive, C = Ceramic&quot;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you order tips use F/T/C in the tip part number to get the correct temp range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know about the tips for the part you listed but the MX-500 tips the 4 temperature grades are 575F,675F,775F,905F.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Judging by the name of the temperature grades for the iron you linked either the 575 or 675 is the one thats not available.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-13T16:10:14.783" LastActivityDate="2010-11-13T16:10:14.783" />
  <row Id="6691" PostTypeId="2" ParentId="6687" CreationDate="2010-11-13T17:02:07.837" Score="1" ViewCount="" Body="&lt;p&gt;You might be better off buying a second-hand STSS power unit (they often come up on Ebay) with the later MX-500 handpiece and cartridges. That's what I did. It works out a lot cheaper and you get a better system.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-13T17:02:07.837" CommentCount="1" />
  <row Id="6692" PostTypeId="2" ParentId="6686" CreationDate="2010-11-13T17:06:07.397" Score="4" ViewCount="" Body="&lt;p&gt;A crystal set radio would be a good start. My father bought me the bits for one when I was 12, and I progressed from there.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-13T17:06:07.397" CommunityOwnedDate="2011-02-09T13:31:09.723" CommentCount="4" />
  <row Id="6693" PostTypeId="2" ParentId="6686" CreationDate="2010-11-13T17:21:56.213" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.snapcircuits.net/&quot; rel=&quot;nofollow&quot;&gt;Snap Circuits&lt;/a&gt; is great for that, or 7+ years with minimal supervision.  It's like breadboarding, but easier.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-11-13T17:21:56.213" CommunityOwnedDate="2011-02-09T13:31:09.723" CommentCount="1" />
  <row Id="6694" PostTypeId="2" ParentId="3644" CreationDate="2010-11-13T17:25:41.467" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.snapcircuits.net/&quot; rel=&quot;nofollow&quot;&gt;Snap Circuits&lt;/a&gt; has some nice ones for kids.  Very easy to build is the reason I recommend them to people with kids.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-11-13T17:25:41.467" CommunityOwnedDate="2010-11-13T17:25:41.467" />
  <row Id="6695" PostTypeId="2" ParentId="6657" CreationDate="2010-11-13T17:27:28.813" Score="0" ViewCount="" Body="&lt;p&gt;In short and oversimplifying:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The dots indicate which winding terminals have the same phases of induced AC voltages. That assumes you're driving one winding and others are not loaded.&lt;/p&gt;&#xA;" OwnerUserId="1880" LastActivityDate="2010-11-13T17:27:28.813" />
  <row Id="6696" PostTypeId="2" ParentId="3644" CreationDate="2010-11-13T18:51:46.953" Score="3" ViewCount="" Body="&lt;p&gt;TV-B-Gone is cool: &lt;a href=&quot;http://www.ladyada.net/make/tvbgone/&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/make/tvbgone/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It turns of all TVs. That is all.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-13T18:51:46.953" CommunityOwnedDate="2010-11-13T18:51:46.953" />
  <row Id="6697" PostTypeId="2" ParentId="3644" CreationDate="2010-11-13T19:39:41.860" Score="0" ViewCount="" Body="&lt;p&gt;RadioShack has an &lt;a href=&quot;http://www.radioshack.com/product/index.jsp?productId=3814337&quot; rel=&quot;nofollow&quot;&gt;Electronics Learning Lab&lt;/a&gt; for $70 which is pretty decent for learning both analog and digital electronics.  I'm an EE and have one because it is handy for prototyping circuits.  Fairly high quality.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as actual kits go, SparkFun has some, including a &lt;a href=&quot;http://www.sparkfun.com/commerce/product_info.php?products_id=9484&quot; rel=&quot;nofollow&quot;&gt;digital oscilloscope kit&lt;/a&gt; for $60.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-11-13T19:39:41.860" CommunityOwnedDate="2010-11-13T19:39:41.860" />
  <row Id="6698" PostTypeId="1" AcceptedAnswerId="6725" CreationDate="2010-11-13T19:54:43.967" Score="5" ViewCount="613" Body="&lt;p&gt;How do I tell which wire is which if I have a copper wire, red and green coded wire? Is the unshielded copper wire ground?&lt;/p&gt;&#xA;" OwnerUserId="1944" LastActivityDate="2010-11-14T06:00:42.247" Title="Headphone wire color coding" Tags="&lt;wire&gt;&lt;code&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="6699" PostTypeId="2" ParentId="6698" CreationDate="2010-11-13T20:08:50.880" Score="3" ViewCount="" Body="&lt;p&gt;It's probably the case, check resistances between the wires with a DVM to make sure. Listening to the noise made will tell you which is connected to right or left.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-13T20:08:50.880" />
  <row Id="6700" PostTypeId="2" ParentId="5951" CreationDate="2010-11-13T20:16:30.300" Score="4" ViewCount="" Body="&lt;p&gt;Quick answer: If you already know which PCB fab will make your boards, use their &quot;preferred minimum hole size&quot; for your vias.&#xA;This should be posted in the capabilities section of their web site.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't already know which PCB fab will make your board, 0.020 inch (0.5 mm) vias are pretty conservative -- a few years ago I found lots of PCB fab houses can handle 0.020 inch (0.5 mm) vias -- it was greater than or equal to their &quot;preferred minimum hole size&quot;.&#xA;I'm sure the &quot;preferred minimum hole size&quot; has dropped even smaller since then.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Long answer:&#xA;In principle, you can specify vias of any size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In practice, there is a balance between:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;If you make the vias too big, they require lots of space on your PCB (on every layer), making it more difficult to route and perhaps requiring a bigger, more expensive PCB.&lt;/li&gt;&#xA;&lt;li&gt;If you make the vias a little too small (less than the &quot;preferred minimum hole size&quot; of a particular manufacturer), then that particular manufacturer will claim it requires a &quot;special process&quot; which adds expense.&lt;/li&gt;&#xA;&lt;li&gt;If you make the vias much too small (less than the &quot;absolute minimum hole size&quot; of a particular manufacturer), then that manufacturer can't make it at all, and you'll be forced to find a different (probably more expensive) manufacturer or redesign the board.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The &quot;metal barrel&quot; of a via is practically free if you have any plated through holes. The PCB fab throws the PCB in the through-hole-plating bath until an appropriate thickness of metal grows in every hole.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I generally pick a via size that I know is greater than or equal to the &quot;preferred minimum hole size&quot; capability at many different PCB fab houses, so I'm not locked into a single manufacturer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alas, the &quot;capabilities&quot; page of some PCB fab houses is sometimes hard to find.&#xA;Please help me find the &quot;capabilities&quot; page of fab houses and post the URL of that capabilities page to the wiki at&#xA;&lt;a href=&quot;http://opencircuits.com/PCB_Manufacturers&quot; rel=&quot;nofollow&quot;&gt;http://opencircuits.com/PCB_Manufacturers&lt;/a&gt;&#xA;... which also briefly summarizes the &quot;preferred minimum hole size&quot; and &quot;absolute minimum hole size&quot; and a few other capabilities of each manufacturer.&#xA;(A few of them have a limited number of &quot;standard drill sizes&quot; listed, which may be what you are looking for).&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-11-13T20:16:30.300" />
  <row Id="6701" PostTypeId="2" ParentId="6686" CreationDate="2010-11-13T20:27:09.460" Score="1" ViewCount="" Body="&lt;p&gt;You could make some &lt;a href=&quot;http://www.evilmadscientist.com/article.php/bristlebot&quot; rel=&quot;nofollow&quot;&gt;Bristle Bots&lt;/a&gt; or &lt;a href=&quot;http://www.smfr.org/robots/&quot; rel=&quot;nofollow&quot;&gt;Solar Bots&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="103" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-11-14T17:26:19.640" LastActivityDate="2010-11-14T17:26:19.640" CommunityOwnedDate="2011-02-09T13:31:09.723" />
  <row Id="6702" PostTypeId="1" CreationDate="2010-11-13T20:33:52.590" Score="5" ViewCount="106" Body="&lt;p&gt;Say I have a large soft surface such as a jacket and I want to register it getting hit by a paintball from a paintball gun, how would I do that? What type of sensors could I use?&lt;/p&gt;&#xA;" LastActivityDate="2010-11-16T10:09:49.830" Title="How to repond to a kinetic impact electronically" Tags="&lt;accelerometer&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="6703" PostTypeId="2" ParentId="6702" CreationDate="2010-11-13T21:42:52.577" Score="2" ViewCount="" Body="&lt;p&gt;a &lt;a href=&quot;http://en.wikipedia.org/wiki/Piezoelectric_sensor&quot; rel=&quot;nofollow&quot;&gt;piezoelectric sensor&lt;/a&gt; will create an electrical signal when hit. They are used in many different types of devices and would most certainly register a paintable hitting a jacket.&lt;/p&gt;&#xA;" OwnerUserId="81" LastActivityDate="2010-11-13T21:42:52.577" CommentCount="1" />
  <row Id="6704" PostTypeId="2" ParentId="6702" CreationDate="2010-11-13T21:46:54.377" Score="2" ViewCount="" Body="&lt;p&gt;Not going to be easy, i don't think an accelerometer is going to cut it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the easiest answer would be to modify the jacket (or make an under shirt) which is pressure sensitive.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could do this by using 2 layers of conductive fabric and a sparse semi insulator in between and carefully sewing it all together.  Setup a circuit to measure the resistance between the 2 conductive fabric layers and when something compresses them (such as a paintball) the resistance should drop. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, if a paintball is really your use case, you could use a microcontroller with a little microphone somewhere on the jacket and process the audio looking for the sound of the impact.  More math work, less sewing.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-13T21:54:34.530" LastActivityDate="2010-11-13T21:54:34.530" CommentCount="1" />
  <row Id="6705" PostTypeId="1" AcceptedAnswerId="6707" CreationDate="2010-11-13T22:28:27.460" Score="1" ViewCount="264" Body="&lt;p&gt;I found an old 15 GB HDD lying around in a pile of spare computer parts. I decided to see if it would still work because it could be an emergency backup. So I plugged it into my ATX PSU only to find one of the chips on the board had several holes in it glowing red hot and it was smoking. A catastrophic failure! But why? What could cause the IC to fail so badly? The IC glowed for about 30 seconds before the supply tripped off. I have no idea on the circumstances of this failure - I did not do extensive tests, and I didn't examine the drive beforehand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It was something like this, &lt;a href=&quot;http://www.youtube.com/watch?v=ni_PA0as47g&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=ni_PA0as47g&lt;/a&gt;, but a different IC, and a different drive.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-12-09T12:43:27.690" LastActivityDate="2010-12-09T12:43:27.690" Title="What causes an IC to glow RED hot??" Tags="&lt;failure&gt;" AnswerCount="2" />
  <row Id="6706" PostTypeId="1" AcceptedAnswerId="6708" CreationDate="2010-11-13T22:36:03.670" Score="0" ViewCount="71" Body="&lt;p&gt;Hi all. I'm learning about the different kinds and functionalities of electronic memories (i.e. ram, flash, etc) but I'm a little confused because all the sources show something different and I don't know which of them is correct.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody know about manuals or documents which are accurate in its contents?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S: Documentation about micro-controllers would be good too. The purpuse of this is only learning. I'm not looking for documentation about a specific device.&lt;/p&gt;&#xA;" OwnerUserId="1613" LastActivityDate="2010-11-15T01:13:38.787" Title="Where can I find good documentation about memories?" Tags="&lt;learning&gt;&lt;documentation&gt;" AnswerCount="2" />
  <row Id="6707" PostTypeId="2" ParentId="6705" CreationDate="2010-11-13T22:41:26.567" Score="5" ViewCount="" Body="&lt;p&gt;I guess it could be a lot of things, anything that causes a short inside any IC could cause this, maybe a high ESD spike hit the IC and it fused some of the transistors.  But if I had to venture a guess in regards to the video: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That IC is the motor driver for the spindle motor and that location on the IC is where the drive transistor is located.  The IC is controlling 12V to the motor and a computer power supply can provide a lot of current at 12V, supply in my computer has 4 25A +12V rails.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If something had happened to the spindle motor that locked it in place, the drive current would be massive (think the start up current for a DC motor but never reducing once its spinning).  The current was enough to push the drive transistor past its thermal breakdown point and it got hot enough to melt the IC package, resulting in the hole and the glowing.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-13T22:41:26.567" CommentCount="3" />
  <row Id="6708" PostTypeId="2" ParentId="6706" CreationDate="2010-11-13T22:46:05.317" Score="1" ViewCount="" Body="&lt;p&gt;EDN has a sub-site dedicated to memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.professormemory.edn.com/&quot; rel=&quot;nofollow&quot;&gt;Professor Memory&lt;/a&gt; may be the right place for you to learn about memory and about newer technologies.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-13T22:46:05.317" />
  <row Id="6709" PostTypeId="2" ParentId="6657" CreationDate="2010-11-13T22:55:33.793" Score="1" ViewCount="" Body="&lt;p&gt;Normally we apply AC voltage on the (input) primary coil of the transformer and we have an (approximately) resistive load on each (output) secondary coil of the transformer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In that case, the dotted end of every coil will reach the positive peak voltage relative to the non-dotted end of that coil at (approximately) the same time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also at that same instant current will be flowing &lt;em&gt;into&lt;/em&gt; the dotted end of the primary coil and current will be flowing &lt;em&gt;out&lt;/em&gt; of the dotted end of each secondary coil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The dots describe which way each coil was wound.&#xA;If I take a CAT5 cable and wind it around a ferrite core, each wire-end at one end of the CAT5 cable is dotted. Each wire-end at the other end of the cable is not-dotted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I honestly don't know if dot orientation makes any difference for a SEPIC converter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that the dots &lt;em&gt;are&lt;/em&gt; important in the very similar &quot;Coupled Inductor Cuk Converter&quot; and &quot;Integrated Magnetics Cuk Converter&quot; ( &lt;a href=&quot;http://boostbuck.com/TheFourTopologies.html&quot; rel=&quot;nofollow&quot;&gt;The Four Topologies&lt;/a&gt;  ).&#xA;If one accidentally swaps the two ends of a coil in that converter, you get increased (worse) ripple on the input or output or both.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-11-13T22:55:33.793" />
  <row Id="6710" PostTypeId="2" ParentId="6686" CreationDate="2010-11-13T23:01:40.653" Score="2" ViewCount="" Body="&lt;p&gt;Since Christmas is coming up, how about a LED Christmas tree?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All you need is a piece of hardboard, cut to a tree shape and painted green, with holes for LEDs. Both red &amp;amp; green LEDs, either flashing or always on. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I once built a similar shop sign with an 8 year old, and he was perfectly capable of doing the work with supervision.&lt;/p&gt;&#xA;" OwnerUserId="776" LastActivityDate="2010-11-13T23:01:40.653" CommunityOwnedDate="2011-02-09T13:31:09.723" />
  <row Id="6711" PostTypeId="2" ParentId="6686" CreationDate="2010-11-13T23:40:17.113" Score="2" ViewCount="" Body="&lt;p&gt;You can make a simple electric motor with stuff that you can find at a craft store - and there are any number of ways to make them. All it takes is a few turns of enamel covered wire, a suitable magnet, and a single flashlight battery is usually enough to move it. The tricky part is arranging the commutation, but there are lots of websites that show different ways to do that.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-13T23:40:17.113" CommunityOwnedDate="2011-02-09T13:31:09.723" />
  <row Id="6712" PostTypeId="1" AcceptedAnswerId="6715" CreationDate="2010-11-14T00:15:06.363" Score="5" ViewCount="248" Body="&lt;p&gt;With higher voltages (more than about 5V), microcontrollers may be damaged. Is this because the voltage actually physically damages them, or because it allows excessive current to flow? - and thus increases power dissipation beyond safe limits. How does this apply for other devices?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-23T16:27:48.853" Title="Is it current (and power dissipation) which damages things, not voltage?" Tags="&lt;component&gt;&lt;damage&gt;" AnswerCount="7" CommentCount="5" FavoriteCount="1" />
  <row Id="6713" PostTypeId="1" AcceptedAnswerId="6722" CreationDate="2010-11-14T00:22:00.557" Score="2" ViewCount="190" Body="&lt;p&gt;How do these electronic calipers work?:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/AtTpr.gif&quot; alt=&quot;Caliper&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know they work by measuring the capacitance of the running track, somehow. But how do they use capacitance to measure distances - is it a linear relationship of capacitance to distance, or is there something else going on? These are really accurate - specification of ±0.02mm from 0-100mm, and the resolution is down to 0.01mm. I'm also surprised at how these can meet the specifications at the very low price point - I picked up mine for £8 and tried it against a few common objects I knew the dimensions of, and it checks out.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-15T21:45:07.630" Title="How does an electronic caliper work?" Tags="&lt;caliper&gt;&lt;how-does-it-work&gt;" AnswerCount="2" />
  <row Id="6714" PostTypeId="1" AcceptedAnswerId="6723" CreationDate="2010-11-14T00:27:05.657" Score="4" ViewCount="187" Body="&lt;p&gt;This is in danger of becoming a computer question, but I've always wondered why do computer power supplies have so many 12V &quot;rails&quot;. I have a 800W dead supply with four 12V 16A &quot;rails&quot;, but internally, they are all connected to the same transformer, use the same diodes and the same capacitors - in fact, they are all electrically connected to each other. So why call them separate rails (given they are in fact the same rail), is it just marketing or is there some proper reason?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-14T02:10:40.897" Title="What's all this &quot;rails&quot; nonsense on a computer power supply?" Tags="&lt;psu&gt;&lt;atx&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="6715" PostTypeId="2" ParentId="6712" CreationDate="2010-11-14T00:33:54.007" Score="11" ViewCount="" Body="&lt;p&gt;It's primarily because the insulating layers in the device can only withstand a certain voltage. The insulation breaks down with excessive voltage and causes internal shorts.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-14T00:33:54.007" CommentCount="3" />
  <row Id="6716" PostTypeId="2" ParentId="6712" CreationDate="2010-11-14T00:34:28.977" Score="1" ViewCount="" Body="&lt;p&gt;Power, &lt;code&gt;P = IV&lt;/code&gt;, is a measure of heat generated, so that is one way to damage things. However, some semi-conductor devices are sensitive to a over-voltage &lt;em&gt;per se&lt;/em&gt;. &lt;/p&gt;&#xA;" OwnerUserId="1882" LastActivityDate="2010-11-14T00:34:28.977" CommentCount="2" />
  <row Id="6717" PostTypeId="2" ParentId="6705" CreationDate="2010-11-14T00:39:32.640" Score="3" ViewCount="" Body="&lt;p&gt;If you were using really old IDE cables without the bump to position it properly, it's possible you were off by a row/column of pins. I did this once in a highschool computers class and it definitely burned something on the drive, smoke and all.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2010-11-14T00:39:32.640" CommentCount="2" />
  <row Id="6718" PostTypeId="2" ParentId="6712" CreationDate="2010-11-14T00:52:25.630" Score="6" ViewCount="" Body="&lt;p&gt;Reverse biased PN junctions can only take so much voltage before they start to conduct. Sometimes they are designed for this, like zener diodes, but more often they're not. When multiple transistors are fab'd into an integrated circuit, reverse biased junctions can be used to isolate them. If you get one of these normally reverse biased junctions conducting, for example by exceeding the peak reverse voltage it can take, all sorts of unintended conduction paths can be opened, a cook the IC. &lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2010-11-14T01:04:52.660" LastActivityDate="2010-11-14T01:04:52.660" />
  <row Id="6719" PostTypeId="2" ParentId="6714" CreationDate="2010-11-14T01:04:36.403" Score="1" ViewCount="" Body="&lt;p&gt;rails refers to the number of cables coming in carrying power. you put them in parallel to reduce effective resistance, this reduces power consumption of the cable, stopping potential thermal runaway. This also reduces the voltage sags on the wire.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-14T01:04:36.403" CommentCount="0" />
  <row Id="6720" PostTypeId="2" ParentId="5819" CreationDate="2010-11-14T01:10:05.607" Score="1" ViewCount="" Body="&lt;p&gt;Linear Technology LT1172CS8 appears too meet your criteria:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Input voltage range: 3 V to 60 V&lt;/li&gt;&#xA;&lt;li&gt;Internal 1.25 A switch&lt;/li&gt;&#xA;&lt;li&gt;Applications: Logic supply 5V, etc.&lt;/li&gt;&#xA;&lt;li&gt;8-SOIC package&lt;/li&gt;&#xA;&lt;li&gt;100 kHz&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://cds.linear.com/docs/Application%20Note/an19fc.pdf&quot; rel=&quot;nofollow&quot;&gt;AN19 - LT1070 Design Manual&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://cds.linear.com/docs/Application%20Note/an30fa.pdf&quot; rel=&quot;nofollow&quot;&gt;AN30 - Switching Regulator Circuit Collection&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Is the 20SOIC package too big? ( LT1176CSW and LT1176CSW-5 )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to tweak one of the &lt;a href=&quot;http://www.romanblack.com/smps/smps.htm#apps&quot; rel=&quot;nofollow&quot;&gt;&quot;Black regulator designs&quot;&lt;/a&gt; to meet your criteria?&#xA;If you can't find a monolithic integrated solution, then you have no other choice but to build it up from discrete components like this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;May I ask what in the world you are doing that needs 5 W of power, but is so space-sensitive that a TO-263 package is &quot;too big&quot;?&#xA;In my experience, tiny devices are typically micro-power,&#xA;and devices that require more than 4 W generally have plenty of room for the TO220-5 through-hole or TO-263 packages that many switching regulators use.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-11-14T01:10:05.607" />
  <row Id="6721" PostTypeId="2" ParentId="6712" CreationDate="2010-11-14T01:16:40.500" Score="7" ViewCount="" Body="&lt;p&gt;P,I,V are well known, but rarely designers and users pay attention to dV/dt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In power electronics the damage is caused by dV/dt, say about 5000V/microsecond. At this speed the multiple layers of semiconductors (which very often have parasitic thyristor somewhere) open wide and cause avalanche of destructive events.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it is possible to damage 1000V 200A device with momentary combination of much lesser current and voltage, because energy will dissipate in parts/places of structure different to normally expected. &lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-14T01:16:40.500" CommentCount="2" />
  <row Id="6722" PostTypeId="2" ParentId="6713" CreationDate="2010-11-14T01:41:11.377" Score="3" ViewCount="" Body="&lt;p&gt;Its position to capacitance ratio to frequency ratio to value conversion. The key is using unevenly patterned conductors in proximity of two capacitors. The circuit has slow response, but works remarkably as caliper.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-14T01:41:11.377" CommentCount="3" />
  <row Id="6723" PostTypeId="2" ParentId="6714" CreationDate="2010-11-14T02:10:40.897" Score="10" ViewCount="" Body="&lt;p&gt;Allow me to quote &lt;a href=&quot;http://en.wikipedia.org/wiki/Power_supply_unit_%28computer%29&quot; rel=&quot;nofollow&quot;&gt;Wikipedia: Power supply unit (computer)&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;In computer power supplies that have more than one +12V power rail...&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Multiple 12V power supply rails are separately current limited as a safety feature; they are not generated separately.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;... the IEC 60950 standard, which requires that no more than 240 volt-amps be present between any two accessible points. Thus, each {12 V} wire must be current-limited to no more than 20 A; ... Unlike a fuse or circuit breaker, these limits reset as soon as the overload is removed.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;Because of the above standards, almost all high-power supplies claim to implement separate rails, however this claim is often false; many omit the necessary current-limit circuitry,{5} both for cost reasons and because it is an irritation to customers.{1} (The lack is sometimes advertised as a feature under names like &quot;rail fusion&quot; or &quot;current sharing&quot;.)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;...&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it's apparently for exactly the same reason that electricians claim that different outlets in your house are on &quot;different circuits&quot;, even when they are all electrically connected to each other.&#xA;Each circuit is allegedly current-limited with a fuse or circuit breaker.&#xA;And yet it is an irritation to customers when a circuit breaker blows because I have too much stuff plugged into it, when that same stuff works just fine if they are plugged into outlets in different rooms, or if someone replaces that fuse with a penny :-/.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-11-14T02:10:40.897" CommentCount="2" />
  <row Id="6724" PostTypeId="2" ParentId="5819" CreationDate="2010-11-14T03:05:47.257" Score="0" ViewCount="" Body="&lt;p&gt;How about the CS51414 from On-semi.&lt;/p&gt;&#xA;" OwnerUserId="820" LastActivityDate="2010-11-14T03:05:47.257" />
  <row Id="6725" PostTypeId="2" ParentId="6698" CreationDate="2010-11-14T03:12:13.880" Score="3" ViewCount="" Body="&lt;p&gt;Red is for RIGHT. bLue (or green) is for Left. Copper is for ground. All 3 are coated in a lacquer you need to burn or scrape off before you solder.   With standard headphone plugs, with the plug facing away from you, the right pin is right, the center pin is ground, and the left pin is left.&lt;/p&gt;&#xA;" OwnerUserId="1870" LastEditorUserId="1870" LastEditorDisplayName="" LastEditDate="2010-11-14T06:00:42.247" LastActivityDate="2010-11-14T06:00:42.247" />
  <row Id="6726" PostTypeId="2" ParentId="6599" CreationDate="2010-11-14T03:56:14.807" Score="0" ViewCount="" Body="&lt;p&gt;You might also look at the MiniPOV.&#xA;It's the simplest, smallest, and lowest-cost way to flash LEDS with a microcontroller that I've ever seen.&#xA;But I'm sure you can find some way to &quot;trim the fat&quot; on this project :-).&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ladyada.net/make/minipov/&quot; rel=&quot;nofollow&quot;&gt;MiniPOV 1&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ladyada.net/make/minipov2/&quot; rel=&quot;nofollow&quot;&gt;MiniPOV v2&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ladyada.net/make/minipov3/&quot; rel=&quot;nofollow&quot;&gt;MiniPOV v3&lt;/a&gt; has a &lt;a href=&quot;http://www.ladyada.net/make/minipov3/parts.html&quot; rel=&quot;nofollow&quot;&gt;parts list&lt;/a&gt; that links directly to a distributor of each part&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://forums.adafruit.com/viewforum.php?f=11&quot; rel=&quot;nofollow&quot;&gt;MiniPOV discussion forum&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.adafruit.com/index.php?main_page=index&amp;amp;cPath=5&quot; rel=&quot;nofollow&quot;&gt;MiniPOV 3 kit for sale&lt;/a&gt; -- note that this price does not include an outer case or batteries, which could easily double the materials cost of this item.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I've been told that lots of designers find it easier to make a new system when they can start with a &quot;scaffolding&quot; of a known-working system, even when they end up completely changing everything so there isn't any part of the scaffolding remaining.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a microcontroller for a simple LED sequencer seems like overkill, but any alternative I can think of requires more than 1 components to replace the 1 microcontroller chip -- and how can &quot;more components&quot; be simpler?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-11-14T03:56:14.807" />
  <row Id="6727" PostTypeId="2" ParentId="6712" CreationDate="2010-11-14T05:06:02.753" Score="2" ViewCount="" Body="&lt;p&gt;Answer is, it depends on the device and how the voltage/current is applied.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you put too much voltage on a CMOS transistors gate, then it'll punch through damaging it. Maybe enough that the circuit doesn't work, or maybe not.  It's classic problem with analog IC's, they get zapped, then they get noisy.  Same thing can happen to bi-polar transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Classic failure in CMOS IC's is latch up, where a current spike flips on parasitic SCR's associated with CMOS transistors.  Current then flows from VCC to ground, potentially overheating the device.  And also high currents frying the protection diodes on inputs, causing them to leak.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And as the man said, dV/dt tends to kill power devices. Often because it causes them to partially turn on in localized areas, which then overheat and punch through.  Which is why rolling your own motor controller usually results in big smoke.&lt;/p&gt;&#xA;" LastActivityDate="2010-11-14T05:06:02.753" />
  <row Id="6728" PostTypeId="1" AcceptedAnswerId="6730" CreationDate="2010-11-14T06:09:40.923" Score="3" ViewCount="172" Body="&lt;p&gt;I was going to use the LY330 or the LY530 from ST Microelectronics and they should do the job very well. However, due to the stupid US Export Restrictions, Digikey won't sell any to me (I live in Australia).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any recommended gyroscopes that I can buy (Z-axis) that are easily sourced (no export restrictions from digikey), offer ranges of at least 300 deg/sec (don't care if it is digital or analogue), and are highly accurate?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-14T17:02:31.130" Title="Looking for a ~300 degree/sec gyro" Tags="&lt;gyro&gt;&lt;digikey&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="6729" PostTypeId="2" ParentId="6615" CreationDate="2010-11-14T07:33:34.893" Score="5" ViewCount="" Body="&lt;p&gt;I don't have my degree. I didn't go to university or college, but I partied there with all of my friends who did go. I helped them with their homework. :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been doing this stuff professionally for over 15 years. I know that in some places in the world it's not legal to call yourself an engineer unless you have the degree, and I know in other places of the world that they call the garbage men &quot;sanitation engineers.&quot; There is no hard and fast rule.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have always maintained that unless you have the degree, you're not an engineer. To me, it's a matter of principle. I go as far as to correct people when they call me an engineer. When people ask me what I do and want a short answer, however, I do answer with &quot;hardware development&quot; or &quot;software development&quot; and it's very infrequently that I refer to what I do as &quot;engineering.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As I said, I do this as a matter of principle. It's not enforced where I live (Canada) but I think that it's an important enough thing to distinguish between those who went and go their degree and those who did it another way. It certainly hasn't cost me anything other than jobs at big firms, but I've never been interested in that kind of work anyway. If I wanted to work somewhere like that I would probably have gotten the education in order to be able to get through the H.R. interviews in the first place. :-)&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-11-14T07:33:34.893" />
  <row Id="6730" PostTypeId="2" ParentId="6728" CreationDate="2010-11-14T08:17:43.513" Score="1" ViewCount="" Body="&lt;p&gt;Check &lt;a href=&quot;http://invensense.com/index.html&quot; rel=&quot;nofollow&quot;&gt;Invensense&lt;/a&gt;. They have a nice range of gyroscopes and seem to sell directly from their site. Don't know about export restrictions though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it is only for a single project or a prototype, you can always try to gut a Wii motionplus for its part: the invensense &lt;a href=&quot;http://www.dynacam3d.com/files/bibliographie/Wii-motion/IDG600_ProductBrief_English.pdf&quot; rel=&quot;nofollow&quot;&gt;IDG-600&lt;/a&gt;. Cheap motionplus modules can be found on &lt;a href=&quot;http://www.dealextreme.com/advsearch.dx/search.wii%20motionplus&quot; rel=&quot;nofollow&quot;&gt;dealextreme&lt;/a&gt;. &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.32506&quot; rel=&quot;nofollow&quot;&gt;This one&lt;/a&gt; for instance, appears to have an &lt;a href=&quot;http://invensense.com/mems/gyro/idg650.html&quot; rel=&quot;nofollow&quot;&gt;Invensense IDG-650&lt;/a&gt; which has a selectable range of 440 deg/s.&lt;/p&gt;&#xA;" OwnerUserId="10" LastEditorUserId="10" LastEditorDisplayName="" LastEditDate="2010-11-14T13:56:29.547" LastActivityDate="2010-11-14T13:56:29.547" CommentCount="1" />
  <row Id="6731" PostTypeId="1" AcceptedAnswerId="6733" CreationDate="2010-11-14T09:33:41.937" Score="1" ViewCount="285" Body="&lt;p&gt;Hi everyone&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a light dimmer i want to connect to a a floor lamp. I have tried to look for some diagrams but haven't been able to find some.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a diagram on the dimmer but I don't understand it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have made an illustration to show how the small diagram looks (it's the diagram in the middle, the lamp and the 4 wires and the power plug are my additions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://000fff.org/uploads/LightDimmer.pdf&quot; rel=&quot;nofollow&quot;&gt;http://000fff.org/uploads/LightDimmer.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone tell me how to connect this. I have 1 wire from the lamp to the dimmer with a blue and a brown wire and 1 wire from the dimmer to the power with a blue and a brown wire.&lt;/p&gt;&#xA;" OwnerUserId="1949" LastEditorUserId="1949" LastEditorDisplayName="" LastEditDate="2010-11-14T11:17:23.957" LastActivityDate="2010-11-14T11:21:33.420" Title="How to connect a light dimmer for my lamp" Tags="&lt;light&gt;&lt;dimming&gt;" AnswerCount="1" CommentCount="8" />
  <row Id="6733" PostTypeId="2" ParentId="6731" CreationDate="2010-11-14T10:37:12.213" Score="2" ViewCount="" Body="&lt;p&gt;Looking at your illustration, it seems that the mains wires are the two left wires, and the lamp would connect to the two right wires. You mentioned that the dimmer is in an enclosure. I would strongly recommend ensuring that there is absolutely no way that a determined toddler could get a screwdriver, paperclip, ham sandwich, etc... into the enclosure. Also ensure that the wires are protected with some sort of strain relief, so that when the dog trips on the cord, the wires won't come out.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;h2&gt;EDIT:&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;I looked at your drawing again. It seems that there are two possibilities:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;First Possibility&lt;/em&gt;&lt;/strong&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are seeing 4 wires because they are 2 from the cord, and 2 from the socket. This one's easy. Connect the two wires from the plug to the left two wire positions on the dimmer. Connect the other two wires to the right two wire positions on the dimmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;Second Possibility&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your lamp socket is wired for a three-way lamp. Usually these have 3 wires, though. One would be the neutral, one would be low, and one would be medium. With power applied to both low and medium, you get high power. You would need to check this with an ohmmeter. With a 3-way bulb installed, measure resistances across all of the wires. You should come up with something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Pair    Measurement&#xA;1-2 360&#xA;1-3 240&#xA;1-4 0&#xA;2-3 600&#xA;2-4 360&#xA;3-4 240&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that these numbers are approximate, and depend on the wattage of your bulb. This table is built on the assumption of a 40-60-100 Watt bulb. In this case, 1 and 4 are Neutral and Ground, and can be tied together. 2 is low power, and 3 is medium power. Using an external dimmer, these should also tie together for the hot side. Check across the neutral/ground and &#xA;the hot side. If it reads short, there's a problem!&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;&lt;em&gt;&lt;strong&gt;CAUTION&lt;/em&gt;&lt;/strong&gt;&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;If you can't figure out exactly what each wire is for, get help! Magic smoke stinks, and so do house fires. (Been there. Not cool.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As tronixstuff mentioned before, though, mains can kill. I've been &quot;tagged&quot; a few times (lucky -- I'm still here to write about it) and you need to exercise the utmost caution. &lt;/p&gt;&#xA;" OwnerUserId="965" LastEditorUserId="965" LastEditorDisplayName="" LastEditDate="2010-11-14T11:12:00.500" LastActivityDate="2010-11-14T11:12:00.500" CommentCount="3" />
  <row Id="6736" PostTypeId="2" ParentId="6728" CreationDate="2010-11-14T14:28:31.783" Score="0" ViewCount="" Body="&lt;p&gt;Mouser don't show these parts as being export controlled.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-14T14:28:31.783" />
  <row Id="6737" PostTypeId="2" ParentId="6728" CreationDate="2010-11-14T15:06:22.463" Score="0" ViewCount="" Body="&lt;p&gt;Can't you order one from Element 14(Formerly Farnell) in Australia? Ive found the first part in their &lt;a href=&quot;http://au.element14.com/stmicroelectronics/ly330alh/gyroscope-mems-10lga/dp/1838548?Ntt=LY330&quot; rel=&quot;nofollow&quot;&gt;system&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2010-11-14T17:02:31.130" LastActivityDate="2010-11-14T17:02:31.130" />
  <row Id="6738" PostTypeId="2" ParentId="5819" CreationDate="2010-11-14T19:27:09.360" Score="1" ViewCount="" Body="&lt;p&gt;Maybe something like the &lt;a href=&quot;http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1042,C1032,C1064,P2154,D3864&quot; rel=&quot;nofollow&quot;&gt;LT1765-5.0&lt;/a&gt; or the &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/tps54232.pdf&quot; rel=&quot;nofollow&quot;&gt;TPS54232&lt;/a&gt;? Both are SOIC-8, plenty of power and high frequent which makes for very small inductors. If you get regulators that only switch at 250kHz or even slower, you get rather large inductors (&gt;47uH) for these applications. It also depends on how much current you are typically using , so read the datasheets properly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please note that the board design is very crucial if you're working with any type of switching regulator, but especially these regulators that switch at 1MHz or so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I also recommended to do with these regulators is to calculate the maximum power dissipation. I haven't checked the datasheets extensively so I don't know how much the SOIC-8 will have to dissipate. Usually a SOIC-8 package is terrible, and if the chip is available in something like a SOT263 (which cools much better - especially with planes) you will not be able to completely use the chip specs in that package (but it will still work to some extent).&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-11-14T19:27:09.360" CommentCount="1" />
  <row Id="6739" PostTypeId="2" ParentId="5635" CreationDate="2010-11-14T21:52:50.667" Score="1" ViewCount="" Body="&lt;p&gt;There is also Sci-lab which has a simulink modeling type thing built in.&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2010-11-14T21:52:50.667" />
  <row Id="6740" PostTypeId="1" AcceptedAnswerId="6744" CreationDate="2010-11-14T22:20:57.927" Score="5" ViewCount="234" Body="&lt;p&gt;I am trying to develop a very high reliability product, with a MTBF exceeding 100,000 hours, hopefully in the 250,000 hours range. Yep, I know - stupidly high reliability, at least 10 years. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most LED's I've seen have a reliability rating of only 20,000 hours. What happens after this? Do they reduce in output too much? Are they usable as power indicators past this point?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-14T23:00:55.053" LastActivityDate="2010-11-15T18:02:23.223" Title="How do LEDs fail?" Tags="&lt;reliability&gt;" AnswerCount="4" CommentCount="7" FavoriteCount="1" />
  <row Id="6741" PostTypeId="1" AcceptedAnswerId="7172" CreationDate="2010-11-14T22:27:53.770" Score="4" ViewCount="207" Body="&lt;p&gt;If I had the following NXC code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/*&#xA;byte USSingleShot(port, waitTime=0)&#xA;Puts the US Sensor into Single Shot mode (if it isn't already) and asks the&#xA;sensor to send a new shot (of sound) to measure distance. Then, it waits the&#xA;specified amount of wait time. Finally, it reads and returns the value of the&#xA;sensor [in centimeters].&#xA;*/&#xA;byte USSingleShot(byte port, unsigned long waitTime = 0)&#xA;{&#xA;    SetSensorLowspeed(port);&#xA;    WriteI2CRegister(port, I2C_ADDR_DEFAULT, I2C_REG_CMD, US_CMD_SINGLESHOT);&#xA;    Wait(waitTime);&#xA;    //byte values[];&#xA;    //ReadSensorUSEx(port, values);&#xA;    //return(values[0]);&#xA;    return(SensorUS(port));&#xA;}&#xA;&#xA;task main()&#xA;{&#xA;    while(1)&#xA;    {&#xA;        NumOut(0, LCD_LINE1, USSingleShot(S1, 40), DRAW_OPT_CLEAR_WHOLE_SCREEN);&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Is it a good idea to have &lt;code&gt;SetSensorLowspeed(port);&lt;/code&gt; included in &lt;code&gt;USSingleShot()&lt;/code&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NOTE: Asking this question is a bit awkward, but hopefully this site will get more Mindstorms questions...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NOTE: If you have enough reputation (150+), can you please add &quot;NXC&quot; as a tag? Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1940" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-15T02:36:42.713" LastActivityDate="2010-12-06T11:08:29.853" Title="Is it safe to configure a US (I2C) Sensor to the same port multiple times?" Tags="&lt;sensor&gt;&lt;i2c&gt;&lt;nxc&gt;&lt;lego-mindstorms&gt;" AnswerCount="1" CommentCount="5" FavoriteCount="2" />
  <row Id="6742" PostTypeId="2" ParentId="6740" CreationDate="2010-11-14T22:40:57.667" Score="5" ViewCount="" Body="&lt;p&gt;I think you are utterly doomed trying to get to MTBF of 250000 hours on any usefully complex product, but then you haven't said what it is, so it might be very simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LEDs tend to age faster if they're hotter / driven at higher currents, and the failure mechanism is different for white leds (which are fluorescent) and natural-coloured LEDs.  But generally they get dimmer as they age.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would expect that you would get very long life if you significantly under-drove the LED (modern traditional-colour (red, etc)) LEDs are incredibly bright and tend to need very little current to act as a useful indicator, and if you weren't too fussy about the specific output you could play faster-and-looser about the failure condition.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if I was trying to make a fantastically reliable product, one way I'd do that is to dispense with absolutely every component I possibly could.  I expect the power-on LED would fail to make the cut in that regard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update: Well, clearly I know even less about reliability than I thought I did - it seems lots of diskdrives claim MTBFs well over 250k hours - so good luck with your product!&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-14T22:40:57.667" CommentCount="6" />
  <row Id="6743" PostTypeId="2" ParentId="5635" CreationDate="2010-11-14T23:05:55.580" Score="1" ViewCount="" Body="&lt;p&gt;There's also:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.gnu.org/software/octave/&quot; rel=&quot;nofollow&quot;&gt;Octave&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rlab.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;Rlab&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;which may have some of the functionality you're looking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The site &lt;a href=&quot;http://www.dspguru.com/&quot; rel=&quot;nofollow&quot;&gt;dspGuru&lt;/a&gt; may have other useful suggestions for you too.&lt;/p&gt;&#xA;" OwnerUserId="103" LastActivityDate="2010-11-14T23:05:55.580" />
  <row Id="6744" PostTypeId="2" ParentId="6740" CreationDate="2010-11-14T23:13:25.240" Score="7" ViewCount="" Body="&lt;p&gt;Must say I've always been highly sceptical of the meaningfulness of MTBF figures. &#xA;LEDs will gradually reduce brightness over time, but it will be many times their stated life before they cease to be useable as a power indicator. Running at well below the specc'd current will increase lifetime many-fold.&#xA;And would failure of a power-on LED be counted as a failure of the product?&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-14T23:13:25.240" CommentCount="3" />
  <row Id="6745" PostTypeId="1" AcceptedAnswerId="6751" CreationDate="2010-11-14T23:38:42.477" Score="1" ViewCount="101" Body="&lt;p&gt;24AA1025: operates from 1.7V - 5.5V, 400kHz, $2.37&lt;/p&gt;&#xA;&#xA;&lt;p&gt;24FC1025: operates from 2.5V - 5.5V, 1 MHz, $2.37&lt;/p&gt;&#xA;&#xA;&lt;p&gt;24LC1025: operates from 2.5V - 5.5V, 400kHz, $2.37&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=70012&amp;amp;mid=&amp;amp;lang=en&quot; rel=&quot;nofollow&quot;&gt;See here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;24AA1025 is unique, because of the lower operating range. What I don't understand is why Microchip produce both 24FC1025 and 24LC1025 at the same price with different maximum clock frequencies. Why not just make one? Am I missing something?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-15T00:56:15.403" Title="What's the difference between 24AA1025, 24FC1025 and 24LC1025" Tags="&lt;eeprom&gt;&lt;pricing&gt;" AnswerCount="3" />
  <row Id="6746" PostTypeId="2" ParentId="6745" CreationDate="2010-11-14T23:46:34.933" Score="1" ViewCount="" Body="&lt;p&gt;I've always been amazed at the number of different parts Microchip make, however the 'same price' thing may differ as quantities increase. It may also be the case that a new, faster part is introduced at a premium price, and at some point the products both use the new die, but both numbers are retained to avoid changing customers ordering/parts lists etc. I've not looked at the data but there may also be some other subtle spec differences, like standby or operating power draw. Looking at the LC/FC256 data I have to hand, the LC is avaialble in automotive temp range, the FC is not.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-14T23:46:34.933" />
  <row Id="6747" PostTypeId="2" ParentId="6745" CreationDate="2010-11-14T23:47:11.027" Score="5" ViewCount="" Body="&lt;p&gt;The standby current is much lower for the 24LC1025 (100 nA vs 5 uA). That would be important for low-power applications where the faster speed isn't required.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-14T23:47:11.027" />
  <row Id="6748" PostTypeId="1" AcceptedAnswerId="6750" CreationDate="2010-11-14T23:57:13.630" Score="4" ViewCount="137" Body="&lt;p&gt;&lt;a href=&quot;http://microchip.com/ParamChartSearch/chart.aspx?branchID=11015&amp;amp;mid=11&amp;amp;lang=en&amp;amp;pageId=79&quot; rel=&quot;nofollow&quot;&gt;Many, many choices&lt;/a&gt;. And this is just Microchip's offerings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm going to be amplifying by a maximum of 5x using an op-amp. So I choose an op-amp with a GBWP of 50 kHz * 5 = 250 kHz. That still leaves many op-amps. What slew rate should I be looking for? (with low distortion on the output.) And are there any other parameters to look out for, like input noise and offset?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: It seems I need to clarify. I'm only looking for a single channel op-amp for amplifying a mono signal with reasonable levels of distortion. I'm not looking for high quality prosumer gear audio.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-15T13:12:04.853" LastActivityDate="2010-11-15T18:28:00.270" Title="Regarding slew rates, what would be the minimum for amplifying audio using an op-amp?" Tags="&lt;analog&gt;&lt;op-amp&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="6749" PostTypeId="2" ParentId="5524" CreationDate="2010-11-15T00:12:41.127" Score="1" ViewCount="" Body="&lt;p&gt;I used VeeCAD.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You export your netlist to it and lay the parts out on the virtual stripboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The free version does well enough for educational/hobby use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;You need to install the part libraries into your schematic tool to get the netlist to import usefully.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;If you can hack netlists, you can do it after the event&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used TinyCAD instead of Eagle ( I know both, but I knew eagle have a steeper learning curve for my co-workers if they ever looked at it later)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used it for a fairly small project, on a 5&quot; square board. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It worked really well, and there were REAL drawings to make the parts from. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I made 3 copies of a board.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-11-15T00:12:41.127" />
  <row Id="6750" PostTypeId="2" ParentId="6748" CreationDate="2010-11-15T00:18:00.547" Score="7" ViewCount="" Body="&lt;p&gt;the slew rate needs to be &gt;= 2*pi*f*Vpp to not impart distortion on a sinusoidal signal.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;f = frequency of the sinusoid and Vpp = peak to peak voltage swing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So in your case you'd probably use 20khz for the frequency and whatever your Vpp is to find your minimum slew rate.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-15T00:18:00.547" CommentCount="3" />
  <row Id="6751" PostTypeId="2" ParentId="6745" CreationDate="2010-11-15T00:56:15.403" Score="4" ViewCount="" Body="&lt;p&gt;It seems clear to me. The FC component has a higher clock frequency, but it also has a lower maximum operating temperature. The LC extends this maximum operating temperature, but at the cost of some of the clock frequency. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That gives you the choice of either high temperature, or high clock frequency. &lt;/p&gt;&#xA;" OwnerUserId="776" LastActivityDate="2010-11-15T00:56:15.403" />
  <row Id="6752" PostTypeId="2" ParentId="6706" CreationDate="2010-11-15T01:13:38.787" Score="1" ViewCount="" Body="&lt;p&gt;Some basic information about different types of memory. Nice place to get started:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://computer.howstuffworks.com/computer-memory.htm&quot; rel=&quot;nofollow&quot;&gt;http://computer.howstuffworks.com/computer-memory.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have an idea of the different types of memory out there, each one's purpose etc., then you can go into the detailed architecture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basic information about Microcontrollers, also to get you started:&#xA;&lt;a href=&quot;http://www.howstuffworks.com/microcontroller.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.howstuffworks.com/microcontroller.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1785" LastActivityDate="2010-11-15T01:13:38.787" CommentCount="1" />
  <row Id="6753" PostTypeId="2" ParentId="6740" CreationDate="2010-11-15T02:45:04.920" Score="3" ViewCount="" Body="&lt;p&gt;MTBF is based off of actual run time. So at a goal of 250,000 hours you are hoping your product can run 24/7/365 for almost 30 years.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A MTBF of 20,000 gives you just over 2.25 years of constant run time at recommended max power. This time is pretty good for most commercial products right now. If your LED is on for 8 hours a day, you are looking at a life of almost 7 years. Now if you decrease the power your putting into the LED you can even extend this life longer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now with all of that said, if it is just a power indicator you wont be switching it often so you will put less wear on the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know I haven't directly answered your question, but I am hoping you are starting to realize that MTBF isn't something you should worry about too much. I realize  you want your device to last awhile, which is a good thing, but you will probably find that if you always go with the highest life items they will generally be more expensive which will cause your product to be inflated in price, resulting in very few wanting to buy it. What good is a device that lasts for 30 years if no one buys it?&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-15T02:45:04.920" />
  <row Id="6754" PostTypeId="2" ParentId="6681" CreationDate="2010-11-15T06:44:50.463" Score="1" ViewCount="" Body="&lt;p&gt;I'm playing around with TI's &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tlc5925.html&quot; rel=&quot;nofollow&quot;&gt;TLC5925&lt;/a&gt;, which is functionally very similar to what you're asking for. It is designed for driving LED's at a constant current, and the logic is 3.3/5V CMOS. The output is tolerant of up to 17V, although I don't know how well it would drive the outputs to logic levels. Not sure if this is suitable - just taking a wild guess at your intended application.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-11-15T06:44:50.463" />
  <row Id="6755" PostTypeId="2" ParentId="6676" CreationDate="2010-11-15T06:51:41.937" Score="1" ViewCount="" Body="&lt;p&gt;I'm working on a LED POV project, and I'm using TI's &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tlc5925.html&quot; rel=&quot;nofollow&quot;&gt;TLC5925&lt;/a&gt;. It's pretty much a latched shift register with constant current sinking outputs. They have more advanced chips as well; some with digital brightness control and even PWM settings for each channel. It also has 16 output channels. Non-SMT versions are also available.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-11-15T06:51:41.937" CommentCount="4" />
  <row Id="6756" PostTypeId="1" AcceptedAnswerId="6758" CreationDate="2010-11-15T08:02:29.230" Score="2" ViewCount="237" Body="&lt;p&gt;Can somebody please explain how can I convert from Moore FSM to Mealy FSM and vice versa?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="1760" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-15T10:41:16.973" LastActivityDate="2010-11-15T10:41:16.973" Title="conversion from Moore To Mealy" Tags="&lt;convert&gt;&lt;state-machines&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="6757" PostTypeId="2" ParentId="1635" CreationDate="2010-11-15T08:26:35.530" Score="3" ViewCount="" Body="&lt;p&gt;I have put together an oscilloscope comparison table where you can filter and sort devices to find the one best for your needs:  &lt;a href=&quot;http://www.gabotronics.com/resources/hobbyists-oscilloscopes.htm&quot; rel=&quot;nofollow&quot; title=&quot;Oscilloscope for Hobbyists&quot;&gt;Digital oscilloscopes for hobbyists&lt;/a&gt;&lt;/p&gt;&#xA;" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-26T23:56:41.890" LastActivityDate="2011-01-26T23:56:41.890" CommentCount="1" />
  <row Id="6758" PostTypeId="2" ParentId="6756" CreationDate="2010-11-15T10:37:38.163" Score="2" ViewCount="" Body="&lt;p&gt;Here's a worked example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://web.cs.mun.ca/~paul/cs3724/material/web/notes/node25.html&quot; rel=&quot;nofollow&quot;&gt;http://web.cs.mun.ca/~paul/cs3724/material/web/notes/node25.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-15T10:37:38.163" />
  <row Id="6759" PostTypeId="2" ParentId="6436" CreationDate="2010-11-15T10:50:42.050" Score="4" ViewCount="" Body="&lt;p&gt;Dave Jones has posted a tutorial on high volume PCB design:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.eevblog.com/2010/11/15/eevblog-127-pcb-design-for-manufacture-tutorial&quot; rel=&quot;nofollow&quot;&gt;http://www.eevblog.com/2010/11/15/eevblog-127-pcb-design-for-manufacture-tutorial&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-15T10:50:42.050" CommentCount="1" />
  <row Id="6760" PostTypeId="1" AcceptedAnswerId="6763" CreationDate="2010-11-15T11:06:28.767" Score="8" ViewCount="265" Body="&lt;p&gt;In all the computer power supplies and other power supplies I've taken apart, I've noticed they are fully isolated from the mains. Galvanic isolation through transformers, and often optical isolation for feedback. There is usually a very visible gap in the traces between the primary and secondary sides, at least 8mm across. Why is it important that these supplies be isolated?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-16T08:34:05.523" Title="Why is it important for mains power supplies to be isolated?" Tags="&lt;power&gt;&lt;isolation&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="6761" PostTypeId="2" ParentId="6760" CreationDate="2010-11-15T11:30:33.217" Score="0" ViewCount="" Body="&lt;p&gt;Short answer - Try holding a screwdriver while sticking it in to a mains power outlet. (Disclaimer - Don't try this at home unless you like recovering in a hospital or have a strong desire to spend eternity looking at the inside of a coffin.  Actually, just don't try this.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Slightly longer answer - Corporate legal departments object to handling the claims from the relatives of those electrocuted while handling equipment that is shorted to the power main.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In switch mode power supplies used in computers there are often intermediate values that are much higher than the normal 240V mains supplies.  IIRC 600 or 800V is not unusual.  These must be isolated from the mains and the final output rails.&lt;/p&gt;&#xA;" OwnerUserId="400" LastEditorUserId="400" LastEditorDisplayName="" LastEditDate="2010-11-15T12:10:05.820" LastActivityDate="2010-11-15T12:10:05.820" CommentCount="1" />
  <row Id="6762" PostTypeId="2" ParentId="6748" CreationDate="2010-11-15T12:19:47.307" Score="1" ViewCount="" Body="&lt;p&gt;Two AmpOps in the same package could be a good choise if you're planning to design stereo sound amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the two of them in the same package the distortion from temperature variation would be the same.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-15T12:19:47.307" CommentCount="1" />
  <row Id="6763" PostTypeId="2" ParentId="6760" CreationDate="2010-11-15T12:46:33.027" Score="13" ViewCount="" Body="&lt;p&gt;Because the mains supply is very unpredictable, and can do all sorts of things outside its nominal specification, which might damage components or at least break the nominal design assumptions.   A non-isolated design also has all its voltages referenced to one of the mains conductors, which might or might not have a useful/safe relationship to other potentials in your environment (like earth/ground, for example).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the only stuff on the low-voltage side is inaccessible electronics, then non-isolated supplies are fine - they tend to much be cheaper/simpler than isolated supplies, and lots of household equipment uses them.  Even things like televisions used to work like this, if you go right back to before the time when they had external video/audio connections.  The antenna connection was the only external socket, and that was capacitor-isolated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a human being or 3rd party piece of equipment needs to interconnect with the low-voltage side of your design, then an isolated supply both gives you a clear barrier across which dangerous voltages won't pass, even in the case of component failure, &lt;em&gt;and&lt;/em&gt; it means your circuit is now 'floating' relative to the mains.  In turn, that means you can arrange for all the electronics to operate near ground potential, with all your interconnected equipment having at least roughly the same voltage reference to work from.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastEditorUserId="1844" LastEditorDisplayName="" LastEditDate="2010-11-16T08:34:05.523" LastActivityDate="2010-11-16T08:34:05.523" CommentCount="2" />
  <row Id="6764" PostTypeId="2" ParentId="1635" CreationDate="2010-11-15T13:13:47.693" Score="1" ViewCount="" Body="&lt;p&gt;Take a look at &lt;a href=&quot;http://dangerousprototypes.com/2010/02/25/prototype-open-logic-sniffer-logic-analyzer-2/&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; and &lt;a href=&quot;http://dangerousprototypes.com/2010/01/07/open-source-digital-sampling-oscilloscope/&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-11-15T13:13:47.693" />
  <row Id="6765" PostTypeId="1" AcceptedAnswerId="6772" CreationDate="2010-11-15T13:24:51.190" Score="1" ViewCount="182" Body="&lt;p&gt;For a project we're thinking of generating electricity out of wet newspapers. Is that possible? How much current would it generate?&lt;/p&gt;&#xA;" OwnerUserId="1957" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T21:02:15.033" LastActivityDate="2011-04-27T21:02:15.033" Title="Generating electricity with wet newspapers?" Tags="&lt;circuit&gt;&lt;generator&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="6766" PostTypeId="2" ParentId="6760" CreationDate="2010-11-15T13:35:23.517" Score="4" ViewCount="" Body="&lt;p&gt;Short answer (oooh, this is a pun, wait for it...): safety.  What would the effect of a short from 240V or higher to... well, anything, be?  Low voltage devices?  Dead!  House?  On fire! Lawsuit?  Pending!  Isolation at least makes a &lt;em&gt;direct&lt;/em&gt; short to wall voltage impossible and an &lt;em&gt;indirect&lt;/em&gt; short less dangerous and less likely.  For instance, if the wall voltage totally fries everything on one side of the transformer you have a non-working transformer.  A non-working transformer means no coupling and no voltage on the other side, so no damage.  Plus there are more protection options for the lower voltage side (less expensive protection options anyhow).&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-15T13:35:23.517" />
  <row Id="6767" PostTypeId="1" AcceptedAnswerId="6770" CreationDate="2010-11-15T13:40:47.650" Score="0" ViewCount="168" Body="&lt;p&gt;I have taken an interest in a current effort to create a (mini- or micro-) ATX &lt;a href=&quot;http://natami.net/&quot; rel=&quot;nofollow&quot;&gt;motherboard with a custom CPU&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But ideally, I would want this system in a laptop instead.&#xA;I got this idea, how hard would it be to rip out a motherboard from a laptop, such as the EeePC or Thinkpad, and replace it with a custom board?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could parts of the laptop electronics be reused, such as the power supply etc? Or are laptop motherboard form factors etc changed too often for this to be useful as a semi-reliable source of laptops to be remade? (The goal being a laptop Natami built to order, or in small runs.)&lt;/p&gt;&#xA;" OwnerUserId="1877" LastEditorUserId="1877" LastEditorDisplayName="" LastEditDate="2010-11-16T12:12:20.683" LastActivityDate="2010-11-16T12:12:20.683" Title="Recad laptop motherboard PCB?" Tags="&lt;pcb-fabrication&gt;&lt;cad&gt;&lt;pcb-design&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="6768" PostTypeId="2" ParentId="6765" CreationDate="2010-11-15T13:53:02.917" Score="3" ViewCount="" Body="&lt;p&gt;It mostly depends on &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;the chemicals the newspaper has been soaked in. &lt;/li&gt;&#xA;&lt;li&gt;The material of the electrodes placed in/on the newspaper. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I seem to remember a project a while back which used copper and zinc for +/-. Something about the different metal properties allowed electricity to flow. Do some searches with those keywords. &lt;/p&gt;&#xA;" OwnerUserId="1033" LastActivityDate="2010-11-15T13:53:02.917" CommentCount="1" />
  <row Id="6770" PostTypeId="2" ParentId="6767" CreationDate="2010-11-15T13:59:45.513" Score="3" ViewCount="" Body="&lt;p&gt;Laptop electronics could be reused but you might have trouble finding/using the connectors.  For one, they're TINY - full of flex cables and iddy biddy surface mount contacts that you certainly won't be able to hand-solder.  Also, some of the connectors are proprietary so you'll be reduced to scavenging them from old boards - have an SMD rework station handy.  Or, they might just be plain hard to find.  If it's a connector dedicated for use in a computer you might not be able to find it in quantities fewer than 1000, or the places you'll find them don't sell in the US or really anywhere other than China/Hong Kong/Taiwan.  As far as they're concerned there's no reason to sell them abroad - everything's manufactured in that area so why ship?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But as far as designing the PCB I doubt you'll have too many problems.  You'll have to generate CAD drawings of the interior to determine where to put mounting holes, place connectors, etc.  You'll have to watch out and make sure you use the right parts - I'd imagine laptops have low-profile &lt;em&gt;everything&lt;/em&gt; so don't assume you can use standard height components.  You'll have to keep an eye on how you're dissipating heat - the cases are probably designed for one and only one solution for removing heat so if you can't fit the same heat pipe they use on your board you might be out of luck.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-15T13:59:45.513" CommentCount="1" />
  <row Id="6771" PostTypeId="2" ParentId="6765" CreationDate="2010-11-15T14:40:16.797" Score="2" ViewCount="" Body="&lt;p&gt;The newspapers themselves won't generate any electricity as they don't react with anything.  Batteries are formed by compounds with dissimilar &lt;a href=&quot;http://en.wikipedia.org/wiki/Electrochemical_series&quot; rel=&quot;nofollow&quot;&gt;electrode potentials&lt;/a&gt;, so you will require some sort of additional reactants (usually metals) that you could keep separate with newspaper.  Copper/zinc as Brad mentions are fairly easy to obtain and cheap, though the possibilities are vast (magnesium, lithium, iron, tin, nickel, silver...)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current any battery generates is based on the speed it can react components, which is governed by the geometry of the cell above all else.  If you only know the materials (we don't here anyways), the best you can do is estimate the voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you could use wet newspaper as a spacer for aluminum electrolytic capacitors.  Roll up paper-foil-paper-foil, apply a reverse voltage to grow the aluminum oxide dielectric, and presto, capacitor.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-15T14:40:16.797" />
  <row Id="6772" PostTypeId="2" ParentId="6765" CreationDate="2010-11-15T15:25:27.770" Score="5" ViewCount="" Body="&lt;p&gt;You will need to soak your newspapers in a suitable electrolyte, water will not work.  You could try lemon juice as a weak acid (vinegar could work).  You will then need two dis-similar metals one for the Anode and the other for the Cathode.  Let us say a piece of copper and a piece of zinc (galvanised steel will do).  Place the two metals in contact with the sodden newspaper and measure the voltage between the plates.  You should get around 0.85V.  You will not get much current out of this cell as the internal resistance of the soggy newspaper will be quite high.  It should light up an LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could just get a &lt;a href=&quot;http://en.wikipedia.org/wiki/Lemon_battery&quot; rel=&quot;nofollow&quot;&gt;lemon&lt;/a&gt; and stick the two metals through the skin into the fruit, dispensing with a messy pile of soggy newspaper.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-11-15T15:25:27.770" />
  <row Id="6773" PostTypeId="1" AcceptedAnswerId="6774" CreationDate="2010-11-15T16:30:59.897" Score="6" ViewCount="314" Body="&lt;p&gt;I don't do my own CAD work.  I have a mental checklist of what to look for when the PCB is placed, critical routed and routed.  But is there a good checklist you have or can point me to?  I'm not looking for schematic items, that is covered &lt;a href=&quot;http://electronics.stackexchange.com/questions/6644/good-schematic-checklist&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-06T19:25:34.593" Title="Good checklist for PCB design to be used by the EE (not by the PCB designer)" Tags="&lt;pcb&gt;&lt;checklist&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="3" />
  <row Id="6774" PostTypeId="2" ParentId="6773" CreationDate="2010-11-15T16:33:17.943" Score="2" ViewCount="" Body="&lt;p&gt;From the previous question, &lt;a href=&quot;http://www.aqdi.com/check.htm&quot; rel=&quot;nofollow&quot;&gt;this link&lt;/a&gt; also contains Atlantic Quality Design's PCB checklist. And one from &lt;a href=&quot;http://www.avanthon.com/layout_checklist.php&quot; rel=&quot;nofollow&quot;&gt;Avanton Engineering is here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit Jan 6 2011: &lt;a href=&quot;http://www.electronic-products-design.com/geek-area/electronics/pcb-design/general-pcb-design/a-good-pcb-design-checklist/&quot; rel=&quot;nofollow&quot;&gt;Electronic Product Design&lt;/a&gt; has one with some unique items.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-06T19:25:34.593" LastActivityDate="2011-01-06T19:25:34.593" />
  <row Id="6775" PostTypeId="2" ParentId="6760" CreationDate="2010-11-15T17:55:19.590" Score="1" ViewCount="" Body="&lt;p&gt;I can think of a few:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Helps isolate the outputs from dangerous line-level events (lightning strikes, surges, etc.) since most transformers are step-down in commercial power supplies&lt;/li&gt;&#xA;&lt;li&gt;Allows you to use the chassis of the equipment as a safety shield, by earthing it (any conduction from the mains to the chassis will instigate a fuse blow or breaker trip, rapidly disconnecting the fault)&lt;/li&gt;&#xA;&lt;li&gt;Ensures that sufficient margin exists in the design to prevent arc-over from primary to secondary even under  less-than-clean environments (toner dust is a particularily nasty gap-bridger)&lt;/li&gt;&#xA;&lt;li&gt;Reduces the 'stiffness' of the power source - a small transformer will saturate out much more quickly than the mains, which also has the effect of driving the primary current higher and activating some sort of safety device (fuse, breaker, etc.)&lt;/li&gt;&#xA;&lt;li&gt;Regulatory organizations require it in most applications: IEC 60950, CSA C22.2, etc.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-15T17:55:19.590" />
  <row Id="6776" PostTypeId="2" ParentId="6740" CreationDate="2010-11-15T18:02:23.223" Score="1" ViewCount="" Body="&lt;p&gt;MTBF is assurance that reasonable derating guidelines are met. Nothing more. An MTBF of 250k hours does not mean any single piece of equipment will last 30 years. It's possible to get that sort of MTBF on equipment that uses electrolytic capacitors, which almost certainly will dry out in much less time than that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Drive the LED with the minimum amount of current that provides a useful amount of 'signal' (i.e. is viewable under whatever conditions you deem inportant.) The LED manufacturer should have datasheet information about operating current / temperature rise / ambient temperature, so you can judge how 'hard' you're driving it and make your own decision about reliability.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-15T18:02:23.223" />
  <row Id="6777" PostTypeId="2" ParentId="6748" CreationDate="2010-11-15T18:28:00.270" Score="2" ViewCount="" Body="&lt;p&gt;As Mark said, if you want to look at the distortion of a 20kHz sine wave with 1Vpp you get about 0.125V/us every Vpp. It depends how much your output peak-peak is. Because your amplification is only 5 times, I don't think you're going for 30Vpp but more something like 10Vpp? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because you're amplifying audio, you could use an AC coupling so you don't have to worry about the offset very much.   The noise can be significant, but not with these amplifications. You can calculate the RMS noise RTI according to your bandwidth:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e_noise = sqrt(Bandwidth) * NoiseFigure (nV/sqrt(Hz))&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So your Bandwidth = 20kHz (ideal situation, a simple low pass will add penalties), your noise figure is for example 50nV/rt Hz (not counting 1/f noise), which means your RTI (input) noise RMS value is 7.071uV. If you amplify the signal by 5 times, you RTO (Output) noise, taking away external noise sources (resistors, etc.) you get 35.4uV rms noise added. At this gain and bandwidth, that isn't very much, but please note that your input noise (from the source) may already be 120uV, which means you would get 0.6mV RMS noise at the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Noise becomes a significant factor at high gain and/or higher bandwidths.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-11-15T18:28:00.270" CommentCount="1" />
  <row Id="6778" PostTypeId="1" AcceptedAnswerId="6780" CreationDate="2010-11-15T20:06:06.470" Score="4" ViewCount="283" Body="&lt;p&gt;I have this crazy idea of using a computer SMPS with active PFC boost to take high voltage DC battery banks (144V+) and drop it down to 3.3V, 5V and 12V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my thinking: the power supply internally rectifies the AC to DC, and the PFC boost should then boost the 144V to an acceptable 350V-400V for the power supply. The 144V input is okay for it because it falls in the 100VAC range, and most are rated down to 85VAC if not lower. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not looking for a guaranteed solution - it's a one-off problem I'm trying to solve, but I think it could be a cheap and viable solution.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-25T03:31:53.587" Title="Would this work? Using a computer SMPS as a DC-DC converter." Tags="&lt;smps&gt;&lt;dc-dc&gt;" AnswerCount="8" CommentCount="4" FavoriteCount="0" />
  <row Id="6779" PostTypeId="2" ParentId="6712" CreationDate="2010-11-15T20:12:33.047" Score="2" ViewCount="" Body="&lt;p&gt;I know this is gross simplification, but the way I always looked at it was; over voltage breaks down the insulation layer between conductors and damages devices, over current damages the conductors themselves primarily through over heating. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-11-15T20:12:33.047" />
  <row Id="6780" PostTypeId="2" ParentId="6778" CreationDate="2010-11-15T20:26:22.467" Score="2" ViewCount="" Body="&lt;p&gt;I would not rely on the AC fuses in the PSU - you probably have some HVDC fuses kicking about with that much battery to hand anyway :-)&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2010-11-15T20:26:22.467" CommentCount="2" />
  <row Id="6781" PostTypeId="1" AcceptedAnswerId="6784" CreationDate="2010-11-15T20:50:18.587" Score="2" ViewCount="123" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I am controlling two stepper motors in from a Genie Microcontroller and driving them by a ULN2803A. I want to know what is the shortest time i can change the phase. Is it dependent on the ULN2803A?&lt;br&gt;&#xA;Thanks in Advance,&lt;br&gt;&#xA;Dean&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-11-15T21:27:44.917" Title="Controlling Stepper Motors" Tags="&lt;genie&gt;&lt;stepper-motor&gt;" AnswerCount="1" />
  <row Id="6782" PostTypeId="1" AcceptedAnswerId="6785" CreationDate="2010-11-15T21:18:46.980" Score="3" ViewCount="193" Body="&lt;p&gt;I'm looking for a right-angle PCB board mate for the standard 12V hobby battery connectors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where can I find these connectors?&lt;/p&gt;&#xA;" OwnerUserId="1960" LastActivityDate="2010-11-16T10:26:40.697" Title="What are the standard connectors used on 12V hobby batteries?" Tags="&lt;pcb&gt;&lt;battery&gt;&lt;connector&gt;&lt;12v&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="6784" PostTypeId="2" ParentId="6781" CreationDate="2010-11-15T21:27:44.917" Score="6" ViewCount="" Body="&lt;p&gt;The maximum rate you can move a stepper motor is based on the shaft torque and coil current.  Attempting to move too fast against too high a torque will cause the motor to become desynchronized with the step impulses and move unpredictably/uncontrollably.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a generalized graph:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2XTRn.jpg&quot; alt=&quot;Stepper motor graph&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The whole curve shifts up and down with current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most drivers' speed will be orders of magnitude faster than any motor, the few exceptions are things with a bunch of protection/intelligence (of which the Darlington driver you linked has neither)&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-15T21:27:44.917" CommentCount="1" />
  <row Id="6785" PostTypeId="2" ParentId="6782" CreationDate="2010-11-15T21:39:14.203" Score="2" ViewCount="" Body="&lt;p&gt;Also called the &lt;strong&gt;&quot;(Standard or Large) Tamiya Connector&quot;&lt;/strong&gt; in R/C speak (&lt;a href=&quot;http://www.batteryspace.com/connectoradaptorstandardmaletamiyaconnectorwith14awgwires5long.aspx&quot; rel=&quot;nofollow&quot;&gt;ref&lt;/a&gt;); not sure if other manufacturers make them (guaranteed someone somewhere does), but here are the &lt;a href=&quot;http://www.molex.com/&quot; rel=&quot;nofollow&quot;&gt;Molex&lt;/a&gt; part numbers (Digi-Key) &lt;em&gt;for the Wire-to-Wire connectors&lt;/em&gt;:&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Device Side (usually)&lt;/h3&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Plug - 35143-0201 (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=WM2308-ND&quot; rel=&quot;nofollow&quot;&gt;WM2308-ND&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;li&gt;Socket - 35728-0201 (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=WM2311-ND&quot; rel=&quot;nofollow&quot;&gt;WM2311-ND&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;h3&gt;Battery Side&lt;/h3&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Cap - 35141-0201 (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&amp;amp;site=US&amp;amp;WT.z_homepage_link=hp_go_button&amp;amp;KeyWords=WM2309-ND&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;WM2309-ND&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;li&gt;Pin - 35727-0201 (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=WM2310-ND&quot; rel=&quot;nofollow&quot;&gt;WM2310-ND&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Molex does not make this style in Wire-to-Board; so any knockoffs of just Molex product probably won't either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An easy-to-use replacement with both Wire-to-Wire and Wire-to-Board that I've used are the Molex Mini MATE-N-LOK 2 connectors (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&amp;amp;lang=en&amp;amp;site=us&amp;amp;keywords=A32471&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;like these&lt;/a&gt;), depending on the current you may need regular MATE-N-LOK.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-15T21:52:00.123" LastActivityDate="2010-11-15T21:52:00.123" />
  <row Id="6786" PostTypeId="2" ParentId="6713" CreationDate="2010-11-15T21:45:07.630" Score="3" ViewCount="" Body="&lt;p&gt;The capacitance forms a resolver allowing you read a sin and cos value that when compared to the master signal lets you determine the position very accurately.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a good web &lt;a href=&quot;http://www.biotele.com/digital_caliper.htm&quot; rel=&quot;nofollow&quot;&gt;page&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-11-15T21:45:07.630" />
  <row Id="6787" PostTypeId="2" ParentId="6615" CreationDate="2010-11-15T22:41:42.293" Score="1" ViewCount="" Body="&lt;p&gt;I wouldn't do it, for the simple reason that it is a lie.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But more than that, it (like any lie) is grounds for termination the moment anyone at the company has a problem with you.  Best to put &quot;BS in Physics, addiction to electronics&quot; or something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no degree in software, and don't put &quot;Software Engineer&quot; on my resume even though I have over 20 years professional experience in the field.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(By the way I normally put something tongue-in-cheek like &quot;Software God&quot; or &quot;Bit wrangler&quot; on my resume - some people think it's unprofessional, but HR people &lt;strong&gt;remember&lt;/strong&gt; me. :)&lt;/p&gt;&#xA;" OwnerUserId="1961" LastActivityDate="2010-11-15T22:41:42.293" CommentCount="1" />
  <row Id="6788" PostTypeId="1" AcceptedAnswerId="6794" CreationDate="2010-11-15T23:07:28.497" Score="3" ViewCount="67" Body="&lt;p&gt;In Electronics class today we were using a TL081 op-amp. When I disconnected the inverting and noninverting inputs, the op-amp's output (driving an LED) started switching on and off rapidly. What causes these weird oscillations?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-15T23:45:52.153" Title="Why does my op-amp swing randomly when the inputs are disconnected?" Tags="&lt;op-amp&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="6789" PostTypeId="1" AcceptedAnswerId="6795" CreationDate="2010-11-15T23:11:46.997" Score="6" ViewCount="263" Body="&lt;p&gt;Why are power supplies almost always made using through hole components? Every computer PSU I've taken apart uses through hole components, though occasionally (not in all cases) surface mount components are found on the bottom. Don't these have to be hand assembled? (before reflow or wave soldering) If so, why are they still doing this, even though labour costs are low in China, it still must cost less for a machine to pick and place SMT stuff... or am I missing something?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-16T06:45:34.197" Title="Why are power supplies almost always made using through hole components?" Tags="&lt;surface-mount&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="6790" PostTypeId="1" AcceptedAnswerId="6808" CreationDate="2010-11-15T23:17:57.863" Score="5" ViewCount="513" Body="&lt;p&gt;Is it possible to control a bicolor LED with just one pin of a microcontroller?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instinct says NO, because you can have one end grounded and the other going to the micro's pin, allowing you to turn it on or off but not change its color.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But maybe someone has a better idea?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-16T13:06:50.220" Title="Control a bicolor LED with just one pin." Tags="&lt;led&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="6791" PostTypeId="2" ParentId="6790" CreationDate="2010-11-15T23:29:47.903" Score="3" ViewCount="" Body="&lt;p&gt;If you didn't need an off state, and your Voh was sufficiently large (edit: to overcome the forward bias voltage of the LED), you might be able to hook one end of the LED to a mid-rail voltage.  Outputting a 1 gets one color, outputting a 0 gets the other color.  To turn it off...ha, good luck.  Maybe you could try putting a capacitor in there, and then driving the output with a PWM that the cap would smooth out to mid-rail?&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-11-15T23:29:47.903" CommentCount="11" />
  <row Id="6792" PostTypeId="2" ParentId="1754" CreationDate="2010-11-15T23:31:45.887" Score="3" ViewCount="" Body="&lt;p&gt;You may enjoy an article series I wrote on this long ago for Circuit Cellar magazine,&#xA;&lt;a href=&quot;http://fpgacpu.org/xsoc/cc.html&quot; rel=&quot;nofollow&quot;&gt;Building a RISC System in an FPGA&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Happy hacking!&lt;/p&gt;&#xA;" OwnerUserId="1962" LastActivityDate="2010-11-15T23:31:45.887" CommentCount="1" />
  <row Id="6793" PostTypeId="2" ParentId="6778" CreationDate="2010-11-15T23:40:32.827" Score="0" ViewCount="" Body="&lt;p&gt;Is cost a factor?  If not, then how about using the batteries in series-parallel to get 24VDC and using a PSU that is made for 24VDC?   I had this setup some time ago when I had 5 machines running in a 19&quot; rack.  Worked quite well as a very efficient UPS.  (Although the 24VDC PSUs are more expensive than standard ones)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just ran a very simple step-down/rectify/regulate circuit to trickle-charge the batteries.&lt;/p&gt;&#xA;" OwnerUserId="1961" LastActivityDate="2010-11-15T23:40:32.827" CommentCount="1" />
  <row Id="6794" PostTypeId="2" ParentId="6788" CreationDate="2010-11-15T23:45:52.153" Score="7" ViewCount="" Body="&lt;p&gt;Op-amps are very high gain differential amplifiers, with high input impedance. A few millivolts difference between the disconnected inputs can be enough to drive the output to one rail or the other. So chances are your amp is picking up noise enough from the environment to drive it one way and another.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-15T23:45:52.153" />
  <row Id="6795" PostTypeId="2" ParentId="6789" CreationDate="2010-11-15T23:47:27.820" Score="13" ViewCount="" Body="&lt;p&gt;Because PSUs use many big lumpy parts that are not SMDable and/or need good mechanical fixing. Also, for minimum cost they like to use single-layer PCBs - TH is a little more amenable to this as parts act as jumpers over tracks. TH parts can be machine-inserted - e.g. &lt;a href=&quot;http://www.youtube.com/watch?v=eOQ3pZkKX24&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=eOQ3pZkKX24&lt;/a&gt; (30kparts/hour!)&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-15T23:47:27.820" CommentCount="2" />
  <row Id="6796" PostTypeId="2" ParentId="6789" CreationDate="2010-11-15T23:49:27.660" Score="2" ViewCount="" Body="&lt;p&gt;The power dissipation for a component is much higher for TH. They get better airflow from fans also.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-15T23:49:27.660" />
  <row Id="6797" PostTypeId="2" ParentId="6789" CreationDate="2010-11-15T23:50:51.853" Score="6" ViewCount="" Body="&lt;p&gt;Half the parts are too big or for other reasons can't be re-flowed (power dissipation, etc) and the cost of doing a re-flow run and a hand process run is higher than just doing it all by hand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would be amazed how cheap hand soldering is in Asia.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-15T23:50:51.853" CommentCount="6" />
  <row Id="6801" PostTypeId="2" ParentId="6778" CreationDate="2010-11-16T04:08:48.103" Score="3" ViewCount="" Body="&lt;p&gt;Technically, any DC power supply powered from a PFC stage &lt;em&gt;is&lt;/em&gt; a DC-DC converter, so your idea has some merit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It mainly depends on the PFC controller IC. Simple ones (which look only at bulk DC for UVLO) should run. More complex ones which sample the input AC for waveform shaping may not work if 'correct' waveforms are absent. YMMV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The input bridge AC rating shouldn't be far off from it's DC rating. You'd be passing all the power through two diodes, mind you, so they may get hotter than you'd expect (under AC, each pair of diodes in the bridge gets a break every half-cycle). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The warnings about DC fuse ratings are 100% correct. Batteries can be nasty.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there's some exotic auxiliary supply (quasi resonant) that is expecting sinusoidal AC in, the whole thing may not start. Most ATX supplies aren't exotic, so I expect that the aux converter would be powered from the bulk DC voltage which should be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-16T04:08:48.103" />
  <row Id="6802" PostTypeId="2" ParentId="1754" CreationDate="2010-11-16T05:39:27.573" Score="3" ViewCount="" Body="&lt;p&gt;A lot depends on what is your purpose of studying the code? In other words, what does &lt;em&gt;interesting&lt;/em&gt; mean to you?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are doing it in order to see how much complexity can go into a CPU, you may be more interested in studying the source of &lt;a href=&quot;http://www.opensparc.net/&quot; rel=&quot;nofollow&quot;&gt;OpenSPARC&lt;/a&gt; architectures. It will take a long time to dive in but you will get an appreciation for the overall &lt;strong&gt;big picture&lt;/strong&gt; view of a complex microprocessor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, if it is to study specific computer microarchitecture features, you will want to look at some straightforward RISC machines like the &lt;a href=&quot;http://www.aeste.my/aemb&quot; rel=&quot;nofollow&quot;&gt;AEMB&lt;/a&gt;, a small and fast &lt;strong&gt;multi-threaded&lt;/strong&gt; 32-bit RISC processor (shameless plug). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, if what you want is to learn good coding styles and conventions, the LEON2 design is a good place to learn good VHDL coding style.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if your purpose in studying a processor is to learn how to design one yourself, your best bet would be to start with one of the simple 8-bit machines (there are many AVR, 8051, PIC examples on the net).&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2010-11-16T05:39:27.573" />
  <row Id="6803" PostTypeId="2" ParentId="6789" CreationDate="2010-11-16T06:45:34.197" Score="5" ViewCount="" Body="&lt;p&gt;One last reason that I haven't seen here (And it's likely the most relevant one): &lt;/p&gt;&#xA;&#xA;&lt;p&gt;SMD components are too small.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mean literally. When you're dealing with high voltage, you have to worry about &lt;a href=&quot;http://en.wikipedia.org/wiki/Creepage#Design&quot; rel=&quot;nofollow&quot;&gt;flashover/board creepage&lt;/a&gt; distances, which means that the connections for high voltage have to be separated by a certain amount (There are standards for this, which are required to get UL or similar ratings).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With 240V AC, the distance is (off the top of my head) ~.25&quot;, which is far larger then even 1206 parts.&lt;br&gt;&#xA;This is also the explanation behind the slots cut into the PCB, which you often see under optocouplers/input filter caps. Basically, to pass testing, the separation on the component's leads is not great enough, so they have to actually mill slots the board. This increases the overall path-length between component pins on the PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lastly, most of the power devices are through hole because through hole packages can dissipate more power than SMT parts. It's much easier and cheaper to mount a TO-220 package to a cheap extruded aluminium heatsink then have a board with very thick copper fabbed that can dissipate the same amount of power from a TO-263 device.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-11-16T06:45:34.197" CommentCount="2" />
  <row Id="6804" PostTypeId="2" ParentId="6790" CreationDate="2010-11-16T07:26:45.860" Score="1" ViewCount="" Body="&lt;p&gt;You can &lt;a href=&quot;http://en.wikipedia.org/wiki/Charlieplexing&quot; rel=&quot;nofollow&quot;&gt;Charlieplex&lt;/a&gt; it&lt;/p&gt;&#xA;" OwnerUserId="1832" LastActivityDate="2010-11-16T07:26:45.860" CommunityOwnedDate="2010-11-16T07:27:26.060" CommentCount="4" />
  <row Id="6805" PostTypeId="1" AcceptedAnswerId="6807" CreationDate="2010-11-16T08:05:00.490" Score="6" ViewCount="346" Body="&lt;p&gt;Hey all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to use a simple non-inverting amp circuit in a small project I am working on. The project is battery powered, so naturally the only voltage I have access to is 3.3v. My question is: how should I get the voltage for the -ve rail? Of course I can add a DC-DC converter but I'm sure this is already a solved problem so I figured I'd ask first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="417" LastActivityDate="2010-11-16T15:43:33.427" Title="using an op amp in a battery powered circuit" Tags="&lt;battery&gt;&lt;op-amp&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="6806" PostTypeId="1" CreationDate="2010-11-16T08:18:22.457" Score="0" ViewCount="70" Body="&lt;p&gt;Hi,&#xA;who of you in this forum uses R (&lt;a href=&quot;http://www.r-project.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.r-project.org/&lt;/a&gt;) with the multicore, SNOW or CUDA packages, so for advanced calculations that need more power than a workstation CPU? On which hardware do you compute?&#xA;The background of these questions is the following: I am currently writing my M.Sc. thesis about R and High-Performance-Computing and need a strong knowledge about who actually uses R.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for you anwers!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;heinrich&lt;/p&gt;&#xA;" OwnerUserId="1965" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T21:02:07.297" LastActivityDate="2011-04-27T21:02:07.297" ClosedDate="2010-11-16T09:38:44.887" Title="Who uses R with multicore, SNOW or CUDA package?" Tags="&lt;robotics&gt;&lt;math&gt;&lt;r&gt;" CommentCount="4" />
  <row Id="6807" PostTypeId="2" ParentId="6805" CreationDate="2010-11-16T08:42:32.243" Score="10" ViewCount="" Body="&lt;p&gt;It's common in modern battery-powered audio electronics not to reference audio to 'true' ground, with +/- supply rails.  Instead, you make an audio reference half way between ground and your voltage rail (often with a pair of resistors and a buffer of some kind).  Then you arrange your audio signal to swing either side of this mid-rail reference - one tends to end up with quite a lot of series coupling capacitors to let you shift the DC point of the signal around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, if you don't like that (and there are reasons not to - getting the reference quiet enough and stiff enough can be a pain, as can the series caps, and at 3v3 you're fairly short of headroom once you've cut it in half), then a -ve rail can be produced using a charge-pump device like a MAX660 (there are lots of other sources for basically the same part) - that's a lot simpler than a full-up DC-DC converter.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-16T08:42:32.243" CommentCount="4" />
  <row Id="6808" PostTypeId="2" ParentId="6790" CreationDate="2010-11-16T09:49:50.650" Score="5" ViewCount="" Body="&lt;p&gt;You can do this with a bi-color LED that has the two LEDs back-to-back if you connect one LED terminal to an intermediate voltage eg 2.5V on a 5V design and connect the other side to the MCU via a suitable resistor (I used 560R). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then a low output gives one colour, high gives the other and tri-state leaves the LED off. Pulse width modulation will allow you to control brightness (switching output between active and tri-state) or mix the colours (switching output low to high).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can adjust the intermediate voltage to compensate for different LED forward voltages too. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used an LM2904 op-amp to provide the intermediate voltage - it works with supply voltage down to 5V. There are plenty of other devices that can operate at lower voltages and still sink and source enough current to drive the LEDs.&lt;/p&gt;&#xA;" OwnerUserId="1897" LastActivityDate="2010-11-16T09:49:50.650" />
  <row Id="6809" PostTypeId="2" ParentId="6702" CreationDate="2010-11-16T10:09:49.830" Score="0" ViewCount="" Body="&lt;p&gt;How about piezo film sheet eg &lt;a href=&quot;http://www.meas-spec.com/product/t_product.aspx?id=2488&quot; rel=&quot;nofollow&quot;&gt;http://www.meas-spec.com/product/t_product.aspx?id=2488&lt;/a&gt; ?&lt;/p&gt;&#xA;" OwnerUserId="1897" LastActivityDate="2010-11-16T10:09:49.830" />
  <row Id="6810" PostTypeId="2" ParentId="6782" CreationDate="2010-11-16T10:26:40.697" Score="0" ViewCount="" Body="&lt;p&gt;First of all there is no standard for 12V hobby battery connectors, so if you are designing a new product or working on your own gear then by all means feel free to pick your own connector type.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have any choice at all go with Deans style connectors in stead, the Tamiya connectors are utter shit, they have comparatively high resistance and will get loose and unreliable with a little use.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-16T10:26:40.697" />
  <row Id="6811" PostTypeId="1" AcceptedAnswerId="6812" CreationDate="2010-11-16T11:44:08.277" Score="7" ViewCount="272" Body="&lt;p&gt;I found a device which has a ferrite core and 3 coils on it. It looks like some type of transformer. What would be its use? I found it in a compact fluorescent lamp.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-09T11:44:55.650" LastActivityDate="2011-04-09T11:44:55.650" Title="What is the use of transformers with 3 pairs of wires?" Tags="&lt;transformer&gt;&lt;resonant-converter&gt;&lt;compact-fluorescent-lamp&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="3" />
  <row Id="6812" PostTypeId="2" ParentId="6811" CreationDate="2010-11-16T11:59:36.073" Score="11" ViewCount="" Body="&lt;p&gt;You are looking at the transformer of a very elegant and basic resonant converter (a.k.a. Royer converter).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A very basic explanation is this: There are two windings with an equal number of turns that are used to drive two transistors, and there is one winding that connects to the lamp. During each switching cycle, at a certain current, determined by the core material and the number of turns of the winding that goes to the lamp, the transformer will saturate and thereby define the power that is transferred to the lamp. Each time a saturation event occurs, one transistor will block and the other transistor will start to conduct, which keeps the circuit oscillating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Royer converter was invented long before switch-mode power supplies were the norm for power conversion circuits and is still very popular. Considering its age, it is amazing that efficiencies of &gt; 85 % can be achieved easily.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good application note with many details can be found here: &lt;a href=&quot;http://www.nxp.com/documents/application_note/AN00048.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.nxp.com/documents/application_note/AN00048.pdf&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also an article on Wikipedia: &lt;a href=&quot;http://en.wikipedia.org/wiki/CCFL_inverter&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/CCFL_inverter&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another good App'note: &lt;a href=&quot;http://www.diodes.com/zetex/_pdfs/3.0/appnotes/apps/an14.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.diodes.com/zetex/_pdfs/3.0/appnotes/apps/an14.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a good manual about fixing compact flourescent lamps (CFLs). It includes many schematics: &lt;a href=&quot;http://www.en-genius.net/includes/files/col_081307.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.en-genius.net/includes/files/col_081307.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The original reference to the circuit is here:&#xA;Bright, Pittman and Royer, “Transistors As On-Off Switches in Saturable Core Circuits,” Electrical Manufacturing, December 1954.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2010-11-16T12:40:28.643" LastActivityDate="2010-11-16T12:40:28.643" CommentCount="2" />
  <row Id="6813" PostTypeId="2" ParentId="6811" CreationDate="2010-11-16T12:00:52.493" Score="7" ViewCount="" Body="&lt;p&gt;Transformers can have any number of coils. Usually only one of them is used to put power into the core, and is called the primary, while the others take power out and are called secondaries. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can have as many secondaries as you need. One thing you can do with two secondaries is to make isolated supply sections. Another purpose is not so much to pull power out, but feedback signals, which can be used to drive an oscillator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course I went and said 'usually' only one of them is used to put power in. There are cases where two coils can be used to put power in. So called Push-Pull amplifier sections do this, as do some DC to AC inverters.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-16T12:00:52.493" />
  <row Id="6814" PostTypeId="2" ParentId="6790" CreationDate="2010-11-16T13:06:50.220" Score="3" ViewCount="" Body="&lt;p&gt;Check out &lt;a href=&quot;http://www.neufeld.newton.ks.us/electronics/?p=151&quot; rel=&quot;nofollow&quot;&gt;http://www.neufeld.newton.ks.us/electronics/?p=151&lt;/a&gt;, which discusses driving a two-lead bicolor LED from a single pin using a resistor divider.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-16T13:06:50.220" CommentCount="3" />
  <row Id="6815" PostTypeId="1" AcceptedAnswerId="6833" CreationDate="2010-11-16T13:25:56.340" Score="1" ViewCount="181" Body="&lt;p&gt;At the moment I'm using an amplifier based around a NPN transistor and some resistors. Its configuration is as an emitter follower. Pin 25 supplies internal audio from a DAC on the chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://super-osd.googlecode.com/hg/hardware/V3%20Lite/OSD.png&quot; rel=&quot;nofollow&quot;&gt;See this schematic, on the righthand side&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This handles DC offset (offsetting the AC signal into a DC signal), overvoltage input protection, switching between internal/external audio, and output. It is a bit distorted, but it works well. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally, I'd like to integrate this on to one or two IC's with the minimum space usage. It'd be nice if cost was lower, but this is not critical. (Currently component cost is around $2.50 total for all components in the audio amp, in low quantities.) Also, it would be ideal if the IC did not require a dual rail power supply.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-16T15:44:56.027" LastActivityDate="2010-11-16T16:22:43.693" Title="Smallest audio amplifier?" Tags="&lt;amplifier&gt;" AnswerCount="2" CommentCount="9" />
  <row Id="6816" PostTypeId="1" AcceptedAnswerId="6823" CreationDate="2010-11-16T13:46:19.000" Score="2" ViewCount="159" Body="&lt;p&gt;No matter where I look I can't find any bicolor red-green LED's in 0603 packages. I'm thinking that they might not exist because the package is too small. Does anyone know of any bicolor LED's in 0603? Power output is not critical - these will be used as indicators.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please note bi-color in this sense means two LEDs in inverse parallel and not two LEDs in a package with distinct pins. &lt;a href=&quot;http://www.play-hookey.com/digital/experiments/bicolor_led.html&quot; rel=&quot;nofollow&quot;&gt;See here for a definition&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-16T14:57:21.213" LastActivityDate="2010-11-16T14:57:21.213" ClosedDate="2010-11-16T15:42:53.170" Title="Bicolor LED in 0603" Tags="&lt;led&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="6817" PostTypeId="1" AcceptedAnswerId="6820" CreationDate="2010-11-16T14:23:13.227" Score="3" ViewCount="170" Body="&lt;p&gt;Currently, I'm using standard headers with a pitch of 2.54mm (0.1&quot;). These are quite big on my boards. Are there any surface mount standard headers, say in 0.05&quot;?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-16T16:40:35.113" Title="Standard small header size" Tags="&lt;pcb&gt;&lt;header&gt;" AnswerCount="4" />
  <row Id="6818" PostTypeId="1" AcceptedAnswerId="6819" CreationDate="2010-11-16T14:32:05.060" Score="2" ViewCount="101" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/2209/jtag-cable-and-device-interchangeability&quot;&gt;JTAG cable and device interchangeability&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I've seen a lot of JTAG ports on a lot of equipment but none seem to have a standard pin out. Can it be arbitrary, or should a standard one be used?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-16T14:57:40.773" ClosedDate="2010-11-16T15:41:45.857" Title="Standard pin out for JTAG" Tags="&lt;jtag&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="6819" PostTypeId="2" ParentId="6818" CreationDate="2010-11-16T14:42:21.957" Score="1" ViewCount="" Body="&lt;p&gt;The signals are defined (although some of them are optional), but the connector and pinout are not. &lt;a href=&quot;http://www.etoolsmiths.com/blog/jtag-connector-pinouts/&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; are some examples. A 20-pin connector seems to be fairly universal for ARM JTAG.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-16T14:42:21.957" CommentCount="2" />
  <row Id="6820" PostTypeId="2" ParentId="6817" CreationDate="2010-11-16T14:45:49.850" Score="4" ViewCount="" Body="&lt;p&gt;Samtec has a pretty wide range of small headers. 0.050&quot; pitch is a standard size. They probably go smaller as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few examples:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://samtec.com/ProductInformation/TechnicalSpecifications/Overview.aspx?series=FTS&quot; rel=&quot;nofollow&quot;&gt;male headers&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://samtec.com/ProductInformation/TechnicalSpecifications/Overview.aspx?series=FLE&quot; rel=&quot;nofollow&quot;&gt;surface mount sockets&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-16T14:45:49.850" CommentCount="2" />
  <row Id="6821" PostTypeId="2" ParentId="6765" CreationDate="2010-11-16T14:45:59.457" Score="2" ViewCount="" Body="&lt;p&gt;Once upon a time you might have been able to get a weak voltage from soggy newspapers. The ink that was used had small amounts of various metals that would be conductors. The paper itself was bleached and certain amount would not get rinsed out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Today the ink is soy based, it does not contain any metal. The paper has little if any chemicals left in it from processing. You could add metal as electrodes and add a electrolyte like acetic acid (citrus juice), but if you do that you don't need the newspaper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There has been some attempts to use cellulose (paper) with carbon nano tubes suspended in ink for manufacturing batteries, but this is much more the wet newspapers. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-11-16T14:45:59.457" CommentCount="1" />
  <row Id="6822" PostTypeId="2" ParentId="6817" CreationDate="2010-11-16T14:48:57.940" Score="1" ViewCount="" Body="&lt;p&gt;If you want really small board-board and board-cable connectors (down to 0.4 mm pitch), have a look at Hirose.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-16T14:48:57.940" />
  <row Id="6823" PostTypeId="2" ParentId="6816" CreationDate="2010-11-16T14:50:50.747" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=516-1419-1-ND&quot; rel=&quot;nofollow&quot;&gt;Here's one&lt;/a&gt; on DK, Kingbright has &lt;a href=&quot;http://www.kingbrightusa.com/category.asp?catalog_name=LED&amp;amp;category_name=KCTop-Emitting+Bi-Color+SMD+LED&amp;amp;Page=5&amp;amp;orderby=&quot; rel=&quot;nofollow&quot;&gt;others&lt;/a&gt; (1.6x0.8mm).&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-16T14:50:50.747" CommunityOwnedDate="2010-11-16T14:51:27.267" CommentCount="6" />
  <row Id="6824" PostTypeId="2" ParentId="6818" CreationDate="2010-11-16T14:55:19.793" Score="0" ViewCount="" Body="&lt;p&gt;Here's a good collection of JTAG pinouts:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.jtagtest.com/pinouts/&quot; rel=&quot;nofollow&quot;&gt;http://www.jtagtest.com/pinouts/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-16T14:55:19.793" CommentCount="1" />
  <row Id="6826" PostTypeId="2" ParentId="6805" CreationDate="2010-11-16T15:43:33.427" Score="2" ViewCount="" Body="&lt;p&gt;Will is correct, but on the other hand if this project isn't audio or simply doesn't require positive and negative voltages then you just need to use an op-amp that can operate with unbalanced supplies such as (pulls random op-amp out of digikey) LT1494IN8.  You just connect -ve to ground and +ve to your rail and you're good.  You are of course limited to your voltage range for output (0-12V or whatever your battery is) so if you are using audio you'd need to do what Will says, but if you just want to amplify something you can use this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm sure this is a typical question BTW.  When I was in school they never let on that single-supply op-amps existed.  We always used +/-15V and I always figured that was the only way to use op-amps.  But positive and negative supplies are so uncommon in the real world that it pays to learn about these things.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-16T15:43:33.427" CommentCount="3" />
  <row Id="6827" PostTypeId="2" ParentId="6815" CreationDate="2010-11-16T15:45:22.343" Score="2" ViewCount="" Body="&lt;p&gt;You don't need to MUX audio.  Just mix the two audio sources together.  Maybe have the external audio muted. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why are you using a discrete-transistor buffer?  Use an op-amp for a buffer.  Better sound quality, fewer components, smaller overall footprint.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a design that does what you want.  To amplify external audio, switch the micro pin to an analog input.  Switch it to a DAC output to amplify internal audio.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Input voltage 1Vdc+1Vp-p&lt;/li&gt;&#xA;&lt;li&gt;Output voltage 1Vp-p&lt;/li&gt;&#xA;&lt;li&gt;Load impedance 600 ohms&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The value of C1 depends on the lower limit of frequency you care to amplify.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/sRplQ.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-11-16T16:19:32.763" LastActivityDate="2010-11-16T16:19:32.763" CommentCount="9" />
  <row Id="6828" PostTypeId="2" ParentId="2209" CreationDate="2010-11-16T15:49:40.400" Score="3" ViewCount="" Body="&lt;p&gt;It would be best to match your tool.  &lt;a href=&quot;http://www.jtagtest.com/pinouts/&quot; rel=&quot;nofollow&quot;&gt;This site&lt;/a&gt; lists quite a few (doesn't have any references, so double-checking is an absolute must before you lay it out)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For AVRs, &lt;a href=&quot;http://www.jtagtest.com/pinouts/avr&quot; rel=&quot;nofollow&quot;&gt;their recommended pinout&lt;/a&gt; matches what the &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2562.pdf&quot; rel=&quot;nofollow&quot;&gt;AVR JTAGICE mkII&lt;/a&gt; uses (see page 3).&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-16T15:49:40.400" />
  <row Id="6829" PostTypeId="2" ParentId="6778" CreationDate="2010-11-16T15:49:41.173" Score="2" ViewCount="" Body="&lt;p&gt;Someone once claimed that it was possible to supply 170V DC directly to a computer power supply (switch-mode) and it would work as normal.  I can only see this succeeding if the power supply has no transformer (I don't know if this is common for SMPS computer power supplies).  Otherwise if it's isolated the DC won't do anything and the power supply won't work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if it does work then you have nothing to worry about.  Fully-rectified AC is about 170VDC with ripple.  It won't hurt to remove the ripple and the power supply will work as normal.  I'm fairly sure that 144VDC would be sufficient as well, but the power supply might have to work a bit harder.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should have no problem with this as long as the supply has no transformer  But put some fuses in - I'll bet your battery pack can supply some insane current.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-16T15:49:41.173" CommentCount="4" />
  <row Id="6830" PostTypeId="1" AcceptedAnswerId="6831" CreationDate="2010-11-16T15:50:06.773" Score="1" ViewCount="197" Body="&lt;p&gt;In what way is a Craft Port different from a conventional RS-232 Port? It seems to be similar. Are there any interface or other important differences? Does craft port imply a higher level protocol on top of RS-232 as well?&lt;/p&gt;&#xA;" OwnerUserId="1968" LastActivityDate="2010-11-16T16:01:07.707" Title="In what way is a Craft Port different from a conventional RS-232 Port" Tags="&lt;rs232&gt;" AnswerCount="2" />
  <row Id="6831" PostTypeId="2" ParentId="6830" CreationDate="2010-11-16T15:57:50.977" Score="1" ViewCount="" Body="&lt;p&gt;Quick search reveals that it may be essentially a marketing term for Analog Devices series of RS-232 transceivers meant for low-power portable applications.  This web page seems to corroborate: &lt;a href=&quot;http://forum.wordreference.com/showthread.php?t=1944943&quot; rel=&quot;nofollow&quot;&gt;http://forum.wordreference.com/showthread.php?t=1944943&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a datasheet for one of their CraftPort devices: &lt;a href=&quot;http://www.analog.com/static/imported-files/data_sheets/ADM101E.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.analog.com/static/imported-files/data_sheets/ADM101E.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So in short, it doesn't seem to be a protocol, but instead the name of the transceiver line.  Shouldn't be any different from regular RS-232.  I guess people like the sound of the name and use it on their products.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ah, one edit:  It seems that the output voltage levels are +/4.2V and it allows full +/-15V input.  Some 'RS-232' transceivers don't like the full +/-15V range and only produce 0-5V output.  This is a step above those in terms of compatibility with the true RS-232 standard, which is not often completely met nowadays in terms of input/output voltages.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-16T15:57:50.977" CommentCount="2" />
  <row Id="6832" PostTypeId="2" ParentId="6830" CreationDate="2010-11-16T16:01:07.707" Score="0" ViewCount="" Body="&lt;p&gt;From &lt;a href=&quot;http://www.experts-exchange.com/Networking/Misc/Q_20115107.html&quot; rel=&quot;nofollow&quot;&gt;this Expert sexchange question&lt;/a&gt; (scroll to bottom):&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;A craft interface is a direct connection to a device, usually, as you have read, through an RS232 port using an RJ45 type connector or a DB9 or DB25 connector. This interface provides access to a command line for the purpose of configuring the device or diagnosing problems, or for whatever reason the &quot;user traffic&quot; interfaces are inaccessible. In any event, the craft interface provides access to diagnostic and configuration functions.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;It sounds like you provided the proper answer, where &quot;Craft&quot; is just a protocol that sits on top of lower level links--RS-232 perhaps being the most common.  Perhaps analogous to &lt;a href=&quot;http://en.wikipedia.org/wiki/Hayes_command_set&quot; rel=&quot;nofollow&quot;&gt;AT commands&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-16T16:01:07.707" />
  <row Id="6833" PostTypeId="2" ParentId="6815" CreationDate="2010-11-16T16:03:17.660" Score="2" ViewCount="" Body="&lt;p&gt;If you really need to mux the inputs, how about something like this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Z5G0C.jpg&quot; alt=&quot;mux and buffer&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since your DAC output is already DC biased, if the bias it uses is provided on another pin, you could eliminate the cap and resistor for the DAC output, and use that pin as the bias for the other input.  Otherwise use one of these:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/yIERi.png&quot; alt=&quot;DC bias source&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on what your inputs and outputs are connected to, you might need grounded resistors on the other side of the coupling caps, RF bypass caps to ground, etc.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-16T16:22:43.693" LastActivityDate="2010-11-16T16:22:43.693" CommentCount="2" />
  <row Id="6834" PostTypeId="2" ParentId="6817" CreationDate="2010-11-16T16:33:48.437" Score="1" ViewCount="" Body="&lt;p&gt;2mm pitch is the next 'standard' down from 2.54.  And though it &lt;em&gt;sounds&lt;/em&gt; like it's not that much smaller, it really is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may find that 0.05&quot; (1.25-ish mm) is really &lt;em&gt;too&lt;/em&gt; small for a lot of stuff, particularly prototype/low volume.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-16T16:33:48.437" />
  <row Id="6835" PostTypeId="1" AcceptedAnswerId="6838" CreationDate="2010-11-16T16:39:21.917" Score="4" ViewCount="168" Body="&lt;p&gt;I would like to use a Arduino as &quot;simulator&quot; in a training class. It would connect to an industrial controller that has 24 VDC inputs and outputs. The Arduino program would simulate the IO from a production line (sensor inputs and motor controls for example)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a shield which can interface  with 24 VDC IO? I know I could use separate relays, but I want to see if there is a better solution. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could use 12 VDC instead of 24, but nothing lower. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am considering the Arduino as cost is factor. So I want to keep the component count and price as low as I can.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-11-16T16:47:26.497" Title="24 VDC control using Arduino" Tags="&lt;arduino&gt;" AnswerCount="1" />
  <row Id="6836" PostTypeId="2" ParentId="6817" CreationDate="2010-11-16T16:40:35.113" Score="1" ViewCount="" Body="&lt;p&gt;0.100&quot; headers come in SMT versions which can save a great deal of space while still being easy to work with.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-16T16:40:35.113" />
  <row Id="6838" PostTypeId="2" ParentId="6835" CreationDate="2010-11-16T16:47:26.497" Score="2" ViewCount="" Body="&lt;p&gt;If the input impedance of the PLC/controller is fairly high, you could get away with pullups and low-side transistors for inputs (to the PLC), and run outputs through a voltage divider.  Analog inputs would be a little more complex, but a basic op-amp should work fine for that unless you need high BW signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know of a shield for this, but if you only need a couple you could get one of the stripboard/breadboard type shields and bang them out.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-16T16:47:26.497" />
  <row Id="6839" PostTypeId="1" AcceptedAnswerId="6845" CreationDate="2010-11-16T17:20:05.377" Score="14" ViewCount="599" Body="&lt;p&gt;When working with radios, I've seen the term &quot;dBm&quot;. What does this mean?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/DBm&quot; rel=&quot;nofollow&quot;&gt;wikipedia page&lt;/a&gt; gives a table showing the equivalent power in Watts. Is the dBm output just the power level of a transmitter?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How does this differ from signal strength measured in dB?&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-17T09:32:28.367" Title="What does dBm mean?" Tags="&lt;radio&gt;&lt;db&gt;&lt;dbm&gt;" AnswerCount="5" CommentCount="0" FavoriteCount="2" />
  <row Id="6840" PostTypeId="2" ParentId="6839" CreationDate="2010-11-16T17:28:24.293" Score="8" ViewCount="" Body="&lt;h3&gt; What is it?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;dBm is a dB scale relative to 1mW.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;0dBm = 1mW&lt;/p&gt;&#xA;&#xA;&lt;p&gt;30dBm = 1W = 0dBW&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Why use dBm? &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Transmit power of 20dBm is 100mW. You know something interesting. This is the max you can output with Bluetooth or Zigbee operating at 2.4GHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a transmit power is 10dB you know nothing about your power. You must know both your amplification factor, as was noted in comments, and you need to know what is being amplified.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-17T09:32:28.367" LastActivityDate="2010-11-17T09:32:28.367" CommentCount="4" />
  <row Id="6841" PostTypeId="2" ParentId="6839" CreationDate="2010-11-16T17:33:58.703" Score="2" ViewCount="" Body="&lt;p&gt;Signal strength that is measured as dB with no m usually is actually dBm. However you need to be careful because high power applications may use dBW which you have to add 30 to get from dBW to dBm (30dBm=0dBW, 60dBm=30dBW...)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Kortuk is correct that 0dBm = 1mW. But also 0dBW = 1W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;10*log(linear_ratio) is what is used to get dB.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-16T17:33:58.703" CommentCount="4" />
  <row Id="6842" PostTypeId="2" ParentId="6773" CreationDate="2010-11-16T17:44:45.617" Score="1" ViewCount="" Body="&lt;p&gt;Preliminary&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Check the footprints, especially for connectors, parts that are available in multiple packages and new footprints.&lt;/li&gt;&#xA;&lt;li&gt;Have PCB fab check your controlled impedance calculations.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Placement&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Check that the decoupling caps are where you wish.  Since they go from power to ground, it isn't obvious where they were intended to go without looking at the schematic.&lt;/li&gt;&#xA;&lt;li&gt;Check connector placement, board size, etc.  Don't forget mounting holes.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Critical Route&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Inspect every critical route, including before and after and resistors used for termination.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Full Route&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Report on all net lengths.  Check for ones that are too long.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-07T15:51:30.710" LastActivityDate="2010-12-07T15:51:30.710" CommunityOwnedDate="2011-01-11T23:04:42.447" />
  <row Id="6843" PostTypeId="2" ParentId="6839" CreationDate="2010-11-16T17:45:53.847" Score="-3" ViewCount="" Body="&lt;p&gt;dBm is with respect to 1mW being dissipated in a 600 ohm load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Being a power the conversion is 10 * log (power actual/1 mW).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it tells you how much power with respect to 1 mW is being received or transmitted.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 600 ohm is important as it considers the complete picture of actual power being transmitted by an antenna (different from what the actual power amplifier can produce) or power being received.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-16T17:45:53.847" CommentCount="7" />
  <row Id="6844" PostTypeId="2" ParentId="6839" CreationDate="2010-11-16T18:08:20.797" Score="3" ViewCount="" Body="&lt;p&gt;Dave Jones has an &lt;a href=&quot;http://www.youtube.com/watch?v=mLMfUi2yVu8&quot; rel=&quot;nofollow&quot;&gt;interesting video on decibels&lt;/a&gt;. He also discusses dBm in the video.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-16T18:08:20.797" CommentCount="1" />
  <row Id="6845" PostTypeId="2" ParentId="6839" CreationDate="2010-11-16T19:38:50.513" Score="4" ViewCount="" Body="&lt;p&gt;A &lt;em&gt;decibel is a unitless ratio and needs a reference point&lt;/em&gt;.  &lt;strong&gt;Never use it without one.&lt;/strong&gt; Especially you audio engineers! dBSPL!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the application, a signal strength may be measured in dBW or dBm.  Both being units of power with a difference of 1000, conversion between dBw and dBm can be obtained by adding or subtracting 10log(1000) or 30.  &lt;/p&gt;&#xA;" OwnerUserId="1297" LastEditorUserId="1297" LastEditorDisplayName="" LastEditDate="2010-11-16T19:45:17.840" LastActivityDate="2010-11-16T19:45:17.840" CommentCount="7" />
  <row Id="6846" PostTypeId="1" CreationDate="2010-11-16T19:42:58.467" Score="7" ViewCount="626" Body="&lt;p&gt;How much will reflected signals matter in audio applications (say between an amp and a speaker, or a pre-amp and an amp)?  Mostly with regards to fidelity and not power transfer.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the different options of matching the impedance and their pro's/cons? This can be on the output terminal, input terminal, or modifying the cable?&lt;/p&gt;&#xA;" OwnerUserId="1297" LastEditorUserId="1297" LastEditorDisplayName="" LastEditDate="2010-11-16T20:58:52.397" LastActivityDate="2011-06-02T23:02:51.353" Title="How important is impedance matching in audio applications?" Tags="&lt;audio&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="6848" PostTypeId="1" AcceptedAnswerId="6850" CreationDate="2010-11-16T20:05:01.693" Score="0" ViewCount="228" Body="&lt;p&gt;I'm considering using an AT32UC3B in my project (the Super OSD Pro version.) However, something about the datasheet has me worried.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Page 31&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;0 Wait State Access at up to 30 MHz in Worst Case Conditions&lt;/li&gt;&#xA;&lt;li&gt;1 Wait State Access at up to 60 MHz in Worst Case Conditions&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;What is a &quot;worst case condition&quot;? The output stage for my OSD needs to be able run at 60 MIPS (the processor's maximum operating frequency), and I presume a &quot;wait state&quot; means it has to wait to load data from the memory... which would limit me to &amp;lt;60 MIPS. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suppose, worst case, I could load the code into RAM and execute it from there (I presume this is possible with AVR32s?), but it still has me confused.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-16T20:43:43.760" Title="What does &quot;Wait State&quot; access mean on a MCU's datasheet and how does it affect me?" Tags="&lt;microcontroller&gt;&lt;avr&gt;" AnswerCount="3" CommentCount="9" />
  <row Id="6849" PostTypeId="2" ParentId="6848" CreationDate="2010-11-16T20:16:38.877" Score="1" ViewCount="" Body="&lt;p&gt;Often operations are going to run faster then external memory. It is saying that when you are having to load from memory you will have to have wait states. Now they have in their datasheet that it is 30MHz no wait state from flash. they do have it optimized to allow pipelined access to flash to hide the delay cycle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;you are correct that ram is an option, but you should test your algorithm and see if you have issues. If you keep your keep branch instructions out of your code it should be able to pipeline and hide the wait states. &lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-16T20:16:38.877" CommentCount="2" />
  <row Id="6850" PostTypeId="2" ParentId="6848" CreationDate="2010-11-16T20:21:16.140" Score="3" ViewCount="" Body="&lt;p&gt;The wait state is an extra bus clock cycle that is added to the memory access to allow time for the information to be extracted and appear on the processor bus.  This addition of wait states will limit your processing speed to less than 60MIPS (whatever that means).  The AVR32 has a banked/interleaved flash memory design so that the wait states are hidden for straight line code allowing it to access program flash at the full 60MHz but as soon as you execute a branch or CALL then this will break the interleaving and incur a wait state penalty.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The AVR32 can run code from its RAM but this is a somewhat limited resource on the 32B devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you REALLY need the full 60MIP operation for your code to function then you will have problems.  How will you cope with interrupts taking processor time.....&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-11-16T20:21:16.140" CommentCount="29" />
  <row Id="6851" PostTypeId="2" ParentId="6846" CreationDate="2010-11-16T20:23:21.477" Score="5" ViewCount="" Body="&lt;p&gt;Impedance matching isn't really a concern for audio frequencies and in your examples its not really preferred.  However you do need to pay attention to your input and output impedances.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You generally impedance match for 2 reasons:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Minimize Reflections - Reflections become an issue when the length of the transmission line gets into the same order as the wavelength of the signal.  There are varying rules of thumb here.  Some say worry when the length of the wire is 1/4 the wavelength, some say 1/6, 1/10 etc.  It depends on the signal and reactance of the transmission line.  In this case it really doesn't matter because the electrical wavelength of a 20khz signal is ~49,000ft.  In other words reflections are a non issue for the application your asking about.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Maximum power transfer - Matching the output impedance of a driver to the input impedance of a load allows max power transfer.  At first this sounds important for driving a speaker but there are more important considerations (see below).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Amp example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a modern amp design (active power stage, no output transformer) your actual goal is the highest dampening factor possible, among other things.  When you drive a speaker, the speaker itself actually generates current as its being driven, this should make sense considering that your driving a devices to move a coil inside a magnetic field.  In the ideal case, this wouldn't matter since the cone/coil would react instantly to the incoming signal.  In reality there is delay and overshoot of the cone due to the mechanical nature of the speaker.  As a result the speaker produces currents that are sent back at the amplifier.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To put this in simpler, more applicable terms.  A high dampening factor allows the amplifier to have better control over the speaker cone.  This is especially important near the resonance point of the speaker.  The dampening factor is (speaker resistance) / (amp output resistance) and some correction for wire resistance.  So in this case your goal is the smallest possible output resistance in the amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;line level between devices (pre amp):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again impedance matching isn't the goal.  You generally want the lowest output impedance and highest input impedance possible.  This minimizes current draw and as a result voltage drop.  This is the lowest distortion configuration and allows maximum voltage transfer.  &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-16T20:23:21.477" CommentCount="5" />
  <row Id="6852" PostTypeId="2" ParentId="6846" CreationDate="2010-11-16T20:29:54.120" Score="1" ViewCount="" Body="&lt;p&gt;The seminal article on speaker cables was written by &lt;a href=&quot;http://en.wikipedia.org/wiki/Bob_Pease&quot; rel=&quot;nofollow&quot;&gt;Bob Pease&lt;/a&gt; of National Semiconductors in 1990, titled &lt;a href=&quot;http://www.national.com/rap/Story/0,1562,3,00.html&quot; rel=&quot;nofollow&quot;&gt;&quot;What's All This Splicing Stuff, Anyhow?&quot;&lt;/a&gt;.  Read and enjoy - then get on with your life while safely ignoring the snake oil salesmen!&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-11-16T20:29:54.120" CommentCount="3" />
  <row Id="6853" PostTypeId="2" ParentId="6848" CreationDate="2010-11-16T20:43:43.760" Score="0" ViewCount="" Body="&lt;p&gt;The AVR32A architecture is a 3 stage pipeline and it doesn't look like that model supports branch prediction so any branches in your code will stall the pipeline.  Also not all instructions are single cycle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally speaking never choose a processor based on its MIPS rating.  In almost all real world scenarios you'll never get close to its theoretical peak MIPS rating.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-16T20:43:43.760" CommentCount="3" />
  <row Id="6854" PostTypeId="2" ParentId="6846" CreationDate="2010-11-16T20:44:34.123" Score="9" ViewCount="" Body="&lt;p&gt;Impedance matching is not used in modern audio electronics.  (It was used in the telephone systems that audio systems evolved from, and might have been used in vacuum tube amplifiers, but I'm not sure.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A mic output might be around 600 Ω, while mic preamp inputs are 1 kΩ or more&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A line output will be something like 100 Ω, while a line input is more like 10 kΩ.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A loudspeaker amplifier will be less than 0.5 Ω, while loudspeakers are more like 4 Ω.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In all these cases, the load impedance is significantly larger than the source; they are not matched.  This configuration maximizes fidelity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a wavelength &lt;a href=&quot;http://www3.wolframalpha.com/input/?i=%282%2F3%29c+%2F+20+kHz&quot; rel=&quot;nofollow&quot;&gt;of at least 10 km&lt;/a&gt; (for 20 kHz), I think the most effect you'd ever see from reflection is some comb filtering (HF roll-off) with lines a few km long?  But that's totally unrealistic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Maximum_power_theorem&quot; rel=&quot;nofollow&quot;&gt;Maximum power theorem&lt;/a&gt; doesn't apply, since low-level signals are carried by voltage, not power, and high-level amplifier outputs can be made small compared to the speakers they drive.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Impedance matching went out with vacuum tubes, Edsels and beehive hairdos. Modern transistor and op-amp stages do not require impedance matching. If done, impedance matching degrades audio performance.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;For why impedance matching is not necessary (and, in fact, hurtful) in pro audio applications, see William B. Snow, &quot;Impedance -- Matched or Optimum&quot; [written in 1957!], &lt;a href=&quot;http://www.aes.org/publications/anth.cfm&quot; rel=&quot;nofollow&quot;&gt;Sound Reinforcement: An Anthology&lt;/a&gt;, edited by David L. Klepper (Audio Engineering Society, NY, 1978, pp. G-9 - G-13), and the RaneNote Unity Gain and Impedance Matching: Strange Bedfellows. &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rane.com/note124.html#fig2&quot; rel=&quot;nofollow&quot;&gt;Rane Corporation&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;For audio circuits, is it important to match impedance?&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Not any more. In the early part of the 20th century, it was important to match impedance. Bell Laboratories found that to achieve maximum power transfer in long distance telephone circuits, the impedances of different devices should be matched. Impedance matching reduced the number of vacuum tube amplifiers needed, which were expensive, bulky, and heat producing.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;In 1948, Bell Laboratories invented the transistor — a cheap, small, efficient amplifier. The transistor utilizes maximum voltage transfer more efficiently than maximum power transfer. For maximum voltage transfer, the destination device (called the &quot;load&quot;) should have an impedance of at least ten times that of the sending device (called the &quot;source&quot;). This is known as BRIDGING. Bridging is the most common circuit configuration when connecting audio devices. With modern audio circuits, matching impedances can actually degrade audio performance.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://shure.custhelp.com/app/answers/detail/a_id/224&quot; rel=&quot;nofollow&quot;&gt;Shure Brothers&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-18T16:10:21.083" LastActivityDate="2010-11-18T16:10:21.083" CommentCount="12" />
  <row Id="6856" PostTypeId="2" ParentId="4482" CreationDate="2010-11-16T23:04:45.013" Score="1" ViewCount="" Body="&lt;p&gt;You may be interested in using the types &lt;code&gt;unsigned&lt;/code&gt; and &lt;code&gt;signed&lt;/code&gt; from &lt;code&gt;ieee.numeric_std&lt;/code&gt;. They're compatible with &lt;code&gt;std_logic_vector&lt;/code&gt;, but have a numeric interpretation (binary or 2-complement). There's also the option to put such an interpretation on &lt;code&gt;std_logic_vector&lt;/code&gt;, but this is &lt;a href=&quot;http://vhdlguru.blogspot.com/2010/03/why-library-numericstd-is-preferred.html&quot; rel=&quot;nofollow&quot;&gt;not recommended&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-11-16T23:04:45.013" />
  <row Id="6857" PostTypeId="1" AcceptedAnswerId="6869" CreationDate="2010-11-16T23:43:15.933" Score="2" ViewCount="146" Body="&lt;p&gt;Does anyone know if there exists an electrical/electronic standard for high definition video on a single wire, like composite TV which integrates luma, chroma and sync? I'm still interested in this long distance high bandwidth project, and maybe transmitting analog HD is the answer. 720p would be good, 1080p would be fantastic. And a way to convert between component and composite would need to be figured out by me, but I figure a very fast DSP or even FPGA ought to be the solution.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-17T08:49:15.893" Title="High definition video on a composite cable" Tags="&lt;video&gt;&lt;hd&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="6858" PostTypeId="1" AcceptedAnswerId="6871" CreationDate="2010-11-16T23:58:15.733" Score="0" ViewCount="248" Body="&lt;p&gt;For my product's blurb, it would be really great if I could find out how many transistors average MCU's have, as a comparison to something bigger, like a computer, or even a low-end x86 processor. The blurb is about the virtual challenges part of it which offloads rendering of 3D games to the Real World™ (augmented reality), so I'm comparing GPUs to Super OSD. It sounds a bit obtuse but it's fun and I think it's a cool metaphor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking of asking the manufacturers, but I suspect I'll just get &quot;that's proprietary information&quot; back. Some chips, especially those from Analog Devices and ONsemi, have &quot;chip complexity&quot; or &quot;number of transistors&quot; in the datasheet, but others don't. I'm wondering why they don't include this information, because you could hardly build another chip just by knowing the number of fets, and if you were really dedicated (and paid a lot), you could probably count them yourself with a microscope or an image of the die, or at the very least estimate them by knowing the die area and average feature size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm interested in the AT32UC3B0512, dsPIC33FJ128GP802, dsPIC33FJ256GP506A, PIC24F64GA002 and PIC16F689, as well as some non-MCU's, like LMH1980, LM1881 and 24AA1025 (EEPROM.) But even if someone can hint towards a general number of transistors in their respective classes (AT32, dsPIC33F, PIC24F, PIC16F) it would be great!&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-17T08:02:27.757" LastActivityDate="2010-11-17T11:46:47.393" Title="How many transistors on an IC?" Tags="&lt;transistors&gt;" AnswerCount="4" CommentCount="13" />
  <row Id="6859" PostTypeId="2" ParentId="6858" CreationDate="2010-11-17T00:22:31.313" Score="0" ViewCount="" Body="&lt;p&gt;I doubt you'll get exact numbers for the parts but you can probably estimate.  Take a look around on &lt;a href=&quot;http://opencores.org/projects&quot; rel=&quot;nofollow&quot;&gt;Opencores.org&lt;/a&gt; for comparable cores and peripherals to get a gate count.  1 gate is usually 4 transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For those parts with memory you can probably look up the memory type and estimate based on number of bits and transistors per cell for that memory type.  Those parts with lots of memory probably use as many if not a lot more transistors for the memory than they do for the core/other logic.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-17T00:22:31.313" CommentCount="0" />
  <row Id="6860" PostTypeId="1" AcceptedAnswerId="6868" CreationDate="2010-11-17T00:36:36.213" Score="3" ViewCount="183" Body="&lt;p&gt;One of my older prototypes for Super OSD always had one little bug. A single pixel in the video, about midway in the frame would always be off. It did not really affect anything as most pixels normally stayed in the off mode, but it was noticeable during test patterns. I could never narrow down what the cause was.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thinking about it now, could it have been a failed bit in the memory array? Is this at all common with MCU's with SRAM? The prototype was not abused: a fixed +3.38V (within the rated 3.0V - 3.6V), room temperature operation, minimal load on the outputs. It was a dsPIC33FJ128GP802.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm designing a new prototype now and I think it's the same chip as I used last time, so I will see if the problem occurs again. Does anyone know if it is prudent to run a &quot;memory test&quot; on a chip? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-17T23:21:41.577" Title="Can MCU memory be subject to bit errors and failures?" Tags="&lt;microcontroller&gt;&lt;memory&gt;" AnswerCount="4" />
  <row Id="6861" PostTypeId="2" ParentId="6857" CreationDate="2010-11-17T00:39:58.120" Score="2" ViewCount="" Body="&lt;p&gt;cable television (at least in the US, not sure in other places) uses QAM-256 encoding for transmitting digital channels, including HD, over a single coax cable.  Thats for a compressed digital stream however.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know of anything for analog HD other than 3 wire component signaling.  I doubt you'll find much other than that for HD, its almost exclusively transmitted around in a compressed digital format (MPEG2).&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-17T00:39:58.120" />
  <row Id="6862" PostTypeId="1" AcceptedAnswerId="6865" CreationDate="2010-11-17T00:49:03.753" Score="1" ViewCount="153" Body="&lt;p&gt;I've noticed that certain types of capacitors seem to be used more commonly in certain applications. I've got a few over-sized 1uf PET caps that are a little too large for the application I originally got them for, and I should have enough spares to build &lt;a href=&quot;http://www.tkk.fi/Misc/Electronics/circuits/lm317.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; power supply design. On the other hand, I've never seen anyone use anything but electrolytic caps in power supplies (and in general nothing but PET and other plastic capacitors for audio use, other than a handful of tantalum capacitors). Would it be OK? I'm feeding it off a switch mode power supply, and I'd like to get as clean an output as possible.&lt;/p&gt;&#xA;" OwnerUserId="1870" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-17T00:59:36.973" LastActivityDate="2010-11-17T15:55:21.813" Title="Can I use a PET capacitor in a power supply? What's the difference?" Tags="&lt;capacitor&gt;&lt;power-supply&gt;" AnswerCount="1" />
  <row Id="6863" PostTypeId="1" AcceptedAnswerId="6866" CreationDate="2010-11-17T00:51:30.210" Score="2" ViewCount="114" Body="&lt;p&gt;I'm just wondering about this. Luckily I'm not faced with the problem myself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I design a product around a specific MCU and have that produced in a niche market, selling maybe a few hundred every year (maximum), would that MCU going NRND (not recommended for new designs) affect me badly? I can imagine I'd have to start a redesign around another chip... how long would I have to do this? Why does a chip go NRND anyway? Is it due to insufficient demand? What if I were a bigger company and just had an order for 10,000 units - would the manufacturer reconsider their decision?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any experience with this? I'm worrying about this, because I'd like the same design to work for as long as possible.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-17T01:18:06.957" Title="Does NRND spell the end for a niche product?" Tags="&lt;nrnd&gt;&lt;availability&gt;" AnswerCount="2" />
  <row Id="6865" PostTypeId="2" ParentId="6862" CreationDate="2010-11-17T00:58:01.563" Score="1" ViewCount="" Body="&lt;p&gt;The main things that you need to look at when selecting capacitors for a power supply is the voltage rating of the capacitor, if it needs to be polarized, and the equivalent series resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet of the IC that you are using will specify what value of capacitor you need and many times will specify the actual type of capacitor required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Electrolytic Caps are polarized which doesn't work well for AC signal, but is the cheapest way to get a high value capacitance, which is why they are used a lot in power supplies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, in short, yes, any cap should work OK as long as you are in the allowable voltage range.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-17T00:58:01.563" CommentCount="1" />
  <row Id="6866" PostTypeId="2" ParentId="6863" CreationDate="2010-11-17T01:08:38.933" Score="5" ViewCount="" Body="&lt;p&gt;NRND could be translated as End of Life is coming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could just be a 'better' part exists.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Time to look at manufacturers roadmap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NRND is the fist step to Last time buy, then End of life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;It will normally take years to go to last time buy.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll be able to buy chips from scalpers for years after that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't buy millions, generally manufacturers ignore you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stick with industrial, long lifespan parts. Consumer parts turn over fast.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-11-17T01:08:38.933" CommentCount="1" />
  <row Id="6867" PostTypeId="2" ParentId="6863" CreationDate="2010-11-17T01:18:06.957" Score="3" ViewCount="" Body="&lt;p&gt;Companies try their best to keep products around as long as they can. However, every product has cost associated with it in order to just keep it as a separate SKU. Usually an end of life product either has a replacement that can replace the old component with no changes needed by you. If they haven't done this then they probably have very few orders for that item and are just selling off all remaining stock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;10,000 units probably isn't enough for a company to go back on their decision. There is always a chance for negotiation, but financially they have already decided they are better off selling other components.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-17T01:18:06.957" />
  <row Id="6868" PostTypeId="2" ParentId="6860" CreationDate="2010-11-17T01:32:40.643" Score="4" ViewCount="" Body="&lt;p&gt;yes, they can, but any decent programmer verifies programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is normally done by taking a check-sum of the program. I would actually guess that if it is repeatable, I would reprogram just to be sure, and if it is still repeatable your software is has a small bug. This type of bug can be hell to find.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To check ram, you need to write test characters and read them out, one byte at a type and see if it fails to match.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-17T15:39:31.910" LastActivityDate="2010-11-17T15:39:31.910" CommentCount="12" />
  <row Id="6869" PostTypeId="2" ParentId="6857" CreationDate="2010-11-17T01:48:15.277" Score="2" ViewCount="" Body="&lt;p&gt;Composite cables have a very poor quality factor associated with their construction. The RCA connectors can create a lot of reflection and the soldering jobs on the wires are not always great. Also, many composite cables aren't shield causing noise and unintentional radiation to be an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the lower bandwidths used by analog TV these issues weren't really a huge issue. However, be definition, HD has to use more bandwidth. At the higher bandwidth situations a poor cable can really eat your lunch. This is one reason why no one has ever put high def on a composite cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now if you are looking to use something other then composite, but just want it to be 1 wire, then you can use any serial communication method you wish that is able to handle the bandwidth over the distance you wish. By &quot;1 wire&quot; I am going to assume you mean 2wires in a single line (1 signal, 1 ground), if this isn't the case you are going to have a horrible time with noise when you have no reference point or way of shielding.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-17T01:48:15.277" CommentCount="1" />
  <row Id="6870" PostTypeId="1" AcceptedAnswerId="6877" CreationDate="2010-11-17T02:30:17.783" Score="4" ViewCount="200" Body="&lt;p&gt;I'm working on debugging a boot problem with an Atmel AT91SAM9G20 board. Everything goes great for the first 700 ms or so. It seems that about 700 ms after reset, the processor freezes. What's curious is that the CPU drives the reset line after I release the reset button.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a scope shot that shows what's going on. The yellow trace is the reset line. The first dip is the time I'm actually holding down the reset button. The second dip is, I believe, generated by the CPU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The blue trace is serial data coming out of the CPU. The first two bursts come from the initial bootloader. The third burst is U-boot starting. The CPU stops sending out characters when the third blue burst ends.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I'm interpreting the traces correctly, this means that the reset line is low for almost exactly the time that the processor is loading U-boot from NAND flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Bw5YK.png&quot; alt=&quot;two oscilloscope traces&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a few questions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Is this sort of CPU-controlled reset normal?&lt;/li&gt;&#xA;&lt;li&gt;Any suggestions about how to debug this?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;A few more details: I should add that I've looked at the power rails, and they look clean. The behavior below is reproducible. I can vary the length of the initial reset dip (in yellow) by a few seconds, and the rest of the behavior happens the same way. If I plug in the JTAG cable, the behavior changes-- sometimes it boots, sometimes it doesn't, but after a few seconds, JTAG takes over, and the processor is halted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Under JTAG, I can boot successfully. Here's what a successful JTAG-controlled boot looks like:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/9SJcx.png&quot; alt=&quot;another scope screenshot, but with more serial data evident&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that the timescale is different, and I'm not pushing the reset button-- it's software controlled. The same reset dip occurs. In both cases, the length is around 500 ms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update (still baffled)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Prompted by Mr. Taffey's suggestion below, I have investigated the watchdog timer and the reset controller in more detail. The watchdog timer is in fact disabled by the first bootloader; I'm pretty sure that code is being executed because it occurs before text is sent out the debug serial port, and I can read the text successfully.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In reading about the details of the reset controller, I learned that the processor is &lt;em&gt;supposed&lt;/em&gt; to grab control of the reset pin and pull it low for a short period. This is to ensure that other hardware on the board listening to the same line receive a long enough reset. Digging through U-boot, I found that the duration of the reset was set to 0x0D using the ERSTL field:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;at91_sys_write(AT91_RSTC_MR, AT91_RSTC_KEY |&#xA;  (AT91_RSTC_ERSTL &amp;amp; (0x0D &amp;lt;&amp;lt; 8)) |&#xA;  AT91_RSTC_URSTEN);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The datasheet explains that the duration is set to 2^(ERSTL + 1) slow clock periods.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reset duration looks around 500 ms long, the slow clock crystal is 32768 Hz, and Google tells me that log(0.500 * 32768) / log(2) = 14, and 0x0D + 1 = 14, so this all makes sense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the real problem may be U-boot crashing; the fact that it happens just after this reset is probably irrelevant. What's confusing is why U-boot would crash only when JTAG is &lt;em&gt;not&lt;/em&gt; connected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Second update&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I still don't know what's going awry or why JTAG makes it behave differently, but I think I have figured out a workaround (sort of). It looks like the U-boot crash is being caused in some way by the NAND flash on the board. By chance, the next revision of the board, which just arrived recently, uses a microSD card rather than NAND flash for bulk nonvolatile storage (well, there's NAND flash inside the microSD card, but you see the point).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My &quot;solution&quot; is just to start using the next revision of the board. U-boot also crashes on that, but for known reasons-- it is configured to look for a NAND flash, which it cannot find. Hence, it dies a fiery death.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, problem &quot;solved.&quot; (Expect another question shortly along the lines of &quot;How do I make AT91Bootstrap load U-boot from a serial flash?&quot; or &quot;How do I make U-boot work with a microSD card?&quot; or &quot;Why am I doing this?&quot;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess the green check mark goes to Joby for noticing that the reset line can be driven by the micro, even though it turned out to be irrelevant in the long run. Thanks for the help, all of you. I appreciate it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Third update (about a week later)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been mostly working on other stuff recently, but I did figure out what the problem was eventually. My last mystery I summarized above as:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;What's confusing is why U-boot would&#xA;  crash only when JTAG is not connected.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;In fact, it turns out that I was mistaking U-boot failing to send characters out the debug serial port for U-boot crashing. I still don't understand the details, but I've discovered that it's not JTAG that makes U-boot work-- it's a common ground between my circuit and the USB host of my PC, which JTAG was providing, because it runs through the USB port. In fact, U-boot was working fine the entire time, but whenever JTAG was disconnected, the RS-232-to-USB level shifter I had breadboarded would stop working, the serial port would fail, and I would assume U-boot was dead. In reality, I discovered that I could, for example, still type ping commands and see the ICMP packets produced, even though my characters weren't echoed on the terminal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't understand exactly what was going wrong, but I don't really care-- I can easily find another way to read the serial port, and in the short term, I can just make the connection to USB ground with a wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for the help, all.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-11-24T22:46:58.443" LastActivityDate="2010-11-24T22:46:58.443" Title="(Updated) Strange reset behavior with ARM9 processor" Tags="&lt;embedded&gt;&lt;reset&gt;&lt;arm9&gt;&lt;debugging&gt;&lt;u-boot&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="6871" PostTypeId="2" ParentId="6858" CreationDate="2010-11-17T02:36:56.657" Score="1" ViewCount="" Body="&lt;p&gt;Mark does have a good answer, but I would like to add a few things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why not ask the company? The worst they can do is tell you no. You would actually be amazed at how much information I have been able to get from companies that I never thought I would be able to get.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as your question about why they don't include those numbers in the datasheets. I think the best way to answer this is to ask why would they want to include those numbers in the datasheet? Datasheets are specifically designed to give you all of the information you need to select and operate the chip, no more and no less. Now no datasheet is perfect so there always is areas that are lacking and other areas that are overboard, but in general they are aiming to be as concise as possible while still giving you everything you need. So, in the chip selection and operation process, why would a user ever need to know how many transistors are in a PIC?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The marketing process for an IC is very much different then the market process for a computer. With computers they are able to use the &quot;it has more transistors so its better&quot; argument. With ICs, generally the people using them don't fall for this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, there was a time when the number of transistors in an IC was actually a marketing item to compete against others building similar products. However, in today's world this isn't really needed.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-17T02:36:56.657" CommentCount="1" />
  <row Id="6872" PostTypeId="2" ParentId="6870" CreationDate="2010-11-17T03:16:11.103" Score="2" ViewCount="" Body="&lt;p&gt;Are the JTAG lines af any device connected to things they shoudn't be ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like, say address bus lines ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(It took months to debug that one time.)&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-11-17T03:16:11.103" CommentCount="3" />
  <row Id="6873" PostTypeId="2" ParentId="6870" CreationDate="2010-11-17T04:30:03.783" Score="4" ViewCount="" Body="&lt;p&gt;This may be a long shot. On a much lower end microcontroller, a PIC, I have helped people with strange resets many time due to a low voltage programming pin being enabled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;when a programmer is connected it holds lines similar to this at a set voltage, when the programmer was disconnected they could float easily. On one project when the device crossed over metal it would reset. They did not check LVP when I asked them to, they worked for 2 more weeks and then disabled it and the problem was solved.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-17T04:30:03.783" CommentCount="1" />
  <row Id="6875" PostTypeId="2" ParentId="6857" CreationDate="2010-11-17T08:49:15.893" Score="5" ViewCount="" Body="&lt;p&gt;Yes, it's called SDI: &lt;a href=&quot;http://en.wikipedia.org/wiki/Serial_digital_interface&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Serial_digital_interface&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With one coax cable you can transmit 720p or 1080i, with two coax cables you can do 1080p.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-17T08:49:15.893" />
  <row Id="6876" PostTypeId="2" ParentId="6858" CreationDate="2010-11-17T09:15:39.833" Score="1" ViewCount="" Body="&lt;p&gt;Similarly-minded people have already compiled a Wikipedia page about this sort of stuff:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Transistor_count&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Transistor_count&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So for modern large processors and GPUs, it's in the 100s-1000s of millions.  I don't think you'd be counting them with a microscope...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 8-bit PIC is probably of the order of 10K, and a 32-bit risc micro more like 100K.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously for both microcontrollers and large micros, there are huge numbers of gates/transistors in memory (flash or cache), which can rather distort the meaning of the figures if you're really trying to reason about core complexity.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-17T09:15:39.833" />
  <row Id="6877" PostTypeId="2" ParentId="6870" CreationDate="2010-11-17T09:43:13.100" Score="5" ViewCount="" Body="&lt;p&gt;Looking at the datasheet:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;14.3.4.5 Watchdog Reset The Watchdog Reset is entered when a watchdog fault&#xA;  occurs. This state lasts 3 Slow Clock&#xA;  cycles.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;When in Watchdog Reset, assertion of&#xA;  the reset signals depends on the&#xA;  WDRPROC bit in WDT_MR: If WDRPROC is&#xA;  0, the Processor Reset and the&#xA;  Peripheral Reset are asserted. &lt;strong&gt;The&#xA;  NRST line is also asserted&lt;/strong&gt;, depending&#xA;  on the programming of the field ERSTL.&#xA;  However, the resulting low level on&#xA;  NRST does not result in a User Reset&#xA;  state.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Could it be that the watchdog is firing and driving the reset line?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-17T10:07:09.973" LastActivityDate="2010-11-17T10:07:09.973" CommentCount="1" />
  <row Id="6878" PostTypeId="2" ParentId="6858" CreationDate="2010-11-17T11:27:18.190" Score="2" ViewCount="" Body="&lt;p&gt;As found at &lt;a href=&quot;http://en.wikipedia.org/wiki/List_of_Intel_microprocessors&quot; rel=&quot;nofollow&quot;&gt;Wiki&lt;/a&gt; there are &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&quot;Number of Transistors 29,000 at 3 µm&quot;&lt;/strong&gt; on an x86, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&quot;Number of transistors 3.1 million&quot;&lt;/strong&gt; on a 32-bit processor original pentium, and &lt;/p&gt;&#xA;&#xA;&lt;p&gt;in a 64 bit xeon processor &lt;strong&gt;&quot;781 million transistors&quot;&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="1413" LastEditorUserId="1413" LastEditorDisplayName="" LastEditDate="2010-11-17T11:46:47.393" LastActivityDate="2010-11-17T11:46:47.393" />
  <row Id="6879" PostTypeId="2" ParentId="6591" CreationDate="2010-11-17T11:38:45.637" Score="3" ViewCount="" Body="&lt;p&gt;LED Christmas lights are wired in series to &quot;gobble&quot; up the 110V applied to them.  A great site to read up on this is &lt;a href=&quot;http://www.ciphersbyritter.com/RADELECT/LITES/LEDLITES.HTM&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1413" LastActivityDate="2010-11-17T11:38:45.637" CommentCount="3" />
  <row Id="6880" PostTypeId="2" ParentId="4807" CreationDate="2010-11-17T12:37:48.310" Score="0" ViewCount="" Body="&lt;p&gt;Check also the &lt;a href=&quot;http://www.igep-platform.com/index.php?option=com_content&amp;amp;view=article&amp;amp;id=46&amp;amp;Itemid=55&quot; rel=&quot;nofollow&quot;&gt;IGEPv2 board&lt;/a&gt;. It has Ethernet and WiFi.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-17T12:37:48.310" />
  <row Id="6881" PostTypeId="2" ParentId="6860" CreationDate="2010-11-17T13:00:17.983" Score="2" ViewCount="" Body="&lt;p&gt;It is always &lt;strong&gt;prudent&lt;/strong&gt; to do memory checking. I typically put a simple memory test routine as part of the startup sequence for my firmware code. While a full-blown test can take a longer time depending on the memory size, a faster test can be done to catch major errors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This &lt;a href=&quot;http://embedded-systems.com/2000/0007/0007feat1.htm&quot; rel=&quot;nofollow&quot;&gt;article&lt;/a&gt; at embedded.com has a good explanation and some example code on how to do simple memory testing on an embedded device.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2010-11-17T13:00:17.983" CommentCount="3" />
  <row Id="6882" PostTypeId="2" ParentId="6860" CreationDate="2010-11-17T13:19:35.467" Score="1" ViewCount="" Body="&lt;p&gt;It is also good to observe that for memories (DRAM, SRAM) transient bit errors are typically some orders of magnitude more likely than permanent errors. Checksums are not effective against transient bit errors, so in order to tackle these error detection and correction (EDC) is required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The good news for non-safety related systems with a small amount of RAM the failure rates are still fairly low (500-5000 FIT per Mbit).&lt;/p&gt;&#xA;" OwnerUserId="1815" LastActivityDate="2010-11-17T13:19:35.467" CommentCount="1" />
  <row Id="6883" PostTypeId="1" AcceptedAnswerId="6898" CreationDate="2010-11-17T14:31:21.493" Score="4" ViewCount="142" Body="&lt;p&gt;I'm doing an electronics project (well just designing the initial concept) and part of the specification is a small projector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The projector needs to fit in roughly a 15mm(H) x 75mm(D) x 150mm (W) box. (It's not exactly a box but that's the average measurements).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible for a micro projector to fit inside this, the maximum size screen it will project is less than 15&quot; square. I have seen a camera with a projector that projects out the front of it.&lt;/p&gt;&#xA;" OwnerUserId="1982" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-01T13:35:23.140" LastActivityDate="2011-06-01T13:35:23.140" Title="Smallest projector" Tags="&lt;projector&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="6884" PostTypeId="1" AcceptedAnswerId="6888" CreationDate="2010-11-17T14:32:16.237" Score="6" ViewCount="296" Body="&lt;p&gt;I recently read an &lt;a href=&quot;http://mediasensation.be/r/?iJo&quot; rel=&quot;nofollow&quot;&gt;article&lt;/a&gt; about button debouncing and was wondering if I should keep this in mind when working with, for example, an Arduino (ATMega mC)? I assume it is an issue, especially when working with interrupts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So is it better to detect bounce in code, or should this be taken care of with hardware? Please elaborate.&lt;/p&gt;&#xA;" OwnerUserId="1124" LastActivityDate="2010-11-17T19:35:24.547" Title="Debouncing buttons" Tags="&lt;button&gt;&lt;debounce&gt;" AnswerCount="3" />
  <row Id="6885" PostTypeId="2" ParentId="6884" CreationDate="2010-11-17T14:36:23.690" Score="4" ViewCount="" Body="&lt;p&gt;That article is the &quot;bible&quot; on debouncing. Contact bounce can be a problem with any application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's generally best to debounce switches in software as it's easier to adjust for the delays for particular switches, as they differ in their amount of contact bounce. Debouncing the key release is often necessary, as well. Switch manufacturers often specify the amount of bounce for their products, it's typically around 10ms - 20ms.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-17T14:47:38.157" LastActivityDate="2010-11-17T14:47:38.157" CommentCount="5" />
  <row Id="6886" PostTypeId="2" ParentId="6884" CreationDate="2010-11-17T14:38:41.393" Score="8" ViewCount="" Body="&lt;p&gt;There are lots (and lots) of different ways to debounce buttons. Whether you do it in software or hardware is going to depend on your project requirements and switch type.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some links to different methods:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ganssle.com/debouncing.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.ganssle.com/debouncing.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2010/11/09/debounce-code-one-post-to-rule-them-all/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2010/11/09/debounce-code-one-post-to-rule-them-all/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-17T14:38:41.393" CommentCount="6" />
  <row Id="6887" PostTypeId="2" ParentId="4482" CreationDate="2010-11-17T14:51:12.917" Score="3" ViewCount="" Body="&lt;p&gt;As LoneTech says, &lt;code&gt;use ieee.numeric_std&lt;/code&gt; is your friend.  You can convert a std_logic_vector to an integer, but you'll have to cast it as signed or unsigned first (as the compiler has no idea which you mean).  VHDL is a strongly typed language.  I've &lt;a href=&quot;http://www.parallelpoints.com/node/3&quot; rel=&quot;nofollow&quot;&gt;written more&lt;/a&gt; on this subject &lt;a href=&quot;http://www.parallelpoints.com/&quot; rel=&quot;nofollow&quot;&gt;on my blog&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fundamentally, I'd change your 7seg converter to take in an &lt;code&gt;integer&lt;/code&gt; (or actually a &lt;code&gt;natural&lt;/code&gt;, given that it's only going to deal with positive numbers) - the conversion is then a simple array lookup. Set up a constant array with the conversions in and just index into it with the integer you use on the entity as an input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, as you mention Quartus, there's a &lt;a href=&quot;http://area51.stackexchange.com/proposals/20632/&quot;&gt;stackexchange FPGA group attempting to form which you may wish to follow here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2010-11-17T14:51:12.917" CommentCount="1" />
  <row Id="6888" PostTypeId="2" ParentId="6884" CreationDate="2010-11-17T14:51:45.097" Score="8" ViewCount="" Body="&lt;p&gt;I would highly recommend hooking a scope (hopefully you have one or can get your hands on one to use) up to your switch. I have seen a student's project that had a bounce on their switch that went from 5v down to -5v up to 4v down to -3v then up to 2v then back down to 0v. When we looked at the current draw on a scope there were some a very very large spike.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In his particular case it was very very much needed for him to debounce his switch in hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, on the other hand, I have seen switches that have a much smaller effect that could easily just be removed in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You do need to weigh your options though. If you have a very complex amount of firmware, adding the overhead on both you as a programmer and the cpu usage may not be worth it and you would be better off to just add a little bit of hardware. Now on the other hand, if you are trying to get costs and size down, you will want to remove as much hardware as possible and do it all in firmware if you can.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-17T19:35:24.547" LastActivityDate="2010-11-17T19:35:24.547" CommentCount="9" />
  <row Id="6889" PostTypeId="1" AcceptedAnswerId="6890" CreationDate="2010-11-17T14:55:52.247" Score="4" ViewCount="233" Body="&lt;p&gt;I've been trying to find a good description of the TTL serial &quot;standard&quot; without much luck.  I understand that serial transmit (TX) and receive (RX) lines idle high (at VCC) and that they drop to ground when a bit is transmitted.  As such, they're inverted from the norm, where a &quot;1&quot; is high and &quot;0&quot; is low.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I don't understand is who's responsible for holding the line high and how a zero is transmitted.  Does the sender drive the line to high and low? Or does the receiver hold the line high with the sender pulling the line low (open collector)?&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-11-17T16:35:33.937" Title="How does TTL serial work?" Tags="&lt;microcontroller&gt;&lt;serial&gt;&lt;ttl&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="6890" PostTypeId="2" ParentId="6889" CreationDate="2010-11-17T15:13:24.283" Score="7" ViewCount="" Body="&lt;p&gt;With TTL serial, there are two unidirectional data lines. Each is driven by the sender, both high and low. A 0 bit is represented by 0V a 1 bit by VCC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The receiver's pin should be set to an input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, for a microcontroller to send a byte (8-N-1 no flow control) it could do something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define BAUDRATE 9600&#xA;#define DELAY (SYS_CLK/BAUDRATE)&#xA;&#xA;#define UART_BITBANG_OFF     UART_BITBANG_PORT |= _BV(UART_BITBANG_PIN)&#xA;#define UART_BITBANG_ON      UART_BITBANG_PORT &amp;amp;= ~ _BV(UART_BITBANG_PIN)&#xA;&#xA;#define UART_BITBANG_BIT(bit) {if (bit) UART_BITBANG_ON; else UART_BITBANG_OFF; _delay_us(DELAY);}&#xA;&#xA;void uart_bitbang_init(void)&#xA;{&#xA;    UART_BITBANG_DDR &amp;amp;= ~ _BV(UART_BITBANG_PIN);        // TX output&#xA;}&#xA;&#xA;void uart_bitbang_putc(uint8_t c)&#xA;{&#xA;    UART_BITBANG_BIT(1)&#xA;    UART_BITBANG_BIT((c &amp;amp; 0x1) == 0);&#xA;    UART_BITBANG_BIT((c &amp;amp; 0x2) == 0);&#xA;    UART_BITBANG_BIT((c &amp;amp; 0x4) == 0);&#xA;    UART_BITBANG_BIT((c &amp;amp; 0x8) == 0);&#xA;    UART_BITBANG_BIT((c &amp;amp; 0x10) == 0);&#xA;    UART_BITBANG_BIT((c &amp;amp; 0x20) == 0);&#xA;    UART_BITBANG_BIT((c &amp;amp; 0x40) == 0);&#xA;    UART_BITBANG_BIT((c &amp;amp; 0x80) == 0);&#xA;    UART_BITBANG_BIT(0);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(This code reads a bit backwards as it was originally meant for inverted TTL serial)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, most MCUs have hardware UARTs which do all this for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's what you'd see on a scope:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.pololu.com/docs/0J25/4.a&quot; rel=&quot;nofollow&quot;&gt;http://www.pololu.com/docs/0J25/4.a&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.pololu.com/picture/0J1035.600.png&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a great video from ladyada explaining serial:&#xA;&lt;a href=&quot;http://www.adafruit.com/blog/2010/09/15/usb-serial-and-you-video-an-adafruit-after-school-special/&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/blog/2010/09/15/usb-serial-and-you-video-an-adafruit-after-school-special/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-17T16:35:33.937" LastActivityDate="2010-11-17T16:35:33.937" CommentCount="5" />
  <row Id="6891" PostTypeId="1" AcceptedAnswerId="6896" CreationDate="2010-11-17T17:27:50.837" Score="2" ViewCount="290" Body="&lt;p&gt;I am looking for a small USB to RS232 (or TTL serial) converter. FTDI was the first stop, but the smallest IC they have is in SSOP28 or QFN32. I'm looking to go even smaller. I don't need high speed - max probably 38400 baud, and USB Low Speed or Full Speed class. I can see how the pins are used up: some for data (TX, RX, CTS, RTS), USB pins (D+, D-, 5V), voltage regulator, crystal, etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure what product category I should be looking for, other than FTDI's website, which I already checked. I suppose I could also use a USB micro (I already have two micros on the board), but this adds size and complexity to an already complex product. Does anyone know of any possible chips? (preferably also low component count, this is not critical but would be nice.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-20T23:08:54.677" LastActivityDate="2011-02-20T23:08:54.677" Title="Small &quot;FTDI&quot;-like chip" Tags="&lt;usb&gt;&lt;uart&gt;&lt;ftdi&gt;" AnswerCount="3" />
  <row Id="6892" PostTypeId="2" ParentId="6891" CreationDate="2010-11-17T17:36:06.977" Score="4" ViewCount="" Body="&lt;p&gt;The only way you are going to really save space is to just use a microcontroller already on your board. This can easily be done by using a microcontroller, which I am sure you have at least a few of, and make sure one was USB. Have it handle the USB, no need for an extra chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are wanting what FTDI does, as well as FTDI does it, with the same thing but a smaller chip, you are going to be disappointed. The only other way to get around this is remove the need by not using a TTL connection.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-17T17:36:06.977" CommentCount="7" />
  <row Id="6893" PostTypeId="2" ParentId="6891" CreationDate="2010-11-17T17:36:28.317" Score="3" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardUno&quot; rel=&quot;nofollow&quot;&gt;Arduino Uno&lt;/a&gt; uses the &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=4600&quot; rel=&quot;nofollow&quot;&gt;Atmega8U2&lt;/a&gt; programmed as a USB to serial converter running &lt;a href=&quot;http://www.fourwalledcubicle.com/LUFA.php&quot; rel=&quot;nofollow&quot;&gt;LUFA&lt;/a&gt;. It's a QFN32.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This chip is a general purpose AVR microcontroller with USB hardware, so can be programmed to support many other USB classes (MIDI, keyboard, mouse etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another choice could be the &lt;a href=&quot;http://www.silabs.com/products/interface/usbtouart/Pages/default.aspx&quot; rel=&quot;nofollow&quot;&gt;Silabs CP2102&lt;/a&gt; (QFN28).&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-17T17:36:28.317" CommentCount="2" />
  <row Id="6894" PostTypeId="1" CreationDate="2010-11-17T17:45:27.287" Score="1" ViewCount="209" Body="&lt;p&gt;I can find a number of LCD TN 8 digit 7 segment displays but they are far to big. The kind of size I'm looking for is the ones you usually find in mini calculators.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The size im looking for is around 10mm by 50mm. The smaller the better really. The other specs of the LCD are not really important at this time other than getting the smallest possible. Maybe I'm wrong in my search for an TN LCD?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help is greatly appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Scott&lt;/p&gt;&#xA;" OwnerUserId="1936" LastActivityDate="2010-11-17T23:13:49.280" Title="Need help finding smallest possible 8 digit 7 Segment LCD TN Display" Tags="&lt;lcd&gt;&lt;7segmentdisplay&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="6895" PostTypeId="2" ParentId="6894" CreationDate="2010-11-17T18:26:11.397" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.datasheetarchive.com/pdf-datasheets/Datasheets-316/624780.html&quot; rel=&quot;nofollow&quot;&gt;Densitron DG-067&lt;/a&gt; package is 38 mm wide x 15.2 mm high.  The viewing area is 34 mm x 12.1 mm.  The characters are 6 mm (1/4&quot;) high. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW the datasheet doesn't mention TN, but &lt;a href=&quot;http://www.densitron.com/displays/segmented_lcd_glass.aspx&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; where it is listed is titled &quot;LCD Glass, Segmented Glass, TN Glass&quot;&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-11-17T23:13:49.280" LastActivityDate="2010-11-17T23:13:49.280" CommentCount="3" />
  <row Id="6896" PostTypeId="2" ParentId="6891" CreationDate="2010-11-17T18:37:40.137" Score="3" ViewCount="" Body="&lt;p&gt;Something like this from Microchip?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en546923&quot; rel=&quot;nofollow&quot;&gt;MCP2200&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1985" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-17T19:33:55.887" LastActivityDate="2010-11-17T19:33:55.887" CommentCount="17" />
  <row Id="6897" PostTypeId="2" ParentId="6883" CreationDate="2010-11-17T18:53:20.837" Score="1" ViewCount="" Body="&lt;p&gt;I'll venture to say that it's possible (assuming you have the resources of a major consumer electronics company behind you). Judging by the dimensions of &lt;a href=&quot;http://www.dpreview.com/news/0908/09080402nikons1000pj.asp#specs&quot; rel=&quot;nofollow&quot;&gt;a projector camera&lt;/a&gt;, you can probably fit a projector into a 15 mm tall slot if you only need a small image. The rest of the dimensions are relatively large and presumably you can leave out a lot of the other junk inside a camera.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-17T18:53:20.837" />
  <row Id="6898" PostTypeId="2" ParentId="6883" CreationDate="2010-11-17T18:59:35.033" Score="3" ViewCount="" Body="&lt;p&gt;The smallest pico projector I remember seeing is the Optoma PK10x series.  It's the thinnest projector I know of, fits your 15mm spec perfectly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.optomausa.com/Product_detail.asp?productsubcat=26&amp;amp;productcategory=Pico+Pocket+Projector&amp;amp;product_id=399&amp;amp;itemno=EPPK101&quot; rel=&quot;nofollow&quot;&gt;http://www.optomausa.com/Product_detail.asp?productsubcat=26&amp;amp;productcategory=Pico+Pocket+Projector&amp;amp;product_id=399&amp;amp;itemno=EPPK101&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the image is pretty crappy.  Most other pico projectors are larger, because you only get about 10 lumens out of a projector that small.  Aaxa is another pico projector manufacturer, but their smallest (P1 Jr.) is 20mm thick.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2010-11-17T18:59:35.033" />
  <row Id="6899" PostTypeId="1" AcceptedAnswerId="6902" CreationDate="2010-11-17T21:43:04.487" Score="7" ViewCount="360" Body="&lt;p&gt;I'd like to build a bot that when placed in an area would have the ability to find the perimeter of the area and map the obstacles present.  Later it should be able to navigate to different parts of the area on demand (e.g. navigate to the NW corner or continually monitor the entire area or return to a specific point in the area).  What hardware/software would be necessary to make this happen?  I've considered using IR to detect the obstacles &amp;amp; wall but it seems like the resolution may be a bit low for these purposes (could IR recognize an area is just large enough for the bot to fit into?).  What prior work is available on these subjects, what sensors might I consider to get started?&lt;/p&gt;&#xA;" OwnerUserId="1841" LastEditorUserId="1477" LastEditorDisplayName="" LastEditDate="2010-11-18T19:31:26.097" LastActivityDate="2010-12-14T15:21:38.907" Title="Strategies for mapping an area perimeter with a mobile robot" Tags="&lt;arduino&gt;&lt;robotics&gt;&lt;linux&gt;&lt;software&gt;&lt;mobile&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="6900" PostTypeId="2" ParentId="6899" CreationDate="2010-11-17T21:46:58.483" Score="2" ViewCount="" Body="&lt;p&gt;Excluding doing computer vision with a camera, which NI has some hardware to help you with, for a cost. I would suggest you look into using a &lt;a href=&quot;http://en.wikipedia.org/wiki/LIDAR&quot; rel=&quot;nofollow&quot;&gt;LIDAR&lt;/a&gt;. These are not overly expensive by my recollection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the robots a team did at my school last semester for an autonomous robot competition used a LIDAR mounted on a servo that it would rotate constantly to keep track of obstacle locations.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-14T15:21:38.907" LastActivityDate="2010-12-14T15:21:38.907" CommentCount="8" />
  <row Id="6901" PostTypeId="2" ParentId="3682" CreationDate="2010-11-17T22:07:19.877" Score="1" ViewCount="" Body="&lt;p&gt;Looks like it is a 0-1V output signal if my quick glance at the specs is right. If so, you can use a ADC to snag the values and then record them on your machine. You'll need to get something with a fast enough sample rate to get a clean signal. Have you looked at the output with a 'scope to see if the values match your expectations?&lt;/p&gt;&#xA;" OwnerUserId="1990" LastActivityDate="2010-11-17T22:07:19.877" />
  <row Id="6902" PostTypeId="2" ParentId="6899" CreationDate="2010-11-17T22:10:58.997" Score="9" ViewCount="" Body="&lt;p&gt;To successfully accomplish this, you probably want the following:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Localization Sensors - If you are on a smooth surface, wheel odometry should be enough.  The rougher the area that you are operating in, the more sensors you would need.  Other common sensors for localization: Digital Compass, IMU, GPS, Vision Tracking (Fiducial Recognition), Stargazer (Indoors).  You can also use LIDAR sensors data to do localization.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Obstacle Detection - As Kortuk says, probably a LIDAR.  Possibly a Kinect, since that's the new hotness.  A decent LIDAR will probably start around 1000 USD for a Hokuyo, and go up from there.  You can then put this data into a map.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;From a software point of view, there are several options, but the one that I've had good luck with is ROS.  It has a lot of the software features such as localization, mapping, LIDAR drivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as the actual path, just spiraling out from a central point would work, taking into account obstacles and whatnot.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-11-17T22:10:58.997" CommentCount="5" />
  <row Id="6903" PostTypeId="2" ParentId="4807" CreationDate="2010-11-17T23:15:01.133" Score="0" ViewCount="" Body="&lt;p&gt;I would suggest having a look at a chinese MID. They can be had for 100$ online, but if you have the chance to buy one in china you can get one for around half that price in a copy market. While offering a lower product quality you can get started for a lower price than any development board.&#xA;One of the tablets I bought gives me a Wondermedia armv5 compatible processor with 256mb ram and 2gb flash memory which is a way better deal than the friendly arm compatible kit I used at work.&lt;/p&gt;&#xA;" OwnerUserId="1992" LastActivityDate="2010-11-17T23:15:01.133" CommentCount="1" />
  <row Id="6904" PostTypeId="2" ParentId="6883" CreationDate="2010-11-17T23:18:38.243" Score="2" ViewCount="" Body="&lt;p&gt;The TI DLP pico devkit unit is 70x15x45mm I have the MK.1 version but the current one looks similar. No internal battery, hence a lot smaller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&amp;amp;site=UK&amp;amp;WT.z_homepage_link=hp_go_button&amp;amp;KeyWords=pico+projector&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&amp;amp;site=UK&amp;amp;WT.z_homepage_link=hp_go_button&amp;amp;KeyWords=pico+projector&amp;amp;x=0&amp;amp;y=0&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-17T23:18:38.243" />
  <row Id="6905" PostTypeId="2" ParentId="6860" CreationDate="2010-11-17T23:21:41.577" Score="1" ViewCount="" Body="&lt;p&gt;Highly unlikely.  On-chip memory on MCUs doesn't fail. RAM tests are only needed for external RAM. Far more likely it is a code problem putting something in RAM where it shouldn't - bad pointer etc.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-17T23:21:41.577" CommentCount="3" />
  <row Id="6906" PostTypeId="2" ParentId="1009" CreationDate="2010-11-18T05:02:58.347" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;replace the case statement with an&#xA;  array of function pointers&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Which is how the QP stuff works. The representation of a state is just a function pointer (to the function for the current state). In C++ it could be a pointer to member function, but basically the same. The current state function is called with events, as well as with some pseudo-events (entry, exit), one of which is always unhandled and is used to determine the state nesting when doing nested transitions (QP supports hierarchical state machines).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Miro Samek says that he's going to be doing an Arduino-targeted port soon.&lt;/p&gt;&#xA;" LastActivityDate="2010-11-18T05:02:58.347" />
  <row Id="6907" PostTypeId="1" AcceptedAnswerId="6908" CreationDate="2010-11-18T08:48:20.867" Score="1" ViewCount="162" Body="&lt;p&gt;This halloween, I outdid myself by making mini-throwies (basically CR2032+LED+tape but no magnet.) They worked &lt;a href=&quot;http://www.youtube.com/watch?v=B7bhYeIg6Mw&quot; rel=&quot;nofollow&quot;&gt;really well&lt;/a&gt;. I also made some flashing pumpkins, involving a 555 timer and a 9V battery. The total cost to me was about £11.99 for 36 lithium CR2032 batteries (about 10 of which I used) and £2.49 for a 9V battery (pricey!) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, for Christmas this year instead of reusing the old decorations I was thinking of using rainbow LEDs with CR2032's. I've already bought a few but the price was quite high. I can't find these cool little LEDs anywhere. Their function is to light red, then fade to green, then fade to blue, and all colours in between. Although rated for 3.6V, they work very well on a 3V lithium, and they will work up to 6V without getting very warm. (Interestingly, the pattern starts malfunctioning at higher voltages, but they will work again if you lower the voltage.) I've tried looking for &quot;rainbow LED&quot; and &quot;color changing LED&quot; in Farnell's catalog. I've found them in &lt;a href=&quot;http://www.rapidonline.com/Electronic-Components/Optoelectronics/5mm-LEDs/Rainbow-colour-cycling-5mm-LED/75160&quot; rel=&quot;nofollow&quot;&gt;Rapid Electronics' catalog&lt;/a&gt;, but they are about £0.65 each which is quite expensive (I plan to purchase 50) plus £3.99 shipping. I'm not yet open to ordering from Digikey due to VAT issues. So does anyone know of a cheap source of these LEDs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-18T12:06:02.820" ClosedDate="2010-11-18T14:21:25.590" Title="Cheap source of rainbow LEDs" Tags="&lt;led&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="6908" PostTypeId="2" ParentId="6907" CreationDate="2010-11-18T09:15:49.143" Score="2" ViewCount="" Body="&lt;p&gt;Search eBay for &quot;color changing led&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://cgi.ebay.co.uk/10-ULTRA-BRIGHT-5mm-FAST-COLOUR-CHANGING-RGB-LEDs-/400173196892?pt=UK_BOI_Electrical_Components_Supplies_ET&amp;amp;hash=item5d2c2e665c&quot; rel=&quot;nofollow&quot;&gt;http://cgi.ebay.co.uk/10-ULTRA-BRIGHT-5mm-FAST-COLOUR-CHANGING-RGB-LEDs-/400173196892?pt=UK_BOI_Electrical_Components_Supplies_ET&amp;amp;hash=item5d2c2e665c&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-18T09:15:49.143" />
  <row Id="6909" PostTypeId="1" AcceptedAnswerId="6913" CreationDate="2010-11-18T09:20:49.573" Score="1" ViewCount="135" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am planning of building a solar water fountain which would serve as a bird bath in my backyard this summer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My requirements are simple:&#xA;The fountain should be powered by solar energy, a small output motor (or whatever) connected to this solar source which pumps out the water. I just need a small working model in a economic price.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no experience in building basic electronics model, please guide me on how this can be accomplished, where I can get solar panels and how do I configure it with a motor etc. I am from India and would like to purchase raw materials available in India rather than getting it shipped from elsewhere. Any help is greatly appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&#xA;Raj&lt;/p&gt;&#xA;" OwnerUserId="2002" LastEditorUserId="2002" LastEditorDisplayName="" LastEditDate="2010-11-18T10:23:09.383" LastActivityDate="2010-11-18T13:12:15.870" Title="Solar powered water fountain" Tags="&lt;motor&gt;&lt;battery&gt;&lt;solar-cell&gt;&lt;waterproof&gt;" AnswerCount="2" />
  <row Id="6910" PostTypeId="2" ParentId="6909" CreationDate="2010-11-18T10:22:46.037" Score="1" ViewCount="" Body="&lt;p&gt;Look at the effect requirements of the pump motor, then buy solar panels with peak effects maybe five times that, unless where you live is very, very sunny.&lt;/p&gt;&#xA;" OwnerUserId="1877" LastActivityDate="2010-11-18T10:22:46.037" CommentCount="3" />
  <row Id="6911" PostTypeId="2" ParentId="6907" CreationDate="2010-11-18T11:52:47.427" Score="2" ViewCount="" Body="&lt;p&gt;Your cheapest source of LED's in small quantities is to buy a strand of &#xA;LED's from the store and harvest the LED's from the strands.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.walmart.com/ip/Hoilday-Time-Multi-Color-LED-C4-Teardrop-Light-Set-60-Count/12080783&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; for example you can purchase 100 LED's for $10 or £6.29&lt;/p&gt;&#xA;" OwnerUserId="1413" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-18T12:06:02.820" LastActivityDate="2010-11-18T12:06:02.820" />
  <row Id="6912" PostTypeId="1" CreationDate="2010-11-18T12:16:49.863" Score="3" ViewCount="191" Body="&lt;p&gt;I have a simple robot with two DC motors. Using the L298N Dual H-Bridge, what's the minimum number of control pins I can use to give me forward, back and turn?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a typical setup for the chip. It looks like I'll need 6 control lines to control 2 motors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I tied Ven high and relied on the &quot;C=D Fast Motor Stop&quot; when idle would this be bad?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://letsmakerobots.com/files/userpics/u4107/L298N.png&quot; rel=&quot;nofollow&quot;&gt;http://letsmakerobots.com/files/userpics/u4107/L298N.png&lt;/a&gt;&#xA;&lt;img src=&quot;http://letsmakerobots.com/files/userpics/u4107/L298N.png&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-18T17:03:20.630" LastActivityDate="2010-11-18T21:17:53.843" Title="How many control pins needed for L298N H-Bridge?" Tags="&lt;motor&gt;&lt;h-bridge&gt;&lt;l298n&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="6913" PostTypeId="2" ParentId="6909" CreationDate="2010-11-18T13:12:15.870" Score="3" ViewCount="" Body="&lt;p&gt;The problem with this question in my opinion is that it is too broad. If you want good answers, you should separate it in several questions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd start by first getting the fountain part done. Find appropriate fountain body and see what volume of water you'd need for it. This will probably give you a starting point for pump selection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't recommend you a good pump, because I have no experience in that field, but &lt;a href=&quot;http://www.backwoodshome.com/articles2/yago91.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; article seems like an interesting starting point. Basically, you'll need a low voltage DC pump. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;While selecting a pump, you should be checking put what types of solar power sources are available in your area. After you research that, it would be a good time to post a question here about driving a specific pump with specific solar power source. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next comes the assembly part. How difficult it is going to be will depend on previous steps. You could probably find a prefabricated pump controller which will most likely going to be just plug and play or you could be building your own. This is where it gets really complicated. If you are going to be making your own, you will need to make a circuit will require soldering skills and equipment. You will also need a circuit board which you can make yourself or get one from a factory (if you can find one which will take small orders in your area) or use some type of prototyping board. If you are going to be making it yourself, you'll probably need to ask several questions for that step alone, since making a controller will require some experience.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that, if something goes wrong, comes the debugging part. If the design is good, most likely the only problem would be bad solder joint. A good multimeter will come in handy there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do know that this answer isn't very specific, but your question as I said is very very very broad so I'm posting this more to give you idea for size of your project, because what you are asking here is pretty much equivalent of asking &quot;How do I make simple text editor with absolutely no programming experience?&quot; on StackOverflow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You mentioned voltage details in your comment. A good question when asking for that would be something like &quot;I have a pump which needs XX volts and YYY milliamps. I have ZZZ, XXX, YYY solar panels available. How do I make a circuit which could drive the pump using one of them?&quot; or something like that. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-11-18T13:12:15.870" CommentCount="1" />
  <row Id="6914" PostTypeId="2" ParentId="6912" CreationDate="2010-11-18T15:28:34.667" Score="1" ViewCount="" Body="&lt;p&gt;With two pins you have full control. This allows both forward, reverse and stop. if you want to allow coasting, you will need three pins to bring Ven low. If you do not need fast stop, you could use an XOR to control the Ven from the 2 control lines. When they are equal drive t low. Then it has forward reverse and coast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you hold Ven High when you decide to stop moving it will full brake. If you use a simple XOR gate to do the Ven signal then you can only coast. It is decided based on what you want the motor to do. If you need the option, use three lines. from a micro this is almost no cost.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-18T15:44:39.777" LastActivityDate="2010-11-18T15:44:39.777" CommentCount="3" />
  <row Id="6915" PostTypeId="1" AcceptedAnswerId="6925" CreationDate="2010-11-18T17:58:42.830" Score="0" ViewCount="191" Body="&lt;p&gt;I'm trying to get the Timer2 period match interrupt on my dsPIC33FJ128GP802 working. I want it to interrupt after ~480 cycles. I'm using MPLAB C30.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have, to initialize the timer and interrupt:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// Initialize Timer2, which is used for output timing.&#xA;T2CONbits.TON = 1;&#xA;T2CONbits.TSIDL = 0;&#xA;T2CONbits.TCKPS = 0;&#xA;T2CONbits.TCS = 0;&#xA;T2CONbits.T32 = 0;&#xA;// Initialize Timer2 interrupt with a slightly&#xA;// higher priority.&#xA;IPC1bits.T2IP = 5;&#xA;IFS0bits.T2IF = 0;&#xA;IEC0bits.T2IE = 0;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(the timer interrupt is initially disabled)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have already got pin change interrupts working with a priority of 4. I want the Timer2 interrupt to have a higher priority.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And to set up the interrupt I have this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;T2CONbits.TON = 1;&#xA;TMR2 = 0;&#xA;timer2_osd = 480 + vid_hoffset;&#xA;PR2 = timer2_osd;&#xA;IEC0bits.T2IE = 1;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I also have an ISR,&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void _MY_ISR _T2Interrupt()&#xA;{&#xA;    IFS0bits.T2IF = 0;&#xA;    return;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;However I find the processor just resets and will not run with this enabled. It will work with a busy loop checking the timer, but that wastes cycles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone see where I've gone wrong?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-18T20:33:27.717" Title="Timer2 period match interrupt on dsPIC33F not working" Tags="&lt;microcontroller&gt;&lt;dspic&gt;&lt;code&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="6916" PostTypeId="2" ParentId="6915" CreationDate="2010-11-18T19:02:05.407" Score="0" ViewCount="" Body="&lt;p&gt;The datasheet seems to suggest you should clear TON, initialize the timer, then set TON.  Many example sequences end with setting TON, they don't start with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many devices latch working values out of their configuration registers when they're enabled...  so you should always disable, configure, then enable.  Be very careful when changing registers on a running peripheral.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm also not clear on how the interrupt code gets tied to the timer2 interrupt event.  What's _MY_ISR?&lt;/p&gt;&#xA;" OwnerUserId="2004" LastActivityDate="2010-11-18T19:02:05.407" CommentCount="8" />
  <row Id="6917" PostTypeId="1" CreationDate="2010-11-18T19:05:54.870" Score="2" ViewCount="244" Body="&lt;p&gt;Hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given I have designed and produced an RF circuit with an output for connecting an antenna. I know this antenna has an input impedance of 50Ω. I now wish to measure the actual output impedance of my circuit, before connecting the antenna, to ensure that the impedance matches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How do I actually measure the output impedance of my circuit?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;And additionally, can I do this with hobby friendly priced equipment?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update: I know the basic theory of impedance matching, but I have never understood how to actually do it. So I am really asking for input on the specific hardware and equipment to use, and how perform actual tests.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The RF circuit is operating in the UHF range, and transmits about 10dBm, if this helps.&lt;/p&gt;&#xA;" OwnerUserId="718" LastEditorUserId="718" LastEditorDisplayName="" LastEditDate="2010-11-18T20:01:00.860" LastActivityDate="2010-11-20T13:42:16.377" Title="Measuring output impedance" Tags="&lt;rf&gt;&lt;impedance&gt;" AnswerCount="3" CommentCount="8" FavoriteCount="1" />
  <row Id="6918" PostTypeId="1" AcceptedAnswerId="6928" CreationDate="2010-11-18T19:40:46.253" Score="1" ViewCount="300" Body="&lt;p&gt;How can I design a system that would allow me to put multiple receivers on a single 4-20mA current loop? Assume that I have design control over only one of the receivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sensor:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Loop powered (2-wire)&lt;/li&gt;&#xA;&lt;li&gt;Supply voltage: 12-28VDC&lt;/li&gt;&#xA;&lt;li&gt;Max Load: 250 Ohms @ 12VDC (500 Ohms @ 24VDC)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Current Receiver Design:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;250 Ohm resistor to ground&lt;/li&gt;&#xA;&lt;li&gt;Loop power supply ground is connected to ADC ground&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-11-18T19:47:29.067" LastActivityDate="2010-11-19T21:18:57.890" Title="Multiple receivers in a 4-20mA current loop?" Tags="&lt;sensor&gt;&lt;current-measurement&gt;&lt;4-20ma&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="6919" PostTypeId="1" AcceptedAnswerId="6924" CreationDate="2010-11-18T19:41:46.417" Score="4" ViewCount="265" Body="&lt;p&gt;I have a switch which reads 6A 125VAC / 3A 250VAC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't figure out why this would be the case. The only reason I can think of the rating is the wires and contacts are only rated to take so much current and so much power dissipation. A higher voltage should not lead to more power dissipation. So why do switches and relays have lower current ratings at higher voltages?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-19T11:17:08.327" Title="Why do switches and relays have lower current ratings at higher voltages?" Tags="&lt;relay&gt;&lt;switch&gt;" AnswerCount="3" CommentCount="10" FavoriteCount="3" />
  <row Id="6920" PostTypeId="2" ParentId="6917" CreationDate="2010-11-18T19:55:14.677" Score="1" ViewCount="" Body="&lt;p&gt;In general, to measure an output impedance, you just connect a known impedance across it and measure the drop in voltage level.  You can then calculate the source impedance using the voltage divider rule.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Cj4sf.png&quot; alt=&quot;voltage divider&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;V&lt;sub&gt;out&lt;/sub&gt; = Z&lt;sub&gt;2&lt;/sub&gt;/(Z&lt;sub&gt;1&lt;/sub&gt;+Z&lt;sub&gt;2&lt;/sub&gt;)*V&lt;sub&gt;in&lt;/sub&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You know these:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Z&lt;sub&gt;2&lt;/sub&gt; (known load)&lt;/li&gt;&#xA;&lt;li&gt;V&lt;sub&gt;out&lt;/sub&gt; (voltage with load)&lt;/li&gt;&#xA;&lt;li&gt;V&lt;sub&gt;in&lt;/sub&gt; (unloaded voltage)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So you can calculate the output impedance:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Z&lt;sub&gt;1&lt;/sub&gt; = ((V&lt;sub&gt;in&lt;/sub&gt; - V&lt;sub&gt;out&lt;/sub&gt;)*Z&lt;sub&gt;2&lt;/sub&gt;)/V&lt;sub&gt;out&lt;/sub&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In other words, V&lt;sub&gt;in&lt;/sub&gt; and Z&lt;sub&gt;1&lt;/sub&gt; are inside your device that you're measuring, and Z&lt;sub&gt;2&lt;/sub&gt; is the test load you connect across its output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/D48gG.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the impedance varies with frequency, you can do the same measurement multiple times with sine waves of different frequencies.  If you need to know the reactance, you'll have to measure the phase change with and without the load connected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At low frequencies, this can all be done with a single channel scope and hobbyist equipment.  At UHF I'm not sure how much effect the test equipment, scope's impedance, probe capacitance and line length, etc. will have on the measurements.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-18T20:30:11.103" LastActivityDate="2010-11-18T20:30:11.103" CommentCount="4" />
  <row Id="6922" PostTypeId="2" ParentId="5713" CreationDate="2010-11-18T20:00:57.243" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.romanblack.com/shift1.htm&quot; rel=&quot;nofollow&quot;&gt;Roman Black describes the shift1 system&lt;/a&gt; that allows you to independently control any number of LEDs from a single microcontroller pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;@Fake Name, @Tim, @pingswept all suggest chaining some shift registers together, the DO data output pin on one feeding the DI data input pin on the next. The 74HC595 would work fine.&#xA;(Perhaps &lt;a href=&quot;http://electronics.stackexchange.com/questions/6676/which-sipo-chip-is-better-74hc4094-or-74hc595-or-something-else&quot;&gt;some other chip would work slighly better&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(@reemrevnivek, with this kind of daisy-chained SPI, each device after the first does not require any more pins on the microcontroller, contrary to what many people claim -- why do you listen to them? :-).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally this requires 4 pins on the microcontroler -- MISO, MOSI, SCLK, and latch.&#xA;Since you are only doing output, you don't need a MISO input pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Roman Black has figured out that with a some very careful timing on on a single microcontroller output, and with some careful tweaking of an analog circuit, a single microcontroller pin can drive a simple-looking analog circuit that separates out the common SCLK, the DI pin of the first chip in the chain (MOSI), and the common latch signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then that microcontroller can control 25 LEDs from a single pin.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-11-18T20:00:57.243" />
  <row Id="6924" PostTypeId="2" ParentId="6919" CreationDate="2010-11-18T20:06:11.443" Score="7" ViewCount="" Body="&lt;p&gt;I would imagine that the current derating at higher voltages would be due to arcing when the contacts open. Keeping the same current as voltages increase will allow arcs to persist longer and cause more damage to the contact surfaces. On small relays and contactors, these arcs are tiny, but if viewed in a darkened room, you can see that they do exist. Over several thousand cycles, (especially with inductive loads such as motors) the arcing will cause pitting and oxidation of the contact surfaces. Damaged surfaces are more resistive, which heats the contacts, and promotes more arcs. Failure will come much sooner under these conditions of accelerated wear.&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-11-18T20:06:11.443" />
  <row Id="6925" PostTypeId="2" ParentId="6915" CreationDate="2010-11-18T20:24:07.923" Score="2" ViewCount="" Body="&lt;p&gt;I just looked at the code I wrote a while ago to set up timer 2 for a periodic interrupt of 1 ms for a PIC24F (essentially same timer hardware as dsPIC33F), and it looks like so:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define CPU_CLK_RATE 32000000L&#xA;#define PERIPH_CLOCK_RATE (CPU_CLK_RATE/2L)&#xA;&#xA;#define TIMER_2_RATE 1000L&#xA;#define TIMER_2_PRE  64L        // clock rate is (32000000/2)/64 = 250 KHz&#xA;#define TIMER_2_MATCH (PERIPH_CLOCK_RATE/(TIMER_2_RATE * TIMER_2_PRE))  &#xA;&#xA;    T2CON = 0; // set control register to defaults&#xA;&#xA;    T2CONbits.TSIDL = 1;  // discontinue when idle&#xA;    T2CONbits.TCKPS1 = 1; // prescaler of 64&#xA;    T2CONbits.TCKPS0 = 0; // prescaler of 64&#xA;    T2CONbits.T32 = 0;    // 16 bit timer&#xA;    T2CONbits.TCS = 0;    // FOSC/2 (32Mhz/2)&#xA;    TMR2 = 0-TIMER_2_MATCH*19;  // 20 millisecond delay before starting&#xA;    PR2 = TIMER_2_MATCH; &#xA;&#xA;    SetPriorityIntT2(TIMER2_INTERRUPT_PRIORITY); // set to very high priority&#xA;    EnableIntT2; // enable interrupts&#xA;&#xA;    T2CONbits.TON = 1&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Very similar to yours, except I pre-initialized TMR2 so there would be a delay before the first interrupt. Don't know if that would help in your case or not, but you might try it.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-11-18T20:33:27.717" LastActivityDate="2010-11-18T20:33:27.717" CommentCount="1" />
  <row Id="6928" PostTypeId="2" ParentId="6918" CreationDate="2010-11-18T20:49:57.693" Score="2" ViewCount="" Body="&lt;p&gt;Current loops were initially designed to connect multiple teletypewriters in series (originally 60 ma was used instead of 20 ma).  This scheme was latter adapted for instrumentation use, with 4-20 ma as the standard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your current receiver design, one end of the resistor is connected to ground.  Instead it should be passed on to the next receiver, like the old series Christmas tree light strings.  The last receiver connects to a lead which goes back to the transmitter ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At each receiver, a 250 ohm resistor is placed in the loop.  The two sides of the resistor can then be fed into an optical coupler, which will turn a transistor on/off which you can feed to your circuit.  (Or if you need to still be able to power your sensor from the loop, you will need to make the sensor run off a floating ground reference tied to one end of the sensor.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the sensor requires a minimum of 12v, using a 250 ohm resistor this implies a current of 48 ma, not 20 -- so I'm not sure if this is really a 4-20 ma loop or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have to use the current receiver design, it should be placed last.  All of the others must allow the loop to be passed on.  (Which limits you to two receivers, one new and one original design if you are allowed only one new receiver.)&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-11-18T22:13:54.003" LastActivityDate="2010-11-18T22:13:54.003" CommentCount="3" />
  <row Id="6929" PostTypeId="2" ParentId="6918" CreationDate="2010-11-18T20:50:38.353" Score="0" ViewCount="" Body="&lt;p&gt;As the sensor you are using has a maximum load I think that one (maybe good) alternative is use a hall sensor on the loop. This way you can extract the information on the current without interfering in the main loop. The other receiver can be a regular one.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-18T20:50:38.353" />
  <row Id="6930" PostTypeId="2" ParentId="6599" CreationDate="2010-11-18T20:55:58.810" Score="0" ViewCount="" Body="&lt;p&gt;Have you seen the Throwie that blinks in Morse code?&#xA;&lt;a href=&quot;http://www.instructables.com/id/LED-Throwie-Talkie/&quot; rel=&quot;nofollow&quot;&gt;Instructables&lt;/a&gt; and &lt;a href=&quot;http://c2.com/cybords/?ComputerizedThrowie&quot; rel=&quot;nofollow&quot;&gt;Ward's own website&lt;/a&gt;.&#xA;It uses an 8 pin DIP microcontroller&#xA;(less than $3 in ones).&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-11-18T20:55:58.810" />
  <row Id="6931" PostTypeId="2" ParentId="6917" CreationDate="2010-11-18T21:16:27.773" Score="2" ViewCount="" Body="&lt;p&gt;You really need one of a number of options, none of them are hobby friendly if you are above a few MHz. I would guess you are at 2.4GHz, or at 900MHz.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Professional Options&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;If you might know someone whom has access to equipment that would help you have a few options.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Network_analyzer_%28electrical%29&quot; rel=&quot;nofollow&quot;&gt;VNA&lt;/a&gt;- Vector Network Analyzer. This can give you a smith chart over a frequency range and make sure it shows you at 50 ohms. You can also measure S11 which should be less than -20dB&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Spectrum_analyzer&quot; rel=&quot;nofollow&quot;&gt;Spectrum Analyzer&lt;/a&gt;- This should allow you to determine your power received at your frequency. This is not ideal, but it should get more output power as you get closer to a proper match.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/SWR_meter&quot; rel=&quot;nofollow&quot;&gt;SWR Meter&lt;/a&gt;-&lt;a href=&quot;http://electronics.stackexchange.com/questions/6917/measuring-output-impedance/6970#6970&quot;&gt;As Is noted in another answer&lt;/a&gt; and I always forget about, you can use an Standing Wave Ratio meter, but I would still suggest a VNA. They have significantly more features, and can do anything a spectrum analyzer or SWR meter can do.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;h3&gt; Hacker style ways to approach it&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;There is another funny way to approach this, the problem being you will need to build one of a few microwave components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use an &lt;a href=&quot;http://en.wikipedia.org/wiki/Isolator_%28microwave%29&quot; rel=&quot;nofollow&quot;&gt;isolator&lt;/a&gt; and measure its temperature, hotter isolator is equivalent to a worse mismatch. this is not even close to good method as at 10dBm it will be very hard to detect a temperature failure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could build your own &lt;a href=&quot;http://en.wikipedia.org/wiki/Frequency_mixer&quot; rel=&quot;nofollow&quot;&gt;mixer&lt;/a&gt; and feedback your output signal and mix it with your signal returning from the connection. To take away your signal from the feedback you need to use what is called a &lt;a href=&quot;http://en.wikipedia.org/wiki/Circulator&quot; rel=&quot;nofollow&quot;&gt;circulator&lt;/a&gt;. This is not fun, but it is doable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you would like to try either method, which is similar to creating your own VNA, I can get you more information on how to build these devices.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-20T13:42:16.377" LastActivityDate="2010-11-20T13:42:16.377" CommentCount="3" />
  <row Id="6932" PostTypeId="2" ParentId="6912" CreationDate="2010-11-18T21:17:53.843" Score="1" ViewCount="" Body="&lt;p&gt;The minimum number of pin you need to control is only '&lt;strong&gt;one&lt;/strong&gt;' per motor, I use this configuration in most of my robot. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connect a not gate or a transistor to provide inverted the output between C and D pin and supply a &lt;strong&gt;PWM&lt;/strong&gt; signal as a input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this setup you'll have only one input controlling both the speed and direction of the motor and comes in very handy in robotics, you can control it by varying the duty cycle.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;h2&gt;Direction    V/s     Duty cycle&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;stop    ----&gt;     50%&lt;/p&gt;&#xA;&#xA;&lt;p&gt;forward ----&gt;     51-100%  (forward speed increases with increase in duty &#xA;                               cycle where 100% as max forward speed)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;reverse ----&gt;      0-49%    (reverse speed increases with decrease in duty&#xA;                               cycle where 0% is max reverse speed)&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2010-11-18T21:17:53.843" CommentCount="2" />
  <row Id="6933" PostTypeId="2" ParentId="6919" CreationDate="2010-11-18T22:06:23.210" Score="5" ViewCount="" Body="&lt;p&gt;The information you see on a relay is really a condensed from of what is called a load limit curve. It's better to really think that the relay can switch a maximum power, rather than a given current and voltage. To a large extent, this limit is due to arcing - both from the point of an arc forming and being sustained and destroying the relay, or in terms of the contacts becoming pitted and not reaching the rated number of switching cycles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you take a look at a data sheet e.g. &lt;a href=&quot;http://www.farnell.com/datasheets/50789.pdf&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; on page 7, you will see load limit curves. In the top chart, they have drawn a constant power line at 40W, which is entirely below the load limit curve. This means that the switching capacity of the relay is 40W across the range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The switching capacity is the largest DC load that the relay can switch, irrespective of current or voltage. It has nothing to do with power dissipation in the relay itself, which should be minimal. The quoted numbers on a relay are generally just indications of current at line voltage in a few countries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Load limit curves can be derived experimentally, but I think quite a few are just based off theory on switch geometry, contact material, speed of opening etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the extremes of very low current and low voltage, arcing isn't as much of an issue, so the rating will be slightly higher here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC is more prone to sustaining an arc than AC, so the curve is for DC. Sometimes they also show lines with derating applied for inductive loads.&lt;/p&gt;&#xA;" OwnerUserId="2005" LastEditorUserId="2005" LastEditorDisplayName="" LastEditDate="2010-11-19T11:17:08.327" LastActivityDate="2010-11-19T11:17:08.327" />
  <row Id="6934" PostTypeId="1" AcceptedAnswerId="6943" CreationDate="2010-11-18T22:52:52.487" Score="2" ViewCount="147" Body="&lt;p&gt;I have this rangefinder &lt;a href=&quot;http://www.hobbyengineering.com/H2951.html&quot; rel=&quot;nofollow&quot;&gt;http://www.hobbyengineering.com/H2951.html&lt;/a&gt; and my MCU is running on 3.3v (MSP430G2231), will this thing work poorly if I feed it 3.3v instead of 5v? I really don't want to have TWO voltage regulators on this board. If not what else can I do to get it the voltage it needs? The power source is a 9.6v battery pack with a LD33V - 3.3V regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Spec sheet:&#xA;&lt;a href=&quot;http://www.parallax.com/dl/docs/prod/acc/PingDocs.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.parallax.com/dl/docs/prod/acc/PingDocs.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-11-20T00:31:32.197" Title="What will happen if I feed this rangefinder 3.3v?" Tags="&lt;voltage-regulator&gt;&lt;msp430&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="6935" PostTypeId="2" ParentId="6934" CreationDate="2010-11-18T23:00:50.270" Score="2" ViewCount="" Body="&lt;p&gt;It's not likely to work very well unless you feed it with 5V. Just add a 5V regulator to your board. MSP430 inputs aren't 5V-compatible, IIRC; a 1k series resistor might be all that you need to avoid damage.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-18T23:00:50.270" CommentCount="2" />
  <row Id="6936" PostTypeId="1" AcceptedAnswerId="6938" CreationDate="2010-11-18T23:23:59.907" Score="1" ViewCount="87" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I'm buying a LM317 and it comes in 3 different packages. Which is the best for attaching a heat sink? The options are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;TO-3&lt;/li&gt;&#xA;&lt;li&gt;TO-220&lt;/li&gt;&#xA;&lt;li&gt;TO-92      &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Thanks in Advance,&lt;br&gt;&#xA;Dean &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-11-19T00:12:29.690" LastActivityDate="2010-11-19T00:12:29.690" Title="Best package for heat sinking?" Tags="&lt;packages&gt;" AnswerCount="3" />
  <row Id="6937" PostTypeId="2" ParentId="6936" CreationDate="2010-11-18T23:27:46.340" Score="1" ViewCount="" Body="&lt;p&gt;TO-220 would be the easiest/best for attaching a heatsink in your application, I'd suspect&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-18T23:27:46.340" />
  <row Id="6938" PostTypeId="2" ParentId="6936" CreationDate="2010-11-18T23:44:37.407" Score="5" ViewCount="" Body="&lt;p&gt;LM317 in TO-92 only does 100mA, wheras the TO-3 and TO-220 are both 1.5A - so it depends on how much current you need!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Best for attaching a heat sink&quot; - hard to say. It's easy to attach a TO-220 to a heatsink, just a hole and thermal compound (or one of the clip on ones). You can also just attach them to the PCB for a bit of extra cooling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;T0-3 can have a lower thermal resistance to the heatsink, but generally are more awkward to mount.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TO-92 isn't really possible to attach to a heatsink.&lt;/p&gt;&#xA;" OwnerUserId="2005" LastEditorUserId="2005" LastEditorDisplayName="" LastEditDate="2010-11-18T23:57:22.783" LastActivityDate="2010-11-18T23:57:22.783" CommentCount="3" />
  <row Id="6939" PostTypeId="2" ParentId="6936" CreationDate="2010-11-18T23:47:43.880" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CBcQFjAA&amp;amp;url=http%3A%2F%2Fwww.linear.com%2Fdesigntools%2Fpackaging%2FLinear_Technology_Thermal_Resistance_Table.pdf&amp;amp;ei=5LnlTPaZDsP58Ab1t-ChCQ&amp;amp;usg=AFQjCNGZJwO3JZqS9RJQdtfy6Ze3ieLbIA&quot; rel=&quot;nofollow&quot;&gt;Linear publishes this information&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Theta JA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TO-3: 35C/W&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TO-92: 160C/W&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TO-220: 50C/W &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the TO-3 wins in theta JA, which implies that it would be able to transfer the most heat to a heatsink as well.  Never seen a TO-92 attached to a heatsink, i would thing it would require a lot of support to try to do so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In terms of physical attachment, the TO-220 and TO-3 are about the same, just a different type of heatsink is needed.  TO-3 would take up more space in most applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Several other companies publish similar charts but a quick google-fu didn't turn one up for national, send em an e-mail, I'm sure they have the data somewhere.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-18T23:53:36.017" LastActivityDate="2010-11-18T23:53:36.017" />
  <row Id="6940" PostTypeId="1" AcceptedAnswerId="6941" CreationDate="2010-11-19T00:34:49.580" Score="8" ViewCount="218" Body="&lt;p&gt;Has many of you acquired used parts (motors, expensive IC chips, sensors, actuators, etc.) from the dumpsters, recycling, or trash and used them for your projects? &lt;strong&gt;How did you feel benefited from such choices, on top of saving the environment, despite the challenges of finding the true specifications?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance for the feedback!&lt;/p&gt;&#xA;" OwnerUserId="1944" LastActivityDate="2010-11-20T03:36:53.317" CommunityOwnedDate="2010-11-20T02:29:55.593" Title="Electronics Freeganism" Tags="&lt;parts&gt;" AnswerCount="7" CommentCount="8" FavoriteCount="1" />
  <row Id="6941" PostTypeId="2" ParentId="6940" CreationDate="2010-11-19T00:37:51.187" Score="8" ViewCount="" Body="&lt;p&gt;I wish I didn't think that was a waste of time. I have a large collection of scavenged parts, but it's rare that I actually use them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, as long as I'm willing to plan ahead a few days, the collective warehouse of Digikey, Mouser, Sparkfun, and so forth will give me what I need for just a few minutes of engineering salary.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-11-19T15:48:19.433" LastActivityDate="2010-11-19T15:48:19.433" CommunityOwnedDate="2010-11-20T02:29:55.593" CommentCount="4" />
  <row Id="6942" PostTypeId="2" ParentId="6940" CreationDate="2010-11-19T00:41:11.267" Score="2" ViewCount="" Body="&lt;p&gt;I'm very much a novice with electronics with a background in computer science. Just like I was fascinated by &quot;tearing apart&quot; open-source libraries and tweaking and poking (even if I didn't understand much originally) I've really enjoyed doing the same with old electronics. It's fun! Sites like &lt;a href=&quot;http://hackaday.com/&quot; rel=&quot;nofollow&quot;&gt;Hack a Day&lt;/a&gt; often have projects using some interesting recycled parts and I love that I can actually try this myself without buying a bunch of components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can definitely say that I would not have gotten involved with electronics if I hadn't had the opportunity to do this with &quot;junk&quot; that no one wanted.&lt;/p&gt;&#xA;" OwnerUserId="1970" LastActivityDate="2010-11-19T00:41:11.267" CommunityOwnedDate="2010-11-20T02:29:55.593" />
  <row Id="6943" PostTypeId="2" ParentId="6934" CreationDate="2010-11-19T00:45:20.383" Score="3" ViewCount="" Body="&lt;p&gt;You shouldn't have any problems with two regulators. You really aren't putting the two in parallel. Both inputs will be connected to the voltage source and the differnt voltage outputs will go to the different sections of the circuit. (You still need your input and output caps). I do this quite frequently with 12V and 5V regulators without any problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I didn't see a minimum trigger voltage spec for the TTL trigger pulse going to the range finder so you'll need to ensure that it will recognise the signals from your 3V MCU as high.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the worst, you would need a logic level converter like &lt;a href=&quot;http://www.sparkfun.com/products/8745&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; from Sparkfun.&lt;/p&gt;&#xA;" OwnerUserId="425" LastActivityDate="2010-11-19T00:45:20.383" CommentCount="1" />
  <row Id="6944" PostTypeId="1" CreationDate="2010-11-19T03:54:55.760" Score="0" ViewCount="71" Body="&lt;p&gt;Anybody have any good suggestions for a source of portable and convenient flame beyond matches for removing lacquer insulation, etc?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was originally considering just a standard metal Zippo lighter, but then I learned that the fluid evaporates pretty quickly (as in inside of a week).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess there is just a portable Bic (I'm not sure if it suffers from the same issue?), but I was looking for something a bit more permanent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My main requirements are reasonably small, easy to start, and that fluid does not evaporate with any speed (since it would see use only occasionally). It would mostly just sit with the rest of my tools until I needed it.&lt;/p&gt;&#xA;" OwnerUserId="647" LastActivityDate="2010-11-19T05:25:36.633" ClosedDate="2010-11-19T16:49:08.250" Title="Good source of convenient flame?" Tags="&lt;tools&gt;&lt;flame&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="6945" PostTypeId="2" ParentId="6940" CreationDate="2010-11-19T03:55:18.943" Score="2" ViewCount="" Body="&lt;p&gt;For a lot of amateur radio operators, the &quot;Junk Box&quot; is their primary source of supply. I've kept old dead computer power supplies and the like specifically for their parts. Sometimes it's a pain to do, but it's great for non-critical specs such as power supply caps and heat sinks.&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-11-19T03:55:18.943" CommunityOwnedDate="2010-11-20T02:29:55.593" />
  <row Id="6946" PostTypeId="1" AcceptedAnswerId="6949" CreationDate="2010-11-19T04:42:12.703" Score="4" ViewCount="176" Body="&lt;p&gt;I made a power supply using two 47uf electrolytic (aluminum, I believe) caps and a L7805CV 5v power regulator. I also added a 100ohm resistor and an led to vout. I'm using a battery pack of 4 NiMH AA batteries. The pack reads 5.43 on the multimeter with no load. When I hook up a motor to vout and ground, I get 3.85v instead of the expected 5v. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wired up like so:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;battery positive -&gt; vin&lt;/li&gt;&#xA;&lt;li&gt;battery negative -&gt; ground&lt;/li&gt;&#xA;&lt;li&gt;vout -&gt; 100ohm resistor -&gt; led -&gt; ground&lt;/li&gt;&#xA;&lt;li&gt;vin -&gt; 47uf cap -&gt; gnd&lt;/li&gt;&#xA;&lt;li&gt;vout -&gt; 47uf cap -&gt; gnd&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Here's a pic: &lt;img src=&quot;http://i.imgur.com/SGlNB.jpg&quot; alt=&quot;Photo of the circuit from:http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1169.snc4/154180_170665839624424_100000430264071_471279_1472098_n.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="2006" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-19T05:04:10.563" LastActivityDate="2010-11-19T05:21:03.113" Title="Why is my power supply putting out 3.85v instead of 5v?" Tags="&lt;arduino&gt;&lt;voltage-regulator&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="6947" PostTypeId="2" ParentId="6946" CreationDate="2010-11-19T04:57:25.933" Score="4" ViewCount="" Body="&lt;p&gt;Did you measure the voltage of your battery pack under load?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Battery packs can have a small dip in voltage due to charge level, but often the way a battery fails is best simulated as an ideal voltage source with an increasing resistance in series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means they measure almost full charge for most of their life if there is no load. If you then place a load their charge can change significantly. The lithium battery I use at work measures 2.7V under no load but under a 1mA load drops below 1.6V. These batteries are effectively dead, but still show quite a bit of voltage if you do not need current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Chances are your battery pack is between 4.3 and 4.9V under load. this depends on your regulator.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-19T04:57:25.933" CommentCount="3" />
  <row Id="6948" PostTypeId="2" ParentId="6946" CreationDate="2010-11-19T05:03:12.717" Score="3" ViewCount="" Body="&lt;p&gt;This may seem obvious, but did you wire it correctly. linear regulators cause a rather large drop if you mix up ground and power. There are a number of other ways dependent on your package that can cause odd problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It just takes mixing up power and ground to cause funny things to happen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Secondly, try removing the caps to see if it helps. They are required for transients, not for a constant DC(although still suggested). You may have a bad one.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-19T05:03:12.717" CommentCount="7" />
  <row Id="6949" PostTypeId="2" ParentId="6946" CreationDate="2010-11-19T05:21:03.113" Score="11" ViewCount="" Body="&lt;p&gt;The L7805C has a dropout voltage of 2v typical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So with 5.43 volts input you can expect an output of 3.43 volts typical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Although dropout is not really spec'd when the output is below regulation voltage.)&#xA;&lt;img src=&quot;http://i.imgur.com/cTy8G.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-19T05:21:03.113" CommentCount="2" />
  <row Id="6950" PostTypeId="2" ParentId="6944" CreationDate="2010-11-19T05:25:36.633" Score="3" ViewCount="" Body="&lt;p&gt;The portable bic might work, but a microtorch would be your best bet - they use a standard disposable lighter for fuel, but burn much hotter. there dosen't seem to be much evaporation, but you could refill it off a standard can of lighter fluid if need be.&lt;/p&gt;&#xA;" OwnerUserId="1870" LastActivityDate="2010-11-19T05:25:36.633" CommentCount="3" />
  <row Id="6951" PostTypeId="2" ParentId="5713" CreationDate="2010-11-19T07:46:13.827" Score="0" ViewCount="" Body="&lt;p&gt;You can connect another microcontroller via that single pin, and talk to it via 1wire (or your own protocol if you need high speed). Then that other microcontroller deals with LEDs.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastEditorUserId="1129" LastEditorDisplayName="" LastEditDate="2010-11-25T07:55:26.613" LastActivityDate="2010-11-25T07:55:26.613" />
  <row Id="6952" PostTypeId="1" AcceptedAnswerId="6955" CreationDate="2010-11-19T08:51:01.017" Score="6" ViewCount="118" Body="&lt;p&gt;Is there any point in using a big crystal over a smaller one? Apart from the tolerance spec, how come crystal manufacturers have all these different models of crystals from really tiny ones to big ones? I don't think I know the advantage to using a big crystal.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-19T22:31:02.550" Title="Difference between crystals?" Tags="&lt;crystal&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="6953" PostTypeId="2" ParentId="6919" CreationDate="2010-11-19T09:09:28.450" Score="2" ViewCount="" Body="&lt;p&gt;6A @ 125V (assume DC for simplicity) is 750 Watts.&#xA;3A @ 250V = 750 Watts&#xA;That sis why they have same rating.&#xA;Its expressed this way because this switch is designed for switching mains current. In USA thats 115V and in UK/Asia its 230-250V&#xA;So the manufacturer is trying to help you select this switch based on your current draw. The same applies to wiring in the USA and elsewhere. In the USA you need a thicker cable to carry more current at a lower voltage than in Europe (for example) - all to supply the same power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But we generally do not rate these items by power - so the conversion to V/A is printed to make your life easier.&lt;/p&gt;&#xA;" OwnerUserId="2008" LastActivityDate="2010-11-19T09:09:28.450" CommentCount="4" />
  <row Id="6954" PostTypeId="2" ParentId="6899" CreationDate="2010-11-19T09:15:46.433" Score="1" ViewCount="" Body="&lt;p&gt;Use SLAM and the code from here as a start.&#xA;Use a camera and a high power DSP like the blackfin. or dedicate a PC (depending on your size, costs, ability)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.robots.ox.ac.uk/~gk/PTAM/&quot; rel=&quot;nofollow&quot;&gt;http://www.robots.ox.ac.uk/~gk/PTAM/&lt;/a&gt;&#xA;http://www.robots.ox.ac.uk/~bob/research/research_ptamm.html&lt;/p&gt;&#xA;" OwnerUserId="2008" LastActivityDate="2010-11-19T09:15:46.433" />
  <row Id="6955" PostTypeId="2" ParentId="6952" CreationDate="2010-11-19T11:55:25.987" Score="4" ViewCount="" Body="&lt;p&gt;Smaller packages tend to be more expensive for the same spec. There are also often differences in frequency ranges, tempco, accuracy etc. available in different sizes&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-19T11:55:25.987" />
  <row Id="6956" PostTypeId="1" AcceptedAnswerId="7261" CreationDate="2010-11-19T12:27:24.220" Score="1" ViewCount="567" Body="&lt;p&gt;How do I define a tented via-in-pad in a parts library in Eagle PCB? (&lt;a href=&quot;http://screamingcircuits.typepad.com/.a/6a00d8341c008a53ef0120a6ca866f970b-800wi&quot; rel=&quot;nofollow&quot;&gt;Example of result here&lt;/a&gt;:)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once I define the large pad underneath the QFN, I seem to be able to turn the soldermask on and off. However, once I turn the soldermask off, it seems impossible to just define little circular areas of soldermask (soldermask layer in Eagle is just tStop).&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-19T13:35:13.633" LastActivityDate="2010-11-29T05:39:41.480" Title="How do I define a tented via-in-pad in Eagle?" Tags="&lt;pcb&gt;&lt;eagle&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="6957" PostTypeId="2" ParentId="6940" CreationDate="2010-11-19T12:43:02.197" Score="2" ViewCount="" Body="&lt;p&gt;The dumpsters around my old university were always great value... I used a bunch of brand new relays found in there, coax cable, banana leads, and sold two brand new Macbook Pro restore DVDs for $200 on eBay which weren't removed from the computer box found in the bin. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However at the moment there is so much ewaste floating around, you can /almost/ get what you want for some things. There is a &lt;a href=&quot;http://www.littlebirdelectronics.com/products/Benchtop-Power-Board-Kit.html&quot; rel=&quot;nofollow&quot;&gt;kit&lt;/a&gt; which turns an ATX power supply into a nice simple bench PSU, many old computers on the street still have working PSU for this purpose. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-11-19T12:43:02.197" CommunityOwnedDate="2010-11-20T02:29:55.593" />
  <row Id="6958" PostTypeId="1" AcceptedAnswerId="6962" CreationDate="2010-11-19T13:42:45.487" Score="2" ViewCount="359" Body="&lt;p&gt;What kind of capacitors should I use to couple audio? I'm dealing with line level 1Vp-p audio, with a 1V dc offset (typ.) I want to convert this into 1Vp-p ac, at up to 20 kHz. My first version used ceramic 10u 10V caps - a similation showed attenutation by about 15% at 20 kHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt; I eventually went for 10u 6.3V. I did not need hi-fi quality and the fact that 10u 6.3V caps were available in 0603 packages was useful for me.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-02-08T22:35:52.077" LastActivityDate="2011-02-08T22:35:52.077" Title="Audio coupling capacitors" Tags="&lt;capacitor&gt;&lt;audio&gt;" AnswerCount="2" CommentCount="11" />
  <row Id="6959" PostTypeId="1" AcceptedAnswerId="6961" CreationDate="2010-11-19T13:46:05.313" Score="6" ViewCount="373" Body="&lt;p&gt;My oscilloscope has 100 MHz -3dB bandwidth. -3dB is 0.707 units (sqrt(2) / 2). What does this mean, why 70.7% attenuation? Is there any particular reason for this attenuation level?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-19T18:15:37.540" Title="What is the significance of -3dB?" Tags="&lt;decibel&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="6960" PostTypeId="2" ParentId="6959" CreationDate="2010-11-19T13:53:43.737" Score="8" ViewCount="" Body="&lt;p&gt;The modulus graphic on the bode diagram of a first order high pass or low pass filter, can be approximated by two lines. The point which the two lines meet, when compared to the real line gives us the number of -3db. This point is called the cutoff frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/eHzVi.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, lots of systems are designed to operate in normal conditions until they met the cutoff frequency when they lose at maximum 3db. If you operate with signal above that frequency the signal can be more attenuated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More info in Wikipedia about &lt;a href=&quot;http://en.wikipedia.org/wiki/Low-pass_filter#Continuous-time_low-pass_filters&quot; rel=&quot;nofollow&quot;&gt;continuous low pass filters&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-19T13:53:43.737" />
  <row Id="6961" PostTypeId="2" ParentId="6959" CreationDate="2010-11-19T14:09:27.577" Score="14" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Voltage vs Power when using dB&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The -3db point is also known as the &quot;half power&quot; point. In voltage it may not make not make tons of sense as to why we use (sqrt(2) / 2), but lets look at an example of what it means in the sense of power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First off, power=V^2/R, but lets assume R is a constant 1ohm. Because of the constant 1ohm, we can remove it from the equation all together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lets say you have a signal at 6v, its power would then be 6v^2=36W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I take the -3db point, 6v*(sqrt(2) / 2) = 4.2426V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now lets get the power at the -3db point, 4.2426V^2=18W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So originally we had 36W, now we have 18W (which of course is half of 36W).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Application of -3dB in Filters&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The -3db point is very commonly used with filters of all types (low pass, band pass, high pass...). It is just saying the filter cuts off half of the power at that frequency. The rate at which it drops off depends on the order of the system you are using. Higher order can get closer and closer to a &quot;brick wall&quot; filter. Brick wall filter being one that just before the cutoff frequency you are at 0dB (no change to you signal) and just after you are at -∞ dB (no signal passes through).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Why filter the input to an Oscope?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, many reasons. All devices (analog or digital) have to do something with the signal. You can go as simple as a voltage follower up to something more complex like showing the signal on a screen or turning the signal into audio. All of the devices required to convert your signal into something that is usable have attributes about them that are frequency dependent. One simple example of this is an opamp and its GBWP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, on an Oscope they will add a low pass filter so that none of the internal devices are having to deal with frequencies above what they can handle. When an oscope says its -3db point is 100MHz they are saying they have placed a low pass filter on its input has a cut off frequency (-3dB point) of 100MHz.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-19T18:15:37.540" LastActivityDate="2010-11-19T18:15:37.540" CommentCount="7" />
  <row Id="6962" PostTypeId="2" ParentId="6958" CreationDate="2010-11-19T14:23:34.493" Score="4" ViewCount="" Body="&lt;p&gt;When you are using capacitors to couple a circuit you need to be worrying about the low frequencies. A coupling capacitor is by definition a high pass circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The larger the capacitor value you chose, the lower your cut off frequency will be on the high pass circuit. &lt;a href=&quot;http://en.wikipedia.org/wiki/High-pass_filter&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt; shows an example circuit as well as how to pick your capacitor value in respect to your desired cut off frequency and resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the type of capacitor, since audio is AC you will need to have a non-polarized capacitor. In my experience, I have never found anything better then a ceramic capacitor for this application.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-19T14:23:34.493" CommentCount="5" />
  <row Id="6963" PostTypeId="1" AcceptedAnswerId="6967" CreationDate="2010-11-19T14:54:15.430" Score="4" ViewCount="201" Body="&lt;p&gt;I have a 4.8v battery pack and I made a simple power supply with a L7805CV voltage regulator, which has a 2v dropout. So I'm only getting like 3.5v out. Is it possible to throw an op-amp or something like that before the voltage regulator to make sure I get at least the 7v I need to achieve 5v on vout?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not, what is best practice?&lt;/p&gt;&#xA;" OwnerUserId="2006" LastEditorUserId="2006" LastEditorDisplayName="" LastEditDate="2010-11-19T15:00:19.713" LastActivityDate="2010-11-19T15:11:25.220" Title="Can I use an amp before my voltage regulator to ensure I get 5v?" Tags="&lt;arduino&gt;&lt;voltage-regulator&gt;" AnswerCount="5" />
  <row Id="6964" PostTypeId="2" ParentId="6958" CreationDate="2010-11-19T14:57:39.580" Score="5" ViewCount="" Body="&lt;p&gt;Ceramic capacitors can be microphonic and might introduce distortion, mylar or polycarbonate would be better.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-19T14:57:39.580" CommentCount="4" />
  <row Id="6965" PostTypeId="2" ParentId="6963" CreationDate="2010-11-19T15:00:33.493" Score="6" ViewCount="" Body="&lt;p&gt;Use a switching boost regulator. One of the National Semiconductor Simple Switchers would be ideal, you could use a 3V input and you won't need the 7805.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-19T15:00:33.493" />
  <row Id="6966" PostTypeId="2" ParentId="6963" CreationDate="2010-11-19T15:02:24.723" Score="7" ViewCount="" Body="&lt;p&gt;A switching voltage regulator can produce 5V from a lower voltage and you will not need the L7805C at all. On the other hand, 4.8V (when the battery is fully charged) is very close to 5V. Your electronics may work fine without any power supply circuitry.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2010-11-19T15:02:24.723" CommentCount="1" />
  <row Id="6967" PostTypeId="2" ParentId="6963" CreationDate="2010-11-19T15:04:42.967" Score="8" ViewCount="" Body="&lt;p&gt;Leon is correct here. Let me approach your question in more detail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The issue here is simple, for an op-amp to output 7V it needs to have a rail that is at-least 7V, so you will still need another power source to power the op-amp. In most designing for op-amp they also do no pull much power from the first source(actually dissipating this power to ground) so this is not the method you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you need is something that takes power from your first source and delivers it at an increased voltage. You could step up your voltage and then use your 2V drop Linear regulator to step it back down, which they have very good noise characteristics, so if you need low noise, you just have to cope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now if you get a &lt;a href=&quot;http://en.wikipedia.org/wiki/Buck%E2%80%93boost_converter&quot; rel=&quot;nofollow&quot;&gt;buck/boost style switching regulator&lt;/a&gt; you can step it to 5V from the 5.4V input voltage, all the way down to 2V input with still getting 5V out. These are nasty to layout so you want to purchase a solution that has already been done.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-19T15:04:42.967" CommentCount="5" />
  <row Id="6968" PostTypeId="2" ParentId="6963" CreationDate="2010-11-19T15:05:43.050" Score="4" ViewCount="" Body="&lt;p&gt;Opamps can never output more voltage then what is given to them on their rails. Also, even if they could, opamps generally can't output much current, so they aren't great solutions for anything requiring power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A switching boost regulator will do what you need it to do, but sometimes this can be a little difficult for DIYers to use depending on what you buy. You might want to look into a &lt;a href=&quot;http://en.wikipedia.org/wiki/Charge_pump&quot; rel=&quot;nofollow&quot;&gt;charge pump&lt;/a&gt;. In many ways they aren't as good as boost chips, but I think they are easier to use.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-19T15:05:43.050" />
  <row Id="6969" PostTypeId="2" ParentId="6963" CreationDate="2010-11-19T15:11:25.220" Score="5" ViewCount="" Body="&lt;p&gt;No, you can't do that with an op amp.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Op-amps require power supplies.  Many opamps have dropouts just like your 7805, so the output cannot quite reach the power rails. Others, called rail-to-rail opamps, can operate over the entire supply voltage.  They're just drawn as triangles in some textbooks because it gets tedious to draw the power supplies every time (same with logic symbols).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if you could power an op-amp to beyond the rails, it's not advisable as a replacement for a 7805.  Most opamps are low current (&amp;lt;20mA), and suitable only as precision voltage references.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your options are, from easiest and cheapest to most difficult and expensive.:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Tolerate the 4.8V and associated droop as the battery discharges (4.8V is a nominal value, not exact/constant).  Many simple circuits can run off of 4.8V just as well as 5V.&lt;/li&gt;&#xA;&lt;li&gt;Use to get a higher voltage battery pack or put more battery packs in series to raise the supply voltage.&lt;/li&gt;&#xA;&lt;li&gt;Use a low dropout regulator[LDO] to regulate to a slightly lower voltage (3.3V, for example).  78XX isn't the only series of regulators!  Many LDOs are available with dropout voltages of less than 0.2V.&lt;/li&gt;&#xA;&lt;li&gt;Use a boost regulator.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The final option uses switching of current through an inductor to generate voltages above the input.  You will probably need a boost/buck regulator, since your input is so close to your output.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-19T15:11:25.220" />
  <row Id="6970" PostTypeId="2" ParentId="6917" CreationDate="2010-11-19T15:57:01.587" Score="0" ViewCount="" Body="&lt;p&gt;Another approach would be to use what is known as a &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/Dummy_load&quot; rel=&quot;nofollow&quot;&gt;dummy&lt;/a&gt;&quot; load. It basically a large resistor with the same impedance as your antenna. This will simulate your antenna.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For &quot;tuning&quot; most people use a SWR meter. If the impedance does not match a standing wave is reflected back to the transmitter from the antenna. With a prefect match the &lt;a href=&quot;http://en.wikipedia.org/wiki/Standing_wave_ratio&quot; rel=&quot;nofollow&quot;&gt;SWR ratio&lt;/a&gt; should be 1 to 1. There are several ways to adjust the impedance including shortening the antenna.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-11-19T15:57:01.587" />
  <row Id="6971" PostTypeId="2" ParentId="6940" CreationDate="2010-11-19T17:15:02.050" Score="1" ViewCount="" Body="&lt;p&gt;Although not strictly electronics, all except two of my computers (I have about 7 but not all on at once!) were given to me by people who didn't want to remove the virus or fix Windows (hint: the fix was to install Ubuntu.) The only two computers I've ever bought were a media PC and a laptop. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For hardware I tend to buy components. But I did manage to salvage some big capacitors from a UPS, as well as the two lead acid batteries. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-19T17:15:02.050" CommunityOwnedDate="2010-11-20T02:29:55.593" CommentCount="3" />
  <row Id="6972" PostTypeId="1" AcceptedAnswerId="7065" CreationDate="2010-11-19T17:38:01.293" Score="1" ViewCount="150" Body="&lt;p&gt;I have a thin 2x2 mm surface that I'm trying to cool by 5-10 degrees Celsius in 1 second or less.  Some very rough back-of-the-envelope calculations reveal that I need to remove ~50 mJ of energy to do this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been thinking of using a Peltier module, but have no real experience with TECs, and therefore don't know exactly what to look for in terms of specs.  The speed of the temperature change is my primary consideration.  My questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Are there any manufacturers that sell very small Peltier modules that would roughly match my specifications, in prototyping quantities?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Are there any further considerations that I've missed?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2015" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T21:02:23.130" LastActivityDate="2011-04-27T21:02:23.130" Title="Is it possible to obtain very small Peltier modules with fast response times?" Tags="&lt;peltier&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="6973" PostTypeId="1" AcceptedAnswerId="6974" CreationDate="2010-11-19T18:32:20.713" Score="2" ViewCount="237" Body="&lt;p&gt;Several other questions are posted about methods for flashing an LED, but one additional requirement I have is the ability to turn the circuit on or off with a micro controller (Netduino, 3.3v).  This schematic is very close:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.reconnsworld.com/ir_ultrasonic_555timer40khzir.html&quot; rel=&quot;nofollow&quot;&gt;http://www.reconnsworld.com/ir_ultrasonic_555timer40khzir.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What changes would be necessary to acheive 38.5kHz?  Also, how could I make an additional adjustment to start or stop the circuit via a pin on the Netduino?&lt;/p&gt;&#xA;" OwnerUserId="1841" LastActivityDate="2010-11-19T22:24:31.390" Title="Create a circuit that can flash IR LEDs at 38.5kHz and be turned on or off by microprocessor" Tags="&lt;led&gt;&lt;timer&gt;&lt;netduino&gt;&lt;blink&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="6974" PostTypeId="2" ParentId="6973" CreationDate="2010-11-19T18:43:15.847" Score="2" ViewCount="" Body="&lt;p&gt;You can tweak the frequency with the 5k potmeter. I think you can get a pretty good range with that. If it's not enough, you could probably change the other resistor to something or a little larger value so the frequency drops.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make it possible to switch the LEDs on and off I would probably a transistor (or a MOSFET) after the two leds. You could then connect the base or gate to your netduino with a 1k resistor or so. It doesn't start/stop the circuit, but it does start/stop the LEDs which I think is the result you want to go after. &lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-11-19T18:43:15.847" />
  <row Id="6975" PostTypeId="2" ParentId="6972" CreationDate="2010-11-19T18:45:36.140" Score="1" ViewCount="" Body="&lt;p&gt;Small coolers of this order of size are used inside laser diode modules for fibre-optic comms- not sure how easy or otherwise it would to obtain seperately. Look at datasheets for peltiers to get an idea of heat pumping capacity versus size and power. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-19T18:45:36.140" />
  <row Id="6976" PostTypeId="2" ParentId="6972" CreationDate="2010-11-19T19:51:18.163" Score="0" ViewCount="" Body="&lt;p&gt;Could you use a hybrid mechanical/electrical solution? You pre-cool a relatively large block of aluminum to a very low temperature. When you want to cool your mystery object, you quickly drop it on top (or maybe you drop the mystery object on the block instead).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect that the limiting factor will be the thermal conductivity of your surface. If you really need to cool just the surface, just clamping on a cold block will do it instantly. To the extent that you need the surface plus a small depth, you just need to be sure that the block is much colder and more conductive than your mystery object.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-19T19:51:18.163" />
  <row Id="6977" PostTypeId="1" AcceptedAnswerId="6980" CreationDate="2010-11-19T21:08:33.783" Score="4" ViewCount="226" Body="&lt;p&gt;Most devices seem to be characterised over -40°C to ≥85°C. What limits them to cold temperatures? Can an IC be damaged by keeping it too cold? Does this apply to other devices, e.g. diodes, transistors?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-19T21:56:00.857" LastActivityDate="2010-11-19T23:56:38.453" Title="What prevents semiconductors working below -40°C or so?" Tags="&lt;temperature&gt;&lt;ic&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="6978" PostTypeId="2" ParentId="6918" CreationDate="2010-11-19T21:18:57.890" Score="0" ViewCount="" Body="&lt;p&gt;Have a look in to the HART protocol - it allows multi-drop communications over existing 4-20mA lines&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2010-11-19T21:18:57.890" />
  <row Id="6980" PostTypeId="2" ParentId="6977" CreationDate="2010-11-19T21:25:46.500" Score="10" ViewCount="" Body="&lt;p&gt;Damage to an IC package at low temperatures while unpowered would be due to mechanical effects; differences in thermal expansion coefficients between the epoxy, lead-frame, and die.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Problems with operation would be due to increased resistance (semiconductors' temperature coefficient of resistance is negative).  When the temperature and doping concentration is low enough, semiconductors will essentially become insulators and not conduct at all, causing unspecified operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some ICs will operate just fine at cryogenic temperatures but they must start up warm to allow bandgap voltage references to boot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In theory if some transistor &quot;fails&quot; due to carrier freezeout, the IC could damage itself elsewhere (not very likely, as most failure modes are thermal, and everything on the die is very tightly coupled.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See the tutorial pages &lt;a href=&quot;http://www.extremetemperatureelectronics.com/tutorial1.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; for more.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Edit:&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;As you note, most devices are &lt;em&gt;characterized&lt;/em&gt; between usually -40 °C to +85 °C.  Nothing says they will not work down to cryogenic temperatures.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-19T22:39:09.797" LastActivityDate="2010-11-19T22:39:09.797" CommentCount="4" />
  <row Id="6981" PostTypeId="2" ParentId="6973" CreationDate="2010-11-19T22:24:31.390" Score="1" ViewCount="" Body="&lt;p&gt;If you're using Netduino, maybe you can drop the 555 circuit and use software temporization. Here (&lt;a href=&quot;http://www.netduino.com/projects/&quot; rel=&quot;nofollow&quot;&gt;http://www.netduino.com/projects/&lt;/a&gt;) we have two tutorials on how to blink the led and also how to turn it on and off using a button.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will just need to attach the infrared led to an I/O port and map it in the software.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-19T22:24:31.390" CommentCount="2" />
  <row Id="6982" PostTypeId="2" ParentId="6952" CreationDate="2010-11-19T22:31:02.550" Score="1" ViewCount="" Body="&lt;p&gt;Smaller crystals of the same rated frequency may operate differently, series/parallel or fundamental/overtone.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-19T22:31:02.550" />
  <row Id="6983" PostTypeId="1" AcceptedAnswerId="6988" CreationDate="2010-11-19T22:49:00.757" Score="1" ViewCount="297" Body="&lt;p&gt;Is it possible to hand solder a DFN package? It's leadless, so it could be tricky. I can't find any videos on YouTube about it, so I'm sort of thinking it as difficult, if not impossible.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-20T01:39:02.373" LastActivityDate="2010-11-20T15:22:11.490" Title="Is Hand Soldering a DFN Package Possible?" Tags="&lt;soldering&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="6984" PostTypeId="1" CreationDate="2010-11-19T22:52:12.627" Score="4" ViewCount="152" Body="&lt;p&gt;I am researching some embedded applications that will leverage the use of a single-board computer (SBC). I am looking for a SBC that has a very small form factor, supports wireless networking, and can boot from a memory chip or USB memory stick. Does anyone have experience with something like this and can recommend a manufacturer to use?&lt;/p&gt;&#xA;" OwnerUserId="2018" LastActivityDate="2010-11-19T23:36:08.183" Title="Single-board computer" Tags="&lt;computers&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="6985" PostTypeId="2" ParentId="6983" CreationDate="2010-11-19T22:55:44.103" Score="1" ViewCount="" Body="&lt;p&gt;Its possible, its much easier if the leads are exposed on the sides as well as the bottom.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hot air is really the best hand approach especially if there is a pad under the package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should be able to find lots of tutorials by searching for QFN soldering as that package is the same general structure as a DFN but much more common.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-19T22:55:44.103" CommentCount="1" />
  <row Id="6986" PostTypeId="1" AcceptedAnswerId="7007" CreationDate="2010-11-19T23:05:16.490" Score="4" ViewCount="233" Body="&lt;p&gt;hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;im having some trouble finding an example of the time-instability that motivates the flip-flop. wherever i look, the explanations are awfully airy-fairy (or at least my understanding is). for example, &lt;a href=&quot;http://wearcam.org/ece385/lectureflipflops/flipflops/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; they explain that there can be instability if the clock pulse is sampling from combinational circuits. im looking for a concrete example of such instability (i need these things explained to me like im a six-year-old kid), not just saying &quot;things can be unstable&quot;. if i wrote in a maths exam &quot;the given implication can be problematic&quot; without providing a counter example i wouldnt get half a mark, and by the same token if i were authoring an article that discusses motivating flip-flops i would see it essential to &quot;prove&quot; their necessity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;my problem is that if i have worked out that if the [maximum] propogation delay for a given circuit, i dont need to wait for a clock pulse edge, i can just sample the output after that amount of time. meaning, even with a flip-flop i have to work out my clock-pulse speed, so why go to all the trouble of having 2 latches when i know that the desired ouput will exist after 1 pulse-length of time?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;so if i had many different circuits that relied on each others output, instead of flip-flopping them all, i would just activate them in the relevant order according to a clock-pulse. im obviously missing something simple here because as far as i can see the flip-flop functioning to save from instability isnt necessary...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the JK flip-flop is a nice way to &quot;regulate&quot; the ouput because it solves an altogether different problem, that when j=k=1 the toggle that the JK latch would otherwise perform for the entire cycle that the clock-pulse is 1, happens only once, which means the final output is deterministic - as opposed to undefined. although that doesnt explain why its necessary on a D latch and an RS latch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;on that note, ill add a second question. whats the use of the JK latch/flip-flop? it seems to be introduced in many texts as an improvement on the RS latch, because of the problematic s=r=1 situation and resulting race condition. however if we setup the RS in a flip flop, we provide ourselves with a better alternative to the JK flip-flop: this acts like an RS latch but when r=s=1 on the clock's rising edge both Q and Q' are 0, and on the falling edge theres no change in the slave latch. so the problematic situation of r=s=1 becomes stable. the only advantage JK has over this setup is that r=s=1 actually provides a new functionality of toggle, im not sure if thats a desired thing or not...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;hoping for some insight...&lt;/p&gt;&#xA;" OwnerUserId="2017" LastEditorUserId="2017" LastEditorDisplayName="" LastEditDate="2010-11-20T00:38:20.680" LastActivityDate="2011-03-01T16:39:24.630" Title="master-slave flip-flops" Tags="&lt;clock&gt;&lt;flipflop&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="6987" PostTypeId="2" ParentId="6984" CreationDate="2010-11-19T23:10:09.760" Score="6" ViewCount="" Body="&lt;p&gt;It depends a lot on which embedded system are you planning to use.&#xA;A good alternative to desktop replacement (with all your requirements) is &lt;a href=&quot;http://www.gadgetgrid.com/2009/02/04/intel-dg45fc-mini-atx-motherboard-a-good-choice-for-dyi-htpc/&quot; rel=&quot;nofollow&quot;&gt;Intel DG45FC mini-atx&lt;/a&gt;. With a core 2 duo socket and an embedded graphic processor you can make any application run as in a desktop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/4tLIe.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A cheaper and smaller alternative is &lt;a href=&quot;http://www.mini-itx.com/2010/01/14/intel-revamps-the-atom-with-pine-trail&quot; rel=&quot;nofollow&quot;&gt;D410PT&lt;/a&gt; (or D510MO for dual core processor) with intel atom processor. Its also an x86 processor which is pretty good if you're not planning to go on more embedded kind of operational systems, but still powerfull enought for the majority of the tasks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ScB4X.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another alternative is &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;beagle board&lt;/a&gt;. The built in processor is an core ARM. In this case you'll need to build your program based in Android, Win CE or some Linux flavors. I think that maybe this is the alternative that may suit you better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/QSwIR.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-19T23:10:09.760" />
  <row Id="6988" PostTypeId="2" ParentId="6983" CreationDate="2010-11-19T23:10:58.450" Score="4" ViewCount="" Body="&lt;p&gt;Heres a vid I made on reflowing a QFN without hot air &lt;a href=&quot;http://www.youtube.com/watch?v=d-f-SBC0GrU&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=d-f-SBC0GrU&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-19T23:10:58.450" CommentCount="1" />
  <row Id="6989" PostTypeId="2" ParentId="6984" CreationDate="2010-11-19T23:36:08.183" Score="6" ViewCount="" Body="&lt;p&gt;If a small form-factor is really important, &lt;a href=&quot;http://gumstix.com&quot; rel=&quot;nofollow&quot;&gt;Gumstix&lt;/a&gt; will win. They're a little more expensive, but they're tiny. They run Linux, and they have a wireless module.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-19T23:36:08.183" CommentCount="1" />
  <row Id="6990" PostTypeId="2" ParentId="6977" CreationDate="2010-11-19T23:56:38.453" Score="1" ViewCount="" Body="&lt;p&gt;You can characterize parts yourself below -40, and mechanical failures can be largely avoided if the temperature cycle is slow. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some package options work, some don't.  heheh. you have to do that experiment yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can characterize parts below 0C yourself ( easily using a domestic freezer.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Astronomers just love dunking stuff in liquid nitrogen to get rid of thermal noise in their camera chips and A/D converters. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For extreme conditions, fit heaters to significant parts (large caps, problem IC's.) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then your power sequencing systems turns the heaters on till the parts are in a temperature range you've characterized.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-11-19T23:56:38.453" />
  <row Id="6992" PostTypeId="1" AcceptedAnswerId="7000" CreationDate="2010-11-20T00:05:16.837" Score="2" ViewCount="103" Body="&lt;p&gt;I am designing a circuit which may fail to start up. It has a power good output which is high when the supply is working. When the power good output goes low, the circuit has failed to start oscillating properly, and needs to be restarted. I thought about using a 555 timer but couldn't figure out how to make the output stay high when the input signal was low. Any ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit must do this because it fails to start under high current set points. It drives an LED. The idea is at higher currents the output folds back, but doesn't require an actual restart of the circuit to get it working again, and the fold-back mechanism makes the LED blink on and off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an image to show what I mean. Green shows the LED current. It has been set too high and the supply's overvoltage protection circuit kicks in to prevent more than 4.7V being applied across the LED (to prevent breakdown of the LED if in reverse.) The blue trace represents the power good output. During the oscillations the supply is outputting correctly, so it is high. It drops low after the oscillations stop. A short delay after it drops low, I need the supply to reset and try again - this would be accomplished by turning the supply controller IC on and off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/IEFlY.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-20T00:44:34.183" LastActivityDate="2010-11-20T02:00:29.337" Title="Power cycling circuit" Tags="&lt;555&gt;&lt;psu&gt;" AnswerCount="2" />
  <row Id="6993" PostTypeId="2" ParentId="6940" CreationDate="2010-11-20T00:06:21.377" Score="2" ViewCount="" Body="&lt;p&gt;try &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.opencircuits.com/Free_From_Salvage&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/Free_From_Salvage&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-11-20T00:06:21.377" CommunityOwnedDate="2010-11-20T02:29:55.593" />
  <row Id="6994" PostTypeId="1" CreationDate="2010-11-20T00:09:02.790" Score="3" ViewCount="180" Body="&lt;p&gt;I salvaged from an old microwave, the motor that spins the food tray. I'm trying to figure out how much voltage I need to apply to it in order to get it to spin, but I cant make any sense out of the numbers on it. It's a Synchronous Motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is what's on it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;100/120v~  50/60Hz  4W&#xA;4/4.8r/min  CW/CCW&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can guess that it rotates from 4 to 4.8 rotations per minute? but other than that, I'm clueless. What do these other things mean? Thanks so much!&lt;/p&gt;&#xA;" LastActivityDate="2010-12-05T23:19:07.927" Title="What do the numbers on motors mean (How do I read them?)" Tags="&lt;motor&gt;" AnswerCount="2" />
  <row Id="6995" PostTypeId="2" ParentId="6994" CreationDate="2010-11-20T00:22:55.777" Score="2" ViewCount="" Body="&lt;p&gt;Taking a few guesses here, but:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;100-120V~: operating voltage, &quot;~&quot; (tilde) indicates AC voltage&lt;/p&gt;&#xA;&#xA;&lt;p&gt;50-60Hz: operating AC frequency&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4W: power consumption (maximum stall perhaps?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CW/CCW: works in both ways (clockwise and counterclockwise.) This usually means it is a synchronous motor, and its direction depends on either the sign of the incoming AC waveform, or whichever direction has the least torque - in other words, it's more or less random.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-20T00:29:46.753" LastActivityDate="2010-11-20T00:29:46.753" CommentCount="8" />
  <row Id="6996" PostTypeId="2" ParentId="6992" CreationDate="2010-11-20T00:25:04.730" Score="0" ViewCount="" Body="&lt;p&gt;I would recommend the 555 timer. For the high/low problem, use a NOT gate. That way, the 555 gets to behave in its normal manner, and your PS gets the signal it needs.&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-11-20T00:25:04.730" CommentCount="8" />
  <row Id="6997" PostTypeId="2" ParentId="6934" CreationDate="2010-11-20T00:31:32.197" Score="1" ViewCount="" Body="&lt;p&gt;Another option is to put the regulators in series.  A rangefinder and MSP430 are both going to be very low-power, but when you're regulating from 9.6V, 12V, or more, it's usually cheaper to put one heavy-duty regulator at your highest voltage, and then run your lower voltage regulators off of that.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually, you can get away with heatsinking just the pre-regulator in this situation, instead of heatsinking two independent regulators.  You'll just have to make sure that you have sufficient capacitance that you don't get any oscillation from their interaction.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-20T00:31:32.197" />
  <row Id="6998" PostTypeId="2" ParentId="6983" CreationDate="2010-11-20T00:42:08.547" Score="1" ViewCount="" Body="&lt;p&gt;You can hand assemble or disassemble QFN/DFN with a toaster oven (or hot plate). It's worth learning because the process is about the same as a real SMT line. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The toaster oven is $30.  Solder paste is $3 from dealextreme. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unlike hand soldering, there is no technique to learn -- just cook it in the oven until the solder melts.  Then turn it off and let it cool down.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-20T00:42:08.547" />
  <row Id="6999" PostTypeId="2" ParentId="4319" CreationDate="2010-11-20T00:52:38.650" Score="0" ViewCount="" Body="&lt;p&gt;If you use a distributor such as Arrow and Avnet they can help you.  At least in the U.S. and if you aren't a hobbyist.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-11-20T00:52:38.650" />
  <row Id="7000" PostTypeId="2" ParentId="6992" CreationDate="2010-11-20T01:32:15.277" Score="4" ViewCount="" Body="&lt;p&gt;You want a low-going &quot;power good&quot; to temporarily turn off the supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This circuit will do what you want.  Choose R and C to get your desired delay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: there should probably be a resistor between the PNP base and NPN collector instead of a direct connection as shown.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kEeCM.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-11-20T02:00:29.337" LastActivityDate="2010-11-20T02:00:29.337" CommentCount="8" />
  <row Id="7001" PostTypeId="2" ParentId="6168" CreationDate="2010-11-20T01:35:48.007" Score="0" ViewCount="" Body="&lt;p&gt;cksa361, I am confused by your bounty because I am not sure what else you need answered except for the comment you left me, so I will answer that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you pick between different chip antennas you will normally not find one that is significantly better than another in every way unless a new process was developed. In most cases you will have to pick the one that better fits your application, and to you this will seem significantly better.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Radiation Strength&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;The larger one, &lt;a href=&quot;http://antenova.com/?id=408&quot; rel=&quot;nofollow&quot;&gt;Mica&lt;/a&gt;, has better radiation characteristics(more power out for the same power in). This means that for two transmitters radiating the same power, this antenna will get greater range. This also means the Mica antenna will receive from a source at a great distance much better.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Size&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.taoglas.com/images/product_images/original_images/PA.15%20FR4%20SMT%202.4GHz%20Antenna%20090810.pdf&quot; rel=&quot;nofollow&quot;&gt;Taoglas&lt;/a&gt; is smaller. This is self explanatory, if space is an issue, or if the odd size of the mica causes problems, the Taoglas wins.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Tuning&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;&lt;strike&gt; You will need to tune the matching circuit for the Mica one. For the Taoglas it seems they have a set matching circuit.  This problem is approached in the question about &lt;a href=&quot;http://electronics.stackexchange.com/questions/6917/measuring-output-impedance&quot;&gt;measuring output impedance&lt;/a&gt;. This can be challenging if you do not have the right equipment. A mistuned antenna will severely hurt your range, if you cannot tune you may find the Taoglas will be easier to use.&lt;/strike&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I misread the datasheets, they both have reference designs. If you are going to vary your layout from the reference design (ie. You do not have room to do the exact say layout) on either antenna you will need to re-tune the circuit, as was linked in the paragraph with the strike-though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-20T16:25:49.357" LastActivityDate="2010-11-20T16:25:49.357" CommentCount="2" />
  <row Id="7002" PostTypeId="2" ParentId="6940" CreationDate="2010-11-20T03:36:53.317" Score="1" ViewCount="" Body="&lt;p&gt;As an amateur radio operator, removing components from old pcbs is one of my favorite ways of building up my junk box.  Always good to have some stuff on hand.  Here's some hints:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.overclock.net/faqs/33671-info-perfectly-preserving-removing-electronic-components.html&quot; rel=&quot;nofollow&quot;&gt;Using hot air gun.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/Recycle-old-PCB-components/&quot; rel=&quot;nofollow&quot;&gt;An Instructable.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.qsl.net/iz7ath/web/02_brew/14_howto/04_rec/index.htm&quot; rel=&quot;nofollow&quot;&gt;Another &quot;hot air&quot; system.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try not to burn the house down or breath too much solder smoke.&lt;/p&gt;&#xA;" OwnerUserId="1720" LastActivityDate="2010-11-20T03:36:53.317" CommunityOwnedDate="2010-11-20T03:36:53.317" />
  <row Id="7003" PostTypeId="1" AcceptedAnswerId="7064" CreationDate="2010-11-20T07:12:31.967" Score="29" ViewCount="1183" Body="&lt;p&gt;Hello stack!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have finally built up a lab to design electronics in. I have quite a few designs I would like to test. I have tried the printer toner/iron technique a few times but have found that I cannot create small pitch sizes as they tear off while removing the printer paper. A few people have mentioned that this is due to using a Samsung laserjet versus a HP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am wondering what methods you use to develop PCBs for one-offs in your lab or at home (like me). I am trying to fast track a move to SMT/SMD components and would like some tips from seasoned experts on the best PCB creation methods to test board concepts before sending them off to a PCB MFG. I would like something that balances cost, time, and beauty of the finished product geared towards a hobbyist (at this point) and geared towards SMT/SMD components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please include pics/documentation of your preferred method. Thank you in advance for your post.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-19T01:06:24.423" LastActivityDate="2011-05-25T01:38:28.267" CommunityOwnedDate="2011-05-25T02:31:53.593" Title="Best One-Off DIY PCB Creation Technique" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;&lt;pcb-design&gt;" AnswerCount="7" FavoriteCount="19" />
  <row Id="7004" PostTypeId="1" CreationDate="2010-11-20T08:19:18.390" Score="1" ViewCount="85" Body="&lt;p&gt;Vacuum relay vs solid state&#xA;I have an unusual circuit that needs to be designed. What I need to do is mimic two 12volt relays ( in principal anyway ) to control an ac source. The source goes to the common terminals of the two relays. When the relays are energized the ac flows out of the normally open terminal. When at rest the ac source then flows out of the normally closed terminal. This all has to be performed at a rather high rate of speed ( about 20 kHz ). Also the source is high voltage about 2000 volts and about 30 amps. I was considering using a DPDT vacuum tube relay, it will easily handle the voltage and the current.. However they are not designed to switch at a high rate of speed continuously. This is my dilemma. I would like to go solid state but I'm not sure that it is possible. This is going to require a VERY clever individual. Any thoughts?    &lt;/p&gt;&#xA;" OwnerUserId="1600" LastActivityDate="2010-11-20T10:33:26.333" Title="Vacuum relay vs silicon" Tags="&lt;relay&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="7005" PostTypeId="1" AcceptedAnswerId="7010" CreationDate="2010-11-20T09:11:18.217" Score="6" ViewCount="192" Body="&lt;p&gt;I moved my Arduino-logic-level-5V-to-12V-LED strip circuit off project board and onto Veroboard and I'm very proud to say everything worked first time:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/KYgSl.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I'm not at all proud of the soldering job, so you don't get to see that.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So this is the point where you all tell me I can replace the whole shebang with a $0.65 IC. The LED strips pull a few hundred mA per channel and I want to drive them off the Arduino's PWM pins. I've found the &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet2/5/0w2oz7jig6lt2chlgy7joisuwipy.pdf&quot; rel=&quot;nofollow&quot;&gt;ULN2803A&lt;/a&gt;, but that's 8 Darlington Pair array in a DIP18 package, I want a 3 or 4 Darlington Pair array in a DIP8 or thereabouts. &lt;a href=&quot;http://electronics.stackexchange.com/questions/6145/using-an-uln2803-with-netduino&quot;&gt;This question&lt;/a&gt; might actually contain the answer I'm looking for, but I don't know enough to even work that out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Secondary question: how do you even know things like the ULN2803A exist? I happened upon it randomly and from there I worked out that &quot;transistor array&quot; was the search term I wanted. But aside from simply hanging around here, how does one answer the question, &quot;What IC can I buy that will replace this portion of this circuit?&quot;&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2010-11-20T13:33:58.200" Title="Can I replace this circuit with an IC?" Tags="&lt;arduino&gt;&lt;led&gt;&lt;microchip&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="7006" PostTypeId="2" ParentId="7003" CreationDate="2010-11-20T09:22:34.687" Score="6" ViewCount="" Body="&lt;p&gt;I'm no seasoned expert but... I have learned from them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have the &lt;a href=&quot;http://www.amazon.co.uk/gp/product/B002P9Q1ZC/ref=oss_product&quot; rel=&quot;nofollow&quot;&gt;second cheapest Samsung mono printer&lt;/a&gt; available and I have no problems with fine traces; I doubt it is your printer.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have had good success with laminators but someone recently told me this could be dangerous on cheaper models with improper shielding (as the board is highly conductive).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have returned to ironing for double sided boards as it seems to be a tad more accurate. If you're not getting good transfers try using an electric sander with a very high grit rate to get it much cleaner than any abrasive brush can. Then, the most important thing to do when using an iron is to &lt;strong&gt;push hard&lt;/strong&gt;, like &lt;strong&gt;really hard&lt;/strong&gt; and hold it in place for at least 30s at a time. If you have &lt;a href=&quot;http://www.amazon.co.uk/gp/product/B00014SKOI/ref=oss_product&quot; rel=&quot;nofollow&quot;&gt;normal glossy paper&lt;/a&gt; and can't see the traces, you're probably not ready to soak.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing I have found to help is to have a 2mm or so border around the whole circuit. This then tends to stick first and helps prevent the paper from moving while you are ironing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currently my kit features the following items:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.co.uk/Plasplugs-Compact-Plus-Electric-Cutter/dp/B0001P0HP2/ref=sr_1_8?ie=UTF8&amp;amp;qid=1290244832&amp;amp;sr=8-8&quot; rel=&quot;nofollow&quot;&gt;Tile Cutter (for cutting PCB)&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.co.uk/gp/product/B003K7B4I2/ref=oss_product&quot; rel=&quot;nofollow&quot;&gt;FFP3 Mask (important if you value your lungs)&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.co.uk/Black-Decker-KA161BC-Detail-Accessories/dp/B001G7PR3Q/ref=sr_1_1?ie=UTF8&amp;amp;qid=1290244638&amp;amp;sr=8-1&quot; rel=&quot;nofollow&quot;&gt;Black &amp;amp; Decker Mouse Sander&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&amp;amp;item=220693877584&amp;amp;ssPageName=STRK%3aMEWNX%3aIT&quot; rel=&quot;nofollow&quot;&gt;Bubble etch tank (not needed I'm just impatient)&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.wickes.co.uk/5-Speed-Bench-Pillar-Drill/invt/186886&quot; rel=&quot;nofollow&quot;&gt;Wickes 5-Speed Bench Pillar Drill&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;My new camera arrives today and I intend to launch a &quot;website of journey&quot; as I both learn and experiment with electronics. One of the first videos I will put out will be my PCB production process.&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-11-20T12:36:20.977" LastActivityDate="2010-11-20T12:36:20.977" CommunityOwnedDate="2011-05-25T02:31:53.593" CommentCount="4" />
  <row Id="7007" PostTypeId="2" ParentId="6986" CreationDate="2010-11-20T09:30:43.823" Score="1" ViewCount="" Body="&lt;p&gt;The master-slave arrangement doesn't strictly solve the metastability issue, AFAICT. It is commonly used to cross over between different clock domains of synchronous logic, but I don't quite see what improvement it does on purely asynchronous input (the slave gets a clear state, but it may be derived of a metastable transition anyway). It could simply be an incomplete description, as you could add a hysteresis function by combining the outputs of the two registers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the differences between SR, JK, D or even T flip-flops, it tends to boil down to which inputs are asynchronous. The simplest SR latches do not toggle with S=R=1, but simply keep whichever state was kept last (or in the worst case, oscillate with a gate delay), that's the race. The JK, on the other hand, will transition on the clock edge - synchronous behaviour. It is thus their nature that a T register can only be synchronous, and an asynchronous D latch is transparent while latching. The SR register you describe doesn't have the T function, which can be useful depending on the function. For instance, a ripple counter can be described purely with T registers. Simply put, the JK gives you a complete set of operations (set, clear, toggle, and no-op) without costing an extra control line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In synchronous logic, we frequently use wide sets of registers to implement a larger function. It doesn't strictly matter there if we use D, T, JK or whatever registers, as we can just redesign the logic function that drives them to include feedback (unless we need to build that logic - i.e. in 74 family logic). That's why FPGAs and such tend to have only D registers in their schematic representations. What does matter is that the register itself introduces the synchronous operation - steady state until the next clock. This allows combining plenty of side-by-side registers or ones with feedback functions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the choice between delayed-pulse and clock-synchronous logic, it's not an automatic one. Some early computers (f.e. PDP-1) and even some highly energy efficient ones (f.e. GreenArrays) use the delayed-pulse design, and it is in fact comparable to a pipelined design in synchronous logic. The &lt;a href=&quot;http://en.wikipedia.org/wiki/Carry_save_adder&quot; rel=&quot;nofollow&quot;&gt;Carry-Save adder&lt;/a&gt; demonstrates the crucial difference - it's a pipelined design where you actually don't have a known value, not even intermediate, until the pulse from the last new value to enter has come out the other end. If you know at the logic design stage repeated accumulation but only the final sum is used, it may be the best choice. Meanwhile, FPGAs are typically designed with only a few clock nets and therefore do not adapt well to delayed-pulse logic (though it can be approximated with clock gating).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this is more helpful than further confusing... interesting questions!&lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="1181" LastEditorDisplayName="" LastEditDate="2010-11-20T09:38:12.190" LastActivityDate="2010-11-20T09:38:12.190" CommentCount="3" />
  <row Id="7008" PostTypeId="2" ParentId="7003" CreationDate="2010-11-20T10:23:40.577" Score="5" ViewCount="" Body="&lt;p&gt;I get excellent results (down to 8/8 mil) using the photo-etch technique. I use a cheap HP 5940 inkjet printer with Mega Electronics JetStar Premium film for the transparencies with pre-coated positive resist boards, exposed in a home-made UV exposure unit. Boards are developed in sodium hydroxide solution and etched in ferric chloride in a small plastic container in an old washing-up bowl with about 1&quot; of very hot water in it. The small container is agitated manually, and etching takes about 5 minutes. I can make a board in about 20 minutes, not including drilling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://i.imgur.com/X5e06.gif&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is one of my boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tech.groups.yahoo.com/group/Homebrew_PCBs/&quot; rel=&quot;nofollow&quot;&gt;This group&lt;/a&gt; is a very good resource for making PCBs at home.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-20T11:27:09.680" LastActivityDate="2010-11-20T11:27:09.680" CommunityOwnedDate="2011-05-25T02:31:53.593" CommentCount="3" />
  <row Id="7009" PostTypeId="2" ParentId="7004" CreationDate="2010-11-20T10:33:26.333" Score="3" ViewCount="" Body="&lt;p&gt;IGBTs would probably be the switching element of choice at this level of power and voltage.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-20T10:33:26.333" CommentCount="2" />
  <row Id="7010" PostTypeId="2" ParentId="7005" CreationDate="2010-11-20T12:38:59.370" Score="2" ViewCount="" Body="&lt;p&gt;The best I found was an ULN2065B, in a DIP-14. I used Farnell's parametric search to do this, but you could also use Digi-key, or a vendor independent site like FindChips or Octopart.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you're going to struggle to get DIP-8 for four channels: there would not be a pin available for ground, unless it used some kind of serial interface to communicate. You might be able to find a triple driver in this: one pin for ground, three for control signals, three outputs and maybe a pin for Vcc, if the chip requires it. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-20T12:38:59.370" CommentCount="1" />
  <row Id="7011" PostTypeId="1" AcceptedAnswerId="7015" CreationDate="2010-11-20T12:39:03.803" Score="5" ViewCount="303" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm learning to layout PCBs and lately I came across practice that made me curious. The chip passives' pads are etched with oblong / rounded shape, instead of rectangular shape that is used in all example libraries and even the &lt;a href=&quot;http://landpatterns.ipc.org/default.asp&quot; rel=&quot;nofollow&quot; title=&quot;IPC-7351B standard&quot;&gt;IPC-7351B standard&lt;/a&gt; (you can download LP Viewer for free registration and see for yourself). Here are the examples (I marked the interesting pads with yellow):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot; title=&quot;Beagle Board&quot;&gt;Beagle Board&lt;/a&gt;:&#xA;&lt;img src=&quot;http://i.imgur.com/DGAsA.png&quot; alt=&quot;Beagle Board&quot;&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardMega2560&quot; rel=&quot;nofollow&quot; title=&quot;Arduino Mega&quot;&gt;Arduino Mega&lt;/a&gt;:&#xA;&lt;img src=&quot;http://i.imgur.com/56kul.png&quot; alt=&quot;Arduino Mega&quot;&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The question is: what are these rounded pads good for? Should I use them instead of rectangular ones to make my board look more &quot;pro&quot;?&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first thought was that it might be because it might be better for reflow soldering, but I'm bit puzzled about that reasoning. The one advantage I see with these is more routing space around such rounded pad (no &quot;sharp&quot; edges).&lt;/p&gt;&#xA;" OwnerUserId="1177" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T20:34:33.523" LastActivityDate="2011-04-27T20:34:33.523" Title="Using oblong / rounded surface mounted pads for chip resistors, capacitors and inductors" Tags="&lt;pcb&gt;&lt;surface-mount&gt;&lt;layout&gt;&lt;pads&gt;" AnswerCount="3" />
  <row Id="7012" PostTypeId="1" AcceptedAnswerId="7020" CreationDate="2010-11-20T12:42:59.730" Score="4" ViewCount="105" Body="&lt;p&gt;I've read &lt;a href=&quot;http://electronics.stackexchange.com/q/6583/1240&quot;&gt;this&lt;/a&gt; question and in its comments it is said:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;LDO and IC heatsinks will generally&#xA;  have a very different answer then&#xA;  computer motherboard heat sink. This&#xA;  question really doesn't belong here&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;What I'm asking is how to use coolers with IC packages. For example let's say I have  a device in TO220 package which according to my calculations needs cooling. How would I cool it? Most obvious answer is of course using a cooler, but that part isn't very clear to me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen that sometimes heatsink is directly connected to the package by a screw but sometimes insulator is used to prevent direct contact between screw and package. Some other times, heat conductive insulator is used together with insulator for screw to prevent direct contact between package and heatsink. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes silicon paste is used and sometimes it isn't. How would I determine when it is needed and when it isn't needed? My experience with computers tells me to always use it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also seen silicon pastes marketed as for use in electronics. How are they different that ones used in computers? Would thermal pastes for computers work well with ICs? &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-11-20T14:51:28.310" Title="How to cool ICs?" Tags="&lt;cooling&gt;" AnswerCount="2" />
  <row Id="7013" PostTypeId="2" ParentId="7012" CreationDate="2010-11-20T12:57:46.543" Score="3" ViewCount="" Body="&lt;p&gt;Cooling is pretty tricky to get right. In most cases, a heatsink is all that is necessary, however, for higher loads, you will need a fan. Look at a computer power supply. They all use fans, but many will run without them. The heatsinks are usually quite big because the supplies are not very efficient (it turns out it's cheaper to make an inefficient power supply with a big fan than an efficient power supply with a smaller fan.) The fan helps circulate air inside the case, and prevent the other components in the computer from overheating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first question you need to ask is whether or not the IC you are using can actually dissipate enough power to require a heatsink and/or fan. Many cannot. For example, the LM7805 has a 5°C/W J-CC rating, which means at best (assuming an infinitely large heatsink attached to it), running at the maximum junction temperature of 150°C, at room temperature, the power dissipation is limited to 25W. In most cases you can get away with just a heatsink with this amount of power, but if you're wasting this much power in a linear regulator, you have more problems than cooling!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dave Jones has &lt;a href=&quot;http://www.youtube.com/watch?v=8ruFVmxf0zs&quot; rel=&quot;nofollow&quot;&gt;an interesting video&lt;/a&gt; on this. He discusses heatsinks and fans.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-20T14:03:12.837" LastActivityDate="2010-11-20T14:03:12.837" CommentCount="1" />
  <row Id="7014" PostTypeId="2" ParentId="7003" CreationDate="2010-11-20T12:59:06.810" Score="20" ViewCount="" Body="&lt;p&gt;Unless you're on the tinyest of tiny budgets, just have the boards professionally fabbed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Really, you can get such a good deal on PCBs, with suppliers like:  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://33each.com&quot; rel=&quot;nofollow&quot;&gt;33Each.com&lt;/a&gt; - 60 Square inches, double sided, 6/6 spacing. $33 ea, Minimum Order : 4 (1 if you have a University address)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://batchpcb.com&quot; rel=&quot;nofollow&quot;&gt;BatchPCB&lt;/a&gt; - &lt;strong&gt;Great&lt;/strong&gt; for tiny boards. Double sided, 8/8 spacing. Minimum board cost is $12.50, quantity of one)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.goldphoenixpcb.biz/index.php&quot; rel=&quot;nofollow&quot;&gt;GoldPhoenix&lt;/a&gt; - Good for bigger runs, cost varies depending on requirements.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.expresspcb.com/ExpressPCBHtm/SpecsMiniboard.htm&quot; rel=&quot;nofollow&quot;&gt;ExpressPCB&lt;/a&gt; - 3 boards for $51 total, double sided, no soldermask or silk, rigid size requirement of 3.8 x 2.5&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.apcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;AP Circuits&lt;/a&gt; - No personal experience, see comments below.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;On the whole, I've found that (for me, at least), it's just completely not worth it to try and make my own boards, when I can buy a much nicer board or ~$50.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, with most professionally fabbed boards, you get all the niceties, like soldermask and silkscreen. Having a soldermask makes soldering small pitch components far easier, and the silk makes populating components much easier, particularly when boards get large.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How much is your time worth to you?&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-24T06:50:54.493" LastActivityDate="2010-12-24T06:50:54.493" CommunityOwnedDate="2011-05-25T02:31:53.593" CommentCount="12" />
  <row Id="7015" PostTypeId="2" ParentId="7011" CreationDate="2010-11-20T13:08:29.000" Score="8" ViewCount="" Body="&lt;p&gt;Rounded pads are better for lead-free surface mount assembly using reflow, because lead-free solder doesn't flow as well as leaded solder, and the higher temperature causes problems with the flux at the corners. They are recommended by IPC. &lt;a href=&quot;http://electronica.ugr.es/~amroldan/pcb/2006/rohs/rohs_y_pcb.htm&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a reference I found.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-20T18:40:34.917" LastActivityDate="2010-11-20T18:40:34.917" CommentCount="6" />
  <row Id="7016" PostTypeId="1" AcceptedAnswerId="7047" CreationDate="2010-11-20T13:20:32.020" Score="4" ViewCount="208" Body="&lt;p&gt;One of my students are planning to make a simple musical keyboard with PIC microcontrolers, using MIDI output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main problem now is about the pressure/force sensor. I've found a good alternative in this question about &lt;a href=&quot;http://electronics.stackexchange.com/q/6621/1757&quot;&gt;flexiforce&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wondering if there is a simpler sensor alternative, without ampops, to be used in AD input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-21T22:48:59.867" Title="Pressure/Force sensor" Tags="&lt;pic&gt;&lt;sensor&gt;&lt;music&gt;&lt;midi&gt;" AnswerCount="3" />
  <row Id="7017" PostTypeId="2" ParentId="7005" CreationDate="2010-11-20T13:33:58.200" Score="4" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;Secondary question: how do you even know things like the ULN2803A exist?&quot;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Search Google for something like &quot;transistor array&quot;.  Add words like &quot;IC&quot; or &quot;semiconductor&quot; to weed out unrelated stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/search?q=transistor+array+semiconductor&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/search?q=transistor+array+semiconductor&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;finds&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.onsemi.com/PowerSolutions/product.do?id=ULQ2003ADR2G&quot; rel=&quot;nofollow&quot;&gt;http://www.onsemi.com/PowerSolutions/product.do?id=ULQ2003ADR2G&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you find a manufacturer's listing of a specific part that looks vaguely relevant, use the manufacturer's site navigation to &quot;go up one directory&quot; and see what similar parts they have.  That page has a breadcrumbs navigation at the top &quot;Home &gt;  Products &gt;  Product Catalog &gt;  Drivers &gt;  Load / Relay Drivers &gt;  ULN2003&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Click &quot;Load / Relay Drivers&quot; to see similar stuff.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-11-20T13:33:58.200" CommentCount="3" />
  <row Id="7018" PostTypeId="1" AcceptedAnswerId="7019" CreationDate="2010-11-20T14:33:46.863" Score="4" ViewCount="133" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;The other day I was playing with a ULN2803a and a stepper motor. I spent ages trying to work out why it wasn't working and why i was reading ~14V as an output on the PIC I was using. So why did I have to connect the 0V of both supplies together?&lt;br&gt;&#xA;Thanks in Advance,&lt;br&gt;&#xA;Dean &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-11-20T14:41:45.303" Title="Why do 0v have to be connected when using two power supplies and ULN2803A?" Tags="&lt;power-supply&gt;&lt;transistor-array&gt;" AnswerCount="1" />
  <row Id="7019" PostTypeId="2" ParentId="7018" CreationDate="2010-11-20T14:41:45.303" Score="7" ViewCount="" Body="&lt;p&gt;Just because two different supplies both have a terminal labeled 'ground' doesn't necessarily mean that those nodes are at the same voltage. In fact, if you have two supplies that have isolated output, you could have almost any potential between their ground lugs, unless you strap them together. You could find a DC offset or even significant AC between the grounds of two isolated supplies. To establish a proper relative voltage levels within your system, each component needs to have a common voltage reference, and usually that's the ground node, so you connect them for that purpose.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-11-20T14:41:45.303" CommentCount="3" />
  <row Id="7020" PostTypeId="2" ParentId="7012" CreationDate="2010-11-20T14:51:28.310" Score="3" ViewCount="" Body="&lt;p&gt;When you see a heatsink with a screw, that is because the chip it is mounted to has a hole for a screw mount.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes the plate that you have to heatsink is going to be a different voltage then the surrounding board, so you need to use something that is electrically isolating, but thermally conductive. These replace the need for conductive paste.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have the area of the regulator/IC that generates heat at a voltage like ground, and the other connections for your heat-sink will be ground, you can connect them directly, and you normally want to use a form of thermal paste. I have attached a heatsink without thermal paste and still had a device temperate at almost 90 degrees C. After adding thermal paste it measured at 5 degrees C above room temperature. Often being able to connect your heatsink to ground via solder helps dissipation as it dissipates to the ground plane.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In computers you have a very specific task, cooling the Processor. In electronics it can be a very large range of tasks, and often you are willing to pay more to cool something because you design calls for it, or you are willing to pay less because your design does not need some very nice thermal paste.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, you are going to just want to use thermal paste, you do not have to worry about insulating your heat-sink if you leave it floating in the air, or ensure where it mounts to the board there is not a voltage connection. This keeps things simpler for a tinkerer. For any chip you get that you think needs heat-sinking, read what they suggest to do (on the datasheet), and follow it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Last but not least, thermal paste for computer processors will work for ICs.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-20T14:51:28.310" CommentCount="0" />
  <row Id="7021" PostTypeId="2" ParentId="6983" CreationDate="2010-11-20T15:22:11.490" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;PCB Manufacturing&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are manufacturing the pcb in house it may be a little difficult to do. Preferably you really need to have plated holes and soldermask. The plated holes are a must as the center pad is usually for thermal purposes and must have a good thermal connection to your ground plane. This means you will have to have several of them across this center pad. There are some via techniques that you can use at home that will work, but I do not have any experience with them. You can get away with no soldermask, but it makes life much easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The Footprint&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are 2 things you can do to make your soldering life easier while making the footprint. The first is to extend your pads out long enough that you can stick a soldering iron to it. The second is to round the corners of the pads on the inside of the chip. Typically I see students have issues with solder liking to bridge from the center pad to the others. They have found that rounding the back corners has extremely helped prevent this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Time to Solder&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Apply flux.&lt;/li&gt;&#xA;&lt;li&gt;Place your IC.&lt;/li&gt;&#xA;&lt;li&gt;Tack 1 pin on each corner down by pushing solder into the pad along your extended pad.&lt;/li&gt;&#xA;&lt;li&gt;Flip your board over and apply solder to all of your vias. Make sure you get it nice and hot first, it will take it a bit longer for the heat to transfer to the IC. You want the IC to be hot when solder gets to it. This is a bit hard to tell so you will just have to do some guess work. You have put enough solder down when your vias becomes completely filled with solder.&lt;/li&gt;&#xA;&lt;li&gt;Flip it back over and continue soldering all other pads with the method of pushing the solder into the pad.&lt;/li&gt;&#xA;&lt;li&gt;Check the board and your done.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-20T15:22:11.490" />
  <row Id="7022" PostTypeId="1" CreationDate="2010-11-20T18:04:54.033" Score="7" ViewCount="552" Body="&lt;p&gt;I'm getting back into hobbyist electronics after a very long hiatus and was wondering what the current state of circuit simulation software is. What is the industry standard for macs or PCs? What are the open-source alternatives?  &lt;/p&gt;&#xA;" OwnerUserId="2024" LastEditorUserId="2024" LastEditorDisplayName="" LastEditDate="2010-11-22T16:38:49.733" LastActivityDate="2011-03-05T23:23:55.447" Title="Circuit Simulation Software" Tags="&lt;design&gt;&lt;software&gt;&lt;circuit-design&gt;" AnswerCount="6" CommentCount="6" FavoriteCount="4" />
  <row Id="7023" PostTypeId="2" ParentId="7022" CreationDate="2010-11-20T18:15:53.767" Score="4" ViewCount="" Body="&lt;p&gt;Well some programs I've had chance to work are &lt;a href=&quot;http://sine.ni.com/nips/cds/view/p/lang/en/nid/203434&quot; rel=&quot;nofollow&quot;&gt;Multisim&lt;/a&gt; and &lt;a href=&quot;http://www.labcenter.com/index.cfm&quot; rel=&quot;nofollow&quot;&gt;Proteus&lt;/a&gt; (form what I've seen, I'd put them in &quot;industry standard&quot; slot (disputed for Multisim), as even the cheapest versions seem to be very expensive).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are generally nice and come with large libraries of components. They are also point and click, so you just select item from the list of items and place it on the circuit board. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also come with virtual lab instruments such as multimeter, oscilloscope and so on, so you can see how each part of the circuit behaves. Another interesting thing in Multisim is that you can use for example input form computer's microphone and redirect it to the virtual circuit or connect speaker of the circuit to computer's speaker.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also come with some microcontrollers, but selection is very limited in Multisim (some PICs only, if I remember correctly, but I never used that feature much). Proteus is supposed to be better, but I haven't used it much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both programs were very easy to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One limitation I found in Multisim which I couldn't circumvent is that only 4 wires can connect to each joint, so sometimes circuits can look a bit messy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the free software, I haven't had good experiences in that field. I've tried to use &lt;a href=&quot;http://www.gpleda.org/index.html&quot; rel=&quot;nofollow&quot;&gt;gEDA&lt;/a&gt;, but it proved to be too complicated for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also &lt;a href=&quot;http://www.gnucap.org/dokuwiki/doku.php?id=gnucap%3astart&quot; rel=&quot;nofollow&quot;&gt;gnucap&lt;/a&gt;, but I haven't had any experience with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also &lt;a href=&quot;http://en.wikipedia.org/wiki/Comparison_of_EDA_software&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; list form Wikipedia that could be interesting.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-11-21T19:31:16.533" LastActivityDate="2010-11-21T19:31:16.533" CommentCount="3" />
  <row Id="7024" PostTypeId="2" ParentId="7022" CreationDate="2010-11-20T18:16:24.843" Score="2" ViewCount="" Body="&lt;p&gt;If you've got an iPad, &lt;a href=&quot;http://itunes.com/apps/iCircuit&quot; rel=&quot;nofollow&quot;&gt;iCircuit&lt;/a&gt; is pretty neat. Needs a few updates but it's obviously the way forward for this kind of thing. &lt;/p&gt;&#xA;" OwnerUserId="1633" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-11-22T04:48:17.670" LastActivityDate="2010-11-22T04:48:17.670" CommentCount="2" />
  <row Id="7025" PostTypeId="2" ParentId="7022" CreationDate="2010-11-20T18:32:52.710" Score="7" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.linear.com/designtools/software/#LTspice&quot; rel=&quot;nofollow&quot;&gt;LTspice&lt;/a&gt; is free and works well for switching power supply designs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also use Paul Falstad's &lt;a href=&quot;http://www.falstad.com/circuit&quot; rel=&quot;nofollow&quot;&gt;Circuit Sim&lt;/a&gt; for concepts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When it comes down to designing power supplies (which is pretty much the only thing I use circuit simulators for) I usually rely on application notes and already designed supplies. If they use LT parts, I might try and optimise the design. WEbench by National Semiconductor is quite good, but I wish it gave you more freedom.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-05T23:23:55.447" LastActivityDate="2011-03-05T23:23:55.447" CommentCount="1" />
  <row Id="7026" PostTypeId="2" ParentId="7022" CreationDate="2010-11-20T18:33:32.413" Score="3" ViewCount="" Body="&lt;p&gt;I use the SPICE supplied with the Pulsonix PCB software I use. It's actually SIMetrix SPICE, and a free version is available &lt;a href=&quot;http://www.simetrix.co.uk/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. It has a very good reputation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.linear.com/designtools/software/&quot; rel=&quot;nofollow&quot;&gt;LTSpice&lt;/a&gt; is very popular, and is free.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-20T18:33:32.413" />
  <row Id="7027" PostTypeId="2" ParentId="4868" CreationDate="2010-11-20T19:38:20.077" Score="1" ViewCount="" Body="&lt;p&gt;If reading the decoded data from that DTMF signal is all you want to do, programming a microcontroller seems unnecessarily complicated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead, I would use one of the USB-to-parallel interface devices available from many companies, such as the &lt;a href=&quot;http://www.sparkfun.com/products/7841&quot; rel=&quot;nofollow&quot;&gt;Breakout Board for FT245RL USB to FIFO&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the (relatively cheap) DTMF transmitters I have,&#xA;if you hold down one button for 0.1 seconds, then continue holding it down while pushing a second button, it transmits an (impossible to decode) mishmash of more than 2 frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I'm reading your data sheet right, it ignores such impossible-to-decode signals, and during such times acts the same as when it hears nothing but silence.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I'm reading your data sheet right, the latency from pushing a button on a hard-wired DTMF encoder to the rising edge on DSO is less than 0.1 second.&#xA;I don't know anything about the delay your FM modulator and demodulator will add to the system, but I suspect the total latency will still be well under 0.2 second.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2010-11-20T19:38:20.077" />
  <row Id="7028" PostTypeId="1" AcceptedAnswerId="7048" CreationDate="2010-11-20T20:30:08.177" Score="1" ViewCount="177" Body="&lt;p&gt;I'm playing with &lt;a href=&quot;http://www.allegromicro.com/en/Products/Part_Numbers/2981/2981.pdf&quot; rel=&quot;nofollow&quot;&gt;UDN2981 source driver IC&lt;/a&gt;. But its inputs are so sensitive that the noise collected by connector wire switches them on. A simple touch is enough to set it on, but actually I don't want to make a touch sensor :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried using pulldown resistors, but only under 1K worked successfully in all conditions, which is too small for pulldown, I think. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there other tricks to avoid false switching?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: added schematic&#xA;&lt;img src=&quot;http://i.imgur.com/t3lh5.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should display 3&#xA;&lt;img src=&quot;http://i.imgur.com/1XFa1.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1514" LastEditorUserId="1514" LastEditorDisplayName="" LastEditDate="2010-11-21T16:43:19.953" LastActivityDate="2010-11-21T20:05:57.313" Title="How to avoid input noise?" Tags="&lt;noise&gt;" AnswerCount="4" CommentCount="4" />
  <row Id="7030" PostTypeId="1" CreationDate="2010-11-20T21:29:52.810" Score="2" ViewCount="312" Body="&lt;p&gt;Is there an IDE which will allow me to develop for the .net Micro Framework on Linux? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe &lt;a href=&quot;http://monodevelop.com/&quot; rel=&quot;nofollow&quot;&gt;MonoDevelop&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="1298" LastEditorUserId="103" LastEditorDisplayName="" LastEditDate="2010-11-21T12:28:06.150" LastActivityDate="2010-11-21T12:28:06.150" Title="How to develop for .NET Micro Framework on Linux?" Tags="&lt;linux&gt;&lt;netduino&gt;&lt;.net-micro-framework&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="7031" PostTypeId="2" ParentId="7028" CreationDate="2010-11-20T21:32:56.143" Score="-1" ViewCount="" Body="&lt;p&gt;Don't touch the inputs! Just wire them up and leave them alone.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-20T21:32:56.143" CommentCount="2" />
  <row Id="7032" PostTypeId="2" ParentId="7030" CreationDate="2010-11-20T21:52:21.160" Score="3" ViewCount="" Body="&lt;p&gt;From the &lt;a href=&quot;http://forums.netduino.com/index.php?/topic/21-preview-of-mono-support/&quot; rel=&quot;nofollow&quot;&gt;Netduino forums&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Soon, we'll be launching an open source project to port the .NET Micro Framework SDK to Mono for use on Mac and Linux.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;They have released the &lt;a href=&quot;http://forums.netduino.com/index.php?/topic/285-mfdeploy-v41-for-mac-os-x-and-linux-alpha-1/&quot; rel=&quot;nofollow&quot;&gt;first alpha release&lt;/a&gt; of MFDeploy for Mono (Mac and Linux). &lt;/p&gt;&#xA;" OwnerUserId="1298" LastActivityDate="2010-11-20T21:52:21.160" />
  <row Id="7033" PostTypeId="1" AcceptedAnswerId="7035" CreationDate="2010-11-20T22:35:46.557" Score="1" ViewCount="248" Body="&lt;p&gt;A transformer has a fixed output ratio. E.g. 10:1, for a 23Vac supply from 230Vac. But it is found that under light load the voltage rises above the nominal (at rated load) - why?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-21T13:23:48.143" Title="Why are transformers unregulated?" Tags="&lt;transformer&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="7035" PostTypeId="2" ParentId="7033" CreationDate="2010-11-20T23:20:18.000" Score="10" ViewCount="" Body="&lt;p&gt;The voltage rises because the transformer has been designed for a specific load. If the load is removed the voltage will rise, perhaps by 50%. It's caused by the core flux being maximum with no load on the transformer. Current in the windings will generate an opposing field that reduces the flux, reducing the voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regulated transformers are called constant voltage transformers. &lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage_regulator&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is how they work. The additional winding and capacitor makes them more expensive than unregulated transformers.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-20T23:42:24.157" LastActivityDate="2010-11-20T23:42:24.157" CommentCount="5" />
  <row Id="7036" PostTypeId="2" ParentId="7028" CreationDate="2010-11-20T23:37:29.493" Score="0" ViewCount="" Body="&lt;p&gt;Instead of pull down resistors you can try to use a capacitor to ground and a series resistor. Just remember to keep the time constant (R×C) lower than the speed of changing of the input. A factor of two to ten times lower could be enough. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The noise seems to be a kind of EMI noise, as you said that you're touching the wire and the lamp. Independente this case and pi filter could be a better alternative as it can reduce the noise from both sides of the circuit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;From wikipedia: [http://en.wikipedia.org/wiki/Capacitor-input_filter]&lt;/p&gt;&#xA;" OwnerUserId="1757" LastEditorUserId="1757" LastEditorDisplayName="" LastEditDate="2010-11-20T23:43:56.480" LastActivityDate="2010-11-20T23:43:56.480" />
  <row Id="7037" PostTypeId="2" ParentId="7016" CreationDate="2010-11-20T23:48:05.137" Score="1" ViewCount="" Body="&lt;p&gt;This question seems related to one &lt;a href=&quot;http://electronics.stackexchange.com/questions/158/how-would-i-get-a-full-range-voltage-reading-from-a-pressure-sensor&quot;&gt;I asked a while ago&lt;/a&gt;. If accuracy is not your main concern, simple voltage dividers may suffice. Take a look at &lt;a href=&quot;http://www.instructables.com/id/DIY-Force-Sensitive-Resistor-FSR/&quot; rel=&quot;nofollow&quot;&gt;this instructable&lt;/a&gt; on how to make a very cheap pressure sensor from anti-static, conductive foam.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2010-11-20T23:48:05.137" CommentCount="1" />
  <row Id="7038" PostTypeId="1" AcceptedAnswerId="7040" CreationDate="2010-11-21T00:47:38.453" Score="1" ViewCount="298" Body="&lt;p&gt;One of the things I've noticed in a few power supplies is the use of a TL431, a voltage reference, as a comparator of sorts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems to be set up in a configuration where when the voltage across it exceeds some point, it conducts, and this turns on an optocoupler. But I thought, almost like a zener, the 431 would only drop a few millivolts across the optocoupler - not enough to turn it on - until it exceeded the set point plus some volts for the optocoupler's LED, but that would be too indeterminate to produce a precise set point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is &lt;a href=&quot;http://www.onsemi.com/pub/Collateral/NCP1027-D.PDF&quot; rel=&quot;nofollow&quot;&gt;one example&lt;/a&gt;. Page 28 of the datasheet shows exactly what I'm talking about. It's quite useful in this configuration, because it turns out if you put a potentiometer across one of the resistors, configured as a rheostat, you can adjust the feedback and output voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So how can it work or am I missing something?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-21T01:38:03.893" LastActivityDate="2010-11-21T01:38:03.893" Title="TL431 as a comparator??" Tags="&lt;smps&gt;&lt;tl431&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="7039" PostTypeId="2" ParentId="7033" CreationDate="2010-11-21T00:53:01.340" Score="3" ViewCount="" Body="&lt;p&gt;Better regulation needs more copper and steel = more cost/size/weight.&#xA;And anyway there wouldn't be any point, as the mains voltage isn't precise, so even a perfect transformer wouldn't produce a consistent voltage in a freal-world application.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-21T00:53:01.340" />
  <row Id="7040" PostTypeId="2" ParentId="7038" CreationDate="2010-11-21T01:03:53.283" Score="4" ViewCount="" Body="&lt;p&gt;look at the triangle&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/p9PAE.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-21T01:03:53.283" CommentCount="7" />
  <row Id="7041" PostTypeId="1" AcceptedAnswerId="7043" CreationDate="2010-11-21T11:20:48.173" Score="3" ViewCount="187" Body="&lt;p&gt;I am working on a project that requires the usage of a AD7656 16-bit high speed converter. This chip comes in a 64-LQFP package, which means the package is rather small. Because the prototype boards will be hand soldered, I'm using 100nF 0603 X7R decoupling capacitors in combination with 10uF 1210 ceramic, as a minimum recommended amount in the datasheet. I can't use smaller capacitors, furthermore the footprints are set on Medium density to make it possible to hand solder them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately there isn't a recommended layout specification of this IC available. I have problems routing the decoupling caps. It's impossible to place both the 100nF and 10uF together closely to the IC, whilst maintaining space for the signals (parallel bus, etc.) to get out as well. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I have got 2 choices:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;I place the decoupling caps to the back of the PCB, which I don't use around the A/D and MCU for noise purposes. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I place the caps further away, but that might get to a distance of 5 cm.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Placing the caps to the back of the PCB seems like the easiest solution, maybe with paralleling 2 via's to the top to reduce the loss of the PCB. My question is, will this 'work' i.e. how will this affect the performance and noise? Or would I be better of keeping all of the capacitors at the top of the PCB?&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-11-21T13:07:06.683" Title="Decoupling of A/D converter" Tags="&lt;pcb&gt;&lt;analog&gt;&lt;noise&gt;&lt;pcb-design&gt;&lt;decoupling&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="7042" PostTypeId="1" AcceptedAnswerId="7051" CreationDate="2010-11-21T11:23:27.793" Score="12" ViewCount="489" Body="&lt;p&gt;I have browsed several ASIC manufacturer's webs, but I haven't found an actual number.&#xA;I assume there would be a fixed cost associated with creating masks and such and then there will be a cost per unit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that I don't actually want to have an ASIC made, I'm just curious.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I don't have the rep to create the &quot;asic&quot; tag, so I tagged with related terms. Please bear with me.)&lt;/p&gt;&#xA;" OwnerUserId="1850" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-11-21T13:00:58.327" LastActivityDate="2010-11-22T17:02:43.587" Title="How much does it cost to have a custom ASIC made?" Tags="&lt;hdl&gt;&lt;asic&gt;" AnswerCount="4" CommentCount="6" FavoriteCount="4" />
  <row Id="7043" PostTypeId="2" ParentId="7041" CreationDate="2010-11-21T13:07:06.683" Score="3" ViewCount="" Body="&lt;p&gt;I almost always place the decoupling caps immediately under the device for which they are decoupling (though if you can fit the 100 nf on the top side, that's fine).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, you want 1 via per power pin, and you want to place the via as close to the pin as possible, and the 100 nF cap as close to the vias as possible. Also, make the vias as large as will fit. This devices does not have a exposed pad on the bottom, which makes things easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bottom layer is then used for power routing, and the top is for signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Putting the decoupling components directly under the part is generally only a problem when you are doing manufacturing, because boards with all components on the top are cheaper than boards with components on both sides.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-11-21T13:07:06.683" CommentCount="6" />
  <row Id="7044" PostTypeId="2" ParentId="7033" CreationDate="2010-11-21T13:23:48.143" Score="3" ViewCount="" Body="&lt;p&gt;Your question is not clear. Are you looking at a rectified DC output, or the raw AC output?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're looking at the raw AC, it's likely that the transformer is not in fact 10:1, it's something like 11:1 or 12:1, and the manufacturer's rating is simply compensating for the copper losses at the specified current draw (see copper losses below).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're looking at the smoothed DC output:&lt;br&gt;&#xA;There are several things interacting here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First: If you directly rectify 120V AC, what would you expect to get?&lt;br&gt;&#xA;You will get ~170V DC, not 120V (Specifically you get ~ √2 * AC RMS, or ~169V).&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;This is because the 120V rating is &lt;em&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Root_mean_square&quot; rel=&quot;nofollow&quot;&gt;RMS&lt;/a&gt;&lt;/em&gt;, or the average power provided by the AC. Therefore, when you directly rectify it, you're smoothing capacitor will charge to the &lt;em&gt;peak&lt;/em&gt; voltage of the AC.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As soon as you start to load your rectified and smoothed transformer output, the voltage begins to be drawn down. However, since current will only flow when the transformer output voltage (which is a sine wave) is higher than the capacitor voltage (well, less the diode drops), the period of time where energy is flowing from the secondary of the transformer are quite short.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here, another factor comes into play.&lt;br&gt;&#xA;&lt;em&gt;Copper Losses&lt;/em&gt;: or the DC resistance of the secondary of the transformer.  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Since the period of time where the secondary is sourcing current is quite short, the current flow must be fairly large to enable the transformer to effectively source any power.&lt;br&gt;&#xA;Since we have a large current flow, any resistance in the winding of the transformer will translate into a large drop in voltage.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Now, since small transformers are wound with fine wire, they have a large DC R. Therefore, transformers are designed so the losses in the transformer balance out the increased voltage from the fact that the output rectifiers charge to the peak AC voltage.&lt;br&gt;&#xA;Therefore, when you load a transformer to it's specified load, the output DC rectified voltage will correspond to it's labeled specs.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-11-21T13:23:48.143" CommentCount="3" />
  <row Id="7045" PostTypeId="2" ParentId="7042" CreationDate="2010-11-21T14:42:07.413" Score="3" ViewCount="" Body="&lt;p&gt;A year ago I was in contact with a company that did fab for universities and such and would get everyone to share the wafer space, but I cannot remember the company name. It seems &lt;a href=&quot;http://electronics.stackexchange.com/users/566/joby-taffey&quot;&gt;Joby&lt;/a&gt; did remember &lt;a href=&quot;http://www.mosis.com/&quot; rel=&quot;nofollow&quot;&gt;mosis&lt;/a&gt;. I remembered it being a few grand if you were willing to use this method, but I think it can be significantly less.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found &lt;a href=&quot;http://www.edaboard.com/thread25173.html&quot; rel=&quot;nofollow&quot;&gt;this thread&lt;/a&gt; that discusses it and says for putting orders together and getting someone to broker the order together it is a few thousand.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-22T01:38:18.363" LastActivityDate="2010-11-22T01:38:18.363" CommentCount="1" />
  <row Id="7046" PostTypeId="2" ParentId="7028" CreationDate="2010-11-21T18:29:01.143" Score="1" ViewCount="" Body="&lt;p&gt;Change R1 to be 40-50kohm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;100kohm is way off the charts (literally its not even on the chart in the datasheet) for the device so i would venture a guess that the current limit is so low that they 7221 can't drive the inputs of the 2981 adequately causing the output voltage to drop to the point that its causing the malfunction.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have a second problem as well.  The DIG0 pin has to sink all the current from the common cathode.  Are you sure your within the limits of the 7221's current sinking limits?  Even more a problem, when the DIG0 isn't driving it doesn't tri-state but pulls to V+ which +5V vs the LED drivers +12V.  In this one digit case that may be ok but it means that digit will never turn all the way off, you couldn't hook up a second digit like this.  It also could mean that if DIG0 goes high and a segment is driven low, it will see a reverse 5V across the LED, i have no idea the reverse voltage specs on such a driver, but worth a safety check.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One interesting idea.  When the LED drive is high (+12V) if the DIG0 line is released (+5V) your basically applying 12-LEDdrop to the +5V line on the 7221, that should result is fairly high current, as much as the LED will pass.  It looks like the 7221 survives this, but if its current limit kicks in for all IO, this current may be triggering the rest of the chip into current limiting mode causing the SEG-IO pins to drop in voltage.  Just a random guess tho, either way use a P-channel FET to control the common cathode to ground and see if that solves the problem.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-11-21T19:49:49.503" LastActivityDate="2010-11-21T19:49:49.503" CommentCount="3" />
  <row Id="7047" PostTypeId="2" ParentId="7016" CreationDate="2010-11-21T19:08:51.350" Score="1" ViewCount="" Body="&lt;p&gt;A simple keyboard likely wouldn't even have a force sensor. Most of the pro keyboards only have velocity sensing, i.e. detect two separate positions (released and pressed) and determine the velocity from the time between. Of those that do have pressure sensing, it's often not individual per key.&#xA;See &lt;a href=&quot;http://home.roadrunner.com/~jgglatt/tech/midispec/pressure.htm&quot; rel=&quot;nofollow&quot;&gt;Channel Pressure&lt;/a&gt;. I'd really like to see your results!&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-11-21T19:08:51.350" CommentCount="1" />
  <row Id="7048" PostTypeId="2" ParentId="7028" CreationDate="2010-11-21T20:05:57.313" Score="1" ViewCount="" Body="&lt;p&gt;From a quick look at the two datasheets:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;You should &lt;em&gt;expect&lt;/em&gt; the 2981 to have very sensitive inputs - these are voltage driven logic inputs, which take a few hundred uA max to turn them on.  They're expecting to be driven by a source which is confident about what voltage it's driving.  If you disconnect them, you can expect them to wander around.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The segment outputs of the 7219 are current source outputs, which are expecting to supply current (mA) to the anode of an LED - instead you've connected them to a high-impedance input which basically draws no current at all.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'm not really clear what the 2981 is bringing to the party here, but I guess you want more segment drive.  If that's the case, you should convert the SEGx current outputs to voltage outputs, by arranging a pull-down resistor on each one.  You will need to chose the current programming for the SEGx drives, and the resistor value, to give you sensible input voltages for the 2981.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-21T20:05:57.313" CommentCount="1" />
  <row Id="7049" PostTypeId="1" AcceptedAnswerId="7050" CreationDate="2010-11-21T20:17:02.197" Score="-1" ViewCount="203" Body="&lt;p&gt;I have some buggy code, which is causing my processor to crash. I'm almost certain in what function it's in, but I don't know how to narrow down what the crash is, or where it is, for that matter. I know this isn't a Microchip support forum but I suspect someone there knows how to find out what the problem is. I am &lt;strong&gt;not asking for the solution&lt;/strong&gt; but instead how to find the solution. I have a PICkit 2 with software v2.32.0, and I'm debugging a dsPIC33FJ128GP802.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-21T21:20:02.517" LastActivityDate="2011-03-02T21:58:30.463" Title="PICkit 2: find out why my processor is crashing" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;pickit&gt;" AnswerCount="5" CommentCount="14" />
  <row Id="7050" PostTypeId="2" ParentId="7049" CreationDate="2010-11-21T20:19:58.493" Score="6" ViewCount="" Body="&lt;p&gt;Try a breakpoint. Place a breakpoint in the function where you think it is crashing. I am not sure if the PICkit 2 supports this.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Why Firmware Guys/Gals Love Extra Digital I/O&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Even easier, use a couple of those debug lines. You may know them as unused digital I/O, but they are debug lines as far as I am concerned. At key points bring the line high and after that key point is done bring it low. Move these about and find which one does not go low again. The clock cycle required to bring the line high or low will only mildly affect code but allow your oscope to tell you an important story!&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;More about breakpoints.&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Place your break-point in your possibly faulty function and single step it. If you have too many interrupts for this to work, try placing the break point at intervals, removing the last one if you hit your maximum number of breakpoints. when you do not hit one you have found your bug. if you think there is a specific case where it crashes, put an if statement that will be true in that case and place a _nop() that you can breakpoint on.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Interrupt service Routines&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Place all unused ISRs to go to a special function that will set pins to an error state and lock in place so that you can see an ISR that should not be enabled is.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-21T21:30:19.347" LastActivityDate="2010-11-21T21:30:19.347" CommentCount="0" />
  <row Id="7051" PostTypeId="2" ParentId="7042" CreationDate="2010-11-21T20:53:59.453" Score="13" ViewCount="" Body="&lt;p&gt;There are two major ways to get an ASIC made if you're looking at third party processes, such as IBM, ONsemi, STMicro, etc. The first is to work directly with the foundry (manufacturer), and the second is to work with a group that processes smaller orders.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Working directly with the manufacturer, you are typically buying a production run for a particular chip. This will give you multiple wafers with multiple copies of a reticule. A reticule will typically be around 15mm to 20mm square. You would be able to put whatever you want in that space, and you would then later divide the wafer into the individual designs. If you were making a production run of a single chip, your design would be tiled here. I don't know the prices for this, but it would probably run something like: Cost = Masks + N*Wafers, where the masks are a dominant portion of your cost. I would estimate that for the latest 40nm processes, the costs start around $2 million. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are not looking for large volumes, or you are wanting to prototype a design, then there are companies that will buy a run from a foundry for one or two wafers, and then sell out space in the reticule. There are two major companies: &lt;a href=&quot;http://www.mosis.com/&quot; rel=&quot;nofollow&quot; title=&quot;MOSIS&quot;&gt;MOSIS&lt;/a&gt; and &lt;a href=&quot;http://cmp.imag.fr/&quot; rel=&quot;nofollow&quot; title=&quot;CMP&quot;&gt;CMP&lt;/a&gt;. They plan on buying only one or two wafers and a set of masks, so their production costs are basically fixed. Their prices are typically based on the size of your design in mm^2. MOSIS doesn't publish their rates, but CMP's cheapest rate on a 0.35 micron process for 650 Euros/mm^2. A non-trivial design will probably cost $3000 or more for 40 chips. The finer the feature size, the more expensive it is to make the masks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another item to consider is that the design software needed to design and verify IC's is NOT cheap, unless you're doing it from a university setting. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-11-21T20:53:59.453" CommentCount="7" />
  <row Id="7052" PostTypeId="2" ParentId="7049" CreationDate="2010-11-21T21:20:36.340" Score="4" ViewCount="" Body="&lt;p&gt;You say that you don't know how to narrow it down:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Divide and conquer - remove as much code as you can until the fault goes away. With some experimentation you'll likely cut your search down hugely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As suggested, use spare I/O lines to signal points in your code. Ideally, you might be able to have a line showing entry and exit from a subroutine and correlate this on a scope with the fault occurring.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some general tips:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Build a good test case so you can reproduce the fault on demand&lt;/li&gt;&#xA;&lt;li&gt;Remove &lt;em&gt;everything&lt;/em&gt; non-essential to reproducing the fault&lt;/li&gt;&#xA;&lt;li&gt;Keep your ISRs as short as possible - do what you have to then return&lt;/li&gt;&#xA;&lt;li&gt;Understand and use the volatile keyword in C&lt;/li&gt;&#xA;&lt;li&gt;Don't rely on debuggers, know your code and rely on a debug LED. Generally debuggers just don't work well for realtime systems&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-21T21:33:52.077" LastActivityDate="2010-11-21T21:33:52.077" CommentCount="4" />
  <row Id="7053" PostTypeId="2" ParentId="7049" CreationDate="2010-11-21T21:21:56.440" Score="3" ViewCount="" Body="&lt;p&gt;The Freescale HCS08 family has a &quot;System Reset Status&quot; register which is set based on the source for the last reset, identifying things like LVD, POR, debugger reset, illegal op-code, illegal address access, watchdog timeout, loss of clock, and hardware (external reset).   Might there be an equivalent on PICs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has saved me maybe 50% pain after learning to use it as it clues you into the possible source of the error.  A breakpoint only works if you know roughly where &lt;em&gt;and when&lt;/em&gt; the code will cause a fatal error, otherwise you may have to step thousands of times, likely through the same code, until you hit the snafu.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; Here's the stupid code I wrote for it (HCS08-only obviously).  Not that pretty, but hey, I'm a hardware developer, not software.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#ifdef Debug_MP16VLF&#xA;    const char rstsrc[] = &quot;Source  :&quot;;&#xA;    const char clrColors[] = &quot;\x1B[0m&quot;;&#xA;&#xA;    const char * const rst_srcs[] = {&#xA;        &quot; \x1B[32mPower On Reset&quot;,      &quot; \x1B[32mReset Pin&quot;, &#xA;        &quot; \x1B[31mWatchdog&quot;,            &quot; \x1B[35mIllegal Opcode&quot;,&#xA;        &quot; \x1B[36mIllegal Address&quot;,     &quot; \x1B[33mLow Voltage Detect&quot;,&#xA;        &quot; \x1B[33mDebugger Reset&quot;&#xA;    };&#xA;    enum rst_srcs_idxs{&#xA;        RST_POR,                        RST_PIN,&#xA;        RST_COP,                        RST_ILOP,&#xA;        RST_ILAD,                       RST_LVD, &#xA;        RST_DBG&#xA;    };&#xA;#endif&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;...&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#   ifdef Debug_MP16VLF&#xA;        // Find reason(s) for reset and display&#xA;        print_str(rstsrc, 0, 1);&#xA;        if (SRS_LVD) {&#xA;            if (SRS_POR) print_str(rst_srcs[RST_POR], 0, 1);&#xA;            print_str(rst_srcs[RST_LVD], 0, 1);&#xA;        } else if (SRS) {&#xA;            // possible multiple reset sources&#xA;            uint8_t i, j;&#xA;            for (i = SRS_ILAD_MASK, j = RST_ILAD;&#xA;                 i &amp;lt;= SRS_PIN_MASK;&#xA;                 i &amp;lt;&amp;lt;= 1, j--) {&#xA;                if (i &amp;amp; SRS) print_str(rst_srcs[j], 0, 1);&#xA;            }&#xA;        } else {&#xA;            print_str(rst_srcs[RST_DBG], 0, 1);&#xA;        }&#xA;        print_str(clrColors, 1, 1);&#xA;#   endif&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-21T21:40:40.440" LastActivityDate="2010-11-21T21:40:40.440" CommentCount="9" />
  <row Id="7054" PostTypeId="1" CreationDate="2010-11-21T22:29:27.590" Score="1" ViewCount="219" Body="&lt;p&gt;Here are the sensors I am trying to measure and then convert into a 0-5V analog output:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;pH (acid or base):  my understanding is you can use DC voltage to measure this sensor, just not sure what kind it is... impedance / resistive / inductive?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EC (electrical conductivity):  Resistive I believe, with an EC of zero giving a 1/1megaohm measurement?  has to be AC or you risk the probe wearing out real quick.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;10k thermistor (temp):  same as EC i believe, a simple resistive sensor&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DO (dissolved oxygen): no idea&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ion selective probes(nitrates, ammonium, etc): no idea either, possibly the same as EC?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once I get a grasp of how each type of probe is measured, what resources should I be looking at to tie it all together?  How do I reduce noise on the sensors if they are in the same container?  What are some of the better methods to test these out if I already have the sensors?  breadboarding? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good example of sensors:  &lt;a href=&quot;http://www.vernier.com&quot; rel=&quot;nofollow&quot;&gt;http://www.vernier.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2034" LastEditorUserId="2034" LastEditorDisplayName="" LastEditDate="2010-11-22T04:27:34.067" LastActivityDate="2010-11-22T05:46:19.500" Title="How to measure EC, pH, 10k thermistor, DO, and Ion-selective probes" Tags="&lt;sensor&gt;&lt;measurement&gt;&lt;thermistor&gt;" AnswerCount="2" CommentCount="8" />
  <row Id="7055" PostTypeId="2" ParentId="7016" CreationDate="2010-11-21T22:48:59.867" Score="0" ViewCount="" Body="&lt;p&gt;Force gauges are basically variable resistors.  They change their resistance relative to a force or pressure applied.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem in detection lies in the variation of resistance relative to the force being applied.  This is not great, so often a good detection method and amplification are required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A wheatstone bridge is a really good circuit that allows the for small changes in resistance to be converted into changes in voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A simple but crude method is to connect the output of the wheatstone bridge to you A/D input which will be able to measure the delta V.  Alternatively you might even be able to buffer the two outputs, and feed them into a comparator with some hystersis and this can give you a binary output.  Very crude, but will allow for detection of force/no force applied.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, if you want to know the amount of force being applied, you will need to perform some analysis to work out the voltage variation relative to pressure change.  The derivation of the wheatstone bridge equations is a bit tricky but there are plenty of summaries around the interwebs.  You will need a good excitation source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you know the force/pressure that you trying to detect, you can calculate the change in resistance, and then the change in voltage, and compare this to the resolution of the A/D.  If you are after crude changes, this may be sufficient.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are after a more precise value you will need an instrumentation amplifier to perform the difference amplification and you can feed this into your A/D.  Texas Instruments make some of the best IA's around with respect to CMRR and PSRR against frequency.  These were originally made by Burr Brown before TI bought them out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For precision measurement you will need to have your bridge completing resistors close as possible to your strain gauge to ensure that you can compensate for temperature variations, also a good precise excitation voltage will be needed.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-21T22:48:59.867" />
  <row Id="7056" PostTypeId="2" ParentId="7054" CreationDate="2010-11-21T23:18:43.490" Score="1" ViewCount="" Body="&lt;p&gt;Thermistor:  To measure the temperature of a thermistor, first determine your temperature range that you are interested in, and convert that to delta R of your thermistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With this information it will be possible to determine the optimum circuit for detecting that range of temperatures.  You may find that a thermocouple may be better suited to your application for larger temperature ranges, at the expense of the circuit and software complexity, involved with instrumentation amplifiers and software to perform cold junction compensation.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-21T23:18:43.490" />
  <row Id="7057" PostTypeId="2" ParentId="7049" CreationDate="2010-11-22T03:27:06.920" Score="2" ViewCount="" Body="&lt;p&gt;In terms of narrowing a crash down, use a &lt;strong&gt;binary search&lt;/strong&gt; technique.  Using one of the methods described in the other answers (breakpoints or I/O lines going to a scope or LED), pick a point halfway through the function you suspect the problem is in, and set the BP there.  If the BP is hit (or the LED lights), the problem is in the second half of the code (since the program didn't crash).  If it isn't, it is in the first half.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whichever half is suspect, divide that section in half and set a new BP at the midpoint.  If the BP is hit, the problem is in the other part of the code (now narrowed down to a quarter if the function).  Keep repeating this process if necessary and it will isolate the problem down to a single line of code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because it is using a binary search, this is the fastest method to narrow down where a crash is occurring.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-11-22T03:27:06.920" CommentCount="3" />
  <row Id="7058" PostTypeId="1" CreationDate="2010-11-22T04:10:47.850" Score="0" ViewCount="248" Body="&lt;p&gt;Hi, I have built a Ponyprog programmer to find out Windows 7 cannot recognize the drivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was wondering if I could use this &quot;&lt;a href=&quot;http://www.sparkfun.com/products/9825&quot; rel=&quot;nofollow&quot;&gt;Pocket AVR Programmer&lt;/a&gt;&quot; to program an atmega 8535? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If so, how do I connect the atmega to this board? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or can you recommend something for me?&lt;/p&gt;&#xA;" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-22T04:42:59.993" LastActivityDate="2010-11-22T17:33:43.917" Title="programming atmega chip" Tags="&lt;atmega&gt;&lt;atmel&gt;&lt;programming&gt;" AnswerCount="3" />
  <row Id="7059" PostTypeId="2" ParentId="7058" CreationDate="2010-11-22T04:41:28.197" Score="2" ViewCount="" Body="&lt;p&gt;From &lt;a href=&quot;http://www.sparkfun.com/products/9825&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;This programmer works really well for&#xA;  ATmega168 and ATmega328 and should&#xA;  work with all the AVR micros supported&#xA;  by AVRDUDE. We've played a bit with&#xA;  the ATtinys but we cannot guarantee&#xA;  that this board will be compatible&#xA;  with anything but ATmega168/328.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;From &lt;a href=&quot;http://www.ladyada.net/learn/avr/avrdude.html&quot; rel=&quot;nofollow&quot;&gt;Ladyada&lt;/a&gt; the ATMEGA8535 is listed as being supported by AVRDUDE.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And there is a pinout for the standard ISP connectors and an example schematic on how to hook it up at &lt;a href=&quot;http://my.opera.com/CrazyTerabyte/blog/2008/02/02/first-contact-with-atmega8-microcontroller-part-4&quot; rel=&quot;nofollow&quot;&gt;http://my.opera.com/CrazyTerabyte/blog/2008/02/02/first-contact-with-atmega8-microcontroller-part-4&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Page 2 of your &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2502.pdf&quot; rel=&quot;nofollow&quot;&gt;data sheet&lt;/a&gt; shows you the pin out of the chip. You will need to hook up all of these pins: reset, sck, miso, mosi, vcc(power), and ground&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-22T05:03:18.313" LastActivityDate="2010-11-22T05:03:18.313" CommentCount="2" />
  <row Id="7060" PostTypeId="2" ParentId="7054" CreationDate="2010-11-22T04:49:18.620" Score="0" ViewCount="" Body="&lt;p&gt;When I use a thermistor it is normally part of a voltage divider. You chose a resistance to place in series with the thermistor that will allow you diverse readings over its operating range. In an Ideal world a thermistor would go from an open(infinite resistance) to a short(no resistance) over the exact operating range you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In reality you want to choose a resistance to go with the 10k thermistor to give you readable change. Tie one side to a microcontroller and only turn it on to read it, then turn it off, otherwise the current can cause a significant heating effect. I have a simple schematic, control the 0V or 5V with your micro to stop constant dissipation: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/RF6J8.png&quot; alt=&quot;Schematic with resistor and thermistor&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-22T05:46:19.500" LastActivityDate="2010-11-22T05:46:19.500" />
  <row Id="7061" PostTypeId="2" ParentId="6972" CreationDate="2010-11-22T06:04:14.030" Score="1" ViewCount="" Body="&lt;p&gt;I found some information by looking around online.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here I found some &lt;a href=&quot;http://www.customthermoelectric.com/mini-tecs.html&quot; rel=&quot;nofollow&quot;&gt;mini-TEC&lt;/a&gt; (ThermoElectric Coolers). They seem to be able to do Watts, which I think converts to joules per second, with an efficiency of 5% they should be able to do what you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may need to buy a few and test them, or tomorrow I will look on their site more and get more info. I know that this is done, so I am sure you can find a way. They are not cheap though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are also quite small. I hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-23T10:06:10.257" LastActivityDate="2010-11-23T10:06:10.257" />
  <row Id="7062" PostTypeId="1" AcceptedAnswerId="7063" CreationDate="2010-11-22T06:04:16.840" Score="0" ViewCount="269" Body="&lt;p&gt;Hi, I need to control my pc with an IR remote control.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The piece of software I think I can use is WinLIRC (or can someone can suggest something else?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please can someone give me the simplest hardware design for an IR-Receiver??&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="2037" LastEditorUserId="3028" LastEditorDisplayName="" LastEditDate="2011-06-01T03:22:13.210" LastActivityDate="2011-06-01T03:22:13.210" Title="Design for a simple IR-Receiver for PC?" Tags="&lt;ir&gt;&lt;circuit-design&gt;" AnswerCount="1" />
  <row Id="7063" PostTypeId="2" ParentId="7062" CreationDate="2010-11-22T08:55:31.797" Score="6" ViewCount="" Body="&lt;p&gt;The IR &lt;em&gt;receiver&lt;/em&gt; is trivial - you just buy one of the three-terminal IR receiver modules, which will give you a nice clean set of pulses.  (for example, search for GP1U on Digikey)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting the pulses into the PC is harder, and if you're planning to use someone else's software to decode them (e.g. WinLIRC), then you should follow their recommendations - the WinLIRC site has a page of stuff about this.   If I was doing this from scratch, I'd probably decode it all in a micro and send something higher-level up a USB cable - perhaps pretend to be a HID keyboard, but that's quite a lot to get going if you haven't done something like that before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In real life, I wouldn't develop anything like this, as it's a tedious commodity building-block, which has already been done a million times - I'd go here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/#q=ir+usb+receiver&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/#q=ir+usb+receiver&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and buy something someone has already made.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-22T08:55:31.797" />
  <row Id="7064" PostTypeId="2" ParentId="7003" CreationDate="2010-11-22T09:18:38.620" Score="22" ViewCount="" Body="&lt;p&gt;For one-offs or prototypes I use:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Press-n-Peel transfer film with a laser printer (the blue one)&lt;/li&gt;&#xA;&lt;li&gt;Steel wool and detergent to clean the PCB blank, then a short etch in ammonium persulphate: that gives a very clean surface, important for a good transfer from the film&lt;/li&gt;&#xA;&lt;li&gt;A laminator to transfer the pattern to the PCB; I modified the laminator to raise its operating temperature a bit, and the PCB is a bit thick for the laminator but it works&lt;/li&gt;&#xA;&lt;li&gt;Ammonium persulphate made with hot water in an ice-cream container, and that sits in a bath of hot water (a larger ice-cream container)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This gives good results down to 10 mil trace widths; could probably go finer but haven't needed to yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For double-sided boards I tape the two layers of Press-n-Peel film to two scraps of PCB at the edges so that I can get the two layers well aligned, then put the PCB blank in and feed it through the laminator. Here are some pictures to illustrate:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2oFY4.jpg&quot; alt=&quot;alt text&quot;&gt; The bottom (left) and top (right) of a simple double-sided board (the top one is printed out mirrored so they overlay when its turned over). Normally I would print onto the blue Press-n-Peel film, just using paper here for illustration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Q2Lbe.jpg&quot; alt=&quot;alt text&quot;&gt; With one side taped to the scrap PCB (left side) and the printed sides facing each other, hold them up to the light and align the other one so that all the holes and the board outline line up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/lVjV8.jpg&quot; alt=&quot;alt text&quot;&gt; Here they are both stuck to the PCB scrap. You can now put the clean blank PCB between the two (probably best to tape it to both sides to avoid any movement) and run it through the laminator (or iron it) to transfer the toner onto the PCB. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can tape the two pieces of film or paper together without using the scrap of PCB, but when you put the blank PCB between them you can get some relative movement as they flex around the thick PCB. With the scrap piece the same thickness as the blank PCB they stay in the right place.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A bench drill is good for any drilling. I use drills down to 0.5 mm diameter but with 3 mm shanks so they are easily held in the drill chuck.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For through holes I solder thin copper wire to the pads on either side. The wire comes from a multi-core flexible cable; individual strands are or about 0.2 mm or 8 mil diameter. This takes some time!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And to solder I place solder paste with a fine-tipped syringe, place parts with fine tweezers then reflow in an electric frying pan. A few more pictures:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/O6UYe.jpg&quot; alt=&quot;alt text&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Syringing solder paste onto SMD pads. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/4ZpFi.jpg&quot; alt=&quot;alt text&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Placing component with tweezers&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/im1VH.jpg&quot; alt=&quot;alt text&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A finshed board - the PCB was professionally made but I assembled components and soldered as described here. These are 0402-size resistors and capacitors (quite small, amazingly easy to lose), an accelerometer in a QFN-16 package (4x4 mm) and a memory chip in an 8 pin leadless package, similar size to a SOIC-8. (This is part of a small accelerometer data logger, see &lt;a href=&quot;http://vastmotion.com.au&quot; rel=&quot;nofollow&quot;&gt;vastmotion.com.au&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="1897" LastEditorUserId="1897" LastEditorDisplayName="" LastEditDate="2010-11-22T11:13:37.037" LastActivityDate="2010-11-22T11:13:37.037" CommunityOwnedDate="2011-05-25T02:31:53.593" CommentCount="4" />
  <row Id="7065" PostTypeId="2" ParentId="6972" CreationDate="2010-11-22T09:37:28.407" Score="2" ViewCount="" Body="&lt;p&gt;As well as the other stuff people have said, you may also need to be careful about the lifetime of the modules under such aggressive cycling.  Differential thermal expansion rates mean cycling is a cause of 'wear' to Peltier modules, and it's reasonable to think that the faster the ramp-rates are, the worse this wear will be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can certainly get small coolers, though - somewhere like here, for example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.kryothermusa.com/indexf526.html?tid=48&quot; rel=&quot;nofollow&quot;&gt;http://www.kryothermusa.com/indexf526.html?tid=48&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-22T09:37:28.407" />
  <row Id="7066" PostTypeId="1" AcceptedAnswerId="7078" CreationDate="2010-11-22T09:53:36.263" Score="2" ViewCount="186" Body="&lt;p&gt;Someone told me that if we used something like 1 kHz AC instead of 50 or 60 Hz AC, it would end up being much cheaper and efficient, because we could use smaller transformers. Is this true? It seems like it would probably cost more as the generators would have to spin much faster - also, it could lead to more losses due to the skin effect. (Just out of curiosity.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-22T22:49:05.870" Title="High frequency mains transmission" Tags="&lt;ac&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="7067" PostTypeId="2" ParentId="6468" CreationDate="2010-11-22T10:11:57.767" Score="2" ViewCount="" Body="&lt;p&gt;So for the sake of closure, my own answer is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vlogic needs to be 1.8V or less, in spite of what the specifications say. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe its just me, these things are supposed to work with any Vlogic between 1.7V and Vdd.&lt;/p&gt;&#xA;" OwnerUserId="1897" LastActivityDate="2010-11-22T10:11:57.767" />
  <row Id="7068" PostTypeId="2" ParentId="7058" CreationDate="2010-11-22T10:34:43.700" Score="0" ViewCount="" Body="&lt;p&gt;I am sure that on this &lt;a href=&quot;http://www.obdev.at/products/vusb/prjprog.html&quot; rel=&quot;nofollow&quot;&gt;list&lt;/a&gt; you will be able to find simple and easy to build USB programmer for AVR.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-11-22T10:34:43.700" />
  <row Id="7069" PostTypeId="1" AcceptedAnswerId="7087" CreationDate="2010-11-22T10:43:36.723" Score="2" ViewCount="406" Body="&lt;p&gt;I need to buffer an input signal such that I do not load down the source, which is a 100k resistor. However, I need to buffer at least 6 channels, and for more advanced models I'd like to move to 10 channels (for the more advanced one I'd be okay using multiple chips though.) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd rather &lt;strong&gt;not use op-amps&lt;/strong&gt;, because they will take up considerable space - just wiring the inverting or noninverting to the output, for example, uses a lot of space for traces - also, half the pins would be unneeded. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure what chip or type of chip to be looking for - all the buffers I've found so far only work for digital logic, not analog signals. The buffer should have very low input bias current (nanoamps to hundreds of picoamps), like a JFET op-amp.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-22T20:17:31.960" Title="Analog buffer without op-amps" Tags="&lt;analog&gt;&lt;ic&gt;&lt;buffer&gt;" AnswerCount="3" CommentCount="30" FavoriteCount="1" />
  <row Id="7070" PostTypeId="2" ParentId="7066" CreationDate="2010-11-22T10:43:37.050" Score="6" ViewCount="" Body="&lt;p&gt;You would certainly see problems related to skin effect on long cables, but you would get huge capacitive losses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It takes some energy to charge a wire to several hundred kV, so doing that more often will need more energy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The longer the wires the higher the capacity and the higher the losses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is actually done is to switch to DC for long / high-voltage lines, with DC the ends of the wire get more expensive because you have to have high-voltage semiconductors to handle rectification at one end and to turn the DC into AC at the other end, but modern semiconductors have brought down the price on those stations a bit, so but for very long transmission lines it's a huge win.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See: &lt;a href=&quot;http://en.wikipedia.org/wiki/High-voltage_direct_current&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/High-voltage_direct_current&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-22T10:43:37.050" CommentCount="11" />
  <row Id="7071" PostTypeId="2" ParentId="7069" CreationDate="2010-11-22T11:24:39.277" Score="7" ViewCount="" Body="&lt;p&gt;One alternative is to build a &lt;a href=&quot;http://en.wikipedia.org/wiki/Common_collector&quot; rel=&quot;nofollow&quot;&gt;common collector with a BJT&lt;/a&gt; or a common drain with JFET. It works almost as a buffer: high input impedance, low output impedance and almost a unity gain. Being a simple circuit you can implement without problem. JFET produces a better alternative to low input current needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/3Oq6F.png&quot; alt=&quot;Common Collector&quot;&gt; &lt;img src=&quot;http://i.imgur.com/07yzf.png&quot; alt=&quot;Common Drain&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Common Collector and Common Drain&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need more inputs/outputs you can use a common collector array chip such as &lt;a href=&quot;http://www.digchip.com/datasheets/parts/datasheet/235/CA3082-pdf.php&quot; rel=&quot;nofollow&quot;&gt;CA3082&lt;/a&gt;. It will save you lots of space. Unfortunately I don't know a chip with common drain array built in. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/R2Su0.png&quot; alt=&quot;Common Collector Array Chip&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1757" LastEditorUserId="1757" LastEditorDisplayName="" LastEditDate="2010-11-22T13:52:11.423" LastActivityDate="2010-11-22T13:52:11.423" CommentCount="5" />
  <row Id="7073" PostTypeId="2" ParentId="7069" CreationDate="2010-11-22T11:51:46.173" Score="6" ViewCount="" Body="&lt;p&gt;I find it hard to believe that wiring up little SC70 (or smaller) op amps is going to take up too much space on your board. Digikey has 5 pages of SC70 sized buffer amps that would probably do a good sight better job performance-wise than a common-collector BJT, and you could sprinkle them around the board as needed, meaning they'd take up no more space than that BJT.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-11-22T11:51:46.173" CommentCount="7" />
  <row Id="7074" PostTypeId="2" ParentId="259" CreationDate="2010-11-22T12:57:43.773" Score="1" ViewCount="" Body="&lt;p&gt;I haven't try this myself. But looking through wacom tablet patent, you could place the sensor behind LCD (between lcd and shield). Therefore it should be possible put Pic16707 sensor board behind lcd.&lt;/p&gt;&#xA;" OwnerUserId="2038" LastActivityDate="2010-11-22T12:57:43.773" CommentCount="1" />
  <row Id="7075" PostTypeId="2" ParentId="7011" CreationDate="2010-11-22T13:47:51.830" Score="0" ViewCount="" Body="&lt;p&gt;I prefer the rounded pads when I'm etching a board myself.  I find that by using a rounded pad and making it a bit larger than it needs to be I have more room for errors in etching or drilling.  It's especially useful for through-hole components.  If your hole isn't exactly where it needs to be and your pad is circular then a rounded rectangle leaves more area in case the hole is off.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-22T13:47:51.830" />
  <row Id="7076" PostTypeId="2" ParentId="7042" CreationDate="2010-11-22T13:55:50.230" Score="0" ViewCount="" Body="&lt;p&gt;Have you considered using an FPGA? With an FPGA you can reorganize hardware components on a chip without the expense of creating your own chip. If you are in a university it's possible they have their own small FAB. The university I went to did. If they don't maybe you could talk to someone at a university that has a FAB and see if you could get them to make your chip, the fees would probably be lower that from a foundry.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-11-22T13:55:50.230" CommentCount="1" />
  <row Id="7077" PostTypeId="1" CreationDate="2010-11-22T16:11:58.310" Score="4" ViewCount="140" Body="&lt;p&gt;Yesterday, there was a huge power surge in my area, and I wasn't able to connect to the internet any more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason was that the Wifi modem was somehow automatically reset to its factory configuration. I had to reset it to my settings today to get it working again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this a normal thing? How does it happen?&lt;/p&gt;&#xA;" OwnerUserId="1546" LastActivityDate="2010-11-22T16:35:27.993" Title="How does a power surge reset a modem?" Tags="&lt;electronics&gt;&lt;current&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="7078" PostTypeId="2" ParentId="7066" CreationDate="2010-11-22T16:31:56.760" Score="9" ViewCount="" Body="&lt;p&gt;Yes, transformers could be lighter.  400 Hz power is used on aircraft for this reason.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The generator wouldn't need to spin faster if it is designed with more poles.  Motors would also have to be redesigned to run at normal speeds with 1000 Hz power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But how often are 60 Hz transformers used in modern electronics?  There is a big one on the pole outside of my house, and in my boat-anchor hi-fi amps and tube guitar amps.  All the other power supplies in my house use switching supplies that run their transformers at a much higher frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit:  Another thing, transformers tend to vibrate slightly during operation.  A 60 Hz transformer will &quot;hum&quot; a little bit.  But imagine all the appliances in your house buzzing at 1 kHz.  1000 Hz is two octaves above middle C, and our ears are 30dB more sensitive to this frequency than 60 Hz:&#xA;&lt;img src=&quot;http://i.imgur.com/JxCvh.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Image source: &lt;a href=&quot;http://en.wikipedia.org/wiki/Equal-loudness_contour&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Equal-loudness_contour&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-11-22T20:24:09.413" LastActivityDate="2010-11-22T20:24:09.413" CommentCount="6" />
  <row Id="7079" PostTypeId="2" ParentId="7077" CreationDate="2010-11-22T16:35:27.993" Score="10" ViewCount="" Body="&lt;p&gt;Often what happens in this sort of situation is not that the surge resets the configuration, but that it's sufficient to flip one bit of the configuration, such that a checksum then fails and the software decides to reset all the config to its factory settings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, high voltages push high currents, and fast-changing high currents can induce current in adjacent conductive objects, which can create the right conditions for the very tiny and delicate structures which make up non-volatile memory to change state.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-22T16:35:27.993" CommentCount="4" />
  <row Id="7080" PostTypeId="2" ParentId="7022" CreationDate="2010-11-22T17:00:56.913" Score="2" ViewCount="" Body="&lt;p&gt;The industry standard is PCs with Windows and all the major simulation packages support it.  No one that I know or have heard of in industry does any circuit simulation on Macs.  Linux is more common than OS X.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-17T17:38:12.513" LastActivityDate="2010-12-17T17:38:12.513" CommentCount="5" />
  <row Id="7081" PostTypeId="2" ParentId="7042" CreationDate="2010-11-22T17:02:43.587" Score="0" ViewCount="" Body="&lt;p&gt;A choice is doing a FPGA conversion.  Both Altera and Xilinx has that.  I'd go with Altera.  The prices are in the $100's k US.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-11-22T17:02:43.587" />
  <row Id="7082" PostTypeId="1" AcceptedAnswerId="7085" CreationDate="2010-11-22T17:05:48.697" Score="6" ViewCount="251" Body="&lt;p&gt;Hi Guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the moment i want to build a machine that counts money (money counter machine). When the user puts in the money bills, it will scan them and count them and send the results to a program running on a PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really don't know the kind of hardware i need to build this machine. I have been googling for a while but can't seem to find any place that will give me a good answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will also create a software that will receive the counting from the machine. Creating the software is not a problem. What i need now is how to build this machine and where to get the hardwares. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My main concern now is which hardware do i need to create this machine and probably where to get them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If i decide to buy an existing machine without building it myself, is it possible to create one software that will work with any machine or i have to write the software for each particular machine i may choose(in case i may change the machine later).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where can i buy an existing machine?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="2041" LastActivityDate="2010-11-22T18:35:51.323" Title="Money Counting Machine" Tags="&lt;electronics&gt;&lt;robotics&gt;&lt;hardware&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="2" />
  <row Id="7083" PostTypeId="2" ParentId="7082" CreationDate="2010-11-22T17:26:42.633" Score="1" ViewCount="" Body="&lt;p&gt;I found a bill counter (only worked with 1 dollar bills) that communicated over a simple serial connection from an electronic salvage place in Tacoma, WA. I got the basic communication to work but something appeared damaged as it simply would not scan bills correctly. Probably explains why it was at a salvage place.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The manufacturer had a simple protocol doc that listed the expected responses, time intervals, etc. It seemed very straightforward.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't recall the model number or any details but I'll see if I can dig it up and post it here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE: Didn't read the original request very clearly. The thing I found is technically a &quot;bill validator&quot; or &quot;bill accepter&quot; -- i.e. it's used for vending machines to input money so it's not designed for speedy counting. It's made by iCT, model BL-700R-USD4P2. Still can't find the PDF with protocol details.&lt;/p&gt;&#xA;" OwnerUserId="1970" LastEditorUserId="1970" LastEditorDisplayName="" LastEditDate="2010-11-22T18:35:51.323" LastActivityDate="2010-11-22T18:35:51.323" CommentCount="1" />
  <row Id="7084" PostTypeId="2" ParentId="7058" CreationDate="2010-11-22T17:33:43.917" Score="0" ViewCount="" Body="&lt;p&gt;Yes your programmer will do the job for all common atmega and attiny.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;for atmel micro you have to connect this way :&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;programmer           target&#xA;GND         &amp;lt;-&amp;gt;      GND&#xA;SCK         &amp;lt;-&amp;gt;      SCK&#xA;MISO        &amp;lt;-&amp;gt;      MISO&#xA;MOSI        &amp;lt;-&amp;gt;      MOSI&#xA;RESET       &amp;lt;-&amp;gt;      RESET&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;easy !&lt;/p&gt;&#xA;&#xA;&lt;p&gt;you can add VCC, if you want to power the target from the programmer (pay attention to the maximum of current it can provide)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;they are two standart header (2x3 and 2x5), but I'm not using them in my personal design as they doesn't follow the common pinout of the atmega. I use a 1x5 header in the order i listed the connection because it is so much easier to route with less via and bigger trace ! I found it &lt;a href=&quot;http://tuxgraphics.org/electronics/200901/tuxgraphics-isp-header.shtml&quot; rel=&quot;nofollow&quot;&gt;with this programmer&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also dont forget to put a pull up resistor on the reset line (~ 4k). You will also need one on MISO if you are using another SPI IC.&lt;/p&gt;&#xA;" OwnerUserId="2040" LastActivityDate="2010-11-22T17:33:43.917" CommentCount="2" />
  <row Id="7085" PostTypeId="2" ParentId="7082" CreationDate="2010-11-22T17:43:39.240" Score="3" ViewCount="" Body="&lt;p&gt;eBay has a bunch of &lt;a href=&quot;http://shop.ebay.com/?_nkw=bill+counter&quot; rel=&quot;nofollow&quot;&gt;bill counters&lt;/a&gt; currently listed.  If you just need one (rather than needing an OEM part so you can design something for production), this may be a good source.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-11-22T17:43:39.240" CommentCount="4" />
  <row Id="7087" PostTypeId="2" ParentId="7069" CreationDate="2010-11-22T17:53:36.737" Score="4" ViewCount="" Body="&lt;p&gt;It seems after some discussion that you are looking for a &lt;a href=&quot;http://en.wikipedia.org/wiki/Buffer_amplifier&quot; rel=&quot;nofollow&quot;&gt;buffer amplifier&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digikey has a section for this. if you go to the main area for &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556125&quot; rel=&quot;nofollow&quot;&gt;linear amplifiers&lt;/a&gt; and then select for buffer type and in stock you get quite a list. I selected for those with an input current of 2nA typical I got a relatively short list(like 10). This however does not give me an easy way to share the links, so you will have to click it yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are designed to give you the features you want and in a small package, now they normally come in groups of 2^n, so you will have to get a package of 8, but I am sure you can make it work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/users/411/markrages&quot;&gt;Markrages&lt;/a&gt; had a bit of extra input to add in a comment:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Cautions about those buffer amps: Most of them are made for video signals and so they are high bandwidth / high current designs. That's a consideration if the circuit is battery powered. Also note that (the ones I looked at) are specialized, single vendor parts. More expensive and more availability risk than op-amps or transistors with standardized footprints. Engineers have a duty to only use oddball parts when their special features are necessary and relevant to the design.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-22T20:17:31.960" LastActivityDate="2010-11-22T20:17:31.960" CommentCount="12" />
  <row Id="7088" PostTypeId="2" ParentId="4937" CreationDate="2010-11-22T17:58:33.767" Score="1" ViewCount="" Body="&lt;p&gt;This sounds like you might be having a baud rate mismatch. I have seen many cases where a device or library will default to a particular baud rate and wont be an issue until switching devices or platforms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other possibility is using a serial class that only works on linux.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-22T17:58:33.767" />
  <row Id="7089" PostTypeId="1" AcceptedAnswerId="7396" CreationDate="2010-11-22T18:46:45.160" Score="2" ViewCount="230" Body="&lt;p&gt;I am using DxDesigner for the first time (9.2).  When running a Design Rules Check (DRC) there are many rules that can be applied.  Many of them make sense to check, e.g. &quot;Property name exceeds maximum length&quot;.  Others are giving me trouble, e.g. Un-driven Net is an error if I enable it when a net is driven by a transformer with pin type analog.  Which ones do you use?  Disable?  Check, but often ignore the notes or warnings?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Updated 11/23/2010:  Under Connectivity here are some I had questions on.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;drc-101 Output and bidirectional pins connected together&#xA;drc-102 Output and tristate pins connected together&#xA;drc-103 Un-loaded net&#xA;drc-105 Un-driven Net&#xA;drc-106 Multiple Output Drivers&#xA;drc-116 Output directly connected to Power or Ground&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that I am not doing circuit simulation.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-23T18:57:04.163" LastActivityDate="2010-12-01T21:33:40.087" Title="Suggested schematic check DRC settings for Tools&gt;Verify in DxDesigner" Tags="&lt;schematics&gt;&lt;dxdesigner&gt;&lt;drc&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="7090" PostTypeId="2" ParentId="4502" CreationDate="2010-11-22T20:40:09.343" Score="3" ViewCount="" Body="&lt;p&gt;If you really want zero clicks, then you want to fade to zero instead of shutting off suddenly, because that is still introducing a step change to the signal.  Or maybe you could shut off on a zero crossing, but I can't think of an obvious circuit to do so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think I would feed the signal into a divider made of a resistor and FET to ground, and put an RC on the gate of the FET so it would switch slowly into conduction.  This will introduce a severe DC bias in the output, so it could be capacitively coupled into the opamp.  If the DC bias is applied and removed slowly, it won't cause a pop.  Remind me and I will sketch the circuit up.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-22T20:40:09.343" CommentCount="2" />
  <row Id="7091" PostTypeId="2" ParentId="7066" CreationDate="2010-11-22T22:49:05.870" Score="2" ViewCount="" Body="&lt;p&gt;I suspect losses due to capacitance would be somewhat more significant than skin effect&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-22T22:49:05.870" CommentCount="1" />
  <row Id="7092" PostTypeId="1" AcceptedAnswerId="7093" CreationDate="2010-11-22T23:07:24.673" Score="2" ViewCount="336" Body="&lt;p&gt;What is meant by the skin effect?&lt;/p&gt;&#xA;" OwnerUserId="1457" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-27T23:03:08.897" LastActivityDate="2011-02-27T23:03:08.897" Title="What is the skin effect?" Tags="&lt;high-frequency&gt;" AnswerCount="4" CommentCount="10" />
  <row Id="7093" PostTypeId="2" ParentId="7092" CreationDate="2010-11-22T23:15:26.867" Score="11" ViewCount="" Body="&lt;p&gt;The skin effect is a usually undesirable effect which occurs when using AC signals. It causes the outer surface - the &quot;skin&quot; of the wire - to be used more than the inner surface for carrying current - engineers say the surface has a higher &quot;current density&quot;, or amperes per meter squared. This causes an increase in the effective resistance of the wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because the outer surface must carry more current the wire is more expensive, because you can't get rid of the inner surface easily. In electrical power distribution, the skin effect is very important, because it decides the type and thickness of the wire you use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Skin depth reduces at higher frequencies. Carrying a 50 Hz signal takes less wire than a 1 kHz signal, for example. Skin depth also varies with the type of wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Skin_effect&quot; rel=&quot;nofollow&quot;&gt;See here for more info&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-25T17:07:43.960" LastActivityDate="2010-11-25T17:07:43.960" CommentCount="2" />
  <row Id="7094" PostTypeId="2" ParentId="7089" CreationDate="2010-11-23T00:14:09.940" Score="4" ViewCount="" Body="&lt;p&gt;I can answer for Altium, and maybe you can translate to DxDesigner.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I pay heavy attention to the group of rules labeled &quot;Electrical&quot;: clearance, short-circuit, un-routed net, and un-connected pin. I also pay attention to minimum trace width, minimum annular ring, minimum hole size, silkscreen over component pads, minimum soldermask sliver, and net antennae.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I totally ignore everything in the groups &quot;Testpoint,&quot; &quot;SMT,&quot; &quot;High Speed,&quot; &quot;Placement,&quot; and &quot;Signal Integrity.&quot; I bet I'll need to worry about those eventually, but they haven't hurt me yet (so far as I am aware).&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-11-23T00:14:09.940" CommentCount="2" />
  <row Id="7095" PostTypeId="1" CreationDate="2010-11-23T02:17:18.847" Score="2" ViewCount="154" Body="&lt;p&gt;I recently obtained an electric typewriter and am trying to intercept the keyboard circuitry for an arduino project. The keyboard has a 17 pin ribbon cable that goes into a plastic connector on the main board. The holes are too small to fit any wires through and my soldering skills are not good enough to attach any wires to the solder points. The holes are a pretty standard spacing, and seem to line up spacing wise with the headers on my arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My thought is I can solder a strip of header onto the board and just set the ribbon connector into the header. That doesn't solve my problem though, because I still can't connect extra wires to it. What I need is some kind of header strip that has an extra row of connectors to tap into the main set, or something like that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone done anything similar to this, or have any tips, or know a part that may help me.&lt;/p&gt;&#xA;" OwnerUserId="1686" LastActivityDate="2010-11-23T11:56:20.223" Title="Intercepting ribbon connector" Tags="&lt;soldering&gt;&lt;connector&gt;&lt;header&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="7096" PostTypeId="2" ParentId="5139" CreationDate="2010-11-23T07:40:09.743" Score="1" ViewCount="" Body="&lt;p&gt;Hatched plane reduce the magnetic field going vertically into the board.&lt;/p&gt;&#xA;" LastActivityDate="2010-11-23T07:40:09.743" />
  <row Id="7097" PostTypeId="1" AcceptedAnswerId="7101" CreationDate="2010-11-23T09:07:44.133" Score="2" ViewCount="223" Body="&lt;p&gt;Creating the Electronic circuits is &lt;code&gt;Ok&lt;/code&gt; not so much complicated for experts. But needs to think about the persistence of the electronic circuits. Its very difficult to make the circuits to work for life time. But its important to have the long run electronic circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course it depends on individual components that we assemble on the PCB. And are there any factors that need to be keep in mind while choosing and assembling the components to have high durability.&lt;/p&gt;&#xA;" OwnerUserId="1731" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T21:02:55.813" LastActivityDate="2011-04-27T21:02:55.813" Title="Things that to be considered while choosing electronic components to get high Durability" Tags="&lt;circuit&gt;&lt;durability&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="7098" PostTypeId="2" ParentId="7097" CreationDate="2010-11-23T09:44:02.453" Score="4" ViewCount="" Body="&lt;p&gt;Run all components well inside their ratings, and avoid high temperatures.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-23T09:44:02.453" />
  <row Id="7099" PostTypeId="2" ParentId="7097" CreationDate="2010-11-23T10:14:37.067" Score="4" ViewCount="" Body="&lt;p&gt;Choose electrolytic capacitors 1.5x - 2.5x required voltage rating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Run components at least 20 degrees C cooler than rated temperature. E.g. for 105C cap, run it at a maximum of 85C. A general rule is for each 10C drop in operating temparature lifespan is doubled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where possible avoid electrolytics where something like ceramics would work - although with careful consideration they can be used, they are generally pretty poor components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Input protection on all inputs - including ESD and overvoltage protection. Ensure your project can survive voltage spikes on the power supply, if necessary.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-23T10:14:37.067" CommentCount="1" />
  <row Id="7100" PostTypeId="2" ParentId="7095" CreationDate="2010-11-23T11:56:20.223" Score="4" ViewCount="" Body="&lt;p&gt;You may use an new IDE connector and attach it on the ribbon cable (I'm supposing they are using the standard size of wires). This way you can create a derivation without damaging the cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/oNpRq.jpg&quot; alt=&quot;Ribbon Cable Connector&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another good practice is to use a buffer for all the pins. I know its a bit costly but otherwise the input impedance could cause interference in the system.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-11-23T11:56:20.223" CommentCount="4" />
  <row Id="7101" PostTypeId="2" ParentId="7097" CreationDate="2010-11-23T13:30:15.447" Score="5" ViewCount="" Body="&lt;p&gt;Don't use anything mechanical if you can avoid it - use solid state (like SSR's instead of mechanical relays, capacitive sensing/force sensing instead of switches, etc).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use protection for every possible contingency - if it gets struck by lightning it needs to keep working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't require any active cooling - fans break or get dirty too easily. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's in any kind of high-vibration environment, don't use connectors.  Solder everything to the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If necessary, use redundant modules.  I believe one of the Voyager probes has five independent computers any three of which are on at a time.  They all work on the same problem and the solution that at least two of them agree on is used.  The computer that created the bad solution is turned off and another is turned on in its place.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have the ability to update any software on the device in the field when you find errors.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-23T13:30:15.447" CommentCount="6" />
  <row Id="7102" PostTypeId="2" ParentId="5139" CreationDate="2010-11-23T13:49:30.477" Score="2" ViewCount="" Body="&lt;p&gt;My understanding was that solid panes could cause bubbling during through-hole wave-solder processes due to outgassing from the laminate, but the slower heat/cool times of SMD reflow probably make this less of an issue -I have certainly seen some (very) old boards with bubbled copper planes. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-23T13:49:30.477" />
  <row Id="7103" PostTypeId="1" AcceptedAnswerId="7104" CreationDate="2010-11-23T14:01:05.540" Score="0" ViewCount="209" Body="&lt;p&gt;I'd like to add some kind of illumination to the buttons on my project. To that end, I was thinking of illuminated pushbuttons, with built in LEDs. However, the ones I found are very big (I'm looking for small microswitches, or at the largest 6mmx6mm tactile switches) and/or they use 120V/240V neon bulbs, not LEDs, and are designed to switch mains.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was also considering getting transparent switches (made of clear plastic of one form or another) and putting LEDs underneath them. The idea is that the project can be used at night so a green or orange colour would probably work well. Does anyone have experience with this, have you done something similar, what types of buttons did you use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something &lt;a href=&quot;http://uk.farnell.com/alps/skhhaka010/switch-tactile-pcb-0-98n/dp/1656423&quot; rel=&quot;nofollow&quot;&gt;like these&lt;/a&gt; but with LEDs in them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please note I'm not looking for specific part numbers - those would be helpful though - but instead ideas on how to accomplish this and types of switches to be looking out for.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-23T16:08:42.687" LastActivityDate="2010-11-24T22:34:40.100" Title="Illuminating buttons" Tags="&lt;led&gt;&lt;button&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="7104" PostTypeId="2" ParentId="7103" CreationDate="2010-11-23T16:54:37.090" Score="5" ViewCount="" Body="&lt;p&gt;Well, I have a idea which may not be the best but you can use it if you don't get those switch. Have you tried using acrylic sheet ?? thats a very good and neat option and you can get the job done with less number of led's &amp;amp; less power consumption.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;as its very easy to work with these sheets and for better illumination around the switch etch the acrylic sheet, Its going to look gr8 :)&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2010-11-23T16:54:37.090" CommentCount="4" />
  <row Id="7105" PostTypeId="2" ParentId="5647" CreationDate="2010-11-23T17:04:53.977" Score="4" ViewCount="" Body="&lt;p&gt;If power consumption isn't an issue (compared to the reed switch), I think I would go with an IR LED and a phototransistor. You could either have it break the beam when it opens or when it's closed and read from the transistor on you digital in pin.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastEditorUserId="2006" LastEditorDisplayName="" LastEditDate="2010-11-23T17:09:57.763" LastActivityDate="2010-11-23T17:09:57.763" />
  <row Id="7106" PostTypeId="2" ParentId="7103" CreationDate="2010-11-23T17:07:18.100" Score="2" ViewCount="" Body="&lt;p&gt;I farnell'd for &quot;LED Tactile Switch&quot; and got this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1000190&amp;amp;Ntk=gensearch_001&amp;amp;Ntt=led+tactile+switch&amp;amp;Ntx=mode+matchallpartial&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1000190&amp;amp;Ntk=gensearch_001&amp;amp;Ntt=led+tactile+switch&amp;amp;Ntx=mode+matchallpartial&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-23T17:07:18.100" CommunityOwnedDate="2010-11-23T17:07:18.100" CommentCount="8" />
  <row Id="7107" PostTypeId="2" ParentId="5647" CreationDate="2010-11-23T18:06:29.950" Score="3" ViewCount="" Body="&lt;p&gt;If you don't mind disassembling the drive you could look into the interlock or drive open switch, which should be fairly easy to wire in to. It may even have a pull-up, providing a logic signal directly to your device of choice.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-23T18:06:29.950" CommentCount="3" />
  <row Id="7108" PostTypeId="2" ParentId="7089" CreationDate="2010-11-23T18:56:34.320" Score="2" ViewCount="" Body="&lt;p&gt;un driven nets, net mismatch, no output, two inputs and so on are DRC errors from the schematic checks.  They can be useful and bring your awarness to certain areas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Trying to fix each one individually can take some effort, but you are on the right track in identifying the issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my 10 years of various cad packages (mentor, altium, cadence/orcad) I have never used the full schematic DRC.  Either I down grade those errors to warnings, or ignore them, depending on the job (for example aviation you cannot ignore them!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most useful schematic DRC's are net name checks (review this often V5+ is not V5 and so on even if you intended it to be so), unconnected nets (force you to place a no connect object), and nets with only one connection.  Reviewing these three I have found to be most useful, as many projects I have been caught out on subtle typos on net names not being connected, are parts that look schematically connected but are not (Altium I am looking at you).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So do review the net name summary from the checker and ensure all is well, and check for unconnected nets!  Not sure how DxDesigner handles netnames, but I have been burnt with Orcad in the past, so always stick to short net names with no spaces or punctuation.  &lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-23T18:56:34.320" />
  <row Id="7109" PostTypeId="1" AcceptedAnswerId="7111" CreationDate="2010-11-23T19:39:41.820" Score="5" ViewCount="211" Body="&lt;p&gt;I have two digital devices to connect, both use 20 data lines but one works at 3.3V and the other at 1.8V, and most of the lines are bidirectional. The operating frequency should be at least 5 MHz. I stumbled upon this solution:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rocketnumbernine.com/2009/04/10/5v-33v-bidirectional-level-converter/&quot; rel=&quot;nofollow&quot;&gt;http://www.rocketnumbernine.com/2009/04/10/5v-33v-bidirectional-level-converter/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which seems adequate (provided I make the corresponding changes for the desired voltage levels) but I don't like the fact that it needs 1 IC and 2 resistors for each data line. Does anyone know about an IC that does a similar job but has many channels (ideally 20 or near that) in a single package, or any equivalent solution to the problem?&lt;/p&gt;&#xA;" OwnerUserId="1078" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-11-24T22:53:18.077" LastActivityDate="2010-11-26T20:49:57.347" Title="Is there a bidirectional level converter IC for multiple I/O channels?" Tags="&lt;signal&gt;&lt;digital&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="7110" PostTypeId="2" ParentId="7003" CreationDate="2010-11-23T19:47:51.603" Score="3" ViewCount="" Body="&lt;p&gt;A &lt;a href=&quot;http://www.t-tech.com/&quot; rel=&quot;nofollow&quot;&gt;Quick Circuit&lt;/a&gt; machine.  It is a CNC machine that removes the copper mechanically and without nasty chemicals.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-11-23T19:47:51.603" CommunityOwnedDate="2011-05-25T02:31:53.593" />
  <row Id="7111" PostTypeId="2" ParentId="7109" CreationDate="2010-11-23T19:52:16.997" Score="7" ViewCount="" Body="&lt;p&gt;Find a voltage-level translation device with this tool at TI:&#xA;&lt;a href=&quot;http://focus.ti.com/logic/docs/translationselection.tsp?sectionId=458&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/logic/docs/translationselection.tsp?sectionId=458&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-24T13:23:45.460" LastActivityDate="2010-11-24T13:23:45.460" CommentCount="1" />
  <row Id="7113" PostTypeId="1" AcceptedAnswerId="7114" CreationDate="2010-11-23T22:17:55.003" Score="15" ViewCount="433" Body="&lt;p&gt;Whenever I turn on my desk lamp, my board crashes. Sometimes I get garbage out of the serial port, sometimes it resets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried adding some extra bypass capacitors on my breadboard, but that made no difference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(My desk lamp uses a 20W, 12V halogen bulb. It has a transformer in the base)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone offer suggestions as to why this might happen and how I can stop it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are two of the boards - they were USB dongles, but are both now powered from a single wall-wart via a 3.3V voltage regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Watching on a scope, when I flick the light switch I see a spike on both 3V3 and wall wart lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/54388270@N04/5185260619/lightbox/&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4128/5185260619_6f731b2d43.jpg&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;b&gt;Edit:&lt;/b&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are traces of the input and output of the 3V3 regulator when turning the light on and off respectively.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/54388270@N04/5203005660/sizes/l/in/photostream/&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://farm6.static.flickr.com/5243/5203005660_fe875771ea_m.jpg&quot;&gt;&lt;/a&gt;&lt;a href=&quot;http://www.flickr.com/photos/54388270@N04/5203003890/sizes/l/in/photostream/&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://farm5.static.flickr.com/4110/5203003890_7a4a748f72_m.jpg&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5V is on the top, 3V3 on the bottom&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The regulator is a &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet/zetexsemiconductors/ZSR.PDF&quot; rel=&quot;nofollow&quot;&gt;ZSR330&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some careful reading of the datasheet threw this up:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The RESET_N pin is sensitive to noise&#xA;  and can cause unintended reset of the&#xA;  chip. For a long reset line add an&#xA;  external RC filter with values 1 nF&#xA;  and 2.7 k&amp;Omega; close to the RESET_N pin.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;My programming cable connects a long wire via a breadboard to the reset pin. I suspect that this was the problem.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-28T23:32:43.817" LastActivityDate="2011-01-28T23:32:43.817" Title="Why does turning on my desk lamp crash my board?" Tags="&lt;line-power&gt;" AnswerCount="6" CommentCount="10" />
  <row Id="7114" PostTypeId="2" ParentId="7113" CreationDate="2010-11-23T22:29:55.047" Score="11" ViewCount="" Body="&lt;p&gt;The transient is getting through the regulated supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try adding an inductor to the power supply positive output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That may suppress the positive-going transient.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastEditorUserId="1481" LastEditorDisplayName="" LastEditDate="2010-11-24T01:07:07.467" LastActivityDate="2010-11-24T01:07:07.467" CommentCount="8" />
  <row Id="7115" PostTypeId="2" ParentId="7113" CreationDate="2010-11-23T22:35:14.833" Score="3" ViewCount="" Body="&lt;p&gt;I had a similar issue with my powerline ethernet network adapters. When communicating they would induce up to 200mVp-p noise on the 3.3V line of my breadboard. It didn't cause any problems, because my MCU was rated from 3V to 3.6V, but it was interfering with my ability to scope the system. I never really sorted out the problem until I moved the adapter to another plug extension. This might have provided sufficient isolation between the power supply I was using (old computer ATX), or it could have been something else.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-23T22:35:14.833" CommentCount="1" />
  <row Id="7116" PostTypeId="2" ParentId="7113" CreationDate="2010-11-23T22:57:03.443" Score="2" ViewCount="" Body="&lt;p&gt;If I was going to power USB dongles directly from a PSU, it would be a 5V one, not a 3V3 one, because USB VBus power is 5V not 3V3.   Not sure if that's the problem, but if they're incredibly marginal on supply voltage, that wouldn't help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But probably your problems are just the kind of craptastic grounding you get on breadboard - your supply rails probably form a vast weak loop, just waiting to have problematic voltages induced on it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't say where your bypass caps were added, nor their value, but you should make sure that you have plenty of capacitance right at the point the supply is used, not the far end of 6&quot; of cable from the load.   You will probably struggle to measure induced spikes sensibly with a scope, because so much will be picked-up on the scope's ground lead, but if you're going to try, then make sure you measure with both the ground-lead and the probe at the load, not somewhere else in the circuit.&lt;/p&gt;&#xA;" OwnerUserId="1844" LastActivityDate="2010-11-23T22:57:03.443" CommentCount="2" />
  <row Id="7117" PostTypeId="1" CreationDate="2010-11-23T22:59:23.753" Score="8" ViewCount="277" Body="&lt;p&gt;As a hobby project I'm building a power line monitor to detect when a load is switched on and turns on some additional loads.  I have &lt;strike&gt;120 V&lt;/strike&gt; 220 V running through my board and was curious what the standard board spacing is for high voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm sure there's some specs by UL or other agencies for this, but I'm cheap.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Edit:&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Correction, the voltage I'm working with is 220 V, powers a cabinet saw.  In any case, is there a general formula, possibly even for higher voltages (e.g. flyback for fluorescent lights)&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-24T01:40:38.340" LastActivityDate="2010-11-24T02:40:17.880" Title="How far apart should PCB traces be for mains isolation?" Tags="&lt;pcb&gt;&lt;power&gt;&lt;high-voltage&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="7118" PostTypeId="2" ParentId="7117" CreationDate="2010-11-23T23:07:22.400" Score="4" ViewCount="" Body="&lt;p&gt;Minimum 2.5mm for standard insulation (across mains), 5mm for reinforced (&quot;double&quot;) insulation (mains to low-voltage) &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-23T23:07:22.400" CommentCount="3" />
  <row Id="7119" PostTypeId="2" ParentId="7113" CreationDate="2010-11-24T00:01:36.437" Score="5" ViewCount="" Body="&lt;p&gt;Is that mains circuit overloaded?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Halogen bulbs draw a large amount of current when they are cold, like 10+ times their normal current draw.  This should only last for a split second, just long enough to heat the filament up to operational temperatures.  Halogen bulbs do run very hot so perhaps this affect last longer / draws more current than your average incandescent, i'm not sure.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would say that current spike is causing some issues on your mains lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Did you scope the input to the 3.3V regulator?&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-11-24T00:01:36.437" CommentCount="9" />
  <row Id="7120" PostTypeId="1" AcceptedAnswerId="7124" CreationDate="2010-11-24T00:05:49.513" Score="1" ViewCount="231" Body="&lt;p&gt;I've found some &lt;a href=&quot;http://uk.farnell.com/yageo-phycomp/rv0805jr-07100kl/resistor-0805-high-voltage-5-100k/dp/1376988&quot; rel=&quot;nofollow&quot;&gt;400V 0805 resistors&lt;/a&gt;. However, as in my previous question, I noted that &lt;a href=&quot;http://electronics.stackexchange.com/questions/6789/why-are-power-supplies-almost-always-made-using-through-hole-components&quot;&gt;almost no power supplies used surface mount components&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the things I'm working on is a capacitive power supply. This is connected to the mains and has no isolation, but operates inside a completely sealed box so there is no hazard to the user there. However, I'm not entirely sure if it's okay to use 0805's when dealing with such high voltages... it just seems like arc-over or something similar would happen. And, say there was a fault - would through hole be better at handling a line transient than SMT?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-04-13T21:56:07.280" LastActivityDate="2011-04-13T21:56:07.280" Title="Is it okay to use SMT for 250VAC parts?" Tags="&lt;surface-mount&gt;&lt;line-power&gt;&lt;powerline&gt;&lt;through-hole&gt;" AnswerCount="4" />
  <row Id="7121" PostTypeId="2" ParentId="7117" CreationDate="2010-11-24T02:40:17.880" Score="1" ViewCount="" Body="&lt;p&gt;Consider looking at footprint of smallest 400-600V capacitor (which is minimum DC for 220V AC, with peak-to-peak 310V, so overrate is extra 33..100%). &#xA;If its pins are 15..20 mm apart (I have not seen less than this), then with traces it makes about 11..17 mm. gap.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-24T02:40:17.880" />
  <row Id="7122" PostTypeId="2" ParentId="7113" CreationDate="2010-11-24T02:48:14.867" Score="3" ViewCount="" Body="&lt;p&gt;I see ground loop and may be you have lots of power, signal loops. effectively you have large area of single turn inductances. This loops work like secondary coils of air transformer (magnet antenna) which reacts to AC magnetic fields. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The midpoints of loops where you have joints are some center-points of this coils and produce variety of signals with very low source impedance and short circuit currents up to milliamperes, which make voltage of noise signals that high.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To fix it, try to rewire all inter-board symmetrically with single &quot;grounding tree&quot; and power, signals coming over twisted pair wires. &lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2010-11-24T02:48:14.867" />
  <row Id="7123" PostTypeId="2" ParentId="7120" CreationDate="2010-11-24T03:09:27.820" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Direct connection of rail to rail&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;250VAC gives you amplitude of 354V (twice that for peak to peak). So at 100Kohms you are looking at a power dissipation of almost 1 watt peak and the resistor is only rated for 0.125W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now since it is actually AC your rms voltage will be about 250V, but even using that number you are still looking at an average power dissipation of .625W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Other Cases&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can see cases where you would be using a resistor like this in a power supply circuit, but it wouldn't be having 250VAC across the pads, instead it would be some other smaller voltage.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-24T15:00:51.023" LastActivityDate="2010-11-24T15:00:51.023" CommentCount="4" />
  <row Id="7124" PostTypeId="2" ParentId="7120" CreationDate="2010-11-24T04:44:34.980" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.google.com/search?aq=f&amp;amp;sourceid=chrome&amp;amp;ie=UTF-8&amp;amp;q=creepage&amp;amp;qscrl=1&quot; rel=&quot;nofollow&quot;&gt;Creepage&lt;/a&gt; is the term you're looking for.  You'll want to use that for trace spacing too.  If the part is rated for 400V it's good for it.  However, you may have more than 400V.  240Vac is actually RMS voltage and has a tolerance.  Add 10% to the line voltage (240*.1= 264Vac) to accommodate its tolerance and remember to design your circuit with the possibility of being supplied 10% less of 240V.  Convert to peak-peak voltage (264x1.414= 373.3) because flash-overs pay little attention to time.  Now, you could fret about aging components, temperature cycling, dust, moisture, bad luck and worse math then decide to add another 10% to the figure (373.3+10%= 410.6Vp-p) &quot;just to be sure.&quot;  That's cutting it close, but if you throw an MOV across the line (behind the fuse, of course) then &lt;em&gt;maybe&lt;/em&gt; that'll be enough to redeem you from omitting that last 10% and keep your house from burning down.  Maybe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Concerning SMT vs. TH transients, the components are rated as they're rated.  400V applies whether you're reading a TH or SMT datasheet.&lt;/p&gt;&#xA;" OwnerUserId="2051" LastActivityDate="2010-11-24T04:44:34.980" CommentCount="2" />
  <row Id="7125" PostTypeId="2" ParentId="7003" CreationDate="2010-11-24T05:07:01.613" Score="1" ViewCount="" Body="&lt;p&gt;Thanks to everyone so far for your answers. I believe I have made a decision concerning future circuit board design. I have been doing some crazy research and ran into a piece of equipment that I believe might be the best route. It is not only eco friendly but useful in many other ways. Props have to go to Brian for triggering the research that led to the epiphany.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead a dealing with chemicals which requires disposal, time, and is not ideal since I live in a condo, I have decided to build a CNC Mill. There are numerous tutorials out there and it appears one can be built for ~$500 (or less if salvaged parts are used). Here are a few links I have found so far.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/How-to-Make-a-Three-Axis-CNC-Machine-Cheaply-and-/&quot; rel=&quot;nofollow&quot;&gt;Instructables&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Engaget &lt;a href=&quot;http://www.engadget.com/2006/06/29/how-to-build-your-own-cnc-machine-part-1/&quot; rel=&quot;nofollow&quot;&gt;(1of3)&lt;/a&gt;, &lt;a href=&quot;http://www.engadget.com/2006/07/04/how-to-build-your-own-cnc-machine-part-2/&quot; rel=&quot;nofollow&quot;&gt;(2of3)&lt;/a&gt;, and &lt;a href=&quot;http://www.engadget.com/2006/07/11/how-to-build-your-own-cnc-machine-part-3/&quot; rel=&quot;nofollow&quot;&gt;(3of3)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The mill would not only serve the purpose of removing the copper but can also be used to build a solder mask. This would enable easier SMD/SMT manufacturing using the skillet reflow method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I plan on doing further research to see if a 'combo' cnc machine can be put together which also takes advantage of the &lt;a href=&quot;http://reprap.org&quot; rel=&quot;nofollow&quot;&gt;RepRap 3D plastic printer&lt;/a&gt;. Imagine the possibilities of this killer combo. You could fabricate almost anything and it should cost under $1000.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="1575" LastEditorDisplayName="" LastEditDate="2010-11-24T06:14:59.953" LastActivityDate="2010-11-24T06:14:59.953" CommunityOwnedDate="2011-05-25T02:31:53.593" CommentCount="4" />
  <row Id="7126" PostTypeId="1" AcceptedAnswerId="7127" CreationDate="2010-11-24T07:06:22.733" Score="1" ViewCount="198" Body="&lt;p&gt;In hobby market (rc planes, cars, robots) one of the parameters manufacturers of the brushless motor ESC specify is resistance. ESC in this case means &quot;electronic speed controller&quot; and is a device used for commutation and speed control of the electric engine.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a standard (written or informal) how this parameter is characterized? If yes how it is done?&lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-11-24T14:48:58.613" LastActivityDate="2010-11-24T14:48:58.613" Title="How is resistance in brushless motor ESC calculated by the manufacturers?" Tags="&lt;esc&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="7127" PostTypeId="2" ParentId="7126" CreationDate="2010-11-24T08:41:55.707" Score="1" ViewCount="" Body="&lt;p&gt;I suspect the resistance is the resistance of the internal power MOSFET(s). In which case it's an utterly pointless measurement as the internal resistance of the battery, the resistance of copper tracks, and the virtual &quot;resistance&quot; created by charging and discharging the MOSFET's gate will easily overwhelm this tiny Rds(on). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to know the effective resistance of your ESC you can perform an experiment. Set up a motor on your ESC. Wire it in for maximum speed (this would probably involve wiring the throttle input to a battery line.) Turn on the motor, making sure nothing is attached to the rotor. Put an ammeter in series - preferably a clamp-on one - current will easily exceed the 10A rating of most series meters - and measure the current going to the motor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, measure the voltage across the battery, and across the motor. You could try measuring the drop across the ESC as well but it wouldn't work if it employs some virtual ground or has a current shunt built in, as this will skew your readings. Calculate the voltage drop across the ESC and put this into Ohm's law: R = V/I. Note this is only an average resistance and depends on the state of the battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For yuks, measure the current from the battery to the ESC and use that to make input-output power figures. The efficiency is the output divided by the input, in percent. This will probably be more useful than any resistance figure.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-24T08:59:23.617" LastActivityDate="2010-11-24T08:59:23.617" CommentCount="3" />
  <row Id="7128" PostTypeId="2" ParentId="7120" CreationDate="2010-11-24T09:57:18.490" Score="2" ViewCount="" Body="&lt;p&gt;In the case of resistors that actually have mains across them, use multiple parts  in series -resistors are cheap. As well as increasing creepage for safety, it improves reliability, as resistors with high voltage across them are prone to failure.&#xA;The main difference between TH and SM is thermal mass, i.e. SM parts tend to have lower surge withstand capability.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-24T09:57:18.490" />
  <row Id="7129" PostTypeId="1" CreationDate="2010-11-24T16:56:16.273" Score="2" ViewCount="455" Body="&lt;p&gt;How to implement delay function in Keil ARM MDK that waits given time in microseconds that can be recompiled to any reasonable clock speed defined in Keil project settings ?  And all of this without using timers. &lt;/p&gt;&#xA;" OwnerUserId="1736" LastActivityDate="2011-05-31T22:03:43.117" Title="How to implement delay functions in Keil ARM MDK" Tags="&lt;arm&gt;&lt;delay&gt;&lt;keil&gt;" AnswerCount="3" CommentCount="7" />
  <row Id="7130" PostTypeId="2" ParentId="7129" CreationDate="2010-11-24T17:38:16.003" Score="1" ViewCount="" Body="&lt;p&gt;You will have to determine the length of a NOP, then using #Defines make it so that based on clock speed it inserts the correct number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically you want to know the exact number of clock cycles it takes to get 1 loop to be completed of the style:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;for(long i=0;i&amp;lt;NUMBER_OF_LOOPS_REQUIRED;i++)&#xA;{&#xA;  __NOP();&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;By making the #define for number of loops required reconfigure itself to be automatic based on the requested delay and the clock speed you are currently running at. This can all be wrapped up in a macro.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-24T17:38:16.003" CommentCount="5" />
  <row Id="7131" PostTypeId="2" ParentId="7129" CreationDate="2010-11-24T17:51:37.880" Score="1" ViewCount="" Body="&lt;pre&gt;&lt;code&gt;#if _Main_Crystal == 25000000&#xA;   #define LOOP_DELAY 400&#xA;#elif  _Main_Crystal == 16000000&#xA;   #define LOOP_DELAY 256&#xA;#else&#xA;   #error microsecond delay must be adjusted!&#xA;#endif&#xA;void usDelay( void )&#xA;{&#xA;   for (int i = 0; i &amp;lt; LOOP_DELAY; i++)&#xA;   {&#xA;      SERVICE_WATCH_DOG();&#xA;   }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;where &lt;code&gt;SERVICE_WATCH_DOG()&lt;/code&gt; is a macro to service the watch dog timer.  This can also be replaced with a &lt;code&gt;NOP&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use a test function to figure out what your LOOP_DELAY constants need to be for each clock frequency:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void TestDelay( void )&#xA;{&#xA;   SetIOPin();    // Use a scope to start measuring elapsed time here.&#xA;   usDelay();&#xA;   ResetIOPin();  // use a scope to end measuring elapsed time here.&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-11-24T17:51:37.880" CommentCount="1" />
  <row Id="7132" PostTypeId="2" ParentId="7120" CreationDate="2010-11-24T18:36:20.557" Score="2" ViewCount="" Body="&lt;p&gt;Bear in mind that even though the part is OK for 400V, you may need a slot in the PCB to ensure that there's sufficient clearance between the pads. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, axial devices beat SMT for transients simply because they have higher power handling capability. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Power supplies often use tons of surface mount components - cheap, made in Asia commodity power supplies often don't use any SM because they're cheap and commodity products.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Power supplies that I've help design have hundreds, if not thousands of SM parts - not in the power train, but in control and monitoring.)&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-11-24T18:36:20.557" />
  <row Id="7133" PostTypeId="1" AcceptedAnswerId="7134" CreationDate="2010-11-24T21:00:16.177" Score="6" ViewCount="295" Body="&lt;p&gt;I've got 4 launchpads (I'm a hog, I know, I got 'em while I could) and I'm getting used to the programming, e.g. the timers, ADC, PWM, LPM, etc. I don't have a lot of money and would like to do some projects to solidify my knowledge. What are some little projects I could do on a budget to have fun? The blinky apps only go so far.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2011-04-12T17:12:14.707" Title="What are some good ideas to practice on the MSP430" Tags="&lt;electronics&gt;&lt;msp430&gt;" AnswerCount="4" FavoriteCount="5" />
  <row Id="7134" PostTypeId="2" ParentId="7133" CreationDate="2010-11-24T21:12:08.367" Score="9" ViewCount="" Body="&lt;p&gt;Here are some of my projects:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.hodgepig.org/tag/launchpad/&quot; rel=&quot;nofollow&quot;&gt;http://blog.hodgepig.org/tag/launchpad/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll also find loads of great ideas over at &lt;a href=&quot;http://www.43oh.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.43oh.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-24T21:12:08.367" CommentCount="7" />
  <row Id="7135" PostTypeId="2" ParentId="7103" CreationDate="2010-11-24T21:36:46.513" Score="2" ViewCount="" Body="&lt;p&gt;Farnell also sells these:&#xA;&lt;a href=&quot;http://www.omron.com/ecb/products/pdf/en-b3w-9.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.omron.com/ecb/products/pdf/en-b3w-9.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2058" LastActivityDate="2010-11-24T21:36:46.513" CommentCount="1" />
  <row Id="7136" PostTypeId="2" ParentId="7103" CreationDate="2010-11-24T22:34:40.100" Score="0" ViewCount="" Body="&lt;p&gt;I don't usually answer my own questions but I think with a few days of internet research I've found the best one I can get. TL1240 comes in a 6mm x 6mm package and has an LED built in. I'll look for alternatives, but so far this is the best, and even better, is almost the same size as my original non-illuminated switches. &lt;a href=&quot;http://gb.mouser.com/ProductDetail/E-Switch/TL1240GQ1JCLR/?qs=sGAEpiMZZMsqIr59i2oRcmmDUi6NoIX9MEv1LMXmH2s%3d&quot; rel=&quot;nofollow&quot;&gt;Mouser stock them&lt;/a&gt; (in the UK) for £1.39 each, which is a pretty good price. Microswitches with LEDs would be good but I think I'd be hoping for too much there!&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-24T22:34:40.100" />
  <row Id="7137" PostTypeId="2" ParentId="7133" CreationDate="2010-11-24T22:41:12.107" Score="6" ViewCount="" Body="&lt;p&gt;Try using the ultra-low power modes of the MSP430's. This is one area where TI apparently rules king, though I haven't dealt with low power MCU's so don't really know. TI has a video &lt;a href=&quot;http://www.youtube.com/watch?v=ZxGZIiyyxrM&quot; rel=&quot;nofollow&quot;&gt;showing them being powered from fruit&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-24T22:41:12.107" CommentCount="1" />
  <row Id="7138" PostTypeId="2" ParentId="3343" CreationDate="2010-11-24T22:52:05.707" Score="1" ViewCount="" Body="&lt;p&gt;Everyone else says great things.  So I'll give you general advice: read read read read read read read read!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Read every article on &lt;a href=&quot;http://embeddedgurus.com&quot; rel=&quot;nofollow&quot;&gt;http://embeddedgurus.com&lt;/a&gt;  If you don't understand something, research it.  If in the explanation of those things you find something you don't understand, read some more.  I'm about to head into an embedded software position and my experience is a handful of professional projects over the past few years and a lot a LOT of reading.  Experience lets you try things, but reading lets you know whether the things you've tried have been done before, maybe better than you could.  It introduces you to concepts that you can work with in any circumstance. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just read!&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-11-24T22:52:05.707" CommunityOwnedDate="2010-11-24T22:52:05.707" />
  <row Id="7139" PostTypeId="1" AcceptedAnswerId="7140" CreationDate="2010-11-24T23:04:16.363" Score="2" ViewCount="223" Body="&lt;p&gt;I'm trying to identify a part I removed from a compact fluorescent lamp manufactured around 9 years ago (date on the PCB is 17.12.01).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a gray hexahedron and it's 7 mm wide, 2 mm long and about 4.5 mm high. Contacts are on the 2 mm sides.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The inscription on it says in the first line 2n2 and in the second line 630.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Judging by the inscription, device seems to be manufactured in a long sheet on which numbers were printed and then cut into 5 mm high segments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At first I thought it could be some sort of capacitor (PCB has capacitor mark on its location), but after some testing, I was unable to charge it and then measure its voltage (on the other hand, it could be that it has very low capacitance so could discharge itself in the time it takes me to switch my multimeter form ohmmeter mode to voltmeter mode). Also, part which is obviously resistor was next to the unknown device and it too had capacitor mark on PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did some research on the Internet, but as far as I can tell, 2n2630 is a transistor and this definitely does not look like a transistor, so I'm looking here for ideas on what it could be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;&#xA;I finally managed to get a nice picture of the part on 1 mm grid. Here it is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/G4JIU.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-11-25T00:09:51.450" LastActivityDate="2010-11-25T16:23:13.607" Title="What is this part: 2n2 630?" Tags="&lt;parts&gt;&lt;device&gt;&lt;identification&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="0" />
  <row Id="7140" PostTypeId="2" ParentId="7139" CreationDate="2010-11-24T23:39:08.490" Score="9" ViewCount="" Body="&lt;p&gt;I'd say its a Capacitor with 2,2nF capacity and voltage up to 630 V. A usual multimeter has 10µA (or more) current flow, which will discharge this low capacity very very quickly - no chance for reading a voltage here.&lt;/p&gt;&#xA;" OwnerUserId="1472" LastActivityDate="2010-11-24T23:39:08.490" CommentCount="1" />
  <row Id="7141" PostTypeId="1" AcceptedAnswerId="7395" CreationDate="2010-11-25T04:59:39.707" Score="3" ViewCount="233" Body="&lt;p&gt;I am looking for suitable display options for a battery-powered device, kind of like an e-book reader/tablet/mid device. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;size - 10&quot; or so.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;resolution - preferably a high DPI&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;colour - mono/gray&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;static - low refresh rate/static is&#xA;fine&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;power - low enough to last 12 hours&#xA;on a ~1000 mAH battery assuming 80%&#xA;static usage.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;Brightness - readable in-doors, mainly. &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I know of the existence of E-ink, Pixel-Qi and even ChLCD displays. I am wondering if there are any other display options available?&lt;/p&gt;&#xA;" OwnerUserId="1938" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-28T21:08:25.413" LastActivityDate="2010-12-01T22:23:08.523" Title="Suitable low-power ~10&quot; graphical display options" Tags="&lt;display&gt;" AnswerCount="2" CommentCount="6" FavoriteCount="4" />
  <row Id="7142" PostTypeId="2" ParentId="7109" CreationDate="2010-11-25T06:18:36.597" Score="1" ViewCount="" Body="&lt;p&gt;this PDF should explain what you need for one &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://wwwasic.kip.uni-heidelberg.de/lhcb/Publications/external/AN97055.pdf&quot; rel=&quot;nofollow&quot;&gt;http://wwwasic.kip.uni-heidelberg.de/lhcb/Publications/external/AN97055.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;as for a single IC i dont know any good candidates, I have seen 6 channel FET arrays &lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2060" LastEditorDisplayName="" LastEditDate="2010-11-25T06:24:55.640" LastActivityDate="2010-11-25T06:24:55.640" CommentCount="1" />
  <row Id="7143" PostTypeId="1" AcceptedAnswerId="7144" CreationDate="2010-11-25T12:20:54.137" Score="6" ViewCount="499" Body="&lt;p&gt;Hello everyone,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking for some material (books/sites) related to embedded system programming in C language. &#xA;Here in the lab we have available three plataforms: one Microchip PIC18f4550, one Freescale HC12 and one ARM (Beagleboard).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are willing to teach embedded C with the PIC, assembler with Freescale and embedded operational systems with Beagleboard.  Each class will be a six month course.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Open to all advices. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks &lt;/p&gt;&#xA;" OwnerUserId="1757" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-25T12:26:39.243" LastActivityDate="2011-01-18T08:53:00.513" Title="Embedded C programming material" Tags="&lt;embedded&gt;&lt;programming&gt;&lt;teaching&gt;" AnswerCount="8" CommentCount="3" FavoriteCount="8" />
  <row Id="7144" PostTypeId="2" ParentId="7143" CreationDate="2010-11-25T12:24:28.613" Score="10" ViewCount="" Body="&lt;p&gt;For C programming - embedded or otherwise, you need K&amp;amp;R.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://cm.bell-labs.com/cm/cs/cbook/&quot; rel=&quot;nofollow&quot;&gt;http://cm.bell-labs.com/cm/cs/cbook/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://cm.bell-labs.com/cm/cs/cbook/covers/main.gif&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have one book on PICs, I like it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://seng.ulster.ac.uk/eme/sidk/quintessential/images/quintessential_2_2.jpg&quot; width=&quot;195&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/185233942X&quot; rel=&quot;nofollow&quot;&gt;http://www.amazon.com/Quintessential-Microcontroller-Computer-Communications-Networks/dp/185233942X&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the BeagleBoard, some background in embedded Linux will be important. Here's a good book written by a good friend:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://images.amazon.com/images/P/059600222X.01.LZZZZZZZ.jpg&quot; width=&quot;195&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://oreilly.com/catalog/9780596529680&quot; rel=&quot;nofollow&quot;&gt;http://oreilly.com/catalog/9780596529680&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-25T16:02:27.917" LastActivityDate="2010-11-25T16:02:27.917" CommentCount="3" />
  <row Id="7145" PostTypeId="2" ParentId="7143" CreationDate="2010-11-25T13:14:45.550" Score="2" ViewCount="" Body="&lt;h2&gt;Books:&lt;/h2&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Beagleboard: &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/1430234822&quot; rel=&quot;nofollow&quot;&gt;Practical Beagleboard&lt;/a&gt;, but the estimated ship date for this item will be only in April 28, 2011&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Y71BE.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/1584503785&quot; rel=&quot;nofollow&quot;&gt;Microprocessors: From Assembly Language to C Using the PICI8FXX2&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0750686111&quot; rel=&quot;nofollow&quot;&gt;Advanced PIC Microcontroller Projects in C: From USB to RTOS with the PIC 18F Series&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I have both books about PIC18, and I recommend them.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-25T16:30:07.607" LastActivityDate="2010-11-25T16:30:07.607" />
  <row Id="7146" PostTypeId="2" ParentId="7139" CreationDate="2010-11-25T16:23:13.607" Score="3" ViewCount="" Body="&lt;p&gt;Like Turbo says it's a 2.2 nF, 630V capacitor. It's an MK* type, where the * designates the dielectricum, this could be an MKM, meaning metal layer (first M), plastic (the K) with polycarbonate dielectricum (the second M).&lt;br&gt;&#xA;Note that the sides are not insulated.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-11-25T16:23:13.607" />
  <row Id="7147" PostTypeId="2" ParentId="7092" CreationDate="2010-11-25T16:31:12.947" Score="4" ViewCount="" Body="&lt;p&gt;The skin effect means that the current of AC signals will be concentrated near the surface, the &quot;skin&quot;, of a conductor. The higher the frequency the thinner this layer. For very high frequencies it's no use to have a massive conductor; the core wouldn't carry current. Hence for HF braided copper wires are used, which have a larger combined surface.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-11-25T16:31:12.947" />
  <row Id="7148" PostTypeId="2" ParentId="7143" CreationDate="2010-11-26T00:06:18.517" Score="3" ViewCount="" Body="&lt;p&gt;An excellent resource for learning Embedded Linux is the following book:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0131679848&quot; rel=&quot;nofollow&quot;&gt;Embedded Linux Primer:A Practical Real-World Approach By Christopher Hallinan&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/jZ3Mf.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It isn't too expensive for students to buy and starts off with the basics and builds on them thereon. An excellent read with lots to learn, with tons of practical examples you can try out on the development boards you mentioned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another source for some excellent everyday encountered Embedded systems dilemmas (to arouse your students curiosity and enthusiasm) can be found under:&lt;br&gt;&#xA;&lt;a href=&quot;http://www.ganssle.com/articles.htm&quot; rel=&quot;nofollow&quot;&gt;Ganssle's Articles&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1785" LastEditorUserId="1785" LastEditorDisplayName="" LastEditDate="2010-11-26T00:42:29.057" LastActivityDate="2010-11-26T00:42:29.057" />
  <row Id="7149" PostTypeId="2" ParentId="7143" CreationDate="2010-11-26T00:46:48.180" Score="2" ViewCount="" Body="&lt;p&gt;What about &lt;a href=&quot;http://www.freertos.org/&quot; rel=&quot;nofollow&quot;&gt;FreeRTOS&lt;/a&gt;, it's very well supported and documented and furthermore should be portable across all of your development boards.&lt;/p&gt;&#xA;" OwnerUserId="820" LastActivityDate="2010-11-26T00:46:48.180" CommentCount="1" />
  <row Id="7150" PostTypeId="1" AcceptedAnswerId="7154" CreationDate="2010-11-26T04:35:11.810" Score="1" ViewCount="128" Body="&lt;p&gt;Fundamental mixers (in the context of RF Electronics). What are they? What do they do?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.hittite.com/products/view.html/view/HMC557LC4&quot; rel=&quot;nofollow&quot;&gt;http://www.hittite.com/products/view.html/view/HMC557LC4&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-26T11:35:39.010" Title="What are fundamental mixers?" Tags="&lt;rf&gt;" AnswerCount="2" />
  <row Id="7151" PostTypeId="2" ParentId="3343" CreationDate="2010-11-26T08:05:59.510" Score="6" ViewCount="" Body="&lt;p&gt;The other answers are great, but the biggest difference between a hobbyist and a professional should be a mindset about quality. So have your project go all the way, don't stop when you are 80% done with a project. Take it all the way, prove that it is working, and document it correctly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure your code is readable and maintainable. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And don't forget to have some fun as well :)&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-11-26T08:05:59.510" CommunityOwnedDate="2010-11-26T08:05:59.510" />
  <row Id="7152" PostTypeId="2" ParentId="3343" CreationDate="2010-11-26T09:37:54.303" Score="5" ViewCount="" Body="&lt;p&gt;Apart from the obvious, like learning C and start with some developer board, you'll want to &lt;strong&gt;learn to read microcontroller datasheets&lt;/strong&gt;.&lt;br&gt;&#xA;Manufacturers add more and more features to microcontrollers, which therefore become more and more complex. The datasheet doesn't only provide electrical characteristics (which is more interesting for the electronical engineer than the software developer), but also detailed description of registers, memory maps, etc.&lt;br&gt;&#xA;On first reading a datasheet may look daunting, but failing to understand them can cause a more severe headache in the debugging phase.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-11-26T09:37:54.303" CommunityOwnedDate="2010-11-26T09:37:54.303" />
  <row Id="7153" PostTypeId="2" ParentId="7150" CreationDate="2010-11-26T09:52:40.560" Score="2" ViewCount="" Body="&lt;p&gt;The particular device you linked to is an RF mixer. It can work as an upconverter or downconverter, depending on the filtering used after the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An RF mixer takes an intermediate frequency signal and a local oscillator signal, and mixes them together. The output from an RF mixer is 4 different frequecies: A, B, A+B, and A-B (or B-A).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By filtering for what frequency you want (either A+B or A-B) you determine if the device is upconverting or downconverting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll admit that I don't fully understand the significance of &quot;fundamental&quot;, but if it's like with crystal oscillators, it means that the device doesn't operate at some harmonic of the local oscillator frequency (&quot;overtone&quot; in crystals.) It simply mixes the two signals exactly as presented to it.&lt;/p&gt;&#xA;" OwnerUserId="965" LastActivityDate="2010-11-26T09:52:40.560" />
  <row Id="7154" PostTypeId="2" ParentId="7150" CreationDate="2010-11-26T10:03:39.857" Score="5" ViewCount="" Body="&lt;p&gt;Fundamental means that the local oscillator is simply the difference between the IF and the input frequency. The other type is termed a sub-harmonic mixer, which is driven at a lower frequency which is multiplied in the mixer. The latter is used at much higher input frequencies, making it easier to generate the local oscillator signal.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-26T11:35:39.010" LastActivityDate="2010-11-26T11:35:39.010" CommentCount="1" />
  <row Id="7155" PostTypeId="2" ParentId="5713" CreationDate="2010-11-26T11:46:07.623" Score="0" ViewCount="" Body="&lt;p&gt;If you really have only 1 pin available the Dallas 1-wire bus looks like the most obvious thing. However, since this is output-only, there are cheaper solutions. A serial PWM bus which carries both data and clock is easy to set up; see for instance &lt;a href=&quot;http://www.romanblack.com/shift1.htm&quot; rel=&quot;nofollow&quot;&gt;Roman Black's page&lt;/a&gt; as also mentioned by davidcary. You only need serial-in parallel-out shift registers like the &lt;a href=&quot;http://www.fairchildsemi.com/ds/74/74VHC164.pdf&quot; rel=&quot;nofollow&quot;&gt;74VHC164&lt;/a&gt;, which you can cascade for as many outputs as you want (one '164 has 8 outputs).&lt;br&gt;&#xA;In this solution LEDs are driven statically.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do have other I/O you can share, like SPI of I2C, you may go for more luxurious solutions, like Maxim's &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/3195&quot; rel=&quot;nofollow&quot;&gt;MAX6950&lt;/a&gt;. The MAX6950 has blinking and brightness control, and slew-rate limiting, to name a few features. LEDs are multiplexed, which means you only need one 16-pin driver.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-11-26T11:46:07.623" />
  <row Id="7156" PostTypeId="1" AcceptedAnswerId="7157" CreationDate="2010-11-26T11:59:00.920" Score="1" ViewCount="115" Body="&lt;p&gt;Does anyone know which acceleration sensor was used in the HTC Touch Diamond mobile phone?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-30T18:48:22.707" LastActivityDate="2010-11-30T18:48:22.707" Title="Acceleration sensor in HTC phone" Tags="&lt;accelerometer&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="7157" PostTypeId="2" ParentId="7156" CreationDate="2010-11-26T13:24:04.867" Score="5" ViewCount="" Body="&lt;p&gt;I think that is the &lt;a href=&quot;http://www.kionix.com/accelerometers/accelerometer-KXSD9.html&quot; rel=&quot;nofollow&quot;&gt;KXSD9&lt;/a&gt; from Kionix&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-11-26T13:24:04.867" CommentCount="5" />
  <row Id="7158" PostTypeId="2" ParentId="7133" CreationDate="2010-11-26T14:32:15.250" Score="2" ViewCount="" Body="&lt;p&gt;You could look at interesting projects on other platforms and try to find neat ways to do them on the 430. Things like PoV, IR remotes/receivers, robots, meters (internal ADC), dataloggers, alarm systems, PIR sensors, rotary encoders, keypads, game controllers, games (that might be pushing it), clocks (put that 32k crystal to good use), fan controller... Perhaps find out if some of them can neatly be done in the interrupt driven bursty fashion to minimize active time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, see what neat parts (chips, displays, rotary encoders, buttons, sensors...) you can find and how to use them on the 430. Use parts with I2C, SPI, PS/2, shift regs etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;New poject ideas I'd love to see:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt; Full blown 430 JTAG and software using the launchpad.&#xA;&lt;li&gt; Other pogrammers. Maybe a 430 Bus Pirate.&#xA;&lt;li&gt; A programmer for the USB SoC on the launchpad so you could use one LP to reprogram another for some other use.&#xA;&lt;li&gt;Full writeup on a data logger.&#xA;&lt;li&gt; SD(HC) card interface.&#xA;&lt;li&gt; MIDI master/slave skeleton/library.&#xA;&lt;li&gt; Interfaces to game controllers, keypads, rotary encoders, pots...&#xA;&lt;li&gt; Join the two above :)&#xA;&lt;li&gt; Adapters for wiring random commonly available controllers to vintage computers/consoles for which compatible controllers are hard to come by today.&#xA;&lt;li&gt; Adjustable PID controller (heater, motor revs, whatever).&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Photograph, write notes and publish everything of course. You're bound to get feedback and more ideas :)&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-11-26T14:32:15.250" />
  <row Id="7159" PostTypeId="1" CreationDate="2010-11-26T14:41:17.193" Score="1" ViewCount="128" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/724/what-are-the-best-beginner-project-using-an-arduino&quot;&gt;What are the best beginner project using an arduino&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;What are some fun but easy projects that I could do on an Arduino Duemilanove? &lt;/p&gt;&#xA;" OwnerUserId="2074" LastActivityDate="2010-11-26T14:41:17.193" ClosedDate="2010-11-26T15:23:10.773" Title="Beginner Arduino Project Suggestions" Tags="&lt;arduino&gt;" CommentCount="1" FavoriteCount="0" />
  <row Id="7160" PostTypeId="1" AcceptedAnswerId="7162" CreationDate="2010-11-26T17:07:58.483" Score="4" ViewCount="278" Body="&lt;p&gt;Specifically, the PIC24 series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried out microchips C30 compiler, but it seems to be a bit too complicated for me, and I couldn't find any libraries with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then I tried CCS, and it seems far too simple, and I cannot view the code for say, I2C_write, which is quite unnerving for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What about Hi-tech C? I did not get a chance to check it out yet, is it in your opinion good or bad?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any other C compilers for pic24 out there? Does not matter if they are free or not, as long as they have some examples.&lt;/p&gt;&#xA;" OwnerUserId="2050" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-11-26T18:58:04.950" LastActivityDate="2010-11-26T23:54:46.643" Title="What PIC24 C compilers are out there, and what is your opinion or review on them?" Tags="&lt;pic&gt;&lt;c&gt;&lt;compiler&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="7161" PostTypeId="2" ParentId="7160" CreationDate="2010-11-26T17:12:56.967" Score="1" ViewCount="" Body="&lt;p&gt;Hitech full version is very good but the free 'lite' version has very poor code density.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-26T17:12:56.967" CommentCount="1" />
  <row Id="7162" PostTypeId="2" ParentId="7160" CreationDate="2010-11-26T17:28:58.587" Score="8" ViewCount="" Body="&lt;p&gt;Microchip's C30 compiler comes with extensive libraries for all the peripherals, and lots of other stuff can be downloaded. I bought the full version but the free version is adequate for most users. All the Microchip code examples use it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most people use C30 for the PIC24 and dsPIC. The other compilers don't have a very good reputation, judging from comments on the Microchip forum.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-26T17:45:57.957" LastActivityDate="2010-11-26T17:45:57.957" CommentCount="5" />
  <row Id="7163" PostTypeId="1" AcceptedAnswerId="7167" CreationDate="2010-11-26T17:47:19.143" Score="6" ViewCount="235" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;what book titles would you recommend to get started with FPGAs and VHDL?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;I noticed that a few of the recommended books date back from 1996. I can imagine that the devices referred to will be seriously outdated, but has VHDL also much evolved since?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-29T15:00:50.337" LastActivityDate="2011-03-21T16:16:26.030" Title="book recommendations on FPGA" Tags="&lt;fpga&gt;&lt;books&gt;&lt;vhdl&gt;" AnswerCount="5" CommentCount="4" FavoriteCount="4" />
  <row Id="7164" PostTypeId="2" ParentId="7163" CreationDate="2010-11-26T18:31:30.217" Score="1" ViewCount="" Body="&lt;p&gt;Rapid Prototyping of Digital Systems by Hamblen, Hall and Furman. It makes a very good introduction to FPGAs (based on Altera hardware and software) and contains lots of interesting projects that can be implemented on a low-cost board available from Altera. I designed a small PCB using a Flex 10K10 FPGA that was suitable for most of the examples in the first edition, including a small 8-bit CPU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought my copy for about £22, brand new, via Amazon. It's very good value.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-27T15:58:23.727" LastActivityDate="2010-11-27T15:58:23.727" CommentCount="2" />
  <row Id="7165" PostTypeId="2" ParentId="7092" CreationDate="2010-11-26T19:05:47.597" Score="3" ViewCount="" Body="&lt;p&gt;At very high AC frequencies, basically RF, all the current goes through the &quot;skin&quot;. In radar systems, we use hollow wave guides instead of solid conductors. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-11-26T19:05:47.597" />
  <row Id="7166" PostTypeId="1" AcceptedAnswerId="7169" CreationDate="2010-11-26T20:06:35.617" Score="3" ViewCount="532" Body="&lt;p&gt;I'd like to make a GPS logger. I've got a GPS from Microsoft Streets and Trips. I read that it communicates at 4800 baud over RS232 at 3.3 or 5v. I've got an MSP430G2231 from the launchpad kit and I'm a bit fuzzy on how to talk RS232 to this thing. I also want to write to an SD card, preferably to a file so I can pull the data off with a computer. The raw NMEA strings are fine,  I can parse those on the computer. The more detail the better. Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-11-26T20:44:21.577" Title="GPS Data logger using MSP430" Tags="&lt;msp430&gt;&lt;rs232&gt;&lt;sd&gt;&lt;gps&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="7167" PostTypeId="2" ParentId="7163" CreationDate="2010-11-26T20:22:36.403" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0120887851&quot; rel=&quot;nofollow&quot;&gt;The Designer's Guide to VHDL, Volume 3, Third Edition&lt;/a&gt; by Ashenden is quite good.  Others I have found useful are &#xA;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0201895730&quot; rel=&quot;nofollow&quot;&gt;VHDL for Programmable Logic&lt;/a&gt; by Skahill and&#xA;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0136507638&quot; rel=&quot;nofollow&quot;&gt;VHDL Made Easy!&lt;/a&gt; by Perrilin.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-11-26T20:22:36.403" CommentCount="1" />
  <row Id="7168" PostTypeId="2" ParentId="7166" CreationDate="2010-11-26T20:24:10.850" Score="3" ViewCount="" Body="&lt;p&gt;I'd choose a different chip, with a UART. A software UART can be implemented on that chip, of course.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-26T20:24:10.850" CommentCount="1" />
  <row Id="7169" PostTypeId="2" ParentId="7166" CreationDate="2010-11-26T20:25:12.817" Score="7" ViewCount="" Body="&lt;p&gt;The MSP430G2231 doesn't have a hardware UART. The best option is to use a timer to clock your bits in and out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a good example of how to do this:&#xA;&lt;a href=&quot;http://www.msp430launchpad.com/2010/08/half-duplex-software-uart-on-launchpad.html&quot; rel=&quot;nofollow&quot;&gt;http://www.msp430launchpad.com/2010/08/half-duplex-software-uart-on-launchpad.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wire your GPS to TX, RX and GND on your Launchpad board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Writing to an SD card is more tricky. SD cards talk a protocol on top of SPI.&#xA;I've written a Bus-Pirate-like SPI explorer for the MSP430 which should get you some of the way there:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.hodgepig.org/2010/09/10/575/&quot; rel=&quot;nofollow&quot;&gt;http://blog.hodgepig.org/2010/09/10/575/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On top of the SPI code you'll also need an SD card driver and a filesystem driver (likely FAT if you want Windows compatability). You could simplify things by writing raw data to the SD card - though this will make it harder to read at the Windows end. Linux could read it with &lt;code&gt;dd&lt;/code&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-26T20:44:21.577" LastActivityDate="2010-11-26T20:44:21.577" CommentCount="4" />
  <row Id="7170" PostTypeId="2" ParentId="7160" CreationDate="2010-11-26T20:28:26.913" Score="2" ViewCount="" Body="&lt;p&gt;MPLAB C30 is a very powerful variant of GCC. I'd recommend you use it because it's what Microchip use for all their code examples and thus gives compatibility. I'm currently using it for my project; but I am not using any libraries apart from standard stuff (e.g. printf.) &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-26T20:28:26.913" CommentCount="2" />
  <row Id="7171" PostTypeId="2" ParentId="7109" CreationDate="2010-11-26T20:49:57.347" Score="0" ViewCount="" Body="&lt;p&gt;best to split your bidirectional signal into a send and receive line and then you can level shift each individual and do what you need to on the other side with them.  Split them using a open collector transistor or open drain mosfet for the transmit side, and use a driver to pass the signal in the opposite direction for the recieve side.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-11-26T20:49:57.347" />
  <row Id="7172" PostTypeId="2" ParentId="6741" CreationDate="2010-11-26T21:08:05.430" Score="5" ViewCount="" Body="&lt;p&gt;first off I assume SetSensorLowspeed is function on the hardware port of your uC, and if so setting it every time your function is called is generally good practice.   The reason for this is that your main code could call another function which changes the speed of the I2C bus for other sensors.  So by including the speed setting with the function means all you ever have to call USSingleshoot and you know it will operate correctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I said generally earlier, as sometimes you may need highly optimised code for speed, and in these instance every clock cycle counts.  In these cases your would maintain the state of the port in the main loop, and the main loop would set the port speed and then call the read/write functions as needed.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastEditorUserId="1397" LastEditorDisplayName="" LastEditDate="2010-12-06T11:08:29.853" LastActivityDate="2010-12-06T11:08:29.853" />
  <row Id="7173" PostTypeId="2" ParentId="7163" CreationDate="2010-11-26T21:50:26.843" Score="3" ViewCount="" Body="&lt;p&gt;To complement these answers -- there is also a lot to be said for also spending some real quality time with the vendor's data sheets and app notes for the FPGA devices, libraries, and tools themselves.  Otherwise you may well miss a beneficial feature or dangerous pitfall of the particular device, library, or tools that you are going to be using, that are often not covered in an introductory textbook.  Also devices and tools tend to evolve faster than textbooks can keep up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See also my old bit on the Art of High Performance FPGA Design&#xA;&lt;a href=&quot;http://www.fpgacpu.org/log/aug02.html#art&quot; rel=&quot;nofollow&quot;&gt;http://www.fpgacpu.org/log/aug02.html#art&lt;/a&gt; .&lt;/p&gt;&#xA;" OwnerUserId="1962" LastActivityDate="2010-11-26T21:50:26.843" />
  <row Id="7174" PostTypeId="1" AcceptedAnswerId="9163" CreationDate="2010-11-26T23:01:38.200" Score="6" ViewCount="145" Body="&lt;p&gt;What determines the speed of rotation of a &lt;a href=&quot;http://en.wikipedia.org/wiki/Homopolar_motor&quot; rel=&quot;nofollow&quot;&gt;homopolar motor&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Homopolar_motor&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/FYsbh.jpg&quot; alt=&quot;homopolar motor&quot; title=&quot;homopolar motor&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1229" LastActivityDate="2011-01-18T08:35:33.197" Title="What determines the speed of a homopolar motor?" Tags="&lt;motor&gt;&lt;speed&gt;" AnswerCount="2" />
  <row Id="7175" PostTypeId="1" AcceptedAnswerId="7196" CreationDate="2010-11-26T23:09:01.563" Score="3" ViewCount="134" Body="&lt;p&gt;Electrolytic capacitors are often rated -40°C to +105°C. I've always wondered about the extra 5°C. This also seems to be the temperature range for some types of microcontrollers, and is marketed as an &quot;extended temperature range&quot;, although in reality extended usually goes to +125°C. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any particular reason for this temperature - was it chosen to be 5.0161°C above the boiling point of water at 1 atm (99.9839°C or 100°C), or is there another reason?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Curiosity question - not going to be running any components at 105°C any time soon!&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-27T16:12:22.727" Title="Is there any reasoning behind making capacitors go to 105°C?" Tags="&lt;capacitor&gt;&lt;temperature&gt;" AnswerCount="2" />
  <row Id="7176" PostTypeId="2" ParentId="7175" CreationDate="2010-11-26T23:46:20.897" Score="1" ViewCount="" Body="&lt;p&gt;It probably originates from the temperature that it's practical to make them work reliably due to the fluids used.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-26T23:46:20.897" />
  <row Id="7177" PostTypeId="2" ParentId="7174" CreationDate="2010-11-26T23:48:57.040" Score="3" ViewCount="" Body="&lt;p&gt;Running speed is the speed at which the input energy equals losses due to friction (contact and air resistance) and any instability due to poor balancing. Sort of like terminal velocity of a falling object&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-26T23:48:57.040" CommentCount="1" />
  <row Id="7178" PostTypeId="2" ParentId="7160" CreationDate="2010-11-26T23:54:46.643" Score="1" ViewCount="" Body="&lt;p&gt;C30 is OK but has a major downside in that (unless they've fixed this recently) the linker is so dumb it can't be told to eliminate ( or even identify) unused code sections. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason that this is an issue is Microchip provide lots of nice source libraries for networking, graphics, USB etc, and as these are general-purpose, they will inevitably contain features that any particular user won't use, yet they get included anyway, wasting space. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's hardly rocket science  I can't believe anyone has the nerve to charge for a compiler without such a fundamental optimisation - pathetic.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-26T23:54:46.643" />
  <row Id="7179" PostTypeId="1" AcceptedAnswerId="7180" CreationDate="2010-11-26T23:56:46.577" Score="8" ViewCount="235" Body="&lt;p&gt;I've heard that leaving a pin floating on an MCU when configured as an input (vs. the default output) is bad for the pin, and can eventually cause it to fail prematurely. Is this true? N.B. in my instance the pin is floating somewhere between 0.3V and 1.3V due to an incoming video signal. This sometimes falls in the no man's zone of 0.8V - 2.0V when operating from 3.3V.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-27T00:14:32.880" LastActivityDate="2010-11-27T10:18:41.987" Title="Is it really a bad idea to leave an MCU input pin floating?" Tags="&lt;microcontroller&gt;&lt;pin&gt;" AnswerCount="4" CommentCount="4" />
  <row Id="7180" PostTypeId="2" ParentId="7179" CreationDate="2010-11-27T01:49:55.637" Score="5" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Problem:&lt;/strong&gt;&lt;br&gt;&#xA;Leaving a pin configured as an input floating is dangerous simply because you cannot be sure of the state of the pin. Like you mentioned, because of your circuit, your pin was sometimes LOW or sometimes in no-man's land or could sometimes go to HIGH.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Result:&lt;/strong&gt;&lt;br&gt;&#xA;Essentially, the floating input WILL definitely cause erratic chip operation or unpredictable behaviour. I have noticed some chips froze by simply moving my hand closer to the board (I wasn't wearing a ESD wrist band) or some would have different startup behaviour each time the board would powerup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Why:&lt;/strong&gt;&lt;br&gt;&#xA;This happens simply because if there is external noise on that pin, the pin would oscillate, which would drain power as CMOS logic gates drain power when they switch states.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Solution:&lt;/strong&gt;&lt;br&gt;&#xA;Most micros nowdays have internal pullups as well, so that could prevent this behaviour from occuring.&#xA;Another option would be to configure the pin as an output so it does not affect the internals.&lt;/p&gt;&#xA;" OwnerUserId="1785" LastEditorUserId="1785" LastEditorDisplayName="" LastEditDate="2010-11-27T02:14:13.463" LastActivityDate="2010-11-27T02:14:13.463" CommentCount="4" />
  <row Id="7181" PostTypeId="2" ParentId="7179" CreationDate="2010-11-27T01:51:05.917" Score="2" ViewCount="" Body="&lt;p&gt;The input will toggle between 0 and 1 based on any EMI.  I'm not sure if it will cause the input to fail, but it will cause more power to be used because the transitions from 0 to 1 to 0.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Set it to an output and be done with it.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-11-27T01:51:05.917" CommentCount="3" />
  <row Id="7182" PostTypeId="1" AcceptedAnswerId="7767" CreationDate="2010-11-27T02:11:52.137" Score="6" ViewCount="182" Body="&lt;p&gt;I'm looking for a good set of beginner hardware and / or Python libraries (mostly the hardware for now). Do you have any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="1442" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-09T08:15:36.620" LastActivityDate="2011-02-09T08:15:36.620" Title="Robotics for a Python programmer - where to start?" Tags="&lt;python&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="7183" PostTypeId="2" ParentId="7179" CreationDate="2010-11-27T03:11:40.327" Score="4" ViewCount="" Body="&lt;p&gt;It's a little worse than just being in an unknown state, or toggling needlessly. Digital circuits nowadays are mostly of CMOS type, with transistors switching both high and low sides; when we have clear 1s and 0s, they are either off or saturated, the two most efficient states for the transistors to be in. In between, however, is a region of linear operation; it's used for analog amplifiers, but it is not as efficient as the extremes - meaning more power is wasted as heat in the transistor. In the worst case, both the high and low side transistors leak thus (because the pin is in fact neither high nor low), and they can then combine to cause a notable current within the chip as they try to drive the internal state both high and low - possibly doing the same to the next gate in a chain reaction. The heat could become a problem even if the power isn't. IntelliChick's solutions still apply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For pins also connected to ADCs, some microcontrollers offer the function to disable the digital input buffer, to prevent both this problem and leakage distorting the signal.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-11-27T03:11:40.327" CommentCount="3" />
  <row Id="7184" PostTypeId="1" AcceptedAnswerId="7203" CreationDate="2010-11-27T04:05:32.513" Score="7" ViewCount="272" Body="&lt;p&gt;I'm at a standstill on ideas for what to get him and would really, really appreciate any recommendations you guys can provide! (Also, he frequents this site but promised to not read this.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far, I got him an MSP430 (LaunchPad) dev kit. I'm also getting him a box of random components from Mouser or Element14 with things that he could use. What can I get for him to go with the LaunchPad kit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any ARM development books that you guys could recommend? He constantly links me to ARM dev boards that he wants (one with an LCD, ethernet, USB, good MCU; pref ARM9, Cortex-M3). Any suggestions on what dev board I could get him?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was also thinking of getting him a subscription to Nuts and Volts magazine. What other electronics hobbyist magazines are there?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For further information, he also was really interested in high voltage stuff (microwave transformers, spark gaps, etc.) and has recently acquired a nonfunctional (ancient) ham radio, bass amp, several broken TVs (that he has repaired/is repairing).. And he has a logic sniffer, oscilloscope, function generator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks! :)&lt;/p&gt;&#xA;" OwnerUserId="2077" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-04T00:26:32.133" LastActivityDate="2011-02-04T00:26:32.133" Title="Suggestions on what to get my boyfriend for Christmas? (interested in PIC24, MSP430, Propeller, FPGA, ARM, etc..)" Tags="&lt;arm&gt;&lt;msp430&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="7185" PostTypeId="2" ParentId="7182" CreationDate="2010-11-27T04:08:02.463" Score="2" ViewCount="" Body="&lt;p&gt;I don't know if there are specific libraries for robotics, but I do have an example where python is communicating over serial via FTDI to an Arduino to spin a servo. You can check it out &lt;a href=&quot;http://appdelegateinc.com/blog/2010/10/06/rfid-auth-using-arduino-and-python/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-11-27T04:08:02.463" CommentCount="1" />
  <row Id="7186" PostTypeId="1" AcceptedAnswerId="7188" CreationDate="2010-11-27T05:00:48.643" Score="5" ViewCount="185" Body="&lt;p&gt;For software hackers/developers there are many. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I need a hardware guy (or girl?) for a relatively small project. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a site where I can search for people and see ranks, recommendation, etc.?&lt;/p&gt;&#xA;" OwnerUserId="2078" LastActivityDate="2010-11-28T19:02:36.237" Title="Any reliable site where *hardware* engineers can be hired for small (work-from-home/telecommute) projects?" Tags="&lt;hardware&gt;&lt;electrical-engineering&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="2" />
  <row Id="7187" PostTypeId="1" AcceptedAnswerId="7291" CreationDate="2010-11-27T05:24:01.183" Score="3" ViewCount="302" Body="&lt;p&gt;I am trying to utilize an ATMEGA2560 and it's interrupt.  I have some code that must execute until a button is pressed at which time I need the code to stop and wait for another button press to continue.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is anyone familiar with this type of circuit and the interrupts?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is what I am currently referencing for the &lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=printview&amp;amp;t=67358&amp;amp;start=0&quot; rel=&quot;nofollow&quot;&gt;ATMEGA2560 interrupts&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1413" LastEditorUserId="1413" LastEditorDisplayName="" LastEditDate="2010-11-29T16:31:31.073" LastActivityDate="2010-11-29T16:48:58.957" Title="Does anyone have any examples or suggestions utilizing Atmel's ATMEGA2560 and external interrupt's?" Tags="&lt;atmega&gt;&lt;atmel&gt;&lt;interrupts&gt;&lt;interrupt&gt;&lt;atmega2560&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="4" />
  <row Id="7188" PostTypeId="2" ParentId="7186" CreationDate="2010-11-27T05:42:04.873" Score="6" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.elance.com&quot; rel=&quot;nofollow&quot;&gt;Elance.com&lt;/a&gt; and &lt;a href=&quot;http://www.ifreelance.com&quot; rel=&quot;nofollow&quot;&gt;iFreelance.com&lt;/a&gt; both have listings for hardware engineers.  Elance is far larger, and currently has over 8500 providers listed under Electrical Engineering.  I am listed under both and have gotten work through them in the past.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another one suggested by a comment below is &lt;a href=&quot;http://www.freelancer.com&quot; rel=&quot;nofollow&quot;&gt;freelancer.com&lt;/a&gt;, formerly known as getafreelancer.com.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-11-28T19:02:36.237" LastActivityDate="2010-11-28T19:02:36.237" CommentCount="4" />
  <row Id="7189" PostTypeId="2" ParentId="7184" CreationDate="2010-11-27T08:39:57.677" Score="2" ViewCount="" Body="&lt;p&gt;Will you marry me? Your BF is a lucky one :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would focus more on ARM / FPGA, these PICs and Propellers should be nothing really new to what he know/have already.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you ask dev board suggestion, you need to specify price limit ;-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-11-27T08:39:57.677" />
  <row Id="7190" PostTypeId="1" AcceptedAnswerId="7215" CreationDate="2010-11-27T10:07:46.273" Score="0" ViewCount="141" Body="&lt;p&gt;Can I connect a DC motor directly to an Arduino??&lt;/p&gt;&#xA;" OwnerUserId="2074" LastActivityDate="2010-11-27T22:27:09.177" Title="Arduino motor control" Tags="&lt;arduino&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="7191" PostTypeId="2" ParentId="7179" CreationDate="2010-11-27T10:18:41.987" Score="2" ViewCount="" Body="&lt;p&gt;In practice the main effect is increased power consumption. If a pin is actually floating as opposed to connected to some indeterminate voltage source, it is possible for oscillation to occur, which as well as increasing power draw may introduce noise into other parts  of the system. &#xA;Any pin which has the ability to be used for an ADC or comparator input will have the facility to disconnect the digital input buffer to avoid this problem. (DIDR on AVR, ADCON1/ANSEL on PIC)&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-27T10:18:41.987" CommentCount="1" />
  <row Id="7192" PostTypeId="2" ParentId="7163" CreationDate="2010-11-27T10:41:38.257" Score="1" ViewCount="" Body="&lt;p&gt;When learning any sort of HDL (Verilog, VHDL...) it is important to keep one thing in mind. It is not software programming and things work in parallel. That being said, I find that the best way to learn any HDL is to learn how to think in hardware and describe the hardware (that's why it is called a hardware description language).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far, I have rarely seen books that show you how your HDL gets translated into hardware. I've read through one when I was at Synopsys (pages filled with code and schematics) but it was an internal publication. However, even lacking this book, you can still see how your code gets turned into hardware by running it through synthesis on free-software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason that I wish to stress this is because there are many ways to solve a problem. You will only be able to write code that solves it efficiently, from a gate count and timing stand point, if you understand how it gets translated into underlying hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2010-11-27T10:41:38.257" />
  <row Id="7193" PostTypeId="2" ParentId="7184" CreationDate="2010-11-27T10:47:06.333" Score="3" ViewCount="" Body="&lt;p&gt;My ex once got me a subscription to &lt;a href=&quot;http://www.circellar.com/&quot; rel=&quot;nofollow&quot;&gt;Circuit Cellar&lt;/a&gt; and I think that it is far better than any gift of a development board. I ended up renewing the subscription on my own for a few years. So, I would recommend that you get him a subscription to what electronics magazine he particularly likes.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2010-11-27T10:47:06.333" />
  <row Id="7194" PostTypeId="2" ParentId="7190" CreationDate="2010-11-27T11:09:37.463" Score="2" ViewCount="" Body="&lt;p&gt;You will need some extra components:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.tigoe.net/pcomp/labs/lab-motors.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.tigoe.net/pcomp/labs/lab-motors.shtml&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flickr.com/photos/irisphotos/5090745217/&quot; rel=&quot;nofollow&quot;&gt;http://www.flickr.com/photos/irisphotos/5090745217/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2054" LastActivityDate="2010-11-27T11:09:37.463" />
  <row Id="7196" PostTypeId="2" ParentId="7175" CreationDate="2010-11-27T11:59:42.937" Score="3" ViewCount="" Body="&lt;p&gt;I can't say for certain how it started, but it's right in between the two MIL-PRF temperature ratings (85C and 125C, see &lt;a href=&quot;http://www.dscc.dla.mil/Downloads/MilSpec/Docs/MIL-PRF-39018/prf39018.pdf&quot; rel=&quot;nofollow&quot;&gt;MIL-PRF-39018&lt;/a&gt;, section 6.1 ). As a standard rule, aluminum electrolytics double their lifespan for each 10C drop in operating temperature, so it may be a convenient middle ground used for industrial and high performance consumer products.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect Mike's correct in stating that the electrolyte chemistry has something to do with it and I would guess that improvements over time have made it more economical to produce 105C rated capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For further reading I'd suggest &lt;a href=&quot;http://electrochem.cwru.edu/encycl/misc/c04-appguide.pdf&quot; rel=&quot;nofollow&quot;&gt;Cornell Dubilier's excellent application guide for electrolytic capacitors&lt;/a&gt;. They mention a connection between maximum rated temperature and total capacitance that implies that lower rated capacitors will likely be smaller than their higher rated counterparts. Extending the low end of the temperature range is possible but with a rapidly rising ESR.&lt;/p&gt;&#xA;" OwnerUserId="2081" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-11-27T16:12:22.727" LastActivityDate="2010-11-27T16:12:22.727" CommentCount="2" />
  <row Id="7197" PostTypeId="1" CreationDate="2010-11-27T13:29:11.880" Score="1" ViewCount="362" Body="&lt;p&gt;I am an Arduino beginner and want to build a obstacle detection system. I've IR Leds and TSOP receivers(38kHz). How can I modulate the LED to &lt;em&gt;blink&lt;/em&gt; at 38kHz? Could you please help me out with some code!&lt;/p&gt;&#xA;" OwnerUserId="2074" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-27T16:28:35.727" LastActivityDate="2010-11-27T16:28:35.727" Title="IR Led Modulation with Arduino" Tags="&lt;arduino&gt;&lt;ir-modulation&gt;" AnswerCount="2" />
  <row Id="7198" PostTypeId="1" AcceptedAnswerId="7202" CreationDate="2010-11-27T13:58:08.527" Score="2" ViewCount="143" Body="&lt;p&gt;I just read on the description of a &lt;a href=&quot;http://www.youtube.com/watch?v=pgqmJyFpWDM&quot; rel=&quot;nofollow&quot;&gt;YouTube vid&lt;/a&gt; that Parrot AR Drone creates its own wifi hotspot. How does it do that? Is it possible to do a similar thing for a UAV project I've been thinking about?&lt;/p&gt;&#xA;" OwnerUserId="2074" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-11-28T13:35:36.873" LastActivityDate="2010-11-28T13:35:36.873" Title="How do I add a wireless hotspot to my project?" Tags="&lt;wifi&gt;" AnswerCount="3" />
  <row Id="7199" PostTypeId="2" ParentId="7197" CreationDate="2010-11-27T14:09:32.953" Score="1" ViewCount="" Body="&lt;p&gt;Since you're mentioning Vishay's TSOP I guess the 38Hz should be 38kHz.&lt;br&gt;&#xA;I don't know the Arduino platform, but the usual way to do this is set up a timer to interrupt at 76kHz (twice the frequency you want) and toggle the LED output on every interrupt as long as a &quot;send&quot; flag is set.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit&lt;br&gt;&#xA;Be sure to shield the receiver from HF fluorescent lamps; they are often controlled at +/-40kHz, which a 38kHz receiver may easily pick up. If your robot is too far from obstacles to receive the LED's reflected signal, the receiver's AGC may lock upon the lamp's &quot;signal&quot;.&lt;br&gt;&#xA;Don't worry if you can't have a heartbeat interrupt exactly every 13.16us. A small deviation may even be a good idea because the receiver's sensitivity is lower the farther from the center frequency. This means that you won't reacting to signals reflected from meters away, which commercial IR remotes tend to do. Of course you can always reduce the LED current to the same effect.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-11-27T14:47:22.187" LastActivityDate="2010-11-27T14:47:22.187" CommentCount="6" />
  <row Id="7200" PostTypeId="2" ParentId="7197" CreationDate="2010-11-27T15:34:50.837" Score="1" ViewCount="" Body="&lt;p&gt;Some of the newer PICs, such as the 16F1826, have a digital modulator hardware module that makes that sort of thing quite trivial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/search?ie=UTF-8&amp;amp;oe=UTF-8&amp;amp;q=IR+modulation&amp;amp;btnG=search&amp;amp;domains=http%3A%2F%2Fwww.arduino.cc&amp;amp;sitesearch=http%3A%2F%2Fwww.arduino.cc%2Fcgi-bin%2Fyabb2%2F&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; are lots of hits I obtained on the Arduino forum when I searched on IR modulation. You should find some code amongst those. It's also the best place to get Arduino-related questions answered.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-27T15:48:10.353" LastActivityDate="2010-11-27T15:48:10.353" />
  <row Id="7201" PostTypeId="2" ParentId="7190" CreationDate="2010-11-27T15:51:27.963" Score="2" ViewCount="" Body="&lt;p&gt;The easiest way to interface motors to the Arduino is to use an appropriate shield, like &lt;a href=&quot;http://www.ladyada.net/make/mshield/&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-27T15:51:27.963" />
  <row Id="7202" PostTypeId="2" ParentId="7198" CreationDate="2010-11-27T16:05:11.603" Score="4" ViewCount="" Body="&lt;p&gt;It has hardware inside that allows it to act just like a wireless router.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you wanted to add a wifi hot spot to the UAV project you would effectively need to add a wireless router inside your device. If you had a PC connect you could them give it special drives so what it sends over wifi is what your device needs to be controlled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To keep it simple, this will not be an easy task.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Simpler methods&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rovingnetworks.com/&quot; rel=&quot;nofollow&quot;&gt;Roving Networks&lt;/a&gt; has some great solutions if you have a connection point. Your microcontoller interfaces through serial and it can act as a bluetooth hotspot. They also have modules that connect to wifi and then you can connect through sockets. This is relatively easy to do with C or java, as they have examples. The microcontroller will still just pipe serial data.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Past Experience with Roving Networks&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;In my senior design project we used a roving networks bluetooth module to get a bluetooth signal from a sensor connected to the OBD-1 Connector on a car. We placed the device underneath the dash and with a dongle from 40 feet (no line of sight as it was under the dash) still had a signal without a problem. This allowed easy debugging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you pick bluetooth the class determines the maximum range, you can get a class one radiator and they can actually use what could be licensed as class three. They just paid the licensing fee to go higher, but chose not to. The roving networks module actually used the maximum power of a class one bluetooth device and coupled that with good receiver sensitivity. The range was very well done.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-28T02:05:15.177" LastActivityDate="2010-11-28T02:05:15.177" CommentCount="2" />
  <row Id="7203" PostTypeId="2" ParentId="7184" CreationDate="2010-11-27T16:17:12.703" Score="7" ViewCount="" Body="&lt;p&gt;The Launchpad is much, much cheaper than pretty much any other development kit you'll find.   Many dev kits are several hundred dollars - How much are you willing to spend?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my opinion, a dev kit should:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Not be much more expensive than the components which were used to manufacture it. Some manufacturers put significant markup on their kits, imagining that they have their buyers locked in.  They don't.  If a kit is ridiculously priced, I buy a different one.&lt;/li&gt;&#xA;&lt;li&gt;Not lock you into a toolchain, and really should have an open-source and free toolchain available. The Launchpad does miss this point, but if he's interested in PICs and MSP430s, he'll have MPLAB installed already. For some tools, you won't find  this option anywhere.&lt;/li&gt;&#xA;&lt;li&gt;Have some on-board peripherals and connectors, but should also make all of the microcontroller pins available with jumper or solder blob options, preferably through breadboard-friendly .1&quot; pitch connectors.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Luminary Micro (aka TI/Stellaris) makes some &lt;a href=&quot;http://www.luminarymicro.com/products/evaluation_kits.html/&quot; rel=&quot;nofollow&quot;&gt;evaluation kits&lt;/a&gt; which fit that bill today.  I have the LM3S6965, which satisfies each of my above criteria, and has the components you specified: LCD, Ethernet, USB, and Cortex-M3.  If you're reading this next Christmas, you'll have to re-evaluate the options.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your search for an assortment of components, you should consider three things:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What he already has. I can't help you on this one.&lt;/li&gt;&#xA;&lt;li&gt;What is in assortments that are available from places like &lt;a href=&quot;http://www.sparkfun.com/products/10003&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt; and &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;products_id=68&amp;amp;zenid=5b42ec2686fef0cc04191384d106a71d&quot; rel=&quot;nofollow&quot;&gt;Adafruit&lt;/a&gt; (and &lt;a href=&quot;http://www.elexp.com/pro_bppk.htm&quot; rel=&quot;nofollow&quot;&gt;elexp&lt;/a&gt;).  Sometimes, one of these will fit the bill and have a quantity discount.  Other times, these will have a selection markup, and be more expensive than buying individually from a major distributor.&lt;/li&gt;&#xA;&lt;li&gt;What he needs for his specific discipline. There are related questions about &lt;a href=&quot;http://electronics.stackexchange.com/questions/3382/what-equipment-for-electronics-should-i-always-have-on-hand&quot;&gt;Equipment&lt;/a&gt;, &lt;a href=&quot;http://electronics.stackexchange.com/questions/3501/what-is-a-general-set-of-components-for-a-robotics-hacker&quot;&gt;Robotics&lt;/a&gt;, &lt;a href=&quot;http://electronics.stackexchange.com/questions/966/which-electronics-components-should-i-always-have-on-hand&quot;&gt;Components in general&lt;/a&gt;, and &lt;a href=&quot;http://electronics.stackexchange.com/questions/2320/what-are-the-best-useful-variety-ics-to-have-around-for-pic-microcontrollers&quot;&gt;ICs to Interface with Microcontrollers&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;That should get you started on a component search.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for hobbyist magazines, I'd strongly recommend &lt;a href=&quot;http://www.circellar.com/&quot; rel=&quot;nofollow&quot;&gt;Circuit Cellar&lt;/a&gt;.  It's a good deal more advanced than &lt;a href=&quot;http://www.nutsvolts.com/&quot; rel=&quot;nofollow&quot;&gt;Nuts and Volts&lt;/a&gt;, but shouldn't be over his head if he's already looking into ARM processors and high-voltage stuff.  In fact, Nuts and Volts might be too simple at times, but Circuit Cellar will never be too basic.  The goal is always to improve, right?  &lt;a href=&quot;http://ask.slashdot.org/comments.pl?sid=1687116&amp;amp;cid=32583780&quot; rel=&quot;nofollow&quot;&gt;Jerrry [sic] from Slashdot&lt;/a&gt; posted a good overview of the magazine options a while back  that I just found when trying to remember how to spell &lt;a href=&quot;http://www.elektor.com/&quot; rel=&quot;nofollow&quot;&gt;Elektor&lt;/a&gt;, another option to consider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But before you buy anything, consider what you want it to mean to him.  If you buy him components, they'll go in the parts cabinet and be put into projects over time, and your impact will probably be forgotten. For an example outside of the electronics realm, would you rather he buy you socks or a pretty scarf?  Socks are more basic to your hobby of keeping warm, but when you wear the scarf you'll think of him, and when you wear the socks you won't.  With that motivation, ignoring the technical evaluations of dev kits, components, and magazines, I recommend that you look for something that could cause him to think of you.  A subscription to a magazine would be good (for 30 seconds a month, then, if he's like me, he'd be distracted by the articles...), but a tool might be better.  You didn't mention that he had a bench power supply or multimeter - These would be tools that would last a long time, wouldn't become obsolete, and would be used every time he sat down at his bench. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry for the long answer - I've been thinking about what to put on a wish list for Christmas for my girlfriend. &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-11-27T16:17:12.703" />
  <row Id="7204" PostTypeId="2" ParentId="7187" CreationDate="2010-11-27T16:59:48.830" Score="2" ViewCount="" Body="&lt;p&gt;Plenty of people are familiar with it, yes, as it's no different than any other AVR. The details depend on which compiler and library you use, and you should check their documentation, as well as the datasheet. AVRfreaks, which you linked to yourself, has lots more on the subject and is probably a better place to ask if you get stuck (rather than just never started to read up...). For instance, &lt;a href=&quot;http://www.nongnu.org/avr-libc/user-manual/group__avr__interrupts.html&quot; rel=&quot;nofollow&quot;&gt;avr-libc&lt;/a&gt; is used with GCC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a sidenote, the situation you describe doesn't make apparent why you'd need interrupts. It's typically easier to just poll the button.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-11-27T16:59:48.830" CommentCount="4" />
  <row Id="7205" PostTypeId="2" ParentId="4792" CreationDate="2010-11-27T17:32:27.927" Score="2" ViewCount="" Body="&lt;p&gt;The major thing missing in your list is on-chip peripherals, like (peripherals you may or may not find on certain NXP Cortex-M3 controllers) &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;General purpose timers (how many?)&lt;br&gt;&#xA;  External interrupts (how many?)&lt;br&gt;&#xA;  Real Time Clock&lt;br&gt;&#xA;  Watchdog timer&lt;br&gt;&#xA;  (Motor) PWM (how many?)&lt;br&gt;&#xA;  UARTs (how many?)&lt;br&gt;&#xA;  I2C interfaces (how many?)&lt;br&gt;&#xA;  CAN interfaces (how many?)&lt;br&gt;&#xA;  SPI interfaces (how many?)&lt;br&gt;&#xA;  USB interfaces (how many?, speed?, on-the-go?)&lt;br&gt;&#xA;  LCD controller&lt;br&gt;&#xA;  Ethernet&lt;br&gt;&#xA;  ADC channels (how many?, how many bits?)&lt;br&gt;&#xA;  DAC channels (how many?, how many bits?)  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So there's a lot more to a microcontroller than a memory map and I/Os. BTW, even general purpose I/O needs specifying: some may have high current drivers, others may have interrupt capabilities.&lt;br&gt;&#xA;Each of these has to be described in a programming model; which registers control the interface and at which addresses can they be accessed. What happens if you read from the register? (Contrary to what you're used to with common storage, reading a register may modify bits in other registers.)&lt;br&gt;&#xA;All this are reasons why the NXP LPC1759 has a 73-page datasheet, complemented by a 840-page user manual (which describes the family's common features).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you take all features into account, not all vendors make the same thing, even controllers built around the same core (like ARM Cortex) show great differences between manufacturers. One thing they try to make themselves stand out with is the choice of on-chip peripherals. Except for the smallest ones almost all microcontrollers have a couple of UARTs. Seems some users need more of them, so certain manufacturers provide up to 8 UARTs (last I heard).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If engineers use less Atmel AVRs in projects (I don't know if that's true), it may have to do with more than just the product's specs. A few things which come to mind:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;price,&lt;br&gt;&#xA;  supplier's support (does he have an FAE specialized in the product?),&lt;br&gt;&#xA;  available toolchain(s),&lt;br&gt;&#xA;  product lead times,&lt;br&gt;&#xA;  number of engineering changes (how stable is the product?),&lt;br&gt;&#xA;  is there a complete family offered?  (can I easily switch to similar devices, pin-compatible or in another package)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-11-27T17:32:27.927" />
  <row Id="7206" PostTypeId="2" ParentId="7198" CreationDate="2010-11-27T17:55:30.337" Score="2" ViewCount="" Body="&lt;p&gt;I would buy a &lt;a href=&quot;http://www.dd-wrt.com/site/index&quot; rel=&quot;nofollow&quot;&gt;DD-WRT&lt;/a&gt; compatible router and flash DD-WRT on it, so you can get features like attached storage and hotspot management. Add ethernet to your device with whatever module you can get and connect them with a patch cable. Then on the software side, you could use &lt;a href=&quot;http://www.zeroconf.org/&quot; rel=&quot;nofollow&quot;&gt;Zerconf&lt;/a&gt; to let your client know what services it can access, e.g. video and control streams. I believe that many of these routers also support adding an RS232 serial port, and maybe you can communicate to the network via that, but I'm not sure, so you wouldn't have to add an ethernet module.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-11-27T17:55:30.337" CommentCount="3" />
  <row Id="7208" PostTypeId="1" CreationDate="2010-11-27T18:01:39.597" Score="2" ViewCount="301" Body="&lt;p&gt;Can I somehow use Vishay's &lt;a href=&quot;http://www.vishay.com/ir-receiver-modules/&quot; rel=&quot;nofollow&quot;&gt;TSOP series&lt;/a&gt; IR receivers and IR LEDs to measure the distance from an object? Has anyone done that before or has any idea how one could do it(clever programming or circuitry, maybe?)?&lt;/p&gt;&#xA;" OwnerUserId="2074" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-11-28T13:30:02.327" LastActivityDate="2010-11-28T13:30:02.327" Title="Using 38 KHz IR receivers to measure distance" Tags="&lt;led&gt;&lt;ir&gt;&lt;distance&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="7209" PostTypeId="2" ParentId="7208" CreationDate="2010-11-27T18:56:40.053" Score="3" ViewCount="" Body="&lt;p&gt;I doubt you could do better than just detect the obstacle this way. What you need is a device like &lt;a href=&quot;http://nenya1.net/files/gp2d12.pdf&quot; rel=&quot;nofollow&quot;&gt;Sharp GP2D12&lt;/a&gt;, which measures distance between 10cm and 80cm. About USD 10, IIRC.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-11-27T19:03:36.303" LastActivityDate="2010-11-27T19:03:36.303" CommentCount="1" />
  <row Id="7210" PostTypeId="2" ParentId="7208" CreationDate="2010-11-27T19:07:50.940" Score="0" ViewCount="" Body="&lt;p&gt;You will need to have to approach it one of a different ways. one method would be to sweep what power you are radiating with the LED (something like a digital potentiometer to control the current) so that different range of objects will be detected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is very important that you recognize different materials will reflect IR differently making it very hard to get accurate results unless you know what materials will exist. The Receivers also have automatic gain control that will remove a continuous signal at the frequency and can remove yours if you send it continuously.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-27T19:07:50.940" />
  <row Id="7211" PostTypeId="1" CreationDate="2010-11-27T19:37:47.333" Score="-1" ViewCount="69" Body="&lt;p&gt;(&lt;em&gt;This SE was the best match I could find so feel free to move this Q.&lt;/em&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for &lt;a href=&quot;http://www.ksmetals.com/resources/cuttolength.pdf&quot; rel=&quot;nofollow&quot;&gt;small diameter metal tubing&lt;/a&gt;, specifically 3/16 OD .014&quot; wall (the inside diameter is the critical dimension). I prefer it in stainless steel (or if possible, any grade of Titanium).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone know a a source?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Just to clarify, I'm not looking for a walk up retail source (I'd be slightly surprised if one could be found). Rather I'm looking for a supplier I can place an order with that will ship stuff to me. Also, the question is emphatically &lt;em&gt;not&lt;/em&gt; &quot;Where can I get the best price?&quot; My quantities are so small that if price is an issue, the project gets canned.&lt;/p&gt;&#xA;" OwnerUserId="1182" LastEditorUserId="1182" LastEditorDisplayName="" LastEditDate="2010-11-27T20:25:18.057" LastActivityDate="2010-11-27T20:30:54.847" ClosedDate="2010-11-27T21:01:27.877" Title="Sources or materials?" Tags="&lt;materials&gt;" AnswerCount="1" CommentCount="8" />
  <row Id="7212" PostTypeId="2" ParentId="7186" CreationDate="2010-11-27T19:47:37.590" Score="4" ViewCount="" Body="&lt;p&gt;Try: &lt;a href=&quot;http://www.adafruit.com/jobs/&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/jobs/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-11-27T19:47:37.590" />
  <row Id="7213" PostTypeId="2" ParentId="7211" CreationDate="2010-11-27T20:30:54.847" Score="2" ViewCount="" Body="&lt;p&gt;You might want to check &lt;a href=&quot;http://www.onlinemetals.com/merchant.cfm?id=18&amp;amp;step=2&amp;amp;top_cat=1&quot; rel=&quot;nofollow&quot;&gt;OnlineMetals.com&lt;/a&gt;. They seem to have a very good selection of metals of various size and shapes, including some options in 3/16&quot; OD.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2010-11-27T20:30:54.847" CommentCount="1" />
  <row Id="7214" PostTypeId="1" AcceptedAnswerId="7225" CreationDate="2010-11-27T21:31:05.530" Score="2" ViewCount="240" Body="&lt;p&gt;For my Super OSD project I'm going to need to program large batches of MCU's, probably about 10-15 boards an hour. I could just use my trusty PICkit 2 to program them (there are two - maybe three - on each board) but it would be very laborious to load each file (up to 128KB and 256KB in size), hit program, and repeat for each MCU, and probably wouldn't allow me to meet my target speed. Also, the MCU's are surface mount, so I have to have headers on the board to allow this. Ideally, I'd like to remove these headers, but it may not be an option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what options are there for mass programming of MCU's - are there faster ways to do it? I'm kind of on a budget of less than $100 USD, so things like Microchip's MPLAB PM3 at $895 USD, while nice, wouldn't be an option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm dealing with PIC microcontrollers of various types. There's a PIC16F887, PIC24FJ64GA002 and dsPIC33FJ128GP802. However, I am also interested in options for AT32 and STM32 processors, as I may also be using them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please note, I'm not currently considering ordering chips from the manufacturers pre-programmed because the software may change by the time the chips arrive, and because of the additional cost involved. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-11-28T01:44:01.443" LastActivityDate="2010-11-28T05:41:31.147" Title="What options are there for programming MCU's in production?" Tags="&lt;microcontroller&gt;&lt;programmer&gt;" AnswerCount="7" CommentCount="3" />
  <row Id="7215" PostTypeId="2" ParentId="7190" CreationDate="2010-11-27T21:39:34.740" Score="1" ViewCount="" Body="&lt;p&gt;No.  The pins of the Arduino only can only provide a few tens of milliamps, not enough for a typical DC motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pololu's line of &lt;a href=&quot;http://www.pololu.com/docs/0J44/1&quot; rel=&quot;nofollow&quot;&gt;Simple Motor Controllers&lt;/a&gt; lets you control motors by sending serial commands from the Arduino (you can use the NewSoftSerial library).  The advantage of this method is that you can control multiple motors using a single pin on the Arduino.  The user's guide for these controllers comes with example Arduino code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also get a simpler product such as a &lt;a href=&quot;http://www.pololu.com/catalog/product/755&quot; rel=&quot;nofollow&quot;&gt;motor driver&lt;/a&gt;, but then you would have to generate your own PWM signals and it would take more of your Arduino's I/O lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You're also going to need a battery or other power source; driving motors from USB power usually doesn't work because USB ports can only provide 500 mA.&lt;/p&gt;&#xA;" OwnerUserId="1545" LastActivityDate="2010-11-27T21:39:34.740" />
  <row Id="7216" PostTypeId="2" ParentId="7214" CreationDate="2010-11-27T21:52:17.607" Score="1" ViewCount="" Body="&lt;p&gt;There is a command-line utility called &lt;a href=&quot;http://www.microchip.com/pickit2/&quot; rel=&quot;nofollow&quot;&gt;PK2CMD&lt;/a&gt; for Windows and Linux that lets you program your PICs with the PicKit (so you don't have to use MPLAB or some other GUI).  You could use your favorite scripting language to make a little program that runs the correct PK2CMD command when you press a key.  This would make the computer side of your production less laborious (just 1 key press per MCU) but you would still need a way to connect the PicKit to each of your 3 MCUs.&lt;/p&gt;&#xA;" OwnerUserId="1545" LastActivityDate="2010-11-27T21:52:17.607" />
  <row Id="7217" PostTypeId="2" ParentId="7214" CreationDate="2010-11-27T22:01:22.687" Score="4" ViewCount="" Body="&lt;p&gt;The PICkit 2 isn't a production programmer. You really need to get an ICD 3, which is classed as a production programmer, if you want to be sure that the devices are being programmed properly. Alternatively, you could buy your chips pre-programmed from Microchip or a distributor, if you have the code finalised.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-27T22:07:12.980" LastActivityDate="2010-11-27T22:07:12.980" CommentCount="3" />
  <row Id="7218" PostTypeId="2" ParentId="7190" CreationDate="2010-11-27T22:27:09.177" Score="0" ViewCount="" Body="&lt;p&gt;You'll need an extra chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For $2.35 + shipping, I was able to control two motors using the &lt;a href=&quot;http://www.sparkfun.com/products/315&quot; rel=&quot;nofollow&quot;&gt;SN754410&lt;/a&gt; using &lt;a href=&quot;http://www.instructables.com/id/Duel-Motor-Driver-with-Arduino-using-a-SN754410NE-/&quot; rel=&quot;nofollow&quot;&gt;this instructable&lt;/a&gt; to wire it up. It's really easy.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-11-27T22:27:09.177" />
  <row Id="7219" PostTypeId="2" ParentId="7214" CreationDate="2010-11-27T22:42:41.450" Score="3" ViewCount="" Body="&lt;p&gt;One method you could use is to make a clamp or something akin to a test bed (&lt;a href=&quot;http://www.youtube.com/user/sparkfun#p/search/0/v_THCk52WD4&quot; rel=&quot;nofollow&quot;&gt;example video&lt;/a&gt;) with &lt;a href=&quot;http://www.sparkfun.com/products/9174&quot; rel=&quot;nofollow&quot;&gt;pogo pins&lt;/a&gt;, so that you don't need to solder pins for the programming connectors. A PCB edge connector, such as an old style floppy cable, might be a cheaper (but more board area demanding) option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll have to come up with a way to program each microcontroller, probably using either multiple programmers or a batch file like David suggested. You could combine it with a large switch (perhaps one of the &lt;a href=&quot;http://www.sparkfun.com/products/9174&quot; rel=&quot;nofollow&quot;&gt;rotary switches&lt;/a&gt; from an old printer sharing switchbox, or a few relays), to reconnect the programmer from one PIC to another without moving the connector. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The techniques also apply for other in-system programmable controllers, although the JTAG capable ones may make it yet easier because JTAG TAP is designed to be chained, so there'd be no moving the programmer from chip to chip. Also, for chips like AVRs that can use ordinary logic levels for programming, the switching could become easier.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="1181" LastEditorDisplayName="" LastEditDate="2010-11-27T22:49:06.463" LastActivityDate="2010-11-27T22:49:06.463" CommentCount="2" />
  <row Id="7220" PostTypeId="2" ParentId="7214" CreationDate="2010-11-27T22:51:26.883" Score="0" ViewCount="" Body="&lt;p&gt;Microchip's programming service is very cheap last time I used it, Once you cover the setup cost it's very cheap - pennies per chip for 12F's - not looked at higher end ones. &#xA;They can also do marking/labelling etc.&#xA;Even if you intend to change the FW, having a bootloader preprogrammed may make this easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a production programmer I like the &lt;a href=&quot;http://tools.asix.net/prg_presto.htm&quot; rel=&quot;nofollow&quot;&gt;Asix Presto&lt;/a&gt; - tons of options for stuff like serialising, and very fast&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-27T22:51:26.883" />
  <row Id="7221" PostTypeId="2" ParentId="7208" CreationDate="2010-11-27T22:56:19.903" Score="0" ViewCount="" Body="&lt;p&gt;You can get some effective LED power control by adjusting the mark/space ratio of the 37khz carrier. However it isn't a good way to get any sort of repeatable distance info - could be useful for object detection and approach/retreat discrimination .&#xA;Elmos's &lt;a href=&quot;http://www.elmos.de/englisch/about-us/profil/optoelektronic-halios.html&quot; rel=&quot;nofollow&quot;&gt;Halios&lt;/a&gt; can do IR ranging by comparing reflected light with a local reference signal, but unless you're designing high volumes there are cheaper and simpler ways.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-27T22:56:19.903" />
  <row Id="7222" PostTypeId="2" ParentId="7214" CreationDate="2010-11-27T23:45:48.020" Score="4" ViewCount="" Body="&lt;p&gt;Microcontroller programming is usually a small part of a larger functional testing process.  What is the rest of your test plan like?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For any non-trivial product, you will need to design another board to test the board under production.  Generally, the test board will have a computer interface and will connect the target to test equipment with RS-232 or GPIB capabilities.   Then a computer can run through a script, programming the board, then running whatever tests are appropriate.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is helpful to have this test board running for firmware development as well.  Implement enough tests to catch regressions in the firmware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The start of your test board is probably the PICkit 2 circuit.  The firmware is open-source, it will take care of the programming part, it has a handy bootloader, and you can extend it to do anything else your functional test will need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I like to write my production test scripts in Python, but I think the industry standard is Labview.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-27T23:45:48.020" CommentCount="1" />
  <row Id="7224" PostTypeId="2" ParentId="7214" CreationDate="2010-11-28T00:23:39.780" Score="2" ViewCount="" Body="&lt;p&gt;Get a pickit 3 and put it in programmer to go mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You tell it you want programmer to go mode and you load your rom, then you no longer need a usb port for more than power(yes, you still need it for power).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you plug into devices you hit the program button and it loads the program and lets you know when it is done, takes less then 20 seconds a board. Costs no more than 50$&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-28T00:23:39.780" />
  <row Id="7225" PostTypeId="2" ParentId="7214" CreationDate="2010-11-28T00:36:49.450" Score="7" ViewCount="" Body="&lt;p&gt;What we do for production, is to first load a program into the PIC that tests out the board (using a small test board that independently verifies the 3.3v rail is within spec using a couple of comparators, and then we use the ADC on the PIC to check everything else out.  We had enough pins left over to allow this (it required some extra resistors to act as voltage dividers for the voltages over 3v).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After the tests pass, the real production code is flashed into the micro.  Some additional tests are run, and the PCB is ready for assembly into a case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is all done via a program on the PC that only requires an operator to connect the board, click one button, and wait for the result PASS/FAIL.  All test results (including ADC readings) are logged.  The entire process (including the programming of the PICs via an ICD 3) is controlled via the PC program, which runs batch scripts to do the actual programming.  Communication to the PIC to control the tests is done via one of the UARTs, whose pins are brought out to the test board (so in addition to the pins required for programming, we also have TX/RX as a minimum).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We set up several stations like this at our contract manufacturer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW the ICD 3 is &lt;em&gt;much&lt;/em&gt; faster than the ICD 2 (USB 2.0 vs 1.1).&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-11-28T05:41:31.147" LastActivityDate="2010-11-28T05:41:31.147" CommentCount="1" />
  <row Id="7226" PostTypeId="2" ParentId="7184" CreationDate="2010-11-28T01:00:28.483" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://dangerousprototypes.com/2010/11/25/dangerous-prototypes-gift-guide-stuff-we-love/&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com/2010/11/25/dangerous-prototypes-gift-guide-stuff-we-love/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-28T01:00:28.483" />
  <row Id="7227" PostTypeId="1" CreationDate="2010-11-28T01:39:07.173" Score="1" ViewCount="179" Body="&lt;p&gt;I have an old keyboard (circa 1998) with a male DB9, and I'd like to use it on a modern PC with a female PS/2. The keyboard is AT&amp;amp;T branded, Comcode #405748401, FCC ID CIG8AVE03417 Keytronic corporation. I suspect, but I'm not certain, that the DB9 pinout is the same as an AT&amp;amp;T 6300: &lt;a href=&quot;http://pinouts.ru/Inputs/KeyboardAtt6300_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;http://pinouts.ru/Inputs/KeyboardAtt6300_pinout.shtml&lt;/a&gt;. From that site I also found wiring pinouts for 5-pin DIN keyboard sockets and female PS/2 sockets, both of which seem compatible except the keyboard pinout shows +12VDC while the standard keyboard sockets show +5VDC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone confirm the pinout for my keyboard? If it does match the 6300, can I just wire a DB9 to PS2 adapter and expect it to work? Am I likely to fry my motherboard if I get this wrong? This keyboard came from an old AT&amp;amp;T PC, and it's possible that the keyboard connector was proprietary or a serial port. I'd hate to damage either the keyboard or my new computer with a bad guess.&lt;/p&gt;&#xA;" OwnerUserId="2089" LastActivityDate="2010-11-28T11:51:16.193" Title="Adaptor to use old AT&amp;T / keytronic keyboard with DB9 connector?" Tags="&lt;adapter&gt;&lt;keyboard&gt;&lt;db&gt;" AnswerCount="2" CommentCount="9" />
  <row Id="7229" PostTypeId="1" CreationDate="2010-11-28T03:02:39.657" Score="2" ViewCount="86" Body="&lt;p&gt;I'm about to design a PCB for a project with a TI DSP (TMS320C6720). What is the best method to use as an interface for getting the program onto the DSP? I haven't done this part myself before. I'll be using CCS v4 and my motherboard has usb 2.0 pots and a parallel port but I'd rather use the USB so that I could keep using whatever cable I need to get in the future. I'd prefer a low cost solution, I saw some JTAG emulators that cost 100's which is more expensive than I thought would be necessary, however it would be helpful to be able to debug when I'm programming.&#xA;Thanks&lt;/p&gt;&#xA;" OwnerUserId="927" LastActivityDate="2010-11-28T12:04:26.357" Title="Programming Interface for TI DSP" Tags="&lt;dsp&gt;&lt;interface&gt;&lt;programming&gt;&lt;jtag&gt;" AnswerCount="1" />
  <row Id="7231" PostTypeId="1" AcceptedAnswerId="7239" CreationDate="2010-11-28T07:22:51.267" Score="5" ViewCount="324" Body="&lt;p&gt;I've been using 8-bit AVRS for a few years now. Lately, I've been feeling limited by the peripheral data transfer speeds and higher level libraries. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm having trouble finding/picking a new line of microcontrollers to explore.  I've looked at &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;NXP        - Can't find a programmer&lt;/li&gt;&#xA;&lt;li&gt;Freescale  - Have to register for IDE&lt;/li&gt;&#xA;&lt;li&gt;AVR32      - Limited chip selection on digikey&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The NXP chips look really nice, but as with anything that isn't PIC/AVR/Ardiuno the learning curve is pretty steep. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was wondering if anybody could suggest a line of micro controllers that satisfy (in order of importance) the following requirements&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Hand solder-able chips. (I can do LQFP 100)&lt;/li&gt;&#xA;&lt;li&gt;32 bit&lt;/li&gt;&#xA;&lt;li&gt;Linux host&lt;/li&gt;&#xA;&lt;li&gt;Free toolchain&lt;/li&gt;&#xA;&lt;li&gt;Good/free IDE&lt;/li&gt;&#xA;&lt;li&gt;&amp;lt;500$ startup cost for unlimited programming/debugging/compiling&lt;/li&gt;&#xA;&lt;li&gt;CAN support&lt;/li&gt;&#xA;&lt;li&gt;Ethernet/USB support&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I'm willing to look at Freescale and NXP again, if somebody can show me that I've missed some information on their toolchain and programmers. I guess you could say AVR32s are exactly what I'm looking for, but I'm just not happy with their chip selection. They all have higher pin counts and low stock on digikey. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2092" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-07T15:37:22.777" LastActivityDate="2011-02-07T15:37:22.777" Title="out growing 8-bit AVRs, not sure where to move on to" Tags="&lt;microcontroller&gt;&lt;arm&gt;" AnswerCount="9" CommentCount="6" FavoriteCount="3" />
  <row Id="7232" PostTypeId="2" ParentId="7231" CreationDate="2010-11-28T07:52:34.970" Score="4" ViewCount="" Body="&lt;p&gt;I'd go for NXP. In a short time Cortex-M3 has become the standard for ARM controllers (I'm assuming that by Freescale you mean Coldfire). Since ARM7TDMI NXP also has a tradition of an extensive family of devices to choose from.&lt;br&gt;&#xA;As for a programmer for NXP, IMO any JTAG programmer should do the job (CMIIW).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;I'm currently reading about &lt;a href=&quot;http://mbed.org/&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt;, which looks like the easiest way to get started with the NXP Cortex M3 (controller used is LPC1768). You program/compile on-line (so Linux is not a problem), and you program through USB (the device appears as a mass storage device where you can copy your compiled program to). No programmer required. Programs written for mbed should be directly portable to LPC1768s on other boards.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-11-28T18:12:16.837" LastActivityDate="2010-11-28T18:12:16.837" />
  <row Id="7233" PostTypeId="1" CreationDate="2010-11-28T08:04:05.490" Score="0" ViewCount="476" Body="&lt;p&gt;How do I send signals from a 38 kHz Vishay's  &lt;a href=&quot;http://www.vishay.com/ir-receiver-modules/&quot; rel=&quot;nofollow&quot;&gt;TSOP series&lt;/a&gt;  IR receivers to an Arduino and make the Arduino act accordingly(eg. move a motor)?&lt;/p&gt;&#xA;" OwnerUserId="2074" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-11-28T13:33:41.353" LastActivityDate="2010-11-29T08:19:40.727" Title="Interfacing TSOP IR Receiver with Arduino" Tags="&lt;arduino&gt;&lt;interface&gt;&lt;ir&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="7234" PostTypeId="2" ParentId="7227" CreationDate="2010-11-28T08:14:56.447" Score="3" ViewCount="" Body="&lt;p&gt;I'd strongly recommend &lt;a href=&quot;http://www.keytronic.com/home/contact/contact.html&quot; rel=&quot;nofollow&quot;&gt;sending Keytronic an email&lt;/a&gt; on this one. They're one of the few who will know for sure without disassembling and reverse engineering what you already have. They'd probably be thrilled to hear from such a fan of their work!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I went through something similar with a heavy IBM tactile keyboard from 1984. The cable unplugged on both ends and was lost in a move, so I was looking for the pinout of their slightly squashed RJ19 looking connector. It was manufactured by Lexmark, and they helped sort me out via email after routing me to their 'old man on the mountain' keyboard guy. Sadly, it died it's final death about a year later from a close encounter with a four year old. I still hit the thrift stores once in a while looking for another to pop up, but I've pretty much adjusted to my $9-on-sale keyboard now.&lt;/p&gt;&#xA;" OwnerUserId="2081" LastActivityDate="2010-11-28T08:14:56.447" CommentCount="1" />
  <row Id="7235" PostTypeId="1" AcceptedAnswerId="7236" CreationDate="2010-11-28T08:31:32.067" Score="1" ViewCount="497" Body="&lt;p&gt;Is it possible to build a motor driver using only a 2N2222 transistor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If yes, then how?&lt;/p&gt;&#xA;" OwnerUserId="2074" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-15T00:57:51.203" LastActivityDate="2010-12-15T00:57:51.203" Title="Motor driver using only a 2N2222 transistor?" Tags="&lt;motor&gt;&lt;transistor&gt;&lt;driver&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="2" />
  <row Id="7236" PostTypeId="2" ParentId="7235" CreationDate="2010-11-28T10:01:27.603" Score="9" ViewCount="" Body="&lt;p&gt;Well, by motor driver... you could mean anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the motor AC or DC? Do you want to be able to vary the direction of the motor? How about the speed? What about braking the motor? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 2N2222 is quite a powerful transistor, but is only good up to 800mA or so. So any motor you use must not consume more than this current when spinning and when stalled, or the transistor may burn. Also, the 2N2222 is rated for 40V maximum, so you can't drive high voltage motors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is probably the simplest circuit:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;+12V ---------+---------+&#xA;              |         |&#xA;             / \        |&#xA;             |M| motor ---  1N4001&#xA;             \ /       / \&#xA;              |         |&#xA;              +---------+&#xA;              |&#xA;            |/&#xA;CTL -/\/\/--|    2N2222 NPN&#xA;      1k    |\&amp;gt;&#xA;              |&#xA;             ---&#xA;              -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The 1N4001 is a flywheeling diode. As the motor is an inductor, when you turn it off the energy has to go somewhere. The diode provides a path for this; otherwise, the transistor could be burnt out by switching the output off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This &quot;driver&quot; allows you to run the motor forwards and coast it. With PWM, you can vary the speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a H-bridge using four 2N2222 transistors.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;+12V --------+------------------------+&#xA;             |                        |&#xA;      1k    /  c                    c  \   1k&#xA;1 --/\/\/---|   2N2222        2N2222   |--/\/\/--- 3&#xA;            \&amp;gt; e                    e &amp;lt;/&#xA;             |       +       -        |&#xA;             |-------- MOTOR ---------|&#xA;             |                        |&#xA;     1k     /  c                    c  \   1k&#xA;2 --/\/\/---|   2N2222        2N2222   |--/\/\/--- 4&#xA;            \&amp;gt; e                    e &amp;lt;/&#xA;             |                        |&#xA;            ---                      ---&#xA;             -                        -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Making S1 = 1, S2 = 0, S3 = 0, S4 = 1 the motor would go forwards&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Making S1 = 0, S2 = 1, S3 = 1, S4 = 0 the motor would go backwards&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Making S1 = 0, S2 = 0, S3 = 0, S4 = 0 the motor coasts&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Making S1 = 1, S2 = 0, S3 = 1, S4 = 0 the motor would brake (slow down quickly)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Making S1 = 0, S2 = 1, S3 = 0, S4 = 1 the motor would also brake&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Making S1 = 1, S2 = 1 &lt;strong&gt;would be bad and should be avoided&lt;/strong&gt;. It would cause both&#xA;transistors to come on giving a direct path to ground. The transistors would burn up, and you could damage your power source. The same applies for&#xA;S3 = 1, S4 = 1, as well as setting all switches on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There should also be diodes across each transistor, anode to the emitter.&#xA;For simplicity and due to the text-only media, I omitted these. Use the same&#xA;1N4001's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also replace the 2N2222's with something else to allow it to&#xA;drive heavier loads. With heavier loads it's a good idea to use heatsinks&#xA;on each transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The inputs can be controlled from an Arduino.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-11-28T16:57:37.120" LastActivityDate="2010-11-28T16:57:37.120" CommentCount="22" />
  <row Id="7237" PostTypeId="2" ParentId="7198" CreationDate="2010-11-28T11:20:31.667" Score="0" ViewCount="" Body="&lt;p&gt;As an alternative to putting an access point onboard, there are some cellphones and PDA's that might have this functionality. They might be smaller and carry their own batteries but might add weight.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-11-28T11:20:31.667" />
  <row Id="7238" PostTypeId="1" CreationDate="2010-11-28T11:41:32.413" Score="1" ViewCount="129" Body="&lt;p&gt;I'm planning on building my first robot using an Arduino. It's going to be a small obstacle avoiding robot powered with a 9V battery. What should the voltage of the DC motor used in the robot be? Also, if you you've done this before please give some tips, or refer me to some link.Thanks. &lt;/p&gt;&#xA;" OwnerUserId="2074" LastActivityDate="2010-11-29T11:56:45.603" Title="Suitable motor for robot" Tags="&lt;arduino&gt;&lt;motor&gt;&lt;robotics&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="7239" PostTypeId="2" ParentId="7231" CreationDate="2010-11-28T11:41:58.733" Score="2" ViewCount="" Body="&lt;p&gt;I'd definitely reccommend NXP - decent range of chips, good peripherals (UART with flexible baudgen and FIFOS, SPI with FIFO etc.) excellent documentation* and flexible programming options. Get a JTAG/SWD debugger (Cortex parts use SWD - fewer pins than JTAG and can do stuff like setting breakpoints while running).&#xA;I use the free kickstart version of IAR embedded workbench - this has a 32K code limit which is fine for me but be aware the code size upgrades are expensive. Plenty  of people seem to do OK with GCC/winarm.&#xA;Some Cortex parts (eg LPC1343) can load firmware from a USB stick using the onboard bootloader.&#xA;Part availability is generally good - I've never struggled to find stock. There are also plenty of devboards/breakouts available for NXP parts.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;the documentation in the User Manuals is good, however most things are mentioned precisely once, so it is worth the time spent to read the &lt;strong&gt;whole&lt;/strong&gt; of each section relating to each peripheral you'll be using. Manuals for later parts have improved in that at the start  of each section they point you to a few critical non-obvious things like clock/pin enables documented elsewhere that are needed to get that peripheral running&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-28T11:41:58.733" />
  <row Id="7240" PostTypeId="2" ParentId="7231" CreationDate="2010-11-28T11:45:52.000" Score="2" ViewCount="" Body="&lt;p&gt;Try the 16-bit PIC24 and dsPICs. Many of them are available in DIL, and they deliver up to 40 MIPS. Free development software is available and the PICkit 3 debugger/programmer is quite cheap at $50. The next version of MPLAB will have Linux support, a beta version is available.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-28T11:45:52.000" />
  <row Id="7241" PostTypeId="2" ParentId="7227" CreationDate="2010-11-28T11:51:16.193" Score="0" ViewCount="" Body="&lt;p&gt;I think you'd need to positively identify what system that keyboard fit and what their protocol is like. Maybe you could make a microcontroller or other standalone circuit that would interface to that keyboard. Once you know what both sides expect and deliver, it should be easier to decide what an adapter should be like.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do want to experiment instead, you might want to get a scrap PC (motherboard) with PS/2 port and start working on attaching the keyboard to that. If you do happen to fry the PC, it wasn't a precious one. At least here, old computers are toxic waste that businesses are just dying to get rid of with least effort.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A nutty option might be to see if you can rewire that keyboard to be a genuine USB or PS/2 keyboard with modern internals but old keyswitch matrix.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just try not to break the precious antique from better, vanished time :)&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-11-28T11:51:16.193" />
  <row Id="7242" PostTypeId="2" ParentId="7229" CreationDate="2010-11-28T12:04:26.357" Score="1" ViewCount="" Body="&lt;p&gt;Would one of the &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/tmdx5505ezdsp.html&quot; rel=&quot;nofollow&quot;&gt;USB ezdsp&lt;/a&gt; sticks work as a replacement for the JTAG?  At least you can have a look at the schematics to see how those do the programming interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI's documentation is really dense, especially outside MSP430 realm. The DSP's still seem to be firmly in deep pockets territory having expensive tools and proprietary compilers and hard to get information.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-11-28T12:04:26.357" />
  <row Id="7243" PostTypeId="2" ParentId="7231" CreationDate="2010-11-28T12:07:15.263" Score="1" ViewCount="" Body="&lt;p&gt;I thought you'd be able to get free-as-in-freedom tools for ARMs. Programming should be doable from serial bootloader or (open) JTAG. There are some STM32 and NXP chips and modules I've looked at that left me with this impression.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was also reminded of &lt;a href=&quot;http://electronics.stackexchange.com/questions/5658/searching-for-atmel-arm-mcu-in-a-breadboard-setup-like-arduino-nano-but-obvio/5817#5817&quot;&gt;this question&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="883" LastEditorUserId="883" LastEditorDisplayName="" LastEditDate="2010-11-28T12:12:41.953" LastActivityDate="2010-11-28T12:12:41.953" />
  <row Id="7244" PostTypeId="1" AcceptedAnswerId="7245" CreationDate="2010-11-28T13:03:39.410" Score="4" ViewCount="346" Body="&lt;p&gt;I'm trying to make a bipolar H-Bridge motor driver (http://www.robotroom.com/BipolarHBridge.html). But instead of the mentioned diode(1N4001), I've got a 1N4007 diode. Can I use that instead??&lt;/p&gt;&#xA;" OwnerUserId="2074" LastActivityDate="2010-12-11T17:30:43.467" Title="1N4007 comparable with 1N4001 diode?" Tags="&lt;diode&gt;&lt;h-bridge&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="7245" PostTypeId="2" ParentId="7244" CreationDate="2010-11-28T13:12:37.143" Score="9" ViewCount="" Body="&lt;p&gt;Yes. The 1N4007 can withstand a higher reverse voltage(Vr), 1000V vs. 50V. The 1N4007 may even be a better choice, esp. if your motor is powered by a voltage near 35V. (The 1N4001 is rated for a Vr(RMS) of 35V.)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;While diodes like 1N400x may be well suited as freewheeling diodes in terms of voltage and current (rated at 1A), they're not exactly fast. To protect your transistors Schottky diodes would be a better choice, but they usually have limited Vr.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the Vr for the 1N400x series:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;1N4001: 50V&lt;br&gt;&#xA;  1N4002: 100V&lt;br&gt;&#xA;  1N4003: 200V&lt;br&gt;&#xA;  1N4004: 400V&lt;br&gt;&#xA;  1N4005: 600V&lt;br&gt;&#xA;  1N4006: 800V&lt;br&gt;&#xA;  1N4007: 1000V&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-11T17:30:43.467" LastActivityDate="2010-12-11T17:30:43.467" CommentCount="2" />
  <row Id="7246" PostTypeId="2" ParentId="7231" CreationDate="2010-11-28T13:46:38.033" Score="1" ViewCount="" Body="&lt;p&gt;If you really want to go 32-bit, try the PIC32's. High availability from Microchip. For Linux debugging, MPLAB X is in beta 4 and supports Linux, Windows and Mac OS X. I think you'll also need a PICkit 3 or similar programmer for $50-60.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I'd be more slanted towards the 16-bit dsPIC's and PIC24's because they are much cheaper, can be debugged with a PICkit 2 and are easy to program. Also they are available in DIP packages, though this doesn't matter to you(?) I'm slightly biased towards them given that I use them in my project.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-28T13:46:38.033" />
  <row Id="7247" PostTypeId="1" CreationDate="2010-11-28T13:58:27.160" Score="4" ViewCount="488" Body="&lt;p&gt;What should someone study at university level if he/she wants to get into robotics and build robotics? So far 'Mechatronics' seems to be the field I'm looking for? I looked at a few plain 'robotics' courses but they seem to be only about the electrical and computer work, and don't include any details on building the mechanical components of robots?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S my background is computer programming with no electronics or mechanics knowledge.&lt;/p&gt;&#xA;" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-28T18:27:06.597" LastActivityDate="2010-11-28T18:27:06.597" Title="What to study to get into robotics?" Tags="&lt;education&gt;" AnswerCount="3" />
  <row Id="7248" PostTypeId="2" ParentId="7247" CreationDate="2010-11-28T14:18:34.810" Score="1" ViewCount="" Body="&lt;p&gt;Get an engineering degree and/or one in electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will give you the qualifications to work for companies involved with this, but it won't actually let you build robots - to do that, you should do it as a hobby. Pick up one of the many &quot;build a robot&quot; project books and work on your project in your spare time. Also, keep computer programming in your list of subjects, as it is often used in robotics.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-28T14:18:34.810" CommentCount="2" />
  <row Id="7249" PostTypeId="2" ParentId="7247" CreationDate="2010-11-28T15:23:08.417" Score="1" ViewCount="" Body="&lt;p&gt;With information you provided us, we can't give you good answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I myself don't do any robotics (at the moment) but am familiar with education which robotics people get in my country. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your first step should be to get familiar with each of study courses and see exactly what they study. Get lists of subjects, descriptions of each subject and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next step should be to get an idea what you're really interested in in robotics. It's a HUGE HUGE and once again HUGE filed. On a robot project in my university we've one had something like 3 different types of electric engineers and 2 or 3 different types of mechanical engineers plus there were manufacturing engineers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to go general, you'd probably make best choice with mechatronics, since it's a multidisciplinary field which is supposed to cover everything needed for a robot. On the other hand, it can very easily happen that some aspect of robotics which could interest you isn't studied in great detail. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you go for mechanical or electrical engineering, you'll probably learn one aspect of robotics in great detail and just skim over the rest, if you do it at all. You should see what kinds of specializations are available at your university in electrical engineering and mechanical engineering fields. For example at my university we have specializations in both mechanical engineering and electrical engineering for robotics and automatics and students there do other areas of robotics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So basically, the answer is &quot;It depends&quot;. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-11-28T15:23:08.417" />
  <row Id="7250" PostTypeId="2" ParentId="7247" CreationDate="2010-11-28T15:47:47.960" Score="10" ViewCount="" Body="&lt;p&gt;Robotics is a huge field.  Keep that in mind as you want to study &quot;robotics.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a practical standpoint, robotics encompasses electrical, mechanical, and software engineering.  I like to think of mechanical and software engineering as either end of a spectrum with electrical engineering in the middle.  Choosing which field to study depends on where your interests lie.  I can summarize (from the best of my knowledge) what each field does.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Mechanical Engineering: Responsible for creating the actual physical interfaces to the world.  This includes the drive train and any actuators that will be necessary for the robot's design.  Mechanical engineers are also incredibly helpful when it comes to determining kinematic and dynamic models of the system (for building controllers for the system).  Typically, the additional statics and dynamics classes that the mechanical engineers get aid in creating these models.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Electrical Engineering: Responsible for the selection of sensors and interfacing actuators to the software world.  I like to think that software engineers/computer scientists work in an idealized world, and the electrical engineers try and make the sensors and interfaces as close to the idealized world as possible.  This allows you to compartmentalize the design process of your robot into simulation and real world.  The electrical engineers are often best at designing controllers for the robot.  That is to say, taking a control input and making the robot react in the desired way.  High-level controls classes (both classical and modern) allow electrical engineers take a model that mechanical engineers design, and create a way for the software engineers to accurately interface with it.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Software Engineering: Responsible for the high-level algorithms for the control and decision-making in the robot.  It would be a great oversight to attempt a robotics project without at least one software engineer.  Their insights as far as design and layout of the software are necessary in a larger-scale robotics project.  There is a lot of software engineering and computer science in robotics.  This can be from path planning, obstacle detection and avoidance, localization and mapping, vision processing, and more.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As far as actual classes at university level, I would suggest a few to be a well rounded roboticist.  You need statics and dynamics classes to understand the mechanical perspective on the project.  I would also suggest a computer-aided design class as well as a manufacturing (machining) class for hands-on knowledge.  From the electrical world, I would take a classical and modern controls class.  A basic microprocessor class, linear signals and systems, random signals and systems, and digital signal processing are also incredibly practical and useful.  Finally, I would take a software process, algorithms, and data structures class.  You may be able to find a mechatronics class that combines several of these concepts into one class.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Certain universities offer a mesh of the three curricula, such as Carnegie Mellon's Robotics Institute.  If you are unable to attend one of these universities, you may be able to check out their schedule of courses to get a better idea of what those students would learn.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wish you the best of luck.  Robotics is a very rewarding field.  To gain additional experience, I would find one of your undergraduate competitive teams (I know IEEE sponsors an annual &quot;robotics&quot; competition), or help out with one of your local BEST/FIRST/VEX high-school teams.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-11-28T15:47:47.960" CommentCount="5" />
  <row Id="7251" PostTypeId="2" ParentId="7238" CreationDate="2010-11-28T15:53:49.213" Score="4" ViewCount="" Body="&lt;p&gt;You probably want to step up to a larger battery pack than a 9V.  You'll find that the 9V doesn't really supply the current that you need, and will run out very quickly.  You can probably find a small rechargeable pack online or at a local hobby store that will do the trick.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as the motor, if the robot is suitably small, I would use a modified hobby servo.  They come in many sizes/speeds/torques, and you will probably be able to find one that meets your specifications.  You can also interface with them using the Servo library on the Arduino.  You can either buy a servo pre-modified, or you can modify it yourself using the instructions found on &lt;a href=&quot;http://www.acroname.com/robotics/info/ideas/continuous/continuous.html&quot; rel=&quot;nofollow&quot;&gt;Acroname&lt;/a&gt;, for example. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For finding these parts and more, I have compiled a list for our undergraduate projects, you can check it out here: &lt;a href=&quot;http://redmine.ausparc.com/projects/sparc/wiki/SparcSuppliers&quot; rel=&quot;nofollow&quot;&gt;Auburn SPaRC Suppliers&lt;/a&gt;.  This is a list of common suppliers that we use for many different robotics pieces and parts.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-11-28T15:53:49.213" CommentCount="2" />
  <row Id="7252" PostTypeId="1" CreationDate="2010-11-28T16:33:28.030" Score="0" ViewCount="136" Body="&lt;p&gt;What kind of stuff do they teach at Electronics Engineering and Robotics courses in college? Could I benefit from learning electronics as a hobby (things such as Arduinos, and robot kits)? &lt;/p&gt;&#xA;" OwnerUserId="2074" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-29T13:09:55.760" LastActivityDate="2010-11-30T14:59:34.720" ClosedDate="2010-11-30T14:58:17.620" Title="Robotics in college" Tags="&lt;electrical-engineering&gt;&lt;university&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="7253" PostTypeId="2" ParentId="6148" CreationDate="2010-11-28T17:29:46.523" Score="0" ViewCount="" Body="&lt;p&gt;I ended up buying these and some pin headers from ebay. Not the prettiest solution but probably the handiest.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/qAEM7.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="819" LastActivityDate="2010-11-28T17:29:46.523" />
  <row Id="7254" PostTypeId="2" ParentId="7252" CreationDate="2010-11-28T18:21:03.043" Score="2" ViewCount="" Body="&lt;p&gt;I am not sure this is a question that really can be answered. They will teach control theory, they will teach about motors, they will probably teach about microcontrollers. They will teach about sensors, they will normally(if the university is worth its salt) have you work with robots and develop algorithms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are planning to earn a degree in EE with a specialty in robotics you will find that hands on experience with microcontrollers and hardware will not hurt you. Now, on that note, you will need to challenge yourself, I know many people whom do hobbyist electronics that are fun, but will not result in professional growth as they are almost a basic textbook case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you love doing electronics and robotics in your free time, it will not hurt you. If you dislike doing it, you will be able to make it through the degree without prior experience.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-28T18:21:03.043" />
  <row Id="7255" PostTypeId="2" ParentId="7003" CreationDate="2010-11-28T21:40:08.577" Score="1" ViewCount="" Body="&lt;p&gt;I have just finished creating a tutorial on how to build a Bubble Etch Tank (unheated), at home, with minimal cost and effort.  Hopefully this will be helpful to someone:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=rIwmf_0KK2k&quot; rel=&quot;nofollow&quot;&gt;What You’ll Need&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=SylNoBb6Soo&quot; rel=&quot;nofollow&quot;&gt;Plumbing the Air System&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=oF1uynTKRDQ&quot; rel=&quot;nofollow&quot;&gt;Making Bubbles&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=JbY908CzUDM&quot; rel=&quot;nofollow&quot;&gt;The PCB Basket&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I'd recommend increasing the resolution to 720p but of course, this is optional.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll be adding further updates (such as seeing the tank in action) at &lt;a href=&quot;http://www.13volts.com&quot; rel=&quot;nofollow&quot;&gt;13 Volts&lt;/a&gt; fairly soon.&lt;/p&gt;&#xA;" OwnerUserId="1333" LastActivityDate="2010-11-28T21:40:08.577" CommunityOwnedDate="2011-05-25T02:31:53.593" />
  <row Id="7256" PostTypeId="1" AcceptedAnswerId="7260" CreationDate="2010-11-28T21:46:43.380" Score="1" ViewCount="166" Body="&lt;p&gt;I want to remove the Vcc pin from a USB cable and connect my computer to a device. My goal is to allow the device to communicate with the computer while not charging the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does some section of the USB spec permit this?&#xA;Is my plan flawed in some way?&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Will communication fail to happen?&lt;/li&gt;&#xA;&lt;li&gt;Is the device likely to charge the battery anyway from the D+ pin?&lt;/li&gt;&#xA;&lt;li&gt;Is there an error in this plan that I'm not anticipating?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2099" LastActivityDate="2010-11-28T23:40:52.347" Title="USB without Vcc" Tags="&lt;power&gt;&lt;usb&gt;" AnswerCount="3" />
  <row Id="7258" PostTypeId="2" ParentId="7256" CreationDate="2010-11-28T22:04:26.167" Score="2" ViewCount="" Body="&lt;p&gt;The spec allows a device to expect to have 100mA available.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Communication should not fail.&lt;/li&gt;&#xA;&lt;li&gt;No, no device should pull power from D+.&lt;/li&gt;&#xA;&lt;li&gt;I often design devices to use the USB power to power whichever chip I use as an interface. This means that without 5V power my communication chip does not power.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In the end you may just want to try it out and see if your device specifically has a problem. What is the device that you need to disconnect power for? If you have a device that has a primary function of charging a battery they probably designed the device around your power as a charger does not need to function if there is no power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you will still have ground as a reference, and the differential signal uses differential signaling with an occasional common mode signal but it should work with a ground reference, unless they designed their circuit as I noted above.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-28T22:04:26.167" CommentCount="1" />
  <row Id="7259" PostTypeId="2" ParentId="7256" CreationDate="2010-11-28T23:24:55.503" Score="0" ViewCount="" Body="&lt;p&gt;You can prevent charging by splicing a Schottky diode in series with the battery.  Current goes out, it doesn't go in.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-28T23:24:55.503" CommentCount="4" />
  <row Id="7260" PostTypeId="2" ParentId="7256" CreationDate="2010-11-28T23:40:52.347" Score="4" ViewCount="" Body="&lt;p&gt;Yes, communication should fail - the reason is, devices are not allowed to feed any current into D+ or D- (which is how they communicate) until they observe Vbus (the 5V) high. This is actually guaranteed by the cable in many cases, because the device will 1) only have power from Vbus, and 2) not be connected to D+/D- until after Vbus and Gnd. Obviously 1 does not apply to self-powered devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's assuming the device operates to the USB spec, and many devices do not. Another part of the spec they tend to ignore is that they may only draw 100mA until more has been negotiated. Requests for more are typically rejected only when connected to bus-powered hubs, as they don't have more power to grant. That's also why they tend to have four ports, as the hub registers to draw 500mA, needs a bit of power itself, and then must provide those 100mA on each downstream port. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In all, you'll probably have to modify the device or its battery connection rather than the USB cable to prevent charging. The specifics will depend on your device.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-11-28T23:40:52.347" CommentCount="4" />
  <row Id="7261" PostTypeId="2" ParentId="6956" CreationDate="2010-11-28T23:52:13.987" Score="3" ViewCount="" Body="&lt;p&gt;If you're willing to live with octagonal soldermasks on your vias, then try the following:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Define the SMD ground pad, and disable the stop mask.&lt;/li&gt;&#xA;&lt;li&gt;Place pads where you want your vias. Make the pads have the same characteristics as the vias you want. We will delete these pads later.&lt;/li&gt;&#xA;&lt;li&gt;Show the soldermask layer (tStop)&lt;/li&gt;&#xA;&lt;li&gt;Draw a polygon on the tStop layer in strips. This is to prevent your polygons from enclosing any area, and so that it's easier to draw. If you want a 3x3 grid of vias, then you would need four polygons.&lt;/li&gt;&#xA;&lt;li&gt;Delete pads used as a template. The package is now done.&lt;/li&gt;&#xA;&lt;li&gt;Place package in layout&lt;/li&gt;&#xA;&lt;li&gt;Place vias&lt;/li&gt;&#xA;&lt;li&gt;Use the &quot;NAME&quot; function to change the via net to the same net as the pad - probably &quot;GND&quot;&lt;/li&gt;&#xA;&lt;li&gt;Route vias / add pour&#xA;&lt;img src=&quot;http://i.imgur.com/NhCBJ.png&quot; alt=&quot;My package in progress. You can see the dummy guide pins (green) and the STOP mask fill polygon&quot;&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;After this, you will have the vias on the correct net, and your soldermask will come out as you wanted. The drawbacks that I see are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The vias must be manually placed in the final board&lt;/li&gt;&#xA;&lt;li&gt;Each via must be renamed to the target net (I couldn't get the GROUP function to work).&lt;/li&gt;&#xA;&lt;li&gt;The soldermask is an octagon instead of a circle&lt;/li&gt;&#xA;&lt;li&gt;There isn't an automatic way to draw the STOP mask for the package&lt;/li&gt;&#xA;&lt;li&gt;Each via gives an overlap error in DRC (can be ignored).&lt;/li&gt;&#xA;&lt;li&gt;No easy way for a STOP mask on the bottom side without drawing it manually&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I was able to get this to work using Eagle 5.1 in about 15-20 minutes, so not too bad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OfbhK.png&quot; alt=&quot;A simple layout showing the finished STOP mask&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-29T05:39:41.480" LastActivityDate="2010-11-29T05:39:41.480" CommentCount="1" />
  <row Id="7263" PostTypeId="2" ParentId="7233" CreationDate="2010-11-29T02:27:35.523" Score="1" ViewCount="" Body="&lt;p&gt;While there isn't an Arduino library available for this type of sensor, there are a few resources that you may find useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy the &lt;a href=&quot;http://www.sparkfun.com/products/8545&quot; rel=&quot;nofollow&quot; title=&quot;TSOP85 Sensor&quot;&gt;sensor&lt;/a&gt; from SparkFun along with a &lt;a href=&quot;http://www.sparkfun.com/products/8554&quot; rel=&quot;nofollow&quot; title=&quot;TSOP85 Breakout Board&quot;&gt;breakout board&lt;/a&gt;.  Keep in mind that these are very small, and you'll have to be careful when hand-soldering them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as the software aspect, there is a project on &lt;a href=&quot;http://tinkerish.com/blog/?p=50&quot; rel=&quot;nofollow&quot;&gt;tinkerish.com&lt;/a&gt; that has some AVR code (the chip that the Arduino is based on) for using the interrupt pin when receiving data from the IR receiver.  In the example, he is using the INT1 external interrupt on the Arduino to receive the data, and processing the data in an interrupt included in his main.c file.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should be able to duplicate this functionality using the Arduino software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also a second project in pure Arduino, &lt;a href=&quot;http://sites.google.com/site/projectarduino/blog/remotecontrolledrgblight&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  This example is using the hardware serial port on the Arduino to grab data off of the IR signal, and is unpacking the data in the getRC5Key function.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-11-29T02:27:35.523" />
  <row Id="7264" PostTypeId="1" AcceptedAnswerId="7266" CreationDate="2010-11-29T03:26:24.673" Score="2" ViewCount="276" Body="&lt;p&gt;Since we know that a 555 timer configured as an astable multivibrator depends on the resistance the timing capacitor sees, what stops people from using a 555 as an ohmmeter? How does the accuracy compare to using a traditional ADC to sense resistance via a resistive divider and looking at the voltage drop?&lt;/p&gt;&#xA;" OwnerUserId="2101" LastActivityDate="2010-11-29T03:58:26.567" Title="What are the disadvantages of using a 555 timer as a resistance to frequency converter?" Tags="&lt;555&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="7265" PostTypeId="2" ParentId="7264" CreationDate="2010-11-29T03:46:18.553" Score="4" ViewCount="" Body="&lt;p&gt;Capacitors usually do not have very good tolerances, and may change greatly due to applied voltage and temperature. This will affect your measured resistance.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-11-29T03:46:18.553" />
  <row Id="7266" PostTypeId="2" ParentId="7264" CreationDate="2010-11-29T03:58:26.567" Score="3" ViewCount="" Body="&lt;p&gt;I think generally the reason that this approach wouldn't be used is first in the answer that @cksa361 gave.  Capacitors tend to vary pretty wildly over the course of one production run.  One capacitor may be an order of magnitude larger or smaller than one immediately next in the line.  Also, high-precision capacitors tend to be more expensive than high-precision resistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The traditional resistor-divider method can be easily produced into one monolithic package.  You can find several of these on Digikey or other providers.  Another reason that the resistors would provide a better solution is that they would have a much more predictable temperature coefficient than capacitors.  This would lend itself to a high-accuracy circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, the frequency output of the 555 timer would probably be less useful than the straight voltage output of a traditional resistor divider.  High-precision ADC chips are much easier to come by than high-precision frequency-counters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, the 555 timer would work in theory, but the practical manufacturing considerations drive the design towards the one that you see in many ohmmeters.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-11-29T03:58:26.567" CommentCount="2" />
  <row Id="7267" PostTypeId="1" AcceptedAnswerId="9064" CreationDate="2010-11-29T04:11:18.447" Score="6" ViewCount="268" Body="&lt;p&gt;I asked this question ago. (Don't need to read it to answer this one)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/7231/out-growing-8-bit-avrs-not-sure-where-to-move-on-to&quot;&gt;out growing 8-bit AVRs, not sure where to move on to&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really liked the answers about the NXP line of microcontrollers. I'm about to invest in some hardware to get started playing with them, and I wanted to run it by this forum to make sure that I'm not paying too much or buying the wrong part. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not interested in the mbed chip. I prefer to have the option to build something from scratch using the full line of micro-controllers. That means I have to buy a programmer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm interested in the ULINK2 from Keil. It is 411 CND on digikey.ca. &#xA;&lt;a href=&quot;http://www.keil.com/ulink2/&quot; rel=&quot;nofollow&quot;&gt;http://www.keil.com/ulink2/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It integrates with the Keil Development environment. If it turns out I can't or don't want to use the Keil IDE can I use the ULINK2 with FOSS on Linux? What about on windows without Keil? If I decide now that I don't want to go with Keil, is it worth getting another generic JTAG programmer? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ultimately the goal is to be able to compile and program&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;LPC2921/2923/2925  (ARM9)  (this is the least important category for me)&lt;/li&gt;&#xA;&lt;li&gt;All LPC21/22/23  (ARM7)&lt;/li&gt;&#xA;&lt;li&gt;All Cortex M0 and M3&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I wasn't able to find any instructions on setting up a toolchain and flash/debugger program for NXP microcontrollers, and that is the only reason I'm talking about Keil related products. I would rather just use GCC and some other uploader. I'm used to avrdude for AVRs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of setup do you guys use for ARM or NXP uCs? What JTAG programmers do you recommend? Any other FOSS toolchain instructions or other software I should know about?&lt;/p&gt;&#xA;" OwnerUserId="2092" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-07T15:36:48.003" LastActivityDate="2011-02-07T15:36:48.003" Title="getting started with NXP microcontrollers - Programmers/IDEs/Compilers/Eval Boards" Tags="&lt;microcontroller&gt;&lt;arm&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="7268" PostTypeId="2" ParentId="7267" CreationDate="2010-11-29T04:48:58.180" Score="3" ViewCount="" Body="&lt;p&gt;Have you checked out the LPC1343 (Cortex M3) board from Microbuilder? (&lt;a href=&quot;http://www.microbuilder.eu/Projects/LPC1343ReferenceDesign.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.microbuilder.eu/Projects/LPC1343ReferenceDesign.aspx&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could be a cheap stepping stone to get familiar with ARM dev environments. You can easily upload the program via USB (it appears as a USB flash drive, and you just dump your hex file in there).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microbuilder also has tutorials to get you up and programming with free tools (Codelite/YAGARTO).&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-29T10:32:23.913" LastActivityDate="2010-11-29T10:32:23.913" CommentCount="2" />
  <row Id="7269" PostTypeId="2" ParentId="7141" CreationDate="2010-11-29T06:30:07.110" Score="1" ViewCount="" Body="&lt;p&gt;It seems like your requirements have narrowed it down to a display type you already listed: e-ink.  The others you mentioned all seem very experimental or in very specific applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know how many e-ink manufacturers there are, but &quot;E Ink Corp.&quot; has a &lt;a href=&quot;http://www.nexternal.com/eink/Product17&quot; rel=&quot;nofollow&quot;&gt;9.7&quot; prototype kit&lt;/a&gt; for sale (out of stock as of 2010 Nov 28).  You might also be able to hack a Kindle DX (same 9.7&quot; screen), not sure what's in them.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-29T06:30:07.110" />
  <row Id="7270" PostTypeId="1" AcceptedAnswerId="7290" CreationDate="2010-11-29T06:47:23.817" Score="7" ViewCount="323" Body="&lt;p&gt;I want to record some lectures I am giving next semester.  I have a video camera, and can change its direction using a servo of some sort.  However I have no idea how to detect where I am.  Me carrying some broadcasting device would be fine.  Mostly the sensitivity should be able to determine if I am in the left or right side of the room, but I do not need much more than that.&lt;/p&gt;&#xA;" OwnerUserId="1773" LastEditorUserId="1773" LastEditorDisplayName="" LastEditDate="2010-12-03T04:54:02.557" LastActivityDate="2010-12-14T02:16:44.157" Title="Making a camera follow me." Tags="&lt;sensor&gt;" AnswerCount="7" CommentCount="6" FavoriteCount="3" />
  <row Id="7271" PostTypeId="2" ParentId="7270" CreationDate="2010-11-29T06:59:17.923" Score="5" ViewCount="" Body="&lt;p&gt;What you are looking for may be related to &quot;blob tracking&quot;.  It's a commonly used technique in robotics and vision processing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your programming chops, you can use OpenCV (open source computer vision libraries) available in both C++ and Python.  Other languages may have libraries that support blob tracking.  I believe that LabVIEW and Matlab also have libraries to support this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, the setup will be a computer processing the video and finding a blob (you) of a particular color.  You can then use the information of the position of the blob in the camera frame to determine where to point the camera.  If you are, for example, driving the servo on the camera with an Arduino (or any other microcontroller), you can send commands via the serial port to update the desired position of the camera.  When the blob leaves some desired &quot;box&quot; in the center of the frame.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want, you can do some more clever tracking by implementing some combination of Proportional, Integral, and Derivative control (PID, if you are searching around the internet), to try and keep yourself centered in the frame, but this may be more than you need for your application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&#xA;A bit of searching yielded this result: &lt;a href=&quot;http://www.creativeapplications.net/tutorials/arduino-servo-opencv-tutorial-openframeworks/&quot; rel=&quot;nofollow&quot;&gt;Creative Applications&lt;/a&gt;.  This is more or less the solution that I explained.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastEditorUserId="1477" LastEditorDisplayName="" LastEditDate="2010-11-29T18:24:53.350" LastActivityDate="2010-11-29T18:24:53.350" CommentCount="5" />
  <row Id="7272" PostTypeId="1" CreationDate="2010-11-29T08:10:54.910" Score="3" ViewCount="220" Body="&lt;p&gt;Hi,  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to implement an algorithm on audio signals. The algo operates on the signal on a frame-by-frame basis. One of the intermediate stages requires addition of the signal to the previous frames. The output frame is saturated at the end of this stage.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Clarification: The output frame of the addition operation is in double, though the final output frame HAS to be in short. Thus the problem with saturation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried the following for prevention of saturation:&lt;br&gt;&#xA;1. hard-limiting: Limit any sample to a pre-defined max_val.&lt;br&gt;&#xA;2. Normaliation: Compute the max. of the frame and then scale every sample in the frame appropriately.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;None of these approaches have worked since I have to work on a frame by frame basis.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help on preventing saturation of signals is most welcome.&lt;/p&gt;&#xA;" OwnerUserId="2103" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-29T14:26:46.983" LastActivityDate="2011-02-15T20:25:26.697" Title="Preventing audio signal saturation" Tags="&lt;audio&gt;&lt;dsp&gt;" AnswerCount="6" CommentCount="4" FavoriteCount="1" />
  <row Id="7273" PostTypeId="2" ParentId="7233" CreationDate="2010-11-29T08:19:40.727" Score="3" ViewCount="" Body="&lt;p&gt;The IR receiver will output a high or low level depending on the presence/absence of the 38kHz carrier in the received IR signal. The scope screenshot shows what that looks like in a typical remote control signal. The top trace shows the signal as seen by the IR-photodiode, the first component in the receiver chain. You can see intermittent bursts of the 38kHz carrier. After this signal is demodulated the pulses of the RC command (in this example RC5) show up, see bottom trace.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/fyUIE.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now this is when you send data pulses like a remote control would. You will send the 38kHz signal continuously, so the receiver will see the carrier continuously, or not at all. In the former case the output of the receiver will be high, otherwise low. You just connect this signal to an input pin of the Arduino and test the level. A high level would mean an obstacle reflects the transmitted signal to the receiver, a low level means the way is clear.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(The scope screenshot was taken from &lt;a href=&quot;http://nenya1.net/electronics/rc5/index.php&quot; rel=&quot;nofollow&quot;&gt;my webpage on RC5&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-11-29T08:19:40.727" />
  <row Id="7274" PostTypeId="2" ParentId="7231" CreationDate="2010-11-29T09:14:07.110" Score="0" ViewCount="" Body="&lt;p&gt;Take a look at &lt;a href=&quot;http://www.tinyclr.com/hardware/1/fez-domino/&quot; rel=&quot;nofollow&quot;&gt;FEZ Domino&lt;/a&gt;. It doesn't meet all your requirements but offers quite a lot if you don't need lowest possible level control. &lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-11-29T09:14:07.110" />
  <row Id="7275" PostTypeId="2" ParentId="5658" CreationDate="2010-11-29T09:24:51.680" Score="1" ViewCount="" Body="&lt;p&gt;Take a look at these low cost boards:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.tinyclr.com/hardware/2/fez-mini&quot; rel=&quot;nofollow&quot;&gt;http://www.tinyclr.com/hardware/2/fez-mini&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.tinyclr.com/hardware/1/fez-domino&quot; rel=&quot;nofollow&quot;&gt;http://www.tinyclr.com/hardware/1/fez-domino&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.tinyclr.com/hardware/16/fez-panda&quot; rel=&quot;nofollow&quot;&gt;http://www.tinyclr.com/hardware/16/fez-panda&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-11-29T09:24:51.680" />
  <row Id="7276" PostTypeId="2" ParentId="7184" CreationDate="2010-11-29T09:52:47.270" Score="1" ViewCount="" Body="&lt;p&gt;I think that you should make a list of potential gift candidates and let him choose what he most wants. He will see how much money you want to spend, and he will probably make some suggestions on his own within that budget. That way you will avoid to buy him something that will collect dust, and avoid him lie to you that your present is the best in the world and just what he needs. It is very hard for a girl/woman to buy a tech present to a tech geak. Even asking his friends will not help you much, since probably no one of his close friends follows the exact same trends and news he does. I know that it ruins the surprise, but you can make it up with buying some compatible add on boards. That will be a real surprise for him, and you will buy exactly what he wants. Both happy.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-11-29T09:52:47.270" />
  <row Id="7277" PostTypeId="2" ParentId="7267" CreationDate="2010-11-29T10:09:33.160" Score="0" ViewCount="" Body="&lt;p&gt;No too familiar with all the options but make sure you get something that will do JTAG and SWD - later Cortex parts use the latter, which uses fewer pins for debug.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-29T10:33:28.297" LastActivityDate="2010-11-29T10:33:28.297" />
  <row Id="7278" PostTypeId="2" ParentId="7231" CreationDate="2010-11-29T10:45:38.830" Score="8" ViewCount="" Body="&lt;p&gt;ARM, ARM, ARM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ARM license their processor cores to many companies. This means that you'll find good tools, support and documentation from more than one source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PIC, AVR and MSP430 all suffer from the problem of being wholly owned by one company.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bear in mind with ARM microcontrollers that a Cortex-M3 from NXP is going to be closer to a Cortex-M3 from ST or Luminary than an ARM9 or ARM7TDMI from NXP. More often than not, compilers, debuggers and programmers are common across cores rather than manufacturers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting the Codesourcery GCC ARM toolchain and a cheap ARM JTAG dongle will get you a long way.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-29T10:45:38.830" CommentCount="1" />
  <row Id="7279" PostTypeId="2" ParentId="7238" CreationDate="2010-11-29T11:56:45.603" Score="0" ViewCount="" Body="&lt;p&gt;6v solarbotics motors are good, they are very powerful and only take a small current,  you will also need an ultrasound pinger and some sharp ir distance measurements. +1 for the nicd packs.  &lt;/p&gt;&#xA;" OwnerUserId="2108" LastActivityDate="2010-11-29T11:56:45.603" />
  <row Id="7280" PostTypeId="1" AcceptedAnswerId="7667" CreationDate="2010-11-29T11:59:50.467" Score="1" ViewCount="199" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I have a rail of unidentified SOIC-8 ICs with marking  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;501  &#xA;115  &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Nothing else. No manufaturers logo, no nothing. Does anybody know what this could be?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;(picture added)&lt;br&gt;&#xA;At 3mm they're quite high for SOIC-8, so they could be optocouplers or so?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/50qyE.jpg&quot; alt=&quot;alt text&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Grid is 5mm. (Yes, I know the devices aren't properly aligned, but I did this on my scanner with a sheet of paper over the devices...:-))  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;update/conclusion&lt;/strong&gt;&lt;br&gt;&#xA;It's almost certainly an Agilent HCPL-0501. The marking matches completely: the &lt;code&gt;501&lt;/code&gt; refers to the type number, the &lt;code&gt;115&lt;/code&gt; means week 15 of the year 2001. And the date code appears below the type number (which was a problem with the TR115).&lt;br&gt;&#xA;Also diode tests all pass. The 5-6 test which passed was an error; I probably held the testprobe on pin 6 and 7 simultaneously, and 5-7 is the transistor's base-emitter diode.&lt;br&gt;&#xA;Thanks for all the replies.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-09T10:53:58.610" LastActivityDate="2010-12-09T10:53:58.610" Title="Identifying IC w/ marking &quot;501 115&quot;" Tags="&lt;identification&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="7281" PostTypeId="1" CreationDate="2010-11-29T12:59:10.347" Score="2" ViewCount="166" Body="&lt;p&gt;I have a ultrasonic sensor which moves to 3 turns and gets the data off each of them. How can I make the robot move to the one that was the lowest value? I have to use the Lego NXT Mindstorms software which uses blocks.&lt;/p&gt;&#xA;" LastEditorUserId="106" LastEditorDisplayName="" LastEditDate="2010-11-29T17:50:50.320" LastActivityDate="2010-11-29T22:53:10.033" Title="How can I compare 3 data values in Lego NXT?" Tags="&lt;lego-mindstorms&gt;&lt;nxt-g&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="7282" PostTypeId="2" ParentId="7272" CreationDate="2010-11-29T13:05:49.630" Score="2" ViewCount="" Body="&lt;p&gt;If this is at all similar to how values overflow in C, by the time you have done the addition, you would have overflowed. So you would need to halve the current frame and the previous frame value that you are adding &lt;em&gt;before&lt;/em&gt; you add, then add, then optionally normalise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But in any case, you will have a hard time keeping a consistent level (audio compression) if you have only one frame to work on at a time, because you need a long term average that doesn't jump around.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2010-11-29T13:05:49.630" CommentCount="1" />
  <row Id="7283" PostTypeId="2" ParentId="7280" CreationDate="2010-11-29T14:16:25.170" Score="0" ViewCount="" Body="&lt;p&gt;Could be these low cost digital isolators:&#xA;&lt;a href=&quot;http://www.nve.com/Downloads/il5xx.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.nve.com/Downloads/il5xx.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or something similar...&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-29T14:43:32.463" LastActivityDate="2010-11-29T14:43:32.463" CommentCount="2" />
  <row Id="7284" PostTypeId="2" ParentId="7270" CreationDate="2010-11-29T14:23:06.887" Score="3" ViewCount="" Body="&lt;p&gt;Wearing one or more IR led's might let a camera like a wi controller track you &lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-11-29T14:23:06.887" />
  <row Id="7285" PostTypeId="2" ParentId="7272" CreationDate="2010-11-29T14:24:36.063" Score="1" ViewCount="" Body="&lt;p&gt;I take it you are having to carry over the result because you are doing real time dsp with audio. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have seen this issue before when students make an error in how they carry over the result of the idft. Often they incorrectly carry things over and end up causing a continuous buildup. Based on your comment to martin you seem to have avoided this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, This is why the radio has a volume knob you have to use. When you change radio stations from a transmitter nearby to one that is far away you have to change what your volume level is to hear it at the same volume. I would suggest you add a user controllable gain knob, then if it saturates it is in their control to change it. A user will normally do this automatically as it gets louder as they do not like it. They will also turn it up when needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This knob would change what you are scaling your values by. I hope this helps, with more information about your application I could give other help. You could create a very slow response average(Low Low pass filter) that takes many frames to change significantly and use it to give gain control. This means a sudden spike will cause saturation, but if your audio volume changes slowly you will easily compensate for it. Even if your audio changes quickly, this type of filter will save the user turning it down and up if each relative volume level is sustained for an extended period.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-29T14:24:36.063" CommentCount="1" />
  <row Id="7286" PostTypeId="1" AcceptedAnswerId="7287" CreationDate="2010-11-29T14:35:42.470" Score="5" ViewCount="274" Body="&lt;p&gt;I happen to have some 500 old AT89C52 controllers and am looking for ideas how to use them in a project. That's an 8051-based controller with 8K Flash, so you get an idea. And no,  trashing them is not a project! :-)&lt;br&gt;&#xA;I remember that in the 80s Steve Ciarcia (of Circuit Cellar fame) wrote in Byte Magazine about a &quot;supercomputer&quot; he built with sixty-four 8048s. Nowadays a quad core Pentium will easily beat five hundred 89C52s, so maybe that's not the way to go. Instead I'm thinking of a series of separate devices, each with its own controller (where a single Pentium would be of little use).&lt;br&gt;&#xA;Suggestions?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:24:54.703" LastActivityDate="2010-12-10T22:24:54.703" Title="Project ideas for five hundred AT89C52s?" Tags="&lt;8051&gt;&lt;ideas&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="7287" PostTypeId="2" ParentId="7286" CreationDate="2010-11-29T14:44:59.950" Score="7" ViewCount="" Body="&lt;p&gt;Independent sychronising fireflies:&#xA;&lt;a href=&quot;http://tinkerlog.com/2008/07/27/synchronizing-fireflies-ng/&quot; rel=&quot;nofollow&quot;&gt;http://tinkerlog.com/2008/07/27/synchronizing-fireflies-ng/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-29T14:44:59.950" CommentCount="5" />
  <row Id="7288" PostTypeId="2" ParentId="7272" CreationDate="2010-11-29T15:13:44.510" Score="1" ViewCount="" Body="&lt;p&gt;The only way to do this is to ensure that you &lt;em&gt;can't&lt;/em&gt; saturate.  Your algorithm presumably has some kind of &quot;maximum-gain&quot; which means you know the most the signal can grow per frame.  You have to ensure that the first frame has enough headroom for the signal not to saturate by the end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your example has an addition, which (unless you know more than you've said so far about it) grows your output by at most one bit over the input (with more knowledge about the system, you may be able to say it will average no more than eg. 2.4 bits over the whole set of frames).  But in this simple case, if you have 8 frames, you'll have to leave 8-bits of headroom over the original samples.  So if you sample at 8 bits and calculate in 16 bits, you should be OK.&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2010-11-29T15:13:44.510" CommentCount="1" />
  <row Id="7289" PostTypeId="2" ParentId="7270" CreationDate="2010-11-29T15:15:45.773" Score="2" ViewCount="" Body="&lt;p&gt;Sounds like an ideal job for a Kinect and some processing software - it can separate subjects with the 3d info, has pan-tilt motors and a video output.&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2010-11-29T15:15:45.773" CommentCount="1" />
  <row Id="7290" PostTypeId="2" ParentId="7270" CreationDate="2010-11-29T15:27:53.847" Score="7" ViewCount="" Body="&lt;p&gt;You could wear some simple IR LEDs, you could then also place a number of IR receivers, just simple IR photo-diodes would work, with a narrow viewing angle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you place these around the base of the camera and then have a microcontroller read which one has the greatest signal you can point the camera towards the IR source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sounds complicated, but it is very simple, and does not require a computer. The hardware is easy to do, although you will probably find in noisy environments (bright light) you will want to modulate your IR to get away from broadband noise you receive.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-29T15:27:53.847" CommentCount="6" />
  <row Id="7291" PostTypeId="2" ParentId="7187" CreationDate="2010-11-29T15:49:32.267" Score="4" ViewCount="" Body="&lt;p&gt;@ LoneTech: I figured this site was to help people. Not put them down for lack of information, but to provide it for them if the need is there.  Also, Interrupts can be used to interrupt other code without hurting the speed of your main loop.  If your button is supposed to change a process and your main loop is controlling a wave or something.  INT0 could be used.  You also don't know what other operations this individual plans on using it for.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;@ Michael: This code took me a while to track down and understand as well.  I have written code for AVRs for 5+ years now and for PC 13+ years.  Its amazing how little documentation is there at your fingertips.  I ran across a nice tutorial and finally it clicked.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void InitINT0()&#xA;{&#xA;    // Enable INT0 External Interrupt&#xA;    EIMSK |= 1&amp;lt;&amp;lt;INT0;&#xA;&#xA;    // Falling-Edge Triggered INT0 - This will depend on if you&#xA;    // are using a pullup resistor or a pulldown resistor on your&#xA;    // button and port&#xA;    MCUCR |= 1&amp;lt;&amp;lt;ISC01;&#xA;}&#xA;&#xA;int main(void)&#xA;{&#xA;    //Init Timer&#xA;    InitINT0();&#xA;&#xA;    //Which Interrupt pin you need to enable&#xA;    //can be found in the datasheet, look at the pin&#xA;    //configuration, usually within the first 5 pages&#xA;    //track down INT0 - which is PORTD pin 0.&#xA;    //This needs to be an input.&#xA;    DDRD &amp;amp;= 0;&#xA;&#xA;    // Enable Interrupts&#xA;    sei();&#xA;&#xA;    //Givin that PORTD0 is the INT0, your button should&#xA;    //be hooked up to it.&#xA;&#xA;    while(1)&#xA;    {&#xA;        //Do your operation&#xA;    }&#xA;}&#xA;&#xA;// External Interrupt 0 ISR&#xA;ISR(INT0_vect) &#xA;{&#xA;    while (/*Button is down*/) //0 is the pin for your button&#xA;    { &#xA;        //Pause your operation , this will pause everything though&#xA;        //because Interrupts take priority over pretty much everything&#xA;        //This includes other interrupts and your main loop&#xA;    }&#xA;} &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1414" LastEditorUserId="1414" LastEditorDisplayName="" LastEditDate="2010-11-29T16:48:58.957" LastActivityDate="2010-11-29T16:48:58.957" CommentCount="1" />
  <row Id="7292" PostTypeId="2" ParentId="7280" CreationDate="2010-11-29T15:59:28.373" Score="0" ViewCount="" Body="&lt;p&gt;From size I'd say optoisolator - easy to confirm - infinite resistance across body, about 1v diode drop on LED.&#xA;Another possibility is inductor/transformer. Maybe crack one in half with sidecutters...&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-29T15:59:28.373" />
  <row Id="7293" PostTypeId="2" ParentId="5819" CreationDate="2010-11-29T16:02:56.263" Score="1" ViewCount="" Body="&lt;p&gt;Semtech SC4524A looks a good fit 3-28V in, 2A out, SO8 (Thermal pad), up to 2MHz for small inductors/caps. Vary cheap.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-29T16:02:56.263" />
  <row Id="7294" PostTypeId="2" ParentId="7272" CreationDate="2010-11-29T16:36:00.043" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Your Attempts&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By definition when you &quot;hard-limit&quot; values in your code you are causing saturation. It may not be saturation in the sense of overflowing your short, but you are still distorting the wave when it goes over a certain point. Here's an example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/89EM4.png&quot; alt=&quot;Saturation&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I realize you probably aren't hard-limiting on the bottom, but I had already drawn it before I realized that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, in other words, the hard limiting method won't work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now for your second approach, this method will cause you to do what some audio people actually do intentionally. You are causing every frame to be as loud as it possibly can. This method can work OK if you get the scaling right and are fine with your music sounding loud all of the time, but it isn't great for most people.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;One Solution&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you know the max possible effective gain that your system can create, you can divide your input by this much. To figure out what this would be you will need to step through your code and determine what the max input is, give it a gain of x, figure out what the max output is in terms of x, and then determine what x should be in order to not ever saturate. You would apply this gain to your incoming audio signal before you do anything else to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This solution is OK, but isn't great for everyone as your dynamic range can be hurt a little since you usually wont be running at max input all of the time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other solution is to do some auto-gaining. This method is similar to the previous method, but your gain will change over time. To do this you can check your max value of each frame of your input. You will use will store this number and place a simple low pass filter on your max values and decide what gain to apply with this value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is an example of what your gain versus input volume would be:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/NQRLw.png&quot; alt=&quot;auto-gain&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This type of system will cause most of your audio to have a high dynamic range, but as you start getting close to the max volume you can have you slowly reduce your gain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Data Analysis&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are wanting to find out what type of values your system is actually getting in real time then you will need to have some type of debugging output. This output will change depending on what platform your running on, but here's a general gist of what you would do. If you are on an embedded environment you will need to have some serial output. What you will do is at certain stages in your code output to a file or screen or something you can grab the data from. Take this data and put it in excel of matlab and graph all of them versus time. You will probably very easily be able to tell where stuff is going wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Very Simple Method&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you saturating your double? It doesn't sound like it, instead it sounds like you are saturating when you switch to a short. A very simple and &quot;dirty&quot; way of doing this is to convert the max of your double (this value is different depending on your platform) and scale that to be the max value of your short. This will guaranty that assuming you don't overflow your double that you wont overflow your short either. Most likely this will result in your output being much softer then your input. You will just need to play around and use some of the data analysis that I described above to make the system work perfectly for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;More Advanced Methods that probably don't apply to you&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the digital world there is a trade off between resolution and dynamic range. What this means is that you have a fixed number of bits given to your audio. If you decrease the range that your audio can be in then you increase the bits per range that you have. If you think about this in the sense of volts and you have 0-5v input and 10bit adc then you have 10bits to give to a 5v range, usually this is done linearly. So 0b0000000000 = 0v, 0b1111111111 = 5v and you linearly assign the voltages to the bits. In reality, with audio, this isn't always a good use of your bits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of voice, your voltages versus probability of those voltages look something like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Jlban.png&quot; alt=&quot;pdf&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means that you have a lot more of your voice in the lower amplitude and just a little amount in the high amount. So instead of assigning your bits lineally, you can remap your bits to have more steps in the lower amplitude range and thus less in the upper amplitude range. This gives you the best of both worlds, resolution where most of your audio is at, but limit your saturation by increasing your dynamic range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, this remapping will change how your filters act and will probably need to rework your filters, but that is why this is in the &quot;advanced&quot; section. Also, since you are doing your work with a double and then converting it to a short, your short will probably need to be linear anyways. Your double already gives you much more precision then what your short will give you so there is probably no need for this method.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-29T18:07:24.610" LastActivityDate="2010-11-29T18:07:24.610" CommentCount="3" />
  <row Id="7295" PostTypeId="2" ParentId="7280" CreationDate="2010-11-29T16:38:36.593" Score="3" ViewCount="" Body="&lt;p&gt;A &lt;a href=&quot;http://www.ssousa.com/pdf/TR115.pdf&quot; rel=&quot;nofollow&quot;&gt;TR115 optocoupler&lt;/a&gt;?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ringing out a suspected optocoupler/isolator with a multimeter is a slight step above reading a passive.  They are almost always isolated from side to side, so you only have 12 possible combinations for each 4-pin side.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-29T16:38:36.593" CommentCount="3" />
  <row Id="7296" PostTypeId="1" CreationDate="2010-11-29T17:01:00.747" Score="-3" ViewCount="306" Body="&lt;p&gt;I set &lt;a href=&quot;http://www.instructables.com/id/H-Bridge-on-a-Breadboard/step7/Getting-a-Clear-Picture/&quot; rel=&quot;nofollow&quot;&gt;up a H-bridge&lt;/a&gt; but am not sure how I can use it with an Arduino. Please help me with this.&lt;/p&gt;&#xA;" OwnerUserId="2074" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-29T17:45:54.360" LastActivityDate="2010-11-29T19:39:03.567" ClosedDate="2010-11-29T20:18:38.683" Title="Connecting H-bridge with Arduino" Tags="&lt;arduino&gt;&lt;motor&gt;&lt;driver&gt;&lt;h-bridge&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="0" />
  <row Id="7297" PostTypeId="2" ParentId="7286" CreationDate="2010-11-29T17:03:46.867" Score="4" ViewCount="" Body="&lt;p&gt;If you are looking for something a bit more challenging, you could use them as a sensor mesh network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Get a transceiver to allow objects to report their distance from some sensor event. Or just the magnitude of some sensor event. You could measure light, sound, even RF energy at a frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Place your mesh network around the room at mapped locations and have them all report back to a computer what their strengths were and map the strengths in relation to points an locate the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also place them all at the same height and use a dipole antenna (due to it having equal radiation strength in all directions) and have them record RSSI of every message they receive from others and try to map their locations and then use that to map the even location. This step could easily be used to make up a thesis project for a masters, even a dissipation if you increase the complexity and develop sexy algorithms(I think algorithms can be sexy so sue me). &lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-29T17:03:46.867" CommentCount="1" />
  <row Id="7298" PostTypeId="2" ParentId="7272" CreationDate="2010-11-29T17:24:27.237" Score="0" ViewCount="" Body="&lt;p&gt;You can use Linear predictive coding to compress the signal down into a &quot;residual&quot; and a filter to recreate that frame of audio later on. It's pretty complicated, but here is a good paper. If you keep the residual exactly, this is a lossless algorithm. You can also just use fewer bits to encode the residual and keep good quality. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;J. Makhoul. Linear prediction: A tutorial review. Proceedings of the IEEE,&#xA;63(4):561–580, April 1975.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And a chapter in DAFX has MATLAB algorithms written for you. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;U. Zolzer, editor. DAFX - Digital Audio Effects. John Wiley &amp;amp; Sons, Ltd,&#xA;Baffins Lane, Chichester, West Sussex, PO 19 1UD, England, 2002.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically given an input signal frame you can compute a spectral envelope and a residual. See the pictures below, and note the amplitude of the residual. &#xA;&lt;img src=&quot;http://i.imgur.com/lr6h2.png&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/IiZKx.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use the filter from the second figure and give it the residual when you want to recreate the sound. Notice that the residual has a fairly stable amplitude, and note the units. You need to be able to encode at least that. The filter is an &quot;LTI&quot; filter and has nice properties you could probably use to combine frames. &lt;/p&gt;&#xA;" OwnerUserId="2092" LastActivityDate="2010-11-29T17:24:27.237" CommentCount="5" />
  <row Id="7299" PostTypeId="2" ParentId="7296" CreationDate="2010-11-29T17:39:33.943" Score="1" ViewCount="" Body="&lt;p&gt;Just connect the control pins to your mcu (Arduino), and dont enable them at the same time, use the first or the second one. (but never both).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And your link is a little bit confusing for me, but if you google for H-Bridge you will find other examples that may be a little clearer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;here is a couple of links that will push you in the right direction:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/H-bridge&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/H-bridge&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.modularcircuits.com/h-bridge_secrets1.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.modularcircuits.com/h-bridge_secrets1.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.discovercircuits.com/H/hbridge.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.discovercircuits.com/H/hbridge.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://library.solarbotics.net/circuits/driver_4varHbridge.html&quot; rel=&quot;nofollow&quot;&gt;http://library.solarbotics.net/circuits/driver_4varHbridge.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://library.solarbotics.net/circuits/driver_tilden.html&quot; rel=&quot;nofollow&quot;&gt;http://library.solarbotics.net/circuits/driver_tilden.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-11-29T17:39:33.943" CommentCount="4" />
  <row Id="7300" PostTypeId="2" ParentId="3047" CreationDate="2010-11-29T19:32:35.650" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Bluetooth_protocols&quot; rel=&quot;nofollow&quot; title=&quot;Wikipedia link&quot;&gt;This Wikipedia article&lt;/a&gt; on Bluetooth protocols may have what you are after...&lt;/p&gt;&#xA;" OwnerUserId="1990" LastActivityDate="2010-11-29T19:32:35.650" />
  <row Id="7301" PostTypeId="2" ParentId="7296" CreationDate="2010-11-29T19:39:03.567" Score="1" ViewCount="" Body="&lt;p&gt;I highly recommend getting a dedicated H-Bridge IC. Here's how you can use it: &lt;a href=&quot;http://itp.nyu.edu/physcomp/Labs/DCMotorControl&quot; rel=&quot;nofollow&quot;&gt;http://itp.nyu.edu/physcomp/Labs/DCMotorControl&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-11-29T19:39:03.567" />
  <row Id="7302" PostTypeId="2" ParentId="7281" CreationDate="2010-11-29T20:01:25.783" Score="1" ViewCount="" Body="&lt;p&gt;Create a loop that repeats 3 times.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try storing the US [UltraSonic] values in the Variable Block as a number. Name it &quot;Number 1&quot; or something. The block is located [IIRC] in the Advanced section. [Make sure you have the advanced view turned on.] Maybe it's in the one above the Advanced section - I'm not sure. It has a picture of a briefcase. Place it outside the loop, to the left. Set the value to 0.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Create a Ultrasonic Block [just one that reads values; I think it's in the Sensors section], and place it inside the loop. The Ultrasonic Block should be coloured yellow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, click on the &quot;hub&quot; at the bottom of the Ultrasonic block. (It's the grey line at the bottom of the block.) Also, make sure the &quot;hub&quot; is open on the Variable Block, too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Create a Comparing Block (with the picture of a check mark and &quot;X&quot; mark), and place it right of the Ultrasonic Block. Open the &quot;hub&quot;. Change the settings of the Compare Block to &quot;Less Than&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Create another Variable Block (same name as the ones before) and place it right before the Comparing block. Connect the &quot;#&quot; on the hub of the Variable Block with the &quot;B&quot; on the Comparing Block.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Create a data wire from the output of the Ultrasonic Block, and place it in &quot;A&quot; of the Comparing Block.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Create a Switch block to the right of the the compare block. Set it to &quot;Logic&quot; or something similar.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, take the output (should be the bottom most) of the Comparing Block, and place it in the Switch Block.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inside the &quot;true&quot; value in the Switch Block, add a US Sensor Block and then a Variable Block (the same name you've been using so far). Connect the output of the US Sensor block to the &quot;#&quot; sign on the Variable Block.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the loop, there's a &quot;Counter&quot; check box or something. Check it. A little place where you can put the data wires should appear on the left of the loop. This counts how many times the loop has repeated so far.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Create a Variable Block (call it &quot;Count&quot;; make sure it's of the Number type) inside the loop, inside the switch block, inside the true value, before the US Sensor Block. Connect the data wire from the &quot;Counter&quot; of the loop, and place it in the &quot;#&quot; sign of the &quot;Counter&quot; Variable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, add a move block inside the loop (at the end, preferably) so your robot moves each time you take a reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The counter variable indicates where the robot was at its least value. [You can change it to least value by changing the &quot;Greater Than&quot;/&quot;Less Than&quot; value of the Compare Block.]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;A tutorial on Data Wires should help you out. (Included in the Help Section of NXT-G.)&#xA;After you read the tutorial, re-read this, and see if you understand.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Please EDIT This, I haven't used NXT-G for a long time [2 years], so it's probably inaccurate.&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="1940" LastActivityDate="2010-11-29T20:01:25.783" CommunityOwnedDate="2010-11-29T20:01:25.783" />
  <row Id="7303" PostTypeId="1" CreationDate="2010-11-29T20:35:11.137" Score="3" ViewCount="214" Body="&lt;p&gt;I need to get some Heat shrink tubing around something that is too big on the ends for it to slide over.  Is it possible to cut the heat shrink along it's length and somehow reattach it before applying heat to get it to shrink?&lt;br&gt;&#xA;If you have any alternative suggestions I need the material to be transparent.&lt;/p&gt;&#xA;" OwnerUserId="2115" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-08T15:45:15.077" LastActivityDate="2011-01-08T15:45:15.077" Title="Possible to cut Heat Shrink tubing lengthwise and reattach?" Tags="&lt;cable-assemblies&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="7305" PostTypeId="2" ParentId="7303" CreationDate="2010-11-29T21:50:28.567" Score="3" ViewCount="" Body="&lt;p&gt;You can sometimes get away with cutting it if your heatshrink has adhesive, but this generally isn't a good method. Ideally you want to put the heatshrink on before the connector goes on. If you haven't done this you can get away with getting larger heatshrink if it is able to shrink enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your other option is to use electrical tape or heatshrink tape.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-29T21:50:28.567" />
  <row Id="7306" PostTypeId="1" AcceptedAnswerId="7307" CreationDate="2010-11-29T22:25:04.317" Score="0" ViewCount="172" Body="&lt;p&gt;Well, I have a little problem in my hands, I need to clone an Altera Max EPM7128ELC84, luckily the PLD comes in a socketable PLCC84 package and has a JTAG interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now my question: what approach should I take? this can be done?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A generic JTAG-USB adapter&lt;/li&gt;&#xA;&lt;li&gt;The means to make a socket with the cables attacehd to the JTAG&lt;/li&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://www.altera.com/literature/ds/m7000.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;A little experience programming FPGAs &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance&lt;/p&gt;&#xA;" OwnerUserId="1673" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-10T17:30:26.120" LastActivityDate="2010-12-10T17:31:22.017" Title="Reading the configuration array of a MAX7000 PLD" Tags="&lt;jtag&gt;&lt;altera&gt;" AnswerCount="2" />
  <row Id="7307" PostTypeId="2" ParentId="7306" CreationDate="2010-11-29T22:50:14.013" Score="3" ViewCount="" Body="&lt;p&gt;The Altera Quartus software is unlikely to recognise your USB JTAG hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a parallel port it's very easy to make an Altera JTAG interface, I have a design &lt;a href=&quot;http://www.leonheller.com/Blaster/Blaster.zip&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. Terasic makes a low-cost Altera USB JTAG interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the CPLD hasn't been protected you should be able to read it with the Quartus software.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-11-29T22:59:45.740" LastActivityDate="2010-11-29T22:59:45.740" CommentCount="4" />
  <row Id="7308" PostTypeId="2" ParentId="7303" CreationDate="2010-11-29T22:50:40.737" Score="2" ViewCount="" Body="&lt;p&gt;Cutting won't work. You can get heatshrink with shrink ratio up to about 4:1, but possibly not transparent. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-29T22:50:40.737" />
  <row Id="7310" PostTypeId="2" ParentId="7303" CreationDate="2010-11-30T00:12:44.863" Score="3" ViewCount="" Body="&lt;p&gt;My alternate suggestion would be to use a self-annealing (self-amalgamating, self-fusing) tape.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your local electrical supply store should have some - it is a step up from regular electrician tape.  It is usually similar to double-sided tape, in that both sides have &quot;something&quot; on them, and that as you wrap it, and stretch it a bit, it binds with itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is one specific &lt;a href=&quot;http://parts.digikey.ca/1/1/103829-tape-rubber-self-fusing-1-x-30-70-1-x30.html&quot; rel=&quot;nofollow&quot;&gt;example&lt;/a&gt; and a hopefully long-lived link at &lt;a href=&quot;http://www.3m.com/product/information/Scotch-Self-Fusing-Silicone-Rubber-Electrical-Tape.html&quot; rel=&quot;nofollow&quot;&gt;3M&lt;/a&gt;, one manufacturer of the stuff (not used that specific brand, but mine is from a very local supplier)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good Luck&lt;/p&gt;&#xA;" OwnerUserId="2117" LastActivityDate="2010-11-30T00:12:44.863" CommentCount="1" />
  <row Id="7311" PostTypeId="1" AcceptedAnswerId="7312" CreationDate="2010-11-30T01:34:09.940" Score="2" ViewCount="98" Body="&lt;p&gt;This is a specific question about a specific circuit, but I'm trying to use it as a learning experience as I'm still new to electronics and need to take practical knowledge where I can get it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recently purchased a box online that plugs into the cd-changer port on my stock Honda car stereo and will allow me to use any RCA stereo source as an input. It's got one plug on it and an exposed wire coming off of the box-side of the plug. The included diagram has this single hanging wire labeled as &quot;Chassis ground when using portable device&quot; and the step-by-step instructions say &quot;NOTE: Chassis ground BLACK/WHITE wire ONLY when installing a battery operated audio device. (i.e. MP3 Player)&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm reading this as &quot;if the AUX device you're using is not connected to the car battery, you need to ground the box,&quot; but my question is: why? Why would I have to ground the circuit box only when the AUX device is not using the same power source? Would it hurt to ground the box when the AUX is connected to the car battery? I'm not really interested in this specific device, but the principles involved in the decision.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. &lt;a href=&quot;http://www.logjamelectronics.com/piehon98aux.html&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is the box.&lt;/p&gt;&#xA;" OwnerUserId="2024" LastActivityDate="2010-11-30T04:57:03.183" Title="Question About the Ground Wire on Aux Attachment Circuit for my Car" Tags="&lt;audio&gt;&lt;car&gt;" AnswerCount="1" />
  <row Id="7312" PostTypeId="2" ParentId="7311" CreationDate="2010-11-30T02:19:02.913" Score="3" ViewCount="" Body="&lt;p&gt;This is an issue with what is called a ground loop. When you have a device that powered by its own internal battery ground loops aren't an issue, but is an issue otherwise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest way I know how to explain a ground loop is that when you have 2 devices that have grounds at slightly different potentials they will start to fight with each other causing an audible hum to enter into your sound system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/FpsKO.png&quot; alt=&quot;ground loop&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a simple diagram of how your grounds will be connected. In an ideal world your wires has no inductance, resistance, or capacitance. Also in an ideal world ground is ground is ground. However, we don't live in an ideal world. In our world our wires have a resistance and you can generate a slight voltage difference between the ground of each device. When each of these devices creates its slight voltage offset on its ground lines, I am sure you could start to imagine a nasty problem to solve in order to determine whats actually going to happen in the loop. In general a resonance will be found in the fluctuations of voltages on the ground resulting in the hum I mentioned before. In addition to this, a loop like this can pick up lots of noise from the environment around it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, if you leave the connection between the car battery and interface disconnected you leave a single ground path for current to follow. As you add more devices you will want to follow a star or tree style topology. These topologies will remove all loops preventing all of the issues I described above. You will still have cases were there will be slightly different ground potentials, but this isn't a huge issue as they won't be having to battle with each other.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-11-30T04:57:03.183" LastActivityDate="2010-11-30T04:57:03.183" CommentCount="4" />
  <row Id="7313" PostTypeId="1" CreationDate="2010-11-30T02:42:27.220" Score="0" ViewCount="59" Body="&lt;p&gt;I have a MSI k9n6gm motherboard. It looks like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://us.msi.com/index.php?func=proddesc&amp;amp;maincat_no=1&amp;amp;prod_no=1872#&quot; rel=&quot;nofollow&quot;&gt;http://us.msi.com/index.php?func=proddesc&amp;amp;maincat_no=1&amp;amp;prod_no=1872#&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see, the fan's holes aren't really in a square; it's more of a rectangle. After asking a TigerDirect representative, I tried a fan. It didn't fit and I'm going to get a return/refund.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now they're suggesting this one:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Masscool 5F9001B1H3 CPU Cooling Fan - Socket 939, 940, AM2, AM2+ (I can't post more than one link, it's on TigerDirect)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since they failed me once, I want to investigate on my own this time.  How does one find fans that will fit their motherboard?&lt;/p&gt;&#xA;" LastActivityDate="2010-11-30T02:42:27.220" ClosedDate="2010-11-30T04:10:10.877" Title="How Do I Find Out Which Fan Will Fit My Motherboard?" Tags="&lt;fan&gt;&lt;processor&gt;" CommentCount="1" />
  <row Id="7314" PostTypeId="1" AcceptedAnswerId="7315" CreationDate="2010-11-30T02:58:18.357" Score="2" ViewCount="108" Body="&lt;p&gt;I have an application where I need to place something conductive, like aluminum foil, to a contact where an object will be sliding onto.  So it needs to be adhesive on one side, yet conduct from the top side to the bottom side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What product will do this or can be modified to do this?  Both thinness and durability are helpful variables but the requirements do not appear high.&lt;/p&gt;&#xA;" OwnerUserId="1297" LastEditorUserId="1297" LastEditorDisplayName="" LastEditDate="2010-11-30T15:36:00.707" LastActivityDate="2010-11-30T15:36:00.707" Title="Is there a conductive tape product that conducts from top to bottom?" Tags="&lt;conductive&gt;" AnswerCount="1" CommentCount="7" />
  <row Id="7315" PostTypeId="2" ParentId="7314" CreationDate="2010-11-30T04:54:03.497" Score="4" ViewCount="" Body="&lt;p&gt;What you want is foil tape with conductive &lt;em&gt;adhesive&lt;/em&gt; - used for EMI shielding. Most foil tapes that I've found are not made this way, however 3M does have a range specifically for this purpose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://solutions.3m.com/wps/portal/3M/en_US/electronics/home/productsandservices/products/ProductNavigator/TapeReel/?PC_7_RJH9U5230GE3E02LECIE20KAB4_nid=4LT3S54QPSbeRQ89J1RQDXgl&quot; rel=&quot;nofollow&quot;&gt;3M™ EMI Aluminum Foil Shielding Tape 1170, Conductive Acrylic Adhesive&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find it through various suppliers:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://au.element14.com/3m/1170/tape-adhesive-aluminium-19mm/dp/1208990?Ntt=1208990&quot; rel=&quot;nofollow&quot;&gt;Farnell&lt;/a&gt; (now Element 14 in&#xA;AU/NZ)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.amazon.com/3M-Aluminum-Foil-Cond-Acrylic/dp/B0000WRJIE/ref=sr_1_1?ie=UTF8&amp;amp;s=hi&amp;amp;qid=1291092759&amp;amp;sr=1-1&quot; rel=&quot;nofollow&quot;&gt;Amazon&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; You mention a sliding contact, so I thought it was worth mentioning that this product is just like aluminium foil - so may not be durable enough for that application. YMMV.&lt;/p&gt;&#xA;" OwnerUserId="554" LastActivityDate="2010-11-30T04:54:03.497" />
  <row Id="7316" PostTypeId="2" ParentId="3139" CreationDate="2010-11-30T09:46:48.623" Score="0" ViewCount="" Body="&lt;p&gt;Java buttons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;they exist. TI did it. Java Card IIRC&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-11-30T09:46:48.623" />
  <row Id="7317" PostTypeId="2" ParentId="7252" CreationDate="2010-11-30T10:18:12.470" Score="2" ViewCount="" Body="&lt;p&gt;Kinematics and Dynamics. Control Systems. Embedded Systems. Actuators. Sensors. AI. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That is it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I learned this things in &quot;Mechatronics&quot;. which is more or less Robotics and Electronics. As a professional, you will need to know many things and will need college. As a hobbyist, this forum is enough. :)&lt;/p&gt;&#xA;" OwnerUserId="1312" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-30T14:59:34.720" LastActivityDate="2010-11-30T14:59:34.720" CommentCount="1" />
  <row Id="7318" PostTypeId="1" CreationDate="2010-11-30T13:57:20.417" Score="1" ViewCount="91" Body="&lt;p&gt;In industrial automation, often parts need to be separated and aligned/oriented for a machine to pick them up in manufacturing.&#xA;The easiest object or part is probably a sphere: it infinitely rolls in any direction (as its center of gravity coincides with its geometrical center).&#xA;But even spheres may jam in a funnel. I've &lt;a href=&quot;http://www.youtube.com/user/denha#p/u/52/BUjoAXhu46Q&quot; rel=&quot;nofollow&quot;&gt;found a few mechanisms for marble machines&lt;/a&gt;, but no literature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now in addition to more general, 'scientific' readings, I need to dispense four balls simultaneously and am grateful for ideas!&lt;/p&gt;&#xA;" OwnerUserId="2123" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-30T15:11:21.170" LastActivityDate="2010-12-01T03:09:52.133" Title="Separate marbles / balls from a funnel/hopper? Engineering branch and literature for design of industrial feeders?" Tags="&lt;robotics&gt;&lt;engineering&gt;&lt;automation&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="7319" PostTypeId="1" AcceptedAnswerId="7320" CreationDate="2010-11-30T14:56:01.683" Score="0" ViewCount="262" Body="&lt;p&gt;I made a simple motor driver as suggested &lt;a href=&quot;http://electronics.stackexchange.com/questions/7235/motor-driver-using-only-2n2222-transistor&quot;&gt;here&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;+12V ---------+---------+          &#xA;              |         |&#xA;             / \        |&#xA;             |M| motor ---  1N4001&#xA;             \ /       / \&#xA;              |         |&#xA;              +---------+&#xA;              |&#xA;            |/&#xA;CTL -/\/\/--|    2N2222 NPN       &#xA;      1k    |\&amp;gt;&#xA;              |&#xA;             ---&#xA;              -                    &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;How do I connect and control this with and Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you please post instructions or direct me to some links I may find useful.&lt;/p&gt;&#xA;" OwnerUserId="2074" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-30T15:46:37.903" LastActivityDate="2010-11-30T15:51:59.210" Title="DC Motor driver with Arduino" Tags="&lt;arduino&gt;&lt;motor&gt;&lt;driver&gt;" AnswerCount="2" CommentCount="11" />
  <row Id="7320" PostTypeId="2" ParentId="7319" CreationDate="2010-11-30T15:02:06.093" Score="3" ViewCount="" Body="&lt;pre&gt;&lt;code&gt;+12V ---------+---------+          (Connect to the Vin or 9v on the Arduino)&#xA;              |         |&#xA;             / \        |&#xA;             |M| motor ---  1N4001&#xA;             \ /       / \&#xA;              |         |&#xA;              +---------+&#xA;              |&#xA;            |/&#xA;CTL -/\/\/--|    2N2222 NPN        (Connect CTL to your Digital out pin)&#xA;      1k    |\&amp;gt;&#xA;              |&#xA;             ---&#xA;              -                    (Connect this to Gnd)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-11-30T15:02:06.093" CommentCount="2" />
  <row Id="7321" PostTypeId="2" ParentId="7319" CreationDate="2010-11-30T15:02:55.523" Score="1" ViewCount="" Body="&lt;p&gt;Connect the control pin for your motor driver to a digital output pin of the Arduino, 13 is a good choice.&#xA;Connect the Arduino's ground pin to the ground of your driver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an Arduino sketch to loop, turning it on and off.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int CTLPin = 13;                 // CTL connected to digital pin 13&#xA;&#xA;void setup()&#xA;{&#xA;  pinMode(CTLPin, OUTPUT);      // sets the digital pin as output&#xA;}&#xA;&#xA;void loop()&#xA;{&#xA;  digitalWrite(CTLPin, HIGH);   // sets the motor on&#xA;  delay(1000);                  // waits for a second&#xA;  digitalWrite(CTLPin, LOW);    // sets the motor off&#xA;  delay(1000);                  // waits for a second&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-30T15:51:59.210" LastActivityDate="2010-11-30T15:51:59.210" />
  <row Id="7322" PostTypeId="1" AcceptedAnswerId="7371" CreationDate="2010-11-30T15:29:52.490" Score="13" ViewCount="494" Body="&lt;p&gt;I have a decent amount of experience designing hardware and embedded systems in general, but I have never written a driver for an operating system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to know if there are any good guides, preferably online, although good books would interest me, that will give me a good start on what I need to know to design and implement drivers for an operating system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will probably have people shooting at me, and although I would love to see a good guide no matter what OS it is based on, I would like to see a guide that is windows based, mostly due to the fact that most of the people I would sell a product would have windows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please let me know if there is any extra information I can add to make this more clear.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-01T06:08:58.660" Title="Are there resources for learning to write drivers?" Tags="&lt;driver&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="10" />
  <row Id="7323" PostTypeId="1" AcceptedAnswerId="7328" CreationDate="2010-11-30T15:40:44.653" Score="1" ViewCount="112" Body="&lt;p&gt;To &lt;a href=&quot;http://electronics.stackexchange.com/questions/3139/1-wire-parasitically-powered-microcontroller&quot;&gt;follow up and enhance the question&lt;/a&gt; on powering MCU with parasitc one-wire interface.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How to ensure proper power on reset of MCU in such situation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example this two standard method of generating power on reset may fail:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;a) resistor/capacitor delay generated reset -&gt; during power rump up, for extensive period of time data line can be low (for example due to data transmission) or pulled up only by significant resistance. This may slow MCU local supply rise time to the level that will render RC delay useless.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;b) global, board level reset may not work as most probably will be removed before local MCU supply will stabilize as the &quot;master&quot; side of 1-wire will provide power only after reset is removed (not to mention that routing reset line defy point of using one-wire interface)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of precautions needs to be taken in such situations? Should MCU be equipped with brownout detection? Is that enough?&lt;/p&gt;&#xA;" OwnerUserId="1471" LastActivityDate="2010-11-30T16:28:38.120" Title="How to ensure proper power on reset in one-wire parasiticly supplied MCU?" Tags="&lt;microcontroller&gt;&lt;one-wire&gt;&lt;power-on-reset&gt;" AnswerCount="1" />
  <row Id="7324" PostTypeId="2" ParentId="7322" CreationDate="2010-11-30T15:42:17.313" Score="9" ViewCount="" Body="&lt;p&gt;A good driver encapsulates the capabilities of the hardware and makes these available to the OS/applications in a natural way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How best to do this, depends a lot on which operating system you're targetting and what sort of hardware the driver is for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My experience is all with Linux and small custom real-time OSen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For Linux, I'd recommend reading &lt;a href=&quot;http://lwn.net/Kernel/LDD3/&quot; rel=&quot;nofollow&quot;&gt;Linux Device Drivers&lt;/a&gt;. It's give a good introduction to the different flavours of Linux drivers and the abstractions the operating system provides for them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Devices like serial ports where data is read sequentially are usually handled by character device drivers with a device node in userspace for applications to read from. &lt;code&gt;cat&lt;/code&gt; can read from these.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Random access devices like flash storage and hard disks are handled by block devices. &lt;code&gt;dd&lt;/code&gt; can access these. For a good example, have a look at the &lt;a href=&quot;http://www.linux-mtd.infradead.org/&quot; rel=&quot;nofollow&quot;&gt;Linux MTD&lt;/a&gt; system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Drivers which do low level fiddling with hardware will almost certainly need to be implemented in kernel space. You might choose to make a runtime loadable kernel module or to place your code in statically in the linux kernel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Drivers which build on top of existing generic drivers, like USB, may be written in userspace. Using, for example, &lt;a href=&quot;http://www.libusb.org/&quot; rel=&quot;nofollow&quot;&gt;libusb&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-30T16:22:57.733" LastActivityDate="2010-11-30T16:22:57.733" CommentCount="4" />
  <row Id="7325" PostTypeId="1" AcceptedAnswerId="7331" CreationDate="2010-11-30T16:04:46.937" Score="1" ViewCount="81" Body="&lt;p&gt;I have a signal that consists of N frequencies all with unknown phase and frequency(N) = frequency(N-1) + 2Hz. I would like to selectively scale the amplitudes of some of those signals in such a way that I can change which frequencies to scale and how much to scale them on the fly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this possible?&#xA;How complex of a circuit would this be?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Analog? Digital? or Both?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where should I start?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="2085" LastActivityDate="2010-11-30T16:48:15.617" Title="Frequency Filtration" Tags="&lt;circuit&gt;&lt;frequency&gt;&lt;filter&gt;&lt;signal&gt;" AnswerCount="4" CommentCount="8" FavoriteCount="2" />
  <row Id="7326" PostTypeId="2" ParentId="7322" CreationDate="2010-11-30T16:11:54.833" Score="2" ViewCount="" Body="&lt;p&gt;I don't have any experience in this issue, but I'm going to give my two cents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can start here &lt;a href=&quot;http://www.osr.com/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.osr.com/index.html&lt;/a&gt; or here &lt;a href=&quot;https://www.osronline.com/index.cfm&quot; rel=&quot;nofollow&quot;&gt;https://www.osronline.com/index.cfm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here in Brazil we have a &lt;a href=&quot;http://driverentry.com.br/en/blog&quot; rel=&quot;nofollow&quot;&gt;good blog&lt;/a&gt; about this issue. It's written in Portuguese and English. Most articles are in Portuguese unfortunately. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a post in Portuguese about books in this blog: &lt;a href=&quot;http://translate.google.com.br/translate?hl=pt-BR&amp;amp;ie=UTF-8&amp;amp;sl=pt&amp;amp;tl=en&amp;amp;u=http://driverentry.com.br/blog/%3Fp%3D825&amp;amp;twu=1&quot; rel=&quot;nofollow&quot;&gt;http://translate.google.com.br/translate?hl=pt-BR&amp;amp;ie=UTF-8&amp;amp;sl=pt&amp;amp;tl=en&amp;amp;u=http://driverentry.com.br/blog/%3Fp%3D825&amp;amp;twu=1&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope I have helped a little&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-11-30T17:12:06.897" LastActivityDate="2010-11-30T17:12:06.897" CommentCount="3" />
  <row Id="7327" PostTypeId="2" ParentId="7325" CreationDate="2010-11-30T16:16:56.747" Score="1" ViewCount="" Body="&lt;p&gt;It would need to be digital for any good number of N.  Start with a basic digital filter book.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-11-30T16:16:56.747" />
  <row Id="7328" PostTypeId="2" ParentId="7323" CreationDate="2010-11-30T16:28:38.120" Score="2" ViewCount="" Body="&lt;p&gt;As you've noticed, RC on the reset pin is not going to work when you have very slow voltage rise times.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Built-in brownout detection may work, but read the microprocessor's datasheet carefully to see if there is a minimum rise time on the supply voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are not sure built-in brownout detection will work, you can use a &quot;voltage supervisor&quot; chip.  The basic supervisor is a three-terminal device that connects to power and ground, and pulls the output low when the power voltage is below the setpoint.  Connect it to reset and you're good to go.  You can buy these in a variety of voltages and turn-on delays.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-30T16:28:38.120" CommentCount="1" />
  <row Id="7329" PostTypeId="2" ParentId="7325" CreationDate="2010-11-30T16:35:49.750" Score="0" ViewCount="" Body="&lt;p&gt;You will probably need to use digital signal processing.&lt;br&gt;&#xA;Check out &lt;a href=&quot;http://www.dspguide.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.dspguide.com/&lt;/a&gt; for a primer on DSP.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-11-30T16:35:49.750" />
  <row Id="7330" PostTypeId="1" AcceptedAnswerId="7332" CreationDate="2010-11-30T16:38:31.197" Score="1" ViewCount="352" Body="&lt;p&gt;I'm working on getting an ATMega168 to talk to my GPS that I ripped out of the casing from Microsoft Streets and Trips. I know it talks RS232 @ 5v (according to &lt;a href=&quot;http://www.flickr.com/photos/imager/4383334403/&quot; rel=&quot;nofollow&quot;&gt;this post&lt;/a&gt;) and I just need to listen on pin 3 and apply 5v to pin 5 and ground to pin 2. I'm having a hard time finding good info on how to use the MAX232 and I just followed a diagram from somewhere but I omitted all capacitors as I need to get some. I'm using the FTDI from an Arduino to forward any TTL to my computer and I get a special &quot;y&quot; symbol coming in when I unplug the data out from the GPS and I get the initial &quot;Hello World&quot; serial message I have in there, so I think the MCU side is all good. Do I really need these caps that I ommitted on the MAX232 chip? Why? Is there some other issue? How do I troubleshoot? I've got no scope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my pinout for the MAX232:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;2 -&amp;gt; +5v&#xA;6 -&amp;gt; GND&#xA;8 -&amp;gt; GPS RX (pin 3)&#xA;9 -&amp;gt; MCU Digital in (software UART)&#xA;15 -&amp;gt; GND&#xA;16 -&amp;gt; +5v&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-12-01T16:42:32.413" Title="Arduino + MAX232 + Pharos GPS360" Tags="&lt;atmega&gt;&lt;rs232&gt;&lt;gps&gt;" AnswerCount="2" />
  <row Id="7331" PostTypeId="2" ParentId="7325" CreationDate="2010-11-30T16:41:46.463" Score="2" ViewCount="" Body="&lt;p&gt;To expand on Brian, making a filter with analog components that has a very small passband with a fast transition into the stop band is nearly impossible, while this is very very easy with a digital system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will have to sample at-least twice as fast as the fastest signal. I would suggest making sure you are at-least 2.1 times faster.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For will need to design one gigantic filter that changes each frequency by the amount you want. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to control the magnitude of each signal separately then you will have to make N digital filters, create N datasets, apply the N different gains, and then recombine the signals, if you filtering is good you will just be able to sum to recombine. Do not take too much solace in this as it is the only easy step.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sharper you want your transitions the more data-points the filter will need. There is no way around this, it has been proven mathematically. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me know in a comment if I can add more to help.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-30T16:41:46.463" CommentCount="4" />
  <row Id="7332" PostTypeId="2" ParentId="7330" CreationDate="2010-11-30T16:44:08.913" Score="4" ViewCount="" Body="&lt;p&gt;The MAX232 is a charge pump.  It fills a cap with charge, then moves it to the other side of the supply rail.  For example, if you charge a cap on the 5V rail, then disconnect it and connect the low side of the cap to +5V, the high side will now be at +10V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In short, the capacitors are how the MAX232 makes its high voltages from the lower supply voltage.  It will not function without caps.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-30T16:44:08.913" CommentCount="6" />
  <row Id="7333" PostTypeId="1" CreationDate="2010-11-30T16:46:24.200" Score="2" ViewCount="235" Body="&lt;p&gt;I am sending off a pcb for manufactering, but it would be nice to round off the corners for them to mill off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I make nice rounded corners? I have used the three point arc thing before but I dont really like that...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In what layer should I specify what should be milled off?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm also intrested in how to specify a small rectangle (ca 20 x 10 mm) to be milled in the middle of the card?&lt;/p&gt;&#xA;" OwnerUserId="1605" LastEditorUserId="1605" LastEditorDisplayName="" LastEditDate="2010-11-30T18:26:54.230" LastActivityDate="2010-11-30T18:26:54.230" Title="Rounded corners in Eagle Cad" Tags="&lt;pcb&gt;&lt;eagle&gt;&lt;manufacturing&gt;&lt;cad&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="7334" PostTypeId="1" AcceptedAnswerId="7341" CreationDate="2010-11-30T16:47:14.433" Score="1" ViewCount="93" Body="&lt;p&gt;For a 24MHz system, the local clock error associated with transmitting 10-bit character frames at 38.4 Kbaud using the SCI of a Freescale Micro is 0.16%. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How? I can't figure out the math that actually makes sense to get that number. Any ideas? I'm sure it's easy.&lt;/p&gt;&#xA;" LastActivityDate="2010-11-30T17:13:41.853" Title="Serial Communication and Local Clock error calculation" Tags="&lt;electrical-engineering&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="7335" PostTypeId="2" ParentId="7325" CreationDate="2010-11-30T16:48:15.617" Score="2" ViewCount="" Body="&lt;p&gt;For that many passbands, you can take your signal, chunk it into windows, then FFT the window.  (You will need a huge window for a million bins.)  Then scale the magnitude of each frequency bin as desired, then do the inverse FFT, then reassemble the chunks into a continuous stream.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will scramble phase a little bit, but it works well enough in many applications.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-30T16:48:15.617" CommentCount="4" />
  <row Id="7336" PostTypeId="2" ParentId="7334" CreationDate="2010-11-30T16:54:38.573" Score="2" ViewCount="" Body="&lt;p&gt;I don't have the Freescale datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But 24MHz / 38400 baud is exactly 625 cycles per symbol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will guess that there is an unavoidable divide in the clock or baudrate generator, so the desired ratio is half of 625 or 312.5.  The closest an integer counter can come is 312.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;312 is 0.16% lower than 312.5&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-30T16:54:38.573" CommentCount="8" />
  <row Id="7337" PostTypeId="2" ParentId="7333" CreationDate="2010-11-30T17:01:00.280" Score="1" ViewCount="" Body="&lt;p&gt;You will need to send the fab house a gerber file of the board outline. It is in this layer that you will want the rounded corners. You might want to see if you can place a rectangle with rounded corners or change an existing rectangle to have rounded corners. I am not sure of the specifics of this in eagle, maybe someone else can help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Warning though, not all fab houses will do rounded corners without any extra charge. Check this with your fab house.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-11-30T17:01:00.280" CommentCount="1" />
  <row Id="7338" PostTypeId="1" CreationDate="2010-11-30T17:06:21.347" Score="1" ViewCount="58" Body="&lt;p&gt;I have a custom driver I have written.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the source code to communicate to the driver in C:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;windows.h&amp;gt;&#xA;#include &amp;lt;stdio.h&amp;gt;&#xA;&#xA;/*********************************************************&#xA;* Main Function Entry&#xA;*&#xA;*********************************************************/&#xA;int _cdecl main(void)&#xA;{&#xA;HANDLE hFile;&#xA;DWORD dwReturn;&#xA;&#xA;hFile = CreateFile(&quot;\\\\.\\Example&quot;, GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);&#xA;&#xA;if(hFile)&#xA;{&#xA;WriteFile(hFile, &quot;Hello from user mode!&quot;, sizeof(&quot;Hello from user mode!&quot;), &amp;amp;dwReturn, NULL);&#xA;CloseHandle(hFile);&#xA;}&#xA;&#xA;return 0;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I want to be able to do this in .NET preferaly in VB.NET.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know how to do the conversion?&lt;/p&gt;&#xA;" OwnerUserId="1413" LastActivityDate="2010-11-30T17:06:21.347" ClosedDate="2010-11-30T17:17:40.820" Title="I need help converting my driver user interface code" Tags="&lt;driver&gt;&lt;c&gt;&lt;.net&gt;&lt;conversion&gt;" CommentCount="4" FavoriteCount="1" />
  <row Id="7339" PostTypeId="2" ParentId="7334" CreationDate="2010-11-30T17:07:47.600" Score="1" ViewCount="" Body="&lt;p&gt;Here's a tool (for AVR) that demonstrates the calculations. It's all about integer divison of the baud rate and system clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.wormfood.net/avrbaudcalc.php&quot; rel=&quot;nofollow&quot;&gt;http://www.wormfood.net/avrbaudcalc.php&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-11-30T17:13:41.853" LastActivityDate="2010-11-30T17:13:41.853" />
  <row Id="7340" PostTypeId="1" AcceptedAnswerId="7342" CreationDate="2010-11-30T17:10:58.457" Score="5" ViewCount="249" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I found on SparkFun a &lt;a href=&quot;http://www.sparkfun.com/products/9623&quot; rel=&quot;nofollow&quot;&gt;module&lt;/a&gt; which detects movement in 9 degrees of freedom (DOF). I'm only aware of 6 DOF: translation in X, Y, Z direction, and rotation about X, Y and Z axis. What are the other three?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;I'm aware that there are robots with more than 6 DOF, but in these each segment has only 6 DOF maximum. The human hand (including wrist) has 23 DOF.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-11-30T17:26:24.900" LastActivityDate="2010-11-30T17:26:24.900" Title="What are 9 degrees of freedom in robotics?" Tags="&lt;sensor&gt;&lt;dof&gt;" AnswerCount="1" CommentCount="11" />
  <row Id="7341" PostTypeId="2" ParentId="7334" CreationDate="2010-11-30T17:12:16.630" Score="2" ViewCount="" Body="&lt;p&gt;Typically an asynchronous communication pin is sampled at 16 times the bit rate.  This implies a baudrate generator of:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;24000000 / 16 / 38400 = 39.0625&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Since the resulting integer value is 39, the resulting error is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;0.0625 / 39.0625 = 0.0016 or 0.16%&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-11-30T17:12:16.630" CommentCount="1" />
  <row Id="7342" PostTypeId="2" ParentId="7340" CreationDate="2010-11-30T17:13:07.267" Score="6" ViewCount="" Body="&lt;p&gt;I think that the other three with that module are the outputs from the magnetometer.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-30T17:13:07.267" CommentCount="4" />
  <row Id="7343" PostTypeId="2" ParentId="7333" CreationDate="2010-11-30T17:47:45.663" Score="1" ViewCount="" Body="&lt;p&gt;In Eagle, the &quot;Dimension&quot; layer represents the perimeter of your board. You can create a new board perimeter by drawing an enclosed shape using the WIRE command to draw a new enclosed polygon. When you draw your lines, you have the option of changing the wire bend to go straight and then arc (option 6 and 7). I used a width of 0 for the shape.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you go to export the design, you can export the outline separately or on a existing layer. For example, BatchPCB suggests adding the outline to the silkscreen layer, or having a separate outline gerber. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll second Kellenjb's comment that not all board houses are thrilled at the idea of arbitrary board shapes, so you may pay extra for the rounding.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-11-30T17:47:45.663" CommentCount="2" />
  <row Id="7344" PostTypeId="1" AcceptedAnswerId="7345" CreationDate="2010-11-30T18:30:06.193" Score="1" ViewCount="294" Body="&lt;p&gt;This question is continuation of &lt;a href=&quot;http://electronics.stackexchange.com/q/6629/1240&quot;&gt;this&lt;/a&gt; question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did some research on previous question and made a circuit as a starting point. Here's a picture: &#xA;&lt;img src=&quot;http://i.imgur.com/CoK9t.png&quot; alt=&quot;image of the circuit as displayed in a simulator&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now my problem is that TS555 device I plan to use can't drive those LEDs, so I'll most likely have to use a transistor for switching. My problem is that I have no idea where to start looking for a suitable transistor and that I'm generally confused about transistor naming schemes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, general comments are welcome.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-11-30T21:33:57.573" Title="LED flashlight project: Need transistor ideas" Tags="&lt;led&gt;&lt;transistor&gt;&lt;555&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="7345" PostTypeId="2" ParentId="7344" CreationDate="2010-11-30T19:45:59.757" Score="9" ViewCount="" Body="&lt;h3&gt;Short Answer&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Transistor part numbers are totally arbitrary and seldom have anything to do with a particular parameter.  The best way to find one you need is 1) look through what you have, and if that fails 2) use parametric searches on distributors (e.g. Digi-Key &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1376376&quot; rel=&quot;nofollow&quot;&gt;BJTs&lt;/a&gt; or &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1376381&quot; rel=&quot;nofollow&quot;&gt;MOSFETs&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 2N2222 (very common NPN) should be able to power 10x LEDs well.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Long Answer&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;You're using a moderate amount of current, so I might use an N-channel MOSFET instead of a BJT, it's the easiest to control and doesn't have a fixed voltage drop.  A &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=ZVN4206A-ND&quot; rel=&quot;nofollow&quot;&gt;ZVN4206A&lt;/a&gt; would be a TO-92 that might work.  Regardless between that and a BJT, you need a transistor with:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A voltage rating, &lt;em&gt;Vds&lt;/em&gt; (or &lt;em&gt;Vce&lt;/em&gt; for a BJT), greater than your supply (1.5x or more recommended)&lt;/li&gt;&#xA;&lt;li&gt;A current rating, &lt;em&gt;Id&lt;/em&gt; (or &lt;em&gt;Ic&lt;/em&gt;), greater than the current that your LEDs will take (this depends on temperature; if you will be running it outside of room temperature you will have to derate this)&lt;/li&gt;&#xA;&lt;li&gt;A threshold voltage, &lt;em&gt;Vgs(th)&lt;/em&gt;, that will allow it to be fully turned on with your input voltage (&quot;logic-level&quot; is something to look for)&#xA;&lt;ul&gt;&#xA;&lt;li&gt;For a BJT you need to make sure you can drive enough current into the base to saturate the transistor against the base-emitter saturation voltage, &lt;em&gt;Vbe(sat)&lt;/em&gt;.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Connect it like so (image from &lt;a href=&quot;http://www.electronics-tutorials.ws/transistor/tran_7.html&quot; rel=&quot;nofollow&quot;&gt;Electronics Tutorials&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/6AsA9.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(For a BJT, it would be similar, but Collector instead of D(rain), Base for G(ate), and Emitter--S(ource))&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;lamp&quot; would be your string of LEDs, however you want to configure them.  The diode isn't required for non-inductive loads (generally &quot;things that aren't motors&quot;).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the advantages of this low-side switch configuration is your logic can be at a fairly low voltage (3.3-5 V), while your load supply voltage can be whatever your transistor can withstand (500-1000 V, whatever).&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;h2&gt;Edit&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;You mention this is for a specific LED flashlight project.  If your main focus is powering LEDs, you could look at something more advanced: an LED driver.  The Linear Technology &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1035,P2079&quot; rel=&quot;nofollow&quot;&gt;LT1618&lt;/a&gt; can step up voltage from 1.8 V allowing you to supply it with 2 or 3 alkaline cells, and provides current regulation, so you can eliminate all (or at least most of) the LED ballast resistors.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example from the datasheet:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/1TG3M.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LT1618 or a similar step-up regulator would provide you with the most efficient driving method, both from an electrical point of view and mechanical, as you can use more space-efficient cells (D &gt; C &gt; AA &gt;&gt; AAA &gt;&gt;&gt; 9V)&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-30T21:33:57.573" LastActivityDate="2010-11-30T21:33:57.573" CommentCount="8" />
  <row Id="7346" PostTypeId="1" AcceptedAnswerId="7347" CreationDate="2010-11-30T21:36:07.427" Score="2" ViewCount="207" Body="&lt;p&gt;In my project I am planning on using 10 AAA Batteries(to give me 12v as each battery is 1.2v) to power my project. I am wondering if there will be any voltage drop when I connect a load. If so how can it be calculated? This is so that I can account for it.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-11-30T22:37:26.907" LastActivityDate="2010-11-30T23:42:51.483" Title="Will there be any voltage drop when connecting load to batteries?" Tags="&lt;batteries&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="7347" PostTypeId="2" ParentId="7346" CreationDate="2010-11-30T21:41:54.370" Score="3" ViewCount="" Body="&lt;p&gt;Yes, the voltage will drop.  A reasonable approximation would be the internal resistance of the cells and other resistances in the wires, switches, etc, times the current consumption.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On an unrelated note, using 10 AAA cells sounds like a bad idea; AAAs have very poor energy density (wasted space due to the casing, etc) compared to AAs.  I would suggest using larger cells and a step-up regulator.  On a related note, larger cells also have lower internal resistances.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Energizer Datasheets/Whitepapers:&lt;/h3&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://data.energizer.com/PDFs/BatteryIR.pdf&quot; rel=&quot;nofollow&quot;&gt;Battery Internal Resistance&lt;/a&gt; technical bulletin&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://data.energizer.com/PDFs/E92.pdf&quot; rel=&quot;nofollow&quot;&gt;E92 cell&lt;/a&gt; datasheet (AAA)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-11-30T22:30:14.090" LastActivityDate="2010-11-30T22:30:14.090" CommentCount="6" />
  <row Id="7348" PostTypeId="1" AcceptedAnswerId="7352" CreationDate="2010-11-30T21:49:57.287" Score="3" ViewCount="202" Body="&lt;p&gt;Most microcontrollers (e.g. AVRs,MSP430s, PICs, etc) support a number of different sleep modes. The &quot;deepest&quot; sleep mode is the one that purports the lowest power draw (e.g. &quot;Power Down&quot;, &quot;Shut Down&quot;), but all the clock systems are typically halted in these modes and it seems to me that the only way to &quot;wake up&quot; from them is via external stimulus (e.g. pin change interrupts, chip reset). Am I missing something? Are there awesomely low power methods of generating a periodic wakeup signal for an MCU?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming my goal is to minimize power consumption (i.e. sleep deeply for as long as possible, stay awake as briefly as possible), while periodically waking up to execute a function, what's the common way to achieve this type of behavior? To further simplify matters, lets assume that my function is stateless (I don't have to remember anything from the past to perform it). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've had some success using the WDT on the MSP430 to get this effect. I just made my main routine be my function, with the last line enabling the watchdog timer to expire after a certain period and going into LPM4.5 or whatever the &quot;deep sleep&quot; mode is called. The net result is the function is performed, the MCU sleeps, the WDT expires, and the chip resets, ad nauseum. Seems to work, just wondering if there is a &quot;better&quot; or &quot;more elegant&quot; or &quot;more power efficient&quot; way of getting this type of behavior?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't tried this approach with an AVR yet, but I think the WDT is more &quot;power hungry&quot; in the AVRs than on the MSP430 so it may be less attractive for low power work. Perhaps there is not a &quot;universal&quot; approach to low power, and you have to use the tools afforded by a given product line? I know the new picoPower line has lots of whiz-bang features like the Event System and Sleep Walking that in some cases hardly require the CPU to be awake at all if you can make your application fit into that structure...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK enough of my wandering, lets here what ya'll have to say :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Edit&lt;/em&gt; &#xA;Concrete examples illustrating techniques would also be cool!&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-11-30T22:10:34.707" LastActivityDate="2010-11-30T23:48:16.127" Title="Waking Up From Deep Sleep Modes" Tags="&lt;microcontroller&gt;&lt;avr&gt;&lt;msp430&gt;&lt;low-power&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="7349" PostTypeId="2" ParentId="5549" CreationDate="2010-11-30T21:51:05.757" Score="0" ViewCount="" Body="&lt;p&gt;You should avoid acute angles where tracks meet pads; I can see one near the centre of the image, and you might have some more on the rest of the board. They can cause problems in manufacture, and look ugly.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-11-30T21:51:05.757" />
  <row Id="7350" PostTypeId="2" ParentId="5549" CreationDate="2010-11-30T22:00:51.207" Score="2" ViewCount="" Body="&lt;p&gt;You are setting up DRC at the wrong end of the process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whether you set the DRC values to reasonable values (for an open-source project) or specific values for a particular manufacturer, you need to do it at the beginning of a project.  Then you run the DRC checker periodically during layout and keep it DRC-clean.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most pcb layout software, including the one you are using, includes an option to &quot;auto-enforce DRC clearance.&quot;  This option will help you keep out of trouble.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you are at the end of the layout trying to fix up DRC at the end.  This is going to be a pain.  You may end up re-laying-out most of the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Experience is a hard teacher, the lessons come after the tests.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-11-30T22:00:51.207" />
  <row Id="7351" PostTypeId="2" ParentId="556" CreationDate="2010-11-30T22:03:23.693" Score="0" ViewCount="" Body="&lt;p&gt;I have worked up a schematic from the &quot;the cube&quot; hardware from Dave Hiller. The difference&#xA;is that it uses an external 12v power source (does not draw power from usb) and drives&#xA;three NPN power transistors to power 5m of RGB LED Strip (1A). Or, to generate a signal for an external signal amplifiers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am posting this to get feed back (I don't have a test suite to test it out) to see if it should work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://i51.photobucket.com/albums/f382/sfranzyshen/usbrgbledstrip.png&quot; rel=&quot;nofollow&quot;&gt;schematic&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2129" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T14:11:23.433" LastActivityDate="2011-05-16T14:11:23.433" />
  <row Id="7352" PostTypeId="2" ParentId="7348" CreationDate="2010-11-30T22:05:33.977" Score="7" ViewCount="" Body="&lt;p&gt;Most micros support a low-power 32.768 kHz watch crystal oscillator with some kind of prescaler and timer interrupt.  Set the prescaler so the timer is counting slowly and the interrupt happens at the period you desire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some micros also have a built-in low-power RC timer if exact timing isn't critical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet for any low-power micro will list the power with 32.768 oscillator (and nothing else) running.  It's pretty close to zero.  You can do the math to see if this is acceptable, and compare it to the current drawn by the watchdog.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK, for example on the msp430f2013, let's look at power in the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;0.5 μA is almost zero, although it is five times the true OFF mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For more detail, we can look inside the datasheet.&lt;br&gt;&#xA;Going from LPM4 (everything off) to LPM3 (running the oscillator) is the difference between 0.5 μA and 1 μA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Suppose the battery is CR2032 with 225 mAh capacity.  Then standby in LPM4 is about 50 years and in LPM3 is about 25 years.  25 years is long enough for many applications, because the ON-current (during the measurement itself) dominates the consumption.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/u5pnE.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-11-30T22:36:27.780" LastActivityDate="2010-11-30T22:36:27.780" CommentCount="3" />
  <row Id="7353" PostTypeId="2" ParentId="7346" CreationDate="2010-11-30T22:06:33.663" Score="2" ViewCount="" Body="&lt;p&gt;The short answer is it depends how much current your load draws. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The longer answer is, I believe, that if you are attempting to draw more current than the batteries can source chemically (batteries are not an &quot;ideal voltage source&quot;), you will see a the battery voltage dip sharply attempting to compensate for this imbalance. Regardless of this effect, the internal resistance of the battery will induce a voltage drop proportional to the current drawn by the load as well. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can calculate the internal resistance of a battery (Rb) by (1) measuring the open circuit voltage (V) of the battery using a voltmeter, then (2) using a known resistor (R) (e.g. 5% 10kOhm resistor) and measuring the current (I) it draws from the battery (using an ammeter to complete the circuit). The deviation from V = I * R is due to the internal battery resistance, i.e. in reality V = I * (R + Rb) so... Rb = V/I - R. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously the quality of that calculation is tied pretty much directly to the accuracy of the known resistor as well as the accuracy of your measurement equipment.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-11-30T22:06:33.663" />
  <row Id="7354" PostTypeId="1" AcceptedAnswerId="7356" CreationDate="2010-11-30T22:10:54.883" Score="5" ViewCount="333" Body="&lt;p&gt;I am debating which micro-controller to use for a new open source hardware project.  Spec wise, I would rather use an ARM Cortex M3, which is at a similar price-point to an Arduino(avr) based solution but with more processing power/peripherals.  The only concern I have going with ARM based hardware is I don't want to lose potential contributors/developers who might be put off by working with ARM.  Or competition wise--someone reproducing the project but with an arduino instead(e.g. Ardupilot overtaking Paparazzi)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I realize there is no straightforward answer to this question but I would like to hear your thoughts on the topic, and what other factors you think might weigh more on the success of the project.&lt;/p&gt;&#xA;" OwnerUserId="2115" LastActivityDate="2010-12-02T13:14:43.110" Title="Does my open source project need be Arduino based to be successful?" Tags="&lt;arduino&gt;&lt;arm&gt;&lt;open-source&gt;" AnswerCount="7" />
  <row Id="7355" PostTypeId="2" ParentId="2024" CreationDate="2010-11-30T22:15:10.040" Score="0" ViewCount="" Body="&lt;p&gt;Scratch for Arduino (S4A) &lt;a href=&quot;http://seaside.citilab.eu/scratch/arduino&quot; rel=&quot;nofollow&quot;&gt;http://seaside.citilab.eu/scratch/arduino&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-11-30T22:15:10.040" />
  <row Id="7356" PostTypeId="2" ParentId="7354" CreationDate="2010-11-30T22:27:36.833" Score="9" ViewCount="" Body="&lt;p&gt;I think it depends who you're trying to attract. Having an Arduino derivative which can be programmed directly from the Arduino IDE will attract Arduino users.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, in my experience, the average Arduino user is not neccessarily a skilled developer who will contribute usefully to a project. Of course, there are many expert Arduino users, but it's a device aimed at the beginner.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, the kind of user who can get a toolchain and debugger going for ARM Cortex-M3 is also likely to be capable of fixing your bugs for you. But, there are considerably less of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd say - pick what's right for your project. If it's good, users will get involved.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-11-30T22:27:36.833" CommentCount="5" />
  <row Id="7357" PostTypeId="2" ParentId="991" CreationDate="2010-11-30T22:49:23.123" Score="2" ViewCount="" Body="&lt;p&gt;I use Yagarto + Eclipse + J-link edu debugger.&#xA;(Gnu toolchain)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.yagarto.de/&quot; rel=&quot;nofollow&quot;&gt;http://www.yagarto.de/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2115" LastActivityDate="2010-11-30T22:49:23.123" />
  <row Id="7358" PostTypeId="2" ParentId="7354" CreationDate="2010-11-30T22:54:27.953" Score="8" ViewCount="" Body="&lt;p&gt;The way to have a successful open source project is to get people interested in it.  &lt;strong&gt;Just because your project is open source doesn't mean anyone will want to work on it&lt;/strong&gt; (or care).  Your project needs to be interesting beyond &quot;oh, I know [language] and have the toolchain for [development environment]&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The product engineer in me thinks that being unable to select between Arduino (an extremely limited subset of AVRs) and ARM is a big hint you don't really know what you want to do; though I guess you're trying to figure out if you want to trade off extensibility versus accessibility?&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-11-30T22:54:27.953" CommentCount="5" />
  <row Id="7359" PostTypeId="2" ParentId="5148" CreationDate="2010-11-30T22:54:38.390" Score="0" ViewCount="" Body="&lt;p&gt;Hi! I've written a crude SES-to-SCR converter for my own use. It supports a subset of SES (2 layers, only wires and vias) with a bunch of limitations, but it does the trick for me. If you are interested, go ahead and give it a try:&#xA;&lt;a href=&quot;http://www.element-14.com/community/thread/5588&quot; rel=&quot;nofollow&quot;&gt;http://www.element-14.com/community/thread/5588&lt;/a&gt; (scroll down)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Matthias&lt;/p&gt;&#xA;" LastActivityDate="2010-11-30T22:54:38.390" CommentCount="2" />
  <row Id="7360" PostTypeId="2" ParentId="7346" CreationDate="2010-11-30T23:20:28.593" Score="1" ViewCount="" Body="&lt;p&gt;If minimum weight is the aim then a converter with fewer. larger batteries will likely end up lighter overall, as you have fewer battery casings. Don't know offhand the weight difference between AA and AAA but capacity is about double.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-30T23:20:28.593" />
  <row Id="7361" PostTypeId="2" ParentId="991" CreationDate="2010-11-30T23:23:48.247" Score="2" ViewCount="" Body="&lt;p&gt;IAR is excellent, and if you are doing small projects there is a free 32K code-size limited kickstart edition. Size upgrades are however a bit expensive I believe.&#xA;They also come with tons of good example projects, usually several for each processor family. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-30T23:23:48.247" CommentCount="1" />
  <row Id="7362" PostTypeId="2" ParentId="7348" CreationDate="2010-11-30T23:27:02.703" Score="1" ViewCount="" Body="&lt;p&gt;Some parts have pretty low-power oscillators (a few uA) for wakeup, and some PICs also have hardware to allow a very slowly rising voltage on a pin to wake - this can be from an external capacitor set up before sleeping to charge over the required wake period.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-11-30T23:27:02.703" />
  <row Id="7363" PostTypeId="2" ParentId="7346" CreationDate="2010-11-30T23:42:51.483" Score="1" ViewCount="" Body="&lt;p&gt;There are two types of battery resistance:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Electrical resistance which is virtually instantaneous and usually constant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ionic resistance which is what causes the terminal voltage of the battery to rise after the load is disconnected and the battery has been left alone for a while; and vice versa, causing the voltage to decay after a few hundred milliseconds when a load is added.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're driving a stepper motor, both will be important. The first is important for any load really; but pulse loads such as stepper motors will be affected by ionic resistance more. If you step your motor on a battery with high ionic resistance you will find it runs fast for a few seconds but then slows down. The effect is more prominent on batteries near their end of life.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-30T23:42:51.483" />
  <row Id="7364" PostTypeId="2" ParentId="5294" CreationDate="2010-11-30T23:47:27.843" Score="1" ViewCount="" Body="&lt;p&gt;We do alot of work with IR in rooms. CFL put off a larger amount of IR radiation, modulated, so it can make certain tests change.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-11-30T23:47:27.843" CommunityOwnedDate="2010-11-30T23:47:27.843" CommentCount="1" />
  <row Id="7365" PostTypeId="2" ParentId="7348" CreationDate="2010-11-30T23:48:16.127" Score="1" ViewCount="" Body="&lt;p&gt;PICs with RTCs can have the RTC set to an alarm state, so it will wake up the MCU at a given time, with an external 32.768kHz crystal. They draw ~450nA IIRC in RTC+sleep mode, but only 20nA with RTC off.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-11-30T23:48:16.127" />
  <row Id="7366" PostTypeId="1" AcceptedAnswerId="7368" CreationDate="2010-12-01T01:22:01.250" Score="1" ViewCount="115" Body="&lt;p&gt;More details from the motor casing:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Electrocraft&lt;/li&gt;&#xA;&lt;li&gt;Model: E19-2&lt;/li&gt;&#xA;&lt;li&gt;Serial: A01314&lt;/li&gt;&#xA;&lt;li&gt;Part #: 0643-08-013&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;It looks like it was made by Robbins Myers Motor &amp;amp; Control Systems Division.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In case anyone is wondering, this motor comes from inside of a PUMA 560 robotic arm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It also has an encoder/potentiometer attached to it which I am interested in getting datasheets for as well:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;esoline (? it's actually kind of hard to read the first character on the label) encoder.&lt;/li&gt;&#xA;&lt;li&gt;Type: P.4201717&lt;/li&gt;&#xA;&lt;li&gt;S. No.: 70754086&lt;/li&gt;&#xA;&lt;li&gt;7223C30903&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Any help in finding datasheets, or at the very least pinouts for either of these would be much appreciated.&lt;/p&gt;&#xA;" OwnerUserId="2133" LastActivityDate="2010-12-01T12:17:12.103" Title="Does anyone know where to find the datasheet for an Electrocraft Model E19-2 motor?" Tags="&lt;motor&gt;&lt;datasheet&gt;" AnswerCount="1" />
  <row Id="7367" PostTypeId="2" ParentId="7318" CreationDate="2010-12-01T03:09:52.133" Score="2" ViewCount="" Body="&lt;p&gt;Vibration! Just give it a kick every few ms.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-01T03:09:52.133" CommentCount="1" />
  <row Id="7368" PostTypeId="2" ParentId="7366" CreationDate="2010-12-01T03:16:40.160" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.cnczone.com/forums/servo_motors_drives/9435-techical_specification_electrocraft_0643-08-013_a.html&quot; rel=&quot;nofollow&quot;&gt;http://www.cnczone.com/forums/servo_motors_drives/9435-techical_specification_electrocraft_0643-08-013_a.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I have the catalogue specs on&#xA;  0643-31-011 &amp;amp; 0643-32-011 models,&#xA;  these were the 0643 off-the-shelf&#xA;  models and I believe the other numbers&#xA;  are special order and may have been&#xA;  just different mounts or shaft size&#xA;  etc.&lt;br&gt;&#xA;  Al  &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;I will post them here in case someone&#xA;  has the same question in the future.&#xA;  Of the two models, one show the specs&#xA;  in oz-in and the other in lb-in, but&#xA;  converted they appear to be close to&#xA;  the same.&#xA;  0643-33-004&lt;br&gt;&#xA;  continuous stall 155 oz-in&lt;br&gt;&#xA;  pk torque 720 oz-in&lt;br&gt;&#xA;  max terminal voltage 60&lt;br&gt;&#xA;  max speed 4800 rpm&lt;br&gt;&#xA;  inertia .0304 oz-in-sec^&lt;br&gt;&#xA;  Kt 16.8 oz-in/amp&lt;br&gt;&#xA;  Ke 12.4 v/krpm&lt;br&gt;&#xA;  max pulse current 43 amp&lt;br&gt;&#xA;  Inductance .5mH  &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;0643-32-004&lt;br&gt;&#xA;  continuous stall 9.7 lb-in&lt;br&gt;&#xA;  pk torque 45 lb-in&lt;br&gt;&#xA;  max terminal voltage 60&lt;br&gt;&#xA;  max speed 3700 rpm&lt;br&gt;&#xA;  inertia .0019 lb-in-sec^&lt;br&gt;&#xA;  Kt 1.34 lb-in/amp&lt;br&gt;&#xA;  Ke 15.9 v/krpm&lt;br&gt;&#xA;  max pulse current 33 amp&lt;br&gt;&#xA;  Inductance .8mH&lt;br&gt;&#xA;  Good luck&lt;br&gt;&#xA;  Al  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-01T03:22:25.833" LastActivityDate="2010-12-01T03:22:25.833" CommentCount="1" />
  <row Id="7369" PostTypeId="1" AcceptedAnswerId="7370" CreationDate="2010-12-01T03:22:32.700" Score="3" ViewCount="279" Body="&lt;p&gt;With the LPC1343 microcontroller (Cortex M3), there is a USB_CONNECT line which goes low when the micro is ready to connect to the computer via USB. This &quot;soft connect&quot; feature is implemented on the LPC Baseboard with a PNP transistor circuit. Would I be able to use a p-channel mosfet instead? I have already built the p-channel mosfet equivalent, and it works, but wondering about its reliability and whether it is &quot;good practice&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Possible issues that (I think) may arise could be due to the fact that mosfets are voltage controlled devices, and on power up of the device, the gate voltage may not rise as fast as the voltage supply (3V3) (although they are tied via a 33k resistor in my implementation), and the mosfet would erroneously &quot;conduct&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: My p-channel mosfet circuit just consists of replacing Q1 with a p-channel, R69 remaining the same, eliminating R68, and changing R66 to a 33K (no particular choice, had one on hand)&lt;img src=&quot;http://i.imgur.com/Oj5LW.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="1471" LastEditorDisplayName="" LastEditDate="2010-12-02T08:02:37.567" LastActivityDate="2010-12-02T08:02:37.567" Title="Using a P-channel mosfet instead of a PNP" Tags="&lt;usb&gt;&lt;mosfet&gt;&lt;pnp&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="7370" PostTypeId="2" ParentId="7369" CreationDate="2010-12-01T03:51:11.453" Score="2" ViewCount="" Body="&lt;p&gt;if the line is high when it is non-active(instead of floating) you should be able to remove the pullup and leave the 3k and have it work without modification.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the P Channel has it's gate high it should be in cutoff, as you would want. When the gate goes low you can expect it to saturate, allowing full conduction through the mosfet like a short. MOSFETs are slower, you want to make sure you have one that has a switching frequency that is relatively close to the rate they suggest, but you should have no issues with this, the USB control will not be toggled at an extremely high rate(&gt;10MHz).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 3k resistor you have in series you can leave to avoid you pulling too much current when changing states, but it will probably work better if you reduce that a significant amount. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You want to make sure that the change in Voltage your output pin must drive divided by your resistance is less than the maximum current you pin can drive. This will protect your circuit without slowing the drive time of the MOSFET. The MOSFET is effectively a capacitance, so you can think of the capacitance with the resistance causing a delay to your signal (4 tau or 5 tau, depending on philosophy).&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-01T03:51:11.453" CommentCount="1" />
  <row Id="7371" PostTypeId="2" ParentId="7322" CreationDate="2010-12-01T04:34:53.113" Score="5" ViewCount="" Body="&lt;p&gt;Most of my recent experience in writing actual OS drivers has been with Linux, and the best reference IMO is Linux Device Drivers, 3rd Edition by Jonathan Corbet, Alessandro Rubini, and Greg Kroah-Hartman (2005), which has already been mentioned.  It is available on &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596005903&quot; rel=&quot;nofollow&quot;&gt;Amazon&lt;/a&gt;, &lt;a href=&quot;http://my.safaribooksonline.com/operating-systems-and-server-administration/linux/0596005903&quot; rel=&quot;nofollow&quot;&gt;Safari Books On-Line&lt;/a&gt;, and also as a &lt;a href=&quot;http://lwn.net/Kernel/LDD3/&quot; rel=&quot;nofollow&quot;&gt;free download&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A couple more books on the same subject are &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0132396556&quot; rel=&quot;nofollow&quot;&gt;Essential Linux Device Drivers&lt;/a&gt;, by Sreekrishnan Venkateswaran (2008) (also available on &lt;a href=&quot;http://my.safaribooksonline.com/operating-systems-and-server-administration/linux/9780132396554&quot; rel=&quot;nofollow&quot;&gt;Safari Books Online&lt;/a&gt;) and &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/1448672384&quot; rel=&quot;nofollow&quot;&gt;Writing Linux Device Drivers: a guide with exercises (Volume 3)&lt;/a&gt; by Dr Jerry Cooperstein (2009).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For Windows device drivers, the latest book on the subject (published two weeks ago) appears to be &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0321670213&quot; rel=&quot;nofollow&quot;&gt;Windows 7 Device Driver&lt;/a&gt;, by Ronald D. Reeves, Ph.D. (2010).  It is also available on &lt;a href=&quot;http://my.safaribooksonline.com/programming/microsoft-windows/9780321670540&quot; rel=&quot;nofollow&quot;&gt;Safari Books Online&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An older book, which would cover Windows XP, is: &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0735618038&quot; rel=&quot;nofollow&quot;&gt;Programming the Microsoft Windows Driver Model, Second Edition&lt;/a&gt;, by Walter Oney (2002).  It is also available on &lt;a href=&quot;http://my.safaribooksonline.com/programming/9780735642140&quot; rel=&quot;nofollow&quot;&gt;Safari Books Online&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another book, which appears to be out of print but available on Safari Books Online, is &lt;a href=&quot;http://my.safaribooksonline.com/programming/9780735623743&quot; rel=&quot;nofollow&quot;&gt;Developing Drivers with the Windows Driver Foundation&lt;/a&gt;, by Penny Orwick and Guy Smith (2007).  I assume it would cover Windows Vista.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, Microsoft has pointers to a lot of &lt;a href=&quot;http://www.microsoft.com/whdc/resources/blogs.mspx&quot; rel=&quot;nofollow&quot;&gt;blogs etc.&lt;/a&gt; discussing driver development.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-12-01T06:08:58.660" LastActivityDate="2010-12-01T06:08:58.660" CommentCount="1" />
  <row Id="7372" PostTypeId="2" ParentId="3139" CreationDate="2010-12-01T05:26:17.520" Score="0" ViewCount="" Body="&lt;p&gt;i&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just stumbled on this thread...The real question is why you want to parasitically power your slave. Not all 1-wire devices are parasitic devices, and in general I recommend against powering them this way. Its a hold over from the need for devices on PCB's where the addition of a single trace was an issue. It can be the cause of several issues on a 1-Wire network depending on its overall design. Of course a lot depends on the bus master designs too. which may support active pull-ups.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microprocessor 1-Wire slaves have been successfully done but you do need to meet the general 1-Wire timing specs. which most implementations I've seen do not (especially if this is for anything besides personal use). I'd be glad to talk about actual details with anyone. Its been done successfully on a 16Mhz AVR Mega8 with proper device specs. Meeting the critical response times with something slower would be a real challenge and interrupt service times and wakeups generally will slow the response time down too much to meet specs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several different ways to put a micro on the 1-Wire bus that have been done over the past several years and 1-Wire micro slaves is a special interest area for me so I can give several design ideas to anyone interested.  Opcodes (functions) should never be designed adhoc as it can easily cause trouble with other 1-Wire devices on a network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry about the 1-Wire.org web site, I've just kept it up out of my own pocket for the last few years so people had a starting point for their efforts with 1-Wire. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway if anyone needs about 1-wire design issues feel free to contact me directly at dml (at) sprynet.com or thru admin@1wire.org and I'll try to help if I can.&lt;/p&gt;&#xA;" OwnerUserId="2135" LastActivityDate="2010-12-01T05:26:17.520" />
  <row Id="7373" PostTypeId="1" AcceptedAnswerId="7374" CreationDate="2010-12-01T07:26:06.100" Score="4" ViewCount="163" Body="&lt;p&gt;I recently figured out the cause of a nasty bug I've been working on with an Atmel AT91SAM9G20 SBC running &lt;a href=&quot;http://www.denx.de/wiki/U-Boot&quot; rel=&quot;nofollow&quot;&gt;U-boot&lt;/a&gt;, an open source bootloader. The core of the problem was that U-boot expected the hardware to be configured differently than I had built it, so some of the device registers were misconfigured.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now that I've figured out the problem, I need to tweak U-boot to configure the registers correctly. I can do this blindly by adding a few lines of code at the end of the program, but that's messy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This brings me to my question: how can I figure out how U-boot works more efficiently than starting at main() and reading all possible code paths across all files? I've tried grepping around in the files and looking at the code near relevant identifiers. This has proved ineffective; it seems that most of the code is drivers for subsystems I don't care about. I actually understand how the bootloader works pretty well by now, but I'm hoping there exists a better method than my naive approach.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-01T14:57:17.940" Title="Good tools or methods for understanding structure of bootloader?" Tags="&lt;embedded&gt;&lt;software&gt;&lt;bootloader&gt;&lt;debugging&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="3" />
  <row Id="7374" PostTypeId="2" ParentId="7373" CreationDate="2010-12-01T09:22:25.467" Score="4" ViewCount="" Body="&lt;p&gt;There are several tools/strategies that might help:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Better tools for making sense of the source code:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://cscope.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;cscope&lt;/a&gt; is a tool for exploring C code, it's like grep but understands syntax&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Call_graph#Free_software_call-graph_generators&quot; rel=&quot;nofollow&quot;&gt;Call graph generators&lt;/a&gt; to draw a picture of the function calling structure&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://lcamtuf.coredump.cx/fenris/whatis.shtml&quot; rel=&quot;nofollow&quot;&gt;Fenris&lt;/a&gt; looks interesting though I haven't tried it&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Runtime analysis&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Step through interesting sections with a debugger and analyse what's going on&lt;/li&gt;&#xA;&lt;li&gt;Use gcc's instrumentation features to call a chunk of good on entry/exit of every function. eg. &lt;a href=&quot;http://ndevilla.free.fr/etrace/&quot; rel=&quot;nofollow&quot;&gt;http://ndevilla.free.fr/etrace/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Writing your own mini bootloader&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I often find that the best way to understand something is to recreate it myself&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, there's no magic recipe which works for everything.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-01T09:22:25.467" CommentCount="4" />
  <row Id="7375" PostTypeId="1" AcceptedAnswerId="7393" CreationDate="2010-12-01T10:38:04.297" Score="2" ViewCount="101" Body="&lt;p&gt;I relies the displacement is very small and with up to a decent frequency. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/r2cfA.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is details of the Magnet data&#xA;Magnet poles North/South over the height(h) = 1.5 mm &#xA;Coating: Nickel&#xA;Length(a) = 8.5 mm &#xA;Width(b) = 2 mm &#xA;Height(h) = 1.5 mm &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Material/grade: 48H&#xA;max.operation temperature = 120 °C&#xA;Flux density inside the magnet = 1.37 Tesla = 13700 Gauss&#xA;Flux density on the surface = 2600 Gauss&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dead weight: 0.19 g&#xA;Holding force on a steel plate: 4.64 Newton&#xA;Weight, which the magnet can lift: 0.47 kg&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Small displacement needs to be measured of around  +-.3mm&#xA;Sensor can be up to 3cm away  (min 1mm) from the stationary point of the displacement.  But there is a second margent not moving 1.5mm away from the first.&#xA;Frequency of change between the max and min could be as high as 400Hz and displacement could be as low as +-0.05mm at times.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sensor has to be of little effect on the system as possible although a small effect can be compensated for. System should be non contact to the moving base.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One idea that was suggested was a hall effect sensor. However such a large gauss with a small displacement and the other magnet nearby with such a large offset makes me think this idea is possibly not going to work although I could be wrong.&#xA;The surface for sensing is the size of the magnet if using hall effect or inductance or a maximum of around 8.5mm x 15mm &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another two options suggested where a capacitive sensor as the moving part is grounded and conducting however there is also ground all around so good shielding would have to be implemented or some form of optical sensor probably based on intensity  with fiber wires for the sending and receiving light using some form of modulation and filtering to keep costs down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am open to any other suggestions or where someone might know a good sensor suitable, circuit diagram or informational website. I know this system is a lot to ask.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the displacement oscillates at a sinusoidal waveform the output should reflect this and be analog if possible. if there is a phase shift that shift would have to be known and frequency would need to remain the same but the amplitude does not have to accurately represent the total displacement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for any ideas or suggestions&lt;/p&gt;&#xA;" OwnerUserId="2138" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-12-01T18:56:27.600" LastActivityDate="2010-12-01T20:47:19.120" Title="Small displacement measurement of a conducting beam with Neodymium magnets." Tags="&lt;sensor&gt;&lt;electromagnetism&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="7377" PostTypeId="2" ParentId="7354" CreationDate="2010-12-01T12:17:50.630" Score="4" ViewCount="" Body="&lt;p&gt;The short answer: No.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The longer answer: Well...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A major incentive for outside developers to get involved and help your project is how much it costs for them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An Arduino is a relatively expensive and clunky piece of hardware compared to just a bare AVR, so if you are building something that's supposed to be in actual use then using an actual Arduino is a horrible idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Making a system Arduino compatible is a whole different matter, it can be as easy as bringing out TXD, RXD and RESET on a header with an FTDI-cable pinout and using one of the AVRs that the Arduino IDE has support for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Casual tinkerers might then use the Arduino IDE with your board, while more advanced users could use plain C and a make file.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-12-01T12:17:50.630" />
  <row Id="7378" PostTypeId="2" ParentId="7354" CreationDate="2010-12-01T14:17:40.287" Score="5" ViewCount="" Body="&lt;p&gt;You can't limit yourself.  An ARM Cortex M3 can do thing an Arduino just can't.  In fact the Arduino uC is one of the more basic/vanilla/limited processors in the AVR line itself.  Don't hamstring your project and yourself just to try to gain followers.  If this project doesn't help you learn and extend your own boundaries then I don't think it's worth doing.  If you've outgrown the Arduino, move on.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-12-01T14:17:40.287" />
  <row Id="7379" PostTypeId="2" ParentId="7354" CreationDate="2010-12-01T14:39:15.100" Score="1" ViewCount="" Body="&lt;p&gt;A Cortex M3 based target doesn't have to be more complicated... have a look at the &lt;a href=&quot;http://leaflabs.com/docs/maple/&quot; rel=&quot;nofollow&quot;&gt;Maple&lt;/a&gt;, an STM32 based &quot;Arduino copy&quot;. To program and debug you can use OpenOCD based JTAG or just use the USB cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And the answer to your question is, no it does not have to be Arduino based to become a great success....&lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-01T14:48:11.020" LastActivityDate="2010-12-01T14:48:11.020" CommentCount="1" />
  <row Id="7380" PostTypeId="2" ParentId="5330" CreationDate="2010-12-01T14:48:33.723" Score="2" ViewCount="" Body="&lt;p&gt;I'm not that sure (like Joby).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your device is going to live 5-15 years, the problems with IPv4 could have become worse. And at some point there is going to be a switch, IPv4 can't live forever and we can't ignore the problems forever.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But on the other hand NAT will continue to save IPv4, &#xA;so your guess is as good as mine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my advice is to play it safe and at least see if there is a possibility to upgrade your device to IPv6 if you need it....&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-12-01T14:48:33.723" CommentCount="1" />
  <row Id="7381" PostTypeId="2" ParentId="7373" CreationDate="2010-12-01T14:57:17.940" Score="2" ViewCount="" Body="&lt;p&gt;How did you configure it to build for the AT91?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The code tree appears to be designed such that any architecture specific stuff is located in the 'arch/(cpu class)/(cpu type)/...' tree.  I found AT91 code under arch/arm/cpu/arm926ejs/at91...  is the variant specific stuff you're looking to alter not located there?  There's not that awfully much to look through in that directory, especially since almost half the files are individual AT91 variant-specific.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry if this is obvious...  but you didn't mention checking this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hadn't looked at the uBoot code tree yet, but your post scared me into doing so.  A back burner project of mine involves eventually using uBoot and Linux on a custom iMX233 PCB.  I'm very interested in getting this sort of feedback on how well the uBoot architecture and variant-specific stuff is isolated and how big of a pain that's going to be.&lt;/p&gt;&#xA;" OwnerUserId="1270" LastActivityDate="2010-12-01T14:57:17.940" CommentCount="5" />
  <row Id="7382" PostTypeId="1" CreationDate="2010-12-01T15:06:41.630" Score="8" ViewCount="181" Body="&lt;p&gt;At my company we do a lot of original hardware designs each of which are designed by only a small sub-section of our engineers. We are looking at ways to better document and distribute what has been done on each project so that information can be distributed and potentially reused. How does your company handle this?&lt;/p&gt;&#xA;" OwnerUserId="2140" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-01T22:26:19.923" LastActivityDate="2010-12-01T22:26:19.923" Title="How does your company manage hardware reuse?" Tags="&lt;hardware&gt;&lt;collaboration&gt;" AnswerCount="3" CommentCount="6" FavoriteCount="5" />
  <row Id="7383" PostTypeId="2" ParentId="7382" CreationDate="2010-12-01T16:16:46.750" Score="3" ViewCount="" Body="&lt;p&gt;Some EDA tools like the one I use, Altium Designer, provide methods to save varying portions of circuits to make them somewhat portable.  For small circuits, you can use &quot;&lt;a href=&quot;http://wiki.altium.com/display/ADOH/Snippets&quot; rel=&quot;nofollow&quot;&gt;Snippets&lt;/a&gt;&quot;, or for larger, multi-sheet reuse, &quot;&lt;a href=&quot;http://wiki.altium.com/display/ADOH/Using+Device+Sheets&quot; rel=&quot;nofollow&quot;&gt;Device Sheets&lt;/a&gt;&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know of any standard for hardware schematics (SPICE is too abstract; to my knowledge you can't tie it in with footprints, your part numbers, suppliers, their part numbers...) so any sort of reuse would be highly dependent the EDA package your company uses and the features it provides, or the organizational methods you implement surrounding it.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-01T16:16:46.750" CommentCount="6" />
  <row Id="7384" PostTypeId="2" ParentId="7354" CreationDate="2010-12-01T16:28:56.523" Score="0" ViewCount="" Body="&lt;p&gt;I would say being another &lt;em&gt;*&lt;/em&gt;*duino project will make it less interesting, but there probably is a group of people who only care about or have access to that platform. I expect that applies to a lot of other platforms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My personal take on platform choice is that you shouldn't care or think about popularity. If you're after a project, you pick the tools that make sense to you and use those.&lt;/p&gt;&#xA;" OwnerUserId="883" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-02T11:21:14.890" LastActivityDate="2010-12-02T11:21:14.890" />
  <row Id="7385" PostTypeId="2" ParentId="7286" CreationDate="2010-12-01T16:32:38.207" Score="2" ViewCount="" Body="&lt;p&gt;Do you really want to use them in a single project? Two things that come to mind are: Sell them or make a batch of 500 (kits?) of some '51 project. Educational SBC with Paulmon or some other monitor, some external memory and peripherals comes to mind.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-12-01T16:32:38.207" CommentCount="1" />
  <row Id="7386" PostTypeId="2" ParentId="7330" CreationDate="2010-12-01T16:42:32.413" Score="2" ViewCount="" Body="&lt;p&gt;If the GPS has a TTL async serial port and the AVR has as a TTL async serial port, I don't think you need a (MAX232) level shifter, since neither does the full voltage RS232 (like a PC, modem or a terminal). Are you sure this whole thing is necessary? &lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-12-01T16:42:32.413" CommentCount="1" />
  <row Id="7387" PostTypeId="2" ParentId="7382" CreationDate="2010-12-01T17:16:11.437" Score="1" ViewCount="" Body="&lt;p&gt;I know TinyCAD allows a schematic to be saved to a hierarchical symbol - you can draw how you want the circuit to be represented in a larger circuit and specify what inputs and outputs there are.  Your circuit pretty much shows up as a box with pins in the larger schematic and a simple double click lets you see what's underneath and edit it.  All the parts in the sub-circuit show up in the parts list, the netlist has all of the sub-circuit connections, etc.  It's been a while, but don't other EDA tools allow this or similar behavior?&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-12-01T17:16:11.437" CommentCount="1" />
  <row Id="7388" PostTypeId="1" AcceptedAnswerId="7390" CreationDate="2010-12-01T17:16:59.610" Score="2" ViewCount="106" Body="&lt;p&gt;How is soldering RoHS components with good old Pb-Sn solder different from soldering non-RoHS components? I'm talking about hand-soldering, not wave or reflow.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-01T19:00:05.513" Title="Soldering RoHS components with Pb-Sn solder" Tags="&lt;soldering&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="7389" PostTypeId="2" ParentId="7382" CreationDate="2010-12-01T17:17:28.810" Score="5" ViewCount="" Body="&lt;p&gt;When you say &quot;hardware&quot; designs, I know you're probably talking about PCB and discrete component solutions, but I have some experience with designing ASICs that may be useful in a conceptual level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When we design an ASIC that is fairly complicated, we use hierarchy from the beginning. One major reason for that is that as the designs get bigger, your ability to thoroughly evaluate and simulate them decreases. Also, ASIC designs can get quite large, and without a well organized hierarchy it can be difficult to manage the whole design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We have a strong culture of reuse for our building blocks. For example, if we have an op-amp design that someone spent a lot of time designing and validating, that design would be packaged so that another designer could easily import that design into their own workspace. We have a centralized server for storing these packages, so all the parts you need are easy to find.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While an individual block may have been designed for a specific circuit (e.g. a voltage reference for an op-amp), it usually can be re-used without modifying the original design. The design cycle lasts for a month or longer, and includes validation of a layout. Designing one of these blocks takes time to familiarize oneself with the problem set, so even if the block isn't ideal, you would probably try to use it anyways. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-01T17:17:28.810" CommentCount="4" />
  <row Id="7390" PostTypeId="2" ParentId="7388" CreationDate="2010-12-01T17:47:09.977" Score="4" ViewCount="" Body="&lt;p&gt;You don't need to make any process changes, as most RoHS components are plated with 100% matte tin, which is compatible with PbSn.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've only heard of problems when mixing RoHS and non-RoHS for very fine-pitch, leadless packages as the stresses they can generate (leaded components have a little give) are much less tolerant of any undesirable intermetallics, and especially BGAs as they bring their own solder (balls) to the party (though hand soldering BGAs is extremely dubious at best.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming you've been using leaded solder with non-RoHS components before, keep the temperature the same, the matte tin coating needs negligible additional heat relative to everything else to dissolve into the tin-lead solder.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-01T19:00:05.513" LastActivityDate="2010-12-01T19:00:05.513" CommentCount="3" />
  <row Id="7391" PostTypeId="1" AcceptedAnswerId="7392" CreationDate="2010-12-01T19:16:26.803" Score="2" ViewCount="121" Body="&lt;p&gt;Do Karnaugh maps use a base ten numbering system??&lt;/p&gt;&#xA;" OwnerUserId="2143" LastActivityDate="2010-12-02T00:11:36.927" Title="Do Karnaugh maps use a base ten numbering system?" Tags="&lt;karnaugh-map&gt;" AnswerCount="3" />
  <row Id="7392" PostTypeId="2" ParentId="7391" CreationDate="2010-12-01T19:20:24.040" Score="8" ViewCount="" Body="&lt;p&gt;No, binary &lt;a href=&quot;http://en.wikipedia.org/wiki/Gray_code&quot; rel=&quot;nofollow&quot;&gt;Gray code&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-12-01T21:05:09.513" LastActivityDate="2010-12-01T21:05:09.513" CommentCount="2" />
  <row Id="7393" PostTypeId="2" ParentId="7375" CreationDate="2010-12-01T20:47:19.120" Score="1" ViewCount="" Body="&lt;p&gt;You mentioned:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;some form of optical sensor probably based on intensity with fiber wires for the sending and receiving light using some form of modulation and filtering&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This is a good idea. You can do very precise measurements with lasers, measuring phase differences to get distance. This is sometimes done with the laser wavelength itself to get micron resolution; for larger resolution and range, you modulate the beam to a specific wavelength.&lt;br&gt;&#xA;I'm not sure I understand the application entirely, but it seems like you will be measuring two different points at the same time, each with a different range. For a certain range, I would choose a wavelength at least 4x that -- this sets a maximum modulation frequency. For example, &lt;em&gt;c/(4x6cm)=1.25GHz&lt;/em&gt; for the end of the beam. (You can use a much lower frequency, too). Resolution has a theoretical minimum set by the wavelength as well, but will be practically set by your detection setup. The idea is to compare the reflected phase with a reference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's how &lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=profile&amp;amp;mode=viewprofile&amp;amp;u=135348&quot; rel=&quot;nofollow&quot;&gt;Brad&lt;/a&gt; did it to pick up minute sound vibrations on surfaces far away -- a laser spy device: &lt;a href=&quot;http://www.lucidscience.com/pro-laser%20spy%20device-1.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.lucidscience.com/pro-laser%20spy%20device-1.aspx&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-01T20:47:19.120" CommentCount="1" />
  <row Id="7394" PostTypeId="2" ParentId="1151" CreationDate="2010-12-01T21:04:29.260" Score="1" ViewCount="" Body="&lt;p&gt;I've always used 1.6mm copper clad but I have always been a bit dissapointed at the options available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried the following methods:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Utility Knife: Works but is labourious and hard to get accurate results.&lt;/li&gt;&#xA;&lt;li&gt;Paper Guillotine: Don't even bother unless you're using a very thin PCB.&lt;/li&gt;&#xA;&lt;li&gt;Tile Saw: Excellent results but the noise and mess just aren't worth it.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.thirteenvolts.com/2010/12/01/cutting-a-pcb-with-a-metal-shear-guillotine/&quot; rel=&quot;nofollow&quot;&gt;I've had some excellent results using a metal shear&lt;/a&gt;, which are about a third of the price of the cheapest PCB shear I have found.&lt;/p&gt;&#xA;" OwnerUserId="1333" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-12-01T22:33:11.883" LastActivityDate="2010-12-01T22:33:11.883" />
  <row Id="7395" PostTypeId="2" ParentId="7141" CreationDate="2010-12-01T21:18:45.487" Score="4" ViewCount="" Body="&lt;p&gt;1000 mAh / 0.8 / 12 hours = about 100 mA, which is plenty. A parametric search on DigiKey landed half a dozen monochrome LCDs (&lt;em&gt;Display Modules - LCD, OLED, Graphic&lt;/em&gt;), and they're all expensive ($200). First on the list is DMF-50036ZNBU-FW-BAN, which draws 30-40mA. I wouldn't recommend getting any of these as they are expensive, but you may be able to source similar ones from China.&#xA;I meant to put this as a comment to the OP, but I don't have the points yet.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-01T22:23:08.523" LastActivityDate="2010-12-01T22:23:08.523" CommentCount="1" />
  <row Id="7396" PostTypeId="2" ParentId="7089" CreationDate="2010-12-01T21:25:41.017" Score="1" ViewCount="" Body="&lt;p&gt;Here's my working list.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Migration are all on:                   &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;drc-001 Property can't be mapped to Common Properties   ^(~?[a-zA-Z_0-9+-@.# ]+)$   Error&#xA;drc-002 Invalid net name format ^(~?[a-zA-Z_0-9+-.]+)$  Error&#xA;drc-003 Invalid property value format       Error&#xA;drc-004 Invalid symbol name format  ^(~?[a-zA-Z_0-9+-]+)$   Error&#xA;drc-005 Property name exceeds maximum length    40  Error&#xA;drc-006 Property value exceeds maximum length   80  Error&#xA;drc-007 Net name exceeds maximum length 120 Error&#xA;drc-008 Symbol name exceeds maximum length  120 Error&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Electrical doesn't check voltage and power&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;drc-201 Open collector pin not pulled up        Error&#xA;drc-202 Open emitter pin not pulled down        Error&#xA;drc-206 Tristate buffer not pulled up or down       Error&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Since I'm not using Links these may not be useful&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;drc-820 Isolated link       Error&#xA;drc-821 Un-named link       Error&#xA;drc-822 Multiple destinations       Note&#xA;drc-823 Link and net naming consistency     Warning&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-01T21:33:40.087" LastActivityDate="2010-12-01T21:33:40.087" CommunityOwnedDate="2010-12-22T22:41:52.350" />
  <row Id="7397" PostTypeId="2" ParentId="7391" CreationDate="2010-12-01T21:49:03.657" Score="1" ViewCount="" Body="&lt;p&gt;You may find &lt;a href=&quot;https://homepages.westminster.org.uk/electronics/Sixth%20Form/karnaugh_maps.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; of interest. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-12-01T21:49:03.657" />
  <row Id="7398" PostTypeId="2" ParentId="2641" CreationDate="2010-12-01T22:04:41.517" Score="0" ViewCount="" Body="&lt;p&gt;Since many Altera's current CPLDs are FPGAs with built-in configuration memory, you can get them for http://www.altera.com/products/devices/cpld/max2/mx2-index.jsp&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-01T22:04:41.517" />
  <row Id="7399" PostTypeId="1" CreationDate="2010-12-01T22:25:10.203" Score="5" ViewCount="256" Body="&lt;p&gt;I have probably a few hundred datasheets and app notes that I've collected for all sorts of parts in projects I've worked on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Previously, I used to keep these on a basic network share sorted maybe 2-3 folders deep by rough category, but then Google Docs added a PDF reader and the ability to upload them, so I tossed them on there.  The &quot;folders&quot; are more abstract (a la Gmail categories), so you can put a datasheet into multiple folders (e.g. a voltage regulator also could go into LED driver folder or under the manufacturer), though this has some limitations, such as searching for text in large documents only shows the first few, and of course, dependency on an internet connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What other methods are there to store hundreds of datasheets/PDFs in an easily accessible manner?  Would it make any sense to use some sort of VCS? &lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-05T09:14:29.070" Title="How do you organize your datasheets?" Tags="&lt;datasheet&gt;&lt;organizational&gt;" AnswerCount="12" />
  <row Id="7400" PostTypeId="1" AcceptedAnswerId="7417" CreationDate="2010-12-01T22:26:13.697" Score="3" ViewCount="290" Body="&lt;p&gt;Large, through-hole capacitors (typically electrolytic) sometimes have a foam pad on the bottom like the one in this picture:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tZYPs.jpg&quot; alt=&quot;Capacitor with foam pad&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the pad for?&lt;/p&gt;&#xA;" OwnerUserId="1256" LastEditorUserId="1256" LastEditorDisplayName="" LastEditDate="2010-12-03T06:45:20.727" LastActivityDate="2010-12-03T06:45:20.727" Title="What is the foam pad on the bottom of a large, through-hole capacitor for?" Tags="&lt;capacitor&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="7401" PostTypeId="2" ParentId="7399" CreationDate="2010-12-01T22:37:09.297" Score="5" ViewCount="" Body="&lt;p&gt;I have all of mine haphazard all over my disk, then rely on Mac OS X's Spotlight to find anything I need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm sure there are similar products for Windows and Linux.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Spotlight indexes the text inside of PDF files and lets me search for them. When the file opens, it opens at the phrase being searched for.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-01T22:37:09.297" CommentCount="1" />
  <row Id="7402" PostTypeId="2" ParentId="7399" CreationDate="2010-12-01T22:46:08.467" Score="4" ViewCount="" Body="&lt;p&gt;I put all mine in a directory called PDFs, with sub-directories for the different manufacturers, and further sub-directories for the chip families. For instance, under Microchip I have 16F, 18F, dsPIC, PIC24, etc. sub-directories. I add the device name to the manufacturer's often meaningless file name if necessary - &quot;16F88 30487c.pdf&quot; is typical.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-01T22:46:08.467" CommentCount="4" />
  <row Id="7403" PostTypeId="2" ParentId="7399" CreationDate="2010-12-01T22:48:29.107" Score="13" ViewCount="" Body="&lt;p&gt;Leave them on the internet and use google to find them.&lt;/p&gt;&#xA;" OwnerUserId="1773" LastActivityDate="2010-12-01T22:48:29.107" CommentCount="16" />
  <row Id="7404" PostTypeId="2" ParentId="2632" CreationDate="2010-12-01T22:58:31.183" Score="1" ViewCount="" Body="&lt;p&gt;All of the above answers are good and valid.  I especially like the point about being humble and looking hard at what you might have missed. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The only point I have to add is to look at Errata.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Often we read datasheets and specify parts for our design, quite early on in the project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can be a month at the very least before we actually have a fully populated board. :) During such time, often chip manufacturers find slight issues with their parts, and update the Errata for these parts. Most often than not, they usually specify a workaround for the problem which we might need to incorporate in our design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, I learnt the hard way, after months of trying to debug an issue, read the datasheet over and over, and then found that I had not read the errata. :) &lt;/p&gt;&#xA;" OwnerUserId="1785" LastActivityDate="2010-12-01T22:58:31.183" />
  <row Id="7405" PostTypeId="2" ParentId="2641" CreationDate="2010-12-01T23:26:08.183" Score="1" ViewCount="" Body="&lt;p&gt;FPGA pricing is odd - once you get talking to a franchised  disti you find that prices quoted at Digikey, Mouser etc. can be several times higher than what they can be got for. &#xA;Cheapest I'm aware of is Lattice EC1 in QFP100 for a little under GBP3 in tray qtys. Add GBP0.40 or so for an SPI flash memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Putting CPUs in FPGA fabric is generally not good value in terms of silicon cost, but other factors like tight coupling between CPU and FPGA, and reduced number of packages may alter the optimum tradeoff against using a seperate CPU.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-01T23:26:08.183" />
  <row Id="7406" PostTypeId="2" ParentId="7399" CreationDate="2010-12-01T23:53:16.760" Score="0" ViewCount="" Body="&lt;p&gt;I keep it all in a folder called &quot;Datasheets&quot; on my desktop for the most commonly used ones, and all the others go in the &quot;Downloads&quot; folder totalling almost 1.2GB just for PDF's...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Organised datasheets: &lt;a href=&quot;http://i.imgur.com/kCgks.png&quot; rel=&quot;nofollow&quot;&gt;http://i.imgur.com/kCgks.png&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Disorganised datasheets: &lt;a href=&quot;http://i.imgur.com/ogMgN.png&quot; rel=&quot;nofollow&quot;&gt;http://i.imgur.com/ogMgN.png&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-01T23:53:16.760" CommentCount="1" />
  <row Id="7407" PostTypeId="2" ParentId="7391" CreationDate="2010-12-02T00:11:36.927" Score="4" ViewCount="" Body="&lt;p&gt;The essential thing about Karnaugh maps is that when you compare the binary numbers assigned to adjacent cells, they will differ in exactly one bit. This is what enables you graphically simplify an expression by collecting adjacent cells. You could write in the decimal equivalents of the binary patterns if you like, but doing so doesn't really provide any useful advantages.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-12-02T00:11:36.927" />
  <row Id="7408" PostTypeId="2" ParentId="7400" CreationDate="2010-12-02T00:42:56.263" Score="11" ViewCount="" Body="&lt;p&gt;It is a rubber seal. It keeps the magic smoke in.  Or at least the electrolyte.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;From &lt;a href=&quot;http://www.nichicon.co.jp/english/products/pdf/aluminum.pdf&quot; rel=&quot;nofollow&quot;&gt;Nichicon tech data&lt;/a&gt;: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Pu0lF.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.vishay.com/doc?28356&quot; rel=&quot;nofollow&quot;&gt;Vishay tech data&lt;/a&gt; gives a better view of the seal:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Vybov.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-12-02T08:26:57.520" LastActivityDate="2010-12-02T08:26:57.520" CommentCount="6" />
  <row Id="7409" PostTypeId="2" ParentId="2379" CreationDate="2010-12-02T00:51:35.893" Score="0" ViewCount="" Body="&lt;p&gt;I recall reading on some paste datasheet that the shelf-life of stenciled boards was about 12-18 hours, but the life of boards with placed parts was significantly longer, about 2-3 days.  I would surmise this is due to the parts physically containing the paste's flux, reducing dry-out where it matters most, between the part and the board.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-02T00:51:35.893" />
  <row Id="7410" PostTypeId="1" AcceptedAnswerId="7413" CreationDate="2010-12-02T03:02:28.630" Score="1" ViewCount="111" Body="&lt;p&gt;I recently picked up a cnc mill that I'm planning to use to etch pcbs.  I have a few sources for copper clad, but I would tend to only buy one or two pieces from them locally.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions on a website or other to buy a nice big stack of copper clad - sizes probably around 5&quot; X 5&quot; +/- 1&quot; or so...&lt;/p&gt;&#xA;" OwnerUserId="991" LastActivityDate="2010-12-02T12:06:01.513" Title="PCB Subtractive Mill users - any suggestions for best locations to source copper clad? Especially in quantity?" Tags="&lt;pcb-fabrication&gt;&lt;parts&gt;&lt;etching&gt;&lt;cnc&gt;" AnswerCount="3" />
  <row Id="7411" PostTypeId="2" ParentId="7410" CreationDate="2010-12-02T03:07:29.953" Score="3" ViewCount="" Body="&lt;p&gt;I have found that most of the typical online electronic suppliers sell copper board. I buy my copper from &lt;a href=&quot;http://www.mouser.com/ProductDetail/MG-Chemicals/550/?qs=nnh8%2fA0SuH%252buQH8CIqVpSA%3d%3d&quot; rel=&quot;nofollow&quot;&gt;mouser&lt;/a&gt;, but I have see them at other places.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-02T03:07:29.953" />
  <row Id="7412" PostTypeId="2" ParentId="7399" CreationDate="2010-12-02T03:17:10.377" Score="2" ViewCount="" Body="&lt;p&gt;I'm keeping them in a &quot;Datasheets&quot; directory, with subfolders by manufacturer. I'm using Google Desktop to search, but I'd love an OS enabled way to tag them. &lt;/p&gt;&#xA;" OwnerUserId="2148" LastActivityDate="2010-12-02T03:17:10.377" />
  <row Id="7413" PostTypeId="2" ParentId="7410" CreationDate="2010-12-02T03:17:53.917" Score="5" ViewCount="" Body="&lt;p&gt;If you want to save money, look at the surplus places.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.elexp.com/pro_7bs1.htm&quot; rel=&quot;nofollow&quot;&gt;Electronix Express&lt;/a&gt; has some good prices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http:///www.goldmine-elec.com/&quot; rel=&quot;nofollow&quot;&gt;Electronics Goldmine&lt;/a&gt; and &lt;a href=&quot;http://www.allelectronics.com/make-a-store/category/445/PCB-Materials/1.html&quot; rel=&quot;nofollow&quot;&gt;All Electronics&lt;/a&gt; occasionally get some good stuff in.  Not much at the moment. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or search ebay for &quot;copper clad&quot; and scroll past the cookware.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-02T03:17:53.917" CommentCount="4" />
  <row Id="7414" PostTypeId="2" ParentId="7399" CreationDate="2010-12-02T03:56:00.713" Score="2" ViewCount="" Body="&lt;p&gt;I drop mine in &lt;a href=&quot;https://www.dropbox.com/referrals/NTE0NTczMTc5OQ?src=global0&quot; rel=&quot;nofollow&quot;&gt;Dropbox&lt;/a&gt; so I can view them on my iPhone on move.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-12-02T03:56:00.713" CommentCount="3" />
  <row Id="7415" PostTypeId="2" ParentId="7400" CreationDate="2010-12-02T04:13:13.063" Score="-1" ViewCount="" Body="&lt;p&gt;If you look across a few different varieties of caps, the materials used varies for that base piece - but it's generally made of a non-conducting material.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In surface mount caps, the plastic is more rigid and then it's softer and more flexible in larger PTH sizes/values like you suggest... I'd suspect your guess at strain relief is probably a safe assumption.  The SMD caps have such short leads that it's not nearly as likely that they would move enough to break the plastic bottom.&lt;/p&gt;&#xA;" OwnerUserId="991" LastActivityDate="2010-12-02T04:13:13.063" CommentCount="1" />
  <row Id="7417" PostTypeId="2" ParentId="7400" CreationDate="2010-12-02T04:55:46.897" Score="3" ViewCount="" Body="&lt;p&gt;That doesn't necessarily look like a foam pad from the picture (textured plastic?), have you poked at a few at your bench?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having said that, the picture does show a 400 V cap with (w.a.g.) 5 mm lead spacing, so something to isolate it as you suggest might be in order.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, that piece under the capacitor is some rubber or soft plastic that allows the capacitor to vent the hydrogen it produces during operation.  The rubber is usually covered by a plastic spacer so the bottom of the can can't sit tight against the board forming a seal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As to &lt;em&gt;why&lt;/em&gt;, see CDE's &lt;a href=&quot;http://www.cde.com/catalogs/AEappGUIDE.pdf&quot; rel=&quot;nofollow&quot;&gt;Aluminum Electrolytic Capacitor Application Guide&lt;/a&gt; (pp. 3-4)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;h3&gt;Impregnation&lt;/h3&gt;&#xA;  &#xA;  &lt;p&gt;[...]&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Water in the electrolyte plays a big role. It increases conductivity thereby reducing the capacitor’s resistance, but it reduces the boiling point so it interferes with high temperature performance, and it reduces shelf life. A few percent of water is necessary because the electrolyte maintains the integrity of the aluminum oxide dielectric. &lt;strong&gt;When&#xA;  leakage current flows, water is broken into hydrogen and oxygen&lt;/strong&gt; by hydrolysis, and the oxygen is bonded to the anode foil to heal leakage sites by growing more oxide. The&#xA;  &lt;strong&gt;hydrogen escapes by passing through the capacitor’s rubber seal.&lt;/strong&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;h3&gt;Sealing&lt;/h3&gt;&#xA;  &#xA;  &lt;p&gt;The capacitor element is sealed into a can. While most cans are aluminum, phenolic cans are often used for motor-start capacitors. In order to release the hydrogen the seal is not&#xA;  hermetic and it is usually a pressure closure made by rolling the can edge into a rubber gasket, a rubber end-plug or into rubber laminated to a phenolic board. In small capacitors molded phenolic resin or polyphenylene sulfide may replace the rubber. Too tight a seal causes pressure build up, and too loose a seal shortens the life by permitting drying out, loss of electrolyte.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-02T16:32:12.627" LastActivityDate="2010-12-02T16:32:12.627" CommentCount="2" />
  <row Id="7418" PostTypeId="2" ParentId="7400" CreationDate="2010-12-02T05:00:43.973" Score="0" ViewCount="" Body="&lt;p&gt;I'd say for electrical insulation. It could easily arc since it's rated for 400v.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-12-02T05:00:43.973" CommentCount="2" />
  <row Id="7419" PostTypeId="2" ParentId="74" CreationDate="2010-12-02T05:15:19.887" Score="7" ViewCount="" Body="&lt;p&gt;The MPLAB X (runs on Java, based on Netbeans) is available for Mac OS 10.5 and 10.6.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/mplab/X_Beta/index.html&quot; rel=&quot;nofollow&quot;&gt;http://ww1.microchip.com/downloads/mplab/X_Beta/index.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2150" LastActivityDate="2010-12-02T05:15:19.887" CommentCount="1" />
  <row Id="7420" PostTypeId="2" ParentId="7399" CreationDate="2010-12-02T05:43:26.617" Score="1" ViewCount="" Body="&lt;p&gt;On MacOS, I use &lt;a href=&quot;http://www.ironicsoftware.com/yep/&quot; rel=&quot;nofollow&quot;&gt;Yep.&lt;/a&gt;  It's an awesome utility for keeping datasheets as well as other PDFs and documents organized.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The tagging and search features are even better than Spotlight, in my opinion.  It also auto-organizes your PDFs much like iTunes, so you don't have to worry about the underlying folder hierarchy.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-12-02T05:43:26.617" CommentCount="2" />
  <row Id="7421" PostTypeId="2" ParentId="2379" CreationDate="2010-12-02T05:45:22.903" Score="4" ViewCount="" Body="&lt;p&gt;Solder paste drying out is not the problem. It's the fact that the flux is hygroscopic!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, this may not apply to all solderpaste, But I have left some unsoldered boards with paste on them lying about for varying amounts of time, and they become progressively more difficult to solder as time passes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, what happens is apparently the water flash-vaporizes, and literally causes the parts to go flying. I wound up having to use an old (dry) sponge to hold the parts down as they reflowed (this was the hot-plate reflow method).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a bit mystified by the whole affair, as I would imagine the water would gradually boil off, not create a percussive effect powerful to actually launch 1206 parts about, but it is what happened.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is with kester paste (variety is from digikey, don't know which specifically (not at my workstation at the moment).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt; - It looks like I'm currently using &lt;a href=&quot;http://www.all-spec.com/products/KPS50005.html&quot; rel=&quot;nofollow&quot;&gt;Kester R500&lt;/a&gt;. I prefer a more aggressive flux because I'm often doing unusual things to prototypes, and the boards are often a bit abused (the place I work has a terrible feature-creep problem). Other fluxes may behave differently.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget to wash your boards if you use a stronger flux.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-04T02:57:29.900" LastActivityDate="2010-12-04T02:57:29.900" CommentCount="2" />
  <row Id="7422" PostTypeId="2" ParentId="7399" CreationDate="2010-12-02T08:14:21.913" Score="0" ViewCount="" Body="&lt;p&gt;Datasheets are part of my insane system of component filing. Each one is listed in my components database (type, quantity, specs, etc.,) which also lists supplier part number (RS, Element 14, Jaycar etc). As a part is procured I save the .pdf of the data sheet with the part number as the file name. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-12-02T08:14:21.913" />
  <row Id="7423" PostTypeId="1" AcceptedAnswerId="7425" CreationDate="2010-12-02T12:05:33.697" Score="6" ViewCount="348" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;Can some one explain this terminology please I think I understand it but not completely sure. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think pull down is where you place a resistor between +V and the other component and pull up is where you place the resistor between 0v and the component.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I am completely wrong then let me know!&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-02T18:52:35.673" LastActivityDate="2010-12-02T21:58:31.570" Title="What is a pull up and pull down?" Tags="&lt;resistor&gt;&lt;terminology&gt;" AnswerCount="5" CommentCount="0" FavoriteCount="3" />
  <row Id="7424" PostTypeId="2" ParentId="7410" CreationDate="2010-12-02T12:06:01.513" Score="4" ViewCount="" Body="&lt;p&gt;It's a little harder to find, but you might want to try to find some FR-2 copper clad boards. I found that when milling PCBs on a hobby milling machine (Roland Modela), FR-4 would break the end mill pretty readily due to the woven glass in it. FR-2 being just cotton paper, doesn't have that same problem.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2010-12-02T12:06:01.513" CommentCount="1" />
  <row Id="7425" PostTypeId="2" ParentId="7423" CreationDate="2010-12-02T12:16:20.773" Score="16" ViewCount="" Body="&lt;p&gt;It's the other way around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pull up is where you place a resistor between a signal and +V, pull down is pulling it to ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(from &lt;a href=&quot;http://roguescience.org/wordpress/?page_id=11&quot; rel=&quot;nofollow&quot;&gt;http://roguescience.org/wordpress/?page_id=11&lt;/a&gt;)&#xA;&lt;img src=&quot;http://www.roguescience.org/wordpress/images/pullupdown.png&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here, you can see that when the switch is open, in the pullup scenario the input pin will read high, but for pull down it will read low.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-02T12:27:24.133" LastActivityDate="2010-12-02T12:27:24.133" CommentCount="2" />
  <row Id="7426" PostTypeId="2" ParentId="7423" CreationDate="2010-12-02T12:27:40.670" Score="5" ViewCount="" Body="&lt;p&gt;The basic function of a pull-up or pull-down resistor is to insure that given no other input, a circuit assumes a default value. But one pulls the line high, the other pulls it low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good source to learn: &lt;a href=&quot;http://www.seattlerobotics.org/encoder/mar97/basics.html&quot; rel=&quot;nofollow&quot;&gt;http://www.seattlerobotics.org/encoder/mar97/basics.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-12-02T12:27:40.670" CommentCount="1" />
  <row Id="7427" PostTypeId="1" AcceptedAnswerId="7432" CreationDate="2010-12-02T12:30:02.807" Score="0" ViewCount="236" Body="&lt;p&gt;Assume that I do &lt;strong&gt;not&lt;/strong&gt; want to replace a factory Engine Control Unit (ECU) with a custom ECU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the other possible intercept points that I can use to allow/prevent a car from starting up? I only want to allow/prevent starting up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can think of possibly connecting the car battery through a relay and turning the relay on/off. Any other good ways to do it?&lt;/p&gt;&#xA;" OwnerUserId="1938" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-02T12:32:25.313" LastActivityDate="2010-12-02T16:03:16.537" Title="What are the ways to allow/prevent a car engine from starting up?" Tags="&lt;car&gt;&lt;ecu&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="7428" PostTypeId="2" ParentId="7354" CreationDate="2010-12-02T12:40:34.323" Score="-1" ViewCount="" Body="&lt;p&gt;I think it is about a balance between features, development tool chain and cost. I would go for SunSPOTs (www.sunspotworld.com):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;features: they are ARM based and have more computing power as compared with an Arduino. Also they have some sensors already built in (a 3-axis accelerometer, a temperature and a light sensor); they also have built in radio.&lt;/li&gt;&#xA;&lt;li&gt;development tool chain: based on Java, Netbeans, works on Linux, Windows, Mac, Solaris&lt;/li&gt;&#xA;&lt;li&gt;cost: compared with 3 Arduinos + sensors + radio I think a SunSPOTs kit is cheaper. The drawback is that you have to buy a whole kit (1 basestation + 2 freerange spots).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2152" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-02T13:14:43.110" LastActivityDate="2010-12-02T13:14:43.110" CommentCount="1" />
  <row Id="7429" PostTypeId="2" ParentId="7423" CreationDate="2010-12-02T12:54:55.137" Score="2" ViewCount="" Body="&lt;p&gt;A pullup resistor will be found connected between some signal and v+.&#xA;A pulldown resistor will be found connected between some signal and signal_ground(0V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Common uses are where an input to some component requires one of two voltage states to operate reliably but you are driving the input with some component that can only drive a signal in one way.&#xA;Maybe the input is the gate of a FET, maybe an input to a microcontroller or a logic gate.&#xA;Maybe the output is coming from an open drain fet or an open collector BJT transistor or maybe you have a situation where many outputs got diode or'ed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The deal is that the input can deal with the driven signal from the output but when that signal is no longer present, there's a good chance that you now have a situation where the input sees high impedance. Under these circumstances, what signal the input &quot;sees&quot; is unpredictable. It could pick up noise from nearby electrical cables. It could pick up static electricty discharges from nearby etc. The input may end up switching states at undesirable frequencies. Of course usually you don't want the input to be able to &quot;switch&quot; on its own at all. So you pull the signal up or down when the opposite driven signal is idle. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The value of a pull resistor depends on your power budget, the max current/voltage/power the output components can deliver and what voltage/current the input requires to see a steady state that is opposite to the &quot;driven&quot; output state.&lt;/p&gt;&#xA;" OwnerUserId="1891" LastActivityDate="2010-12-02T12:54:55.137" />
  <row Id="7430" PostTypeId="2" ParentId="7427" CreationDate="2010-12-02T13:11:03.313" Score="3" ViewCount="" Body="&lt;p&gt;Rather than intercept the battery cable feed, you could intercept the signal from the key to the ignition relays/contacters. That way you won't loose your radio station programming due to battery being disconnected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I say intercept I mean break the connection, insert a relay or transistor and drive it with some circuit that allows\disallows engine start, run. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whatever you're doing, try to make it so the engine won't stop in the middle of driving. This safety message has been brought to you by.....&lt;/p&gt;&#xA;" OwnerUserId="1891" LastActivityDate="2010-12-02T13:11:03.313" />
  <row Id="7431" PostTypeId="2" ParentId="7427" CreationDate="2010-12-02T13:11:33.527" Score="0" ViewCount="" Body="&lt;p&gt;It depends on tech level of the car and how difficult for  you want the system to be and &lt;strong&gt;WHY YOU WANT TO PREVENT THE CAR FROM STARTING&lt;/strong&gt;. The why part is very important because if you just want the car to not start, the ignition key/switch is the most obvious way and has been in use for a really long time. If you want to prevent someone form stealing your car, you'd need to know what would the thief be capable of and how difficult you want the system to be for day to day use. I mean, you could always take the battery with you, but that would add a few minutes of setup time every time you want to start the car, plus problems related with carrying the battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some cars have electrical central locks which will not work if the battery is disconnected. It could also cause problems with internal clocks, microcontroller settings, radio settings and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to stop the car from starting, maybe it wouldn't be a bad idea to put some sort of switch at the starter itself. This way, the rest of the car's electronics could still work. To me this looks like the safest place because, as far as I can see, attempting to start a car with disconnected starter will cause the least amount of damage. Please note that the last car I worked on was a Volkswagen Golf Mk1 and that was quite a while ago, so I'm probably out of date.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another idea would be to analyze how car's starting procedure goes. Some cars have a key controlled rotary switch which is used to start the starter. If you add another switch in series with the starter switch, you could prevent car from starting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some other cars I've seen have a start button which is directly connected to a microcontroller, and they would be a bit more difficult to intercept.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-12-02T13:11:33.527" CommentCount="3" />
  <row Id="7432" PostTypeId="2" ParentId="7427" CreationDate="2010-12-02T13:20:38.987" Score="5" ViewCount="" Body="&lt;p&gt;There are many ways to achieve this.  Some are better than others in certain situations, and some only work on certain cars.  I'll try to describe a few.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;This is the most commonly used way.  Put a switch (relay, etc.) in line with the starter control signal.  This would generally be put before the starter relay itself.  It prevents the starter from turning over the engine.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Pro: Works on nearly all cars.&lt;/li&gt;&#xA;&lt;li&gt;Con: The car can still be started if you find a way to turn over the engine (pushing the car in gear if it has a manual transmission).&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Intercepting a major sensor.  These sensors generally deal with crank angle/position.  A lot of times a car would only have one, angle or position.  They may also be called a cam angle/position.  Activated with a switch (relay) intercepting the signal wire coming back from the sensor.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Pro: The car will not start no matter what you do since the ECU will think the engine is not turning over and will not provide spark.&lt;/li&gt;&#xA;&lt;li&gt;Con: Only works on cars that use these sensors.  Older cars relied on mechanical versions of these.&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Intercepting main power like you mentioned.  This would require a hefty relay or switch.  It is not uncommon for cars to have fuses larger than 100A for the main input.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Pro: Would work on most cars.&lt;/li&gt;&#xA;&lt;li&gt;Con: Difficult to do.  Easier to find than others (I'm assuming this is to prevent the car from being stolen).  Does not work on really old cars that used generators instead of alternators.  May mess with modern electronics in the car itself possibly leading to damage.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;There are other ways but pretty much all of them would fall under these categories if you want to be able to control it electronically.  Don't forget that the car can always just be towed.  Once again, I'm assuming you are thinking of theft prevention.&lt;/p&gt;&#xA;" OwnerUserId="1819" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-02T15:40:29.100" LastActivityDate="2010-12-02T15:40:29.100" CommentCount="4" />
  <row Id="7433" PostTypeId="2" ParentId="7423" CreationDate="2010-12-02T13:25:26.860" Score="3" ViewCount="" Body="&lt;p&gt;I think your confusion stems from what you're pulling. You may see the resistor between V++ and the output either as pulling down from V++, or pulling up from output/input. The thing is that it is no use pulling V++; it will remain V++ (as long as you don't exaggerate the pull). Likewise you can't pull ground up; it's ground, it's your reference!&lt;br&gt;&#xA;Hence the explanation is that you pull the output/input. Towards V++ is up, towards ground is down.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-02T13:32:30.473" LastActivityDate="2010-12-02T13:32:30.473" />
  <row Id="7434" PostTypeId="2" ParentId="7427" CreationDate="2010-12-02T13:39:22.760" Score="1" ViewCount="" Body="&lt;p&gt;Another possibility is a cut off switch for the fuel pump. No fuel, engine will turn over but not start. This can be a hidden toggle switch or a separate key switch.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-12-02T13:39:22.760" CommentCount="4" />
  <row Id="7435" PostTypeId="1" AcceptedAnswerId="7439" CreationDate="2010-12-02T14:34:48.437" Score="1" ViewCount="148" Body="&lt;p&gt;The idea struck my mind while I was looking at this typical application for the PCF8563.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/UsMBX.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This RTC requires typically 250nA (interface inactive, like in circuit in power-down), but a general-purpose diode like the 1N4148 already leaks 10% of that. The gate reverse current of a JFET is only a fraction of that; max 1nA for the MMBF4391.&lt;br&gt;&#xA;The whole circuit is very low voltage and dito power. Are there reasons not to use a JFET as a blocking diode here?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-03T15:43:56.713" Title="JFET as blocking diode?" Tags="&lt;diode&gt;&lt;jfet&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="7436" PostTypeId="2" ParentId="6151" CreationDate="2010-12-02T14:43:20.990" Score="0" ViewCount="" Body="&lt;p&gt;I was also thought that paralleling diodes is a bad idea, but thinking about it I'm not sure. If the current in diode 1 is greater than that in diode 2, the forward voltage drop (Vf) of the former will increase, which means more current will take the &quot;shorter&quot; route of diode 2. This looks like an auto-regulating circuit which keeps itself balanced.&lt;br&gt;&#xA;Condition is that Vf-If characteristics should be comparable, which should be the case for diodes from the same batch.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;For Vf-If characteristics to be the same both devices should have the same temperature, so should be thermally coupled, best in the same package.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-02T14:43:20.990" CommentCount="2" />
  <row Id="7437" PostTypeId="2" ParentId="7427" CreationDate="2010-12-02T15:14:55.830" Score="0" ViewCount="" Body="&lt;p&gt;I second Jim's idea: switch off fuel pump/injector(s). If the motive is theft prevention this has a major advantage: when you try to start the engine the starter motor will still run, but the main engine doesn't. The thief may think there's something wrong with the engine and leave the car alone (car thieves don't really want to interrupt their criminal business to repair a car engine).&lt;br&gt;&#xA;OTOH, if nothing happens, like when the main contact is switched off, they may have a clue of what the protection is about, and quickly &quot;fix&quot; it.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-02T15:14:55.830" />
  <row Id="7438" PostTypeId="2" ParentId="7427" CreationDate="2010-12-02T16:03:16.537" Score="0" ViewCount="" Body="&lt;p&gt;I'd just add a toggle switch that's normally open, cutting either the park/neutral (automatic) or clutch (manual) switch.  You're dealing with very minimal current, and the car is designed to not start without said signal; you're not placing it in some uncommon failure mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Granted, if someone troubleshoots this it would be one of the first things to check, but &lt;strong&gt;determining where the problem is and how to fix it can take a long time&lt;/strong&gt; depending on how you wire it up.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-02T16:03:16.537" />
  <row Id="7439" PostTypeId="2" ParentId="7435" CreationDate="2010-12-02T16:11:56.980" Score="3" ViewCount="" Body="&lt;p&gt;1N4148 is a general-purpose, legacy diode that you shouldn't use if you're looking for some level of performance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a very cursory glance at Digi-Key, the &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=BAS116-FDICT-ND&quot; rel=&quot;nofollow&quot;&gt;BAS116&lt;/a&gt; (in stock, 0.25/10, 0.035/reel) has a typical ~400 pA, max 5 nA leakage at 75 V, 25 °C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure if it's an actual &quot;series&quot;, but BASx16 seems to go to &lt;a href=&quot;http://www.nxp.com/#/pip/pip=%5bpip=BAS416%5d|pp=%5bt=pip,i=BAS416%5d&quot; rel=&quot;nofollow&quot;&gt;BAS416&lt;/a&gt;, a 75 V, 200 mA diode with 3 pA typical, 5 nA max reverse leakage @ 75 V, 25 °C.  In-stock at &lt;a href=&quot;http://www.mouser.com/ProductDetail/NXP/BAS416115/?qs=me8TqzrmIYXN%2fT0VMI6NXg%3d%3d&quot; rel=&quot;nofollow&quot;&gt;Mouser&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The JFET you linked (MMBF4391) doesn't shut off until -10 V (though the MMBF4393 in that datasheet shuts off at -3 V), and the quoted 1 nA leakage is at &lt;strong&gt;-12 V&lt;/strong&gt; (for either -1 or -3), which you can obtain?  &quot;Shutoff&quot; is defined as where the JFET conducts 10 nA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The diode's leakage is specified at 75 V, so if you're running it at 3-5 V the leakage will be much lower.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-03T15:43:56.713" LastActivityDate="2010-12-03T15:43:56.713" CommentCount="2" />
  <row Id="7440" PostTypeId="1" CreationDate="2010-12-02T16:41:11.413" Score="1" ViewCount="244" Body="&lt;p&gt;I have an RC helicopter with a dead 250 mAh lipoly battery with a voltage of 3.7 V.&#xA;Could I use 3 button cells at 4.5 V and a diode with 0.7 voltage drop&#xA;to power the circuit, which is somewhat complex?&#xA;It has a couple of Atmel uc's and some very small BGA parts.&#xA;Or do you think it will tolerate 0.8 V difference?&lt;/p&gt;&#xA;" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-02T18:53:58.137" LastActivityDate="2010-12-02T19:34:17.300" Title="Can I drop 4.5 V to 3.7 V with a diode?" Tags="&lt;battery&gt;&lt;diode&gt;&lt;lithium&gt;" AnswerCount="2" CommentCount="8" />
  <row Id="7442" PostTypeId="2" ParentId="7440" CreationDate="2010-12-02T17:00:00.513" Score="8" ViewCount="" Body="&lt;p&gt;Let me answer some basic misconceptions that you may have before going too far:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The difference between button cells and LiPo's is extreme; the current they can deliver is just about as far apart as you can get (few milliamps for a button cell, dozens of amps for some LiPo) Substituting one for another sounds like a bad idea. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally, a &quot;3.7 V&quot; lithium-polymer battery has an enormous voltage change as it discharges, how fast, and at what temperature:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/1URew.jpg&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/AcekX.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Source: &lt;a href=&quot;http://www.rfcafe.com/references/electrical/battery-li-poly.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.rfcafe.com/references/electrical/battery-li-poly.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-02T17:00:00.513" CommentCount="7" />
  <row Id="7443" PostTypeId="1" AcceptedAnswerId="7445" CreationDate="2010-12-02T17:24:16.057" Score="1" ViewCount="198" Body="&lt;p&gt;I am working on a circuit design that has multiple IC's on it. My MCU requires 2.5-3.3 VDC for it's power. Another IC that I am using requires 5V for it's logic power. So what is the cheapest and simplest solution for powering both of these devices. I figure my options are:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A) Use two voltage regulators a 3.3 and a 5V.&#xA;B) Use just a 5V regulator and used diodes or something to drop the voltage down the an acceptable level for the PIC.&#xA;C) Maybe there is a dual voltage regulator out there?&#xA;D) Something else?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2010-12-02T21:18:51.603" Title="Is there a Dual Voltage Regulator?" Tags="&lt;voltage-regulator&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="7444" PostTypeId="2" ParentId="7443" CreationDate="2010-12-02T17:33:21.180" Score="-3" ViewCount="" Body="&lt;p&gt;You could use a 5v regulator and run a 3v from there by adding a resistor to the vout of the regulator. Alternatively, you could make it adjustable by using a potentiometer.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-12-02T17:33:21.180" CommentCount="8" />
  <row Id="7445" PostTypeId="2" ParentId="7443" CreationDate="2010-12-02T17:41:25.040" Score="4" ViewCount="" Body="&lt;p&gt;Microchip has a document called &lt;a href=&quot;http://www.microchip.com/stellent/groups/techpub_sg/documents/devicedoc/en026368.pdf&quot; rel=&quot;nofollow&quot;&gt;3V Tips ‘n Tricks&lt;/a&gt;. It has some options you can chose that will help you.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-12-02T17:41:25.040" />
  <row Id="7446" PostTypeId="2" ParentId="7443" CreationDate="2010-12-02T17:50:38.970" Score="0" ViewCount="" Body="&lt;p&gt;Dual LDOs (even triple) are very common.  &lt;a href=&quot;http://micrel.com/page.do?page=/product-info/dual_ldos.shtml&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is what Micrel offers, though ST, National, and Linear should have additional options.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're concerned about efficiency for battery life or heat dissipation's sake, it is also fairly common to use a SMPS to step some input voltage rail to 5 V, then use a LDO from there to 3.3 V.  Providing standby power to the 3.3 V rail is somewhat difficult then...not knowing much else about your design I'll stop guessing though.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-02T17:50:38.970" />
  <row Id="7447" PostTypeId="2" ParentId="7443" CreationDate="2010-12-02T18:26:56.583" Score="3" ViewCount="" Body="&lt;p&gt;What you're asking for is pretty common since there are a lot of mixed-voltage IC applications out there with the same constraints (especially the two voltages you listed since most ICs operate off either of those two).  Here are two options for you:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://www.micrel.com/_PDF/mic5211.pdf&quot; rel=&quot;nofollow&quot;&gt;MIC5211-LXYM6&lt;/a&gt; from Micrel should do what you want.  It's a dual-output, +3.3V/+5V linear regulator but only can output 80mA.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/tps767d301-q1.pdf&quot; rel=&quot;nofollow&quot;&gt;TPS767D301&lt;/a&gt; from Texas Instruments if you require more power than that.  It has a +3.3V fixed output and an adjustable output which will go up to +5.5V.  It can output up to 1A (per supply) and should be able to source most projects that I could think of.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you require more power than either of these two, it would make sense to go to two separate supplies.&lt;/p&gt;&#xA;" OwnerUserId="1571" LastEditorUserId="1571" LastEditorDisplayName="" LastEditDate="2010-12-02T21:18:51.603" LastActivityDate="2010-12-02T21:18:51.603" />
  <row Id="7448" PostTypeId="1" AcceptedAnswerId="7449" CreationDate="2010-12-02T18:44:22.013" Score="10" ViewCount="384" Body="&lt;p&gt;I noticed when walking home the other day that the high voltage (200kv I believe) lines running through here were hissing in the rain. What is causing them to hiss?&lt;/p&gt;&#xA;" OwnerUserId="536" LastEditorUserId="536" LastEditorDisplayName="" LastEditDate="2010-12-02T19:08:32.060" LastActivityDate="2010-12-03T01:07:44.247" Title="Why do high voltage power lines hiss when it's raining?" Tags="&lt;power&gt;&lt;sound&gt;&lt;high-voltage&gt;" AnswerCount="4" CommentCount="7" FavoriteCount="1" />
  <row Id="7449" PostTypeId="2" ParentId="7448" CreationDate="2010-12-02T18:51:25.747" Score="7" ViewCount="" Body="&lt;p&gt;High-voltage partial discharges across the insulators.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-02T18:51:25.747" CommentCount="4" />
  <row Id="7450" PostTypeId="2" ParentId="7443" CreationDate="2010-12-02T18:53:32.453" Score="2" ViewCount="" Body="&lt;p&gt;There are plenty of sual regs,  but it is often cheaper to use two seperate ones unless you have severe space constraints, as there are many more parts to choose from in single-output versions.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-02T18:53:32.453" CommentCount="2" />
  <row Id="7451" PostTypeId="2" ParentId="4328" CreationDate="2010-12-02T19:19:44.247" Score="1" ViewCount="" Body="&lt;p&gt;If we want to broaden &quot;battery&quot; to mean some sort of device that generates electricity based on a chemical reaction (via &lt;a href=&quot;http://en.wikipedia.org/wiki/Clarke%27s_three_laws&quot; rel=&quot;nofollow&quot;&gt;magical&lt;/a&gt; means), the upper 100% efficient limit would be the chemical enthalpy of the reaction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Calculations for a theoretical &quot;sugar+air&quot; battery:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Standard enthalpy of combustion of glucose: −2805 kJ/mol (I think this is a shortcut beyond decomposition into standard elements?)&lt;/li&gt;&#xA;&lt;li&gt;2805 kJ/mol / 180 g/mol = &lt;a href=&quot;http://tinyurl.com/24fqztl&quot; rel=&quot;nofollow&quot;&gt;4328 W·h/kg&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Not sure what the most chemically dense compound is, but you could just plug it into that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nuclear powered cells could be even more magical, E=mc²:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;1 kg × c² = 2.5 × 10**13 W·h&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-02T19:19:44.247" CommentCount="3" />
  <row Id="7452" PostTypeId="2" ParentId="7440" CreationDate="2010-12-02T19:34:17.300" Score="1" ViewCount="" Body="&lt;p&gt;As said, a li-po battery can give a huge boost in energy if required. You really don't want to short those batteries without electrical protection - they will get dangerous (i.e. explosive)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More into the diode as a solution - I've used this 'trick' once before where I had an estimation error. I had an mini servo which could work from 4.8V - 6V and my whole system designed for 6V. The batterypack I had were double packs of 5x NiMH in series. If fully charged, I got 6.7V from them. That burned a servo out quite quickly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I dropped 2 schottky diodese in there that made a 0.6 - 0.8V drop depending on the current. Luckily my college had some diodes of &gt;4A around, so I was able to easily hook this up. But it's not recommdend, because at low current the voltage drop may be undesired low (like 0.4V) and thus you get a too high voltage at your system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget too that if you do with this solution and find a battery pack capable of delivering the current, you will need to dissipate that power as well. P=I*U. If I is 5A and U is 0.5V, you get a diode of 2.5W. That will make it pretty hot.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-12-02T19:34:17.300" />
  <row Id="7453" PostTypeId="2" ParentId="7448" CreationDate="2010-12-02T21:24:33.050" Score="5" ViewCount="" Body="&lt;p&gt;They'll actually do it when it's not raining too.  It's called &lt;a href=&quot;http://en.wikipedia.org/wiki/Mains_hum&quot; rel=&quot;nofollow&quot;&gt;mains hum&lt;/a&gt;.  Power lines carry AC voltage at either 50 or 60 Hz which is at the low end of the audible range of most humans.  In the presence of an electromagnetic field (like the one generated by AC power), the molecules of ferromagnetic materials (the metallic conductors inside of power lines) will not only try and align themselves with the field but sometimes &lt;a href=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/a/af/Magnetostriction_by_Zureks.gif/220px-Magnetostriction_by_Zureks.gif&quot; rel=&quot;nofollow&quot;&gt;change or distort their shape&lt;/a&gt; if the applied potential is strong enough.  This alignment/change in shape can cause collisions between the molecules comprising the power-lines which, given enough of them, can be heard by an observer.&lt;/p&gt;&#xA;" OwnerUserId="1571" LastEditorUserId="1571" LastEditorDisplayName="" LastEditDate="2010-12-03T01:07:44.247" LastActivityDate="2010-12-03T01:07:44.247" CommentCount="3" />
  <row Id="7454" PostTypeId="2" ParentId="7399" CreationDate="2010-12-02T21:31:23.593" Score="0" ViewCount="" Body="&lt;p&gt;I give them names like &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;MAX4475 MAX4476 MAX4477 MAX4478 MAX4488 MAX4489 SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op Amps.pdf&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;put them in a &lt;em&gt;Datasheets&lt;/em&gt; directory, and then find them with a desktop search tool, like the &quot;Search programs and files&quot; in Windows 7.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This loads faster than the web, and is always available even if the site or internet are down, but the web version is always up to date, and my saved files might not be.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-12-02T21:31:23.593" />
  <row Id="7455" PostTypeId="1" AcceptedAnswerId="7456" CreationDate="2010-12-02T21:43:47.277" Score="0" ViewCount="186" Body="&lt;p&gt;I'm looking for USB to serial FTDI cables. However, the cheapest I can find is $20 US each, which is &lt;em&gt;way&lt;/em&gt; too expensive, given my price target for the entire product is $70. I'm hoping they can be found for $5 each somewhere, but even FTDI themselves has them for £16 (about $25) each. Anyone know of any other options?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-03T00:43:49.187" Title="Low cost FTDI cables?" Tags="&lt;usb&gt;&lt;rs232&gt;&lt;ftdi&gt;" AnswerCount="5" CommentCount="3" />
  <row Id="7456" PostTypeId="2" ParentId="7455" CreationDate="2010-12-02T21:48:15.443" Score="4" ViewCount="" Body="&lt;p&gt;Nokia data cables are USB to serial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2010/02/25/nokia-usb-cable-is-usb-to-serial-in-disguise/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2010/02/25/nokia-usb-cable-is-usb-to-serial-in-disguise/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also want to look at non-FTDI serial to USB chips, like the Prolific 2303 (PL2303) which is in this Nokia cable.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-02T21:56:30.133" LastActivityDate="2010-12-02T21:56:30.133" CommentCount="2" />
  <row Id="7457" PostTypeId="2" ParentId="7455" CreationDate="2010-12-02T21:51:43.820" Score="2" ViewCount="" Body="&lt;p&gt;Why not design in your own USB/UART device on the board? All these cables have in them is an FTDI FT232R or similar&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2010-12-02T21:51:43.820" CommentCount="2" />
  <row Id="7458" PostTypeId="2" ParentId="7423" CreationDate="2010-12-02T21:58:31.570" Score="4" ViewCount="" Body="&lt;p&gt;Lots of valid points here, examples of what pull-ups &lt;em&gt;are&lt;/em&gt;, and certainly you can work out which way is up from them, but I'm going to aim this at the 'explain the terminology' aspect.. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The mnemonic that makes sense (to me anyway) is that the resistor is used to 'pull' the pin to some established voltage; so usually one speaks of pulling 'up' toward the positive supply voltage, or pulling 'down' toward ground or a negative supply voltage.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-12-02T21:58:31.570" />
  <row Id="7459" PostTypeId="2" ParentId="7448" CreationDate="2010-12-02T22:03:32.597" Score="5" ViewCount="" Body="&lt;p&gt;My wild guess would be that the hanging water droplets might be causing corona discharges. Corona is usually worst around points of sharper curvature, where the electric field gradient is most intense. Higher voltages, like the 200kV you mention, would make this more pronounced.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-12-02T22:03:32.597" CommentCount="1" />
  <row Id="7460" PostTypeId="2" ParentId="7448" CreationDate="2010-12-02T22:04:37.010" Score="7" ViewCount="" Body="&lt;p&gt;I was taught that this is due to the Corona effect.  Basically, the power lines ionize the air around them, causing audible hum, along with havoc in the EM spectrum.  This is why really high voltage lines and transformers will sometimes have a slight aura around them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, the effect is undesired, because it robs the transmission lines of energy (the hum/light/heat dissipates energy), so a lot of equipment is manufactured to try and stop this effect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Corona_discharge&quot; rel=&quot;nofollow&quot;&gt;Wikipedia article&lt;/a&gt; will do this subject much more justice than I can.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-12-02T22:04:37.010" CommentCount="2" />
  <row Id="7461" PostTypeId="2" ParentId="7455" CreationDate="2010-12-02T22:25:18.343" Score="2" ViewCount="" Body="&lt;p&gt;I've found that the PL2303 is far more reliable than FTDI.  They both do the same job though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find a full adapter here for under $4:&#xA;&lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.5859&quot; rel=&quot;nofollow&quot;&gt;http://www.dealextreme.com/details.dx/sku.5859&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do a Google Product Search for PL2303, you will find others.&lt;/p&gt;&#xA;" OwnerUserId="1554" LastActivityDate="2010-12-02T22:25:18.343" CommentCount="3" />
  <row Id="7462" PostTypeId="2" ParentId="7455" CreationDate="2010-12-02T22:51:01.027" Score="3" ViewCount="" Body="&lt;p&gt;Assuming your product already has a micro, the cheapest way is usually to use one with onboard USB. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-02T22:51:01.027" CommentCount="3" />
  <row Id="7463" PostTypeId="1" AcceptedAnswerId="7465" CreationDate="2010-12-02T23:56:25.487" Score="3" ViewCount="310" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;On the &lt;a href=&quot;http://www.rapidonline.com/netalogue/specs/47-3290e.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; it doesn't mention an input voltage. Does the input voltage must be higher than the output voltage or does it increase to 12v if i input 8v for example if so what is the current like that it outputs?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-12-03T00:51:47.973" Title="7812 Minimum input voltage?" Tags="&lt;voltage-regulator&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="7464" PostTypeId="1" AcceptedAnswerId="7473" CreationDate="2010-12-03T00:15:40.787" Score="1" ViewCount="86" Body="&lt;p&gt;Should I choose a linear regulator that has good transient response? or ultra low Vrms noise? or high accuracy?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using digital accelerometers and gyros (BMA180 and ITG3200).&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-12-03T02:46:21.187" Title="Choosing regulator for gyro's and accelerometer" Tags="&lt;power-supply&gt;&lt;accelerometer&gt;&lt;gyro&gt;&lt;ldo&gt;" AnswerCount="1" />
  <row Id="7465" PostTypeId="2" ParentId="7463" CreationDate="2010-12-03T00:16:12.730" Score="9" ViewCount="" Body="&lt;p&gt;A 7812 is a linear regulator, and does not step up the input voltage if the input is below the output (for that you need a DC-DC boost regulator).  The input voltage must be above the output.  All linear regulators have a minimum &lt;em&gt;dropout voltage&lt;/em&gt;, or difference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 7812 is not a LDO (low-dropout regulator), as the typical dropout voltage is around 2 volts.  (An LDO might have a dropout voltage of 0.7 volts).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On page 6 of the datasheet, the maximum dropout voltage Vd is listed as 2.5 volts, meaning you need a minimum of 14.5 volts input to the device to guarantee an output of 12 volts..&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-12-03T00:51:47.973" LastActivityDate="2010-12-03T00:51:47.973" CommentCount="3" />
  <row Id="7467" PostTypeId="2" ParentId="7455" CreationDate="2010-12-03T00:43:49.187" Score="0" ViewCount="" Body="&lt;p&gt;If you are looking for a specific distributor for a FTDI USB to serial cable then this questions is too localized and should be closed. So, because of this I will provide some advice on technical options that you have (which is an acceptable question to have asked).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could go with a &lt;a href=&quot;http://www.acroname.com/robotics/parts/S13-SERIAL-INT-CONN.html&quot; rel=&quot;nofollow&quot;&gt;4pin brainstem connector&lt;/a&gt; instead of the 6pin serial connector you mentions. This will save save space and allow for the device to be a little bit more flexible on how they use it. There are &lt;a href=&quot;http://www.acroname.com/robotics/parts/S27-USB-SERIAL.html&quot; rel=&quot;nofollow&quot;&gt;USB versions&lt;/a&gt; of the brainstem as well.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-03T00:43:49.187" />
  <row Id="7468" PostTypeId="1" CreationDate="2010-12-03T00:49:17.960" Score="1" ViewCount="171" Body="&lt;p&gt;I know &lt;a href=&quot;http://www.oracle.com/technetwork/java/codeconv-138413.html&quot; rel=&quot;nofollow&quot;&gt;code conventions for the Java&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/Coding_conventions#External_links&quot; rel=&quot;nofollow&quot;&gt;others&lt;/a&gt; programming languages, but I like to know one for assembly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe that this information is not relevant, but I use assembly to program PIC microcontrollers.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-12-03T02:46:42.990" ClosedDate="2010-12-03T18:57:01.370" Title="Are there any Code Conventions for Assembly?" Tags="&lt;microcontroller&gt;&lt;assembly&gt;&lt;code&gt;&lt;code-convention&gt;" AnswerCount="2" CommentCount="13" FavoriteCount="1" />
  <row Id="7470" PostTypeId="2" ParentId="7468" CreationDate="2010-12-03T01:04:48.490" Score="4" ViewCount="" Body="&lt;p&gt;How about this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://people.msoe.edu/~lavinn/SeniorDesign/asm-coding-standard-brown.pdf&quot; rel=&quot;nofollow&quot;&gt;Assembly Coding Style&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think like with every language:&lt;br&gt;&#xA;1) Well thought out design&lt;br&gt;&#xA;2) Modular code - group code that is meant to achieve a particular purpose&lt;br&gt;&#xA;3) Clear/Well thought of names for your subroutines&lt;br&gt;&#xA;4) And you can't go past good comments!  &lt;/p&gt;&#xA;" OwnerUserId="1785" LastActivityDate="2010-12-03T01:04:48.490" CommentCount="2" />
  <row Id="7471" PostTypeId="2" ParentId="5800" CreationDate="2010-12-03T01:32:32.150" Score="1" ViewCount="" Body="&lt;p&gt;If your micro has I2C and that many free IO's, does it have a built in DAC?  If so then what reemrevnivek suggested would work.  You don't need a separate DAC chip if you have one onboard...&lt;/p&gt;&#xA;" LastActivityDate="2010-12-03T01:32:32.150" />
  <row Id="7472" PostTypeId="1" CreationDate="2010-12-03T02:27:04.903" Score="3" ViewCount="118" Body="&lt;p&gt;I'm looking for tips that are not on the site of the Digilent.&lt;/p&gt;&#xA;" OwnerUserId="2162" LastActivityDate="2011-02-07T16:12:04.013" Title="Where I can find good examples to run with Digilent Spartan 3E Starter Board?" Tags="&lt;fpga&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="4" />
  <row Id="7473" PostTypeId="2" ParentId="7464" CreationDate="2010-12-03T02:46:21.187" Score="2" ViewCount="" Body="&lt;p&gt;You're right to look within linear regulators if you want to get the best performance from analog chips (&quot;digital&quot; accelerometers/gyros are still analog at their core), SMPS almost always have much more ripple unless you're looking at really old linear regulators with tons of input ripple&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Accuracy shouldn't matter (within part tolerances) as the sensors are generally ratiometric, though as always, check the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You want low noise, but how you minimize that depends on the broader context.  If this is battery powered there shouldn't be much input noise, so a general low-noise regulator would be best.  However, if you also have other parts on the same voltage rail (e.g. a radio) that might switch on occasionally and eat tons of current, choosing one with good transient response might be better.  If it's line driven, you may want better input rejection (if you have a terrible AC/DC supply).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best performance you could squeeze out of them would be to put them (and other analog parts) on their own voltage supply where you would know that nothing would be switching in and out very fast, putting noise on the supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From my limited experience with some MEMS accelerometers five years ago, it's pretty easy to hit the noise limits of the device (though they've come way down in price and performance has probably gone up as well), so don't go overboard unless you know your supply is what ails you.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-03T02:46:21.187" CommentCount="2" />
  <row Id="7474" PostTypeId="2" ParentId="7468" CreationDate="2010-12-03T02:46:42.990" Score="1" ViewCount="" Body="&lt;p&gt;Okay, this answer may not be applicable to OP, but I personally prefer coding with very low-level C along with &lt;strong&gt;inline assembly&lt;/strong&gt;. I find that it gives both low-cost and readability. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As large chunks of the code are in C syntax, it becomes easy to understand the overall programme structure (big picture) - functions are clearly demarked and grouped in blocks, variables can be scoped, allows the use of larger data structures. It also allows me to go tight with the assembly for regions where performance/cost is important and the compiler is not doing a good job of it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GCC has very good inline assembly support. It can even do some optimisation on the inline assembly code. A lot depends on the tool-chain.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2010-12-03T02:46:42.990" />
  <row Id="7475" PostTypeId="2" ParentId="3343" CreationDate="2010-12-03T03:20:57.483" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://translate.google.com/translate?js=n&amp;amp;prev=_t&amp;amp;hl=en&amp;amp;ie=UTF-8&amp;amp;layout=2&amp;amp;eotf=1&amp;amp;sl=auto&amp;amp;tl=en&amp;amp;u=http://www.sergioprado.org/2010/02/24/como-se-tornar-um-desenvolvedor-de-software-embarcado/&quot; rel=&quot;nofollow&quot;&gt;This article&lt;/a&gt; (auto-translated from Portuguese to English) has a good overview of developing a career as a developer of embedded software.  Note: The original is &lt;a href=&quot;http://www.sergioprado.org/2010/02/24/como-se-tornar-um-desenvolvedor-de-software-embarcado/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It begins by outlining the spheres of knowledge you must develop: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;&lt;p&gt;Knowledge: You must know the theory involved in embedded systems. This&#xA;  means hardware and software. It is&#xA;  impossible to be a competent developer&#xA;  of embedded software without getting&#xA;  to know the hardware architecture&#xA;  which is working.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;Skill: You need to get experience in the area. Needs practice. You can&#xA;  decorate all the PIC assembler&#xA;  mnemonics, but it is no use if you can&#xA;  not drive a LED with this knowledge.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;Attitude: Above all, you need to attitudes that will make you grow in&#xA;  this area. It is a very dynamic with&#xA;  frequent changes and developments. You&#xA;  need to always be motivated (a) be&#xA;  self-taught, enjoy learning, &quot;tweak&quot;&#xA;  and understand how things work.&#xA;  Without such attitudes will give you&#xA;  soon. Because this area you need to be&#xA;  very, very persistent.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;It then gives the following tips for mastering these areas (and develops them with further text, these are just the headings):&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;What you need to learn hardware (at least)&lt;/li&gt;&#xA;  &lt;li&gt;What you need to learn the software (at least)&lt;/li&gt;&#xA;  &lt;li&gt;In addition, study operating systems&lt;/li&gt;&#xA;  &lt;li&gt;You need a training&lt;/li&gt;&#xA;  &lt;li&gt;Do not stop, keep learning and developing your networking!&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2162" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-03T14:52:58.140" LastActivityDate="2011-05-03T14:52:58.140" CommunityOwnedDate="2010-12-03T03:20:57.483" CommentCount="1" />
  <row Id="7476" PostTypeId="2" ParentId="3377" CreationDate="2010-12-03T03:37:08.303" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0131851373&quot; rel=&quot;nofollow&quot;&gt;RFID Sourcebook&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2162" LastActivityDate="2010-12-03T03:37:08.303" />
  <row Id="7477" PostTypeId="2" ParentId="7270" CreationDate="2010-12-03T04:51:37.160" Score="0" ViewCount="" Body="&lt;p&gt;I am the person who asked this question, and I really like both the OpenCV answer and the IR led answer and will be playing with them both.  At this point both have some issues for me though: my IR led order is getting delayed, and my webcam is unwilling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being the case my eye fell on an LV-Maxsonar EZ that I bought to play with a little while ago.  I never really got to it, but now it seems like it might give rise to a decent solution here.  I am the only person moving in front of the room, so no interference, and no computer needed either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This device gives distance measurements in a specific direction.  If this distance changes someone moved in front of it, and the camera should move in the direction that that sensor is pointing.&lt;/p&gt;&#xA;" OwnerUserId="1773" LastActivityDate="2010-12-03T04:51:37.160" />
  <row Id="7478" PostTypeId="1" AcceptedAnswerId="7483" CreationDate="2010-12-03T04:59:03.487" Score="2" ViewCount="237" Body="&lt;p&gt;Ultimately, my goal is to have a &quot;keypad&quot; with between 5 and 10 buttons, where pressing one of those buttons effectively presses some key on two computers simultaneously.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the ideal scenario, the &quot;keypad&quot; would just plug into both computers, sending whatever signal I generated out over 2 USB lines. As far as I can tell, this flat doesn't work (a single USB device cannot connect to two hosts).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I saw online some &lt;a href=&quot;http://www.instructables.com/id/DOUBLE-KEYBOARD/&quot; rel=&quot;nofollow&quot;&gt;instructions&lt;/a&gt; for connecting a USB keyboard to a hacked-together pair of PS2-USB adapters (connecting the PS2 side, which apparently is happy to have multiple &quot;hosts&quot; with a single device). Even without doing the hacking part, my current &lt;a href=&quot;http://xkeys.com/xkeys/xkstick.php&quot; rel=&quot;nofollow&quot;&gt;keypad&lt;/a&gt; won't work when plugged in via keypad-&gt;USB to PS2-&gt;PS2 to USB-&gt;computer. Cutting apart connectors to allow it to be keypad-&gt;USB to PS2-&gt;2 x PS2 to USB-&gt;computer isn't likely to improve that any. I'm not clear if Windows no longer supports PS2 (saw that somewhere online), if the hardware keypad doesn't send the necessary signal to be &quot;converted&quot; to PS2, or what.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any other approaches I'm missing? Any intelligent ways to do it with software (so the keypad plugs into one computer and that computer sends the signal to the other computer)? Immediacy is pretty important, but that route seems to have some legs.&lt;/p&gt;&#xA;" OwnerUserId="2163" LastActivityDate="2010-12-03T07:22:57.620" Title="How can I plug an arbitrary USB device into two computers?" Tags="&lt;usb&gt;&lt;adapter&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="7479" PostTypeId="1" AcceptedAnswerId="7482" CreationDate="2010-12-03T05:07:03.910" Score="4" ViewCount="169" Body="&lt;p&gt;I've just recently gotten my Cortex M3 (LPC1343) up and running, following Microbuilder's instructions to get a GNU C compiler working for it. I've run some example code and in general, the code seems to be a lot more complex than what I've been used to with AVR's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the major differences in programming AVR's (8-bit ATMEGAs) and Cortex M3's? Anything I should watch out for?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="1688" LastEditorDisplayName="" LastEditDate="2010-12-03T06:39:45.677" LastActivityDate="2010-12-03T07:19:59.590" Title="What are the things to watch out for when switching from AVRs to Cortex M3?" Tags="&lt;avr&gt;&lt;cortex-m3&gt;&lt;lpc&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="7480" PostTypeId="1" CreationDate="2010-12-03T05:20:45.123" Score="2" ViewCount="94" Body="&lt;p&gt;I am a computer Science student, and I have to write a program that models the expected reliability of a circuit given a circuit diagram. The issue is that I have no idea what that means, and my research has only come up with things that are very technical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So can anyone give me a basic idea of what this means?&lt;/p&gt;&#xA;" OwnerUserId="2164" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-03T08:04:17.913" LastActivityDate="2010-12-03T10:02:47.017" Title="What does Expected Reliability of a Circuit Mean?" Tags="&lt;circuit&gt;&lt;reliability&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="7481" PostTypeId="2" ParentId="7478" CreationDate="2010-12-03T05:51:50.617" Score="2" ViewCount="" Body="&lt;p&gt;You could avoid mucking about with hardware quite easily by relaying key-presses on one Windows computer to another with something like &lt;a href=&quot;http://sourceforge.net/apps/mediawiki/pykeylogger/index.php?title=Main_Page&quot; rel=&quot;nofollow&quot;&gt;PyKeyLogger&lt;/a&gt; and &lt;a href=&quot;http://win32com.goermezer.de/content/view/136/291/&quot; rel=&quot;nofollow&quot;&gt;SendKeys&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-03T05:51:50.617" CommentCount="4" />
  <row Id="7482" PostTypeId="2" ParentId="7479" CreationDate="2010-12-03T07:19:59.590" Score="5" ViewCount="" Body="&lt;p&gt;May as well copy the best responses from a relevant AVRFreaks thread: &lt;a href=&quot;http://goo.gl/Yv2aa&quot; rel=&quot;nofollow&quot;&gt;http://goo.gl/Yv2aa&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Q: (toalan)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I just got my ARM cortex M3 dev board. I was able to compile and debug a simple example program. I read through the datasheet a bit. Everything looks really good, almost too good. Are there any landmines that I should be aware of?  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;A: (toalan)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I tried using ARM GCC, but there are so many things to configure and the IDE for it was like a flashback from the early 90's. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Currently I use an evalutation copy of Keil, and I bought a Ulink debugger clone from ebay for $50. Ulink is the official Keil debugger. Ulink2 is out now, you can pickup a clone on ebay for $100. I read that Ulink1 can not debug cortex, but mine seems to work for cortex. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Also I find that the datasheet for Cortex is much better than the ARM7 datasheet. This is because typically for ARM there is 1 super huge datasheet that covers a large number of ARM7 devices and you have to figure out what sections apply to what ARM7 uC. There are not many Cortex devices on the market yet, so it is easier to figure which section applies to which Cortex uC. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;I spent in total about 4 hours to install the software and debug my first program. It was a night a day difference from my frustration with ARM7. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;I got this board from futurlec, &lt;a href=&quot;http://www.futurlec.com/STM32_Development_Board.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.futurlec.com/STM32_Development_Board.shtml&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;A: (leon_heller)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I built my own LPC2106 board when the chip first came out. I downloaded gcc for the ARM, got it working in a few minutes, and wrote a simple test program for my hardware. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;I now use Rowley CrossWorks for LPC2000 ARM7 development. The compiler is gcc, with their own libraries, with their excellent IDE.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;A: (Thomas Strand)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;GCC always works right away. But I think OpenOCD (for flash writing and debugging) is a mess. Configuration files and scripts all over the place. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;When it coms to IDE's, I think it's hard to beat Eclipse. Granted, it is a bit daunting at first, but I went through a setup tutorial and got comfortable with it. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Eclipse has some nice features I like:&lt;br&gt;&#xA;  - Macro expansion on mouseover&lt;br&gt;&#xA;  - Function implementation popup on mouseover&lt;br&gt;&#xA;  - Refactoring&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;A: (jesper)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;clawson wrote:&lt;/p&gt;&#xA;  &#xA;  &lt;blockquote&gt;&#xA;    &lt;p&gt;but on ARM7 TDMI parallel I/O is slower &lt;/p&gt;&#xA;  &lt;/blockquote&gt;&#xA;  &#xA;  &lt;p&gt;You mean on an Atmel SAM7 using an ARM7TDMI the I/O is slower? I/O is slower on all ARM7's because of the internal bus structure, pipeline breaks e.t.c.&#xA;  For instance, the code &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;while (1) {&lt;br&gt;&#xA;       PORTX = 1;&lt;br&gt;&#xA;       PORTX = 0;&lt;br&gt;&#xA;     }&lt;br&gt;&#xA;  on a 90 MHz ARM7 (Philips LPC series), creates a frequency of about 3.5 MHz on the I/O port. An AVR would create about fCLK/4.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;It IS possible to get OCD to (sorta) work, however you'll have about as much hair as me when you get it work reasonably. Getting it to work reliably, is probably impossible.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;A: (jesper)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;clawson wrote:&lt;/p&gt;&#xA;  &#xA;  &lt;blockquote&gt;&#xA;    &lt;p&gt;Are you aware that the LPC also has &quot;fast IO&quot;? The following diagram (8-17) from the LPC 2101/2102/2103 User manual shows the difference between traditional slow IO and the fast IO. This is on a chip with the PLL running at 60MHz. It's true the 4.26MHz from a 60MHz clock is a bit sad. But the 15.4mHz ain't too shabby.&lt;/p&gt;&#xA;  &lt;/blockquote&gt;&#xA;  &#xA;  &lt;p&gt;Aha, this is new since I used the LPC's. But it seems it's only the 2101/2102/2103 that has this special feature. I didn't read the DS about it, but if there's no special limitations in using it, it sure is very useful. However, the 15.4 MHz above is probably from four consecutive instructions, set/clear/set/clear or something like that. But it a loop the effect of a broken pipeline may make it may be slower. Can't remember exactly how much the penalty is.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://goo.gl/NTWtI&quot; rel=&quot;nofollow&quot;&gt;The second link&lt;/a&gt; leads to a 26-page long dialogue concerning ARM. I'll read it later!&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-03T07:19:59.590" CommentCount="1" />
  <row Id="7483" PostTypeId="2" ParentId="7478" CreationDate="2010-12-03T07:22:57.620" Score="12" ViewCount="" Body="&lt;p&gt;You are missing the fact that USB is bidirectional serial protocol, and having two USB hosts talking to a single USB device is not supported neither on physical neither on logical level of the protocol.&#xA;What you can do is to make each key of the keyboard connected to two MCUs each capable of beeing USB HID, and have their USB cables connected to two PCs. You can use two cheap AVR MCUs for this and use USB HID software implementation, just make two identical &lt;a href=&quot;http://www.obdev.at/products/vusb/prjhid.html&quot; rel=&quot;nofollow&quot;&gt;HIDkeys&lt;/a&gt; and connect each key to both. Btw, read the license carefully.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-12-03T07:22:57.620" CommentCount="6" />
  <row Id="7484" PostTypeId="1" CreationDate="2010-12-03T08:36:43.690" Score="4" ViewCount="182" Body="&lt;p&gt;When working on a design I always work with minimum/maximum values from the datasheet (whichever is worst case), never typical values. I was reminded when in another discussion the leakage current for a BAS416 diode came up: 3pA typical, 5nA maximum. That's a factor 1000! In this case I surely would dismiss the 3pA.&lt;br&gt;&#xA;What's the relevance of &quot;typical values&quot; in general? Do you use them in a design?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-04T23:45:39.543" LastActivityDate="2010-12-09T18:53:48.163" Title="What is the relevance of &quot;typical values&quot; in datasheets?" Tags="&lt;datasheet&gt;&lt;error-budget&gt;" AnswerCount="4" />
  <row Id="7485" PostTypeId="2" ParentId="7484" CreationDate="2010-12-03T09:09:50.867" Score="4" ViewCount="" Body="&lt;p&gt;When estimating battery life in a device, I tend to use the typical values. If you use maximum values, you'd end up with a much shorter battery lifetime than would &quot;typically&quot; be achieved. Usually it is the typical battery life that one would be interested in, and not some extremely short time that will never result anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sure, when you're designing power supplies..etc, I would take max current consumption values for all the devices that it's going to power as a safeguard. &lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-12-03T09:09:50.867" CommentCount="6" />
  <row Id="7486" PostTypeId="2" ParentId="7399" CreationDate="2010-12-03T09:30:29.073" Score="0" ViewCount="" Body="&lt;p&gt;I only stash particularly rare ones and use &lt;a href=&quot;http://datasheetcatalog.com/&quot; rel=&quot;nofollow&quot;&gt;http://datasheetcatalog.com/&lt;/a&gt; for everything else. Google and other sites work much worse and a lot of the time you just end up with (spam) links to resellers instead of data. Their search also shows partial hits pretty well (unlike Google) so it can be a handy tool in deciphering part numbers on mystery chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I'm actually using something actively, I often print just the front page or pinout (screen capture) so I have it at hand. I have a small spring-clip folder to keep some recent ones in.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-12-03T09:30:29.073" />
  <row Id="7487" PostTypeId="2" ParentId="7480" CreationDate="2010-12-03T10:02:47.017" Score="2" ViewCount="" Body="&lt;p&gt;The simple way of thinking:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each component has a failure rate. It can be measured in MTBF (&lt;a href=&quot;http://en.wikipedia.org/wiki/Mean_time_between_failures&quot; rel=&quot;nofollow&quot;&gt;mean time between failure&lt;/a&gt;) (as @Nick T said) or &lt;a href=&quot;http://en.wikipedia.org/wiki/Failure_rate&quot; rel=&quot;nofollow&quot;&gt;Failure Rate&lt;/a&gt;. &lt;a href=&quot;http://en.wikipedia.org/wiki/Reliability_%28engineering%29&quot; rel=&quot;nofollow&quot;&gt;Reliability&lt;/a&gt; is a number which states the probability that a component would still being working after an amount of time. In general for eletronic components it follows an &lt;a href=&quot;http://en.wikipedia.org/wiki/Exponential_distribution&quot; rel=&quot;nofollow&quot;&gt;exponential distribution&lt;/a&gt;. You can use it to calculate the probability of a component still being functional after a given time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a circuit with no security systems (back-ups, redundant circuitry, etc) the overall reliability is the product of each reliability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a backup circuit, for example two redundant capacitors on the power supply, the probability that the capacitor bank is still working is the sum of the two probabilities.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-12-03T10:02:47.017" />
  <row Id="7488" PostTypeId="2" ParentId="7484" CreationDate="2010-12-03T11:45:20.647" Score="2" ViewCount="" Body="&lt;p&gt;One thing to bear in mind when reading technical datasheets, is they are finalised by marketeers!!!  not engineers.  If it was up to engineers to publish datasheets you would only have the min/max relevant values and more information about the statiscal variations that you can expect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many people are involved with the writing of the datasheets, and ultimately it is people in marketing that have the final say!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So when you read a typical value that is so far away from the min/max values that is simply marketers doing there thing.  Generally when doing a parametric search typical values are what are listed and get you in to review the datasheet.  Latter on you discover that 3pA is a maximum of 5 nA, sometimes latter in the design process!!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will generally review the min/max values to really appreciate the range and perform worst case calculations/montecarlo analysis to really work out the expected performance!&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-12-03T11:45:20.647" CommentCount="1" />
  <row Id="7489" PostTypeId="1" AcceptedAnswerId="7490" CreationDate="2010-12-03T13:54:28.203" Score="3" ViewCount="502" Body="&lt;p&gt;How do you remove insulation from headphone wires (these tiny) to prepare it for soldering?&lt;/p&gt;&#xA;" OwnerUserId="1392" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-03T15:49:57.723" LastActivityDate="2010-12-06T09:39:48.757" Title="How do you remove insulation from headphone wires?" Tags="&lt;soldering&gt;&lt;wire&gt;" AnswerCount="5" CommentCount="5" />
  <row Id="7490" PostTypeId="2" ParentId="7489" CreationDate="2010-12-03T14:03:32.947" Score="4" ViewCount="" Body="&lt;p&gt;Usually, you can remove laquer by melting solder onto the wires&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-03T14:03:32.947" CommentCount="9" />
  <row Id="7491" PostTypeId="2" ParentId="7489" CreationDate="2010-12-03T14:27:56.783" Score="3" ViewCount="" Body="&lt;p&gt;I just did some soldering with small wires and noticed that if you heat up the cable, insulation will shrink back from the heated part. I usually use sharp scissors to remove a bit of insulation at the start of the cable and then just start soldering on the small exposed part. If I'm quick enough, insulation will shrink just enough to not be a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to remove insulation from the middle of the cable, I have no idea how to help you. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I just did some soldering to a middle of a cable and I've noticed that on thin audio cables it is possible to just solder directly over the insulation. It requires a bit more time and heat, but insulation will break and shrink from the heated area leaving a piece of copper conductor exposed.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-12-06T09:39:48.757" LastActivityDate="2010-12-06T09:39:48.757" CommentCount="6" />
  <row Id="7492" PostTypeId="2" ParentId="7489" CreationDate="2010-12-03T14:59:43.257" Score="3" ViewCount="" Body="&lt;p&gt;On smaller, thin wires, simply applying heat from the iron will delaminate (ie, remove insulation from) the wire.  I've done this (by accident - creates interesting situations in a wiring harness if you are lame like me and try to shrink heat-shrink tubing with an iron - don't do it!).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might be able to use a chemical agent to strip the insulation too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also try a razor blade, but you need ninja-class hand-steadying abilities.&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-12-03T15:04:50.393" LastActivityDate="2010-12-03T15:04:50.393" />
  <row Id="7493" PostTypeId="1" AcceptedAnswerId="7496" CreationDate="2010-12-03T15:16:56.760" Score="2" ViewCount="233" Body="&lt;p&gt;Is there any special tool used to adjust trimmer potentiometers?&lt;br&gt;&#xA;I have some similar to the one on the picture:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/d0h2U.jpg&quot; alt=&quot;PIHER PT10LV trimmer potentiometer&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried using small slot, Phillips and Pozidriv screwdrivers, but they all don't seem to fit nicely giving me impression that there is some special tool used to adjust trimmer potentiometers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there isn't any special tool, what has proven to work well for you?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1397" LastEditorDisplayName="" LastEditDate="2010-12-04T18:36:06.337" LastActivityDate="2010-12-10T13:17:22.483" Title="Are there any special tools used to adjust trimmer potentiometers?" Tags="&lt;tools&gt;&lt;potentiometer&gt;" AnswerCount="7" CommentCount="2" />
  <row Id="7494" PostTypeId="2" ParentId="7493" CreationDate="2010-12-03T15:19:58.363" Score="4" ViewCount="" Body="&lt;p&gt;Just use a small flat-head screwdriver.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-12-03T15:19:58.363" CommentCount="2" />
  <row Id="7495" PostTypeId="2" ParentId="7493" CreationDate="2010-12-03T15:25:54.687" Score="3" ViewCount="" Body="&lt;p&gt;I have found that the screwdrivers in glasses repair kits work very well for me.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-03T15:25:54.687" />
  <row Id="7496" PostTypeId="2" ParentId="7493" CreationDate="2010-12-03T15:49:00.620" Score="12" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.19878&quot; rel=&quot;nofollow&quot;&gt;Goot Zirconia Cross Screwdriver for Electronics DIY&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a very interesting key for those who working with radio, or anything else that requires adjustment in bobbins, trimpots, trimmers and the like.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its tip is a type of a white ceramic (the package says &quot;zirconia&quot; but it is actually &lt;a href=&quot;http://en.wikipedia.org/wiki/Zirconium_dioxide&quot; rel=&quot;nofollow&quot;&gt;Zirconium dioxide&lt;/a&gt;), which gives a high stiffness and does not change the tuning coils because it is not obviously of magnetic material.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/TKhHH.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Source (Portuguese): &lt;a href=&quot;http://badulaquesdachina.blogspot.com/2010/03/chave-de-alinhamento-de-ceramica.html&quot; rel=&quot;nofollow&quot;&gt;http://badulaquesdachina.blogspot.com/2010/03/chave-de-alinhamento-de-ceramica.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-12-03T18:52:38.800" LastActivityDate="2010-12-03T18:52:38.800" CommentCount="2" />
  <row Id="7497" PostTypeId="2" ParentId="7493" CreationDate="2010-12-03T15:55:05.363" Score="4" ViewCount="" Body="&lt;p&gt;They do make tools like this &lt;a href=&quot;http://www.alliedelec.com/search/productdetail.aspx?SKU=9701025&quot; rel=&quot;nofollow&quot;&gt;one&lt;/a&gt;, but most people use a small screw driver. The only real advantage of the special tools is that they are often nonconductive plastic.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-12-03T15:55:05.363" />
  <row Id="7499" PostTypeId="2" ParentId="7489" CreationDate="2010-12-03T16:10:31.467" Score="1" ViewCount="" Body="&lt;p&gt;My usual approach to removing insulation is to bend the cable to put the insulation under stress and then cut it carefully with a sharp knife until it comes apart. I don't know if this would work for these tiny cables, though.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-12-03T16:10:31.467" />
  <row Id="7501" PostTypeId="2" ParentId="7484" CreationDate="2010-12-03T16:49:04.303" Score="1" ViewCount="" Body="&lt;p&gt;Often when companies spec those values they have not done that much work determining it. I have talked to many companies that their specs are purely off of simulation of what variances they will have in production.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are making a million phones, check the spec on what you are buying, determine what is feasible. if you have to trash 1 phone out of 1/1000 because you get a perfect storm of devices being out of spec, that is probably much better than manufacturing problems. If the diode is almost always worst case, get a different diode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are making 3, fab them for typical, allowing some tolerance, and if it ends up having a major variance in one part, replace it with another. If it is mission critical part, check it first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If over-spec is not an issue for your 3, just spec worst case. You will spend more on components then you need, but you are building three, 10 dollars only makes 30. No real cost lost. If you are making millions, you need to confirm conformance yourself.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-03T16:49:04.303" CommentCount="1" />
  <row Id="7502" PostTypeId="2" ParentId="7493" CreationDate="2010-12-03T17:11:40.610" Score="5" ViewCount="" Body="&lt;p&gt;The only time you need something more than a small screwdriver is on things which have a protruding screw like multiturn pots and trimmer caps, as standard screwdrivers slip off too easily, especially when doing multiple turns - a proper trim tool with recessed blade works a lot better for these.&#xA;e.g. &lt;a href=&quot;http://uk.farnell.com/vishay-spectrol/acctritob308-t000/trimming-tool/dp/145507&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/vishay-spectrol/acctritob308-t000/trimming-tool/dp/145507&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;recessed blade one end, protruding blade on other&lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-12-10T12:32:35.930" LastActivityDate="2010-12-10T12:32:35.930" />
  <row Id="7503" PostTypeId="2" ParentId="105" CreationDate="2010-12-03T17:21:26.247" Score="1" ViewCount="" Body="&lt;p&gt;I can't help with the RFID portion, but to lock the door you can purchase surplus &lt;a href=&quot;http://www.allelectronics.com/make-a-store/item/DLA-1/DOOR-LOCK-ACTUATOR//1.html&quot; rel=&quot;nofollow&quot; title=&quot;door lock actuators&quot;&gt;car lock actuators&lt;/a&gt;, they are simple solenoids that works off of 12Vdc. I have not used them yet but I plan on using them for a locking chest.&lt;/p&gt;&#xA;" OwnerUserId="984" LastActivityDate="2010-12-03T17:21:26.247" CommentCount="1" />
  <row Id="7505" PostTypeId="1" AcceptedAnswerId="8175" CreationDate="2010-12-03T20:32:34.860" Score="6" ViewCount="253" Body="&lt;p&gt;I would like to mount a slow-moving robotic &quot;car&quot; to a linear track of any incline from horizontal to vertical. The track should be rigid (attached to a boom if necessary) so that it can be propped up on one end or leaned against a wall to provide the incline.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The car should be able to:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;carry an 800 g load when the track is exactly vertical,&lt;/li&gt;&#xA;&lt;li&gt;move approximately 5 cm/min,&lt;/li&gt;&#xA;&lt;li&gt;hold position without power, and&lt;/li&gt;&#xA;&lt;li&gt;travel several meters or more.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I suspect I need hardware such as the following, but I don't know where to begin. Can anyone help narrow my search?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Track hardware&lt;/li&gt;&#xA;&lt;li&gt;Drive system for a small platform weighing upwards of a kilogram&lt;/li&gt;&#xA;&lt;li&gt;Brake (to allow the car to remain at rest with zero work)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2172" LastEditorUserId="2172" LastEditorDisplayName="" LastEditDate="2010-12-27T23:50:45.500" LastActivityDate="2011-01-06T15:13:55.870" Title="Track-mounted drive system" Tags="&lt;mechanical&gt;" AnswerCount="6" CommentCount="6" FavoriteCount="5" />
  <row Id="7506" PostTypeId="2" ParentId="5671" CreationDate="2010-12-03T20:59:31.497" Score="1" ViewCount="" Body="&lt;p&gt;A software DDS with a suitable MCU is a low-cost way to make a function generator. &lt;a href=&quot;http://webspace.webring.com/people/jl/leon_heller/minidds.html&quot; rel=&quot;nofollow&quot;&gt;This design of mine&lt;/a&gt; will go up to 200 kHz or so.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-03T20:59:31.497" />
  <row Id="7507" PostTypeId="2" ParentId="7493" CreationDate="2010-12-03T21:30:31.333" Score="2" ViewCount="" Body="&lt;p&gt;I think the thing is, &lt;strong&gt;you want something that isn't magnetic or conductive to adjust the device&lt;/strong&gt;.  Maybe that isn't a big deal for potentiometers, and a regular metallic screwdriver works ok (in my experience, at least) but for tunable inductors or tuned circuits I would think it might be an an issue.  Many screwdrivers, even the small ones, are easily magnetized.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a kit from school I got a small plastic &quot;screwdriver&quot; for this purpose.  O Engenheiro's answer describes another device that does something similar.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-12-03T21:30:31.333" CommentCount="1" />
  <row Id="7508" PostTypeId="2" ParentId="7505" CreationDate="2010-12-03T21:41:15.377" Score="8" ViewCount="" Body="&lt;p&gt;Drive the car with a threaded rod rotated by a stepper motor.  A captive nut on the car attaches to the motor.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-12-03T21:41:15.377" CommentCount="3" />
  <row Id="7509" PostTypeId="2" ParentId="7489" CreationDate="2010-12-03T22:24:31.813" Score="3" ViewCount="" Body="&lt;p&gt;I've used a microtorch to burn off the insulation with a lot of sucess - use the microtorch on the tip of the wire, and let a little more burn off on its own and you're good&lt;/p&gt;&#xA;" OwnerUserId="1870" LastActivityDate="2010-12-03T22:24:31.813" CommentCount="2" />
  <row Id="7510" PostTypeId="1" AcceptedAnswerId="7511" CreationDate="2010-12-04T01:42:36.593" Score="2" ViewCount="104" Body="&lt;p&gt;I have a very simple low-pass filter with an AC source a capacitor and a resistance in series. Now I set C and R so that R*C=100 but when I plot the diagram whit db(out), it looses 3dB at 156Hz instead of 100Hz.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Vin  in    0  DC 0.0  AC 1.0 0.0&#xA;C1   out 0   1uF&#xA;R1   in     out   1kOhm&#xA;&#xA;ac dec 50 0.1Hz 100kHz&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I'm just starting with this things, can someone help me?&lt;/p&gt;&#xA;" OwnerUserId="2175" LastActivityDate="2010-12-04T02:15:14.260" Title="Very simple circuit on spice." Tags="&lt;mac&gt;&lt;filter&gt;&lt;spice&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="7511" PostTypeId="2" ParentId="7510" CreationDate="2010-12-04T02:15:14.260" Score="6" ViewCount="" Body="&lt;p&gt;The 3db cut-off frequency is 1/(2*PI*R*C) = 159 Hz, which is quite close to your 156 Hz.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-04T02:15:14.260" CommentCount="1" />
  <row Id="7513" PostTypeId="2" ParentId="7399" CreationDate="2010-12-04T05:53:05.893" Score="0" ViewCount="" Body="&lt;p&gt;I have two systems.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a design is finalized (turned in/delivered/mass manufactured), I store the datasheets in the same folder as the rest of the project.  Usually, I'm able to organize this by folders pertaining to a sheet on the schematic or a block in the block diagram (which are often equivalent).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a design is not finalized (i.e., I'm going to be ordering new parts), I don't save them.  I run a search for something like &lt;code&gt;filetype:pdf site:manufacturer.com Part-Number&lt;/code&gt; and it usually brings up the manufacturer's link, which is guaranteed to be current, unlike anything that I have on my hard disk.  That whole &quot;may be changed without notice&quot; warning means that I don't want to be working with old datasheets that may lack important errata (or other updates) that I need to know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be really, really nice if manufacturers published (and updated, and maintained indefinitely) version-controlled repositories of their datasheets.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-04T05:53:05.893" />
  <row Id="7514" PostTypeId="1" CreationDate="2010-12-04T06:53:28.510" Score="1" ViewCount="187" Body="&lt;p&gt;Hi there,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm developing on a PC/104 stack which aparently has an I2C interface. However, on further investigation it is actually an SMBus interface but says the two are interchangable up to 400kHz.&#xA;However, the only way I can access it is through a DLL provided by the vendor. The DLL only has SMBus specific commands but reading up on SMBus I can see that the read_byte functionality seems to be the same as that for I2C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DLL shows the interface for read_byte as:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;//&#xA;// Call this function to reads a byte on the SMBus. This function&#xA;// requires the proper values to be setup in the SMB_REQUEST structure.&#xA;// This call is valid after a successful OPEN call has been made.&#xA;//&#xA;// Parameters: handle - Handle to open SMBus API&#xA;//      request - input SMB_REQUEST structure &#xA;//&#xA;// Returns: 0=SUCCESS, non-zero = FAIL&#xA;//&#xA;SMBUS_API int SmBusReadByte( SMBUS_HANDLE handle, SMB_REQUEST *request );&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;....defining the SMB_REQUEST struct as&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;typedef struct _SMB_REQUEST&#xA;{&#xA; unsigned char Address;&#xA; unsigned char Command;&#xA; unsigned char BlockLength;&#xA; unsigned char Data[SMB_MAX_DATA_SIZE];&#xA;} SMB_REQUEST;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Relating this to I2C I'm thinking that:&#xA;Address is the address of the I2C device&#xA;Command is the register to read from&#xA;BlockLength the amount of bytes to read&#xA;Data is the memory buffer used to give back the result.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, using it like this doesn't seem to work. There is also a SmReceiveReadByte() function with the same interface so I'm not sure whether I'm supposed to be using that or this funcion.&#xA;There is also a SmBusReadWord() function with the same interface so that leads me to beleive that I have the wrong idea about BlockLength above. What else could it be?&#xA;I'm probably not using this correctly at all.&#xA;Would anyone be able to shed some light on this for me?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="2178" LastActivityDate="2010-12-05T06:59:32.960" Title="Using I2C Devices on SMBus interface" Tags="&lt;i2c&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="7515" PostTypeId="1" CreationDate="2010-12-04T09:19:55.130" Score="2" ViewCount="192" Body="&lt;p&gt;I've stumbled upon &lt;a href=&quot;http://pe2er.nl/wifiswr/&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;, but it only works for outputs between 15db and 20dBm. How can I modify it to work for 0dBm sources?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm planning to use this to roughly tune my matching circuit for the interface between a RF transmitter and a chip antenna.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-04T20:58:52.850" LastActivityDate="2010-12-04T21:52:55.857" Title="How can i create a SWR meter that works for 0dBm sources @ 2.4Ghz?" Tags="&lt;rf&gt;&lt;swr-meter&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="7516" PostTypeId="1" CreationDate="2010-12-04T16:52:59.553" Score="4" ViewCount="344" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Solid State Relay (SSR) Crydom CN240A24: Eur 10.72  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/R3JYL.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same function with basic components &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Optocoupler MOC3043 (zero-crossing detect, triac out): Eur 0.726&lt;br&gt;&#xA;      Triac BTA06-600CWRG (snubberless): Eur 1.16&lt;br&gt;&#xA;      2 resistors: Eur 0.212&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Total for the second solution: Eur 2.10, or 80% less than the SSR solution.&#xA;Prices from the Mouser catalogue. Similar devices from other manufacturers have similar prices (quick check).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/GlPBp.png&quot; alt=&quot;alt text&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, the question is: what's so special about Solid State Relays that they cost so much?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;I guess at Crydom the LED and photo-triac are bonded directly to the thin PCB. Packaged components may be used for small production runs, though.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-05-19T20:50:55.703" LastActivityDate="2011-05-19T20:50:55.703" Title="Why do Solid State Relays cost so much?" Tags="&lt;components&gt;&lt;solid-state-relay&gt;&lt;pricing&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="3" />
  <row Id="7517" PostTypeId="1" AcceptedAnswerId="7518" CreationDate="2010-12-04T17:00:36.117" Score="2" ViewCount="128" Body="&lt;p&gt;Picked up my first Arduino shield today and I was surprised to see that it doesn't have any pins on it - just empty mount holes.  What's the cusomary thing to solder to the shield to get it to mount to my arduino?  From what I understand these shields should be stackable so I need to solder something to both the top and bottom sides of the shield.&lt;/p&gt;&#xA;" OwnerUserId="1841" LastActivityDate="2010-12-04T23:22:56.827" Title="Arduino shield - what should I solder to the pin mounts?" Tags="&lt;arduino&gt;" AnswerCount="1" />
  <row Id="7518" PostTypeId="2" ParentId="7517" CreationDate="2010-12-04T17:42:54.793" Score="2" ViewCount="" Body="&lt;p&gt;Sparkfun has a handy package: &lt;a href=&quot;http://www.sparkfun.com/products/10007&quot; rel=&quot;nofollow&quot;&gt;Arduino Stackable Header Kit&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the actual Arduino itself, you would use these &lt;a href=&quot;http://www.sparkfun.com/products/115&quot; rel=&quot;nofollow&quot;&gt;0.100&quot; breakaway female headers&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-04T23:22:56.827" LastActivityDate="2010-12-04T23:22:56.827" CommentCount="1" />
  <row Id="7519" PostTypeId="2" ParentId="7516" CreationDate="2010-12-04T18:26:44.957" Score="4" ViewCount="" Body="&lt;p&gt;You are comparing the component cost against a manufacturer item with heat sink (the back plate), housing, screw terminals and pcb.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Add a few euros for those items and your true bill of materials cost is getting closer to 3-4 Euro.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally manufacturer the items in china, and they will wont some money too!  ship it, handle it, distribute it, and you can quickly see where the costs are going.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, design your own, and you incur the NRE, buy one pre done and it is much cheaper for low volumes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So yes you are paying more, but it is off the shelf and ready to go and allows you to focus on the bigger picture - your application.  When you need to make 1000+ of them, then doing your own will work out cheaper.  As you know the application you can add more electronics to the circuit board and design it to fit within your enclosure as needed.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-12-04T18:26:44.957" CommentCount="5" />
  <row Id="7520" PostTypeId="2" ParentId="7514" CreationDate="2010-12-04T18:35:14.763" Score="1" ViewCount="" Body="&lt;p&gt;thats very interesting I never noticed that PC/104 had a SMbus and I2C interface!! thanks :)  I have always used off the shelf cards but I degres.....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would suggest that you monitor the lines with a scope that has I2C interpretation and connect and see what happens with the equivalent write commands.  This may give you a better idea of what the commands are actually doing.  Follow this with connecting a microcontroller and some simple code to read and write stuff on the i2c as a slave device and then try the read commands again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By knowing what you are putting on the bus with the microcontroller and monitoring communication with the scope, it will make it easier to try to figure out the API. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know the above will take some time to set up, but when you have it will simplify all further testing and debugging on the PC104 computer.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-12-04T18:35:14.763" />
  <row Id="7521" PostTypeId="2" ParentId="5671" CreationDate="2010-12-04T20:15:06.750" Score="0" ViewCount="" Body="&lt;p&gt;As far as a good all-around tool, I've had pretty good luck with the National Instruments myDAQ (not an advertisement, we bought a couple to evaluate for our EE department).  They can be had for 175 dollars with the educational discount, and it covers most of the basic needs.  It is basically a function generator, an oscilloscope, and a multimeter all in one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The analog output (function generator) operates at up to 200 kS/s, meaning that you can pretty accurately generate waveforms for the audio spectrum (I believe that the software allows up to 20kHz).  Much higher, and you'll have to shell out more money. The feature that I like is the arbitrary waveform generator, which can be very useful depending on the circuits that you are building.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, the need for most test equipment is determined by what sorts of projects that you are working on.  If you are doing hobby-level projects, you may not need any sort of expensive hardware.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-12-04T20:15:06.750" />
  <row Id="7522" PostTypeId="1" AcceptedAnswerId="7536" CreationDate="2010-12-04T20:37:30.957" Score="1" ViewCount="323" Body="&lt;p&gt;I have some boards with Xilinx Spartan 3 FPGAs, I would like to upload new bitstreams over JTAG. I was planning on using &lt;A href=&quot;http://urjtag.sourceforge.net/book/index.html&quot; rel=&quot;nofollow&quot;&gt;UrJTAG&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I already have a couple of &lt;a href=&quot;http://www.olimex.com/dev/arm-usb-ocd.html&quot; rel=&quot;nofollow&quot;&gt;FTDI based JTAG adapters&lt;/a&gt; for ARM targets - can these be used?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They run at 3V3, I read that the Xilinx JTAG is at 2V5 will this be a problem?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, I have a few FTDI FT232s, is there a simple cable I could build?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-04T22:20:33.823" LastActivityDate="2010-12-05T10:38:27.040" Title="FTDI based Xilinx JTAG" Tags="&lt;fpga&gt;&lt;jtag&gt;&lt;ftdi&gt;&lt;xilinx&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="7523" PostTypeId="2" ParentId="7515" CreationDate="2010-12-04T21:52:55.857" Score="2" ViewCount="" Body="&lt;p&gt;The host has another project, &lt;a href=&quot;http://pe2er.nl/wififsm/index.htm&quot; rel=&quot;nofollow&quot;&gt;&lt;em&gt;Field Strength Sensor for Wifi ISM band (2.4 GHz)&lt;/em&gt;&lt;/a&gt;, that incorporates a preamplifier. WiFi signals are &amp;lt;5mW (&amp;lt;7dBm) broadcast, so this must be picking up &amp;lt;&amp;lt;5mW.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't see a reason why you couldn't adapt this preamp stage into the bridge of the SWR meter. The host uses a diode detector in the bridge; you would want to swap out the diode and everything to the right of it in &lt;a href=&quot;http://pe2er.nl/wifiswr/bridgediagram.gif&quot; rel=&quot;nofollow&quot;&gt;his/her diagram&lt;/a&gt;. Resistor values all seem sensible; I'm not sure about the caps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Disclaimer: I am not an RF engineer! I have made a few GHz amps and played with some microwave structures, but I certainly can't guarantee this will work. (It certainly sounds like fun, though!)&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-04T21:52:55.857" CommentCount="3" />
  <row Id="7524" PostTypeId="2" ParentId="4244" CreationDate="2010-12-04T23:37:09.977" Score="3" ViewCount="" Body="&lt;p&gt;Yes, pure tin is wettable with solder.  However, I believe there are some alloys that make it particularly difficult.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you just try to solder something directly to a large tin part (e.g. casting), it will be extraordinarily difficult because of its large thermal mass.  You would have to use a torch or high-power soldering iron to accomplish that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, if you're attaching a wire to a huge part, using a stud (or bolt), nut, and ring-terminal would be more convenient in many cases. &lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-04T23:37:09.977" />
  <row Id="7525" PostTypeId="1" AcceptedAnswerId="7529" CreationDate="2010-12-04T23:48:26.473" Score="2" ViewCount="491" Body="&lt;p&gt;I need to switch 128 solenoids either on or off individually, several times a second.  I'd like to drive this from either a PC, or an embedded device. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would you recommend I do this?  Perhaps there is a way I can enable addressing of a group of (8 or 16) solenoids and send a &lt;code&gt;turn on&lt;/code&gt;, or &lt;code&gt;turn off&lt;/code&gt; command to them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Considering what's out there, what is the easiest way to go about this?  What is the best or most preferred way?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking at these solenoid valves that run at about $50 each. Do share information if you know of any cheaper/better ones.  The purpose is to control an indoor waterfall.  It's low-pressure so all the water drips downwards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ascovalve.com/Applications/ProductSearch/ProductInfo.aspx?productid=8262H001AC120/60,110/50D&amp;amp;userAction=view&quot; rel=&quot;nofollow&quot;&gt;http://www.ascovalve.com/Applications/ProductSearch/ProductInfo.aspx?productid=8262H001AC120/60,110/50D&amp;amp;userAction=view&lt;/a&gt;  &lt;/p&gt;&#xA;" OwnerUserId="2180" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-21T00:55:16.010" LastActivityDate="2011-02-25T00:00:21.170" Title="How can I control 128 (or more) solenoids?" Tags="&lt;multiplexing&gt;&lt;solenoid&gt;" AnswerCount="7" CommentCount="13" FavoriteCount="2" />
  <row Id="7526" PostTypeId="2" ParentId="7505" CreationDate="2010-12-05T00:03:41.177" Score="1" ViewCount="" Body="&lt;p&gt;If you are going very far, adding a winch to your car may be the best as you can extend it without much trouble.  A simple spool driven by a worm gear would prevent movement when unpowered.  If you want the powered portion to be fixed, just attach the winch to the top of the elevator (or via pulley to wherever else) and tie it to the car.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as a track is concerned, I'd use a couple small wheels (if you don't want to do much fabrication yourself, &lt;a href=&quot;http://shop.lego.com/Product/?p=6118&quot; rel=&quot;nofollow&quot;&gt;Lego&lt;/a&gt; might be an option) and have them hold a rail (circular or square rod) captive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Speaking of toys, I'm not sure what's in a K'nex roller coaster, but it might be useful if you can get a cheap/used one.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-05T00:11:38.810" LastActivityDate="2010-12-05T00:11:38.810" CommentCount="3" />
  <row Id="7528" PostTypeId="2" ParentId="7525" CreationDate="2010-12-05T01:14:00.870" Score="0" ViewCount="" Body="&lt;p&gt;I would put 16 of &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/3564&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; or something similar in series could drive. Not sure how you want to determine on/off but a low-end 8 pin PIC (&#xA;" OwnerUserId="2157" LastActivityDate="2010-12-05T01:14:00.870" />
  <row Id="7529" PostTypeId="2" ParentId="7525" CreationDate="2010-12-05T01:37:22.513" Score="11" ViewCount="" Body="&lt;p&gt;FTDI USB chip + daisy-chained '595 shift register. Put a separate transistor on each relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More detail:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A chain of &lt;a href=&quot;http://www.fairchildsemi.com/ds/MM/MM74HC595.pdf&quot; rel=&quot;nofollow&quot;&gt;74hc595&lt;/a&gt; is described here: &lt;a href=&quot;http://www.arduino.cc/en/Tutorial/ShiftOut&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Tutorial/ShiftOut&lt;/a&gt; (Only two are shown, but the concept can be expanded to any number of '595s.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To drive a the chain, three signals are needed, data, latch, and clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use an FTDI part in &quot;bitbang&quot; mode to generate three signals from computer control.  To use the FTDI in bitbang mode, use &lt;a href=&quot;http://www.intra2net.com/en/developer/libftdi/&quot; rel=&quot;nofollow&quot;&gt;libftdi&lt;/a&gt; (You could also use FTDI's official drivers, but libftdi is less hassle in my experience).  A &lt;a href=&quot;http://ftdichip.com/Products/ICs/FT232R.htm&quot; rel=&quot;nofollow&quot;&gt;FT232R&lt;/a&gt; has enough pins to do this.  FTDI sells a DIP breakout, and Sparkfun sells some breakouts too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/5IrcJ.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice you will need 128 2N2222s and 128 330 ohm resistors.  (you can get resistor arrays that might be easier to manage.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've drawn the circuit assuming a 12V supply for your relays and no less than 24 ohm coils.  If this is not the case, you might need a sturdier transistor or logic-level MOSFETs.  The 2222 is about as cheap a transistor as you will find, and when you're buying 128 pieces that makes a difference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I didn't show bypass caps or the exact 232R hookup.  Read the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK, I just saw the solenoid you are trying to control.  2N2222 won't work.  You need to switch 120VAC to the solenoid.  So you can either have a small relay (with 2N2222) to switch the 120V, or use a solid-state relay that can take logic inputs and connect it directly to the '595 output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK, here's code to drive this using libftdi.  Pin assigments in the source code.  apt-get install libftdi-dev, then compile like this: &quot;gcc test_595.c -lftdi&quot;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/* This program is distributed under the GPL, version 2 */&#xA;&#xA;#include &amp;lt;stdio.h&amp;gt;&#xA;#include &amp;lt;ftdi.h&amp;gt;&#xA;&#xA;#define HC595_CT (1) // number of '595 chips&#xA;&#xA;int main(int argc, char **argv)&#xA;{&#xA;    struct ftdi_context ftdic;&#xA;    int f,i;&#xA;&#xA;    unsigned char buf[2*8*HC595_CT+1]; // latch pulse, 8*HC595_CT clock pulses&#xA;&#xA;    if ((f=ftdi_init(&amp;amp;ftdic)) &amp;lt; 0)&#xA;    {&#xA;        fprintf(stderr, &quot;ftdi_init failed\n&quot;);&#xA;        return f;&#xA;    }&#xA;&#xA;    f = ftdi_usb_open(&amp;amp;ftdic, 0x0403, 0x6001);&#xA;&#xA;    if (f &amp;lt; 0 &amp;amp;&amp;amp; f != -5)&#xA;    {&#xA;        fprintf(stderr, &quot;unable to open ftdi device: %d (%s)\n&quot;, f, ftdi_get_error_string(&amp;amp;ftdic));&#xA;        exit(-1);&#xA;    }&#xA;&#xA;    printf(&quot;ftdi open succeeded: %d\n&quot;,f);&#xA;&#xA;    // FTDI cable assignments:&#xA;#define BIT_DATA (1&amp;lt;&amp;lt;0)  // 1: orange. TXD, &quot;data&quot;&#xA;                         // 2: yellow. RXD, unused&#xA;#define BIT_CLOCK (1&amp;lt;&amp;lt;2) // 4: green. RTS, &quot;clock&quot;&#xA;#define BIT_LATCH (1&amp;lt;&amp;lt;3) // 8: brown. CTS, &quot;latch&quot;&#xA;&#xA;    ftdi_enable_bitbang(&amp;amp;ftdic, BIT_DATA | BIT_CLOCK | BIT_LATCH);&#xA;&#xA;    // set zero&#xA;    *buf=0;&#xA;    f = ftdi_write_data(&amp;amp;ftdic, buf, 1);    &#xA;&#xA;    unsigned char *b=buf;&#xA;&#xA;&#xA;    unsigned char data;&#xA;    unsigned char state;&#xA;&#xA;    if (argc == 2) {&#xA;      data=atof(argv[1]);&#xA;    } else {&#xA;      data=0x5a;&#xA;    }&#xA;&#xA;    printf(&quot;sending data %d\n&quot;,data);&#xA;&#xA;    for (i=0; i&amp;lt;8; i++) {   &#xA;      state=(data &amp;amp; (128L&amp;gt;&amp;gt;i))?BIT_DATA:0;&#xA;      *b++=state;&#xA;      state |= BIT_CLOCK;&#xA;      *b++=state;&#xA;    }&#xA;    *b++=BIT_LATCH;&#xA;&#xA;    f = ftdi_write_data(&amp;amp;ftdic, buf, (b-buf));    &#xA;&#xA;    ftdi_disable_bitbang(&amp;amp;ftdic);&#xA;    ftdi_usb_close(&amp;amp;ftdic);&#xA;    ftdi_deinit(&amp;amp;ftdic);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And here's a picture of my test setup:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kZzFH.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I used the &lt;a href=&quot;http://ftdichip.com/Products/Cables/USBTTLSerial.htm&quot; rel=&quot;nofollow&quot;&gt;TTL-232R-3V3&lt;/a&gt; cable.)&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-12-05T23:48:16.500" LastActivityDate="2010-12-05T23:48:16.500" CommentCount="13" />
  <row Id="7530" PostTypeId="1" AcceptedAnswerId="7557" CreationDate="2010-12-05T02:02:00.373" Score="0" ViewCount="543" Body="&lt;p&gt;I'm working on a Netduino based mobile robot that's controlled by software on a PC or phone (WP7).  One goal of the project is to be able to steer the robot from another room of the house.  Is there a small wireless (wifi) web cam that runs on battery that may work for this situation?  I don't think the Netduino has enough processing power to stream video, though technially it could using a wifi shield.  If that's out of the question would it be possible to sporatically take pictures using some other camera sensor &amp;amp; the Netduino (photos could be stored on the SD card and later served up over wifi to the client)?&lt;/p&gt;&#xA;" OwnerUserId="1841" LastActivityDate="2010-12-10T13:28:53.287" Title="Wireless, battery operated web cam for mobile robot" Tags="&lt;arduino&gt;&lt;video&gt;&lt;netduino&gt;&lt;mobile-robot&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="7531" PostTypeId="2" ParentId="7525" CreationDate="2010-12-05T06:08:59.087" Score="0" ViewCount="" Body="&lt;p&gt;Is there some reason a 7 to 128 decoder wouldn't be appropriate? Using a FTDI chip and serial shift register seems like overkill.&lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2010-12-05T06:08:59.087" CommentCount="3" />
  <row Id="7532" PostTypeId="2" ParentId="7514" CreationDate="2010-12-05T06:59:32.960" Score="0" ViewCount="" Body="&lt;p&gt;If you take some time and poke around &lt;a href=&quot;http://en.wikipedia.org/wiki/System_Management_Bus&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt; you'll find a page describing the differences between I2C and SMBus; the one that's probably getting you is the packet checksumming or PEC; this is not required for I2C transfers but SMBus devices want it. It's not difficult to calculate and append to the transfer, so you might want to start there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously if you have a logic analyzer it'd be prudent to throw that on first and see if that really is what's causing your troubles before going to the effort of writing the code. :-) You can also probably lift the PEC generation code from the linux kernel, as it has I2C and SMBus drivers and the places like the &lt;a href=&quot;http://lxr.no&quot; rel=&quot;nofollow&quot;&gt;Linux Cross Reference&lt;/a&gt; are excellent at helping you find out where the code you're interested is hiding.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2010-12-05T06:59:32.960" />
  <row Id="7533" PostTypeId="2" ParentId="7399" CreationDate="2010-12-05T09:14:29.070" Score="1" ViewCount="" Body="&lt;p&gt;At my previous workplace we stored them in a common directory, structured two to three levels deep so that they were easily accessible by everyone.  The datasheets crossed over between mechanical and electronic and everything inbetween. This was useful as we needed cross discipline access to components from a mechanical and electronic perspective.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my current workplace we have a PLM tool that has all the components on there and access to the datasheets in the plm database. This allows us to keep track of datahseet versions against when the products they were designed for (datasheets do change!).  This is important for safety, defence, and aerospace applications.  DO-254 in particular requires that datasheets are version controlled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not having a PLM and having need for them, the next best system would be some sort of wiki database or version control software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course not having these requirements google is very useful.  The issue I have with google is the first links are to annoying sights like various datasheet repositories and part searching databases, all with lots of adds and stuff.  It makes finding the actual manufactures website with the correct database a real pain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using Altium with a database you can link directly to the datasheets so it makes it easy while working on schematics to bring up the datasheets for each component.  &lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-12-05T09:14:29.070" />
  <row Id="7534" PostTypeId="1" CreationDate="2010-12-05T09:14:43.100" Score="2" ViewCount="96" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/3199/how-do-i-connect-a-relay-and-transistor-to-an-arduino&quot;&gt;How do I connect a relay and transistor to an Arduino?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I have my NPN transistor and my flyback diode and then I have  a 9v battery that is the power source that needs to be switched on. I am trying to figure out how to connecting everything but I cannot get it to work. &#xA;&lt;a href=&quot;http://www.tycoelectronics.com/catalog/common/images/PartImages/1v99011b.jpg&quot; rel=&quot;nofollow&quot;&gt;http://www.tycoelectronics.com/catalog/common/images/PartImages/1v99011b.jpg&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2184" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-05T10:49:20.413" LastActivityDate="2010-12-05T10:49:20.413" ClosedDate="2010-12-06T15:35:43.187" Title="How do I control a SPST relay with an Arduino?" Tags="&lt;relay&gt;" CommentCount="1" />
  <row Id="7535" PostTypeId="1" AcceptedAnswerId="7550" CreationDate="2010-12-05T09:48:59.070" Score="4" ViewCount="232" Body="&lt;p&gt;What precautions should I take when mixing analog audio and digital (uC control) on the same board? I don't want to hear the I2C bus in my speakers. I'm thinking about  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;Separate power supplies  &lt;/li&gt;&#xA;  &lt;li&gt;Separate ground planes, with each part within its own ground plane  &lt;/li&gt;&#xA;  &lt;li&gt;A single connection over a ferrite bead between ground planes  &lt;/li&gt;&#xA;  &lt;li&gt;Lots of decoupling, preferably by RC instead of simply a C  &lt;/li&gt;&#xA;  &lt;li&gt;Slew rate control, esp. on serial buses (lots of edges!)  &lt;/li&gt;&#xA;  &lt;li&gt;Physical distance between both world  &lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The RC decoupling may or may not be overkill, but it costs only a resistor.&lt;br&gt;&#xA;Other suggestions?  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-05T10:50:50.100" LastActivityDate="2011-01-15T23:17:48.307" Title="What precautions should I take when mixing analog audio and digital on the same board?" Tags="&lt;analog&gt;&lt;design&gt;&lt;layout&gt;&lt;digital&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="3" />
  <row Id="7536" PostTypeId="2" ParentId="7522" CreationDate="2010-12-05T10:38:27.040" Score="3" ViewCount="" Body="&lt;p&gt;You'll want a look at &lt;a href=&quot;http://forums.xilinx.com/t5/Spartan-Family-FPGAs/Spartan3-JTAG-interface-3-3V/m-p/51026&quot; rel=&quot;nofollow&quot;&gt;Xilinx app note 453&lt;/a&gt;, title &quot;The 3.3V Configuration of Spartan-3 FPGAs&quot;. Basically the advice is putting resistors in series to limit the current through the protection diodes, and one over the 2.5V to sink the remaining current. Using level shifting circuitry instead would also work.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-12-05T10:38:27.040" CommentCount="1" />
  <row Id="7537" PostTypeId="2" ParentId="7516" CreationDate="2010-12-05T12:18:55.643" Score="1" ViewCount="" Body="&lt;p&gt;You are also paying for assembly, packaging, testing, approvals, sales &amp;amp; marketing and a whole bunch of other things. Also bear in mind that pricing in Mouser is not a particularly good representaton of the 'real' cost, as different manufacturers have different pricing structures for low volumes, and different distributour discounts. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-05T12:18:55.643" CommentCount="2" />
  <row Id="7538" PostTypeId="1" CreationDate="2010-12-05T12:59:54.670" Score="1" ViewCount="334" Body="&lt;p&gt;I plan to buy an &lt;a href=&quot;http://mbed.org/&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt; module to get started with NXP LPC17XX. Developing and downloading code seem the easiest possible. What are my options for in-system programming this code in non-mbed devices? I understand the bootloader only requires a UART connection to my host PC.&lt;br&gt;&#xA;What tools are available for Windows PCs? Can they directly work with the object code I created on the mbed site?&lt;br&gt;&#xA;Can I use code for the LPC1759 directly on other LPC17XX devices? &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-06T01:07:56.197" Title="How do I in-system program LPC17XX?" Tags="&lt;arm&gt;&lt;programming&gt;&lt;isp&gt;&lt;lpc17xx&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="7539" PostTypeId="2" ParentId="7535" CreationDate="2010-12-05T14:31:56.880" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Star grounds.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connect both grounds at only one point to avoid ground loops and other nasty things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Use power layers only for power or ground.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It might seem sensible but try to avoid putting signal traces on the ground or power layers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Separate analog supplies.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes it's just enough to isolate two supplies using a bead or resistor-capacitor network. For example most microcontroller manufacturers suggest a 10 ohm or so resistor between analog and digital supplies, as well as a separate 100n capacitor. Other times you'll need a completely separate supply. It really depends on the application.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-05T14:31:56.880" CommentCount="3" />
  <row Id="7540" PostTypeId="1" AcceptedAnswerId="7543" CreationDate="2010-12-05T14:34:18.800" Score="0" ViewCount="443" Body="&lt;p&gt;I am asked as a term project to design a circuit that is somewhat similar to a park sensor. Let me first say that I am a 2nd year undergrad student, and we are very newly beginning to get into the circuit design stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the project, I roughly have what to do in mind, except I have no idea how to utilize the TK-19 sensor. I have provided the link to the datasheet below, I would be very glad if someone can tell me what happens when this thing detects IR radiation, or does not, that is the main question in my mind.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the link to the datasheet: &lt;a href=&quot;http://www.datasheetcatalog.org/datasheets/restul/305097_DS.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.datasheetcatalog.org/datasheets/restul/305097_DS.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Let me note that we are only allowed to use diodes(including LEDs and IR LEDs), capacitors, resistors and opamps.&lt;/p&gt;&#xA;" OwnerUserId="2188" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-11T03:45:06.420" LastActivityDate="2011-05-28T03:00:35.333" Title="How can I use a Integrated IR Receiver IC in a sensor circuit without microprocessors?" Tags="&lt;sensor&gt;&lt;ir&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="7541" PostTypeId="1" AcceptedAnswerId="7542" CreationDate="2010-12-05T14:40:45.687" Score="1" ViewCount="109" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I have some stepper motors with a step angle of 1.8 degrees and I am wondering if it is possible that powering the coils next to each would it get the spindle to go to midpoint between the two coils? So for example power coil 3 and 4 to get it to go between both points(so step angle between 0.9 degrees) or will it keep moving very slightly? I only ask as the stepper motors are at college and its the weekend so can't test it. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-12-05T14:57:03.480" Title="Is half stepping possible by powering the two consecutive coils?" Tags="&lt;stepper-motor&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="7542" PostTypeId="2" ParentId="7541" CreationDate="2010-12-05T14:57:03.480" Score="8" ViewCount="" Body="&lt;p&gt;Generally yes, although the half step positions may be slightly less accurate than the full ones. Bear in mind you are putting twice the power through the motor so heat may be more of an issue.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-05T14:57:03.480" CommentCount="1" />
  <row Id="7543" PostTypeId="2" ParentId="7540" CreationDate="2010-12-05T15:12:49.360" Score="2" ViewCount="" Body="&lt;p&gt;The sensor outputs a high level if it detects the proper input signal, being an IR carrier of 30..56 kHz, depending on the type you chose. Build a IR transmitter which transmits such a carrier. You don't need a microcontroller for that. (I leave it to you to solve this; I'm not going to do your homework completely! :-)) Direct the transmitter to any possible obstacles. If the receiver looks in the same direction it will pick up the reflected signal if you get close enough to the obstacle.&lt;br&gt;&#xA;Success!&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-05T15:32:54.757" LastActivityDate="2010-12-05T15:32:54.757" CommentCount="3" />
  <row Id="7544" PostTypeId="1" AcceptedAnswerId="7546" CreationDate="2010-12-05T15:24:57.167" Score="2" ViewCount="328" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got a PCB (from a multimeter) that apparently has 2 traces on the PCB burned away.&#xA;How they did it, I don't exactly know, but the traces are really gone completely.&#xA;The problem is however, that these traces disappeared up to a via they were connecting to...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So little graphical representation(&quot;=&quot; = trace, &quot;-&quot; = disappeared trace, &quot;o&quot; = via) : =====-----o&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another complication: if I would solder a small wire through the via, it can't protrude at the other side, because the other side are the sliding contacts of the dial of this multimeter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, who's got the best option to repair these traces? Thanks!&lt;/p&gt;&#xA;" OwnerUserId="2189" LastActivityDate="2010-12-06T13:16:12.527" Title="Repair a burned trace on a PCB" Tags="&lt;pcb&gt;&lt;repair&gt;&lt;damage&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="7545" PostTypeId="2" ParentId="7538" CreationDate="2010-12-05T15:34:36.367" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://mbed.org/forum/mbed&quot; rel=&quot;nofollow&quot;&gt;mbed forum &lt;/a&gt; is the best place for questions like that, it's been answered there. However, mbed binaries can be executed on any target using the same device. &lt;a href=&quot;http://mbed.org/users/chris/notebook/prototype-to-hardware/&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; are the details from the mbed Notebook.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-05T15:39:40.873" LastActivityDate="2010-12-05T15:39:40.873" CommentCount="5" />
  <row Id="7546" PostTypeId="2" ParentId="7544" CreationDate="2010-12-05T15:42:57.987" Score="5" ViewCount="" Body="&lt;p&gt;Scrape any solder mask away from the via and solder to the via itself.  Use very thin wire, since this trace is acting as a fuse.  Or throw this meter in the trash before someone gets hurt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's probably something you can do with conductive glue, but I have no experience with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where else does the trace go?  You can connect anywhere else on the circuit node and it should work.  (Not always.)&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-05T15:42:57.987" CommentCount="6" />
  <row Id="7547" PostTypeId="2" ParentId="7544" CreationDate="2010-12-05T15:46:25.417" Score="0" ViewCount="" Body="&lt;p&gt;Can you place a piece of tinned copper foil on the dial side? You could solder a wire on it, feed it through the via, and solder it to the damaged trace.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-05T15:46:25.417" />
  <row Id="7548" PostTypeId="2" ParentId="7535" CreationDate="2010-12-05T16:59:10.190" Score="1" ViewCount="" Body="&lt;p&gt;Those look pretty good.  The only other thing you may want to consider is if any audio cables are shielded you'll want to make sure the shielding gets grounded intelligently.  I think that's usually that's best done to the chassis but I'm no expert on the subject.  I suppose if you really want to be thorough and you have a metal chassis you can create a third ground just for it and make sure that the shields get shorted to it.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-12-05T16:59:10.190" CommentCount="5" />
  <row Id="7549" PostTypeId="1" AcceptedAnswerId="7553" CreationDate="2010-12-05T18:54:04.493" Score="5" ViewCount="434" Body="&lt;p&gt;Now I know in order to have an I2C address reserved for yourself you have to pay the I2C people some money. But I don't want to do this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm asking for advice on what address I should choose for my slave and master MCUs on my project. There will also be an EEPROM on the board. So I will avoid using the address of the EEPROM. I plan for the master to connect to a wide range of sensors, including gyros and accelerometers, and perhaps additional memory devices. Are there any blocks of addresses I should stay clear of? I was thinking of just using 0x00 for the master and 0x01 for the slave, because those seem to be rarely used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another question: would it be a bad idea to mix 10-bit devices and 7-bit devices on the same bus? I was considering the possibility of having my MCUs communicate with 10-bit addressing, but only using 7-bit addresses for sensors.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-06T12:39:22.933" Title="What I2C address should I choose?" Tags="&lt;i2c&gt;" AnswerCount="4" CommentCount="14" FavoriteCount="4" />
  <row Id="7550" PostTypeId="2" ParentId="7535" CreationDate="2010-12-05T19:18:28.570" Score="5" ViewCount="" Body="&lt;p&gt;I've never had an issue with I2C being audible in a circuit including using I2C adjustable resistors in a 60dB gain microphone pre-amp so i doubt you'll have much issue but here are some thoughts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Avoid using multiple ground planes unless you really need it.  You can easily cause more noise problems than you solve if your not very careful to avoid routing any signal over the split in the plane.  Unless your goal is very high fidelity, use a single solid ground plane.  In general you will find almost every mixed signal IC will call for separate analog and digital grounds/supplies.  While this is great in an ideal world, if you don't have the space to do this properly, you will cause more noise problems than you will solve.  For instance your better off using a single power supply with an LC filter in front of the analog input than you are running a separate supply across the board on a 15mil trace.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other thoughts:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Use an I2C clock above the audio range, 40khz or higher.  Use the largest pull up resistors you can given your bus speed.  This limits the current and hence noise generation.  Also make sure the I2C bus isn't ringing, if it is use series termination at all devices (40-50ohm resistor should be fine).  Match the I2C traces to 50ohm if you can and make 1 long run through all devices rather than T-ing off the bus.&lt;/li&gt;&#xA;&lt;li&gt;A single, solid ground plane.  Remember that high frequency signals will follow the path of least inductance to ground, not the path of least resistance.  With this in mind lay out the PCB such that ground currents from the digital portions are not traveling under the analog portions.&lt;/li&gt;&#xA;&lt;li&gt;Proper decoupling, do not use resistors.  You have to calculate this for your particular design but a 0.1uF and a 10nF ceramic cap per power pin and larger, 10uF caps per major IC or section is generally a safe bet.  Always place caps as close as possible to the power pin and get to ground ASAP.  Don't be stingy with the vias, even using multiple vias to ground for each decoupling cap is not a bad idea if you have the space.&lt;/li&gt;&#xA;&lt;li&gt;Use either a separate regulated power supply or use an LC filter to segment off an analog supply from the digital supply.  If you use a split plane, you again can't cross this split on an adjacent layer with ANY traces.&lt;/li&gt;&#xA;&lt;li&gt;Use protection around any sensitive analog components or pins.  Ground rings around op amp inputs, etc.  In fact a ground pour on the surface of the analog section is not a bad idea as long as its properly coupled to the ground plane (lots of vias) and doesn't have orphaned copper.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-12-05T19:18:28.570" />
  <row Id="7551" PostTypeId="2" ParentId="7549" CreationDate="2010-12-05T19:26:26.897" Score="4" ViewCount="" Body="&lt;p&gt;Here is a list of allocated addresses as of 1999: &lt;a href=&quot;http://www.nxp.com/acrobat_download2/selectionguides/SELGUIDE.PDF&quot; rel=&quot;nofollow&quot;&gt;http://www.nxp.com/acrobat_download2/selectionguides/SELGUIDE.PDF&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They don't release a full list with this reasoning:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Q: Is it possible to receive a list of&#xA;  all I²C-slave addresses used to date?&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;A: No. NXP Semiconductors do not issue&#xA;  this list of all previously assigned&#xA;  slave addresses, as this is the only&#xA;  way we can guarantee the list stays up&#xA;  to date and each assigned address is&#xA;  unique. If this list were made&#xA;  available, I²C-bus licensees would&#xA;  start selecting slave addresses&#xA;  themselves and the central list would&#xA;  soon become incomplete, which could&#xA;  lead to address conflicts. The&#xA;  principle established, proven to work&#xA;  well, is that each licensee sends a&#xA;  slave address request to a single&#xA;  contact within NXP Semiconductors, who&#xA;  then allocates the slave address based&#xA;  on a single master list.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;From &lt;a href=&quot;http://www.nxp.com/products/interface_control/i2c/faq/&quot; rel=&quot;nofollow&quot;&gt;http://www.nxp.com/products/interface_control/i2c/faq/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, if everything is going to be internal to your project, there is no reason you can't just select any address that you want as long as it doesn't conflict with anything you plan on connecting.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-05T19:26:26.897" />
  <row Id="7552" PostTypeId="2" ParentId="7549" CreationDate="2010-12-05T19:38:50.243" Score="0" ViewCount="" Body="&lt;p&gt;As Kellenjb says you won't get a full list of slave device addresses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However there are several reserved addresses which you can not use (0x00 for example is the general call address).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.i2c-bus.org/addressing/&quot; rel=&quot;nofollow&quot;&gt;The list is here&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mixing 10 and 7 bit addressing is fine as long as the 7bit slaves obey the I2C standard and ignore 10 bit addresses.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-12-05T19:38:50.243" />
  <row Id="7553" PostTypeId="2" ParentId="7549" CreationDate="2010-12-05T19:39:16.687" Score="4" ViewCount="" Body="&lt;p&gt;First, don't use 0x00 and 0x01, those are reserved!  Table 3 of the &lt;a href=&quot;http://ics.nxp.com/support/documents/interface/pdf/i2c.bus.specification.pdf&quot; rel=&quot;nofollow&quot;&gt;I2C Bus Specification&lt;/a&gt; lists the reserved addresses (and reasons why): &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;Slave addr  R/W   Description&#xA;0000 000    0     General call address[1]&#xA;0000 000    1     START byte[2]&#xA;0000 001    X     CBUS address[3]&#xA;0000 010    X     Reserved for different bus format[4]&#xA;0000 011    X     Reserved for future purposes&#xA;0000 1XX    X     Hs-mode master code&#xA;1111 1XX    X     Reserved for future purposes&#xA;1111 0XX    X     10-bit slave addressing&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You should also steer clear of 0x00 because that has no edge transitions, and might be an error condition (and it's hard to debug). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than that, I'd say &quot;Just make it configurable.&quot; If you want to be able to plug in a wide variety of sensors, then you can either pay NXP for an address, or give it adjustable addresses.  Software modifications should be obvious if you want to distribute the source code.  A hardware option to toggle one or two bits of your selected address (solder jumpers on digital pins) is cheap and easy, or a ladder network of resistors with jumpers connected to an A/D pin could give you complete control in the hardware.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-05T19:39:16.687" CommentCount="2" />
  <row Id="7554" PostTypeId="2" ParentId="7538" CreationDate="2010-12-05T19:55:05.167" Score="0" ViewCount="" Body="&lt;p&gt;Looks like the LPC17XX series is all the same core, just different peripherals, memory size and clock speeds.  So the code should work, as long as you don't run out of memory, try to use a peripheral that isn't there or have timing dependent code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can program the chip via JTAG or its built-in bootloader which allows programming via UART0 which could be attached to a RS232 port, a UART to USB chip, or whatever you want.  There is a pin that needs to be held low at during reset to get into the on chip bootloader.  &lt;a href=&quot;http://ics.nxp.com/support/documents/microcontrollers/pdf/user.manual.lpc17xx.pdf&quot; rel=&quot;nofollow&quot;&gt;See the user manual for more details.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-12-05T19:55:05.167" />
  <row Id="7555" PostTypeId="1" AcceptedAnswerId="7556" CreationDate="2010-12-05T21:21:23.057" Score="2" ViewCount="280" Body="&lt;p&gt;I've been inspired by the guys at &lt;a href=&quot;http://diydrones.com/&quot; rel=&quot;nofollow&quot;&gt;DIY Drones&lt;/a&gt; and I'm toying with the idea of making a UAV. To transmit the sensor data, I was thinking I'd go with a 60mW XBee, but I also would like to transmit live video. I'm having a hard time finding a way to transmit live video because I think the XBee will only transmit at low speed. Any idea what camera/transmitter/receiver combo would be possible? I think 1-5 miles range would be ok.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for specific products/links.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastEditorUserId="2006" LastEditorDisplayName="" LastEditDate="2010-12-06T03:23:25.103" LastActivityDate="2010-12-06T03:23:25.103" Title="Want to make a UAV" Tags="&lt;wireless&gt;&lt;radio&gt;&lt;video-transmitter&gt;&lt;uav&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="3" />
  <row Id="7556" PostTypeId="2" ParentId="7555" CreationDate="2010-12-05T22:08:47.117" Score="5" ViewCount="" Body="&lt;p&gt;I believe that the legal option here would be a 900MHz or 2.4GHz solution.  There are some specialty RC Wireless and Video suppliers like &lt;a href=&quot;http://hobbywireless.com/cart/index.php&quot; rel=&quot;nofollow&quot;&gt;Hobby Wireless&lt;/a&gt; that carry several different camera/transmitter/receiver solutions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember that it is currently illegal to fly R/C aircraft outside of your line-of-sight (both the AMA and FAA are pretty strict on this).  All model aircraft must remain in the pilot's sight during the entire duration of the flight.  I'm not sure how enforced this is, but you would probably be wise to stay on the legal side of things as you are doing your UAV experiments.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-12-05T22:08:47.117" CommentCount="4" />
  <row Id="7557" PostTypeId="2" ParentId="7530" CreationDate="2010-12-05T22:16:51.583" Score="2" ViewCount="" Body="&lt;p&gt;I don't believe that the Netduino has the processing power that you want to stream video over the network.  I believe that you could get any wifi webcam to work with the robot, though.  You would just need a little extra space in your power budget to account for the camera's additional power usage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on how soon you need the camera, I would just watch the winter sales on any of the big technology suppliers (Newegg, Tigerdirect, Amazon) for a deal on a wifi webcam that meets the specifications that you are looking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are looking to make your project entirely self-contained, then you may want to check out the &lt;a href=&quot;http://www.cmucam.org/&quot; rel=&quot;nofollow&quot;&gt;CMUcam&lt;/a&gt;.  It provides a good vision sensor, without having to do much processing on your Netduino chip.  It can do most basic vision processing on-board, without the need for your chip to handle the processor intensive image processing.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-12-05T22:16:51.583" />
  <row Id="7558" PostTypeId="2" ParentId="7555" CreationDate="2010-12-05T22:29:23.370" Score="3" ViewCount="" Body="&lt;p&gt;Legal issues aside, use a separate communication channel for the video stream.  This way it will simplify your hardware and allow you use commercial off the shelf wireless transmitter and receiever the video, and a dedicated control and sensor channel using Xbee (or alternative) communication channel.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-12-05T22:29:23.370" CommentCount="0" />
  <row Id="7559" PostTypeId="1" AcceptedAnswerId="7561" CreationDate="2010-12-05T23:11:51.260" Score="3" ViewCount="177" Body="&lt;p&gt;I am making a PCB with a subtractive PCB mill, and I am having difficulty soldering some components to the finished copper. The solder isn't flowing onto the traces easily, and by the time it does flow, the pad lifts. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure if the boards need to be cleaned more, or if they need to be covered with a tinning solution (or both). What can I do to make the board easier to solder?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When should I clean my boards - just before or after milling?&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-06T01:36:52.687" Title="Improving ease-of-soldering in home-made boards" Tags="&lt;pcb&gt;&lt;soldering&gt;&lt;pcb-fabrication&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="7560" PostTypeId="2" ParentId="7559" CreationDate="2010-12-05T23:14:17.550" Score="2" ViewCount="" Body="&lt;p&gt;Clean with wire wool after milling, then a coat of flux to prevent forther oxidisation.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-05T23:14:17.550" CommentCount="4" />
  <row Id="7561" PostTypeId="2" ParentId="7559" CreationDate="2010-12-05T23:15:43.957" Score="4" ViewCount="" Body="&lt;p&gt;Immersion tinning would help, but I'd simply use a flux pen on the pads. Rubbing them lightly with Scotchbrite will also help.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-06T01:36:52.687" LastActivityDate="2010-12-06T01:36:52.687" CommentCount="2" />
  <row Id="7562" PostTypeId="2" ParentId="6994" CreationDate="2010-12-05T23:19:07.927" Score="1" ViewCount="" Body="&lt;p&gt;CW/CCW - Clockwise &amp;amp; Counterclockwise. a lot of turntable motors for microwaves will alternate the spin direction to help even out cooking, each time it is powered up the spin will reverse from the previous time...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1st time, let say clockwise&#xA;2nd time, then counterclockwise&#xA;3rd time, clockwise again...&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2010-12-05T23:19:07.927" />
  <row Id="7563" PostTypeId="2" ParentId="7559" CreationDate="2010-12-05T23:50:30.770" Score="-1" ViewCount="" Body="&lt;p&gt;Use soft wire wool after milling and then a spray coat such as &lt;a href=&quot;http://www.kaisertech.co.uk/acatalog/Products__Servisol_Plastic_Seal_60_65_Conformal_Coating_476.html&quot; rel=&quot;nofollow&quot;&gt;Servisol plastic seal 60&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2010-12-05T23:50:30.770" CommentCount="2" />
  <row Id="7564" PostTypeId="2" ParentId="7555" CreationDate="2010-12-06T00:36:49.270" Score="1" ViewCount="" Body="&lt;p&gt;Use analog video and a video transmitter/receiver pair.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Total cost less than $50 US.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-06T00:36:49.270" CommentCount="2" />
  <row Id="7565" PostTypeId="2" ParentId="7538" CreationDate="2010-12-06T01:07:56.197" Score="0" ViewCount="" Body="&lt;p&gt;You can use the lpc21isp programmer which was originally written for the LPC21xx series but  recent versions also support the LPC17xx series. It requires only a serial port but it is helpful to connect the RESET and ISP pins because they will have to be manipulated to force the chip into the bootloader.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are binaries for Windows and the code compiles without problems on both Linux and OS X.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. There is also JTAG but how would want to use that. :)&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-12-06T01:07:56.197" />
  <row Id="7566" PostTypeId="1" AcceptedAnswerId="7568" CreationDate="2010-12-06T01:09:36.117" Score="2" ViewCount="202" Body="&lt;p&gt;I have a PIC24FJ32GA002.  I think I killed by accidently exposing it to 5V instead of the rated 3.3V. It was very quick, less than half a second. I am not able to get it to communicate with my programmer, but I didn't test it beforehand, so I am not sure if my circuit is wrong or I have wired something up incorrectly. Unfortunately I can't get any more MCUs any time soon. Is there any way to determine if the MCU is truly dead?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-12-09T12:42:51.917" LastActivityDate="2010-12-09T12:42:51.917" Title="Is there a sure-fire way to determine if an MCU is fried?" Tags="&lt;microcontroller&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="7567" PostTypeId="2" ParentId="7516" CreationDate="2010-12-06T01:13:26.333" Score="0" ViewCount="" Body="&lt;p&gt;I would guess that probably the MOC+triac combination is so good and cheap that almost nobody wants to buy the packaged version (maybe someone with very restricted board area but I am not sure if the SSR is much smaller). It is expensive to manufacture such components in low volumes.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2010-12-06T01:13:26.333" />
  <row Id="7568" PostTypeId="2" ParentId="7566" CreationDate="2010-12-06T01:27:19.790" Score="3" ViewCount="" Body="&lt;p&gt;You could try wiring up the bare minimum you need - supply and ground pins (decoupled), MCLR, PGC  and PGD - and seeing if you can program it. If that doesn't work the only sure way to find out if the chip is functional is to get another one. If that works, the first chip is faulty.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I always buy at least two of any MCU.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-06T01:34:37.713" LastActivityDate="2010-12-06T01:34:37.713" CommentCount="1" />
  <row Id="7569" PostTypeId="2" ParentId="7566" CreationDate="2010-12-06T01:38:23.767" Score="2" ViewCount="" Body="&lt;p&gt;Are you looking for a general solution to verify RAM, Flash, and peripherals, or just to determine if it's still programmable?  It reads like you're looking for the latter, but I'm not sure that's wise.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you've exposed it to conditions outside its ratings, it's likely to have &lt;em&gt;something&lt;/em&gt; wrong with it.  Whether you discover it now, later, or never (there was nothing wrong), I wouldn't want to have to keep asking myself &quot;Is it the MCU?&quot; every time there was a fault.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is for production, you should have a test set, which verifies all the functions of your device.  In that case, if it passes the tests, it's good.  If not, toss it.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-06T01:38:23.767" CommentCount="1" />
  <row Id="7570" PostTypeId="1" AcceptedAnswerId="7578" CreationDate="2010-12-06T02:53:12.700" Score="1" ViewCount="152" Body="&lt;p&gt;I am trying to make some Arduino code count on a 7 segment display. I have the wiring all right but this code will not delay one second and go to next function. Any ideas?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/*&#xA;  Blink&#xA;  Turns on an LED on for one second, then off for one second, repeatedly.&#xA;  This example code is in the public domain.&#xA; */&#xA;&#xA;void setup() {                &#xA;  // initialize the digital pin as an output.&#xA;  // Pin 13 has an LED connected on most Arduino boards:&#xA;  pinMode(3,OUTPUT);    pinMode(4,OUTPUT);    pinMode(5,OUTPUT);&#xA;  pinMode(6,OUTPUT);    pinMode(7,OUTPUT);    pinMode(8,OUTPUT);&#xA;  pinMode(9,OUTPUT); &#xA;}   &#xA;&#xA;void n0() {&#xA;  digitalWrite(3,LOW);  digitalWrite(4,LOW);  digitalWrite(5,LOW);&#xA;  digitalWrite(6,LOW);  digitalWrite(7,LOW);  digitalWrite(8,LOW);&#xA;  digitalWrite(9,HIGH);&#xA;}&#xA;&#xA;void ndash() {&#xA;  digitalWrite(3,HIGH); digitalWrite(4,HIGH); digitalWrite(5,HIGH);&#xA;  digitalWrite(6,HIGH); digitalWrite(7,HIGH); digitalWrite(8,HIGH);&#xA;  digitalWrite(9,LOW);&#xA;}&#xA;&#xA;void loop() {&#xA;  n0();&#xA;  delay(1000);&#xA;  ndash();&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2184" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-06T07:29:27.603" LastActivityDate="2010-12-06T07:29:27.603" Title="What is wrong with my Arduino 7-segment display code?" Tags="&lt;arduino&gt;&lt;software&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="7572" PostTypeId="1" AcceptedAnswerId="7576" CreationDate="2010-12-06T04:36:17.673" Score="1" ViewCount="119" Body="&lt;p&gt;Hello. I'm still pretty novice at electronics. I've recently been thinking of a project to make. The difference in this from my other projects is that for this I would need quite a bit of power. I'm use to using only a USB or battery powers supply. For this one though I think a PC power supply will be needed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What precautions and considerations should I have when working with more amps(though the same amount of voltage)? If I hook an LED up to 5V, 500ma then it lights and works well. Will that be the same if I hook it up to 5V, 22A? What about for microcontrollers and other integrated circuits? Will they not be fried by the higher amperage? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I do have something that does specify a max amperage rating, how do I decrease the amperage without affecting the voltage?&lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-05-13T00:26:53.777" LastActivityDate="2011-05-13T00:26:53.777" Title="What considerations should I have for high-current power supplies?" Tags="&lt;power-supply&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="7573" PostTypeId="2" ParentId="7572" CreationDate="2010-12-06T04:40:12.303" Score="3" ViewCount="" Body="&lt;p&gt;In your case, the current rating of your power supplies is the current AVAILABLE, not the current actually PROVIDED. a 5V 500mA load (like your LED) will always draw 500mA from a 5V power supply. &lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-12-06T04:40:12.303" CommentCount="4" />
  <row Id="7574" PostTypeId="2" ParentId="7566" CreationDate="2010-12-06T04:50:41.577" Score="1" ViewCount="" Body="&lt;p&gt;Is there a sure-fire way to detect &lt;em&gt;every&lt;/em&gt;  failure? No.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Failure or damage can occur in a variety of ways, some of which are very subtle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fundamentally, ass you can really do is exercise whatever aspects of a device you are intending to use, in such a way that any erroneous behavior is detected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some failures are obvious (failure short-to-ground, for example). On the other hand, if you have damage to an onboard peripheral which causes 1 bit error every 500 bytes, how would you check for it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyways, I would imagine that the PIC &lt;em&gt;may&lt;/em&gt; be ok. I once accidentally ran a PIC12 on 12V for long enough that it actually melted my breadboard (the voltage regulator failed short input-output), and it apparently kept working fine, it just got really hot.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-12-06T04:50:41.577" />
  <row Id="7575" PostTypeId="2" ParentId="7516" CreationDate="2010-12-06T04:59:10.257" Score="6" ViewCount="" Body="&lt;p&gt;Principally, you're paying for the testing. UL and CE testing is &lt;em&gt;Very&lt;/em&gt; expensive. Also, lifetime and reliability testing (the crydom relays are specced to 100,000 cycles), which means that crydom has actually run a number of the devices through 100,000 cycles at load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Furthermore, you're also paying for liability insurance. If an appliance fails and kills someone, and the only AC-facing component was a crydom relay, it's crydom's problem. If the AC components are your own, it's your problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lastly, while it's true that a discrete relay solution is preferable in large volumes, you often see SSRs in small-volume or specialty products, where assembly and testing costs dominate the expenses, rather than raw component costs.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-12-06T04:59:10.257" />
  <row Id="7576" PostTypeId="2" ParentId="7572" CreationDate="2010-12-06T05:01:43.670" Score="8" ViewCount="" Body="&lt;p&gt;This is a pretty common mistake for people new to electronics. Most power supplies are designed to provide a constant voltage (5v in your case). Your circuit then provides a resistance of some sort, with microcontrollers and capacitors and such the resistance will change with time, but for beginners its usually best to think of your circuit has having a constant resistance as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So V/R=I, since V and R are constant, I will stay the same also.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current that is given for your power supply is just the max that the power supply can output and guaranty a steady 5v. So if you work the V/R equation out and get 1Amp, then a 500mA power supply wont work for you, but a 22Amp supply will.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Sometimes this analogy helps people understand what is happening&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think of:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;voltage as the height above the ground you are&lt;/li&gt;&#xA;&lt;li&gt;current being the act of an object falling&lt;/li&gt;&#xA;&lt;li&gt;max current as how much area you have to fall down in&lt;/li&gt;&#xA;&lt;li&gt;an orange and an elephant as being 2 different circuits you have built&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So if you have an elevator shaft that you drop an orange in from 100ft it will act the same (or close to if you ignore stuff like wind) as dropping an orange from 100ft off the top of the building. Now if you try to drop an elephant down an elevator shaft it will act much differently then if you drop an elephant off the top of a 100ft building.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So in the case of your original circuit (the orange) a 500mA max power supply (the elevator shaft) will act just the same as a 22amp power supply. (Off the top of the roof)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But when you go to your new circuit (the elephant) a 500mA max power supply will act much differently then a 22amp power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Warning&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A power supply that can output more current means that you have a greater chance of killing components if hooked up wrong. If you always hook stuff up correctly it wont ever be an issue, but I don't know anyone who has never accidentally hooked something up wrong.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-06T05:01:43.670" CommentCount="2" />
  <row Id="7577" PostTypeId="2" ParentId="7525" CreationDate="2010-12-06T05:27:57.710" Score="3" ViewCount="" Body="&lt;p&gt;Cleaned Schematic with niceties (bypass caps, pin numbers, etc...):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://i.imgur.com/3VjEc.jpg&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/3VjEc.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the FT245 you could use multiple shorter shift-register chains, since you have more IO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I didn't draw it like that, but there you are. Anyways, the schematic is done in Altium Designer. If you want the schematic files, I can send them to you, but you need the software to open it.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-07T00:32:39.967" LastActivityDate="2010-12-07T00:32:39.967" CommentCount="7" />
  <row Id="7578" PostTypeId="2" ParentId="7570" CreationDate="2010-12-06T05:35:50.943" Score="6" ViewCount="" Body="&lt;p&gt;If I understand your symptoms correctly, you need a second delay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's what the code looks like if you executed the loop a few times:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  n0();&#xA;  delay(1000);&#xA;  ndash();&#xA;  n0();&#xA;  delay(1000);&#xA;  ndash();&#xA;  n0();&#xA;  delay(1000);&#xA;  ndash();&#xA;  n0();&#xA;  delay(1000);&#xA;  ndash();&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;ndash() is only displayed for however long it takes for n0() to execute, which is probably too fast to see.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-06T05:35:50.943" CommentCount="2" />
  <row Id="7579" PostTypeId="1" AcceptedAnswerId="7580" CreationDate="2010-12-06T11:33:47.950" Score="2" ViewCount="150" Body="&lt;p&gt;I'm trying to buy &lt;a href=&quot;http://www.sparkfun.com/products/10206&quot; rel=&quot;nofollow&quot;&gt;these recently stocked connectors from Sparkfun&lt;/a&gt; from either Farnell or Digikey, but have no idea what they are called or how to find them. Also, what about the female connector that mates to this? And would I be easily (without an expensive tool) be able to crimp connectors for this series of connectors?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2010-12-06T18:19:10.517" Title="Where to find Sparkfun's 1.0mm pitch connectors?" Tags="&lt;connector&gt;&lt;sparkfun&gt;" AnswerCount="2" />
  <row Id="7580" PostTypeId="2" ParentId="7579" CreationDate="2010-12-06T12:38:54.770" Score="3" ViewCount="" Body="&lt;p&gt;This type of connector is known as &quot;wafer connectors&quot; or &quot;PCB SMT connector&quot; or &quot;Conn Header&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My suggestion for a search on google for a similar product: &lt;a href=&quot;http://www.google.com.br/search?sourceid=chrome&amp;amp;ie=UTF-8&amp;amp;q=conn+header+2pos+1mm+right+angle&quot; rel=&quot;nofollow&quot;&gt;conn header 2pos 1mm right angle&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-12-06T12:38:54.770" CommentCount="2" />
  <row Id="7581" PostTypeId="2" ParentId="7549" CreationDate="2010-12-06T12:39:22.933" Score="1" ViewCount="" Body="&lt;p&gt;Pick a device you positively won't be using in your design and use it's I2C address. For instance, if you won't be needing a RTC, you can use 0xA2 and 0xA3, which are used by the NXP PCF8563 (and probably other RTCs).&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-06T12:39:22.933" />
  <row Id="7582" PostTypeId="2" ParentId="7544" CreationDate="2010-12-06T13:16:12.527" Score="1" ViewCount="" Body="&lt;p&gt;The burnt traces are a symptom. Something shorted out and caused them to burn. Unless you can find and fix the root cause, there is no sense in repairing the traces.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-12-06T13:16:12.527" CommentCount="1" />
  <row Id="7583" PostTypeId="1" AcceptedAnswerId="7601" CreationDate="2010-12-06T14:45:27.607" Score="2" ViewCount="265" Body="&lt;p&gt;Hey,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using a PIC micro with a 10bit ADC to take readings from an analog signal with a frequency less than 300 hz. However that analog signal is in the range of -2 V and +2 V. How can I condition the signal to get it into a usable range (assuming the input to the ADC has to be positive) Also I do not have a positive and negative power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be much appreciated,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank You :)&lt;/p&gt;&#xA;" OwnerUserId="2200" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-06T23:44:19.503" LastActivityDate="2010-12-06T23:44:19.503" Title="How do I sample a -2 V to +2 V analog signal with a PIC microcontroller?" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;analog&gt;&lt;adc&gt;&lt;op-amp&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="7584" PostTypeId="2" ParentId="7583" CreationDate="2010-12-06T14:51:22.050" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.leonheller.com/images/Bipolar-unipolar.gif&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is the standard circuit for that. You need to scale the resistor values for your required impedance.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-06T14:51:22.050" CommentCount="3" />
  <row Id="7585" PostTypeId="1" CreationDate="2010-12-06T15:10:14.753" Score="1" ViewCount="115" Body="&lt;p&gt;The &lt;a href=&quot;http://ics.nxp.com/products/pca/datasheet/pca8574.pca8574a.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet for the NXP PCA8574/74A&lt;/a&gt; contains the following line on addressing (p.6):&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;When AD2, AD1 and AD0 are held to VDD or VSS, the same address as the PCF8574 or&#xA;  PCF8574A is applied.  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I'm afraid I don't understand what is meant here. Can someone clarify please?&lt;br&gt;&#xA;Also, while address ranges are given as (depending on inputs AD0..AD2)   &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;PCF8574: 0x20 - 0x27&lt;br&gt;&#xA;  PCF8574A: 0x38 - 0x3F  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;both the text and fig.7 suggest that the device address can freely be chosen between 0x01 and 0x7F (though I don't see how this would be done).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Kr6hl.png&quot; alt=&quot;alt text&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or am I reading this wrong?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-06T16:19:59.573" Title="Confused about I2C addressing in PCA8574/74A" Tags="&lt;i2c&gt;&lt;addressing&gt;" AnswerCount="1" />
  <row Id="7586" PostTypeId="1" AcceptedAnswerId="7588" CreationDate="2010-12-06T15:43:28.993" Score="4" ViewCount="206" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking at an electrolytic capacitor (and old blue, Philips one used in electronics classes) and am wondering why it is printed with &lt;strong&gt;4µ7-M&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried Googling, figuring that it was a common enough occurrence, but found nothing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is that supposed to be a 47µF cap? Why is the µ in the middle of the number? What is the -M for?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2042" LastActivityDate="2010-12-06T17:35:32.267" Title="µ in the Middle of a Capacitor Rating" Tags="&lt;capacitor&gt;&lt;capacitance&gt;&lt;ratings&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="7588" PostTypeId="2" ParentId="7586" CreationDate="2010-12-06T15:48:10.377" Score="11" ViewCount="" Body="&lt;p&gt;The &quot;µ&quot; symbol is put in place of the decimal point, 4µ7 translates to 4.7 µ farads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not too sure about the &quot;-M&quot; part tho - sorry&lt;/p&gt;&#xA;" OwnerUserId="399" LastActivityDate="2010-12-06T15:48:10.377" CommentCount="2" />
  <row Id="7589" PostTypeId="1" AcceptedAnswerId="7592" CreationDate="2010-12-06T16:08:04.017" Score="4" ViewCount="148" Body="&lt;p&gt;I am wanting to connect 2 boards together with a cable.  I want the connectors on the boards to be surface mount and have clips to hold the cable onto it.  I need about 8 - 10 pins.  I don't want to have to crimp wires or solder them, I would prefer something like a ribbon cable.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been searching all morning and cannot find anything really to fit the bill.  I checked at mouser and digikey.  I really don't know what all the keywords mean e.g. &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Interconnects &#xA;  • Attenuators (146) &#xA;  • Audio / Video Connectors (5,867) &#xA;  • Automotive Connector Accessories (410) &#xA;  • Automotive Connectors (5,458) &#xA;  • Circular Connectors (66,507) &#xA;  • D-Subminiature Connectors (20,969) &#xA;  • DC Power Connectors (597) &#xA;  • Fiber Optic Connectors (2,042) &#xA;  • I/O Connectors (4,135) &#xA;  • IC &amp;amp; Component Sockets (9,755) &#xA;  • Lighting Connectors (320) &#xA;  • Memory Card Connectors (1,610) &#xA;  • Photovoltaic (Solar) Connectors (139) &#xA;  • Power Entry Modules (2,273) &#xA;  • Power Line Filters (3,257) &#xA;  • Rectangular Connectors (146,383) &#xA;  • RF Connectors (8,466) &#xA;  • Telecom &amp;amp; Ethernet Connectors (6,423) &#xA;  • Terminal Blocks (46,818) &#xA;  • Terminals (12,834) &#xA;  • Test Connectors, Probes &amp;amp; Testleads (2,002) &#xA;  • Test Points (124) &#xA;  • Unspecified Connectors (84) &#xA;  • USB &amp;amp; Firewire Connectors (1,130) &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Some of them I can figure out.  Any help would be appreciated.  I can find really anything but cables.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="1414" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-06T17:02:29.880" LastActivityDate="2010-12-06T17:02:29.880" Title="Looking for a board-to-board cable." Tags="&lt;cables&gt;&lt;interconnect&gt;" AnswerCount="1" CommentCount="5" FavoriteCount="1" />
  <row Id="7590" PostTypeId="2" ParentId="7585" CreationDate="2010-12-06T16:13:53.757" Score="1" ViewCount="" Body="&lt;p&gt;The data sheet clearly indicates that there are &quot;8 programmable slave addresses using 3 address pins&quot; right there in Section 2 bullet 7. In other words, there is a 7-bit address, 4 of those bits are the same for all chips (&lt;strong&gt;internally hard coded&lt;/strong&gt;), and 3 of them (bits 0, 1, and 2 in particular) are programmable by setting (i.e. &lt;strong&gt;electrically connecting&lt;/strong&gt;) the pin values to either Vss (GND) or Vdd (i.e. 5V). What the top 4 bits are &lt;strong&gt;internally hard coded&lt;/strong&gt; to depends on the chip you are using - table 4 indicates that those bits are A[6:3] = 0100 for the PCA8574 and table 5 indicates that those bits are A[6:3] = 0111 for the PCA8574A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make it crystal clear, for the PCA8574 the lowest address possible is&#xA;010 0000 == 0x20 and the highest address possible is 010 0111 == 0x27. Likewise for the PCA8574A the lowest address possible is 011 1000 == 0x38 and the highest address possible is 011 1111 == 0x3F. &lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-06T16:19:59.573" LastActivityDate="2010-12-06T16:19:59.573" CommentCount="3" />
  <row Id="7591" PostTypeId="2" ParentId="7586" CreationDate="2010-12-06T16:14:50.017" Score="7" ViewCount="" Body="&lt;p&gt;Like Jim said, the µ indicates the place of the decimal point. This isn't restricted to capacitors, but also used for resistors and inductors:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;resistor 31k6 = 31.6 kiloOhm&lt;br&gt;&#xA;  resistor 5M6 = 5.6 megaOhm&lt;br&gt;&#xA;  capacitor 2n2 = 2.2 nanoFarad&lt;br&gt;&#xA;  inductor 4µ7 = 4.7 microHenry&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-06T16:14:50.017" CommentCount="4" />
  <row Id="7592" PostTypeId="2" ParentId="7589" CreationDate="2010-12-06T16:56:32.397" Score="4" ViewCount="" Body="&lt;p&gt;For SMT if you want something reasonably small you could use flat flexible cables (FFC).  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1638962&quot; rel=&quot;nofollow&quot;&gt;Digi-Key / Cables, Wires / FFC, FPC (Flat Flexible)&lt;/a&gt; (spools of the stuff)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1573391&quot; rel=&quot;nofollow&quot;&gt;Digi-Key / Cable Assemblies / FFC, FPC (Flat Flexible), Ribbon - Jumpers&lt;/a&gt; (pre-cut)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Example:&#xA;&lt;img src=&quot;http://i.imgur.com/EJ4DY.jpg&quot; alt=&quot;8-pin FFC&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They mate with, surprise, FFC connectors, like these:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1442849&quot; rel=&quot;nofollow&quot;&gt;Digi-Key / Connectors, Interconnects / FFC, FPC (Flat Flexible) - Connectors - Board Mount&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/bT2Ei.jpg&quot; alt=&quot;Tyco FFC&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get them in zero-insertion force (ZIF) with a locking clasp, or LIF without, right-angle, vertical, etc.  Mind that &quot;pin 1&quot; to the same connector will be backwards if the cable is stripped on the same side--you can get &quot;upside down&quot; connectors however.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are very compact and easy to use, but their major downfall (especially for prototype use) is their low cycle life.  If you have to disconnect/reconnect it a dozen plus times, they aren't a solution&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-06T16:56:32.397" CommentCount="6" />
  <row Id="7593" PostTypeId="2" ParentId="7586" CreationDate="2010-12-06T17:19:19.887" Score="4" ViewCount="" Body="&lt;p&gt;It caused less confusion than sometimes arose with a decimal point, which was missed sometimes when documents were copied or faxed. That's not such a problem these days, but it is in common use, especially here in Europe. I always use that notation.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-06T17:35:32.267" LastActivityDate="2010-12-06T17:35:32.267" CommentCount="2" />
  <row Id="7594" PostTypeId="2" ParentId="7583" CreationDate="2010-12-06T17:23:52.100" Score="2" ViewCount="" Body="&lt;p&gt;If the signal is not DC, or if a DC reference isn't important, the signal can be capacitively coupled to the input of the ADC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, if your ground for the PIC is floating, you could tie your signal ground to 1/2 VDD of the PIC. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-06T17:23:52.100" CommentCount="2" />
  <row Id="7595" PostTypeId="1" CreationDate="2010-12-06T17:34:05.237" Score="3" ViewCount="182" Body="&lt;p&gt;I'm a .NET developer interested in the &lt;a href=&quot;http://research.microsoft.com/en-us/projects/gadgeteer/default.aspx&quot; rel=&quot;nofollow&quot;&gt;.NET Gadgeteer&lt;/a&gt;.  Based on what's public, how does it compare to other devices?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're interested, &lt;a href=&quot;http://channel9.msdn.com/Blogs/Clint/NET-Gadgeteer&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; is a Channel9 video that shows you how to use VS2010 to create an embedded application. It is due to release in Spring of 2011...&lt;/p&gt;&#xA;" OwnerUserId="2180" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-06T17:47:04.693" LastActivityDate="2010-12-07T17:48:49.723" Title="How does the proposed Microsoft .NET Gageteer compare to other systems?" Tags="&lt;.net-micro-framework&gt;&lt;.net&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="3" />
  <row Id="7596" PostTypeId="2" ParentId="7595" CreationDate="2010-12-06T18:03:04.657" Score="0" ViewCount="" Body="&lt;p&gt;Looks like it tries to do the same as a normal Embedded linux with Qt platform can do today. &#xA;Feel free to compare with the MeeGo project and let's say a Beagleboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But my guess is that you will be locked in on this .net platform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I get the feeling that they have created a more flashy version of the Lego Mindstorms system, but without the lego parts and with a little cooler hardware....&lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2010-12-06T18:10:31.247" LastActivityDate="2010-12-06T18:10:31.247" />
  <row Id="7597" PostTypeId="1" AcceptedAnswerId="7602" CreationDate="2010-12-06T18:18:42.780" Score="1" ViewCount="238" Body="&lt;p&gt;I have a signal from 0 to 10V dc.  I need to 24bit or better ADC that signal at 100ksps or greater.  I can't find ADCs that will do that, they either read at lower voltages or not as fast.  I have contemplated using a normal ADC with a MUX &lt;a href=&quot;http://www.sparkfun.com/products/9907&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/9907&lt;/a&gt; and tune each section to a seperate voltage range, then scan till its in range and ADC the signal then.  I didn't want to have to manipulate the data that much.  Or use a 4 2.5V ADCs using relative ADC line references and scan 0 - 2.5, 2.5 - 5, 5 - 7.5 , and 7.5 - 10.  Then add them together in the end to get the total ADC.  I would like to do this on one chip or know a &quot;good&quot; way to do it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for the help.&lt;/p&gt;&#xA;" OwnerUserId="1414" LastEditorUserId="1414" LastEditorDisplayName="" LastEditDate="2010-12-07T13:27:32.873" LastActivityDate="2010-12-07T15:10:17.730" Title="24bit or better ADC at 10V with at least 100ksps?" Tags="&lt;adc&gt;" AnswerCount="3" CommentCount="10" />
  <row Id="7598" PostTypeId="2" ParentId="7579" CreationDate="2010-12-06T18:19:10.517" Score="2" ViewCount="" Body="&lt;p&gt;Are 1.0mm pitch terminals easy to crimp? No.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having bought some 1mm crimp connectors in the past thinking &quot;that's huge&quot; (in soldering pitch terms), I soon regretted it after having crimped 30.  In later projects when I needed a bunch of low-current connections I used &lt;a href=&quot;http://electronics.stackexchange.com/questions/7589/looking-for-a-board-to-board-cable/7592#7592&quot;&gt;FFCs&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you only have two crimps to make, it might be worth a shot, though if you can find pre-crimped pigtails, I would jump on that.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-06T18:19:10.517" />
  <row Id="7599" PostTypeId="2" ParentId="7597" CreationDate="2010-12-06T19:14:48.287" Score="0" ViewCount="" Body="&lt;p&gt;Try a &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/1042&quot; rel=&quot;nofollow&quot;&gt;MAX197&lt;/a&gt;.  There are a couple of other versions that are similar, but this is a starting point.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-12-06T19:14:48.287" />
  <row Id="7600" PostTypeId="2" ParentId="7597" CreationDate="2010-12-06T19:42:23.660" Score="3" ViewCount="" Body="&lt;p&gt;Robert's MAX197 has a multiplexer, which you maybe don't need. You also don't mention word width. Here are a few single channel ADCs from Maxim:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/3738&quot; rel=&quot;nofollow&quot;&gt;MAX1156&lt;/a&gt;: 14-bit, 135ksps&lt;br&gt;&#xA;  &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/4040&quot; rel=&quot;nofollow&quot;&gt;MAX1177&lt;/a&gt;: 16-bit, 135ksps&lt;br&gt;&#xA;  &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/3647&quot; rel=&quot;nofollow&quot;&gt;MAX1187&lt;/a&gt;: 16-bit, 135ksps&lt;br&gt;&#xA;  &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/3640&quot; rel=&quot;nofollow&quot;&gt;MAX1157&lt;/a&gt;: 14-bit, 135ksps&lt;br&gt;&#xA;  &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/3068&quot; rel=&quot;nofollow&quot;&gt;MAX1132&lt;/a&gt;: 16-bit, 200ksps&lt;br&gt;&#xA;  &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/2533&quot; rel=&quot;nofollow&quot;&gt;MAX1142&lt;/a&gt;: 14-bit, 200ksps  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-06T19:42:23.660" CommentCount="2" />
  <row Id="7601" PostTypeId="2" ParentId="7583" CreationDate="2010-12-06T20:32:05.583" Score="0" ViewCount="" Body="&lt;p&gt;Although it is a more expensive solution you may use an AmpOp as a Summing Amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would be handfull if you need to change the DC offset or the sensor range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/DGfxv.png&quot; alt=&quot;Summing Amplifier&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Operational_amplifier_applications#Summing_amplifier&quot; rel=&quot;nofollow&quot;&gt;Summing Amplifier&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If negative supply is a problem you may use &lt;a href=&quot;http://www.national.com/mpf/LM/LM324.html#Overview&quot; rel=&quot;nofollow&quot;&gt;LM324&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-12-06T20:32:05.583" CommentCount="1" />
  <row Id="7602" PostTypeId="2" ParentId="7597" CreationDate="2010-12-06T21:06:05.320" Score="7" ViewCount="" Body="&lt;p&gt;If you're feeding this to a MCU or similar, I would use a basic resistor voltage divider to cut the 0-10 V to 0-5 V or similar.  I might pad the range a little to avoid saturation near the top-end due to tolerances, and maybe add some clamping diodes depending on the application.  Many MCUs are capable of 100 ksps nowadays, some DSPICs can even do 1 Msps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Random anecdote: One of my first PCBs I had made as an intern was a big resistor divider array for our test engineers who had to connect automotive analog stuff (0 V to BATT; 9 to 16 volts) to their 0-5 V DAQs.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Additions&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;24-bit @ 100 ksps...not doable with any MCU (I know of).  You can use &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8003.pdf&quot; rel=&quot;nofollow&quot;&gt;oversampling and decimation&lt;/a&gt; to hit 24 bits, but you take an effective 4x sample rate hit per bit of increased resolution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know about your application, but I might try to cheat and go with a 96 ksps rate.  96 kHz audio is fairly common nowadays, so it might be easier/cheaper to get an ADC for that.&lt;/p&gt;&#xA;&#xA;&lt;em&gt;Possible parts available @ DK:&lt;/em&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Cirrus Logic CS5343-CZZ - &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=598-1189-ND&quot; rel=&quot;nofollow&quot;&gt;IC ADC AUD 98DB 108KHZ 10-TSSOP&lt;/a&gt; (Cirrus has a few others, CS5346-CQZ, CS53L21-CNZ)&lt;/li&gt;&#xA;&lt;li&gt;Analog Devices AD1974YSTZ-ND - &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=AD1974YSTZ-ND&quot; rel=&quot;nofollow&quot;&gt;IC ADC 4CH W/ON-CHIP PLL 48LQFP&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Texas Inst. PCM1808PWR - &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=296-26307-1-ND&quot; rel=&quot;nofollow&quot;&gt;IC ADC 24BIT STER &lt;strong&gt;96KHZ&lt;/strong&gt; 14-TSSOP&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In any case, regardless of the IC, halving the range per bit with a voltage divider is a very clean and basic method, almost assuredly lower noise than passing through any demultiplexer.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-07T15:10:17.730" LastActivityDate="2010-12-07T15:10:17.730" CommentCount="1" />
  <row Id="7603" PostTypeId="1" AcceptedAnswerId="7680" CreationDate="2010-12-06T22:21:26.000" Score="0" ViewCount="232" Body="&lt;p&gt;I'm trying to get an I2C bus working. I'm using a PIC24FJ32GA002 micro. At the moment it's not connected to any other devices. It doesn't work. I then run a screwdriver along the pins of the MCU and it starts working. Power cycle and it's not working, same trick with the screwdriver and it starts working. The most confusing thing is I do not need to hold the screwdriver there - simply running it across the pins once or twice is enough to get it working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The software is basic, just an infinite loop sending out I2C data. What could be wrong? It's on a breadboard. I'm beginning to suspect a faulty connection, but what about a breadboard would cause it to stop working after power is reset?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-12-06T22:34:59.660" LastActivityDate="2010-12-09T13:44:24.520" Title="My board works intermittently... when I short some pins" Tags="&lt;microcontroller&gt;&lt;breadboard&gt;" AnswerCount="5" CommentCount="4" />
  <row Id="7604" PostTypeId="2" ParentId="7603" CreationDate="2010-12-06T22:33:14.293" Score="1" ViewCount="" Body="&lt;p&gt;Here's a checklist - useful to anyone with this kind of problem.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Do you have pullups on both of your I2C lines?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In an I2C bus, both clock and data lines float, so they can be driven by any device on the chain. An I2C bus needs 2 pullup resistors.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Have you checked your I2C signals on an oscilloscope?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Are the edges clean, are the timings right?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Is your microcontroller connected up correctly?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Is reset tied? are all power and ground pins connected up?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Do you have enough bypass caps?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Is your power supply clean?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Is your I2C running at a sane speed?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Breadboards and high speed signals don't mix.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-06T22:57:13.550" LastActivityDate="2010-12-06T22:57:13.550" CommentCount="13" />
  <row Id="7605" PostTypeId="2" ParentId="7603" CreationDate="2010-12-06T22:36:48.223" Score="2" ViewCount="" Body="&lt;p&gt;That PIC24 might not work properly on a breadboard. Good decoupling of all supply pins is essential with the 16-bit PICs, which would be difficult to achieve.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-06T22:36:48.223" CommentCount="9" />
  <row Id="7606" PostTypeId="2" ParentId="7603" CreationDate="2010-12-06T22:40:49.610" Score="1" ViewCount="" Body="&lt;p&gt;All VDD and VSS pins connected appropriately, including VDDCORE?  ENVREG tied high or low?  MCLR pulled up?&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-12-06T22:40:49.610" CommentCount="2" />
  <row Id="7607" PostTypeId="2" ParentId="7603" CreationDate="2010-12-07T00:06:47.770" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;I then run a screwdriver along the pins of the MCU and it starts working.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Do you mean that the I2C part starts working, or the MCU? Flash an LED during startup to show if the microcontroller is running or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming you're not shorting adjacent pins together, then the screwdriver is probably introducing a small capacitance as it touches the pins. This may be stabilising the oscillator source enough to allow the MCU to start up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're using an external crystal oscillator, make sure that you've got the appropriate load capacitors connected (usually in the order of 20pF). Sometimes it will work without the caps (especially on breadboards which introduce a small capacitance), but I wouldn't recommend it.&lt;/p&gt;&#xA;" OwnerUserId="554" LastEditorUserId="554" LastEditorDisplayName="" LastEditDate="2010-12-07T00:24:41.017" LastActivityDate="2010-12-07T00:24:41.017" CommentCount="2" />
  <row Id="7608" PostTypeId="1" CreationDate="2010-12-07T03:25:36.737" Score="0" ViewCount="57" Body="&lt;p&gt;Hey guys, this is my first time posting on this flavor of the StackExchange so I hope it's the right one! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to set up a local media share between my PC and my PS3. I have been messing with it for a few days now with no luck. I have finally been able to get my Laptop to connect and its files are visible on the PS3. To do this I added the PS3 and Laptop to my router's Wireless Card Access List. My PC is wired to the router so it's not showing up in the list. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried turning the Windows Firewall off for the home network but that didn't get it either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my stats:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Wired PC running Win7x64&lt;/li&gt;&#xA;&lt;li&gt;Wireless Laptop running Win7x86&lt;/li&gt;&#xA;&lt;li&gt;PS3&lt;/li&gt;&#xA;&lt;li&gt;Netgear Wireless-N WNR2000&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Thanks so much for the help and please let me know if there's any other info I can provide!&lt;/p&gt;&#xA;" OwnerUserId="2207" LastEditorUserId="2207" LastEditorDisplayName="" LastEditDate="2010-12-07T03:39:46.813" LastActivityDate="2010-12-07T03:39:46.813" ClosedDate="2010-12-07T04:24:35.463" Title="Setting up Local Media Share with PS3 and PC" Tags="&lt;wireless&gt;&lt;routing&gt;" CommentCount="3" />
  <row Id="7609" PostTypeId="1" AcceptedAnswerId="9407" CreationDate="2010-12-07T03:32:37.237" Score="2" ViewCount="224" Body="&lt;p&gt;I am using the well-known I²C level shifter from that &lt;a href=&quot;http://ics.nxp.com/support/documents/interface/pdf/an97055.pdf&quot; rel=&quot;nofollow&quot;&gt;appnote from Philips&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/CgUKc.gif&quot; alt=&quot;schematics&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 3V side is supplied by an LP2950-3.0 regulator and is loaded only moderate (a few quite lazy 74's).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem I'm obserivng is that the 3V side is being pulled to 5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I loaded the 3V side with a resistor and calculated that the level shifter presents a resistance of only 2.7 kOhms. I consider this rather low and I wonder:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Is that normal behaviour or did I make some mistake?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Isn't this harmful for the devices on the 3V side? There are several ICs that according to the datasheet are explicitly not 5V tolerant, not to forget the regulator.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1950" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T21:46:43.113" LastActivityDate="2011-01-25T02:17:52.750" Title="I²C level shifter pulls low side up" Tags="&lt;i2c&gt;&lt;level-shifting&gt;" AnswerCount="3" />
  <row Id="7610" PostTypeId="1" AcceptedAnswerId="7612" CreationDate="2010-12-07T04:53:55.093" Score="2" ViewCount="539" Body="&lt;p&gt;What is the maximum clock difference between a transmitter and receiver for error-free asynchronous serial communication?&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-07T13:34:27.803" Title="What is the maximum acceptable baud rate error for RS-232 serial communication?" Tags="&lt;serial&gt;&lt;rs232&gt;&lt;baudrate&gt;" AnswerCount="3" FavoriteCount="0" />
  <row Id="7611" PostTypeId="2" ParentId="2446" CreationDate="2010-12-07T05:44:44.270" Score="1" ViewCount="" Body="&lt;p&gt;Not trying to resurrect an old thread but my Zaurus SL5500 ran embedded linux on an ARM processor with gobs of RAM, and further gobs of storage  via CF and SD slots.  As far as I know the MMU was implemented mostly in software(makes sense for a linux system anyway).  General purpose computing was not only possible, but made thoroughly available via third party software, compilers, and a flexible command shell which provided most of the standard *nix utilities and features.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wasn't the fastest GP computer in the world, but sure made the ARM (and/or Samsung equivalents - I'm not 100 percent sure which it contained) look awfully capable.  Feature and performance-wise it compared quite nicely with a WinMobile Ipaq of much more recent vintage (definite Samsung StrongArm clone).  Both machines had lots of RAM and lots of storage so lots of memory managing going on - I suppose we have to blur the line a bit between microprocessors and microcontrollers when we get to this performance level. &lt;/p&gt;&#xA;" OwnerUserId="2208" LastActivityDate="2010-12-07T05:44:44.270" />
  <row Id="7612" PostTypeId="2" ParentId="7610" CreationDate="2010-12-07T06:46:21.143" Score="1" ViewCount="" Body="&lt;p&gt;Feel free to edit in more values. These are the ones I'm using now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Atmel ATmega UART:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;5 bits, normal speed : ±3.0%&#xA;5 bits, double speed : ±2.5%&#xA;10 bits, normal speed: ±1.5%&#xA;10 bits, double speed: ±1.0%&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;NXP LPC111x (Cortex-M0) UART: 1.1% (no table)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip PIC 18F2XK20/4XK20: not defined. (wtf.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the venerable Mr. Horowitz &amp;amp; Hill put it:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;By resynchronizing on the START and STOP bits of each character, the receiver doesn't require a highly accurate clock; it only has to be accurate and stable enough for the transmitter and receiver to stay synchronized to a fraction of a bit period of the time of one character, i.e., an accuracy of a few percent.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Note that conductor length plays a large part in serial clock errors. I stay under 19200 baud for regular ribbon cable more than 2' long. Makes me jealous of 4' 60Gb/s USB lines.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-07T06:46:21.143" CommunityOwnedDate="2010-12-07T06:46:21.143" />
  <row Id="7613" PostTypeId="1" AcceptedAnswerId="7790" CreationDate="2010-12-07T07:37:25.467" Score="0" ViewCount="341" Body="&lt;p&gt;I am trying to create a small motor driver for a DC motor, 9v-12v, max current and stall current i do not know, but I am using the stock motor of a Blade CP Helicopter. I just want to know if i am using parts that will work, and what parts i should replace. &#xA;The FET i am using is a 22N50 N channel FET. Any advice or things i should look out for?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Motor will be only going one direction and will be controlled from a 3v-5v PWM&lt;/p&gt;&#xA;&#xA;&lt;p&gt;yes i know about the diode across the motor which is a 1N4000&#xA;&lt;a href=&quot;http://justinstech.org/wp-content/uploads/2010/12/DSCN05511.jpg&quot; rel=&quot;nofollow&quot;&gt;link to diagram&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2010-12-12T23:57:22.323" Title="Simple Motor driver circuit diagram help" Tags="&lt;schematics&gt;&lt;dc-motor&gt;&lt;fet&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="7614" PostTypeId="2" ParentId="7609" CreationDate="2010-12-07T09:49:54.103" Score="3" ViewCount="" Body="&lt;p&gt;I've just checked quickly, but your diagram looks good to me. I suspect it might be some other problem, maybe assembly of the parts or something along that line. Could you please check the following for both the SCL and the SDA line, using an ordinary Multimeter:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Are you able to measure one diode drop (approx. 0.5-0.75V) across the parasitic diode in the MOSFETs from the 3V side to the 5V side?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Do you get a reading of nearly infinite resistance (or at least some kOhms) when connecting the Multimeter's test leads the other way round, i.e. from SCL's or SDA's 5V end to their 3V ends?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Please note that these single MOSFET transistors are very (!) sensitive to ESD discharge, so even if you assembled the right parts the right way, they may have some hidden type of damage.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-12-07T09:49:54.103" CommentCount="1" />
  <row Id="7615" PostTypeId="1" CreationDate="2010-12-07T10:11:11.713" Score="2" ViewCount="143" Body="&lt;p&gt;Today I was talking about ripping CDs with a colleague, and the fact that if you rip the same CD twice the md5sum is different. This is what I personally experienced, and I knew out of reading around, but I am not well informed about the underlying hardware reason for this. To be fair, I start to question even my experience, which could have been the result of a mistaken execution of the cd ripping program. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you know if this makes sense from the hardware/error correction point of view, and what is the underlying hardware reason for unreliability of audio cd data extraction? &lt;/p&gt;&#xA;" OwnerUserId="1272" LastActivityDate="2010-12-07T11:26:56.063" Title="ripping audio cd gives different checksum. Real? fake? Underlying reason?" Tags="&lt;compact-disk&gt;&lt;error-correction&gt;" AnswerCount="2" />
  <row Id="7616" PostTypeId="1" AcceptedAnswerId="7625" CreationDate="2010-12-07T10:22:33.733" Score="2" ViewCount="173" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why did Germany choose NXP's SmartMX chip in the new Electronic ID Card (see &lt;a href=&quot;http://egovasia.enterpriseinnovation.net/content/germany-issue-national-identity-card-smartmx-chip&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) instead of having a more conventional solution, like an old credit-card-like approach? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In fact, the question is more general: Why is the chip solution considered the best approach for identity cards vs. magnetic bands, MRZ et al.?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FTR, I think that a much more cost-effective solution would be by having the cryptographic engine in the reader/writer and the card should be a rather dumb storage media which will store the encrypted data. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Also, we all know that there are also solution to 'workaround' the chip's security features. See &lt;a href=&quot;http://www.dw-world.de/dw/article/0,,6211080,00.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What do you think?&lt;/p&gt;&#xA;" OwnerUserId="2210" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-07T20:43:58.100" LastActivityDate="2010-12-07T20:43:58.100" Title="Why are chips used in electronic identity cards?" Tags="&lt;magstripe&gt;&lt;nxp&gt;&lt;smart-card&gt;" AnswerCount="2" />
  <row Id="7617" PostTypeId="1" CreationDate="2010-12-07T10:26:42.607" Score="0" ViewCount="131" Body="&lt;p&gt;Is it possible that the socket orientation (in Europe: one pin 230V, the other ground) can have an effect (albeit very small) on the amplifier behavior of a very old stereo sound system? What is, if any, the underlying reason ?&lt;/p&gt;&#xA;" OwnerUserId="1272" LastEditorUserId="1272" LastEditorDisplayName="" LastEditDate="2010-12-07T11:02:30.657" LastActivityDate="2010-12-08T14:44:52.980" Title="Does socket orientation have an effect on sound ?" Tags="&lt;power&gt;&lt;audio&gt;&lt;amplification&gt;" AnswerCount="2" CommentCount="8" FavoriteCount="1" />
  <row Id="7618" PostTypeId="2" ParentId="7615" CreationDate="2010-12-07T10:53:07.247" Score="4" ViewCount="" Body="&lt;p&gt;In almost all cd readers today, there is a system to correct data from a missreading from the CD. If a single data is not available, the hardware can interpolate the last and the next data in order to find a good aproximation to the lost data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a human point of view this is unnoticable and the sound seems to still be the original one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the PC point of view, any data modification can change the MD5sum completely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://home.btconnect.com/geffers/cd.html&quot; rel=&quot;nofollow&quot;&gt;This site&lt;/a&gt; explains how the data correction occurs on the cd.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://web.ncf.ca/aa571/daefaq.htm&quot; rel=&quot;nofollow&quot;&gt;This site&lt;/a&gt; has some more information about digital audio extraction (DAE).&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-12-07T10:53:07.247" CommentCount="3" />
  <row Id="7619" PostTypeId="2" ParentId="7617" CreationDate="2010-12-07T11:11:04.190" Score="1" ViewCount="" Body="&lt;p&gt;I can think in one effect but only for a very specific hardware. If You're using a &lt;a href=&quot;http://electroschematics.com/5678/capacitor-power-supply/&quot; rel=&quot;nofollow&quot;&gt;capacitive supply&lt;/a&gt; with a &lt;a href=&quot;http://en.wikipedia.org/wiki/Rectifier#Half-wave_rectification&quot; rel=&quot;nofollow&quot;&gt;half-wave rectifier&lt;/a&gt; - In this case the circuit ground is connected directly at one of the socket pins. If this pin is the ground its ok. If this is the 220 AC, although the circuit still operates, you may have some noise coupled on the circuit via ground, as your new ground is oscilating at 60Hz with a amplitude of 220 volts&#xA;.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-12-07T11:11:04.190" CommentCount="2" />
  <row Id="7620" PostTypeId="1" AcceptedAnswerId="7622" CreationDate="2010-12-07T11:21:51.780" Score="2" ViewCount="190" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;When i've driven coils in the past(such as mechanical relays) i've had to put a diode to protect it against back EMF once turned off. Do i need to do that when driving stepper motors with a ULN2803a?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-12-08T08:15:23.663" Title="When driving stepper motors do i need to worry about back EMF?" Tags="&lt;stepper-motor&gt;" AnswerCount="1" />
  <row Id="7621" PostTypeId="2" ParentId="7615" CreationDate="2010-12-07T11:26:56.063" Score="3" ViewCount="" Body="&lt;p&gt;Errors occur all the time when reading CDs. A CD contains additional information to correct read errors to a certain level (Reed-Solomon Error Correction). But if there are too many bits which can't be read, i.e. because of scratches, there's a problem.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With CD-ROMs errors are not tolerated; even 1 single bit error may render a complete database useless or cause a program to crash. You really need every bit to be correct, that's why CD drives retry to read data a few times before giving up and displaying an error message if they can't.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With audio CDs it's different. You can't spend a few seconds retrying to read the data because the audio stream will be interrupted. That's why the decoder will interpolate erroneous bit sequences, a process which is inaudible in most cases, only when the CD is badly damaged you may have dropouts. Which bits are interpolated may be different each time the CD is read, resulting in a different checksum every time.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-07T11:26:56.063" />
  <row Id="7622" PostTypeId="2" ParentId="7620" CreationDate="2010-12-07T11:51:11.073" Score="6" ViewCount="" Body="&lt;p&gt;Diodes are advisable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you had bothered to read the data sheet you would have seen that the chip includes clamp diodes!&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-07T12:11:50.173" LastActivityDate="2010-12-07T12:11:50.173" CommentCount="3" />
  <row Id="7623" PostTypeId="2" ParentId="7610" CreationDate="2010-12-07T11:52:36.200" Score="1" ViewCount="" Body="&lt;p&gt;&lt;em&gt;[First off, the &quot;RS&quot; in RS-232 denotes &quot;Recommended Standard&quot;, which it was when it was released in the 1960s. Since eons however it is an accepted standard by the EIA as EIA-232, and the old name was officially abandoned since. But it seems there's nothing like killing old habits :-) ]&lt;/em&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On topic: the allowed clock tolerance depends on the detection method. IIRC the old 68HC11 sampled a few times at a bit start, a few times in the middle of a bit, and the at the end. (Sampling occurred at 16x bit rate.) This allows for &lt;strong&gt;half a bit difference on the last bit&lt;/strong&gt;. Most communication on EIA-232 :-) consists of 10 bits (1 start, 8 data, 1 stop), so half a bit in the stop bit is &lt;strong&gt;5%&lt;/strong&gt;.&lt;br&gt;&#xA;Tyblu quotes Horowitz about resynchronisation. You can't count on that however; if your data is 0x00 you simply don't have the edges required to resync.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-07T11:52:36.200" CommentCount="1" />
  <row Id="7624" PostTypeId="1" AcceptedAnswerId="7627" CreationDate="2010-12-07T12:57:22.270" Score="9" ViewCount="303" Body="&lt;p&gt;We had a very short FPGA/Verilog course at university (5 years ago), and we always used clocks everywhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am now starting out with FPGAs again as a hobby, and I can't help but wonder about those clocks. Are they absolutely required, or can an FPGA-based design be completely asynchronous? Can one build a complex bunch of logic and have stuff ripple through it as fast as it can?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I realise that there are a whole lot of gotchas with this, like knowing when the signal has propagated through all parts of the circuit and the output has stabilised. That's beside the point. It's not that I want to actually build a design that's entirely asynchronous, but just to improve my understanding of the capabilities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To my beginner eye, it appears that the only construct that absolutely requires a clock is a &lt;code&gt;reg&lt;/code&gt;, and my understanding is that a typical FPGA (say, a Cyclone II) will have its flip-flops pre-wired to specific clock signals. Is this correct? Are there any other implicit clocks like this and can they typically be manually driven by the design?&lt;/p&gt;&#xA;" OwnerUserId="1951" LastActivityDate="2011-02-28T22:32:17.087" Title="Can an FPGA design be mostly (or completely) asynchronous?" Tags="&lt;fpga&gt;&lt;verilog&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="1" />
  <row Id="7625" PostTypeId="2" ParentId="7616" CreationDate="2010-12-07T13:18:39.620" Score="8" ViewCount="" Body="&lt;p&gt;Smartcards have chips so that the reader can do challenge response authentication. The chip is a black-box which can authenticate by correctly answering a cryptographic challenge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a dumb storage medium was used, it would be copyable.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-07T20:39:45.043" LastActivityDate="2010-12-07T20:39:45.043" />
  <row Id="7626" PostTypeId="2" ParentId="7624" CreationDate="2010-12-07T13:31:06.217" Score="2" ViewCount="" Body="&lt;p&gt;Yes. If you have no process type constructs then it shouldn't do things like inferring registers. &#xA;There will be things like onboard memory that require clocks, although if you really want to you could probably generate these asynchronously.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-07T13:31:06.217" CommentCount="1" />
  <row Id="7627" PostTypeId="2" ParentId="7624" CreationDate="2010-12-07T13:31:47.173" Score="13" ViewCount="" Body="&lt;p&gt;A short answer would be: yes; a longer answer would be: it is not worth your time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An FPGA itself can run a completely asynchronous design no problem.  The result you get is the problem since timing through any FPGA is not very predictable.  The bigger problem is the fact that your timing and resultant design will almost definitely vary between different place and route sessions.  You can put in constraints on individual asynchronous paths making sure that they do not take too long, but I'm not quite sure that you can specify a minimum delay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end it means that your design will be unpredictable and potentially completely variable with even a slight design change.  You'd have to look through the entire timing report every time you change anything at all just to make sure that it would still work.  On the other hand, if the design is synchronous, you just look for a pass or fail at the end of place and route (assuming your constraints are setup properly, which doesn't take long at all).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In practice people aim for completely synchronous designs but if you need to simply buffer or invert a signal, you don't need to go through a flip flop as long as you constrain it properly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this clears it up a bit.&lt;/p&gt;&#xA;" OwnerUserId="1819" LastActivityDate="2010-12-07T13:31:47.173" CommentCount="1" />
  <row Id="7628" PostTypeId="2" ParentId="7616" CreationDate="2010-12-07T13:32:37.307" Score="2" ViewCount="" Body="&lt;p&gt;In Serbia, we too have chips in ID cards, but they aren't mandatory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm going to write a bit about what I found out here. I assume that at least some of that could apply to other users of electronic ID cards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd say that first step is to have large amount of information.  Smart cards can hold larger amount of information that magnetic cards (or at least I got that idea from somewhere).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next interesting point is that because smart card itself is &quot;active&quot; you can make relatively easy upgrades without modifying entire infrastructure. For example here we added fully qualified certificates for electronic signatures into ID cards some time after they rolled out. With smart cards, he private doesn't leave the card itself, so it is more secure than other storage mediums. Magnetic strip cards can be copied and data from them removed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another interesting thing is that it is easier to hide information your government doesn't want you to know it's there in a smart card. For example, ID cards here have fields for apartment number and floor number as a part of the address, but officially government shouldn't have access to such information and those fields weren't supposed to be in ID cards. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd also say that smart card format itself is more accessible than magnetic card. Smart card readers are more common than magnetic card readers, so users who want to use their ID cards for signing documents, registering vehicles and so on could just buy a regular smart card reader instead of a more expensive proprietary one with encryption functionalities which may or may not be safe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, smart cards can be used to encrypt data in Windows and for logging in (but I couldn't figure out how to do the second part). Users of smart ID cards could avoid having to obtain another smart card for those functions.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-12-07T13:32:37.307" />
  <row Id="7629" PostTypeId="2" ParentId="7610" CreationDate="2010-12-07T13:34:27.803" Score="2" ViewCount="" Body="&lt;p&gt;Bear in mind error is peak-to-peak - this can be an issue at high baudrates on a jittery clock - RC oscillators can have quite a lot of jitter, so a 1% (avarage or RMS) calibrated clock may actually have instantaneous errors larger than that. At lower baudrates this will tend to get avaraged out.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-07T13:34:27.803" />
  <row Id="7630" PostTypeId="2" ParentId="7624" CreationDate="2010-12-07T14:05:32.657" Score="2" ViewCount="" Body="&lt;p&gt;Of course if your design requirements are slow enough that a lot of internal delays are still orders of magnitude longer than times that you care about, then it's not a problem, and you can look at the timing report to keep an eye on this, but there's a limit to what you can usefully do with no internal state info. If you just want to make something like a 100 input multiplexer then fine, just remember that each input will have a different propagation delay. &#xA;In fact you may get some interesting and chaotic effects with large numbers of  unpredictable-delay oscillating feedback loops - maybe a fully async FPGA based synthesiser could be the next 'analogue'..&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-07T14:05:32.657" />
  <row Id="7631" PostTypeId="1" CreationDate="2010-12-07T14:20:51.450" Score="2" ViewCount="185" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/7555/want-to-make-a-uav&quot;&gt;Want to make a UAV&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I want to make a remotely flyable drone (quadrocopter). To be fully remote, I want to have a camera mounted on it so I can fly it from my PC with joysticks inside. The camera is likely to be a webcam or (more likely) a standard CMOS or CCD camera with a 3 wire interface (+ve, -ve and signal), much like &lt;a href=&quot;http://www.sparkfun.com/products/8739&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;. Would someone be able to offer a circuit capable of transmitting that video over a wireless link with a range of about 5 miles? It's a long shot (no pun intended), but I'd like to be able to have that range, even if the batteries can't manage it :-P&lt;/p&gt;&#xA;" OwnerUserId="2212" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-12-07T15:24:31.103" LastActivityDate="2010-12-07T15:24:31.103" ClosedDate="2010-12-07T21:00:04.380" Title="Wireless video transmitter ~5 mile range?" Tags="&lt;wireless&gt;&lt;camera&gt;" CommentCount="0" FavoriteCount="1" />
  <row Id="7632" PostTypeId="1" AcceptedAnswerId="7636" CreationDate="2010-12-07T14:42:15.353" Score="11" ViewCount="356" Body="&lt;p&gt;I will be building a 4 propeller quadrocopter drone at some point. I want to make it relatively easy to fly by getting it to hover still when the controls are not touched.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone offer some information on how I'd get the quadrotor to stay put in the air? I was thinking accelerometers to measure drift and roll/pitch/yaw, but they're not sensitive enough to detect very slow drift due to, for example, a light breeze. Is GPS accurate enough to stamp out drift on the 10cm scale (that is, detect a 10cm drift (or less, maybe?) from the drone's original position)?&lt;/p&gt;&#xA;" OwnerUserId="2212" LastEditorUserId="1477" LastEditorDisplayName="" LastEditDate="2010-12-08T21:32:10.313" LastActivityDate="2011-02-13T07:41:32.757" Title="Stopping drift in hovering quadrocopter" Tags="&lt;sensor&gt;&lt;robotics&gt;&lt;uav&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="7633" PostTypeId="1" AcceptedAnswerId="9140" CreationDate="2010-12-07T14:43:59.130" Score="1" ViewCount="230" Body="&lt;p&gt;I am trying to get a can sniffer working, based on LPC2368. I keep getting a bus error interrupt, of type &quot;form error&quot;. I suspect my timing settings. I verified that the sending party is transmitting at 125K(8us bit duration). Here is my setting for 72MHz CPU clock and 125Kbps bus speed&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define PULSE_BEFORE_SAMPLE 8&#xA;#define PULSE_AFTER_SAMPLE 3&#xA;#define PULSE_PER_BIT (PULSE_BEFORE_SAMPLE + PULSE_AFTER_SAMPLE + 1) &#xA;#define TSEG1 (PULSE_BEFORE_SAMPLE - 1)&#xA;#define TSEG2 (PULSE_AFTER_SAMPLE - 1)&#xA;#define SJW 3 //sync jump width&#xA;#define SAM 0 //sampling 0=single sample 1=triple sample&#xA;&#xA;#define CAN_PRESCALER 7 //((CPU_CLK_HZ / PCLK_DIVIDER / CAN1_BAUDRATE / PULSE_PER_BIT) - 1 )&#xA;...&#xA;PCLKSEL0 |= PCLK_CAN1 &amp;lt;&amp;lt; 26; //clock source = CCLK/6&#xA;...&#xA;CAN1BTR = (CAN_PRESCALER | (SJW &amp;lt;&amp;lt; 14) | (TSEG1 &amp;lt;&amp;lt; 16) | (TSEG2 &amp;lt;&amp;lt; 20) | (SAM &amp;lt;&amp;lt; 23));&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Am I making an obvious mistake here? The controller is running in listen-only mode, all other mode bits are set to 0.&lt;/p&gt;&#xA;" OwnerUserId="2213" LastActivityDate="2011-01-17T16:41:24.333" Title="Debugging LPC23XX canbus sniffer" Tags="&lt;lpc&gt;&lt;can&gt;&lt;timing&gt;&lt;bus&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="7635" PostTypeId="2" ParentId="7632" CreationDate="2010-12-07T15:23:36.860" Score="2" ViewCount="" Body="&lt;p&gt;GPS isn't accurate enough.  Accelerometers can only measure acceleration, not a constant drift.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe a localized positioning system using beacons and &lt;a href=&quot;http://en.wikipedia.org/wiki/Trilateration&quot; rel=&quot;nofollow&quot;&gt;trilateration&lt;/a&gt; or something?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe cheap cameras to detect drift relative to the ground or other stationary objects?  You can cancel out rotations using the gyroscopes, and then do a cross-correlation between subsequent frames to detect drift relative to the ground, the way an optical mouse works.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-12-07T15:59:01.353" LastActivityDate="2010-12-07T15:59:01.353" />
  <row Id="7636" PostTypeId="2" ParentId="7632" CreationDate="2010-12-07T15:37:32.537" Score="15" ViewCount="" Body="&lt;p&gt;I think that you will want to use a combination of sensors.  The accelerometers and gyroscopes will be able to correct for strong breezes.  You can then use GPS to counter out the longer-term drift (or bias, as it is sometimes called).  I think that the combination of these two sensors in some sort of filter (probably a Kalman) will keep your position drift minimized.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GPS won't be accurate enough by itself though.  An alternative approach to the Kalman filter (which can get a bit math heavy) is to use the DCM algorithm from &lt;a href=&quot;http://diydrones.com/profiles/blogs/dcm-imu-theory-first-draft&quot; rel=&quot;nofollow&quot;&gt;DIYdrones&lt;/a&gt;.  There seems to be a lot of success in using this so far.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, the Parrot drone quadrotor uses a downward-facing 60fps camera to cancel out drift.  It looks down and extracts features from the ground under it, then uses a type of visual odometry (I'm assuming some sort of optical flow algorithm) to determine how far the quadrotor has drifted.  I believe that this only works at low altitudes on the Parrot, but I see no reason why it couldn't be extended to a higher altitude.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-12-07T15:37:32.537" CommentCount="8" />
  <row Id="7637" PostTypeId="1" AcceptedAnswerId="7640" CreationDate="2010-12-07T15:54:37.770" Score="7" ViewCount="279" Body="&lt;p&gt;Can you identify the logo on these ICs?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/IzODI.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-07T16:14:19.997" Title="Can you identify this logo?" Tags="&lt;identification&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="7638" PostTypeId="2" ParentId="7624" CreationDate="2010-12-07T15:56:33.340" Score="1" ViewCount="" Body="&lt;p&gt;As @Andrey pointed out it is not worth your time.  Specifically the tools don't do this, so you would be completely on your own.  Plus since they have built-in registers, you wouldn't save anything by not using them.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-07T15:56:33.340" />
  <row Id="7639" PostTypeId="2" ParentId="7624" CreationDate="2010-12-07T16:01:42.993" Score="2" ViewCount="" Body="&lt;p&gt;Yes, you can.  You can ignore the flipflops completely and build it all out of LUTs.  And/or you can use the state elements of most Xilinx FPGAs as (level triggered) latches instead of (edge-triggered) flipflops.&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2010-12-07T16:01:42.993" />
  <row Id="7640" PostTypeId="2" ParentId="7637" CreationDate="2010-12-07T16:01:44.270" Score="16" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/w7dfE.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Micro Power Systems: &lt;a href=&quot;http://www.datasheetarchive.com/pdf-datasheets/Datasheets-111/DSAP0025577.html&quot; rel=&quot;nofollow&quot;&gt;http://www.datasheetarchive.com/pdf-datasheets/Datasheets-111/DSAP0025577.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-12-07T16:14:19.997" LastActivityDate="2010-12-07T16:14:19.997" CommentCount="1" />
  <row Id="7641" PostTypeId="1" CreationDate="2010-12-07T16:34:29.700" Score="4" ViewCount="197" Body="&lt;p&gt;This question is inspired by &lt;a href=&quot;http://electronics.stackexchange.com/q/7637/1240&quot;&gt;this&lt;/a&gt; question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm interested in on-line resources which can be used to identify logos. Are there any databases of commonly and not so commonly used logos on ICs which can help there?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that &lt;a href=&quot;http://www.datasheetcatalog.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.datasheetcatalog.com/&lt;/a&gt; brings up logos of manufacturers when searching for datasheet, but it happened to me few times that I was looking for a component with unknown manufacturer and none on the logos matched.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-07T21:27:01.430" LastActivityDate="2010-12-08T07:10:12.173" CommunityOwnedDate="2010-12-07T17:28:29.047" Title="Identifying manufacturer logos on components" Tags="&lt;components&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="2" />
  <row Id="7642" PostTypeId="1" CreationDate="2010-12-07T17:01:56.597" Score="2" ViewCount="302" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm new here, and I'm new to electronics. I have a keen interest in building a wind powered battery charger and I'm having a crack at the charge controller. I found a circuit that is published free on the 'net and after a few false starts and blind alleys I finally finished my charge controller- or so I thought! My mosfet exploded (well,it went pop and split apart really but it surprised me).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone tell me what I might have done wrong? Will it have damaged any other components on the board?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it helps, its an IRF9520 P channel mosfet. I'm not sure whether it should have been an N channel - would this have caused the problem?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Grateful for any help or advice.&lt;/p&gt;&#xA;" OwnerUserId="2215" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-12-08T18:16:37.910" LastActivityDate="2010-12-08T18:16:37.910" Title="Why did my MOSFET explode?" Tags="&lt;mosfet&gt;&lt;troubleshooting&gt;&lt;magic-smoke&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="7643" PostTypeId="2" ParentId="7641" CreationDate="2010-12-07T17:18:42.223" Score="7" ViewCount="" Body="&lt;p&gt;I've found this link at Google: &lt;a href=&quot;http://www.advanced-tech.com/ic_logos/ic_logos.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.advanced-tech.com/ic_logos/ic_logos.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-12-07T17:18:42.223" CommentCount="2" />
  <row Id="7644" PostTypeId="2" ParentId="4448" CreationDate="2010-12-07T17:43:53.583" Score="0" ViewCount="" Body="&lt;p&gt;Friend, I managed after several attempts! You have to configure the adapter to COM1 port, and then with open source software, you connect the transceiver.&lt;/p&gt;&#xA;" OwnerUserId="2217" LastActivityDate="2010-12-07T17:43:53.583" />
  <row Id="7645" PostTypeId="2" ParentId="7595" CreationDate="2010-12-07T17:48:49.723" Score="1" ViewCount="" Body="&lt;p&gt;You might want to take a look at the &lt;a href=&quot;http://netduino.com/&quot; rel=&quot;nofollow&quot;&gt;Netduino platform&lt;/a&gt; . It also uses .NET Micro framework, so you can develop and debug in standard Visual Studio. And it is largely hardware compatible with Arduino accessories, so there are a lot of hardware modules out there that you can connect to it without having to design them from scratch. Not all Arduino shields are compatible, so you may want to check out the list on the forums on the Netduino site.&#xA;Low-cost as well ($35 from SparkFun and some other vendors). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Netduino Plus has just been released, and it adds onboard Ethernet and microSD, with libraries to drive them. There is also a Netduino Mini, on a small DIP carrier. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, if you want something small and cheap that you can use to control hardware and still be able to develop in .NET, take a look.&lt;/p&gt;&#xA;" OwnerUserId="2216" LastActivityDate="2010-12-07T17:48:49.723" />
  <row Id="7646" PostTypeId="2" ParentId="7642" CreationDate="2010-12-07T19:13:24.837" Score="10" ViewCount="" Body="&lt;p&gt;Some things that can make a MOSFET pop:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Too high Vds voltage, i.e. a 20V MOSFET on a 24V system wouldn't last long.&lt;/li&gt;&#xA;&lt;li&gt;Exceeding power dissipation (could be a short circuit, but can also be due to very high frequency switching. If you're not using a SMPS, this probably isn't relevant.)&lt;/li&gt;&#xA;&lt;li&gt;Exceeding Vgs(max), which is usually ±20V. This is quite a common failure leading to the breakdown of the delicate gate insulator.&lt;/li&gt;&#xA;&lt;li&gt;Reverse biasing the drain and source making the body diode conduct (as Nick T mentioned.)&lt;/li&gt;&#xA;&lt;li&gt;Mechanical stress can cause bonding wires to fail or short to places they shouldn't, but this is rare.&lt;/li&gt;&#xA;&lt;li&gt;If you mounted it on a heatsink remember that the tab of the MOSFET is connected to a pin, usually source, but sometimes drain. If you grounded the heatsink it could cause Bad Things to happen.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-07T19:13:24.837" CommentCount="2" />
  <row Id="7647" PostTypeId="2" ParentId="7633" CreationDate="2010-12-07T21:42:10.753" Score="2" ViewCount="" Body="&lt;p&gt;I've worked with the Microchip CAN Controller w/ SPI bus interface MCP2515. One of the most difficult parts of setting up CAN is making sure that all the baud rate registers are set properly for all of devices on the bus. I'm not sure if you have access to the registers on the sending device, but being able to read the exact baud rate register values from the sender may give you an idea as to which register you have configured incorrectly. Also knowing the type of error if any is being detected by the sender may help you solve your CAN bus problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip has an Application Note &lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/00754.pdf&quot; rel=&quot;nofollow&quot;&gt;AN754&lt;/a&gt; that provides a guide to setting the CAN bus timing. It's not specific to Microchip. There are a few basic timing parameters you must set properly in order for the CAN bus communication to work they are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Tq = Time Quanta&lt;/li&gt;&#xA;&lt;li&gt;Nominal Bit Time&lt;/li&gt;&#xA;&lt;li&gt;Synchronization segment width&lt;/li&gt;&#xA;&lt;li&gt;Propagation segment width&lt;/li&gt;&#xA;&lt;li&gt;Phase segment 1 width&lt;/li&gt;&#xA;&lt;li&gt;Phase segment 2 width&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Make sure these values all match in your sender and receiver.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-12-08T18:12:17.667" LastActivityDate="2010-12-08T18:12:17.667" CommentCount="1" />
  <row Id="7648" PostTypeId="2" ParentId="7609" CreationDate="2010-12-07T22:50:48.930" Score="0" ViewCount="" Body="&lt;p&gt;The gate threshold of these parts can be as low as 0.4V at 25C according to the &lt;a href=&quot;http://www.nxp.com/documents/data_sheet/BSN20.pdf&quot; rel=&quot;nofollow&quot;&gt;NXP datasheet&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would guess that loading on the +3V side of the MOSFETs is creating enough Vgs to turn the FETs on in the linear region. What is the measured gate-source voltage? If it's too high you'll have to adjust your pull-ups or choose a MOSFET with a higher Vgs threshold.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-12-07T22:50:48.930" CommentCount="4" />
  <row Id="7649" PostTypeId="2" ParentId="7143" CreationDate="2010-12-08T00:44:37.887" Score="3" ViewCount="" Body="&lt;p&gt;Hi - I wanted to comment on &quot;Practical BeagleBoard&quot; above. This book was posted by Apress by mistake. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In fact, the book does not actually exist yet - I am the author and I haven't finished writing it yet.  It should be ready in late spring 2011 (Note:  it will not be published by Apress.)  I apologize for the confusion.  Please feel free to contact me with any questions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a further comment, I also highly recommend Chris Hallinan's Embedded Linux Primer, for which the 2nd edition was just released.  It is an excellent introduction to embedded Linux, and to embedded systems programming in general.&lt;/p&gt;&#xA;" OwnerUserId="2222" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-08T02:55:38.987" LastActivityDate="2010-12-08T02:55:38.987" CommentCount="3" />
  <row Id="7650" PostTypeId="2" ParentId="7143" CreationDate="2010-12-08T01:29:55.437" Score="1" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/84e1Q.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have found &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596009836&quot; rel=&quot;nofollow&quot;&gt;Programming Embedded Systems: With C&lt;/a&gt; to be very good reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not able to purchase the hardware they reference in the book, but the example code could be ported to whatever target you choose fairly easily.&lt;/p&gt;&#xA;" OwnerUserId="2223" LastActivityDate="2010-12-08T01:29:55.437" />
  <row Id="7651" PostTypeId="2" ParentId="7143" CreationDate="2010-12-08T03:27:36.207" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.smileymicros.com/&quot; rel=&quot;nofollow&quot;&gt;smileymicros.com&lt;/a&gt; carries a line of embedded C books, kits, and tutorials. He uses the Atmel Butterfly kit and Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/qiCgb.jpg&quot; alt=&quot;$100&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/qduI0.jpg&quot; alt=&quot;$125&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-08T03:27:36.207" />
  <row Id="7652" PostTypeId="2" ParentId="7641" CreationDate="2010-12-08T07:10:12.173" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.icphotos.org/&quot; rel=&quot;nofollow&quot; title=&quot;IC Photos Site&quot;&gt;IC Photos&lt;/a&gt; site is also a useful tool for this type of effort.&lt;/p&gt;&#xA;" OwnerUserId="1990" LastActivityDate="2010-12-08T07:10:12.173" CommunityOwnedDate="2010-12-08T07:10:12.173" />
  <row Id="7653" PostTypeId="1" AcceptedAnswerId="7656" CreationDate="2010-12-08T07:34:52.457" Score="1" ViewCount="248" Body="&lt;p&gt;I have an ATmega328P that seems to be fried. It was in an Arduino board (Freakduino-chibi, specifically) and working when it suddenly stopped responding at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Investigation showed that the fault followed the chip from board to board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a BusPirate, I tried to access the chip via avrdude and the ICSP header on the Arduino. No dice: avrdude failed to initialize the chip. Using the same board and a different 328P, avrdude was successful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any thoughts on how to possibly resurrect the broken chip?&lt;/p&gt;&#xA;" OwnerUserId="1990" LastEditorUserId="1333" LastEditorDisplayName="" LastEditDate="2010-12-09T12:42:34.383" LastActivityDate="2010-12-14T00:39:02.957" Title="Suggestions for rescue of an ATmega328P" Tags="&lt;arduino&gt;&lt;atmega&gt;&lt;avrdude&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="7654" PostTypeId="2" ParentId="7653" CreationDate="2010-12-08T07:44:31.720" Score="4" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://mightyohm.com/blog/2010/12/new-product-hv-rescue-shield-2-0/&quot; rel=&quot;nofollow&quot;&gt;HV Rescue Shield 2.x&lt;/a&gt; is a high voltage parallel mode fuse programmer for Atmel AVR microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/dFjFz.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that doesn't fix it...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WJ99b.jpg&quot; width=&quot;200&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-14T00:39:02.957" LastActivityDate="2010-12-14T00:39:02.957" CommentCount="1" />
  <row Id="7656" PostTypeId="2" ParentId="7653" CreationDate="2010-12-08T08:41:46.513" Score="5" ViewCount="" Body="&lt;p&gt;If you &quot;fried&quot; it by burning your fuses incorrectly, then you just need some high voltage programmer like original STK500 or &lt;a href=&quot;http://www.obdev.at/products/vusb/avrdoper.html&quot; rel=&quot;nofollow&quot;&gt;similar&lt;/a&gt;. Otherwise buy the new AVR MEGA chip and simply replace the bad one. If you are lucky then nothing else was burnt.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-12-08T08:41:46.513" CommentCount="4" />
  <row Id="7657" PostTypeId="1" AcceptedAnswerId="7663" CreationDate="2010-12-08T09:28:09.970" Score="1" ViewCount="757" Body="&lt;p&gt;I am looking for a cheap way to get +24V DC max 3A from computer power supply. I prefer easy soldering solution like DIP, and standard components that do not need to be purchased over internet. Any ideas, please?&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-12-08T15:17:04.120" Title="24V 3A from ATX power supply?" Tags="&lt;power-supply&gt;&lt;atx&gt;&lt;24v&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="7658" PostTypeId="2" ParentId="7657" CreationDate="2010-12-08T11:36:21.343" Score="2" ViewCount="" Body="&lt;p&gt;I am not sure you can get 3A out of it, but there are both +12V and -12V leads in ATX. You have -12V on blue wire, 0V on black, and +12V on yellow. So it's 24V betweeen blue and yellow. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need +24V from black wires, you'll have to arrange a boost converter and draw about 6A from the 12V. You'll likely want to use more than one lead then.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2010-12-08T11:36:21.343" CommentCount="6" />
  <row Id="7659" PostTypeId="2" ParentId="7657" CreationDate="2010-12-08T13:33:17.623" Score="2" ViewCount="" Body="&lt;p&gt;I have done this in the past using 2 supplies in series.  The ground for the supply is the wall ground so to make it work I had to take one of the supplies apart and mount the board on nylon bolts to isolate it from the case.  Then that supply floats and can be put in series.  Not quite sure what happens around the current limit of the supply.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2010-12-08T13:33:17.623" CommentCount="2" />
  <row Id="7660" PostTypeId="1" AcceptedAnswerId="7695" CreationDate="2010-12-08T14:03:41.487" Score="2" ViewCount="318" Body="&lt;p&gt;I have a problem with writing interrupt handlers in Keil ARM compiler for LPC1114. When I write program in C++ and specify --cpp compiler option all code from interrupt handlers disappears, it is replaced with infinite loop. I wrote simple program that illustrates my trouble.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &quot;LPC11xx.h&quot;           // LPC11xx definitions&#xA;#define SYSTICK_DELAY 120000   // for 10 ms systick @ 12MHz osc&#xA;&#xA;void SysTick_Handler(void)&#xA;{&#xA;  __NOP();&#xA;}&#xA;&#xA;int main (void) &#xA;{&#xA;  SystemInit();                   // from system_LPC11xx.c&#xA;  SysTick_Config(SYSTICK_DELAY);  // from core_cm0.h&#xA;  // Loop forever&#xA;  while (1) __NOP();&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;When trying to compile this code with --cpp compiler option I get infinite loop in disasm:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;SysTick_Handler PROC&#xA;            EXPORT  SysTick_Handler           [WEAK]&#xA;            B       .&#xA;            ENDP&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This is the place where __NOP() from above program must be. And it is there when I'm compiling code with --c99 compiler option or without additional options. Keil MDK version is 4.12. Can anyone tell me is there any solution or workaround ?&lt;/p&gt;&#xA;" OwnerUserId="1736" LastActivityDate="2011-02-12T11:03:06.173" Title="Bug in Keil ARM compiler with interrupt handlers and C++ ?" Tags="&lt;c++&gt;&lt;interrupt&gt;&lt;keil&gt;&lt;mdk&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="7662" PostTypeId="2" ParentId="7617" CreationDate="2010-12-08T14:44:52.980" Score="0" ViewCount="" Body="&lt;p&gt;I would imagine this could introduce some unexpected ground loops and so increase both hum and noise levels. - especially if the amp is connected to other kit with hot (live) and neutral (connected to ground/earth) wired the other way round.&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2010-12-08T14:44:52.980" />
  <row Id="7663" PostTypeId="2" ParentId="7657" CreationDate="2010-12-08T15:17:04.120" Score="3" ViewCount="" Body="&lt;p&gt;You can open the supply and look for the TL431 chip.  There will be two resistors forming a voltage divider from the 5V rail to the 2.5V that the TL431 compares against.   If you calculate the right resistor values, you can set this divider to output half the voltage it currently does.  Then you can get the output up so that the +5V rail becomes +10V and the +12V rail becomes +24V.  You will probably need to install new output filter capacitors of higher voltage rating as well.  And if you modify an ATX supply this way, please cut off the ATX connector and install something else, so it won't plug in to a motherboard.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-08T15:17:04.120" CommentCount="1" />
  <row Id="7664" PostTypeId="1" AcceptedAnswerId="7665" CreationDate="2010-12-08T15:53:00.997" Score="10" ViewCount="448" Body="&lt;p&gt;Convention?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Easier to implement?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another reason?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a reason things like MCLR or RESET on microcontrollers are active-low, that is, you have to pull them down to reset the IC, and pull them up to &quot;run&quot; the IC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm just curious because this causes me some problems. If it were active high, I could avoid the capacitor on MCLR required in some instances and deal with just a pull-down resistor. It seems only to add to complexity.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-12-08T16:13:12.017" LastActivityDate="2011-01-08T16:02:57.260" Title="Why are things like RESET/MCLR active low on most ICs?" Tags="&lt;microcontroller&gt;&lt;logic&gt;&lt;level&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="7665" PostTypeId="2" ParentId="7664" CreationDate="2010-12-08T16:15:08.877" Score="19" ViewCount="" Body="&lt;p&gt;Look at what happens during power-up: Vcc rises to a point where it's high enough to make everything work properly. However, that point isn't clearly defined and may vary from device to device. It makes sense not to use this voltage to reset the controller.&lt;br&gt;&#xA;It's easy, however, to keep a level low regardless of Vcc. After all, Reset is already active the instant you switch power on, since at that moment everything is at a low level.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;The graph below illustrates how the output voltage of the reset controller (i.c. an &lt;a href=&quot;http://www.onsemi.com/pub_link/Collateral/MC34064-D.PDF&quot; rel=&quot;nofollow&quot;&gt;MC34064&lt;/a&gt;) remains low until Vcc is high enough to have the complete microcontroller stable.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/TeD18.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-01-07T14:38:42.960" LastActivityDate="2011-01-07T14:38:42.960" CommentCount="4" />
  <row Id="7666" PostTypeId="2" ParentId="7664" CreationDate="2010-12-08T16:15:38.373" Score="10" ViewCount="" Body="&lt;p&gt;Wikipedia &lt;a href=&quot;http://en.wikipedia.org/wiki/Logic_level&quot; rel=&quot;nofollow&quot;&gt;says&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Many control signals in electronics&#xA;  are active-low signals (usually&#xA;  reset lines, chip-select lines and so&#xA;  on). This stems from the fact that&#xA;  &lt;strong&gt;most logic families can sink more current than they can source&lt;/strong&gt;, so&#xA;  fanout and noise immunity increase. It&#xA;  also allows for wired-OR logic if the&#xA;  logic gates are&#xA;  open-collector/open-drain with a&#xA;  pull-up resistor. Examples of this are&#xA;  the I²C bus and the Controller Area&#xA;  Network (CAN), and the PCI Local Bus.&#xA;  RS232 signaling, as used on some&#xA;  serial ports, uses active-low signals.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="1082" LastActivityDate="2010-12-08T16:15:38.373" CommentCount="7" />
  <row Id="7667" PostTypeId="2" ParentId="7280" CreationDate="2010-12-08T18:20:46.237" Score="2" ViewCount="" Body="&lt;p&gt;I had the same problem with a similar component, but finally i found it.  You were right; it is an optocoupler: HCPL-0501.  Check &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet/fairchild/hcpl-0501.pdf&quot; rel=&quot;nofollow&quot;&gt;this datasheet&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to look for similar components just type HCPL-0xxx and the mark code on your IC.  Good luck!&lt;/p&gt;&#xA;" OwnerUserId="2230" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-08T18:36:23.590" LastActivityDate="2010-12-08T18:36:23.590" CommentCount="3" />
  <row Id="7668" PostTypeId="1" AcceptedAnswerId="7669" CreationDate="2010-12-08T20:37:53.117" Score="4" ViewCount="273" Body="&lt;p&gt;I have seen wide varieties at previous companies, from too few to too many with boilerplate, old revisions of standards, etc.  Can you suggest a middle of the road list?  This is for regular PCB fabrication for production.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-13T21:14:07.163" Title="What standard PCB notes should I use?" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="7669" PostTypeId="2" ParentId="7668" CreationDate="2010-12-08T20:39:36.593" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.pcbdesignschool.com/2009/01/05/sample-fabrication-drawing-notes/&quot; rel=&quot;nofollow&quot;&gt;Here is one I found&lt;/a&gt;, but I don't know if it's good or complete.  I don't see UL-94V, for example.  &lt;em&gt;Printed Circuit Board Designer's Reference; Basics&lt;/em&gt; gives &lt;a href=&quot;http://ptgmedia.pearsoncmg.com/images/0130674818/samplechapter/0130674818_ch02.pdf&quot; rel=&quot;nofollow&quot;&gt;this example chapter&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-09T23:54:51.453" LastActivityDate="2010-12-09T23:54:51.453" CommentCount="2" />
  <row Id="7670" PostTypeId="1" AcceptedAnswerId="7671" CreationDate="2010-12-08T21:23:22.987" Score="3" ViewCount="193" Body="&lt;p&gt;I'm building a quadrocopter and would like to prevent drift using a down facing camera. To do this properly, I need to get the height of the drone from the ground. Obviously the ground can vary, so maybe something like radar would be an idea, but I was wondering... how accurate are altimeters (electronic) these days?&lt;/p&gt;&#xA;" OwnerUserId="2212" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-09T00:04:02.240" LastActivityDate="2010-12-09T11:01:11.617" Title="How accurate are altimeters?" Tags="&lt;sensor&gt;&lt;robotics&gt;&lt;uav&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="7671" PostTypeId="2" ParentId="7670" CreationDate="2010-12-08T21:31:19.593" Score="5" ViewCount="" Body="&lt;p&gt;If you base your design loosely on the Parrot drone, they use a downward facing ultrasonic rangefinder.  I'm not sure of the exact brand, but it looks like a PING or Devantech rangefinder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Different model numbers vary in their range and accuracy.  Most are in the 2-5 meter range and have an accuracy of about 2-5cm.  Obviously, the more you pay for the sensor will determine how accurate the sensor is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both &lt;a href=&quot;http://acroname.com/robotics/parts/c_Sensors.html&quot; rel=&quot;nofollow&quot;&gt;Acroname&lt;/a&gt; and &lt;a href=&quot;http://www.sparkfun.com/categories/84&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt; have good selections of ultrasonic rangefinders.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may be able to also use a different type of rangefinding technology.  I have seen IR and laser rangefinders used in many robotics applications.  For a quadrotor, the ultrasonic rangefinder seems to be the best in terms of cost and performance.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2010-12-08T21:31:19.593" CommentCount="1" />
  <row Id="7672" PostTypeId="1" AcceptedAnswerId="7673" CreationDate="2010-12-08T23:35:43.803" Score="5" ViewCount="295" Body="&lt;p&gt;Hello, I've been trying to turn on an ATX power supply I had lying around and I plan to use it for some electronic experiments. Note: I don't want to have to open up the PSU for any reason. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I've tried doing is connecting the green wire(PS-ON) and a black wire(ground) but nothing happens. The fan doesn't come on or anything. I heard something about a SENSE wire and other things. What should I do to make the power supply work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: &#xA;Ok, I got it to turn on now. Apparently it was on the entire time, but the fan in it is super quiet so I didn't notice it. But still what of the SENSE wires and of minimum loads?&lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="708" LastEditorDisplayName="" LastEditDate="2010-12-08T23:44:06.843" LastActivityDate="2010-12-09T00:13:58.543" Title="How to use an ATX Power Supply for my own experiments?" Tags="&lt;power-supply&gt;&lt;atx&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="3" />
  <row Id="7673" PostTypeId="2" ParentId="7672" CreationDate="2010-12-08T23:53:27.960" Score="4" ViewCount="" Body="&lt;p&gt;I don't want to whine too much about safety and I don't like kilometers long safety notices which don't say anything, but I feel that my behavior is justified in this case, so here it goes: If you're uncomfortable with opening the supply, DON'T USE IT AT ALL!!! IT COULD BE VERY DANGEROUS!!! I'll try to explain a bit later why.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm actually planing to modify a PC power supply for my project too, so I have several useful links to share.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take a look at following links:&lt;br&gt;&#xA;&lt;a href=&quot;http://web2.murraystate.edu/andy.batts/ps/powersupply.htm&quot; rel=&quot;nofollow&quot;&gt;http://web2.murraystate.edu/andy.batts/ps/powersupply.htm&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply&quot; rel=&quot;nofollow&quot;&gt;http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.instructables.com/id/Yet-Another-ATX--Lab-Bench-Power-Supply-Conversion/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Yet-Another-ATX--Lab-Bench-Power-Supply-Conversion/&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.mbeckler.org/powersupply/&quot; rel=&quot;nofollow&quot;&gt;http://www.mbeckler.org/powersupply/&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.marcee.org/Articles/PCPowerSupply.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.marcee.org/Articles/PCPowerSupply.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They show several projects where people used ATX power supplies for home experimenting. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd also recommend that you read some basic theory about switching power supplies. It will be clear to you then why yours isn't starting. I don't have any interesting links at the moment, but &lt;a href=&quot;http://en.wikipedia.org/wiki/Switched-mode_power_supply&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;'s a start.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, for SMPS to work, they need a minimum load. That's why yours isn't starting. When power supply is correctly connected to a computer, the computer will provide minimum load to start the supply. As you can see, if you follow the links above, people get around that by providing a low resistance resistor with high power rating and connecting it to the supply. The resistor will provide load for the supply to start. Some articles say that one on the +5 V line is needed, but on some supplies a resistor may be needed on each of the power lines. That's one of the reasons why you should open the supply and take a look how it's working inside. You should be able to identify which cable is connected to which power line. If you can't then I'd recommended that you do some more researching before doing anything. Some articles mention that they use 10 Ω 2 W resistors on + 5 V. I'd use a bit stronger resistor, so its power rating wouldn't be exceeded (but articles also mention that resistors are cool).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;About sensing wires: They are there to allow supply to regulate itself and some supplies may have as much as one for each power line. Articles I linked talk about them and on how to identify them. If I'm correct, they should already be connected to the 24 pin connector and ready to work, but as you mentioned, you didn't connect anything to the connector, so it's not surprising that they are making problems. You'd have to modify PSU cable if you want to solve the problem with them, but if you're still uncomfortable with opening the supply, I'd recommend that you don't try modifying the cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for detecting if the supply is working correctly, use the &lt;a href=&quot;http://pinouts.ru/Power/atx_v2_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;PWR_OK&lt;/a&gt; pin and a voltmeter. You should get +5 V once the supply has stabilized itself.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-12-09T00:13:58.543" LastActivityDate="2010-12-09T00:13:58.543" CommentCount="3" />
  <row Id="7674" PostTypeId="1" CreationDate="2010-12-09T01:50:17.467" Score="1" ViewCount="136" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am the president of my high school's robotics club. We own several VeX robot kits which we have been using for a few years now.  The physics department also owns several Vernier LabPro sonic rangefinders. To save money, I want to be able to utilize the rangefinders in a navigation challenge. However, I do not know if it possible to do so mostly in software, i.e. without constructing interface boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Vernier website provides that the five applicable pins are Echo, Init, AutoID, V+, and GND, in that order.  My question, for anyone who is familiar with this equipment, is: is it possible to connect to these pins through the inputs and outputs on a VeX so that the incoming data (Echo, I believe) can be used for ranging, or am I asking too much of this hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="2231" LastActivityDate="2011-05-03T14:56:35.220" Title="Interfacing Vernier equipment and microcontrollers" Tags="&lt;sensor&gt;&lt;robotics&gt;&lt;sound&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="7675" PostTypeId="1" CreationDate="2010-12-09T04:45:51.937" Score="9" ViewCount="504" Body="&lt;p&gt;Today Scouting New York ran some &lt;a href=&quot;http://www.scoutingny.com/?p=3219&quot; rel=&quot;nofollow&quot;&gt;photographs of the mechanicals of an old, working elevator&lt;/a&gt; that dates back to the 1920s.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was especially intrigued by this amazing picture of the control system:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OsMoV.jpg&quot; alt=&quot;picture of outdated electronic motor controller&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anybody explain what the heck is going on there?&lt;/p&gt;&#xA;" OwnerUserId="2233" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-18T16:12:53.263" LastActivityDate="2011-02-13T21:57:16.310" Title="How do old school, electromechanical elevators work?" Tags="&lt;mechanical&gt;" AnswerCount="2" CommentCount="6" FavoriteCount="1" />
  <row Id="7676" PostTypeId="2" ParentId="7675" CreationDate="2010-12-09T05:49:34.370" Score="12" ViewCount="" Body="&lt;p&gt;It looks like a relay panel capable of handling a serious amount of current.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Way-back-when &lt;a href=&quot;http://en.wikipedia.org/wiki/Relay_logic&quot; rel=&quot;nofollow&quot;&gt;logic circuits were built out of relays&lt;/a&gt;.  They are big, bulky (&lt;em&gt;a&lt;/em&gt; gate is &lt;em&gt;a&lt;/em&gt; relay or two), and costly, so not as common today, but near impossible to kill and can handle all the current you have the space for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The coils of various relays would be connected to the buttons and position sensors, while the contacts of the large relays appear from the video to carry the main motor current.  I would imagine there are some additional low-power relays elsewhere for more logic; I doubt what's seen just there could provide control for more than a couple floors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Relay logic is still used today (in spirit) in PLCs in the form of &lt;a href=&quot;http://en.wikipedia.org/wiki/Ladder_logic&quot; rel=&quot;nofollow&quot;&gt;ladder logic&lt;/a&gt;.  There are seldom any physical relays, save the occasional one on the logic's output. &lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-09T05:49:34.370" CommentCount="4" />
  <row Id="7677" PostTypeId="1" AcceptedAnswerId="7678" CreationDate="2010-12-09T08:12:00.797" Score="2" ViewCount="254" Body="&lt;p&gt;Hi, I'm trying to use a photodiode to measure light levels via an ADC on an ATMega168.  I've got the microcontroller code working properly (measuring values on a pin and reporting it as an led brightness) but I'm having trouble getting the photodiode to report a voltage dependent on light levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see that I could accomplish this with an op amp (&lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/photdet.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) but I'd like to be able to do this without an op amp if possible.  I have a 5 volt source and I'd like to make the photodiode spit out values between 0 and 5 volts.  Is there a crafty circuit I could use for this purpose that doesn't require an amplifier? I'm asking this question because I'd like to know how to use a photodiode for this purpose (I don't want to use an LDR). Thanks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh yeah, &lt;a href=&quot;http://www.vishay.com/docs/81509/81509.pdf&quot; rel=&quot;nofollow&quot;&gt;here is the datasheet for the photodiode I am using.&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="954" LastEditorUserId="954" LastEditorDisplayName="" LastEditDate="2010-12-09T08:17:30.527" LastActivityDate="2010-12-10T11:33:43.633" Title="Measuring light levels with a photodiode and an ADC" Tags="&lt;sensor&gt;&lt;adc&gt;&lt;light&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="7678" PostTypeId="2" ParentId="7677" CreationDate="2010-12-09T09:34:27.913" Score="7" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Important notice&lt;/strong&gt; This is an IR diode: &lt;code&gt;Daylight blocking filter matched with 870 nm to&#xA;950 nm emitters&lt;/code&gt;. IR photodiodes usually have an opaque black package, while visible light photodiodes are in clear packages. You could look for a photodiode (a phototransistor is even more sensitive) with an eye sensitivity curve. I remember having used the SFH 3410 from Infineon here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then the good news: a photodiode or phototransistor acts as a current source, so a series resistor is sufficient to convert the current to a voltage. In your datasheet the graph of figure 3 is the one you need. The reverse current varies between 1uA and 100uA. A series resistor of 10k converts this to 10mV - 1V. You could increase this to get a higher voltage, you'll have to experiment with light levels and resistor value to achieve a full range of 5V. Also keep in mind that the input impedance of the ADC is parallel to the measurement resistor, reducing sensitivity.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The graphs below are from the SFH3410's datasheet. If you keep in mind that you need a Vce of at least 0.5V (right graph), you'll be limited to 4.5V output from a 5V power supply.&#xA;&lt;img src=&quot;http://i.imgur.com/eqAiT.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-10T11:33:43.633" LastActivityDate="2010-12-10T11:33:43.633" CommentCount="1" />
  <row Id="7679" PostTypeId="2" ParentId="7670" CreationDate="2010-12-09T11:01:11.617" Score="1" ViewCount="" Body="&lt;p&gt;The answer effectively boils down to two questions:&lt;br&gt;&#xA;&quot;How Much do you want to spend&quot;&lt;br&gt;&#xA;&quot;What are your size requirements?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Realistically, there are three way to measure altitude without looking at the ground below:  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;GPS - Not very precise (~3m), unless you know people in the military.&lt;/li&gt;&#xA;&lt;li&gt;Inertial Measurement - Expensive, if you want decent precision. Theoretically could work anywhere.&lt;/li&gt;&#xA;&lt;li&gt;Barometry - Requires an air column. Sparkfun &lt;a href=&quot;http://www.sparkfun.com/products/8128&quot; rel=&quot;nofollow&quot;&gt;has one&lt;/a&gt; that claims a resolution of 9 cm.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-12-09T11:01:11.617" CommentCount="4" />
  <row Id="7680" PostTypeId="2" ParentId="7603" CreationDate="2010-12-09T13:44:24.520" Score="1" ViewCount="" Body="&lt;p&gt;Ah! I think I fixed it!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And I learned some things about my MCU in the process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I2C is not working properly because of a &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/80470e.pdf&quot; rel=&quot;nofollow&quot;&gt;chip errata&lt;/a&gt;. Item 10.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Module: I2C™ (I2C1, SDA Line State)&#xA;&#xA;When using I2C1, the SDA1 line state may not be&#xA;detected properly unless it is first held low for&#xA;150 ns after enabling the I2C module.&#xA;&#xA;In Master mode, this error may cause a bus collision&#xA;to occur instead of a Start bit transmission.&#xA;Transmissions after the SDA1 pin has been held&#xA;low will occur correctly.&#xA;&#xA;In Slave mode, the device may not Acknowledge&#xA;the first packet sent after enabling the I2C module.&#xA;In this case, it will return a NACK instead of an&#xA;ACK. The device will correctly respond to packets&#xA;after detecting a low level on the line for 150 ns.&#xA;&#xA;The I2C2 module operates as expected and does&#xA;not exhibit this issue.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This explains why the screwdriver trick works. I was shorting SDA to Vss when I ran the screwdriver along the pins, which allowed the module to start correctly. It only affects A3/A4 silicon.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-09T13:44:24.520" />
  <row Id="7681" PostTypeId="2" ParentId="7484" CreationDate="2010-12-09T18:53:48.163" Score="2" ViewCount="" Body="&lt;p&gt;You may optimize for the typical case.  For example if I need 5 A max but 2 A typical, I will design/buy a 5 A supply but choose the one that is most efficient at 2 A.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-09T18:53:48.163" />
  <row Id="7682" PostTypeId="1" AcceptedAnswerId="7689" CreationDate="2010-12-09T18:58:38.703" Score="2" ViewCount="128" Body="&lt;p&gt;I'm thinking of migrating from an I2C bus at 400 kHz to one running at nearly 1 MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using 1.2k pull-ups at the moment and on the clock and data lines, I get a rise time of 383ns average when sending out pulses. Fall time is approaching the limits of a 100 MHz oscilloscope at ~15ns. Are there potential issues with this kind of rise time? What about noise and signal integrity? Clock jitter? etc. Would there be significant issues? I will probably stick with 400 kHz on my breadboard which works fine, but the final product may use 1 MHz I2C. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-09T20:31:07.990" Title="What kind of issues might I face when moving from 400 kHz I2C to 1 MHz I2C?" Tags="&lt;microcontroller&gt;&lt;i2c&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="7683" PostTypeId="2" ParentId="7682" CreationDate="2010-12-09T19:42:01.067" Score="0" ViewCount="" Body="&lt;p&gt;Clock jitter isn't an issue in I2C since each clock is treated separately.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-09T19:42:01.067" />
  <row Id="7684" PostTypeId="1" AcceptedAnswerId="7686" CreationDate="2010-12-09T19:58:05.740" Score="4" ViewCount="246" Body="&lt;p&gt;What causes turning ON an single output pin on a Microchip PIC16F690 to spontaneously turn OFF another pin on the same port? I can work around this problem by writing a byte to the entire port, controlling all pins simultaneously, instead of just a bit to control the pin state. I'm using the Hi-Tech C compiler here. I am determining the state of the pin with 9 LEDs each consuming 3 mA. This is way below the max power specs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The mplab header file has the 0 pin on port A declared as such:&#xA;volatile       bit RA0  @ ((unsigned)&amp;amp;PORTA*8)+0;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am turning the pin on by writing a high value to it.&#xA;RA0 = 1;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the problem that the complier is treating the &quot;1&quot; as a byte and writing to the whole port?&#xA;Do I need to cast it? If so, shouldn't have the complier given me an error?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RA0 = (bit) 1;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I write to the whole port everything works as expected:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PORTA = 0b00000001;&lt;/p&gt;&#xA;" OwnerUserId="1900" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-10T02:36:39.183" LastActivityDate="2010-12-10T22:14:30.967" Title="What causes turning ON an single output pin on a Microchip PIC16F690 to spontaneously turn OFF another pin on the same port?" Tags="&lt;pic&gt;&lt;programming&gt;&lt;microchip&gt;" AnswerCount="4" />
  <row Id="7685" PostTypeId="1" CreationDate="2010-12-09T20:13:29.470" Score="2" ViewCount="299" Body="&lt;p&gt;Does anyone know how I could make a card the size of a credit card with something like a GPS/bluettoth/RFID module that could be detected from a relatively long range. The purpose is to see where this card is on a map for example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there GPS modules that are that small?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If someone could direct me to some tutorials or help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Really the idea is, If I ever lost my wallet for example, I could track where in the house I lost this wallet. A lame example but this is the basic idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you.&lt;/p&gt;&#xA;" OwnerUserId="2236" LastEditorUserId="2236" LastEditorDisplayName="" LastEditDate="2010-12-22T06:05:09.007" LastActivityDate="2010-12-23T12:20:20.540" Title="Making a plastic card that looks like a credit card with a long-range module inside" Tags="&lt;bluetooth&gt;&lt;rfid&gt;&lt;gps&gt;" AnswerCount="6" CommentCount="6" FavoriteCount="2" />
  <row Id="7686" PostTypeId="2" ParentId="7684" CreationDate="2010-12-09T20:17:51.537" Score="12" ViewCount="" Body="&lt;p&gt;It's the well-known read-modify-write problem, you will find details in the data sheet. You have to write to the whole register, as you have found. The 18F and 16-bit devices don't have the problem. There is a good description on page 2 in &lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/93009A.pdf&quot; rel=&quot;nofollow&quot;&gt;this document&lt;/a&gt;. Changing bits in a &quot;shadow&quot; register then writing the register to the output port is often used to get round the problem. &lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-09T21:47:39.007" LastActivityDate="2010-12-09T21:47:39.007" CommentCount="3" />
  <row Id="7687" PostTypeId="2" ParentId="7684" CreationDate="2010-12-09T20:18:19.913" Score="0" ViewCount="" Body="&lt;p&gt;I use Microchip's compiler.  It has a header file where all the registers have a union with the bits defined.  So, in my code I write:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;LATAbits.LATA0 = 1;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Also, I would use the latch register instead of the PORT register to set the output.  I think some chips don't care, but some do.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-12-09T20:18:19.913" CommentCount="2" />
  <row Id="7688" PostTypeId="2" ParentId="7684" CreationDate="2010-12-09T20:27:03.270" Score="0" ViewCount="" Body="&lt;p&gt;I'm 99% sure the compiler is doing this.  Whatever structure is defined to access the pin has ambiguity in it that the compiler is resolving to create this behavior.  The bit casting might help but I don't know how (bit) is defined so I can't be sure.  The compiler won't necessarily give you an error if the value being written to the pin is of the proper type - I'm guessing the (bit) mask might trigger some logic to preserve the state of the other pins but still return the same type as your constant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not surprising that writing to the port itself works - but working with individual pins is much more complicated.  Either there's a bug in the code provided, it wasn't meant to be used with this compiler or you're just not using it correctly.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-12-09T20:27:03.270" CommentCount="1" />
  <row Id="7689" PostTypeId="2" ParentId="7682" CreationDate="2010-12-09T20:31:07.990" Score="2" ViewCount="" Body="&lt;p&gt;If you are going to run an I2C bus with mixed speeds, and you have devices on the bus that can &lt;em&gt;only&lt;/em&gt; work at 400 KHz and below, then they must be disabled somehow (e.g. powering them down, so their I2C bus leads will be tristated) when running the bus at the 1 MHz speed, since they will not be able to parse the high-speed addresses and may respond incorrectly.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-12-09T20:31:07.990" CommentCount="4" />
  <row Id="7690" PostTypeId="2" ParentId="7685" CreationDate="2010-12-10T00:52:13.917" Score="1" ViewCount="" Body="&lt;p&gt;If your goal is to make some sort of tracking device that you could find somewhere further than you could throw a ball, RFID and BT are out.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could take the components commonly found in cell phones and boil it down to only what matters for this application: a GPS module and a cellular radio.  Both could be made quite thin, the limiting factor would essentially be PCB thickness, IC height, RF shielding, and battery.  To access anyone's cell network you will need a SIM card or other method for them to bill you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be aware that designing a circuit to be thin (let alone credit-card thin) and with a high level of integration is a very difficult and very costly problem.  There's a reason a Droids and iPhones cost $500+, even when sold by the millions.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-10T00:52:13.917" />
  <row Id="7691" PostTypeId="2" ParentId="7668" CreationDate="2010-12-10T02:46:44.873" Score="2" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;Board Name&lt;/li&gt;&#xA;&lt;li&gt;Company/personal name&lt;/li&gt;&#xA;&lt;li&gt;Copyright year&lt;/li&gt;&#xA;&lt;li&gt;Thickness&lt;/li&gt;&#xA;&lt;li&gt;Board material type&lt;/li&gt;&#xA;&lt;li&gt;Copper weight&lt;/li&gt;&#xA;&lt;li&gt;Panelization instructions&lt;/li&gt;&#xA;&lt;li&gt;Tolerances&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1256" LastEditorUserId="1256" LastEditorDisplayName="" LastEditDate="2010-12-13T21:14:07.163" LastActivityDate="2010-12-13T21:14:07.163" />
  <row Id="7692" PostTypeId="1" AcceptedAnswerId="7711" CreationDate="2010-12-10T03:13:08.703" Score="5" ViewCount="347" Body="&lt;p&gt;&lt;strong&gt;What is the maximum temperature you would recommend for an isolated trace on the surface of FR-4?&lt;/strong&gt; (I.e.: not an inner-layer track.) &lt;strong&gt;Is there an IPC recommendation?&lt;/strong&gt; Does it really matter if it is past the &lt;em&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Glass_transition&quot; rel=&quot;nofollow&quot;&gt;glass transition temperature&lt;/a&gt;&lt;/em&gt;? (What is this value for FR-4? Wikipedia says &quot;above 120C&quot;.) I mean, even if it's soft, will the track still stick with high reliability? 'Suppose what I'm looking for is a MTTF vs. temperature (vs. trace area) set of curves, but experienced guesses are encouraged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is useful when calculating trace widths vs. temperature rise. I've always limited traces to the lower of about 100C or whatever the connected parts can manage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[For the Mech-E, Chem-E, and Mat-E: I guess the question can be boiled down to the intersection of shear stress between copper and FR-4 caused by differences in thermal expansion, which would be related to track width, and the decrease in shear modulus as temperature rises.]&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-10T17:08:20.023" Title="maximum trace temperature on FR-4" Tags="&lt;pcb&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="2" />
  <row Id="7693" PostTypeId="2" ParentId="7692" CreationDate="2010-12-10T08:50:37.570" Score="0" ViewCount="" Body="&lt;p&gt;I suspect you will render any ICs on the board useless due to high temperature long before the copper and FR-4 become a problem.&lt;/p&gt;&#xA;" OwnerUserId="1990" LastActivityDate="2010-12-10T08:50:37.570" CommentCount="1" />
  <row Id="7694" PostTypeId="2" ParentId="7685" CreationDate="2010-12-10T10:58:57.453" Score="0" ViewCount="" Body="&lt;p&gt;What's available depends on where you operate and what you can get and are willing to use I suppose. A couple of ideas:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Closest that comes to mind is a modern cellphone with GPS (for locating itself) and GSM/3G/other network for communicating that location. Not quite credit card, but same kind of shape. Imagine the data modem and GPS parts there and it might give you an idea of the complexity and size of that method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also be able to make a small (more or less legal) simple radio beacon (quite slim with SMT) and see if you can track that with RSSI or AOA or other location methods. Reception might be enough for &quot;detecting&quot; it, as the question says.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also some microcontroller devkits that carry radios in 400-800-900-2400 MHz bands that might have fair range outdoors (maybe even legally). Bluetooth is clumsy, elaborate and primarily short range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then there's also PMR, but I'm not aware of anything smaller than a stripped radio phone / baby monitor for that.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-12-10T10:58:57.453" />
  <row Id="7695" PostTypeId="2" ParentId="7660" CreationDate="2010-12-10T11:24:22.533" Score="3" ViewCount="" Body="&lt;p&gt;The &quot;weak&quot; reference just means that the routine will be replaced by a routine in your code of the same name.  When using C this is simple, the names will always be identical but C++ name mangles the functions (for function overloading etc) so the compiled name will probably not match the default ISR name.  You need to wrap the function (or at least a forward reference, I'm not sure of specifics I mostly work in C) in an extern &quot;C&quot; wrapper to force the compiler to not mangle the name.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;extern &quot;C&quot; {&#xA;  void SysTick_Handler(void)&#xA;  {&#xA;    // do whatever&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="820" LastActivityDate="2010-12-10T11:24:22.533" CommentCount="2" />
  <row Id="7696" PostTypeId="1" AcceptedAnswerId="7698" CreationDate="2010-12-10T11:39:48.713" Score="0" ViewCount="169" Body="&lt;p&gt;I am looking for a small IC that provides a regulated dc voltage based on the duty cycle of the input. This is probably asking for a lot but does anyone know if one exists. Essentially I need a low pass filter but I need to conserve board space as much as possible as I am VERY limited. Also, I have done LPF's in the past with just a resistor and capacitor but I can never seem to get the noise out. I usually end up with at least 20mA of ripple. My PWM would likely be 3.3V pk-to-pk but I could also manage 5V as well. Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-12-10T14:32:13.020" LastActivityDate="2010-12-10T14:40:59.837" Title="Is there a voltage regulator IC that takes PWM input?" Tags="&lt;voltage-regulator&gt;&lt;filter&gt;&lt;pwm&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="7697" PostTypeId="1" AcceptedAnswerId="8661" CreationDate="2010-12-10T11:50:23.203" Score="2" ViewCount="170" Body="&lt;p&gt;I'm &lt;em&gt;not&lt;/em&gt; looking for a graphic or text LCD display here, just essentially a single, large pixel, capable of going from dark-light-dark in under 1ms. The faster, the better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea is to create a secondary shutter for a still camera, increasing the &lt;a href=&quot;http://www.kenrockwell.com/tech/syncspeed.htm#why&quot; rel=&quot;nofollow&quot;&gt;flash sync speed&lt;/a&gt; of the camera. Here's a video of a similar idea, but on a CMOS video camera. Seems like they're using a pane from a pair of 3d shutter glasses, which operate at video speeds (60 or 120 hz, not fast enough.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something like the panel in an auto-darkening welding helmet would be along the lines of what I need, providing they can also transition from dark-light at high speeds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are these called? What can I search for (LCD panel obviously doesn't help)? Where might I be able to find one? (Aside from hacking apart a welding helmet.)&lt;/p&gt;&#xA;" OwnerUserId="2240" LastActivityDate="2011-01-06T18:01:52.647" Title="Where can I find a fast (1KHz) LCD plate?" Tags="&lt;lcd&gt;&lt;camera&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="7698" PostTypeId="2" ParentId="7696" CreationDate="2010-12-10T11:55:24.457" Score="3" ViewCount="" Body="&lt;p&gt;I doubt such a device exists. A PWM signal as such is not a good start to generate a stable output voltage with as little ripple as possible. The regulator would require a filter with a rather large capacitor (I guess you want to draw some current from it), which will need to be external anyway. It wouldn't save you any space in any case.&lt;br&gt;&#xA;If your PWM signal is to supply power, and not just a voltage, you'll have to provide a power driver, since PWM signals usually only provide a voltage.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-10T11:55:24.457" CommentCount="1" />
  <row Id="7699" PostTypeId="1" AcceptedAnswerId="7701" CreationDate="2010-12-10T12:08:40.853" Score="4" ViewCount="156" Body="&lt;p&gt;Both my microcontrollers on my project (dsPIC33FJ128GP804 and PIC24FJ64GA004) support JTAG boundary scan testing. Should I wire these up and expose a JTAG port for hackers? The product is intended to be open hardware and as such be modified. ICSP and ICD ports will also be exposed. Of course these ports and traces take up space - so is it worth it? Would people be able to use them with basic PIC micros?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-10T17:29:07.620" Title="Should I include a JTAG port on my product?" Tags="&lt;jtag&gt;&lt;icd&gt;&lt;icsp&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="1" />
  <row Id="7700" PostTypeId="2" ParentId="7696" CreationDate="2010-12-10T12:18:34.173" Score="2" ViewCount="" Body="&lt;p&gt;You didn't provide any specs on how small you want to go but you could consider an op-amp as a voltage regulator with a small pass transistor and LPF for the reference. Or, you could look for programmable voltage regulators; these are usually SPI or I2C. If you have an adjustable regulator, consider a digital potentiometer.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-10T12:18:34.173" />
  <row Id="7701" PostTypeId="2" ParentId="7699" CreationDate="2010-12-10T13:12:23.173" Score="6" ViewCount="" Body="&lt;p&gt;How expensive is half a square inch of board space? Bring out the traces to some small pitch pads. Those who are interested can solder their own header adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(EE who says &quot;yes please&quot;)&lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2010-12-10T13:12:23.173" CommentCount="2" />
  <row Id="7702" PostTypeId="2" ParentId="7493" CreationDate="2010-12-10T13:17:22.483" Score="1" ViewCount="" Body="&lt;p&gt;While at first sight they may look that way, trimmer potmeters are not meant to be trimmed with a cruciform screwdriver like a Phillips or Pozidriv. What appears to be a cross is actually a slot with an arrow in it, which points to the position of the wiper.&lt;br&gt;&#xA;So simply use a small flat-head screwdriver, like one from a jeweler's set.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-10T13:17:22.483" />
  <row Id="7703" PostTypeId="2" ParentId="7699" CreationDate="2010-12-10T13:20:13.503" Score="-2" ViewCount="" Body="&lt;p&gt;These pins will surely be needed for the firmware debugging/loading.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could always bring them out onto a section of the board that can be snapped off before delivery/installation.  This means that the developer has access to the connector/debug interfaces that are absent from the final product.  If you place the debug traces on an inner board layer then this will make the hacker's life more difficult but, assuming that you have not disabled the JTAG in the processor, they will always have access to the device pins and so to the interface.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-12-10T13:20:13.503" CommentCount="1" />
  <row Id="7704" PostTypeId="2" ParentId="7692" CreationDate="2010-12-10T13:28:13.987" Score="1" ViewCount="" Body="&lt;p&gt;AFAIK, safety regulations (e.g. UL) require that the temperature on solder joints and traces be lower than 130°C for regular FR-4 material.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Individual parts may become hotter (e.g. a MOSFET or diode in a TO220), but the solder joints (and the traces) must be at or below 130°C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This maximum temperature of 130°C seems to be reasonable not only with regard to safety approvals, but also with regard to what the board really can take. I have taken boards out of the climatic chamber with some parts' temperature readings at ca. 170°C, and dames en heren, that smell was bad and that board was black!&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2010-12-10T13:44:36.157" LastActivityDate="2010-12-10T13:44:36.157" CommentCount="1" />
  <row Id="7705" PostTypeId="2" ParentId="7530" CreationDate="2010-12-10T13:28:53.287" Score="1" ViewCount="" Body="&lt;p&gt;I would suggest to use your phone as a camera as well as the controller. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is what I am planning to do in the near future with an Android phone and Arduino BT (or Arduino + Bluetooth chip) connecting the to devices via Bluetooth.&lt;/p&gt;&#xA;" OwnerUserId="1649" LastActivityDate="2010-12-10T13:28:53.287" />
  <row Id="7706" PostTypeId="2" ParentId="7699" CreationDate="2010-12-10T13:31:39.257" Score="4" ViewCount="" Body="&lt;p&gt;JTAG is very rarely used with those devices. All you need is the usual connector for an ICD 2/3 or PICkit.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-10T13:31:39.257" CommentCount="1" />
  <row Id="7707" PostTypeId="2" ParentId="7696" CreationDate="2010-12-10T14:40:59.837" Score="1" ViewCount="" Body="&lt;p&gt;If you have access to the regulator's voltage reference, you could use the PWM signal to lower the V_ref according to the PWM's duty cycle. Will be slow, because you will need a significant low pass filter, but it might work.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-12-10T14:40:59.837" />
  <row Id="7708" PostTypeId="2" ParentId="4423" CreationDate="2010-12-10T15:46:29.603" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://ditaa.org/ditaa/&quot; rel=&quot;nofollow&quot;&gt;ditaa&lt;/a&gt; does what your'e looking for.  The following image is generated from your raw text above.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/6vgZ8.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Might need a bit of editing to get the formatting right...&lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-12-10T17:13:13.020" LastActivityDate="2010-12-10T17:13:13.020" CommentCount="1" />
  <row Id="7709" PostTypeId="1" CreationDate="2010-12-10T16:42:35.280" Score="4" ViewCount="473" Body="&lt;p&gt;A lot of times in circuits I see a resistor placed in series in a signal line and sometimes even in series with an MCU's VDD line. Is the intention of this to smooth out noise in the line? How is this different that using a small cap, like a .1uF to do the same thing?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-10T16:47:12.023" LastActivityDate="2011-03-04T16:07:33.130" Title="Why put a resistor in series with signal line?" Tags="&lt;capacitor&gt;&lt;resistor&gt;&lt;signal&gt;&lt;signal-integrity&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="7710" PostTypeId="2" ParentId="7709" CreationDate="2010-12-10T16:46:46.610" Score="6" ViewCount="" Body="&lt;p&gt;Yes, signal integrity is the reason.  Using a cap will slow the edge down a lot and ins't as clean.  The standard book on the subject is &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0133957241&quot; rel=&quot;nofollow&quot;&gt;High Speed Digital Design: A Handbook of Black Magic&lt;/a&gt;.  As a rule of thumb, 22.1 ohms is typically used as a starting point.  You can use a signal integrity simulation tool such as Mentor Graphics' HyperLynx to get a better analysis before the board is built.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the VDD line that isn't the reason.  Some people might put a milliohm resistor there to measure power, then replace it with a 0 ohm for production.  Others, especially analog may put an RC filter on there to get rid of noise.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-10T17:40:09.383" LastActivityDate="2010-12-10T17:40:09.383" CommentCount="5" />
  <row Id="7711" PostTypeId="2" ParentId="7692" CreationDate="2010-12-10T17:08:20.023" Score="2" ViewCount="" Body="&lt;p&gt;This is not my area of expertise so I cannot point you towards any MTBF data but I work with tools that routinely operate in environments up to 175°C so I can tell you from experience what I watch out for.  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Voltage regulators with thermal protection.  These usually cut out about 125°C.&lt;/li&gt;&#xA;&lt;li&gt;Solder.  Depends on the lead/tin ratio this can vary greatly.  You have to check the rating on each type but you can typically get solder that doesn't melt until around 220°C&lt;/li&gt;&#xA;&lt;li&gt;Components vary greatly.  You have to read the datasheets carefully.  For instance, a microcontroller might be rated to operate at 125°C but that is 100 MHz.  If you only run it at 12 MHz it might run much hotter.  There is a good article &lt;a href=&quot;http://www.eetimes.com/design/signal-processing-dsp/4209479/Go-beyond-the-datasheet--Part-2--Understand-the-considerations&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; that talks a bit more about this.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I haven't experienced any trouble with traces separating from the boards before these other failures occurred.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-12-10T17:08:20.023" CommentCount="1" />
  <row Id="7712" PostTypeId="2" ParentId="7699" CreationDate="2010-12-10T17:29:07.620" Score="0" ViewCount="" Body="&lt;p&gt;Yes, you should.  It can be used to check connections between the chips.  If there are a lot of such connections, it can really help.  If they mainly go to other chips w/o JTAG (e.g. memories), then it won't be as helpful.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-10T17:29:07.620" />
  <row Id="7713" PostTypeId="2" ParentId="7306" CreationDate="2010-12-10T17:31:22.017" Score="0" ViewCount="" Body="&lt;p&gt;Use the Altera USB blaster.  Then read it out as @Leon Heller suggsted.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-10T17:31:22.017" />
  <row Id="7714" PostTypeId="2" ParentId="7709" CreationDate="2010-12-10T17:42:54.920" Score="4" ViewCount="" Body="&lt;p&gt;I'm not sure if this is what you're talking about, but a smallish resistor (&amp;lt;100 ohm) can be placed at the output of an op-amp that's driving a long line, so that the capacitive load doesn't cause the amplifier to oscillate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can also be used to ensure that two amplifiers have the exact same output impedance, to create a &lt;a href=&quot;http://en.wikipedia.org/wiki/Balanced_line&quot; rel=&quot;nofollow&quot;&gt;balanced line&lt;/a&gt; that rejects interference.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-12-10T17:42:54.920" />
  <row Id="7715" PostTypeId="1" AcceptedAnswerId="7723" CreationDate="2010-12-10T19:01:08.943" Score="1" ViewCount="254" Body="&lt;p&gt;I'm looking for a way to send binary data over an audio channel on a video/audio transmitter. This will be an add-on feature to my product because it already has an audio interface. I'm hoping to be able to reach about 1 kbit/s data rate at a minimum, but higher would be nice. The requirements for any such protocol would be:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;High noise immunity - so a signal with some noise and interference on it doesn't cause problems. Ideally, data would be either error free or flagged as having errors, as corrupt data could cause lots of problems. Weaker signals may introduce jitter and other nasties into the signal, so it should be capable of withstanding these.&lt;/li&gt;&#xA;&lt;li&gt;Be able to work on a bandwidth limited (approx 8 kHz) audio channel. This includes slew rate limitations and variable jitter, including between clocks or bytes.&lt;/li&gt;&#xA;&lt;li&gt;Be easy to implement, both transmitting and receiving, on a small microcontroller.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The protocol only needs to be one way as data will only be sent. The reason I ask this is because I've gone through lots of possible options (FSK, PSK, duty cycle modulation, Manchester, etc.) but have no idea which would be the best. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-10T23:59:19.253" Title="Best method for sending data over a mono audio channel" Tags="&lt;data&gt;&lt;modem&gt;&lt;fsk&gt;&lt;psk&gt;" AnswerCount="2" CommentCount="12" />
  <row Id="7717" PostTypeId="2" ParentId="7709" CreationDate="2010-12-10T19:15:02.090" Score="4" ViewCount="" Body="&lt;p&gt;On what kind of product?  On a consumer part, it's probably for signal integrity (See Brian's answer). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On a development tool, it might be for current limiting.  I often drop some 470-ohm resistors on signal lines for my projects for data lines which connect to external modules.  The current drawn by a digital input isn't enough to cause a major voltage drop across this resistor.  The current limiting means that nothing (usually) goes up in smoke if I make a mistake connecting stuff, or if something shorts a connection on an exposed board.  It's different from a cap because a cap will draw a lot of current on a digital edge (for a short but sometimes non-negligible time), having the opposite effect of a resistor.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-10T19:15:02.090" />
  <row Id="7718" PostTypeId="1" CreationDate="2010-12-10T19:25:07.873" Score="3" ViewCount="174" Body="&lt;p&gt;I have a relatively new soldering iron. I can't remember when this started(and I've only used the iron 5-10 times) but I stopped being able to tin the tip. When I stick soldering to it it just balls up in one spot on the iron and then after 5 or 10 seconds on the tip, the solder turns a dull gray color(rather than shiny silver).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have used nothing out of the ordinary on it. Only a brass sponge, a wet piece of cloth, and solder tip tinner/cleaner(which I only just started trying to use). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even with the tip tinner, the tip will stay shiny(and conductive) for about 5 seconds and then rapidly turn a dull gray color, eventually even with a few black spots.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there something I can do to fix this? Did I just get a lemon tip or is this all normal(note I'm sorta new to soldering still)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the soldering iron is &lt;a href=&quot;http://www.sparkfun.com/products/9507&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; with the included tip&lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T20:53:37.557" LastActivityDate="2010-12-10T21:00:38.673" Title="Why does solder turn dull grey on my iron and exhibit poor wetting?" Tags="&lt;soldering&gt;&lt;soldering&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="7719" PostTypeId="2" ParentId="7718" CreationDate="2010-12-10T19:43:00.020" Score="2" ViewCount="" Body="&lt;p&gt;Either it's oxidized, not getting hot enough, or both. Unscrew the tip and check the contact with the heater. Scrub the heck out of the tip with your brass sponge and dip it in a bit of flux. Hopefully it's not pitted.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-10T19:43:00.020" />
  <row Id="7720" PostTypeId="2" ParentId="7718" CreationDate="2010-12-10T20:00:43.423" Score="4" ViewCount="" Body="&lt;p&gt;You get what you pay for with soldering equipment, you can't expect much for $9.95! Get a good quality temperature-controlled iron.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-10T20:00:43.423" CommentCount="4" />
  <row Id="7721" PostTypeId="1" CreationDate="2010-12-10T20:14:35.283" Score="4" ViewCount="273" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Class_D_Amplifier&quot; rel=&quot;nofollow&quot;&gt;Class D PWM switching power amplifiers&lt;/a&gt; use an LC filter at the output to filter out the switching harmonics:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/9FMDB.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than the inductance value, what properties are important for this inductor?  What types, specifically, are best?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Concerns would include distortion (from hysteresis/saturation of the core?), efficiency, EMI (toroidal shape, shielding), etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think some of the important qualities would also be shared by inductors in switch-mode power supplies.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-01-11T13:13:45.317" Title="Choosing output filter inductors for switching power amplifiers" Tags="&lt;amplifier&gt;&lt;pwm&gt;&lt;smps&gt;&lt;inductor&gt;&lt;class-d&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="7722" PostTypeId="2" ParentId="7718" CreationDate="2010-12-10T20:30:47.983" Score="5" ViewCount="" Body="&lt;p&gt;Soldering iron tips should never be &quot;clean&quot; from everything.  You &lt;strong&gt;must&lt;/strong&gt; maintain a small amount of solder on them at all times to avoid oxidizing the iron plating (as in &lt;code&gt;Fe&lt;/code&gt; iron, major component of steel, iron).  After brushing excess solder and flux from the tip with a sponge, reapply a tiny bit of clean solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your &lt;em&gt;solder&lt;/em&gt; turns a dull grey, that would be due to it's oxidization, which means you're either waiting way too long or the iron is way too hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tip tinner should only be used sparingly as it is fairly aggressive and will ultimately eat through the iron coating.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T20:39:03.590" LastActivityDate="2010-12-10T20:39:03.590" CommentCount="2" />
  <row Id="7723" PostTypeId="2" ParentId="7715" CreationDate="2010-12-10T20:44:08.863" Score="4" ViewCount="" Body="&lt;p&gt;I think RQDQ has the right idea.  The best method of sending digital data over restricted bandwidth audio lines is a problem that has already been solved for &lt;a href=&quot;http://en.wikipedia.org/wiki/Modem#Increasing_speeds_.28V.21.2C_V.22.2C_V.22bis.29&quot; rel=&quot;nofollow&quot;&gt;modems&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The 300 bit/s modems used &lt;a href=&quot;http://en.wikipedia.org/wiki/Audio_frequency-shift_keying&quot; rel=&quot;nofollow&quot;&gt;audio frequency-shift keying&lt;/a&gt; to send data. In this system the stream of 1s and 0s in computer data is translated into sounds which can be easily sent on the phone lines. In the Bell 103 system the originating modem sends 0s by playing a 1,070 Hz tone, and 1s at 1,270 Hz, with the answering modem putting its 0s on 2,025 Hz and 1s on 2,225 Hz. These frequencies were chosen carefully, they are in the range that suffer minimum distortion on the phone system, and also are not harmonics of each other.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;In the 1,200 bit/s and faster systems, &lt;a href=&quot;http://en.wikipedia.org/wiki/Phase-shift_keying&quot; rel=&quot;nofollow&quot;&gt;phase-shift keying&lt;/a&gt; was used. In this system the two tones for any one side of the connection are sent at the similar frequencies as in the 300 bit/s systems, but slightly out of phase. ...&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-12-10T20:44:08.863" />
  <row Id="7724" PostTypeId="2" ParentId="7721" CreationDate="2010-12-10T20:52:31.927" Score="3" ViewCount="" Body="&lt;p&gt;Taking high enough current without saturation is important.  Check peak and average current, and derate it some.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-10T20:52:31.927" />
  <row Id="7725" PostTypeId="2" ParentId="7718" CreationDate="2010-12-10T21:00:38.673" Score="0" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;I have used nothing out of the ordinary on it. Only a brass sponge, a wet piece of cloth, and solder tip tinner/cleaner(&lt;strong&gt;which I only just started trying to use&lt;/strong&gt;)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So you've never tinned your tip?  If that's the case then that's your problem.  Buy another tip, TIN it, and always make sure you tin it before storing it.  NEVER store it &quot;clean&quot; or it will oxidize and you will have a bad tip.&lt;/p&gt;&#xA;" OwnerUserId="2203" LastActivityDate="2010-12-10T21:00:38.673" CommentCount="1" />
  <row Id="7726" PostTypeId="1" AcceptedAnswerId="7732" CreationDate="2010-12-10T21:26:01.793" Score="0" ViewCount="156" Body="&lt;p&gt;Is there any way to get -12 V (DC) using only:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;+12 V DC&lt;/li&gt;&#xA;&lt;li&gt;Ground&lt;/li&gt;&#xA;&lt;li&gt;OPAMPs&lt;/li&gt;&#xA;&lt;li&gt;Resistors&lt;/li&gt;&#xA;&lt;li&gt;Capacitors&lt;/li&gt;&#xA;&lt;li&gt;Inductors&lt;/li&gt;&#xA;&lt;li&gt;Diodes&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2188" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-10T22:09:45.790" LastActivityDate="2010-12-10T22:09:45.790" Title="Is there any way to acquire -12 V from +12 V?" Tags="&lt;smps&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="7727" PostTypeId="2" ParentId="7726" CreationDate="2010-12-10T21:33:33.397" Score="3" ViewCount="" Body="&lt;p&gt;LM7660 or equivalent *7660 part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have a look how it works, it is fairly easy to implement with an op-amp and a few external components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not going to do &lt;em&gt;all&lt;/em&gt; your homework, though.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-10T21:33:33.397" />
  <row Id="7728" PostTypeId="1" CreationDate="2010-12-10T21:34:12.967" Score="2" ViewCount="599" Body="&lt;p&gt;I want to use my arduino to make a simple mains power line voltage wave oscilloscope.&lt;Br&gt;&#xA;questions:&lt;br&gt;&#xA;&lt;strong&gt;1&lt;/strong&gt;. how to connect the mains power line (230V, 50Hz) to the arduino safely and efficient (I think a simple resistor voltage divider wouldn't cut it here)?&lt;br&gt;&#xA;&lt;strong&gt;2&lt;/strong&gt;. can i use serial communication to get this data in real time to the PC and then do some analysis in processing or some other software (maybe a simple labview analyzing the serial data because I'm familiar with this)?&lt;br&gt;&#xA;&lt;br&gt;any links for documentation would be highly appreciated, 10x guys ;)&lt;/p&gt;&#xA;" OwnerUserId="2245" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-20T15:05:04.230" LastActivityDate="2010-12-20T15:05:04.230" Title="How to connect 230V 50Hz to arduino analog input" Tags="&lt;arduino&gt;&lt;oscilloscope&gt;&lt;powerline&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="7730" PostTypeId="2" ParentId="7726" CreationDate="2010-12-10T21:44:44.377" Score="4" ViewCount="" Body="&lt;p&gt;Of course, you can make nearly anything with all of those. Depending on your current/power requirements, you are looking at one of the following switching supplies:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;charge pump : a personal favourite, requiring only a cap and uC pin&lt;/li&gt;&#xA;&lt;li&gt;boost, with its many variants&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Normally one would use a dedicated SMPS controller, with internal oscillator, and gate driver along with a handful of transistors to implement these, but apparently you can't use them. You must design a harmonic oscillator out of inductors and capacitors, then buffer and clean up (make square) this signal with op amps. With this chopper signal you can implement either of the above SMPSs as well as stabilize the LC oscillator (it will die).&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-10T21:44:44.377" CommentCount="2" />
  <row Id="7731" PostTypeId="1" AcceptedAnswerId="7738" CreationDate="2010-12-10T21:47:44.323" Score="4" ViewCount="264" Body="&lt;p&gt;Background -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I programmed my first SBC on an MEK6800D2 evaluation Kit (that I had build) in the late 70's and other boards of that time like the Rockwell 6502 Kim-1, 8085, etc. Now I'm a 61 a Big Box MS C# vs2010 programmer, but my real interest has always been embedded, but it's been oh so many years. Now that I'm close to retirement I would like move to recreation programming back to my roots of embedded. C, objective C, ASM, other? (OK I draw the line at forth).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inquiry -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So now I'm looking at the latest embedded chip sets and oh wow I only understand about half of it. Is there a resource, you might recommend for someone like me? Books, Sites etc. ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW - I've found this particular stack exchange style site very useful. many Thanks&lt;/p&gt;&#xA;" OwnerUserId="2243" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-12-29T01:26:33.480" LastActivityDate="2010-12-29T01:26:33.480" Title="Tips for an old previous and renewed embedded programmer" Tags="&lt;microcontroller&gt;" AnswerCount="6" CommentCount="2" />
  <row Id="7732" PostTypeId="2" ParentId="7726" CreationDate="2010-12-10T22:07:51.113" Score="6" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;Label the wire which is currently ground &quot;-12V&quot;.&lt;/li&gt;&#xA;&lt;li&gt;Label the wire which was previously 12V &quot;GND&quot;.&#xA;(There is no step 3)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;To test: Connect a DMM's ground lead to the wire you've labeled &quot;GND&quot;.  Connect the positive lead to the wire you've labeled &quot;-12V&quot;.  The display will read -12 volts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;br&gt;&#xA;Of course, this won't work if you've got any other signals referenced to the original ground, so it's rather tongue-in-cheek.  Just wanted to point it out in case it wasn't obvious.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More seriously, my solution would be a charge pump driven by an RC oscillator.  Without transistors, this will limit you to the output current of your opamps.  On further consideration, it might not be possible due to the problem of bootstrapping your opamp power supplies.   &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-10T22:07:51.113" CommentCount="4" />
  <row Id="7733" PostTypeId="2" ParentId="7684" CreationDate="2010-12-10T22:14:30.967" Score="-2" ViewCount="" Body="&lt;p&gt;Writing the whole port to 1 shows you the problem.  In binary, that's 0b00000001, so you are in fact setting the first seven bits off and the last bit on.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to use binary operators to make sure you're only making the change to that specific bit. Do this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;PORTA = PORTA | 1;&#xA;// Equivalently:&#xA;current = PORTA;&#xA;new = current | 1;&#xA;PORTA = new;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If pins 2-8 are currently high, the OR operation will return true and the bit will remain set.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make a bit low, use a binary AND operation:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;PORTA &amp;amp;= 1;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that some compilers will have specific macros to do this (i.e, _BV() on avr-gcc) and some micros will have specific addresses aliased to each peripheral bit so you don't have to do this read-modify-write cycle (bit-banded memory on Cortex-M3)&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-10T22:14:30.967" />
  <row Id="7734" PostTypeId="2" ParentId="7685" CreationDate="2010-12-10T22:44:20.960" Score="1" ViewCount="" Body="&lt;p&gt;I've looked in to this a fair amount for some projects that I was considering. In short, it is possible(ish), but hard. A handful of companies offer solutions doing this intended to track items in warehouses, and they are expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rfidtoys.net/forum/forum_posts.asp?TID=139&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a more detailed (although slightly old) discussion on using RFID tags and multiple readers to determine 3-space position of the tag. There have been some advances, but the fundamental theory and difficulties are the same.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main problem you will run in to if utilizing another solution is power storage. RFID in its various incarnations is the only passive communication technology. You can get much more accurate results from sound or possibly some sort of RF beacon (would be expensive due to the tight timings needed to get accuracy), but you need some sort of battery to run the thing. Batteries are thick, so that probably knocks the &quot;credit card&quot; size out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wireless power and low-power micros have come a long way in the last few years, so it might be possible to blast your space in enough power to get something more complex to work. I'm not aware of any wireless power technologies on the market that work at more than inches, but they are coming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck :)&lt;/p&gt;&#xA;" OwnerUserId="875" LastActivityDate="2010-12-10T22:44:20.960" CommentCount="1" />
  <row Id="7735" PostTypeId="2" ParentId="7731" CreationDate="2010-12-10T23:14:53.003" Score="5" ViewCount="" Body="&lt;p&gt;Hi, I've been doing embedded system design for the last 35 years (I'm just a couple of years older than you), and currently have projects going on using 8-bit (Silicon Labs 8051 and Freescale 68HCS08), 16-bit (Microchip 24FJ and dsPIC33FJ), and 32-bit (TI TMS320DM365) processors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 8-bit chips are probably going to be what you will initially feel the most comfortable with, and are still fun to program in assembly in addition to C.  The 68HCS08 is an update of the Motorola 68HC05 line, and I particularly like its instruction set (not as nice as the old 6809, which was a wonderful processor to write assembly code for).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compared to the old days when development boards and associated ICE's cost hundreds or even thousands of dollars, you can now get pretty decent evaluation boards for &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=DEMO9S08LL16-ND&quot; rel=&quot;nofollow&quot;&gt;under $100&lt;/a&gt;, and free compilers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just for fun, I recently bought a development board for the &lt;a href=&quot;http://www.parallax.com/tabid/407/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;Parallax Propeller&lt;/a&gt; chip, which has 8 cores (Parallax calls them &quot;gogs&quot;) that run in parallel.  &lt;em&gt;All&lt;/em&gt; I/O is done in software, which means with very little external hardware the chip supports things like PS/2 keyboards and mice, and VGA output.  There is a &lt;a href=&quot;http://www.parallax.com/Store/Microcontrollers/PropellerDevelopmentBoards/tabid/514/CategoryID/73/List/0/SortField/0/Level/a/ProductID/340/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;demo board&lt;/a&gt; available for $80.  (I have its &lt;a href=&quot;http://www.parallax.com/Store/Microcontrollers/PropellerDevelopmentBoards/tabid/514/CategoryID/73/List/0/SortField/0/Level/a/ProductID/515/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;big brother&lt;/a&gt;, which is currently on sale for $150.)&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-12-11T00:15:28.373" LastActivityDate="2010-12-11T00:15:28.373" CommentCount="3" />
  <row Id="7736" PostTypeId="2" ParentId="7731" CreationDate="2010-12-10T23:15:49.227" Score="1" ViewCount="" Body="&lt;p&gt;8/16 bit flash micros (PIC/AVR etc) are probably the way to go. You can program these in C or assembler, you have control of the entire machine, and you basically get a whole system on a chip. Not to mention they're inexpensive. The biggest difference between programming these and, say, a 6502 is that they have separate code and data spaces.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are lots of single-boards that use more sophisticated processors, that are way more powerful, but you don't really get the most from these without full-blown operating systems. Programming on these sorts of platforms are quite a bit different from bit-banging on a 6800. This can be a blessing or curse depending on your point of view. On the one hand, you can't just bang a port, you have to work through a device driver (or &lt;em&gt;write&lt;/em&gt; the device driver) but on the other hand, you get nice things like multitasking.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2010-12-10T23:15:49.227" CommunityOwnedDate="2010-12-10T23:15:49.227" CommentCount="1" />
  <row Id="7737" PostTypeId="2" ParentId="7709" CreationDate="2010-12-10T23:37:24.500" Score="9" ViewCount="" Body="&lt;p&gt;Two common reasons are signal integrity and current limiting in lazy level conversion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For signal integrity, any mismatch in impedance of the transmission line formed by a pcb trace and attached components can cause reflections of signal transitions.  If these are allowed to bounce back and forth along the trace reflecting off the mismatches at the end for many cycles until they die out, the signals &quot;ring&quot; and may be misinterpreted either by level or as additional edge transitions.   Typically an output pin has a lower impedance than the trace and an input pin a higher impedance.  If you put a series resistor of value matching the transmission line impedance on the output pin, this will instantaneously form a voltage divider and the voltage of the wavefront traveling down the line will be half the output voltage.  At the receiving end, the higher impedance of the input essentially looks like an open circuit, which will produce an in-phase reflection doubling the instantaneous voltage back to the original.  But if this reflection is allowed to reach back to the low-impedance output of the driver it would reflect out of phase and constructively interfere, subtracting again and producing ringing.  Instead it is absorbed by the series resistor at the driver which is selected to match the line impedance.  Such source termination works pretty well in point-to-point connections, but not so well in multipoint ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current limiting in lazy level translation is another common reason.  CMOS IC technologies of different generations have different optimal operating voltages, and may have damage limits set by the tiny physical size of the transistors. Additionally, they cannot natively tolerate having an input at a higher voltage than their supply.  So most chips are built with tiny diodes from the inputs to the supply to protect against overvoltage.  If driving a 3.3v part from a 5v one (or more likely today, driving a 1.2 or 1.8 v one from a 3.3v source) it's tempting to just rely on those diodes to clamp the signal voltage to a safe range.  However, they often cannot handle all the current that can potentially be sourced by the higher voltage output, so a series resistor is used to limit the current through the diode.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2010-12-10T23:37:24.500" CommentCount="2" />
  <row Id="7738" PostTypeId="2" ParentId="7731" CreationDate="2010-12-10T23:44:54.070" Score="2" ViewCount="" Body="&lt;p&gt;You may want to start with an arduino to get an idea of what the AVR chips are capable of, then perhaps ditch the custom interface and work with more generic tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For somewhat larger systems, ARM cores from a number of vendors are pretty popular and scarcely more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally, while I don't find it of personal interest, and am generally uneasy with the marketing idea of transitioning desktop programmers to embedded without a major change in thinking habits, there are some tiny ARM boards running a version of .NET that might leverage some of what you have been doing lately - examples would be netduino and fez panda.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2010-12-10T23:44:54.070" CommentCount="1" />
  <row Id="7739" PostTypeId="2" ParentId="7715" CreationDate="2010-12-10T23:59:19.253" Score="2" ViewCount="" Body="&lt;p&gt;With an 8KHz channel I would consider the very simple 1200 baud BELL 202 AFSK widely used for packet radio.  Note that this is different than the 1200 baud PSK used on the very narrow bandwidth of voice telephone circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would then put a software-based verification scheme on top of this.  That's going to be a bit trickier in a one-way link than in a two-way one where you can use acks and resend corrupted data.  If you can just discard bad packets and wait for good ones, that's better.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2010-12-10T23:59:19.253" CommentCount="3" />
  <row Id="7740" PostTypeId="1" AcceptedAnswerId="7742" CreationDate="2010-12-11T00:35:13.263" Score="2" ViewCount="206" Body="&lt;p&gt;Hello, I recently made a USB charger that takes a 9V battery. I've noticed it doesn't work with a lot of devices though. It was very simple though, just a 5volt regulator hooked to a USB plug and 9V battery and a switch. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I'm wanting to use what I have on hand(all sorts of capacitors, resistors, and 5v regulators) so the minty boost is out of the question(requires some components I don't have any of, such as inductors) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what did I do wrong? I just shorted together the data+/- pins(bad idea now that I've thought about it). Should I have these hooked to something or just left unhooked? Also, should I worry about installing a 500mA PTC fuse? And lastly do I need any kind of capacitors to handle any rippling and such? &lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2010-12-11T01:41:11.297" Title="Best way of making a battery powered USB charger?" Tags="&lt;usb&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="7741" PostTypeId="2" ParentId="7740" CreationDate="2010-12-11T00:57:11.503" Score="3" ViewCount="" Body="&lt;p&gt;What devices are you charging?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Latest generation iPod touches and their ilk require some resistors on the data lines; apparently to detect if the charger is an authorised Apple one. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ladyada.net/make/mintyboost/icharge.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/make/mintyboost/icharge.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's pretty simple - just 4 resistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't worry about the PTC. Most linear regulators have thermal limiting and current limiting. It's pretty difficult to damage a properly designed linear regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember with a linear regulator excess energy is dissipated as heat. Power dissipation in a linear regulator is (Vin - Vout) x Iout. So for 0.5A out, 9V in and 5V out, the regulator is dissipating 2W and providing 2.5W to the device; 4.5W in total, with an efficiency of about 55%, which is pretty poor. But, it may be fine for your application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Almost all linear regulators require small decoupling capacitors. It varies from regulator to regulator. Most require 100n caps on input and output, but some require larger bulk decoupling. Specifying exactly which regulator you are using would help.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-11T00:57:11.503" CommentCount="2" />
  <row Id="7742" PostTypeId="2" ParentId="7740" CreationDate="2010-12-11T01:19:50.783" Score="4" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;I just shorted together the data+/- pins(bad idea now that I've thought about it). &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Nope.  That's the standard, actually.  The official USB &lt;a href=&quot;http://www.usb.org/developers/devclass_docs/Battery_Charging_V1_2.zip&quot; rel=&quot;nofollow&quot;&gt;Battery Charging v1.2 Spec&lt;/a&gt; is almost completely unreadable, but it does say:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;A Dedicated Charging Port (DCP) is a downstream port on a device that outputs power through a USB connector, but is not capable of enumerating a downstream device. ... A DCP shall short the D+ line to the D- line.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Of course, Apple has to do it their own proprietary incompatible way for iPods and iPhones:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ladyada.net/make/mintyboost/icharge.html&quot; rel=&quot;nofollow&quot;&gt;The mysteries of Apple device charging&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And the phone manufacturers had their own ways before the standard, usually using the ID pin:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://wiki.openmoko.org/wiki/USB_charger&quot; rel=&quot;nofollow&quot;&gt;USB charger specifications and compatibility list&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2010-12-11T01:19:50.783" CommentCount="3" />
  <row Id="7743" PostTypeId="2" ParentId="7740" CreationDate="2010-12-11T01:41:11.297" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/5498/how-to-get-more-than-100ma-from-a-usb-port/5581#5581&quot;&gt;I am going to link you to an answer I wrote with respect to the USB charging spec. I hope it can be of help.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-11T01:41:11.297" />
  <row Id="7744" PostTypeId="1" AcceptedAnswerId="13922" CreationDate="2010-12-11T01:54:51.533" Score="4" ViewCount="147" Body="&lt;p&gt;How do you extract the maximum amount of energy from a piezoelectric element?  (For energy harvesting purposes.)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Maximum_power_theorem&quot; rel=&quot;nofollow&quot;&gt;maximum power theorem&lt;/a&gt; would seem to say that you need to load it with a resistance equal to the piezo's internal resistance, but a piezo's internal impedance is capacitive rather than resistive.  So the load would have to be an inductor?  Or a resistance tailored for a specific frequency of vibration?  How would you use this to do something more normal, like charge a capacitor for powering other circuitry?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-05-05T15:41:25.020" Title="Maximum power out of a piezo?" Tags="&lt;energy&gt;&lt;piezoelectricity&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="7745" PostTypeId="2" ParentId="7744" CreationDate="2010-12-11T02:58:41.680" Score="3" ViewCount="" Body="&lt;p&gt;Maximum power specifies that you should load it with a load equal in magnitude, but opposite in phase. So if it is capacitive, you need an inductive load to cancel the capacitive components, then a resistor equal to its resistance to get max power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, the load would be tuned for a specific frequency. &lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-11T02:58:41.680" CommentCount="2" />
  <row Id="7746" PostTypeId="1" CreationDate="2010-12-11T04:11:11.077" Score="0" ViewCount="184" Body="&lt;p&gt;I know the good old-fashioned way of shining a remote at a camera to see if it picks up infrared, but I'd like to know if there's any code that does it for you. That'd be much more professional.&lt;/p&gt;&#xA;" OwnerUserId="2248" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-11T22:48:31.267" LastActivityDate="2010-12-11T22:48:31.267" Title="Test if webcam picks up infrared" Tags="&lt;software&gt;&lt;camera&gt;&lt;infrared&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="7747" PostTypeId="2" ParentId="7746" CreationDate="2010-12-11T05:02:00.597" Score="1" ViewCount="" Body="&lt;p&gt;It likely has an infrared filter in the optical path so that it doesn't have to do expensive DSP. All you need to do is take it off. &lt;a href=&quot;http://hackaday.com/2005/03/14/make-an-infrared-webcam/&quot; rel=&quot;nofollow&quot;&gt;Hackaday&lt;/a&gt; featured this, but &lt;a href=&quot;http://www.hoagieshouse.com/IR/&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; is a better guide.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-11T05:02:00.597" CommentCount="4" />
  <row Id="7748" PostTypeId="1" AcceptedAnswerId="7763" CreationDate="2010-12-11T07:22:30.920" Score="2" ViewCount="371" Body="&lt;p&gt;So I have this crazy idea to illuminate a few Christmas lights on the exterior of my house this weekend. I plan on running 2 Cat5e cables about 11.5 meters (~38 feet) from an Arduino board to sensors and Solid State Relays (all DC and all around 5VDC). I would like to take this &quot;network&quot; next year and setup a little home automation. The current setup would use: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The SSRs can crunch anything from 3-32 VDC. &#xA;The sensors are looking for 5 VDC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you believe that Cat5e cable can deliver what the input and output requires? Am I going to loose power running with Cat5e at that distance? (It is twisted pair but not plenum or shielded twist pair)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not, should I be looking at thicker wire, a power boost at the end, or is this just not feasible?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I plan to test the setup in the morning either way, but I value your input!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you in advance for your reply!&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="1575" LastEditorDisplayName="" LastEditDate="2010-12-11T07:27:35.860" LastActivityDate="2010-12-11T22:35:35.997" Title="Arduino Input/Output Range (Cable Length)" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;voltage&gt;&lt;wire&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="7750" PostTypeId="2" ParentId="7728" CreationDate="2010-12-11T09:32:05.183" Score="3" ViewCount="" Body="&lt;p&gt;What exactly do you want to see? Just the sine, or do you want to measure frequency or amplitude variations? Spikes maybe?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, you have a number of options:  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;the simple resistor divider will do, if you can accept that your whole circuit is connected to the mains! You can't simply connect it to your PC that way, unless you can use an isolated EIA-232 connection.  &lt;/li&gt;&#xA;&lt;li&gt;a small mains transformer. The secondary is isolated from mains, and the voltage level is closer to what you need. A transformer acts as a filter, however, so smaller spikes may not appear on the secondary side. You could use it for frequency or amplitude measurements however.  &lt;/li&gt;&#xA;&lt;li&gt;A linear optocoupler, like &lt;a href=&quot;http://www.vishay.com/docs/83622/il300.pdf&quot; rel=&quot;nofollow&quot;&gt;Vishay's IL300&lt;/a&gt;. This one has excellent servo linearity of 0.01%. You'll need some extra circuitry though, see schematic below. The left side is connected to mains; the Vin is your mains voltage from a resistor divider. You can use a classic power supply with a transformer, or directly derive the power supply from mains.  &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/qnTPb.png&quot; alt=&quot;alt text&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whatever solution you choose, make sure that you separate mains and arduino well enough. I don't know what standards are in the rest of the world, but here in Europe it's 6mm IIRC. This includes the distance between PCB pads both sides of the optocoupler! The trafo shouldn't give you problems here.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for connecting to your PC through EIA-232, you can do so if your controller is not connected to mains (trafo or optocoupler solution). I'm afraid you'll may have to write your own software to display the waveform.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-11T09:45:12.053" LastActivityDate="2010-12-11T09:45:12.053" CommentCount="5" />
  <row Id="7751" PostTypeId="2" ParentId="7728" CreationDate="2010-12-11T09:43:06.627" Score="7" ViewCount="" Body="&lt;p&gt;It appears that you are not an electrician, so this requires a bit of a boilerplate:&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Working with mains power should be performed according to your region's laws. It is dangerous and can seriously injure and kill you. Even the &lt;em&gt;Earth&lt;/em&gt; wire is not at 0V with respect to the objects around you, due to unequal split-phase loading (or other more scary possibilities, like &lt;em&gt;&quot;That ain't the Earth wire, Jed! I just ran out of black!&quot;&lt;/em&gt;). Please consult your local electrical codes before attempting to fiddle with it. Be careful using a cheap multimeter, as they are sometimes inappropriately labeled for CAT-II, III, and IV.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;That said, there are two things that need to get done:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Voltage transformation - the Arduino accepts only 0V to +5V or -5V to 5V, depending on type.&lt;/li&gt;&#xA;&lt;li&gt;Isolation - this is the safety bit, plus it'll save your parts.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Isolation&lt;/strong&gt; : this is typically done using a transformer or &lt;a href=&quot;http://en.wikipedia.org/wiki/Opto-isolator&quot; rel=&quot;nofollow&quot;&gt;optoisolators&lt;/a&gt;. While not technically achieving isolation, large resistors or capacitors (or a diode, but that is a story for another day) can serve if electrical code permits. Whichever is chosen, ensure they are rated for mains power in your region, the proper connectors are used, and care is taken near live circuits. I suggest a transformer followed by a voltage divider.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;transformer&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;We all know what a transformer does. Since your aim is to measure instantaneous voltage, ensure that little distortion is introduced into the signal. This means it cannot come near (magnetic) saturation. The datasheets will have this information. Note that if you can characterize the distortion and it is a linear function (ie: not saturating the core), then you can account for this distortion in code with a simple &lt;a href=&quot;http://en.wikipedia.org/wiki/Lookup_table&quot; rel=&quot;nofollow&quot;&gt;LUT&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;optoisolators&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;These are normally digital devices as they distort analog signals, but some are made for analag, like &lt;a href=&quot;http://parts.digikey.ca/1/3/analog-opto-isolator&quot; rel=&quot;nofollow&quot;&gt;these ones&lt;/a&gt;. You'll want to look for a linear region in the &lt;em&gt;output voltage vs. forward current&lt;/em&gt; graph. Again, if it is nearly linear, you can calibrate for it with a LUT. There is a catch, though: they're based on an LED, so they only work for a bit less than half of the waveform; it takes a bit of creativity to overcome this.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;capacitor&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;A capacitor has impedance -j/wC. At 60Hz (or 50Hz, or 400Hz, or whatever it is) one can be used as a generalized impedance in a divider to limit the current throughput and generate a small voltage, but it does not provide isolation. This capacitor must be bipolar and rated for mains power use. A cap is also used for &lt;em&gt;ac-coupling&lt;/em&gt;, discussed below.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;resistive divider&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This limits current and reduces voltage to safe levels, but does not provide isolation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Voltage Transformation&lt;/strong&gt; : All of the isolation methods except optoisolators produce bipolar outputs in various amplitudes. To map this +Vp/-Vp to +Vcc/-Vss, where -Vss may be GND, one can use either &lt;em&gt;AC coupling&lt;/em&gt; or &lt;em&gt;direct coupling&lt;/em&gt;. &lt;em&gt;Direct coupling&lt;/em&gt; requires the use of a DC voltage source twice the peak voltage of your mains line, so that is scrapped. AC coupling requires a capacitor : &#xA;&lt;img src=&quot;http://i.imgur.com/HA9Cp.png&quot; alt=&quot;alt text&quot;&gt;&#xA;This can be improved in a number of ways but is likely sufficient. It requires isolation beforehand, and the capacitor can't be polarized or under-spec'd for the voltages it will support.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I've mucked something up I'll fix it tomorrow as I'm tired and this answer is long.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-11T09:43:06.627" CommentCount="1" />
  <row Id="7752" PostTypeId="2" ParentId="5024" CreationDate="2010-12-11T11:51:25.093" Score="0" ViewCount="" Body="&lt;p&gt;The best way to learn any new chip/language/devtool/whatever is to have a definite project that you want/need to get working. This means you are forced to work through problems, which is usually where you learn the most, as problem solving requires more knowledge of more aspects of the system to track down the problem. If you are just tinkering, you tend to wander aimlessly around problems instead of working through them. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think of it like learning your way round a city. &quot;Go find this particular resturant&quot; will make you learn more of the area than &quot;go find any resturant&quot;.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-11T11:51:25.093" />
  <row Id="7753" PostTypeId="2" ParentId="7746" CreationDate="2010-12-11T12:08:44.340" Score="4" ViewCount="" Body="&lt;p&gt;There is no way in software to determine if a webcam is sensitive to infrared, unless you have a separate computer controlled IR emitter which is visible to the camera.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The aspects of a webcam that determine it's infrared sensitivity are both hardware, and non-electronic, which renders them completely invisible from the computers perspective.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only exception I can think of to this is a webcam which specifically advertises itself as being IR sensitive, in which case you could do an online lookup based off the VID and PID to find the model, and look at it's specifications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To be specific, the optical component responsible for blocking IR is a &lt;a href=&quot;http://en.wikipedia.org/wiki/Hot_mirror&quot; rel=&quot;nofollow&quot;&gt;&lt;em&gt;hot mirror&lt;/em&gt;&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fortunately, removing the hot mirror is very easy, and there are &lt;a href=&quot;http://tech.blorge.com/Structure%3a%20/2007/10/04/how-to-turn-your-webcam-into-an-ir-night-vision-camera/&quot; rel=&quot;nofollow&quot;&gt;many&lt;/a&gt;, &lt;a href=&quot;http://www.wikihow.com/Make-a-Webcam-Into-an-Infrared-Camera&quot; rel=&quot;nofollow&quot;&gt;many&lt;/a&gt;, &lt;a href=&quot;http://www.instructables.com/id/Infrared-IR-Webcam/?ALLSTEPS&quot; rel=&quot;nofollow&quot;&gt;many&lt;/a&gt;, &lt;a href=&quot;http://www.scroogle.org/cgi-bin/nbbw.cgi?Gw=webcam+ir&quot; rel=&quot;nofollow&quot;&gt;many&lt;/a&gt; walkthroughs.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-12-11T12:08:44.340" CommentCount="3" />
  <row Id="7754" PostTypeId="2" ParentId="7731" CreationDate="2010-12-11T13:18:27.753" Score="2" ViewCount="" Body="&lt;p&gt;1) Get a good reference book for C programming. I have really liked this book:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/1934015253&quot; rel=&quot;nofollow&quot;&gt;Let us C - Y. Kanetkar&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/CnXG8.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Get a good reference book that goes through some of the building block concepts of Embedded systems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/020161569X&quot; rel=&quot;nofollow&quot;&gt;An Embedded Softfware Primer - David.E.Simon&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/YLLC0.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Get a good dev kit, such as the beagle board that has a very active and supportive online community to help with queries etc. Their website has tons of ideas for projects that you can get your hands dirty with.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;Beagleboard website&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Yerkk.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) You can't go past Ganssle's website for excellent Embedded Programming related information. He has excellent articles about the intricacies of Embedded Systems.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ganssle.com/&quot; rel=&quot;nofollow&quot;&gt;The Ganssle Group&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5) You can refer to a related question that has been posted:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/7143/embedded-c-programming-material/7148#7148&quot;&gt;Embedded C Programming Material&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;6) At most of all, don't forget to have fun with it. Read, Read and Read, and get your hands dirty! You will run into some challenging issues, that will baffle you for maybe days, but that's the best part. Just keep at it, and you will get there! &lt;/p&gt;&#xA;" OwnerUserId="1785" LastActivityDate="2010-12-11T13:18:27.753" CommentCount="7" />
  <row Id="7755" PostTypeId="1" AcceptedAnswerId="7756" CreationDate="2010-12-11T13:25:34.317" Score="4" ViewCount="402" Body="&lt;p&gt;I want to wire 10 of &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=37&amp;amp;products_id=301&amp;amp;zenid=99e4189acfc892bbd3a7b70a40c4783e&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; LEDs into a circuit with a 9-V battery. The site states that the forward voltage is 3.2-3.8 V at 20 mA current. Should I assume 20 mA is the max amount of current that can flow throw this circuit? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using &lt;code&gt;V = RI&lt;/code&gt;, I calculate that I need a resistor that is 450 Ω (9/0.02). Is this correct? Secondly, if I want to have 10 LEDs here do I need a higher voltage (38 V)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the first LED circuit that I am making, so I'm not familiar with most of the basics.&lt;/p&gt;&#xA;" OwnerUserId="2254" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:20:22.310" LastActivityDate="2011-03-05T16:20:22.310" Title="What resistor should I use when wiring 10 LEDs in series?" Tags="&lt;led&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="7756" PostTypeId="2" ParentId="7755" CreationDate="2010-12-11T13:56:55.240" Score="12" ViewCount="" Body="&lt;p&gt;If you put all these LEDs in series you'll indeed need 38V, plus a bit for the series resistor. But you can make a circuit with several branches. Put 2 LEDs in series and you'll need 7.6V. So the remaining 9V - 7.6V = 1.4V is the voltage over your resistor. If you want 20mA through your circuit You divide this 1.4V / 20mA = 70 ohm, so a standard 68 ohm will do nicely.&lt;br&gt;&#xA;Now that's for 2 LEDs, you could go for more if you had a higher voltage. the way to calculate the resistor is the same. If you want 10 LEDs from 9V, in theory you could put the circuit 5 times in parallel. That would be a total current of 100mA though (5 x 20mA), and that's a bit much for a 9V battery.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;It's been suggested that you could replace the 5 resistors by a single one, and branch from beneath this. In an ideal world that would be true; the resistor value would then be 1.4V / 100mA = 14 ohm. But this isn't an ideal world, and there may be small differences in LED voltages. In that case the branch with the lowest voltage will draw most of the current (100mA!) while the other LEDs will hardly light at all.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-13T07:35:28.963" LastActivityDate="2010-12-13T07:35:28.963" CommentCount="17" />
  <row Id="7758" PostTypeId="2" ParentId="7755" CreationDate="2010-12-11T14:01:24.707" Score="1" ViewCount="" Body="&lt;p&gt;A 9V battery is a poor choice. Use a 6V battery with a boost converter; National Semiconductor has some suitable designs using their Simple Switcher chips.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-11T14:01:24.707" CommentCount="4" />
  <row Id="7759" PostTypeId="2" ParentId="7748" CreationDate="2010-12-11T15:23:33.497" Score="2" ViewCount="" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some general info about the cable:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Category_5_cable&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Category_5_cable&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can read: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maximum current per conductor  0.577   A&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC-Loop resistance  ≤ 0.188   Ω/m&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Off course, you are, currently, running almost DC signals (compared with the 100Mhz the cable is reated for), so... you can get a pretty good approximation with DC parameters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A more detailed answer, would require more info on your devices (SSR specifications, and sensor specifications).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this helps,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ildefonso Camargo&lt;/p&gt;&#xA;" OwnerUserId="1777" LastActivityDate="2010-12-11T15:23:33.497" />
  <row Id="7762" PostTypeId="2" ParentId="7755" CreationDate="2010-12-11T20:20:35.173" Score="1" ViewCount="" Body="&lt;p&gt;I recently made a circuit with 10 LEDs which works on 6 V. &lt;a href=&quot;http://ledcalc.com/#calc&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt;  site was of great help for me. You just supply parameters you gave us to it and it will produce a schematic of a circuit and will provide information on type of resistors which need to be used  and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if you want to use a battery, check out its datasheet for its voltage when discharged. This way, you'll be able to calculate how well circuit works with used batteries. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I agree on Leon Heller that 9 V batteries are a bad choice. the thing is that they start out at 9 V, but for example VARTA No.4922 battery has end voltage between 4.8 and 5.2 volts. It's too low to use 2 LEDs in series. Also capacity is lower than in the 1.5 V batteries.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-12-11T20:20:35.173" />
  <row Id="7763" PostTypeId="2" ParentId="7748" CreationDate="2010-12-11T22:18:43.337" Score="2" ViewCount="" Body="&lt;p&gt;I'm going to assume that you're using a relay similar to this one I found on &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=CC1118-ND&quot; rel=&quot;nofollow&quot;&gt;Digikey.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It lists the control current at 5V as 3mA, which I'll use as a good ballpark number. If we want to know if the relay will turn on, then we want to be sure that the control voltage at the relay will be greater than the minimum control voltage of 3V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first check is whether or not we can source the current. In this case, 3mA is well below the typical maximum current source/sink of a microcontroller (20mA), so we're fine. If your relay uses more current than that, you may need to look at using a transistor to drive the relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second check is to see what the voltage at the relay will be after the resistive losses of the wire. If we assume the worst-case resistance of the wire, then that is 0.188 Ω/m, like Ildefonso stated. Note that this is the loop resistance, not the resistance for a single wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At 11.5 meters length, you will have a total wire resistance of 2.2Ω. (11.5m * 0.118Ω/m). At 3mA current, this creates a voltage drop of 6.5mV (2.2Ω * 3mA). If you drive the relay using a 5V source, the voltage that the relay would see is 4.993V (5V - 6.5mV), which shows that &lt;em&gt;at DC&lt;/em&gt; those wire lengths are negligible. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would need to be drawing 900mA, or using a wire length of 5km to start seeing a voltage close to the minimum threshold (3V) of the relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For powering a sensor, the same calculations will hold true. If you know the DC current your sensor requires, then you will probably find that CAT5 will power your sensor fine. If the sensor has an analog output, there shouldn't be a big issue, and with a digital signal you probably will need to go slower than if the sensor was on the Arduino board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To answer your other sub-questions,&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You always loose power in wiring, but at low current DC, it usually isn't much. What you're probably meaning is will I lose too much voltage.&lt;/li&gt;&#xA;&lt;li&gt;The plenum/shielding would not impact your ohmic/resistive losses.&lt;/li&gt;&#xA;&lt;li&gt;If the wire resistance was too high, you could use twice as many wires to cut the resistance by half. The wire in CAT5 is fairly high gauge, so using a low gauge wire would help in a similar way.&lt;/li&gt;&#xA;&lt;li&gt;If you couldn't afford to use more wire, but wanted to send more power down the line, you could increase the voltage sent over the wire, and use a DC-DC switching supply to reduce the voltage. This is similar to what goes on in Power over Ethernet, and AC Power Grid Transmission.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-12-11T22:35:35.997" LastActivityDate="2010-12-11T22:35:35.997" />
  <row Id="7764" PostTypeId="2" ParentId="7731" CreationDate="2010-12-12T03:30:09.433" Score="3" ViewCount="" Body="&lt;p&gt;What sounds like fun to you?  What's your budget?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many 8/16 bit controllers that would likely feel very nostalgic for a bit. (since they really are basically the same as what you used to play with).  You'd be surprised how many professional embedded systems still use 8051s.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An Arduino would give you a lot of interesting add-on choices, but to me it really seems geared more for hobbyists who have to program to accomplish a task... not to people who like to get down and dirty with C and ASM. If you want a lot of embedded control options, this is good though. Be sure to check out SparkFun.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Propeller looks fun... although it never seems to fit anything I'm doing. I restarted my electronics interest maybe ten years ago with Parallax's Basic Stamp II (VERY quickly moved to their SX stuff (PIC-like system, now Ubicom))&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ARM processors vary widely. On the low end, they're powerful but the tools usually cost too much.  On the medium and high end, they can run a full Linux system and do amazing things. (Just about all phones use them now) I'm moving into the medium end ARM range myself (lowest end capable of Linux, really) My definition of medium fits the chips that are simple enough to design a 4-6 layer PCB for. The big ones can require 8+ layers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I was to take a guess, I'd say that after a few months getting your sea legs back you might find FPGAs really interesting.  You can get nice FPGA demo boards for $100-$200. The vendor tools are free (I'd recommend Altera followed closely by Xilinx) You can have a lot of fun designing your own logic, including small microprocessors. There are a LOT of 'soft' processors for FPGAs, and complete toolchains for developing and debugging them. I'd guess that it best fits the feeling of the late 70s/early 80s (not that I'd know) in that you can design so much of a system yourself from scratch. You can then go find just about any sensor or device whatever you want, and write custom glue logic to talk to it (no matter what bizarre interface they're using) There's also OpenCores, where you can grab functional modules that people have written if you don't want to write it yourself or don't know how. If you're interested, comment and I'll look for a decent starter board for you. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, you can't go TOO far with FPGAs (unless you really like playing with logic alone and not interfacing with things) without also designing PCBs yourself. I think it's a lot easier than it sounds... datasheets these days pretty much tell you how to do everything. However, it's certainly a whole lot more to manage.&lt;/p&gt;&#xA;" OwnerUserId="1270" LastActivityDate="2010-12-12T03:30:09.433" CommentCount="2" />
  <row Id="7765" PostTypeId="1" CreationDate="2010-12-12T04:12:48.273" Score="1" ViewCount="216" Body="&lt;p&gt;I need 1300mA at 3.5V, but the highest power AC-DC wall adaptor I have is 1A 12V. Is it possible to use two of these to get ~2A? I'm thinking that diodes would be needed from the positive pins of the supplies?&lt;/p&gt;&#xA;" OwnerUserId="2156" LastActivityDate="2010-12-12T12:26:15.810" Title="Using multiple power supplies to increase current" Tags="&lt;power-supply&gt;" AnswerCount="2" />
  <row Id="7766" PostTypeId="2" ParentId="7765" CreationDate="2010-12-12T04:25:43.237" Score="7" ViewCount="" Body="&lt;p&gt;1A at 12V is 12W (&lt;code&gt;P = IV&lt;/code&gt;). You can step the voltage down to convert this power into more amperage. Specifically, at 3.5V you could get up to 3.4A. Bear in mind that conversions will introduce power losses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the load? You may not even have to limit voltage -- only current.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;To answer your question directly, it depends on the type of wall wart. There is a danger when paralleling sources that one of them takes more of the load than the other. This is especially true with regulated or switching supplies, which have feedback systems to regulate their output voltage. It should not be much of an issue when using identical supplies that are a simple transformer, full-bridge and low-pass filter. They won't be perfectly matched, so don't use them to a full 200% of either's power limits. You could put current-sense resistors inline with both to measure their contribution to various loads.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-12T06:40:05.213" LastActivityDate="2010-12-12T06:40:05.213" CommentCount="1" />
  <row Id="7767" PostTypeId="2" ParentId="7182" CreationDate="2010-12-12T07:50:52.393" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Custom Hardware&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are building custom hardware you might find the &lt;a href=&quot;http://pyusb.sourceforge.net&quot; rel=&quot;nofollow&quot;&gt;PyUSB&lt;/a&gt; library useful. It's an awesome tool for driver developement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Scipy and numpy&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://scipy.org&quot; rel=&quot;nofollow&quot;&gt;Scipy&lt;/a&gt; and numpy are great tools form signal processing and mathematics in python.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Pyrobotics&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Google will probably point you in this direction: &lt;a href=&quot;http://pyrorobotics.org&quot; rel=&quot;nofollow&quot;&gt;http://pyrorobotics.org&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1627" LastActivityDate="2010-12-12T07:50:52.393" />
  <row Id="7768" PostTypeId="2" ParentId="66" CreationDate="2010-12-12T07:52:43.113" Score="0" ViewCount="" Body="&lt;p&gt;The Storage Shield utilizes an on-board Atmega328 processor so your project can now access gigabytes of storage while using very little memory or processing power of the Arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.chipstobits.com/blog/storage-shield/&quot; rel=&quot;nofollow&quot;&gt;http://www.chipstobits.com/blog/storage-shield/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2263" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T14:29:59.037" LastActivityDate="2011-05-16T14:29:59.037" CommentCount="1" />
  <row Id="7769" PostTypeId="1" CreationDate="2010-12-12T08:58:25.157" Score="1" ViewCount="622" Body="&lt;p&gt;I have my new Arduino Mega 2560 and I might have overwritten the bootloader when uploading another program through AVR studio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really need advice and instruction of how to burn it using AVR Studio 4 and AVR ISP external programmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried to do everything mentioned on the Arduino website but it was not a successful attempt.&lt;/p&gt;&#xA;" OwnerUserId="2264" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-02T07:41:26.800" LastActivityDate="2011-02-02T07:41:26.800" Title="How to burn arduino mega 2560 bootloader?" Tags="&lt;arduino&gt;&lt;bootloader&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="7770" PostTypeId="2" ParentId="7182" CreationDate="2010-12-12T10:28:24.613" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/python-on-a-chip/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/python-on-a-chip/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2010-12-12T10:28:24.613" />
  <row Id="7771" PostTypeId="1" AcceptedAnswerId="7774" CreationDate="2010-12-12T11:03:16.377" Score="2" ViewCount="68" Body="&lt;p&gt;So, I recently saw &lt;a href=&quot;http://electronics.stackexchange.com/questions/7746/test-if-webcam-picks-up-infrared&quot;&gt;this question&lt;/a&gt; and thought it looked simple enough. Instead of a webcam  though i used an actual (but old, 3MP) digital camera. The camera was a bit broken anyway(always exposed with weird colors and too dark usually). Well, I've confirmed the IR works now by holding my TV remote up to it. I don't actually have any IR LEDs on hand though. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The two prevalent kinds I see seem to be 950nm and 850nm. For the purposes of making a night vision camera, which one would be more bright? I would think 950nm because it's closer to the visible spectrum, but everyone else seems to say 850nm is brighter. So which one works better? Or should I just buy one of each and see for myself which one is brighter?(as in, it depends on the camera) &lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2010-12-12T12:01:14.523" Title="Best wavelength for IR LEDs to be used with a hacked up IR camera?" Tags="&lt;camera&gt;&lt;infrared&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="7772" PostTypeId="1" CreationDate="2010-12-12T11:34:33.040" Score="2" ViewCount="312" Body="&lt;p&gt;If I put in batteries the wrong way (+ and - sides reversed), is there a risk that I will break them? Or the device? Or start a fire? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In particular, I am talking about rechargeable Ni-MH eneloops and cheap electronic toys for kids, and most of the time not all of the batteries are put in the wrong way, just some of them are reversed (which is probably even worse, right).&lt;/p&gt;&#xA;" OwnerUserId="2266" LastActivityDate="2010-12-12T17:07:42.723" Title="Can I break batteries by putting them in the wrong way?" Tags="&lt;batteries&gt;&lt;damage&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="7773" PostTypeId="2" ParentId="7772" CreationDate="2010-12-12T11:50:53.533" Score="1" ViewCount="" Body="&lt;p&gt;If you put one of two batteries the wrong way, then there's no problem, neither for the batteries nor for the device; total voltage is +Vbat - Vbat = 0V. No voltage is no current, so your batteries won't discharge. It's just that the device won't do a thing.&lt;br&gt;&#xA;If you reverse both batteries the result may be worse: most likely the device will be damaged, esp. if it's electronic. The batteries may survive without too much damage unless the reversal causes a short circuit. &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-12T11:50:53.533" CommentCount="9" />
  <row Id="7774" PostTypeId="2" ParentId="7771" CreationDate="2010-12-12T11:52:38.243" Score="2" ViewCount="" Body="&lt;p&gt;&lt;code&gt;EDIT:&lt;/code&gt;After seeing &lt;a href=&quot;http://electronics.stackexchange.com/users/1681/mikeselectricstuff&quot;&gt;mikeselectricstuff&lt;/a&gt;'s comment, I agree: &lt;strong&gt;buy both.&lt;/strong&gt; Then upvote his comment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pick the 850nm one. As shown in the following image (from &lt;a href=&quot;http://www.microscopyu.com/articles/digitalimaging/ccdintro.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;), it is attenuated less than 950nm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/SIAR2.jpg&quot; alt=&quot;http://www.microscopyu.com/articles/digitalimaging/ccdintro.html&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The green and blue portion of your camera's Bayer filter will attenuate the IR light considerably, making their channels noisy, so you may want to look into getting raw image data output such that it can be processed on your PC, rejecting those channels. &lt;a href=&quot;http://public.fotki.com/ROBERT1010/scitech/photosensor_array.html&quot; rel=&quot;nofollow&quot;&gt;The filter&lt;/a&gt; cannot be removed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be careful with your IR &quot;flash bulb&quot;, or whatever it ends up being. Although we can't see it, it still hurts and damages eyes. Many animals/insects are more sensitive to and can even see IR.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-12T12:01:14.523" LastActivityDate="2010-12-12T12:01:14.523" CommentCount="1" />
  <row Id="7775" PostTypeId="2" ParentId="7772" CreationDate="2010-12-12T12:22:30.887" Score="1" ViewCount="" Body="&lt;p&gt;If you put in both batteries the wrong way and apply a negative voltage, your device may be damaged. The designers may not added a protection circuit (i.e. a diode) because it's battery powered and they need all the voltage they can get.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a device causes a short, that can damage the batteries. Otherwise it's more likely that the batteries will damage(destroy) any IC that gets a voltage outside their maximum ratings.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-12-12T12:22:30.887" />
  <row Id="7776" PostTypeId="2" ParentId="7765" CreationDate="2010-12-12T12:26:15.810" Score="0" ViewCount="" Body="&lt;p&gt;You could 'solve' the need for parallel supplies by using a switch mode supply after your adapter to get the voltage down and have a respectable amount of current going out. Basically a DC-DC converter will do that, but I guess the cost of making/buying such device is more than another adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could maybe add 2 diodes in series of the output of an adapter and connect them together after that, so they won't be able to feed each other. If you're using a linear regulator after that to get down to 3.5V, that won't be much of a problem.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-12-12T12:26:15.810" CommentCount="1" />
  <row Id="7777" PostTypeId="2" ParentId="7769" CreationDate="2010-12-12T16:26:16.283" Score="1" ViewCount="" Body="&lt;p&gt;You should be able to burn it using the Arduino software with the AVR ISP. See the Tools menu.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that doesn't work, try the Arduino forum.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-12T20:45:37.323" LastActivityDate="2010-12-12T20:45:37.323" CommentCount="1" />
  <row Id="7778" PostTypeId="2" ParentId="7772" CreationDate="2010-12-12T16:50:33.080" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Consumer Devices&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Almost all consumer electronics have protection in place to prevent any damage when connecting the battery backwards. Companies know they can't trust consumer to put the batteries in the correct orientation and it is usually cheaper for them to add the protection then it is to deal with support calls and returns.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Batteries in your own device&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are wanting to make your own device, you will need to add protection or it will be almost guaranteed that you will have ICs that smoke. The battery itself probably wont be hurt. They can output ALOT of current. All of your ICs and polarized caps will usually break in such away that they will act like an open circuit. Because of this the batter will only have a short time where it is having to put out a lot of current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How to protect your device&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The easiest way to protect your electronics is to put a fuse in-line with your battery. This is a good all-purpose fail safe. Fuses are too slow to blow to protect all ICs, but at least it prevents your project from catching on fire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you place a single diode in series with your battery you can prevent any current flowing in the wrong direction. Do be prepared to see a 0.7v drop across the diode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also use a 4 diode configuration to allow your circuit to continue to work regardless of how to battery gets connected. This disadvantage of this method is that you have 2 diode drops (about 1.4v).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/YaU2N.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-12-12T17:07:42.723" LastActivityDate="2010-12-12T17:07:42.723" CommentCount="6" />
  <row Id="7779" PostTypeId="1" AcceptedAnswerId="7780" CreationDate="2010-12-12T17:01:44.943" Score="1" ViewCount="185" Body="&lt;p&gt;I have a number of Freescale MC9S08GT32 devices I plan to use in some projects if I can find the right toolchain. Code development would be Codewarrior, which is free for up to 32K of C code.&lt;br&gt;&#xA;Programmer/debugger is Background Debug Module (BDM), but this doesn't seem to be standardized; at least I couldn't find one on the Freescale website. I found the following, with varying prices:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://www.cncgeeker.com/index.php?main_page=product_info&amp;amp;cPath=7_4&amp;amp;products_id=10&quot; rel=&quot;nofollow&quot;&gt;CNCgeeker&lt;/a&gt;&lt;br&gt;&#xA;      &lt;a href=&quot;http://www.pemicro.com/products/product_viewDetails.cfm?product_id=27&quot; rel=&quot;nofollow&quot;&gt;PEmicro&lt;/a&gt;&lt;br&gt;&#xA;      &lt;a href=&quot;http://www.softecmicro.com/products.html?type=detail&amp;amp;title=inDART-One&quot; rel=&quot;nofollow&quot;&gt;Softec microsystems&lt;/a&gt;&lt;br&gt;&#xA;      &lt;a href=&quot;http://www.witztronics.com/index.php?main_page=product_info&amp;amp;cPath=2_25&amp;amp;products_id=53&quot; rel=&quot;nofollow&quot;&gt;Witztronics&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I guess there are others. I would like to know if you have experience with certain BDMs and which type you can recommend.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-03T08:34:42.203" LastActivityDate="2011-02-03T08:34:42.203" Title="Background Debug Module (BDM) recommendation for HCS08 controllers wanted" Tags="&lt;programmer&gt;&lt;debugger&gt;" AnswerCount="2" />
  <row Id="7780" PostTypeId="2" ParentId="7779" CreationDate="2010-12-12T18:53:01.133" Score="2" ViewCount="" Body="&lt;p&gt;I've been using the P&amp;amp;E Micro &lt;a href=&quot;http://www.pemicro.com/products/product_viewDetails.cfm?product_id=33&quot; rel=&quot;nofollow&quot;&gt;USB BDM Multilink Cable&lt;/a&gt; on a couple of HCS08 projects along with the Freescale/CodeWarrior HCS08 C compiler and it seems to work well (the CodeWarrior debugger &quot;knows&quot; about the P&amp;amp;E device).  A little more expensive ($99) than the lower cost bare-board units, but I like the fact that it is enclosed in a little case.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-12-12T18:53:01.133" CommentCount="1" />
  <row Id="7781" PostTypeId="1" AcceptedAnswerId="7785" CreationDate="2010-12-12T20:31:44.347" Score="1" ViewCount="196" Body="&lt;p&gt;I want something for my power that acts like a diode, but without the voltage drop, to protect the circuit from damage if the batteries are connected the wrong way. Is this even possible?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-14T01:28:24.743" LastActivityDate="2010-12-14T01:28:24.743" Title="Circuit Protection" Tags="&lt;protection&gt;" AnswerCount="4" CommentCount="11" FavoriteCount="1" />
  <row Id="7782" PostTypeId="2" ParentId="7781" CreationDate="2010-12-12T20:41:40.000" Score="4" ViewCount="" Body="&lt;p&gt;A MOSFET can be used to protect a circuit with a low voltage drop.  See the following for more information:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronicdesign.com/article/power/fet-supplies-low-voltage-reverse-polarity-protecti.aspx&quot; rel=&quot;nofollow&quot;&gt;FET Supplies Low-Voltage Reverse-Polarity Protection&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.irf.com/technical-info/designtp/dt94-8.pdf&quot; rel=&quot;nofollow&quot;&gt;Reverse Battery Protection with Hexfets doubles Battery Life&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.geofex.com/Article_Folders/mosswitch/mosswitch.htm&quot; rel=&quot;nofollow&quot;&gt;Advanced Power Switching and Polarity Protection for Effects&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2010-12-12T20:41:40.000" CommentCount="2" />
  <row Id="7783" PostTypeId="1" AcceptedAnswerId="7788" CreationDate="2010-12-12T20:56:16.347" Score="0" ViewCount="139" Body="&lt;p&gt;I've scoured the internet for an EAGLE library with the SN754410NE part. I found one, but it's for a version previous to 4.11 and I'm on a Mac and have no way to convert it 55.10. The original file is at &lt;a href=&quot;http://db.tt/66pnv4Y&quot; rel=&quot;nofollow&quot;&gt;http://db.tt/66pnv4Y&lt;/a&gt;. Can anyone hook me up with a recent version?&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-12-12T22:56:19.113" Title="Please convert Eagle Library" Tags="&lt;eagle&gt;&lt;library&gt;&lt;h-bridge&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="7784" PostTypeId="1" AcceptedAnswerId="7787" CreationDate="2010-12-12T21:38:17.000" Score="1" ViewCount="153" Body="&lt;p&gt;See image. Camera shot of my oscilloscope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Vfz5F.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm having this weird problem with my project. I'm using a dsPIC33FJ128GP802 DSC/MCU. In this application, I'm sync-separating a CVBS signal using a LM1881 and feeding it into the MCU (channel 1.) The MCU is set up to interrupt on pin change. This part works correctly, and it drives an on screen display which I have written perfectly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, the weird part is that on each interrupt I'm briefly pulsing the pin RB12 to debug something. This is causing the weird decaying waveform on channel 4!! I'm expecting only a brief pulse, but it takes almost 64 microseconds (the line time) to decay to zero, almost like there is a very large capacitor on the pin (but there isn't.) Also, you can see the same effect on the falling edge, as the interrupt also triggers on that. What could be causing this? It has me completely lost!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using this code in my ISR:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TRISBbits.TRISB12 = 0;&#xA;asm(&quot;nop&quot;);&#xA;PORTBbits.RB12 = 1;&#xA;asm(&quot;nop&quot;);&#xA;TRISBbits.TRISB12 = 1;&#xA;asm(&quot;nop&quot;);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The nops are to ensure read-modify-write problems don't occur, but it happens with or without those nops.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-12-12T21:44:11.990" LastActivityDate="2010-12-13T05:42:35.553" Title="What is causing this weird decaying waveform on one of my MCU pins?" Tags="&lt;microcontroller&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="7785" PostTypeId="2" ParentId="7781" CreationDate="2010-12-12T21:49:13.917" Score="5" ViewCount="" Body="&lt;p&gt;Put the diode across the supply connections so that it is non-conducting, with a fuse ahead of it. The diode will conduct if the supply is reversed, and blow the fuse. There won't be any voltage drop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Wv0Hj.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-12-13T05:55:57.647" LastActivityDate="2010-12-13T05:55:57.647" CommentCount="10" />
  <row Id="7786" PostTypeId="2" ParentId="7781" CreationDate="2010-12-12T22:13:20.167" Score="1" ViewCount="" Body="&lt;p&gt;I am planning to use the &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1142,C1029,P131997&quot; rel=&quot;nofollow&quot;&gt;LTC4365&lt;/a&gt;, but that's overkill, because it has overvoltage and undervoltage protection built in (which I have a use for because it may be used in an automotive environment, but you might not.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-12T22:13:20.167" CommentCount="2" />
  <row Id="7787" PostTypeId="2" ParentId="7784" CreationDate="2010-12-12T22:44:14.383" Score="8" ViewCount="" Body="&lt;p&gt;What is Channel 4 - is it the pin RB12&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at your code, you are turning pin RB12 to an output, setting it high, then setting the pin back to high impedance (an input)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What do you have loading the pin apart from the scope ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks to me like the pin is just floating, at the value you left it at - high, and the scope is pulling the pin down to ground via its input impedance...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;try changing the TRISBbits.TRISB12=0; to PortBBits.RB12=0; (Leaving the pin as an output but changing it to a low)&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2010-12-12T22:44:14.383" CommentCount="1" />
  <row Id="7788" PostTypeId="2" ParentId="7783" CreationDate="2010-12-12T22:56:19.113" Score="4" ViewCount="" Body="&lt;p&gt;As others have said, make your own footprints.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/tutorials/110&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/tutorials/110&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-12T22:56:19.113" CommentCount="1" />
  <row Id="7789" PostTypeId="2" ParentId="3065" CreationDate="2010-12-12T23:21:42.230" Score="1" ViewCount="" Body="&lt;p&gt;A point about LED's - most led have a very low reverse breakdown voltage, so a standard led may fail if connected the wrong way round on about 12 volts (Yes I know - car batteries are 13.8 approx, but can be anything from 10 to 16 V, with a lot of 'noise' on the supply)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So to protect the LED from being put in the wrong way round use a standard diode...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The high watt resistors are there to 'disable' the blown bulb detection circuit in some cars... (They are just across the socket to 'waste' power)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some cars will display a warning that a bulb is blown. To prevent this you must take about the current a bulb should take...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;if your Led's just took 20ma (0.02A) at 14v (0.28W) and the original bulb was 5W - around 357ma (0.357A) - a circuit that expected .36A seeing .02 would trigger an error...&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2010-12-12T23:21:42.230" CommentCount="1" />
  <row Id="7790" PostTypeId="2" ParentId="7613" CreationDate="2010-12-12T23:57:22.323" Score="0" ViewCount="" Body="&lt;p&gt;A quick search on the 'net' gives the following&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Model: R370&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Round type diameter: 24.4 x 30.8 (L)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage (V): 6.0&#xA;No load current 0.03 A; speed 4,950 rpm&#xA;Max efficiency current 0.19 A; speed 4,280 rpm; torque 19 gcm&#xA;Max output current 0.625 A; speed 2,475 rpm; torque 170 gcm&#xA;Stall current 1.22 A; torque 140 gcm &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage (V): 31.0&#xA;No load current 0.035 A; speed 11,140 rpm&#xA;Max efficiency current 0.2 A; speed 9,530 rpm; torque 43 gcm&#xA;Max output current 0.63 A; speed 5,570 rpm; torque 149 gcm&#xA;Stall current 1.22 A; torque 298 gcm &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;This sounds like a possible for your motor...&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If the motor you have is about this size (24.4mm Dia x 30.8mm L), then its stall current will be about the same.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And for your FET - a max current around 22A peak around 80A&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This FET should easy handle the stall current for your motor.&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2010-12-12T23:57:22.323" CommentCount="5" />
  <row Id="7791" PostTypeId="1" AcceptedAnswerId="7798" CreationDate="2010-12-13T00:22:05.420" Score="5" ViewCount="367" Body="&lt;p&gt;Is it possible to passively pipe GPS satellite signals indoors via a waveguide, or 2 antennas connected by a coax?  If so, with what type of waveguide, antennas, coax, etc. should I try and experiment?  Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1908" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-12-13T00:27:18.023" LastActivityDate="2011-04-15T19:11:21.920" Title="Is passive GPS retransmission possible?" Tags="&lt;antenna&gt;&lt;gps&gt;&lt;transmission-line&gt;" AnswerCount="5" CommentCount="5" FavoriteCount="2" />
  <row Id="7792" PostTypeId="2" ParentId="7791" CreationDate="2010-12-13T00:52:00.030" Score="5" ViewCount="" Body="&lt;p&gt;You could use a large antenna on the roof, pipe the data through an RF channel and then radiate it into the building with another antenna.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Expected Problems&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;If you place an antenna on the roof and pipe signals into the building and then receive them in the building, you are effectively making the point you are receiving at the antenna upstairs. Once they hit this point they are piped in series into the building.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The noise will be a problem, each antenna will lose power and the cabling with have loss. I would suggest an RF amplifier connect at the antenna end on the roof, if not, one inside will still give an improvement. This will make getting a lock much easier (if you do have problems).&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Some suggestions&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;I would suggest coax cable, running a waveguide is not very feasible. A waveguide will be easier to pipe the signal in with, but will make your power amplifier hard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your antenna on the roof needs to have a wide receive angle. This will take some research, you will probably want a high effective area to receive as much power as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inside you will want an antenna that is very directed at the location you want your device for the best receive. I would suggest a horn antenna.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did this quickly, I will spend more time on it later if I can, I think this gives a general idea. Getting this to work will not be easy. Please let me know if there is something specific I can add to help.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-13T00:52:00.030" CommentCount="7" />
  <row Id="7793" PostTypeId="2" ParentId="7779" CreationDate="2010-12-13T03:48:30.893" Score="2" ViewCount="" Body="&lt;p&gt;The P&amp;amp;E Micro Multilink works great, but if you are looking for a cheaper solution there is the open source BDM project. Freescale maintains a forum at:&#xA;&lt;a href=&quot;http://forums.freescale.com/t5/OSBDM-JM60-Open-Source-BDM-for/bd-p/OSBDM08&quot; rel=&quot;nofollow&quot;&gt;http://forums.freescale.com/t5/OSBDM-JM60-Open-Source-BDM-for/bd-p/OSBDM08&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bare circuit boards are available from:&#xA;Batchpcb dot com&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The '9S08GT32 is a nice part, I have used it too.&lt;/p&gt;&#xA;" OwnerUserId="2273" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-13T04:57:58.057" LastActivityDate="2010-12-13T04:57:58.057" />
  <row Id="7794" PostTypeId="2" ParentId="7791" CreationDate="2010-12-13T05:23:50.817" Score="3" ViewCount="" Body="&lt;p&gt;This seems like a lot of work, for very little gain, to me.  You would have to subtract the lengths of each of the waveguides from the distances calculated by the GPS receiver electronics.  In fact it's more complicated than that: the signal would reflect around inside the wave guide, making the apparent length longer than the actual length.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My suggestion: put the receiver on the roof, in a weather-proof housing, and then send the coordinates wherever you need them, wired or wirelessly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I think I didn't understand the point of the OPs question.  I thought he was interested in putting GPS in a moving vehicle like an RV.  If Ian's assumption is correct and OPs goal is to test a GPS from indoors, then my suggestion won't really work either.  I think the only solution possible would be to use a piece of coax with an external antenna.  But make sure the coax is just the right length for the frequencies used - GPS signals are very weak and any line losses would certainly cause problems.&lt;/p&gt;&#xA;" OwnerUserId="2257" LastEditorUserId="2257" LastEditorDisplayName="" LastEditDate="2010-12-14T16:48:25.137" LastActivityDate="2010-12-14T16:48:25.137" CommentCount="6" />
  <row Id="7795" PostTypeId="2" ParentId="7784" CreationDate="2010-12-13T05:42:35.553" Score="2" ViewCount="" Body="&lt;p&gt;You should use LATx for outputs, to avoid R-M-W problems.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-13T05:42:35.553" CommentCount="1" />
  <row Id="7796" PostTypeId="1" AcceptedAnswerId="7799" CreationDate="2010-12-13T05:46:27.623" Score="2" ViewCount="192" Body="&lt;p&gt;Hello, not sure if &quot;digital circuit design&quot; is exactly what I'm aiming for, but someone can tell me and I'll edit it if another name matches better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, circuit design interest me a lot. I like the idea of working with AND OR NOT etc gates and building things with them. I've been wanting to build a CPU for quite a few years now, but I lack the knowledge. I'm fairly decent at programming however, so I can think &quot;logically&quot;, but with circuit design it all is very difficult for me to understand past simple adders and such. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I'm looking for a beginner's book on the subject. I plan on doing all design and testing in a simulator such as Logisim, but being shown how to actually put circuits together on a breadboard out of gates(or even transistors and such) would be a definite plus, but I wouldn't want for that to be the focus of it all. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My end result hopefully is to build a CPU in a simulator. So, tell me what book(s) I need to buy to get there for someone who is a novice at electronics and a decent computer programmer. &lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-17T19:56:23.320" LastActivityDate="2010-12-17T19:56:23.320" Title="Book recommendations for digital circuit design?" Tags="&lt;circuit-design&gt;&lt;digital&gt;&lt;books&gt;" AnswerCount="2" CommentCount="0" FavoriteCount="1" />
  <row Id="7797" PostTypeId="2" ParentId="7796" CreationDate="2010-12-13T05:52:42.360" Score="1" ViewCount="" Body="&lt;p&gt;Designing CPUs is much easier if you use VHDL or Verilog. &lt;a href=&quot;http://www.symphonyeda.com/&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a good VHDL simulator. Once you have it working you can put it into an FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://users.ece.gatech.edu/~hamblen/book/bookse.htm&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is a very good book on VHDL. It includes a simple CPU that I've implemented on a little FPGA development system I designed, using free Altera software.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-13T06:33:01.327" LastActivityDate="2010-12-13T06:33:01.327" CommentCount="1" />
  <row Id="7798" PostTypeId="2" ParentId="7791" CreationDate="2010-12-13T06:51:50.177" Score="10" ViewCount="" Body="&lt;p&gt;We've done this for a development project that involved GPS reception. We just wanted to be able to get a GPS signal indoors at our engineering office, for basic development of the GPS drivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We put a good quality GPS antenna on the roof, with coax going down into the office below. On the ceiling of the office, the coax connected to a GPS-band RF amplifier, which output through an antenna also on the ceiling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It was a low power amplifier, so it only radiated an effective signal over a short distance within the office space--less than 10 metres. But that was enough to serve our purposes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other equipment we used sometimes was a GPS simulator, which simulated a bunch of satellites, and could convince a GPS unit that it was at any location of our choosing. It radiated through an antenna, again, at low signal levels so it disrupted only a small area. And we only used it indoors, within our offices.&lt;/p&gt;&#xA;" OwnerUserId="1025" LastActivityDate="2010-12-13T06:51:50.177" CommentCount="3" />
  <row Id="7799" PostTypeId="2" ParentId="7796" CreationDate="2010-12-13T07:42:45.153" Score="3" ViewCount="" Body="&lt;p&gt;You might find it interesting to look at the open courseware site for the MIT 6.004 lecture/lab course.  Look at both the lecture slides and the labs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-004-computation-structures-spring-2009/&quot; rel=&quot;nofollow&quot;&gt;http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-004-computation-structures-spring-2009/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not familiar with the content of the 2009 version (having taken it back when it was breadboards &amp;amp; modules) but later used the 2004? OCW version (java iirc simulation) as a reference, then implemented that processor architecture in verilog and subsequently in an FPGA kit.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2010-12-13T07:42:45.153" CommentCount="4" />
  <row Id="7800" PostTypeId="1" AcceptedAnswerId="7801" CreationDate="2010-12-13T09:11:59.083" Score="3" ViewCount="262" Body="&lt;p&gt;I want to use a crystal as the base clock for a watch.&#xA;Most reference designs I could find use a 32.768 kHz crystal at 20 ppm (parts per million) precision.&#xA;According to my calculations, this leads to an error of max 52 seconds in a month.&#xA;After 6 months, that 5 minutes. I would like something better!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some solutions I could think of (better crystal, or compensate in SW), but I am surprised not to find any reference online.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Surely I am not the first person to try and address this problem. Do you have any suggestion as to how to deal with this, and possibly reference design?&lt;/p&gt;&#xA;" OwnerUserId="2275" LastActivityDate="2011-06-01T18:38:52.520" Title="Real-time clock and Crystal precision" Tags="&lt;clock&gt;&lt;crystal&gt;" AnswerCount="1" CommentCount="9" FavoriteCount="4" />
  <row Id="7801" PostTypeId="2" ParentId="7800" CreationDate="2010-12-13T10:01:04.033" Score="4" ViewCount="" Body="&lt;p&gt;A better crystal is one way to solve it, but it's going to cost. And even then you get maybe 10ppm, good (or bad) for 5 minutes after 1 year.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Temperature compensated crystals are good to get a predictable stability, but they don't solve the tolerance problem; if you have a 20ppm deviation from nominal frequency, you're sure you'll always have this deviation. BTW, this is also more expensive, and I haven't seen it for 32kHz crystals.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Software compensation is a cheap solution, and I've used it a few times. For production runs you'll have to measure the frequency and program the compensation value on a test jig.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also use a trimmer capacitor for the oscillator's load capacitor.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I find the nicest solution, however, is to add an atomic clock receiver module (WWVB for North-America, DCF77 for Europe), and resync once a day or so. The picture shows an (unfortunately no longer available) miniature DCF77 module from &lt;a href=&quot;http://www.conrad.com/&quot; rel=&quot;nofollow&quot;&gt;Conrad&lt;/a&gt;. This is really miniature: something like \$2\mbox{ cm}{^2}\$. You'll need a ferrite rod antenna, though. If you can't find something like this you can demolish a module complete with display.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/fyfTW.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;For those who are wondering what's the use of demolishing a clock module to build another one: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;the fun of creating something new; &lt;/li&gt;&#xA;&lt;li&gt;existing clock modules never have the features you need. This goes for everything electronic, BTW.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-01T18:38:52.520" LastActivityDate="2011-06-01T18:38:52.520" CommentCount="4" />
  <row Id="7802" PostTypeId="1" AcceptedAnswerId="7804" CreationDate="2010-12-13T10:16:23.143" Score="3" ViewCount="121" Body="&lt;p&gt;Im looking for some placement help for 2 sensors, &lt;a href=&quot;http://www.sparkfun.com/products/10122&quot; rel=&quot;nofollow&quot;&gt;A gyro&lt;/a&gt;     and an accelerometer &#xA;both are going into a helicopter.  my guess is to put the gyro and the accelerometer right below the main rotor, getting it as close to the center as possible, but on the rc receiver (has been removed) the gyro was mounted to the front. The data sheets do not give any placement suggestions either. any help would be appreciated.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2010-12-13T12:36:07.777" Title="Placement of sensors, Gyro + accelorometer" Tags="&lt;sensor&gt;&lt;accelerometer&gt;&lt;gyro&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="7803" PostTypeId="2" ParentId="7802" CreationDate="2010-12-13T11:57:39.090" Score="1" ViewCount="" Body="&lt;p&gt;If the device has a tendency to rotate, I'd try to place them as close to the rotation centre(s) as possible and keep axes aligned to &quot;natural&quot; horizontal/vertical as much as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So for a helicopter, I'd also say anywhere directly below the rotor axle, maybe at the height of the tail. Or wherever is convenient.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It probably mostly only matters to how you intend to use the readings. There may also be differences like the Z axis being less sensitive than X/Y in 3d accelerometer that you may want to consider.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-12-13T11:57:39.090" CommunityOwnedDate="2010-12-13T11:57:39.090" />
  <row Id="7804" PostTypeId="2" ParentId="7802" CreationDate="2010-12-13T12:36:07.777" Score="2" ViewCount="" Body="&lt;p&gt;From a control system perspective it really does not matter where you place your sensors.  The most important thing is that you know where they actually are!!! I mean this with regards to knowing where the sensor is relative to the centre of the rotary wings.  As long as you know the offsets you can apply translations to calculate what your vehicle is doing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From an electrical and performance perspective away from motor wiring and h bridges, away from vibrations sources and suitably mounted and damped.  The dampening is important for the accelerometers to ensure that they do hit mechanical rails from high frequency vibration (do the math to work out the maximum displacement your accelerometer can with stand at various frequencies and you will understand this point).  Similar for, but not as important for the gyros.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-12-13T12:36:07.777" CommentCount="3" />
  <row Id="7805" PostTypeId="2" ParentId="3099" CreationDate="2010-12-13T12:49:43.413" Score="0" ViewCount="" Body="&lt;p&gt;Does your company host student projects? I'm thinking about master thesis and such. If yes, you could ask to be a mentor for a student project in your company and supervise students implementing your ideas. I suppose you could set some of your working time as supervision.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, I have no clue if your ideas could apply to student projects...&lt;/p&gt;&#xA;" OwnerUserId="2275" LastActivityDate="2010-12-13T12:49:43.413" CommentCount="1" />
  <row Id="7806" PostTypeId="1" CreationDate="2010-12-13T13:23:12.170" Score="1" ViewCount="177" Body="&lt;p&gt;I have been checking out nice 1D linear slides such as &lt;a href=&quot;http://www.zaber.com/products/product_detail.php?detail=T-LSR075A&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; and &lt;a href=&quot;http://www.thorlabs.de/NewGroupPage9.cfm?ObjectGroup_ID=2131&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; and &lt;a href=&quot;https://www.elfa.se/elfa3~eu_en/elfa/init.do?item=54-226-76&amp;amp;toc=19909&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Especially the first one is really nice since it has a built in encoder and a controller with RS232 interface. However, the downside is that these have a starting price around $1,700.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The specs should be something like:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;100 mm travel&lt;/li&gt;&#xA;&lt;li&gt;1 mm precision&lt;/li&gt;&#xA;&lt;li&gt;Encoder&lt;/li&gt;&#xA;&lt;li&gt;RS232 / USB interface&lt;/li&gt;&#xA;&lt;li&gt;Speed is not critical&lt;/li&gt;&#xA;&lt;li&gt;The load will not be large (&amp;lt;5N)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any suggestion how you could do this on a budget of say $500?&#xA;Or does anyone have a suggestion for something completely different with the same function?&lt;/p&gt;&#xA;" OwnerUserId="1605" LastEditorUserId="1605" LastEditorDisplayName="" LastEditDate="2010-12-13T13:31:21.177" LastActivityDate="2010-12-14T05:03:47.593" Title="Budget alternative to fancy linear slide" Tags="&lt;motor&gt;&lt;linear&gt;&lt;alternatives&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="7807" PostTypeId="1" CreationDate="2010-12-13T13:27:53.743" Score="3" ViewCount="164" Body="&lt;p&gt;I am looking at using this crystal for a new circuit design. It will provide the main oscillator for my PIC application. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the part on digikey: &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=644-1034-1-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=644-1034-1-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet indicates that it has a load capacitance of 8pF. This seems very low compared to most. I have read that the load capacitance should be equal to (C1*C2)/(C1+C2) + Cstray where Cstray is the capacitance of the PCB traces which are typically between 5 and 15 pF. This equation is provided in a Microchip FAQ sheet. If this is correct my PCB trace capacitance is likely already equal to the load capacitance of the oscillator. So does this mean that I really don't need any capacitors connected between the crystal and ground? &lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-12-13T15:28:44.433" LastActivityDate="2010-12-13T15:28:44.433" Title="How do I choose the correct capacitors to use with my Crystal?" Tags="&lt;capacitance&gt;&lt;crystal&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="4" />
  <row Id="7808" PostTypeId="2" ParentId="3099" CreationDate="2010-12-13T13:38:01.710" Score="1" ViewCount="" Body="&lt;p&gt;Have you described your projects to the boss?  Instead of worrying about process too much, just ask him to give you a couple days to work on it.  You are a low-paid intern, so use this to your advantage.   If you waste a couple of days on a project, the company hasn't wasted a senior engineer's salary on the idea.  But be pretty sure you can get the project done on time before suggesting it, because your success will lead to further opportunities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's OK to be enthusiastic as an intern.  That's really what you were hired for, not experience or knowledge.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-13T13:38:01.710" />
  <row Id="7809" PostTypeId="2" ParentId="7807" CreationDate="2010-12-13T13:41:36.407" Score="0" ViewCount="" Body="&lt;p&gt;A good tip for getting optimum cap values is that an oscillator like this is happiest when  the amplitudes of the signals at each side of the crystal are similar. PCB capacitance will be a factor, so this needs to be tweaked on the actual board, and using a x100 scope probe to avoid the probe affecting the reading. A 10M resistor right on the tip of a standard probe is an alternative if you don't have a x100 - accuracy doesn't matter as you're just looking at relative amplitudes.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-13T13:41:36.407" CommentCount="1" />
  <row Id="7810" PostTypeId="2" ParentId="7807" CreationDate="2010-12-13T13:46:11.637" Score="1" ViewCount="" Body="&lt;p&gt;A standard 20 pF crystal would be more suitable, and make the design much easier.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-13T13:46:11.637" />
  <row Id="7811" PostTypeId="2" ParentId="7685" CreationDate="2010-12-13T14:11:48.947" Score="1" ViewCount="" Body="&lt;p&gt;Is that form factor absolutely necessary?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Consider if instead of a thin card, you could have a small box - smaller than a matchbox. Would it be an option?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm asking because Telit has a module that integrates GPS+GSM, and is programmable via python. You only have to add the antennas, a battery and a SIM chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.telit.com/en/products/gsm-gprs.php?p_ac=show&amp;amp;p=7&quot; rel=&quot;nofollow&quot;&gt;http://www.telit.com/en/products/gsm-gprs.php?p_ac=show&amp;amp;p=7&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know about other manufactures, but probably Telit isn't the only one to offer such a product.&lt;/p&gt;&#xA;" OwnerUserId="1078" LastActivityDate="2010-12-13T14:11:48.947" />
  <row Id="7812" PostTypeId="2" ParentId="7806" CreationDate="2010-12-13T14:31:00.817" Score="2" ViewCount="" Body="&lt;p&gt;You could possibly salvage the mechanism from an old printer. The print head is normally carried using a toothed belt and small motor with some type of encoder feedback.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-12-13T14:31:00.817" CommentCount="1" />
  <row Id="7813" PostTypeId="2" ParentId="7781" CreationDate="2010-12-13T14:45:32.927" Score="2" ViewCount="" Body="&lt;p&gt;You might try what's called a Schottky diode. A normal diode has a drop of around 0.6 V, but Schottky's are around 0.2 V. At very low currents, the drop can be even lower.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-13T14:45:32.927" CommentCount="3" />
  <row Id="7814" PostTypeId="2" ParentId="7806" CreationDate="2010-12-13T14:48:04.470" Score="2" ViewCount="" Body="&lt;p&gt;Take apart an old inkjet printer and use the slide that controls the printer head.  Just remove the print head and install a plate.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A lot of the folks making 'open source' 3D printers are using this approach, you can probably even find some drivers for the stepper motors in particular models if you look around on their sites.  There are several projects doing this so I'd just google &quot;open source 3D printer&quot; for more information.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want a more off the shelf solution, &lt;a href=&quot;http://www.makerbot.com/&quot; rel=&quot;nofollow&quot;&gt;the MakerBot folks&lt;/a&gt; use a moving platform and i believe they sell the parts individually.  &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-12-13T14:48:04.470" CommentCount="3" />
  <row Id="7815" PostTypeId="1" CreationDate="2010-12-13T15:44:22.303" Score="4" ViewCount="288" Body="&lt;p&gt;I am trying to read analogic signal for a sort of &lt;em&gt;mouse&lt;/em&gt; with a pic18f14k50 controller. Here the simple circuit: &lt;a href=&quot;http://dl.dropbox.com/u/14663091/schematiconew.pdf&quot; rel=&quot;nofollow&quot;&gt;http://dl.dropbox.com/u/14663091/schematiconew.pdf&lt;/a&gt; . I have to read analogic signal from AN9 circuit port. Main function reads from the port, and blinks 30 time if threshold is reached:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void main(void) &#xA;{&#xA;    InitializeSystem();&#xA;&#xA;    #if defined(USB_INTERRUPT)&#xA;        USBDeviceAttach();&#xA;    #endif&#xA;&#xA;    while(1) {&#xA;&#xA;        if ((USBDeviceState &amp;lt; CONFIGURED_STATE) || (USBSuspendControl == 1)) continue;&#xA;&#xA;        if (!HIDTxHandleBusy(lastTransmission)) {&#xA;            int readed = myReadADC2(); //Here i tried both myReadADC2() or myReadADC1()&#xA;            if (readed &amp;gt; 40) { //If read threshold &amp;gt; 40, blink led 30 times&#xA;                int i;&#xA;                for (i = 0; i &amp;lt; 30; i++) {&#xA;                    Delay1KTCYx(0);&#xA;                    mLED_1_On();&#xA;                    Delay1KTCYx(0);&#xA;                    mLED_1_Off();&#xA;                }&#xA;            }&#xA;        lastTransmission = HIDTxPacket(HID_EP, (BYTE*)hid_report_in, 0x03);&#xA;&#xA;        } /* [Ed: added] */&#xA;    }//end while&#xA;}//end main&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I used two method to read from the AN9 port, myReadADC() that uses OpenADC() API method:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int myReadADC(void) &#xA;{&#xA;    #define ADC_REF_VDD_VDD_X 0b11110011                      &#xA;    OpenADC(ADC_FOSC_RC &amp;amp; ADC_RIGHT_JUST &amp;amp; ADC_12_TAD,&#xA;            ADC_CH9 &amp;amp; ADC_INT_OFF,&#xA;            ADC_REF_VDD_VDD_X &amp;amp; ADC_REF_VDD_VSS,&#xA;            0b00000010); // channel 9&#xA;    SetChanADC(ADC_CH9);&#xA;    ConvertADC();                 // Start conversion&#xA;    while (BusyADC());             // Wait for completion&#xA;    return ReadADC();           // Read result&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;and myReadADC2(), that implements manual read from the port.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int myReadADC2() &#xA;{&#xA;    int iRet;&#xA;    OSCCON = 0x70;         // Select 16 MHz internal clock&#xA;    ANSEL = 0b00000010;  // Set PORT AN9 to analog input&#xA;    ANSELH = 0;          // Set other PORTS as Digital I/O&#xA;    /* Init ADC */&#xA;    ADCON0 = 0b00100101;   // ADC port channel 9 (AN9), Enable ADC&#xA;    ADCON1 = 0b00000000;   // Use Internal Voltage Reference (Vdd and Vss)&#xA;    ADCON2 = 0b10101011;   // Right justify result, 12 TAD, Select the FRC for 16 MHz&#xA;    iRet = 100;&#xA;&#xA;&#xA;    ADCON0bits.GO = 1;&#xA;    while (ADCON0bits.GO);   // Wait conversion done&#xA;    iRet = ADRESL;           // Get the 8 bit LSB result&#xA;    iRet += (ADRESH &amp;lt;&amp;lt; 8); // Get the 2 bit MSB result&#xA;    return iRet; &#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Both cases doesn't works, i touch (sending analogic signal) port AN9 but when I set high threshold (~50) led don't blinks, with low threshold (~0) it blinks immidiatly when i provide power to the PIC. Maybe i'm using wrong port? I'm actually passing AN9 as reading port? Or maybe threshold is wrong? How can i found the right value? Thank you&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here the MPLAB C18 Apis &lt;a href=&quot;http://dl.dropbox.com/u/14663091/API%20microchip%20C18.pdf&quot; rel=&quot;nofollow&quot;&gt;http://dl.dropbox.com/u/14663091/API%20microchip%20C18.pdf&lt;/a&gt; .&lt;/p&gt;&#xA;" OwnerUserId="2276" LastEditorUserId="2276" LastEditorDisplayName="" LastEditDate="2010-12-14T15:45:18.897" LastActivityDate="2011-01-16T00:29:58.860" Title="Problems with PIC A/D conversion" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;analog&gt;&lt;c&gt;&lt;convert&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="7816" PostTypeId="1" AcceptedAnswerId="7817" CreationDate="2010-12-13T16:48:11.993" Score="3" ViewCount="266" Body="&lt;p&gt;What is the formula to obtain the resistor value I should use to drive a LED to its maximum luminance for a given input voltage?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And for the maximum power effectiveness (luminance / watt)?&lt;/p&gt;&#xA;" OwnerUserId="1298" LastActivityDate="2010-12-13T17:10:56.483" Title="How to get the maximum luminance out of a LED?" Tags="&lt;led&gt;&lt;resistor&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="7817" PostTypeId="2" ParentId="7816" CreationDate="2010-12-13T17:06:49.857" Score="5" ViewCount="" Body="&lt;p&gt;I assume you're talking about the basic resistor voltage regulator.  A basic equation for the resistor's value would involve the LED minimum forward voltage (&lt;code&gt;Vf&lt;/code&gt;), LED maximum current (&lt;code&gt;If&lt;/code&gt;), and power supply maximum voltage (&lt;code&gt;Vs&lt;/code&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;R = (Vs - Vf) / If&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With supply voltages nearly equal to the LED voltage, it is somewhat hairy as the current may become overly sensitive to the resistor, so I would avoid going below 100 ohms.  A very conservative equation would be as above, but set &lt;code&gt;Vf&lt;/code&gt; to zero.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The maximum luminous efficiency of the LED alone would obviously depend on the LED itself, so you would have to look at the datasheet.  For the maximum efficiency of the system as a whole, if driving more than a few LEDs (or any &gt;100 mA LEDs) it would be best to use a switching regulator with current sensing.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-13T17:06:49.857" />
  <row Id="7818" PostTypeId="2" ParentId="7816" CreationDate="2010-12-13T17:10:56.483" Score="3" ViewCount="" Body="&lt;p&gt;An LED has two important characteristics called, respectively, &quot;Forward Voltage Drop&quot; (often denoted Vf in datasheets), and maximum forward current (often listed under absolute maximum ratings as DC Forward Current) or If . You are also usually operating from a known supply voltage (lets call it Vcc, e.g. 5 volts). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To operate the LED at its brightest you want to use a current limiting resistor that will draw just about the maximum rated forward current (that's what governs brightness of LEDs). If you attach the cathode of the LED to ground, you know it's anode will be at V_f. So the voltage drop across a resistor in series with the LED from Vcc to the anode, will have a voltage drop across it of (Vcc - Vf), and will draw a current of (Vcc - Vf) / R. Therefore, to size the resistor, use the formula:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;R = (Vcc - Vf) / If &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;R calculated from this equation is the &lt;strong&gt;minimum value&lt;/strong&gt; of resistance you should ever use for the current limiting resistor, as smaller values would yield higher forward currents, and therefore exceed the absolute maximum rating of the LED.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-12-13T17:10:56.483" />
  <row Id="7819" PostTypeId="2" ParentId="7815" CreationDate="2010-12-13T19:51:31.460" Score="2" ViewCount="" Body="&lt;p&gt;I think there is a bug in your  myReadADC2() sub...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;try return iRet; instead of return iDelay; &lt;/p&gt;&#xA;" OwnerUserId="2280" LastActivityDate="2010-12-13T19:51:31.460" CommentCount="1" />
  <row Id="7820" PostTypeId="1" AcceptedAnswerId="7826" CreationDate="2010-12-13T21:04:15.363" Score="4" ViewCount="230" Body="&lt;p&gt;As and after the PCB is designed, I check it using the native CAD tools. What do I need to check to make sure the generated Gerber files are ok?&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-22T00:47:29.150" LastActivityDate="2011-01-22T00:47:29.150" Title="After the PCB is designed, what do I need to check in the Gerber files?" Tags="&lt;pcb&gt;&lt;pcb-design&gt;&lt;checklist&gt;&lt;gerber&gt;" AnswerCount="6" CommentCount="3" FavoriteCount="1" />
  <row Id="7821" PostTypeId="2" ParentId="7820" CreationDate="2010-12-13T21:11:07.383" Score="2" ViewCount="" Body="&lt;p&gt;Check them with a Gerber viewer, I use GC-Prevue.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-13T21:11:07.383" CommentCount="2" />
  <row Id="7822" PostTypeId="2" ParentId="7806" CreationDate="2010-12-13T21:38:14.800" Score="2" ViewCount="" Body="&lt;p&gt;1 mm precision (±0.5-mm) is not very precise for this type of tool. As you can see the linked examples are ±12-µm and ±15.29-µm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means you can go with something cheap: &lt;a href=&quot;http://www.alibaba.com/&quot; rel=&quot;nofollow&quot;&gt;alibaba.com&lt;/a&gt;. I found &lt;a href=&quot;http://shinheome.en.alibaba.com/productgrouplist-210203217/Motorized_Translation_Stages.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;:&#xA;&lt;a href=&quot;http://shinheome.en.alibaba.com/productgrouplist-210203217/Motorized_Translation_Stages.html&quot; rel=&quot;nofollow&quot;&gt;Precision Motorized Translation Stages&lt;/a&gt;, from &lt;em&gt;Beijing Shinhe Optical And Electrical Equipment Co., Ltd.&lt;/em&gt;. It looks like the &lt;a href=&quot;http://shinheome.en.alibaba.com/product/320440462-210203217/DYT102_Motorized_Translation_Stages.html&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;DYT102&lt;/strong&gt;&lt;/a&gt; is the smallest that fits your requirements (100mm). They claim 8.12-µm resolution, 127-µm repeatability, and 15-kg maximum load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is &lt;strong&gt;$650&lt;/strong&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Tyler Lucas: Hello. How much is the DYT102 Motorized Translation Stage? (2010-12-13 13:34:51)&#xA;  Jason Zhang: the unit price of DYT102: $650/p, for your reference&#xA;  (2010-12-13 21:00:44)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-14T05:03:47.593" LastActivityDate="2010-12-14T05:03:47.593" CommentCount="4" />
  <row Id="7824" PostTypeId="2" ParentId="7820" CreationDate="2010-12-13T21:53:41.287" Score="4" ViewCount="" Body="&lt;p&gt;If you have the components on hand already, print the outer layers out at 1:1 and place all the parts on there.  Ordering parts and boards at the same time is a little faster, but this would have saved me a couple board respins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your layout software should have checked the design rules.  It's unlikely you'll find design rule errors on the gerbers that the PCB software missed.  On the other hand, using gEDA-pcb's &lt;a href=&quot;http://electronics.stackexchange.com/questions/6078/have-a-look-at-my-pcb-design-and-tell-me-how-i-can-improve/6086#6086&quot;&gt;photorealistic rendering output&lt;/a&gt;, I've caught a few errors before fab, mostly soldermask.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your fab will have a checklist of capabilities on their website.  Go through this line-by-line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.eevblog.com/2010/11/15/eevblog-127-pcb-design-for-manufacture-tutorial/&quot; rel=&quot;nofollow&quot;&gt;EEVblog #127&lt;/a&gt; discusses such things as panelization and fiducials.  Worth watching, especially if you are designing for machine assembly.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-13T21:53:41.287" />
  <row Id="7825" PostTypeId="2" ParentId="7815" CreationDate="2010-12-13T22:00:01.767" Score="2" ViewCount="" Body="&lt;p&gt;The PIC ADC has a surprisingly low input impedance.  I'm not sure touching the input is going to work well.  Most of the time, you will need an op-amp to buffer the signal into the PIC, unless your signal is naturally low-impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Read the datasheet carefully.  It would be nice if datasheets put known limitations and gotchas is large bold print, but usually they are hidden in footnotes and electrical characteristic tables.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-13T22:00:01.767" CommentCount="1" />
  <row Id="7826" PostTypeId="2" ParentId="7820" CreationDate="2010-12-13T22:17:23.347" Score="6" ViewCount="" Body="&lt;p&gt;The main point for me about looking at the Gerbers outside my primary CAD is to make sure everything &lt;em&gt;looks&lt;/em&gt; OK. I put a lot of trust in my main CAD package, and use the Gerber viewer as a qualitative verification.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Things I look for:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;All layers are aligned&lt;/li&gt;&#xA;&lt;li&gt;All layers are present (file exists)&lt;/li&gt;&#xA;&lt;li&gt;All layers have data (not just vias)&lt;/li&gt;&#xA;&lt;li&gt;Board outlines have the correct dimensions&lt;/li&gt;&#xA;&lt;li&gt;Fill polygons have the right isolation, orphan settings&lt;/li&gt;&#xA;&lt;li&gt;Make sure your soldermask is correct near high-density parts (tented vias, etc.)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Making sure that Eagle merges the layers correctly is my biggest worry when I'm checking the Gerbers, because if you aren't using a 100% verified CAM flow, what you see on the page might not be what you get in the Gerbers. Other than that, everything should be the same. Think of it as looking at a printer's proof before ordering a lot of copies.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-13T22:17:23.347" CommentCount="1" />
  <row Id="7827" PostTypeId="2" ParentId="7806" CreationDate="2010-12-13T22:33:43.460" Score="-1" ViewCount="" Body="&lt;p&gt;Theodor as people have already answered, make it your self from old parts (printers and such) or buy one!  They are your two real options ....&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-12-13T22:33:43.460" />
  <row Id="7828" PostTypeId="1" AcceptedAnswerId="7829" CreationDate="2010-12-13T22:47:34.087" Score="2" ViewCount="169" Body="&lt;p&gt;I need to solder some headers onto an Arduino shield - what's the recommended wattage for working on that scale?  I ask because the shield is already populated with ICs and I don't want to burn them out.&lt;/p&gt;&#xA;" OwnerUserId="1841" LastActivityDate="2010-12-14T22:32:28.703" Title="Proper soldering iron wattage for working with uP scale electronics?" Tags="&lt;arduino&gt;&lt;soldering&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="7829" PostTypeId="2" ParentId="7828" CreationDate="2010-12-13T22:58:59.833" Score="8" ViewCount="" Body="&lt;p&gt;Selecting an iron that is too low in wattage requires the user to apply heat for a longer amount of time. This actually makes the surrounding area heat up more than if a more powerful iron were used to heat the component. Although a &lt;strong&gt;25W iron&lt;/strong&gt; will likely do this job without any trouble, and &lt;strong&gt;80W temperature controlled iron&lt;/strong&gt; is much more versatile. Make sure you use flux, and tin the iron afterwards.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-13T22:58:59.833" />
  <row Id="7830" PostTypeId="2" ParentId="7828" CreationDate="2010-12-13T23:05:58.593" Score="3" ViewCount="" Body="&lt;p&gt;The correct choice is a sufficiently powerful temperature-controlled iron (50W, say) set to the right temperature for the solder used, with an appropriate size tip. I use Metcal equipment and they recommend a tip roughly the same size as the item being soldered, for optimum heat transfer.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-13T23:13:27.060" LastActivityDate="2010-12-13T23:13:27.060" />
  <row Id="7831" PostTypeId="2" ParentId="7653" CreationDate="2010-12-14T00:13:16.120" Score="0" ViewCount="" Body="&lt;p&gt;It's either dead or needs fuses resetting as other have said.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have access to an electron microscope and some impossibly thin wires or a very precise and glitchy power supply, other options are available:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cl.cam.ac.uk/~sps32/mcu_lock.html&quot; rel=&quot;nofollow&quot;&gt;http://www.cl.cam.ac.uk/~sps32/mcu_lock.html&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-14T00:13:16.120" />
  <row Id="7832" PostTypeId="2" ParentId="7270" CreationDate="2010-12-14T01:10:05.633" Score="0" ViewCount="" Body="&lt;p&gt;Check out the PrimeSense devkit (the makers of the Kinect)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The manufacturer released the Kinect's (and DevKit) Windows and Unix drivers here: &lt;a href=&quot;http://www.openni.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.openni.org/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2180" LastActivityDate="2010-12-14T01:10:05.633" />
  <row Id="7833" PostTypeId="2" ParentId="6899" CreationDate="2010-12-14T01:11:29.550" Score="0" ViewCount="" Body="&lt;p&gt;As far as the Kinect goes, check out the &lt;a href=&quot;http://www.joystiq.com/2010/12/10/primesense-releases-open-source-drivers-middleware-for-kinect/&quot; rel=&quot;nofollow&quot;&gt;PrimeSense devkit&lt;/a&gt; (the makers of the Kinect)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The manufacturer released the Kinect's (and DevKit) Windows and Unix drivers here: &lt;a href=&quot;http://www.openni.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.openni.org/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2180" LastActivityDate="2010-12-14T01:11:29.550" />
  <row Id="7834" PostTypeId="1" AcceptedAnswerId="7842" CreationDate="2010-12-14T01:53:05.783" Score="2" ViewCount="279" Body="&lt;p&gt;I'm trying to determine if the Kinect or the &lt;a href=&quot;http://www.primesense.com/?p=487&quot; rel=&quot;nofollow&quot;&gt;PrimeSensor&lt;/a&gt; is right for general purpose hobbyist work (X10 light control, relay activation, etc).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know the difference?&lt;/p&gt;&#xA;" OwnerUserId="2180" LastEditorUserId="2180" LastEditorDisplayName="" LastEditDate="2010-12-14T15:07:46.197" LastActivityDate="2010-12-14T15:07:46.197" Title="Difference between the Kinect and PrimeSensor?" Tags="&lt;usb&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="7835" PostTypeId="2" ParentId="7270" CreationDate="2010-12-14T02:16:44.157" Score="0" ViewCount="" Body="&lt;p&gt;have a look at &lt;a href=&quot;http://www.lavrsen.dk/foswiki/bin/view/Motion/MotionFeatureList&quot; rel=&quot;nofollow&quot;&gt;motion&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;if you don't run linux you may be able to get it to work with &lt;a href=&quot;http://www.andlinux.org/&quot; rel=&quot;nofollow&quot;&gt;andlinux&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="2051" LastActivityDate="2010-12-14T02:16:44.157" />
  <row Id="7836" PostTypeId="2" ParentId="7834" CreationDate="2010-12-14T02:34:59.820" Score="3" ViewCount="" Body="&lt;p&gt;PrimeSense is the company that developed Kinect hardware. The only difference is marketing and software. If you are wanting to develop a product for commercial use you will need to go through PrimeSense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&#xA;For hobbyist work it will probably be easier to use a Kinect. There are already tons of people who have hacked it and there are now drivers public for the Kinect.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-12-14T04:13:49.313" LastActivityDate="2010-12-14T04:13:49.313" CommentCount="3" />
  <row Id="7837" PostTypeId="2" ParentId="7820" CreationDate="2010-12-14T03:05:37.003" Score="4" ViewCount="" Body="&lt;p&gt;A few gotcha's:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mirrored/Rotated Layers:&lt;br&gt;&#xA;Make sure that the top and bottom layers are oriented the same way.  An easy way to do this is to check that the soldermask for the top and bottom line up on a few through-hole vias and pads.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Gerber vs. Drill alignment:&lt;br&gt;&#xA;Sometimes, the drill holes and the Gerbers will be grossly misaligned.  Perhaps the gerbers are centered on the origin, and the drills have their bottom left corner at the origin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Font not rendering correctly:&lt;br&gt;&#xA;Unlike your PCB editor, Gerbers don't have a font library.  Make sure to use a vector font, which can be defined as a series of vectors in the gerber, rather than a proportional font, which might be different (and may not) on the gerbers.  This may only show up as a difference in character widths, which may or may not cause trouble.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are easy to see in a Gerber viewer like GC-Prevue, but hard to detect in your export settings.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-14T03:05:37.003" />
  <row Id="7838" PostTypeId="2" ParentId="7828" CreationDate="2010-12-14T05:48:00.660" Score="1" ViewCount="" Body="&lt;p&gt;You generally want the biggest iron that still lets you work on the parts easily. You then want to put the biggest tip on the iron that still lets you work on the parts easily.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Overall power is not important, really. The critical factor in a soldering iron is the instantaneous heat capacity, e.g. how rapidly it heats up what it is in contact with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, a slightly too hot iron is better than a slightly too cold iron. Basically, if you can make each solder joint quickly, less heat is conducted up the leads of whatever component you are soldering, to the IC die. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, there is a non-trivial amount of thermal resistance between the IC pins and the die. Therefore, the pins spending 10 seconds at 600F is worse than 5 seconds at 750F, since the internal temperature effectively follows the same curve as a RC filter.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-14T09:50:34.523" LastActivityDate="2010-12-14T09:50:34.523" />
  <row Id="7839" PostTypeId="1" AcceptedAnswerId="7840" CreationDate="2010-12-14T06:00:21.580" Score="3" ViewCount="230" Body="&lt;p&gt;Hello, I have a project planned where I want for some LEDs to turn on when it's dark and turn off when it's light. I have some transistors, diodes, and a photoresistor(and of course other basic components). The photoresistor has lower resistance when in daylight though. How do I 'NOT' this so that I can turn something on when it's night instead of daylight? &lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-06-03T12:04:05.917" Title="How to make a simple daylight on-off switch?" Tags="&lt;sensor&gt;&lt;light&gt;" AnswerCount="3" />
  <row Id="7840" PostTypeId="2" ParentId="7839" CreationDate="2010-12-14T06:37:39.330" Score="2" ViewCount="" Body="&lt;p&gt;evil mad scientist did a great write up on LED throwies, should give you a good place to start  &lt;a href=&quot;http://www.evilmadscientist.com/article.php/nightlight&quot; rel=&quot;nofollow&quot;&gt;http://www.evilmadscientist.com/article.php/nightlight&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="3028" LastEditorDisplayName="" LastEditDate="2011-06-03T12:04:05.917" LastActivityDate="2011-06-03T12:04:05.917" />
  <row Id="7841" PostTypeId="2" ParentId="7839" CreationDate="2010-12-14T06:39:44.980" Score="3" ViewCount="" Body="&lt;p&gt;If you use the photoresistor in a voltage divider (i assume you know what that is) to supply the base current of the transistor, you can achieve your aim. When the resistance of the photoresistor is lower (daytime), more base current flows to the transistor and turns it 'on' (it's best to use a variable resistor for the second part of the voltage divider).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;if you look at the below image, when enough current (controlled by both resistors) flows at point A, the transistor will turn on and drive whatever load you put on it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/SzDw0.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2283" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-14T15:02:48.477" LastActivityDate="2010-12-14T15:02:48.477" CommentCount="3" />
  <row Id="7842" PostTypeId="2" ParentId="7834" CreationDate="2010-12-14T10:29:20.620" Score="0" ViewCount="" Body="&lt;p&gt;One difference is you probably can't get the Primesense unit unless you are a volume manufacturer. Hardware-wise, the Kinect includes an audio processor and tilt motor.&#xA;The performance of the depth sensor is likely to be the same. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-14T10:29:20.620" CommentCount="1" />
  <row Id="7843" PostTypeId="1" CreationDate="2010-12-14T11:27:06.853" Score="2" ViewCount="375" Body="&lt;p&gt;I have an Arduino BT V06 that I could connect to my Mandriva 2010 linux laptop: &quot;rfcomm connect&quot; is working, /dev/rfcomm0 virtual serial port is created, &quot;hcitool con&quot; shows the connection and &quot;hcidump&quot; displays my upload attempts.&#xA;However when I try to upload the BlinkWithoutDelay example I got the following error message (upload.verbose set to true in .arduino/preferences.txt):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/usr/local/arduino-0021/hardware/tools/avrdude -C/usr/local/arduino-0021/hardware/tools/avrdude.conf -v -v -v -v -patmega168 -cstk500v1 -P/dev/rfcomm0 -b19200 -D -Uflash:w:/tmp/build8547029001705996442.tmp/BlinkWithoutDelay.cpp.hex:i&#xA;&#xA;avrdude: Version 5.4-arduino, compiled on Oct 22 2007 at 13:15:12&#xA;        Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/&#xA;&#xA;        System wide configuration file is &quot;/usr/local/arduino-0021/hardware/tools/avrdude.conf&quot;&#xA;        User configuration file is &quot;/root/.avrduderc&quot;&#xA;        User configuration file does not exist or is not a regular file, skipping&#xA;&#xA;        Using Port            : /dev/rfcomm0&#xA;        Using Programmer      : stk500v1&#xA;        Overriding Baud Rate  : 19200&#xA;avrdude: Send: 0 [30]   [20]&#xA;avrdude: Send: 0 [30]   [20]&#xA;avrdude: Send: 0 [30]   [20]&#xA;avrdude: ser_recv(): programmer is not responding&#xA;avrdude: stk500_recv(): programmer is not responding&#xA;avrdude: Send: Q [51]   [20]&#xA;avrdude: ser_recv(): programmer is not responding&#xA;avrdude: stk500_recv(): programmer is not responding&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I was struggling for several hours to solve the problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using Arduino-0021 but I have also tried it in 0018 and 0015 without luck. I have also tried with board type BT Atmega 168 and BT Atmega 328. My Arduino Duemilanove works fine with the same computer, Arduino 0021, and settings.&#xA;I have seen several question with the same topic &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1290646119/1&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1290646119/1&lt;/a&gt; or &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1247005623&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1247005623&lt;/a&gt;. They mention differing error messages and anyway I cannot see how can I press the reset button on the Arduino during the upload when I have to type the PIN in a different window.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What could be the solution to the problem?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I could imagine is to buy a BlueGiga WT11 chip extension to my Duemilanove and do the upload via USB. But how could I be sure that the connection for the communication will work?&#xA;Moreover I still would like to use the not-so-cheap Arduino BT board. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Based on Nick T's answer I have tried again but the BT still does not work.&#xA;I have tried to press the reset button&#xA;- 3 seconds before,&#xA;- just before,&#xA;- at the same time of the upload button hit&#xA;and &#xA;- when the first two/three avrdude lines appeared&#xA;- after the first two programmer is not responding lines appeared.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Altogether 20 times without success.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even when the arduino environment has not been started and I press the reset button on the board the connection is lost (checked by hcitool con) after 1-4 presses. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Are there any other ways to solve the problem?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I have to buy a BlueGiga WT11 and hope that the bluetooth connection will work while the USB connection stays OK?&lt;/p&gt;&#xA;" OwnerUserId="1649" LastEditorUserId="1649" LastEditorDisplayName="" LastEditDate="2010-12-14T22:20:34.280" LastActivityDate="2011-01-12T04:34:55.263" Title="Arduino BT upload problem" Tags="&lt;arduino&gt;&lt;bluetooth&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="7844" PostTypeId="1" AcceptedAnswerId="7866" CreationDate="2010-12-14T11:39:42.540" Score="1" ViewCount="353" Body="&lt;p&gt;Has anybody experienced using the Invensense IMU3000 gyroscope with some microcontroller? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The hardware comes with a really good library integrating full control of its features. This library is structured in 3 different layers, the bottom one is the one that implements the communication with the chip itself. The vendor provides this layer for using the IMU3000 with an adapter board in WindowsXP. Basically, what I need to do (and what is suggested in the application note) is rewrite this layer to use the whole library with my PIC (I2C communication). After that, I can just use the library (this is what it's said in the application note).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to build the IMU library in Visual Studio 2005 (the project was originally made this way) for a PIC but I am stuck with the dependencies..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, I can compile the .lib with the PIC IDE, but.. is it possible=&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any hint, even with other platforms, would help!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you all!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. Unfortunately I cannot find the DS online.. just after you install the package you find it.&lt;/p&gt;&#xA;" OwnerUserId="2285" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-14T14:22:46.173" LastActivityDate="2011-02-12T07:30:41.990" Title="Invensense IMU3000 with PIC" Tags="&lt;pic&gt;&lt;i2c&gt;&lt;c&gt;&lt;imu&gt;&lt;mplab&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="7845" PostTypeId="1" CreationDate="2010-12-14T11:42:24.723" Score="3" ViewCount="145" Body="&lt;p&gt;I am trying to setup the SPI1 port on my PIC24HJ206GP256 micro. I have set the SPI1CON1 control register with 0x0020, the SPI1STAT control register with 0x8000 (I.E. turn on the SPIEN) and SPI1CON2 = 0. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the moment a simple write to the SPI1BUF is written like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; void writeSPI1(char data){&#xA;     _SPI1IF = 0;             //set interrupt flag to zero&#xA;     SPI1BUF = data;          //write data to SPI1BUF&#xA;     while( _SPI1IF == 0);    //wait to flag to go high&#xA; }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;However when the data is written, the SPI1IF should go high, however it never reaches this point so the program simply remains in the loop forever. So it seems no data will ever be clocked out of the SPI port through MOSI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried to make it work by setting TRISF = 0x0000. Although I have read that the SPI port should take care of SPI pin configuration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using a watch window to view the contents of the SPI1BUF. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried with different settings within the control registers but have had no luck. Also have tried enabling the SPI1IF (IEC0: Interrupt Enable Control Register 0) and still the problem persists.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any extra configurations I have forgotten, like some odd functionality of PORTF which takes precedence over the SPI port. Any help would be greatly appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="2286" LastActivityDate="2010-12-14T17:11:32.097" Title="PIC24H SPI Problems" Tags="&lt;pic&gt;&lt;spi&gt;&lt;problem&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="7846" PostTypeId="2" ParentId="7844" CreationDate="2010-12-14T12:11:10.793" Score="0" ViewCount="" Body="&lt;p&gt;Uh? Has MS Visual Studio suddenly sprouted support for PIC cross compilation?&#xA;... or are you doing something sneaky to get MSVC to use your crosscompiler?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of PIC are you using?&#xA;What cross compiler are you using?&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2010-12-14T12:11:10.793" CommentCount="2" />
  <row Id="7847" PostTypeId="2" ParentId="7845" CreationDate="2010-12-14T14:04:21.087" Score="1" ViewCount="" Body="&lt;p&gt;Use the SPI peripheral library, it'll make things much easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check the data sheet for the alternative functions of the pins you are using. If they are shared with the ADC that will be the default function and you will need to enable them for digital I/O.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should use the Microchip forums for this type of question, many more people there will be using the 16-bit PICs.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-14T14:04:21.087" />
  <row Id="7848" PostTypeId="2" ParentId="4080" CreationDate="2010-12-14T14:21:04.637" Score="2" ViewCount="" Body="&lt;p&gt;You've received a ton of great information on microcontrollers, but if you want to simplify your job on the display end, you might want to take a look at some LCDs that make designing GUI and displaying graphics easy.  Although I haven't used its graph functions before, I have used Amulet Technologies' LCDs (both monochrome and color) and have been very pleased with how easy it is to use in combination with a little microcontroller.  You just have to implement its RS232 serial protocol, which is pretty simple.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-14T14:21:04.637" />
  <row Id="7849" PostTypeId="2" ParentId="7839" CreationDate="2010-12-14T14:25:46.200" Score="0" ViewCount="" Body="&lt;p&gt;Ultimately, you're going to take the output of the photoresistor and convert it into a logic high or logic low, which turns your light on or off.  If you need to flip this, one simple way is to take the digital output (assuming you are using a comparator) and pass it through an inverter, like a 74LS04 or equivalent.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-14T14:25:46.200" CommentCount="2" />
  <row Id="7850" PostTypeId="1" AcceptedAnswerId="10614" CreationDate="2010-12-14T14:34:25.263" Score="6" ViewCount="535" Body="&lt;p&gt;How can I use &lt;code&gt;malloc()&lt;/code&gt; and &lt;code&gt;free()&lt;/code&gt; functions in a PIC?&#xA;I've checked the &lt;code&gt;stdlib.h&lt;/code&gt; header and there's no mention of them.&#xA;I'm using MCC18.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anybody had to use them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need them because I am porting a library from Windows XP to the PIC. The porting guide says to &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;adapt the Operating System's specific&#xA;  functions to my PIC ones&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;But I don't know how to &quot;translate&quot; the &lt;code&gt;malloc()&lt;/code&gt; and &lt;code&gt;free()&lt;/code&gt; functions.&lt;/p&gt;&#xA;" OwnerUserId="2285" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-14T22:10:05.560" LastActivityDate="2011-03-13T17:55:56.810" Title="Use of malloc in PIC" Tags="&lt;pic&gt;&lt;memory&gt;" AnswerCount="7" CommentCount="5" FavoriteCount="1" />
  <row Id="7851" PostTypeId="2" ParentId="7731" CreationDate="2010-12-14T14:43:29.490" Score="2" ViewCount="" Body="&lt;p&gt;I totally understand your desire to hook something up and have a toolkit that &lt;em&gt;just works&lt;/em&gt;.  As Chris already mentioned, you can go with Netduino, which might be more familiar to you since it uses the .NET 4.0 Micro Framework.  I personally haven't used it because I can't get it anywhere!  Totally out of stock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did, however, just receive an mbed microcontroller to use, and in my opinion, it's way easier to use all around than Arduino and its environment.  The compiler is quite nice, the editor is online (which might be the only bad thing if you don't have the local toolchain installed, which I don't know anything about).  But you literally plug it in, launch the webpage that's stored in its flash, register it, and you can hop into the compiler and start twiddling bits.  I was at least flashing and PWMing its LEDs in about 5 minutes from the time I opened the box.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-14T14:43:29.490" CommentCount="2" />
  <row Id="7852" PostTypeId="2" ParentId="7850" CreationDate="2010-12-14T14:52:30.220" Score="9" ViewCount="" Body="&lt;p&gt;I don't know if the C18 standard library supports &lt;code&gt;malloc&lt;/code&gt; and &lt;code&gt;free&lt;/code&gt;, but &lt;a href=&quot;http://www.microchip.com/Stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en012157&quot; rel=&quot;nofollow&quot;&gt;Microchip App Note AN914&lt;/a&gt; shows how you can implement your own.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In any case, Thomas and other posters have suggested, using dynamic memory on PICs with their &lt;em&gt;very&lt;/em&gt; small RAM space is fraught with peril.  You can rapidly run out of contiguous space due to the lack of more advanced &lt;a href=&quot;http://en.wikipedia.org/wiki/Virtual_memory&quot; rel=&quot;nofollow&quot;&gt;virtual memory&lt;/a&gt; managers that full blown OS's give you, leading to failed allocations and crashes.  Worse, it may not be deterministic, and will likely be a pain to debug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If what you are doing is truly dynamically determined at run-time (rare for most embedded things), and you only need to allocate space on a couple &lt;em&gt;very special&lt;/em&gt; occasions, I could see &lt;code&gt;malloc&lt;/code&gt; and &lt;code&gt;free&lt;/code&gt; being acceptable.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-14T16:32:43.877" LastActivityDate="2010-12-14T16:32:43.877" />
  <row Id="7853" PostTypeId="2" ParentId="7850" CreationDate="2010-12-14T14:53:18.030" Score="1" ViewCount="" Body="&lt;p&gt;Well, how big is your PIC in terms of memory?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;malloc is a &lt;em&gt;very&lt;/em&gt; inefficient way of allocating memory. The problem with it is that memory can become fragmented with frequent frees and mallocs and with only a few kilobytes of memory, allocation failures are all too common. It's quite likely that if you're using a smaller chip or an earlier PIC18 there is no support for malloc, as Microchip either viewed it as very difficult to implement (or maybe even impossible in some cases) or not used enough for it to be worth it. Not to mention it, but it's also quite slow, you're looking at 1 cycle to use a static buffer already available and 100s to 1,000's of cycles to do a malloc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to allocate statically, create things like a buffer for your sprintf functions (if any, around 128 bytes), a buffer for your SD card (if any), and so on, until you remove the need for malloc. Ideally, you only use it where you absolutely need it and can't get away with static allocation, but these situations are usually rare and maybe a sign that you should be looking at bigger/more powerful microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And if you're developing/porting an &quot;operating system&quot; on the PIC18 and if it supports microcontrollers it probably has support for static allocation. For example, SQLite3 supports static allocation - you allocate it a large buffer array and it uses that where possible, even though it isn't for microcontrollers. If it doesn't, then are you sure it's designed for a small PIC18?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-12-14T15:29:11.477" LastActivityDate="2010-12-14T15:29:11.477" CommentCount="6" />
  <row Id="7854" PostTypeId="2" ParentId="7850" CreationDate="2010-12-14T15:09:58.647" Score="9" ViewCount="" Body="&lt;p&gt;This is hardly an answer to your question, but dynamic memory allocation is generally frowned upon small RAM environments and in the absence of an operating system (e.g. in the microcontroller world)... the heap space you have available in an embedded environment is typically measured in hundreds of bytes... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Implementing malloc and free is essentially maintenance of a linked list of &quot;free segment&quot; structures, and as you can imagine, the metadata associated with free segments is not insubstantial when compared to the amount of memory typically available... that is the &quot;overhead&quot; of managing a dynamic memory pool consumes a significant amount of the available resources.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-12-14T15:09:58.647" />
  <row Id="7855" PostTypeId="2" ParentId="7843" CreationDate="2010-12-14T15:14:10.310" Score="2" ViewCount="" Body="&lt;p&gt;To be able to bootload code on the Arduino, the programmer must attempt to connect within about 3 seconds of the AVR coming out of reset.  I the ArduinoBT I have &lt;em&gt;lacks&lt;/em&gt; a connection that the traditional USB versions have, which allows the programming software to reset the Arduino by itself.  In lieu of that, you must physically hit the button to do it yourself.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I cannot see how can I press the reset button on the Arduino during the upload when I have to type the PIN in a different window.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;You should only have to type the Bluetooth passkey once, so after the BT module is paired with your computer, the computer should be able to freely connect, so long as it is powered.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Bluetooth module and AVR are very separate; you can hold the AVR in reset, and the Bluetooth module will happily run along.  If you're &lt;em&gt;cutting power&lt;/em&gt; to the entire board to reset it, it may indeed be difficult to have the BT module come online, connect to it, and initiate programming all within 3 seconds.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-14T15:14:10.310" CommentCount="6" />
  <row Id="7856" PostTypeId="2" ParentId="7820" CreationDate="2010-12-14T15:15:58.970" Score="1" ViewCount="" Body="&lt;p&gt;I use ViewPlot to view my gerber files generated by Eagle. Mainly, what I'm looking for is that my silk screen is all there, and that my drill holes line up with my solder mask.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-12-14T15:15:58.970" />
  <row Id="7857" PostTypeId="1" AcceptedAnswerId="7868" CreationDate="2010-12-14T15:32:42.210" Score="3" ViewCount="163" Body="&lt;p&gt;You can use cascaded full adders to add any two binary numbers together. Is there a circuit for when I only want to add 1 (incrementing the value)? Is there a similar circuit for subtracting (i.e. adding 0b1111 1110)? I'm working with 8 bit numbers, but this applies for all word lengths.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-14T19:24:49.273" Title="Logic circuit to handle incrementing by 1" Tags="&lt;logic&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="7858" PostTypeId="2" ParentId="7857" CreationDate="2010-12-14T15:43:43.060" Score="4" ViewCount="" Body="&lt;p&gt;If you're talking about discrete logic, like 7400 series logic, then the chip you're looking for is called a counter. Two 74191 (4-bit up/down synchronous counter) chips cascaded will give you what you want, and there are other chips that do a similar function. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want the most compact way to add '1', then you could use half-adders for each bit instead of full adders. Not too sure about subtraction though.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-14T15:43:43.060" CommentCount="7" />
  <row Id="7859" PostTypeId="1" AcceptedAnswerId="7863" CreationDate="2010-12-14T16:47:29.460" Score="3" ViewCount="568" Body="&lt;p&gt;I'm following this &lt;a href=&quot;http://hlt.media.mit.edu/wiki/pmwiki.php?n=Main.ArduinoATtiny4585&quot; rel=&quot;nofollow&quot;&gt;tutorial&lt;/a&gt;, programming the ATtiny85 with an Arduino, using it to play some tones (through a piezo speaker). I'm struggling with getting the tones at the right pitch (I'm creating the wave forms manually, as the tone() function is unsupported on the ATtiny85). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe the problem may be down to differing clock speeds on the Arduino and ATtiny. I understand the clock speed can be altered on the ATtiny, how do I accomplish this using the arduino environment?&lt;/p&gt;&#xA;" OwnerUserId="623" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-03T16:31:05.913" LastActivityDate="2011-01-03T16:31:05.913" Title="How do I set the clock speed fuses on an ATtiny85 when using an Arduino as a programmer?" Tags="&lt;arduino&gt;&lt;attiny&gt;&lt;fuse-bits&gt;&lt;clock-speed&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="7860" PostTypeId="2" ParentId="7859" CreationDate="2010-12-14T16:59:52.527" Score="1" ViewCount="" Body="&lt;p&gt;It appears you are using ArduinoISP, try using &lt;a href=&quot;http://www.atmel.com/dyn/products/tools_card.asp?tool_id=2725&quot; rel=&quot;nofollow&quot;&gt;AVR Studio&lt;/a&gt; or the command line options for &lt;a href=&quot;http://www.nongnu.org/avrdude/user-manual/avrdude_4.html#Option-Descriptions&quot; rel=&quot;nofollow&quot;&gt;&lt;code&gt;avrdude&lt;/code&gt;&lt;/a&gt;.  Depending on how the ArduinoISP was written, it may function just like an Atmel AVRISP mkII or similar.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-14T16:59:52.527" CommentCount="2" />
  <row Id="7861" PostTypeId="2" ParentId="7791" CreationDate="2010-12-14T17:02:40.063" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Note:  I think the other answers for this are better than mine.  Just wanted to throw this out there, especially if you use an active device.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is effectively building a GPS repeater.  To my knowledge, at least in the US, &lt;a href=&quot;http://www.gpssource.com/files/GPSSourceRepeaterRegulations.pdf&quot; rel=&quot;nofollow&quot;&gt;there are regulations as to when/where you can use one&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can be done, there are devices to do it if you look around (how else would people design devices that use GPS if they had to be outside all the time???), but you need to meet regulatory standards and the rules so as to not interfere with others.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-12-14T17:02:40.063" CommentCount="1" />
  <row Id="7862" PostTypeId="2" ParentId="7845" CreationDate="2010-12-14T17:11:32.097" Score="0" ViewCount="" Body="&lt;p&gt;Have you tried polling on the SPI1STAT:SPITBF register instead of the SPI1IF? If the interrupt flag does not toggle when it should, does the SPI1STAT:SPITBF register toggle at all either? According to the data sheet that register should set when data is loaded into the TX buffer, via SPI1BUF, and clear when data exits the TX buffer and gets transmitted over the pin. For a first try, I'd just wait to see if SPI1STAT:SPITBF to goes to 0 after loading SPI1BUF. If you have on oscilliscope, that'd be a great way to see if anything is being transmitted over the output pins at all. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, where does the definition of _SPI1IF come from? If you're using MPLAB as your dev environment, make you use the register definitions from the chip header file. I'm wondering if _SPI1IF is even mapped to the correct register.&lt;/p&gt;&#xA;" OwnerUserId="1614" LastActivityDate="2010-12-14T17:11:32.097" />
  <row Id="7863" PostTypeId="2" ParentId="7859" CreationDate="2010-12-14T17:24:34.720" Score="1" ViewCount="" Body="&lt;p&gt;I believe the Arduino software (libraries and all) assumes you are operating at 16MHz. If you apply that assumption to the clock you are actually running at... things should work out. Assuming you are running the Tiny85 on it's internal oscillator I think it runs at 1MHz, so just multiply all your delay statements (and other notions of time) by 16. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need better accuracy than the internal oscillator provides you should think about using an external crystal or a resonator, but you will need to change the fuse settings of the AVR for that to work, and I think you will need a programmer like the AVRISP mkII to do that with AVR Studio (my recommendation). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know much about the ArduinoISP sketch but to me it looks like it bit bangs the ISP protocol to upload a program to the target chip (not the on board Mega328), not sure it is equipped to manipulate fuses. ArduinoISP is documented here &lt;a href=&quot;http://arduino.cc/en/Tutorial/ArduinoISP&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Tutorial/ArduinoISP&lt;/a&gt;, fwiw. Note that you can't use a UNO currently to run the ArduinoISP sketch. It doesn't look to me like you can use the sketch to make the Arduino a viable interface for using the AVR Studio GUI tools.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-16T00:44:23.750" LastActivityDate="2010-12-16T00:44:23.750" CommentCount="3" />
  <row Id="7864" PostTypeId="1" AcceptedAnswerId="7865" CreationDate="2010-12-14T17:35:24.733" Score="3" ViewCount="133" Body="&lt;p&gt;I'd like to make a beacon system for robots where the beacon will have some IR LEDs around it pulsing at some known frequency. The module that hooks up to the robot will have a few IR photostransistors (are photodiodes better?) to detect direction. I'm thinking I'll have an MSP430 as the brains for each and speak I2C or TTL to indicate direction on the robot side. How do I detect that specific frequency so I don't mistake sunlight, etc. as the signal? How sensitive would this be? Do I need really powerful LEDs? What are all the considerations?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want something like a 1 way version of &lt;a href=&quot;http://www.pololu.com/catalog/product/701&quot; rel=&quot;nofollow&quot;&gt;this pololu beacon&lt;/a&gt; except one way (although two way might be a good idea too).&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-12-14T20:02:17.180" Title="How would I make an IR beacon system" Tags="&lt;robotics&gt;&lt;ir&gt;" AnswerCount="2" />
  <row Id="7865" PostTypeId="2" ParentId="7864" CreationDate="2010-12-14T18:03:24.150" Score="2" ViewCount="" Body="&lt;p&gt;Consider &lt;a href=&quot;http://uk.farnell.com/jsp/search/browse.jsp;jsessionid=GSKM152HFIUIWCQLCIPZLTQ?N=0&amp;amp;Ntk=gensearch_001&amp;amp;Ntt=38+kHz+receiver&amp;amp;Ntx=mode+matchallpartial&amp;amp;suggestions=false&amp;amp;ref=globalsearch&amp;amp;_requestid=673531&quot; rel=&quot;nofollow&quot;&gt;these receiver &quot;phototransistors&quot;&lt;/a&gt;. They automatically decode a 38 kHz signal, which is what most remote controls use. Because it is pulsing it is virtually immune to ambient IR light including sunlight, although there is a limit as to how much ambient light they can reject. There are plenty of code examples and projects on the net which send out 38 kHz signals to control TVs, DVD players, etc. but the idea is applicable to IR beacons; just choose a code/sequence which won't interfere with other products.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-14T18:03:24.150" CommentCount="2" />
  <row Id="7866" PostTypeId="2" ParentId="7844" CreationDate="2010-12-14T18:11:02.023" Score="2" ViewCount="" Body="&lt;p&gt;I doubt you'll be able to compile the libraries (meant for Visual Studio from what I can tell) in MPLAB - the targets are insanely different (desktop PC vs PIC microcontroller).  It seems to me that the directions they gave you with the libraries are meant to be followed if you want to use the chip with your desktop PC.  I doubt you'll be able to modify the libraries to allow them to compile and run with the PIC.  Instead, you should examine the code and try to re-implement it on your own for the PIC.  The code can give you an idea of what to do but you won't be saving yourself any time trying to use it directly.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-12-14T18:11:02.023" />
  <row Id="7867" PostTypeId="2" ParentId="7857" CreationDate="2010-12-14T19:16:17.933" Score="1" ViewCount="" Body="&lt;p&gt;What you are looking for is a edge triggered T-triggers.&#xA;Input = output of previous stage AND count clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is schematics for transistor-based T-trigger:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://forum.cxem.net/index.php?app=core&amp;amp;module=attach&amp;amp;section=attach&amp;amp;attach_rel_module=post&amp;amp;attach_id=45908&quot; rel=&quot;nofollow&quot;&gt;http://forum.cxem.net/index.php?app=core&amp;amp;module=attach&amp;amp;section=attach&amp;amp;attach_rel_module=post&amp;amp;attach_id=45908&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-12-14T19:16:17.933" />
  <row Id="7868" PostTypeId="2" ParentId="7857" CreationDate="2010-12-14T19:24:49.273" Score="2" ViewCount="" Body="&lt;p&gt;Let's see.  In a simple ripple carry adder, sum,carry-out = a + b + carry-in&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;c[0] = carry-in&#xA;for i in n&#xA;    sum[i] = a[i] ^ b[i] ^ c[i]&#xA;    c[i+1] = (a[i]&amp;amp;b[i]) | (a[i]&amp;amp;c[i]) | (b[i]&amp;amp;c[i])&#xA;carry-out = c[n]&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Now if we want to compute sum,carry-out = a + 0 + 1, set b[] = all 0 and simplify:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;c[0] = 1&#xA;for i in n&#xA;    sum[i] = a[i] ^ c[i]&#xA;    c[i+1] = a[i] &amp;amp; c[i]&#xA;carry-out = c[n]&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;which is simpler.  Subtraction by 1 can be similarly simplified (exercise for reader: what is b[] and carry-in in that case?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Happy hacking!&lt;/p&gt;&#xA;" OwnerUserId="1962" LastActivityDate="2010-12-14T19:24:49.273" />
  <row Id="7869" PostTypeId="1" CreationDate="2010-12-14T19:55:17.663" Score="0" ViewCount="30" Body="&lt;p&gt;Hi guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm after a wireless speaker system where I can install multiple speakers in the office and be able to control it using a computer/server.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers,&#xA;WD&lt;/p&gt;&#xA;" OwnerUserId="2289" LastActivityDate="2010-12-14T19:55:17.663" ClosedDate="2010-12-14T20:05:01.657" Title="Suggestion on a wireless speaker system" Tags="&lt;audio&gt;&lt;speakers&gt;" CommentCount="1" />
  <row Id="7870" PostTypeId="2" ParentId="7864" CreationDate="2010-12-14T20:02:17.180" Score="1" ViewCount="" Body="&lt;p&gt;You could do this cheaply by repurposing several old TV remote controls. Then, you can just use an RC5 decoder on the robot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your beacon could be 4 TV remotes each with a different button glued down.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-14T20:02:17.180" />
  <row Id="7871" PostTypeId="2" ParentId="7850" CreationDate="2010-12-14T20:28:43.847" Score="9" ViewCount="" Body="&lt;p&gt;&lt;code&gt;malloc()&lt;/code&gt; in microcontrollers is generally considered a &quot;bad thing&quot;. But, if you absolutely need it then you'll want to find a third party version.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're lucky, the code you're porting may not rely on reusing blocks of memory. If this is the case, you can write a simple allocator which returns a pointer into a RAM buffer, then advances the pointer by the requested block size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've successfully used this approach before in porting PC libraries to microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Below, you'd setup the allocator with &lt;code&gt;my_malloc_init()&lt;/code&gt; and allocate memory with &lt;code&gt;my_malloc()&lt;/code&gt;. &lt;code&gt;my_free()&lt;/code&gt; is there to satisfy the dependency but won't actually do anything. Eventually you'll run out of space, of course.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make this work, you'll need to measure the worst-case memory requirement of your code (do this on a PC if possible) then set up &lt;code&gt;HEAP_SIZE&lt;/code&gt; accordingly. Before entering the part of your library requiring dynamic memory, call &lt;code&gt;my_malloc_init()&lt;/code&gt;. Before re-use, make sure nothing still points at &lt;code&gt;heap&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;uint8_t heap[HEAP_SIZE];&#xA;uint8_t *heap_ptr;&#xA;&#xA;void my_malloc_init(void)&#xA;{&#xA;    heap_ptr = heap;&#xA;}&#xA;&#xA;void *my_malloc(size_t len)&#xA;{&#xA;    uint8_t *p = heap_ptr;&#xA;    heap_ptr += len;&#xA;    if (heap_ptr &amp;gt;= heap + HEAP_SIZE)&#xA;        return NULL;&#xA;    else&#xA;        return p;&#xA;}&#xA;&#xA;void my_free(void)&#xA;{&#xA;    // do nothing&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(note: in the real world, you might need to consider pointer alignment, ie. rounding up &lt;code&gt;heap_ptr&lt;/code&gt; by 2 or 4 bytes)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to use a simpler allocation structure than &lt;code&gt;malloc()&lt;/code&gt; usually provides, like a &lt;a href=&quot;http://en.wikipedia.org/wiki/Free_list&quot; rel=&quot;nofollow&quot;&gt;FreeList&lt;/a&gt;, though this may not allow you to allocate variable sized blocks.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-15T00:43:31.443" LastActivityDate="2010-12-15T00:43:31.443" CommentCount="4" />
  <row Id="7872" PostTypeId="1" AcceptedAnswerId="7873" CreationDate="2010-12-14T20:58:33.317" Score="3" ViewCount="134" Body="&lt;p&gt;I have a small motor which I removed from a mobile phone. I want to control it from a digital output on my Arduino board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will I damage it if I connect the motor directly to to the board and it needs more power?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I use 2 outputs of the Arduino together?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know the best way to do this would be to use a transistor as a driver but I'd really like to avoid it since I don´t have it on stock and it is cold in Copenhagen now.&lt;/p&gt;&#xA;" OwnerUserId="1637" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-15T00:47:45.920" LastActivityDate="2010-12-15T00:47:45.920" Title="Using 2 outputs on an arduino to drive a motor." Tags="&lt;arduino&gt;&lt;dc-motor&gt;" AnswerCount="4" />
  <row Id="7873" PostTypeId="2" ParentId="7872" CreationDate="2010-12-14T21:05:38.743" Score="4" ViewCount="" Body="&lt;p&gt;You need a suitable driver, like a BJT or MOSFET. Use an L293D if the motor is to operate bidirectionally.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-14T21:05:38.743" CommentCount="1" />
  <row Id="7874" PostTypeId="1" AcceptedAnswerId="7876" CreationDate="2010-12-14T21:08:16.760" Score="0" ViewCount="274" Body="&lt;p&gt;I'm designing a microcontroller based device which spends most of the time in deep sleep.&#xA;Every 10 seconds it wakes up, reads a potentiometer connected on an ADC line then goes back to sleep. My aim is to achieve a long battery life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How should I wire the potentiometer up to the microcontroller in order to minimise power use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For my first attempt, I wired a 1K pot to 3V3 and GND with the wiper attached to the ADC. No matter what resistance is set on the pot, this seems to consume 3-5mA continuously.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should one or more of the pot pins be connected to GPIOs and driven only when needed?&#xA;If so, should the pins be driven low or tristated when not in use?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-15T00:37:34.677" LastActivityDate="2010-12-15T08:14:45.377" Title="How to wire a potentiometer to an ADC for low power" Tags="&lt;adc&gt;&lt;potentiometer&gt;&lt;low-power&gt;" AnswerCount="2" />
  <row Id="7875" PostTypeId="2" ParentId="7872" CreationDate="2010-12-14T21:16:53.543" Score="0" ViewCount="" Body="&lt;p&gt;The problem is the motor's current requirement, it's likely about 70mA which is much more than can be safely drawn from an AVR pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can probably scavenge a transistor from the mobile phone where you got the motor.&#xA;Don't forget to add a diode to protect from the back-EMF too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(If you're looking for an easy motor to interface with Arduino, consider micro servos - these require no other components)&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-14T21:22:59.063" LastActivityDate="2010-12-14T21:22:59.063" />
  <row Id="7876" PostTypeId="2" ParentId="7874" CreationDate="2010-12-14T21:41:56.697" Score="5" ViewCount="" Body="&lt;p&gt;Your 1k pot is causing most of your quiescent (standby/off-state) current: I=V/R, and you've got 3-5mA and 3.3V/1000 = 3.3mA.  You can either connect one side to a GPIO pin and drive it only when needed (as you suggested) and/or use a larger pot.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be careful when using very large pots (1M and higher), as the input impedance of your A/D pin might cause a slight variation in the voltage you read.  This may or may not be significant for your project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd compromise by using a 100k pot and connecting one side of the pot straight to ground, and the other to the source of a P-channel MOSFET.  Connect the center to your A/D pin, and the MOSFET gate to the microcontroller.  That way, you can allow the microcontroller's weak internal pull-up resistor to bring it to 3V3, and dissipate minimal power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An additional power savings might be to add a constant voltage divider to your circuit (and an additional A/D line), and run straight from the batteries, eliminating the voltage regulator and its quiescent current requirements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you might want to run the numbers and see what kinds of battery life you get with quicker pulses.  Even if you slow your microcontroller down to 100kHz or so, you can probably take an A/D reading in a millisecond.  Ten seconds between pulses gives you a duty cycle of 0.01%, which isn't that different from 0.1% or 0.3% for many applications.  I'd speed it up to take a reading every 300ms or so to avoid having users resetting and otherwise fiddling with the device when it doesn't respond instantly.   On second thought, I'm assuming a human is turning the pot, which may not be the case.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-14T21:41:56.697" CommentCount="3" />
  <row Id="7877" PostTypeId="2" ParentId="7872" CreationDate="2010-12-14T21:50:06.290" Score="0" ViewCount="" Body="&lt;p&gt;Check the datasheet for the particular AVR chip you're using. Some modern MCUs have a high current source/sink (I seem to recall the PIC 2550 having a pin able to source/sink 50mA) pin that can be used to directly drive an LED, for example. It might be enough for the motor if its current requirements are low.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2010-12-14T21:50:06.290" />
  <row Id="7878" PostTypeId="2" ParentId="7872" CreationDate="2010-12-14T21:54:22.103" Score="1" ViewCount="" Body="&lt;p&gt;What is the current requirement of the motor?  If it's less than 60mA, you can probably get away with sinking the current. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be aware that some digital pins can sink more current than they source.  At 60mA, you will still be at 1.5V out (so watch your power dissipation!), but you won't get far at all trying to source that kind of current.  40mA is a generous maximum for sourcing.  Therefore, you should connect to the negative terminal of your motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to use multiple outputs together, be aware that the transistors in those outputs will likely have subtle differences, and not share the current very accurately.  A &amp;lt;10 ohm resistor on each output should help them to share the current more evenly.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try to split shared outputs between different ports on the microcontroller, because this will separate the heat on the chip.  This has the drawback that it takes more time to set multiple ports, so try to avoid doing read/write/modify if you can help it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, as Joby noted, don't forget a diode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I'm assuming this is a simple DC motor, and you want to operate it in one direction.  If you have anything more complex, you should brave the cold and get yourself a proper driver. &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-14T21:54:22.103" CommentCount="1" />
  <row Id="7879" PostTypeId="2" ParentId="7828" CreationDate="2010-12-14T22:32:28.703" Score="0" ViewCount="" Body="&lt;p&gt;To add to the other answers, I would be cautious if you're soldering on a board where you have an internal power/ground plane or some other sea of copper. Remember that the more copper your pin comes into contact with, the more heat dissipation will occur and the longer you need to heat the pin before the solder will flow properly. I haven't creamed a chip this way but I have noticed my board makes a nice temporary hotplate after soldering around copper planes. Conversely this may bite you if you then turn to pins hooked up to normal traces and use the same technique to solder those pins in that you did with the power/ground plane pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also when soldering fine pitch parts (like a QFN package) I find solder-wick invaluable. That way I can allow some amount of bridging between pins and 'soak-up' the excess with the solder-wick. Usually I find the solder-wick will definitely soak up the bridge and leave just enough to make a connection between pin and pad which I either leave or touch up with a little additional solder.&lt;/p&gt;&#xA;" OwnerUserId="1614" LastActivityDate="2010-12-14T22:32:28.703" />
  <row Id="7880" PostTypeId="1" AcceptedAnswerId="7892" CreationDate="2010-12-14T23:27:45.863" Score="3" ViewCount="245" Body="&lt;p&gt;How close can I place two 0603 resistors on a PCB?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-16T16:33:33.973" LastActivityDate="2010-12-16T16:35:14.050" Title="How close can I place 0603 resistors?" Tags="&lt;pcb&gt;&lt;surface-mount&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="7881" PostTypeId="2" ParentId="7880" CreationDate="2010-12-14T23:39:15.673" Score="2" ViewCount="" Body="&lt;p&gt;This can vary a lot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Fab&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How is it being soldered? By hand or pick and place? What fab house are you using? What are their requirements?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are things you should ask yourself and get answers for in order to determine how close is possible for the fab process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Signal Integrity&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will also need to look at what signals are on each resistor. When you have high speed lines you can have issues. Also if you have high voltage you can have issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this is rather broad. If you have a specific case I will be willing to add more.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-14T23:39:15.673" CommentCount="1" />
  <row Id="7882" PostTypeId="1" AcceptedAnswerId="8673" CreationDate="2010-12-14T23:50:11.470" Score="5" ViewCount="323" Body="&lt;p&gt;I've got an RF transceiver (Nordic's nRF24L01+) which shows a typical circuit to match its antenna output to a single ended 50 ohm impedance.&lt;img src=&quot;http://i.imgur.com/wsvWW.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also got a chip antenna which comes with an example circuit to match a 50 ohm line to the antenna feed point.&lt;img src=&quot;http://i.imgur.com/YrJnl.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I am going to place the transciever and the chip antenna very close, then there is no need for a 50 ohm transmission line right? If so, can I somehow merge those two matching circuits into one and thus reducing component count?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-14T23:54:01.420" LastActivityDate="2011-01-07T16:22:32.467" Title="Can I merge two impedance matching circuits?" Tags="&lt;rf&gt;&lt;antenna&gt;&lt;matching&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="7883" PostTypeId="1" AcceptedAnswerId="7886" CreationDate="2010-12-15T00:53:25.630" Score="3" ViewCount="156" Body="&lt;p&gt;If this has already been ask I apologize as I cannot find it using the search option, please send link.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For my first project I'm thinking of building a monitor, in stages, for my outdoor pond (about 30 feet from the house) with wireless data transmission for various conditions like water level, waterfall pump failure, icing, and maybe even the occasional Heron that likes to feed on my Koi. I'm also leaning heavily towards the Netduino board as I would like to leverage my C# skills.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyhow, when I look at the specification for the Netduino board, it specifies an operating temperature of 0 to 70C. Right now it's -8C outside and will probably go to -13C tonight. The coldest I ever remember it being here (Rochester NY) is maybe about -28C (-18F maybe -20F) but that is very very rare.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino site lists no specific temperature specification, but links to the Atmel specification.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Atmel processors (&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8161.pdf&quot; rel=&quot;nofollow&quot;&gt;ATmega328&lt;/a&gt; and &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/6120s.pdf&quot; rel=&quot;nofollow&quot;&gt;AT91SAM7X512&lt;/a&gt;) for both both boards are rated from -40C to +85C; well withing my requirements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the question is, can I also assume the Arduino board is also limited to some range less than the microcontroller? What board factors might limit the temperature range for such a project?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="2243" LastActivityDate="2010-12-15T21:42:44.250" Title="Ambient operating temperatures for *duino boards" Tags="&lt;arduino&gt;&lt;netduino&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="7884" PostTypeId="2" ParentId="7882" CreationDate="2010-12-15T01:44:04.460" Score="0" ViewCount="" Body="&lt;p&gt;You should be able to do that. On the Antenna side, looking into that 2.2pF cap you should see 50 Ohm. On the transmitter side, you should see 50 Ohms looking in to the node between C5 and C6. Now, this might be a little narrow band, and require some tweaking, but you should be fine. I'd do some tweaking at the antenna range to make sure you got the range you really wanted, though. &lt;/p&gt;&#xA;" OwnerUserId="2148" LastActivityDate="2010-12-15T01:44:04.460" CommentCount="1" />
  <row Id="7885" PostTypeId="2" ParentId="3772" CreationDate="2010-12-15T03:21:07.370" Score="1" ViewCount="" Body="&lt;p&gt;Pasternack is OK, but reasonably low end. I'd use them for generic cables, but not for phase stable stuff. Gore sells/sold some good stuff. Take a look at these web sites&lt;/p&gt;&#xA;&#xA;&lt;p&gt;www.mwjournal.com Microwave Journal&#xA;www.wmrf.com Microwaves and RF magazine&#xA;www.rfcafe.com Good RF site. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dave&lt;/p&gt;&#xA;" OwnerUserId="2148" LastActivityDate="2010-12-15T03:21:07.370" />
  <row Id="7886" PostTypeId="2" ParentId="7883" CreationDate="2010-12-15T03:34:17.407" Score="3" ViewCount="" Body="&lt;p&gt;Well, my first guess is that temperature operation would be limited by the oscillator. Now, I'm flying completely by the seat of my pants here, as I haven't looked at the parts on the Arduino. If you pull the specifications on the parts, my guess is that the oscillator is the part with the most limited range. Typically, the bigger the temperature range, the more expensive the oscillator. The other factor that may come into play is the frequency offset. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the temperature shifts, the oscillator frequency will shift as well. For a wireless system, this may mean that the transmitter/receiver frequency will shift as well, possibly enough to make the range decrease. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dave&lt;/p&gt;&#xA;" OwnerUserId="2148" LastActivityDate="2010-12-15T03:34:17.407" />
  <row Id="7887" PostTypeId="1" CreationDate="2010-12-15T04:49:32.950" Score="1" ViewCount="230" Body="&lt;p&gt;I was reading this tutorial and I was confused on how I would control a motor with a 9v battery while powering my arduino with just the USB cable plugged in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://itp.nyu.edu/physcomp/Labs/DCMotorControl&quot; rel=&quot;nofollow&quot;&gt;http://itp.nyu.edu/physcomp/Labs/DCMotorControl&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2291" LastActivityDate="2010-12-15T12:10:25.893" Title="Controlling a motor with arduino and H bridge and external power supply" Tags="&lt;arduino&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="7888" PostTypeId="1" AcceptedAnswerId="7889" CreationDate="2010-12-15T05:05:24.130" Score="5" ViewCount="179" Body="&lt;p&gt;I often see those phrases in tutorials with microcontroller I/O. An example use is &quot;set pin 3 high&quot;, or &quot;set pin 5 low for 20 ms&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also recall reading several different definitions on what that terminology means. Does the low in &quot;set low&quot; mean low impedance? Does it mean low logic level (0 volts)? Or does it mean low as in negative voltage? Or is there even a universal meaning for those phrases?&lt;/p&gt;&#xA;" OwnerUserId="790" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-09T01:20:31.643" LastActivityDate="2011-04-01T18:59:19.613" Title="meaning of set low/set high" Tags="&lt;microcontroller&gt;&lt;output&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="7889" PostTypeId="2" ParentId="7888" CreationDate="2010-12-15T05:21:27.107" Score="12" ViewCount="" Body="&lt;p&gt;In the root of the expression, it is &quot;set the bit high/low (=1/0)&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It usually means set the corresponding pin &quot;high logic level&quot; and &quot;low logic level&quot;, accordingly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would have to consult the documentation of your microcontroller, but it almost always is &quot;set the output voltage to Vss/Vdd&quot; (VssIO/VddIO if your micro has separate IO and core power supplies).&lt;/p&gt;&#xA;" OwnerUserId="2292" LastActivityDate="2010-12-15T05:21:27.107" CommentCount="4" />
  <row Id="7890" PostTypeId="1" AcceptedAnswerId="7899" CreationDate="2010-12-15T07:26:11.897" Score="0" ViewCount="105" Body="&lt;p&gt;I just received an &lt;a href=&quot;http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/28440/List/0/SortField/4/ProductID/688/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;RFID reader from Parallax&lt;/a&gt; (#28440) to play with, and am having some problems getting it to send me data.  I'm interfacing it with the mbed microcontroller that I also just received.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The RFID reader interfaces via RS232 (5V level), so that matches my mbed serial port perfectly.  I have written test code on the mbed side so I know my RS232 code works.  However, whenever I send commands to the reader (e.g. &quot;!RW\x0F&quot;), I get result codes that aren't even in the documentation.  Specifically, most of the time I get back 0xE1 or 0xF8, when the actual result codes should be something like 0x01 - 0x07.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's annoying is that their documentation doesn't give any timing tables, so I'm just guessing when I send all of the data at once and read immediately.  I've tried different time delays, and nothing works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am powering both mbed and RFID reader from the USB port.  Since USB supplies 500mA without external power, and the mbed uses 100ma and the RFID reader uses &amp;lt; 200mA, I figure I have plenty of headroom.  Perhaps tomorrow I should hook up the lab supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone here used this reader with reasonable success?&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-15T20:26:17.987" Title="Having some issues with RFID reader" Tags="&lt;rfid&gt;&lt;mbed&gt;&lt;parallax&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="7891" PostTypeId="2" ParentId="7874" CreationDate="2010-12-15T08:14:45.377" Score="2" ViewCount="" Body="&lt;p&gt;Instead of connecting the high end of the potmeter to +3V3 you could connect it to an I/O pin. Before going in sleep mode set the pin to input, so that there's no current running through the potmeter. (The resistor keeps both the high end and the wiper at ground.) When the uC wakes up set the I/O pin to output and set it to high level.&lt;br&gt;&#xA;Though 1K may not be a problem -- you'll draw 3.3mA from the output pin -- I suggest you take at least a 10K potmeter. &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-15T08:14:45.377" />
  <row Id="7892" PostTypeId="2" ParentId="7880" CreationDate="2010-12-15T08:43:11.250" Score="3" ViewCount="" Body="&lt;p&gt;I have a silk layer bounding box of 2.6mm x 1.4mm around the pads of 0603s, and I often place resistors with touching bounding boxes. Lengthwise placed next to each other this leaves 0.2mm between pads. For reflow soldering this has never caused problems. For wave soldering you will need more space, esp. in the wave direction. For hand soldering it depends on the soldering skills of the person who assembles the board. 0.2mm may be possible if you don't use too much solder.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;While 0.2mm may look like very tight, remember that this is reflow soldering. When the solder paste melts it's capillarily drawn to the contact surfaces of the resistor, so it won't flow to adjacent pads.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-16T16:35:14.050" LastActivityDate="2010-12-16T16:35:14.050" />
  <row Id="7893" PostTypeId="2" ParentId="7890" CreationDate="2010-12-15T09:00:11.243" Score="1" ViewCount="" Body="&lt;p&gt;Yes I have used it successfully (I used the receive-only version).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the mbed, do you have the correct baud rate selected?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing to try is hook it up to your serial port on the PC and send it commands to see if that works.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-15T20:26:17.987" LastActivityDate="2010-12-15T20:26:17.987" CommentCount="4" />
  <row Id="7894" PostTypeId="2" ParentId="7887" CreationDate="2010-12-15T11:09:02.357" Score="1" ViewCount="" Body="&lt;p&gt;The USB connection provides 5V or 3.3V power for the Arduino. The 9V battery provides power to the H-bridge, which drives the motor. The connection between the two sources is made with the H-bridge chip using transistor driver circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a basic H-bridge:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/S2SLz.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;V+ is 9V. The P-channel FETs require ~9V gate drivers to turn off, while the N-channel ones may only require a 5V signal to turn on. In reality, then both likely have similar transistor driver circuits, both of which only require 5V inputs, which the Arduino provides, to fully react.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The parts indicated in the tutorial, SN754410 or L293, are &lt;em&gt;half H-bridges&lt;/em&gt; and use BJTs, otherwise known as &lt;em&gt;push-pull&lt;/em&gt; drivers. They only have the connection on one side of the classic H-bridge (one NPN, one PNP).&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-15T11:09:02.357" />
  <row Id="7896" PostTypeId="2" ParentId="7887" CreationDate="2010-12-15T12:10:25.893" Score="1" ViewCount="" Body="&lt;p&gt;If you have problems with that motor interface just buy one of &lt;a href=&quot;http://www.ladyada.net/make/mshield/index.html&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; kits, which uses two L293D chips. I recently got one, it was very easy to assemble and works very well.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-15T12:10:25.893" />
  <row Id="7897" PostTypeId="2" ParentId="1199" CreationDate="2010-12-15T13:38:03.637" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://zilog.com&quot; rel=&quot;nofollow&quot;&gt;Zilog&lt;/a&gt; also has some microcontrollers. Personally I have not tried to program the &lt;a href=&quot;http://en.wikipedia.org/wiki/Z8_Encore!&quot; rel=&quot;nofollow&quot;&gt;Z8 Encore&lt;/a&gt; line of chips, but they do send samples. They have a lot of different chips ranging from 1 KB to 16 KB (maybe more) with peripherals including UART, ADC, &lt;a href=&quot;http://en.wikipedia.org/wiki/I%C2%B2C&quot; rel=&quot;nofollow&quot;&gt;I2C&lt;/a&gt;, SPI, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my opinion, this is not a very good hobbyist microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2010-12-16T18:09:40.230" LastActivityDate="2010-12-16T18:09:40.230" CommunityOwnedDate="2010-12-15T13:38:03.637" />
  <row Id="7898" PostTypeId="2" ParentId="7880" CreationDate="2010-12-15T14:15:27.580" Score="3" ViewCount="" Body="&lt;p&gt;If you need several resistors with the same value as close together as possible, use resistor arrays instead of individual parts. They save a lot of space.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-15T14:15:27.580" CommentCount="2" />
  <row Id="7899" PostTypeId="2" ParentId="7890" CreationDate="2010-12-15T15:05:38.330" Score="2" ViewCount="" Body="&lt;p&gt;As I said in my original question, I thought about hooking up a lab supply even though, according to the specs, both devices combined fall under the 500mA USB spec.  I put a voltmeter across the 5V bus, and sure enough, it was dropping well below 2.5V anytime I sent a command to the reader.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hooked up my lab power supply, and immediately my !RW\x0F command returned 12 bytes as expected.  Not the correct 12 bytes, but at least the data was being sent.  It's possible that my reader just doesn't support this &quot;legacy&quot; command.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I then sent the login command, using the default password.  Without a tag, I would receive 0x02, which is &quot;could not find a listen window from the tag&quot;.  Makes sense!  I then put my tag over the reader, and unfortunately got a 0x03, which is a &quot;received NAK&quot; message.  Oh well.  I have other things to sort out, but at least I know my mbed code and RFID reader are functioning properly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully, this basic debugging technique is helpful to someone.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-15T15:05:38.330" />
  <row Id="7900" PostTypeId="1" AcceptedAnswerId="7903" CreationDate="2010-12-15T15:16:28.773" Score="0" ViewCount="86" Body="&lt;p&gt;I'm designing a device which contains a Freescale HCS08 (9S08GT32). In the datasheet I found this drawing (page 237):  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/STEAH.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't tell from the text whether this is a view on the PCB's header or on the BDM' cable connector. Can you tell me which it is?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-15T19:10:25.887" Title="Freescale HCS08 Background Debug Module (BDM) connector: clarification wanted" Tags="&lt;connector&gt;&lt;bdm&gt;" AnswerCount="1" />
  <row Id="7901" PostTypeId="1" AcceptedAnswerId="7905" CreationDate="2010-12-15T15:58:19.873" Score="4" ViewCount="609" Body="&lt;p&gt;My hardware team is planning to use an Atmel AVR 8-bit microcontroller for a future project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far as I know, it must be programmed in C. I have found a &lt;a href=&quot;http://www.harbaum.org/till/nanovm/index.shtml&quot; rel=&quot;nofollow&quot;&gt;JVM&lt;/a&gt; for AVR, though it is more limited than the native C libraries from Atmel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you suggest me an 8-bit microcontroller which supports Java?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. I don't know C and I am inexperienced in microprocessor programming.&lt;/p&gt;&#xA;" OwnerUserId="2296" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-15T20:22:59.253" LastActivityDate="2010-12-19T19:39:48.217" Title="Microcontroller with Java API" Tags="&lt;microcontroller&gt;&lt;avr&gt;&lt;java&gt;" AnswerCount="8" CommentCount="6" FavoriteCount="1" />
  <row Id="7902" PostTypeId="2" ParentId="7901" CreationDate="2010-12-15T16:19:51.810" Score="4" ViewCount="" Body="&lt;p&gt;I want to make it clear that I haven't used one before, but there used to be one years ago called the Javelin.  It's possible that Parallax has acquired them or something, because now the only one that comes up is the &quot;Javelin Stamp&quot;.  Years ago there also used to be a company called Velocity Semiconductor, that made a (supposedly) drop-in replacement for Rabbit Semiconductor's core modules, and it had a JVM in hardware, but that company has apparently vanished.  Good luck in your search!&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-15T16:19:51.810" />
  <row Id="7903" PostTypeId="2" ParentId="7900" CreationDate="2010-12-15T16:32:59.873" Score="1" ViewCount="" Body="&lt;p&gt;This is the view looking straight down (top view) on the header pins as they stick out of the board.  The cable on my P&amp;amp;E Micro BDM would plug in from the left, with the red stripe at the top.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-12-15T19:10:25.887" LastActivityDate="2010-12-15T19:10:25.887" CommentCount="1" />
  <row Id="7904" PostTypeId="2" ParentId="7820" CreationDate="2010-12-15T16:46:32.807" Score="0" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;Check that the layers are all present and numbered correctly.  This can be a problem when adding layers to a design.&lt;/li&gt;&#xA;&lt;li&gt;Check inner layers for missing pads.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-15T16:46:32.807" />
  <row Id="7905" PostTypeId="2" ParentId="7901" CreationDate="2010-12-15T18:45:28.490" Score="18" ViewCount="" Body="&lt;p&gt;If you're inexperienced in the microprocessor/microcontroller programming field, you should probably learn C first, so that you can understand when and why Java is a poor choice for most microcontroller projects.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Did you read the restrictions on the JVM you linked?  It includes the following problems:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;As little as 512 bytes of program memory (not KB, and definitely not MB) &lt;/li&gt;&#xA;&lt;li&gt;As little as 768 bytes of RAM (where your variables go.  You're limited to 768 characters of strings by this restriction.)&lt;/li&gt;&#xA;&lt;li&gt;About 20k Java opcodes per second on 8 Mhz AVR. &lt;/li&gt;&#xA;&lt;li&gt;Only includes java.lang.Object, java.lang.System, java.io.PrintStream, java.lang.StringBuffer, a JVM control class, and a native IO class.  You will not be able to do an import java.util.*; and get all the classes not in this list.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you're not familiar with what these restrictions mean, make sure that you have a plan B if it turns out that you can't actually do the project with Java due to the space and speed restrictions.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you still want to go with Java, perhaps because you expect the device to be programmed by a lot of people who only know Java, I'd strongly suggest getting bigger hardware, likely something that runs embedded Linux.  See &lt;a href=&quot;http://www.oracle.com/technetwork/java/embedded/overview/sys-reqs-embedded-159989.html&quot; rel=&quot;nofollow&quot;&gt;this page from Oracle&lt;/a&gt; for some specs to shoot for to run the embedded JVM, in the FAQ of their discussion they recommend a minimum of 32MB of RAM and 32MB of Flash. That's about 32,000 times the RAM and 1,0000 times the Flash of the AVR you're looking at.  Oracle's &lt;a href=&quot;http://www.oracle.com/technetwork/java/embedded/overview/embedded-intro-159985.html&quot; rel=&quot;nofollow&quot;&gt;Java Embedded Intro&lt;/a&gt; page goes into more detail about the restrictions of the JVM.  Their tone of voice is, as you might guess, a good deal more Java-friendly than mine.  Be aware that this kind of hardware is much more difficult to design than an 8-bit AVR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a computer engineering student with a computer science minor.  My university's CS department has drunk the Java Kool-aid, so a lot of students in the engineering program come in knowing only Java (which is a sad state of affairs for a programmer, at least learn some Python or C++ if you don't want to learn C...), so one of my professors published a &lt;a href=&quot;http://claymore.engineer.gvsu.edu/~steriana/226/C.CheatSheet.pdf&quot; rel=&quot;nofollow&quot;&gt;C Cheat Sheet&lt;/a&gt; for students with a year of Java experience.  It's only 75 pages; I suggest you read or skim it before making a decision.  In my opinion, C is the most efficient, durable, and professional language in which to develop an embedded project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another alternative to consider is the &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; framework.  It uses &lt;a href=&quot;http://arduino.cc/en/Reference/HomePage&quot; rel=&quot;nofollow&quot;&gt;a stripped down version&lt;/a&gt; of the &lt;a href=&quot;http://wiring.org.co/&quot; rel=&quot;nofollow&quot;&gt;Wiring&lt;/a&gt; language, which is like C++ without objects or headers.  It can run on many AVR chips, it's definitely not restricted to their hardware.  It will give you an easier learning curve than just jumping straight into C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In conclusion,&#xA;&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/rUjwD.png&quot; alt=&quot;XKCD Golden Hammer&quot;&gt;&lt;br&gt;&#xA;Alt text: Took me five tries to find the right one, but I managed to salvage our night out--if not the boat--in the end.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-18T09:03:55.160" LastActivityDate="2010-12-18T09:03:55.160" CommentCount="4" />
  <row Id="7906" PostTypeId="2" ParentId="7880" CreationDate="2010-12-15T18:58:51.497" Score="2" ViewCount="" Body="&lt;p&gt;From &lt;a href=&quot;http://www.edaboard.com/thread128769.html%22here%22&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; &quot;The document is &quot;IPC-7351A Generic Requirements for Surface Mount Design and Land Pattern Standard&quot;. You have to buy it from www.ipc.org.&quot;  You CAD package may have it already.  There are 3 variantes, so you would use the &quot;least&quot; (i.e. smallest one).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;If you want to look at the recommended footprints, without buying the standard, you can download a free viewer at: &lt;a href=&quot;http://landpatterns.ipc.org/default.asp&quot; rel=&quot;nofollow&quot;&gt;http://landpatterns.ipc.org/default.asp&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's more info available at: &lt;a href=&quot;http://www.ipc.org/ContentPage.aspx?pageid=4.6&quot; rel=&quot;nofollow&quot;&gt;http://www.ipc.org/ContentPage.aspx?pageid=4.6&lt;/a&gt;&quot;&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-15T18:58:51.497" CommentCount="2" />
  <row Id="7907" PostTypeId="2" ParentId="7883" CreationDate="2010-12-15T20:02:07.457" Score="2" ViewCount="" Body="&lt;p&gt;If you can't identify the exact parts used on the Arduino board, you aren't going to be able to verify that the Arduino/Netduino board is &lt;em&gt;rated&lt;/em&gt; for those temperatures. This would apply to everything in your system, from the water level sensor to the wireless transmitter. Some parts are harder to find based on markings. I wouldn't worry too much about resistors and capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most manufacturers won't tell you what happens when you exceed the temperature ratings. I'd recommend you take your system and put it in a cooler full with dry ice, and see what happens. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-15T20:02:07.457" CommentCount="2" />
  <row Id="7908" PostTypeId="2" ParentId="7901" CreationDate="2010-12-15T20:22:30.860" Score="6" ViewCount="" Body="&lt;p&gt;The most popular programming environment for the Atmel AVR is &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt;. The Arduino language is a subset of C++. For some applications, Arduino &quot;sketches&quot; (programs) are  almost indistinguishable from Java.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The language will be very familiar to a Java programmer - but, importantly, Arduino sketches are compiled into native code which runs at full speed with full hardware access. This is critical for getting the most from your microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the &lt;a href=&quot;http://arduino.cc/en/Reference/HomePage&quot; rel=&quot;nofollow&quot;&gt;API&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Arduino provides everything you need to get going: low cost hardware, a free integrated development environment and a bootloader (so you can load code over USB/serial).&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-15T22:11:10.840" LastActivityDate="2010-12-15T22:11:10.840" CommentCount="6" />
  <row Id="7909" PostTypeId="2" ParentId="7901" CreationDate="2010-12-15T21:03:16.717" Score="3" ViewCount="" Body="&lt;p&gt;Sun Microsystems used to make a platform called the Sun Spot which was an embedded java platform basically. Now obviously Sun Microsystems is not around anymore (Oracle bought them), but it seems like you can still buy Sun Spots - &lt;a href=&quot;http://www.sunspotworld.com/products/&quot; rel=&quot;nofollow&quot;&gt;http://www.sunspotworld.com/products/&lt;/a&gt;. I'm not big on the idea of using Java in an embedded environment (wrong level of abstraction for the job imho) but this would seem to be the most natural embedded platform for Java. Note the specs on these things - they are heavy duty 180MHz / 512k RAM, and they are not cheap at $400 for a starter kit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'll be a second or third to the Arduino advocacy responders to this question. There is one hell of a community out there to support you if you need help. And if you need peripheral hardware, look up &quot;Arduino Shields&quot; on google and be amazed - you can do anything from control servo motors to hop on an 802.11 wireless network with the right combination of shields. It's not practical to learn C (pointer says what!?) without some practice time, but you can start writing Arduino sketches in next to no time... You can also get &quot;real&quot; Arduino platforms around $30 and clones (e.g. RBBB or DorkBoard) for under $15. &lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-15T21:09:23.500" LastActivityDate="2010-12-15T21:09:23.500" CommentCount="2" />
  <row Id="7910" PostTypeId="2" ParentId="7883" CreationDate="2010-12-15T21:42:44.250" Score="2" ViewCount="" Body="&lt;p&gt;Most electronics will still operate at temperatures lower then their rating, it's just that they may drift outside their specifications.  Wireless communications would be the only thing that would be fairly sensitive to this; the tolerance on most wired embedded communications is fairly loose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I would be more concerned of besides temperature is condensation on the board.  If you put the Arduino into a relatively enclosed box in your warm house then take it into the freezing cold, all the excess moisture will come out, possibly onto your board.  Despite me being &quot;more concerned&quot; about this, my level of concern would still be very low unless you're doing high precision analog readings or the like.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-15T21:42:44.250" />
  <row Id="7911" PostTypeId="2" ParentId="7901" CreationDate="2010-12-15T22:58:29.600" Score="1" ViewCount="" Body="&lt;p&gt;Ajile systems make a variety of native embedded, real time java chips and eval boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They run bare metal java. It's very pleasant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;www.ajile.com make the chips and eval boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;www.systronix.com sell a variety of embedded java hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used AJ-100 from ajile for demanding work, they are very nice to work with.&#xA;And no, they aren't as cheap as an avr but they process data like a low-end pentium.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ajiles' chips respond to interrupts  (interrupt latency) in under 1 microsecond.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastEditorUserId="1481" LastEditorDisplayName="" LastEditDate="2010-12-18T03:43:50.647" LastActivityDate="2010-12-18T03:43:50.647" CommentCount="4" />
  <row Id="7913" PostTypeId="1" AcceptedAnswerId="7918" CreationDate="2010-12-15T23:51:52.427" Score="5" ViewCount="635" Body="&lt;p&gt;I've always wondered this: every single modern PCB is routed at 45 degree angle increments. Why does the industry prefer this so much? Doesn't any-angle routing offer more flexibility?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One plausible theory would be that the existing tools only support 45 degree increments and that there isn't much pressure to move away from this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But having just researched this topic on google, I stumbled across &lt;a href=&quot;http://www.toporouter.com/&quot; rel=&quot;nofollow&quot;&gt;TopoR - Topological Router&lt;/a&gt; - which does away with the 45 degree increments, and according to their marketing materials it does a considerably better job than the 45-degree-limited competitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What gives? What would it take for you personally to start routing arbitrary angles? Is it all about support in your favourite software, or are there more fundamental reasons?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example of non-45-degree routing:&#xA;&lt;img src=&quot;http://i.imgur.com/y5y1Q.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. I also wondered the same about component placement, but it turns out that many pick &amp;amp; place machines are designed such that they can't place at arbitrary angles - which seems fair enough.&lt;/p&gt;&#xA;" OwnerUserId="1951" LastEditorUserId="1951" LastEditorDisplayName="" LastEditDate="2011-04-25T10:42:07.253" LastActivityDate="2011-04-25T10:42:07.253" Title="Why is there such a strong preference for 45 degree angles in PCB routing?" Tags="&lt;pcb&gt;&lt;routing&gt;&lt;eda&gt;" AnswerCount="6" CommentCount="12" FavoriteCount="2" />
  <row Id="7914" PostTypeId="2" ParentId="7913" CreationDate="2010-12-16T00:08:19.787" Score="4" ViewCount="" Body="&lt;p&gt;For my own PCBs I like rounded &amp;amp; curved tracks, no problems there as long as you are routing manually.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In most of industrial PCBs it's just a tradition due to limitations on early/current routing software. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Less sharp angles = /*marginally */ better signal quality.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2010-12-16T08:38:12.377" LastActivityDate="2010-12-16T08:38:12.377" CommentCount="2" />
  <row Id="7915" PostTypeId="2" ParentId="7913" CreationDate="2010-12-16T00:08:31.380" Score="7" ViewCount="" Body="&lt;p&gt;It looks more tidy, and enables the most tracks to be put into a given area. it's also better for controlled impedance tracks.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-16T00:08:31.380" CommentCount="8" />
  <row Id="7918" PostTypeId="2" ParentId="7913" CreationDate="2010-12-16T01:51:51.023" Score="6" ViewCount="" Body="&lt;p&gt;Fundamentally, it basically boils down to the fact that the software is way easier to design with only 45° angles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Modern autorouters are getting better, but most of the PCB tools available have roots that go back to the DOS days, and therefore there is an enormous amount of legacy pressure to not completely redesign the PCB layout interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Furthermore, many modern EDA packages let you &quot;push&quot; &lt;em&gt;groups&lt;/em&gt; of traces, with the autorouter stepping in to allow one trace to force other traces to move, even during manual routing. This is also much harder to implement when you aren't confined to rigid 45­° angles.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-12-16T01:51:51.023" CommentCount="3" />
  <row Id="7919" PostTypeId="1" AcceptedAnswerId="7924" CreationDate="2010-12-16T04:12:08.150" Score="2" ViewCount="177" Body="&lt;p&gt;What is the part in the picture below? It's like a make header, but with long pins on both sides. I've got some temperature probes I've built that end in female connectors and I like to use something like what's in the picture to be able to use the probes with a breadboard. I've looked on digikey under headers and haven't been able to find anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/v6MW4.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2170" LastActivityDate="2011-01-04T18:22:24.977" Title="What part is like a male header with long pins on both sides?" Tags="&lt;breadboard&gt;&lt;parts&gt;&lt;header&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="7920" PostTypeId="1" CreationDate="2010-12-16T04:29:46.683" Score="1" ViewCount="135" Body="&lt;p&gt;I have near 5 keyboards broken because poured water or juice, etc...&#xA;Most problems are keys that don't work or swapped keys.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to know (just for electronics exercise - I know that keyboards are cheap) if it can be fixed or tested with basic electronics tools, and how I do it?&lt;/p&gt;&#xA;" OwnerUserId="1800" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-09T01:18:35.357" LastActivityDate="2011-02-09T01:18:35.357" Title="Keyboard fixing" Tags="&lt;keyboard&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="7921" PostTypeId="2" ParentId="7920" CreationDate="2010-12-16T04:39:21.283" Score="7" ViewCount="" Body="&lt;p&gt;You could try putting them through the &lt;a href=&quot;http://boingboing.net/2005/05/30/clean-your-keyboard-.html&quot; rel=&quot;nofollow&quot;&gt;dishwasher&lt;/a&gt; :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Quoting a quote (sic) from that site:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I can report that not only will the&#xA;  keyboard come out clean, but it will&#xA;  probably work once it dries&#xA;  completely. Every key on the keyboard&#xA;  works and feels just right - the Caps&#xA;  Lock light even works! This ‘hack’ is&#xA;  not for the weakhearted, and I would&#xA;  probably avoid putting a $100+&#xA;  keyboard in the dishwasher. But if you&#xA;  don’t have any other options, it’s a&#xA;  pretty good bet&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; The dishwasher fix basically just cleans out the mechanism (be it mechanical switches or diaphragm) and is a good fix for 'sticky' keys. This may work for your orange juice problem, if the sugary residue is stopping the key presses from working. Hand cleaning would also be of help here if you disassemble the keyboard. The trick is to make sure it is completely dry before plugging it back in. I'd suggest to wait a week or so after washing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a keyboard died due to spilled water, then most likely it caused an electrical short and damaged something on the circuit board. This doesn't mean that it is impossible to fix - standard fault finding applies, and you'll need some tools for the job (multimeter, oscilloscope come to mind).&lt;/p&gt;&#xA;" OwnerUserId="554" LastEditorUserId="554" LastEditorDisplayName="" LastEditDate="2010-12-16T04:59:28.153" LastActivityDate="2010-12-16T04:59:28.153" CommentCount="6" />
  <row Id="7922" PostTypeId="2" ParentId="7901" CreationDate="2010-12-16T05:08:55.323" Score="1" ViewCount="" Body="&lt;p&gt;While I'd generally be of the &quot;learn C and understand what processors actually do&quot; camp where embedded work is concerned, it's worth pointing out that a small arm chip is not that much more expensive than an AVR, and is in an almost plausible position to handle simple tasks on top of a jvm.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2010-12-16T05:08:55.323" />
  <row Id="7923" PostTypeId="2" ParentId="7920" CreationDate="2010-12-16T05:54:19.147" Score="6" ViewCount="" Body="&lt;p&gt;Inexpensive keyboards are usually made with an elastomeric (&quot;rubber&quot;) membrane that sits over a large printed circuit board.  When you press a button, the plastic key collapses the dome, whose bottom has a conductive pad that can short contacts on the PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If keys are not responding, it may simply be due to fouling of the pad/contact, so disassembling and cleaning should fix the problem.  Clean up as much bulk residue as you can on the PCB with water, then do a final clean with alcohol.  The elastomeric membrane you should be able to immerse to clean, but a final clean with alcohol may be prudent on the bottoms of the domes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keys being confused with one-another may indicate some additional damage to the logic, parts may be damaged irreparably, or the juice residue may simply be shorting some high impedance pins, causing confusion.  A good first step would be to clean it in any case.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-16T05:54:19.147" CommentCount="1" />
  <row Id="7924" PostTypeId="2" ParentId="7919" CreationDate="2010-12-16T06:01:06.630" Score="3" ViewCount="" Body="&lt;p&gt;Here you go: &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=PCC36SFAN-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=PCC36SFAN-ND&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PDF of drawing: &lt;a href=&quot;http://www.sullinscorp.com/drawings/77_G_C___S___N,_P_C___S___N,_STRAIGHT,_C10436-C.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.sullinscorp.com/drawings/77_G_C_&lt;strong&gt;S&lt;/strong&gt;_N,_P_C_&lt;strong&gt;S&lt;/strong&gt;_N,_STRAIGHT,_C10436-C.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's just a single row male header.  What I've done when the lengths aren't quite right is just order it longer on one end, and then push the plastic bit so it shifts to the middle and leaves equal-length conductors on each side.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-16T06:01:06.630" CommentCount="1" />
  <row Id="7925" PostTypeId="1" CreationDate="2010-12-16T06:26:02.420" Score="2" ViewCount="315" Body="&lt;p&gt;I'm designing a robot and I'm looking to use mainly I2C to control different sensors and stuff. I'm now looking into motors, specifically &lt;a href=&quot;http://www.sparkfun.com/products/9697&quot; rel=&quot;nofollow&quot;&gt;this motor&lt;/a&gt;. However all of the ESCs I have seen use a PWM interface. I'm wondering if there are any ESCs which use I2C, or if anyone knows of an easy way I could implement one myself? I've already seen a couple of application notes which provide reference implementations of an ESC on an AVR (&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8012.pdf&quot; rel=&quot;nofollow&quot;&gt;AVR444&lt;/a&gt; and &lt;a href=&quot;http://www.efo.ru/ftp/pub/atmel/_AVR_MCUs_8bit/_Technical_Library/appnotes/pdf_avr/AVR493.pdf&quot; rel=&quot;nofollow&quot;&gt;AVR493&lt;/a&gt;) but they are old and use IAR so id rather not re-impliment them. I'm wondering if anyone has an already functional implementation?&lt;/p&gt;&#xA;" OwnerUserId="81" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-18T01:05:49.633" LastActivityDate="2010-12-18T01:05:49.633" Title="I2C brushless DC motor controller?" Tags="&lt;i2c&gt;&lt;dc-motor&gt;&lt;speed-controller&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="7926" PostTypeId="2" ParentId="7920" CreationDate="2010-12-16T08:43:26.990" Score="4" ViewCount="" Body="&lt;p&gt;I really like M$ natural 4000 keyboard which are not cheap, and surely I pour liquids on it from time to time, and it's worth try fixing. Here are the results:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Clean damaged areas to remove parasitic conduction layer&#xA;2) Redraw damaged tracks using conductive glue. Also, you may plant tiny copper wires along damaged tracks to reduce resistence of glue if needed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Success ratio 80%, some KBDs were fixed several times :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-12-16T08:43:26.990" CommentCount="3" />
  <row Id="7927" PostTypeId="1" CreationDate="2010-12-16T10:41:04.850" Score="2" ViewCount="137" Body="&lt;p&gt;I'm looking for a device that allows me to supervise an existing BTicino home alarm system.  The system can communicate via RS-232 (or USB) interface using an open protocol, Openwebnet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to be able to:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;intercept events from the RS-232 communication (known messages coming from the serial port), and then&lt;/li&gt;&#xA;&lt;li&gt;provide feedback through a GSM network (SMS messages).&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The basic requirements I have are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;very low power consumption (&amp;lt;= 5 W),&lt;/li&gt;&#xA;&lt;li&gt;RS232 or USB interface (communication with the alarm system gateway),&lt;/li&gt;&#xA;&lt;li&gt;another RS232 or USB interface (communication with a GSM module),&lt;/li&gt;&#xA;&lt;li&gt;12 V supply (or UPS battery backup), and&lt;/li&gt;&#xA;&lt;li&gt;programmability (to host the logic for interecept and react to events).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Up until now I have evaluated these solutions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.fit-pc.com/web/fit-pc2/&quot; rel=&quot;nofollow&quot;&gt;FIT PC-2&lt;/a&gt;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A full computer with very green power supply (5W).&lt;/li&gt;&#xA;&lt;li&gt;In addition it could host a web server for further connection capability. &lt;/li&gt;&#xA;&lt;li&gt;Too expensive.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.globalscaletechnologies.com/t-guruplugdetails.aspx&quot; rel=&quot;nofollow&quot;&gt;Sheeva Plug / GuruPlug&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.telit.com/en/products.php?p_id=3&amp;amp;p_ac=show&amp;amp;p=4&quot; rel=&quot;nofollow&quot;&gt;Telit GM 862&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;???&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Which hardware platform do I need?&lt;/p&gt;&#xA;" OwnerUserId="2302" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-16T17:51:02.033" LastActivityDate="2010-12-16T21:23:45.333" Title="Home automation Controller/server needed" Tags="&lt;gsm&gt;&lt;home-automation&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="3" />
  <row Id="7928" PostTypeId="2" ParentId="3423" CreationDate="2010-12-16T11:33:51.267" Score="0" ViewCount="" Body="&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Some AVR interpreters:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.cqham.ru/tbcgroup/index_eng.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.cqham.ru/tbcgroup/index_eng.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.jcwolfram.de/projekte/avr/chipbasic2/main.php&quot; rel=&quot;nofollow&quot;&gt;http://www.jcwolfram.de/projekte/avr/chipbasic2/main.php&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.jcwolfram.de/projekte/avr/chipbasic8/main.php&quot; rel=&quot;nofollow&quot;&gt;http://www.jcwolfram.de/projekte/avr/chipbasic8/main.php&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.jcwolfram.de/projekte/avr/main.php&quot; rel=&quot;nofollow&quot;&gt;http://www.jcwolfram.de/projekte/avr/main.php&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://code.google.com/p/python-on-a-chip/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/python-on-a-chip/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?module=Freaks%20Academy&amp;amp;func=viewItem&amp;amp;item_id=688&amp;amp;item_type=project&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?module=Freaks%20Academy&amp;amp;func=viewItem&amp;amp;item_id=688&amp;amp;item_type=project&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?module=Freaks%20Academy&amp;amp;func=viewItem&amp;amp;item_id=626&amp;amp;item_type=project&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?module=Freaks%20Academy&amp;amp;func=viewItem&amp;amp;item_id=626&amp;amp;item_type=project&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?module=Freaks%20Academy&amp;amp;func=viewItem&amp;amp;item_id=460&amp;amp;item_type=project&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/index.php?module=Freaks%20Academy&amp;amp;func=viewItem&amp;amp;item_id=460&amp;amp;item_type=project&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Some AVR compilers:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://winavr.sourceforge.net&quot; rel=&quot;nofollow&quot;&gt;http://winavr.sourceforge.net&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.iar.com/website1/1.0.1.0/107/1/&quot; rel=&quot;nofollow&quot;&gt;http://www.iar.com/website1/1.0.1.0/107/1/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.mcselec.com&quot; rel=&quot;nofollow&quot;&gt;http://www.mcselec.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.e-lab.de/index_en.html&quot; rel=&quot;nofollow&quot;&gt;http://www.e-lab.de/index_en.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.mikroe.com/eng/categories/view/21/avr-compilers&quot; rel=&quot;nofollow&quot;&gt;http://www.mikroe.com/eng/categories/view/21/avr-compilers&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;hr&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-12-16T11:33:51.267" CommunityOwnedDate="2010-12-16T11:33:51.267" />
  <row Id="7929" PostTypeId="1" AcceptedAnswerId="7930" CreationDate="2010-12-16T12:11:28.067" Score="4" ViewCount="196" Body="&lt;p&gt;I often see a marking like the following pattern on the top of radial PTH elcos.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/mQjFu.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What does it mean? Is it an identification of the manufacturer? &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-16T15:51:06.037" Title="What are markings on top of electrolytic capacitors?" Tags="&lt;identification&gt;&lt;markings&gt;" AnswerCount="3" />
  <row Id="7930" PostTypeId="2" ParentId="7929" CreationDate="2010-12-16T12:17:47.923" Score="13" ViewCount="" Body="&lt;p&gt;I believe they are vents when the pressure inside a capacitor would build up due to heating of some sort. It will pop open instead of just blowing up.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-12-16T12:17:47.923" CommentCount="6" />
  <row Id="7931" PostTypeId="2" ParentId="7925" CreationDate="2010-12-16T13:13:39.393" Score="2" ViewCount="" Body="&lt;p&gt;To create one you could use a low power uC like a the msp430. It would be fairly cheap to build. Most of the msp430 value line chips have I2C or SPI built in. you would have to look up how to drive the brushless motor and those 2 links could give you a good start.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2010-12-16T13:13:39.393" CommentCount="2" />
  <row Id="7932" PostTypeId="2" ParentId="7925" CreationDate="2010-12-16T13:27:42.333" Score="0" ViewCount="" Body="&lt;p&gt;Another vote for using a low power uC! I would suggest a small PIC - it would be easy to write some software to convert I2C to PWM outputs as these devices have good built peripheral options.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The advantage is you can also implement a local control loop by measuring feedback from the A/D port of actual position or velocity and use the I2C as a setpoint with a small PI or PID control loop.  And presto you have a closed loop controller!!&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-12-16T13:27:42.333" />
  <row Id="7938" PostTypeId="2" ParentId="7929" CreationDate="2010-12-16T15:18:25.760" Score="0" ViewCount="" Body="&lt;p&gt;They are strategically weakened parts of the casing which will bulge upwards and help the capacitor release hydrogen and/or electrolyte. They work quite well. Don't try this at home, but if you blow up an old capacitor with no release vents it will explode violently sending electrolyte and alfoil flying everywhere. The vents are designed to prevent such a catastrophic failure from happening.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's interesting to see how different manufacturers have different vent patterns. It might be due to cost - most have four vents in a cross/plus sign fashion, but some cheaper ones have only two or three. It might save some money on the production line to score only two or three times. And some smaller ones have no vents at all. That's probably another question, though.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-16T15:18:25.760" CommentCount="1" />
  <row Id="7939" PostTypeId="2" ParentId="7929" CreationDate="2010-12-16T15:51:06.037" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=JCPXckfT-6g&quot; rel=&quot;nofollow&quot;&gt;Here's a (somewhat artistic) video&lt;/a&gt; of those features in action.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first two events (0:00, 0:03) are what happens when the stamped features do &lt;strong&gt;not&lt;/strong&gt; work, but all the subsequent electrolytic capacitor failures (0:14, 0:16, 0:18, 0:34, 0:36, 0:39...) rip the case open in a relatively safe and controlled manner, notably not causing shrapnel to fly around.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-16T15:51:06.037" CommentCount="1" />
  <row Id="7940" PostTypeId="1" AcceptedAnswerId="7952" CreationDate="2010-12-16T16:03:33.633" Score="5" ViewCount="264" Body="&lt;p&gt;I have a 200V DC power input and I need to, with no external voltages, generate a 12V-24V voltage to run the control electronics off, at about 50mA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've considered zener diodes and potential dividers but they waste too much power; the resistor at the top must dissipate 9.4W to provide 0.6W, which is a ridiculous waste and difficult to handle. I've tried to look at how switch mode wall warts do it, but they seem to have some kind of fancy mechanism of powering themselves from the output, which I don't really understand. (Neither do I understand how they initially get a voltage.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-17T17:36:49.067" LastActivityDate="2010-12-17T17:36:49.067" Title="Best way to get a low DC voltage from a high DC voltage for a power supply?" Tags="&lt;power-supply&gt;&lt;high-voltage&gt;" AnswerCount="7" CommentCount="6" />
  <row Id="7941" PostTypeId="1" CreationDate="2010-12-16T16:19:42.190" Score="5" ViewCount="294" Body="&lt;p&gt;I'm still using PCAD2006 for my schematic capture and PCB layout. I'm not very happy with this; it is rather buggy, but it's a leftover for which I have an extensive library.&lt;br&gt;&#xA;Due to the problems I'm having with PCAD and the fact that it is no longer supported by Altium I'm looking for an alternative. Shopping list:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;Free or low cost (Altium Designer is out) &lt;/li&gt;&#xA;  &lt;li&gt;No restrictions in board size beyond the obvious. E.g. Eurocard (160x100mm) or 200x150mm should be possible. 1 meter square shouldn't. Some free packages have a 100x80mm limit IIRC.  &lt;/li&gt;&#xA;  &lt;li&gt;Gerber output  &lt;/li&gt;&#xA;  &lt;li&gt;Extensive library of both PTH and SMT components  &lt;/li&gt;&#xA;  &lt;li&gt;Nice to have: real-time DRC  &lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Suggestions?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-16T17:42:20.653" LastActivityDate="2010-12-16T21:23:58.073" Title="Schematic capture/PCB layout program recommendations" Tags="&lt;schematics&gt;&lt;layout&gt;&lt;eda&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="7942" PostTypeId="2" ParentId="7940" CreationDate="2010-12-16T16:26:40.987" Score="2" ViewCount="" Body="&lt;p&gt;What you're looking for, I think, is a High Voltage DC-DC Converter. Something like those found here: &lt;a href=&quot;http://www.powerstream.com/dcdc.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.powerstream.com/dcdc.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For theory of operation, I recommend reading &lt;a href=&quot;http://en.wikipedia.org/wiki/Buck_converter&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Buck_converter&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/Switched-mode_power_supply&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Switched-mode_power_supply&lt;/a&gt;. The short answer to how it gets power is through a feedback circuit.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-16T18:53:10.830" LastActivityDate="2010-12-16T18:53:10.830" />
  <row Id="7943" PostTypeId="2" ParentId="7913" CreationDate="2010-12-16T16:28:22.930" Score="2" ViewCount="" Body="&lt;p&gt;The primary reason is that it makes for an easier problem set, and can be easier to design. There are some useful properties that a 45/90 degree system provides. The primary reason I'll say is that it lets you keep your desired grid spacing without a big penalty. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you start from a point in a grid, each cardinal direction (up, right, down, left) will arrive at an adjacent grid point at 1 unit. Any 45 degree angle will also arrive at an adjacent point, although the distance will be (sqrt 2) units. If you were to use an angle such as 30 or 60 degrees, you would arrive at a midpoint between a grid point, which would require you to have a finer grid. A finer grid increases the computation time for path evaluation and may make it more difficult to cleanly optimize the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The TopoR software uses a completely different algorithm from the typical router, which makes it unique. The PCB designs that TopoR makes looks similar to old hand-drawn PCB layouts from the 60's-70's.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-16T16:28:22.930" CommentCount="3" />
  <row Id="7944" PostTypeId="2" ParentId="7940" CreationDate="2010-12-16T16:50:29.590" Score="1" ViewCount="" Body="&lt;p&gt;First, are you able to float your controller at +176V? This way you would not have to drop the voltage. I/O circuitry would have to be fancier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are two ways to drop voltages: dissipate power (linear regulation) or switch it and smooth the output (buck). Ideally one would draw only 6mA from the 200V line, but there will be losses in a buck converter. I've never seen a HV DC-DC buck made for low power. You may need to make one on your own, if it's worth it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure which will have larger losses. How much is it worth? :D&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-16T16:50:29.590" CommentCount="7" />
  <row Id="7945" PostTypeId="2" ParentId="7940" CreationDate="2010-12-16T16:51:53.063" Score="1" ViewCount="" Body="&lt;p&gt;The switching mode wall worts are pretty simple.  The rectify the input voltage (which you don't need to worry about since you have 200VDC already) then turn it into a PWM waveform at fairly high frequency.  The transformer can then be rather small and light weight as its operating at the PWM frequency.  The turns ratio of the transformer is used to step down to the desired voltage and then filtered or further regulated as you would with any switching regulator.  The feedback loop to the PWM controller (which is operating at mains/high voltage) is usually done with an opto-coupler so there is complete isolation between the high voltage and low voltage sides.  You may be able to skip that in your case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be ideal is a flyback or a feed forward switching controller.  &lt;a href=&quot;http://parametric.linear.com/html/flyback,_foward_and_isolated_controllers&quot; rel=&quot;nofollow&quot;&gt;Here are some examples from linear.&lt;/a&gt;  But your problem is going to be that 200VDC is really high, i've never seen a DC-DC controller that supports more than ~100V input.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you should be able to adapt an AC-DC switching controller which are normally designed for use with rectified mains voltages which can be much higher than 200V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance &lt;a href=&quot;http://www.st.com/internet/analog/subclass/432.jsp&quot; rel=&quot;nofollow&quot;&gt;ST makes a bunch of such controllers&lt;/a&gt;.  I think that you can use this type of topology with 200VDC with minimal modification although i've never tried, you should study the modes of operation further.  I'm sure there are many more manufacturers for similar parts as well.  &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2010-12-16T16:51:53.063" CommentCount="7" />
  <row Id="7946" PostTypeId="2" ParentId="7941" CreationDate="2010-12-16T17:25:18.163" Score="6" ViewCount="" Body="&lt;p&gt;I would go with the professional version of Eagle-- $1000, plus $500 if you want the autorouter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried Kicad and GEDA; despite Jim's comment above, I think neither are comparable in stability or features. They've improved a lot from the past, and you can't beat the price, but I think Eagle is worth the money. I also think that Eagle has a promising future in that they are alleged developing an open file specification, according to Adafruit. If that actually happens, it will be huge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the even longer run, I hope that GEDA and Kicad get better, but I've been literally hoping that for a decade (about GEDA). (And yes, I realize that I should shut up and start contributing patches. So should you, dear critic.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Altium is $3500 plus an optional yearly subscription for updates; I'd say it's not worth it unless you need specific features that Altium provides-- for most boards, Eagle wins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you have an old PCAD license from Altium, you might also investigate Mentor's deals. They were recently offering a large discount to switch from Altium to their stuff. Though I haven't used Mentor's stuff, I suspect it's like most established EDA software-- powerful, but with frustrating interface quirks that go unreplicated in the rest of the software world.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd also think seriously about what boat you want to be in for the long term. I learned Altium back when it was Protel 98, and now the transition to anything else would be a sizable productivity hit. I do use the free version of Eagle for small stuff, but it's painful (mostly because of my experience with Altium). If I could restart now, I probably wouldn't invest the time to learn a package that I couldn't afford for personal projects.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-12-16T17:34:49.167" LastActivityDate="2010-12-16T17:34:49.167" CommentCount="5" />
  <row Id="7947" PostTypeId="2" ParentId="7941" CreationDate="2010-12-16T17:28:08.857" Score="5" ViewCount="" Body="&lt;p&gt;I use the GEDA suite of tools, obviously you get what you pay for, but I've managed to work around most of its limitations and am pretty happy with the price I paid for it ($0).&lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2010-12-16T17:28:08.857" CommentCount="2" />
  <row Id="7948" PostTypeId="2" ParentId="7941" CreationDate="2010-12-16T17:34:00.393" Score="3" ViewCount="" Body="&lt;p&gt;TinyCAD/FreePCB combo.  You'll probably have to create some symbols and footprints yourself, but you always have to be certain of your footprints with any PCB application.  It's all free (of cost) and open-source.  FreePCB has no limitations and produces gerbers.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-12-16T17:34:00.393" />
  <row Id="7949" PostTypeId="2" ParentId="4242" CreationDate="2010-12-16T17:48:05.703" Score="1" ViewCount="" Body="&lt;p&gt;The usuall problem is the the SD card needs to be fat16, and less than 2G.  Try reformating the card &lt;/p&gt;&#xA;" OwnerUserId="2305" LastActivityDate="2010-12-16T17:48:05.703" />
  <row Id="7951" PostTypeId="2" ParentId="7940" CreationDate="2010-12-16T18:50:11.870" Score="2" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/llEZO.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/10214&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/10214&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;While this charger is rated for 100 - 240 VAC, the first thing that a switchmode supply does is rectify the input voltage, so 200 VDC will work fine to power it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(You can of course buy this kind of supply in a variety of output voltages.)&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-16T18:50:11.870" />
  <row Id="7952" PostTypeId="2" ParentId="7940" CreationDate="2010-12-16T18:55:43.987" Score="2" ViewCount="" Body="&lt;p&gt;This problem is known as bootstrapping.  It's even more of a problem when designing low-voltage boost converters.  If you've got a .1V 10A source, sure, you've got 1W of power, and could probably generate close to 200mA at 5V from it, but you need a voltage usable for some electronics.  A 5V power supply is conveniently and indefinitely available on your devices' output soon after you solve this problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I won't go into design of bootstrapping a boost converter here (because I don't know how...) but I would suggest how you might go about designing a buck converter.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We'll assume that you have a circuit which can generate 12V from 120V when powered with 12V.  That's not so hard, there are several designs which could do this.  &lt;a href=&quot;http://en.wikipedia.org/wiki/Buck_converter&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt; has a simple one, you might look into others in various application notes.  If your switch oscillates at a few hundred kilohertz, you should be generating a usable 12V signal in a few milliseconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you need, therefore, is a way to generate a voltage to power your device for just a few milliseconds, and then turn it off.  A simple resistor/&gt;12V zener diode system with a transistor just after the resistor will be fine.  A PMOS with the gate to your circuit's output should switch this source off soon after your regulator starts working.  You'll want to ensure that your load is disconnected when starting up, because this could cause your shunt regulator to go out of regulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Break your problem down into two steps: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Generate 12V from 200V while powered from an external 12V source.&lt;/li&gt;&#xA;&lt;li&gt;Generate 12V from 200V for a few milliseconds without an external source.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Then combine the two.  The first one is arguably more interesting, many textbooks will skip over the second problem.  My professor mentioned it as a side note when lecturing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other answers have pointed out that you can probably just tap an AC switch-mode regulator after the rectification circuit, but I suspect that you also want to know how it works.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-16T18:55:43.987" CommentCount="4" />
  <row Id="7953" PostTypeId="2" ParentId="7940" CreationDate="2010-12-16T20:09:03.747" Score="1" ViewCount="" Body="&lt;p&gt;Check out Power Integrations &lt;a href=&quot;http://www.powerint.com/en/products/linkswitch-family/linkswitch-tn&quot; rel=&quot;nofollow&quot;&gt;Linkswitch TN&lt;/a&gt; devices - these will do exactly what you want with good effficiency and low cost, assuming you don't need isolation.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-16T20:09:03.747" CommentCount="1" />
  <row Id="7954" PostTypeId="2" ParentId="532" CreationDate="2010-12-16T20:11:14.447" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.samtec.com&quot; rel=&quot;nofollow&quot;&gt;Samtec&lt;/a&gt; make every kind of header you can imagine, and have a very good sample service&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-16T20:11:14.447" />
  <row Id="7955" PostTypeId="2" ParentId="7941" CreationDate="2010-12-16T20:16:40.320" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Bartels AutoEngineer&lt;/strong&gt; - Light: 159EUR; Econ.: 2690EUR; Prof.: 6490EUR; High-End: 15kEUR+&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Microsoft Windows, Linux and various X11/Unix systems.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;PDF output with symbol/part notes&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;separate autorouter&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;hierarchically structured, including schematics and parts&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;copies libraries to local project, but maintains link&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;default menu seems cruddy, and must be customized for it to work for you&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Did everything and more than I expected while allowed to use it a year ago&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-16T20:16:40.320" CommentCount="2" />
  <row Id="7956" PostTypeId="1" CreationDate="2010-12-16T21:09:25.510" Score="6" ViewCount="290" Body="&lt;p&gt;I'm searching for a low power system-on-chip that combines:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A processor (any achitecture)&lt;/li&gt;&#xA;&lt;li&gt;A radio (any frequency/bitrate/tx power)&lt;/li&gt;&#xA;&lt;li&gt;2 or more I/O pins (ADC would be a bonus)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Can anyone recommend a device?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which chip companies should I be looking at?&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-30T01:28:59.213" Title="Low power radio + microcontroller recommendation?" Tags="&lt;microcontroller&gt;&lt;radio&gt;&lt;low-power&gt;&lt;system-on-chip&gt;" AnswerCount="11" CommentCount="2" FavoriteCount="4" />
  <row Id="7957" PostTypeId="2" ParentId="7920" CreationDate="2010-12-16T21:13:11.140" Score="0" ViewCount="" Body="&lt;p&gt;Disassemble case, rinse with warm water, then dry it in a warm place. Repeat if keys are still stuck.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At least that's what I did after I spilled a glass of white wine into a keyboard 15 years ago. After the first cleaning the down arrow key was still sticking sometimes. After the second cleaning it worked perfectly again.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-12-16T21:13:11.140" />
  <row Id="7958" PostTypeId="2" ParentId="7956" CreationDate="2010-12-16T21:17:01.837" Score="1" ViewCount="" Body="&lt;p&gt;Nordic Semi and TI.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-16T21:17:01.837" CommentCount="1" />
  <row Id="7959" PostTypeId="2" ParentId="7956" CreationDate="2010-12-16T21:21:48.527" Score="4" ViewCount="" Body="&lt;p&gt;I've only read up on &lt;strong&gt;Atmel&lt;/strong&gt;'s stuff. They have the &lt;strong&gt;ZigBee&lt;/strong&gt; line, &lt;a href=&quot;http://www.atmel.com/products/zigbee/single-chip.asp?family_id=676&quot; rel=&quot;nofollow&quot;&gt;with system-on-chip solutions&lt;/a&gt;: &lt;em&gt;ATmega128RFA1&lt;/em&gt;. It has a 10-bit 330kS/s ADC, analog comparator, on-chip temp. sensor, &amp;lt;250nA sleep, max 14.5mA for Tx.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=4692&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/products/product_card.asp?part_id=4692&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-16T21:21:48.527" />
  <row Id="7960" PostTypeId="2" ParentId="7927" CreationDate="2010-12-16T21:23:45.333" Score="3" ViewCount="" Body="&lt;p&gt;As I understand it, you're looking for a device which can monitor a serial port and send SMS messages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The list of devices you gave are roughly in descending order of price, so I would guess that you want low cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some ideas (substitute Arduino for your favourite microcontroller board):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/products/9950&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; ($30) + &lt;a href=&quot;http://www.sparkfun.com/products/9607&quot; rel=&quot;nofollow&quot;&gt;Cellular shield&lt;/a&gt; ($100)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/products/9950&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; ($30) + &lt;a href=&quot;http://www.sparkfun.com/products/757&quot; rel=&quot;nofollow&quot;&gt;Telit GM862&lt;/a&gt; ($100) (&lt;a href=&quot;http://tinkerlog.com/2009/05/15/interfacing-arduino-with-a-telit-gm862/&quot; rel=&quot;nofollow&quot;&gt;example&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/products/9950&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; ($30) + old mobile phone with data interface ($free?) (&lt;a href=&quot;http://blog.makezine.com/archive/2009/01/sserial2mobile_sms_library_for_ardu.html&quot; rel=&quot;nofollow&quot;&gt;Arduino library&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you have a broadband connection at the remote site:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/products/9950&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; ($30) + &lt;a href=&quot;http://www.sparkfun.com/products/9026&quot; rel=&quot;nofollow&quot;&gt;Ethernet shield&lt;/a&gt; ($46) (&lt;a href=&quot;http://code.google.com/p/arduino/source/browse/trunk/libraries/Ethernet/examples/TelnetClient/TelnetClient.pde?r=1093&quot; rel=&quot;nofollow&quot;&gt;telnet example&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-16T21:23:45.333" />
  <row Id="7961" PostTypeId="2" ParentId="7941" CreationDate="2010-12-16T21:23:58.073" Score="1" ViewCount="" Body="&lt;p&gt;Pulsonix is excellent, I've used it for years. It starts at $3,000. I run the users group and we have lots of former PCAD users.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-16T21:23:58.073" CommentCount="1" />
  <row Id="7962" PostTypeId="2" ParentId="7956" CreationDate="2010-12-16T21:26:07.853" Score="7" ViewCount="" Body="&lt;p&gt;I would suggest a TI product. The MSP430, a low power microcontroller, combined with their transceiver line gives you:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ti.com/corp/docs/landing/cc430/index.htm?DCMP=D_MCU_MSP430&amp;amp;CMP=KNC-GoogleTI&amp;amp;247SEM&quot; rel=&quot;nofollow&quot;&gt;The CC430&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These chips can be very very effective. I currently use the CC1100 and the MSP430 and we have been wanting to make a hardware revision to switch to one of these very tiny SoC. They have AES support in most of them. TI has a zigbee stack available also, allowing you to plug-n-play-n-sell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will get many extra pins, ADC, SPI/I2C, UART. These chips can be the core of an overall system and add transceiver. &lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-16T22:03:44.810" LastActivityDate="2010-12-16T22:03:44.810" CommentCount="6" />
  <row Id="7963" PostTypeId="2" ParentId="7956" CreationDate="2010-12-16T21:26:59.600" Score="0" ViewCount="" Body="&lt;p&gt;For the radio &lt;a href=&quot;http://www.digi.com/products/wireless/point-multipoint/xbee-series1-module.jsp#overview&quot; rel=&quot;nofollow&quot;&gt;XBee&lt;/a&gt; should be easy to use. It appears to your uC as a UART, so basically TxD and RxD are all you need.&lt;br&gt;&#xA;Microcontroller can be anything as long as it has this serial connection, which will be true for most controllers these days.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-16T21:26:59.600" CommentCount="5" />
  <row Id="7964" PostTypeId="1" AcceptedAnswerId="7969" CreationDate="2010-12-16T21:55:27.953" Score="2" ViewCount="277" Body="&lt;p&gt;This is a problem that's always baffled me a bit. How does high frequency(more than 100mhz anyway) wireless communication actually work? I understand that it has an antennae and for receiving it amplifies it and checks for a logical 1 or 0 and reversed for transmitting. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I do not understand is how an IC can communicate at such speeds? Take for example wifi, 2.4Ghz. Is there a chip that is actually processing each bit 2.4 billion times per second? That seems impossible. Could someone explain how a transmitter and a receiver actually work electrically? &lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2010-12-17T05:04:58.860" Title="How does wireless communication work?" Tags="&lt;wireless&gt;" AnswerCount="4" />
  <row Id="7965" PostTypeId="1" AcceptedAnswerId="7968" CreationDate="2010-12-16T21:58:54.793" Score="1" ViewCount="317" Body="&lt;p&gt;So I am attempting to tie a real time clock (&lt;a href=&quot;http://pdfserv.maxim-ic.com/en/ds/DS1302.pdf&quot; rel=&quot;nofollow&quot;&gt;DS1302&lt;/a&gt;) into an Arduino and then eventually a AVR chip directly. From all of the schematics I have seen, it appears a crystal is required. I read through the datasheet (above) and did not get the feeling you can run the chip without one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I mistaken? I hope so as I would just like to hook this up to the Arduino and also have a coin cell battery back it up. Does this IC require a crystal or does it have its own built on board?&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-12-17T13:49:27.347" LastActivityDate="2010-12-17T13:49:27.347" Title="DS1302 Real Time Clock Question" Tags="&lt;arduino&gt;&lt;timer&gt;&lt;timing&gt;&lt;rtc&gt;" AnswerCount="2" />
  <row Id="7966" PostTypeId="2" ParentId="7956" CreationDate="2010-12-16T22:00:58.497" Score="1" ViewCount="" Body="&lt;p&gt;If you just need a couple I/O, ANT's SensrCore might be all you need.  It's essentially a prefab 2.4GHz module or chipset that can be set up to read a few pins and report on them over the radio:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marketing speak: &lt;a href=&quot;http://www.thisisant.com/technology/sensrcore&quot; rel=&quot;nofollow&quot;&gt;http://www.thisisant.com/technology/sensrcore&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.thisisant.com/images/Resources/PDF/1199920257_esc%20boston%202007.ppt.pdf&quot; rel=&quot;nofollow&quot;&gt;Powerpoint presentation&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.thisisant.com/images/Resources/PDF/1186013376_ant%20sensrcore%20messaging%20and%20usage.pdf&quot; rel=&quot;nofollow&quot;&gt;Datasheet&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-16T22:00:58.497" />
  <row Id="7967" PostTypeId="2" ParentId="7964" CreationDate="2010-12-16T22:02:18.397" Score="0" ViewCount="" Body="&lt;p&gt;100 mHz is the carrier frequency, not the data transmission rate. A modulation of the carrier frequency is what carries the data. AM radio varies the amplitude of the signal to modulate it. FM varies the frequency slightly from the carrier frequency. FSK is phase shift keying. It change the phase of the carrier signal. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A modulator tasks the data and applies modulation to the carrier to send it. A demodulator receives the carrier and separates the modulation from it extracting the data.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2010-12-16T22:02:18.397" />
  <row Id="7968" PostTypeId="2" ParentId="7965" CreationDate="2010-12-16T22:08:51.497" Score="2" ViewCount="" Body="&lt;p&gt;Yep, it needs a 32768 Hz crystal clock.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The DS1302 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or capacitors to operate.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://pdfserv.maxim-ic.com/en/an/AN58.pdf&quot; rel=&quot;nofollow&quot;&gt;App. Note 58: Crystal Considerations with Dallas Real-Time Clocks (RTCs)&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-16T22:08:51.497" />
  <row Id="7969" PostTypeId="2" ParentId="7964" CreationDate="2010-12-16T22:21:11.033" Score="6" ViewCount="" Body="&lt;p&gt;The important thing to note here is carrier frequency and modulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2.4GHz is your carrier frequency, in modern modulation formats it is going to be in the air at all times. The transmitter radiates the entire time you are sending the signal.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; How is the data actually sent?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Phase-shift_keying&quot; rel=&quot;nofollow&quot;&gt;Phase modulation&lt;/a&gt; is the most common method. You can think about what is happening very clearly, on a set timer you are going to either change phase or not. &lt;a href=&quot;http://en.wikipedia.org/wiki/Phase-shift_keying&quot; rel=&quot;nofollow&quot;&gt;Wikipedia has a good graph of QPSK&lt;/a&gt;, where you are actually sending two signals at the same time out of phase and each one encodes a bit.&#xA;&lt;img src=&quot;http://i.imgur.com/iv9xc.png&quot; alt=&quot;Picture of QPSK from :http://upload.wikimedia.org/wikipedia/commons/b/be/QPSK_timing_diagram.png&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This may look a little confusing, but you see whenever they change what bit they are sending there is a sudden shift in the signal. PSK has the lowest bit-error rate of the different modulation techniques for the same baud rate. This means that for the same allowable bit-error rate you have the highest link speed with PSK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope the image allows you to understand what is going on behind the scenes. Let me know if I can post more to help make this understandable.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;What hardware does this?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;This section I am keeping short because there are many different ways to approach this with hardware. The circuit that allows most ICs to do internal TX or RX  comes from the &lt;a href=&quot;http://en.wikipedia.org/wiki/Gilbert_cell&quot; rel=&quot;nofollow&quot;&gt;gilbert cell&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;When to do it?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;If you modulate to the correct frequency directly before radiating and demodulate directly before receiving the signal your circuit deals with everywhere else is going to be a slower speed signal that is digital and your circuit can deal with.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-17T04:24:24.680" LastActivityDate="2010-12-17T04:24:24.680" CommentCount="4" />
  <row Id="7970" PostTypeId="2" ParentId="7956" CreationDate="2010-12-16T22:22:13.790" Score="1" ViewCount="" Body="&lt;p&gt;Freescale has the &lt;a href=&quot;http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MC13213&quot; rel=&quot;nofollow&quot;&gt;MC13213&lt;/a&gt; and &lt;a href=&quot;http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MC13233&quot; rel=&quot;nofollow&quot;&gt;13233&lt;/a&gt; SOC systems which combine a ZigBee radio with an HCS08 microcontroller.  The MC13213 has 60 KB Flash and 4KB RAM memory and sells for around $3.50 in 1K quantities.  8-channel, 10-bit ADC and lots of I/O pins.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2010-12-16T22:45:39.817" LastActivityDate="2010-12-16T22:45:39.817" />
  <row Id="7971" PostTypeId="2" ParentId="7940" CreationDate="2010-12-16T23:06:00.933" Score="2" ViewCount="" Body="&lt;p&gt;Going with @markranges' suggestion, &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=102-1573-ND&quot; rel=&quot;nofollow&quot;&gt;here's one at Digi-Key&lt;/a&gt; that does 85-264 V AC 110-340V DC in and 12 V, 420 mA out.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-17T17:36:16.540" LastActivityDate="2010-12-17T17:36:16.540" />
  <row Id="7972" PostTypeId="2" ParentId="7850" CreationDate="2010-12-16T23:09:27.137" Score="2" ViewCount="" Body="&lt;p&gt;If you are considering &lt;code&gt;malloc()&lt;/code&gt; and &lt;code&gt;free()&lt;/code&gt; for your embedded software I suggest you take a look at uC/OS-II and &lt;code&gt;OSMemGet()&lt;/code&gt; and &lt;code&gt;OSMemPut()&lt;/code&gt;. While &lt;code&gt;malloc()&lt;/code&gt; let you allocate an arbitrary block of memory, &lt;code&gt;OSMem*()&lt;/code&gt; give you a fixed-sized block from a pre-allocated pool. I find this approach a good balance between the flexibility of &lt;code&gt;malloc()&lt;/code&gt; and the robustness of static allocation.&lt;/p&gt;&#xA;" OwnerUserId="1627" LastActivityDate="2010-12-16T23:09:27.137" />
  <row Id="7973" PostTypeId="2" ParentId="7964" CreationDate="2010-12-16T23:18:50.470" Score="2" ViewCount="" Body="&lt;p&gt;While I'll dodge the modulation question, I'm fairly well acquainted with the IC side of things. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;How can a IC communicate at speeds greater than 100MHz?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll start with a simple case. Intel has designed a processor that operates at a clock frequency of 3.8GHz. This is performing multiple logic operations and storing the results each cycle. Thus, not only can signals be processed at 2.4GHz+, your computer probably does this already. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason for this is that transistors on a IC are FAST! In a 130nm SiGe BiCMOS process, the unity gain frequency is listed as &lt;a href=&quot;http://cmp.imag.fr/products/ic/?p=STBiCMOS9MW&quot; rel=&quot;nofollow&quot;&gt;230GHz.&lt;/a&gt; I figure that I could make a circuit that works at least 5-10% of that value, and this isn't even a leading edge process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you wanted to maximize the serial clock rate, you could use a circuit called a De-Serializer, which is basically a high frequency shift register. You would need the very high frequency circuitry for the input, and then convert it into a parallel format at a lower data rate. This is commonly used in high speed protocols like HDMI.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-16T23:18:50.470" CommentCount="5" />
  <row Id="7974" PostTypeId="1" CreationDate="2010-12-16T23:29:12.310" Score="0" ViewCount="232" Body="&lt;p&gt;I'm currently coding .Net WCF code to port a work project from &quot;in Proc&quot; to a WCF SOA rather than (my?) usual .Net Remoting solution. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I got to thinking about Netduino as a WCF endpoint (not for work but for me) for the &quot;cloud&quot; or any other SO client. Some very shallow research indicates that .Net Micro Frameworks supports WCF (assuming there is a good (large!) memory footprint).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the question is has anyone experimented with .Net micro frameworks and WCF (with or without the &quot;cloud&quot;)? - caveats welcome - many thanx&lt;/p&gt;&#xA;" OwnerUserId="2243" LastEditorUserId="2243" LastEditorDisplayName="" LastEditDate="2010-12-16T23:44:26.843" LastActivityDate="2011-05-17T02:44:06.187" Title="WCF / Netduino and &quot;the cloud&quot;" Tags="&lt;netduino&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="7975" PostTypeId="1" AcceptedAnswerId="7976" CreationDate="2010-12-17T03:33:43.937" Score="4" ViewCount="199" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have run into a problem where I believe my stack is overflowing. The reason I am inclined to think this way, is due to the following:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Compile code, dump into the device: - no activity from the device (I am expecting an 'I am alive' message)&lt;br&gt;&#xA;2) In this situation, I increased the stack size by 10 bytes, recompiled and dumped to the device, and the problem went away.&lt;br&gt;&#xA;3) Tried the above two steps 10 times, back and forth, and can reproduce the problem reliably, and fix it reliably.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to see the stack falling over, how do I do this? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am currently using an M16 Microcontroller, with 2K RAM (30 bytes left), 256 Bytes Stack size. &#xA;The IAR Workbench that I am using, does not have the call graph utility.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there other ways to do this - check the stack falling over and by how much in code?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help will really be appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1785" LastEditorUserId="1785" LastEditorDisplayName="" LastEditDate="2010-12-17T21:58:35.883" LastActivityDate="2010-12-17T21:58:35.883" Title="How to check for Stack overflow in an embedded application?" Tags="&lt;embedded&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="3" />
  <row Id="7976" PostTypeId="2" ParentId="7975" CreationDate="2010-12-17T03:53:10.670" Score="5" ViewCount="" Body="&lt;p&gt;A common way to check for memory usage is to prefill memory with a constant value before your program runs.  eg a sequence of 0xde 0xad could be written out to your stack area by your startup code.  During the program's operation, the stack will grow and write over these sequences.  If you then have the ability to examine memory, then you can easily see the untouched 0xde 0xad bytes in memory and so determine how much stack has been used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's usually hard to detect an overflow as it occurs since function call return addresses are stored on the stack and any function return will send the program off into the weeds.  In this case, if your watchdog is enabled and you can set a breakpoint at the reset vector, you may still be able to examine the memory and look for your prefill bytes to determine if this is what has caused a reset.&lt;/p&gt;&#xA;" OwnerUserId="2308" LastActivityDate="2010-12-17T03:53:10.670" CommentCount="3" />
  <row Id="7977" PostTypeId="2" ParentId="7964" CreationDate="2010-12-17T05:04:58.860" Score="3" ViewCount="" Body="&lt;p&gt;While there are some special exceptions, most radio communication is usually achieved with the aid of upconversion and downconversion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, a transmitter starts with a circuit for modulating information (be it voice or data) onto a signal of conveniently low frequency that is easy to work with - a few tens or hundreds of kilohertz for narrowband applications, often somewhere between 10 and 45 MHz for wider band ones.  At these frequencies analog circuits work well, or one can actually use a D/A converter at the output of a DSP that does the modulation mathematically.  (For data rates higher than a &quot;DSP chip&quot; can handle, parallel logic in an ASIC or FPGA is used, so each individual path may only have to calculate every 8th or 32nd or whatevereth sample needed by the DA).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The transmitter also contains an oscillator or synthesizer for generating a signal closer to the desired transmitter frequency, and a mixer which multiplies the two signals together, causing generation of sum and difference frequencies.  Either the sum or the difference will be the desired transmission frequency, and is selected by a filter, amplified and sent to the antenna.  (Occasionally multiple stages of conversion are needed)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The receiver works the same way, only in reverse.   A local oscillator signal is subtracted from the amplified antenna signal (or the other way around), creating an intermediate difference frequency that is back down in the range more convenient to work with (In AM broadcast receivers, typically 455 KHz - for FM, traditionally 10.7 KHz and then converted down againto to 455 KHz, though today staying at 10.7 MHz works too).  This intermediate frequency can be processed by a demodulator circuity, or digitized in a fast A/D converter and fed into a potentially parallel DSP to complete the process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the desired bandwidth of data to be transmitted is less than about 10 KHz, one can actually use a computer soundcard to make a high performance receiver or transmitter, by positioning the intermediate frequency at say 10 KHz and using software to process a bandwidth spanning 5-15 KHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Today a common technique is to exploit some properties of complex numbers, and do the modulation/demodulation balanced around a center frequency of 0, such that it contains both positive and negative frequencies.  By using two phases of the oscillator and something called an image reject mixer, one of the two resulting frequencies cancels and the other reinforces.  However, two D/A or A/D converters are needed - one for the &quot;I&quot; phase and the other for the &quot;Q&quot;.  You can sort of do this with a stereo soundcard, though the DC blocking caps will create a hole in the passband right in the middle, at what gets converted to 0 frequency.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2010-12-17T05:04:58.860" />
  <row Id="7978" PostTypeId="2" ParentId="7956" CreationDate="2010-12-17T05:21:53.277" Score="3" ViewCount="" Body="&lt;p&gt;I am very familiar with the MC13224V chip from Freescale Semiconductor. What's nice about it is that the balun and matching components are on chip, so all you need to do is supply a 50 ohm antenna. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use the development boards from Redwire LLC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://redwirellc.com/store/node/1&quot; rel=&quot;nofollow&quot;&gt;http://redwirellc.com/store/node/1&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2010-12-17T05:21:53.277" />
  <row Id="7979" PostTypeId="1" AcceptedAnswerId="7981" CreationDate="2010-12-17T05:37:54.660" Score="8" ViewCount="269" Body="&lt;p&gt;Ok, so I recently have been seeing the name XMOS appear in places. I've looked on their website and searched online but I can't quite figure out what it is? So what is it? It appears to be a cross between a microcontroller and an FPGA? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also looked on &lt;a href=&quot;http://xmos.com&quot; rel=&quot;nofollow&quot;&gt;their site&lt;/a&gt; and I wasn't able to see anything I could understand (just example designs and other reference documents) for what XMOS is and what is different about it from other microcontroller lines. &lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-05-16T06:39:13.430" Title="What is the XMOS series?" Tags="&lt;microcontroller&gt;&lt;fpga&gt;&lt;xmos&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="7980" PostTypeId="2" ParentId="7979" CreationDate="2010-12-17T05:43:38.727" Score="0" ViewCount="" Body="&lt;p&gt;XMOS is a powerful, multicore, 32bit microcontroller. There is no FPGA involved, but they go great together.&lt;/p&gt;&#xA;" OwnerUserId="1134" LastActivityDate="2010-12-17T05:43:38.727" />
  <row Id="7981" PostTypeId="2" ParentId="7979" CreationDate="2010-12-17T07:00:00.377" Score="12" ViewCount="" Body="&lt;p&gt;I've got a lot of XMOS hardware. The chips can replace FPGAs and DSPs in a lot of applications, with development being much quicker and cheaper. They are mainly programmed in XC (a superset of C intended for parallel processing), C, C++ and assembler. The languages can be mixed in the same application. Other programming languages are becoming available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are basically very fast multicore controllers, with up to eight hardware threads per 400 MIPS core, operating in round-robin fashion. Each thread can run at 50 or 100 MIPS, and can be thought of as a separate processor. The four-core device thus offers up to 32 threads, delivering a total of 1600 MIPS. Threads, cores and chips communicate via very fast  communication channels, making it very easy to design parallel processing systems using arbitrary numbers of chips. Peripherals like UARTs, SPI etc. are implemented in software. They are fast enough to handle high-speed (480 MBit/s) USB and 100 MHz Ethernet in software. Single-core, dual-core, and four-core devices are available with 64 I/Os per core. On-chip RAM is 64k per core.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Killer applications include those massive LED displays used at sporting arenas, where FPGAs have been used up to now. They typically use hundreds of XMOS chips, one per display tile. They are also ideal for high-end robotic applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Board prices start at about 50 dollars for a prototyping board with a single core device. The JTAG interface needed for programming and debugging applications is another 50 dollars. Development software is free. Support is good, via the XMOS web site and a users forum. They are getting popular with hobbyists.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A new $7 XS1-L01A-TQ48 device is now in production. They are listed on Digi-Key.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-12T13:01:49.707" LastActivityDate="2011-05-12T13:01:49.707" CommentCount="3" />
  <row Id="7982" PostTypeId="2" ParentId="7956" CreationDate="2010-12-17T07:27:49.803" Score="1" ViewCount="" Body="&lt;p&gt;Jeelabs.com  -- Try the &lt;strong&gt;JeeNode&lt;/strong&gt;&#xA;17.5eur with RF included, has adc included also&#xA;used it happily for some time now&#xA;there are very good developed libraries for low power usage (it can even run on 1AAA battery)&lt;/p&gt;&#xA;" OwnerUserId="2245" LastActivityDate="2010-12-17T07:27:49.803" CommentCount="3" />
  <row Id="7983" PostTypeId="2" ParentId="4222" CreationDate="2010-12-17T09:00:24.267" Score="1" ViewCount="" Body="&lt;p&gt;Here is what I had answered you on stackoverflow: don't know if you had read this answer: &lt;a href=&quot;http://stackoverflow.com/questions/3583472/how-to-enable-and-configure-usb-otg-for-device-mode-on-imx31-litekit/3600203#3600203&quot;&gt;answer&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1099" LastActivityDate="2010-12-17T09:00:24.267" />
  <row Id="7984" PostTypeId="2" ParentId="7979" CreationDate="2010-12-17T10:13:01.500" Score="0" ViewCount="" Body="&lt;p&gt;XMOS is an event-driven processor, perhaps check some out their videos&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xmos.com/videos&quot; rel=&quot;nofollow&quot;&gt;http://www.xmos.com/videos&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2315" LastActivityDate="2010-12-17T10:13:01.500" CommentCount="1" />
  <row Id="7985" PostTypeId="1" AcceptedAnswerId="8010" CreationDate="2010-12-17T10:58:31.323" Score="1" ViewCount="144" Body="&lt;p&gt;Hi,&#xA;I'm planning to use a PIC for a MIDI pedal that can be configured from a PC (through USB). Is there a way to do crossplatform (at least mac/windows, better if also linux) USB in userland (or another way to avoid the hassle of writing a device driver)? I know there's libUSB but I want to know if there's a better solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip own drivers are windows-only, if I'm not wrong.&#xA;Thank you.&lt;/p&gt;&#xA;" OwnerUserId="2316" LastActivityDate="2010-12-17T16:50:17.787" Title="Pic-PC (Crossplatform) USB interfacing without writing custom drivers." Tags="&lt;pic&gt;&lt;usb&gt;&lt;driver&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="7986" PostTypeId="1" AcceptedAnswerId="7989" CreationDate="2010-12-17T11:09:51.820" Score="1" ViewCount="127" Body="&lt;p&gt;I've got a spare battery for my cell phone. I'm wondering what the correct way to store it would be, so as to maximize the battery time. Should I recharge the battery to 100%, then leave it aside, or should I use about 20-30% of the battery before putting it aside?&lt;/p&gt;&#xA;" OwnerUserId="1999" LastEditorUserId="1999" LastEditorDisplayName="" LastEditDate="2010-12-17T11:42:18.300" LastActivityDate="2010-12-17T14:12:03.600" Title="How to correctly store spare Cell Phone Battery?" Tags="&lt;battery&gt;&lt;cellphone&gt;&lt;storage&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="7987" PostTypeId="2" ParentId="7975" CreationDate="2010-12-17T11:21:19.857" Score="0" ViewCount="" Body="&lt;p&gt;There are some programs that can do statically analysis. You can get some information using &lt;a href=&quot;http://www.splint.org/&quot; rel=&quot;nofollow&quot;&gt;Splint&lt;/a&gt;, as it check for problems using your source code. I think it does not check for stack problems, but can give you some insights on the problem.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2010-12-17T11:21:19.857" />
  <row Id="7988" PostTypeId="2" ParentId="7965" CreationDate="2010-12-17T11:33:39.377" Score="3" ViewCount="" Body="&lt;p&gt;Few RTC ICs have a crystal integrated in their package. The crystal is always a &quot;watch crystal&quot; of 32.768Hz, and these are too big to place inside a SOIC-8 package many RTCs appear in. Hence the crystal is external. (The Maxim DS32kHz, a 32.768 kHz oscillator with integrated crystal comes in a 16-pin package, despite that only 4 pins are used.)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally the crystal is connected to two pins of the RTC, with a capacitor on each pin to ground (a Pierce oscillator configuration). Because the DS1302 has a separate pin for the battery, one pin for the crystal had to be sacrificed, and the crystal is directly connected to ground. It looks to me that you loose the possibility to trim the crystal frequency this way, as the load capacitor is integrated.&lt;br&gt;&#xA;You may want to trim the oscillator however, because even a 20ppm crystal results in an error of a minute a month, see &lt;a href=&quot;http://electronics.stackexchange.com/questions/7800/real-time-clock-and-crystal-precision&quot;&gt;this discussion&lt;/a&gt;. I don't know how attached you are to the Maxim RTC, but for instance NXP has the &lt;a href=&quot;http://www.nxp.com/documents/data_sheet/PCF8563.pdf&quot; rel=&quot;nofollow&quot;&gt;PCF8563&lt;/a&gt;, which has the classic Pierce layout.  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-17T12:10:02.277" LastActivityDate="2010-12-17T12:10:02.277" />
  <row Id="7989" PostTypeId="2" ParentId="7986" CreationDate="2010-12-17T11:47:26.667" Score="3" ViewCount="" Body="&lt;p&gt;This Battery University &lt;a href=&quot;http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries&quot; rel=&quot;nofollow&quot;&gt;page&lt;/a&gt; recommends you store them at 40% charge.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-17T11:47:26.667" CommentCount="4" />
  <row Id="7990" PostTypeId="1" AcceptedAnswerId="8004" CreationDate="2010-12-17T11:51:51.097" Score="1" ViewCount="119" Body="&lt;p&gt;I've noticed that if I recharge my cell phone battery to 100%, then take it out, and put it back in and put the phone back on charging, it resumes charging the battery and continues to do this for upto 30 mins, despite having just received a 'battery full' message about 30 minutes ago. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why does this happen? Is this normal or does this indicate that the battery is degrading?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a Li-Ion battery.&lt;/p&gt;&#xA;" OwnerUserId="1999" LastEditorUserId="1999" LastEditorDisplayName="" LastEditDate="2010-12-17T11:58:35.113" LastActivityDate="2010-12-17T19:49:12.017" Title="Could my Cell Phone Battery be degrading?" Tags="&lt;battery&gt;&lt;cellphone&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="7992" PostTypeId="1" AcceptedAnswerId="8003" CreationDate="2010-12-17T12:15:17.603" Score="3" ViewCount="387" Body="&lt;p&gt;If I leave my cell phone with the charger plugged in all the time, would this weaken the batter, and why? I've heard that you should only charge the cell phone when you receive a 'battery low' message and leave it off the charger at other times?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The cell phone has got a Li-Ion battery.&lt;/p&gt;&#xA;" OwnerUserId="1999" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-17T13:38:33.403" LastActivityDate="2010-12-17T15:39:44.430" Title="Does leaving a cell phone on charge all the time weaken the battery, and why?" Tags="&lt;battery&gt;&lt;cellphone&gt;" AnswerCount="1" CommentCount="6" FavoriteCount="1" />
  <row Id="7993" PostTypeId="1" AcceptedAnswerId="7994" CreationDate="2010-12-17T13:03:32.113" Score="4" ViewCount="223" Body="&lt;p&gt;The Below is a H-Bridge Schematic from this site: &lt;a href=&quot;http://www.societyofrobots.com/schematics_h-bridgedes.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.societyofrobots.com/schematics_h-bridgedes.shtml&lt;/a&gt;. Wouldn't the 10-100nF cap be rendered useless by the 10000 uf cap? Wouldn't the caps just have a equivalent capacitance of 10000 uf + 10-100nf  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/DMFul.jpg&quot; alt=&quot;&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1337" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2010-12-17T15:37:29.857" LastActivityDate="2010-12-27T13:56:17.213" Title="Cap's on H-Bridge... Seem a bit redundant?" Tags="&lt;capacitor&gt;&lt;h-bridge&gt;&lt;decoupling-capacitor&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="7994" PostTypeId="2" ParentId="7993" CreationDate="2010-12-17T13:07:54.617" Score="13" ViewCount="" Body="&lt;p&gt;Large capacity electrolytic capacitors are very bad at high frequencies, where their inductive behavior becomes stronger than their capacitance. This means that due to the capacitance the impedance decreases to a certain frequency, from where it starts to rise again. For those higher frequencies you need a smaller capacitor, which doesn't show this inductive behavior.&lt;br&gt;&#xA;The impedance curve below is for a typical 1000uF elco  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/3YS4N.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-27T13:56:17.213" LastActivityDate="2010-12-27T13:56:17.213" CommentCount="2" />
  <row Id="7995" PostTypeId="2" ParentId="7993" CreationDate="2010-12-17T13:09:53.850" Score="10" ViewCount="" Body="&lt;p&gt;The smaller capacitor is able to filter out higher frequency noise that the large capacitor is unable to. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This has to do with the non-ideal aspects of capacitor, mostly their internal inductance and resistance.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-17T13:09:53.850" CommentCount="1" />
  <row Id="7996" PostTypeId="1" AcceptedAnswerId="8005" CreationDate="2010-12-17T13:33:00.253" Score="3" ViewCount="103" Body="&lt;p&gt;It's becoming quite frequent to me having a new digital subsystem which I want to test in isolation before trying to make a prototype circuit. I've been using the digital analyzer by Saleae for inputs, which is quite handy, but I'm wondering if I could find or build its counterpart. Ideally it would be a device to plug in an USB port, would have many digital outputs (let's say 20 or more) and would come with software that would enable me to do a playback from a prerecorded file, or generate the output with a program or script.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know about such a product, or have guidelines to build on my own?&lt;/p&gt;&#xA;" OwnerUserId="1078" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-17T21:31:27.323" LastActivityDate="2010-12-17T21:31:27.323" Title="Recommendation for a USB digital simulator" Tags="&lt;prototyping&gt;&lt;output&gt;&lt;logic-analyzer&gt;&lt;pattern-generator&gt;" AnswerCount="3" />
  <row Id="7997" PostTypeId="2" ParentId="7986" CreationDate="2010-12-17T14:12:03.600" Score="3" ViewCount="" Body="&lt;p&gt;The answer to this would be impacted by how often you swap the batteries, i.e. how long do you store them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use a battery until it is dead, then put in the fresh one, while the now-used one is put in a charger, then I would not consider this &lt;em&gt;storage&lt;/em&gt; at all, but merely normal use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you usually use just the one battery, and have a second for emergencies, then @Thomas answer makes more sense.&lt;/p&gt;&#xA;" OwnerUserId="2117" LastActivityDate="2010-12-17T14:12:03.600" CommentCount="1" />
  <row Id="7998" PostTypeId="2" ParentId="7996" CreationDate="2010-12-17T14:52:27.343" Score="1" ViewCount="" Body="&lt;p&gt;This sounds like a crude definition of a microcontroller. It has &lt;a href=&quot;http://en.wikipedia.org/wiki/General_Purpose_Input/Output&quot; rel=&quot;nofollow&quot;&gt;GPIOs&lt;/a&gt; and can fetch instructions from memory. Hardware requirements are based on the following:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;memory: How much &lt;em&gt;playback&lt;/em&gt; do you need? The Salae uses 10bit samples at up to 24MHz, or 30MB/s (also the single channel USB 2.0 limit). You may require external memory modules to support long traces. This can be done directly from USB, with minimal on-board memory, and would depend on your computer's USB bandwidth, like the Salae does. If you're using both at once your computer's USB controller may reach its limit. I wouldn't want to depend on this.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;IO speed: Producing multiple 10-bit 24MHz patterns is no small feat. Look for chips with many hardware PWM modules. You may need to use multiple slave PWM chips. How much greater the clock speed must be than the PWM frequency depends on the chip family.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;noise: On a 5V digital system, an 8-bit LSB is about 20mV and a 10-bit LSB is about 5mV. For these bits to be effective your noise level must be below that. This will be important when running so many parallel conductors, all with 24MHz digital* signals. Although this speed is not high, it can have &gt;20mV crosstalk if traces are coupled. I don't think special drivers (bipolar, etc.) or EMI protection is required - just space them out.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;USB: Look for hardware USB support, or go with an external FDTI chip. It can be done in software as well, and is an option at least for M3s and XMOS, but keep in mind it reduces thread slices for your PWM memory fetching, etc., especially if it is being used to fetch PWM data from USB (limited on-board memory).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Possibilities include the PIC24 family, &lt;a href=&quot;http://www.xmos.com/products/development-kits/usbaudio2mc&quot; rel=&quot;nofollow&quot;&gt;XMOS&lt;/a&gt;, and many of the ARM family. There are some great parametric tables out there: &lt;a href=&quot;http://uk.rs-online.com/web/compChooser/compChooserAction.html?method=retrieveTfg&amp;amp;intialAttributePageFlag=Y&amp;amp;Ne=4294957561&amp;amp;N=4294611773&quot; rel=&quot;nofollow&quot;&gt;RS&lt;/a&gt;, &lt;a href=&quot;http://www.microchip.com/productselector/MCUProductSelector.html&quot; rel=&quot;nofollow&quot;&gt;Microchip&lt;/a&gt;. It would be worth getting to know the differences between ARM implementations to see if one will do everything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that you may also want to drop to 8-bit PWM, as you could then lower your hardware requirements.&#xA;*Yes, they are analog, but they're also a recording of a digital signal. Hopefully they appear so.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-17T14:52:27.343" CommentCount="2" />
  <row Id="7999" PostTypeId="2" ParentId="7975" CreationDate="2010-12-17T15:15:50.537" Score="2" ViewCount="" Body="&lt;p&gt;Create a variable that is located at the top (or bottom) of your stack.  Initialize the variable at the beginning of main.  You can check the value of the variable in the main loop to see after-the-fact that the stack has overflowed.  Or if your debugger allows, set a breakpoint when that variable is written.  It should be written only when it is initialized.  &lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-12-17T15:15:50.537" />
  <row Id="8000" PostTypeId="1" AcceptedAnswerId="8006" CreationDate="2010-12-17T15:30:39.493" Score="3" ViewCount="142" Body="&lt;p&gt;As you can probably tell from the question I am a beginner in the embedded world. The extent of my experience is some playing around with C and assembly using the Arduino. I'd like to make the jump to the more complex embedded chips that use surface mount device package types rather than through hole device package types. How does one integrate them into an amateur project?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there breakout boards or CPU sockets for them? I was particularly thinking about Motorola ColdFire devices or ARM Cortex M3 devices. Apologies for the question but I'm somewhat lost by the vast array of devices on offer and just need a starting point really.&lt;/p&gt;&#xA;" OwnerUserId="441" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T23:49:54.607" LastActivityDate="2011-02-08T23:49:54.607" Title="How to use multiple terminal surface mount chips in amateur project?" Tags="&lt;surface-mount&gt;&lt;ic&gt;" AnswerCount="2" />
  <row Id="8001" PostTypeId="1" AcceptedAnswerId="8002" CreationDate="2010-12-17T15:34:20.890" Score="2" ViewCount="225" Body="&lt;p&gt;If I put 3 1MΩ resistors in series, is that the equivalent of one 3MΩ resistor?&lt;/p&gt;&#xA;" OwnerUserId="2006" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-12-17T15:56:46.040" LastActivityDate="2010-12-18T00:45:58.870" Title="Can I put multiple resistors in series to get higher resistance?" Tags="&lt;resistor&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="8002" PostTypeId="2" ParentId="8001" CreationDate="2010-12-17T15:38:09.917" Score="9" ViewCount="" Body="&lt;p&gt;The short answer: Yes. It's the same.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/x0ROW.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The current through resistors in&#xA;  series stays the same, but the voltage&#xA;  across each resistor can be different.&#xA;  The sum of the potential differences&#xA;  (voltage) is equal to the total&#xA;  voltage. To find their total&#xA;  resistance:&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/N8d3M.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Resistor#Series_and_parallel_resistors&quot; rel=&quot;nofollow&quot;&gt;By Wikipedia&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;But this the ideal value. In the real word, resistors have tolerances and you have take in count. E.g., tolerance of 10%. The final value can vary between 2.7MΩ to 3.3MΩ.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2010-12-17T16:12:02.887" LastActivityDate="2010-12-17T16:12:02.887" CommentCount="1" />
  <row Id="8003" PostTypeId="2" ParentId="7992" CreationDate="2010-12-17T15:39:44.430" Score="6" ViewCount="" Body="&lt;p&gt;All newer phones use Lithium polymer batteries.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Why is it Partially Charged?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;To decrease their aging they are intended to be stored at 40% charge. This means when you receive your phone it should be at 40% charge, otherwise they will have aged your battery for you. (you are probably used to the effects of aging, like a 2 year old phone seeming to have very short battery life). When you get your phone you can use it until it is discharged, but they normally say 'charge it' because people will not notice the partial charge.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Do Not Fully Discharge&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;You should not fully worry about fully discharging, this is superstition to earlier battery technologies. Fully discharging a lithium battery is one of the best ways to make it fail. below a certain charge they will have their overcharge protection circuitry fail and you cannot charge it at all. I have seen studies that show that this makes up more than 75% of &quot;failed&quot; lithium batteries.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Lithium Battery Aging&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Lithium batteries have a set number of charge discharge cycles before they fail. This might be a number like 500 cycles. You actually get more like 1000 cycles if you only discharge to 50% before recharge. Lithiums really do not like a deep discharge, I cannot stress this enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you would like more information about lithium battery technology let me know, I can get you many links, just drop me a comment. I have a few answers on the electronics and robotics stack exchange about it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;H3&gt; Can I leave it plugged in all the time?&lt;/h3&gt;&#xA;Yes, and no. This is very dependent on whom makes your device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, my Lenovo laptop will not apply a charge to the battery unless it is under 97%. When it does charge the battery it charges directly to 100%, then stops until the battery sags below 97%. Many laptops did not do this, on most just applying charge if it is not 100%. This would put the battery through thousands of charge cycles in a week when you are not using the battery. This ages a battery quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your phone maker took the time and paid the extra cash then your phone will stop charging once it reaches full charge and just power the system from the wall outlet. It is significantly more likely that your phone is charging your battery on a short cycle and aging it thoroughly.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Myths&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Some people have some confusion from some of the myths that go about. The primary one is memory. As &lt;a href=&quot;http://batteryuniversity.com/learn/article/memory_myth_or_fact&quot; rel=&quot;nofollow&quot;&gt;Battery University will say, this is mostly extinct, and actually applies to nickel-cadmium batteries&lt;/a&gt;. As was stated in a comment about crystals Battery university has in reference to nickel-cadmium:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;With memory, the crystals grow and conceal the active material from the electrolyte. In advanced stages, the sharp edges of the crystals penetrate the separator, causing high self-discharge or electrical short.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Now, talking about Lithium batteries, which your phone uses, there is even more difference. To quote them battery university directly from their simple guidelines:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries&quot; rel=&quot;nofollow&quot;&gt;Avoid frequent full discharges because this puts additional strain on the battery. Several partial discharges with frequent recharges are better for lithium-ion than one deep one. Recharging a partially charged lithium-ion does not cause harm because there is no memory. (In this respect, lithium-ion differs from nickel-based batteries.) Short battery life in a laptop is mainly cause by heat rather than charge / discharge patterns.&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I understand how this may go against what you have been taught, but I am someone who not only has research this but uses lithium batteries in my day to day work as an engineer.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-17T15:39:44.430" CommentCount="1" />
  <row Id="8004" PostTypeId="2" ParentId="7990" CreationDate="2010-12-17T15:43:11.060" Score="3" ViewCount="" Body="&lt;p&gt;Your battery is degrading from the charging station. The person whom makes your charging station probably expects you will use it before placing it in. They are then pumping a top-off charge into for 30 minutes when, although it did self discharge a little in those couple seconds, it should not get one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is possible the charging station is pumping way too much charge, but I am hoping the system can recognize it is almost done charging and go to slow-charge. From battery university about lithiums:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://batteryuniversity.com/index.php/learn/article/charging_lithium_ion_batteries&quot; rel=&quot;nofollow&quot;&gt;No trickle charge is applied because&#xA;  lithium-ion is unable to absorb&#xA;  overcharge. A continuous trickle&#xA;  charge above 4.05V/cell would causes&#xA;  plating of metallic lithium that could&#xA;  lead to instabilities and compromise&#xA;  safety. Instead, a brief topping&#xA;  charge is provided to compensate for&#xA;  the small self-discharge the battery&#xA;  and its protective circuit consume.&#xA;  Depending on the battery, a topping&#xA;  charge may be repeated once every 20&#xA;  days. Typically, the charge kicks in&#xA;  when the open terminal voltage drops&#xA;  to 4.05V/cell and turns off at a high&#xA;  4.20V/cell.&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;There are phases to charging a lithium battery, as show in this picture:&#xA;&lt;img src=&quot;http://i.imgur.com/2ZGcv.gif&quot; alt=&quot;Battery University Gif from :http://www.batteryuniversity.com/images/partone-12.gif&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have seen charging circuity before, when I have helped students build these, that will start with the heavy current phase and test the voltage, this means that if you unplug and plug in you can degrade the battery significantly.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-17T19:49:12.017" LastActivityDate="2010-12-17T19:49:12.017" CommentCount="7" />
  <row Id="8005" PostTypeId="2" ParentId="7996" CreationDate="2010-12-17T15:45:41.390" Score="3" ViewCount="" Body="&lt;p&gt;The product you're looking for is a digital pattern generator. While &lt;a href=&quot;http://www.movingpixel.com/main.pl?products.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; one is overkill for your specification, it's the one that I'm most familiar with. It'll probably set you back about $12-20k for a full setup. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically their setup is a FPGA hooked up to a bunch of RAM driving 16 logic outputs. It's really fancy because you can set the frequency and output voltage of the module. Cheaper, slower, and less-flexible modules should be available from someone else.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-17T15:45:41.390" CommentCount="2" />
  <row Id="8006" PostTypeId="2" ParentId="8000" CreationDate="2010-12-17T15:51:25.140" Score="7" ViewCount="" Body="&lt;p&gt;For SMD there are adapter boards SMD-to-PTH, like  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/02n4o.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Soldering the parts takes some exercise. You may want parts with a 0.8mm pitch instead of the higher density 0.5mm pitch. The latter you'll find mostly on devices with 48 pins or more.&lt;br&gt;&#xA;The other option is that you design your own boards for which you need an EDA (Elecronic Design Automation) package like &lt;a href=&quot;http://www.cadsoftusa.com/&quot; rel=&quot;nofollow&quot;&gt;Eagle&lt;/a&gt;. This has a free version with limitations, or a full version which has to be payed for. This design has a long learning curve. When you designed stuff this way you have to option of etching your own board or have it produced by a PCB production shop. The latter is the best choice for quality, the DIY is cheaper and faster.&lt;br&gt;&#xA;For starters I recommend the adapter boards I mentioned at the beginning of this answer.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-17T15:51:25.140" />
  <row Id="8007" PostTypeId="2" ParentId="7996" CreationDate="2010-12-17T15:58:49.907" Score="1" ViewCount="" Body="&lt;p&gt;You could program an Arduino with a pretty basic sketch to give you this capability... and you could write a fancy little C# application to do the pattern definition... that would be the easiest imo. That should cost you not more than $30 and a couple hours of free time :). Maybe someone's already done it... &lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-12-17T15:58:49.907" CommentCount="6" />
  <row Id="8008" PostTypeId="2" ParentId="7985" CreationDate="2010-12-17T16:10:20.703" Score="0" ViewCount="" Body="&lt;p&gt;You can use the Atmel ATmega8U2 as USB to serial converter, like Arduino UNO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It doesn't require to install any drivers on Mac and Linux and on Windows all you need is a simple &lt;code&gt;.inf&lt;/code&gt; file&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2010-12-17T16:10:20.703" CommentCount="1" />
  <row Id="8009" PostTypeId="2" ParentId="8001" CreationDate="2010-12-17T16:37:27.940" Score="5" ViewCount="" Body="&lt;p&gt;If you place resistors in series the total resistance is the sum of the resistances of all resistors in the chain. There are two main reasons why you would do this.  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;to obtain a value you don't have in you box. For instance a 30k resistor is not an E12 series value, but you can obtain it by putting two 15k resistors in series  &lt;/li&gt;&#xA;&lt;li&gt;to allow a higher voltage. 0603 resistors have a working voltage of 50V, So if you want to use them in a 70V circuit you'll have to place at least two of them in series. Care should be taken if you pick unequal values. Divide the voltage by the total resistance to get the current flowing through the resistors, and multiply this current by each of the resistances in turn to get the voltage over this resistor. In the 0603 example none of the voltages should exceed 50V.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-17T16:37:27.940" CommentCount="1" />
  <row Id="8010" PostTypeId="2" ParentId="7985" CreationDate="2010-12-17T16:50:17.787" Score="2" ViewCount="" Body="&lt;p&gt;The major thing you want to do is get your device to use drivers that are already there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/USB_human_interface_device_class&quot; rel=&quot;nofollow&quot;&gt;USB HID specification&lt;/a&gt; allows you to tunnel through drivers that are of a standard type and already available on the system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To my knowledge Windows/Mac/Linux all have this.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-17T16:50:17.787" CommentCount="3" />
  <row Id="8011" PostTypeId="1" AcceptedAnswerId="8013" CreationDate="2010-12-17T16:52:35.270" Score="8" ViewCount="203" Body="&lt;p&gt;Is there anyway I can connect resistors to allow them to take more power such as using 4 1/4 watt resistors to get a 1 watt resistors. Or do i just have to use 1 1 Watt resistor. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-09T02:11:13.027" Title="Getting higher power output by using more resistors" Tags="&lt;resistor&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="8012" PostTypeId="2" ParentId="8001" CreationDate="2010-12-17T16:54:13.940" Score="2" ViewCount="" Body="&lt;p&gt;Yes of course, and to add some marginally more interesting content to my answer, you can also put resistors in parallel to get a lower resistance, though the effective resistance is not quite as straightforward as the simple sum for series resistance. Parallel resistance is calculated as (R1 * R2) / (R1 + R2), which equals R/2 for R = R1 = R2...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More formally, for n resistors in series: R_effective = SUM(i=1, i=n, R_i)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;...and for n resistors in parallel: R_effective = 1 / SUM(i=1, i=n, 1/R_i)&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-17T16:59:55.180" LastActivityDate="2010-12-17T16:59:55.180" />
  <row Id="8013" PostTypeId="2" ParentId="8011" CreationDate="2010-12-17T16:59:58.963" Score="24" ViewCount="" Body="&lt;p&gt;Yes, you can use (4) 0.25 W resistors to dissipate 1 W and still remain within each individual resistor's power rating.  This can be accomplished a few different ways:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Place them all in &lt;strong&gt;series&lt;/strong&gt;:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;In which case you will need to use resistors with &lt;strong&gt;1/4 the resistance&lt;/strong&gt; that you want overall.&lt;/li&gt;&#xA;&lt;li&gt;e.g. If you want 1 kΩ total, put (4) 250 Ω (240 Ω nearest 5% standard) resistors in series.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Place them all in &lt;strong&gt;parallel&lt;/strong&gt;:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;In which case you will need to use ones with &lt;strong&gt;4 times&lt;/strong&gt; the overall desired resistance&lt;/li&gt;&#xA;&lt;li&gt;e.g. If you want 1 kΩ total, put (4) 4 kΩ (3.9 kΩ nearest std.) resistors in series.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Placing them in a &lt;strong&gt;2x2 array&lt;/strong&gt;:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Where you can use resistors of the &lt;strong&gt;same resistance&lt;/strong&gt; you want overall (2 in parallel gives half, but you place 2 sets of parallel in series, doubling the effective resistance)&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In all the mentioned cases, in order to have each resistor dissipate an equal share of power, they all must be equal in value (ohms).  This isn't the &lt;em&gt;only&lt;/em&gt; way to do it, there are several other combinations you could use with differing values, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pragmatically, if you're only operating this circuit very intermittently (few seconds at a time), you &lt;em&gt;might&lt;/em&gt; be able to get away with a single 1/4 W resistor, especially if this is on a breadboard (be careful not to melt stuff).  Higher power resistors often are specified to survive surges of 8-10x their normal power dissipation for several seconds, though the typical 1/4 W thru-hole resistors are carbon film, which is a little less tolerant of this.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-17T17:11:14.883" LastActivityDate="2010-12-17T17:11:14.883" CommentCount="4" />
  <row Id="8014" PostTypeId="2" ParentId="8011" CreationDate="2010-12-17T17:00:29.043" Score="5" ViewCount="" Body="&lt;p&gt;Yep, putting them in parallel increases the group power dissipation and lowers group resistance. You still need to calculate power dissipation separately.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$R1 \parallel R2 = \frac{R_{1}R_{2}}{R_{1}+R_{2}}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$P = IV = I^{2}R = \frac{V^{2}}{R}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have N resistors in parallel and they are all the same value, power dissipation will be N-times their individual rating and group resistance will be 1/N times their individual rating.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-09T02:11:13.027" LastActivityDate="2011-03-09T02:11:13.027" />
  <row Id="8015" PostTypeId="1" CreationDate="2010-12-17T17:00:39.403" Score="2" ViewCount="187" Body="&lt;p&gt;Which means do we have to sense (relatively) fast voltage transition from &lt;strong&gt;one&lt;/strong&gt; value to &lt;strong&gt;another&lt;/strong&gt;. The exact point of &lt;strong&gt;transition start&lt;/strong&gt;, &lt;strong&gt;transition end&lt;/strong&gt; and the &lt;strong&gt;intermediate state&lt;/strong&gt;. Which schematic gives us indication of these points.&lt;br&gt;&#xA;And the special case: how do ICs sense voltage raise or fall?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;: Last edit turned question to the wrong direction, so I rolled it back and rephrased.&lt;/p&gt;&#xA;" OwnerUserId="1651" LastEditorUserId="1651" LastEditorDisplayName="" LastEditDate="2010-12-19T06:41:24.990" LastActivityDate="2010-12-19T06:41:24.990" Title="Voltage transition sense - rapid raise or fall." Tags="&lt;signal&gt;&lt;level&gt;" AnswerCount="3" CommentCount="11" />
  <row Id="8016" PostTypeId="2" ParentId="8015" CreationDate="2010-12-17T17:04:06.720" Score="5" ViewCount="" Body="&lt;p&gt;See Schmitt Trigger - &lt;a href=&quot;http://en.wikipedia.org/wiki/Schmidt_trigger&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Schmidt_trigger&lt;/a&gt; basically it's an amplifier circuit with positive feedback.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-17T17:18:24.440" LastActivityDate="2010-12-17T17:18:24.440" CommentCount="3" />
  <row Id="8017" PostTypeId="2" ParentId="8000" CreationDate="2010-12-17T17:40:44.420" Score="5" ViewCount="" Body="&lt;p&gt;Most manufacturers offer development kits for their various families. They often also have a blank, 0.1&quot; pitch plate via area for DIP as well as a few common SMD pads for prototyping. The &lt;a href=&quot;http://www.futurlec.com/ET-STM32_Stamp.shtml&quot; rel=&quot;nofollow&quot;&gt;ET-STM32 Stamp&lt;/a&gt; is one example; a great kit is the &lt;a href=&quot;http://ics.nxp.com/lpcxpresso/&quot; rel=&quot;nofollow&quot;&gt;LPCXpresso&lt;/a&gt; - make sure you get the right one, as there are two: one -M0 and one -M3(LPC1343).&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-17T17:40:44.420" />
  <row Id="8018" PostTypeId="2" ParentId="7022" CreationDate="2010-12-17T17:45:56.180" Score="2" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://www.macspice.com/&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;MacSpice&lt;/strong&gt;&lt;/a&gt; with OSX. It is completely text (netlist) and command line-based, &lt;a href=&quot;http://www.macspice.com/MacSpice-ScreenShot.png&quot; rel=&quot;nofollow&quot;&gt;though it produces decent graphical output&lt;/a&gt;. I'm not a SPICE expert, but apparently this one is done well, whatever that means.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I like it.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-17T17:45:56.180" />
  <row Id="8019" PostTypeId="1" AcceptedAnswerId="8020" CreationDate="2010-12-17T17:53:17.517" Score="1" ViewCount="67" Body="&lt;p&gt;I developed my own circuit board which reads temperature from a thermocouple.  This board also plugs into a computer via USB and my software communicates with the firmware on the board.  It's fairly simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is being used to record temperature readings from coffee roasters (&lt;a href=&quot;http://my.jaho.com/photo/probat-l12-coffee-roaster&quot; rel=&quot;nofollow&quot;&gt;here is an example&lt;/a&gt;).  Sometimes, a voltage develops between the roaster and computer.  What happens is that this voltage can be transmitted through the TC wire to the circuitry and throw off the temperature reading (since TCs work on the principle that the potential changes between the two wires as a function of temperature).  I've gotten around this by using ungrounded thermocouples exclusively, which isolate the actual TC wires from the outside world.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I'd really like to understand &lt;em&gt;why&lt;/em&gt; this happens.  I'm not an EE genius...I prototyped this board on an Arduino and paid a real EE to build and program the actual circuit.  I'm simply confused about what is going on exactly, and how I can be sure to eliminate any stray potentials which can interfere with the temperature readings.&lt;/p&gt;&#xA;" OwnerUserId="2307" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:19:53.713" LastActivityDate="2011-03-05T16:19:53.713" Title="Understanding extra thermocouple voltage between computer and machinery" Tags="&lt;voltage-measurement&gt;&lt;thermocouple&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="8020" PostTypeId="2" ParentId="8019" CreationDate="2010-12-17T18:32:07.373" Score="1" ViewCount="" Body="&lt;p&gt;It sounds like you're describing a &lt;a href=&quot;http://en.wikipedia.org/wiki/Ground_loop_%28electricity%29&quot; rel=&quot;nofollow&quot;&gt;ground loop&lt;/a&gt;, also an obnoxious problem in audio applications.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even though your computer and roaster are presumably grounded, &quot;ground&quot; is not perfect.  There are all sorts of high impedance paths between various ground points, and all sorts of effects, from mechanical triboelectric to electrochemical to stay fields from other conductors will cause small, subtle variations in the voltage.  In short, it's total chaos, so you have to deal with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a coffee roaster I assume you have motors which are relatively noisy, and there might be an actual (very small) electrical current flowing out a vent, as all the rubbing and heat is bound to create charged particles.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-17T18:32:07.373" />
  <row Id="8021" PostTypeId="1" AcceptedAnswerId="8022" CreationDate="2010-12-17T18:48:59.647" Score="1" ViewCount="296" Body="&lt;p&gt;This question is inspired by some basic questions on resistors I've read here lately. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the most accurate/precise technique for measuring the value of a resistor you can think of? What level of precision can be practically achieved? Can you repeatably measure a resistance to +/- 1 micro-ohm? +/- milli-ohm? Can you somehow distinguish between a resistor of a given value and equivalent series resistors? equivalent parallel resistors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not to limit answers too much, but I'd be interested in using a microcontroller plus external circuitry to take the measurements. Sorry if this is too vague of a question, I struggled to narrow down the scope. I'm thinking of techniques that incorporate GPIO pins and onboard peripherals like ADC and Analog Comparators. &lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-02-02T22:24:49.840" LastActivityDate="2011-02-02T22:24:49.840" Title="Precise Resistance Measurement Techniques" Tags="&lt;resistor&gt;&lt;measurement&gt;&lt;resistance&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="8022" PostTypeId="2" ParentId="8021" CreationDate="2010-12-17T19:01:29.187" Score="8" ViewCount="" Body="&lt;p&gt;A common accurate method to resistance is the &lt;a href=&quot;http://en.wikipedia.org/wiki/Four-terminal_sensing&quot; rel=&quot;nofollow&quot;&gt;4-point probe&lt;/a&gt;. The issue with a standard resistance measurement, using 2 probes, is that it uses the same contacts to deliver current and measure voltage. This means there is a voltage drop in the probes themselves (as well as contact resistance, but that isn't overcome with a 4-point). To get around this, 4 probes are used: 2 of them deliver current, the other two measure voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is commonly done using expensive bench-type multimeters, but can also be performed with 2 decent multimeters, a current source, and a pocket calculator. Use the current source to drop a voltage across the resistor in question, and measure this current with one meter. Beware that meters have a &lt;a href=&quot;http://www.home.agilent.com/agilent/editorial.jspx?cc=CA&amp;amp;lc=eng&amp;amp;ckey=1000000977%3aepsg%3afaq&amp;amp;nid=-35191.0.00&amp;amp;id=1000000977%3aepsg%3afaq&quot; rel=&quot;nofollow&quot;&gt;burden voltage&lt;/a&gt;, and often cannot measure low currents accurately (Dave Jones makes the &lt;a href=&quot;http://www.eevblog.com/2010/01/05/article-ucurrent-precision-current-adapter-for-multimeters/&quot; rel=&quot;nofollow&quot;&gt;uCurrent&lt;/a&gt; to combat this). With the other meter measure voltage drop across the resistor. Calculate resistance with your calculator with Ohm's Law: R = V/I. This method will be limited by your current meter's burden voltage. You'll find that it will give resistance measurements slightly lower than if you simply measure with 1 meter alone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 4-point probe technique is often used to characterize Si wafers, whose resistivity ranges from 10^12 to 10^18 Ωm!&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-17T19:01:29.187" CommentCount="9" />
  <row Id="8023" PostTypeId="2" ParentId="8021" CreationDate="2010-12-17T19:09:12.050" Score="3" ViewCount="" Body="&lt;p&gt;In addition to tyblu's answer regarding 4-lead measurement, to get good &lt;em&gt;precision&lt;/em&gt; you are going to need excellent temperature stability/reproduction, as coefficients can range from 5 to 250 ppm/K&lt;sup&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Resistor#Thick_and_thin_film&quot; rel=&quot;nofollow&quot;&gt;[1]&lt;/a&gt;&lt;/sup&gt;, depending on composition.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Furthermore, regarding:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Can you somehow distinguish between a resistor of a given value and equivalent series resistors? equivalent parallel resistors?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Resistors could be considered to have millions (billions, etc) of tiny resistors with in them, in a mix of series and parallel.  Defining a &quot;discrete resistor&quot; is fairly arbitrary, based on &lt;em&gt;mechanical&lt;/em&gt; properties, not electrical.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-17T19:09:12.050" CommentCount="3" />
  <row Id="8024" PostTypeId="1" AcceptedAnswerId="8025" CreationDate="2010-12-17T19:46:38.340" Score="1" ViewCount="175" Body="&lt;p&gt;Let's say I have a transformer with 3 coils. When primary coil is connected to 230V, two secondaries output 12V. Wires color coded, but I don't know what colors stand for and there is no information about that on manufacturer's website.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any relatively easy way to determine which wire is primary, which is secondary and which is start to the secondary and which is end of the secondary coil?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2010-12-17T20:38:16.517" Title="How to determine which wire is which on a transformer?" Tags="&lt;transformer&gt;" AnswerCount="1" />
  <row Id="8025" PostTypeId="2" ParentId="8024" CreationDate="2010-12-17T20:38:16.517" Score="3" ViewCount="" Body="&lt;p&gt;In a step-down transformer, the primary winding will have a higher resistance. The resistance will be low, but there should be a noticable difference unless you've got a really big transformer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're trying to identify what a winding is, then here are some notes:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;If 3 wires have continuity, then you probably have a center-tap winding (+, 0, -)&lt;/li&gt;&#xA;&lt;li&gt;If only 2 wires have continuity, then that is a simple winding.&lt;/li&gt;&#xA;&lt;li&gt;If 4 or more wires have continuity, then you have a multi-tap transformer winding.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Transformer windings have a phase relationship, but it's typically not important for power supplies. Unless one of the wires has continuity to the transformer core, the polarity doesn't matter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A relatively safe way to test transformers is to hook up a small AC voltage (1-5VAC) and measure the voltages across the other windings.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-17T20:38:16.517" CommentCount="6" />
  <row Id="8026" PostTypeId="2" ParentId="8015" CreationDate="2010-12-17T22:44:12.740" Score="1" ViewCount="" Body="&lt;p&gt;This really depends how far down you want to go. Keep in mind that every MCU that you will use is composed entirely of simple elements. Specifically, you will find transistors, capacitors, resistors, and diodes in every microcontroller and microprocessor since they stopped using vacuum tubes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without getting into digital logic fundamentals, a MCU can tell if an input changes by storing the digital value of a pin (1 or 0), and then comparing that stored value to the current pin value. The logical comparison is typically an exclusive-or.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could make a very simple edge-detection circuit by using a resistor and capacitor in series to store the input voltage. Then measure the voltage difference between the capacitor and the input - if the difference is close to zero, then there has not been a change. If the difference is large, then the input has just changed.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-17T22:44:12.740" CommentCount="1" />
  <row Id="8027" PostTypeId="1" AcceptedAnswerId="8033" CreationDate="2010-12-17T23:04:55.533" Score="4" ViewCount="147" Body="&lt;p&gt;I have a project that uses an ESC to run a brushless motor (Hobbyist RC plane sized, 24 gram, 1300-1500 KV).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to experiment with eliminating the ESC and driving the motor with my own circuitry and control software.  Are there any good tutorials or other starting points?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I realize it's more practical to just keep using my $8 ESC, but I'm interested in this as a learning exercise.)&lt;/p&gt;&#xA;" OwnerUserId="1756" LastEditorUserId="1756" LastEditorDisplayName="" LastEditDate="2010-12-18T12:13:42.387" LastActivityDate="2010-12-18T12:13:42.387" Title="Implementing my own ESC (electronic speed controller)?" Tags="&lt;esc&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="8028" PostTypeId="2" ParentId="8027" CreationDate="2010-12-17T23:18:03.337" Score="1" ViewCount="" Body="&lt;p&gt;Have you looked at PICs (e.g. &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en012037&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en012037&lt;/a&gt;) or I think the Arduino crowd is doing this too.&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2010-12-17T23:18:03.337" />
  <row Id="8029" PostTypeId="2" ParentId="7974" CreationDate="2010-12-17T23:27:59.830" Score="0" ViewCount="" Body="&lt;p&gt;I found this blog about WCF on .NET Micro.&#xA;&lt;a href=&quot;http://blogs.msdn.com/b/andrewarnottms/archive/2007/08/21/the-wcf-subset-supported-by-netcf.aspx&quot; rel=&quot;nofollow&quot;&gt;http://blogs.msdn.com/b/andrewarnottms/archive/2007/08/21/the-wcf-subset-supported-by-netcf.aspx&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2010-12-17T23:27:59.830" />
  <row Id="8030" PostTypeId="2" ParentId="7956" CreationDate="2010-12-17T23:33:52.523" Score="0" ViewCount="" Body="&lt;p&gt;I would suggest PICs and Zigbee chip or Microchip's version of it. CCS has some low-cost PIC development kits w/ wiresless.&#xA;&lt;a href=&quot;http://ccsinfo.com/product_info.php?products_id=wirelesszigb&quot; rel=&quot;nofollow&quot;&gt;http://ccsinfo.com/product_info.php?products_id=wirelesszigb&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For 1 one communication, I would suggest looking at the RFID radio chipsets and similar devices in that spectrum. &lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2010-12-17T23:33:52.523" />
  <row Id="8031" PostTypeId="2" ParentId="7956" CreationDate="2010-12-17T23:46:58.693" Score="1" ViewCount="" Body="&lt;p&gt;Something like an &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010386&quot; rel=&quot;nofollow&quot;&gt;rfPIC&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-17T23:46:58.693" />
  <row Id="8032" PostTypeId="2" ParentId="7925" CreationDate="2010-12-18T00:02:53.633" Score="0" ViewCount="" Body="&lt;p&gt;Use an MSP430 as an I2C slave. I just used the standard I2C code that you can download on the TI wiki. It doesn't work for MSPGCC though and you need to use a chip that supports I2C, such as an MSP430F2013 (which you can get free samples of). &lt;a href=&quot;https://gist.github.com/745942&quot; rel=&quot;nofollow&quot;&gt;Check out the sample code here&lt;/a&gt; or you can download all the samples at &lt;a href=&quot;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_(MSP-EXP430G2)?DCMP=launchpad&amp;amp;HQS=Other+OT+launchpadwiki#Download_all_MSP430G2xx_code_examples&quot; rel=&quot;nofollow&quot;&gt;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_(MSP-EXP430G2)?DCMP=launchpad&amp;amp;HQS=Other+OT+launchpadwiki#Download_all_MSP430G2xx_code_examples&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just set the PWM duty to whatever byte you receive from the master.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2010-12-18T00:02:53.633" />
  <row Id="8033" PostTypeId="2" ParentId="8027" CreationDate="2010-12-18T00:05:52.523" Score="3" ViewCount="" Body="&lt;p&gt;Here is an introduction to electronic speed control systems: &lt;a href=&quot;http://www.stefanv.com/electronics/escprimer.html&quot; rel=&quot;nofollow&quot;&gt;http://www.stefanv.com/electronics/escprimer.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actual design depends on the type of motor you want to drive. A 300A high-torque gear motor is much different from those tiny featherweight propeller motors. At the heavy-duty end of the scale (300A) is something like this: &lt;a href=&quot;http://www.robotpower.com/products/osmc_info.html&quot; rel=&quot;nofollow&quot;&gt;Open Source Motor Control&lt;/a&gt;. All designs are online and there are a few articles explaining what the heck is going on. At the other end of the scale are small prop motors, like those in the &lt;a href=&quot;http://www.mikrokopter.com/ucwiki/en/BrushlessCtrl&quot; rel=&quot;nofollow&quot;&gt;MikroKopter&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-18T00:05:52.523" CommentCount="1" />
  <row Id="8034" PostTypeId="1" CreationDate="2010-12-18T00:19:35.540" Score="2" ViewCount="241" Body="&lt;p&gt;Let's exclude ICs in my consideration because they might contain hidden resistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since resistors waste energy, I think that we should not use them to build electronic devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, how can we get the role provided by resistors such as the current division, etc ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, is it possible to design  functional and useful devices composed of discrete components other than ICs and resistors? &lt;/p&gt;&#xA;" OwnerUserId="2179" LastActivityDate="2010-12-20T18:31:37.657" ClosedDate="2010-12-20T21:18:55.250" Title="Is it possible to build functional devices composed of discrete components other than ICs and resistors?" Tags="&lt;circuit-design&gt;" AnswerCount="7" CommentCount="6" />
  <row Id="8035" PostTypeId="2" ParentId="7925" CreationDate="2010-12-18T00:30:53.673" Score="0" ViewCount="" Body="&lt;p&gt;There is a similar question &lt;a href=&quot;http://electronics.stackexchange.com/questions/8027/implementing-my-own-esc&quot;&gt;here&lt;/a&gt;. This was my answer:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Here is an introduction to electronic speed control systems: &lt;a href=&quot;http://www.stefanv.com/electronics/escprimer.html&quot; rel=&quot;nofollow&quot;&gt;http://www.stefanv.com/electronics/escprimer.html&lt;/a&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Actual design depends on the type of motor you want to drive. A 300A high-torque gear motor is much different from those tiny featherweight propeller motors. At the heavy-duty end of the scale (300A) is something like this: &lt;a href=&quot;http://www.robotpower.com/products/osmc_info.html&quot; rel=&quot;nofollow&quot;&gt;Open Source Motor Control&lt;/a&gt;. All designs are online and there are a few articles explaining what the heck is going on. At the other end of the scale are small prop motors, like those in the &lt;a href=&quot;http://www.mikrokopter.com/ucwiki/en/BrushlessCtrl&quot; rel=&quot;nofollow&quot;&gt;MikroKopter&lt;/a&gt;.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The motor you chose is sold with an ESC &lt;a href=&quot;http://www.rcecho.com/tekmodel-4300-kv-9t-brushless-motor-35a-program-esc.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. This controller is designed for 35A continuous, 190A peak, so dinky designs won't cut it. The &lt;a href=&quot;http://www.robotpower.com/products/osmc_info.html&quot; rel=&quot;nofollow&quot;&gt;OSMC&lt;/a&gt; page has several designs that would probably do it as well, but I believe they are all PWM input. Even the smallest and cheapest of microcontrollers should be able to handle I2C to PWM conversion (e.g.: ATtiny family).&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-18T00:30:53.673" />
  <row Id="8036" PostTypeId="1" AcceptedAnswerId="8193" CreationDate="2010-12-18T00:37:36.063" Score="3" ViewCount="204" Body="&lt;p&gt;I'm looking for a device to switch video signals; a video switch. I want to use a dual/triple switch for two purposes, first to switch between two video signals, and secondly to switch the signal between open and +3.3V (which drives the pixel on the frame high.) (The third  channel may be used to switch between on and off for the pixel.) It's for an on screen display application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, most chips I've seen have an on resistance of nearly 60-80 ohms. This is way too much surely for video which is terminated with 75 ohms? If I'm switching with 75 ohms in series with the required 75 ohm termination, I've effectively created a voltage divider and halved the video signal. It might work, but the video would probably lose considerable quality; at worst, I'd probably lose sync.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an additional question, related to this one, would there be any bandwidth issues with video switches? I'm using composite (CVBS) NTSC or PAL colour video.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-22T21:39:54.570" Title="How much resistance is too much resistance for a video switch?" Tags="&lt;video&gt;&lt;mux&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="0" />
  <row Id="8037" PostTypeId="2" ParentId="8034" CreationDate="2010-12-18T00:42:52.073" Score="3" ViewCount="" Body="&lt;p&gt;Simply, no. Resistors usually aren't used in IC design - rather transistors at specific operating points are used to provide a certain resistance across its channel, giving either voltage regulation, constant current, or constant resistance (or some other weird jigamaroo). We must use resistive circuitry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is similar to the distinction between linear regulators and switching regulators. A linear regulator dissipates power, lowering voltage, in one or more transistors (&quot;pass transistors&quot;). It can be seen as a resistor for a constant load. A switching regulator switches a high voltage on and off through an inductor then averages the output, making the load &lt;em&gt;see&lt;/em&gt; a different voltage (higher or lower). In either case, resistive circuitry - not necessarily resistors - is used extensively.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you could design some of the main building blocks in electronics using only fully &lt;em&gt;ON&lt;/em&gt; or &lt;em&gt;OFF&lt;/em&gt; transistors, the world would be a better place: mixers, ADCs, DACs, op-amp, oscillators, PLLs, etc.. Lower power is one of the main design requirements in today's electronics, so please give it a shot.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-18T15:01:48.640" LastActivityDate="2010-12-18T15:01:48.640" CommentCount="3" />
  <row Id="8038" PostTypeId="2" ParentId="8001" CreationDate="2010-12-18T00:45:58.870" Score="0" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;If I put 3 1MΩ resistors in series, is that the equivalent of one 3MΩ resistor?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I don't know exactly whether your question contains a trap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you put at most 2 resistors in super cold environment and the remaining one(s) in hotter place, the combined resistance will probably no longer equal to 3 mega ohms.&lt;/p&gt;&#xA;" OwnerUserId="2179" LastActivityDate="2010-12-18T00:45:58.870" CommentCount="1" />
  <row Id="8039" PostTypeId="2" ParentId="8034" CreationDate="2010-12-18T00:54:50.470" Score="5" ViewCount="" Body="&lt;p&gt;Unfortunately you need resistors in electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had someone once ask me this. They were surprised that a resistor dissipated power. About 10mW in my simulation. They asked if it could be put back in the circuit. So I asked them how they would do this. They said they would use a small peltier or heat to potential device (like a thermocouple) and generate electricity from this which would then go into a boosting circuit of some kind to provide extra energy. It would probably be less than 10% efficient. Of course you can see the futility of this, given the amount of effort and cost you have gone through to get maybe 1mW more power, and for something that doesn't really matter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Resistors play a crucial role in electronics. They waste power, but that is unavoidable - they are dropping voltage. It's not possible to drop voltage with a given current without wasting energy without using many more components, probably wasting more for something like a smal resistor. You will find that in total more energy is wasted by your microcontroller or something else than in your resistors. In general, it is a bad sign if your resistors are wasting current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Seriously though, analog devices DON'T waste that much power, if designed correctly. While it is true most transistors waste less power in and on and off state this doesn't apply for cleverly designed electronics. For example, this op-amp: &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en551077&quot; rel=&quot;nofollow&quot;&gt;MCP6441&lt;/a&gt; consumes only 650nA in typical operation, about the same as a microcontroller in deep sleep.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-18T00:54:50.470" CommentCount="3" />
  <row Id="8040" PostTypeId="2" ParentId="8015" CreationDate="2010-12-18T01:35:27.847" Score="0" ViewCount="" Body="&lt;p&gt;I don't understand the insistence on using &quot;MCUs&quot; instead of &quot;ICs&quot;. &lt;strong&gt;MCUs are ICs&lt;/strong&gt;, and many ICs also have digital inputs. Furthermore, a MCU is basically just a specialty IC, and you can actually make a MCU out of a bunch of ICs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The behavior of the inputs and outputs of a Schmitt trigger are thus:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/znz2c.png&quot; alt=&quot;alt text&quot;&gt;&lt;br&gt;&#xA;Both axes are in voltage. (&lt;a href=&quot;http://en.wikipedia.org/wiki/Schmitt_trigger&quot; rel=&quot;nofollow&quot;&gt;Shamelessly pillaged from wikipedia&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see, the Schmitt-Trigger is specifically designed to &lt;em&gt;not have&lt;/em&gt; an &quot;intermediate state&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;transition start, transition end and the intermediate state&quot; are all part dependent, and there is no blanket answer. Read the datasheets for your part for the answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a simulation of how edge triggering works at the logic-level:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.play-hookey.com/digital/rs_nand_flip-flop.html&quot; rel=&quot;nofollow&quot;&gt;http://www.play-hookey.com/digital/rs_nand_flip-flop.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/users/771/vicatcu&quot;&gt;vicatcu&lt;/a&gt; has already covered the analog underpinning to building a schmitt trigger.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Interestingly enough, for logic devices without buffered/schmitt-trigger inputs, if you wrap negative feedback around the device, you can actually use it in an &quot;analog mode&quot;, kind of like an amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not a good idea, though, and it may damage some parts. Also, there may be wide variations between parts from the same manufacturer, since analog performance is not specified or controlled.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-19T05:13:46.683" LastActivityDate="2010-12-19T05:13:46.683" CommentCount="3" />
  <row Id="8041" PostTypeId="1" AcceptedAnswerId="8055" CreationDate="2010-12-18T01:46:12.167" Score="0" ViewCount="87" Body="&lt;p&gt;Hello, I've been trying to learn to use the ISE WebPack and the link they give in their documentation( &lt;a href=&quot;http://bit.ly/fsy8iD&quot; rel=&quot;nofollow&quot;&gt;http://bit.ly/fsy8iD&lt;/a&gt; page 11) points to &lt;a href=&quot;http://www.xilinx.com/support/documentation/dt_ise12-3_tutorials.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.xilinx.com/support/documentation/dt_ise12-3_tutorials.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On that page I do not see any zip files or any tutorial files at all except for PDF files. Where do you get these files? &lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2010-12-18T14:47:53.833" Title="Where are the tutorial files for ISE WebPack?" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;webpack&gt;" AnswerCount="1" />
  <row Id="8042" PostTypeId="1" CreationDate="2010-12-18T03:40:10.467" Score="3" ViewCount="213" Body="&lt;p&gt;I bought a cheap USB hard drive enclosure off eBay. It turns out that the power supply has absolutely no electrical certifications for either the US or EU (no UL, CE marks). Is electrical certification required for these power adapters (that come with USB drive enclosures)? Is it safe to use a power supply that doesn't have the electrical certification?&lt;/p&gt;&#xA;" OwnerUserId="2320" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-05-13T00:24:18.707" LastActivityDate="2011-05-13T17:36:18.197" Title="Are power supplies for USB drive enclosures required to have UL certification?" Tags="&lt;power-supply&gt;&lt;adapter&gt;&lt;certification&gt;&lt;ul&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="8043" PostTypeId="1" CreationDate="2010-12-18T03:49:58.483" Score="0" ViewCount="176" Body="&lt;p&gt;I've been playing around with an Arduino and the SparkFun GPS shield.  For about a week, it was working well, but it has now developed an interesting error.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While my latitude, longitude, date, time and course are correct, the GPS is telling me that it is 10 000 000 m above sea level.  Previously, it was giving readings between 90 and 110 m, which would be correct for my local area.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried everything I can think of to fix the problem; reinstalling the libraries and using a couple of different sketches off the internet, but they all have the same problem. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure if the GPS module has gone bad because all other outputs are working, but this being my first GPS project I'm not 100% on how it determines altitude figures. I am willing to pay another $80 to get a new module but I'd rather not if it's not the problem.&lt;/p&gt;&#xA;" OwnerUserId="2321" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-18T06:53:46.633" LastActivityDate="2010-12-18T12:22:21.273" Title="Arduino GPS shield giving incorrect altitude readings" Tags="&lt;arduino&gt;&lt;arduino&gt;&lt;gps&gt;" AnswerCount="2" />
  <row Id="8044" PostTypeId="2" ParentId="8034" CreationDate="2010-12-18T05:18:20.280" Score="7" ViewCount="" Body="&lt;p&gt;I'm not sure why you are excluding ICs, because many digital ICs fit your criteria pretty closely.  Most digital ICs are made almost entirely of transistors, and use zero current (save leakage) except when they are clocked, and only dissipate during the time when they are switching states.  Their power dissipation is linear with frequency.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-12-20T16:44:11.480" LastActivityDate="2010-12-20T16:44:11.480" CommentCount="6" />
  <row Id="8045" PostTypeId="2" ParentId="8043" CreationDate="2010-12-18T07:08:28.240" Score="1" ViewCount="" Body="&lt;p&gt;I doubt that you somehow only damaged the logic that determines altitude in your GPS module.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My best guess would be that your software is looking at the wrong part of the &lt;a href=&quot;http://www.gpsinformation.org/dale/nmea.htm&quot; rel=&quot;nofollow&quot;&gt;NMEA sentence&lt;/a&gt; the module is transmitting to your Arduino.  I'm not sure how the GPS shield is wired (there are seemingly a couple variants on SparkFun, but I'd attach a separate TTL converter (e.g. board with an FTDI chip) and look at what the GPS is actually sending.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't have to use the TTL converter, just get a glimpse somehow of the raw NMEA data.  The reason I suggest that is because I think the GPS uses the serial port that you'd normally use to talk with your PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fact it worked before makes me think that either your software was modified initially then all the stock versions you've tried don't have that tweak in them, or you may have reconfigured the GPS module somehow to change the fields it transmits.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-18T07:08:28.240" CommentCount="2" />
  <row Id="8046" PostTypeId="1" CreationDate="2010-12-18T07:58:50.767" Score="1" ViewCount="115" Body="&lt;p&gt;&lt;code&gt;S&lt;/code&gt; (uppercase ess) is the abbreviation for &lt;a href=&quot;http://en.wikipedia.org/wiki/Siemens_%28unit%29&quot; rel=&quot;nofollow&quot;&gt;the SI unit siemens&lt;/a&gt;, aka &quot;mho&quot;, aka 1/ohm, unit of conductance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;s&lt;/code&gt; (lowercase ess) is the abbreviation for seconds, unit of time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where did this irritating abuse of &lt;code&gt;S&lt;/code&gt; come from?&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-18T10:34:39.977" ClosedDate="2010-12-18T10:54:24.147" Title="Why do people use a capital S for &quot;seconds&quot;?" Tags="&lt;units&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="8047" PostTypeId="2" ParentId="8046" CreationDate="2010-12-18T08:28:06.523" Score="5" ViewCount="" Body="&lt;p&gt;SI units are lowercase, except when they are derived from a person's name, like in the case of Siemens, or Volta (&lt;code&gt;V&lt;/code&gt;), or Ampère (&lt;code&gt;A&lt;/code&gt;), for instance. I must say that I haven't often seen seconds as &lt;code&gt;S&lt;/code&gt;. What I do often see is the prefix &lt;code&gt;m&lt;/code&gt; instead of &lt;code&gt;M&lt;/code&gt; for mega, like &lt;code&gt;a 10mHz crystal&lt;/code&gt;. &lt;code&gt;m&lt;/code&gt; is for milli-.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-18T08:28:06.523" CommentCount="3" />
  <row Id="8048" PostTypeId="2" ParentId="8021" CreationDate="2010-12-18T08:42:28.660" Score="2" ViewCount="" Body="&lt;p&gt;use of a wheatstone bridge will be able to give you far greater accuracy than four point probes.  It is what is used to instrument strain guages where mechanical change in stress and strain results in very low change in resistance.  The only way to measure these small changes in resistance is to use a wheatstone bridge.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-12-18T08:42:28.660" CommentCount="2" />
  <row Id="8049" PostTypeId="2" ParentId="7901" CreationDate="2010-12-18T09:12:12.110" Score="1" ViewCount="" Body="&lt;p&gt;Parallax make the &lt;a href=&quot;http://www.parallax.com/Store/Microcontrollers/JavelinStamp/tabid/517/CategoryID/13/List/0/Level/a/ProductID/5/Default.aspx?SortField=ProductName%2cProductName&quot; rel=&quot;nofollow&quot;&gt;Javelin Stamp&lt;/a&gt;, a CoM (Computer-on-Module) that runs a JVM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's $60 and executes a blazing ~8,500 Java instructions/sec.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the PCB is pink (Really!)&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-12-18T09:12:12.110" />
  <row Id="8050" PostTypeId="1" AcceptedAnswerId="8054" CreationDate="2010-12-18T10:30:54.777" Score="1" ViewCount="159" Body="&lt;p&gt;For a University project I have to build a small box containing ice cubes. The box is a shoe box, isolated with newspaper and aluminium foil, cooled by thermal packs. In this box I want to store ice cubes for about one to three hours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now comes the tricky part: The ice cubes should drop out of the box, one after another, about every minute.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking of a motor with an oval disk which opens a flap gate. The second idea was a small conveyor band which transports the cubes out. Are there better solutions than that? What minimum motor power do I need for this? How do I control the motor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a low-budget project, so the cheapest solution is the best.&lt;/p&gt;&#xA;" OwnerUserId="1957" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-18T17:10:44.827" LastActivityDate="2010-12-19T00:12:12.523" Title="How to release ice cubes out of a box?" Tags="&lt;motor&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="8051" PostTypeId="2" ParentId="8042" CreationDate="2010-12-18T10:34:36.310" Score="3" ViewCount="" Body="&lt;p&gt;Does the power supply plug into the mains?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure if it's illegal to go without UL certification as UL aren't a federal requirement (although I believe it is a requirement to have some sort of certification, UL or otherwise) It does make the product look dodgy. It is certainly illegal to not have FCC/CE certification especially as switch mode adapters like those emit hideous amounts of EMI unless properly designed.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-18T10:34:36.310" CommentCount="8" />
  <row Id="8052" PostTypeId="2" ParentId="8046" CreationDate="2010-12-18T10:34:39.977" Score="1" ViewCount="" Body="&lt;p&gt;Well most people do not understand that s and S is not the same letter, I really think it as simple as that.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-12-18T10:34:39.977" />
  <row Id="8053" PostTypeId="2" ParentId="8034" CreationDate="2010-12-18T11:41:09.147" Score="3" ViewCount="" Body="&lt;p&gt;If you have current in a circuit, all parts in the circuit that aren't ideal superconductors (i.e. everything) cause voltage loss and thus power loss. The trick is to try to keep the current and unnecessary voltage losses down. Correct resistors and IC's help with this rather than hurt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe the hot word today is duty cycle. If you can make a device shut itself down whenever it's not needed and only turn it on briefly, you can cut the total power losses down by the duty cycle. Being on one second out of ten means you only use 10% of your operating current over time plus standby current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Making bias currents lower (bigger resistors :) and cutting the operating voltage down may also help, but high impedance and low voltage circuits have their own problems (speed, sensitivity to interference).&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2010-12-18T11:41:09.147" />
  <row Id="8054" PostTypeId="2" ParentId="8050" CreationDate="2010-12-18T11:46:10.830" Score="9" ViewCount="" Body="&lt;p&gt;These are hard questions to answer, not because the information you need is hard to come by, but because answering them in a straightforward way will keep you from learning how to do it yourself, which is presumably why you're going to college in the first place. On the other hand, it reasonable to say, &quot;Look, I don't know how to do this, and there is no point in trying to reinvent motor control from first principles.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So how about this for an answer that will get you started.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You're trying to do a task where the motor will need to spin a little bit, then stop and wait, then repeat. Also, overall, this is a pretty low power task-- you're not trying to move a car or train. For this kind of low-power, intermittent duty task, I'd probably start with a small &lt;strong&gt;stepper motor&lt;/strong&gt;, like you find in old disk drives or printers. You could also use a small &lt;strong&gt;DC motor&lt;/strong&gt;, like you find in most motorized toys, but you'll probably need some clever ratcheting mechanism to make the intermittent motion you're after.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, motor power is proportional to volume; you want a motor that is bigger than a grape and smaller than an apple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The next step is to google &quot;stepper motor&quot; and &quot;dc motor controller.&quot; I'm afraid Wikipedia will be incomprehensible at this stage; I'd look for tutorials from robotics clubs or intro electronics sites. You might start with:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.doc.ic.ac.uk/~ih/doc/stepper/&quot; rel=&quot;nofollow&quot;&gt;http://www.doc.ic.ac.uk/~ih/doc/stepper/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.seattlerobotics.org/encoder/200001/simplemotor.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.seattlerobotics.org/encoder/200001/simplemotor.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;After that, since you say this is a low-budget project, I'd try to find something with a motor in it that you can reuse-- maybe the mechanism from an inkjet printer (stepper motor) or an RC car (DC motor). You might be able to reuse something without taking it apart-- like maybe you could just have the printer print a page once a minute, and the motion would pull on a string that somehow moved the ice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From there, draw a lot of pictures of what you want to build and try building some crappy prototypes out of cardboard, string, and paper. You'll learn faster by testing and failing than by trying to plan it all out in your head first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-18T11:46:10.830" CommentCount="5" />
  <row Id="8055" PostTypeId="2" ParentId="8041" CreationDate="2010-12-18T12:22:05.153" Score="1" ViewCount="" Body="&lt;p&gt;On my system they are here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C:\Xilinx\12.3\ISE_DS\ISE\ISEexamples&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ones you mentioned can be downloaded as zip files from that web page. You want the ISE In-Depth Tutorial and the associated zip files. They are included amongst those that should already be on your system in the ISEExamples directory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think that the hardware for that example is still available. If you get a Digilent Spartan 3 kit a similar alarm clock example can be downloaded from the Digilent web site.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best place to get questions about Xilinx software answered are the &lt;a href=&quot;http://forums.xilinx.com/&quot; rel=&quot;nofollow&quot;&gt;Xilinx forums&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-18T14:47:53.833" LastActivityDate="2010-12-18T14:47:53.833" />
  <row Id="8056" PostTypeId="2" ParentId="8043" CreationDate="2010-12-18T12:22:21.273" Score="2" ViewCount="" Body="&lt;p&gt;If the GPS module sees only 3 Satellites, the altitude can not be computed (that needs at least 4 SV). So the GPS may just try to tell you that it has no altitude data for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But this is just guesswork without the NMEA sentences...&lt;/p&gt;&#xA;" OwnerUserId="1472" LastActivityDate="2010-12-18T12:22:21.273" />
  <row Id="8057" PostTypeId="2" ParentId="8050" CreationDate="2010-12-18T12:42:20.900" Score="0" ViewCount="" Body="&lt;p&gt;I had a similer project the best thing will be to have some sort of chain the you will load Ice Cubes in it, and you make a Hole with size of Ice Cubes in the box and then put Ice Cube chain in a way that will block the hole and when you move the chain ahead it shoulld bring the Ice Cube on the whole so it will drop out. Sorta like machine gun strip magazines.&lt;/p&gt;&#xA;" OwnerUserId="2194" LastEditorUserId="2194" LastEditorDisplayName="" LastEditDate="2010-12-18T14:12:01.353" LastActivityDate="2010-12-18T14:12:01.353" />
  <row Id="8058" PostTypeId="2" ParentId="7913" CreationDate="2010-12-18T13:39:25.073" Score="2" ViewCount="" Body="&lt;p&gt;This predates any issues with PCB software and routing: The three main reasons we were given in electronic engineering classes in the late 1970s were:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) The sharp outside corner of the bend can cause issues at higher frequencies as the points can act as mini antennas and radiate the signals&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Because the outside corner of a 90 degree bend is a thin point it can be etched away easily if etching times are not very carefully controlled and so affect the thickness of the trace &lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) The 90 degree inside and outside corners make that area more susceptible to problems where the etching process eats underneath the trace.&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2010-12-18T13:39:25.073" CommentCount="1" />
  <row Id="8059" PostTypeId="1" AcceptedAnswerId="8061" CreationDate="2010-12-18T15:00:11.370" Score="6" ViewCount="128" Body="&lt;p&gt;Frequency synthesizers, like &lt;a href=&quot;http://www.analog.com/static/imported-files/data_sheets/ADF4110_4111_4112_4113.pdf&quot; rel=&quot;nofollow&quot;&gt;Analog's ADF411x&lt;/a&gt; often have prescalers in their PLL which divide by 16/17, 32/33 or 64/65? What's the 2^N+1 value used for?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-19T05:38:10.997" Title="Why do frequency synthesizers often use N/N+1 prescalers?" Tags="&lt;pll&gt;&lt;synthesizer&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="8060" PostTypeId="1" CreationDate="2010-12-18T15:10:05.940" Score="1" ViewCount="376" Body="&lt;p&gt;With four different sensors, V1, V2 V3, and V4 I need to develope an operational amplifier circuit to measure average temperature with following specifications:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The output voltage range of each sensor is limited to 0-5 V&lt;/li&gt;&#xA;&lt;li&gt;The output voltage range of average temperature measurement circuit is 0-5V&lt;/li&gt;&#xA;&lt;li&gt;The span adjustment range is +/- 1V&lt;/li&gt;&#xA;&lt;li&gt;Total system accuracywith +/- 0.1% of FSO&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Please help me to design the above circuit.&lt;/p&gt;&#xA;" OwnerUserId="2325" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-19T16:51:02.430" LastActivityDate="2010-12-19T16:51:02.430" Title="Develop an OpAmp circuit to measure average voltages" Tags="&lt;op-amp&gt;&lt;homework&gt;" AnswerCount="3" CommentCount="7" />
  <row Id="8061" PostTypeId="2" ParentId="8059" CreationDate="2010-12-18T15:19:42.200" Score="6" ViewCount="" Body="&lt;p&gt;A dual-modulus (fractional N) pre-scaler gives the PLL increased resolution, without compromising things like lock time and noise. See &lt;a href=&quot;http://focus.ti.com/lit/an/swra029/swra029.pdf&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; app note.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-18T15:19:42.200" CommentCount="2" />
  <row Id="8062" PostTypeId="2" ParentId="8060" CreationDate="2010-12-18T15:28:07.320" Score="1" ViewCount="" Body="&lt;p&gt;Try the Handbook of Operational Amplifier Applications pg 65.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: &lt;a href=&quot;http://focus.ti.com.cn/cn/lit/an/sboa092a/sboa092a.pdf&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com.cn/cn/lit/an/sboa092a/sboa092a.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2183" LastEditorUserId="2183" LastEditorDisplayName="" LastEditDate="2010-12-18T16:50:37.343" LastActivityDate="2010-12-18T16:50:37.343" CommentCount="5" />
  <row Id="8063" PostTypeId="2" ParentId="8060" CreationDate="2010-12-18T16:35:57.963" Score="4" ViewCount="" Body="&lt;p&gt;For an average voltage you need a voltage adder  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/l2Jb6.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output voltage is determined by the resistor values:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/QxbEO.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To average N inputs Rf should be 1/N-th of Rin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For zero adjustment just add another input to which you can apply a variable voltage by means of a potmeter. You'll want to include negative voltages in the control range.&lt;br&gt;&#xA;Range adjustment can be done by modifying Rf (for all inputs simultaneously) or Rin (for each input individually).   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(images taken from &lt;a href=&quot;http://www.electronics-tutorials.ws/opamp/opamp_4.html&quot; rel=&quot;nofollow&quot;&gt;http://www.electronics-tutorials.ws/opamp/opamp_4.html&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-18T16:41:53.250" LastActivityDate="2010-12-18T16:41:53.250" CommentCount="2" />
  <row Id="8064" PostTypeId="2" ParentId="8034" CreationDate="2010-12-18T16:39:31.750" Score="4" ViewCount="" Body="&lt;p&gt;You may be able to get some things that require voltage division using a chain of diodes, however, I doubt that it would be more efficient than simply using resistors for this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing to note is that nearly all output devices, speakers, lamps, motors, have a resistance in them - so perhaps their useful work can be combine with their resistance to also provide the R in an RC or RL tuned circuit/ossilator.&lt;/p&gt;&#xA;" OwnerUserId="2326" LastActivityDate="2010-12-18T16:39:31.750" CommentCount="4" />
  <row Id="8065" PostTypeId="2" ParentId="8050" CreationDate="2010-12-18T16:55:48.757" Score="3" ViewCount="" Body="&lt;p&gt;I'm not sure how easy it is to come by, but I'd look for an old refrigerator with ice dispenser.  All dispensing mechanisms I've seen are screws/augers that grab some ice and push it forwards to drop it down a hole into your drink.  You may be able to modify the &quot;intake&quot; to grab one cube at a time, or if it's not that critical you get 1 cube/min, just use it stock.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-18T16:55:48.757" />
  <row Id="8066" PostTypeId="2" ParentId="8060" CreationDate="2010-12-18T17:02:20.937" Score="1" ViewCount="" Body="&lt;p&gt;There are many ways of averaging voltage. Any circuit is an &quot;op amp circuit&quot;, once it has an op amp. First, voltages average naturally, like temperature. This can be shown using a passive method, with resistors:&#xA;&lt;img src=&quot;http://i.imgur.com/cTZyY.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A high impedance voltage follower (op amp circuit) is required to maintain accuracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another passive method is with capacitors, using charge redistribution. &lt;a href=&quot;http://focus.ti.com/lit/an/slyt176/slyt176.pdf&quot; rel=&quot;nofollow&quot;&gt;This is related to how many modern analog-to-digital converters (ADCs) are being designed today.&lt;/a&gt; It works by &lt;em&gt;storing&lt;/em&gt; a voltage on a capacitor, disconnecting from the source signal, then connecting to and &lt;em&gt;redistributing&lt;/em&gt; charge with another parallel capacitor, which halves the initial voltage. This can be extended to average four voltages by having them share and redistribute total charge:&#xA;&lt;img src=&quot;http://i.imgur.com/cSyiK.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again, a high impedance voltage follower is required to maintain accuracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Either of these concepts can be improved upon in many different ways, using op amps or otherwise. Since this appears to be a homework assignment, I'll leave this bit to you!&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-18T17:02:20.937" CommentCount="1" />
  <row Id="8068" PostTypeId="1" AcceptedAnswerId="8073" CreationDate="2010-12-18T21:05:41.000" Score="0" ViewCount="139" Body="&lt;p&gt;I need a prototyping adapter for a ssop 24-pin package. Google turns up plenty of dip adapters for 5-7mm chips, but the chip I have is 3.9mm across the body and 6mm to the tips of the pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone know of source of a suitable adapter?  Doesn't necessarily have to be a dip, just something solderable by humans.&lt;/p&gt;&#xA;" OwnerUserId="2327" LastEditorUserId="2327" LastEditorDisplayName="" LastEditDate="2010-12-19T01:30:00.360" LastActivityDate="2010-12-20T01:41:39.250" Title="Source for a ssop to dip adapter?" Tags="&lt;prototyping&gt;&lt;adapter&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="8070" PostTypeId="2" ParentId="8050" CreationDate="2010-12-19T00:12:12.523" Score="1" ViewCount="" Body="&lt;p&gt;I believe that the ice maker in a refrigerator uses an auger-type delivery system.  You could make something like that with copper tubing or something else that's malleable enough to bend into that shape.  I'd use a stepper motor as suggested above and have a photosensor determine when a single ice cube has dropped and then open a door (if it absolutely has to be one-at-time).&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-12-19T00:12:12.523" />
  <row Id="8071" PostTypeId="5" CreationDate="2010-12-19T01:16:20.033" Score="0" ViewCount="0" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/N2N3c.jpg&quot; width=&quot;300&quot; height=&quot;200&quot;/&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;A resistor is a two-terminal electronic component that produces a voltage across its terminals that is proportional to the electric current through it in accordance with Ohm's law:&lt;/p&gt;&#xA;  &#xA;  &lt;blockquote&gt;&#xA;    &lt;p&gt;V = IR&lt;/p&gt;&#xA;  &lt;/blockquote&gt;&#xA;  &#xA;  &lt;p&gt;Resistors are elements of electrical networks and electronic circuits and are ubiquitous in most electronic equipment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel-chrome).&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The primary characteristics of a resistor are the resistance, the tolerance, the maximum working voltage and the power rating. Other characteristics include temperature coefficient, noise, and inductance. Less well-known is critical resistance, the value below which power dissipation limits the maximum permitted current, and above which the limit is applied voltage. Critical resistance is determined by the design, materials and dimensions of the resistor.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits. Size, and position of leads (or terminals), are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;From the &lt;a href=&quot;http://en.wikipedia.org/wiki/Resistor&quot; rel=&quot;nofollow&quot;&gt;Resistor&lt;/a&gt; article on Wikipedia, the free encyclopedia.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Schematic Symbol (American):&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/0s2N0.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Schematic Symbol (European):&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/9MeBS.gif&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-04T17:12:02.637" LastActivityDate="2011-03-04T17:12:02.637" />
  <row Id="8072" PostTypeId="4" CreationDate="2010-12-19T01:16:20.033" Score="0" ViewCount="0" Body="A resistor is one of the most basic electric components.  It produces a voltage proportional to the current that passes through it in accordance with Ohm's law." OwnerUserId="-1" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-19T01:16:20.033" LastActivityDate="2010-12-19T01:16:20.033" />
  <row Id="8073" PostTypeId="2" ParentId="8068" CreationDate="2010-12-19T01:42:23.380" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.national.com/packaging/mkt/msa24.pdf&quot; rel=&quot;nofollow&quot;&gt;Standard SSOP&lt;/a&gt; land pads should fit this device. 8.8mm from the extreme ends of the pads, width-wise, leaves 1.1mm on each side within which to solder, according to your 6mm measurement. &lt;a href=&quot;http://www.sparkfun.com/products/500&quot; rel=&quot;nofollow&quot;&gt;The breakout board on Sparkfun's site&lt;/a&gt; looks like it has 1.5mm pads, but they just barely start at 6mm apart. These ones from Aries may be a better bet: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://www.arieselec.com/Web_Data_Sheets/18036/18036.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.arieselec.com/Web_Data_Sheets/18036/18036.htm&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://www.arieselec.com/results.php?searchtype=3&amp;amp;partno=24-351000-10&quot; rel=&quot;nofollow&quot;&gt;http://www.arieselec.com/results.php?searchtype=3&amp;amp;partno=24-351000-10&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://www.arieselec.com/results.php?searchtype=3&amp;amp;partno=24-351000-11&quot; rel=&quot;nofollow&quot;&gt;http://www.arieselec.com/results.php?searchtype=3&amp;amp;partno=24-351000-11&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://www.arieselec.com/results.php?searchtype=3&amp;amp;partno=24-651000-10&quot; rel=&quot;nofollow&quot;&gt;http://www.arieselec.com/results.php?searchtype=3&amp;amp;partno=24-651000-10&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://www.arieselec.com/results.php?searchtype=3&amp;amp;partno=28-555000-00&quot; rel=&quot;nofollow&quot;&gt;http://www.arieselec.com/results.php?searchtype=3&amp;amp;partno=28-555000-00&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-19T02:30:26.210" LastActivityDate="2010-12-19T02:30:26.210" CommentCount="1" />
  <row Id="8074" PostTypeId="2" ParentId="8059" CreationDate="2010-12-19T03:50:22.873" Score="1" ViewCount="" Body="&lt;p&gt;Another Excellent PLL reference is this one&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.national.com/analog/timing/pll_designbook&quot; rel=&quot;nofollow&quot;&gt;http://www.national.com/analog/timing/pll_designbook&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2148" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-19T05:38:10.997" LastActivityDate="2010-12-19T05:38:10.997" />
  <row Id="8076" PostTypeId="1" CreationDate="2010-12-19T14:00:00.733" Score="3" ViewCount="146" Body="&lt;p&gt;Hi,&#xA;I'm trying to use parallax ping ultrasonic sensor to measure distance but I'm having some problems. Here is the code that I'm uploading to my arduiono (duemilanove) that is kinda similar to the one in the example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// this constant won't change.  It's the pin number&#xA;// of the sensor's output:&#xA;const int pingPin = 7;&#xA;&#xA;void setup() {&#xA;  // initialize serial communication:&#xA;  Serial.begin(9600);&#xA;}&#xA;&#xA;void loop()&#xA;{&#xA;  // establish variables for duration of the ping,&#xA;  // and the distance result in inches and centimeters:&#xA;  long duration, inches, cm;&#xA;&#xA;  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.&#xA;  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:&#xA;  pinMode(pingPin, OUTPUT);&#xA;  digitalWrite(pingPin, LOW);&#xA;  delayMicroseconds(2);&#xA;  digitalWrite(pingPin, HIGH);&#xA;  delayMicroseconds(5);&#xA;  digitalWrite(pingPin, LOW);&#xA;&#xA;  // The same pin is used to read the signal from the PING))): a HIGH&#xA;  // pulse whose duration is the time (in microseconds) from the sending&#xA;  // of the ping to the reception of its echo off of an object.&#xA;  pinMode(pingPin, INPUT);&#xA;  duration = pulseIn(pingPin, HIGH);&#xA;&#xA;  // convert the time into a distance&#xA;  inches = microsecondsToInches(duration);&#xA;  cm = microsecondsToCentimeters(duration);&#xA;&#xA;  Serial.print(duration);&#xA;  Serial.print(&quot; ms &quot;);&#xA;  Serial.print(inches);&#xA;  Serial.print(&quot;in, &quot;);&#xA;  Serial.print(cm);&#xA;  Serial.print(&quot;cm&quot;);&#xA;  Serial.println();&#xA;&#xA;  delay(1000);&#xA;}&#xA;&#xA;long microsecondsToInches(long microseconds)&#xA;{&#xA;  // According to Parallax's datasheet for the PING))), there are&#xA;  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per&#xA;  // second).  This gives the distance travelled by the ping, outbound&#xA;  // and return, so we divide by 2 to get the distance of the obstacle.&#xA;  // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf&#xA;  return microseconds / 74 / 2;&#xA;}&#xA;&#xA;long microsecondsToCentimeters(long microseconds)&#xA;{&#xA;  // The speed of sound is 340 m/s or 29 microseconds per centimeter.&#xA;  // The ping travels out and back, so to find the distance of the&#xA;  // object we take half of the distance travelled.&#xA;  return microseconds / 29 / 2;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The problem is that the serial keeps returning &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;21491 ms 145in, 370cm&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;regardless of object infront of the sensor or no object at all. I've tried modifying the delayMicroseconds in the code and it still comes out the same. I've tried different pins as well. So I'm guessing its not a software problem but maybe hardware? I also read the parallax documentation and it doesn't specify if ambient sounds might effect it or not or if there is some sort of initial calibration that needs to be done? I've read the arduino documentation and double and triple checked everything but I can't seem to find what might be causing this. The wires are connected up correctly and everything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, does anyone have any suggestions on what I might be doing wrong here? Thanks for any help &lt;/p&gt;&#xA;" OwnerUserId="2331" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-12-19T15:03:44.160" LastActivityDate="2010-12-19T15:03:44.160" Title="problem with parallax ping" Tags="&lt;arduino&gt;&lt;sensor&gt;" AnswerCount="1" />
  <row Id="8077" PostTypeId="2" ParentId="8076" CreationDate="2010-12-19T14:13:36.233" Score="1" ViewCount="" Body="&lt;p&gt;Please try to format the program code with code sample button.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your code seems to be correct, I could use it with my Duemilanove and Parallax Ping.&#xA;Are the wires of the Ping correctly connected? 5 V to 5 Volt, GND to ground and SNG to Pin 7?&lt;/p&gt;&#xA;" OwnerUserId="1649" LastActivityDate="2010-12-19T14:13:36.233" CommentCount="6" />
  <row Id="8078" PostTypeId="1" CreationDate="2010-12-19T17:26:21.527" Score="4" ViewCount="590" Body="&lt;p&gt;Hello everyone, I want two atmega32s to communicate over a range of 1000ft, so I decided to use a serial wire for it. I know rs232 is not a good way to communicate over this large range, so I decided to use RS485 which is a balanced pair. For this I want to use MAX485 chips like these.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/NeQ4e.jpg&quot; alt=&quot;MAX485 Chip diagram&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I wrote all the code to use it and got it working for short wire communication with a battery powering my ATmegas (and the MAX485 chips) (I cannot produce the code here as it is for a company where I am just an intern, but as it works in short wire the code is not the problem). What the program basically does is, one atmega sends &quot;Paresh&quot; on serial, the other atmega receives it, does a strcmp if it is indeed recieved as &quot;Paresh&quot; it sends out &quot;Mathur&quot;. If the first atmega receives &quot;Mathur&quot; it again sends paresh and the cycle continues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All this works just fine for serial mode, short wire and on a 6V battery. But as soon as I switch to a CAT-5 cable I get packet loss. I printed what ever one receives on an LCD and after a few cycles (and sometimes even for the first transfer) there is strange strings received. The problems are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;It works for short wire but not a 30ft CAT-5 cable&lt;/li&gt;&#xA;&lt;li&gt;It works for 6V battery but not for 12 volt battery or a 12V adapter.&lt;/li&gt;&#xA;&lt;li&gt;It works for normal serial wire upto 10ft but not more than that.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The things I have tried are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Added capacitors to fade out any ripples in the supply. (470uf caps).&lt;/li&gt;&#xA;&lt;li&gt;Increased delays between switching from transmit to receive modes ( _delay_ms(3); ).&lt;/li&gt;&#xA;&lt;li&gt;added caps to the supply to the modules.&lt;/li&gt;&#xA;&lt;li&gt;Adding 120ohm terminal resistance to both modules.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;What should I do? Please do no suggest any alternatives to the the thing, it would hurt the hacker in me. Why cannot I use an RS485 communication for exactly the purpose it was designed .i.e long distance communication over serial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update 1:&lt;/strong&gt; I used 120ohm terminal resistance.&#xA;&lt;strong&gt;Update 2:&lt;/strong&gt; I am on a 9600 baudrate.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="1200" LastEditorDisplayName="" LastEditDate="2010-12-19T18:01:39.997" LastActivityDate="2011-02-08T15:27:26.930" Title="MAX485 half duplex Atmega communication problem" Tags="&lt;avr&gt;&lt;atmega&gt;&lt;rs485&gt;" AnswerCount="5" CommentCount="7" />
  <row Id="8079" PostTypeId="2" ParentId="8078" CreationDate="2010-12-19T17:43:24.833" Score="3" ViewCount="" Body="&lt;p&gt;One thing that you haven't mentioned is using termination resistors. RS485 needs termination resistors at each point of the bus, usually 120 ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/763&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; document published by Maxim on RS485 wiring.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-19T17:43:24.833" CommentCount="1" />
  <row Id="8080" PostTypeId="1" AcceptedAnswerId="8084" CreationDate="2010-12-19T18:18:23.170" Score="4" ViewCount="119" Body="&lt;p&gt;I am working on a project where I want to get very accurate data from an accelerometer. I plan on sending my data over bluetooth to be interpreted by a computer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am assuming that bluetooth will have some unknown delays that come from things such as how Windows handles the data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, since the accelerometer data is time depended, would I be benefited by using a clock that can easily create time in some even divisor of seconds? Or possibly add a RTC? I would then be able to &quot;time-stamp&quot; my data before sending it over bluetooth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this worth it or am I just over thinking how accurate I can actually get my data to be? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Clarification:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will be pulling in data based off of a timer interrupt. I am wondering if my timer needs to be something like 0.5ms. I would go ahead and &quot;time-stamp&quot; the messages I am sending so I know if I loose a message for some reason.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I am using a digital accelerometer, so I am not doing an ADC, instead I am getting the measurements over I2C.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-12-19T19:23:47.933" LastActivityDate="2010-12-19T19:34:13.043" Title="Do I need an accurate clock for an accelerometer?" Tags="&lt;bluetooth&gt;&lt;accelerometer&gt;&lt;rtc&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="8081" PostTypeId="2" ParentId="8078" CreationDate="2010-12-19T18:36:55.027" Score="3" ViewCount="" Body="&lt;p&gt;In my [in]experience, 99% of serial communication errors are due to timing mismatches; the other* 99% is due to wiring hoopla. &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;It works for short wire but not a 30ft CAT-5 cable&lt;/li&gt;&#xA;  &lt;li&gt;It works for normal serial wire upto 10ft but not more than that.&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;CAT-5 cable is twisted pair (also, all of what I have used is also shielded, but apparently this is not common); I assume the &quot;normal serial wire&quot; is two loose wires. As wiring gets longer, your nice digital rise times stretch out, effectively shrinking the available window for sampling incoming data. Twisted pair helps this a bit. What this really means is that your UART clock must be prescaled more accurately to the baud rate being used. System clocks for perfect USART communications should be multiples of 1.8432MHz. &lt;a href=&quot;http://electronics.stackexchange.com/questions/7610/what-is-the-maximum-acceptable-baud-rate-error-for-rs-232-serial-communication&quot;&gt;Short-range communications can tolerate a few percentage error&lt;/a&gt;, but as your sampling window shrinks it must be more accurate. What your prescaler (int), and baud error?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;prescaler = (int)(F_CPU / (USART_baudrate * 16) - 1)&#xA;actual_baudrate = F_CPU / (prescaler * 16)&#xA;baud_error = 100% * (1 - actual_baudrate / USART_baudrate)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;It works for 6V battery but not for 12 volt battery or a 12V adapter.&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This sounds fishy! This may be a completely different problem, perhaps causing your widget to reset due to a dirty supply or poor regulation. There are stability issues with LDO linear regulators and varying capacitive loads; there may be dissipation issues from a 12V supply; if one isn't using a LDO regulator, then a 6V battery will really be giving you 4.5V to 5V, and won't be well regulated. Power supply issues are in a class all their own, and must be rectified before peripherals can be effectively debugged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than this, there is always the issue with environmental interference, or &lt;a href=&quot;http://en.wikipedia.org/wiki/Electromagnetic_interference&quot; rel=&quot;nofollow&quot;&gt;EMI&lt;/a&gt;. RS-485 is made for this, but should be used with twisted pair[, shielded wire,] like the CAT-5 cable you've used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*&lt;em&gt;(What, my math is wrong? Do you know who I am!? ;)&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-21T21:55:48.140" LastActivityDate="2010-12-21T21:55:48.140" CommentCount="5" />
  <row Id="8082" PostTypeId="1" CreationDate="2010-12-19T19:03:22.347" Score="2" ViewCount="215" Body="&lt;p&gt;I'm currently in an &quot;Information Technology&quot; program, and this program includes some electronics courses. So, I know a little bit about voltage sources, current sources, resistors, capacitors, inductors, operational amplifiers, basic first-order filters, and soon I should know a little bit about diodes and transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In class, we hear some theory. In labs, we play with oscilloscopes. And these things are all fine and good, but I'd like to building something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm tapping you fine folks for resources, simple and informative beginner's projects that will help me learn these topics more solidly. Start me with educative tutorials on blinking lights and finish with educative tutorials on line-following robots (or something like that). I'll emphasize that the recurring theme is 'educative'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to make it clear that I do not come from an electronics background. (I just pretend like I do when I'm at school.)&lt;/p&gt;&#xA;" OwnerUserId="2332" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-19T22:40:19.173" LastActivityDate="2010-12-20T18:37:57.283" Title="What are some simple and informative beginners projects?" Tags="&lt;education&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="8083" PostTypeId="2" ParentId="8082" CreationDate="2010-12-19T19:28:49.413" Score="6" ViewCount="" Body="&lt;p&gt;You've come to the right place to find out! It's a good idea to search for previous questions. One trick is to click a tag, like &lt;a href=&quot;http://electronics.stackexchange.com/questions/tagged/beginner&quot;&gt;&lt;code&gt;[beginner]&lt;/code&gt;&lt;/a&gt;, then organize the returned results by clicking one of the headings: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/tags/beginner/info&quot;&gt;about the beginner tag&lt;/a&gt; | &lt;a href=&quot;http://electronics.stackexchange.com/tags/beginner/faq&quot;&gt;faq&lt;/a&gt; | &lt;a href=&quot;http://electronics.stackexchange.com/tags/beginner/topusers&quot;&gt;top users&lt;/a&gt; | &lt;a href=&quot;http://electronics.stackexchange.com/tags/beginner/hot&quot;&gt;hot answers&lt;/a&gt; | &lt;a href=&quot;http://electronics.stackexchange.com/tags/beginner/new&quot;&gt;new answers&lt;/a&gt; | &lt;a href=&quot;http://electronics.stackexchange.com/tags/beginner/synonyms&quot;&gt;synonym&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Clicking &quot;&lt;a href=&quot;http://electronics.stackexchange.com/tags/beginner/hot&quot;&gt;hot answers&lt;/a&gt;&quot; gives a bunch of results, of which these look promising:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/1763/what-are-the-best-hardware-hacking-magazines/1766#1766&quot;&gt;What are the best hardware hacking magazines?&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/3366/learning-electrical-engineering&quot;&gt;Learning Electrical Engineering&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/3834/what-are-the-ways-i-can-make-my-circuit-communicate-with-a-computer&quot;&gt;What are the ways I can make my circuit communicate with a computer?&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/724/what-are-the-best-beginner-project-using-an-arduino/733#733&quot;&gt;What are the best beginner project using an arduino&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In my opinion, digging into one of the Arduino kits is a great way to learn electronics. You have to work on fundamental electrical issues, like which way to plug in an LED and what value resistor to use with it, at the same time as successfully using a complete microcontroller implementation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's another great project to get you started, with plenty of got'chas and complicated electrical schtuff, &lt;a href=&quot;http://www.ladyada.net/make/mintyboost/process.html&quot; rel=&quot;nofollow&quot;&gt;Adafruit's Mintyboost&lt;/a&gt;. It is a boost regulator, which is much more complicated and exciting than those linear regulators. Understanding how this project works will leave your classmates in the dust, and is essential knowledge later in your career (as a professional or hobbyist).&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-19T19:51:34.383" LastActivityDate="2010-12-19T19:51:34.383" CommentCount="1" />
  <row Id="8084" PostTypeId="2" ParentId="8080" CreationDate="2010-12-19T19:34:13.043" Score="8" ViewCount="" Body="&lt;p&gt;It sounds like your measurements are already on an even interval controlled by your device, so you could simply add a serial number to each measurement or block of measurements to ensure that you don't lose one. This could be as simple as a single byte, which would have lower overhead than a full time stamp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While a dedicated RTC could provide very accurate time stamps, it would not necessarily make the timing of your measurements any more accurate unless you drive those samples off an interrupt from the RTC. What matters from a filtering standpoint is how low the jitter is on the sampling of the signal, not on receiving the data. &lt;/p&gt;&#xA;" OwnerUserId="1409" LastActivityDate="2010-12-19T19:34:13.043" CommentCount="1" />
  <row Id="8085" PostTypeId="2" ParentId="7901" CreationDate="2010-12-19T19:39:48.217" Score="2" ViewCount="" Body="&lt;p&gt;My personal experience is that the C code to program and get started with AVR is pretty easy, I also come from many years of doing java, and after about 2 months of using arduino sketches I dropped the environment and went for avr-gcc, sites like avrfreaks make easy to find answers to common problems. (I still do all on my trusty Arduino Duemillenove)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using eclipse to compile and &quot;deploy&quot; i.e. write to the chip, is also nice as I don't have to deal with another IDE&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think is actually harder to get your head around registers, 16 bit registers and read them in the appropriate order, interrupts, timers, hardware PWM, than the programming language itself.&lt;/p&gt;&#xA;" OwnerUserId="187" LastActivityDate="2010-12-19T19:39:48.217" />
  <row Id="8086" PostTypeId="1" CreationDate="2010-12-19T22:01:07.117" Score="0" ViewCount="89" Body="&lt;p&gt;HI all,&#xA; I was wondering if a Weller EC2002m base use other Weller soldering irons and/or soldering fingers? I am finding it hard to find tips for my EC1201A soldering iron and would like to switch to a better soldering iron to facilitate better tip selections. &lt;/p&gt;&#xA;" OwnerUserId="2334" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-19T22:13:43.240" LastActivityDate="2010-12-20T12:42:24.190" Title="Can a weller EC2002m base use other weller solder irons?" Tags="&lt;soldering&gt;" AnswerCount="1" />
  <row Id="8087" PostTypeId="2" ParentId="8082" CreationDate="2010-12-19T22:25:43.180" Score="3" ViewCount="" Body="&lt;p&gt;What do you mean &quot;Play with oscilloscopes&quot;? If you're saying that you're demonstrating your filters and voltage sources with input from a function generator and output to an oscilloscope, you should be aware that this is a lot of what analog electronics are about. Packaging some variation of the circuits you've built with a speaker or antenna and battery isn't a very big jump.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're more interested in blinking lights and robots, you need to get out of your analog classes and take computer engineering classes in digital design, embedded systems, the C programming language, etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Analog and digital are two very different domains.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-19T22:25:43.180" CommentCount="1" />
  <row Id="8088" PostTypeId="2" ParentId="8068" CreationDate="2010-12-19T23:27:31.973" Score="1" ViewCount="" Body="&lt;p&gt;Some other sites that might carry something suitable - I've not ordered from any of them so I can't endorse them personally, but I thought the links might be helpful.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.proto-advantage.com&quot; rel=&quot;nofollow&quot;&gt;proto-advantage.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.winslowadaptics.com&quot; rel=&quot;nofollow&quot;&gt;winslowadaptics.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.schmartboard.com&quot; rel=&quot;nofollow&quot;&gt;schmartboard.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.beldynsys.com&quot; rel=&quot;nofollow&quot;&gt;beldynsys.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2336" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-12-20T01:41:39.250" LastActivityDate="2010-12-20T01:41:39.250" CommentCount="1" />
  <row Id="8089" PostTypeId="2" ParentId="7850" CreationDate="2010-12-19T23:37:48.927" Score="0" ViewCount="" Body="&lt;p&gt;AFAIK, to do this correctly, you really need to be looking at a device with some kind of memory-management unit (MMU). While dynamic allocation mechanisms for the PIC18 series do exist, they're not really going to be that solid - and speaking as someone who's worked on firmware that pushes the limits of the PIC18 series, I can say that you're not going to get a sizable application in there if you spend all the overhead on a memory manager.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Better solution: try to understand what it's doing, and why it needs dynamic allocation. See if you can't re-factor it to work with static allocation. (It may be the case that this is simply not possible - if the library/application is designed to do something that scales freely, or doesn't have bounds of the amount of input it can accept.) But sometimes, if you really think about what you're trying to do, you might find it is possible (and possibly even quite easy) to use static allocation instead.&lt;/p&gt;&#xA;" OwnerUserId="2336" LastActivityDate="2010-12-19T23:37:48.927" CommentCount="2" />
  <row Id="8090" PostTypeId="2" ParentId="8034" CreationDate="2010-12-20T02:00:22.573" Score="1" ViewCount="" Body="&lt;p&gt;You can get a resistor's function by using a MOSFET in the triode region, where the gate to source voltage is less than the drain to source voltage but greater than the threshold voltage (usually a couple volts).  In this region, the MOSFET acts roughly as a resistor controlled by the gate voltage.  In this region, Ohm's law - Voltage and current have a constant ratio - is roughly approximated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a valuable technique for manufacturing integrated circuits, where large-value resistances take too much surface area on the chip.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is not a valuable technique for reducing power consumption, as you seem to hope.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-20T02:00:22.573" />
  <row Id="8091" PostTypeId="1" AcceptedAnswerId="8092" CreationDate="2010-12-20T02:09:46.903" Score="1" ViewCount="118" Body="&lt;p&gt;As in the title. I've just noticed in one of my PCB designs the components are not aligned to a grid and neither are the traces. It passes DRC, but I'm wondering if it will cause further problems. I'll be using standard PCB houses like PCBcart, SeeedStudio etc.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-20T02:36:16.737" Title="Is it important to keep components and traces on a PCB aligned to a grid?" Tags="&lt;pcb&gt;" AnswerCount="1" />
  <row Id="8092" PostTypeId="2" ParentId="8091" CreationDate="2010-12-20T02:36:16.737" Score="2" ViewCount="" Body="&lt;p&gt;Ultimately, the grid your design actually uses is built into the Gerber file you export from your PCB tool. The files that I generate from Eagle are in inches, with either 3 or 4 digits to the right of the decimal place. That puts me on a 1 mil grid. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you're using parts with different units (Metric vs. Inches), you're bound to have some grid mis-alignment, but it will be very small. If your design uses the minimum spacing rules, it's possible some spacing violations may come up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In short, the only grid that really matters is the one you export your design to. Any other grid is for convenience.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-20T02:36:16.737" CommentCount="2" />
  <row Id="8093" PostTypeId="1" AcceptedAnswerId="8119" CreationDate="2010-12-20T03:12:51.780" Score="11" ViewCount="152" Body="&lt;p&gt;After taking classes in control theory as an undergraduate, I ended up not using them at all after I graduated. I've started to fix that by starting a hobby project in controls. My textbooks are pretty good references for the theory, but my biggest problem is that I have not found a good reference on determining system parameters in models. For example, say I have a temperature sensor located some distance away from a heating element, and on top of that it has some non-trivial amount of thermal mass. How should I model this non-ideality? And even after I've modeled the error function for the element, how do I determine the actual numerical coefficients from bench experiments?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone here have any good textbooks or references to recommend? &lt;/p&gt;&#xA;" OwnerUserId="2183" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-20T14:48:34.963" LastActivityDate="2010-12-20T22:17:22.827" Title="System Modeling for Control Systems" Tags="&lt;control-system&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="4" />
  <row Id="8094" PostTypeId="1" AcceptedAnswerId="8095" CreationDate="2010-12-20T11:48:58.010" Score="1" ViewCount="100" Body="&lt;p&gt;I was installing a heatsink which didn't quite fit and after installing it, I noticed that I've twisted the L200CV about 5° when looking from above the chip. What kind of damage, if any, can I expect? &lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-20T14:42:53.097" LastActivityDate="2010-12-20T14:42:53.097" Title="I twisted a L200CV in Pentawatt package; what kind of damage can I expect?" Tags="&lt;mechanical-assembly&gt;" AnswerCount="1" />
  <row Id="8095" PostTypeId="2" ParentId="8094" CreationDate="2010-12-20T12:06:12.527" Score="5" ViewCount="" Body="&lt;p&gt;If you bent the leads after the package was soldered in, the solder joints may have cracked. It is worth touching them up. Ensure you don't dry them out by using flux and a reasonable temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The regulator itself will be fine. Leads are meant to be bent.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-20T12:06:12.527" CommentCount="4" />
  <row Id="8096" PostTypeId="2" ParentId="8086" CreationDate="2010-12-20T12:42:24.190" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.cooperhandtools.com/brands/electronic_applications/Manuals/EC2002M_OI_PL.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a document with a list of the hand pieces compatible with the EC2002M.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-20T12:42:24.190" />
  <row Id="8097" PostTypeId="1" AcceptedAnswerId="8101" CreationDate="2010-12-20T14:48:25.000" Score="1" ViewCount="322" Body="&lt;p&gt;I want my Arduino project to listen to the ambient music and sync its light show output to the beat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems that &lt;a href=&quot;http://www.gamedev.net/reference/programming/features/beatdetection/&quot; rel=&quot;nofollow&quot;&gt;doing BPM detection properly&lt;/a&gt; is fiendishly difficult in software, but if your music is sufficiently &lt;a href=&quot;http://en.wikipedia.org/wiki/Techno&quot; rel=&quot;nofollow&quot;&gt;doofy&lt;/a&gt; in nature and you use a little bit of hardware you can cheat and get away with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my plan is to hook a &lt;a href=&quot;http://www.sparkfun.com/products/9964&quot; rel=&quot;nofollow&quot;&gt;mic/opamp breakout board&lt;/a&gt; to a simple &lt;a href=&quot;http://www.electronics-tutorials.ws/filter/filter_2.html&quot; rel=&quot;nofollow&quot;&gt;1st order passive low-pass filter&lt;/a&gt; and sample the input on an interrupt every 5ms or so. &lt;a href=&quot;http://audacity.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;Audacity&lt;/a&gt; tells me a bass beat is around 15ms long, so every 5ms should be plenty to make sure I don't, er, &quot;miss a beat&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If my low-pass'd sample is over a volume threshold, I'll record the time since the last beat, do some kind of weighted average calculation over the past few samples and that will allow me to predict how many ms until the next beat (some other software trickery might be necessary to account for bass drops and &lt;a href=&quot;http://www.youtube.com/watch?v=5SaFTm2bcac&quot; rel=&quot;nofollow&quot;&gt;breakbeats&lt;/a&gt;.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Firstly, do I have roughly the right idea?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Secondly, can anyone tell me what order-of-magnitude values I'll need for the resistor and capacitor? I figure I want my cutoff frequency to be something like 500-1000Hz. I also gather the resistance of the rest of my circuit counts but I'm not sure where to measure that resistance across. A little fiddling with &lt;a href=&quot;http://sim.okawa-denshi.jp/en/CRtool.php&quot; rel=&quot;nofollow&quot;&gt;this tool&lt;/a&gt; gives me answers that look reasonable (500Hz = 330Ω/1uF) but I don't know enough to really know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An example schematic showing where I measure the resistance of the existing circuit and where the low pass filter goes in the context of the rest would be exceedingly helpful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, Robert. &lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2010-12-20T18:29:35.753" Title="Low pass audio filter design" Tags="&lt;arduino&gt;&lt;audio&gt;&lt;filter&gt;&lt;basic&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="8098" PostTypeId="2" ParentId="8034" CreationDate="2010-12-20T14:53:00.280" Score="0" ViewCount="" Body="&lt;p&gt;If the device used a voltage that was not DC it would be possible.  There are many passive RF components that consume negligible DC current.  This is because at AC frequencies, reactive components (inductors and capacitors) look like resistances to AC.  Using AC current would not have resistive losses, but there would still be reactive losses (which equates to power-consumption just the same) so you still can't outsmart thermodynamics &amp;amp; conservation of energy. The trouble, with both AC and DC circuits, is that even purely reactive components still have some internal resistance.  Even the traces on a PCB have inherent resistance, that will make resistive losses hard to overcome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You were wondering if we could have a device that consumes practically no current due to the lack of resistive losses.  Though you could get voltage division by using either diodes or MOSFETS in a clever fashion, your end goal is still somewhat limited due to the fact that no ideal reactive components exist and that even PCB traces have non-zero resistances and that if you want to do any &quot;work&quot; that takes energy and thus, thermodynamics limits you to using some energy to perform that work.&lt;/p&gt;&#xA;" OwnerUserId="1571" LastEditorUserId="1571" LastEditorDisplayName="" LastEditDate="2010-12-20T18:31:37.657" LastActivityDate="2010-12-20T18:31:37.657" />
  <row Id="8099" PostTypeId="1" AcceptedAnswerId="8102" CreationDate="2010-12-20T14:57:23.660" Score="6" ViewCount="170" Body="&lt;p&gt;I have seen questions like &lt;a href=&quot;http://electronics.stackexchange.com/questions/5850/how-critical-are-uart-frequencies&quot;&gt;this&lt;/a&gt; that talk about selecting a crystal for UART and I have seen questions like &lt;a href=&quot;http://electronics.stackexchange.com/questions/7800/real-time-clock-and-crystal-precision&quot;&gt;this&lt;/a&gt; that mention 32.768 kHz for RTC. But how do I decide the right crystal for my application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At this point I am not sure what UART baud I will be using, but it will be one of the standard one. It would be nice to be able to get semi-accurate time in milliseconds, but not a requirement. Intuitively I think going with the fastest crystal that my micro can use will give me the most flexibility, but is there something I am missing? Is there a &quot;general-purpose&quot; frequency that people use?&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-20T18:28:06.750" Title="How should I select my crystal frequency?" Tags="&lt;crystal&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="8100" PostTypeId="2" ParentId="8097" CreationDate="2010-12-20T15:11:27.107" Score="2" ViewCount="" Body="&lt;p&gt;I hate linking to wikipedia for answers, but here is a good explanation: &lt;a href=&quot;http://en.wikipedia.org/wiki/Low-pass_filter&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Low-pass_filter&lt;/a&gt; under Electronic low-pass filters&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do have some concerns with your plan though. A first order filter will give you a drop off of −6 dB per octave. This means that if you set your cut off frequency at 500Hz, you will only have a 6db drop off by 1khz. In music there is a lot going on in the sub 5khz frequency that you will still be passing through a decent amount. The digital filtering (weighted average calculation) you are doing may help you out, but not sure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get a better frequency response by going to a higher order filter. Either way I think you will be much happier with an opamp low pass filter. You can also look into some digital filtering, its nothing to be scared of. &lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-12-20T15:19:55.490" LastActivityDate="2010-12-20T15:19:55.490" CommentCount="4" />
  <row Id="8101" PostTypeId="2" ParentId="8097" CreationDate="2010-12-20T15:12:56.507" Score="4" ViewCount="" Body="&lt;p&gt;A fair share of the spectral content of most music is below 500-1000 Hz, and with a fairly weak first-order filter falloff of 6 dB/octave, your waveform will be relatively unaffected.  A much higher-order filter would be required, preferably at a much lower cutoff (440 Hz is concert A, bass hits should be &lt;em&gt;way&lt;/em&gt; below that), with envelope detection (a diode and cap).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you don't care about the actual fidelity of the audio, a passive filter should suffice, though the order required may significantly reduce your amplitude and reduce the effective resolution.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Addendum:&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Just to reiterate other's concerns, the main problem of just filtering audio like this is that if you have some very loud hit (e.g. cymbal crash), it will still go through your LPF (low-pass filter) and give you spikes that you may interpret wrong.  Another problem would be inability to cope with much dynamic range (music getting softer/louder); though you may be able to add some variable threshold.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you've correctly stated, this approach will work best with Techno, but that still might not be very good.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-20T18:29:35.753" LastActivityDate="2010-12-20T18:29:35.753" CommentCount="5" />
  <row Id="8102" PostTypeId="2" ParentId="8099" CreationDate="2010-12-20T15:20:30.390" Score="7" ViewCount="" Body="&lt;p&gt;Honestly I could spend hours describing the different frequencies and why to use them, but someone already has!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Crystal_oscillator_frequencies&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Crystal_oscillator_frequencies&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This table has a UART column to tell you what UART frequencies it divides to well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It also tells you when a frequency is a standard crystal for a specific comm system.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-20T15:20:30.390" CommentCount="2" />
  <row Id="8103" PostTypeId="1" AcceptedAnswerId="8105" CreationDate="2010-12-20T15:27:06.013" Score="4" ViewCount="471" Body="&lt;p&gt;I've played with AVRs before with my atmel development kit and have seen recently the use of Arduinos increasing. I have a few questions from users:  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is it the same as using a microcontroller?&lt;/li&gt;&#xA;&lt;li&gt;Are there any restrictions with the use of the Arduino instead of using the microcontroller?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I am interested in moving to them but also which should i get as there are so many to choose from.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-20T15:38:10.037" LastActivityDate="2011-05-07T13:15:34.803" CommunityOwnedDate="2011-05-07T13:15:59.843" Title="Arduino: is it worth it?" Tags="&lt;arduino&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="8104" PostTypeId="2" ParentId="8103" CreationDate="2010-12-20T15:33:18.590" Score="5" ViewCount="" Body="&lt;p&gt;An Arduino is basically a cheap, unsupported (&quot;open-source&quot;) development board.  You can use the Arduino libraries and software for a gentle introduction to MCUs, or you could go all out and use none of it and develop on the &lt;a href=&quot;http://www.atmel.com/products/AVR/&quot; rel=&quot;nofollow&quot;&gt;Atmel AVR&lt;/a&gt; directly with &lt;a href=&quot;http://www.atmel.com/dyn/products/tools_card.asp?tool_id=2725&amp;amp;source=redirect&quot; rel=&quot;nofollow&quot;&gt;AVR Studio&lt;/a&gt; and &lt;a href=&quot;http://winavr.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;WinAVR&lt;/a&gt; (containing the &lt;code&gt;avr-gcc&lt;/code&gt; compiler).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if you don't use Arduino software, the board is still going to be physically the same size, so there's nothing preventing you from using &lt;a href=&quot;http://www.arduino.cc/playground/Main/SimilarBoards&quot; rel=&quot;nofollow&quot;&gt;shields&lt;/a&gt;, which is a convenient way for hobbyists to add hardware if you don't want to do much component assembly (let alone make/drill PCBs).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For what it's worth, I somewhat like the Arduino concept, but the use of C++ is obnoxious, and I fail to see the value in hiding &lt;code&gt;main();&lt;/code&gt; from the user.  Fortunately, that can all be done away with.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-20T15:38:34.623" LastActivityDate="2010-12-20T15:38:34.623" CommunityOwnedDate="2011-05-07T13:15:59.843" CommentCount="3" />
  <row Id="8105" PostTypeId="2" ParentId="8103" CreationDate="2010-12-20T15:36:24.223" Score="8" ViewCount="" Body="&lt;p&gt;The various Arduino boards use AVR micro-controllers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the appropriate software, using the Arduino is the same as using any other micro-controller. However, the Arduino software doesn't support in-circuit debugging, which is available with other development software like Atmel's AVR Studio. You can use the Arduino hardware with AVR Studio and Atmel hardware tools like the Dragon programmer/debugger. The Arduino software supports downloading to the target via a bootloader.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino web site and forums&lt;/a&gt; are very useful if you need help.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-20T15:36:24.223" CommunityOwnedDate="2011-05-07T13:15:59.843" />
  <row Id="8106" PostTypeId="2" ParentId="8103" CreationDate="2010-12-20T15:51:38.943" Score="3" ViewCount="" Body="&lt;p&gt;My first question for you is -- what are you going to do with it?  While getting Arduino up and running is easy and there are quite a few sketches available to play with, development isn't all that fun.  IMO, the IDE is a little quirky and some of the keyboard shortcuts are really obnoxious to Visual Studio developers.  :)  Like Leon said, you won't have in-circuit debugging, but some of the other ease-of-entry devices like mbed don't have it, either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're just playing around and bitbanging to learn about LCDs, or want to read sensor data, or interact with serial devices, it's great.  However, if I were deciding on a platform for a consumer-ish product, I would choose something else that provided in-circuit debugging.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-20T15:51:38.943" CommunityOwnedDate="2011-05-07T13:15:59.843" CommentCount="5" />
  <row Id="8107" PostTypeId="2" ParentId="7913" CreationDate="2010-12-20T17:25:11.250" Score="1" ViewCount="" Body="&lt;p&gt;Another thing to consider is that it makes Gerber files smaller.  Gerber files define a series of lines (among other shapes).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e.g. To draw a true circle in a Gerber file takes hundreds (thousands?) of lines.  But to draw an octagon takes only eight lines.&lt;/p&gt;&#xA;" OwnerUserId="2257" LastActivityDate="2010-12-20T17:25:11.250" CommentCount="5" />
  <row Id="8108" PostTypeId="2" ParentId="8093" CreationDate="2010-12-20T17:34:09.843" Score="4" ViewCount="" Body="&lt;p&gt;I've had a similar history with control theory. Last year, I tried to solve the same problem, but I was only somewhat successful. I learned a few things:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;This part of the field is called &quot;system identification.&quot;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Unfortunately, most engineering literature on the topic covers dynamic system identification, meaning the task of adjusting control parameters because, for example, the mass of your robotic arm changed because it picked up a box.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For a lot of physical parameters, there are tests you can do that will give you decent estimates. For example, in mechanical systems, you can measure the stiffness of a beam by weighing it down with a few different masses and measuring how far it deflects. For the specific example of thermal mass, I'd think your best bet is probably estimation by material properties and volume, unless you have a calorimeter.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For estimating gains for PID systems that actually exist outside the computer, I've found the Ziegler-Nichols method to be a good start: &lt;a href=&quot;http://www.mstarlabs.com/control/znrule.html&quot; rel=&quot;nofollow&quot;&gt;http://www.mstarlabs.com/control/znrule.html&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;From what I can tell, the general procedure often involves building a prototype with a powerful actuator, and then seeing how the system reacts to different inputs. See, for example, this Matlab tutorial that describes how you can estimate the damping coefficient and natural frequency of a system by measuring its response to a step input (i.e. jerking a spring and seeing how it wiggles): &lt;a href=&quot;http://www.me.cmu.edu/ctms/modeling/tutorial/systemidentification/mainframes.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.me.cmu.edu/ctms/modeling/tutorial/systemidentification/mainframes.htm&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-20T17:34:09.843" />
  <row Id="8109" PostTypeId="2" ParentId="2377" CreationDate="2010-12-20T17:42:45.403" Score="0" ViewCount="" Body="&lt;p&gt;If you're short on space, try IAR's Embedded workbench - their free 'kickstart' version has a 4K word  code size limit, so plenty for ATTiny's, and probably better optimisation than gcc&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-20T17:42:45.403" CommentCount="1" />
  <row Id="8110" PostTypeId="2" ParentId="8099" CreationDate="2010-12-20T18:28:06.750" Score="2" ViewCount="" Body="&lt;p&gt;Intuitively, &lt;em&gt;I&lt;/em&gt; would use the SLOWEST crystal that works for my application. You'll get less clock drift and circuit traces generally behave nicer at lower frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an aside, if you want to do things every few milliseconds, you can do something along the lines of the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Fosc = 25MHz. &#xA;T=1/Fosc = 40ns; &#xA;1ms/40ns = 25000 cycles/ms;&#xA;0xFFFF-25000=0x9E57;&#xA;&#xA;on overflow TMR1:  //assuming TMR1 is 16 bit and counts every clock cycle&#xA;doEveryMillisecond;&#xA;incrementMillisecondTimer;&#xA;TMR1 = 0x9E57;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Not sure what micro you're using but MPLAB has utilities to time how long events take, so you can use that to adjust the reset value of TMR1 to deal with any overhead and/or an inaccurate clock. Crystals might vary enough that this is infeasible in a production environment... not sure.&lt;/p&gt;&#xA;" OwnerUserId="2344" LastActivityDate="2010-12-20T18:28:06.750" CommentCount="7" />
  <row Id="8111" PostTypeId="2" ParentId="8082" CreationDate="2010-12-20T18:37:57.283" Score="1" ViewCount="" Body="&lt;p&gt;You might be interested in &lt;a href=&quot;http://www.meetup.com/find/?keywords=hackerspace&amp;amp;userFreeform=New+York+City,+New+York,+USA&amp;amp;mcId=c10001&amp;amp;mcName=New+York+City,+New+York,+USA&amp;amp;lat=&amp;amp;lon=&amp;amp;gcResults=&amp;amp;op=search&amp;amp;events=&amp;amp;submitButton=Search&quot; rel=&quot;nofollow&quot;&gt;finding a hackerspace&lt;/a&gt; near your school and seeing what projects people are working on there.&lt;/p&gt;&#xA;" OwnerUserId="2344" LastActivityDate="2010-12-20T18:37:57.283" />
  <row Id="8112" PostTypeId="1" AcceptedAnswerId="8114" CreationDate="2010-12-20T19:10:45.260" Score="6" ViewCount="664" Body="&lt;p&gt;What's a good way to reduce the output from a 9V battery to the 1.8V to 5V required by an ATmega328 controller? The context is a small robotics platform with low power requirements (very slow movement).&lt;/p&gt;&#xA;" OwnerUserId="2172" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-21T14:54:33.583" LastActivityDate="2011-03-02T04:38:41.213" Title="How do I convert 9 V DC to 5 V?" Tags="&lt;power-supply&gt;&lt;voltage-regulator&gt;" AnswerCount="7" CommentCount="2" FavoriteCount="1" />
  <row Id="8113" PostTypeId="2" ParentId="8112" CreationDate="2010-12-20T19:22:18.163" Score="5" ViewCount="" Body="&lt;p&gt;It depends how efficient you need it to be. Simplest would be an LM317, but it will waste a lot of power. A switcher would be better, like those made by Nat Semi.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wouldn't use a 9V battery, though.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-20T19:22:18.163" CommentCount="5" />
  <row Id="8114" PostTypeId="2" ParentId="8112" CreationDate="2010-12-20T19:34:42.517" Score="14" ViewCount="" Body="&lt;p&gt;I would use a 7805 to get 5 volts simple circuit. Here is a image:&#xA;&lt;img src=&quot;http://i.imgur.com/MApBh.gif&quot; alt=&quot;7805&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-12-20T19:34:42.517" CommentCount="6" />
  <row Id="8115" PostTypeId="2" ParentId="7505" CreationDate="2010-12-20T20:02:30.157" Score="3" ViewCount="" Body="&lt;p&gt;How about a linear Toothed rubber belt running along the track.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen this used in machinery that worked quite well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A pair of pickup rollers pick the belt up, and a driver pulley apply torque.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;lLnear toothed belt is relatively maintenance free, doesn't need lubrication and will drive equally will in either direction. Fancy big belt stock is silicone rubber and Kevlar, never stretches much, and doesn't need lubricants.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;800g is a very small belt ( which is cheaper per metre )&#xA;The belt is mounted on the track, tooth side towards the track.&#xA;the belt is held in tension at both ends, and the pickup rollers and drive pulley have a fixed relationship so it can be pretty backlash free. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;excuse my ascii art. &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#-----------------0     0------------------#&#xA;                  |  O  |&#xA;                   \___/&#xA;&#xA;&#xA;--- belt&#xA;0  pickup roller&#xA;O center of drive pulley.&#xA;# belt tensioner ( belt is stretched with a bolt thread )&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2010-12-20T20:02:30.157" CommentCount="4" />
  <row Id="8116" PostTypeId="2" ParentId="8103" CreationDate="2010-12-20T20:29:44.407" Score="4" ViewCount="" Body="&lt;p&gt;Actually avr-gcc is under the covers in Arduino as well... you just have to use C++-ish syntax if you're using their libraries or writing your own. Otherwise, the only constraint is that you are 'forced' to use the pattern equivalent to: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int main(int argc, char *argv[]){ &#xA;  setup(); &#xA;  for(;;){ &#xA;    loop();&#xA;  } &#xA;  return 0;&#xA;} &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;which is a pattern that fits a large cross-section (arguably the entirety) of embedded design. You just implement setup() and loop(). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also it's not a choice between Arduino and a micro-controller. In principle, you could take the ATMega328P out of an Arduino board context, programmed with a sketch, and transplant it into a more tightly integrated solution. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I guess I disagree with the sentiment of some of the other answers here suggesting that Arduino is just a &quot;toy&quot; platform. In my opinion it's viable for more &quot;serious&quot; development. It just lowers the barrier to entry into the embedded world. The ability to program it without a separate programmer (e.g. AVRISP mkII, STK500, etc.) is kind of a big deal in this regard. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't really think that it demands significant compromise from more advanced users. &lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-20T20:36:46.510" LastActivityDate="2010-12-20T20:36:46.510" CommunityOwnedDate="2011-05-07T13:15:59.843" CommentCount="4" />
  <row Id="8117" PostTypeId="2" ParentId="8112" CreationDate="2010-12-20T21:18:42.060" Score="2" ViewCount="" Body="&lt;p&gt;Another way to drop the voltage down from 9V would be to put an appropriate number of forward biased diodes in series with the positive supply. Typically you get about 0.7V drop per diode, so to bring it down to 5V from 9V you'd need something like 6 diodes in series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fine... or a single Zener diode!&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-20T22:12:38.290" LastActivityDate="2010-12-20T22:12:38.290" CommentCount="11" />
  <row Id="8118" PostTypeId="2" ParentId="8112" CreationDate="2010-12-20T21:22:34.467" Score="8" ViewCount="" Body="&lt;p&gt;I might consider just providing the ATmega328 unregulated power unless you have something that actually requires it on the board.  2-3 AA cells should remain within 1.8 to 5.5 V over their life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A schottky might be prudent if you insert the batteries the wrong way (probably will need 3 cells then), and you could add a TVS if you want to be even safer.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-20T21:22:34.467" CommentCount="4" />
  <row Id="8119" PostTypeId="2" ParentId="8093" CreationDate="2010-12-20T22:17:22.827" Score="5" ViewCount="" Body="&lt;p&gt;I've also had this problem...even though I've done controls work for a living.  My part of the controls work has been dealing with what the system identification guys give me, so I never developed that skill as well as I wanted.  After a while, I've picked up a couple of additional books and relearned how to do it in some cases.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The method that I use is by constructing lagrangian equations that describe the system.  The lagrangian describes the kinetic and potential energy in a system.  I've found that &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0486442780&quot; rel=&quot;nofollow&quot;&gt;Control system design: An Introduction to state-space methods&lt;/a&gt; (cheap) actually has a decent reference for performing system identification.  I recommend going through all of the examples and problems in chapter 2.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally, the thermal problem you describe can be handled by converting the components of the model to electrical equivalents. This can be found in the book or by doing a bit of googling.&lt;/p&gt;&#xA;" OwnerUserId="2346" LastActivityDate="2010-12-20T22:17:22.827" CommentCount="1" />
  <row Id="8120" PostTypeId="1" AcceptedAnswerId="8127" CreationDate="2010-12-20T22:45:50.027" Score="16" ViewCount="367" Body="&lt;p&gt;In this time where &lt;a href=&quot;http://en.wikipedia.org/wiki/2007_Boston_bomb_scare&quot; rel=&quot;nofollow&quot;&gt;electronics devices are blown up by bomb squads&lt;/a&gt;, &lt;a href=&quot;http://news.cnet.com/8301-13578_3-10004646-38.html&quot; rel=&quot;nofollow&quot;&gt;laptops may be seized&lt;/a&gt; when crossing borders, and the paranoia driving security theatre seems to be increasing, is there anything I ought to know before taking electronic or robotic devices with me on a long distance flight?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I imagine that if I put it in my checked baggage, it'll be fine, and that, if I don't need it for a couple of weeks, I should just send myself a package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't particularly expect trouble, as in this instance the robot is considered to be a toy (a LEGO Mindstorms NXT kit), and my round trip is from southern Canada to the southern United States, but I'd be curious to have tips for any international flights, especially with something that is not so obviously innocuous (such as a handful of microcontrollers on breadboards with wires going everywhere in a mess).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any tips for getting from A to B without hassle?&lt;/p&gt;&#xA;" OwnerUserId="106" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T19:45:02.987" LastActivityDate="2011-02-08T19:45:02.987" Title="Taking electronics/robotics project on a commercial passenger jet" Tags="&lt;travel&gt;" AnswerCount="6" CommentCount="2" FavoriteCount="2" />
  <row Id="8121" PostTypeId="1" AcceptedAnswerId="8123" CreationDate="2010-12-20T22:58:45.367" Score="3" ViewCount="299" Body="&lt;p&gt;It says in the datasheet these values in this picture: &#xA;&lt;img src=&quot;http://i.imgur.com/awG8M.gif&quot; alt=&quot;7805 1&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I've also seen it with these values:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/Wph1i.gif&quot; alt=&quot;7805 2&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what values should i use or doesn't it matter? And its for when its first starting.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-12-21T19:51:57.387" Title="Capacitor Sizes for 7805 Regulator" Tags="&lt;voltage-regulator&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="8122" PostTypeId="2" ParentId="8120" CreationDate="2010-12-20T23:02:28.590" Score="5" ViewCount="" Body="&lt;p&gt;I read this account a few months ago: &lt;a href=&quot;http://www.chemhacker.com/2010/08/stms-on-a-plane-prototype-electronics-and-security-checkpoints/&quot; rel=&quot;nofollow&quot;&gt;http://www.chemhacker.com/2010/08/stms-on-a-plane-prototype-electronics-and-security-checkpoints/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-20T23:02:28.590" />
  <row Id="8123" PostTypeId="2" ParentId="8121" CreationDate="2010-12-20T23:03:05.143" Score="8" ViewCount="" Body="&lt;h3&gt; First Starting?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Build it with either, it will work fine for you. The second option with the large capacitors and the extra small one is &quot;more stable.&quot; Just build this, do not worry about why if you are just wanting to start your project. Let us know if something does not work.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;100nF&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Use the values that are suggested in the datasheet. If you add capacitors a factor of 10 smaller(called decade capacitors) it will help with higher frequency noise(RF, or radio band noise), as an effects of the impedance of a capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Feel free to add as many decade capacitors as you want, but you will not need them unless you start having FCC testing. They cannot hurt.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;100uF&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;When someone increases this they are allowing their circuit to pull power from the power source for longer. If you have a long power line this will act as a small tank of power, if yuo are going to have long power lines, or very inductive power lines, add this.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-20T23:11:02.300" LastActivityDate="2010-12-20T23:11:02.300" CommentCount="2" />
  <row Id="8124" PostTypeId="2" ParentId="8120" CreationDate="2010-12-20T23:03:27.220" Score="2" ViewCount="" Body="&lt;p&gt;I'd do these things:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Ensure it's in an identifiable box, like a LEGO Mindstorms box, or at least put a label on it to identify electronics. A sticker from Digikey packages or similar as well as your contact information wouldn't hurt either.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Don't carry &lt;strong&gt;lithium&lt;/strong&gt; batteries at all. Ship them if you must, or just buy one at your destination.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If you want to check it into baggage storage, present it to the clerk (use a clerk, not the automatic ticket dispenser) and ask about it.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If you want to carry it on-board, put it through security by itself, not packed in a bag.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-20T23:03:27.220" CommentCount="2" />
  <row Id="8125" PostTypeId="2" ParentId="8112" CreationDate="2010-12-20T23:06:04.327" Score="6" ViewCount="" Body="&lt;p&gt;A similar question, but with different voltages: &lt;a href=&quot;http://electronics.stackexchange.com/questions/2314/what-is-the-coolest-way-using-passive-cooling-only-to-step-12v-dc-down-to-5v-dc/2315#2315&quot;&gt;What is the coolest way (using passive cooling only) to step 12V DC down to 5V DC&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-20T23:06:04.327" CommentCount="1" />
  <row Id="8126" PostTypeId="2" ParentId="8120" CreationDate="2010-12-20T23:44:57.090" Score="5" ViewCount="" Body="&lt;p&gt;I read this account recently: &lt;a href=&quot;http://teachmetomake.wordpress.com/traveling-with-diy-electronics/&quot; rel=&quot;nofollow&quot;&gt;http://teachmetomake.wordpress.com/traveling-with-diy-electronics/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-20T23:44:57.090" />
  <row Id="8127" PostTypeId="2" ParentId="8120" CreationDate="2010-12-21T00:54:00.673" Score="15" ViewCount="" Body="&lt;p&gt;I've brought a lot of small electronic prototypes on flights, both on plane and checked.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of my classmates brought his senior project (EE college, circa ~2005) on a plane and it was a railgun that could fire a nail 300m/sec out of an arrow shaft, fast enough to stick into 1 inch lexan at 5 feet.  The thing had like 10 farad worth of capacitors and 3 100w incandescent bulbs to burn off the inductive backlash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Point being it was a rather diabolical device and he was able to fly domestic in the US with it.  In addition he was of a heritage that sadly attracts additional attention.  As I remember he called ahead and showed up very early to have the security folks go over it.  It was rather large and scary looking so I would think of this as a near worst case for carrying prototype electronics on a plane.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best advice is to be completely upfront with whatever your transporting.  Don't try to hide it. Don't put it in some random unrelated commercial box in an attempt to make it appear mundane.  Doing these types of things just make it appear your trying to hide whatever it is you have.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do put it in your checked baggage if its large, even better separately packed and tell them upfront when you check in what it is.  Count on some extra time when checking in to take it out of the packaging and give a tour.  If its scary looking don't carry it on the plane, you'll just freak out the people on the plane who are already worried about flying.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Trying to wrap it up inside the rest of your checked luggage and not saying anything is about the worst possible thing you can do.  If its anything remotely interesting looking they will flag it anyway and now you have to explain what it is and why its buried deep in your luggage from the position of a suspect rather than on your terms. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my experience if your just up front and act like your not doing anything wrong, because you aren't, you'll actually probably enjoy it.  The TSA folks i've dealt with were more interested in what it was and how it worked than they were in it being a danger.  I've never even had them bother with running a device through the chemical sensor.  At least not that I knew about.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In addition, don't dress weird.  By that i mean dress as yourself.  I wear jeans/shorts and hoodies/tshirts when i travel, its not a problem.  You attract more attention by wearing a suit when your a jeans and hoody guy than you do just being yourself, you just look uncomfortable, you shouldn't be, your not doing anything remotely wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having traveled a lot probably helps as well, i mean if your in their system traveling all the time it seems your less likely to get screwed with.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I travel a lot, the people who I see get screwed with act like they are doing something wrong, 99.999% of the time its just nerves, anxiety or the person is just being rude/obnoxious to security. These are the things that attract attention and cause problems.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should of course make sure your not trying to transport something that isn't allowed on the plane, some types of batteries for instance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your traveling internationally you do want to look into the required paperwork.  Some locales will give you a hard time without a CE stamp for instance.  This is generally more of a customs issue wherever your landing rather than an issue with getting it on the plane.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: wrote this very quickly originally, cleaned up to be more readable.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2010-12-21T15:15:33.957" LastActivityDate="2010-12-21T15:15:33.957" CommentCount="1" />
  <row Id="8128" PostTypeId="1" AcceptedAnswerId="8196" CreationDate="2010-12-21T01:00:35.257" Score="3" ViewCount="271" Body="&lt;p&gt;I recently made a voltage and current controlled supply from a kit I found. It worked for about 15 minutes and then fuses started popping. Unfortunately, I have no idea why, because power supply worked for some time fine then and there were no changes to (just voltmeter connected all the time to output) it when fuse problems started. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At first, I thought that some part overheated and malfunctioned, but everything felt cool. Next idea was that a piece of debris inside the box might have caused a short circuit somewhere. I carefully checked the box and didn't find anything which could have caused short circuit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next thought was that maybe IC died. I already asked about that &lt;a href=&quot;http://electronics.stackexchange.com/q/8094/1240&quot;&gt;here&lt;/a&gt;, so I decided to separate circuit board and transformer and check transformer to make sure it was working correctly. So on one side I had PCB and on the other 50 VA transformer connected to a Graetz bridge rectifier. Here's the picture of the transformer part of the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/loFcb.png&quot; alt=&quot;transformer and rectifier&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I connected ends of the rectifier to my multimeter and powered on the transformer and got around 25 V, as expected. A minute or two later, fuse died again. To me this looked very strange, because the rectifier wasn't actually connected to anything. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since I run out of required fuses, I decided to connect my multimeter in place of the fuse and see what's going on with current. At first, I connected it to 20 A range and saw that at the time I press the power switch, I get around 0.02 A. In less then a second, that falls to zero. I switched to milliamp scale and got same 20 mA. After power-cycling transformer again, the 200 mA fast multimeter fuse for milliamp scale died.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By this time I was left only with a 10 A fuse, so I decided to do some testing with it. Since the original recommended fuses were of 315 mA fast type, I decided to be extra careful. I checked insides of the box again, checked both switches, all wires and as far as I can see, everything is working correctly. I turned the transformer on with 10 A fuse and did some voltage measurements. I get around 27 V when the ends are serially connected and around 13.5 V when I'm using only one end of the transformer. When measuring DC voltage at the rectifier, I get around 25 V for both secondary coils and around 13 V for one secondary coil. I also get around 9 V AC at the rectifier for both secondary coils and around 3.5 V AC for single secondary coil. I also noticed that when power switch is in OFF position, I get around 3 V AC at the rectifier input and around 3 V DC at the rectified output. These only disappear when I pull the power plug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After all this, I concluded that there must be something in the transformer/rectifier part of the circuit that is making fuses blow. Any ideas how to find out exactly what it is?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, is the behavior of the rectifier normal and should I change the switch to double pole switch which would control both power lines?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT 1&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I connected the PCB to the rectifier and turned it on with 10 A fuse. I'm running a small 9 V DC radio from the power source and it seems to be working correctly. Could it be that the recommended fuse current is wrong? The transformer's maximum output current is 2.1 A, so if I'm calculating correctly, maximum input current should be 230 mA. I used 315 mA fuses, so the should have survived full load on the transformer. IS there something I'm missing here?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT 2&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looks like the fuses could be blowing because of inrush current of the transformer. How would I solve that problem? One of the fuses I used and which blew was a slow acting fuse, so they aren't the solution.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-12-22T01:05:54.880" LastActivityDate="2010-12-22T23:36:28.860" Title="Need help debugging my project: Fuses popping like crazy, but I can't find the reason why." Tags="&lt;transformer&gt;&lt;debug&gt;&lt;fuses&gt;&lt;rectifier&gt;&lt;debugging&gt;" AnswerCount="4" CommentCount="16" />
  <row Id="8129" PostTypeId="1" AcceptedAnswerId="8136" CreationDate="2010-12-21T01:47:45.903" Score="5" ViewCount="269" Body="&lt;p&gt;How do components fail?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;General rules with an answer per component type would be valuable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We can work as a community to build up a single question that holds valuable information about how components fail.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-21T16:23:29.903" LastActivityDate="2011-01-05T13:09:51.320" CommunityOwnedDate="2010-12-21T02:40:32.603" Title="How do components fail?" Tags="&lt;component-reliability&gt;" AnswerCount="7" CommentCount="3" FavoriteCount="3" />
  <row Id="8130" PostTypeId="2" ParentId="8128" CreationDate="2010-12-21T02:48:45.593" Score="3" ViewCount="" Body="&lt;p&gt;If you think it is happening due to inrush current, then it could probably be solved by a &lt;a href=&quot;http://en.wikipedia.org/wiki/Choke_%28electronics%29&quot; rel=&quot;nofollow&quot;&gt;choke coil&lt;/a&gt;. They are there specifically to stop inrush current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would check to see if one of the diode's is fried. If you had one fried it will open-circuit for one half of the phase. When it open-circuits the coil will just become a floating load. This will cause a much higher current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Test it by replacing the diodes. try measuring them to see if one has a higher resistance than the others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Someone correct me if I am wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Addendum:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;more about choke coils.&lt;br&gt;&#xA;Here are some:&lt;br&gt;&#xA;&lt;a href=&quot;http://industrial.panasonic.com/www-ctlg/ctlg/qAGL0000_WW.html&quot; rel=&quot;nofollow&quot;&gt;http://industrial.panasonic.com/www-ctlg/ctlg/qAGL0000_WW.html&lt;/a&gt;&lt;br&gt;&#xA;I googled choke coil to find the best explanation, I read the first paragraph of this and it sounded like it would be of help, so here you go:&lt;br&gt; &lt;a href=&quot;http://www.wisegeek.com/what-is-a-choke-coil.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.wisegeek.com/what-is-a-choke-coil.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-21T05:06:25.997" LastActivityDate="2010-12-21T05:06:25.997" CommentCount="8" />
  <row Id="8131" PostTypeId="2" ParentId="7505" CreationDate="2010-12-21T06:49:11.843" Score="0" ViewCount="" Body="&lt;p&gt;In order for you to get the best answers to your question, I think you need to provide more information about the terrain that you want to attach this track to.  You say it can go from horizontal to vertical -- how vertical, and how quickly does the grade increase or decrease?  What are the limitations involved in laying down the track?  Do you have free reign over what hardware you lay on the ground?&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-21T06:49:11.843" CommentCount="1" />
  <row Id="8132" PostTypeId="1" AcceptedAnswerId="8135" CreationDate="2010-12-21T07:00:31.940" Score="4" ViewCount="125" Body="&lt;p&gt;I am looking for connecters to connect two PCB boards together for prototyping. Can anyone recommend any models in particular.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Features I am looking for are decent price available from some where like Farnell or RS Components in Australia&#xA;3 wire mainly doesn't need speacilized tools to make the connects standard pin spacing for  prototyping board&#xA;Also up to 10+ connections&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have looked my self but there is hundreds of models and it's hard to work out how they make there connects&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone recommend any models that they use? &lt;/p&gt;&#xA;" OwnerUserId="665" LastActivityDate="2010-12-23T11:33:32.693" Title="Board to board connections" Tags="&lt;prototyping&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="8133" PostTypeId="2" ParentId="8112" CreationDate="2010-12-21T08:40:16.970" Score="6" ViewCount="" Body="&lt;p&gt;Since you want to power from a 9V battery we have to look out for possible current losses. While a three-legger like LM7805 may be an obvious choice, this regulator has a ground current of 8mA maximum. An LDO (low drop-out) regulator typically needs far less, e.g. the ground current of an LP2981 is only 800uA maximum. That's only 10%!&lt;br&gt;&#xA;LDOs are as easy to use as an LM7805. The output capacitor is a bit larger, though, important for stability.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Johan wanted an example:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/MhuI6.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not used, the ON/OFF input must be tied to Vin. The output capacitor value of 3.3uF is the minimum required for stability. &quot;More capacitance provides superior dynamic performance and additional stability margin&quot; (&lt;a href=&quot;http://www.national.com/ds/LP/LP2981.pdf&quot; rel=&quot;nofollow&quot;&gt;dixit NS&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-22T15:14:33.977" LastActivityDate="2010-12-22T15:14:33.977" CommentCount="2" />
  <row Id="8134" PostTypeId="2" ParentId="8132" CreationDate="2010-12-21T08:52:49.813" Score="-1" ViewCount="" Body="&lt;p&gt;Uh, what's wrong with using bog standard 0.1&quot; headers? There's tons of models because EVERYBODY uses them and they are a commodity product.&lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2010-12-21T08:52:49.813" CommentCount="4" />
  <row Id="8135" PostTypeId="2" ParentId="8132" CreationDate="2010-12-21T09:35:52.153" Score="6" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://www.rapidonline.com/Cables-Connectors/Connectors-Multipole/PCB-Interconnect/Single-row-sockets/76075&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; with standard headers for stacking boards. I buy the longer ones and cut them to size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For wire connections between boards I use &lt;a href=&quot;http://www.rapidonline.com/Cables-Connectors/Connectors-Multipole/PCB-Interconnect/Crimp-2.54mm-PCB-connection-system/63798&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; connectors with &lt;a href=&quot;http://www.rapidonline.com/Cables-Connectors/Connectors-Multipole/PCB-Interconnect/2.54mm-Crimp-terminal/63799&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; terminals and &lt;a href=&quot;http://www.rapidonline.com/Cables-Connectors/Connectors-Multipole/PCB-Interconnect/Crimp-2.54mm-PCB-connection-system/63798&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; housings. The &lt;a href=&quot;http://www.rapidonline.com/Tools-Fasteners-Production-Equipment/Hand-Tools/Tacking-Crimping/Crimping-tool-for-PCB-connectors/30535&quot; rel=&quot;nofollow&quot;&gt;crimp tool&lt;/a&gt; is quite cheap.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-21T09:35:52.153" />
  <row Id="8136" PostTypeId="2" ParentId="8129" CreationDate="2010-12-21T09:42:25.770" Score="7" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Switches and pushbuttons:&lt;/strong&gt; failure to make contact.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you've listed looks like the severity part of an FMEA (Failure Mode and Effect Analysis), at least at component level. While it's not impossible, &lt;strong&gt;it's a hell of a job&lt;/strong&gt; to account for every possible component failure if your design has, say, over a hundred components. One failing component may cause an avalanche of other components failing. Most failures aren't subtle.&lt;br&gt;&#xA;You'll experience that adding components to cope with other components failing only adds complexity; you'll have to do an FMEA for these components as well!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative approach, FMEA-wise, may be to start from occurrences. What's the MTTF (Mean Time To Failure)? Most components are quite robust; tens of thousands of POH (power-on hours) are feasable. (A notable weaker component is the Al elco, but even there are solutions). Anyway, an IC usually doesn't short just like that. So, while component failure may be caused by aging, &lt;strong&gt;most failures are caused by external factors&lt;/strong&gt;, like overvoltage on the grid, or user error like misconnecting. Try to reduce these risks. Power spikes may be handled by overvoltage protection diodes. Misconnection can be avoided by using different connectors so that they can't be switched. Color code wires and use matching colors on connectors.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bottom line: it may be more important to know &lt;em&gt;why&lt;/em&gt; components fail than &lt;em&gt;how&lt;/em&gt; they do.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-21T09:42:25.770" CommunityOwnedDate="2010-12-21T09:42:25.770" CommentCount="2" />
  <row Id="8137" PostTypeId="2" ParentId="8129" CreationDate="2010-12-21T09:43:50.147" Score="2" ViewCount="" Body="&lt;p&gt;electr.CAP - short is possible due to deformation =&gt; explodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ICs: internal wires fail open, internal safety diodes shorts, gate latchups(might be not fatal), degraded performance due to semiconductor degradation (when working at &gt;100C), soft errors due to radiation. Power ICs might explode (I got hit by one) when failing under load.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-12-21T09:43:50.147" CommunityOwnedDate="2010-12-21T09:43:50.147" />
  <row Id="8138" PostTypeId="2" ParentId="8129" CreationDate="2010-12-21T11:51:23.833" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;MOSFETs:&lt;/strong&gt; Short circuit usually (with a bang), eventually leading to open failure due to melting of device&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Resistors:&lt;/strong&gt; Almost always open circuit&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Capacitors (Electrolytic):&lt;/strong&gt; Reduction in capacitance, leakage of electrolyte, eventually leading to open circuit&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Capacitors (Ceramic):&lt;/strong&gt; Reduction in capacitance - eventually failing open&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;LEDs:&lt;/strong&gt; Gradual dimming then failing open&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Zeners:&lt;/strong&gt; Fails shorted in 90% of cases but can fail open due to extreme overheating (device can split into two pieces)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-21T16:51:52.280" LastActivityDate="2010-12-21T16:51:52.280" CommunityOwnedDate="2010-12-21T11:51:23.833" CommentCount="5" />
  <row Id="8140" PostTypeId="2" ParentId="8129" CreationDate="2010-12-21T14:22:17.987" Score="1" ViewCount="" Body="&lt;p&gt;Ceramics can also fail short circuit, which can be exciting if they are decoupling a high-current supply...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.kemet.com/kemet/web/homepage/kfbk3.nsf/vaFeedbackFAQ/B1DF60638A9F8F9D85256EDF004CA494&quot; rel=&quot;nofollow&quot;&gt;Kemet's capacitor failures page&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.syfer.com/category_docs/AN0005_Mechanical_Cracking.pdf&quot; rel=&quot;nofollow&quot;&gt;Syfer's appnote on capacitor cracking&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.avx.com/techinfo_documentdetail.asp?ID=46&amp;amp;Heading=Cracks%3a+The+Hidden+Defect&amp;amp;Category=Ceramic+Capacitors&quot; rel=&quot;nofollow&quot;&gt;AVX's appnote on cracking&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="763" LastEditorUserId="763" LastEditorDisplayName="" LastEditDate="2011-01-05T13:09:51.320" LastActivityDate="2011-01-05T13:09:51.320" CommunityOwnedDate="2010-12-21T14:22:17.987" CommentCount="1" />
  <row Id="8141" PostTypeId="1" AcceptedAnswerId="8144" CreationDate="2010-12-21T14:40:42.677" Score="1" ViewCount="151" Body="&lt;p&gt;I want to receive 5-bit serial words using a microcontroller's hardware UART at 45 Baud. This is the basic protocol for teletype machines. Since the baud rate is 45, I really want this done in hardware so that I am not spending all the processor time polling a pin, and for ease of programming. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there microcontrollers that can do 5-bit serial data in hardware? Is there a reasonable hardware/software implementation that won't tie up the processor?&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-31T10:47:44.013" Title="Microcontroller support for Teletype" Tags="&lt;microcontroller&gt;&lt;uart&gt;" AnswerCount="5" CommentCount="0" />
  <row Id="8142" PostTypeId="2" ParentId="8141" CreationDate="2010-12-21T14:51:33.147" Score="2" ViewCount="" Body="&lt;p&gt;You will probably have to bit-bang the interface. Any MCU will be suitable.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-21T14:51:33.147" CommentCount="2" />
  <row Id="8143" PostTypeId="2" ParentId="8129" CreationDate="2010-12-21T14:53:28.500" Score="0" ViewCount="" Body="&lt;p&gt;Electronic system reliability is an ugly problem, but you can get a idea of how it's done in the aerospace business by reading MIL-HDBK-217.  Mil standards can be found at &lt;a href=&quot;https://assist.daps.dla.mil/quicksearch/&quot; rel=&quot;nofollow&quot;&gt;The DOD Website ASSIST&lt;/a&gt;.  The Wikipedia entry: Reliability Engineering has a good overview.&lt;/p&gt;&#xA;" OwnerUserId="2351" LastActivityDate="2010-12-21T14:53:28.500" CommunityOwnedDate="2010-12-21T14:53:28.500" />
  <row Id="8144" PostTypeId="2" ParentId="8141" CreationDate="2010-12-21T15:08:07.987" Score="8" ViewCount="" Body="&lt;p&gt;If you have sufficient intercharacter space (~3 extra stop bits), you could use the MCU UART port, as there isn't really a difference between an 8-bit character (0x00 through 0x1F) on a UART and a 5-bit character with 4 stop bits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Barring that, your best bet would be to use a level interrupt (pin change, etc) to detect the leading edge of the start bit, then configure a timer to interrupt you either once per bit or possibly a couple times so you can do some extra verification.  45 baud is &lt;em&gt;really&lt;/em&gt; slow, so unless you're using upwards of 95% of the MCU time (or all it's peripherals), this shouldn't cause any problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Atmel AVR USART module supports 5-9 bit modes, so any (newer) ATtiny (e.g. ATtiny2313) or ATmega (e.g. ATmega328P) will allow you to do this in hardware, vastly simplifying your software, saving your time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The maximum clock divider you can apply to the UART on an AVR is 2&lt;sup&gt;16&lt;/sup&gt;, so if you have a clock of 16 MHz, the lowest rate it can run at is 244 bps with no system clock divider.  If you use an ATmega, like on an Arduino, the clock prescale register (&lt;code&gt;CLKPR&lt;/code&gt;, §8.12.2 in Atmega48/88/168/328 datasheet) can be used to slow down the system clock up to 256x at run-time, or simply program the CKDIV8 fuse to set the prescale register's default to 8.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The real determining factor on what you should use is what else you're doing besides talking with the TTY.  If you are going to plug this into a computer, you will want to reserve a (or the, if there's only 1) UART for communicating with the PC and do a software UART if required (as mentioned by everyone, this is near trivial at 45 bps).  If you want to press a button and have the TTY do something, using the only UART for that would be fine.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-21T20:01:36.567" LastActivityDate="2010-12-21T20:01:36.567" CommentCount="5" />
  <row Id="8145" PostTypeId="1" AcceptedAnswerId="8172" CreationDate="2010-12-21T15:09:21.713" Score="3" ViewCount="174" Body="&lt;p&gt;I've been tasked with interfacing with the on-board diagnostics of a vehicle. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some systems use 7 V signalling, some use 5 V signalling, some signal up to the battery voltage (which can be as high as 28 V on some bigger vehicles.) I need some way to handle these high voltage inputs which may exceed my microcontroller's 5V rating. I was thinking of an optoisolated system, but communications need to be bidirectional and fast (100kbits second maximum.) As it's OBD-II, I'll need two channels; some vehicles use transmit and receive channels, while others use one channel for both transmit and receive. Are there any options for me to consider?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-21T18:22:23.747" LastActivityDate="2010-12-21T23:40:37.033" Title="How do I interface with ODB-II?" Tags="&lt;level-shifting&gt;&lt;obd&gt;" AnswerCount="2" CommentCount="8" FavoriteCount="2" />
  <row Id="8146" PostTypeId="2" ParentId="8120" CreationDate="2010-12-21T15:49:05.160" Score="3" ViewCount="" Body="&lt;h3&gt;Batteries&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;You &lt;a href=&quot;http://safetravel.dot.gov/whats_new_batteries.html&quot; rel=&quot;nofollow&quot;&gt;can't check loose (spare) lithium batteries&lt;/a&gt; on passenger planes, but you can carry them on.  Batteries with capacities &lt;a href=&quot;http://safetravel.dot.gov/larger_batt.html&quot; rel=&quot;nofollow&quot;&gt;greater than 300 W·h&lt;/a&gt; are banned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.iata.org/WHATWEDO/CARGO/DANGEROUS_GOODS/Pages/lithium_batteries.aspx&quot; rel=&quot;nofollow&quot;&gt;IATA has some additional regulations&lt;/a&gt; regarding batteries with capacities above 100 W·h, barring spare batteries in checked baggage.  Spares are permitted in carry-on baggage, limited to two above 160 W·h.  If they are not marked with their capacity, they may be also be forbidden.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;None of these regulations guarantee that you will be able to actually do this, as the TSA officers are righteous beyond belief.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Batteries greater than 100 W·h are classified as Hazardous Materials (class 9), and must follow additional rules when being &lt;em&gt;shipped&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Tools&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Those &lt;a href=&quot;http://www.tsa.gov/travelers/airtravel/prohibited/permitted-prohibited-items.shtm#7&quot; rel=&quot;nofollow&quot;&gt;longer than 7 inches&lt;/a&gt;  must be in checked luggage according to the US TSA.  Almost got my 8P8C crimp tool taken away (twice, there and back), but fortunately they determined it (or I) was harmless.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2010-12-21T23:13:07.370" LastActivityDate="2010-12-21T23:13:07.370" CommentCount="6" />
  <row Id="8148" PostTypeId="2" ParentId="8141" CreationDate="2010-12-21T16:33:37.897" Score="2" ViewCount="" Body="&lt;p&gt;The first three datasheets I looked at all show support for 5 bit serial communication.  Here is the list:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.atmel.com/products/at91/sam3s.asp&quot; rel=&quot;nofollow&quot;&gt;Atmel SAM3S&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.luminarymicro.com/&quot; rel=&quot;nofollow&quot;&gt;TI Stellaris&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.freescale.com/webapp/sps/site/homepage.jsp?code=KINETIS&quot; rel=&quot;nofollow&quot;&gt;Freesscale Kinetis&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="529" LastActivityDate="2010-12-21T16:33:37.897" CommentCount="1" />
  <row Id="8149" PostTypeId="1" AcceptedAnswerId="8151" CreationDate="2010-12-21T16:35:43.297" Score="1" ViewCount="132" Body="&lt;p&gt;I am getting a Cyclone II-based &lt;a href=&quot;http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&amp;amp;No=83&quot; rel=&quot;nofollow&quot;&gt;Altera DE1&lt;/a&gt; FPGA board to experiment with. I know a lot about programming, a bit about electronics and very little about FPGAs. What books or other resources would you recommend to someone like me to get started?&lt;/p&gt;&#xA;" OwnerUserId="2096" LastActivityDate="2010-12-21T16:41:55.300" Title="Getting started with Altera FPGAs" Tags="&lt;fpga&gt;&lt;books&gt;&lt;learning&gt;&lt;altera&gt;" AnswerCount="1" />
  <row Id="8150" PostTypeId="2" ParentId="8129" CreationDate="2010-12-21T16:37:39.500" Score="2" ViewCount="" Body="&lt;h2&gt;Resistors&lt;/h2&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;h3&gt;Failure Modes&lt;/h3&gt;&#xA;  &#xA;  &lt;p&gt;Resistor failures are considered to be electrical opens, shorts or a radical variation from the resistor specifications. The failure modes experienced vary with the type of construction. A fixed composition resistor normally fails in an open configuration when overheated or overly stressed due to shock or vibration.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Excessive humidity may cause an increase in resistance. A variable composition resistor may wear after extensive use, and worn away particles may cause high resistance short circuits. Wirewound resistors may experience open windings due to overheating or stress, or short circuited windings due to accumulation of dirt, dust, breakdown of the insulation coating or high humidity. Film resistors fail for the same reasons as wirewound and composition, but have also failed due to changes in resistive material characteristics resulting in reduction and increase in resistance value.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Electronic Components - Resistors. (1978). FDA Inspection Technical Guides.  Retrieved from &#xA;&lt;a href=&quot;http://www.fda.gov/iceci/inspections/inspectionguides/inspectiontechnicalguides/ucm072904.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.fda.gov/iceci/inspections/inspectionguides/inspectiontechnicalguides/ucm072904.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-21T16:37:39.500" CommunityOwnedDate="2010-12-21T16:37:39.500" />
  <row Id="8151" PostTypeId="2" ParentId="8149" CreationDate="2010-12-21T16:41:55.300" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://users.ece.gatech.edu/~hamblen/book/bookse.htm&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; book is based on Altera hardware and development tools. You need the fourth edition for the DE1.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-21T16:41:55.300" />
  <row Id="8152" PostTypeId="1" AcceptedAnswerId="8170" CreationDate="2010-12-21T16:49:31.983" Score="1" ViewCount="180" Body="&lt;p&gt;I am working with Invensense IMU3000 and a PIC18 microcontroller. I am migrating a library, written in MSVS2005, to MPLAB, doing the proper modifications to run on it.. the code itself provides just warnings, but when it comes to linking, I get this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Error - section '.idata_dmpDefault.o' can not fit the section. Section '.idata_dmpDefault.o' length=0x000004b0&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What does it mean?&lt;/p&gt;&#xA;" OwnerUserId="2285" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-21T23:05:27.440" LastActivityDate="2011-02-12T15:35:35.750" Title="MPLAB linking error" Tags="&lt;pic&gt;&lt;mplab&gt;" AnswerCount="4" CommentCount="7" />
  <row Id="8153" PostTypeId="2" ParentId="8141" CreationDate="2010-12-21T16:49:47.180" Score="2" ViewCount="" Body="&lt;p&gt;For normal asynchronous operation on the ATTiny2313 AVR, lets say running at 1.8432MHz set:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;UBRR  = 0x9FF; //(f_osc / (16 * BAUD)) - 1 = 2559 =&#xA;UCSRA = 0x00;  // 1x trasnmit speed, multi-processor mode disabled&#xA;UCSRB = 0xD8;  // enable rx and tx complete interrupts, enable tx and rx hardware&#xA;UCSRC = 0x00;  // 5 data-bits, 1 stop-bit, no parity bits&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then implement the RX and TX complete interrupts and you should be good to go.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-12-21T16:49:47.180" />
  <row Id="8154" PostTypeId="2" ParentId="8129" CreationDate="2010-12-21T17:26:01.393" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;PCBs:&lt;/strong&gt; cracks in vias  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The story:&lt;br&gt;&#xA;my brother had one of Philips' first CD players. One time it stopped working, but when I looked into it it worked again. This happened a few times. Trying to find out about the circumstances when it happened my brother said that the last time there was a thunderstorm. A lightning strike may do bad things to electronics, though in those cases the device doesn't start working again all by itself.&lt;br&gt;&#xA;One day I was discussing the problem with a colleague when the conversation was overheard by a product manager (I was working for Philips Audio at the time). PM said that only after much searching they had found the cause of this problem: the PCB was made from some cheap material (I don't recall which, it may have been FR-2) which tended to expand when there was much moisture in the air, like during a thunderstorm. As a consequence the few vias on the board would crack open. When the air became drier again the PCB's thickness returned to normal, restoring the vias. That was one reason why I couldn't find anything. Another was that touching the PCB with a multimeter's probe caused enough pressure to close the cracks (these are microcracks!).&lt;br&gt;&#xA;The remedy: soldering a wire in each via. Design solution: use FR-4 for PCBs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like I already said in my other answer it's important to know &lt;em&gt;why&lt;/em&gt; the vias crack; it's no good just knowing &lt;em&gt;how&lt;/em&gt; they do.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-21T17:26:01.393" CommunityOwnedDate="2010-12-21T17:26:01.393" CommentCount="2" />
  <row Id="8155" PostTypeId="2" ParentId="8145" CreationDate="2010-12-21T17:38:18.403" Score="1" ViewCount="" Body="&lt;p&gt;To read from a higher voltage just use a voltage divider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To write to a higher voltage, use a line driver with a disable. Two MOSFETs will do the job. possibly one extra on each gate to help step up your output voltage so that the Final mosfet is closer to a short.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On your side of the voltage divider use a zener or similar device to protect against over-voltage and use large resistors in the divider so that there is very low power dissipation. This will protect your inputs. I would use a Schottky diode in reverse to protect against reverse voltage, their low turn on voltage will protect your micro.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-21T17:38:18.403" CommentCount="18" />
  <row Id="8157" PostTypeId="1" CreationDate="2010-12-21T18:30:40.857" Score="2" ViewCount="350" Body="&lt;p&gt;A spring based catapult is at rest vertically. It gets pulled back to a horizontal position to arm, which activates a self-ball loader. On firing, it springs forward and launches ball. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The arming mechanism will be motor based but the issue I can't get past is the motor on the launch portion. My ideas include:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Bike chain and gearing.&lt;/li&gt;&#xA;&lt;li&gt;Some sort of clutch on motor that releases on launch.&lt;/li&gt;&#xA;&lt;li&gt;Some sort of indexed cog off the motor that pushes the catapult to the horizontal but at that point the catapult releases back forward and the cog spins around again to pick up.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I've considered stepper motors but I'd like to keep it as simple as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Further Details&lt;/strong&gt; - &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The spring in question is actually a car engine belt tensioner. So we are talking roughly maybe 30 foot lbs to compress. It is bolted to a 3 ton jack stand which is bolted to a frame.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The frame right now is roughly 30 in long, the catapult arm length is still in question due to distance requirements of projectile. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am considering making the arm length adjustable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ball feed mechanism is basically PVC with spring gate that gets compressed when arm is pulled down. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Projectiles are baseballs, softballs. snowballs etc....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am currently stuck on finding the right motor. So far I've ripped apart a belt sander and an Oreck vacuum looking for answers, with no luck. I am also considering winch methodology or possibly chain hoist theory. Thanks for the responses.&lt;/p&gt;&#xA;" OwnerUserId="2352" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-01-01T10:30:02.113" LastActivityDate="2011-01-07T23:29:51.937" Title="Building an electrically controlled spring based catapult." Tags="&lt;dc-motor&gt;" AnswerCount="5" CommentCount="3" />
  <row Id="8158" PostTypeId="1" AcceptedAnswerId="8161" CreationDate="2010-12-21T19:51:18.020" Score="1" ViewCount="151" Body="&lt;p&gt;I have a &lt;a href=&quot;http://www.caltek.com.hk/cm1200.htm&quot; rel=&quot;nofollow&quot;&gt;cheap handheld multimeter&lt;/a&gt; that has stopped working. It basically behaves as if the leads weren't connected: the &lt;code&gt;Vdc&lt;/code&gt; readout stays at zero, and the resistance readout stays at &quot;1.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've checked the battery and have tested the leads with a bench meter. Now, before I chuck the meter in the bin (it's long overdue an upgrade anyway), is there anything else relatively obvious that may be worth checking?&lt;/p&gt;&#xA;" OwnerUserId="2096" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-08T03:48:45.840" LastActivityDate="2011-01-08T03:48:45.840" Title="Failed multimeter" Tags="&lt;multimeter&gt;&lt;multimeter&gt;&lt;failure&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="8159" PostTypeId="2" ParentId="8121" CreationDate="2010-12-21T19:51:57.387" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.fairchildsemi.com/ds/LM/LM7805.pdf&quot; rel=&quot;nofollow&quot;&gt;Fairchild datasheet&lt;/a&gt; says on page 23&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;2. C&lt;sub&gt;I&lt;/sub&gt; is required if regulator is located an appreciable distance from power supply filter.&#xA;&lt;br&gt;&#xA;3. C&lt;sub&gt;O&lt;/sub&gt; improves stability and transient response.&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;where C&lt;sub&gt;I&lt;/sub&gt; is the input capacitor and C&lt;sub&gt;O&lt;/sub&gt; is the output capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So depending on your circuit you have some freedom in picking C&lt;sub&gt;I&lt;/sub&gt;.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-12-21T19:51:57.387" />
  <row Id="8160" PostTypeId="2" ParentId="8158" CreationDate="2010-12-21T20:00:37.693" Score="4" ViewCount="" Body="&lt;p&gt;I think the leads have a fuse inline to protect the internals.  Try opening it up and look for some blown fuses.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-12-21T20:00:37.693" CommentCount="2" />
  <row Id="8161" PostTypeId="2" ParentId="8158" CreationDate="2010-12-21T20:06:15.377" Score="6" ViewCount="" Body="&lt;p&gt;A few more things to check:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Broken wires in your test leads&lt;/li&gt;&#xA;&lt;li&gt;Broken test lead terminals (where you plug the leads in), they may have bent and broken&lt;/li&gt;&#xA;&lt;li&gt;Fuse (as Robert suggests)&lt;/li&gt;&#xA;&lt;li&gt;&quot;Fuse&quot;: some thin traces on the board that may have acted like a fuse for you.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-21T20:06:15.377" CommentCount="1" />
  <row Id="8162" PostTypeId="2" ParentId="8152" CreationDate="2010-12-21T20:07:36.037" Score="1" ViewCount="" Body="&lt;p&gt;Reading FAQ-8 and FAQ-10 In the &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/MPLAB_C18_Getting_Started_51295f.pdf&quot; rel=&quot;nofollow&quot;&gt;Microchip C18 Compiler Getting Started Guide&lt;/a&gt; should help you resolve the issues. I'm not sure if you are using C18 or not to compile your code, but even if you aren't you will likely need to modify your linker script to increase the RAM bank size.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2010-12-21T20:21:34.800" LastActivityDate="2010-12-21T20:21:34.800" />
  <row Id="8163" PostTypeId="1" CreationDate="2010-12-21T21:08:18.597" Score="1" ViewCount="295" Body="&lt;p&gt;I am interested in making the netduino establish a BUS connection to the IPhone via the audio jack. Does anyone have any experience doing this? I have read a few things online...but I am somewhat lost.&lt;/p&gt;&#xA;" OwnerUserId="2354" LastActivityDate="2011-01-15T04:48:40.490" Title="Interface netduino with Iphone via audio jack" Tags="&lt;netduino&gt;&lt;iphone&gt;&lt;bus&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="8164" PostTypeId="1" CreationDate="2010-12-21T21:25:08.200" Score="10" ViewCount="327" Body="&lt;p&gt;Capacitors and inductors are &lt;a href=&quot;http://en.wikipedia.org/wiki/Duality_%28electrical_circuits%29&quot; rel=&quot;nofollow&quot;&gt;duals of each other&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A transformer is made of two inductors, and transfers power through a magnetic &lt;a href=&quot;http://en.wikipedia.org/wiki/Near_and_far_field&quot; rel=&quot;nofollow&quot;&gt;near-field&lt;/a&gt;, right?  And you can vary the ratio of voltages or currents by changing the ratio of turns on the core.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there an electric dual of the transformer?  Something that uses capacitance and transfers power through the &lt;em&gt;electric&lt;/em&gt; near-field over an isolation barrier?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that an isolated supply can be built using two capacitors, but I'm not sure if that's exactly a dual, or if there's an equivalent to adjusting the ratio of turns:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/stDpG.gif&quot; alt=&quot;enter image description here&quot;&gt; &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/4553&quot; rel=&quot;nofollow&quot;&gt;source&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or maybe something like this? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/xY7KD.gif&quot; alt=&quot;alt text&quot;&gt; &lt;a href=&quot;http://amasci.com/tesla/nearfld1.html&quot; rel=&quot;nofollow&quot;&gt;source&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-31T16:02:05.627" LastActivityDate="2011-05-31T20:44:45.600" Title="Is there a dual of the transformer?" Tags="&lt;components&gt;&lt;transformer&gt;&lt;capacitance&gt;&lt;theory&gt;" AnswerCount="6" CommentCount="4" FavoriteCount="3" />
  <row Id="8165" PostTypeId="2" ParentId="8128" CreationDate="2010-12-21T21:45:05.227" Score="0" ViewCount="" Body="&lt;p&gt;Use a higher rated fuse.  The transformer will require magnetising current to set up its field in addition to the current the load will take.  Dont forget that the fuse is there only to protect against a 'catastrophic failure' of the downstream kit, not to give you a precision current limit &lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2010-12-21T21:45:05.227" CommentCount="2" />
  <row Id="8166" PostTypeId="1" CreationDate="2010-12-21T21:45:38.723" Score="5" ViewCount="151" Body="&lt;p&gt;I'm looking for manufacturers that can print resistive traces on PCBs (or other materials) for use as basic resistive position sensor.  It would essentially be core of a potentiometer, either rotary or linear.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you know of any that can do production and/or prototype, it would be welcome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm aware of companies that print resistors onto PCBs to reduce the number of discrete that need placement (&quot;screen printed resistors&quot;, &quot;printed circuit resistors&quot;, etc), but that's not necessarily what I'm looking for, as they are typically meant to be sealed and not to be wiped over.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are obviously companies that print resistive traces onto phenolic, ceramic, and other surfaces for use in slide and rotary pots (they may also do the aforementioned printed resistors too).  I'm looking for those.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-22T15:34:24.553" LastActivityDate="2010-12-24T06:57:20.973" Title="What manufacturers print resistive circuits, e.g. for potentiometers?" Tags="&lt;manufacturing&gt;&lt;potentiometer&gt;" AnswerCount="2" />
  <row Id="8167" PostTypeId="2" ParentId="8164" CreationDate="2010-12-21T21:49:51.023" Score="4" ViewCount="" Body="&lt;p&gt;I'll start by saying I don't know for sure. However, I'm inclined to say no. Transformers are not &quot;elemental&quot; electrical components. Capacitors and Inductors (and Resistors for that matter) are all fundamental (complex) impedence devices. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A transformer is a composition of two inductors. As you noted, it transforms energy through the principle of magnetic inductance. In particular, it operates on the basis of spatial side effect of current flowing through a coil (i.e. coupling of time varying magnetic field lines). All the &quot;action&quot; in a capacitor is sort of confined to what's going on between the plates, so to speak. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The closest thing I can think of to a dual-analogy to what's going on in a transformer is the idea of capacitative coupling that causes &quot;cross-talk&quot; between adjacent traces in high speed signalling buses...&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2010-12-21T21:49:51.023" />
  <row Id="8168" PostTypeId="2" ParentId="8078" CreationDate="2010-12-21T21:52:23.630" Score="0" ViewCount="" Body="&lt;p&gt;You have connected the grounds between the 2 nodes right?&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2010-12-21T21:52:23.630" CommentCount="1" />
  <row Id="8169" PostTypeId="2" ParentId="8128" CreationDate="2010-12-21T22:05:25.217" Score="2" ViewCount="" Body="&lt;p&gt;As transformers take a surge when turned on, I would suggest an Anti-Surge Fuse on the input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also does the fuse blow when you operate the switch to change ranges - some rotary switches are make before break - this means that when switching the output is connected to both inputs, this will short out one winding on the transformer and this will blow the fuse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How does the fuse look after it has blown, on clear fuses you can see the wire inside, if the wire has a 'small' gap this means it is a 'minor' overload, if the wire has a large gap, or has vaporised and covers the inside with a dark stain, this indicates a 'major' overload.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A minor overload is either an long overload just above the rating of the fuse, e.g. 2 x fuse rating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A Major overload is e.g. 10-20 (or more) x rating of fuse.&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2010-12-21T22:05:25.217" CommentCount="2" />
  <row Id="8170" PostTypeId="2" ParentId="8152" CreationDate="2010-12-21T22:14:29.980" Score="4" ViewCount="" Body="&lt;p&gt;All the variables in the program take space, and you're using too much for the chip you're trying to compile it for.  The program you're trying to compile needs 0x4B0 bytes (1200 in decimal), and you have something less than this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Figure out how much RAM space your PIC18 has. Make sure it matches what you're compiling against. There's possibly a linker definition file someplace defining the sizes of the various sections. Section IDATA is your current problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Someone more familiar with MPLAB may be able to fill in details on what your actual constraints are and how to properly configure the compiler for your chip.&lt;/p&gt;&#xA;" OwnerUserId="1270" LastActivityDate="2010-12-21T22:14:29.980" />
  <row Id="8172" PostTypeId="2" ParentId="8145" CreationDate="2010-12-21T23:40:37.033" Score="1" ViewCount="" Body="&lt;p&gt;Maybe look at using an off the shelf chip solution such as the &lt;a href=&quot;http://www.obd-ii.de/prodelm327.html&quot; rel=&quot;nofollow&quot;&gt;ELM327&lt;/a&gt;.  This looks like it will handle all of the various voltage and protocol issues.&lt;/p&gt;&#xA;" OwnerUserId="820" LastActivityDate="2010-12-21T23:40:37.033" CommentCount="2" />
  <row Id="8173" PostTypeId="2" ParentId="8164" CreationDate="2010-12-21T23:51:27.103" Score="6" ViewCount="" Body="&lt;p&gt;Actually, this is a common thing to wonder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a dual to this. When you have devices sharing a common winding and magnetic flux(Magnetic &quot;current&quot;) it makes a perfect dual for devices sharing a common electric conductor. Nice picture from wikipedia:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/jfVnd.gif&quot; alt=&quot;wikipedia image of flux in a transformer :http://upload.wikimedia.org/wikipedia/commons/thumb/9/98/Transformer_flux.gif/300px-Transformer_flux.gif&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also take a look at &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/Magnetic_circuit&quot; rel=&quot;nofollow&quot;&gt;Magnetic Circuits&lt;/a&gt;&quot;. You can start learning some fun terms when you go into these concepts in detail, like &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/Magnetic_capacitance&quot; rel=&quot;nofollow&quot;&gt;Magnetic Capacitance&lt;/a&gt;,&quot; it seems that my flux does have capacitance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way you can determine how much energy passes through a transformer can be broken down into a magnetic circuit that works just like an electric circuit with different units. &lt;a href=&quot;http://en.wikipedia.org/wiki/Magnetic_circuit&quot; rel=&quot;nofollow&quot;&gt;Magnetic Circuits&lt;/a&gt; are an analog of &lt;a href=&quot;http://en.wikipedia.org/wiki/Electronic_circuit&quot; rel=&quot;nofollow&quot;&gt;Electric Circuits&lt;/a&gt;, which are much easier to work with for many many reasons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think of it like a voltage source or a current source. They are direct analogs, but when you build a voltage source it is a hell of a lot easier than a current source.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Side Note&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;The magnetic flux is shared in a core due to the fact that magnetic flux is perpendicular to the wire, the issue with electric flux is that it points between two surfaces, not looped around. If it looped around a dielectric would get the job done.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;In relation to the capacitor inside the other&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;IF the smaller becomes bigger, it will end up acting like two coupling capacitors with a series resistor between them, as it gets smaller, the overall electric field will be minimal, but you could put a big big E-Field in there, not nearly as effective as a transformer.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-22T00:04:59.230" LastActivityDate="2010-12-22T00:04:59.230" />
  <row Id="8174" PostTypeId="2" ParentId="8152" CreationDate="2010-12-22T01:11:03.867" Score="0" ViewCount="" Body="&lt;p&gt;You are either&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(A) running out of flash memory to store the initial values of variables, or&lt;br&gt;&#xA;(B) your variables are bigger than the segment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The linker is trying to link the dmpDefault file but it overflows the linker's defined memory segments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OR&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With MCC18, each file creates 1 data section with a maximum of 256 bytes (1 bank).  .idata_dmpDefault is much larger than that.  You can create named data sections by combining banks in the linker and put #pragmas around the variables to locate those variables in that section.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2010-12-22T01:11:03.867" />
  <row Id="8175" PostTypeId="2" ParentId="7505" CreationDate="2010-12-22T01:22:16.650" Score="3" ViewCount="" Body="&lt;p&gt;Here's what I would do with my 35-mm camera if I needed it to travel along an accurate trajectory, and consider it to be simple to customize to a specific trajectory and stable enough for a heavy camera. Use a strip of 1/16&quot; to 1/8&quot; thick, 3/4&quot; by 1.5&quot; angle-iron to go from point A to point B, bending to whatever vector you wish at different lengths -- it's possible to bend this by hand (or over your knee). You would need to construct a trolly to grip the track. There are a zillion different ways of doing this; here is one:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.tyblu.ca/misc/camtrolley1.jpeg&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/camtrolley1_sm.jpg&quot; alt=&quot;Note: this is also a link.&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've put in servo-motors (mounted on gearboxes), but you could use stepper motors. A brake is a chock or wedge shoved under the wheel by a solenoid or spring -- the spring would save you a solenoid, but make the trolley 1-way only. You may not need every wheel to be powered. Also, once one has a trolley they can mount whatever they want however they want on it, so long as it can support the weight and torque. Those &lt;a href=&quot;http://joby.com/&quot; rel=&quot;nofollow&quot;&gt;Gorilla camera stands&lt;/a&gt; look like they could be mounted then positioned arbitrarily. If you really want to get fancy you could &lt;a href=&quot;http://www.envisiongear.com/images/EG_Mast_Gimbal.png&quot; rel=&quot;nofollow&quot;&gt;give the camera degrees of motion like pan, tilt, and roll&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Path length or position can be tracked in a number of ways; here are some: rotary encoder, using a pre-marked disk attached to one of the shafts, an LED and a photodiode; optical mouse sensor, sensing either wheel rotation or relative angle-iron movement; feedback from servo motors. Note that if resultant travel from incremental motor actuation is well defined, you may be able to deduce total travel and not have to track the path.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;I'd fight with myself between this solution and parallel threaded rods. I've used ready-rod before, and it's really easy, but it would be more difficult to secure it, as you could only do it at the ends, whereas this one can be secured along its length.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-22T04:15:00.430" LastActivityDate="2010-12-22T04:15:00.430" CommentCount="4" />
  <row Id="8176" PostTypeId="1" AcceptedAnswerId="8177" CreationDate="2010-12-22T04:50:26.150" Score="1" ViewCount="167" Body="&lt;p&gt;I have a IPhone wall charger. Can I plug my netduino into it to power it via USB?&lt;/p&gt;&#xA;" OwnerUserId="2354" LastActivityDate="2010-12-22T06:23:31.630" Title="Netduino powerd by USB wall charger" Tags="&lt;power&gt;&lt;usb&gt;&lt;netduino&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="8177" PostTypeId="2" ParentId="8176" CreationDate="2010-12-22T05:09:00.490" Score="4" ViewCount="" Body="&lt;p&gt;Yep. I'm guessing you have &lt;a href=&quot;http://manuals.info.apple.com/en_US/iPod_2ndGen_USB_Power_Adapter-EN.pdf&quot; rel=&quot;nofollow&quot;&gt;this little gizmo&lt;/a&gt; and a random USB extension cable. Looking at the &lt;a href=&quot;http://netduino.com/netduino/schematic.pdf&quot; rel=&quot;nofollow&quot;&gt;Netduino schematics&lt;/a&gt; you can clearly see that the USB input is fused, kinda buffered (can see current limiting op amp and RC PDN arrangement, if I'm reading it correctly), and regulated. The Apple product is supposed to output 5V; I didn't check to see which LDO the Netduino is using, but it'll likely have a drop ~0.3V, however there's a pass transistor as well which may bring that up a bit (maybe ~0.1V drop) -- looks like it may be on the fence between linear and saturation, though, so don't count on it. Surely the Netduino will be fine with a bit less than 5V.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-22T05:09:00.490" CommentCount="3" />
  <row Id="8178" PostTypeId="2" ParentId="8176" CreationDate="2010-12-22T06:23:31.630" Score="1" ViewCount="" Body="&lt;p&gt;The Netduino requires power of 7.5-12v on its power connector. However, the Netduino can also pull it's power from the 5v USB connector. So yes, your IPhone wall charger should work just fine for you.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-22T06:23:31.630" />
  <row Id="8179" PostTypeId="2" ParentId="8166" CreationDate="2010-12-22T08:53:50.277" Score="0" ViewCount="" Body="&lt;p&gt;I doubt that you can do potentiometer using these PCB manufacturers.&#xA;Resistive layers are burried, and I doubt they have physical durability to serve in potentiometers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I would need prototype, I would do it myself - using graphite traces for example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And finally, could you tell us why you need potentiometers in 2011? :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-12-22T08:53:50.277" CommentCount="4" />
  <row Id="8180" PostTypeId="2" ParentId="8158" CreationDate="2010-12-22T10:02:52.983" Score="1" ViewCount="" Body="&lt;p&gt;I had this exact problem with my multimeter. I don't recall testing it with any high current/voltage sources, but I opened it up and sure enough I had blown the fuse. Double check to make sure the fuse isn't blown also. I couldn't see any kind of disconnect in my fuse but checking it with a (homemade) continuity tester showed that it was blown. I took the fuse down to radioshack and they gave me a pack of 4 replacement fuses for like $2. My meter has been working fine since. &lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2010-12-22T10:02:52.983" CommentCount="1" />
  <row Id="8181" PostTypeId="2" ParentId="8158" CreationDate="2010-12-22T11:39:37.440" Score="3" ViewCount="" Body="&lt;p&gt;I've had a similar problem years ago. What helped was &lt;strong&gt;disassembly and cleaning of the contacts below the rotating switch&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will find little spring contacts assembled in cavities of the rotating plastic part and contacts on the PCB that the little spring contacts brush over. A bit like the wiper of a potentiometer. Ethanol or isopropyl alcohol (or contact spray) will likely help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Seems like even the analog signals are routed along the contacts of the rotating switch, which sometimes gives not only complete open contacts but also resistance measurements that are just a bit too high, especially for the 200 Ohm range.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-12-22T11:39:37.440" CommentCount="2" />
  <row Id="8182" PostTypeId="1" AcceptedAnswerId="8187" CreationDate="2010-12-22T12:13:02.150" Score="2" ViewCount="237" Body="&lt;p&gt;I'm going to try to build some throwies soon and am ordering some LEDs and other needed things for the task. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is my understanding that a CR2032 battery is 2.6-3.1 volts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, I have &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=37&amp;amp;products_id=299&quot; rel=&quot;nofollow&quot;&gt;these LEDs&lt;/a&gt; picked out.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;660 nm wavelength&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;1.85-2.5V Forward Voltage, at 20mA current&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Would this be ok to use without any resistors? I'm ok if LED life is shortened, but I definitely don't want for the LED to just light up and then be burnt out a second later.&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2010-12-22T20:53:38.943" Title="Will these LEDs work for throwies?" Tags="&lt;led&gt;&lt;battery&gt;" AnswerCount="5" CommentCount="5" />
  <row Id="8183" PostTypeId="2" ParentId="7674" CreationDate="2010-12-22T12:15:27.270" Score="1" ViewCount="" Body="&lt;p&gt;Try this link&#xA;&lt;a href=&quot;http://www.nerdkits.com/videos/digital_calipers_dro/&quot; rel=&quot;nofollow&quot;&gt;http://www.nerdkits.com/videos/digital_calipers_dro/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Step-by-step description of adding a USB interface and pair of digital calipers to a milling machine for digital readout). &lt;/p&gt;&#xA;" OwnerUserId="2360" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-03T14:56:35.220" LastActivityDate="2011-05-03T14:56:35.220" CommentCount="1" />
  <row Id="8184" PostTypeId="2" ParentId="8182" CreationDate="2010-12-22T12:32:36.287" Score="4" ViewCount="" Body="&lt;p&gt;You need a series resistor to limit the LED current. You can find out how to calculate its value &lt;a href=&quot;http://electronics.stackexchange.com/questions/7755/what-resistor-should-i-use-when-wiring-10-leds-in-series&quot;&gt;here&lt;/a&gt;. In this case your problem is that you have little overhead combined with large tolerances in voltages. The voltage difference between Vbat and Vled can vary between 0.1V and 1.25V. A new battery should give you over 3V; I've measured voltages of 3.4V on CR2032s. OTOH, 2.5V for a red LED is rather high, so I would use the 1.85V for my calculation (even that is a bit high!). So, taking 3.1V for the battery and 1.85V for the LED you need a series resistor of (3.1 - 1.85)V / 20 mA = 62 ohm. A E12 value of 56 ohm will do fine.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;You probably have seen the battery directly placed between the legs of the LED, no resistor, but this will drain the battery fast.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-22T12:58:39.877" LastActivityDate="2010-12-22T12:58:39.877" />
  <row Id="8185" PostTypeId="2" ParentId="8182" CreationDate="2010-12-22T14:10:59.523" Score="0" ViewCount="" Body="&lt;p&gt;This is the question I was puzzled myself.&#xA;In theory, even without resistor it might work as battery and LED have internal resistance, but for lithium batteries it's rather low so most likely LED will operate out of specs (but will probably work if you take a powerful one).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'd better use series resistor, you may solder SMD one right on LED legs, so it will not increase dimensions. Values to try 10-100 Ohms.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-12-22T14:10:59.523" />
  <row Id="8186" PostTypeId="2" ParentId="8182" CreationDate="2010-12-22T14:15:33.753" Score="1" ViewCount="" Body="&lt;p&gt;According to the &lt;a href=&quot;http://data.energizer.com/PDFs/cr2032.pdf&quot; rel=&quot;nofollow&quot;&gt;Energizer CR2032 datasheet&lt;/a&gt; I'd say the internal resistance of the battery (10 to 40 Ohm) is too low, so you need a series resistor.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-12-22T14:15:33.753" />
  <row Id="8187" PostTypeId="2" ParentId="8182" CreationDate="2010-12-22T14:20:49.663" Score="4" ViewCount="" Body="&lt;p&gt;Here is some interesting info on &lt;a href=&quot;http://www.evilmadscientist.com/article.php/throw&quot; rel=&quot;nofollow&quot;&gt;throwies&lt;/a&gt; from evilmadscientist.com&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;[Connecting a 1.7 V LED directly to a CR2032]&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/cMatq.jpg&quot; alt=&quot;CR2032 discharge curve, direct connection to 1.7 V red LED&quot;&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Wait-- &lt;em&gt;107 mA?!&lt;/em&gt;--‽&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Yes, this is reproducible. (That is to say, we &lt;strike&gt;wasted&lt;/strike&gt; used up another battery just because we didn't believe it either.) But holy cow anyway.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&quot;And they said this was safe?&quot; There are a couple of legitimate concerns here. Lithium coin cells aren't designed to source nearly that much power-- and aren't lithium batteries a fire hazard? And why does my LED-- rated for 25 mA continuous current survive this? I've certainly seen enough LEDs destroyed by overcurrent, and this one was over 25 mA for ten minutes solid. But, and perhaps against my better judgement, I do believe that this actually &lt;em&gt;is&lt;/em&gt; safe in practice. With all of the throwies and similar things out there -- don't forget the keychain flashlights -- they just don't seem to be exploding or catching on fire. (Breaking, falling apart, running out of photons, yes-- but those modes of failure are usually not as dangerous.)&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;[...]&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;So.... Do you need a resistor? No, not really. As we said, it seems to be reasonably safe without one. Should you use a resistor? Yeah you should, if you want a red, yellow, or orange LED to last more than a day or so. So you can solder a resistor in place, but that somewhat defeats the purpose of easy to assemble throwies.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;So to make it not a total pain-in-the rear to add resistors, here's a way to do it without soldering: just twist it.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/369QY.jpg&quot; alt=&quot;Throwie with an easily inserted resistor&quot;&gt;&#xA;  &lt;img src=&quot;http://i.imgur.com/aT2Qt.jpg&quot; alt=&quot;Assembled &amp;amp; folded over LED&quot;&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Source: &lt;a href=&quot;http://www.evilmadscientist.com/article.php/throw&quot; rel=&quot;nofollow&quot;&gt;http://www.evilmadscientist.com/article.php/throw&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-22T20:53:38.943" LastActivityDate="2010-12-22T20:53:38.943" CommentCount="2" />
  <row Id="8188" PostTypeId="2" ParentId="8182" CreationDate="2010-12-22T14:44:30.103" Score="2" ViewCount="" Body="&lt;p&gt;Take a peek at the &lt;a href=&quot;http://data.energizer.com/PDFs/cr2032.pdf&quot; rel=&quot;nofollow&quot;&gt;pulsed characteristics for the CR2032&lt;/a&gt;. This load may pull down the voltage to 2.3V-2.9V and IR is ~30Ω. Using &lt;a href=&quot;http://data.energizer.com/PDFs/cr2032.pdf&quot; rel=&quot;nofollow&quot;&gt;the &quot;Pulse&quot; data in the 4th graph (bottom right)&lt;/a&gt;: (2.4V-1.85V)/(20mA)=27.5Ω. Your milage may vary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, looking at &lt;a href=&quot;http://www.adafruit.com/datasheets/WP7113SRD-D.pdf&quot; rel=&quot;nofollow&quot;&gt;the &quot;Spacial Distribution&quot; graph in the LED datasheet&lt;/a&gt;, you can see that its viewing angle is only about 20°. If you want it to look brighter despite poor viewing angle (I bet it is often non-ideal when all you're doing is &quot;throwing&quot; them on out-of-reach surfaces), look for an LED with a better viewing angle. While you're at it, you can get high-efficiency ones that only need a few mA for the same lumens. These are often in surface mount packages, so constructing a &lt;em&gt;throwie&lt;/em&gt; would be quite different. Examples: &lt;a href=&quot;http://www.lumex.com/specs/SSL-LX203CSRT.pdf&quot; rel=&quot;nofollow&quot;&gt;SSL-LX203CSRT&lt;/a&gt;, &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=475-2820-1-ND&quot; rel=&quot;nofollow&quot;&gt;LR T68F-U1AA-1-1-Z&lt;/a&gt;, &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=475-2835-6-ND&quot; rel=&quot;nofollow&quot;&gt;LY T68F-T2V2-35-1-Z&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-22T15:18:45.127" LastActivityDate="2010-12-22T15:18:45.127" />
  <row Id="8189" PostTypeId="2" ParentId="8164" CreationDate="2010-12-22T14:55:28.680" Score="0" ViewCount="" Body="&lt;p&gt;A capacitor configured as a high pass filter, &lt;em&gt;is&lt;/em&gt; transferring information (and energy) across the gap using the electric field.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is worth noting in this context that the usual &quot;capacitor&quot; you put on a board has two poles, but there is nothing necessary about this arrangement. A loose conductor hangin out in space has a (small!) capacitance and is a capacitor.&lt;/p&gt;&#xA;" OwnerUserId="1882" LastActivityDate="2010-12-22T14:55:28.680" CommentCount="1" />
  <row Id="8190" PostTypeId="2" ParentId="7769" CreationDate="2010-12-22T15:14:06.503" Score="1" ViewCount="" Body="&lt;p&gt;you can see &lt;a href=&quot;http://arduino.cc/en/Guide/Environment?from=Tutorial.Bootloader&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; that your mega 2560 normally have an stk500v2 bootloader. (ctrl-F &quot;2560&quot;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you'll find the .hex to upload (and c to compile if needed), via avr studio and your external programmer in :&lt;/p&gt;&#xA;&#xA;&lt;p&gt;arduino-0021/hardware/arduino/bootloader/stk500v2/stk500boot_v2_mega2560.hex&lt;/p&gt;&#xA;&#xA;&lt;p&gt;pay attention that the version of avrdude using to upload via the bootloader (in arduino/hardware/tools/avrdude is a patched version of the normal one you should have in avr-studio.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;so to upload via the bootloader -&gt;  arduino's avrdude, &lt;/li&gt;&#xA;&lt;li&gt;to upload via isp&#xA;-&gt; normal avrdude (don't know avr-studio and where it has instal&#xA;it.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;as an extra, you can see the command line used by the arduino software to communicate with the bootloader by pressing MAJ when compiling/uploading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To upload a bootloader, somme tricks with the fuse are needed, to lock his part of the memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I reload the bootloader with an external programmer and those command line (arduino uno):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;avrdude -p atmega328p -c stk500 -P /dev/STK500 -e -Ulock:w:0x3F:m -Uefuse:w:0x05:m -Uhfuse:w:0xde:m -Ulfuse:w:0xff:m&#xA;avrdude -p atmega328p -c stk500 -P /dev/STK500 -Uflash:w:optiboot_atmega328.hex:i -Ulock:w:0x0f:m&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Again, I found those with the arduino software, using MAJ to see what it does.&lt;/p&gt;&#xA;" OwnerUserId="2040" LastEditorUserId="2040" LastEditorDisplayName="" LastEditDate="2011-01-09T20:36:25.903" LastActivityDate="2011-01-09T20:36:25.903" CommentCount="1" />
  <row Id="8191" PostTypeId="2" ParentId="8157" CreationDate="2010-12-22T16:25:33.857" Score="1" ViewCount="" Body="&lt;p&gt;You could probably do the whole thing with one motor and a solenoid using the same principle as a car's start motor / starter solenoid.  Basically, mount a gear to the main arm.  The solenoid would push the drive gear (which is attached to the motor with a worm gear) against the main arm gear to lower it down.  To launch, disengage the solenoid.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that you can make your own simple solenoid with a simple electromagnet / spring in opposition.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't thought a whole lot about the loading mechanism... Some more information on the size of the apparatus would be helpful.&lt;/p&gt;&#xA;" OwnerUserId="1823" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2010-12-22T16:43:24.603" LastActivityDate="2010-12-22T16:43:24.603" />
  <row Id="8192" PostTypeId="2" ParentId="8152" CreationDate="2010-12-22T17:43:40.987" Score="0" ViewCount="" Body="&lt;p&gt;Thank you all for your kind help!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe a part of the solution can be of general help:&#xA;I found out I had large constant arrays (I hadn't written the code myself..) and I drastically reduced the RAM need by putting them into Flash instad of RAM by using the &quot;rom&quot; keyword in their declaration.&lt;/p&gt;&#xA;" OwnerUserId="2285" LastActivityDate="2010-12-22T17:43:40.987" />
  <row Id="8193" PostTypeId="2" ParentId="8036" CreationDate="2010-12-22T20:07:20.213" Score="7" ViewCount="" Body="&lt;p&gt;All the video processing I've seen happens at high impedance, then the video is re-amplified for transmission.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, in my sketch below, the resistance of the switch doesn't matter because it is feeding the high-impedance video buffer amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you search your favorite distributor for &quot;video buffer amplifier&quot; you will find this is a relatively common part.  You can find them with fixed gain of two for exactly this application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/TrOlo.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-22T20:30:04.393" LastActivityDate="2010-12-22T20:30:04.393" CommentCount="1" />
  <row Id="8194" PostTypeId="2" ParentId="8036" CreationDate="2010-12-22T20:16:27.983" Score="4" ViewCount="" Body="&lt;p&gt;In my breif examination, it appears that there are two basic approaches. The first is to use an analog mux such as the one you have identified, and then buffer the resulting signal with a high input impedance amplifier. &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/3823&quot; rel=&quot;nofollow&quot;&gt;Maxim&lt;/a&gt; has a pretty good write-up on how to do this using a separate mux and amplifier. They use the switch on-resistance as part of the 75 ohm matching network.  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;(95 ohms in parallel with (300 ohms + mux resistance))&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/PCHQD.gif&quot; alt=&quot;Maxim example video switching circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found a single chip &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=NJM2244M%23-ND&quot; rel=&quot;nofollow&quot;&gt;(NJM2244)&lt;/a&gt; that combines the analog switches with a matched 75 ohm driver. This would allow you to have only one very small chip with very simple controls.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/gYqxB.png&quot; alt=&quot;NJM2244 Block Diagram&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another &lt;a href=&quot;http://www.engadget.com/2007/03/13/how-to-make-a-solid-state-a-v-switcher/&quot; rel=&quot;nofollow&quot;&gt;method&lt;/a&gt; uses much lower resistance switches. This particular writeup uses &lt;a href=&quot;http://www.mouser.com/ProductDetail/NXP-Semiconductors/CBT3244AD118/?qs=sGAEpiMZZMutXGli8Ay4kDE4J8KCiPsF9uIMu%2F9QFBU%3D&quot; rel=&quot;nofollow&quot;&gt;switches&lt;/a&gt; intended for high-speed logic, and they have an on-resistance of about 5-8 ohms. That small of a resistance could probably be tolerated fairly easily.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/aJb39.jpg&quot; alt=&quot;Bus wiring diagram&quot;&gt;&lt;img src=&quot;http://i.imgur.com/WtfNP.jpg&quot; alt=&quot;Bus switching chip CBT3244A&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each bus switch chip has two banks of SP4T switches, so you could switch stereo audio in addition to the video signal. If you're switching only two sources, this could be a single-chip solution as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding the bandwidth of composite video, the highest figure I've seen is 6.5MHz, which isn't really that high frequency. You won't have difficulty finding amplifiers for these frequencies, and the wiring shouldn't be very sensitive (aside from adjacent noise sources).&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-12-22T21:39:54.570" LastActivityDate="2010-12-22T21:39:54.570" CommentCount="2" />
  <row Id="8196" PostTypeId="2" ParentId="8128" CreationDate="2010-12-22T23:36:28.860" Score="2" ViewCount="" Body="&lt;p&gt;A 50VA transformer will take about 0.21 Amps when correctly loaded (VA / Input voltage)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So a fuse of about 1.5 x the input is suggested and should be Anti Surge (Usually marked T or TT - T stands for &quot;träge&quot; which is german for Lazy or slow) - so 315mA A/S or 400mA A/S &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your fuses are vaporized and cover insides with remains of the wire -  This indicates a major short...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What type of transformer are you using - is it a toroidal - if so have you got a shorted turn (if you mount a toroidal transformer incorrectly you can add an extra winding which is shorted out - this is creates by mounting the transformer with a conductive clamp which is bolted down in the middle - if you are using a toroidal - try removing the clamp...)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is possible that you have a faulty diode in your bridge - I have seen diodes that measure OK when tested with a meter, but when either loaded, or subjected to a higher voltage, break down and become shorts, or leak - the easiest way to prove is to replace ALL the diodes, as I have found if one is faulty, it usually subjects others in the bridge to stress, which may make them more likely fail, and for the cost of 4 diodes of 1N400X or 1N540X - I usually use 1N4007 or 1N5408...&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2010-12-22T23:36:28.860" CommentCount="7" />
  <row Id="8197" PostTypeId="1" CreationDate="2010-12-23T01:45:33.320" Score="2" ViewCount="147" Body="&lt;p&gt;I have a dehumidifying cabinet which requires 5V 900mA, and I have a universal adapter that is rated at 1000mA 12V, however the slider doesn't have a 5V marking, only 4.5 and 6V. Is it okay to point the slider to somewhere between 4.5 and 6 in hope of getting around 5V?&lt;/p&gt;&#xA;" OwnerUserId="2364" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-23T01:52:16.043" LastActivityDate="2010-12-28T00:14:51.433" Title="Can I set the slider on my universal adapter between 4.5V and 6V to get 5V?" Tags="&lt;adapter&gt;" AnswerCount="2" CommentCount="7" FavoriteCount="1" />
  <row Id="8198" PostTypeId="2" ParentId="8197" CreationDate="2010-12-23T03:32:18.480" Score="5" ViewCount="" Body="&lt;p&gt;If the slider is a switch, then you won't be able to set the output to an intermediate value (5.0V). The only way that you would be able to get a 5.0V output is if the slider is a linear potentiometer, although I find that unlikely. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's more likely to be a switch because switches are cheaper and don't require calibration for specific positions (4.5V, 6.0V, etc...). It may still work at the 4.5V setting, depending on the electronics since 4.5V is only -10% from the specified voltage.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-23T03:32:18.480" />
  <row Id="8199" PostTypeId="1" AcceptedAnswerId="8207" CreationDate="2010-12-23T05:37:28.453" Score="4" ViewCount="402" Body="&lt;p&gt;I have a product using the MSP430 microprocessor, which has been selling for a couple years now.  One of the MSP430's jobs is to communicate over async serial to a low-power radio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the onset of this winter, there has been an unacceptable failure rate (several percent) in cold temperature.  Investigation has found that the serial communication with the radio is failing. The baudrate generator for the serial port is fed by SMCLK, which is divided from the MSP430's digitally-controlled oscillator (DCO).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why is serial communication failing at low temperatures?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Note: I have already solved the problem and will be posting the answer soon.  Hint: it was a software bug.)&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-23T17:29:13.500" Title="MSP430 serial communication failing in cold weather" Tags="&lt;serial&gt;&lt;temperature&gt;&lt;msp430&gt;&lt;baudrate&gt;" AnswerCount="3" />
  <row Id="8200" PostTypeId="2" ParentId="8199" CreationDate="2010-12-23T06:13:56.267" Score="5" ViewCount="" Body="&lt;p&gt;The low temperatures caused the DCO frequency to rise enough to cause the UART baud rate to rise too high? You measured the temperature and then compensated the oscillator in software?&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-23T06:13:56.267" />
  <row Id="8201" PostTypeId="2" ParentId="8157" CreationDate="2010-12-23T07:37:27.523" Score="1" ViewCount="" Body="&lt;p&gt;If you can get a motor with enough torque, I bet you can accomplish this the easiest by putting a larger gear on the motor shaft, and a smaller gear on the catapult arm's pivot point.  The larger gear should have more teeth than the smaller gear.  Then remove / grind off a few adjacent teeth on the larger gear.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the motor spins the larger gear, the teeth are engaged with the catapult gear and causes it to move down, compressing the spring.  Before the last tooth on the larger gear disengages from the smaller gear, the ball should get loaded.  When the last tooth on the larger gear disengages, the catapult arm's gear is able to spin freely -- this allows the spring to uncoil and launch the object.  If you get the gears sized properly, the catapult arm will come to rest before the next tooth on the larger gear re-engages the catapult arm's gear.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just keep spinning the motor, and it'll just reload and launch over and over again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sounds like a great project to print on my 3D printer.  I'll look into this.  This also made me think of the geared motor used in the extruder -- you should have no problem finding a motor with enough torque to compress your spring (although I don't know what sort of spring rate you're using).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- I didn't realize that you also might need info about the loading mechanism.  Try drawing up something where the catapult arm, when lowered, hits a shelf with a ball on it.  This makes the shelf tilt, and the ball falls into the catapult bucket.  The act of tilting also prevents the other balls from coming out.  When the catapult fires, the shelf tilts back the other way, allowing the next ball to advance.  I think it's a pretty simple singulation device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your best bet is to prototype this with Lego.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT #2 -- does it need to operate like a real catapult, i.e. angular motion?  I think an even easier way is to use linear motion for the firing mechanism, with the same sort of gearing that I described above.  I think this would simplify the ball singulation.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-01-03T03:49:29.130" LastActivityDate="2011-01-03T03:49:29.130" />
  <row Id="8202" PostTypeId="1" AcceptedAnswerId="8211" CreationDate="2010-12-23T07:42:14.703" Score="2" ViewCount="113" Body="&lt;p&gt;Hi, could you please suggest printer for printer photomasks at home?&#xA;Target is to have 0.1x0.1 features or better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My tests shows that inkjet are pretty bad when working under 0.3x0.3.&#xA;So obviously, only lasers left.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is 1200x1200 worth it? Any experience showing one models better than others? Any specific examples?&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-12-23T12:06:42.590" Title="Suggest printer for printing photomasks for homemade PCBs" Tags="&lt;pcb&gt;&lt;photomasks&gt;" AnswerCount="2" />
  <row Id="8203" PostTypeId="1" CreationDate="2010-12-23T08:02:41.613" Score="2" ViewCount="169" Body="&lt;p&gt;What is the best way of stripping enamel off of magnet wire using things available in a common electronic setup? I mean, I have some wire cutters and I can use it to strip the enamel off of thicker magnet wire but I have two thin types of wire. For one of them I can burn the enamel off effectively but it still seems to not be consistently conductive. For the thinnest wire I have when I burn it off the copper(I assume it's copper, the wire is of unknown origin) the copper burns and vaporizes with it and the wire just falls apart becomes disconnected. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the best way of stripping enamel with common tools? (as in, without special acids and such)&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2010-12-25T05:55:08.500" Title="What's the best (cheap) way of stripping enamel off of magnet wire?" Tags="&lt;tools&gt;&lt;magnet-wire&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="8204" PostTypeId="2" ParentId="8202" CreationDate="2010-12-23T08:17:23.277" Score="2" ViewCount="" Body="&lt;p&gt;I get excellent results with a cheap HP inket printer and Mega Electronics Premium Jetstar film - down to 8 mil tracks. I've even done 5 mil as an experiment. It does 1200 dpi.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-23T12:06:42.590" LastActivityDate="2010-12-23T12:06:42.590" CommentCount="2" />
  <row Id="8205" PostTypeId="1" AcceptedAnswerId="8208" CreationDate="2010-12-23T08:26:20.833" Score="0" ViewCount="146" Body="&lt;p&gt;Hello Stack!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Had a quick question. I am using a &lt;a href=&quot;http://www.crouzet-ssr.com/english/products/download/GA1GA8.pdf&quot; rel=&quot;nofollow&quot;&gt;Crouzet GA8-6D05&lt;/a&gt; SSR to relay xmas lights for the holidays. I basically hacked an extension cord (120VAC US &amp;lt;1Amp) to do this. I am currently using a spliced extension cord to perform on and off operations via a micro controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;During the summer, we commonly use this same outlet for a water fountain on our patio (also 120VAC US &amp;lt;1Amp). I was thinking to use the SSR mentioned above to switch the water fountain on and off also. I am thinking that the best way to make this work would be to hack the actual outlet. I already know that you can separate a two plug receptacle by cutting the metal plate which connects positive on one side and negative on the other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is: What will happen to the SSR if the load exceeds more than the max 5 amps it is rated for? Will it blow up, start a fire, or just reject the call for the extra amps? I am concerned about fire hazards, not really concerned about the thing dieing necessarily. I worry about leaving this in the wall if I sell the house as I do not plan to use the outlet for anything more than what is stated above, but the next home owners may not follow directions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance for your help!&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="1575" LastEditorDisplayName="" LastEditDate="2010-12-23T09:16:10.570" LastActivityDate="2010-12-23T09:28:47.027" Title="What Happens When You Exceed a Solid State Relay's Max Amps?" Tags="&lt;microcontroller&gt;&lt;power&gt;&lt;relay&gt;&lt;solid-state-relay&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="8206" PostTypeId="2" ParentId="8203" CreationDate="2010-12-23T08:45:59.187" Score="0" ViewCount="" Body="&lt;p&gt;It could be that the thinnest type of wire you have is actually some sort of plastic with just a bit of metal in it. Headphones or flexible telephone cords often use such wires because the polymer (often nylon) string is more robust to tension and torsion than copper alone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Soldering these is hardly possible; they are often crimped. I don't know if acid works (I think formic acid is used quite often).&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-12-23T08:45:59.187" CommentCount="1" />
  <row Id="8207" PostTypeId="2" ParentId="8199" CreationDate="2010-12-23T08:47:12.140" Score="5" ViewCount="" Body="&lt;p&gt;Which MSP430 are you using?  The different families have different clock structures and capabilities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DCO will change frequency with temperature causing the USART baud rate to drift out of specification.  The MSP has a temperature sensor (not very accurate).  You can change the values in the DCO control registers to bring the DCO frequency back in range but this would require calibrated lookup tables covering the range of temperatures that you expect to see.  Some of the MSP devices have DCO calibration tables programmed into one of the flash sectors at manufacture but these are only useful if they cover the frequency that you wish to use, and I do not think that they have temperature compensation values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have a reference crystal oscillator that you could use as a calibration source?  I would always design in a 32kHz crystal and use this on the ACLK.  For baud rates up to 9600 this can be used directly.  For higher baud rates you will have to calibrate the DCO against the ACLK signal.  The newer parts have a hardware FLL that will do this automatically.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2010-12-23T08:47:12.140" />
  <row Id="8208" PostTypeId="2" ParentId="8205" CreationDate="2010-12-23T09:28:47.027" Score="2" ViewCount="" Body="&lt;p&gt;With the concerns you state, and especially with having the relay installed in a wall, I guess the answer is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might add a fuse, but then, you'd have to find a rating in the relay's data sheet telling you if it is approved for usage with a fuse, and if so, what the fuse's rating would have to be. All in all, you would have to do the same qualification for the entire system (relay, fuse, type of outlet socket, possible loads) that the original vendor did for the combinaiton of the relay and fountain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The relay will not limit the current (amps) to a level that is safe to itself. When overloaded, it will likely act like a short circuit for moderate overload conditions and will fail open (or explode, or burn) for severe or ongoing overload conditions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing to remember is this: Once you exceed any of the ratings, the manufacturer won't guarantee anything they tell you in the data sheet any more and you are on your own.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, with having the relay installed in a wall where it can't really get rid of any heat it produces, I recommend using the derating curve for 60...70 °C, which tells you to rather not exceed 2...3 A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A hacker's answer, however, is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, your setup might work, ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... but you would have to make sure all is well and within the specified limits and characteristics.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-12-23T09:28:47.027" />
  <row Id="8209" PostTypeId="2" ParentId="7685" CreationDate="2010-12-23T09:37:17.653" Score="0" ViewCount="" Body="&lt;p&gt;Since your goal is to track a lost wallet in your house, you could just look for an appendage for a key ring chain that replies when you whistle to it, and put it into your wallet. Then just whistle around the house and it will reply. Cheap and simple.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2010-12-23T09:37:17.653" />
  <row Id="8210" PostTypeId="2" ParentId="8132" CreationDate="2010-12-23T11:23:54.220" Score="3" ViewCount="" Body="&lt;p&gt;I use these, I had the same issue looking for PCB connectors, then I found these and they work great. &lt;img src=&quot;http://i.imgur.com/IN5Gf.jpg&quot; alt=&quot;Female wire connectors&quot;&gt;&lt;br&gt;&#xA;I bought them from adafruit - &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=33&amp;amp;products_id=266&quot; rel=&quot;nofollow&quot;&gt;product page&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-23T11:33:32.693" LastActivityDate="2010-12-23T11:33:32.693" CommentCount="1" />
  <row Id="8211" PostTypeId="2" ParentId="8202" CreationDate="2010-12-23T11:52:01.217" Score="2" ViewCount="" Body="&lt;p&gt;I use an old Lexmark Optra R+ on tracing paper. 1200dpi is worth having for finer-pitch stuff but I do routine boards at 600dpi, &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-23T11:52:01.217" CommentCount="3" />
  <row Id="8212" PostTypeId="2" ParentId="7685" CreationDate="2010-12-23T12:20:20.540" Score="0" ViewCount="" Body="&lt;p&gt;If you limit yourself to staying indoors and place location beacons around your house, you can track position using ZigBee.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Overview: &lt;a href=&quot;http://www.smallformfactors.com/articles/id/?3041&quot; rel=&quot;nofollow&quot;&gt;http://www.smallformfactors.com/articles/id/?3041&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;App Note: &lt;a href=&quot;http://focus.ti.com/lit/an/swra095/swra095.pdf&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/lit/an/swra095/swra095.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Essentially, you place a bunch of radio beacons in known positions then use the RSSI (Received Signal Strength Indicator) in the mobile node to calculate location.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-23T12:20:20.540" />
  <row Id="8213" PostTypeId="2" ParentId="8203" CreationDate="2010-12-23T13:20:05.693" Score="1" ViewCount="" Body="&lt;p&gt;The traditional way for enamelled copper wire was a methylated spirits burner.&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2010-12-23T13:20:05.693" />
  <row Id="8214" PostTypeId="1" AcceptedAnswerId="8215" CreationDate="2010-12-23T14:51:03.083" Score="0" ViewCount="77" Body="&lt;p&gt;Usually Google guides me to &lt;a href=&quot;http://www.alldatasheet.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.alldatasheet.com/&lt;/a&gt; or a similar site when I'm looking for a datasheet, but no such luck this time. The &lt;code&gt;XC&lt;/code&gt; prefix reminds me of Xicor, but after being directed by Google to the Intersil site I couldn't find it there either.&lt;br&gt;&#xA;Does anyone have a datasheet for the XC34064P?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-01-23T05:08:31.833" Title="Datasheet for XC34064P wanted" Tags="&lt;datasheet&gt;" AnswerCount="2" />
  <row Id="8215" PostTypeId="2" ParentId="8214" CreationDate="2010-12-23T15:06:19.123" Score="1" ViewCount="" Body="&lt;p&gt;Found it as &lt;a href=&quot;http://www.onsemi.com/PowerSolutions/product.do?id=MC34064&quot; rel=&quot;nofollow&quot;&gt;MC34064&lt;/a&gt; at On Semiconductor.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="1181" LastEditorDisplayName="" LastEditDate="2011-01-22T16:46:39.340" LastActivityDate="2011-01-22T16:46:39.340" CommentCount="2" />
  <row Id="8216" PostTypeId="1" AcceptedAnswerId="8220" CreationDate="2010-12-23T15:26:36.023" Score="9" ViewCount="391" Body="&lt;p&gt;My wife bought these &lt;strong&gt;flameless candles&lt;/strong&gt;.  They have 3 LEDs in them that have a seemingly random flicker to them. (Get bright, fade out a bit, fade in a bit etc...).  Since there are three when you see it through wax it looks like a flame flickering.  Very cool.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I though it would be a fun project to get back into electronics.  I am a computer engineer but I fell into software - so while I understand concepts and how things work, I have no clue how to start this unless I got a pic chip or whatever people use now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?  The simpler(cheaper) the better.  I just need some general ideas to get me pointed in the right direction.  What kind of circuits should I be looking at or does this need to be done with some kind of controller like a PIC?&lt;/p&gt;&#xA;" OwnerUserId="2366" LastActivityDate="2011-01-10T16:29:57.910" Title="LED Flame Emulation" Tags="&lt;led&gt;&lt;projects&gt;" AnswerCount="6" FavoriteCount="4" />
  <row Id="8217" PostTypeId="2" ParentId="8216" CreationDate="2010-12-23T15:51:00.660" Score="2" ViewCount="" Body="&lt;p&gt;If you want an all electronics solution I guess I would build three slow oscillators, one for each LED. For a more random effect oscillators could influence the other oscillators' frequencies.&lt;br&gt;&#xA;This requires a fair amount of discrete components, though, and I wonder if the flameless candles don't use a microcontroller. (A 15 component discrete solution can easily be more expensive than a small microcontroller.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your choice for a solution will depend on whether you want to be an electronics engineer or a software engineer. If you plan to go ahead with microcontrollers I would suggest a uC solution. Today microcontrollers are easy to use, but still have a learning curve, depending on the tools available.  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-23T15:51:00.660" />
  <row Id="8218" PostTypeId="2" ParentId="8216" CreationDate="2010-12-23T16:05:47.787" Score="2" ViewCount="" Body="&lt;p&gt;There's an instructable on how to create a realistic flickering flame effect with LED's, using an Atmega uC (on an Arduino board): &lt;a href=&quot;http://www.instructables.com/id/Realistic-Fire-Effect-with-Arduino-and-LEDs/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Realistic-Fire-Effect-with-Arduino-and-LEDs/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Easy hardware setup, easy code. Any controller capable of PWM on 3 outputs would work.&lt;/p&gt;&#xA;" OwnerUserId="1124" LastActivityDate="2010-12-23T16:05:47.787" CommentCount="5" />
  <row Id="8219" PostTypeId="1" CreationDate="2010-12-23T16:21:20.967" Score="3" ViewCount="215" Body="&lt;p&gt;In a box with old components I found a 16 character, 19-segments Futaba VFD:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/JOYs3.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to use it for &quot;something&quot; but I haven't the foggiest how to drive such a display. Even the filament is an unknown factor to me. The device dates at least from the early '90s. I guess at that time there were drivers for it, but I don't know if this kind of displays is still being designed-in. So, information about a driver would be nice, as would some schematic about the whole (i.e. what voltage does the filament require with respect to the driver voltages?)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-24T03:57:24.630" Title="Help wanted with Vacuum Fluorescent Display (VFD)" Tags="&lt;driver&gt;&lt;vfd&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="8220" PostTypeId="2" ParentId="8216" CreationDate="2010-12-23T16:55:20.190" Score="8" ViewCount="" Body="&lt;p&gt;Using a red/yellow or green/red bi-colour LED, you can also shift the 'flame' position.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Flame flickering isn't random in the sense of white noise. You'll get good results if you &lt;a href=&quot;http://www.instructables.com/id/How-to-Listen-to-Light/step8/LED-tea-light-candles-play-music-for-some-reason/&quot; rel=&quot;nofollow&quot;&gt;drive it with a melody&lt;/a&gt;. The &lt;a href=&quot;http://www.atmel.com/dyn/products/tools_card.asp?tool_id=3146&quot; rel=&quot;nofollow&quot;&gt;AVR Butterfly&lt;/a&gt; comes with Fur Elise preprogrammed, I believe. A fun way to experiment with this may be to build a &lt;a href=&quot;http://www.techlib.com/electronics/crystal.html&quot; rel=&quot;nofollow&quot;&gt;classic crystal radio&lt;/a&gt; and have it drive an LED (would have to be powered to drive LED); or with a &lt;em&gt;line out&lt;/em&gt; audio jack. Two more options are to capture the driver signal going to your consumer LEDs with an oscilloscope, or measure a candle's flicker with a photocell (photodiode). Putting together the little bits of analog buffering required to measure a candle's flicker accurately may be just what you need to get back in the spirit!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.horrorseek.com/home/halloween/wolfstone/Flicker/flktch_FlickerTechniques.html&quot; rel=&quot;nofollow&quot;&gt;Here are analog 'flicker' circuits.&lt;/a&gt; Many of them appear to be higher power. Parallax put together &lt;a href=&quot;http://www.parallax.com/dl/docs/cols/nv/vol6/col/nv126.pdf&quot; rel=&quot;nofollow&quot;&gt;this How-To: Tricks and Treats with LEDs&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-23T18:19:03.333" LastActivityDate="2010-12-23T18:19:03.333" CommentCount="3" />
  <row Id="8221" PostTypeId="2" ParentId="8219" CreationDate="2010-12-23T17:06:50.900" Score="2" ViewCount="" Body="&lt;p&gt;You'll find lots of information if you lookup &quot;&lt;a href=&quot;http://www.google.com/search?&amp;amp;q=VFD+clock&quot; rel=&quot;nofollow&quot;&gt;VFD clock&lt;/a&gt;&quot;. Conveniently, Ladyada detailed her &lt;a href=&quot;http://www.ladyada.net/make/icetube/design.html&quot; rel=&quot;nofollow&quot;&gt;VFD clock design&lt;/a&gt;, including the boost controller.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Tubes such as VFDs, Nixies, Decatrons, etc require high voltage to light the gas in the tube. For nixies, this iabout 170VDC. VFDs aren't as bad they only need about 30-50VDC.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The current draw for the IV-18 tubes is about 8mA per digit and 11mA for the grid. Remember, though, that we only light up one digit at a time! So we need about 20mA total (we also meaured this in-circuit to verify).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;'Suppose you'll have to trace the pins to figure out which ones are connected where, though! It looks like Futuba's &lt;a href=&quot;http://www.futaba.com/products/display_modules/module_products/character/index.asp&quot; rel=&quot;nofollow&quot;&gt;current selection&lt;/a&gt; have integrated drivers.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-23T17:06:50.900" CommentCount="1" />
  <row Id="8222" PostTypeId="2" ParentId="8199" CreationDate="2010-12-23T17:29:13.500" Score="4" ViewCount="" Body="&lt;p&gt;So here's the answer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The product has a 32 kHz crystal, and I had coded a routine to adjust the DCO frequency.  The frequency adjustment used two timers, one from DCO and one from the 32kHz ACLK.  It was driven by an interrupt off of capture/compare system, so that it could periodically recalibrate itself during operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, I inserted the initial calibration in the wrong part of my startup code, where interrupts were turned off.  Therefore calibration didn't happen before the first use of the serial port, and initialization would hang waiting for a response on the serial port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DCO frequency starts at the factory calibrated value, which is why it was working at room temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These plots tell the story:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, the DCO-temperature curve:&#xA;&lt;img src=&quot;http://i.imgur.com/ZChOM.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now the curve after calibration is actually working:&#xA;&lt;img src=&quot;http://i.imgur.com/VXpgD.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-23T17:29:13.500" CommentCount="3" />
  <row Id="8223" PostTypeId="2" ParentId="4639" CreationDate="2010-12-23T17:32:02.640" Score="-6" ViewCount="" Body="&lt;p&gt;Check out this website I found today, it should get you going. They have a demo video (which is MP4 and can be easily downloaded if you know HTML). &lt;a href=&quot;http://www.teslasecret.com/&quot; rel=&quot;nofollow&quot;&gt;Tesla Secret&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Here is the example on the website:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;4 Germanium diodes (1N34)&lt;/li&gt;&#xA;&lt;li&gt;2 100F 50v electrolytic capacitors&lt;/li&gt;&#xA;&lt;li&gt;0.2F 50v ceramic capaciters&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Here is the electrical diagram (hopefully it makes sense):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/21Q4R.png&quot; alt=&quot;Diagram of generator&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And they powered a cell phone with it. I am not sure what kind of antenna to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; This isn't a spam link. I know it looks like one, but I just found this website today and am looking for more info on it also. I am ordering it and will fill you in on the details. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt; Ordered it and found that it seems quite simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Note: If the site is no longer up, I can post the video (if legel), as they have been getting threats.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="794" LastEditorUserId="794" LastEditorDisplayName="" LastEditDate="2010-12-23T20:11:36.700" LastActivityDate="2010-12-23T20:11:36.700" CommunityOwnedDate="2010-12-30T18:00:40.803" CommentCount="9" />
  <row Id="8224" PostTypeId="2" ParentId="8216" CreationDate="2010-12-23T18:05:25.713" Score="3" ViewCount="" Body="&lt;p&gt;I created something similar, it just goes through some colors on an RGB led. I Used a MSP430G2211 uC that came with the &lt;a href=&quot;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_%28MSP-EXP430G2%29?DCMP=launchpad&amp;amp;HQS=Other+OT+launchpadwiki&quot; rel=&quot;nofollow&quot;&gt;launch pad&lt;/a&gt;. My project &lt;a href=&quot;http://justinstech.org/projects/msp430-rgb-flower-pot/&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;. The code could be easily changed to create a flame or flicker effect and by changing the leds. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2010-12-23T18:05:25.713" />
  <row Id="8225" PostTypeId="2" ParentId="3440" CreationDate="2010-12-23T21:01:05.283" Score="1" ViewCount="" Body="&lt;p&gt;I've used an old Nokia LCD display (GLCD5110) and it's quite simple to use as it uses SPI to communicate with the CPU (LPC2103 in my case).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it uses basically the MOSI, CLK, CE (Chip Enable) and RST pins and you can send commands and data to the LCD through the SPI interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought it here: &lt;a href=&quot;http://www.robotshop.com/inex-graphic-lcd-5110.html&quot; rel=&quot;nofollow&quot;&gt;http://www.robotshop.com/inex-graphic-lcd-5110.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2370" LastActivityDate="2010-12-23T21:01:05.283" CommentCount="1" />
  <row Id="8226" PostTypeId="2" ParentId="8203" CreationDate="2010-12-23T22:27:05.053" Score="1" ViewCount="" Body="&lt;p&gt;Cigarette lighter - done in 2 seconds!&lt;/p&gt;&#xA;" OwnerUserId="2371" LastActivityDate="2010-12-23T22:27:05.053" />
  <row Id="8227" PostTypeId="2" ParentId="7472" CreationDate="2010-12-23T22:41:00.143" Score="2" ViewCount="" Body="&lt;p&gt;Have you looked at &lt;a href=&quot;http://opencores.org/&quot; rel=&quot;nofollow&quot;&gt;opencores.org&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="2371" LastActivityDate="2010-12-23T22:41:00.143" />
  <row Id="8229" PostTypeId="2" ParentId="3440" CreationDate="2010-12-23T23:28:34.533" Score="1" ViewCount="" Body="&lt;p&gt;I discovered &lt;a href=&quot;http://www.8051projects.net/lcdpinouts.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; the other day it might be of some use for pin layouts. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-12-23T23:28:34.533" />
  <row Id="8230" PostTypeId="2" ParentId="8216" CreationDate="2010-12-23T23:37:11.327" Score="1" ViewCount="" Body="&lt;p&gt;It's actually quite easy to do this with no microcontroller. You use automatically color changing LEDs - these have three LEDs (red, green and blue diodes) with built in circuitry which makes them change color through the rainbow. Unfortunately, I've only found rainbow LEDs - I haven't yet found bicolor (e.g. red/yellow) LEDs which change color automatically, though I imagine a simple filter to block out blue and green light and only allow yellow and red would work well - you could probably find these online or at a camera shop.) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simply put the three or four LEDs in series with each other and drive them with about 9V (dc.) To limit the current through the array put a 220 to 470 ohm resistor in series with them. (I didn't do this on my first attempt and found the LEDs were very dim the next day because they had been damaged by the excess current.) The LEDs flicker randomly because the voltage drop across each varies which also causes them to restart occasionally. Also, they are not precise so the frequency on each is different which causes each LED to follow its own pattern. I'm currently using these as a christmas decoration on my tree; I use 5 in series with a 560 ohm 1/4w resistor and run them at about 18V.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-23T23:37:11.327" CommentCount="1" />
  <row Id="8231" PostTypeId="1" AcceptedAnswerId="8233" CreationDate="2010-12-24T00:12:27.117" Score="8" ViewCount="397" Body="&lt;p&gt;Programmable logic can be implemented in your widget in many different spectrums, from burning a few gates or using a MUX to the latest FPGA with built-in microcontroller and IO peripherals, not to mention ARM's &lt;a href=&quot;http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0190b/index.html&quot; rel=&quot;nofollow&quot;&gt;PrimeCell GPIO&lt;/a&gt; or &lt;a href=&quot;http://www.actel.com/products/smartfusion/default.aspx&quot; rel=&quot;nofollow&quot;&gt;other, more specific examples&lt;/a&gt;. &lt;strong&gt;For what applications are the various levels of programmable logic device complexity used?&lt;/strong&gt; Although the grouping appear to blend together near the extremes of &lt;a href=&quot;http://en.wikipedia.org/wiki/Programmable_logic_device&quot; rel=&quot;nofollow&quot;&gt;their definitions&lt;/a&gt;, I think this is an acceptable list:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;em&gt;&lt;strong&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Programmable_array_logic#Output_logic&quot; rel=&quot;nofollow&quot;&gt;PAL/PLA&lt;/a&gt;/&lt;a href=&quot;http://en.wikipedia.org/wiki/Generic_array_logic&quot; rel=&quot;nofollow&quot;&gt;GAL&lt;/a&gt;&lt;/strong&gt;: Programmable Logic Array;&lt;/em&gt; appear to be listed as &lt;em&gt;'Embedded - PLDs'&lt;/em&gt; at Digikey, covering asynchronous 10/8 I/O (&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/DOC0425.PDF&quot; rel=&quot;nofollow&quot;&gt;ATF16V8C&lt;/a&gt;) to 50MHz, 192 macrocell,  (&lt;a href=&quot;http://media.digikey.com/pdf/Data%20Sheets/Cypress%20PDFs/CY7C341B.pdf&quot; rel=&quot;nofollow&quot;&gt;CY7C341B&lt;/a&gt;), and are mostly reprogrammable.&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;&lt;strong&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/CPLD&quot; rel=&quot;nofollow&quot;&gt;CPLD&lt;/a&gt;&lt;/strong&gt;: Complex Programmable Logic Device;&lt;/em&gt; Digikey lists them as such, available in 7.5ns 10 I/O (&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc0776.pdf&quot; rel=&quot;nofollow&quot;&gt;ATF750C&lt;/a&gt;) to 233 MHz, 428 I/O &quot;CPLDs at FPGA Densities&quot; (&lt;a href=&quot;http://download.cypress.com.edgesuite.net/design_resources/datasheets/contents/cy39030v_8.pdf&quot; rel=&quot;nofollow&quot;&gt;CY39100V484B&lt;/a&gt;).&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;&lt;strong&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Field-programmable_gate_array&quot; rel=&quot;nofollow&quot;&gt;FPGA&lt;/a&gt;&lt;/strong&gt;: Field-Programmable Gate Array;&lt;/em&gt; available in 58 I/O (&lt;a href=&quot;http://media.digikey.com/pdf/Data%20Sheets/Xilinx%20PDFs/XC2000%20Families.pdf&quot; rel=&quot;nofollow&quot;&gt;XC2064&lt;/a&gt;) to 1023 I/O BGA beasts (&lt;a href=&quot;http://www.altera.com/literature/hb/stx/stratix_section_1_vol_1.pdf&quot; rel=&quot;nofollow&quot;&gt;EP1S80F1508C7N&lt;/a&gt;).&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;&lt;strong&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556750&quot; rel=&quot;nofollow&quot;&gt;FPGA with hard MCU&lt;/a&gt;&lt;/strong&gt;: this is when an MCU is physically laid out in the FPGA IC, not emulated.&lt;/em&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Wikipedia quote:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The difference between FPGAs and CPLDs is that FPGAs are internally based on Look-up tables (LUTs) whereas CPLDs form the logic functions with sea-of-gates (e.g. sum of products). CPLDs are meant for simpler designs while FPGAs are meant for more complex designs. In general, CPLDs are a good choice for wide combinational logic applications while FPGAs are more suitable for large state machines (i.e. microprocessors).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This doesn't explain the difference between using &lt;a href=&quot;http://download.cypress.com.edgesuite.net/design_resources/datasheets/contents/cy39030v_8.pdf&quot; rel=&quot;nofollow&quot;&gt;a 233 MHz, 400 I/O CPLD&lt;/a&gt; and a &lt;a href=&quot;http://www.altera.com/literature/hb/cyc3/cyc3_ciii51001.pdf&quot; rel=&quot;nofollow&quot;&gt;comparable FPGA&lt;/a&gt;; or between a &lt;a href=&quot;http://media.digikey.com/pdf/Data%20Sheets/Cypress%20PDFs/CY7C341B.pdf&quot; rel=&quot;nofollow&quot;&gt;192 macrocell PLD&lt;/a&gt; and a &lt;a href=&quot;http://www.altera.com/literature/hb/max2/max2_mii5v1_01.pdf&quot; rel=&quot;nofollow&quot;&gt;comparable CPLD&lt;/a&gt;. I can't grep reliable guidelines by which to narrow design options. Note that I don't currently have a specific application in mind, but have often wondered, &quot;what would I use to do that?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;I've received excellent advice &lt;a href=&quot;http://chat.stackexchange.com/&quot;&gt;off-site&lt;/a&gt; regarding specific requirements, but still think this question could benefit from some examples showing preference over one family of PLDs when another may have appeared to be equally or more suitable.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-27T19:44:39.293" LastActivityDate="2010-12-29T00:33:45.840" Title="What are programmable logic ICs of different complexity used for?" Tags="&lt;fpga&gt;&lt;programmable-logic&gt;&lt;cpld&gt;&lt;pal&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="2" />
  <row Id="8232" PostTypeId="2" ParentId="3312" CreationDate="2010-12-24T01:45:45.507" Score="1" ViewCount="" Body="&lt;p&gt;Does it look like &lt;a href=&quot;http://www.sparkfun.com/products/10245&quot; rel=&quot;nofollow&quot;&gt;this sensor&lt;/a&gt;? If so, put the power (maybe try 3 to 5V for starters) across black and white; signal is on red. Even if you apply the maximum force (50kg), you can expect the signal to change by an incredibly small amount. Make sure your voltmeter is up to the task; the sensor sold by SparkFun will vary 1mV per 1V of input, when the max force is applied. Additionally, it'll handle up to 10V of input, so you'll want to get as close to that as you can.&lt;/p&gt;&#xA;" OwnerUserId="1213" LastActivityDate="2010-12-24T01:45:45.507" CommentCount="2" />
  <row Id="8233" PostTypeId="2" ParentId="8231" CreationDate="2010-12-24T03:32:47.407" Score="6" ViewCount="" Body="&lt;p&gt;There's two criteria that you can use to evaluate a digital project that help you decide which part best matches your criteria. The first is design size/complexity - how much logic is involved. The second is the input and output requirements in terms of pin count. Speed can be factored in if you can estimate what your slowest function would be. The vendor tools (Altera Quartus II, Xilinx ISE, etc.) will help you once you get in the right ballpark.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;PAL/PLA/GAL: These are intended to replace a small to medium size circuits that you might normally implement as LSI logic chips (7400, 4000 series). These can offer better board layouts due to I/O remapping, and lots of simple logic functions. These chips contain non-volatile memory (or one time programmable fuses) and require no power-up configuration time. They may not contain data storage elements. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;CPLD: These are larger cousins of the PLA. The designs can be small state machines, or even a very simple microprocessor core. Most of the CPLD chips that I have seen do not have any on-chip SRAM, although the large Cypress CPLD you linked does. CPLDs are more likely to be re-programmable with flash memory, and they also do not require configuration time on power-up.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;FPGA: Unlike the CPLD, the logic blocks are based on SRAM instead of flash memory, resulting in faster logic operations. The major down-side with FPGAs is that since the configuration is stored in SRAM, every time the device is powered up the FPGA must load its programming into this SRAM. Depending on the size of your design and the speed of your non-volatile storage, this can cause a noticeable delay from power-on to fully functioning. Some FPGAs have on-chip flash for storing their data, but most use separate memory chips. FPGAs will often have hard-wired multipliers, PLLs, and other logic functions to improve computing speed. Large blocks of on-chip RAM is also available. You will also be able to use high-performance I/O specifications like LVDS, PCI, and PCI-Express. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;FPGA with Microprocessor Hard Core: I'm not familiar with these, but I would imagine that your design would center around the microcontroller programming, and the FPGA would augment the microcontroller. The parts you identified make it look like you would start your design with a microcontroller and a FPGA, and then combine the two into one chip/package.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How to decide which is right for you:&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best way is to have your code (Verilog/VHDL) finished, and then use the vendor's tools to try and fit it into the smallest part possible. I know Altera's tool lets you change programming targets fairly easily, so you could keep picking smaller FPGAs, and then smaller CPLDs until your design usage gets close to about 75%. If you require performance, then try to pick devices that have features (fast multipliers) that decrease the speed requirements of the logic. Again, the vendor tools will help you identify if you need to upgrade or if you can downgrade.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another factor of which part to use is ease-of-use. Using PAL/PLA/GAL logic is probably more effort than constructing the function using discrete logic gates (74HC*, 4000, etc). CPLDs typically require only a single supply voltage, and don't require additional circuitry. They are effectively stand-alone. FPGAs begin to use multiple power supplies for I/O and the logic core, complex I/O standards, separate program memory, multi-layer (&gt;2) PCBs, and BGA packages. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Steps to narrowing down your design requirements would include:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Identify all inputs and outputs for your FPGA/CPLD. This is usually an easy part of the design stage. This way you know what package you're looking at, and how close you can cut it to that margin.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Draw a block diagram of the internal logic. If your blocks look simple (each block would have a hand-full of logic gates and registers), then you probably can use a CPLD. If, however, your blocks have labels such as &quot;Ethernet transciever&quot;, &quot;PCI-Express x16 interface&quot;, &quot;DDR2 Controller&quot;, or &quot;h264 Encode/Decode&quot;, then you are almost certainly looking at a FPGA and using HDL. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;Look and see if your interfaces have special I/O requirements, such as special voltages, LVDS, DDR, or high speed SERDES. It's easier to get a chip that supports it than to get an additional translator chip.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Example CPLD Applications:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Multi-channel PWM with SPI interface&lt;/li&gt;&#xA;&lt;li&gt;I/O Expander&lt;/li&gt;&#xA;&lt;li&gt;CPU Address Space Decoding&lt;/li&gt;&#xA;&lt;li&gt;Clocks (Time keeping)&lt;/li&gt;&#xA;&lt;li&gt;Display Multiplexors&lt;/li&gt;&#xA;&lt;li&gt;Simple DSP&lt;/li&gt;&#xA;&lt;li&gt;Some simple programs can be converted into a CPLD design&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Example Hobbyist FPGA Applications:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Small System-on-Chip (SoC) designs&lt;/li&gt;&#xA;&lt;li&gt;Video&lt;/li&gt;&#xA;&lt;li&gt;Complex protocol bridges&lt;/li&gt;&#xA;&lt;li&gt;Signal processing&lt;/li&gt;&#xA;&lt;li&gt;Encryption/Decryption&lt;/li&gt;&#xA;&lt;li&gt;Legacy system emulation&lt;/li&gt;&#xA;&lt;li&gt;Logic Analyzer/Pattern Generator&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For most hobbyist work, you'll be limited to relatively small FPGAs unless you want to solder BGA packages. I would choose between a large CPLD or a cheap FPGA, and the size/speed requirements would dictate which one I needed.  &lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-12-29T00:33:45.840" LastActivityDate="2010-12-29T00:33:45.840" CommentCount="2" />
  <row Id="8234" PostTypeId="2" ParentId="8219" CreationDate="2010-12-24T03:52:01.423" Score="1" ViewCount="" Body="&lt;p&gt;VFDs are functionally equivalent to vacuum tubes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In fact, since some have an Control &lt;a href=&quot;http://en.wikipedia.org/wiki/Control_grid&quot; rel=&quot;nofollow&quot;&gt;Grid&lt;/a&gt; to let the display be multiplexed, they can actually be used as a &lt;a href=&quot;http://en.wikipedia.org/wiki/Triode&quot; rel=&quot;nofollow&quot;&gt;triode&lt;/a&gt;, and &lt;a href=&quot;http://www.eham.net/articles/20809+&quot; rel=&quot;nofollow&quot;&gt;amplify&lt;/a&gt; a &lt;a href=&quot;http://www.5volt.eu/archives/62&quot; rel=&quot;nofollow&quot;&gt;signal&lt;/a&gt;!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To use a VFD, you have to have a basic understanding of how vacuum tubes work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, a vacuum tube, has three components:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The Filament (Also called the Cathode)&lt;/li&gt;&#xA;&lt;li&gt;The Grid&lt;/li&gt;&#xA;&lt;li&gt;The Plate (Also called the Anode)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The filament is heated, which causes it to release electrons, a process called &lt;a href=&quot;http://en.wikipedia.org/wiki/Thermionic_emission&quot; rel=&quot;nofollow&quot;&gt;thermionic emission&lt;/a&gt;.  Since electrons are negatively charged, if there is a nearby piece of metal with a electrical charge more positive then the electrons from the cathode, the electrons will be attracted to it, allowing a current to flow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The grid is positioned between the Anode and Cathode. If the grid is driven more negative than the cathode, it repels the electron cloud, which prevents any current from flowing. Since the grid is not heated, it does not emit any electrons itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This forms the basis of every vacuum tube.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;A VFD is basically triode, except the anode is coated with phosphor. Therefore, when the the anode is more positive then the cathode, the free electrons in the cathode's electron cloud flow towards the anode, and in the process strike the phosphor, exciting it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This process is very similar (basically identical) to how CRT televisions work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, since your display has control grids (the rectangular mesh sections above the digits), there is another thing required to drive your VFD.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, it behaves very similar to a multiplexed display. Every segment in every display is connected in parallel. Therefore, if you leave all the control grids floating, any signal you drive the display with will be present on every character. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;By driving all the control grids but one more negative than the filament/cathode, only that digit will be active, since the control grids will prevent current from the cathode from reaching any of the other characters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;VFDs use directly heated cathodes, so the cathode is easily visible. The three very fine horizontal wires running the entire width of the display are the cathode. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would guess that the filament probably takes about 2-6V at a hundred ma or so. It should NOT glow visibly at all. The anode voltage should probably be about 30-60v, and the grid a few V- (though I think driving the grid positive might also work, if it successfully depletes the available local electrons. I've only played with single digit VFD tubes without grids).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your best bet is to trace out the connections on the back of the unit, and try powering on a bench supply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The yellow traces you see on the rear-view are the internal electrical connections. You should be able to figure out the pinout from them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The pin on each end is almost definitely the filament connections.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a few bench power-supplies (three, though I think you could manage with two), you should be able to get at least part of the display to light up without too much trouble. Getting it to display useful numbers is another matter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It still easier then nixie tubes, though.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Useful References:&lt;br&gt;&#xA;&lt;a href=&quot;http://www.cjseymour.plus.com/elec/valves/valves.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.cjseymour.plus.com/elec/valves/valves.htm&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://simple.wikipedia.org/wiki/Vacuum_tube&quot; rel=&quot;nofollow&quot;&gt;http://simple.wikipedia.org/wiki/Vacuum_tube&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Vacuum_tube&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Vacuum_tube&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Control_grid&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Control_grid&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Triode&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Triode&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Vacuum_fluorescent_display&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Vacuum_fluorescent_display&lt;/a&gt;  &lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-24T03:57:24.630" LastActivityDate="2010-12-24T03:57:24.630" />
  <row Id="8235" PostTypeId="2" ParentId="8166" CreationDate="2010-12-24T06:16:51.180" Score="1" ViewCount="" Body="&lt;p&gt;There are a ton of mfgrs out there who's been doing this for a VERY long time ...  hundreds/maybe thousands of companies that print resistive traces (see NOTE below).   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to narrow the population to prototypers that provide SERVICE and engineering support; you want to find the ones who are best at this NOW, not necessarily the ones someone used in 2008.  Google the keywords &quot;manufacturers print resistive traces on PCBs&quot; and make a contact list of companies who are buying AdWords ... there are LOTS of companies who can do this type of thing, the ones who actually buy/use AdWords are the companies are companies who are savvy enough in addressing the mfg rapid prototyping market ... companies that are not savvy enough to understand AdWords could eventually be a good long term solution for you when you start buying these boards by the boatload, but those companies don't get prototyping, rapid-turnarounds and customer service.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Develop a &quot;Top Ten&quot; list from both on the Google search itself AND on the ones who buy ads on the top pages in the Google search ... contact those &quot;Top Ten&quot; and start having a discussion, don't buy -- get quotes ... you will probably get a pretty good feel from the conversation/email exchange whether they know what they doing ... you will also learn something about what they can do, can't do, what other options you might want to consider.  After you have had a conversation with your Top Ten, narrow the list to your Top Three and get down to brass tacks with the quotes and getting your boards.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Save the list for the future, but  ...  &lt;strong&gt;Google again the next time you do this to see who the new players are ... the world of mfg prototyping is extremely aggressive ... there's always somebody new, somebody trying harder -- always something to learn from interacting with prototypers.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NOTE:  I suspect it'll be tougher for you to find someone who can correctly stamp the dimples you'll need on contractor that travels on [rather than cutting] the resistive strip and you'll need to select the correct electrical lubricant, so that your product works and doesn't wear out prematurely ... there are a people who know way more about contact theory, spring forces, nanotechnology, tribology and different types of materials for resistive traces than you want to learn ... you could search through patents on potentiometers and other components that use resistive strips, but that's only the tip of the iceberg ... my advice would be to buy a component that does what you need, rather than re-invent one, but you probably already know that -- in other words, I've assumed you've already done your homework bought a few pots from Panasonic or someone else, have torn them apart looked at the action, component's features closely and you want want to procede with this rev engineering exercise ... &lt;/p&gt;&#xA;" OwnerUserId="2253" LastEditorUserId="2253" LastEditorDisplayName="" LastEditDate="2010-12-24T06:57:20.973" LastActivityDate="2010-12-24T06:57:20.973" />
  <row Id="8236" PostTypeId="1" CreationDate="2010-12-24T06:55:47.043" Score="3" ViewCount="217" Body="&lt;p&gt;Can someone explain &quot;constant-current&quot; circuits?&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;When are they necessary?&lt;/li&gt;&#xA;&lt;li&gt;What happens without one?&lt;/li&gt;&#xA;&lt;li&gt;What's the simplest version of such a circuit?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I bought some 20W LEDs off ebay intending to make a bike light.  &quot;Simple,&quot; I thought, &quot;The LED and my laptop battery are both 11Vdc, so I'll just connect them.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't actually tried this, but an EE friend suggested that if I do so, it will draw too much current and burn out -- but he didn't know why; he doesn't do power electronics.&lt;/p&gt;&#xA;" OwnerUserId="2375" LastActivityDate="2010-12-24T13:35:08.270" Title="Constant-Current for a 20W LED" Tags="&lt;led&gt;&lt;power&gt;&lt;current&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="8237" PostTypeId="1" CreationDate="2010-12-24T07:02:48.563" Score="3" ViewCount="163" Body="&lt;p&gt;I've recently been transliterating some old schematics for a friend of mine (Basically taking paper schematics from the 40s and drawing them in a modern EDA package) and have come across some very interesting/old electronics terms that are not in common parlance anymore. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since I didn't know what they meant, I had to ask.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Therefore, I figure having a list of interesting/esoteric/old electronics terms would be useful, so here we are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Note: Try to stick to terms which were/are at least somewhat common, not things which you or someone you know thought up)&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-02-06T13:22:13.090" CommunityOwnedDate="2010-12-24T22:48:02.900" Title="Interesting/Unusual/Old Electronics nomenclature." Tags="&lt;terminology&gt;" AnswerCount="4" CommentCount="5" FavoriteCount="3" />
  <row Id="8238" PostTypeId="2" ParentId="8237" CreationDate="2010-12-24T07:06:07.890" Score="1" ViewCount="" Body="&lt;h2&gt;uuF&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Also known as &lt;em&gt;micro-micro-Farads&lt;/em&gt;. It has basically entirely been displaced by the modern  equivalent &lt;strong&gt;picoFarads&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I encountered this in old schematics. Many capacitor values were noted as uuf&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically, since a pico is 1E-12, and a micro is 1e-6, a micro-micro is 1E-6 * 1E-6, which == 1E-12 .&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-24T07:11:28.180" LastActivityDate="2010-12-24T07:11:28.180" CommunityOwnedDate="2010-12-24T22:48:02.900" CommentCount="6" />
  <row Id="8239" PostTypeId="2" ParentId="8237" CreationDate="2010-12-24T07:09:18.370" Score="2" ViewCount="" Body="&lt;h2&gt;CPS&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Also known as &lt;em&gt;Cycles per Second&lt;/em&gt;. It has basically entirely been displaced by the modern equivalent &lt;strong&gt;Hertz&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Commonly encountered in old texts. It was commonly used up until ~1960, when the SI officially replaced it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may also see kilocycle, megacycle and kilomegacycle, which are kilohertz, megahertz and gigahertz, respectively.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See:&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Cycle_per_second&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Cycle_per_second&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Hertz&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Hertz&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2010-12-24T07:09:18.370" CommunityOwnedDate="2010-12-24T22:48:02.900" />
  <row Id="8240" PostTypeId="2" ParentId="8236" CreationDate="2010-12-24T07:39:22.817" Score="3" ViewCount="" Body="&lt;p&gt;P = V * I.  In your case for the LED, P = 20 W, V = 11 V and therefor I = 1.82 A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To drive the LED correctly you will need to limit the current to 1.82 A.  (you will also need to provide adequate heat sinking as 20 W is a lot of power to dissipate and most of it will be in the form of heat!!!! .... but that is another matter)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Diodes, using a PN junction have forward voltage drop, in your case that drop is 11 V.  When referring to the diode datasheet they will include a V I curve, this will relate how much current flows for a given voltage.  When you examine this curve you will notice that the current heads toward infinite for the given voltage drop.  If you allow this to happen, you diode will simply burn out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest method to limit the current is to use a resistor.  V = I * R.   For a given voltage drop, a fixed resistor will limit the current to a fixed amount. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming you have a 18 V battery and an 11 V LED, the difference, 7 V will need to be dropped across the resistor.  This is fixed.  Also fixed is the desired current, of 1.82 A.   Rearranging the equation you get R = V / I =&gt; R = 3.8 ohm.  This resistor will need to be rated to a minimum of 12 W.  That is a large resistor that will get hot!!!!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The brings up the second issue - heat.  At a total of 32 W to dissipate, you will need some serious heatsinking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can probably do away with the resistor and replace it with a controlled current circuit based on transistor and or mosfets but I will leave that to someone else to answer.  The same issue of heat dissipation may still be present depending on the circuit design!!!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know you mentioned you have an 11 V battery and an 11 V LED.  Unless the LED has built in current limiting circuit, or the battery has, it will be difficult to drive it at the same voltage (depending on the VI curve of the diode) without a boost converter.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2010-12-24T07:39:22.817" />
  <row Id="8241" PostTypeId="2" ParentId="8120" CreationDate="2010-12-24T07:44:06.520" Score="1" ViewCount="" Body="&lt;p&gt;Sending it as package has a certain good outcome ... might be cheaper, since it might give you the flexibility to carry other things you'll like to have along on the trip.  If you take it along, you will necessarily have to unpack everything in an environment where packing/unpacking is more failure prone -- you'll leave a piece of it behind or maybe you'll leave something else (e.g. digital camera) why you're trying to re-pack and forget something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My rule in flying is never unnecessarily introduce a failure mode into the process ... something weird happens to probability distributions around airports ... some people see the glass as half empty; I see the glass as a collection of razor-sharp shards that have not yet severed the tendons on my bloody hand or embedded themselves in my forehead -- but the glass will do that, if I let it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you choose to take it on the plane, make sure you are wearing your &lt;a href=&quot;http://images2.cpcache.com/product/358544882v2_480x480_Front_Color-Yellow.jpg&quot; rel=&quot;nofollow&quot;&gt;t-shirt&lt;/a&gt;.  It will explain something to the people who have to wait behind you ... possibly missing their flights, while they wait for for the team of security personnel that your situation draws to return to their stations and start processing people again.  A sense of humor is helpful in times like this -- not as helpful as avoiding the issue so that things go smoothly for others behind you ... but helpful.&lt;/p&gt;&#xA;" OwnerUserId="2253" LastEditorUserId="2253" LastEditorDisplayName="" LastEditDate="2010-12-24T08:22:50.230" LastActivityDate="2010-12-24T08:22:50.230" />
  <row Id="8242" PostTypeId="1" CreationDate="2010-12-24T09:45:03.237" Score="-1" ViewCount="93" Body="&lt;p&gt;I am connecting a few Geze GC 302C radar motion detectors to my arduino&lt;br&gt;&#xA;I see on the PCB that there are 2 pushbuttons and 1 dip-switch, is anyone out there who know how can i use this ? do you have an installation manual or something ?&lt;br&gt;&#xA;It also has an IR receiver, i think used for some sort of programing remote control, again i have no more info regarding this&lt;/p&gt;&#xA;" OwnerUserId="2245" LastActivityDate="2010-12-24T14:37:54.963" ClosedDate="2010-12-24T17:33:50.167" Title="Connecting a geze GC 302 R" Tags="&lt;sensor&gt;&lt;motion&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="8243" PostTypeId="2" ParentId="8236" CreationDate="2010-12-24T09:59:49.233" Score="2" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;When you are using non-linear power device, like a LED. Other notable example are gas-discharge lamps &amp;amp; lasers.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Something burns or explodes. LED or power supply. Or both :-)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For 20W the only reasonable solution is constant-current DC-DC circuit, but it's not simple. Simplest solution is linear regulator with powerful BJT transistor, but this will dissipate at least 10W of heat. Simple resistor will not give you linear current, but acceptable in low-power cases (let's say for 0.1W).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-12-24T09:59:49.233" />
  <row Id="8244" PostTypeId="1" AcceptedAnswerId="8246" CreationDate="2010-12-24T10:02:23.207" Score="0" ViewCount="96" Body="&lt;p&gt;Where is photodiode in the CD/DVD drives?&#xA;What is his frequency response &amp;amp; sensetivity usuallY?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am going to try laser data transfer, but finding decent photodiode is my weak point.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-12-24T10:38:41.070" Title="Where is photodiode in the CD/DVD drives?" Tags="&lt;phototransistor&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="8245" PostTypeId="2" ParentId="8236" CreationDate="2010-12-24T10:14:57.963" Score="2" ViewCount="" Body="&lt;p&gt;Most LED control circuits just have a series resistor to control the LED current. This is OK if the supply voltage is more or less constant, but it the voltage varies so will the LED current and luminosity. If you want constant luminosity you also want constant current. This means that the series resistance must vary with supply voltage. This is about the simplest circuit for it:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tyGNr.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a constant current source dimensioned for 1mA, which is too little for your application, but the principle remains the same. The base-emitter voltage of the transistor is 0.6V, so given that the zener creates a drop of 5.6V between V+ and the transistor's base there remains 5V for the resistor. 5V / 5kohm = 1mA.&lt;br&gt;&#xA;If your LED is 20W @ 11V then you need 1.8A of current, so I'll calculate the other components for this value. Replace the zener by 3 x 1N4148, this gives you a 0.6V drop over R1 (three diodes because we'll use a darlington, which has 2 x 0.6V between base and emitter). R1 = the third 0.6V/1.8A = 0.33ohm/1W. The TIP125 darlington transistor has an Hfe of 1000, R2 should be 5k = 10V / (1.8A/1000).&lt;br&gt;&#xA;Since Vce(sat) for the transistor is 2V, and you have an additional voltage drop over R1 of 0.6V, you'll need a 14V power supply to be sure that there's enough left for the LED!&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-24T10:14:57.963" />
  <row Id="8246" PostTypeId="2" ParentId="8244" CreationDate="2010-12-24T10:36:20.577" Score="1" ViewCount="" Body="&lt;p&gt;I assume you're talking about the photodiode that is used to read the disk and not about the one for the IR remote control. This diode is buried below the lense of the laser assembly. Not sure if it will work for your intended purpose because it's a four-quadrant diode, i.e. it has four light-sensitive areas that are used to keep the laser in track.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2010-12-24T10:36:20.577" CommentCount="2" />
  <row Id="8247" PostTypeId="2" ParentId="8244" CreationDate="2010-12-24T10:38:41.070" Score="1" ViewCount="" Body="&lt;p&gt;You'll want a PIN photodiode. The Osram BPW34 may be a good starting point.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-24T10:38:41.070" />
  <row Id="8248" PostTypeId="2" ParentId="8236" CreationDate="2010-12-24T13:35:08.270" Score="0" ViewCount="" Body="&lt;p&gt;If you want a simple constant current LED driver, on All About Circuits &lt;a href=&quot;http://forum.allaboutcircuits.com/showthread.php?t=41320&amp;amp;highlight=buck+led&quot; rel=&quot;nofollow&quot;&gt;we've been designing one&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, it's only rated to 1W. You'd probably need to upgrade the fet and driver to get it to run at 20W, the fet would also need heatsinking and you'd probably need a bigger inductor.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-24T13:35:08.270" />
  <row Id="8249" PostTypeId="2" ParentId="8242" CreationDate="2010-12-24T14:37:54.963" Score="2" ViewCount="" Body="&lt;p&gt;I'll post some information that I found while looking this up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Geze is a German company that basically makes moving doors/windows. The GC302 is a radar unit like you would see for a sliding door. I was able to find a &lt;a href=&quot;http://www.geze.de/uploads/tx_gezedownloads/GB-128819-GC302R-0608.pdf&quot; rel=&quot;nofollow&quot;&gt;product brochure (pdf)&lt;/a&gt; and mechanical DXF drawings, but I can't find anything else. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since they have a product brochure, they intend/intended to sell it alone (not just as a replacement part) so they should have a technical document or datasheet for it. Try contacting them and see if they'll give it to you.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-24T14:37:54.963" />
  <row Id="8250" PostTypeId="1" AcceptedAnswerId="8259" CreationDate="2010-12-24T15:57:51.903" Score="5" ViewCount="420" Body="&lt;p&gt;I'm working on a DC jack powered Ethernet design and I've downloaded many Ethernet Layout guidelines from many semi vendors with varying recommendations.  I've read app notes recommending almost every possible termination resistor position, for example.  Placing termination resistors at the PHY, at the Magnetics, the TX at the PHY and the RX at the magnetics, and visa versa.  The most popular seem to be at the PHY, and this seems to make the most sense.  Ethernet uses balanced differential pairs, which are typically terminated at the extremes to filter any common mode noise injected into the transmission lines, and the RX / TX traces on the board constitute part of the transmission line (these are being run at 100 ohm impedance to match CAT5 cable impedance).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other controversy here is what to do with the ground plane.  If this wasn't a DC jack powered app my life would be easier.  Many app notes recommend no ground plane under the magnetics (which are built into the RJ45 connector in my case) to avoid coupling into the ground plane.  But... that is exactly what I want.  Better coupling into the ground plane then into the conformity testing antenna!  A ground plane under the jack will help close the metal enclosure around the rest of the connector.  I've read at least one example of anecdotal evidence on the net claiming better radiation performance with a solid ground plane in a DC jack application as opposed to a separate isolated Ethernet plane tied in with caps.  So... I think I'm going to keep a solid plane under the RJ45 jack.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some papers also recommend no plane under the RX / TX pairs.  I can't make my mind up about this.  I want to avoid coupling any ground noise into the RX and TX pairs but my experience seems to be any ground plane splitting / opening is usually based on hocus pocus type thinking instead of sound physics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone here have any experience or suggestions related to Ethernet layout, specifically with regard to the RX / TX termination resistor placement and whether or not to use a ground plane under the RJ45 connector (with magnetics) as well as under the TX / RX pairs?  Any suggestions greatly appreciated.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastEditorUserId="2377" LastEditorDisplayName="" LastEditDate="2010-12-24T18:42:35.677" LastActivityDate="2010-12-25T13:09:09.467" Title="Ethernet Layout Guidelines" Tags="&lt;pcb&gt;&lt;ethernet&gt;&lt;layout&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="2" />
  <row Id="8251" PostTypeId="1" CreationDate="2010-12-24T15:59:53.710" Score="2" ViewCount="136" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am working as a winter intern at a robotics company. My job is to assist the lead embedded developer in...whatever he wants my assistance in. About a week back, I was handed a NXP blueboard with LPC2148 on it. Although I loved the more processing power (compared to the Atmega32s I had been working on), I found something very odd about the ARM7 based controller. If you look at the pinout here&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/VlhM9.jpg&quot; alt=&quot;LPC2148 pinout&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;you would notice that the port pins are jut all over the place. In the avr series everything is arranged cleanly with all the port pins together. Why is it not so in the lpc21xx? I cannot find any logic at all, they are not arranged by pin number or by functionality (like all the jtag pins together). It seems like the designers just stacked the pins in a random form. Can any body please explain the reason behind this?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-12-24T23:52:21.460" Title="Why are the pinouts of lpc21xx all over the place?" Tags="&lt;lpc21xx&gt;&lt;blueboard&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="8252" PostTypeId="2" ParentId="8251" CreationDate="2010-12-24T16:06:11.553" Score="0" ViewCount="" Body="&lt;p&gt;LOL!  I've used an LPC2478 recently with a similar issue.  I used the SDRAM peripheral which literally had pins spaced around the entire peripheral of the quad-pack.  It makes keeping equal line length a nightmare.  My only guess is it's easier for them to manufacture it that way.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2010-12-24T16:06:11.553" CommentCount="1" />
  <row Id="8253" PostTypeId="1" CreationDate="2010-12-24T16:37:23.803" Score="6" ViewCount="270" Body="&lt;p&gt;OK, so the uA741 is 42 years old now. For its time it may have been a great opamp; the requirements weren't as high as today, and there was far less competition. But I was wondering what's the 741's appeal today.   &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;it's slow. GBW 1MHz, slew rate &amp;lt; 0.5 V/us&lt;br&gt;&#xA;  it's not low power, nor low voltage&lt;br&gt;&#xA;  it doesn't have low bias current FET inputs&lt;br&gt;&#xA;  it doesn't have rail-to-rail inputs or outputs&lt;br&gt;&#xA;  it's not low noise&lt;br&gt;&#xA;  many more modern opamps have comparable price  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Why is the 741 still used today?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-28T18:45:13.523" Title="What's the uA741's appeal?" Tags="&lt;op-amp&gt;&lt;741&gt;" AnswerCount="5" CommentCount="0" FavoriteCount="1" />
  <row Id="8254" PostTypeId="2" ParentId="8253" CreationDate="2010-12-24T16:50:24.917" Score="4" ViewCount="" Body="&lt;p&gt;Is it really &lt;em&gt;used&lt;/em&gt; per se, or simply kept around for legacy designs? Changing an op-amp in an application where those specific parameters are important (i.e. feedback loops) can be problematic at best (or outright dangerous at worst) - best to let sleeping dogs lie in these situations, sometimes...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can speak to the fact that in both of my career stops thus far, there haven't been any new designs that I've seen or touched using the 741. For me, the LM358/LM324 is the 'go-to' part where things like input offset voltage or rail-to-rail capabilities aren't critical. It's well understood, it 'works', and it's cheap.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2010-12-24T16:50:24.917" CommentCount="1" />
  <row Id="8255" PostTypeId="2" ParentId="8253" CreationDate="2010-12-24T16:52:48.767" Score="6" ViewCount="" Body="&lt;p&gt;Many old designs are still around.  Plus, some positives are&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) It is readily available from multiple sources (ST, TI, National) which (having multiple sources) can be a big issue for certain industries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) It has been around for a while, is well understand, reliable, and will most likely will continual to be available for a while, again, very important for long life applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) It has a large voltage range, many newer op-amps don't.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) Output short circuit protection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5) It's slow.  This is good for many applications.  Why is faster always better?  Having an overly fast op-amp just increases susceptibility to noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;6) Many people know it and use it, there's something to be said about not having to evaluate, test, etc., a new chip, as well as not having to stock a new part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;7) It doesn't have FET inputs.  There are pros and cons to such inputs.  Certain designs may be better with them.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2010-12-24T16:52:48.767" CommentCount="1" />
  <row Id="8256" PostTypeId="2" ParentId="8237" CreationDate="2010-12-24T16:55:08.393" Score="2" ViewCount="" Body="&lt;h2&gt;condensers&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Some old drawings refer to capacitors as &lt;em&gt;condensers&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also seem to recall seeing diodes referred to as &lt;em&gt;crystal rectifiers&lt;/em&gt; and/or &lt;em&gt;crystal detectors&lt;/em&gt; - some packages still use CRxxx for diode reference designators, which is a nice historical nod.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-02-06T13:22:13.090" LastActivityDate="2011-02-06T13:22:13.090" CommunityOwnedDate="2010-12-24T22:48:02.900" CommentCount="1" />
  <row Id="8257" PostTypeId="2" ParentId="8253" CreationDate="2010-12-24T16:56:20.183" Score="10" ViewCount="" Body="&lt;p&gt;It's an &lt;em&gt;ideal&lt;/em&gt; op amp to learn the basics on due to its &lt;em&gt;non-ideal&lt;/em&gt; nature. The first thing we learn is infinite input impedance, infinite gain, as well as a few other silly things. The 741 obeys none of these idealities, forcing students to learn the hard way how to cope. They see bandwidth limitations without using expensive oscillators or function generators; they see early saturation, nowhere near the rails, allowing the use of cheap multimeters. Many textbooks use the 741 as an example due to its ubiquitous availability and simple verification of non-idealities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Today, we can buy op-amps with mV offset and noise, 100s MHz bandwidth, nA leakage, etc.. One of the most time consuming part of a design is looking for parts, especially for the inexperienced. Academics aren't experienced design engineers, and will use the parts they know, as they have better things to do than look for parts (like write that grant application, right? :). This outdated part therefor gets introduced into new designs from copying legacy modular designs, and familiarity from instruction.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-24T16:56:20.183" CommentCount="4" />
  <row Id="8258" PostTypeId="2" ParentId="8251" CreationDate="2010-12-24T18:48:06.157" Score="1" ViewCount="" Body="&lt;p&gt;If you look carefully you can see they are in order, but not grouped together. It probably comes down to how easy the chip is to manufacture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/GSWPS.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-24T18:48:06.157" CommentCount="8" />
  <row Id="8259" PostTypeId="2" ParentId="8250" CreationDate="2010-12-24T19:13:01.877" Score="3" ViewCount="" Body="&lt;p&gt;Look for application notes for your PHY and magnetics.  The manufacturer would know best in regards to what works with their parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally there is no ground/power or routing under the magnetics and try to avoid ground/power under the TX/RX pairs.  If you can't route the whole trace without a ground/power plane under it, leave the plane under it.  It is worse if you go over a break in the plane.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For termination, check with manufacturers of the PHY and magnetics.  Like you said, there are a few different schemes, the manufacturer should know best about their device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We follow what I described above at work and don't have any problems with ethernet.&lt;/p&gt;&#xA;" OwnerUserId="1819" LastActivityDate="2010-12-24T19:13:01.877" />
  <row Id="8260" PostTypeId="1" CreationDate="2010-12-24T13:42:26.060" Score="2" ViewCount="252" Body="&lt;p&gt;What will happen if I send an analog signal through a digital regenerator? &lt;/p&gt;&#xA;" OwnerUserId="2378" LastActivityDate="2010-12-28T00:27:31.677" Title="What will happen if I send an analog signal through a digital regenerator?" Tags="&lt;signal&gt;&lt;digital&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="8261" PostTypeId="2" ParentId="8260" CreationDate="2010-12-24T14:01:42.357" Score="0" ViewCount="" Body="&lt;p&gt;I'd imagine it'll get sampled much like music does on a computer. So it'll take the value of the signal at a given rate (the sample rate), and record it as a discreet level, that value of which depends on how many levels it uses to distinguish the wave. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just a guess.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a good enough digital regenerator, the wave should look similar.&lt;/p&gt;&#xA;" LastActivityDate="2010-12-24T19:14:39.317" />
  <row Id="8262" PostTypeId="2" ParentId="8260" CreationDate="2010-12-24T15:48:15.483" Score="5" ViewCount="" Body="&lt;p&gt;A &lt;a href=&quot;http://www.freepatentsonline.com/5197082.html&quot; rel=&quot;nofollow&quot;&gt;digital regenerator&lt;/a&gt; will ruin an &lt;a href=&quot;http://en.wikipedia.org/wiki/Analog_signal&quot; rel=&quot;nofollow&quot;&gt;analog signal&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some analog signals will ruin some digital regenerators.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most digital signals should have two distinct signal levels, labelled &quot;0&quot; and &quot;1&quot;.&#xA;A digital regenerator will attempt to force any input signal into a sequence of these two levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An analogue signal has an infinite number of values between certain fixed limits. It is vital to the fidelity of the signal that this range of possible values not be reduced (quantised) below some quality threshold. For an analog signal that threshold is much much greater than two.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.antonine-education.co.uk/Electronics_AS/Electronics_Mod2/topic_2_4/graph_1.gif&quot; alt=&quot;ANalogue and DIgital Signals&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the above diagram, a digital regenerator might convert the signal on the right to that on the left. If you fed this result to an analogue amplifier and into a loudspeaker the result would not be pleasant and the equipment might not survive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More complex digital signals encode multiple bits of data per bit of signal - this may involve more than two signal states - for example more than two voltage levels. However it is very unlikely that a digital signal regenerator attempting to find such a digital signal in an unrelated analogue signal will happen to do anything useful.&lt;/p&gt;&#xA;" OwnerUserId="2191" LastActivityDate="2010-12-24T19:14:39.317" />
  <row Id="8263" PostTypeId="1" CreationDate="2010-12-24T19:41:28.570" Score="0" ViewCount="275" Body="&lt;p&gt;i have a panel multimeter that i use for my whole house that has RS485, Modbus RTU comunication.&lt;br&gt;&#xA;I know what registers to read in order to get currents, voltages, power factor etc&lt;Br&gt;&#xA;How can i use this and get the data to a PC, i have an arduino but i don't know how to get this started&lt;br&gt;&#xA;I've tried using a RS485-&gt;Ethernet converter and then tried to send comunicate with the device via TCP-IP but it's rather difficult (this method would be the best, netowk conectivity ensures i can have the data parsed at my server)&lt;Br&gt;&#xA;I have sucessfuly conected an RS232 device -&gt; Ethernet convertor -&gt; PC, but in this case the device (a PBX) sends the data clearly in ASCII and it i manage it easily with a small Python program that reads the data and then puts it in a mysql DB&lt;br&gt;&lt;hr&gt;&#xA;How would you reccomand to connect and program sometging like this:&lt;br&gt;&#xA;Meter with RS485, Modbus RTU -&gt; RS485 to Ethernet convertor -&gt; PC with python script getting all the data (it's gonna have to be a lot of HEX coding that i would need a getting started point :D )&lt;/p&gt;&#xA;" OwnerUserId="2245" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-02-09T21:59:47.807" LastActivityDate="2011-02-09T21:59:47.807" Title="Reading MODBUS RTU slave device Registers via RS485" Tags="&lt;ethernet&gt;&lt;power-meter&gt;&lt;modbus&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="8264" PostTypeId="1" AcceptedAnswerId="8265" CreationDate="2010-12-24T20:09:41.653" Score="4" ViewCount="296" Body="&lt;p&gt;Are there any micro-controllers which support writing data to large sized SATA disks?&lt;/p&gt;&#xA;" OwnerUserId="2068" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-01T19:49:39.727" LastActivityDate="2011-01-01T19:49:39.727" Title="Micro Controllers Supporting SATA" Tags="&lt;microcontroller&gt;&lt;sata&gt;" AnswerCount="3" CommentCount="0" />
  <row Id="8265" PostTypeId="2" ParentId="8264" CreationDate="2010-12-24T21:44:37.110" Score="3" ViewCount="" Body="&lt;p&gt;SATA works at very high frequencies. If I look at this &lt;a href=&quot;http://en.wikipedia.org/wiki/SATA#Data&quot; rel=&quot;nofollow&quot;&gt;data connector sheet&lt;/a&gt; I basically see a TX/RX connection with differential signals because of the very high speed. 1.5Gbit of data would need to be proccesed, that's 1.5GHz signals. I've a feeling that it is a very high speed for a microcontroller to handle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My best bet for you is to get a SATA to PATA converter and work with the PATA interface instead. It lowers the speed you need to look at bits, because the data is offered in a parallel way. That's still the easier way to work with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know whether you still want to use a microcontroller for that. I think a FPGA might become the better choice in such projects, but that depends on your goal.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2010-12-24T21:44:37.110" CommentCount="3" />
  <row Id="8266" PostTypeId="2" ParentId="8253" CreationDate="2010-12-24T23:31:29.457" Score="1" ViewCount="" Body="&lt;p&gt;My guess:  people tend to stick with what they know.  If you've learned the errata and gotchas of the 741 and it works for your application you'll use it rather than learn something new for no reason.  Also, my guess is that many applications don't require terribly high performance, so the 741 works just fine.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-12-24T23:31:29.457" />
  <row Id="8267" PostTypeId="2" ParentId="8237" CreationDate="2010-12-24T23:41:27.043" Score="2" ViewCount="" Body="&lt;p&gt;Having just gone through a ton of drawings for a rather old system I should know more of these.  But what I can say so far:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Using the term 'return' instead of ground (although 'return' has in my mind a more specific connotation of being assigned to a specific signal rather than a general ground)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll keep editing this as I think of more.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-12-24T23:41:27.043" CommunityOwnedDate="2010-12-24T23:41:27.043" CommentCount="1" />
  <row Id="8268" PostTypeId="2" ParentId="8264" CreationDate="2010-12-24T23:47:38.017" Score="4" ViewCount="" Body="&lt;p&gt;Another option may be a  high-end MCU with USB2 HS host, and use a USB-SATA adapter.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-24T23:47:38.017" />
  <row Id="8269" PostTypeId="2" ParentId="8251" CreationDate="2010-12-24T23:52:21.460" Score="1" ViewCount="" Body="&lt;p&gt;It will certainly be a consequence of how the chip is laid out internally, combined with the fact that it is fairly rare on microcontroller applications to need blocks of consecutive IO pins to make wide buses etc., so grouping together isn't a high priority and not worth  spending additional silicon area on. &#xA;Of course this logic breaks down somewhat on parts with  external bus interfaces, making layout, particularly with QFPs something of a nightmare, but volume users will probably be using BGAs anyway to save space - I've always thought 208QFPs  look a bit ridiculous..!  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-24T23:52:21.460" CommentCount="2" />
  <row Id="8270" PostTypeId="1" CreationDate="2010-12-25T01:43:56.510" Score="1" ViewCount="282" Body="&lt;p&gt;Is there any (preferably open source, preferably python; &lt;em&gt;only linux&lt;/em&gt;) software for microcontroller board prototyping simulation? I'm an EE and we used spice in classes to simulate circuit level stuff. Is there anything like that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a specific term for what this would be called? Just simulation software?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Also&lt;/em&gt;: I crossposted this on &lt;a href=&quot;http://stackoverflow.com/questions/4528990/arduino-mcb-protyping-simulation-software&quot;&gt;SO&lt;/a&gt; because I totally forgot this place existed. Hope that's ok.&lt;/p&gt;&#xA;" OwnerUserId="1360" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-25T08:28:40.817" LastActivityDate="2010-12-25T08:28:40.817" Title="Arduino protyping simulation software" Tags="&lt;arduino&gt;&lt;prototyping&gt;&lt;simulation&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="1" />
  <row Id="8271" PostTypeId="1" AcceptedAnswerId="8274" CreationDate="2010-12-25T01:51:34.880" Score="4" ViewCount="239" Body="&lt;p&gt;I'm interested in measuring the spectral amplitudes / frequency content of RF frequencies up to &lt;strong&gt;30 GHz&lt;/strong&gt;. This can be done using a digital sampling oscilloscope &lt;em&gt;(I'll call it a SO)&lt;/em&gt; with FFT or a digital spectrum analyzer &lt;em&gt;(SA)&lt;/em&gt; [or a fantastic digital storage 'scope, noted below]. &lt;a href=&quot;http://www.cbtricks.com/miscellaneous/tech_publications/scope/sampling.pdf&quot; rel=&quot;nofollow&quot;&gt;As I understand it&lt;/a&gt;, a &lt;em&gt;SO&lt;/em&gt; samples the signals directly with known sample jitter, then recreates the signal using regression. A &lt;em&gt;SA&lt;/em&gt;, on the other hand, first downconverts the high-frequency signal with a mixer, then samples. It would seem that a &lt;em&gt;SA&lt;/em&gt; should deliver greater frequency resolution given comparable ADC sampling rates to the sampling oscilloscope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;What are the limits of functionality of each type? How is one better than the other at spectral analysis?&lt;/strong&gt; (They both rely on the FFT, right?) What makes either expensive?&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Unrelated POIs: &lt;a href=&quot;http://www.home.agilent.com/agilent/product.jspx?nid=-34363.937136.00&amp;amp;cc=CA&amp;amp;lc=eng&quot; rel=&quot;nofollow&quot;&gt;32 GHz Agilent&lt;/a&gt;, &lt;a href=&quot;http://www.lecroy.com/Oscilloscope/OscilloscopeSeries.aspx?mseries=329&amp;amp;capid=102&amp;amp;mid=504&quot; rel=&quot;nofollow&quot;&gt;120 GS/s Lecroy&lt;/a&gt;, &lt;a href=&quot;http://www.tek.com/products/oscilloscopes/dpo70000_dsa70000/&quot; rel=&quot;nofollow&quot;&gt;100 GS/s Tek&lt;/a&gt;, &lt;a href=&quot;http://ece.nsit.ac.in/website/eclub/projects/gba.pdf&quot; rel=&quot;nofollow&quot;&gt;Gameboy SA&lt;/a&gt;.&lt;/em&gt;&lt;br&gt;&#xA;&lt;strong&gt;&lt;em&gt;edit:&lt;/strong&gt; There seems to be some confusion between digital storage 'scopes (DSOs) and digital sampling oscilloscopes (what I called SOs) -- they are not the same, although they both sample digitally. I've also updated the question.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-29T06:05:02.090" LastActivityDate="2010-12-29T06:05:02.090" Title="What are the functional differences between a digital sampling 'scope and a digital spectrum analyzer?" Tags="&lt;rf&gt;&lt;oscilloscope&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="2" />
  <row Id="8272" PostTypeId="2" ParentId="8270" CreationDate="2010-12-25T02:01:39.600" Score="3" ViewCount="" Body="&lt;p&gt;If you're looking for Arduino simulator, there is &lt;a href=&quot;http://www.virtualbreadboard.net/Shop/tabid/206/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;virtualbreadboard.net&lt;/a&gt;. It can do stuff like this:&#xA;&lt;img src=&quot;http://i.imgur.com/XXFEH.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-25T02:01:39.600" CommentCount="8" />
  <row Id="8273" PostTypeId="1" AcceptedAnswerId="8336" CreationDate="2010-12-25T02:07:49.320" Score="2" ViewCount="68" Body="&lt;p&gt;I’ve got a MCF5282 that I’m trying to use PDD4 as a GPIO on.  In my setup code, I’ve got:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;MCF5282_GPIO_DDRDD = 0x10;    /* cs on dd4. */&#xA;MCF5282_GPIO_PORTDD = 0x10; /* active-low. */&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And in my main loop, I’ve got:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;for( mainloop_cnt = 0; true; mainloop_cnt++ )&#xA;{&#xA;    MCF5282_GPIO_PORTDD = (mainloop_cnt &amp;amp; 0x10);&#xA;    /* other stuff. */&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Which should give me a nice square wave on the oscilloscope, but the port doesn’t seem to be doing as I say.  Am I missing some setup steps?  I can’t find anything in the 5282 manual about a “Port DD pin-assignment register” to repurpose it from its “primary” role as DDATA.&lt;/p&gt;&#xA;" OwnerUserId="1555" LastEditorUserId="1555" LastEditorDisplayName="" LastEditDate="2010-12-27T00:59:08.573" LastActivityDate="2010-12-27T16:06:23.980" Title="Using Port DD as GPIO on MCF5282" Tags="&lt;embedded&gt;&lt;freescale&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="8274" PostTypeId="2" ParentId="8271" CreationDate="2010-12-25T04:37:19.830" Score="4" ViewCount="" Body="&lt;p&gt;Well, you're not going to be making RF measurements up to 30 GHz without spending a bunch of money, so either path is big bucks. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Typically, Spectrum analyzers are used to do frequency domain measurements. You'll get a display of power vs frequency on the display. The controls in the SA are setup for relevant things, Center frequency, bandwidth, resolution bandwith, signal powers in dBm/dBc etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digital oscilloscopes don't directly have sampling rates to directly sample a 30 Ghz signal, so they'll undersample and assume that the signal repeats. probably a safe assumption, although with no front end filters built into them, you've got dynamic range issues, as well as aliasing concerns that aren't present in a Spectrum Analyzer. You won't directly get spectral plots out of a Digital oscilloscope, you'll need to do an FFT on that. Now, that opens up a can of worms. FFT bin width/windowing function selection, etc. All stuff that can be worked through, but another question to deal with. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You won't get eye diagrams out of a spectrum analyzer, it's a useless measurement @ RF. That's a demodulated signal measurement. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ultimately, if you want time domain data, then use an oscilloscope. If you want Spectral information, use a spectrum analyzer.&lt;/p&gt;&#xA;" OwnerUserId="2148" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-27T19:49:36.503" LastActivityDate="2010-12-27T19:49:36.503" CommentCount="3" />
  <row Id="8275" PostTypeId="2" ParentId="8203" CreationDate="2010-12-25T05:55:08.500" Score="0" ViewCount="" Body="&lt;p&gt;I've used very fine sandpaper. It's a time consuming and dirty process, but if you only need to strip the insulation off a short length of wire it works.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2010-12-25T05:55:08.500" />
  <row Id="8276" PostTypeId="1" CreationDate="2010-12-25T08:34:10.677" Score="1" ViewCount="145" Body="&lt;p&gt;Hey guys. I'm building a 9 RGB LED chaser, using an ATTiny2313 to drive it. The cathodes are connected to all of PORTB and pin 6 of PORTD. I wrote some code to drive them all, but for some reason it's really slow. If red is set to 200 and blue to 100, you can see the red staying on for twice the amount of time, and you can almost time it. This should be happening many, many times a second but it's going very slow.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;avr/interrupt.h&amp;gt;    // Defines pins, ports, etc to make programs easier to read&#xA;#define F_CPU 1000000UL       // Sets up the default speed for delay.h&#xA;#include &amp;lt;util/delay.h&amp;gt;&#xA;#include &amp;lt;stdint.h&amp;gt;&#xA;#include &amp;lt;stdlib.h&amp;gt;&#xA;#include &amp;lt;math.h&amp;gt;&#xA;&#xA;#define bit_get(p,m) ((p) &amp;amp; (m))&#xA;#define bit_set(p,m) ((p) |= (m))&#xA;#define bit_clear(p,m) ((p) &amp;amp;= ~(m))&#xA;#define bit_flip(p,m) ((p) ^= (m))&#xA;#define bit_write(c,p,m) (c ? bit_set(p,m) : bit_clear(p,m))&#xA;#define BIT(x) (0x01 &amp;lt;&amp;lt; (x))&#xA;#define LONGBIT(x) ((unsigned long)0x00000001 &amp;lt;&amp;lt; (x)) &#xA;&#xA;#define RED 1&#xA;#define BLUE 0&#xA;#define GREEN 2&#xA;&#xA;&#xA;void delay_ms(uint16_t ms) {&#xA;  while ( ms ){&#xA;    _delay_ms(1);&#xA;    ms--;&#xA;  }&#xA;}&#xA;struct LED {&#xA;    uint8_t r;&#xA;    uint8_t g;&#xA;    uint8_t b;&#xA;};&#xA;&#xA;volatile struct LED strip[9];&#xA;uint8_t x;&#xA;uint8_t y;&#xA;&#xA;int main(void)&#xA;{&#xA;DDRD = 0xFF;&#xA;DDRB = 0xFF;&#xA;for(x = 0; x &amp;lt;= 8; x++){&#xA;    strip[x].r = 0;&#xA;    strip[x].g = 0;&#xA;    strip[x].b = 255;&#xA;}&#xA;while(1){&#xA;    PORTB = 0xFF;&#xA;    PORTD = (1 &amp;lt;&amp;lt; 6);&#xA;    for(x = 0; x &amp;lt;= 255; x++){&#xA;        for(y = 0; y &amp;lt;= 8; y++){&#xA;&#xA;            if(strip[y].r &amp;gt; x)&#xA;                bit_set(PORTD, BIT(RED));&#xA;            else&#xA;                bit_clear(PORTD, BIT(RED));&#xA;            if(strip[y].g &amp;gt; x)&#xA;                bit_set(PORTD, BIT(GREEN));&#xA;            else&#xA;                bit_clear(PORTD, BIT(GREEN));&#xA;            if(strip[y].b &amp;gt; x)&#xA;                bit_set(PORTD, BIT(BLUE));&#xA;            else&#xA;                bit_clear(PORTD, BIT(BLUE));    &#xA;&#xA;            _delay_us(1);&#xA;            if(y == 0){&#xA;                bit_clear(PORTD, BIT(6));&#xA;                PORTB = 0xFF;&#xA;            }else{&#xA;                bit_clear(PORTB, BIT(y-1));&#xA;                bit_set(PORTD, BIT(6));&#xA;            }&#xA;            _delay_us(10);&#xA;            PORTB = 0xFF;&#xA;            PORTD |= (1 &amp;lt;&amp;lt; 6);&#xA;            _delay_us(1);&#xA;        }&#xA;    }&#xA;}&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Any help would be greatly appreciated :)&lt;/p&gt;&#xA;" OwnerUserId="2381" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2010-12-25T10:10:09.037" LastActivityDate="2010-12-25T12:00:46.903" Title="Why is my code running so slow?" Tags="&lt;led&gt;&lt;multiplexing&gt;&lt;pwm&gt;" AnswerCount="2" />
  <row Id="8277" PostTypeId="2" ParentId="8276" CreationDate="2010-12-25T10:08:36.293" Score="3" ViewCount="" Body="&lt;p&gt;Do the math how many cycles this uses:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;255 * 9 * ca 100 cycles per iteration / 1 MHz = ca 0.25s&lt;/p&gt;&#xA;&#xA;&lt;p&gt;where the 100 is a very rough ballpark estimate, it could easily be more depending on the implementation of delay_us.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd increase the clock frequency and use an interrupt-driven approach.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But it's still going to be hard to do do proper dimming when you also do multiplexing, you'll be limited to a few colors to avoid too much flickering.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2010-12-25T10:08:36.293" />
  <row Id="8278" PostTypeId="2" ParentId="8276" CreationDate="2010-12-25T12:00:46.903" Score="1" ViewCount="" Body="&lt;p&gt;Did you reprogram the CLK8DIV fuse from its default setting? The factory setting divides the clock frequency by 8. &#xA;It is possible  to do fast PWM dimming of a reasonable number of LEDs on AVR but the code needs to be very carefully written. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-25T12:00:46.903" CommentCount="1" />
  <row Id="8279" PostTypeId="2" ParentId="8250" CreationDate="2010-12-25T13:09:09.467" Score="0" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Hzcdf.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is my final solution.  The digital ground plane is filtered at the DC jack.  The unfiltered plane is tied to the Ethernet jack and its ground.  This will hopefully keep ESD off the digital ground and still provide a nice ground for the jack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I ended up using a keepout area under the TX and RX pairs, so there is no ground plane under them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The TX and RX termination resistors are placed close to the PHY (built into the PIC18F in this case).&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2010-12-25T13:09:09.467" CommentCount="3" />
  <row Id="8280" PostTypeId="1" AcceptedAnswerId="8281" CreationDate="2010-12-25T13:13:15.893" Score="3" ViewCount="179" Body="&lt;p&gt;In a lot of circuits, I've seen ferrite beads on the Vdd lines to microcontrollers. For my high speed dsPIC33F (80 MHz, 40 MIPS) microcontroller, should I have ferrite beads on the Vdd lines or should I not bother? The datasheet doesn't suggest using them. I'd like to limit EMI/RF interference, as the module will be used on a model plane and this type of interference could cause problems for the onboard radios.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-25T13:40:55.790" Title="When is it appropriate to use ferrite beads?" Tags="&lt;rf&gt;&lt;emi&gt;" AnswerCount="1" />
  <row Id="8281" PostTypeId="2" ParentId="8280" CreationDate="2010-12-25T13:40:55.790" Score="6" ViewCount="" Body="&lt;p&gt;To filter high frequency noise.  Inductors' windings are capacitive at high frequency so they are effectively useless.  If you're worried about your circuit affecting other circuits (or being affected by them), I would only filter the I/O and power entry to your module, so that conducted noise doesn't leave your module on the I/O and power lines, which can act like antennas and radiate the noise, or pick up noise from other modules.  The other use, inside a module, is for sharing a voltage rail with sensitive analog components, such as an ADC with a micro.  In the case of your PIC, it usually doesn't need such a thing.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2010-12-25T13:40:55.790" CommentCount="3" />
  <row Id="8282" PostTypeId="1" AcceptedAnswerId="8283" CreationDate="2010-12-25T14:54:08.357" Score="3" ViewCount="144" Body="&lt;p&gt;Hi,&#xA;for my current project I'm planning to use an input &quot;device&quot; like this in the photo (don't know its real name):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/MztUQ.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is used in a lot of musical instruments and it is like a potentiometer that can be rotated as many times as you want. I think it isn't read like an analog value.&#xA;Can someone give me some hints?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you very much.&lt;/p&gt;&#xA;" OwnerUserId="2316" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-25T18:08:12.740" LastActivityDate="2010-12-25T18:08:12.740" Title="How to implement a &quot;rotary switch&quot; like in audio equipment?" Tags="&lt;switch&gt;&lt;input&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="2" />
  <row Id="8283" PostTypeId="2" ParentId="8282" CreationDate="2010-12-25T14:58:56.007" Score="14" ViewCount="" Body="&lt;p&gt;It's a &lt;strong&gt;rotary encoder&lt;/strong&gt;. It has two outputs giving pulses in quadrature (see image), as to determine the way it's rotated.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/9YUkf.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the image you can see that the level of the B channel is low on the rising edge of the A channel if the knob is rotated clockwise, but high if rotated counterclockwise.&lt;br&gt;&#xA;Differences in models are the number of pulses per rotation, often between 15 and 20, and the number of channels. More than 2 channels are used to obtain the absolute position of the knob. E.g. 10 channels give 1024 unique codes per rotation. Gray coding is used.&lt;br&gt;&#xA;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Another parameter is the detent. Detents are click-positions, which require a certain momentum to overcome. Some models have 2 detents per pulse, others don't have detents and rotate rather smoothly, so that it feels like a potmeter without stops.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-25T15:22:23.850" LastActivityDate="2010-12-25T15:22:23.850" CommentCount="5" />
  <row Id="8284" PostTypeId="1" CreationDate="2010-12-25T18:20:50.783" Score="2" ViewCount="391" Body="&lt;p&gt;I want to:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Input an analog audio track&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Using the microcontroller ADC, convert it to a digital output&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Then have the microcontollers/boards timer sample the data at selected intervals&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Resample the &quot;Sampled audio track&quot; at twice the highest frequency content&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Convert it back to analog as a perfect reconstruction of the initial audio track&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Using Fourier Analysis I will determine the highest frequency at which I will sample the track at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It sounds easy enough and straight forward, but what I need is to program this in C and utilize my MSP430 chip/experimenters board to sample the track.&#xA;I'm going to be using Texas Instruments CCS and Octave for my programming and debugging. I am using the &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/msp-exp430f5438.html&quot; rel=&quot;nofollow&quot;&gt;MSP430F5438 Experimenter Board&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Is C the right language for this? Can I get any examples of how to sample the track at Nyquist frequency using C? What code in C will tell the board to utilize the ADC component?&lt;/strong&gt; And any recommended information that is similar or that will help me on this project.&lt;/p&gt;&#xA;" OwnerUserId="2386" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-26T18:05:35.347" LastActivityDate="2010-12-27T00:27:23.817" Title="How to sample audio at Nyquist frequency with MSP430F5438?" Tags="&lt;audio&gt;&lt;adc&gt;&lt;dac&gt;&lt;sampling&gt;" AnswerCount="5" CommentCount="8" />
  <row Id="8285" PostTypeId="1" CreationDate="2010-12-25T18:52:46.640" Score="2" ViewCount="438" Body="&lt;p&gt;I'm doing a DSP project using the MSP430. I want to take an analog signal and convert it to a digital output using a microcontroller attached to an ADC on a DSP board. How would I program this in C?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  Input  --&amp;gt;  Output&#xA; Analog  --&amp;gt; Digital&#xA;Digital  --&amp;gt;  Analog&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2386" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-26T08:58:00.510" LastActivityDate="2010-12-26T08:58:00.510" Title="ADC and DAC code for MSP430" Tags="&lt;adc&gt;&lt;msp430&gt;&lt;dac&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="8286" PostTypeId="2" ParentId="8284" CreationDate="2010-12-25T19:10:30.243" Score="2" ViewCount="" Body="&lt;p&gt;You will have to use the family guide and the Data sheet - &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/msp430f5438.html&quot; rel=&quot;nofollow&quot;&gt;found here&lt;/a&gt; It will tell you how to setup the ADC and give some basic examples, also TI has sample code for the MSP430 line of chips which includes ADC10 and ADC12 examples. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2010-12-25T19:10:30.243" CommentCount="9" />
  <row Id="8288" PostTypeId="2" ParentId="8284" CreationDate="2010-12-25T21:00:04.903" Score="2" ViewCount="" Body="&lt;p&gt;You will find things much easier if you use a proper DSP, I'd use a dsPIC. Microchip has FFT libraries.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-25T21:00:04.903" CommentCount="9" />
  <row Id="8289" PostTypeId="1" CreationDate="2010-12-25T21:01:26.697" Score="-1" ViewCount="319" Body="&lt;p&gt;I am doing my masters in Information Technology and Robotics. I am in my 3rd semester at the moment. For my final semester, I will have to do a thesis project. I would like to do my thesis in the field of robotics or more specifically &quot;practical robotics&quot;. And I am having a difficult time coming up with &lt;strong&gt;cool and interesting&lt;/strong&gt; projects to work on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been searching Google non-stop for the past 2 weeks and I haven't been completely satisfied with some of the ideas I came across. The problem is, if its cool, its not interesting and if its interesting, its not cool. And if it is interesting and cool, it doesn't seem like it could be something that could be done as a thesis project by a couple of students in a span of 5 or 6 months. I know, it is silly, to look for cool projects, because it is much more important for the project to be interesting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the reason, I want to do something &lt;strong&gt;cool&lt;/strong&gt; is because, I want it to look good on my resume afterwards. Once I finish my degree next June, I want to work for a robotics company like &lt;strong&gt;Willow Garage&lt;/strong&gt; or &lt;strong&gt;iRobot&lt;/strong&gt; for instance. And I believe, doing a project that is &lt;strong&gt;cool&lt;/strong&gt; and has some kind of &lt;strong&gt;practical application&lt;/strong&gt; will make me look good as a potential employee.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far, I've had a passing interest in,&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A &lt;a href=&quot;http://www.youtube.com/watch?v=aMQ6t13ID9o&quot; rel=&quot;nofollow&quot;&gt;ball&lt;/a&gt; that is controllable as it moves&lt;/li&gt;&#xA;&lt;li&gt;Using &lt;a href=&quot;http://www.youtube.com/watch?v=7Qxvyw5tUko&quot; rel=&quot;nofollow&quot;&gt;artificial muscles&lt;/a&gt; to construct something of practical application. &lt;a href=&quot;http://www.youtube.com/watch?v=ddEoQWVy9MQ&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a small explanation of how it works&lt;/li&gt;&#xA;&lt;li&gt;Constructing something that has practical application using the new &lt;strong&gt;Kinect&lt;/strong&gt; and the OpenCV vision library&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Taken individually, the ones I mentioned above, are all interesting and have an element of coolness about them. But I'm not sure they have any practical value if used by themselves. For instance, the sphero ball project I mentioned above is cool and interesting yes. But it doesn't have any practical application other than being entertaining. Though I did think, of using it as a controllable grenade on the battlefield by putting a small grenade inside. That has some practical value. But I'm not sure, it can be done as thesis project because, I think the idea is too simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In any case, these were some of the ideas, I came up with. It would be very helpful if anyone can propose any interesting ideas that I could work on as a thesis project. I'm sure there might be some of you that have some interesting ideas that you haven't been able to work on due to a lack of time or some other reason. I would be happy to know about them and work on them, if its not a secret and if its something related to robotics and programming and has some practical use.&lt;/p&gt;&#xA;" OwnerUserId="2385" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2010-12-25T21:14:31.970" LastActivityDate="2010-12-26T09:11:48.847" ClosedDate="2010-12-26T17:11:06.937" Title="Master Thesis Project Ideas" Tags="&lt;projects&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="8290" PostTypeId="2" ParentId="8284" CreationDate="2010-12-25T22:46:30.010" Score="1" ViewCount="" Body="&lt;p&gt;You might want to check out the &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en534506&quot; rel=&quot;nofollow&quot;&gt;DSC Starter Kit&lt;/a&gt;. It provides you with all of the software and hardware needed to get started with audio recording on a microcontroller. It also has some example programs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DFT is a little bit more difficult, but there are prebuilt libraries for it. The problem is finding a free one and making sure you have enough ram to do all of the computations needed.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-25T22:46:30.010" CommentCount="6" />
  <row Id="8291" PostTypeId="1" AcceptedAnswerId="8293" CreationDate="2010-12-25T23:47:43.217" Score="6" ViewCount="101" Body="&lt;p&gt;I've got a Weller soldering station with settable temperature and interchangeable tips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a table or general guidelines for temperatures and tips for different soldering tasks, such as:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;wire-wire, thick&lt;/li&gt;&#xA;&lt;li&gt;wire-wire, 20 gauge&lt;/li&gt;&#xA;&lt;li&gt;wire to PC board&lt;/li&gt;&#xA;&lt;li&gt;through-hole chip on PC board&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1756" LastActivityDate="2010-12-26T06:14:57.063" Title="soldering temperature/tip guides?" Tags="&lt;soldering&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="8292" PostTypeId="2" ParentId="8291" CreationDate="2010-12-25T23:53:46.310" Score="5" ViewCount="" Body="&lt;p&gt;You should select the correct tip for a particular joint, keeping the temperature constant. The tip should be about the same size as the object being soldered. The temperature depends on the type of solder.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2010-12-25T23:53:46.310" />
  <row Id="8293" PostTypeId="2" ParentId="8291" CreationDate="2010-12-26T00:28:55.553" Score="0" ViewCount="" Body="&lt;p&gt;Some soldering experts may disagree with me but I usually always use 750-800 degrees.  It seems the biggest variable is the tip.  For through hole and wire to wire I use a very big tip.  I use a smaller tip for SMT.  It has always seemed to me, for correct heat transfer, tip size is much more important than temperature.  If you find yourself needing to hold the iron against your parts too long (more than a few seconds) I'd use a bigger tip.  Wire to wire usually isn't as critical or easy to damage as ICs, usually just don't want to start melting the insulation.  Following this method I've never burnt a chip to death.  Killed them plenty of other ways though, and I'm definitely not a professional solderer.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2010-12-26T00:28:55.553" />
  <row Id="8294" PostTypeId="1" CreationDate="2010-12-26T00:51:02.570" Score="5" ViewCount="215" Body="&lt;p&gt;What techniques are useful when layout a circuit on a breadboard? Specifically, making it as least cluttered and readable as possible. My circuits always come out looking horrible and really messy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a technique on where to start? Or some rules on what to connect first?&lt;/p&gt;&#xA;" OwnerUserId="1360" LastActivityDate="2010-12-28T04:45:13.130" Title="Breadboard component layout design" Tags="&lt;design&gt;&lt;layout&gt;&lt;breadboard&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="3" />
  <row Id="8295" PostTypeId="1" AcceptedAnswerId="8303" CreationDate="2010-12-26T01:41:15.463" Score="2" ViewCount="466" Body="&lt;p&gt;This question may be borderline between superuser and here, but I think it's more suitable for this site. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a 3-pin 12 V computer fan and I want to interpret its speed sensor output. At the yellow wire I get something that looks like pulse-with modulation. How would I interpret the output without actually connecting the fan to a computer?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2010-12-26T01:46:39.410" LastActivityDate="2010-12-26T06:29:11.687" Title="How to interpret output of 3-pin computer fan speed sensor?" Tags="&lt;pwm&gt;&lt;fan&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="8296" PostTypeId="2" ParentId="8295" CreationDate="2010-12-26T02:09:02.487" Score="2" ViewCount="" Body="&lt;p&gt;The fan signal is the rate of rotation, 1 Hz = 1 RPS (rotation/revolution per second.) Connect a PIC or your favourite brand of microcontroller to the signal, count each rising or falling edge in one (or however many you want - more seconds, more accuracy) second and multiply to get RPM. If your processor is fast, you could even measure the period of the waveform and from this determine the speed to a high degree of accuracy (1/t = f). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For most fans the 1 Hz represents one rotation, as it is more expensive to include multiple switches in the fan, but don't rely on this.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-12-26T02:17:55.477" LastActivityDate="2010-12-26T02:17:55.477" CommentCount="5" />
  <row Id="8297" PostTypeId="2" ParentId="8294" CreationDate="2010-12-26T02:14:16.120" Score="2" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Plan it on paper first or by using a CAD program&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Decide on the optimum position for your ICs, keeping signal lines short. Use the centre, empty track to your advantage. See that power and ground is necessary wherever needed.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Connect power and grounds first, then signals.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Modularise your circuit: build the pre-amp, then the oscillator, the the microcontroller (or whatever your circuit uses) in distinct sections: even better on separate boards.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;General cleanliness:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Clip wires to short lengths keeping insulation on them right up to the sockets. Ideally, use a dedicated wire stripper tool, as that gives cleaner results.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Clip component lengths short.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Use the bus lines for carrying power or commonly used signals&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Use DIP sockets for DIP packages.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-12-26T02:54:27.490" LastActivityDate="2010-12-26T02:54:27.490" />
  <row Id="8298" PostTypeId="2" ParentId="8295" CreationDate="2010-12-26T02:15:06.523" Score="2" ViewCount="" Body="&lt;p&gt;In most fans that I've worked with, the yellow wire is referred to as the TACH or tachometer wire.  It is essentially a PWM output whose frequency is related to rotation of the fan.  Sometimes it is 1:1 and one period output on the TACH line is equal to one revolution of the fan; sometimes there are 3 periods on the TACH to 1 revolution of the fan, you need to check the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can connect the TACH signal to an I/O pin on a microprocessor and determine the RPM value of the fan pretty easily.&lt;/p&gt;&#xA;" OwnerUserId="107" LastActivityDate="2010-12-26T02:15:06.523" CommentCount="2" />
  <row Id="8299" PostTypeId="2" ParentId="8294" CreationDate="2010-12-26T03:08:54.777" Score="5" ViewCount="" Body="&lt;p&gt;Look at the breadboard view of &lt;a href=&quot;http://fritzing.org/&quot; rel=&quot;nofollow&quot;&gt;Fritzing&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have never bothered with a complicated circuit on a solderless breadboard.  It's usually less trouble to just start soldering things together on a 0.1&quot; protoboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Breadboards are best for quick, small &quot;will this work&quot; circuits.  And who cares if those look a bit messy.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-26T03:08:54.777" />
  <row Id="8300" PostTypeId="1" CreationDate="2010-12-26T03:52:38.090" Score="-3" ViewCount="107" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/7022/circuit-simulation-software&quot;&gt;Circuit Simulation Software&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Hi, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a newbie with electronics and looking for a good software for simulation (analog, digital circuits ..ect..).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm aware this is not a specific question about something clear in electronics, but wondered if someone can share any name of any good simulation software. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards!&lt;/p&gt;&#xA;" OwnerUserId="2382" LastEditorUserId="2382" LastEditorDisplayName="" LastEditDate="2010-12-26T14:30:37.840" LastActivityDate="2010-12-26T14:30:37.840" ClosedDate="2010-12-26T15:57:47.117" Title="Softwares for simulation" Tags="&lt;software&gt;&lt;simulation&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="8301" PostTypeId="2" ParentId="8291" CreationDate="2010-12-26T06:14:57.063" Score="0" ViewCount="" Body="&lt;p&gt;I don't think the temperature matters much, just that you get the material you are soldering to hot. Once the material is hot, allow the solder to flow from the heated material to your soldering iron. If you are getting big beads of solder on your soldering iron, you are doing things backwards. Make sure to move your soldering Iron away from the solder as it flows. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your not able to maintain a hot temperature on the object being soldered to, then you may want to try either a larger tip, and or a higher temperature.&lt;/p&gt;&#xA;" OwnerUserId="2391" LastActivityDate="2010-12-26T06:14:57.063" />
  <row Id="8302" PostTypeId="2" ParentId="8300" CreationDate="2010-12-26T06:24:06.040" Score="1" ViewCount="" Body="&lt;p&gt;Verilog is your basic language for simulating circuits. It can simulate just about anything, and their are GUI's to make the the simulation a little bit easier. If you are looking to experiment/are new to electronics, I'd suggest finding a hardware project you'd like to do, and purchasing the physical objects to implement that project. &lt;/p&gt;&#xA;" OwnerUserId="2391" LastActivityDate="2010-12-26T06:24:06.040" CommentCount="1" />
  <row Id="8303" PostTypeId="2" ParentId="8295" CreationDate="2010-12-26T06:29:11.687" Score="4" ViewCount="" Body="&lt;p&gt;Brief background: The tachometer output comes from a Hall-effect sensor mounted on the motor driver PCB on the fan frame. One or more magnets embedded in the fan rotor hub activate the Hall-effect sensor as they pass by. The sensor is amplified, and eventually drives a logic circuit. The fans that I have seen use an open drain/open collector output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One (or more) pulse is generated every time the the fan rotor completes a revolution. The number of pulses counted in one minute is directly proportional to the RPM of the fan. In your fan's case, I think it would be reasonable to guess that there are two pulses generated for each revolution. With the frequency that you have measured, about 1500 RPM sounds right, given that you are running it at 10V (12V nominal) and the typical is 1800-2000 RPM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want a more visual approach, you can make a crude strobe tachometer using just a LED and resistor. Connect a LED (brighter is better) and an appropriate current-limiting resistor between power and the tachometer pin. If you mark one of the fan blades with something easy to see, like a sticker, you should be able to shine the LED on the fan blades and see the sticker illuminated in two places. You can use this technique to count the number of times the tachometer output goes low each rotation, and to approximate the duty cycle of the signal.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-26T06:29:11.687" CommentCount="3" />
  <row Id="8304" PostTypeId="2" ParentId="8289" CreationDate="2010-12-26T08:30:30.710" Score="0" ViewCount="" Body="&lt;p&gt;The project don't have to be super cool, focus on using super cool techniques to make a ordinary project become a cool one instead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And sites like &lt;a href=&quot;http://hackaday.com&quot; rel=&quot;nofollow&quot;&gt;hackaday&lt;/a&gt; can provide inspiration for ideas.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2010-12-26T08:30:30.710" CommentCount="1" />
  <row Id="8305" PostTypeId="2" ParentId="8285" CreationDate="2010-12-26T08:31:37.197" Score="4" ViewCount="" Body="&lt;p&gt;This is the case where reading the datasheet is truly the best thing for you to do -- they will tell you exactly how to initialize, start [and stop], and use both an ADC and DAC. Since you haven't named a specific MSP430, ADC chip, or analog signal characteristics, I'm guessing that the design is very much in the initial planning stages. I suggest nailing down some requirements for each block in your system diagram, &lt;a href=&quot;http://focus.ti.com/en/multimedia/flash/selection_tools/mcu/mcu.html&quot; rel=&quot;nofollow&quot;&gt;looking for parts&lt;/a&gt; that will do those things, then  reading their datasheets. Examples of requirements would be sampling rate/frequency (remember Nyquist) and depth (in bits, which can be translated from Volts); you can get an MSP430 with a 12-bit ADC and DAC on the chip. Something else is peripheral support: are you using a user interface? Comparators or trigger interrupt pins, used with hardware timers, are great for interfacing with and &lt;a href=&quot;http://hackaday.com/2010/11/09/debounce-code-one-post-to-rule-them-all/&quot; rel=&quot;nofollow&quot;&gt;debouncing&lt;/a&gt; buttons; SPI, UART or I2C/TWI are serial protocols used to drive a screen. Note that there are a variety of ways to generate analog signals -- no need to limit searches to DAC peripherals or ICs: given some parameters, such as ripple and precision, you can determine what frequency and number of bits to use to do PWM with a single (or two) pins. You can also use a traditional R2R DAC, but make the LSB a PWM output to give you both R2R resistor calibration as well as additional precision.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-26T08:31:37.197" />
  <row Id="8306" PostTypeId="2" ParentId="8289" CreationDate="2010-12-26T09:11:48.847" Score="0" ViewCount="" Body="&lt;p&gt;Your post screams (something I would not like to say in public, mail me if you really want to listen).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, you are a masters student, I have a believe that most of the masters students have something in their mind before they join the masters program. They have a small inkling of what they want from this masters program, think back to that time (the time before all the forced classes washed that off your mind) and maybe you would get some inspiration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I am getting your meaning of cool correctly then you should work on a robot which actually interacts with its users. I would personally like to see a robot which does things like giving recommendations of food based on my previous orders. A lot of AI and robotics will go into that. The robot can learn about where I like to sit and check if that table is empty and sit me there. Basically a waiter robot which can replace a typical waiter (as they are in such a shortage, they wouldn't in practice replace waiters but actually raise their importance).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is something that can be done on a small scale (if the robot is not that intelligent) if you are 2-3 guys/gals working on it dedicatedly for 5 months.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-12-26T09:11:48.847" CommunityOwnedDate="2010-12-26T09:11:48.847" />
  <row Id="8307" PostTypeId="2" ParentId="2103" CreationDate="2010-12-26T12:41:30.310" Score="1" ViewCount="" Body="&lt;p&gt;I'd agree with many of the above, although breadboards are useable for low-power mains voltage applications with suitable external safety precautions (isolation, current-limiting/fusing).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing you really shouldn't try to use them for is any sort of switching regulator.&#xA;SMD is asily handled with breakouts - SM discretes can be easily soldered  to 0.1&quot; pin headers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The probability of dodgy connections means that larger designs are more prone to problems and should probably be avoided, but BBs are the ideal way to check out small bits of circuitry that you're not sure about. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-26T12:41:30.310" />
  <row Id="8308" PostTypeId="1" CreationDate="2010-12-26T14:16:57.583" Score="0" ViewCount="140" Body="&lt;p&gt;I need to know which platform would be the cheapest, most creative (in terms of flexibility and audience support). I want to introduce a hobby platform. Thus far, I'm toggling between Arduino and PIC. I need to take the cost of the board to the bare minimum possible. &#xA;My audience are novices. It shouldn't be too complicated, yet it should be flexible enough to let us create as many projects as possible. This means compatibility with external sensors should be good.&lt;/p&gt;&#xA;" OwnerUserId="2392" LastActivityDate="2010-12-27T00:02:17.830" Title="Introducing hobby projects" Tags="&lt;prototyping&gt;" AnswerCount="4" />
  <row Id="8309" PostTypeId="2" ParentId="8308" CreationDate="2010-12-26T14:38:54.297" Score="1" ViewCount="" Body="&lt;p&gt;Bare minimum? What about supplying them with a MSP430 Launchpad dev kit? I don't think you can get cheaper than $4.90.&lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2010-12-26T14:38:54.297" CommentCount="4" />
  <row Id="8310" PostTypeId="2" ParentId="8308" CreationDate="2010-12-26T14:44:57.827" Score="2" ViewCount="" Body="&lt;p&gt;You are not really comparing like with like. PIC is a family of microcontrollers. Arduino is a prototyping platform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino platform is popular and easy for novice hobbyists to get started with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is probably an equivalent PIC prototyping platform (or several) but, so far as I know, there isn't one with the same sort of appeal or success in the novice/hobbyist marketplace&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Low cost Arduino clones&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://appliedplatonics.com/breaduino/&quot; rel=&quot;nofollow&quot;&gt;http://appliedplatonics.com/breaduino/&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.instructables.com/id/uDuino-Very-Low-Cost-Arduino-Compatible-Developme/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/uDuino-Very-Low-Cost-Arduino-Compatible-Developme/&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.instructables.com/id/Stripboard-Arduino/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Stripboard-Arduino/&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://blog.makezine.com/archive/2009/01/arduino_on_stripboard.html&quot; rel=&quot;nofollow&quot;&gt;http://blog.makezine.com/archive/2009/01/arduino_on_stripboard.html&lt;/a&gt;  &lt;/p&gt;&#xA;" OwnerUserId="2191" LastEditorUserId="2191" LastEditorDisplayName="" LastEditDate="2010-12-26T15:30:41.687" LastActivityDate="2010-12-26T15:30:41.687" CommentCount="2" />
  <row Id="8311" PostTypeId="1" AcceptedAnswerId="8356" CreationDate="2010-12-26T16:23:24.917" Score="6" ViewCount="972" Body="&lt;p&gt;How can I easily start off professional development with the BeagleBoard XM?&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Which OS should I work with? .. my choices include:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Ubuntu&lt;/li&gt;&#xA;&lt;li&gt;Android&lt;/li&gt;&#xA;&lt;li&gt;MeeGo&lt;/li&gt;&#xA;&lt;li&gt;WinCE&lt;/li&gt;&#xA;&lt;li&gt;QNX&lt;/li&gt;&#xA;&lt;li&gt;Angstrom  (preinstalled)&lt;/li&gt;&#xA;&lt;li&gt;Symbian&lt;/li&gt;&#xA;&lt;li&gt;Gentoo&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;How do I install an OS onto the board?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Which IDE do I use?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;How do I debug or run my code on the target?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I bought a brand new Beagleboard XM to interface to a &lt;a href=&quot;http://www.ovt.com/products/sensor.php?id=65&quot; rel=&quot;nofollow&quot;&gt;camera module&lt;/a&gt;, capture video and do some image processing. The camera uses an 8-bit parallel port interface to transfer images. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What do you recommend?&lt;/p&gt;&#xA;" OwnerUserId="444" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-27T00:07:52.273" LastActivityDate="2010-12-28T16:28:28.190" Title="Recommended first steps with the BeagleBoard" Tags="&lt;development&gt;&lt;ide&gt;&lt;beagleboard&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="8312" PostTypeId="2" ParentId="8263" CreationDate="2010-12-26T17:54:16.890" Score="2" ViewCount="" Body="&lt;p&gt;Take a look at &lt;a href=&quot;http://www.modbusdriver.com/modpoll.html&quot; rel=&quot;nofollow&quot;&gt;MODPOLL&lt;/a&gt;. With this simple utility you can read registers from MODBUS TCP/RTU/ASCII slaves. When you make it work and read first registers, then you can analyze it's source code and use it from your PC. To use MODBUS from python, you can use &lt;a href=&quot;http://code.google.com/p/pymodbus/&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;, or just parse console output result of MODPOLL. You choose.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastEditorUserId="1129" LastEditorDisplayName="" LastEditDate="2010-12-30T20:35:41.837" LastActivityDate="2010-12-30T20:35:41.837" />
  <row Id="8313" PostTypeId="2" ParentId="8284" CreationDate="2010-12-26T19:10:49.130" Score="0" ViewCount="" Body="&lt;p&gt;A program can only identify frequencies at half its sampling rate. There are two ways to deal with this:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;oversampling&lt;/strong&gt;: sample at more than twice the maximum possible frequency (eg. 48kHz &gt; 2x20kHz), then compress the data by low-passing it (decimation) at the highest computed frequency.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;undersampling&lt;/strong&gt;: sample at some minimum frequency, then decide to sample at a higher frequency based on the power level in your highest computed frequency bin (FFT term). If it is above a certain threshold, increase the ADC sampling frequency.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The only way to succeed in &lt;em&gt;real-time&lt;/em&gt; is with &lt;em&gt;oversampling&lt;/em&gt;, as &lt;em&gt;undersampling&lt;/em&gt; will have to either skip resampling the parts it has already sampled at too-low a frequency or request it to be replayed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/msp-exp430f5438.html&quot; rel=&quot;nofollow&quot;&gt;linked dev board&lt;/a&gt; seems expensive for this application. Is there more to your project? It has code examples of audio sampling and processing: &lt;a href=&quot;http://www.ti.com/lit/zip/slac227&quot; rel=&quot;nofollow&quot;&gt;SLAC227&lt;/a&gt; (look in FFT.c).&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-26T19:10:49.130" CommentCount="1" />
  <row Id="8314" PostTypeId="1" AcceptedAnswerId="8316" CreationDate="2010-12-26T20:02:14.230" Score="2" ViewCount="246" Body="&lt;p&gt;As a follow up to this question: &lt;a href=&quot;http://electronics.stackexchange.com/questions/8284/how-to-sample-audio-at-nyquist-frequency-with-msp430f5438&quot;&gt;How to sample audio at Nyquist frequency with MSP430F5438?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What type of circuit would I use to generate something that a microcontroller could use to determine the max frequency of an input? I was thinking it would preferably provide a voltage that is lineally related to the frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The information provided by the frequency detector could then be used by the microcontroller to know what frequency it needed to be sampled at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any ICs that do this? or any circuit that will do this?&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-12-26T22:13:33.800" LastActivityDate="2010-12-26T22:13:33.800" Title="Analog Max Frequency Detector Circuit" Tags="&lt;frequency-measurement&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="8315" PostTypeId="2" ParentId="8314" CreationDate="2010-12-26T20:30:41.417" Score="1" ViewCount="" Body="&lt;p&gt;Feed the signal into a counter/timer, after conditioning it with a Schmitt trigger or a BJT and diode circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should know the maximum frequency, however. Base your sampling frequency on that.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2010-12-26T20:46:24.390" LastActivityDate="2010-12-26T20:46:24.390" CommentCount="2" />
  <row Id="8316" PostTypeId="2" ParentId="8314" CreationDate="2010-12-26T20:54:31.973" Score="1" ViewCount="" Body="&lt;p&gt;I had two fleeting thoughts: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;One could use a &lt;a href=&quot;http://en.wikipedia.org/wiki/Audio_crossover&quot; rel=&quot;nofollow&quot;&gt;crossover&lt;/a&gt;, which is an implementation of several bandpass filters, followed by power measurement in order to obtain a rough power spectral density. The highest frequency pass-band achieving a threshold would indicate maximum significant input frequency. If each crossover channel were input to trigger/comparator interrupt pins, some &lt;a href=&quot;http://hackaday.com/2010/11/09/debounce-code-one-post-to-rule-them-all/&quot; rel=&quot;nofollow&quot;&gt;good debounce code&lt;/a&gt; may be able to take care of the rest. The crossover could be as simple as an array of diode detectors with RC filtering. &#xA;Circuit complexity would be dependent on the bandwidth and resolution of the crossover. I'm sure we've all &lt;em&gt;ooo'd&lt;/em&gt; &amp;amp; &lt;em&gt;aaw'd&lt;/em&gt; at quality audio crossovers; diode detectors are very simple; RF range adds complications, but can use diode detectors as well. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;One could &lt;a href=&quot;http://en.wikipedia.org/wiki/Frequency_mixer&quot; rel=&quot;nofollow&quot;&gt;mix down&lt;/a&gt; the input frequency, followed by a LPF. Using a continous LO frequency, start at some minimum (~kHz) and increasing to a maximum expected frequency (20 kHz for audio), one could setup a trigger based on a threshold DC or low frequency output, or just record and compare over the entire range. I've never looked for a low frequency mixer, but it would be simple to make a crude one (diode bridge; Gilbert cell); RF mixer ICs are available.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Both of these methods are inferior to oversampling, but much more fun. There are frequency-to-voltage conversion ICs &lt;em&gt;(DigiKey: PMIC - V/F and F/V Converters, &lt;a href=&quot;http://dkc3.digikey.com/CA/images/datasheet.gif&quot; rel=&quot;nofollow&quot;&gt;1MHz max&lt;/a&gt;)&lt;/em&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-26T21:03:39.703" LastActivityDate="2010-12-26T21:03:39.703" CommentCount="2" />
  <row Id="8317" PostTypeId="2" ParentId="8308" CreationDate="2010-12-26T22:32:44.913" Score="0" ViewCount="" Body="&lt;p&gt;While the Arduino has a nice community, I think the PICs from Microchip offer a lot more options and flexibility. With the free Microchip compiler and $25 to get started with a &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en548414&quot; rel=&quot;nofollow&quot;&gt;Microstick&lt;/a&gt; it's pretty low cost too.   &lt;/p&gt;&#xA;" OwnerUserId="2157" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2010-12-27T00:02:17.830" LastActivityDate="2010-12-27T00:02:17.830" CommentCount="1" />
  <row Id="8318" PostTypeId="2" ParentId="8284" CreationDate="2010-12-26T22:44:47.217" Score="3" ViewCount="" Body="&lt;p&gt;You can do your entire project in a desktop PC.  In fact, if I had to do it, I would start with the desktop:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;a .wav file is already sampled at a high frequency, often 44100 or 48000 Hz.&lt;/li&gt;&#xA;&lt;li&gt;determining the highest frequency can be done with an FFT.  For prototyping, I would link &lt;a href=&quot;http://www.fftw.org/&quot; rel=&quot;nofollow&quot;&gt;FFTW&lt;/a&gt;. &lt;/li&gt;&#xA;&lt;li&gt;downsampling to an arbitrary frequency is a bit hard, because downsampling involves low-pass filtering.  You need to set up a filter for each frequency.  Look at &lt;a href=&quot;http://www.mega-nerd.com/SRC/&quot; rel=&quot;nofollow&quot;&gt;libsamplerate&lt;/a&gt; and see how it sets up a SINC function to convolve against.&lt;/li&gt;&#xA;&lt;li&gt;Converting back to the original sample rate will involve another low-pass filter.  See again libsamplerate.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I believe I would implement this in several passes, for ease of debugging:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Get everything working in Matlab or Octave first.  Octave has libraries to do all the filtering and Fourier analysis.&lt;/li&gt;&#xA;&lt;li&gt;Get everything working in C on PC, linking FFTW and libsamplerate for the downsampling / upsampling.&lt;/li&gt;&#xA;&lt;li&gt;Rewrite the C code with explicit-width variable types (e.g., int16_t instead of &quot;short&quot;) and replace FFTW and libsamplerate with own code so that it compiles standalone.&lt;/li&gt;&#xA;&lt;li&gt;In C for the MSP430 or whatever DSP you've got, write interrupt routines to sample data on the ADC and output it on the DAC.  Test that this works, just going from input to output.&lt;/li&gt;&#xA;&lt;li&gt;Take the working code from step 3 and compile it for the MSP430 or whatever.  Then wedge it in to the working code from step 4 to operate on the sampled data between ADC and DAC.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;This may seem like a lot of steps, but it is much more likely to make a working result than heroically coding everything up in one huge MSP430 application, then trying to debug it on the dev board.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2010-12-27T00:27:23.817" LastActivityDate="2010-12-27T00:27:23.817" CommentCount="25" />
  <row Id="8319" PostTypeId="1" AcceptedAnswerId="8321" CreationDate="2010-12-26T23:00:41.000" Score="1" ViewCount="211" Body="&lt;p&gt;My project Super OSD fits on a PCB with dimensions of approximately 40mm x 70mm. It's very space constrained and I can't expand the PCB too much. How should I approach this problem? I realise it's not strictly electronics, but it is a problem many have presumably solved before. I first considered screws but I didn't find any ones small enough - I need to go as small, or smaller than 4mm diameter. I was thinking of using heatshrink to keep the module secure if screws were not an option. Any opinions?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-30T15:30:50.243" Title="Mounting my PCB project" Tags="&lt;pcb&gt;&lt;hardware&gt;" AnswerCount="5" CommentCount="13" FavoriteCount="1" />
  <row Id="8320" PostTypeId="2" ParentId="8308" CreationDate="2010-12-26T23:07:54.853" Score="2" ViewCount="" Body="&lt;p&gt;I am in the same position, and I chose the Arduino.  There's a nice software development platform, lots of instructional materials, and numerous vendors to choose from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's even a really nice open-source &quot;getting started&quot; tutorial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out this beginner's kit.  I bet you can adapt this with the clones mentioned by RedGrittyBrick and have a very nice, low-cost setup.  Let us know what you end up doing!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sparkfun Inventors Kit&#xA;&lt;a href=&quot;http://www.sparkfun.com/products/10173&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/10173&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1756" LastActivityDate="2010-12-26T23:07:54.853" />
  <row Id="8321" PostTypeId="2" ParentId="8319" CreationDate="2010-12-27T00:01:16.443" Score="5" ViewCount="" Body="&lt;p&gt;I'd probably go for M3 or M4 stainless steel socket head cap screws. They're strong, corrosion resistant, and readily available around the world. If you google DIN 912 A4, (DIN 912 meaning a metric socket head cap screw and A4 meaning stainless steel), you'll find lots of suppliers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One such supplier: &lt;a href=&quot;http://www.mcmaster.com/#din-912-a4-socket-head-cap-screws/&quot; rel=&quot;nofollow&quot;&gt;http://www.mcmaster.com/#din-912-a4-socket-head-cap-screws/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd have those screws pass through nylon unthreaded standoffs and thread into whatever you're mounting the board to. Here's what I'm talking about: &lt;a href=&quot;http://www.mcmaster.com/#catalog/116/3240/&quot; rel=&quot;nofollow&quot;&gt;http://www.mcmaster.com/#catalog/116/3240/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also try snap-on plastic standoffs like these: &lt;a href=&quot;http://www.mcmaster.com/#catalog/116/3245/&quot; rel=&quot;nofollow&quot;&gt;http://www.mcmaster.com/#catalog/116/3245/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They're designed to snap into a 5/32&quot; (3.97 mm) hole, so they should just fit.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-27T00:01:16.443" />
  <row Id="8322" PostTypeId="2" ParentId="8311" CreationDate="2010-12-27T00:12:09.457" Score="2" ViewCount="" Body="&lt;p&gt;I would start with Angstrom Linux, and then move to Ubuntu if you have to. I doubt that you will need to switch just to make the camera work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe the OS for the Beagleboard XM is stored on the SD card, so if you decide you do need to switch to something else, you might get a second SD card, so you can leave the original OS intact. Depending on the OS, you can probably find a prebuilt SD card image that will allow the Beagleboard to boot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an IDE, I would recommend starting with a text editor that works over SSH. You might start with Nano, unless you've used Vim or Emacs before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure about debugging C++ on the Beagleboard, but you can start compiling in Angstrom  with g++. You'll be able to execute code from the commandline.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-27T00:12:09.457" CommentCount="5" />
  <row Id="8323" PostTypeId="2" ParentId="8273" CreationDate="2010-12-27T01:04:08.727" Score="1" ViewCount="" Body="&lt;p&gt;is mainloop_cnt correctly declared as an unsigned char?&#xA;(can't comment anywhere yet, sorry)&lt;/p&gt;&#xA;" OwnerUserId="2344" LastActivityDate="2010-12-27T01:04:08.727" CommentCount="1" />
  <row Id="8324" PostTypeId="2" ParentId="8311" CreationDate="2010-12-27T08:36:09.413" Score="2" ViewCount="" Body="&lt;h1&gt;OS&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;It really depends on what you would like to do?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have three options that is Linux kernel based:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Angstrom is a classic GNU/Linux distribution created for this type of devices.&lt;/li&gt;&#xA;&lt;li&gt;MeeGo is the cool Nokia/Intel Qt based platform that will be used a lot in infotainments systems in cars (and in some Nokia phones). &lt;/li&gt;&#xA;&lt;li&gt;Android the google phone OS, mostly Java&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;And some Desktop Linux distributions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Ubuntu&lt;/li&gt;&#xA;&lt;li&gt;Gentoo&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;And then some other OS:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Symbian that is a 99% phone OS (I would not recommend it)&lt;/li&gt;&#xA;&lt;li&gt;QNX I think is has some real time stuff that could be fun to play with&lt;/li&gt;&#xA;&lt;li&gt;WinCE And you have the classic looked down Windows platform.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;And I would actually start to play with the stuff in this order&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Angstrom, since it seems to be easiest on the Beagleboard&lt;/li&gt;&#xA;&lt;li&gt;MeeGo since Qt is a really nice lib to work with&lt;/li&gt;&#xA;&lt;li&gt;Android since it is good to know&lt;/li&gt;&#xA;&lt;li&gt;QNX &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;But for the rest of this question I will only focus on the Linux based options.&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Install OS&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;It depends, but most of them uses the SD card.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But in debug mode you can use a combination that loads the kernel over tftp and the the runs the root filesystem over nfs&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;IDE and debug&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;To play the kernel you need the command line, a good editor like vim/emacs.&#xA;To debug the kernel you need a debugger to run over the jtag.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But for application development you could use the classical way (with a good editor and a lot of makefiles). Or maybe something like eclipse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Application debugging is usually done with gdb.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the linux based you could use a normal text editor or maybe Eclipse.&lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2010-12-27T08:45:47.080" LastActivityDate="2010-12-27T08:45:47.080" CommentCount="4" />
  <row Id="8325" PostTypeId="1" AcceptedAnswerId="8339" CreationDate="2010-12-27T08:43:49.423" Score="3" ViewCount="119" Body="&lt;p&gt;I Am currently looking for battery suggestions for use in one of my projects. My projects current consumption (calculated) is&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;360mA for the main rotor 2.5A stall Link (my exact part RK370SD-4045)&lt;/li&gt;&#xA;&lt;li&gt;400mA for the Mbed uC&lt;/li&gt;&#xA;&lt;li&gt;tail motor ? unknown specs, N30 is the only part reference&lt;/li&gt;&#xA;&lt;li&gt;3x servos &lt;a href=&quot;http://www.e-fliterc.com/Products/Default.aspx?ProdID=EFLRS75&quot; rel=&quot;nofollow&quot;&gt;Link&lt;/a&gt; unknown mA &lt;/li&gt;&#xA;&lt;li&gt;sensor 100mA or less&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Voltage has to be 7.2V to 12V&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I would like to know is what are the pros and cons of each battery? This &lt;a href=&quot;http://batteryuniversity.com/learn/article/whats_the_best_battery&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt; gives some great info but i want real world recommendations and things I should look out for and any other pertinent information when selecting my new battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currently I have looked for batteries and have come to this conclusion, Lead Acid batteries are not a choice in this project, which leaves me with Li-ion batteries, Li-Po, Nimh, NiCd. The original battery was a 9.6V 650mAh Nimh battery and the helicopter had about 20 mins of flight time with the original equipment.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2060" LastEditorDisplayName="" LastEditDate="2010-12-27T10:40:42.550" LastActivityDate="2010-12-27T16:41:03.110" Title="What type of battery to use?" Tags="&lt;power&gt;&lt;battery&gt;" AnswerCount="2" />
  <row Id="8326" PostTypeId="1" AcceptedAnswerId="8335" CreationDate="2010-12-27T09:16:25.163" Score="3" ViewCount="381" Body="&lt;p&gt;I'm new to the amazing wold of electronics and starting out small. I think...&#xA;Early 2010 me and the wife bought a house that was build in 1979. Now I started replacing light switches and encountered something that appears to me as a weird setup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a simple schematic of what I managed to figure out so far:&#xA;&lt;img src=&quot;http://i.imgur.com/Al4II.png&quot; alt=&quot;schematic hallway lights&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this makes no sense at all. What I try to explain is that I have 5 switches that turn on the same light. Each switch has 3 wires, a red, black and blue wire. The light bulb has 2 wires and a ground wire. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The Switches&lt;/strong&gt;&lt;br&gt;&#xA;I can't figure what kind of switches these are and I can't find the location where the yellow wire from the light bulb is connected to the hot wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Below is a picture I've taken from the switch.&#xA;&lt;img src=&quot;http://i.imgur.com/GLijc.jpg&quot; alt=&quot;alt text&quot;&gt;&#xA;The mechanism works like this: When the button is pushed down, I measure zero~ resistance between the top-left and the bottom connection point. Once I release it though the resistance is infinite again. All the other connections always measure infinite resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any pointers on the type of switches or how this could all work is greatly appreciated! I want to learn how all this stuff works and I have a multimeter to measure current/resistance and a lot of other things I don't know much about.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;&lt;br&gt;&#xA;Maybe I shouldn't have drawn the schema as it adds to the confusion but the point is that I have 5 switches with each 3 wires connected. A red one, a blue one and a black one. From what I've measured:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Between blue and red: 230V &lt;/li&gt;&#xA;&lt;li&gt;Between blue and black: 230V &lt;/li&gt;&#xA;&lt;li&gt;Between red and black: 0V (These short circuit if you would connect them)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The button on these switches is indeed sort-of like a pushbutton. You push it down and it comes back up automatically. From what I've measured is when pushed down there is no resistance but once it's back up (you release it), there is again infinite resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I would like to know is how could this be done? What sort of switch is this as I have no clue. A cross switch would need four wires and I only have 3.&lt;/p&gt;&#xA;" OwnerUserId="2403" LastEditorUserId="2403" LastEditorDisplayName="" LastEditDate="2010-12-27T14:18:01.047" LastActivityDate="2011-03-02T23:13:31.903" Title="Home light switch circuit with 5 switches" Tags="&lt;circuit&gt;&lt;light&gt;&lt;switch&gt;" AnswerCount="7" CommentCount="1" />
  <row Id="8327" PostTypeId="1" AcceptedAnswerId="8370" CreationDate="2010-12-27T10:45:50.427" Score="3" ViewCount="191" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to regulate the voltage from a battery down to 5v to power an arduino and a wi-fi webcam. I'm not too keen on a linear regulator as a lot of power is wasted, so that's led me to look at switching regulators. I've also stumbled on UBEC's, which seem to do a similar thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The two components I am looking at are these: -&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Dimension Engineering Switching 5V Regulator 1A - www.technobots.co.uk/acatalog/Shop_Front_Switching_5V_Regulator_1A_516.html&lt;/li&gt;&#xA;&lt;li&gt;Hobbywing 3amp UBEC - www.giantcod.co.uk/hobbywing-3amp-ubec-p-402342.html&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;What's the main difference between these (my load will be under 1A)? Is either one more suitable for my purposes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2393" LastActivityDate="2010-12-28T04:00:28.933" Title="What's the difference between a &quot;Switching Regulator&quot; and a &quot;UBEC&quot;" Tags="&lt;power&gt;&lt;voltage-regulator&gt;" AnswerCount="2" />
  <row Id="8328" PostTypeId="2" ParentId="8325" CreationDate="2010-12-27T11:08:22.710" Score="0" ViewCount="" Body="&lt;p&gt;Does it have any circuit/battery protection if not then Lithium Ion Batteries are out. I would say Nimh and then get a bigger capacity if possible(would make the flight time longer). &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-12-27T11:08:22.710" CommentCount="2" />
  <row Id="8329" PostTypeId="2" ParentId="8231" CreationDate="2010-12-27T11:10:48.853" Score="2" ViewCount="" Body="&lt;p&gt;A simple answer could be that there are two ways:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1.&#xA;You first design your system on high abstraction level (say HDL or schematics).&#xA;Then you try to fit it into PAL/CPLD/FPGA and choose ones that satisfies your requirements (number of gates/logic-elements, performance, etc.) and then choose the cheapest one of these depending what you define cheapest (development cost vs. production cost, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2.&#xA;But usually before you start any HDL coding or schematic development you already can estimate the complexity of the system (how much gates do you need, if it looks like you need 8-bit MCU or 32-bit MCU, or no microcontroller at all). Based on that you can choose your programmable device as well. This would be less precise but will allow to design your non-programmable analog and digital hardware in parallel with programmable hardware and software (if any).&lt;/p&gt;&#xA;" OwnerUserId="2404" LastActivityDate="2010-12-27T11:10:48.853" CommentCount="1" />
  <row Id="8330" PostTypeId="1" CreationDate="2010-12-27T11:21:14.813" Score="2" ViewCount="94" Body="&lt;p&gt;I'm searching a software tool for teaching purpose in order to teach students digital hardware (starting from logic gates level).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have something in mind that will allow making simple graphical schematics and simulate them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In best case it should be free (or at least with time-unlimited demo) and run on Windows, Linux and Mac OS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it could simulate VHDL or any other HDL it would be a plus. &lt;/p&gt;&#xA;" OwnerUserId="2404" LastActivityDate="2010-12-27T14:06:19.523" Title="Is there a free cross-platform tool for pure digital gate-level schematic design and simulation?" Tags="&lt;software&gt;&lt;schematics&gt;&lt;logic&gt;&lt;vhdl&gt;&lt;hdl&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="8331" PostTypeId="2" ParentId="8326" CreationDate="2010-12-27T11:56:06.653" Score="1" ViewCount="" Body="&lt;p&gt;From an electrician's perspective, what you're dealing with is a 6-way switch circuit. 5 switches plus the load (the light) = 6 way switch. The way to make this work is to install a 3-way switch at either end of the run of switches and 4-way switches in the middle. &lt;a href=&quot;http://www.electrical-online.com/wiring-4-way-switch/&quot; rel=&quot;nofollow&quot;&gt;See this page&lt;/a&gt; for decent details on how it works. Electrical standards and &lt;a href=&quot;http://www.allaboutcircuits.com/vol_5/chpt_2/2.html&quot; rel=&quot;nofollow&quot;&gt;color coding are different&lt;/a&gt; in the EU, when looking at that page, remember that here in the States, Black=Hot, White=Neutral, Bare or Green=Earth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you might have your diagram a bit wrong. You show neutral and hot connections to every switch. I think your diagram has neutral and earth/ground backwards. This is an easy mistake as neutral carries no potential and is often connected to earth anyway. You have a mix of blacks and reds connecting the switches. Some of those must be 'travelers' (as discussed in the 4 way switch page above.) What might help is to pull all the switches from the circuit and figure out which of those wires are travelers and to which boxes they connect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Seems like an odd kind of switch you have there. Does it not stay up or down when you switch it one way or the other?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2010-12-27T11:56:06.653" CommentCount="2" />
  <row Id="8332" PostTypeId="2" ParentId="8326" CreationDate="2010-12-27T13:11:23.337" Score="2" ViewCount="" Body="&lt;p&gt;The circuit you've drawn doesn't seem to make much sense. Are you sure there isn't a component missing? Like a device which switches the yellow wire on or off on each pulse on the red wire. Your description of the &quot;switch&quot; makes it sound like a pushbutton.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, the standard circuit for controlling a single light point from several switches is  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/bhuiD.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Left is your phase (brown wire), right is your neutral (blue wire). In Dutch (Peter is from Belgium, I presume the Dutch speaking part) this kind of circuit is often called a &quot;hotelschakeling&quot; (&quot;hotel circuit&quot;), though I don't think that's the official name for it.&lt;br&gt;&#xA;If you have two switch positions you use the top circuit. For three or more the other circuit is used. Middle and bottom are the same circuit, with switch &lt;code&gt;C&lt;/code&gt; in either of its two positions. In Dutch the &lt;code&gt;C&lt;/code&gt;-type switch is called a &quot;kruisschakelaar&quot; (&quot;cross switch&quot;). For more than three switches insert cross switches between &lt;code&gt;A&lt;/code&gt; and &lt;code&gt;C&lt;/code&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-27T13:21:23.327" LastActivityDate="2010-12-27T13:21:23.327" CommentCount="3" />
  <row Id="8333" PostTypeId="2" ParentId="8327" CreationDate="2010-12-27T13:35:12.410" Score="0" ViewCount="" Body="&lt;p&gt;From the pages Google shows when looking up &lt;code&gt;UBEC&lt;/code&gt; it looks like &lt;code&gt;UBEC&lt;/code&gt; is a brand name. In any case it seems to be an ordinary SMPS (switch-mode power supply).&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-27T13:35:12.410" />
  <row Id="8334" PostTypeId="2" ParentId="8330" CreationDate="2010-12-27T13:50:08.377" Score="2" ViewCount="" Body="&lt;p&gt;tkgate. Purely digital event driven gate-level circuit simulation and presumably schematic capture. Should work on many operating systems, including Windows, Mac OS X, Linux and FreeBSD. Also, it's open source.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2010-12-27T14:06:19.523" LastActivityDate="2010-12-27T14:06:19.523" CommentCount="1" />
  <row Id="8335" PostTypeId="2" ParentId="8326" CreationDate="2010-12-27T14:44:30.963" Score="6" ViewCount="" Body="&lt;p&gt;You say that, when you release the button, the contact opens again (resistance goes to infinity). But the light stays on, right? That means there must be some device which has a &quot;memory&quot; of the last action: you push a button, the light goes on and stays on, until you press the button again (or another button). I'm sure there is a device in the cabinet (Dutch: &quot;schakelkast&quot;) which toggles its output on every pulse it receives, and which in this way controls the lamp.&lt;br&gt;&#xA;The wire on the top right of the switch also hints in this direction; it's a signal wire, it's too thin to be a power wire. My hunch is that it carries the pulses to the actual switching device (I don't know what it's called).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Y5yq3.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-27T14:54:25.883" LastActivityDate="2010-12-27T14:54:25.883" CommentCount="3" />
  <row Id="8336" PostTypeId="2" ParentId="8273" CreationDate="2010-12-27T16:06:23.980" Score="2" ViewCount="" Body="&lt;p&gt;The datasheet makes it sound like you need to disconnect the on-chip debugger from port DD before you can use it as a normal port.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;h2&gt;26.4 Functional Description&lt;/h2&gt;&#xA;  &#xA;  &lt;h3&gt;26.4.1 Overview&lt;/h3&gt;&#xA;  &#xA;  &lt;p&gt;[...]&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;In single-chip mode, all pins are configured as digital I/O by default, except for debug data pins (DDATA[3:0]) and processor status pins (PST[3:0]). These pins are configured for their primary functions by default in all modes.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;— &lt;em&gt;&lt;a href=&quot;http://cache.freescale.com/files/32bit/doc/ref_manual/MCF5282UM.pdf?pspll=1&quot; rel=&quot;nofollow&quot;&gt;MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3&lt;/a&gt;, § 26, p. 27&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In most MCUs I've used, alternate functions usually override GPIOs, which has the lowest priority.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-27T16:06:23.980" CommentCount="1" />
  <row Id="8337" PostTypeId="1" AcceptedAnswerId="8342" CreationDate="2010-12-27T16:18:31.113" Score="1" ViewCount="719" Body="&lt;p&gt;I found a website recently about harvesting energy from the air, and I am wondering if someone could tell me why the following wouldn't work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Their &quot;generator&quot; is supposed to make electricity from the ionosphere (not UV, X-Ray, etc). Some claim it can knock out your electric bill totally (a bigger version, not this example). From what I understand, this is possible (it was discovered by Nikola Tesla), however this diagram doesn't look like it would work. Any help would be appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;An example from the website:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;(4) 1N34 germanium diodes&lt;/li&gt;&#xA;&lt;li&gt;(2) 100 µF 50 V electrolytic capacitors&lt;/li&gt;&#xA;&lt;li&gt;0.2 µF 50 V ceramic capacitors&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Here is the electrical diagram they provide:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/21Q4R.png&quot; alt=&quot;Diagram of generator&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And they claimed to power a cell phone with it. I am not sure what kind of antenna to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While this seems like a sham, I just found this website recently and am looking for more info on the physics behind it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps Teslo's patent explains things better, so here it is: &lt;a href=&quot;https://docs.google.com/viewer?a=v&amp;amp;pid=explorer&amp;amp;chrome=true&amp;amp;srcid=0B6Qd42rbY4FvYTdlN2E2MDctN2VhZi00YWYxLThkNTQtMzhiMzllY2E2ODk5&amp;amp;hl=en&quot; rel=&quot;nofollow&quot;&gt;Patent 685958.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Found something:&lt;/strong&gt; Here is a page that explains it. &lt;a href=&quot;http://www.nuenergy.org/alt/tesla_energy.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.nuenergy.org/alt/tesla_energy.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="794" LastEditorUserId="794" LastEditorDisplayName="" LastEditDate="2010-12-29T14:55:16.267" LastActivityDate="2011-01-03T06:08:55.963" Title="Can you harvest electrical energy from the air?" Tags="&lt;power&gt;" AnswerCount="10" CommentCount="15" FavoriteCount="1" />
  <row Id="8338" PostTypeId="2" ParentId="8337" CreationDate="2010-12-27T16:33:39.980" Score="5" ViewCount="" Body="&lt;p&gt;The &quot;air&quot; is full of electric fields. When I touch the probe of my scope with my finger I can see a 50Hz sine wave of 6Vpp. The problem is that your antenna (your finger or anything else) doesn't capture any serious amounts of energy from the fields: once you load the detected voltage it drops to almost nothing. The same with the circuit in your question. So, electricity yes, electrical energy no.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The energy stored in a capacitor is equal to 1/2 * C * V^2. This means that for the same amount of energy the voltage over a capacitor decreases as the capacity increases. So, if you want to use a 10uF capacitor instead of a 1nF the voltage will only be 1% of your starting value, and most likely too low to overcome the diode's voltage drop, even for a germanium diode. BTW, germanium is not going to help, as its voltage drop is almost half of a silicium diode. The solution is a tin diode, which has a neglectible voltage drop. You'll have to cool it to tens of degrees belows zero, however...&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-27T17:08:50.777" LastActivityDate="2010-12-27T17:08:50.777" CommentCount="9" />
  <row Id="8339" PostTypeId="2" ParentId="8325" CreationDate="2010-12-27T16:41:03.110" Score="5" ViewCount="" Body="&lt;p&gt;For hobby flight applications, &lt;strong&gt;lithium polymer&lt;/strong&gt; (&quot;Lipo's&quot;) generally offers the &lt;strong&gt;best performance&lt;/strong&gt; from a weight-to-power or weight-to-energy ratio.  Compared with the theoretical energy density of most cells, Lipo's are quite close as they usually lack the steel casing of most other chemistries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Their downside is a somewhat fussy nature about how they are charged (you must use a Lithium battery charger) and discharged (going below a certain voltage can severely damage the cells, turning them into a potential fire hazard when recharged), and their poor mechanical robustness, due to the aforementioned lack of a steel case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An additional potential negative in using lithium batteries with a NiMH-designed circuit is that their voltage varies dramatically over their discharge curve, from up to 4.4 V when charging down to 3 V when fully discharged.  To fall within a 7.2 to 12 V input, a 2 or 3-cell Lipo should work.  They are usually charged at 4.3-4.4 V/cell, so a 3-cell's open-circuit voltage may be above 12 V.  If the upper limit you cite is absolute, you would be stuck with a 2-cell Lipo, which will drift well below the lower limit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if you're looking for an upgrade from NiMH, Lipo is the way to go.  Respect their hazards and they will provide much entertainment.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2010-12-27T16:41:03.110" CommentCount="3" />
  <row Id="8340" PostTypeId="2" ParentId="8337" CreationDate="2010-12-27T17:17:23.530" Score="5" ViewCount="" Body="&lt;p&gt;To answer the question in your title of &quot;Can you harvest electrical energy from the air?&quot;, yes you can.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you do it efficiently and actually make it a marketable product? If someone has already done it, wouldn't you think it would be all over the news and be very popular?&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-27T18:35:58.690" LastActivityDate="2010-12-27T18:35:58.690" CommentCount="4" />
  <row Id="8341" PostTypeId="2" ParentId="8231" CreationDate="2010-12-27T17:40:44.190" Score="2" ViewCount="" Body="&lt;p&gt;The FPGA with hard core is used since it is less area than a separate microcontroller and faster than a soft-core microprocessor.  However the price is usually worst than a FPGA and a separate microcontroller.  In general software and therefore a microcontroller is better for (relatively) slow and rare cases such as configuration of parameters and error handling; logic is better for continuous processes.  For example in packet processing, writing to a memory should be in logic; handling time-to-live timeout should stay in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Within the FPGA space there are cheap/low power parts and expensive/fast parts.  Generally the microcontroller is only in the expensive one; this make the cost trade vs. a discrete MCU even worse for the on-FPGA solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No one uses PALs in new designs, at least for 10+ years.  CPLDs have taken over that niche.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the last 5? years CPLDs are FPGA-like inside, but with memory to hold the configuration on-chip.  Since FPGAs are now 100's of MHz, speed is much less of a reason to put logic in a CPLD than it was 10-15 years ago.  However the FPGAs still have other features such as multipliers, serializers and many memories that may force a design into one even if it doesn't have that much logic.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2010-12-28T20:51:53.977" LastActivityDate="2010-12-28T20:51:53.977" CommentCount="2" />
  <row Id="8342" PostTypeId="2" ParentId="8337" CreationDate="2010-12-27T17:48:55.233" Score="7" ViewCount="" Body="&lt;p&gt;To address the original question of &quot;Is Nikola Tesla's free energy discovery...&quot;, Tesla never created a &quot;free energy device&quot;.  One of his noted ideas, however, was a system to &lt;strong&gt;intentionally&lt;/strong&gt; &lt;a href=&quot;http://en.wikipedia.org/wiki/Wardenclyffe_Tower&quot; rel=&quot;nofollow&quot;&gt;transmit power wirelessly&lt;/a&gt;.  Power companies don't intentionally radiate energy (as it's a pure loss for them).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an aside, Nikola Tesla was one of the first true electrical engineers, taking arcane, hard-to-understand forces and turning them into marketable solutions.  While there is no doubt he was brilliant, this revolutionary engineer would quickly tell you that if you wanted to harvest &lt;em&gt;naturally occurring&lt;/em&gt; electrical fields (not those he intentionally radiated) it would take an antenna (or an array of them) on a truly grand scale.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Regarding the document you linked:&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Chapter 4 - Tesla's Radiant Energy Device&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;This chapter discusses &lt;a href=&quot;https://docs.google.com/viewer?a=v&amp;amp;pid=explorer&amp;amp;chrome=true&amp;amp;srcid=0B6Qd42rbY4FvYTdlN2E2MDctN2VhZi00YWYxLThkNTQtMzhiMzllY2E2ODk5&amp;amp;hl=en&quot; rel=&quot;nofollow&quot;&gt;a patent by Tesla&lt;/a&gt; which discusses using either the &lt;a href=&quot;http://en.wikipedia.org/wiki/Photoelectric_effect&quot; rel=&quot;nofollow&quot;&gt;photoelectric effect&lt;/a&gt; via &quot;ultra-violet light [...] and Roentgen rays [X-rays]&quot; to generate a positive charge by ejecting electrons, or cathodic rays to capture electrons and generate a negative charge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While you might be able to use the photoelectric effect from solar UV on metals, with great care, you are going to derive an extraordinary small current, certainly far less than you would get with a photo&lt;i&gt;voltaic&lt;/i&gt; (solar) cell.  PV cells use the photoelectric effect, but within a semiconductor.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Chapter 5 - The Tesla Coil&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Tesla coils are essentially antennas that can radiate and receive a great deal of power.  In order to actually capture an appreciable amount, much, much more must be broadcast on the particular wavelength that the coil is tuned to.  Because they are tuned, they cannot capture broadband noise&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-27T22:04:17.713" LastActivityDate="2010-12-27T22:04:17.713" CommentCount="0" />
  <row Id="8343" PostTypeId="1" AcceptedAnswerId="8349" CreationDate="2010-12-27T18:29:19.727" Score="-1" ViewCount="90" Body="&lt;p&gt;I recently got a Sony BRAVIA 46&quot;. When I was mounting to an existing mount, I used the requested machine screws (it says 8 to 12 mm in length. I used 10 mm). I tightened one side and it fit great, nice and snug. However on the other side, i heard a loud crack! I quickly stopped tightening tried to loosen the bolt. I heard what seemed like a piece of plastic fell in the tv and now the screw seems to spin in place. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I think happened was the end of the mounting screw broke the reservoir which held the threading. My options are as follows :&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Leave as is. It still holds tight,&#xA;just doesn't come out.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Take off the back of the tv and drill&#xA;out the bolt and get another even smaller&#xA;one. (I'm afraid to try this in case&#xA;I stripped it completely)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Another option in which comes in a reply.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;What do you all think I should do?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I have contacted Sony and awaiting a reply to see if I can purchase the female mount threading. &lt;/p&gt;&#xA;" OwnerUserId="2407" LastActivityDate="2010-12-27T18:47:32.360" ClosedDate="2010-12-27T21:40:21.137" Title="Internal threading fix for Sony Bravia" Tags="&lt;lcd&gt;&lt;tv&gt;&lt;mount&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="8344" PostTypeId="2" ParentId="8337" CreationDate="2010-12-27T18:36:56.757" Score="0" ViewCount="" Body="&lt;p&gt;Let's suppose the circuit you show works. I don't know if it would, but it seems at least possible that you could harvest small amounts of energy from the electrical noise in the air. How small is small?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit you showed has 4 capacitors-- two 100 uF caps and two that are 500x smaller. Let's ignore the small ones, as they're not used for storage, as David Cary points out in the comments. How much energy can they hold at their peak voltage of 50 V?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The energy capacity of a capacitor is 0.5 * C * V&lt;sup&gt;2&lt;/sup&gt; joules. We have 2 of them, so the total energy is just C * V&lt;sup&gt;2&lt;/sup&gt; joules. Substituting in the actual numbers, that's 100 * 10&lt;sup&gt;-6&lt;/sup&gt; * 50 * 50 = 0.250 joules. We're talking about electricity, so let's convert that to units of kWh, which is how the electric utilities measure energy. 0.250 joules is 7 * 10&lt;sup&gt;-8&lt;/sup&gt; kWh, i.e. 0.00000007 kWh. In the USA, one kWh costs around $0.10, so this is worth around $0.000000007. If I have my zeros right, that circuit (assuming it works perfectly) can store a maximum of about &lt;strong&gt;7 billionths of a dollar worth of energy&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, by hooking the circuit to a cellphone battery, you'd be limiting the capacitor voltage at 3 V, or whatever the battery voltage is. In this case, the capacitors don't actually serve any purpose as their storage capacity is dwarfed by that of the battery, and they also allow some reverse current leakage as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bad news is that if you remove the capacitors, all you have left is some diodes. It's actually common practice to put diodes in this configuration when driving inductive loads like motors to reduce arcing when the motor stops; they're called &quot;flyback&quot; or &quot;freewheeling&quot; diodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, I can say with authority that if you leave a lead acid battery sitting in your garage with just a flyback diode connected, it will not charge itself. With lead acid batteries, they eventually undergo a process known as sulfation, which means that they stop accepting charge. In the long run, you have to load them into your trunk and take them to a household hazardous waste dropoff on a Saturday morning.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll stick with the electric bill, thanks.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-01-03T03:04:26.020" LastActivityDate="2011-01-03T03:04:26.020" CommentCount="14" />
  <row Id="8345" PostTypeId="1" AcceptedAnswerId="8357" CreationDate="2010-12-27T18:37:19.517" Score="3" ViewCount="146" Body="&lt;p&gt;I have a wireless security system at home, and the wireless node is too far from the receiver. I was thinking that I could splice about 10 extra meters of wire into the existing line to move the node close enough to the receiver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From my university days, I remember the I = V / R equation, meaning that with a fixed voltage (from the two AA batteries), if I increase the resistance, the current that gets through will be smaller - possibly not enough to power the wireless node.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How do I determine the resistance of the wire? Is there a standard calculation I can use?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't picked up the wire yet, so I can use another type of wire and a small gauge if that would help.&lt;/p&gt;&#xA;" OwnerUserId="2406" LastActivityDate="2010-12-27T21:26:42.903" Title="is the resistance in ten meters of copper wire too high to use in a circuit powered by AA batteries?" Tags="&lt;battery&gt;&lt;wire&gt;&lt;resistance&gt;" AnswerCount="3" />
  <row Id="8346" PostTypeId="2" ParentId="8337" CreationDate="2010-12-27T18:40:44.163" Score="1" ViewCount="" Body="&lt;p&gt;I've heard of rural inhabitants coming under legal scrutiny for &quot;harvesting energy from the air&quot; by means of massive coils made from, say, chicken-wire (read inductors) situated strategically under certain high-voltage electric transmission lines... anyway remember your ECON101, TNSTAAFL.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt; Apparently it's more efficient to use long perpendicular wire (see comment) &lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-28T00:11:55.067" LastActivityDate="2010-12-28T00:11:55.067" CommentCount="4" />
  <row Id="8347" PostTypeId="2" ParentId="8345" CreationDate="2010-12-27T18:42:35.970" Score="6" ViewCount="" Body="&lt;p&gt;Resistance (&lt;em&gt;R&lt;/em&gt;) is equal to the resistivity of the material (&lt;em&gt;ρ&lt;/em&gt;, Greek rho), divided by the area (&lt;em&gt;A&lt;/em&gt;), times the length (&lt;em&gt;ℓ&lt;/em&gt;).  The resistivity of copper is 1.68 × 10&lt;sup&gt;−8&lt;/sup&gt; Ω·m&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/lFN1Q.png&quot; alt=&quot;resitivity eqn.&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd use a table to just look up what the resistance is, &lt;a href=&quot;http://www.powerstream.com/Wire_Size.htm&quot; rel=&quot;nofollow&quot;&gt;here's one I use occasionally&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To know if this is &lt;em&gt;too much&lt;/em&gt;, one would need to know how much current you intend to draw.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2010-12-27T20:05:35.897" LastActivityDate="2010-12-27T20:05:35.897" CommentCount="2" />
  <row Id="8348" PostTypeId="2" ParentId="8345" CreationDate="2010-12-27T18:43:31.757" Score="2" ViewCount="" Body="&lt;p&gt;If you google &quot;ampacity,&quot; you can find standard charts like &lt;a href=&quot;http://www.cerrowire.com/default.aspx?id=46&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; that will help you figure out what current different size wires can handle. But that won't really be helpful, as AA batteries are so small that most any wire you can buy will handle the current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd just buy a small spool of 24 AWG wire and see if there's any voltage drop across the wire once it's installed-- good chance it will just work.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-27T18:43:31.757" />
  <row Id="8349" PostTypeId="2" ParentId="8343" CreationDate="2010-12-27T18:47:32.360" Score="1" ViewCount="" Body="&lt;p&gt;(Seems like the wrong place for this question, but anyway . . .)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the TV is secure, I'd leave it as is. I suspect that the broken-off threaded piece is acting like a nut inside the case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that seems sketchy, and Sony is no use, I'd remove the back of the TV and use a bolt and nut with a decent sized washer to spread out the pressure on the plastic back of the TV.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-27T18:47:32.360" CommentCount="1" />
  <row Id="8350" PostTypeId="2" ParentId="8271" CreationDate="2010-12-27T19:46:31.710" Score="0" ViewCount="" Body="&lt;p&gt;You use a sampling scope for repetitive signals, e.g. clocks and other signal-integrity issues.  You use a regular DSO (that is the correct term, not a SO) for most everything else.  You use a scope at baseband and a spectrum analyzer for RF.  The FFTs in scopes are for lower-frequency signals, not at RF.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-27T19:46:31.710" CommentCount="1" />
  <row Id="8351" PostTypeId="2" ParentId="6091" CreationDate="2010-12-27T19:47:54.657" Score="0" ViewCount="" Body="&lt;p&gt;Your pricing data is questionable.  For the same series, same bandwidth the 4-channel is usually ~1.5x the 2-channel.  After all the box, display, power supply are shared.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-27T19:47:54.657" CommentCount="2" />
  <row Id="8352" PostTypeId="2" ParentId="8326" CreationDate="2010-12-27T20:02:33.170" Score="0" ViewCount="" Body="&lt;p&gt;@stevenvh is right. &quot;Hotelschakeling&quot; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if the yellow cable is in fact yellow-brown striped, it MUST be the ground or &quot;randaarde of grond&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See all on &lt;a href=&quot;http://en.wikipedia.org/wiki/Multiway_switching&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Multiway_switching&lt;/a&gt; (you can change switch to an similar article in your native language via the left side, right under &quot; languages &quot; )&lt;/p&gt;&#xA;" OwnerUserId="2408" LastActivityDate="2010-12-27T20:02:33.170" />
  <row Id="8353" PostTypeId="2" ParentId="8231" CreationDate="2010-12-27T20:27:26.873" Score="3" ViewCount="" Body="&lt;p&gt;A good &quot;rule-of-thumb&quot; list would go something like this:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;strong&gt;PAL/PLA/GAL:&lt;/strong&gt; Used in place of discrete IC logic gates on a PCB&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;CPLD:&lt;/strong&gt; Used where complex, nonDSP, and possibly time-critical tasks are required (loading boot code onto an FPGA from memory, LUT sinewave generator for DAC, etc)&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;FPGA:&lt;/strong&gt; Used when time critical, multiplication, or DSP capability is required (FIR Filters, FFTs, etc)&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;FPGA with hard MCU:&lt;/strong&gt; Used when FPGA functionality is required and peripherals on the FPGA must be accesed (temp sensors) or to allow a less-time-sensitive task to be implimented in C rather than VHDL for simplicity (UART/serial port functionality, PCB housekeeping, etc)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1571" LastActivityDate="2010-12-27T20:27:26.873" CommentCount="2" />
  <row Id="8354" PostTypeId="2" ParentId="8337" CreationDate="2010-12-27T20:44:00.293" Score="7" ViewCount="" Body="&lt;p&gt;SPICE simulation: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Bogus Tesla Generator&#xA;Vin 1 0 0 SIN(0 1 34k 1ns 1e10)&#xA;C1  1 3 0.2u&#xA;C2  1 2 0.2u&#xA;C3  4 6 100u&#xA;C4  5 4 100u&#xA;D1  3 4 Dgermanium&#xA;D2  4 2 Dgermanium&#xA;D3  6 3 Dgermanium&#xA;D4  2 5 Dgermanium&#xA;RL  5 6 10k&#xA;.model Dgermanium D IS=200p RS=84m N=2.19 TT=144n CJO=4.82p M=0.333 VJ=0.75 EG=0.67 BV=60 IBV=15u&#xA;.control&#xA;delete all&#xA;tran 600u 60&#xA;plot V(5,6)&#xA;.endc&#xA;.END&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;34kHz was chosen for transient analysis &lt;a href=&quot;http://chat.stackexchange.com/transcript/message/264960#264960&quot;&gt;almost arbitrarily&lt;/a&gt;, but it is the AC analysis that tells the story.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vin: 1Vpp 34kHz signal, no load:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/bogustesla4.png&quot; alt=&quot;transient analysis, 1Vpp 34kHz, no load&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vin: 1Vpp 34kHz signal, 10kΩ load:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/bogustesla5.png&quot; alt=&quot;transient analysis, 1Vpp 34kHz&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's check the AC response, from 0.1Hz to 1GHz, again with a 10kΩ load:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/bogustesla6.png&quot; alt=&quot;AC analysis, 1Vpp, 10kΩ load&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's all floating, you say? Well, here's the results with node 4 grounded:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/bogustesla2.png&quot; alt=&quot;transient analysis, 1Vpp 34kHz, no load, node 4 grounded&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/bogustesla3.png&quot; alt=&quot;transient analysis, 1Vpp 34kHz, node 4 grounded&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/bogustesla1.png&quot; alt=&quot;AC analysis, 1Vpp, node 4 grounded&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although 1Vpp is massive to be floating around, what happens when it is large, such as standing in front of a microwave transmitter? (Other than the blocking caps blowing up.)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Vin 1 0 SIN(0 10k 34k 1ns 1e10)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/bogustesla8.png&quot; alt=&quot;transient analysis, 10kVpp 34kHz&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/bogustesla7.png&quot; alt=&quot;AC analysis, 10kVpp&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And with node 4 grounded:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/bogustesla10.png&quot; alt=&quot;transient analysis, 10kVpp 34kHz&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/bogustesla9.png&quot; alt=&quot;AC analysis, 10kVpp 34kHz&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nothin'. Guess it doesn't work. Any corrections or suggestions are appreciated. Code is Berkeley Spice3 compatible'ish, but really isn't fit for anything, including merchantability.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-27T20:54:25.090" LastActivityDate="2010-12-27T20:54:25.090" CommentCount="7" />
  <row Id="8355" PostTypeId="1" AcceptedAnswerId="8358" CreationDate="2010-12-27T21:20:48.743" Score="1" ViewCount="136" Body="&lt;p&gt;I couldn't find an equation for this on Google/Wikipedia, but does the frequency of a function generator (we'll say that it's a sine wave) impact the current output. Example, if I had a 5 volt source and applied it to a 10 ohm load at 50Hz what would be the current seen by the load?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;" OwnerUserId="2409" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-27T22:10:28.940" LastActivityDate="2010-12-27T22:10:28.940" Title="Calculate Current out of Function Generator" Tags="&lt;resistor&gt;&lt;current&gt;&lt;function-generator&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="8356" PostTypeId="2" ParentId="8311" CreationDate="2010-12-27T21:22:06.743" Score="2" ViewCount="" Body="&lt;p&gt;I tried Meego and Angstrom, and settled on Angstrom. It's far easier to make it work, and very stable. The Meego port for beagleboard, on the other hand, had many glitches. I didn't test the other OSes, but I'd say Angstrom seems to be the best choice for both community support and stability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To install the OS is quite simple: you download an OS image to an SD card and make some changes in the bootloader to make it boot from the SD. There are some ready-made OS images at the Angstrom website, along with recipes to install it on the SD. Basically you'll create two partitions: a smaller FAT for the boot and kernel, and the other for the root filesystem containing everything else. Here's one site containing instructions for SD boot:&#xA;&lt;a href=&quot;http://www.xora.org.uk/2009/08/14/omap3-sd-booting/&quot; rel=&quot;nofollow&quot;&gt;http://www.xora.org.uk/2009/08/14/omap3-sd-booting/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also make it boot from the NAND flash, but I'd recommend to save this option for later when you're more comfortable with the device. Since the NAND is limited, you'll need to create a custom image using bitbake to make it fit, that's the kind of work you won't want to do right now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;About debugging, the best way is for you to buy an ethernet-to-usb interface + usb hub. Then you run gdbserver in your beagleboard and can use any gdb-compatible debugging IDE at your PC (I use Eclipse CDT).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the camera interface, the easiest way would be to use the GPIO pins at the expansion connector; the drawback is that you may have a limited frame rate due to the bandwidth limitation, and also yo'll make the processor busy while transfering the image; on the other hand the GPIO is so flexible that you probably won't need any additional circuit to connect them - provided their voltage is compatible (the GPIO works at 1.8 V). There can be other ways if you want a higher frame rate and need the processor available for other parallel tasks, but I'd recommend to leave that for a second round of design.&lt;/p&gt;&#xA;" OwnerUserId="1078" LastEditorUserId="1078" LastEditorDisplayName="" LastEditDate="2010-12-28T16:28:28.190" LastActivityDate="2010-12-28T16:28:28.190" CommentCount="9" />
  <row Id="8357" PostTypeId="2" ParentId="8345" CreationDate="2010-12-27T21:26:42.903" Score="7" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.epanorama.net/documents/wiring/wire_resistance.html&quot; rel=&quot;nofollow&quot;&gt;24 AWG wire is 30.2 milliohms per foot.&lt;/a&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/search?q=10+meters+in+ft&quot; rel=&quot;nofollow&quot;&gt;10 meters is 32.8 feet&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;so &lt;a href=&quot;http://www.google.com/search?q=32.808399+%2a+0.0302&quot; rel=&quot;nofollow&quot;&gt;10 meters of 24 AWG wire is 990 milliohms&lt;/a&gt;.  But you actually have twice that, because the current goes from the battery and back.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So 2 ohms for wire resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;AA batteries have &lt;a href=&quot;http://data.energizer.com/PDFs/BatteryIR.pdf&quot; rel=&quot;nofollow&quot;&gt;a series resistance of about 0.5 ohms new&lt;/a&gt;, and more as they age, so the circuit is probably happy with a little series resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the wireless transmitter draws a peak of 100 mA (a guess) the voltage will dip an extra 0.2 V because of the wiring resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think it would work better with 18 AWG wire, which has about 1/4th the resistance of 24 AWG.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-27T21:26:42.903" />
  <row Id="8358" PostTypeId="2" ParentId="8355" CreationDate="2010-12-27T21:57:51.230" Score="0" ViewCount="" Body="&lt;p&gt;Ideally the function generator is a perfect voltage source for any load. A 5V 50Hz sine wave has the form &lt;code&gt;V(t) = 5*sin(2*pi*50Hz*t) [V]&lt;/code&gt;. &lt;code&gt;V = IR&lt;/code&gt;, giving &lt;code&gt;I(t) = 0.5*sin(2*pi*50Hz*t)&lt;/code&gt;, or a 0.5A-peak, 50Hz sine wave. It looks like your linked device behaves this way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The source and load will be in phase so long as the impedance is real (no inductors, capacitors, etc.).&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-27T22:05:50.473" LastActivityDate="2010-12-27T22:05:50.473" CommentCount="1" />
  <row Id="8359" PostTypeId="2" ParentId="8355" CreationDate="2010-12-27T21:58:08.777" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;if I had a 5 volt source and applied it to a 10 ohm load at 50Hz what would be the current seen by the load?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This is a simple Ohm's law problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5V / 10 ohms = 500 mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the 5 V are RMS, then the mA are RMS.  If the 5V are peak-to-peak, then the mA are peak-to-peak.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-27T21:58:08.777" CommentCount="2" />
  <row Id="8360" PostTypeId="2" ParentId="8355" CreationDate="2010-12-27T22:03:43.703" Score="1" ViewCount="" Body="&lt;p&gt;This comes down to a simple i=v/r. There are 2 things you will most likely need to worry about assuming you aren't at very high frequencies:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What is the max current your function generator can output?&lt;/li&gt;&#xA;&lt;li&gt;Is your load frequency dependent.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;For point 1, you just need to check to see if you are hitting a current limit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For point 2, if your circuit is frequency dependent (has capacitance and/or inductance) then with a fixed voltage, the magnitude of your resistance, and thus your current, will change with frequency.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2010-12-27T22:03:43.703" CommentCount="3" />
  <row Id="8361" PostTypeId="2" ParentId="8326" CreationDate="2010-12-27T23:52:37.340" Score="0" ViewCount="" Body="&lt;p&gt;What you have here is a house where all the switches are wired in parallel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is usually done for a stairway where each floor has a switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your Buttons are a mechanical time delay - you press them in and they slowly come out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;how it should be wired&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/uWHBf.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In some older houses the Live and Neutral to light fitting may be crossed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DO NOT TRUST THE COLOURS OF THE WIRES - If the wiring is from the 1970's then it depends on how the electricians were feeling and what cables they had when wiring.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The UK Colours for 1970 were &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Red - Live&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Black - Neutral&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Green - Earth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Switch could all be in either the live side or neutral side....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your Switches seem to have 2 working terminals &#xA;They seem to be marked O and P the other terminal does nothing (But seems to be connected to O)&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2010-12-27T23:52:37.340" />
  <row Id="8362" PostTypeId="2" ParentId="8197" CreationDate="2010-12-28T00:14:51.433" Score="1" ViewCount="" Body="&lt;p&gt;NO, depending on the type of switch and the design of the circuit - the output could be either&#xA;much lower, 4.5v, 6v or a lot higher.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are different ways of controlling a regulator with a switch&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and there are 4 possible answers... &#xA;A) Both 4.5v and 6V Inputs are selected at once&#xA;B) 4.5V Input Selected&#xA;C) 6V Input Selected&#xA;D) No Input Selected&lt;/p&gt;&#xA;&#xA;&lt;p&gt;B and C are harmless. - Just the same a normal use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A and D cause problems - if both are selected or neither are selected - depending on the design this will cause either a higher or lower voltage - it is impossible to guess without more information... and could cause damage to the unit.&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2010-12-28T00:14:51.433" />
  <row Id="8363" PostTypeId="1" CreationDate="2010-12-28T00:21:14.400" Score="4" ViewCount="310" Body="&lt;p&gt;My objective is to show the results of:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;How do I go about intentionally aliasing a signal?&lt;/li&gt;&#xA;  &lt;li&gt;undersampling&lt;/li&gt;&#xA;  &lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Nyquist_rate&quot; rel=&quot;nofollow&quot;&gt;Nyquist rate&lt;/a&gt; sampling and oversampling&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I'm first going to get the MATLAB code working well, then I'll rewrite it for the MSP430.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First I need to downsample the .wav file to get an incomplete or impartial data stream that I can then reconstuct. Here the flow chart:&lt;br&gt;&#xA;&lt;sub&gt;&lt;strong&gt;analog -&gt; sampling analog filter -&gt; ADC -&gt; resample down -&gt; resample up -&gt; DAC -&gt; reconstruction analog filter&lt;/strong&gt;&lt;/sub&gt;&#xA;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is my first signal processing project using MATLAB (v2010), so be nice. Original code below; updated code &lt;a href=&quot;http://pastebin.com/D0QzMkzy&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    %Play decimated file ( soundsc(y,fs) ) &#xA;%Play Original file ( soundsc(play,fs ) )&#xA;%Play reconstucted File ( soundsc(final,fs) )&#xA;&#xA;[piano,fs]=wavread('piano.wav'); % loads piano&#xA;play=piano(:,1); % Renames the file as &quot;play&quot;&#xA;&#xA;t = linspace(0,time,length(play));          % Time vector&#xA;x = play;&#xA;y = decimate(x,25);&#xA;&#xA;stem(x(1:30)), axis([0 30 -2 2])   % Original signal&#xA;title('Original Signal')&#xA;figure&#xA;stem(y(1:30))                        % Decimated signal&#xA;title('Decimated Signal')&#xA;&#xA;%changes the sampling rate&#xA;&#xA;fs1 = fs/2;&#xA;fs2 = fs/3;&#xA;fs3 = fs/4;&#xA;fs4 = fs*2;&#xA;fs5 = fs*3;&#xA;fs6 = fs*4;&#xA;&#xA;wavwrite(y,fs/25,'PianoDecimation');&#xA;&#xA;&#xA;%------------------------------------------------------------------&#xA;&#xA;%Downsampled version of piano is now upsampled to the original&#xA;[PianoDecimation,fs]=wavread('PianoDecimation.wav'); % loads piano&#xA;play2=PianoDecimation(:,1); % Renames the file as &quot;play&#xA;&#xA;%upsampling&#xA;UpSampleRatio = 2;  % 2*fs = nyquist rate sampling&#xA;play2Up=zeros(length(PianoDecimation)*UpSampleRatio, 1);&#xA;play2Up(1:UpSampleRatio:end) = play2; % fill in every N'th sample&#xA;&#xA;%low pass filter&#xA;&#xA;ResampFilt = firpm(44, [0 0.39625 0.60938 1], [1 1 0 0]);&#xA;&#xA;&#xA;fsUp = (fs*UpSampleRatio)*1;&#xA;wavwrite(play2Up,fsUp,'PianoUpsampled');&#xA;&#xA;%Plot2&#xA;%data vs time plot&#xA;time=(1/44100)*length(play2);&#xA;t=linspace(0,time,length(play2));&#xA;stem(t,play2)&#xA;title('Upsampled graph of piano')&#xA;xlabel('time(sec)');&#xA;ylabel('relative signal strength')&#xA;&#xA;&#xA;&#xA;[PianoUpsampled,fs]=wavread('PianoUpsampled.wav'); % loads piano&#xA;final=PianoUpsampled(:,1); % Renames the file as &quot;play&quot;&#xA;&#xA;&#xA;%-------------------------------------------------------------&#xA;%resampleing&#xA;[piano,fs]=wavread('piano.wav'); % loads piano&#xA;x=piano(:,1); % Renames the file as &quot;play&quot;&#xA;m = resample(x,3,2);&#xA;&#xA;**%this is were i would need to sample it at the different frequecys (both above and below and at) nyquist frequency.*I think.***&#xA;&#xA;soundsc(left,fs) % shows the resaultant audio file , which is the same as original ( only at or above nyquist frequency however) &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;How can I improve this? How do I sample at different frequencies?&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;sup&gt;&lt;em&gt;Note that I've crossposted this on SO, &lt;a href=&quot;http://stackoverflow.com/questions/4542829/how-would-i-down-sample-a-wav-file-then-reconstruct-it-using-nyquist-in-matla&quot;&gt;here&lt;/a&gt;.&lt;/em&gt;&lt;/sup&gt;&lt;/p&gt;&#xA;" OwnerUserId="2386" LastEditorUserId="2386" LastEditorDisplayName="" LastEditDate="2010-12-29T03:24:32.257" LastActivityDate="2010-12-29T03:24:32.257" Title="How do I go about intentionally aliasing a signal, and upsampling work with audio file in MATLAB" Tags="&lt;dsp&gt;" AnswerCount="2" CommentCount="9" />
  <row Id="8364" PostTypeId="2" ParentId="8260" CreationDate="2010-12-28T00:27:31.677" Score="4" ViewCount="" Body="&lt;p&gt;I'm not sure what a &lt;em&gt;digital regenerator&lt;/em&gt; is, as digital signals are reconstructed whenever they pass through a digital element (simplest would be an inverter), but I'll go with this: a buffer, made from two inverters.&#xA;&lt;img src=&quot;http://i.imgur.com/cMpq2.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Inverter&#xA;Vin 1 0 SIN(2.5 2.5 10k 1ns 0)&#xA;Vcc 2 0 5&#xA;M1  3 1 2 2 MP&#xA;M2  3 1 0 0 MN&#xA;M3  4 3 2 2 MP&#xA;M4  4 3 0 0 MN&#xA;RL  4 0 1Meg&#xA;.model MP PMOS level=2&#xA;.model MN NMOS level=2&#xA;.control&#xA;delete all&#xA;tran 30ns 6ms 0 100ns&#xA;plot V(1) V(4)&#xA;.endc&#xA;.END&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/inverter2.png&quot; alt=&quot;sinusoid input, asynchronous&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the inverter is clocked, however, it will look a bit different. Here's the same example with a 32.768 kHz clock:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Inverter&#xA;Vin 1 0 0 SIN(2.5 2.5 10k 10ns 0)&#xA;Vcc 2 0 5&#xA;Vclk    9 0 0 PULSE(0 5 0 10ns 10ns 0.5us 1us)&#xA;M1  3 9 2 2     MP&#xA;M2  4 1 3 2     MP&#xA;M3  4 1 5 0     MN&#xA;M4  5 10 0 0    MN&#xA;M5  6 10 2 2    MP&#xA;M6  7 4 6 2     MP&#xA;M7  7 4 8 0     MN&#xA;M8  8 9 0 0     MN&#xA;M9  10 9 2 2    MP&#xA;M10 10 9 0 0    MN&#xA;RL  7 0 10k&#xA;.model MP PMOS level=2&#xA;.model MN NMOS level=2&#xA;.control&#xA;delete all&#xA;tran 4ns 400us&#xA;plot V(1) V(4)&#xA;.endc&#xA;.END&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/inverter1.png&quot; alt=&quot;32kHz clocked buffer&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... and with a 1 MHz clock:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/inverter3.png&quot; alt=&quot;1MHz clocked buffer&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many variation this can and is likely to take, such as Schmitt trigger input conditioning, different clock schemes, and output voltage clamping.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-28T00:27:31.677" />
  <row Id="8365" PostTypeId="1" AcceptedAnswerId="8368" CreationDate="2010-12-28T00:29:33.237" Score="2" ViewCount="160" Body="&lt;p&gt;Where can one find information on how to put together a minimal linux bootable board based on the cortex A family (like the beagleboard)? Programming information is plentyfull, but hardware knowledge appear more arcane. I'm especially curious about:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;What external components are needed and why.&lt;/li&gt;&#xA;&lt;li&gt;Why dev boards seems to end up around 200$, even though I could get an omap3517 for 15$?&lt;/li&gt;&#xA;&lt;li&gt;What kind of equipment is needed to create prototypes around a chip such as the omap3517?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="941" LastActivityDate="2010-12-28T02:59:44.790" Title="Beginning arm cortex Ax hardware development" Tags="&lt;arm&gt;&lt;hardware&gt;&lt;circuit-design&gt;" AnswerCount="4" />
  <row Id="8366" PostTypeId="2" ParentId="8365" CreationDate="2010-12-28T00:37:28.500" Score="0" ViewCount="" Body="&lt;p&gt;Based on your questions, I fear you are over your head.  You are asking about components rather than specific memories.  You ask about building prototypes, not footprints.  You should stick to a built board.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2010-12-28T00:37:28.500" CommentCount="1" />
  <row Id="8367" PostTypeId="2" ParentId="8365" CreationDate="2010-12-28T02:38:11.173" Score="2" ViewCount="" Body="&lt;p&gt;People don't build their own OMAP boards because you need either 1) an x-ray machine, or 2) extreme patience and experience with re-balling bgas and hot-air rework in order to successfully solder high density bga packages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also asking why the board costs $200 while the chip costs $15 is like complaining about why software costs money even if you use free and open source compiler and libraries.&lt;/p&gt;&#xA;" OwnerUserId="2183" LastEditorUserId="2183" LastEditorDisplayName="" LastEditDate="2010-12-28T02:44:32.413" LastActivityDate="2010-12-28T02:44:32.413" CommentCount="1" />
  <row Id="8368" PostTypeId="2" ParentId="8365" CreationDate="2010-12-28T02:47:32.377" Score="3" ViewCount="" Body="&lt;p&gt;I've been blogging about the Linux board I've been working on starting &lt;a href=&quot;http://pingswept.org/2010/03/31/picking-a-cortex-a8-processor-for-an-embedded-linux-board-in-2010/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and continuing &lt;a href=&quot;http://rascalmicro.com/blog/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. I started thinking I would use a Cortex A8, but eventually settled on the Atmel AT91SAM9G20.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To try to answer your other questions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You can see the components I used in my schematic, but I don't know of a more general explanation of why each is necessary.&lt;/li&gt;&#xA;&lt;li&gt;The processor is only about 10-20% of the total cost of parts. Assembly is another $4-40, depending on the quantity built. I suspect the profit margin is 30-50%.&lt;/li&gt;&#xA;&lt;li&gt;Depending on the package, the OMAP3517 BGA package has either a 1 mm or 0.65 mm ball pitch. Generally, below 0.8 mm pitch, you need to X-ray at least some fraction of the finished boards to check for errors. (Just for the record, the OMAP3517 1 mm packages aren't actually available yet.)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you have other, more specific questions, I'd be glad to try to answer them.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-28T02:47:32.377" CommentCount="1" />
  <row Id="8369" PostTypeId="2" ParentId="8365" CreationDate="2010-12-28T02:59:44.790" Score="2" ViewCount="" Body="&lt;p&gt;For a linux system your essential components will be a processor, ram (probably at least ddr) and flash.  Then you'll need all the extra stuff, power, lcd connectors, usb, ethernet... any peripherals you want, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Beagle board uses a special POP (package on package) technology where the Flash and RAM are literally mounted onto the top of the OMAP.  This is how they can get the board so small.  But... it cost some serious dough, like way more than $15.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2010-12-28T02:59:44.790" />
  <row Id="8370" PostTypeId="2" ParentId="8327" CreationDate="2010-12-28T04:00:28.933" Score="6" ViewCount="" Body="&lt;p&gt;A UBEC (Ultimate Battery Elimination Circuit) is basically a step-down voltage regulator. I feel that the jargon deserves a bit of explanation and history, so here goes:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In hobbyist grade remote control cars/planes/boats/etc. the electronics (receiver, speed controller, servos) need a power source. With engine powered craft, a small 6V battery pack was used to power the electronics. When electric motors became more popular, people wanted to use the large motor battery packs to power the low-power electronics. Typically, the electronic speed controller absorbed this function, and it became known as a Battery Elimination Circuit (BEC). With battery packs usually in the 9V-11V range, the electronics would probably need 5-6V to be happy. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Evidently there has been a push to use higher voltage battery packs (10V-25V), probably to take advantage of the brush-less motors. As a result, if the servos draw any appreciable current, a linear regulator would burn a lot of power. Obviously, when your flight/driving time is based on how efficiently you use your battery, a linear regulator is not what you want. Ultimate Battery Elimination Circuits are basically separate regulators (usually switch-mode) that deliver 5V-6V at hopefully high efficiency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now for the comparison. Your parts basically have two different end-use requirements. The Dimension Engineering product tries to match the form factor of a common linear regulator (7805). It would probably integrate better with any finished PCB you would make, and has a metal shell which hopefully shields EMI. The Hobbywing regulator is a more cost-conscious physical design, with a bit better efficiency spec. Honestly they're pretty much the same thing, so you could probably go with the cheaper one (Hobbywing).&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-28T04:00:28.933" CommentCount="2" />
  <row Id="8371" PostTypeId="2" ParentId="8363" CreationDate="2010-12-28T04:22:47.430" Score="2" ViewCount="" Body="&lt;p&gt;If you want to downsample in a way that produces aliasing, just throw away some fraction of the samples, ie, only keep every 2nd sample, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to downsample in a way that doesn't alias, precede the decimation with a lowpass filter having a cutoff below the nyquist frequency of the sample rate you'll have after you decimate.  Since decimating involves throwing away samples and an FIR lowpass filter has no future dependence on its results, you don't have to bother doing a convolution dot product for the outputs you'd only discard in the decimation, instead you can just skip to the next one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To upsample, insert zeroes between the input samples (use zeroes, &lt;em&gt;do not&lt;/em&gt; repeate the input values).  This produces alias frequencies, so follow with a lowpass filter below the nyquist rate of the original sample rate.  Again, you can design the convolution computation to skip over the zero inputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For small integer ratios of sample rates, discarding or zero inserting samples and FIR filters work very well.  For larger ratios, CIC filters may be preferred as they can be efficiently computed in hardware using wrapping binary computation (you intentionally let the calculations overflow!), though they have a sinc function-shaped rather than rectangular frequency response and so need a clean up filter to select only the rectangular area near the tip of the sinc response and/or compensate for the droop of the sinc.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastEditorUserId="2246" LastEditorDisplayName="" LastEditDate="2010-12-28T06:00:47.903" LastActivityDate="2010-12-28T06:00:47.903" CommentCount="5" />
  <row Id="8372" PostTypeId="2" ParentId="8294" CreationDate="2010-12-28T04:40:04.287" Score="2" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Find a size wire (usually 22 or 24 guage, but insulation thickness matters too) that fits the breadboard nicely.  Ideally you will have multiple colors.  Old multipair telecom/network cable can sometimes be a source.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Place all chips the same side up&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Don't wire over chips.  Space them a few rows apart so you have a wiring channel between them.  Make horizontal runs between the power busses of one breadboard unit and the next below (if you have double busses)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Route and bend wires deliberately.  Solid core wire will stay where you put it if you shape it firmly (don't use the stranded wire with end pins except maybe for jumpers you will move in operation)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Tack wire bundles down.  I've used short jumpers between two holes of the same power bus, and in one case even hot glue to the carrier board.  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If you have 4 or 8 colors available, wire data busses in a spectral order.  If two wires pop out you don't have to trace them, you already &quot;know&quot; which goes where.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If you have a resistor or a cap spanning any distance, use scraps of wire insulation on its leads&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Get some white label stock and stick it on your chips, then using a fine mechanical pencil notate pin numbers or important pins, like &gt; for the clocks, etc.  Or you could probably laser print the whole pinout, like they used to sell... &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You should have the pinout of 74xx series logic and buffers memorized anyway ;-)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;When debugging, always check the power to each chip.  They can confusingly &quot;almost work&quot; with a missing power lead but exhibit odd behavior.  Also remember that many logic families will usually see an open input as a high - though your finger or a probe may change that!&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2246" LastEditorUserId="2246" LastEditorDisplayName="" LastEditDate="2010-12-28T04:45:13.130" LastActivityDate="2010-12-28T04:45:13.130" />
  <row Id="8373" PostTypeId="2" ParentId="8337" CreationDate="2010-12-28T05:05:57.897" Score="3" ViewCount="" Body="&lt;p&gt;Is it possible?  Yes.  But unless you are talking about 'receiving' a man-made source such as a nearby broadcast station or a power line, and even then in conjunction with a huge receiving antenna, it's impractical as a way to obtain more than a tiny amount of power.  But a tiny amount can be enough for a crystal radio, or to power a microcircuit which transmits an extremely weak signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For most power-generation purposes, you'd get orders of magnitude more return on investment from photovoltaics or a wind turbine.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2010-12-28T05:05:57.897" />
  <row Id="8374" PostTypeId="1" AcceptedAnswerId="8375" CreationDate="2010-12-28T06:18:05.367" Score="4" ViewCount="216" Body="&lt;p&gt;Hello, I'm wanting to make a type of electronic &quot;trip wire&quot;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My basic idea is to have like a laser and basically when the laser is interrupted then it sends some signal to a microprocessor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not tied to a laser but it was the first thing that comes to mind. The attributes it needs to have is it needs to be only like a &quot;wire&quot;(as in, it doesn't detect motion anywhere but head on) and it needs to be low power(like run for a few days at least off of 2 AAs). Also, an actual wire is out of the question because it needs to be capable of being &quot;reset&quot; after a certain time out(of say 1 second or so) The range it needs to work with is only 5 or 10 feet though. Also, it's not possible to have two parts to this device like a typical laser-photodiode setup. This needs to be contained all in one (preferably small) package. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is my best bet with this? I was thinking maybe super-sonic sound like &lt;a href=&quot;http://www.sparkfun.com/products/639&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; but I think there would probably be a better way. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So basically what I have in mind for the device is like when you first set it up, you &quot;calibrate&quot; it for a certain distance. So for instance if there is a wall five feet in front of it, then this device would work if there was anything that came head-on with it in 5 feet. And etc. &lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="708" LastEditorDisplayName="" LastEditDate="2010-12-28T09:37:55.583" LastActivityDate="2010-12-29T07:33:42.963" Title="Best way of making a trip-wire type device?" Tags="&lt;infrared&gt;&lt;motion&gt;&lt;laser&gt;&lt;range-detector&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="2" />
  <row Id="8375" PostTypeId="2" ParentId="8374" CreationDate="2010-12-28T07:03:56.453" Score="2" ViewCount="" Body="&lt;p&gt;There are multiple options for such a thing. &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Ultra sonic sonar&lt;/li&gt;&#xA;&lt;li&gt;PIR sensor, used in security systems&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Your best bet I think is to use a PIR sensor like &lt;a href=&quot;http://www.sparkfun.com/products/8630&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-28T10:14:13.990" LastActivityDate="2010-12-28T10:14:13.990" />
  <row Id="8376" PostTypeId="1" AcceptedAnswerId="8378" CreationDate="2010-12-28T10:35:47.083" Score="1" ViewCount="141" Body="&lt;p&gt;I need to test the bandwidth of a variety of video transmitters to figure out the maximum resolution I can safely output without losing detail. To this end, I came up with a solution using a TV pattern generator to generate a proper PAL or NTSC video signal with colour bars or with just blackness, and a 10 MHz signal generator, to generate a pixel clock. However, the 10 MHz signal generator is too expensive for a student like me - about £300 here. The TV pattern generator is only £75, which I can afford. I need a way to generate an adjustable square wave signal from 5 MHz to about 12 MHz, synchronised with a video signal. The frequency doesn't have to be precise, because I can verify it with an oscilloscope. I just need to see the point at which a typical video TX can handle no more pixels, because I have the opportunity to make a high resolution on screen display - but it doesn't matter if no-one can see the pixels!&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-28T17:10:50.917" Title="Testing a video transmitter for video bandwidth" Tags="&lt;signal&gt;&lt;tv&gt;&lt;hf&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="8377" PostTypeId="2" ParentId="7664" CreationDate="2010-12-28T16:02:30.237" Score="3" ViewCount="" Body="&lt;p&gt;Sinking more at low levels, and active-low signals in general dates back to the days of TTL  - now it's just a common convention - no reason to chnage it.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-28T16:02:30.237" />
  <row Id="8378" PostTypeId="2" ParentId="8376" CreationDate="2010-12-28T16:50:15.827" Score="3" ViewCount="" Body="&lt;p&gt;It's not hard to make a oscillator of a few MHz.  In fact, I've done it by accident many times.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use the VCO from a &lt;a href=&quot;http://datasheet.octopart.com/74HCT4046AD-Philips-datasheet-67108.pdf&quot; rel=&quot;nofollow&quot;&gt;74HC4046&lt;/a&gt;.  Supply the chip with power, and setup a pot to feed the VCO input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the VCO isn't a strong enough square wave, feed the output through a few stages of 74HC14 to square it up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really need a phase lock with the video signal, you can phase lock this against the sync output of an LM1881.  Use phase detector II in the '4046 and add your own dividers according to how many pixels you want in a line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With all this said, surely the vendor of the video transmitter has a spec for the video bandwidth it will support?  Also, NTSC kinda defines its own bandwidth requirements. From &lt;a href=&quot;http://en.wikipedia.org/wiki/File%3aNtsc_channel.svg&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Mc6wT.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-28T16:50:15.827" CommentCount="3" />
  <row Id="8379" PostTypeId="2" ParentId="8376" CreationDate="2010-12-28T17:10:50.917" Score="1" ViewCount="" Body="&lt;p&gt;Almost any FPGA evaluation board of the last 6 years vintage will give you an ability to generate clock signals of varied frequency using PLL multipliers and dividers; they probably have too much jitter for radio transmission carrier frequencies, but are fine for modulation.  And you can make actual test pictures using the fpga logic.  A resistive ladder DAC, or just a few resistors from various outputs to give you two video levels and a sync pulse can be used.  You will want to take the input impedance of the video transmitter (probably 75 ohms, but you can test it by making a resistive divider with it as the lower leg) into account when designing these.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you have a scope available, you may do better to use that to measure the voltage for various modulation frequencies and plot a transfer function rather than to rely on a test that also depends on the bandwidth of your display (which if LCD is going to be sampled and then pixelated itself).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may well have a video audio gain control to contend with, so you might want to make a circuit which generates a few cycles of a reference wave at low frequency (say 500 KHz or 1 MHz) and then skips up to a test frequency you control with DIP switches on the board, and outputs that for a half line of video or so, and then goes back to the low frequency.  What you will do is measure the amplitude of the high frequency signal in comparison to that of the low frequency reference, which is there to set the AGC level.  Doing this with square waves you will probably see a rounded off leading edge of the pulses, but the low frequency one will get to a flat top.  The high frequency one will at some frequency never get beyond the rounded portion, and then start not even completing the rise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your scope has good measurement cursors, you might also simply be able to measure the rise time of the low frequency square wave until it reaches its full excursion, and calculate the bandwidth from that.  &lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2010-12-28T17:10:50.917" />
  <row Id="8380" PostTypeId="1" CreationDate="2010-12-28T18:24:27.550" Score="2" ViewCount="90" Body="&lt;p&gt;My harddrive is too loud and it eventually broke after using it 24/7 in a camera monitoring thing over a year, no need for big storage. I am planning to replace it with CF card but I not sure where to find the connector from IDE to my laptop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Things I need&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;CF card&lt;/li&gt;&#xA;&lt;li&gt;CF card to IDE connector such as this &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.10310&quot; rel=&quot;nofollow&quot;&gt;one&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;IDE to some-head connector (?)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;or&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;some SD card rack or similar thing&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;What do you suggest? Which/Where do you get the things to replace harddrive?&lt;/p&gt;&#xA;" OwnerUserId="2387" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-12-28T19:56:08.860" LastActivityDate="2010-12-29T03:24:20.267" ClosedDate="2010-12-29T16:51:55.810" Title="Things for replacing Harddrive with CF card or equivalent?" Tags="&lt;connector&gt;&lt;data&gt;&lt;storage&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="8381" PostTypeId="2" ParentId="8380" CreationDate="2010-12-28T18:31:25.683" Score="1" ViewCount="" Body="&lt;p&gt;Sounds like you don't need a large one so a dedicated solid state disk product may not be needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Probably your laptop has the 44 pin IDE connector to a 1.8&quot; HDD rather than the 40 pin one to a 3.5&quot;.  They are comparable, but the 44 pin has power.  You should be able to find a CF adapter to that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also be able to use a USB memory stick in place of a hard drive if your computer will boot from a usb device.  This is likely to be cheaper than a CF card.  For comparable generations it might be slower, but USB sticks are still popular and advancing while CF cards seem to have fallen from favor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SD cards tend to be slower than USB sticks of the same generation, so you probably don't want to go with that unless your laptop has a built in reader, in which case it could be a neat solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be aware that any flash memory technology may eventually wear out if you are doing a lot of re-write cycles.  On the other hand, if you use a commodity technology it's cheap to replace.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2010-12-28T18:31:25.683" CommentCount="4" />
  <row Id="8382" PostTypeId="2" ParentId="8319" CreationDate="2010-12-28T18:37:03.777" Score="1" ViewCount="" Body="&lt;p&gt;Is there no open space anywhere on the board? Remember that mounting holes don't &lt;strong&gt;have&lt;/strong&gt; to go on the outside edges: you can put them in the middle if need be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there open space around the edges of the PCB? Bud, etc., make enclosures with slots that a board can be placed into, but you'd have to have designed the board to fit an existing enclosure.&#xA;Alternately you can purchase supports that look like square columns with slots in them that will work as board standoffs. I have even used double-sided tape to get a PC board to fit into a small area when I couldn't add space for mounting holes.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2010-12-28T18:37:03.777" CommentCount="1" />
  <row Id="8383" PostTypeId="2" ParentId="2000" CreationDate="2010-12-28T18:44:07.723" Score="1" ViewCount="" Body="&lt;p&gt;I have been working on my project &lt;a href=&quot;http://code.google.com/p/super-osd/&quot; rel=&quot;nofollow&quot;&gt;Super OSD&lt;/a&gt; which supports 192x128 pixel graphics and is open source. I'm planning to migrate to a high resolution display - up to 512x384 pixels bilevel (black and white pixels) or 320x240 with 2-bit greyscale, on a PIC32. A dsPIC33F with SPI and external muxes can easily do it (it's even possible without muxes or SPI, but you get less processing time that way), and it's available in DIP. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-28T18:44:07.723" />
  <row Id="8384" PostTypeId="2" ParentId="8253" CreationDate="2010-12-28T18:45:13.523" Score="3" ViewCount="" Body="&lt;p&gt;In many cases I've seen in online electronics forums, the 741 is designed in by beginners who just don't know of any other opamps. They may have read about it in a textbook or seen it in another old design and assumed it was a reasonable choice. Once they learn that LM324, etc. is readily available, cheap and easier to use, they'll normally switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other big reason already stated is legacy designs. Something works, is still in production, and there's no compelling reason to change it. If you've been selling a product for 30 years and you won't run out of parts, and you won't make any more money by changing to a newer opamp, they why change?&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2010-12-28T18:45:13.523" />
  <row Id="8385" PostTypeId="2" ParentId="8363" CreationDate="2010-12-28T18:47:03.803" Score="2" ViewCount="" Body="&lt;p&gt;I am going to start simple, and build up.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;&lt;pre&gt;&lt;code&gt;F= Frequency&#xA;&#xA;F(Hz=1/s) E.x. 100Hz = 1000 (Cyc/sec) F(s)= 1/(2f)&#xA;&#xA;Example problem: 1000 hz = Highest frequency 1/2(1000hz) = 1/2000 = &#xA;5x10(-3) sec/cyc or a sampling rate of 5ms&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If your highest frequency is 1000Hz and you sample with a period of 5mS(500Hz) your signal has already lost a large amount of its information. You are sampling at 1/4th of the nyquist  rate. For a 1000Hz wave, you must sample at at least 2000Hz, and that is in a perfect world. You really need to go a bit faster than this due to technology limitations, but this is beyond what you need to know.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; What is my nyquist frequency?&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Wait, do you mean &lt;a href=&quot;http://en.wikipedia.org/wiki/Nyquist_frequency&quot; rel=&quot;nofollow&quot;&gt;Nyquist Frequency&lt;/a&gt; or &lt;a href=&quot;http://en.wikipedia.org/wiki/Nyquist_rate&quot; rel=&quot;nofollow&quot;&gt;Nyquist rate&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is probably seeming a pretty trivial distinction, but many people are referencing different things when they switch terms, hell, some people can control they &quot;Symbol Rate&quot; some can control the &quot;Sampling Rate,&quot; some can control both(lucky engineers).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to sample at a frequency that is &lt;strong&gt;greater than double your highest frequency&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you go lower than this your signal will alias, this is irreversible once it has happened, the best you can do is filter off the corrupted part of your signal, but this does not recover information, just removes the corrupted frequencies.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt; Downsampling in Matlab&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Lets say that you have your signal, you have avoided aliasing, and you want to downsample to half the points. This is very easy in matlab. Take a look at the &lt;a href=&quot;http://www.mathworks.com/help/toolbox/signal/decimate.html&quot; rel=&quot;nofollow&quot;&gt;decimate function&lt;/a&gt;. This will handle the mess of making sure your down-sampling does not introduce aliasing, at a cost. When it filters off the higher frequencies, they are lost. This is what you ask for when you half your datapoints. You can just use the &lt;a href=&quot;http://www.mathworks.com/help/toolbox/signal/downsample.html&quot; rel=&quot;nofollow&quot;&gt;downsample function&lt;/a&gt;. If you had the higher frequencies, it will alias. If you know there should not be those frequencies there, you can always use decimate to make sure that noise does not sneak into your system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to go into more detail, but I had to cut myself short as I am out of time for today. Leave me a comment if there is more that would help you, and I will come back and add more information. I am sure I did not cover everything you wanted.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2010-12-28T18:47:03.803" CommentCount="6" />
  <row Id="8386" PostTypeId="2" ParentId="2000" CreationDate="2010-12-28T20:04:22.300" Score="0" ViewCount="" Body="&lt;p&gt;what about a BOB4 - &lt;a href=&quot;http://www.decadenet.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.decadenet.com/&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;not really cheap but I used them in my last job to good effect&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2010-12-28T20:04:22.300" />
  <row Id="8387" PostTypeId="1" AcceptedAnswerId="8397" CreationDate="2010-12-28T21:21:41.943" Score="2" ViewCount="336" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;Reading questions on converting negative voltages to positive ones it has left me with a question that I can't seem to work out. The circuit looks like this:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/8LbjM.gif&quot; alt=&quot;Op Amp Adder&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But you only have the one going to the inverting input.  My question is:   &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;When inputting a positive voltage it doesn't change/very slightly change. So do you have to implement something else for when the voltage is positive? &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;EDIT: &#xA;Image borrowed from Kortuk's answer &lt;a href=&quot;http://electronics.stackexchange.com/questions/3105/how-do-i-measure-a-negative-voltage-with-a-adc/3109#3109&quot;&gt;here&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;                                R&#xA;                               ___&#xA;                       .------|___|----.&#xA;                       |               |&#xA;                       |               |&#xA;                       |               |&#xA;                       |        VCC    |&#xA;                       |         +     |&#xA;          R            |         |     |&#xA;         ___           |       |\|     |&#xA; Input -|___|----------o-------|-\     |   Output&#xA;                               |  &amp;gt;----o----&#xA;                        .------|+/&#xA;                        |      |/|&#xA;                        |        |&#xA;                       ===      ===&#xA;                       GND      GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2010-12-28T21:37:40.427" LastActivityDate="2010-12-29T05:57:34.407" Title="Op amp Adder circuit and positive voltages" Tags="&lt;op-amp&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="8388" PostTypeId="2" ParentId="8387" CreationDate="2010-12-28T21:35:49.647" Score="8" ViewCount="" Body="&lt;p&gt;This circuit will not work with the negative supply pin connected to ground.  It is an inverting circuit, which causes the input voltage to be &quot;mirrored&quot; around the + input, in this case 0V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the opamp's output cannot go beyond the supply rails, which are at 0V and +9V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To fix this you can connect the + input to 4.5V instead of 0V. (This assumes Rf is equal to R0..Rn)  One way to accomplish this is a voltage divider, equal resistors to +9V and ground.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-28T21:35:49.647" />
  <row Id="8389" PostTypeId="1" CreationDate="2010-12-28T22:03:40.893" Score="0" ViewCount="92" Body="&lt;p&gt;I'm trying to fix the floppy drive in my Roland MC-500. The floppy drive inside is a Matsushita DDF3-1 which doesn't seem to be in production anymore. The DDF3-2 is still available, however it is an HD drive. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know off the top of their heads if there is any issue with simply swapping the two drives? Could the power usage be different on the drives? Since the machine is expecting a 720k DD drive, are there any jumper settings to have the HD drive function as a DD drive?&lt;/p&gt;&#xA;" OwnerUserId="2418" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2010-12-28T22:28:35.500" LastActivityDate="2010-12-28T22:41:43.207" ClosedDate="2010-12-29T01:01:50.033" Title="Can a Double-Density Floppy drive be swapped out for a High-Density drive?" Tags="&lt;hardware&gt;&lt;computers&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="8390" PostTypeId="2" ParentId="8389" CreationDate="2010-12-28T22:41:43.207" Score="0" ViewCount="" Body="&lt;p&gt;Don't know...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The difference between DD and HD, I believe is the number of tracks - DD was 40 Tracks and HD was 80 Tracks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A HD drive could read DD disks, but a disk written by a HD drive could not be read by a DD drive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The HD drive had double the number of tracks, which were half the width of DD drive tracks&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Off on a tangent - early PC would work out what type of drive was fitted by counting the number of tracks - step the head out 80 tracks then count when the zero track sensor was triggered.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;HD drives had a extra sensor to detect HD disks and this was an extra signal back to the 'computer'&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Interface for the drive is almost the same - just an extra signal for HD disks.&#xA;The HD signal on a DD drive - is a pin usually described as N/C (Not connected)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A HD Drive can only read DD disks if the controller on the computer Knows to double step the head when reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current requirements would be almost the same. (Possibly lower current requirement for the HD drive)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you try the newer drive - remember that you can only read DD disks and not write them - you should copy all your disks to 'newer' HD disks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the Rowland Device was created in 1988 and 3.5 HD Driver were created in 1987 I don't think the unit would be able to double step the drive....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can post the ID of the FDD controller then I could see if the controller knows how to talk to a HD drive.&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2010-12-28T22:41:43.207" />
  <row Id="8391" PostTypeId="2" ParentId="8319" CreationDate="2010-12-28T23:13:26.233" Score="1" ViewCount="" Body="&lt;p&gt;You can get &lt;a href=&quot;http://www.toby.co.uk/content/catalogue/products.aspx?series=BTS-Lxx-AFx-xxx&quot; rel=&quot;nofollow&quot;&gt;threaded spacers&lt;/a&gt; down to M2 - these are about 4mm dia&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-28T23:13:26.233" />
  <row Id="8392" PostTypeId="2" ParentId="8271" CreationDate="2010-12-28T23:29:49.567" Score="0" ViewCount="" Body="&lt;p&gt;This is a guess (I would have put this into a comment but I don't have the points for it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would guess that Digital Sampling O-scopes probably use heterodyning to mix the incoming high frequency with a fixed carrier frequency, to bring it down to something more manageable, i.e. an Intermediate Frequency, just like a HF radio receivers do.  For instance if you mix a ~5.1Ghz incoming signal with a fixed 5Ghz carrier signal, you end up with a ~.1Ghz beat frequency signal.  (I've long since forgotten all the RF stuff my dad taught me years ago so I may have that wrong)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect SAs do the same thing, at least those capable of working with RF frequencies, anyway.&lt;/p&gt;&#xA;" OwnerUserId="2257" LastActivityDate="2010-12-28T23:29:49.567" CommentCount="4" />
  <row Id="8393" PostTypeId="2" ParentId="8326" CreationDate="2010-12-29T01:54:10.293" Score="1" ViewCount="" Body="&lt;p&gt;They may be remote switches to a controlling device.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do all of the switches look the same?  Some systems use momentary switches to send a pulse of line voltage to the control switch.  The control switch typically looks different because it has the control circuitry.  The remote switches are wired similarly to what you show.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you hear a click (other than the switch you're pressing) when the light is switched?  Some systems use a control device that is mounted in the lamp base or in a basement/ceiling junction box.  The control device likely uses a relay which will &lt;em&gt;click&lt;/em&gt; when switched.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do the lights come on gradually or snap on/off instantly?  In either of the systems above, a light that comes on gradually is controlled by a TRIAC dimmer rather than a relay.  You won't hear the click.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In either case, look for the odd switch or switch sized box hiding in a junction box somewhere. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Google &quot;&lt;a href=&quot;http://www.google.com/search?aq=f&amp;amp;sourceid=chrome&amp;amp;ie=UTF-8&amp;amp;q=home+automation&amp;amp;qscrl=1&quot; rel=&quot;nofollow&quot;&gt;Home Automation&lt;/a&gt;&quot;, specifically &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/X10_%28industry_standard%29&quot; rel=&quot;nofollow&quot;&gt;X10&lt;/a&gt;&quot; if it was done in the 70's&lt;/p&gt;&#xA;" OwnerUserId="2051" LastEditorUserId="2051" LastEditorDisplayName="" LastEditDate="2010-12-29T02:04:19.007" LastActivityDate="2010-12-29T02:04:19.007" />
  <row Id="8394" PostTypeId="2" ParentId="8380" CreationDate="2010-12-29T03:24:20.267" Score="1" ViewCount="" Body="&lt;p&gt;I have used &lt;a href=&quot;http://www.buyextras.com/syhiquidetoc1.html?gclid=CMyE9J7BkKYCFYa7Kgod2zVanQ&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; in the past. They use them a lot in POS equipment or thin clients&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2010-12-29T03:24:20.267" />
  <row Id="8395" PostTypeId="2" ParentId="8374" CreationDate="2010-12-29T04:27:00.823" Score="1" ViewCount="" Body="&lt;p&gt;Use a 555 timer to output 38khz to an &lt;a href=&quot;http://www.sparkfun.com/products/9349&quot; rel=&quot;nofollow&quot;&gt;infrared led&lt;/a&gt; and use an &lt;a href=&quot;http://www.sparkfun.com/products/10266&quot; rel=&quot;nofollow&quot;&gt;IR detector&lt;/a&gt; to output a high signal when the led is pointed at the detector. when the beam is broken, you can trigger an interrupt on the micro. There are lots of details &lt;a href=&quot;http://www.ladyada.net/learn/sensors/ir.html&quot; rel=&quot;nofollow&quot;&gt;on this ladyada tutorial&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2006" LastEditorUserId="2006" LastEditorDisplayName="" LastEditDate="2010-12-29T04:37:27.080" LastActivityDate="2010-12-29T04:37:27.080" />
  <row Id="8396" PostTypeId="2" ParentId="8374" CreationDate="2010-12-29T05:47:41.060" Score="2" ViewCount="" Body="&lt;p&gt;Your requirements:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;strong&gt;line-of-sight activation&lt;/strong&gt;: this means focusing lenses &amp;amp; apertures for LEDs, or a laser.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;self-contained unit&lt;/strong&gt;: this means it must register a reflection from a variety of surfaces.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;low power&lt;/strong&gt;: doesn't really limit implementations, but puts some design constraints on them.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;There are two options:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;strong&gt;Infrared emitter and detector package&lt;/strong&gt;, like the &lt;a href=&quot;http://www.ladyada.net/media/sensors/PNA4602.pdf&quot; rel=&quot;nofollow&quot;&gt;one linked&lt;/a&gt; in &lt;a href=&quot;http://electronics.stackexchange.com/questions/8374/best-way-of-making-a-trip-wire-type-device/8395#8395&quot;&gt;Matt's answer&lt;/a&gt;, but with a &lt;a href=&quot;http://www.dialight.com/Assets/Brochures_And_Catalogs/Illumination/MDEXLUMADBOGD.pdf&quot; rel=&quot;nofollow&quot;&gt;focusing lens&lt;/a&gt; or aperture or a small viewing angle.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Focusing lens, aperture, or small viewing angle is required to maintain directionality.&lt;/li&gt;&#xA;&lt;li&gt;Focusing lens or aperture would be a pain in the butt, and could only be tuned for certain distance ranges.&lt;/li&gt;&#xA;&lt;li&gt;Viewing angles as low as 6&lt;sup&gt;o&lt;/sup&gt; are available. Geometry will tell you what kind of directionality this gives you at a distance.  &lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Laser and photodiode&lt;/strong&gt;: Lasers are available with focusing lens and aperture &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.13378&quot; rel=&quot;nofollow&quot;&gt;for less than $5 each&lt;/a&gt;; photodiodes are &lt;a href=&quot;http://ca.mouser.com/ProductDetail/TAOS/TSL252R-LF/?qs=sGAEpiMZZMtWNtIk7yMEscFVjdrg3sSauchWfwSrPGg%3d&quot; rel=&quot;nofollow&quot;&gt;about the same&lt;/a&gt;. I would use a visible one to make aiming it easier (but require bandpass filtering around carrier frequency to filter out ambient), but it's up to you: there are IR and &lt;sup&gt;(expensive!)&lt;/sup&gt; UV laser diodes. It may take a bit of experimentation to develop an algorithm that filters out ambient effectively and detects weak reflections. &lt;a href=&quot;http://www.lucidscience.com/pro-laser%20spy%20device-1.aspx&quot; rel=&quot;nofollow&quot;&gt;This guy&lt;/a&gt; did something like it. Note that some surfaces will simply gobble up a visible beam (eg. flat black).&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;For &lt;strong&gt;low power operation&lt;/strong&gt;, use sleep modes, pull-up PMOS FETs for &lt;em&gt;always-on&lt;/em&gt; devices, including voltage divider branches (stop current drain when controller is &lt;em&gt;off&lt;/em&gt;), and activate the sensor intermittently. It doesn't sound like it needs to capture any fast single-shot events; going with 20km/h and 10cm objects, a 0&lt;sup&gt;o&lt;/sup&gt; (perfect line) detector would get &lt;strong&gt;18ms&lt;/strong&gt; to react, or just over 55Hz. You could wake-up every 10-15ms, check the &lt;em&gt;line-of-sight&lt;/em&gt; a few times, then go back to sleep. With a switching (or &lt;a href=&quot;http://electronics.stackexchange.com/questions/8112/how-do-i-convert-9-v-dc-to-5-v/8118#8118&quot;&gt;no&lt;/a&gt;) regulator and some intelligent power budgeting in the design phase, you'll easily get this to run for days on AAs.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-29T07:33:42.963" LastActivityDate="2010-12-29T07:33:42.963" />
  <row Id="8397" PostTypeId="2" ParentId="8387" CreationDate="2010-12-29T05:57:34.407" Score="3" ViewCount="" Body="&lt;p&gt;Your first image has an implicit positive and negative power supply, which allows the output to swing above and below the reference voltage (ground). If you assume an ideal op-amp (usually reasonable for these circuits), then the inverting output is a virtual ground - it is driven to the same voltage as the non-inverting input. The current through the feedback resistor (Rf) must be equal to the sum of the currents flowing through the input resistors (R0, R1, Rn...).&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;(V0-Vref)   (V1-Vref)   (V2-Vref)   (Vref-Vout)&#xA;--------- + --------- + --------- = -----------&#xA;   R0           R1         R2           Rf&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;To make the math easy, lets make Rin=R0=R1=R2. The output voltage becomes:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;       -Rf(V0+V1+V2 - 3*Vref)&#xA;Vout = ---------------------- + Vref&#xA;                Rin&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;In the first example, Vref=Ground=0V, which simplifies the equations a bit. If (V0+V1+V2) &gt; 0, then Vout will be negative. If Vout can't be negative, due to a lack of a negative rail or negative voltage headroom, then the circuit stops functioning as intended.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nothing explicity requires you to have a negative rail, and single-supply operation is usually desirable for its simplicity. In order to get the expected signal swing, you need to set Vref to some value between VDD and Ground. A pair of resistors acting as a voltage divider will work, or a poteniometer would allow you to adjust the reference voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the context of &lt;a href=&quot;http://electronics.stackexchange.com/q/3105/638&quot;&gt;this question&lt;/a&gt;, the object was to measure voltages that were always below your ground reference, without having a negative power supply. In that case, a reference voltage of 0 would be OK because the output voltage would never need to swing below the negative rail.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-29T05:57:34.407" />
  <row Id="8398" PostTypeId="1" CreationDate="2010-12-29T07:51:06.397" Score="4" ViewCount="483" Body="&lt;p&gt;So from a general high level standpoint I need to grab data from a serial device and then send this data over bluetooth. I have a bluetooth modem picked out. I understand how to hook it up to the arduino. I however do no know how to hook the a serial device that will talk to the arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems like I am trying to do too many simultaneousness serial connections.&lt;/p&gt;&#xA;" OwnerUserId="2291" LastActivityDate="2011-01-04T16:25:21.620" Title="Using an Arduino to read data from serial device then send data over bluetooth" Tags="&lt;arduino&gt;&lt;serial&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="8399" PostTypeId="2" ParentId="8398" CreationDate="2010-12-29T10:06:41.917" Score="5" ViewCount="" Body="&lt;p&gt;A serial protocol mostly uses a master/slave configuration with different addressing schemes:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;strong&gt;SPI&lt;/strong&gt;: &lt;em&gt;Serial Peripheral Interface&lt;/em&gt;; pins often labeled &lt;em&gt;MOSI, MISO, SS&lt;/em&gt; or &lt;em&gt;Select,&lt;/em&gt; and &lt;em&gt;S&lt;sub&gt;CLK&lt;/sub&gt;&lt;/em&gt; or &lt;em&gt;CLK&lt;/em&gt;.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/playground/uploads/Code/Spi.zip&quot; rel=&quot;nofollow&quot;&gt;Here is a library&lt;/a&gt; and &lt;a href=&quot;http://arduino.cc/en/Reference/SPI&quot; rel=&quot;nofollow&quot;&gt;user guide&lt;/a&gt;. Pins 10-13 are used.&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;I&lt;sup&gt;2&lt;/sup&gt;C&lt;/strong&gt; / &lt;strong&gt;TWI&lt;/strong&gt;: &lt;em&gt;Inter-Integrated Circuit&lt;/em&gt; / &lt;em&gt;Two Wire Interface&lt;/em&gt;; pins often labeled &lt;em&gt;SDA&lt;/em&gt; and &lt;em&gt;SCL&lt;/em&gt;.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/en/Reference/Wire&quot; rel=&quot;nofollow&quot;&gt;The library is included, called &lt;strong&gt;Wire&lt;/strong&gt;&lt;/a&gt;, and &lt;a href=&quot;http://www.neufeld.newton.ks.us/electronics/?p=241&quot; rel=&quot;nofollow&quot;&gt;here is a user guide&lt;/a&gt;. Pins 4 and 5 are used with the Arduino Diecimila.&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;1-Wire&lt;/strong&gt;: Actually needs two or more wires -- at least power/data and ground.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.pjrc.com/teensy/td_libs_OneWire.html&quot; rel=&quot;nofollow&quot;&gt;Here is a library and user guide&lt;/a&gt; or &lt;a href=&quot;http://www.arduino.cc/playground/Learning/OneWire&quot; rel=&quot;nofollow&quot;&gt;two&lt;/a&gt;. Uses any free &lt;a href=&quot;http://en.wikipedia.org/wiki/General_Purpose_Input/Output&quot; rel=&quot;nofollow&quot;&gt;GPIO&lt;/a&gt;.&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/UNI/O&quot; rel=&quot;nofollow&quot;&gt;UNI/O&lt;/a&gt;&lt;/strong&gt;: used with some EEPROM ICs from &lt;a href=&quot;http://microchip.com&quot; rel=&quot;nofollow&quot;&gt;Microchip&lt;/a&gt;; will likely have to &lt;a href=&quot;http://arduino.cc/en/Hacking/LibraryTutorial&quot; rel=&quot;nofollow&quot;&gt;write your own library&lt;/a&gt;.&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;U[S]ART&lt;/strong&gt;: &lt;em&gt;Universal [Synchronous/] Asynchronous Receiver/Transmitter&lt;/em&gt;; typically does not use master/slave configuration, only being used for point-to-point communication.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The library is built in, and there are &lt;a href=&quot;http://www.arduino.cc/playground/Code/SimpleMessageSystem&quot; rel=&quot;nofollow&quot;&gt;extensions&lt;/a&gt; (&lt;a href=&quot;http://arduino.cc/en/Reference/Firmata&quot; rel=&quot;nofollow&quot;&gt;two&lt;/a&gt;) and &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1235799875/13&quot; rel=&quot;nofollow&quot;&gt;optimizations&lt;/a&gt;. It uses pins 0 and 1.&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;USB&lt;/strong&gt;: &lt;em&gt;Universal Serial Bus&lt;/em&gt;; uses a host/device scheme akin to master/slave. Pins often labeled &lt;em&gt;V&lt;sub&gt;CC&lt;/sub&gt;, DATA+, DATA-,&lt;/em&gt; and &lt;em&gt;ground&lt;/em&gt; or &lt;em&gt;GND&lt;/em&gt;.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2007/blh36_cdl28_dct23/blh36_cdl28_dct23/index.html&quot; rel=&quot;nofollow&quot;&gt;Although possible without&lt;/a&gt;, usually requires extra hardware and interpreters for 8-bit micros like the Arduino to use. Ready-made Arduino platforms have USB-to-serial converter chips for IDE communication and &lt;a href=&quot;http://arduino.cc/en/Reference/Firmata&quot; rel=&quot;nofollow&quot;&gt;extensions&lt;/a&gt;; there are also &lt;a href=&quot;http://www.practicalarduino.com/projects/virtual-usb-keyboard&quot; rel=&quot;nofollow&quot;&gt;some shields&lt;/a&gt; (&lt;a href=&quot;http://code.google.com/p/vusb-for-arduino/&quot; rel=&quot;nofollow&quot;&gt;with libraries&lt;/a&gt;).&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;PS/2&lt;/strong&gt;: &lt;em&gt;Personal System/2 connector&lt;/em&gt;, an old IBM PC std. connector; pins are often labeled &lt;em&gt;V&lt;sub&gt;CC&lt;/sub&gt;, DATA, CLK,&lt;/em&gt; and &lt;em&gt;ground&lt;/em&gt; or &lt;em&gt;GND&lt;/em&gt;; often made interchangeable with USB sockets.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/playground/uploads/Main/PS2Keyboard002.zip&quot; rel=&quot;nofollow&quot;&gt;Here is a library&lt;/a&gt; and &lt;a href=&quot;http://www.arduino.cc/playground/Main/PS2Keyboard&quot; rel=&quot;nofollow&quot;&gt;guide&lt;/a&gt;. Any GPIO can be used for &lt;em&gt;DATA&lt;/em&gt;, but pin 3 must be &lt;em&gt;CLK&lt;/em&gt;.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The library &lt;a href=&quot;http://arduiniana.org/libraries/NewSoftSerial/&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;NewSoftSerial&lt;/strong&gt;&lt;/a&gt; by &lt;a href=&quot;http://arduiniana.org/&quot; rel=&quot;nofollow&quot;&gt;Mikal Hart&lt;/a&gt; allows the user to implement an interrupt-driven software (as opposed to hardware, like UART peripherals) routine for serial communications. Use it if you need to, but be aware that debugging clashing interrupts is more challenging than debugging polling routines (which is apparently what the default libraries do).&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-29T10:06:41.917" />
  <row Id="8400" PostTypeId="2" ParentId="433" CreationDate="2010-12-29T10:57:32.277" Score="4" ViewCount="" Body="&lt;p&gt;While I would love to dive into the various programming methods available, someone else already has. Here is &lt;strong&gt;Dean Camera&lt;/strong&gt;'s tutorial on AVRFreaks, &lt;em&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=38691&amp;amp;start=0&amp;amp;postdays=0&amp;amp;postorder=asc&amp;amp;highlight=&quot; rel=&quot;nofollow&quot;&gt;AVR Programming Methods&lt;/a&gt;:&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;There are many ways to program AVR&#xA;  microcontrollers. Since many people&#xA;  ask about different ones at one time&#xA;  or another, I thought I'd outline them&#xA;  here so that their questions can be&#xA;  answered quickly and efficiently.&#xA;  Please forgive me if I miss a method&#xA;  or make an error. &lt;/p&gt;&#xA;  &#xA;  &lt;h2&gt;METHOD 1: In System Programming (ISP)&lt;/h2&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Supported By:&lt;/strong&gt; Vast majority of AVRs (see below posts)&lt;br&gt;&#xA;  &lt;strong&gt;Supported Programmers:&lt;/strong&gt; AVRISP MKI/II, JTAG MKII, STK500, STK600,&#xA;  Dragon, AVRISP clones, AVR910&#xA;  Programmers, AVRONE   In System&#xA;  Programming is perhaps the most common&#xA;  method of programming the flash,&#xA;  EEPROM, fuse and lockbytes of the&#xA;  entire AVR line. ISP can program AVRs&#xA;  at extremely high clock rates&#xA;  (assuming the target AVR is running at&#xA;  a high frequency and the programmer&#xA;  supports it) and is the method of&#xA;  choice for almost all AVR hobbyists.&#xA;  There are many, many AVRISP clones and&#xA;  AVR910 programmers on the market in&#xA;  addition to simple do-it-yourself&#xA;  dongles which connect to your&#xA;  computer's parallel port. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Recent new dongle designs may use the&#xA;  computer's serial port, however&#xA;  anecdotal evidence has said that this&#xA;  method is &lt;em&gt;extremely&lt;/em&gt; slow due to&#xA;  technical limitations. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;ISP requires that the target AVR is&#xA;  running at a clock rate of at least&#xA;  four times that of the ISP clock. This&#xA;  is a common pitfall and a source of&#xA;  confusion to many new to AVRs.&lt;/p&gt;&#xA;  &#xA;  &lt;h2&gt;METHOD 2: JTAG&lt;/h2&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Supported By:&lt;/strong&gt; See AVRStudio Tools help for MKI and MKII device support&lt;br&gt;&#xA;  &lt;strong&gt;Supported Programmers:&lt;/strong&gt; JTAG-ICE, JTAG-ICE MKII, Dragon, JTAG-ICE&#xA;  clones, AVRONE, STK600 (programming&#xA;  only)   Technically JTAG is a&#xA;  debugging system, not a programming&#xA;  method. Still, the JTAG interface&#xA;  allows for the programming of an AVR&#xA;  which supports it. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;JTAG is an in-system debugging tool&#xA;  which allows you to manipulate and&#xA;  examine the status of a supported AVR&#xA;  while it is running in a circuit. JTAG&#xA;  allows the user to stop execution at&#xA;  any time, the manipulation of the&#xA;  AVR's internal registers and much&#xA;  more. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The official JTAG-ICE units from ATMEL&#xA;  have been superseded by the JTAG-ICE&#xA;  MKII, which supports the newer and&#xA;  more widely supported across the AVR&#xA;  range DebugWire debugging protocol as&#xA;  well as programming via the ISP method&#xA;  (see above). &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;JTAG-ICE clones are available for low&#xA;  prices, however their limited&#xA;  compatibility with only a handful of&#xA;  AVRs limits their usefulness.&#xA;  Regardless of this, if your AVR&#xA;  supports the JTAG interface the&#xA;  JTAG-ICE remains a very nice and&#xA;  effective debugging method and&#xA;  programmer.&lt;/p&gt;&#xA;  &#xA;  &lt;h2&gt;METHOD 3: DebugWire&lt;/h2&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Supported By:&lt;/strong&gt; Many smaller AVRs&lt;br&gt;&#xA;  &lt;strong&gt;Supported Programmers:&lt;/strong&gt; JTAG-ICE MKII, Dragon, AVRONE   Again DebugWire&#xA;  is a debugging rather than a&#xA;  programming interface, but can be used&#xA;  to load in programs into supported&#xA;  AVRs. The dW interface uses a single&#xA;  AVR pin (the /RESET line) for all&#xA;  communications, making it ideal for&#xA;  the low-pin count AVR devices.&lt;/p&gt;&#xA;  &#xA;  &lt;h2&gt;METHOD 4: Bootloader&lt;/h2&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Supported By:&lt;/strong&gt; Most newer AVRs&lt;br&gt;&#xA;  &lt;strong&gt;Supported Programmers:&lt;/strong&gt; N/A   Again technically not a programming method.&#xA;  A bootloader is a small AVR program&#xA;  which sits in a user-settable reserved&#xA;  section of the regular flash.&#xA;  Bootloaders make use of the flash&#xA;  self-modification features available&#xA;  in the newer AVRs to allow the AVR to&#xA;  program itself via program data loaded&#xA;  from an external source. Bootloaders&#xA;  may source their data from any&#xA;  location (eg external dataflash or SD&#xA;  card) however by far the most common&#xA;  type of Bootloader communicates with a&#xA;  PC via the AVR's RS-232 (serial) port.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Bootloaders are limited in that they&#xA;  do consume flash space (limiting the&#xA;  size of the flash available to the&#xA;  AVR's application) and they are unable&#xA;  to change the AVRs fusebits. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Bootloaders are widely available on&#xA;  the internet for download, but they&#xA;  suffer from a &quot;chicken and egg&quot;&#xA;  problem; you need another type of&#xA;  programmer listed here to program in&#xA;  the bootloader in the first place.&#xA;  This is usually solved by the&#xA;  construction of a simple parallel port&#xA;  dongle (See ISP section) or by the&#xA;  purchase of an AVR already preloaded&#xA;  with a bootloader (eg the AVRButterfly&#xA;  board).&lt;/p&gt;&#xA;  &#xA;  &lt;h2&gt;METHOD 5: High Voltage Parallel Programming (HVPP)&lt;/h2&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Supported By:&lt;/strong&gt; Most non-TINY AVRs (with exceptions)&lt;br&gt;&#xA;  &lt;strong&gt;Supported Programmers:&lt;/strong&gt; STK500, STK600, Dragon, Homebrew Dongles,&#xA;  AVRONE   High Voltage Parallel&#xA;  Programming is a method of programming&#xA;  which is rarely used, because of the&#xA;  hassle it requires to set up. Despite&#xA;  this, HVPP programming is commonly&#xA;  used to &quot;resurrect&quot; AVRs whose&#xA;  fusebits have been mis configured via&#xA;  another programming method. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Both the STK500 and the Dragon&#xA;  supports HVPP. During HVPP, the&#xA;  target's /RESET pin is raised to the&#xA;  unusually high value of 12V which&#xA;  engages the internal parallel&#xA;  programming circuitry. The /RESET pin&#xA;  is the only pin of the AVR (on HVPP&#xA;  supported AVRs) which can be safely&#xA;  raised to this level. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;You can make your own HVPP dongle&#xA;  using online plans such as this one.&lt;/p&gt;&#xA;  &#xA;  &lt;h2&gt;METHOD 6: High Voltage Serial Programming (HVSP)&lt;/h2&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Supported By:&lt;/strong&gt; Many TINY AVRs (with exceptions)&lt;br&gt;&#xA;  &lt;strong&gt;Supported Programmers:&lt;/strong&gt; STK500, STK600, Dragon, Homebrew Dongles,&#xA;  AVRONE   HVSP is similar to HVPP,&#xA;  except the data transfer is performed&#xA;  serially rather than in parallel. This&#xA;  is the alternate programming method&#xA;  used on many TINY series AVRs who lack&#xA;  enough pins for HVPP.&lt;/p&gt;&#xA;  &#xA;  &lt;h2&gt;METHOD 7: PDI&lt;/h2&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Supported By:&lt;/strong&gt; XMEGA AVRs&lt;br&gt;&#xA;  &lt;strong&gt;Supported Programmers:&lt;/strong&gt; STK600, AVRONE, JTAG MKII, Dragon, AVRISP MKII&#xA;  PDI is the new programming interface&#xA;  based on the debugWire protocol, for&#xA;  the XMEGA line of AVRs. It's not&#xA;  currently used on any other 8-bit AVR&#xA;  microcontrollers.&lt;/p&gt;&#xA;  &#xA;  &lt;h2&gt;METHOD 8: TPI&lt;/h2&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Supported By:&lt;/strong&gt; 6-Pin TINY AVRs (ATTINY10, etc.)&lt;br&gt;&#xA;  &lt;strong&gt;Supported Programmers:&lt;/strong&gt; STK600, Dragon, AVRISP MKII   TPI is a very&#xA;  tiny programming interface for the&#xA;  newer TINY line of AVRs with limited&#xA;  pins, like the 6 pin ATTINY10. Like&#xA;  dW, TPI uses the device's /RESET line&#xA;  as part of the communication&#xA;  interface, but there the similarity&#xA;  ends. Since the pint-sized TINY AVRs&#xA;  lack a on-chip debugging circuit, the&#xA;  TPI protocol uses a new programming&#xA;  interface of three pins, in a&#xA;  half-duplex protocol. Because the&#xA;  /RESET line needs to be raised to +12V&#xA;  for programming when the device's&#xA;  RSTDSB pin is set, this is currently&#xA;  only supported by the newer STK600&#xA;  programming board.&lt;/p&gt;&#xA;  &#xA;  &lt;h3&gt;Bonus FAQ Section!&lt;/h3&gt;&#xA;  &#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;&lt;p&gt;&lt;em&gt;Which is the best method?&lt;/em&gt;   There is no universal &quot;best&quot; method. ISP&#xA;  programming is simple and extremely&#xA;  popular, however all the above methods&#xA;  will work. The two high voltage&#xA;  programming modes (whichever is&#xA;  applicable to your device) are the&#xA;  most feature rich, as they allow for&#xA;  the repair of an AVR which has had its&#xA;  fuses misconfigured. However, those&#xA;  methods are a pain to set up, hence&#xA;  the reason most users go with with&#xA;  ISP. &lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;&lt;em&gt;I've made a parallel port dongle. Can I use it with AVRStudio?&lt;/em&gt;   I'm&#xA;  afraid not. AVRStudio cannot interface&#xA;  with any &quot;dumb&quot; dongles - it requires&#xA;  a smart programming device -&#xA;  containing a microcontroller itself -&#xA;  to decipher the communication protocol&#xA;  it sends. Simple dongles without a&#xA;  microcontroller must be &quot;bit-banged&quot;&#xA;  (ie. the appropriate signals simulated&#xA;  through the dongle via the computer)&#xA;  itself. &lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;&lt;em&gt;So my dongle's useless then?&lt;/em&gt;   No. You can still program through a&#xA;  home made dongle with a third party&#xA;  programming software tool. AVRDude is&#xA;  a good, known, free command line&#xA;  utility - and it comes included with&#xA;  the WinAVR package. &lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;&lt;em&gt;What are my options if I want my programmer to work with AVRStudio?&lt;/em&gt;&lt;br&gt;&#xA;  Choose a programmer that uses an&#xA;  AVRStudio-supported protocol. This can&#xA;  be the simple &quot;AVR910&quot; protocol&#xA;  (deprecated) or a custom&#xA;  implementation of the protocol used by&#xA;  the STK500/AVRISP. Note that these&#xA;  programmers require a micro controller&#xA;  in them, leading to a catch-22&#xA;  situation. This may be solved by&#xA;  having the programmer's AVR&#xA;  pre-programmed at time of purchase&#xA;  with the appropriate firmware, or by&#xA;  having the AVR pre-programmed with a&#xA;  bootloader. &lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;&lt;em&gt;Ok, I want to use a bootloader. How do I get it in there in the first&#xA;  place?!&lt;/em&gt;   To use a bootloader in an&#xA;  AVR, you first have to have the&#xA;  bootloader programmed in. If you do&#xA;  not have an existing programmer (even&#xA;  a simple dumb dongle will suffice for&#xA;  the initial programming), you can&#xA;  alternatively purchase AVRs&#xA;  pre-programmed with a bootloader from&#xA;  several suppliers.  &lt;br&gt;&lt;br&gt; Atmel&#xA;  also manufactures the Butterfly demo&#xA;  board, whose MEGA169 AVR comes&#xA;  pre-loaded with an AVR-Studio&#xA;  compatible bootloader. &lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;&lt;em&gt;Help! I've messed with the fuses and knackered my AVR while using ISP!&lt;/em&gt;&#xA;  The most common mistake is changing&#xA;  the clock selection fuses to an&#xA;  invalid setting. Try putting an&#xA;  external clock on the AVR's XTAL1 pin&#xA;  and see if that helps.  &lt;br&gt;&lt;br&gt;&#xA;  Failing that, if possible use one of&#xA;  the high-voltage methods. These will&#xA;  fix any misconfiguration, including&#xA;  ones involving the clock source as the&#xA;  high-voltage methods provides its own&#xA;  clock to the AVR for programming. &lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;&lt;em&gt;How do I interface with my programmer?&lt;/em&gt;   Which software you use&#xA;  to interface with your programmer&#xA;  depends on the type of programmer you&#xA;  are using.  &lt;br&gt;&lt;br&gt; Simple &quot;dumb&quot;&#xA;  dongles require third party software,&#xA;  such as PonyProg or AVRDude. These may&#xA;  be command line or GUI tools - look&#xA;  around on the web and you will fine&#xA;  one to fit your needs.  &lt;br&gt;&lt;br&gt;&#xA;  Programmers and bootloaders based on&#xA;  the AVR910 protocol can be used within&#xA;  AVRStudio. From the Tools menu, select&#xA;  the &quot;AVRProg&quot; option to open up a GUI&#xA;  screen to interface with your&#xA;  programmer. As an alternative, third&#xA;  party tools such as AVRDude are also&#xA;  AVR910 compatible.  &lt;br&gt;&lt;br&gt; Official&#xA;  tools are tightly integrated into&#xA;  AVRStudio, especially in the case of&#xA;  the debugging variants&#xA;  (JTAG/Dragon/etc). From the AVRStudio&#xA;  Tools menu, select the &quot;Program&#xA;  AVR...&quot; submenu and click the&#xA;  &quot;Connect&quot; item. From the new window,&#xA;  select your tool and its connection&#xA;  interface and click ok.  &lt;br&gt;&lt;br&gt; As&#xA;  is the case with the dumb dongles and&#xA;  AVR910 programmers, the official tools&#xA;  may also be used with third party&#xA;  programming software. &lt;/p&gt;&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;  &#xA;  &lt;p&gt;&lt;sup&gt;(C) Dean Camera, 2009. All rights&#xA;  reserved. Not for reproduction on any&#xA;  website other than AVRFreaks.net&#xA;  without prior explicit&#xA;  permission.&lt;/sup&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;sup&gt;Reproduced &lt;strong&gt;with&lt;/strong&gt; prior explicit permission, of course!&lt;/sup&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-29T10:57:32.277" />
  <row Id="8401" PostTypeId="2" ParentId="8319" CreationDate="2010-12-29T13:30:35.623" Score="0" ViewCount="" Body="&lt;p&gt;Is this unit going to be provided for people to fit themselves or are you going to fit the unit into a specific model plane and sell it as a whole, or fit it for people in their planes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this a fit-and-forget project or will it be fitted and taken out regularly?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am wondering whether standoffs are a no-go because you'd have to fix the pillars into the plane and that will mean drilling holes - possibly on a non-flat surface or where the screws will show on the outside? I also doubt self adhesive standoffs will survive the vibration and moisture/dust for very long.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the unit is pretty much a fit-and-forget thing then I wonder whether it could be secured with some expanding polyurethane foam (PU foam) around the base and edges - or even across the whole unit with masking (eg adhesive tape) left in place to allow slots to be formed for the connectors and switches - this would 'pot' the unit against environmental issues and avoid the need for a case. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The foam would give a vibration-tolerant mount and the unit could be cut out later with a knife if really necessary. The only issues are whether the foam is OK on the plane's plastics and the customers accept this form of mounting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bonus: No PCB land required for the mounting holes so you can make it even smaller!&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2010-12-29T13:30:35.623" CommentCount="1" />
  <row Id="8402" PostTypeId="1" AcceptedAnswerId="8403" CreationDate="2010-12-29T13:54:21.740" Score="3" ViewCount="346" Body="&lt;p&gt;I'm trying to build a stereo speaker system for use on a laptop. I want to keep it as simple as possible, so I'm thinking of using laptop's audio output to for the audio signal and a USB port for power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I know, each port should be able to provide 100 mA for devices. Is there any need to signal to the computer that I'm going to try to draw 100 mA, or is it acceptable to just connect the device?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, how stabilized and filtered is USB power? I'm thinking of using &lt;a href=&quot;http://www.quasarelectronics.com/kit-files/datasheets/tda7053a.pdf&quot; rel=&quot;nofollow&quot;&gt;TDA7053A&lt;/a&gt; to drive the speakers and its minimum voltage is 4.5 V. If that doesn't work, I'd use two &lt;a href=&quot;http://kitsrus.com/projects/tda7052.pdf&quot; rel=&quot;nofollow&quot;&gt;TDA7052&lt;/a&gt; amplifiers, but I'd like to keep number of parts as low as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for power consumption, I already have a small radio which uses one 50 Ω speaker and a TDA7052 and it uses at most 25 mA, so even with two of those speakers, I should have lots of power to spare with a maximum supply current of 100 mA.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2010-12-30T06:30:12.090" LastActivityDate="2011-01-18T09:32:12.333" Title="What's needed to get 100 mA from a USB port?" Tags="&lt;power&gt;&lt;power-supply&gt;&lt;usb&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="8403" PostTypeId="2" ParentId="8402" CreationDate="2010-12-29T14:00:56.410" Score="4" ViewCount="" Body="&lt;p&gt;I haven't experimented with USB power, but &lt;a href=&quot;http://www.girr.org/mac_stuff/usb_stuff.html&quot; rel=&quot;nofollow&quot;&gt;this analysis&lt;/a&gt; seems to point to it working just fine. At 100ma all tested devices remain above 4.5v. I believe you can just connect to the port... you can test this simply by plugging in a USB cable and checking the pins on the other end with a multimeter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the &lt;a href=&quot;http://www.usb.org/developers/docs/usb_20_081810.zip&quot; rel=&quot;nofollow&quot;&gt;full USB spec&lt;/a&gt;&#xA;and here's &lt;a href=&quot;http://www.usb.org/developers/docs/&quot; rel=&quot;nofollow&quot;&gt;all other docs from usb.org&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2344" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-29T14:37:32.273" LastActivityDate="2010-12-29T14:37:32.273" CommentCount="2" />
  <row Id="8404" PostTypeId="2" ParentId="8398" CreationDate="2010-12-29T14:04:54.323" Score="0" ViewCount="" Body="&lt;p&gt;From what i remember, you should be able to use USART and SPI or USART and I2C on the arduino at the same time. If you can give us more details on the Blue-tooth and the serial device, someone should be able to give you a definitive answer.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2010-12-29T14:04:54.323" />
  <row Id="8405" PostTypeId="1" AcceptedAnswerId="8407" CreationDate="2010-12-29T15:19:37.840" Score="5" ViewCount="244" Body="&lt;p&gt;&lt;strong&gt;Assumption:&lt;/strong&gt; I &lt;em&gt;think&lt;/em&gt; it's generally true that commercially available AC/DC wall-worts can be expected to be pretty noisy (e.g. you can't count on much better than 5% stability).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Background:&lt;/strong&gt; I'm dorking around with an RF application right now, and I hypothesize that some significant subset of my headaches is coming from powering my RF receiver with 5VDC coming directly from an AC/DC wall-wart (i.e. no RF choke, no regulator, nothing).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Question:&lt;/strong&gt; What's the simplest way (e.g. fewest parts) and cheapest mechanism for converting the &quot;angry&quot; 5VDC off a wall-wort into a &quot;happy&quot; 5VDC for my RF receiver? I think the other subsystems are more tolerant to noisy power. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Aside:&lt;/strong&gt; I wish I could give more definitive characterization of the noise coming out of the wall-wart, but sadly I am sans o-scope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit1:&lt;/strong&gt; In response to the request for more detail on parts being used:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.powerconversion.com/assets/dch3_ds_1222495015.pdf&quot; rel=&quot;nofollow&quot;&gt;Wall-Wart&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/datasheets/Wireless/General/MO-RXLC-A%20data%20sheet.pdf&quot; rel=&quot;nofollow&quot;&gt;RF Receiver&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-29T16:43:36.377" LastActivityDate="2010-12-30T12:45:05.750" Title="Advice on cleaning up 5VDC from a wall-wart" Tags="&lt;power&gt;&lt;rf&gt;&lt;noise&gt;&lt;wall-wart&gt;" AnswerCount="4" CommentCount="12" FavoriteCount="2" />
  <row Id="8406" PostTypeId="1" AcceptedAnswerId="8408" CreationDate="2010-12-29T15:38:46.990" Score="3" ViewCount="218" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to use a MLX90614 (from melexis &lt;strong&gt;not paralax&lt;/strong&gt;) with Atmega8. I have failed in all my attempts till now. I tried sending this sequence &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;slave address(as 0x00 and 0x5A) --&amp;gt; opcode to read SMBus address --&amp;gt; data byte high --&amp;gt; data byte low&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I get a slave address NACK for both SMBus addresses. Is it because I am using an I2C library? I understand we have to give a PEC also, but as the Slave address is NACK'd I don't think the sensor is responding to my commands. I tried using the write opcode and got ACK's for that. So the communication is ok. Can anyone tell me what kind of problem may be here?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also how would one generate a PEC for SMBus protocol?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I looked at this code &lt;a href=&quot;https://github.com/a1ronzo/SparkFun-IR-Evaluation-Board/blob/master/IR_eval/main.c&quot; rel=&quot;nofollow&quot;&gt;https://github.com/a1ronzo/SparkFun-IR-Evaluation-Board/blob/master/IR_eval/main.c&lt;/a&gt; and it just sends 0x00 and 0x07 over i2c to fetch two bytes of temperature. How can that be possible? In the datasheet it is specifically mentioned how to read one word and how to write one word. How can this be bypassed?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2010-12-29T16:35:39.290" Title="Using MLX90614 OR is I2C and SMBus compatible?" Tags="&lt;i2c&gt;&lt;smbus&gt;&lt;atmega8&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="8407" PostTypeId="2" ParentId="8405" CreationDate="2010-12-29T15:42:40.813" Score="4" ViewCount="" Body="&lt;p&gt;I have never had noise problems with wall warts, but then again, I never trust power supplies either and always add at least minimal filtering on my boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I usually add a 10 - 47uF electrolytic in parallel with a 0.1uF cap at the power inlet &quot;just in case.&quot; This has never failed to clean up any ripple or spikiness from wallwarts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the power supply regulated? Have you verified that the voltage is really 5V?&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2010-12-29T15:42:40.813" CommentCount="1" />
  <row Id="8408" PostTypeId="2" ParentId="8406" CreationDate="2010-12-29T15:51:17.833" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Theoretically&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I2C and SMBUS are essentially compatible as long as you are operating at 100kHz bus speed. The datasheet on page 15 (7.4.3.1.1) suggests to read a register you (as a master) have to do:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Start&#xA;SLA+W               (slave acks)&#xA;Command             (slave acks)&#xA;Repeated Start&#xA;SLA+R               (slave acks)&#xA;READ data byte low  (you ack)&#xA;READ data byte high (you ack)&#xA;READ PEC            (you ack)&#xA;STOP&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The appropriate SLA is 0x5A. Just like with I2C, you will need pullup resistors on the SCK and SDA lines (3.3kOhm should be fine). Command value will depend on what you are trying to do as described on page 16 (7.4.6).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Reality (?)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, there is a paragraph (7.4.1) on page 13 that says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;In order to provide access to any&#xA;  device or to assign an address to a SD&#xA;  before it is connected to the bus&#xA;  system, the communication must start&#xA;  with zero SA followed by low RWB bit.&#xA;  &lt;strong&gt;When this command is sent from the MD,&#xA;  the MLX90614 will always respond and&#xA;  will ignore the internal chip code&#xA;  information.&lt;/strong&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;... now that is a vague description of a specialization of the protocol at best, but it appears to be what the github code is exploiting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If one is to believe the github code, it is actually illustrating an undocumented protocol behavior. Namely:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;START&#xA;SLA(0)+W   (slave acks)&#xA;Command(7) (slave acks) (writes to the RAM read-address register the value 7 = TOBJ1?)&#xA;STOP&#xA;&#xA;START&#xA;SLA(0)+R        (slave acks)&#xA;READ low byte   (master acks)&#xA;READ high byte  (master acks)&#xA;READ pec        (master nacks)&#xA;STOP&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I've seen this &quot;flavor&quot; of I2C interaction before, but I'm with you that it's not described that way in the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Sidenote on PEC&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for &quot;how you generate the PEC&quot; it's described on page 14 at the bottom of the page:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The PEC calculation includes all bits&#xA;  except the START, REPEATED START,&#xA;  STOP, ACK, and NACK bits. The PEC is a&#xA;  CRC-8 with polynomial X8+X2+X1+1. The&#xA;  Most Significant Bit of every byte is&#xA;  transferred first.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Basically it's CRC-8-CCITT (see &lt;a href=&quot;http://en.wikipedia.org/wiki/Cyclic_redundancy_check&quot; rel=&quot;nofollow&quot;&gt;wikipedia&lt;/a&gt;) - implementations exist, just google for it, or post a separate question about CRC...&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-29T16:35:39.290" LastActivityDate="2010-12-29T16:35:39.290" CommentCount="2" />
  <row Id="8409" PostTypeId="1" AcceptedAnswerId="8414" CreationDate="2010-12-29T16:39:15.510" Score="3" ViewCount="326" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I am thinking of starting a project where I will need to interface a microcontroller output and mains for a lighting system. My question is about relays. I have found this &lt;a href=&quot;http://www.rapidonline.com/netalogue/specs/60-2008.pdf&quot; rel=&quot;nofollow&quot;&gt;one&lt;/a&gt;. And I am wondering will it be ok to put 230v through the switch of the relay? Also what am I looking for in the data sheet to tell me what is the maximum voltage that the switch will take?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2010-12-30T14:00:37.483" Title="Interfacing microcontroller and mains via a relay" Tags="&lt;relay&gt;" AnswerCount="5" />
  <row Id="8410" PostTypeId="2" ParentId="8409" CreationDate="2010-12-29T16:52:43.080" Score="2" ViewCount="" Body="&lt;p&gt;The Max. switching voltage is apparently 277V AC and 30V DC. What you should be asking however, is how much current you need to be rated for. This is not a simple thing to answer because depending on the type of load you are switching, you actually need to derate the current differently to account for inrush current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suggest reading through &lt;a href=&quot;http://www.home.agilent.com/agilent/redirector.jspx?action=ref&amp;amp;cc=US&amp;amp;lc=eng&amp;amp;ckey=1000002263%3aepsg%3aapn&amp;amp;cname=AGILENT_EDITORIAL&quot; rel=&quot;nofollow&quot;&gt;this application note&lt;/a&gt; to give you an in depth idea of what I'm talking about. Don't mess around with this stuff without taking appropriate precautions. You will note that for incandescant lighting, you need to derate by a factor of 10%. That means if your lighting draws 5 amps, you better get a relay that can switch 50 amps. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the reason that incandescent lighting is derated so much is because when the filaments are cold, they have much lower resistance than when they heat up, and so draw a huge amount of current from a cold start. I'm really just guessing at this though.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2010-12-29T16:58:57.050" LastActivityDate="2010-12-29T16:58:57.050" CommentCount="2" />
  <row Id="8411" PostTypeId="2" ParentId="8398" CreationDate="2010-12-29T16:55:54.887" Score="2" ViewCount="" Body="&lt;p&gt;Maybe have a look at &lt;a href=&quot;http://www.arduino.cc/en/Tutorial/SoftwareSerial&quot; rel=&quot;nofollow&quot;&gt;software serial&lt;/a&gt; - it allows multiple serial connections. Any of the digital pins on the Arduino can be used for serial communication, and the normal serial pins can continue to be used for your bluetooth modem.&lt;/p&gt;&#xA;" OwnerUserId="2393" LastActivityDate="2010-12-29T16:55:54.887" />
  <row Id="8412" PostTypeId="2" ParentId="8409" CreationDate="2010-12-29T17:16:36.680" Score="2" ViewCount="" Body="&lt;p&gt;I've done this kind of thing before, and it worked fine. The relay you've chosen looks about right, and as long as your not switching a huge load it will be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your unsure about the load, then do a simple calculation, for example if your switching a 100w bulb on and off, then 100w divided by 230v = about 0.4 amps. The datasheet says that the relay is rated at 10A... so its way more than enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your calculations are out, and things go wrong the worst that can happen is it burns out a cheap relay, or blows a fuse or MCB or something... it's not the end of the world.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2010-12-29T17:16:36.680" CommentCount="6" />
  <row Id="8413" PostTypeId="2" ParentId="8405" CreationDate="2010-12-29T17:23:31.010" Score="4" ViewCount="" Body="&lt;p&gt;The way to do this with the fewest parts - the &lt;em&gt;only&lt;/em&gt; way to get 5Vdc from less than 5V - is to use a switching regulator. There are a few options, based on how much current you need. All of these can have inputs from ~1V-5.5V:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;strong&gt;&lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/reg711-25.pdf&quot; rel=&quot;nofollow&quot;&gt;TI REG711&lt;/a&gt;&lt;/strong&gt;: 1MHz; 40mVpp ripple; 50mA; regulation not listed.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/CpaEs.png&quot; alt=&quot;REG711 layout&quot;&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;&lt;a href=&quot;http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1039,C1133,P1796,D2175&quot; rel=&quot;nofollow&quot;&gt;Linear LTC1754&lt;/a&gt;&lt;/strong&gt;: 600kHz; 65mVpp ripple; 50mA; 4% regulation.&#xA;&lt;img src=&quot;http://i.imgur.com/aSMg8.png&quot; alt=&quot;Linear LTC1754 layout&quot;&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;&lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/MAX1759.pdf&quot; rel=&quot;nofollow&quot;&gt;Maxim MAX1759&lt;/a&gt;&lt;/strong&gt;: 1.5MHz; 60mVpp ripple; 100mA; regulation not listed.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/1j2Xs.png&quot; alt=&quot;alt text&quot;&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;&lt;a href=&quot;http://cache.national.com/ds/LM/LM2750.pdf&quot; rel=&quot;nofollow&quot;&gt;National LM2750&lt;/a&gt;&lt;/strong&gt;: 1.7MHz; 4mVpp-15mVpp ripple; 120mA; 4% regulation.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/nK0vh.png&quot; alt=&quot;alt text&quot;&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/21752a.pdf&quot; rel=&quot;nofollow&quot;&gt;Microchip MCP1252/1253&lt;/a&gt;&lt;/strong&gt;: 650kHz/1MHz; 50mVpp ripple; 120mA; 2% regulation.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/vE6TQ.png&quot; alt=&quot;alt text&quot;&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;There are others that will give 140mA and more, but the linked RF widget doesn't need it, these were pretty cheap, simple because they're just charge pumps, take up little space and are entirely surface mount due to the high switch frequency. Those with MHz switch frequencies are less likely to interfere with your 315MHz-434MHz project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Easiest way to do it, in my opinion, is to get a different wall-wart!&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2010-12-29T17:23:31.010" CommentCount="13" />
  <row Id="8414" PostTypeId="2" ParentId="8409" CreationDate="2010-12-29T18:28:27.680" Score="2" ViewCount="" Body="&lt;p&gt;The relay is a good one for resistive loads like incandescent lamps. The AgSnO2 contacts can handle higher inrush currents than AgNi.&lt;br&gt;&#xA;Note that all given currents refer to cos phi = 1, i.e. fully resistive loads. If you want to switch reactive loads like fluorescent lamps you're limited to a fraction of the given maximum current. You also want a safety margin for the inrush when switching a cold incandescent lamp when the voltage is maximum, but I find a factor of 10 like vicatcu suggests overkill; a factor 4-5 will do.&lt;br&gt;&#xA;Your 10A then become 2.5A. Since a 60W bulb draws 0.25A at 230V you should be able to switch up to 10 lamps with 1 relay.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Forget I mentioned incandescent lamps. I was in the supermarket today and I needed a replacement bulb. While in the past there was an offer of at least 30 or 40 different incandescent bulbs in all sizes and shapes today &lt;strong&gt;&lt;em&gt;they were all gone!&lt;/em&gt;&lt;/strong&gt; Same variety in CFL (compact fluorescent), so that's no problem, but I didn't think the incandescent effectively would be gone before 1st January 2011.&lt;br&gt;&#xA;Anyway, for your relay. Relays like the resistive load of an incandescent bulb much better that the reactive load of a (compact) fluorescent lamp. While in theory you should derate the relay further for the changed load, in practice CFLs are only 20% the power of incandescent lamps, so your load will remain within the limits set earlier: you should still be able to switch 10 CFLs with 1 relay.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-30T12:01:54.143" LastActivityDate="2010-12-30T12:01:54.143" CommentCount="5" />
  <row Id="8415" PostTypeId="2" ParentId="8409" CreationDate="2010-12-29T19:43:25.973" Score="3" ViewCount="" Body="&lt;p&gt;If you are in any doubt about dealing with mains power - don't do it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might want to consider a ready made unit like this one from Adafruit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=44&amp;amp;products_id=268&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=44&amp;amp;products_id=268&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.adafruit.com/images/medium/powerswitchtail_MED.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-29T19:43:25.973" CommentCount="2" />
  <row Id="8416" PostTypeId="2" ParentId="8402" CreationDate="2010-12-29T22:26:30.253" Score="3" ViewCount="" Body="&lt;p&gt;The USB specification requires that a host port be able to source 100mA at a nominal 5V on the VBUS pin. That much power is barely enough to allow some devices to enumerate on the bus. (Early versions of the popular Cypress EZ-USB FX2 required a waiver because they drew slightly more than 100mA during enumeration.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, there is also an elaborate power management scheme that permits the host to shed loads by turning off ports individually. (I've never personally seen power management implemented on individual ports: on systems I've examined carefully either all host ports are powered, or none are. Your mileage will certainly vary.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In particular, whether your ports are powered when the laptop is sleeping is more than a little OS, platform, and configuration specific.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A device is permitted to draw up to 100mA without asking permission if VBUS is present. For a device to consume more than 100mA, it is supposed to have permission, and to be able to gracefully handle being denied.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Similar rules apply to hubs, with complications for bus-powered hubs which are permitted to restrict downstream devices to only 100mA, while never consuming more than 500mA from the upstream port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One reason for an external device to include a second USB cable for power is that effectively allows it to double its power budget.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; I weakened the implication that PCs don't manage power per port. Just because I haven't actually seen it happen has little bearing on whether it is found in the wild. The white-box PC with an MSI MB that I was last actively developing a USB device driver on had fairly limited power management capabilities. The brand new Dell on my desk seems to turn off individual PCIe cards under some conditions, so the world of power management in PCs has been advancing (or at least getting more complicated) steadily while I wasn't looking. &lt;/p&gt;&#xA;" OwnerUserId="1494" LastEditorUserId="1494" LastEditorDisplayName="" LastEditDate="2011-01-18T09:32:12.333" LastActivityDate="2011-01-18T09:32:12.333" CommentCount="5" />
  <row Id="8417" PostTypeId="2" ParentId="8405" CreationDate="2010-12-30T03:21:28.053" Score="2" ViewCount="" Body="&lt;p&gt;It's a switching wall wart.  The easiest solution may be to just get a linear wall wart, or even just a transformer and regulate the voltage at your board.  It's bulky, but 50/60Hz won't give you any RF problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Switching wall warts can be noisy, and there is little filtering you can do about it in terms of RF.  All component filtering will do is filter conducted noise, not radiated, which is what could be your problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also consider other sources of interference.  I have an RF remote that won't work anywhere in my house when I run my dishwasher.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2010-12-30T03:21:28.053" />
  <row Id="8418" PostTypeId="1" AcceptedAnswerId="8420" CreationDate="2010-12-30T03:53:52.817" Score="6" ViewCount="346" Body="&lt;p&gt;I need a trace on my PCB to carry up to 2.5 amps (average) current, with 5-6 amp spikes (it's going to a switch mode power supply.) How wide should the traces be? I've got a trade off between reliability and size, as the product is space constrained. Any tips would be appreciated. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-05T23:37:34.110" LastActivityDate="2011-01-06T21:23:17.460" Title="Sizing a trace on a PCB to carry 2.5 amps" Tags="&lt;pcb&gt;&lt;current&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="8420" PostTypeId="2" ParentId="8418" CreationDate="2010-12-30T04:10:41.720" Score="11" ViewCount="" Body="&lt;p&gt;After doing a quick google of &quot;PCB Current Calculator&quot;, I found a &lt;a href=&quot;http://www.desmith.net/NMdS/Electronics/TraceWidth.html&quot; rel=&quot;nofollow&quot;&gt;PCB Current Calculator&lt;/a&gt;. It bases the width of the track on how much of a temperature rise the trace is allowed to have. It's nice in that it shows how much power you waste through your trace. I would design for your worst-case RMS current, since it's going to be a periodic signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use 2oz/ft&lt;sup&gt;2&lt;/sup&gt; copper instead of the standard 1oz/ft&lt;sup&gt;2&lt;/sup&gt; copper, you won't need as wide of a trace to achieve the same resistance. For example, allowing for a &lt;strong&gt;10&lt;sup&gt;o&lt;/sup&gt;C rise&lt;/strong&gt;, you can get away with these numbers at &lt;strong&gt;3A&lt;/strong&gt;:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;280 thou (7.11 mm) on &lt;sup&gt;1&lt;/sup&gt;/&lt;sub&gt;2&lt;/sub&gt; oz/ft&lt;sup&gt;2&lt;/sup&gt; copper&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;140 thou (3.56 mm) on 1 oz/ft&lt;sup&gt;2&lt;/sup&gt; (35µm) copper&lt;/strong&gt;&lt;/li&gt;&#xA;&lt;li&gt;70 thou (1.78 mm) on 2 oz/ft&lt;sup&gt;2&lt;/sup&gt; (70µm) copper&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="638" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-31T00:44:10.470" LastActivityDate="2010-12-31T00:44:10.470" CommentCount="11" />
  <row Id="8421" PostTypeId="1" AcceptedAnswerId="8446" CreationDate="2010-12-30T09:29:30.277" Score="2" ViewCount="183" Body="&lt;p&gt;Is it possible to build a circuit to make a fluorescent tube flash on and off for use as a lighting effect? If so, how?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if the above is possible, can it be used to flash more than one tube at a time without having to repeat the control circuitry for each tube?&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-05T23:35:56.000" LastActivityDate="2011-01-05T23:35:56.000" Title="Flash a fluorescent tube" Tags="&lt;light&gt;&lt;flash&gt;&lt;fluorescent&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="8422" PostTypeId="2" ParentId="8421" CreationDate="2010-12-30T09:42:07.203" Score="4" ViewCount="" Body="&lt;p&gt;Well, first of all, you need to have electrodes hot all the time.&#xA;If you will try to heat them at the moment of pulse you will kill your tubes in a matter of hours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you can turn on your main &lt;em&gt;constant-current&lt;/em&gt; (ballast circuit) power supply for whatever time you need as long as it's fast enough to stabilize during your 1-10-100ms pulses. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use 1 constant-current device for multiple lamps if you connect then in series, but the required voltage will be much higher, so I believe it's cheaper to have 1 device per lamp.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-12-30T09:42:07.203" CommentCount="8" />
  <row Id="8423" PostTypeId="2" ParentId="8418" CreationDate="2010-12-30T09:45:21.973" Score="10" ViewCount="" Body="&lt;p&gt;Common practice for high-current devices is to solder thick copper wire on top of your 2-3mm trace.&#xA;1mm^2 wire can handle 10A easily.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2010-12-30T09:45:21.973" CommentCount="4" />
  <row Id="8424" PostTypeId="2" ParentId="8405" CreationDate="2010-12-30T12:45:05.750" Score="2" ViewCount="" Body="&lt;p&gt;An an alternative, &lt;a href=&quot;http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply&quot; rel=&quot;nofollow&quot;&gt;turn an ATX power supply from an old computer into a benchtop power supply.&lt;/a&gt; I can't speak for how clean the power is (I imagine quite good) but it's a cool project!&lt;/p&gt;&#xA;" OwnerUserId="2344" LastActivityDate="2010-12-30T12:45:05.750" />
  <row Id="8425" PostTypeId="1" AcceptedAnswerId="8432" CreationDate="2010-12-30T12:58:28.793" Score="4" ViewCount="222" Body="&lt;p&gt;I am working on a device that uses the Microchip MDDFS library to store data to an SD card. The logger will log data at a maximum rate of 1 entry (56bytes) every minute. The problem is the device may lose power at any time, potentially in the middle of a write sequence.  I am wondering what is the best way to protect my data against corruption.  I have found that if the file is open when the power is lost, all data that was written to the file after the last file-close is lost. I don't know if the same holds true if power is lost in the middle of the write sequence. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the write procedure doesn't happen very frequently I could open the file, write the data, and then close the file, every time data is logged. Would this approach damage the sd card over time? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another approach could be to keep the file open but after every 10 or 50 writes I could close the file and then re-open it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could also buffer data in memory, then flush the data occasionally maybe after a kbyte or so. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The last idea I had was, in my circuit, I could add a large capacitor that would provide power to my pic/sd card long enough after the power is disconnected to quickly close the file. The problem with this approach is that the time it takes to close the file and/or save data is very inconsistent. From my understanding, this time can very depending on the current place in a flash page that the file is in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyways, what would you guys suggest?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="1235" LastEditorDisplayName="" LastEditDate="2011-01-03T13:01:02.640" LastActivityDate="2011-01-03T15:05:46.353" Title="How do I protect SD card against unexpected power failures?" Tags="&lt;power&gt;&lt;sd&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="8426" PostTypeId="2" ParentId="8409" CreationDate="2010-12-30T14:00:37.483" Score="2" ViewCount="" Body="&lt;p&gt;If money is no object, then the first thing I go to is a solid state relay (SSR), instead of the mechanical switch variety.  I've had to switch 120VAC with a DC control voltage many times in the past, and I've alwyas started with Crydom SSRs.  SSRs make interfacing with AC voltage really, really simple.  Crydom has &lt;a href=&quot;http://www.alliedelec.com/Search/SearchResults.aspx?N=0&amp;amp;Ntk=Primary&amp;amp;Ntt=Crydom&amp;amp;gclid=CL3GjvyQlKYCFQYnbAodVC_goQ&quot; rel=&quot;nofollow&quot;&gt;several models&lt;/a&gt; that can switch 230VAC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, everything I have used them in is for prototype and R&amp;amp;D automation.  It would be interesting to hear how others here feel about it.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-30T14:00:37.483" />
  <row Id="8427" PostTypeId="1" CreationDate="2010-12-30T14:25:54.503" Score="5" ViewCount="323" Body="&lt;p&gt;One thing that it seems I have many of are cords and connector/patch cables.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't want to throw out all of them, but am looking for useful storage tips?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most are under 6 foot / 2 metres long, they are the usual assortment of TV cable, stereo-cable, serial cable, ethernet, 12-volt power, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking for some way to store them efficiently, while I can still see both ends.  Coiling is a possibility, but then there's just a stack of circles that I have to dig through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally, some sort of hanging method, that has them semi-secur, but still accessable/visible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you store all those cables? (and hope this is Electronics-enough!)&lt;/p&gt;&#xA;" OwnerUserId="2117" LastActivityDate="2011-01-04T21:49:24.180" CommunityOwnedDate="2011-03-30T14:19:10.187" Title="How to store all those spare cables and connector cords?" Tags="&lt;storage&gt;&lt;workbench&gt;" AnswerCount="9" CommentCount="1" />
  <row Id="8428" PostTypeId="1" AcceptedAnswerId="8429" CreationDate="2010-12-30T14:41:07.950" Score="2" ViewCount="234" Body="&lt;p&gt;First this is the setup:&#xA;&lt;img src=&quot;http://i.imgur.com/81rsE.png&quot; alt=&quot;Two serial devices talking to each other, plus two FT232RL with Rx pins connected to each device's Tx lines&quot;&gt;&#xA;(please note that one of the grounds is not connected, both FTDIs working properly)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, I have used PuTTY to look at these two serial streams, both exchanging data at 9600 bauds, but my problem is logging the activity time-wise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also tried some serial monitors that I found on the tubes, but the time resolution is in seconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Is there a tool for monitoring these two streams at the same time?&lt;/strong&gt; If there is not, I should program one myself in Processing (it will take less time in this language I suppose).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS: the ultimate goal of this is to replace the remote device (an actual wired remote) with a little MCU like the ATtiny85 or ATtiny2313 with a simulated input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS2: I only have these two FTDIs, an analog oscilloscope and a multimeter.&lt;/p&gt;&#xA;" OwnerUserId="1673" LastEditorUserId="374" LastEditorDisplayName="" LastEditDate="2010-12-30T17:20:25.753" LastActivityDate="2011-05-01T20:41:45.817" Title="Monitoring two serial lines at the same time" Tags="&lt;microcontroller&gt;&lt;serial&gt;&lt;uart&gt;&lt;ftdi&gt;&lt;reverse-engineering&gt;" AnswerCount="6" CommentCount="4" FavoriteCount="2" />
  <row Id="8429" PostTypeId="2" ParentId="8428" CreationDate="2010-12-30T15:04:08.047" Score="5" ViewCount="" Body="&lt;p&gt;If you're on a 32bit Windows OS, I would recommend using &lt;a href=&quot;http://technet.microsoft.com/en-us/sysinternals/bb896644&quot; rel=&quot;nofollow&quot;&gt;PortMon&lt;/a&gt;.  It goes down to the millisecond at least.  It might even be microsecond resolution.  I've used it a lot in the past with great success.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your particular case, you will put each FTDI chip on its own serial port.  Then in PortMon, simply select the ports you want to monitor from the pulldown menu.  Both sets of data get logged at high resolution, and you can even add filters to reduce the amount of data.  For serial protocol monitoring, I add the include filter &lt;code&gt;IRP_MJ*&lt;/code&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2010-12-30T15:09:49.910" LastActivityDate="2010-12-30T15:09:49.910" CommentCount="6" />
  <row Id="8430" PostTypeId="2" ParentId="8427" CreationDate="2010-12-30T15:13:04.900" Score="1" ViewCount="" Body="&lt;p&gt;I put my cables in logical groups, in separate bins.  I do the coil method, but put twist ties at the connector ends (i.e. 2 twist ties per cable).  You should save twist ties every time you get them with other products.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I don't have twist ties, I use plastic (saran) wrap.  Just cut a thin strip and wrap.  Remember to fold over the end when you're done wrapping, so it's easy to locate.  And don't go crazy on the wraps or you'll go just more crazy when you try to undo them.  :)&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-30T15:13:04.900" CommunityOwnedDate="2011-03-30T14:19:10.187" />
  <row Id="8431" PostTypeId="2" ParentId="8319" CreationDate="2010-12-30T15:30:50.243" Score="0" ViewCount="" Body="&lt;p&gt;I would propose designing your enclosure so that the board is seated in a groove on one end, and has a plastic leaf spring-like catch on the opposite side.  Gently pull back on the catch and then lift out the board when you need to remove it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm coming from this standpoint since I have a 3D printer and can print pretty much whatever I need to fit around PCBs, but even if you don't have access to one, services like Ponoko and Shapeways can help you out.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2010-12-30T15:30:50.243" CommentCount="1" />
  <row Id="8432" PostTypeId="2" ParentId="8425" CreationDate="2010-12-30T15:40:16.533" Score="6" ViewCount="" Body="&lt;p&gt;A few things can happen when you write data to a file. I'm going to describe the sequence that needs to happen for data to be safe, not necessarily library calls.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you're writing, and adding on to the end of the file (normal write mode), you read the last block of the file into memory, modify it with your write data, and then write the whole block back to the SD card. If the block is full, then a new block must be found in the File Allocation Table (FAT). After finding a new block, the FAT must be updated, which is a read-modify-write cycle. If we're done with the file, then we need to update the file attributes (such as file length) in the root directory, which causes another read-modify-write cycle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Minimizing your write time&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Make sure that the file is already holding your data when you write a sector. If you start out with a large file and overwrite the data instead of appending the data, the data will be safe as soon as the SD card sector write is finished. You can eliminate one to two read-modify-write cycles that way. My start-up code would write 0's to a file in sector increments until the SD card is full, and then rewind to the beginning of the file.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Make the size of your data entries such that an integer number of entries fit in a sector. I would bump up your entries to 64 bytes. While this is less efficient, it will prevent you from needing to read-modify-write two sectors.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Create a variant of the FSwrite function that allows you to write whole sectors. If you keep the whole sector in SRAM, then your cycle goes from &quot;read-modify-write&quot; to &quot;modify-write&quot;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Keep your PIC and SD power on as long as possible&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Big capacitors are good. 470uF should give you more than enough power to finish a write cycle.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Make sure your power source won't suck the power out of your back-up capacitor! Add a diode if necessary.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Know when you're out of power&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A big power supply cap will give you 10ms or more to wrap things up with a SD card, but don't press your luck. Use a pin on your microcontroller to see if your power source is still good, and don't start a write if your source is dead.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="638" LastActivityDate="2010-12-30T15:40:16.533" CommentCount="4" />
  <row Id="8433" PostTypeId="2" ParentId="8428" CreationDate="2010-12-30T15:40:25.253" Score="0" ViewCount="" Body="&lt;p&gt;I wrote something like this explicitly to watch the conversation between my iPod and the iPod adapter in my car.  The source is &lt;a href=&quot;https://github.com/blalor/arduinaap/blob/master/iPodSerial/iPodWatcher.py&quot; rel=&quot;nofollow&quot;&gt;here on GitHub&lt;/a&gt;.  It's pretty specific to the iPod protocol, but I need to be able to see the data being transmitted to and received from the iPod in real-time and match a response with its request as closely as possible.  This works quite well for me.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2010-12-30T15:40:25.253" />
  <row Id="8434" PostTypeId="2" ParentId="8427" CreationDate="2010-12-30T15:51:08.937" Score="2" ViewCount="" Body="&lt;p&gt;The high dollar approach &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.pomonaelectronics.com/index.php?i=prodmain&amp;amp;getDetails=1&amp;amp;parent=TSTLEADHLDR&quot; rel=&quot;nofollow&quot;&gt;http://www.pomonaelectronics.com/index.php?i=prodmain&amp;amp;getDetails=1&amp;amp;parent=TSTLEADHLDR&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These keep them untangled and straight&lt;/p&gt;&#xA;" OwnerUserId="2148" LastActivityDate="2010-12-30T15:51:08.937" CommunityOwnedDate="2011-03-30T14:19:10.187" CommentCount="3" />
  <row Id="8435" PostTypeId="2" ParentId="8427" CreationDate="2010-12-30T15:52:43.143" Score="1" ViewCount="" Body="&lt;p&gt;I'm lazy :-) Most of my electronics &amp;amp; electromechanical stuff is housed in bins in a large closet in my lab/office (OK, it's a spare bedroom!). I have a couple of large hooks on the wall and hang cables by type: USB, serial, power cords, Ethernet, etc. It's easy to see the cable type and length at a glance. You can get big hooks at Home Depot and other home improvement stores.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2010-12-30T15:52:43.143" CommunityOwnedDate="2011-03-30T14:19:10.187" />
  <row Id="8436" PostTypeId="2" ParentId="8425" CreationDate="2010-12-30T16:32:15.377" Score="1" ViewCount="" Body="&lt;p&gt;Perhaps &lt;a href=&quot;http://www.sparkfun.com/products/10317&quot; rel=&quot;nofollow&quot;&gt;this supercapacitor&lt;/a&gt; at Sparkfun would solve the problem.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2010-12-30T16:32:15.377" CommentCount="1" />
  <row Id="8437" PostTypeId="2" ParentId="8425" CreationDate="2010-12-30T17:16:16.227" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Since the write procedure doesn't&#xA;  happen very frequently I could open&#xA;  the file, write the data, and then&#xA;  close the file, every time data is&#xA;  logged. Would this approach damage the&#xA;  sd card over time?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;As with any engineering problem, you'll need to deal with tradeoffs here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Is it critical that no-data be lost at all?&lt;/em&gt;  Then I'd do the above.  You'd have more damage done by losing the data than by ruining a card.  You may want to do a stress test, of sorts, to determine how many times you could perform that operation before the card becomes corrupted.  If your'e cool with the length of time it took before the card became unusuable, and it seems to be an acceptable length of time before changing the card, I'd go with that route.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2010-12-30T17:16:16.227" />
  <row Id="8438" PostTypeId="2" ParentId="8427" CreationDate="2010-12-30T17:40:04.777" Score="7" ViewCount="" Body="&lt;p&gt;I found a really neat cheap way to bundle them - use the cardboard tubes from toilet rolls, and loop them inside. This prevents them being in a tangle. Also, those cardboard tubes can be written on with a marker to clearly ID the cables. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since each side will have a loop, you can probably hang these on pegs, but I simply keep them in a box.&lt;/p&gt;&#xA;" OwnerUserId="2326" LastActivityDate="2010-12-30T17:40:04.777" CommunityOwnedDate="2011-03-30T14:19:10.187" />
  <row Id="8439" PostTypeId="2" ParentId="8428" CreationDate="2010-12-30T17:48:46.933" Score="1" ViewCount="" Body="&lt;p&gt;Docklight is the tool you're looking for: &lt;a href=&quot;http://www.docklight.de/&quot; rel=&quot;nofollow&quot;&gt;http://www.docklight.de/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used it before and it's great.  Give it a try as well as PortMon.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2010-12-30T17:48:46.933" CommentCount="1" />
  <row Id="8440" PostTypeId="1" AcceptedAnswerId="8442" CreationDate="2010-12-30T18:39:04.110" Score="4" ViewCount="192" Body="&lt;p&gt;I heard in a recent presentation that the XBox 360 uses an &lt;strong&gt;eFuse&lt;/strong&gt; to prevent users from reverting back to prior boot/firmware image. What is an eFuse and how do they work?&lt;/p&gt;&#xA;" OwnerUserId="619" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-01T21:30:57.273" LastActivityDate="2011-01-01T21:30:57.273" Title="What is an eFuse" Tags="&lt;fuse-bits&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="8441" PostTypeId="2" ParentId="8440" CreationDate="2010-12-30T18:46:06.103" Score="3" ViewCount="" Body="&lt;p&gt;According to Wikipedia  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;In computing, eFUSE is a technology invented by IBM which allows for the dynamic real-time reprogramming of computer chips. Speaking abstractly, computer logic is generally 'etched' or 'hard-coded' onto a chip and cannot be changed after the chip has finished being manufactured. By utilizing an eFUSE (or more realistically, a number of individual eFUSEs), a chip manufacturer can allow for the circuits on a chip to change while it is in operation.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-30T18:46:06.103" CommentCount="2" />
  <row Id="8442" PostTypeId="2" ParentId="8440" CreationDate="2010-12-30T18:53:45.560" Score="4" ViewCount="" Body="&lt;p&gt;It's an irreversible part of the chip which is &quot;burnt&quot; out (without causing damage to the rest of the chip) and is usually a single configuration bit. The bit (and subsequent bits) might control something like software version, or whether the Xbox supports 1080p, or whether you can play certain region discs... Pretty much anything you can imagine. Like a one time programmable read only memory. They are a concern because it effectively allows a manufacturer to obsolete a product remotely without any consent from the owner.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's the paranoid view, anyway. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-30T18:53:45.560" CommentCount="11" />
  <row Id="8443" PostTypeId="2" ParentId="8427" CreationDate="2010-12-30T19:03:16.547" Score="7" ViewCount="" Body="&lt;p&gt;I used to store these in a big plastic ammo box.  The problem is they end up all twisted together after the 100th time I dig through them looking for a spare null modem cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The solution was to coil the cables and put them in large Ziploc bags, then put them in the box.  The freezer bags even have an area for marking, so I can write &quot;USB&quot; on one bag, &quot;RS-232&quot; on one bag, and so forth.  And when I'm looking for a null modem, it's easy to pull the RS-232 bag, and see that I still haven't acquired one...&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2010-12-30T19:03:16.547" CommunityOwnedDate="2011-03-30T14:19:10.187" CommentCount="2" />
  <row Id="8444" PostTypeId="2" ParentId="8427" CreationDate="2010-12-30T19:36:07.380" Score="1" ViewCount="" Body="&lt;p&gt;The low dollar approach: &lt;a href=&quot;http://www.monoprice.com/products/product.asp?c_id=105&amp;amp;cp_id=10520&amp;amp;cs_id=1052003&amp;amp;p_id=5809&amp;amp;seq=1&amp;amp;format=2&quot; rel=&quot;nofollow&quot;&gt;velcro cable ties&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been using those ones from Monoprice for a few months, they're as good as commercial grade velcro ties but cost $1.37 for ten.&lt;/p&gt;&#xA;" OwnerUserId="2344" LastActivityDate="2010-12-30T19:36:07.380" CommunityOwnedDate="2011-03-30T14:19:10.187" CommentCount="1" />
  <row Id="8445" PostTypeId="2" ParentId="8402" CreationDate="2010-12-30T19:58:05.817" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.usb.org/developers/docs/usb_20_081810.zip&quot; rel=&quot;nofollow&quot;&gt;USB spec&lt;/a&gt; allows any device to draw 100mA from a port.  No communication with the host is required.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, 500mA is available by communicating with the host unless you're plugged into an unpowered hub. Many computers allow you to draw this 500mA without properly requesting it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is a personal project, put a 10 ohm power resistor across the terminals of your USB port and see how much the voltage drops.  If it works, you're golden.  Just remember that it might not work if you plug it into a different computer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is something you want to distribute, you'll have to tell the host that you want 500mA.  If you don't have a micro on the project that can handle this task, the easiest way to do this is to put the cheapest USB hub controller IC you can find on the board, and configure it to do the communication.  The TI TUSB2036 is about $3, and just requires you to pull a pin high (Or low, I can't remember) to get the 500mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you'll want the 500mA to get a decent audio volume.  I don't know about the 50 ohm speaker you have, but in general, your power is limited to Vrms^2/R.  A pair of 50 ohm speakers operating from 0V to 5V will draw .125W (assuming 100% efficiency).  That's hardly better than the stock speakers.  Four 8-ohm speakers will bring you up to a more respectable 1.5W of power, which is well under your 2.5W allowable power from the USB port. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're operating on a device which has a FireWire (IEEE 1394) port, you might consider using that as it has much more power available (Up to tens of amps, but possibly less. &lt;a href=&quot;http://support.apple.com/kb/HT2952&quot; rel=&quot;nofollow&quot;&gt;Apple products&lt;/a&gt; guarantee that there's a minimum of 7W available, but the spec allows for as much as 45W of power to be delivered. &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2010-12-30T19:58:05.817" CommentCount="2" />
  <row Id="8446" PostTypeId="2" ParentId="8421" CreationDate="2010-12-30T21:09:23.343" Score="2" ViewCount="" Body="&lt;p&gt;You could try an EHT inverter circuit and avoid messing around with mains power, ballasts and starter circuits entirely. I used inverters salvaged from old fluorescent camping lights with some larger 4ft tubes for stage special effects a few years back. In my case the fact that the tubes didn't glow at full brightness was not an issue. I found this article which may be of use: &lt;a href=&quot;http://talkingelectronics.com/projects/FluorescentInverter/FluorescentInverter.html&quot; rel=&quot;nofollow&quot;&gt;http://talkingelectronics.com/projects/FluorescentInverter/FluorescentInverter.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2010-12-30T21:09:23.343" CommentCount="2" />
  <row Id="8447" PostTypeId="1" AcceptedAnswerId="8451" CreationDate="2010-12-30T21:58:27.770" Score="1" ViewCount="214" Body="&lt;p&gt;Can a phone be &quot;paired&quot; with 2 bluetooth devices at the same time?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im wondering this because I have 2 very different use cases of devices that I want to use with a cell phone.  One is a headset. the other has a different function...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you know of a reference for this type of stuff please forward it to me!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks&lt;/p&gt;&#xA;" OwnerUserId="2437" LastActivityDate="2010-12-30T23:27:31.543" ClosedDate="2010-12-31T00:12:13.957" Title="Can a phone be &quot;paired&quot; with 2 bluetooth devices at the same time?" Tags="&lt;bluetooth&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="8448" PostTypeId="1" CreationDate="2010-12-30T22:18:42.067" Score="-2" ViewCount="126" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/1404/low-cost-bluetooth&quot;&gt;Low Cost Bluetooth&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I'm looking for the simplest type of bluetooth module available with an audio output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to figure out how to cut costs on a device that I'm making for a client.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="2437" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2010-12-31T00:17:11.113" LastActivityDate="2011-01-30T00:17:59.137" ClosedDate="2011-05-09T21:49:48.533" Title="Is there a Bluetooth module that doesn't have a microphone and doesnt have a voice codec?" Tags="&lt;bluetooth&gt;" AnswerCount="1" CommentCount="6" />
  <row Id="8450" PostTypeId="2" ParentId="8421" CreationDate="2010-12-30T23:15:45.950" Score="1" ViewCount="" Body="&lt;p&gt;Perhaps use the LED-based tube replacements and a microcontroller of some sort to simulate the flashing patterns you need.&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2010-12-30T23:15:45.950" CommentCount="1" />
  <row Id="8451" PostTypeId="2" ParentId="8447" CreationDate="2010-12-30T23:27:31.543" Score="2" ViewCount="" Body="&lt;p&gt;Yes, but maybe the concept of &quot;pairing&quot; you are using is not what you intended.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To pair two devices is to make them exchange keys that would allow them to connect later. There's no limit (in the protocol) for how many devices you pair your phone to. It's a matter of the maximum size for the table the phone OS supports, which usually is quite large.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your question was about the possibility of connecting your phone simultaneously with many devices, the answer is also yes, provided it uses Bluetooth 1.2 or above.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice that when two BT devices are connected, one of them is a &quot;master&quot; and the other is &quot;slave&quot;. A master device can connect simultaneously to up to 7 slaves. With each of them it can establish as many as 60 sessions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are protocol-defined limits, but specific devices can have more limited capabilities, eventually.&lt;/p&gt;&#xA;" OwnerUserId="1078" LastActivityDate="2010-12-30T23:27:31.543" CommentCount="2" />
  <row Id="8452" PostTypeId="2" ParentId="8448" CreationDate="2010-12-31T00:15:59.820" Score="0" ViewCount="" Body="&lt;p&gt;When you say &quot;module&quot;, I'm not sure what you're looking for. Your cost will vary depending on volume.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For bluetooth system-on-chips, look at CSR and Broadcom. These would be suitable only for high volume products.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For off-the-shelf dev boards for medium quantities, there are plenty of cheap CSR BC04 modules available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For small quantities you might try hacking a bluetooth headset.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2010-12-31T00:15:59.820" />
  <row Id="8453" PostTypeId="1" AcceptedAnswerId="8455" CreationDate="2010-12-31T04:27:32.963" Score="1" ViewCount="196" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is going to be the first PCB board that I have made. So I just want to make sure that I have it correct. I have drawn up the schematic based off another in eagle 5.11.0 (Cadsoft). I just want to make sure that it's correct as I have never used eagle before. If it is I will move on to the board layout and etch the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The drawings are located below&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Original: &lt;a href=&quot;https://files.me.com/ashley.hughes/d4z93m&quot; rel=&quot;nofollow&quot;&gt;JPG Here&lt;/a&gt;&#xA;&lt;br&gt;My Version: &lt;a href=&quot;https://files.me.com/ashley.hughes/ovpicg&quot; rel=&quot;nofollow&quot;&gt;PNG Here&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I Have connected all the parts and pin that I need to (All but the data out and Green LED's).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have only messed around a bit in the board view in eagle, so can anyone recommend how to place the VCC and GND onto the board? As they don't come across as a part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I am going to be using Press-N-Peel onto single a single sided board, etching with Ferric Chloride.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks any comments and/or hints would be great&lt;/p&gt;&#xA;" OwnerUserId="665" LastActivityDate="2010-12-31T06:03:22.803" Title="Is my schematic Correct, MAX7219CNG (Tips for etching)" Tags="&lt;eagle&gt;&lt;etching&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="8454" PostTypeId="1" CreationDate="2010-12-31T04:39:28.130" Score="0" ViewCount="68" Body="&lt;p&gt;Does anyone know of a resource that tells us what the bluetooth capabilities are of each cell phone and/or chipset #?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a project, and Im trying to determine if I pair my bluetooth device with various kinds of cell phones if it will also disconnect their previous devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example:&#xA;User A has a bluetooth headset paired with their phone X&#xA;User A buys a mobile screen printing bluetooth device and pairs their phone X with the new mobile printing bluetooth device&#xA;Does User A now have both devices paired with phone X, or is only one device paired with phone X&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this tied to the chipset that the manufacturer used or the software that they provide in the cell phone devices?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="2437" LastActivityDate="2010-12-31T04:39:28.130" ClosedDate="2011-03-23T09:45:33.143" Title="Bluetooth capabilities by cell phone" Tags="&lt;bluetooth&gt;" CommentCount="2" />
  <row Id="8455" PostTypeId="2" ParentId="8453" CreationDate="2010-12-31T05:06:36.127" Score="1" ViewCount="" Body="&lt;p&gt;Looks good. Are you going to connect the green ones? I'm guessing you made your own symbol and layout for the &lt;em&gt;&lt;a href=&quot;http://www.sparkfun.com/datasheets/Components/LED/YSM-1288CR3G2C.pdf&quot; rel=&quot;nofollow&quot;&gt;8x8 LED matrix&lt;/a&gt;&lt;/em&gt;, or got it from Sparkfun. I'm not sure how its connected internally, but the external connections look good. Anyway, here's the breakdown, as I traced it:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;        Maxim   Yours&#xA;SegDP   col0    RED1&#xA;SegA    col1    RED2&#xA;SegB    col2    RED3&#xA;SegC    col3    RED4&#xA;SegD    col4    RED5&#xA;SegE    col5    RED6&#xA;SegF    col6    RED7&#xA;SegG    col7    RED8&#xA;&#xA;Dig0    row0    ROW1&#xA;Dig1    row1    ROW2&#xA;Dig2    row2    ROW3&#xA;Dig3    row3    ROW4&#xA;Dig4    row4    ROW5&#xA;Dig5    row5    ROW6&#xA;Dig6    row6    ROW7&#xA;Dig7    row7    ROW8&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Sometimes it is better to use busses, the fat blue lines, to 'carry' many related nets, like a data bus or parallel drivers. If they are not related and appear cluttered, you can simply name physically separated nets the same thing to connect them. In all cases, and especially the last one, label them. It helps in board layout, too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To connect V&lt;sub&gt;CC&lt;/sub&gt; and GND to your board you can use one of these:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;em&gt;Copper lands:&lt;/em&gt; you can solder wires directly to large copper pads. They are in the native library &lt;strong&gt;wirepad&lt;/strong&gt;.&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;Female Headers:&lt;/em&gt; this is what the Arduino uses to connect all its shields, etc. Solid core wires simply plug into them. They are in the native libraries &lt;strong&gt;con-lsta&lt;/strong&gt;, &lt;strong&gt;con-lstb&lt;/strong&gt;, &lt;strong&gt;con-molex&lt;/strong&gt;, and &lt;strong&gt;pinhead&lt;/strong&gt; (male headers). You can get 100mil pitch headers for pennies if you buy the large format type (20+ in one row), then break off whatever you need.&lt;/li&gt;&#xA;&lt;li&gt;Other than the above, there are many connectors made especially for these types of connections. &lt;strong&gt;con-jack&lt;/strong&gt; comes to mind, though I would make my own layout once a jack was picked out.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In any case, the native libraries are a poor example of what is available. It's best to find your parts with your favourite distributor first, then make your own layout or triple-check the native match.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/MAX7219-MAX7221.pdf&quot; rel=&quot;nofollow&quot;&gt;the MAX7219 datasheet&lt;/a&gt;, you may have trouble getting it on on a single side without jumpers. Note that you can do &lt;em&gt;byte translations&lt;/em&gt; in software to take into account swapped wires or traces on parallel busses, like column or row drivers. For example, if you want to turn on the LEDs at column 5 and rows 3 and 4, you would may provide bytes like these (note that I haven't read the datasheet, so don't follow directly):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;0b0001100&#xA;0b0010000&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;But if rows 4 and 5 are swapped, then you should really be sending this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;0b0010100&#xA;0b0010000&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This means you need to translate row 4 -&gt; and 5 -&gt; 4; for example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;uint8_t translate_row(uint8_t row_byte)&#xA;{&#xA;  return  ((row_byte &amp;amp; (1&amp;lt;&amp;lt;0))&amp;lt;&amp;lt;0) |&#xA;          ((row_byte &amp;amp; (1&amp;lt;&amp;lt;1))&amp;lt;&amp;lt;0) |&#xA;          ((row_byte &amp;amp; (1&amp;lt;&amp;lt;2))&amp;lt;&amp;lt;0) |&#xA;          ((row_byte &amp;amp; (1&amp;lt;&amp;lt;3))&amp;lt;&amp;lt;0) |&#xA;          ((row_byte &amp;amp; (1&amp;lt;&amp;lt;4))&amp;lt;&amp;lt;1) |  // shift bit 4 to bit 5&#xA;          ((row_byte &amp;amp; (1&amp;lt;&amp;lt;5))&amp;gt;&amp;gt;1) |  // shift bit 5 to bit 4&#xA;          ((row_byte &amp;amp; (1&amp;lt;&amp;lt;6))&amp;lt;&amp;lt;0) |&#xA;          ((row_byte &amp;amp; (1&amp;lt;&amp;lt;7))&amp;lt;&amp;lt;0);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;With this strategy you don't have to worry much about swapping traces from one pin to another.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2010-12-31T06:03:22.803" LastActivityDate="2010-12-31T06:03:22.803" CommentCount="1" />
  <row Id="8460" PostTypeId="2" ParentId="8264" CreationDate="2010-12-31T10:23:37.780" Score="2" ViewCount="" Body="&lt;p&gt;Think twice: You will also need a File System for large disks, and FAT32 has some design limits, esp. that Files must be &amp;lt; 4GB. Ohter file systems are much harder to implement on a µC. In most cases its easier to use a SD card, as it supports SPI.&lt;/p&gt;&#xA;" OwnerUserId="1472" LastActivityDate="2010-12-31T10:23:37.780" />
  <row Id="8461" PostTypeId="2" ParentId="8141" CreationDate="2010-12-31T10:47:44.013" Score="0" ViewCount="" Body="&lt;p&gt;Looking at the datasheet: &lt;a href=&quot;http://www.nxp.com/#/pip/pip=%5bpip=LPC1769_68_67_66_65_64_63,jp=Features%5d|pp=%5bt=pip,i=LPC1769_68_67_66_65_64_63%5d&quot; rel=&quot;nofollow&quot;&gt;LPC17xx&lt;/a&gt; has support for 5 Bit data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SiLabs 80C51F0XX has only 8 and 9 bit.&lt;/p&gt;&#xA;" OwnerUserId="1472" LastActivityDate="2010-12-31T10:47:44.013" />
  <row Id="8462" PostTypeId="1" AcceptedAnswerId="8463" CreationDate="2010-12-31T14:12:53.727" Score="3" ViewCount="181" Body="&lt;p&gt;I understand that the NE5532 is an evergreen in audio applications. Which other op-amps would you consider for preamp, filter and other high fidelity audio applications?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2010-12-31T14:20:25.657" LastActivityDate="2011-01-04T22:20:29.220" Title="Which op-amp for audio?" Tags="&lt;audio&gt;&lt;op-amp&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="3" />
  <row Id="8463" PostTypeId="2" ParentId="8462" CreationDate="2010-12-31T14:48:45.350" Score="2" ViewCount="" Body="&lt;p&gt;I've found a few interesting parts at Analog Devices:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://www.analog.com/static/imported-files/data_sheets/OP275.pdf&quot; rel=&quot;nofollow&quot;&gt;OP275&lt;/a&gt;: very low noise (5nV/sqrt(Hz)), high slew rate and low distortion&lt;br&gt;&#xA;  &lt;a href=&quot;http://www.analog.com/static/imported-files/data_sheets/AD823.pdf&quot; rel=&quot;nofollow&quot;&gt;AD823&lt;/a&gt;: comparable specs, a bit higher noise  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Looks like I have to answer my own question... :-)&lt;br&gt;&#xA;I read somewhere that the LME series is National Semiconductor's selection of high performance, high fidelity devices. You find the lot of them &lt;a href=&quot;http://www.national.com/pf/master_LME.html&quot; rel=&quot;nofollow&quot;&gt;on National's site&lt;/a&gt;; there's too many to list here.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-01-04T10:47:58.070" LastActivityDate="2011-01-04T10:47:58.070" CommentCount="1" />
  <row Id="8464" PostTypeId="1" AcceptedAnswerId="8465" CreationDate="2010-12-31T15:05:18.707" Score="4" ViewCount="247" Body="&lt;p&gt;I'm in the R&amp;amp;D stages of a V4 of my project, which may replace the high-speed DSP with an FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was looking at this FPGA, because it is cheap: XC3S50A (about £6.50/each.) I think I can probably fit the project onto there, with one concern. I can't find anywhere in the datasheet about how much current it will consume. Is it a fixed amount, or does it vary, depending on how much logic I am using? Is there a quiescent current draw by it, when no logic is in use? What about the current draw by its clocks/PLLs? I've looked through the datasheet - it has many characteristics, but these ones in particular don't seem to be mentioned.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-14T21:41:14.523" Title="How much current does an FPGA consume, anyway?" Tags="&lt;fpga&gt;" AnswerCount="5" CommentCount="4" />
  <row Id="8465" PostTypeId="2" ParentId="8464" CreationDate="2010-12-31T15:15:24.123" Score="6" ViewCount="" Body="&lt;p&gt;It varies hugely with clock rate, exactly what is being clocked internally, and I/O usage. It is sufficiently hard to determine that most FPGA softare has a utility to estimate current draw of a design given the external clock/data rates, however it will need a lot of detailed info to give a reliable estimate, so the easiest option is often to just build it &amp;amp; measure, or load a comparable design into a devboard and measure that.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2010-12-31T15:15:24.123" CommentCount="5" />
  <row Id="8466" PostTypeId="1" CreationDate="2010-12-31T16:39:51.293" Score="0" ViewCount="236" Body="&lt;p&gt;Hello-&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was told by the local electronic parts outlet store that I could use a Tamura Micro PL10-24 to reduce voltage from a 16V AC source to approximatly 12V.  I need assistance with the correct wiring scheme.  The 12V taps are labled 1-3-4 and 6.  The 115V taps are lable 7-9-10 and 12.  It's my understanding that I can use the positive side source to wire to tap 6, Bridge taps 3 and 4 and bride tap 1 and 7.  Use tap 9 to wire to neutral side of source.  Use tap 10 and 12 for output of 12 V. Any assistance would be greatly appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you.  &lt;/p&gt;&#xA;" OwnerUserId="2442" LastActivityDate="2011-01-01T02:51:41.297" Title="Wiring Input Diagram for a Dual Winding - 2 tap / winding. 2 x 115V and 2 x 12 V." Tags="&lt;transformer&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="8467" PostTypeId="2" ParentId="8428" CreationDate="2010-12-31T17:19:19.873" Score="1" ViewCount="" Body="&lt;p&gt;Another option could be &lt;a href=&quot;http://com0com.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;com0com&lt;/a&gt; or its sister project hub4com. &lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2010-12-31T17:19:19.873" CommentCount="1" />
  <row Id="8468" PostTypeId="2" ParentId="8427" CreationDate="2010-12-31T17:51:30.407" Score="2" ViewCount="" Body="&lt;p&gt;For my long cables, I do the electrician's wrap &lt;a href=&quot;http://www.ehow.com/how_2153427_wrap-electrical-cord-like-pro.html&quot; rel=&quot;nofollow&quot;&gt;like this&lt;/a&gt;.  I would post step-by-step instructions here, but it's easier to see than describe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For my short cord, I do the &quot;figure 8&quot; wrap &lt;a href=&quot;http://lifehacker.com/software/ipod/how-to-wrap-a-headphone-cord-225310.php&quot; rel=&quot;nofollow&quot;&gt;like this&lt;/a&gt;, like many people do for their headphones.  Once they are wrapped, I put them in a small Ziploc bag.  You can pick up a ton of these for cheap at a hobby store like hobby lobby or Michael's.  These are usually in the craft storage or photograph storage section of the store.  I think I bought something like 200 for 5 bucks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of these are stored in Rubbermade bins, by category.  It really depends on how many cables you have, but I found this to be the best storage method.  If you have less, I would suggest a duffel bag (it's portable!).  Putting the cables and bits and pieces in the ziploc bags keeps them from getting tangled together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if you have trouble remembering what a cable is (or what it's for), you can always write it on a 4x6 notecard and shove it in the bag with the cable (I usually do part numbers, etc) to help keep everything sorted out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:  Here are the storage boxes I was talking about from &lt;a href=&quot;http://shop.hobbylobby.com/products/storage-box-with-lid-361220/&quot; rel=&quot;nofollow&quot;&gt;Hobby Lobby&lt;/a&gt;.  They go on sale for 3/6$ occasionally, so you can just watch the circular ads.  And here are the bags, also from &lt;a href=&quot;http://shop.hobbylobby.com/products/self-sealing-poly-bags-445650/&quot; rel=&quot;nofollow&quot;&gt;Hobby Lobby&lt;/a&gt;.  They come in different sizes, but they also go on sale for 200/3$.  So for about 15 bucks, you can store cables and wires to your heart's content.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I keep mine categorized by Power (transformers and line cables)/AV (composite, component, and audio cables)/USB(micro, mini, a/b)/Odds and ends&lt;/p&gt;&#xA;" OwnerUserId="1477" LastEditorUserId="1477" LastEditorDisplayName="" LastEditDate="2010-12-31T17:57:16.063" LastActivityDate="2010-12-31T17:57:16.063" CommunityOwnedDate="2011-03-30T14:19:10.187" />
  <row Id="8469" PostTypeId="1" AcceptedAnswerId="8473" CreationDate="2010-12-31T18:18:28.730" Score="2" ViewCount="208" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am a newbie in FPGA world, working out on Verilog these days. I have thought of a couple of Projects for my FinalYearProject at my college. One of them is Handheld Ebook Reader. Well, I will workout the other things required, what i am most concerned about is, How am i going to read a pdf file through FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, in the project, i will be interfacing a MicroSD card module with FPGA, the FPGA would read the file from pdf and would display it on LCD, interfacing with LCD wouldnt be a big problem as i have got a couple of good resources for that, interfacing the memory card module too. But the thought that has been troubling me in choosing this project is, how am I going to read PDF. I may work on the pdf which has texts only, i wont work on images, on the other hand if i plan to work on images as well, i will have to do a lot of work for several tasks, say for zooming in and others. &#xA;  Kindly help me on this.&#xA;  Plus, i am pretty keen about this task. Kindly tell me if this can be done more easily with microcontroller. I have a little bit of experience working with them.&lt;/p&gt;&#xA;" OwnerUserId="2445" LastActivityDate="2011-01-01T12:36:38.210" Title="Reading PDF through FPGA" Tags="&lt;fpga&gt;&lt;reader&gt;" AnswerCount="5" />
  <row Id="8470" PostTypeId="2" ParentId="8469" CreationDate="2010-12-31T18:26:45.150" Score="4" ViewCount="" Body="&lt;p&gt;I'm not sure if images will make things harder; zooming in on text is hard enough as it is. If you want to do things by FPGA you definitely want a soft processor, i.e. a microcontroller on a part of your FPGA. Decoding PDFs is not something you want to do parallel like an FPGA works. FPGA suppliers like Xilinx and Altera offer IP for controllers, but the problem may be that a PDF library may not be available for them. In this you'll have better chances with an external controller, which uses the FPGA as a display driver.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2010-12-31T18:26:45.150" CommentCount="3" />
  <row Id="8471" PostTypeId="2" ParentId="8469" CreationDate="2010-12-31T18:39:21.847" Score="3" ViewCount="" Body="&lt;p&gt;Put a CPU (some kind of micro-controller core) into your FPGA, and then program a PDF reader for that CPU. Going this route, you might want to consider NOT doing PDF, but doing HTML instead, as that format is a bit more amenable to the sort of wrapping and re-sizing that you'll want to do on a reader. There are any number of HTML rendering libraries out there that you could re-purpose to whatever CPU you embed. &lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2010-12-31T18:39:21.847" />
  <row Id="8472" PostTypeId="2" ParentId="8469" CreationDate="2010-12-31T18:48:20.503" Score="1" ViewCount="" Body="&lt;p&gt;As others have said, you probably want to do the PDF decoding as software on a soft-core processor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the major requirements this will impose is that you are likely to need a number of megabytes of external ram, for both the program code and the data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Theoretically, with enough memory, any processor could be made to decode a PDF... it just may be slow in operation and painful to develop if you have to write it from scratch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also you will likely need more RAM than is available on chip in an affordable FPGA in order to form the video frame buffer for an LCD of a size worth displaying a PDF on (though a monochrome smartphone-size display probably would fit).  You'll either need to have dual port video memory or craft an arbiter to allow the processor logic to write to it interleaved with the display logic clocking bits out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Frankly speaking, an e-reader is not a good FPGA appliction, it's a system-on-chip one, architecturally very similar to a smartphone.  One might add a cheap fpga as a pin-remapper to make the same PCB usable with a variety of commodity LCD glass modules, but the logic belongs in a nice modern ARM core or similar.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2010-12-31T18:48:20.503" />
  <row Id="8473" PostTypeId="2" ParentId="8469" CreationDate="2010-12-31T20:43:26.637" Score="3" ViewCount="" Body="&lt;p&gt;First of all you need to determine what you're going to do with the PDF. If you're displaying it, you'll need some memory for the frame buffer, and a way to interface with the display. That should be your primary concern. Then, start thinking about rendering the PDF itself. As PDFs are essentially compressed PostScript of one form or another with embedded fonts, you can divide your tasks into some major elements:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;part of the FPGA to load data from SD card or other media including file system access&lt;/li&gt;&#xA;&lt;li&gt;part of the FPGA to decompress chunks of data, or to accelerate this process&lt;/li&gt;&#xA;&lt;li&gt;part of the FPGA to decompress image data (JPEG, PNG, etc.) and copy to memory&lt;/li&gt;&#xA;&lt;li&gt;part of the FPGA to decode/execute PostScript&lt;/li&gt;&#xA;&lt;li&gt;part of the FPGA to figure out what needs to be displayed (such as the current page); this could be simple bounding logic or complex scaling logic handling a variety of different display modes&lt;/li&gt;&#xA;&lt;li&gt;a floating point unit for the floating point coordinates in PostScript&lt;/li&gt;&#xA;&lt;li&gt;an integer ALU&lt;/li&gt;&#xA;&lt;li&gt;several &quot;GPU&quot; engines which render primitives from the PostScript engine (ideally, in parallel) e.g. draw line, draw polygon, ...&lt;/li&gt;&#xA;&lt;li&gt;a font engine or two to render fonts (this will likely be very complex as you will need to support complex features like hinting and antialiasing.)&lt;/li&gt;&#xA;&lt;li&gt;a display interface and memory interface&lt;/li&gt;&#xA;&lt;li&gt;a UI controller of some kind, perhaps implementing copy/paste, selections, menus, etc.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Ideally the engines 1-5 would be pipelined to get maximum throughput. You'll be looking at a big FPGA to do all of this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could probably do this on a CPU, but if you realllly want to do it on an FPGA, this is probably the route to take.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2010-12-31T20:43:26.637" />
  <row Id="8474" PostTypeId="2" ParentId="8337" CreationDate="2010-12-31T20:58:39.277" Score="0" ViewCount="" Body="&lt;p&gt;The vital thing missing from the circuit is that the 'antenna' has a whirly thing on top that produces 48kW in a good breeze.&lt;/p&gt;&#xA;" OwnerUserId="1158" LastActivityDate="2010-12-31T20:58:39.277" CommentCount="2" />
  <row Id="8475" PostTypeId="1" CreationDate="2011-01-01T01:51:15.457" Score="0" ViewCount="96" Body="&lt;p&gt;I am really enjoying reading this book, &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0133957241&quot; rel=&quot;nofollow&quot;&gt;&quot;High Speed Digital Design: A Handbook of Black Magic&quot;&lt;/a&gt;, in particular the more in-depth material covered than in undergrad courses and the practical approach the author takes instead of being bogged down with endless theory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was wondering if there were such similarly good books but in the field of say RF/Microwave circuits or say... analog design?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-01T02:49:26.407" LastActivityDate="2011-01-01T02:51:41.817" Title="Similar books to &quot;High Speed Digital Design: A Handbook of Black Magic&quot;" Tags="&lt;analog&gt;&lt;rf&gt;&lt;books&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="8476" PostTypeId="2" ParentId="8157" CreationDate="2011-01-01T01:56:33.830" Score="0" ViewCount="" Body="&lt;p&gt;Don't mind the updated name, had to register. Here are some of the answers so far. The spring in question is actually a car engine belt tensioner. So we are talking roughly maybe 30 foot lbs to compress. It is bolted to a 3 ton jack stand which is bolted to a frame. Frame right now is roughly 30 in long. Catapult arm length is still in question due to distance requirements of projectile. Considering making arm length adjustable. Ball feed mech is basically pvc with spring gate that gets compressed when arm is pulled down. Projectiles are baseballs, softballs. snowballs etc....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stuck on finding the right motor at this point. So far I've ripped apart a belt sander and an oreck vacuum looking for answers, with no luck. Also considering winch methodolgy or possibly chain hoist theory. Thanks for the responses.&lt;/p&gt;&#xA;" OwnerUserId="2447" LastActivityDate="2011-01-01T01:56:33.830" CommentCount="3" />
  <row Id="8477" PostTypeId="2" ParentId="8466" CreationDate="2011-01-01T02:51:41.297" Score="1" ViewCount="" Body="&lt;p&gt;You have a transformer with two 120V primary windings, and two 12V secondary windings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what your saying, you are wiring both secondary windings and one primary winding in series, and then taking the output from the other primary winding?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will &lt;strong&gt;not&lt;/strong&gt; give you 12 VAC from 16VAC input, but it will get you close.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The transformer ratio between primary and secondary is 10:1&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the way you are describing it, you get a ratio of 10+1+1:10, or 12:10, so 16VAC in will give you 16*(10/12) VAC out, or 13.333~ VAC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: You have the primary and secondary backwards. The 120 VAC taps are 1,3,4,6, and the secondary is 7,9,10,12 - See datasheet &lt;a href=&quot;http://www.tamuracorp.com/clientuploads/pdfs/engineeringdocs/PL10-XX-130B.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;It's worth noting that this is a horrible hack, and I really wouldn't recommend doing it unless you have no choice. Also, the transformer will not achieve anything near it's rated power spec in this configuration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's probably also a really good idea to lash-up a test rig and check your input and output voltages before soldering the whole affair into place. You may have to reverse the direction of the secondary (e.g. swap pin 7 and 12, though I don't think so).&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-01-01T02:51:41.297" />
  <row Id="8478" PostTypeId="2" ParentId="8475" CreationDate="2011-01-01T02:51:41.817" Score="1" ViewCount="" Body="&lt;p&gt;There's the sequel &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/013084408X&quot; rel=&quot;nofollow&quot;&gt;High Speed Signal Propagation: Advanced Black Magic&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-01T02:51:41.817" />
  <row Id="8479" PostTypeId="2" ParentId="8464" CreationDate="2011-01-01T02:56:10.737" Score="3" ViewCount="" Body="&lt;p&gt;For that part the answer is &lt;a href=&quot;http://www.xilinx.com/ise/power_tools/license_spartan3a.htm&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  For other parts, Xilinx has &lt;a href=&quot;http://www.xilinx.com/products/design_resources/power_central/&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-01T17:02:57.847" LastActivityDate="2011-01-01T17:02:57.847" />
  <row Id="8480" PostTypeId="1" AcceptedAnswerId="8482" CreationDate="2011-01-01T12:35:19.430" Score="1" ViewCount="164" Body="&lt;p&gt;I Have started making my 1st PCB, as per my other question &lt;a href=&quot;http://electronics.stackexchange.com/questions/8453/is-my-schematic-correct-max7219cng-tips-for-etching&quot;&gt;(Located Here)&lt;/a&gt; and have been looking at the datasheet for the &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/MAX7219-MAX7221.pdf&quot; rel=&quot;nofollow&quot;&gt;MAX7219CNG&lt;/a&gt; and studying the library to run it on an Arduino &lt;a href=&quot;http://www.wayoda.org/arduino/ledcontrol/index.html&quot; rel=&quot;nofollow&quot;&gt;(Located Here)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now my question is from what I can see in the library, there is a method called spiTransfer that sends the data to the IC to turn on and off the various LEDs. This is done by shifting data containing opcode and data bits. The opcodes are at the top of the .cpp file. For example &#xA;&lt;code&gt;#define OP_SHUTDOWN 12&lt;/code&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't find where the related information is in the datasheet to say that 12 = Shutdown.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am i reading the datasheet wrong or understanding the library wrong. I want to learn how to read a datasheet and implement code to run an IC with out relying on code written by others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And guidance would be great thanks&lt;/p&gt;&#xA;" OwnerUserId="665" LastActivityDate="2011-01-01T13:53:03.997" Title="Help understanding SPI and Arduino" Tags="&lt;arduino&gt;&lt;spi&gt;&lt;datasheet&gt;" AnswerCount="1" />
  <row Id="8481" PostTypeId="2" ParentId="8469" CreationDate="2011-01-01T12:36:38.210" Score="1" ViewCount="" Body="&lt;p&gt;An FPGA is really not the right device to do this sort of task. There are CPUs with all the required peripherals to do the job (e.g.LPC2478) which will be cheaper and draw a ton less power.&#xA;If you want to do it with an FPGA as a learning excercise, I'd suggest you break the task down and start off By making your life easier by preprocessing the book content on a PC into a file format that is easier to display than PDF, e.g. uncompressed bitmap or run length coded bitmaps. And start off using a simple block-oriented filesystem, as doing FAT stuff on an FPGA will be quite complicated.&#xA;That way you should be able to get something working reasonably quickly, then look at doing more complex stuff like other file format etc. later. If you start off trying to do it all, there is a high chance you will spend a ton of time and have nothing working to show for it when you get bored or run out of time.&#xA;At some point you definitely will need to using be using a CPU, either external or on the FPGA.   &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-01T12:36:38.210" />
  <row Id="8482" PostTypeId="2" ParentId="8480" CreationDate="2011-01-01T13:53:03.997" Score="5" ViewCount="" Body="&lt;p&gt;That's because it's in the datasheet in hex. :-) Page 7, table 2.  I'd have written the define as &lt;code&gt;#define OP_SHUTDOWN 0x0C&lt;/code&gt; to be consistent with the datasheet…&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-01-01T13:53:03.997" CommentCount="4" />
  <row Id="8484" PostTypeId="2" ParentId="110" CreationDate="2011-01-01T16:08:57.147" Score="3" ViewCount="" Body="&lt;p&gt;Actually sometimes you just MUST make your own ESC. ESCs sold on the maket are &quot;commercilized&quot; and have their own control codes for RC stuff like airplanes, helis, cars...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example sometimes you need to have a double side regenerative brake. From back to stop and from forward to stop. There is NO RC ESC that has that feature. They either have only one regenerative brake from forward to stop or none. Or you may need a sensor control BLDC but there are only a few sensored ESCs in the market, and they only have (the same for common sensorless ESCs) built in features that you do not need and don't have some that you absolutely need!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Designing your own ESC is a perfect choice and much cheaper even than the cheapest $10 one with HUGE power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is true that the control code and the hardware can be a pain but after some reading it is just a toy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a good tutorial here on how to make a BLDC controller with an arduino using 6 mosfets and some other stuff you can easily find at Jameco's site (very nice)&#xA;This is where I buy my stuff for cheap but spurkfun can be a nice alternative if you don't find some sensors like gyros, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/BLDC-Motor-Control-with-Arduino-salvaged-HD-motor/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/BLDC-Motor-Control-with-Arduino-salvaged-HD-motor/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;very nice and easy to follow guide. You can make ANY power from low to ultra high ESCs using this guide and almost any combination of regen brake, using resistance, motor windings or battery charger...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using mosfets is just a toy, you can do almost anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The prob is that you can't control this mosfet very efficiently with an MCU like an arduio board which outputs only 5V I think and the gate voltage of the mosfet for medium voltages is pretty much higher in the range of 16-30V easily. So you must use some other tansisor to step up arduino's voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck and God bless you.&lt;/p&gt;&#xA;" OwnerUserId="2448" LastActivityDate="2011-01-01T16:08:57.147" />
  <row Id="8485" PostTypeId="1" AcceptedAnswerId="9158" CreationDate="2011-01-01T16:31:50.133" Score="2" ViewCount="183" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I am here talking about macros for functions and not constants).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been doing my first serious work of programming these days. I have been exposed to a lot of code by different developers. One thing I find confusing is how do these developers decide when to use a macro definition and when to use a inline function. Both have essentially the same function, they place a certain code at the place they are called from. So is there some logic for selection or is it just at the whimsy of the developer?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-18T02:56:06.700" LastActivityDate="2011-01-18T02:59:46.770" Title="Macros V/S inline functions while programming for avr-gcc" Tags="&lt;avr&gt;&lt;c&gt;&lt;code&gt;&lt;avr-gcc&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="8486" PostTypeId="2" ParentId="8485" CreationDate="2011-01-01T16:44:25.233" Score="5" ViewCount="" Body="&lt;p&gt;Inline functions may or may not be inlined by the compiler. Macros, on the other hand, are handled by the precompiler, and are thus guaranteed to be inlined (code replicated). Often one will use a macro for a short but complex operation to add readability to the code, without taking a performance penalty for a function call. For example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define SWAP(a,b)({a ^= b; b ^= a; a ^= b;})&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;... provides a way to swap variables a and b without a function call and without a temporary variable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a &lt;a href=&quot;http://stackoverflow.com/questions/1137575/inline-functions-vs-preprocessor-macros&quot;&gt;stackoverflow question&lt;/a&gt; to the same effect (though not specifically about avr-gcc).&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-01T17:00:55.153" LastActivityDate="2011-01-01T17:00:55.153" />
  <row Id="8487" PostTypeId="2" ParentId="7882" CreationDate="2011-01-01T17:29:43.180" Score="1" ViewCount="" Body="&lt;p&gt;Yes, you can, but you probably don't want to.  There are second order effects of the components that you have to be aware of.  For example ESR (Equivalent Series Resistance) in caps.  These caps are small and cheap, so I would look to save area/components elsewhere.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-01T17:29:43.180" />
  <row Id="8488" PostTypeId="2" ParentId="4712" CreationDate="2011-01-01T17:31:47.110" Score="0" ViewCount="" Body="&lt;p&gt;You don't need to make the traces the same length unless your circuit requires it.  For example DDR memories require it within a certain amount and differential traces require it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The standard for simulation is &lt;a href=&quot;http://www.mentor.com/products/pcb-system-design/circuit-simulation/hyperlynx-signal-integrity/%22HyperLynx%22&quot; rel=&quot;nofollow&quot;&gt;HyperLynx&lt;/a&gt; (by Mentor).  LineSim does it pre-layout; BoardSim does it post-layout.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-01T17:38:41.063" LastActivityDate="2011-01-01T17:38:41.063" />
  <row Id="8489" PostTypeId="1" CreationDate="2011-01-01T20:44:44.243" Score="0" ViewCount="173" Body="&lt;p&gt;Despite doing a Google search and finding &lt;a href=&quot;http://www.avanthon.com/dvt_checklist.php&quot; rel=&quot;nofollow&quot;&gt;this from Avanthon Engineering&lt;/a&gt;, I haven't found a good checklist.  Theirs is more for board bring up than making sure a design really works before it goes to production.  I'm thinking of checks such as&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Check at high/low voltage&lt;/li&gt;&#xA;&lt;li&gt;Check at high/low temperature&lt;/li&gt;&#xA;&lt;li&gt;Check more than one unit&lt;/li&gt;&#xA;&lt;li&gt;Check signal integrity on clocks and other critical signals&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In this case the design is an analog one.  But since I mainly do digital designs, suggestions there are welcome.  I have a mental checklist, but I'm sure I could use a written one.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-03T04:36:56.440" LastActivityDate="2011-01-03T10:37:36.823" CommunityOwnedDate="2011-05-15T04:13:17.403" Title="What should be on a DVT (Design Verification Test) checklist?" Tags="&lt;checklist&gt;&lt;dvt&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="8490" PostTypeId="1" CreationDate="2011-01-02T03:01:21.450" Score="1" ViewCount="67" Body="&lt;p&gt;I'm using several pieces of equipment from Minicircuits, namely an amplifier and a bias-T. Each of them have a strange power connector - it looks like a small metal post with a disk on the top, or a bare wire that sticks out of insluation (see the pictures on their homepage &lt;a href=&quot;http://minicircuits.com/&quot; rel=&quot;nofollow&quot;&gt;http://minicircuits.com/&lt;/a&gt;). I'd like to find cables that properly attach to this. Any input?&lt;/p&gt;&#xA;" OwnerUserId="2454" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-01-02T16:40:33.353" LastActivityDate="2011-01-03T00:50:34.097" Title="What type of cable do I use to connect to the power pins on RF equipment?" Tags="&lt;rf-connector&gt;" AnswerCount="2" />
  <row Id="8491" PostTypeId="2" ParentId="8427" CreationDate="2011-01-02T03:55:50.807" Score="0" ViewCount="" Body="&lt;p&gt;A few photos of John Doran's lab&#xA;&lt;a href=&quot;http://www.timefracture.org/lab.html&quot; rel=&quot;nofollow&quot;&gt;http://www.timefracture.org/lab.html&lt;/a&gt;&#xA;show a single piece of sheet metal bent and cut to form a row of hooks, then attached to the wall used to hang cables from their midpoint.&#xA;(Is there a commercial source for these? The bend at their tips looks slightly different than the Pomona Test Lead Holders that Dave mentioned).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen several workshops with a similar row of hooks, or that approximate this with a row of nails nailed into a horizontal board attached to the wall.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-02T03:55:50.807" CommunityOwnedDate="2011-03-30T14:19:10.187" />
  <row Id="8492" PostTypeId="2" ParentId="8490" CreationDate="2011-01-02T03:56:07.303" Score="1" ViewCount="" Body="&lt;p&gt;I believe those are &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=11301K-ND&quot; rel=&quot;nofollow&quot;&gt;solder terminals&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/O17St.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-02T03:56:07.303" CommentCount="1" />
  <row Id="8493" PostTypeId="1" AcceptedAnswerId="8499" CreationDate="2011-01-02T05:12:04.740" Score="1" ViewCount="327" Body="&lt;p&gt;Hello.&#xA;There is a core i7 cpu&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/PCLmp.jpg&quot; alt=&quot;i7&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It have some contact pads on top side, some grouped in 4 or 6 and a two big groups.&#xA;Is there a pinout of this pads? Where is a JTAG?&lt;/p&gt;&#xA;" OwnerUserId="1994" LastActivityDate="2011-05-09T06:49:16.147" Title="What is a pinout of TOP side of Intel Core i7?" Tags="&lt;pin&gt;&lt;pins&gt;&lt;cpu&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="8494" PostTypeId="2" ParentId="4904" CreationDate="2011-01-02T05:24:05.393" Score="0" ViewCount="" Body="&lt;p&gt;There are several ways to do what you want.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Program another &quot;buffer MCU&quot; to sit between your two CPUs and buffer the communication -- something like the &quot;Baudrate converter&quot; shown at &lt;a href=&quot;http://www.romanblack.com/PICthread.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.romanblack.com/PICthread.htm&lt;/a&gt; . Program it to present &quot;dual-port&quot; an indepent interface on each side. The (internal or external) SRAM is directly connected only to this buffer MCU.&lt;/li&gt;&#xA;&lt;li&gt;Reprogram your &quot;transmitter&quot; MCU to store a buffer in SRAM, instead of directly sending it to the receiver, and act as a slave to pull data from that buffer and send it only when your &quot;receiver&quot; MCU (acting as a master) requests it. The (external or internal) SRAM buffer is directly connected only to the transmitter. (i.e., combine the functionality of both what your receiver is doing now, and the above &quot;buffer MCU&quot;).&lt;/li&gt;&#xA;&lt;li&gt;Use some GPIO lines, as Andrew Kohlsmith and mjh2007 suggested, to arbitrate between the transmitter and receiver who gets access to a shared external 32 KByte SRAM chip such as the RAMTRON FM24C256.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-02T05:24:05.393" />
  <row Id="8495" PostTypeId="1" CreationDate="2011-01-02T09:22:26.043" Score="4" ViewCount="248" Body="&lt;p&gt;I have a digital camera (Panasonic DMC-FT1) and will be going multi-day hiking with it soon. I'm looking to build a solar charger for it using something like &lt;a href=&quot;http://www.sparkfun.com/products/726&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; and strap it to my pack. Does anyone have any experience doing something like this, or any pitfalls in general that I may fall into (ie will my battery explode if I do xyz) ? There will be plenty of sun on my trip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Battery markings: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Model: DMW-BCF10E&lt;/li&gt;&#xA;&lt;li&gt;3.6V 940mAh 3.4Wh Li-ion&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Charger markings:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Model: DE-A60A&lt;/li&gt;&#xA;&lt;li&gt;Input: 110-240V~50/60Hz 0.2A&lt;/li&gt;&#xA;&lt;li&gt;Output: 4.2V 0.65A&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="417" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-01-03T20:37:55.920" LastActivityDate="2011-01-03T20:37:55.920" Title="How do I charge a commercial lithium battery with solar cells?" Tags="&lt;charging&gt;&lt;lithium-ion&gt;&lt;solar-cell&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="8496" PostTypeId="1" AcceptedAnswerId="8502" CreationDate="2011-01-02T09:59:33.157" Score="6" ViewCount="216" Body="&lt;p&gt;Several ICs are manufactured in packages with more pins than it supports. For example, the LM317 in an SO8 package has 4 V&lt;sub&gt;OUT&lt;/sub&gt; pins and 2 N/C &lt;em&gt;(no connection)&lt;/em&gt; pins. I often want to run traces through N/C pins to ease routing, but wonder if it would make them give up the ghost. &lt;strong&gt;&lt;em&gt;If it exists, what is the standard or rule by which manufacturers follow concerning the electrical characteristics of N/C pins?&lt;/strong&gt; Or do I have to scour the datasheet / do my own testing every time?&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.tyblu.ca/misc/LM317_SO8pinout.png&quot; alt=&quot;LM317 SO8 pinout&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-02T19:30:11.917" Title="Can I run traces through &quot;No Connection&quot; pins?" Tags="&lt;layout&gt;&lt;pcb-design&gt;" AnswerCount="4" />
  <row Id="8497" PostTypeId="2" ParentId="8496" CreationDate="2011-01-02T10:06:47.083" Score="7" ViewCount="" Body="&lt;p&gt;Normally &lt;code&gt;&quot;n.c.&quot;&lt;/code&gt; means that the pin is not connected to the die, and you should be safe running a trace over it. In some rare occasions I've read &lt;code&gt;&quot;n.c. DO NOT CONNECT&quot;&lt;/code&gt;, which rises the question why I shouldn't, if it's not connected internally anyway. In any case I expect the datasheet to mention it expressly when I shouldn't connect to the pin.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One example is pin 4 on the LP2981. Texas Instruments says &lt;code&gt;&quot;Pin 4 (NC) must be left open. Do not connect anything to this pin&quot;&lt;/code&gt;, without further explanation. National specifies: &lt;code&gt;&quot;Post package trim. **do not** connect to this pin&quot;&lt;/code&gt;. So the pin seems to be connected as expected, otherwise it would be safe to connect. In this case &lt;code&gt;&quot;not connected&quot;&lt;/code&gt; should be read as &lt;code&gt;'no end user connection&quot;&lt;/code&gt;.  Both manufacturers indicate clearly not to connect.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-01-02T10:20:23.373" LastActivityDate="2011-01-02T10:20:23.373" CommentCount="11" />
  <row Id="8498" PostTypeId="2" ParentId="8495" CreationDate="2011-01-02T11:40:41.480" Score="3" ViewCount="" Body="&lt;p&gt;You'd probably be better off taking a bigger spare battery. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if you really want to charge using solar energy, you have to understand that there isn't much. If you have a 3cm^2 solar panel and go on the basis of 15% efficiency for the solar cell (which is pretty good), then plug that into the solar energy per square meter on Earth, which is from 1,413 to 1,321 W/m^2, which gives you about 59mW. Your battery is 3.4Wh, so it will take over 2 days to recharge it, nevermind that the sun is only around for a fraction of that or conversion efficiency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Working backwards with those numbers, if one wants to charge a 3.4Wh cell within 4 hours, they would need a &lt;code&gt;(3.4Wh)/(4h)/((1321W/m^2)*0.15)=43cm^2&lt;/code&gt; solar cell.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-02T12:16:35.787" LastActivityDate="2011-01-02T12:16:35.787" CommentCount="7" />
  <row Id="8499" PostTypeId="2" ParentId="8493" CreationDate="2011-01-02T12:04:37.553" Score="6" ViewCount="" Body="&lt;p&gt;Why do you want to do this? Do you know you need to provide this chip with about 1.1V @ 10 amps (up to 145 amps at full load) for it to even work, and that all signals have to be at this same level?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Likely, the pins are not documented. &lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=2&amp;amp;sqi=2&amp;amp;ved=0CBoQFjAB&amp;amp;url=ftp%3A%2F%2Fdownload.intel.com%2Fdesign%2Fprocessor%2Fdatashts%2F320834.pdf&amp;amp;rct=j&amp;amp;q=intel%20core%20i7%20datasheet&amp;amp;ei=L2ggTeawK4bOhAeNq5y3Dg&amp;amp;usg=AFQjCNH67Re0EqGaYBN5Jqb_XU7mLZ0z7Q&amp;amp;sig2=h45UaGaUXILXYq8TnvkWLA&amp;amp;cad=rja&quot; rel=&quot;nofollow&quot;&gt;Here is the datasheet&lt;/a&gt;. The pins don't seem to be documented in that datasheet, and it's likely they are for factory specific testing (i.e. testing maximum operating frequency so they can bin chips into the various speed grades.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-02T12:04:37.553" CommentCount="5" />
  <row Id="8500" PostTypeId="2" ParentId="8496" CreationDate="2011-01-02T13:24:26.073" Score="2" ViewCount="" Body="&lt;p&gt;If you must do it, at least check an actual device with a  meter - check resistance between the pin and +ve and the pin and ground using both polarites on the meter - if this shows infinite resistance it probably isn't bonded and is safe to connect.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-02T13:24:26.073" CommentCount="1" />
  <row Id="8501" PostTypeId="2" ParentId="8157" CreationDate="2011-01-02T16:19:00.403" Score="1" ViewCount="" Body="&lt;p&gt;A good source for a drive for something like this would be a cheap electric drill/driver. Easy to control and plenty of torque.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-01-02T16:19:00.403" />
  <row Id="8502" PostTypeId="2" ParentId="8496" CreationDate="2011-01-02T16:26:01.753" Score="7" ViewCount="" Body="&lt;p&gt;It's a grey area. Some manufacturers tell you that's used for calibrating. Some manufacturers even will tell that you that certain pin has a function, only used by them for calibrating. Some tell you only not to connect it, or just say it's an unconnected pin.. You can't know for sure. The datasheet is information the manufacturer want to tell to you about using the device, but it might not be everything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recommended you do not connect them. If you get some generic IC from a different manufacturer or even batch the behaviour might be different. If you're engineering a project, you don't want to throw in unpredictability. You would have to test every single batch before you're going to use that particular batch. It depends on whatever you want to do that.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-01-02T16:26:01.753" />
  <row Id="8503" PostTypeId="2" ParentId="8495" CreationDate="2011-01-02T16:48:44.703" Score="2" ViewCount="" Body="&lt;p&gt;I have read that Lithium Polymer batteries can, in fact, be dangerous. I think they are actually a fire-hazard when overcharged. You're also not supposed to &quot;trickle-charge&quot; Li-Po batteries. They require a pretty specific charge cycle characteristic from what I understand. Basically, what I'm saying is I don't think you want to DIY when it comes to Li-Po battery charging. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used them once before, on an academic high-altitude ballooning project, and we were required to charge them in a metal enclosure because of the fire hazard, even though we were using a commercial charger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also on a somewhat unrelated note, I believe they are also pretty sensitive to being discharged to lower than 3V, and will not recharge if you take them down too low.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-03T15:13:45.367" LastActivityDate="2011-01-03T15:13:45.367" CommentCount="2" />
  <row Id="8504" PostTypeId="1" CreationDate="2011-01-02T18:29:14.790" Score="3" ViewCount="125" Body="&lt;p&gt;My kids have been tearing apart a number of different gadgets, from RC cars, to toys, to coffee makers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a variety of cool little motors and lights in these devices that we would like to use on oddball projects.  (For serious projects, I prefer to spec out the component and purchase it directly)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far, I've been using a variable voltage DC power supply to guess the right voltage based on what seems to be the correct speed, brightness, etc... without burning the item out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any scientific or mathematical technique that can be used to know when you are at a correct level of current or voltage for a given device, or does it simply depend on the specifications of the device?&lt;/p&gt;&#xA;" OwnerUserId="2457" LastActivityDate="2011-01-03T00:59:53.530" Title="A proper way to determine correct voltage of unmarked components?" Tags="&lt;motor&gt;&lt;voltage-measurement&gt;&lt;current-measurement&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="8505" PostTypeId="2" ParentId="8493" CreationDate="2011-01-02T19:00:21.540" Score="8" ViewCount="" Body="&lt;p&gt;TAP is on the bottom side. AH10 TCK, AJ9 TDI, AJ10 TDO, AG10 TMS, AH9 TRST#&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TCK I TCK (Test Clock) provides the clock input for the processor Test Bus (also known&#xA;as the Test Access Port).&#xA;&#xA;TDI I TDI (Test Data In) transfers serial test data into the processor. TDI provides the&#xA;serial input needed for JTAG specification support.&#xA;&#xA;TDO O TDO (Test Data Out) transfers serial test data out of the processor. TDO&#xA;provides the serial output needed for JTAG specification support.&#xA;&#xA;TESTLOW I TESTLOW must be connected to ground through a resistor for proper processor&#xA;operation.&#xA;&#xA;TMS I TMS (Test Mode Select) is a JTAG specification support signal used by debug&#xA;tools.&#xA;&#xA;TRST# I TRST# (Test Reset) resets the Test Access Port (TAP) logic. TRST# must be&#xA;driven low during power on Reset.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;UPDATE: here are some adapters for i7: &lt;a href=&quot;http://www.asset-intertech.com/products_interposers.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.asset-intertech.com/products_interposers.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Intel® Core™ i7 processors and the Intel® Xeon® processor 5500 series use LGA1366 sockets, similar in design to the LGA775/771 sockets. However, the high speeds of these processors mean that the use of an interposer between the socket and the CPU could interfere with signal integrity. Intel has therefore provided pads on the top side of the CPU, which mirror the required signals. To access these top-side pads, ASSET has developed a top-side probe.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The LGA1366 top-side probe consists of a PCB with a ring connector attached below it that contains small, spring-loaded probe tips. These tips make contact with the CPU's top-side pads, allowing the debug port signals to be broken out onto a flexible cable, which terminates in a small PCB carrying a Intel®-specified XDP header. The standard socket load mechanism is used above the probe's PCB to depress the CPU into its socket. The heatsink and fan are mounted onto a heatsink location plate supplied with the probe.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1994" LastEditorUserId="1994" LastEditorDisplayName="" LastEditDate="2011-03-22T22:40:36.463" LastActivityDate="2011-03-22T22:40:36.463" CommentCount="4" />
  <row Id="8506" PostTypeId="1" AcceptedAnswerId="8510" CreationDate="2011-01-02T19:07:05.157" Score="0" ViewCount="71" Body="&lt;p&gt;I've got a few NTSC security cameras I'd like to set up around the perimeter of the house. They output standard NTSC video and require 12V for power. I was hoping to power them and take video off the same cable, but I haven't been able to figure out a slick way to do it yet. Structured cable isn't all that expensive but if I could stick with standard RG59 or RG136 I think that'd be best.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately it's not like injecting power into RF signals; NTSC video sits around 1Vp-p and has high frequency components to it so it's not as simple as just using a DC blocking cap. Has anyone done something like this before and what kind of success have you had?&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-01-02T23:56:58.660" Title="slick way of muxing power+NTSC video over RG59/RG136?" Tags="&lt;power&gt;&lt;video&gt;&lt;multiplexing&gt;&lt;ntsc&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="8507" PostTypeId="2" ParentId="8496" CreationDate="2011-01-02T19:30:11.917" Score="1" ViewCount="" Body="&lt;p&gt;Sometimes.  On the TDA89xx, the recommended layout has traces routed through the NC pins.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-01-02T19:30:11.917" />
  <row Id="8508" PostTypeId="2" ParentId="8504" CreationDate="2011-01-02T19:38:55.610" Score="6" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wNvfb.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-02T19:38:55.610" CommentCount="1" />
  <row Id="8510" PostTypeId="2" ParentId="8506" CreationDate="2011-01-02T23:56:58.660" Score="1" ViewCount="" Body="&lt;p&gt;How did you get your Nintendo to display on a TV without baseband inputs?   You used an &lt;a href=&quot;http://www.amazon.com/dp/B0014KKV7W/&quot; rel=&quot;nofollow&quot;&gt;RF modulator&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So set up an RF modulator at the camera, then the normal DC block capacitor will work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It shouldn't be too hard to find an NTSC demodulator for the other end.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-02T23:56:58.660" CommentCount="1" />
  <row Id="8511" PostTypeId="1" AcceptedAnswerId="8531" CreationDate="2011-01-03T00:42:14.350" Score="6" ViewCount="275" Body="&lt;p&gt;What cheap LCD pixel displays are available which are 1&quot; or smaller which could be interfaced to a microcontroller? (AVR, PIC24, etc.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to make an interactive keyfob.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The important factor is small size, 1.5&quot;^2 maximum. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen small colour displays in LCD keychains which look ideal - but, it looks as though they use some custom controller logic which only talks USB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://ecx.images-amazon.com/images/I/41-2vncLzOL._SL500_AA300_.jpg&quot; width=&quot;200&quot;&gt;&#xA;&lt;img src=&quot;http://ecx.images-amazon.com/images/I/31NuaZi%2B1yL._SL500_AA300_.jpg&quot; width=&quot;200&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something like these 16x16 monochrome LCDs would be ok, if I could find a display controllable with SPI (this device has a custom epoxied blob).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://img.skitch.com/20090406-8dargu3hrnwdnfpgdu35k3tu78.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-07T23:26:07.733" Title="Cheap 1&quot; LCD suitable for use with microcontroller?" Tags="&lt;microcontroller&gt;&lt;lcd&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="2" />
  <row Id="8512" PostTypeId="2" ParentId="8490" CreationDate="2011-01-03T00:50:34.097" Score="2" ViewCount="" Body="&lt;p&gt;The ones with turned ridges are simple solder terminals - quite often screwing directly into the housing for a ground connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The plain ones (especially if they appear to be a wire potted in glass with a hex head surrounding them) are quite likely to be feedthrough capacitors, used for power or control signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally you would solder 22 gauge +/- stranded wire (or heavier if high current) onto them.  It goes best if you pre-tin both the terminal and the wire, especially for the ground terminals screwed into the housing which may take quite a bit of heat.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We used to use individual pin contacts from 2mm molex connectors in heatshrink on feedthroughs in the lab, but always directly soldered wires on shipping builds.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-01-03T00:50:34.097" />
  <row Id="8513" PostTypeId="2" ParentId="8504" CreationDate="2011-01-03T00:59:53.530" Score="3" ViewCount="" Body="&lt;p&gt;You may be able to deduce the operating voltage from what they came out of - for example, in a toy count the number of cells in the battery pack.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Things in plug-in appliances may be more complicated. Components may not be meant for the full mains voltage - for example I recall a curling iron where a small can motor was probably in series with (part of?) the heating element.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For small motors, there's also the can you touch it after it has run for several minutes (and had power disconnected) test.  Many toys (especially cars/planes/helicopters) will push motors harder than this and get away with it for a lifetime comparable to the rest of the toy's brief endurance.  But if it stays cool enough that it's not painful to touch, there's a good chance you aren't overdriving it.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-01-03T00:59:53.530" />
  <row Id="8514" PostTypeId="2" ParentId="8511" CreationDate="2011-01-03T01:18:48.400" Score="1" ViewCount="" Body="&lt;p&gt;Could you not salvage one from an old nokia(or other phone)? Such as the 3310. This &lt;a href=&quot;http://www.instructables.com/id/Connecting-Nokia-3310-LCD-to-USB-using-AVR/&quot; rel=&quot;nofollow&quot;&gt;instructables&lt;/a&gt; has a nice tutorial on the Nokia LCD and ATMega8. Just found this &lt;a href=&quot;http://www.amontec.com/lcd_nokia_3310.shtml&quot; rel=&quot;nofollow&quot;&gt;site&lt;/a&gt; that has useful information on sizing and pin layouts for the screen.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/ZbwZg.jpg&quot; alt=&quot;Nokia 3310&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-01-03T01:33:56.040" LastActivityDate="2011-01-03T01:33:56.040" />
  <row Id="8515" PostTypeId="1" CreationDate="2011-01-03T01:34:21.717" Score="2" ViewCount="315" Body="&lt;p&gt;I got an electrical engineering degree 15 years ago that I barely use.  Although I bought a fairly fancy multimeter, I will freely admit to having only a vague recollection of what I did back then... which was mostly discrete math and signal processing  (as opposed to circuits).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A friend of mine who has a lot more real-world &quot;electrician&quot; experience was trying to figure out what was wrong with some cameras he owned.  They were powered by cheap wall-warts and failing.  We were trying to check these power supplies to make sure they were working, as we didn't know if the problem was with the power or the camera.  Sure enough, some of the supplies were dead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We tried to substitute in some switchable supplies to get them working.  In the process, I noted with the multimeter that the polarity was different on the switchable supply from the adapters we were trying to replace.  As we were plugging in these 2-prong plugs haphazardly into 3-prong outlets, I wondered out loud if we might have the plugs in upside-down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;He looked at me condescendingly and said &lt;i&gt;&quot;Oh, I see.  You have a degree in this, do you?&quot;&lt;/i&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well firstly, it's been 15 years, and secondly...while he may know a lot about being an electrician I know about the diode bridge inside the stupid wall wart.  And yes, diodes can tell the difference between electron source and electron sink.  But if the power is an AC sine wave then it spends as much time in an up cycle as down cycle and so the decision about polarity is in the circuit post-rectification, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(So it was; to change the polarity on the adapter you just changed the terminals on the plug once it had been converted to DC, not before.  Fine.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the hypothetical question kept nagging me.  Given that one of the terminals is ostensibly true ground, would it be &lt;i&gt;possible&lt;/i&gt; to build an AC/DC converter whose DC polarity would flip based on which way you plugged it in (and I'm talking about no connection to 3rd prong)?  Do such things exist?&lt;/p&gt;&#xA;" OwnerUserId="2462" LastActivityDate="2011-05-11T00:24:45.327" Title="Can a 2-prong AC/DC converter switch polarity based on inverting the plug?" Tags="&lt;dc&gt;&lt;ac&gt;" AnswerCount="5" />
  <row Id="8516" PostTypeId="2" ParentId="8515" CreationDate="2011-01-03T01:44:03.493" Score="1" ViewCount="" Body="&lt;p&gt;No way. Given just a differential, just a pair of connections, there's no way for a circuit to tell which is which. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you had access to phase information about the grid, you might be able to do it, but as the mains frequency isn't terribly constant, you would not be able to rely on predicting this. Your device would have to get information about the present phase angle of the mains from someplace.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you &lt;em&gt;do&lt;/em&gt; have a real earth-ground reference from some place, you could build a circuit to look at the voltage of each supply line with respect to ground. One will be a small drop below the full 120 (or whatever the local mains supply) whereas the other will be slightly &lt;em&gt;above&lt;/em&gt; ground. (Neutral return current vs your neutral run's resistance). This would just let you know which leg was 'hot', and you could swap your output polarity accordingly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;A Second Thought&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the power supply has only four connections with the world, two from the mains plug, and two to output the DC, there's no way I can think of that you could &lt;em&gt;deterministically&lt;/em&gt; set output polarity based on plug orientation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BUT&lt;/p&gt;&#xA;&#xA;&lt;p&gt;if you're willing to make your otherwise simple supply a lot more complex, you could conceivably make it so that if you pulled the plug and flipped it, and plugged it back in straight away, the output would flip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the idea: You stuff some kind of micro-controller in the box, that monitors the line voltage, and determines when rising-crossing-zero (or some other phase point) happens on one of the legs. You'd have to reference this to the midpoint of the two supply legs via a voltage divider. The micro could then anticipate when the next such phase point would occur. Now you'd also have to put some kind of super-cap in the box and pick a low power micro that could live off the super-cap long enough for the user to flip the plug. When power comes back, either the anticipated phase change happens when you expect, or half-way between. Half-way between means the user flipped the plug, so your micro flips the output polarity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, that still would be problematic. If the thing had been unplugged for a while, the micro would be dead, and you'd have to make an assumption about what the output polarity should be. Finding a micro that could last maybe 10 seconds on a cap's worth power while actively chugging away could be easier said than done. Last and not least, this would really only be a novelty gadget.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-01-03T02:18:42.540" LastActivityDate="2011-01-03T02:18:42.540" CommentCount="4" />
  <row Id="8517" PostTypeId="2" ParentId="8515" CreationDate="2011-01-03T01:46:21.157" Score="1" ViewCount="" Body="&lt;p&gt;Short answer is, no, it is not possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a rectifier you are taking the negative part of the sine wave and flipping it to be a positive wave or to just ignore it. Because of this it doesn't matter what way you plug it in, negative will always be chopped off.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-03T01:46:21.157" CommentCount="4" />
  <row Id="8518" PostTypeId="1" AcceptedAnswerId="8520" CreationDate="2011-01-03T02:23:54.557" Score="3" ViewCount="139" Body="&lt;p&gt;The DALLAS DS1220ABs that I have were mostly manufactured in 1992 and 1993, I have a bunch of pulls.  The datasheet speaks of a &quot;lithium&quot; battery inside (not &quot;lithium-ion&quot;).  Do people here think that applying GND and VCC would recharge the &quot;lithium&quot; battery inside to make these chips quite usable, or is that just not the way it works? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(for e.g.  &lt;a href=&quot;http://cgi.ebay.com/Dallas-DS1220AB-200-16K-NonVolatile-SRAM-/170576839051&quot; rel=&quot;nofollow&quot;&gt;http://cgi.ebay.com/Dallas-DS1220AB-200-16K-NonVolatile-SRAM-/170576839051&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="2463" LastActivityDate="2011-01-03T23:12:51.513" Title="DALLAS DS1220AB Non-volatile SRAM from 20 years ago --- reusable?" Tags="&lt;ram&gt;" AnswerCount="2" />
  <row Id="8519" PostTypeId="2" ParentId="8515" CreationDate="2011-01-03T02:48:18.330" Score="4" ViewCount="" Body="&lt;p&gt;Actually yes, you can.  Ever used one of those nifty non contact voltage testers?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.fluke.com/fluke/usen/electrical-test-tools/electrical-testers/fluke-1ac-ii.htm?PID=56048&quot; rel=&quot;nofollow&quot;&gt;http://www.fluke.com/fluke/usen/electrical-test-tools/electrical-testers/fluke-1ac-ii.htm?PID=56048&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They can pretty reliably figure out which wire is phase and which is neutral, so all you'd need to do to build a magical wall wart would be to integrate such a sensor (just an antenna and an opamp).&lt;/p&gt;&#xA;" OwnerUserId="1179" LastEditorUserId="1179" LastEditorDisplayName="" LastEditDate="2011-01-03T02:53:30.900" LastActivityDate="2011-01-03T02:53:30.900" CommentCount="6" />
  <row Id="8520" PostTypeId="2" ParentId="8518" CreationDate="2011-01-03T02:53:38.297" Score="3" ViewCount="" Body="&lt;p&gt;The batteries are not rechargeable and the modules are designed to be replaced when they fail, not recharged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this because the modules are quite popular in old HP digitising oscilloscopes, of which I own one. After about 20 years the battery hits minimum voltage and calibration as well as some settings get reset back to defaults. I have heard of people having success with removing the battery from the package and replacing it, although I am not sure how well this would actually work. Applying a voltage to Vcc will not serve to charge the battery: this is because there is protection circuitry built into the module such that it does not recharge the non-rechargeable cell and damage the cell in the process.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-03T02:53:38.297" CommentCount="2" />
  <row Id="8522" PostTypeId="2" ParentId="8511" CreationDate="2011-01-03T03:43:46.767" Score="1" ViewCount="" Body="&lt;p&gt;I usually check &lt;a href=&quot;http://www.earthlcd.com&quot; rel=&quot;nofollow&quot;&gt;EarthLCD&lt;/a&gt; to see what they have available.  They tend to have a pretty good selection of small LCDs, and I have purchased many from them in the past.  I can't really comment on how good their prices are, but they at least have what I need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They don't have any in stock right now, but I purchased a 1.5&quot; color Seiko LCD from them before, part #RNH942209R1A.  $15.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-01-03T03:43:46.767" />
  <row Id="8523" PostTypeId="2" ParentId="8511" CreationDate="2011-01-03T04:02:03.177" Score="3" ViewCount="" Body="&lt;p&gt;Sparkfun sells these:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/569&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/569&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-03T04:02:03.177" CommentCount="1" />
  <row Id="8524" PostTypeId="2" ParentId="8511" CreationDate="2011-01-03T04:11:13.967" Score="1" ViewCount="" Body="&lt;p&gt;Does it have to be LCD? I have used some OLED displays with a micro-controller before. I have gotten them from &lt;a href=&quot;http://www.osddisplays.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.osddisplays.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-03T04:11:13.967" />
  <row Id="8525" PostTypeId="2" ParentId="8337" CreationDate="2011-01-03T04:21:08.770" Score="6" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/uQKpb.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-03T04:21:08.770" CommentCount="1" />
  <row Id="8526" PostTypeId="2" ParentId="8515" CreationDate="2011-01-03T04:43:26.183" Score="6" ViewCount="" Body="&lt;p&gt;This circuit will do what you want (for a literal interpretation of the question):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/vXExQ.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-03T04:43:26.183" CommentCount="5" />
  <row Id="8527" PostTypeId="2" ParentId="8337" CreationDate="2011-01-03T06:08:55.963" Score="1" ViewCount="" Body="&lt;p&gt;There were some guys at MIT a few years back that did wireless electricity transmission. They called it &quot;&lt;a href=&quot;http://web.mit.edu/newsoffice/2007/wireless-0607.html&quot; rel=&quot;nofollow&quot;&gt;WiTricity&lt;/a&gt;&quot;. In this case though they were intentionally trying to transmit electricity wirelessly and it only works over very short distances (~7m). If you don't have a very powerful energy source near your receiver it's not going to work.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-01-03T06:08:55.963" CommentCount="1" />
  <row Id="8528" PostTypeId="1" CreationDate="2011-01-03T07:39:56.990" Score="2" ViewCount="211" Body="&lt;p&gt;From:  &lt;a href=&quot;http://sharkshield.com/&quot; rel=&quot;nofollow&quot;&gt;http://sharkshield.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Shark Shield is a unique shark deterrent system utilising a technologically advanced three dimensional electrical wave form. Shark Shield technology is available for recreational users and water sports professionals to help all people enjoy the water with a new dimension – peace of mind; for themselves, their families and employees.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm referring to Shark Shield as an example.  &lt;strong&gt;What does a shark repellent circuit look like?&lt;/strong&gt;  What would be the maximum range you get under water and does it depend on the power source?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this simply putting + and - nodes under water and pulsating them with DC power?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any advice appreciated.&lt;/p&gt;&#xA;" OwnerUserId="561" LastEditorUserId="561" LastEditorDisplayName="" LastEditDate="2011-01-04T04:44:01.960" LastActivityDate="2011-01-04T04:44:01.960" Title="What would a Shark Shield circuit look like? (Not related to Arduino!)" Tags="&lt;circuit&gt;&lt;schematics&gt;" AnswerCount="2" CommentCount="10" FavoriteCount="1" />
  <row Id="8529" PostTypeId="2" ParentId="8528" CreationDate="2011-01-03T09:25:46.063" Score="1" ViewCount="" Body="&lt;p&gt;There FAQ has a little more information &lt;a href=&quot;http://sharkshield.com/?/m/faqs&quot; rel=&quot;nofollow&quot;&gt;http://sharkshield.com/?/m/faqs&lt;/a&gt; -&#xA; From what I gather from the limited info on the site, is that there is a small signal coming from the antenna. As for the specifics of the circuit and signal, its probably fairly simple, just a signal generator and an amp to the antenna. (just a guess) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The question is does it truly work, I have no clue im not a scuba diver or ever plan on being in the area where there are sharks present.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;one interesting quote that gives some clue to the power is&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Has the Shark Shield been proven to be safe to humans?&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The field generated by the Shark Shield, when used in accordance with the instructions &gt;contained in the instruction booklet supplied with each unit, poses no danger to the &gt;user, to sharks or to the environment. The field can be detected if the electrodes come &gt;into very close contact with the skin.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Direct contact with, or very close proximity to the antenna, may cause twitching of the &gt;surface muscles of the skin, in time with the slow pulsing of the signal. The conductive &gt;field readily travels through seawater, it being a better conductor than the human body. &gt;Thus the field tends to surround the body rather than penetrate it. Scientific tests show that the type of signal generated by the Shark Shield is unable to pass through body tissues, unlike radio waves or microwaves that readily penetrate the body, and therefore it poses no health problems for users.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-01-03T09:25:46.063" CommentCount="1" />
  <row Id="8530" PostTypeId="1" AcceptedAnswerId="8533" CreationDate="2011-01-03T09:35:07.073" Score="7" ViewCount="377" Body="&lt;p&gt;Well this is a continuation of my question on FPGA over &lt;a href=&quot;http://electronics.stackexchange.com/questions/5435/fpga-development-kit-for-beginners-spartan6-or-spartan3&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I finally selected a &lt;a href=&quot;http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,836&amp;amp;Prod=ATLYS&quot; rel=&quot;nofollow&quot;&gt;Digilent Atlys&lt;/a&gt; with a Spartan 6 FPGA, I don't have any prior experience of FPGA's although I have done some amount of work with micro-controllers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I spent the last few days reading through data sheets of the FPGA, and I think it would be a good choice to start off with Verilog. I couldn't find any code examples though and even the data sheets are not newbie friendly.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to do some hand's on programming, simulation, synthesis now and this is what I want to do&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Generate an odd frequency, say 54Mhz from the FPGA (it runs on a 100Mhz clock) and route it to one of the pins. I would probably have to use the DCM or PLL for this, but no idea how to start here?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Implement some sort of I2C read write from the FPGA.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;What I'm looking for is a reference, possibly an online one or a book that gives me code examples and description of each of the hardware components available inside the FPGA, like DCM's, slices, clb's etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess that should get me started into the world of FPGA's.&lt;/p&gt;&#xA;" OwnerUserId="444" LastActivityDate="2011-01-12T09:42:52.933" Title="FPGA, first steps" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;spartan&gt;" AnswerCount="3" FavoriteCount="4" />
  <row Id="8531" PostTypeId="2" ParentId="8511" CreationDate="2011-01-03T09:58:39.870" Score="3" ViewCount="" Body="&lt;p&gt;A guy named Rossum (know for the worlds &lt;a href=&quot;http://rossum.posterous.com/building-the-rbox&quot; rel=&quot;nofollow&quot;&gt;smallest, cheapest game console&lt;/a&gt;) did a nice job of reviewing and reverse engineering lots of &lt;a href=&quot;http://rossum.posterous.com/screen-play-lots-of-other-screens-for-microco&quot; rel=&quot;nofollow&quot;&gt;cheap LCD displays&lt;/a&gt;. In his latest post he reverse engineered an &lt;a href=&quot;http://rossum.posterous.com/a-smarter-display&quot; rel=&quot;nofollow&quot;&gt;iPod Nano 2g display&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="10" LastActivityDate="2011-01-03T09:58:39.870" />
  <row Id="8532" PostTypeId="2" ParentId="8489" CreationDate="2011-01-03T10:37:36.823" Score="3" ViewCount="" Body="&lt;p&gt;A DVT should cover everything you promise to your customer in the data sheet. Ideally, you also have made a spec long before you've written the data sheet, and the spec may even have more details than the data sheet because you don't want all the little things to be published.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you do the DVT, you test each and every parameter you specified before or while you designed the gadget. It's as simple (and as much work) as this.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-01-03T10:37:36.823" CommunityOwnedDate="2011-05-15T04:13:17.403" CommentCount="1" />
  <row Id="8533" PostTypeId="2" ParentId="8530" CreationDate="2011-01-03T11:03:13.163" Score="8" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Code Examples&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hop over to &lt;a href=&quot;http://www.opencores.org&quot; rel=&quot;nofollow&quot;&gt;OpenCores&lt;/a&gt; and you will find dozens of open source projects. There are many written in Verilog and cover the gamut from I/O devices through to processors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, do not forget the many Application Notes available from Xilinx. They are very helpful with their own devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Design Flow&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pick up a book or two on design flow so that you get an overview on the steps involved in FPGA design. In summary, they will involve:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Design entry - in your case, Verilog.&lt;/li&gt;&#xA;&lt;li&gt;Functional simulation - using various tools.&lt;/li&gt;&#xA;&lt;li&gt;Synthesis - in your case, using the Xilinx ISE tools.&lt;/li&gt;&#xA;&lt;li&gt;Simulation - to verify your post-synthesis design because some aspects of Verilog are not synthesisable.&lt;/li&gt;&#xA;&lt;li&gt;Place &amp;amp; Route - using the Xilinx ISE tools.&lt;/li&gt;&#xA;&lt;li&gt;Implementation - downloading the design onto the FPGA.&lt;/li&gt;&#xA;&lt;li&gt;Testing.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;FPGA Components&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for using the FPGA components, there are different ways to use them. But assuming that you are using a Verilog design entry, you can either &lt;em&gt;infer&lt;/em&gt; or &lt;em&gt;instantiate&lt;/em&gt; the different components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Inference&lt;/em&gt; generally involves getting the synthesis tool to pick the best components to use based on the functionality that you require. The best example of this would be to design an adder. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;By doing &lt;code&gt;q &amp;lt;= a + b&lt;/code&gt; or &lt;code&gt;q = a + b&lt;/code&gt; you can infer an adder. Both will infer the adder but there is a difference in when you use the blocking/non-blocking syntax.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Instantiation&lt;/em&gt; generally involves calling the exact library component in code. Some components just cannot be easily inferred in code - such as the DCM. You can use the ISE tools and examples to learn more about this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The actual list of components themselves are provided by Xilinx in the &lt;a href=&quot;http://www.xilinx.com/itp/xilinx4/pdf/docs/lib/lib.pdf&quot; rel=&quot;nofollow&quot;&gt;Libraries&lt;/a&gt; Guide. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Protip&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best way to learn this is actually to experiment with short bits of code and run them through the ISE synthesis to see what it spits out. There are also plenty of examples in the ISE toolset itself.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-01-03T11:03:13.163" CommentCount="1" />
  <row Id="8534" PostTypeId="1" AcceptedAnswerId="8535" CreationDate="2011-01-03T11:44:13.707" Score="5" ViewCount="466" Body="&lt;p&gt;this is a noob question but here it is:&lt;br&gt;&#xA;How can i connect an osciloscope to the 230V mains power line to see the voltage sine wave ?  &lt;br&gt;&#xA;- what schematic do i need&lt;br&gt;&#xA;- how safe is it ?&lt;/p&gt;&#xA;" OwnerUserId="2245" LastActivityDate="2011-01-04T12:28:52.790" Title="Connect 230V AC 50Hz to oscilloscope" Tags="&lt;oscilloscope&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="8535" PostTypeId="2" ParentId="8534" CreationDate="2011-01-03T12:22:19.567" Score="11" ViewCount="" Body="&lt;p&gt;Use a transformer (12V, say), it will be much safer even if your scope will handle the mains voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That particular scope will probably be damaged, DO NOT connect it to the mains! 230 V is the rms voltage, the peak voltage is 230 * 1.412 V.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-03T12:28:10.033" LastActivityDate="2011-01-03T12:28:10.033" />
  <row Id="8536" PostTypeId="2" ParentId="8534" CreationDate="2011-01-03T12:41:08.887" Score="8" ViewCount="" Body="&lt;p&gt;The &lt;strong&gt;ground clips&lt;/strong&gt; on your probes are connected to &lt;strong&gt;Earth ground&lt;/strong&gt; by means of the &lt;strong&gt;oscilloscope power plug&lt;/strong&gt;, in a roundabout fashion. &lt;strong&gt;&lt;em&gt;This means you can't connect it anywhere but Earth ground&lt;/em&gt;&lt;/strong&gt; (green wire in North America), and even then the path between your circuit and your oscilloscope plug may be so long that there is a voltage differential and capacitance, making for a rough transition back to 0V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get around this, isolate one of your 'scope or circuit with an isolation transformer. This gives &lt;a href=&quot;http://en.wikipedia.org/wiki/Galvanic_isolation&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;&lt;em&gt;galvanic isolation&lt;/em&gt;&lt;/strong&gt;&lt;/a&gt;, &lt;em&gt;allowing you to use a circuit ground at a different potential than your oscilloscope ground&lt;/em&gt;. Not all transformers isolate, but many common ones do. You can use 2 like step transformers from wall warts, if you want; for example: two 120V-to-12V step down transformers with the secondaries (12V-side) wired &lt;em&gt;back to back&lt;/em&gt;; 1:1 isolation transformers are also available. It is &lt;strong&gt;good practice&lt;/strong&gt; to &lt;em&gt;measure the potential between system grounds while taking other measurements&lt;/em&gt;. Keep a voltmeter hooked up, in high voltage mode, between your oscilloscope ground and circuit ground, one of which should be the Earth ground. (A banana plug fits pretty well into the ground hole in North American sockets.) This will give you an indication as to how dangerous &lt;em&gt;completing the circuit&lt;/em&gt;, be it with your hands, a spanner, or unisolated grounds, might be!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option, if you only want to measure AC waveforms, is to &lt;strong&gt;use a small 1:1 transformer for the probe alone&lt;/strong&gt;. The probe ground reference clips to primary #1 (X1), the probe itself clips to primary #2 (X2), then the secondary taps are used as your probing tools. This is not as safe as isolating the 'scope or circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that isolating your oscilloscope is also dangerous, as it can lead to a &lt;em&gt;hot chassis&lt;/em&gt;. This means that the 'scope case can be charged to dangerous levels. It is better to isolate the &lt;a href=&quot;http://en.wikipedia.org/wiki/Device_under_test&quot; rel=&quot;nofollow&quot;&gt;DUT&lt;/a&gt; itself, and treat it with care.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to isolate a system is to put it on battery power. If not practical for the DUT, you can do it to the 'scope, though you may have to build your own unit if the &quot;old Russian scope&quot; didn't come with one. Note that ground potential safety with the multimeter applies here, too. It is possible to &lt;em&gt;equalize&lt;/em&gt; grounds using a current limiting resistor in between. Once the voltage is within ~100V you can use a 100kohm pot and turn it from 100kohm to 0ohm over a few seconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will be measuring +/-325V (230Vac). Ensure you have the proper probes for this and your 'scope.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-04T12:28:52.790" LastActivityDate="2011-01-04T12:28:52.790" CommentCount="1" />
  <row Id="8537" PostTypeId="2" ParentId="8425" CreationDate="2011-01-03T15:05:46.353" Score="0" ViewCount="" Body="&lt;p&gt;I would also suggest using some sort of &lt;strong&gt;checksum&lt;/strong&gt; to verify the data on the SD is &lt;em&gt;correct&lt;/em&gt; whenever it needs to be read.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-01-03T15:05:46.353" />
  <row Id="8538" PostTypeId="2" ParentId="8528" CreationDate="2011-01-03T15:20:39.983" Score="1" ViewCount="" Body="&lt;p&gt;This sounds like a complete joke to me, but I will entertain an answer. Electrical energy does not propagate very well at all under water. The &quot;skin depth&quot; of water is something like half a meter @ 1MHz and maybe 7m @ 1kHz. As a rule of thumb, the lower the frequency (i.e. the longer the wavelength), the bigger the antenna you need to radiate at that frequency. As a point of reference, I think a 1kHz quarter-wave dipole antenna would be something like 25 miles tall. I would be more inclined to believe a shark deterent system (if such a thing exists) would be based on very low frequency acoustic technology... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, the article linked by @jsolarski above makes it sound like there is some actual scientific research out there that supports it experimentally... &lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-03T16:14:36.830" LastActivityDate="2011-01-03T16:14:36.830" CommentCount="2" />
  <row Id="8539" PostTypeId="1" CreationDate="2011-01-03T17:46:07.037" Score="3" ViewCount="247" Body="&lt;p&gt;Looking for resources on how to start taking my creations to the next level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Where I'm at:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I'm a software developer nerd with limited hardware design experience&lt;/li&gt;&#xA;&lt;li&gt;Comfortable creating stuff with the Arduino Duelimanove / Uno pre-fab boards w/ breadboards, project boxes, and lots of tape and zip ties&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Where I want to go:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Turn a &quot;breadboard&quot; solution into a custom, non-ghetto PCB&lt;/li&gt;&#xA;&lt;li&gt;Integrate Arduino / Netduino chips into designs&lt;/li&gt;&#xA;&lt;li&gt;Being a software guy, I don't really have a desire to make PCB's by hand with the newer &quot;design in computer and have it shipped to you&quot; model&lt;/li&gt;&#xA;&lt;li&gt;Have designs made in very small quantities (1 at a time, maybe 5 at a time max)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In my google-ing so far, I've tried looking for an outsourced PCB manufacturer that might have an Arduino template component that I can drop on a virtual PCB board and start messing around, but haven't found anything. I assume there are some specific measurements that would allow me to create my own component, but no idea what they are called to search for them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any recommendations here would be appreciated on vendors, software, concepts I need to educate myself on, and such.&lt;/p&gt;&#xA;" OwnerUserId="2469" LastActivityDate="2011-01-03T21:34:43.213" Title="Where do I start for Arduino PCB design?" Tags="&lt;software&gt;&lt;design&gt;&lt;pcb-design&gt;" AnswerCount="3" />
  <row Id="8540" PostTypeId="2" ParentId="8539" CreationDate="2011-01-03T18:10:43.073" Score="1" ViewCount="" Body="&lt;p&gt;If you use Eagle you can load the Arduino files into it and create your own template - the boards were designed using Eagle. I use Pulsonix PCB software, and imported the files to create a template for that program. You can then create your own shields.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-03T18:10:43.073" />
  <row Id="8541" PostTypeId="1" CreationDate="2011-01-03T18:35:51.580" Score="1" ViewCount="97" Body="&lt;p&gt;I want to know how to make a sample solar cell which can generate power of a very small magnitude.  What material is required and how would I assemble it to make a simple solar cell?&lt;/p&gt;&#xA;" OwnerUserId="2470" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-03T23:26:08.303" LastActivityDate="2011-01-03T23:42:00.597" Title="How do I make a small sample solar cell?" Tags="&lt;solar-cell&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="8542" PostTypeId="2" ParentId="8495" CreationDate="2011-01-03T18:57:33.913" Score="1" ViewCount="" Body="&lt;p&gt;good app note here if you want to build your own &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1037,C1078,C1089,P89360&quot; rel=&quot;nofollow&quot;&gt;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1037,C1078,C1089,P89360&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2472" LastActivityDate="2011-01-03T18:57:33.913" />
  <row Id="8543" PostTypeId="2" ParentId="8541" CreationDate="2011-01-03T19:06:50.053" Score="2" ViewCount="" Body="&lt;p&gt;For my optoelectronics class final project, my group attempted to make a &lt;a href=&quot;http://mrsec.wisc.edu/Edetc/nanolab/TiO2/index.html&quot; rel=&quot;nofollow&quot;&gt;nanocrystalline titanium dioxide solar cell&lt;/a&gt;.  Short of having access to silicon fab equipment, I think this &lt;a href=&quot;http://en.wikipedia.org/wiki/Dye-sensitized_solar_cell&quot; rel=&quot;nofollow&quot;&gt;dye-sensitized solar cell&lt;/a&gt; is the best you can do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The (slightly) less-common materials it uses are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Tin-oxide-coated glass plates/slides&lt;/li&gt;&#xA;&lt;li&gt;Nanocrystalline TiO&lt;sub&gt;2&lt;/sub&gt;&lt;/li&gt;&#xA;&lt;li&gt;Potassium iodide&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Ours ended up failing, I believe it was because the consistency of our TiO&lt;sub&gt;2&lt;/sub&gt; paste wasn't that good, or some possible shorts between the plates.  This seems to be a fairly common educational cell, and the &lt;a href=&quot;http://www.chem.yale.edu/~cas/tio2.html&quot; rel=&quot;nofollow&quot;&gt;mechanism of action&lt;/a&gt; is well-described.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-03T19:06:50.053" />
  <row Id="8544" PostTypeId="2" ParentId="8539" CreationDate="2011-01-03T19:38:14.410" Score="0" ViewCount="" Body="&lt;p&gt;There is very little to gain from reusing the Arduino files, as the basic construction is so simple, so don't put too much value in that, it's much more important that you understand what's going on and you get a good EDA package that you can use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I was you, then I'd start out looking into a simple clone like the &quot;DC Boarduino&quot;, which is basically an Arduino as that's simple enough to understand a clone quite easily.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The trick with the &quot;DC Boarduino&quot; is that is leaves out the FTDI USB chip, which is very cool if you only use the USB connection when developing, so you can buy only one FTDI adaptor and reuse it for all your Arduino-like boards, like this one:&#xA;&lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=19&amp;amp;products_id=284&amp;amp;zenid=42367bcc145ecc7da8c87d51db3b70be&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=19&amp;amp;products_id=284&amp;amp;zenid=42367bcc145ecc7da8c87d51db3b70be&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;WRT the EDA package recommendation:  I've used EAGLE before, but it really is limited and that can bite you in the ass when you start building bigger things, so I can recommend skipping EAGLE and using Kicad in stead.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-01-03T19:38:14.410" CommentCount="2" />
  <row Id="8545" PostTypeId="2" ParentId="8539" CreationDate="2011-01-03T21:28:00.660" Score="2" ViewCount="" Body="&lt;p&gt;Whatever CAD package you use (I use Eagle and the &quot;limitations&quot; have never caused me any grief so far), what you're going to need is gerber files. In Eagle you generate these using what's called a CAM job (I use the &lt;a href=&quot;http://www.sparkfun.com/tutorial/Eagle-DFM/sfe-gerb274x.cam&quot; rel=&quot;nofollow&quot;&gt;one from Sparkfun&lt;/a&gt;). Incidentally, the &lt;a href=&quot;http://www.sparkfun.com/tutorials/108&quot; rel=&quot;nofollow&quot;&gt;Sparkfun Eagle Tutorial&lt;/a&gt; is also pretty good to get you started if you go that route, and there's also an ok &lt;a href=&quot;http://www.adafruit.com/blog/2009/11/19/pcb-routing-with-eagle-video/&quot; rel=&quot;nofollow&quot;&gt;screencast from Adafruit&lt;/a&gt;. You can also get the Eagle files for the Arduino boards &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardUno&quot; rel=&quot;nofollow&quot;&gt;right off their website&lt;/a&gt; (also for their &lt;a href=&quot;http://arduino.cc/en/Main/Boards&quot; rel=&quot;nofollow&quot;&gt;older boards&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have the gerber files, you just need to zip those up and send them to a fab house. For low volumes, the cheapest decent quality prototyping service I've come across is &lt;a href=&quot;http://dorkbotpdx.org/wiki/pcb_order&quot; rel=&quot;nofollow&quot;&gt;DorkbotPDX&lt;/a&gt; for small boards. I've also used &lt;a href=&quot;http://batchpcb.com/index.php/Products&quot; rel=&quot;nofollow&quot;&gt;BatchPCB&lt;/a&gt; but have found them both more expensive and longer delay.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-03T21:34:43.213" LastActivityDate="2011-01-03T21:34:43.213" />
  <row Id="8546" PostTypeId="2" ParentId="1600" CreationDate="2011-01-03T21:31:44.777" Score="0" ViewCount="" Body="&lt;p&gt;I've used &lt;a href=&quot;http://www.expresspcb.com/&quot; rel=&quot;nofollow&quot;&gt;Express PCB&lt;/a&gt; for strip board development.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-03T21:31:44.777" />
  <row Id="8547" PostTypeId="2" ParentId="8530" CreationDate="2011-01-03T21:59:08.187" Score="1" ViewCount="" Body="&lt;p&gt;For the clock you use the DLL/PLL megacore.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-03T21:59:08.187" CommentCount="1" />
  <row Id="8548" PostTypeId="1" CreationDate="2011-01-03T22:02:20.767" Score="2" ViewCount="100" Body="&lt;p&gt;I'm using a couple of continuous rotation servos to drive the wheels on a mobile robot.  One issue I have is that the servos produce a loud, whining sound when in use.  Do higher quality servos exist that make less noise?  It would also be great if the robot could move a bit faster - are speedier servos available?&lt;/p&gt;&#xA;" OwnerUserId="1841" LastActivityDate="2011-01-04T00:32:48.557" Title="Quieter, faster continuous rotation servos" Tags="&lt;servo&gt;&lt;mobile-robot&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="8549" PostTypeId="2" ParentId="8548" CreationDate="2011-01-03T22:54:31.037" Score="0" ViewCount="" Body="&lt;p&gt;I believe you just need separate(and more powerfull) brushless motors + reductors for this.&#xA;This way you can control speed, not spefic angle of each whell.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-03T22:54:31.037" />
  <row Id="8550" PostTypeId="2" ParentId="484" CreationDate="2011-01-03T22:54:54.950" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://macclesfieldlaser.com/index.html&quot; rel=&quot;nofollow&quot;&gt;Macclesfield Laser&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've not used the service, but I know the people who run the place and when I finally set up my own electronics biz I &lt;strong&gt;will&lt;/strong&gt; be using them.&lt;/p&gt;&#xA;" OwnerUserId="2433" LastActivityDate="2011-01-03T22:54:54.950" CommentCount="1" />
  <row Id="8551" PostTypeId="1" AcceptedAnswerId="8556" CreationDate="2011-01-03T22:58:05.710" Score="5" ViewCount="387" Body="&lt;p&gt;Are there any UK electronics shop other than Maplins?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or any local to Bristol?&lt;/p&gt;&#xA;" OwnerUserId="2433" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-04T21:58:04.397" LastActivityDate="2011-04-11T16:56:38.460" ClosedDate="2011-04-12T02:48:03.207" Title="UK electronics shop other than Maplins?" Tags="&lt;components&gt;&lt;uk&gt;" AnswerCount="6" CommentCount="3" FavoriteCount="5" />
  <row Id="8552" PostTypeId="2" ParentId="8551" CreationDate="2011-01-03T23:03:50.757" Score="1" ViewCount="" Body="&lt;p&gt;originally, Maplins was mostly a stockist of discrete electronic components and related tools and accessories. Nowadays it seems to have shifted it's line of business and electronic consumer gadgets of all sorts form a large part of it's inventory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the former there is mail order from Farnell and others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the latter there is Curry's I suppose.&lt;/p&gt;&#xA;" OwnerUserId="2191" LastActivityDate="2011-01-03T23:03:50.757" CommentCount="1" />
  <row Id="8553" PostTypeId="2" ParentId="8518" CreationDate="2011-01-03T23:12:51.513" Score="0" ViewCount="" Body="&lt;p&gt;Dallas also did a unit with a real time clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you have is several parts in one package.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Lithium battery (or Cell) - Non rechargeable - Not designed to be recharged&lt;/li&gt;&#xA;&lt;li&gt;SDRAM ic (or Real time Clock IC with SDRAM - External xtal)&lt;/li&gt;&#xA;&lt;li&gt;Power control IC - e.g. DS1210 - this switches from external to internal battery, and disables the write control signal when external supply falls.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The RTC versions had visible terminal for the battery, which if you were careful you could remove (Damaging the Package) and replace with another cell/battery or cell/battery holder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The one shown in your link was made in 1996 - and is now about 14 years old. - the internal battery will be dead as even if it was not used - it would be past it's shelf life. It could be used as a SDRAM but would not hold data when power is removed.&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2011-01-03T23:12:51.513" />
  <row Id="8554" PostTypeId="2" ParentId="8551" CreationDate="2011-01-03T23:20:29.997" Score="3" ViewCount="" Body="&lt;p&gt;Maplins - not as good for parts as it was.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These days for parts - On-line - from CPC / Farnell or RS &#xA;(CPC/Farnell/RS do have trade counters - But I'm not sure how to get service)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you require spare parts - then if you can give an idea of what is required then suggestions can be made.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Curry's &amp;amp; Comet are retailers of consumer items - not electronic parts.&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2011-01-03T23:20:29.997" />
  <row Id="8555" PostTypeId="2" ParentId="8548" CreationDate="2011-01-03T23:24:00.830" Score="2" ViewCount="" Body="&lt;p&gt;Any standard PMDC motor would work for this, brushed or brushless.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Continuous rotation servos if I recall correctly are basically just a hack.  The typical servo has a radial pot, motor, gearing, and a little controller to get the position right.  Their goal is to provide repeatable, precise control, not be efficient or very fast.  The reason they make so much noise is because you have a tiny, tiny motor spinning a massive step-down transmission.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using &quot;just a motor&quot; and gearing it down yourself (or with an integrated gear head on the motor) is the best solution.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-03T23:24:00.830" />
  <row Id="8556" PostTypeId="2" ParentId="8551" CreationDate="2011-01-03T23:26:18.613" Score="11" ViewCount="" Body="&lt;p&gt;As Well as Maplin in the UK, there's Farnell (as mentioned by RedGrittyBrick) and:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rapid: &lt;a href=&quot;http://www.rapidonline.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.rapidonline.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bitsbox: &lt;a href=&quot;http://www.bitsbox.co.uk/&quot; rel=&quot;nofollow&quot;&gt;http://www.bitsbox.co.uk/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bowood: &lt;a href=&quot;http://www.bowood-electronics.co.uk/&quot; rel=&quot;nofollow&quot;&gt;http://www.bowood-electronics.co.uk/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RSH: &lt;a href=&quot;http://www.rshelectronics.co.uk/&quot; rel=&quot;nofollow&quot;&gt;http://www.rshelectronics.co.uk/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ESR: &lt;a href=&quot;http://www.esr.co.uk/&quot; rel=&quot;nofollow&quot;&gt;http://www.esr.co.uk/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All mail order.&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2011-01-03T23:26:18.613" />
  <row Id="8557" PostTypeId="2" ParentId="8541" CreationDate="2011-01-03T23:42:00.597" Score="2" ViewCount="" Body="&lt;p&gt;Shining bright sunlight on an LED or any optical, junction device (photodiode etc.) will cause it to generate a very small amount of electricity - you might have a play with that phenomenon.&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2011-01-03T23:42:00.597" />
  <row Id="8558" PostTypeId="1" AcceptedAnswerId="8563" CreationDate="2011-01-03T23:55:47.420" Score="1" ViewCount="134" Body="&lt;p&gt;Perhaps impractical, but let's say I did want to build some kind of circuit / project that would have a better chance of detecting whether the dishes in the dishwasher were clean or dirty. What do you all think?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some ideas:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Webcam - image &amp;amp; sound detection, if it detects the sound of the dishwasher, set status to clean until it sees an empty dishwasher?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Laser / IR something that will detect if anything is breaking the plane just above one of the racks?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2258" LastActivityDate="2011-01-05T00:44:03.717" Title="What are some ideas to build a clean/dirty detector for the dishwasher?" Tags="&lt;electronics&gt;&lt;home-automation&gt;&lt;hack&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="8560" PostTypeId="2" ParentId="8548" CreationDate="2011-01-04T00:32:48.557" Score="0" ViewCount="" Body="&lt;p&gt;If it doesn't have position feedback, it's not a servo.  Continuous rotation &quot;servos&quot; are just gearmotors in the hobby-servo form factor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what you want to do is get proper gearmotors to run the wheels.  There are lots to choose from.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-04T00:32:48.557" CommentCount="1" />
  <row Id="8561" PostTypeId="2" ParentId="8558" CreationDate="2011-01-04T01:01:09.483" Score="2" ViewCount="" Body="&lt;p&gt;A very difficult but accurate method &lt;em&gt;(and supercool)&lt;/em&gt; to do this is with an array of &lt;strong&gt;sonar&lt;/strong&gt; transducers. One could characterize the &lt;em&gt;empty&lt;/em&gt; state with a small range of sonar maps of the interior. The device would continuously map the inside with the ability to detect changes outside of the range of &lt;em&gt;empty&lt;/em&gt; states (there will be a range due to rack movement, temperature &amp;amp; humidity gradients, and whether or not the door is open). I haven't implemented a sonar system myself, but the analog design appears to be quite involved.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You mentioned &lt;strong&gt;infra-red&lt;/strong&gt;: this is a good idea. An array of IR transceivers could also map the empty state(s), sending from 1 unit and receiving at all of them (requires &lt;em&gt;smart, independent&lt;/em&gt; sensors). One could compare the received intensity as a result of each sending unit to each of the small ranges of mapped &lt;em&gt;empty&lt;/em&gt; state intensities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both of these methods allow the ability to keep track of the order of states. The &lt;strong&gt;state machine&lt;/strong&gt; would include all permutations of: empty, not empty (sonar); cycle off, cycle incomplete, cycle complete (tap off of dishwasher indicators); door open, door closed (tap off of dishwasher switch). It would be easily fooled by putting a dirty item in before allowing a scan of an empty dishwasher.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Personally, if I or roommates had trouble remembering this, I'd just hang a dry erase marker on the handle by a string and write &quot;clean&quot; or &quot;dirty&quot; on the front panel!&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-04T03:46:44.537" LastActivityDate="2011-01-04T03:46:44.537" CommentCount="1" />
  <row Id="8562" PostTypeId="2" ParentId="1454" CreationDate="2011-01-04T01:24:20.027" Score="1" ViewCount="" Body="&lt;p&gt;Hey! I'm glad to have discovered a place like this. I am a beginning enthusiast, and was searching for the exact same thing--a decent little scope with a price I can handle. I too searched the eBay and Craigslist sites for hours. The scopes there all seem risky, since only one of hundreds of sellers offered a guarantee, and due to the (already mentioned) fact that many are offered incomplete. I found something GREAT tonight, though. There's a pro hobbyist selling &quot;project&quot; scopes for under $100 new! The site even offers FREE probes for those who purchase the fully assembled or kit versions. Info concerning the &quot;DPScope&quot; can be found here: &lt;a href=&quot;http://www.pdamusician.com/dpscope/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.pdamusician.com/dpscope/index.html&lt;/a&gt;    The obvious compromise of this design is also its meager max bandwidth of 1.3Mhz.  I'm new at this, too, so some of you experienced ones can check the spec's on the same site. One of my many books listed a 20-25Mhz maximum as the perfect starting point for a hobbyist, with two channels (dual-trace) as a must-have, and &quot;storage&quot; as a great help, but not a necessity. The said book is about two decades old, though! Happy hunting :--)&lt;/p&gt;&#xA;" OwnerUserId="2475" LastActivityDate="2011-01-04T01:24:20.027" CommentCount="1" />
  <row Id="8563" PostTypeId="2" ParentId="8558" CreationDate="2011-01-04T01:50:11.283" Score="3" ViewCount="" Body="&lt;p&gt;I would break down the system into 2 parts&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Detecting when the Dishwasher is running&lt;/li&gt;&#xA;&lt;li&gt;Detecting when the Dishwasher has been emptied&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I would then consider some options for each one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For Detecting when the Dishwasher is running:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Figure out how to tie into the Dishwashers electrical system and find a line that changes when the washer is running&lt;/li&gt;&#xA;&lt;li&gt;Watch the current on the power lines going into the washer, higher current means its running.&lt;/li&gt;&#xA;&lt;li&gt;Use audio to detect if it is running&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For Detecting when the Dishwasher has been emptied there are lots of options, but I would go for a simple approach. Watch how long the door has been open for. If you open it to just pull an item or 2 out then it wont take you long. Start a timer and if the door is open for longer then lets say 30 seconds then you know it wasn't long enough to empty it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option could be to wait until the dishwasher has been closed before resetting it to dirty. You just have to remind yourself to not close the door all of the way until you have emptied it.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-04T01:50:11.283" CommentCount="1" />
  <row Id="8564" PostTypeId="2" ParentId="6684" CreationDate="2011-01-04T03:57:06.027" Score="3" ViewCount="" Body="&lt;p&gt;Agree with the answers above. Just wanted to add that the zero-ohm type is not so uncommon these days. This could be a very popular PIFA antenna. &#xA;You will not measure exactly zero ohm with PIFAs, loops or folded dipoles, the DC resistance would be a couple of ohms.&lt;/p&gt;&#xA;" OwnerUserId="2477" LastActivityDate="2011-01-04T03:57:06.027" />
  <row Id="8565" PostTypeId="1" AcceptedAnswerId="8566" CreationDate="2011-01-04T07:27:38.357" Score="6" ViewCount="525" Body="&lt;p&gt;This question popped up to me a few moments ago.&#xA;I was measuring what is intended to be a 50Mhz square wave of level 0 to 2.5, however what I saw on the screen is a sine wave that was centered around 1.2V and level of 0.5 to 2.0V, the frequency was 4MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I checked up my oscilloscopes datasheet and it showed that the bandwidth was 10MHz with a sampling rate of 50 MS/s. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wondering what these figures are all about. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Are they a measure of the upper&#xA;frequency limit an oscilloscope can&#xA;measure? &lt;/li&gt;&#xA;&lt;li&gt;Is this oscilloscope capable&#xA;of measuring 50Mhz at all?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="444" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-05T20:29:55.253" LastActivityDate="2011-01-05T20:29:55.253" Title="Oscilloscope Bandwidth, what's it all about?" Tags="&lt;oscilloscope&gt;&lt;frequency-measurement&gt;&lt;bandwidth&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="4" />
  <row Id="8566" PostTypeId="2" ParentId="8565" CreationDate="2011-01-04T08:14:57.443" Score="14" ViewCount="" Body="&lt;p&gt;System bandwidth is a combination of probe bandwidth and oscilloscope input bandwidth. Each can be approximated by an RC lowpass circuit, which means delays add geometrically:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;t_system^2 = (t_probe^2 + t_scope^2)&#xA;f_system = 1/sqrt((1/f_probe)^2 + (1/f_scope)^2)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This means that a 10MHz 'scope with 60MHz probes can measure sinusoids of frequency 9.86MHz with -3dB (100*10^{-3/20}%) attenuation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When measuring digital pulse trains it's not so much the periodicity that matters, but the rise and fall times, as they &lt;em&gt;contain&lt;/em&gt; the high-frequency information. Rise times can be approximated mathematically by an RC rise or a Gaussian rise, and are defined as the time for the signal to go from 10% of the difference between &lt;em&gt;low&lt;/em&gt; voltage &lt;em&gt;(logical 0)&lt;/em&gt; and &lt;em&gt;high&lt;/em&gt; voltage &lt;em&gt;(logical 1)&lt;/em&gt;, to 90% of the difference. For example, in a 5V/0V system, it is defined as the time to get from &lt;code&gt;0.1*5V=0.5V&lt;/code&gt; to &lt;code&gt;0.9*5V=4.5V&lt;/code&gt;. With these constraints and some &lt;a href=&quot;http://en.wikipedia.org/wiki/Rise_time#Simple_examples_of_calculation_of_rise_time&quot; rel=&quot;nofollow&quot;&gt;fancy math&lt;/a&gt;, one can work out that each type of characteristic rise time has frequency content up to about &lt;code&gt;0.34/t_rise&lt;/code&gt; for Gaussian and &lt;code&gt;0.35/t_rise&lt;/code&gt; for RC. (I use &lt;code&gt;0.35/t_rise&lt;/code&gt; for no good reason and will do so for the rest of this answer.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This information works the other way, too: a particular system bandwidth is only able to measure rise times up to &lt;code&gt;0.35/f_system&lt;/code&gt;; in your case, 35 to 40 nanoseconds. You're seeing something similar to a sine wave because that is what the analog front-end is letting through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Aliasing&lt;/strong&gt; is a digital sampling artifact, and is also in effect in your measurement (aren't you lucky!). Here's a borrowed image &lt;a href=&quot;http://en.wikipedia.org/wiki/Aliasing&quot; rel=&quot;nofollow&quot;&gt;from WP:&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/2/28/AliasingSines.svg/350px-AliasingSines.svg.png&quot; alt=&quot;Aliasing example.&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the analog front-end is only letting rise times 35ns to 40ns through, the ADC sampling bridge &lt;em&gt;sees&lt;/em&gt; something like an attenuated 50MHz sine wave, but it's only sampling at 50MS/s, so it can only &lt;em&gt;read&lt;/em&gt; sinusoids below 25MHz. Many 'scopes have an &lt;strong&gt;antialiasing filter&lt;/strong&gt; (LPF) at this point, which would attenuate frequencies above 0.5 times the sample rate (Shannon-Nyquist sampling criteria). Your scope doesn't seem to have this filter, though, as the peak-to-peak voltage is still fairly high. What model is it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After the sampling bridge the data gets shoved into a few DSP processes, one of which is called &lt;strong&gt;decimation&lt;/strong&gt; and &lt;strong&gt;cardinal spans&lt;/strong&gt;, which further reduces sample rate and bandwidths in order to better display and analyze it (especially helpful for FFT calculation). The data is further massaged such that it doesn't display frequencies above ~0.4 times the sample rate, called a &lt;a href=&quot;http://en.wikipedia.org/wiki/Guard_band&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;guard band&lt;/strong&gt;&lt;/a&gt;. I would have expected you to see a ~20MHz sinusoid -- do you have averaging (5-point) turned on?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; I'll stick my neck out and guess that your oscilloscope has digital antialiasing, using decimation and cardinal spans, which basically means a digital LPF then resampling of an interpolated path. The DSP program &lt;em&gt;sees&lt;/em&gt; a 20MHz signal, so it decimates it until it is below 10MHz. Why 4MHz and not closer to 10MHz? &quot;Cardinal span&quot; means halving the bandwidth, and decimation is often by a power of two as well. Some integer power of 2 or a simple fraction of it resulted in a 4MHz sinusoid being spat out instead of ~20MHz. This is why I say every enthusiast needs an analog 'scope. :)&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;sub&gt;&lt;strong&gt;EDIT2:&lt;/strong&gt; Since this is getting so many views, I'd better correct the above embarrassingly thin conclusion.&lt;/sub&gt;&lt;br&gt;&#xA;&lt;strong&gt;EDIT2:&lt;/strong&gt; The particular tool &lt;a href=&quot;http://www.picotech.com/handheld-oscilloscope.html&quot; rel=&quot;nofollow&quot;&gt;you liked to&lt;/a&gt; can use undersampling, for which a windowing analog BPF input is required for antialiasing, which this tool doesn't seem to have, so it must only have a LPF, restricting it to sinusoids of less than 25MHz even when using &lt;a href=&quot;http://www.picotech.com/education/oscilloscopes/equivalent-time-sampling.html&quot; rel=&quot;nofollow&quot;&gt;equiv. time sampling&lt;/a&gt;. Although I also suspect the quality of the analog side, the digital side likely does not do the aforementioned DSP algorithms, instead streaming data or transferring one &lt;em&gt;capture&lt;/em&gt; at a time for brute force number crunching on a PC. 50MS/s and 8-bit word lengths means this is generating ~48MB/s of raw data -- far too much to stream over USB despite its theoretical 60MB/s limit (practical limit is 30MB/s-40MB/s), nevermind the packetizing overhead, so there is some decimation right out of the box to reduce this. Working with 35MB/s gives ~37MS/s sample rate, pointing to a theoretical measurement limit of 18MHz, or 20ns rise time, when streaming, though it is likely lower as 35MB/s is amazing (but possible!). &lt;a href=&quot;http://www.picotech.com/document/pdf/ps2100.en-3.pdf&quot; rel=&quot;nofollow&quot;&gt;The manual&lt;/a&gt; indicates a &lt;em&gt;Block Mode&lt;/em&gt; exists for capturing data at 50MB/s 'til the internal 8k memory &lt;em&gt;(cough)&lt;/em&gt; is full (160us), then sending it to the computer at a leisurely pace. I would assume that the difficulties encountered in designing a quality analog input were partially overcome by &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8003.pdf&quot; rel=&quot;nofollow&quot;&gt;oversampling&lt;/a&gt; by 2X (extra half-bit accuracy), giving an effective sample rate of 25MS/s, maximum frequency 12.5MHz, and a 10% guard band (&lt;code&gt;(0.5*25-10)/25&lt;/code&gt;), all of which could be reduced in the hand-tool itself. &lt;em&gt;In conclusion, I'm not sure why you're seeing a 4MHz sinusoid as there are ways for this to happen, but would want to make the same measurement in Block Mode then analyze the data with a third-party program. &lt;sub&gt;I have always been hard on PC-based oscilloscopes, but this one seems to have decent inputs...&lt;/sub&gt;&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-05T00:20:05.827" LastActivityDate="2011-01-05T00:20:05.827" CommentCount="14" />
  <row Id="8567" PostTypeId="2" ParentId="8565" CreationDate="2011-01-04T08:26:33.757" Score="3" ViewCount="" Body="&lt;p&gt;10 MHz analog bandwidth means that a 10 MHz signal at 10 V will look like a 5 V, in other words your amplitude will be halved at 10 MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 10 MHz bandwidth means that your 50 MHz signal will be dampened down quite a bit, but how much is hard to speculate on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 50 MS/s means that you cannot realistically work with signals much over 5 MHz if you hope to do single-shot capture of the signal, which is really the only reason to have a DSO in the first place.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ignoring the bandwidth problem for a minute, you might be able to put the scope into repetitive sampling mode and capture a repetitive signal that way, just like an analog scope does.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd get a proper DSO (The Rigol ds1052e modded to 100 MHz analog bandwidth gets my recommendations), failing that a used Tektronix analog scope might be a good way to go (I use the 2236, 2246 and 2247A models from time to time and they are all fine analog scopes)&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-01-04T08:26:33.757" CommentCount="8" />
  <row Id="8568" PostTypeId="2" ParentId="8565" CreationDate="2011-01-04T08:34:45.977" Score="1" ViewCount="" Body="&lt;pre&gt;&lt;code&gt;* Are they a measure of the upper frequency limit an oscilloscope can measure?&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Yes for direct measurment.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;* Is this oscilloscope capable of measuring 50Mhz at all?&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Yes, using some tricky ways:&#xA;1) peak detection (useful when you need to see AM modulated signal)&#xA;2) Freq shift (again, useful when signal is modulated) - If you mix 50Mhz signal with 49Mhz sine wave, you'll get 1Mhz signal near the frequency you want. &lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-04T08:34:45.977" CommentCount="2" />
  <row Id="8569" PostTypeId="1" AcceptedAnswerId="8572" CreationDate="2011-01-04T09:20:40.460" Score="3" ViewCount="117" Body="&lt;p&gt;Hi!&#xA;I am building an RC aircraft, 10kg weight range.&#xA;It is supposed to perform long flights (20km+), so reliability is my main concern, mainly on servos controlling Flight control surfaces.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How reliability is maintained on RC planes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am afraid if any flight control surface servo would be jammed while manouvering, crash would be quite horrible :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-04T18:40:56.090" Title="Reliability of servos" Tags="&lt;servo&gt;&lt;rc&gt;&lt;reliability&gt;" AnswerCount="2" />
  <row Id="8570" PostTypeId="2" ParentId="8569" CreationDate="2011-01-04T10:36:24.810" Score="2" ViewCount="" Body="&lt;p&gt;It really depends on the servos you are looking at, I personally would use the ones with brass or metal gears (usually higher end servos or bought as an upgrade kit). You will have to do some math on what kind of torque/power you will need to control those surfaces. Reliability will depend on lots of factors, but most RC plane servos last for quite a bit of time as long as you don't crash lol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With My micro servos in my blade CP helicopter I had very few issues with the small servos until i crashed horribly, the crash was my fault..... after that it had chipped the gearing in the servo. In total i had about 25 flights with those servos over a year time span.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for maintenance on the servos themselves, very little to none, but it never hurt to give them a little grease here and there.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-01-04T10:36:24.810" />
  <row Id="8571" PostTypeId="2" ParentId="8551" CreationDate="2011-01-04T11:03:19.540" Score="3" ViewCount="" Body="&lt;p&gt;Not in Bristol but good for getting parts quickly &#xA;&lt;a href=&quot;http://www.cricklewoodelectronics.com/Cricklewood/home.php&quot; rel=&quot;nofollow&quot;&gt;Cricklewood Electronics&lt;/a&gt;. For interesting &lt;em&gt;surplus electronics&lt;/em&gt; &lt;a href=&quot;http://www.distel.co.uk/home.htm&quot; rel=&quot;nofollow&quot;&gt;Display Electronics&lt;/a&gt;. Otherwise, not always the cheapest, but still can be very useful &lt;a href=&quot;http://www.ebay.co.uk/&quot; rel=&quot;nofollow&quot;&gt;eBay&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="1380" LastEditorUserId="1380" LastEditorDisplayName="" LastEditDate="2011-01-04T11:40:48.977" LastActivityDate="2011-01-04T11:40:48.977" />
  <row Id="8572" PostTypeId="2" ParentId="8569" CreationDate="2011-01-04T11:04:19.757" Score="5" ViewCount="" Body="&lt;p&gt;Get the most reliable servos (and other gear) you can in the first place and over spec the servos and their attachments greatly so any mechanical stickyness can be forced out of the way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are still not convinced that you have enough reliability, then look into how commercial airliners get higher reliability:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Have multiple batteries, all of them feeding the bus though diodes, so that if one battery craps out it will not bring down the others.&lt;/li&gt;&#xA;&lt;li&gt;Split control surfaces and use independent servos to control each, mixed so each control surface is held below 25% authority in normal operations, that way you can count on being able to counter a stuck surface with the one left operational, just by switching off the excursion limit and accepting a lot of drag.&lt;/li&gt;&#xA;&lt;li&gt;Fuse each servo at the central controller, so it cannot bring down the power bus if it shorts out.&lt;/li&gt;&#xA;&lt;li&gt;Use servos which can report back their position and other data, like motor current like: &lt;a href=&quot;http://www.openservo.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.openservo.com/&lt;/a&gt; so the flight controller can detect stuck servos and try to fix the problem or at least let you know.&lt;/li&gt;&#xA;&lt;li&gt;Run all servos from a controller that is able to power down individual servos, so if one servo goes nuts, then it can be turned off and allowed to weather vane.&lt;/li&gt;&#xA;&lt;li&gt;Stick a complete autopilot with GPS and IMU in the plane (see: ArduPilot), to take it back to the launch site, if the radio craps out.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In the end I doubt any of those enhancements would do a lot of good in practice as all the redundancy will also add complexity and thus new sources of errors, just look at all the problems Airbus had getting their flight systems debugged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... but I bet a whole lot of fun could be had building all of that redundancy.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-01-04T11:04:19.757" />
  <row Id="8573" PostTypeId="2" ParentId="8551" CreationDate="2011-01-04T12:19:02.077" Score="2" ViewCount="" Body="&lt;p&gt;I use Rapid Electronics, Farnell and occasionally Mouser GB.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-04T12:19:02.077" />
  <row Id="8574" PostTypeId="2" ParentId="8398" CreationDate="2011-01-04T12:34:07.277" Score="1" ViewCount="" Body="&lt;p&gt;Yea, Using Software serial (as linked too, above) is your answer, it's fairly robust as long as you arn't doing to much other heavy stuff on the arduino at the same time and the baud rate is something sensible.  It's your choice if you use the hardware UART for the modem or the device, and which you link up to the software serial port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm assuming you are using UART for the both devices, but if so, are you aware that you don't need an arduino in the loop? just wire the device straight into the blutooth modem's uart in/out (make sure that both use TTL or otherwise compatible voltages) and you can pick up the data on the other end of the bluetooth link using SPP (as you would be doing anyway I assume)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jim&lt;/p&gt;&#xA;" OwnerUserId="2481" LastActivityDate="2011-01-04T12:34:07.277" />
  <row Id="8575" PostTypeId="1" AcceptedAnswerId="8587" CreationDate="2011-01-04T15:29:09.640" Score="4" ViewCount="226" Body="&lt;p&gt;Who makes the touch screens for the iPhone or Android devices? Specifically I'm wondering what the sampling rate is for dragging, etc. that gives these devices such smooth touch and drag performance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also is there a common standard of measurement for touch screen performance? How do you quantify a touch screens drag performance?&lt;/p&gt;&#xA;" OwnerUserId="2484" LastActivityDate="2011-01-09T04:39:42.123" Title="Touchscreen Performance (iPhone, iPad, Android, Nexus S, etc.)" Tags="&lt;iphone&gt;&lt;android&gt;&lt;touchscreen&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="8576" PostTypeId="1" CreationDate="2011-01-04T15:48:09.107" Score="3" ViewCount="551" Body="&lt;p&gt;I just received my TI Launchpad and I'm wondering how can I add something like an Ethernet Shield from Arduino, in order to display a simple webpage... ?&lt;br&gt;&lt;br&gt;&#xA;Do you know any Ethernet shield for Launchpad?&lt;/p&gt;&#xA;" OwnerUserId="2245" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-04T16:14:10.863" LastActivityDate="2011-01-04T16:14:10.863" Title="TI MSP430 Launchpad + Ethernet" Tags="&lt;ethernet&gt;&lt;msp430&gt;&lt;launchpad&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="8577" PostTypeId="2" ParentId="8576" CreationDate="2011-01-04T16:01:01.157" Score="3" ViewCount="" Body="&lt;p&gt;The Arduino Ethernet shield is built around the Wiznet W5100. The chip provides a complete TCP/IP stack and can ethernet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Porting the Arduino driver code to the Launchpad should be fairly straightforward, you'll need SPI and a few control lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/arduino/source/browse/trunk/libraries/Ethernet/utility/w5100.cpp&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/arduino/source/browse/trunk/libraries/Ethernet/utility/w5100.cpp&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's some Launchpad SPI code of mine to get you started:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.hodgepig.org/2010/09/10/575/&quot; rel=&quot;nofollow&quot;&gt;http://blog.hodgepig.org/2010/09/10/575/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Launchpad currently has no official shield standard though there are efforts afoot:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.43oh.com/forum/viewtopic.php?f=19&amp;amp;t=16&amp;amp;start=10&quot; rel=&quot;nofollow&quot;&gt;http://www.43oh.com/forum/viewtopic.php?f=19&amp;amp;t=16&amp;amp;start=10&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.msp430launchpad.com/2010/08/shield-standard-proposal.html&quot; rel=&quot;nofollow&quot;&gt;http://www.msp430launchpad.com/2010/08/shield-standard-proposal.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-04T16:07:18.263" LastActivityDate="2011-01-04T16:07:18.263" />
  <row Id="8578" PostTypeId="2" ParentId="8575" CreationDate="2011-01-04T16:10:00.093" Score="4" ViewCount="" Body="&lt;p&gt;Atmel is selling lots of their &lt;a href=&quot;http://www.atmel.com/products/touchscreens/default.asp?family_id=701&amp;amp;source=home&quot; rel=&quot;nofollow&quot;&gt;maXTouch&lt;/a&gt; devices for touch screen implementations. I don't think that Apple uses them, though. You should get some idea of the performance achievable from the data sheets. They take a lot of the load off the processor, given that they have stuff like gesture recognition built-in.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-04T18:58:14.080" LastActivityDate="2011-01-04T18:58:14.080" />
  <row Id="8579" PostTypeId="2" ParentId="8398" CreationDate="2011-01-04T16:25:21.620" Score="0" ViewCount="" Body="&lt;p&gt;The quickest (though limited) method would be to simply connect the device you want to read from (assuming it's an async. serial stream) to the AVR's RX, then the AVR TX pin to the BT module's RX pin.  You could then simply read from the UART, do whatever processing you want (or none at all), then write back out to the UART.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The major limitation is that the baud rate of the BT radio and your device must match.  You can adjust the baud rate on most BT radios, however.  You're also stuck with single-direction communications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're doing no processing, you could directly connect them.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-04T16:25:21.620" />
  <row Id="8580" PostTypeId="1" AcceptedAnswerId="8596" CreationDate="2011-01-04T16:32:35.820" Score="4" ViewCount="414" Body="&lt;p&gt;I've been playing around with PIC microcontrollers for a while now, and have had a fair bit of success, however I sometimes get unexplained resets and sometimes need to cycle the power a few times to get my device to start working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think this is down to my simplistic PSU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I normally throw together a mains transformer, bridge rectifier, linear regulator and a few capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have a circuit diagram of a better more efficient PSU that is easy to build on stripboard and doesn't cost too much?&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-13T17:26:58.627" Title="A better power supply for microcontroller circuits" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;psu&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="2" />
  <row Id="8581" PostTypeId="2" ParentId="8580" CreationDate="2011-01-04T16:46:35.813" Score="7" ViewCount="" Body="&lt;p&gt;It's not on stripboard, but it's simple, cheap and decent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ladyada.net/make/bbpsup/&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/make/bbpsup/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm3.static.flickr.com/2520/3724192415_64598c1b3d.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Project files:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ladyada.net/make/bbpsup/download.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/make/bbpsup/download.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.ladyada.net/make/bbpsup/bbsupplyschem.png&quot; width=&quot;500&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-04T16:46:35.813" CommentCount="5" />
  <row Id="8582" PostTypeId="1" AcceptedAnswerId="8631" CreationDate="2011-01-04T17:45:53.107" Score="1" ViewCount="285" Body="&lt;p&gt;I'm working on a development board which will mount on a solderless breadboard.  It uses a 100 pin TQFP IC and Ethernet jack, among other things, so it would be a nightmare to get it to fit on a single section of breadboard at only 1.1&quot; wide, and I'd like it to be big enough for users to make some edits.  I'd also like to be able to plug into power distribution rails on the breadboard (like the &lt;a href=&quot;http://www.sparkfun.com/products/114&quot; rel=&quot;nofollow&quot;&gt;Sparkfun Breadboard Power Supply&lt;/a&gt;). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, after comparing my breadboard with a few friends and coworkers, I see that there are a number of differences in layout.  I hope that I can accommodate some if not all of these differences by including multiple places to mount the headers for various breadboards. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a dimensioned diagram so we're all on the same page.  Imagine that there are two full strips side by side (one mostly off to the left), with power rails on both sides.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/C3Sip.png&quot; alt=&quot;breadboard diagram&quot;&gt;&#xA;[Whoops!  I forgot the horizontal dimension between B and C. Let's call it E, since I don't have the source for this image anymore.]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;1.&lt;/strong&gt; What are the dimensions of popular, currently manufactured/used breadboards?&lt;br&gt;&#xA;In addition to the measurements in the diagram I'd like to know the following:&lt;br&gt;&#xA; &lt;strong&gt;2.&lt;/strong&gt; Is there an electrical discontinuity between the top and of the power rails? (If so, is measurement '3' different at this location?)&lt;br&gt;&#xA; &lt;strong&gt;3.&lt;/strong&gt; What is the configuration of the breadboard?  Using the convention that P is a two-column power strip and M is a middle section (rows of connections with a gap for DIP ICs in the center), my breadboard looks like: PMPPMPPMP&lt;br&gt;&#xA; &lt;strong&gt;4.&lt;/strong&gt; How many rows are in the breadboard middle section and power sections? Mine has 64 pairs of 5-pin rows in the middle and 10 5x2 blocks.&lt;br&gt;&#xA; &lt;strong&gt;5.&lt;/strong&gt; Any other discrepancies I missed which would affect PCB layout?&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-05T19:03:02.353" LastActivityDate="2011-01-05T19:03:02.353" Title="Breadboard Dimensions for making DIP PCB" Tags="&lt;breadboard&gt;&lt;pcb-design&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="8583" PostTypeId="2" ParentId="7919" CreationDate="2011-01-04T18:10:54.497" Score="0" ViewCount="" Body="&lt;p&gt;See &lt;a href=&quot;http://www.opencircuits.com/Solderless_protoboard#More%20Tips&quot; rel=&quot;nofollow&quot;&gt;these tips on OpenCircuits.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;In one salvage job I found some&#xA;  &quot;double ended&quot; headers, long pins on&#xA;  both ends. These can be very handy&#xA;  because once plugged in they can be&#xA;  used to let you plug in female&#xA;  connectors ( like those on hard drive&#xA;  cables ( but just one of the two sides&#xA;  ) to the board. See pictures below.&#xA;  Hard part to find. But wait, you can&#xA;  solder two regular headers back to&#xA;  back.    &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Expanding on the &quot;double ended&quot; header&#xA;  above. Right angle headers are long&#xA;  enough to bend the pins so they are&#xA;  long on both sides. Take a dual row&#xA;  one and bend the pins to fit across&#xA;  the gap at the center of the proto&#xA;  board. Then you can plug in a dual&#xA;  plug like those on hard drive cables&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1498" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-04T18:18:58.567" LastActivityDate="2011-01-04T18:18:58.567" />
  <row Id="8584" PostTypeId="2" ParentId="8103" CreationDate="2011-01-04T18:13:22.887" Score="0" ViewCount="" Body="&lt;p&gt;Dave Jones did a &lt;a href=&quot;http://www.eevblog.com/2009/11/21/eevblog-45-arduino-picaxe-and-idiot-assembler-programmers/&quot; rel=&quot;nofollow&quot;&gt;video blog&lt;/a&gt; on the Arduino. If the link doesn't work search for the EEVBlog #45. &lt;/p&gt;&#xA;" OwnerUserId="1498" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-05-07T13:15:34.803" LastActivityDate="2011-05-07T13:15:34.803" CommunityOwnedDate="2011-05-07T13:15:59.843" CommentCount="1" />
  <row Id="8586" PostTypeId="2" ParentId="7919" CreationDate="2011-01-04T18:22:24.977" Score="0" ViewCount="" Body="&lt;p&gt;If you can still find wire wrap headers, they are a great material to cut up for things like this.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But for insertion in a breadboard you probably don't want &quot;full size&quot; (.025&quot; square iirc) pins but smaller diameter ones to avoid damaging the breadboard (unless you are willing to dedicate those rows to this header)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's only three leads and you have the female socket on the cable, I might personally be tempted to insert three pieces of bare wire in the socket and plug the other ends into the breadboard, then tack the socket down with a wire strap, or hot glue or something.   You could also make up a three wire twisted or braided cable of 22 or 24 gauge solid, insert one end in the socket and cover the joint with heat shrink and run the other end into the breadboard.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-01-04T18:22:24.977" />
  <row Id="8587" PostTypeId="2" ParentId="8575" CreationDate="2011-01-04T18:30:35.457" Score="4" ViewCount="" Body="&lt;p&gt;All but the cheapest phones and tablets are using capacitive sensors rather than resistive ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I think a lot of the user experience is not with the touch screen itself, but rather with the graphics engine and the software stack driving it.  For example, a first generation android phone like the G1 is probably a faster processor than the first generation iphone was, but flipping through an image gallery on the original iphone was much smoother because they put a lot more thought into engineering a system where that could be done efficiently.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-01-04T18:30:35.457" />
  <row Id="8589" PostTypeId="1" AcceptedAnswerId="8590" CreationDate="2011-01-04T18:50:22.217" Score="6" ViewCount="261" Body="&lt;p&gt;I'm working on a development board, and need to let users set some configurations.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will be used by students and engineers who are trying to build circuits on a breadboard; I'm not dealing with consumers.  Usually, the settings will stay the same, but it's possible that every new project could use a different configuration. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will be dedicating some pins to interfaces like USB and Ethernet, but I'd like to give users the option of using those pins for a different purpose.  Some kind of configuration will be required.  The options I've considered so far are:&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Solder bridges:&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/iCzRd.jpg&quot; alt=&quot;0-ohm resistor&quot;&gt;&lt;br&gt;&#xA;Either 0603 resistor packages to allow 0-ohm resistors to be used, or nearby pads for a solder blob.&lt;br&gt;&#xA;Pros:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Cheapest option possible&lt;/li&gt;&#xA;&lt;li&gt;Smallest PCB area required&lt;/li&gt;&#xA;&lt;li&gt;No accidental changes&lt;/li&gt;&#xA;&lt;li&gt;Customizable by soldering directly to pad&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Cons: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Requires soldering iron to make changes&lt;/li&gt;&#xA;&lt;li&gt;Possible to damage board with repeated soldering/desoldering&lt;/li&gt;&#xA;&lt;li&gt;0-ohm resistors require having those parts on hand.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;h1&gt;DIP switches:&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/dOdih.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;br&gt;&#xA;Tiny mechanical switches in an IC package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pros: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Easiest to change&lt;/li&gt;&#xA;&lt;li&gt;Fairly durable&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Cons: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Most expensive option by far&lt;/li&gt;&#xA;&lt;li&gt;Might be changed by accident&lt;/li&gt;&#xA;&lt;li&gt;Large area on PCB&lt;/li&gt;&#xA;&lt;li&gt;Lowest current of the options&lt;/li&gt;&#xA;&lt;li&gt;Hard to make changes to PCB&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;h1&gt;Pin Jumpers&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/1UvBl.jpg&quot; alt=&quot;pin jumper for IDE hard drive&quot;&gt;&lt;br&gt;&#xA;Removable Jumpers for .1&quot; headers like those found on PC motherboards and drives.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pros: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Less expensive than DIP switches&lt;/li&gt;&#xA;&lt;li&gt;Easy to make changes to PCB&lt;/li&gt;&#xA;&lt;li&gt;Good balance between easy-to-change and semi-permanent&lt;/li&gt;&#xA;&lt;li&gt;Easy to see configuration&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Cons: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Large PCB area required&lt;/li&gt;&#xA;&lt;li&gt;Tallest profile; usually .5&quot; or so required vertically&lt;/li&gt;&#xA;&lt;li&gt;Jumpers might be lost&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;h1&gt;Electronic Bus Switching&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/cnjVT.jpg&quot; alt=&quot;TI SN74CBT3384ADBQR&quot;&gt;&lt;br&gt;&#xA;Use FETs or a bus switching IC like the TI 74CBT series, and control with an EEPROM/microcontroller.  Suggested by &lt;a href=&quot;http://electronics.stackexchange.com/questions/8589/8593#8593&quot;&gt;Brian Carlton&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pros: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Small PCB area&lt;/li&gt;&#xA;&lt;li&gt;Configurable in software&lt;/li&gt;&#xA;&lt;li&gt;Can put both to High-Z or connected&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Cons: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Requires another couple ICs; medium cost.&lt;/li&gt;&#xA;&lt;li&gt;Less current than other options&lt;/li&gt;&#xA;&lt;li&gt;Has real resistance&lt;/li&gt;&#xA;&lt;li&gt;Can now confuse hardware bugs with software bugs and vice versa&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The solder bridge option makes me worry about weakening the pad with repeated resoldering and delaminating it from the PCB. How many times can a good soldering tech change a part on 1-ounce copper with an ENIG finish?  Would covering the edges of the pad with soldermask and adding thermal reliefs (for adhesion, not heatsinking) on several sides of the pad increase the durability?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I missing anything?  What configuration methods do you like to use on a dev board?&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-04T23:02:52.320" LastActivityDate="2011-01-04T23:02:52.320" Title="Choosing Configuration Jumpers - Solder bridges, 0-ohm resistors, DIP switches, pin jumpers..." Tags="&lt;development&gt;&lt;switch&gt;&lt;configuration&gt;&lt;jumper&gt;" AnswerCount="4" CommentCount="10" FavoriteCount="1" />
  <row Id="8590" PostTypeId="2" ParentId="8589" CreationDate="2011-01-04T19:24:50.280" Score="5" ViewCount="" Body="&lt;p&gt;For straight-up &lt;strong&gt;development boards&lt;/strong&gt; (for your &lt;em&gt;internal use&lt;/em&gt;), I go with a solder jumper or put two back-to-back (3 pads) to make an SPDT switch (here's &lt;a href=&quot;http://i.imgur.com/S0zNO.png&quot; rel=&quot;nofollow&quot;&gt;a footprint I use&lt;/a&gt;).  If it's small enough, it's fast to both close and open with a touch of solder or desolder braid.  Using an actual resistor makes it much more difficult to rework with a standard iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&#xA;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is a &lt;strong&gt;product&lt;/strong&gt; (as in, the Atmel STK500 development board is a &lt;em&gt;product&lt;/em&gt;), you should use something like jumpers or DIP switches, because you don't want some dumb user poking around your board with a 1000°F iron.  I'd tend towards DIP switches if you have more options or you are going to put it in an enclosure, otherwise jumpers would be cheaper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main question should be &quot;&lt;strong&gt;is this something that will be changed as part of normal use?&lt;/strong&gt;&quot;  If the answer is yes, requiring a soldering iron and skills is inappropriate.  If it's something that an end user might modify 1-5 times (or preferably someone skilled, e.g. a lab tech), a solder jumper might be OK.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-04T20:28:09.663" LastActivityDate="2011-01-04T20:28:09.663" CommentCount="4" />
  <row Id="8591" PostTypeId="2" ParentId="8589" CreationDate="2011-01-04T20:22:36.297" Score="1" ViewCount="" Body="&lt;p&gt;How often will it be changed? If only very occasionally or even just once then a solder pad is fine. If you expect it to be changed often I would go with the dip Switch. The jumpers are somewhere in between. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-01-04T20:22:36.297" CommentCount="1" />
  <row Id="8592" PostTypeId="2" ParentId="8427" CreationDate="2011-01-04T21:49:24.180" Score="0" ViewCount="" Body="&lt;p&gt;Depending on how much room you have, you may want to hang the most commonly used ones on a hatrack or pegboard on the wall. I store most of mine tied with velcro cable ties, in ziploc bags, in plastic bins. (Like the other posters)&lt;/p&gt;&#xA;" OwnerUserId="2258" LastActivityDate="2011-01-04T21:49:24.180" CommunityOwnedDate="2011-03-30T14:19:10.187" />
  <row Id="8593" PostTypeId="2" ParentId="8589" CreationDate="2011-01-04T21:52:37.757" Score="1" ViewCount="" Body="&lt;p&gt;Don't use DIP switches for something going out of house.  Users will change them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would put solder holes for jumpers, but only install them on the prototype if you are changing them frequently.  But for what you describe (i.e. board variants) I would go with putting the settings in your EEPROM -&gt; can set in software, less area.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-04T21:52:37.757" CommentCount="2" />
  <row Id="8594" PostTypeId="2" ParentId="8582" CreationDate="2011-01-04T21:57:21.993" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2359510&amp;amp;k=breadboard&quot; rel=&quot;nofollow&quot;&gt;Breadboards at Digikey&lt;/a&gt;  will give you some sizes.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-04T22:34:48.357" LastActivityDate="2011-01-04T22:34:48.357" CommentCount="1" />
  <row Id="8595" PostTypeId="2" ParentId="8462" CreationDate="2011-01-04T22:20:29.220" Score="0" ViewCount="" Body="&lt;p&gt;TI has &lt;a href=&quot;http://focus.ti.com/en/download/aap/selectiontools/audio/tool.htm&quot; rel=&quot;nofollow&quot;&gt;this tool to help you choose one&lt;/a&gt; and has a &lt;a href=&quot;http://focus.ti.com/lit/sl/slyy013e/slyy013e.pdf&quot; rel=&quot;nofollow&quot;&gt;selector guide&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-04T22:20:29.220" />
  <row Id="8596" PostTypeId="2" ParentId="8580" CreationDate="2011-01-04T22:22:10.590" Score="7" ViewCount="" Body="&lt;p&gt;What is &lt;strong&gt;REALLY important&lt;/strong&gt; is to have 0.01-1uF ceramic capacitor soldered right on the power pins of &lt;strong&gt;every&lt;/strong&gt; digital IC in your circuit no matter what is the power source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I belive even your current PSU will be fine if you add ceramic caps where needed. Linear regulators provide very stable power, so you should be good with what you have now (unless it is oscilating - might happen if ESR of caps does not match regulator requirements - usually happens on LDO regulators rarely).&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;In my projects I use USB as my main power source. It gives you stable 5v and it does have current limiter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can ether get it from your PC(should be careful a little) or from tiny mains adaptors which have USB output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you use your linear regulator if you need less then 5V.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-04T22:22:10.590" CommentCount="4" />
  <row Id="8597" PostTypeId="2" ParentId="4502" CreationDate="2011-01-04T22:22:22.400" Score="0" ViewCount="" Body="&lt;p&gt;If you have high-resistance (i.e. not input or speaker) use an analog switch to mute/unmute the input.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-04T22:22:22.400" CommentCount="1" />
  <row Id="8598" PostTypeId="2" ParentId="8589" CreationDate="2011-01-04T22:57:43.697" Score="1" ViewCount="" Body="&lt;p&gt;I've grappled with this question a few times myself. Clearly, there is a time and a place for all of these techniques. That being said, there are no hard and fast rules or conventions I know of that are standardized (or even necessarily broadly agreed upon). My take is:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The solder-bridge/0-ohm technique is appropriate for building in an &quot;option&quot; into a board that is &quot;supported&quot; but not the typical use case. This is often called a &quot;population option&quot; so the idea is generally you either add the bridge once or not at all. It's not typically used for settings that change more than a couple times. An example might be an alternative signal routing through an optionally populated transceiver.&lt;/li&gt;&#xA;&lt;li&gt;The jumper/header technique is appropriate for situations where you want to be able to &quot;break-in&quot; to a signal, or for a very few &quot;this-or-that&quot; type settings. Also, think of using this when the setting changes infrequently. Example maybe a current probe break-in point or a &quot;voltage select&quot; setting.&lt;/li&gt;&#xA;&lt;li&gt;The DIP switch technique is appropriate for configuration settings that may change often and require a beefy/permanent user interface. Example maybe &quot;address bits&quot; for an IC.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Again, not an authorative answer, but my opinion / rules of thumb.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-01-04T22:57:43.697" />
  <row Id="8599" PostTypeId="2" ParentId="2628" CreationDate="2011-01-04T23:02:06.610" Score="-1" ViewCount="" Body="&lt;p&gt;For 60 A think about safety too.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-04T23:02:06.610" CommentCount="1" />
  <row Id="8600" PostTypeId="2" ParentId="8582" CreationDate="2011-01-05T00:41:23.110" Score="0" ViewCount="" Body="&lt;p&gt;Usually .1&quot; pitch between rows and columns with either .1&quot; or .15&quot; from the last column in an area to the first column of a power rail.  Sometimes there's one column for a power bus, sometimes 2. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually the bus columns are split in the middle of the board with either .1&quot; or .15&quot; between the rows across the split.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-05T00:41:23.110" CommentCount="2" />
  <row Id="8601" PostTypeId="2" ParentId="8558" CreationDate="2011-01-05T00:44:03.717" Score="0" ViewCount="" Body="&lt;p&gt;Roombas detect dirt being sucked up by using piezo sensors - when something hits the sensor with enough force it generates a small voltage.  When it notices lots of hits it decides this is because of dirt and cleans more thoroughly.  Something like that but for water might be possible.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-05T00:44:03.717" />
  <row Id="8602" PostTypeId="1" CreationDate="2011-01-05T02:03:39.940" Score="2" ViewCount="866" Body="&lt;p&gt;I am establishing a serial connection with my Arduino. In order to get data from it I have to send data in the form of byte arrays. I am able to send the command and read the ACK. But I can't figure out how to get the data after the ACK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The developer documentation for the protocol I am using says it goes:&#xA;command to access data -&gt; ACK REPONSE -&gt;DATA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't figure out how to get the data after the ack response. It should be a byte array of 14 hex values. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is my code&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;byte GetData[] = {0x02,0x12,0x00}&#xA;byte GetDataACK[] = {0x02,0x06,0x06,0x06,0x06,0x06}; &#xA;&#xA;void setup(){&#xA;&#xA;  Serial.begin(9600); &#xA;  Serial.write(GetData,sizeof(GetData)); //Send the byte array&#xA;  delay(200); &#xA;  if(Serial.available() &amp;gt; 5) {&#xA;    for(int i=0;i&amp;lt;6;i++){&#xA;      if(ackmodule[i]!=Serial.read()){&#xA;        // Do something&#xA;      }&#xA;    }&#xA;  }&#xA;&#xA;}&#xA;&#xA;void loop(){&#xA;&#xA;}  &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2487" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-20T22:57:53.770" LastActivityDate="2011-02-20T22:57:53.770" Title="Serial communication and reading byte arrays with Arduino" Tags="&lt;arduino&gt;&lt;uart&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="8603" PostTypeId="1" CreationDate="2011-01-05T03:30:47.497" Score="3" ViewCount="362" Body="&lt;p&gt;Hello&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This question is about gate delay in VLSI (microchips). (Yes, it is a CMOS)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Every digital chip consists of 2 kinds of elements, Register Logic (trigger or latch stations) and combination logic (between the registers, does the actual computation). Most chips can be expressed as &lt;a href=&quot;http://en.wikipedia.org/wiki/Register_transfer_level&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Register_transfer_level&lt;/a&gt; which describes logic and registers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The maximal clock frequency of microchip is determined (limited) by the delay of the slowest combination path. This delay depends from kind of elements, used in it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most popular metric of this critical delay is FO4 &lt;a href=&quot;http://en.wikipedia.org/wiki/FO4&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/FO4&lt;/a&gt; or Fan-out of 4:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;process independent delay metric used in digital CMOS technologies.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;It is counted as chain of length N of NOT gates. Each gate have output power enough to drive 4-fold more powerful inverter (according to wiki). I get this metric as tree of inverters with N levels, where each inverter drives 4 same inverters. Tree looks like &lt;a href=&quot;http://www.mathworks.com/help/toolbox/wavelet/ug/wptreed2.gif&quot; rel=&quot;nofollow&quot;&gt;http://www.mathworks.com/help/toolbox/wavelet/ug/wptreed2.gif&lt;/a&gt; but with NOT gates (transistors) at nodes. (better description is at &lt;a href=&quot;http://www.realworldtech.com/page.cfm?ArticleID=RWT081502231107&quot; rel=&quot;nofollow&quot;&gt;http://www.realworldtech.com/page.cfm?ArticleID=RWT081502231107&lt;/a&gt; )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, the any modern processor have a metric FO4, which can be equal to 14, or 20 or 40. If the processor have small FO4, it can have more frequency, than a processor with large FO4 at the same silicon technology.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a metric for critical path of some chip, expressed in terms of fan-in-2 and fan-out-3:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;18 fan-in-2 fan-out-3 NAND gates&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;How can I convert this to FO4? (Fan-out of 4)&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to compare this chip with modern CPUs. FO4 will give me a clear way to check, how fast the chip can be on technology of modern CPU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Update:&lt;/em&gt; There is a book which says &lt;a href=&quot;http://books.google.com/books?id=oDWRAxCU-g8C&amp;amp;pg=PA175&amp;amp;lpg=PA175&amp;amp;dq=&quot; rel=&quot;nofollow&quot;&gt;http://books.google.com/books?id=oDWRAxCU-g8C&amp;amp;pg=PA175&amp;amp;lpg=PA175&amp;amp;dq=&lt;/a&gt;&quot;fan-in-2&quot;+fan-out-2&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;This fan-out-of-four (FO4) inverter delay, t_4, is a good estimate of the delay of typical logic gate (fan-in=2) driving a typical load (fan-out=2) over relatively short wires.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So, Fan-in=2 and Fan-out=3 is close to 2/2 or to FO4. For the first estimation I will use this 18 fi2/fo3 as equal to 18 FO4.&lt;/p&gt;&#xA;" OwnerUserId="1994" LastEditorUserId="1994" LastEditorDisplayName="" LastEditDate="2011-03-07T20:46:43.563" LastActivityDate="2011-03-07T20:46:43.563" Title="Convert fan-in-2 fan-out-3 NAND gates to FO4" Tags="&lt;cmos&gt;&lt;vlsi&gt;&lt;fanout&gt;" AnswerCount="2" CommentCount="8" FavoriteCount="1" />
  <row Id="8604" PostTypeId="1" CreationDate="2011-01-05T04:22:25.087" Score="1" ViewCount="99" Body="&lt;p&gt;Got a question about &lt;a href=&quot;http://www.sparkfun.com/products/8495&quot; rel=&quot;nofollow&quot;&gt;the Sparkfun radio modem  WRL-08495&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A pair of these replace an RS-232 cable, right? simple as that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What if my neighbor also has a pair of these?  Is there mutual interference&#xA;or is there encryption?&lt;/p&gt;&#xA;" OwnerUserId="2488" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-05T05:09:05.753" LastActivityDate="2011-01-05T05:18:59.877" Title="Sparkfun Bluetooth modem" Tags="&lt;bluetooth&gt;&lt;communication&gt;" AnswerCount="1" />
  <row Id="8605" PostTypeId="2" ParentId="6561" CreationDate="2011-01-05T04:50:57.330" Score="1" ViewCount="" Body="&lt;p&gt;For the monitor on the target-side, ISD51 has these advantages over Mon51:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;It's linked into the firmware image&#xA;as extra functions and ISRs so&#xA;linking and locating is easy. &lt;/li&gt;&#xA;&lt;li&gt;All source is available so that it can be&#xA;modified to communicate thru serial&#xA;ports and can be modified to write to&#xA;code-space using any platform-specific tricks to write to code-space.  &lt;/li&gt;&#xA;&lt;li&gt;It's very small yet supports break-points (which is why write-to-code-space is required), variable watching and register inspection.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For the host-side debugger, ISD51 talks to Keil's Windows-based debugger (which I'm using) and I don't know if the interface is compatible with other debuggers. As Rowan suggested, it would be very cool to have other options available such as Visual Studio, Eclipse, DDD on Windows etc.&lt;/p&gt;&#xA;" OwnerUserId="1912" LastActivityDate="2011-01-05T04:50:57.330" />
  <row Id="8607" PostTypeId="2" ParentId="8604" CreationDate="2011-01-05T05:18:59.877" Score="2" ViewCount="" Body="&lt;p&gt;Here's what I get from the &lt;a href=&quot;http://www.rovingnetworks.com/documents/firefly-ref-guide.pdf&quot; rel=&quot;nofollow&quot;&gt;FireFly User Manual&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Overview&lt;/strong&gt;&lt;br&gt; The FireFly serial adapter is compact, versatile Class 1&#xA;  Bluetooth serial adapter.  It enables&#xA;  wireless connections  to any legacy&#xA;  serial port and supports&#xA;  bi-directional RS232 or RS422&#xA;  signaling at a rate of up to 464Kbps. &#xA;  Just  attach the FireFly to your&#xA;  device's RS232/EIA232/422 port,&#xA;  connect over Bluetooth, and you have a&#xA;  wireless cable  replacement solution.&#xA;  The transmit range can be up to 330'&#xA;  (100M), depending upon environmental&#xA;  factors.&lt;br&gt;FireFly Bluetooth adapter&#xA;  can be used as a Bluetooth Master or&#xA;  Slave device. The SPP connection to&#xA;  the unit  appears via a virtual COM&#xA;  interface.  Data is sent and received&#xA;  on the client exactly as if a serial&#xA;  cable was  connected to a real COM&#xA;  port on the client.   FireFly can also&#xA;  be used in cable replacement mode&#xA;  where two Roving Networks Bluetooth&#xA;  devices are paired  using the&#xA;  configuration switches.  The USB to&#xA;  Bluetooth (RN-USB-X) has pairing&#xA;  switches and can be used with  the&#xA;  FireFly BP to create a wireless&#xA;  connection to a PC without using the&#xA;  PC’s Bluetooth stack.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.rovingnetworks.com/documents/cable-replacement-ap.pdf&quot; rel=&quot;nofollow&quot;&gt;Cable Replacement Application Note&lt;/a&gt; indicates that proper &lt;a href=&quot;http://www.bluetomorrow.com/about-bluetooth-technology/general-bluetooth-information/bluetooth-pairing.html&quot; rel=&quot;nofollow&quot;&gt;Bluetooth pairing&lt;/a&gt; is accomplished, meaning the channel is encrypted, either by small switches or with a serial monitor (they use &lt;a href=&quot;http://hp.vector.co.jp/authors/VA002416/teraterm.html&quot; rel=&quot;nofollow&quot;&gt;TeraTerm&lt;/a&gt;, to which I give a thumbs up).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Looks like a very cool gadget!&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-05T05:18:59.877" />
  <row Id="8608" PostTypeId="1" AcceptedAnswerId="8609" CreationDate="2011-01-05T06:11:19.933" Score="1" ViewCount="201" Body="&lt;p&gt;I might not be able to find an LCD with a 24 bit parallel interface, which is what my controller requires.  I have seen 18 bit parallel interfaces, though.  I assume that I could really just use the lower 6 bits of each color and not use the other two bits per color channel.  All I would have to do is make sure that my color palettes are adjusted accordingly, right?&lt;/p&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-02-03T05:23:14.627" LastActivityDate="2011-02-06T20:20:50.057" Title="LCD parallel interfaces" Tags="&lt;lcd&gt;&lt;interface&gt;&lt;parallel&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="8609" PostTypeId="2" ParentId="8608" CreationDate="2011-01-05T06:36:49.213" Score="6" ViewCount="" Body="&lt;p&gt;You can do this without issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you want to use the &lt;em&gt;Upper&lt;/em&gt; (e.g. MSBs) of the digital output, discard the least significant bits. Otherwise, you will get all sorts of interesting effects.&lt;br&gt;&#xA;(for instance, a gradient would be &quot;Multiplied&quot;, in that a simple span from black to red would repeat twice, provided you're discarding the MSB of the signal).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I currently have a similar project, which uses a 16 bit graphics controller, with a 18 bit LCD. In this case, you connect the 16 bit interface to the MSBs of the LCD, and ground the additional LSBs. What you are proposing is simply the inverse.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Note: I've always thought of the MSBs as being &quot;Upper&quot; - This may simply be a terminology disconnect. Anyways, MSB and LSB are a far better way to describe the bus.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-01-05T23:30:23.923" LastActivityDate="2011-01-05T23:30:23.923" CommentCount="1" />
  <row Id="8610" PostTypeId="1" AcceptedAnswerId="8613" CreationDate="2011-01-05T10:43:25.527" Score="3" ViewCount="187" Body="&lt;p&gt;A question concerning my current repair project of an audio amp that uses big (600 W) but otherwise rather classic complementary output stages:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume when testing an audio power amp with 6 pairs of paralleled npn/pnp transistors, it is o.k. to assemble just 1 pair while testing as long as you have no significant output load connected. The advantage would be that, while testing, I would not blow as many of the precius MJ15022/23 transistors I have available as spare parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In what ways (if any) will the bias current circuit be affected?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any problems I may not have considered but may be important for this repair technique?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any other really good tricks for fixing big amps?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once I am closer to finishing the repair: Does 10...15 mA of bias current per transitor branch sound like a good number to you?&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-03-24T09:37:02.427" LastActivityDate="2011-03-24T09:37:02.427" Title="Testing an Audio Power Amp with Paralleled Transistors" Tags="&lt;power&gt;&lt;audio&gt;&lt;transistor&gt;&lt;amplifier&gt;&lt;repair&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="8611" PostTypeId="1" CreationDate="2011-01-05T11:45:55.993" Score="1" ViewCount="124" Body="&lt;p&gt;I've been given a handful of wireless microphones that transmit in the 36 MHz band, but unfortunately no receiver was included and proper receivers for that wireless mikes seem to be crazy-expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've taken at look at the RF with a scope and it looks a lot like simple FM with a pilot tone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm guessing that the pilot tone is used only to detect if a channel is being used and not drowned in noise, so the receiver can squelch the noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know how the audio is modulated?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking around for a simple, cheap FM receiver that I can modify to receive the mike signal and I've noticed that 36 MHz RC receivers are insanely cheap, so I'm thinking that I ought to be able to grab the demodulated analog signal before it enters the digital RC part of the receiver and pass that off to my own low pass and squelch circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any better suggestions for a source of cheap 36-37 MHz FM receivers?&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-05-06T00:31:29.237" Title="Modulation of 36 MHz wireless microphones" Tags="&lt;audio&gt;&lt;rf&gt;&lt;modulation&gt;&lt;receiver&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="8612" PostTypeId="2" ParentId="8602" CreationDate="2011-01-05T13:21:54.610" Score="1" ViewCount="" Body="&lt;p&gt;Shouldn't some of that code be inside of &lt;code&gt;loop()&lt;/code&gt;? Specifically, everything but &lt;code&gt;Serial.begin(9600)&lt;/code&gt;? Anyway, this code won't work because &lt;code&gt;ackmodule&lt;/code&gt; is not defined. Is it supposed to be &lt;code&gt;GetDataACK&lt;/code&gt;? It's also a good idea to implement &lt;a href=&quot;http://www.arduino.cc/en/Serial/Read&quot; rel=&quot;nofollow&quot;&gt;error handling&lt;/a&gt;, especially when having to debug, like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  if(Serial.available() &amp;gt; 0) {&#xA;    received_byte[i] = Serial.read();&#xA;    if(received_byte[i++] == -1) {  // no data available&#xA;      // error handling&#xA;    }&#xA;  }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I'm not sure what types the Arduino &lt;em&gt;sketch&lt;/em&gt; libraries support, but &lt;code&gt;i&lt;/code&gt; can just be an &lt;code&gt;unsigned char&lt;/code&gt; (I would call it &lt;code&gt;uint8_t&lt;/code&gt;) instead of a full singed 16-bit number (&lt;code&gt;int&lt;/code&gt;). As Chris Stratton mentioned, there are better ways to wait for characters; for example the error handling example, or this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;while(Serial.available() &amp;lt; 5) {}; // 5 can be 0 to fetch 1 char at a time&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This can be implemented without the library in this form:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;char rx()&#xA;{&#xA;        while ((UCSRA &amp;amp; (1&amp;lt;&amp;lt;RXC)) == 0) {};&#xA;        return UDR;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;... Calling it with something like &lt;code&gt;char nextbyte = rx()&lt;/code&gt;. &lt;a href=&quot;http://www.ladyada.net/learn/arduino/lesson4.html&quot; rel=&quot;nofollow&quot;&gt;Arduino serial tutorial is here.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-05T13:51:24.857" LastActivityDate="2011-01-05T13:51:24.857" CommentCount="4" />
  <row Id="8613" PostTypeId="2" ParentId="8610" CreationDate="2011-01-05T13:35:12.243" Score="1" ViewCount="" Body="&lt;p&gt;1 bank of 6 at a time ok.&#xA;Bias not affected significantly.&#xA;10-15 mA plausible.&lt;/p&gt;&#xA;" OwnerUserId="2488" LastActivityDate="2011-01-05T13:35:12.243" CommentCount="3" />
  <row Id="8614" PostTypeId="1" CreationDate="2011-01-05T13:46:20.740" Score="2" ViewCount="268" Body="&lt;p&gt;I have a PIC24F based device that normally connects to a PC via USB. The device can be controlled through PC software this way. I want to add an optional hand control box that can also be plugged into a separate connector on the main device and can be used to control the device and read/display data from the main device. This hand control box will also be PIC based. I am trying to decide which communication technique to use between the main device and the optional hand control box. I like the idea of SPI but I know that is not intended to be used over long distances. Do you think my best option would just be to use the UART modules with RS-232 line tranceievers to boost the signal to +/-12 volts? Are there really any other options?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-01-05T15:32:13.597" LastActivityDate="2011-02-25T16:05:59.993" Title="Communicating between PICs over 30 feet" Tags="&lt;pic&gt;&lt;spi&gt;&lt;rs232&gt;&lt;rs485&gt;" AnswerCount="7" CommentCount="2" />
  <row Id="8615" PostTypeId="2" ParentId="8602" CreationDate="2011-01-05T13:58:34.873" Score="0" ViewCount="" Body="&lt;p&gt;If you just want to send the command once at startup, and then read the response you want to do this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;byte GetData[] = {0x02,0x12,0x00}&#xA;byte GetDataACK[] = {0x02,0x06,0x06,0x06,0x06,0x06}; &#xA;&#xA;void setup(){   &#xA;  Serial.begin(9600); &#xA;  Serial.write(GetData,sizeof(GetData)); //Send the byte array    &#xA;}&#xA;&#xA;void loop(){&#xA;  if(Serial.available() &amp;gt; 5) {&#xA;    for(int i=0;i&amp;lt;6;i++){&#xA;      if(GetDataACK[i]!=Serial.read()){&#xA;        // Do something&#xA;      }&#xA;    }&#xA;  }    &#xA;}  &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Now I'm not sure what you're trying to accomplish with the inner if statement of loop, but it seems kind of backwards to me. Wouldn't you only want to &quot;do something&quot; after you have successfully read the data Ack? I think what you really want is a little state machine:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define DATA_LENGTH           14 // or whatever the length of your data segment is&#xA;&#xA;#define STATE_IDLE            0&#xA;#define STATE_SEND_COMMAND    1&#xA;#define STATE_WAITING_FOR_ACK 2&#xA;#define STATE_GET_DATA        3&#xA;&#xA;byte GetData[] = {0x02,0x12,0x00}&#xA;byte GetDataACK[] = {0x02,0x06,0x06,0x06,0x06,0x06}; &#xA;byte RxData[DATA_LENGTH] = {0};&#xA;byte state = STATE_SEND_COMMAND;&#xA;&#xA;void setup(){   &#xA;  Serial.begin(9600); &#xA;  state = STATE_SEND_COMMAND;            // redundant&#xA;}&#xA;&#xA;void loop(){&#xA;  switch(state){&#xA;  case STATE_IDLE: break;&#xA;  case STATE_SEND_COMMAND:&#xA;     Serial.write(GetData,sizeof(GetData)); //Send the byte array             &#xA;     state = STATE_WAITING_FOR_ACK;&#xA;     break;&#xA;  case STATE_WAITING_FOR_ACK:&#xA;     if(Serial.available() &amp;gt; 5) {&#xA;        for(int i=0;i&amp;lt;6;i++){&#xA;           if(GetDataACK[i]!=Serial.read()){&#xA;           // ACK doesn't match what you expect&#xA;           // you should go to some other state at this point&#xA;           // i'll just send you to idle&#xA;              state = STATE_IDLE;&#xA;              break;&#xA;           }&#xA;        }&#xA;     }&#xA;     break;&#xA;  case STATE_GET_DATA:&#xA;     if(Serial.available() &amp;gt; DATA_LENGTH) {&#xA;        for(int i = 0; i &amp;lt; DATA_LENGTH; i++){&#xA;           RxData[i] = Serial.read();&#xA;        }&#xA;&#xA;        // congratulations you have data in your array&#xA;        // presumably now you want to something with it&#xA;&#xA;        // and then switch back to some other state&#xA;        // i'll send you back to IDLE :)&#xA;        state = STATE_IDLE;&#xA;        break;&#xA;     }       &#xA;  }      &#xA;}  &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-05T15:38:56.117" LastActivityDate="2011-01-05T15:38:56.117" />
  <row Id="8616" PostTypeId="2" ParentId="8614" CreationDate="2011-01-05T14:01:21.840" Score="1" ViewCount="" Body="&lt;p&gt;I have used these,&lt;a href=&quot;http://www.sparkfun.com/products/8947&quot; rel=&quot;nofollow&quot;&gt;RF Link 4800bps Receiver - 315MHz&lt;/a&gt; and &lt;a href=&quot;http://www.sparkfun.com/products/8945&quot; rel=&quot;nofollow&quot;&gt;RF Link Transmitter - 315MHz&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i have 2 different frequencies one for send and one for receive. I have successfully used them up to 30 feet using 5v to power them. &lt;a href=&quot;http://www.sparkfun.com/categories/16&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt; has other wireless communication devices as well.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-01-05T14:01:21.840" CommentCount="4" />
  <row Id="8617" PostTypeId="2" ParentId="8614" CreationDate="2011-01-05T15:13:29.360" Score="2" ViewCount="" Body="&lt;p&gt;I've implemented the DMX protocol used for theatrical lighting systems which is a flavour of RS-485, and this worked in a noisy environment at least as far as 100ft. This was using a PIC16F877A and a RS-485 line driver to transmit, and several other receiver units with the same microcontrollers, daisy chained together along the 100ft line with a terminating resistor at the end.... it worked well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip actually has a very good &lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/01076A.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; on the subject with some circuit diagrams and example assembler code.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-05T15:36:07.117" LastActivityDate="2011-01-05T15:36:07.117" />
  <row Id="8618" PostTypeId="2" ParentId="8614" CreationDate="2011-01-05T15:31:30.943" Score="2" ViewCount="" Body="&lt;p&gt;RS-485 will work well, but you will need to add a RS-485 transceiver between your UART and the RS-485 bus. There are many software protocols that use this physical layer. Modbus is one of them that I've used in the past. It's very simple to implement and there are lots of industrial controllers out there that support it.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-01-05T15:31:30.943" />
  <row Id="8619" PostTypeId="2" ParentId="5773" CreationDate="2011-01-05T15:45:44.343" Score="2" ViewCount="" Body="&lt;p&gt;I currently have an Arduino, mbed, and finally, a Netduino at my disposal for development / hobbyist use.  I never liked working with the Arduino, perhaps because the editor is not very good, and I'm definitely spoiled as a C# developer.  When I received my mbed, I liked development on that much, much better, but debugging is still painful because you have to use print statements to figure out what's going on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you're developing a product, or just screwing around, a vast majority of your time at first is spent debugging... and when you are debugging, you want to have breakpoints.  I have a very difficult time going back to embedded hardware that doesn't offer any sort of breakpoints.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't have experience with JTAG yet, but every micro I've seen up until now (besides the RabbitCore modules) requires it to allow debugging via breakpoints.  Imagine my surprise when I hooked up my Netduino today and was able to single step through my code in VS2010!  I was extremely pleased by this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I would not worry about the footprint size, evils of .NET and Microsoft, etc. etc.  I would only care about being able to debug quickly and efficiently, so I &lt;em&gt;can just get stuff done&lt;/em&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-01-05T15:45:44.343" CommunityOwnedDate="2011-02-27T07:33:15.000" CommentCount="6" />
  <row Id="8620" PostTypeId="1" AcceptedAnswerId="8623" CreationDate="2011-01-05T15:47:10.200" Score="2" ViewCount="194" Body="&lt;p&gt;According to &lt;a href=&quot;http://www.ecircuitcenter.com/Circuits/smps_buck_vm1/smps_buck_vm1.htm&quot; rel=&quot;nofollow&quot;&gt;this site&lt;/a&gt; in a buck converter with voltage mode control the duty cycle is set directly by comparing a voltage ramp to an error voltage. I agree with that. But this is where my headache starts: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If Vo &amp;lt; Vref,  then Ierr is positive               - increase V(10) and the PWM duty cycle.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;If Vo &gt; Vref,  then Ierr is negative              - decrease V(10) and the PWM duty cycle.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;If Vo ~ Vref,  then Ierr is close to zero       - maintain V(10) and the PWM duty cycle&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;where Vo is the output voltage and Vref is the reference voltage. Well, the first two lines are ok for me, but i can't imagine how the duty cycle is maintained, when Vo ~ Vref.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My assumption here is, that when Vo ~ Vref holds, then the duty cycle should be set to 50% and &lt;strong&gt;not&lt;/strong&gt; maintained. Or am i missing something here?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Macs&lt;/p&gt;&#xA;" OwnerUserId="2277" LastActivityDate="2011-01-05T23:23:04.443" Title="Buck converter with feedback loop" Tags="&lt;smps&gt;&lt;buck&gt;" AnswerCount="3" />
  <row Id="8621" PostTypeId="1" AcceptedAnswerId="8629" CreationDate="2011-01-05T15:54:07.423" Score="4" ViewCount="262" Body="&lt;p&gt;In school, I was told not to leave components in a breadboard for extended periods of time.  However, this length of time was never quantified.  The reasoning was that the contacts would eventually lose their &quot;springiness&quot;; at some point later in time, you'd be debugging issues with a circuit, only to find out that the contacts were bad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no idea if this is really true, or if breadboards are now made so well that it's not an issue.  I have some nice ones, but in the end they seem to use the same narrow white piece that everyone else uses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got some prototypes put together that I don't want to take apart yet, and I also don't know when I'll get back to it.  My mbed board has now taken a back seat to the Netduino that I just received.  :)&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-01-05T18:17:03.637" Title="How long can I leave components in a breadboard?" Tags="&lt;prototyping&gt;&lt;breadboard&gt;" AnswerCount="6" CommentCount="5" FavoriteCount="1" />
  <row Id="8622" PostTypeId="2" ParentId="8621" CreationDate="2011-01-05T15:59:40.660" Score="6" ViewCount="" Body="&lt;p&gt;I've never had any problems, and I've left components in the board for months.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Component leads seem to be quite a tight fit anyway, so whether it's springy or not I think it will make contact anyway.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-05T15:59:40.660" CommentCount="4" />
  <row Id="8623" PostTypeId="2" ParentId="8620" CreationDate="2011-01-05T16:34:25.223" Score="0" ViewCount="" Body="&lt;p&gt;When Vo is not the correct value (Ierr != 0) the duty cycle has to be adjusted. If Vo approaches Vref the adjustments become smaller until there's the point where Vo = Vref, and no adjustments are necessary anymore. If you would change the duty cycle to 50% at that point, Vo will no longer be equal to Vref.&lt;br&gt;&#xA;Besides, if your duty cycle would always be 50% for the correct Vo, then there wouldn't be any regulation, would it? You would just set it to 50, and that would be that.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-01-05T16:34:25.223" CommentCount="2" />
  <row Id="8624" PostTypeId="2" ParentId="8620" CreationDate="2011-01-05T16:38:38.777" Score="0" ViewCount="" Body="&lt;p&gt;The Duty Cycle of a buck converter is D = t_on / T = V_out / V_in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This (and not 50 %) is the ratio that has to be maintained once things are up and running.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you &lt;strong&gt;set&lt;/strong&gt; is the sample of the output voltage in relation to the reference voltage (via the resistive divider). From then on, the control loop will &lt;strong&gt;maintain&lt;/strong&gt; the duty cycle such that the output will stay in regulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will be very hard (or plain impossible) to &lt;strong&gt;set&lt;/strong&gt; the duty cycle by using a function generator, even one with a crystal clock, with the great precision that would be required in order to not have the output drift somewhere because you would have to take care of all the tiny parasitics in your circuit. With a control loop, all that stuff can be taken care of and &lt;strong&gt;maintained&lt;/strong&gt; easily.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-01-05T23:23:04.443" LastActivityDate="2011-01-05T23:23:04.443" />
  <row Id="8625" PostTypeId="2" ParentId="8620" CreationDate="2011-01-05T16:44:26.363" Score="1" ViewCount="" Body="&lt;p&gt;A buck duty cycle is fundamentally defined by Vout / Vin. If you have 12V in and 5V out, 5 / 12 ~= 0.416 which is 41.6 percent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The error amplifier compares a sample of the output voltage (usually with some frequency compensation) to a fixed, precise reference voltage. This is what is referred to as the error signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the output voltage goes high for some reason, the error signal will cause the PWM to reduce duty cycle in an attempt to bring the error to zero.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the output voltage goes low for some reason, the error signal will cause the PWM to increase duty cycle in an attempt to bring the error to zero.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the output voltage matches the reference voltage, the duty cycle will be as per the above formula (which is a first-order approximation; losses and delays will add some extra duty cycle to the result.)&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-01-05T16:44:26.363" CommentCount="1" />
  <row Id="8626" PostTypeId="2" ParentId="8621" CreationDate="2011-01-05T16:46:21.000" Score="3" ViewCount="" Body="&lt;p&gt;I would only worry about the &quot;spring&quot; if you are using over size leads. You could see a issue with oxidation. Usually removing and reinserting the wire or component will &quot;wipe&quot; the oxidation on the contacts.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-01-05T16:46:21.000" />
  <row Id="8627" PostTypeId="2" ParentId="8621" CreationDate="2011-01-05T17:09:33.210" Score="2" ViewCount="" Body="&lt;p&gt;As I understand it, springs only wear out when they move. Leaving them loaded, or leaving them unloaded should be fine. What you'd want to avoid is unnecessarily unloading and reloading them.&lt;/p&gt;&#xA;" OwnerUserId="1213" LastActivityDate="2011-01-05T17:09:33.210" />
  <row Id="8628" PostTypeId="2" ParentId="8621" CreationDate="2011-01-05T17:10:25.650" Score="4" ViewCount="" Body="&lt;p&gt;I'm mostly using common sense here, but let's see what would happen to a board when it's left with components in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oxidation would occur even with no components. Probably some parts of the springs would oxidate differently without components than if components are in, but contact surfaces would probably be more exposed without components in, so I don't think that having components in would make more bigger impact then just having board sit in same conditions without any components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, let's take a look at problems which could come from components themselves. Most components don't produce any debris by just lying around, so only problem could be bad electrolytic capacitors which could leak and contaminate the board. Maybe broken LCD could contaminate board too? I can't think of any other components which leak at the time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If we take a look at the contacts themselves, cold welding could cause problems if the components need to be removed and board repurposed for another use. I don't think that cold welding would cause problems with signal quality on the parts which were left there and allowed to weld, because that's what we use for standard network cables and it works. If the components are removed, contact surface of the springs could be damaged or contaminated by remains of the weld. How big problems this is would depend on materials used for springs and component leads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really don't know what happens to springs which are left in a certain non-relaxed position for extended periods of time, but there could be problems with that. But then again, I think that springs would wear out more by inserting and removing components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, I don't think there would be any reason for anything bad to happen if prototypes do remain assembled on a breadboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the myth comes from a school, maybe the biggest issue would be simple mechanical damage and problematic storage of breadboards. As far as I see it, components are exposed on top of a breadboard and can be damaged very easily. Also, it would be difficult to stack populated breadboards. On the other hand, I don't see anything breadboard specific here. Same rules would apply to any other type of prototyping board.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-01-05T17:18:27.113" LastActivityDate="2011-01-05T17:18:27.113" CommentCount="3" />
  <row Id="8629" PostTypeId="2" ParentId="8621" CreationDate="2011-01-05T18:02:55.970" Score="6" ViewCount="" Body="&lt;p&gt;Here's a picture of a board which had some headers forced into it which were too large, damaging the contacts:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/RNXWP.jpg&quot; alt=&quot;Bad board&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The outer rows of the Sharpie'd area make intermittent contact, so we avoid the whole section.  Notice that some of the numbers are rubbed off, and also notice the burnt spot at the top of the picture where something burned up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The breadboard still has two other middle sections, and this section is only 20 rows tall, so that leaves 172 good rows.  On a university budget, that doesn't merit replacing the board.  If you are demonstrating breadboarded circuits to a client, you should probably replace the whole thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By the way, this board is at least 8 years old, and still works fine except for the indicated area.  I've only been around it for three years, but no one has had any problems with it that I've heard of.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-05T18:02:55.970" CommentCount="1" />
  <row Id="8630" PostTypeId="2" ParentId="8621" CreationDate="2011-01-05T18:17:03.637" Score="6" ViewCount="" Body="&lt;p&gt;Addressing the matter of &quot;losing springiness&quot;, or more technically setting the springs by exceeding their yield strength, all that really matters is how much stress (pressure) you subject them to, which will depend on the strain (displacement).  Over a very long time, they may take a set, but it would take years or extremely elevated temperatures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, avoid inserting extremely large component leads (diodes are the most common offender when breadboarding I think) into the holes.  That's your enemy, not time.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-05T18:17:03.637" CommentCount="2" />
  <row Id="8631" PostTypeId="2" ParentId="8582" CreationDate="2011-01-05T19:02:29.730" Score="1" ViewCount="" Body="&lt;p&gt;Given the lack of actual measurements thus far, I've decided to upload some measurements of my own.  I used a ruler and a magnifier because I don't have anything more accurate, but I verified the measurements by pulling some pins out of a .1&quot; header and test fitting it in the measurements indicated.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;| BB  | A  | B  | C  | D  | E  | 1  | 2  | 3  | 4  | R4 |&#xA;|-----|----|----|----|----|----|----|----|----|----|----|&#xA;| Top | .3-| .1 | .4 | .3 | .3 | .2-| .4 | .2 | .2 | 0  |&#xA;| 2nd | NA | .1 | .4 | .3 | .3 | .2 | .4 | .2 | .3 | inf|&#xA;| 3rd | .2+| .15| .4 | .3 | .3 | .2 | .4 | .2 | .3 | inf|&#xA;| Bot | .3-| .1 | .4 | .3 | .3 | .2-| .4 | .2 | .2 | 0  |&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;A measurement like .3- means that it was slightly smaller than .3, but not .25 or .3.&#xA;Measurement 4 is the distance between the center two power rails (notice that it's different on the middle 2), and R4 is the resistance between the top and bottom of the measurement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The breadboards I used are shown in the following picture, numbered 1 (on the bottom) to 4.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Ehcwf.jpg&quot; alt=&quot;Breadboards. Larger version at imgur.com/fST77, but E&amp;amp;R won't upload it.&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The one on top of the stack is from RSR, the next is a couple old 3M Super Strips.  I think that the third might be a Twin Industries model, but I don't know that.  It and the bottom one were purchased by my school and the guys who would know where they're from don't get back until Monday.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd love to have some Twin Industries, Parallax, Global Specialties, Sparkfun, Seeedstudio, and Adafruit measurements. I'm about ready to just email all of those manufacturers and ask them to take some calipers out to the warehouse, but I feel bad asking for that kind of a favor without intending to buy one of them.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-05T19:02:29.730" />
  <row Id="8632" PostTypeId="1" AcceptedAnswerId="8636" CreationDate="2011-01-05T19:54:49.863" Score="3" ViewCount="279" Body="&lt;p&gt;I'm using some 0.1% precision 10k and 150k resistors. They are thin film 0603 surface mount. For a lot more, there are also thick film types. Fundamentally and practically, what is the difference between these two? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.farnell.com/susumu/rg1608p-154-b-t1/resistor-thin-film-150kohm-100mw/dp/1797111&quot; rel=&quot;nofollow&quot;&gt;Thin film example&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.farnell.com/tyco-electronics-holsworthy/rp73d2a150kbtg/resistor-thick-film-150kohm-125mw/dp/1785447?Ntt=RESISTOR%2C+THICK+FILM%2C+150KOHM&quot; rel=&quot;nofollow&quot;&gt;Thick film example&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-05T22:40:03.360" Title="Difference between thin film and thick film precision surface mount resistors" Tags="&lt;surface-mount&gt;&lt;resistor&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="8633" PostTypeId="1" AcceptedAnswerId="8634" CreationDate="2011-01-05T20:03:07.177" Score="4" ViewCount="197" Body="&lt;p&gt;At the moment, I use 0.1% resistors to get accurate voltage measurement through a voltage divider. However, the cost is high, so I was thinking of using 0.5% or 1% resistors and calibrating out the error in software by using a precision voltage reference during production. Has anyone done this successfully? What pitfalls might I encounter?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-01-05T20:08:34.130" LastActivityDate="2011-01-06T15:48:22.623" Title="How viable is it to just use 1% resistors and calibrate out the error?" Tags="&lt;calibration&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="8634" PostTypeId="2" ParentId="8633" CreationDate="2011-01-05T20:33:48.283" Score="5" ViewCount="" Body="&lt;p&gt;So you've got:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;          R_x         R_fixed&#xA;Vcc -----^v^v^----+----^v^v^------- Gnd&#xA;                  |&#xA;                  |&#xA;                  +--- V_sensed --- ADC input&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Rx is some unknown resistance (probably a sensor of some kind). And you're using R_fixed at 0.1% right now in order to effectively calculate R_x, but you want to use a cheaper fixed resistor with a lower tolerance of perhaps 1%. In doing so you want to perform some kind of calibration during production to correct for the increased error, is that right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way you end up doing this is putting an byte in EEPROM (or some other non-volatile memory) that acts as an &quot;offset&quot; in your calculation, and it's a perfectly viable thing to do.  The thing is it's going to cost you some time during production to do the calibration activity. In order to do the calibration, you'll need one of those 0.1% resistors (call it R_cal) of nominally comparable value to your 1% resistor to substitute into the circuit for R_x. Measuring V_sensed, you can infer more precisely the value of R_fixed (i.e. to something like 0.2%). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If R_cal and R_fixed are nominally the same value, you would expect V_sensed to be equal to Vcc / 2. You would store the measured deviation from Vcc / 2 as a calibration offset byte, and always add it to V_sensed as perceived by your ADC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The pitfall, as I see it, is that there is a bunch of work involved in doing the measurement and subsequently in storing the value. Another thing to consider as a pitfall is that temperature can play a role in causing a resistance to deviate from it's nominal value, so you'll want a reasonably well temperature controlled calibration environment. Finally don't forget to use calibrated measurement equipment, as that's another potential source of additive error. One last pitfall I can think of is that the calibration byte should be stored in units of the lsb of your ADC (so if you have a 12-bit ADC, units of calibration offset byte should be &quot;Vcc/2^12 Volts&quot;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using two fixed resistors to divide a large voltage down to a lower scale as follows:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;        R1_fixed       R2_fixed&#xA;V_in -----^v^v^----+----^v^v^------- Gnd&#xA;                   |&#xA;                   |&#xA;                   +--- V_sensed --- ADC input&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Re-edited Section&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So now you want to use a precision voltage reference (call it V_cal) to stimulate V_in during a calibration step in production. What you've got there is in theory:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;V_sensed = V_predicted = V_cal * R2_fixed / (R1_fixed + R2_fixed) = V_cal * slope_fixed&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;But what you've got in reality is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;V_sensed = V_measured = V_cal * R2_actual / (R1_actual + R2_actual) = V_cal * slope_actual&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;In effect you have a different transfer function slope in reality than what you would predict from the resistor values. The deviation from the predicted divider transfer function will be linear with respect to the input voltage, and you can safely assume that 0V in will give you 0V out, so making one precision voltage reference measurement should give you enough information to characterize this linear scale factor. Namely:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;V_measured / V_predicted = slope_fixed / slope_actual &#xA;slope_actual = slope_fixed * V_measured / V_predicted&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And you would use slope_actual as your calibrated value to determine the voltage in as a function of the voltage measured.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;below courtesy of @markrages&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get the actual slope sensitivity to resistor values requires partial differentiation:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Oe5UV.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-06T15:48:22.623" LastActivityDate="2011-01-06T15:48:22.623" CommentCount="4" />
  <row Id="8635" PostTypeId="2" ParentId="8633" CreationDate="2011-01-05T20:42:51.977" Score="3" ViewCount="" Body="&lt;p&gt;That approach works well going from 5% to 1%. Going from 1% to 0.1%, I suspect that you will start to have your accuracy ruined by temperature fluctuations changing the resistance and thus the voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If, for some unknown reason, you're operating in an isothermal environment and your resistors are all constant current, so self-heating is predictable, it's still viable. &lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-01-05T20:42:51.977" CommentCount="4" />
  <row Id="8636" PostTypeId="2" ParentId="8632" CreationDate="2011-01-05T22:40:03.360" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Thick film&lt;/strong&gt; resistors are screen printed; the alumina substrate is metalized then a resistive paste is deposited on top of the terminals.  It is later trimmed, coated, metalized on the edges, and plated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Thin film&lt;/strong&gt; (or &lt;strong&gt;metal film&lt;/strong&gt;) resistors are pretty much the same except instead of screen printing a resistive paste, the film is vacuum deposited, allowing for a much more uniform and controlled resistive element.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a result, thick film resistors are generally cheaper than their thin film counterparts, but the tolerance and temperature coefficients one can get out of thin film resistors are generally better.  Depending on the materials used, there is plenty of overlap between the two, but all things equal, thin film offer better performance for a cost premium.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vishay has &lt;a href=&quot;http://www.vishay.com/docs/28771/basics.pdf&quot; rel=&quot;nofollow&quot;&gt;a decent app-note&lt;/a&gt; (PDF) on this.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-05T22:40:03.360" CommentCount="2" />
  <row Id="8637" PostTypeId="2" ParentId="8611" CreationDate="2011-01-05T23:49:30.167" Score="1" ViewCount="" Body="&lt;p&gt;Personally, I would try to mod stardand single-chip FM radio receivers (ones which usually work at 100-108Mhz range) with higher values in it's input circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Easiest &amp;amp; cheapiest way to test this would be mod working chineese 1$ FM radio and see if it would work on lower freq. &lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-05T23:49:30.167" />
  <row Id="8639" PostTypeId="1" CreationDate="2011-01-06T03:29:16.290" Score="2" ViewCount="409" Body="&lt;p&gt;I'm using a simple DC motor and the wheels from a small toy car to build a basic ping pong ball launcher.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got one of the wheels rotating clockwise, mounted directly on the motor's spindle, and the other wheel is free running (with 40mm distance between the two outer rims).  So it does sort of launch the ball, but because one wheel is not connected to the motor it has a real large side spin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would I connect the second wheel to the same motor so that it spins in the opposite direction?&lt;/p&gt;&#xA;" OwnerUserId="2500" LastActivityDate="2011-01-16T22:50:22.820" Title="Spin two wheels in opposite directions with single DC motor?" Tags="&lt;dc-motor&gt;&lt;wheel&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="8640" PostTypeId="2" ParentId="8639" CreationDate="2011-01-06T03:50:37.593" Score="0" ViewCount="" Body="&lt;p&gt;You also could use a second motor, if you have the room on your project,&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2060" LastEditorDisplayName="" LastEditDate="2011-01-06T13:40:35.603" LastActivityDate="2011-01-06T13:40:35.603" CommentCount="2" />
  <row Id="8642" PostTypeId="2" ParentId="8614" CreationDate="2011-01-06T04:01:43.407" Score="1" ViewCount="" Body="&lt;p&gt;Yes, RS232 will work.  Keep the baudrate nice and low, and 30 feet is no problem.  But long cable runs are a hassle, so wireless seems attractive.  Especially since a quality 30' RS-232 cable costs some money. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other ideas to consider:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;if one way communication is acceptable, put an IR receiver on the box and program it to listen to a consumer IR control.  Use a popular remote's codes so that an $8 universal remote will work.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;if you control the host software on the PC, have it open an ethernet port and serve web pages with the desired functions and controls on them.  Any wifi-enabled iPad or smartphone becomes a remote control, and remote monitoring is easy.  You could even replace the USB with an ethernet port, but that will add some complexity to the box.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Look at the ISM-band wireless modules like the 24L01 stuff from Nordic and the CCxxxx parts from TI.  Sparkfun sells some on modules.  If this is for a real product, using FCC precertified modules can save some money because FCC cert is expensive.  I would say modules make sense in product volumes up to 5000 pieces. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Edit: &lt;a href=&quot;http://www.engadget.com/2011/01/05/samsungs-rmc30d-universal-touch-control-tv-remote-touts-three-i/&quot; rel=&quot;nofollow&quot;&gt;You should use this remote.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-01-06T04:26:52.723" LastActivityDate="2011-01-06T04:26:52.723" CommentCount="1" />
  <row Id="8643" PostTypeId="2" ParentId="8639" CreationDate="2011-01-06T05:55:06.633" Score="6" ViewCount="" Body="&lt;p&gt;You can connect the two with gears, or, since the ping pong balls are light weight, just find a pair of wheels with a diameter about 40mm greater than your current wheels and let the friction play the role of gear teeth. Four wheels would reduce the load your bearings need to apply to keep the shafts aligned; just put the small wheels in the middle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/PtMe4.jpg&quot; alt=&quot;Diagram&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you could just forgo the second axle altogether, and spin the ball against a static plate.  It would have a lot of spin when launched, but that might be useful, especially if you can get backspin on it so it curves upwards in flight. &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-07T19:55:31.170" LastActivityDate="2011-01-07T19:55:31.170" CommentCount="3" />
  <row Id="8644" PostTypeId="2" ParentId="8603" CreationDate="2011-01-06T07:23:52.580" Score="0" ViewCount="" Body="&lt;p&gt;Unfortunately, I would say it's impossible to have a formula.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FO4 delay consists of &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Charging time of your invertor input capacitance&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Invertor transition time&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Charging time of your invertor output capacitance&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When going from FO2 to FO4 there are different factors on each of these items, specifically, 1 and 3 going to be about twice slower, but 2 is going to be just a little bit slower (as channel length is more or less the same).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On your place I would try to resimulate FO4 circuit for your tech.process and see simulated delay.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-06T07:23:52.580" CommentCount="4" />
  <row Id="8645" PostTypeId="1" AcceptedAnswerId="8666" CreationDate="2011-01-06T08:04:55.237" Score="6" ViewCount="194" Body="&lt;p&gt;What free tools are there to simulate RF circuits?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-06T10:45:23.613" LastActivityDate="2011-01-08T09:14:54.667" Title="Free RF Simulation Software" Tags="&lt;rf&gt;&lt;simulation&gt;" AnswerCount="3" FavoriteCount="4" />
  <row Id="8646" PostTypeId="2" ParentId="8603" CreationDate="2011-01-06T08:48:07.443" Score="3" ViewCount="" Body="&lt;p&gt;According to&#xA;&lt;a href=&quot;http://www.ece.ucsb.edu/bears/class/ece224a/Harris_logical_effort.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.ece.ucsb.edu/bears/class/ece224a/Harris_logical_effort.pdf&lt;/a&gt; (slides 6-11 and 47) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Delay d is g*h+p&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the &lt;a href=&quot;http://en.wikipedia.org/wiki/Logical_effort&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Logical_effort&lt;/a&gt; there are some examples too:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Delay in an inverter. By definition, the logical effort g of an inverter is 1&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Delay in NAND and NOR gates. The logical effort of a two-input NAND gate is calculated to be g = 4/3 &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;For NOT gate with FO1 (drive the same NOT gate):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;g=1; h=1; p=1;  so d = 1*1 + 1 = 2&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For NOT gate with FO4 (the FO4 metric itself):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;g=1; h=4 (Cout is 4 times more than Cin); p=1  so d = 1*4+1 =5  (the same result is in p20 of books &quot;Logical Effort: Designing Fast CMOS Circuits, draft from 1998)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1 FO4 delay is equal to 5 process-independent units (defined by harris, slide 6)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For NAND gate with two inputs (p=2) which drives the same:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;g=4/3; h=1; p=2; d= 4/3 * 1 + 2 = 10/3 = 3,3  (a 1.5 times slower than NOT with FO1, but faster than NOT FO4)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For NAND gate asked by me - 2 inputs which drives 3 same NANDs:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;g=4/3; h=3; p=2; d= (some magic inside) 4/3 * 3 + 2 = 6&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Delay of 1 FO4 gate is equal to 5/6 delay of NAND (2-in, 3 FO).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The last problem is to convert chain delay of 18 NANDs to chain delay of FO4. (slide 41 of harris)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hmm.. seems I need only to multiply 18 NANDs delay with 6/5... 21,6 FO4.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1994" LastEditorUserId="1994" LastEditorDisplayName="" LastEditDate="2011-01-07T11:22:32.100" LastActivityDate="2011-01-07T11:22:32.100" CommentCount="2" />
  <row Id="8647" PostTypeId="1" CreationDate="2011-01-06T09:44:04.843" Score="1" ViewCount="247" Body="&lt;p&gt;I read an article which tells power consumption by many devices. It say that a desktop computer (computer and monitor) use 400 to 600 watt.&lt;br&gt;&#xA;While when i checked my computer and monitor with meter, it was about 60 + 60 = 120 watt (computer + 17&quot; CRT monitor) after loading windows xp and running an application. The voltage is 220V here.&lt;br&gt;&#xA;Which one is correct? How much power does it consume?&lt;/p&gt;&#xA;" OwnerUserId="2502" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-06T18:05:29.480" LastActivityDate="2011-01-06T18:05:29.480" ClosedDate="2011-01-06T17:05:22.453" Title="What is the Power Consumption of a desktop computer?" Tags="&lt;power-supply&gt;&lt;computers&gt;&lt;power-meter&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="8648" PostTypeId="2" ParentId="8647" CreationDate="2011-01-06T10:30:30.107" Score="10" ViewCount="" Body="&lt;p&gt;If you've measured it, and your confident that your meter is accurate, then I would go with 120w.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the 400w/600w are the maximum ratings of what the PSU can handle, rather than the actual load that the hardware draws from it.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-06T10:30:30.107" CommentCount="4" />
  <row Id="8649" PostTypeId="2" ParentId="8647" CreationDate="2011-01-06T10:50:09.473" Score="4" ViewCount="" Body="&lt;p&gt;Try doing something compute-intensive and maybe which also taxes the GPU, e.g. play a game with 3D graphics or rip a DVD - you'll probably find that the power consumption then increases significantly.&lt;/p&gt;&#xA;" OwnerUserId="1489" LastActivityDate="2011-01-06T10:50:09.473" CommentCount="1" />
  <row Id="8650" PostTypeId="1" CreationDate="2011-01-06T12:54:39.417" Score="8" ViewCount="296" Body="&lt;p&gt;&lt;strong&gt;What are some excellent resources related to advanced analog circuit design?&lt;/strong&gt; This includes RF, sonar, audio, low-frequency, high power, low power, noise, amplifiers, etc.. To get the most obvious contender out of the way, I currently refer to...&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;The Art of Electronics &lt;sup&gt;&lt;sup&gt;2&lt;sup&gt;nd&lt;/sup&gt; ed.&lt;/sup&gt;&lt;/sup&gt;&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;by Paul Horowitz and Winfield Hill, 1989&lt;/em&gt;&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/ZBMkB.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;br&gt;&#xA;It isn't exactly a cookbook, but it also doesn't go into detail about each design, so it requires an electronics background to use. As such, it is excellent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I know there are more specialized and advanced resources available. What do you use?&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-09T13:49:34.037" Title="analog circuit design resource recommendations" Tags="&lt;analog&gt;&lt;design&gt;&lt;books&gt;&lt;website&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="8" />
  <row Id="8651" PostTypeId="2" ParentId="8614" CreationDate="2011-01-06T13:16:26.437" Score="2" ViewCount="" Body="&lt;p&gt;One option (assuming your desired device supports it... many Microchip PIC's do) is a CAN messaging system. It's extensively used in automobiles, e.g. so a tire rotation speed sensor and an accellerometer can communicate with the airbag computer. The protocol is designed such that you can have an unlimited number of devices communicating on one bus without collisions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use it at my company to communicate up to about 200 feet between a product and a controller. Highest standard baud rate is 1Mbit/s. It's fairly easy to implement in C. You'll need a CAN transceiver if you choose to do this; something like Microchip's MCP2551.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the &lt;a href=&quot;http://esd.cs.ucr.edu/webres/can20.pdf&quot; rel=&quot;nofollow&quot;&gt;specification&lt;/a&gt;, here's pertinent app notes &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en011694&quot; rel=&quot;nofollow&quot;&gt;AN713&lt;/a&gt; and &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en011947&quot; rel=&quot;nofollow&quot;&gt;AN754&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2344" LastActivityDate="2011-01-06T13:16:26.437" CommentCount="3" />
  <row Id="8652" PostTypeId="2" ParentId="2320" CreationDate="2011-01-06T15:02:20.953" Score="2" ViewCount="" Body="&lt;p&gt;I know this is an old topic, but also see ( and possibly contribute to )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://opencircuits.com/Popular_Parts#X.3DPIC.27s&quot; rel=&quot;nofollow&quot;&gt;http://opencircuits.com/Popular_Parts#X.3DPIC.27s&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;which is also linked here.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-01-06T15:02:20.953" />
  <row Id="8653" PostTypeId="2" ParentId="7505" CreationDate="2011-01-06T15:13:55.870" Score="0" ViewCount="" Body="&lt;p&gt;Some printers have a clear striped ( across the axis ) material that is scanned by photo cells to make a long linear encoder.  This does not move.  You could use your current drive ( or almost any other ) and use the encoder for feedback to make the motion as precise as the stripes.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-01-06T15:13:55.870" />
  <row Id="8654" PostTypeId="2" ParentId="8647" CreationDate="2011-01-06T15:45:37.610" Score="1" ViewCount="" Body="&lt;p&gt;120W is ok for idling computer.&#xA;I have about ~380W for 2 computers with lots of HDDs and 2 monitors (I have a powermeeter attached permanently for my PCs).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But when I load something which loads both CPU &amp;amp; GPU consumption might jump +150-250W.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-06T15:45:37.610" CommentCount="1" />
  <row Id="8655" PostTypeId="2" ParentId="8650" CreationDate="2011-01-06T16:35:31.503" Score="6" ViewCount="" Body="&lt;p&gt;Jim Williams and friends, &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0750696400&quot; rel=&quot;nofollow&quot;&gt;Analog Circuit Design&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/AtU6B.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bob Pease, &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0750694998&quot; rel=&quot;nofollow&quot;&gt;Troubleshooting Analog Circuits&lt;/a&gt;.  Despite the name, this is as much about design as it is about troubleshooting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/0n6Bt.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-06T16:35:31.503" CommentCount="7" />
  <row Id="8656" PostTypeId="1" AcceptedAnswerId="8659" CreationDate="2011-01-06T16:51:39.887" Score="4" ViewCount="285" Body="&lt;p&gt;I cannot afford a function generator and oscope right now, so I'm trying to learn analog electronics with Spice (MacSpice, to be specific). Below is the Spice model for a simple emitter-follower circuit.  Vcc is 15V, and the input at the base is a 5V 60Hz sine wave with a 0V DC offset.  R1 sits between the transistor base and the sine input, and R2 sits between the transistor emitter and ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output at the emitter has me a bit puzzled and I would appreciate it if anyone has an explanation for the behavior.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;* Simple Emitter Follower&#xA;Vcc 3 0 DC 15&#xA;Vin 1 0 SIN(0 5 60) dc 0&#xA;R1  1 2 270&#xA;R2  4 0 3.3k&#xA;Q1  3 2 4 generic&#xA;.model generic npn&#xA;.control&#xA;tran 1ms 60ms&#xA;plot v(1) v(4)&#xA;.endc&#xA;.end&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The output of the transient analysis plot command is below.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/br8vj.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was surprised by this output.  As expected, there is a slight voltage drop in the amplitude due to the base-emitter junction of the NPN.  However, the output is clipped and does not swing below zero.  What would I need to do to catch the negative part of the sine wave?&lt;/p&gt;&#xA;" OwnerUserId="2059" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-01-07T01:46:50.390" LastActivityDate="2011-01-08T17:44:15.473" Title="Emitter Follower Output" Tags="&lt;bjt&gt;&lt;spice&gt;&lt;emitter-follower&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="8657" PostTypeId="2" ParentId="8650" CreationDate="2011-01-06T16:58:55.213" Score="1" ViewCount="" Body="&lt;p&gt;This is a practical RF design book, with just enough math, sort of the RF equivalent to Art of Electronics: &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0750685182&quot; rel=&quot;nofollow&quot;&gt;Chris Bowick, RF Circuit Design&lt;/a&gt;.  I've only read the first edition.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/JuBiE.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-06T16:58:55.213" />
  <row Id="8658" PostTypeId="2" ParentId="8656" CreationDate="2011-01-06T17:05:01.797" Score="3" ViewCount="" Body="&lt;p&gt;You need to add a dc bias to vin to prevent the base-emitter junction from becoming reversed biased during the negative half cycle. When the base voltage is below the emitter voltage no current flows and the transistor is in cutoff.&lt;/p&gt;&#xA;" OwnerUserId="1409" LastEditorUserId="1409" LastEditorDisplayName="" LastEditDate="2011-01-08T17:44:15.473" LastActivityDate="2011-01-08T17:44:15.473" CommentCount="2" />
  <row Id="8659" PostTypeId="2" ParentId="8656" CreationDate="2011-01-06T17:13:34.457" Score="7" ViewCount="" Body="&lt;p&gt;You need to connect R2 to a negative supply voltage with enough headroom for your signal, or bias the input waveform so that it doesn't clip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output voltage an emitter-follower is usually &lt;code&gt;V_out = V_in - 0.7V&lt;/code&gt;, but there are bounds on where this function works. For the expected behavior, &lt;code&gt;VCC + 0.7V &amp;gt; V_in &amp;gt; VEE + 0.7V&lt;/code&gt; must be maintained, where VEE is your negative supply. In your case, VEE is equal to 0V since you don't have a negative supply. When your input voltage swings below 0.7V, the transistor turns off, and your output stays at the negative voltage rail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Modify these lines to add in a negative power supply.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;R2  4 5 3.3k&#xA;Vee 0 5 DC 15&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Modify this line to bias the sine wave for the existing circuit.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Vin 1 0 SIN(7.5 5 60) dc 0&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-01-06T17:13:34.457" CommentCount="2" />
  <row Id="8660" PostTypeId="2" ParentId="8656" CreationDate="2011-01-06T17:22:57.373" Score="6" ViewCount="" Body="&lt;p&gt;So if I am decoding your netlist correctly, you have the circuit on the upper left.  The reason the output doesn't go below zero is that the thing pulling down on the output is connected to ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One solution is shown in &quot;A&quot;, which is to have the pulldown pull from -15V instead of 0V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another solution is shown in &quot;B&quot;, which is to replace the pulldown with a PNP transistor.  This wastes less power, because there isn't the 3.3k resistor always dissipating.  Class-B amplifiers form the basis of most audio amplifiers and op-amp output stages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/TNg7U.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-06T17:22:57.373" CommentCount="5" />
  <row Id="8661" PostTypeId="2" ParentId="7697" CreationDate="2011-01-06T17:57:11.527" Score="2" ViewCount="" Body="&lt;p&gt;What you're looking for sounds like an &lt;strong&gt;LCD shutter&lt;/strong&gt;, specifically a &lt;strong&gt;Pi Cell LCD Shutter&lt;/strong&gt;. The more modern welding helmets use the &lt;strong&gt;TN LCD Shutters&lt;/strong&gt; which have the same slower speeds as 3D shutter glasses. From what I've read the Pi Cell LCD Shutters can have a switching speed of up to 1000Hz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.liquidcrystaltechnologies.com/products/LCDShutters.htm&quot; rel=&quot;nofollow&quot;&gt;Liquid Crystal Technologies&lt;/a&gt; claim they'll send you a free 1&quot;x1&quot; or 4&quot;x1.5&quot; TN LCD shutter or a 1&quot;x1.5&quot; pi cell shutter. The pi cell shutter will be the faster one. I've never needed an LCD shutter, so I can't verify anything any company claims about theirs, but free is certainly worth a try if you can get them to send you one.&lt;/p&gt;&#xA;" OwnerUserId="2495" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-06T18:01:52.647" LastActivityDate="2011-01-06T18:01:52.647" CommentCount="1" />
  <row Id="8662" PostTypeId="1" AcceptedAnswerId="8665" CreationDate="2011-01-06T18:07:51.303" Score="0" ViewCount="123" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using a Microchip PIC18 and I need to use matrices in my code. I know DSPIC do have matrix libraries, that simplifies the implementation.&#xA;Does anybody know whether any is available also for the 18 family (my present PIC18 embeds an hw multiplier)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you all!&lt;/p&gt;&#xA;" OwnerUserId="2285" LastActivityDate="2011-01-06T18:22:31.697" Title="Microchip PIC18 matrix routines" Tags="&lt;pic&gt;&lt;microchip&gt;&lt;library&gt;&lt;matrix&gt;" AnswerCount="2" />
  <row Id="8663" PostTypeId="2" ParentId="8662" CreationDate="2011-01-06T18:13:48.457" Score="2" ViewCount="" Body="&lt;p&gt;Microchip themselves doesn't have any suitable libraries for the PIC18. Someone on the Microchip forums might have written some routines you can use, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd be inclined to use a 16-bit PIC, it would make things much easier.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-06T18:13:48.457" CommentCount="2" />
  <row Id="8664" PostTypeId="2" ParentId="8645" CreationDate="2011-01-06T18:21:56.407" Score="1" ViewCount="" Body="&lt;p&gt;There's some possibility that &lt;a href=&quot;http://www.5spice.com/index.htm&quot; rel=&quot;nofollow&quot;&gt;5Spice&lt;/a&gt; will do what you're looking for, although I can't guarantee it; you'll just have to give it a try and see.&lt;/p&gt;&#xA;" OwnerUserId="2495" LastActivityDate="2011-01-06T18:21:56.407" />
  <row Id="8665" PostTypeId="2" ParentId="8662" CreationDate="2011-01-06T18:22:31.697" Score="1" ViewCount="" Body="&lt;p&gt;If you're just using simple, fixed size matrices like 2x2 or 3x3 affine transforms, it's not &lt;a href=&quot;http://local.wasp.uwa.edu.au/~pbourke/miscellaneous/determinant/&quot; rel=&quot;nofollow&quot;&gt;very difficult to implement them yourself&lt;/a&gt;. That link shows how to compute the determinant and inverse of a matrix. Multiplication, addition, etc. are much easier. In fact, the Cairo source code, a drawing library, has GPL/LGPL/MPL licensed code for dealing with matrices (2D affine only):  &lt;a href=&quot;http://cgit.freedesktop.org/cairo/tree/src/cairo-matrix.c&quot; rel=&quot;nofollow&quot;&gt;cairo-matrix.c&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-06T18:22:31.697" />
  <row Id="8666" PostTypeId="2" ParentId="8645" CreationDate="2011-01-06T19:08:19.990" Score="2" ViewCount="" Body="&lt;p&gt;For normal lumped circuits, your favorite version of spice will work fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For analyzing matching networks, I've used &lt;a href=&quot;http://www.qsl.net/ik5nax/&quot; rel=&quot;nofollow&quot;&gt;gsmc&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For analyzing a layout and extracting parasitics and computing fields, I dunno.  It's usually easier to just build the circuit and see what happens.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-01-06T19:16:31.903" LastActivityDate="2011-01-06T19:16:31.903" />
  <row Id="8667" PostTypeId="2" ParentId="8614" CreationDate="2011-01-06T19:17:33.207" Score="1" ViewCount="" Body="&lt;p&gt;There are various ZigBee devices that can be used just like a UART and should be simple to control from a PIC device.  For example, the &lt;a href=&quot;http://www.digi.com/products/wireless/point-multipoint/xbee-series1-module.jsp#overview&quot; rel=&quot;nofollow&quot;&gt;XBee&lt;/a&gt; is quite easy to use and is very affordable.  In my experience I've been able to transmit and receive data in a crowded office at distances greater than 100 ft, and in a wide open space we could do much better, especially with good antennae.  In my opinion wireless is much preferred to a 30-ft. long cable!&lt;/p&gt;&#xA;" OwnerUserId="2059" LastActivityDate="2011-01-06T19:17:33.207" />
  <row Id="8668" PostTypeId="2" ParentId="8650" CreationDate="2011-01-06T19:28:08.203" Score="3" ViewCount="" Body="&lt;p&gt;I have always liked ARRL's &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0872594920&quot; rel=&quot;nofollow&quot;&gt;Introduction to Radio Frequency Design&lt;/a&gt; book.  It is certainly not shy on using equations, but it offers circuits rather than high-level system diagrams and covers many crucial parts of RF systems.  The accompanying CD comes with a lot of nice tools, though they are MS-DOS only.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/bAs7Q.jpg&quot; alt=&quot;cover&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2059" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-09T13:39:28.973" LastActivityDate="2011-01-09T13:39:28.973" />
  <row Id="8669" PostTypeId="1" CreationDate="2011-01-06T21:01:14.663" Score="2" ViewCount="195" Body="&lt;p&gt;Hey guys,&#xA;I would like to design a device that is capable of connecting to a PC via WiFi or a wired connection (ideally Ethernet as well). I would like for it to be possible for a wired connection to be used while a wireless connection to a remote device is also able to communicate with the device (using the WiFi). So for this to be possible i believe that I would need a WiFi module and a wired Ethernet adapter controller. I would prefer to use Microchip devices and I have been studying their line of Ethernet controllers but it seems like it would be quite a challenge to configure their firmware stack to work with a wired connection and a wireless connection at the same time. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess my other alternative would be to use WiFi and RS-232 so that way I only need the stack for the wireless connection. That would simplify things greatly but I lose my ability to have true remote control from outside the building on my wired connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess this project would be similar to a printer that can be connected to using either WiFi, or a wired connection, or possibly both at the same time. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone worked on a project like this or have any suggestions for me?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="1235" LastEditorDisplayName="" LastEditDate="2011-01-06T21:21:24.963" LastActivityDate="2011-04-04T18:01:01.733" Title="Wired AND Wireless Embedded Ethernet Project" Tags="&lt;ethernet&gt;&lt;uart&gt;&lt;wifi&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="8670" PostTypeId="2" ParentId="8669" CreationDate="2011-01-06T21:17:41.130" Score="4" ViewCount="" Body="&lt;p&gt;I think you can get a &lt;a href=&quot;http://www.dd-wrt.com/&quot; rel=&quot;nofollow&quot;&gt;DD-WRT&lt;/a&gt; capable router for USD$50, or maybe even less than that. I think you'll be hard pressed to put WiFi and wired ethernet onto a pic for much less than that. IIRC most of those routers have I2C or SPI you can pull out, and then you can just do whatever you've got to in Linux on a 200+MHz processor.&lt;/p&gt;&#xA;" OwnerUserId="1213" LastActivityDate="2011-01-06T21:17:41.130" CommentCount="1" />
  <row Id="8671" PostTypeId="2" ParentId="8418" CreationDate="2011-01-06T21:23:17.460" Score="1" ViewCount="" Body="&lt;p&gt;Another option would be to use PCB Busbar soldered into the PCB - they would also add some nice rigidity to your PCB should it need it&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-01-06T21:23:17.460" />
  <row Id="8672" PostTypeId="1" AcceptedAnswerId="8698" CreationDate="2011-01-06T21:34:41.623" Score="2" ViewCount="462" Body="&lt;p&gt;I'm designing a digital phase-controlled light dimmer, and I need a zero-crossing detector circuit. From what I've read, it's a bad idea to wire the AC main directly to the microcontroller through a resistor, and folks have suggested using optoisolation instead. However, I don't know how the circuit actually falls together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would seem elegant to me if the zero cross circiut's output is a 5V logic pulse for use as a rising-edge interrupt. But I'm not married to that idea if some other output is easier to use.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Input: 120V AC @ 60 Hz&#xA;Output: 5V pulse at zero crossing&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Interesting related post, with not enough detail for me: &lt;a href=&quot;http://electronics.stackexchange.com/questions/4679/detecting-zero-cross-in-ac&quot;&gt;detecting zero cross in ac ?&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2172" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-07T05:08:24.053" LastActivityDate="2011-01-07T10:17:23.157" Title="120VAC 60Hz Zero Cross Detector" Tags="&lt;power&gt;&lt;ac&gt;&lt;opto-isolator&gt;&lt;zero-crossing&gt;" AnswerCount="3" />
  <row Id="8673" PostTypeId="2" ParentId="7882" CreationDate="2011-01-06T21:40:45.627" Score="5" ViewCount="" Body="&lt;p&gt;I'll take a shot at this one as I'll be doing the exact same exercise for my work soon.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the antenna impedance appears to be 60-j21 ohms:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/gwhgX.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And the impedance looking out into L3 is 31-j7 ohms:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Cm2CZ.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(This would imply a source impedance of 31+j7 ohms).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So how can we get from 60-j21 to 31-j7 ohms?  A two-element matching network can do it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All that's necessary to make a match is two components.  Here are a couple possibilities:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/355rr.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/XyaDf.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the two two-component possibilities are high-pass (series L, parallel C) or low-pass (series C, parallel L).  If the matching network is used as a filter for harmonic suppression, then the low-pass form is preferred. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, the 24L01 outputs have a DC level at the power supply voltage.  If you don't want DC on your antenna, a topology with a series capacitor for DC blocking may be desirable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the matching network is being used for filtering, it is desirable to be able to set the Q of this filter to get a steeper shape factor.  Two topologies for this are the &quot;PI match&quot; and the &quot;Tee match.&quot;  Essentially they are two back to back two-element networks, matching to an intermediate impedance to set the desired Q.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(to be continued)&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-01-07T16:22:32.467" LastActivityDate="2011-01-07T16:22:32.467" CommentCount="4" />
  <row Id="8674" PostTypeId="2" ParentId="8672" CreationDate="2011-01-06T22:19:39.837" Score="2" ViewCount="" Body="&lt;p&gt;A while ago I created the exact same thing... a light dimmer using a triac with the timings calculated from the zero crossing signal send to the interrupt pin on a pic16f877a.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I took the zero crossing signal from the PSU that powers the circuit before it's smoothed and regulated. There are a few components to change the rectified humps of the AC into very short +5v pulses of around 200uS. Most of the time, the transistor (shown as Q in the diag) is conducting pulling the RB0/INT pin low, but when the AC dips below 4.7V briefly it stops conducting and the signal is pulled high by the resistor R.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/jUYZC.jpg&quot; alt=&quot;Zero Crossing Schematic&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The pulse is centred around the zero crossing, and it should be short enough to roughly detect the zero crossing moment. But you can fine tune this in software, by first detecting the rising edge of the pulse, then timing when the falling edge happens, then dividing this in half and adding this time period to the next rising edge... this will give you the exact zero crossing.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-07T10:17:23.157" LastActivityDate="2011-01-07T10:17:23.157" CommentCount="10" />
  <row Id="8675" PostTypeId="2" ParentId="8672" CreationDate="2011-01-06T22:56:38.633" Score="0" ViewCount="" Body="&lt;p&gt;I needed a similar solution. I happened to also require 3.3V to power a microcontroller, through a non-isolated supply. In this case it provides a square wave at 50 or 60 Hz; a rising or falling edge signals a zero crossing point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Danger of Death&lt;/strong&gt; - Non-isolated power supply, trained people only.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ZSSyW.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-06T22:56:38.633" CommentCount="3" />
  <row Id="8676" PostTypeId="1" CreationDate="2011-01-06T23:05:41.420" Score="9" ViewCount="422" Body="&lt;p&gt;What are the cheapest microcontrollers available?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would be in volumes over 1000, though hobbyist availability would be nice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for the cheapest of all microcontrollers - my requirements are minimal, 1 IO pin, any supply voltage, single chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(This is a &quot;community-wiki&quot;, so anyone with &gt;100 reputation can refine and improve answers)&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-29T06:50:37.407" LastActivityDate="2011-03-04T15:44:29.767" CommunityOwnedDate="2011-01-06T23:14:02.133" Title="What are the cheapest microcontrollers?" Tags="&lt;microcontroller&gt;" AnswerCount="8" CommentCount="8" FavoriteCount="1" />
  <row Id="8677" PostTypeId="2" ParentId="8676" CreationDate="2011-01-06T23:08:40.920" Score="7" ViewCount="" Body="&lt;p&gt;Texas Instruments have a &quot;&lt;a href=&quot;http://www.ti.com/ww/en/mcu/valueline/index.shtml?DCMP=Value_Line&amp;amp;HQS=Other+BA+430value-promo&quot; rel=&quot;nofollow&quot;&gt;Value Line&lt;/a&gt;&quot; MSP430 range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Flash: 0.5/1k&#xA;RAM:   128 B&#xA;Package: 14TSSOP (cheapest) / 14DIP / 16QFN&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's the only 16-bit device in this class, and it's also the only one with 10 IO pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/msp430g2001.html&quot; rel=&quot;nofollow&quot;&gt;MSP430G2001 is $0.34 @ 1ku&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-04T15:44:29.767" LastActivityDate="2011-03-04T15:44:29.767" CommentCount="3" />
  <row Id="8678" PostTypeId="1" AcceptedAnswerId="8697" CreationDate="2011-01-06T23:20:19.363" Score="4" ViewCount="283" Body="&lt;p&gt;I'm planning to build a digitally-controlled light dimmer circuit. I'm not trained in electrical engineering, and I don't want to do something that an electrician would immediately recognize as dangerous and stupid.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please suggest a reasonable home set up for prototyping circuits involving 120V AC power.&lt;/p&gt;&#xA;" OwnerUserId="2172" LastEditorUserId="2172" LastEditorDisplayName="" LastEditDate="2011-05-30T17:17:58.133" LastActivityDate="2011-05-30T17:17:58.133" Title="Basic Training for working with 120V AC" Tags="&lt;prototyping&gt;&lt;safety&gt;&lt;ac&gt;&lt;high-voltage&gt;" AnswerCount="8" CommentCount="2" FavoriteCount="1" />
  <row Id="8679" PostTypeId="2" ParentId="8676" CreationDate="2011-01-06T23:40:28.610" Score="5" ViewCount="" Body="&lt;p&gt;Given your modest requirements. the &lt;a href=&quot;http://octopart.com/partsearch/#search/requestData&amp;amp;q=pic10f200&quot; rel=&quot;nofollow&quot;&gt;pic10f200&lt;/a&gt; is worth a look.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Flash:    256B&lt;br&gt;&#xA;RAM:      16 B&lt;br&gt;&#xA;Package:  SOT23-6&lt;br&gt;&#xA;Price@1:  &lt;a href=&quot;http://www.microchipdirect.com/ProductSearch.aspx?keywords=PIC10F200T-I/OT&quot; rel=&quot;nofollow&quot;&gt;$0.41&lt;/a&gt;&lt;br&gt;&#xA;Price@1k: &lt;a href=&quot;http://www.microchipdirect.com/ProductSearch.aspx?keywords=PIC10F200T-I/OT&quot; rel=&quot;nofollow&quot;&gt;$0.32&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/41239D.pdf&quot; rel=&quot;nofollow&quot;&gt;Datasheet&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-04T15:04:42.673" LastActivityDate="2011-03-04T15:04:42.673" CommunityOwnedDate="2011-01-06T23:40:28.610" CommentCount="2" />
  <row Id="8680" PostTypeId="1" AcceptedAnswerId="8844" CreationDate="2011-01-06T23:43:07.297" Score="4" ViewCount="853" Body="&lt;p&gt;NFC has a mode called &quot;card emulation&quot; in which it can communicate with a RFID reader because it acts as an RFID card. All the literature I have and the web serches I did only got me so far as with card emulation the device should at least &quot;emit a unique ID&quot;. But I would like to know if it&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;is possible, according to the NFC&#xA;defintion, for such a card emulation&#xA;information to be configured&#xA;completly free (probably going as far&#xA;as emulating a RFID card with a java&#xA;routine on with it's top limit beeing&#xA;the maximum of bytes allowed on a&#xA;RFID card in the RFID protocol), and&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;if such a uniqe ID (if not freely &#xA;configurable) is hardcoded by the&lt;br&gt;&#xA;manufacturer or dependent on the sim &#xA;card.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;On some sidenote it probably would be interesting what manufacturers enable you as a user to do and what should be theoretically possible because of protocol definitions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example the Nexus S's NFC chip is read only and does not offer any card emulation mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I thank you in advance for all answers.&lt;/p&gt;&#xA;" OwnerUserId="2510" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-06T23:46:59.513" LastActivityDate="2011-03-19T18:42:32.563" Title="Questions about NFC's card emulation mode" Tags="&lt;rfid&gt;" AnswerCount="2" />
  <row Id="8681" PostTypeId="2" ParentId="8676" CreationDate="2011-01-06T23:53:16.693" Score="1" ViewCount="" Body="&lt;p&gt;Atmel &lt;a href=&quot;http://www.atmel.com/dyn/products/Product_card.asp?part_id=3175&quot; rel=&quot;nofollow&quot;&gt;ATtiny13&lt;/a&gt;. Short datasheet &lt;a href=&quot;http://atmel.com:80/dyn/resources/prod_documents/2535S.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-06T23:55:32.520" LastActivityDate="2011-01-06T23:55:32.520" CommunityOwnedDate="2011-01-06T23:53:16.693" CommentCount="5" />
  <row Id="8682" PostTypeId="2" ParentId="8676" CreationDate="2011-01-07T00:14:07.760" Score="1" ViewCount="" Body="&lt;p&gt;All uC vendors have chips under 1$. It's more about what you can buy in your local shops in small quantity. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, I was paying for Attiny13 ~1.5$ which is much more it costs at the manufacturer. And I don't have msp430 for any money here. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, check your shops, that's the only way to go. &lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-07T00:14:07.760" CommunityOwnedDate="2011-01-07T00:14:07.760" CommentCount="3" />
  <row Id="8683" PostTypeId="2" ParentId="8678" CreationDate="2011-01-07T00:32:57.177" Score="4" ViewCount="" Body="&lt;p&gt;If you're not comfortable with it, don't do it.  I wouldn't mess with AC unless you're totally confident in what your doing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you must, use the one hand rule, and keep one hand in your pocket while working with live AC.  Also use insulated tools.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-01-07T00:32:57.177" CommentCount="2" />
  <row Id="8684" PostTypeId="2" ParentId="8678" CreationDate="2011-01-07T00:45:04.757" Score="4" ViewCount="" Body="&lt;p&gt;Apart from what @bt2 said&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Don't be alone, so someone can call 911.&lt;/li&gt;&#xA;&lt;li&gt;Show them where the off switch is.&lt;/li&gt;&#xA;&lt;li&gt;Don't wear a ring, watch, necklace.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-07T00:45:04.757" CommentCount="1" />
  <row Id="8685" PostTypeId="1" AcceptedAnswerId="8688" CreationDate="2011-01-07T01:15:03.097" Score="8" ViewCount="591" Body="&lt;p&gt;This has just dawned on me that if you're writing an operating system then what are you writing it on? I ask this as I am reading a microprocessor fundamentals book from 1980 and this question popped in to my head: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How was the first microprocessor chip programmed?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The answer may be obvious but its bugging me. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-07T19:22:17.347" LastActivityDate="2011-04-15T01:13:42.523" Title="How were the first microprocessors programmed?" Tags="&lt;microprocessor&gt;" AnswerCount="8" CommentCount="3" FavoriteCount="3" />
  <row Id="8686" PostTypeId="2" ParentId="8676" CreationDate="2011-01-07T01:26:06.673" Score="3" ViewCount="" Body="&lt;p&gt;The 6-pin (SMD) or 8-pin (DIP) &lt;a href=&quot;http://www.freescale.com/files/microcontrollers/doc/data_sheet/MC9RS08KA2.pdf&quot; rel=&quot;nofollow&quot;&gt;Freescale MC9RS08KA1&lt;/a&gt;, is &lt;a href=&quot;http://mouser.com/search/ProductDetail.aspx?qs=r8OyiFxb6RdLUxUWAaybug==&amp;amp;cm_mmc=findchips-_-na-_-na-_-na&quot; rel=&quot;nofollow&quot;&gt;68 cents quantity one&lt;/a&gt; (&lt;a href=&quot;http://mouser.com/search/ProductDetail.aspx?qs=r8OyiFxb6RdLUxUWAaybug==&amp;amp;cm_mmc=findchips-_-na-_-na-_-na&quot; rel=&quot;nofollow&quot;&gt;72 cents quantity 10, and 42 cents quantity 100&lt;/a&gt;,  or &lt;a href=&quot;http://mouser.com/search/ProductDetail.aspx?qs=r8OyiFxb6RdLUxUWAaybug==&amp;amp;cm_mmc=findchips-_-na-_-na-_-na&quot; rel=&quot;nofollow&quot;&gt;40 cents quantity 1000&lt;/a&gt;.  It has 2 or 4 I/O pins, and has 1 KB of Flash and 63 bytes of RAM.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-04T15:36:34.143" LastActivityDate="2011-03-04T15:36:34.143" CommunityOwnedDate="2011-01-07T01:26:06.673" />
  <row Id="8687" PostTypeId="2" ParentId="8685" CreationDate="2011-01-07T01:27:00.510" Score="5" ViewCount="" Body="&lt;p&gt;An operating system is a computer program which runs directly on the processor. It can be written in any language which can be compiled or assembled down to machine instructions. Assembly and C are common choices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Code is loaded into processors a single instruction at a time from a store - a ROM or RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Z3_%28computer%29&quot; rel=&quot;nofollow&quot;&gt;Z3&lt;/a&gt;, the first programmable processor was built out of electromechanical relays and read instructions from punched film.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Altair 8800, the first personal computer, was programmed by toggling switches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To learn how a processor is constructed from digital logic, see &lt;a href=&quot;http://electronics.stackexchange.com/questions/5516/a-fun-book-to-learn-computer-architecture-for-not-exactly-beginners&quot;&gt;A fun book to learn computer architecture (for not-exactly-beginners).&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a history, see &lt;a href=&quot;http://en.wikipedia.org/wiki/History_of_computing_hardware&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/History_of_computing_hardware&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-07T01:34:44.813" LastActivityDate="2011-01-07T01:34:44.813" />
  <row Id="8688" PostTypeId="2" ParentId="8685" CreationDate="2011-01-07T01:46:26.897" Score="19" ViewCount="" Body="&lt;p&gt;I will take your question literally and discuss mostly microprocessors, not computers in general.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All computers have some sort of machine code.  An instruction consists of an opcode and one or more operands.  For example, the ADD instruction for the &lt;a href=&quot;http://en.wikipedia.org/wiki/Intel_4004&quot; rel=&quot;nofollow&quot;&gt;Intel 4004&lt;/a&gt; (the very first microprocessor) was encoded as 1000RRRR where 1000 is the opcode for ADD and RRRR represented a register number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The very first computer programs were written by hand, hand-encoding the 1's and 0's to create a program in machine language.  This is then programmed into the chip.  The first microprocessors used ROM (Read-Only Memory); this was later replaced by &lt;a href=&quot;http://en.wikipedia.org/wiki/EPROM&quot; rel=&quot;nofollow&quot;&gt;EPROM&lt;/a&gt; (Erasable Programmable ROM, which was erased with UV light); now programs are usually programmed into &lt;a href=&quot;http://en.wikipedia.org/wiki/EEPROM&quot; rel=&quot;nofollow&quot;&gt;EEPROM&lt;/a&gt; (&lt;em&gt;&quot;Electrically...-EPROM&quot;&lt;/em&gt;, which can be erased on-chip), or specifically Flash memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most microprocessors can now run programs out of RAM (this is pretty much standard for everything but microcontrollers), but there has to be a way of loading the prgoram into RAM in the first place.  As Joby Taffey pointed out in his answer, this was done with toggle switches for the Altair 8080, which was powered by an Intel 8080 (which followed the 4004 and 8008).  In your PC, there is a bit of ROM called the &lt;a href=&quot;http://en.wikipedia.org/wiki/BIOS&quot; rel=&quot;nofollow&quot;&gt;BIOS&lt;/a&gt; which is used to start up the computer, and load the OS into RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Machine language gets tedious real fast, so assembler programs were developed that take a mnemonic assembler language and translate it, usually one line of assembly code per instruction, into machine code.  So instead of 10000001, one would write ADD R1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the very first assembler had to be written in machine code.  Then it could be rewritten in its own assembler code, and the machine-language version used to assemble it the first time.  After that, the program could assemble itself.  This is called &lt;a href=&quot;http://en.wikipedia.org/wiki/Bootstrapping_%28compilers%29&quot; rel=&quot;nofollow&quot;&gt;bootstrapping&lt;/a&gt; and is done with compilers too -- they are typically first written in assembler (or another high-level language), and then rewritten in their own language and compiled with the original compiler until the compiler can compile itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the first microprocessor was developed long after mainframes and minicomputers were around, and the 4004 wasn't really suited to running an assembler anyway, Intel probably wrote a cross-assembler that ran on one of its large computers, and translated the assembly code for the 4004 into a binary image that could be programmed into the ROM's.  Once again, this is a common technique used to port compilers to a new platform (called &lt;a href=&quot;http://en.wikipedia.org/wiki/Cross_compiler&quot; rel=&quot;nofollow&quot;&gt;cross-compiling&lt;/a&gt;).&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-01-07T18:29:00.307" LastActivityDate="2011-01-07T18:29:00.307" CommentCount="7" />
  <row Id="8689" PostTypeId="2" ParentId="8639" CreationDate="2011-01-07T01:47:45.303" Score="4" ViewCount="" Body="&lt;p&gt;Another (easier) option than gears is a figure-eight belt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, it's the same as a normal belt, but the belt crosses between the pulleys.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://chestofbooks.com/crafts/machinery/Shop-Practice-V2/Belting.html&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/2Z69i.png&quot; alt=&quot;z&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It also works with v-groove belts, and round belts, assuming they slide over themselves easily.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-01-07T01:55:36.430" LastActivityDate="2011-01-07T01:55:36.430" CommentCount="4" />
  <row Id="8690" PostTypeId="1" AcceptedAnswerId="8693" CreationDate="2011-01-07T02:42:19.123" Score="4" ViewCount="255" Body="&lt;p&gt;I want to be able to determine the location of an object that will be moving around in a rectangle about 15&quot; X 10&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The location must be accurate to within about 1/4&quot; and be measured at least 100 times per second.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first idea I had for accomplishing this is to have the object transmit a pulse signal every 10ms and have a receiver in each corner wired to a micro controller and measure the difference in time between when each receiver gets the signal to triangulate it's source.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first thought was to use IR receivers and transmitters, but I would have no idea how to do the triangulation with signals that move so fast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So then my second thought was to use sound. I would want to transmit at a frequency above the human hearing range. And it seems to me that higher hertz = greater accuracy. The speed of sound is about 13,400 inches per second. So that means to get 1/4&quot; resolution, I would need 56kHz or higher.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First off, I've never dealt with sounds above the human hearing range. This will probably be on for periods of about an hour, and may be just a few feet away from ears. As long as I use low power, is there any way that this could be a hazard?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Secondly, what kind of speakers are capable of transmitting 56kHz? And similarly, what kind of microphones could pick up 56kHz?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other methods of triangulation would also be appreciated.&lt;/p&gt;&#xA;" OwnerUserId="790" LastActivityDate="2011-02-18T07:55:14.463" Title="Signal triangulation" Tags="&lt;audio&gt;&lt;wireless&gt;&lt;signal&gt;&lt;triangulation&gt;" AnswerCount="4" CommentCount="5" FavoriteCount="5" />
  <row Id="8691" PostTypeId="2" ParentId="8669" CreationDate="2011-01-07T03:07:13.753" Score="0" ViewCount="" Body="&lt;p&gt;I think an embedded microcontroller running a free OS (e.g. Linux) is a good way to go. &lt;a href=&quot;http://electronics.stackexchange.com/questions/6984/single-board-computer/6989#6989&quot;&gt;This question&lt;/a&gt; has some good suggestions for boards with wireless capability; most of them also can handle Ethernet.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-01-07T03:07:13.753" />
  <row Id="8692" PostTypeId="2" ParentId="8685" CreationDate="2011-01-07T03:14:35.217" Score="4" ViewCount="" Body="&lt;p&gt;Here's a bit about really old computers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I know, back in the days, you had a big &lt;a href=&quot;http://en.wikipedia.org/wiki/Front_panel&quot; rel=&quot;nofollow&quot;&gt;computer front panel&lt;/a&gt; which was used to program them. Basically, each memory cell in those computers was connected to switches. You'd power the memory and then use switches to set data in each cell. This way, you'd input program bit by bit into computer's memory. Then you'd set starting point of the program and start execution. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As technology progressed, so called bootloader programs were developed. They are short programs whose whole point is to start another program from computer's memory. The problem with entering programs bit by bit (and the later more than one bit using octal and later hexadecimal numbers) was that it was very slow and there was big chance that operator would make a mistake while loading the program. So short programs would be used to load larger programs stored in computer's memory. As time progressed, portion of code which had to be entered by hand decreased and in modern computers we often have bootloaders written in some sort of ROM or even flash memory.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-01-07T03:14:35.217" CommentCount="1" />
  <row Id="8693" PostTypeId="2" ParentId="8690" CreationDate="2011-01-07T03:35:00.130" Score="3" ViewCount="" Body="&lt;p&gt;About RF:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea is to cast let's say 100Mhz signal and measure phase shift between received signals in different points. Then you'll be able to calculate the location.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Measuring time difference directly could be tricky, as you will need 0.1ns or better accuracy (1ns = 30cm in air).&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Piezo-emitters are very capable going into sub-Mhz sound range. Nearly any mic(probably except coal one) can receive 50-100Khz sound with proper amplification. Safety is usually not a problem as long as you are under-1W range, and I doubt you would need more than 0.01 :-)&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;RF way is way harder to implement but I belive more reliable.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-07T03:35:00.130" CommentCount="10" />
  <row Id="8694" PostTypeId="2" ParentId="8685" CreationDate="2011-01-07T04:06:29.060" Score="4" ViewCount="" Body="&lt;p&gt;I few years ago came across a microcontroller programmer which had a 4 digit seven segment display, and a hex keypad. I'm sure this didn't have a microcontroller on board and allowed you to enter machine code directly a byte at a time. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So this would allow you to (painfully) compile a list of Op codes manually one by one and enter them into the chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no idea if you can still get them, but I'm guessing that something similar was used back when microcontrollers were relatively new.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-07T04:06:29.060" CommentCount="2" />
  <row Id="8695" PostTypeId="2" ParentId="8678" CreationDate="2011-01-07T05:15:55.110" Score="5" ViewCount="" Body="&lt;p&gt;You don't have to probe a live circuit.  Get test leads with insulated clips on them.  Clip onto the circuit with power off.  Turn it on, stand back, and look at the reading.  Never use an oscilloscope on a non-isolated circuit.  I would also suggest some kind of pilot light in the circuit so you know when the power is on.  (Just unplugging is not enough if you have large capacitors that store high voltage, but I don't think you will for a light dimmer.)&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-07T05:15:55.110" CommentCount="1" />
  <row Id="8696" PostTypeId="2" ParentId="8685" CreationDate="2011-01-07T05:32:06.773" Score="9" ViewCount="" Body="&lt;p&gt;Originally, programs were written on paper, and then transposed to whatever input method the computer had available. This went from knobs, switches, and jumper wires on the first computers, to punch cards, to keypads/boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The illustration below shows what present-day &lt;em&gt;real&lt;/em&gt; programmers use:&#xA;&lt;img src=&quot;http://i.imgur.com/KdxxS.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-01-08T23:30:23.650" LastActivityDate="2011-01-08T23:30:23.650" CommentCount="3" />
  <row Id="8697" PostTypeId="2" ParentId="8678" CreationDate="2011-01-07T08:29:34.983" Score="4" ViewCount="" Body="&lt;p&gt;As far as lab equipment goes, a 1:1 safety transformer (AC mains : AC mains) is worth a lot. They aren't cheap, but I would not want to work without one. Mine is home-built and uses two 250 W transformers back-to-back.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The trick of the 1:1 transformer is this: Current from its secondary winding can only go back to the other end of this exact winding. As long as you touch any circuit connected to the 1:1 transformer with one hand only, you are safe because the current from your finger can not go anywhere. You are a bit like a bird on a wire. A regular wall outlet is referenced to earth, just like you are when standing on the floor: In a fault, current from the live pin of the outlet runs through you, the floor and to earth, which is equal to the other end (neutral) of the wall outlet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that current always needs a loop to flow in: Any energy that comes from the transformer can go back to this transformer only, and can not go anywhere else, especially not to the ground via your body.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-03-27T10:30:43.707" LastActivityDate="2011-03-27T10:30:43.707" CommentCount="5" />
  <row Id="8698" PostTypeId="2" ParentId="8672" CreationDate="2011-01-07T08:37:38.910" Score="3" ViewCount="" Body="&lt;p&gt;Why not use an optocoupler? Vishay's &lt;a href=&quot;http://www.vishay.com/docs/83675/sfh620a.pdf&quot; rel=&quot;nofollow&quot;&gt;SFH6206&lt;/a&gt; has two LEDs in anti-parallel, so it works over the full cycle of the mains voltage. If the input voltage is high enough the output transistor is switched on, and the collector is at a low level. Around the zero crossing, however, the input voltage is too low to activate the output transistor and its collector will be pulled high. So you get a positive pulse at every zero crossing.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-01-07T08:37:38.910" />
  <row Id="8699" PostTypeId="2" ParentId="8690" CreationDate="2011-01-07T09:44:59.413" Score="1" ViewCount="" Body="&lt;p&gt;Vision might be a better solution. You could track your object with cameras.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take a look into OpenCV.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-07T09:44:59.413" CommentCount="2" />
  <row Id="8700" PostTypeId="2" ParentId="2320" CreationDate="2011-01-07T09:46:49.270" Score="1" ViewCount="" Body="&lt;p&gt;Op amps for analog signal processing before signals get to the ADC, LM358 is a good all-round chip with two amplifiers, and it's very common and cheap.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-01-07T09:46:49.270" />
  <row Id="8701" PostTypeId="2" ParentId="2320" CreationDate="2011-01-07T10:30:21.543" Score="1" ViewCount="" Body="&lt;p&gt;For regulators, I keep the &lt;strong&gt;LM317&lt;/strong&gt; and &lt;strong&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=4326593&amp;amp;k=102%201709%20nd&quot; rel=&quot;nofollow&quot;&gt;V7805-500&lt;/a&gt;&lt;/strong&gt; (500mA, 5V DC/DC switcher; pin-compatible with 7805 and no external parts).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found that I don't need to keep many parts on-hand because distributors can get what I want within a week, and there is always a lot to do before plugging into a breadboard or populating a prototype PCB! If DigiKey or Mouser can't get my parts within a week, it probably has sourcing issues and aught to be avoided (not that I have actually made a commercial product, but this is the idea!), though there are plenty of exceptions.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-07T10:30:21.543" />
  <row Id="8702" PostTypeId="2" ParentId="8678" CreationDate="2011-01-07T10:52:58.027" Score="1" ViewCount="" Body="&lt;p&gt;The inimitable Dan of &lt;a href=&quot;http://www.dansdata.com/&quot; rel=&quot;nofollow&quot;&gt;Dan's Data&lt;/a&gt; has an entertaining article on &lt;a href=&quot;http://www.dansdata.com/gz013.htm&quot; rel=&quot;nofollow&quot;&gt;avoiding electrocution&lt;/a&gt;. The &lt;a href=&quot;http://www.dansdata.com/danletters146b.htm&quot; rel=&quot;nofollow&quot;&gt;follow&lt;/a&gt; &lt;a href=&quot;http://www.dansdata.com/danletters165.htm&quot; rel=&quot;nofollow&quot;&gt;up&lt;/a&gt; &lt;a href=&quot;http://www.dansdata.com/danletters071.htm&quot; rel=&quot;nofollow&quot;&gt;mail&lt;/a&gt; on the subject contains &lt;a href=&quot;http://www.dansdata.com/io108.htm&quot; rel=&quot;nofollow&quot;&gt;further tidbits&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2011-01-07T10:52:58.027" CommentCount="1" />
  <row Id="8703" PostTypeId="2" ParentId="8685" CreationDate="2011-01-07T12:22:32.620" Score="6" ViewCount="" Body="&lt;p&gt;Well I was around when micros first came out, we wrote cross assemblers and compilers on mainframes and minis, then we bootstrapped them onto 8-bit hardware, people didn't really bother building compilers/assemblers on micros until they had enough local storage to make it useful &lt;/p&gt;&#xA;" OwnerUserId="2514" LastActivityDate="2011-01-07T12:22:32.620" />
  <row Id="8704" PostTypeId="2" ParentId="8676" CreationDate="2011-01-07T12:33:54.220" Score="1" ViewCount="" Body="&lt;p&gt;Especially when you're talking small quantities the price of the controller is only part of the picture. Suppose you need a 500 euro programmer to program the devices. This is OK if you need 100 000 devices a year, but if you need 50 controllers, the programmer adds 10 euro to a device which at 1 euro may be cheap in itself.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-01-07T12:33:54.220" CommunityOwnedDate="2011-01-07T12:33:54.220" CommentCount="2" />
  <row Id="8705" PostTypeId="1" AcceptedAnswerId="8706" CreationDate="2011-01-07T12:56:04.663" Score="4" ViewCount="119" Body="&lt;p&gt;I'm using a 22u 6.3V X5R 0805 ceramic capacitor to filter out a 3.3V supply (for a buck converter.) I've heard that applied voltage has an effect on the capacitance of certain ceramic caps; a higher voltage causes a reduction in capacitance. How true is this? Would it decrease too much as to not work as a suitable filter cap? I think 10-15u is probably the minimum for it to remain stable, although the ripple will probably increase at lower capacitance. Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-07T13:47:05.370" Title="Ceramic caps and applied voltage" Tags="&lt;capacitor&gt;&lt;ceramic&gt;" AnswerCount="1" />
  <row Id="8706" PostTypeId="2" ParentId="8705" CreationDate="2011-01-07T13:19:57.583" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://my.execpc.com/~endlr/ceramic.html&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; has the following table:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/U6PCP.gif&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, if the 22uF is a 20% tolerance part such that is may actually be 17.6uF (-20%), and it is really 15uF (-15%) due to heating, it may be reduced to ~10.5uF (-30%) near its tolerance or &lt;strong&gt;~14uF&lt;/strong&gt; (-5%) near its operating point. To reduce the effect, use a higher breakdown value capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although &lt;a href=&quot;http://www.cliftonlaboratories.com/capacitor_voltage_change.htm&quot; rel=&quot;nofollow&quot;&gt;this webpage&lt;/a&gt; tests much higher breakdown voltage ceramics, the results are illustrative:&#xA;&lt;img src=&quot;http://i.imgur.com/dpiSY.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.avx.com/docs/Catalogs/cx5r.pdf&quot; rel=&quot;nofollow&quot;&gt;This part&lt;/a&gt;, the &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=478-3647-2-ND&quot; rel=&quot;nofollow&quot;&gt;08056D226MAT2A&lt;/a&gt; by AVX, states that it meets its tolerance tested at 0.5 V&lt;sub&gt;RMS&lt;/sub&gt;, not close to its breakdown:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;For Cap &gt; 10 μF, 0.5Vrms @ 120Hz&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;It also mentions that capacitance may change up to 12.5% over its load life, 7.5% due to soldering thermal shock, and 12% due to &lt;em&gt;flexure fissures&lt;/em&gt; (cracks).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;sub&gt;&lt;strong&gt;&lt;em&gt;Info tidbit:&lt;/strong&gt; The term &lt;strong&gt;X5R&lt;/strong&gt; means it is composed of a &lt;strong&gt;class 2 dielectric&lt;/strong&gt; (ie: ceramic) that will maintain its capacitance to within 15% (18.7uF - 25.3uF) over a temperature range -55&lt;sup&gt;o&lt;/sup&gt;C to 85&lt;sup&gt;o&lt;/sup&gt;C.&lt;/em&gt;&lt;/sub&gt;&lt;br&gt;&#xA;Something that may interest you, though it has more to do with the final application than the question -- &lt;a href=&quot;http://en.wikipedia.org/wiki/X7R&quot; rel=&quot;nofollow&quot;&gt;the great 'pedia also mentions:&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Due to its piezoelectric properties, they are subject to microphonics.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;... And the previously &lt;a href=&quot;http://my.execpc.com/~endlr/ceramic.html&quot; rel=&quot;nofollow&quot;&gt;linked page&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;High-K ceramic capacitors can show significant piezoelectric effects; if you tap them they will produce a voltage spike.  This is caused by the barium titanate, the main material in high K ceramics.  The higher the K, the stronger this affect.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-07T13:47:05.370" LastActivityDate="2011-01-07T13:47:05.370" CommentCount="6" />
  <row Id="8707" PostTypeId="1" AcceptedAnswerId="8716" CreationDate="2011-01-07T15:46:10.277" Score="3" ViewCount="272" Body="&lt;p&gt;I have a question regarding stepper motor control while using the TCP/IP stack. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the past I have used a timer for my stepper motor control. I set the period of a timer to the required time between pulses and then I change the motor phase outputs as needed in the timer tick ISR.  In the cases where I have done this my stepper was moving at a maximum rate of around 400 pulses per second which means the interrupt was occurring every 2.5 milliseconds. And I was using USB for communication to the host. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am now working on a new product which will use the TCP/IP stack to communicate with a PC over Ethernet. It will also be communicating with other devices via SPI and UART modules. This new device must be capable of operating a stepper up to 2000 pulses per second which means the interrupt may be firing every .5 milliseconds if I use the same timer/ISR approach to drive the stepper. The stepper is turned on and off based on commands received from the host, so communication with the host and operation of the motor need to occur harmoniously and simultaneously.  If the stepper speed varies slightly that would not be a problem but it is not ideal. Also, if the stepper were to pause for say a 30ms in the middle of it's move that WOULD not be acceptable. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am considering using a PIC24F with the instruction clock speed of 16MHz (32Mhz/2 using the internal FRC+PLL) for this project. Do you think that the interrupts for the stepper will disrupt the Ethernet communication or vise-versa? Is there a better way of doing this? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have considered using a separate PIC for the stepper control and then I could send that pic target position commands or halt commands to start and stop the movement but that would add another firmware into the mix and complicate things all around. &lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2011-01-07T21:24:51.543" Title="Stepper Motor Control Timing" Tags="&lt;pic&gt;&lt;timing&gt;&lt;interrupt&gt;&lt;stepper-motor&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="8708" PostTypeId="2" ParentId="8707" CreationDate="2011-01-07T16:28:38.810" Score="1" ViewCount="" Body="&lt;p&gt;You will probably need to use a PWM module to generate your pulses. I've had a hard time a hard time generating pulses in software at frequencies &gt; 1kHz in PICs. Just look for a PIC with the right number of CCP/ECCP Modules and PWM outputs for your application.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-01-07T16:28:38.810" />
  <row Id="8709" PostTypeId="2" ParentId="8678" CreationDate="2011-01-07T17:26:09.690" Score="2" ViewCount="" Body="&lt;p&gt;I recommend going to your local hardware store and buying a light switch with a neon tube in the switch. Also buy the metal junction box to install the switch in and a faceplate. Run your AC input into one side of the switch, and the other side to whatever circuit you're playing with. This is a good way to be able to see at a glance whether power's on, and to have an easy cut off. At work, I have this installed on a wooden board with the output wires going to a pair of terminal blocks. This makes it easier to change what's connected. Whatever you do, make it perfectly clear which switch position is 'on' and which is 'off' for safety.&lt;/p&gt;&#xA;" OwnerUserId="2344" LastActivityDate="2011-01-07T17:26:09.690" />
  <row Id="8710" PostTypeId="2" ParentId="8707" CreationDate="2011-01-07T19:20:25.947" Score="2" ViewCount="" Body="&lt;p&gt;The main question is &lt;em&gt;what is actually going to handle the data coming over the wire?&lt;/em&gt;  The amount of crap (stuff that is not addressed to you) Ethernet can provide is staggering.  If you're going to use a low-end MCU (PIC24F), you're going to need some sort of co-processor, e.g. an &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en022889&quot; rel=&quot;nofollow&quot;&gt;ENC28J60&lt;/a&gt;, to provide MAC address filtering at the very least.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Someone in chat mentioned that the PIC24F has interrupt priorities, so if maintaining isochronicity is critical, you could just set the timer priority higher.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A minor aside: be aware that TCP/IP &lt;em&gt;and&lt;/em&gt; Ethernet are non-deterministic (independently).  For example, don't expect to be able to send a command over Ethernet to stop your stepper motor &quot;now&quot; when you're right at position X and it to respond repeatably.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-07T19:20:25.947" CommentCount="1" />
  <row Id="8711" PostTypeId="2" ParentId="8678" CreationDate="2011-01-07T20:07:58.083" Score="-1" ViewCount="" Body="&lt;p&gt;If you take a regular rotary dimmer switch (Potentiometer/variable resistor/rheostat) and hook that up with a stepper motor you could get away with not knowing a whole lot more than how to control a stepper, how to keep up with the stepper's position, and how to wire up the dimmer switch (very easy).  Oh, and you've got to power the whole switch control setup somehow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to do more than that, like use solid state switches or pretty much anything else living on a board you've designed, you've got more issues, and even your power supply may become a lot more complicated since you don't want your control circuits to become a possible path for shorting out the system.  High voltage can cause arching at some distance normally, and with residential AC you've also got to worry about extremely high current from lightning.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want this system to be energy efficient then you've got a lot more problems ahead of you.  The easiest way to dim the lights is by introducing resistance, but is wasteful, and if you want the lights to run off AC it's difficult to get around easily.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might want to have a look at the NEC (National Electrical Code) if you are in the US.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not an EE or electrician, btw.&lt;/p&gt;&#xA;" OwnerUserId="2517" LastActivityDate="2011-01-07T20:07:58.083" CommentCount="2" />
  <row Id="8712" PostTypeId="1" AcceptedAnswerId="8714" CreationDate="2011-01-07T20:16:37.910" Score="4" ViewCount="301" Body="&lt;p&gt;My oscilloscope is rated: 1Mohm || 12pF. It's a 100 MHz oscilloscope. However, I don't get the point of the capacitance. If I set my probe on 10X (it's switchable), then it inserts 9Mohm in series. Now we've created an RC filter with -3dB break point of: ~1.473 kHz, and yet, I get higher bandwidth with 10X probes and I certainly don't get a 1.4 kHz bandwidth limiter! What am I missing?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I was simulating the circuit on a circuit simulator. With no probe resistance a 10pF cap conducts 1A at 100 MHz, which would be massive loading compared to the 1 Mohm impedence.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-08T13:11:03.200" Title="What does input capacitance mean on an oscilloscope?" Tags="&lt;oscilloscope&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="8713" PostTypeId="2" ParentId="8712" CreationDate="2011-01-07T20:30:14.780" Score="0" ViewCount="" Body="&lt;p&gt;Suppose you were checking a 100 MHz signal across a resonant parallel tuned circuit. The 12 pF would affect the accuracy of the measurement considerably, as it would be large compared with the capacitance across the coil, and would detune the circuit.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-07T20:30:14.780" CommentCount="9" />
  <row Id="8714" PostTypeId="2" ParentId="8712" CreationDate="2011-01-07T20:44:15.737" Score="3" ViewCount="" Body="&lt;p&gt;Like pretty much all real circuits, oscilloscope inputs have a parasitic capacitance. No matter how small you made it by good design, it would still affect RF signal acquisition, except maybe for a defined 50 Ohm connection and attenuation directly at the scope's input, for which case, with the numbers from your qúestion, f_-3dB = 1 / (2 * pi * 50 Ohm * 12 F) = 256 MHz. Or even much higher, if we would make C_in,scope smaller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually, though, we don't want to load the circuit under test with a defined 50 Ohm connection, and therefore, it was chosen to use the capacitance in a clever way in the &lt;strong&gt;probe-and-scope combination&lt;/strong&gt;. So clever, actually, that any unknown capacitance that may be caused by probe cables and other things in your connection can be compensated just like the scope's input capacitance, and all of them become don't-cares for most cases of practical measurement applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 1:10 probe has an internal resistor of 9 MOhm &lt;strong&gt;and&lt;/strong&gt;, in parallel, &lt;strong&gt;an internal capacitor&lt;/strong&gt; of [1/9 * (scope input capacitance)].&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is adjustable because the probe doesn't know the exact capacitance of the particular scope it is connected to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the capacitor in the probe properly adjusted, you have not only a resistive divider for the DC part of the signal, but also a capacitive divider for the higher-frequency AC part of the signal, and the combination works beautifully up to or beyond, say, 500 MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you get the advantage of inserting not 1 MOhm and 12 pF into your circuit when probing, but 10 MOhm and [the series equivalent of 12 pF and (12 pF / 9)] = 1.2 pF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Link for picture of a probe schematic: &lt;a href=&quot;http://www.hobbyprojects.com/oscilloscope_tutorial/oscilloscope_probes.html&quot; rel=&quot;nofollow&quot;&gt;Here.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(What the picture in the link doesn't mention is the capacitance of the probe cable, this would just add to the cap at the input and can also be compensated when turning the variable cap in the probe.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a 1:10 probe, the probe's small capacitance is in series with the scope's larger input capacitance. The total capacitance (approx. 1.2 pF) is in parallel to the point of your circuit that you are probing. Connecting the scope directly to the circuit, e.g. with just a straight BNC cable, you are indeed putting the entire input capacitance of the scope in parallel to what you are measuring.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be possible to build scopes with a much smaller input capacitance, but then, there would be no way compensating the probe's cable capacitance with a small variable capacitor near the probe tip. After all, the 12 pF at the scope's input have been put there &lt;em&gt;on purpose&lt;/em&gt;, to make the scope work well &lt;em&gt;together&lt;/em&gt; with a good probe.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-01-08T13:11:03.200" LastActivityDate="2011-01-08T13:11:03.200" CommentCount="2" />
  <row Id="8715" PostTypeId="2" ParentId="8678" CreationDate="2011-01-07T20:51:24.290" Score="2" ViewCount="" Body="&lt;p&gt;Since it would be impossible to turn you into an electrician in a single answer, I'll recommend some reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the US, home wiring is governed by the NEC (National Electrical Code).  It's a huge, detailed, expensive publication.  For a DIYer, I strongly recommend purchasing the most recent edition of &lt;em&gt;Wiring Simplified&lt;/em&gt;.  It's probably available at your local (or big-box) hardware stores (I've seen it at Ace Hardware and Home Depot), or &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0971977933&quot; rel=&quot;nofollow&quot;&gt;here on Amazon&lt;/a&gt;, should be around $10. I use it when planning any electrical job at my house, parents' cottage, or workshop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the Amazon description:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Revised and completely updated for the&#xA;  2008 National Electric Code, this&#xA;  small manual continues its 75-year&#xA;  history of demonstrating how to&#xA;  install safe, convenient, and&#xA;  economical wiring. Encouraging readers&#xA;  to tackle jobs small and large, the&#xA;  guide covers everything from repairing&#xA;  a table lamp to wiring a whole house.&#xA;  After introducing the&#xA;  basics—standards, codes, safety&#xA;  practices, and an overview of how&#xA;  electricity is measured and&#xA;  delivered—chapters show how to design&#xA;  a layout for lights, switches, and&#xA;  receptacles; run a line from a utility&#xA;  pole; install wires, circuits, and&#xA;  grounds; and handle special projects&#xA;  such as replacing old wiring and&#xA;  wiring detached garages and accessory&#xA;  buildings.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;There is a section on safety, and the book recommends good practices, but it's not a replacement for training. It's a good reference for knowing what you're working with, though, and common-sense rules (like the one-hand rule, disconnecting the breaker, and wearing rubber-soled shoes) together with this book will make you a much better electrician.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-07T20:51:24.290" CommentCount="1" />
  <row Id="8716" PostTypeId="2" ParentId="8707" CreationDate="2011-01-07T21:24:51.543" Score="1" ViewCount="" Body="&lt;p&gt;As Nick T mentioned, TCP/IP is unfiltered and non-deterministic.  You said you want to also interface with SPI and UART devices, and previous versions used USB.  These are difficult to do in real time, and probably require significant code space.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, you want real-time control of your stepper motors, which requires deterministic execution and rapid interrupts but not a lot of program space. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;While you said you wanted to avoid using a separate microcontroller because it would complicate things, this is a &lt;em&gt;perfect&lt;/em&gt; example of when you need a co-processor, and I believe that it would make things simpler in the end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can develop simple stepper motor controller firmware that run on small, cheap microcontrollers.  Design (or discover) a protocol that can use a communication bus available &lt;strong&gt;in hardware&lt;/strong&gt;  on whatever controller you choose. I'd recommend SPI for this (on a different channel than the device you mentioned in your question; your master should have two SPI peripherals), you don't want to mess with address conflicts given the small number of controllers you'll have. Don't do anything with this controller but run the stepper according to the data it receives over the protocol.  You can probably buy something that does this already.  The goal is to be able to treat this as a hardware peripheral.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, you can develop USB or Ethernet controllers that will plug into these devices.  You will have flexibility in the host protocols (Need to use RS485 this time?  No problem!), you can use different numbers of motors, and you have greater modularity for designing, testing, debugging, repairing, and replacing.  The only reasons I'd try to implement something like this in a single controller would be extreme cost/size restrictions, and/or a lack of hardware modules (like PWM?  Did I miss something?) that could do this without interrupting the host processor.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-07T21:24:51.543" />
  <row Id="8717" PostTypeId="2" ParentId="8676" CreationDate="2011-01-07T21:51:52.700" Score="1" ViewCount="" Body="&lt;p&gt;The price of anything is dependent on what you can negotiate. If you are only looking at hobbyist quantities, I'd ask why it matters, since the price difference between 10 cheap MCUs can be a penny or two and you'd spend more time selecting a chip than your time would be worth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're buying large production quantities, then the price you pay will depend on your relationship with the vendor, how many they think you will order in the future, what else you're bundling with your order, what particular chip that vendor has overstock of and wants to dump, how much they paid for that stock, how much it costs them to keep carrying the excess inventory, etc...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There really is no simple answer.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-01-07T21:51:52.700" CommunityOwnedDate="2011-01-07T21:51:52.700" />
  <row Id="8718" PostTypeId="2" ParentId="8650" CreationDate="2011-01-07T22:03:35.270" Score="1" ViewCount="" Body="&lt;p&gt;I used to have a huge pile of Analog Dialogue: the monthly magazine from Analog Devices. I believe they're all available online.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jung's &lt;em&gt;IC OpAmp cookbook&lt;/em&gt;, &lt;em&gt;The Operational Amplifier Design Guide&lt;/em&gt;; just about &lt;em&gt;any&lt;/em&gt; book from Analog Devices. I have found their &lt;em&gt;Nonlinear Circuits handbook&lt;/em&gt; useful over the years. and their guide to Mixed Signal design saved my butt a couple of times.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/MFlMR.jpg&quot; alt=&quot;alt text&quot;&gt; &lt;img src=&quot;http://i.imgur.com/Ofjwq.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I miss the days when mfr's used to give out entire books of Application Notes. I have a bunch of National Semiconductor appnotes from the late 70's to early 90's that I inherited when my first employer went belly-up and I wouldn't give them up for anything. The individual appnotes are available as pdf's but I don't know if you can get the whole books any more.&#xA;Signetics Linear Appnotes, Motorola Switching &amp;amp; Linear Regulator guide, Volumes of Linear Technology appnotes. These are all books that describe the theory of the circuits in addition to how to use the chips in a variety of applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd haven't done analog design in years (not paid, anyway) but I have to say that over time, I've found that &lt;em&gt;good&lt;/em&gt; manufacturer's appnotes are more useful than textbooks. Good meaning that they aren't just a guide to using a chip, but go into detail on the theory of operation of entire classes of circuits and how to use them to good effect.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-09T13:49:34.037" LastActivityDate="2011-01-09T13:49:34.037" CommentCount="3" />
  <row Id="8719" PostTypeId="2" ParentId="8511" CreationDate="2011-01-07T23:26:07.733" Score="1" ViewCount="" Body="&lt;p&gt;Perhaps you could use a &quot;programmable display pushbutton&quot; as a combined display and user interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/search/results?term=screenkey&amp;amp;what=products&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/search/results?term=screenkey&amp;amp;what=products&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.nkksmartswitch.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.nkksmartswitch.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.nkkswitches.com/SmartSwitch-Development-Tools.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.nkkswitches.com/SmartSwitch-Development-Tools.aspx&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are extremely small.&#xA;They can be programmed with 4 wire SPI.&#xA;Alas, they are not exactly what I would call &quot;cheap&quot;.&#xA;Still, fulfilling 2 out of 3 wishes is pretty good ...&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-07T23:26:07.733" />
  <row Id="8720" PostTypeId="2" ParentId="8676" CreationDate="2011-01-07T23:26:37.373" Score="2" ViewCount="" Body="&lt;p&gt;Atmel has a 6-pin SOT-23-6/DFN-6 line of AVRs, the &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=4606&quot; rel=&quot;nofollow&quot;&gt;ATtiny4/5/9/10&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Flash:      512 B (4/9) / 1k (5/10)&lt;br&gt;&#xA;RAM:        32 B&lt;br&gt;&#xA;Package:    SOT23-6/DFN-6&lt;br&gt;&#xA;Price@1:    &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=ATTINY4-TSHRCT-ND&quot; rel=&quot;nofollow&quot;&gt;$0.95&lt;/a&gt;&lt;br&gt;&#xA;Price@4.5k: &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=ATTINY4-TSHRTR-ND&quot; rel=&quot;nofollow&quot;&gt;$0.53&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 4/9 parts have no ADC (and are cheaper), the 5/10 parts have ADCs.  The ATtiny4u3 has an integral boost regulator and runs from as low as 0.7V, which might save some money if you're running from a battery. If course, the extra features cost more. Cheapest part is the ATtiny4.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I've heard though, Atmel has legendarily &lt;em&gt;bad&lt;/em&gt; availability for production quantities.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-04T15:22:21.970" LastActivityDate="2011-03-04T15:22:21.970" CommunityOwnedDate="2011-01-07T23:26:37.373" />
  <row Id="8721" PostTypeId="2" ParentId="8157" CreationDate="2011-01-07T23:29:51.937" Score="0" ViewCount="" Body="&lt;p&gt;Back to the gear idea.... wouldn't the large torque from the motor spinning the gear cause a large stress on the gear possibly breaking it when the gear teeth come back around to launch the item again?&lt;/p&gt;&#xA;" OwnerUserId="2522" LastActivityDate="2011-01-07T23:29:51.937" />
  <row Id="8722" PostTypeId="2" ParentId="8685" CreationDate="2011-01-07T23:33:41.093" Score="4" ViewCount="" Body="&lt;p&gt;I'm not sure that anyone has addressed the OP's real question, which seems to be &lt;em&gt;&quot;How does the computer know how to get started?&quot;&lt;/em&gt;, so I'll take a crack at it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Start with an analogy. &lt;em&gt;&quot;How does a transistor know how to get started?&quot;&lt;/em&gt; Of course, it doesn't, it just works in accordance with physics, and the engineer builds the circuit so that it starts in a known state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Computers know how to get started because they are circuits (very complicated, of course) and they are built to start in a particular state. In a modern machine that state might be one in which the main bus remaps part of the address space to user a ROM on the motherboard as low memory (the ROM having been burned with a BIOS). In a first generation machine the initial state might have been CPU halted, the program counter at zero, and memory toggle sub-system active.&lt;/p&gt;&#xA;" OwnerUserId="1882" LastActivityDate="2011-01-07T23:33:41.093" />
  <row Id="8723" PostTypeId="1" AcceptedAnswerId="8724" CreationDate="2011-01-07T23:34:11.310" Score="1" ViewCount="106" Body="&lt;p&gt;I'm writing firmware for a PIC16F877A in assembler, and I want to set some constants at the top of my source code to indicate which port is used for what, so that if needed I can easily change all the i/o pins around by changing the constant values and recompiling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;O_LEDS   EQU      PORTA&#xA;CONSTANT O_RED    = RA1&#xA;CONSTANT O_GREEN  = RA2&#xA;CONSTANT O_BLUE   = RA3&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;In my code, I need a bitmask to represent the ports I'm using. My question is, how can I write an expression using assembler directives to calculate the bitmask?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using my example above:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;O_RED = 1&#xA;O_GREEN = 2&#xA;O_BLUE = 3&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;and the bitmask I want is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;movlw b'00001110'&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If there was a &lt;em&gt;to the power of&lt;/em&gt; operator, I could do something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;movlw (2 ^ O_RED) | (2 ^ O_GREEN) | (2 ^ O_BLUE)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;but &lt;code&gt;^&lt;/code&gt; in MPASM is a Bitwise exclusive OR, not &lt;em&gt;to the power of&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone think of another way to do this?&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-08T01:17:20.387" LastActivityDate="2011-01-08T01:17:20.387" Title="Bit position to bitmask conversion using MPASM directives" Tags="&lt;pic&gt;&lt;assembly&gt;&lt;firmware&gt;" AnswerCount="1" />
  <row Id="8724" PostTypeId="2" ParentId="8723" CreationDate="2011-01-08T00:31:16.417" Score="5" ViewCount="" Body="&lt;p&gt;I haven't used MPASM before, but does this work?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;movlw (1 &amp;lt;&amp;lt; O_RED) | (1 &amp;lt;&amp;lt; O_GREEN) | (1 &amp;lt;&amp;lt; O_BLUE)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Shifting to the left doubles a number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;1 &amp;lt;&amp;lt; x&lt;/code&gt; == 2&lt;sup&gt;x&lt;/sup&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-08T00:41:01.873" LastActivityDate="2011-01-08T00:41:01.873" CommentCount="1" />
  <row Id="8725" PostTypeId="1" AcceptedAnswerId="8730" CreationDate="2011-01-08T01:26:56.560" Score="2" ViewCount="237" Body="&lt;p&gt;Context: A digital phase-controlled light dimmer system.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;120V AC mains&lt;/li&gt;&#xA;&lt;li&gt;I use an isolating transformer (and rectifying circuit) to generate +12V and +5V DC rails.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I want to use reverse phase control (I've read that this produces less EM noise), so I'm looking to switch the AC mains using 2 Power MOSFETS (e.g. FDB14N30) with the source pins connected together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to put the MOSFETs into the &quot;on&quot; state, I need to raise V&lt;sub&gt;gs&lt;/sub&gt; to 10V-30V, but in order to do this, I think I need to hook up the MOSFET source pins to my isolated ground rail, and the gate pins to my +12V switching signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By doing this, have I defeated the whole purpose of an isolated power supply, in terms of danger of death and damage to components?&lt;/p&gt;&#xA;" OwnerUserId="2172" LastActivityDate="2011-01-08T02:59:45.877" Title="Switching 120V AC with Digital Logic on Isolated Power Supply" Tags="&lt;power-supply&gt;&lt;switch&gt;&lt;mosfet&gt;&lt;safety&gt;&lt;isolation&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="8726" PostTypeId="2" ParentId="8725" CreationDate="2011-01-08T01:30:55.407" Score="0" ViewCount="" Body="&lt;p&gt;You can use an optoisolater for this... Search for MOC3020&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-08T01:30:55.407" />
  <row Id="8728" PostTypeId="2" ParentId="8725" CreationDate="2011-01-08T02:12:47.087" Score="1" ViewCount="" Body="&lt;p&gt;You're switching AC. Use a TRIAC. For isolation, use an opto-isolator with zero crossing detection - for example, &lt;a href=&quot;http://www.fairchildsemi.com/tree/optoelectronics/triac-driver-optocouplers/zero-crossing-triac-driver/&quot; rel=&quot;nofollow&quot;&gt;many of these would be suitable&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-08T02:12:47.087" CommentCount="3" />
  <row Id="8729" PostTypeId="1" AcceptedAnswerId="11514" CreationDate="2011-01-08T02:42:26.847" Score="6" ViewCount="139" Body="&lt;p&gt;I am trying to make a high voltage measurement on an industrial sputtering machine.  The voltages are in the 50V to 1000V range.  Right now, we're using a Fluke DMM because we need a true floating voltage measurement (there's a lot of random common-mode noise that can't be eliminated).  It works great, but it is battery powered and doesn't have any computer output capability.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We'd really like to replicate this function with a powered meter that can talk to a computer, so the data can be automatically logged.  I've read a lot about this (although I still understand little).  I understand that, in order to get a good floating, differential measurement, the meter must be well electrically isolated from our chassis with all the common mode noise and also from its own power signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I could find something that could make this measurement and scale it to, say, a 0-10V output, I would be enthralled.  Any suggestions or educations would be appreciated!&lt;/p&gt;&#xA;" OwnerUserId="2524" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-07T13:36:09.623" LastActivityDate="2011-03-15T22:05:42.080" Title="Can anyone suggest a voltmeter that can do the job?" Tags="&lt;multimeter&gt;&lt;voltage-measurement&gt;" AnswerCount="2" />
  <row Id="8730" PostTypeId="2" ParentId="8725" CreationDate="2011-01-08T02:59:45.877" Score="1" ViewCount="" Body="&lt;p&gt;If you want to maintain isolation (I assume you have some legitimate reason for it beyond it being &quot;good&quot;, i.e. user-accessible low-voltage electronics) and still drive your floating MOSFETs, you could generate a gate voltage with a full-wave rectifier and a shunt regulator, then switch it using a standard optoisolator.  The drive current will be incredibly low if you're only switching at 60 Hz, so your regulator's Iq can also be quite low.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-08T02:59:45.877" CommentCount="1" />
  <row Id="8731" PostTypeId="1" CreationDate="2011-01-08T03:19:31.250" Score="4" ViewCount="125" Body="&lt;p&gt;I need some ideas for designing a catapult that runs on a motor. Basic requirements:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;able to launch a cookie 30m,&lt;/li&gt;&#xA;&lt;li&gt;capable of continuous operation,&lt;/li&gt;&#xA;&lt;li&gt;fits within a 0.4 m × 0.6 m × 0.4 m high box,&lt;/li&gt;&#xA;&lt;li&gt;allows 2 seconds minimum between each launch to load,&lt;/li&gt;&#xA;&lt;li&gt;self-sufficient (once the motor is turned on it can't be touched)&lt;/li&gt;&#xA;&lt;li&gt;made of steel,&lt;/li&gt;&#xA;&lt;li&gt;springs, bearings, and gears can be used, but no hydraulics.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any ideas? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking of a gear attached to a motor connected to another gear on the launch arm that would wind the launch arm horizontally. The gear on the motor would have teeth grinded off so that when the arm became horizontal it would release.  The problem with this is that I think that when the gear came back around it would interfere with the arm launching the cookie and/or that the teeth on the gears would break because of the large torque required by the motor to compress a spring with a large enough stiffness to give the cookie a flight distance of 30 m. Anyone have any other ideas or possible fixes to mine?&lt;/p&gt;&#xA;" OwnerUserId="2522" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-08T04:23:26.693" LastActivityDate="2011-01-09T17:01:01.260" Title="Builiding a catapult that runs continuously with a motor" Tags="&lt;motor&gt;&lt;robotics&gt;&lt;design&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="2" />
  <row Id="8732" PostTypeId="2" ParentId="8729" CreationDate="2011-01-08T03:46:38.447" Score="1" ViewCount="" Body="&lt;p&gt;46Fluke (US), Multimeters, select a multimeter&#xA;Then 1000 V &#xA;USB thumb drive logging gives the 8846A&#xA;With USB interface 789, 289, 287 are possibilities.  What EN61010-1 CAT do you need?&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-07T15:38:24.013" LastActivityDate="2011-02-07T15:38:24.013" CommentCount="1" />
  <row Id="8733" PostTypeId="1" AcceptedAnswerId="9076" CreationDate="2011-01-08T04:42:45.390" Score="2" ViewCount="124" Body="&lt;p&gt;Can you point me to a good online resource to learn how to understand and design LC filters?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The goal is digital forward phase control to dim a light bulb. I've read that the EMI produced by the voltage spikes when a TRIAC goes into the &quot;on&quot; state can be bad news for other electrical devices nearby on on the same supply circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.epanorama.net/documents/lights/lightdimmer.html&quot; rel=&quot;nofollow&quot;&gt;http://www.epanorama.net/documents/lights/lightdimmer.html&lt;/a&gt; gives an example circuit with a 50-to-100 microhenry inductor in series with the TRIAC, and a 100 nF capacitor in parallel with it, but I don't know how the author came up with those numbers.&lt;/p&gt;&#xA;" OwnerUserId="2172" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-01-09T13:03:35.600" LastActivityDate="2011-01-15T23:23:32.230" Title="LC Filter for Phase Control" Tags="&lt;filter&gt;&lt;interference&gt;&lt;emi&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="8734" PostTypeId="1" AcceptedAnswerId="8740" CreationDate="2011-01-08T05:25:00.530" Score="2" ViewCount="298" Body="&lt;p&gt;I want to use an &lt;a href=&quot;http://www.hoperf.com/rf_fsk/rfm12b.htm&quot; rel=&quot;nofollow&quot;&gt;RF12B&lt;/a&gt; to communicate over radio with an arduino, but the transceiver is rated at 3.3v. I hear I need to use a voltage level shifter, but what do these look like and where can I find a schematic to help me hook it up?&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2011-01-08T13:22:53.970" Title="How do I shift voltage levels?" Tags="&lt;arduino&gt;&lt;level-shifting&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="2" />
  <row Id="8735" PostTypeId="2" ParentId="8734" CreationDate="2011-01-08T05:45:28.500" Score="1" ViewCount="" Body="&lt;p&gt;There's a couple of ways to to voltage level shifting, depending on how fancy you want to get. Just to name a single manufacturer, &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?familyId=705&amp;amp;family=analog&amp;amp;uiTemplateId=NODE_STRY_PGE_T&quot; rel=&quot;nofollow&quot;&gt;Texas Instruments&lt;/a&gt; has a whole section devoted to mixed-voltage interfacing between different protocols. You can almost guarantee that there's a chip that will fill your needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, as pointed out in &lt;a href=&quot;http://electronics.stackexchange.com/questions/546/voltage-level-shifter/547#547&quot;&gt;this answer&lt;/a&gt;, SparkFun makes a &lt;a href=&quot;http://www.sparkfun.com/products/8745&quot; rel=&quot;nofollow&quot;&gt;small board&lt;/a&gt; that will probably be the easiest solution to implement. Your radio appears to use SPI, which should be workable with that board.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-01-08T05:45:28.500" />
  <row Id="8736" PostTypeId="2" ParentId="8731" CreationDate="2011-01-08T05:49:57.593" Score="2" ViewCount="" Body="&lt;p&gt;This sounds like a description for an &lt;a href=&quot;http://nativeoutdoors.stores.yahoo.net/doww1.html&quot; rel=&quot;nofollow&quot;&gt;automatic clay pigeon thrower&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Gi2cK.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-01-08T05:49:57.593" CommentCount="3" />
  <row Id="8737" PostTypeId="2" ParentId="8734" CreationDate="2011-01-08T07:47:35.070" Score="2" ViewCount="" Body="&lt;p&gt;Microchip has &lt;a href=&quot;http://www.microchip.com/stellent/groups/techpub_sg/documents/devicedoc/en026368.pdf&quot; rel=&quot;nofollow&quot;&gt;this document&lt;/a&gt; with 19 tips about mixing 3V and 5V parts in a circuit (not just level shifting).&lt;br&gt;&#xA;The tips:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;Powering 3.3V Systems From 5V Using an LDO Regulator  &lt;/li&gt;&#xA;  &lt;li&gt;Low-Cost Alternative Power System Using a Zener Diode  &lt;/li&gt;&#xA;  &lt;li&gt;Lower Cost Alternative Power System Using 3 Rectifier Diodes  &lt;/li&gt;&#xA;  &lt;li&gt;Powering 3.3V Systems From 5V Using Switching Regulators  &lt;/li&gt;&#xA;  &lt;li&gt;3.3V → 5V Direct Connect  &lt;/li&gt;&#xA;  &lt;li&gt;3.3V → 5V Using a MOSFET Translator  &lt;/li&gt;&#xA;  &lt;li&gt;3.3V → 5V Using A Diode Offset  &lt;/li&gt;&#xA;  &lt;li&gt;3.3V → 5V Using A Voltage Comparator  &lt;/li&gt;&#xA;  &lt;li&gt;5V → 3.3V Direct Connect&lt;/li&gt;&#xA;  &lt;li&gt;5V → 3.3V With Diode Clamp  &lt;/li&gt;&#xA;  &lt;li&gt;5V → 3.3V Active Clamp  &lt;/li&gt;&#xA;  &lt;li&gt;5V → 3.3V Resistor Divider  &lt;/li&gt;&#xA;  &lt;li&gt;3.3V → 5V Level Translators  &lt;/li&gt;&#xA;  &lt;li&gt;3.3V → 5V Analog Gain Block  &lt;/li&gt;&#xA;  &lt;li&gt;3.3V → 5V Analog Offset Block  &lt;/li&gt;&#xA;  &lt;li&gt;5V → 3.3V Active Analog Attenuator  &lt;/li&gt;&#xA;  &lt;li&gt;5V → 3V Analog Limiter  &lt;/li&gt;&#xA;  &lt;li&gt;Driving Bipolar Transistors  &lt;/li&gt;&#xA;  &lt;li&gt;Driving N-Channel MOSFET Transistors&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-01-08T13:22:53.970" LastActivityDate="2011-01-08T13:22:53.970" />
  <row Id="8739" PostTypeId="2" ParentId="8645" CreationDate="2011-01-08T09:14:54.667" Score="2" ViewCount="" Body="&lt;p&gt;HP AppCAD, available from: &lt;a href=&quot;http://www.avagotech.com&quot; rel=&quot;nofollow&quot;&gt;http://www.avagotech.com&lt;/a&gt;, may be helpful&lt;/p&gt;&#xA;" OwnerUserId="2526" LastActivityDate="2011-01-08T09:14:54.667" />
  <row Id="8740" PostTypeId="2" ParentId="8734" CreationDate="2011-01-08T10:46:51.073" Score="1" ViewCount="" Body="&lt;p&gt;It depends what direction the signals are going to.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;If the 5V device is going to drive a signal on the 3V3 device, use a simple resistor division.&lt;/li&gt;&#xA;&lt;li&gt;If the 3V3 device is going to drive a signal on the 5V device, you could use 2 invertors with the last stage tied to 5V. However, this requires 4 resistors and 2 transistors, which is quite an expense. You could also try out the implementation as shown in &lt;a href=&quot;http://www.sparkfun.com/datasheets/BreakoutBoards/Level-Converter-v10.pdf&quot; rel=&quot;nofollow&quot;&gt;Sparkfun's breakbout board&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;If the signal is bidirectional (I2C), maybe something in &lt;a href=&quot;http://www.kip.uni-heidelberg.de/lhcb/Publications/external/AN97055.pdf&quot; rel=&quot;nofollow&quot;&gt;this appnote on page 10&lt;/a&gt; will work (seems similar to what Sparkfun is using)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-01-08T10:46:51.073" />
  <row Id="8741" PostTypeId="1" CreationDate="2011-01-08T12:47:42.730" Score="1" ViewCount="128" Body="&lt;p&gt;I asked this on Superuser a while ago, but since fans are often used for cooling electronic devices, I think that the question would be on-topic here too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So how long is life expectancy of fan with magnetic bearing? I did some looking on catalogs of popular stores and datasheets of some manufacturers, but I couldn't find any information about life expectancy.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-01-10T14:45:06.947" Title="Life expectancy of fan with magnetic bearing?" Tags="&lt;fan&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="8742" PostTypeId="1" AcceptedAnswerId="8751" CreationDate="2011-01-08T15:35:53.670" Score="3" ViewCount="214" Body="&lt;p&gt;I typically use 2 ounce copper as rule for all my PCBs.  On a recent board I am using a 0.5mm pitch, relatively large micro, and noticed the pads aren't very flat.  Assembly went fine with the protos, but I'm wondering if 1 once copper would provide for a flatter landing service.  Does anyone have any experience with using 1 and 2 ounce copper with small pitch devices and/or any advice on assembly reliability related to copper thickness for such devices?&lt;/p&gt;&#xA;" OwnerUserId="2377" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-01-08T18:24:04.927" LastActivityDate="2011-01-08T18:24:04.927" Title="PCB copper thickness with small pitch SMT components" Tags="&lt;pcb&gt;&lt;surface-mount&gt;&lt;pcb-assembly&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="8743" PostTypeId="2" ParentId="7664" CreationDate="2011-01-08T16:02:57.260" Score="2" ViewCount="" Body="&lt;p&gt;In addition to Igor's answer, there are two minor reasons why active-low signals are used:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;In addition to the amount of sink current available being higher than source current, it is easier for TTL circuits to produce a &lt;em&gt;voltage&lt;/em&gt; that is close to ground (just a Vce drop) than a voltage close to Vcc (Vbe drop + usually a little more).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;It is easier for external passive circuits (e.g. pushbuttons or limit switches) to safely produce an active low signal: just use a pullup resistor on the receiving end, and on the external source end, short the circuit node in question to the ground potential. If you use an active high signal, you need to make Vcc available to those external circuits, which carries a risk of the Vcc node being shorted to ground.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-01-08T16:02:57.260" />
  <row Id="8744" PostTypeId="1" AcceptedAnswerId="8752" CreationDate="2011-01-08T16:18:06.490" Score="2" ViewCount="353" Body="&lt;p&gt;I have 12 AAA NiMH batteries(1000mAH and 1.2V per battery) and I want to know what is the optimum voltage for charging them. I am using a simple Constant Current charger(LM317 and 68 Ohm Resistor(R in the circuit diagram). But i'm unsure on what the input voltage needs to be. My circuit doesn't have the diode.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/lQEBG.gif&quot; alt=&quot;LM317 Battery Charger&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-01-09T15:50:48.800" Title="Voltage input for charging NiMH Batteries." Tags="&lt;battery-charging&gt;" AnswerCount="2" />
  <row Id="8745" PostTypeId="1" CreationDate="2011-01-08T16:18:29.437" Score="4" ViewCount="217" Body="&lt;p&gt;Hello,&#xA;I was wondering how that so-called &quot;coilgun&quot; works, I know what it does but I was wondering how it works under-the-hood and eventually how to make a basic one ? Also, how much energy would be required ?&lt;/p&gt;&#xA;" OwnerUserId="2528" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T22:15:13.257" LastActivityDate="2011-04-27T22:15:13.257" Title="How does a &quot;coilgun&quot; work ?" Tags="&lt;electromagnetism&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="8746" PostTypeId="1" CreationDate="2011-01-08T16:49:11.597" Score="4" ViewCount="242" Body="&lt;p&gt;Hi all&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody here knows an good windows program t ocontrol the Arduino Uno Board?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simple thinks like graph view to test values of sensors... you know... something simple like this program to other board:&#xA;&lt;a href=&quot;http://www.gogoboard.org/cocoon/gogosite/software/monitor/images/screenshot.jpg&quot; rel=&quot;nofollow&quot;&gt;http://www.gogoboard.org/cocoon/gogosite/software/monitor/images/screenshot.jpg&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks.&lt;/p&gt;&#xA;" OwnerUserId="1539" LastActivityDate="2011-01-12T10:01:37.703" Title="Arduino Control Panel for windows" Tags="&lt;arduino&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="8747" PostTypeId="1" AcceptedAnswerId="8835" CreationDate="2011-01-08T17:12:46.650" Score="3" ViewCount="145" Body="&lt;p&gt;I want to have a go at building a Tesla Coil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anybody here tried to build one before? How much do all the parts cost? Is it possible to make a small scale one? When can I get the plans, and what equipment/tools do I need?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UPDATE&lt;/strong&gt; To make this question a little more specific... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a few parts of the general design of a Telsa coil that I'm unsure about.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The HV transformer - I've seen that some plans say you can use a microwave oven transformer for this, and other plans say that you need to stack them by wiring the primarys in parallel and secondarys in series, but then you can get insulation breakdown. Is a MOT a good choice? If it's not good to use an MOT, then what?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The tank cap - the general idea is to get a load of lower voltage caps and solder strings of them in series to get the voltage rating you need, then parallel the strings together to get the capacitance you need... but how do you stop it arcing across the leads?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Whats an RF ground? Does it mean drive a stake into the ground and attach one side of the secondary to that?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Finally, nearly every circuit I build fails to work the first time for one reason or another, and I use my meter and scope to work out whats wrong... How can I safely test parts of the circuit without being zapped with 20KV?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-10T09:55:01.217" LastActivityDate="2011-01-10T15:52:29.927" Title="Building a Tesla Coil" Tags="&lt;high-voltage&gt;&lt;tesla-coil&gt;" AnswerCount="4" CommentCount="7" />
  <row Id="8748" PostTypeId="2" ParentId="8742" CreationDate="2011-01-08T17:33:01.090" Score="3" ViewCount="" Body="&lt;p&gt;1 oz (35 um) copper is much more suitable for SMD. Most board suppliers provide it as standard.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-08T17:33:01.090" />
  <row Id="8749" PostTypeId="2" ParentId="8747" CreationDate="2011-01-08T17:38:32.020" Score="0" ViewCount="" Body="&lt;p&gt;I always thought about it but never did.  there is a chap in western australia who built some big ones and records videos and has a blog about it, not sure of the name now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck with it should be fun!  do be careful around it tough, cos they can generate some seriously high voltages :)&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2011-01-08T17:38:32.020" CommentCount="3" />
  <row Id="8750" PostTypeId="2" ParentId="8747" CreationDate="2011-01-08T17:49:42.630" Score="-2" ViewCount="" Body="&lt;p&gt;There are a gazillion designs out there - do some research&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-08T17:49:42.630" CommentCount="2" />
  <row Id="8751" PostTypeId="2" ParentId="8742" CreationDate="2011-01-08T17:51:07.337" Score="4" ViewCount="" Body="&lt;p&gt;Unless you need high-current capability, 1 oz is the default thisckness. Line definition can  be impaired with increased thickness, so only use when necessary.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-08T17:51:07.337" CommentCount="1" />
  <row Id="8752" PostTypeId="2" ParentId="8744" CreationDate="2011-01-08T18:01:58.967" Score="3" ViewCount="" Body="&lt;p&gt;A constant current source adjusts its output voltage with the load in order to maintain a constant current.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;V = IR // holy s*#% it's Ohm's Law&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;NiMH batteries are fickle fiends to charge, exhibiting temperature-dependent changes in charge and discharge curves. They also don't have a &lt;a href=&quot;http://en.wikipedia.org/wiki/Float_voltage&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;&lt;em&gt;float voltage&lt;/em&gt;&lt;/strong&gt;&lt;/a&gt;, so constant voltage charging doesn't work, as you've likely discovered. Energizer has &lt;a href=&quot;http://data.energizer.com/PDFs/nickelmetalhydride_appman.pdf&quot; rel=&quot;nofollow&quot;&gt;some recommendations&lt;/a&gt; regarding charge times:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Typically a moderate rate (2 to 3&#xA;  hour) smart charger is preferred for&#xA;  NiMH batteries. &lt;strong&gt;The batteries are &#xA;  protected from overcharge by the smart&#xA;  charger circuitry.&lt;/strong&gt; Extremely fast&#xA;  charging (less than 1 hour) can impact&#xA;  battery cycle life and should be&#xA;  limited to an as needed basis. &lt;strong&gt;Slow&#xA;  overnight timer based chargers are&#xA;  also  acceptable and can be an&#xA;  economical alternative to smart&#xA;  chargers. A charger that applies a 0.1&#xA;  C rate for 12 to  14 hours is well&#xA;  suited for NiMH batteries. Finally a&#xA;  maintenance (or trickle) charge rate&#xA;  of less than 0.025 C  (C/40) is&#xA;  recommended.&lt;/strong&gt; The use of very small&#xA;  trickle charges is preferred to reduce&#xA;  the negative effects of  overcharging.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://data.energizer.com/PDFs/nh12-850.pdf&quot; rel=&quot;nofollow&quot;&gt;AAA NiMH batteries&lt;/a&gt; have a capacity of &lt;strong&gt;850mAh&lt;/strong&gt; &lt;sup&gt;&lt;sub&gt;[varies by manufacturer]&lt;/sub&gt;&lt;/sup&gt;, so charging with a rate of &lt;strong&gt;C/2 to C/3&lt;/strong&gt; can be done with a constant current of...&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;850mAh / (2 to 3 hours) = 283mA to 425mA&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;An overnight, &lt;strong&gt;C/12&lt;/strong&gt; trickle charge can be done with a constant current of &lt;strong&gt;71mA&lt;/strong&gt;. This page mentions that:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Modern cells have an oxygen recycling catalyst which prevents damage to the battery on overcharge, but this recycling cannot keep up if the charge rate is over C/10.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The recommended &lt;strong&gt;maintenance charge&lt;/strong&gt; rate of &lt;strong&gt;C/40&lt;/strong&gt; can be done with...&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;850mAh / h / 40 = 21mA&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Smart Chargers&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Listed are charging techniques from &lt;a href=&quot;http://data.energizer.com/PDFs/charger_appman.pdf&quot; rel=&quot;nofollow&quot;&gt;Energizer&lt;/a&gt;, &lt;a href=&quot;http://www1.duracell.com/oem/Pdf/others/TECHBULL.pdf&quot; rel=&quot;nofollow&quot;&gt;Duracell&lt;/a&gt;, and &lt;a href=&quot;http://www.powerstream.com/NiMH.htm&quot; rel=&quot;nofollow&quot;&gt;Powerstream&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;ΔV charging&lt;/strong&gt;: charge at recommended constant current until the cell reaches a peak voltage and decreases (eg. -15mV).&lt;br&gt; &lt;img src=&quot;http://i.imgur.com/h66ac.png&quot; alt=&quot;alt text&quot;&gt; &lt;br&gt;This technique is accurate enough to safely charge at C/2 to C/3 (283mA to 425mA).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;dT/dt charging&lt;/strong&gt;: monitor cell temperature to both limit maximum temperature and look for characteristic heating rate.&lt;br&gt; &lt;img src=&quot;http://i.imgur.com/mmNas.png&quot; alt=&quot;alt text&quot;&gt; &lt;br&gt;This technique may be used in conjunction with ΔV charge termination to more precisely monitor and terminate the process, allowing the use of higher currents (C/1 to C/2, or 425mA to 850mA).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Soft start&lt;/strong&gt;: &lt;em&gt;If the temperature is above 40 degrees C or below zero degrees C start with a C/10 charge. If the discharged battery voltage is less than 1.0 Volts/cell start with a C/10 charge. If the discharged battery voltage is above 1.29 V/cell start with a C/10 charge.&lt;/em&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;1.78V maximum&lt;/strong&gt;: a single cell must never exceed this.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;But what does it all mean!?&lt;/em&gt; The input voltage to your &lt;a href=&quot;http://www.national.com/ds/LM/LM317.pdf&quot; rel=&quot;nofollow&quot;&gt;LM317 constant current circuit&lt;/a&gt; must be enough to support the voltage drop across the regulator and resistor (1.47Ω), drive the required current, and exceed the maximum cell voltage. To source C/1 or 850mA to a AAA NiMH battery, whose internal resistance is at most around 120mΩ, requires &lt;code&gt;(120mΩ + 1.47Ω) * 850mA + 1.2V + 1.78V = 4.3315V&lt;/code&gt;. I recommend at least 2V more to reduce the effects of source irregularities like regulation and noise and account for other circuit losses (like that diode you don't have yet). If you're charging 4 cells in series as your diagram indicates, you'll need at least 9.978V (ie: &lt;strong&gt;12V+&lt;/strong&gt;); 25.034V (27V+) for 12 in series, though I would worry about uneven charging.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-09T15:50:48.800" LastActivityDate="2011-01-09T15:50:48.800" CommentCount="6" />
  <row Id="8753" PostTypeId="2" ParentId="8745" CreationDate="2011-01-08T18:42:53.580" Score="1" ViewCount="" Body="&lt;p&gt;First take a look at &lt;a href=&quot;http://en.wikipedia.org/wiki/Coilgun&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;. The article is interesting starting point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I see, since you just started studying them, the best start is to make an &lt;a href=&quot;http://en.wikipedia.org/wiki/Electromagnet&quot; rel=&quot;nofollow&quot;&gt;electromagnet&lt;/a&gt;. This way, you can familiarize yourself with calculation needed for your project since a coilgun is basically a special case of an electromagnet. I'll let you calculate what current and voltage you need. Just keep in mind the impedance of the coil and protection circuitry needed for transitions between on and off states. There are programs which can calculate inductance of a coil based on diameter of wire, number of turns and so on. I'll post a link as soon as I dig up from where I got mine. As for protection, you can find lots of tutorials for electric motors on the Internet. What you need should be pretty similar, since the coil is the main problem in both of them. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After you get your most basic magnet, you should take your time to calculate what type of projectile you'll use, what range you want and so on. Again, &lt;a href=&quot;http://en.wikipedia.org/wiki/Projectile_motion&quot; rel=&quot;nofollow&quot;&gt;Wikipedia comes to rescue&lt;/a&gt;, but there are many other good sources on the Internet. When you get the force needed, you can start calculating parameters of the electromagnets you'd want to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that, you'd need a circuit that can rapidly switch several electromagnets on and off. You may want to refresh your skills with digital electronics, since you could probably use some sort of counter for that, but I don't have much experience in that field, so I can't give you good advice. Microcontrollers would also be interesting, since you do C programming. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course you'd need a power supply too. If you go for low voltage capacitors with high capacity and high current, you could have a simple power supply, but it would take some time for it to charge the capacitors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's this guy called &lt;a href=&quot;http://www.youtube.com/user/Afrotechmods?blend=2&amp;amp;ob=1#g/u&quot; rel=&quot;nofollow&quot;&gt;Afrotechmods&lt;/a&gt; on Youtube which has some tutorials on power supplies, large capacitors and catastrophic failures of electronic components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another easily overlooked aspect in this scenario are internal connection cables. You should make sure that they can sustain the currents which you plan to put through them. Just to be safe, use stronger cables that necessary. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also the safety issue. Best advice would be to get someone who has a lot of experience in this field to work with you. I do understand why your teacher doesn't want to provide you with information about this project. Capacitors can easily explode and supercapacitors even more so, power cables can melt and catch on fire, even if your calculations show that they should be able to sustain the current (this happened to me few days ago), you could get a short-circuit somewhere which could start fire, a part of the device which should be isolated may be under power when you touch it and that can lead to burns and so on. So my advice to you is to research how each component can fail, how to react when it fails and to be ready for it. Also, it would be a good idea to use components with higher rating than the one you need, just to be safe. Some newer components also have internal protections against over- (voltage, heating, current), short-circuits and so on. If you can obtain such components, do use them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the end, I'll just add that I'm intentionally vague in this answer. Each of the points I made is very wide and could take few questions just for itself. My idea was to give you an overview of what's needed before you start. You will need to do a lot of research!&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-01-08T18:42:53.580" />
  <row Id="8754" PostTypeId="1" AcceptedAnswerId="8759" CreationDate="2011-01-08T19:13:43.880" Score="3" ViewCount="306" Body="&lt;p&gt;I have a TTC103 NTC thermistor. It has zero-power resistance of 10 kΩ at 25°C and B25/50 value of 4050. How do I use it to measure temperature?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-01-08T23:10:54.857" LastActivityDate="2011-01-09T03:01:43.123" Title="How to measure temperature using a NTC thermistor?" Tags="&lt;thermistor&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="8755" PostTypeId="1" AcceptedAnswerId="8766" CreationDate="2011-01-08T19:32:38.783" Score="2" ViewCount="211" Body="&lt;p&gt;I am trying to design an oscilloscope/BNC input circuit for a side project and to learn more about filters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The requirements are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;150-200 MHz -3dB bandwidth&lt;/li&gt;&#xA;&lt;li&gt;1 megohm impedance&lt;/li&gt;&#xA;&lt;li&gt;50 ohm termination option (I can omit this if it causes problems.)&lt;/li&gt;&#xA;&lt;li&gt;Can be switched between 2x and 20x attenuation&lt;/li&gt;&#xA;&lt;li&gt;Measures up to 80Vpk (160Vp-p), tolerates up to 400Vpk (800Vp-p) (5Vpk on 50 ohm mode.)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I designed a neat circuit that allowed switching between 2x and 20x attenuation while keeping 1 Mohm (or thereabouts) attenuation, as below:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;                499k        442k&#xA;( Input ) -----/\/\/---+---/\/\/---+----- To JFET input buffer&#xA;                       |           |&#xA;                       /           /&#xA;                  499k \           \ 49.9k&#xA;                       /           /&#xA;                       |           |&#xA;                       +---+   +---+&#xA;                           |   |     &#xA;                            \       relay to switch&#xA;                             |     attenuation 2x/20x&#xA;                            ---&#xA;                             -&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(All resistors 1%.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, then I learned oscilloscopes have input capacitance, and I'm not sure how to add it. Also, if I want the input to tolerate 400Vp-p swing but on the wrong input range (2x attenuation leaving 200Vp-p to damage the inputs of the JFETs), I couldn't use diodes as the lowest capacitance I found was 0.13pF for an RF diode, which would limit me to about 612kHz for two diodes (one to each rail, reverse biased.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-01-08T19:52:29.757" LastActivityDate="2011-01-08T22:47:14.790" Title="Oscilloscope input circuit" Tags="&lt;oscilloscope&gt;" AnswerCount="2" />
  <row Id="8756" PostTypeId="2" ParentId="8745" CreationDate="2011-01-08T19:49:34.813" Score="6" ViewCount="" Body="&lt;p&gt;A coilgun is a series of coils that are successively energized as a conductive projectile made from &lt;a href=&quot;http://en.wikipedia.org/wiki/Magnetic_materials&quot; rel=&quot;nofollow&quot;&gt;magnetic material&lt;/a&gt; passes by them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ymzji.png&quot; alt=&quot;coilgun&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each stage acts on similar principles to those of a &lt;a href=&quot;http://en.wikipedia.org/wiki/Solenoid&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;solenoid&lt;/strong&gt;&lt;/a&gt;. Current loops &lt;a href=&quot;http://en.wikipedia.org/wiki/Amp%C3%A8re%27s_circuital_law&quot; rel=&quot;nofollow&quot;&gt;induce magnetic flux&lt;/a&gt; through their center:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/YHlbP.png&quot; alt=&quot;http://en.wikipedia.org/wiki/File:VFPt_Solenoid_correct2.svg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the conductive projectile approaches the air-core current loops, two things happen: the &lt;strong&gt;loop inductance increases&lt;/strong&gt; and the &lt;strong&gt;projectile &lt;a href=&quot;http://en.wikipedia.org/wiki/Electromagnet&quot; rel=&quot;nofollow&quot;&gt;becomes magnetized&lt;/a&gt;&lt;/strong&gt;. The magnetized projectile is then attracted to the loop magnetic field, accelerating towards it. As it approaches, inductance increases, completing a &lt;strong&gt;positive feedback loop&lt;/strong&gt; such that the pull on the projectile and magnetic field created by the loops increase.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/JdClu.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This process reaches a peak when the projectile is completely enclosed by the coil, where further travel decreases the loop's inductance. At this point, current through the loop is &lt;strong&gt;abruptly turned off&lt;/strong&gt; so the projectile won't be slowed down by its continued attraction to the coil's magnetic field.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/ggLfN.png&quot; alt=&quot;alt text&quot;&gt; &lt;img src=&quot;http://i.imgur.com/VRdai.png&quot; alt=&quot;alt text&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/O9Lcl.gif&quot; alt=&quot;WikiPedia gif&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;These are the basic physics principles by which a coil gun operates, which appears to be what you are interested in. There are many practical implementations.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-08T19:49:34.813" />
  <row Id="8757" PostTypeId="2" ParentId="8746" CreationDate="2011-01-08T19:54:45.383" Score="3" ViewCount="" Body="&lt;p&gt;I'm judging from the tone of the question that you think the Uno is a general purpose I/O board for which it is simple to interface sensors or relays or other analog/digital devices and read/control them using software already on the board.  This is not the case.  The Uno is a general purpose microcontroller board that has no specific function unless you program it yourself.  It is certainly possible to use it in the manner you describe but you'll have to do all the work - analog/digital interface and software for both the Uno and PC.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good path to creating the PC-side software would by Python I'd think.  You can create GUIs fairly easily and it's pleasant to work with.  Otherwise I don't know of any projects for the Arduino that mimic the functionality of the gogoboard.  Anyone know of any?&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-08T19:54:45.383" CommentCount="3" />
  <row Id="8758" PostTypeId="2" ParentId="8754" CreationDate="2011-01-08T19:58:01.593" Score="3" ViewCount="" Body="&lt;p&gt;Use it as one leg (say the &quot;upper&quot; leg) in a voltage divider circuit with the other leg being a known resistance. Measure the voltage at the midpoint of the divider (e.g. with an analog-to-digital converter). Infer the thermistor resistance from the measured voltage as:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;R_thermistor = ((V_cc / V_measured) - 1) * R_known &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Use the equation:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;T = B / ln(R_thermistor / (R_0 * exp(-B / T_0)))&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;in your case, R_0 = 10000, B = 4050, and T_0 = (273 + 25) = 298. Plug those numbers, plus the measured resistance of the thermistor into the equation and out pops a temperature in degrees Kelvin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Read &lt;a href=&quot;http://en.wikipedia.org/wiki/Thermistor&quot; rel=&quot;nofollow&quot;&gt;this wikipedia article&lt;/a&gt; for more details.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-01-08T19:58:01.593" />
  <row Id="8759" PostTypeId="2" ParentId="8754" CreationDate="2011-01-08T20:01:25.833" Score="4" ViewCount="" Body="&lt;p&gt;NTC (negative temperature coefficient) thermistors change their effective resistance over temperature.  The most common equation used to model this change is the &lt;a href=&quot;http://en.wikipedia.org/wiki/Steinhart%E2%80%93Hart_equation&quot; rel=&quot;nofollow&quot;&gt;Steinhart-Hart equation&lt;/a&gt;.  It uses three coefficients to characterize the NTC material with great accuracy.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many manufacturers provide application notes (e.g. &lt;a href=&quot;http://www.ilxlightwave.com/appnotes/AN%204%20REV02%20Thermistor%20Calibration%20and%20Steinhart%20Hart.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) detailing on how to calibrate a given NTC if you desire accuracy better than the quoted manufacturing tolerance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The provided B-coefficient can be used in a simplified Steinhart-Hart equation as described on the &lt;a href=&quot;http://en.wikipedia.org/wiki/Thermistor#B_parameter_equation&quot; rel=&quot;nofollow&quot;&gt;Wikipedia Thermistor article under &quot;B parameter equation&quot;&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-08T20:01:25.833" CommentCount="1" />
  <row Id="8760" PostTypeId="2" ParentId="8754" CreationDate="2011-01-08T20:01:38.303" Score="2" ViewCount="" Body="&lt;p&gt;An NTC has a non-linear response to temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can work out the resistance of a thermistor by measuring the voltage across it in a potential divider circuit. Then, you can get a resistance &lt;code&gt;R&lt;/code&gt; from this using Ohm's law. For example, say you have a 5V supply use a 1k resistor in series with the NTC and if you measure 0.5V, just divide 1k by 0.5V and get 10k ohms as the resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also need, &lt;code&gt;T_0&lt;/code&gt; and &lt;code&gt;R_0&lt;/code&gt;, a 'fixed' temperature in kelvins and at that temperature, its resistance. It's usually given at room temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, given these details, put it into this equation to get &lt;code&gt;T&lt;/code&gt;, the temperature.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;T = 1 / ((1 / T_0) + ((1 / B) * ln(R / R_0)))&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-01-09T02:45:56.897" LastActivityDate="2011-01-09T02:45:56.897" />
  <row Id="8761" PostTypeId="2" ParentId="8744" CreationDate="2011-01-08T20:02:00.743" Score="1" ViewCount="" Body="&lt;p&gt;Are the batteries arranged in series like your drawing shows?  If so your discharged voltage will be around 15V and your charged voltage will be about 16.8V (1.25V/cell discharged, 1.4V/cell charged). LM317 reference is 1.25V across the 68 ohm resistor for charge current of (1.25/68) &lt;strong&gt;18mA charge current&lt;/strong&gt;.  Dropout voltage on the LM317 is for that rate is never more than 2V (page 6 from the datasheet tyblu linked to, very conservative estimate).So minimum input voltage needs to be (conservatively) 2V + 1.25V + 16.8v = &lt;strong&gt;20.05V&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How did you choose the value for the resistor?  A safe charge rate (if you're watching it to turn it off) is C/10 which should be (100-mAh/10) &lt;strong&gt;100mA charge current&lt;/strong&gt;.  That gives a resistor value of (1.25V/.1A) &lt;strong&gt;12.5 ohms&lt;/strong&gt; with power rating of (.1^2*12.5) &lt;strong&gt;.125W&lt;/strong&gt;.  Are these 12 cells in series or parallel?&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="249" LastEditorDisplayName="" LastEditDate="2011-01-08T20:09:14.933" LastActivityDate="2011-01-08T20:09:14.933" CommentCount="2" />
  <row Id="8762" PostTypeId="2" ParentId="8755" CreationDate="2011-01-08T20:59:42.270" Score="1" ViewCount="" Body="&lt;p&gt;For attenuation, you may consider looking at what a probe does. The factor is the same (1/10 = 2/20). Just short the additional resistor and capacitor from the probe circuit with a switch, like 1:1 and 1:10 switchable probes do.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-01-08T20:59:42.270" CommentCount="2" />
  <row Id="8763" PostTypeId="2" ParentId="5429" CreationDate="2011-01-08T21:38:24.107" Score="0" ViewCount="" Body="&lt;p&gt;The threads on eevblog are very extensive.  It includes independent testing by various modders, including those with high end radio-frequency equipment as well as high quality pulse generators.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Know the mod only changes the input amp limitations, not the real time sampling rate.  Unchanged, that still is the rate limiting step in reducing aliasing errors, at 500Ms/s for 2 channels active, or 1Gs/s for a single channel used, the scope will be prone to aliasing errors if 2 channels are used past 50 MHz.&lt;/p&gt;&#xA;" OwnerUserId="2529" LastActivityDate="2011-01-08T21:38:24.107" CommentCount="1" />
  <row Id="8764" PostTypeId="1" AcceptedAnswerId="8765" CreationDate="2011-01-08T22:04:14.437" Score="1" ViewCount="153" Body="&lt;p&gt;What's the simplest way at low speeds (sub 100 Hz) to shift 0-5V to ±2.5V? I was thinking of using a comparator or op-amp, but there must be a simpler / cheaper way. I wanted to avoid a dedicated chip, unless it is cheaper than a discrete solution. Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-08T22:32:34.267" Title="Shift 0-5V logic to ±2.5V logic" Tags="&lt;level-shifting&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="8765" PostTypeId="2" ParentId="8764" CreationDate="2011-01-08T22:26:24.113" Score="2" ViewCount="" Body="&lt;p&gt;If you have -2.5V available, replace the two resistors with a single resistor to -2.5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/en4e4.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-01-08T22:32:34.267" LastActivityDate="2011-01-08T22:32:34.267" CommentCount="2" />
  <row Id="8766" PostTypeId="2" ParentId="8755" CreationDate="2011-01-08T22:33:29.743" Score="1" ViewCount="" Body="&lt;p&gt;Input capacitance is significant for capturing high frequency content signals. Given that you are using discrete parts and not considering RF parasitics, this system will be restricted to the 100's of kHz for 1% accuracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/BlWgG.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The goal is to maintain constant attenuation and input impedance over the entire frequency range. Assume C&lt;sub&gt;p&lt;/sub&gt; is 100pF, R&lt;sub&gt;p&lt;/sub&gt; is 941kΩ, C&lt;sub&gt;s&lt;/sub&gt; is 1000pF and R&lt;sub&gt;s&lt;/sub&gt; is 49kΩ (ignore adjustment cap for now) The capacitors' impedance will vary as follows:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Z&lt;sub&gt;C&lt;sub&gt;p&lt;/sub&gt;&lt;/sub&gt; : 1.6GΩ @ 1Hz; 1.6MΩ @ 1kHz; 16kΩ @ 100kHz&lt;/li&gt;&#xA;&lt;li&gt;Z&lt;sub&gt;C&lt;sub&gt;adj.&lt;/sub&gt;&lt;/sub&gt; : 16GΩ @ 1Hz; 16MΩ @ 1kHz; 159kΩ @ 100kHz&lt;/li&gt;&#xA;&lt;li&gt;Z&lt;sub&gt;C&lt;sub&gt;s&lt;/sub&gt;&lt;/sub&gt; : 159GΩ @ 1Hz; 159kΩ @ 1kHz; 1.6kΩ @ 100kHz&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This results in the following range of impedances:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Z&lt;sub&gt;probe&lt;/sub&gt; : 940kΩ @ 1Hz; 591kΩ @ 1kHz; 15kΩ @ 100kHz&lt;/li&gt;&#xA;&lt;li&gt;Z&lt;sub&gt;'scope&lt;/sub&gt; : 49kΩ @ 1Hz; 37kΩ @ 1kHz; 1.5kΩ @ 100kHz&lt;/li&gt;&#xA;&lt;li&gt;Z&lt;sub&gt;input&lt;/sub&gt; : 989kΩ @ 1Hz; 628kΩ @ 1kHz; 16.5kΩ @ 100kHz&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;approximate attenuation: 20X @ 1Hz; 17X @ 1kHz; 11X @ 100kHz&lt;/em&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As you can see, adjustment capacitors are required to tune the input. The grander issue is that this calls for &lt;em&gt;wideband matching networks&lt;/em&gt;. Another option, and what is done in addition to matching networks in professional equipment, is characterizing the input impedance and compensating for irregularities in software. Standardizing at 50Ω impedances allows the construction of modular probing hardware while maintaining wideband matching and constant attenuation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your requirements for switching impedances and an optional 50Ω input will need some more complication. &lt;em&gt;A fantastic project, and I wish I could partake!&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-08T22:47:14.790" LastActivityDate="2011-01-08T22:47:14.790" CommentCount="3" />
  <row Id="8767" PostTypeId="1" AcceptedAnswerId="8774" CreationDate="2011-01-08T23:07:22.487" Score="19" ViewCount="634" Body="&lt;p&gt;What are some of the good versioning systems for hardware projects? Is there equivalents of Google Code, CVS and SVN? Are such version control systems suitable for hardware projects involving PCB files, schematics..(even firmware code)?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-09T02:30:21.460" LastActivityDate="2011-05-27T20:16:37.153" Title="Version control systems for hardware projects?" Tags="&lt;project-management&gt;&lt;version-control&gt;" AnswerCount="12" CommentCount="2" FavoriteCount="7" />
  <row Id="8768" PostTypeId="2" ParentId="8767" CreationDate="2011-01-08T23:13:28.373" Score="4" ViewCount="" Body="&lt;p&gt;Why not just use Google Code or a SVN repo? As this is a revision control system. There is no defined use for it. It is just incredibly useful for multiple developers and monitoring changes in source code. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-01-08T23:18:31.033" LastActivityDate="2011-01-08T23:18:31.033" CommentCount="6" />
  <row Id="8769" PostTypeId="2" ParentId="8767" CreationDate="2011-01-08T23:32:04.527" Score="8" ViewCount="" Body="&lt;p&gt;I use VisualSVN Server + TortoiseSVN client, and it works just fine&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-01-08T23:32:04.527" CommentCount="2" />
  <row Id="8770" PostTypeId="2" ParentId="8767" CreationDate="2011-01-09T02:08:32.783" Score="7" ViewCount="" Body="&lt;p&gt;I've used Subversion with Altium before. It worked successfully, but at the time the lack of a diff tool made it less useful than version control is with code. I still think it was worth doing, even without diff capability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For firmware, Subversion or Git are both great. If you haven't used Git before, try Subversion first (even though it will make learning Git later harder).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Altium has recently introduced a diff tool for schematics and PCBs, so I expect that Subversion would now be great, modulo the usual insanity that EDA vendors manage to build into their products.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been meaning to try this out with the new diff tool; if I do, I'll try to remember to post a link to the repo here as an example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried this out, and I have to say that I'm a little underwhelmed with the Altium diff tool. It's functional, but the changes between board revs are substantial enough that it's not that useful, at least for me. Having seen this, I've decided to forget about the diff tool and just use Github. Here's the repo if you're interested: &lt;a href=&quot;https://github.com/rascalmicro/pcb&quot; rel=&quot;nofollow&quot;&gt;https://github.com/rascalmicro/pcb&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-01-10T01:52:19.423" LastActivityDate="2011-01-10T01:52:19.423" CommentCount="7" />
  <row Id="8772" PostTypeId="2" ParentId="8767" CreationDate="2011-01-09T02:38:56.883" Score="6" ViewCount="" Body="&lt;p&gt;I use Google Code to host &lt;a href=&quot;http://super-osd.googlecode.com/&quot; rel=&quot;nofollow&quot;&gt;Super OSD&lt;/a&gt;, an electronics project of mine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I exclusively use the gEDA suite to manage my schematics and PCBs. Usefully, gEDA produces text files (which are mostly human readable, although it's difficult to interpret them) for the schematics, instead of binary blobs, like Eagle. For example, &lt;a href=&quot;http://code.google.com/p/super-osd/source/diff?spec=svne5f0a5cc4a9a51de29d66d37698e259c9954b0ef&amp;amp;r=e5f0a5cc4a9a51de29d66d37698e259c9954b0ef&amp;amp;format=side&amp;amp;path=/hardware/V3.2+Lite/mcu.sch&amp;amp;old_path=/hardware/V3.2+Lite/mcu.sch&amp;amp;old=ca1233a25cb1607317c77294660256c932b88a1f&quot; rel=&quot;nofollow&quot;&gt;this is a diff between two schematics&lt;/a&gt;, one about 5 days old and one I just pushed. It's not particularly useful as you can't actually see much changes in text files, but it can show relative change - i.e. massive rework, vs. single component change - and it does let you go back to prior versions.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-09T02:38:56.883" CommentCount="1" />
  <row Id="8774" PostTypeId="2" ParentId="8767" CreationDate="2011-01-09T02:52:13.013" Score="11" ViewCount="" Body="&lt;p&gt;Basically, all VCS systems can handle text &amp;amp; binary files gracefully.&#xA;Of course you cannot merge binary ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So as long as you are not using obsolete things like CVS you will be good with ANY system.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-09T02:52:13.013" CommentCount="5" />
  <row Id="8775" PostTypeId="2" ParentId="8746" CreationDate="2011-01-09T02:56:04.503" Score="4" ViewCount="" Body="&lt;p&gt;You may want to take a look at Firmata.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a Firmata example that can be loaded into the Arduino from File &gt; Examples &gt; Firmata &gt; StandardFirmata menu in the Arduino development environment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can download a PC host program from &lt;a href=&quot;http://firmata.org/wiki/Main_Page&quot; rel=&quot;nofollow&quot;&gt;http://firmata.org/wiki/Main_Page&lt;/a&gt; for Linux, Windows, or Mac OS-X.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From Firmata main page,&#xA;&quot;If you need to quickly test your hardware, this stand-alone program can access all pins. It runs from a single file (no installation needed), for quick and easy testing!&quot;&lt;/p&gt;&#xA;" OwnerUserId="2489" LastActivityDate="2011-01-09T02:56:04.503" />
  <row Id="8776" PostTypeId="1" CreationDate="2011-01-09T03:36:32.737" Score="1" ViewCount="156" Body="&lt;p&gt;Hi all.&#xA;I need to quickly assemble a simple thing, a LED strip driver with ATTiny/Atmega. My powersource is (as always) an universal laptop brick (17-21V output @ up to 4A)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So AVR would be hooked into a number of ULN2003 to control overall drain (near 2A, 12V)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is, it would take few days to deliver me anything better than a couple of resistors (have a lot of those here), so can make only a common-ground resistor divider. Almost a MacGyver situation (I do not need a flashing HELP message to attact alligator to make him turn the wheel to raise the castle door, but really out of parts, local store is temporarily closed ).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Problems:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How to calculate the resistors to power both parts correctly?&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;(even worse) how to limit the current for ICs to about 500mA? Only resistors, remember. Maybe a bit of transistors/capacitors, but (almost? ideas?) nothing smarter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/rbFrS.png&quot; alt=&quot;two resistors form a resistor divider&quot;&gt;.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2187" LastActivityDate="2011-01-09T06:51:19.153" Title="Resistor-only solution to split 19V 3A to 3.3/5V and 12V 2A with common ground?" Tags="&lt;resistor&gt;&lt;divide&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="8777" PostTypeId="2" ParentId="8776" CreationDate="2011-01-09T04:24:50.373" Score="1" ViewCount="" Body="&lt;p&gt;You can only use resistor dividers as a voltage source if you know the resistance of your load and it is constant.  If you are switching LEDs on and off, for example, the load is changing and so will your voltage.  But even if you had a constant load, trying to get 2A from a resistor divider seems crazy.  You'd need very large power resistors.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have transistors, perhaps you could rig together some simple transistor regulators.  These usually require zeners, but do you have diodes???  You could put a bunch in series to the get the required voltage drop to set the base voltage.  Still... your transistor will be getting HOT at 2A and a 7V drop.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-01-09T04:24:50.373" />
  <row Id="8778" PostTypeId="2" ParentId="8575" CreationDate="2011-01-09T04:39:42.123" Score="0" ViewCount="" Body="&lt;p&gt;There is a report in Apple's iOS developer forum that the iPhone touchscreen is capable of a maximum of a 60 Hz position sampling or reporting rate, as the touchscreen sensor driver is synced to the display refresh rate.&lt;/p&gt;&#xA;" OwnerUserId="1908" LastActivityDate="2011-01-09T04:39:42.123" />
  <row Id="8779" PostTypeId="2" ParentId="8163" CreationDate="2011-01-09T04:42:21.420" Score="0" ViewCount="" Body="&lt;p&gt;The Arduino CPU might be able to handle bidirectional BPSK at a low enough baud rate.&lt;/p&gt;&#xA;" OwnerUserId="1908" LastActivityDate="2011-01-09T04:42:21.420" />
  <row Id="8780" PostTypeId="2" ParentId="4780" CreationDate="2011-01-09T04:48:56.703" Score="0" ViewCount="" Body="&lt;p&gt;This might be possible with a small FPGA, and a digital rate multiplier circuit (measures the period of the input pulses from the audio jack, and (re)output the pulses at, say, 4X the frequency).  For IR input, a 4X frequency divider working the other way might also be interesting to try.   Might be possible to implement this in software as well on a reasonably fast microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="1908" LastActivityDate="2011-01-09T04:48:56.703" />
  <row Id="8781" PostTypeId="1" AcceptedAnswerId="8783" CreationDate="2011-01-09T05:15:18.303" Score="2" ViewCount="364" Body="&lt;p&gt;I wrote a program to turn on LEDs on PORTB. The programmer erased, programmed, verified, so far so good. But then nothing happened. No lights. My programmer is a MPLAB Compatible Mini USB PIC Programmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are some things that novices miss?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Below is my code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;p18f4550.h&amp;gt; &#xA;#pragma config WDT = OFF &#xA;void delay (void) &#xA;{ &#xA;  unsigned int i; &#xA;  for (i = 0; i &amp;lt; 65535 ; i++) ; &#xA;} &#xA;&#xA;void main (void) &#xA;{ &#xA;  TRISB = 0; &#xA;  while (1) &#xA;  { &#xA;    PORTB = 0; &#xA;    delay (); &#xA;    PORTB = 0xFF; &#xA;    delay (); &#xA;  } &#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2488" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-01-10T05:02:49.957" LastActivityDate="2011-01-10T14:11:02.390" Title="PICs for beginners using MPLAB Compatible Mini USB PIC Programmer" Tags="&lt;microcontroller&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="8782" PostTypeId="2" ParentId="8776" CreationDate="2011-01-09T05:37:21.510" Score="4" ViewCount="" Body="&lt;p&gt;This is a bad idea! In order to use a resistor divider, you need to have a good feel for how much current your devices use. Also, while you may have a lot of resistors, you will need high power resistors. Resistor-divider power supplies are &lt;strong&gt;EXTREMELY&lt;/strong&gt; inefficient&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For powering the microcontroller, we need to make sure that the voltage doesn't exceed the maximum rating, or else it will die. For ATMega parts that tolerate 5V, the maximum input voltage is 5.5V (5V +10%). Lets suppose that the current through R1 and R2 is 10mA. R1 will drop &lt;code&gt;(Vin-Vreg)&lt;/code&gt; volts, and then using Ohm's law we can find the resistance of R1: &lt;code&gt;(21V - 5.5V)/(10mA) = 1.55 kOhm&lt;/code&gt; . R2 will drop the voltage Vreg, so once again Ohm's law shows us &lt;code&gt;(5.5V)/(10mA) = 550 Ohm&lt;/code&gt; .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How much current can this supply source before we start having funky issues? This is hard to tell for me because the AVR has such a range of operational voltages (5.5V to 2.7V). If we say that we shouldn't fall below 4.0V, then the maximum load current is equal to: &lt;code&gt;(Vin - Vreg_min)/(R1) - (Vreg_min/R2)&lt;/code&gt; or &lt;code&gt;(21V - 4V)/(1.55kOhm) - (4V/550Ohm) = 3.7 mA&lt;/code&gt; . R1 will dissipate the most power, and if you're using 1/4W resistors, you need to be careful here. The power dissipation of R1 will be most when the load is drawing the maximum current: &lt;code&gt;P = (Itot)^2*R1 =10.97mA^2 * 1.55kOhm = 187mW&lt;/code&gt; . Increasing &lt;code&gt;Iquiescent&lt;/code&gt; (decreasing R1 and R2) will increase your maximum current, at a major cost to power. Increasing the operating range will decrease the power, but may cause issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can identify the current for each leg that you are switching, you may be able to just add a series resistor with the light bar. For example, if one of the legs normally draws 100mA at 12V, then you could add a series resistor &lt;code&gt;(Vin - 12V) / (Iload) = 90 Ohms&lt;/code&gt;&#xA;and things should just work out without providing a constant 12V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Note:&lt;/strong&gt; Use as low of a voltage on your power supply as possible. I'm not sure if this is adjustable, but if it is, use 17V instead of 21V.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-01-09T05:37:21.510" />
  <row Id="8783" PostTypeId="2" ParentId="8781" CreationDate="2011-01-09T05:50:34.203" Score="3" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;Did you forget to set the LED pins to output?&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Each pin you want to drive a LED must be set as an output in your code. This involves setting the TRIS bits for that pin to '0'.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Did you connect the LED backwards?&#xA;&lt;ul&gt;&#xA;&lt;li&gt;LEDs will turn on only when the anode-cathode voltage is positive.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Do you have a clock source?&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Make sure you're using a clock source that's hooked up, or the internal RC oscillator. Without a clock, your program won't run. &lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Do you have the LED connected to the correct pin?&lt;/li&gt;&#xA;&lt;li&gt;Is power applied to the circuit?&lt;/li&gt;&#xA;&lt;li&gt;Do you have bypass capacitors for the PIC?&lt;/li&gt;&#xA;&lt;li&gt;Is there a resistor pull-up for MCLR?&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Without this pull-up, your chip will stay in reset and never execute your program.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Check your wiring again. Wiring and connection errors are very common in beginner's circuits.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-01-09T05:50:34.203" CommunityOwnedDate="2011-01-09T05:50:34.203" CommentCount="5" />
  <row Id="8784" PostTypeId="2" ParentId="8781" CreationDate="2011-01-09T05:54:18.570" Score="2" ViewCount="" Body="&lt;p&gt;Most common is using pins that are shared with the ADC. You need to enable them for digital I/O as they are analogue inputs by default.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Quote from &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/39632e.pdf&quot; rel=&quot;nofollow&quot;&gt;PIC18F2455/2550/4455/4550&#xA; datasheet&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Note: On a Power-on Reset, RB4:RB0 are&#xA;  configured as analog inputs by default&#xA;  and read as ‘0’; RB7:RB5 are&#xA;  configured as digital inputs.  By&#xA;  programming the Configuration bit,&#xA;  PBADEN (CONFIG3H&amp;lt;1&gt;), RB4:RB0 will&#xA;  alternatively be configured as digital&#xA;  inputs on POR.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That is probably the cause of the problem. Some of the PortB pins of the PIC18F4550 are shared with the ADC.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-10T14:11:02.390" LastActivityDate="2011-01-10T14:11:02.390" />
  <row Id="8785" PostTypeId="2" ParentId="8776" CreationDate="2011-01-09T06:51:19.153" Score="1" ViewCount="" Body="&lt;p&gt;Resistor only?  Very bad idea. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're open to using transistors though, as you mention, you could use one with a resistor divider as a crude linear regulator.  A basic NPN emitter follower should work for a positive regulator, giving a voltage roughly equal to V&lt;sub&gt;B&lt;/sub&gt; (the resistor divider) - V&lt;sub&gt;BE(sat)&lt;/sub&gt; (characteristic of the transistor, usually 0.5 - 1 V)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a resistor divider as your voltage reference means it's obviously just a ratio of the input voltage, so ideally you'd use a Zener as a reference.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't want to use Zeners, you could chain normal diodes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't want to use diodes, you can use transistors like diodes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to avoid that, you might be able to (severely abuse) the leakage current of capacitors (especially electrolytics) near their rating to provide a voltage reference.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-09T06:51:19.153" />
  <row Id="8786" PostTypeId="1" AcceptedAnswerId="8803" CreationDate="2011-01-09T07:26:47.737" Score="2" ViewCount="153" Body="&lt;p&gt;Hey Stack!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the title says, I am looking for a smoke detection sensor. Took a look from SparkFun to Mouser and did not find anything. Is there a part you would recommend? I would prefer something that interfaces with the ATMEGA168/ATMEGA328 via a single wire or two wire interface. Would prefer to avoid a SPI or Serial interface as my circuit already utilizes those pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bumped into a few sensors on Ebay but they were $15+. Is this normal? Is there a cheaper alternative that works great? Should I just buy a cheap smoke alarm and extract the sensor that way?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance for your help.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-01-09T18:42:15.277" LastActivityDate="2011-01-09T18:42:15.277" Title="Looking for an inexpensive Smoke Detection Sensor" Tags="&lt;sensor&gt;&lt;atmega328&gt;&lt;atmega168&gt;&lt;smoke-sensor&gt;" AnswerCount="5" />
  <row Id="8787" PostTypeId="2" ParentId="8786" CreationDate="2011-01-09T07:54:29.977" Score="1" ViewCount="" Body="&lt;p&gt;If you're looking for the optical type, it looks like one can use an analog infrared photodiode/sensor and emitter module along with a controller, like &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/22179b.pdf&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-09T10:13:42.033" LastActivityDate="2011-01-09T10:13:42.033" CommentCount="2" />
  <row Id="8788" PostTypeId="2" ParentId="8786" CreationDate="2011-01-09T08:14:18.913" Score="2" ViewCount="" Body="&lt;p&gt;Well, if you have some time to test, you can go for LED + Photodiode.&#xA;Should be &amp;lt;1$ :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea is that LED should not shine directly on photodiode, air should be able to fly around, but not light.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In ultrapure air photodiode should see 0, the more smoke in the air - the more diffused light will get to diode, and you'll be able to measure it via ADC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But this definitely require some testing.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Personally I would go for UV diode, not IR/visible one, as there is less UV light noise (except xenon flashlights from cameras, be sure to test &amp;amp; filter for it). This surely require some experimenting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a side note, I love to see air quality in beam of 100mw green lazer, but this is definitely not cost effective :-D&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-09T08:14:18.913" CommentCount="3" />
  <row Id="8789" PostTypeId="2" ParentId="8741" CreationDate="2011-01-09T08:22:22.230" Score="1" ViewCount="" Body="&lt;p&gt;True magnetic bearing have near to infinite mechanical life expectancy, limited only to MTBF of support electronics (which is also can be &gt;10years if properly designed). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As long as it's not overheated, and not damaged mechanically, it should last.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-09T08:22:22.230" />
  <row Id="8790" PostTypeId="2" ParentId="8786" CreationDate="2011-01-09T09:11:42.900" Score="3" ViewCount="" Body="&lt;p&gt;I'd go for the cheap smoke alarm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The actual sensor is a black plastic chamber with a LED and a photo sensor.&#xA;It is constructed so that with clean air no light reaches the sensor,&#xA;it passes the center of the chamber and is absorbed on another side.&#xA;With smoke particles in the air some light is reflected towards the sensor and off goes the alarm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the electronics, I opened up one such alarm and found an &lt;a href=&quot;http://www.freescale.com/files/analog/doc/data_sheet/MC145010.pdf&quot; rel=&quot;nofollow&quot;&gt;MC145010&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-01-09T09:11:42.900" />
  <row Id="8791" PostTypeId="1" AcceptedAnswerId="8792" CreationDate="2011-01-09T11:02:43.290" Score="4" ViewCount="92" Body="&lt;p&gt;I have a capacitor which is marked with &quot;1200uF200wv&quot;. What does the &quot;w&quot; mean?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-01-09T11:06:22.457" Title="Need help deciphering markings on an electrolytic capacitor" Tags="&lt;capacitor&gt;&lt;markings&gt;" AnswerCount="1" />
  <row Id="8792" PostTypeId="2" ParentId="8791" CreationDate="2011-01-09T11:06:22.457" Score="6" ViewCount="" Body="&lt;p&gt;The &lt;code&gt;W&lt;/code&gt; is for &lt;code&gt;Working&lt;/code&gt;; &lt;code&gt;WV&lt;/code&gt; = Working Voltage&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-01-09T11:06:22.457" CommentCount="2" />
  <row Id="8793" PostTypeId="1" AcceptedAnswerId="8804" CreationDate="2011-01-09T11:36:09.530" Score="3" ViewCount="181" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a DC motor that is controlled by a PWM output on an Ardiono and I want to know if I can safely assume that by setting the output to 50% duty cycle, the current in the motor will be 50 % as well&#xA;The output is connected to the base on an BC338 transistor through a 1K resistor that I use as a driver.&lt;/p&gt;&#xA;" OwnerUserId="1637" LastEditorUserId="1637" LastEditorDisplayName="" LastEditDate="2011-01-09T11:41:53.770" LastActivityDate="2011-01-10T01:15:40.140" Title="Will PWM on 50% duty cycle cut the current in a DC motor in half" Tags="&lt;pwm&gt;&lt;dc-motor&gt;&lt;current-measurement&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="8794" PostTypeId="1" AcceptedAnswerId="8800" CreationDate="2011-01-09T12:02:08.913" Score="9" ViewCount="478" Body="&lt;p&gt;Do electrolytic capacitors have a limited shelf life? I would like to know for both aluminium and tantalum.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-09T15:58:05.830" LastActivityDate="2011-01-10T12:40:37.043" Title="Do electrolytic capacitors have a limited shelf life?" Tags="&lt;capacitor&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="8795" PostTypeId="2" ParentId="4784" CreationDate="2011-01-09T12:36:55.313" Score="0" ViewCount="" Body="&lt;p&gt;Decoupling capacitors serve several purposes. First they're a safeguard against variations in the power supply. It the capacitor wasn't there a dip could reset the whole circuit. Likewise, some power-hungry parts of the circuit may switch on and off during operation. Switching on also creates a dip; much current suddenly needed in one place means that it's no longer available elsewhere. The capacitor is a buffer storage that makes sure there's enough current for all components at these switching moments.  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-01-09T12:36:55.313" CommunityOwnedDate="2011-01-09T12:36:55.313" />
  <row Id="8798" PostTypeId="1" AcceptedAnswerId="8802" CreationDate="2011-01-09T13:21:24.533" Score="5" ViewCount="355" Body="&lt;p&gt;A &lt;strong&gt;load dump&lt;/strong&gt; occurs when the load to which a generator is delivering current is abruptly disconnected. In automotive electronics, this applies to disconnecting a battery while it is being charged by the alternator. It is apparently well-described in &lt;a href=&quot;http://standards.sae.org/j1113/11_200706/&quot; rel=&quot;nofollow&quot;&gt;this $65 SAE document&lt;/a&gt;; &lt;a href=&quot;http://en.wikipedia.org/wiki/Load_dump&quot; rel=&quot;nofollow&quot;&gt;Wikipedia claims&lt;/a&gt; it can be &lt;em&gt;&quot;as high as 120 V and may take up to 400 ms to decay&quot;&lt;/em&gt;. &lt;a href=&quot;http://www.radiocad.com/_downloads/LoadDumpPaper-final.pdf?PHPSESSID=hfh147l&quot; rel=&quot;nofollow&quot;&gt;This document&lt;/a&gt; claims a 12V system dump can be as high as 87V and 400ms long:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;&lt;pre&gt;&lt;code&gt;       12V system      24V system&#xA;Us     65V to 87V      123V to 174V     // maximum voltage&#xA;Ri     0.5Ω to 4Ω      1Ω to 8Ω         // source resistance&#xA;td     40ms to 400ms   100ms to 350ms   // pulse length&#xA;tr     10ms??          5ms??            // rise time&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The last linked document also has a table listing TVS energy absorption, as follows:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Table 2 - Energy [J] absorbed (V&lt;sub&gt;clamp&lt;/sub&gt;=45V)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;td [ms]   source resistance [Ω]&#xA;     0.5    1     1.5   2     2.5   3     3.5   4&#xA; 50  18.57  9.62  6.26  4.50  3.41  2.68  2.17  1.80&#xA;100  37.15  19.23 12.51 8.99  6.83  5.36  4.34  3.59&#xA;150  55.72  28.85 18.77 13.49 10.24 8.04  6.51  5.39&#xA;200  74.30  38.46 25.02 17.98 13.65 10.72 8.68  7.18&#xA;250  92.87  48.08 31.28 22.48 17.07 13.40 10.85 8.98&#xA;300  111.44 57.69 37.53 26.98 20.48 16.08 13.02 10.77&#xA;350  130.02 67.31 43.79 31.47 23.89 18.76 15.19 12.57&#xA;400  148.59 76.92 50.05 35.97 27.31 21.44 17.37 14.3&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Now, I want to clamp much lower than 45V (say 20V), and would like to recalculate these values. The author writes:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;Calculated using the method given in &lt;a href=&quot;http://xenona.com/xenonaupl/AHDPO/EMC/ISO/ISO_7637-2_2004.pdf&quot; rel=&quot;nofollow&quot;&gt;Annex E.1.1.(e)&lt;/a&gt;&#xA;  where R&lt;sub&gt;i&lt;/sub&gt;=R&lt;sub&gt;L&lt;/sub&gt; (for maximum power transfer).&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This reveals the formula:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;W&lt;sub&gt;e&lt;/sub&gt; = (U&lt;sub&gt;s&lt;/sub&gt;)&lt;sup&gt;2&lt;/sup&gt; &lt;sub&gt;&lt;sup&gt;x&lt;/sup&gt;&lt;/sub&gt; t&lt;sub&gt;d&lt;/sub&gt; / R&lt;sub&gt;i&lt;/sub&gt; / 4.6&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;... And updates the table as follows:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Energy [J] absorbed (V&lt;sub&gt;clamp&lt;/sub&gt;=20V)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;&lt;pre&gt;&lt;code&gt;td [ms]   source resistance [Ω]&#xA;     0.5    1      1.5    2      2.5    3      3.5    4&#xA; 50  97.59  48.79  32.53  24.40  19.52  16.26  13.94  12.20&#xA;100  195.17 97.59  65.06  48.79  39.03  32.53  27.88  24.40&#xA;150  292.76 146.38 97.59  73.19  58.55  48.79  41.82  36.60&#xA;200  390.35 195.17 130.12 97.59  78.07  65.06  55.76  48.79&#xA;250  487.93 243.97 162.64 121.98 97.59  81.32  69.70  60.99&#xA;300  585.52 292.76 195.17 146.38 117.10 97.59  83.65  73.19&#xA;350  683.11 341.55 227.70 170.78 136.62 113.85 97.59  85.39&#xA;400  780.70 390.35 260.23 195.17 156.14 130.12 111.53 97.59&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This gives a maximum value of 781J. Did I do this correctly? My TVS system must absorb up to ~800J, passing nearly 30A? It seems like a heck of a lot, though it will be for up to 6 parallel semi truck batteries (~100AH each) in addition to its 130A+ alternator. (Could the source resistance be even lower than 0.5Ω?) &lt;strong&gt;What combination of TVS elements can effectively pass 800J without violating its clamping voltage by much, and what makes it more effective than other solutions?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;sub&gt;I am protecting low-voltage digital and analog circuitry, which also have their own power filtering.&lt;/sub&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-09T16:42:40.563" LastActivityDate="2011-01-09T20:07:05.700" Title="How do I protect against an automotive load dump?" Tags="&lt;protection&gt;&lt;automotive&gt;&lt;tvs&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="3" />
  <row Id="8799" PostTypeId="2" ParentId="8794" CreationDate="2011-01-09T15:32:49.980" Score="1" ViewCount="" Body="&lt;p&gt;Define limited: weeks, months, centuries?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For most applications the answer would be no, as long as they have been stored in conditions within spec. If the capacitors have been in hot, or very cold regions for extended time, then the electrolyte might leak out under pressure, or dry out with time. There are electronic devices that are decades old and still working just fine, capacitors and all. Sitting unused is essentially the same behavior as &quot;shelf life.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having said that, there is some behavior with electrolytics where the plates are &quot;formed&quot; when power is first applied and after sitting idle for years may need to be re-formed again. This really hasn't been an issue with capacitors for decades, so unless you're trying to use a bunch of caps that have been sitting on a shelf since 1945, I wouldn't worry about it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have packages of various components that are approaching 20 years old and I don't think twice before using them in new circuits.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-01-09T15:32:49.980" />
  <row Id="8800" PostTypeId="2" ParentId="8794" CreationDate="2011-01-09T15:55:46.420" Score="8" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Aluminium Electrolytic Capacitors:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Epcos:&#xA;2 years, cf. &lt;a href=&quot;http://www.epcos.com/web/generator/Web/Sections/ProductCatalog/Capacitors/AluminumElectrolytic/PDF/PDF__GeneralTechnicalInformation,property=Data__en.pdf;/PDF_GeneralTechnicalInformation.pdf&quot; rel=&quot;nofollow&quot;&gt;this applications information&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cornell Dubilier:&#xA;3 years as per &lt;a href=&quot;http://www.cde.com/catalog/smt/storage.pdf&quot; rel=&quot;nofollow&quot;&gt;this document&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nichicon:&#xA;2 years; section 2-6 in &lt;a href=&quot;http://www.nichicon.co.jp/english/products/pdf/aluminum.pdf&quot; rel=&quot;nofollow&quot;&gt;this document&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Several documents say that longer storage is well possible, but will require reforming before use. Panasonic, amongst others, has a number: Apply the rated voltage via a series resistor of 1 kOhm for 30 minutes (see here: &lt;a href=&quot;http://www.panasonic.com/industrial/components/pdf/aluminum_app_dne.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.panasonic.com/industrial/components/pdf/aluminum_app_dne.pdf&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without reforming and by applying the rated voltage after a long storage duration, the reforming current might be so high that capacitors may get (too) warm and even blow up, which we do not like because we are not Beavis or Butt-Head (he he).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Tantalum Capacitors:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I couldn't find similar data after my initial search, but it seems like the usual MSL (moisture sensitivity levels) ratings for surface-mount parts are given and applicable.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-01-09T15:55:46.420" CommentCount="2" />
  <row Id="8801" PostTypeId="2" ParentId="8731" CreationDate="2011-01-09T15:58:19.230" Score="0" ViewCount="" Body="&lt;p&gt;Not difficult, but without drawing tools, this may be hard to describe.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Your launch mechanism is a coil spring with a rod through the center to keep it from bending. We'll assume there is a plate of some kind on the end that the cookie will sit on. A tab extends off the end of this plate. You'll need to drill a hole in the plate for the rod to pass through.&lt;/li&gt;&#xA;&lt;li&gt;Almost(1) parallel to the spring is a belt/wire that runs on two pulleys and is driven continuously by a motor. Gear down the motor as appropriate for the torque you need. Attach a hook to the belt.&lt;/li&gt;&#xA;&lt;li&gt;Arrange these two so with the spring extended, the hook is around the tab, nearest the plate.&lt;/li&gt;&#xA;&lt;li&gt;Remember we said the belt was &quot;almost&quot; parallel? Well, it's at enough of an angle so when the spring is fully retracted, the hook will slide off the end of the tab and the spring will fire.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In operation, the belt runs continuously. The hook grabs the tab and pulls the spring back, and as it does so, the hook is sliding down the length of the tab until the spring is fully compressed and the hook slides off the end of the tab, releasing the cocked spring. Now the hook just runs along the bottom and when it comes back around, it catches the tab again and the whole cycle repeats.&#xA;There are other ways, but this seems to be the easiest one to build.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[edit]&#xA;A simpler idea may be to use a disk that can fit inside a PVC tube with the spring behind it. Then just milling a slot along the length of the tube will allow the tab to protrude and make it easier to build. This is becoming interesting enough that I might make one for the heck of it.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastEditorUserId="2255" LastEditorDisplayName="" LastEditDate="2011-01-09T17:01:01.260" LastActivityDate="2011-01-09T17:01:01.260" />
  <row Id="8802" PostTypeId="2" ParentId="8798" CreationDate="2011-01-09T16:42:09.723" Score="3" ViewCount="" Body="&lt;p&gt;I can't speak to SAE J1113, but for SAE J1455 (12-V heavy truck, where the loads should be larger) the load dump is defined as a 100 V peak with about ~0.6 s fall time and ~0.6 Ω impedance, which is a pain to live through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The two broad methods to survive are either &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Disconnect yourself and let it pass:&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Which is usually preferable and cheaper.  Load dumps are in a class of faults that many devices &lt;em&gt;are not expected to operate during&lt;/em&gt; (unlike coupled inductive transients), so unless you're some critical device (ABS, ECU), you're allowed to shut down and reset when you see a load dump.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Very broadly speaking, to do this you could have a Zener diode on your input, where once it breaks down and starts conducting, switches some pass transistor to disconnect yourself entirely.  Obviously your pass transistor will have some voltage rating, so selecting a TVS is still needed (see following), but it won't have to clamp anywhere near as much voltage, energy, and power.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;clamp the whole thing.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This is also quite possible with TVS as you mention, and then it really depends on how hard you want to clamp it.  If you're fine with 75 V coming through, I think I've seen 500 W SMC's used.  If you want it like almost nothing ever happened, you can do as I've seen and use (2) 5 kW &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=5KP22CALFCT-ND&quot; rel=&quot;nofollow&quot;&gt;5KP22CA&lt;/a&gt; TVS in parallel.  They alone can clamp the entire load dump themselves; I've tested a pair that survived (5) 100 V dumps in a row, about 10 seconds apart between each.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The math behind it is somewhat hazy to me, as the figures provided on the datasheets don't seem as though they were meant for transients any slower than 60 Hz.  The 5 KW rating is for a 1 ms pulse, which is obviously just 5 J.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The peak energy it dissipates will be &lt;code&gt;(100 V - 24 V)/0.4 ohms * 24 V = 4560 W&lt;/code&gt;, but this will decay roughly exponentially to nothing with a tc of about 300 msec.  If we just call that a triangle (very conservative), it's &lt;code&gt;0.5 * 4560 W * 0.3 s = 684 J&lt;/code&gt;.  If we extrapolate the Figure 1 rating curve on the 5KP datasheet, it suggests that a 100 ms pulse can have a maximum power rating 1000 W, or total energy of 100 J, and even more energy if we smear it out further, so we're in the ball park with 2 of them in parallel and tests seem to bore it out.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Littelfuse 5KP-series TVS datasheet, Figure 1&lt;/strong&gt;&#xA;  &lt;img src=&quot;http://i.imgur.com/aN47E.png&quot; alt=&quot;&quot;&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If you wanted something better, I'd come up with an equation for the curve and give it an asymptote at the maximum steady-state dissipation (8 W...though that might not make a difference), then do some integration with that over your pulse to see how much of the rating you use up :P&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-09T16:42:09.723" />
  <row Id="8803" PostTypeId="2" ParentId="8786" CreationDate="2011-01-09T17:31:18.853" Score="2" ViewCount="" Body="&lt;p&gt;The MQ-2 Flammable Gas/Smoke sensor might be what you are looking for.&lt;br&gt;&#xA;Datasheet: &lt;a href=&quot;http://www.pololu.com/file/download/MQ2.pdf?file_id=0J309&quot; rel=&quot;nofollow&quot;&gt;http://www.pololu.com/file/download/MQ2.pdf?file_id=0J309&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is one source: &lt;a href=&quot;http://www.pololu.com/catalog/product/1480&quot; rel=&quot;nofollow&quot;&gt;http://www.pololu.com/catalog/product/1480&lt;/a&gt;&lt;br&gt;&#xA;They also have a carrier board to make it easy to interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It does not provide a digital interface, but provides an analog voltage that could easily be read by the ATMEGA168/ATMEGA328&lt;/p&gt;&#xA;" OwnerUserId="2489" LastActivityDate="2011-01-09T17:31:18.853" />
  <row Id="8804" PostTypeId="2" ParentId="8793" CreationDate="2011-01-09T17:50:08.317" Score="2" ViewCount="" Body="&lt;p&gt;No. It can be anywhere from 0% to 100% depending on load &amp;amp; motor specifics.&#xA;If you need 50%, you need some feedback, like shunt with opamp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;//RPM counting using optical-interrupter&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-01-10T00:31:50.623" LastActivityDate="2011-01-10T00:31:50.623" CommentCount="3" />
  <row Id="8805" PostTypeId="2" ParentId="8794" CreationDate="2011-01-09T17:52:45.983" Score="3" ViewCount="" Body="&lt;p&gt;With electrolytic caps you should &lt;strong&gt;always&lt;/strong&gt; pass them through LCR meter for C &amp;amp; ESR check (unless you are using new caps from top-end supplier).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As long as you see that C &amp;amp; ESR match your requirement with some margin you can use this cap no matter how old is it. This way it's safe so reuse used caps too. Just validate them all.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-09T17:52:45.983" CommentCount="1" />
  <row Id="8806" PostTypeId="2" ParentId="8786" CreationDate="2011-01-09T18:10:41.763" Score="1" ViewCount="" Body="&lt;p&gt;Microchip make the required ICs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=9032&amp;amp;mid=11&amp;amp;lang=en&amp;amp;pageId=79&quot; rel=&quot;nofollow&quot;&gt;For photo detection&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=9035&amp;amp;mid=11&amp;amp;lang=en&amp;amp;pageId=79&quot; rel=&quot;nofollow&quot;&gt;For ionisation detection&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-09T18:10:41.763" />
  <row Id="8807" PostTypeId="1" CreationDate="2011-01-09T19:12:06.163" Score="1" ViewCount="140" Body="&lt;p&gt;I have an idea of an electronic device, some kind of a gadget. It will have a bluetooth chip, some memory in it, some led indicators and some controlling chips, not sure yet how it should be constructed. What I need now is to estimate an approximate cost of the gadget hardware itself including the board, chips and the plastic case. What is a good way to calculate the cost?&lt;/p&gt;&#xA;" OwnerUserId="2543" LastActivityDate="2011-01-11T23:23:33.483" Title="How to estimate the cost for creating a device for test purposes" Tags="&lt;pic&gt;&lt;hardware&gt;" AnswerCount="4" CommentCount="6" />
  <row Id="8808" PostTypeId="1" AcceptedAnswerId="8880" CreationDate="2011-01-09T19:32:04.407" Score="1" ViewCount="272" Body="&lt;p&gt;I have been using two &lt;a href=&quot;http://www.loc8tor.com/Store/product/Loc8tor-Lite,154,110.aspx&quot; rel=&quot;nofollow&quot;&gt;Loc8tor&lt;/a&gt; devices (an active, highly directional RFID consumer device) on a personal robot to try to locate an RFID tag.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While the Loc8tor has served its purpose of showing an active, directional RFID sensor with high resolution can be used for locating an RFID tag, the Loc8tor itself is not very hacker friendly. I am looking for an alternative reader and tag that can be integrated into my robot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally, it would meet the following specifications:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Each reader would be less than $100, cheaper is definitely better&lt;/li&gt;&#xA;&lt;li&gt;The reader should be around the size of a credit card to a dollar bill&lt;/li&gt;&#xA;&lt;li&gt;The tag will be placed in ranges of 0.5 to 3 meters from the reader&lt;/li&gt;&#xA;&lt;li&gt;The reader should run on some voltage less than 5v, ideally 3.3v or less&lt;/li&gt;&#xA;&lt;li&gt;The higher the resolution of the reader, the better. Say 3 cm resolution at a 1 meter distance.&lt;/li&gt;&#xA;&lt;li&gt;The (RSSI?) value from the sensor is easily accessible. Meaning I could wire that into an Arduino input pin and use the value.&lt;/li&gt;&#xA;&lt;li&gt;Could buy in small (1 to 2) or large quantities (100+)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;These specifications are ideal, but not all are required (though the price is the most important). I should hopefully be able to list better specifications after I see what alternatives are out there.&lt;/p&gt;&#xA;" OwnerUserId="2542" LastEditorUserId="2542" LastEditorDisplayName="" LastEditDate="2011-01-09T19:54:58.013" LastActivityDate="2011-01-11T07:16:07.523" Title="Recommendations for an active, directional RFID sensor" Tags="&lt;arduino&gt;&lt;rfid&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="8809" PostTypeId="2" ParentId="8807" CreationDate="2011-01-09T19:43:11.553" Score="2" ViewCount="" Body="&lt;p&gt;A ballpark figure for the manufacturing cost can be obtained by multiplying the parts cost by 3 to 5.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-09T19:43:11.553" />
  <row Id="8810" PostTypeId="2" ParentId="8807" CreationDate="2011-01-09T19:53:27.313" Score="1" ViewCount="" Body="&lt;p&gt;Estimating project cost is an art. It can be guesstimated by kludging together development time, parts and manufacturing cost. Time really is money, so the first thing to do is break down how long each part of the development cycle is going to take, &lt;strong&gt;then multiply by 3X.&lt;/strong&gt; Only you know how much your time is worth -- I go by 5CAD/hr-15CAD/hr for personal projects, 25CAD/hr-50CAD/hr for contract work (experienced EE's use 100-200/hr). As &lt;a href=&quot;http://electronics.stackexchange.com/questions/8807/how-to-estimate-the-cost-for-creating-a-device-for-test-purposes/8809#8809&quot;&gt;Leon mentioned&lt;/a&gt;, multiply parts cost by ~3X for manufacturing, including enclosure.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-09T19:53:27.313" />
  <row Id="8811" PostTypeId="2" ParentId="8807" CreationDate="2011-01-09T19:54:50.877" Score="3" ViewCount="" Body="&lt;p&gt;Here is what I use for estimates, they are not accurate by any means be at least gives me an idea:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;$0.50 per part to be soldered&lt;/li&gt;&#xA;&lt;li&gt;$300-$400 for a PCB order under a quantity of 100. Divide by the number of boards you want to get the cost per board&lt;/li&gt;&#xA;&lt;li&gt;If you already know what parts you are using, add up their cost&lt;/li&gt;&#xA;&lt;li&gt;Add on an extra buffer to account for all of the stuff you haven't thought of&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-09T19:54:50.877" CommentCount="13" />
  <row Id="8812" PostTypeId="2" ParentId="8798" CreationDate="2011-01-09T20:07:05.700" Score="3" ViewCount="" Body="&lt;p&gt;Here is how you can protect against an automotive load dump&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1142,C1029,P38400&quot; rel=&quot;nofollow&quot;&gt;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1142,C1029,P38400&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-01-09T20:07:05.700" CommentCount="2" />
  <row Id="8813" PostTypeId="1" AcceptedAnswerId="8814" CreationDate="2011-01-09T20:26:25.867" Score="3" ViewCount="119" Body="&lt;p&gt;What are the best practices for recharging a 12V lead acid battery with a manual recharger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a 12V lead acid battery (7.2AH/20HR &lt;a href=&quot;http://www.mkbattery.com/images/ES7-12.pdf&quot; rel=&quot;nofollow&quot;&gt;MK ES7-12&lt;/a&gt; (PDF)). I've read the advice here on &lt;a href=&quot;http://electronics.stackexchange.com/questions/5522/battery-level-how-to-check&quot;&gt;how to check the battery level&lt;/a&gt; (I have ~12.2 V under no stress, and when powering the system it still currently reads ~12.2 V on the DMM).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When it starts to run low, I'd like to know how best to recharge the battery. I have a manual battery charger (&lt;a href=&quot;http://www.batterychargers.com/ProductDetail.aspx?ProductName=94026702&quot; rel=&quot;nofollow&quot;&gt;Schumacher MC-1&lt;/a&gt;). I realize the &lt;strong&gt;manual&lt;/strong&gt; part means that I cannot just plug the battery in and walk away. How best to monitor the charge? With what frequency? What likely problems should I be aware of?&lt;/p&gt;&#xA;" OwnerUserId="1774" LastActivityDate="2011-01-09T22:23:23.810" Title="How to recharge a battery with a manual battery charger" Tags="&lt;battery&gt;&lt;battery-charging&gt;" AnswerCount="1" />
  <row Id="8814" PostTypeId="2" ParentId="8813" CreationDate="2011-01-09T22:23:23.810" Score="2" ViewCount="" Body="&lt;p&gt;Not many issues charging big lead acids. Just hook the sucker up, turn it on, wait a while, test the battery for either loaded voltage or charge current (&amp;lt;0.3A), then disconnect or continue. Some issues I've had with standard sealed lead acids:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Killing the battery separates the water from solute, which can then freeze. This happens if it dies in the cold. It's basically pooched at this point, but there's nothing stopping you from trying to thaw it out and charge it back up. Sometimes they still work!&lt;/li&gt;&#xA;&lt;li&gt;Don't use the &lt;em&gt;boost&lt;/em&gt; function, if there is one, to attempt to charge the battery more quickly than usual. This is strictly for boosting, and will reduce a battery's MTTF. Note that maximum charge current is 2.16A.&lt;/li&gt;&#xA;&lt;li&gt;Charge it in a ventilated area. I know it's sealed, but I do this anyway, just in case!&lt;/li&gt;&#xA;&lt;li&gt;Don't put it on a concrete floor -- stick a piece of cardboard or wood under it. This has been proven a myth a dozen times over, but I still do it to keep Murphy at bay.&lt;/li&gt;&#xA;&lt;li&gt;Don't use too large a maintenance charge. The battery datasheet states 13.5V-13.8V float voltage.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Why did you get a manual charger, anyway? I'd definitely screw that up within a season.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-09T22:23:23.810" CommentCount="6" />
  <row Id="8815" PostTypeId="2" ParentId="8808" CreationDate="2011-01-10T00:27:29.830" Score="0" ViewCount="" Body="&lt;p&gt;Let me show some skepticism here - RFID frequencies are so low, that any directional antennas would completely fail (on small robots). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would recommend to do the following: 1 usual RFID reader forcing your tag to reply + 3-4 simple(dumb) manual RF receivers tuned on your RFID frequency. Then you detect the signal on each of receivers, average it with low-pass filter &amp;amp; measure with precision ADC (16-bit should be enough). Then you'll be able to calculate (more-or-less) exact direction to the tag.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will be definitely cheaper than 100$.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-10T00:27:29.830" CommentCount="2" />
  <row Id="8816" PostTypeId="2" ParentId="8793" CreationDate="2011-01-10T01:15:40.140" Score="2" ViewCount="" Body="&lt;p&gt;Average current may well be half (not always), but instantaneous current could also be (not always) 100%. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had some 3V motors I was PWMing from a 12V supply a couple of years back. PWM'ing them worked well in staying within the RPM range of those motors, but the instantaneous voltage/current wore out the brushes pretty quickly.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-01-10T01:15:40.140" />
  <row Id="8818" PostTypeId="2" ParentId="8794" CreationDate="2011-01-10T02:23:49.717" Score="0" ViewCount="" Body="&lt;p&gt;They definitely have a use-by date. A few years at best, eventually the electrolyte disintegrates.&lt;/p&gt;&#xA;" OwnerUserId="2488" LastActivityDate="2011-01-10T02:23:49.717" CommentCount="4" />
  <row Id="8820" PostTypeId="2" ParentId="8163" CreationDate="2011-01-10T03:51:05.563" Score="7" ViewCount="" Body="&lt;p&gt;There is a project developed by David Jurick, Adam Stolarz, Damien Stolarz that is described in the book &lt;a href=&quot;http://oreilly.com/catalog/9780596516642/&quot; rel=&quot;nofollow&quot;&gt;iPhone Hacks&lt;/a&gt;. They use the audio jack as a Frequency Shift Keying (FSK) modem that operates at about 1200 baud. Their project interfaces with a Cypress PSoC microcontroller to convert the audio signal to RS232. &lt;a href=&quot;http://www.perceptdev.com/labs/iphonehacks&quot; rel=&quot;nofollow&quot;&gt;Source Code&lt;/a&gt; can be found at the www.perceptdev.com site.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A similar project using an Arduino to convert the signal can be found &lt;a href=&quot;http://sree.cc/iphone/iphone-as-temperature-detector&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another project called &lt;a href=&quot;http://eecs.umich.edu/~prabal/projects/hijack/&quot; rel=&quot;nofollow&quot;&gt;HiJack&lt;/a&gt; harvests power and bandwidth from the iPhone's audio jack.&lt;/p&gt;&#xA;" OwnerUserId="2489" LastEditorUserId="2489" LastEditorDisplayName="" LastEditDate="2011-01-15T04:48:40.490" LastActivityDate="2011-01-15T04:48:40.490" CommentCount="1" />
  <row Id="8821" PostTypeId="2" ParentId="8741" CreationDate="2011-01-10T04:40:51.577" Score="2" ViewCount="" Body="&lt;p&gt;Here's some examples:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.globefan.com/new_product.htm&quot; rel=&quot;nofollow&quot;&gt;M0802512&lt;/a&gt; -- &lt;em&gt;&quot;Life Time: On-going testing&quot;&lt;/em&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sunon.com.tw/products/pdf/maglev.pdf&quot; rel=&quot;nofollow&quot;&gt;Sunon Maglev&lt;/a&gt; -- N/A (&lt;a href=&quot;http://www.sunon.com/uFiles/file/03_products/08-catalog%20download/DR_en.pdf&quot; rel=&quot;nofollow&quot;&gt;two sources&lt;/a&gt;)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In comparison to these non-magnetic bearing statistics:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Sintec sleeve: &lt;a href=&quot;http://img.ebmpapst.com/products/datasheets/412FH-ENG.pdf&quot; rel=&quot;nofollow&quot;&gt;45'000h @ 20&lt;sup&gt;o&lt;/sup&gt;C; 15'000h @ 60&lt;sup&gt;o&lt;/sup&gt;C&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Superflo: &lt;a href=&quot;http://media.digikey.com/pdf/Data%20Sheets/Delta%20PDFs/AUB0912VH-CIT.pdf&quot; rel=&quot;nofollow&quot;&gt;50'000h @ 40&lt;sup&gt;o&lt;/sup&gt;C&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Ball: &lt;a href=&quot;http://media.digikey.com/pdf/Data%20Sheets/Delta%20PDFs/EFC0812DB-F00.pdf&quot; rel=&quot;nofollow&quot;&gt;70'000h @ 40&lt;sup&gt;o&lt;/sup&gt;C&lt;/a&gt;; &lt;a href=&quot;http://www.eminebea.com/content/pdf/TMP00123/I/2410rl.pdf&quot; rel=&quot;nofollow&quot;&gt;40'000h @ 25&lt;sup&gt;o&lt;/sup&gt;C&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;HydroWave: &lt;a href=&quot;http://www.eminebea.com/content/pdf/TMP00123/I/fba09a.pdf&quot; rel=&quot;nofollow&quot;&gt;50'000h @ 40&lt;sup&gt;o&lt;/sup&gt;C&lt;/a&gt;&lt;br&gt;&lt;sub&gt;&lt;strong&gt;&lt;em&gt;Note: 1 year = 8766 hours.&lt;/em&gt;&lt;/strong&gt;&lt;/sub&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Looks like traditional bearing MTTF wins! My point is that at the moment this technology is marketing fluff, regardless of its merits. Real MTTF numbers will tell the story... not that &lt;em&gt;these&lt;/em&gt; are real numbers: take them with a grain of salt, as they are subject to lawyer jibbajabba and marketing hype. &lt;sup&gt;&lt;em&gt;(And no, that doesn't mean manufacturers have to wait 70'000h+ to characterize MTTF -- it is characterized much earlier using techniques to speed up the working hours.)&lt;/em&gt;&lt;/sup&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-10T14:45:06.947" LastActivityDate="2011-01-10T14:45:06.947" CommentCount="2" />
  <row Id="8822" PostTypeId="1" AcceptedAnswerId="8964" CreationDate="2011-01-10T05:06:59.440" Score="1" ViewCount="121" Body="&lt;p&gt;What solutions are there, preferably single chip solutions, for getting HD video over DVI/HDMI?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My googling is not giving me much, only about the Blackfin chip from Analog.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know about the Propellor from Parallax and that it can give SD video out easily, and how FPGA's can do it too, but other than those three I do not know of any other single chip solutions that can give me HD video over DVI/HDMI.&lt;/p&gt;&#xA;" OwnerUserId="2050" LastEditorUserId="2050" LastEditorDisplayName="" LastEditDate="2011-01-10T05:13:39.237" LastActivityDate="2011-01-13T09:10:04.680" Title="What solutions are there for getting HD video?" Tags="&lt;video&gt;&lt;hd&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="8824" PostTypeId="1" AcceptedAnswerId="8913" CreationDate="2011-01-10T09:17:26.450" Score="2" ViewCount="235" Body="&lt;p&gt;I'd like to find a source for extruded aluminum profiles for use as cases, in Europe, like this &lt;a href=&quot;http://www.lincolnbinns.com/e-case-d.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.lincolnbinns.com/e-case-d.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems to me that it ought to be possible to buy a good length (3 m) of extrusion and chop it into cases as needed, but so far I've only found suppliers of pre-cut and crazy expensive cases.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically I'd like a profile with space for a 100 mm wide and 20-50 mm high PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there really not any suppliers that will sell the profiles in bulk?&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-01-11T23:10:03.327" Title="Extruded aluminium cases" Tags="&lt;cases&gt;&lt;enclosure&gt;&lt;aluminum&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="8825" PostTypeId="1" CreationDate="2011-01-10T09:55:42.987" Score="3" ViewCount="155" Body="&lt;p&gt;So I'm looking to get some LM335 ICs to measure temperature, and I'm confronted by &quot;LM335A&quot; and &quot;LM335Z&quot; models (and possibly others).  Ordinarily I wouldn't think much of it, but there seems to be a reasonable price difference (the Z is about twice the price of the A).  I've tried googling and reading the LM335 datasheet, but I can't seem to figure out the difference between the two.  Or is there no practical difference?  Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="2553" LastActivityDate="2011-01-10T11:32:40.003" Title="Difference between LM335A and LM335Z?" Tags="&lt;lm335&gt;" AnswerCount="1" />
  <row Id="8828" PostTypeId="2" ParentId="8822" CreationDate="2011-01-10T10:31:37.353" Score="1" ViewCount="" Body="&lt;p&gt;An FPGA comes to mind. Jeri Ellsworth has demonstrated an FPGA driving a VGA monitor at 1024x768, which isn't HD, but it shouldn't be too much extra to reach 1280x720, or even 1920x1080. The problem you might encounter is that HDMI uses differential high speed signalling, and it's digital, unlike VGA, which is analog. With VGA, you might be able to get away with a bit of a noisy signal or high capacitive load... probably not so much with HDMI.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-10T10:31:37.353" />
  <row Id="8829" PostTypeId="2" ParentId="8825" CreationDate="2011-01-10T11:32:40.003" Score="7" ViewCount="" Body="&lt;p&gt;The two models are &lt;code&gt;LM335&lt;/code&gt;, and &lt;code&gt;LM335A&lt;/code&gt;. The &lt;code&gt;Z&lt;/code&gt; suffix indicates package type.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this case, the &lt;code&gt;A&lt;/code&gt; version has an &quot;Uncalibrated Temperature Error&quot; of 1°c nominal, 3°c max, while the non &lt;code&gt;A&lt;/code&gt; version is 2°c nominal, 6°c max.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is all in the datasheet, which you should read if you are thinking about implementing a circuit using this device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet is &lt;a href=&quot;http://www.national.com/profile/snip.cgi/openDS=LM335&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. The specs which differentiate the two models are primarily on page two.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Manufacturers almost universally offer varying accuracy grades with temperature sensors. This is an example.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-01-10T11:32:40.003" CommentCount="1" />
  <row Id="8830" PostTypeId="1" CreationDate="2011-01-10T11:33:29.070" Score="2" ViewCount="237" Body="&lt;p&gt;I am doing a project in which I use 230V mains to charge a battery. If mains power is down, I have to use solar power for charging; and if the solar power is not good I have to switch to the diesel generated power. I have to do this using a microcontroller. Also, I should display the the source with which the battery is being sourced on a lcd  display. How do I do this?&lt;/p&gt;&#xA;" OwnerUserId="2556" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-10T18:00:06.440" LastActivityDate="2011-01-10T18:54:25.873" Title="Switching between 3 power sources using a microcontroller" Tags="&lt;power&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="8831" PostTypeId="2" ParentId="8824" CreationDate="2011-01-10T11:47:30.280" Score="2" ViewCount="" Body="&lt;p&gt;Companies like that design their own extruded material and have it manufactured in bulk. They are very different from standard extrusions, and therefore aren't generally available. You could do the same, but the die will be very expensive.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-10T11:47:30.280" />
  <row Id="8832" PostTypeId="2" ParentId="8794" CreationDate="2011-01-10T12:40:37.043" Score="0" ViewCount="" Body="&lt;p&gt;I know what I've seen. I've seen banks of ageing capacitors fail one by one year after year.&lt;/p&gt;&#xA;" OwnerUserId="2488" LastActivityDate="2011-01-10T12:40:37.043" CommentCount="1" />
  <row Id="8833" PostTypeId="2" ParentId="8747" CreationDate="2011-01-10T12:49:22.507" Score="0" ViewCount="" Body="&lt;p&gt;Lots of info to research can be found &lt;a href=&quot;http://www.google.com/custom?domains=amasci.com/&amp;amp;q=tesla+coil&amp;amp;sa=Search&amp;amp;sitesearch=amasci.com&amp;amp;client=pub-6310699831332590&amp;amp;forid=1&amp;amp;ie=ISO-8859-1&amp;amp;oe=ISO-8859-1&amp;amp;cof=GALT%3a%23008000;GL:1;DIV%3a%23336699;VLC:663399;AH%3acenter;BGC%3aFFFFFF;LBGC:336699;ALC:0000FF;LC:0000FF;T:000000;GFNT:0000FF;GIMP:0000FF;FORID:1;&amp;amp;hl=en&quot; rel=&quot;nofollow&quot;&gt;here.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2344" LastActivityDate="2011-01-10T12:49:22.507" CommentCount="1" />
  <row Id="8834" PostTypeId="1" AcceptedAnswerId="8845" CreationDate="2011-01-10T13:07:05.590" Score="7" ViewCount="461" Body="&lt;p&gt;To avoid public transport and the car, I decided to go to work on foot everyday but I have to pass a small, but dark (in the evening) and scaring wood.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if I use flashlights, I'd like to have a kind a &quot;life scanner&quot;, like the one used by Predator vs Alien to detect alive (hot/moving) creatures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Beside the sci fiction side of the question, I was wondering if PIR can be used while moving, so that I can mount on my backpack and control it with an arduino while I'm walking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's not possible, do you have any other ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I need it's just a way to know if there are alive, enough big to be scaring, creatures in the wilderness around me (for not alive creatures we will discuss later).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has pointed out, a good alternative can be an Infrared camera, there are some good tutorial and Howtos in the Net.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't need a detailed image, but just to know if and (more or less) where there are alive creatures (hot blood animals?), as an image sometime is better then 1000 words:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/JzqoH.png&quot; alt=&quot;Alien Radar&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit 2&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As it has been pointed out, is this feasible or it's just sci-fiction?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thermographic cameras exists and are widely used: &lt;a href=&quot;http://en.wikipedia.org/wiki/Thermographic_camera&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Thermographic_camera&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found a solution here &lt;a href=&quot;http://www.embedds.com/interactive-diy-infrared-and-ultrasonic-scanner/&quot; rel=&quot;nofollow&quot;&gt;http://www.embedds.com/interactive-diy-infrared-and-ultrasonic-scanner/&lt;/a&gt; , but the range is really small (21 inches = 0.5 meters)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit 3&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is another way to create a &quot;radar&quot; starting from a home made thermographic camera.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2009/07/01/poor-mans-thermographic-camera/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2009/07/01/poor-mans-thermographic-camera/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2557" LastEditorUserId="2557" LastEditorDisplayName="" LastEditDate="2011-01-11T15:16:34.527" LastActivityDate="2011-03-10T08:24:18.900" Title="Moving PIR sensor (or IR camera), aka Predator like alien scanner." Tags="&lt;arduino&gt;&lt;infrared&gt;&lt;safety&gt;" AnswerCount="4" CommentCount="6" FavoriteCount="1" />
  <row Id="8835" PostTypeId="2" ParentId="8747" CreationDate="2011-01-10T13:08:01.377" Score="2" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;The problem with MOTs is the voltage is too low to make a sparkgap work reliably. A pair is just-about doable but still not ideal. A neon-sign transformer is an easier and safer transformer for a first-time coil. &lt;/li&gt;&#xA;&lt;li&gt;Insulation and /or spacing &lt;/li&gt;&#xA;&lt;li&gt;A ground with a low inductance path, and one that will not damage anything if it sees a HV discharge to it. i.e.  not the ground pin on an AC outlet. Stake in the ground is ideal as long  as the cable length isn't very long. &lt;/li&gt;&#xA;&lt;li&gt;You won't need to do any measuraments on the HV side. You will know if there is HV present - corona hiss, ozone smell, arc-overs etc.  &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-10T15:52:29.927" LastActivityDate="2011-01-10T15:52:29.927" CommentCount="0" />
  <row Id="8836" PostTypeId="2" ParentId="2679" CreationDate="2011-01-10T13:20:51.497" Score="4" ViewCount="" Body="&lt;p&gt;Take a peek at Alibre Design. It's more affordable than the other options, and has a free trial. I bought it recently and I'm very satisfied. Not only it meets all of my needs, I compared it to Rhino, SolidWorks and others and found it way better, both in capabilities and user interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.alibre.com/products/mainpage.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.alibre.com/products/mainpage.asp&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1078" LastActivityDate="2011-01-10T13:20:51.497" CommentCount="1" />
  <row Id="8837" PostTypeId="2" ParentId="8781" CreationDate="2011-01-10T13:36:23.057" Score="0" ViewCount="" Body="&lt;p&gt;All of these answers have valid potential issues, especially Leon's point that analog pins can be tricky and W5VR's point about MCLR not being pulled high. Also - depending on your chip, you may need to write to the &lt;strong&gt;LATB&lt;/strong&gt; register for output and read from the &lt;strong&gt;PORTB&lt;/strong&gt; register for input. Docs on the difference between LATB and PORTB are iffy and in the pst I've had to use some trial and error to make it work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;LATB is the port B output latch. This will contain the most recent values that you wrote into the latch. Under some conditions (say, your output pin is heavily loaded) the actual value on that pin may drop quite low. This can cause an erroneous reading of PORTB, i.e. it will return 0 when it should return 1. Thus, it's safer to read LATB because this will still contain the 'correct' value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;@kellenjb: You should be able to run the program without removing the ICSP cable, IF you use Debug mode in MPLAB. Otherwise, if you build the project as Release, you will have to pull the cable out. Debug mode may not be supported for OP's programmer; it works on my Pickit2.&lt;/p&gt;&#xA;" OwnerUserId="2344" LastActivityDate="2011-01-10T13:36:23.057" CommentCount="1" />
  <row Id="8838" PostTypeId="2" ParentId="8834" CreationDate="2011-01-10T14:04:12.770" Score="3" ViewCount="" Body="&lt;p&gt;You may want an infrared camera and display module. &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.15756&quot; rel=&quot;nofollow&quot;&gt;This cheap security camera&lt;/a&gt; apparently works well up to 5 meters. It has its own IR LED cluster, requires a 12V (500mA) DC source, and outputs via RCA cables. One could connect a small screen like &lt;a href=&quot;http://www.dealextreme.com/details.dx/sku.15001&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;, with RCA inputs (also req's 12V DC source).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure what type of animals you're worried about, but it's generally true that they want to keep away! Make some noise -- this is where &lt;em&gt;&lt;a href=&quot;http://i.imgur.com/nPl8z.jpg&quot; rel=&quot;nofollow&quot;&gt;&quot;bear bells&quot;&lt;/a&gt;&lt;/em&gt; came from.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-10T14:29:03.040" LastActivityDate="2011-01-10T14:29:03.040" CommentCount="1" />
  <row Id="8839" PostTypeId="2" ParentId="2679" CreationDate="2011-01-10T14:32:45.840" Score="4" ViewCount="" Body="&lt;p&gt;I would also recommend Alibre Design PE, which is a bargain at $100.  I'd also like to add another option that is free (just like Blender), called &lt;a href=&quot;http://openscad.org/&quot; rel=&quot;nofollow&quot;&gt;OpenSCAD&lt;/a&gt;.  It is highly capable, and for doing simple PCB enclosures, I would pick it over Blender anyday because it's so much easier to understand.  In many cases (pardon the pun), I would use it instead of Alibre Design because you can share your designs more easily with the community.  It exports STL and DXF as well.  There's something really cool about changing a few variables in the code that generates your model, and getting back a new part that fits a new PCB.  Tweaking due to measurement errors is just as easy, provided that you wrote the code properly.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-01-10T14:32:45.840" CommentCount="2" />
  <row Id="8840" PostTypeId="2" ParentId="8830" CreationDate="2011-01-10T15:16:08.523" Score="1" ViewCount="" Body="&lt;p&gt;Required:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;method to measure voltage and current of each source&lt;/li&gt;&#xA;&lt;li&gt;method to switch between sources&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Mains monitoring can be done by measuring only voltage. To do this, I suggest you read &lt;a href=&quot;http://electronics.stackexchange.com/q/7728/2118&quot;&gt;How to connect 230V 50Hz to arduino analog input&lt;/a&gt;. Solar monitoring solutions can range from a simple current sense resistor to &lt;a href=&quot;http://en.wikipedia.org/wiki/Maximum_power_point_tracker&quot; rel=&quot;nofollow&quot;&gt;maximum power point trackers&lt;/a&gt;. It's up to you whether or not you need a generator monitor -- perhaps a simple &lt;em&gt;&quot;is it on?&quot;&lt;/em&gt; indicator. A switch solution depends entirely on the power requirements. For moderate to low power, I suggest you read &lt;a href=&quot;http://electronics.stackexchange.com/q/8409/2118&quot;&gt;Interfacing microcontroller and mains via a relay&lt;/a&gt;; high power will need more buffering. Each of the mentioned sources produce different types of electricity, so you need circuitry to address this, like a &lt;a href=&quot;http://www.xantrex.com/power-products/backup-power/xantrex-powerhub.aspx&quot; rel=&quot;nofollow&quot;&gt;Xantrex power hub&lt;/a&gt; or other AC-DC &amp;amp; DC-DC converters. Interfacing with an LCD is a different issue altogether, so start a new question with a specific LCD in mind and read &lt;a href=&quot;http://electronics.stackexchange.com/q/159/2118&quot;&gt;Serial Enabled LCD&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-10T15:16:08.523" />
  <row Id="8841" PostTypeId="2" ParentId="8216" CreationDate="2011-01-10T16:29:57.910" Score="1" ViewCount="" Body="&lt;p&gt;I know the question specifies that LEDs are the required illuminating device, but if you want to scale things up a bit, you can make a very convincing flame effect with a yellow 25w GLS incandescent bulb and a standard fluorescent tube starter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All you need to do, is connect the starter in series with the bulb, and it will happily flicker on and off indefinitely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connect a few bulbs, all with their own starters, and mix up the colours between yellow orange and red to make a nice warm fireglow effect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Very simple, and few parts required!&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-10T16:29:57.910" />
  <row Id="8842" PostTypeId="1" CreationDate="2011-01-10T16:45:41.867" Score="6" ViewCount="217" Body="&lt;p&gt;My fridge is sending bad clacks to my loudspeakers when it turns on/off, I fear for the tweeters. I'd add a snubber/suppressor to the compressor but my notions about RC filters from school are 15 years old and I have no idea how to dimension it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's an old european fridge, so mains are 220V 50Hz, and the compressor mentions two other values In=0.8 and Icc=6.3, which I suppose are nominal and startup current. Do I need to compute the motor inductance? What condensator/resistor values to pick? Is an RC snubber even the correct fix?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How to estimate the RC values for snubbing an A/C motor?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Trying another approach. I've found a some usual R/C values for suppressors. For instance &lt;a href=&quot;http://www.redlion.net/Products/Groups/NoiseSuppression/SNUB/Docs/12027.pdf&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; is 47ohm / 0.1µF, giving 33kHz of cutoff frequency... but the datasheet says up to 62Hz? Why is there 3 orders of magnitude difference ?&lt;/p&gt;&#xA;" OwnerUserId="2560" LastEditorUserId="2560" LastEditorDisplayName="" LastEditDate="2011-01-20T16:39:03.877" LastActivityDate="2011-01-20T16:39:03.877" Title="Sizing an RC snubber" Tags="&lt;power&gt;&lt;capacitor&gt;&lt;rc&gt;&lt;decoupling-capacitor&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="8843" PostTypeId="2" ParentId="8842" CreationDate="2011-01-10T16:59:19.817" Score="3" ViewCount="" Body="&lt;p&gt;You may want to consider using an &lt;a href=&quot;http://en.wikipedia.org/wiki/Inrush_current_limiter&quot; rel=&quot;nofollow&quot;&gt;NTC inrush limiter&lt;/a&gt; in series with the compressor instead of a snubber. Make sure you choose one well-sized for the steady-state current of the appliance. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may also wish to try putting an appropriately-sized &lt;a href=&quot;http://en.wikipedia.org/wiki/Varistor&quot; rel=&quot;nofollow&quot;&gt;metal-oxide varistor&lt;/a&gt; across the mains to clamp any badness generated by the compressor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A &lt;a href=&quot;http://en.wikipedia.org/wiki/Filter_capacitor&quot; rel=&quot;nofollow&quot;&gt;safety-recognized X-capacitor&lt;/a&gt; across the mains may also help suppress noise. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also &lt;a href=&quot;http://www.lcr-inc.com/catalog/095-02-series.pdf&quot; rel=&quot;nofollow&quot;&gt;off-the-shelf EMI filters&lt;/a&gt; that could help with the noise if you prefer a pre-fab solution. I would guess that the motors in a washing machine wouldn't be so different from those in a fridge from an EMI standpoint.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-01-10T20:54:14.167" LastActivityDate="2011-01-10T20:54:14.167" CommentCount="3" />
  <row Id="8844" PostTypeId="2" ParentId="8680" CreationDate="2011-01-10T17:21:27.360" Score="4" ViewCount="" Body="&lt;p&gt;After quite some research I figured it out myself and wanted to share my findings with you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;NFC card emulation types&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please bear in mind that NFC is still not a finished protocoll and changes are possible. This is just the list of what I found as the latest version. (Copied from &lt;a href=&quot;http://weblog.cenriqueortiz.com/touch-nfc/&quot; rel=&quot;nofollow&quot;&gt;C. Enrique Ortizes' blog&lt;/a&gt; on January 10, 2011)&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;NFC Forum Type 1 Tag Operation&#xA;Specification – Type 1 tag is based&#xA;on ISO14443A. Tags are read and&#xA;re-write capable; users can configure&#xA;the tag to become read-only. Memory&#xA;availability is 96 bytes and&#xA;expandable to 2 kbyte; communication&#xA;speed is 106 kbit/s.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;NFC Forum Type 2 Tag Operation&#xA;Specification – Type 2 tag is based&lt;br&gt;&#xA;on ISO14443A. Tags are read and&lt;br&gt;&#xA;re-write capable; users can configure&#xA;the tag to become read-only. Memory&lt;br&gt;&#xA;availability is 48 bytes and&lt;br&gt;&#xA;expandable to 2 kbyte; communication &#xA;speed is 106 kbit/s.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;NFC Forum Type 3 Tag Operation&#xA;Specification – Type 3 tag is based&lt;br&gt;&#xA;on the Japanese Industrial Standard&lt;br&gt;&#xA;(JIS) X 6319-4, also known as FeliCa.&#xA;Tags are pre-configured at&lt;br&gt;&#xA;manufacture to be either read and&lt;br&gt;&#xA;re-writable, or read-only. Memory&lt;br&gt;&#xA;availability is variable, theoretical&#xA;memory limit is 1MByte per service;&lt;br&gt;&#xA;communication speed is 212 kbit/s or &#xA;424 kbit/s.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;NFC Forum Type 4 Tag Operation&#xA;Specification – Type 4 tag is fully&lt;br&gt;&#xA;compatible with ISO14443A and B&lt;br&gt;&#xA;standards. Tags are pre-configured at&#xA;manufacture to be either read and&lt;br&gt;&#xA;re-writable, or read-only. Memory&lt;br&gt;&#xA;availability is variable, up to 32&lt;br&gt;&#xA;KBytes per service; communication&lt;br&gt;&#xA;speed is up to 424 kbit/s.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;NFC card emulation technology&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basicly a RFID card is emulated by a Java MIDlet using &lt;a href=&quot;http://jcp.org/en/jsr/detail?id=257&quot; rel=&quot;nofollow&quot;&gt;Contactless API (JSR 257)&lt;/a&gt;. That is able to access the place (either SIM card, a smart card, a secure internal memory, or a secure external memory) where the emulation information is saved.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The exact how and wheres of NFC card emulation seem to be a matter of intense discussion right now as there are two basic concepts that directly correspondent with my second question (provider vs manufracture (vs user)). That this discussion makes a right answer very hard and fundamental changes can also happen is best shown by this example: &lt;a href=&quot;http://java.sun.com/developer/technicalArticles/javame/nfc/&quot; rel=&quot;nofollow&quot;&gt;Sun's official developer introduction to NFC&lt;/a&gt; uses an older copy of a graph from &lt;a href=&quot;http://weblog.cenriqueortiz.com/touch-nfc/&quot; rel=&quot;nofollow&quot;&gt;C. Enrique Ortiz&lt;/a&gt; to explain how card emulation mode works, that now is completly outdated and wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The GSMA pushes for the simcard to be the storage of the smart card information giving the provider total controll over NFC card emulation. I personally would favour a solution among the lines of &quot;make everything possible&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Programming Approaches&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While searching for programming examples I found out that with the currently available NFC enabled devices (mainly from Nokia) that there is one always stated advice: One MIDlet per RFID card issuer (Assuming that cards from the same issuer are from the same type and work alike).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since there is no final decision on where to store the smart card information, implementations go as far as having a download manager to download various smartcards to emulate over the internet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Manufracture / Provider limitations&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems possible that a manufracture can implement as much NFC functionality as he wants. Nexus S, if not updated to Android 2.3.3, for example has has only TAG reading functionality.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it would be decided that the sim card should be the only storage area for card information, space limitations can become a problem, especially if you want to emuluate several cards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This has been just a quick summary of what I found out and will probably be wrong because of NFC protocoll changes in the future, but for now I hope it helps some one that askes the same questions as me.&lt;/p&gt;&#xA;" OwnerUserId="2510" LastEditorUserId="2510" LastEditorDisplayName="" LastEditDate="2011-03-19T18:42:32.563" LastActivityDate="2011-03-19T18:42:32.563" CommentCount="1" />
  <row Id="8845" PostTypeId="2" ParentId="8834" CreationDate="2011-01-10T17:24:39.760" Score="5" ViewCount="" Body="&lt;p&gt;PIR sensors usually have 2-4 pixels.  That, coupled with the intended optics that appear to be designed with &quot;blind spots&quot; (so something moving in/out of them will cause a change) wouldn't really be that helpful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As tyblu suggests, an IR camera&amp;mdash;the cheap ones are NIR, not LWIR (thermal)&amp;mdash;may be more helpful, and may even be able to couple it with some FPV (first-person view) goggles for R/C aircraft to make your own hack NVGs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, some FPV goggles and IR cameras can be kinda spendy, so paying just a little more for the convenience (batteries, mechanical package, etc) of some commercial NVGs (or just a scope) might be worth it.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-10T17:24:39.760" CommentCount="2" />
  <row Id="8846" PostTypeId="1" CreationDate="2011-01-10T18:00:28.747" Score="1" ViewCount="118" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First of all, I am a total newbie to image processing. I have a project idea, part of which will involve doing the following&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;I have a white board and a camera (a normal webcam by z-star). I will draw a shape&#xA;on the white board. The camera will capture the video and process it to identify&#xA;the shape I have drawn. To keep it simple, the shapes that can be identified using&#xA;by the program will be limited.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I want to execute this idea and will learn anything that is required to make it happen. I want to get started in image processing, but just enough so I can execute this for now. Will incrementally study more. Can you give me any pointers on where to get started?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2011-01-10T20:37:32.060" Title="I want to learn enough image and video processing to execute a project idea, pointers?" Tags="&lt;learning&gt;&lt;imageprocessing&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="8847" PostTypeId="2" ParentId="8846" CreationDate="2011-01-10T18:08:25.010" Score="0" ViewCount="" Body="&lt;p&gt;I have no idea how to do it, but maybe you could interface with the new xbox 360 Kinetic device to capture and recognise the shapes.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-10T18:08:25.010" CommentCount="5" />
  <row Id="8848" PostTypeId="1" CreationDate="2011-01-10T18:50:31.387" Score="3" ViewCount="93" Body="&lt;p&gt;Is there any GPS tracker available in which I can set server's location (some IP) to which that device will send notifications (GPS data).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to create my own GPS receiver server.&lt;/p&gt;&#xA;" OwnerUserId="2563" LastActivityDate="2011-01-11T05:03:02.983" Title="customize server in GPS Tracker" Tags="&lt;gps&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="1" />
  <row Id="8849" PostTypeId="2" ParentId="8830" CreationDate="2011-01-10T18:54:25.873" Score="2" ViewCount="" Body="&lt;pre&gt;&lt;code&gt;o-------------+--- &amp;gt;| ---- + ---------- power output&#xA;              |            |&#xA;3 sources     |            |&#xA;o---------+---|--- &amp;gt;| ---- + &#xA;          |   |            |&#xA;          |   |            |&#xA;o-----+---|---|--- &amp;gt;| -----/&#xA;      |   |   |&#xA;      |   |   |&#xA;      measure here (digital inputs with proper resistors)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;beter use Schottky diodes&lt;/p&gt;&#xA;" OwnerUserId="2471" LastActivityDate="2011-01-10T18:54:25.873" CommentCount="1" />
  <row Id="8850" PostTypeId="2" ParentId="8848" CreationDate="2011-01-10T19:09:35.013" Score="3" ViewCount="" Body="&lt;p&gt;Your question is a bit ambiguous, but I think what you're asking is:  Is there a way to track entities that send out location information by having them send their data to a server?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Essentially, you need some method of:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A) Figuring out where on earth you are (you use a GPS receiver for that)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;B) Way to send that information to like a server somewhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C) A server that handles and manages that information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Automatic_Packet_Reporting_System&quot; rel=&quot;nofollow&quot;&gt;APRS&lt;/a&gt;, an amateur radio service, supports doing this.  For example, from reporting stations, you can plot their &lt;a href=&quot;http://aprs.fi&quot; rel=&quot;nofollow&quot;&gt;locations on a map&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2011-01-10T19:09:35.013" CommentCount="3" />
  <row Id="8851" PostTypeId="2" ParentId="8846" CreationDate="2011-01-10T20:04:52.103" Score="3" ViewCount="" Body="&lt;p&gt;A good place to start would be to use OpenCV for video processing: &lt;a href=&quot;http://opencv.willowgarage.com/wiki/&quot; rel=&quot;nofollow&quot;&gt;http://opencv.willowgarage.com/wiki/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a book published by O'Reilly &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596516134&quot; rel=&quot;nofollow&quot;&gt;Learning OpenCV: Computer Vision with the OpenCV Library&lt;/a&gt; that would probably be a big help.&lt;/p&gt;&#xA;" OwnerUserId="2489" LastActivityDate="2011-01-10T20:04:52.103" />
  <row Id="8852" PostTypeId="2" ParentId="8846" CreationDate="2011-01-10T20:37:32.060" Score="0" ViewCount="" Body="&lt;p&gt;There are a few steps here that need to be taken.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Identify the area you care about. This means either positioning the camera to only include the white board or to do some cropping on your image. If you use black and white images, you can think of them as a 3d array. For cropping you can just say that you will start at column 15 and end at column 506 in order to crop left and right.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Now that you have identified the area, you will probably need to do some edge detection. In the simplest sense, edge detection is looking for drastic changes in one pixel to the next. There are ways of doing this &quot;pretty&quot;, but for someone that wants to keep it simple you could step through each row of each pixel looking for a jump in value. You may even have to compare to several previous versions depending on how sharp your image is. Create a 3d array that is the same size as your original image. Whenever you see a jump, place some value in your new array. This value could be boolean for simplistic sake or it could be some range that represents how big of jump there was.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Now that you have an array that tells you where there are edges it is time to figure out what shape it is. There is a chance you will need to do some filtering on your data before this, but in a perfect world your previous step should just give you whatever you need to know. This is probably the most difficult part. You will need to find someway to define what each object is in a way that a computer can understand. An example of this would be to scan each row, once you find a row that has an edge on it then look at the next row to see if the spacing of the edges is growing. Keep stepping through until you have no more edge and see if it looks like it started out small, then bigger, then smaller.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-10T20:37:32.060" CommentCount="4" />
  <row Id="8853" PostTypeId="1" CreationDate="2011-01-10T21:05:41.493" Score="1" ViewCount="149" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/7011/using-oblong-rounded-surface-mounted-pads-for-chip-resistors-capacitors-and-in&quot;&gt;Using oblong / rounded surface mounted pads for chip resistors, capacitors and inductors&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;When creating a new SMT component footprint, one of the options is to have the pads round or rectangular.  What are the pros and cons of these approaches?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I googled but all I could find is an edaboard post &lt;a href=&quot;http://www.edaboard.com/thread13374.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; (and a bunch of trampoline parts).  From what I gather, round pads are slightly better for a few reasons relating to manufacturing, because the corner tips of the pad will heat up to reflow temp before the rest of the pad, burning off excess flux, possibly interfering with the heel of the solder joint.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the author also made a good point that if you're having manufacturing problems, it probably has more to do with a bad land pattern than pad geometry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So..does pad geometry have any practical implications?&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-01-10T22:29:35.463" ClosedDate="2011-01-10T23:01:34.163" Title="Are round pads better than rectangular pads?" Tags="&lt;soldering&gt;&lt;surface-mount&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="8854" PostTypeId="1" CreationDate="2011-01-10T22:22:01.400" Score="3" ViewCount="76" Body="&lt;p&gt;We have an industrial floor that is opened and closed by a variable speed drive motor. This is controlled by a PLC device. Recently we had to do maintenance on the VSD. The serviceman incorrectly diagnosed that the VSD wasn't working because the battery had died. We had the VSD serviced and its all working again. The problem was with the VSD. However we determined it wasn't the battery since it was drawing power from the PLC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm interested to know if it is common for this type of configuration? Should the serviceman (he was employeed due to claimed extensive knowledge of such systems) have known about this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;sorry I can't provide the hardware details of the VSD/PLC don't have these handy. &#xA;I will try and get the specific config details this weekend.&lt;/p&gt;&#xA;" OwnerUserId="1457" LastEditorUserId="1457" LastEditorDisplayName="" LastEditDate="2011-01-13T22:52:16.187" LastActivityDate="2011-01-14T16:22:33.393" Title="Is it standard for a VSD to pull its power from the controlling PLC? Is this the better solution?" Tags="&lt;power-supply&gt;&lt;programmable-logic&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="8855" PostTypeId="2" ParentId="8853" CreationDate="2011-01-10T22:29:35.463" Score="0" ViewCount="" Body="&lt;p&gt;I use rounded pads whenever I can, I've heard that lead free solder paste flows better on rounded pads (because it can't get to the edges of a rectangular pad), but really, the REAL reason I use it in my designs is because they just look really awesome :P&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(doesn't take too much effort on my part as I make all my footprints by myself)&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-01-10T22:29:35.463" />
  <row Id="8856" PostTypeId="1" AcceptedAnswerId="8860" CreationDate="2011-01-10T23:18:44.550" Score="3" ViewCount="206" Body="&lt;p&gt;During manufacture, integrated circuits are tested at varying frequencies and temperatures to categorise them into speed grades. However, why don't all ICs come out the same and work the same? They all come from the same photolithographic mask, right? Am I missing something?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-14T03:23:00.647" Title="Why do chips not always &quot;meet the grade&quot;?" Tags="&lt;integrated-circuit&gt;" AnswerCount="5" />
  <row Id="8857" PostTypeId="1" AcceptedAnswerId="8865" CreationDate="2011-01-10T23:40:22.393" Score="3" ViewCount="183" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I asked this question a few days ago, but I don't think I was clear enough, so I'm going to try again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a rough diagram of my sputtering system:&lt;br/&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/RDocL.png&quot; alt=&quot;Chamber electrical sketch&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, a DC voltage supply holds the substrate at a large negative voltage (~-1000V) relative to the chamber chassis (Vs) and a DC current supply pushes a large current (~120A) through a plasma into the chassis and substrate (It).  Only a small fraction of the total plasma current actually goes through the substrate (~2A out of the total 120A).  Most of the current passes directly into the chassis.  So, to clarify, there are two power supplies.  The voltage supply is providing -1000V to the substrate through which ~2A are passing.  The current supply is providing 120A through the target/plasma (at about 20V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistor between the chassis and ground indicates that the chassis is poorly grounded.  Furthermore, the resistor should be taken to be variable as the current flow through the stainless steel chassis fluctuates, meaning that the voltage of the chassis relative to earth ground fluctuate significantly over time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the problem:  I want to measure the voltage between the substrate and a particular spot on the chassis without measuring any of the voltage due to the large current flowing through the chassis.  The measurement doesn't have to be very precise, it's only used as a check (i.e., +/- 5V is fine).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right now, this is accomplished using a Fluke battery powered DMM.  Since it's battery powered, it makes a real floating differential measurement.  What I'd like to do is replace this handheld meter with a non-battery powered solution that could also be hooked to a computer for data-logging purposes.  I thought maybe using a 110V AC to 9V DC wall adapter that could hook into the Fluke's battery terminals might be an idea, but I guess there is no electrical isolation and all the current in the chassis would get dumped through the Fluke to the mains ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone suggest an approach?  I'm pretty ignorant about this stuff.  I've tried reading up on it but can't figure out anything that might work.  If I can clarify in any way, I'd be happy to.  Any suggestions (including &quot;you're stupid.  this can never work&quot;) would be appreciated!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks a lot in advance,&#xA;Brian&lt;/p&gt;&#xA;" OwnerUserId="2524" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:18:58.940" LastActivityDate="2011-03-05T16:18:58.940" Title="High voltage, high common mode current measurement. Any suggestions?" Tags="&lt;current-measurement&gt;&lt;high-voltage&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="8858" PostTypeId="1" AcceptedAnswerId="8866" CreationDate="2011-01-10T23:58:19.133" Score="3" ViewCount="144" Body="&lt;p&gt;I need to test that my project will not interfere with radios in the 27 - 72 MHz band.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't afford a spectrum analyser. Nor can I afford to buy all tx/rx pairs in between 27 and 72 MHz (27, 35, 47, 72...) My budget is a maximum of £100.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking of modifying a radio to have a much larger tuning range, but it would need to be sensitive to very low EMI emissions. I've found AM radios are slightly sensitive to noise but probably not enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-11T17:29:27.540" LastActivityDate="2011-02-11T17:29:27.540" Title="What's the cheapest way to do basic EMI testing?" Tags="&lt;rf&gt;&lt;emi&gt;&lt;spectrum-analyzer&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="8859" PostTypeId="2" ParentId="195" CreationDate="2011-01-11T00:16:46.160" Score="0" ViewCount="" Body="&lt;p&gt;Lou already gave an excellent explanation of how the IR module work, but I wanted to elaborate on a few of the approaches that can be taken.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A programmable, universal remote is like the one here: &lt;a href=&quot;http://www.arcfn.com/2009/09/arduino-universal-remote-record-and.html&quot; rel=&quot;nofollow&quot;&gt;http://www.arcfn.com/2009/09/arduino-universal-remote-record-and.html&lt;/a&gt;. I consider this the old school universal remote. You point a plain remote you already have at the universal remote, you press a button (like Power) on the plain remote, then the universal remote records the IR signal, which it can then replay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Apple IR Remote W. Craig Trader mentioned already has the IR instructions programmed for Play, Pause, etc. for the Apple device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The programmable, universal remote and the Apple IR remote both tend to be only compatible with the specific manufacturer's hardware they were programmed for. This is because each manufacturer has their unique IR signal codes. The TV-B-Gone's approach is store the Power Off code for hundreds of manufacturers around the world and literally iterate through each code, sending out the IR signal. This is why TV-B-Gone's site says &quot;It may take up to 69 seconds for the television to turn off, but most TVs will turn off within the first few seconds.&quot;&lt;/p&gt;&#xA;" OwnerUserId="2542" LastActivityDate="2011-01-11T00:16:46.160" />
  <row Id="8860" PostTypeId="2" ParentId="8856" CreationDate="2011-01-11T00:29:21.340" Score="7" ViewCount="" Body="&lt;p&gt;Modern ICs are REALLY small. Tolerances are huge during processes such as ion implantation and oxide growth. At such small sizes, these things can't be treated as anything but a probabilistic process. Lines also tend to be smeared due to the feature size being the minimum possible given the wavelength of light. When you get worst-case performance in a bunch of these different steps, then you get a non-functioning IC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Companies don't design the IC so that it functions at the worst-case - it would be too costly. So instead they do Monte Carlo simulation of the manufacturing parameters, estimate a yield, and do testing after the fact.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Typical &lt;em&gt;&lt;a href=&quot;http://www.cmosvlsi.com/lect15.ppt&quot; rel=&quot;nofollow&quot;&gt;&quot;design corners&quot;:&lt;/a&gt;&lt;/em&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/CnMkB.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Source: What I remember from my IC manufacturing class.&lt;/p&gt;&#xA;" OwnerUserId="2183" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-13T06:28:57.750" LastActivityDate="2011-01-13T06:28:57.750" CommentCount="3" />
  <row Id="8861" PostTypeId="2" ParentId="8857" CreationDate="2011-01-11T00:33:19.307" Score="1" ViewCount="" Body="&lt;p&gt;The current flowing through the signals your trying to meter doesn't matter in this instance at all, all that matters is the voltage your attempting to measure.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any decent voltage metering device will be relatively high impedance (like 10M ohm) the only current that will flow through the meter is a function of the voltage differential being measured between signals and that internal resistance.  The current flowing in the signals being metered doesn't matter at all (other than how it influences the signals voltage).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are correct that you want to measure differentially, if your meter is earth grounded it most likely needs to withstand the common-mode voltage of the signals.  However its probably easiest just to use a resistor network to divide the voltage down to something safer to plug into your meter.  Again the design of this resistor network doesn't depend on the currents in the signals, just their voltages.  Obviously as this high a voltage you want to use fairly high value resistors.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-01-11T00:33:19.307" CommentCount="2" />
  <row Id="8862" PostTypeId="2" ParentId="8858" CreationDate="2011-01-11T00:36:29.133" Score="4" ViewCount="" Body="&lt;p&gt;Well, you can't be sure about 'very low EMI emissions' with all these tricks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just find a mate in city with spectrum analyzer and do a proper test. Even if he would ask for money, it is not gonna be much.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-11T00:36:29.133" />
  <row Id="8863" PostTypeId="1" AcceptedAnswerId="8867" CreationDate="2011-01-11T00:38:23.500" Score="2" ViewCount="191" Body="&lt;p&gt;I need to be able to simulate communications with a sensor device over a large length of wire (0-10km).  This is for quite low-speed comms (10khz max, usually 1-2khz though). This would be FSK... but at some point I may have to handle a low baud RS232-like signal as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mostly, I'm looking for voltage drop and signal distortions.  Delay doesn't matter much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would you go about it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been able to determine the cable is indeed a (fairly nonstandard) type of coax. I now know resistance and capacitance per unit length, cross section geometry, and that the insulation resistance is high enough not to matter. It wasn't initially clear if the return line was a separate run or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would be a test setup for multiple target devices. Most are FSK of various frequency choices under 10khz, some are ASK (you could almost use a standard UART after bandpass/filtering). All are riding on a high DC offset (comms over power).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the past, I've seen people build a simple rotary switch that swaps in resistors, capacitors, and maybe inductors to simulate a given line length. Could that be good enough?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm currently trying to build a few simulations in LTspice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT 2:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Okay, if I go with just adding resistors, caps, and inductors... what does the model look like?  The RLGC network below is assuming the grounds are at the same potential I believe (a safe assumption on PCBs w/ground planes). The return in this case is through the outer shell, and it's resistance is probably 3 times higher than the inner conductor. Does that change things significantly? Do I just add another resistor on the bottom rail, and split the capacitance on both sides of it?&lt;/p&gt;&#xA;" OwnerUserId="1270" LastEditorUserId="1270" LastEditorDisplayName="" LastEditDate="2011-01-11T15:57:34.793" LastActivityDate="2011-01-11T15:57:34.793" Title="Transmission line simulation (physical)" Tags="&lt;simulation&gt;&lt;transmission-line&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="8864" PostTypeId="2" ParentId="8856" CreationDate="2011-01-11T00:38:42.907" Score="1" ViewCount="" Body="&lt;p&gt;IC chips are just shrinked to the point where they &quot;barely&quot; work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can make chips on 3um process with nearly 100% good rate and very little variation, but it's just too expensive (and slow).&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-11T00:38:42.907" CommentCount="2" />
  <row Id="8865" PostTypeId="2" ParentId="8857" CreationDate="2011-01-11T00:42:00.827" Score="1" ViewCount="" Body="&lt;p&gt;While a wall adapter &lt;em&gt;is&lt;/em&gt; usually isolated, it likely isn't rated to 1kV. A simple solution would be to find a DMM with logging capability and CAT III/IV 1kV isolated external power source or long battery life. Here are some candidates:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.home.agilent.com/agilent/product.jspx?nid=-34618.956187.00&amp;amp;cc=CA&amp;amp;lc=eng&quot; rel=&quot;nofollow&quot;&gt;Agilent U1271A&lt;/a&gt;: &lt;a href=&quot;http://cp.literature.agilent.com/litweb/pdf/5990-6425EN.pdf&quot; rel=&quot;nofollow&quot;&gt;IR USB connectivity; 300 hour battery life&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.gossenmetrawatt.com/resources/marcom/prospekte/207_p_gb.pdf&quot; rel=&quot;nofollow&quot;&gt;Gossen Metrawatt Metrahit X-Tra&lt;/a&gt;: &lt;em&gt;&quot;bidirectional IR interface&quot;&lt;/em&gt;; &lt;a href=&quot;http://www.gossenmetrawatt.com/resources/tt/hit_xtra_pro_base/db_gb.pdf&quot; rel=&quot;nofollow&quot;&gt;200 hour battery life&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.fluke.com/Fluke/usen/Digital-Multimeters/Fluke-289.htm?PID=56061&quot; rel=&quot;nofollow&quot;&gt;Fluke 289&lt;/a&gt;/&lt;a href=&quot;http://www.fluke.com/Fluke/usen/Digital-Multimeters/Fluke-287.htm?PID=56058&quot; rel=&quot;nofollow&quot;&gt;287&lt;/a&gt;: &lt;em&gt;&quot;Isolated Optical Interface&quot;&lt;/em&gt;; 200 hours battery life&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Another option is to use a simple micro with an ADC, float the whole circuit at chassis voltage, then use proper isolation techniques (more than just optoisolation -- if you're not sure I suggest another question) to communicate with a PC over your preferred serial connection (&lt;code&gt;UART -&amp;gt; opto -&amp;gt; RS232 -&amp;gt; USB -&amp;gt; opto -&amp;gt; PC&lt;/code&gt;, with cable shield voltage measurement and warning, would be my choice). Note that this means you can't touch anything on the floating (hot chassis) side of the widget. This way you can eliminate the power supply isolation worries by just using a battery, and still run it easily for 6 months to a year without replacing it, following thought on power consumption and sleep modes (ie: &lt;a href=&quot;http://focus.ti.com/mcu/docs/mcuorphan.tsp?contentId=61835&amp;amp;DCMP=MSP430&amp;amp;HQS=Other+OT+ulp&quot; rel=&quot;nofollow&quot;&gt;MSP430&lt;/a&gt;). Also note that a sputtering machine generates electrical noise, so you may need to use RS485 with error detection/correction algorithms.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-11T00:42:00.827" CommentCount="3" />
  <row Id="8866" PostTypeId="2" ParentId="8858" CreationDate="2011-01-11T00:46:33.487" Score="5" ViewCount="" Body="&lt;p&gt;If my time was worth nothing, or I was doing this as my own fun project, I would design and build my own rf power meter. There are schematics available for this in AARL back-issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is for work, I would go and rent the tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this isn't for work, and you don't know very much about RF, and you don't have a lot of money - go make friends with amateur ham radio people in your area and butter them up.&lt;/p&gt;&#xA;" OwnerUserId="2183" LastEditorUserId="2183" LastEditorDisplayName="" LastEditDate="2011-01-11T03:13:46.597" LastActivityDate="2011-01-11T03:13:46.597" />
  <row Id="8867" PostTypeId="2" ParentId="8863" CreationDate="2011-01-11T00:47:38.323" Score="3" ViewCount="" Body="&lt;p&gt;Transmission lines have a complex characteristic impedence. The characteristic impedence is typically specified &quot;per unit length&quot; for a given tranmission line. For practical purposes, you might have four values &quot;per unit length&quot; for a transmission line: resistance, capacitance, inductance, and conductance. There's a pretty extensive article on this &lt;a href=&quot;http://en.wikipedia.org/wiki/Transmission_line&quot; rel=&quot;nofollow&quot;&gt;on Wikipedia&lt;/a&gt;, and &quot;for high frequencies and small losses&quot; the approximate equation is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/YcavS.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;where:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;x is the distance along the tranmission line &lt;/li&gt;&#xA;&lt;li&gt;t is elapsed time&lt;/li&gt;&#xA;&lt;li&gt;L is the inductance per unit length &lt;/li&gt;&#xA;&lt;li&gt;C is the capacitance per unit length&lt;/li&gt;&#xA;&lt;li&gt;R is the resistance per unit length &lt;/li&gt;&#xA;&lt;li&gt;G is the conductance per unit length&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Now this is probably going to be of limited use to you because, if I read between the lines here, it sounds like you're planning to transmit a digital signal (i.e. a square wave). The edges in the square wave are really &quot;broad spectrum.&quot; That's why most communication systems go through a modulation and demodulation step so as to limit the spectrum of the signal &quot;on the line.&quot; But I think the above equation does apply because a the &quot;signal&quot; in a square wave is analytically &quot;high frequency&quot; content.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At any rate, in the &quot;steady state&quot; high level of your input signal, assuming your receiver is a high impedence, what your signal sees is a voltage divider based on the characteristic resistance and conductance. So you should see (approximately) Vout/Vin = G/(R+G), based on the model:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/FBrD8.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit 1&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I missed the FSK (Frequency Shift Keying) comment in the question earlier. I also had another thought. You can use something like Matlab Simulink to model the transfer characteristic of the circuit, and feed the model with a representative input waveform to see what comes out the other side...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if you want to know how much of a voltage drop you'll see, for a sinusoidal signal, you've still got an effective voltage divider with a top leg having effective impedence of length*(R + jwL) and a bottom leg impedence of (G*length || 1/(jwC*length)). You can do the complex math to find the real part of that transfer function at a given frequency ( w = 2 * pi * f).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit 2&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In response to the clarification of what you meant by physical simulation, if you are trying to physically introduce the effect of a transmission line, just set up the circuit in the figure with appropriate values of capacitors, inductors, and resistors - sized in accordance with the properties and length of the transmission line you are trying to emulate.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-11T14:46:46.947" LastActivityDate="2011-01-11T14:46:46.947" CommentCount="5" />
  <row Id="8868" PostTypeId="2" ParentId="8863" CreationDate="2011-01-11T00:58:29.307" Score="1" ViewCount="" Body="&lt;p&gt;Cable manufacturers will tell you how much the signal will be attenuated per unit length given the frequency of the signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding signal distortions, I'm not aware of anything significant so long as you use shielded cable. But don't take my word for it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transmitting RS232 level signals over such a long run of cable will be difficult. &lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2011-01-11T00:58:29.307" />
  <row Id="8869" PostTypeId="2" ParentId="4121" CreationDate="2011-01-11T01:04:08.660" Score="3" ViewCount="" Body="&lt;p&gt;Mainly it's a thermal issue.  &lt;a href=&quot;http://en.wikipedia.org/wiki/Electromigration&quot; rel=&quot;nofollow&quot;&gt;Electromigration&lt;/a&gt; can break the chip due to too much current.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-11T01:33:08.297" LastActivityDate="2011-01-11T01:33:08.297" />
  <row Id="8870" PostTypeId="2" ParentId="195" CreationDate="2011-01-11T01:52:33.823" Score="0" ViewCount="" Body="&lt;p&gt;I'm currently working on an open source project that is essentially a network enabled universal remote.  The idea is, if you keep all your A/V equipment in a closet somewhere (with an Ethernet line into the closet) you can connect this device, and control your TV, cable, dvd player, etc. with any networked device.  Assuming you have wifi, for example, this means you can use your iPhone, laptop, or whatever, as a remote.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic pain is setup.  I don't know of any open source IR libraries so you will literally have to &quot;teach&quot; the device every code for every remote by pointing the remote at the device, telling it which button/device you are about to program through the web page interface, and pressing the button.  The codes will all be stored in EEPROM.  I haven't set up a site yet but I can probably give you schematic / pcb files if you're interested.  I'm just getting started on software.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-01-11T01:52:33.823" CommentCount="1" />
  <row Id="8871" PostTypeId="2" ParentId="8842" CreationDate="2011-01-11T02:45:04.470" Score="1" ViewCount="" Body="&lt;p&gt;Your fridge may have poor grounding. I've run into more than a few old ones that had a floating ground that intermittently 'closed' to Earth, one of which gave me my first close encounter with mains power (and later used to shock people at parties, but that is another tale). Measure the compressor chassis voltage versus mains Earth/ground (or see if there's only 2 prongs in the plug). Of course ya can't just short the chassis to ground straight away if this is the issue -- see if there's a constant current path, first. I'm not sure why there would be, but it's possible! If there is, I'd look into it some more: &lt;em&gt;why is the chassis energized? Is some insulation worn through?&lt;/em&gt; Oh yeah - don't get killed or anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other way to go about this is to protect the speakers directly. This can be done with clamping diodes or &lt;a href=&quot;http://electronics.stackexchange.com/q/8798/2118&quot;&gt;other TVS parts&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-11T02:45:04.470" CommentCount="1" />
  <row Id="8872" PostTypeId="1" CreationDate="2011-01-11T03:19:24.140" Score="2" ViewCount="239" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have got some existing low power 2mW XBee series 2 with an Explorer that I've used successfully to communicate between a PC with the XBee Explorer and a remote Arduino based project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd now like to create a one way link to send telemetry data from a model rocket with an Arduino based telemetry board that has a ZigBee option. I'm thinking I'd be able to get away with the existing low power XBee I have plugged into the XBee explorer as the base station to receive the data and just purchase a high power XBee with an aerial to mount inside the rocket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any experience or comments about combining a low and high power XBee to create this one way link from the rocket to a base ground station?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I realise the XBee must be of the same series (1 or 2/2.5) to be able to successfully communicate. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ones I currently have are these www.sparkfun.com/products/8691 and I'm thinking if I bought something like this &lt;a href=&quot;http://www.littlebirdelectronics.com/products/XBee-Pro-50mW-Series-2.5-RPSMA.html#&quot; rel=&quot;nofollow&quot;&gt;http://www.littlebirdelectronics.com/products/XBee-Pro-50mW-Series-2.5-RPSMA.html#&lt;/a&gt; I'd be able to create a reasonably good distance link for a smallish model rocket to send it's telemetry data through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One issue I'm seeing is that the transmitter may need to be in some sort of broadcast or no sync/acknowledge mode as the receiver would be low power and not be able to transmit data/acknowledgements back to the rocket to acknowledge data being received. It also may (given a very good flight) go out of range and so coping with nobody listening/receiving needs to be configured into the transmitter end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, what aerial or version of the 50mw XBee would make sense to use in the rocket? The link to the one I've shown above requires an external RSPMA aerial to be plugged in. Assuming the combination of high to low power sending only would work, would this be the right aerial type to use being mounted internally in a rocket?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or am I just trying to make this all to complicated and should ignore the fact that I have low power XBee modules now and buy 2 high power ones that I won't be transmitting from one with?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2568" LastActivityDate="2011-01-12T00:13:14.513" Title="Combine a low power XBee receiver with high power XBee transmitter in a model rocket" Tags="&lt;wireless&gt;&lt;communication&gt;&lt;xbee&gt;" AnswerCount="2" />
  <row Id="8873" PostTypeId="2" ParentId="8863" CreationDate="2011-01-11T03:58:21.500" Score="0" ViewCount="" Body="&lt;p&gt;If I wanted to do it for real use a standard telephone modem and a line voltage generator, if needed.  For simulation @krapht is right.  Use STP or coax.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-11T03:58:21.500" />
  <row Id="8874" PostTypeId="1" CreationDate="2011-01-11T04:47:31.167" Score="4" ViewCount="262" Body="&lt;p&gt;I think it is possible due to how I can run vi straight from my serial port looking via TeraTerm. There, I can edit some text, go to the next line, then come back and edit the first line! How do they do this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What character over UART could I send through to go &quot;up a line&quot;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Apparently line feed works. &quot;\f&quot; to clear the screen. However, this only works for Hyperterminal on my machine and not Teraterm. Anyone know why?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-11T23:08:46.300" LastActivityDate="2011-01-11T23:08:46.300" Title="Is it possible to send characters through serial to go up a line on the console window?" Tags="&lt;serial&gt;&lt;uart&gt;" AnswerCount="3" />
  <row Id="8875" PostTypeId="2" ParentId="8848" CreationDate="2011-01-11T05:03:02.983" Score="1" ViewCount="" Body="&lt;p&gt;I would personally setup a LAMP server, make a simple API out of your choice of language, I would use PHP. When you want to send data you would send a POST or GET request to your server with your data and the SQL Database would store it, from there you can do what ever you want with the data, like adding a googlemaps.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;another idea would be to send it over ssh and store it in a file. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question to you is, how are you sending the data to the server? ( TCP, Serial, smoke signals)&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-01-11T05:03:02.983" CommentCount="1" />
  <row Id="8876" PostTypeId="2" ParentId="8856" CreationDate="2011-01-11T05:15:02.510" Score="3" ViewCount="" Body="&lt;p&gt;Mostly what krapht said. I'd add that parts are getting so small that even without variation in geometry, the number of doping atoms per transistor are also becoming small, so simple statitical variation means some will be faster and some lower, and the gain also varies. You'll end up with some that either can't work, or can only work at say a slower clock rate. Also you might see some computers offered with say a three-core chip. Such a chip is probably a four-core chip, but a faulty core has been disconneted in postprocessing, and the chip sold as a cheep 3banger. I would add, nothing wrong with that, if that's the capability you need, then the manufacturers bad luck is our gain.&lt;/p&gt;&#xA;" OwnerUserId="2569" LastActivityDate="2011-01-11T05:15:02.510" />
  <row Id="8877" PostTypeId="2" ParentId="8874" CreationDate="2011-01-11T05:23:52.053" Score="1" ViewCount="" Body="&lt;p&gt;This is an indirect answer to your question. If you are in VI, then all you need to do to move the cursor up is to send 'k'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at this &lt;a href=&quot;http://braun-home.net/michael/info/misc/VT100_commands.htm&quot; rel=&quot;nofollow&quot;&gt;VT100 command page&lt;/a&gt;, it looks like the up arrow key is represented by sending the following sequence: &lt;code&gt;ESC [ A&lt;/code&gt; or &lt;code&gt;0x1B, 0x5B, 0x41&lt;/code&gt;. I don't know if this will work, but I am interested to know if it does.&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-01-11T05:35:20.003" LastActivityDate="2011-01-11T05:35:20.003" />
  <row Id="8878" PostTypeId="2" ParentId="8874" CreationDate="2011-01-11T05:50:05.307" Score="2" ViewCount="" Body="&lt;p&gt;What you see on a console window is the result of an automatic echo (which can often be turned off or on), where the console program draws the characters you send on the screen, or the result of receiving characters. This means there are two ways of changing it:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Have a local program, on the PC, redraw the screen.&lt;/li&gt;&#xA;&lt;li&gt;Have the connected device redraw the screen.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;There are many ways to do this, but this is how I'd approach a simplistic hobby implementation:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Set a default line width, like 80, and number of rows, like 24. Turn off automatic echo.&lt;br&gt; &lt;img src=&quot;http://i.imgur.com/Y4WQu.png&quot; alt=&quot;alt text&quot;&gt;&lt;/li&gt;&#xA;&lt;li&gt;An 80x24 screen means 1920 characters per &lt;em&gt;'frame'&lt;/em&gt;, which means, if the connected device is doing the work, a maximum refresh rate of around &lt;code&gt;1920/BAUDRATE/11&lt;/code&gt; or about 5Hz at 115200 baud (using 1 start bit, 1 stop, 1 parity, 8 data).&lt;/li&gt;&#xA;&lt;li&gt;Map the arrow keys to &lt;a href=&quot;http://josh.flagrancy.net/manuals/tf/topics/keybindings.html&quot; rel=&quot;nofollow&quot;&gt;specific characters or strings&lt;/a&gt;. This may already be done behind the scenes. (For OSX Terminal, &lt;em&gt;left&lt;/em&gt;:&lt;code&gt;\033[5D&lt;/code&gt;; &lt;em&gt;right&lt;/em&gt;:&lt;code&gt;\033[5C&lt;/code&gt;; &lt;em&gt;up&lt;/em&gt; &amp;amp; &lt;em&gt;down&lt;/em&gt; undefined by default.)&lt;/li&gt;&#xA;&lt;li&gt;Program the connected device to recognize these characters and/or strings, and move the cursor reference accordingly.&lt;/li&gt;&#xA;&lt;li&gt;Output over the serial line not by character or character array, but by frame. Specifically, keep a two 1921 (1920+terminator) character-long arrays: one to write to while the other is being transmitted (assuming the use of hardware UART and interrupts).&lt;/li&gt;&#xA;&lt;li&gt;Writing to the frame buffer can be accomplished by using a function like this:&lt;br&gt;&#xA;&lt;code&gt;uint8_t framewrite(const char *s, uint8_t row, uint8_t col)&lt;/code&gt;&lt;br&gt;&#xA;... Where &lt;code&gt;*s&lt;/code&gt; is your [terminated] char array, and &lt;code&gt;row&lt;/code&gt; and &lt;code&gt;col&lt;/code&gt; are where you want the first character to appear. (Return &lt;code&gt;uint8_t&lt;/code&gt; is for error catching.)&lt;/li&gt;&#xA;&lt;li&gt;You'll probably want functions like &lt;code&gt;uint8_t frame_clear(void)&lt;/code&gt;, &lt;code&gt;uint8_t frame_shiftrowsdown(void)&lt;/code&gt;, etc.&lt;/li&gt;&#xA;&lt;li&gt;To indicate cursor position you can alternate the current character and a black box or the character of your choice (&lt;code&gt;pblinkchar&lt;/code&gt;), using &lt;code&gt;framewrite(pblinkchar,cursor_row,cursor_col)&lt;/code&gt;.&lt;/li&gt;&#xA;&lt;li&gt;The same method can be used to echo characters back to the cursor position.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;I'm sure there are much simpler (I think software guys call it &quot;elegant&quot;) ways to do this by programming a PC window, and you can probably figure out how by digging through &lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=43481&quot; rel=&quot;nofollow&quot;&gt;this tutorial&lt;/a&gt;, but the above is similar to what I've done in the past and works for simple user interfaces with micros with plenty of spare memory.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-11T06:03:44.693" LastActivityDate="2011-01-11T06:03:44.693" />
  <row Id="8879" PostTypeId="2" ParentId="8872" CreationDate="2011-01-11T06:02:20.023" Score="2" ViewCount="" Body="&lt;p&gt;I guess you are not trying to get range &gt;1km, right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you really sure you need telemetry? Logging data into microSD card is way easier &amp;amp; more reliable. microsd card can survive even the most horrible crash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really need to extend range, I would suggest directional antenna on ground receiver with servos to track rocket. That would be very fun and will extend the range much more than 50mW transmitter.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-11T06:02:20.023" CommentCount="1" />
  <row Id="8880" PostTypeId="2" ParentId="8808" CreationDate="2011-01-11T07:16:07.523" Score="1" ViewCount="" Body="&lt;p&gt;What about using the difference between the signals from two antennas? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In theory, if two antennas are &lt;em&gt;exactly&lt;/em&gt; the same distance from the target, then the two signals should cancel each other out if subtracted.  If they are slightly off, then they would be slightly out of phase, and they wouldn't cancel.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could only use this technique to find the angle to the target.  You would have to rotate the antennas to actually read the RFID (because their would be no signal when you were pointing directly at it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(This technique is used in Ham Radio circles as a poor man's way to find people who interfere with radio repeaters so they can be reported to the FCC.)&lt;/p&gt;&#xA;" OwnerUserId="2257" LastActivityDate="2011-01-11T07:16:07.523" CommentCount="1" />
  <row Id="8881" PostTypeId="2" ParentId="8874" CreationDate="2011-01-11T09:08:49.737" Score="5" ViewCount="" Body="&lt;p&gt;Use &lt;a href=&quot;http://www.termsys.demon.co.uk/vtansi.htm&quot; rel=&quot;nofollow&quot;&gt;VT100 escape codes&lt;/a&gt; to control the cursor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Eg.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;puts(&quot;\033[2J&quot;);   // clear screen&#xA;puts(&quot;\033[0;0H&quot;); // set cursor to 0,0&#xA;puts(&quot;\033[10B&quot;);  // move cursor down 10 lines&#xA;puts(&quot;\033[5A&quot;);  // move cursor up 5 lines&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-11T09:08:49.737" CommentCount="5" />
  <row Id="8882" PostTypeId="1" CreationDate="2011-01-11T09:40:11.027" Score="3" ViewCount="113" Body="&lt;p&gt;I have an XBee and an XBee Arduino shield.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I program my XBee through my &lt;a href=&quot;http://www.freetronics.com/products/twentyten&quot; rel=&quot;nofollow&quot;&gt;Arduino Twenty-Ten&lt;/a&gt; and an XBee shield?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I do anything with just one XBee?&lt;/p&gt;&#xA;" OwnerUserId="2571" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-11T22:49:40.037" LastActivityDate="2011-01-12T00:00:56.087" Title="Can an XBee be programmed with an XBee Shield" Tags="&lt;xbee&gt;" AnswerCount="2" />
  <row Id="8883" PostTypeId="2" ParentId="8834" CreationDate="2011-01-11T09:51:30.480" Score="2" ViewCount="" Body="&lt;p&gt;If you really want to detect body heat, I don't thing anything short of a thermal imager will work, which will cost a few $000. PIR won't give you the absolute measurement or resolution to be useful. It might be feasible to use something like a thermopile sensor with a PIR lens to get enough coverage angle, but all that will tell you is there is something warm somewhere in th efield of vide, which may end up giving too many false alarme&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-11T09:51:30.480" />
  <row Id="8885" PostTypeId="1" AcceptedAnswerId="8893" CreationDate="2011-01-11T10:43:20.983" Score="4" ViewCount="282" Body="&lt;p&gt;Howdy,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm in the very early stages of trying to build a robot that wanders around and builds up a map of its environment.  I'm using an Arduino and I currently have a Sharp IR sat on top of a servo so it can take a 180 degree sweep in 10 degree increments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The trouble is that the voltage readings back from the Sharp IR sensor aren't consistent.  If I write an app that simple sends the value it reads from the sensor through the serial port and display it on my laptop, sitting the sensor pointing at an object, the values bounce around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Watching the values, I can see that it tends to report one value more than the rest, so I wrote a SharpReader class that takes 20 samples and then returns the Mode of these values.  This now means I get more consistent values, but not as good as I would like.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have some code that performs the 180 degree scan and sends the angle and distance down the serial.  I then have a python script that receives these values and draws what it sees on screen, ignoring any values at either end of the sensors range.  So putting it in front of a box, it should draw a straight line on screen, but it doesn't - the line is crooked and not consistently crooked, which confirms to me that it's the readings that are off, not my code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have read in the datasheet that it is advisable to put a capacitor (can't remember the value offhand) inbetween the GND and PWR lines on the Sharp IR - I tried forcing the legs of the capacitor into the JST connector of the Sharp IR, but it made no difference.  I'll try soldering it to the sensor and see if that makes any difference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone recommend anything else to try, or am I just expecting too much from the Sharp IR?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm also considering buying a second servo and Sharp IR and running two at the same time like a pair of eyes, then trying to take an average of the two values to see if that increases the accuracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, I'm a newbie to electronics, my background is in programming.&lt;/p&gt;&#xA;" OwnerUserId="2573" LastActivityDate="2011-01-11T16:27:31.833" Title="Can't get consistent readings from Sharp IR" Tags="&lt;arduino&gt;&lt;range-detector&gt;&lt;sharp&gt;" AnswerCount="3" CommentCount="6" FavoriteCount="1" />
  <row Id="8886" PostTypeId="2" ParentId="8834" CreationDate="2011-01-11T13:12:26.097" Score="1" ViewCount="" Body="&lt;p&gt;I just wonder - if something like this was remotely feasible, wouldn't it have been made by someone and commercialized already? I'm in the opinion that (with the level of technology available today) this is sadly still science fiction stuff, or else requires a disproportionate amount of money.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Added:&lt;/strong&gt; From the comments, the idea about am IR thermometer might be worth looking into. If you could get one that can provide realtime measurements (I suppose 4 per second might be needed for a fair operation), you could then attach some optics to get a bigger FoV and get a sort of &quot;measuring gun&quot; that you could point to suspicions places. I think...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting such a thermometer might be expensive if at all possible, but maybe you could dismantle some cheap ones and hack them... I don't know. :P&lt;/p&gt;&#xA;" OwnerUserId="2575" LastEditorUserId="2575" LastEditorDisplayName="" LastEditDate="2011-01-11T15:36:34.437" LastActivityDate="2011-01-11T15:36:34.437" CommentCount="6" />
  <row Id="8887" PostTypeId="2" ParentId="7721" CreationDate="2011-01-11T13:13:45.317" Score="3" ViewCount="" Body="&lt;p&gt;In a switching power supply, the output inductor is designed to meet several criteria, including:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;ripple voltage due to inductor current imposed on the ESR of the output capacitors&lt;/li&gt;&#xA;&lt;li&gt;transient response, since larger inductance = slower response&lt;/li&gt;&#xA;&lt;li&gt;non-saturation&lt;/li&gt;&#xA;&lt;li&gt;zero or controlled roll-off of inductance due to DC biasing (permeability roll-off)&lt;/li&gt;&#xA;&lt;li&gt;core loss / copper loss targets&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Some of these are applicable to amplifier output filters. Permability roll-off due to DC biasing wouldn't be a concern since an audio amp isn't providing DC to the loudspeaker, whereas a buck converter output inductor is technically a 'choke' since there is a DC component which has to be taken into account.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-01-11T13:13:45.317" />
  <row Id="8888" PostTypeId="2" ParentId="8885" CreationDate="2011-01-11T13:44:17.863" Score="3" ViewCount="" Body="&lt;p&gt;Good things to do at this stage:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Determine where the noise is coming from: this can be done by using the FFT function on a DSO while measuring the signal from another IR sensor (IR LED would work), or using a PC to transform the collected data. There are many sources of IR in our households, often modulated near 38kHz. A analog input antialiasing filter set to less than half of your sample rate (max ~7kHz) may be all that's required, though the sensor may already have one. Note that the micros in the Arduino series can't sample at more than about 15kSps, but 38kHz signals can still sneak through by aliasing, so digital filters wouldn't be at 38kHz but something under 15kHz.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Ensure you're testing within the device's range (max &amp;amp; min).&lt;br&gt; &lt;a href=&quot;http://www.acroname.com/robotics/info/articles/sharp/sharp.html&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/HgWNB.png&quot; alt=&quot;alt text&quot;&gt;&lt;/a&gt; &lt;br&gt;The 0A700 has a range of 5.5 meters.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Calibrate and linearize the sensor. Identical models will read differently, and their output is non-linear. &lt;a href=&quot;http://www.acroname.com/robotics/info/articles/irlinear/irlinear.html&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; describes one way to linearize the data, ending up with something like &lt;code&gt;R = (6787 / (V - 3)) - 4&lt;/code&gt;. Another method is to use an 8 to 10-bit lookup table. Linearization won't help with the noise issue, but gives a better idea as to its effect and how much mitigation is actually necessary.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Eat Oreos, torquing them in half and licking out the white stuff first. Makes for much more successful debugging sessions.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-11T15:19:46.430" LastActivityDate="2011-01-11T15:19:46.430" CommentCount="5" />
  <row Id="8889" PostTypeId="1" AcceptedAnswerId="8891" CreationDate="2011-01-11T14:09:04.387" Score="2" ViewCount="175" Body="&lt;p&gt;I've &lt;a href=&quot;http://electronics.stackexchange.com/questions/5144/how-to-clean-my-soldering-iron-tip-or-how-to-determine-that-its-beyond-repair&quot;&gt;read&lt;/a&gt; the &lt;a href=&quot;http://electronics.stackexchange.com/questions/4470/going-through-soldering-tips-quickly&quot;&gt;other&lt;/a&gt; posts on &lt;a href=&quot;http://electronics.stackexchange.com/questions/216/soldering-iron-maintenance&quot;&gt;iron cleaning&lt;/a&gt; technique and I'm pretty sure I left it dirty often enough that &lt;a href=&quot;http://electronics.stackexchange.com/questions/7718/why-does-solder-turn-dull-grey-on-my-iron-and-exhibit-poor-wetting&quot;&gt;it's toast&lt;/a&gt;, it seems the iron coating on the tip has flaked off completely; since I've got nothing to lose I'll attack it with a file in a second and see if I can get another small job out of it. $15 lesson learned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The real question is why the plating up near the catalyst is flaking off and the whole tip is bending. Does this indicate I'm using too much heat? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/obogg.jpg&quot; width=&quot;400&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1633" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-01T02:40:34.203" LastActivityDate="2011-02-01T02:40:34.203" Title="Is my butane soldering iron's tip dead? (pic)" Tags="&lt;soldering&gt;" AnswerCount="3" />
  <row Id="8891" PostTypeId="2" ParentId="8889" CreationDate="2011-01-11T15:14:55.857" Score="4" ViewCount="" Body="&lt;p&gt;NEVER USE A FILE!!!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use a file on a (long life) soldering iron tip you will ruin it!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are running the iron much too hot, turn it all the way down so the catalyst is only just glowing, if that's too cold turn it up slowly!!!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get your tip back use tip tinner or a soft wire brush, such as brass to avoid damaging the tip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again, NEVER, EVER get a file anywhere near a non-shitty soldering iron.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-01-11T15:14:55.857" CommentCount="7" />
  <row Id="8892" PostTypeId="1" CreationDate="2011-01-11T15:16:41.670" Score="4" ViewCount="122" Body="&lt;p&gt;Bluetooth 4.0 is the latest specification to be adopted by the Bluetooth cabal, which notably adds Bluetooth low energy into the mix, which is designed to allow radios that sip battery like 802.15.4 (&quot;ZigBee&quot;) to directly connect to consumer devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It sounds great, and according to a search for &quot;bluetooth 4.0 devices&quot;, we are swimming in them because they all showed up Q4 2010, however I can barely find more than a single chip (TI CC2540), let alone &lt;em&gt;any&lt;/em&gt; consumer product that is BT 4.0.  Where are they?&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-11T17:14:12.840" Title="What Bluetooth 4.0 devices and radios are available?" Tags="&lt;bluetooth&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="8893" PostTypeId="2" ParentId="8885" CreationDate="2011-01-11T15:48:29.957" Score="2" ViewCount="" Body="&lt;p&gt;The sensor isn't perfect, if you aim even a really, really good sensor (Better than the, um, 'classic' Sharp IR sensors) at the same spot on the wall and take a few readings, there will be some variation.  If you discard some number of least significant bits, it's possible to get the same reading every time, but your readings will be more granular.  You should probably keep the maximum precision, and then try to fix errors in software (i.e., change your data so that an almost straight line really is straight).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What sensor are you using, and what range of measurement do you expect? The output of the sensor is very much nonlinear.  This graph (from the datasheet) compares the output voltage on a linear scale with the distance:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/4aZHE.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;br&gt;&#xA;You'll notice that it looks a lot like the graph of y=1/x, i.e volts=k(1/distance).  This can be used to get a decent first approximation, but division on an Arduino is expensive. You'll have better luck calibrating the sensor and storing the voltage/distance pairs in a look-up table (in program memory, of course).  This one comes calibrated from the factory such that a measurement at precisely 24cm measures to 24cm +/- 3cm.  Unfortunately, they don't give you a way of knowing what the voltage at 24cm should be except by squinting at this graph.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sensor will have higher precision at certain ranges.  Imagine that there is a random variation of, say, +/- 250mV in your readings (Gaussian if you like, but random is easier).  It's hopefully a lot smaller than that, but it makes it easy to visualize.  The variation means that your readings with this sensor at, say, 50cm or 70cm will vary over 20 or 30cm, but measurements at 15cm should be within a few cm.  This sensor is rated for 10-80cm, but you'll get more accurate readings if you only trust it for 10-25cm or so.  If you're controlling the robot, you should be able to move to these distances and get the best readings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sensor draws current in large bursts and is probably mounted on a fairly long cable.  A capacitor will help stabilize the readings.  Don't jam it into the JST; solder it to the PCB on the back.  It's drawing a lot of current and it's pretty slow, so small capacitances traditionally used for decoupling (0.1uF) probably won't work. I'd use a 10uF 1206 or 1210 ceramic SMD cap in parallel with a 100uF electrolytic. If you find that high frequency noise is still present, add a 0.1uF 1206 on top of the 10uF.  Here's a picture of the locations for soldering (original image from Sparkfun):&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/6y27R.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;br&gt;&#xA;You could also try adding a small capacitance on the Vo line to smooth the output.  You should experiment to see whether or not that helps.  I'd keep it below 100pF, starting at around 10pF.  This will create a moving average of the readings in hardware.  More circuitry (a series resistor) would enhance the effect, post a comment or another question if you want to build a more complex low-pass filter system for this purpose.  Note: The Sharp sensor may not handle driving into a large capacitance well, and might balk or break if asked to change the voltage quickly.  It's also possible that it's a single-sided output, and might require a resistor to ground to discharge the capacitor if you add more capacitance than is currently present in the parasitics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Twisting the cables together will help reduce noise coupled on from external sources like 60Hz mains.  Keeping them short will also help mitigate noise.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-11T15:48:29.957" CommentCount="8" />
  <row Id="8894" PostTypeId="2" ParentId="8885" CreationDate="2011-01-11T16:27:31.833" Score="2" ViewCount="" Body="&lt;p&gt;These sensors really do need a decent decoupling cap across the supply, and a clean 5V supply, i.e. not the same supply as a servo.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-11T16:27:31.833" />
  <row Id="8895" PostTypeId="2" ParentId="8882" CreationDate="2011-01-11T16:46:56.153" Score="1" ViewCount="" Body="&lt;p&gt;Recommend you get yourself one of &lt;a href=&quot;http://www.sparkfun.com/products/9819&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt;.   It's well worth the price and will save you a lot of headaches.   Programming can get complex, if you're doing it manually instead of using &lt;a href=&quot;http://www.digi.com/support/kbase/kbaseresultdetl.jsp?kb=125&quot; rel=&quot;nofollow&quot;&gt;X-CTU&lt;/a&gt;.  Since you really only have to do it once, it's much easier to tweak the settings in X-CTU and not bother with the programming code within your application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;About the only thing you can really do with a single XBee is learn about it: fiddle with the settings and whatnot.  When you've learned all you can, you'll have to buy another one.  :)&lt;/p&gt;&#xA;" OwnerUserId="2257" LastActivityDate="2011-01-11T16:46:56.153" CommentCount="1" />
  <row Id="8896" PostTypeId="2" ParentId="8892" CreationDate="2011-01-11T17:14:12.840" Score="3" ViewCount="" Body="&lt;p&gt;CSR8000&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.csr.com/products/54/csr8000-platform&quot; rel=&quot;nofollow&quot;&gt;http://www.csr.com/products/54/csr8000-platform&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-11T17:14:12.840" />
  <row Id="8897" PostTypeId="2" ParentId="8872" CreationDate="2011-01-11T17:27:12.717" Score="1" ViewCount="" Body="&lt;p&gt;It's been a couple years since I worked with ZigBee, but I think that most commands require ACK sequences.  This is the case for most (if not all) popular RF networking protocols.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should be possible to implement your own protocol.  This could be as simple as an uninterrupted stream of data if you're just logging it to a PC or laptop.  You would get much higher data rates with such a system when comparing to ZigBee. A line encoding that gives you DC balance would help, as would clock synchronization, bounded disparity, and/or error correction.  But, if it's not a big deal to loose a few data points every once in a while, you should be able to develop a simple protocol that wouldn't require replies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edits: &#xA;Reading the datasheet confirms that ZigBee requires acknowledge packets.  It even says that &quot;It is possible in rare circumstances for the destination to receive a data packet, but for the source&#xA;to not receive the network acknowledgment. In this case, the source will retransmit the data....&quot; - This is exactly what you don't want.  Transparent mode appears to be a system by which the XBee does the ZigBee configuration automatically-not a low-level version of the API.  You'll want to check this.  The last RF job I did used the Microchip &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en535967&quot; rel=&quot;nofollow&quot;&gt;MRF24J40&lt;/a&gt;, which took the opposite approach: The whole communication stack was on the host processor.  It looks like you'll need custom firmware for your XBee to work with a custom protocol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To understand why the communication will be unidirectional, you should know that the 2mW and 50mW specs refer to the &lt;strong&gt;transmit power only.&lt;/strong&gt;  The receiver sensitivity is almost the same for both at about -100dBm: The high-power version is actually a little bit &lt;em&gt;less&lt;/em&gt; sensitive on the receiving end than the low power version, probably due to parasitics of the active antenna circuit. Since they're both operating on the same frequency, they should be perfectly able to communicate - There's no way of knowing whether an incoming signal is a low-power transmitter close by or a high-power transmitter far away.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-12T00:13:14.513" LastActivityDate="2011-01-12T00:13:14.513" CommentCount="2" />
  <row Id="8898" PostTypeId="1" CreationDate="2011-01-11T17:41:03.597" Score="5" ViewCount="242" Body="&lt;p&gt;I want to get 15V output from a  1 cell lithium polymer battery which has a voltage range of 3v-4v.  I am thinking about using a &lt;a href=&quot;http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00001232.pdf&quot; rel=&quot;nofollow&quot;&gt;34063&lt;/a&gt; to accomplish this.  But will this work over a 1v range or do I need a different ic?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit:&#xA;I want to get around 250mA&lt;/p&gt;&#xA;" OwnerUserId="2115" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-01-26T09:17:39.103" LastActivityDate="2011-01-26T09:17:39.103" Title="Obtaining 15 V from a single lithium polymer cell" Tags="&lt;power-supply&gt;&lt;voltage-regulator&gt;&lt;smps&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="8899" PostTypeId="1" AcceptedAnswerId="8904" CreationDate="2011-01-11T17:46:40.470" Score="5" ViewCount="232" Body="&lt;p&gt;In the documentation for &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/cc1110f32.html&quot; rel=&quot;nofollow&quot;&gt;a radio chip&lt;/a&gt;, I keep seeing the term 2-FSK, which seems to be a modulation scheme.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My understanding is that in FSK, data is encoded by emitting a carrier wave on a number of different frequencies. Is this right? How does this differ to 2-FSK?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-11T20:24:30.070" LastActivityDate="2011-01-11T20:24:30.070" Title="What is 2-FSK modulation?" Tags="&lt;rf&gt;&lt;fsk&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="8900" PostTypeId="2" ParentId="8899" CreationDate="2011-01-11T17:52:22.597" Score="2" ViewCount="" Body="&lt;p&gt;I believe 2-FSK is just an encoding scheme that says:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A &quot;one&quot; is encoded by transmitting a sine wave frequency f_1 &lt;/li&gt;&#xA;&lt;li&gt;A &quot;zero&quot; is encoded by transmitting a sine wave with frequency f_2&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-01-11T17:52:22.597" />
  <row Id="8901" PostTypeId="2" ParentId="8898" CreationDate="2011-01-11T17:59:33.873" Score="2" ViewCount="" Body="&lt;p&gt;A big concern is that the datasheet you described characterizes many of the crucial parameters at VCC=5V. You may find that getting the performance you want could be tricky, and part-to-part variations could play a big role. You'll need to prototype the circuit and test in the 3-4V range (and also most likely below 3V) to see what you're getting yourself into.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-01-11T17:59:33.873" />
  <row Id="8902" PostTypeId="2" ParentId="8898" CreationDate="2011-01-11T18:01:06.810" Score="2" ViewCount="" Body="&lt;p&gt;See figure 12. Output current is not specified for input voltages under 5v, but if you need few hundreds milliamps it might be fine. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would looks for another dc-dc, with higher switching speed &amp;amp; efficiency &gt;80%. Anyway, using such a high-voltage chip for 3-4v power source is just a waste of silicon.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-11T18:01:06.810" CommentCount="3" />
  <row Id="8903" PostTypeId="2" ParentId="8889" CreationDate="2011-01-11T18:04:46.557" Score="0" ViewCount="" Body="&lt;p&gt;It's just a good excuse to switch to a soldering iron with replaceable tips (butane or more conventional) ;-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-11T18:04:46.557" CommentCount="1" />
  <row Id="8904" PostTypeId="2" ParentId="8899" CreationDate="2011-01-11T18:15:44.490" Score="7" ViewCount="" Body="&lt;p&gt;The number '2' refers to the number of tones used to encode the signal. For example, 2-FSK is essentially sending binary data using two frequencies. One symbol (time slice) has the potential for two values only. &lt;strong&gt;2-FSK is usually what is meant by an unqualified mention of FSK&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's possible to use more than two tones. These modulation schemes usually are called &lt;a href=&quot;http://en.wikipedia.org/wiki/Multiple_frequency-shift_keying&quot; rel=&quot;nofollow&quot;&gt;MFSK&lt;/a&gt; for Multiple Frequency Shift Keying. A common MFSK scheme in amateur radio is MFSK16, which uses 16 different frequencies to represent 4 binary bits in each symbol. By your notation, this would be 16-FSK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The more frequencies that you use in a symbol, the more complicated your modulation/demodulation circuit. Typical MFSK applications in amateur radio require a computer sound card and CPU for signal processing. Analog circuitry can be developed somewhat easily for FSK using two band-pass filters.&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-11T18:40:10.753" LastActivityDate="2011-01-11T18:40:10.753" />
  <row Id="8905" PostTypeId="2" ParentId="8898" CreationDate="2011-01-11T19:10:46.273" Score="4" ViewCount="" Body="&lt;p&gt;The 1V range from 3-4V isn't the problem.  The IC regulates by comparing the output voltage with an internal reference voltage, so as long as the input stays within spec (some unpublished minimum voltage to a max of 50V) and below your desired Vout (this isn't a buck/boost converter), you should be fine.  It's the minimum voltage requirements are worrying.  Your desired operation from a single coin cell is really a special application, and, as Madmanguruman said, it looks like this IC was made for much less imaginative applications - boosting a 5V supply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since your users might be tempted to stick in an alkaline battery or a dead battery, why not use something that's designed to work with a lower voltages? Linear Technology's &lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1042,P1627&quot; rel=&quot;nofollow&quot;&gt;LT1308&lt;/a&gt; switcher will work down to 1V, and has a switch current of up to 3A, so you should be able to get 15V at 250mA out of it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Disclaimer: I like Linear products; I go to their site first to look up stuff like this.  I didn't compare with other manufacturers, but you should.)  &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-11T23:15:12.023" LastActivityDate="2011-01-11T23:15:12.023" CommentCount="6" />
  <row Id="8906" PostTypeId="2" ParentId="8824" CreationDate="2011-01-11T21:19:35.307" Score="2" ViewCount="" Body="&lt;p&gt;What is crazy expensive?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a company called Xtech that might be able to supply what you need.&lt;/p&gt;&#xA;" OwnerUserId="2578" LastActivityDate="2011-01-11T21:19:35.307" />
  <row Id="8907" PostTypeId="2" ParentId="8889" CreationDate="2011-01-11T22:27:04.260" Score="1" ViewCount="" Body="&lt;p&gt;A good dip and rummage in a tip tinner will help your tip. I've rescued many tips this way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Image from &lt;a href=&quot;http://store.curiousinventor.com/guides/how_to_solder/cleantip/&quot; rel=&quot;nofollow&quot;&gt;http://store.curiousinventor.com/guides/how_to_solder/cleantip/&lt;/a&gt;&#xA;&lt;img src=&quot;http://curiousinventor.com/images/how_to_solder/tip_tinner_cleaner.jpg?1248414321&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-11T22:33:44.380" LastActivityDate="2011-01-11T22:33:44.380" />
  <row Id="8908" PostTypeId="1" AcceptedAnswerId="8917" CreationDate="2011-01-11T22:29:41.777" Score="2" ViewCount="193" Body="&lt;p&gt;I'm looking to measure current consumption of my microcontroller as an in-built feature of the final design. Should I buy and use high-side current monitors that are available on the market (e.g. &lt;a href=&quot;http://www.farnell.com/datasheets/10146.pdf&quot; rel=&quot;nofollow&quot;&gt;Zetex ZXCT1009&lt;/a&gt;)? Or is it possible to build one out of discrete parts that's cheaper and better?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Device operating out of a lithium polymer battery, so 3.7V typical only. Drawing around 0 to 30mA.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-12T01:09:18.953" LastActivityDate="2011-01-12T02:44:10.853" Title="Use a current monitor IC or roll my own?" Tags="&lt;current-measurement&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="8909" PostTypeId="1" AcceptedAnswerId="8911" CreationDate="2011-01-11T22:50:28.343" Score="1" ViewCount="93" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I have a Atmel STK500. And I can't get my head around what half of the board does. Does any one know of any good resources for learning about it. I have the following books: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/RCbFD.jpg&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/UFoTi.jpg&quot; width=&quot;250&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The primer book is good with the STK500 but only talks about the mega16(I think I maybe wrong on that don't have it to hand). But then stops after the first couple of pages and tells you how to only program the one microcontroller with it. Is there anything else I can look at to use my STK500 to its full potential? And configuring the jumpers as they confuse me being a novice. I would like to program other microcontrollers from atmel with it. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-11T23:10:05.987" LastActivityDate="2011-01-11T23:10:05.987" Title="Good resources for learning about my STK500" Tags="&lt;avr&gt;" AnswerCount="2" />
  <row Id="8910" PostTypeId="2" ParentId="8882" CreationDate="2011-01-11T22:59:04.260" Score="1" ViewCount="" Body="&lt;p&gt;The XBee is a ZigBee module with a serial interface. It is designed to act as a radio communication peripheral for a microcontroller or PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The program code inside of the module cannot (without specialised tools) be modified, instead, you're limited to the commands listed in the &lt;a href=&quot;http://site.gridconnect.com/docs/MaxStream/XBee_Manual_GC.pdf&quot; rel=&quot;nofollow&quot;&gt;user guide&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The XBee can be controlled either &lt;a href=&quot;http://www.ladyada.net/make/xbee/arduino.html&quot; rel=&quot;nofollow&quot;&gt;via your Arduino&lt;/a&gt; or with a PC and serial port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A single unit is not very useful, unless you have access to &lt;a href=&quot;http://www.zigbee.org/Products/Overview.aspx&quot; rel=&quot;nofollow&quot;&gt;other ZigBee devices&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-11T22:59:04.260" CommentCount="5" />
  <row Id="8911" PostTypeId="2" ParentId="8909" CreationDate="2011-01-11T23:02:54.040" Score="1" ViewCount="" Body="&lt;p&gt;Go into the AVR Studio help files at &lt;code&gt;Help &amp;gt; AVR Tools User Guide&lt;/code&gt; and click on the STK-500. It's the same files that come with the kit, but those are likely stuck on a CD-ROM somewhere in the sock drawer (mine certainly are). Pretty good info therein, anyway. If you're using Eclipse or something else, I can upload them or Google can reveal them.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-11T23:02:54.040" />
  <row Id="8912" PostTypeId="2" ParentId="8909" CreationDate="2011-01-11T23:03:44.773" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.nongnu.org/avrdude/user-manual/avrdude_1.html&quot; rel=&quot;nofollow&quot;&gt;AVRDude&lt;/a&gt; supports programming AVR microcontrollers via the STK500.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The STK500 appears to have many peripherals. You might want to look at projects like &lt;a href=&quot;http://www.mil.ufl.edu/~chrisarnold/components/microcontrollerBoard/AVR/avrlib/&quot; rel=&quot;nofollow&quot;&gt;avrlib&lt;/a&gt;. Alternatively, you might choose to ignore the peripherals and focus on the basics.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-11T23:03:44.773" />
  <row Id="8913" PostTypeId="2" ParentId="8824" CreationDate="2011-01-11T23:10:03.327" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.evatron.com/index-pag-products-cid-13-sid-91-l-2.html&quot; rel=&quot;nofollow&quot;&gt;Evatron&lt;/a&gt; do some fairly creasonably priced extruded cases - may be worth asking them aout bulk extrusion&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-11T23:10:03.327" />
  <row Id="8914" PostTypeId="2" ParentId="8807" CreationDate="2011-01-11T23:13:21.367" Score="2" ViewCount="" Body="&lt;p&gt;Parts cost is all about volumes. If you're making a handful, go with the prices on Farnell/Digikey/Mouser/etc. and buy from there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're making in even modest quantities, you need to get on the phone with suppliers and request quotes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As others have said, accurately predicting manufacturing costs is also hard.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-11T23:23:33.483" LastActivityDate="2011-01-11T23:23:33.483" />
  <row Id="8915" PostTypeId="1" AcceptedAnswerId="8920" CreationDate="2011-01-11T23:14:31.293" Score="1" ViewCount="158" Body="&lt;p&gt;Following on from this &lt;a href=&quot;http://electronics.stackexchange.com/questions/8885/cant-get-consistent-readings-from-sharp-ir&quot;&gt;question&lt;/a&gt;. Can I place the capacitor anywhere in the circuit before the IR Distance Sensor? In my project I have 2 PCBs: A power circuit and a Processing Circuit. In the Diagram below you see the two PCBs Power Board and Processing as well as the Sharp distance sensor. Following the diagram, can I place the capacitor on the power board or will it be ineffective by the time it reaches the sensor? I don't want to damage my expensive sensors. &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;---------------         12V             ------------------&#xA;|             |-------------------------|                |&#xA;| Power board |          5V             |  Processing    |&#xA;|             |-------------------------|     Board      |&#xA;|             |         GND             |                |&#xA;|_____________|-------------------------|________________|&#xA;                                          |       |     |&#xA;                                          |       |     |&#xA;                                      GND |   Out |  5V |&#xA;                                          |       |     |&#xA;                                        ------------------&#xA;                                        |    Sensor      |&#xA;                                        ------------------&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-01-12T08:36:15.443" LastActivityDate="2011-01-12T08:36:15.443" Title="Where to put stabilising capacitor ?" Tags="&lt;capacitor&gt;&lt;sharp&gt;" AnswerCount="2" CommentCount="0" FavoriteCount="1" />
  <row Id="8916" PostTypeId="1" CreationDate="2011-01-11T23:20:11.120" Score="2" ViewCount="124" Body="&lt;p&gt;I need to find a inexpensive replacement stepper motor and I am wondering if all of the specs need to be matched or are there some that don't need to be exact.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right now they are using a six wire motor, but only four of the wires are in use. The center wire on each side is cut off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the motors is a Astrosyn 23LY-C205-03V&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a .9 degree motor but if they are only using four wires does that change this spec? Can I get a 1.8 degree four wire?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I need to match resistance, voltage, inductance, and current? Or will it still work if they are close but not exact.&lt;/p&gt;&#xA;" OwnerUserId="2579" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-01-12T22:58:02.657" LastActivityDate="2011-01-12T22:58:02.657" Title="Stepper motor substitution" Tags="&lt;motor&gt;&lt;stepper&gt;" AnswerCount="2" />
  <row Id="8917" PostTypeId="2" ParentId="8908" CreationDate="2011-01-11T23:22:30.473" Score="5" ViewCount="" Body="&lt;p&gt;You can build one with a simple op amp circuit, but it will take more design work, more external components and likely more board space.  There really isn't a reason to do so unless you have specialty application which requires something out of the norm.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current monitoring for battery powered devices is a very normal application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are current monitors out there that output a PWM signal that you can monitor instead of a voltage that to be read with an ADC.  This type of monitor may be easier to interface with and require less power to monitor depending on the type of microcontroller your using and available peripherals.  You can also get regulators with built in current monitoring circuitry which can reduce part count, cost, board size, power usage and increase accuracy in some applications.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2011-01-12T00:40:11.397" LastActivityDate="2011-01-12T00:40:11.397" />
  <row Id="8918" PostTypeId="2" ParentId="8916" CreationDate="2011-01-11T23:24:46.353" Score="0" ViewCount="" Body="&lt;p&gt;Ideally if you replace one you should also do the other. And no you can't as that means the 0.9 degree stepper motor will have to have two pulses to catch up with the 1.8 degree one. Yes you should try to match voltage, resistance and current. They sound as if they are using them in bipolar mode. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-01-11T23:24:46.353" CommentCount="2" />
  <row Id="8919" PostTypeId="2" ParentId="8915" CreationDate="2011-01-11T23:33:11.060" Score="3" ViewCount="" Body="&lt;p&gt;All of the above.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There should be bypass caps on the power board at the regulator output, perhaps more than 1 depending on the type of regulator and ripple required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There should also be bypass caps at the input to every IC, again more than 1 may be required and every power pin should be bypassed.  A 0.1uF and a 10nF on each pin is a good general practice.  You may also need a 10uF or more on each rail on each board for bulk bypass.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sensor board likely has bypass caps on the sensor board for the +5V line.  If not, add some, 0.1uF is a decent start but you may need some more storage there, 10uF or something to supply the IR pulse current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your best bet is to post your entire schematic, especially the interface between the sensor and the &quot;processing board&quot;.  There are likely things that can be done to improve accuracy in your preprocessing of the sensors output signal before sampling it.  For instance, what does your ADC anti-aliasing filter look like?&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-01-11T23:33:11.060" CommentCount="8" />
  <row Id="8920" PostTypeId="2" ParentId="8915" CreationDate="2011-01-11T23:37:13.057" Score="4" ViewCount="" Body="&lt;p&gt;See my answer to your previous question &lt;a href=&quot;http://electronics.stackexchange.com/questions/8885&quot;&gt;here&lt;/a&gt;, specifically this image:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/6y27R.jpg&quot; alt=&quot;this image&quot;&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You want the caps to be as close as possible to the components which are drawing current.  The voltage varies due to to trace/wire inductance, so it doesn't help to locate the cap before this inductance.  The caps absolutely must be on the sensor.  You should already have output caps on your power board and decoupling caps near every IC on your 'processing board'. &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-11T23:37:13.057" />
  <row Id="8922" PostTypeId="2" ParentId="8916" CreationDate="2011-01-12T00:45:58.227" Score="2" ViewCount="" Body="&lt;p&gt;&lt;em&gt;I am wondering if all of the specs need to be matched or are there some that don't need to be exact.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It completely depends on the application.  Unfortunately you don't give us enough information to provide you with a good answer.  However, in general stepper motors are fairly standardized.  If you get one with the same step size, and the same general shape and size, and you can wire it up correctly (since the driver uses 4 wires it's pretty easy to convert a 6 or 8 wire to 4 wire use) then you should be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the device that uses the stepper is using it near its limits in terms of speed, torque, etc then you may have problems if you don't match the winding impedance, mechanical resonance, etc.  This is only a problem in high performance machines, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would contact the manufacturer, if possible, and get their recommendation.  If not, try a different motor out and see if it works.  Chances are good it'll be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The step size is independent of the wiring - a four wire stepper at 0.9 degrees per step is the same as a 6 wire and 8 wire, just the coils have taps in them (or separated).  So you will need to match the step size regardless of the wiring.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2011-01-12T00:45:58.227" CommentCount="1" />
  <row Id="8923" PostTypeId="2" ParentId="8908" CreationDate="2011-01-12T02:02:31.840" Score="0" ViewCount="" Body="&lt;p&gt;There are nice 1-wire devices like the DS2438 from Maxim-IC&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1-wire is fairly easy and some micros can even talk to them natively.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://pdfserv.maxim-ic.com/en/ds/DS2438.pdf&quot; rel=&quot;nofollow&quot;&gt;http://pdfserv.maxim-ic.com/en/ds/DS2438.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1481" LastEditorUserId="1481" LastEditorDisplayName="" LastEditDate="2011-01-12T02:44:10.853" LastActivityDate="2011-01-12T02:44:10.853" />
  <row Id="8924" PostTypeId="1" AcceptedAnswerId="8927" CreationDate="2011-01-12T03:32:47.520" Score="1" ViewCount="351" Body="&lt;p&gt;I would like to use an ATtiny2313 to emulate a Super Nintendo controller because I have an ATtiny2313 but I do not have an input shift register and I don't feel like soldering wires onto an existing SNES controller board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This application requires 12 inputs (bits 13-16 are always 1) and a latch, clock, and data out pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have this code lying around? It can't be more than 20 instructions.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2011-01-13T19:23:28.247" LastActivityDate="2011-01-29T21:00:10.753" Title="Does anyone have code to emulate a 16-bit input shift register with an ATtiny2313?" Tags="&lt;attiny&gt;&lt;shift-register&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="8925" PostTypeId="2" ParentId="8924" CreationDate="2011-01-12T04:20:35.643" Score="2" ViewCount="" Body="&lt;p&gt;I don't have this code lying around, but I do have the next best things:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc0856.pdf&quot; rel=&quot;nofollow&quot;&gt;AVR Instruction Set&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.atmel.com/dyn/Products/Product_card.asp?part_id=3229&quot; rel=&quot;nofollow&quot;&gt;ATtiny2313 information&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=97850&quot; rel=&quot;nofollow&quot;&gt;guide to starting in AVR assembler&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=101529&quot; rel=&quot;nofollow&quot;&gt;Macros in assembler&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;sup&gt;You might say I &lt;strong&gt;do&lt;/strong&gt; have the code laying around, but it's not organized and concatenated correctly... ;)&lt;/sup&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-12T04:20:35.643" CommentCount="4" />
  <row Id="8927" PostTypeId="2" ParentId="8924" CreationDate="2011-01-12T05:49:36.470" Score="4" ViewCount="" Body="&lt;p&gt;There's already an 8-bit shift register built into the &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=3229&quot; rel=&quot;nofollow&quot;&gt;Universal Serial Interface (USI)&lt;/a&gt;. All you have to do is use it twice in a row. &lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-12T17:08:20.993" LastActivityDate="2011-01-12T17:08:20.993" />
  <row Id="8928" PostTypeId="2" ParentId="8530" CreationDate="2011-01-12T06:19:04.763" Score="4" ViewCount="" Body="&lt;p&gt;Your absolute references will be the &lt;a href=&quot;http://www.xilinx.com/support/documentation/spartan-6.htm&quot; rel=&quot;nofollow&quot;&gt;Spartan 6 user guides&lt;/a&gt;. For instance, the Clocking Resources guide (UG382) covers how to configure the DCMs. For examples of how the actual code looks, ISE has a database of them. Open Language Templates (the lightbulb in the toolbar), then look in language (VHDL or Verilog) -&gt; Device Primitive Instantiation -&gt; chip family (Spartan-6) -&gt; Clock Components. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Details specific to your board are available from Digilent, in particular you'll want the UCF (which names all the IOs) and the reference manual (which explains the peripheral circuitry).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The general structure of your language, including how to make a component, is probably better picked up from books and examples. I haven't used Verilog so don't have any specific suggestions. Still, the templates include snippets of various generic contructs as well.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="1181" LastEditorDisplayName="" LastEditDate="2011-01-12T09:42:52.933" LastActivityDate="2011-01-12T09:42:52.933" CommentCount="4" />
  <row Id="8929" PostTypeId="1" AcceptedAnswerId="8933" CreationDate="2011-01-12T07:42:07.763" Score="4" ViewCount="257" Body="&lt;p&gt;First of I have no experience with electronics so I am not sure what I should be searching for to get this done. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;All I have with me at the moment is a arduino and a few connectors and LED's. Is it possible to switch the kettle on/off using just these basics (i.e. I dont want to buy more stuff for now).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The kettle is the most basic kind , i.e. the ones that plug into a wall outlet and have a single switch to turn it on or off. Let me know if you need more info.&lt;/p&gt;&#xA;" OwnerUserId="2333" LastActivityDate="2011-01-12T22:44:51.637" Title="Switching a Kettle On/Off using a arduino" Tags="&lt;arduino&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="8930" PostTypeId="2" ParentId="8929" CreationDate="2011-01-12T08:19:09.310" Score="1" ViewCount="" Body="&lt;p&gt;Use a mains relay controlled by the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to take the usual precautions to ensure safety, of course.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-12T08:19:09.310" />
  <row Id="8931" PostTypeId="2" ParentId="8929" CreationDate="2011-01-12T08:21:16.213" Score="2" ViewCount="" Body="&lt;p&gt;No, you don't have enough parts to build a circuit to switch on your kettle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it really is a basic kettle with no logic or low-voltage controls, then the switch is controlling your house voltage (110V/230V) directly. The practical limit to an Arduino or any microcontroller is about 5V. Additionally, microcontrollers can only handle DC voltages. If you tried to connect your Arduino to the kettle without any additional components, it would probably explode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would recommend that you use a relay to switch on and off your kettle. It is relatively easy to find 110V/230V AC rated relays, with current ratings large enough for safe switching. It is a fairly simple circuit to set up; you need a relay, a driver transistor, and a diode for relay coil.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-01-12T08:21:16.213" />
  <row Id="8933" PostTypeId="2" ParentId="8929" CreationDate="2011-01-12T10:47:05.723" Score="8" ViewCount="" Body="&lt;p&gt;There's a particular problem here with the kettle that a relay will not solve. Kettles always have their own switch which trips off when they boil. So even if your relay is on, the kettle will not heat up unless this switch is also on. If you took the kettle apart and shorted out the switch, it would not trip off when the boiling point was reached, so this is very dangerous. If you think you can also replace the boiling point sensor and run the logic through your processor, you should think about the fail safe implications of this and consider your house insurance situation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the type of switch used in kettle, it might be possible to fill it and switch it on mechanically, waiting for mains to be switched on by the micro. But you could only boil it once before having to mechanically reset the switch. If that works for you, fine, but bear in mind that kettle are not like lamps that you could just switch on and off whenever you like, and interfering with the switch is hazardous.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most kettles that I have come across do allow the switch to be on even when there is no mains, but most toasters don't allow the basket to be latched in the down position without incoming mains, so you can see this could be a problem.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-01-12T10:47:05.723" CommentCount="5" />
  <row Id="8934" PostTypeId="2" ParentId="8929" CreationDate="2011-01-12T11:19:40.440" Score="2" ViewCount="" Body="&lt;p&gt;The current issue of MAKE (Vol. 25) has an article on controlling a crock pot, which is almost identical to what you'd need to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://makeprojects.com/Project/Yobot-Arduino-Yogurt-Maker/499/1&quot; rel=&quot;nofollow&quot;&gt;http://makeprojects.com/Project/Yobot-Arduino-Yogurt-Maker/499/1&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-01-12T11:19:40.440" CommentCount="1" />
  <row Id="8935" PostTypeId="2" ParentId="4163" CreationDate="2011-01-12T11:39:18.217" Score="1" ViewCount="" Body="&lt;p&gt;Like Tim Ring suggested, combining an Arduino with a more powerful device would be your best bet.  Using a cheap Netbook as the brains would give you that additional power, you could even use the built in webcam as the camera, and do all of your image processing on the Netbook.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino would plug into a USB port on the netbook and could easily send and receive commands over a serial port - this way you could program all of your IO code into the Arduino and write your higher level &quot;brain&quot; code to run on the Netbook.  For example, the Netbook could then issue commands like &quot;Drive Forward For 2 Seconds&quot; to the Arduino and the Arduino could control the motors to perform the task.  You could ask it for the reading from the compass or GPS and the Arduino could send the value back.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also have your &quot;brain&quot; code monitoring the serial port for any data the Arduino wanted to send, for example, if it was driving forwards and a bumper sensor detected a collision, it could send a &quot;Collision&quot; command to the brain and the brain could decide what to do about it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The huge benefit of using a Netbook would be the ability to display diagnostic and debug information on it's LCD.  Coming from a PC prgramming background, I find debugging an Arduino with no visual feedback to be very tricky indeed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino would get it's power from the Netbook too, meaning you only needed to supply a separate power source for the motors/servos.&lt;/p&gt;&#xA;" OwnerUserId="2573" LastActivityDate="2011-01-12T11:39:18.217" />
  <row Id="8936" PostTypeId="2" ParentId="8929" CreationDate="2011-01-12T12:15:02.253" Score="1" ViewCount="" Body="&lt;p&gt;If you want to control a 110V mains power device, a &quot;power switch tail&quot; is available for markets that use the US-style 110V outlets: &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=44&amp;amp;products_id=268&quot; rel=&quot;nofollow&quot;&gt;powerswitch tail&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2011-01-12T12:15:02.253" />
  <row Id="8937" PostTypeId="1" AcceptedAnswerId="8939" CreationDate="2011-01-12T12:15:27.260" Score="2" ViewCount="177" Body="&lt;p&gt;Not sure if this is the best place to ask.  I am looking for a &quot;real&quot; SIM card programmer (as opposed to a $10 backup/restore thingy), which enables me to write the entire SIM card as would a cell 'phone's protocol stack.&lt;/p&gt;&#xA;" OwnerUserId="3396" LastActivityDate="2011-01-12T13:25:50.147" Title="Seeking affordable SIM programmer" Tags="&lt;hardware&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="8938" PostTypeId="2" ParentId="8937" CreationDate="2011-01-12T13:08:58.970" Score="5" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=27&amp;amp;products_id=101&quot; rel=&quot;nofollow&quot;&gt;SIM Reader Kit&lt;/a&gt; from &lt;a href=&quot;http://www.adafruit.com/&quot; rel=&quot;nofollow&quot;&gt;Adafruit Industries&lt;/a&gt; will read and write SIM cards. This is a kit, so it must be assembled. However, that should be fairly easy for just about anyone.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/lJo13.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2489" LastActivityDate="2011-01-12T13:08:58.970" CommentCount="1" />
  <row Id="8939" PostTypeId="2" ParentId="8937" CreationDate="2011-01-12T13:25:50.147" Score="4" ViewCount="" Body="&lt;p&gt;The Bus Pirate is a flexible USB protocol converter. It supports access to a range of SIM and Smart Cards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dangerousprototypes.com/bus-pirate-manual/&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com/bus-pirate-manual/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://dangerousprototypes.com/2009/08/31/bus-pirate-sle4442-smart-card-update/&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com/2009/08/31/bus-pirate-sle4442-smart-card-update/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.adafruit.com/adablog/wp-content/uploads/2010/03/buspiratepcb_LRG.jpg&quot; width=&quot;200&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-12T13:25:50.147" CommentCount="2" />
  <row Id="8940" PostTypeId="1" AcceptedAnswerId="8943" CreationDate="2011-01-12T14:20:56.500" Score="2" ViewCount="281" Body="&lt;p&gt;I've been wanting to make a laser gun sound effect attachment for my son's bike.  Currently, I'm using the electronics salvaged from his old laser gun toys.  All of them seem to use electronics hidden under a black blob of resin or epoxy, which I assume is an ASIC?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd love to be able to make this more cheaply, and was wondering if there's any resource out there to show how to make something like this with analog components.  I have an old fart machine that seems to use a combination of resistors, capacitors, and inductors to generate multiple sounds (i.e. no microcontroller), so I figure that it must be possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I only need one sound, but it would be great to be able to select from multiple, or somehow use a &lt;a href=&quot;http://electronics.stackexchange.com/questions/2057/polyphonic-sounds-from-a-microcontroller&quot;&gt;microcontroller + DAC&lt;/a&gt; to do it, although the latter would increase the price.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- &lt;a href=&quot;http://www.web-tronics.com/gunbombsounds.html&quot; rel=&quot;nofollow&quot;&gt;something like this&lt;/a&gt;, but cheaper than $10 would be nice&#xA;EDIT -- also found &lt;a href=&quot;http://circuitzoo.com/2010/05/24/electronics/simple-sound-effect-generator-circuit-diagram-using-ht2884&quot; rel=&quot;nofollow&quot;&gt;this schematic&lt;/a&gt; but it needs an IC called the HT2884&lt;/p&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-01-12T18:12:44.417" LastActivityDate="2011-01-13T00:51:34.607" Title="Plans / tutorial for sound effect generator using only analog components?" Tags="&lt;microcontroller&gt;&lt;capacitor&gt;&lt;resistor&gt;&lt;sound&gt;&lt;inductor&gt;" AnswerCount="3" CommentCount="6" FavoriteCount="1" />
  <row Id="8941" PostTypeId="2" ParentId="3027" CreationDate="2011-01-12T14:31:44.623" Score="1" ViewCount="" Body="&lt;p&gt;I think other answers made a pretty good case for the pros and cons and decision factors, so I'd like just to summarize and add a few comments. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For small microcontrollers (8-bit), no way. You're just asking to hurt yourself, there's no gain and you'll give up too much resources.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For high-end microcontrollers (e.g. 32-bit, 10s or 100s of MB for RAM and storage) that have a decent OS it's perfectly OK and, I'd dare to say, even recommended.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the question is: where's the boundary? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know for sure, but once I developed a system for a 16-bit uC with 1 MB RAM &amp;amp; 1 MB storage in C++, only to regret it later. Yes, it worked, but the extra work I had wasn't worth it. I had to make it fit, make sure things like exceptions wouldn't produce leaks (the OS+RTL support was pretty buggy and unreliable). Moreover, an OO app typically does lots of small allocations, and the heap overhead for those was another nightmare. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given that experience, I'd assume for future projects that I'll choose C++ only in systems at least 16-bit, and with at least 16 MB for RAM &amp;amp; storage. That's an arbitrary limit, and probably will vary according to things like the type of application, coding styles and idioms, etc. But given the caveats, I'd recommend a similar approach.&lt;/p&gt;&#xA;" OwnerUserId="1078" LastEditorUserId="1078" LastEditorDisplayName="" LastEditDate="2011-01-12T14:41:53.713" LastActivityDate="2011-01-12T14:41:53.713" CommunityOwnedDate="2011-01-12T14:31:44.623" CommentCount="2" />
  <row Id="8942" PostTypeId="2" ParentId="8940" CreationDate="2011-01-12T14:41:27.943" Score="1" ViewCount="" Body="&lt;p&gt;I think some of the answers for the question you've linked to give you some good ideas about how to do this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;PWM is a simple way to create a DAC, and you just need to program your microcontroller to output different frequencies until you find something that sounds like what your looking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use some sound wave editing software like &lt;a href=&quot;http://en.wikipedia.org/wiki/Adobe_Audition&quot; rel=&quot;nofollow&quot;&gt;Adobe Audition&lt;/a&gt; that has a wave generator that you can use to easily play around with different frequencies and immediately hear what they sound like. When you find something that sounds good, you can then try to write an algorithm to match it in code on your microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to just use discrete components, then maybe you could build two &lt;a href=&quot;http://en.wikipedia.org/wiki/Multivibrator&quot; rel=&quot;nofollow&quot;&gt;Multivibrator&lt;/a&gt; circuits with different frequencies, and combine the outputs using an &lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/Electronic/opampvar6.html#c1&quot; rel=&quot;nofollow&quot;&gt;Op Amp&lt;/a&gt; circuit to drive a speaker.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-12T15:22:49.607" LastActivityDate="2011-01-12T15:22:49.607" CommentCount="6" />
  <row Id="8943" PostTypeId="2" ParentId="8940" CreationDate="2011-01-12T16:30:35.613" Score="3" ViewCount="" Body="&lt;p&gt;Back when I were a lad, the &lt;a href=&quot;http://en.wikipedia.org/wiki/Texas_Instruments_SN76477&quot; rel=&quot;nofollow&quot;&gt;SN76477&lt;/a&gt; sound effects generator ruled supreme. If you fancy a bit of nostalgia they can be had for just over $9. Admittedly, you need a few other components but they can make a ton and a half of sounds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.bgmicro.com/ICS76477.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.bgmicro.com/ICS76477.aspx&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Just as an afterthought, one of the more irritating circuits that the lads in the electronics club at school used to make up was a 555 oscillator where the timing resistor from Pin 7 to Vcc was replaced by 10 variable resistors with diodes (or LEDs) in series, hooked to the outputs of a 4017 decade counter, which was clocked by another 555 timer. By adjusting the variable resistors and the frequency of the 555 clocking the 4017 you could generate a string of 10 notes in a loop. When this ran at a fast clock speed you got some weird noises.&lt;/p&gt;&#xA;" OwnerUserId="1750" LastEditorUserId="1750" LastEditorDisplayName="" LastEditDate="2011-01-13T00:51:34.607" LastActivityDate="2011-01-13T00:51:34.607" CommentCount="3" />
  <row Id="8945" PostTypeId="2" ParentId="8940" CreationDate="2011-01-12T17:58:20.753" Score="2" ViewCount="" Body="&lt;p&gt;it is not analog, but &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;you can use R-2R Resistor ladder (acting as a simple DAC) on the outputs of a controller &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;or you can create a chain of counters addressing an E/EPROM in a loop, on Memory outputs again R-2R ladder. You can usee 2, 3 or more of the MSB address lines with switch to choose different sound&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/uPznS.gif&quot; alt=&quot;like this&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2471" LastActivityDate="2011-01-12T17:58:20.753" CommentCount="2" />
  <row Id="8946" PostTypeId="1" AcceptedAnswerId="8961" CreationDate="2011-01-12T18:57:14.990" Score="4" ViewCount="392" Body="&lt;p&gt;I want to build a circuit that shows the real-time frequency components of an audio signal on a number of bar graphs of some sort. Currently, my plan is to build 12 band-pass op-amp filters, and then use a rectifier and RC circuit to create a DC envelope for each output, and then use that signal to drive a LED bargraph or something similar.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit will use a single +3.3V supply, and using 12 band-pass filters is not really negotiable. If I want a 12-channel bar graph, am I stuck using &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=160-1066-ND&quot; rel=&quot;nofollow&quot;&gt;12 bar-graph LEDs&lt;/a&gt; and &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=LM3914N-1-ND&quot; rel=&quot;nofollow&quot;&gt;bar-graph LED Driver&lt;/a&gt; pairs? That comes out to $45! Is there a better/less expensive/simpler method of getting a similar result? Ideally, I would not need a microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-05-08T20:01:21.387" Title="Multi-channel bar graph LED drivers" Tags="&lt;audio&gt;&lt;display&gt;" AnswerCount="7" CommentCount="0" />
  <row Id="8947" PostTypeId="2" ParentId="8946" CreationDate="2011-01-12T20:33:35.377" Score="1" ViewCount="" Body="&lt;p&gt;Analog spectrum analyzers mix down the input over a range of frequencies and display the RMS or power level of a thin, low frequency passband range - you could do the same. Instead of using op-amp filters at your input, you can use an input antialiasing filter (10kHz-20kHz LPF) followed by a mixer with LO input from a VCO driven by a ramp (the &lt;em&gt;swept&lt;/em&gt; part of &lt;em&gt;swept-tuned spectrum analyzer&lt;/em&gt;), then a great bandpass filter. The mentioned peak detector follows. &lt;em&gt;This approach is quite a bit more involved than a bank of filters followed by amplifiers, but way more fun. Much hair-pulling and brain-fuzzing will result.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You likely know more about mixers than I do, so I'll leave that alone. Note that an &lt;em&gt;&quot;audio mixer&quot;&lt;/em&gt; is not the same thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage-controlled_oscillator&quot; rel=&quot;nofollow&quot;&gt;Wikipedia has an audio VCO example, and leads to some popular designs.&lt;/a&gt; Dedicated VCO and voltage-to-frequency converter ICs are available, but they are mostly for the 100's of MHz-range; &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/21483d.pdf&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; may be of use, but generates square waves. (Another question may be in order to determine an ideal VCO for this application.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A simple diode peak detector can be improved with two op-amps, as described in &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0521370957&quot; rel=&quot;nofollow&quot;&gt;AoE&lt;/a&gt; on pg. 217. Especially useful for small amplitude input signals (error ~0.6/Vp).&#xA;&lt;img src=&quot;http://i.imgur.com/NQhKN.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-12T20:33:35.377" CommentCount="2" />
  <row Id="8948" PostTypeId="1" CreationDate="2011-01-12T20:37:38.240" Score="5" ViewCount="147" Body="&lt;p&gt;I have been modifying AVR and PIC microcontroller code for a few years now for work but have never written anything from scratch, I understand it pretty well. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am starting to write my own code now and am having trouble getting started. I was wondering how other people start writing code and if there is a book or tutorial people would recommend on this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you start with coding your initialization function then interrupts then timers then the main while(1) loop... I am wondering what the best way to get started is. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you&lt;/p&gt;&#xA;" OwnerUserId="2590" LastActivityDate="2011-01-12T21:08:44.393" Title="avr microcontrollers and how to get started coding init or main loop or timers or interrupts" Tags="&lt;avr&gt;&lt;pic&gt;" AnswerCount="2" />
  <row Id="8949" PostTypeId="2" ParentId="8948" CreationDate="2011-01-12T21:03:23.083" Score="5" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;The first thing one does in any microcontroller project is blink an LED; keep it blinking and give it a name &lt;em&gt;(&quot;Blinky&quot;)&lt;/em&gt;, too. It's the &lt;strong&gt;&lt;em&gt;heart beat&lt;/em&gt;&lt;/strong&gt; of your widget, and will always work so long as your program doesn't get stuck.&lt;/li&gt;&#xA;&lt;li&gt;Commit to the local version control repository.&lt;/li&gt;&#xA;&lt;li&gt;Next is to fly through the entire program in pseudo/crapcode, based on your program flow diagrams or whatever planning methods you've subscribed to. If something doesn't work or you just don't like it, comment it out but keep it there so you know to fix it later. If you don't know how to do something, write down what it's supposed to do in comments.&lt;/li&gt;&#xA;&lt;li&gt;Commit to the local version control repository.&lt;/li&gt;&#xA;&lt;li&gt;Time to fill in the blanks! Implement one function at a time, for example the timer, &lt;em&gt;and test it&lt;/em&gt;. Your program should always compile and work as expected. I like to implement any user interface connections at this point, like UART -&gt; RS232 -&gt; PC links or LCD displays. Don't forget about &lt;em&gt;Blinky&lt;/em&gt;.&lt;/li&gt;&#xA;&lt;li&gt;Commit to the local version control repository.&lt;/li&gt;&#xA;&lt;li&gt;Try to break your code with rigorous test routines; debug. &lt;a href=&quot;http://area51.stackexchange.com/proposals/11464/code-review&quot;&gt;Have others review your code&lt;/a&gt;; debug. Run your widget through its design parameters regularly, like temperature variations; debug.&lt;/li&gt;&#xA;&lt;li&gt;Commit to the local version control repository.&lt;/li&gt;&#xA;&lt;li&gt;Disconnect &lt;em&gt;Blinky&lt;/em&gt; if you're a heartless fool, and ship.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.avrfreaks.net/&quot; rel=&quot;nofollow&quot;&gt;AVRFreaks&lt;/a&gt; has an excellent tutorial written by Dean Camera (aka. &lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=profile&amp;amp;mode=viewprofile&amp;amp;u=55749&quot; rel=&quot;nofollow&quot;&gt;abcminuser&lt;/a&gt;) called &lt;strong&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?name=PNphpBB2&amp;amp;file=viewtopic&amp;amp;t=48535&quot; rel=&quot;nofollow&quot;&gt;Modularizing C Code: Managing large projects&lt;/a&gt;&lt;/strong&gt;. You may also be interested in reading &lt;a href=&quot;http://www.proaxis.com/~wagnerj/StateMachines/State%20Machines%20for%20Microprocessors.pdf&quot; rel=&quot;nofollow&quot;&gt;State Machines for Microprocessors&lt;/a&gt; by James Wagner.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-12T21:08:44.393" LastActivityDate="2011-01-12T21:08:44.393" CommentCount="2" />
  <row Id="8950" PostTypeId="2" ParentId="8948" CreationDate="2011-01-12T21:05:49.493" Score="3" ViewCount="" Body="&lt;p&gt;My favourite AVR-from-scratch-in-C tutorial is &lt;a href=&quot;https://www.mainframe.cx/~ckuethe/avr-c-tutorial/&quot; rel=&quot;nofollow&quot;&gt;https://www.mainframe.cx/~ckuethe/avr-c-tutorial/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Everyone has their own style for small embedded systems. Here's mine:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I like to use lots of C files, with the name of each making up a prefix for functions. For example, &lt;code&gt;led_init()&lt;/code&gt; and &lt;code&gt;led_tick()&lt;/code&gt; are both in &lt;code&gt;led.c&lt;/code&gt;. This keeps things modular and helps with portability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use a &lt;code&gt;common.h&lt;/code&gt; header file to define types, but individual includes for each module.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tend to use a single freerunning system timer (in a &lt;code&gt;systime.c&lt;/code&gt;) then have modules call out to a &lt;code&gt;systime_get()&lt;/code&gt; function to fetch the current time in system ticks or milliseconds. Each module can then schedule events through software timers using the &lt;code&gt;X_tick()&lt;/code&gt; functions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;common.h:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#ifndef COMMON_H&#xA;#define COMMON_H&#xA;#include &amp;lt;stdio.h&amp;gt;  // general purpose headers&#xA;#include &amp;lt;stdint.h&amp;gt;&#xA;#include &amp;lt;stdbool.h&amp;gt;&#xA;...&#xA;#endif&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;uart.h:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#ifndef UART_H&#xA;#define UART_H&#xA;#include &amp;lt;avr/usart.h&amp;gt;  // microcontroller specific headers for uart&#xA;...&#xA;&#xA;void uart_init(void);&#xA;void uart_putc(uint8_t ch);&#xA;...&#xA;&#xA;#endif&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;uart.c:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &quot;common.h&quot;&#xA;#include &quot;uart.h&quot;&#xA;&#xA;void uart_isr(void) __interrupt VECTOR&#xA;{&#xA;  // handle incoming data&#xA;}&#xA;&#xA;void uart_init(void)&#xA;{&#xA;  // setup hardware&#xA;}&#xA;&#xA;void uart_putc(uint8_t ch)&#xA;{&#xA;  UART_TX_FIFO_REGISTER = ch;&#xA;  while(!TX_COMPLETE_REGISTER);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;led.h:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#ifndef LED_H&#xA;#define LED_H&#xA;#include &amp;lt;avr/ioports.h&amp;gt;  // microcontroller specific headers for port io&#xA;...&#xA;&#xA;#define LED_DDR   PORTAD&#xA;#define LED_PIN   5&#xA;#define LED_MASK  (1 &amp;lt;&amp;lt; LED_PIN)&#xA;#define LED_PORT  PORTA&#xA;&#xA;void led_init(void);&#xA;void led_set(void);&#xA;void led_tick(void);&#xA;...&#xA;&#xA;#endif&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;led.c:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &quot;common.h&quot;&#xA;#include &quot;led.h&quot;&#xA;&#xA;void led_init(void)&#xA;{&#xA;  LED_DDR |= LED_MASK;&#xA;}&#xA;&#xA;void led_set(void)&#xA;{&#xA;  LED_PORT |= LED_MASK;&#xA;}&#xA;&#xA;void led_tick(void)&#xA;{&#xA;  // animate LEDs in an amusing fashion&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;main.c:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &quot;common.h&quot;&#xA;#include &quot;led.h&quot;&#xA;#include &quot;uart.h&quot;&#xA;&#xA;int main(void)&#xA;{&#xA;  led_init();&#xA;  uart_init();&#xA;  ...&#xA;&#xA;  led_set();&#xA;&#xA;  while(1)&#xA;  {&#xA;    led_tick();&#xA;    uart_tick();&#xA;  }&#xA;&#xA;  return 0;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Here are two &quot;real world&quot; projects using this style for &lt;a href=&quot;http://blog.hodgepig.org/busninja/&quot; rel=&quot;nofollow&quot;&gt;AVR&lt;/a&gt; and &lt;a href=&quot;http://blog.hodgepig.org/2010/09/10/575/&quot; rel=&quot;nofollow&quot;&gt;MSP430&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-12T21:05:49.493" />
  <row Id="8951" PostTypeId="2" ParentId="8946" CreationDate="2011-01-12T21:27:15.180" Score="9" ViewCount="" Body="&lt;p&gt;Sometimes it's cheaper to use a general purpose IC and program it to do what you want, then trying to find a bunch of special purpose ICs that aren't programmable, that do exactly what you want. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This guy did a 64-band spectrum analyzer on a low end microcontroller, so doing 12 channels should be cake. (he also included a LCD driver...in your case you would have the software drive a matrix of LEDs instead). The circuit is fairly simple as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The microcontroller &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=ATMEGA88A-PU-ND&quot; rel=&quot;nofollow&quot;&gt;is cheap&lt;/a&gt;. To drive the LEDs, you will have 120 of them (10 x 12). You would just wire them in a matrix, and you could drive it with 4 shift registers &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=568-2621-5-ND&quot; rel=&quot;nofollow&quot;&gt;which are also cheap&lt;/a&gt;. (Would take 6 I/O pins, plus or minus, depending on how you wired it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://elm-chan.org/works/akilcd/report_e.html&quot; rel=&quot;nofollow&quot;&gt;http://elm-chan.org/works/akilcd/report_e.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/eCNWe.jpg&quot; alt=&quot;LCD output&quot;&gt; &lt;img src=&quot;http://i.imgur.com/6taD3.jpg&quot; alt=&quot;PCB layout&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2011-01-12T21:27:15.180" CommentCount="2" />
  <row Id="8952" PostTypeId="2" ParentId="8929" CreationDate="2011-01-12T22:44:51.637" Score="0" ViewCount="" Body="&lt;p&gt;This is a somewhat different approach, and no arduino involved, but you may like the &lt;a href=&quot;http://www.instructables.com/id/The-Automatic-Button-Pusher/&quot; rel=&quot;nofollow&quot;&gt;Automatic Button Pusher&lt;/a&gt; for inspiration.&lt;/p&gt;&#xA;" OwnerUserId="623" LastActivityDate="2011-01-12T22:44:51.637" />
  <row Id="8953" PostTypeId="1" AcceptedAnswerId="8957" CreationDate="2011-01-12T23:11:42.710" Score="2" ViewCount="221" Body="&lt;p&gt;I need to compare a negative voltage with a positive one, each on the order of a few hundred millivolts each; I want to compare the magnitudes, ignoring the signs, although only for this particular quadrant (I don't need all other signs.) How can I do it? I thought of using resistors to pull the negative voltage positive, but it only gives me a small signal on top of a DC offset, and that is difficult to compare with.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-13T15:01:43.730" Title="Compare negative with positive, ignoring sign" Tags="&lt;comparator&gt;&lt;negative&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="8954" PostTypeId="2" ParentId="8856" CreationDate="2011-01-12T23:27:39.810" Score="1" ViewCount="" Body="&lt;p&gt;For analog functionality, sometimes the chip can be intentionally hobbled and the same die sold cheaper with not-so-good performance. Blowing on-chip fuses to reduce bias currents (for example) can reduce the overall performance of the chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For digital chips that are required to run at speeds approaching the capabilities of the manufacturing process, final test will weed out the best performers from the not-so-good performers and 'bin' them accordingly. Differences in speeds are usually caused by statistical variations in the manufacturing process.&lt;/p&gt;&#xA;" OwnerUserId="814" LastActivityDate="2011-01-12T23:27:39.810" CommentCount="2" />
  <row Id="8955" PostTypeId="2" ParentId="8953" CreationDate="2011-01-12T23:30:55.947" Score="0" ViewCount="" Body="&lt;p&gt;I had some doubts about your needs. What you want is to &quot;remove&quot; the signal and then find the difference between the signals?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it is you may acompplish it using an precision rectifier to &quot;remove&quot; the negative signal ( &lt;a href=&quot;http://en.wikipedia.org/wiki/Precision_rectifier&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Precision_rectifier&lt;/a&gt; ) and then an differential amplifier to get the delta between the signals ( &lt;a href=&quot;http://www.electronics-tutorials.ws/opamp/opamp_5.html&quot; rel=&quot;nofollow&quot;&gt;http://www.electronics-tutorials.ws/opamp/opamp_5.html&lt;/a&gt; )&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2011-01-12T23:30:55.947" CommentCount="3" />
  <row Id="8956" PostTypeId="2" ParentId="8953" CreationDate="2011-01-12T23:40:37.127" Score="1" ViewCount="" Body="&lt;p&gt;Multiple methods making &lt;sub&gt;&lt;em&gt;electro&lt;/em&gt;&lt;/sub&gt;magnetics malleable:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Invert the negative voltage with an inverting buffer (op amp).&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;li&gt;Use one of the following active full-wave rectifiers:&#xA;&lt;ol&gt;&#xA;&lt;li&gt;This just works!&lt;br&gt;&lt;img src=&quot;http://i.imgur.com/Kv7Bq.png&quot; alt=&quot;alt text&quot;&gt;&lt;/li&gt;&#xA;&lt;li&gt;The other one described in &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0521370957&quot; rel=&quot;nofollow&quot;&gt;AoE&lt;/a&gt; on page 222 (requires bipolar source).&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&lt;/li&gt;&#xA;&lt;li&gt;When you say &lt;em&gt;&quot;small signal&quot;&lt;/em&gt;, that tells me you are comparing AC signals riding different biases, which means you can block both biases with blocking caps and compare with a differential amplifier &lt;em&gt;(eg. &quot;long tailed pair&quot;)&lt;/em&gt;. Some diff amps take out bias by default (not related to &lt;a href=&quot;http://en.wikipedia.org/wiki/Common-mode_rejection_ratio&quot; rel=&quot;nofollow&quot;&gt;CMRR&lt;/a&gt;). &lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;li&gt;Another idea: scale the negative voltage up to above 0V with a few resistors, as in your first idea, then take care of subsequent bias with math and diff amp resistors.&lt;br&gt; &lt;img src=&quot;http://i.imgur.com/ULZ5U.png&quot; alt=&quot;alt text&quot;&gt; &lt;br&gt; V&lt;sub&gt;OUT&lt;/sub&gt; will be this:&lt;br&gt; &lt;img src=&quot;http://i.imgur.com/woCVQ.png&quot; alt=&quot;alt text&quot;&gt; &lt;br&gt; Scale R&lt;sub&gt;1&lt;/sub&gt; and R&lt;sub&gt;2&lt;/sub&gt; such that the op amp positive input is always positive.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-13T06:25:47.300" LastActivityDate="2011-01-13T06:25:47.300" CommentCount="2" />
  <row Id="8957" PostTypeId="2" ParentId="8953" CreationDate="2011-01-12T23:56:55.417" Score="3" ViewCount="" Body="&lt;p&gt;Couldn't you just place two equal resistors in series between the two signals? The junction of those resistors would be their average, and has a sign matching the greater side. It could then be compared to zero for amplification.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2011-01-12T23:56:55.417" CommentCount="12" />
  <row Id="8958" PostTypeId="2" ParentId="8953" CreationDate="2011-01-13T00:26:56.560" Score="1" ViewCount="" Body="&lt;p&gt;If you can tolerate a slight current into the circuit (adjustable by modifying the pullup resistors), you can use a diode to offset the voltage:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;         /-- o ----------o-------------------\&#xA;         |   |  ___      -  ___              |&#xA;         |   `-|___|-\   `-|___|-\         |\|&#xA;         |        .--o-----------)---------|-\  Output&#xA;         |        |          .---|         |  &gt;---&#xA;         |        |          |   \---------|+/&#xA;        --- 5V    V          V             |/|&#xA;         -        -          -               |&#xA;         |        |          |               |&#xA;   /-----o--------)-------o--)---------------/&#xA;   |     |        |       |  |   |&#xA;  ===    |        |  ___  |  |  .-.&#xA;  GND   --- V-    |-|___|-/  \-&gt;| |POT&#xA;         -        |  SHUNT      | |&#xA;         |     // |  Res        '-'&#xA;         o-----&amp;lt;|-/              |&#xA;         |     LED       ___     |&#xA;         \--------------|___|----/&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You'll need to give the pot the same polarity and ground reference as the shunt resistor, and you'll want to make sure that your diodes have identical forward voltages (use the same diode, and try to find one that characterizes Vf very precisely).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The pullup resistors to 5V should be very large, and the currents through them very small in comparison with the resistances of the pot and shunt resistor and their current values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Mega ASCII circuit created with &lt;a href=&quot;http://www.tech-chat.de/aacircuit.html&quot; rel=&quot;nofollow&quot;&gt;AACircuit&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-13T15:01:43.730" LastActivityDate="2011-01-13T15:01:43.730" CommentCount="1" />
  <row Id="8959" PostTypeId="2" ParentId="8924" CreationDate="2011-01-13T01:02:39.437" Score="2" ViewCount="" Body="&lt;p&gt;As @tyblu says, it's all right there in the manual for the USI. In particular what you want is to use it in &quot;Three-Wire Master Mode Operation.&quot; Take a look at Figure 61 on page 143 of the datasheet. The datasheet is even kind enough to provide an optimized (8 instruction) assembler routine (SPITransfer) for this exact purpose:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;SPITransfer:&#xA;  out USIDR,r16&#xA;  ldi r16,(1&amp;lt;&amp;lt;USIOIF)&#xA;  out USISR,r16&#xA;  ldi r16,(1&amp;lt;&amp;lt;USIWM0)|(1&amp;lt;&amp;lt;USICS1)|(1&amp;lt;&amp;lt;USICLK)|(1&amp;lt;&amp;lt;USITC)&#xA;SPITransfer_loop:&#xA;  out USICR,r16&#xA;  sbis USISR,USIOIF&#xA;  rjmp SPITransfer_loop&#xA;  in r16,USIDR&#xA;  ret&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If you wire it up so that the you have a 2313 pin connected to the controller's &quot;latch&quot; wire (orange), the USCK pin connects to the controller's &quot;pulse&quot; wire (red), and the DI pin connects to the controller's &quot;data&quot; wire (yellow) - you should be good to go. Per the datasheet, the code example assumes that the DO and USCK pins are enabled as outputs in the DDRB Register. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once the hardware is set up, all you need to do is generate a 12us high pulse on the &quot;latch&quot; pin, drop the pin low for 6us, then call the above assembly routine twice (saving the return value away) after each call.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found &lt;a href=&quot;http://www.mit.edu/~tarvizo/nes-controller.html&quot; rel=&quot;nofollow&quot;&gt;this reference&lt;/a&gt; very informative regarding the (S)NES interface.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-01-13T01:02:39.437" CommentCount="3" />
  <row Id="8960" PostTypeId="2" ParentId="8946" CreationDate="2011-01-13T01:08:42.597" Score="0" ViewCount="" Body="&lt;p&gt;I'm not sure I understand what the problem is; you've locked down your requirements pretty well. The 12 bandpass filters cannot be avoided, and you want to use 12-LEDs per bandpass filter; you could eliminate the LM3914 and use a single microcontroller with 12 ADC inputs, or include an external MUX.  You could eliminate the RC filter and envelope circuit and do it in software if you're sampling fast enough, and if you would relax the 12 bandpass filter requirement you could even calculate the FFT in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically what I am saying is that given your requirements I'm not really sure why $45 in parts for the bar graph driver and output LEDs is such an issue. You haven't really left yourself a lot of flexibility.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-01-13T01:08:42.597" />
  <row Id="8961" PostTypeId="2" ParentId="8946" CreationDate="2011-01-13T01:11:11.483" Score="6" ViewCount="" Body="&lt;p&gt;I did a seven-channel version of this project a few months ago.  I designed 7 separate opamp bandpass filters (using the Bessel filter topology to minimize distortion).  I went with the LM3914 and a prepackaged LED bar graph because cost wasn't the issue; development time was, but you can take the opposite route.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I passed the filtered signals through the following peak detector:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tSCkr.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a lot cheaper than the opamp circuits you'll find elsewhere.  The Vce of the transistor and Vf of the diode should cancel out.  The 1uF capacitor and 470k resistor was a good decay rate for watching the audio signals that I was tracking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With respect to the cost, the LM3914 that you were looking at is just a cascade of comparators with one input connected through a resistor network to a fixed voltage, and the other to the peak detector input.  If you don't need the LED current control that this chip provides, you can probably do it cheaper with a classic quad comparator like the LM339 or LM2901 (you don't need anything fancy), which will run you about $\$$0.30 in quantities of 25 (you need 24 for twelve 8-channel graphs). Assuming that resistors are basically free, you need a diode, a transistor, decoupling caps (also essentially free), a 1uF peak storage capacitor, and an LED graph.  Just use some bulk 1206 LEDs for the graph and arrange them on your PCB instead of paying for the prepackaged bar graph. If you go with 8 elements in your graph, and you need 12*8 ~= 100 LEDs, you can do that for $\$$0.042 cents apiece with &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=475-1407-1-ND&quot; rel=&quot;nofollow&quot;&gt;these green indicator LEDs&lt;/a&gt;, or about $\$$0.34 per channel.  I'd say you can get away with the bar graph part for under $\$$1 per channel if you shop around.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-07T18:21:08.270" LastActivityDate="2011-05-07T18:21:08.270" />
  <row Id="8962" PostTypeId="2" ParentId="4163" CreationDate="2011-01-13T02:29:33.930" Score="0" ViewCount="" Body="&lt;p&gt;Consider an &lt;a href=&quot;http://en.wikipedia.org/wiki/ESMexpress&quot; rel=&quot;nofollow&quot;&gt;ESMini&lt;/a&gt; module in conjunction with an Arduino.  At 95x55mm you should have no trouble fitting it inside the torso or maybe even the head of a small humanoid robot, and it has the processing power of a low-end netbook.&lt;/p&gt;&#xA;" OwnerUserId="1285" LastActivityDate="2011-01-13T02:29:33.930" />
  <row Id="8963" PostTypeId="2" ParentId="8946" CreationDate="2011-01-13T06:03:49.353" Score="2" ViewCount="" Body="&lt;p&gt;An alternative to dedicated drivers and LED arrays is to make your own, borrowing the idea behind &lt;strong&gt;&lt;em&gt;R2R ladders&lt;/strong&gt; and &lt;strong&gt;flash ADCs&lt;/em&gt;&lt;/strong&gt;. The output from the aforementioned edge detector is fed through something similar to an R2R ladder (not necessarily with equal value resistors), which provides a number of nodes with voltages from the input to ground. A FET can be selected such that its &lt;em&gt;knee voltage&lt;/em&gt; or &lt;em&gt;turn-on voltage&lt;/em&gt; is something manageable, like 0.5V to 1V, its source grounded and gate connected to the various R2R nodes. When a node exceeds the &lt;em&gt;knee voltage&lt;/em&gt;, the FET turns on and drives an LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sound amplitude is traditionally (and biologically!) logarithmic, so the voltage at which each should turn on is linear on a logarithmic scale. For an input of max 3.3V to light 10 LED's per channel logarithmically with voltage, assuming a &lt;em&gt;knee voltage&lt;/em&gt; of 0.5V, the absolute node voltages will be: (MATLAB)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;EDU&amp;gt;&amp;gt; logspace(log10(0.5),log10(3.3),10)&#xA;ans =&#xA;    0.5  0.6166  0.7605  0.9379  1.1567  1.4265  1.7593  2.1697  2.6758  3.3&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If one aims for a maximum current of ~1mA, total R2R resistance should be near 3.3kΩ. This reveals resistor values of: (use voltage divider iteratively)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;R1 = 624.2  (620)&#xA;R2 = 506.1  (510)&#xA;R3 = 410.4  (430)&#xA;R4 = 332.8  (300)&#xA;R5 = 269.8  (270)&#xA;R6 = 218.8  (240)&#xA;R7 = 177.4  (160)&#xA;R8 = 143.9  (150)&#xA;R9 = 116.6  (120)&#xA;R10= 500    (500)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;sup&gt;Note: standard 5% resistor values in brackets are not simply the closest match, but are calculated iteratively. To redo calculations with other standard values or specs, the formula is: R&lt;sub&gt;i&lt;/sub&gt; = R&lt;sub&gt;TOTAL&lt;/sub&gt; &lt;sub&gt;&lt;sup&gt;x&lt;/sup&gt;&lt;/sub&gt; (1 - V&lt;sub&gt;i&lt;/sub&gt; / 3.3V) - {sum from 1 to &lt;em&gt;i&lt;/em&gt; of R&lt;sub&gt;i&lt;/sub&gt;}, derived from voltage divider formula.&lt;/sup&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Final circuit will look something like this:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/neNzK.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another method of achieving this effect is to use &lt;strong&gt;diode drops&lt;/strong&gt;. 3.3V can support about 8 Schottky drops (~0.4V) if transistor threshold voltage is less than or equal to 0.4V (otherwise, 7 drops). &lt;a href=&quot;http://tyblu.ca/misc/VuMeter3.png&quot; rel=&quot;nofollow&quot;&gt;In a chain of 8 Schottky diodes, pull down voltages at each intermediate node with a resistor that will also function as a current limiter (allow something close to the &lt;em&gt;test current&lt;/em&gt; from the datasheet to flow when diode is forward biased). Each node is then connected to transistors in the same way as above.&lt;/a&gt; Current through the diodes will change by over 8X, based on how many diodes are forward biased, so ensure each will work in all cases. This method is linear w.r.t. voltage or amplitude, which isn't quite authentic. Also, Schottky's are more expensive than 5% resistors...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A final hint -- one I haven't explored -- is to &lt;a href=&quot;http://www.tyblu.ca/misc/VuMeter4.png&quot; rel=&quot;nofollow&quot;&gt;use the BE-drop in BJT transistors instead of Schottky diodes&lt;/a&gt;, saving several parts per LED but also having to deal with a larger diode drop and bipolars.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-13T08:09:30.997" LastActivityDate="2011-01-13T08:09:30.997" />
  <row Id="8964" PostTypeId="2" ParentId="8822" CreationDate="2011-01-13T09:10:04.680" Score="1" ViewCount="" Body="&lt;p&gt;The Spartan 6 FPGA certainly can drive HDMI/DVI signals directly, demonstrated in the &lt;a href=&quot;http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,836&amp;amp;Prod=ATLYS&quot; rel=&quot;nofollow&quot;&gt;Atlys&lt;/a&gt; board. I've personally driven 1920x1200 VGA from a Spartan 3A starter kit, but the signal wasn't very clean then. You're looking at very high bandwidth signals, however, so the boards must be designed carefully. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is for a single hobbyist build, you might be better off using a premade graphics card with its own framebuffer, for instance a USB one. DisplayLink comes to mind. &lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2011-01-13T09:10:04.680" />
  <row Id="8965" PostTypeId="1" CreationDate="2011-01-13T09:26:28.700" Score="4" ViewCount="555" Body="&lt;p&gt;I am looking for a good microcontroller to learn electronics.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;EDIT&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;I want develop on linux, and I wish there is a good linux supported simulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want use C language.&lt;/p&gt;&#xA;" OwnerUserId="2596" LastEditorUserId="2596" LastEditorDisplayName="" LastEditDate="2011-01-14T04:12:09.137" LastActivityDate="2011-01-14T10:56:31.790" Title="Which microcontroller has good linux supported simulator?" Tags="&lt;microcontroller&gt;&lt;linux&gt;&lt;simulation&gt;" AnswerCount="3" CommentCount="6" FavoriteCount="3" />
  <row Id="8966" PostTypeId="1" AcceptedAnswerId="9035" CreationDate="2011-01-13T09:35:13.447" Score="1" ViewCount="251" Body="&lt;p&gt;I'm building a basic thermometer that displays the temperature on 4 seven segment LEDs. I want to put the circuit in a &lt;a href=&quot;http://cpc.farnell.com/boss-enclosures/33102005/box-clear-lid-190x115x75mm/dp/EN82380&quot; rel=&quot;nofollow&quot;&gt;box with a clear plastic lid&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll mount the LEDs on the PCB around the other components, and fix this flat against the base of the box so the LEDs shine up through the clear plastic lid.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is how can I hide the electronics (i.e. the MCU, temp sensor, resistors, etc) but still be able to see the LED display, by some how darkening the clear plastic lid, and make it look more professional?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, can you get enclosures with a translucent lid? I've searched but can't find any.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-15T16:49:57.570" Title="7 Segment Display - Hiding the electronics" Tags="&lt;enclosure&gt;&lt;7segmentdisplay&gt;&lt;optoelectronics&gt;" AnswerCount="5" />
  <row Id="8967" PostTypeId="2" ParentId="8965" CreationDate="2011-01-13T09:47:32.067" Score="9" ViewCount="" Body="&lt;p&gt;There is good Linux support for many microcontrollers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Atmel's AVRs are well supported, with the &lt;a href=&quot;http://www.linuxfocus.org/~katja/electronics/200901/avr-gcc-linux.shtml&quot; rel=&quot;nofollow&quot;&gt;GCC&lt;/a&gt; compiler and &lt;a href=&quot;http://www.nongnu.org/avrdude/&quot; rel=&quot;nofollow&quot;&gt;avrdude&lt;/a&gt; for loading code. An &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; makes a good development board for starting out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip's PICs are supported by &lt;A href=&quot;http://ww1.microchip.com/downloads/mplab/X_Beta/index.html&quot; rel=&quot;nofollow&quot;&gt;MPLABX&lt;/a&gt; which provides compilers, IDE and code loading (using a &lt;a href=&quot;http://en.wikipedia.org/wiki/PICKit&quot; rel=&quot;nofollow&quot;&gt;PICkit&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://sdcc.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;SDCC&lt;/a&gt; compiler supports 8051, Z80, HC08 and more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ARM microcontrollers are well supported, with GCC and &lt;a href=&quot;http://openocd.berlios.de/web/&quot; rel=&quot;nofollow&quot;&gt;OpenOCD&lt;/a&gt;+GDB for JTAG loading/debugging. A good precompiled GCC toolchain comes from &lt;A href=&quot;http://www.codesourcery.com/sgpp/lite/arm&quot; rel=&quot;nofollow&quot;&gt;CodeSourcery&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI's MSP430 microcontrollers are supported with GCC and mspdebug. See, &lt;a href=&quot;http://hackaday.com/2010/08/11/how-to-launchpad-programming-with-linux/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2010/08/11/how-to-launchpad-programming-with-linux/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-13T11:48:11.620" LastActivityDate="2011-01-13T11:48:11.620" CommentCount="5" />
  <row Id="8968" PostTypeId="2" ParentId="8966" CreationDate="2011-01-13T10:13:43.107" Score="1" ViewCount="" Body="&lt;p&gt;I'll try with a small square of those mirror films used to filter out sun rays from offices with lot of windows, or the black films used to darken car glasses. &lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-01-13T10:13:43.107" CommentCount="5" />
  <row Id="8969" PostTypeId="1" AcceptedAnswerId="8971" CreationDate="2011-01-13T11:01:59.103" Score="1" ViewCount="364" Body="&lt;p&gt;I know there are several solutions for V-USB using only DIP Parts (especially the ATtiny) like&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IgorPlug&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://obdev.at/products/vusb/easylogger.html&quot; rel=&quot;nofollow&quot;&gt;http://obdev.at/products/vusb/easylogger.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://cesko.host.sk/IgorPlugUSB/IgorPlug-USB%20%28AVR%29_eng.htm&quot; rel=&quot;nofollow&quot;&gt;http://cesko.host.sk/IgorPlugUSB/IgorPlug-USB%20%28AVR%29_eng.htm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.recursion.jp/avrcdc/cdc-232.html&quot; rel=&quot;nofollow&quot;&gt;http://www.recursion.jp/avrcdc/cdc-232.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;But they are limited to 38400bps!&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Why?&lt;/li&gt;&#xA;&lt;li&gt;Are there other solutions only using DIP packaged parts for easy soldering?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2587" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-20T22:54:07.940" LastActivityDate="2011-02-20T22:54:07.940" Title="ATtiny V-USB with 115200bps? DIP only" Tags="&lt;usb&gt;&lt;uart&gt;&lt;attiny&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="8970" PostTypeId="2" ParentId="8966" CreationDate="2011-01-13T11:06:40.740" Score="1" ViewCount="" Body="&lt;p&gt;There are these mirror foils for smartphones:&#xA;&lt;a href=&quot;http://www.amazon.com/gp/search/ref=sr_nr_seeall_6?rh=k%3Amirror+foil%2Ci%3Amobile&amp;amp;keywords=mirror+foil&amp;amp;ie=UTF8&amp;amp;qid=1294916698&quot; rel=&quot;nofollow&quot;&gt;http://www.amazon.com/gp/search/ref=sr_nr_seeall_6?rh=k%3Amirror+foil%2Ci%3Amobile&amp;amp;keywords=mirror+foil&amp;amp;ie=UTF8&amp;amp;qid=1294916698&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These could work!&lt;/p&gt;&#xA;" OwnerUserId="2587" LastActivityDate="2011-01-13T11:06:40.740" CommentCount="1" />
  <row Id="8971" PostTypeId="2" ParentId="8969" CreationDate="2011-01-13T12:09:32.507" Score="3" ViewCount="" Body="&lt;p&gt;Because software USB on AVR can only be 1.0 which is 1mbit max. If we subtract overheads on USB protocol and processing, even 384kbit looks awesome. If you need more - take specialized chip from FTDI for example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SOIC soldering is not hard, and possible without fancy equipment.&#xA;If you want to prototype with SOIC you can solder tiny wires to leads.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-13T12:09:32.507" CommentCount="3" />
  <row Id="8972" PostTypeId="2" ParentId="8965" CreationDate="2011-01-13T12:49:19.617" Score="3" ViewCount="" Body="&lt;p&gt;I am a big fan of the ARM-based microcontrollers; regular old GCC works (I use CodeSourcery's free compiler), regular old gdb works (as do all the gcc/gdb frontends), and JTAG interfaces such as the Olimex are inexpensive and work beautifully.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used to be a big fan of PICs but having the development system stuck on a Windows machine just wasn't cutting it anymore. I know about sdcc and other PIC compiler efforts but let's face it, why mess around? Get something that works, has a large support base and doesn't require you to goof around. An LPC2103 is inexpensive (2101/2102 being cheaper), has a decent amount of memory and resources and is offered in an LQFP footprint which is relatively easy to work with. There are dozens of ARM7 or Cortex M3 based microcontrollers on digikey in LQFP packages. (there are also hundreds more if you are willing to work with exposed pad or BGA packages.) What you want depends on how many IO you're after, which peripherals and so on. NXP, ST Micro and TI all offer parts though digikey that are in stock right now, and I'm sure there are many more if you want to check mouser, arrow, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really like the ARMs, but if they're not your bag CodeSourcery also offers gcc for MIPS (this should include PIC32), NIOS (for your CPU embedded in an FPGA), and SuperH based microcontrollers. I have no direct experience with any of these, as I'm more than happy with ARM. You don't need to use their gcc either; you're free to build your own compiler, but I've been really happy with them and plug them whenever I can. They put out a free version that technically has no support, but they are receptive to queries from hobbyists and their mailing lists are great.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-01-13T12:49:19.617" />
  <row Id="8973" PostTypeId="1" CreationDate="2011-01-13T13:45:39.850" Score="5" ViewCount="248" Body="&lt;p&gt;Hello, I am doing a thesis project. I need to make a FPGA implementation of a neural network. I want to implement some mathematical functions such as an exponential function.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know of any good books about FPGAs, VHDL or digital architecture implementation of floating point arithmetic operations?&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-04-14T16:34:19.687" LastActivityDate="2011-04-15T01:48:48.877" CommunityOwnedDate="2011-01-29T15:49:06.390" Title="Any good reference for digital architecture implementations of floating point arithmetic operations?" Tags="&lt;fpga&gt;&lt;hardware&gt;&lt;books&gt;&lt;vhdl&gt;&lt;floating-point&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="2" />
  <row Id="8974" PostTypeId="2" ParentId="8973" CreationDate="2011-01-13T14:07:50.853" Score="6" ViewCount="" Body="&lt;p&gt;There are ANN techniques that don't require floating-point. You will find things much easier if you adopt one of those.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cs.york.ac.uk/arch/neural-networks/technologies&quot; rel=&quot;nofollow&quot;&gt;Jim Austin's work&lt;/a&gt; at York University comes to mind. He uses FPGAs and fixed-point DSPs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: (Leon, I hope you don't mind me adding this list here)&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://www.fpga4fun.com/Forum/viewtopic.php?p=6820&quot; rel=&quot;nofollow&quot;&gt;&quot;fpga neural networks&quot;&lt;/a&gt; discussion forum, in particular a FPGA NN where &quot;The neuron uses 8bit numbers&quot;.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.91.1999&amp;amp;rep=rep1&amp;amp;type=pdf&quot; rel=&quot;nofollow&quot;&gt;&quot;FPGA Implementations of Neural Networks - a Survey of a Decade of Progress&quot;&lt;/a&gt; by Zhu and Sutton: lists many implementation techniques, and briefly mentions that floating point implementation technique has not yet been successful.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://scholar.google.com/scholar?q=FPGA%20neural%20net&amp;amp;hl=en&amp;amp;as_sdt=0&amp;amp;as_vis=1&amp;amp;oi=scholart&quot; rel=&quot;nofollow&quot;&gt;&quot;FPGA neural net&quot;&lt;/a&gt; search on Google Scholar&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="305" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-04-15T01:31:26.073" LastActivityDate="2011-04-15T01:31:26.073" CommunityOwnedDate="2011-01-29T15:49:06.390" CommentCount="5" />
  <row Id="8975" PostTypeId="1" CreationDate="2011-01-13T14:09:46.037" Score="1" ViewCount="135" Body="&lt;p&gt;I am wondering if it is possible to sense the position of a &lt;a href=&quot;http://en.wikipedia.org/wiki/Ball_joint&quot; rel=&quot;nofollow&quot;&gt;ball joint&lt;/a&gt; using:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A photodiode array from an &lt;a href=&quot;http://en.wikipedia.org/wiki/Optical_mouse&quot; rel=&quot;nofollow&quot;&gt;optical mouse&lt;/a&gt;, embedded in the socket&lt;/li&gt;&#xA;&lt;li&gt;A specific pattern deposited onto the ball&lt;/li&gt;&#xA;&lt;li&gt;A processor that can use the exposed part of the pattern to identify which part of the ball it is looking at and how it is oriented.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I imagine something similar to a &lt;a href=&quot;http://en.wikipedia.org/wiki/De_Bruijn_torus&quot; rel=&quot;nofollow&quot;&gt;de Bruijn Torus&lt;/a&gt;, that can be projected onto a spherical surface rather than a torus or plane, would do the trick.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a known algorithm for generating and/or decoding such an image?&lt;/p&gt;&#xA;" OwnerUserId="1285" LastEditorUserId="1285" LastEditorDisplayName="" LastEditDate="2011-01-13T16:37:53.350" LastActivityDate="2011-01-13T22:45:32.403" Title="Determine the position of a ball joint by image processing" Tags="&lt;encoder&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="8976" PostTypeId="2" ParentId="8975" CreationDate="2011-01-13T15:19:17.757" Score="0" ViewCount="" Body="&lt;p&gt;1) I would suggest to draw lots of QR codes at random positions covering &gt;50% of area which have both X &amp;amp; Y coordinates encoded. Then you decode QR code nearest to the center of the image and extrapolate coordinates a little to count for off-center code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt;&#xA;2) You can probably live with smaller resolution if you can draw on ball in color. Then you light your ball with RGB led - each color separately -&gt; twice smaller QR codes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) If ball is not metallic, you can put magnet inside it, and sence direction using couple of Hall sensors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) You can just put regular structure there, and track relative position just like optical mouse&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would worry about dirt on the ball.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-01-13T17:31:33.960" LastActivityDate="2011-01-13T17:31:33.960" CommentCount="3" />
  <row Id="8977" PostTypeId="2" ParentId="4678" CreationDate="2011-01-13T15:28:09.183" Score="1" ViewCount="" Body="&lt;p&gt;The most essential tool for me is a headband magnifier:&#xA;&lt;img src=&quot;http://i.imgur.com/MjmWh.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1285" LastActivityDate="2011-01-13T15:28:09.183" CommentCount="2" />
  <row Id="8978" PostTypeId="2" ParentId="4678" CreationDate="2011-01-13T16:03:05.580" Score="2" ViewCount="" Body="&lt;p&gt;If building in any quantity, we use a pick and place machine.  Or have your CM (Contract Manufacturer) use one.  There are even CM's that do short runs.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-21T16:24:44.283" LastActivityDate="2011-01-21T16:24:44.283" CommentCount="2" />
  <row Id="8979" PostTypeId="2" ParentId="3911" CreationDate="2011-01-13T17:17:21.677" Score="0" ViewCount="" Body="&lt;p&gt;The answers listed here all sound good. Judging from your budget, you may be able to recruit a college student (who's also a hacker) in the subject area that you need expertise in. You may need an engineering friend to help you with the recruiting though for filters.&lt;/p&gt;&#xA;" OwnerUserId="1944" LastActivityDate="2011-01-13T17:17:21.677" />
  <row Id="8980" PostTypeId="2" ParentId="8580" CreationDate="2011-01-13T17:26:58.627" Score="2" ViewCount="" Body="&lt;p&gt;How stable is the power supply's output when you connect it a volt-meter (multimeter)? Is it quite close (less than 10% error) to the nominal value? (e.g. 5.06V for a 5V supply is good)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One potential addition source for glitches caused by the power supply, would be if the power transformer's output voltage is too close to the necessary input voltage of the linear regulator. For example the 7805 linear regulator requires an input voltage of 2 volts higher than the output (i.e. 7V input), and I like to add 1V as a margin of tolerance to make it more reliable. Adding the voltage drop of the (diode) bridge rectifier (1.4V), you want 9.4V peak-peak Vac from the power transformer. That works out to around 9.4 / sqrt(2) = 6.6 or 7Vrms AC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So a 6Vrms rated transformer would work most of the time, but does not have much (sufficient?) margin of tolerance (AC mains may vary by 10% from nominal value, e.g 108-132 for 120Vac) to withstand potential AC main voltage drops. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ref: &lt;a href=&quot;http://knol.google.com/k/electronic-circuits-design-for-beginners-chapter-1#&quot; rel=&quot;nofollow&quot;&gt;Electronic Circuits Design For Beginners - Chapter 1&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-01-13T17:26:58.627" />
  <row Id="8981" PostTypeId="1" AcceptedAnswerId="8983" CreationDate="2011-01-13T17:44:19.573" Score="1" ViewCount="63" Body="&lt;p&gt;I am evaluating whether it can use &quot;resistive touch film&quot; in project-based cards using &lt;a href=&quot;http://www.tinyclr.com/hardware/2/fez-mini/&quot; rel=&quot;nofollow&quot;&gt;USBizi Chipset-100&lt;/a&gt; in place of a conventional keyboard.&lt;br&gt;&#xA;I would like to see some similar design to see howto make interface.&lt;br&gt;&#xA;Any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="1888" LastActivityDate="2011-01-13T18:28:50.247" Title="touch film replacing keyboard" Tags="&lt;interface&gt;&lt;touchscreen&gt;&lt;touch-panel&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="8982" PostTypeId="2" ParentId="8946" CreationDate="2011-01-13T18:07:49.867" Score="0" ViewCount="" Body="&lt;p&gt;One option is to use a small microcontroller to perform an FFT. A PIC 18F is capable of doing this, as &lt;a href=&quot;http://www.youtube.com/watch?v=EJiUaGdABmI&quot; rel=&quot;nofollow&quot;&gt;this example demonstrates&lt;/a&gt; (code is open source) - 10 fps isn't difficult, and you could improve the apparent update rate by averaging between subsequent FFTs or by adding in random noise. You can then use &lt;a href=&quot;http://en.wikipedia.org/wiki/Charlieplexing&quot; rel=&quot;nofollow&quot;&gt;charlieplexing&lt;/a&gt; or some other form of multiplexing to drive the display. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If FFT sounds too difficult, or requires too much processing power for you, you can try doing it by mixing analog and digital concepts. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could make a configurable band pass filter by using capacitors connected to microcontroller IOs. Connect a 1k or so in series to an ADC input. Make the IO high impedance to effectively disconnect the capacitor, and drive the output low to connect it.  By using almost binary values of capacitor, such as 10n, 22n, 39n and 82n, you can make a 16-way filter. That's for the high pass part; to do the low pass part, put a 100n cap (or so) in series at the middle node of the RC high-pass, and use resistors on the IOs (again, using binary values of 1k, 2.2k, 3.9k and 8.2k), doing the same with the caps: drive them low to use them, and drive them to high-Z to disconnect them. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, you can either use a peak detector circuit to measure the peaks, or just take a series of measurements from the ADC and average them out. If you only need an 8 way filter, that's 6 IOs, plus the ADC input, so 7 IOs total, and a 8x8 display will take only 9 IOs to control using charlieplexing.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-13T18:07:49.867" CommentCount="1" />
  <row Id="8983" PostTypeId="2" ParentId="8981" CreationDate="2011-01-13T18:28:50.247" Score="2" ViewCount="" Body="&lt;p&gt;I'm assuming you want help with connections to the touchscreen, not with making your FEZ look like a keyboard to the computer (or with configuring a keyboard as input for the FEZ, depending on your project).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are essentially two options: Use ADC (analog-to-digital converter) lines on your FEZ to directly connect to the touchscreen, or use a touchscreen controller IC to do the low-level stuff and then connect with SPI or I2C to the controller to get the digital data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first option is cheaper (you don't have to buy anything special), but will take more processing time on your FEZ, and will require you to do a little bit of analog design work.  Atmel's appnote &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8091.pdf&quot; rel=&quot;nofollow&quot;&gt;AVR341&lt;/a&gt; is a good reference, and easily translates to other microcontrollers.  Page 7 gives some good requirements: You need a fairly accurate A/D source, 15-25mA source/sink currents, and a processor capable of taking new measurements 70-200 times per second.  I'm not sure how well the FEZ works with frequent interrupts like that, so the second option might be more attractive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second option eases the processing you'll have to do.  Chips like TI's &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/tsc2200.pdf&quot; rel=&quot;nofollow&quot;&gt;TSC2200&lt;/a&gt; even go as far as to give you a keypad  interface so that you can simply wait for the chip to tell you that someone's pressed a key (it's 4x4 keys, not a keyboard!).  However, the more features you ask of it, the more complexity will be present in the interface.  For a .NET application, you probably want to see an interface rather than connecting right to the hardware,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding the suitability of a touchscreen interface, consider that it can be uncomfortable to type on a rigid surface for a long time, and resistive touchscreens are even worse because you need to apply significant pressure.  Don't expect to sustain high typing speeds for very long without causing pain in your fingertips.  Also, you'll want some kind of feedback mechanism.  The Apple iPod/iPhone/iPad screens are as nice as they are because they (1) indicate the letter you're touching and (2) increase the sensing radius of letters that are likely to come up with predictive algorithms and dictionaries.  It's very hard to get a touchscreen keyboard to feel natural.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-13T18:28:50.247" CommentCount="2" />
  <row Id="8984" PostTypeId="2" ParentId="8975" CreationDate="2011-01-13T18:44:42.523" Score="1" ViewCount="" Body="&lt;p&gt;This leads into a more mathematical answer, but if you have apriori knowledge of the pattern you're going to put onto the ball, any sufficiently random pattern should work, so long as there are sufficient dissimilarities (both in translation and rotation) between all possible regions you can capture at once.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-13T18:44:42.523" />
  <row Id="8985" PostTypeId="1" CreationDate="2011-01-13T18:49:18.697" Score="6" ViewCount="199" Body="&lt;p&gt;I'll be putting on a robotics competition in a month, and would love to see a list of different sorts of events I might be able to run.  What are the types of competitions you are aware of, at all levels of complexity, suitable for the novice LEGO roboticist to the corporate-backed team of pros?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some ideas off the top of my head, from extremely simple to rather advanced:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;tug of war&lt;/li&gt;&#xA;&lt;li&gt;drag racing&lt;/li&gt;&#xA;&lt;li&gt;line following&lt;/li&gt;&#xA;&lt;li&gt;mini sumo&lt;/li&gt;&#xA;&lt;li&gt;maze solving&lt;/li&gt;&#xA;&lt;li&gt;soccer&lt;/li&gt;&#xA;&lt;li&gt;robo magellan (navigating waypoints in an outdoor course)&lt;/li&gt;&#xA;&lt;li&gt;land-mine identification&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Please list one idea per answer (perhaps with minor variations), upvote, don't duplicate, provide a brief description of the event, and, if you know of rules or more details, provide a link!&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2011-01-22T20:57:25.300" CommunityOwnedDate="2011-01-13T19:15:34.797" Title="Robotics Events" Tags="&lt;robotics&gt;&lt;competition&gt;" AnswerCount="9" CommentCount="6" FavoriteCount="3" />
  <row Id="8986" PostTypeId="2" ParentId="3911" CreationDate="2011-01-13T19:00:04.610" Score="2" ViewCount="" Body="&lt;p&gt;LinkedIn would be a place to start.  Perhaps a friend of a contact knows one.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-13T19:00:04.610" />
  <row Id="8987" PostTypeId="2" ParentId="8973" CreationDate="2011-01-13T19:02:00.443" Score="3" ViewCount="" Body="&lt;p&gt;They are starting on a package at &lt;a href=&quot;http://www.vhdl.org/fphdl/old_index.html&quot; rel=&quot;nofollow&quot;&gt;VHDL.org&lt;/a&gt;.  &lt;a href=&quot;http://optngn.com/place/index.php?option=com_virtuemart&amp;amp;page=shop.browse&amp;amp;category_id=2&amp;amp;Itemid=53&amp;amp;TreeId=2&quot; rel=&quot;nofollow&quot;&gt;OptNgn&lt;/a&gt; also have a library that is free (GPLv3).&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-13T19:02:00.443" CommunityOwnedDate="2011-01-29T15:49:06.390" />
  <row Id="8988" PostTypeId="2" ParentId="8924" CreationDate="2011-01-13T19:50:23.463" Score="0" ViewCount="" Body="&lt;p&gt;The following code works great. The latch signal is connected to &lt;code&gt;PB5&lt;/code&gt;. The &lt;code&gt;SIG_PIN_CHANGE&lt;/code&gt; handler does its work on both edges of the latch signal but it doesn't matter, and the last time I tried adding the check it did not work.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;avr/io.h&amp;gt;&#xA;#include &amp;lt;avr/interrupt.h&amp;gt;&#xA;#include &amp;lt;avr/sleep.h&amp;gt;&#xA;&#xA;ISR(SIG_PIN_CHANGE)&#xA;{&#xA;    USIDR = PINA | (PIND &amp;amp; 0b01111100) | (PINB &amp;lt;&amp;lt; 7);&#xA;    USISR = (1 &amp;lt;&amp;lt; USIOIF); // clear overflow bit, set counter to 0&#xA;    USICR |= (1 &amp;lt;&amp;lt; USIOIE); // enable overflow interrupt&#xA;}&#xA;&#xA;ISR(SIG_USI_OVERFLOW)&#xA;{&#xA;    USIDR = (PINB &amp;lt;&amp;lt; 3) | 0x0f;&#xA;    USISR |= (1 &amp;lt;&amp;lt; USIOIF); // clear overflow bit&#xA;    USICR &amp;amp;= (0xff ^ (1 &amp;lt;&amp;lt; USIOIE)); // disable overflow interrupt&#xA;}&#xA;&#xA;int main() {&#xA;&#xA;    USIDR = 0xff;&#xA;    USICR = (1 &amp;lt;&amp;lt; USIWM0) | (1 &amp;lt;&amp;lt; USICS1); // 3-wire mode; external, positive edge.&#xA;&#xA;    DDRA = 0;&#xA;    DDRD = 0;&#xA;    DDRB = 1 &amp;lt;&amp;lt; 6; // MISO&#xA;&#xA;    // Enable pullups&#xA;    PORTA = 0x3;&#xA;    PORTB = 0b11111;&#xA;    PORTD = 0xfc;&#xA;&#xA;    // USIDR is shifted out MSB first.&#xA;&#xA;    // pin change interrupt for latch pin&#xA;    PCMSK = (1 &amp;lt;&amp;lt; 5);&#xA;    GIMSK |= (1 &amp;lt;&amp;lt; PCIE);&#xA;&#xA;    sei();&#xA;&#xA;    while (1) {&#xA;        sleep_mode();&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2011-01-29T21:00:10.753" LastActivityDate="2011-01-29T21:00:10.753" CommentCount="6" />
  <row Id="8989" PostTypeId="1" CreationDate="2011-01-13T20:51:46.390" Score="2" ViewCount="116" Body="&lt;p&gt;Can more experienced engineers give me their input on this. If I open a CD player, what electronic parts should I expect to find?&lt;/p&gt;&#xA;" OwnerUserId="2600" LastActivityDate="2011-01-13T21:07:18.283" Title="What are the electronics parts of a CD player" Tags="&lt;electronics&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="8990" PostTypeId="2" ParentId="8989" CreationDate="2011-01-13T20:54:04.873" Score="4" ViewCount="" Body="&lt;p&gt;By searching the web, you'll find plenty of information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a teardown of a CD player.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=gpi_8Vodi5w&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=gpi_8Vodi5w&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a picture of the internals:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://static.howstuffworks.com/gif/cd-parts.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a basic guide to the workings &lt;a href=&quot;http://electronics.howstuffworks.com/cd4.htm&quot; rel=&quot;nofollow&quot;&gt;http://electronics.howstuffworks.com/cd4.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, the best way to find out is to take it apart.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-13T21:07:18.283" LastActivityDate="2011-01-13T21:07:18.283" CommentCount="2" />
  <row Id="8991" PostTypeId="2" ParentId="4121" CreationDate="2011-01-13T21:29:42.583" Score="2" ViewCount="" Body="&lt;p&gt;This reminds me of a great little article entitled &lt;a href=&quot;http://doi.ieeecomputersociety.org/10.1109/MC.2004.1273994&quot; rel=&quot;nofollow&quot;&gt;The Zen of Overclocking&lt;/a&gt; by &lt;a href=&quot;http://en.wikipedia.org/wiki/Bob_Colwell&quot; rel=&quot;nofollow&quot;&gt;Bob Colwell&lt;/a&gt; who was the chief IA-32 architect for the Intel Pentium Pro to Pentium 4 processors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately the document is not available to the general public, but should be available to IEEE Computer Society members, and many/most universities networks. It was originally published in &lt;a href=&quot;http://www.computer.org/portal/web/computer/home&quot; rel=&quot;nofollow&quot;&gt;Computer&lt;/a&gt; magazine, March 2004 (Vol. 37, No. 3) pp. 9-12.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A couple of brief quotes:&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Abstract&lt;/strong&gt;: &lt;em&gt;Overclocking is a large, uncontrolled experiment in better-than-worst-case system operation.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;...&#xA;&lt;em&gt;This issue of Computer [magazine issue] spotlights what I call &quot;better-than-worst-case&quot; design. With normal worst-case design, any computing system is a conglomeration of components, operating within frequencies, power supply voltages, and temperature ranges that were set to simultaneously accommodate worst-case values of every single component. (Modern CPUs don't really do it quite this way anymore, but they once did, and it's easiest to think of worst-case design this way.)&lt;/em&gt;&#xA;...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;...&lt;em&gt;Compare the seat-of-the-pants, maybe-it-will-work approach of the overclockers to the engineering challenge confronting Intel and AMD. First, note that this challenge isn't just the flip side of the overclocker's coin. Chip manufacturers must design and produce tens or hundreds of millions of chips; overclockers only worry about one. Manufacturers must set a quantifiable reliability goal, and no, it's not &quot;zero failures, ever.&quot; That would be an unreachable—and not very productive—target because hitting it would require avoiding cosmic rays. Even at sea level, that would require more meters of concrete than any laptop buyer is going to find attractive. And even then, the concrete would only improve the odds. It would remain a statistical game.&lt;/em&gt;&#xA;...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;If you don't floss your teeth, they won't necessarily rot away. The vast majority of car trips do not include any metal bending, so why wear seat belts? And why not smoke? Not all smokers get cancer. Or you could adopt Oscar London's compromise, &quot;If you smoke, why bother wearing a seat belt?&quot; And some rock musicians from the 1960s are still alive, so maybe all those drugs are really beneficial, acting as some kind of preservative.&#xA;As for me, well, I'm an engineer, and I live in a statistical world. I'm going with the odds.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;As to the specifics of whether over-clocking can cause permanent damage? Yes, in particular as the lithography technology improves at creating smaller scale dies (e.g. 35 nanometre) the thickness of the insulator / oxide is decreased as well. This means that this ever thinner barrier could fail due to high voltage or deterioration. So the related margin for acceptable error is decreasing (or the margin for failure is rising). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe MOSFET transistors are still used for CPU design, so looking at some of the difficulties with &lt;a href=&quot;http://en.wikipedia.org/wiki/MOSFET#Difficulties_arising_due_to_MOSFET_size_reduction&quot; rel=&quot;nofollow&quot;&gt;MOSFET size reduction&lt;/a&gt; may highlight other potential issues that overclocking may cause. At the system-level, overclocking may also cause internal / cross-channel EMI / RFI within the CPU die or any of the other subsystems (e.g. RAM bus), and may reduce the Signal-Noise-Ratio (SNR) such that mechanical or external EMI/RFI are no longer tolerable, and end up producing random errors on the digital buses. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And for the record I have damaged processors due to &lt;em&gt;stupid&lt;/em&gt; over-clocking, and poor thermal dissipation. So beyond the theory, it is actually possible. &lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-01-13T21:29:42.583" CommentCount="4" />
  <row Id="8992" PostTypeId="2" ParentId="8985" CreationDate="2011-01-13T21:47:13.200" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Line Following&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Robots follow a line (typically black electrical tape on a white surface) around a course.  Robots try to be quick and accurate.  Easy courses have rounded edges; more advanced courses have sharp edges or gaps in the line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.robotgames.net/robotgames/Event_rules/2002_line_follower.htm&quot; rel=&quot;nofollow&quot;&gt;Sample rules&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.ca/search?sourceid=chrome&amp;amp;ie=UTF-8&amp;amp;q=line+following#q=line+following&amp;amp;hl=en&amp;amp;prmd=ivns&amp;amp;source=univ&amp;amp;tbs=vid:1&amp;amp;tbo=u&amp;amp;ei=ZXIvTbaXJo32tgPf_qzfBQ&amp;amp;sa=X&amp;amp;oi=video_result_group&amp;amp;ct=title&amp;amp;resnum=1&amp;amp;ved=0CCQQqwQwAA&amp;amp;fp=bf7e8c81604a9a8f&quot; rel=&quot;nofollow&quot;&gt;Sample videos&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2011-01-13T21:47:13.200" CommunityOwnedDate="2011-01-13T21:47:13.200" />
  <row Id="8993" PostTypeId="2" ParentId="8985" CreationDate="2011-01-13T21:53:48.007" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Sumo&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two robots face off in a black ring with a white border.  Each tries to push the other out.  Typically there are three rounds; the first robot to go out loses the round, and, if the robots are stuck together for too long, the round ends in a tie.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are different weight-classes for robots of different sizes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.robotroom.com/SumoRules.html&quot; rel=&quot;nofollow&quot;&gt;Sample rules&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Robot-sumo&quot; rel=&quot;nofollow&quot;&gt;Wikipedia article&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.ca/search?sourceid=chrome&amp;amp;ie=UTF-8&amp;amp;q=robot+sumo#q=robot+sumo&amp;amp;hl=en&amp;amp;prmd=ivns&amp;amp;source=univ&amp;amp;tbs=vid:1&amp;amp;tbo=u&amp;amp;ei=A3QvTaOANo72tgPC9KjOBQ&amp;amp;sa=X&amp;amp;oi=video_result_group&amp;amp;ct=title&amp;amp;resnum=1&amp;amp;ved=0CC0QqwQwAA&amp;amp;fp=bf7e8c81604a9a8f&quot; rel=&quot;nofollow&quot;&gt;Sample videos&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2011-01-13T21:53:48.007" CommunityOwnedDate="2011-01-13T21:53:48.007" />
  <row Id="8994" PostTypeId="1" AcceptedAnswerId="8996" CreationDate="2011-01-13T21:56:03.313" Score="2" ViewCount="188" Body="&lt;p&gt;I see tubing used all over the place in machines, but I do not know what it is called. The cross section looks somewhat like this drawn picture. Can someone clue me in on it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/GDDlb.png&quot; alt=&quot;Tubing&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2578" LastActivityDate="2011-01-15T05:41:43.933" Title="What is the name of this common metal tubing?" Tags="&lt;hardware&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="8995" PostTypeId="2" ParentId="8985" CreationDate="2011-01-13T22:00:48.113" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Micromouse (Maze Solving)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Robots are placed inside a maze and need to navigate through it as quickly as possible.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Micromouse&quot; rel=&quot;nofollow&quot;&gt;Wikipedia article&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://micromouse.cs.rhul.ac.uk/mtech/rules_main.shtml&quot; rel=&quot;nofollow&quot;&gt;Sample rules&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.google.ca/search?sourceid=chrome&amp;amp;ie=UTF-8&amp;amp;q=micromouse#q=micromouse&amp;amp;hl=en&amp;amp;prmd=ivnslb&amp;amp;source=univ&amp;amp;tbs=vid:1&amp;amp;tbo=u&amp;amp;ei=03UvTca6CpGisQPctfy5BQ&amp;amp;sa=X&amp;amp;oi=video_result_group&amp;amp;ct=title&amp;amp;resnum=2&amp;amp;ved=0CD0QqwQwAQ&amp;amp;fp=bf7e8c81604a9a8f&quot; rel=&quot;nofollow&quot;&gt;Sample videos&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="106" LastActivityDate="2011-01-13T22:00:48.113" CommunityOwnedDate="2011-01-13T22:00:48.113" />
  <row Id="8996" PostTypeId="2" ParentId="8994" CreationDate="2011-01-13T22:17:17.580" Score="8" ViewCount="" Body="&lt;p&gt;Structural aluminum extrusion:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.8020.net/&quot; rel=&quot;nofollow&quot;&gt;http://www.8020.net/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.minitecframing.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.minitecframing.com/&lt;/a&gt; (my favorite)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www13.boschrexroth-us.com/framing_shop/&quot; rel=&quot;nofollow&quot;&gt;http://www13.boschrexroth-us.com/framing_shop/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-13T22:17:17.580" CommentCount="1" />
  <row Id="8997" PostTypeId="2" ParentId="8994" CreationDate="2011-01-13T22:33:53.963" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.tslots.com/&quot; rel=&quot;nofollow&quot;&gt;T-Slot&lt;/a&gt; is the name I recognize it as. I assume there are also generic T-slotted aluminum extrusions available as well.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-01-13T22:33:53.963" />
  <row Id="8999" PostTypeId="2" ParentId="8975" CreationDate="2011-01-13T22:45:32.403" Score="0" ViewCount="" Body="&lt;p&gt;Like tyblu said in his comment, use an optical sensor and track distance and direction traveled then calculate your new position based on the distance and direction from the old position. This will be your simplest method to get the information you need. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Image processing like that can be pretty slow and tedious with a fair margin of error and isn't a path I would take for determining position.&lt;/p&gt;&#xA;" OwnerUserId="2495" LastActivityDate="2011-01-13T22:45:32.403" CommentCount="5" />
  <row Id="9000" PostTypeId="2" ParentId="8994" CreationDate="2011-01-13T22:50:54.297" Score="1" ViewCount="" Body="&lt;p&gt;Would Fischertechnik not do the job?&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/dkneG.jpg&quot; alt=&quot;Fischertechnik&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-01-13T22:50:54.297" />
  <row Id="9001" PostTypeId="1" CreationDate="2011-01-13T23:39:11.767" Score="5" ViewCount="316" Body="&lt;p&gt;I have a dilemma. The schematics for a development board I am using specifies that it uses 20 milli-ohm resistors for current sensing (7 current sense channels). However, by calibration (using low burden voltage fluke ammeter), I have &quot;calculated&quot; that the resistance is 27 milli ohms (plotted around 6 operating points, fitted a linear curve to it, gradient of V-I graph is 27.004 with R^2 = 0.9996).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I am now confused. Is it really 27 milliohms or 20 milliohms? These are 0603 resistors, and common multimeters don't range down to the milliohms. :(&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-01-14T11:36:31.480" Title="How to work out resistance of milli-ohm resistors?" Tags="&lt;resistors&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="9002" PostTypeId="1" CreationDate="2011-01-13T23:51:34.563" Score="1" ViewCount="147" Body="&lt;p&gt;I have searched for 478 motherboard circuit schematics on the internet, but have found none. Are any available publicly?&lt;/p&gt;&#xA;" OwnerUserId="2466" LastActivityDate="2011-01-15T05:25:48.383" Title="Where to find 478 motherboard circuit schematics?" Tags="&lt;circuit&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="9003" PostTypeId="2" ParentId="9001" CreationDate="2011-01-14T00:13:34.590" Score="2" ViewCount="" Body="&lt;p&gt;What you are probably experiencing is contact resistance. The resistance of your ammeter, for example, is going to be on the order of 10 milliohms, which would account for your 7 milliohm extra measurement (including a reasonable tolerance in other components.) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can measure the resistance of a very low ohm resistor by using 4-wire measurement. Expensive bench multimeters support this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However... I suspect you have only 2-wire measurement on low cost meters. So there is another way to do it. It however requires you to have two multimeters; it is not possible to use one, unfortunately, because removing one from the circuit will change the result. However, even cheap $5 meters will be fine for decent 1% measurement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will need a 5V or so power supply, a 100 ohm 5% resistor, your test resistor and two multimeters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's how to do it: Place the 100 ohm resistor in series with the test resistor and apply power using the power supply. The output voltage is not critical, but don't go too high. Connect a multimeter as an ammeter in series with the resistor or supply. Then, connect one of the multimeters as a voltmeter right across the resistor - you want to be right up to the edges of the resistor's casing, just touching the terminals, to get the most accurate reading, as any resistance of the leads will affect the result. Then, use Ohm's law to solve for R given V and I. (Hint: R = V / I.) What you've effectively done is cancelled out the series resistance of the ammeter, power supply, wires and 100 ohm resistor by measuring the voltage drop across the resistor directly.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-14T00:13:34.590" CommentCount="3" />
  <row Id="9004" PostTypeId="2" ParentId="9002" CreationDate="2011-01-14T00:29:19.957" Score="3" ViewCount="" Body="&lt;p&gt;I wouldn't hold out much hope.  I've looked at motherboards and while they don't look complicated per se the sheer size of the design (number of nets) is bound to be daunting.  Plus I imagine the file format of the schematics will be for a rather high-powered schematic capture program costing several thousands of dollars.  I see you didn't find much for reference designs.  You might have luck finding reference designs for each individual chip (sound codec, south bridge, north bridge, etc) on the board and looking for reference designs.  Ideally a motherboard should just be all of those designs put together, but I'm sure there's several hundred catches (matching impedance for long traces for instance).&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-14T00:29:19.957" CommentCount="2" />
  <row Id="9005" PostTypeId="1" AcceptedAnswerId="9007" CreationDate="2011-01-14T00:38:43.190" Score="6" ViewCount="183" Body="&lt;p&gt;What tools and techniques can I use to identify an unknown IC with no markings?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Today I encountered a microcontroller under an epoxy blob. The blob had 11 pads on each of four sides, perhaps 44tqfp. From the board, I know which pin is the reset line and I probably know which pins make up an SPI interface. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there such a thing as an expert system for answering these puzzles with the information I have?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any searchable databases of pinouts online?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would X-raying/Decapping the package be worthwhile?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-14T00:55:11.263" LastActivityDate="2011-01-14T14:13:01.807" Title="Tips for identifying an unknown chip?" Tags="&lt;pcb&gt;&lt;chip&gt;&lt;identify&gt;" AnswerCount="1" CommentCount="6" FavoriteCount="3" />
  <row Id="9006" PostTypeId="1" AcceptedAnswerId="9010" CreationDate="2011-01-14T01:19:41.500" Score="2" ViewCount="129" Body="&lt;p&gt;Hi, I'm trying to use an 8 channel EL sequencer (&lt;a href=&quot;http://www.sparkfun.com/products/9203&quot; rel=&quot;nofollow&quot;&gt;found here&lt;/a&gt;) to control eight 10-foot segments of EL wire.  I'm having trouble figuring out what the appropriate length rating is that I need on an inverter.  I've read conflicting opinions.  One states I need my inverter to handle the &quot;total&quot; length (in my case 80 feet), while another says it just needs to handle the longest strand (10 feet then).  Which is correct? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking at &lt;a href=&quot;http://www.coolight.com/product-p/ifw-3294.htm&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; currently (rated 5 to 15 feet).  Is that enough? Or do I need to find one rated for at least 80 feet? Thanks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I need an inverter that can handle 80 feet of EL wire then I'm worried that this will conflict with a sequencer.  If the sequencer turns off say 3 channels (30 feet of the wire), then my load would only be 50 feet I would think.  I've read that this is an issue because the inverter might break if I have less than the minimum load.  Is this the case?&lt;/p&gt;&#xA;" OwnerUserId="954" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-28T03:39:24.333" LastActivityDate="2011-01-28T03:39:24.333" Title="Correct EL Driver Rating for 8 Channel Sequencer" Tags="&lt;avr&gt;&lt;power-supply&gt;&lt;light&gt;&lt;inverter&gt;&lt;el-wire&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9007" PostTypeId="2" ParentId="9005" CreationDate="2011-01-14T02:22:16.260" Score="9" ViewCount="" Body="&lt;p&gt;X-ray won't tell you much.  Dimensions of the chip and where the bonds are attached.  Decap is probably necessary.  You should be able to get the manufacturer from text on the die, which will be a big clue.  If you are really lucky, the manufacturer will put something on the die to help you ID the part number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a subscription to a tear-down company, you could scan their die photos and if you are luck find a match.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a fee, a tear-down company will do this work for you and send you a full report on the part. Here's a list of a few such companies:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.teardown.com/&quot; rel=&quot;nofollow&quot;&gt;TechInsights&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.isuppli.com/Pages/Home.aspx&quot; rel=&quot;nofollow&quot;&gt;iSuppli Market Intelligence&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.chipworks.com/&quot; rel=&quot;nofollow&quot;&gt;Chipworks&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2603" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-14T14:13:01.807" LastActivityDate="2011-01-14T14:13:01.807" CommentCount="1" />
  <row Id="9008" PostTypeId="1" AcceptedAnswerId="9009" CreationDate="2011-01-14T02:39:17.693" Score="2" ViewCount="150" Body="&lt;p&gt;I have a project where I need to detect whether a 12V circuit is live or not.  If it is I want to close a switch (actually close a digital IO input on an Adicon SECU16 Digital IO controller).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not an EE and would prefer to find a component off the shelf that I can tie into the 12V circuit and provide the relay.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I &lt;em&gt;could&lt;/em&gt; choose to not use digital (Supervised) input and instead do analog, but I really don't care how much voltage I'm seeing just whether it's on or off. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm capable of soldering a few components on a prototype board, but my lack of EE knowledge means I need some serious help selcting the right components.  The simpler the better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="2604" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:17:55.260" LastActivityDate="2011-03-05T16:17:55.260" Title="Need circuit to close switch on detecting current (12V)" Tags="&lt;relay&gt;&lt;switch&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="9009" PostTypeId="2" ParentId="9008" CreationDate="2011-01-14T03:07:19.763" Score="1" ViewCount="" Body="&lt;p&gt;You actually can do this with two resistors. Connect a 7kohm resistor from the signal line to your pin. Then connect a 5k resistor from your pin to your ground.(This is for 5V input, if you have 3.3 us a ~4k and a ~8k)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When 12V is input, it will show up as the logic level the chip knows, when 0V is there you will get 0V on the pin.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-01-14T03:07:19.763" CommentCount="8" />
  <row Id="9010" PostTypeId="2" ParentId="9006" CreationDate="2011-01-14T03:11:33.943" Score="3" ViewCount="" Body="&lt;p&gt;Lady Ada did a great &lt;a href=&quot;http://www.ladyada.net/learn/el-wire/&quot; rel=&quot;nofollow&quot;&gt;write up&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;EL wire modeling&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;EL wire is not a resistive light (like an incandescent bulb) and it is not a diode light (like an LED), it acts like more like a capacitor! The stiff inner wire is one 'plate' of the capacitor, the corona wire is the other 'plate' and the phosphor coating being the insulator/dielectric (for more details on capacitors, see Wikipedia ). This means you cannot use dimming methods such as triac/chopping for resistive incandescents or PWM for LEDs.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;In terms of thinking of how EL wire 'acts' you should model it as a capacitor that increases with the length of the wire. It is not a perfect capacitor, there is also some leakage which we will model as a resistor.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Pyy1G.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Adding another meter, we duplicate the RC model in parallel&#xA;  &lt;img src=&quot;http://i.imgur.com/tNtEJ.png&quot; alt=&quot;alt text&quot;&gt;&#xA;  Of course, we can simplify by calculating the new capacitance and reistance. Remember that capacitance increases in parallel and resistance decreases&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/04Ext.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The capacitance and resistance per meter depends on the 'thickness' of the EL wire, the brand and make, the voltage and frequency applied&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Current draw&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;We can use this information to determine the power draw.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Assuming you have LyTec EL wire, 2.3mm diameter 'standard'...if have one meter, that is 6nF and 100KΩ in parallel. The capacitance has an impedance of 1/(2πfC) so at 2000 Hz, the impedence per meter is 12 KΩ, in parallel with 100 KΩ it is 11 KΩ total. For a 100V AC power source, the current draw is 100V/11KΩ = 9mA per meter. 100V * 9mA/meter = 0.9 Watts/meter!&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;If you are using our 'high brightness, long life' stuff, its about 1.5 Watts per meter.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Thus an inverter with a 100mA output capability can drive 10M or so of LyTec and 5M of 'high brightness' EL. The transformer and transistors used in an inverter are a big part of how much current an inverter can provide!&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-01-14T03:11:33.943" />
  <row Id="9011" PostTypeId="2" ParentId="8856" CreationDate="2011-01-14T03:23:00.647" Score="3" ViewCount="" Body="&lt;p&gt;There isn't really a &quot;worst case&quot; - manufacturing IC's is a statistical process, there will be some (small) percentage of transistors that are a very long way from typical speed (imagine a statistical distribution curve drawn here).  The distribution of speeds for the two types of transistors in CMOS (NMOS and PMOS) don't correlate well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thus, they pick those 4 corners: Fast/Fast, Slow/Slow, Fast/Slow, Slow/Fast out of their two transistor speed yield curves.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The further out from typical they choose to make the corners, the higher their yield, but the more difficult it is to design.  If the corners are too far apart, design for operation at the 4 corners takes too much development time and can increase the die size.  Increasing the die size will decrease yield.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The four corners often form more of a parallelogram than a rectangle.  If both types of transistors, across one whole die, are all very fast, the part will probably work, maybe well beyond the rated speed, and same for both transistors getting slower - the part will work, but at a very slow speed.  The difficult corners are the fast/slow and slow/fast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The design is indeed fully simulated at typical/typical, and the four corners.  Monte Carlo simulation is used to check some of the intermediate combinations. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To increase yield, they can sort the die into bins after manufacture and thus sell the slow/slow parts that would otherwise be thrown away, and sell the fast/fast parts for a premium.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And yes, some manufacturers will use fuses to restrict a part to a certain speed grade.  Because manufacturing yield curves and market demand being uncorrelated functions, sometimes they have to down-grade parts.&lt;/p&gt;&#xA;" OwnerUserId="2603" LastActivityDate="2011-01-14T03:23:00.647" />
  <row Id="9012" PostTypeId="1" CreationDate="2011-01-14T04:13:56.817" Score="3" ViewCount="266" Body="&lt;p&gt;I want to make a device that can control a small solenoid valve for dispensing fluids. Basically a circuit which powers on and off the solenoid at different time to allow the fluid to flow.  The fluids will be gravity fed so very little pressure is needed. Most of the solenoid valves that I have found are like 100 dollars or more which is way too expensive for this project. Does anyone know of if there are any small inexpensive solenoids, or something similar, that would do what I want? I'd like the flow rate to be about 1 ounce per 5 seconds or somewhere around there but I can reduce the flow if it's more than that...&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2011-01-14T07:31:02.263" Title="small cheap electronic solenoid valve?" Tags="&lt;solenoid&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="9013" PostTypeId="2" ParentId="9012" CreationDate="2011-01-14T05:21:14.460" Score="2" ViewCount="" Body="&lt;p&gt;Valves4projects has some valves that may work for your application around $16.00&#xA;&lt;a href=&quot;http://www.valves4projects.com/servlet/StoreFront&quot; rel=&quot;nofollow&quot;&gt;http://www.valves4projects.com/servlet/StoreFront&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2489" LastActivityDate="2011-01-14T05:21:14.460" />
  <row Id="9014" PostTypeId="2" ParentId="9012" CreationDate="2011-01-14T07:31:02.263" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.pneuaire.com/solenoidvalves.html&quot; rel=&quot;nofollow&quot;&gt;Pneuaire&lt;/a&gt; has a selection as well. I've purchased their low watt gas solenoids, and they seem to work. (I've only played around with them, and haven't subjected them to any real use.)&lt;/p&gt;&#xA;" OwnerUserId="1213" LastActivityDate="2011-01-14T07:31:02.263" />
  <row Id="9015" PostTypeId="1" AcceptedAnswerId="9023" CreationDate="2011-01-14T08:06:30.257" Score="7" ViewCount="373" Body="&lt;p&gt;I want to design a circuit such that the microcontroller can toggle a GPIO pin and shut the whole system (including microcontroller itself) down. And when the user presses a momentary button, the power is brought back up again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this possible?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-25T18:16:20.133" LastActivityDate="2011-01-25T18:16:20.133" Title="How to implement a soft power switch controllable by microcontroller?" Tags="&lt;microcontroller&gt;&lt;power-supply&gt;&lt;design&gt;" AnswerCount="3" FavoriteCount="5" />
  <row Id="9016" PostTypeId="2" ParentId="9015" CreationDate="2011-01-14T08:23:15.303" Score="0" ViewCount="" Body="&lt;p&gt;Yes, this is certainly possible, but how you achieve this depends on what kind of load you're going to be switching on and off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's probably as simple as just using a relay connected to the output PIN of the microcontroller (via a transistor and protection diode), and a push button switch connected to a pin configured as an input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a simple example circuit diagram:&#xA;&lt;img src=&quot;http://i.imgur.com/oXGqg.png&quot; alt=&quot;schematic of relay controlled by a microcontroller&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When using a momentary push button switch, be careful of &lt;a href=&quot;http://en.wiktionary.org/wiki/debounce&quot; rel=&quot;nofollow&quot;&gt;debounce&lt;/a&gt; though, you'll need to implement a delay in your microcontroller code to ensure that you check the status of the push button over a period of time (e.g. 1ms) before switching your relay back on. If you don't, then the microcontroller might pick up multiple signals and switch your relay several times in a very short space of time, and you'll find that your button works intermittently.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UPDATE&lt;/strong&gt;&#xA;I just saw your edit about powering the microcontroller down as well. Can you give some more information about what your actually trying to do? It's difficult to answer your question without understanding the whole system. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to shut the microcontroller down as well, then you'd need some way of getting power back to the microcontroller. Maybe you could use the relay to power everything including the microcontroller, that way the microcontroller can switch itself off, but not back on. Then your push button could be connected across your relay switch, to effectively short it out giving it enough time to power up and hold the relay open itself.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-14T09:20:38.883" LastActivityDate="2011-01-14T09:20:38.883" />
  <row Id="9017" PostTypeId="2" ParentId="9015" CreationDate="2011-01-14T10:25:59.093" Score="0" ViewCount="" Body="&lt;p&gt;One way of doing this is to enter a deep sleep mode on the microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many microcontrollers support being woken up by an external interrupt, such as an edge on an IO pin.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-14T13:54:47.400" LastActivityDate="2011-01-14T13:54:47.400" CommentCount="3" />
  <row Id="9018" PostTypeId="2" ParentId="8965" CreationDate="2011-01-14T10:48:09.240" Score="2" ViewCount="" Body="&lt;p&gt;I don't know of any quite good simulators - because the few free simulators I know of are not updated for new MCUs. For AVRs we have &lt;a href=&quot;http://www.nongnu.org/simulavr/&quot; rel=&quot;nofollow&quot;&gt;SimulAVR&lt;/a&gt;, and for PICs we have &lt;a href=&quot;http://gpsim.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;gpsim&lt;/a&gt;. A few manufacturers, like &lt;a href=&quot;http://www.xmos.com/products/development-tools&quot; rel=&quot;nofollow&quot;&gt;XMOS&lt;/a&gt;, make an effort to provide tools for multiple platforms. Most do not include simulators, but theirs should.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When simulating an instruction set for academic purposes, rather than an entire microcontroller, I've used &lt;a href=&quot;http://gxemul.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;GXemul&lt;/a&gt;. For higher performance emulation &lt;a href=&quot;http://wiki.qemu.org/Main_Page&quot; rel=&quot;nofollow&quot;&gt;QEMU&lt;/a&gt; can be useful.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="1181" LastEditorDisplayName="" LastEditDate="2011-01-14T10:56:31.790" LastActivityDate="2011-01-14T10:56:31.790" />
  <row Id="9019" PostTypeId="1" CreationDate="2011-01-14T10:53:00.457" Score="2" ViewCount="125" Body="&lt;p&gt;I've seen on designs where there is a TVS transient suppression diode on the voltage supply. For example, when the voltage supply is say a wall plug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, are such diodes really necessary in a battery powered system? I can't think of any way where the battery supply could &quot;overshoot&quot; the rated voltage.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-01-14T14:24:37.763" Title="Are transient suppression diodes necessary for a battery powered system?" Tags="&lt;transient-suppression&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="9020" PostTypeId="2" ParentId="9019" CreationDate="2011-01-14T11:13:38.197" Score="3" ViewCount="" Body="&lt;p&gt;If you have ESD-sensitive device inside, it may die when user replaces the battery and touches contacts. Other than that, I can't think of anything.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-14T11:13:38.197" />
  <row Id="9021" PostTypeId="2" ParentId="3911" CreationDate="2011-01-14T11:31:25.837" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://adafruit.com/jobs&quot; rel=&quot;nofollow&quot;&gt;adafruit&lt;/a&gt; now have a moderated &lt;a href=&quot;http://adafruit.com/jobs&quot; rel=&quot;nofollow&quot;&gt;jobs board&lt;/a&gt;. Lots of EEs and other people capable of your requirements would most likely have a look there. Even I got a job from it. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2011-01-14T11:31:25.837" />
  <row Id="9022" PostTypeId="2" ParentId="9001" CreationDate="2011-01-14T11:36:31.480" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Kelvin_bridge&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Kelvin_bridge&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;A Kelvin bridge (also called a Kelvin double bridge and in some countries a Thomson bridge) is a measuring instrument invented by William Thomson, 1st Baron Kelvin. It is used to measure an unknown electrical resistance below 1 Ω.&quot;&lt;/p&gt;&#xA;" OwnerUserId="2607" LastActivityDate="2011-01-14T11:36:31.480" />
  <row Id="9023" PostTypeId="2" ParentId="9015" CreationDate="2011-01-14T11:59:44.033" Score="8" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/valXi.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This example uses a &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/2455&quot; rel=&quot;nofollow&quot;&gt;Maxim MAX1835&lt;/a&gt; step-up regulator, but could be applied to others as well that have a shutdown pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit is normally powered down.  When the user presses the pushbutton, the battery is fed into the -SHDN pin, enabling the regulator and turning on the 3.3V to the microcontroller.  The microcontroller then puts a logic 1 on the POWER ON lead, holding the power on after the user releases the pushbutton.  When the microcontroller wants to shut itself off, it sets the POWER ON lead to 0.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-01-14T14:07:08.603" LastActivityDate="2011-01-14T14:07:08.603" CommentCount="4" />
  <row Id="9024" PostTypeId="2" ParentId="5884" CreationDate="2011-01-14T12:52:45.237" Score="5" ViewCount="" Body="&lt;p&gt;You're basically asking two questions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-- &quot;Are FPGAs as powerful as the number of gates they have?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd actually say that the answer is &quot;no&quot;. The size tells you how &quot;big&quot; they are, but not how &quot;powerful&quot; they are, because:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&quot;powerful&quot; is very subjective to your end application.&lt;/li&gt;&#xA;&lt;li&gt;&quot;powerful&quot; is typically more associated with the technology node than the die's size (a small device from current generation can be the same size as one from an older generation -- are they equally &quot;powerful&quot;?)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;-- Paraphrasing: &quot;Can I divide the number of required &quot;gates&quot; by the number of total &quot;gates&quot; and get the number of cores I could fit in the device?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The answer to this is also &quot;no&quot;. This is because FPGAs are routing limited, which means that:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Even though there may be enough logic resources on the chip, the software won't be able to route that many cores, particularly if there's connectivity overhead.&lt;/li&gt;&#xA;&lt;li&gt;The design, overall, is likely not to meet the timing performance of the individual core.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Another problem is how to handle off-chip I/O -- will there be enough bandwidth and number of I/O to supply/read data from that amount of cores?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(BTW, we're trying to start an SE site dedicated to FPGAs... consider supporting it... &lt;a href=&quot;http://area51.stackexchange.com/proposals/20632/programmable-logic-and-fpga-design?referrer=YmxhQ2OJUo-FAaI1gMp5oQ2&quot;&gt;http://area51.stackexchange.com/proposals/20632/programmable-logic-and-fpga-design?referrer=YmxhQ2OJUo-FAaI1gMp5oQ2&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="2531" LastEditorUserId="2531" LastEditorDisplayName="" LastEditDate="2011-01-15T11:10:10.177" LastActivityDate="2011-01-15T11:10:10.177" />
  <row Id="9025" PostTypeId="2" ParentId="9019" CreationDate="2011-01-14T14:24:37.763" Score="3" ViewCount="" Body="&lt;p&gt;It could still happen.  Static discharge is one method, inductive switching is another, or perhaps some odd grounding issues bumping up voltages.  I would still use TVS diodes on sensitive components.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-14T14:24:37.763" />
  <row Id="9026" PostTypeId="1" AcceptedAnswerId="9030" CreationDate="2011-01-14T15:35:56.237" Score="3" ViewCount="68" Body="&lt;p&gt;Hi there,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have to do some work on a PC/104 &lt;a href=&quot;http://www.eurotech.com/en/products/embedded+boards/pc104+cpu+modules/cpu+pc104/isis+xl&quot; rel=&quot;nofollow&quot;&gt;CPU board&lt;/a&gt;. Until now I have been powering this from a separate power module (acs-5151 at the same link) that took in 8-40V and gave +12, +5, and +3.3 out. Until now, I was able to power the CPU module with the 5V line but don't have access to that anymore. The CPU module is an 8W system and in the past we were able to see that it was only drawing about 0.5A. I tried using a small lab power supply but it didn't boot up the CPU (although some of the LEDs did light up). As this supply says it is only capable of 0.75A continuous I thought that perhaps this wasn't enough to boot the it up. Then I was thinking that I could use the 5V line from a normal PC power supply. When I check the supply though it says 5V /22A. A friend suggested that the CPU might only draw what it needs but wasn't sure. I'm afriad to try it as it's a very expensive piece of hardware and can't afford to damage it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was wondering if anyone could tell me whether a PC power supply will only give the current needed or if there a danger of it damaging the PC/104 module?&lt;/p&gt;&#xA;" OwnerUserId="2178" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-14T19:01:58.150" LastActivityDate="2011-01-14T19:01:58.150" Title="PC Power supply for a PC/104. Current output" Tags="&lt;power-supply&gt;&lt;current&gt;" AnswerCount="1" />
  <row Id="9027" PostTypeId="1" AcceptedAnswerId="9043" CreationDate="2011-01-14T15:47:34.500" Score="2" ViewCount="283" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I'm reading about a microprocessors at the moment and wondering if i could get started with an 8-bit microprocessor. What would i need to get started. I understand that they need external RAM and ROM. I don't know whether it is still possible to get an Intel 8-bit one as my book is from 1980. So are there any other recommendations. I am looking for circuit diagrams for creating my own PCBs, is this advisable? Something like a single board computer is what i'm looking for. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-01-14T19:18:30.467" LastActivityDate="2011-01-15T17:45:21.497" Title="Getting started with a microprocessor." Tags="&lt;microprocessor&gt;" AnswerCount="8" CommentCount="3" FavoriteCount="2" />
  <row Id="9028" PostTypeId="2" ParentId="9027" CreationDate="2011-01-14T15:59:52.897" Score="2" ViewCount="" Body="&lt;p&gt;Here are two tutorials from my bookmarks:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Breadboarding a 6502:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://mysite.du.edu/~jcalvert/tech/6504.htm&quot; rel=&quot;nofollow&quot;&gt;http://mysite.du.edu/~jcalvert/tech/6504.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Homebuilt 8bit micros:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://6502.org/homebuilt&quot; rel=&quot;nofollow&quot;&gt;http://6502.org/homebuilt&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-14T15:59:52.897" />
  <row Id="9029" PostTypeId="2" ParentId="9027" CreationDate="2011-01-14T16:00:28.990" Score="0" ViewCount="" Body="&lt;p&gt;I suggest you just start browsing relevant questions on the site. There are lots of options for 8-bit/16-bit microcontrollers out there, and they don't typically require external memories (though this depends on your application I suppose). Popular microcontrollers with good development tools out there today are Atmel AVRs, TI MSP430s, and Microchip PICs.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-01-14T16:00:28.990" CommentCount="5" />
  <row Id="9030" PostTypeId="2" ParentId="9026" CreationDate="2011-01-14T16:12:42.167" Score="4" ViewCount="" Body="&lt;p&gt;It will only draw what it needs.  The .75A supply probably didn't work because the board will draw more at startup and the supply couldn't source it.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-14T16:12:42.167" CommentCount="2" />
  <row Id="9031" PostTypeId="2" ParentId="8854" CreationDate="2011-01-14T16:22:33.393" Score="1" ViewCount="" Body="&lt;p&gt;You might want to try asking this question at &lt;a href=&quot;http://www.plcs.net/&quot; rel=&quot;nofollow&quot;&gt;PLC's .net&lt;/a&gt;, since it geared toward industrial automation.&lt;/p&gt;&#xA;" OwnerUserId="2612" LastActivityDate="2011-01-14T16:22:33.393" />
  <row Id="9032" PostTypeId="2" ParentId="8464" CreationDate="2011-01-14T16:26:52.703" Score="3" ViewCount="" Body="&lt;p&gt;There are two main &quot;types&quot; of power consumption:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Static: the power consumed while the device is on but doing nothing. The proportion of static power in the total power generally increases as technology dimensions shrink. In 90 nm and below it is a significant portion that must be factored into the power budget.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dynamic: the power consumed while the gates inside of the device (including I/Os) change state (i.e., got from 0 to 1 or 1 to 0). That's why the operating frequency and functionality increases the accuracy of the estimate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Xilinx has two tools for estimating power:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;An excel sheet, as pointed by Brian Carlton.&lt;/li&gt;&#xA;&lt;li&gt;A binary called 'xpwr' (part of ISE) that takes your placed-and-routed design (.ncd) and tries to estimate the power based on actual (well, predicted) use.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Obviously, the second method will be more accurate, but you could get a ballpark for your power budget with the excel sheet before you have a complete design if you need to design your board. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, the best method is to complete your design, run it on a prototyping board, and then measure the consumption. That rarely happens in practice, though, because the FPGA design and board bring-up usually happen in parallel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(BTW, we're trying to start an SE site dedicated to FPGAs... consider supporting it... &lt;a href=&quot;http://area51.stackexchange.com/proposals/20632/programmable-logic-and-fpga-design?referrer=YmxhQ2OJUo-FAaI1gMp5oQ2&quot;&gt;http://area51.stackexchange.com/proposals/20632/programmable-logic-and-fpga-design?referrer=YmxhQ2OJUo-FAaI1gMp5oQ2&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="2531" LastActivityDate="2011-01-14T16:26:52.703" />
  <row Id="9034" PostTypeId="2" ParentId="8966" CreationDate="2011-01-14T17:10:19.397" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.tapplastics.com/shop/product.php?pid=314&amp;amp;PHPSESSID=20110114093329169628690&quot; rel=&quot;nofollow&quot;&gt;This website&lt;/a&gt; has some tinted plastic normally used for windows and is pretty cheap.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastEditorUserId="2006" LastEditorDisplayName="" LastEditDate="2011-01-14T17:35:31.110" LastActivityDate="2011-01-14T17:35:31.110" CommentCount="2" />
  <row Id="9035" PostTypeId="2" ParentId="8966" CreationDate="2011-01-14T17:59:07.820" Score="3" ViewCount="" Body="&lt;p&gt;You could mask off the section of the box above the 7-segment displays and then spray-paint the inside of the box to whatever color you like.  If the alignment is correct, you'll just see the display.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternately (or additionally), take a piece of black paper or card stock and carefully cut out holes for the individual displays.  Slide the paper over the PCB, and you'll be covering up your electronics.  You could even add labels (or a logo) to the paper, if necessary.&lt;/p&gt;&#xA;" OwnerUserId="2616" LastActivityDate="2011-01-14T17:59:07.820" />
  <row Id="9036" PostTypeId="2" ParentId="9027" CreationDate="2011-01-14T18:00:53.217" Score="3" ViewCount="" Body="&lt;p&gt;I will advise to build some Single Board Computer with already developed firmware (monitor) - you can practice programming immediately without need to burn E/EPROMS, and later replace firmware with yours&lt;/p&gt;&#xA;&#xA;&lt;p&gt;if you prefer intel CPUs - something like &lt;a href=&quot;http://www.kmitl.ac.th/~kswichit/mtk-85/index.html&quot; rel=&quot;nofollow&quot;&gt;this based on i8085&lt;/a&gt; - you can download Hex file monitor program, PLD's JEDEC file and &#xA;Complete Hardware Schematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can populate only necessary portion of components &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/pfbHT.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2471" LastActivityDate="2011-01-14T18:00:53.217" CommentCount="1" />
  <row Id="9037" PostTypeId="2" ParentId="9027" CreationDate="2011-01-14T18:32:06.403" Score="1" ViewCount="" Body="&lt;p&gt;I have a few simple PCB designs &lt;a href=&quot;http://webspace.webring.com/people/jl/leon_heller/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; for a variety of MCUs. Some of the chips have been superseded, but there are current devices that will drop straight in. Appropriate programming and debugging tools will be needed, they are available quite cheaply from the chip manufacturers.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-14T18:32:06.403" />
  <row Id="9038" PostTypeId="2" ParentId="9027" CreationDate="2011-01-14T19:04:00.050" Score="1" ViewCount="" Body="&lt;p&gt;Start by getting a more current book.  Lots have changed, for example current microprocessor shave memory controllers on board.  Then buy (don't build) a SBC, similar to as @jet suggested.  And you may just want a higher-end microcontroller rather than a microprocessor.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-14T19:04:00.050" CommentCount="1" />
  <row Id="9039" PostTypeId="2" ParentId="8464" CreationDate="2011-01-14T19:06:12.870" Score="1" ViewCount="" Body="&lt;p&gt;Looking at power use, there are two primary differences in FPGA types.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, there's the SRAM-based families from the leading vendors like Xilinx &amp;amp; Altera.  They draw a lot of static power. Too much, I think, to be useful for anything that's really &quot;low power&quot;. When these two companies say low power, they mean lower power than before (or than the other big guy).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second class is non-volatile. There's a few people with these, but Actel's probably the biggest company that I've actually seen in people's products. They generally use orders of magnitude less static power. They tend to be slower devices. They're also highly resistant to IP theft.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just went through this looking for an FPGA for a low power industrial temperature grade system I'm working on... I want to use Actel but I can't convince myself I'd be able to actually get the I-suffix parts when I needed them. I still haven't really solved this problem. I'll probably just try to squeeze the design into CPLDs.&lt;/p&gt;&#xA;" OwnerUserId="1270" LastActivityDate="2011-01-14T19:06:12.870" />
  <row Id="9040" PostTypeId="1" CreationDate="2011-01-14T19:59:40.547" Score="0" ViewCount="51" Body="&lt;p&gt;I am looking for a reliable vendor to supply my company with either large touch screen devices (monitors) or overlay type devices which can be fitted to any leading brand plasma or LCD screens. &lt;/p&gt;&#xA;" OwnerUserId="2619" LastActivityDate="2011-01-14T19:59:40.547" ClosedDate="2011-01-14T21:09:34.603" Title="Retail Vendor for 42&quot; or Larger Touch Screen Devices or Overlays" Tags="&lt;hardware&gt;&lt;touchscreen&gt;&lt;device&gt;" CommentCount="1" />
  <row Id="9041" PostTypeId="1" AcceptedAnswerId="9154" CreationDate="2011-01-14T20:13:50.493" Score="3" ViewCount="214" Body="&lt;p&gt;&lt;em&gt;&lt;strong&gt;How would one approach designing a &lt;a href=&quot;http://en.wikipedia.org/wiki/Radio_spectrum&quot; rel=&quot;nofollow&quot;&gt;SHF&lt;/a&gt; 3GHz - 30GHz bandpass filter&lt;/strong&gt; for a 50Ω spectrum analyzer or sampling oscilloscope? I've learned all about how I can implement some simple RF designs, and some of what to look out for, but I'm really green.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;What active and passive circuit topologies are used?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;How are the circuit elements implemented -- lumped elements or microstrip/stripline structures?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;What bandwidths and falloffs can be expected?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-14T22:22:47.530" LastActivityDate="2011-01-18T02:59:31.937" Title="How to approach designing a 30GHz bandpass filter?" Tags="&lt;rf&gt;&lt;pcb-design&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="9042" PostTypeId="2" ParentId="8464" CreationDate="2011-01-14T21:41:14.523" Score="1" ViewCount="" Body="&lt;p&gt;It's true that the power estimation tools made by the vendors are the best tool to get information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, to get a feelinig, A &quot;full&quot; Altera Cyclone 3 I have recently encountered uses something like 0.8 A on the 1.2 V rail and not much (1...50 mA) on its 3.3 V and 2.5 V rails. It totals to a bit more than 1 W when running.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the 3.3 V rail is pretty much just used for the IOs, the FPGA will draw whatever the connected circuitry requires from this supply rail.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-01-14T21:41:14.523" />
  <row Id="9043" PostTypeId="2" ParentId="9027" CreationDate="2011-01-14T22:18:42.910" Score="5" ViewCount="" Body="&lt;p&gt;What are your design requirements or goals? Any areas you expect to need to learn more about, or any areas you wish to focus on?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because most of the Intel 8-bit microprocessors were so popular they are fairly easy to find as New Old Stock (NOS) or Pulled/Refurbished (reclaimed/recycled, usually tested). At least the 8080, 8088, 8086, and 8085 are available from distributors or obsolete / old-stock supplies. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two others that are worth considering would be the &lt;a href=&quot;http://www.zilog.com/&quot; rel=&quot;nofollow&quot;&gt;Zilog&lt;/a&gt; - &lt;a href=&quot;http://z80.info/&quot; rel=&quot;nofollow&quot;&gt;Z80&lt;/a&gt; (&lt;a href=&quot;http://en.wikipedia.org/wiki/Zilog_Z80#Technical_description&quot; rel=&quot;nofollow&quot;&gt;technical description&lt;/a&gt;), and MOS Technology &lt;a href=&quot;http://6502.org/&quot; rel=&quot;nofollow&quot;&gt;6502&lt;/a&gt; (&lt;a href=&quot;http://en.wikipedia.org/wiki/MOS_Technology_6502#Technical_description&quot; rel=&quot;nofollow&quot;&gt;technical description&lt;/a&gt;). The Z80 was created by Federico Faggin, who designed Intel's 8080, and made the Z80 a binary compatible (but enhanced) processor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Z80 requires fewer support chips than the i8080 with built-in DRAM refresher, a single (5V) voltage supply requirement (i8080 required +/-5V and +12V), and can be run at any clock speed up to its specified speed (e.g. 2.5 MHz for the first NMOS models). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Combined with 5V power supply, oscillator clock (e.g. TTL/CMOS oscillator &quot;can&quot;), Static RAM (rather than Dynamic RAM, DRAM) you only need a ROM/EPROM/EEPROM and interface (e.g. interface chips for parallel or serial interfaces) to built a minimal microcomputer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One fairly popular book on building your own microcomputer using the Z80 was &lt;a href=&quot;http://www.scribd.com/doc/13388965/Build-Your-Own-Z80-Computer&quot; rel=&quot;nofollow&quot;&gt;Build Your Own Z80 Computer&lt;/a&gt; (available with copyright permission of author/publisher) by Steve Ciarcia. Also check out the (dated) &lt;a href=&quot;http://www.faqs.org/faqs/homebuilt-comp-FAQ/&quot; rel=&quot;nofollow&quot;&gt;alt.comp.hardware.homebuilt&lt;/a&gt; FAQ, and the &lt;a href=&quot;http://n8vem-sbc.pbworks.com/&quot; rel=&quot;nofollow&quot;&gt;N8VEM community&lt;/a&gt; for additional resources and references.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The MOS 6502 was the another popular microprocessor, in part because it was so much cheaper ($25 USD) than the Motorola 6800 which was originally $300 USD circa 1975. It was used in popular systems such as the Apple I from Apply Computers, Commodore KIM-1, PET, and Vic-20, BBC Micro, and the Commodore 64 and Atari 2600 game system used 6502 derivatives (6510 and 6507). So there is a lot of material available from retro-computing and retro-gaming people online, and parts. The 6502, like the Z80 was produced by several sources (i.e. second sourcing) including Rockwell in additional to the primary designer / manufacturer, MOS Technology.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a particular (strong) interest in the x86 or IBM &lt;a href=&quot;http://en.wikipedia.org/wiki/IBM_Personal_Computer&quot; rel=&quot;nofollow&quot;&gt;PC&lt;/a&gt; / &lt;a href=&quot;http://en.wikipedia.org/wiki/IBM_Personal_Computer_XT&quot; rel=&quot;nofollow&quot;&gt;XT&lt;/a&gt; history then a 8088 or 8086 might be a educational target to consider. Otherwise I would lean towards the Z80 as my first pick, and the 6502 as my second choice due to parts availability and resource material availability. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The range of options is unlimited from a &lt;a href=&quot;http://www.6502.org/users/dieter/mt15/mt15.htm&quot; rel=&quot;nofollow&quot;&gt;microcomputer built from almost exclusively discrete transistors&lt;/a&gt;, to a 25MHz 32-bit &lt;a href=&quot;http://web.archive.org/web/20020109104448/http://www.derivation.com/~cyliax/ws030.html&quot; rel=&quot;nofollow&quot;&gt;MC68030 workstation&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-01-14T22:18:42.910" CommentCount="2" />
  <row Id="9044" PostTypeId="1" CreationDate="2011-01-14T22:46:55.357" Score="1" ViewCount="115" Body="&lt;p&gt;Hey,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I live in the Netherlands and can't recharge my Japanese cellphone because I think it's due to the difference in voltage.&#xA;What should I use in order to recharge it anyways?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!!&lt;/p&gt;&#xA;" OwnerUserId="2621" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:16:28.193" LastActivityDate="2011-03-05T16:16:28.193" Title="My country's voltage is 220 and I want to recharge a Japanese cellphone (100V), what should I use?" Tags="&lt;line-power&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="9045" PostTypeId="2" ParentId="9044" CreationDate="2011-01-14T22:55:42.460" Score="4" ViewCount="" Body="&lt;p&gt;If its a major brand Nokia, SE, Samsung to name a few. Get a local charger and use it, its the safest approach. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-01-14T22:55:42.460" />
  <row Id="9046" PostTypeId="2" ParentId="9044" CreationDate="2011-01-14T22:56:32.007" Score="1" ViewCount="" Body="&lt;p&gt;What is the nameplate rating? A lot of newer chargers use PFC, which allows them to work from 85Vac all the way up to 265Vac...&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-14T22:56:32.007" CommentCount="3" />
  <row Id="9047" PostTypeId="2" ParentId="9027" CreationDate="2011-01-14T23:36:54.623" Score="2" ViewCount="" Body="&lt;p&gt;If you want to play around with an 8 bit cpu, the z80 and 6502 are probably electrically the least complicated, as they present non-multiplexed buses, operate from a single 5V supply, and don't require multi-phase clocks. Older chips like the 8080 or the 6800 need multiple supply voltages. The 8035 and 8085 multiplex address and data, requiring you to supply an external register to latch part of the address bus. The 6809 has more powerful instructions, but the single clock 6809 variant is harder to find than the quadrature-phase clock 6809E.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only real reason to build an SBC around one of these is for the fun of it. A system based on a modern microcontroller will be smaller, use less power, and out-perform the old dinosaurs in terms of instruction set and integrated peripherals.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-01-14T23:36:54.623" CommentCount="2" />
  <row Id="9048" PostTypeId="1" AcceptedAnswerId="9049" CreationDate="2011-01-15T01:04:01.560" Score="5" ViewCount="261" Body="&lt;p&gt;Last week we had very cold weather; and as a result there were lots of frosted pipes (iron and plastic). I spent a lot of time defrosting metal pipes with a torch, but could not do the same with plastic ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could a practical gadget be made to thaw the ice trapped inside metal/plastic pipes based on induction? What would a blueprint of such look like?&lt;/p&gt;&#xA;" OwnerUserId="2466" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-15T19:05:13.177" LastActivityDate="2011-01-17T00:40:20.443" Title="Could induction thaw ice?" Tags="&lt;rf&gt;&lt;design&gt;&lt;device&gt;&lt;inductance&gt;" AnswerCount="6" CommentCount="3" FavoriteCount="1" />
  <row Id="9049" PostTypeId="2" ParentId="9048" CreationDate="2011-01-15T01:46:36.567" Score="7" ViewCount="" Body="&lt;p&gt;Induction uses magnetic fields to move free electrons in a regular lattice (ie: a conductor). Ice doesn't have very many free electrons or a regular lattice, so no. It does have a few large ions and protons, but they are at least 1600X more massive, so they don't move much. In &lt;a href=&quot;http://www.youtube.com/watch?v=aLwaPP9cxT4&quot; rel=&quot;nofollow&quot;&gt;this YouTube video&lt;/a&gt;, iron filings are dispersed in ice in order to provide a conductive heat sink -- otherwise it would not heat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An inductive heating device could be used to heat the pipe directly, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something that could heat the ice directly is microwaves. I don't recommend it, however, as there wouldn't be much stopping the energy from bouncing around and heating you!&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-15T02:49:27.283" LastActivityDate="2011-01-15T02:49:27.283" CommentCount="1" />
  <row Id="9050" PostTypeId="1" CreationDate="2011-01-15T04:30:13.163" Score="1" ViewCount="65" Body="&lt;p&gt;hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im trying to make a device that will act as a caller id to cell phones.  Essentially I want the device to show the phone number of the person calling from say from a device sitting on a conference table.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the question on my mind is that if I pick up the call with one bluetooth connection to display the phone number, would a person be able to answer the phone call with a headset that is also connected to the device?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm doing some due diligence before giving a proposal to a client and would appreciate any information that you can provide from your own experiences.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks  &lt;/p&gt;&#xA;" OwnerUserId="2437" LastActivityDate="2011-01-15T04:30:13.163" ClosedDate="2011-03-10T10:47:30.043" Title="2 Bluetooth Connections concurrently?" Tags="&lt;bluetooth&gt;" CommentCount="4" />
  <row Id="9051" PostTypeId="2" ParentId="9044" CreationDate="2011-01-15T05:12:32.707" Score="1" ViewCount="" Body="&lt;p&gt;First you need to check the voltage rating on Japanese cell phone charger. If the rating on the converter is ~110v to ~220v, that means the charger can take 220v as well. All you need is a plug adapter which you can use with existing charger. The plug adapter just allows you to plug-in your charger with square pins to your power socket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the voltage on the charger is just ~220v, there are two options:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;You can purchase a 'step down voltage converter' which can convert your power voltage to 110v for your phone. You can purchase a converter at local electronic store.&lt;/li&gt;&#xA;&lt;li&gt;Or Buy a new cell phone charger with the same output voltage as your Japanese cell charger.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2624" LastActivityDate="2011-01-15T05:12:32.707" CommentCount="1" />
  <row Id="9052" PostTypeId="2" ParentId="9002" CreationDate="2011-01-15T05:25:48.383" Score="2" ViewCount="" Body="&lt;p&gt;I agree with AngryEE -- it's unlikely you will find a complete schematic for a 478 motherboard.&#xA;However, would something slightly different, such as one of the following, be adequate for whatever it is you are trying to do?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are looking for the complete schematic for a relatively modern motherboard,&#xA;there are several &quot;motherboards that run Linux&quot; with a complete and freely-available schematic.&#xA;&lt;a href=&quot;http://opencircuits.com/motherboards_that_run_Linux&quot; rel=&quot;nofollow&quot;&gt;http://opencircuits.com/motherboards_that_run_Linux&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are trying to lookup what all those pins in a (obsolete) 478 socket do,&#xA;perhaps you will find the answers in the datasheet for&#xA;&quot;The Intel® Pentium® 4 Processor in the 478-pin Package socket&quot;.&#xA;&lt;a href=&quot;http://www.intel.com/design/pentium4/datashts/249887.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.intel.com/design/pentium4/datashts/249887.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-15T05:25:48.383" />
  <row Id="9053" PostTypeId="2" ParentId="8994" CreationDate="2011-01-15T05:41:43.933" Score="2" ViewCount="" Body="&lt;p&gt;While you're probably looking at &quot;full size&quot; structural extruded aluminum T-slot,&#xA;for completeness I'm going to mention miniature versions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MakerBeam is developing the Mini-T standard for open source hardware. &lt;a href=&quot;http://www.makerbeam.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.makerbeam.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MicroRAX a light weight mini T-Slot building kit.&#xA;&lt;a href=&quot;http://www.microrax.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.microrax.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Cjp6o.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/uenXI.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-15T05:41:43.933" />
  <row Id="9054" PostTypeId="5" CreationDate="2011-01-15T06:43:45.050" Score="0" ViewCount="0" Body="" OwnerUserId="-1" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-01-15T06:43:45.050" LastActivityDate="2011-01-15T06:43:45.050" />
  <row Id="9055" PostTypeId="4" CreationDate="2011-01-15T06:43:45.050" Score="0" ViewCount="0" Body="HDL, or Hardware Description Language, is a programming language such as Verilog or VHDL used to describe electronics." OwnerUserId="-1" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-01-15T06:43:45.050" LastActivityDate="2011-01-15T06:43:45.050" />
  <row Id="9056" PostTypeId="2" ParentId="9048" CreationDate="2011-01-15T07:46:15.417" Score="1" ViewCount="" Body="&lt;p&gt;Induction can thaw ice if metal were dissolved in the water, so say you had the water pass through a metal filter that allowed the water to pick up some metal particles then you could. With a metal pipe you can simply heat the pipe with induction pretty efficiently. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would look like a thick coil of wire. &lt;/p&gt;&#xA;" OwnerUserId="2625" LastActivityDate="2011-01-15T07:46:15.417" CommentCount="4" />
  <row Id="9057" PostTypeId="2" ParentId="7267" CreationDate="2011-01-15T08:06:25.903" Score="1" ViewCount="" Body="&lt;p&gt;LPC2138/48 would be a good start. There lots of examples written for these micros.&lt;/p&gt;&#xA;" OwnerUserId="2626" LastActivityDate="2011-01-15T08:06:25.903" CommentCount="1" />
  <row Id="9058" PostTypeId="1" AcceptedAnswerId="9061" CreationDate="2011-01-15T10:27:30.897" Score="3" ViewCount="74" Body="&lt;p&gt;Where can I find those metal shield cans that you can solder directly on a pcb for EMI shielding? Just like the ones on the back of XBee modules? I'm not having any luck searching on farnell, perhaps with the wrong keywords, or maybe it's not a commonly bought item?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-01-15T13:09:58.530" Title="Buying RF metal shields" Tags="&lt;rf&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="9059" PostTypeId="1" AcceptedAnswerId="10792" CreationDate="2011-01-15T10:56:21.543" Score="2" ViewCount="99" Body="&lt;p&gt;Carrying on the conversation discussed in &lt;a href=&quot;http://electronics.stackexchange.com/questions/3911/how-can-i-find-a-good-local-electrical-engineer&quot;&gt;how to find a good local EE&lt;/a&gt;, I would like to pose this question from another angle. I am a recent college graduate from an electrical engineering background with 2 years worth of work terms in circuit prototyping/design/assembly and computer programming while I was still in school. While I am interested in learning other tools, I want to use the strengths I have now in a telecommuting role while I grow my toolset. Despite having 2 years of work experience (and I've lost track of when I have started programming), my status as a recent college graduate may be an obstacle of my credibility to compete for telecommuting (or in fact any) opportunities. I don't know how I can go about finding telecommute opportunities for someone with my situation, even though I have done some digging through sites like oDesk, iFreelance, Freelancer, vWorker, Adafruit, etc. Overall, many of previous places I've worked at liked my work. What are your suggestions?&lt;/p&gt;&#xA;" OwnerUserId="1944" LastEditorUserId="536" LastEditorDisplayName="" LastEditDate="2011-01-15T15:31:28.500" LastActivityDate="2011-02-28T02:15:36.470" CommunityOwnedDate="2011-02-28T04:38:11.237" Title="Finding Telecommuting Opportunities as a Recent College Graduate" Tags="&lt;hire&gt;&lt;career&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="9060" PostTypeId="2" ParentId="9048" CreationDate="2011-01-15T11:21:52.393" Score="4" ViewCount="" Body="&lt;p&gt;How about a good old fashioned &lt;a href=&quot;http://www.amazon.com/s/?ie=UTF8&amp;amp;keywords=heating+blanket&amp;amp;tag=mh0b-20&amp;amp;index=aps&amp;amp;hvadid=21165049&amp;amp;ref=pd_sl_4b9brbrp5q_e#/ref=nb_sb_noss?url=search-alias%3Daps&amp;amp;field-keywords=electric+heating+blanket&amp;amp;rh=i%3Aaps%2Ck%3Aelectric+heating+blanket&quot; rel=&quot;nofollow&quot;&gt;heating blanket&lt;/a&gt;?  That would use electricity to get hot without having to fish heating coils either in or around the pipe and wouldn’t be as dangerous as playing with a microwave’s magnetron. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Induction from a standard electromagnet wouldn't be able to cause normal water to get hot.  If you had something of high enough frequency such as a magnetron you would be able to use &lt;a href=&quot;http://en.wikipedia.org/wiki/Dielectric_heating&quot; rel=&quot;nofollow&quot;&gt;dielectric heating&lt;/a&gt; to slowly melt the water.  &lt;/p&gt;&#xA;" OwnerUserId="2412" LastEditorUserId="2412" LastEditorDisplayName="" LastEditDate="2011-01-15T11:26:55.383" LastActivityDate="2011-01-15T11:26:55.383" CommentCount="1" />
  <row Id="9061" PostTypeId="2" ParentId="9058" CreationDate="2011-01-15T11:24:35.327" Score="3" ViewCount="" Body="&lt;p&gt;RS stocks &lt;a href=&quot;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=retrieveTfg&amp;amp;binCount=5&amp;amp;Nty=1&amp;amp;Ntx=mode%2bmatchallpartial&amp;amp;Ntk=I18NAll&amp;amp;Ne=4294957561&amp;amp;Nr=AND%28avl%3auk%2csearchDiscon_uk%3aN%29&amp;amp;N=4294957537&amp;amp;Ntt=pcb+screening&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-15T11:30:47.707" LastActivityDate="2011-01-15T11:30:47.707" />
  <row Id="9062" PostTypeId="2" ParentId="9058" CreationDate="2011-01-15T13:04:09.990" Score="2" ViewCount="" Body="&lt;p&gt;On Farnell they found by searching for 'Screening Cans'. Most of them are from the brand PERANCEA. I got some of them as well, they seem to work fine. Make sure you order them and fit them on your PCB design before you sent out an order to make dozens.. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It might require some fitting before you want to be sure to get them designed in. What I mean is that the ones that have a removable lid might be a bit larger from the drawings. The case itself folds over itself within the case, making it twice as thick as shown. On wrong measurements, it might also mean you end up with a screening case that is slightly rotated to make it fit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you search for 'screening' (at farnell) you might also find metal strips that you can place on PCB's as 'dividers'. I don't know what Digikey or Mouser has to offer, but I suspect they might have more. Screening, shielding, all EMC terms should give good results.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I do know distrelec has got many items under the search result 'screening'. They also got SMD mounted screening cans etc.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastEditorUserId="1476" LastEditorDisplayName="" LastEditDate="2011-01-15T13:09:58.530" LastActivityDate="2011-01-15T13:09:58.530" />
  <row Id="9063" PostTypeId="2" ParentId="7267" CreationDate="2011-01-15T13:24:20.840" Score="1" ViewCount="" Body="&lt;p&gt;I use Rowley CrossWorks with their CrossConnect Pro for ARM development. Support is very good.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-15T13:24:20.840" CommentCount="1" />
  <row Id="9064" PostTypeId="2" ParentId="7267" CreationDate="2011-01-15T14:28:42.907" Score="2" ViewCount="" Body="&lt;p&gt;For professional type use, your major options are IAR, Keil or Rowley CrossWorks.  Keil is owned by ARM, which may or may not give them a slight advantage.  I'd say the performance between IAR and Keil is nearly identical.  Rowley is bargain of the 3.  Rowley also let's you use cheaper debuggers, such as the J-link.  You might be able to use the J-link with IAR as well, but I think Keil forces you to use their Ulink products, which can be a bit more expensive.  As far as support, I believe Rowley is purely through their website.  IAR and Keil offer 1 year or so of phone support.  From what I've been told, Keil seems to offer better support in the US, while IAR is more focused on Europe.  I've used Keil without any issues and support was good.  That being said, any of these 3 will probably perform just as well.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-01-15T14:28:42.907" CommentCount="1" />
  <row Id="9065" PostTypeId="2" ParentId="9048" CreationDate="2011-01-15T15:06:15.330" Score="1" ViewCount="" Body="&lt;p&gt;The melting point of ice is somewhat lower than that of plastic - all you need to do is use hot air with a controlled temperature. Like a hairdryer or fan-heater.&#xA;Or hot water. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-15T15:06:15.330" CommentCount="1" />
  <row Id="9066" PostTypeId="1" CreationDate="2011-01-15T16:44:40.730" Score="5" ViewCount="311" Body="&lt;p&gt;hello, i am trying to get a 3x3 matrix with multiplexing up and running. here is my setup:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/6x9xE.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i have connected each rows cathodes and each columns anodes and connected that one to pins 0,1,2 resp. 8,9,10&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the only thing i can get to light is the lowest row, but if i want to light the middle row for example with this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;digitalWrite(8, HIGH);     &#xA;digitalWrite(9, HIGH);     &#xA;digitalWrite(10, HIGH);     &#xA;&#xA;digitalWrite(0, HIGH);&#xA;digitalWrite(1, LOW);&#xA;digitalWrite(2, HIGH);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;nothing happens.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;is my wiring setup wrong maybe?&lt;/p&gt;&#xA;" OwnerUserId="2629" LastActivityDate="2011-04-02T12:47:20.487" Title="arduino 3x3 LED matrix" Tags="&lt;arduino&gt;&lt;led&gt;&lt;matrix&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="9067" PostTypeId="2" ParentId="8966" CreationDate="2011-01-15T16:49:57.570" Score="0" ViewCount="" Body="&lt;p&gt;Could you attach a translucent sheet, like the thin Styrene sheet in the Sparkfun clock?&#xA;&quot;12ft GPS Wall Clock&quot; tutorial&#xA;&lt;a href=&quot;http://www.sparkfun.com/tutorials/47&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/tutorials/47&lt;/a&gt; .&#xA;Perhaps a few layers of HDPE milk jug would be adequately translucent?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or even simpler:&#xA;Could you use sandpaper to convert the clear plastic lid to a translucent plastic lid?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-15T16:49:57.570" />
  <row Id="9068" PostTypeId="2" ParentId="9027" CreationDate="2011-01-15T17:45:21.497" Score="1" ViewCount="" Body="&lt;p&gt;Whatever you do, start with a higher level language like C.  I know you would learn more about the internals with asm, but if you want to get something done in a finite time asm is usually not the best route.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And look at the cost of the compiler ( and other tools ) in making price comparisons.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-01-15T17:45:21.497" />
  <row Id="9069" PostTypeId="2" ParentId="9006" CreationDate="2011-01-15T17:48:55.687" Score="0" ViewCount="" Body="&lt;p&gt;Depends on how many feet your are planning to light at the same time.  If not sure go with the total.  Some inverters also have a min. number of feet, check that, you can always hang on some that is always on, or put in a dummy cap.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-01-15T17:48:55.687" />
  <row Id="9070" PostTypeId="2" ParentId="9066" CreationDate="2011-01-15T18:30:34.530" Score="5" ViewCount="" Body="&lt;p&gt;Here's a sketch of what you've described for clarity and benefit to others:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/3zjWA.png&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good things to do at this point:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Make sure you have &lt;strong&gt;current limiting resistors&lt;/strong&gt; in series with each LED. 560Ω will limit to ~6mA. If these are not presently in place, some LEDs may be burned out, so check them. The ATmega128/328 (whichever is on your board) is limited to &lt;em&gt;20mA per pin&lt;/em&gt;*.&lt;/li&gt;&#xA;&lt;li&gt;Verify that the pins are actually going &lt;em&gt;high&lt;/em&gt; or &lt;em&gt;low&lt;/em&gt; when you program them to do so, with a voltmeter or logic probe.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;*I must correct myself, here. This is the actual restriction:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;27.1 Absolute Maximum Ratings&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;sub&gt;&lt;em&gt;NOTICE: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.&lt;/em&gt;&lt;/sub&gt;&#xA;  ...  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;DC Current per I/O Pin             40.0 mA  &#xA;DC Current V and GND Pins       200.0 - 400.0 mA &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;  &#xA;  &lt;p&gt;...&lt;br&gt;&#xA;  Although each I/O port can sink more than the test conditions (20 mA at VCC = 5V, 10 mA at VCC = 3V) under steady state &#xA;  conditions (non-transient), the following must be observed: &#xA;  TQFP and QFN/MLF Package: &#xA;  1] The sum of all IOL, for all ports, should not exceed 400 mA. &#xA;  2] The sum of all IOL, for ports A0 - A7, G2, C3 - C7 should not exceed 100 mA. &#xA;  3] The sum of all IOL, for ports C0 - C2, G0 - G1, D0 - D7, XTAL2 should not exceed 100 mA. &#xA;  4] The sum of all IOL, for ports B0 - B7, G3 - G4, E0 - E7 should not exceed 100 mA. &#xA;  5] The sum of all IOL, for ports F0 - F7, should not exceed 100 mA. &#xA;  If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater &#xA;  than the listed test condition. &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-15T20:56:54.330" LastActivityDate="2011-01-15T20:56:54.330" CommentCount="1" />
  <row Id="9071" PostTypeId="1" AcceptedAnswerId="9073" CreationDate="2011-01-15T19:51:46.107" Score="0" ViewCount="127" Body="&lt;p&gt;I bought a Metcal STSS-PS2V-02 soldering iron from eBay, it was cheap and in need of repair. The previous owner had some problems with the handpiece and tried to fix it himself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't get it to heat up at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I turn the base station on without the handpiece connected, it draws virtually no power. With it connected, about 10W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It appears that he has sawn the handpiece in two, then attempted to resolder the cable. With no soldering tip attached, I am seeing 0Ω between the inner and wire and sheath of the cable, does this mean that his resoldering has shorted it, or should I expect this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm6.static.flickr.com/5241/5357993910_5b5acde271_m.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://farm6.static.flickr.com/5126/5357377339_aece186fee.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next week, I'll be able to test the base station against a known working handpiece and determine if the base is working properly, but is there any other way I can tell?&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-15T21:06:42.700" Title="Fixing a broken Metcal handpiece" Tags="&lt;soldering&gt;&lt;metcal&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="9072" PostTypeId="2" ParentId="5884" CreationDate="2011-01-15T20:22:51.833" Score="1" ViewCount="" Body="&lt;p&gt;Yes, FPGAs are excellent for implementing massively parallel things.&#xA;Many people have put 8 or more CPUs on a FPGA -- it's not merely &quot;in principle&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out the floorplan image in the article&#xA;&lt;a href=&quot;http://www.design-reuse.com/articles/21583/processor-noc-fpga.html&quot; rel=&quot;nofollow&quot;&gt;&quot;A 24 Processors System on Chip FPGA Design with Network on Chip&quot;&lt;/a&gt;&#xA;by Zhoukun WANG and Omar HAMMAMI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That floorplan makes it pretty obvious that that particular FPGA is pretty much packed full of stuff.&#xA;The 24 CPU cores -- each one a 32 bit MicroBlaze CPU with 32 KByte total of local instruction and data memory -- fill up roughly half the FPGA (around the perimeter).&#xA;The routing between the CPU cores and the 4 independent external buses pretty much fills up all the rest of the FPGA.&#xA;(The external buses are each 64 data bits wide plus some control signals, each one leading to an independent DDR2 memory module).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(This particular IC also includes two PowerPC 405 CPU hard cores in addition to the FPGA fabric -- Zhoukun and Omar apparently didn't bother using them).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As other people here have pointed out, dividing &quot;number of gates in a FPGA&quot; by &quot;number of gates in a CPU&quot; is overly optimistic.&#xA;In this case, 142,128 LUTs on a Xilinx FPGA Virtex-4 FX140 divided by about 1000 LUTs required for a minimum-size MicroBlaze gives (optimistically) 142 CPUs per chip.&#xA;So are you disappointed that apparently &quot;only&quot; 24 CPUs fit in that FPGA fabric (not counting the two PowerPC 405 hard cores outside the FPGA fabric on that IC)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 1 million gate FPGA divided by a 50k gate CPU gives (optimistically) 20 CPUs per chip.&#xA;I think you will be lucky to squeeze even 4 CPUs onto that FPGA.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;It is amazing what you can squeeze&#xA;  onto these parts if you design the&#xA;  machine architecture carefully to&#xA;  exploit FPGA resources.  In contrast,&#xA;  there was a very interesting article&#xA;  in a recent EE Times by a fellow from&#xA;  VAutomation doing virtual 6502's in&#xA;  VHDL, then synthesizing them down into&#xA;  arbitrary FPGA architectures. &#xA;  Although the 6502 design used only&#xA;  about 4000 &quot;ASIC gates&quot; it didn't&#xA;  quite fit in a XC4010, a so- called&#xA;  &quot;10,000 gate&quot; FPGA.  That a dual-issue&#xA;  32-bit RISC should fit, and a 4 MHz&#xA;  6502 does not, states a great deal&#xA;  about VHDL synthesis vs. manual&#xA;  placement, about legacy architectures&#xA;  vs. custom ones, and maybe even&#xA;  something about CISC vs. RISC...&quot;&#xA;  -- &lt;a href=&quot;http://www.fpgacpu.org/usenet/homebrew.html&quot; rel=&quot;nofollow&quot;&gt;Jan Gray&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/soft_microprocessor&quot; rel=&quot;nofollow&quot;&gt;Wikipedia: &quot;soft processor&quot; article&lt;/a&gt; has more information on packing multiple CPUs on a single FPGA.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-15T20:22:51.833" />
  <row Id="9073" PostTypeId="2" ParentId="9071" CreationDate="2011-01-15T21:01:28.837" Score="1" ViewCount="" Body="&lt;p&gt;I've got a similar Metcal system. If the handpiece and cartridge are working properly just the green LED on the STSS power unit should be on, otherwise the amber one will be lit as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They use RF heating at about 14 MHz, via a coaxial cable. It's very unlikely that you will get that handpiece working properly, I'd just buy a new one. You could try testing the power unit with a suitable 100W 50R resistor, it'll need to be non-inductive. Just the green LED should come on. I can't be sure that test will work as I don't think the impedance has been published, but it won't do any damage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I got mine second-hand from a supplier here in the UK, with a new MX-500 handpiece and selection of cartridges. I subsequently picked up a spare STSS unit on Ebay, as a spare. The power units are very reliable, so yours is probably OK.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-15T21:06:42.700" LastActivityDate="2011-01-15T21:06:42.700" />
  <row Id="9074" PostTypeId="2" ParentId="7624" CreationDate="2011-01-15T21:38:21.193" Score="2" ViewCount="" Body="&lt;p&gt;&quot;Can one build a complex bunch of logic and have stuff ripple through it as fast as it can?&quot;&#xA;Yes.&#xA;Entire CPUs have been built that are completely asynchronous -- at least one of them was the fastest CPU in the world.&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Asynchronous_circuit#Asynchronous_CPU&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Asynchronous_circuit#Asynchronous_CPU&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It irks me that people reject asynchronous design techniques, even though they theoretically have several advantages over synchronous design techniques, merely because (as others here have said) asynchronous designs are not as well supported by the available tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To me, that's like recommending that all bridges be made out of wood, because more people have woodworking tools than steel-working tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fortunately, some of the advantages of asynchronous design can be gained while still using mostly synchronous design techniques by using a &lt;a href=&quot;http://en.wikipedia.org/wiki/globally_asynchronous_locally_synchronous&quot; rel=&quot;nofollow&quot;&gt;global asynchronous local synchronous (GALS)&lt;/a&gt; design.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-15T21:38:21.193" CommentCount="2" />
  <row Id="9075" PostTypeId="2" ParentId="3686" CreationDate="2011-01-15T22:09:30.347" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.stephenhobley.com/blog/2009/03/01/pixartwiimote-sensor-library-for-arduino/&quot; rel=&quot;nofollow&quot;&gt;The author mentions&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Either the sensor is bad or your line level conversion is not working.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;To figure out why, let's look at the library code. This is how the Arduino gets the raw data:&lt;sup&gt;&lt;br&gt;&lt;em&gt;Note: I've taken a few liberties with the code to clarify and shorten it, but it is practically identical.&lt;/em&gt;&lt;/sup&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;while(Wire.available() &amp;amp;&amp;amp; i &amp;lt; 16) {&#xA;    data_buf[i++] = Wire.receive();&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;As explained by &lt;a href=&quot;http://www.kako.com/neta/2008-009/2008-009.html&quot; rel=&quot;nofollow&quot;&gt;the original hacker&lt;/a&gt; and emulated in the library, the data is in the following format:&lt;br&gt;&#xA;&lt;code&gt;[Top byte][Coordinate1][Coordinate2][Coordinate3][Coordinate4]&lt;/code&gt;&lt;br&gt;&#xA;... where each coordinate block is 3 bytes, and the (X,Y) coordinates are calculated like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Blob1.X = (Byte3 &amp;amp; 0b00110000) &amp;lt;&amp;lt;4 + Byte1;&#xA;Blob1.Y = (Byte3 &amp;amp; 0b11000000) &amp;lt;&amp;lt;2 + Byte2;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Whether or not the IR spot is detected is determined by this code, which is repeated for 4 &quot;Blobs&quot;:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Blob1.Size = (Byte3 &amp;amp; 0b00001111);&#xA;blobcount |= (Blob1.Size &amp;lt; 15)? 0x01 : 0; // Is Blob.Size less than 0x0F?&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You are getting (0,0) for all of them, meaning all blobs are detected (&lt;code&gt;blobcount&lt;/code&gt; is &lt;code&gt;0x00001111&lt;/code&gt;). This can result from all data being zero, as &lt;code&gt;(0x00 &amp;lt; 15)&lt;/code&gt; is &lt;code&gt;TRUE&lt;/code&gt;. To make a long story short, &lt;em&gt;&quot;Either the sensor is bad or your line level conversion is not working.&quot;&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At this point you want to do these things:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Check &lt;a href=&quot;http://stephenhobley.com/blog/wp-content/uploads/2009/02/wiicam_schem.gif&quot; rel=&quot;nofollow&quot;&gt;your oscillator circuit&lt;/a&gt; with an oscilloscope to verify its operation (don't measure crystal directly as 'scope capacitance will skew it, but inverter output).&lt;/li&gt;&#xA;&lt;li&gt;Ensure proper voltages are present.&lt;/li&gt;&#xA;&lt;li&gt;Make sure SDA and SCL are being pulled up to 3.3V with 30kΩ resistors on the sensor side and to 5V with 1.5kΩ resistors on the Arduino side of the level converter (&lt;a href=&quot;http://cds.linear.com/docs/Datasheet/4301Lfa.pdf&quot; rel=&quot;nofollow&quot;&gt;LTC4301L&lt;/a&gt;).&lt;/li&gt;&#xA;&lt;li&gt;Try communicating with a different 3.3V I&lt;sup&gt;2&lt;/sup&gt;C device to ensure it is working properly.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://cds.linear.com/docs/Datasheet/4301Lfa.pdf&quot; rel=&quot;nofollow&quot;&gt;LTC4301L datasheet&lt;/a&gt; recommends a 10nF cap on the supply pin.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If all checks out, chances are the sensor is damaged from overheating, static electricity or overvoltage conditions.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-15T22:09:30.347" />
  <row Id="9076" PostTypeId="2" ParentId="8733" CreationDate="2011-01-15T22:42:41.487" Score="1" ViewCount="" Body="&lt;p&gt;Are you talking about this circuit?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;     R1                       R2&#xA;     180                      1K&#xA;+---/\/\/\----------+   +----/\/\/-------------+------------+-----------&amp;gt; 230V&#xA;                   1|   |6                     |            |             Hot&#xA;                   +=====+ IC1                 | MT1        |&#xA;                   | MOC | TRIAC              +-+           |&#xA;                   | 3020| Driver           G | | TRIAC     |&#xA;                   +=====+                   /| | TIC226D   |&#xA;                   2|   |4                  / +-+           |&#xA;+-------------------+   |                   |  | MT2        |&#xA;                        +-------------------+  |            |&#xA;                                            |  |            |&#xA;                                            \  |            |&#xA;                                      R4    /  |            |  C1&#xA;                                      1K    \  |           --- 100 nF&#xA;                                            /  |           --- 400V&#xA;                                            |  |            |&#xA;                                            |   )           |&#xA;                                            |  (   L1       |&#xA;                                            |   ) 50..100   |&#xA;                                            |  (    uH      |&#xA;                                            |  |            |              Neutral&#xA;                                            +--+------------+----o    o--&amp;gt; 230V&#xA;                                                                  load&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The values are standard &lt;em&gt;&quot;band-aid&quot;&lt;/em&gt; values to improve ripple. They both store energy for the load to use during transitions. The author most likely picked these values from experience instead of calculations, just like one would choose decoupling values for digital IC Vcc pins &lt;em&gt;(&quot;Hmm, this one uses about 10mA max, so a single 100nF cap aught'a do'er!&quot;)&lt;/em&gt; . It's not like a &lt;a href=&quot;http://en.wikipedia.org/wiki/Switched-mode_power_supply&quot; rel=&quot;nofollow&quot;&gt;SMPS&lt;/a&gt;, where an inductor's precise value is critical to the device's range of operation. One can make rough estimates by comparing the maximum energy used by the load during &lt;em&gt;&quot;dead time&quot;&lt;/em&gt; (time between zero-crossing and SCR switch) and energy stored in the inductor: &lt;em&gt;E&lt;sub&gt;L&lt;/sub&gt; = &lt;sup&gt;1&lt;/sup&gt;/&lt;sub&gt;2&lt;/sub&gt;LI&lt;sup&gt;2&lt;/sup&gt;&lt;/em&gt; (use RMS current). For this application, though, the inductor will likely saturate and empty very quickly, so the stored energy really just smoothes the transitioning voltages.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-15T23:23:32.230" LastActivityDate="2011-01-15T23:23:32.230" />
  <row Id="9077" PostTypeId="1" AcceptedAnswerId="9079" CreationDate="2011-01-15T22:43:44.193" Score="2" ViewCount="115" Body="&lt;p&gt;How can I apply process corners (TT, SS, FF) to my simulation in HSPICE? &lt;/p&gt;&#xA;" OwnerUserId="2633" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-16T07:24:34.937" LastActivityDate="2011-01-16T07:24:34.937" Title="How to apply process corners in HSPICE?" Tags="&lt;simulation&gt;&lt;spice&gt;" AnswerCount="2" />
  <row Id="9079" PostTypeId="2" ParentId="9077" CreationDate="2011-01-15T22:56:08.657" Score="1" ViewCount="" Body="&lt;p&gt;Use the &lt;code&gt;.ALTER&lt;/code&gt; command, found in the &lt;a href=&quot;http://www.ece.rochester.edu/courses/ECE222/hspice/hspice_cmdref.pdf&quot; rel=&quot;nofollow&quot;&gt;HSPICE Command Reference&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-15T22:56:08.657" />
  <row Id="9080" PostTypeId="2" ParentId="7535" CreationDate="2011-01-15T23:17:48.307" Score="3" ViewCount="" Body="&lt;p&gt;Those all sound like excellent ideas.&#xA;A few comments:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Do not split the ground plane. Use one solid plane under both analog and digital sections of the board.&quot; -- Henry W. Ott (EMI consultant), in &lt;a href=&quot;http://www.hottconsultants.com/pdf_files/june2001pcd_mixedsignal.pdf&quot; rel=&quot;nofollow&quot;&gt;&quot;Partitioning and Layout of a Mixed Signal PCB&quot;&lt;/a&gt; &lt;em&gt;printed circuit design&lt;/em&gt; magazine (June 2001).&#xA;The Massmind has some more information on the &lt;a href=&quot;http://techref.massmind.org/techref/noises.htm#unsplit_ground&quot; rel=&quot;nofollow&quot;&gt;split vs unsplit ground plane controversy&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Slew rate control&quot;&#xA;Yes, as long as you do this by adding a &lt;a href=&quot;http://techref.massmind.org/techref/electips.htm#series_resistor&quot; rel=&quot;nofollow&quot;&gt;series resistor&lt;/a&gt; right at the source output pin.&#xA;(Too many misguided individuals add a &quot;smoothing capacitor&quot; near the destination input pin, which only makes things worse).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a few more mixed-signal &lt;a href=&quot;http://opencircuits.com/Techniques&quot; rel=&quot;nofollow&quot;&gt;PCB design techniques at the Open Circuits wiki&lt;/a&gt; and the &lt;a href=&quot;http://en.wikibooks.org/wiki/Practical_Electronics/PCB_Layout&quot; rel=&quot;nofollow&quot;&gt;Practical Electronics Wikibook&lt;/a&gt;.&#xA;They are wiki -- feel free to make further improvements.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-15T23:17:48.307" />
  <row Id="9081" PostTypeId="2" ParentId="7815" CreationDate="2011-01-15T23:33:13.530" Score="0" ViewCount="" Body="&lt;p&gt;Your schematic seems to indicate that nothing is connected to pin 9, which happens to be AN9.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you, at least temporarily, put a button with a pullup resistor -- identical to the one you already have on pin 5 -- so we know that the pin actually is being pulled high and low?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-15T23:33:13.530" />
  <row Id="9082" PostTypeId="2" ParentId="7815" CreationDate="2011-01-16T00:29:58.860" Score="1" ViewCount="" Body="&lt;p&gt;Add a connector for ICSP/debugging, and use a PICkit or ICD 3 for debugging your code. You can then concentrate on getting the ADC working, and then sort out the USB code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will find things much easier if you use the Microchip ADC code in their libraries.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-16T00:29:58.860" />
  <row Id="9083" PostTypeId="1" CreationDate="2011-01-16T00:36:35.573" Score="5" ViewCount="191" Body="&lt;p&gt;Do batteries last longer with constant current draw or spiky current draw?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, as is implied by the accepted answer to&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/4970/making-a-battery-last-a-long-time-in-a-microcontroller-circuit&quot;&gt;&quot;Making a battery last a long time in a microcontroller circuit&quot;&lt;/a&gt;,&#xA;do some battery chemistries last longer with a constant current draw,&#xA;while other battery chemistries last longer with a spiky current draw?&#xA;And if so, which battery chemistries are which?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In other words:&#xA;Say I have a microcontroller programmed to wake up and do a few things once a minute, and then go back to sleep for the rest of the minute.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which kind of batteries last longer with minimum capacitance across the capacitor (so the battery sees a big current spike once a minute)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which kind of batteries last longer with a big capacitor (or some kind of LC filter)  hooked up to battery (so the MCU pulls a big spike of current from the capacitor once a minute, and then the battery very slowly trickle-charges the capacitor)?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-16T15:37:09.020" Title="Do batteries last longer with constant current draw or spiky current draw?" Tags="&lt;battery&gt;&lt;current-measurement&gt;&lt;low-power&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="2" />
  <row Id="9084" PostTypeId="1" AcceptedAnswerId="9086" CreationDate="2011-01-16T00:43:32.123" Score="-5" ViewCount="240" Body="&lt;p&gt;How can I power a caller ID circuit through the phone line?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the maximum current that can be drawn from the phone line to power a caller ID circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A link to an electronic schematics that does the magic would be great.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I am not asking for legal advice. I am asking for a TECHNICAL information. Rest assured that &lt;strong&gt;if&lt;/strong&gt; anything is going to be done in this regard, it will be 100% compliant with the law. So, if you don't have a TECHNICAL answer, or all you can offer is &quot;please google&quot;, please don't answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2634" LastEditorUserId="2634" LastEditorDisplayName="" LastEditDate="2011-01-16T19:57:12.410" LastActivityDate="2011-01-17T18:36:30.800" Title="How can I power a caller ID circuit through the phone line?" Tags="&lt;power-supply&gt;&lt;telephone&gt;" AnswerCount="3" CommentCount="0" FavoriteCount="1" />
  <row Id="9085" PostTypeId="1" AcceptedAnswerId="9091" CreationDate="2011-01-16T01:08:04.490" Score="1" ViewCount="284" Body="&lt;p&gt;The problem I am having is with my PIC24FJ64GA002 and the UART module(s). The 24F I have is in a SPDIP28 package and it is a new B5 chip (just one under the latest B8 revision) from Microchip Direct. I have checked for errata issues which afflicted me last time with the I2C module.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, I am setting the UART1 module up as a simple transmitter. I am using PPS pin RP8 as the RX, RP9 as the TX and RP11 as the CTS pin. For now I have grounded RX and CTS as I do not need them. I have set the BRG at 115,200 (actual rate ~114,285.7, but it's close enough.) I am using the code below. I expect to see a series of bytes streaming out on RP9, but I do not. RB15 is a debug output: it pulses on each byte being sent. On RB15 I get a really slow clock, about 700 Hz, which is very low for a 115,200 baud link; I'd expect about 14 kHz.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;p24fj64ga002.h&amp;gt;&#xA;&#xA;#include &amp;lt;uart.h&amp;gt;&#xA;#include &amp;lt;pps.h&amp;gt;&#xA;&#xA;void init_osc()&#xA;{&#xA;    // Must be programmed for FRCPLL mode.&#xA;    //UNLOCK_OSC();&#xA;    CLKDIVbits.RCDIV = 0;&#xA;    //LOCK_OSC();&#xA;}&#xA;&#xA;void main()&#xA;{&#xA;    int i = 0x55;&#xA;    PPSUnLock;&#xA;    // Initialize oscillator (set FRC to 8 MHz.)&#xA;    init_osc();&#xA;    // Initialize UART1 PPS.&#xA;    iPPSInput(IN_FN_PPS_U1RX, IN_PIN_PPS_RP8);&#xA;    iPPSInput(IN_FN_PPS_U1CTS, IN_PIN_PPS_RP11);&#xA;    iPPSOutput(OUT_PIN_PPS_RP9, OUT_FN_PPS_U1TX);&#xA;    PPSLock;&#xA;    // Interrupts disabled for now.&#xA;    //ConfigIntUART1(UART_RX_INT_EN | UART_RX_INT_PR6 | UART_TX_INT_EN | UART_TX_INT_PR6);&#xA;    OpenUART1(UART_EN &amp;amp; UART_BRGH_SIXTEEN &amp;amp; UART_NO_PAR_8BIT &amp;amp; UART_1STOPBIT, UART_TX_ENABLE, 34);&#xA;    TRISBbits.TRISB15 = 0;&#xA;    while(1)&#xA;    {&#xA;        LATBbits.RB15 = 1;&#xA;        LATBbits.RB15 = 0;&#xA;        while(BusyUART1());&#xA;        WriteUART1(i);&#xA;        i++;&#xA;    }&#xA;    CloseUART1();&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I feel like I have missed something obvious, but cannot figure out what it is. If anyone has had previous experience with the UART module on 24F series devices, please let me know! I've had little luck with the Microchip forums.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-16T07:39:22.547" LastActivityDate="2011-01-16T07:39:22.547" Title="Problem with PIC24F UART" Tags="&lt;pic&gt;&lt;uart&gt;&lt;microchip&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="9086" PostTypeId="2" ParentId="9084" CreationDate="2011-01-16T01:08:17.860" Score="3" ViewCount="" Body="&lt;p&gt;It seems that one can derive an answer to the 2nd question from here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.electro-tech-online.com/electronic-projects-design-ideas-reviews/20863-charge-batteries-using-tel-lines.html&quot; rel=&quot;nofollow&quot;&gt;http://www.electro-tech-online.com/electronic-projects-design-ideas-reviews/20863-charge-batteries-using-tel-lines.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.electro-tech-online.com/electronic-projects-design-ideas-reviews/12101-phone-line-used-power-phone-charger.html&quot; rel=&quot;nofollow&quot;&gt;http://www.electro-tech-online.com/electronic-projects-design-ideas-reviews/12101-phone-line-used-power-phone-charger.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, it seems that powering anything while ON-hook is out of question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But... caller ID only shows up when the phone rings. This is a nice 70V-90V with enough power to drive several ringers. Why not use this to temporarily a small battery?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is another useful source for arriving to a fuller answer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Ringer_equivalence_number&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Ringer_equivalence_number&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting closer to a fuller answer: A chip made by Motorola, named TCA3385, is labeled a &quot;Telephone ring signal converter&quot;. Its data sheet can be found here: &lt;a href=&quot;http://www.digchip.com/datasheets/parts/datasheet/311/TCA3385-pdf.php&quot; rel=&quot;nofollow&quot;&gt;http://www.digchip.com/datasheets/parts/datasheet/311/TCA3385-pdf.php&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2634" LastEditorUserId="2634" LastEditorDisplayName="" LastEditDate="2011-01-17T18:36:30.800" LastActivityDate="2011-01-17T18:36:30.800" CommentCount="1" />
  <row Id="9087" PostTypeId="2" ParentId="7231" CreationDate="2011-01-16T01:25:17.260" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;em&gt;only&lt;/em&gt; 32-bit processor currently being manufactured in a DIP package is the &lt;a href=&quot;http://www.parallax.com/propeller&quot; rel=&quot;nofollow&quot;&gt;Parallax Propeller&lt;/a&gt;.&#xA;(The same chip is also available in much smaller 44-Pin QFP and 44-Pin QFN packages, all with 32 general-purpose I/O pins).&#xA;There's also a few &lt;a href=&quot;http://propeller.wikispaces.com/Linux+Development&quot; rel=&quot;nofollow&quot;&gt;development tools for it that run under Linux&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it easily meets your first 2 criteria and most (alas, not all) of your remaining criteria.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-16T01:25:17.260" />
  <row Id="9088" PostTypeId="2" ParentId="7231" CreationDate="2011-01-16T01:42:25.087" Score="0" ViewCount="" Body="&lt;p&gt;The Cypress PSoC series of chips have combination of features I haven't seen in any other IC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PSoC5 chip includes a 32-bit ARM Cortex M3, but as far as I can tell they are all packaged in something like a TQFP100.&#xA;The PSoC1 and PSoC3 series of chips includes many DIP packaged chips, but they all have one 8 bit core or another.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In addition to the CPU, the chip also have a programmable interconnect something like a small FPGA, and a few on-chip analog op-amps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.psocdeveloper.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.psocdeveloper.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-16T01:42:25.087" />
  <row Id="9089" PostTypeId="2" ParentId="9084" CreationDate="2011-01-16T02:32:49.067" Score="4" ViewCount="" Body="&lt;p&gt;You need to follow the national regulator's regulations (E.g. &lt;a href=&quot;http://www.fcc.gov/wcb/iatd/part_68.html&quot; rel=&quot;nofollow&quot;&gt;Part 68&lt;/a&gt; FCC in USA). I believe the device &lt;strong&gt;must&lt;/strong&gt; be certified by the national regulator (again for example, FCC in USA) for compliance before it can be legally connected to a phone line. I do not know of any exemptions for homemade devices, in fact these are most likely to run afoul of the laws, and could risk being charged with wiring tapping laws as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The device must present a resistance of at least 5 Megaohms, and a continuous current drain must not exceed 10 microamps for the USA (and I believe similar in Canada). Other countries phone networks may have different limits based on their designs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry, but it is not recommended (or &lt;a href=&quot;http://www.acronymfinder.com/AFAIK.html&quot; rel=&quot;nofollow&quot;&gt;AFAIK&lt;/a&gt; legal) for amateurs to do such. If you are developing your invention for commercial development, you would likely need to hire an external engineering firm or qualifying lab to evaluate your invention for compliance, so start the process by hiring a professional telecommunications engineering consultant.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-01-16T02:32:49.067" CommentCount="8" />
  <row Id="9090" PostTypeId="2" ParentId="9083" CreationDate="2011-01-16T02:59:52.863" Score="1" ViewCount="" Body="&lt;p&gt;You might want to go look through the archives of &lt;a href=&quot;http://www.consumerreports.org/&quot; rel=&quot;nofollow&quot;&gt;Consumer Reports&lt;/a&gt; (you'll need to be a member to see everything). They've done a lot of battery longevity testing over the years, and when the recent generation of batteries intended for non-smooth draw applications came along they had a bit of catching up to do in their testing. It might behoove you to read up on what they've done.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2011-01-16T02:59:52.863" />
  <row Id="9091" PostTypeId="2" ParentId="9085" CreationDate="2011-01-16T03:33:30.080" Score="2" ViewCount="" Body="&lt;p&gt;See page 110 of the data sheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you need to disable the analogue inputs on the pins you are using.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-16T04:00:54.200" LastActivityDate="2011-01-16T04:00:54.200" CommentCount="3" />
  <row Id="9092" PostTypeId="2" ParentId="8985" CreationDate="2011-01-16T04:02:20.237" Score="1" ViewCount="" Body="&lt;p&gt;rope climbing -- perhaps tweak the &lt;a href=&quot;http://en.wikipedia.org/wiki/Elevator:2010&quot; rel=&quot;nofollow&quot;&gt;Elevator:2010&lt;/a&gt; competition rules to make it a little easier.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-16T04:02:20.237" CommunityOwnedDate="2011-01-16T04:02:20.237" />
  <row Id="9093" PostTypeId="2" ParentId="9084" CreationDate="2011-01-16T04:07:24.063" Score="2" ViewCount="" Body="&lt;p&gt;Also, if the gadget connected to the phone line damages the telco's equipment, or one of their employees is injured, you will be prosecuted and would have to pay out lots of money in fines etc.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-16T04:07:24.063" CommentCount="2" />
  <row Id="9094" PostTypeId="2" ParentId="9077" CreationDate="2011-01-16T04:12:11.890" Score="1" ViewCount="" Body="&lt;p&gt;There are several ways to get corner simulations, but without seeing your models we can only guess as to how it is implemented. Also, keep in mind that not every model supports corner simulations! The best advice I can give you is to read the documentation that came with your models - if corner or Monte Carlo simulation is available they will tell you how to access it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are a few ways that I've seen process corners implemented (some of these I've seen using Spectre):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Separate model files for each corner&lt;/li&gt;&#xA;&lt;li&gt;The models have different sections for each corner case that must be selected&lt;/li&gt;&#xA;&lt;li&gt;You edit the sigma values for the models in one of the include files.&lt;/li&gt;&#xA;&lt;li&gt;FF/SS corners are not defined but models still have statistical data for Monte Carlo&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-01-16T04:12:11.890" />
  <row Id="9095" PostTypeId="2" ParentId="9083" CreationDate="2011-01-16T05:06:34.087" Score="0" ViewCount="" Body="&lt;p&gt;For alkaline, it matters how much the peak is.  Past a certain point the resistance goes up and you loose power there.  &lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-16T05:06:34.087" CommentCount="1" />
  <row Id="9096" PostTypeId="2" ParentId="6171" CreationDate="2011-01-16T06:04:37.133" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.pabr.org/pcbprt/pcbprt.en.html&quot; rel=&quot;nofollow&quot;&gt;&quot;pcbprt - Experiments in inkjet PCB printing&quot;&lt;/a&gt; by pascal. Some inkjet printers can print directly CD and DVD. They can print on copper-clad FR4 to make reasonably good etch resist. The main trick seems to be baking the freshly-printed boards to dry out the ink and get the dyes/pigments to stick to the copper -- otherwise the water-based ink immediately washes off as soon as you drop the board in the etch tank.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-16T06:04:37.133" />
  <row Id="9097" PostTypeId="1" CreationDate="2011-01-16T07:45:00.073" Score="1" ViewCount="239" Body="&lt;p&gt;I am triying to make a webserver of the ethernet shield to send SMS messages via the squidbee GSM shield&lt;br&gt;&#xA;Apparently i can't connect both the GSM shield and Ethernet Shield to the Arduino...&lt;br&gt;&#xA;Is this possible? Is there any sort of pin incompatilibity i have to reroute ?&lt;br&gt;&#xA;edit:&lt;br&gt;&#xA;GSM shield: &lt;a href=&quot;http://www.libelium.com/squidbee/index.php?title=New_GPRS_module_for_Arduino_%28Hilo_-_Sagem%29&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;&lt;br&gt;&#xA;ArduinoEthernetShield: &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoEthernetShield&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2245" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-02-20T21:31:18.687" LastActivityDate="2011-04-21T22:28:23.397" Title="Arduino +squidbee GSM shield + ethernet shield" Tags="&lt;arduino&gt;&lt;ethernet&gt;&lt;gsm&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="9098" PostTypeId="2" ParentId="9083" CreationDate="2011-01-16T15:37:09.020" Score="3" ViewCount="" Body="&lt;p&gt;This is a very good question and I don't have a good (complete) answer.  So I'll just give you a tidbit one of my old bosses used in a design.  There is a certain type of battery with very high internal resistance that he used for a long-life application.  Since it's high resistance, it has low leakage and its charge won't dissipate well on its own, but you can't source a lot of current from it.  Since it was a periodic application (similar to yours) he paired it with a supercapacitor.  The cap would charge up and when the uC was ready it would turn on, perform its actions.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But for the life of me I can't remember the words he used to describe it.  I've tried searching for low leakage, high internal resistance and other terms I thought it was but I can't seem to find exactly it.  It wasn't a coin cell, but more like a AA (but it certainly wasn't that form factor).  I perused the Wikipedia article in Lithium batteries and the closest I could find was the Lithium-Iodide battery.  There's plenty of info in that article as well:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Lithium_battery&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Lithium_battery&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many different chemistries and a comparison table.  Good read.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-16T15:37:09.020" />
  <row Id="9099" PostTypeId="1" AcceptedAnswerId="9107" CreationDate="2011-01-16T16:11:22.000" Score="2" ViewCount="132" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;I'm trying to calculate the internal resistance of my rechargeable batteries and haven't got a single battery holder so using I am having to using Banana plugs and Crocodile clips for holding my resistor. Then holding the banana clip on the negative end of my battery and reading the current. But could this be affecting my readings as I've tried different resistors and I'm still out in my calculation first time i got ~1000(with a 10k load) ohm now down to 10 ohm(with 68 ohm load). I have even smaller loads to test with now 1 ohm and 0.1 ohm. But this just popped in to my head as it might be problem. The leads I'm using are what we normally use for connecting our PCBs to the PSU, this is why I thought it could be ignored but maybe not when trying to calculate some thing very accurately.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-01-16T21:34:25.183" Title="Can Resistance of wires be ignored?" Tags="&lt;resistance&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="9100" PostTypeId="1" AcceptedAnswerId="9101" CreationDate="2011-01-16T16:28:06.887" Score="2" ViewCount="235" Body="&lt;p&gt;I have a project I am looking to power where the secondary load is more than my Arduino can provide amp-wise. I need to know the simplest way to power the whole system. I will be powering the Arduino and a 5v 1.2amp load. Diagrams I have seen show a common ground with two power supplies but I don't know the math for anything beyond a simple circuit. Links to other resources are welcome with all answers. I am looking to learn more about power and circuits in general so more info is better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I use one supply, how should I design the circuit? e.g. Series or Paralell. Also, how would I go about determining the requirements for that power supply?&lt;/p&gt;&#xA;" OwnerUserId="2617" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-25T18:14:21.167" LastActivityDate="2011-01-25T18:14:21.167" Title="Beyond board power, understanding multiple power supplies and loads in a circuit." Tags="&lt;arduino&gt;&lt;power-supply&gt;&lt;circuit-design&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="9101" PostTypeId="2" ParentId="9100" CreationDate="2011-01-16T19:02:46.237" Score="1" ViewCount="" Body="&lt;p&gt;Without knowing more specifics about your particular set-up, here are some ideas:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best and safest option would be to use one strong (1.5A or 2A) regulated power supply that powers both the microcontroller (arduino) and the heavier load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would also be possible to use two separate supplies, but then, you would have to make sure that the stuff connected to the microcontroller will not back-supply the I/O pins, possibly causing damage to the microcontroller (see: clamp diodes), i.e. you would have to make sure that both supplies provide almost exactly the same voltage (within +/- 0.3 V).&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-01-16T19:02:46.237" CommentCount="3" />
  <row Id="9102" PostTypeId="2" ParentId="6099" CreationDate="2011-01-16T19:14:01.200" Score="1" ViewCount="" Body="&lt;p&gt;3 led on/off by one swoft switch to 8051 in asm51 code.&lt;/p&gt;&#xA;" OwnerUserId="2641" LastActivityDate="2011-01-16T19:14:01.200" CommentCount="1" />
  <row Id="9103" PostTypeId="2" ParentId="9100" CreationDate="2011-01-16T19:45:36.233" Score="1" ViewCount="" Body="&lt;p&gt;You usually need a common ground but don't want to connect power rails, even if they are the same potential (don't tie two separate 5V rails together, for example).  There are some exceptions. You can communicate across isolated grounds using opto isolators and there are some regulators designed to be safely used in parallel, such as Linear Technology's LT3080.  Otherwise, there is not much math.  You just need to make sure you can provide enough current for each of you rails' load requirements.  The only other thing I would mention is that if you do use separate rails of the same potential, and communicate between them, make sure you can't violate any I/O specs of your devices.  If you are using two separate 5V rails, for example, each +/-10% , one rail could be 4.5V and the other 5.5V.  Outputting a 5.5V signal to an input pin with a 4.5V supply could potentially damage the IC.  This is why, when using the same potential across multiple devices that communicate with each other, it's usually preferred to use a single supply rail for all devices.  This isn't always easy to do when connecting kits, however, such as the Arduino to some external device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit, if you use one supply, tie all loads to it in parallel.  If you were to tie two loads in series to a 5V supply, for example, each load wouldn't be getting 5V.  If the two loads were exactly equal, they'd be seeing 2.5V each.  You design the supply for the rated load, taking into account heat considerations.  1.5A is a large load which will generate a lot of heat with a linear regulator.  You'd need to make sure that A) your regulator can provide at least your maximum load (with some room to spare) and B) can radiate the heat generated by the voltage drop.  This means you may require a heat sink.  Almost all regulator's data sheets will tell you how much heat is generated for a given amount of power.  The National Semi LM317, for example, says it's TO-3 package increases 39 degrees C for each Watt of dissipation.  If you are regulating 5V off a 9V rail at 1 Amp, the package would be dissipating (9V-5V) x 1A which equals 4W, or 146 degrees C over ambient temp!  Well beyond the maximum spec'd temp.  This is where heat sinks come into play, or the use of a switching regulator which are much more efficient, but probably too advanced for your first project.  The other thing to be concerned about for regulators is dropout voltage.  The supply rail needs to be some amount of voltage greater than your regulated voltage.  This is all assuming you have a AC to DC power supply to give you your main power rail.  But if this is the case, why not just buy a regulated AC to DC supply at the voltage or voltages you require with the current capability you require.  You can buy cheap wall warts with regulated output voltages in most common voltages and with various current capacities.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastEditorUserId="2377" LastEditorDisplayName="" LastEditDate="2011-01-17T02:54:56.303" LastActivityDate="2011-01-17T02:54:56.303" />
  <row Id="9104" PostTypeId="2" ParentId="9048" CreationDate="2011-01-16T20:50:10.770" Score="1" ViewCount="" Body="&lt;p&gt;Would microwave work? It would be safe on plastics while heating the water as it does with food in a microwave.&lt;/p&gt;&#xA;" OwnerUserId="1927" LastActivityDate="2011-01-16T20:50:10.770" CommentCount="1" />
  <row Id="9106" PostTypeId="1" AcceptedAnswerId="9142" CreationDate="2011-01-16T21:30:04.350" Score="3" ViewCount="158" Body="&lt;p&gt;Hi. I'm looking around for a decent GPS module for a project of mine. The &lt;a href=&quot;http://www.sparkfun.com/tutorials/127&quot; rel=&quot;nofollow&quot;&gt;Sparkfun GPS Buying Guide&lt;/a&gt; is nice, but focuses mostly on modules with patch antennae.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My project is a wrist- or upper-arm-mounted GPS logger. It will be displayless and log continually, and thus there can be no assumptions about the orientation of the device (as there probably could be if the user were to read a display). As far as I've understood, this means I should go for a helical antenna instead of a patch one for better omnidirectionality. Is this correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If so, does anyone have any recommendations for a decent (and decently priced) GPS module with a helical antenna? An antenna-less module with a third-party antenna is also possible, but I'd prefer a complete module. The last time I looked into this a few months ago, the most interesting device I found was the &lt;a href=&quot;http://www.falcom.de/products/gps-modules/fsa03/&quot; rel=&quot;nofollow&quot;&gt;Falcom FSA03&lt;/a&gt; based on the u-blox UBX-G5010. I also see there's a UBX-G6010 based FSA03-LP out now. Does anybody have any experience with these?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; I've also been hearing about PCB loop antennae. Any experiences with those? From what I've understood, these are often used in cellphones...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't have very specific requirements, but the size should be small. I'm not looking for the tiniest of the tiny, but it shouldn't be bulky either - this is vague, I know, but I'm looking for something suited to a small wrist-mounted device. Low power consumption is important. And of course, the more reasonably priced, the better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance for any recommendations!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Conclusion&lt;/strong&gt; (in case anybody comes across this at a later point): I went for a &lt;a href=&quot;http://www.u-blox.com/en/gps-modules/pvt-modules/lea-6-family.html&quot; rel=&quot;nofollow&quot;&gt;u-blox LEA-6H&lt;/a&gt; module ($50 on eBay) and a &lt;a href=&quot;http://sarantel.com/products/index.php&quot; rel=&quot;nofollow&quot;&gt;Sarantel SL1300&lt;/a&gt; antenna (€10 at &lt;a href=&quot;http://www.mirifica.it/&quot; rel=&quot;nofollow&quot;&gt;Mirifica&lt;/a&gt;). I haven't had the time to try things out yet, but it seems to be exactly what I need.&lt;/p&gt;&#xA;" OwnerUserId="2642" LastEditorUserId="2642" LastEditorDisplayName="" LastEditDate="2011-02-11T11:41:45.803" LastActivityDate="2011-02-11T11:41:45.803" Title="Suggestion for a GPS module with helical/omnidirectional antenna" Tags="&lt;antenna&gt;&lt;gps&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9107" PostTypeId="2" ParentId="9099" CreationDate="2011-01-16T21:34:25.183" Score="6" ViewCount="" Body="&lt;p&gt;No, it cannot be ignored.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Internal resistance of LiIon/NiMh batteries is comparable to one of the wires. Also, you should keep in mind, that significant part of resistance is in connections to the battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, for precise measurement you can go for 4-wire measurement, or accurately measure resistance of the wires+&lt;strong&gt;connections&lt;/strong&gt;, and subtract.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-16T21:34:25.183" CommentCount="1" />
  <row Id="9108" PostTypeId="1" AcceptedAnswerId="9145" CreationDate="2011-01-16T21:50:18.573" Score="4" ViewCount="271" Body="&lt;p&gt;I am considering whether to use parity or not with my UART. It is a board level high speed (upwards of 115,200 baud) signal. The traces are very short (less than 2 cm), MCU to DSP, but they could pick up noise. During a logic analysing session using my logic sniffer I noticed one byte was captured incorrectly, it was just a single error. I couldn't replicate it. Now I'm wondering whether I should include parity. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My application is somewhat safety critical in that a failure would lead to a graphical error on a HUD/OSD which could provide incorrect information to someone piloting a model aircraft. However, the HUD is updated at 30 frames per second, so any glitch would be temporary. One problem that could happen is it could send a command which put the OSD into an incorrect state where it did not display anything, leaving the pilot blind about 25 km away from home... which is not good. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will including parity protect me against common glitches or will it just make the protocol slower? Why is it that most UART protocols do not have parity? And is there a reason to select odd or even parity over each other?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-01T15:57:16.053" Title="For UART, should I use parity on a board level?" Tags="&lt;uart&gt;&lt;parity&gt;" AnswerCount="8" />
  <row Id="9109" PostTypeId="2" ParentId="9108" CreationDate="2011-01-16T22:03:00.820" Score="12" ViewCount="" Body="&lt;p&gt;In my experience, almost all the equipment and systems I've ever worked with skip parity, and just use message checksums or CRC's to detect errors.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-01-16T22:03:00.820" CommentCount="6" />
  <row Id="9110" PostTypeId="2" ParentId="8639" CreationDate="2011-01-16T22:50:22.820" Score="0" ViewCount="" Body="&lt;p&gt;Sorry I don't have a way to illustrate this, but here goes ..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assume your two ball-launching wheels are in a horizontal plane. Now imagine that the DC motor is under one of the wheels, with its shaft also horizontal, but in line with the two ball-launching wheels' centers, so if you put a small wheel on the motor's shaft, it will be upright. If this small wheel contacts one of the ball-launcher wheels, it will drive it, sort of like a bevel gear. From here, you should be able to see that if you put two such drive wheels on the motor shaft, such that each contacts one of the ball-launching wheels, just either side of the gap between the launch wheels, then the launch wheels will turn in opposite directions, i.e., in the gap, the rims of the launch wheels will go in the &lt;em&gt;same&lt;/em&gt; direction, thereby projecting the ball out of the gap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, ok, here's some questionable ascii art. You are looking at the business end of the machine, the ball comes at you from where the '*' is. The launcher wheels are seen horizontal, rim-on, on top, and the drive wheels are also seen rim-first, but are vertical and below.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;=====|===== * =====|=====&#xA;        -|-----|--[motor]&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that if you do it this way, you can vary the relative speeds of the launch wheels by varying the contact points with the drive wheels. If one drive wheel is 10cm from the axis of its launch wheel, and the other drive wheel is only 9cm from the other launch wheel axis, the ball will get some side-spin.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-01-16T22:50:22.820" />
  <row Id="9111" PostTypeId="2" ParentId="9108" CreationDate="2011-01-16T22:53:14.960" Score="8" ViewCount="" Body="&lt;p&gt;If you have the capability of interrupting a message, a parity error can be used to kill a bad transmission faster than a CRC check, especially for large packet sizes.  Otherwise, a CRC check will catch anything a parity check will, and more.  If you are really concerned, you can use additional software detection methods, such as context checking and message mirroring.  Timeouts can be used to prevent the OSD from falling into an incorrect state permanently.  &lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-01-16T22:53:14.960" CommentCount="1" />
  <row Id="9112" PostTypeId="1" CreationDate="2011-01-17T00:26:40.960" Score="3" ViewCount="120" Body="&lt;p&gt;Hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know a &lt;a href=&quot;http://en.wikipedia.org/wiki/Computer-on-module&quot; rel=&quot;nofollow&quot;&gt;COM&lt;/a&gt; which is put on a PCIe card, which has some flash memory, some RAM, JTAG support (or some kind of debugging support), some input ports like USB, perhaps support some output like via VGA or LVDS, just like this board: &lt;a href=&quot;http://www.knjn.com/FPGA-PCIe.html&quot; rel=&quot;nofollow&quot;&gt;http://www.knjn.com/FPGA-PCIe.html&lt;/a&gt; but not for FPGA development, but for microprocessors, preferably x86.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something similar &lt;a href=&quot;http://hardware.slashdot.org/hardware/08/10/02/2244229.shtml&quot; rel=&quot;nofollow&quot;&gt;has been done&lt;/a&gt; in the past, but the link is dead, and it should have enough documentation and be hacker-friendly (and cheap, not more than 100-150 USD).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will be writing the driver for the host system (linux), for inter-system communication, but the PCIe board itself should be pretty stand-alone (beside the operating system for the &quot;guest OS&quot; on the PCIe card which I will also have to write).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Addendum&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(upon more research)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sun used to have &lt;a href=&quot;http://en.wikipedia.org/wiki/SunPCi&quot; rel=&quot;nofollow&quot;&gt;SunPCI&lt;/a&gt;, but those cards are hard to get. Besides, I want something more modern.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="2645" LastEditorUserId="2645" LastEditorDisplayName="" LastEditDate="2011-01-17T21:19:16.110" LastActivityDate="2011-01-18T13:58:44.577" Title="Programmable system on chip (SOC) pluggable on a host via PCIe" Tags="&lt;psoc&gt;&lt;system-on-chip&gt;" AnswerCount="2" FavoriteCount="0" />
  <row Id="9113" PostTypeId="2" ParentId="9048" CreationDate="2011-01-17T00:40:20.443" Score="5" ViewCount="" Body="&lt;p&gt;An non-electronic solution to a similar problem in Canada, which is that mobile homes and cottages can have exposed water or waste (sewage) pipes that can freeze in winter. The majority of this piping is plastic now. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most common approach is to use a thermostat controlled &lt;a href=&quot;http://homerepair.about.com/od/plumbingrepair/ss/thaw_frzn_pipe_4.htm&quot; rel=&quot;nofollow&quot;&gt;electric heat &quot;tape&quot;&lt;/a&gt;, which has a waterproof coated &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Heating_element&quot; rel=&quot;nofollow&quot;&gt;heating element&lt;/a&gt; (high resistance wire, such as used in electric blankets) which is based on &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Joule_heating&quot; rel=&quot;nofollow&quot;&gt;Joule heating&lt;/a&gt; rather than induction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ad-hoc solutions could include using hair dyers or heat lamps. Even incandescent light bulbs could be used. &lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-01-17T00:40:20.443" CommentCount="1" />
  <row Id="9114" PostTypeId="1" CreationDate="2011-01-17T01:23:21.090" Score="1" ViewCount="65" Body="&lt;p&gt;I want to turn a Moroccan &lt;strong&gt;cast iron&lt;/strong&gt; lantern into a table lamp. Could I use a &lt;a href=&quot;http://en.wikipedia.org/wiki/Bakelite&quot; rel=&quot;nofollow&quot;&gt;Bakelite&lt;/a&gt; MES globe holder to wire in a light globe?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bakelight MES Globe Holder: &lt;img src=&quot;http://i.imgur.com/fWDI2.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2646" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-17T05:56:45.633" LastActivityDate="2011-02-16T10:31:47.303" Title="Can I use a Bakelite MES Globe Holder to convert a lantern into a table lamp?" Tags="&lt;electronics&gt;&lt;wiring&gt;" AnswerCount="2" />
  <row Id="9115" PostTypeId="2" ParentId="5341" CreationDate="2011-01-17T01:47:08.733" Score="1" ViewCount="" Body="&lt;p&gt;You can custom order multi-conductor cable to your own specifications from Multi/Cable Corp. - &lt;a href=&quot;http://www.multicable.com&quot; rel=&quot;nofollow&quot; title=&quot;Multi/Cable Corp.&quot;&gt;www.multicable.com&lt;/a&gt; is their website. They have low minimum orders &amp;amp; good customer service.&lt;/p&gt;&#xA;" OwnerUserId="2647" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-17T05:42:42.047" LastActivityDate="2011-01-17T05:42:42.047" />
  <row Id="9116" PostTypeId="2" ParentId="9114" CreationDate="2011-01-17T06:27:03.157" Score="1" ViewCount="" Body="&lt;p&gt;I would say &lt;em&gt;&quot;eyup!&quot;&lt;/em&gt; This, however requires dealings with high voltage, high power electronics, so the first thing to look for is safety precautions. I have a boilerplate:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Working with mains power should be performed according to your region's laws. It is dangerous and can seriously injure and kill you. Even the Earth wire may not be at 0V with respect to the objects around you due to its uncommon use as a return (or other more scary possibilities, like &quot;That ain't the Earth wire, Jed! I just ran out of black!&quot;). Please consult your local electrical codes before attempting to fiddle with it. Be careful using a cheap multimeter, as their maximum voltage ratings are sometimes inappropriately labeled CAT-II, III, and IV. I do not endorse messing with mains without &lt;a href=&quot;http://www.tableauellis.ca/tr.1d.2ch.1rt@-eng.jsp?&amp;amp;tid=51&quot; rel=&quot;nofollow&quot;&gt;training&lt;/a&gt;.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;'Round where I live in Alberta, Canada, the Earth wire is green, and should be wired directly to the cast iron lamp. The hot (&lt;em&gt;not&lt;/em&gt; green, gray, or white; often black or red) and neutral (gray or white) are connected to the two screws. &lt;a href=&quot;http://images.meredith.com/diy/images/2009/03/l_SCW_053_01.jpg&quot; rel=&quot;nofollow&quot;&gt;They should only be stripped/exposed enough to wrap around the screw once, and not over itself.&lt;/a&gt; Ensure the Earth wire is connected to the Earth prong on the socket plug with a multimeter continuity test. Try it out! If a breaker trips, pat yourself on the back for connecting the Earth wire, as it may have just saved your life -- there is a short to the lamp, and power should be shut off and all connections checked with a multimeter.&lt;br&gt;&lt;br&gt;&lt;sup&gt;&lt;sub&gt;&lt;em&gt;The Earth wire connection is not required for operation -- just safety.&lt;/em&gt;&lt;/sub&gt;&lt;/sup&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-17T07:20:16.990" LastActivityDate="2011-01-17T07:20:16.990" CommentCount="1" />
  <row Id="9117" PostTypeId="1" CreationDate="2011-01-17T07:39:37.900" Score="1" ViewCount="153" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/616/basic-electronics-book&quot;&gt;Basic Electronics Book&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am a newb, I try a lot to find good electronics books, I have 2 awesome books now, but I still cann't getting start with electronics and robots? There must be some awesome books should be list in my books list. Thank you for tell me which awesome book I missed in this list.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My awesome books list:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/The_Art_of_Electronics&quot; rel=&quot;nofollow&quot;&gt;The Art of Electronics:Paul Horowitz and Winfield Hill&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/1558608745&quot; rel=&quot;nofollow&quot;&gt;ARM System Developer's Guide: Designing and Optimizing System Software &lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2596" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-17T07:54:53.483" LastActivityDate="2011-01-17T08:45:21.820" ClosedDate="2011-01-17T12:50:05.190" Title="My electronics books" Tags="&lt;microcontroller&gt;&lt;electronics&gt;&lt;robotics&gt;&lt;books&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9118" PostTypeId="2" ParentId="9117" CreationDate="2011-01-17T08:45:21.820" Score="1" ViewCount="" Body="&lt;p&gt;You don't need books :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just get some Arduino kit or make it yourself and start playing around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will learn what is needed as you go.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-17T08:45:21.820" />
  <row Id="9119" PostTypeId="2" ParentId="9108" CreationDate="2011-01-17T08:49:22.017" Score="5" ViewCount="" Body="&lt;p&gt;I would work on shielding this wire first of all. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Put ground planes around it (and/or) burry it into inner layers between ground planes. Then rely on CRC. Use parity if it's free.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-17T08:49:22.017" CommentCount="4" />
  <row Id="9120" PostTypeId="1" AcceptedAnswerId="9126" CreationDate="2011-01-17T10:29:51.383" Score="0" ViewCount="107" Body="&lt;p&gt;I was originally considering using a 10u 6.3V 0603 ceramic capacitor for stabilising the onboard voltage regulator on my microcontrollers. However, it may not be capable because of temperature coefficients, tolerances and applied voltage (losing up to 60% of rating), therefore, I am considering moving to using tantalums. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The microcontroller LDOs output 2.25V - 2.75V for powering the internal core. I am using a PIC24FJ64GA004 and dsPIC33FJ128GP804. Would it be fine to use a 4V cap here? I have always used 2-3x rating for electrolytics, but maybe the same problems with aluminum electrolytics as for tantalums do not apply (with lifetime decreasing over applied voltage considerably.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally I'd like to reach a 50,000-100,000 hr MTTF. If tantalums aren't an option I'm considering using a 22u 6.3V 0805 ceramic in place (might have to resize the footprint), because even with a loss of 60% it stays within the minimum requirement of 4.7u. Any tips? Has anyone used tantalums before? What about ceramics for microcontroller LDOs? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-01-17T13:30:23.767" LastActivityDate="2011-01-17T15:15:28.933" Title="Voltage rating and tantalum capacitors" Tags="&lt;capacitor&gt;&lt;ldo&gt;&lt;ceramic&gt;&lt;tantalum&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="9121" PostTypeId="1" AcceptedAnswerId="9123" CreationDate="2011-01-17T10:34:01.547" Score="5" ViewCount="116" Body="&lt;p&gt;I want to make sure my product will work over a large temperature range of -40C to +75C. I can verify on the low end down to about -18C using a household freezer (which is probably good enough) but I'm not sure how to test it on the high end. Any tips?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-17T22:47:48.510" Title="Cheap way of temperature testing my boards" Tags="&lt;temperature&gt;" AnswerCount="5" CommentCount="0" FavoriteCount="1" />
  <row Id="9122" PostTypeId="1" AcceptedAnswerId="9124" CreationDate="2011-01-17T10:37:59.223" Score="2" ViewCount="88" Body="&lt;p&gt;Well, I have a 6-pin SOT23 and it is absolutely tiny. When I say tiny I mean it. Anyway, it is unclear which way it goes around as it has no indicator, so I don't know how I can install them on my boards. It has some writing on it but that is the only clue on how they are aligned. For those who need to know it is an LT1933 or LM2734Y (depending on the version.) I'm actually starting to wonder how feasible it will be to assemble these boards of mine with such tiny components, even using a reflow method.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-17T15:44:37.977" Title="How do you know which way round a 6-pin SOT23 goes?" Tags="&lt;surface-mount&gt;&lt;sot23&gt;" AnswerCount="2" />
  <row Id="9123" PostTypeId="2" ParentId="9121" CreationDate="2011-01-17T10:49:03.983" Score="4" ViewCount="" Body="&lt;p&gt;For the high end, you could use a hacked sous vide cooker with a PID controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2010/11/06/hacking-together-a-sous-vide-cooker/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2010/11/06/hacking-together-a-sous-vide-cooker/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-17T10:49:03.983" CommentCount="2" />
  <row Id="9124" PostTypeId="2" ParentId="9122" CreationDate="2011-01-17T10:53:22.213" Score="10" ViewCount="" Body="&lt;p&gt;There are two ways to identify pin 1 on a SOT23-6. One is a dot next to pin 1 on the top of the package. Most often it's not printed with the marking, but molded as a small pit in the plastic of the package, often no more than 2/10s of a millimeter in depth. A second method is a chamfer over the length of the package on the side of pin 1. From the drawing in the datasheet both the LT1933 and the LM2734Y should have the pit/dot.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;FAEs often have warned me &lt;em&gt;never&lt;/em&gt; to refer to the marking printed to determine which is pin 1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/fsCC1.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-17T15:44:37.977" LastActivityDate="2011-01-17T15:44:37.977" CommentCount="1" />
  <row Id="9125" PostTypeId="2" ParentId="9121" CreationDate="2011-01-17T11:43:27.933" Score="3" ViewCount="" Body="&lt;p&gt;Can you use an oven?  Mine can be set to a low around 75 degrees C.  I've done cheap temperature cycling tests before by quickly swapping a device between my oven and my refrigerator freezer.  I'd just use a TC to measure the actual temperature as the oven readout may not be very accurate.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-01-17T11:43:27.933" CommentCount="1" />
  <row Id="9126" PostTypeId="2" ParentId="9120" CreationDate="2011-01-17T11:44:45.030" Score="1" ViewCount="" Body="&lt;p&gt;It depends heavily on the temperature you expect in your application. Recommendations say that 80 % of the rated voltage should never be exceeded, and at 85 °C, you should not apply more than 50 % of the rated voltage. &lt;a href=&quot;http://www.avx.com/docs/masterpubs/tantniob.pdf&quot; rel=&quot;nofollow&quot;&gt;The catalog in this link, for example,&lt;/a&gt; has many derating diagrams for various types of tantalum capacitors.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-01-17T11:44:45.030" />
  <row Id="9127" PostTypeId="2" ParentId="9120" CreationDate="2011-01-17T12:01:24.560" Score="1" ViewCount="" Body="&lt;p&gt;10u 0603 will probably be Y5V dielectric which has poor tempco and voltage dependance. &#xA;X7R dielectric (will be a larger case) should be fine. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-17T12:01:24.560" CommentCount="2" />
  <row Id="9128" PostTypeId="2" ParentId="9122" CreationDate="2011-01-17T12:02:30.610" Score="2" ViewCount="" Body="&lt;p&gt;Sometimes they have a line along one edge. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-17T12:02:30.610" />
  <row Id="9129" PostTypeId="1" AcceptedAnswerId="9130" CreationDate="2011-01-17T12:02:58.893" Score="3" ViewCount="140" Body="&lt;p&gt;Howdy,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought a mixed bag of ceramic capacitors from Maplin and I'm struggling to identify most of them. I'm a bit of an electronics newb, but I understood that a capacitor usually has 3 numbers on and sometimes a letter at the end of the numbers.  The third number indicates the amount of zeros you add to the first two to get the value in pF.  Am I correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well with that in mind, I introduce you to:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/YWfrO.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/rRvEm.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first one is a bit blurry, but it seems to have 8P2 printed on it.  Next has n51 with Sy below it.  The 3rd and 5th ones have a horizontal line under the number, and what might be a number one, or a corresponding vertical line, can't decide which it is.  The 4th one seems a bit more clear now that I can see the writing more clearly in the picture - I assume this is 180pF?  Finally the last one has 82 on it, is this simply 82pF?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a way to test the capacitance at all?  I have countless smaller ones with either blurry text, or nothing written on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anthony&lt;/p&gt;&#xA;" OwnerUserId="2573" LastActivityDate="2011-01-17T15:53:08.747" Title="Identifying Capacitors" Tags="&lt;capacitor&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="9130" PostTypeId="2" ParentId="9129" CreationDate="2011-01-17T12:44:23.640" Score="6" ViewCount="" Body="&lt;p&gt;8p2 = 8.2 pF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;n51 = 0.51 nF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;220 pF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;180 pF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;560 pF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;82 pF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amqrp.org/kits/elsie/&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; gadget is useful for measuring low value capacitors (as well as inductors and frequency). I have a PCB design for it, if anyone is interested in building it.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-17T14:39:08.650" LastActivityDate="2011-01-17T14:39:08.650" CommentCount="3" />
  <row Id="9131" PostTypeId="2" ParentId="9129" CreationDate="2011-01-17T13:25:29.797" Score="5" ViewCount="" Body="&lt;p&gt;The three numbers form, let's say XYZ(J), means XY x {10^Z} pF, e.g. 560 = 56 pF, 561 = 560 pF, 562 = 5.6 nF etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheap digital multimeters don't usually measure capacitances in this range, but you can build capacitance meter easily, there's plenty of schematics on the internet, just google &quot;capacitance meter schematics&quot;.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-01-17T13:25:29.797" />
  <row Id="9132" PostTypeId="2" ParentId="9121" CreationDate="2011-01-17T13:26:29.777" Score="3" ViewCount="" Body="&lt;p&gt;I've resorted to cardboard boxes with air holes cut into them - allow the product to slowly warm the air inside to the desired temperature and control ventilation to keep it somewhat steady. If more heat is needed, put a power resistor inside the box and use a regulated DC supply to control how much heat it adds to the environment.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-01-17T13:26:29.777" CommentCount="2" />
  <row Id="9133" PostTypeId="2" ParentId="9121" CreationDate="2011-01-17T14:54:43.570" Score="1" ViewCount="" Body="&lt;p&gt;Heat gun / paint stripper with adjustable temperature control pointed into an enclosure around your PCB works for the high range, and Circuit Freeze will work on the low end (goes down to -62F).&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-01-17T14:54:43.570" />
  <row Id="9134" PostTypeId="2" ParentId="9120" CreationDate="2011-01-17T15:15:28.933" Score="1" ViewCount="" Body="&lt;p&gt;4v tantalum caps will be just fine, but personally I love ceramic ones so much. Also, each uF of ceramic cap is &quot;better&quot; than tantalum one due to lower ESR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So before going for tantalum, I would check price of ceramic caps with better dielectric which still gives you 4.7uF at 85C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should check your LDO spec on ESR limits. Some might oscillate with too-low ESR. And if it's stable with 1uF ceramic one at 85C - I would personally stay with ceramic. Just more reliability.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-17T15:15:28.933" />
  <row Id="9135" PostTypeId="2" ParentId="9129" CreationDate="2011-01-17T15:53:08.747" Score="2" ViewCount="" Body="&lt;p&gt;I found &lt;a href=&quot;http://www.elecraft.com/Apps/caps.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; page interesting, when I had similar problems.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-01-17T15:53:08.747" />
  <row Id="9136" PostTypeId="2" ParentId="9041" CreationDate="2011-01-17T16:04:10.087" Score="1" ViewCount="" Body="&lt;p&gt;30 odd GHz is quite a bit of bandwith.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There may be some useful info for you &lt;a href=&quot;http://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/Homebrew_RF_Circuit_Design_Ideas.htm&quot; rel=&quot;nofollow&quot;&gt;{here}&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2651" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-18T02:59:31.937" LastActivityDate="2011-01-18T02:59:31.937" CommentCount="0" />
  <row Id="9137" PostTypeId="1" AcceptedAnswerId="9139" CreationDate="2011-01-17T16:13:17.863" Score="13" ViewCount="438" Body="&lt;p&gt;In low-cost mass-produced items I often run into black blobs of what looks like resin applied directly on top of something on the PCB. What are these things exactly? I suspect this is some kind of custom IC that is layed out directly on the PCB to save on the plastic  housing/connector pins. Is this correct? If so, what is this technique called?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/eeENZ.jpg&quot; alt=&quot;The Blob&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a photograph of the inside of a cheap digital multimeter. The black blob is the only non-basic piece of circuitry present, along with an op-amp (top) and a single bipolar junction transistor.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-01-17T16:22:01.947" Title="What kind of components are black blobs on a PCB?" Tags="&lt;components&gt;&lt;ic&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="3" />
  <row Id="9139" PostTypeId="2" ParentId="9137" CreationDate="2011-01-17T16:22:01.947" Score="22" ViewCount="" Body="&lt;p&gt;It's called chip-on-board. The die is glued to the PCB and wires are bonded from it to pads. The Pulsonix PCB software I use has it as an optional extra.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main benefit is reduced cost.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-17T16:22:01.947" CommentCount="5" />
  <row Id="9140" PostTypeId="2" ParentId="7633" CreationDate="2011-01-17T16:41:24.333" Score="1" ViewCount="" Body="&lt;p&gt;The problem was about selecting the wrong pins. Case is closed.&lt;/p&gt;&#xA;" OwnerUserId="2213" LastActivityDate="2011-01-17T16:41:24.333" CommentCount="1" />
  <row Id="9141" PostTypeId="2" ParentId="8985" CreationDate="2011-01-17T17:49:51.333" Score="1" ViewCount="" Body="&lt;p&gt;For more complex competitions, you may be able to draw from various student hardware competitions.  An obvious choice would be the &lt;a href=&quot;http://www.usfirst.org/aboutus/content.aspx?id=880#fll_history&quot; rel=&quot;nofollow&quot;&gt;FIRST Lego League&lt;/a&gt; competitions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have complete rule sets available (including field drawings and competition formats) for 2006-2010, all of which were pretty interesting and challenging competitions, as I recall.  You may be able to use small portions of the actual competition based on time available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another source would be previous IEEE Student Hardware Competitions.  I've been doing IEEE SoutheastCon competitions for the past couple years, and there are a few that could be solved using only LEGOs.  Once again, field drawings and competition format is available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of particular interest would be the &lt;a href=&quot;http://www.southeastcon.com/2007/students/#StuHardComp&quot; rel=&quot;nofollow&quot;&gt;2007: Basketball&lt;/a&gt; and &lt;a href=&quot;http://ewh.ieee.org/reg/3/secon/08/competition.html&quot; rel=&quot;nofollow&quot;&gt;2008: Return to the Moon&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-01-17T17:49:51.333" CommunityOwnedDate="2011-01-17T17:49:51.333" />
  <row Id="9142" PostTypeId="2" ParentId="9106" CreationDate="2011-01-17T18:06:08.983" Score="4" ViewCount="" Body="&lt;p&gt;As far as commercial-off-the-shelf, SparkFun sells a helical antenna based receiver, also using the u-Blox chipset, the &lt;a href=&quot;http://www.sparkfun.com/products/9436&quot; rel=&quot;nofollow&quot;&gt;GS407 Helical GPS Receiver&lt;/a&gt;.  It's using a Sarantel SL1206 Antenna.  You may be able to find more antennas to your liking directly available from &lt;a href=&quot;http://www.sarantel.com/products/index.php&quot; rel=&quot;nofollow&quot;&gt;Sarantel&lt;/a&gt;.  Also, if you are eventually looking to embed this into a product, purchasing from SparkFun may prove to be more costly, so going directly from the manufacturer may save money.  One drawback to the SparkFun product is that it's limited to 4Hz update, according to the datasheet, and 2Hz according some of the comments on the product page.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are feeling more DIY, then you can check out &lt;a href=&quot;http://www.helenav.nl/antlinks.htm&quot; rel=&quot;nofollow&quot;&gt;this page of DIY GPS antennas&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are looking for more ideas, it might be worthwhile to purchase a few of the &quot;runners watches&quot; that are currently available on the market and see what they do.  I know that Garmin and the like manufacture these in pretty tightly-integrated packages, so they have approached the problem before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, as an additional data point, I believe that the iPhone uses a patch antenna (I wouldn't imagine that there is much room for much else in there), and it seems to successfully track me when mounted on my arm during runs, so patch may be a viable option with some clever design.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-01-17T18:06:08.983" CommentCount="1" />
  <row Id="9143" PostTypeId="2" ParentId="9108" CreationDate="2011-01-17T18:49:35.487" Score="4" ViewCount="" Body="&lt;p&gt;If you use parity think about how you will manage the error in you code.  If you do not have a graceful way of managing the error detecting it will not help much.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-01-17T18:49:35.487" />
  <row Id="9144" PostTypeId="2" ParentId="9108" CreationDate="2011-01-17T19:15:24.590" Score="4" ViewCount="" Body="&lt;p&gt;Parity is useless, in my opinion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With short chip-to-chip connections on a single board like this,&#xA;as long as you properly drive the lines, it should be practically noise-free -- at least compared to, say, your DRAM.&#xA;Some people expect one soft bit error, per day, per gigabyte of DRAM.&#xA;How do you know the error you saw wasn't caused by such a soft bit error, rather than noise on the communication wires?&#xA;If you have induced noise big enough to flip a bit on a properly-driven PCB trace, you probably have other bigger problems to worry about.&#xA;(By &quot;properly driven&quot;, I mean either actively drive each line all the time, or use a pull-up resistor or pull-down resistor to set the state between messages).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With longer-range off-board connections, it's often unavoidable to occasionally have floating wires that present an input pin with more-or-less continuous random noise,&#xA;and even when you are transmitting a message you often get bit errors.&#xA;In this case, parity is better than nothing.&#xA;As bt2 mentioned, you'll want to use CRC so you can catch many errors that parity completely misses, and once you have CRC, adding parity to it doesn't help significantly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's possible to put your system in a &quot;bad state&quot;, try to design things such that it returns to a good state in a reasonable amount of time.&#xA;Use communication timeouts and watchdog timers as markrages and bt2 mentioned.&#xA;Periodically re-transmit the initialization commands so that no matter what weird state the receiver is in, it gets reset to the correct state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Static in the satellite affected its computer which read the noise as a command to shut down. To overcome the problem, controllers sent a continuous stream of ON commands to the satellite to keep it turned on.&quot;&#xA;-- &lt;a href=&quot;http://www.spacetoday.org/Satellites/Hamsats/Hamsats1970s.html&quot; rel=&quot;nofollow&quot;&gt;Amateur Radio Satellites: OSCAR-6&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-17T19:15:24.590" />
  <row Id="9145" PostTypeId="2" ParentId="9108" CreationDate="2011-01-17T20:25:31.970" Score="5" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Odd vs Even Parity&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will depend slightly on what communication you are using. I know you said you are using UART, but I am going to answer a bit broader. If you do decide to go with parity, select the option that will cause your &quot;idle&quot; state to require the parity bit to switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have an active high system, then all 0's is idle. So make it odd parity so that the parity bit will have to change state from idle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In an active low system you should look at how many bits the parity will be over. If it is 8 bits, then even parity will result in a 0 parity bit, which follows the idea of forcing a change in state for the parity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Should you use Parity?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well this is a bit of a difficult questions. In general we like to model the noise as Gaussian noise which means that the bit errors will be completely random. In actuality noise that has an effect on our system is not always random. The reason for this is things that can cause errors on a PCB are radiators from something else. If you think about it, in order for a trace that short to have enough noise to cause bit error then it had to be something rather extreme. When you have a noise source like this, there is a decent chance that you will flip more then one bit. Parity is useless against an even number of bit errors. With out diving into the math, parity will help, but doesn't help tons. If you can't afford to do much processing then parity may be the best that you can do..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Why use a CRC?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First of all, you say you have a built in CRC generator, this means it should be very easy for you to compute. CRCs are much better at catching multiple bit errors. In an environment where you want a very low chance of getting any errors, you really want to use a CRC. In fact, go with the biggest CRC you can afford in your system. One little trick that I know works for atleast crc16 if not others is if you CRC the message you received with the CRC on it you should get 0 as your answer. If you have hardware to compute the CRC then this is a very efficient way of both generating CRC and checking CRC.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-17T20:25:31.970" CommentCount="1" />
  <row Id="9146" PostTypeId="1" CreationDate="2011-01-17T22:09:35.840" Score="2" ViewCount="249" Body="&lt;p&gt;A bit of background: I have a masters in engineering, mostly electronics. That was years ago however, and I've been working in finance since college. I've learned a great deal of programming as a part of my job, but when I was a kid, I always thought I'd one day learn how the insides of electronics worked. These days though, the easiest form of &quot;designing something cool to play with&quot; is done by programming, so I never really got into electronics design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do recall I made a radio back in Uni, and we designed a simple CPU using Cadence as well. Of course I'm not fresh on the details of how that works, though I believe I still have my semiconductor physics books somewhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What are some interesting projects I can start with building?&lt;/strong&gt; What kind of books/magazines/software/websites do you guys recommend? What kind of tools would I need?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My partners and I are going to be building a car later this year. I was wondering if that's the kind of thing people on this board get involved in? What about things that interface with a computer? Home equipment?&lt;/p&gt;&#xA;" OwnerUserId="2655" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-31T17:56:36.953" LastActivityDate="2011-01-31T19:44:03.397" Title="Entry level books/magazines/software/websites for a beginner" Tags="&lt;books&gt;&lt;website&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="9147" PostTypeId="1" AcceptedAnswerId="9151" CreationDate="2011-01-17T22:22:41.697" Score="5" ViewCount="164" Body="&lt;p&gt;After a simple flashy-LED kit's worth of practice, through-hole soldering is fairly straightforward. What I'm still having trouble with is wire-to-pad and wire-to-wire soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first problem is keeing stuff still. Blu-tac helps but gets melty, and I've never used a &quot;third hand&quot; that was worth a damn. Is it worth paying more for a better one? Any other tips?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My particular application is soldering &lt;a href=&quot;http://www.google.com.au/images?q=sil+sockets&amp;amp;oe=UTF-8&amp;amp;hl=en&amp;amp;client=safari&amp;amp;um=1&amp;amp;ie=UTF-8&amp;amp;source=univ&amp;amp;ei=pb80TZr8Co7NrQfcy-HvCA&amp;amp;sa=X&amp;amp;oi=image_result_group&amp;amp;ct=title&amp;amp;resnum=1&amp;amp;ved=0CCQQsAQwAA&quot; rel=&quot;nofollow&quot;&gt;0.1&quot; SIL sockets&lt;/a&gt; to flat flex cable (&lt;a href=&quot;http://electronics.stackexchange.com/questions/5620/mechanical-connectors-for-flexible-pcbs&quot;&gt;me again!&lt;/a&gt;). Would solder paste and the heat gun attachment on my butane iron work well?&lt;/p&gt;&#xA;" OwnerUserId="1633" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-01T02:38:27.060" LastActivityDate="2011-02-01T02:38:27.060" Title="Tips for wire-to-pad and wire-to-wire soldering?" Tags="&lt;soldering&gt;&lt;ffc&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="9149" PostTypeId="2" ParentId="9121" CreationDate="2011-01-17T22:47:48.510" Score="1" ViewCount="" Body="&lt;p&gt;When I was temperature testing an industrial design I used an old refrigerator; cut a hole in the door and used a heater to drive the temp up to 40C. It didn't smell particularly good but I imagine an insulated metal &quot;box in a box&quot; type design would work very well for your 75C test.  Take a look around to see how people make casting furnaces and do something similar.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-01-17T22:47:48.510" />
  <row Id="9150" PostTypeId="2" ParentId="9146" CreationDate="2011-01-17T22:55:32.497" Score="1" ViewCount="" Body="&lt;p&gt;Since you have experience programming. I would recommend an &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; variants are around of each of their boards. Its quick and easy to get projects running with them. Then you could advance on to other microprocessors if you don't feel they would do the job that you want. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-18T00:08:32.893" LastActivityDate="2011-01-18T00:08:32.893" CommentCount="1" />
  <row Id="9151" PostTypeId="2" ParentId="9147" CreationDate="2011-01-17T23:31:20.173" Score="7" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Wire to SIL socket:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Put the socket on a bench vice to hold it still.&lt;/li&gt;&#xA;&lt;li&gt;Heat up the pin with your soldering iron, then apply a bit of solder. Don't heat too much or you'll melt the plastic spacer between the sockets. Repeat for all pins.&lt;/li&gt;&#xA;&lt;li&gt;Strip wire ends. If using multithreaded wire, it might be a good idea to pre-solder the wire ends too.&lt;/li&gt;&#xA;&lt;li&gt;Now, holding the iron in one hand and the wire in the other, heat up the pin and touch the wire end on the iron. Once the solder melts, move the wire end into the molten solder, then move the soldering iron away. Hold the wire still until the solder solidifies. A stable posture will help.&lt;/li&gt;&#xA;&lt;li&gt;Inspect. If it looks like a cold joint (matte grey, brittle), add a bit of fresh solder and redo the joint applying afterheat a bit longer.&lt;/li&gt;&#xA;&lt;li&gt;Put a 2-3 cm. piece of &amp;lt;3mm heat shrink tube over the joint, pin and wire. Shrink it tight to make it more durable.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/xsZhQ.jpg&quot; alt=&quot;Wires soldered to pins&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Wire to pad:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Basically the same thing - apply enough pre-solder on the pad to immerse the wire end.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/XZoqt.jpg&quot; alt=&quot;Wires soldered to pad&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;General advice:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The thicker the wire / the larger the foil you're soldering, the longer pre-heating is required on that surface.&lt;/li&gt;&#xA;&lt;li&gt;If the metal you're trying to solder is in contact with eg. metal pliers or bench vice, the tool will conduct lots of heat away making your work difficult.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2545" LastEditorUserId="2545" LastEditorDisplayName="" LastEditDate="2011-01-17T23:52:56.160" LastActivityDate="2011-01-17T23:52:56.160" CommentCount="4" />
  <row Id="9152" PostTypeId="2" ParentId="9147" CreationDate="2011-01-17T23:37:35.767" Score="2" ViewCount="" Body="&lt;p&gt;You need to tin the wires and pins (I usually tin both, especially if using stranded wire) before bringing them together.  Put one in a third hand/vice/under a heavy object, making sure that the grip is far enough away to avoid melting the insulation.  Flux both ends, because the flux which was in the solder before tinning the wires has been activated and is no longer useful.  Then, hold the one wire in one hand and your soldering iron in another, and bring the two together. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Always include some heat shrink or other strain relief (I like hot glue) for any of these joints.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-17T23:37:35.767" CommentCount="2" />
  <row Id="9153" PostTypeId="1" CreationDate="2011-01-18T00:25:16.450" Score="3" ViewCount="266" Body="&lt;p&gt;I have the &lt;a href=&quot;http://www.sparkfun.com/products/9695&quot; rel=&quot;nofollow&quot;&gt;Sparkfun MPR121 I2C Capacitive touch sensor breakout board&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have read that it uses 3.3 V, I know that I can't just connect up the 3.3 V power supply output from the Arduino as the communications lines would require 3.3 V as well. How do I connect up the other lines?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have found a &lt;a href=&quot;http://www.sparkfun.com/tutorials/65&quot; rel=&quot;nofollow&quot;&gt;tutorial at Sparkfun's website&lt;/a&gt;. The 3rd diagram using the diode - would that be the best way to interface the sensor to the Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas or information would be great, my knowledge is pretty low.&lt;/p&gt;&#xA;" OwnerUserId="665" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:15:17.790" LastActivityDate="2011-03-05T16:15:17.790" Title="How do I get an Arduino (5 V) and MPR121 (3.3 V) to talk?" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;i2c&gt;&lt;level-shifting&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="9154" PostTypeId="2" ParentId="9041" CreationDate="2011-01-18T00:25:49.103" Score="2" ViewCount="" Body="&lt;p&gt;For 30ghz, there likely are no commonly used active filter topologies.  However you can use galium arsenide FETs in this region to build various circuits (PA, LNA, mixer, VCO, etc), never seen them used at 30ghz but have seen them used for 24 Ghz I would think you could extend their operation to 30Ghz if care was taken.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Passive filters will definitely be implemented with microstrip structures, lumped elements will not be useful at these frequencies.  You'll also need to find a very good substrate to work at 30Ghz.    &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Falloff is dependent on the topology you use and the number of poles in the filter much as it would be at lower frequencies.  For instance Chebyshev filters are common.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My only experience near such frequencies was a 24Ghz FMCW radar front end, that used GaAs FETS for the PA, VCO, mixer, a hairpin bandpass filter and was built on Roger 5870 substrate.  I didn't do the RF design this was an externally sourced design and we ended up using a 10.5Ghz variant of it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My initial thought is that your desired bandwidth is really wide, and that will greatly complicate the design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your best bet is to get a couple books on RF filter design, make sure your up on your calculus and start running some simulations using various topologies.  &lt;a href=&quot;http://www.ansoft.com/products/hf/ansoft_designer/&quot; rel=&quot;nofollow&quot;&gt;Ansoft Designer&lt;/a&gt; and &lt;a href=&quot;http://web.awrcorp.com/&quot; rel=&quot;nofollow&quot;&gt;Microwave Office&lt;/a&gt; are the two simulation packages that i've bumped into in the past for RF circuit simulation.  I believe they both have free trials.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-01-18T00:25:49.103" CommentCount="3" />
  <row Id="9155" PostTypeId="2" ParentId="9146" CreationDate="2011-01-18T00:30:56.350" Score="7" ViewCount="" Body="&lt;p&gt;That's a really, really, broad question.  I can't give you a right answer, I don't know what you remember and don't remember from your masters' degree, and I couldn't answer all of those questions in one post if I tried.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, since it's your first post, and since you can't learn the rules of the site without using it for a while, I'll try to help get you started.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For your car project, what you need to learn about right now is communication busses and automotive wiring.  A Bus Pirate or other development board for automotive communications (Would ideally have CAN, the venerable Bus Pirate does not, sadly) will help you interface various modules in the car, and allow you to develop custom modules for your car if you need that.  You'll need a DMM to check the voltage, current, and resistances between wires as you connect your wiring harness.  A solderless breadboard will also be a good tool to quickly and easily prototype low-speed digital circuitry.  However, you'll want a temperature-controlled soldering iron when it's time to actually build something.  An oscilloscope and/or logic analyzer are also great to have, but they're quite expensive.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as websites go, this one is great! :)   &lt;a href=&quot;http://www.edaboard.com/&quot; rel=&quot;nofollow&quot;&gt;edaboard.com&lt;/a&gt;, &lt;a href=&quot;http://www.ladyada.net&quot; rel=&quot;nofollow&quot;&gt;ladyada.net&lt;/a&gt;, and &lt;a href=&quot;http://www.adafruit.com&quot; rel=&quot;nofollow&quot;&gt;adafruit.com&lt;/a&gt; are other popular sites, but there are far too many to list.  You'll want to know a few distributor websites as well, like &lt;a href=&quot;http://www.digikey.com&quot; rel=&quot;nofollow&quot;&gt;Digikey&lt;/a&gt; or &lt;a href=&quot;http://www.sparkfun.com&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt; from which to order your components and tools. I like the Circuit Cellar magazine, and I have a lot of books but it's hard to nail down a specific one that covers electronics in general.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've never built a car, but I work at a company that builds electronics for cars, and I'm in a club converting a gasoline-engine car to a plug-in electric with my school.  A number of us are in the automotive industry, and a lot of us like to work on our cars; not sure if anyone's built one.  Most everything interfaces with a computer, and I've seen a lot of questions on household electronics and home automation.  I'm sure you'll get plenty of good answers for questions in all of those departments here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope that gets you started.  When you have a better idea of what you think you want to do, feel free to ask for clarification and advice here.  When you have a problem with something you're working on, &lt;em&gt;that's&lt;/em&gt; what we're really here for.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-18T00:30:56.350" CommentCount="5" />
  <row Id="9156" PostTypeId="2" ParentId="9153" CreationDate="2011-01-18T00:34:20.277" Score="2" ViewCount="" Body="&lt;p&gt;Depending on the current draw of the device in question the 3.3V output of the arduino should suffice. As for the communication lines, you'll need some type of level shifter. Looks like SparkFun has a solution for that too:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/8745&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/8745&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2654" LastEditorUserId="2654" LastEditorDisplayName="" LastEditDate="2011-01-18T04:28:50.093" LastActivityDate="2011-01-18T04:28:50.093" CommentCount="3" />
  <row Id="9157" PostTypeId="2" ParentId="9108" CreationDate="2011-01-18T00:53:51.717" Score="1" ViewCount="" Body="&lt;p&gt;Despite the plethora of answers I'll add my piece.  Parity will work on a byte level, and a CRC works (generally) on a packet level.  Packets schemes are in my opinion superior to raw byte-type communications.  If your hardware rejects a single byte based on parity, that's great for a raw bytestream, but not so good for a packet. All of a sudden, boom, you've missed a byte in the middle of a packet - that screws up your parsing.  In the best case, your whole packet is gone, but if your packet finding algorithm isn't good, you could potentially lose more (and I've seen some brain-dead packet detection algorithms used in real products).  Use packets and CRCs like was suggested.&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-18T00:57:25.553" LastActivityDate="2011-01-18T00:57:25.553" />
  <row Id="9158" PostTypeId="2" ParentId="8485" CreationDate="2011-01-18T02:43:25.673" Score="4" ViewCount="" Body="&lt;p&gt;There are many benefits to inline functions over preprocessor macros:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;strong&gt;Type checking&lt;/strong&gt;. The compiler will complain if the arguments are of incorrect type.&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;No risk of &lt;strong&gt;multiple evaluation&lt;/strong&gt;: macros can be dangerous when the argument is an expression, consider:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;stdio.h&amp;gt;&#xA;#define square(n) ((n)*(n))&#xA;&#xA;int main(void)&#xA;{&#xA;    int x, i = 0;&#xA;    while (i &amp;lt; 10) {&#xA;        x = square(i++);&#xA;        printf(&quot;%d\r\n&quot;, x);&#xA;    }&#xA;    return 0;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&lt;/li&gt;&#xA;&lt;li&gt;Can include &lt;strong&gt;multiple lines&lt;/strong&gt; of code without trailing backlashes.&lt;/li&gt;&#xA;&lt;li&gt;Inline functions have their &lt;strong&gt;own scope for variables&lt;/strong&gt; and they can &lt;strong&gt;return a value&lt;/strong&gt;.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Macros can be useful e.g. when concatenating tokens into code, so as to simplify some complex declarations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Consider macros as just a dumb text replacement functionality.&lt;/em&gt; A good rule of thumb is to &lt;strong&gt;avoid function-like macros, unless there is no other viable solution&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a common misconception that inlining always equals faster code. Keep in mind, that &lt;em&gt;every inlined call from more than one place adds up to code size&lt;/em&gt;. &lt;a href=&quot;http://en.wikipedia.org/wiki/Optimization_%28computer_science%29#When_to_optimize&quot; rel=&quot;nofollow&quot;&gt;Premature optimization&lt;/a&gt; is not a virtue, even when working with the constrained resources of a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GCC interprets the &lt;code&gt;inline&lt;/code&gt; keyword as a mere hint. There is no guarantee thet the function will actually be inlined. To have GCC inline your function regardless of optimization level, declare the function with the &lt;code&gt;always_inline&lt;/code&gt; attribute:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void function() __attribute__((always_inline));&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2545" LastEditorUserId="2545" LastEditorDisplayName="" LastEditDate="2011-01-18T02:59:46.770" LastActivityDate="2011-01-18T02:59:46.770" />
  <row Id="9159" PostTypeId="2" ParentId="9153" CreationDate="2011-01-18T03:25:06.217" Score="7" ViewCount="" Body="&lt;p&gt;You can do it using exactly two transistors, which is pretty slick.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wnhj7.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This comes straight from a &lt;a href=&quot;http://ics.nxp.com/support/documents/interface/pdf/an97055.pdf&quot; rel=&quot;nofollow&quot;&gt;Phillips application note&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-01-18T03:25:06.217" CommentCount="3" />
  <row Id="9160" PostTypeId="1" AcceptedAnswerId="9161" CreationDate="2011-01-18T04:28:34.387" Score="2" ViewCount="138" Body="&lt;p&gt;I'd like to formally understand this simple biasing circuit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ZpcOS.png&quot; alt=&quot;circuit diagram&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let V&lt;sup&gt;+&lt;/sup&gt; be the supply voltage, V&lt;sub&gt;i&lt;/sub&gt; be the input voltage at the seemingly unconnected terminal of the capacitor, and let V&lt;sub&gt;o&lt;/sub&gt; be the output voltage at the junction between the resistors and capacitor. Let S be the impedance unit (i*omega)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;using VI relations and Kirchoffs laws:&#xA;(V&lt;sup&gt;+&lt;/sup&gt; - V&lt;sub&gt;o&lt;/sub&gt;) / R&lt;sub&gt;1&lt;/sub&gt; - V&lt;sub&gt;o&lt;/sub&gt;/R&lt;sub&gt;2&lt;/sub&gt; + (V&lt;sub&gt;i&lt;/sub&gt;-V&lt;sub&gt;o&lt;/sub&gt;) * C*S = 0&lt;/p&gt;&#xA;&#xA;&lt;p&gt;which after rearranging gives:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;V&lt;sub&gt;o&lt;/sub&gt; = (V&lt;sup&gt;+&lt;/sup&gt;/R&lt;sub&gt;1&lt;/sub&gt; + V&lt;sub&gt;i&lt;/sub&gt;*C*S) / (1/R&lt;sub&gt;1&lt;/sub&gt; + 1/R&lt;sub&gt;2&lt;/sub&gt; + C*S)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;decomposing the numerator it becomes clear that the biasing term is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;= (V&lt;sup&gt;+&lt;/sup&gt;/R&lt;sub&gt;1&lt;/sub&gt;) / (1/R&lt;sub&gt;1&lt;/sub&gt; + 1/R&lt;sub&gt;2&lt;/sub&gt; + C*S) = V&lt;sup&gt;+&lt;/sup&gt; / (1+R&lt;sub&gt;1&lt;/sub&gt;/R&lt;sub&gt;2&lt;/sub&gt; + R&lt;sub&gt;1&lt;/sub&gt;*C*S)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does the amount of bias really depend on the driving frequency? At DC, S=0 and everything reduces to a voltage divider regardless of the voltage at V&lt;sub&gt;i&lt;/sub&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Sorry for the eye-sore math. Is it possible to do math input on this website like it is on math.stackexchange ?)&lt;/p&gt;&#xA;" OwnerUserId="2656" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-18T04:36:20.813" LastActivityDate="2011-01-18T19:37:39.887" Title="Simple Biasing Circuit" Tags="&lt;circuit&gt;&lt;bias&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="1" />
  <row Id="9161" PostTypeId="2" ParentId="9160" CreationDate="2011-01-18T05:32:00.797" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;quick explanation:&lt;/strong&gt; The biased voltage can be regarded as a superposition of the contribution from V&lt;sup&gt;+&lt;/sup&gt; (calculated above, called &lt;em&gt;biasing term&lt;/em&gt;) and the contribution from V&lt;sub&gt;i&lt;/sub&gt; (the other term, with V&lt;sub&gt;i&lt;/sub&gt;sC in the numerator):&lt;br&gt; V&lt;sub&gt;o&lt;/sub&gt; = V&lt;sub&gt;o,V&lt;sup&gt;+&lt;/sup&gt;&lt;/sub&gt; + V&lt;sub&gt;o,V&lt;sub&gt;i&lt;/sub&gt;&lt;/sub&gt; = V&lt;sup&gt;+&lt;/sup&gt;/(&lt;sup&gt;1&lt;/sup&gt;/&lt;sub&gt;R&lt;sub&gt;1&lt;/sub&gt;&lt;/sub&gt; + &lt;sup&gt;1&lt;/sup&gt;/&lt;sub&gt;R&lt;sub&gt;2&lt;/sub&gt;&lt;/sub&gt; + sC) + (V&lt;sub&gt;i&lt;/sub&gt;/sC)/(&lt;sup&gt;1&lt;/sup&gt;/&lt;sub&gt;R&lt;sub&gt;1&lt;/sub&gt;&lt;/sub&gt; + &lt;sup&gt;1&lt;/sup&gt;/&lt;sub&gt;R&lt;sub&gt;2&lt;/sub&gt;&lt;/sub&gt; + sC), where&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;V&lt;sub&gt;o,V&lt;sup&gt;+&lt;/sup&gt;&lt;/sub&gt; = V&lt;sup&gt;+&lt;/sup&gt;/(&lt;sup&gt;1&lt;/sup&gt;/&lt;sub&gt;R&lt;sub&gt;1&lt;/sub&gt;&lt;/sub&gt; + &lt;sup&gt;1&lt;/sup&gt;/&lt;sub&gt;R&lt;sub&gt;2&lt;/sub&gt;&lt;/sub&gt; + sC) and&lt;/li&gt;&#xA;&lt;li&gt;V&lt;sub&gt;o,V&lt;sub&gt;i&lt;/sub&gt;&lt;/sub&gt; = (V&lt;sub&gt;i&lt;/sub&gt;sC)/(&lt;sup&gt;1&lt;/sup&gt;/&lt;sub&gt;R&lt;sub&gt;1&lt;/sub&gt;&lt;/sub&gt; + &lt;sup&gt;1&lt;/sup&gt;/&lt;sub&gt;R&lt;sub&gt;2&lt;/sub&gt;&lt;/sub&gt; + sC)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;When one uses superposition, they redraw the circuit with all other voltage sources shorted and other current sources opened (other than the one being considered). This means that when considering the contribution from V&lt;sup&gt;+&lt;/sup&gt;, V&lt;sub&gt;i&lt;/sub&gt; is grounded, so the frequency[-ies] in the V&lt;sub&gt;o,V&lt;sup&gt;+&lt;/sup&gt;&lt;/sub&gt; term is that present in V&lt;sup&gt;+&lt;/sup&gt;, which should be near zero for a DC source. Using the same arguments, the frequency in the V&lt;sub&gt;o,V&lt;sub&gt;i&lt;/sub&gt;&lt;/sub&gt; term is that present in V&lt;sub&gt;i&lt;/sub&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Superposition makes sense for many reasons; one of the arguments I've made to justify it to myself is to look at Fourier analysis, which shows that any signal can be decomposed into the superposition of sinusoids, and those sinusoids can be extracted by filtering out the others; the &lt;a href=&quot;http://en.wikipedia.org/wiki/Gibbs_phenomenon&quot; rel=&quot;nofollow&quot;&gt;Gibbs phenomenon&lt;/a&gt; is often seen in practice as &lt;a href=&quot;http://en.wikipedia.org/wiki/Ringing_%28signal%29&quot; rel=&quot;nofollow&quot;&gt;ringing&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;simplified analysis:&lt;/strong&gt; The capacitor in this circuit is called a &lt;strong&gt;&lt;em&gt;DC blocking capacitor&lt;/em&gt;&lt;/strong&gt;, because it doesn't pass any DC signals. A common and useful technique to analyzing circuits that separate &lt;em&gt;high frequency&lt;/em&gt; AC and DC signals like this is to approximate the blocking capacitor as an &lt;strong&gt;open circuit to DC signals&lt;/strong&gt; and &lt;strong&gt;short circuit to AC signals&lt;/strong&gt;. This greatly simplifies analysis of more complicated systems. For &lt;em&gt;mid-band&lt;/em&gt; frequencies -- those for which the capacitor presents an impedance comparable, over 5%-10%, to that of R&lt;sub&gt;1&lt;/sub&gt;||R&lt;sub&gt;2&lt;/sub&gt; -- the complicated impedance formula needs to be used. For low frequency signals, where the capacitor impedance is more than ~100·R&lt;sub&gt;1&lt;/sub&gt;||R&lt;sub&gt;2&lt;/sub&gt;, the cap can be regarded as an open circuit. Of course, this depends on the sensitivities of your circuitry, but that will be apparent if these considerations are of value.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-18T19:37:39.887" LastActivityDate="2011-01-18T19:37:39.887" CommentCount="5" />
  <row Id="9162" PostTypeId="2" ParentId="9112" CreationDate="2011-01-18T07:01:31.990" Score="1" ViewCount="" Body="&lt;p&gt;I'm not really sure if this is what you're looking for, but thought it might be useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.advantech.com.tw/products/PCE-5120/mod_B16C5C03-4498-49DD-BEF8-1ECF1890B322.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.advantech.com.tw/products/PCE-5120/mod_B16C5C03-4498-49DD-BEF8-1ECF1890B322.aspx&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the site:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;LGA775 Core™ 2 Duo Processor Card with&#xA;  PCI Express/VGA/Dual GbE LAN &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Complies&#xA;  with PICMG 1.3 Supports LGA 775 Intel®&#xA;  Core™ 2 Duo with 1066/800/533 MHz FSB&#xA;  Supports dual-channel DDR2 533/667&#xA;  SDRAM up to 4 GB One PCIe x16 and four&#xA;  PCIe x1 links to backplane Dual&#xA;  Gigabit Ethernet via two PCIe x1 ports&#xA;  Onboard IPMI module (optional) Four&#xA;  SATA2 channels with software RAID 0,&#xA;  1, 5 and 10&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="554" LastActivityDate="2011-01-18T07:01:31.990" CommentCount="1" />
  <row Id="9163" PostTypeId="2" ParentId="7174" CreationDate="2011-01-18T08:35:33.197" Score="6" ViewCount="" Body="&lt;p&gt;The angular speed attained by the motor is limited by &lt;strong&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Counter-electromotive_force&quot; rel=&quot;nofollow&quot;&gt;counter-electromotive force&lt;/a&gt;&lt;/strong&gt;, aka. back EMF.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Current flowing through the wire causes a torque at all points where the wire is not parallel to the magnet's field lines (&lt;a href=&quot;http://en.wikipedia.org/wiki/Lorentz_force&quot; rel=&quot;nofollow&quot;&gt;Lorentz force&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the wire starts rotating, the motor will exhibit the property of a generator: a voltage (back EMF) opposing the current flow from the battery is induced, because the magnetic flux through the wire loop &lt;a href=&quot;http://en.wikipedia.org/wiki/Faraday%27s_law_of_induction#Example%3a_Moving_loop_in_uniform_Magnetic_field&quot; rel=&quot;nofollow&quot;&gt;changes due to movement&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The motor will accelerate until the back EMF is roughly equal to the battery's voltage, with only enough current flowing to provide torque to overcome the friction at this speed.&#xA;&lt;img src=&quot;http://i.imgur.com/KOmEi.png&quot; alt=&quot;Homopolar motor: field lines&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The more voltage is applied, the more rotation speed is required to reach this state of equilibrium.&lt;/p&gt;&#xA;" OwnerUserId="2545" LastActivityDate="2011-01-18T08:35:33.197" />
  <row Id="9164" PostTypeId="2" ParentId="7143" CreationDate="2011-01-18T08:53:00.513" Score="1" ViewCount="" Body="&lt;p&gt;I find the articles at &lt;a href=&quot;http://www.netrino.com/Embedded-Systems/How-To/&quot; rel=&quot;nofollow&quot;&gt;netrino.com&lt;/a&gt; very insightful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also see the Microchip &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/01146B.pdf&quot; rel=&quot;nofollow&quot;&gt;Compiled Tips 'N Tricks Guide&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2545" LastActivityDate="2011-01-18T08:53:00.513" />
  <row Id="9165" PostTypeId="1" AcceptedAnswerId="9166" CreationDate="2011-01-18T10:42:09.483" Score="4" ViewCount="346" Body="&lt;p&gt;Hello!&#xA;How do I implement drone-to-ground distance-measuring for autopilot landings for heights over 10m? I found ultrasonic to be too inacurate, let alone GPS. Maximum height is 1000m, Vmax is 100 km/h, Vaverage is 72 km/h. The drone is plane-like, no *copter or so. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you for any input!&lt;/p&gt;&#xA;" OwnerUserId="2659" LastEditorUserId="2659" LastEditorDisplayName="" LastEditDate="2011-01-19T14:35:31.650" LastActivityDate="2011-02-22T05:27:54.683" Title="How do I implement accurate distance measuring (to ground) on a plane-like UAV for heights over 10m?" Tags="&lt;sensor&gt;&lt;uav&gt;&lt;distance&gt;" AnswerCount="7" CommentCount="5" FavoriteCount="2" />
  <row Id="9166" PostTypeId="2" ParentId="9165" CreationDate="2011-01-18T11:25:54.873" Score="9" ViewCount="" Body="&lt;p&gt;You are probably looking for a radar altimeter, but I think that 1000m height will be a challenge if you want to build it yourself, because of power required to get detectable reflection at such distance. Couple hundred meters may be more realistic target for home made low power radar.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://lea.hamradio.si/~s53mv/radalt/radalt.html&quot; rel=&quot;nofollow&quot;&gt;Here is schematics&lt;/a&gt; of radar landing altimeter that is usefull to about 1000 feet.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-01-18T11:25:54.873" CommentCount="6" />
  <row Id="9167" PostTypeId="2" ParentId="9165" CreationDate="2011-01-18T11:26:44.703" Score="3" ViewCount="" Body="&lt;p&gt;A barometer would do quite well you get something like 10 cm resolution, the only tricky bit is that your drone will need to know the barometric pressure at ground level and that tends to change with the weather.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want really high performance location control, then you will probably not get around a vision based system with a high-power computer that can recognize the the landing strip and hit the right zone at the right speed.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-01-18T11:26:44.703" CommentCount="1" />
  <row Id="9168" PostTypeId="2" ParentId="3092" CreationDate="2011-01-18T12:40:15.030" Score="1" ViewCount="" Body="&lt;p&gt;Some projects and ideas with eLua are kept in the eLua User Labs wiki at &lt;a href=&quot;http://wiki.eluaproject.net&quot; rel=&quot;nofollow&quot;&gt;http://wiki.eluaproject.net&lt;/a&gt;&#xA;v0.8 is coming out of the oven sometime this month (Jan 2011).&lt;/p&gt;&#xA;" OwnerUserId="2661" LastActivityDate="2011-01-18T12:40:15.030" CommentCount="1" />
  <row Id="9169" PostTypeId="2" ParentId="9112" CreationDate="2011-01-18T13:58:44.577" Score="1" ViewCount="" Body="&lt;p&gt;Perhaps not what you're looking for, but I'd probably build a little board. Go with an Altera Cyclone IV GX FPGA (it's got a hardware PCIe core) and throw on some kind of CPU core, whether it be one of the NIOS ones (there's a free one) or something maybe from OpenEmbedded. The FPGA is about $60 and that includes the PCIe core and PHY. You could also toss in a SDRAM controller and a hardware USB interface (USB cores are expensive) and you'd be pretty close to what you're after, albeit with some design time.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-01-18T13:58:44.577" />
  <row Id="9170" PostTypeId="2" ParentId="9165" CreationDate="2011-01-18T15:07:32.360" Score="2" ViewCount="" Body="&lt;p&gt;If you are going to land on landing sites under your control, I would place several radio emitters around the site and compare signal power. That's the only reliable &amp;amp; easy to implement way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to land anywhere - only GPS (+-1m possible in USA), ultrasonic or laser measurements are valid options, but none of them are perfect.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-18T15:07:32.360" CommentCount="4" />
  <row Id="9171" PostTypeId="2" ParentId="9165" CreationDate="2011-01-18T15:08:27.553" Score="4" ViewCount="" Body="&lt;p&gt;On real aircraft, they will have both a Radar Altimeter and a Barometric Altimeter. The Barometric Altimeter is used at higher altitudes and the Radar Altimeter is used during takeoff and landing to gauge distance to the actual ground (i.e. at altitudes where terrain elevation changes are a significant concern - typically 5000 feet).&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-01-18T15:08:27.553" CommentCount="3" />
  <row Id="9172" PostTypeId="1" CreationDate="2011-01-18T15:21:51.913" Score="1" ViewCount="165" Body="&lt;p&gt;Hello All,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think I have used enough of the AVR series by atmel to say that I understand how to use it. I know somethings about how it actually works, but I would like to know more. Are there any good resources which describe the architecture of Atmega or RISC architecture in general? I know the datasheet has all this (and I really looooovvee the datasheet, its kinda my bible) but I need something little more simple than that. Any help?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-19T00:56:53.747" LastActivityDate="2011-01-19T00:56:53.747" Title="Resources to learn about the AVR/RISC architecture" Tags="&lt;avr&gt;&lt;atmega&gt;&lt;atmel&gt;&lt;architecture&gt;&lt;risc&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="9173" PostTypeId="2" ParentId="9172" CreationDate="2011-01-18T16:25:31.283" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.avrfreaks.net/&quot; rel=&quot;nofollow&quot;&gt;AVR Freaks&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-18T16:25:31.283" CommentCount="1" />
  <row Id="9174" PostTypeId="2" ParentId="9172" CreationDate="2011-01-18T16:54:10.570" Score="3" ViewCount="" Body="&lt;p&gt;Learn AVR assembly, it's the best practical way to learn about the architecture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.avr-asm-tutorial.net/avr_en/&quot; rel=&quot;nofollow&quot;&gt;http://www.avr-asm-tutorial.net/avr_en/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-18T16:54:10.570" />
  <row Id="9175" PostTypeId="2" ParentId="9165" CreationDate="2011-01-18T17:22:11.997" Score="2" ViewCount="" Body="&lt;p&gt;A &lt;a href=&quot;http://en.wikipedia.org/wiki/Laser_rangefinder&quot; rel=&quot;nofollow&quot;&gt;laser rangefinder&lt;/a&gt; will give you good precision and accuracy, and is designed for your expected distance,  but may be heavy (due to the optics) and will resolve the distance to a point rather than a larger area.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The measured result may change rapidly if you're going over terrain that has a lot of variation (such as a forest or city), and it may be hard to get a reading over reflective surfaces such as water which will not return much of the beam in the direction it came.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, this should be considered as an option.  Consumer handheld rangefinders for hunting or golf run from $50 to over $200; I'm not sure about commercial prices for integration into a system like a  UAV.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-18T17:22:11.997" CommentCount="1" />
  <row Id="9176" PostTypeId="2" ParentId="9172" CreationDate="2011-01-18T18:42:37.817" Score="2" ViewCount="" Body="&lt;p&gt;Check out the white papers in the &lt;em&gt;Other Docs&lt;/em&gt; section of Atmel's website: &lt;a href=&quot;http://www.atmel.com/dyn/products/other_docs.asp?family_id=607#White_Paper&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/products/other_docs.asp?family_id=607#White_Paper&lt;/a&gt; .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A long time ago I read the one called &lt;em&gt;The AVR Microcontroller and C Compiler Co-Design&lt;/em&gt; which explains why they think the AVR instruction set is well-suited for the C language. Some of the other documents there explain the AVR architecture or a series of chips in general.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2011-01-18T18:42:37.817" />
  <row Id="9177" PostTypeId="2" ParentId="9165" CreationDate="2011-01-18T19:22:12.760" Score="2" ViewCount="" Body="&lt;p&gt;I always wanted to try this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mount a downward-facing camera on the UAV.  The quality is mostly irrelevant.  Grab frames from it at some fixed interval.  Analyze pairs of images to determine how fast the ground appears to be moving.  There are a lot of options here for algorithms.  Now, given your GPS speed (not airspeed!) you how how fast you are actually going and how fast the ground appears to be moving.  At 0 altitude the (properly scaled) apparent movement would be 1:1.  As you gain altitude the apparent speed of the ground would slow down.&lt;/p&gt;&#xA;" OwnerUserId="2664" LastActivityDate="2011-01-18T19:22:12.760" CommentCount="4" />
  <row Id="9178" PostTypeId="1" CreationDate="2011-01-18T19:46:39.537" Score="2" ViewCount="102" Body="&lt;p&gt;I'm working on a project which requires using EM antennas or sensors array to identify and locate surrounding electrical devices such as cellphone, laptop, ipod, remote... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not a EMF guy. I don't know which frequency band I should be using. Is there any commercial sensors available? &lt;/p&gt;&#xA;" OwnerUserId="1353" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-19T02:53:46.207" LastActivityDate="2011-01-19T02:53:46.207" Title="Detecting surrounding electronics or electrical devices" Tags="&lt;sensor&gt;&lt;detection&gt;&lt;emi&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="9179" PostTypeId="1" CreationDate="2011-01-18T20:07:38.923" Score="0" ViewCount="103" Body="&lt;p&gt;Hello,&#xA;Has any of you any experience with Invensense products? I'm working with the IMU3000.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you all!&lt;/p&gt;&#xA;" OwnerUserId="2285" LastActivityDate="2011-01-18T20:07:38.923" ClosedDate="2011-01-18T22:54:52.770" Title="Any experience with Invensense IMU?" Tags="&lt;imu&gt;" CommentCount="7" />
  <row Id="9180" PostTypeId="2" ParentId="9165" CreationDate="2011-01-18T20:09:15.023" Score="4" ViewCount="" Body="&lt;p&gt;In reality, a single sensor will probably not be accurate enough to do what you want.  Most of what I know is related to AGVs (Ground Vehicles), but I think that some of the same principles apply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You probably want to use a combination of sensors to get the accuracy that you need.  Some of these can be quite expensive.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;GPS: A standard GPS module should be able to get you down to about 1m +/- accuracy.  If you step up to a differential setup (one station on the ground, one on the plane), then you should be able to get significantly more accuracy, but at a much higher cost.  Something like 10cm or even 1cm should be possible (with velocity data), but with a significantly higher cost.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;INS: You can supplement your GPS system with intertial measurements.  The boom in MEMS devices has made relatively decent solid-state sensors available at consumer prices.  Adding accelerometer, gyrometer, and magnetometer data to the GPS data should make the signal more accurate, and account for possible &quot;glitches&quot; in you GPS readings.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Radio-assisted navigation: I'm not entirely up on this, but many airports use a radio-assist to help land the planes.  You may be able to research how these systems actually work and implement your own (legally, of course).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For a more detailed look at some of these considerations, I would check out DIYDrones.  They have put together some pretty tightly-integrated systems using GPS, INS, Barometers, and a large array of other sensors.  They have also tackled some of the difficult filtering challenges that come with multiple sources of data in an airborne system.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-01-18T20:09:15.023" CommentCount="2" />
  <row Id="9181" PostTypeId="2" ParentId="76" CreationDate="2011-01-18T20:21:08.290" Score="0" ViewCount="" Body="&lt;p&gt;So-called &quot;12 V&quot; batteries hardly ever put out precisely 12.0 V.&#xA;Typically 12 V lead-acid &lt;a href=&quot;http://opencircuits.com/battery&quot; rel=&quot;nofollow&quot;&gt;batteries&lt;/a&gt; (used in practically all UPS, whether it's AGM or gell-cell) require something around 14 V to charge, and put out around 10 V open-circuit when nearly drained -- and even lower voltage when trying to power a heavy load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the rest of your system cannot tolerate such wide fluctuations, then some ways to work around the fact are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Add a big capacitor. This will temporarily supply a power surge -- is that all you need for your system to work? Alas, a capacitor it does nothing for longer-term voltage droop.&lt;/li&gt;&#xA;&lt;li&gt;switch to a different kind of battery with some other battery chemistry with less voltage droop. This may be expensive.&lt;/li&gt;&#xA;&lt;li&gt;Use bigger batteries, or more batteries in parallel, or both. This reduces the effective resistance (the voltage drop for a given surge current).&lt;/li&gt;&#xA;&lt;li&gt;Put some sort of voltage regulator between the batteries and the rest of your system. Perhaps a cheap linear voltage regulator will be adequate; this also gives you the option of using 2 batteries in series. Perhaps a switching voltage regulator will be better for your application; this also gives you the option of using a 6 V battery.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-18T20:21:08.290" />
  <row Id="9182" PostTypeId="2" ParentId="9178" CreationDate="2011-01-18T22:21:50.370" Score="1" ViewCount="" Body="&lt;p&gt;One cheap idea is to use an &lt;a href=&quot;http://ossmann.blogspot.com/2010/03/16-pocket-spectrum-analyzer.html&quot; rel=&quot;nofollow&quot;&gt;IM-me as a sub-1Ghz spectrum analyser&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.metageek.net/&quot; rel=&quot;nofollow&quot;&gt;Wi-Spy&lt;/a&gt; is a cheap 2.4GHz spectrum analyser, which can help characterise WiFi and ZigBee.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A fun site to look at is &lt;a href=&quot;http://1010.co.uk/org/scrying.html&quot; rel=&quot;nofollow&quot;&gt;http://1010.co.uk/org/scrying.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have a range of projects designed to pick up signals.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-18T23:14:58.790" LastActivityDate="2011-01-18T23:14:58.790" />
  <row Id="9183" PostTypeId="1" AcceptedAnswerId="9184" CreationDate="2011-01-18T22:57:54.630" Score="4" ViewCount="166" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;Why is it when you connect a battery to a heavy load does the voltage coming out of the supply drop?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-01-18T23:29:45.400" LastActivityDate="2011-01-18T23:31:38.910" Title="Why do battery/power supply supply voltages drop under a load?" Tags="&lt;battery&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="9184" PostTypeId="2" ParentId="9183" CreationDate="2011-01-18T23:31:38.910" Score="8" ViewCount="" Body="&lt;p&gt;Batteries have an internal resistance, this is generally measured in milli-ohms.  As more current is drawn from the battery there will be a progressively larger voltage drop due to this internal resistance.  V = I*R.  This is obviously a high level answer, the details can vary based on battery chemistry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A battery's voltage will also generally drop as the battery ages (runs out of juice).  The exact chemical process varies based on battery chemistry but simply put the battery is running out of charge.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-01-18T23:31:38.910" CommentCount="1" />
  <row Id="9185" PostTypeId="1" AcceptedAnswerId="9186" CreationDate="2011-01-19T00:08:57.943" Score="4" ViewCount="290" Body="&lt;p&gt;I'd like to build a power supply for my desk. I've found a few projects based on the &lt;a href=&quot;http://www.st.com/stonline/books/pdf/docs/1678.pdf&quot; rel=&quot;nofollow&quot;&gt;L200&lt;/a&gt; adjustable voltage regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the example below, how could I replace R3 with a microcontroller, so that varying the current limit can be automated?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2tM4W.png&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Likewise, how can R2/R1 be controlled?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a better device for a task like this?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-19T00:26:33.397" LastActivityDate="2011-01-26T23:58:54.350" Title="Voltage regulation and current limiting with a microcontroller" Tags="&lt;microcontroller&gt;&lt;psu&gt;" AnswerCount="5" FavoriteCount="3" />
  <row Id="9186" PostTypeId="2" ParentId="9185" CreationDate="2011-01-19T00:36:07.447" Score="4" ViewCount="" Body="&lt;p&gt;Use an MCU as a switching regulator, with a suitable MOSFET and inductor. Microchip has several application notes on such techniques.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-19T00:36:07.447" CommentCount="2" />
  <row Id="9187" PostTypeId="1" AcceptedAnswerId="9193" CreationDate="2011-01-19T00:52:41.317" Score="1" ViewCount="140" Body="&lt;p&gt;I recently bought a 0-35V 0-3A (105W) CC/CV linear power supply, made by Takasago in Japan, second hand. It's a nice unit, and inside of it is a massive power transformer along with three pass transistors on a very large heatsink (it is interesting why there are three transistors but I can only suspect that they are to reduce the load on an individual transistor), and it weighs a ton. I've fully tested it to 105W, although only for about 5 seconds as even my 2x25W resistors were getting too hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I originally had plans to put it on top of my HP 54501A, a digitising oscilloscope with a CRT raster monitor (unlike a normal CRT scope which draws a trace by moving the electron beam - this sets pixels on and off representing the trace.) However, I found that when turned on, whether above the scope or on the bench below, the CRT would have a weird ripple effect or would shift position randomly. It didn't matter if the supply was loaded down or not. The trace was not affected, just the display (even text and graphics). Why would the supply cause this? I suspect it has something to do with the transformer because that makes a humming sound in operation if you listen carefully.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-19T00:58:47.367" LastActivityDate="2011-01-19T15:04:54.337" Title="Why would a power supply mess with my scope?" Tags="&lt;power-supply&gt;&lt;oscilloscope&gt;&lt;transformer&gt;&lt;emi&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="9188" PostTypeId="2" ParentId="9185" CreationDate="2011-01-19T01:08:32.007" Score="1" ViewCount="" Body="&lt;p&gt;Pin 3 is a ground. Use this to your advantage; the outputs on a microcontroller can be set to either tristate or ground. Then, using an array of resistors, you can program the voltage by pulling down binary combinations. For best results use binary or close to binary values, for example, 10, 22, 39, 82, 150, 330, 680, 1.2k... It's limited in resolution to 2^n steps, where n is the number of resistors. Not sure how to control current limit but you could try a similar approach with an op-amp as a current limiter and a similar voltage divider as a reference and just set the regulator current at a high limit so a short doesn't damage it.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-19T01:08:32.007" />
  <row Id="9189" PostTypeId="2" ParentId="8985" CreationDate="2011-01-19T03:38:33.503" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Obstacle Course&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Robots are built to go down a &quot;hallway&quot; over obstacles.  The one that goes the farthest wins, or, in the event of a tie, the one that traverses the distance faster wins.  When we did it, using wheeled/tracked Lego robots, obstacles included things like:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;pencils&lt;/li&gt;&#xA;&lt;li&gt;candles&lt;/li&gt;&#xA;&lt;li&gt;books&lt;/li&gt;&#xA;&lt;li&gt;bins&lt;/li&gt;&#xA;&lt;li&gt;ramps&lt;/li&gt;&#xA;&lt;li&gt;chocolate bars&lt;/li&gt;&#xA;&lt;li&gt;pop bottles&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;While I don't have any photos handy, I've run the event twice now at it was a big hit!&lt;/p&gt;&#xA;" OwnerUserId="106" LastActivityDate="2011-01-19T03:38:33.503" CommunityOwnedDate="2011-01-19T03:38:33.503" />
  <row Id="9190" PostTypeId="1" AcceptedAnswerId="9423" CreationDate="2011-01-19T05:10:03.423" Score="1" ViewCount="119" Body="&lt;p&gt;I'd like to drive a pair of mechanical shutter / apertures with an electromagnet. For those curious, we're using a &lt;a href=&quot;http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1461&quot; rel=&quot;nofollow&quot;&gt;shutter from Edmond optical&lt;/a&gt;. For the particular application, I'd like to design a compact actuator to drive it. (I had considered just hacking a camera lens with a shutter, but couldn't find one that was large enough for my needs).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So at present I am thinking about attaching a neodymium magnet to the lever of the shutter and then using a series of electromagnets to push it between open and closed. Which all leads to my first question: how can build compact electromagnet?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems like the steps involved are to find a solenoid and then to drive it with a decent voltage difference. I wonder if anyone could recommend a good small solenoid for such purposes. Does it make more sense to roll my own with an iron core and insulated wire?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My second question is more open-ended: can you think of a better way to drive such a shutter? How would you design the shutter motor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE: in response to comments:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;@tyblu the shutter needs to be open or closed in about 500 microseconds (but exactness is not important). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;@bt2 a solenoid is interesting, are you thinking of hitting the lever and letting momentum carry it across to the close position?&lt;/p&gt;&#xA;" OwnerUserId="2668" LastEditorUserId="2668" LastEditorDisplayName="" LastEditDate="2011-01-19T06:30:01.373" LastActivityDate="2011-01-26T04:09:03.453" Title="Controlling a mechanical shutter with an electromagnet" Tags="&lt;electromagnetism&gt;&lt;actuator&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="9191" PostTypeId="1" CreationDate="2011-01-19T05:43:10.953" Score="3" ViewCount="139" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do all bluetooth chips have the same hardware, or does the hardware that is part of the chip defined by the bluetooth profile that we choose to use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="2669" LastActivityDate="2011-01-19T14:44:51.380" Title="Bluetooth profiles - What is the hardware difference?" Tags="&lt;bluetooth&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="9192" PostTypeId="2" ParentId="9185" CreationDate="2011-01-19T06:13:20.427" Score="4" ViewCount="" Body="&lt;p&gt;To replace R2 you can use a digital potentiometer or &quot;digipot&quot;. It acts like a resistor where the resistance can be controlled over a digital bus such as SPI. It might also work for R3 but I'm not sure how much current it has to carry; if it's small a digipot would work there as well of course.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A switching approach might be smarter though, since it would be cheaper and more efficient although more complicated to design.&lt;/p&gt;&#xA;" OwnerUserId="2671" LastActivityDate="2011-01-19T06:13:20.427" CommentCount="1" />
  <row Id="9193" PostTypeId="2" ParentId="9187" CreationDate="2011-01-19T06:16:39.957" Score="7" ViewCount="" Body="&lt;p&gt;The power transformer in the power supply is producing stray flux lines, which are causing the scope electron beam to deflect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The magnetic flux in a transformer is never entirely constrained to the transformer core, and as transformers get bigger, it becomes progressively more involved to minimize the stray flux as much as possible. Also, the standard EI core used in power transformers is not the best type when it comes to low stray flux (that would probably be a pot-core).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, the transformer is acting like an electromagnet, modulated at the frequency of the mains.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The effect is akin to waving a magnet around your TV, since the monitor in your DSO is effectively a little TV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even scopes which use electrostatic deflection to steer the electron beam are magnetic fields. since it's a beam of electrons in either case, and electrons are charged particles, rendering them influenced by magnetic fields.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have the same problem with a bit 100 V 10A power supply I have a work. Whenever I turn it on, it drives my (analog) scope nuts.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-01-19T06:22:48.000" LastActivityDate="2011-01-19T06:22:48.000" />
  <row Id="9194" PostTypeId="1" AcceptedAnswerId="9196" CreationDate="2011-01-19T06:24:05.620" Score="1" ViewCount="215" Body="&lt;p&gt;I need to solder some breakout boards onto an Arduino shield.  What's the general procedure to do this?  Do I solder it onto a header?  Do I need any other mechanical connection or hold-down?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, I would like solder this gyro sensor onto this aeroquad shield:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;gyro sensor: &lt;a href=&quot;http://www.aeroquadstore.com/ProductDetails.asp?ProductCode=SEN-09801&quot; rel=&quot;nofollow&quot;&gt;http://www.aeroquadstore.com/ProductDetails.asp?ProductCode=SEN-09801&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;aeroquad shield: &lt;a href=&quot;http://www.aeroquadstore.com/ProductDetails.asp?ProductCode=AQ2-000&quot; rel=&quot;nofollow&quot;&gt;http://www.aeroquadstore.com/ProductDetails.asp?ProductCode=AQ2-000&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1756" LastEditorUserId="1756" LastEditorDisplayName="" LastEditDate="2011-01-19T07:05:04.133" LastActivityDate="2011-01-19T07:05:04.133" Title="How do I solder a Sparkfun breakout board to a shield?" Tags="&lt;arduino&gt;&lt;soldering&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="9195" PostTypeId="1" AcceptedAnswerId="9210" CreationDate="2011-01-19T06:40:20.647" Score="7" ViewCount="227" Body="&lt;p&gt;Are there any places on the globe where magnetometers won't work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, if you took a &lt;a href=&quot;http://www.sparkfun.com/products/9441&quot; rel=&quot;nofollow&quot;&gt;Honeywell HMC5843&lt;/a&gt; to the North or South magnetic pole, would they fail to function properly?&lt;/p&gt;&#xA;" OwnerUserId="1756" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-21T05:35:22.720" LastActivityDate="2011-01-22T10:30:48.680" Title="magnetometers: do they work all over the globe?" Tags="&lt;sensor&gt;&lt;magnetometer&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="9196" PostTypeId="2" ParentId="9194" CreationDate="2011-01-19T06:43:06.860" Score="2" ViewCount="" Body="&lt;p&gt;As far as your question about soldering the gyro sensor to the aeroquad shield goes, if you look a the tiny picture on their website, in the center of the board there is a region marked &quot;gyro&quot;.  You'll take the single inline pin strips (also pictured) and break off 7 pins as a group.  Then you'll solder the short end into the gyro board.  Then (unfortunately) it looks like you'll have to solder the gyro board into aeroquad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as shields go, in my experience (Arduino Duemilanove) the spirit behind the shield concept is to allow them to stack up.  The aeroquad &quot;shield&quot; doesn't appear to allow this, so I imagine you'll want to get single inline headers and solder them into the aeroquad so you can plug in the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if you want to add more breakout boards, the general procedure would be to get the headers with the extra long pins, and put those through your protoboards so that other shields can stack on top of them.  This allows everyone access to the pins in the Arduino that they need.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-01-19T06:43:06.860" CommentCount="3" />
  <row Id="9197" PostTypeId="2" ParentId="9097" CreationDate="2011-01-19T06:58:40.513" Score="0" ViewCount="" Body="&lt;p&gt;You can take a look on the Tutorials section of Cooking-Hacks in order to know the pins used by GPRS Module. &lt;a href=&quot;http://www.cooking-hacks.com/index.php/documentation/tutorials/arduino-gprs-quadband&quot; rel=&quot;nofollow&quot;&gt;Tutorial GPRS&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2673" LastActivityDate="2011-01-19T06:58:40.513" />
  <row Id="9198" PostTypeId="2" ParentId="9097" CreationDate="2011-01-19T07:08:41.550" Score="0" ViewCount="" Body="&lt;p&gt;And there is an example of how to send the incoming data through GPRS in this tutorial.&lt;a href=&quot;http://www.sensor-networks.org/index.php?page=0823923911&quot; rel=&quot;nofollow&quot;&gt;Tutorial sending SMS with SquidBee&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2673" LastActivityDate="2011-01-19T07:08:41.550" />
  <row Id="9199" PostTypeId="1" CreationDate="2011-01-19T08:13:52.490" Score="2" ViewCount="85" Body="&lt;p&gt;As you know, the MAX1555 is a popular single cell lithium polymer charger. It can take USB power directly, restricting the charge current to 100mA or so. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any other MAX1555 alternatives that are your favourites? I'm just browsing around for alternatives at the moment, seeing if they offer some other features.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-01-19T12:23:20.280" Title="MAX1555 Alternatives" Tags="&lt;lithium&gt;&lt;charge&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="2" />
  <row Id="9200" PostTypeId="2" ParentId="9097" CreationDate="2011-01-19T09:07:52.863" Score="1" ViewCount="" Body="&lt;p&gt;You should be able to use both of them, the GSM modlule uses some sort or serial connected to the Tx and Rx pins per the tutorials, I have seen. the ether net shield uses SPI for its comms on pins 11,12,13. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-01-19T09:07:52.863" />
  <row Id="9201" PostTypeId="2" ParentId="9097" CreationDate="2011-01-19T09:20:11.360" Score="0" ViewCount="" Body="&lt;p&gt;However, if you have some doubts when you try to do that, you can post in the forum too.&lt;a href=&quot;http://www.cooking-hacks.com/index.php/forum-1.html&quot; rel=&quot;nofollow&quot;&gt;Forum&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this information helps you with your project.&lt;/p&gt;&#xA;" OwnerUserId="2673" LastActivityDate="2011-01-19T09:20:11.360" CommentCount="1" />
  <row Id="9202" PostTypeId="1" CreationDate="2011-01-19T10:16:28.720" Score="1" ViewCount="78" Body="&lt;p&gt;I'm looking for similar buttons to &lt;a href=&quot;http://au.element14.com/schurter/12411104791/switch-spno-round-yellow/dp/150243&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; . A button where I can solder directly on the pcb. I plan to CNC mill out an acrylic bracket on top of this pcb, and was hoping i could just mill out a round hole, and have these buttons stick out for the user to press. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This button is a bit expensive, and it's got those plastic tabs, which I can't fit in my design (looking to get my whole setup as thin as I can, and those plastic tabs sticking out underneath the pcb isn't going to help :P)&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-01-19T10:59:39.180" Title="Looking for buttons" Tags="&lt;button&gt;" AnswerCount="1" />
  <row Id="9203" PostTypeId="2" ParentId="9191" CreationDate="2011-01-19T10:41:16.253" Score="6" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Profiles&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bluetooth profiles provide different types of services, such as Hands-Free Profile (HFP), Headset Profile (HSP), and Serial Port Profile (SPP) on top of a core set of Bluetooth capabilities.  In general, they are not tied to a particular hardware implementation since they are implemented in firmware.  Sometimes a particular profile will have hardware associated with it, for example the Advanced Audio Distribution Profile (A2DP) will usually have a stereo codec but most profiles do not require extra hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Profiles are defined and adopted by the &lt;a href=&quot;http://www.bluetooth.com/ENGLISH/SIG/Pages/default.aspx&quot; rel=&quot;nofollow&quot;&gt;Bluetooth SIG&lt;/a&gt;.  This &lt;a href=&quot;http://en.wikipedia.org/wiki/Bluetooth_profile&quot; rel=&quot;nofollow&quot;&gt;article in Wikipedia&lt;/a&gt; defines 28 different profiles.  Most modules implement many but not all of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Classes&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, hardware differences in Bluetooth devices are more associated with the class of the device:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Class 1:  100 mw or 20 dBm, range approx. 100m&lt;/li&gt;&#xA;&lt;li&gt;Class 2:  2.5 mw or 4 dBm, range approx. 10m&lt;/li&gt;&#xA;&lt;li&gt;Class 3:  1 mw or 0 dBm range approx. 1m&#xA;(seldom used)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Some manufacturers have modules that fall between Class 1 and 2, i.e. they have a longer range than Class 2 but don't have the power amplifier (PA) needed by Class 1.  These are informally sometimes called Class 1.5 but that is not a standard term nor defined by the Bluetooth SIG.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As mentioned in a comment below by Kortuk, some manufacturers pay for a higher class but then actually radiate a lower level of power.  So check the power level in the module's specification.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Core Specification Level&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These classes are often confused with the core Bluetooth specification level, which may be 1.0 (original), 1.1 (1st IEEE standard), 1.2 (many enhancements), 2.0+EDR (enhanced data rate, released in 2004), 2.1+EDR (simple pairing enhancement, 2007), 3.0+HS (high speed, 2009) or 4.0 (low power, 2010).  Most current devices conform to level 2.1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that classes (1,2,3) have a single digit and specification levels always have a decimal point and tenths digit (e.g. 1.2, 2.1).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the specification levels are also defined by firmware, older devices can often be updated to support a newer level of the specification, except where new hardware features are supported.  Levels in general are backwards compatible; the same profile may exist on several different core specification levels (with perhaps different capabilities), depending on when it was first introduced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Other differences&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Besides the Bluetooth class, another major difference between modules is whether the module supports the higher level profiles internally, or just provides a low-level Bluetooth Host Controller Interface (HCI), which means the host microcontroller must implement the Bluetooth software stack.  Although these modules are generally a few bucks cheaper, since the processor requirements for the Bluetooth module are lower, this generally is a lot of work unless you have a Bluetooth stack provided by the manufacturer of your microcontroller, or you are doing a high-volume product where you can amortize the cost over many units.  You may also need to go this route if you need to support profiles not implemented by the module.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whether implementing a high or low-level interface, Bluetooth modules may physically connect with the host microcontroller using either a UART, SPI, I2C or SDIO interface -- another potential hardware difference.  A few modules allow you to run additional applications of your own on them, so that you can get by with not having to have a separate microcontroller in the your system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.bluegiga.com/Bluetooth_Modules&quot; rel=&quot;nofollow&quot;&gt;Here is an example&lt;/a&gt; of five different Bluetooth modules (i.e. different hardware), all running the same core Bluetooth specification (2.1) and &lt;em&gt;the same 14 profiles (except the one with an HCI interface) but providing different hardware features&lt;/em&gt; as described above.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-01-19T14:44:51.380" LastActivityDate="2011-01-19T14:44:51.380" CommentCount="1" />
  <row Id="9204" PostTypeId="2" ParentId="9202" CreationDate="2011-01-19T10:59:39.180" Score="1" ViewCount="" Body="&lt;p&gt;You can, in most cases, snap off the plastic tabs and then gently file off the stub if needed. The tabs are there for mechanical stability... maybe you can cut them to the required length?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How many do you need? Here's a handy &quot;trick&quot; if you only need a few, though this mostly works with ICs. Call up the distributor for the company in your area and ask for samples. Depending on the company, they'd be happy to send you some -- if you're a student this works even better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise, try browsing through the distributors' online catalog for alternate parts; you may find alternatives you haven't yet considered. Or, search for &quot;SWITCH, SPNO, ROUND&quot;.&lt;/p&gt;&#xA;" OwnerUserId="2531" LastActivityDate="2011-01-19T10:59:39.180" />
  <row Id="9205" PostTypeId="2" ParentId="9199" CreationDate="2011-01-19T12:23:20.280" Score="1" ViewCount="" Body="&lt;p&gt;I know adafruit.com sells two LiPoly charger boards, one uses the &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en027785&quot; rel=&quot;nofollow&quot;&gt;MCP73833&lt;/a&gt; the other uses &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en020210&quot; rel=&quot;nofollow&quot;&gt;MCP73861&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2654" LastActivityDate="2011-01-19T12:23:20.280" />
  <row Id="9206" PostTypeId="2" ParentId="9195" CreationDate="2011-01-19T12:24:56.160" Score="4" ViewCount="" Body="&lt;p&gt;Surely they would not fail, they will show you the magnetic field just like anywhere else, it will just be quite wierd.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You still will be able to use it as a compass there if you would get approximate GPS fix to correct for magnetic pole location (but math would be way harder in comparison to usual &quot;dumb&quot; compass).&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-19T12:24:56.160" />
  <row Id="9207" PostTypeId="2" ParentId="8767" CreationDate="2011-01-19T13:22:10.957" Score="1" ViewCount="" Body="&lt;p&gt;This is indeed a very good question. Since FPGAs fall into the category of &quot;hardware&quot;, you might be interested in a version-control friendly project structure I propose for FPGA projects:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.saardrimer.com/fpgaproj/&quot; rel=&quot;nofollow&quot;&gt;http://www.saardrimer.com/fpgaproj/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the ideas and concepts could easily be applies to other hardware projects, and in general. (Comments on this proposal are very welcome, btw.)&lt;/p&gt;&#xA;" OwnerUserId="2531" LastEditorUserId="2531" LastEditorDisplayName="" LastEditDate="2011-01-19T13:28:26.283" LastActivityDate="2011-01-19T13:28:26.283" />
  <row Id="9208" PostTypeId="1" CreationDate="2011-01-19T14:26:03.247" Score="1" ViewCount="110" Body="&lt;p&gt;Hi all!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using &lt;a href=&quot;http://cache.freescale.com/files/32bit/doc/ref_manual/MCF5253RM.pdf&quot; rel=&quot;nofollow&quot;&gt;MFC5253 controller&lt;/a&gt;. It has 2 CAN Channels- CAN 1 and CAN 2. In my project, I am using both of them. Their registers are same just name (1 and 2).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can transmit and recieve data correctly from CAN1 but not from CAN 2.... I couldn't understand the problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone used this controller?? &lt;/p&gt;&#xA;" OwnerUserId="2574" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-19T17:45:41.157" LastActivityDate="2011-05-28T09:33:24.243" Title="MCF5253 CAN Controller Transmission Problem" Tags="&lt;can&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="9209" PostTypeId="2" ParentId="8767" CreationDate="2011-01-19T14:40:50.820" Score="3" ViewCount="" Body="&lt;p&gt;The trick is to use something that works well with binaries.  If you are using binaries a lot and sharing with others, it might be beneficial to implement a locking mechanism on those binary files.  We've run into lots of issues with using Subversion with binary files and sharing with others that arose due to a lack of locking semantics and over-writing/merging binary files together.  Adding a locking mechanism on those files removes human error in communication on who edited/changed the binary file.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you haven't used version control before, I recommend reading up on the different ways they work, and select one to meet your needs that you and/or your team can be comfortable with.  Distributed version control systems provide many benefits over client-server systems, but tend to be more complicated to work with.&lt;/p&gt;&#xA;" OwnerUserId="374" LastActivityDate="2011-01-19T14:40:50.820" />
  <row Id="9210" PostTypeId="2" ParentId="9195" CreationDate="2011-01-19T15:02:02.207" Score="6" ViewCount="" Body="&lt;p&gt;You wouldn't be able to use it as a compass exactly at the magnetic pole, as the magnetic field would be vertical.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You probably already know about the need to correct for &lt;a href=&quot;http://en.wikipedia.org/wiki/Magnetic_declination&quot; rel=&quot;nofollow&quot;&gt;magnetic declination&lt;/a&gt;, which is the angle between magnetic north and true north.  It varies irregularly over the earth and over time.  Take a look at a declination map (such as &lt;a href=&quot;http://en.wikipedia.org/wiki/File%3aMv-world.jpg&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;), and notice that there is no unique value for declination at the magnetic poles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the magnetometer works everywhere since it gives you the correct magnetic field X/Y/Z components; you just can't always use it as compass.&lt;/p&gt;&#xA;" OwnerUserId="2677" LastActivityDate="2011-01-19T15:02:02.207" CommentCount="2" />
  <row Id="9211" PostTypeId="2" ParentId="9187" CreationDate="2011-01-19T15:04:54.337" Score="3" ViewCount="" Body="&lt;p&gt;Fake Name pretty much took care of the &quot;Why&quot;, I'll try to help with the &quot;What now&quot;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, since the field strength is inversely proportional to the distance squared, moving the scope and PSU away from each other could also do the trick.  Similarly, changing the orientation of the two devices so the CRT screen is perpendicular to the magnetic field lines could reduce the distortion and flicker to something more readable. Finally, I'm guessing that this is a linear power supply with only low frequencies on the transformer, so if having the scope and the controls for the PSU in the same location or on top of each other is important, you could probably put the transformer in its own box, and run a cable back to the PSU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another easy (but expensive) fix is to get a scope with an LCD.  Most new scopes are like this.  Now your oscilloscope won't be affected by the magnetic field.  However, remember that you still have a significant magnetic field at your workstation.  You can forget about working with magnetometers.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The third option is to encase the transformer in a material with a high magnetic permeability, like mu-metal.  This will form the equivalent of a Faraday cage (which should, analogously, have high conductivity) to block stray magnetic forces.  &lt;a href=&quot;http://en.wikipedia.org/wiki/Mu-metal&quot; rel=&quot;nofollow&quot;&gt;Mu-metal&lt;/a&gt; is a nickle/iron alloy with traces of copper and molybdenum that is often used for this purpose.  Other nickle/iron alloys will also work.   Layers of encasement will increase the attenuation exponentially if a single layer is insufficient to do the job.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get shielding from &lt;a href=&quot;http://www.aircraftspruce.com/catalog/elpages/edmomumetal.php&quot; rel=&quot;nofollow&quot;&gt;aircraft supply companies&lt;/a&gt; in tape form, used to wrap the magnetos and prevent radio interference.   &lt;a href=&quot;http://www.lessemf.com/mag-shld.html&quot; rel=&quot;nofollow&quot;&gt;LessEMF.com&lt;/a&gt; sells various other forms such as sheet metal, 1&quot; tape, and a more flexible mesh; shields were more popular when CRT monitors and TVs were in wide use so there are probably lots of other sources.  You are probably dealing with relatively week magnetic fields, though, so it might be worthwhile to try out cheap steel sheet metal before buying something more exotic and expensive.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-19T15:04:54.337" CommentCount="2" />
  <row Id="9212" PostTypeId="2" ParentId="4746" CreationDate="2011-01-19T15:55:52.967" Score="1" ViewCount="" Body="&lt;p&gt;you can solve this by using &lt;code&gt;mtools&lt;/code&gt; (userspace fat utilities):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;mdel -i /dev/sdf ::/firmware.bin&#xA;mcopy -i /dev/sdf new_firmware.bin ::/&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2679" LastActivityDate="2011-01-19T15:55:52.967" />
  <row Id="9213" PostTypeId="2" ParentId="9185" CreationDate="2011-01-19T16:27:09.193" Score="1" ViewCount="" Body="&lt;p&gt;Consider using a DAC output and a high resistance (relative to R1) to inject / sink current into the pin 4 network to facilitate a 'trim' feature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Controlling the OCP limit would most likely require a digipot, as would significant adjustment of the setpoint.  &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-01-19T16:27:09.193" />
  <row Id="9214" PostTypeId="2" ParentId="2854" CreationDate="2011-01-19T17:09:56.543" Score="5" ViewCount="" Body="&lt;p&gt;There has been discussion related to this question here: &lt;a href=&quot;http://tech.groups.yahoo.com/group/nuttx/message/685&quot; rel=&quot;nofollow&quot;&gt;http://tech.groups.yahoo.com/group/nuttx/message/685&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Extracts:&#xA;The Linux Journal article that is referred to is here: www.linuxjournal.com/article/10785#mpart4&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that the 8052 and the M68HC12 ports are especially bad choices to characterize NuttX because they both have some issues. And NuttX is now at version 5.16 with 63 releases.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did fill out the interview in the &quot;Publisher&quot; tab here:&#xA;download.famouswhy.com/publisher/gregory_nutt/. There is a review there too:  download.famouswhy.com/nuttx/&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Extensive NuttX documentation is available here: www.nuttx.org&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The issues with the hcs12 and 8051 parts are as follows:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;8051/80c52: This architecture is really RTOS hostile. It has a tiny hardware stack (128 bytes on the 8051, 256 on the 80c52) at a dedicated memory location (address 0). To switch tasks, you have to copy the whole stack of the task to be blocked from its dedicated address to some save location, and then copy the whole stack of the task to be started from its save location to the dedicated stack location. YECH!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And since, the stack is so tiny. It is very, very easy to overrun the stack -- especially during interrupt handling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The NuttX 8051 port is complete and functional (at least the last time I used it). But in order to make it useful, you would probably have to copy the whole stack on each interrupt as well to keep it from overflowing. Basically, I lost interest at that point but if some one were really motivated to use the 8051, it is doable (if perhaps not well-advised).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What was good about the 8051 port is that it was a great exercise in getting NuttX into a very small memory location. The 8051 port runs in 32Kb of RAM -- that includes the RTOS, libc, compiler libraries, a substantial test program, .data/.bss, and and heap. And with a little memory to spare!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;hcs12: This is a project that I work on in my spare time when I am not doing anything else. It is just not finished and not ready for prime time yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With regard to comparison to other RTOSs, I really don't have any good, authoratative answers because I don't use other RTOSs. But here is my naive understanding:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FreeRTOS. Has tons of downloads and a really tiny footprint of about 4Kb. It is the RTOS of choice for the really small MCUs. A FreeRTOS port is bundled by silicon vendors with just about every MCU. So it is the default RTOS choice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are dozens of competitors with FreeRTOS out there. ChiBIOS comes to mind immediately. These are all tiny schedulers of varying types.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to do a real comparison, one thing we need to do first is to define what we mean by an RTOS: Is it just a scheduler? Or is it an integrated set of standard OS features -- like scheduler, filesystem, device drivers, memory management, networking, etc. Most operating system, Linux for example, are full development environments, not just schedulers. NuttX is a full operating system is the same sense as Linux. Here are a couple of others:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RTEMS. I've worked with this one. It has been around forever and should be very stable. It is big. Think &gt;100Kb. I think it aims a little above the MCU market.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;uCOS. Never used it, but this the RTOS under several popular bootloaders, isn't it? My impression is that is it similar to RTEMS, but I don't really know what I am talking about.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would I compare NuttX to those: Well, it is a lot smaller. The starting footprint is around 20Kb. A full featured configation is some 10-20Kb more.  Another difference from these RTOSs is that NuttX is very standards oriented.  You can think of NuttX as a tiny, Linux work-alike. Most code that compiles and runs on Linux will also run on NuttX (some system code like networking code or daemons might need some tweaking).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think RTEMS is more focused on micro-processors; NuttX is more focused on micro-controllers.&lt;/p&gt;&#xA;" OwnerUserId="2680" LastEditorUserId="2680" LastEditorDisplayName="" LastEditDate="2011-01-19T17:42:22.240" LastActivityDate="2011-01-19T17:42:22.240" />
  <row Id="9215" PostTypeId="2" ParentId="2854" CreationDate="2011-01-19T17:56:45.503" Score="0" ViewCount="" Body="&lt;p&gt;Licensing is another difference to keep in mind when selecting an open source RTOSs.  Especially if you plan to use the RTOS in a commericial project.  Most open source RTOSs have a modified GPL license.  The license modification usually specifies that you do not have to your proprietary code that links with the GPL RTOS (but you still have to release the RTOS files with your modifications).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NuttX (and probably others) have a non-restrictive, modified BSD license.  With the BSD license, you can essentially take the code and use it as if it were own with no obligations other than retaining the licensing and copyright information within the files.&lt;/p&gt;&#xA;" OwnerUserId="2680" LastActivityDate="2011-01-19T17:56:45.503" CommentCount="3" />
  <row Id="9216" PostTypeId="1" AcceptedAnswerId="9218" CreationDate="2011-01-19T19:29:12.040" Score="9" ViewCount="277" Body="&lt;p&gt;I've been playing around with an Arduino for a while now, and while I know just enough about simple circuits to get little projects up and running, I still don't know enough to figure out what's going on in all but the simplest of circuits. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've read a few books on electronics and a handful of online articles, and while I think I understand how voltage, current, resistors, capacitors and other components work; when I see a schematic with lots of them in, I don't know what's going on where. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a bit to finally get to grips with it, I bought a 300-in-1 Electronics Project Set, however it seems to jump from &quot;Here is a circuit with two resistors in parallel&quot; to things more complex, without explaining how it works. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, it shows an inverter circuit: a simple battery-&gt;resistor-&gt;LED circuit, but shows that if you wire a button up in parallel with the LED, pressing the button turns the LED off. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I get that the current must be travelling through the path of least resistance, but I don't understand &lt;strong&gt;&lt;em&gt;why it doesnt travel through both&lt;/em&gt;&lt;/strong&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm taught that wiring two resistors up in parallel causes the current to flow through both, and so more current flows in the circuit. I've also tried replacing the button in the circuit above with resistors of varying values, and as I suspected, a high value resistor doesn't affect the bulb at all, but lower values start to dim the bulb. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure &lt;strong&gt;&lt;em&gt;how to apply the E = IR equation&lt;/em&gt;&lt;/strong&gt; to all of this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, &lt;strong&gt;&lt;em&gt;how much resistance does an LED have?&lt;/em&gt;&lt;/strong&gt; I tried measuring it with my multimeter, but it wouldn't give a reading. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry if I've waffled on loads here, but I'm trying to paint a picture of what I think I understand and what I want to understand. Not sure I've achieved that!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh yeah, and expect lots more of this as I delve deeper into my 300-in-1 project kit!&lt;/p&gt;&#xA;" OwnerUserId="2573" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-20T02:36:48.290" LastActivityDate="2011-01-20T15:52:59.000" Title="Simple Circuit Question" Tags="&lt;led&gt;&lt;circuit&gt;&lt;diode&gt;&lt;resistance&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="9217" PostTypeId="2" ParentId="9216" CreationDate="2011-01-19T19:43:03.710" Score="6" ViewCount="" Body="&lt;p&gt;You cannot directly apply E=IR to this because the LED is a diode, which is a nonlinear device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simplified: a diode will not conduct current unless sufficient, correct-polarity voltage is present across its terminals to forward-bias it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistance of the switch shorting the diode out is very small, so the voltage generated across it is also very small, certainly many orders of magnitude too small to forward bias the diode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you replace the switch with a resistor, things can change. Imagine the LED is out of the circuit. If the resistor limits the current sufficiently to develop a voltage drop across it that is equal to or greater than the forward-bias requirement of the LED, once you put the LED in the circuit you will see that the LED will be on dimly as you observed. There is current being 'shared' by the LED and the resistor- you will observe that the voltage across the resistor in parallel with the diode is 'clamped' by the diode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Diodes are not intrinsically resistive like resistors are. Their resistance is extremely small - this is why an LED circuit requires a series resistor - to provide resistance which limits the current and protects the diode from failing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See the &lt;a href=&quot;http://en.wikipedia.org/wiki/Diode&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt; article on diodes.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-19T20:36:57.853" LastActivityDate="2011-01-19T20:36:57.853" />
  <row Id="9218" PostTypeId="2" ParentId="9216" CreationDate="2011-01-19T19:44:52.973" Score="5" ViewCount="" Body="&lt;p&gt;Well, I'm studying electrical engineering right now and I can tell you that such jumps as you described take around two years of lectures at my university.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First thing which is important is to know which elements are &lt;a href=&quot;http://en.wikipedia.org/wiki/Passive_electronic_component&quot; rel=&quot;nofollow&quot;&gt;passive&lt;/a&gt; and which are active. Then you need to know which elements are &lt;a href=&quot;http://en.wikipedia.org/wiki/Linear_element&quot; rel=&quot;nofollow&quot;&gt;linear&lt;/a&gt; and which aren't.&#xA;Next step is to get equivalent schematics for elements which you have and to see how they behave. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, let's take the switch. In off state, it functions as an &lt;a href=&quot;http://en.wikipedia.org/wiki/Open-circuit_voltage&quot; rel=&quot;nofollow&quot;&gt;open circuit&lt;/a&gt;, while in on state it functions as &lt;a href=&quot;http://en.wikipedia.org/wiki/Short_circuit&quot; rel=&quot;nofollow&quot;&gt;short circuit&lt;/a&gt;. Next, if you have sensitive equipment, you'll be able to notice that the switch isn't actually short circuit because it has some resistance, but that it's very low. Now let's take a look at the &lt;a href=&quot;http://en.wikipedia.org/wiki/Diode&quot; rel=&quot;nofollow&quot;&gt;diode&lt;/a&gt;. Diode isn't linear component, so it doesn't have resistance in the classical sense in which for example resistors have. Instead there's the V-I curve of the diode. On a resistor, it's a linear function and we can use resistance as its characteristic, but on diode, it looks exponential.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/nV2aF.png&quot; alt=&quot;diode curve from wikipedia&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see from the image, certain voltage is needed for diode to start working properly and when you trigger the switch, that voltage disappears.  That means, that the &quot;resistance&quot; of the diode just became huge. To get a feeling for this, use the parallel resistor calculation for say 1 mΩ resistor and 1MΩ resistor and take a look how much current goes through each of them. This is the way the circuit you mentioned behaves.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-01-19T19:44:52.973" CommentCount="3" />
  <row Id="9219" PostTypeId="1" AcceptedAnswerId="9221" CreationDate="2011-01-19T20:04:03.660" Score="4" ViewCount="450" Body="&lt;p&gt;Hi all, can anyone tell me how to make a simple electric shocking device (like a electric pen or hand buzzer style). I'v seen people use piezoelectric elements from lighters (is that correct?) but I would like to know how to create one from scratch, and also what current and voltage is needed to give a small shock. Thanks, ell.&lt;/p&gt;&#xA;" OwnerUserId="2681" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:13:27.730" LastActivityDate="2011-03-05T16:13:27.730" Title="Simple Electric Shock Device" Tags="&lt;high-voltage&gt;&lt;piezoelectricity&gt;" AnswerCount="1" CommentCount="7" FavoriteCount="1" />
  <row Id="9220" PostTypeId="2" ParentId="9216" CreationDate="2011-01-19T21:56:16.963" Score="2" ViewCount="" Body="&lt;p&gt;A diode is not characterized by an impedance, whereas resistors, capacitors, and inductors can be cast in the same electrical mold - each having a &quot;resistance&quot; (that potentially varies with respect to the &quot;frequency&quot; of the applied voltage signal). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A diode, on the other, hand draws an amount of current that depends non-linearly on the voltage applied across its terminals. A switch in parallel with it, when closed effectively makes the voltage drop across it zero, and it therefore does not conduct current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incidentally, and for a different reason, you would observe a similar phenomenon if you replaced the LED with a resistor. Pushing the switch is like putting a 0-ohm (or very small anyway) resistor in parallel with it. Almost all of the current will flow through the short circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In response to the addendum question in the comment on my response. There are many ways to show this, but lets say you have:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;                        R_1&#xA;                   +---^v^v^----+&#xA;          R_x      |            |      R_y&#xA;   Vcc---^v^v^-----+            +-----^v^v^----GND&#xA;               V_x |    R_2     | V_y&#xA;                   +---^v^v^----+&#xA;&#xA;Let Delta_V = V_x - V_y&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;We know that Delta_V is the drop across R_1 and R_2 (i.e. the drop across R_1 is the same as the drop across R_2 is equal to Delta_V). That voltage drop implies a current through both resistors. Namely:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;                        R_1&#xA;                   +---^v^v^----+&#xA;          R_x      |    --&amp;gt;     |      R_y&#xA;   Vcc---^v^v^-----+    i_1     +-----^v^v^----GND&#xA;          --&amp;gt;      |    R_2     | &#xA;        i_total    +---^v^v^----+&#xA;                        --&amp;gt;&#xA;                        i_2&#xA;&#xA;Delta_V = i_1 * R_1&#xA;Delta_V = i_2 * R_2&#xA;&#xA;therefore:    i_1 * R_1 = i_2 * R_2&#xA;equivalently: i_2 = i_1 * R_1 / R_2&#xA;equivalently: i_1 = i_2 * R_2 / R_1&#xA;equivalently: i_1 / i_2 = R_2 / R_1&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;That is to say, current is distributed among the parallel resistors in inverse proportion to their relative resistance. So if one resistor is R_1 three times &lt;em&gt;smaller&lt;/em&gt; than the R_2 it was draw three times &lt;em&gt;more&lt;/em&gt; current than R_2. You can further reduce the total circuit shown down into a single resistor through collapsing the parallel and series resistors to calculate the total current drawn by the circuit, i_total. Using the additional formula:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;i_total = i_1 + i_2&#xA;&#xA;therefore:    i_total = i_1 + i_1 * R_1 / R_2&#xA;equivalently: i_total = i_1 * ( 1 + R_1 / R_2 ) = i_1 * (R_1 + R_2) / R_2&#xA;equivalently: i_1 = i_total * (R_2 / R_1 + R_2)&#xA;equivalently: i_2 = i_total * (R_1 / R_1 + R_2)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that it's not important what Delta_V actually is to understand how the total current distributes among the parallel paths.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-20T15:52:59.000" LastActivityDate="2011-01-20T15:52:59.000" CommentCount="5" />
  <row Id="9221" PostTypeId="2" ParentId="9219" CreationDate="2011-01-19T22:13:14.907" Score="1" ViewCount="" Body="&lt;p&gt;This is actually quite a simple circuit which works by stepping up the collapse of a magnetic field in a small audio transformer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The schematic looks like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/K1uzd.jpg&quot; alt=&quot;schematic&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think something &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=MT4135-ND&quot; rel=&quot;nofollow&quot;&gt;like this part&lt;/a&gt; should work for the transformer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you touch the two output wires, you'll get a very small electric shock as you release the push button.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-19T22:13:14.907" CommentCount="8" />
  <row Id="9222" PostTypeId="1" AcceptedAnswerId="9252" CreationDate="2011-01-19T22:45:13.070" Score="7" ViewCount="350" Body="&lt;p&gt;What's the point below which electrical current is generally considered safe for &quot;casual&quot; human contact?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is either voltage or amperage more &quot;dangerous&quot; (e.g. high voltage / low amperage vs. low voltage / high amperage), or is the only consideration the total current?&lt;/p&gt;&#xA;" OwnerUserId="1756" LastActivityDate="2011-01-21T03:35:59.780" Title="Safe current limit for human contact?" Tags="&lt;safety&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="4" />
  <row Id="9223" PostTypeId="2" ParentId="7011" CreationDate="2011-01-19T23:14:31.287" Score="1" ViewCount="" Body="&lt;p&gt;As Leon noted, 90&lt;sup&gt;o&lt;/sup&gt; corners are undesirable because they heat up faster. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another downside even if you're not doing reflow work is that the corners are the first thing to lift if you abuse the board during rework, just like the corners of a sticker are the easiest and first things to peel up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I route at 45 degree angles, so an octagon is a better shape than a round pad.  It minimizes the space required of the trace around the pad, while simultaneously maximizing the area of said pad for soldering strength, board-to-copper adhesion, and heat dissipation.   Here's a diagram in hopes that it will help you see why.The diagram is for a through-hole component, but the same logic applies to SMDs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/cH8hd.png&quot; alt=&quot;trace rounding octagon at even spacing&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 135&lt;sup&gt;o&lt;/sup&gt; angles are better than 90&lt;sup&gt;o&lt;/sup&gt;; but I'm not convinced that going to fully rounded corners is significantly better than 135&lt;sup&gt;o&lt;/sup&gt;.  Also, (insignificantly)I like the uniform look that octagonal pads and 45 degree routing produces; I think round pads look out of place.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-19T23:14:31.287" />
  <row Id="9224" PostTypeId="1" AcceptedAnswerId="9225" CreationDate="2011-01-19T23:50:15.300" Score="1" ViewCount="122" Body="&lt;p&gt;I'm putting together a footprint for a 100-pin, 14x14mm TQFP, and I'm finding conflicting designs.  The pitch and width of the pads are all basically the same, but the length and centering of the pads horizontally varies a good deal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The following images are from the Microchip &lt;a href=&quot;http://www.microchip.com/stellent/groups/techpub_sg/documents/packagingspec/en012702.pdf&quot; rel=&quot;nofollow&quot;&gt;packaging specifications document&lt;/a&gt; (see page 282-283), so that we can have names to use for the dimensions.&lt;br&gt;&#xA;&lt;b&gt;Physical Package:&lt;/b&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/cqlXs.png&quot; alt=&quot;overall pins&quot;&gt; &lt;img src=&quot;http://i.imgur.com/VgWee.png&quot; alt=&quot;pin lengths&quot;&gt;   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;b&gt;Recommended Footprint:&lt;/b&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/LOHoX.png&quot; alt=&quot;center to center overall&quot;&gt; &lt;img src=&quot;http://i.imgur.com/zDu1b.png&quot; alt=&quot;pad length&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;sub&gt;There's a table with numbers for each dimension, but the exact details aren't really important here.&lt;/sub&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where should the pin go on the pad lengthwise? &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt; Should the pin be centered on the pad? &lt;/li&gt;&#xA;(C1 = D - L) If so, what should Y1 be?  L, L+tolerance, 2L?&#xA;&lt;li&gt; Should the inner edge of the pad line up with the inner edge of the pin?&lt;/li&gt;&#xA;(C1 - Y1 = D - 2L)  If so, how far should the pad stick out in front of the pin?&#xA;&lt;li&gt; Should the pad and pin have some other dimension?&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Note that the question is basically moot if Y1=L.  I'm assuming that I'll want a little extra pad to hit with the soldering iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It might be relevant that L1 is allowed to vary by ±25%, which feels like a bigger variation  if you read 'between 0.45 and 0.75mm'. It might not be relevant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm interested in solderability, avoiding invisible solder bridges under the chip, routing traces underneath (and outside of) the chip.  Of course, I don't want to use absurdly long pads for heat dissipation and board space reasons.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-20T00:14:02.680" LastActivityDate="2011-01-20T00:14:02.680" Title="Pad dimensions and land patterns for QFPs" Tags="&lt;pcb&gt;&lt;soldering&gt;&lt;surface-mount&gt;&lt;library&gt;&lt;tqfp&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="9225" PostTypeId="2" ParentId="9224" CreationDate="2011-01-19T23:57:58.403" Score="1" ViewCount="" Body="&lt;p&gt;If you're interested in solderability and manufacturability, then you should follow the recommended pad layout. I've never had a manufacturer's recommended pad layout give me grief, although I have run across a few vendors whose dimensioning requires a fair bit of headscratching and pencil-and-paper chicken-scratching in order to figure out offsets and spacing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are making some bad assumptions in your calculations though.  No, pins are not often centered on the pads &quot;lengthwise&quot; but they are often centered widthwise. Y1 and C1 would most certainly be given by the manufacturer. The recommended land pattern will (in my experience) give more space for the pin on the &quot;outside&quot; of the pad and less underneath it. My guess is that that gives a good shape to the solder connection. You won't have anything in terms of heat dissipation unless there are a lot of grounds or you have a ground pad underneath. In the case of a lot of ground pins, you'll want to give them a lot of copper fairly quickly, but you'll want to connect the pad to the copper with thermals or you'll have soldering problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wouldn't worry about minimizing board space, especially if you're not building a million of these. The half a millimeter you might save by shaving Y1 a little isn't worth it.&lt;/p&gt;&#xA;" OwnerUserId="974" LastEditorUserId="974" LastEditorDisplayName="" LastEditDate="2011-01-20T00:03:29.117" LastActivityDate="2011-01-20T00:03:29.117" CommentCount="3" />
  <row Id="9226" PostTypeId="1" AcceptedAnswerId="9242" CreationDate="2011-01-20T00:11:33.243" Score="4" ViewCount="223" Body="&lt;p&gt;I'm trying to jump in the USB world with &lt;a href=&quot;http://www.fourwalledcubicle.com/LUFA.php&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;LUFA&lt;/strong&gt;&lt;/a&gt; on a &lt;a href=&quot;http://www.pjrc.com/teensy/&quot; rel=&quot;nofollow&quot;&gt;Teensy dev board&lt;/a&gt;, but I'm stuck in the understanding of the descriptors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currently I'm trying to add one button to the joystick demo without sucess. &lt;strong&gt;&lt;em&gt;Does anyone know some resource that explains step by step how to set up a USB descriptor?&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edti :&#xA;After reading USB in a nutshel, I think I may not modified the Descriptor at all but the HIDReport instead...&lt;/p&gt;&#xA;" OwnerUserId="2040" LastEditorUserId="2040" LastEditorDisplayName="" LastEditDate="2011-01-20T09:58:52.193" LastActivityDate="2011-01-20T22:28:46.093" Title="USB descriptor (LUFA)" Tags="&lt;avr&gt;&lt;usb&gt;&lt;software&gt;&lt;lufa&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="9227" PostTypeId="1" AcceptedAnswerId="9229" CreationDate="2011-01-20T01:19:57.857" Score="3" ViewCount="277" Body="&lt;p&gt;Is it possible to add short circuit protection to a boost converter?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My initial instinct was &lt;em&gt;no&lt;/em&gt;, as the switch does not directly control the input to the inductor and this means the minimum output is Vin or so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But are there ways to protect such a converter?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-21T18:01:27.373" Title="Short circuit protection for a boost converter" Tags="&lt;smps&gt;&lt;protection&gt;&lt;boost&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="9228" PostTypeId="2" ParentId="9222" CreationDate="2011-01-20T01:46:02.223" Score="5" ViewCount="" Body="&lt;p&gt;voltage doesn't really matter, its a requirement to get to a certain voltage to pass through the skin, but voltage doesn't have any impact on &quot;damage&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current is what does damage.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've heard tons of claims as to what will kill you.  In EE school is was 60mA AC and ~100mA DC across your chest that would send your heart into fibrillation.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen claims that &amp;lt;10mA directly through your heart could do the same.  Honestly both are probably correct.  I don't know what a real electrical model of the body looks like but i don't have a hard time believing that if there were 100mA running through my body from 1 hand to the other that only 10% would pass through my heart directly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've worked on live phone lines before (~58V DC with off hook) and that didn't pass through my skin initially.  A half hour of being in the 105F degree attic and sweaty hands later it made my finger twitch and didn't feel good.  On another occasion i was working on a phone line when someone dialed it...that sucked...the ring pulse is 120V AC (current limit though) and does not feel good at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It only takes a couple milliamps to seriously get your attention, 10+mA will lock up muscles, this is highly frequency dependent though.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get back to your point...greater than 100-200mA is when you'd expect to start to see flesh burning and things like that.  But obviously from the heart discussion above, localized currents that are much smaller can be deadly.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't really know if there is a firm rule as to whats &quot;safe&quot; the current debate over the use of tazers for example would seem to indicate there isn't much conclusive evidence.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-01-20T01:46:02.223" CommentCount="12" />
  <row Id="9229" PostTypeId="2" ParentId="9227" CreationDate="2011-01-20T02:40:12.343" Score="1" ViewCount="" Body="&lt;p&gt;Here's a linear tech app note&#xA;&lt;a href=&quot;http://cds.linear.com/docs/Design%20Note/dn154f.pdf&quot; rel=&quot;nofollow&quot;&gt;http://cds.linear.com/docs/Design%20Note/dn154f.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're not using much current, sometimes a simple solution is to just use a thermal fuse in front of the converter, or even a simple lm317 type current limiter.  The second will give you a voltage drop, which may or may not be a problem.  Another easy solution is a good current limited voltage regulator in front of the boost converter and dedicated only to the boost converter, so if there is a short it doesn't bring the rest of your rail down.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-01-20T02:40:12.343" />
  <row Id="9231" PostTypeId="2" ParentId="8985" CreationDate="2011-01-20T04:12:32.177" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Tug Of War&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two robots, each less than 1000g, are tied together with a string, and one must pull the other 30 cm within one minute to win.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://homepage.mac.com/mrlaurie/robo/rules.html#tugowar&quot; rel=&quot;nofollow&quot;&gt;Sample Rules&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=3TI93NDDpkQ&quot; rel=&quot;nofollow&quot;&gt;10 minute tutorial video&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://homepage.mac.com/mrlaurie/robo/tugowartutorial.html&quot; rel=&quot;nofollow&quot;&gt;Tutorial Page&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="106" LastEditorUserId="106" LastEditorDisplayName="" LastEditDate="2011-01-22T20:57:25.300" LastActivityDate="2011-01-22T20:57:25.300" CommunityOwnedDate="2011-01-20T04:12:32.177" />
  <row Id="9232" PostTypeId="2" ParentId="8985" CreationDate="2011-01-20T04:20:08.187" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Robo-Magellan&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GPS-equipped robots navigate outdoor waypoints autonomously.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.robogames.net/rules/magellan.shtml&quot; rel=&quot;nofollow&quot;&gt;Sample Rules&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.google.ca/search?hl=en&amp;amp;tbs=vid%3A1&amp;amp;q=robo-magellan&amp;amp;aq=f&amp;amp;aqi=&amp;amp;aql=&amp;amp;oq=&quot; rel=&quot;nofollow&quot;&gt;Sample Videos&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="106" LastActivityDate="2011-01-20T04:20:08.187" CommunityOwnedDate="2011-01-20T04:20:08.187" />
  <row Id="9233" PostTypeId="2" ParentId="8985" CreationDate="2011-01-20T04:46:55.850" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Drag Racing&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A robot needs to race straight down a track as quickly as possible.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://homepage.mac.com/mrlaurie/robo/rules.html#dragrace&quot; rel=&quot;nofollow&quot;&gt;Sample Rules&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="106" LastActivityDate="2011-01-20T04:46:55.850" CommunityOwnedDate="2011-01-20T04:46:55.850" />
  <row Id="9234" PostTypeId="2" ParentId="9227" CreationDate="2011-01-20T08:57:36.123" Score="1" ViewCount="" Body="&lt;p&gt;The problem with  boost converters is there is a DC  path through the diode, so shutting off he converter doesn't stop the DC path. A seperate overcurrent protection circuit is usually the only solution.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-20T08:57:36.123" CommentCount="2" />
  <row Id="9235" PostTypeId="2" ParentId="9227" CreationDate="2011-01-20T08:59:01.127" Score="1" ViewCount="" Body="&lt;p&gt;A SEPIC converter can be current limited, here's an example: &lt;a href=&quot;http://dren.dk/carpower.html&quot; rel=&quot;nofollow&quot;&gt;http://dren.dk/carpower.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-01-20T08:59:01.127" />
  <row Id="9236" PostTypeId="2" ParentId="9226" CreationDate="2011-01-20T09:21:28.670" Score="3" ViewCount="" Body="&lt;p&gt;Here's the USB in a Nutshell page on descriptors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.beyondlogic.org/usbnutshell/usb5.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.beyondlogic.org/usbnutshell/usb5.shtml&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-20T09:21:28.670" />
  <row Id="9237" PostTypeId="1" AcceptedAnswerId="9238" CreationDate="2011-01-20T14:42:47.720" Score="2" ViewCount="135" Body="&lt;p&gt;I was thinking of giving each switch it's own pull-up resistor, but this seems like it would be expensive and a little bit of overkill. But using just one pull-up for the entire block seems like it might overload the resistor (unless I just use a big one).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any guidelines in this situation?&lt;/p&gt;&#xA;" OwnerUserId="876" LastActivityDate="2011-01-20T18:48:59.497" Title="How many resistors do I need for an 8 switch DIP switch block?" Tags="&lt;resistor&gt;&lt;current&gt;&lt;switch&gt;&lt;dip&gt;" AnswerCount="3" />
  <row Id="9238" PostTypeId="2" ParentId="9237" CreationDate="2011-01-20T14:52:39.483" Score="2" ViewCount="" Body="&lt;p&gt;SMD resistors are as cheap as dirt. Especially if you would buy full roll of let's say 10k ones (i.e. something widely-used, so that you could use in multiple projects). It's hard to overload pull-up resistors, as they can dissipate 0.125W usually. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also 4 and 8 resistors in 1 package, this will be even chipper if you are on large scale.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You cannot use single resistor for multiple wires - as they will be shorted (or you will need diodes :-D )&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-20T14:52:39.483" CommentCount="2" />
  <row Id="9239" PostTypeId="2" ParentId="9237" CreationDate="2011-01-20T15:08:42.023" Score="2" ViewCount="" Body="&lt;p&gt;Depending on the application, you may have built-in pull-up resistors.  AVRs like the ATmega168 and '328 do…&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-01-20T15:08:42.023" CommentCount="2" />
  <row Id="9240" PostTypeId="2" ParentId="9226" CreationDate="2011-01-20T15:40:01.873" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.usb.org/developers/hidpage/&quot; rel=&quot;nofollow&quot;&gt;HID page&lt;/a&gt; at &lt;a href=&quot;http://www.usb.org/&quot; rel=&quot;nofollow&quot;&gt;USB.org&lt;/a&gt; has a wealth of information about the HID spec.&#xA;Of particular interest on that page is the HID Descriptor Tool, that can be used to create, edit and validate HID report descriptors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are going to be doing a lot of work with USB, I highly recommend getting Jan Axelson's book &lt;a href=&quot;http://www.lvr.com/usbc.htm&quot; rel=&quot;nofollow&quot;&gt;USB COMPLETE&lt;/a&gt;. More information can be found here: &lt;a href=&quot;http://www.lvr.com/usb.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.lvr.com/usb.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2489" LastActivityDate="2011-01-20T15:40:01.873" />
  <row Id="9241" PostTypeId="2" ParentId="9208" CreationDate="2011-01-20T16:13:17.717" Score="2" ViewCount="" Body="&lt;p&gt;It seems that you have a situation where one node can RX/TX, but the other cannot TX, but still RXs. This is relatively common failure mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RX can work without TX working, but TX must have RX feedback, so if only RX is working, you have isolated it to your TX line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I start with easy, which involves checking for cold joints and for disconnected pins. Do connectivity checks towards from the device sending the signal. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is your issue, it seems you may have a problem. Also, if you have a slope control pin, make sure that it has the required signal.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-01-20T16:13:17.717" />
  <row Id="9242" PostTypeId="2" ParentId="9226" CreationDate="2011-01-20T18:10:17.273" Score="4" ViewCount="" Body="&lt;p&gt;You need to edit the HID report descriptor, but also the main code. Change this portion of the HID descriptor:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    0x05, 0x09,          /*   Usage Page (Button)                              */&#xA;    0x09, 0x02,          /*   Usage (Button 2)                                 */&#xA;    0x09, 0x01,          /*   Usage (Button 1)                                 */&#xA;    0x15, 0x00,          /*   Logical Minimum (0)                              */&#xA;    0x25, 0x01,          /*   Logical Maximum (1)                              */&#xA;    0x75, 0x01,          /*   Report Size (1)                                  */&#xA;    0x95, 0x02,          /*   Report Count (2)                                 */&#xA;    0x81, 0x02,          /*   Input (Data, Variable, Absolute)                 */&#xA;    0x75, 0x06,          /*   Report Size (6)                                  */&#xA;    0x95, 0x01,          /*   Report Count (1)                                 */&#xA;    0x81, 0x01,          /*   Input (Constant)                                 */&#xA;    0xc0                 /* End Collection                                     */&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;To this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    0x05, 0x09,          /*   Usage Page (Button)                              */&#xA;    0x09, 0x03,          /*   Usage (Button 3)                                 */&#xA;    0x09, 0x02,          /*   Usage (Button 2)                                 */&#xA;    0x09, 0x01,          /*   Usage (Button 1)                                 */&#xA;    0x15, 0x00,          /*   Logical Minimum (0)                              */&#xA;    0x25, 0x01,          /*   Logical Maximum (1)                              */&#xA;    0x75, 0x01,          /*   Report Size (1)                                  */&#xA;    0x95, 0x03,          /*   Report Count (3)                                 */&#xA;    0x81, 0x02,          /*   Input (Data, Variable, Absolute)                 */&#xA;    0x75, 0x06,          /*   Report Size (5)                                  */&#xA;    0x95, 0x01,          /*   Report Count (1)                                 */&#xA;    0x81, 0x01,          /*   Input (Constant)                                 */&#xA;    0xc0                 /* End Collection                                     */&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And set the third bit of the Buttons element in the element in the &lt;code&gt;CALLBACK_HID_Device_CreateHIDReport()&lt;/code&gt; function of the main source file, i.e. to &quot;push&quot; the new third button, use:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; if (ButtonStatus_LCL &amp;amp; BUTTONS_BUTTON1)&#xA;   JoystickReport-&amp;gt;Button |= (1 &amp;lt;&amp;lt; 2);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2695" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-20T22:28:46.093" LastActivityDate="2011-01-20T22:28:46.093" CommentCount="3" />
  <row Id="9243" PostTypeId="2" ParentId="9237" CreationDate="2011-01-20T18:48:59.497" Score="0" ViewCount="" Body="&lt;p&gt;If your micro has no pullups, another approach is to common one side of all switches, connect to an input with a pullup, and connect each of the switches to other IO pins. The latter pins are all tri-stated except one at a time, which is pulled low to read the state of its switch on the input pin. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-20T18:48:59.497" />
  <row Id="9244" PostTypeId="2" ParentId="9222" CreationDate="2011-01-20T19:01:50.343" Score="8" ViewCount="" Body="&lt;p&gt;Here is an article titled &lt;a href=&quot;http://bme.ccny.cuny.edu/faculty/mbikson/biksonmsafevoltagereview.pdf&quot; rel=&quot;nofollow&quot;&gt;&quot;A review of hazards associated with exposure to low voltages&quot;&lt;/a&gt; which I used as a reference when answering a medical safety question (I design embedded hardware and firmware for medical devices which go through FDA approval).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because the body has a minimum resistance of around 550 ohms, to get enough current to do damage a minimum &lt;em&gt;theoretical&lt;/em&gt; voltage level of around 16.5 V&lt;sub&gt;PEAK&lt;/sub&gt; is required (corresponding to a current of 30 ma&lt;sub&gt;PEAK&lt;/sub&gt;, which can induce respiratory paralysis if conducted across the chest for several minutes of contact at this low voltage).  Based on the cases studied by the author, the single lowest voltage reported to cause transdermal electrocution in an adult is 25 volts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For less than one minute of contact, currents &gt;40 ma are required to cause ventricular fibrillation, corresponding to a &lt;em&gt;theoretical&lt;/em&gt; voltage of 27.5 V&lt;sub&gt;PEAK&lt;/sub&gt;.  For less than one second exposure, &gt;100 ma&lt;sub&gt;PEAK&lt;/sub&gt; and 55 V&lt;sub&gt;PEAK&lt;/sub&gt; are required.  The author states that in all the cases he studied, there was no accidental electrocution from short-term exposures to voltages below 50 V&lt;sub&gt;PEAK&lt;/sub&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-01-21T00:07:15.987" LastActivityDate="2011-01-21T00:07:15.987" CommentCount="4" />
  <row Id="9245" PostTypeId="2" ParentId="4257" CreationDate="2011-01-20T19:40:37.847" Score="1" ViewCount="" Body="&lt;p&gt;It appears &lt;a href=&quot;http://www.adorama.com/QTES2.html&quot; rel=&quot;nofollow&quot;&gt;it exists&lt;/a&gt;, and is called a &quot;dummy battery&quot;.  But at $7 each, I think I'd opt for JustJeff's dowel-rod route.&lt;/p&gt;&#xA;" OwnerUserId="2697" LastActivityDate="2011-01-20T19:40:37.847" />
  <row Id="9246" PostTypeId="1" AcceptedAnswerId="9247" CreationDate="2011-01-20T21:39:24.203" Score="5" ViewCount="179" Body="&lt;p&gt;Hi,&lt;br&gt;&#xA;How does a Force-Sensitive Resistor work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does it work by sensing the number of tracks the user covers meaning that the more force the user pushes on the sensor the less resistance it causes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a picture of one:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/G8FlZ.jpg&quot; width=&quot;500&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-20T21:41:49.630" LastActivityDate="2011-01-22T10:48:38.573" Title="How do Force-Sensitive Resistors work?" Tags="&lt;sensor&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="9247" PostTypeId="2" ParentId="9246" CreationDate="2011-01-20T21:53:26.530" Score="2" ViewCount="" Body="&lt;p&gt;A piece of flexible conductive material with a high resistance is under the tracks, and the resistance between the tracks reduces when the sensor is pressed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I once made a crude one from a piece of conductive foam, which worked in a similar fashion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Piezo film is another technique that is sometimes used. I've also experimented with that, and it works very well.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-20T22:19:20.893" LastActivityDate="2011-01-20T22:19:20.893" CommentCount="2" />
  <row Id="9248" PostTypeId="2" ParentId="9195" CreationDate="2011-01-20T22:02:27.140" Score="3" ViewCount="" Body="&lt;p&gt;Justin's answer is spot on -- the magnetometer will work anywhere, but the readings may not be useful to you at the magnetic poles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding magnetic declination &amp;amp; inclination, there's software for a World Magnetic Model published by the US NGA &amp;amp; UK DGC that returns the expected magnetic fields strength &amp;amp; direction for a given location/date.&#xA;&lt;a href=&quot;http://www.ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2699" LastActivityDate="2011-01-20T22:02:27.140" />
  <row Id="9249" PostTypeId="2" ParentId="9246" CreationDate="2011-01-20T22:13:22.480" Score="0" ViewCount="" Body="&lt;p&gt;Is it the &lt;a href=&quot;http://en.wikipedia.org/wiki/Piezoresistive_effect&quot; rel=&quot;nofollow&quot;&gt;Piezo-resistive Effect&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-01-20T22:13:22.480" CommentCount="4" />
  <row Id="9251" PostTypeId="1" AcceptedAnswerId="9270" CreationDate="2011-01-21T00:11:08.873" Score="10" ViewCount="523" Body="&lt;p&gt;I've seen many PID articles, such as &lt;a href=&quot;http://www.eetimes.com/design/embedded/4212241/Case-Study-of-PID-Control-in-an-FPGA-?cid=NL_Embedded&amp;amp;Ecosystem=embedded&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;, use a Z transform of the generic PID equation to derive some crazy difference equation which can then be implemented in software (or in this case an FPGA).  My question is, what is the advantage to such an implementation versus the traditional and much more intuitive, &lt;a href=&quot;http://igor.chudov.com/manuals/Servo-Tuning/PID-without-a-PhD.pdf&quot; rel=&quot;nofollow&quot;&gt;PID without a PhD&lt;/a&gt; type implementation?  The second seems easier to understand and implement.  The P term is straight multiplication, the integral uses a running sum and the derivative is estimated by subtracting the previous sample from the current sample.  If you need to add a feature such as Integral Windup protection, it is straight forward algebra.  Trying to add Integral Windup protection or other features to a difference type algorithm, such as linked above, seems like it would be much more complicated.  Is there any reason to use such an implementation, other than the &quot;I'm a bad ass who likes to do Z transforms for fun&quot; type bragging rights that go along with it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: The PID without a PHD article I linked is an example of the simpler implementation that uses a running sum for the integral term and the difference between consecutive samples for the derivative term.  It can be implemented with fixed point math in a deterministic manner and can include real time time constant information in the calculation, if desired.  I'm basically looking for a practical advantage to the Z transform method.  I can't see how it could be faster, or use less resources.  Instead of keeping a running sum of the integral, the Z method appears to use the previous output and subtract the previous P and D components (to arrive at the integral sum by calculation).  So, unless someone can point to something I'm missing, I will accept AngryEE's comment that they are essentially the same.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FINAL EDIT:&#xA;Thanks for the responses.  I think I've learned a bit about each but in the end, think Angry is correct in that it is just a matter of preference.  The two forms:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$ u(k) = u(k-1) + K_p(e(k) - e(k-1) + K_i T_i e(k) + \frac{K_d}{T_i}(e(k)-2e(k-1)+e(k-2)) $$&#xA;$$ e(k-2) = e(k-1), \quad e(k-1) = e(k) $$&#xA;$$ u(k-1) = u(k) $$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;or&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$ \mbox{sum} = \mbox{sum} + e(k) $$&#xA;$$ u(k) = K_p e(k) + K_i T_i\cdot \mbox{sum} + \frac{K_d}{T_i}(e(k)-e(k-1)) $$&#xA;$$ e(k-1) = e(k) $$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;will evaluate to essentially the same thing.  Some mention the first can be implemented in a DSP or FPGA faster, but I don't buy that.  Either could be vectorized.  The first requires two post operations, the second requires one pre and one post operation, so it appears to even out.  The first also requires 1 more multiplication in the actual calculation.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-23T01:23:13.657" LastActivityDate="2011-03-23T01:23:13.657" Title="What is the advantage of a Z transform derived PID implemenation?" Tags="&lt;control&gt;&lt;pid-controller&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="4" />
  <row Id="9252" PostTypeId="2" ParentId="9222" CreationDate="2011-01-21T03:35:59.780" Score="5" ViewCount="" Body="&lt;p&gt;As rules of thumb, I've generally thought of myself as a 70 kΩ resistor to ground that feels pain at around 1 mA, which can be driven by 70 V or so. In my experience, the pain threshold is slightly above 48 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't say that I have any good medical science to back this up, but there are a few empirically obtained data points in that I'm not dead yet.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-01-21T03:35:59.780" CommentCount="1" />
  <row Id="9253" PostTypeId="1" AcceptedAnswerId="9254" CreationDate="2011-01-21T04:21:21.207" Score="3" ViewCount="192" Body="&lt;p&gt;I am working on my very first PCB design using Eagle. In my design, I will be using a &lt;a href=&quot;http://www.mouser.com/Search/ProductDetail.aspx?R=CP001010R00JE14virtualkey61300000virtualkey71-CP001010R00JE14&quot; rel=&quot;nofollow&quot;&gt;10W 10 Ohm power resistor&lt;/a&gt;. Since it isn't a &quot;standard&quot; size, I'm having trouble finding the component in Eagle. In particular, it has a width of 47mm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No component in rcl.lbr is long enough. resistor-power.lbr seems pretty promising, but many  of the components don't have measurements. And I'm not sure what the closest equivalent is. For example, KH216-8 seems like it is roughly the right size. And it happens to have a measurement. So is it, uh, &quot;safe&quot; to go with that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How could I view the dimensions of a component if it's not in the description?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any other techniques I can use when trying to find a library part that approximates the component I've chosen?&lt;/p&gt;&#xA;" OwnerUserId="1021" LastActivityDate="2011-01-21T05:26:16.307" Title="How to tell size of Eagle library component?" Tags="&lt;eagle&gt;&lt;pcb-design&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="9254" PostTypeId="2" ParentId="9253" CreationDate="2011-01-21T05:01:03.683" Score="3" ViewCount="" Body="&lt;p&gt;I don't think there's an easy way around this. I would open up the &lt;em&gt;resistor-power.lbr&lt;/em&gt; library on its own, in the library editor, open up the first footprint (ACO1), change the major grid to &lt;em&gt;10mm&lt;/em&gt;, then go through each one and note those that are close. There's usually some kind of logic to the footprint names and numbers -- for this library, it appears the &lt;em&gt;letter prefix denote a width&lt;/em&gt; class and the &lt;em&gt;number denotes length&lt;/em&gt;. &lt;sup&gt;&lt;strong&gt;&lt;em&gt;EDIT1:&lt;/strong&gt;&lt;/sup&gt; I went and did this, and none are 47mm wide.&lt;/em&gt;&lt;br&gt;&#xA;&lt;sup&gt;&lt;strong&gt;&lt;em&gt;EDIT2:&lt;/strong&gt;&lt;/sup&gt; After looking at the datasheet, it appears it is 47mm long and only 9mm wide, which fits &lt;strong&gt;HPS947&lt;/strong&gt;. (&lt;strong&gt;KH216-8&lt;/strong&gt;, &lt;strong&gt;RS10-38-39&lt;/strong&gt;, and &lt;strong&gt;RWM8X45&lt;/strong&gt; also seem to fit... sorta.)&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In almost every PCB design you will be making your own parts. I find it useful to make a new EAGLE library for every project, and copy all used part into it. The easiest way to make a new part, if it's just a variation of another, is to copy symbols and possibly even footprints into a new layout, then edit them. For this part, you can copy the &lt;em&gt;power-resistor.lbr &gt; R&lt;/em&gt; symbol by opening it up as if you were going to edit it, selecting the whole thing with the &lt;strong&gt;Group&lt;/strong&gt; function, then copying the group with the &lt;strong&gt;Copy&lt;/strong&gt; function (click &lt;strong&gt;Copy&lt;/strong&gt; button, right-click previously grouped symbol, select &lt;em&gt;&quot;Copy: Group&quot;&lt;/em&gt;. This puts the whole thing into your &lt;em&gt;Paste Buffer&lt;/em&gt;:  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;img src=&quot;http://i.imgur.com/ILNd6.png&quot;&gt; &lt;em&gt;&amp;lt;-- (that button)&lt;/em&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Open up a new library, &lt;em&gt;example.lbr&lt;/em&gt;, then create a new symbol &lt;em&gt;(Library &gt; Symbol)&lt;/em&gt;. Click the &lt;strong&gt;Insert Paste Buffer&lt;/strong&gt; button &lt;em&gt;( ^-- that button)&lt;/em&gt;. The copied symbol should come up, labels and all -- click on the crosshairs to line it up with the symbol anchor. I usually make my own footprints simply to remove all doubt in the library specs, but they can be copied using the same method. Another way to copy a part is to copy the entire library and rename it, then edit the entire thing. &lt;strong&gt;&lt;em&gt;&lt;a href=&quot;http://www.sparkfun.com/tutorials/110&quot; rel=&quot;nofollow&quot;&gt;Sparkfun also has a pretty good tutorial on making parts.&lt;/a&gt;&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, when I make my own parts, I fill out the caption so I won't have to browse the footprints directly in the future!&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-21T05:26:16.307" LastActivityDate="2011-01-21T05:26:16.307" CommentCount="1" />
  <row Id="9255" PostTypeId="1" CreationDate="2011-01-21T05:21:14.807" Score="3" ViewCount="114" Body="&lt;p&gt;Hi, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to connect more than one antenna to a single RFID reader module in order to pick up two different RFID chips at once? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to create an arduino project like this..  &lt;/p&gt;&#xA;" OwnerUserId="2703" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-21T05:33:01.070" LastActivityDate="2011-03-04T23:25:04.003" Title="RFID Antenna Array" Tags="&lt;rfid&gt;&lt;antenna&gt;" AnswerCount="2" />
  <row Id="9256" PostTypeId="2" ParentId="9255" CreationDate="2011-01-21T05:35:17.880" Score="1" ViewCount="" Body="&lt;p&gt;No, unless it is specifically designed to have dual receivers (unlikely).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, if you ok to read them sequentially - you can switch antennas every 5ms for example - this might work then :-D&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-21T05:35:17.880" CommentCount="4" />
  <row Id="9257" PostTypeId="2" ParentId="9251" CreationDate="2011-01-21T06:31:01.800" Score="11" ViewCount="" Body="&lt;p&gt;The Z-transform method of designing the PID controller will eventually yield a much more efficient implementation.  This is critical if you are designing for the smallest FPGA/DSP/Microcontroller for you application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The mentioned &quot;PID without a PHD&quot; is probably the easiest approach to implementing a PID control in software, but it becomes cumbersome at higher sampling rates.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally, the Z-transform lends itself better to designing in a discrete (digital) domain.  The traditional (Laplace transform) method of design is more for continuous time.  There are multiple ways of converting between the two (Zero-Order Hold, Linear Interpolation, Pole Placement, Bilinear/Tustin), each comes with it's strengths and drawbacks in terms of stability and response of the system.  It's generally just easier to do the entire design in the discrete domain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Long story short, if you are using a relatively &quot;slow&quot; system (all of the major behaviors happen significantly under a 100kHz or so), then the first design is probably just fine.  You can implement it on a microcontroller or PC and be done with it.  As the systems get faster, then you may have to use the Z-transform method to get the speeds that you need (the article mentions 9.5MHz, assuming you have A/D and DACs that can keep up).&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-01-21T06:31:01.800" CommentCount="11" />
  <row Id="9258" PostTypeId="1" CreationDate="2011-01-21T07:15:18.143" Score="3" ViewCount="364" Body="&lt;p&gt;If so, could one direct me to a site that tells how to do this? I believe I may have found a &lt;a href=&quot;http://arduinodoodles.hg.sourceforge.net/hgweb/arduinodoodles/arduinodoodles/file/d5f8a54664d1/arduiggler&quot; rel=&quot;nofollow&quot;&gt;way&lt;/a&gt;, but I am unsure as to whether or not it would work yet (need to find something to test it on). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This question is related to a previous question of mine located &lt;a href=&quot;http://stackoverflow.com/questions/4709179/how-to-get-arm-code-unto-an-actual-device-jtag-possible-to-make-impromptu-jtag&quot;&gt;here.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In case more background information is needed.&lt;/p&gt;&#xA;" OwnerUserId="2701" LastActivityDate="2011-02-03T18:11:50.073" Title="Is it possible to make a JTAG interface with an arduino?" Tags="&lt;arduino&gt;&lt;arm&gt;&lt;embedded&gt;&lt;jtag&gt;" AnswerCount="2" />
  <row Id="9259" PostTypeId="1" AcceptedAnswerId="9265" CreationDate="2011-01-21T08:54:04.893" Score="2" ViewCount="99" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using WindRiver JTAG Debugger to debug my code. &#xA;Whenever I run the code with Debugger connected, Code works correctly but If I disconnect it, It fails to even Start!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone faced such kind of Problems?&lt;/p&gt;&#xA;" OwnerUserId="2574" LastActivityDate="2011-01-21T13:20:21.723" Title="Code Running from Debugger but Not Without it" Tags="&lt;jtag&gt;&lt;debug&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="9260" PostTypeId="2" ParentId="9258" CreationDate="2011-01-21T09:02:18.627" Score="7" ViewCount="" Body="&lt;p&gt;Yes, it is possible to turn an Arduino into an ARM JTAG adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are three problems, voltage, speed and drivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino natively runs at 5V. Most ARM microcontrollers are not 5V tolerant on their JTAG pins and require 3.3V. The easiest solution is to run your Arduino at 3.3V, failing that you will need some sort of level conversion (see &lt;a href=&quot;http://electronics.stackexchange.com/questions/708/i2c-3-3-to-5-0-v-conversion&quot;&gt;I2C 3.3 to 5.0 V conversion&lt;/a&gt; for ideas).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino is connected to a PC via a serial link. I doubt it can feasibly go faster than 115200bps, which will make interactive activities like stepping through code in a debugger very slow. But, you'll be able to upload code and reflash devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;JTAG is a high level protocol, specific to each processor family, which uses a SPI like interface to exchange data. Most JTAG dongles just provide a SPI interface over USB then leave the rest of the work to a PC application. OpenOCD and URJTag are popular choices. You will need a driver in one of these for your Arduino JTAG protocol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Bus Pirate is very similar to the Arduino (low speed microcontroller + FTDI chip). &lt;a href=&quot;http://blog.hodgepig.org/2010/04/13/545/&quot; rel=&quot;nofollow&quot;&gt;It supports JTAG&lt;/a&gt; with OpenOCD, so it's certainly possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use a Teensy/Opendous or other AVR-USB board, you could use &lt;a href=&quot;http://code.google.com/p/estick-jtag/&quot; rel=&quot;nofollow&quot;&gt;eStick-JTAG&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, for lost cost JTAG, I'd recommend one of the FTDI2232 based dongles. They're cheap and well supported by OpenOCD.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-21T09:02:18.627" />
  <row Id="9261" PostTypeId="2" ParentId="9259" CreationDate="2011-01-21T10:14:48.923" Score="2" ViewCount="" Body="&lt;p&gt;Generally, that problem is caused by the program failing to start properly from a reset when run without the debugger. For instance, with the Rowley CrossWorks ARM tools, STARTUP_FROM_RESET has to be defined for the pre-processor.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-21T10:14:48.923" />
  <row Id="9262" PostTypeId="2" ParentId="9259" CreationDate="2011-01-21T10:24:25.757" Score="3" ViewCount="" Body="&lt;p&gt;Here are the reasons I have seen this case occur:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;I have seen students not place pull up resistors on their MCLR pins on PICs. When hooked up to the debugger, the debugger pulls it up for them, but once they disconnect it nothing works.&lt;/li&gt;&#xA;&lt;li&gt;A bad ground. This is a bit harder to figure out. But I have seen a case where the programmer was able to provide a better ground connection then when being powered off of a power supply or battery.&lt;/li&gt;&#xA;&lt;li&gt;Does your setup provide power through your JTAG connection? I have seen a case recently where the microcontroller was going into a brown out state because the power was not able to settle fast enough before the micro started trying to turn things on. When plugged into a debugger there was power applied much before starting the code so this was never seen.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-21T10:24:25.757" />
  <row Id="9263" PostTypeId="2" ParentId="9259" CreationDate="2011-01-21T12:11:01.197" Score="1" ViewCount="" Body="&lt;p&gt;Perhaps you are using the Debug version when compiling with the JTAG device plugged in, but using Release when compiling without it? Also, if you are using different debug and release versions make sure you have optimisations set to the same for both variants.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-01-21T13:11:01.107" LastActivityDate="2011-01-21T13:11:01.107" CommentCount="2" />
  <row Id="9264" PostTypeId="1" AcceptedAnswerId="9278" CreationDate="2011-01-21T13:14:28.590" Score="2" ViewCount="267" Body="&lt;p&gt;I know 9600, 19200, 38400, 57600, 115200 and 1.8432 Mbaud, but no others. Why are these values used, and is it simply doubling each time or is there something more complex going on (for example, 38400 quadrupled is not 115200 baud?) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason I ask this question is I'm designing something which may have to interact with a variety of different baud rates. It will initialise in 9600, and then switch to a specific baud rate. But I can't support arbitrary rates because the dsPIC33F I am using does not support arbitrary rates as it is limited to a 16-bit BRG down counter. It's similar in this regard to many other processors.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-01-21T13:19:34.153" LastActivityDate="2011-03-09T20:14:29.477" Title="What standard UART rates are there?" Tags="&lt;uart&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="9265" PostTypeId="2" ParentId="9259" CreationDate="2011-01-21T13:20:21.723" Score="3" ViewCount="" Body="&lt;p&gt;My debugger for a Coldfire does some initialization of the SDRAM controller and other low-level registers that is normally done by the bootloader.  Check to see how your debugger initializes the chip.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-01-21T13:20:21.723" CommentCount="1" />
  <row Id="9266" PostTypeId="1" CreationDate="2011-01-21T13:34:15.400" Score="4" ViewCount="92" Body="&lt;p&gt;When it comes to plan and execute hardware related projects in your organization, do you follow a specific process flow? (like e.g. requirement definition, design definition, test plan). If so, do you have any recommendation or reference I could use?&lt;/p&gt;&#xA;" OwnerUserId="2709" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-01-22T15:13:23.363" LastActivityDate="2011-01-22T15:13:23.363" Title="Which are hardware projects management guidelines in your organization" Tags="&lt;project-management&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9268" PostTypeId="2" ParentId="54" CreationDate="2011-01-21T15:20:28.703" Score="1" ViewCount="" Body="&lt;p&gt;The program &lt;a href=&quot;http://www.mikmo.dk/gobetwino.html&quot; rel=&quot;nofollow&quot;&gt;gobetwino&lt;/a&gt; will log sensor values from an Arduino to a text file or spreadsheet with minimal effort.  It can also automate things on the computer, add timestamps (so you don't need to program them into the arduino), etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/9K0zB.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-01-21T19:00:22.240" LastActivityDate="2011-01-21T19:00:22.240" />
  <row Id="9269" PostTypeId="2" ParentId="9266" CreationDate="2011-01-21T15:55:07.350" Score="2" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;Define product opportunity.&lt;/li&gt;&#xA;&lt;li&gt;Define architecture, review, define implementation.&lt;/li&gt;&#xA;&lt;li&gt;Schematic capture and review&lt;/li&gt;&#xA;&lt;li&gt;PCB design and review&lt;/li&gt;&#xA;&lt;li&gt;Build&lt;/li&gt;&#xA;&lt;li&gt;Debug&lt;/li&gt;&#xA;&lt;li&gt;See if wish to launch product&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="206" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-01-21T15:58:40.717" LastActivityDate="2011-01-21T15:58:40.717" CommentCount="1" />
  <row Id="9270" PostTypeId="2" ParentId="9251" CreationDate="2011-01-21T16:03:03.310" Score="2" ViewCount="" Body="&lt;p&gt;You're getting befuddled by all of the fanciness of the Z-transform.  The two approaches are fundamentally the same - the PID without PHD approach just has fewer subscripts.  They perform the same basic function and use the same basic math. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only major difference between the two that I can see is that the PID without PHD doesn't take sampling time into account.  For doing anything that might be unstable, sampling time is a very important consideration.  The benefit of the Z-transform approach in this case is that you can't use it without taking sampling time into account - it forces you to show your work and helps you design a more stable system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It also looks like the case study you found implementing the Z-transform approach was designed to be highly deterministic.  This explains their use of FPGAs - the calculations will always take the same amount of time.  The PID without PHD implementation is decidedly not deterministic.  The use of doubles as variables instead of a fixed-point implementation is sure to cause non-deterministic behavior on any microcontroller without a floating-point unit (and probably on uCs with an FPU as well).  The case study is working on a whole different level of complexity compared to the PID w/o PHD approach.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So fundamentally the math and control approach is the same, but the case study/Z-transform approach is more rigorous and theoretically grounded.  The PID w/o PHD approach will only work for very simple, non time-critical system that are relatively stable.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-21T16:03:03.310" CommentCount="2" />
  <row Id="9271" PostTypeId="1" AcceptedAnswerId="9282" CreationDate="2011-01-21T16:49:36.430" Score="2" ViewCount="158" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Daily_build&quot; rel=&quot;nofollow&quot;&gt;Daily build&lt;/a&gt; in software is taking the source code, compiling it and generating the executables, then running that nightly.  This is considered a best practice since it catches errors that prevent the build sooner rather than later, which makes it easier to fix.  And if the build works, then others can make sure they aren't introducing errors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be the equivalent for a schematic design?  Clearly I can't build the PCB, but there might be something more than generating the netlist.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit 1/21/11: Also a &lt;a href=&quot;http://en.wikipedia.org/wiki/Smoke_testing#Software_development&quot; rel=&quot;nofollow&quot;&gt;smoke test&lt;/a&gt; is running some tests against the build.  Again, not possible.  I like the DRC (design rule check) idea, I'm thinking of checks such as that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit 1/24/11: I was think of the schematic since that's what I do, rather than the PCB.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-24T16:21:42.197" LastActivityDate="2011-01-24T21:20:55.370" Title="What is equivalent to a daily build (and smoke test) for schematic designs?" Tags="&lt;schematics&gt;" AnswerCount="5" CommentCount="6" />
  <row Id="9272" PostTypeId="1" AcceptedAnswerId="9275" CreationDate="2011-01-21T16:51:20.180" Score="2" ViewCount="184" Body="&lt;p&gt;Is FCC certification required for something you put together for personal use or only for something you actually sell to someone else?&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2011-01-23T13:52:33.807" Title="Is FCC certification required for something that is not sold?" Tags="&lt;fcc&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9273" PostTypeId="2" ParentId="9271" CreationDate="2011-01-21T16:57:09.747" Score="4" ViewCount="" Body="&lt;p&gt;I don't think there's an analogue of the daily build for hardware.  It may be possible to not allow a schematic to be checked in if it doesn't pass DRC (or maybe simulation) but that's about all I can think of.  Software folks have the benefit of actually being able to run the finished product (for the most part) at a moment's notice and they get a lot of automated tools.  Schematic capture programs and simulators are for the most part not up to speed on automation, versioning, etc and it's really a shame.  I'd like to see the software design process mimicked as much as possible for hardware but I doubt it will be entirely possible.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-21T16:57:09.747" />
  <row Id="9274" PostTypeId="2" ParentId="9271" CreationDate="2011-01-21T17:18:22.087" Score="1" ViewCount="" Body="&lt;p&gt;The idea of a daily software build is to catch problems introduced by changes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you change the schematic, you'll need to test the PCB before going to manufacture.&#xA;You can reduce the risks by logging and reviewing all changes.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-21T17:18:22.087" />
  <row Id="9275" PostTypeId="2" ParentId="9272" CreationDate="2011-01-21T17:37:52.537" Score="5" ViewCount="" Body="&lt;p&gt;I believe that you aren't &lt;em&gt;required&lt;/em&gt; to certify hobby electronics, but you still may get a knock at the door if your product is interfering with someone's commercial gear next door.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Certification is required for commercial products. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Certification is also required for anything that plugs into the telephone network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IANAL &lt;sup&gt;&lt;em&gt;(I am not a lawyer)&lt;/em&gt;&lt;/sup&gt;, by the way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some other caveats to keep in mind; if you build something powerful that ends up burning down your house or maiming someone, and your insurance provider finds out that it's not 'approved', your chances of getting coverage are likely slim.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're tinkering with 5V / 12V stuff at low power, not emitting tons of RF and not polluting the mains, you're probably OK.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-21T21:30:33.580" LastActivityDate="2011-01-21T21:30:33.580" CommentCount="1" />
  <row Id="9276" PostTypeId="2" ParentId="8042" CreationDate="2011-01-21T17:56:43.650" Score="2" ViewCount="" Body="&lt;p&gt;Any power supply product sold in North America needs to be certified to certain standards to be safely used without special intervention: UL 60950 for non-medical stuff in the USA, CSA C22.2 for Canada - the standards are largely similar and certification usually happens for both markets simultaneously. There should be some agency marks - a UL mark or an NRTL-equivalent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Safety agencies can be called on to do a field evaluation of a single piece of equipment, against a lower standard than a usual certification. You're on the hook to pay for it yourself, so judge accordingly - it's likely much cheaper to get an approved power supply than pay for an evaluation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're using a product without marks or a field evaluation, you're using it at your own risk. Don't expect any payout from your insurance if your house burns down.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-05-13T16:36:55.897" LastActivityDate="2011-05-13T16:36:55.897" CommentCount="3" />
  <row Id="9277" PostTypeId="2" ParentId="9227" CreationDate="2011-01-21T18:01:27.373" Score="1" ViewCount="" Body="&lt;p&gt;In boost PFC applications, there is peak current limiting usually through a combination of two current transformers (one sensing the switch current, the other sensing the diode current) which works by collapsing the duty cycle of the converter, reducing the output voltage and (if the load is not CC) the current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is no way to protect against a hard short except for opening some sort of limiting device (i.e. fuse)&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-01-21T18:01:27.373" />
  <row Id="9278" PostTypeId="2" ParentId="9264" CreationDate="2011-01-21T18:02:54.553" Score="7" ViewCount="" Body="&lt;p&gt;It started a long long time ago with teletypes - I think 75 baud. Then it's been mostly doubling ever sice, with a  few fractional (x1.5) mutiples, for example 28k8, where there were constraints on phone-line modem tech that didn't quite allow it to double.&#xA;Standard crystal values came from these early baudrates, and their availability dictates future rates.7.3728MHz /16 = 460K8 baud, /64=115K2&#xA;Most UARTS use a clock of 2^n x16 of the baudrate,  more modern parts (e.g. NXP LPC) have fractional dividers to get a wider range by using non-binary multiples. &#xA;Other common standards are 31.25K (MIDI) and 250K (DMX), both likely chosen as nice multiples of 'round' clocks like 1MHz etc.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-21T18:02:54.553" />
  <row Id="9279" PostTypeId="1" AcceptedAnswerId="9289" CreationDate="2011-01-21T18:46:23.720" Score="0" ViewCount="117" Body="&lt;p&gt;I've been playing with voltage swings in a basic emitter-follower circuit.  If I swing the input too large in the negative cycle, the base-emitter junction is reverse-biased and the transister goes into cutoff mode.  I can see the clipping in the output and this makes sense to me.  With the collector, however, I've noticed that I can swing higher and not see symmetrcial clipping.  Eventually I do see the clipping.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a rule of thumb, like with the base-emitter junction, for managing base-collector junction?  May I use VC-VB=0.6/0.7 V for this relationship too?&lt;/p&gt;&#xA;" OwnerUserId="2059" LastActivityDate="2011-01-21T23:34:08.637" Title="BJT transistor junctions: base-collector" Tags="&lt;bjt&gt;&lt;emitter-follower&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="9280" PostTypeId="1" AcceptedAnswerId="9281" CreationDate="2011-01-21T18:59:39.607" Score="4" ViewCount="171" Body="&lt;p&gt;(Sorry, my workplace blocks access to the website for the Java based circuit simulator that everyone uses to put helpful schematics in their posts.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm having trouble understanding the simple voltage regulator that can be built using a zener diode (from section 2.04 in the Art of Electronics).  I know that it would be better to use amplifiers, et cetera, but I'm just trying to understand how this circuit works.  A very crude representation is shown below:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Vin o----/\/\/\/\-----.-------o Vout&#xA;             R        |&#xA;                    ____/&#xA;                   / /\&#xA;                    ----&#xA;                      |&#xA;                      o ground &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I don't really understand how the circuit works, but I am guessing that when a load is applied to the output, it drains current from the source (Vin) and thus causes the voltage to drop?  How does the zener diode help to maintain the voltage and thus make this circuit act as a regulator?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for your help!&lt;/p&gt;&#xA;" OwnerUserId="2059" LastActivityDate="2011-01-21T19:40:07.620" Title="zener diode voltage regulator" Tags="&lt;voltage-regulator&gt;&lt;diode&gt;&lt;zener&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="9281" PostTypeId="2" ParentId="9280" CreationDate="2011-01-21T19:08:57.337" Score="5" ViewCount="" Body="&lt;p&gt;Look at the Zener diode curve. You will see that the device breaks down at the Zener voltage when reverse-biased, and conducts. That property will fix the output voltage at the breakdown voltage, over a range of output currents, when used with a resistor, with relatively small voltage changes. It will also stabilise the output against changes in the input voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Strictly speaking, Zener diodes are low-voltage devices (up to about 5V6). Higher-voltage ones have a different mode of operation and are called avalanche diodes. Both types are commonly referred to as Zeners, though.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-21T19:40:07.620" LastActivityDate="2011-01-21T19:40:07.620" CommentCount="2" />
  <row Id="9282" PostTypeId="2" ParentId="9271" CreationDate="2011-01-21T19:47:29.463" Score="3" ViewCount="" Body="&lt;p&gt;One little nit: Only really sloppy developers use daily builds because one build a day means having to wait up to a day to find out if you broke the build.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best solution is to build and test every single change individually before letting it hit the public branch and revert the change if it breaks the build in any way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doing any sort of automatic testing on a schematic or a board layout might be very hard or impossible, but everything you can automate should be automated via something like Hudson, things that come to mind are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;ERC&lt;/li&gt;&#xA;&lt;li&gt;DRC&lt;/li&gt;&#xA;&lt;li&gt;BOM updating (check that the parts exist, are available and calculate total cost)&lt;/li&gt;&#xA;&lt;li&gt;Generate Gerbers and other manufacuring files.&lt;/li&gt;&#xA;&lt;li&gt;Generate PDFs of the schematic and PCB layers as well as 3d renderings of the PDB, BOM diff and other documentation.&lt;/li&gt;&#xA;&lt;li&gt;Drop a mail to the developer mailing list with the commit message and links to the output files, so developers can review the change easily.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The number of errors that can be caught automatically might not be terribly high, but having the CI system generate the output files means that it will happen correctly every time and that you don't forget some silly setting when doing it manually.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-01-21T19:47:29.463" CommentCount="1" />
  <row Id="9283" PostTypeId="2" ParentId="9271" CreationDate="2011-01-21T19:53:26.890" Score="1" ViewCount="" Body="&lt;p&gt;I suppose if your tools support it you could export netlists and do something with them that you find is very repetitive and mundane.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One useful thing I can think of is generating the bill of parts.  I used to work at a small company that would design the hardware schematics and netlists and specify the parts, and then we outsourced the layout to PCB design experts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We had a very helpful Excel VBA program to read in the netlist and generate the parts list from a database of parts.  &lt;/p&gt;&#xA;" OwnerUserId="2059" LastActivityDate="2011-01-21T19:53:26.890" />
  <row Id="9284" PostTypeId="2" ParentId="9190" CreationDate="2011-01-21T20:05:37.583" Score="0" ViewCount="" Body="&lt;p&gt;As was already stated if you want to be able to control how open it is then you will need some kind of linear actuator and a mechanical linkage to the lever that opens and closes the aperture. If you are just alternating between totally open and totally closed then an electro-magnet may work. A Google search for linear actuators may provide you with what you are looking for.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-01-21T20:05:37.583" />
  <row Id="9285" PostTypeId="2" ParentId="9272" CreationDate="2011-01-21T21:17:55.617" Score="5" ViewCount="" Body="&lt;p&gt;You aren't required to certify hobby stuff, but you still need to stay within guidelines.  You really need to spend some time on the FCC regulations, but the quick rundown is that really low power stuff may be allowed if it only radiates in certain bands (and certain very low power levels).  Higher power requires the &lt;em&gt;user&lt;/em&gt; to be licensed.  Exact license depends on the power level and band.  Some levels and bands are simply not permitted at all.  An amateur radio license gives one a pretty large area to play in (both band-wise and power-wise).&lt;/p&gt;&#xA;" OwnerUserId="1678" LastEditorUserId="1678" LastEditorDisplayName="" LastEditDate="2011-01-23T13:52:33.807" LastActivityDate="2011-01-23T13:52:33.807" />
  <row Id="9286" PostTypeId="2" ParentId="9264" CreationDate="2011-01-21T22:04:43.070" Score="2" ViewCount="" Body="&lt;p&gt;RealTerm, a freeware Windows terminal program, lists these UART rates in its Baud menu:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;110, 150, 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However these are actually bits per second (bps), not baud -- see below.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;110 baud was used by 8-level Teletypes like the ASR-33.  I'm not aware where 150 Baud was used, but it is a doubling of 75 baud, commonly used (along with 60 baud) for 5-level TTYs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;300 bps was the standard for the first widely-used telephone modems in the 1960's.  A number of 30 character per second terminals appeared at the same time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Above 300 bps/300 baud, which used simple frequency shift keying (FSK), the figures for bps and baud (symbols or tones per second) are not the same.  For example, a 1200 bps modem actually runs at 600 baud, and a 4800 bps modem runs at 1600 baud.  Refer to the table under Bandwidths in this &lt;a href=&quot;http://en.wikipedia.org/wiki/List_of_device_bandwidths&quot; rel=&quot;nofollow&quot;&gt;article&lt;/a&gt;.  The difference is because in addition to using a certain number of tone pulses per second, phase-shift keying and &lt;a href=&quot;http://en.wikipedia.org/wiki/Quadrature_Amplitude_Modulation&quot; rel=&quot;nofollow&quot;&gt;other methods&lt;/a&gt; are used to extract additional bandwidth from the same baud rate to get higher and higher bps. (So a 56K modem is actually only running at 8000 baud.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see, the list of UART rates essentially started at 75 and continually doubled (skipping 600), until getting to 38400, where it was multiplied by 1.5 to get 57600.  56K bps is the limit for an analog telephone line.  The higher rates 115200 upwards (once again doubling starting at 57600) are used for hard-wired connections.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As mikeselectricstuff mentioned, 14400 and 28800 bps were introduced as 1.5 x 9600 and 1.5 x 19200 when modems speeds couldn't be doubled at the time, but are seldom used anymore.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-01-22T00:27:55.603" LastActivityDate="2011-01-22T00:27:55.603" CommentCount="2" />
  <row Id="9287" PostTypeId="2" ParentId="9279" CreationDate="2011-01-21T22:26:00.313" Score="1" ViewCount="" Body="&lt;p&gt;BJT is usually asymmetrical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is no rules AFAIK, they all different there - so you need to test each type you need.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-21T22:26:00.313" />
  <row Id="9288" PostTypeId="1" AcceptedAnswerId="9292" CreationDate="2011-01-21T23:08:06.967" Score="4" ViewCount="344" Body="&lt;p&gt;I am (still) designing my first PCB and, according to prices listed on websites, the smaller the board the cheaper it is. That is, batchpcb charges per square inch. goldphoenix will print &quot;as many as they can&quot; on an 100 square inch board. Smaller is cheaper. Got it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So should I try to cram as much as I can in a small space? Obviously one can go overboard doing this, but in all reasonableness, the point stands. Is there a standard guide for minimum distances between components? And are the standards based &quot;this makes it easy to solder&quot; or more technical problems (capacitances, inductances, sparks across components) that are too close together?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, one comment on &lt;a href=&quot;http://www.sparkfun.com/products/9774&quot; rel=&quot;nofollow&quot;&gt;this board from sparkfun&lt;/a&gt; says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;These don't look like they're spaced&#xA;  at standard banana jack spacing. Isn't&#xA;  that important anymore?&quot;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&quot;its low current (5 amps) which&#xA;  shouldn't be enough to spark across&#xA;  the terminals at those voltages&quot;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&quot;I think the point is that most double&#xA;  banana plugs have a spacing of 0.75&quot;.&#xA;  The banana jack spacing on this board&#xA;  appears to be about 0.5&quot;.&quot;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;All implying that there the board has a poor design. But poor based on &lt;em&gt;what&lt;/em&gt;?&lt;/p&gt;&#xA;" OwnerUserId="1021" LastActivityDate="2011-03-04T18:44:54.867" Title="Is there a standard or &quot;safe&quot; distance between PCB components?" Tags="&lt;pcb-design&gt;" AnswerCount="6" CommentCount="2" />
  <row Id="9289" PostTypeId="2" ParentId="9279" CreationDate="2011-01-21T23:34:08.637" Score="1" ViewCount="" Body="&lt;p&gt;If you drive the base positive enough (assuming an NPN) what happens is the transistor 'saturates', and the collector voltage will dip to just a couple tenths above the collector. In this mode, the base-collector junction is actually forward biased, instead of reverse biased as is usually the case.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-01-21T23:34:08.637" />
  <row Id="9290" PostTypeId="2" ParentId="9288" CreationDate="2011-01-21T23:45:36.020" Score="1" ViewCount="" Body="&lt;p&gt;The minimum distance between components is obviously determined by how close you can place them, provided that you don't violate your board supplier's clearance between pads, and you are using typical voltages. You also need to provide room for the tracks between parts. You can use very narrow tracks and clearances between them, but that will push the price up, removing any savings you make on the board size. Like everything else connected with design, you need to come up with the best compromise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The above applies mainly to things like logic. Analogue and RF designs are much more dependent on layout, and need special consideration.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-21T23:52:01.913" LastActivityDate="2011-01-21T23:52:01.913" />
  <row Id="9291" PostTypeId="1" CreationDate="2011-01-21T23:58:29.010" Score="4" ViewCount="113" Body="&lt;p&gt;I am wondering if there is a circuit I can add to a low voltage DC motor or a 110VAC motor that will cut the power if the motor stalls.  I service coin op redemption games and on a few games these small AC/DC gear motors will jam and sit there and burn up.  I know about thermal protection but was wondering if there was something else simple that I can wire into the power leads of the motor that can detect a stall. Is there some type of fuse?? that would do this?  I did an experiment and jammed a motor while monitoring the current draw and it didn't make much of a difference. I would also like to avoid adding a optical wheel encoder type of thing because of the difficulty of mounting the device. One motor uses a Hall effect setup but it might be hard to mount it on other motors. Anything come to mind? &lt;/p&gt;&#xA;" OwnerUserId="2579" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-22T01:32:11.937" LastActivityDate="2011-01-22T01:32:11.937" Title="AC/DC motor stall protection after the fact." Tags="&lt;motor&gt;&lt;dc-motor&gt;&lt;protection&gt;" AnswerCount="1" />
  <row Id="9292" PostTypeId="2" ParentId="9288" CreationDate="2011-01-22T00:16:57.430" Score="4" ViewCount="" Body="&lt;p&gt;Beyond constraints due to voltages or minimum trace/space widths (all important), on a larger scale the mechanical size should be convenient and conform to standards or convention if applicable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, regarding banana plugs, 0.75&quot; is fairly standard for &lt;a href=&quot;http://www.google.com/products/catalog?q=double+banana+plug+to+bnc&amp;amp;hl=en&amp;amp;rlz=1C1CHMU_enUS354US377&amp;amp;prmd=ivns&amp;amp;resnum=3&amp;amp;biw=1618&amp;amp;bih=989&amp;amp;um=1&amp;amp;ie=UTF-8&amp;amp;cid=769823430409721939&amp;amp;ei=ux86TYOQNYHGlQfkx_TTDA&amp;amp;sa=X&amp;amp;oi=product_catalog_result&amp;amp;ct=result&amp;amp;resnum=2&amp;amp;ved=0CF8Q8wIwAQ#&quot; rel=&quot;nofollow&quot;&gt;some adapters&lt;/a&gt;, so while 0.5&quot; isn't inherently bad, it's possibly annoying to deal with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mounting holes should be easily accessible and fit common screw sizes (#4, #6, etc.).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Likewise, I strongly feel that a fairly popular prototype board is poorly designed because it has a non-integer multiple of 0.100&quot; spacing between two of its headers.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-22T00:16:57.430" CommentCount="1" />
  <row Id="9293" PostTypeId="1" AcceptedAnswerId="9300" CreationDate="2011-01-22T00:41:18.017" Score="7" ViewCount="805" Body="&lt;p&gt;I have a BluRay player that can be programmed by accessing to a serial console, as described &lt;a href=&quot;http://bd560.000space.com/hardware/hardware.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an Arduino (a Seeduino, actually), that has a USB interface. According to Arduino's documentation, pins 0 and 1 are RX and TX. Do these pins bypass from what the computer sends? Can I use the Arduino as a USB to serial interface for what I need?&lt;/p&gt;&#xA;" OwnerUserId="2712" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-20T22:21:01.633" LastActivityDate="2011-02-20T22:21:01.633" Title="Can I use an Arduino as a USB to serial interface?" Tags="&lt;arduino&gt;&lt;usb&gt;&lt;uart&gt;" AnswerCount="2" FavoriteCount="3" />
  <row Id="9294" PostTypeId="2" ParentId="9288" CreationDate="2011-01-22T00:46:44.300" Score="4" ViewCount="" Body="&lt;p&gt;There are IPC standards for component footprints.  I recall that there are variations, roughly normal, larger and smaller.  Those standards are based on &quot;easy to solder with machine assembly&quot;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-22T00:46:44.300" CommentCount="3" />
  <row Id="9295" PostTypeId="2" ParentId="9293" CreationDate="2011-01-22T01:09:43.913" Score="1" ViewCount="" Body="&lt;p&gt;The Arduino has only one UART, so it can't act as a bridge between the computer and the Blu-Ray.  I don't speak Polish, but from what I can tell on the site you'll have a lot more luck just using an FTDI USB-&gt;serial cable and connecting to the header.  I recommend the TTL-232RG-VIP-WE from FTDI, found here: &lt;a href=&quot;http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a wire-ended cable, so you'll need to attach some sort of header to it to be able to interface physically to the Blu-Ray, and you'll also need a connection to VCC and ground (so the cable can detect the proper voltage levels).  Then you just have to make sure that the computer's RX is connected to the Blu-Ray player's TX and the Blu-Ray player's RX is connected to the computer's RX.  Then use a serial terminal program to connect and go crazy.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-22T01:09:43.913" CommentCount="2" />
  <row Id="9296" PostTypeId="2" ParentId="9291" CreationDate="2011-01-22T01:14:28.103" Score="1" ViewCount="" Body="&lt;p&gt;For the DC motors a PTC resettable fuse can be put in series with the motor.  You'll have to find one that has hold current high enough to run the motor as normal, but trip current low enough to stop the current if it stalls AND also have maximum voltage greater to the maximum applied motor voltage.  An example of a PTC is here:  &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=F2152TR-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=F2152TR-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digikey has lots of PTCs available. Take a look.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-22T01:14:28.103" />
  <row Id="9297" PostTypeId="1" AcceptedAnswerId="9298" CreationDate="2011-01-22T02:14:27.470" Score="5" ViewCount="84" Body="&lt;p&gt;Maybe when I have the cash to buy one, I will. But my question is more related to how to use one once I've got it. I assume I'll need some kind of antenna to receive the EMI. Are there general rules for self-testing? (Before sending it off for proper FCC/CE/etc. validation.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-22T03:50:06.620" Title="If I buy a spectrum analyser, how do I do an EMI test?" Tags="&lt;analyser&gt;&lt;spectrum&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="9298" PostTypeId="2" ParentId="9297" CreationDate="2011-01-22T02:31:13.640" Score="5" ViewCount="" Body="&lt;p&gt;Hopefully someone can provide a better answer as I only do a quick test before going to a proper EMI testing facility for a first pass.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What i do is use a scope / spectrum analyzer capable of accuracy up to the frequencies i'm concerned about, make a small coil of low gauge wire, and attach it to the end of a probe.  I hover this probe over various sections of the circuit that I had preemptive concerns about (and the rest of it) to look for &quot;hot spots&quot; and use some judgement regarding how hot they are vs past situation with similar circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To ultimately &quot;do it right&quot; you need a spectrum analyzer, an antenna, and a &quot;dead room&quot; or testing box.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your continuing use of the equipment, the best answer may be to not buy the SA (unless you need it for something else too) and rather rent some time in a EMI testing facility, an hour or two with a EMC engineer will give you a very close to definitive answer as to whether or not you'll pass.  Unlimited hours without the proper facility will at best give you a &quot;decent idea&quot; of your chances.  &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-01-22T02:31:13.640" />
  <row Id="9299" PostTypeId="2" ParentId="9297" CreationDate="2011-01-22T03:50:06.620" Score="1" ViewCount="" Body="&lt;p&gt;There are two types of input EMI tests that are done: conducted and radiated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For conducted EMI, you need special hardware known as a LISN, or line impedance stabilization network which essentially standardizes the line impedance going to the unit under test and provides a connection point to the analyzer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For radiated EMI, you need a shielded room of sufficient size to hold the unit under test and an antenna sensitive to the frequencies you are testing at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are analyzers out there that are pre-programmed with all of the EMI settings you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can take a coaxial cable, bare some of the center conductor and make a loop connection to the shield, hook it up to a scope and use it to sniff for noise - prefab probes also exist on the market.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-01-22T03:50:06.620" />
  <row Id="9300" PostTypeId="2" ParentId="9293" CreationDate="2011-01-22T04:12:03.950" Score="6" ViewCount="" Body="&lt;p&gt;Take a look at this post by Ihsan Kehribar: &lt;a href=&quot;http://students.sabanciuniv.edu/kehribar/?p=19&quot; rel=&quot;nofollow&quot;&gt;Using Arduino as serial to usb converter&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this post it is shown that you can use the FTDI chip on the Seeeduino as a serial to usb converter, you just need to run a simple sketch to make sure the AVR does not interfere with the RX and TX lines.&lt;/p&gt;&#xA;" OwnerUserId="2489" LastActivityDate="2011-01-22T04:12:03.950" CommentCount="2" />
  <row Id="9301" PostTypeId="2" ParentId="9195" CreationDate="2011-01-22T10:30:48.680" Score="0" ViewCount="" Body="&lt;p&gt;A magnetometer will 'work' anywhere there is a magnetic field that is large enough to be detected by that particular sensor. This is determined by the noise floor of the sensor, i.e. the magnitude at which the S/N ratio is large enough that the signal information can be recognized over the system noise level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And direction matters. Even for vector sensors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think that there is anywhere on Earth, or in the Solar System inside of the orbit of Venus, where, say, a squid (or a SERF) couldn't detect a magnetic field. I think there are many fluxgates that could detect a magnetic field anywhere on Earth (which, off the top of my head, is around 0.5 Gauss - a very large value).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The important thing to recall is that there are around a dozen major classes of magnetic sensors and they all have different specs, the main one being the resolution (i.e. the smallest signal they can detect, - the noise floor).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why do you want to find a place they don't work? &lt;/p&gt;&#xA;" OwnerUserId="2122" LastActivityDate="2011-01-22T10:30:48.680" />
  <row Id="9302" PostTypeId="2" ParentId="9246" CreationDate="2011-01-22T10:48:38.573" Score="2" ViewCount="" Body="&lt;p&gt;The one you picture here is a polymer film that has conducting particles held within it (think of something like novolac resist or SU8 with metal micro-particles evenly distributed within it). The film has a non-zero conductivity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you press on it some of the micro-particles touch, increasing the conductivity. Pretty simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not the same as the piezo-resistive effect, which depends on the shape of a crystal lattice in the atomic structure. when you bend it, the crystal lattice either expands or contracts, causing the resistance to increase or decrease because of a slight change in the energy bands of the crystal.&lt;/p&gt;&#xA;" OwnerUserId="2122" LastActivityDate="2011-01-22T10:48:38.573" />
  <row Id="9303" PostTypeId="1" AcceptedAnswerId="9315" CreationDate="2011-01-22T10:56:30.317" Score="2" ViewCount="54" Body="&lt;p&gt;I have a loginway PIC-01 Development board (it was sat in a cupboard for years).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does this board require additional adaptor hardware to blow a PIC (ICSP stuff etc), or can the on board serial port be used to do that?&lt;/p&gt;&#xA;" OwnerUserId="2326" LastActivityDate="2011-01-22T13:16:32.533" Title="Can a loginway PIC-01 development board program a PIC?" Tags="&lt;pic&gt;&lt;development&gt;&lt;board&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9304" PostTypeId="1" AcceptedAnswerId="9305" CreationDate="2011-01-22T11:18:07.717" Score="0" ViewCount="107" Body="&lt;p&gt;I am after grabbing an Arduino kit in kind of a hurry, does anyone here know somewhere around London I'd be able to go and pick them up over the counter. Maplin doesn't stock anything.&lt;/p&gt;&#xA;" OwnerUserId="2326" LastActivityDate="2011-01-22T12:34:18.513" ClosedDate="2011-01-22T14:16:22.500" Title="Anywhere in London I can pick up an Arduino kit on the high street?" Tags="&lt;arduino&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="9305" PostTypeId="2" ParentId="9304" CreationDate="2011-01-22T11:29:38.300" Score="2" ViewCount="" Body="&lt;p&gt;Check out &lt;a href=&quot;http://uk.rs-online.com/web/generalDisplay.html?id=arduino&amp;amp;cm_sp=ukpromoblock-_-extendedcontent-_-arduino&quot; rel=&quot;nofollow&quot;&gt;RS&lt;/a&gt;. They have 4 Locations in London(not central), Watford, Gatwick, Bow and Heathrow. Click on trade counters for their locations. Also the link links you to the Ardunio page at RS. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-01-22T11:29:38.300" />
  <row Id="9306" PostTypeId="1" CreationDate="2011-01-22T11:57:04.220" Score="4" ViewCount="102" Body="&lt;p&gt;I am a little confused, since the &lt;a href=&quot;http://en.wikipedia.org/wiki/Rake_receiver&quot; rel=&quot;nofollow&quot;&gt;Rake Receiver&lt;/a&gt; has one finger for each &lt;a href=&quot;http://en.wikipedia.org/wiki/Multipath_propagation&quot; rel=&quot;nofollow&quot;&gt;multipath&lt;/a&gt; path, and the channel estimator models the impulse response of the channel and can be used to find the multipaths, why do I still need a Path Searcher?&lt;/p&gt;&#xA;" OwnerUserId="2714" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-22T18:24:44.453" LastActivityDate="2011-01-29T18:46:58.577" Title="In a RAKE receiver, why is a Path Searcher needed? Can't the delays be found from the Channel Estimator?" Tags="&lt;wireless&gt;&lt;radio&gt;&lt;receiver&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="9307" PostTypeId="1" AcceptedAnswerId="9308" CreationDate="2011-01-22T12:09:47.480" Score="4" ViewCount="385" Body="&lt;p&gt;I'm designing a device powered from USB. The device uses FTDI FT2232 chip for USB connection. Upon a command from a computer FT2232 chip should enable power via a MOSFET switch to rest of the circuit. This additional circuit has a capacitance of 50uF (FPGA + aux stuff) and is powered from the same USB port. After the switch is turned on, this additional 50uF capacitance will sink a huge current until it's charged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How to limit this inrush current 1) to avoid voltage drop on power rails and 2) to avoid USB PTC from disconnecting power to the device?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it enough to put a ferrite bead in series with MOSFET switch to limit the inrush current? Or should I use a special chips, like chips for limiting current or chips for slew rate control? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: all devices are powered from 3.3V. So a small drop on 5V rail should not be a problem if it does not prevent an LDO to output stable 3.3V.&lt;/p&gt;&#xA;" OwnerUserId="1932" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-25T18:13:24.210" LastActivityDate="2011-01-25T18:13:24.210" Title="How to limit inrush current?" Tags="&lt;power-supply&gt;&lt;transient-suppression&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="9308" PostTypeId="2" ParentId="9307" CreationDate="2011-01-22T12:25:31.953" Score="6" ViewCount="" Body="&lt;p&gt;Use an RC circuit in the MOSFET gate to slow downthe turn-on - I think some of the FTDI example circuits have examples of this.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-22T12:25:31.953" CommentCount="2" />
  <row Id="9309" PostTypeId="2" ParentId="9304" CreationDate="2011-01-22T12:29:16.380" Score="0" ViewCount="" Body="&lt;p&gt;RS Trade counters rarely stock electronic type stuff IME. They've also stopped opening on Saturday mornings.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-22T12:29:16.380" />
  <row Id="9310" PostTypeId="2" ParentId="9304" CreationDate="2011-01-22T12:34:18.513" Score="0" ViewCount="" Body="&lt;p&gt;You should be able to get one by Tuesday if you order from the Farnell or RS web site.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-22T12:34:18.513" />
  <row Id="9311" PostTypeId="2" ParentId="9303" CreationDate="2011-01-22T12:36:27.920" Score="0" ViewCount="" Body="&lt;p&gt;Forget it and buy a Microchip PICkit 2 or 3 (under $50). They offer debugging as well as programming, and the latter supports all the current devices.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-22T12:36:27.920" />
  <row Id="9312" PostTypeId="1" AcceptedAnswerId="9317" CreationDate="2011-01-22T13:07:32.603" Score="0" ViewCount="42" Body="&lt;p&gt;I'm looking for a supplier that will sell digital gyro and acceleration sensors individually inside Germany (or even Europe would do). Does anyone know any good suppliers?&lt;/p&gt;&#xA;" OwnerUserId="2251" LastActivityDate="2011-01-22T13:39:46.180" ClosedDate="2011-01-22T14:17:28.660" Title="Inertial MEMS sensors in Germany" Tags="&lt;sensor&gt;&lt;parts&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="9313" PostTypeId="2" ParentId="9288" CreationDate="2011-01-22T13:12:28.773" Score="0" ViewCount="" Body="&lt;p&gt;Take a look at the pricing here, you get flat rate for 10 pcbs of either max 10x10 cm or 5x5 cm, so as long as you get below the 10x10 or 5x5 limit you're ok:&#xA;&lt;a href=&quot;http://iteadstudio.com/store/index.php?main_page=index&amp;amp;cPath=19_20&quot; rel=&quot;nofollow&quot;&gt;http://iteadstudio.com/store/index.php?main_page=index&amp;amp;cPath=19_20&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-01-22T13:12:28.773" />
  <row Id="9314" PostTypeId="1" AcceptedAnswerId="9316" CreationDate="2011-01-22T13:14:22.770" Score="2" ViewCount="141" Body="&lt;p&gt;Hi all, &#xA;I wonder if I could perform floating point operations in a Microblaze controller?&#xA;Thank you to all posible answers with direct references to documentation or articles.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-22T23:59:54.527" LastActivityDate="2011-01-22T23:59:54.527" Title="Microcontrollers: Can I perform floating point operations in a Microblaze controller?" Tags="&lt;microcontroller&gt;&lt;floating-point&gt;&lt;microblaze&gt;" AnswerCount="2" />
  <row Id="9315" PostTypeId="2" ParentId="9303" CreationDate="2011-01-22T13:16:32.533" Score="2" ViewCount="" Body="&lt;p&gt;Yes, it requires additional hardware to program a new PIC (as indicated in the &lt;a href=&quot;http://loginway.com/pdf/manual.pdf&quot; rel=&quot;nofollow&quot;&gt;manual&lt;/a&gt;). &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2519&amp;amp;param=en534451&amp;amp;page=wwwdevMPLABEmulatorDebuggers&quot; rel=&quot;nofollow&quot;&gt;PICkit&lt;/a&gt; is one such with good features for the price, including debugging, serial communication and logging. Once you have a way to program your PIC, it can communicate through the serial port; this could be used to implement a &lt;a href=&quot;http://www.etc.ugal.ro/cchiculita/software/picbootloader.htm&quot; rel=&quot;nofollow&quot;&gt;bootloader&lt;/a&gt; in self programming capable chips, the way boards like Arduino work. Your Loginway PIC-01 is a pretty good host board to build on, and certainly more featureful than the host board in the PICkit bundle.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2011-01-22T13:16:32.533" CommentCount="1" />
  <row Id="9316" PostTypeId="2" ParentId="9314" CreationDate="2011-01-22T13:37:32.640" Score="3" ViewCount="" Body="&lt;p&gt;Floating-point operations are available, see &lt;a href=&quot;http://www.xilinx.com/support/documentation/sw_manuals/mb_ref_guide.pdf&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; document. Try the Xilinx forums for support.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-22T13:37:32.640" CommentCount="1" />
  <row Id="9317" PostTypeId="2" ParentId="9312" CreationDate="2011-01-22T13:39:46.180" Score="1" ViewCount="" Body="&lt;p&gt;Farnell and RS stock a wide range of such parts.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-22T13:39:46.180" CommentCount="1" />
  <row Id="9318" PostTypeId="2" ParentId="9307" CreationDate="2011-01-22T14:01:42.650" Score="3" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.usb.org/developers/docs/&quot; rel=&quot;nofollow&quot;&gt;USB specification&lt;/a&gt; chapter 11, Interoperability and Power Delivery, places rather stringent limits on power draw. The cited capacitance there is only 10µF, to avoid too much voltage drop. There are specialized ICs (like &lt;a href=&quot;http://www.national.com/mpf/LM/LM3525.html#Overview&quot; rel=&quot;nofollow&quot;&gt;LM3525&lt;/a&gt;) to do both current limiting and power switching, which might help, but make sure the circuitry behind it handles the slow voltage rise correctly. A brown-out detector may be enough, but a few devices require many voltages in specific orders.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2011-01-22T14:01:42.650" />
  <row Id="9320" PostTypeId="2" ParentId="9266" CreationDate="2011-01-22T14:37:50.617" Score="3" ViewCount="" Body="&lt;p&gt;As anything, the answer really depends on what the project is and in which environment you're developing. The process will be different if it's a senior project or a commercial board bring-up, for example. Since you have not given details about your particular environment, here are some general unordered guidelines I can think of that may help:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Write down a plan and show it to anyone who would look at it -- take note of their advice and adopt what seems logical to you. There's definitely room for personal preference here.&lt;/li&gt;&#xA;&lt;li&gt;Create milestones for the project and estimate how long they will take to achieve.&lt;/li&gt;&#xA;&lt;li&gt;Decide on a time multiplier (this ranges from x2 to x5 and depends on your experience) and apply it to your timing predictions. This will give you a buffer, and ultimately be more realistic -- most people grossly underestimate the time and effort it takes to accomplish something, and many things are out of your control.  &lt;/li&gt;&#xA;&lt;li&gt;Document all the problems you've encountered, and how you solved them. This will help you in the future, and in writing a report if you're required to.&lt;/li&gt;&#xA;&lt;li&gt;Getting supplies takes time, and sometimes stocks run out just as you want to place an order. When you design a component into your system, make sure you can source it reliably!&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I hope this helps a little bit, and good luck.&lt;/p&gt;&#xA;" OwnerUserId="2531" LastActivityDate="2011-01-22T14:37:50.617" CommunityOwnedDate="2011-01-22T14:37:50.617" />
  <row Id="9321" PostTypeId="1" CreationDate="2011-01-22T15:38:17.367" Score="9" ViewCount="264" Body="&lt;p&gt;There are hundreds of prefixes in IC names, &lt;a href=&quot;http://en.wikibooks.org/wiki/Practical_Electronics/Manufacturers_Prefix&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; lists a number of them. For some it's easy to see that they refer to the manufacturer's name, like &lt;code&gt;AD&lt;/code&gt; for Analog Devices or &lt;code&gt;LT&lt;/code&gt; for Linear Technology. Others can be found with several manufacturers, often three letter prefixes: &lt;code&gt;SAA&lt;/code&gt;, &lt;code&gt;SAF&lt;/code&gt;, &lt;code&gt;SDA&lt;/code&gt;, &lt;code&gt;TCA&lt;/code&gt; and &lt;code&gt;TDA&lt;/code&gt;, to name a few. I wonder if there's some logic in this, like &lt;code&gt;T**&lt;/code&gt; being a specific group with subgroup &lt;code&gt;TD*&lt;/code&gt;, etc. Is there a logical structure?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-03-16T13:57:24.477" Title="Is there some logic in IC name prefixes?" Tags="&lt;identification&gt;" AnswerCount="5" FavoriteCount="4" />
  <row Id="9322" PostTypeId="1" AcceptedAnswerId="9327" CreationDate="2011-01-22T17:21:59.757" Score="5" ViewCount="598" Body="&lt;p&gt;Hi all, I'm very happy I found this place! &#xA;Some questions in my workflow that make them together unique, but separately perhaps valuable to general public as well:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;1] VOLTAGE: 3.6V or 3.7V - 18650 Li Ion Batteries&lt;/strong&gt;&lt;br&gt;&#xA;Are all 18650 lithium ion battery cells 3.6 or 3.7 volts or do they differ?&#xA;I want to replace my current SIGMA DP2 photocamera battery (3.7 1300mAh) with a 18650 2900 mAh battery, sometimes rated 3.6V sometimes 3.7V. (I am not sure whether information provided on eBay is accurate as I have seen conflicting data.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;2] Possible Voltage Shortage?&lt;/strong&gt;&lt;br&gt;&#xA;Does it matter for my project or can i use 3.6 without any Voltage shortage for the camera? In other words, do all 3.6/3.7V li ions use the same way therefore the given voltage is just the same or do they really differ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;3] Fundamental Reason for this Voltage Range&lt;/strong&gt;&lt;br&gt;&#xA;Why do we see only 3.6/3.7 V per Li Ion Cell, and never 3.0V or 4 V per cell?&#xA;I am very curious...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;4] Parallel Cell Charging - One BIG Li-Ion Battery Pack&lt;/strong&gt;&lt;br&gt;&#xA;I was thinking of putting two, or three of those Panasonic/Sanyo 18650 Li Ion cells in parallel, soldering together from the instant the are new, that way giving me about 5800 mAh (2 pcs x 46 grams = 92 grams) or about 8700 mAh (3 pcs x 46 = 1 grams) very light. Equaling to bypassing seven orso charges with my old li ion battery. Is this correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;5] Charging... How?&lt;/strong&gt;&lt;br&gt;&#xA;I found a nice small cheap charger about 30~40$ called Turnigy Accucel-6 (there is also an Accucel-8 for double price and double weight) . Could I attach the + to + of all the cells and the - to all the - poles of the cells without needing any extra in-between-wiring?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks a lot for your opinion.&lt;/p&gt;&#xA;" OwnerUserId="2719" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:12:21.380" LastActivityDate="2011-05-11T20:10:46.880" Title="3.6 or 3.7 Volts: Why 18650 Lithium Ion Battery Cells Differ in Voltage?" Tags="&lt;battery&gt;&lt;battery-charging&gt;&lt;lithium-ion&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="9323" PostTypeId="2" ParentId="9322" CreationDate="2011-01-22T17:58:31.277" Score="1" ViewCount="" Body="&lt;p&gt;The nominal voltage of Li-ion cells is 3.6V-3.7V, depending on the manufacturing technique. I doubt if you will see any difference between one delivering 3.6V and one delivering 3.7V, in practice, as there are many other factors involved.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-22T18:03:47.840" LastActivityDate="2011-01-22T18:03:47.840" CommentCount="1" />
  <row Id="9324" PostTypeId="1" CreationDate="2011-01-22T18:14:37.930" Score="3" ViewCount="241" Body="&lt;p&gt;How many transistors/logic gates are used in the signal path between a TV studio and the restitution of the image on my HD-TV ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You see what I mean ? I need a rough estimation...:-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I especially want to estimate the number of purely digital-purpose transistors (logic gates) : that means how many SoCs (system-on-chip) are needed in the capture-&gt;mpeg encoding-&gt;transmission(source,channel coding)-&gt;etc..-&gt;mpeg decoding, and how many gates are in these SoCs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe some of you know partially (on one of those chips) how many gates are involved.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Together, maybe we can try to count them ?&lt;/p&gt;&#xA;" OwnerUserId="2720" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-05-02T07:45:03.650" LastActivityDate="2011-05-02T07:45:03.650" Title="How many transistors/logic gates are used in the signal path between a TV studio and the restitution of the image on my HD-TV ?" Tags="&lt;system-on-chip&gt;&lt;vlsi&gt;&lt;programmable-logic&gt;" AnswerCount="2" CommentCount="7" FavoriteCount="1" />
  <row Id="9325" PostTypeId="1" AcceptedAnswerId="10345" CreationDate="2011-01-22T18:26:59.630" Score="5" ViewCount="245" Body="&lt;p&gt;I need to modulate a diode laser with a RF source. I've found parts on Minicircuits that can do this, but I'd like to have the Bias-T and amp on my own PCB. So, I need to design a bias-T circuit that will mix my constant current source with the RF source to drive the laser. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm having a hard time choosing the capacitor and inductor values for the Bias-T, since I don't know the load impedance of the diode laser. How can I find this out? Would it just be better to put a 50 ohm resistor in parallel with the diode and then design the Bias-T for a 50 ohm load?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;: After some thought, it seems reasonable to use the I/V characteristics of the diode, after turn-on, to approximate the resistance. This yields a very low value - 5-10 ohms. This, however, doesn't approximate the load while the diode is off - I assume this would be very high. But, the purpose of the Bias-T would be to bias the diode so it's always on, so I presume just the on characteristics would be sufficient. Sound reasonable? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update 2&lt;/strong&gt;:  My design needs to supply ~200 mA to the diode. It's a 405 nm diode, so the operating voltage is ~4-5.5 v. I have a wide bandwidth, so anywhere from a Fc of 5 Mhz to 50 MHz will probably work. My transmit bandwidth is about 2 MHz.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastEditorUserId="2454" LastEditorDisplayName="" LastEditDate="2011-02-21T17:41:58.923" LastActivityDate="2011-02-21T17:41:58.923" Title="I need to design a Bias-T circuit for a diode laser - help choosing component values" Tags="&lt;circuit&gt;&lt;rf&gt;&lt;laser&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="1" />
  <row Id="9326" PostTypeId="2" ParentId="6297" CreationDate="2011-01-22T18:34:38.137" Score="1" ViewCount="" Body="&lt;p&gt;Contact Maxim-IC and ask for their whitepaper number &quot;HFRD40&quot;. It describes a laser rangefinder using time-of-flight. Straightforward to build. It basically uses a time-to-voltage converter (charge a cap) to measure the TOF of a bunch of laser pulses (to average out noise) then uses an ADC to measure the voltage on the cap. Their whitepaper has a complete design. They sent me one of their test units a while back, because I was looking at building one for a scanning lidar system, but ran out of time. You can see some more discussion here: &lt;a href=&quot;http://forums.trossenrobotics.com/showthread.php?t=4357&quot; rel=&quot;nofollow&quot;&gt;http://forums.trossenrobotics.com/showthread.php?t=4357&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-01-22T18:34:38.137" CommentCount="4" />
  <row Id="9327" PostTypeId="2" ParentId="9322" CreationDate="2011-01-22T21:11:49.333" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;1] VOLTAGE: 3.6V or 3.7V - 18650 Li Ion Batteries&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All single cell lithium ion batteries are going to be 3.6-3.7v. There are applications where multiple cells will be tied together in series. This will result in voltages that are multiples of 3.6-3.7v. So as long as you match the number of cells and approximate mAH you should be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;2] Possible Voltage Shortage?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The voltages and battery life responses for all batteries are going to have slight difference. For the most part this won't matter. Most projects that use batteries are not terribly voltage dependent. They will either boost or regulate their voltage to get the voltage they want out, or they will be able to run at a wide range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a note, &quot;Shortage&quot; in this context usually means you are creating a short across your battery. Might want to be careful with that terminology.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;3] Fundamental Reason for this Voltage Range&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not an expert on this, but I know it deals with the chemistry of the battery itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;4] Parallel Cell Charging - One BIG Li-Ion Battery Pack&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This can be done. There are some issues that can come up when doing it. This might be worthy of a question by itself. If you do ask, might want to ask if the same can be done for packs in series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;5] Charging... How?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same as previous answer.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-22T21:54:00.777" LastActivityDate="2011-01-22T21:54:00.777" CommentCount="1" />
  <row Id="9328" PostTypeId="2" ParentId="9324" CreationDate="2011-01-22T22:02:09.983" Score="7" ViewCount="" Body="&lt;p&gt;Here are the functional blocks:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Video camera&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;1920x1080 pixels, CCD, modeled as DRAM for simplicity, giving 1920&lt;sup&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/sup&gt;1080=2073600T&lt;/li&gt;&#xA;&lt;li&gt;columns dump to analog multiplexors, which I'll guess to have 1080&lt;sup&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/sup&gt;10=10800T&lt;/li&gt;&#xA;&lt;li&gt;1080/2^3=135 ADC blocks -- will make them 24-bit delta-sigma ADCs, giving it around 135&lt;sup&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/sup&gt;(24&lt;sup&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/sup&gt;2+50)=13230T&lt;/li&gt;&#xA;&lt;li&gt;memory buffer should hold at least 2 frames, giving 24&lt;sup&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/sup&gt;1920&lt;sup&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/sup&gt;1080=49766400T&lt;/li&gt;&#xA;&lt;li&gt;high speed bus driver will add another 10^3T or so&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Encoding DSP&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;x264 codec requires 32-bit DSP processor with ??? T&lt;/li&gt;&#xA;&lt;li&gt;should buffer (SRAM) at least 10 frames for codec compression, giving 10*9*49766400=4478976000T&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Transmission&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Going with 2 Windows PCs to prep the stream and send it to a server, then 5 LAMP servers to get it to the end user, giving 7&lt;sup&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/sup&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/File%3aTransistor_Count_and_Moore%27s_Law_-_2008.svg&quot; rel=&quot;nofollow&quot;&gt;2000000000&lt;/a&gt;=14000000000T&lt;/li&gt;&#xA;&lt;li&gt;modems and switches ignored&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Decoding DSP&lt;/strong&gt;: make equal to encoding&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Display&lt;/strong&gt;: make equal to capture&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;T&lt;sub&gt;&lt;sup&gt;OTAL&lt;/sup&gt;&lt;/sub&gt;&lt;/strong&gt;:&lt;/em&gt; 23061682060 transistors&lt;br&gt;&#xA;&lt;strong&gt;&lt;em&gt;E&lt;sub&gt;&lt;sup&gt;RROR&lt;/sup&gt;&lt;/sub&gt;&lt;/strong&gt;:&lt;/em&gt; ±2628%, possible error in error calculation&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-22T22:02:09.983" CommentCount="7" />
  <row Id="9329" PostTypeId="1" CreationDate="2011-01-22T22:54:12.567" Score="0" ViewCount="343" Body="&lt;p&gt;Make C program for Atmega16; program should enable Atmega16 to turn on led diode 3 (pin 0C0) each 3 seconds at the port B and hold this diode turned on for 3 seconds which is possible by pressing switch 0 on pin 0,port D. If the switch is pressed for 0 to 5 seconds then the state of led diode is changing inside 3 seconds. If we press switch 1 then the duration time of light on diode 3 is becoming shorter following the same rule as for switch 0. The number of changed states (switching on and off) of the diode should be represented in BCD code at the diodes 4,5,6,7. When this number comes to a value 9 (nine), it should be reduced to a zero. This problem should be solved using hardware and software timer and using interrupts. &lt;/p&gt;&#xA;" OwnerUserId="2721" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T09:53:13.310" LastActivityDate="2011-01-23T09:53:13.310" ClosedDate="2011-01-24T02:49:30.847" Title="Atmega16 stk500 project:" Tags="&lt;atmega&gt;&lt;stk500&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="9330" PostTypeId="1" AcceptedAnswerId="9358" CreationDate="2011-01-22T22:57:11.527" Score="2" ViewCount="222" Body="&lt;p&gt;I'd like to hear some explanations as to how the Arduino Duemilanove resets the ATMega328P over USB through the FTDI FT232R transceiver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know it involves the IDE playing some games with the DTR serial handshaking signal. After looking at the schematics, what I'm really interested in getting a better handle on is how the circuit works:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;        100nF           10kOhm&#xA;DTR -----||------+------^v^v^----- VCC&#xA;                 |&#xA;                 +--/RESET&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The 10k resistor is the usual pull-up on the reset line. So what does the capacitor accomplish in this circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a sidenote, I used this as an excuse to try and learn/use LTSPICE, so I'm no pro at this tool. I modeled it in LTSPICE as follows, but it looks to me like the /RESET signal just matches the DTR signal exactly, which doesn't really make sense to me. I modeled the DTR signal as a Pulse Voltage source, maybe that's the wrong model. Is it the nature of the FTDI's DTR driver (e.g. perhaps it's open collector) or the internals of the /RESET pin on the MCU that are not present in the circuit I've drawn that make this all hang together electrically?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/xF7td.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, here are some of the relevant links to datasheets and schematics for reference.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf&quot; rel=&quot;nofollow&quot;&gt;FTDI FT232RL datasheet&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8271.pdf&quot; rel=&quot;nofollow&quot;&gt;ATMega328P datasheet&lt;/a&gt; [Arduino&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf&quot; rel=&quot;nofollow&quot;&gt;Duemilanove schematics&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-22T23:58:14.690" LastActivityDate="2011-01-24T02:21:00.547" Title="How does the Arduino Deumilanove Auto-Reset Function work?" Tags="&lt;arduino&gt;&lt;reset&gt;&lt;ltspice&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="9331" PostTypeId="2" ParentId="9314" CreationDate="2011-01-22T23:35:32.607" Score="2" ViewCount="" Body="&lt;p&gt;Any microcontroller can implement floating point, it is just that those with hardware can do it much much faster. The compiler can do the required work to get options like floating point division, it can just take 1000s of clock cycles.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-01-22T23:35:32.607" CommentCount="3" />
  <row Id="9332" PostTypeId="2" ParentId="9322" CreationDate="2011-01-23T00:06:14.447" Score="3" ViewCount="" Body="&lt;p&gt;Well, actually I was also interested here.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Rated voltage might be rated different to make it serve more in expense of capacity.&lt;/li&gt;&#xA;&lt;li&gt;LiIon batteries have lots of variants of chimestry - all are LiIon, but different voltages, prices, reliability.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;&lt;pre&gt;&lt;code&gt;LiCoO2    3.7 V   140 mA·h/g  0.518 kW·h/kg&#xA;LiMn2O4   4.0 V   100 mA·h/g  0.400 kW·h/kg&#xA;LiNiO2    3.5 V   180 mA·h/g  0.630 kW·h/kg&#xA;LiFePO4   3.3 V   150 mA·h/g  0.495 kW·h/kg&#xA;Li2FePO4F     3.6 V   115 mA·h/g  0.414 kW·h/kg&#xA;LiCo1/3Ni1/3Mn1/3O2   3.6 V   160 mA·h/g  0.576 kW·h/kg&#xA;Li(LiaNixMnyCoz)O2    4.2 V   220 mA·h/g  0.920 kW·h/kg&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Lithium-ion_battery#Positive_electrodes&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Lithium-ion_battery#Positive_electrodes&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-23T00:06:14.447" CommentCount="2" />
  <row Id="9333" PostTypeId="2" ParentId="9329" CreationDate="2011-01-23T02:48:32.320" Score="0" ViewCount="" Body="&lt;p&gt;Well, this isn't the answer to this particular question, it's more general thoughts on the subject.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First thing you need to do is to familiarize yourself with the system you're using. Check out the board, try to follow the traces, if possible (I don't have STK 500, so I don't know how easy it is to read.) and see which parts of the board are connected to which pins. Next, read the datasheet for ATMega16. &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?PN=ATmega16&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;'s the product page. Since you cant figure out how to make even a basic program such as the one you listed, don't panic if you can't understand half or more of the datasheet. It will come with time. By now you should have some idea how ATMega16 works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next step is to set up your shop. Maybe your school already has list of preferred programs which are to be used. It is has, read it. If not, then try with &lt;a href=&quot;http://winavr.sourceforge.net/helpme.html&quot; rel=&quot;nofollow&quot;&gt;WinAVR&lt;/a&gt; for start. On the page I linked are some tutorials on how to get it running.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After setting up WinAVR, you should start with programming. There are &lt;a href=&quot;http://www.google.com/search?q=WinAVR+tutorial&amp;amp;ie=utf-8&amp;amp;oe=utf-8&amp;amp;aq=t&amp;amp;rls=org.mozilla%3aen-US%3aofficial&amp;amp;client=firefox-a#sclient=psy&amp;amp;hl=sr&amp;amp;client=firefox-a&amp;amp;hs=RYq&amp;amp;rls=org.mozilla%3aen-US%3Aofficial&amp;amp;q=AVR+C+tutorial&amp;amp;aq=f&amp;amp;aqi=&amp;amp;aql=&amp;amp;oq=&amp;amp;pbx=1&amp;amp;fp=e2c44aa287cbd7ed&quot; rel=&quot;nofollow&quot;&gt;tons of tutorials&lt;/a&gt;, &lt;a href=&quot;http://imakeprojects.com/Projects/avr-tutorial/&quot; rel=&quot;nofollow&quot;&gt;but&lt;/a&gt; &lt;a href=&quot;http://www.avr-asm-tutorial.net/avr_en/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; &lt;a href=&quot;http://paul.graysonfamily.org/thoughts/avrlinux/&quot; rel=&quot;nofollow&quot;&gt;are&lt;/a&gt; &lt;a href=&quot;http://kartikmohta.com/tech/avr/tutorial/&quot; rel=&quot;nofollow&quot;&gt;few&lt;/a&gt; &lt;a href=&quot;http://www.ladyada.net/learn/avr/avrdude.html&quot; rel=&quot;nofollow&quot;&gt;I liked&lt;/a&gt;. Some of them are for assembly. Since you need o do it in C, it don't pay too much attention to them, just read them and try to understand basis of how it works on the inside. There's also &lt;a href=&quot;http://electronics.stackexchange.com/q/5302/1240&quot;&gt;this&lt;/a&gt; question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After this, you'll probably be able to ask good specific questions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, make sure that you separate your problem into small components. People generally aren't going to do something this big for you if you just ask. Instead, you should try to keep your objectives simple. For example, program the AVR so that it starts and turns on an LED. After that program it so that it turns on LED after some time. After that program it so that it flashes LED with certain frequency. After that have it flash several LED. After that have it read status on a button and turn an LED on or off depending on the button state. After that have it switch between flashing LED and on LED depending on the duration of the button press. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you turn this into simple tasks, you'll be able to easily find out what's the problem with each task and then you'll be able to do some research on how to solve the problem. You're more likely to get specific help with each problematic step on the Internet forums this way too. As I said, people generally don't want to do whole homework tasks, but if you ask for example:&quot;My LED is on for 2 seconds, but I want to keep it on for 5 seconds. I did XXX to turn it on. What did I do wrong?&quot; or something similar, chances are higher that you'll get specific help on that problem.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-01-23T02:48:32.320" />
  <row Id="9334" PostTypeId="2" ParentId="8214" CreationDate="2011-01-23T05:08:31.833" Score="1" ViewCount="" Body="&lt;p&gt;XC was the designator used by Motorola for their pre-release parts (experimental?), generally parts were developed as XCxxxx then released as MCxxxx.&lt;/p&gt;&#xA;" OwnerUserId="820" LastActivityDate="2011-01-23T05:08:31.833" CommentCount="1" />
  <row Id="9336" PostTypeId="1" AcceptedAnswerId="9337" CreationDate="2011-01-23T09:23:55.380" Score="1" ViewCount="152" Body="&lt;p&gt;Is it OK if I use the controller from a CPU fan without connecting the motor's coils?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All I want is to use the Hall effect sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet is posted &lt;a href=&quot;http://goo.gl/6atkj&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, the driving output circuit uses a darlington pair.&lt;/p&gt;&#xA;" OwnerUserId="2733" LastActivityDate="2011-01-23T10:30:53.280" Title="Using a 4-pin computer fan controller without the load" Tags="&lt;sensor&gt;&lt;transistor&gt;&lt;cpu&gt;&lt;hall-effect&gt;&lt;fan&gt;" AnswerCount="1" />
  <row Id="9337" PostTypeId="2" ParentId="9336" CreationDate="2011-01-23T10:30:53.280" Score="3" ViewCount="" Body="&lt;p&gt;I don't see from datasheet how to use hall sensor separately, but noone should die or explode if you would not connect the load (in the worst case you may connect some resistor as a tiny load).&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-23T10:30:53.280" />
  <row Id="9338" PostTypeId="1" CreationDate="2011-01-23T13:30:20.563" Score="2" ViewCount="106" Body="&lt;p&gt;I have an old settop box, model - humax nd 1000c. I no longer use it for my TV since the city I've moved to doesnt have the relevant service provider (afaik).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to try and hack into the box to just fiddle around with its OS (I believe it to be some flavor of embedded linux) and use it in my robotics projects if possible. I've done a large amount of surfing on the web but haven't really found anything I can use to get ahead. Plus, the fact that the box doesnt have a serial/parallel/usb out compounds my problem. It just has a i/p for a co-ax cable (I assume) and RCA o/p's. Is there any way I can interface with this guy?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me know if a picture or other details will help.&lt;/p&gt;&#xA;" OwnerUserId="1143" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-23T16:51:59.537" LastActivityDate="2011-01-23T16:51:59.537" Title="Humax ND 1000 C set top box" Tags="&lt;robotics&gt;&lt;embedded&gt;&lt;linux&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9340" PostTypeId="1" AcceptedAnswerId="9342" CreationDate="2011-01-23T14:59:25.020" Score="6" ViewCount="275" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to pass some data over an audio cable (i.e from audio card to my cellphone) with a short cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for some ideas for algorithms for achieving this. They of course should include the proper modulation technique to transfer the data over audio signal, so the cellphone could interpret it over it's microphone jack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideas? ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(P.S - my current idea is using Biphase mark code. is it any good for this?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2737" LastActivityDate="2011-01-24T14:40:12.060" Title="How could you transfer data over an audio line?" Tags="&lt;audio&gt;&lt;data&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="9341" PostTypeId="2" ParentId="9340" CreationDate="2011-01-23T15:18:35.690" Score="7" ViewCount="" Body="&lt;p&gt;Consider using Baudot (specification EIA/TIA-825). It is the protocol used for TDD, a modem technology for deaf users. It transmits at 45.5 bits per second and deals well with poor audio coupling environments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen it implemented with some simple frequency analysis(window sampling/filtering at key frequencies) software. I know the Astrix project implements it so there may be some code to review if you aren't concerned with licensing.&lt;/p&gt;&#xA;" OwnerUserId="2738" LastActivityDate="2011-01-23T15:18:35.690" CommentCount="2" />
  <row Id="9342" PostTypeId="2" ParentId="9340" CreationDate="2011-01-23T15:47:22.383" Score="7" ViewCount="" Body="&lt;p&gt;Here are some example projects, using FSK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://sree.cc/electronics/arduino-as-an-fsk-modem&quot; rel=&quot;nofollow&quot;&gt;http://sree.cc/electronics/arduino-as-an-fsk-modem&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/arduino-iphone-shield/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/arduino-iphone-shield/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-23T15:47:22.383" CommentCount="1" />
  <row Id="9343" PostTypeId="2" ParentId="9338" CreationDate="2011-01-23T16:11:34.163" Score="1" ViewCount="" Body="&lt;p&gt;There is likely a serial interface somewhere on the PCB itself, maybe even a header. Open the sucker up and look for suspicious 2-6-pin connections. You may be able to get a part number off of the main micro -- look up the datasheet for its JTAG, ISP, 1-Wire or other programming pins. There's always the possibility that this thing was programmed before being soldered in, but there should still be some kind of test rig setup to interface with it -- with a bit of luck and ingenuity, you may be able to hack even that into a programmer.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-23T16:11:34.163" />
  <row Id="9344" PostTypeId="2" ParentId="1444" CreationDate="2011-01-23T16:29:27.020" Score="1" ViewCount="" Body="&lt;p&gt;I have used the PSoC 1 chips quite a bit. We use them in the tactile sensors in our robot hands. The main advantage here is space. In one 6x6mm chip, I can have a microcontroller, ADC, DAC, programmable gain amplifier, and another amplifier.  Not a lot of microcontrollers can do this. But the IDE is kind of annoying, as people have said.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have also used the PSoC 3 chips. These are so much better than the PSoC 1s. First of all, the chips are much more flexible, and the IDE shows this. As well as writing code, you can basically design a schematic for all the peripherals in the chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Want to make a current controller? Easy, drag in a PWM module, set it up to centre aligned PWM, and wire the centre trigger output to the Start-of-conversion input of the ADC to synchronise the sampling with the PWM so you get accurate current reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Want 5 current controllers? Easy, just drag in 5 PWM modules and a multiplexer. Wire up the multiplexer to automatically switch channels every sample.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Want 5 Quadrature decoders and SPI and a hardware CRC calculator? Sure, just drag them in. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And there, you have a chip which can do motor position control for 5 motors. Hardly any other external chips required. I don't think there's another chip on the market which can do that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hugo&lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2011-01-23T16:29:27.020" CommunityOwnedDate="2011-01-23T16:29:27.020" />
  <row Id="9345" PostTypeId="2" ParentId="1444" CreationDate="2011-01-23T16:31:29.497" Score="0" ViewCount="" Body="&lt;p&gt;Another thing which is worth mentioning is that the configuration of the peripherals is super easy. Unlike the PIC, which I still find hard having used them over the last 10 years. There are no horrible registers to configure, just an easy dialog box for each one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But sadly, the chips aren't really available yet. You can get development kits, and you used to be able to get samples. As soon as they are available, I'm getting rid of all those damn PICs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hugo&lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2011-01-23T16:31:29.497" CommunityOwnedDate="2011-01-23T16:31:29.497" />
  <row Id="9346" PostTypeId="1" CreationDate="2011-01-23T18:48:23.920" Score="5" ViewCount="311" Body="&lt;p&gt;Hi folks, I have bought a cheap but neat Uni-T UT61E multimeter, which only has one display as most multimeters. For 40 Euro's I cant complain. It's on the way to me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Q.1&lt;/strong&gt; If I would like to measure both Voltage and Current, do I have to buy another multimeter? Are there mutlimeters that measure both Voltage and Current in two displays with multiple wires attached to the meter? Have searched but haven't found any hand-multimeter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Q.2&lt;/strong&gt; I would like to put a very tiny voltage/current multimeter lcd on my batery pack so that I can check the volage there (without using my big multimeters) on travels. Any advice on how/where I can find such things?&#xA;So far I only found this which is a self-build kit:&lt;br&gt;&#xA;Do you have better advice and/or know any existing final products that are calibrated and working okay?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/8N9B4.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.electronics-diy.com/store.php?sel=kits&amp;amp;sub=pic_voltmeters&quot; rel=&quot;nofollow&quot;&gt;http://www.electronics-diy.com/store.php?sel=kits&amp;amp;sub=pic_voltmeters&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My new big mutlimeter on its way, with which I guesse I cant view voltage and current simultaneously:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/oObxU.jpg&quot; width=&quot;200&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2719" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-24T06:20:37.847" LastActivityDate="2011-01-24T06:20:37.847" Title="How to measure Voltage &amp; Current with a single multimeter, Simultaneously?" Tags="&lt;lcd&gt;&lt;current-measurement&gt;&lt;voltage-measurement&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9347" PostTypeId="2" ParentId="9346" CreationDate="2011-01-23T19:04:51.373" Score="5" ViewCount="" Body="&lt;p&gt;Q1. They do exist, &lt;a href=&quot;http://www.gossenmetrawatt.com/english/produkte/metrahitenergy.htm&quot; rel=&quot;nofollow&quot;&gt;but they are (much) more expensive&lt;/a&gt;. In most cases you can measure a fixed battery voltage and continue to assume that voltage while measuring current. Or, you can buy a meter with a dual display, but those typically aren't cheap. Most dual display meters though can't do everything you need - for example, they can only measure voltage and frequency at the same time. I'd suggest what you do instead is keep the nice meter for accurately measuring most things but buy one of the cheapie Mastech £3 meters to measure the second quantity. They actually do pretty well, most within 0.5% accuracy. And it's no big deal if you damage one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Q2. I've heard good reviews from &lt;a href=&quot;http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8319&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;, designed for model aircraft. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-23T19:04:51.373" />
  <row Id="9348" PostTypeId="2" ParentId="1444" CreationDate="2011-01-23T19:46:19.770" Score="1" ViewCount="" Body="&lt;p&gt;I've used the PSoC 1 and PSoC 3.  They're okay - great for peripherals, bad for number crunching.  Even clocked as high as possible it's still slow on some things and the latencies for handling interrupts are not great.  I was attempting to read a 5.6MBit serial link with it (without coding anything interesting in Verilog, although that probably would have done the trick) and it could &lt;em&gt;almost&lt;/em&gt; keep up.  A processor clocked at 48MHz should be able to do that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The software used to be awful, but now it's just so okay it's average.  It works with no major hiccups but everything's beta at the moment - chips, software, you name it.  For instance, the die temperature reading didn't work at all on the chip we had and they knew it.  It'll get fixed in production. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You know, there's nothing wrong with using an external ADC.  Your application sounds pretty niche, so if you used an external ADC you could get everything you want there and choose any uC.  Just a thought.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-23T19:46:19.770" CommunityOwnedDate="2011-01-23T19:46:19.770" />
  <row Id="9349" PostTypeId="2" ParentId="9346" CreationDate="2011-01-23T22:10:28.567" Score="4" ViewCount="" Body="&lt;p&gt;To anwer your first question:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to measure both current and voltage at the same time, you're doing a power measurement. A typical multimeter has no support for that. To do accurate power measurements, your best bet is to use 2 multimeters at the same time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use 1 multimeter and swap V/I in 2 tests, you may get a little error due to the internal resistance of the multimeter in the Amp range. That might lower the voltage on your load, which may increase current depending on the type of load (switching supplies draw more current with lower input voltages). &lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-01-23T22:10:28.567" />
  <row Id="9350" PostTypeId="1" AcceptedAnswerId="9356" CreationDate="2011-01-23T22:46:59.500" Score="2" ViewCount="213" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to interface a 6150 Nokia cellphone with an Arduino Duemilanove board, as some have already done through the &lt;strong&gt;FBUS&lt;/strong&gt; protocol (see &lt;a href=&quot;http://www.embedtronics.com/nokia/fbus.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; for example).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The FBUS protocol uses &lt;strong&gt;2.8V&lt;/strong&gt; logic, so I bought &lt;a href=&quot;http://www.sparkfun.com/products/8745&quot; rel=&quot;nofollow&quot;&gt;Sparkfun's &lt;strong&gt;logic level converter&lt;/strong&gt;&lt;/a&gt; to interface with the &lt;strong&gt;5V&lt;/strong&gt; from the Arduino, right ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wfonb.jpg&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They say:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The level converter is very easy to&#xA;  use. The board needs to be powered&#xA;  from the two voltages sources (high&#xA;  voltage and low voltage) that your&#xA;  system is using. High voltage (5V for&#xA;  example) to the 'HV' pin, low voltage&#xA;  (2.8V for example) to 'LV', and ground&#xA;  from the system to the 'GND' pin.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Thus&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;HV  &amp;lt;-&amp;gt;  Arduino 5V&#xA;GND &amp;lt;-&amp;gt;  Arduino GND&#xA;&#xA;LV  &amp;lt;-&amp;gt;  ??&#xA;GND &amp;lt;-&amp;gt;  ??&#xA;&#xA;TXI &amp;lt;-&amp;gt;  Phone TX    (Low Voltage)&#xA;RXO &amp;lt;-&amp;gt;  Phone RX    (Low Voltage)&#xA;TXO &amp;lt;-&amp;gt;  Arduino RX  (High Voltage)&#xA;RXI &amp;lt;-&amp;gt;  Arduino TX  (High Voltage)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The problem I have is with the low voltage source: &lt;em&gt;there is no power output on the phone.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I power the converter LV/GND from another 2.8V source ? Would it be ok with the Arduino 3.3V source ?&lt;/p&gt;&#xA;" OwnerUserId="2653" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-24T03:27:35.117" LastActivityDate="2011-01-24T03:27:35.117" Title="Logic Level Converter, Arduino and Cellphone" Tags="&lt;arduino&gt;&lt;cellphone&gt;&lt;level-shifting&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9351" PostTypeId="1" CreationDate="2011-01-23T23:00:22.750" Score="4" ViewCount="287" Body="&lt;p&gt;I'm wanting to count how often a water pump turns on, how long it's on for and when it turns off for an extended period of time. My plan was just to monitor the pressure switch, which is at 120v on 1 leg and write the data into a MSSQL database. What's the best way to get this data safely?&lt;/p&gt;&#xA;" OwnerUserId="2741" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-24T03:26:40.483" LastActivityDate="2011-03-19T02:13:18.123" Title="What is the easiest way to monitor a 120v line via software?" Tags="&lt;voltage-measurement&gt;&lt;line-power&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="9352" PostTypeId="2" ParentId="9351" CreationDate="2011-01-23T23:16:10.147" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://openenergymonitor.org/emon/node/56&quot; rel=&quot;nofollow&quot;&gt;These pages&lt;/a&gt; contain very interesting information on how to sense voltage and current in a non-invasive way. Have a look at it :)&lt;/p&gt;&#xA;" OwnerUserId="2653" LastActivityDate="2011-01-23T23:16:10.147" CommentCount="1" />
  <row Id="9353" PostTypeId="2" ParentId="9351" CreationDate="2011-01-23T23:20:54.247" Score="2" ViewCount="" Body="&lt;p&gt;I'd put a current transformer in the supply to the pump, and monitor the rectified output with a suitable MCU, sending the data with a time stamp to the data base.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-23T23:20:54.247" />
  <row Id="9354" PostTypeId="2" ParentId="9251" CreationDate="2011-01-23T23:22:06.127" Score="2" ViewCount="" Body="&lt;p&gt;The hard part about a PID controller is not the code itself. The issues actually come in when trying to optimize controller. Sure you can do trial and error and get a pretty decent controller, but some systems are just far too complex for a trial and error method to be easy to perform. These same systems tend to be the ones that need a very good controller instead of just a decent one. In this case the Z-transform is much easier to analyze.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing to think about is the stability of a system. You may be dealing with a system that is rather difficult to become unstable, or even if it does it doesn't hurt anything. But there are many systems that can have catastrophic results if the controller causes it to go unstable. The Z-transform is another place where it is much easier to identify if there will be any issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And 1 final note. When analyzing a system as a whole you will have to get equations for all of the components in your system. Sure you can get it from the PID w/o a PhD, but if you are already have been working with it in the Z-transform method there is far less back and forth work that you have to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, as a personal preference, I always use the PID w/o a PhD method. This is just because I am just using micro-controllers with systems that aren't terribly dependent on the controller.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-23T23:22:06.127" />
  <row Id="9355" PostTypeId="2" ParentId="2869" CreationDate="2011-01-23T23:23:58.273" Score="2" ViewCount="" Body="&lt;p&gt;I am lazy with bad eye sight, I use my multimeter with some crocodile clips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then it goes in a baggie marked with the value.&lt;/p&gt;&#xA;" OwnerUserId="665" LastActivityDate="2011-01-23T23:23:58.273" CommentCount="1" />
  <row Id="9356" PostTypeId="2" ParentId="9350" CreationDate="2011-01-23T23:30:32.320" Score="2" ViewCount="" Body="&lt;p&gt;That website has a photo which shows &quot;2-GND&quot;. This is the ground that you want to connect to the ground that you have for everything else.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as the 2.8v source, you can use any source you want. The voltage is just used to reference the serial signal against. If you tie it to the 3.3V it will probably work. I am not sure of the specifics of that voltage shifter, but I assume it will treat 2.8v on the signal line as being a logic high when comparing to 3.3v.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-23T23:30:32.320" CommentCount="4" />
  <row Id="9357" PostTypeId="2" ParentId="9351" CreationDate="2011-01-24T00:13:23.030" Score="2" ViewCount="" Body="&lt;p&gt;I'd connect this switch through optocoupler to DCD pin on PC serial port or one of the data pins on the parallel port&lt;/p&gt;&#xA;" OwnerUserId="2471" LastActivityDate="2011-01-24T00:13:23.030" CommentCount="1" />
  <row Id="9358" PostTypeId="2" ParentId="9330" CreationDate="2011-01-24T01:04:00.317" Score="3" ViewCount="" Body="&lt;p&gt;IIRC the cap is wired to /RTS not DTR. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When /RTS is high there is 0V across the cap. When /RTS goes low the cap &#xA;can not change voltage instantaneously so the reset line goes low. &#xA;The cap charges through the 10K resistor. Once the reset line is above&#xA;the reset threshold the uC program starts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;@LouisDavis referenced &lt;a href=&quot;http://www.arduino.cc/playground/Main/DisablingAutoResetOnSerialConnection&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt;, which states&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The ATmega168 is reset by pulsing its reset pin to GND. ...by setting the DTR line to LOW ... the reset pin gets sucked to LOW until the capacitor is charged through the internal pull up resistor and R1 - which resets the chip.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Simulated:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Auto-Reset&#xA;VDTR    1 0 PWL(0 5 0.5m 5 0.000500004 0 1m 0)&#xA;Vcc 3 0 5&#xA;C1  1 2 100n&#xA;R1  3 2 10k&#xA;.control&#xA;delete all&#xA;tran 10n 5m&#xA;plot v(1) v(2)&#xA;.endc&#xA;.END&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;V(1) is &lt;code&gt;DTR&lt;/code&gt; or &lt;code&gt;/RTS&lt;/code&gt; and V(2) is &lt;code&gt;/RESET&lt;/code&gt;&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/PNpgm.png&quot; alt=&quot;alt text&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="424" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-24T02:19:03.327" LastActivityDate="2011-01-24T02:19:03.327" CommentCount="8" />
  <row Id="9359" PostTypeId="2" ParentId="9351" CreationDate="2011-01-24T01:57:26.327" Score="4" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;My plan was just to monitor the pressure switch, which is at 120v on 1 leg &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The most common methods would be to use current (I) sensor to detect &lt;strong&gt;current flow&lt;/strong&gt; when the pressure switch is activated (engaged). Such as &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Hall_effect&quot; rel=&quot;nofollow&quot;&gt;Hall effect&lt;/a&gt; IC sensor, &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Current_transformer&quot; rel=&quot;nofollow&quot;&gt;current transformer&lt;/a&gt;, or high voltage input &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Opto-isolator&quot; rel=&quot;nofollow&quot;&gt;Opto-isolator&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;What's the best way to get this data safely?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Using a current detection method that also provides circuit isolation from the AC mains to your digital interface. Basic isolation methods include &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Galvanic_isolation&quot; rel=&quot;nofollow&quot;&gt;galvanic isolated&lt;/a&gt; (no current flow between isolated sides), opto-isolation (&lt;em&gt;optical&lt;/em&gt;), and capacitor-coupled isolators. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe the most basic, yet low cost and non-invasive method of monitoring would be to use a split-core current transformer such as &lt;a href=&quot;http://www.seeedstudio.com/depot/noninvasive-ac-current-sensor-100a-max-p-547.html?cPath=6&quot; rel=&quot;nofollow&quot;&gt;SCT-013-000 (US)&lt;/a&gt; (or &lt;a href=&quot;http://www.efergy.com/Products/efergy-Shop-Accessories/EFERGY/Jackplug-Extra-Sensor/pid-184334.aspx&quot; rel=&quot;nofollow&quot;&gt;UK&lt;/a&gt;). As you only are interested in on/off you can use a &lt;a href=&quot;http://openenergymonitor.org/emon/node/59&quot; rel=&quot;nofollow&quot;&gt;voltage divide circuit&lt;/a&gt; to meet digital &lt;a href=&quot;http://www.interfacebus.com/voltage_threshold.html&quot; rel=&quot;nofollow&quot;&gt;logic level thresholds&lt;/a&gt; or make use of an ADC if available on the microcontroller assuming you are using one. &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;The load resistor (R_burden in the voltage divide circuit) value is based upon the current range, which depends on your motor. If the motor is 1 HP (&lt;em&gt;horsepower&lt;/em&gt;) 110-120V motor, let's assume it is rated at 750 Watts (replace with actual specs from motor), so the current range is less than 8 Amps, let's round that to 10 Amp. Using the previously suggested current transformer sensor, with a &lt;strong&gt;turn ratio&lt;/strong&gt; of 1:1500, that would be:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;10 Amp (&lt;em&gt;rms&lt;/em&gt;) * sqrt(2) = 14.142... Amps (&lt;em&gt;peak-peak&lt;/em&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;14.142 A / 1500 turn ratio = 0.0094280904158206 A = 9.4mA (secondary coil)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2.5 V / 0.00942.. A = ~ &lt;strong&gt;265&lt;/strong&gt; Ohm R_burden so as to provide a mid-point (2.5 V) output at 5 Amp, or full-range  (5 V) at 10 Amp for 5 V dc logic level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the power (P = I*V) is 0.01 Watt, a 1/4 Watt resistor would be fine.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;From there you should be able to interface a low-level (voltage &amp;amp; current) signal to whatever device you wish to use to send such data to the computer with the (logging) database. Typically a microcontroller with an ADC (analog to digital converter) and a serial, Ethernet, or USB interface would be the &quot;glue&quot; device between the sensor's circuit and the database computer. (IMHO MS-SQL is overkill (and expensive), &lt;a href=&quot;http://sqlite.org/features.html&quot; rel=&quot;nofollow&quot;&gt;SQLite&lt;/a&gt; would be fine)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are not familiar with microcontrollers, I would suggest using one with a &lt;em&gt;friendly&lt;/em&gt; high-level easy to user interface, and hobbyist-oriented presentation such as the &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; or &lt;a href=&quot;http://www.rev-ed.co.uk/picaxe/&quot; rel=&quot;nofollow&quot;&gt;PIC-AXE&lt;/a&gt;. They are more expensive than a stand alone or &quot;naked&quot; microcontroller per device or board, but the development environment is more newbie friendlier and for an one-off the one unit cost may be offset by the not having to purchase a SDK, reference documentation, or 3rd-party tools (high level language compilers) for a more traditional device such as the Atmel AVR or Microchip PIC microcontrollers. &lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-01-24T01:57:26.327" />
  <row Id="9360" PostTypeId="2" ParentId="9340" CreationDate="2011-01-24T02:47:33.960" Score="3" ViewCount="" Body="&lt;p&gt;Any particular reason &lt;em&gt;not&lt;/em&gt; to use the &lt;a href=&quot;http://mobileoffice.about.com/od/phonesformobileworkers/a/how-to-tether.htm&quot; rel=&quot;nofollow&quot;&gt;modem&lt;/a&gt; that is likely already contained in your mobile phone?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise I would suggest your look at low-speed &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Modem_standards&quot; rel=&quot;nofollow&quot;&gt;modem standards&lt;/a&gt; used for POTS (plain-old-telephone service/system) land-lines back in the 1980s and 90s. I suspect from Bell 103, 212 (300, 1200bps) to V.32 (9600bps) should be usable using the audio portion which I believe roughly the same as (US) Bell land-line standard of 300 to ~3000 Hz (&lt;em&gt;corrected&lt;/em&gt;) frequency response plus/minus wireless digital voice codec issues. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;300 bps via two-tone audio frequency shift keying (AFSK), &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Modem_standards&quot; rel=&quot;nofollow&quot;&gt;V.21&lt;/a&gt;, is fairly easy to implement in software or hardware if you wish to roll your own. Otherwise a modem IC such as Silicon Labs &lt;a href=&quot;http://www.silabs.com/products/modems/embedded/Pages/DataModems.aspx&quot; rel=&quot;nofollow&quot;&gt;SI2401&lt;/a&gt; or CML Microcircuits &lt;a href=&quot;http://www.cmlmicro.com/products/index.asp?/Products/WTelecom/FX614.htm&amp;amp;searchvalue=fsk&amp;amp;setindex=1&quot; rel=&quot;nofollow&quot;&gt;FX/MX614&lt;/a&gt; or &lt;a href=&quot;http://www.cmlmicro.com/products/index.asp?/Products/WTelecom/CMX869B.htm&amp;amp;searchvalue=v.23&amp;amp;setindex=1&quot; rel=&quot;nofollow&quot;&gt;CMX869B&lt;/a&gt;. (There are many others)&lt;/p&gt;&#xA;" OwnerUserId="2598" LastEditorUserId="2598" LastEditorDisplayName="" LastEditDate="2011-01-24T14:40:12.060" LastActivityDate="2011-01-24T14:40:12.060" CommentCount="1" />
  <row Id="9361" PostTypeId="2" ParentId="9350" CreationDate="2011-01-24T03:19:09.227" Score="2" ViewCount="" Body="&lt;p&gt;You could use a resistive &lt;a href=&quot;http://www.play-hookey.com/dc_theory/voltage_divider.html&quot; rel=&quot;nofollow&quot;&gt;voltage divider&lt;/a&gt; to &lt;em&gt;create&lt;/em&gt; the 2.8 Volt source from the 5 Volt supply (&lt;strong&gt;HV&lt;/strong&gt; on the level shifter board) available from the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/oJwdw.gif&quot; alt=&quot;alt text&quot;&gt; (image src: &lt;a href=&quot;http://www.play-hookey.com/dc_theory/voltage_divider.html&quot; rel=&quot;nofollow&quot;&gt;Play-Hookey&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or you could use a linear voltage regulator such as the &lt;a href=&quot;http://www.national.com/mpf/LP/LP3987.html#Overview&quot; rel=&quot;nofollow&quot;&gt;LP3987-2.8&lt;/a&gt; (SMT) or similar. &lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-01-24T03:19:09.227" />
  <row Id="9362" PostTypeId="1" CreationDate="2011-01-24T03:22:32.433" Score="0" ViewCount="42" Body="&lt;p&gt;I'm looking for a keyboard and pointing device which I can use when my laptop is plugged into my TV. It needs to be able to connect to the laptop via bluetooth (I want to minimize the time and effort connecting the laptop), and the pointing device must be integrated into it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm having a big problem finding a device to fit the bill online. I would have thought it was a very popular problem, and that there'd be plenty of devices out there...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The laptop is a macbook. I don't care if it's designed for windows, so long as it works with OS X.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Recommendations?&lt;/p&gt;&#xA;" OwnerUserId="2743" LastActivityDate="2011-01-24T04:26:33.933" ClosedDate="2011-01-24T05:24:40.817" Title="any bluetooth keyboards with integrated pointing device (trackball/trackpad)?" Tags="&lt;bluetooth&gt;&lt;keyboard&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="9363" PostTypeId="2" ParentId="9362" CreationDate="2011-01-24T03:44:52.777" Score="0" ViewCount="" Body="&lt;p&gt;I'm answering this offtopic question with an answer that should bring it back on-topic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PS3 BT keyboard has a built-in pointing device; both the keyboard and pointer show up as standard HID devices and I've tested it with both OSX and Linux. The keyboard works with the iPhone 4 as well, which was the main reason for getting it. I'd tried a few other keyboards but they all had the keys arranged on a rectangular grid rather than an offset grid like a normal keyboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, as soon as I got it I took it apart; a standard ARM Cortex M3 processor drives it, and it appears that the JTAG lines are brought out. The BT is done via a bluetooth module, very similar to the A7eng.com ones, although not an exact copy. I'm hoping to be able to read out the ARM program and remap a few keys, although I'm aware of how much work that will end up being.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A little wireless keyboard like this would be a lot of use for electronics projects which have infrequent need of a keyboard. BT modules are pretty simple to work with these days, and if your embedded system can use a HID profile device (such as keyboards and mice) then it's really a no brainer.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-01-24T03:44:52.777" CommentCount="1" />
  <row Id="9364" PostTypeId="2" ParentId="9288" CreationDate="2011-01-24T03:53:50.087" Score="2" ViewCount="" Body="&lt;p&gt;In vague hand-wavy generic terms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The voltage (or RFI / EMC) isolation requirements determines the spacing between traces and components. The biggest culprit of the second part may be inductors and transformers on double sided boards, for designers not use to doing analog design or layout. The component or module datasheet may have a &lt;em&gt;keep-out&lt;/em&gt; area information as well as physical dimensions and restrictions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current (amperage) determines the PCB trace width, higher current means wider traces. This can often been single on a PCB with an on-board power supply and low-level digital components as an example in contrast. Large or oversize traces are occasional used as a heat sink in high-intensity LED designs by professionals, I do not believe it is commonly done by amateurs. I don't know if this is due to lack of access to thermal simulation tools or knowledge or some other factors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The component layout and PCB manufacturing process are the ultimate guides for trace restrictions. For example the trace width and spacing on boards I intend for my own etching I give myself about double the spacing and width where possible to mitigate the risk of flaws in my process actually causing problems with the boards I make.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some PCB manufacturers offer DRC (design rule check) file for supported CAD software that checks to ensure the board file complies with their technical manufacturing restrictions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Various &lt;a href=&quot;http://batchpcb.com/index.php/Faq&quot; rel=&quot;nofollow&quot;&gt;companies&lt;/a&gt; have &lt;a href=&quot;http://www.expresspcb.com/expresspcbhtm/tips.htm&quot; rel=&quot;nofollow&quot;&gt;tips&lt;/a&gt; and &lt;a href=&quot;http://www.blackstick.co.uk/pcb%20tips.html&quot; rel=&quot;nofollow&quot;&gt;advice&lt;/a&gt; on PCB layout.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-01-24T03:53:50.087" />
  <row Id="9365" PostTypeId="2" ParentId="9321" CreationDate="2011-01-24T04:14:26.340" Score="5" ViewCount="" Body="&lt;p&gt;Of course not! Obviously in some cases a subsidiary may start with the same first name but in general there is no logic to it.&lt;/p&gt;&#xA;" OwnerUserId="2744" LastActivityDate="2011-01-24T04:14:26.340" CommentCount="3" />
  <row Id="9366" PostTypeId="2" ParentId="9362" CreationDate="2011-01-24T04:26:33.933" Score="0" ViewCount="" Body="&lt;p&gt;Off-topicness notwithstanding, I still feel the need to complete the question. I've found a few sweet bluetooth mouse-keyboard devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fentek has a &lt;a href=&quot;http://www.fentek-ind.com/mini_bluetooth.htm&quot; rel=&quot;nofollow&quot;&gt;mini bluetooth keyboard&lt;/a&gt; with nubbin which seems to be perfectly suitable, and it's about $50.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also an &lt;a href=&quot;http://www.adesso.com/en/component/content/article/43-wireless-keyboards/126-wkb-4000bb.html&quot; rel=&quot;nofollow&quot;&gt;Aldesso bluetooth mouse-keyboard&lt;/a&gt; for about $130.&lt;/p&gt;&#xA;" OwnerUserId="2743" LastActivityDate="2011-01-24T04:26:33.933" />
  <row Id="9367" PostTypeId="2" ParentId="9321" CreationDate="2011-01-24T08:22:18.650" Score="1" ViewCount="" Body="&lt;p&gt;I checked a number of TDA devices &lt;a href=&quot;http://www.chipdocs.com/datasheets/datasheet-pdf/TDA.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and they all seem to be for audio/video applications. Most (not all) analog.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-01-24T08:31:44.110" LastActivityDate="2011-01-24T08:31:44.110" />
  <row Id="9368" PostTypeId="1" AcceptedAnswerId="9369" CreationDate="2011-01-24T08:59:32.483" Score="4" ViewCount="244" Body="&lt;p&gt;Hi folks! For reading both Voltage and Current draw simultaneously one needs two multimeters. In search of a second multimeter, I tought its best to deliberately have the second one from a different brand/model. That way when in doubt having two independent meters give  you more accuracy on same readout. I'm stil searchihg for a second multimeter...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Which Second Multimeter qualifies for both:&lt;br&gt;&#xA;A) same or better than 0,1% Accuracy DC Voltage and&lt;br&gt;&#xA;B) cost less than 200$?&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I expect it to be a short list, since I haven't found ANY other than this. Thanks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Below is my first one (have no second one yet)&lt;br&gt;&#xA;&lt;a href=&quot;http://www.uni-trend.com/UT61E.html&quot; rel=&quot;nofollow&quot;&gt;link manufacturer specs&lt;/a&gt;  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Uni-T  -  UT61E&lt;br&gt;&#xA;   55$~70$&lt;br&gt;&#xA;   22000 counts (or 19999)&lt;br&gt;&#xA;   DC Voltage accuracy 0.1%+2 | DC Current 0.5%+10&lt;br&gt;&#xA;   graphs readings via Serial or USB port&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/rt1Wu.jpg&quot; width=&quot;300&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2719" LastEditorUserId="2719" LastEditorDisplayName="" LastEditDate="2011-01-25T13:11:54.740" LastActivityDate="2011-01-25T13:11:54.740" ClosedDate="2011-01-25T14:09:22.817" Title="Multimeters Shootout: Same or Better than 0,1% DC Voltage ACCURACY and below 200$ PRICEMARK" Tags="&lt;current-measurement&gt;&lt;voltage-measurement&gt;&lt;multimeter&gt;&lt;power-meter&gt;&lt;pricing&gt;" AnswerCount="1" CommentCount="9" FavoriteCount="3" />
  <row Id="9369" PostTypeId="2" ParentId="9368" CreationDate="2011-01-24T09:32:32.550" Score="2" ViewCount="" Body="&lt;p&gt;Well, any tester might be good if you can calibrate them. Personally I use UNI-T ones(10 and 100$ ones), and they can be calibrated. So if you have 1 good multimeter, you can buy cheapo UNI-T one and calibrate it, and you'll get 2 precision one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That is easier if you need just several ranges calibrated, not all of them. Also, it's better to have temperature controlled room ;-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll update details with my meters when I get home :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UT70A&lt;/strong&gt;&#xA;~70$, 1999 counts.&#xA;DC accuracy 0.5%&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UT33B&lt;/strong&gt;&#xA;~15$, 1999 counts.&#xA;DC accuracy 0.5%&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would not trust these 0.5%, it would need to be calibrated anyway for serious business :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So basically, UNI-T are very popular here in Soviet Russia, just because they work fine &amp;amp; cost waaaaaaaay less than fluke :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-01-24T19:12:07.837" LastActivityDate="2011-01-24T19:12:07.837" CommentCount="7" />
  <row Id="9370" PostTypeId="2" ParentId="2869" CreationDate="2011-01-24T12:35:51.557" Score="1" ViewCount="" Body="&lt;p&gt;If the start and end bands are ambiguous, you can usually work out which is &lt;em&gt;probably&lt;/em&gt; the right way to read them by seeing which way round gives you a valid &lt;a href=&quot;http://www.logwell.com/tech/components/resistor_values.html&quot; rel=&quot;nofollow&quot;&gt;E24/E48/E96&lt;/a&gt; etc. value. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;..and there's always 'use a multimeter' to fall back on when you're still not sure.&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2011-01-24T12:35:51.557" />
  <row Id="9371" PostTypeId="2" ParentId="9321" CreationDate="2011-01-24T15:18:03.290" Score="3" ViewCount="" Body="&lt;p&gt;Manufacturers often do use their own prefix for original products, or may continue to use a prefix of a company or product line that was acquired.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the number of IC available has continuously grown the complexity of the naming schemes have become less obvious, and more exceptions exist. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example MAX- prefix typically refers to a &lt;a href=&quot;http://www.maxim-ic.com/&quot; rel=&quot;nofollow&quot;&gt;Maxim&lt;/a&gt; IC, including the well-known &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/1798&quot; rel=&quot;nofollow&quot;&gt;MAX232&lt;/a&gt; except &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/max232.html&quot; rel=&quot;nofollow&quot;&gt;MAX232&lt;/a&gt; is also made by TI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The NE5532 available from &lt;a href=&quot;http://www.jrc.co.jp/eng/&quot; rel=&quot;nofollow&quot;&gt;JRC&lt;/a&gt;, TI and On Semi, was originally designed by &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Signetics&quot; rel=&quot;nofollow&quot;&gt;Signetics&lt;/a&gt; and continue to use the NE- prefix.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than business unit / company (original or acquired), the next most popular prefix convention would be series or technology based. Here I'm thinking of Op-Amps such as TL-, which are JFET or BiFET based op-amp technology &lt;a href=&quot;http://www.acronymfinder.com/As-Far-As-I-Know-%28AFAIK%29.html&quot; rel=&quot;nofollow&quot;&gt;AFAIK&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course there are nearly as many exceptions to the rule as the rule covers, so like life, it's messy.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-01-24T15:18:03.290" />
  <row Id="9372" PostTypeId="1" CreationDate="2011-01-24T17:28:05.633" Score="4" ViewCount="171" Body="&lt;p&gt;I have a 30 feet line with DC supply 12 V. A motor on the end draws about 0.5 Amps initially (100 ms). It's logic shuts down because of the line's voltage drop caused by inrush current.&#xA;A capacitor of 1000 uF prevents the shutdown.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if I calculate the size of the capacitor that prevents a drop of more than 1 V, a much larger (x50) value comes out (0.5 A * 0.1 s / 1 V = 0.05 Farad).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I figure this is because the supply isn't disconnected but continues to supply power, so the capacitor does not have to provide the current alone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I improve my model so the calculation is closer to the real thing?&lt;/p&gt;&#xA;" OwnerUserId="2752" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-25T13:11:22.087" LastActivityDate="2011-01-25T13:11:22.087" Title="Long supply line and capacitor to prevent voltage drop" Tags="&lt;power-supply&gt;&lt;capacitor&gt;&lt;transient-suppression&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="9373" PostTypeId="2" ParentId="9372" CreationDate="2011-01-24T17:33:27.007" Score="2" ViewCount="" Body="&lt;p&gt;You need to treat the line as an in series inductor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This may be the limit of lumped element mode analysis(treating the line as a simple inductor is an example of this), but it will at minimum give you a good starting point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The line has two values, an inductance and a capacitance, if you place the supply entering an inductor, then a capacitor from the line in parallel with your capacitor it should work quite well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many tools for calculating your inductance, &lt;a href=&quot;http://www.consultrsr.com/resources/eis/induct5.htm&quot; rel=&quot;nofollow&quot;&gt;I quickly turned up this one&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you are putting a large capacitance at the end it will probably be so large in comparison to the capacitance of the line that the line capacitance is negligible.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-01-24T17:33:27.007" />
  <row Id="9374" PostTypeId="2" ParentId="9372" CreationDate="2011-01-24T18:59:31.913" Score="0" ViewCount="" Body="&lt;p&gt;replace the wire with thicker one.&lt;/p&gt;&#xA;" OwnerUserId="2471" LastActivityDate="2011-01-24T18:59:31.913" CommentCount="2" />
  <row Id="9375" PostTypeId="1" AcceptedAnswerId="9376" CreationDate="2011-01-24T19:02:46.060" Score="3" ViewCount="113" Body="&lt;p&gt;What is this component? It's between two ICs, probably on a communication bus. One is a microcontroller and the other is some sort of memory. It's as small as an smd capacitor or resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/0nXjZ.jpg&quot; alt=&quot;component written &amp;quot;220&amp;quot; on it&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1514" LastEditorUserId="1514" LastEditorDisplayName="" LastEditDate="2011-01-24T19:26:39.237" LastActivityDate="2011-01-24T19:26:39.237" Title="Help identify this component" Tags="&lt;resistor&gt;" AnswerCount="1" />
  <row Id="9376" PostTypeId="2" ParentId="9375" CreationDate="2011-01-24T19:05:20.580" Score="5" ViewCount="" Body="&lt;p&gt;It's a quad 22.0 Ohm resistor........&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-24T19:05:20.580" CommentCount="3" />
  <row Id="9377" PostTypeId="1" AcceptedAnswerId="9379" CreationDate="2011-01-24T19:46:30.203" Score="3" ViewCount="277" Body="&lt;p&gt;I have a mysterious component covered with yellow &quot;glue&quot; or something. It has very hard surface, but it seems its been poured into the plastic &quot;cage&quot;. The shiny cover on the top is some kind of paper, I can rip it off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any idea how to remove this goo from the PCB? (Without damaging the components underneath)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/W6LcV.jpg&quot; alt=&quot;enter image description here&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/4MYrb.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1514" LastEditorUserId="1514" LastEditorDisplayName="" LastEditDate="2011-01-24T19:56:00.287" LastActivityDate="2011-01-24T21:01:21.807" Title="How to remove &quot;glue block&quot; from PCB?" Tags="&lt;ic&gt;&lt;epoxy&gt;&lt;glue&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="9378" PostTypeId="2" ParentId="9377" CreationDate="2011-01-24T20:07:06.747" Score="2" ViewCount="" Body="&lt;p&gt;I don't know what that glue is, but I would try:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Acetone (nail polish remover)&lt;/li&gt;&#xA;&lt;li&gt;Pliers (pull/chip it off)&lt;/li&gt;&#xA;&lt;li&gt;Hot air (melt it)&lt;/li&gt;&#xA;&lt;li&gt;Alcohol&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Here are some suggestions from another thread: &lt;a href=&quot;http://science.niuz.biz/solvent-t45294.html&quot; rel=&quot;nofollow&quot;&gt;http://science.niuz.biz/solvent-t45294.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-24T20:07:06.747" />
  <row Id="9379" PostTypeId="2" ParentId="9377" CreationDate="2011-01-24T20:07:26.363" Score="4" ViewCount="" Body="&lt;p&gt;That's a potted circuit.  The shiny paper on top likely forms some sort of EMI shield to reduce interference it may cause or receive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Potting is usually an epoxy, which usually cannot be removed either chemically (dissolution) or thermally (melting it), so you are left with mechanical (chip away at it).  Some are soft, and while they stick fairly well, with a bit of time can be removed.  If it's a hard variant, it may well be impossible, and if you really want to figure out what's under there, using an X-ray inspection machine would be a good idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some rare epoxies are susceptible to attack by extremely aggressive organic solvents (dichloromethane, xylene, etc.), but you may well destroy the board in attempt to remove it.  If you have access to some chemicals and can chip off small samples of the epoxy, you could give it a whirl.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-24T20:07:26.363" CommentCount="1" />
  <row Id="9380" PostTypeId="1" AcceptedAnswerId="9391" CreationDate="2011-01-24T20:43:17.987" Score="1" ViewCount="46" Body="&lt;p&gt;Problem:&#xA; An impedance 1000(1 + i)  Ohms  (and note it contains an imaginary &#xA;part) is connected across an AC voltage source of amplitude 10 V &#xA;and frequency 60 Hz. What's the power dissipated during one cycle &#xA;within the impedance? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Relevant equations:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P = Re(V*I), where V* is complex conjugate of voltage&#xA;I=V/Z&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Solution Attempt:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it's alternating current, so I first take the RMS V: 10/\sqrt{2}. Then I = V/Z, so I get&lt;/p&gt;&#xA;&#xA;&lt;p&gt;V*I = V*V/Z = 100/2 1/(1000(1+i)) = (1-i)/(20*2). Then I take the real part of this, which is 1/40. Am I doing this right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="2755" LastActivityDate="2011-01-24T22:21:48.460" Title="Impedance across AC circuit" Tags="&lt;impedance&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="9381" PostTypeId="1" AcceptedAnswerId="9816" CreationDate="2011-01-24T20:57:53.813" Score="6" ViewCount="184" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've just bought some 6mm^2 copper wire for my project where I will have large pulse currents - ~500A peak (driving very large Xenon flash bulbs, 1000J pulse in 2ms). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I know that skin effect make it useless to use thick wires on high frequency, but does it apply to sharp fronts? Is that correct that having multiple non-isolated wires make it even worse? (mine cable have about 20 tiny 'wires')&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-07T04:49:22.203" Title="Skin effect for pulse current" Tags="&lt;skin-effect&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9382" PostTypeId="2" ParentId="9377" CreationDate="2011-01-24T21:01:21.807" Score="2" ViewCount="" Body="&lt;p&gt;Red fuming nitric acid is used to dissolve the epoxy resin used in chip packaging, and might work. It's dangerous stuff, though, and will probably dissolve the epoxy used in the PCB.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-24T21:01:21.807" CommentCount="1" />
  <row Id="9383" PostTypeId="2" ParentId="9271" CreationDate="2011-01-24T21:20:55.370" Score="1" ViewCount="" Body="&lt;p&gt;I think the closest equivalent is to develop the production test&#xA;fixture and test script for your circuit as soon as possible.  Make&#xA;sure you test all important functionality.  The test fixture emulates&#xA;whatever user interface and sensor hardware are attached to the&#xA;circuit. The &quot;design verification&quot; test script will probably have&#xA;more tests and take longer than the production test script, where you&#xA;are mostly testing to see that the pieces are connected together&#xA;properly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So when you are making changes to the firmware or the circuit&#xA;itself, you can occasionally run the design verification test against&#xA;it to make sure you haven't caused any regressions.  It is also&#xA;helpful to make reduced test scripts to test one aspect of the&#xA;circuit's performance, for example testing response across supply&#xA;variations, or a particularly tricky state machine that would require&#xA;two pages of instructions for a human to attempt.  These shorter&#xA;scripts are to save time and give better test coverage than the full&#xA;script.  But you always run the verification test before committing&#xA;changes to the schematic or firmware.  For final released design run the verification test across temperature.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-24T21:20:55.370" />
  <row Id="9384" PostTypeId="2" ParentId="1696" CreationDate="2011-01-24T21:31:39.300" Score="0" ViewCount="" Body="&lt;p&gt;Emacs, specifically with &lt;a href=&quot;http://www.emacswiki.org/emacs/hexview-mode.el&quot; rel=&quot;nofollow&quot;&gt;hexview-mode&lt;/a&gt;.  Unfortunately it doesn't meet your offset viewer requirement.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-24T21:31:39.300" CommunityOwnedDate="2011-02-09T13:48:06.387" />
  <row Id="9385" PostTypeId="2" ParentId="3564" CreationDate="2011-01-24T21:34:25.773" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.xfusionsoftware.com/purchase_timegen.html&quot; rel=&quot;nofollow&quot;&gt;TimeGen&lt;/a&gt; is &#xA;" OwnerUserId="206" LastActivityDate="2011-01-24T21:34:25.773" />
  <row Id="9386" PostTypeId="2" ParentId="1696" CreationDate="2011-01-24T21:35:23.820" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.emacswiki.org/emacs/intel-hex-mode.el&quot; rel=&quot;nofollow&quot;&gt;http://www.emacswiki.org/emacs/intel-hex-mode.el&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-24T21:35:23.820" CommunityOwnedDate="2011-02-09T13:48:06.387" />
  <row Id="9387" PostTypeId="2" ParentId="9381" CreationDate="2011-01-24T21:38:35.673" Score="2" ViewCount="" Body="&lt;p&gt;A sharp pulse is a sum of many different frequencies, you can model each frequency as hitting a different impedance. Then, take how much loss each receives, and recombine to see the new wave front.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Chances are you will get a pulse with a slower rising edge.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt; Stranded vs. Solid&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;The difference will exist, but will be minor to you. Inductance will play a larger part I would suspect. The stranded wire should behave a bit better.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-01-25T00:29:21.937" LastActivityDate="2011-01-25T00:29:21.937" CommentCount="2" />
  <row Id="9388" PostTypeId="1" AcceptedAnswerId="9394" CreationDate="2011-01-24T21:41:02.690" Score="0" ViewCount="200" Body="&lt;p&gt;I accidentally killed my 3 3/4 digit cheapie £20 multimeter when changing the fuse (shorted the 3.3V regulated line to 9V and fried the ASIC.) Since I did this, I realise I should probably buy a more expensive one as I have some monies saved up for it. So I'm in the market for a meter in the £50 to £80 range (about $80 to $130.) My requirements are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Capacitance range up to at least 1 millifarad&lt;/li&gt;&#xA;&lt;li&gt;Resistance range better than 10 Mohm&lt;/li&gt;&#xA;&lt;li&gt;Temperature range (preferably with a K-type thermocouple)&lt;/li&gt;&#xA;&lt;li&gt;Accuracy 0.5% or better&lt;/li&gt;&#xA;&lt;li&gt;High resolution (more than 4000 counts)&lt;/li&gt;&#xA;&lt;li&gt;Input to 1000V with CAT-III protection - decent input protection (MOVs &amp;amp; TVS diodes)&lt;/li&gt;&#xA;&lt;li&gt;If possible True RMS - AC &lt;em&gt;and&lt;/em&gt; DC&lt;/li&gt;&#xA;&lt;li&gt;If possible a frequency range&lt;/li&gt;&#xA;&lt;li&gt;If possible a duty cycle range&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any suggestions? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-27T22:54:53.377" ClosedDate="2011-01-28T02:17:57.180" Title="What multimeter should I get?" Tags="&lt;multimeter&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="1" />
  <row Id="9389" PostTypeId="1" AcceptedAnswerId="9401" CreationDate="2011-01-24T21:42:45.670" Score="4" ViewCount="82" Body="&lt;p&gt;How do you choose what batteries to use for your projects? Are there a set of criteria that they need to be able to do in order for you to consider them? If so what are they?. The only 2 that come to mind are size and capacity. So do I need a PP3 or could I use 6 AAs? Then capacity AAs are better as they have better capacity. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-24T22:50:28.530" LastActivityDate="2011-01-24T23:33:45.353" Title="What to consider when choosing batteries for a project?" Tags="&lt;batteries&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="9390" PostTypeId="1" CreationDate="2011-01-24T22:03:22.503" Score="3" ViewCount="221" Body="&lt;p&gt;I am running a short (2m) CAN bus with about 20 nodes. 1Mb speed, PIC 18F2580s and 18F4580s with MCP2551 transceivers, 10MHz (with PLL to 40MHz) crystal oscillators. Both ends are terminated at 120ohms. Sample point is at 70%.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nodes are in 3 groups, each powered from a separate isolated power supply, but the grounds are all commoned along the bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I get quite a number of message errors, framing, bit stuffing.   Looking at CANH and CANL on a 'scope, everything looks beautiful. No ringing, no reflections, timing correct. Measuring the oscillators with an accurate frequency measurer shows only a tiny variation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far, the only way I have been able to reduce the number of message errors is to beef up the ground wire along the bus until I get the GND difference below about 150mv. The further above that I go, the more errors I get.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why? According to the MCP2551 datasheet, they should be able to cope with GND differences up to 7v!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I misunderstanding something?&lt;/p&gt;&#xA;" OwnerUserId="1024" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-24T22:08:54.917" LastActivityDate="2011-03-08T22:55:04.230" Title="GND difference between CAN nodes ?" Tags="&lt;pic&gt;&lt;can&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="9391" PostTypeId="2" ParentId="9380" CreationDate="2011-01-24T22:21:48.460" Score="1" ViewCount="" Body="&lt;p&gt;I assume:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;source amplitude&quot; means &quot;peak&quot; (as apposed to peak to peak)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The load impedance is actually calculated at 60Hz&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ztotal = 1000 + 1000j  (really should be using j as sqrt(-1) not i in electronics)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ztotal = 1414.21 @ 45deg (just rewritten in a magnitude / phase representation)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;|Ztotal| = 1414.21 Ohms&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vrms = 10/sqrt(2) ~= 7.07 Vrms&lt;/p&gt;&#xA;&#xA;&lt;p&gt;|I| = |Vrms| / |Ztotal| = 7.07 / 1414.21&lt;/p&gt;&#xA;&#xA;&lt;p&gt;|I| ~= 5mA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P(true power) = I^2 * R = (5mA)^2 * 1000 = 25 mW (this is what is dissipated in the load, your answer)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Q(reactive power) = I^2 * X = (5mA)^2 * 1000 = 25 mVAR (this is power bouncing back and forth, not dissipated)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;S(apparent power) = I^2 * Z = (5mA)^2 * 1414.21 = 35.35 mVA (this is the vector sum of the true and reactive power)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Power Factor = P/S = True Power / Apparent Power = 25mW / 35mVA = 0.714&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully I didn't flub up the math there, my calculators batteries just died so i did it all in google.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-01-24T22:21:48.460" CommentCount="2" />
  <row Id="9392" PostTypeId="2" ParentId="9389" CreationDate="2011-01-24T22:23:37.603" Score="5" ViewCount="" Body="&lt;p&gt;Current.  For example coin batteries have very low current capability; a car battery has huge current capability.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-24T22:23:37.603" CommentCount="1" />
  <row Id="9393" PostTypeId="2" ParentId="824" CreationDate="2011-01-24T22:32:26.830" Score="0" ViewCount="" Body="&lt;p&gt;You haven't said much about your application. Whether you use an RTOS depends a lot on what you need to do in the PIC. Unless you're doing several different asynchronous things, which require strict time bounds, or have several threads running, then an RTOS might be overkill.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many ways to organise the time on a microcontroller depending on what's most important:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Constant frame rate: For a PIC running a servo controller which must run at 1000Hz for example. If the PID algorithm takes less than 1ms to execute, then you can use the remainder of the millisecond to do other tasks, like check the CAN bus, read sensors, etc.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;All interrupts: Everything that happens in the PIC is triggered by an interrupt. The interrupts can be prioritised according to the importance of the event.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Stick it in a loop and do everything as fast as you can. You might find this provides suitable time bounds.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2011-01-24T22:32:26.830" CommentCount="1" />
  <row Id="9394" PostTypeId="2" ParentId="9388" CreationDate="2011-01-24T22:39:27.870" Score="2" ViewCount="" Body="&lt;p&gt;Here's &lt;a href=&quot;http://www.eevblog.com/&quot; rel=&quot;nofollow&quot;&gt;some Aussie&lt;/a&gt; using a bunch of bad language (typical) talking about&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=ZoeUgMFLyAw&amp;amp;feature=channel&quot; rel=&quot;nofollow&quot;&gt;$50 multimeters&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=n3WGaiYF2sk&amp;amp;feature=related&quot; rel=&quot;nofollow&quot;&gt;$100 multimeters&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-24T22:39:27.870" CommentCount="1" />
  <row Id="9395" PostTypeId="1" CreationDate="2011-01-24T19:41:36.370" Score="2" ViewCount="443" Body="&lt;p&gt;I've been trying out many different software, such as MS Visio, SmartDRAW, Edraw, Cadsoft EAGLE, PSpice, that allow users to draw electrical related diagrams. They are, to some extent, sufficient for most purposes but some of them either do not encompass a wide range of devices (that I sometimes need) or are not necessarily designed to produce diagrams that are going to be used in publications. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In particular, in the meantime, I am looking for a software that would allow me to draw diagrams such as the ones seen in popular electronic design books such as &lt;em&gt;Microselectronic Circuits&lt;/em&gt; by Sedra Smith or &lt;em&gt;Electronic Circuit Analysis and Design&lt;/em&gt; by Donald Neamen; or another way of putting the question would be: what software was used to draw the diagrams in the books mentioned?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT 1: Thanks for all your answers. Just to emphasize again on what I'm really curious about is what software are usually used to draw the diagrams in published books (like those I've mentioned for example).&lt;/p&gt;&#xA;" OwnerUserId="2761" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-25T18:09:41.777" LastActivityDate="2011-01-25T18:09:41.777" Title="Professional Electrical and Electronic Diagram Drawing Software" Tags="&lt;schematics&gt;&lt;eda&gt;&lt;diagrams&gt;" AnswerCount="7" CommentCount="5" FavoriteCount="2" />
  <row Id="9396" PostTypeId="2" ParentId="9395" CreationDate="2011-01-24T21:05:19.870" Score="0" ViewCount="" Body="&lt;p&gt;I suggest &lt;a href=&quot;http://www.ni.com/multisim/&quot; rel=&quot;nofollow&quot;&gt;Multisim Electronics Workbench&lt;/a&gt; in university years.It has really huge library.&#xA;Student Suite version would be enough for most of designs...&lt;/p&gt;&#xA;" OwnerUserId="3935" LastActivityDate="2011-01-24T21:05:19.870" />
  <row Id="9397" PostTypeId="2" ParentId="9395" CreationDate="2011-01-24T21:46:55.137" Score="0" ViewCount="" Body="&lt;p&gt;I personally use &lt;a href=&quot;http://www.expresspcb.com/expresspcbhtm/download.htm&quot; rel=&quot;nofollow&quot;&gt;Express PCB&lt;/a&gt; for my schematic and PCB designs &lt;/p&gt;&#xA;" LastActivityDate="2011-01-24T21:46:55.137" />
  <row Id="9398" PostTypeId="2" ParentId="9395" CreationDate="2011-01-24T21:54:06.130" Score="0" ViewCount="" Body="&lt;p&gt;Have you tried &lt;a href=&quot;http://usa.autodesk.com/adsk/servlet/pc/index?id=13779270&amp;amp;siteID=123112&quot; rel=&quot;nofollow&quot;&gt;AutoCAD&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="3027" LastActivityDate="2011-01-24T21:54:06.130" CommentCount="2" />
  <row Id="9399" PostTypeId="2" ParentId="9390" CreationDate="2011-01-24T23:01:29.033" Score="1" ViewCount="" Body="&lt;p&gt;Are you sure the message errors are a result of the CAN bus and not a result of the performance of the rest of the node(the PIC circuits)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CAN is differential, as long as you don't exceed the common mode voltage limits of the transceiver the relative ground levels shouldn't matter and there is no need to send a ground connection with the CAN signals (maybe a shield but thats a different story).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However with isolated power supplies yet the ground connection being there you well could have some ground current loops that are causing problems with the rest of the circuit.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-01-24T23:01:29.033" CommentCount="8" />
  <row Id="9400" PostTypeId="2" ParentId="9395" CreationDate="2011-01-24T23:02:51.187" Score="4" ViewCount="" Body="&lt;p&gt;For typeset quality schematics, I'd use TeX.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tex.stackexchange.com/questions/4841/a-good-tool-to-make-electronic-schematics-and-export-them-vectorially&quot;&gt;http://tex.stackexchange.com/questions/4841/a-good-tool-to-make-electronic-schematics-and-export-them-vectorially&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-24T23:02:51.187" CommentCount="1" />
  <row Id="9401" PostTypeId="2" ParentId="9389" CreationDate="2011-01-24T23:19:23.737" Score="6" ViewCount="" Body="&lt;p&gt;Generally, this is how I pick batteries:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Create a Power Budget&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;This should be the voltage, (average) current, and duty cycle required for each component of your system. For example, if you have a mobile robot that will be driving and processing, you could say 12 Volts, 1 Amp, 80% use for the motors and 5 Volts, 200 milliamp, 100% for the processor.  These numbers don't have to be exact, just in the ballpark of what you think that you will need.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Once you have a list of your power draws, figure out what the total energy each component will use.  Find this by multiplying Voltage * Current * Duty, then units will be Watt-Hours.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For the components not at battery voltage (behind a regulator), factor in the energy lost from converting voltages.  Depending on your DC-DC converter, this can be anywhere from 5% - 80% loss (moral of the story, use switching regulators, not linear).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;At this point, I usually fudge a bit and add a 20% margin of error to my average power use.  I then figure out how long I want the system to run on average.  Multiply your average current at battery voltage by the amount of time that you want the system to run. You can then compare this number to the Amp-Hours available on the batteries that you are looking at&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Remember to oversize your batteries a bit, as the Amp-Hour rating is determined by C/20 in most cases. C being the rated current (a 3.3Ah pack has a C of 3.3 Amps, but tested at 165 milliamp).  Picking batteries is not an exact science in most cases, and it may take a few tries to get right.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Choosing Battery Chemistry&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as picking chemistry, it depends on the project.  Weight, size, and cost factor in heavily along with the run time for your system load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few questions to ask about your need:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Budget&lt;/li&gt;&#xA;&lt;li&gt;Size and Weight Constraints&lt;/li&gt;&#xA;&lt;li&gt;Project Lifespan (Charge cycles)&lt;/li&gt;&#xA;&lt;li&gt;Charger cost, maintenance&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;A few choices:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Lead Acid, high cycle count, very reliable, easy to charge, yet they are large and heavy for the capacity.&lt;/li&gt;&#xA;&lt;li&gt;NiMH and NiCd, go-to hobby batteries, average size and energy density&lt;/li&gt;&#xA;&lt;li&gt;LiIon and LiPo, super-light, more expensive, high energy density, can be unstable if treated improperly.  Good for high-current discharge (20*C and higher).&lt;/li&gt;&#xA;&lt;li&gt;LiFePo, high cycle count, about the same energy density as LiPo.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Brief Example&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The attached example is for an autonomous lawnmower project that I worked on.  We began by listing all of the components required at each voltage.  In the end, we choose to run two different battery stacks to help eliminate some of the noise from the high-current devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 12V battery stack also provided power for the 5V electronics, which we ran through a 80% efficient DC-DC converter.  You can see the additional 20% factor in the spreadsheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, budget was the main constraint, with size and weight not constraints for the project (300 pound lawnmower, what's a couple batteries?).  We ended up using a 64Ah 24V lead-acid stack and a 17Ah 12V stack.  Our run times reflected what is in the sheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In practice, the 24 Volt battery stack lasted much longer, as we used current figures that were close to worst case (100% full speed forward and cutters in thick grass).  As a result, on the next iteration, we combined the 24V and 12V stacks together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/80xgC.png&quot; alt=&quot;Example Power Budget&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1477" LastEditorUserId="1477" LastEditorDisplayName="" LastEditDate="2011-01-24T23:33:45.353" LastActivityDate="2011-01-24T23:33:45.353" />
  <row Id="9403" PostTypeId="2" ParentId="9395" CreationDate="2011-01-25T00:49:44.120" Score="2" ViewCount="" Body="&lt;p&gt;If you export an Eagle schematic to PDF it looks decent.  I think with any package, you're going to have to create some of your own parts.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-01-25T00:49:44.120" />
  <row Id="9404" PostTypeId="2" ParentId="9395" CreationDate="2011-01-25T01:57:43.027" Score="0" ViewCount="" Body="&lt;p&gt;I hate to say this, but if it's about looking nice then Visio has a library of circuit symbols.  Plus it's geared towards display (WYSIWYG, etc).&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-01-25T01:57:43.027" CommentCount="1" />
  <row Id="9405" PostTypeId="1" AcceptedAnswerId="9408" CreationDate="2011-01-25T02:08:48.443" Score="2" ViewCount="157" Body="&lt;p&gt;How can one calibrate a multimeter, like a UT61E or any other multimeter in the 50 ~200 $ pricemark, when one does NOT have an expensive FLUKE nor a friend who has a FLUKE) &lt;/p&gt;&#xA;" OwnerUserId="2719" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-25T02:21:57.567" LastActivityDate="2011-01-25T09:10:42.827" Title="What Ways to Calibrate a Multimeter?" Tags="&lt;multimeter&gt;&lt;calibration&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="9406" PostTypeId="2" ParentId="9251" CreationDate="2011-01-25T02:15:00.540" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using the Z-transform makes it easier to combine and simplify LTI systems for &lt;em&gt;analysis&lt;/em&gt;. For example, a cascaded series of k LTI systems with transfer functions H1, H2, ..., Hk will combine as a simple product &lt;code&gt;H = H1*H2*...*Hk&lt;/code&gt;. Also, the transfer function of a negative feedback loop is &lt;code&gt;T = G/(1 + G*H)&lt;/code&gt;, where H is on the feedback path. Once you have an overall transfer function, you can analyze the stability (location of poles) and performance (transients, steady-state error), adding additional filters and feedback to optimize the design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For higher order sub-systems, you can partition the system function and implement it as a series of cascaded biquads (i.e. by pairs of zeros and poles, such as complex conjugates or repeated roots), which decreases instability caused by quantization. A canonical-form biquad:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Cz8CZ.png&quot; alt=&quot;biquad section&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="721" LastEditorUserId="721" LastEditorDisplayName="" LastEditDate="2011-01-26T04:13:17.513" LastActivityDate="2011-01-26T04:13:17.513" CommentCount="11" />
  <row Id="9407" PostTypeId="2" ParentId="7609" CreationDate="2011-01-25T02:17:52.750" Score="2" ViewCount="" Body="&lt;p&gt;OMG, epic fail. I just found out that I grabbed from the wrong box and placed all BC857 where there should be BSN20.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, it could be that I was right (and the BSN20 wrong) in the first place and made the mistake not before I replaced them. I don't know, because I am out of BSN20 and put in BSH108 (which have better specs anyway). Now it works fine.&lt;/p&gt;&#xA;" OwnerUserId="1950" LastActivityDate="2011-01-25T02:17:52.750" CommentCount="1" />
  <row Id="9408" PostTypeId="2" ParentId="9405" CreationDate="2011-01-25T02:36:49.460" Score="2" ViewCount="" Body="&lt;p&gt;Very generally and at the most basic, you need a precision voltage reference and resistors.  Obtaining 0.1% is fairly easy, for resistors it's straightforward, and for voltage references look up &quot;precision voltage reference&quot; (something like &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=AD1580ARTZ-REEL7CT-ND&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;), and bias it with 0.1 to 1 mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The actual calibration procedure will vary from meter to meter, so you will need to dig up the appropriate documents.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-01-25T02:36:49.460" />
  <row Id="9409" PostTypeId="2" ParentId="9395" CreationDate="2011-01-25T06:50:13.327" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.cadence.com/products/orcad/orcad_capture/pages/default.aspx&quot; rel=&quot;nofollow&quot;&gt;OrCAD&lt;/a&gt; sample diagram (&lt;a href=&quot;http://en.wikipedia.org/wiki/File%3aOrcad_schematic_capture.PNG&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/File:Orcad_schematic_capture.PNG&lt;/a&gt;):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/oEc8a.png&quot; alt=&quot;Orcad Schematic Capture&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2298" LastActivityDate="2011-01-25T06:50:13.327" />
  <row Id="9410" PostTypeId="1" AcceptedAnswerId="9412" CreationDate="2011-01-25T07:04:53.133" Score="0" ViewCount="71" Body="&lt;p&gt;Hey all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm interested in capturing analog video in NTSC and transmitting it as efficiently as possible over a digital link, preferably while maintaining as much fidelity to the original signal as possible. My thought was that the video signal might be able to be sampled with a high-speed ADC, the samples transmitted, and the signal reconstructed at the other end with a DAC. Is this possible? If there's a better way of doing this, by all means share!&lt;/p&gt;&#xA;" OwnerUserId="2762" LastActivityDate="2011-01-25T09:05:43.627" Title="Transmitting NTSC over digital link" Tags="&lt;analog&gt;&lt;digital&gt;&lt;ntsc&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="9411" PostTypeId="2" ParentId="1222" CreationDate="2011-01-25T07:49:14.907" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.pcb123.com/&quot; rel=&quot;nofollow&quot;&gt;PCB123&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The latest version of our free PCB design-tool has an intuitive CAD interface that lets you create new PCB designs quickly; offering freedom and flexibility in your schematic and layout editing.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Features:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;New board wizard.&lt;/li&gt;&#xA;&lt;li&gt;Ability to import net lists from multiple CAD vendors.&lt;/li&gt;&#xA;&lt;li&gt;145,000+ parts in the library.&lt;/li&gt;&#xA;&lt;li&gt;Fast, accurate DRC/DFM.&lt;/li&gt;&#xA;&lt;li&gt;Two-, four-, and six-layer support with soldermask and silkscreen.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Link to comparison with other products: &lt;a href=&quot;http://www.sunstone.com/pcb123/compare123.aspx&quot; rel=&quot;nofollow&quot;&gt;Compare PCB Design Tools&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2298" LastActivityDate="2011-01-25T07:49:14.907" />
  <row Id="9412" PostTypeId="2" ParentId="9410" CreationDate="2011-01-25T09:05:43.627" Score="1" ViewCount="" Body="&lt;p&gt;Yes it is possible 100%. A little inefficient due to blanking intervals but 100% possible.&#xA;You should get some 50-100Mhz+ 8-12bit ADC + DAC on other side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But transmitting 8x100Mhz signal might be a problem for long distance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are really cool you may encapsulate it into 1G Ethernet :-D&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-25T09:05:43.627" CommentCount="2" />
  <row Id="9413" PostTypeId="1" AcceptedAnswerId="9415" CreationDate="2011-01-25T09:08:56.463" Score="3" ViewCount="119" Body="&lt;p&gt;I am recently doing a project on robotics.And am following (societyofrobots) 50$ robot tutorial for that purpose.But i can't find ATmega8 chip anywhere as they told but i did found atmega8L instead.Now,is it possible to replace atmega8 by atmega8L though it has low capacity than atmega8? &lt;/p&gt;&#xA;" OwnerUserId="2765" LastActivityDate="2011-01-25T09:12:13.387" Title="Can i use ATmega8L instead of ATmega8?" Tags="&lt;robotics&gt;&lt;atmega8&gt;" AnswerCount="1" />
  <row Id="9414" PostTypeId="2" ParentId="9405" CreationDate="2011-01-25T09:10:42.827" Score="1" ViewCount="" Body="&lt;p&gt;Basically, there are lots of adjustable resistors on the multimeter PCB - don't forget to mark original positions of all of them before you start.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You ether get a precision resistor references (read datasheet on temperature coefficient), or find a guy with precision equipment in your city to compare the readings.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-25T09:10:42.827" />
  <row Id="9415" PostTypeId="2" ParentId="9413" CreationDate="2011-01-25T09:12:13.387" Score="7" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;That's about it. The L version can&#xA;  work at a lower voltage but with a&#xA;  lower clock. It's all there &lt;strong&gt;in the 1st&#xA;  page of the datasheet.&lt;/strong&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Read datasheet first. Always :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, google is your friend. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually all atmel chips can work on 20+ Mhz, so if it's not a production device, you can not worry about these letters. But if your kit uses 8Mhz speed or slower, then it even less reason to worry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/search?q=atmega8L#hl=en&amp;amp;sugexp=ldymls&amp;amp;xhr=t&amp;amp;q=atmega8L+difference&amp;amp;cp=12&amp;amp;pf=p&amp;amp;sclient=psy&amp;amp;aq=0v&amp;amp;aqi=&amp;amp;aql=&amp;amp;oq=atmega8L+dif&amp;amp;pbx=1&amp;amp;fp=9527b76dac6b3bf0&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/search?q=atmega8L#hl=en&amp;amp;sugexp=ldymls&amp;amp;xhr=t&amp;amp;q=atmega8L+difference&amp;amp;cp=12&amp;amp;pf=p&amp;amp;sclient=psy&amp;amp;aq=0v&amp;amp;aqi=&amp;amp;aql=&amp;amp;oq=atmega8L+dif&amp;amp;pbx=1&amp;amp;fp=9527b76dac6b3bf0&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-25T09:12:13.387" />
  <row Id="9416" PostTypeId="2" ParentId="1222" CreationDate="2011-01-25T11:52:38.267" Score="2" ViewCount="" Body="&lt;p&gt;You can also get DesignSparkPCB which is a unlimited package given away free by RS Electroincs - &lt;a href=&quot;http://www.designspark.com/knowledge/pcb&quot; rel=&quot;nofollow&quot;&gt;www.designspark.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2649" LastActivityDate="2011-01-25T11:52:38.267" />
  <row Id="9417" PostTypeId="2" ParentId="9372" CreationDate="2011-01-25T12:41:08.327" Score="0" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Its logic shuts down [...]&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Are you talking about a DC brushless motor? These have higher switching frequencies, and you need to buffer only this switching. Their electroncs can work at much lower voltages, 7V DC is almost always enough to start spinning a 12V DC motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A long wire will interfere with this not only because of its resistance but also because of its inductance. To model this accurately you will need a &lt;em&gt;lot&lt;/em&gt; more parameters, unfortunately, like the switching frequencies (and on-to-off ratios) of your motor.&lt;/p&gt;&#xA;" OwnerUserId="1472" LastActivityDate="2011-01-25T12:41:08.327" CommentCount="1" />
  <row Id="9418" PostTypeId="1" AcceptedAnswerId="9420" CreationDate="2011-01-25T14:35:39.373" Score="2" ViewCount="144" Body="&lt;p&gt;This is a bit of a general question. I have a project I want to put together similar to the 'sentry gun' projects seen on youtube. I've gathered an SSC-32 servo controller and couple of small servos - i think they're around 76oz-in - and I made a little brace so they are attached at right angles. This basically works as a pan-n-tilt mechanism, and I've plugged the controller board into my serial port, and it all works nicely. The problem is that it's a bit too dainty. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need way more muscle, and so my question is in several parts.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Where is a good place to get hefty servos for a good price? I need something that can easily swing a 2x4 around (around 2')&lt;/li&gt;&#xA;&lt;li&gt;Can someone point me at a tutorial for hooking this up? I assume the SSC-32 board and it's 4 AAs won't cut it as I'll need more power for those bigger servos. So How do I control the servos with the board but power them separately?&lt;/li&gt;&#xA;&lt;li&gt;Would there be an advantage to using stepper motors instead? Like, more torque/$? I've never dealt with steppers, but I heard they were similar.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Thanks for any advice!&lt;/p&gt;&#xA;" OwnerUserId="2769" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-25T18:06:49.317" LastActivityDate="2011-01-29T02:24:46.537" Title="High torque servo/stepper setup" Tags="&lt;stepper&gt;&lt;servo&gt;" AnswerCount="2" />
  <row Id="9419" PostTypeId="2" ParentId="7113" CreationDate="2011-01-25T15:15:56.613" Score="2" ViewCount="" Body="&lt;p&gt;This doesn't apply to you, but maybe someone searching will find this:  Semiconductors are light sensitive.  If you have a precision analog circuit, and parts of it are in translucent cases, like glass diodes or metal-can op-amps (the bottom seal is translucent), you can expect significant offset shifts when light shines on the circuit.  Modern black epoxy packages are less susceptible.  It's easy enough to check if this is causing the problem:  If the problem stops when the circuit is covered by a box or something, the problem is the light, not the EMI.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-01-25T21:40:18.017" LastActivityDate="2011-01-25T21:40:18.017" />
  <row Id="9420" PostTypeId="2" ParentId="9418" CreationDate="2011-01-25T15:16:24.660" Score="1" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The Dynamixel servos are quite popular for their precision, high torque, and nice controls. Unfortunately, you'll be paying for all those features. I recommend Trossen Robotics: &lt;a href=&quot;http://www.trossenrobotics.com/c/robotis-dynamixel-robot-servos.aspx&quot; rel=&quot;nofollow&quot;&gt;Dynamixel servos&lt;/a&gt;&#xA;Trossen also sells a full pan/tilt setup for the Dynamixel servos: &lt;a href=&quot;http://www.trossenrobotics.com/c/robot-turrets.aspx&quot; rel=&quot;nofollow&quot;&gt;Trossen Robotics pan/tilt&lt;/a&gt;&#xA;They have a whole range of sizes and torques. ServoCity.com also sells some pan/tilt setups: &lt;a href=&quot;http://servocity.com/html/pan_tilt_roll___accessories.html&quot; rel=&quot;nofollow&quot;&gt;ServoCity pan/tilt&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Trossen provides a nice controller and software. I believe &lt;a href=&quot;http://Pololu.com&quot; rel=&quot;nofollow&quot;&gt;Pololu.com&lt;/a&gt; also sells servo controllers with information.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Servos will be much easier to interface with, while a stepper motor will provide greater angular resolution. How precise does your pointing need to be? The nicer Dynamixel servos will do steps of 0.3 degrees, while a stepper motor will get you much smaller incremets if you do the &quot;micro stepping&quot; method. Try looking at Sparkfun for a stepper/stepper driver: &lt;a href=&quot;http://www.sparkfun.com&quot; rel=&quot;nofollow&quot;&gt;Sparkfun.com&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;PS. When you're done with your project, how about adding it to &lt;a href=&quot;http://robotbox.net&quot; rel=&quot;nofollow&quot;&gt;RobotBox&lt;/a&gt; :)&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-01-25T15:16:24.660" CommentCount="1" />
  <row Id="9421" PostTypeId="2" ParentId="3203" CreationDate="2011-01-25T16:20:54.643" Score="5" ViewCount="" Body="&lt;p&gt;You might take a look at the &lt;a href=&quot;http://jeelabs.net/projects/hardware/wiki/jn4&quot; rel=&quot;nofollow&quot;&gt;Jeenodes&lt;/a&gt;. They are simple and relatively cheap and provide a nice layer on top of basic RF modules for doing serial transmission and point-multi-point communication.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-01-25T16:20:54.643" CommentCount="1" />
  <row Id="9422" PostTypeId="2" ParentId="9388" CreationDate="2011-01-25T20:28:01.113" Score="0" ViewCount="" Body="&lt;p&gt;I have a Fluke 115 and it meets your specifications with the exception of thermocouple temperature measurement. It's a pretty nice multi-meter although it doesn't have as many features as some of the cheaper brands, but it's a Fluke so you can really rely on the functions it does have.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-01-25T20:28:01.113" />
  <row Id="9423" PostTypeId="2" ParentId="9190" CreationDate="2011-01-25T20:33:25.933" Score="2" ViewCount="" Body="&lt;p&gt;You could use a servo with a linkage arm to close the shutter. I'm looking at doing this right now, except I need to precisely control the aperture. A servo will give you (relatively) precise position control, and it's fairly easy to interface with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to close the shutter very rapidly, then your best bet might be a solenoid. I wouldn't, however, recommend building your own. There's plenty out there that'll do the trick and probably work better than you can design - it'll also save you time. You'll need to use a spring to restore the shutter to the open position. You might try searching Digikey.com to find some.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-01-25T20:33:25.933" />
  <row Id="9424" PostTypeId="1" AcceptedAnswerId="9425" CreationDate="2011-01-25T20:52:50.997" Score="3" ViewCount="234" Body="&lt;p&gt;Hello! I am about to develop a portable device to be interfaced with a computer (so, consumer electronics). I only have experiences with Microchip and Texas Instruments and I would like to have some hint to choose the right MCU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Key requirements should be low power (it's a portable device), 16 bit, RAM&gt;10KB, hw multiplier, large program memory (128KB) and available in development kit form or something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any with the possibility of interfacing a on-chip Flash memory (such as the ones in USB keys)? Otherwise, I'll just use an SD card.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Very important, is there any chance I could find one with 3Mbps (3250000bps) UART? (need to interface with a Bluetooth module for high speed communication).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of MCU do you think would be a nice compromise?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you for your help,&lt;/p&gt;&#xA;" OwnerUserId="2285" LastActivityDate="2011-01-26T23:35:33.753" Title="MCU choice, 3Mbps UART," Tags="&lt;microcontroller&gt;&lt;uart&gt;&lt;flash&gt;" AnswerCount="6" CommentCount="6" />
  <row Id="9425" PostTypeId="2" ParentId="9424" CreationDate="2011-01-25T21:35:18.260" Score="3" ViewCount="" Body="&lt;p&gt;Take a look at the &lt;a href=&quot;http://www.atmel.com/products/at91/sam3s.asp&quot; rel=&quot;nofollow&quot;&gt;Atmel SAM3S&lt;/a&gt;.  It is not a 16 bit device but I'm not sure why that is a key requirement.  I'm also not sure what &quot;low&quot; power means to you.  This will be in direct conflict with the requirement for the fast baud rate.  To hit the 3.25 MBps you have to run this part at 52 MHz (It runs at 64 MHz max).  Another nice feature it has is DMA to help move the high speed serial data.  It also meets your memory requirements.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2011-01-25T21:35:18.260" CommentCount="1" />
  <row Id="9426" PostTypeId="2" ParentId="9424" CreationDate="2011-01-25T22:12:22.343" Score="0" ViewCount="" Body="&lt;p&gt;The XMOS XS1-L1 can easily handle 3.25 Mbit/s serial in software:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xmos.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.xmos.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-25T22:12:22.343" CommentCount="3" />
  <row Id="9427" PostTypeId="2" ParentId="9424" CreationDate="2011-01-25T22:19:17.300" Score="1" ViewCount="" Body="&lt;p&gt;I'm using a PIC24F and it's possible to reach 1/4th the Fcy with UART. So with a 16 MHz Fcy you can easily hit 4 Mbit/s. With the dsPIC33F series 10 Mbit/s is doable at 40 MHz Fcy. PIC32 can do almost 20 Mbit/s at 80 MHz Fcy. At higher rates than 10 Mbit/s you will really be pushing UART as it was never intended for high speed transmission and has very poor noise immunity and is single ended (not differential, like USB or CAN.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PIC24F and dsPIC33F are 16-bit, while the PIC32 is 32-bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;dsPIC33F comes in versions up to 30 KB RAM. 16 KB RAM is available in SO28 and SPDIP28. Program memory is available up to 256 KB, up to 128 KB on smaller 28 pin versions. PIC32 has up to 128 KB RAM and 512 KB flash, which is wayyy overkill for your application, but Microchip make smaller ones too. All have hardware multipliers. For a dev kit consider the Explorer 16 board.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-01-25T23:10:43.637" LastActivityDate="2011-01-25T23:10:43.637" CommentCount="12" />
  <row Id="9428" PostTypeId="1" CreationDate="2011-01-25T22:59:03.580" Score="3" ViewCount="296" Body="&lt;p&gt;I have a server room with an air conditioning unit.  The unit is supposed to run 24x7, but ND tends to get 100 °F in the summer and -40 °F in the winter.  This is a little harsh on the equipment and we have had failures.  I have a temperature sensor, but I want a little more warning.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to cook up some solution that monitors the air flow and sends an e-mail when the air stops.  I have looked at various anemometer (wind speed indicators), but they all seem to log data and not provide updates, plus they all seem to be rather large and not a good thing to have spinning in a server room.  I want to hang the sensor from the ceiling in front of the air conditioner.&lt;/p&gt;&#xA;" OwnerUserId="2772" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-29T03:58:41.967" LastActivityDate="2011-01-30T10:27:02.087" Title="How can I detect when the air flow in a room stops and report it?" Tags="&lt;sensor&gt;" AnswerCount="10" CommentCount="4" />
  <row Id="9429" PostTypeId="2" ParentId="9424" CreationDate="2011-01-25T23:04:49.597" Score="0" ViewCount="" Body="&lt;p&gt;Without researching it too much, my internal buzz-word hash-map says TI MSP430 because&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;16-bit&lt;/li&gt;&#xA;&lt;li&gt;low-power&lt;/li&gt;&#xA;&lt;li&gt;hardware multiplier&lt;/li&gt;&#xA;&lt;li&gt;you evidently have experience with TI&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Honestly, when I read your post, I thought the requirements were pulled of an MSP430 marketing brochure. I'm not sure their UARTs support 3Mbit/s - but they have an internal digitally controlled oscillator (DCO) that lets them run at up to 25MHz, so you might be able to keep up... the UART on the 5xx can source an external clock source as well&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have a pretty good &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?&amp;amp;familyId=342&amp;amp;uiTemplateId=PP-T-GSPA_T&amp;amp;techFamId=null&amp;amp;rootFamilyId=null&amp;amp;sectionId=95&amp;amp;tabId=1200&amp;amp;appId=null&amp;amp;viewDeviceCallingPage=null&amp;amp;totalCount=1&amp;amp;showAdditionalParameters=no&amp;amp;lc=2000062&amp;amp;lc=2001227&amp;amp;lc=2001220&amp;amp;lc=2001219&amp;amp;lc=2000886&amp;amp;lc=2000121&amp;amp;lc=2001132&amp;amp;compare=yes&amp;amp;download=yes&amp;amp;sort=yes&amp;amp;customize=yes&amp;amp;paramResults=yes&amp;amp;paramCriteria=yes&amp;amp;familyTree=yes&amp;amp;military=no&amp;amp;baSystem=yes&amp;amp;paramTable=no&amp;amp;sortOption=PA_SUB_FAMILY_NAME&amp;amp;sortMode=DESC&amp;amp;searchPaths=1000342&amp;amp;pageId=342&amp;amp;templateId=0&amp;amp;navigationId=0&amp;amp;family=mcu&amp;amp;paramTable=no&amp;amp;military=no&amp;amp;ul=MSP430FE4242&amp;amp;uiTemplateId=PP-T-GSPA_T&amp;amp;techFamId=null&amp;amp;rootFamilyId=null&amp;amp;sectionId=95&amp;amp;tabId=1200&amp;amp;appId=null&amp;amp;viewDeviceCallingPage=null&amp;amp;resetCompare=true#sdp&quot; rel=&quot;nofollow&quot;&gt;product selector tool&lt;/a&gt; you should check out.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-26T20:15:35.873" LastActivityDate="2011-01-26T20:15:35.873" CommentCount="5" />
  <row Id="9430" PostTypeId="2" ParentId="9428" CreationDate="2011-01-25T23:06:28.753" Score="3" ViewCount="" Body="&lt;p&gt;Use a hot-wire anemometer, they can be very small.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-25T23:06:28.753" CommentCount="5" />
  <row Id="9431" PostTypeId="2" ParentId="9424" CreationDate="2011-01-26T00:04:33.463" Score="1" ViewCount="" Body="&lt;p&gt;NXP ARM7 and Cortex parts should be able to do it - you may need to run at 48MHz to get exactly 3Mbaud&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-26T00:04:33.463" CommentCount="1" />
  <row Id="9432" PostTypeId="2" ParentId="8690" CreationDate="2011-01-26T00:09:34.527" Score="0" ViewCount="" Body="&lt;p&gt;Without more details on your application, here are some stabs at the problem:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) have your object move on &lt;a href=&quot;http://en.wikipedia.org/wiki/Digital_paper&quot; rel=&quot;nofollow&quot;&gt;digital paper&lt;/a&gt;.  It has a pattern of dots such that a very simple camera can determine the position by evaluating some small number of dots.  This is what some pen input devices use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) If the surface on which the object travels is smooth, you could use a mouse attached to the object.  Interpreting the updates from the mouse would give you the changes in position, but you'd also need a reference point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Have a stationary camera mounted above your object, and a target pattern or light on the moving object.  With sufficient resolution and some simple image processing, you can determine the location.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) One scheme using ultrasonic transducers would have a transmitter on the moving object and at least 3 stationary receivers.  The transmitter sends periodic pulses, and you compute the location by triangulating using the differences in arrival times between pairs of receivers, and the known positions of the receivers.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;5) If you wanted much higher resolution at significant cost, there are laser interferometry systems that are commonly used to calibrate CNC equipment.  &lt;a href=&quot;http://www.renishaw.com/en/laser-interferometer-systems--6800&quot; rel=&quot;nofollow&quot;&gt;Here's&lt;/a&gt; one example I found.&lt;/p&gt;&#xA;" OwnerUserId="1264" LastActivityDate="2011-01-26T00:09:34.527" CommentCount="1" />
  <row Id="9433" PostTypeId="2" ParentId="9428" CreationDate="2011-01-26T00:10:07.737" Score="1" ViewCount="" Body="&lt;p&gt;Perhaps a pressure meter would do the trick? Use a tube and align it so that the airflow is going into the tube. Use the pressure meter at the other end of the tube. When the airflow stops, the pressure should drop. Sparkfun sells a barometric pressure sensor that, &quot;Under ideal conditions, this sensor can detect the pressure difference within a 9cm column of air.&quot; &lt;a href=&quot;http://www.sparkfun.com/products/8161&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/8161&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a mechanical solution, you could use a flex sensitive resistor strip (http://www.trossenrobotics.com/c/robot-force-sensor-fsr.aspx). Hang it so that the airflow will force the strip to bend. You'll have to be careful that the strip doesn't oscillate, but that would be very easy to interface to a microcontroller, or a comparator to turn on a LED or a buzzer.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-01-26T00:10:07.737" CommentCount="3" />
  <row Id="9434" PostTypeId="2" ParentId="8898" CreationDate="2011-01-26T00:42:00.980" Score="1" ViewCount="" Body="&lt;p&gt;The easiest solution would be a PoL (Point of Load) converter such as &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/ptn04050c.html&quot; rel=&quot;nofollow&quot;&gt;TI's PTN04050C 12-W, 3.3/5-V Input, Wide Adjust Output Boost Converter&lt;/a&gt;.  However that is almost a 1 A part and so overkill.  If I were cost- or area-sensative I might try &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tps61085.html&quot; rel=&quot;nofollow&quot;&gt;TI's TPS61085&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-26T00:42:00.980" />
  <row Id="9435" PostTypeId="1" AcceptedAnswerId="10031" CreationDate="2011-01-26T01:44:55.560" Score="5" ViewCount="242" Body="&lt;p&gt;Often I have a 3.3V or 5V mixed-signal circuit with a microcontroller running in the 10 MHz range and some analog circuitry, e.g. audio or analog sensor signals, powered from a wall-wart style supply or USB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So a problem I often come across is how to filter the supply for the analog signals. Shall I use a ferrite bead or a choke? More inductance or less? Or just an RC filter?&lt;/p&gt;&#xA;" OwnerUserId="1950" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-28T03:37:30.327" LastActivityDate="2011-02-12T00:51:39.347" Title="Shall I use a choke or a bead to filter analog power supply?" Tags="&lt;power-supply&gt;&lt;filter&gt;&lt;inductor&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9436" PostTypeId="2" ParentId="9428" CreationDate="2011-01-26T02:52:18.497" Score="1" ViewCount="" Body="&lt;p&gt;For something this critical, I'd seriously consider buying off the shelf.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if you want to roll your own the simplest solution is two temperature sensors. One in the airflow and one in a &quot;dead&quot; air spot. With air flowing, measure the two sensors and apply the difference to one as an offset (static_offset below) so the difference == 0. This is your calibration step. Due to self heating the sensors should work as a hot wire anemometer and when the air flow stops, the temp difference will go up and that will be your trigger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically you are constantly reading (T1 - T2 + static_offset). When this calculation exceeds a threshold you identify, send the alarm.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-01-26T02:52:18.497" />
  <row Id="9437" PostTypeId="1" AcceptedAnswerId="9438" CreationDate="2011-01-26T02:57:48.370" Score="4" ViewCount="209" Body="&lt;p&gt;Here's some nice LED's packaged in strips which can be cut apart and used for projects.  Voltage is up to 12 volts, and many people are using 3S 11.1 lipo cells to power them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some people comment that they are too bright, or that different colors (e.g. red and green) do not match in intensity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I solder a resistor in series to reduce the current flow to match the brighness?  Will that improve the battery life?  If I get a dial resistor, can I dial in the desired brightness and then measure the amperage flowing through the circuit to determine the needed resistance?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8941&quot; rel=&quot;nofollow&quot;&gt;http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8941&lt;/a&gt;&#xA;  &lt;img src=&quot;http://hobbyking.com/hobbyking/store/catalog/LED-S-RE.jpg&quot; width=&quot;200&quot;&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1756" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-27T05:26:43.757" LastActivityDate="2011-01-27T05:39:24.370" Title="How to calculate necessary resistance to dim some LEDs?" Tags="&lt;led&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="9438" PostTypeId="2" ParentId="9437" CreationDate="2011-01-26T03:29:38.590" Score="10" ViewCount="" Body="&lt;p&gt;LED brightness varies linearly with the (average) current.  If you double the resistor, that will roughly halve the brightness assuming the supply voltage is much greater than the LED voltage, if they are closer, the effect will be more significant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A more efficient method (but complex, and likely impossible to do in an existing circuit) would be to switch the LEDs on and off, adjusting the duty cycle to adjust the average current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Matching&lt;/em&gt; different LEDs in brightness will require good knowledge of the specifications and a good source that will provide the type and grade specified, not just &quot;a bright green LED&quot;.  The candela rating is weighted by the eye sensitivity, so making them match should make them appear equal &lt;em&gt;at 0 degrees&lt;/em&gt;.  Slightly different viewing angles can make the LEDs look very different as your viewer goes off-axis.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Example:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Matching a green 30 mA, 500 mcd, 3.5 Vf LED and a red, 15 mA, 3000 mcd, 1.8 Vf LED running on a 9 V source with a straight resistor ballast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The desired current through the red LED needs to be reduced to match the green, so it should be by a factor of &lt;code&gt;500 mcd/3000 mcd = 1/6&lt;/code&gt;, &lt;code&gt;15 mA * 1/6 = 2.5 mA&lt;/code&gt;.  The red ballast resistor should be &lt;code&gt;(9 V (supply) - 1.8 V (red LED Vf))/2.5 mA = 2880 Ω&lt;/code&gt;, and the green resistor should be &lt;code&gt;(9 V (supply) - 3.5 V (green LED Vf))/30 mA = 183 Ω&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This assumes &lt;code&gt;Vf&lt;/code&gt; will not change drastically with &lt;code&gt;If&lt;/code&gt; (should be reasonably constant in a 3-30 mA range, but consult graphs in datasheet), the viewing angles are identical, and as mentioned before, that the current is proportional to the intensity (almost always is down to sub-milliamp values, but check datasheet)&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-26T03:42:53.010" LastActivityDate="2011-01-26T03:42:53.010" CommentCount="1" />
  <row Id="9439" PostTypeId="2" ParentId="9190" CreationDate="2011-01-26T04:09:03.453" Score="0" ViewCount="" Body="&lt;p&gt;You need to rethink your requirements. Opening and closing a mechanical shutter in 500 microseconds is an extreme demand. Most mechanical shutters take several times as long to open completely. The shutters in SLRs achieve sub-millisecond exposures by opening partially and moving the opening across the frame so each portion &quot;sees&quot; light for a brief interval, but the overall exposure takes longer. &lt;a href=&quot;http://en.wikipedia.org/wiki/Rapatronic_camera&quot; rel=&quot;nofollow&quot;&gt;Extremely fast opening and closing times&lt;/a&gt; are the domain of &lt;a href=&quot;http://electronics.stackexchange.com/questions/7697/where-can-i-find-a-fast-1khz-lcd-plate&quot;&gt;electro-optical shutters&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1409" LastActivityDate="2011-01-26T04:09:03.453" />
  <row Id="9441" PostTypeId="1" CreationDate="2009-08-12T19:08:36.613" Score="1" ViewCount="129" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; I have been working on a ARM cortex A8 board on mp3 decoder.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;While doing this i have a requirement saying the mp3 decoder solution i am doing should consume 50 milli-watts of power. This generated few questions in my mind when i thought about it:- &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1.) I recall that there is some relation between the Core Voltage applied(V), the clock frequency(f) of a processor and power consumed(P) as something like P is directly proportional to the voltage and frequency squared. But is the exact relation. Given  operating clock Frequency, voltage of a processor, how can we calculate power consumed by it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2.) Now if i get the power consumed from step 1.) at some clock frequency, and i am told that the decoder solution i am giving, can consume only 50 milli-watts, how can i get the maximum limit on MCPS, which will be the upper bound on the MCPS of my decoder solution running on that hardware board?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can i deduce that if power obtained as in step 1.)  say P, is consumed at frequency F, so for 50 milli-watts power, what is clock frequency frequency and calculate accordingly the frequency. And then call this frequency as my code MHz (MCPS) upper bound?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically how does one map(is there any equation) power consumed by a software to MCPS consumed&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you.&#xA;-AD.&lt;/p&gt;&#xA;" OwnerUserId="1092" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-28T18:58:55.243" LastActivityDate="2011-01-28T18:58:55.243" Title="Relation between Power consumed and MCPS (million cycles per second) consumed on a processor." Tags="&lt;power&gt;&lt;frequency&gt;&lt;clock&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9442" PostTypeId="2" ParentId="9441" CreationDate="2011-01-26T05:41:53.597" Score="4" ViewCount="" Body="&lt;p&gt;I hate to give the answer of &quot;look at the datasheet&quot;, but it is going to be your best option. All micro-controllers I have used give their estimated current draw running at various frequencies and voltages. Not all of them will give a graph or equation, but instead will give you a few points in a table. You will just have to interpolate to get what you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is not a single equation that you can use to do this mapping because every device is going to have its own power consumption profile. In fact many embedded devices use their power vs frequency profile as a selling point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You haven't stated in your question at all, but don't forget about things like LEDs and other external devices connected to your device. These will all effect the power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After you get a frequency and voltage to run at, you can also use the datasheet to find out how many instructions you can have per second.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-26T05:41:53.597" />
  <row Id="9443" PostTypeId="2" ParentId="9435" CreationDate="2011-01-26T05:48:43.163" Score="2" ViewCount="" Body="&lt;p&gt;Typically I find that just adding a larger capacitor is all that is needed. If you place multiple capacitors in parallel of values that decades of each other you can help filter out noise at different frequencies. Ex, 0.01uF, 0.1uF, 1uF, 10uF. Using surface mount components is ideal for minimizing noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need cleaner power you can use an LC filter. This is far less common to see on boards though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing you want to look at is a voltage regulator. If you are already using one, check the datasheet to see if you are meeting all of the requirements that are required. These usually include input capacitance, output capacitance, and capacitor ESR. If you aren't using one, look into using one as you will be able to clean up your power a lot.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-26T05:48:43.163" CommentCount="2" />
  <row Id="9444" PostTypeId="1" CreationDate="2011-01-26T10:23:11.343" Score="3" ViewCount="192" Body="&lt;p&gt;I have a number of W2K systems that we are trying to use to program the new Arduino Uno and Mega devices.  These boards now come with a USB connection, an upgrade from the prior FTDI.  I'm not able to download the Arduino code into the board from a W2K system&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The supplied drivers are *.inf files that modify the standard USB driver that comes with Windows (in this case W2K)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I go through the process of setting the port, setting the device and doing the download.  The download fails, and the apparent error is that the PC can not communicate with the board.  I've checked the port, adjusted the baud rates, etc.  I've even moved the port number from a high port number (ie COM12) to a lower port (COM2) without any success.  I do see activity on the rec/xmt lights on the Arduino board, so some type of data is being sent and received.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for:&lt;br&gt;&#xA;Someone who has been able to download files from W2K to the Arduino&lt;br&gt;&#xA;or&lt;br&gt;&#xA;A way to shim inside the USB driver to be able to watch the traffic going up and down to the board so I can continue to debug this.&lt;br&gt;&#xA;or&lt;br&gt;&#xA;Some general tips for things to look at in the .inf file that need to be set/not set to make it work on W2K.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know the boards work I've used them on a different set of XP systems. So I know to some extent the install is good and that most of what I have works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Full dumps can be found on the Arduino forum.&lt;br&gt;&#xA;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1291090110/&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1291090110/&lt;/a&gt;&lt;br&gt;&#xA;This is the information produced by the AVRDude program while it's trying to download the code.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It was suggested at stackoverflow that this be posted here.&lt;/p&gt;&#xA;" OwnerUserId="2775" LastActivityDate="2011-01-28T12:11:53.083" Title="Arduino programming on Uno fails using USB download on Windows 2000" Tags="&lt;arduino&gt;&lt;usb-device&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="9445" PostTypeId="2" ParentId="9306" CreationDate="2011-01-26T11:50:00.387" Score="2" ViewCount="" Body="&lt;p&gt;The RAKE-receiver is a simple parallel correlation receiver. The advantage is, that (if you know the path delays) you can delay the signals and then correlated with the spreading sequence. Afterwards just combine the results.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take a look at the picture below (source: &lt;a href=&quot;http://www.wirelesscommunication.nl/reference/chaptr05/cdma/rake.htm&quot; rel=&quot;nofollow&quot;&gt;wirelesscommunication.nl&lt;/a&gt;). It shows the principles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/jhCuI.gif&quot; alt=&quot;RAKE&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2768" LastEditorUserId="2768" LastEditorDisplayName="" LastEditDate="2011-01-26T14:14:49.543" LastActivityDate="2011-01-26T14:14:49.543" />
  <row Id="9446" PostTypeId="2" ParentId="9441" CreationDate="2011-01-26T12:01:21.707" Score="4" ViewCount="" Body="&lt;p&gt;Hennessy and Patterson give this rule of thumb for CMOS:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Power = Capacitive load * voltage^2 *&#xA;  Frequency switched&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Calculating the power used in a system a priori is hard. The best approach is probably to try using an unoptimised MP3 decoder and characterising the performance. After that, you'll know how much better you need to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's also worth considering the power needed by the entire system, not just the CPU. Your MP3 data will be coming from somewhere, possibly external RAM, flash or even ethernet. This will incur a cost too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that the best approach is to build a system and take measurements.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-26T12:01:21.707" />
  <row Id="9447" PostTypeId="2" ParentId="9428" CreationDate="2011-01-26T12:55:22.203" Score="1" ViewCount="" Body="&lt;p&gt;If you want to monitor just one fan, maybe a Hall sensor on the fan for the rpm.&lt;/p&gt;&#xA;" OwnerUserId="1927" LastActivityDate="2011-01-26T12:55:22.203" CommentCount="1" />
  <row Id="9448" PostTypeId="2" ParentId="9428" CreationDate="2011-01-26T15:12:58.117" Score="1" ViewCount="" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I design equipment for data centres so get where you're coming from here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Gallamine is on the right track, you want a pressure sensor but a differential sensor like the ones you can get from RS or Farnell. Some are just switches and some have a I2C interface or voltage output that you could read. You can then look at the outlet air press compared to some place out the air flow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also use temperature as I guess there could be times the unit will switch off the fan when down to low temperatures and is not required - depends on design, but normally run 24/7.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip make the explorer 16 kit which you can get a Ethernet plug in module that allows you network access. They also have a full TCP/IP stack you can load onto it and this will allow you to send emails - I know cos we have done it. Would also give you a web interface so you can go look at pressure / temperature remotely to have the feel good factor its still working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other options include Arduino and Ethernet shield that again will give you networkable access - seen people sending tweets as alarms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Others are right - not a quick simple project but possible. Finding an off the shelf unit in a one off will be hard and you may well have to give on your requirements.&lt;/p&gt;&#xA;" OwnerUserId="2649" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-01-26T15:27:13.587" LastActivityDate="2011-01-26T15:27:13.587" CommentCount="1" />
  <row Id="9449" PostTypeId="2" ParentId="9437" CreationDate="2011-01-26T15:36:00.087" Score="5" ViewCount="" Body="&lt;p&gt;You could use a constant-current supply to set the current yourself.  There are well-known ones based off of LM317.  Here's another one I sketched up in answer to another question:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/nfuL0.jpg&quot; alt=&quot;&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This also has the advantage of making the brightness independent of supply variation.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-01-27T05:39:24.370" LastActivityDate="2011-01-27T05:39:24.370" CommentCount="4" />
  <row Id="9450" PostTypeId="2" ParentId="9306" CreationDate="2011-01-26T16:12:15.957" Score="2" ViewCount="" Body="&lt;p&gt;You need the Path searcher to find the beacon signals from other basestations (eg 3G towers)&#xA;in order to help with smooth handover, communication must take place to multiple basestations&#xA;Jason&lt;/p&gt;&#xA;" OwnerUserId="2780" LastActivityDate="2011-01-26T16:12:15.957" />
  <row Id="9451" PostTypeId="2" ParentId="9428" CreationDate="2011-01-26T16:20:06.920" Score="3" ViewCount="" Body="&lt;p&gt;For a very simple sensor you could hang two parallel strips of thin (very flexible) foil in front of the air vent. When air is flowing they'd end up pushed together, giving you (essentially) a switch closure you could read.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'd still need something to notice and give a yell, like the Arduino + ethernet shield mentioned elsewhere, but this is about as simple a sensor as you could get.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2011-01-26T16:20:06.920" CommentCount="1" />
  <row Id="9452" PostTypeId="2" ParentId="6436" CreationDate="2011-01-26T16:42:03.900" Score="1" ViewCount="" Body="&lt;p&gt;Have a look at &lt;a href=&quot;http://www.seeedstudio.com/depot/page.html?id=3&amp;amp;zenid=095dc56808bc2be51d6ebf2426f9e043&quot; rel=&quot;nofollow&quot;&gt;SeeedStudio&lt;/a&gt;, they seem to provide many tools for aiding somebody to launch a HW project.&lt;/p&gt;&#xA;" OwnerUserId="2577" LastActivityDate="2011-01-26T16:42:03.900" />
  <row Id="9453" PostTypeId="1" AcceptedAnswerId="9454" CreationDate="2011-01-26T17:47:24.673" Score="2" ViewCount="140" Body="&lt;p&gt;How would I go about detecting at motor controller level, that my PWM signal coming from my microcontroller is at 50% duty cycle.  I would like to design a dead band into my motor controller so that I only have a single PWM signal coming from my uC instead of PWM, CCW, CW signals to free up ports.&lt;/p&gt;&#xA;" OwnerUserId="2781" LastActivityDate="2011-01-26T18:47:42.180" Title="Detect PWM Duty Cycle in Hardware" Tags="&lt;microcontroller&gt;&lt;motor&gt;&lt;pwm&gt;" AnswerCount="1" />
  <row Id="9454" PostTypeId="2" ParentId="9453" CreationDate="2011-01-26T18:35:07.067" Score="3" ViewCount="" Body="&lt;p&gt;I'm assuming you only want to use the PWM to determine CW/CCW direction. If you also want to control motor speed then there's no simple solution.&lt;br&gt;&#xA;You could filter a DC voltage from the PWM signal using a low-pass filter. Use a comparator to compare with 45% of Vpwm (indicates 45% duty cycle). If it's lower run CW. Use a second comparator to compare with 55% of Vpwm. If it's higher run CCW. The dead zone between 45% and 55% ensures that it doesn't switch continuously between CW and CCW around 50% duty cycle. The dead zone means you don't need the Schmitt-trigger, which is normally used for this protection.  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-01-26T18:47:42.180" LastActivityDate="2011-01-26T18:47:42.180" />
  <row Id="9455" PostTypeId="1" AcceptedAnswerId="9837" CreationDate="2011-01-26T20:07:14.467" Score="8" ViewCount="300" Body="&lt;p&gt;&lt;strong&gt;Background&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To kick-start my longstanding ambition of getting back into electronics, I decided to try and make a device that measures the soil moisture of potted plants to determine whether they need to be watered. The aim for the first incarnation is to have a led that shows the plant's current water level (add water is red!), but of course I have wild plans for self-watering plants down the road.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first stab was based on the &lt;a href=&quot;http://www.instructables.com/id/Garduino-Gardening-Arduino/step4/Build-Your-Moisture-Sensor/&quot; rel=&quot;nofollow&quot;&gt;Garduino instructable&lt;/a&gt;, specifically this circuit here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Rc4Ek.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a simple voltage divider using a known resistor and two copper wire electrodes stuck in the soil as measuring device. The voltage measured at &lt;code&gt;A0&lt;/code&gt; using the ADC on my &lt;a href=&quot;http://www.pjrc.com/teensy/&quot; rel=&quot;nofollow&quot;&gt;Teensy++&lt;/a&gt; is proportional to the ratio of the resistances, and I can work back to the actual soil resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, in practice the soil resistance turned out to be subject to a very large drift. Almost immediately after turning on the device, the measured soil resistance started dropping. (This also happens if you stick a multimeter in the plant.) After a few days of measurement, I could find no usable connection between the measurements and the moisture level. Removing the probe and inspecting it revealed considerable tarnish on the anode. To me, this indicates that some sort of chemical reaction is taking place (electrolysis?). A multimeter measures a voltage differential of a few tens of millivolts: I have turned my plant into a battery!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/bRSTy.jpg&quot; alt=&quot;Oxidized anode&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To avoid this problem I moved to a probe constructed out of stainless steel screws. As they are considerably less reactive than copper, the oxidation should be less of a problem. Also, to avoid &quot;charging&quot; the soil, i have put the voltage divider between two digital output pins of the Teensy. The measurement happens as follows:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Both pins are kept low when no measurement is taking place.&lt;/li&gt;&#xA;&lt;li&gt;I drive one pin high. I wait one millisecond and I measure the voltage at the center of the divider.&lt;/li&gt;&#xA;&lt;li&gt;I invert the pin voltages (high&amp;lt;-&gt;low), wait one millisecond and measure again. I should now measure the complement of the first measurement.&lt;/li&gt;&#xA;&lt;li&gt;Both pins are brought low again and the device sleeps until the next measurement.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This does reduce the oxidation problem, but the measured soil resistance still seems to start dropping as soon as I start measuring.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Question&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Can anyone recommend a robust method to measure soil moisture?&lt;/li&gt;&#xA;&lt;li&gt;Can anyone explain what is really going on here?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-02-07T20:03:13.420" Title="Soil moisture measurement" Tags="&lt;measurement&gt;&lt;moisture&gt;" AnswerCount="6" CommentCount="0" FavoriteCount="5" />
  <row Id="9456" PostTypeId="2" ParentId="1222" CreationDate="2011-01-26T20:11:00.967" Score="1" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://www.expresspcb.com/&quot; rel=&quot;nofollow&quot;&gt;ExpressPCB&lt;/a&gt;, which is a free unlimited software package that allows you to design schematics and PCBs. You can also send off your design to &lt;a href=&quot;http://www.expresspcb.com/&quot; rel=&quot;nofollow&quot;&gt;ExpressPCB&lt;/a&gt; and they'll manufacture the board for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Screenshot:&#xA;&lt;img src=&quot;http://i.imgur.com/sfVHl.gif&quot; alt=&quot;ExpressPCB Screenshot&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-26T20:11:00.967" CommentCount="6" />
  <row Id="9457" PostTypeId="2" ParentId="9455" CreationDate="2011-01-26T20:53:50.863" Score="5" ViewCount="" Body="&lt;p&gt;You should be using AC, to avoid polarisation of the electrodes, with a Wenner bridge arrangement.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-26T20:53:50.863" CommentCount="2" />
  <row Id="9458" PostTypeId="2" ParentId="9455" CreationDate="2011-01-26T21:01:32.480" Score="2" ViewCount="" Body="&lt;p&gt;Here's how &lt;A href=&quot;http://www.botanicalls.com/classic/how-it-works/&quot; rel=&quot;nofollow&quot;&gt;botanicalls&lt;/a&gt; does it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.botanicalls.com/archived_kits/1.0/graphics/BotanicallsTwitter_Protoshield_Circuit.png&quot; width=&quot;600&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-26T21:01:32.480" CommentCount="4" />
  <row Id="9459" PostTypeId="1" AcceptedAnswerId="9462" CreationDate="2011-01-26T21:03:44.410" Score="4" ViewCount="200" Body="&lt;p&gt;I have an ADC input that may be connected to an external sensor (based on how the user configures it).  If I leave the input floating, I get a wide range of ADC values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a way to weakly ground this input to get a stable reading if nothing is connected?&lt;/p&gt;&#xA;" OwnerUserId="204" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-20T20:04:08.977" LastActivityDate="2011-03-20T20:04:08.977" Title="How to ground a floating ADC input" Tags="&lt;pic&gt;&lt;adc&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="9460" PostTypeId="2" ParentId="9459" CreationDate="2011-01-26T21:17:15.097" Score="2" ViewCount="" Body="&lt;p&gt;A 100k ohm or lower resistor to ground would be suitable. Make sure the resistor does not load down your sensor too much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OR, if you have a way of the microcontroller determining if the sensor is connected or switched on (for example, the MCU controls power to it), you can disable the analog input. For example, on PIC16F series chips you can set the pin as an output (TRISx), drive it low (PORTx) and turn off the analog input (ANSELx).&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-01-26T21:17:15.097" CommentCount="2" />
  <row Id="9461" PostTypeId="2" ParentId="9424" CreationDate="2011-01-26T21:18:15.703" Score="2" ViewCount="" Body="&lt;p&gt;I think that the ARM7 or Cortex-M3 parts already recommended should fulfill your need if clocked sufficiently quickly, but wanted to add another alternative.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.atmel.com/products/AVR/uc3.asp?family_id=607&quot; rel=&quot;nofollow&quot;&gt;Atmel AVR32&lt;/a&gt; has an  external bus interface that would allow you plug into a very large external SDRAM/SRAM or Flash chip.  The Mizar32 is an open-source board which has an example of this kind of interface; they use it to connect to a 32MB SDRAM chip.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your key requirements were: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Low power: This is relative; everyone claims their parts are low power.  The AVR32 draws about .5mA/MHz, and can be clocked at up to 150MHz.  At 60MHz (a common top speed for other parts), that's 30mA.&lt;/li&gt;&#xA;&lt;li&gt;16 bit: It's 32-bit, which means it exceeds this spec.&lt;/li&gt;&#xA;&lt;li&gt;RAM &gt; 10kB (ftfy), Flash &gt; 128kB: Yes, most of &lt;a href=&quot;http://www.atmel.com/dyn/products/param_table.asp?family_id=607&amp;amp;OrderBy=1197&amp;amp;Direction=ASC#2138&quot; rel=&quot;nofollow&quot;&gt;the options&lt;/a&gt; have 128-512kB Flash and more than half have &gt;64kB of RAM.  It also has the aforementioned memory bus that allows you to increase this to many MB or even 1GB, but that's not single-cycle anymore.&lt;/li&gt;&#xA;&lt;li&gt;HW multiplier: Check.&lt;/li&gt;&#xA;&lt;li&gt;Available in development kit form or something: Check? It's in production, if that's what you mean, and there are dev kits for it.  However, Atmel hasn't always been the best at keeping parts in stock, so an ARM part would give you more flexibility in switching vendors if such a need would appear. PICs and MSP430s will also have the same problem of a single vendor.&lt;/li&gt;&#xA;&lt;li&gt;SD card/Flash memory: Yes, again, it has this. There's also an SD card DMA peripheral.&lt;/li&gt;&#xA;&lt;li&gt;3Mbps (3250000bps) UART? (need to interface with a Bluetooth module for high speed communication).  Eh, I guess so?  Assuming you have Bluetooth hardware that can handle this task, you may be better off using an external UART transceiver that implements its own FIFO (Bluetooth is a packet based transmission channel), and has a parallel interface so you're not so transmitting.  Exar is a company that &lt;a href=&quot;http://www.exar.com/Common/Content/Product.aspx?ID=7250&amp;amp;Parent=4&quot; rel=&quot;nofollow&quot;&gt;has some options&lt;/a&gt;; you'll want to look for an Intel 16C550 interface (since you don't have PCI). &lt;strong&gt;Better yet, get a Bluetooth module with a parallel or synchronous interface.&lt;/strong&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So, add the AVR32 to the lineup of mid-power parts we've presented you with. (That would be ARM7, ARM Cortex-M3, dsPIC, and PIC32) &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-26T23:35:33.753" LastActivityDate="2011-01-26T23:35:33.753" CommentCount="3" />
  <row Id="9462" PostTypeId="2" ParentId="9459" CreationDate="2011-01-26T21:18:53.367" Score="5" ViewCount="" Body="&lt;p&gt;Try using a pull down resistor. 1M might be suitable, try out different values. Higher values may tend to not completely ground your ADC input. Lower values may cause a too heavy load on your sensor.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-01-26T21:18:53.367" />
  <row Id="9463" PostTypeId="1" AcceptedAnswerId="9467" CreationDate="2011-01-26T21:21:25.660" Score="2" ViewCount="162" Body="&lt;p&gt;I have a 4 port USB hub with 3 INCREDIBLY BRIGHT led lights on the circuit board I would prefer removed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've googled a bit and found a user of this site actually describe the process very well.. &lt;a href=&quot;http://reviews.bestbuy.com/answers/3545/product/9775443/rocketfish-4-port-usb-2-0-hub-questions-answers/questions.htm&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My knowledge of working with this stuff is next to none, and I do not have a soldering iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, this user suggests soldering off or 'cut off with a knife', a TINY resistor next to each LED. I've poked at it a bit and it doesn't seem to want to budge. I'm worried I will break something or scratch it if I try much harder..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my main question is, I believe I could much easier pull the led's off with pliers. Would this work as well? Is this dangerous? Or any tips on getting the resistors off without a soldering iron?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a photo of the top with the resistors in question. Click for a high-res version.&#xA;&lt;a href=&quot;http://i.imgur.com/uQ57b.jpg?4098&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/W5mJD.jpg&quot; alt=&quot;http://i.imgur.com/uQ57b.jpg?4098&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And here is a photo of the bottom with the LED's I'd like to yank out.&#xA;&lt;a href=&quot;http://i.imgur.com/JrM8s.jpg?4933&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/1Es23.jpg&quot; alt=&quot;http://i.imgur.com/JrM8s.jpg?4933&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All help is appreciated. Thank you.&lt;/p&gt;&#xA;" OwnerUserId="2785" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-31T05:34:00.343" LastActivityDate="2011-01-31T05:34:00.343" Title="I want to remove 3 LED's from a small circuit board. Need a bit of help." Tags="&lt;led&gt;&lt;usb&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="9464" PostTypeId="2" ParentId="9463" CreationDate="2011-01-26T21:35:55.633" Score="3" ViewCount="" Body="&lt;p&gt;When I'm confronting an INCREDIBLY BRIGHT LED and I don't care about the power consumption, I simply cover it with a small piece of electrical tape or liquid electrical tape. It would also be quite easy to push the resistors off using the tip of a hot soldering iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't yank them off. Snip the leads with a flat cutter.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2011-01-26T21:35:55.633" CommentCount="8" />
  <row Id="9465" PostTypeId="1" CreationDate="2011-01-26T21:38:15.100" Score="1" ViewCount="274" Body="&lt;p&gt;I've been using Arduino for awhile and now I'm interested in programming AVR microcontrollers without the Arduino framework.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is a good reference for beginning AVR programming in C? A book is preferred, but online resources are also welcome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for something that will start with basic setup on a *NIX platform, start with examples and cover a number of core topics. Something similar to K&amp;amp;R, but oriented toward microcontrollers would work well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Related question: &lt;a href=&quot;http://electronics.stackexchange.com/questions/1437/linux-mac-avr-programming-suite&quot;&gt;Linux / Mac AVR Programming Suite?&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2011-01-26T21:53:57.233" LastActivityDate="2011-02-04T10:54:12.713" Title="Beyond Arduino: AVR Programming Book for Beginner" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;books&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="9466" PostTypeId="2" ParentId="9455" CreationDate="2011-01-26T21:44:02.537" Score="2" ViewCount="" Body="&lt;p&gt;I've constructed a soil humidity sensor using two galvanized nails set in a cylinder of Plaster of Paris. I didn't test it over a long enough period of time to draw any conclusions as you have, but you might experiment with that design. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The plaster neutralizes any acid in the moisture, thus isolating humidity content as a variable (but also works as a kind of low-pass filter!) + the galvanization on the nails helps to prevent them from oxidizing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please post if you find a good solution.&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2011-01-26T21:44:02.537" />
  <row Id="9467" PostTypeId="2" ParentId="9463" CreationDate="2011-01-26T21:52:08.250" Score="5" ViewCount="" Body="&lt;p&gt;Hey!  That reminds me, I need to desolder those LEDs and make some throwies.  Those things lighted the room with the fury of a thousand suns.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyways, the goal of the process is to somehow disconnect the trace which goes from the tiny resistors toward the center of the board, and the side of the LED which connects to the ground plane.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can do this by (1) removing the resistor or LEDs with a soldering iron, or (2) by removing the resistor with another tool (pocketknife), (3) by cutting the trace itself, or by (4) cutting the LEDs with flush cutters/dikes, or, as you suggested, (5) by pulling with a pair of pliers.  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&#xA;&lt;li&gt;Removal with a soldering iron is the least destructive and most professional way of doing it.  It's easy, just put your tip next to it, wait for the solder to become shiny, and push it off. &lt;/li&gt;&#xA;&lt;li&gt;OK, you can break the resistor off of the pads.  I got my new USB hub, came home, and started dd'ing two drives to a third (which was why I needed the hub). Then, I turned off the lights (the ones on my ceiling) and tried to go to bed.  I probably acted rashly by not covering them temporarily and waiting until the next day to use a soldering iron, but as long as you don't create any connections that weren't there before, your goal is to break this connection, you can't really do any damage.&lt;/li&gt;&#xA;&lt;li&gt;The trace is probably 1oz copper, which is about 1/4th the thickness of aluminum foil.  It's glued to the sturdy FR4 board, and it's underneath a layer of soldermask, but it's easy enough to cut.  A few scores back and forth should do it.&lt;/li&gt;&#xA;&lt;li&gt;The LEDs are extremely bright, and in an unusual package/pin spacing.  They're probably worth $0.25 plus shipping, and would be hard to replace.  The resistors, on the other hand, are $0.02, and are easy to get. I opted not to cut them off, but if you can disconnect the two pins, you'll succeed in breaking the circuit. &lt;/li&gt;&#xA;&lt;li&gt;The LEDs do have 22ga pins, and are firmly soldered to the PCB.  This is a metal to metal bond; you won't just pull the LED out of the hole.  You will mangle it.  If you mangle it enough, you will likely succeed.  However, cutting something is probably a little easier.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;And yes, I did get to bed, the LEDs ceased to blind me, and the USB hub is still working great.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-26T21:52:08.250" CommentCount="2" />
  <row Id="9468" PostTypeId="2" ParentId="9463" CreationDate="2011-01-26T23:18:14.263" Score="0" ViewCount="" Body="&lt;p&gt;If all you want is to hide them, just use a marker pen to cover them up, or some opaque glue&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-26T23:18:14.263" />
  <row Id="9469" PostTypeId="2" ParentId="9388" CreationDate="2011-01-26T23:43:35.863" Score="0" ViewCount="" Body="&lt;p&gt;Why not to get a cheap one from the &lt;a href=&quot;http://www.eevblog.com/2009/04/29/eevblog-6-part-2-of-2-why-cheap-chinese-multimeters-suck/&quot; rel=&quot;nofollow&quot;&gt;same Aussie&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-26T23:43:35.863" />
  <row Id="9470" PostTypeId="2" ParentId="9185" CreationDate="2011-01-26T23:58:54.350" Score="2" ViewCount="" Body="&lt;p&gt;This looks like a good project which does everything I need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.tuxgraphics.org/electronics/201005/bench-power-supply-v3.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.tuxgraphics.org/electronics/201005/bench-power-supply-v3.shtml&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://shop.tuxgraphics.org/electronic/detail_microcontroller_powersupply.html&quot; rel=&quot;nofollow&quot;&gt;http://shop.tuxgraphics.org/electronic/detail_microcontroller_powersupply.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-26T23:58:54.350" />
  <row Id="9471" PostTypeId="1" AcceptedAnswerId="9472" CreationDate="2011-01-27T13:48:36.530" Score="1" ViewCount="101" Body="&lt;p&gt;I am looking for a case that would work well as a heat sink. Thinking  that something like a car amplifier case? Anyone know where one could find cases like this? Would be using it to house H-Bridges and fill it with thermal conductive epoxy to water proof it....&lt;/p&gt;&#xA;" OwnerUserId="1337" LastActivityDate="2011-01-29T17:20:33.033" Title="Where would one find thermal heat sink cases?" Tags="&lt;heatsink&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="9472" PostTypeId="2" ParentId="9471" CreationDate="2011-01-27T14:24:56.310" Score="4" ViewCount="" Body="&lt;p&gt;One of &lt;a href=&quot;http://www.lincolnbinns.com/e-case.htm&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-27T14:24:56.310" />
  <row Id="9473" PostTypeId="2" ParentId="9428" CreationDate="2011-01-27T15:33:18.537" Score="1" ViewCount="" Body="&lt;p&gt;How about buying a standard wind meter and hooking it up to one of your free computers. &lt;a href=&quot;http://www.weathershop.com/wind_.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.weathershop.com/wind_.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or you can build one @ &lt;a href=&quot;http://www.instructables.com/id/Digital-Anemometer-wind-meter/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Digital-Anemometer-wind-meter/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-01-27T15:33:18.537" />
  <row Id="9474" PostTypeId="2" ParentId="1635" CreationDate="2011-01-27T15:44:13.717" Score="0" ViewCount="" Body="&lt;p&gt;Just to throw this out there, if you're trying to learn from a book and tight on money, another option is to use a circuit simulator.  I've had sucess with SPICE (free versions), but I'm sure there are other options.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not trying to say that hands on practice with circuits is not needed.  At some point you do have to try things with actual hardware.  But if you're just trying to learn and money is a constraint, circuit simulators can be very helpful.&lt;/p&gt;&#xA;" OwnerUserId="2059" LastActivityDate="2011-01-27T15:44:13.717" />
  <row Id="9475" PostTypeId="1" CreationDate="2011-01-27T15:54:50.523" Score="3" ViewCount="287" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Category%3aFunctional_languages&quot; rel=&quot;nofollow&quot;&gt;Functional languages&lt;/a&gt; like Haskell, LISP, or Scheme allow a programmer to work quickly using the &lt;a href=&quot;http://en.wikipedia.org/wiki/Functional_programming&quot; rel=&quot;nofollow&quot;&gt;functional programming&lt;/a&gt; paradigm.  They do have their &lt;a href=&quot;http://en.wikipedia.org/wiki/Functional_programming#Efficiency_issues&quot; rel=&quot;nofollow&quot;&gt;inefficiencies&lt;/a&gt;, but my application places greater emphasis on programmer efficiency than efficiency of the program itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to use functional programming on a microcontroller to do machine control, etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What limitations are there, such as minimum system resources?&lt;br&gt;&#xA;What example implementations of these languages are available? &lt;/p&gt;&#xA;" OwnerUserId="374" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-01-27T21:21:31.497" LastActivityDate="2011-01-28T15:49:25.107" Title="Functional Programming with MCU(s)" Tags="&lt;microcontroller&gt;&lt;programming&gt;&lt;functional-programming&gt;" AnswerCount="6" CommentCount="13" FavoriteCount="1" />
  <row Id="9476" PostTypeId="2" ParentId="9475" CreationDate="2011-01-27T16:04:18.513" Score="8" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;ARMPIT SCHEME is an interpreter for&#xA;  the Scheme language (lexically-scoped&#xA;  dialect of Lisp) that runs on RISC&#xA;  microcontrollers with ARM core. It is&#xA;  based on the description in the&#xA;  Revised Report on the Algorithmic&#xA;  Language Scheme (r5rs), with some&#xA;  extensions (for I/O) and some&#xA;  omissions (to fit within MCU memory).&#xA;  It is further designed to support&#xA;  multitasking and multiprocessing.&#xA;  Armpit Scheme is expected to be well&#xA;  suited to educational settings,&#xA;  including student projects in courses&#xA;  on control and instrumentation, or&#xA;  capstone design courses where&#xA;  microcontrollers are needed. It is&#xA;  meant to enrich the spectrum of&#xA;  interpreted languages available for&#xA;  MCUs (eg. BASIC and FORTH) and can be&#xA;  an alternative to MCU-based bytecode&#xA;  interpreters (eg. for Scheme or Java)&#xA;  and to compiled languages (eg. C).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://armpit.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;http://armpit.sourceforge.net/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You say:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Using C, C++, assembly, etc. is quite inefficient compared to languages like Haskell, LISP, or Scheme&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Using high level languages is a more efficient use of programmer time, but can often be a less effificent use of computing resources. For embedded systems manufactured in volume, cost and performance are often higher priority than development effort.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-27T16:04:18.513" />
  <row Id="9477" PostTypeId="2" ParentId="9475" CreationDate="2011-01-27T16:11:48.810" Score="5" ViewCount="" Body="&lt;p&gt;C, C++, and Assembly are all very close to machine language. By using a higher level language, you are adding additional overhead in exchange for more rapid/easier/etc development.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2011-01-27T16:11:48.810" CommentCount="4" />
  <row Id="9478" PostTypeId="2" ParentId="9475" CreationDate="2011-01-27T16:53:21.567" Score="1" ViewCount="" Body="&lt;p&gt;I've been programming an ARM board in Python recently, and I think it's great. It's no good for real-time control, but I'm doing more web-related stuff, which is &lt;em&gt;far&lt;/em&gt; more pleasant in a high-level language than in C.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-01-27T16:53:21.567" />
  <row Id="9479" PostTypeId="2" ParentId="9475" CreationDate="2011-01-27T17:22:09.353" Score="3" ViewCount="" Body="&lt;p&gt;The majority of microcontrollers are still 8 and 16-bit devices (although this is slowly changing).  The two instances of higher-level languages (Scheme and Python) mentioned in other answers so far are both running on 32-bit ARM cores.  The smaller 8 and 16-bit devices (which may cost only a couple of dollars) don't have enough RAM to support the languages being mentioned -- typically they only have a few KB of RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, these higher-level languages are not designed for writing low latency interrupt handlers and the like.  It's not unusual for a microcontroller interrupt handler to get called hundreds or thousands of times per second, and each time required to perform its task in tens of microseconds or less.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-01-27T17:22:09.353" />
  <row Id="9480" PostTypeId="1" CreationDate="2011-01-27T17:43:48.480" Score="3" ViewCount="141" Body="&lt;p&gt;I was wondering which books on Cadence OrCAD (or Cadence products in general) are good for for reference use and/or have substantial focus on device modelling and simulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currently I am using this book, &lt;em&gt;Complete PCB Design Using OrCad Capture and Layout&lt;/em&gt; by Kraig Mitzner but would like to know other people's preferences.&lt;/p&gt;&#xA;" OwnerUserId="2761" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-19T23:23:06.703" LastActivityDate="2011-05-09T20:27:21.520" Title="Book Recommendations on Cadence OrCAD" Tags="&lt;books&gt;&lt;orcad&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="9481" PostTypeId="2" ParentId="9475" CreationDate="2011-01-27T18:45:13.150" Score="2" ViewCount="" Body="&lt;p&gt;&quot;Are there ways to do functional programming with a functional language on an MCU to solve difficult problems?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, there are ways.  But the downside is you need a 32-bit processor, MMU, 128MB RAM, SSD, an RTOS, and $$$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microcontrollers are different than microprocessors.  The microcontroller may only be a 8-bit CPU, 1K RAM, 8K ROM, but it has a built in UART, PWM, ADC, etc.  And it only costs $1.30.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you could have all that high-level languages running, but it costs a lot more to make.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-01-27T18:45:13.150" CommentCount="1" />
  <row Id="9482" PostTypeId="1" CreationDate="2011-01-27T21:01:39.267" Score="1" ViewCount="134" Body="&lt;p&gt;3M MDR connectors (&lt;a href=&quot;http://solutions.3m.com/wps/portal/3M/en_US/Interconnect/Home/Products/ProductCatalog/&quot; rel=&quot;nofollow&quot;&gt;see here for details&lt;/a&gt;) seem to be a pretty common interconnect system. Has anyone tried making a few cables and boxes with these without buying the 3M tooling kit? Since the kit is $2000 (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=3M3829-ND&quot; rel=&quot;nofollow&quot;&gt;from e.g. Digikey&lt;/a&gt;) it would be nice not to have to buy this if I'm only hooking up a few things. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically, I'm looking at their &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&amp;amp;keywords=10150-3000PE&quot; rel=&quot;nofollow&quot;&gt;50-pin connector&lt;/a&gt; with &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=MB50S-100-ND&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; cable. Is it feasible to connect these with nothing more than a decent soldering iron?&lt;/p&gt;&#xA;" OwnerUserId="2796" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-01-27T23:47:31.853" LastActivityDate="2011-01-31T20:27:41.447" Title="soldering 3M MDR (Mini Delta Ribbon) connectors?" Tags="&lt;soldering&gt;&lt;breakout&gt;&lt;interconnect&gt;" AnswerCount="4" />
  <row Id="9483" PostTypeId="2" ParentId="9482" CreationDate="2011-01-27T21:12:26.403" Score="3" ViewCount="" Body="&lt;p&gt;Don't waste your time trying to solder them, it won't work. Most distributors will make up cables for you, it shouldn't be expensive. Or. choose a connector system that is easier and cheaper to assemble.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-27T21:12:26.403" CommentCount="6" />
  <row Id="9484" PostTypeId="2" ParentId="9428" CreationDate="2011-01-27T21:48:52.107" Score="0" ViewCount="" Body="&lt;p&gt;Surely the core need is to monitor room temp, which you say you are already doing, so isn't trying to monitor airflow just overkill and creating unnecessary complexity? At the end of the day: room = cool enough = happy you?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I looked into automating the monitoring of the server room in which I worked, I ended up with a USB temp sensor off ebay for very little indeed and we just plugged it into one of the PCs already in the room. There were plenty of apps on the internet to read the sensor and dump the temp to a file and I had a simple batch file to read this and send an email if the temp rose above a set value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My only extravagance was to look at a USB IR Tx/Rx module that I planned to program to learn and send the aircon on/off commands as the room was a semi-office area and could be adequately cooled by opening some windows when the room was occupied, but once in a while the occupants would forget to turn on the aircon again when they closed up and left for the night. Ultimately, I left the job before putting this part of the plan into action.&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2011-01-27T21:48:52.107" CommentCount="2" />
  <row Id="9485" PostTypeId="2" ParentId="9482" CreationDate="2011-01-27T22:33:59.610" Score="2" ViewCount="" Body="&lt;p&gt;The connector you linked to is specced as a Solder Cup connector, so it &lt;em&gt;Should&lt;/em&gt; be possible to hand solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may be a bit fiddly though. &lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-01-27T22:33:59.610" />
  <row Id="9486" PostTypeId="2" ParentId="9480" CreationDate="2011-01-27T22:48:47.617" Score="0" ViewCount="" Body="&lt;p&gt;You are better off with that one or Cadence's documentation.  Other than that one, the other books out there are generally not current with the software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My experience is more for the Capture side of things; not the Layout side.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-27T22:48:47.617" />
  <row Id="9487" PostTypeId="2" ParentId="9388" CreationDate="2011-01-27T22:54:53.377" Score="1" ViewCount="" Body="&lt;p&gt;Check out some of the meters on the pages below to see which suits you best and have the specs you require. I use quite a few hand held meters, The cheapest of which is an Extech EX330. It's a good little meter&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Extech EX330 is great for the price and has a 4000 count display, along with decent &amp;amp; necessary built in circuit protection. I use the EX330 on a daily basis with no problems at all. Also check out brands like Amprobe, and higher end Tenma meters which are pretty good nowadays.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also check out Farnells own site for meters (As a noob I can only add 1 link) as they have a larger range but do tend to carry the more expensive stuff too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://cpc.farnell.com/jsp/search/browse.jsp?N=411+1002974+521+500001&amp;amp;Ns=PRICE_PLS_002_PRICE1%7c0&quot; rel=&quot;nofollow&quot;&gt;CPC&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2663" LastActivityDate="2011-01-27T22:54:53.377" CommentCount="1" />
  <row Id="9488" PostTypeId="2" ParentId="9444" CreationDate="2011-01-28T01:43:26.140" Score="2" ViewCount="" Body="&lt;p&gt;Looking at the dump, it says 'Overriding Baud Rate  : 115200'.  look into your /hardware/arduino/boards.txt file, and try changing it to 57600.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;from:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;uno.upload.speed=115200&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;to:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;uno.upload.speed=57600&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I had a similar problem (on ubuntu) with my UNO board and a new Atmega328p-pu chip I ordered. It didn't want to upload.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Atmega328p-pu datasheet specifies that its transfer rate is 57600 baud, but the  boardx.txt file was set to 115200 baud.  It worked as soon as I set it back to 57600.&lt;/p&gt;&#xA;" OwnerUserId="2342" LastEditorUserId="2342" LastEditorDisplayName="" LastEditDate="2011-01-28T12:11:53.083" LastActivityDate="2011-01-28T12:11:53.083" CommentCount="1" />
  <row Id="9489" PostTypeId="1" AcceptedAnswerId="9562" CreationDate="2011-01-28T04:48:02.243" Score="1" ViewCount="108" Body="&lt;p&gt;I'm trying to (hopefully) reuse a smartphone LCD and touchscreen controller, among some other components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first step is to break out the tiny connectors on the board. It appears to be 2 board to FPC connections. See picture here: &lt;a href=&quot;http://i.imgur.com/jctIv.jpg&quot; rel=&quot;nofollow&quot;&gt;http://i.imgur.com/jctIv.jpg&lt;/a&gt; (bottom right, sorry for the poor quality)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this &lt;a href=&quot;http://pewa.panasonic.com/components/connectors/narrow-pitch-board-to-fpc-connectors/a35s/&quot; rel=&quot;nofollow&quot;&gt;resource&lt;/a&gt; but it's almost impossible for me to tell which one specifically is used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions for how I could get to those signals or wire it up to a breadboard?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Much appreciated.&lt;/p&gt;&#xA;" OwnerUserId="2799" LastActivityDate="2011-01-31T02:43:11.280" Title="How to break out Board to FPC connector" Tags="&lt;circuit&gt;&lt;embedded&gt;&lt;hardware&gt;&lt;connector&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="9490" PostTypeId="1" AcceptedAnswerId="9491" CreationDate="2011-01-28T05:52:31.720" Score="2" ViewCount="105" Body="&lt;p&gt;I'd like to break my NXC code into several files and compile and link the files into a single RXE binary using the NBC/NXC compiler that comes with BrixcCC for code comprehension.  Can it be done and what is the typical method for doing this?&lt;/p&gt;&#xA;" OwnerUserId="2260" LastEditorUserId="2260" LastEditorDisplayName="" LastEditDate="2011-02-01T06:37:44.063" LastActivityDate="2011-02-01T06:37:44.063" Title="How can I compile multiple NXC files together?" Tags="&lt;lego-mindstorms&gt;&lt;nxc&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="9491" PostTypeId="2" ParentId="9490" CreationDate="2011-01-28T06:19:47.833" Score="2" ViewCount="" Body="&lt;p&gt;Currently, the creator of BricxCC (John Hansen) recommends you put them all in .nxc files. (No .h files, etc.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use &lt;code&gt;#includes&lt;/code&gt;. For example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Contents of &lt;em&gt;afile.nxc&lt;/em&gt;:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#ifndef __AFILE_NXC__&#xA;#define __AFILE_NXC__&#xA;&#xA;    void displayStuff()&#xA;    {&#xA;        TextOut(0, 0, &quot;Hello World!&quot;, 0);&#xA;    }&#xA;&#xA;#endif&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Contents of &lt;em&gt;main.nxc&lt;/em&gt;:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &quot;afile.nxc&quot;&#xA;&#xA;task main()&#xA;{&#xA;    displayStuff();&#xA;    Wait(2000);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1940" LastEditorUserId="1940" LastEditorDisplayName="" LastEditDate="2011-01-28T06:24:49.983" LastActivityDate="2011-01-28T06:24:49.983" />
  <row Id="9493" PostTypeId="2" ParentId="9482" CreationDate="2011-01-28T10:43:37.170" Score="1" ViewCount="" Body="&lt;p&gt;This looks perfectly solder-able to me. My record is soldering 80-pin cable, so your 50-pin one will eat less of your Patience. Also, you should think about finish insulation &amp;amp; look&amp;amp;feel :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe heat shrink tube on each wire/connection...&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-28T10:43:37.170" />
  <row Id="9494" PostTypeId="2" ParentId="9455" CreationDate="2011-01-28T10:55:47.760" Score="3" ViewCount="" Body="&lt;p&gt;The only robust method for measuring soil moisture that I am aware of is using &lt;a href=&quot;http://vegetronix.com/Products/VG400&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; probes.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-01-28T10:55:47.760" CommentCount="2" />
  <row Id="9495" PostTypeId="1" AcceptedAnswerId="14019" CreationDate="2011-01-28T12:42:42.310" Score="2" ViewCount="130" Body="&lt;p&gt;Can you recommend a programmer for low voltage parallel flash memories like 29LV320? &#xA;(around 100 USD max, if possible:)&lt;/p&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2011-05-07T15:49:37.990" Title="Recommended programmer for parallel flash memory?" Tags="&lt;programmer&gt;&lt;flash&gt;" AnswerCount="3" />
  <row Id="9496" PostTypeId="2" ParentId="9495" CreationDate="2011-01-28T13:43:49.317" Score="1" ViewCount="" Body="&lt;p&gt;I've used ChipMax from www.eetools.com for EPROMs. I think it will program parallel flash memory as well. It was around $100. It works pretty well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: OK maybe it's closer to $\$$300 than $\$$100. It's much less expensive than the other monster programmer we have which was over $\$$1000 and doesn't really work any better.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-07T15:49:37.990" LastActivityDate="2011-05-07T15:49:37.990" CommentCount="2" />
  <row Id="9497" PostTypeId="1" AcceptedAnswerId="10782" CreationDate="2011-01-28T14:01:07.733" Score="0" ViewCount="142" Body="&lt;p&gt;I am developing a portable device embedding BT communication to connect it with a computer. I found out that to reach high bitrate (115ks/s) I need to implement the HCI stack. Is it needed or can it be done someway else?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At present, I'm oriented in choosing the &lt;a href=&quot;http://www.atmel.com/products/at91/sam3s.asp?family_id=605&quot; rel=&quot;nofollow&quot;&gt;Atmel SAM3S&lt;/a&gt;, do you know whether there is some kind of library available for this family?&lt;/p&gt;&#xA;" OwnerUserId="2285" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-01-28T20:34:18.150" LastActivityDate="2011-03-29T22:25:57.983" Title="HCI stack for Atmel" Tags="&lt;bluetooth&gt;&lt;atmel&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="9498" PostTypeId="2" ParentId="9497" CreationDate="2011-01-28T14:03:12.627" Score="1" ViewCount="" Body="&lt;p&gt;BTStack is a portable BSD licensed stack:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/btstack/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/btstack/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-28T14:03:12.627" CommentCount="3" />
  <row Id="9499" PostTypeId="1" AcceptedAnswerId="9501" CreationDate="2011-01-28T14:13:45.017" Score="2" ViewCount="131" Body="&lt;p&gt;Hi!&#xA;I am building some amauter schemes with Atmel uC. And this time I want to implement bluetooth functionality in my device: I want to be able to connect to device from computer and set parameter/get some readings. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) While writing communication software on PC side is trivial, I am puzzled on uC side.&#xA;What is the easiest way of doing so? Which BT chip is the most simple/wide-spread/easy to use/not deadly expensive in 1-10 quantity (&amp;lt;10$)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't need high speed, even 4800 baud would do at this stage :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) How complex to go further and implement keyboard/mouse/other BT protocols?&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-28T16:02:52.317" Title="Bluetooth newbie" Tags="&lt;bluetooth&gt;&lt;atmel&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="3" />
  <row Id="9500" PostTypeId="2" ParentId="9475" CreationDate="2011-01-28T15:49:25.107" Score="1" ViewCount="" Body="&lt;p&gt;It's possible to do some functional programming with the Lua language. Really, Lua is a mutli-paradigm language; &lt;a href=&quot;http://en.wikipedia.org/wiki/Lua_%28programming_language%29&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt; claims that it's a 'scripting, imperative, functional, object-oriented, prototype-based' language. The language doesn't enforce a single paradigm, but instead is flexible enough to allow the programmer to implement whatever paradigm is applicable to the situation.  It's been influenced by Scheme.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lua's features include  &lt;a href=&quot;http://www.lua.org/pil/6.html&quot; rel=&quot;nofollow&quot;&gt;first-class functions&lt;/a&gt;, &lt;a href=&quot;http://www.lua.org/pil/6.1.html&quot; rel=&quot;nofollow&quot;&gt;lexical scoping and closures&lt;/a&gt; and &lt;a href=&quot;http://www.lua.org/pil/9.html&quot; rel=&quot;nofollow&quot;&gt;coroutines&lt;/a&gt;, which are useful for functional programming.  You can see how these features are used on the Lua users wiki, which has &lt;a href=&quot;http://lua-users.org/wiki/FunctionalLibrary&quot; rel=&quot;nofollow&quot;&gt;a page dedicated to functional programming&lt;/a&gt;.  I also came across &lt;a href=&quot;http://code.google.com/p/functional-lua/&quot; rel=&quot;nofollow&quot;&gt;this Google Code project&lt;/a&gt;, but I haven't used it (it does claim to be influenced by Haskell, another language which you mentioned).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.eluaproject.net/&quot; rel=&quot;nofollow&quot;&gt;eLua&lt;/a&gt; is an implementation which is available configured for a number of development boards for the ARM7TMDI, Cortex-M3, ARM966E-S and AVR32 architectures, and is open-source so you can configure it for your own platform.   Lua is implemented in ANSI C and the entire source weighs in at under 200kB, so you should be able to build it for most platforms with a C compiler. At least 128k of Flash and 32k of RAM is recommended. I'm working on a PIC32 port for it (still in the 'Get the PIC32 board' stage, though) at the moment.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The great thing about Lua is that it was designed as a glue language, so it's very easy to write C extensions for the stuff that needs to be fast (like interrupts etc), and use the dynamic, interpreted features of the language to do rapid development in the program logic.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lua isn't a purely functional language, but you can do a lot of functional programming in it, it's fast and small (&lt;a href=&quot;http://shootout.alioth.debian.org/u32/benchmark.php?test=all&amp;amp;lang=lua&amp;amp;lang2=python3&quot; rel=&quot;nofollow&quot;&gt;compared to other scripting languages&lt;/a&gt;), and you don't need to reflash your device to try out a program.  There's even an interactive interpreter!&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-01-28T15:49:25.107" />
  <row Id="9501" PostTypeId="2" ParentId="9499" CreationDate="2011-01-28T16:02:52.317" Score="4" ViewCount="" Body="&lt;p&gt;your quickest way to communicating would be to use a BT module such as those from bluegiga or a7eng or a host of others. They typically show up (expose &quot;profiles&quot; in BT speak) as bluetooth serial ports to the BT world and give you a standard UART interface. These modules use the RFCOMM BT profile.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may be able to find some with HID (mouse, kb), HSP, HFP (headset, handsfree) or other profiles, but they will be much rarer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to do more than RFCOMM you may end up having to buy/write a full HCI stack. I am not aware of any that will fit in the small Atmel uCs. btstack is a free (for non-commercial) stack that was designed for embedded systems. I have personally used it in ARM7TDMI based microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My advice is that unless you're willing to spend a LOT of time with it, stick with the simple RFCOMM-based BT modules. You'll save yourself a LOT of time and anguish. BT is not a simple thing to jump in to.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-01-28T16:02:52.317" />
  <row Id="9503" PostTypeId="1" AcceptedAnswerId="9505" CreationDate="2011-01-28T18:30:21.130" Score="2" ViewCount="98" Body="&lt;p&gt;Hi all, I wonder what is the file extension that described the functionality of my design and is the file that is loaded in a Virtex 4 FPGA to get the behavior of my VHDL design.&#xA;Thank you.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-01-28T20:59:40.203" LastActivityDate="2011-01-28T20:59:40.203" Title="What is the file extension of the file that is loaded in a Xilinx FPGA?" Tags="&lt;fpga&gt;&lt;vhdl&gt;&lt;xilinx&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="9504" PostTypeId="2" ParentId="9455" CreationDate="2011-01-28T18:38:20.107" Score="1" ViewCount="" Body="&lt;p&gt;You might try using the Irrometer Watermark sensors. I'm using them now to measure soil moisture. If you're interested, I can try and dig up the schematic.&lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2011-01-28T18:38:20.107" CommentCount="1" />
  <row Id="9505" PostTypeId="2" ParentId="9503" CreationDate="2011-01-28T20:34:18.810" Score="6" ViewCount="" Body="&lt;p&gt;This file is commonly called a &quot;bitstream&quot;. Xilinx devices' bitstreams have the extension '.bit' and are generated by a program called 'bitgen'. '.bit' files are binaries and those are generated by default; if you want the ASCII representation of the bitstream, run&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;bitgen -b &amp;lt;your design&amp;gt;.ncd&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;and then a '.rbt' file will be generated in addition to the '.bit' file.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For further information about generating Xilinx bistreams, see Chapter 15 in this user guide for ISE version 12.4:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xilinx.com/support/documentation/sw_manuals/xilinx12_4/devref.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.xilinx.com/support/documentation/sw_manuals/xilinx12_4/devref.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For more information about Virtex 4 bistreams specifically, see the configuration guide for that device:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xilinx.com/support/documentation/user_guides/ug071.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.xilinx.com/support/documentation/user_guides/ug071.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2531" LastEditorUserId="2531" LastEditorDisplayName="" LastEditDate="2011-01-28T20:49:29.813" LastActivityDate="2011-01-28T20:49:29.813" CommentCount="0" />
  <row Id="9506" PostTypeId="2" ParentId="9495" CreationDate="2011-01-28T23:39:12.580" Score="0" ViewCount="" Body="&lt;p&gt;Will &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=415-1000-ND&quot; rel=&quot;nofollow&quot;&gt;Xeltek SUPERPROZ&lt;/a&gt; do it? $200 plus any adapter for the package.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-28T23:39:12.580" />
  <row Id="9507" PostTypeId="1" CreationDate="2011-01-29T00:39:16.497" Score="5" ViewCount="194" Body="&lt;p&gt;Anyone knows of any DC DC converter that can produce at least 200V and act as a sink? If it is comes in  DIP package, its better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right now I am using EMCOs DC-DC converter. But it cannot really act as a sink.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Datasheet here: &#xA;&lt;a href=&quot;http://www.emcohighvoltage.com/pdfs/qseries.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.emcohighvoltage.com/pdfs/qseries.pdf&lt;/a&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: When I say sink, I mean an electron (negative current) sink. The application I am working on floats a collector plate to a high negative voltage. ( - 80 V to - 100V) range&lt;/p&gt;&#xA;" OwnerUserId="1581" LastEditorUserId="1581" LastEditorDisplayName="" LastEditDate="2011-02-03T10:33:08.293" LastActivityDate="2011-03-09T02:45:18.943" Title="DC - High Voltage DC converter that acts like a sink" Tags="&lt;dc-dc&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="9508" PostTypeId="1" AcceptedAnswerId="9589" CreationDate="2011-01-29T01:28:12.630" Score="4" ViewCount="387" Body="&lt;p&gt;&lt;strong&gt;Background&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you look at my profile description, you'll see that I'm involved in building and wiring up &lt;a href=&quot;http://www.somersetcarnivals.co.uk/image.asp?id=Nor-07-322.jpg&amp;amp;pos=146&quot; rel=&quot;nofollow&quot;&gt;Carnival floats&lt;/a&gt; that are powered by an &lt;a href=&quot;http://www.aggreko.co.uk/products---services-overview/power-generation-rental/diesel-generator-hire.aspx&quot; rel=&quot;nofollow&quot;&gt;800KVA, 415v, 3 phase Generator&lt;/a&gt;. Electrically, they generally have about 10 or 15 motors, thousands of light bulbs and a 20KW sound system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Problem&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Induction_motor&quot; rel=&quot;nofollow&quot;&gt;3-phase induction motors&lt;/a&gt; are used to drive big spinning steel structures which carry a lot of weight and have a lot of momentum, and therefore need to ramp up (and down) the speed over a period of around 10s so as not to put too much stress on gearboxes, chains and bearings, etc. The running speed also needs to be adjusted to fit the float design, which needs to be done electrically as changing gear ratios is not practical once built.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To control the motors, an &lt;a href=&quot;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&amp;amp;R=7030881&quot; rel=&quot;nofollow&quot;&gt;Inverter Drive&lt;/a&gt; is needed, which is a very expensive piece of kit that has a huge array of parameters that can be adjusted to control motors in all different situations. We have 2 of these units that control a few motors each. So the problem I have is:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;A big single point of failure - one unit fault causes many motors to fail.&lt;/li&gt;&#xA;&lt;li&gt;Many of the motors are limited to being driven at the same speed, when individual speed control is sometimes needed.&lt;/li&gt;&#xA;&lt;li&gt;Costly.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;As we struggle to raise the funds to build our carnival float every year, we cannot afford to buy any more &lt;a href=&quot;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&amp;amp;R=7030881&quot; rel=&quot;nofollow&quot;&gt;Inverter Drives&lt;/a&gt; (unless someone is kind enough to donate one as they have with the two we've got).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Solution&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would love to be able to build my own for a fraction of the cost. I don't know if I'm setting myself an impossible task and am setting my sights way too high, or if this is indeed achievable. Looking inside an &lt;a href=&quot;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&amp;amp;R=7030881&quot; rel=&quot;nofollow&quot;&gt;Inverter Drive&lt;/a&gt;, I can see several SMD circuit boards, some huge capacitors/inductors, and some heat sunk transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have experience of switching/dimming resistive loads using pic based control circuits, but although I know the theory, controlling a 3 phase inductive load at the moment is beyond my skill level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Question&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can any one guide me to where I should start with this. I suppose initially I'm looking for a block diagram of the modules (with a little detail) that I would need to build a home-made inverter drive (e.g. PSU, microcontroller, output stages, etc), and how they fit together. I can then work out if indeed its even worth attempting this, and if so work out which parts I can happily design and make myself, and which parts I'll need more help with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Specs&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Input: 240v single phase or 415v 3 phase.&lt;/li&gt;&#xA;&lt;li&gt;Output: 415v 3 phase variable frequency motor drive.&lt;/li&gt;&#xA;&lt;li&gt;Controls: Stop/Start, Ramp up speed (seconds), Ramp down speed (seconds), Running speed (Hz), Emergency stop.&lt;/li&gt;&#xA;&lt;li&gt;Display: Current speed (Hz), Load (A)&lt;/li&gt;&#xA;&lt;li&gt;Motor wiring: Star&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UPDATE (31st Jan):&lt;/strong&gt;&#xA;From the information provided by pingswept and bt2 in their answers, I think I've come up with a &lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+6.186780925036789+46+5.0+50%0Av+80+256+176+256+0+1+50.0+339.4112549695428+0.0+0.0+0.5%0Av+80+304+176+304+0+1+50.0+339.4112549695428+0.0+2.0943951023931953+0.5%0Av+80+352+176+352+0+1+50.0+339.4112549695428+0.0+4.1887902047863905+0.5%0Aw+80+256+80+304+0%0Aw+80+304+80+352+0%0Ad+208+224+208+144+1+0.805904783%0Ad+240+224+240+144+1+0.805904783%0Ad+272+224+272+144+1+0.805904783%0Ad+208+448+208+368+1+0.805904783%0Ad+240+448+240+368+1+0.805904783%0Ad+272+448+272+368+1+0.805904783%0Aw+208+224+208+256+0%0Aw+208+256+176+256+0%0Aw+208+256+208+368+0%0Aw+176+304+240+304+0%0Aw+240+304+240+224+0%0Aw+240+304+240+368+0%0Aw+176+352+272+352+0%0Aw+272+352+272+368+0%0Aw+272+352+272+224+0%0Aw+208+144+240+144+0%0Aw+240+144+272+144+0%0Aw+208+448+240+448+0%0Aw+240+448+272+448+0%0Af+368+400+432+400+0+1.5%0Af+368+192+432+192+0+1.5%0Aw+432+144+432+176+0%0Aw+432+208+432+288+0%0Aw+432+288+432+304+0%0Aw+432+304+432+384+0%0Aw+432+416+432+448+0%0Aw+560+416+560+448+0%0Aw+560+304+560+384+0%0Aw+560+288+560+304+0%0Aw+560+208+560+288+0%0Aw+560+144+560+176+0%0Af+496+192+560+192+0+1.5%0Af+496+400+560+400+0+1.5%0Aw+688+416+688+448+0%0Aw+688+304+688+384+0%0Aw+688+288+688+304+0%0Aw+688+208+688+288+0%0Aw+688+144+688+176+0%0Af+624+192+688+192+0+1.5%0Af+624+400+688+400+0+1.5%0Al+816+208+816+288+0+0.5+0.07936331972994357%0Al+816+288+768+336+0+0.5+0.04035416326757956%0Al+816+288+864+336+0+0.5+0.039009156462364004%0Aw+432+288+464+288+0%0Aw+464+288+464+256+0%0Aw+752+256+752+208+0%0Aw+752+208+816+208+0%0Aw+768+336+752+336+0%0Aw+752+336+752+272+0%0Aw+864+336+864+368+0%0Aw+864+368+736+368+0%0Aw+736+368+736+288+0%0Aw+272+144+432+144+0%0Aw+432+144+560+144+0%0Aw+560+144+688+144+0%0Aw+272+448+432+448+0%0Aw+432+448+560+448+0%0Aw+560+448+688+448+0%0Ag+240+448+240+496+0%0AI+304+80+352+80+0+0.5%0AL+304+80+272+80+0+1+false+5.0+0.0%0Aw+352+400+368+400+0%0AL+432+80+400+80+0+0+false+5.0+0.0%0AI+432+80+480+80+0+0.5%0AL+560+80+528+80+0+0+false+5.0+0.0%0AI+560+80+608+80+0+0.5%0Aw+608+400+624+400+0%0Aw+480+400+496+400+0%0Aw+352+80+352+400+0%0Aw+480+80+480+400+0%0Aw+608+80+608+400+0%0Aw+304+80+304+112+0%0Aw+304+112+368+112+0%0Aw+368+112+368+192+0%0Aw+432+80+432+112+0%0Aw+432+112+496+112+0%0Aw+496+112+496+192+0%0Aw+560+80+560+112+0%0Aw+560+112+624+112+0%0Aw+624+112+624+192+0%0Aw+576+272+576+288+0%0Aw+576+288+560+288+0%0Aw+752+256+464+256+0%0Aw+576+272+752+272+0%0Aw+736+288+688+288+0%0A&quot; rel=&quot;nofollow&quot;&gt;simulation of the bare bones of what I need&lt;/a&gt;... Rectify the 3-phase to get 586V DC and use 6 IGBTs controlled by an IRS2330 which is controlled by PWM from a microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-01-31T20:44:45.740" LastActivityDate="2011-01-31T23:00:50.373" Title="3-phase Motor Speed Controller" Tags="&lt;motor&gt;&lt;frequency&gt;&lt;speedcontroller&gt;&lt;3-phase&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="9509" PostTypeId="2" ParentId="9418" CreationDate="2011-01-29T02:24:46.537" Score="0" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;a few examples of heavy duty servos &lt;a href=&quot;http://www.active-robots.com/products/motorsandwheels/torxis.shtml&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://www.active-robots.com/products/motorsandwheels/industrial-servomotors.shtml&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, these will easily swing a 2x4 around. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Depending on the servo you can just connect the Control line to your servo control and connect the power of the servo to the recommended power source. for the ones linked i would use a lead-acid battery(car battery) or a good power supply.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Depending on your design a stepper motor probably will not work, and servos are much easier to interface and drive then steppers.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;on a side note a diagram of your design and the estimated weight of the load its moving  would help. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-01-29T02:24:46.537" />
  <row Id="9510" PostTypeId="1" AcceptedAnswerId="9543" CreationDate="2011-01-29T02:42:57.420" Score="6" ViewCount="529" Body="&lt;p&gt;&lt;em&gt;&lt;strong&gt;What diode modifiers are used in practice to model LEDs with SPICE (Berkeley v.3f5)?&lt;/em&gt;&lt;/strong&gt; &lt;a href=&quot;http://www.macspice.com/ug/sec3.html#3.4.2&quot; rel=&quot;nofollow&quot;&gt;These&lt;/a&gt; are available to me:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#       Name    Parameter                    Units      Default Example  Area&#xA;1       IS      Saturation current             A         1e-14   1e-14    *&#xA;2       RS      Ohmic resistance               Ω         0       10       *&#xA;3       N       Emission coefficient           -         1       1.0&#xA;4       TT      Transit-time                   s         0       0.1ns&#xA;5       CJO     Zero-bias junction capacitance F         0       2pF      *&#xA;6       VJ      Junction potential             V         1       0.6&#xA;7       M       Grading coefficient            -         0.5     0.5&#xA;8       EG      Activation energy              eV        1.11    1.11 Si&#xA;                                                                 0.69 Sbd&#xA;                                                                 0.67 Ge&#xA;9       XTI     Saturation-current temperature exponent  3.0     3.0 jn&#xA;                                                                 2.0 Sbd&#xA;10      KF      Flicker noise coefficient      -         0&#xA;11    AF      Flicker noise exponent         -         1&#xA;12    FC      Coeff. for for.-bias dep. cap. formula   0.5&#xA;13    BV      Reverse breakdown voltage      V         ∞       40.0&#xA;14    IBV     Current at breakdown voltage   A         1.0e-3&#xA;15    TNOM    Parameter measurement temp.    °C        27      50&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;&lt;a href=&quot;http://www.macspice.com/ug/sec3.html#3.4.2&quot; rel=&quot;nofollow&quot;&gt;3.4.2 Diode Model (D)&lt;/a&gt;&lt;/strong&gt;&lt;br&gt;&#xA;  The dc characteristics of the diode are determined by the parameters IS and N. An ohmic resistance, RS, is included. Charge storage effects are modeled by a transit time, TT, and a nonlinear depletion layer capacitance which is determined by the parameters CJO, VJ, and M. The temperature dependence of the saturation current is defined by the parameters EG, the energy and XTI, the saturation current temperature exponent. The nominal temperature at which these parameters were measured is TNOM, which defaults to the circuit-wide value specified on the .OPTIONS control line. Reverse breakdown is modeled by an exponential increase in the reverse diode current and is determined by the parameters BV and IBV (both of which are positive numbers).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;For example, using this basic, cheap red: &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=475-1416-1-ND&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://www.digikey.com/Web%20Export/Common/header/digikey_logo.jpg&quot; width=&quot;50&quot;&gt;&lt;/a&gt; &lt;a href=&quot;http://catalog.osram-os.com/jsp/download.jsp?name=LH_N974.pdf&amp;amp;url=/media/_en/Graphics/00042065_0.pdf&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://www.virtualvisiontech.com/system/customcores/VVTStorefront/storefrontimages/PDF_logo.gif&quot; width=&quot;35&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't care much about high-frequency characteristics -- just would like to be able to match it's IV-curve within its operating specs (-10uA/-5V leakage to +100mA/+2.2&lt;sup&gt;'ish&lt;/sup&gt;V forward):&#xA;&lt;img src=&quot;http://i.imgur.com/SJVLd.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-01-30T00:49:07.157" LastActivityDate="2011-02-01T04:27:01.293" Title="How do I model an LED with SPICE?" Tags="&lt;led&gt;&lt;diode&gt;&lt;spice&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="9511" PostTypeId="2" ParentId="9428" CreationDate="2011-01-29T03:01:07.940" Score="1" ViewCount="" Body="&lt;p&gt;A temp sensor in front of the outlet might be better than an airflow sensor, since as monpjc mentioned, the fan could continue to run even if the unit is not cooling.   The temp there will generally be cooler than the ambient temp in the room, so you could probably find a threshold that would give an early indication that the unit is not cooling before the room temp rises noticeably.&#xA;If the airflow does stop, the temp in the airstream area will quickly rise to the general room temp, so you are covered both ways.&lt;/p&gt;&#xA;" OwnerUserId="1295" LastActivityDate="2011-01-29T03:01:07.940" />
  <row Id="9512" PostTypeId="2" ParentId="1848" CreationDate="2011-01-29T03:09:06.533" Score="0" ViewCount="" Body="&lt;p&gt;How many? For anything less than thousands it would probably be cheaper to solder a resistor to an LED and pot the whole assembly in acrylic&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-01-29T03:09:06.533" />
  <row Id="9513" PostTypeId="2" ParentId="6629" CreationDate="2011-01-29T03:11:56.700" Score="0" ViewCount="" Body="&lt;p&gt;Those little T1-3/4 LEDs aren't very good for illumination. The high power ones are more efficient. Check out DIY forums on www.candlepowerforums.com for really good resources on LED lighting and flashlights. &lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-01-29T03:11:56.700" />
  <row Id="9514" PostTypeId="2" ParentId="9508" CreationDate="2011-01-29T03:22:15.583" Score="1" ViewCount="" Body="&lt;p&gt;I would check out these app notes from Microchip&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/devicedoc/70096A.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ww1.microchip.com/downloads/en/devicedoc/70096A.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/00843a.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ww1.microchip.com/downloads/en/AppNotes/00843a.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have a 3 phase development kit, but I believe you have to ask to borrow one of them, and as you're not looking to actually manufacture this, I doubt you'd get high priority.  Still, they have schematics and code available for free use.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-01-29T03:22:15.583" CommentCount="1" />
  <row Id="9515" PostTypeId="2" ParentId="9510" CreationDate="2011-01-29T04:17:59.687" Score="2" ViewCount="" Body="&lt;p&gt;Here are the ones I would use&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#       Name    Parameter                    Units      Default Example  Area&#xA;2       RS      Ohmic resistance               Ω         0       10       *&#xA;6       VJ      Junction potential             V         1       0.6&#xA;13    BV      Reverse breakdown voltage      V         ∞       40.0&#xA;14    IBV     Current at breakdown voltage   A         1.0e-3&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;For your VJ=1.8 typ, BV=5.  That gets you most of the way there.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-29T04:17:59.687" CommentCount="1" />
  <row Id="9516" PostTypeId="2" ParentId="9508" CreationDate="2011-01-29T06:04:35.040" Score="2" ViewCount="" Body="&lt;p&gt;In the big picture, I think you're talking about a 500-1000 hour job and at least a few thousand dollars in materials and circuit board expenses. If you really want the best solution for the money, get a high-paying job and spend the wages from the same 500-1000 hours to buy used motor controllers off Ebay or Craigslist. You'll end up with more motor controllers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But that's not much fun. If you wanted to build one, you'd need 6 MOSFETs or IGBTs (one on the high side and one on the low side of each leg of the star). Then you use a microcontroller to turn the switches on and off to simulate a sine wave.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the voltage you're talking about is quite high, you'd need what's called a high-side driver-- a chip that can control a MOSFET at very high voltages. &lt;a href=&quot;https://ec.irf.com/v6/en/US/adirect/ir?cmd=catProductDetailFrame&amp;amp;productID=IRS2330JPBF&quot; rel=&quot;nofollow&quot;&gt;The IRS2330&lt;/a&gt; from International Rectifier that will do all three phases. Page 19 of &lt;a href=&quot;http://www.irf.com/product-info/datasheets/data/irs2330pbf.pdf&quot; rel=&quot;nofollow&quot;&gt;the IRS2330 datasheet&lt;/a&gt; has a nice diagram of the basic circuit.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-01-29T06:04:35.040" CommentCount="5" />
  <row Id="9517" PostTypeId="1" AcceptedAnswerId="9568" CreationDate="2011-01-29T08:16:21.293" Score="1" ViewCount="153" Body="&lt;p&gt;He all, I was wondering how should be the parameters fo the CORDIC divider block in order to get proper results.&#xA;In this example I´m trying to get 0.1/0.2 = 0.5 but I don´t get it and I don´t know why?&#xA;Please, does anyone know how to do it?&#xA;Thank you!!!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt;&#xA;To take a look to the parameters of the CORDIC block see this question:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/9642/system-generator-how-to-configure-the-cordic-divider-block-understanding-the-bl&quot;&gt;System Generator: How to configure the CORDIC divider block. Understanding the block parameters&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/KKTf8.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T21:03:06.947" LastActivityDate="2011-02-18T15:53:30.007" Title="System Generator: How to configure the CORDIC divider block?" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;floating-point&gt;&lt;xilinx-system-generator&gt;&lt;cordic&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="9518" PostTypeId="1" AcceptedAnswerId="9520" CreationDate="2011-01-29T11:36:29.983" Score="1" ViewCount="160" Body="&lt;p&gt;Hi all, I wonder if I could perform floating point operations in a Picoblaze controller? Thank you to all posible answers with direct references to documentation or articles.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastActivityDate="2011-02-01T17:55:21.100" Title="Microcontrollers: Can I perform floating point operations in a Picoblaze controller?" Tags="&lt;microcontroller&gt;&lt;floating-point&gt;" AnswerCount="3" />
  <row Id="9519" PostTypeId="1" CreationDate="2011-01-29T11:49:37.720" Score="2" ViewCount="166" Body="&lt;p&gt;Hi all, I need to make a implementation of a floating point division using System Generator and I my version of System Generator don´t support the 'divider generator' so I was thinking several options to make the implementation. One is using the Xilinx DSP48 block.&#xA;Does anyone knows if is posible to make a division implementation through a DSP48 xilinx block?&#xA;Thank you for your help.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastActivityDate="2011-01-29T12:36:13.523" Title="DSPs: Can I perform floating point division in a Xilinx DSP48?" Tags="&lt;dsp&gt;&lt;xilinx&gt;&lt;floating-point&gt;" AnswerCount="1" />
  <row Id="9520" PostTypeId="2" ParentId="9518" CreationDate="2011-01-29T12:11:27.500" Score="7" ViewCount="" Body="&lt;p&gt;Unfortunately, I do not think that the Picoblaze has hardware support for floating-point. If it does, you can do it in hardware. Otherwise, you will need to do it in software emulation mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since I noticed that you asked the same question for both the Picoblaze and the Microblaze, maybe you need to ask yourself why you need to do floating-point operations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In many cases, there are alternatives to floating-point operations. Fixed-point operations are a common alternative to floating point. You will need to study your algorithms to determine if it is possible to represent the values in a fixed-point math alternative to floating-point math.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, if you use an 4-bit fixed-point width, you can represent values in quantums of 0.125 between -1.0 to 0.875 with fixed-point representation. Larger values can be scalar multiples of these values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;: &lt;a href=&quot;http://www.eetimes.com/design/programmable-logic/4009455/Converting-floating-point-applications-to-fixed-point&quot; rel=&quot;nofollow&quot;&gt;Article&lt;/a&gt; explaining float-to-fixed-point conversion.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastEditorUserId="1938" LastEditorDisplayName="" LastEditDate="2011-02-01T10:22:45.427" LastActivityDate="2011-02-01T10:22:45.427" CommentCount="5" />
  <row Id="9521" PostTypeId="2" ParentId="9519" CreationDate="2011-01-29T12:36:13.523" Score="3" ViewCount="" Body="&lt;p&gt;I don't know which Xilinx device you're targeting, but here's an overview page of the Xilinx DSP blocks:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xilinx.com/technology/dsp/xtremedsp.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.xilinx.com/technology/dsp/xtremedsp.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a small section about division in the Virtex 5 XtremeDSP user guide (p.74), for example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xilinx.com/support/documentation/user_guides/ug193.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.xilinx.com/support/documentation/user_guides/ug193.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, your best bet is to create a divider using 'coregen'. Launch 'coregen', create a new project and go to 'Math Functions -&gt; Dividers' (the options appear depending on the target device). Then go through the wizard choosing your preferred setup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a bit more information on how to use 'coregen': 'coregen' will create a '.v' or'.vhd' instantiation file depending on the language you've chosen. It will run XST to generate a '.ncg' &quot;blackbox&quot; netlist so the implementation process can include it when you run 'ngdbuild'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, coregen will also generate a '.xco' and '.cgp', which are the only files you actually need (in ISE version 12.x) in order to regenerate the core. In command line, do&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;coregen -p &amp;lt;core&amp;gt;.cgp -b &amp;lt;core&amp;gt;.xco&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;and you'll get the HDL instantiation and the netlist (and a bunch of other things in the process). Note that 'coregen' will generate its output where the input files are, &lt;em&gt;not&lt;/em&gt; where it is invoked from, and there's no switch to indicate an output path!&lt;/p&gt;&#xA;" OwnerUserId="2531" LastActivityDate="2011-01-29T12:36:13.523" CommentCount="4" />
  <row Id="9522" PostTypeId="2" ParentId="9518" CreationDate="2011-01-29T12:37:12.500" Score="0" ViewCount="" Body="&lt;p&gt;The MicroBlaze has hardware floating-point support.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-29T12:37:12.500" CommentCount="2" />
  <row Id="9523" PostTypeId="1" AcceptedAnswerId="9559" CreationDate="2011-01-29T12:42:08.777" Score="1" ViewCount="146" Body="&lt;p&gt;Hi all, Does anyone know any available reference to learn how works CORDIC algorithm to implement a division?&#xA;Thank you!&lt;/p&gt;&#xA;" OwnerUserId="2597" LastActivityDate="2011-01-30T21:53:53.827" Title="References with explanations of how works CORDIC algorithm for division" Tags="&lt;reference&gt;&lt;cordic&gt;&lt;how-does-it-work&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="9524" PostTypeId="1" AcceptedAnswerId="9525" CreationDate="2011-01-29T15:04:16.870" Score="1" ViewCount="125" Body="&lt;p&gt;I'm trying to minimize part count and cost of my project.  It needs to have a 6V power rail with about 1.5A peak current from a 12V input.  I'm shying away from a linear regulator because of the power dissipation but I would like to keep cost and part count down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do switching regulators exist with internal diode and inductor to match these parameters or would it be less expensive to have a linear regulator with a big heatsink?&lt;/p&gt;&#xA;" OwnerUserId="1819" LastActivityDate="2011-01-29T18:29:36.473" Title="Inexpensive switching regulator with internal inductor &amp; diode" Tags="&lt;voltage-regulator&gt;&lt;buck&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="9525" PostTypeId="2" ParentId="9524" CreationDate="2011-01-29T15:14:58.917" Score="3" ViewCount="" Body="&lt;p&gt;lowest cost, lowest part count. Pick one. &#xA;There are many ready-made SMPS modules - some even  have the same footprint as 78xx regulators. A seach for &lt;a href=&quot;http://www.google.co.uk/search?q=integrated+switching+regulators&amp;amp;ie=utf-8&amp;amp;oe=utf-8&amp;amp;aq=t&amp;amp;rls=org.mozilla%3aen-GB%3aofficial&amp;amp;client=firefox-a&quot; rel=&quot;nofollow&quot;&gt;Integrated switching regulators&lt;/a&gt; will find some of them.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-29T15:14:58.917" />
  <row Id="9526" PostTypeId="1" CreationDate="2011-01-29T15:26:06.643" Score="2" ViewCount="135" Body="&lt;p&gt;I just brought GPS module &quot;&lt;a href=&quot;http://www.gtop-tech.com/jsf/moduleproduct.jsf?muid=5a50acc3cd4f20749b345fe86e442ed78a6d204d&amp;amp;suid=d2aafd64c93952bb33c7ee066e322e597947063d&amp;amp;puid=3fff9662f76faafe1e5c3f81e571fa4d3c18ce86&quot; rel=&quot;nofollow&quot;&gt;Global-Top GMS-U1LP&lt;/a&gt;&quot;.&#xA;I want to setup it for its UART configuration.&#xA;In data-sheet there are 4 different ground but I am not able to trace which ground corresponds to which power input or for data.&#xA;&lt;a href=&quot;http://www.google.co.in/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CBoQFjAA&amp;amp;url=http%3A%2F%2Fwww.gtop-tech.com%2FShowAttach%3FUNID%3Dc3147bca3ce9d68a1a3ed4b413b8c80000fe24dd&amp;amp;rct=j&amp;amp;q=gms-u1lp%20datasheet&amp;amp;ei=yhhETeitEMXtrAfLmtTuDw&amp;amp;usg=AFQjCNGT5YhXOI4_ZHIjkK0bD9mbsTxX_w&amp;amp;sig2=i-_yE7yiS83kuE-DW25Znw&amp;amp;cad=rja&quot; rel=&quot;nofollow&quot;&gt;Gms-u1lp dtatsheet&lt;/a&gt;&#xA;So with lot of doubt in mind I made following setup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this configuration correct?&lt;img src=&quot;http://i.imgur.com/qNin0.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;original setup&lt;/strong&gt; according to data-sheet is as below:&#xA;&lt;img src=&quot;http://i.imgur.com/gPBzN.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody know how to setup this GPS receiver IC?&lt;/p&gt;&#xA;" OwnerUserId="1806" LastActivityDate="2011-04-04T08:26:46.293" Title="GPS module(GMS-U1LP) setup help" Tags="&lt;gps&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9527" PostTypeId="1" AcceptedAnswerId="9563" CreationDate="2011-01-29T16:07:21.650" Score="2" ViewCount="177" Body="&lt;p&gt;How does one measure impedance/resistance using SPICE?  I have access to regular SPICE(MacSpice) and HSpice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DC current divider circuit at the bottom of &lt;a href=&quot;http://www.allaboutcircuits.com/vol_6/chpt_3/5.html&quot; rel=&quot;nofollow&quot;&gt;this webpage&lt;/a&gt; seems to be one method.  0V DC sources are used, and the current through these zero volt sources is measured.  Using the node voltage and the current measured, we can deduce resistance.  Of course for circuits where we already know the resistance this is only good for measuring the current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can one do resistance/impedance measurements for AC circuits, such as the inputs or outputs of transistor amps (e.g. resistance looking into base, output at emitter, etc.)?     &lt;/p&gt;&#xA;" OwnerUserId="2059" LastActivityDate="2011-01-31T05:42:28.507" Title="Measuring Resistance/Impedance with SPICE" Tags="&lt;spice&gt;&lt;transistors&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="9529" PostTypeId="1" AcceptedAnswerId="9588" CreationDate="2011-01-29T16:16:32.440" Score="1" ViewCount="257" Body="&lt;p&gt;&lt;strong&gt;Long Story Short&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a &quot;linear/rotary optical encoder,&quot; or, &quot;incremental encoder,&quot; like this one, which costs about \$6:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mouser.com/Search/ProductDetail.aspx?R=AEDS-9641-P10virtualkey63050000virtualkey630-AEDS-9641-P10&quot; rel=&quot;nofollow&quot;&gt;http://www.mouser.com/Search/ProductDetail.aspx?R=AEDS-9641-P10virtualkey63050000virtualkey630-AEDS-9641-P10&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You use it with &quot;optical encoder strips,&quot; or &quot;codestrips,&quot; like this one, which costs about \$.30:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.goldmine-elec-products.com/prodinfo.asp?number=G15602&quot; rel=&quot;nofollow&quot;&gt;http://www.goldmine-elec-products.com/prodinfo.asp?number=G15602&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It uses a single LED with 2 photodetectors. These are exposed as pins labeled Channel A and Channel B. The pins will output either 0 or Vcc V, which is 5V in my case. Since there are 4 distinct states for A and B, you get 4 times the resolution of your codestrip. Since it can handle up to 150 lines per inch on a codestrip, you get 1 600th of an inch resolution. When monitoring the A and B channels, you can determine which direction you are moving by comparing your current state to your last state. For example if A and B are both high, and then A goes low, you've moved up 1 600th of an inch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a great, accurate, affordable system for determining precise linear position.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Original Post&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/BN6qq.jpg&quot; alt=&quot;IR emitter / detector pulled off an inkjet printer&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The red arrow points to the ir emitter / detector. The blue arrow points to where I got it. The printed circuit board under the blue arrow would slide back and forth under that gray band, which is transparent plastic with lots and lots of very skinny black lines. That was probably how the inkjet printer kept track of the position of the print head.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 2 ir diode pins were easy enough to figure out. That's being powered by the fat white wire on the far left. I can't figure out the additional 4 pins on the detector part though. Notice, that's a total of 6 pins. I pulled the cover off the part to get a closer look, and those pins look like this, with the skinny white wire attached to the pin on the far right:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OdXNC.png&quot; alt=&quot;Diagram of what the detector part looks like&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The black cover on the ir e/d has tiny white letters:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;9981&#xA;C526&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and tiny black letters&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Agilent&#xA;18&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried Googling around for datasheets, but I didn't manage to find anything. I tried calling Agilent but just got lost in the phone tree, and they hung up on me at some point, haha.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody have a datasheet for this or a similar component, or have any idea how this 4 pin detector works, or know where to look for a datasheet or who to call, or know a component I could substitute, or anything really?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is all part of a bigger thing I'm trying to get a handle on, which is precise 1 dimensional movement, and then ultimately precise 2 dimensional movement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To be clear, there are 6 pins total. 2 for the diode, and 4 for the detector. I don't understand what all 4 pins on just the detector are for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit 2&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found a very promising blog post about this kind of problem. &lt;a href=&quot;http://benkrasnow.blogspot.com/2010/02/linear-position-tracking-with.html&quot; rel=&quot;nofollow&quot;&gt;http://benkrasnow.blogspot.com/2010/02/linear-position-tracking-with.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a 6 pin linear optical encoder with data sheet which I found from this blog post.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mouser.com/Search/ProductDetail.aspx?R=AEDS-9641-P10virtualkey63050000virtualkey630-AEDS-9641-P10&quot; rel=&quot;nofollow&quot;&gt;http://www.mouser.com/Search/ProductDetail.aspx?R=AEDS-9641-P10virtualkey63050000virtualkey630-AEDS-9641-P10&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2813" LastEditorUserId="2813" LastEditorDisplayName="" LastEditDate="2011-04-06T16:21:27.173" LastActivityDate="2011-04-06T16:21:27.173" Title="Understanding the IR Emitter / Detector I pulled off of an inkjet printer" Tags="&lt;electronics&gt;&lt;ir&gt;&lt;detection&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="9530" PostTypeId="1" AcceptedAnswerId="9532" CreationDate="2011-01-29T17:07:05.000" Score="2" ViewCount="97" Body="&lt;p&gt;I have experience with selecting low end PICs, but haven't had to select a controller for DSP before. Initially I thought about the dsPIC line, but the only reason for this because I am comfortable with the microchip line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, what options do I have to select from? How can I decide what is best for me? Are there in general differences between lines? Example, the MSP430 line is good for very low power, are there any similar type of things for the DSP lines?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For my specific project I am going to have 3 sets of SPI from ADCs that are 24bit at about 400KHz, but I am find with broad description on how to find the proper platform.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-29T20:53:46.173" Title="Selecting a platform for DSP" Tags="&lt;dsp&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="9531" PostTypeId="2" ParentId="9471" CreationDate="2011-01-29T17:20:33.033" Score="2" ViewCount="" Body="&lt;p&gt;Those commercial cases might work, but you'll note that a car amplifier has many, large fins - this dramatically increases the surface area. Those commercial boxes just have some beauty stripes. Also don't forget the volume calculation: I don't know how much thermally conductive epoxy costs, but even, say, a 1 by 3 by 6 inch box has a fair amount of internal volume.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you also could do is to salvage the heat sinks from the inside on an old PC power supply. These come with screws and insulators and are pretty big in terms of surface area. You might be able to bolt these to the outside of an otherwise flat box (you want to use gap filler between them) to heat sink it. Alternatively, just screw your high temp components to them and the encapsulate over them with your epoxy. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're in an environment that can tolerate it, using salvaged heat sinks and salvaged fans inside a salvaged power supply enclosure would likely work well. &lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2011-01-29T17:20:33.033" />
  <row Id="9532" PostTypeId="2" ParentId="9530" CreationDate="2011-01-29T17:56:18.543" Score="7" ViewCount="" Body="&lt;p&gt;If I was asked to look at DSP products, I would look at the architecture. The hardware architectures for DSP processors are more varied than for general purpose processors.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;strong&gt;Word Length&lt;/strong&gt;. As you mentioned, your source data is 24-bits. So, unless you are able to lose some fidelity, you will need a DSP that can handle 24-bits data at least.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Fixed/Floating Point&lt;/strong&gt;. You will need to look at your algorithms to see if floating-point hardware is needed or if it can be entirely implemented in fixed-point. Not all DSPs can do floating-point in hardware.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Addressing Modes&lt;/strong&gt;. You are dealing with buffers all the time. While DSPs have circular addressing modes, some have more advanced modes that are able to chain memory blocks together or flip memory blocks in hardware and more. I would say that this is the &lt;em&gt;most critical&lt;/em&gt; architecture aspect for a DSP.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Special Instructions&lt;/strong&gt;. Every DSP has specialised instructions. At the minimum, they will have a MAC instruction. However, some have far more esoteric ones which may benefit your application.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Data Paths&lt;/strong&gt;. Some DSPs have unique data paths, or even multiple datapaths, which allow different data streams to be manipulated separately or combined together, in hardware.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Execution Units&lt;/strong&gt;. Most DSPs have many parallel execution units that can perform different things at the same time - e.g. multiply, add and shift different registers at the same time. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Then, looking at the algorithms that need to be coded, I would select a DSP architecture that is easier to use to implement the algorithms.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-01-29T17:56:18.543" />
  <row Id="9533" PostTypeId="2" ParentId="9524" CreationDate="2011-01-29T18:28:32.867" Score="1" ViewCount="" Body="&lt;p&gt;Most switching regulators have got an internal switch. There are also plenty switching controllers which would need an external FET.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some regulaturs with an internal diode, but not plenty. I haven't seen internal inductor. Typical required inductors are well pretty large. I don't think they will be able to fit on the die of a chip. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're seeking for a way to decrease the size of the power supply, try using a more faster switching regulator. They are a bit harder to work with (in terms of PCB design and such), but require smaller inductance values and thus smaller inductors (in a smaller package).  &lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-01-29T18:28:32.867" CommentCount="1" />
  <row Id="9534" PostTypeId="2" ParentId="9524" CreationDate="2011-01-29T18:29:36.473" Score="3" ViewCount="" Body="&lt;p&gt;You won't find an integrated inductor for these specs and I doubt they exist for smaller currents. You'll need something in the order of 33-100uH and at &gt;1A this is &lt;em&gt;huge&lt;/em&gt; from an integration point of view.&lt;br&gt;&#xA;Have a look at National's Simple Switcher series, which includes parts like LM22676 which require minimal external components and provide high efficiency (for the LM22676 &gt;90%). National has an online Webench design tool to help you select the right components.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-01-29T18:29:36.473" CommentCount="3" />
  <row Id="9535" PostTypeId="2" ParentId="9523" CreationDate="2011-01-29T18:38:12.627" Score="2" ViewCount="" Body="&lt;p&gt;A &lt;strong&gt;&lt;em&gt;CORDIC division&lt;/em&gt;&lt;/strong&gt; is implemented using &lt;strong&gt;&lt;em&gt;CORDIC multiplication&lt;/em&gt;&lt;/strong&gt;, rearranging as follows:&lt;sup&gt; &lt;a href=&quot;http://www.drdobbs.com/184404244&quot; rel=&quot;nofollow&quot;&gt;[source]&lt;/a&gt;&lt;/sup&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;c = a/b&#xA;a - c*b = 0&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;For the multiplication &lt;code&gt;z = x*y&lt;/code&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;em&gt;&lt;strong&gt;z&lt;/em&gt;&lt;/strong&gt; is composed of shifted versions of &lt;strong&gt;&lt;em&gt;y&lt;/em&gt;&lt;/strong&gt;. The unknown value for &lt;strong&gt;&lt;em&gt;z&lt;/em&gt;&lt;/strong&gt;, may be found by driving &lt;strong&gt;&lt;em&gt;x&lt;/em&gt;&lt;/strong&gt; to zero 1 bit at a time. If the &lt;em&gt;i&lt;sup&gt;&lt;sup&gt; &lt;/sup&gt;th&lt;/sup&gt;&lt;/em&gt; bit of &lt;strong&gt;&lt;em&gt;x&lt;/em&gt;&lt;/strong&gt; is nonzero, &lt;strong&gt;&lt;em&gt;y&lt;/strong&gt;&lt;sup&gt;&lt;sup&gt; &lt;/sup&gt;i&lt;/sup&gt;&lt;/em&gt; is right shifted by &lt;em&gt;i&lt;/em&gt; bits and added to the current value of &lt;strong&gt;&lt;em&gt;z&lt;/em&gt;&lt;/strong&gt;. The &lt;em&gt;i&lt;sup&gt;&lt;sup&gt; &lt;/sup&gt;th&lt;/sup&gt;&lt;/em&gt; bit is then removed from &lt;strong&gt;&lt;em&gt;x&lt;/em&gt;&lt;/strong&gt; by subtracting &lt;em&gt;2&lt;sup&gt;-i&lt;/sup&gt;&lt;/em&gt; from &lt;strong&gt;&lt;em&gt;x&lt;/em&gt;&lt;/strong&gt;. If &lt;strong&gt;&lt;em&gt;x&lt;/em&gt;&lt;/strong&gt; is negative, the &lt;em&gt;i&lt;sup&gt;&lt;sup&gt; &lt;/sup&gt;th&lt;/sup&gt;&lt;/em&gt; bit in the twos complement format would be removed by adding &lt;em&gt;2&lt;sup&gt;-i&lt;/sup&gt;&lt;/em&gt;. In either case, when &lt;strong&gt;&lt;em&gt;x&lt;/em&gt;&lt;/strong&gt; has been driven to zero all bits have been examined and &lt;strong&gt;&lt;em&gt;z&lt;/em&gt;&lt;/strong&gt; contains the signed product of &lt;strong&gt;&lt;em&gt;x&lt;/em&gt;&lt;/strong&gt; and &lt;strong&gt;&lt;em&gt;y&lt;/em&gt;&lt;/strong&gt; correct to &lt;em&gt;B&lt;/em&gt; bits.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;This algorithm is similar to the standard shift and add multiplication algorithm except for two important features:&lt;/p&gt;&#xA;  &#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;Arithmetic right shifts  are used instead of left shifts, allowing signed numbers to be used.&lt;/li&gt;&#xA;  &lt;li&gt;Computing the product to &lt;em&gt;B&lt;/em&gt; bits with the CORDIC algorithm is equivalent to rounding the result of the standard algorithm to the most significant &lt;em&gt;B&lt;/em&gt; bits.&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The division &lt;code&gt;z = x/y&lt;/code&gt; is found...&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;... by driving &lt;strong&gt;&lt;em&gt;x&lt;/em&gt;&lt;/strong&gt; to zero using right-shifted versions of &lt;strong&gt;&lt;em&gt;y&lt;/em&gt;&lt;/strong&gt;. If the current residual is positive, the &lt;em&gt;i&lt;sup&gt;&lt;sup&gt; &lt;/sup&gt;th&lt;/sup&gt;&lt;/em&gt; bit in &lt;strong&gt;&lt;em&gt;z&lt;/em&gt;&lt;/strong&gt; is set. Likewise, if the residual is negative the ith bit in &lt;strong&gt;&lt;em&gt;z&lt;/em&gt;&lt;/strong&gt; is cleared.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;divide_4q(x,y){&#xA;   for (i=1; i=&amp;lt;B; i++){&#xA;      if (x &amp;gt; 0)&#xA;        if (y &amp;gt; 0)&#xA;           x = x - y*2^(-i);&#xA;           z = z + 2^(-i);&#xA;        else&#xA;           x = x + y*2^(-i);&#xA;           z = z - 2^(-i);&#xA;      else          &#xA;         if (y &amp;gt; 0)&#xA;            x = x + y*2^(-i);&#xA;            z = z - 2^(-i);&#xA;         else&#xA;            x = x - y*2^(-i);&#xA;            z = z + 2^(-i);&#xA;   }&#xA;   return(z)&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;You'll have to make a few modifications to use floating point numbers.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-01-29T18:38:12.627" />
  <row Id="9536" PostTypeId="2" ParentId="9306" CreationDate="2011-01-29T18:46:58.577" Score="3" ViewCount="" Body="&lt;p&gt;Freescale AN2253 &lt;a href=&quot;http://cache.freescale.com/files/dsp/doc/app_note/AN2253.pdf&quot; rel=&quot;nofollow&quot;&gt;&quot;Channel Estimation for a WCDMA Rake Receiver&quot;&lt;/a&gt;&#xA;by Ahsan Aziz 2004&#xA;has a pretty good explanation -- see Figure 1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The signal from from an antenna is split into several fingers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each finger takes that input signal and produces one output signal by:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;(a) delays the signal a certain amount of time (often measured in &quot;chips&quot;), different for every finger, compensating for the physical length of that particular path of the multipath between the transmitter and reciever&lt;/li&gt;&#xA;&lt;li&gt;(b) despreads the signal with a fixed despreading code (the same for every finger)&lt;/li&gt;&#xA;&lt;li&gt;(c) multiplies the signal by a &quot;complex attenuation&quot; value, different for every finger -- compensating for some kinds of reflections that turn the signal &quot;upside down&quot; relative to the direct path, and emphasizing paths with better signal/noise ratio over other paths with worse signal/noise ratio.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Then the receiver combines the output from all outputs from all the fingers from all the antennas, hopefully producing a combined signal with a better signal/noise ratio than it would get without all this rake complexity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The part of the radio that independently tunes the delay for each path in part (a) is the Path Searcher.&#xA;The part of the radio that independently tunes the complex attenuation for each path in part (c) is the Channel Estimator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;People familiar with AM and FM radio may think that part (c) is the only one needed -- in those kinds of radios, time delays have approximately the same effect as phase changes.&#xA;But with spread spectrum technology, time delays act very different from phase changes.&#xA;A phase change of +20 degrees can be compensated by either an additional phase change of -20 degrees or a phase change of +340 degrees or a phase change of +700 degrees -- all three methods of compensation are identical.&#xA;A spread-spectrum signal with a relative time delay of -21.5 chips must be compensated by a time delay of close to +21.5 chips; anything below +20.5 chips and anything above +22.5 chips is useless.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The part of the radio that &quot;can be used to find the multipaths&quot; &lt;em&gt;is&lt;/em&gt; the Path Searcher.&#xA;I suppose you might have one integrated component that simultaneously tunes the time delays in (a) and the complex attenuations in (c); that component &lt;em&gt;includes&lt;/em&gt; the Path Searcher and the channel estimator.&#xA;(This happens often with highly-integrated electronics -- you have a bunch of conceptually distinct blocks on the overview block diagram, but often there is some single physical component that is shared between two blocks).&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-29T18:46:58.577" />
  <row Id="9537" PostTypeId="2" ParentId="9530" CreationDate="2011-01-29T20:53:46.173" Score="6" ViewCount="" Body="&lt;p&gt;First, collect some of the data you want to process on a PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, develop your algorithms on the PC.  Start with matlab/octave or numpy. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Third, translate the algorithm into C code on the PC.  Does it behave well as floating-point? 16-bit fixed-point?  Profile it to see how many multiply+accumulates it does per second of sample data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you know the requirements and you have the algorithm ready to go.  You are ready to choose a DSP.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-29T20:53:46.173" CommentCount="2" />
  <row Id="9538" PostTypeId="2" ParentId="1404" CreationDate="2011-01-30T00:24:55.727" Score="0" ViewCount="" Body="&lt;p&gt;Lots of people on ebay selling &lt;a href=&quot;http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&amp;amp;item=280613492955&quot; rel=&quot;nofollow&quot;&gt;these modules&lt;/a&gt; at less than $8 1-off shipped. &lt;a href=&quot;http://www.bestelecs.com/download/bluetooth_module.zip&quot; rel=&quot;nofollow&quot;&gt;Documentation here&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-30T00:24:55.727" />
  <row Id="9539" PostTypeId="2" ParentId="7956" CreationDate="2011-01-30T01:28:59.213" Score="2" ViewCount="" Body="&lt;p&gt;I am a little surprised at how little overlap there is between the devices listed here and the list of &lt;a href=&quot;http://wsn.oversigma.com/wiki/index.php?title=Radio_Transceivers&quot; rel=&quot;nofollow&quot;&gt;radio transceivers for wireless sensor networks&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Forgive me for trying to read your mind, but I guess you plan to hook up that low-power radio to a battery and a sensor or two.&#xA;Rather than re-design everything from scratch,&#xA;have you considered buying an off-the-shelf wireless sensor node that already has all that stuff assembled and tested, or perhaps you could make relatively minor tweaks to one of the &lt;a href=&quot;http://wsn.oversigma.com/wiki/index.php?title=WSN_Platforms&quot; rel=&quot;nofollow&quot;&gt;open-source wireless sensor node platforms&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-01-30T01:28:59.213" />
  <row Id="9540" PostTypeId="2" ParentId="1184" CreationDate="2011-01-30T02:07:21.327" Score="-2" ViewCount="" Body="&lt;p&gt;Pay a short-run assembly company to do it for you.  Much more reliabile, especially with small parts where it just isn't worth the hassle, unless your time is free.  For example &lt;a href=&quot;http://www.aapcb.com/?gclid=CLPPiNfr4KYCFQdMgwodcRBS0g&quot; rel=&quot;nofollow&quot;&gt;Advanced Assembly&lt;/a&gt; and &lt;a href=&quot;http://www.screamingcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;Screaming Circuits&lt;/a&gt;.  Disclaimer:  I haven't used them, nor know anyone who has.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-30T02:07:21.327" CommentCount="2" />
  <row Id="9541" PostTypeId="2" ParentId="1184" CreationDate="2011-01-30T03:32:59.183" Score="2" ViewCount="" Body="&lt;p&gt;I have used the skillet method... without a skillet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I set the burner (electric stovetop) to low and place a 1/4&quot; thick, 6&quot;x6&quot;aluminum slab with the boards on it directly on the burner. After about 2 minutes to get everything to warm up evenly, I crank up the heat to high. When the solderpaste starts to flow, I shut off the heat and slide the slab off. There's enough residual heat to reflow everything and being aluminum, it heats up and cools down evenly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done this a few times and it works much better than hand soldering. Eventually I could get a skillet, I guess. But I also have an old toaster oven I will try out one of these days.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-01-30T03:32:59.183" />
  <row Id="9542" PostTypeId="2" ParentId="1990" CreationDate="2011-01-30T03:37:30.833" Score="2" ViewCount="" Body="&lt;p&gt;+1 for pcbexpress.com&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Great quality and price and good service. I have used them a few times over the last 4 years and will continue to do so. They are based in Texas, and they send the Gerber files to a shop in China that ships directly from there to your home/business.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-01-30T03:37:30.833" />
  <row Id="9543" PostTypeId="2" ParentId="9510" CreationDate="2011-01-30T09:31:30.700" Score="6" ViewCount="" Body="&lt;p&gt;As you stated, there are 3 parameters that dictate the DC response of a diode. Those are the saturation current (&lt;strong&gt;IS&lt;/strong&gt;), the emission coefficient (&lt;strong&gt;N&lt;/strong&gt;), and the ohmic resistance (&lt;strong&gt;RS&lt;/strong&gt;). I was able to fit the curve with a fairly high accuracy, so I'll document my model procedure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The SPICE model for the diode closely matches the Schokley diode equation:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;If = IS(e^(Vf/(N*Vt)) - 1)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;where &lt;code&gt;Vt = kT/q = 26mV&lt;/code&gt; at room temperature.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Get actual values from the graphs provided in the datasheet to use for comparison. The more points the better, and the more accurate the better. Below is a table that I estimated from the figure you provided:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Vf  If (mA)&#xA;1.3 0.001&#xA;1.4 0.010&#xA;1.5 0.080&#xA;1.6 0.700&#xA;1.7 5.000&#xA;1.8 20.000&#xA;1.9 40.000&#xA;2.0 65.000&#xA;2.1 80.000&#xA;&lt;/code&gt;&lt;/pre&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Plug the values into Excel, and change the y-axis to a log scale. You should get a graph that looks identical to the original graph from the datasheet. Add another column for your graph, with &lt;strong&gt;If&lt;/strong&gt; calculated from the forward voltage and the constants &lt;strong&gt;IS&lt;/strong&gt; and &lt;strong&gt;N&lt;/strong&gt;. We can use this configuration to iteratively find &lt;strong&gt;IS&lt;/strong&gt; and &lt;strong&gt;N&lt;/strong&gt;.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Solve for &lt;strong&gt;IS&lt;/strong&gt; and &lt;strong&gt;N&lt;/strong&gt;. We are trying to match the linear part of the graph (1.3 &amp;lt;= &lt;strong&gt;Vf&lt;/strong&gt; &amp;lt;= 1.7). Adjusting &lt;strong&gt;IS&lt;/strong&gt; will move the curve in the y-axis. Get the calculated graph to the same order of magnitude. The next step is to find the emission coefficient (&lt;strong&gt;N&lt;/strong&gt;). &lt;strong&gt;N&lt;/strong&gt; affects both the amplitude and the slope, so some adjustment of &lt;strong&gt;IS&lt;/strong&gt; may be necessary to keep the curve in the same ballpark. Once the slopes match (the lines are parallel), trim &lt;strong&gt;IS&lt;/strong&gt; so that the calculated data matches the datasheet values. I got &lt;code&gt;IS = 1e-18&lt;/code&gt;, and &lt;code&gt;N=1.8&lt;/code&gt; for the diode you listed.&#xA;&lt;img src=&quot;http://i.imgur.com/nwNWf.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Identify &lt;strong&gt;RS&lt;/strong&gt;. This is a bit tricky. &lt;strong&gt;RS&lt;/strong&gt; is responsible for the curving of the current from 1.7V and above. Consider modeling the ohmic resistance as a resistor in series with the diode. As the current through the diode increases, the voltage drop across the ohmic resistance causes the forward diode voltage &lt;strong&gt;Vf&lt;/strong&gt; to increase slower. At small currents, this effect is negligible. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The first thing to do is to get a ballpark estimate of RS to use in the more accurate solutions. You can calculate the effective value of &lt;strong&gt;RS&lt;/strong&gt; from the datasheet values by back-calculating for &lt;strong&gt;Vf&lt;/strong&gt; using the measured &lt;strong&gt;If&lt;/strong&gt;. The voltage difference between the input value and the calculated Vf can be used with the forward current to generate a resistance. At the higher currents, this will be a good starting value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To plot the diode current using &lt;strong&gt;RS&lt;/strong&gt;, you need to first calculate the diode &lt;strong&gt;Vf&lt;/strong&gt; given a voltage for the resistor-diode series combination. Wikipedia lists an &lt;a href=&quot;http://en.wikipedia.org/wiki/Diode_modelling#Iterative_solution&quot; rel=&quot;nofollow&quot;&gt;iterative function&lt;/a&gt; - it converges easily if the resistor voltage drop is significant. This function was easy enough to set up in Excel. For &lt;strong&gt;Vf&lt;/strong&gt; values below 1.8, I hard-coded the input value because the iterative function did not converge. Then take this &lt;strong&gt;Vf&lt;/strong&gt; value to calculate the If of the ideal diode. I plotted this with the original datasheet graph.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using trial and error, you should be able to get a &lt;strong&gt;RS&lt;/strong&gt; value that gets pretty good overlap with the datasheet values. All that's left is to throw the model together in SPICE to verify your work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Below is my diode model that I verified using HSPICE. The simulation data is almost a perfect overlay for the datasheet graph.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;.model Dled_test D (IS=1a RS=3.3 N=1.8)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I used &lt;a href=&quot;http://www.allaboutcircuits.com/vol_3/chpt_3/14.html&quot; rel=&quot;nofollow&quot;&gt;this article&lt;/a&gt;, which helped a lot with the diode spice parameters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I cleaned up my spreadsheet, and tyblu has made it available for download &lt;a href=&quot;http://www.tyblu.ca/misc/diode_modeling.xlsx&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. Use at your own risk, results not guaranteed, etc... etc... &lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-02-01T04:27:01.293" LastActivityDate="2011-02-01T04:27:01.293" CommentCount="1" />
  <row Id="9544" PostTypeId="2" ParentId="9428" CreationDate="2011-01-30T10:27:02.087" Score="0" ViewCount="" Body="&lt;p&gt;There is a cheap alternative that you can put in every point you like. It's a USB Temperature Sensor from Magiant.it that sends email and/or SMS when temperature is above the thresold and could also shutdown the pc/server.&lt;/p&gt;&#xA;" OwnerUserId="2818" LastActivityDate="2011-01-30T10:27:02.087" />
  <row Id="9545" PostTypeId="2" ParentId="4895" CreationDate="2011-01-30T13:39:29.267" Score="0" ViewCount="" Body="&lt;p&gt;Many years ago I used the Signetics NE565 PLL chip to build a 1 MHz frequency standard phase-locked to the BBC 200 kHz long wave transmission.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-30T13:39:29.267" />
  <row Id="9547" PostTypeId="1" CreationDate="2011-01-30T15:55:43.473" Score="4" ViewCount="97" Body="&lt;p&gt;I am working on a project and have decided that I will design the PCB so that it fits a standard enclosure size, as was suggested &lt;a href=&quot;http://electronics.stackexchange.com/questions/2145/plastic-enclosure-for-small-product&quot;&gt;here&lt;/a&gt;. All electronics websites sell some variety of enclosures, and then there are sites like &lt;a href=&quot;http://www.okw.co.uk/&quot; rel=&quot;nofollow&quot;&gt;OKW&lt;/a&gt; (and others) which have every variety imaginable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't want to get locked into a specific company or catalog for an enclosure. Just as LEDs come in 5mm and 3mm sizes, what are common standard enclosure sizes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, radio shack &lt;a href=&quot;http://www.radioshack.com/family/index.jsp?categoryId=2032276&quot; rel=&quot;nofollow&quot;&gt;has&lt;/a&gt; some excellent inexpensive boxes, like a 5&quot;x2.5&quot; for $4. However, Mouser doesn't have any 5x2.5 boxes. The closest box digikey has is 5x2.25. Well I don't want to depend on radio shack exclusively for these things. So what would be a &quot;very common&quot; dimension for a box? For &quot;big boxes&quot; versus &quot;small boxes&quot;?&lt;/p&gt;&#xA;" OwnerUserId="1021" LastActivityDate="2011-01-30T17:52:56.587" Title="Standard enclosure sizes?" Tags="&lt;enclosure&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="9548" PostTypeId="2" ParentId="8078" CreationDate="2011-01-30T16:29:18.533" Score="1" ViewCount="" Body="&lt;p&gt;Are you wired to a twisted pair of the CAT5 cable, and not two halves of two different pairs?&lt;/p&gt;&#xA;" OwnerUserId="906" LastEditorUserId="906" LastEditorDisplayName="" LastEditDate="2011-01-30T16:34:21.707" LastActivityDate="2011-01-30T16:34:21.707" />
  <row Id="9549" PostTypeId="2" ParentId="9547" CreationDate="2011-01-30T16:41:07.660" Score="3" ViewCount="" Body="&lt;p&gt;If you standardise on Eurocard (100 mm x 160 mm) and half Eurocard (100 mm x 80 mm) you will have thousands to choose from.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-30T16:41:07.660" CommentCount="1" />
  <row Id="9550" PostTypeId="1" CreationDate="2011-01-30T17:19:54.817" Score="0" ViewCount="246" Body="&lt;p&gt;Hey,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've just bought a 42 inch plasma TV, and was told a possible &quot;old wives tale&quot; that I may need to wait 24 hours for it to settle after moving it. Is this true? Or just a rumour. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2823" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-01-30T17:52:06.107" LastActivityDate="2011-01-30T17:52:06.107" ClosedDate="2011-01-30T17:48:46.097" Title="How long to wait before turning on a plasma TV after moving it?" Tags="&lt;off-topic&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="9551" PostTypeId="2" ParentId="9550" CreationDate="2011-01-30T17:28:25.630" Score="2" ViewCount="" Body="&lt;p&gt;The problem here is condensation. Let's say you had your piece of electronics hardware shipped to you via truck. It's been sealed up relatively tight and sitting out in the unheated cargo area for a few days.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you take it in to the warm house and unwrap it. Moisture condenses on it, and then you power it on: zap, it shorts out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So conventional wisdom is to unpack it and leave it for 24 hours to allow it to come up to temperature, before applying power.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2011-01-30T17:28:25.630" />
  <row Id="9552" PostTypeId="2" ParentId="9547" CreationDate="2011-01-30T17:52:56.587" Score="0" ViewCount="" Body="&lt;p&gt;Similarly cPCI, VME, PCI and other buses.  But those do assume a backplane.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-30T17:52:56.587" />
  <row Id="9553" PostTypeId="1" CreationDate="2011-01-30T17:59:53.100" Score="4" ViewCount="286" Body="&lt;p&gt;Hi am a Trainee electrician and pc hardware enthusiast. I was just wondering why a mixture of inductors and capacitors are used on motherboards? Why not just use capacitor? I thought the inductor stores electrical charge but it uses magnetism. What's so special about storing it as magnetism?&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-04-07T13:07:03.570" Title="Inductor vs a capacitor" Tags="&lt;electronics&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="9554" PostTypeId="2" ParentId="9553" CreationDate="2011-01-30T18:42:05.357" Score="11" ViewCount="" Body="&lt;p&gt;To answer this properly, you should know the properties of a capacitor and an inductor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inductors are one of the primary components required by a switching regulator. An capacitor and inductor are similar in the way that a capacitor resists a change of a voltage and an inductor resists a change in current. The way how 'strong' they can resist depends on their value. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Capacitors are widely used to clean up a power supply line, i.e. remove noise or ripple at (higher) frequencies. Inductors are used in switching power supplies where a relatively constant current is passed through an inductor. &#xA;A switching power supply works in that a switch is opened and closed very quickly. When the switch is closed, the inductor is 'charged'. When the switch is open, the energy is drawn from the inductor into the load. Usually such a power supply is being decoupled with a capacitor to create a stable power supply line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An inductor is required to make this principle work. If you know a resistor that has an equal resistance for all frequencies of signal, you should view a capacitor as a resistor that will be infinite for DC (0Hz) and 0 for high frequencies. An inductor will be the opposite: it's resistance will be 0 at 0Hz, and infinite at high frequencies. However we don't call this resistance (that's only used for a pure resistor!) but impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A PC motherboard or graphics card is basically not much else than this. They have their main chips and the routing between them, and most other components are power supply or a little bit of interfacing between chips or connectors. &lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-01-30T18:42:05.357" />
  <row Id="9555" PostTypeId="1" AcceptedAnswerId="9557" CreationDate="2011-01-30T19:14:57.903" Score="3" ViewCount="102" Body="&lt;p&gt;My wife and I are planning a Robot themed room for our 1st child which is due in May. My goal for his, yep its a boy, room is to make a wider variety of sensors that will hang on the wall that will each display a different input. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For my first sensor I want to build a simple sound measuring device that will use a moving coil meter and an artsy fartsy backdrop. The problem I'm having is trying to hook up the electret to the moving coil and was wondering if someone out there had a schematic. &lt;/p&gt;&#xA;" OwnerUserId="619" LastActivityDate="2011-01-30T19:23:53.417" Title="Moving Coil Circuit" Tags="&lt;electronics&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9556" PostTypeId="1" AcceptedAnswerId="9578" CreationDate="2011-01-30T19:22:51.860" Score="0" ViewCount="102" Body="&lt;p&gt;I'm pretty new to the world of Arduino and am trying to get it talking to the CM12U X10 power line interface device. I've seen lots of talk about the US based PSC05/TW523 but nothing for the European CM12U.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used the wiring and code found here &lt;a href=&quot;http://www.arduino.cc/playground/X10/ReceiveX10&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/X10/ReceiveX10&lt;/a&gt; and made the suggested changes for 50Hz land, but nothing triggers the receive interrupt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried reversing the order the pins are connected as there seems to be some confusion as to which way round it should be and that seems to almost continually flood the device - LED13 is on for 14 seconds, then off for 2 seconds &amp;amp; and repeat. (LED13 is lit to show something has been received) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've triple checked the wiring and continuity tests suggest things are connected ok. (Of course that doesn't help if my assumption that the wiring is the same as the TW523 is wrong!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone confirm this device actually works before I dig deeper, or am I'm wasting my time?&lt;/p&gt;&#xA;" OwnerUserId="2782" LastActivityDate="2011-01-31T17:12:46.400" Title="Has anyone managed to get Arduino talking to the CM12U X10 device?" Tags="&lt;arduino&gt;&lt;x-10&gt;" AnswerCount="1" />
  <row Id="9557" PostTypeId="2" ParentId="9555" CreationDate="2011-01-30T19:23:53.417" Score="2" ViewCount="" Body="&lt;p&gt;I believe what you want is called an analogue VU meter, and the mic won't generate enough power to move the needle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what you need is a microphone preamp. I found this circuit on the internet which should do the job:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/62ymX.png&quot; alt=&quot;Preamp Circuit&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-30T19:23:53.417" CommentCount="1" />
  <row Id="9558" PostTypeId="2" ParentId="9553" CreationDate="2011-01-30T20:46:19.543" Score="1" ViewCount="" Body="&lt;p&gt;This is the question puzzled me for quite a while too, I even did simulation of &quot;step-down&quot; converter without the inductor so now I figured out what is wrong :-).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, if you skip inductor, it will work. But efficiency would be like in linear regulator - voltage drop would be only due to drop in parasitic resistors from 12v supply to output capacitor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inductor works like a resistor here, but it does not waste any energy, it rather slowly pump it into capacitor.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-01-30T20:46:19.543" />
  <row Id="9559" PostTypeId="2" ParentId="9523" CreationDate="2011-01-30T21:53:53.827" Score="2" ViewCount="" Body="&lt;p&gt;This is an excellent article written by someone on the Parallax forums, called CORDIC For Dummies. Well written and explains things nicely: &lt;a href=&quot;http://forums.parallax.com/showthread.php?127241-CORDIC-for-dummies&quot; rel=&quot;nofollow&quot;&gt;http://forums.parallax.com/showthread.php?127241-CORDIC-for-dummies&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-01-30T21:53:53.827" CommentCount="1" />
  <row Id="9560" PostTypeId="2" ParentId="1184" CreationDate="2011-01-30T23:36:37.530" Score="0" ViewCount="" Body="&lt;p&gt;I've done dozens of proto and production boards in a manually controlled toaster oven with no problems. for 0.5mm QFPs I tend to carefully line it up and then tack a few pins down. Afterwards there may be the odd short but that's mostly down to the paste stencilling not the reflow and easily touched up afterwards.&#xA;Even if I didn't have a  stencil, if there's more than a handful of parts I'd always manually paste, place and reflow in preference to hand soldering - it's quicker and gives more consistent results.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-01-30T23:36:37.530" />
  <row Id="9561" PostTypeId="2" ParentId="9529" CreationDate="2011-01-31T01:59:03.133" Score="1" ViewCount="" Body="&lt;p&gt;Similar products are simply an IR LED + phototransistor. That makes for the 4 leads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Look for a diode with a multimeter, polarize it, and you should get the other 2 pins to conduct.&lt;/p&gt;&#xA;" OwnerUserId="2826" LastActivityDate="2011-01-31T01:59:03.133" CommentCount="2" />
  <row Id="9562" PostTypeId="2" ParentId="9489" CreationDate="2011-01-31T02:43:11.280" Score="2" ViewCount="" Body="&lt;p&gt;These type of connectors are usually called fine pitch board-to-board connectors. I doubt that you'll really find a way to connect to them without having to solder small wire leads. With the right tools, it's not as hard as you think. You'll need some fine gauge wire (wire-wrap works great), magnification, and a soldering iron with a sharp tip. With a little practice, I'm sure you can do it!&lt;/p&gt;&#xA;" OwnerUserId="2827" LastActivityDate="2011-01-31T02:43:11.280" />
  <row Id="9563" PostTypeId="2" ParentId="9527" CreationDate="2011-01-31T05:42:28.507" Score="2" ViewCount="" Body="&lt;p&gt;I know of two methods for impedance measurement. The first deals with DC impedance, and the second deals with AC impedance. They work regardless of whether you are looking at the input or output.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Measuring input impedance: Apply a DC voltage source to the input of your circuit. If any output loading, power supplies, or additional biasing is required, include this in the schematic as well. Sweep the input DC voltage source over the voltage range you expect to use the circuit. Use the equation below to give you the input resistance. Note that it is very possible to not have a flat curve.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;R = 1/(Iin dI/dV)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Explained, this is the inverse of the derivative of the input source's current w.r.t. the input voltage.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Output impedance (or some other port): Apply the required bias voltages to the inputs to cause the device to be at its quiescent point. Apply a voltage source to the node you want to measure, and sweep the DC voltage over the range of expected node voltages. Calculate resistance in the same method as the first technique.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;AC Impedance: Superimpose a small (1 uV) sine wave on the port you want to measure. Measure the amplitude of the current, and the phase difference between the voltage and current waveform. This will give you a current phasor, which can then be used to solve for a value of Z. You may be able to do this with an AC simulation, but a transient simulation with different frequencies should give the result you are looking for. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-01-31T05:42:28.507" />
  <row Id="9564" PostTypeId="1" AcceptedAnswerId="9565" CreationDate="2011-01-31T06:22:26.913" Score="2" ViewCount="192" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I read lot of stuff regarding CAN Bus arbitration, but it didn't clear my doubt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My doubt is:-&#xA;If One Node is already transmitting the data on bus and in between Another Node wants to initiate the data transfer. How that &quot;Another Node&quot; will get to know that Bus is busy?&#xA;All the documents (which I read) take condition that both nodes are starting transmission simultainously and then one with first dominant bit will get the bus but nobody explained the condition which I want to know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anybody clear my doubt&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="2574" LastActivityDate="2011-05-19T05:49:27.273" Title="How to check CAN bus is free or not" Tags="&lt;can&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="9565" PostTypeId="2" ParentId="9564" CreationDate="2011-01-31T08:40:52.193" Score="2" ViewCount="" Body="&lt;p&gt;There are two ways I know of that this could be resolved:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, the CAN controller would always monitor the bus; when it detects a message on the bus it begins the receiving process. Now that it's in the receiving state, it knows the bus is in use when a transmit is requested.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, by bit stuffing, the CAN transceiver will not have the same bit for more then 5 cycles. The exception to this is when nothing is being transmitted on the bus, when a passive bit is always read. A controller just starting could listen to the bus for five cycles before declaring 'probably free'. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do not guarantee that these are the actual processes, but based on my (limited) knowledge of CAN, these would work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Correction to the second method; there is actually a time when you'll see upto 12 dominant bits in a row, which occurs when a bus error is detected.&lt;/p&gt;&#xA;" OwnerUserId="1507" LastEditorUserId="1507" LastEditorDisplayName="" LastEditDate="2011-05-19T05:49:27.273" LastActivityDate="2011-05-19T05:49:27.273" CommentCount="2" />
  <row Id="9566" PostTypeId="2" ParentId="9564" CreationDate="2011-01-31T11:32:08.260" Score="2" ViewCount="" Body="&lt;p&gt;Short answer is that the node must monitor the Can Lines to be idle for a certain time before it attempts to transmit. So if another node is transmitting, it must keep quiet till the other node is done.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A Can bus is based in differential signalling. The two lines CanHigh and CanLow are both at the same potential when the bus is idle. To send bits a CAN transmitter puts a differential voltage on the lines of about 2 volts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A CAN transmitter first sees if the bus is idle and if it is, starts to transmit. How the arbitration works is that a transmitter monitors the bus as its transmitting. Transmission is done as above by either keeping the two lines at the same potential or at a differential potential. So if the transmitter transmits a bit by keeping the lines at the same potential(sic), but sees that the two transmit lines have a differential potential, that means that some other node is transmitting and the first transmitter has lost the arbitration. It must then stop transmitting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When a node first starts transmitting, the bits transmitted are the same until the address of the transmitting node which are obviously different. If two nodes start transmitting together, they will transmit together in sync till the address part is reached. When the address differs, a node will notice a potential difference on the lines even when it is not putting one on the lines. Then it knows it has lost and has to try again. The winning node continues transmitting without knowing that some other node was trying as well. Off course this logic extends to more than two nodes also.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="1927" LastActivityDate="2011-01-31T11:32:08.260" CommentCount="1" />
  <row Id="9567" PostTypeId="2" ParentId="9564" CreationDate="2011-01-31T11:39:37.630" Score="1" ViewCount="" Body="&lt;p&gt;As CoderTao says - the CAN controller is continually monitoring the bus, so it knows when a transmission is already in progress.  So the only time when a collision can happen is when both nodes start to transmit &quot;simultaneously&quot; - within a bit-time of each (+a bit for bus propagation).  Hence those are the only cases you've found in documents :)&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-01-31T11:39:37.630" />
  <row Id="9568" PostTypeId="2" ParentId="9517" CreationDate="2011-01-31T12:09:08.097" Score="2" ViewCount="" Body="&lt;p&gt;From the latency on the cordic block, that looks as if you've chosen to use a single processing element - that will produce results of limited accuracy.  Very limited it appears :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried using 10 elements for example, with [zeros (1,9) 1] for the &quot;latency per processing element&quot; - to get back to your 21 tick latency.  Making sure I ran the simulation long enough (oops), I then got a result (using UFixed_16_11 inputs) of 0.501953125.  Which is closer...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does that help?&lt;/p&gt;&#xA;" OwnerUserId="763" LastEditorUserId="763" LastEditorDisplayName="" LastEditDate="2011-02-18T15:53:30.007" LastActivityDate="2011-02-18T15:53:30.007" CommentCount="2" />
  <row Id="9569" PostTypeId="1" CreationDate="2011-01-31T13:20:04.683" Score="2" ViewCount="115" Body="&lt;p&gt;I am interested in making a small circuit that could sense the vibrational frequency of the object that it is attached to. The resonant frequencies would be in the audible range (likely 5kHz to 10kHz) Imagine a small circuit attached to a tuning fork, I would like to 'ping' the tuning fork and have the circuit be able to output what frequency at which it is resonating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have read that Piezo devices would be capable of this but I haven't been able to find anything suitable. Does anyone have any suggestions of what I could use?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2011-02-01T03:46:03.103" Title="Sense vibrations in audible range" Tags="&lt;audio&gt;&lt;piezoelectricity&gt;" AnswerCount="4" />
  <row Id="9570" PostTypeId="2" ParentId="9564" CreationDate="2011-01-31T13:21:23.290" Score="0" ViewCount="" Body="&lt;p&gt;The node address determines priority, lower addresses being high priority. The transmission starts with the node broadcasting its address. At the same time it transmits, it listens. Lets say node 3 and 2 transmits at the same time. As the last bit of the address, node 3 broadcasts a 1 and node 2 broadcasts a 0. because of the 0, the data line is pulled down to the 0 state. Node three see that instead of the 1 it broadcast, the line is a 0 and stops transmitting. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;CAN was first used in cars and trucks. Some sensors needed to be much higher priority then others. For example anti skid braking needed to have a higher priority the low windshield washer fluid. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-01-31T13:21:23.290" CommentCount="1" />
  <row Id="9571" PostTypeId="2" ParentId="9553" CreationDate="2011-01-31T13:23:37.593" Score="0" ViewCount="" Body="&lt;p&gt;Inductors are put inline to filter electrical noise. Caps are placed in parallel to shunt noise to ground. Both can cause a phase shift between voltage and current, but they do so in opposite directions so the effect cancels out. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-01-31T13:23:37.593" />
  <row Id="9572" PostTypeId="2" ParentId="9569" CreationDate="2011-01-31T13:32:52.267" Score="1" ViewCount="" Body="&lt;p&gt;I would use a &lt;a href=&quot;http://www.goldmine-elec-products.com/prodinfo.asp?number=G9303&quot; rel=&quot;nofollow&quot;&gt;piezoelectric disk&lt;/a&gt; and attach it to your object, connect a small amplifier circuit , and use the output to go to a speaker or a an ADC pin of a uC of your choice.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-01-31T13:32:52.267" CommentCount="1" />
  <row Id="9573" PostTypeId="2" ParentId="9569" CreationDate="2011-01-31T14:02:26.067" Score="0" ViewCount="" Body="&lt;p&gt;If you attach something to the tuning fork the added mass of the device will affect the frequency, so you might be better off using a microphone and MCU to measure the sound frequency directly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could simply use a PC and sound card with a microphone and sound analysis software, if you don't want to build anything.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-01-31T14:18:28.093" LastActivityDate="2011-01-31T14:18:28.093" />
  <row Id="9574" PostTypeId="2" ParentId="9569" CreationDate="2011-01-31T14:21:35.550" Score="2" ViewCount="" Body="&lt;p&gt;You could use a piezoelectric tuner for an acoustic guitar. These clip onto the guitar, amplify the vibrations and measure the frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;eg.&#xA;&lt;a href=&quot;http://guitar.lovetoknow.com/Classical_Guitar_Tuners&quot; rel=&quot;nofollow&quot;&gt;http://guitar.lovetoknow.com/Classical_Guitar_Tuners&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-01-31T14:21:35.550" CommentCount="1" />
  <row Id="9575" PostTypeId="1" AcceptedAnswerId="9577" CreationDate="2011-01-31T16:29:49.823" Score="5" ViewCount="380" Body="&lt;p&gt;note and question&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;* Is it an alternator or dynamo?&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I am not an electrical engineer and neither have any core knowledge but, this is a simple procedure of car battery charging using a dynamo, which is present in all cars and bicycles. But what i don't understand is how can a battery be utilised and charged at the same time?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;* That is, head lights drawing current.&#xA;* But dynamo is giving current.&#xA;* Everything done by using same battery terminals.&#xA;* So BHOOM must be a explosion!!&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2830" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-01T15:48:10.867" LastActivityDate="2011-02-01T15:48:10.867" Title="How can a car battery be charged by dynamo (or is it an alternator?) at the same time it is being used by the car components?" Tags="&lt;battery&gt;&lt;charging&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="9576" PostTypeId="2" ParentId="9575" CreationDate="2011-01-31T16:41:12.993" Score="2" ViewCount="" Body="&lt;p&gt;The same way a laptop battery can be used and be charging.  And if you have more current from your dynamo than is needed to power the lights, etc. those can be powered while charging the battery.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-01-31T16:41:12.993" />
  <row Id="9577" PostTypeId="2" ParentId="9575" CreationDate="2011-01-31T16:54:22.467" Score="7" ViewCount="" Body="&lt;p&gt;In short, it can't. If the battery is being charged then current is flowing &lt;em&gt;into&lt;/em&gt; it, so it can't be powering anything. It is the charger/dynamo/alternator that is powering the components whilst charging. In the case of a dynamo or alternator, if the output drops below the open-circuit terminal voltage of the battery, the battery takes over powering the components and is therefore no longer charging.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-01-31T16:54:22.467" CommentCount="4" />
  <row Id="9578" PostTypeId="2" ParentId="9556" CreationDate="2011-01-31T17:12:46.400" Score="0" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;LED13 is on for 14 seconds, then off for 2 seconds &amp;amp; and repeat. (LED13 is lit to show something has been received)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Is it located electrically near a switch mode power supply, compact fluorescent or any other device known to generate noise on the power line?  That &lt;em&gt;could&lt;/em&gt; make it continually receive (noise).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's an RS232 device so you could hook it to your com port and monitor the transmissions through hyperterm to what is being received.  &lt;/p&gt;&#xA;" OwnerUserId="2051" LastActivityDate="2011-01-31T17:12:46.400" CommentCount="2" />
  <row Id="9579" PostTypeId="2" ParentId="9575" CreationDate="2011-01-31T18:45:31.147" Score="6" ViewCount="" Body="&lt;p&gt;The battery is only being used when the alternator is not running. While the alternator is running (delivering power), the battery is essentially just another load like lights, radio, etc.&#xA;For most of the time, the alternator is just maintaining the battery charge and thus supply little actual current into the battery.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-01-31T18:45:31.147" CommentCount="1" />
  <row Id="9580" PostTypeId="1" CreationDate="2011-01-31T19:20:58.183" Score="3" ViewCount="261" Body="&lt;p&gt;I'm working with Micro Controller Mega-32 (SMD). I'm looking for a Wireless module to transfer and receive the data that I created with the micro.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you please guide me ?&lt;/p&gt;&#xA;" OwnerUserId="2832" LastActivityDate="2011-06-05T23:53:14.853" Title="Wireless Module with over 1.5Km range ?" Tags="&lt;microcontroller&gt;&lt;wireless&gt;" AnswerCount="7" CommentCount="2" />
  <row Id="9581" PostTypeId="2" ParentId="9580" CreationDate="2011-01-31T19:32:36.360" Score="2" ViewCount="" Body="&lt;p&gt;I think you are out of the range of a &quot;wireless module&quot;.  I think you are getting into the realm of &lt;a href=&quot;http://en.wikipedia.org/wiki/Long-range_Wi-Fi&quot; rel=&quot;nofollow&quot;&gt;Long Distance WiFi&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is that you need to go 1.5km.  The solution would be good antennas on either end to transmit and receive the signals and a wireless radio to encode/decode the signals to bit/bytes.  The actual micro you use should not matter.&lt;/p&gt;&#xA;" OwnerUserId="204" LastEditorUserId="204" LastEditorDisplayName="" LastEditDate="2011-01-31T19:53:24.803" LastActivityDate="2011-01-31T19:53:24.803" CommentCount="1" />
  <row Id="9582" PostTypeId="2" ParentId="9146" CreationDate="2011-01-31T19:44:03.397" Score="1" ViewCount="" Body="&lt;p&gt;When I started making things out of electronics, I bought &lt;a href=&quot;http://www.mikroe.com/eng/products/view/297/easypic6-development-system/&quot; rel=&quot;nofollow&quot;&gt;an EasyPIC6&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/KuZL1.jpg&quot; alt=&quot;EasyPIC6&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a pic microcontroller development board with loads of features you can play around with and test, without even having to touch a breadboard or soldering iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to start building systems that need a microcontroller, I'd highly recommend this. Also, they have loads of &lt;a href=&quot;http://www.mikroe.com/eng/categories/view/11/accessory-boards/&quot; rel=&quot;nofollow&quot;&gt;extra addon boards&lt;/a&gt; you can plug into the board to support things like ethernet, WiFi, Bluetooth, Flash cards, TFT Displays, accelerometer, distance meters, etc... all very cool stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can either program it in assembler and upload the HEX file, or use their C, Basic or Pascal compilers.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-31T19:44:03.397" />
  <row Id="9583" PostTypeId="2" ParentId="9580" CreationDate="2011-01-31T19:51:02.003" Score="2" ViewCount="" Body="&lt;p&gt;An XBee pro (if they're still making them) might be able to achieve 1.5km with line-of-sight on the highest power rating. I think I saw them rated for 1km, so 1.5km might be a stretch, but it could be worth testing depending on how often you need to transmit.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2011-01-31T19:51:02.003" CommentCount="6" />
  <row Id="9584" PostTypeId="2" ParentId="9580" CreationDate="2011-01-31T19:55:18.843" Score="4" ViewCount="" Body="&lt;p&gt;You could get to that range in the 900Mhz band with reasonable power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.lsr.com/products/radio_modules/900_MHz/siflex-02.aspx&quot; rel=&quot;nofollow&quot;&gt;LS Research makes a couple 900Mhz modules&lt;/a&gt; that could do it with the right antenna (directional and high gain).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just note that usable range can vary a lot based on environment (through a city? through woods? etc).&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-01-31T19:55:18.843" />
  <row Id="9585" PostTypeId="2" ParentId="9580" CreationDate="2011-01-31T20:02:50.237" Score="2" ViewCount="" Body="&lt;p&gt;There are several Chinese vendors that take ISM-band chips and add a power amplifier (and sometimes LNA) to boost the range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.satistronics.com/nrf24l01-with-pa-and-lna-1000m-long-distance-24g-wireless-module-with-antenna_p2862.html&quot; rel=&quot;nofollow&quot;&gt;http://www.satistronics.com/nrf24l01-with-pa-and-lna-1000m-long-distance-24g-wireless-module-with-antenna_p2862.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is all of dubious legality in the US, of course.  I haven't ordered any of these modules to see if they get seized by customs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An advantage to this approach is that you can prototype with the low power device, and &quot;upgrade&quot; as needed.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-01-31T20:02:50.237" />
  <row Id="9586" PostTypeId="2" ParentId="9482" CreationDate="2011-01-31T20:27:41.447" Score="0" ViewCount="" Body="&lt;p&gt;Thanks everyone for the suggestions! I've upvoted all answers instead of arbitrarily selecting one as &quot;the&quot; answer.&lt;/p&gt;&#xA;" OwnerUserId="2796" LastActivityDate="2011-01-31T20:27:41.447" />
  <row Id="9587" PostTypeId="2" ParentId="9580" CreationDate="2011-01-31T21:24:39.573" Score="3" ViewCount="" Body="&lt;p&gt;A Candian Company called Microhard systems makes the ISM 900Mhz band radio you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bit rates go from hundreds of baud to over 1.5 megabaud.&#xA;Interface to your micro can be serial, USB or ethernet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;we use them on our Robots and they a have a 90-100km range. In a built up area that drops to only 30-40Km or so. If you need to you can run a radio realy an get 2-300 km range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Very handy for us as our biggest robot has a 300km range.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All quite legal in any country, just say where you are and they'll send you the right radios.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-01-31T21:24:39.573" />
  <row Id="9588" PostTypeId="2" ParentId="9529" CreationDate="2011-01-31T21:40:22.690" Score="5" ViewCount="" Body="&lt;p&gt;I believe your part is a dual channel IR position sensor. I can't find your exact part, but I did find a &lt;a href=&quot;http://www.pacer.co.uk/jkcm/Products/Categories/IR+Switches+and+Sensors/Dual+Channel+Sensors&quot; rel=&quot;nofollow&quot;&gt;datasheet for something very similar&lt;/a&gt; although this has 8 pins, this is the OPB822:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/yz58R.jpg&quot; alt=&quot;datasheet&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, yours only has 6 pins. I guess that as you suggest, two pins are the infrared LED, so I think that the two detectors share the same LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other four pins are the opto couplers, and you can identify them using an multimeter that can measure the voltage drop of a diode. Try touching two of the probes to two of the pins while switching the transmitter LED on and off, if the reading changes with the LED, then you've found two of the pins you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The dual sensors can then be used to sense which direction its travelling along the strip, and how far.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-01-31T21:40:22.690" CommentCount="2" />
  <row Id="9589" PostTypeId="2" ParentId="9508" CreationDate="2011-01-31T23:00:50.373" Score="5" ViewCount="" Body="&lt;p&gt;I spent 13 years designing electronics of this exact nature: three phase induction motor reduced voltage soft starters and variable frequency AC drives. I spent the last few of those years as a VFD applications engineer helping customers select and configure this equipment for various loads and industries around the country as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will not be able to build something that is cheap &lt;em&gt;and&lt;/em&gt; safe. The voltages and currents involved are well beyond the safety margin of a hobbyiest, especially someone who is openly avoiding buying commercial units in order to save money. Don't do it!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While the theory behind AC motor control is very straightforward, the detail level work (heat sink sizing, snubbering, gate drive requirements, de-sat protection, motor overload calculations, bus capacitor protection, etc.) can be quite tricky to get down, especially with heavy duty cycling and regenerative power modes which a carnival ride will CERTAINLY be generating. I strongly caution you against trying to build something of this nature unless you have significant experience not only in microcontrollers and embedded systems design but also significant experience in power electronics and three phase circuitry. People get hurt and killed building this stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first question for you is whether speed control is really required, or if you only require a soft start up and slow down. Do you vary the speed of the motor once it is started? If not, you may be able to get away with a MUCH cheaper reduced voltage soft starter. These units act like three phase light dimmers; they only adjust the applied voltage to the motor. You will not have a lot of torque at low speeds, but with the right design of motor (NEMA class D) you can achieve exactly what you're after with a fraction of the cost and maintenance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really do need to vary the full-load speed of the motor then you are more or less stuck using a variable frequency drive. As you are aware these are expensive and if you buy cheap you are likely to replace them sooner due to your high surge current (they call this &quot;constant torque&quot;) application. What I would definitely recommend doing if this is the case would be to contact various manufacturers (Allen-Bradley, Cutler-Hammer, SAF drives, Benshaw, Yaskawa, etc.) and ask for reconditioned units. Ask for a drive capable of delivering 150% rated current for 30s (this is usually known as heavy duty) or size the drive 30-50% larger than your nominal current rating. You will also likely be running off of generator power which is notorious for being undersized and prone to brownouts and surges as the load requirements change with the state of the equipment being run. Drives don't like that (voltage sags cause current spikes as the motor starts slipping and surges can cause you to overvoltage the bus capacitors) and have a tendency to either fault out or blow up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am all about the little guy building something and saving a buck, but this is not the type of project to do this on. If you really want to build a three phase AC drive, start with a little 10HP 480V motor with a hand brake on a test bench. You have all the potential for experiencing the pants-filling sensation of an H-bridge failure or a bus capacitor explosion two feet from your head but without the potential lawsuits and loss of life (except perhaps your own).&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-01-31T23:00:50.373" CommentCount="9" />
  <row Id="9590" PostTypeId="1" AcceptedAnswerId="9593" CreationDate="2011-01-31T23:17:16.117" Score="2" ViewCount="158" Body="&lt;p&gt;When reading a manual on using a PICAXE and an I2C device I saw this diagram.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/H9C6H.png&quot; alt=&quot;Picaxe i2c&quot;&gt;&lt;br&gt;&#xA;I can't work how this would behave as wouldn't it make the connection on the lines constantly high due to the connection to the power rail, so never goes low. I understand that they are open-drain lines and they are needed inorder to make the lines go high but how can it make them go low with that connection to the positive rail?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-01-31T23:28:32.660" LastActivityDate="2011-01-31T23:32:51.347" Title="Don't understand how these resistors operate in this circuit." Tags="&lt;i2c&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="9591" PostTypeId="2" ParentId="9590" CreationDate="2011-01-31T23:31:22.973" Score="1" ViewCount="" Body="&lt;p&gt;Those are pull-up resistors. When devices aren't communicating the resistors pull both lines to high. A device is able to pull the lines low. It has to supply current that gets dissipated by the pull up resistors. You can think of this like a basic V=IR problem to determine how much current is required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reasoning for this setup is the situation where you want to have multiple devices communicating on a single line. If you had a device pulling the line high instead of the pull up resistors, when a different device tries to communicate it will be forced to overcome the other device in order to pull the line low. In this situation you still have a V=IR problem, except this time your R is very very small which makes I very very large.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-01-31T23:31:22.973" CommentCount="2" />
  <row Id="9592" PostTypeId="2" ParentId="9590" CreationDate="2011-01-31T23:32:13.797" Score="0" ViewCount="" Body="&lt;p&gt;They are required by the I2C specification.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They can be driven low by making the output pin low.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-01-31T23:32:13.797" />
  <row Id="9593" PostTypeId="2" ParentId="9590" CreationDate="2011-01-31T23:32:51.347" Score="13" ViewCount="" Body="&lt;p&gt;The resistors you see are called &quot;pull up&quot; resistors; they literally &quot;pull up&quot; the signal to the positive voltage rail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I2C is a communication bus that allows multiple devices to talk on it. Since there is only a clock and data line there is no way to ensure that two devices won't start talking at the same time, or a device mis-identifies a message as being for it and responds out of turn.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If two devices try to control the data line and one wants it '1' and the other '0' you end up with a condition called contention. Internally a normal digital output is built up out of two transistors: one connects the signal line to +V and the other to ground. The device turns on one transistor or the other to set the output signal to the appropriate level. When two devices are trying to make the same signal two different voltages you end up with +V connected to ground through two transistors. This is known as contention and is something you want to avoid because it causes high currents and can damage one or both of the output drivers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to get around this problem, the I2C specification requires the use of &quot;open collector&quot; or &quot;open drain&quot; (same thing) drivers. This means that the devices on the bus can ONLY connect the signal to ground. The only way for a device to output a '1' is to not drive the line to zero.  Something has to bring the line to a logic '1' and that something is the pull-up resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What happens now if two devices try to drive the data line is that one is not doing anything (it wants the line to be '1') and the other device has its output transistor turned on, connecting the signal to ground.  The resulting signal is a '0' -- there is no contention because the only thing holding trying to make the line a '1' is a resistor which by design limits the amount of current it allows through.  Pull-up resistors are usually selected to offer a bit of resistance to a changing signal but not too much. For I2C the value for a pull up is usually 4700-10000 ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out &lt;a href=&quot;http://en.wikipedia.org/wiki/Open_collector&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Open_collector&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/I%C2%B2C&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/I%C2%B2C&lt;/a&gt; for more information.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-01-31T23:32:51.347" CommentCount="1" />
  <row Id="9595" PostTypeId="1" AcceptedAnswerId="9597" CreationDate="2011-02-01T01:21:59.363" Score="2" ViewCount="108" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Althougth I never used one, I know JTAGs are a standardized way to program and debug MCUs. But I see a lot of JTAG from various companies. Can I use a particular JTAG to program/debug MCUs from different companies and with diferent arquitectures?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example: can I use a JTAG to program/debug STM32 and LPC micros? (all Cortex-m3) Can I use the same JTAG to program/debug MSP430 micros? (16bit MCU from TI)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which JTAG do you recommend to buy? And why?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="1074" LastActivityDate="2011-02-01T02:22:14.397" Title="Very basic question about JTAG" Tags="&lt;jtag&gt;" AnswerCount="2" FavoriteCount="0" />
  <row Id="9596" PostTypeId="2" ParentId="9595" CreationDate="2011-02-01T02:14:41.237" Score="3" ViewCount="" Body="&lt;p&gt;In theory, you should be able to use any JTAG interface with any device. However, the software and drivers differ between manufacturers and software suppliers, so a given JTAG interface will only work with one set of tools, and type of device, as a rule.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Amontec makes a JTAG interface based on a CPLD that may be reprogrammed to emulate units made by several manufacturers.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-01T02:22:14.397" LastActivityDate="2011-02-01T02:22:14.397" />
  <row Id="9597" PostTypeId="2" ParentId="9595" CreationDate="2011-02-01T02:21:44.117" Score="2" ViewCount="" Body="&lt;p&gt;At its very basic level, JTAG is a standardized serial protocol. You can build one out of a handful of components for under $20, but it will be slow. Generally speaking the more expensive ones offer higher speed, broader voltage support and even autonomous operation. The software used to drive the particular JTAG interface determines whether you will be able to program the devices you are interested in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally I am happy with the $70ish dollar Olimex JTAG units. They are USB, based on the FT2232, work with 5V and 3.3V devices and have good support for both Linux and Windows (I'm not sure about OSX).  I also have an Atmel USB Blaster for programming Altera FPGAs (supports down to 1.0V IO) and an older USB based one for Xilinx devices.  Finally, I also have a GNICE+ JTAG adapter used primarily for Analog Devices Blackfin processors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have not tried it, but I believe that the Altera USB Blaster should work for anything I connect to, although it does not support RTCK (return clock) support. It is primiarly ARM devices which support RTCK, which is a means for the JTAG interface to detect how fast the JTAG clock can go and still be reliable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My suggestion is to take a look at the particular devices you wish to use and see if you can find a common JTAG unit that is well supported by all. &lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-02-01T02:21:44.117" CommentCount="1" />
  <row Id="9598" PostTypeId="2" ParentId="2551" CreationDate="2011-02-01T03:19:34.843" Score="1" ViewCount="" Body="&lt;p&gt;If you're just trying to measure one golf club (not build a product), I'd try attaching a photosensor and measuring the vibration with an oscilloscope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Set up the photosensor so that the output oscillates between dark (covered by the head of the golf club at one extreme of travel) and bright (exposed to light at the opposite extreme of travel).&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-01T03:19:34.843" />
  <row Id="9599" PostTypeId="1" CreationDate="2011-02-01T03:41:38.633" Score="0" ViewCount="90" Body="&lt;p&gt;A RF receiver project I'm working calls for two 1090 MHz SAW filters. More specifically I need Tai-Saw SAW filters TA1090EC and TA0232A. I'm building this as a hobby and only need 1 or 2 of each filter. I live in the US and checked all usual electronics stores (Jameco, Mouser, Digikey, Newark, etc) and none of them carry Tai-Saw filters. Does anyone know of a source for SAW filters around 1 GHz in low quantities?&lt;/p&gt;&#xA;" OwnerUserId="2839" LastEditorUserId="2839" LastEditorDisplayName="" LastEditDate="2011-02-01T03:47:40.893" LastActivityDate="2011-02-01T03:47:40.893" ClosedDate="2011-02-01T03:54:36.343" Title="Where to buy SAW Filters in low quantity?" Tags="&lt;rf&gt;&lt;filter&gt;" CommentCount="2" />
  <row Id="9600" PostTypeId="2" ParentId="9569" CreationDate="2011-02-01T03:46:03.103" Score="0" ViewCount="" Body="&lt;p&gt;The thing you are looking for is called a Contact Microphone. &lt;a href=&quot;http://www.google.com/search?hl=en&amp;amp;client=opera&amp;amp;hs=7Cn&amp;amp;rls=en&amp;amp;q=contact+microphone&amp;amp;aq=f&amp;amp;aqi=g-c3&amp;amp;aql=&amp;amp;oq=&quot; rel=&quot;nofollow&quot;&gt;There are lots of good DIY links on google&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you should just be able to use any common audio microphone, since the vibrations are in the audible range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All microphones pick up vibrations in the microphone body, in addition to vibrations in the air. Therefore, just touching a microphone to the tuning fork should pick up a pretty strong signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, Since the microphone diaphragm has mass, moving the body will cause it to move around the diaphragm, producing a signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to reduce ambient pickup, you could use something like a little &lt;a href=&quot;http://en.wikipedia.org/wiki/Electret_microphone&quot; rel=&quot;nofollow&quot;&gt;electret capsule&lt;/a&gt;, plug the opening, and mechanically coupling the microphone body to your tuning fork (or what ever you want to sense vibrations in). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's worth noting that most microphones will be much more sensitive to motion in one axis than the others. Basically, since the diaphragm is sprung so it's only free to move along one axis, movement in the other axises will not have much effect.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-02-01T03:46:03.103" />
  <row Id="9601" PostTypeId="1" CreationDate="2011-02-01T04:05:30.237" Score="3" ViewCount="117" Body="&lt;p&gt;A RF receiver project I'm working on calls for a &lt;a href=&quot;http://electronics.stackexchange.com/questions/9599/where-to-buy-saw-filters-in-low-quantity&quot;&gt;very specific&lt;/a&gt; SAW bandpass filter. I've checked all the usual sources here in the US (Jameco, Mouser, Digikey, Newark, etc) without success. What I'm finding is that the part I'm looking for is highly specialized and thus difficult to find anyone that sells them in low, hobbyist quantities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are some approaches for buying difficult-to-find parts in low quantities?&lt;/p&gt;&#xA;" OwnerUserId="2839" LastActivityDate="2011-02-01T09:54:05.587" Title="How to buy difficult-to-find electronic parts?" Tags="&lt;rf&gt;&lt;filter&gt;&lt;buying&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="9602" PostTypeId="1" AcceptedAnswerId="9603" CreationDate="2011-02-01T05:19:54.067" Score="3" ViewCount="120" Body="&lt;p&gt;I'm building a simple Lego Mindstorms NXT robot and I'm trying to detect when a touch sensor has been bumped (pressed and released) in NXC.  My initial approach was to do the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;SetSensorTouch(S1);&#xA;until(SENSOR_1);&#xA;until(!SENSOR_1);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Is there a better way?  Perhaps interpreting some value returned from SensorValue()?&lt;/p&gt;&#xA;" OwnerUserId="2260" LastEditorUserId="2260" LastEditorDisplayName="" LastEditDate="2011-02-01T06:37:10.103" LastActivityDate="2011-02-01T06:37:10.103" Title="How do I detect when my Lego Mindstorms NXT touch button has been bumped in NXC?" Tags="&lt;lego-mindstorms&gt;&lt;nxc&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="9603" PostTypeId="2" ParentId="9602" CreationDate="2011-02-01T06:19:51.760" Score="1" ViewCount="" Body="&lt;p&gt;No, no, that's perfect. I would rather use &lt;code&gt;Sensor(S1)&lt;/code&gt; instead of &lt;code&gt;SENSOR_1&lt;/code&gt;, but it doesn't really matter, because this is how it's defined in the NXC API:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define SENSOR_1 Sensor(S1)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;SensorRaw(S1) is also an option, but this is pointless in this case, since this is a touch sensor. Sensor(S1) will return a processed value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is different for I2C sensors (like Ultrasonic), though. For them, you use:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;SetSensorLowspeed(S1);&#xA;distance = SensorUS(S1);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You'll need to use your own functions for other 3rd party sensors. NXC has many supported already, but you &lt;em&gt;may&lt;/em&gt; need to make your own for custom sensors from Mindsensors or HiTechnic. John adds as many as he can, and Mindsensors always provides a library of functions for the sensors.&lt;/p&gt;&#xA;" OwnerUserId="1940" LastActivityDate="2011-02-01T06:19:51.760" />
  <row Id="9604" PostTypeId="1" AcceptedAnswerId="9620" CreationDate="2011-02-01T06:46:40.563" Score="3" ViewCount="181" Body="&lt;p&gt;I'd like to mount a small (2.5&quot;) graphic LCD or OLED display on a PCB.  I believe it should look something like this: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/mBIiL.png&quot; alt=&quot;Evalbot pic cropped&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen this done (links to pics) on my &lt;a href=&quot;http://i.imgur.com/yAk1C.jpg&quot; rel=&quot;nofollow&quot;&gt;LM3S6965 development kit&lt;/a&gt;, on my &lt;a href=&quot;http://i.imgur.com/MovT0.jpg&quot; rel=&quot;nofollow&quot;&gt;TI Evalbot&lt;/a&gt;, and on &lt;a href=&quot;http://i.imgur.com/v9jz2.png&quot; rel=&quot;nofollow&quot;&gt;this Sparkfun breakout board.&lt;/a&gt; All of those images show a pane of glass, the screen itself, an FFC folded underneath the board, and very little information about the mounting technique.  The LM3S6965 and Evalbot have a bit of foam visible underneath. (I can't speak to the Sparkfun board as I don't own it). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect that the display is adhered to the PCB with double sided tape or an epoxy.  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt; Am I correct in my suspicions, or is there another method of doing this?  I've considered cutting a relief out of some clear acrylic and screwing that to the PCB as an alternative. &lt;/li&gt;&#xA;&lt;li&gt; Is it removable?  I've considered using a solvent or some force.  I'm interested in trying out the screens I already own on other PCBs, and I'm also interested in replacing the screen on my new PCB if I break it or doing edits to the PCB beneath the display. &lt;/li&gt;&#xA;&lt;li&gt; Is it easy to do?  I'd like to distribute the PCB with the components (including the display) as a kit to other engineering students, and I don't want them to have to deal with complex epoxy mixing ratios or risk damaging the LCD in the process.  &lt;/li&gt;&#xA;&lt;li&gt; Is replicating this technique the right thing to do for a development board or in-house tool? I expect users to abuse or break this board, and I expect it to need rework.  &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-01T14:17:32.207" LastActivityDate="2011-02-03T13:43:34.977" Title="How to affix graphic LCD to PCB?" Tags="&lt;display&gt;&lt;cases&gt;&lt;mount&gt;" AnswerCount="1" CommentCount="7" FavoriteCount="1" />
  <row Id="9605" PostTypeId="2" ParentId="9580" CreationDate="2011-02-01T07:05:06.977" Score="3" ViewCount="" Body="&lt;p&gt;I've heard good things about the &lt;a href=&quot;http://www.rfm.com/products/dnt900.shtml&quot; rel=&quot;nofollow&quot;&gt;DNT900&lt;/a&gt; from RFM. The guys over at &lt;a href=&quot;http://diydrones.com/forum/topics/40-mile-range-up-to-500kbs-but&quot; rel=&quot;nofollow&quot;&gt;DIY Drones&lt;/a&gt; say they can get it up to 40 miles at only $69US.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2011-02-01T07:05:06.977" />
  <row Id="9606" PostTypeId="2" ParentId="5691" CreationDate="2011-02-01T07:13:36.207" Score="0" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;Beagle Board&lt;/a&gt; is a pretty nice looking ARM setup too. It also has extras like A/V, but it's a little cheaper than the Panda at $149 vs. $174.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[edit] it looks like you need to bring your own USB ethernet adapter though.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2011-02-01T07:13:36.207" />
  <row Id="9607" PostTypeId="1" CreationDate="2011-02-01T09:36:51.657" Score="3" ViewCount="107" Body="&lt;p&gt;I'm looking to make an array of sensors to record the temperatures in a house at various points &lt;/p&gt;&#xA;&#xA;&lt;p&gt;eg. Above flat metal roof,&lt;br&gt;&#xA;    inside flat roof cavity (above 1st floor),&lt;br&gt;&#xA;    ceiling of room (1st floor),&lt;br&gt;&#xA;    floor of room (1st floor),&lt;br&gt;&#xA;    floor cavity (first floor),&lt;br&gt;&#xA;    ground floor room ceiling,&lt;br&gt;&#xA;    sub-floor/basement space.&lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess I need accuracy tolerance of about ± 1ºC. More important is that once initially calibrated, the sensor do not drift relative to temperature or the data comparison will be bunk. I hope to run the sensors for weeks in winter, summer, spring, autumn to get a full profile of the thermal performance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So which sensors are good for me. Few seem to be good for ± 1ºC and I need a way to deal with the wiring of them too. So IC2 or another digital bus might be good, anything that stops the length of the wire introducing errors into the values. Digital also means I can run a cat5 daisy chain of sensors rather than a separate lead to each sensor which seems reasonable.&lt;/p&gt;&#xA;" OwnerUserId="2842" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-02-03T01:21:01.800" LastActivityDate="2011-02-03T01:21:01.800" Title="What is 'best' temperature sensor for an array of sensors." Tags="&lt;sensor&gt;&lt;temperature&gt;" AnswerCount="3" />
  <row Id="9608" PostTypeId="2" ParentId="9607" CreationDate="2011-02-01T09:41:51.870" Score="2" ViewCount="" Body="&lt;p&gt;I've had very good results from the &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/2815&quot; rel=&quot;nofollow&quot;&gt;DS18S20&lt;/a&gt;. I found it to be very accurate. You can easily get a resolution of 0.5 degrees (Celsius), or if your prepared to do a bit more work you can get 0.1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also string together lots of them on a single data wire, and get readings from each of them by addressing them by their in-built serial code.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-01T09:41:51.870" CommentCount="1" />
  <row Id="9609" PostTypeId="2" ParentId="9607" CreationDate="2011-02-01T09:42:44.273" Score="1" ViewCount="" Body="&lt;p&gt;I've used TI &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tmp100.html&quot; rel=&quot;nofollow&quot;&gt;TMP100&lt;/a&gt; sensors with success.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They're IIC, and support up to 8 devices on a single bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Their absolute precision is only +- 2°C, but they're repeatable, and have 0.0625° relative resolution.&#xA;Also, you can calibrate out (most) of the +- 2° offset, if you put the effort in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can also confirm that ~20' strings with sensors spaced evenly along it work without trouble.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI Also make some higher precision, but more expensive IIC sensors, such as the &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tmp275.html&quot; rel=&quot;nofollow&quot;&gt;TMP275&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a project which scans 14 strings of 8 sensors, and dumps the code out over a serial port a ~2 hz. It's built around a &lt;a href=&quot;http://en.wikipedia.org/wiki/Parallax_Propeller&quot; rel=&quot;nofollow&quot;&gt;Propeller Microcontroller&lt;/a&gt;, and I could post the code and PCB layouts, if you would like.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-02-01T09:42:44.273" />
  <row Id="9610" PostTypeId="2" ParentId="9601" CreationDate="2011-02-01T09:54:05.587" Score="3" ViewCount="" Body="&lt;p&gt;Go to the manufacturer's website, find their list of franchised distributors and talk to them. However don't be surprised if you have to buy a whole reel/tube/tray and wait a few weeks, but you might be lucky and find someone with stock. You may be able to get small qtys as samples from the manufacturer or distributors. &#xA;However there are many parts that you just can't buy in small quantities. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-01T09:54:05.587" />
  <row Id="9611" PostTypeId="1" AcceptedAnswerId="9832" CreationDate="2011-02-01T10:54:57.247" Score="5" ViewCount="504" Body="&lt;p&gt;I want to build an accurate (&amp;plusmn;2 &amp;deg;C) water heater (&lt;a href=&quot;http://en.wikipedia.org/wiki/Sous-vide&quot; rel=&quot;nofollow&quot;&gt;&lt;em&gt;sous vide&lt;/em&gt;&lt;/a&gt;) that heats water somewhere between 30-100 &amp;deg;C according to user input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although I have an engineering background I have no experience whatsover with building controllers and have no clue on how to start. I don't want to spend to much money on the project (&amp;lt; 100 €) thus money is an issue. The good thing is that I already have a power thyristor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I (probably) need:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Temperature sensor PT100&lt;/li&gt;&#xA;&lt;li&gt;Input device to define water temperature (digital?)&lt;/li&gt;&#xA;&lt;li&gt;Controller (PID?)&lt;/li&gt;&#xA;&lt;li&gt;Resistor to heat the water (can be taken from old water cooker I assume)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;My question is how I can best make the link between the sensor and the heating element. I of course need to build/program a circuit that does this but do I make an analog or digital circuit? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a thyristor but is this really necessary or should an on/off regulation also work? Don't forget that I also should be able to define the water temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help is greatly appreciated (also useful links).&lt;/p&gt;&#xA;" OwnerUserId="2843" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-03-01T13:21:09.993" LastActivityDate="2011-03-01T13:21:09.993" Title="Building a temperature-controlled water bath" Tags="&lt;temperature&gt;&lt;pid-controller&gt;&lt;control-system&gt;" AnswerCount="5" FavoriteCount="3" />
  <row Id="9612" PostTypeId="1" CreationDate="2011-02-01T11:05:28.400" Score="2" ViewCount="124" Body="&lt;p&gt;I have very little knowledge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to make a car.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm going to use pic16f84 and I'm not going use any sensors. I just need the car to go forward. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But what materials should I buy?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I do it with just a servo motor and the pic?&#xA;Which pcb can I use?&lt;/p&gt;&#xA;" OwnerUserId="2844" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-02-01T11:11:36.517" LastActivityDate="2011-02-01T12:32:33.727" Title="A simple pic car" Tags="&lt;pic&gt;" AnswerCount="1" CommentCount="6" />
  <row Id="9613" PostTypeId="2" ParentId="9612" CreationDate="2011-02-01T12:32:33.727" Score="5" ViewCount="" Body="&lt;p&gt;The simplest solution would be DC motors, a switch of some sort to turn the motors on ( Transistor or FET) power and a whatever the PIC needs to run. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Parts needed &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;dc motor&lt;/li&gt;&#xA;&lt;li&gt;diode (1n4xxx) for each motor&lt;/li&gt;&#xA;&lt;li&gt;NPN channel FET or transistor, depends on motor&lt;/li&gt;&#xA;&lt;li&gt;PIC and whatever it needs &lt;/li&gt;&#xA;&lt;li&gt;few resistors, pull up and current limiting &lt;/li&gt;&#xA;&lt;li&gt;PCB - any proto or perf board of your choice&lt;/li&gt;&#xA;&lt;li&gt;power of some sort ( battery, solar panel, wall wort)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;as for the servo idea, it would work if you have a continuous rotation servo.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-01T12:32:33.727" CommentCount="1" />
  <row Id="9614" PostTypeId="1" CreationDate="2011-02-01T13:29:34.483" Score="0" ViewCount="59" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just want to ask. Where do you recommend someone to take a &quot;Computer vision/Image processing&quot; related degree ONLINE?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2846" LastActivityDate="2011-02-01T14:37:14.077" ClosedDate="2011-02-01T15:50:15.383" Title="Computer vision/Image processing degrees" Tags="&lt;imageprocessing&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9615" PostTypeId="2" ParentId="9611" CreationDate="2011-02-01T13:30:24.450" Score="1" ViewCount="" Body="&lt;p&gt;I would use an arduino as a controller, it is probabably the easiest for a beginner.  A LM35 may be ok in a wet enviroment up to 100 C but you might also consider a temperature dependent resistor or thermistor.  To control the power a relay might be a good choice ( old microwave ovens can give you these and parts for a power supply )  Coffee cup heaters are a pretty good source of heaters that are well sealed against water or if you can use the whole device an electric kettle, croock pot or similar may serve.  You want to keep the high voltage away from the low voltage, in part for your own safety.  If you use semiconductors consider an optical isolator for this purpose.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-02-01T13:30:24.450" CommentCount="2" />
  <row Id="9616" PostTypeId="2" ParentId="9611" CreationDate="2011-02-01T13:51:01.257" Score="5" ViewCount="" Body="&lt;p&gt;You can build this with a very simple op-amp comparator circuit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/rY88g.png&quot; alt=&quot;schematic&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This uses a thermistor as the temperature sensor, and a potentiometer as the thermostat setting. You then just need to hook up your heater to the relay's switch contacts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll just need to calibrate your pot by testing the water temp with a thermometer in different positions of the pot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The parts should cost no more than around &amp;euro;11/&amp;pound;10/$18. You can power it with an AC adaptor (might be a good idea to add a 470uF capacitor across the supply as well. You can then use the rest of your budget for the heater.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-02-01T14:27:08.200" LastActivityDate="2011-02-01T14:27:08.200" CommentCount="4" />
  <row Id="9617" PostTypeId="2" ParentId="9614" CreationDate="2011-02-01T14:37:14.077" Score="0" ViewCount="" Body="&lt;p&gt;No if you know how to be self-taught. Take a book.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-01T14:37:14.077" />
  <row Id="9618" PostTypeId="1" AcceptedAnswerId="9627" CreationDate="2011-02-01T15:18:24.627" Score="1" ViewCount="137" Body="&lt;p&gt;I'm looking through Digikey's &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556671&quot; rel=&quot;nofollow&quot;&gt;Interface - Switches, Multiplexers, Demultiplexers&lt;/a&gt; section (and, thanks to W5VO, the &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556595&quot; rel=&quot;nofollow&quot;&gt;Logic - Signal Switches, Multiplexers, Decoders&lt;/a&gt; section as well), and I'm having trouble deciphering what circuit/topology I need.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got a processor with a 32-bit coprocessor interface, and I'd like to interface it with a parallel Flash or RAM chip.  Ideally, I would have both, and could swap between the two in software.  I imagined (wrongly, it appears) that this would be a fairly common need, and that I could buy a pair of ICs that would each break out 16 inputs into 2 banks of 16 outputs, with power, ground, a single channel select pin, maybe an enable/high impedance pin.  This would ideally come in a 54-pin TSSOP or 64-pin QFP or something of that size. A 32-switch chip would also work, but I imagine that two switches would make routing the a bit easier. The interface would be digital (I don't really need an analog switch), and I'd like to keep up with the 150MHz maximum speed grade of my processor (but will settle for 72MHz or so of actual performance). I am confident that I don't need some of the $200+ crosspoint switches!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I imagined that this would be a simple task, but it seems that my idea of what AxB:C should mean is different from Digikey's idea.  I thought that the options would include 1x16:32 or 16x1:2, but (1) these options are not available at reasonable prices (I don't see why this device should cost $70 or $234!), and the other options (like 8x2:1, which seems popular) are designed for analog switching of Ethernet signals.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt; Where can I learn about the mux nomenclature?  (An answer on this site would be ideal :)  Also, where can I learn about the various functions listed, like AV/crosspoint/Ethernet/USB?&lt;/li&gt;&#xA;&lt;li&gt; What topology or function should I use for to do this task (digital, ~100MHz, 32 or 16 lines)? &lt;/li&gt;&#xA;&lt;li&gt; If all else fails, how can I build a switch out of discrete components or transistor arrays?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-01T18:39:18.993" LastActivityDate="2011-02-01T19:02:30.773" Title="Deciphering Mux/Demux/Switch Nomenclature: AxB:C?" Tags="&lt;switch&gt;&lt;multiplexing&gt;&lt;terminology&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="9619" PostTypeId="2" ParentId="9618" CreationDate="2011-02-01T16:25:31.677" Score="1" ViewCount="" Body="&lt;p&gt;I think you are making this too hard.  Just run the address and lines to the Flash and RAM in parallel.  Then chip select chooses which to access.  I assumed NOR flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An AV switch is designed for analog signal, so it will have a low impedance and high bandwidth (100's of MHz).  Also don't forget that you need to pass the edge rates of the signals, not just the frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A matrix switch can switch any input to any output.  That is a more expensive and general than a 8x2:1 which is just 8 of 2:1 switches, i.e., 8 of SPDT switches.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-01T18:40:47.517" LastActivityDate="2011-02-01T18:40:47.517" CommentCount="2" />
  <row Id="9620" PostTypeId="2" ParentId="9604" CreationDate="2011-02-01T16:26:11.257" Score="1" ViewCount="" Body="&lt;p&gt;Usually LCD displays come in a plastic &quot;cage&quot; that has pins (more precisely, bumps - they are very short) on each corner of its back. The PCB has holes to fit in, but that's just to prevent the display from sliding horizontally on the board. The board is then attached someway (screws, etc.) against the case &quot;top&quot; which has a window for the display, a little smaller than it in each dimension, and that holds it in place. Usually there's no need for an adhesive or glue, which also makes repair easier; just the LCD ribbon is really mechanically attached to the board. But for hobby projects there's nothing that prevents you to do so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are other, less popular methods. Displaytech's &quot;LCDConnectionMethods.pdf&quot; has a few diagrams, but it's not possible to attach a file here in .pdf format. The link is &lt;a href=&quot;http://www.displaytech.com.hk/pdf/LCDConnectionMethods.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.displaytech.com.hk/pdf/LCDConnectionMethods.pdf&lt;/a&gt;, but it's currently only available in the Google cache.  Through a roundabout conversion method, it's now on E&amp;amp;R's imgur account &lt;a href=&quot;http://i.imgur.com/zKtm7.png&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, sorry for the low quality.&lt;/p&gt;&#xA;" OwnerUserId="1078" LastEditorUserId="1078" LastEditorDisplayName="" LastEditDate="2011-02-03T13:43:34.977" LastActivityDate="2011-02-03T13:43:34.977" CommentCount="5" />
  <row Id="9622" PostTypeId="2" ParentId="9611" CreationDate="2011-02-01T16:41:38.580" Score="3" ViewCount="" Body="&lt;p&gt;BG100's solution will work as a temperature controller, but I don't think it will hold temp within ±2 C unless the volume of water you're heating is fairly small. Water has a lot of thermal capacity and heats up and cools off slowly so it will probably overshoot the set temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you building a sous vide cooker? If so, an easier way to do this, especially with that budget, is to look for a PID temperature controller on one of the surplus sites like All Electronics, surplusdirect, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to build it yourself, you can do it much cheaper though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where to start? Well first do a little research on Proportional control loops. It's simple: basically read the current temperature, subtract your setpoint temperature and use the difference to control the output. In this case the output control can be how long you turn on your thyristor for (duty cycle). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This can be accomplished with an Arduino or a Teensy (I prefer to just wire up raw AVRs since it's easy and they're much cheaper) and an analog sensor like the easy to use LM35 mentioned earlier, or a digital sensor like a MAX6675. You can set the desired temperature with a rotary encoder and use an LCD display for feedback. Even easier is to use an analog input to read a potentiometer that has a dial behind it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Proportional control will result in an offset from the setpoint. If it's small enough you can ignore it, or if it's constant, then you can calibrate the setpoint &quot;dial&quot; to allow for offset. Otherwise, you can add an Integral term to your controller. I'm going to stop here because there are many references online that can explain basic control theory better than I probably can. But I hope you get the gist of it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you're trying to do isn't too difficult and makes for a fun little project and a great learning experience.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-02-01T16:41:38.580" />
  <row Id="9623" PostTypeId="1" AcceptedAnswerId="9624" CreationDate="2011-02-01T16:47:58.820" Score="0" ViewCount="66" Body="&lt;p&gt;I have a Canon SX210 IS which has not a connector to use a external power supply. So I wanted to connect &quot;my&quot; power source to the pins the battery usually touches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the back of my camera, it says 4.2 V but the battery has 3.7 (model NB-L5).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right now, I have in my hands a voltage regulator (7805) and a diode which would drop 0.7 V. &#xA;I plan to connect the 7805 to a car battery so there is no line noise. Do you know if it safe to feed my camera with those 4.3 V?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I use less voltage? Would the camera be damaged if I pass 4.2 V?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't tried anything yet just for precaution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does somebody know about a voltage regultor with arround (3.8 - 4.3)V of output?&lt;/p&gt;&#xA;" OwnerUserId="1613" LastEditorUserId="1613" LastEditorDisplayName="" LastEditDate="2011-02-01T18:50:41.703" LastActivityDate="2011-02-01T18:50:41.703" Title="Is this a good way to power my camera?" Tags="&lt;battery&gt;&lt;voltage-regulator&gt;&lt;camera&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9624" PostTypeId="2" ParentId="9623" CreationDate="2011-02-01T17:05:09.843" Score="2" ViewCount="" Body="&lt;p&gt;The camera likely has a voltage regulator on board between the batteries and the main circuitry.  If you're able to find a part number on that, you should be able to find a datasheet for the part and that will tell you what the max / min input voltages are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; I did some googling, and it looks like there is a power adapter you can purchase:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Canon-ACK-DC30-Adapter-SD700IS-SD800IS/dp/B000EVLS3S&quot; rel=&quot;nofollow&quot;&gt;http://www.amazon.com/Canon-ACK-DC30-Adapter-SD700IS-SD800IS/dp/B000EVLS3S&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's bloody expensive, but if you can find some specs on that power adapter, you should have a better idea of what you can supply the camera with safely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT2*&lt;/strong&gt; I did some more searching, and it appears as though unit expects around 4.3 volts, so you should be good to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.studio3d.com/download/canon_870_user-guide.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.studio3d.com/download/canon_870_user-guide.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;4.3V DC 1.5A&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I would think it would be easiest / most robust to just plug your power supply circuit into the DC jack.&lt;/p&gt;&#xA;" OwnerUserId="1823" LastEditorUserId="1823" LastEditorDisplayName="" LastEditDate="2011-02-01T17:36:37.133" LastActivityDate="2011-02-01T17:36:37.133" CommentCount="7" />
  <row Id="9625" PostTypeId="2" ParentId="1696" CreationDate="2011-02-01T17:53:06.683" Score="0" ViewCount="" Body="&lt;p&gt;For completeness, if you're on a Mac &lt;a href=&quot;http://ridiculousfish.com/hexfiend/&quot; rel=&quot;nofollow&quot;&gt;Hex Fiend&lt;/a&gt; is very good. Works well with very large files (~100GB) and allows all sorts of tricky editing.&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2011-02-01T17:53:06.683" CommunityOwnedDate="2011-02-09T13:48:06.387" />
  <row Id="9626" PostTypeId="2" ParentId="9518" CreationDate="2011-02-01T17:55:21.100" Score="2" ViewCount="" Body="&lt;p&gt;Picoblaze does not have floating point support. The supported instruction set is very limited, but useful for simple applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you require floating point support, it is possible to develop your own interface between picoblaze and a Xilinx Floating Point Core (or other logic).  In this situation, you could write data out to the core, and read the result back.  I have no idea what your performance requirements are... you would have to consider the communication overhead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As previously mentioned, MicroBlaze has hardware single precision FPU, and can handle double precision operations with software emulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Picoblaze documentation is very good and can be found &lt;a href=&quot;http://www.xilinx.com/ipcenter/processor_central/picoblaze/picoblaze_user_resources.htm&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. Additionally, check out the Xilinx User Forums which has support related to Picoblaze and Microblaze.&lt;/p&gt;&#xA;" OwnerUserId="2848" LastActivityDate="2011-02-01T17:55:21.100" />
  <row Id="9627" PostTypeId="2" ParentId="9618" CreationDate="2011-02-01T18:26:59.930" Score="2" ViewCount="" Body="&lt;p&gt;There's a few questions in there, so I'll address them one by one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What does A x B : C Mean?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Read this as &lt;strong&gt;A&lt;/strong&gt; instances of a &lt;strong&gt;B&lt;/strong&gt; number of inputs to &lt;strong&gt;C&lt;/strong&gt; number of outputs. What you are looking for, if I understand correctly, is a 16x2:1 or a 32x2:1 chip. If &lt;strong&gt;C&lt;/strong&gt; is more than 1, then your chip is significantly more complicated - you would no longer be selecting one input and connecting it to the output. Which leads well into the next sub-question -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Why are there $200+ chips for this simple function?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The specific part you linked is a 1x32:16 wide-bandwidth, DC coupled, buffered, video MUX, which can select any of it's 32 video inputs and output them simultaneously on it's 16 buffered outputs, with a gain of 1-2x. You could sorta think of it as a 16x32:1 with a lot of features. It's got quite a bit more inside than just CMOS switches. It isn't really designed for your function, which is...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How do I connect two memories to a master CPU&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most common method for hooking up multiple memory chips to a driver/controller/cpu is to use a tri-state bus. The address lines drive both chips, and the data bus is shared between all chips. Both chips should have a pin like &quot;output enable&quot;, which can be controlled by the CPU. I found &lt;a href=&quot;http://www.doc.ic.ac.uk/~ih/teaching/lectures/comparch/bebop/memory-access.html&quot; rel=&quot;nofollow&quot;&gt;this article&lt;/a&gt; discussing memory buses at a rudimentary level - it has descriptive images. See Figure 8 for the gist of what I think you want. It is the simplest way of hooking things up, and the way I would recommend if the chips support it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How would I make one?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, I think you were on the right track. CPU buses can be bi-directional, so intercepting the right output enable signal may be risky. The part you were probably looking for was a digital switch, something like this &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=296-6395-1-ND&quot; rel=&quot;nofollow&quot;&gt;16x2:1 FET mux&lt;/a&gt;. This is the cheapest one at $1.75 each. Wide bidirectional buses are best handled by ICs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Note&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would check with the maker of your CPU to look for app notes and reference designs regarding memory buses. That will be the easiest way to see if you're on track.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-02-01T18:26:59.930" CommentCount="3" />
  <row Id="9628" PostTypeId="1" AcceptedAnswerId="9630" CreationDate="2011-02-01T18:48:15.630" Score="6" ViewCount="221" Body="&lt;p&gt;Well I finally obtained another multimeter, so now I have a Mastech MS8226T and a Ben Electronic M92A. I decided to measure at which voltages would the low battery warning appear and how much current each of them consumes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So here's my setup: Power supply-&gt;M92A-&gt;9V plug-&gt;MS8226T-&gt;other end of the 9V plug-&gt;power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used M92A to measure current and wanted to use MS8226T to measure voltage. Unfortunately, I couldn't measure the supply's voltage using MS8226T. I always got 0 V. When I swithched the meters, M92A would show voltage out of range for every scale. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I decided to use the powered on meter to measure current and the second meter to measure voltage. I got zero as result on both meters, when I wanted to use them to measure their own curent consumption. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why is that so?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt; &#xA;Here are the schematics.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/BRPB4.png&quot; alt=&quot;first image&quot;&gt;&#xA; On this image, XMM1 is the meter measuring current and it is powered by its battery. Meter XMM2 is powered by the power supply V1. I used R1 as the meter's power plug. When I use MS8226T as XMM2 in such a set-up, I get zero volts on the supply. When I use the M92A, I get out of range on all ranges. The XMM1 meter shows expected values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/R9ECz.png&quot; alt=&quot;second image&quot;&gt;&#xA;On this image meter XMM1 is powered by its internal battery, is measuring voltage and shows expected values. Meter XMM2 is measuring current and reads zero. I'm using resistor R1 instead of meter's power plug here. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T23:49:11.613" LastActivityDate="2011-02-08T23:49:11.613" Title="Why can't a multimeter measure its own current and voltage?" Tags="&lt;current-measurement&gt;&lt;voltage-measurement&gt;&lt;multimeter&gt;" AnswerCount="1" FavoriteCount="3" />
  <row Id="9629" PostTypeId="2" ParentId="9618" CreationDate="2011-02-01T19:02:30.773" Score="2" ViewCount="" Body="&lt;p&gt;I think you're confusing terms. It sounds like what you want is to connect a SRAM and Flash to a microcontroller. This has nothing to do with crosspoint switches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also see you deleted an answer stating the same about 2h ago; if you care to comment why this is wrong we can try to help you out. Otherwise I believe W5VO has answered your question about nomenclature quite well.  (edit: nevermind, deleted by owner appears to me the owner of the answer, not the owner of the question.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Run the address lines together, the data lines together, tie the RD (read strobe) lines together (if the flash has an OE, tie RD to OE as well). The WR lines should be tied together, and now you should be left with two CS (chip select) lines. Either run these to dedicated output enables on the microcontroller (many have built in address decoders) or build up some select logic that gives you a an OE for accesses to one memory range and another OE for another memory range. There are PLENTY of examples online, and the 74HC138 is a great chip for this. Googling for &quot;memory address decoding&quot; or &quot;chip select decode&quot; or even &quot;microcontroller external memory interface&quot; may get you started.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some different ways of going about this (Motorola-style bus vs Intel-style bus) but any book or articles on the older microprocessors or microcontrollers will give you plenty of information.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-02-01T19:02:30.773" CommentCount="2" />
  <row Id="9630" PostTypeId="2" ParentId="9628" CreationDate="2011-02-01T19:04:45.203" Score="4" ViewCount="" Body="&lt;p&gt;It's because of the circuit used inside of the multimeter to create a virtual ground at approximately Vbat - 6.2V, or about 2.8V for a 9V battery; this basically means the COM terminal on the meter is at 2.8V relative to battery ground and readings will be offset by this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried with another meter to measure its 9V battery - it read 6.08V, which is very close to the predicted 2.8V drop.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-01T19:04:45.203" CommentCount="15" />
  <row Id="9631" PostTypeId="1" AcceptedAnswerId="9634" CreationDate="2011-02-01T19:20:17.633" Score="1" ViewCount="154" Body="&lt;p&gt;Okay, I know this is an electronics Q&amp;amp;A site, and this question is mildly computer related. But I've got this problem with my VGA monitor, a graphics card and a computer. The problem is the video output is blurred in one direction quite badly. This looks very similar to a low pass filter - i.e. parasitic capacitance. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The confusing part is - this only occurs with one card, an Nvidia 9800 GT. I have a somewhat broken ATI card (GPU started melting and now all 3D games have misplaced polygons), and this doesn't occur. So I'm thinking something else is up with either the card or some configuration involving it. I've also noticed that there is an odd ripple to the black in the image. Could it be a ground loop? I'm using a cheap DVI to VGA adapter which could also be suspect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've attached an image of the problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/5Vza5.jpg&quot; alt=&quot;Blurred in one direction&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-02T20:57:00.820" Title="Do I have a ground loop or another problem?" Tags="&lt;groundloops&gt;&lt;low-pass&gt;" AnswerCount="3" />
  <row Id="9632" PostTypeId="2" ParentId="3810" CreationDate="2011-02-01T20:13:26.750" Score="0" ViewCount="" Body="&lt;p&gt;The current Xilinx and Altera ones are pretty complete.  They include Ethernet typically 10/100/100, DDR SDRAM (of some generation), Flash.  And they can operate stand-alone or plug into a system as a PCIe cards.  Here's an &lt;a href=&quot;http://www.altera.com/products/devkits/altera/kit-cyclone-iv-gx.html&quot; rel=&quot;nofollow&quot;&gt;Altera Cyclone IV example&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-01T20:13:26.750" CommunityOwnedDate="2011-02-02T16:42:48.233" CommentCount="1" />
  <row Id="9633" PostTypeId="2" ParentId="3810" CreationDate="2011-02-01T20:49:01.133" Score="0" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.xmos.com/products/development-kits/xc-1a-development-kit&quot; rel=&quot;nofollow&quot;&gt;XMOS XC-1A&lt;/a&gt; makes a nice introduction to multi-core systems. For $99 you get a 1600 MIPS four-core chip on a little PCB with plenty of expansion capability for adding your own hardware.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-01T20:49:01.133" CommunityOwnedDate="2011-02-02T16:42:48.233" CommentCount="3" />
  <row Id="9634" PostTypeId="2" ParentId="9631" CreationDate="2011-02-01T20:52:30.147" Score="8" ViewCount="" Body="&lt;p&gt;This looks exactly like VGA ghosting. This is usually caused by a long VGA cable. If you are only seeing it on 1 video card then I would suspect the video card is very poorly designed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To add a technical note, the ghosting is usually caused from a mismatched line causing reflections and ringing which shows up as what you are seeing.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-01T20:52:30.147" CommentCount="10" />
  <row Id="9635" PostTypeId="1" AcceptedAnswerId="9636" CreationDate="2011-02-01T22:07:35.287" Score="2" ViewCount="91" Body="&lt;p&gt;I want to process a PAL or NTSC video signal and pick up colors, like green, orange, blue and red. Is there any way to decode RGB from NTSC/PAL easily, and then detect these colours? I'm looking for a small and cheap solution. The end goal is to build up an array of pixels matching a colour, then filter this to decode shapes and locate targets on a camera. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-02T03:22:49.973" Title="Image processing on PAL/NTSC" Tags="&lt;video&gt;&lt;ntsc&gt;&lt;programmable-logic&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="9636" PostTypeId="2" ParentId="9635" CreationDate="2011-02-01T23:15:43.440" Score="3" ViewCount="" Body="&lt;p&gt;You're probably best off using a dedicated chip to do the decoding. A quick trip to Farnell's website showed a few of these under CODECs/encoders/decoders, with digital output selected. This type of chip forms the front end of frame grabbers and some displays, with chips like Brooktree bt848 recording the data to memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That search found devices from &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/6193/t/al&quot; rel=&quot;nofollow&quot;&gt;Maxim&lt;/a&gt;, &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=375&amp;amp;uiTemplateId=NODE_STRY_PGE_T&quot; rel=&quot;nofollow&quot;&gt;Texas Instruments&lt;/a&gt;, &lt;a href=&quot;http://www.analog.com/en/analog-to-digital-converters/video-decoders/products/index.html&quot; rel=&quot;nofollow&quot;&gt;Analog Devices&lt;/a&gt; and &lt;a href=&quot;http://galaxy.uci.agh.edu.pl/~jamro/xsb/video_adc.pdf&quot; rel=&quot;nofollow&quot;&gt;Philips&lt;/a&gt; (NXP brand, apparently now bought by Trident who &lt;a href=&quot;http://www.tridentmicro.com/producttree/tv/pc-tv/saa/saa7114/&quot; rel=&quot;nofollow&quot;&gt;don't publish the datasheet&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's possible you can build a lower cost alternative using the same analog circuitry an old TV would; a comb filter to separate into Y and C components. &lt;a href=&quot;http://www.freepatentsonline.com/6462790.html&quot; rel=&quot;nofollow&quot;&gt;Digital comb filters are apparently patented&lt;/a&gt;. &lt;a href=&quot;http://www.intersil.com/data/an/an9/an9644/&quot; rel=&quot;nofollow&quot;&gt;Intersil AN9644&lt;/a&gt; might be one document to read.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastEditorUserId="1181" LastEditorDisplayName="" LastEditDate="2011-02-02T03:22:49.973" LastActivityDate="2011-02-02T03:22:49.973" CommentCount="1" />
  <row Id="9637" PostTypeId="1" AcceptedAnswerId="10713" CreationDate="2011-02-02T00:58:33.970" Score="1" ViewCount="88" Body="&lt;p&gt;When connecting a brushless motor to an ESC, we are taught to apply power and switch two of the wires if the blade is spinning in the wrong direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to predict the blade rotation by examining the ESC and motor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(note: learning-style question, I don't have a practical problem with switching wires)&lt;/p&gt;&#xA;" OwnerUserId="1756" LastActivityDate="2011-02-25T23:29:15.307" Title="predicting brushless motor rotation direction?" Tags="&lt;motor&gt;&lt;brushless&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="9638" PostTypeId="1" AcceptedAnswerId="9847" CreationDate="2011-02-02T02:16:19.827" Score="2" ViewCount="91" Body="&lt;p&gt;I am currently looking to purchase laser galvanometers like &lt;a href=&quot;http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&amp;amp;hash=item19c28a1677&amp;amp;item=110638012023&amp;amp;nma=true&amp;amp;pt=LH_DefaultDomain_0&amp;amp;rt=nc&amp;amp;si=ykIfbnG6rxMQVKB7tfa6%252BniDziU%253D&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; and &lt;a href=&quot;http://cgi.ebay.com/Laser-Galvo-Scanning-30Kpps-for-laser-show-light-ILDA_W0QQitemZ220550668048QQcategoryZ29944QQcmdZViewItemQQ_trksidZe11014.m263QQ_trkparmsZalgo%3DSIC%26its%3DI%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D10%26pmod%3D110638012023%26ps%3D63%26clkid%3D6562780343974550774#ht_2653wt_1168&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;. However, as I'm not familiar with lasers, I'm not sure the criteria I should use to evaluate whether a given product is a good buy. What are your suggestions?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!&lt;/p&gt;&#xA;" OwnerUserId="1944" LastEditorUserId="1409" LastEditorDisplayName="" LastEditDate="2011-02-08T05:06:20.657" LastActivityDate="2011-02-08T05:06:20.657" Title="How to choose laser galvanometers" Tags="&lt;laser&gt;&lt;motion&gt;&lt;mechanical&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="2" />
  <row Id="9639" PostTypeId="1" AcceptedAnswerId="9643" CreationDate="2011-02-02T05:34:05.773" Score="3" ViewCount="201" Body="&lt;p&gt;I'm working to design a motor to control a mechanical shutter. After considering some other possibilities I have decided to try using a stepper-type micro motor. We're using a &lt;a href=&quot;http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1461&quot; rel=&quot;nofollow&quot;&gt;shutter from Edmond optical&lt;/a&gt;. I'd like to pair it with one of the &lt;a href=&quot;http://catalog.micromo.com/db/service?domain=micromo&amp;amp;command=locate&amp;amp;category=2_phase_stepper_motors&quot; rel=&quot;nofollow&quot;&gt;Micromo stepper motors&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The critical datasheet specification seems to be the holding torque which is rated as nMn. I take this to be Millinewton/meter. I rigged up the shutter with a simple pulley and found that a weight of 12.8 grams was sufficient to turn the shutter's lever (which opens and closes the aperture). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This explanation might benefit from a diagram, so I drew up one to illustrate the experiment:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/MQ9e9.png&quot; alt=&quot;pulley experiment&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If &lt;strong&gt;w=mg&lt;/strong&gt; then the weight exerts a force of 126 mN on the lever...ignoring the geometry of the pulley and that the lever turns on a circular orbit. My naive self imagines that I need a motor which provides a torque of more than 126 nMn. Is this a correct estimate?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If so it seems all the Micromo stepper motors are too weak to turn the shutter.&lt;/p&gt;&#xA;" OwnerUserId="2668" LastActivityDate="2011-02-02T12:45:29.777" Title="Calculating the amount of torque needed to turn shutter" Tags="&lt;stepper-motor&gt;&lt;torque&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="2" />
  <row Id="9640" PostTypeId="1" AcceptedAnswerId="9668" CreationDate="2011-02-02T08:12:24.140" Score="2" ViewCount="95" Body="&lt;p&gt;I found a few specialized electronic parts that I am interested in buying from eBay and/or Alibaba. However, knowing that I will be traveling to China soon, I felt checking the purchase in person would lower my risks of getting a lemon. What do you think and why?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="1944" LastActivityDate="2011-02-02T17:53:43.510" Title="What're the benefits of checking electronics in person over the exclusive online stores?" Tags="&lt;sourcing&gt;" AnswerCount="5" />
  <row Id="9641" PostTypeId="1" CreationDate="2011-02-02T08:41:49.730" Score="2" ViewCount="156" Body="&lt;p&gt;I am Doing a electronics project for school.&#xA;I need the arduino on request from a button to input to commuincate to the computer to open a media file, this is to help a deaf person be able to play his dvds with out having to put them in the dvd player as he is mostly blind anyway&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any Help will be gratelly appreciated&lt;/p&gt;&#xA;" OwnerUserId="2853" LastActivityDate="2011-05-05T15:39:27.763" Title="Using Arduino to Open File on computer" Tags="&lt;arduino&gt;" AnswerCount="3" />
  <row Id="9642" PostTypeId="1" AcceptedAnswerId="9650" CreationDate="2011-02-02T08:55:45.290" Score="1" ViewCount="132" Body="&lt;p&gt;Hi all,&#xA;I have some dudes about the block parameters of the CORDIC DIVIDER.&#xA;&lt;strong&gt;I would like to someone explain me the parameter called &quot;Latency for each processing element&quot;.&lt;/strong&gt;&#xA;(See the parameters inside the red rectangle)&#xA;I don´t understand the notation that is used, some zeros or ones between two brackets.&#xA;Thank you for your help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By the way, this question is realted with one I asked before: &#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/9517/system-generator-how-to-configure-the-cordic-divider-block&quot;&gt;System Generator: How to configure the CORDIC divider block?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/iFXsS.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T21:03:45.637" LastActivityDate="2011-02-12T21:03:45.637" Title="System Generator: How to configure the CORDIC divider block. Understanding the block parameters" Tags="&lt;xilinx&gt;&lt;floating-point&gt;&lt;xilinx-system-generator&gt;&lt;cordic&gt;&lt;divide&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9643" PostTypeId="2" ParentId="9639" CreationDate="2011-02-02T11:29:17.970" Score="3" ViewCount="" Body="&lt;p&gt;You have calculated the &lt;em&gt;force&lt;/em&gt; required to operate the shutter but not the &lt;em&gt;torque&lt;/em&gt;.&#xA;Assuming that the lever is perfectly horizontal and the pulley cable is perfectly vertical, you must multiply the &lt;em&gt;force&lt;/em&gt; of 126 mN by the &lt;em&gt;distance&lt;/em&gt; between the shutter axis and the point on the lever to which the cable is attached. For example, assuming your diagram shows the shutter displayed 1:1 on my monitor (which I'm sure it doesn't!), I measure the distance as 30mm giving a torque of 30E-3 * 12.8E-3 * 9.81 = &lt;strong&gt;3.8 mNm&lt;/strong&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-02-02T11:29:17.970" />
  <row Id="9644" PostTypeId="1" AcceptedAnswerId="9980" CreationDate="2011-02-02T11:34:16.183" Score="0" ViewCount="86" Body="&lt;p&gt;Hi all, does anyone knows how is the fast way to perform a floating point exponential operation? (like this y = 2.71^(3.45))&#xA;Thank you to all posible links to references or articles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am pondering several possibilities:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doing by System Generator (I am using the 9.2.01 version)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using some Free Xilinx IP&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using some open libraries like:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.vhdl.org/fphdl/old_index.html&quot; rel=&quot;nofollow&quot;&gt;VHDL.org&lt;/a&gt; &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://optngn.com/place/index.php?option=com_virtuemart&amp;amp;page=shop.browse&amp;amp;category_id=2&amp;amp;Itemid=53&amp;amp;TreeId=2&amp;amp;vmcchk=1&amp;amp;Itemid=53&quot; rel=&quot;nofollow&quot;&gt;OptNgn&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Using &lt;a href=&quot;http://electronics.stackexchange.com/questions/9662/looking-for-a-open-source-alu&quot;&gt;an open-source ALU&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-04-14T01:15:42.710" LastActivityDate="2011-04-14T01:15:42.710" Title="Digital Architecture Design Question: Fast way to perform a floating point exponential operation" Tags="&lt;fpga&gt;&lt;floating-point&gt;&lt;architecture&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="9645" PostTypeId="1" CreationDate="2011-02-02T11:39:59.403" Score="2" ViewCount="108" Body="&lt;p&gt;I want to be able to connect an external display to my Windows PC (in addition to the existing one), and stream a selected portion of the screen to this display. For example, if I have a small terminal window open on my main monitor, then this smaller display will show only that terminal window, not the rest of my desktop. I guess it's like Picture In Picture (PIP) on a TV, but for a PC instead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone recommend the easiest way to achieve this? I don't mind getting into the video programming side of it (maybe using DirectShow?), but if there is a hardware solution, eg on a DSP board,then that would be great.&lt;/p&gt;&#xA;" OwnerUserId="2856" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-04-04T09:29:54.687" LastActivityDate="2011-04-05T07:20:24.250" Title="Streaming a section of video to an external display" Tags="&lt;video&gt;&lt;processing&gt;&lt;windows&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="9646" PostTypeId="1" CreationDate="2011-02-02T12:06:52.807" Score="0" ViewCount="106" Body="&lt;p&gt;My new Nintendo DSi XL arrived with a 4.3V US wall charger. Soon, we will be on a vacation abroad and I need a solution for charging it where the outlet voltage is 220V. Before trying the USB port of my laptop, I wanted to make sure that it is safe to do so, provided the lower voltage of the native  charger.&lt;/p&gt;&#xA;" OwnerUserId="2422" LastActivityDate="2011-02-02T12:06:52.807" ClosedDate="2011-02-02T15:40:23.597" Title="Charging Nintendo DSi XL from USB/5V" Tags="&lt;usb&gt;&lt;charger&gt;" CommentCount="4" />
  <row Id="9647" PostTypeId="1" AcceptedAnswerId="9665" CreationDate="2011-02-02T12:22:45.843" Score="1" ViewCount="112" Body="&lt;p&gt;I am considering using a chip, but the datasheet is confusing me as it has several distinct power pins. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;PLL_VDD&lt;/li&gt;&#xA;&lt;li&gt;PLL_GND&lt;/li&gt;&#xA;&lt;li&gt;AVDD&lt;/li&gt;&#xA;&lt;li&gt;AGND&lt;/li&gt;&#xA;&lt;li&gt;DVDD&lt;/li&gt;&#xA;&lt;li&gt;DGND&lt;/li&gt;&#xA;&lt;li&gt;DVDD_IO&lt;/li&gt;&#xA;&lt;li&gt;DGND_IO&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tvp5150am1.html&quot; rel=&quot;nofollow&quot;&gt;This is the chip&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I hook up each? Do I connect AVDD straight to DVDD, and what about PLL_VDD, and the ground pins? The suggested schematic seems to show them all connected to the same potentials (with different symbols for both types of grounds); from a cursory glance it doesn't mention anything about PCB layout. So how should I wire it up?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-02T16:54:34.883" Title="AGND/AVDD on a chip" Tags="&lt;analog&gt;&lt;digital&gt;&lt;ground&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="9648" PostTypeId="2" ParentId="9647" CreationDate="2011-02-02T12:28:40.573" Score="4" ViewCount="" Body="&lt;p&gt;I'd filter the AVdd supply to minimise noise. The data sheet has a schematic on page 80 which shows all the connection details. Careful PCB design will be required, I wouldn't bother unless you have a lot of PCB design experience.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-02T12:49:48.883" LastActivityDate="2011-02-02T12:49:48.883" CommentCount="2" />
  <row Id="9649" PostTypeId="2" ParentId="9639" CreationDate="2011-02-02T12:45:29.777" Score="2" ViewCount="" Body="&lt;p&gt;Well, since I have physics exam in a cople of hours with problesm such as this one, I decided to make a more or less detailed solution. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First let's take a look at the diagram. On it we have 3 major points: weight, pulley wheel and the shutter.&lt;img src=&quot;http://i.imgur.com/AeUrU.png&quot; alt=&quot;wheel image&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll start with the wheel and assume that it will rotate in the negative mathematical direction. Wheel's radius is R and its mass is Mw.&#xA;First we should take a look at the forces acting on it. We have the weight of the wheel Qw=Mw*g actung downward and we have the rection of the surfece, N acting upward. They cancel eachother out. Next, we have rope tension forces. S1 is the force which tenses the rope from the weight side and S2 is from the shutter side. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now we need to write the moment equation for the system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wheel's moment of inertia is Iw=Mw*R^2/2 and its angular acceleration is α.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Iw*α=S1*R-S2*R&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the system to work, we need the α to be greather than zero. So we get the obivous α=(S1*R-S2*R)/Iw from which we can deduct that S1 should be greater than S2. We also know that α=a/R. We'll need that later. Next interesting thing which we can find from the wheel is the ratio between two forces. S1=S2+Iw*α/R. Also, the force S2=S1-Iwα/R&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/TPYhT.png&quot; alt=&quot;shutter&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, let's take a look at the shutter. Let's say that the length of the rod is L2. We have force S2 which is pulling the rod upwards and it's creating the moment of force (torque) which gives us: M2=L2*S2. We also know that we have a minimum moment of force needed to trigger the mechanism and we'll calculate that later.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/EQYOx.png&quot; alt=&quot;weight&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lastly we have the weight side. We want to replace the weight with a motor and we need to calculate its moment of force. The motor has axle whose radius is r. We know that mass of the weight is m=12.8g. We can see that the force S1 which tenses the rope in the wanted direction is S1=Q1=m*g=0.125568 N or 125.568 mN. To achieve such a force, we'll need moment of force which is equal to M1=Q1*r, where r is the radius of the motor's axle. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now let's take a look at what we can tweak. It would be good is we could get the needed moment to operate the shutter. If we know it, we can twaek the rest of the system. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So by taking a look at the wheel equation, Iw*α=S1*R-S2*R, we see that the wheel should be as light as possible and that that its diameter should be as small as possible in order to minimise the losses. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that, if we take a look at the moment equation for the shutter, we have M2=L2*S2. We can increase the length of the rod in order to minimize the needed force. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, let's take a look at the weight side. We know that Q1=125.568 mN and that M1=Q1*r. So if we divide the torque of the motor from the list by the axle diameter, we can get the force it will produce and check if it will be good enough for our needs. Q1=M1/r If we take for example, ADM_1220, we see that it has torque of 4.1 mNm and axle diameter of 12mm. So we get F=4.1mNm/12*10^(-3)m=341.67 mN, which is enough to close the shutter.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-02T12:45:29.777" />
  <row Id="9650" PostTypeId="2" ParentId="9642" CreationDate="2011-02-02T13:16:30.277" Score="2" ViewCount="" Body="&lt;p&gt;The cordic block is split up into a bunch of processing elements (PEs).  Each PE is a bunch of logic operations.  There is some latency associated with each PE already.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can add additional registers at any point in the pipeline by putting non-zero values into the vector you have highlighted.  The vector should have as many elements as you have requested PEs. In your case, you've requested one PE so it will only look at the first value of the vector, resulting in an additional latency of zero.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As regards notation - [] is standard Matlab for a vector (or matrix, depending on how it's used, but I'll not go into that here!). It's a bit like an array in other languages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;so&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;a=[5 6 7 8]&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;creates a 1x4 vector called &lt;code&gt;a&lt;/code&gt;.  Element 1 (which you can access in matlab by doing &lt;code&gt;a(1)&lt;/code&gt; ) has the value &lt;code&gt;5&lt;/code&gt;.  Element 4 has the value &lt;code&gt;8&lt;/code&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that Matlab starts its numbering from '1' not '0' like many other languages!&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-02-02T13:16:30.277" CommentCount="2" />
  <row Id="9651" PostTypeId="2" ParentId="9641" CreationDate="2011-02-02T13:19:51.893" Score="7" ViewCount="" Body="&lt;p&gt;You should probably use serial communication. When the person presses the button, the arduino will send a command through serial to the computer. You will have to create a program on the computer that listens for that serial command, and upon receiving it, launches the program to play the media file.&lt;/p&gt;&#xA;" OwnerUserId="2857" LastActivityDate="2011-02-02T13:19:51.893" />
  <row Id="9652" PostTypeId="1" AcceptedAnswerId="9667" CreationDate="2011-02-02T13:30:36.470" Score="2" ViewCount="123" Body="&lt;p&gt;I'm considering using a chip which outputs 8-bit data on a 27 MHz clock. The data will go from the chip to a FPGA, a distance of a few cm max. Do I need to be concerned about timing differences between traces on a PCB, and if so, how can I mitigate these? I've often seen motherboards with traces in small coil shapes, presumably to act as little delay lines.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-04T01:39:56.810" Title="Timing differences with a 27 MHz data clock" Tags="&lt;pcb&gt;&lt;timing&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="9653" PostTypeId="1" AcceptedAnswerId="9654" CreationDate="2011-02-02T13:38:55.940" Score="2" ViewCount="190" Body="&lt;p&gt;I'm looking for some chassis and cases to put my electronics projects in. My projects tend to involve at least one microcontroller and/or fpga. My boards are often very &quot;verbose&quot; and I put few major features on each board so I often end up with several boards. I would like an easy way to both reuse some of the boards across projects but also have a structured way to connect the boards, not just lay them out on my desk as I do now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like something like this &lt;img src=&quot;http://i.imgur.com/dWpQH.jpg&quot; alt=&quot;http://www.errock.co.uk/motherboard%20rack%20photo%20high%20res.jpg&quot;&gt; except that it shouldn't cost me my first born. It doesn't have to be as big, but I would like something that can hold a handful of boards and have a &quot;useful&quot; backboard. It would be nice if uses standard VME connectors or something similar (even ISA would be useful). Hopefully each board be 100mmx160mm in size, but that's not critical either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, does anyone have an alternate way of organizing the few boards that make up a project?&lt;/p&gt;&#xA;" OwnerUserId="2395" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-02-10T19:07:48.843" LastActivityDate="2011-02-22T11:22:36.597" Title="Chassis / case for electronics projects" Tags="&lt;interconnect&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="3" />
  <row Id="9654" PostTypeId="2" ParentId="9653" CreationDate="2011-02-02T13:49:56.883" Score="1" ViewCount="" Body="&lt;p&gt;Design your own Eurocard motherboard PCB using DIN41612 connectors that will fit in a standard low-cost enclosure like &lt;a href=&quot;http://www.rapidonline.com/sku/Tools-Fasteners-Production-Equipment/Enclosures/Metal-Cases/Steel-cases/62620/30-0240&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; one. That should hold half-length Eurocards (100 mm x 80 mm).&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-02T16:21:49.153" LastActivityDate="2011-02-02T16:21:49.153" CommentCount="1" />
  <row Id="9655" PostTypeId="2" ParentId="9652" CreationDate="2011-02-02T13:52:33.667" Score="2" ViewCount="" Body="&lt;p&gt;At 27 MHz any differences in track length over a few cm will have a negligible effect. Try doing some calculations involving the speed of light, allowing for the velocity factor.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-02T16:20:12.573" LastActivityDate="2011-02-02T16:20:12.573" CommentCount="2" />
  <row Id="9656" PostTypeId="2" ParentId="9640" CreationDate="2011-02-02T14:20:35.763" Score="0" ViewCount="" Body="&lt;p&gt;The only real advantage I see in getting electronics in person is that I can talk to people and see other products that I might not think to look at. When I order online I typically get only what I need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suppose that would make in-person shopping a slight disadvantage. :-)&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-02-02T14:20:35.763" />
  <row Id="9657" PostTypeId="2" ParentId="9640" CreationDate="2011-02-02T14:49:01.573" Score="3" ViewCount="" Body="&lt;p&gt;Don't the places you're shopping have a return policy for DOA or anything?  If they don't I certainly wouldn't buy from them &lt;em&gt;if&lt;/em&gt; you think there's a high chance of a lemon.  So several questions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) What's the realistic chance of a lemon?  I don't know what you're buying, but I almost never worry about lemons when I'm buying things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Will you actually be able to test the components to check for lemony badness while you're there? Do you have a realistic method of doing this and how much effort is it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Can you even be sure you'll be able to get them when you're in China?  I'd take a sure thing over a chance, but if you have time you might as well look.  Which brings me to...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) Can afford to wait?  I prefer having things now as opposed to later, and if you can't get it in China while you're there you're probably looking at a delay of at least a week ordering online thereafter.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-02T14:49:01.573" />
  <row Id="9658" PostTypeId="2" ParentId="9640" CreationDate="2011-02-02T15:26:10.137" Score="3" ViewCount="" Body="&lt;p&gt;What level of parts are these?  Components?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The major concern with electronic components is &lt;a href=&quot;http://www.google.com/search?q=electronic+component+counterfeit&quot; rel=&quot;nofollow&quot;&gt;counterfeiting&lt;/a&gt;, and counterfeit parts aren't simply leaded lumps of epoxy.  They are often made on the same production lines, and can be QA rejects for being outside of spec by a bit (or a lot), and that specification may not be the most obvious or easy to test for (e.g. diode reverse leakage).  Will you have some method to test a good number of them to determine their failure rate or specification deviances?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;China is an enormous country; unless all your potential suppliers are fairly close, you're volumes are very high, or your schedule needs to be compressed for whatever reason, I'd just make sure that it's worth your time.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-02-02T15:26:10.137" />
  <row Id="9659" PostTypeId="2" ParentId="9641" CreationDate="2011-02-02T15:33:07.013" Score="1" ViewCount="" Body="&lt;p&gt;As Ryan says, you will have to create a program on the Computer to launch and play the media file. If its the same file every time then it would be not so difficult. However if the Arduino has to make a selection on the file, then it gets a little bit more interesting to implement.&lt;/p&gt;&#xA;" OwnerUserId="1927" LastActivityDate="2011-02-02T15:33:07.013" />
  <row Id="9660" PostTypeId="2" ParentId="9640" CreationDate="2011-02-02T15:47:13.793" Score="0" ViewCount="" Body="&lt;p&gt;fWell here are some potential problems for on-line shopping that I've noticed:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transportation heavily depends on courier and mail services which could lead to unexpected problems and sometimes experimentation may be necessary in order to find the best way to have components shipped. One time I ordered a power supply and some components from a web-store. It turned out that they didn't have some of the miscellaneous stuff I ordered, so we agreed that the main part of the order be shipped via one of the leading courier agencies and have the rest sent by regular mail once they get the items. I of course paid for express shipping and 3 days later the packet was at my local airport. It took shipping company 3 weeks for the packet to travel from the airport to my address. First there were customs problems because nobody knew under which tariff category ordered items belonged, after that I got sent customs processing certificate for female underwear instead of electronic components so I had to complain to the shipping company and it took them 5 days to dig up my own customs certificate and after that some items were wrongly processed and so on and so on and so on. In the end, I got the regular mail back-order before the expressly shipped main order! Fortunately, I wasn't in a hurry, but imagine you have a project with a deadline and what ws supposed to take 4 days takes 22 and after that you haven't even begun to do any work!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next problem can be shipping costs. For example Digikey charges $120 shipping to my country while I can get other stores to ship for $20. Of course, for large projects, this isn't a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next problem could be returns policy. Some stores won't pay for return shipping and sometimes shipping can be as expensive as ordered articles. Plus, there's the time wasted which needs to be accounted for as well. Of course, there could be problems with customs too. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next problem could be details. There are lots of little things which can become a big problem and which sometimes can't be detected in advance from datasheets or information available on the website. Of course, this can be solved by sending few e-mails, but sometimes people make assumptions. I heard of a guy who one time ordered a large number of potentiometers. There are washers and nuts available as accessories for those potentiometers. In my country, potentiometers made by that manufacturer always come with a washer and a nut, but in the datasheet they are listed as optional accessories. Ones which he got from the Internet didn't have any nuts and washers, so he couldn't mount them and had to pause the project for some time until he managed to obtain the washers and nuts. The problem was that he assumed that he'll get the optional nuts and washers. Similar problem can occur if you’re looking for specific revision of a certain IC or something similar. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand there are problems with buying components personally too. Will the merchant have enough time to dedicate to you as a customer? Employees can be overworked and tired and could be misinformed and so on and so on. On the other hand, would you be able to make a right decision quickly enough? If you're traveling to another country, you're likely going to have a set of objectives which you need to accomplish and are likely to be under pressure to get everything done in the limited time period which you're spending in that country. If everything goes according to plan, you might as well have stayed home and made order over the Internet, but if something comes up, will you be able to manage the problem? AngryEE's list is a great example of that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, you speak of China as if it's San Marino. Are you sure that companies you need to visit are in the area you'll be visiting? If you're going to visit several cities, time pressure problems may turn out to be even worse than expected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that my answer isn't too helpful, but I least I managed to provide some food for thought.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-02T15:47:13.793" CommentCount="1" />
  <row Id="9661" PostTypeId="2" ParentId="9631" CreationDate="2011-02-02T16:01:19.377" Score="0" ViewCount="" Body="&lt;p&gt;Wohhh, now now, wait a bit right there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 9800 GT is a card made by Nvidia, who made the 8800 GTX ultra, the current 4XX cards, and other INCREDIBLY complicated and high end graphic cards. They most certainly did not &quot;very poorly&quot; design this card, besides, it is based on the 8800gt, which is pretty much the same card, and the 8800gt's were very popular and did not have much problems like this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suggest you first try to re install the newest drivers for your graphic card,  which can be found on here.&#xA;&lt;a href=&quot;http://www.nvidia.com/Download/index.aspx?lang=en-us&quot; rel=&quot;nofollow&quot;&gt;http://www.nvidia.com/Download/index.aspx?lang=en-us&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, contact the location you bought it from, such as best buy or where ever you bought the card, and tell them you problem and for them to give you a new 9800 GT. If the stores says no for what ever reason, you can do a RMA with the brad that the graphic card is made from, such as EVGA, BFG, PNY or XFX. If it is neither of those, you contact Nvidia and also ask for a RMA. Most of the time this is a painless process, and you pay only for shipping the card to the company.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a perfect site for computer hardware, it is called Newegg, and it provides you with computer parts for the cheapest you can find (most of the time), and it also has excellent customer support.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need further help, just ask on a forum such as this&#xA;&lt;a href=&quot;http://www.overclock.net/graphics-cards-general/&quot; rel=&quot;nofollow&quot;&gt;http://www.overclock.net/graphics-cards-general/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The people there are very helpful, and can practically hold your hand through the process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best of luck! though I think this question should be closed, because it seeems similar to other questions that are closed usually.&lt;/p&gt;&#xA;" OwnerUserId="2050" LastActivityDate="2011-02-02T16:01:19.377" CommentCount="3" />
  <row Id="9662" PostTypeId="1" AcceptedAnswerId="9664" CreationDate="2011-02-02T16:37:27.070" Score="2" ViewCount="127" Body="&lt;p&gt;I am looking for a open ALU to compute several equations like these:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;y1 = e^((constant1 - x)^2/(2*x))&#xA;y2 = constant2/y1&#xA;y3 = y2*constant3 + x*constant4&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Where x is the input of my system and y3 is the output.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would prefer that the ALU supported floating-point operations.  Where can I find an open or free floating-point ALU?&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-02T17:18:06.063" LastActivityDate="2011-03-15T03:17:37.517" Title="Looking for a open-source ALU" Tags="&lt;architecture&gt;&lt;floating-point&gt;&lt;open-source&gt;&lt;alu&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="9663" PostTypeId="1" AcceptedAnswerId="9669" CreationDate="2011-02-02T16:48:54.917" Score="1" ViewCount="98" Body="&lt;p&gt;Hi all, I am using System Generator and I would like to generate a .bit file in order to load into my FPGA. Does anyone know how to generate a .bit file with SG?&#xA;Thank you.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T21:04:19.817" LastActivityDate="2011-02-12T21:04:19.817" Title="System Generator: How to generate a .bit file?" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;xilinx-system-generator&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="9664" PostTypeId="2" ParentId="9662" CreationDate="2011-02-02T16:54:02.807" Score="4" ViewCount="" Body="&lt;p&gt;As a processor guy and designer of an open-source microprocessor, I can tell you that it will be difficult to find what you are looking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Multiplication, subtraction and addition are very doable in hardware but irrational numbers, arbitrary powers and division are difficult if not infeasible to do in digital hardware. It may be easier to do it in analogue electronics if your equations have a tolerance for errors. Otherwise, you will need to come up with some &lt;em&gt;tricks&lt;/em&gt; to get what you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If performance is not critical, you would be better served by doing it in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From this and some of your other questions, I think that you may need to re-define your problem or come up with a better alternative that does not rely so much on complicated math.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may not be possible to do what you need, in hardware and you may need to resort to software emulation instead.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-02-02T16:54:02.807" CommentCount="2" />
  <row Id="9665" PostTypeId="2" ParentId="9647" CreationDate="2011-02-02T16:54:34.883" Score="4" ViewCount="" Body="&lt;p&gt;Divide your board into those discrete sections: PLL, Analog, Digital, and IO.  Try to keep all of the copper (signal &amp;amp; power) for each section separate except where they require interconnect.  Join the power to each sub-circuit only at near the power supply, within the sub-circuit and at chip when possible.  Bypass each at the chip grounds with a cap or two (you might leave an extra footprint here for test).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may find that the layout doesn't permit total separation of sub-circuits.  If so, at least try to use a wider trace to supply the split and filter where necessary.&lt;/p&gt;&#xA;" OwnerUserId="2051" LastActivityDate="2011-02-02T16:54:34.883" CommentCount="1" />
  <row Id="9666" PostTypeId="1" CreationDate="2011-02-02T17:01:06.213" Score="6" ViewCount="247" Body="&lt;p&gt;What are the mathematics behind twisted pair cabling? I know that the twists are there to help eliminate cross talk and interference, but I want to know about the math of how they find the specific twist rates.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it just experimentation (&quot;Oh looks, it works better now&quot;), or is there actual math behind it that says based on the size of the cable you should twist it this many times per inch/foot to get the desired effect?&lt;/p&gt;&#xA;" OwnerUserId="2859" LastActivityDate="2011-02-03T18:52:42.190" Title="Twisted Pair Twist Rates" Tags="&lt;cables&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="9667" PostTypeId="2" ParentId="9652" CreationDate="2011-02-02T17:02:51.653" Score="4" ViewCount="" Body="&lt;p&gt;Leon is right, it probably doesn't matter for 27MHz signals on traces that are only a few cm long. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you can mitigate skew by making the trace lengths equal.  If you've got the time to ask a question about it, and you have the board space, why wouldn't you want to do this?  There's very little reason to build skew into your circuit.  Make little 45&lt;sup&gt;o&lt;/sup&gt; wiggles in the traces to make the distances the same and avoid building in reflections.  This makes equalizing the trace length easy if your PCB program doesn't do it for you.   Or, you can use rounded traces, but keeping the trace lengths equal gets more difficult.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a PCB which uses LVDS.  There's an NI board connected to this one through a 2m, 100-pin ribbon cable, and the other side of the LVDS transcievers connects to a parallel bus, so there are many sources of skew.  Why not eliminate the PCB as a source of skew?&#xA;&lt;img src=&quot;http://i.imgur.com/CbfBp.jpg&quot; alt=&quot;LVDS transciever with squiggles&quot;&gt;&#xA;Note: On this PCB, the paired traces are supposed to be coupled together.  In a non-differential bus, running pairs like this will give you really bad cross-talk.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-02T17:02:51.653" CommentCount="2" />
  <row Id="9668" PostTypeId="2" ParentId="9640" CreationDate="2011-02-02T17:53:43.510" Score="2" ViewCount="" Body="&lt;p&gt;I lived in China for several years.  If you're looking for specialized electronics pieces (as opposed to consumer or computer pieces such as hard drives), you will probably have difficulty finding retail places to look at them.  Most of the electronics vendors sell to other manufacturers, so if you don't have a certain quantity you wish to buy you will not be able to find many people to talk to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What part of China are you going to?  If it's Shenzhen or one of the other manufacturing cities in the south of China you will have much better luck than if you're going to Beijing, etc.&lt;/p&gt;&#xA;" OwnerUserId="1756" LastActivityDate="2011-02-02T17:53:43.510" CommentCount="2" />
  <row Id="9669" PostTypeId="2" ParentId="9663" CreationDate="2011-02-02T18:31:33.587" Score="1" ViewCount="" Body="&lt;p&gt;Well, I found the how-to.&#xA;Just click on the System Generator token block on the simulink scheme and configure its parameters. In the parameter  compilation it´s neccesary to select 'bitstream'.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastActivityDate="2011-02-02T18:31:33.587" />
  <row Id="9670" PostTypeId="2" ParentId="9666" CreationDate="2011-02-02T20:40:41.447" Score="9" ViewCount="" Body="&lt;p&gt;Its actually a fairly complicated topic, I don't know of any &quot;rule of thumb&quot; calculation but there is an article from &lt;a href=&quot;http://www.edn.com/contents/images/83652.pdf&quot; rel=&quot;nofollow&quot;&gt;EDN here&lt;/a&gt; on transmission line parameters of twisted pair cables including the effects of pitch (twist rate).  The twist rate will change the effective dielectric constant between the 2 conductors which does impact impedance and dielectric losses vs frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are also other things going on.  For instance not many people know that the 4 twisted pairs in an ethernet cable all have slightly different twist rates.  This prevents the same conductors from constantly and periodically being next to each other in the cable which would cause increased non-common-mode interference.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-02-02T20:40:41.447" CommentCount="4" />
  <row Id="9671" PostTypeId="1" AcceptedAnswerId="9676" CreationDate="2011-02-02T20:52:18.700" Score="11" ViewCount="240" Body="&lt;p&gt;Sorry if this is the wrong place, but I'm interested in a scientific and electrical explanation and not some HiFi-voodoo-magic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess you all have seen the discussions about expensive audio cables and &quot;improved&quot; sound quality.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, whats the best cable for a audio signal? Loudspeaker cables are usually a pair of ~12 AVG cables, terminated with &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Banana_connector&quot; rel=&quot;nofollow&quot;&gt;Banana connectors&lt;/a&gt;. As far as I can understand this must be affected by all sorts of noise. To minimize noise its normal to use coax cable for &quot;radio&quot; signals (LF, MF, HF ..). Wouldn't coax with proper connectors like APC-7 or equivalent be the best for audio to?  Or is the frequencies to low so coax for some reason doesn't work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Internet was a bit vague on this topic.. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(sorry for bag tagging, rep limit :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: What I'm really wondering is, why doesn't we use coaxial cables for our loudspeakers in an average home stereo.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lets say a signal level of 50 dBm (100W).&lt;/p&gt;&#xA;" OwnerUserId="2860" LastEditorUserId="2860" LastEditorDisplayName="" LastEditDate="2011-02-02T21:51:25.660" LastActivityDate="2011-02-02T22:13:49.537" Title="Whats the best cable to transfer audio signal?" Tags="&lt;audio&gt;&lt;cables&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="9672" PostTypeId="2" ParentId="2057" CreationDate="2011-02-02T20:54:12.697" Score="2" ViewCount="" Body="&lt;p&gt;The standard way of getting polyphony is to interrupt at some fixed interrupt rate (most often 8000 Hz or 44100 Hz), get a &quot;high&quot; (+1) or &quot;low&quot; (-1) (or something intermediate) from each sound source, add up all the numbers to get a total, then send that total number out the DAC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As others have said here, with a bit of cleverness a high-speed PWM can replace a DAC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://opencircuits.com/microcontroller_polyphony&quot; rel=&quot;nofollow&quot;&gt;&quot;microcontroller polyphony&quot;&lt;/a&gt; page gives some more details and tips.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-02T20:54:12.697" />
  <row Id="9674" PostTypeId="2" ParentId="9631" CreationDate="2011-02-02T20:57:00.820" Score="2" ViewCount="" Body="&lt;p&gt;As you have tried the monitor on two different cards, one it works with, the other smears the signal - this would indicate that the Monitor is OK and the video card is faulty.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have seen this smearing effect on a very old video card, and it was caused by either a faulty DAC (Digital to Analogue Converter) or the smoothing caps around the DAC (And as the caps were quite old - the printing looked grey/brown instead of silver/white - an indication of age or overheating - When Caps get old -  they loose capacitance and the ESR (Effective series resistance) increases.&lt;/p&gt;&#xA;" OwnerUserId="2280" LastActivityDate="2011-02-02T20:57:00.820" />
  <row Id="9675" PostTypeId="2" ParentId="9671" CreationDate="2011-02-02T21:09:15.133" Score="2" ViewCount="" Body="&lt;p&gt;There are 3 main cases that you need to look at for the type of signal being carried:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Digital&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of digital, the quality of the cable doesn't have a huge effect on the audio itself. For the most part it either works or it doesn't work and the quality doesn't change at all. What you will find is that in very high noise environments or long lengths you might start hearing digital noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Low Level Analog&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is cables such as head phone cables, microphone cables, lines running to your amp, etc. These are the most susceptibility to noise, especially in long runs. For Pro audio XLR is used which is a differential line. This eliminates noise that is introduced in the cable. For consumer audio there are cables that are better shielded that can help with noise reduction, but the biggest key here is to try to keep your cables as short as possible and limit the number of connectors used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;High Level Analog&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the situation where you have a cable that is carrying the audio to the speaker after the amplifier. This is an interesting area that could deserve a question in and of itself. You need to have a cable that is big enough to handle the current required, but a larger cable can cause problems with the signal if the level is too low. In this situation noise generally isn't an issue because the signal is much higher then the noise floor. However, there does need to be care taken in not making the line overly long and not passing it directly by sources of high noise energy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The connectors here also make a difference, you mentioned Banana, but there is also terminals that you connect the bare wire to directly as well as speakon connectors that are used in higher end audio. The key is making sure the connector can handle the power being supplied.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Additional Information&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The cable market is littered with overpriced cables that have many claims. I have seen one particular case of an XLR cable that claimed to make a signal &quot;warmer&quot; sounding. I had a reseller try to convince me to buy 50 of these cables to replace the ones I already owned. I asked for a &quot;trial&quot; with one of the cables so I could hear the difference. I ended up hooking them up to a high end audio recorder and found that there was essentially 0 difference between the different cables. The claim was that there wasn't a difference because my recorder was distorting the cable. So my advice, don't buy into that bull.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-02-02T21:33:52.257" LastActivityDate="2011-02-02T21:33:52.257" CommentCount="2" />
  <row Id="9676" PostTypeId="2" ParentId="9671" CreationDate="2011-02-02T21:14:24.893" Score="9" ViewCount="" Body="&lt;p&gt;There are two reasons why Speaker cables are not shielded/screened&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) The signal is so powerful - and any interference would not be noticed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Speakers are not very sensitive - it takes a lot of 'power' to create sound on a speaker&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is why Speakers are connected to an amplifier...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Input to Amplifiers are very sensitive, and so input should use shielded/screened cables.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. If you have a 100W Amp, (Good Amps use about 48V - so you have at least 2A - With peaks higher - lets say a peak of 20A - but for a very short time - so to hear this your speaker cable needs to be thick)&lt;/p&gt;&#xA;" OwnerUserId="2280" LastActivityDate="2011-02-02T21:14:24.893" CommentCount="1" />
  <row Id="9677" PostTypeId="2" ParentId="9671" CreationDate="2011-02-02T21:47:28.053" Score="6" ViewCount="" Body="&lt;p&gt;Impedance is a large factor in this situation, as is sensitivity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of a speaker wire, your driving it with a very low output impedance amplifier (&amp;lt;&amp;lt; 1ohm) and driving a load with a fairly low impedance, a typical speaker may be from 3-50 ohms across the audio spectrum.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The voltage noise you see on a cable is very dependent on these impedances as the noise is really a coupled current, the voltage that is measured on the cable is a product of this current and its impedance path to ground.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of a speaker wire this is a very low impedance so it takes a lot of coupled noise current to induce meaningful voltage changes in the signal.  Shielding a speaker wire is really pointless unless its in a very high noise environment, like if you set a coil on top of a building mains transformer.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to say this is that speakers are really current mode devices, the driving force is large currents and EMI coupled currents are really small in normal applications for speaker wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Line level signals are more sensitive for multiple reasons, one being that the signal they carry is generally later amplified, another being that the input impedance and source impedance for single ended line level audio are much higher.  Input impedance is generally around 10k for single ended line level inputs, it takes far less current to create a large voltage noise on that input than it does with a speaker wire.  This is why almost all line level audio cabling is shielded, be it RCA type running on coax or XLR running on STP.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to say this is that line level transfer is almost always voltage mode, meaning that the receiving end is looking for voltage levels and drawing minimal current, as a result, small currents such as coupled noise become larger voltages and have a much bigger impact on the signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This same concept applies to many other issues.  For instance with high impedance op amp inputs care has to be taken to minimize any coupled noise to that input signal for the same reasons that line level audio signals are more sensitive.  Often guard rings or similar approaches are used.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-02-02T21:47:28.053" />
  <row Id="9678" PostTypeId="2" ParentId="4458" CreationDate="2011-02-02T21:53:27.793" Score="4" ViewCount="" Body="&lt;p&gt;At the time this chip was designed, people used as few transistors as possible in the CPU, to make them small enough to fit on the available chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect that practically every &quot;register&quot; (both programmer-visible instruction-set registers and also internal microarchitecture latches) in a CPU of that era stored data in a transparent &lt;a href=&quot;http://en.wikipedia.org/wiki/gated_D_latch&quot; rel=&quot;nofollow&quot;&gt;gated D latch&lt;/a&gt; or something similar.&#xA;Nowadays, there's plenty of transistors on a chip, so it's simpler to use full master-slave D flip-flops, even though they use twice as many transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many instructions take data from some register A, combine it with some other data with the ALU, and store the result back in register A.&#xA;That is pretty easy to do if register A is implemented with a full master-slave D flip-flop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if register A is a transparent gated D latch, you need non-overlapping clocks.&#xA;You use a pulse on one clock to store some intermediate result somewhere (while register A holds its output constant), and then a pulse on another clock to load register A with the new value (while the intermediate register holds its output constant).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This requires a 2-phase clock.&#xA;The easiest way to make a non-overlapping 2-phase clock (in those days when transistors were scarce) was a little external circuit that takes an input clock and divides it by two.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As time went on, people figured out how to pack more and more transistors onto an IC.&#xA;So people designing CPUs integrated more and more of the stuff around the CPU in a full computer system onto the CPU chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reading between the lines of the &lt;a href=&quot;http://en.wikipedia.org/wiki/clock_signal&quot; rel=&quot;nofollow&quot;&gt;Wikipedia clock signal article&lt;/a&gt;,&#xA;I get the impression that the people who designed the 8085 and the 6502 and other chips of that era had just a little more room than the previous generation of integrated CPUs,&#xA;and they decided the best use of that room was to put that little external circuit on-chip.&#xA;But they kept all the registers the same gated D latch as before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So that's why the clock frequency is divided by two. You can think of the first external clock pulse generating a pulse on the phase_one internal clock signal to update that intermediate result register, and the second pulse from the external clock generating a pulse on the phase_two internal clock signal to update the programmer-visible register.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-02T21:53:27.793" />
  <row Id="9679" PostTypeId="1" AcceptedAnswerId="9686" CreationDate="2011-02-02T21:56:27.527" Score="2" ViewCount="552" Body="&lt;p&gt;I want to get a new microcontroller dev board for just general tinkering and learning (even though I already have an Arduino), and this time I'm thinking that I want to go with something based on the ARM architecture. After extensive research I've narrowed it down to 3 choices. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;ET STM32 --------- $30 &lt;/li&gt;&#xA;&lt;li&gt;LeafLabs Maple --- $55 &lt;/li&gt;&#xA;&lt;li&gt;mbed --------------- $67 &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The prices are the approximate prices including shipping to myself. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do not know which I should get. The mbed seems to be the most powerful, followed closely by the ET STM32, followed by the Maple. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ET STM32 and the mbed have similar form factors, they are meant to be plugged into a breadboard, kind of like a really big DIP package. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The mbed has a USB interface, and one programs it by just dropping a compiled binary into a USB flash drive interface that comes up when you plug it in to the computer. The downside to this one being it is very expensive&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Maple is built in an arduino form factor and there is an effort to port the libaries (but I guess I don't really care THAT much about this), and it is also fairly expensive. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At this point the ET STM32 Seems like the most logical choice. . . However, one can only program it via a serial interface, and I don't have a serial port, not a serial to usb converter. . . (Though I have a dodgy plan to use my arduino as a serial to USB converter or something). Furthermore, I'm not sure how I will go about powering it, since it seems that it wants 3.3 volts, but I am fairly sure I could figure this out later.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These all use Cortex-M3 chips. I was unable to find any similar dev boards with a cortex-A5 or cortex-A8 or something like that sadly ;(. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most ARM microcontroller dev boards seem to be Cortex-M3, or ARM7. And while I would prefer to learn the ARM instruction set as opposed to Thumb-2, I don't think it makes that much of a difference to me right now, I'd rather play with the new cortex-m3 rather than the ARM7.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know any similar Cortex-A5, or Cortex-A8 boards in existence? &#xA;Which of these three would you recommend?&#xA;Are there any other's you would like to recommend, and why?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;/p&gt;&#xA;" OwnerUserId="2701" LastActivityDate="2011-02-03T04:53:07.853" ClosedDate="2011-02-03T16:33:42.957" Title="Which ARM Microcontroller development board should I purchase?" Tags="&lt;microcontroller&gt;&lt;arm&gt;&lt;mbed&gt;&lt;cortex-m3&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="9680" PostTypeId="2" ParentId="9679" CreationDate="2011-02-02T22:07:55.690" Score="1" ViewCount="" Body="&lt;p&gt;Have a look at the &lt;a href=&quot;http://ics.nxp.com/lpcxpresso/&quot; rel=&quot;nofollow&quot;&gt;LPCXpresso&lt;/a&gt; boards. The prices are very good, and a low-cost breadboard is available for them, as well as a more expensive one with lots of interfaces on it. They have a USB JTAG interface, and the interface and target board can be separated for stand-alone applications. Free software tools are provided.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are pin-compatible with the mbed, BTW.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-02T22:07:55.690" CommentCount="1" />
  <row Id="9681" PostTypeId="2" ParentId="9679" CreationDate="2011-02-02T22:13:46.760" Score="1" ViewCount="" Body="&lt;p&gt;There are no Cortex A5 boards out yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a Cortex A8 board, the &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;Beagleboard&lt;/a&gt; is a great choice, though it's about 2-3x the price of your other candidates. I'd probably start with the mbed because it would minimize the mucking around with serial ports or whatever. If you're enjoying yourself, get a Beagleboard in a few months.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-02-02T22:13:46.760" />
  <row Id="9682" PostTypeId="2" ParentId="9671" CreationDate="2011-02-02T22:13:49.537" Score="5" ViewCount="" Body="&lt;p&gt;For driving speakers at 100W, simply use cheap mains cable. It's a waste of money using anything else.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-02T22:13:49.537" CommentCount="8" />
  <row Id="9683" PostTypeId="2" ParentId="9607" CreationDate="2011-02-03T01:17:00.473" Score="2" ViewCount="" Body="&lt;p&gt;For such a sensor network I would absolutely consider using &lt;a href=&quot;http://en.wikipedia.org/wiki/1-Wire&quot; rel=&quot;nofollow&quot;&gt;Dallas 1-wire&lt;/a&gt; components for great flexibility and reasonable price. It is well supported in Linux via &lt;a href=&quot;http://www.owfs.org/&quot; rel=&quot;nofollow&quot;&gt;owfs&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/6NkNU.jpg&quot; alt=&quot;T3-R1-A picture&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At www.hobby-boards.com there is a small &lt;a href=&quot;http://www.hobby-boards.com/catalog/product_info.php?cPath=22&amp;amp;products_id=109&amp;amp;osCsid=d9396861e6297db2ebb00197bae3b067&quot; rel=&quot;nofollow&quot;&gt;T3-R1-A&lt;/a&gt; ready made board which you just connect with cat5/RJ45 priced at 18USD. According to the documentation it uses the &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/2815/t/al&quot; rel=&quot;nofollow&quot;&gt;DS18S20&lt;/a&gt; sensor like already mentioned by BG100. &lt;/p&gt;&#xA;" OwnerUserId="568" LastActivityDate="2011-02-03T01:17:00.473" />
  <row Id="9686" PostTypeId="2" ParentId="9679" CreationDate="2011-02-03T04:53:07.853" Score="1" ViewCount="" Body="&lt;p&gt;Are you looking for something arduino like in that you learn the chip, blink some leds and have a uart or two then you have to solder your own stuff on it to go beyond that?  Or do you want something that has more stuff on the board than just the microcontroller?  displays or buzzers or light sensors, etc?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was very disappointed with the lpcxpresso, and lpc in general.  But the armmite pro, which is arduino form factor, easy to program, etc not a bad choice, not locked into a sandbox.   The mbed2 is good, not locked into a sandbox like the lpcxpresso and the stm32 primers are.  simply copy the .bin file to what looks like a mounted flash drive, press the reset button and you are running.  sparkfun.com, has many solutions, some for less than what you are looking at.  The olimex sam7 header board for example, does not require jtag or anything although if you have jtag then that can only help.  It is arm7, so you can do arm and thumb (not thumb2).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nintendo game boy advances can be had for these kinds of prices and flash carts are about $20-$30.  I recommend finding an SP because of the backlight.  the gba and sp have serial ports, another $20 in parts to get that going.  I have a bootloader on the cart and download programs to ram over serial and not have to keep pulling the cartridge out.  The DS cartridges are as cheap, but the DS is a little harder to program, I recommend gba first then DS.  Lots of things you can do and learn to program if interested in this platform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want something with gadgets on it that you want to learn to program then I recommend the stellaris boards, they are cortex-m3, dont need anything else but a usb cable, which it comes with, and you can learn to program the oled displays and other items on the board at whatever level you are interested (on the metal, rtos, api calls, etc).  the 811 is really easy to brick, and the 6mhz base frequency is a little weird, the others are 8mhz, and harder to brick and/or unbrickable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a thumb emulator (thumbulator) at github if you want to get your feet wet with thumb without spending any money and with much less frustration (compared to a microcontroller chip) as to why you cant figure out why your code wont boot or run.  I made it boot like a cortex-m3 so you can move right over to those cores quickly (thumb2 is a superset of thumb and all thumb2 cores run thumb as well).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;qemu is another emulator that does arm and I assume thumb as well, perhaps even thumb2 (As well as x86 and another of other instruction sets).  Nowhere near as visible as mine, but more visible than a micro, and certainly much more complete as many peripherals are included.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are gba and nds emulators out there as well for that matter, that definitely support arm and thumb.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;sparkfun has the mbed for $60 (before shipping).  Note that if blue leds give you headaches (they do for me) the four on the mbed are an instant migraine, replaced them with green leds to make it tolerable to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are interested in cortex-a5 and a8 then you are in the 300+mhz range and well above this price range.  I prefer the hawkboard to the beagleboard, I prefer any of the beagle board clones to the beagleboard as you have to spend another $75 - $150 above and beyond the beagleboard price to make it useful.  A chinese version I have for $150 has all the things on the clone to make it useful, it is my mail server, and the beagle board is in a dusty box, may never see the light of day again.  The hawkboard is also useful right out of the box, got my first one for like $75 but the price jumped, almost to beagleboard prices, I dont know why.  It is an older and slower omap, but an omap nevertheless and has a dsp on board if you want to get your feet wet with that.  The bootloader is easy to use and you can load programs over serial without needing to use jtag, you can run linux if you like or just have screaming embedded platform if you choose not to use an OS.  I prefer the open-rd to the beagleboard as well, much much faster processor (dual core?) for the same money, better docs.  Very disappointed with the plug computer, avoid it.  The open-rd has a couple of sata connectors you can plug a laptop hard drive right onto the board if you want to run linux on it for example and not have the pain and suffering of usb/flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The cortex-m3 parts use a new/different jtag, which for now is closed source, so that is very disappointing, and almost a good enough reason to boycott using that core.  A good arm jtag wiggler for the normal arm jtag capable cores (most of them not cortex-m3) is the amontek jtag-tiny.  uses openocd.  inexpensive, easy to use, and will get you unstuck and gets you out of being forced into using a vendors sandbox to play with their boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should invest $10-$15 for a usb to serial cable, or one of the generic usb to serial break out boards (based on ftdi chips) at sparkfun, can hook right up to the micro (make sure you get your 3.3 or 5.0 voltages right!).  it is very easy to bit-bang those ftdi chips as well if you want to turn them into jtag or spi or whatever.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Olimex has a number of header boards like the sam7, sparkfun and other places around the world sell olimex products if you dont happen to live in the USA.  Often under $50, the arm7 micro vendors are represented.  The sam7 is atmel which you are familiar with with the avr in your arduino, as you may have figured out atmel does a better than average job with documentation and customer support and on chip peripheral design (A big reason why the avr, with an inferior instruction set when compared to some other micros, has such a huge fan base, even before the arduino was dreamed up.  At least that is my theory based on my experience with the various vendors).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;enough rambling...Based on your list and comments I would recommend the coridium armmite pro (get the proper voltage usb to serial/power board for $14, the one the lilypad uses) or the mbed.  Or if you want a display and stuff the stellaris 1968 eval board.  No matter what, order a msp430 launchpad, its only five bucks.  Not arm but msp430, another micro, competitor to avr, good instruction set, easy to use, etc.  The more instruction sets and more vendors you try the better.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-02-03T04:53:07.853" CommentCount="19" />
  <row Id="9687" PostTypeId="2" ParentId="9465" CreationDate="2011-02-03T04:55:50.363" Score="1" ViewCount="" Body="&lt;p&gt;See &lt;a href=&quot;http://www.dwelch.com/arduino/&quot; rel=&quot;nofollow&quot;&gt;http://www.dwelch.com/arduino/&lt;/a&gt;. No C programming, but I do use Linux, and it does get you out of the Arduino framework. It doesn't work with all the cards, though.  &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardLilyPad&quot; rel=&quot;nofollow&quot;&gt;LilyPad&lt;/a&gt;, yes, &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardProMini&quot; rel=&quot;nofollow&quot;&gt;Pro Mini&lt;/a&gt;, yes, but not the &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardUno&quot; rel=&quot;nofollow&quot;&gt;Uno&lt;/a&gt; and not the &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardPro&quot; rel=&quot;nofollow&quot;&gt;Pro&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="985" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2011-02-04T08:40:20.117" LastActivityDate="2011-02-04T08:40:20.117" CommentCount="2" />
  <row Id="9688" PostTypeId="2" ParentId="2057" CreationDate="2011-02-03T05:48:44.343" Score="1" ViewCount="" Body="&lt;p&gt;Play sound A for a moment, like maybe 50 ms then sound B and switch back and forth. The idea is to switch faster than the ear can tell and it will sound like both playing at the same time.&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2011-02-03T05:48:44.343" />
  <row Id="9689" PostTypeId="2" ParentId="9526" CreationDate="2011-02-03T07:03:10.167" Score="0" ViewCount="" Body="&lt;p&gt;this link might be useful for configuring the circuit&#xA;&lt;a href=&quot;http://www.engineersgarage.com/embedded/avr-microcontroller-projects/gps-interface-circuit&quot; rel=&quot;nofollow&quot;&gt;http://www.engineersgarage.com/embedded/avr-microcontroller-projects/gps-interface-circuit&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2867" LastActivityDate="2011-02-03T07:03:10.167" />
  <row Id="9690" PostTypeId="2" ParentId="9645" CreationDate="2011-02-03T08:45:45.137" Score="0" ViewCount="" Body="&lt;p&gt;would a usb display work? &lt;a href=&quot;http://www.mimomonitors.com/products/mimo-720-s&quot; rel=&quot;nofollow&quot;&gt;http://www.mimomonitors.com/products/mimo-720-s&lt;/a&gt;  it may be easier then trying to stream part of the window and sending it to a display. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;the other option i can see working is if you have a second vga or DVI port and adding a cheap LCD monitor to clone or extend your desktop&lt;/p&gt;&#xA;&#xA;&lt;p&gt;not trying to be discouraging but what you want to do would require you to create a PC program to send that part of the screen ( not sure how in SW) and a communication line like a serial port or usb to control your display.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: after rethinking the whole issue, I would still use a prebuilt solution, but if you want something from scratch, you could get an ARM processor(cortex-Mx) add a LCD screen (your choice on resolution) and build an API so you can send straight data to draw the screen through the com port(rs232 serial) or use Ethernet connection. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2060" LastEditorDisplayName="" LastEditDate="2011-04-04T12:26:57.207" LastActivityDate="2011-04-04T12:26:57.207" CommentCount="2" />
  <row Id="9692" PostTypeId="1" AcceptedAnswerId="9693" CreationDate="2011-02-03T09:56:06.127" Score="2" ViewCount="323" Body="&lt;p&gt;First of all, I'm a newbie regarding electronics&amp;amp;robotics so please bear with me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been working as a programmer for a few years but I just got interested in playing with microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone recommend a book/tutorial for building a development board based on ATMEGA16-16PI &#xA;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As of yesterday I own a breadboard and a atmega16 microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where do I go from here?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="2717" LastActivityDate="2011-02-03T13:29:26.123" Title="Build ATMEGA16 Board" Tags="&lt;microcontroller&gt;&lt;atmega&gt;&lt;board&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="3" />
  <row Id="9693" PostTypeId="2" ParentId="9692" CreationDate="2011-02-03T11:12:35.327" Score="2" ViewCount="" Body="&lt;p&gt;I wanted to do something with microcontrollers for some time now, but it wasn't until yesterday that I collected enough courage to actually buy one. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you said that you're absolute beginner, here are some very basic pointers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First site you may want to visit it Atmel's website for the microcontroller you have. &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?PN=ATmega16&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; it is. There, you'll need to visit the documentation section and get the 2 datasheets. You should read the summary and take a look at the datasheet. While you can read the whole datasheet, I think it may be better to just keep it as a reference. You might want to download AVR Instruction Set and keep it as a reference too, but to me at least, it looks more interesting to assembly fans and compiler writers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;By now you should have an idea of what the device you have is capable of. Next step would be to set up the needed toolchain. On the site I linked, go to tools section and look under design software. There you'll find a link to AVR Studio 4, which is one of the available programming environments. Some of the other IDEs are &lt;a href=&quot;http://winavr.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;WinAVR&lt;/a&gt;, IAR Embedded Workbench for AVR(non-free, but there's a program size limited demo), ImageCraft, CodeVisionAVR, CrossWorks for AVR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a beginner, AVR Studio and WinAVR seem to be the easiest to obtain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that, you can start programming. There's a simulator in AVR Studio, so you can try out and debug programs before you burn them on the controller. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next step which needs to be overcome is how to get program from your computer to the microcontroller. On the tools page, you'll find a list of officially blessed development boards and programmers and debuggers. Problem with them is that they are usually too expensive for a beginner. On the other hand, they should work without any problems and there's a lot of documentation on how to use them. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to save some money, but suffer potential headaches, you can get one of the many alternative programmers. Just search for AVR programmer and you'll get countless results. Unfortuantley, I can't recommend you any specific programmer, since I'm looking for one too. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other option is to build one yourself. There are countless schematics available for AVR programmers and many of them can be very cheap to make. On the other hand, there's the problem with finding specific parts (some programmers need Russian transistors, which are now difficult to obtain and then you'll have to look for compatible replacements and so on) and that you have to build it yourself. Still, building a programmer yourself can be a good learning experience.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After you have a programmer, you'll need a circuit which can power up the controller and provide the basics. You should know by now that AVRs run on 5 volts, so that's what you'll need. There are lots and lots of examples on the Internet for basic boards, so again search. Some sites with programmer schematics will have most basic target boards too. For most basic system, you'll need a 5 V source and that's pretty much it, as ATMega 16 has its own clock source.  If you can't make a basic board, feel free to ask for specific instruction. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next step is to make a basic program which will do something. For microcontrollers, hello world programs are a bit more complicated and are a good project for a bit more advanced users. Instead, the most basic program will turn on an LED. After that comes flashing LED and after that button controlled LED and so on. Circuits for such project are very simple. In addition to the most basic AVR board, you may only need one resistor and LED. I think that ATMega 16 can source enough current to power a LED, but I'm not 100% sure. You can always check the datasheet. If you're feeling a bit more advanced, you could make a circuit which will use a transistor to control the LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, here are some interesting links for beginners:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.avrfreaks.net/&quot; rel=&quot;nofollow&quot;&gt;http://www.avrfreaks.net/&lt;/a&gt; They have a nice forum and they have a list of projects which could be interesting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are several interesting tutorials:&lt;br&gt;&#xA;&lt;a href=&quot;http://imakeprojects.com/Projects/avr-tutorial/&quot; rel=&quot;nofollow&quot;&gt;http://imakeprojects.com/Projects/avr-tutorial/&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://avrbeginners.net/&quot; rel=&quot;nofollow&quot;&gt;http://avrbeginners.net/&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.avr-asm-tutorial.net/avr_en/&quot; rel=&quot;nofollow&quot;&gt;http://www.avr-asm-tutorial.net/avr_en/&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.ladyada.net/learn/avrdevtut/&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/learn/avrdevtut/&lt;/a&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another interesting thing worth mentioning is &lt;a href=&quot;http://en.wikipedia.org/wiki/Arduino&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt;. It's an electronics prototyping platform which is based on AVR microcontrollers. The plus side of them seems to be that you'll be able to skip the background stuff, such as getting a programmer, getting a basic board for the microcontroller and so on. There's an IDE for Arduinos and a simple programming language too. The minus side of them is that you'll be able to skip the background stuff, such as getting a programmer, getting a basic board for the microcontroller and so on. There’s also the problem with the fact that there's an IDE for Arduinos and a simple programming language too.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-03T13:29:26.123" LastActivityDate="2011-02-03T13:29:26.123" CommentCount="1" />
  <row Id="9694" PostTypeId="1" CreationDate="2011-02-03T13:46:41.190" Score="3" ViewCount="154" Body="&lt;p&gt;We have to develop control software to run in an embedded system. The prototype is made in Matlab (using neural network toolbox), and we want to port the software to C or C++. Do you know which libraries or software we could use to do this? Embedded matlab may be another option, but, from their info in the website, it seems that neural network toolbox is not supported. Any of you has worked with it before?&lt;/p&gt;&#xA;" OwnerUserId="2871" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-03T13:01:43.843" LastActivityDate="2011-03-03T13:01:43.843" Title="MATLAB toolbox equivalent for embedded system" Tags="&lt;c&gt;&lt;c++&gt;&lt;matlab&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="0" />
  <row Id="9695" PostTypeId="2" ParentId="2057" CreationDate="2011-02-03T16:02:02.150" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.avrfreaks.net/index.php?module=Freaks%20Academy&amp;amp;func=viewItem&amp;amp;item_type=project&amp;amp;item_id=1192&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is my code for playing 2 tunes at the same time. Sorry, you have to register to AVR freaks to get access.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-02-03T16:02:02.150" CommentCount="1" />
  <row Id="9696" PostTypeId="2" ParentId="9694" CreationDate="2011-02-03T16:04:38.827" Score="0" ViewCount="" Body="&lt;p&gt;If you're planning on porting the software to C/C++ anyway, you could run it on almost any embedded system with an operating system. You might start with an embedded Linux board, since it has free C and C++ compilers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as the actual hardware goes, there are many choices. Take a look at the answers to &lt;a href=&quot;http://electronics.stackexchange.com/questions/2841/linux-sbc-recommendations&quot;&gt;this question&lt;/a&gt; for some suggestions. You might also consider the &lt;a href=&quot;http://mbed.org&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt;, which is cheap, has a free C compiler, and is easy to get started with if you're new to embedded stuff.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-02-03T16:04:38.827" />
  <row Id="9697" PostTypeId="1" AcceptedAnswerId="9700" CreationDate="2011-02-03T16:30:58.913" Score="0" ViewCount="88" Body="&lt;p&gt;The rule of thumb is that when a diode is fully on, it looks like a short circuit (ideally).  So (to make this easy), say I have 100 V source and a diode which breaks down at 10V.  If my power supply/source impedance is 1 Ohm, will the current through my diode be:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;I = (Vsupply - Vdiode)/Rsupply = (100 - 10)/1 = 90/1 = 90 Amps, or&lt;/li&gt;&#xA;&lt;li&gt;I = Vsupply/Rsupply = 100/1 = 100 Amps?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1571" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-02-03T17:41:48.673" LastActivityDate="2011-02-03T17:41:48.673" Title="What is the diode current when used in clipping/clamping" Tags="&lt;power-supply&gt;&lt;diode&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9698" PostTypeId="1" CreationDate="2011-02-03T16:33:29.470" Score="4" ViewCount="91" Body="&lt;p&gt;I have an embedded electronics project in mind, but will use a different example to explain what I wonder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Say we have to PCs, each with a sound card which can sample up to 44kHz. How do I get those to talk to each other over radio?  It helps if the antenna need not be huge, but low parts count and low price is most important. Can the audio signal be modulated in some simple way? Are there ICs which already does the major part?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a decent understanding of digital logic, but when it comes to analog things I need a lot of advice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assume the PCs can do a certain amount of processing of the signal. The sound card is stereo, could that be used for something?  Like use the left channel for data, and the right channel for some kind of modulation shift?&lt;/p&gt;&#xA;" OwnerUserId="1877" LastActivityDate="2011-02-03T16:55:55.443" Title="Low parts count and cheap radio modulation (hack)" Tags="&lt;radio&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="2" />
  <row Id="9699" PostTypeId="2" ParentId="9698" CreationDate="2011-02-03T16:44:28.917" Score="4" ViewCount="" Body="&lt;p&gt;Nordic Semi &lt;a href=&quot;http://www.nordicsemi.com/index.cfm?obj=menu&amp;amp;act=displayMenu&amp;amp;men=2&quot; rel=&quot;nofollow&quot;&gt;2.4 GHz wireless chips&lt;/a&gt; are ideal for low-cost wireless audio, they are cheap and easy to use. Sample the audio from the sound card using a suitable MCU and interface it to one of the Nordic chips.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-03T16:55:55.443" LastActivityDate="2011-02-03T16:55:55.443" CommentCount="3" />
  <row Id="9700" PostTypeId="2" ParentId="9697" CreationDate="2011-02-03T16:46:54.023" Score="3" ViewCount="" Body="&lt;p&gt;The current will be the same for all parts of the circuit, and in this case be about 90A as the diode can be considered to be a low resistance 10V drop.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-03T16:46:54.023" />
  <row Id="9701" PostTypeId="1" AcceptedAnswerId="9702" CreationDate="2011-02-03T17:01:42.293" Score="2" ViewCount="132" Body="&lt;p&gt;I have three small motors, and I know you should use a motor shield or driver when working with the arduino, but would it be safe to use these with the arduino by themselves without a shield? And if so, what would be the best way to work with them and control their speed?&#xA;&lt;img src=&quot;http://i.imgur.com/BN5tW.jpg&quot; alt=&quot;the motors&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2873" LastActivityDate="2011-02-03T21:54:25.217" Title="Using motors with arduino without external hardware" Tags="&lt;arduino&gt;&lt;dc-motor&gt;" AnswerCount="2" />
  <row Id="9702" PostTypeId="2" ParentId="9701" CreationDate="2011-02-03T17:05:39.630" Score="3" ViewCount="" Body="&lt;p&gt;You will damage the Arduino chip if you connect a motor directly to one of the outputs. I've used the &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;products_id=81&quot; rel=&quot;nofollow&quot;&gt;Adafruit motor shield&lt;/a&gt; with motors like that.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-03T17:05:39.630" CommentCount="4" />
  <row Id="9703" PostTypeId="1" AcceptedAnswerId="9705" CreationDate="2011-02-03T17:19:08.530" Score="4" ViewCount="140" Body="&lt;p&gt;I want a master node consisting of a TI Stellaris Cortex M3 core connected to what can be up to 32 slave nodes of TI MSP430 (or possibly more Stellaris slave nodes). These will be maximally 0.5 meters between master to most distant slave. Bit rates of around 0.5-1mbps will be needed. What kind options are available for internal communications? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;From docs they both seem to support SPI, UART and I2C. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;SPI will from what I find, need 1 selector wire pr node. Way too many wires. &lt;/li&gt;&#xA;&lt;li&gt;I2C seems easy, but for from docs I get the max speed is 400KHz. Too slow without degrading quality or maximum number of nodes.&lt;/li&gt;&#xA;&lt;li&gt;UART seems to acheive the speed, but can it be used outside of A to B communication?&lt;/li&gt;&#xA;&lt;li&gt;Did I miss anything?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Update: As noted in comments, updated I2C speed for msp430 to 400KHz. Still too slow though. Also the network is purely one master and n slaves.&lt;/p&gt;&#xA;" OwnerUserId="941" LastEditorUserId="941" LastEditorDisplayName="" LastEditDate="2011-02-06T22:32:31.357" LastActivityDate="2011-02-06T22:32:31.357" Title="Multi node bus options" Tags="&lt;microcontroller&gt;&lt;bus&gt;&lt;sharedbus&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="1" />
  <row Id="9704" PostTypeId="2" ParentId="9703" CreationDate="2011-02-03T17:29:15.883" Score="2" ViewCount="" Body="&lt;p&gt;RS485 might be a good fit.  It uses the UART for the serial stream, but it will need a direction pin to determine which node controls the bus.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Master will transmit a message and then listen for a response.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Slaves will decode all the messages and respond to the messages addressed to it.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-02-03T17:29:15.883" />
  <row Id="9705" PostTypeId="2" ParentId="9703" CreationDate="2011-02-03T17:51:45.800" Score="5" ViewCount="" Body="&lt;p&gt;I would suggest either RS485 or CAN; RS485 has the advantage of almost universal availability (if you've got a UART, you can have RS485; if your UART has automatic RTS control, you have a perfect RS485 solution). You can find cheap, small devices that will go up to several megabaud as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CAN is a little more robust, but if your microcontroller doesn't have the peripheral it can be an additional cost you're not willing to add to the project. CAN's main advantage over RS485 (IMO) is that in the case of bus contention, a complete message will still get through; If two devices start talking on an RS485 network, nothing intelligible is received and there is no built-in means of bus management, so you have to take care of this in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For your given speed and given that I don't believe the microcontrollers you mentioned have built-in CAN controllers, I'd suggest a token-based RS485 network. Essentially none of the nodes speak until it's their turn to speak, and this is done though the passing of a &quot;token&quot; (a short network message granting the use of the bus) to each of the nodes in turn. It's relatively easy to set up, is far more reliable than CSMA/CD and I think you could have something up and running within a day or so.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-02-03T17:51:45.800" />
  <row Id="9706" PostTypeId="2" ParentId="9703" CreationDate="2011-02-03T17:56:19.443" Score="2" ViewCount="" Body="&lt;p&gt;FWIW, I'm pretty sure that the I2C bus can be run at higher speeds than 100kHz. MSP430, I believe, can support 400kHz operation at least.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-02-03T17:56:19.443" CommentCount="2" />
  <row Id="9707" PostTypeId="2" ParentId="9258" CreationDate="2011-02-03T18:11:50.073" Score="1" ViewCount="" Body="&lt;p&gt;Look at openocd.  The backends are mostly based around the parallel port bit bang approach, I think it goes so far as to change only one bit at a time.  It is fairly simple to take what I think they call the dummy backend which is an example.  Send whatever write bit command to the arduino, and have it set or clear that bit.  When asked to read the input bit then send a command to the arduino to perform that task and return the results.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have done exactly this with success, but not with an arduino, I had openocd talk from a host into a simulated arm core running in a hdl simulator.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that some jtag specs are closed, the cortex-m3 for example is some sort of serialized reduced number of pins jtag which last time I looked was not available without an NDA.  that may not matter because openocd takes care of all that for you so long as you are using a jtag interface that openocd supports, the bit banged back end is where your arduino and whatever interface you use to get to/from it come in to play.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As noted already by Joby, you need to be careful with voltages (not all arduino flavors are 5V and not all arm controllers are 3.3 volt) and signal conditioning and grounding and all that stuff.  If your target board is powered by a supply that is at a different level compared to what you power your arduino with you could melt something down when you connect the two.  &lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-02-03T18:11:50.073" />
  <row Id="9708" PostTypeId="2" ParentId="9703" CreationDate="2011-02-03T18:39:17.820" Score="0" ViewCount="" Body="&lt;p&gt;I2C will run at least 400kHz with most parts. It would be the easiest solution for a short distance communication bus. If you wanted something more robust I'd recommend CAN or RS-485, but both would require additional external chips.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-02-03T18:39:17.820" />
  <row Id="9709" PostTypeId="1" AcceptedAnswerId="9715" CreationDate="2011-02-03T18:51:28.103" Score="0" ViewCount="167" Body="&lt;p&gt;I have a &lt;a href=&quot;http://www.luminarymicro.com/jaguar&quot; rel=&quot;nofollow&quot;&gt;Jaguar&lt;/a&gt; motor controller that has a set of 5 inset male header pins to connect an encoder. The encoder has only loose wires coming out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What type of connector should I be buying to solder/crimp onto the end of these?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, there're a couple of sensor boards with a similar arrangement of 0.1&quot; male headers. The control board also has male headers. However, every compatible cable I can find is male to female.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do servo cables with sockets at both ends exist?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;This is what the controller looks like. Encoder slot is on the front, as the freehand-circling below shows&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/nNEIM.jpg&quot; alt=&quot;Jaguar&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1217" LastEditorUserId="1217" LastEditorDisplayName="" LastEditDate="2011-02-04T15:46:51.663" LastActivityDate="2011-02-05T12:38:50.940" Title="What cable do I need to connect rows of male header pins together" Tags="&lt;connector&gt;&lt;cables&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="1" />
  <row Id="9710" PostTypeId="2" ParentId="9666" CreationDate="2011-02-03T18:52:42.190" Score="0" ViewCount="" Body="&lt;p&gt;the twist step depends on the wave length of the signal transmitted &lt;/p&gt;&#xA;&#xA;&lt;p&gt;that is why cables for different frequencies have different twist steps&lt;/p&gt;&#xA;" OwnerUserId="2471" LastActivityDate="2011-02-03T18:52:42.190" CommentCount="1" />
  <row Id="9711" PostTypeId="2" ParentId="9694" CreationDate="2011-02-03T20:03:28.280" Score="2" ViewCount="" Body="&lt;p&gt;First dump it to C/C++, &lt;a href=&quot;http://www.mathworks.com/support/solutions/en/data/1-19HN4/index.html?product=NN&amp;amp;solution=1-19HN4&quot; rel=&quot;nofollow&quot;&gt;instructions here&lt;/a&gt; and profile the application on your computer. neural networks can be rather compute intensive so you need to know how much processing power and what type of processing you need (integer? FP? fixed point? SIMD? etc?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need the network to be trainable while running on your embedded device, then you're stuck developing your own system as MatLab exported code doesn't including the training portions, perhaps based on some external neural network libraries.  I would still start with profiling what you've got to get an idea of what class of device your looking at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All that being said, the &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;beagleboard&lt;/a&gt; is probably a safe bet unless what your doing is very compute intensive, it would also allow you to use most linux libraries.  I used &lt;a href=&quot;http://sourceforge.net/projects/fann/&quot; rel=&quot;nofollow&quot;&gt;the FANN library&lt;/a&gt; for a project maybe 5 years ago and it was good to work with.  I don't know if it will compile for ARM out of the box or if some other library has trumped it recently.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-02-03T21:51:21.047" LastActivityDate="2011-02-03T21:51:21.047" />
  <row Id="9712" PostTypeId="2" ParentId="9701" CreationDate="2011-02-03T21:54:25.217" Score="1" ViewCount="" Body="&lt;p&gt;Not possible...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino can not drive that type of motor - the start up surge would damage the chip, also a diode is needed to handle the 'back emf' when the motor is turned off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A servo has internal electronics to switch the motor. you just provide a repeating pulse of the correct length.&lt;/p&gt;&#xA;" OwnerUserId="2280" LastActivityDate="2011-02-03T21:54:25.217" />
  <row Id="9713" PostTypeId="1" CreationDate="2011-02-03T22:38:34.717" Score="3" ViewCount="110" Body="&lt;p&gt;I'm very interested in building a quad/dual rotor helicopters,etc but I also don't want to spend full retail. For example, I'd like to buy a couple of broken or non-fully working cheap rc helis and then reuse the components. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd also be interested in gears, servos, etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions for where to look, like recycling sites, etc.? &lt;/p&gt;&#xA;" OwnerUserId="1371" LastActivityDate="2011-02-05T00:13:38.763" ClosedDate="2011-03-22T11:20:55.027" Title="Where to find cheap/used dc motors, gears or non-working kits" Tags="&lt;components&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="9714" PostTypeId="1" AcceptedAnswerId="9716" CreationDate="2011-02-03T23:03:07.383" Score="4" ViewCount="80" Body="&lt;p&gt;Analog Devices &lt;a href=&quot;http://www.analog.com/en/press-release/01_25_2011_500-mA_LDOs_Double_the_Power_Rejection/press.html&quot; rel=&quot;nofollow&quot;&gt;just brought out several LDO regulators claiming double the power supply rejection ratio of competing devices, and targeting these devices at battery powered devices&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I thought that batteries were quite noiseless, as opposed to powering up  your device via a switchmode power supply where (i would have thought) a very good PSRR would be handy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why would PSRR be a crucial factor in battery powered systems?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-02-03T23:35:26.147" Title="Power Supply Rejection Ratio for Battery Powered Systems" Tags="&lt;power-supply&gt;" AnswerCount="1" />
  <row Id="9715" PostTypeId="2" ParentId="9709" CreationDate="2011-02-03T23:15:11.387" Score="2" ViewCount="" Body="&lt;p&gt;Are those jumpers beside the connector? Then probably the connector can be connected using the common &lt;a href=&quot;http://www.sparkfun.com/products/9140&quot; rel=&quot;nofollow&quot;&gt;jumper wires&lt;/a&gt; (available with up to at least 10 pins in one housing).&#xA;Servo cables usually have a different kind of connector (rounded corners).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make your own jumper leads, you can buy &lt;a href=&quot;http://pololu.com/catalog/product/1904&quot; rel=&quot;nofollow&quot;&gt;crimp connector housings&lt;/a&gt; from &lt;a href=&quot;http://pololu.com/&quot; rel=&quot;nofollow&quot;&gt;pololu&lt;/a&gt;. They also sell &lt;a href=&quot;http://pololu.com/catalog/category/71&quot; rel=&quot;nofollow&quot;&gt;pre-crimped wires&lt;/a&gt;, if you don't want to crimp them yourself.&lt;/p&gt;&#xA;" OwnerUserId="1950" LastEditorUserId="1217" LastEditorDisplayName="" LastEditDate="2011-02-05T12:38:50.940" LastActivityDate="2011-02-05T12:38:50.940" CommentCount="4" />
  <row Id="9716" PostTypeId="2" ParentId="9714" CreationDate="2011-02-03T23:16:07.720" Score="5" ViewCount="" Body="&lt;p&gt;The reason why PSR is important even in battery supplied devices is that one can (and usually) have several different kinds of circuits supplied from the same battery in the same device. Due to internal resistance of the battery, changes in the current consumption of the one part of the device will be seen as voltage variation for all the circuitry supplied by thereof. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One dramatic example is GSM phone, where power amplifier for transmitter will consume significant amount of current (amps range) every time the frame is transmitted with almost no current consumption in between frames. Assuming* 0.5 Ohm internal resistance and 1A consumption that means 500mV voltage variation repeating several hundreds times a second.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*) those are example numbers, too lazy to check actual GSM numbers &lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="1471" LastEditorDisplayName="" LastEditDate="2011-02-03T23:35:26.147" LastActivityDate="2011-02-03T23:35:26.147" CommentCount="1" />
  <row Id="9717" PostTypeId="1" CreationDate="2011-02-04T01:04:16.880" Score="2" ViewCount="127" Body="&lt;p&gt;I have a simple water pump.  It needs to turn on for a short time then turn off a short time.  The circuit does not need to be powered by the same powr source as the pump. Can anyone help?&lt;/p&gt;&#xA;" OwnerUserId="2880" LastActivityDate="2011-02-04T02:36:19.230" Title="Is there a simple 9v circuit I can build that will power a pump for 3 min on then 3 min off?" Tags="&lt;circuit&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9718" PostTypeId="1" AcceptedAnswerId="9725" CreationDate="2011-02-04T01:05:47.110" Score="6" ViewCount="234" Body="&lt;p&gt;Hi folks,&#xA;If you go to: &lt;a href=&quot;http://www.battery-chargers.com/charging_instructions.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.battery-chargers.com/charging_instructions.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;...Under &quot;Operating Instructions&quot; part &quot;B: Charging battery outside of vehicle&quot;, it says you have to attach an extra jumper cable to the negative battery post, that is then clamped to the charger's actual negative cable. See below:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/0ESB3.gif&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both my charger's instructions and these look identical on this point (Indeed, they might be the same instruction sheet). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Why is this extra cable needed?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Not like I don't have one, just rather curious...)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="2879" LastActivityDate="2011-02-04T14:03:11.033" Title="Extra negative battery cable when charging outside car?" Tags="&lt;battery&gt;&lt;safety&gt;&lt;car&gt;&lt;battery-charging&gt;&lt;automotive&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="9719" PostTypeId="2" ParentId="9718" CreationDate="2011-02-04T01:29:47.717" Score="0" ViewCount="" Body="&lt;p&gt;Just a guess, but perhaps it forms a makeshift switch? Disconnect to stop charging.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-04T01:29:47.717" CommentCount="2" />
  <row Id="9721" PostTypeId="2" ParentId="9652" CreationDate="2011-02-04T01:39:56.810" Score="1" ViewCount="" Body="&lt;p&gt;In addition to the good answers by others, there's still things you can do if you've got functional failures due to trace mismatch on your board (though at 27 MHz, there's not much to worry about). Most modern FPGAs from Xilinx (and maybe Altera, not sure) have reconfigurable delay element inside of the I/O pin so you could adjust with very fine resolution when the signal is captured. Look for the 'IDELAY' and 'ODELAY' primitives.&lt;/p&gt;&#xA;" OwnerUserId="2531" LastActivityDate="2011-02-04T01:39:56.810" />
  <row Id="9722" PostTypeId="1" CreationDate="2011-02-04T02:07:14.087" Score="1" ViewCount="120" Body="&lt;p&gt;Modern electronics are incredibly reliable, however, I have had about 5 ethernet routers experience hardware failure on one or more ports on my home network.  Is this unusual, and if it is, what precautions can I take to avoid it.  If it is &quot;common&quot;, is there a component in the system that is prone to failure?&lt;/p&gt;&#xA;" OwnerUserId="2881" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-04T04:04:50.920" LastActivityDate="2011-05-26T05:30:19.263" Title="What is the most common way ethernet ports experience harware failure?" Tags="&lt;ethernet&gt;" AnswerCount="3" />
  <row Id="9723" PostTypeId="1" CreationDate="2011-02-04T02:17:58.260" Score="1" ViewCount="116" Body="&lt;p&gt;I'm making a small animating diorama as a present.  There is a switch, two servos, and an LED; all being powered by four AA batteries and all controlled by an ATmega168 chip.  I've prototyped the simple stuff on my arduino uno, but now I want to move the ATmega chip and hook up the battery pack, both of which are new to me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm too new to the site to post any inline images, or for some of the links to be completely valid.  I apologize in advance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the design I put together in Frizting: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://dl.dropbox.com/u/3144073/diorama/breadboard.pdf&quot; rel=&quot;nofollow&quot;&gt;http://dl.dropbox.com/u/3144073/diorama/breadboard.pdf&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://dl.dropbox.com/u/3144073/diorama/schema.pdf&quot; rel=&quot;nofollow&quot;&gt;http://dl.dropbox.com/u/3144073/diorama/schema.pdf&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I've used these two articles as reference (remove the spaces):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.html&quot; rel=&quot;nofollow&quot;&gt;http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.instructables.com/id/Standalone-Arduino-ATMega-chip-on-breadboard&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Standalone-Arduino-ATMega-chip-on-breadboard&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I would be very surprised if I had it all wired up correctly. I'd be very grateful if anyone could comment on what I've done wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS.  The software polls the state of the toggle switch.  If the switch is on, it sets the two servos to specific values, and turns on the LED.  If the switch is off, it sets the servos to difference values, and turns off the LED.&lt;/p&gt;&#xA;" OwnerUserId="2875" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-02-04T03:35:44.350" LastActivityDate="2011-02-04T12:33:11.190" Title="Standalone ATmega168, powered by 4xAA batteries" Tags="&lt;battery&gt;&lt;schematics&gt;&lt;breadboard&gt;&lt;atmega168&gt;" AnswerCount="2" />
  <row Id="9724" PostTypeId="2" ParentId="9717" CreationDate="2011-02-04T02:36:19.230" Score="3" ViewCount="" Body="&lt;p&gt;I will tentatively recommend a 555 timer with a relay driver. It will work, provided that:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You can spend some time tuning the circuit to give you roughly the time you want&lt;/li&gt;&#xA;&lt;li&gt;The pump can be turned on and off by plugging it in.&lt;/li&gt;&#xA;&lt;li&gt;The timing for the pump on/off time doesn't need to be precise or absolute.&lt;/li&gt;&#xA;&lt;li&gt;You can tolerate different performance during different temperature conditions (temperature drift)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;A 555 should work fine with a 9V source. I'm assuming it isn't a 9V battery.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-02-04T02:36:19.230" CommentCount="3" />
  <row Id="9725" PostTypeId="2" ParentId="9718" CreationDate="2011-02-04T03:08:56.333" Score="9" ViewCount="" Body="&lt;p&gt;So that you can connect/disconnect while not standing over the battery. The batteries contain sulfuric acid which is not a very pleasant substance to splash. Even the fumes are dangerous.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While connecting inside a vehicle, connect the positive first and the negative on the vehicle body while not facing the battery. The negative can be connected to any exposed metal part on the vehicle (and at a distance from the battery). Similarly while disconnecting, disconnect the negative first and then the positive cable. The reason is that the vehicle body is connected to the negative terminal. If the positive cable slips and touches any other vehicle body part, it will cause a short.&lt;/p&gt;&#xA;" OwnerUserId="1927" LastActivityDate="2011-02-04T03:08:56.333" CommentCount="4" />
  <row Id="9726" PostTypeId="2" ParentId="9722" CreationDate="2011-02-04T03:51:48.950" Score="1" ViewCount="" Body="&lt;p&gt;In my experience for something like that its generally solder joints coming loose/cracking, often times in consumer gear its a result of thermal stress.  Consumer gear isn't usually tested nearly as rigorously as &quot;business&quot; or industrial equipment when it comes to dealing with environmental variations.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They can be hard to find, you usually need to check them carefully like with a magnifying glass or similar equipment.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-02-04T03:51:48.950" CommentCount="1" />
  <row Id="9727" PostTypeId="2" ParentId="9723" CreationDate="2011-02-04T09:49:04.043" Score="2" ViewCount="" Body="&lt;p&gt;I'd say that 4*AA are the problem. You're using 7805 for regulation and your soruce is going to give you at most 6.4 V, but will quickly drop to around 6. You need at least 2 V higher intput voltage to use 7805, so you won't be getting 5 V at the output and AT won't start. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, 7805 will waste some power. If you can, try to find another way of getting the needed 5 V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure about the rest of it. There could be other errors too.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-04T09:49:04.043" />
  <row Id="9728" PostTypeId="2" ParentId="749" CreationDate="2011-02-04T10:22:57.477" Score="0" ViewCount="" Body="&lt;p&gt;Sounds like you want to build a device like John Connor's ATM card/Atari Portfolio hack from the start of Terminator 2. Try googling &lt;a href=&quot;http://hackaday.com/2008/08/04/magnetic-stripe-card-spoofer/&quot; rel=&quot;nofollow&quot;&gt;mag stripe card spoofer&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2011-02-04T10:22:57.477" />
  <row Id="9729" PostTypeId="2" ParentId="9465" CreationDate="2011-02-04T10:54:12.713" Score="1" ViewCount="" Body="&lt;p&gt;Have a look at Joe Pardue's C programming for microcontrollers at Smiley Micros&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.smileymicros.com/index.php?module=pagemaster&amp;amp;PAGE_user_op=view_page&amp;amp;PAGE_id=26&amp;amp;MMN_position=2:2&quot; rel=&quot;nofollow&quot;&gt;http://www.smileymicros.com/index.php?module=pagemaster&amp;amp;PAGE_user_op=view_page&amp;amp;PAGE_id=26&amp;amp;MMN_position=2:2&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has a windows bias but as it relies on WinAVR and therefore AVRdude it is easy to use from a nix perspective with the avr-gcc toolchain. &lt;/p&gt;&#xA;" OwnerUserId="2884" LastActivityDate="2011-02-04T10:54:12.713" />
  <row Id="9730" PostTypeId="2" ParentId="9713" CreationDate="2011-02-04T12:18:40.817" Score="2" ViewCount="" Body="&lt;p&gt;I found some interesting items in this post:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/627/good-motor-supplier&quot;&gt;Good motor supplier?&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="941" LastActivityDate="2011-02-04T12:18:40.817" />
  <row Id="9731" PostTypeId="2" ParentId="9723" CreationDate="2011-02-04T12:33:11.190" Score="2" ViewCount="" Body="&lt;p&gt;The Atmegas are rated to 5.5V. I have run PICs on 6.5V with no problems, but I did not test them for a long time, nor did I verify they met all their specs. I suppose if it was a little toy, you could try using a diode to drop about 0.5V, this way the voltage will always be under 6V, which should be okay.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-04T12:33:11.190" CommentCount="1" />
  <row Id="9732" PostTypeId="1" AcceptedAnswerId="9733" CreationDate="2011-02-04T13:10:00.177" Score="2" ViewCount="232" Body="&lt;p&gt;I have come across a chip which is only available in &lt;a href=&quot;http://en.wikipedia.org/wiki/Land_grid_array&quot; rel=&quot;nofollow&quot;&gt;LGA&lt;/a&gt;. I wouldn't touch &lt;a href=&quot;http://en.wikipedia.org/wiki/Ball_grid_array&quot; rel=&quot;nofollow&quot;&gt;BGA&lt;/a&gt;, but what about LGA? How possible is it to design for one with little experience? Are there any gotchas? I'm planning to reflow solder these using a hot plate.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="568" LastEditorDisplayName="" LastEditDate="2011-02-07T02:46:04.247" LastActivityDate="2011-02-07T02:46:04.247" Title="Difference between BGA and LGA" Tags="&lt;pcb&gt;&lt;lga&gt;" AnswerCount="3" />
  <row Id="9733" PostTypeId="2" ParentId="9732" CreationDate="2011-02-04T13:17:37.637" Score="6" ViewCount="" Body="&lt;p&gt;LGA is similar to BGA, but without the solder balls, so you have to apply solder paste to the pads with a stencil. I don't think you will find them any easier to use than BGA.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-04T13:17:37.637" CommentCount="4" />
  <row Id="9735" PostTypeId="2" ParentId="9722" CreationDate="2011-02-04T13:36:43.533" Score="1" ViewCount="" Body="&lt;p&gt;Static electricity is a killer of ethernet ports too.  I've not yet managed to ever kill a port, but have replaced NICs and routers for other people that grab the cable by the very end, get a &quot;poke&quot; from it, and then it doesn't work...  If the cable is plugged in on either end, make sure you always hold it on the cable behind the connector.  Don't grab the connector itself, the conducting surfaces aren't very deep, doesn't take much static to jump the gap.&lt;/p&gt;&#xA;" OwnerUserId="1678" LastActivityDate="2011-02-04T13:36:43.533" />
  <row Id="9736" PostTypeId="1" CreationDate="2011-02-04T14:02:10.940" Score="1" ViewCount="350" Body="&lt;p&gt;I've got a PDF file with a PCB layout I'de like to produce - however, I need the file in Gerber format first. Is there an easy way to convert between the two? I've found this: &lt;a href=&quot;https://swannman.wordpress.com/projects/pdf2gerb/&quot; rel=&quot;nofollow&quot;&gt;https://swannman.wordpress.com/projects/pdf2gerb/&lt;/a&gt; - does anyone have some experience with it? Does it work well? Are there better alternatives?&lt;/p&gt;&#xA;" OwnerUserId="2886" LastActivityDate="2011-02-04T17:27:36.687" Title="How to convert PDF to Gerber for PCB layout?" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;&lt;gerber&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="9737" PostTypeId="2" ParentId="9718" CreationDate="2011-02-04T14:03:11.033" Score="3" ViewCount="" Body="&lt;p&gt;Lead acid batteries, like those used in vehicles, create hydrogen gas from the sulphuric acid. If the gas concentration is high enough and you get a spark, it explodes, the acid goes everywhere including in your eyes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You almost always get a spark when completing the circuit, sometime even if the charger if off. By making the last connection away from the battery this lessens the chance of an explosion. If the battery is still in the vehicle, attach the positive to the battery terminal then attach the negative to a ground point away from the battery. Many people use a point on the engine block. With the battery removed, you don't have a ground point to connect to, so make the last connection away from the battery by using an extra ground cable. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-02-04T14:03:11.033" CommentCount="1" />
  <row Id="9739" PostTypeId="2" ParentId="9736" CreationDate="2011-02-04T14:38:40.737" Score="2" ViewCount="" Body="&lt;p&gt;It seemed to work OK on the PDF provided in the example - the Gerbers looked OK when I imported them into GC-Prevue. However, when I created a PDF file from a PCB designed in the Pulsonix software I use, and converted it with pdf2gerb.pl, the resultant Gerber file wouldn't import into GC-Prevue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some PCB manufacturers which can work from artwork supplied as Postscript files. You could convert the PDF file to Postscript by printing it to a file, using a Postscript driver.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-04T14:38:40.737" />
  <row Id="9740" PostTypeId="1" AcceptedAnswerId="9742" CreationDate="2011-02-04T14:40:15.623" Score="1" ViewCount="60" Body="&lt;p&gt;I've got a design (PIC microcontroller that uses transistors to turn on banks of LEDs). I have 2 instances of the LED array, so I made a hierarchical design - I have a separate schematic for the LED array, and I put 2 instances of it into my main project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LED arrays are just a bunch of resistor/LED pairs, labeled R1/D1, R2/D2, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem comes when I generate a netlist - the netlist appears to include everything, but it doesn't differentiate between the R1 from the first instance of the array and the R1 of the second instance. So I get things like this in my netlist file:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;*SIGNAL*  _HN_1_!ON&#xA;Q1.3 D1.1 D14.1 D2.1 D15.1 D3.1 D16.1 D4.1 D17.1 D5.1 D18.1 D6.1 D19.1 D7.1 D20.1 D8.1 D21.1 D9.1 D22.1 D10.1 D23.1 D11.1 D24.1 D12.1 D25.1 D13.1&#xA;*SIGNAL*  _HN_2_!ON&#xA;Q2.3 D1.1 D14.1 D2.1 D15.1 D3.1 D16.1 D4.1 D17.1 D5.1 D18.1 D6.1 D19.1 D7.1 D20.1 D8.1 D21.1 D9.1 D22.1 D10.1 D23.1 D11.1 D24.1 D12.1 D25.1 D13.1&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Q1 feeds the first LED array, Q2 feeds the second LED array, but you see that D1 is referenced in both. If I feed that into FreePCB, I'm only going to get one LED array and it's going to be wired ALL wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a way to make TinyCAD do the right thing here?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update: I tried putting the LED arrays on separate sheets, but that didn't help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update again: I suppose I could just copy the LED array design onto separate sheets and then number their reference designators appropriately, but that's giving up the hierarchical design altogether.&lt;/p&gt;&#xA;" OwnerUserId="259" LastEditorUserId="259" LastEditorDisplayName="" LastEditDate="2011-02-04T15:00:15.510" LastActivityDate="2011-02-04T16:05:45.837" Title="How to get TinyCAD to output correct netlist when using hierarchical design?" Tags="&lt;schematics&gt;&lt;tinycad&gt;" AnswerCount="1" />
  <row Id="9741" PostTypeId="1" AcceptedAnswerId="9822" CreationDate="2011-02-04T15:51:38.523" Score="1" ViewCount="77" Body="&lt;p&gt;Hi all, I am programming a FPGA by System Generator. I have done this design:&#xA;&lt;img src=&quot;http://i.imgur.com/wxt2e.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;I don´t know what are the respectives pins of my FPGA for the blocks of my design called 'Gateway In' and 'Gateway Out'&lt;/strong&gt;. I would like to check I would check the design made in my FPGA through a generator waves and a oscilloscope.&#xA;Does anyone know how to assign pins of your design if you made it using System Generator?&#xA;Thank you so much.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T21:04:47.430" LastActivityDate="2011-02-12T21:04:47.430" Title="System Generator: How to configure the pins for the signals of your design?" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;pins&gt;&lt;xilinx-system-generator&gt;&lt;configuration&gt;" AnswerCount="2" />
  <row Id="9742" PostTypeId="2" ParentId="9740" CreationDate="2011-02-04T16:05:45.837" Score="1" ViewCount="" Body="&lt;p&gt;I've looked into it and this seems to be an open bug issue that just hasn't been fixed yet: &lt;a href=&quot;http://sourceforge.net/tracker/index.php?func=detail&amp;amp;aid=2859909&amp;amp;group_id=47763&amp;amp;atid=450703&quot; rel=&quot;nofollow&quot;&gt;http://sourceforge.net/tracker/index.php?func=detail&amp;amp;aid=2859909&amp;amp;group_id=47763&amp;amp;atid=450703&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can use a different type of netlist output that might help but I'm guessing it's not an option for you.  Your best bet at this point is to just abandon hierarchical designs until it gets fixed.  Sorry.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-04T16:05:45.837" CommentCount="1" />
  <row Id="9743" PostTypeId="2" ParentId="9713" CreationDate="2011-02-04T16:07:05.273" Score="2" ViewCount="" Body="&lt;p&gt;There's plenty of gears and motors available from old Roombas.  You can buy them here: &lt;a href=&quot;http://www.roombarecycle.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.roombarecycle.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-04T16:07:05.273" />
  <row Id="9744" PostTypeId="2" ParentId="9703" CreationDate="2011-02-04T16:09:55.333" Score="2" ViewCount="" Body="&lt;p&gt;You could ignore the select line for SPI and treat it as a more generic synchronous serial interface.  I believe the Stellaris will let you configure the SPI as an SSI, but I'm unsure about the MSP430's.  Regardless, you can just have them monitor the bus and only respond if they see their slave address pop up.  You'll have to write the software for this but it will work.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-04T16:09:55.333" CommentCount="2" />
  <row Id="9745" PostTypeId="2" ParentId="9736" CreationDate="2011-02-04T16:35:49.463" Score="1" ViewCount="" Body="&lt;p&gt;The best way is to ask the company that did the layout for Gerbers or CAD originals.  Most companies that sell evaluation boards for their chips (e.g. TI, Altera) will do this.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-04T16:35:49.463" CommentCount="1" />
  <row Id="9746" PostTypeId="2" ParentId="9736" CreationDate="2011-02-04T17:18:26.107" Score="2" ViewCount="" Body="&lt;p&gt;It's not directly possible, as a set of gerber files (including the drill file, which I count as a &quot;gerber&quot; even though it isn't really) contain more information than the average PDF, for example drill sizes and parameters of vias.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-02-04T17:27:36.687" LastActivityDate="2011-02-04T17:27:36.687" CommentCount="7" />
  <row Id="9747" PostTypeId="2" ParentId="9732" CreationDate="2011-02-04T18:29:09.443" Score="1" ViewCount="" Body="&lt;p&gt;I've done LGA on a hot plate before, but only with a stencil. I wouldn't try it without a stencil. If this is a one-off, why not try the LSM303 breakout from Sparkfun?&lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2011-02-04T18:29:09.443" CommentCount="2" />
  <row Id="9748" PostTypeId="1" AcceptedAnswerId="9749" CreationDate="2011-02-04T19:05:37.500" Score="1" ViewCount="90" Body="&lt;p&gt;My Roland cube has stopped working, the guitar input connector for the main channel has been faulty for a while but now its gone completely. I opened it up and it looks like the connector is badly damaged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to take the connector from the clean/line in channel at the back. Its the same connector as the main channel. I have a soldering iron. I am a noob. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a photo of one of the sockets:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/HtYY0.jpg&quot; alt=&quot;photo of PCB&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I remove these connectors? Can I do it with just a soldering iron?&lt;/p&gt;&#xA;" OwnerUserId="2889" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-04T20:06:37.330" LastActivityDate="2011-02-04T20:06:37.330" Title="Roland Microcube modification, need a hand.." Tags="&lt;microcontroller&gt;&lt;circuit&gt;&lt;audio&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9749" PostTypeId="2" ParentId="9748" CreationDate="2011-02-04T19:34:29.887" Score="4" ViewCount="" Body="&lt;p&gt;What you need is:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Soldering Iron&lt;/li&gt;&#xA;&lt;li&gt;A desoldering tool or some solder wick&lt;/li&gt;&#xA;&lt;li&gt;Some solder&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;First you need to locate where the pins are soldered to the board. You need to remove all the solder from these joints.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a desoldering pump (it looks a bit like a syringe with a sprung piston inside it and a release button on the side), this is the easiest way. Heat the pins until the solder has melted, keep the soldering iron on the joint, then at the same time touch the tip of the desoldering pump to the pin and press the button. This will instantly suck all the solder off the pin and into the tool.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have solder wick, this absorbs the solder by soaking it up into the wick. This won't remove it all though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you've got most of the solder off all the pins, nudge the pins with the tip of a screwdriver to release them from any final solder bonds, and you should be able to lift off the socket unharmed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do the same to the faulty socket, replace with the good one, and resolder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Job done.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-04T19:34:29.887" CommentCount="3" />
  <row Id="9750" PostTypeId="1" AcceptedAnswerId="9758" CreationDate="2011-02-04T20:14:04.707" Score="1" ViewCount="98" Body="&lt;p&gt;I want to detect light near 10 micrometer wavelength. It seems like photodiodes are mainly targeted for 1 micrometer range. Is there any detector/sensor for 10 micrometer wavelength ?&lt;/p&gt;&#xA;" OwnerUserId="2891" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-02-05T05:02:20.183" LastActivityDate="2011-02-05T05:02:20.183" Title="IR-near visible light detection" Tags="&lt;sensor&gt;&lt;light&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="9751" PostTypeId="1" CreationDate="2011-02-04T20:28:07.047" Score="1" ViewCount="222" Body="&lt;p&gt;I am looking for a way to detect what sort of terrain a bot is travelling on. To keep it simple lets start with grass vs sand vs tarmac.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is to be used with arduino, and for a hobby project so cant cost an arm and a leg. I figured it could be done with a camera but hoping to find a better way. maybe with sonar or something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;tx&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&#xA;Im taking this info to do some more research on the problem. Will be back with some more info and hopefully and answer. i think bouncing light/sound off the ground and somehow measuring the amount reflected/absorbed, maybe with the color filters to aid the readings as the start.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) I think this is a start. &lt;a href=&quot;http://embedded-lab.com/blog/?p=1671&quot; rel=&quot;nofollow&quot;&gt;http://embedded-lab.com/blog/?p=1671&lt;/a&gt; sending out light and reading how much has been returned. that would just be picking up the highs and lows.&lt;/p&gt;&#xA;" OwnerUserId="2791" LastEditorUserId="2791" LastEditorDisplayName="" LastEditDate="2011-02-06T16:29:02.033" LastActivityDate="2011-02-07T17:58:48.557" Title="Detecting the type of surface/medium a robot is on top of." Tags="&lt;arduino&gt;&lt;sensor&gt;" AnswerCount="5" CommentCount="2" />
  <row Id="9752" PostTypeId="2" ParentId="9750" CreationDate="2011-02-04T20:48:13.440" Score="2" ViewCount="" Body="&lt;p&gt;The lower ends of the Near-IR spectrum (which goes up to about 3uM) can be detected with common CMOS type circuits.  These generally aren't effective past 1uM though which is why you see so many at that wavelength.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;10uM is in the Mid-IR region, detecting it is not easy.  Historically it required exotic materials and generally cooling of the sensor (think liquid nitrogen).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are uncooled devices available now that work in this range called microbolometers.  They are primarily built in arrays for use in thermal cameras and similar applications.  I don't know of any &quot;single cell microbolometers&quot; out there but you may be able to find one.  I doubt it would still be called a microbolometer at that point but i'm not sure what the terminology would be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you'll have a hard time finding such a device off the shelf.  Other than the thermal imaging applications (which will always be arrays of sensors) the only applications i know of for such wavelengths are chemical sensing / spectrometry analysis and those sensor are likely custom built, very sensitive and very expensive.  &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-02-04T20:48:13.440" CommentCount="1" />
  <row Id="9753" PostTypeId="2" ParentId="9732" CreationDate="2011-02-04T21:09:14.380" Score="1" ViewCount="" Body="&lt;p&gt;I've done an LGA without a stencil. But that was a small low pad count part (BMA180). I had to tin the pads with flux and solder, then placed the chip on top, then used hot air reflow to solder it.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-02-04T21:09:14.380" />
  <row Id="9754" PostTypeId="2" ParentId="9751" CreationDate="2011-02-04T21:16:36.950" Score="4" ViewCount="" Body="&lt;p&gt;Have you thought about an accelerometer? Could measure the frequency of bumps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also be best served by a combination of several different methods...&lt;/p&gt;&#xA;" OwnerUserId="2892" LastActivityDate="2011-02-04T21:16:36.950" CommentCount="5" />
  <row Id="9755" PostTypeId="2" ParentId="9611" CreationDate="2011-02-04T22:39:54.617" Score="1" ViewCount="" Body="&lt;p&gt;How about this plan?&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Kill a water heater and use the heat element, this can then be PWM:ed from a mcu with a relay in the middle. (You may need to think about how big pwm window your system needs.)&lt;/li&gt;&#xA;&lt;li&gt;Temperature sensor, there is a lot to choose from. But anything that your mcu can use would do just fine.&lt;/li&gt;&#xA;&lt;li&gt;A mcu with a potentiometer and a small display to show the current temp.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;What mcu to choose is up to you and this forum has a lot of advice on that topic. (Maybe a AVR or a PIC?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then to program the mcu you can read a good article on the topic, &lt;a href=&quot;http://www.eetimes.com/design/embedded/4211211/PID-without-a-PhD&quot; rel=&quot;nofollow&quot;&gt;PID without a PhD&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And then you trim the pid parameters and decide if you need a fast or a heating process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2011-02-04T22:39:54.617" />
  <row Id="9756" PostTypeId="2" ParentId="9751" CreationDate="2011-02-04T23:12:02.037" Score="3" ViewCount="" Body="&lt;p&gt;You might want to look into reflecting a light off of the surface you are driving on. Based off of how much light is reflected you can get a good idea of the type of surface that you are on.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-04T23:12:02.037" CommentCount="2" />
  <row Id="9757" PostTypeId="1" AcceptedAnswerId="9793" CreationDate="2011-02-04T23:52:01.927" Score="1" ViewCount="148" Body="&lt;p&gt;Hi, I am playing around with real implementation of basic logic schemes from transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you suggest any compact implementations of T-trigger? Obviously, classic &quot;CMOS&quot; way eats way too many.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other nonlinear elements are allowed (like tunnel diodes), diodes and other components does not counts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will need this to implement binary counter.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-10T00:42:04.990" Title="T-trigger: minimum transistor count" Tags="&lt;transistor&gt;&lt;t-trigger&gt;&lt;counter&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="9758" PostTypeId="2" ParentId="9750" CreationDate="2011-02-04T23:59:17.547" Score="3" ViewCount="" Body="&lt;p&gt;Certainly there are microbolometers for this spectral range. They are called PIR sensor and are cheap and readily available as they are used in motion detectors.&#xA;See for example &lt;a href=&quot;http://www.futurlec.com/PIR_D203B.shtml&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; (first Google result) sensor: 5-14µm&lt;/p&gt;&#xA;" OwnerUserId="1950" LastActivityDate="2011-02-04T23:59:17.547" CommentCount="1" />
  <row Id="9759" PostTypeId="2" ParentId="9713" CreationDate="2011-02-05T00:13:38.763" Score="2" ViewCount="" Body="&lt;p&gt;I'm sure if you posted on Craigslist asking for broken model helicopters and airplanes you'd get your fill.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-02-05T00:13:38.763" />
  <row Id="9760" PostTypeId="2" ParentId="2591" CreationDate="2011-02-05T00:15:37.917" Score="0" ViewCount="" Body="&lt;p&gt;Just use an old computer that can run Linux. No reason you can't do embedded development on a PC; I do it at my day job all week long.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-02-05T00:15:37.917" />
  <row Id="9761" PostTypeId="1" CreationDate="2011-02-05T03:31:18.810" Score="1" ViewCount="107" Body="&lt;p&gt;I Have got my ID-12 module active and putting out the RFID tags' details to Serial as&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;String valu = port.readStringUntil('\n');&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;... then I print that to serial. But I would like to use the information from the tag to determine changes in Processing environment. For example, change the background color of a box depending on which RFID tag is placed to the reader.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know how I can do this or where I may find coding help?&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Setup:&lt;/h3&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/products/8419&quot; rel=&quot;nofollow&quot;&gt;ID-12&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove&quot; rel=&quot;nofollow&quot;&gt;Arduino Duemilanova&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Serial, which I want to send to processing and use for a condition statement.. &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2703" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-20T22:16:48.767" LastActivityDate="2011-02-20T22:16:48.767" Title="RFID Reader coding." Tags="&lt;arduino&gt;&lt;uart&gt;&lt;rfid&gt;&lt;processing&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9763" PostTypeId="2" ParentId="2591" CreationDate="2011-02-05T04:58:19.400" Score="0" ViewCount="" Body="&lt;p&gt;This PhidgetSBC2 board has &lt;em&gt;everything&lt;/em&gt; you need, including a full Debian Linux distribution (allowing you to add whatever packages you would like).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Only downside is it is a bit more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.phidgets.com/products.php?category=21&amp;amp;product_id=1072&quot; rel=&quot;nofollow&quot;&gt;http://www.phidgets.com/products.php?category=21&amp;amp;product_id=1072&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2457" LastActivityDate="2011-02-05T04:58:19.400" />
  <row Id="9764" PostTypeId="1" CreationDate="2011-02-05T06:32:11.293" Score="2" ViewCount="105" Body="&lt;p&gt;The microcontroller and several sensors of my circuit draw 10µA in sleep mode. I am using a 100mAh lithium polymer battery. Is this quiescent current acceptable? Should I install a physical switch to shut down the device completely?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I install a p channel MOSFET on the voltage rail of my sensors to reduce the quiescent current down to 3µA?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-05T09:28:09.650" LastActivityDate="2011-02-05T09:28:09.650" Title="What quiescent current draw of my circuit would be acceptable for a 100mAh battery?" Tags="&lt;microcontroller&gt;&lt;battery&gt;&lt;sleep&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="9765" PostTypeId="2" ParentId="9764" CreationDate="2011-02-05T06:52:25.697" Score="8" ViewCount="" Body="&lt;p&gt;This is actually a rather straightforward calculation, but you might need more data than &#xA;provided.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wikipedia says LiPo has a 5%/month self-discharge rate, so even with zero current draw you have 20 months standby.  5%/month * 100mAh is about 7 uA current draw.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So we'll say the combined discharge at 10 uA is 17uA.  100mAh / 17uA = 5900 hours standby time.  This is about eight months.  Is this sufficient for you?  If you knock your standby down to 3uA you can get about a year standby.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice that all these calculations are assuming a lot of things.  You won't always be in standby mode if your circuit does something useful, so you should add in active current * duty cycle.  And of course battery chemistry is complicated, so these are just ballpark figures until you actually build and measure the circuit.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-05T06:52:25.697" />
  <row Id="9766" PostTypeId="1" CreationDate="2011-02-05T08:40:26.137" Score="1" ViewCount="147" Body="&lt;p&gt;I came across term &quot;half bandgap voltage reference&quot;. I expect it is somehow related to &lt;a href=&quot;http://en.wikipedia.org/wiki/Bandgap_voltage_reference&quot; rel=&quot;nofollow&quot;&gt;bandgap circuit&lt;/a&gt;. Do you know what it is, know its schematic or principle of operation?&lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="1471" LastEditorDisplayName="" LastEditDate="2011-02-05T08:47:15.940" LastActivityDate="2011-02-07T20:22:23.143" Title="What half-bandgap voltage reference is?" Tags="&lt;voltage-reference&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="9767" PostTypeId="2" ParentId="9766" CreationDate="2011-02-05T09:22:27.707" Score="3" ViewCount="" Body="&lt;p&gt;A bandgap voltage reference is a circuit that is relatively easily made on an integrated circuit. The basic premise is that it uses two different sized NPN transistors driven at the same current, and the sum of these two voltages can be an accurate reference voltage near the bandgap voltage of silicon at 0K, which is 1.25eV. There are many descriptions of the circuit, which began as the Brokaw cell, then the Widlar bandgap, and then the many variations you can see today. The &lt;a href=&quot;http://en.wikipedia.org/wiki/Bandgap_voltage_reference&quot; rel=&quot;nofollow&quot;&gt;Wikipedia page&lt;/a&gt; is a decent brief read. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has several benefits: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;It gives roughly the same result regardless of power supply (PSRR)&lt;/li&gt;&#xA;&lt;li&gt;It can be temperature-compensated to give a very flat response over temperature&lt;/li&gt;&#xA;&lt;li&gt;It derives its accuracy from the ratio of transistors instead of the absolute value of components, which is a major benefit for integrated circuits.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The traditional method for generating the reference voltage is to add the voltages at the two paths, which will give the typical bandgap voltage of 1.25V, or two forward diode drops. As supply voltages have dropped, there has been a push for lower output voltages. They typically use more current mirroring to derive an output voltage that is closer to a single diode drop. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;While I have never seen the term &quot;half-bandgap&quot; while doing research on low-voltage reference circuits, there are plenty of bandgap reference based circuits with an output voltage of 0.5 - 0.7V.&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-02-05T17:37:35.200" LastActivityDate="2011-02-05T17:37:35.200" CommentCount="1" />
  <row Id="9768" PostTypeId="2" ParentId="9751" CreationDate="2011-02-05T09:26:19.013" Score="3" ViewCount="" Body="&lt;p&gt;I wonder if you could do it by sound? A rolling vehicle would make different sounds going over those different terrains, and if the motor is quiet enough...&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-02-05T09:26:19.013" CommentCount="4" />
  <row Id="9769" PostTypeId="1" AcceptedAnswerId="9779" CreationDate="2011-02-05T11:22:38.277" Score="3" ViewCount="197" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using a maxim ADC in my application from this family: &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/MAX1304-MAX1314.pdf&quot; rel=&quot;nofollow&quot;&gt;http://datasheets.maxim-ic.com/en/ds/MAX1304-MAX1314.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The devices have relatively low input impedance. If you look at Figure 5 in the above datasheet, on page 19, you can see the equivalent input circuit. My ADC is 0-5V range. My input signal however is in 0-10V range, so i have to reduce it to match the ADC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I use a resistive divider at the ADC input, it seems to me that I can not get a proper reading from the ADC due to the interaction between my 2 resistors, and R1 and R2 in figure 5. For example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;|                      Vdiv&#xA;|   Vin------Rdivider--------Rdivider---------&amp;gt; GND&#xA;|                       |&#xA;|                       |&#xA;|                       |&#xA;|                       R1 (3.33k)&#xA;|                       |&#xA;|                       |             Csample&#xA;|                       |-------/ ------| |------- &#xA;|                       |&#xA;|                       R2 (5K)&#xA;|                       |&#xA;|                       |&#xA;|                       |&#xA;|                       v&#xA;|                     0.9V&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;In the above figure, no matter what Rdivider values I chose, it seems to me that Vdiv will not be Vin/2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I have to use an amplifier in the input for this case?&lt;/p&gt;&#xA;" OwnerUserId="2893" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-20T20:03:53.750" LastActivityDate="2011-03-20T20:03:53.750" Title="ADC input circuitry and source impedance" Tags="&lt;resistor&gt;&lt;adc&gt;&lt;impedance&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="9770" PostTypeId="2" ParentId="9769" CreationDate="2011-02-05T13:07:07.150" Score="2" ViewCount="" Body="&lt;p&gt;I'm sure you've already read this in the datasheet, but it just seems like the easiest solution. They recommend driving the input with a &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/MAX4430-MAX4433.pdf&quot; rel=&quot;nofollow&quot;&gt;MAX4431&lt;/a&gt; (SOT23-5 package). &lt;/p&gt;&#xA;" OwnerUserId="721" LastActivityDate="2011-02-05T13:07:07.150" CommentCount="2" />
  <row Id="9771" PostTypeId="2" ParentId="9751" CreationDate="2011-02-05T13:36:35.643" Score="5" ViewCount="" Body="&lt;p&gt;Those three different types of ground (grass, sand and tarmac) will be predominantly three different colours - green, yellow and black. Simple light sensors and appropriate colour filters might work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just remembered an aid for the blind that was developed many years ago, based on sonar. The person swept the sound source backwards and forwards in front of him or her, and was able to detect obstacles from the returned signal. It was possible for different textures to be detected, such as grass and leaves. I looked up sonar and texture on Google and found &lt;a href=&quot;http://www.sciencedirect.com/science?_ob=ArticleURL&amp;amp;_udi=B6V16-4F973GT-1&amp;amp;_user=10&amp;amp;_coverDate=04%2F30%2F2005&amp;amp;_rdoc=1&amp;amp;_fmt=high&amp;amp;_orig=search&amp;amp;_origin=search&amp;amp;_sort=d&amp;amp;_docanchor=&amp;amp;view=c&amp;amp;_searchStrId=1631696163&amp;amp;_rerunOrigin=google&amp;amp;_acct=C000050221&amp;amp;_version=1&amp;amp;_urlVersion=0&amp;amp;_userid=10&amp;amp;md5=90ca5c0377e5349bd40d5b72948494c1&amp;amp;searchtype=a&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;. It looks as though the technique is suitable for detecting terrain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both techniques could be used, with some form of sensor fusion, to maximise the probability of a correct identification.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-06T11:33:17.613" LastActivityDate="2011-02-06T11:33:17.613" CommentCount="5" />
  <row Id="9772" PostTypeId="1" AcceptedAnswerId="10630" CreationDate="2011-02-05T18:58:26.223" Score="2" ViewCount="359" Body="&lt;p&gt;I'm looking for a battery solution for the Beagleboard XM, which requires a 5V power supply. I currently have a simple 4x1.2V AA battery pack, but I'm not particularly satisfied with it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) It gets overcharged (~5.2V) and activates the overvoltage detector of the machine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) I have to remove the batteries from the pack to put them on a charger every time I need to charge them. I'd much prefer a solution that with no separate parts and one in which you don't need to move the batteries around.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.liquidware.com/shop/show/GL000149/BeagleJuice&quot; rel=&quot;nofollow&quot;&gt;BeagleJuice&lt;/a&gt; is the closest thing I've found to what I'm looking for, but there's no version out for XM yet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm embarrassingly electronics-illiterate, so I don't really know how to go about this. Any help?&lt;/p&gt;&#xA;" OwnerUserId="2883" LastEditorUserId="2883" LastEditorDisplayName="" LastEditDate="2011-02-05T19:11:18.363" LastActivityDate="2011-02-24T03:33:26.457" Title="Battery-powering up a Beagleboard XM" Tags="&lt;battery&gt;&lt;beagleboard&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="9773" PostTypeId="1" AcceptedAnswerId="9797" CreationDate="2011-02-05T21:35:32.367" Score="1" ViewCount="108" Body="&lt;p&gt;I'm going through the stock Lego Mindstorms projects and I've found that when I duplicate the NXT-G program in NXC that the compiled RXE binary is usually smaller by several factors, sometimes only 3x or 4x but sometimes as much as 10x. For example, NXT-G version of the Color Sorter-step 4 binary is 15,744 bytes while the equivalent in NXC is 4,124 bytes (no NBC optimizations; the Z2 flag drops ~100 bytes while my code reorganization drops the size to 2,548 bytes).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What causes the NXT-G bloat? Is there additional error checking or other important logic that my NXC version might be missing?  Or is there some way to turn on optimizations in NXT-G?&lt;/p&gt;&#xA;" OwnerUserId="2260" LastEditorUserId="1217" LastEditorDisplayName="" LastEditDate="2011-02-07T02:46:17.337" LastActivityDate="2011-02-07T02:46:17.337" Title="Why are NXT-G programs for the Lego Mindstorms NXT so bloated compared to their NXC counterparts?" Tags="&lt;lego-mindstorms&gt;&lt;nxc&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="9774" PostTypeId="1" AcceptedAnswerId="9775" CreationDate="2011-02-05T21:44:49.137" Score="4" ViewCount="120" Body="&lt;p&gt;I am using a microcontroller (PIC32) with a USB interface. The USB interface will be often exposed to human body ESD discharges. Should I protect against these, and if so, how?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-09T19:52:08.403" Title="USB ESD protection" Tags="&lt;usb&gt;&lt;esd&gt;" AnswerCount="2" FavoriteCount="4" />
  <row Id="9775" PostTypeId="2" ParentId="9774" CreationDate="2011-02-05T21:58:00.293" Score="4" ViewCount="" Body="&lt;p&gt;USB pins need protection from ESD. &lt;a href=&quot;http://www.semtech.com/images/promo/Protecting_USB_Ports_from_ESD_Damage.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is one solution using TVS devices.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-05T21:58:00.293" />
  <row Id="9776" PostTypeId="2" ParentId="9774" CreationDate="2011-02-05T22:00:21.230" Score="2" ViewCount="" Body="&lt;p&gt;I have found this to be a good article that explains ESD protection: &lt;a href=&quot;http://focus.ti.com/lit/ml/sszb130a/sszb130a.pdf&quot; rel=&quot;nofollow&quot;&gt;System-Level ESD/EMI&#xA;Protection Guide&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-02-09T19:52:08.403" LastActivityDate="2011-02-09T19:52:08.403" />
  <row Id="9777" PostTypeId="1" AcceptedAnswerId="9780" CreationDate="2011-02-05T22:51:16.020" Score="4" ViewCount="220" Body="&lt;p&gt;How do constant current power supplies work? For example I have a power supply that is constant voltage that can supply up to 5A and I have a 12V motor that takes ~500mA so I crank up the supply to 12v and my motor pulls ~500mA from the supply. But how does this work for a constant current power supply? Would it determine its own voltage output depending on the resistance of the load(ohms law)?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-02-06T03:43:08.167" Title="How do constant current power supplies work?" Tags="&lt;power-supply&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="9778" PostTypeId="1" CreationDate="2011-02-05T22:57:08.457" Score="2" ViewCount="86" Body="&lt;p&gt;I'm using a PIC24F to interface with an SD card in SPI mode. When the card is idle, the device still draws &lt;strong&gt;~200 uA&lt;/strong&gt; of current which is unacceptable for this device's purpose. To correct this, I am using a bit-enabled Linear Regulator (NCP694H33HT1GOSCT-ND) to kill power to the SD card's power rail. However, the leakage current remained at &lt;strong&gt;~200 uA&lt;/strong&gt; even when the SD card's power was cut off. Then I realized that upon physically disconnecting the wires for the SPI clock and Data In to the SD card from the PIC, the current drops down to &lt;strong&gt;~10 uA&lt;/strong&gt;, which is very acceptable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I am assuming that power is somehow leaking through the PIC24F and the signal lines to the SD card. I have tried reconfiguring those pins as digital outputs set to 0 and as digital inputs, but neither methods have had the same results as physically disconnecting those two lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there something I'm missing here? I would think that being set as a digital inputs would result in those pins becoming high impedance and thus blocking out the excessive leakage current, but it doesn't seem to be working. Any help would be appreciated.&lt;/p&gt;&#xA;" OwnerUserId="2895" LastActivityDate="2011-02-06T14:32:57.393" Title="Leakage current for an SD card host" Tags="&lt;pic&gt;&lt;current&gt;&lt;sd&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="9779" PostTypeId="2" ParentId="9769" CreationDate="2011-02-05T23:09:38.197" Score="2" ViewCount="" Body="&lt;p&gt;Yes, from the datasheet:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Due to the analog input resistive divider formed by R1&#xA;  and R2 in Figure 5, any significant analog input source&#xA;  resistance (R SOURCE) results in gain error. Furthermore, R SOURCE causes distortion due to nonlinear&#xA;  analog input currents. Limit RSOURCE to a maximum&#xA;  of 100Ω.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So practically, this means you need to drive the input with an amplifier.  Although, a resistor divider made with a 192 Ω and 200 Ω resistor will meet specs if your signal has a low output impedance.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-02-09T19:52:40.890" LastActivityDate="2011-02-09T19:52:40.890" CommentCount="7" />
  <row Id="9780" PostTypeId="2" ParentId="9777" CreationDate="2011-02-05T23:20:54.933" Score="3" ViewCount="" Body="&lt;p&gt;The simplest constant current supply is a large value resistor in series with a much smaller load resistance. Suppose we have a 12V supply to a 1k resistor in series with a 10R resistor: the current flowing through the load will be 12/1010 amps or 11.88 mA. If the load is 20R, the current will be 11.76 mA. It's almost the same although the load resistance has been doubled. The voltage across the load has been doubled, in the second case, keeping the current at about the same value.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-05T23:54:07.167" LastActivityDate="2011-02-05T23:54:07.167" />
  <row Id="9781" PostTypeId="1" AcceptedAnswerId="9788" CreationDate="2011-02-05T23:32:34.533" Score="1" ViewCount="71" Body="&lt;p&gt;Can you point me some technical resources on how cdrom works and is it possible or lets say how easy to make a diy cdrom ? I am interested in reading and processing raw data from cd, not using a chip to decode EFM etc.&lt;/p&gt;&#xA;" OwnerUserId="2891" LastActivityDate="2011-02-06T02:44:55.147" Title="reading raw data from a cdrom" Tags="&lt;laser&gt;" AnswerCount="1" />
  <row Id="9782" PostTypeId="2" ParentId="9777" CreationDate="2011-02-05T23:45:18.667" Score="4" ViewCount="" Body="&lt;p&gt;Typically it would measure the current using a resistor and regulate the voltage so that the current is the desired value (i.e. doesn't exceed it).&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-02-05T23:45:18.667" CommentCount="1" />
  <row Id="9783" PostTypeId="2" ParentId="9777" CreationDate="2011-02-06T00:08:55.773" Score="4" ViewCount="" Body="&lt;p&gt;The short answer is yes.  The CC supply will output as much voltage as necessary to generate the current.  So a 100 ohm load will have twice the voltage across it as a 50 ohm load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, the CC supply will not be able to increase output voltage forever, just as a CV supply cannot increase output current above a certain limit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A CV supply will supply more power as the load resistance gets smaller, but a CC supply will supply more power as the load resistance gets larger.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-06T00:08:55.773" />
  <row Id="9784" PostTypeId="1" AcceptedAnswerId="9787" CreationDate="2011-02-06T01:13:22.857" Score="3" ViewCount="164" Body="&lt;p&gt;What would be the average speed (an experienced) person would assemble surface mount components on to a PCB?  Assuming they have desk that is correctly set up (pick and place station) and the PCB has solder paste already applied.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reason for the question:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pick and place machines talk about components per hour (CPM) speed, interested to know how to compare this against a person. Looking into doing small runs (100 units) of a product, need to determine if I hire staff or purchase a small scale pick and place machine instead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know Sparkfun say they do this sort of work by hand, but I have a part count of 90! &lt;/p&gt;&#xA;" OwnerUserId="2896" LastActivityDate="2011-02-06T18:10:44.847" Title="what is an average CPH speed for hand SMD assembly?" Tags="&lt;surface-mount&gt;&lt;assembly&gt;&lt;pcb-assembly&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="9785" PostTypeId="2" ParentId="9741" CreationDate="2011-02-06T01:18:13.520" Score="2" ViewCount="" Body="&lt;p&gt;Do you have a '.ucf' (= user constraints file) as part of your project? Pin assignments are defined there. Something like&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;NET &quot;some_net&quot; LOC=&quot;F3&quot;;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;means that the net &quot;some_net&quot; is connected to pin &quot;F3&quot;. You can change these entries so that nets connect to other pins, &lt;em&gt;though you must be careful&lt;/em&gt;. If you're targeting a particular board, every pin will be connected to something, and you don't want to cause contention (by assigning a 0/ground/low to a pin that's connected to 5 V, for example). Also, there are banking rules that you must adhere to, etc.&lt;/p&gt;&#xA;" OwnerUserId="2531" LastActivityDate="2011-02-06T01:18:13.520" />
  <row Id="9786" PostTypeId="2" ParentId="9784" CreationDate="2011-02-06T01:21:41.147" Score="5" ViewCount="" Body="&lt;p&gt;Small runs like that are best sub-contracted. &lt;a href=&quot;http://www.asktechnology.co.uk/About%20ASK.htm&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a company I use.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-06T01:26:59.693" LastActivityDate="2011-02-06T01:26:59.693" />
  <row Id="9787" PostTypeId="2" ParentId="9784" CreationDate="2011-02-06T02:14:58.373" Score="4" ViewCount="" Body="&lt;p&gt;When soldering is done by hand there are lots of aspects that factor into how fast it can be done. Here are the largest factors for me when I am soldering:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The pitch of the components. I have this cover both IC pitch and 2 pin size. The smaller they are the slower the human has to go to get it set properly.&lt;/li&gt;&#xA;&lt;li&gt;Through Hole components or SMD or both? Through hole components will actually take a lot more time to solder in my experience.&lt;/li&gt;&#xA;&lt;li&gt;How closely spaced the components are. Humans will always make mistakes and the closer the parts are together the harder it will be to fix them. Also the closer they are together the more likely a slip of the hand will cause another component to get hit and have to be fixed.&lt;/li&gt;&#xA;&lt;li&gt;How organized the parts and documents of assembly are. This one is pretty clear, if it is hard to figure what to put where it is going to take longer.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In general though, I would say it takes me about 45 seconds per part to place the parts on the board. The board can then be baking while more boards are assembled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where you have to be careful in time estimating is the time it will take to check for shorts and fix them. There will be errors, maybe just a couple out of the whole batch, but there will need to be more testing time when soldered by hand.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-06T02:14:58.373" />
  <row Id="9788" PostTypeId="2" ParentId="9781" CreationDate="2011-02-06T02:44:55.147" Score="1" ViewCount="" Body="&lt;p&gt;Maybe you will get direct links in other answers. I'd suggest googling for the particular components of a CD drive: CD focus, tracking, decoding, etc...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An even better method is probably to open a CD player (preferably an Audio CD because of low data rates) and to look at the signals using a scope. I have even done this with hard disks and it is pretty informative.&lt;/p&gt;&#xA;" OwnerUserId="1950" LastActivityDate="2011-02-06T02:44:55.147" CommentCount="2" />
  <row Id="9789" PostTypeId="1" CreationDate="2011-02-06T03:43:00.730" Score="6" ViewCount="93" Body="&lt;p&gt;Where is collection of data sheets of large table with parameters as columns and models as rows?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Model        Breakdown_voltage On_resistance &amp;lt;other_values&amp;gt;&#xA;QWERTY122AS  120V              6_Ohm         ....&#xA;AWERTY123SD  30V               1_Ohm         ....&#xA;&amp;lt;all other popular models&amp;gt;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;for transistors, diodes and other parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When searching Google it usually provides data for one/few models or even offer download a PDF file. Where to find it in bulk?&lt;/p&gt;&#xA;" OwnerUserId="2898" LastActivityDate="2011-03-16T19:00:35.040" Title="Where to find datasheets in bulk?" Tags="&lt;datasheet&gt;" AnswerCount="3" />
  <row Id="9790" PostTypeId="2" ParentId="9777" CreationDate="2011-02-06T03:43:08.167" Score="3" ViewCount="" Body="&lt;p&gt;A simple model of a real current source is an ideal source I_S in parallel with an internal resistance R_S. The current and voltage at the load R_L is as follows:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;I_L = R_S/(R_S + R_L) * I_S&#xA;&#xA;and&#xA;&#xA;V_L = R_L*I_L&#xA;    = R_S*R_L/(R_S + R_L) * I_S&#xA;    = (R_S // R_L) * I_S         &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;As long as the load resistance R_L is much smaller than the internal resistance R_S, the load receives most of I_S. In this case the equivalent resistance of R_S in parallel with R_L is approximately R_L, and the source voltage is approximately &lt;code&gt;I_S*R_L&lt;/code&gt;.  In the extremely non-ideal case, the load resistance R_L is much larger than the source resistance R_S, and the load current I_L is then approximately zero. Also, the equivalent resistance in this case is approximately R_S, so the source voltage reaches its maximum of &lt;code&gt;I_S*R_S&lt;/code&gt;. To make a current source as ideal as possible, it needs a large internal resistance to be able to source a high voltage.&lt;/p&gt;&#xA;" OwnerUserId="721" LastActivityDate="2011-02-06T03:43:08.167" />
  <row Id="9791" PostTypeId="2" ParentId="9789" CreationDate="2011-02-06T04:11:19.853" Score="6" ViewCount="" Body="&lt;p&gt;Octopart has an API.  That will give you the PDF's in bulk, subject to rate limits.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-06T04:11:19.853" />
  <row Id="9792" PostTypeId="1" AcceptedAnswerId="9809" CreationDate="2011-02-06T04:21:55.610" Score="2" ViewCount="179" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to replace a plug on a mains powered device.  It uses a specialised connector (to make it difficult for hobbyists, I guess) so I want to replace it with a standard mains plug.  Unfortunately the cable connects to the PCB using some kind of spade/Faston connector, but there are millions of different variants of these and I have no idea which parts to buy!  Does anyone know what it might be, from the photo below?  It's kind of hard to get a good view, so let me know if a particular angle would help.  The plastic cover is 9mm wide, and the metal receptacle is about 7mm wide.  The device is rated at 24A, so I'm not sure if that means there is a special high-power variant needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Juyr3.jpg&quot; alt=&quot;In housing&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/Ks5Fc.jpg&quot; alt=&quot;Alternate view&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="548" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-07T15:01:56.213" LastActivityDate="2011-02-07T15:01:56.213" Title="What kind of spade connector is this?" Tags="&lt;connector&gt;" AnswerCount="1" CommentCount="5" FavoriteCount="1" />
  <row Id="9793" PostTypeId="2" ParentId="9757" CreationDate="2011-02-06T05:36:07.607" Score="1" ViewCount="" Body="&lt;p&gt;Most people think of this in two layers of abstraction, the logic gate layer and the transistor layer.&#xA;To minimize total transistor count, you need to (a) minimize the number of logic gates, and (b) minimize the number of transistors per gate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might get some ideas for (a) at &lt;a href=&quot;http://en.wikipedia.org/wiki/flip-flop_%28electronics%29&quot; rel=&quot;nofollow&quot;&gt;Wikipedia: flip-flop&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For (b), my understanding is that &lt;a href=&quot;http://en.wikipedia.org/wiki/resistor%E2%80%93transistor_logic&quot; rel=&quot;nofollow&quot;&gt;resistor–transistor logic&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/integrated_injection_logic&quot; rel=&quot;nofollow&quot;&gt;integrated injection logic&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/DTL&quot; rel=&quot;nofollow&quot;&gt;diode-transistor logic&lt;/a&gt; uses fewer components per logic gate than other logic families.&#xA;In order of number of components:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You can make a 4-input NOR gate out&#xA;of 4 n-channel FETs and a single&#xA;resistor (5 components) with one&#xA;style of RTL, which requires 2 power&#xA;supply rails.&lt;/li&gt;&#xA;&lt;li&gt;You can make a 4-input NOR gate out&#xA;of 6 carefully-chosen resistors and a single&#xA;transistor (7 components) with another&#xA;style of RTL (&quot;threshold logic&quot;), but&#xA;it requires 3 power supply rails.&lt;/li&gt;&#xA;&lt;li&gt;You can make a 4-input NOR gate out&#xA;of 6 diodes, 3 resistors, and a&#xA;single transistor (10 components)&#xA;with one style of DTL, which requires&#xA;2 power supply rails.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Have you seen &quot;The Transistor Clock&quot;?&#xA;It's on &lt;a href=&quot;http://www.youtube.com/watch?v=BwWuAasua74&quot; rel=&quot;nofollow&quot;&gt;Youtube&lt;/a&gt; and &lt;a href=&quot;http://blog.makezine.com/archive/2008/06/transistor-clock-kit-uses.html&quot; rel=&quot;nofollow&quot;&gt;Make Magazine&lt;/a&gt; and the &lt;a href=&quot;http://www.transistor-clock.com/&quot; rel=&quot;nofollow&quot;&gt;transistor clock web site&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;p.s.: Does anyone know what happened to the MT15 CPU, built out of individual discrete transistors?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-06T05:36:07.607" CommentCount="6" />
  <row Id="9794" PostTypeId="2" ParentId="9769" CreationDate="2011-02-06T06:56:58.630" Score="0" ViewCount="" Body="&lt;p&gt;How fast is your signal changing and how fast does your sample rate need to be?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a slow (DC) signal, you can add a capacitor between the divider resistors which will supply the sample capacitor as a capacitor's impedance is very low.  The capacitor just needs to be big enough to hold a steady voltage during the sample time.  This limits your bandwidth significantly though as you now have an RC filter.  It also limits your sample rate as sampling too fast can drain the capacitor.  It needs time to stabilize between samples, the larger the resistor values the longer this time.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-02-06T06:56:58.630" CommentCount="1" />
  <row Id="9795" PostTypeId="1" CreationDate="2011-02-06T10:11:37.960" Score="3" ViewCount="161" Body="&lt;p&gt;Really, I don't know whether this is the right place to ask this. Please move appropriately if not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having a thinclient manufactures by HP (t5720). Following specs are written on the power supply:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Input: 100-240V AC 50-60Hz   2.4A(2,4A)&lt;br&gt;&#xA;Output: 12V DC  4.16A(4,16A)&lt;br&gt;&#xA;Max Output: 50W&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to use the thin client in my car, but don't have any power supply for it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now my thoughts and questions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Do I even need some special transformation device as the supply's output is around 12V? The car has between 10.5 and 13 V, depending whether it's running or not. How tolerant is a device like such a thin client ? Could this actually damage the car?&lt;/li&gt;&#xA;&lt;li&gt;If  I actually need some transformation, how would it be?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;There are websites selling such transforming supplies. But some of them cost a lot of money and before buying something I would like to know whether I even need it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And I wouldn't want to just try it out and plug the thing before I know what could get damaged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've had some very basics about electronics but I can't estimate it&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help is appreciated. Regards&lt;/p&gt;&#xA;" OwnerUserId="2900" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-02-06T13:12:10.430" LastActivityDate="2011-02-06T18:25:39.513" Title="Powering Thinclient PC from Car's battery" Tags="&lt;power-supply&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="9796" PostTypeId="2" ParentId="9795" CreationDate="2011-02-06T11:44:18.820" Score="4" ViewCount="" Body="&lt;p&gt;It is very unlikely to damage the car, especially if it is properly fused (I'd fuse both leads), and should work OK as the nominal input is 12V. However, the car is a somewhat hostile environment for electronic equipment, because of the likelihood of high-voltage spikes on the 12V supply. I would use a suitable filter on the supply input to the unit, combined with transient voltage protection, in addition to the fuses. The units you mention would incorporate such protection, and it might be easier to simply buy one of them.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-06T11:44:18.820" CommentCount="2" />
  <row Id="9797" PostTypeId="2" ParentId="9773" CreationDate="2011-02-06T12:26:11.643" Score="1" ViewCount="" Body="&lt;p&gt;Well for a start, the Move blocks in NXT-G are much more complicated thatn you might think. There was a post about this on the &lt;a href=&quot;http://forums.nxtasy.org&quot; rel=&quot;nofollow&quot;&gt;NXTasy.org forums&lt;/a&gt;, but unfortunately the forums have since been lost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In terms of optimization in NXT-G, the closest you can get is using the mini-blocks. There's an outdated blog post about them &lt;a href=&quot;http://thenxtstep.blogspot.com/2006/11/introducing-minblocks.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1217" LastActivityDate="2011-02-06T12:26:11.643" />
  <row Id="9798" PostTypeId="2" ParentId="9795" CreationDate="2011-02-06T14:08:14.407" Score="3" ViewCount="" Body="&lt;p&gt;You're probably better off getting an inexpensive automotive inverter to bring the automotive DC up to 120VAC, then using an appropriately-rated AC/DC power supply to generate the 12V you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Automotive DC can be very dirty due to the mechanical nature of how it is generated and the non-ideal load characteristics of the rest of the car. Boosting to 120VAC first should help avoid any brown-out issues, plus the inverter will have appropriate protections (fusing/TVS). It should not be hard to find a 12V/5A power supply for the thin client.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-06T14:08:14.407" CommentCount="9" />
  <row Id="9799" PostTypeId="2" ParentId="9778" CreationDate="2011-02-06T14:32:57.393" Score="1" ViewCount="" Body="&lt;p&gt;I believe your assumption is correct in that the card is leaking current from the signal lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Did you ensure that the PIC did not have its weak pull-ups active when you modified the port settings?&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-06T14:32:57.393" CommentCount="5" />
  <row Id="9800" PostTypeId="2" ParentId="9772" CreationDate="2011-02-06T15:32:04.333" Score="1" ViewCount="" Body="&lt;p&gt;You should buy a Li-on Battery pack which will suffice Beagle needs.&#xA;They are the best batteries i have worked with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To charge it, you will need a &quot;Li-ion charger&quot; (DO NOT CHARGE THEM with a normal DC Power Supply), which are cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards,&#xA;Aadeesh&lt;/p&gt;&#xA;" OwnerUserId="2903" LastActivityDate="2011-02-06T15:32:04.333" CommentCount="1" />
  <row Id="9801" PostTypeId="1" CreationDate="2011-02-06T17:37:08.843" Score="1" ViewCount="97" Body="&lt;p&gt;I'm not so good when it comes the analogue end of electronics. My microcontroller has 0-3v inputs and I'm trying to get together a range conditioning circuits. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this I a reasonably broad question as the analogue design will depend on a lot of other factors, but are there any reference designs around for the following:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Analogue 0-3 volt&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now there'll need to be some over voltage protection and something for voltage spikes, but will that do?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Analogue 0-30 volt&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I just use a resistor divider with some 1% resistors and hope for the best?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Digital 0-x volts&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess here I'd be best to use an 'opto' based device that supports the required frequency?&lt;/p&gt;&#xA;" OwnerUserId="2770" LastActivityDate="2011-02-06T18:48:22.753" Title="Reference Designs for Analogue &amp; Digital Inputs to Microcontroller" Tags="&lt;microcontroller&gt;&lt;analog&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9802" PostTypeId="2" ParentId="9784" CreationDate="2011-02-06T18:03:12.033" Score="1" ViewCount="" Body="&lt;p&gt;Agree with Leon, for this number of units.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the product and margins, it can still be economical to contract out at 1000+.&#xA;The big contract manufacture companies (who generally also manufacture PCB's) can source your components at cheaper prices than you. We've even had them suggest changes that can cut costs from a product. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You agree prices at various price breaks and then place orders when you want. If you want, they'll even conduct the required tests, box-up and ship products straight to customers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This all obviously has associated costs, but when you factor in the time for procurement, managing the manufacturing, testing and logistics and delivery, you'll struggle to come close to their prices. That is what these companies specialise in after all!&lt;/p&gt;&#xA;" OwnerUserId="2770" LastActivityDate="2011-02-06T18:03:12.033" CommentCount="1" />
  <row Id="9803" PostTypeId="2" ParentId="9784" CreationDate="2011-02-06T18:10:44.847" Score="2" ViewCount="" Body="&lt;p&gt;I've had a little job at an internship of soldering 250 small boards. It consisted of about 3 resistors, 1 SOT23, 1 chip and 1 capacitor (all SMD). It took a total of about 3 work days (x7 hours) to assemble them. Doing it by a company was expensive (very small run - only 1500 components) and we were interns, so you know how things work out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That was about 12 boards per hour, but I am not an incredible good/fast solderer either. So expect 45 - 1 minute per component. Note that the chip was only a 6 pin device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless you have a board that consists of 25x resistors of the same value right next to each other, it sounds that 9000 components is going to take you at least 10 workdays. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can hardly imagine that sparkfun does their work by hand. It only is worth it in China when loans are a few dollars per hour. If you need to pay someone in a company environment and costs $10 - $15 per hour (which is cheap I suppose), that's still 15 - 20cts per component added.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-02-06T18:10:44.847" CommentCount="5" />
  <row Id="9805" PostTypeId="2" ParentId="9795" CreationDate="2011-02-06T18:25:39.513" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://cds.linear.com/docs/Solutions%20Manual/Automotive_Electronics_Solutions.pdf&quot; rel=&quot;nofollow&quot;&gt;Linear Technology&lt;/a&gt; has various parts and app note that will help.  But I agree with @Leon Heller that the environment is hostile.  I think he is understating it; you may see spikes up to 80 V.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-06T18:25:39.513" />
  <row Id="9806" PostTypeId="2" ParentId="9801" CreationDate="2011-02-06T18:48:22.753" Score="2" ViewCount="" Body="&lt;p&gt;This is a very general question and there are lots of app notes with reference designs for mixed signal boards. &quot;mixed signal&quot;, &quot;digital analog&quot;, &quot;design&quot; and &quot;ground&quot; are your keywords. In addition, usually every datasheet of a mixed signal controller or DAC contains a reference design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A common method for protecting analog inputs is a Z-Diode and a series resistor. You have to realize the overvoltage protection requirements and the DAC leakage current to calculate the series resistor value.&#xA;As you can see in &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2508.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/dyn/resources/prod_documents/doc2508.pdf&lt;/a&gt; a series resistor can protect an analog input even from mains voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, you can use a resistor divider for scaling an analog input. If the input resistance is too low, use an transistor/opamp as a voltage follower.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For digital inputs you can use resistor dividers/series resistors, too, which is the slowest of the mentioned methosd. For up to 15V you can use a 74HC4050 buffer. If it need to be really quick, you're probably better off with a dedicated level shifter IC.&lt;/p&gt;&#xA;" OwnerUserId="1950" LastActivityDate="2011-02-06T18:48:22.753" />
  <row Id="9807" PostTypeId="1" AcceptedAnswerId="9815" CreationDate="2011-02-06T18:50:19.633" Score="3" ViewCount="332" Body="&lt;p&gt;I'm building a CNC mill based on &lt;a href=&quot;http://buildyourcnc.com/default.aspx&quot; rel=&quot;nofollow&quot;&gt;Patrick Hood-Daniel's machines&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm also playing with Arduinos, and I'm beginning to wonder if I have this right:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have 5v 1A steppers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll be using &lt;a href=&quot;http://linuxcnc.org/&quot; rel=&quot;nofollow&quot;&gt;EMC2&lt;/a&gt; (Linux-based CNC) to run the whole thing and I had intended to feed the output from the Ubuntu box that's running EMC2 into an Arduino that then splits the data and sends it to three stepper drivers, probably built with sn754410ne h-bridges. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had thought of possibly building the controllers with an ATtiny2313 per motor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this overkill? Is the Arduino even required or can I feed the h-bridges directly from the EMC2 output?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My main worries are that the Arduino won't be able to control three motors concurrently, although there is a new library available: &lt;a href=&quot;http://www.open.com.au/mikem/arduino/AccelStepper/&quot; rel=&quot;nofollow&quot;&gt;http://www.open.com.au/mikem/arduino/AccelStepper/&lt;/a&gt; that purports to achieve this, and also that I won't be able to get half-stepping (or finer) with this setup.&lt;/p&gt;&#xA;" OwnerUserId="2894" LastActivityDate="2011-02-07T04:19:40.373" Title="EMC2, Arduino &amp; stepper motors - Have I got this right?" Tags="&lt;arduino&gt;&lt;stepper&gt;&lt;cnc&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="9808" PostTypeId="1" CreationDate="2011-02-06T19:51:25.323" Score="3" ViewCount="200" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to make a wrist mounted button pusher, connected to a timer that can be programmed with a routine to push buttons at specific times accurate to a millisecond. I've been told I could use a micro-controller and a servo motor to do this, but I don't know enough about electronics to find a controller I could program or a motor that would be accurate to a millisecond.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First: Is this even possible?&#xA;Is this the best way to approach this?&#xA;Where can I find the materials I need and learn how to put it together?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help/tips would be greatly appreciated! &lt;/p&gt;&#xA;" OwnerUserId="2905" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T22:14:52.663" LastActivityDate="2011-04-27T22:14:52.663" Title="Automatic Button Pushing Device Hardware" Tags="&lt;hardware&gt;" AnswerCount="2" CommentCount="11" />
  <row Id="9809" PostTypeId="2" ParentId="9792" CreationDate="2011-02-06T19:56:07.610" Score="4" ViewCount="" Body="&lt;p&gt;There's generally only two important variables in spade connectors:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;strong&gt;Blade&lt;/strong&gt; (not socket) width (the thickness may vary as well, but it should be prescribed by whatever the width is), &lt;/li&gt;&#xA;&lt;li&gt;and if it's on a wire (versus a board), wire gauge it accepts.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Measure the blade width (I've only ever seen them specified in inch sizes, 0.187, 0.250...), and see if there's a good match on some parts catalogs (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1442842&quot; rel=&quot;nofollow&quot;&gt;here's&lt;/a&gt; the Digi-Key category).  After that, pick the one that fits a wire gauge that will safely carry your current.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-07T05:47:45.183" LastActivityDate="2011-02-07T05:47:45.183" CommentCount="1" />
  <row Id="9810" PostTypeId="2" ParentId="8608" CreationDate="2011-02-06T20:20:50.057" Score="1" ViewCount="" Body="&lt;p&gt;have you looked at the PSP screen? it's 24bit parallel.&#xA;&lt;br /&gt; Where did you find the lcd controller? I looked for a long time for one that works with 24 bit parallel.&lt;/p&gt;&#xA;" OwnerUserId="2906" LastActivityDate="2011-02-06T20:20:50.057" CommentCount="1" />
  <row Id="9811" PostTypeId="1" CreationDate="2011-02-06T23:35:14.750" Score="3" ViewCount="61" Body="&lt;p&gt;I am making a water fountain feature and want to install a changing colour display that is variable in a laminar water jet.  The unit has to be stand alone and start when the power is applied.  The fountain is in the middle of a dam and is connected by a utility supply.  Will the BlinkM MaxM do. I am able to do basic electronics and was hoping that this unit is suitable for the job.  I am attaching acrylic rod to the LEDs as a light transmitter and this is insert into the water stream. I need bright LEDs. Can you recommend the electronics required for the job.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doug &lt;/p&gt;&#xA;" OwnerUserId="2908" LastEditorUserId="1831" LastEditorDisplayName="" LastEditDate="2011-05-07T01:30:15.663" LastActivityDate="2011-05-07T01:30:15.663" Title="Water feature using a BlinkM MaxM led" Tags="&lt;power&gt;&lt;blinkm&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="9812" PostTypeId="2" ParentId="9789" CreationDate="2011-02-07T00:12:28.263" Score="4" ViewCount="" Body="&lt;p&gt;Digikey/Mouser parametric search is probably the most useful tool for finding data on a part based on parameters, assuming that's what you want to do&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-07T00:12:28.263" />
  <row Id="9813" PostTypeId="1" AcceptedAnswerId="9818" CreationDate="2011-02-07T02:41:39.260" Score="4" ViewCount="106" Body="&lt;p&gt;I'm an electronics newbie, and recently purchased empty PCBs for GoodFET and Ubertooth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While trying to put together an order for all the parts in the bill of materials, I realized I'd very much like to have a computer parseable format I could dump into a parts search engine like octopart.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I started hacking up a simple website to do this using the octopart API but I can't find any sort of xml standard for a BoM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone heard of such a thing? I'd be particularly interested in some sort of standard format that's available from gEDA, EagleCAD, etc&lt;/p&gt;&#xA;" OwnerUserId="1650" LastActivityDate="2011-02-07T14:36:52.163" Title="Is there a text or markup standard for describing a Bill of Materials?" Tags="&lt;bom&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="9814" PostTypeId="2" ParentId="9811" CreationDate="2011-02-07T02:43:43.437" Score="1" ViewCount="" Body="&lt;p&gt;the &lt;a href=&quot;http://thingm.com/products/blinkm-maxm.html&quot; rel=&quot;nofollow&quot;&gt;BlinkM maxm&lt;/a&gt; would be work well, but just remember you have to have a way to program it, with an Arduino or a &lt;a href=&quot;http://thingm.com/products/linkm.html&quot; rel=&quot;nofollow&quot;&gt;usb programmer&lt;/a&gt; . the only other thing you would need would be a way to power it at the correct voltage.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-07T02:43:43.437" />
  <row Id="9815" PostTypeId="2" ParentId="9807" CreationDate="2011-02-07T04:19:40.373" Score="1" ViewCount="" Body="&lt;p&gt;I would choose the more modular support, with that ATtinys running the motors, with the ATtiny you could add extra features like position, or encoder data, emegency start/stop and other features. As for the main control unit, the arduino may be under powered for fast work but it is possible. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;you may want to also look at the &lt;a href=&quot;http://reprap.org/&quot; rel=&quot;nofollow&quot;&gt;Reprap project&lt;/a&gt; for more idea for hardware. another resource that may help is the &lt;a href=&quot;http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?EMC2_Supported_Hardware&quot; rel=&quot;nofollow&quot;&gt;emc2 supported hardware&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;you would not be able to hook up emc2 right to the steppers with out have some sort control module.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-07T04:19:40.373" CommentCount="3" />
  <row Id="9816" PostTypeId="2" ParentId="9381" CreationDate="2011-02-07T04:49:22.203" Score="2" ViewCount="" Body="&lt;p&gt;For 6mm2 copper (~1.4mm radius), the skin effect impacts the wire at ~2.5kHz.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your 2ms pulse is equivalent to a 0.25kHz square wave.  Mathematically, that square&#xA;wave is a sum of all the odd-multiple sine waves (0.25kHz, 0.75khz, 1.25khz, etc).  Since the skin effect drastically reduces frequencies above 2.5khz (more as the&#xA;frequency goes higher), you're creating an imperfect square wave (aka slowing down the ramp-up and ramp-down times of your pulse).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, the rise-time on an &quot;ideal&quot; 2ms pulse will get slowed to maybe 80uS.  This assumes&#xA;you're able to generate 500A pulses with very high rise times in the first place.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And yes, having stranded cable (20 tiny wires), does make this a small bit worse, but&#xA;not much.  As one other poster suggested, litz wire (http://en.wikipedia.org/wiki/Litz_wire) helps for 100kHz+ applications by providing many &lt;em&gt;insulated&lt;/em&gt; tiny wires.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ref: &lt;a href=&quot;http://www.marcspages.co.uk/pq/3250.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.marcspages.co.uk/pq/3250.htm&lt;/a&gt;              (Skin Depth Tables)&#xA;     &lt;a href=&quot;http://www.nessengr.com/techdata/skin/skindepth.html&quot; rel=&quot;nofollow&quot;&gt;http://www.nessengr.com/techdata/skin/skindepth.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2909" LastActivityDate="2011-02-07T04:49:22.203" CommentCount="2" />
  <row Id="9817" PostTypeId="1" CreationDate="2011-02-07T06:44:00.563" Score="3" ViewCount="521" Body="&lt;p&gt;How to convert an SOP expression to POS form and vice versa in Boolean Algebra?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Eg: F = xy' + yz'&lt;/p&gt;&#xA;" OwnerUserId="2912" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-07T10:25:41.057" LastActivityDate="2011-06-02T02:56:12.423" Title="How to convert an expression from SOP to POS and back in Boolean Algebra?" Tags="&lt;logic&gt;" AnswerCount="3" CommentCount="8" />
  <row Id="9818" PostTypeId="2" ParentId="9813" CreationDate="2011-02-07T07:45:11.743" Score="4" ViewCount="" Body="&lt;p&gt;I don't think there is a standard, but that doesn't mean that you can't make one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've written my own part searcher for EAGLE and Kicad which loads a bom from EAGLE or the parts list from kicad, produces search URLs for my preferred supplier and accepts SKUs in return.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'd do is to specify an xml format to hold the BOM and write a bunch of converters that can produce that format.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My eagle and kicad scripts are here:&#xA;&lt;a href=&quot;https://github.com/dren-dk/HAL900/tree/master/door-ctrl/kicad2elfa&quot; rel=&quot;nofollow&quot;&gt;https://github.com/dren-dk/HAL900/tree/master/door-ctrl/kicad2elfa&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-02-07T07:45:11.743" />
  <row Id="9819" PostTypeId="1" CreationDate="2011-02-07T09:30:01.370" Score="8" ViewCount="294" Body="&lt;p&gt;In my schematic, I have 4 SPI devices to hook together. I am going to operate the SPI up to 8MHz. Should I be concerned with installing damping resistors? source termination resistors? Should I route them in a star formation, or in a serial fashion? Does adding lots of vias hurt the signal integrity?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also have to add that these devices are quite close together, within 25mm of each other.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-02-08T03:55:17.603" Title="How should I route SPI lines?" Tags="&lt;spi&gt;&lt;pcb-design&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="9820" PostTypeId="1" CreationDate="2011-02-07T10:56:36.297" Score="4" ViewCount="162" Body="&lt;p&gt;I need to source some three-conductor (i.e. stereo) 3.5mm jacks with a DPDT switch (or two isolated SPDT switches), as illustrated below (type C). This type of switch has 9 contacts.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;C. This three-conductor jack has two&#xA;  isolated SPDT switches. They are&#xA;  activated by a plug going into the&#xA;  jack, which disconnects one throw and&#xA;  connects the other. The white&#xA;  arrowheads indicate a mechanical&#xA;  connection, while the black arrowheads&#xA;  indicate an electrical connection.&#xA;  This would be useful for a device that&#xA;  turns on when a plug is inserted, and&#xA;  off otherwise, with the power routed&#xA;  through the switches.  &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;em&gt;Source: Jack (connector) on Wikipedia&lt;/em&gt; &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OvzGD.png&quot; alt=&quot;Phone_jack_symbols.png&quot;&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So far I have only been able to find these:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://products.cui.com/categoryproducts.asp?brand=electronic-components&amp;amp;catky=619701&amp;amp;subcatky1=360287&amp;amp;subcatky2=749477&amp;amp;subcatky3=502193&quot; rel=&quot;nofollow&quot;&gt;CUI SJ-357X series and SJ-358X series&lt;/a&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The minimum order quantity from the manufacturer is 10k pieces. They referred me to DigiKey, who carry the &lt;a href=&quot;http://parts.digikey.com/1/parts/1761066-conn-jack-stereo-r-a-3-5mm-pcb-sj-3571n.html&quot; rel=&quot;nofollow&quot;&gt;SJ-3571N&lt;/a&gt; only. This has a MOQ of 3000 with an estimated next ship date in April. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is I only need 300 of these, so even DigiKey's MOQ is prohibitively expensive for me. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems like I won't get much better than this because the quantity is so low for such a specialised part, but I'd appreciate any suggestions.&lt;/p&gt;&#xA;" OwnerUserId="2914" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-07T11:24:15.437" LastActivityDate="2011-04-22T14:23:21.823" ClosedDate="2011-04-25T19:24:36.693" Title="DPDT stereo minijack suppliers?" Tags="&lt;audio&gt;&lt;switch&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="9821" PostTypeId="2" ParentId="9819" CreationDate="2011-02-07T11:53:34.163" Score="7" ViewCount="" Body="&lt;p&gt;From a signal integrity perspective, 8MHz isn't actually that fast so you can probably get away with any reasonable layout.  You might want to include termination resistors in the layout.  If you don't need them you can just install 0 ohm resistors and then leave them out in the next revision.  I would lay out (star versus serial) with whatever gives you the tighter layout (e.g. shorter traces).  Stubs are considered a bad thing for high speed layout, so I'd pick one or the other and not have some scheme where some parts are tied together serially and others are branched off from that.  When laying out in a serial fashion, keep the stubs off the main lines as short as possible.  Adding vias does hurt signal integrity, but as I mentioned, you most likely have such a large timing budget at 8Mhz that it does not matter.  The other question is, do you have a ground and power plane?  If so, you want to keep the signals referenced to the same plane (e.g. don't run the SCLK trace on one side of the board referenced to the ground plane and then via to the other side and run for a while referenced to the power plane).  You'll probably have to worry about EMC issues here long before you'll have to worry about signal integrity issues, but EMC may not be a concern for you project.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastEditorUserId="2377" LastEditorDisplayName="" LastEditDate="2011-02-08T03:55:17.603" LastActivityDate="2011-02-08T03:55:17.603" CommentCount="2" />
  <row Id="9822" PostTypeId="2" ParentId="9741" CreationDate="2011-02-07T12:04:51.043" Score="1" ViewCount="" Body="&lt;p&gt;If you double-click the Gateway block and click to the &quot;implementation&quot; tab, there's a box you can tick to &quot;Specify IOB location constraints&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can then enter something like this in the IOB pad locations box underneath:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;{'P22', 'P12'}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(if you have 2 bits, repeat as needed if you have more!).  This is for a leaded package with simple numbers on each pin.  If you're using a BGA device, the pins will be named alphanumerically.  It's explained quite well in the HELP for the Gateway blocks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can check this has worked by looking at the .pad file in the same directory as your .bit file was created - you should be able to find the IOBs named and see which pin they were mapped to.  (There's two versions of the pad file, one is a CSV file the other is a text table which looks fine in a monospaced font)&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-02-07T12:04:51.043" />
  <row Id="9823" PostTypeId="2" ParentId="9817" CreationDate="2011-02-07T14:16:24.910" Score="1" ViewCount="" Body="&lt;p&gt;If you want to check your work after doing it by hand you could use a program like &lt;a href=&quot;http://sontrak.com/downloads.html&quot; rel=&quot;nofollow&quot;&gt;Logic Friday&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-07T16:39:14.630" LastActivityDate="2011-02-07T16:39:14.630" />
  <row Id="9824" PostTypeId="1" AcceptedAnswerId="9826" CreationDate="2011-02-07T14:32:09.030" Score="5" ViewCount="318" Body="&lt;p&gt;Let's assume that the cost of goods is an insignificant factor.  If a company lacks a team to produce a custom board for a particular product, but has success with an off-the shelf development platform like Arduino / Netduino / mbed, what sorts of things should be considered before going forward?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I'm not mistaken, Arduino was originally targeting university students because of its low price and ease of use.  It naturally became a popular platform for artists and makers.  I see the Netduino as a logical extension of Arduino -- it allows people to use a robust and rich IDE (Visual Studio 2010) and get things done quickly via the .NET Micro Framework.  mbed is another nice hobbyist platform because of its ease of use, free tools (online compiler), and hardware peripherals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is, why shouldn't companies adopt these development platforms for production usage?  In other words, is it a bad idea to just buy several boards from Sparkfun, program each of them with the code, and then deploy the product to customers?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm specifically interested in Netduino, but arguments for / against Arduino and mbed are also welcome.  On the flip side, would you, or have you done this before?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I personally look at the Netduino development as a &quot;core module&quot; that other processor manufacturers sell for product integrations, but maybe I'm missing something important here.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-03-16T19:14:44.687" Title="What makes a particular platform suitable or unsuitable for production use?" Tags="&lt;arduino&gt;&lt;netduino&gt;&lt;mbed&gt;&lt;production&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="9825" PostTypeId="2" ParentId="9813" CreationDate="2011-02-07T14:36:52.163" Score="7" ViewCount="" Body="&lt;p&gt;What I've run across most often is .CSV files with user-customizable headings. I don't know of any more specific standard for BOMs.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-02-07T14:36:52.163" CommentCount="1" />
  <row Id="9826" PostTypeId="2" ParentId="9824" CreationDate="2011-02-07T14:59:06.887" Score="4" ViewCount="" Body="&lt;p&gt;Some of the things you might look at when sourcing a controller module are issue such as security of supply over time, any licensing issues, any inefficiencies in firmware loading process for production, any code security issues, and any manufacturing quality or regulatory compliance concerns.  Some of those are going to be more of a concern for a proprietary module than a relatively open one you could have someone else make an equivalent to or eventually merge with other functionality in your product.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastEditorUserId="2246" LastEditorDisplayName="" LastEditDate="2011-02-07T18:40:45.847" LastActivityDate="2011-02-07T18:40:45.847" CommentCount="4" />
  <row Id="9827" PostTypeId="2" ParentId="9789" CreationDate="2011-02-07T15:15:34.017" Score="3" ViewCount="" Body="&lt;p&gt;Many manufacturers have parametric tables available for each of their part classes, often available for export to .xls.  For example, &lt;a href=&quot;http://www.fairchildsemi.com/tree/power-management/mosfets/discrete-mosfets/&quot; rel=&quot;nofollow&quot;&gt;here's Fairchild's discrete MOSFET table&lt;/a&gt;.  If you want something very specific, that will probably be the way to go.  You could try compiling these tables.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Different manufacturers will characterize different parameters and use different test setups, so it would be hard to come up with a full list.  However, distributors are in exactly that business.  Either use the Digikey/Mouser search online, or download their catalogs. Digikey's is available as an interactive (downloadable) HTML &lt;a href=&quot;http://dkc1.digikey.com/us/en/pdf/Current.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, and Mouser's is &lt;a href=&quot;http://www.mouser.com/CatalogRequest/Catalog.aspx&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  Note that these documents are a couple hundred megabytes, and a couple thousand pages.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-07T15:15:34.017" CommentCount="1" />
  <row Id="9828" PostTypeId="2" ParentId="9819" CreationDate="2011-02-07T16:02:07.953" Score="3" ViewCount="" Body="&lt;p&gt;It depends on the edge rate.  If it is driven by a fast general-purpose chip, e.g. a FPGA, then you might care.  But at 25 mm you are ok unless the rise time is so very fast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As @bt2 said, vias hurt signal integrity, but I wouldn't worry about it at this distance.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-07T16:02:07.953" />
  <row Id="9829" PostTypeId="2" ParentId="7472" CreationDate="2011-02-07T16:12:04.013" Score="0" ViewCount="" Body="&lt;p&gt;See this link: &lt;a href=&quot;http://www.cosmiac.org/spartan3e_tutorials.html&quot; rel=&quot;nofollow&quot;&gt;http://www.cosmiac.org/spartan3e_tutorials.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They provide some tutorials. See bellow what can be found there:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/MQfIw.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-02-07T16:12:04.013" />
  <row Id="9830" PostTypeId="2" ParentId="9751" CreationDate="2011-02-07T17:58:48.557" Score="1" ViewCount="" Body="&lt;p&gt;Let the robot measure the torque/force at one or more joints of each leg.&#xA;Perhaps measure torque directly using a discrete strain gage or other force/torque sensor.&#xA;Or perhaps you can get an adequate approximation by using &quot;sensorless&quot; measurements of the back-EMF of that leg's motor, or the amount of power going into that leg's motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Say the robot is using some gait that is efficient for tarmac: the robot puts the foot down in front until it touches the tarmac, then it stays at that vertical position and pushes the foot straight straight back, then lifts the leg up a little and pulls it forward, then puts the foot back down and repeats.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really are moving over tarmac, you expect the robot to measure a high torque/force when it is pushing the leg back, and close to zero when it is pulling the leg through the air forwards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the torque in one leg feels low when the robot pushes it back, then perhaps that leg (not necessarily any other leg) is slipping across the surface of some sand.&#xA;So the robot should push that leg down a little deeper into the sand, and perhaps move the leg back a little faster, until that leg gives the robot the forward thrust you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the torque in one leg feels high when the robot pulls it forward, perhaps it is rubbing against grass.&#xA;Or perhaps the other legs have dug in deeply into sand, and that leg is brushing the top layer of sand.&#xA;So the robot should lift that leg up a little higher to avoid that obstacle.&#xA;(And perhaps lift all the legs up a little higher on the return stroke for the next few steps, so other legs can avoid that obstacle or similar nearby obstacles).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm assuming your goal is to get the robot to adaptively change its gait, because different gaits are more efficient on different substrates. If your real goal is to get the robot to stay on a tarmac track, rather than wandering off over grass and sand, you'll need some other approach.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-07T17:58:48.557" CommentCount="1" />
  <row Id="9831" PostTypeId="2" ParentId="9824" CreationDate="2011-02-07T18:07:50.477" Score="2" ViewCount="" Body="&lt;p&gt;I have use an Arduino board in a product (not large scale production) and I wouldn't do it again.  The Arduino boards are geared towards a very closed ecosystem (in the non open-source software meaning of the word).  For instance, if you 'step out' of the Arduino ecosystem by needing to use a pin that isn't brought out to a header on the development board, you immediately lose all the benefits of the Arduino.  You have to modify the board to bring the pin to an existing header or add a new header somehow.  This likely means you won't be able to use any existing shields or possibly even the software libraries for the Arduino. That's most of the benefit of the board gone. I have had to do this with an Arduino Mega.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the boards are huge and not easy to integrate with other PCBs  I made the main board for my application equivalent to a shield for the Arduino Mega that had mounting holes for the enclosure I chose.  So I just plugged the Arduino Mega into the headers I put on my board.  However, this was a lot of up and down size to accommodate, and there was a lot of wasted space due to the size of the development board.  I didn't need half of what was on there and it only took up room.  This required me to have a larger PCB and enclosure than I otherwise would have needed.  That's wasted money.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-07T18:07:50.477" CommentCount="3" />
  <row Id="9832" PostTypeId="2" ParentId="9611" CreationDate="2011-02-07T18:51:12.780" Score="4" ViewCount="" Body="&lt;p&gt;I just put together a sous-vide setup with a commercial PID. Originally I had planned on using a crockpot/slow-cooker, but was able to pick up an indoor turkey fryer via a post holiday sale.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My setup &amp;amp; costs:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.lightobject.com/JLD612-Dual-Display-PID-Temperature-Controller-P43.aspx&quot; rel=&quot;nofollow&quot;&gt;JLD612 PID temperature controller&lt;/a&gt; ($33.50)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.lightobject.com/6ft-PT-100-PID-Precise-01-degree-Thermocouple-P218.aspx&quot; rel=&quot;nofollow&quot;&gt;PT-100 0.1 degree Thermocouple&lt;/a&gt; ($19.00)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.lightobject.com/40A-Solid-State-Relay-SSR-DC-In-DC-Out-P315.aspx&quot; rel=&quot;nofollow&quot;&gt;40A Solid State Relay&lt;/a&gt; ($16.50)&lt;/li&gt;&#xA;&lt;li&gt;Indoor turkey fryer ($25.00)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The JLD612 is pretty much self-contained, and has displays for current &amp;amp; target temperatures. It also has an auto-tune feature that configures the PID parameters for your particular setup. A downside is it's workings are a bit of a black box -- you don't really know what's going on inside. On my To-Do list is to build a combination PID/data-logger on the Arduino platform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FYI, Make Magazine just had a &lt;a href=&quot;http://makeprojects.com/Project/Sous-Vide-Immersion-Cooker/471/1&quot; rel=&quot;nofollow&quot;&gt;Sous Vide Immersion Cooker&lt;/a&gt; project using a similar PID controller.&lt;/p&gt;&#xA;" OwnerUserId="2699" LastActivityDate="2011-02-07T18:51:12.780" CommentCount="1" />
  <row Id="9833" PostTypeId="1" CreationDate="2011-02-07T19:09:48.400" Score="4" ViewCount="392" Body="&lt;p&gt;I've got a power supply circuit that needs the input to be protected against some pretty big voltage spikes.  To do this, I need a really beefy clamping diode (D1) that will handle the voltage and current associated with those spikes.  I also have a second diode in parallel with less current/voltage handling capability, but with a higher breakdown voltage (D2).  My thought was that the secondary diode might react faster, but the primary diode would do the real voltage clamping.  The circuit below is a simplified version (not including additional bias components).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/LJC7H.png&quot; alt=&quot;Simplified Circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My hope is that the two diodes will provide the response as shown below.  Is this a bad idea?  Any cautions or warnings for this type of implementation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OJgdz.png&quot; alt=&quot;Input Voltage Graphs&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1571" LastEditorUserId="1571" LastEditorDisplayName="" LastEditDate="2011-02-10T20:46:56.883" LastActivityDate="2011-02-10T21:05:20.663" Title="Two diodes in parallel for over-voltage protection" Tags="&lt;power-supply&gt;&lt;diode&gt;&lt;high-voltage&gt;" AnswerCount="4" CommentCount="8" />
  <row Id="9834" PostTypeId="2" ParentId="5572" CreationDate="2011-02-07T19:10:31.187" Score="7" ViewCount="" Body="&lt;p&gt;This circuit is one of a category of circuits called a &quot;Transformerless AC to DC Powersupply&quot; or a &quot;CR dropper circuit&quot;.&#xA;For other examples, see&#xA;&lt;a href=&quot;http://techref.massmind.org/techref/microchip/pwr-picmotor.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;Massmind: Transformerless AC to DC Powersupply&quot;&lt;/a&gt; or&#xA;&lt;a href=&quot;http://techref.massmind.org/techref/power/ACcapbleed.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;Massmind: Transformer-less capacitive bleed power conversion&quot;&lt;/a&gt; or&#xA;&lt;a href=&quot;http://www.st.com/stonline/books/pdf/docs/8313.pdf&quot; rel=&quot;nofollow&quot;&gt;&quot;ST AN1476: Low-cost power supply for home appliances&quot;&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Such a device has a power factor near 0, making it questionable whether it meets EU-mandated power factor laws, such as EN61000-3-2.&#xA;Even worse, when such a device is plugged into a &quot;square wave&quot; or &quot;modified sine wave&quot; UPS, it has much higher power dissipation (worse efficiency) than when plugged into mains power -- if the person who builds this circuit does not choose safety resistors and zener big enough to handle this additional power, they may overheat and fail.&#xA;These two drawbacks may be why some engineers consider the &quot;CR dropper&quot; technique &quot;&lt;a href=&quot;http://en.wikibooks.org/wiki/Talk%3aBasic_Electrical_Generation_and_Distribution#damage&quot; rel=&quot;nofollow&quot;&gt;dodgy and dangerous&lt;/a&gt;&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How does the capacitor step down the voltage?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several ways of explaining this.&#xA;One way (perhaps not the most intuitive):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One leg of the capacitor is attached (through a safety resistor) to the &quot;hot&quot; mains which oscillates at over 100 VAC.&#xA;The other leg of the capacitor is connected to something which is always within a few volts of ground.&#xA;If the input were DC, then the capacitor would completely block any current from flowing through it.&#xA;But since the input is AC, the capacitor lets a small amount of current flow through it (proportional to its capacitance).&#xA;Whenever we have a voltage across a component and current flowing through the component,&#xA;we electronics people can't resist calculating the effective impedance using Ohm's law:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Z = V/I.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(Normally we say R = V/I, but we like to use Z when talking about the impedance of capacitors and inductors. It's tradition, OK?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you replace that capacitor with a &quot;equivalent resistor&quot; with a real impedance R equal to the absolute impedance Z of that capacitor, &quot;the same&quot; (RMS AC) current would flow through that resistor as through your original capacitor, and the power supply would work about the same&#xA;(see ST AN1476 for an example of such a &quot;resistor dropper&quot; power supply).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Does the capacitor waste power as heat?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An ideal capacitor never converts any power to heat -- all of the electrical energy that flows into an ideal capacitor eventually flows out of the capacitor as electrical energy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A real capacitor has small amounts of parasitic series resistance (ESR) and parasitic parallel resistance, so a small amount of the input power is converted to heat.&#xA;But any real capacitor dissipates far less power (far more efficient) than a &quot;equivalent resistor&quot; would dissipate.&#xA;A real capacitor dissipates much less power than the safety resistors or a real diode bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;If the zener were gone and the output was let to float around 50V ...&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can tweak the resistance of your load, or swap out the dropping cap for one with a different capacitance of your choice, you can force the output to float at close to whatever voltage you choose.&#xA;But you will inevitably have some ripple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;If the zener were gone and the output was let to float ... would it approach 100% efficiency?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good eye -- the zener is the part that is the least efficient in this circuit.&#xA;A linear regulator here would significantly improve the efficiency of this circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you assume ideal capacitors (which is a good assumption) and ideal diodes (not such an good assumption), no power is lost in those components.&#xA;If you eliminate the safety protection resistors, then no power is lost in those components either.&#xA;Since there's no where else for the power to go, such an idealized circuit would give you 100% efficiency.&#xA;But it would also have some ripple.&#xA;You may be able to follow this no-zener circuit with a linear voltage regulator to eliminate that ripple and still get a net efficiency over 75%.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;law&quot; that &quot;&lt;em&gt;a voltage regulator always has an efficiency of vout/vin&lt;/em&gt;&quot; only applies to linear DC to DC regulators.&#xA;That law doesn't apply to this circuit, because this circuit has AC input, and so this circuit can have much better efficiency than that &quot;law&quot; predicts.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-07T19:10:31.187" />
  <row Id="9836" PostTypeId="2" ParentId="9824" CreationDate="2011-02-07T19:38:32.130" Score="5" ViewCount="" Body="&lt;p&gt;Yikes!  Either you're thoroughly confused, or your idea of production is different from mine.  I consider production to mean selling a product to the general public in quantities of thousands or more, then supporting and updating the design.  Products which don't go to the general public are either internal or contract work, and products which sell in smaller quantities are special-purpose or otherwise different. 'Several boards from Sparkfun' wouldn't fulfill a production need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, the cost of goods is always a significant factor.  Just how significant it is may differ from product to product, and it may be less significant if the particular item is only a small component of a larger system which has been optimized for cost. However, in any environment where you're in competition with other producers (which you must be because if you're in government or have a monopoly you wouldn't be asking this question), cost will be a factor.  The $\$$35 for the Netduino (in cost alone) could usually be reduced to $\$$10 or less for most applications with a custom design.  If you are convinced that the cost doesn't matter, there are further reasons against buying such a design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, all three boards were designed for students, designers, and hobbyists.  They are designed to be reliable enough for a development kit which sits on a desk.  That student should know a few things about safe handling procedures which the general population does not know or practice.  Issues such as ESD, long-term power dissipation, and component derating were likely demoted below things which are less important for production like solderability and simplicity. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your affinity for IDEs and prepackaged solutions is frightening.  In my opinion, you place way too much trust in your tool providers.  If the boards become more expensive, if the license terms are changed, if the server goes down, the software is declared obsolete, the board manufacturer goes out of business (etc. etc. etc...), your business is hosed.   Also, you lack an understanding of what's going on behind the scenes.  If something doesn't work the way the documentation says it should what is your plan? Your idea to buy a few Arduinos, program them, and deploy the product, for example, lacks any plan for code protection.  Someone else could copy your code out of the microcontroller, duplicate the relevant parts of the design for a third the price, and outsell you.&lt;br&gt;&#xA;Relying on an IDE and language for the stuff you don't understand is a recipe for disaster.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a development kit in your design will make your product overpriced, fragile, bulky, power-hungry, and inefficient.  It will also be hard to debug, a pain to support, and you'll be at the mercy of your suppliers.  It will make you look incompetent.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, all is not lost.  If you implement your design on a development board, it will be straightforward to have someone (either on or off your team) customize it to remove these deficiencies.  If you lack a team, you should hire one, bring in a contractor, or have it done by a design firm. &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="2838" LastEditorDisplayName="" LastEditDate="2011-03-16T19:14:44.687" LastActivityDate="2011-03-16T19:14:44.687" CommentCount="11" />
  <row Id="9837" PostTypeId="2" ParentId="9455" CreationDate="2011-02-07T20:03:13.420" Score="1" ViewCount="" Body="&lt;p&gt;Brainstorming:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been reading about &#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/capacitive_sensing&quot; rel=&quot;nofollow&quot;&gt;capacitive sensing&lt;/a&gt;&#xA;recently.&#xA;Capacitive-touch sensors have the great advantage that they can be completely hermetically sealed behind a thin layer of plastic, so there is no exposed metal to corrode.&#xA;(&lt;a href=&quot;http://electronics.stackexchange.com/questions/1253/sensing-touch-through-a-thick-surface&quot;&gt;&quot;Electronics and Robotics: Sensing touch through a thick surface?&quot;&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because you can't get DC current to flow through the plastic, such sensors must use AC, as Leon Heller suggested.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alas, most of the discussion I've seen has been about how to respond only to intelligent finger-presses; what little discussion there is about water an moisture is about how to reduce the sensitivity of capacitive sensors to water splashes.&#xA;(&lt;a href=&quot;http://forum.sparkfun.com/viewtopic.php?f=14&amp;amp;t=22835&quot; rel=&quot;nofollow&quot;&gt;&quot;Sparkfun forums: Capacitive sensors and waterproofing&quot;&lt;/a&gt;).&#xA;So clearly they are sensitive to water, so perhaps you could use this &quot;flaw&quot; and turn it into a feature.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-07T20:03:13.420" CommentCount="2" />
  <row Id="9838" PostTypeId="2" ParentId="9833" CreationDate="2011-02-07T20:14:15.880" Score="6" ViewCount="" Body="&lt;p&gt;It won't work -- if you put 2 diodes in parallel, I can't easily say how they will share current in the forward (conducting) direction, but in blocking, the LOWEST breakdown one will breakdown. The 2nd is useless. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might put 2 in series, but this has its own problems (they don't split the applied V equally). Best to get a single component rated for what you want to do.&lt;/p&gt;&#xA;" OwnerUserId="2918" LastActivityDate="2011-02-07T20:14:15.880" CommentCount="2" />
  <row Id="9839" PostTypeId="2" ParentId="9766" CreationDate="2011-02-07T20:22:23.143" Score="1" ViewCount="" Body="&lt;p&gt;Sometimes we use a phrase like this to represent a portion of a bandgap circuit inside an IC. Often there isn't the feedback loop (which regulates the transistor currents to be equal), or it is used as a comparator with a built-in reference.&lt;/p&gt;&#xA;" OwnerUserId="2918" LastActivityDate="2011-02-07T20:22:23.143" CommentCount="1" />
  <row Id="9840" PostTypeId="2" ParentId="9833" CreationDate="2011-02-07T21:30:25.453" Score="0" ViewCount="" Body="&lt;p&gt;You may want to research Gas Discharge Tube Arrestors.  These usually have higher current ratings than the equivalent TVS diodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would replace the higher breakdown voltage diode with a GDT.  The TVS diode would start conducting for the small spikes and the GDT would suppress the large spikes.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-02-07T21:30:25.453" CommentCount="4" />
  <row Id="9841" PostTypeId="1" CreationDate="2011-02-07T21:55:10.920" Score="3" ViewCount="137" Body="&lt;p&gt;Hi I'm fairly green when it comes to RF technology in circuits. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my problem: I need a low power RF transmitter module (3 - 5v) for my application. It's a small embedded device and all it does is broadcasting a short ID to a base station.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My circuit is very small, it's a battery powered AVR. The AVR holds the unique ID to be broadcast when a certain logic criteria is met.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And to make things complicated, There will be multiple of these broadcasting their IDs to the base station, probably up to 1000 devices broadcasting once per 5 seconds which is 200 times per second. I need the range about 500ft or more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm guessing something that broadcasts in the ISM range will work but I'm open for any design ideas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So long story short; What TX/RX chips would be good to use? Also, how what would be the best way of getting a message through in such a crowded network?&lt;/p&gt;&#xA;" OwnerUserId="2920" LastEditorUserId="2920" LastEditorDisplayName="" LastEditDate="2011-02-08T16:26:37.497" LastActivityDate="2011-02-08T16:26:37.497" Title="What low power RF Transmitter to use for crowded signal area" Tags="&lt;avr&gt;&lt;wireless&gt;&lt;rf&gt;&lt;components&gt;&lt;radio&gt;" AnswerCount="2" CommentCount="0" FavoriteCount="1" />
  <row Id="9842" PostTypeId="2" ParentId="9841" CreationDate="2011-02-07T23:50:49.970" Score="3" ViewCount="" Body="&lt;p&gt;I'd recommend looking at 433MHz or 868MHz (ISM band) transmitters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI/Chipcon have the &lt;a href=&quot;http://focus.ti.com/lit/ds/swrs061f/swrs061f.pdf&quot; rel=&quot;nofollow&quot;&gt;CC1101&lt;/a&gt;, a low cost Sub-1GHz transceiver. There's also an 8051 system-on-chip variant, the &lt;a href=&quot;http://www.ti.com/lit/gpn/cc1110f32&quot; rel=&quot;nofollow&quot;&gt;CC1110&lt;/a&gt; which could remove the need for your AVR (see also CC430).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Silicon Labs have the &lt;a href=&quot;http://www.silabs.com/Support%20Documents/TechnicalDocs/Si403x_short.pdf&quot; rel=&quot;nofollow&quot;&gt;Si403x&lt;/a&gt; or the system-on-chip &lt;a href=&quot;http://www.silabs.com/products/wireless/EZRadio/Pages/Si4010.aspx&quot; rel=&quot;nofollow&quot;&gt;Si4010&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of these chips support data rates up to 128kbit/s, which is plenty of time to transmit a packet. The hardware CRC generation and checking will help weed out bad packets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To stop nodes jabbering all over each other, you will need to invent some kind of MAC (&lt;a href=&quot;http://en.wikipedia.org/wiki/Media_Access_Control&quot; rel=&quot;nofollow&quot;&gt;Media Access Control&lt;/a&gt;). You could use carrier sense to wait for silence, with an exponential backoff (&lt;a href=&quot;http://en.wikipedia.org/wiki/Carrier_sense_multiple_access&quot; rel=&quot;nofollow&quot;&gt;CSMA&lt;/a&gt;). Or, you could coordinate the timings of your nodes and &lt;a href=&quot;http://en.wikipedia.org/wiki/ALOHAnet#Slotted_ALOHA&quot; rel=&quot;nofollow&quot;&gt;assign a slot to each node&lt;/a&gt;. You may also benefit from having a master node transmitting a timer beacon to prevent clock drift.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In theory, ZigBee supports up to 2^16 nodes on a single PAN. ZigBee is built on 802.15.4, which provides a robust MAC layer and mechanisms for network management (joining, leaving, etc). However, an off-the-shelf module like the XBee may struggle with 1000 nodes and it certainly won't be cheap. For a volume ZigBee deployment, consider the TI CC2531 or Ember EM250/EM260. ZigBee usually runs at 2.4GHz, which will not provide such good penetration of terrain as 433/868MHz.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-02-07T23:59:48.417" LastActivityDate="2011-02-07T23:59:48.417" CommentCount="2" />
  <row Id="9843" PostTypeId="2" ParentId="9817" CreationDate="2011-02-08T01:02:15.830" Score="4" ViewCount="" Body="&lt;p&gt;I think the easiest way is to convert to a k-map, and then get the POS. In your example, you've got:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  \ xy&#xA; z \ 00   01   11   10&#xA;   |-------------------|&#xA; 0 |    | x  | x  | x  |&#xA;   |----+----+----+----+&#xA; 1 |    |    |    | x  |&#xA;   |-------------------|&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;In this case, excluding the left column gives (x+y), and excluding the two bottom middle boxes gives (z' + y'), giving an answer of (x + y)(z' + y')&lt;/p&gt;&#xA;" OwnerUserId="2922" LastEditorUserId="2922" LastEditorDisplayName="" LastEditDate="2011-02-08T22:29:25.077" LastActivityDate="2011-02-08T22:29:25.077" CommentCount="3" />
  <row Id="9844" PostTypeId="2" ParentId="9833" CreationDate="2011-02-08T01:02:34.877" Score="1" ViewCount="" Body="&lt;p&gt;Two 5KP22CA (5 kW, 22 V TVS) in parallel can clamp an SAE J1455 load dump (unloaded 100 V peak, 0.4 Ω impedance, 0.4 s fall-time if I recall correctly) to &amp;lt;30 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So long as your duty cycle is fairly low or the diodes thermally coupled, you can parallel TVS fairly well.  They are far from perfect Zeners as their standoff/breakdown/max voltage range is quite broad so one robbing all the surge from the other is unlikely.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-08T02:01:10.257" LastActivityDate="2011-02-08T02:01:10.257" CommentCount="0" />
  <row Id="9845" PostTypeId="2" ParentId="8078" CreationDate="2011-02-08T02:57:20.283" Score="1" ViewCount="" Body="&lt;p&gt;I'm currently working on a maglock door security system, and am using these same chips to transmit data from the RFID reader to an Arduino about 200ft away. I as well have had all kinds of problems with these annoying, but awesome :), chips. I'm not sure I'm operating at 100% fool-proof yet, but here's a few things I've found out:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&amp;bull; There's a tradeoff between transfer rate and susceptibility to EMI. The MAX485 has a high transfer rate, but is very influenced by EMI. Try the MAX483. Same chip with slower transfer rate, but very little EMI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&amp;bull; In some cases, such as with a long cable distance, I've found it to work better without any terminating resistor...don't ask me why. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&amp;bull; Make sure both DE and RE pins are connected to either ground or +5V. They aren't required to be connected depending on whether you're in transmit or receive mode, but I could swear I've had better results when neither of them are left floating.&lt;/p&gt;&#xA;" OwnerUserId="1140" LastEditorUserId="1140" LastEditorDisplayName="" LastEditDate="2011-02-08T15:27:26.930" LastActivityDate="2011-02-08T15:27:26.930" />
  <row Id="9846" PostTypeId="2" ParentId="9841" CreationDate="2011-02-08T05:01:54.073" Score="2" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;There will be multiple of these broadcasting their IDs to the base station, probably up to &gt;1000 devices broadcasting once per 5 seconds which is 200 times per second&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That is a classic application for true spread spectrum modulation.  Implementation details are complicated, but essentially you transform the ID codes into patterns (within an allowed bandwidth) and differentiate the transmitters by finding their pattern in the noise (including interference from each other) rather than by finding a narrowband carrier frequency in it.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-02-08T05:01:54.073" />
  <row Id="9847" PostTypeId="2" ParentId="9638" CreationDate="2011-02-08T05:04:23.840" Score="2" ViewCount="" Body="&lt;p&gt;The galvanometers are rated in terms of how many different angles they can point at per second. The smaller the angle the mirror has to swing through, the more times per second it can do it, which is reflected in the specs for the second galvanometer you pointed to. For a light show application, the desired patterns and level of detail would determine both the required deflection and the number of points.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The generic component selection process is applicable here and goes something like this:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;figure out a performance requirement for the component&lt;/li&gt;&#xA;&lt;li&gt;find some components that meet the requirement&lt;/li&gt;&#xA;&lt;li&gt;cheap enough? you're done!&lt;/li&gt;&#xA;&lt;li&gt;too expensive? try adjusting your design to work with a cheaper version, go to 1.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1409" LastActivityDate="2011-02-08T05:04:23.840" />
  <row Id="9848" PostTypeId="1" CreationDate="2011-02-08T06:39:23.700" Score="2" ViewCount="202" Body="&lt;p&gt;I'm building a circuit powered by a small Li-Ion battery.  The battery will be connected to a 3.3V LDO, which then powers the entire circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Li-Ion batteries are damaged if they are allowed to drain below about 3V. There are chips to do this LVC cutoff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I figure the LDO will already have the pass transistor and voltage reference, so it seems wasteful to add another part.  This seems to be the kind of thing that could be easily integrated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone make an LDO with low-voltage cutoff?  Parametric searches and Google seem to be failing me. &lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-08T13:55:27.977" Title="LDO with low-voltage cutoff?" Tags="&lt;ldo&gt;&lt;lithium-ion&gt;&lt;lvc&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="3" />
  <row Id="9849" PostTypeId="2" ParentId="9848" CreationDate="2011-02-08T07:22:58.743" Score="3" ViewCount="" Body="&lt;p&gt;I have never seen ready-made ICs with such a feature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are, however, ICs that have a shutdown (or enable) input that might be used for such a feature when you add an external comparator and/or reference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also want to consider building your own LDO, using a PMOS (or pnp) pass transistor, a reference  (LT1431, LM4121-ADJ, LM4051-ADJ or even TL431 come to mind), some discrete components and some sort of 2nd comparator for the under-voltage lock out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take care about the regulator's stability (ESR of output capacitor must neither be too small nor too large, cf. &quot;Tunnel of Death&quot;). These links are helpful:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.national.com/an/AN/AN-1148.pdf&quot; rel=&quot;nofollow&quot;&gt;Short and good Application Note by NSC&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://amsc.tamu.edu/SIS/Publications/pub/jounal/2007_29.pdf&quot; rel=&quot;nofollow&quot;&gt;A paper that offers some really good theroetical background&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://repository.tamu.edu/bitstream/handle/1969.1/3275/etd-tamu-2005C-ELEN-Milliken.pdf&quot; rel=&quot;nofollow&quot;&gt;An entire thesis by the same author as the paper, also a good read&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Building your own LDO has the disadvantage that you don't get features like thermal shutdown or short-circuit protection without additional effort, but it offers a great deal of flexibility (and it's fun).&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-02-08T07:22:58.743" CommentCount="3" />
  <row Id="9850" PostTypeId="1" AcceptedAnswerId="9852" CreationDate="2011-02-08T07:49:22.840" Score="2" ViewCount="204" Body="&lt;p&gt;What purpose does the IO shield on computers serve?  I have been reading a lot of articles (mostly forums) on the internet and can't seem to find a definitive answer.&lt;/p&gt;&#xA;" OwnerUserId="2924" LastActivityDate="2011-02-08T11:51:02.520" Title="What is the purpose of an IO shield on a computer case?" Tags="&lt;hardware&gt;&lt;computers&gt;" AnswerCount="1" CommentCount="8" />
  <row Id="9851" PostTypeId="2" ParentId="3501" CreationDate="2011-02-08T07:56:29.490" Score="0" ViewCount="" Body="&lt;p&gt;For quick prototypes I would get some &lt;a href=&quot;http://shapelock.com/&quot; rel=&quot;nofollow&quot;&gt;ShapeLock&lt;/a&gt;, its great for making motor mounts servo arms and horns, or any other plastic piece you can create. I have used this stuff successfully to make a motor mount for a project a few years back.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only other thing that I don't see on the list is a power supply, even a cheap hacked PC power supply would work since it does supply common voltages, +5v and +12v at a decent current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transistors you cant go wrong with a mixed bag of common NPNs like 2n2222 or 2n3904&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PNPs are good to have in stock but not necessary in my opinion&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other miscellaneous parts that may be needed would be some sort of platform to base your bots on,  some use pre-built ones, but i prefer using RC cars and vehicles to modify.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-08T07:56:29.490" CommunityOwnedDate="2011-02-08T07:56:29.490" />
  <row Id="9852" PostTypeId="2" ParentId="9850" CreationDate="2011-02-08T08:34:03.263" Score="8" ViewCount="" Body="&lt;p&gt;I/O shield: &lt;a href=&quot;http://de.wikipedia.org/w/index.php?title=Datei%3aIO_Shield_wiki.jpg&amp;amp;filetimestamp=20100326203704&quot; rel=&quot;nofollow&quot;&gt;Picture from wikipedia&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Shield to keep electro-magnetic radiation inside of the case&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Dust Cover / Air circulation director: The fan in the power supply shall draw air throughout the entire case and not just along the short way from the I/O area to the power supply that's usually right above.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Aesthetics: No ugly hole.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-02-08T11:51:02.520" LastActivityDate="2011-02-08T11:51:02.520" CommentCount="3" />
  <row Id="9853" PostTypeId="1" CreationDate="2011-02-08T12:47:06.220" Score="1" ViewCount="119" Body="&lt;p&gt;Hi, I'm trying to make a device that will record video using embedded camera modules (ccd or cmos) and then pass that information onto my computer where I'll be able to view it. I want to find out which is the best camera module(within reasonable price) and will give the best detail in video mode. Does anyone have any experience with this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should say first of all I am new to working with cameras at the hardware level and am still finding out new things everyday(if not every hour).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need a total of 4 camera modules and using them I'd like to gain a 180 degree coverage(horizontal). So each of the cameras will face a different direction, and then the computer will collect the video feed from them and combine it into one image, sort of like a panorama(I haven't worked out yet how that's going to work, but I presume its possible). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to squeeze out the highest detail possible, while keeping the overall size small(it needs to be portable). The cameras will output (indirectly, through the computer) to a projected screen roughly the size of a A5 paper. Detail will be critical, so the higher the frame rate or resolution possible the better. The overall implementation must be as small as possible, I've looked through how camera phones use really small plug and socket system to connect cameras, something along those lines if possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to spend £30-£60 on each module, so maximum of £240. However, if needed I wouldn't mind going over it. Needs must.&lt;/p&gt;&#xA;" OwnerUserId="2861" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T22:38:44.107" LastActivityDate="2011-02-09T19:20:33.680" Title="Relatively good camera module for video recording?" Tags="&lt;embedded&gt;&lt;camera&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="9854" PostTypeId="2" ParentId="9848" CreationDate="2011-02-08T13:55:27.977" Score="2" ViewCount="" Body="&lt;p&gt;One option is the &lt;a href=&quot;http://cds.linear.com/docs/Datasheet/1120fd.pdf&quot; rel=&quot;nofollow&quot;&gt;LT1120&lt;/a&gt;, which has a comparator, reference and shutdown pin in one package. It's a simple enough matter of tying them together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also get LDOs with a UVLO pin. The UVLO pin has a reference comparator. It could be something like UVLO falling below 1.25V or so triggers the shutdown of the regulator. Tie a voltage divider to the UVLO pin to tweak the shutdown point. &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/tps2140.pdf&quot; rel=&quot;nofollow&quot;&gt;Here's one example&lt;/a&gt;; it's for USB, but I'd expect you'll be able to find more suitable chips.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-08T13:55:27.977" CommentCount="2" />
  <row Id="9855" PostTypeId="1" AcceptedAnswerId="9857" CreationDate="2011-02-08T15:02:02.663" Score="2" ViewCount="163" Body="&lt;p&gt;My company sells devices many devices that use RS-232 line transceivers like the MAX232 chip. In many cases our users run their RS-232 cables in the range of 30 to 50 feet to connect our device to their PC. Over the years we have seen many boards come in for repair because the serial communication stops working and the problem can often be fixed by simply replacing the MAX232 line transceiver. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My guess is that the long serial cable is acting as a giant antenna for EMI or static and the transceiver can only take so much. In our next board design we want to go with a surface mount chip which will be much more difficult to &quot;pop-out&quot; and replace if the problem occurs again. Is there a way that I can protect this chip against such problems without increasing the cost of the board/components greatly?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2011-02-09T20:00:46.520" Title="Is there a way to protect RS-232 Transceiver IC from static death" Tags="&lt;rs232&gt;&lt;emi&gt;&lt;antistatic&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="9856" PostTypeId="1" CreationDate="2011-02-08T15:15:30.433" Score="0" ViewCount="269" Body="&lt;p&gt;Well this as I searched on the net is advertising, making money and fools out of those who want to make/buy such a bug scanner.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I am not an electronics engineer but am being forced to.&lt;/li&gt;&#xA;&lt;li&gt;I do have access to all the hardware I may need.&lt;/li&gt;&#xA;&lt;li&gt;There are lots of shops claiming that they have devices which can scan a area to see if there are bugs or spy listener devices installed, but how do I know if these work?&lt;/li&gt;&#xA;&lt;li&gt;Personally I think this type of device only exists in James Bond movies :))&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;h2&gt;My boss's reason&lt;/h2&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;He seems to hear some sound in the conference room, and his room where he has to stay for another month.&lt;/li&gt;&#xA;&lt;li&gt;He claims the sound is something like &quot;tii-eee, tii, teee ti ti&quot; and so on. lol&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;h2&gt;Deliver&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Okay, so now I have to reply to him with a gadget to scan his rooms for potential wireless transmitter bugs.&lt;/p&gt;&#xA;" OwnerUserId="2830" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-02-08T19:34:49.860" LastActivityDate="2011-02-08T21:56:55.880" Title="My boss has asked me make a device which is capable of scanning rooms for bugs!" Tags="&lt;wireless&gt;&lt;detection&gt;" AnswerCount="5" CommentCount="6" />
  <row Id="9857" PostTypeId="2" ParentId="9855" CreationDate="2011-02-08T15:34:08.250" Score="4" ViewCount="" Body="&lt;p&gt;You may want to consider a &lt;a href=&quot;http://www.maxim-ic.com/products/protection/esd/rs232.cfm&quot; rel=&quot;nofollow&quot;&gt;part with built-in ESD protection&lt;/a&gt; as a first-line of defense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maxim has a good &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/651&quot; rel=&quot;nofollow&quot;&gt;application note&lt;/a&gt; on the topic.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-08T15:34:08.250" />
  <row Id="9858" PostTypeId="2" ParentId="9856" CreationDate="2011-02-08T15:37:39.683" Score="4" ViewCount="" Body="&lt;p&gt;Consider a new job. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from that, you could try and rent a spectrum analyzer from an equipment rental service, build a simple loop antenna (cut the end off a coax cable, loop some wire from the center conductor to the ground braid) and 'sniff' around the room to see if there's any spurious RF transmissions coincident with the &quot;tii-ee, tii, teee ti ti&quot; noises. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-08T15:37:39.683" CommentCount="3" />
  <row Id="9859" PostTypeId="2" ParentId="9856" CreationDate="2011-02-08T15:39:18.040" Score="4" ViewCount="" Body="&lt;p&gt;You can detect some &quot;bugs&quot; which use radio waves to transmit sound (e.g. speech) to a remote listener or recorder. There are devices that cotain radio receivers which can detect a nearby radio transmitter - if the bug uses a radio-frequency in the range detectable by the detector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems unlikely that a properly functioning bug of this sort would emit a noise your boss can hear. Check for faulty &quot;wall-wart&quot; power supplies and other electrical devices. You might have one of &lt;a href=&quot;http://www.thinkgeek.com/gadgets/electronic/b278/&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your shoes I'd get the boss to sign a purchase requisition for a commercial bug detector. I'd suggest to him that if he considers it important enough he allocate you a budget for hiring a security consultant. I'd also get him to purchase some bugs that could be used to test the effectiveness of the bug-detector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If he insists you build a detector yourself, I'd first look for self-construction kits and equipment you can get him to pay for. Maybe he'll pay for training? You can find circuit examples from Google, for example the Talking Electronics' &lt;a href=&quot;http://www.talkingelectronics.com/projects/BugDetector%28mini%29/BugDetector%28mini%29-P1.html&quot; rel=&quot;nofollow&quot;&gt;kit&lt;/a&gt; or an old Popular Electronics' &lt;a href=&quot;http://www.sentex.ca/~mec1995/circ/BugDetec/BugDetec.html&quot; rel=&quot;nofollow&quot;&gt;article&lt;/a&gt; - I've no idea if these are any good but looking at a selection of these might give you an idea where to start.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are very unhappy with this, you will have considered looking for employment elsewhere. In the short term I'd try to look at it as an opportunity to gain experience and/or to demonstrate competence that could later be used (e.g. in an annual-review) to influence promotion or advancement.&lt;/p&gt;&#xA;" OwnerUserId="2191" LastEditorUserId="2191" LastEditorDisplayName="" LastEditDate="2011-02-08T17:20:20.230" LastActivityDate="2011-02-08T17:20:20.230" CommentCount="3" />
  <row Id="9860" PostTypeId="1" CreationDate="2011-02-08T16:07:20.833" Score="0" ViewCount="288" Body="&lt;p&gt;Hello, I am new to Arduino and want to use two 74HC595 shift registers to control 200 leds. What will I need to consider / get to make this possible?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are your average starter LED's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you! &lt;/p&gt;&#xA;" OwnerUserId="2929" LastActivityDate="2011-02-11T12:01:54.787" Title="What is needed to control 200 LED's from an Arduino" Tags="&lt;arduino&gt;&lt;led&gt;&lt;74hc595&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="9861" PostTypeId="1" CreationDate="2011-02-08T16:08:33.530" Score="-2" ViewCount="106" Body="&lt;p&gt;Can I use a radio receiver type deivce, such as those built in cassete players, to scan for RF listeners within an area (a building)? Say a device which goes &lt;em&gt;&quot;Intruder detected!&quot;&lt;/em&gt; at some frequency, and plays what he can hear?&lt;/p&gt;&#xA;" OwnerUserId="2830" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T21:44:04.840" LastActivityDate="2011-02-08T21:44:04.840" Title="Can I use a radio receiver to scan for RF listeners within an area?" Tags="&lt;wireless&gt;&lt;rf&gt;" AnswerCount="1" />
  <row Id="9862" PostTypeId="2" ParentId="9860" CreationDate="2011-02-08T16:16:03.900" Score="1" ViewCount="" Body="&lt;p&gt;The only thing to consider is time to shift out your data. But if you would build 8 parallel shiftout streams, you can do that 8 times faster :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, make sure to provide sufficient power to all these 595's, total power consumption might get quite significant.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-08T16:16:03.900" />
  <row Id="9863" PostTypeId="1" CreationDate="2011-02-08T16:34:58.230" Score="0" ViewCount="68" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/9050/2-bluetooth-connections-concurrently&quot;&gt;2 Bluetooth Connections concurrently?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Hi.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm creating a device that is supposed to be coupled with a cell phone via bluetooth.  It's not a headset, but uses bluetooth technology.  If the user of the phone has a headset paired with the cell phone, it should not matter.  Both the headset and this device should be able to be simultaneously connected to the cell phone (while the cell phone is being talked on).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I heard that this can be done via a piconet, I'm just hoping someone else has solved this problem and can give me some tips/advice/strategies for getting this accomplished....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!&lt;/p&gt;&#xA;" OwnerUserId="2931" LastActivityDate="2011-02-08T16:34:58.230" ClosedDate="2011-02-08T21:30:29.853" Title="How can I pair and connect 2 devices to a cell phone simultaneously?" Tags="&lt;bluetooth&gt;" CommentCount="3" />
  <row Id="9864" PostTypeId="2" ParentId="9860" CreationDate="2011-02-08T16:39:00.013" Score="0" ViewCount="" Body="&lt;p&gt;The only way to control 64 (8&lt;sup&gt;2&lt;/sup&gt;) LEDs from your 2 8-bit registers would be to set up a matrix of LEDs (the matrix is simply how the circuit is electrically, you could place them wherever (in a line, circle...), though you will have a great deal of wiring.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your circuit would then connect a few LEDs to ground, and power whichever ones among them it needs.  A few milliseconds later, you connect a different set of LEDs to ground, and repeat, very quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Among the Arduino pages there is &lt;a href=&quot;http://www.arduino.cc/playground/Main/DirectDriveLEDMatrix&quot; rel=&quot;nofollow&quot;&gt;one that discusses this&lt;/a&gt;.  It doesn't include 595's, as they will slow it down a bit, but it's simple enough to combine the ideas.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-08T23:01:55.067" LastActivityDate="2011-02-08T23:01:55.067" CommentCount="2" />
  <row Id="9865" PostTypeId="1" AcceptedAnswerId="9866" CreationDate="2011-02-08T17:15:51.463" Score="5" ViewCount="137" Body="&lt;p&gt;It seems that to sell a GSM mobile phone, companies like Apple, Motorola, Sony Ericsson and many others invest a considerable amount of money in EMI testing them. Yet they still interfere with my stereo, radio, computer speakers, and other devices. Why?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-17T18:47:31.377" Title="If mobile phones have to go through such extensive FCC/CE/EMI testing, why do they interfere with my radio?" Tags="&lt;radio&gt;&lt;emi&gt;" AnswerCount="4" />
  <row Id="9866" PostTypeId="2" ParentId="9865" CreationDate="2011-02-08T17:20:57.060" Score="8" ViewCount="" Body="&lt;p&gt;The interference caused by GSM phones is an intentional radiator that is within the required limits of regulations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tend to blame the other devices for not shielding well enough. Any wireless device is going to have harmonics, its just a way of life and it just so happens that one of the harmonics with many GSM devices is in an audible range.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-08T17:20:57.060" />
  <row Id="9867" PostTypeId="2" ParentId="9861" CreationDate="2011-02-08T17:23:51.300" Score="1" ViewCount="" Body="&lt;p&gt;Some cheap bugs can use the AM or FM radio spectrum that a cassette player/radio would pick up. You would have to scan through all frequencies listening for a quiet spot on the dial. If you turn the volume of your cassette radio up high enough, you might get a feedback wailing effect when the bug picks up the cassette radio!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But expensive, professional bugs would not use the broadcast bands (because they would be designed for longer range and therefore higher power, and to avoid detection with such simple methods). It's also illegal to transmit on the broadcast bands (see the EMC regulations in Europe and the FCC in US etc), although iPod to FM transmitters seem to have been allowed by the regulators because of their very low power output/short range.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-02-08T17:23:51.300" CommentCount="1" />
  <row Id="9868" PostTypeId="2" ParentId="9865" CreationDate="2011-02-08T17:44:31.930" Score="3" ViewCount="" Body="&lt;p&gt;Take a close look at a typical FCC declaration of conformity:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(1) This device may not cause harmful interference, and&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(2) This device must accept any interference received, including interference that may cause undesired operation.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The key word is &lt;em&gt;harmful&lt;/em&gt;. Distortion or buzzing on speakers is not considered harmful. Annoying, yes, but not harmful. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-08T17:44:31.930" CommentCount="2" />
  <row Id="9869" PostTypeId="2" ParentId="9865" CreationDate="2011-02-08T17:52:03.163" Score="3" ViewCount="" Body="&lt;p&gt;At least in Europe, although the EMC directive does not have a frequency limit, and the specifications often start by saying they cover d.c. to 400 GHz, in practice limits were only given up to 1 GHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe this was because it was deemed unlikely that any device would efficiently emit much unintentionally beyond this frequency, but that was all written before 2.4 GHz became so widely used (Wifi, Bluetooth, Zigbee etc). Therefore the audio kit wasn't tested for immunity beyond 1 GHz. In any case, it is usual to accept temporary deviations in analogue equipment, or any equipment, which self corrects with no intervention from the user. Otherwise you have the problem, in analogue equipment of deciding what level of noise is acceptable during an interference event.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-02-08T17:52:03.163" CommentCount="1" />
  <row Id="9870" PostTypeId="2" ParentId="9865" CreationDate="2011-02-08T18:10:21.760" Score="3" ViewCount="" Body="&lt;p&gt;Consumer goods like radios, stereos, etc. are built down to a price and typically have very poor immunity to out of band signals from devices like mobile phones. You could modify your equipment with filters, better quality mixers, and so on, but it will be expensive and a lot of work. Military equipment has to operate in close proximity to high-power signals, and a lot of attention is paid to screening and filtering, as well as circuit design, to avoid such problems, which is one reason why it is so expensive.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-17T18:47:31.377" LastActivityDate="2011-05-17T18:47:31.377" CommentCount="3" />
  <row Id="9871" PostTypeId="2" ParentId="9856" CreationDate="2011-02-08T18:21:55.267" Score="-1" ViewCount="" Body="&lt;p&gt;Maybe you should build a dummy device, that actually detects a mobile signal, &lt;a href=&quot;http://www.electroniq.net/radio-frequency/cell-phone-detector-circuit-diagram.html&quot; rel=&quot;nofollow&quot;&gt;such as this project&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can then show it to your boss, and test it with a mobile phone to prove it works, and tell him it will also work with eavesdropping bugs... Who knows, it might actually work!&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-08T18:21:55.267" CommentCount="1" />
  <row Id="9872" PostTypeId="1" CreationDate="2011-02-08T18:44:03.807" Score="0" ViewCount="73" Body="&lt;p&gt;Power supply is quite infrequent in the area where I live so I want to create a power backup for my router(rated 9V, 1A). I'm planning to use solar, and possibly wind power. I searched for some solar panels and found some cheap ones rated at 9V, 70mA. How do I use these to create the required output?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you please help me with how I would set this up? I asked in the DIY Stackexchange and was sent here.&lt;/p&gt;&#xA;" OwnerUserId="2074" LastActivityDate="2011-02-21T13:02:34.170" Title="Solar-power backed router" Tags="&lt;power-supply&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="9873" PostTypeId="1" AcceptedAnswerId="9874" CreationDate="2011-02-08T18:58:38.357" Score="2" ViewCount="87" Body="&lt;p&gt;I've read the datasheet and the application notes elated to AVR Hardware Design Considerations and EMI. From them and various Internet sources I came up with pictured design for power supply circuit for &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?PN=ATmega162&quot; rel=&quot;nofollow&quot;&gt;ATmega162&lt;/a&gt;. AVR would be connected after C3. Right now, I plan to run the device form its internal clock source, but later I plan to try with external 16 MHz crystal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/8hA2E.png&quot; alt=&quot;Image 1&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are few things I'm not certain about. First, I'm I overdoing it with 4 capacitors near the microcontroller? Some sources say that decoupling capacitors should be placed in decades while some say that the 100nF is enough. I was thinking about using multilayer capacitors for 100 nF and 10 nF and ceramic disk for 1 nF. Would that work? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next point is the inductor. In one document, it is placed between the electrolytic capacitor and in the other document between last capacitor and power supply. Which location would be better? I'm thinking about placing it after last capacitor close to the microcontroller, but the HDC document made me uncertain about that. As far as I understand it, coils do their best to keep current constant, so the coil should prevent spreading of pulses as the controller switches states.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;AVR Hardware Design Considerations recommend tantalum electrolytic capacitor. Is there any special reason for that? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the board, I'd place a MAX232, couple of 20 mA LEDs and 2*16 character LCD screen. What decoupling capacitor should I use near the power connector of the board?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-08T23:22:06.873" LastActivityDate="2011-02-08T23:22:06.873" Title="Would pictured circuit be good enough to power ATmega162?" Tags="&lt;avr&gt;&lt;power-supply&gt;&lt;decoupling-capacitor&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="9874" PostTypeId="2" ParentId="9873" CreationDate="2011-02-08T19:21:02.307" Score="2" ViewCount="" Body="&lt;p&gt;It depends a lot on your requirements as a simple logic circuit will run properly with just 100 nF and nothing else. If you have sensitive analog voltages the choke (or, maybe better, ferrite) can be helpful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think 1 nF and 10 nF will give you any advantage, but if you have a lot of input ripple or want very low output ripple, I'd add 10 µF on the right side (there are even ceramics in 0805 nowadays).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The inductor needs to be on the power supply side, not near the controller. If it would be there, the controller's supply voltage would drop seriously every time it switches something (internally or externally).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Multilayer ceramics are the new tantalum. ;) I guess, they recommend them in contrast to aluminium electrolytics because of their low ESR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your circuit won't draw much current, so maybe 100 µF electrolytic or less at the input? That's really just a guess because if you have a clean supply you probably don't need any capacitors at the input at all (but they won't hurt).&lt;/p&gt;&#xA;" OwnerUserId="1950" LastActivityDate="2011-02-08T19:21:02.307" CommentCount="2" />
  <row Id="9875" PostTypeId="2" ParentId="9860" CreationDate="2011-02-08T19:21:27.203" Score="0" ViewCount="" Body="&lt;p&gt;It depends a bit on your application.  Do you want individual control of each led?  What is your refresh rate.  How bright do you need the led's..... Can you give some more info?&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-02-08T19:21:27.203" />
  <row Id="9876" PostTypeId="2" ParentId="9856" CreationDate="2011-02-08T19:40:30.833" Score="2" ViewCount="" Body="&lt;p&gt;Get a quote for renting a proper spectrum analyzer for a month.  It probably won't accomplish anything since there's likely nothing there to find, but they are quite fun to play with.  And useful to know about - you might really need one at some point in the future, and knowing your way around test equipment is always good, so make lemons out of lemonade and further your professional experience.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given the cost of such equipment, rental is extremely common amongst even primary users.  There are of course cheap, limited devices out there, but it's good to know about the traditional instrument.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-02-08T19:40:30.833" />
  <row Id="9877" PostTypeId="1" AcceptedAnswerId="9881" CreationDate="2011-02-08T19:42:48.210" Score="2" ViewCount="131" Body="&lt;p&gt;I have an 11.1v lithium polymer battery pack which has 1300 mAh capacity and has a 20 C rating. Therefore I figure the maximum amperage the battery can supply is 26 A. (C * mAh / 1000&lt;sup&gt;&lt;a href=&quot;http://www.cheapbatterypacks.com/?sid=764526&amp;amp;apage=faq.asp&quot; rel=&quot;nofollow&quot; title=&quot;See: 'What does the C mean in 10C, 20C etc ?'&quot;&gt;1&lt;/a&gt;&lt;/sup&gt;) To be safe, I figure the wiring I use with it should be able to handle 30 A in case a higher capacity battery is used later. I figure that I can safely use an ~11.1 V, 1500 mAh, 20 C battery at that current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit this will be used in has a momentary switch (trigger) and a DC motor. (&lt;a href=&quot;http://i235.photobucket.com/albums/ee12/aces31767/MOSFET-WiringDiagram.jpg&quot; rel=&quot;nofollow&quot; title=&quot;Wiring diagram, see: 'Stock Wiring' (top left)&quot;&gt;Airsoft gun wiring diagram&lt;/a&gt;) There will be about a foot and a half of wire from battery terminal to battery terminal. The circuit under nominal conditions would be under load for no more than half a second every few minutes. However it could potentially be under continuous load for up to 5 seconds with an average of those cases being 3 seconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is, the wiring has to fit through small passages. And I need to use the smallest possible wire gauge that will handle the current. I currently have some stranded copper 18 AWG wire for automotive use. I'm pretty sure that this will not handle the current this battery is likely to supply&lt;sup&gt;&lt;a href=&quot;http://www.powerstream.com/Wire_Size.htm&quot; rel=&quot;nofollow&quot; title=&quot;AWG Table&quot;&gt;3&lt;/a&gt;&lt;/sup&gt;. From memory, (without measuring the clearance of the passages) 18 gauge wire seems to be an ideal size, though I think I really need 14 gauge wire to handle the current if it's just stranded copper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have trouble finding any easily understood documentation on the subject and there are so many variables to consider. Such as the length of the wire, the diameter of the strands (if stranded), the number of strands, the coating (if any), the ambient temperature, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My research leads me to believe that if I were to get some 18 or 16 gauge wire with silver coating and a thin insulator (teflon?) that it would fit the bill. &lt;strong&gt;What is the proper gauge (solid or stranded), coating, and/or insulation for this application?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;: I added &quot;duty cycle&quot; information to paragraph 2.&lt;/p&gt;&#xA;" OwnerUserId="2932" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-08T23:16:40.140" LastActivityDate="2011-02-09T12:38:05.913" Title="What wire do I need to carry 30 A for 18&quot;?" Tags="&lt;wire&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="9878" PostTypeId="1" CreationDate="2011-02-08T20:02:58.577" Score="2" ViewCount="196" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/6958/audio-coupling-capacitors&quot;&gt;Audio coupling capacitors&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I am designing an electret microphone input.  The datasheet has a capacitor that couples the audio into to the rest of the circuit.  This capacitor is used to block any DC offset from the microphone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What value should the DC blocking cap be?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen values ranging from 100nF to 10uF.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;===============================&lt;br&gt;&#xA;Edit:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/6958/audio-coupling-capacitors&quot;&gt;Audio Coupling Capacitors&lt;/a&gt; covers this question.  The end result is there is some load resistor that the coupling capacitor feeds.  This forms a low-pass filter.  Set the RC filter values to meet your lowest frequency.&lt;/p&gt;&#xA;" OwnerUserId="204" LastEditorUserId="204" LastEditorDisplayName="" LastEditDate="2011-02-10T17:50:59.340" LastActivityDate="2011-02-10T17:50:59.340" ClosedDate="2011-02-10T18:40:45.920" Title="Audio DC Blocking Capacitor" Tags="&lt;capacitor&gt;&lt;audio&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="9879" PostTypeId="2" ParentId="9878" CreationDate="2011-02-08T20:29:54.993" Score="-1" ViewCount="" Body="&lt;p&gt;It depends on the input impedance of the following stage, but 100 nF should be fine.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-08T20:29:54.993" />
  <row Id="9881" PostTypeId="2" ParentId="9877" CreationDate="2011-02-08T20:51:07.203" Score="3" ViewCount="" Body="&lt;p&gt;Over 18 inches you would drop about 0.675 volts with 18 gauge wire. 12 gauge would drop about 0.1 volts. You would need to use 6 or 7 gauge to handle 30 A over an extended period. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are not using continuous current, but pulses, you could get away with using a smaller gauge wire. However an undersized wire would heat up significantly in just a few seconds. Unless you are sending pulses of less then 1 sec, you will need a large diameter wire. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;AS for the insulation, it depends on how the wire is being used and how it is routed. 30 A is a lot of current. If some one can come in contact with it, you need heavy insulation for safety. Especially if it flexes. If it is total enclosed in a non conductive housing, you could use thinner insulation. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-08T20:58:21.670" LastActivityDate="2011-02-08T20:58:21.670" CommentCount="7" />
  <row Id="9882" PostTypeId="2" ParentId="9856" CreationDate="2011-02-08T21:48:25.273" Score="0" ViewCount="" Body="&lt;p&gt;Think geek &lt;a href=&quot;http://www.thinkgeek.com/gadgets/electronic/c240/&quot; rel=&quot;nofollow&quot;&gt;wi-spy spectrum analyzer&lt;/a&gt;?  Will only do around 2.4GHz (the $300 version says it covers &lt;a href=&quot;http://www.thinkgeek.com/gadgets/electronic/9558/&quot; rel=&quot;nofollow&quot;&gt;2.400 - 2.4835 GHz&lt;/a&gt;), but it will find obvious things (cell phones/wifi devices).  Since he's probably delusional (or legitimately paranoid due to breaking the law), its worth the $90 shot.  Or buy a proper spectrum analyzer for a couple thousand dollars.&lt;/p&gt;&#xA;" OwnerUserId="2935" LastActivityDate="2011-02-08T21:48:25.273" />
  <row Id="9884" PostTypeId="1" AcceptedAnswerId="9885" CreationDate="2011-02-08T22:25:22.900" Score="-2" ViewCount="191" Body="&lt;p&gt;What's the difference between an IC and a transistor?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-08T22:28:09.467" LastActivityDate="2011-02-09T20:59:46.217" Title="IC vs. transistor" Tags="&lt;transistor&gt;&lt;ic&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="9885" PostTypeId="2" ParentId="9884" CreationDate="2011-02-08T23:12:41.780" Score="8" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;A transistor is a semiconductor device used to amplify and switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. [...]&#xA;  Today, some transistors are packaged individually, but &lt;strong&gt;many more are found embedded in integrated circuits.&lt;/strong&gt; (&lt;em&gt;Ed: emphasis added&lt;/em&gt;)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Transistor&quot; rel=&quot;nofollow&quot;&gt;Transistor.&lt;/a&gt; Wikipedia: The Free Encyclopedia.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using electronic components. The integrated circuit's mass production capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time.  Furthermore, much less material is used to construct a packaged IC die than a discrete circuit.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Integrated_circuit&quot; rel=&quot;nofollow&quot;&gt;Integrated circuit.&lt;/a&gt; Wikipedia: The Free Encyclopedia.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-02-08T23:12:41.780" />
  <row Id="9886" PostTypeId="2" ParentId="9884" CreationDate="2011-02-08T23:23:40.757" Score="4" ViewCount="" Body="&lt;p&gt;An IC can have many BJTs, diodes, MOSFETs, resistors, capacitors and sometimes even inductors on the same or stacked pieces of silicon.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A transistor is just a transistor, it behaves either like a MOSFET (voltage controlled) or a BJT (current controlled) device. In some cases, you can buy transistors with built in biasing resistors, which technically puts them in the category of integrated circuits, but they are often known simply as transistors. Here is the only point the line between the two may be blurred.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-08T23:23:40.757" />
  <row Id="9888" PostTypeId="1" AcceptedAnswerId="9892" CreationDate="2011-02-09T00:34:17.597" Score="4" ViewCount="405" Body="&lt;p&gt;I'm making a board which will host an ATmega 162 microcontroller in PDIP package. Unfortunately, VCC and GND pins are diagonally arranged. From what I've read, the capacitors should be as close to the pins as possible for maximum effect. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/hWgn1.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right now, I can see 3 ways to connect the capacitors. Run wires to the capacitors so that they are at equal distance from both pins, place capacitors near ground and run wire to VCC or place capacitors near VCC and run wire to ground. There's always the &quot;none of the above&quot; option too. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I make right decision in this case? Or is is irrelevant?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-10T00:56:40.560" Title="How to connect decoupling capacitor when VCC/GND pins aren't close." Tags="&lt;layout&gt;&lt;decoupling-capacitor&gt;" AnswerCount="5" CommentCount="4" />
  <row Id="9889" PostTypeId="2" ParentId="9888" CreationDate="2011-02-09T00:59:10.133" Score="0" ViewCount="" Body="&lt;p&gt;Overall distance matters, as inductance increases as you increase the wire distance. However, the position of the capacitor along this wire should not matter.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-02-09T00:59:10.133" />
  <row Id="9890" PostTypeId="2" ParentId="9888" CreationDate="2011-02-09T01:09:13.740" Score="3" ViewCount="" Body="&lt;p&gt;For a PCB design, I almost always use a ground plane and for chips with opposite power pins I place a cap next to the power pin and ground the other end. The ground plane has a low inductance which reduces the effect compared to wiring a single trace to Vss. The goal of the decoupling cap is to provide a local current source for the chip, so this works well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's a breadboard, I usually just solder some wires to a 100n cap and wire it over the chip. Messy, but it works.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-09T01:09:13.740" CommentCount="1" />
  <row Id="9891" PostTypeId="2" ParentId="9888" CreationDate="2011-02-09T01:10:59.280" Score="5" ViewCount="" Body="&lt;p&gt;The decoupling capacitor goes as close to the power pin as possible, as the power line has a higher impedance than the ground reference. There should be a large ground plane, ready to provide a very low impedance path. A power plane is sometimes employed in multilayer (4+) designs for, among other things, a low impedance source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You talk about wires, which leads me to believe you are using a breadboard. In this case, decoupling capacitors are just as important, but parasitic inductance and capacitance and ohmic contacts will mask their effects. Use the power rails for power and ground, and tie them together in multiple locations -- no ground loops! I wouldn't bother with anything other than a large electrolytic (10uF) in a breadboard unless it doesn't work, as it is only for prototyping simple circuits. &lt;em&gt;(Does this work?)&lt;/em&gt; Troubleshooting decoupling requires the real layout (if the final product is in a breadboard, then go for it).&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-02-09T01:10:59.280" CommentCount="1" />
  <row Id="9892" PostTypeId="2" ParentId="9888" CreationDate="2011-02-09T03:19:07.973" Score="7" ViewCount="" Body="&lt;p&gt;For these types of packages you should use at least two equal bypass capacitors, one at each side of the IC (one near ground and one near VCC).  The parallel inductance of two traces to two different caps lowers the total trace inductance and the current flowing from each bypass cap in opposite directions helps cancel out EMI.  See Henry Ott's book &quot;Electromagnetic Compatibility Engineering&quot; for more details here.  Apparently this technique reduces noise by a significant amount and will also help functionally.  This technique taken to the extreme would involve using a power and ground plane and surrounding the entire chip with bypass capacitors, or if you have the money to spare, using buried capacitance planes, but simply using two caps at either side of the package makes a large and measurable difference (as opposed to just at the VCC side) (I'm too lazy to look it up but I think we're talking 10dB+ improvement).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/R6f6x.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Added my cheesy drawing.  The arrows are supposed to show the canceling current loops (one clockwise the other counterclockwise), but note the capacitors should be placed closer to the chip then I drew.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastEditorUserId="2377" LastEditorDisplayName="" LastEditDate="2011-02-10T00:56:40.560" LastActivityDate="2011-02-10T00:56:40.560" CommentCount="3" />
  <row Id="9893" PostTypeId="2" ParentId="9761" CreationDate="2011-02-09T03:22:06.047" Score="1" ViewCount="" Body="&lt;p&gt;you may want to try &lt;a href=&quot;http://processing.org/&quot; rel=&quot;nofollow&quot;&gt;http://processing.org/&lt;/a&gt; for the programming language, there are some projects out there that use serial data to manipulate graphics and objects on screen.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-09T03:22:06.047" />
  <row Id="9894" PostTypeId="1" CreationDate="2011-02-09T04:48:30.620" Score="5" ViewCount="84" Body="&lt;p&gt;I'm working on coupling gyro and electronic compass for better accuracy of device orientation (using &lt;a href=&quot;http://en.wikipedia.org/wiki/Particle_filter&quot; rel=&quot;nofollow&quot;&gt;particle filters&lt;/a&gt;). I have one basic question, though: &lt;strong&gt;&lt;em&gt;how do I establish ground truth in this case?&lt;/em&gt;&lt;/strong&gt; I cannot use the compass readings alone, since the whole basis of my experiment is that the compass readings are inaccurate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would taking an average of a number of compass readings be a sufficient approximation? Is there any other idea, besides having a compass of &lt;em&gt;&quot;greater accuracy&quot;?&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2939" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-09T05:58:24.477" LastActivityDate="2011-02-09T14:25:21.907" Title="Establishing ground truth in a particle filter experiment using compass and gyro" Tags="&lt;sensor&gt;&lt;filter&gt;&lt;gyro&gt;&lt;compass&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="2" />
  <row Id="9895" PostTypeId="2" ParentId="9894" CreationDate="2011-02-09T06:25:16.293" Score="1" ViewCount="" Body="&lt;p&gt;The easy answer is  to use a surveyed direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A map, your position, and a landmark out a window, a rifle scope and there you go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Worst case you need to get a couple or three points surveyed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In geodesy, setting up observatories, testing ranging gear, all the same problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you use the correct magnetic variation for your location. ( you'll end up knowing your countries geodesy service pretty well by the end of this).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you just need some known points to calibrate from, then...&#xA;It's relatively simple to get 0, 90, 180 and 270 degrees from that with cheap hardware.&#xA;A rotation stage, even an industrial one for a milling machine will give almost any given angle.&#xA;(Magnetic compensation for metal equipment may be a pain. Just a plastic 360 degree protractor and some wood will do for all but very fine work.) [I have seen it used in compass calibration before.... if you need more accuracy, make a bigger protractor on a huge bit of cardboard.]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We used to used computer-driven rotation stages to calibrate gravity sensors.&#xA;The people we bought IMU's from used a robot arm to test the IMU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For compasses, a cardboard compass rose and wooden/plastic pivots.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need very fine variation, I pity you. Maybe use a coil set.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-02-09T06:25:16.293" CommentCount="1" />
  <row Id="9896" PostTypeId="1" AcceptedAnswerId="9902" CreationDate="2011-02-09T07:46:36.960" Score="1" ViewCount="49" Body="&lt;p&gt;I'm looking for FOSS (for commercial use) VCL components for Delphi or libraries for Visual Basic/C/C++/C# ... basically, just something to abstract the h/w for development, although a h/w simulator might be useful for testing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know what is available? &lt;/p&gt;&#xA;" OwnerUserId="2940" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-02-09T13:32:40.067" LastActivityDate="2011-02-09T13:35:48.660" Title="FOSS ModBus libraries/VCl?" Tags="&lt;hardware&gt;&lt;modbus&gt;" AnswerCount="2" />
  <row Id="9897" PostTypeId="2" ParentId="9888" CreationDate="2011-02-09T08:01:30.317" Score="3" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/TZeQ2.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-09T08:01:30.317" CommentCount="5" />
  <row Id="9898" PostTypeId="1" CreationDate="2011-02-09T08:53:27.247" Score="-1" ViewCount="109" Body="&lt;p&gt;Hi all, I am trying to make a an implementation of a vhdl design. It´s an application for signal processing. Does anyone know what is the fastest development tool Xilinx System Generator or Xilinx ISE.&#xA;Thank you.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T21:05:15.433" LastActivityDate="2011-02-12T21:05:15.433" Title="Choosing a tool for development: System Generator vs Xilinx ISE" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;vhdl&gt;&lt;tools&gt;&lt;xilinx-system-generator&gt;" AnswerCount="1" />
  <row Id="9899" PostTypeId="1" CreationDate="2011-02-09T10:20:24.890" Score="0" ViewCount="305" Body="&lt;p&gt;What I do &lt;strong&gt;not&lt;/strong&gt; want is one of those RFID readers which attaches to serial or USB port and writes its input to stdin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking for cheap &amp;amp; nasty RFID reader which I can query over serial or USB; a bonus is if it is also an RFID writer but doesn't add too much cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Coding something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;fopen(com1);&#xA;fwrite, com1, &quot;hey, you, send me some input&quot;);&#xA;read(com1, ipit_value);&#xA;fclose(com1);&#xA;&lt;/pre&gt;&#xA;" OwnerUserId="2940" LastActivityDate="2011-02-09T14:40:42.473" Title="Seeking cheap RFID reader / writer" Tags="&lt;rfid&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="9900" PostTypeId="2" ParentId="9898" CreationDate="2011-02-09T10:48:36.667" Score="2" ViewCount="" Body="&lt;p&gt;Completing an entire FPGA design purely in system generator is likely to be very-hard to impossible, especially if you have to interface to external peripherals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you already have an FPGA framework developed which you want to drop a signal processing block into, then System Generator can be a good way to go.  You have all the abilities of Matlab behind you for verifying the design, whereas doing it in pure VHDL/Verilog makes the verification harder work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, I developed an implementation of a common image-processing algorithm (a Shi-Tomasi corner detector) fairly quickly with System Generator.  But.... I had already built up the rest of the system (which was pretty big with embedded Microblazes, ram controllers etc) in EDK and with the ISE tools.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing System Generator makes very easy (which is a huge time saver IMO) is linking your block up to an EDK design. You just drag some blocks in for the registers and shared memory blocks and it sorts all the bus interfacing and creation of the files which tell EDK how to use it.  Even the SW boilerplate to access the registers.&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-02-09T10:48:36.667" CommentCount="2" />
  <row Id="9901" PostTypeId="2" ParentId="9899" CreationDate="2011-02-09T11:01:51.927" Score="5" ViewCount="" Body="&lt;p&gt;There are a whole bunch of different RFID types, so it's hard to recommend something without any further information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll assume that you meant EM4100 125kHz tags, those are read only, but very common, so there are many choices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If all you want is to get the rfid ids into a pc, then pick up an USB reader, which simply shows up as a USB keyboard, which spits out the id and hits return:&#xA;&lt;a href=&quot;http://cgi.ebay.com/125Khz-RFID-Proximity-ID-USB-Reader-Free-5-RFID-Cards-/260641368732?pt=LH_DefaultDomain_0&amp;amp;hash=item3caf6faa9c&quot; rel=&quot;nofollow&quot;&gt;http://cgi.ebay.com/125Khz-RFID-Proximity-ID-USB-Reader-Free-5-RFID-Cards-/260641368732?pt=LH_DefaultDomain_0&amp;amp;hash=item3caf6faa9c&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For your own electronics, the cheapest choice is to hook about $2 worth of jellybean components up to an AVR, like I've done here:&#xA;&lt;a href=&quot;http://www.hackaarhus.dk/forum/download/file.php?id=45&quot; rel=&quot;nofollow&quot;&gt;http://www.hackaarhus.dk/forum/download/file.php?id=45&lt;/a&gt;&#xA;Forum thread: &lt;a href=&quot;http://www.hackaarhus.dk/forum/viewtopic.php?f=4&amp;amp;t=113&quot; rel=&quot;nofollow&quot;&gt;http://www.hackaarhus.dk/forum/viewtopic.php?f=4&amp;amp;t=113&lt;/a&gt;&#xA;Sources: &lt;a href=&quot;https://github.com/dren-dk/HAL900/tree/master/door-ctrl/hardware-4&quot; rel=&quot;nofollow&quot;&gt;https://github.com/dren-dk/HAL900/tree/master/door-ctrl/hardware-4&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next step up is a module like this:&#xA;&lt;a href=&quot;http://www.sparkfun.com/products/8419&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/8419&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-02-09T11:01:51.927" CommentCount="2" />
  <row Id="9902" PostTypeId="2" ParentId="9896" CreationDate="2011-02-09T12:36:21.580" Score="1" ViewCount="" Body="&lt;p&gt;Take a look at MODBUS simulator &lt;a href=&quot;http://www.plcsimulator.org/Home&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. &lt;a href=&quot;http://support-omron.fr/MultiwayE.php&quot; rel=&quot;nofollow&quot;&gt;This one&lt;/a&gt; is also worth a look. For Delphi components take a look &lt;a href=&quot;http://sourceforge.net/projects/delphimodbus/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, &lt;a href=&quot;http://mbserver.tripod.com/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, and if you don't mind the nag screen &lt;a href=&quot;http://www.ozm.cz/ivobauer/modlink/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-02-09T12:36:21.580" CommentCount="2" />
  <row Id="9903" PostTypeId="2" ParentId="9877" CreationDate="2011-02-09T12:38:05.913" Score="1" ViewCount="" Body="&lt;p&gt;If space is tight check out Alpha's Ecowire, which has thin but very tough insulation, so the overall diameter is less than PVC wire of the same copper cross-section.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-09T12:38:05.913" CommentCount="1" />
  <row Id="9904" PostTypeId="2" ParentId="9896" CreationDate="2011-02-09T13:35:48.660" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://jamod.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;JaMod&lt;/a&gt; is an open source Java implementation of the Modbus protocol. I've used it before to simulate a Modbus master device. I believe you could use it to simulate the slave device as well.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-02-09T13:35:48.660" CommentCount="1" />
  <row Id="9905" PostTypeId="2" ParentId="2176" CreationDate="2011-02-09T13:36:18.737" Score="3" ViewCount="" Body="&lt;p&gt;Try &lt;a href=&quot;http://www.scilab.org/&quot; rel=&quot;nofollow&quot;&gt;Scilab&lt;/a&gt;, it comes with FIR and IIR filter design and simulation functions. It's free! There are Linux and MAC versions.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-09T15:46:38.920" LastActivityDate="2011-02-09T15:46:38.920" CommunityOwnedDate="2011-02-09T13:36:18.737" />
  <row Id="9906" PostTypeId="2" ParentId="9894" CreationDate="2011-02-09T14:25:21.907" Score="0" ViewCount="" Body="&lt;p&gt;Do you know if (or how fast and in what direction) the device is accelerating?  You can determine orientation by dead reckoning with the gyro, and magnetic orientation with the gyro.  A 3-axis accelerometer system could establish another frame of reference (gravity) which you could then integrate with the other two for greater accuracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need still greater accuracy, I believe that the next step would be optics.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-09T14:25:21.907" />
  <row Id="9907" PostTypeId="2" ParentId="9899" CreationDate="2011-02-09T14:40:42.473" Score="3" ViewCount="" Body="&lt;p&gt;dren.dk has listed some great resources.  I'm a bit bummed to see that the RFID IC is $30 alone.  I have been using the &lt;a href=&quot;http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/RFID/List/0/SortField/4/ProductID/688/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;Parallax RFID read/write module&lt;/a&gt; that interfaces via RS232, and have had good results with it so far, and it's only $13 more (currently $43 on sale) than the IC sold at SparkFun, so it might be more immediately integratable for you.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-09T14:40:42.473" CommentCount="1" />
  <row Id="9908" PostTypeId="1" CreationDate="2011-02-09T15:07:35.810" Score="2" ViewCount="157" Body="&lt;p&gt;I'm a programmer and mathematician by profession, and I would like to get started in electronics/hardware. I have an Arduino, and I've written some basic programs in it (alarm clock with LCD and speaker, etc.), but I would like to learn more about the actual electronics. What books/tutorials are good for this? I don't mind mathematics (esp. calculus since that I would guess is used a lot in EE). In fact, something with good mathematical treatment is welcomed, but I don't want to shy away from intuitive explanations either. Something in the middle would be good. My knowledge right now is:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How a resistor works&lt;/li&gt;&#xA;&lt;li&gt;How a capacitor works&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;and NOTHING ELSE.&lt;/p&gt;&#xA;" OwnerUserId="2944" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-10T15:50:24.550" LastActivityDate="2011-02-10T15:50:24.550" Title="How do I get started with electronics/hardware?" Tags="&lt;arduino&gt;&lt;books&gt;" AnswerCount="3" />
  <row Id="9909" PostTypeId="2" ParentId="9908" CreationDate="2011-02-09T15:16:27.793" Score="3" ViewCount="" Body="&lt;p&gt;Here is a good &lt;a href=&quot;http://www.allaboutcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;site&lt;/a&gt; I got shown. Good for explanations of different theories. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-02-09T15:16:27.793" />
  <row Id="9910" PostTypeId="2" ParentId="6099" CreationDate="2011-02-09T16:00:49.733" Score="1" ViewCount="" Body="&lt;p&gt;Try the MAX485 or MAX483 from Maxim IC: &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/1111&quot; rel=&quot;nofollow&quot;&gt;http://www.maxim-ic.com/datasheet/index.mvp/id/1111&lt;/a&gt;&#xA;Very cheap and easy to use. Plus they can send data up to 4000 feet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's someone's tutorial on using them with Arduino: &#xA;&lt;a href=&quot;http://pskillenrules.blogspot.com/2009/08/arduino-and-rs485.html&quot; rel=&quot;nofollow&quot;&gt;http://pskillenrules.blogspot.com/2009/08/arduino-and-rs485.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1140" LastActivityDate="2011-02-09T16:00:49.733" />
  <row Id="9911" PostTypeId="2" ParentId="3366" CreationDate="2011-02-09T16:25:28.973" Score="1" ViewCount="" Body="&lt;p&gt;As far as books go, I find &lt;a href=&quot;http://www.mhprofessional.com/product.php?isbn=0071452818&quot; rel=&quot;nofollow&quot;&gt;Practical Electronics for Inventors&lt;/a&gt; to be very clear and accessible.&lt;/p&gt;&#xA;" OwnerUserId="2096" LastActivityDate="2011-02-09T16:25:28.973" />
  <row Id="9912" PostTypeId="1" AcceptedAnswerId="9966" CreationDate="2011-02-09T16:30:46.203" Score="3" ViewCount="77" Body="&lt;p&gt;I've tried a few options for reading the signals from thermocouples over the years. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The cheapest way (component cost) is likely to be DIY, and a lot of work involving lots of analogue stuff that I'm not good at! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried the following:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.analog.com/static/imported-files/data_sheets/AD596_597.pdf&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;MAX6675&lt;/strong&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;1+     £14    &#xA;25+    £9    &#xA;100+   £5&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;SPI Thermocouple solution&lt;/li&gt;&#xA;&lt;li&gt;Very easy to use and results are returned with 0.1°C accuracy.&lt;/li&gt;&#xA;&lt;li&gt;Very expensive&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/MAX6675.pdf&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;AD597&lt;/strong&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;1+     £6   &#xA;10+    £4   &#xA;100+   £3&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Feed output voltage into microcontroller ADC&lt;/li&gt;&#xA;&lt;li&gt;I've had good results with these&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Does anybody have any other recommendations? &lt;/p&gt;&#xA;" OwnerUserId="2770" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-10T18:44:35.620" LastActivityDate="2011-02-10T18:52:45.987" Title="More Options for Reading Thermocouple Signals" Tags="&lt;analog&gt;&lt;temperature&gt;&lt;thermocouple&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="9913" PostTypeId="2" ParentId="9908" CreationDate="2011-02-09T16:32:21.070" Score="1" ViewCount="" Body="&lt;p&gt;To repeat a recommendation I've just made in another thread, I find &lt;a href=&quot;http://www.mhprofessional.com/product.php?isbn=0071452818&quot; rel=&quot;nofollow&quot;&gt;Practical Electronics for Inventors&lt;/a&gt; to be very clear and accessible.&lt;/p&gt;&#xA;" OwnerUserId="2096" LastActivityDate="2011-02-09T16:32:21.070" />
  <row Id="9914" PostTypeId="2" ParentId="2176" CreationDate="2011-02-09T17:09:25.990" Score="0" ViewCount="" Body="&lt;p&gt;Analog Devices has a filter wizard:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.analog.com/en/amplifiers-and-comparators/products/dt-adisim-design-sim-tool/Filter_Wizard/resources/fca.html&quot; rel=&quot;nofollow&quot;&gt;http://www.analog.com/en/amplifiers-and-comparators/products/dt-adisim-design-sim-tool/Filter_Wizard/resources/fca.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It designs Sallen Key, Multiple Feedback, State Variable, and Biquad active filters. The attenuation of a low-pass filter is about 12 dB per octave per 2nd order stage (buffer between stages).&lt;/p&gt;&#xA;" OwnerUserId="721" LastEditorUserId="721" LastEditorDisplayName="" LastEditDate="2011-02-09T19:02:27.267" LastActivityDate="2011-02-09T19:02:27.267" CommunityOwnedDate="2011-02-09T17:09:25.990" />
  <row Id="9915" PostTypeId="1" AcceptedAnswerId="9916" CreationDate="2011-02-09T18:49:44.930" Score="7" ViewCount="206" Body="&lt;p&gt;CMOS inputs on microcontrollers and other ICs can be damaged by ESD discharges. Can the gate of a big discrete MOSFET (2N7000, IRF9530, etc.) be damaged by ESD discharges?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-14T10:33:44.153" Title="Are discrete MOSFETs ESD sensitive?" Tags="&lt;mosfet&gt;&lt;esd&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="9916" PostTypeId="2" ParentId="9915" CreationDate="2011-02-09T19:04:58.230" Score="11" ViewCount="" Body="&lt;p&gt;Yes. I've used MOSFETs which had a conductive rubber band around the pins to protect the gate(s) by shorting the pins, to be removed after soldering.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-02-09T19:04:58.230" CommentCount="1" />
  <row Id="9917" PostTypeId="2" ParentId="9908" CreationDate="2011-02-09T19:16:44.263" Score="1" ViewCount="" Body="&lt;p&gt;An excellent site here &lt;a href=&quot;http://www.doctronics.co.uk/design.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.doctronics.co.uk/design.htm&lt;/a&gt;  - very useful for understanding things like voltage dividers and how analogue sensors work and how to use their output in the Arduino. It's written in a very practical context with example circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you have a bit of knowledge start trying to understand the datasheets and schematics for linear devices like 741 op amps and 555 timers. This will really help you start to put electronic concepts together.&lt;/p&gt;&#xA;" OwnerUserId="2894" LastActivityDate="2011-02-09T19:16:44.263" />
  <row Id="9918" PostTypeId="2" ParentId="9853" CreationDate="2011-02-09T19:20:33.680" Score="1" ViewCount="" Body="&lt;p&gt;Just happened to be browsing around on Jameco.com and see they have something that might fit what you're looking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CAMERA,MINI DVR,SOUND ACTIVATE&#xA;4GB,720x480,30FPS,W/ MIC,USB&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Part no. 2124517&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Features:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Built-in microphone&lt;/li&gt;&#xA;&lt;li&gt;Real time audio/video recording in AVI video format (720 x 480), 30 FPS&lt;/li&gt;&#xA;&lt;li&gt;Recharge the built-in Lithium-ion battery via USB or with supplied wall power adapter&lt;/li&gt;&#xA;&lt;li&gt;Up to 90 minutes storage for recorded A/V files&lt;/li&gt;&#xA;&lt;li&gt;Approximately 2 hours battery use time per charge&lt;/li&gt;&#xA;&lt;li&gt;PC video playback (via USB port)&lt;/li&gt;&#xA;&lt;li&gt;Size: 2.2&quot;H x 0.85&quot;W x 0.80&quot;D&lt;/li&gt;&#xA;&lt;li&gt;Weight: 15 grams&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;$70/each.  Here's the &lt;a href=&quot;http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&amp;amp;productId=2124517&amp;amp;catalogId=10001&amp;amp;freeText=2124517&amp;amp;app.products.maxperpage=15&amp;amp;storeId=10001&amp;amp;search_type=jamecoall&amp;amp;ddkey=http%3aStoreCatalogDrillDownView&amp;amp;CID=HPdvr&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;.  Hope it works out for you.&lt;/p&gt;&#xA;" OwnerUserId="2928" LastActivityDate="2011-02-09T19:20:33.680" />
  <row Id="9920" PostTypeId="2" ParentId="9824" CreationDate="2011-02-09T19:45:15.933" Score="3" ViewCount="" Body="&lt;p&gt;Arduinos &amp;amp;co are &lt;em&gt;prototyping and evaluation platforms&lt;/em&gt;. As such, they are simply not economically viable as a basis for even relatively small production runs. They're great for education and mocking up ideas, but a product would sink very quickly if it had to carry the cost of a ready-made sub-assembly that was not optimal in its final use. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be far better to create a new board including required elements of the 'duino and any ancillary circuitry than to have the cost of two boards and the risk of failing connections.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With regard to Visual Studio and anything .net, I wouldn't touch them with someone else's. Go for something platform and manufacturer agnostic - kind of in the spirit of the Arduino project itself.&lt;/p&gt;&#xA;" OwnerUserId="2894" LastActivityDate="2011-02-09T19:45:15.933" CommentCount="11" />
  <row Id="9921" PostTypeId="2" ParentId="9855" CreationDate="2011-02-09T19:54:25.170" Score="0" ViewCount="" Body="&lt;p&gt;Add some EMI suppression filters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Go to Murata, they have a wide range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also make ESD protection parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These days they come in surface mount too.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastEditorUserId="1481" LastEditorDisplayName="" LastEditDate="2011-02-09T20:00:46.520" LastActivityDate="2011-02-09T20:00:46.520" />
  <row Id="9922" PostTypeId="1" AcceptedAnswerId="9925" CreationDate="2011-02-09T20:19:35.297" Score="4" ViewCount="203" Body="&lt;p&gt;I would like to make a circuit that can heat up an object to a very high temperature, similar to an electric griddle or coffee cup warmer. What kind of heating elements do they typically use and where can I buy them? They should be pretty easy to power with 120VAC right? I just need to be able to switch it on and off from an MCU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Target temperature is ~200°C&lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-02-09T23:57:56.113" LastActivityDate="2011-03-09T23:51:16.527" Title="Heating an object with a circuit." Tags="&lt;circuit&gt;&lt;heating&gt;" AnswerCount="9" CommentCount="6" />
  <row Id="9923" PostTypeId="2" ParentId="9884" CreationDate="2011-02-09T20:59:46.217" Score="1" ViewCount="" Body="&lt;p&gt;This is a real layman's explanation (because I am a real layman):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A &lt;strong&gt;transistor&lt;/strong&gt; is one discrete device. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An &lt;strong&gt;integrated circuit&lt;/strong&gt; is several devices, including transistors, that form a complete circuit, usually a module of a larger circuit, shrunk down using micro electronics magic into something about the size of a transistor. In practice the package is often larger as space is required for all the pins that allow you to make connections. But it's still smaller than the same circuit made using components and a PCB. Hence the name, integrated circuit - a circuit integrated into one device.&lt;/p&gt;&#xA;" OwnerUserId="2894" LastActivityDate="2011-02-09T20:59:46.217" />
  <row Id="9924" PostTypeId="2" ParentId="2887" CreationDate="2011-02-09T21:39:32.377" Score="0" ViewCount="" Body="&lt;p&gt;If you turn 24V AC into a half or full wave, you will end up with 27V to 33V.&#xA;7805 will only go up to 20Vdc AND event it you make it work at 20V it will get very hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can turn to an adjustable one like a LM350 for example, you will need a few resistors more, but those have a higher input. I still suggest you put a heat sink .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using an audio transformer might make the voltage drop. but they are not made for high current tranfer. Ratio is directly proportional from the input impedence to the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending how it was made. if you load the secondary too much, it will probably plunge down on the voltage side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;usual way is to use a switching regulator. Look up Digikey. Today there are a multitude of very easy to use switching that uses off the shelf inductors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They come in all type of inputs and outputs and produces zero heat.&lt;/p&gt;&#xA;" OwnerUserId="2946" LastActivityDate="2011-02-09T21:39:32.377" />
  <row Id="9925" PostTypeId="2" ParentId="9922" CreationDate="2011-02-09T21:42:37.790" Score="9" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Resistance_wire&quot; rel=&quot;nofollow&quot;&gt;Resistance wire&lt;/a&gt; is what you want.  This is used in (at least older) space headers.  But make sure you have a fail-safe.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-09T21:42:37.790" CommentCount="4" />
  <row Id="9926" PostTypeId="2" ParentId="9922" CreationDate="2011-02-09T21:58:43.250" Score="1" ViewCount="" Body="&lt;p&gt;Peltier Junction is a thermoelectric device, which is a kind of an electronic heat pump.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you input DC, peltier element transfers heat from one side to another one. Turn the DC around, and hot/cool change sides.&#xA;Just don't change polarity when it is very hot, this will stress the device and blow it up.&#xA;Also it is a good idea to monitor the device and regulate current accordingly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One cool fact, if you heat it up on one side and keep the other cool, it will generate a current..&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Thermoelectric_effect&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Thermoelectric_effect&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://customthermoelectric.com/tecs_imax.html?gclid=CIK45N6F_KYCFYbb4Aodw3MjFg&quot; rel=&quot;nofollow&quot;&gt;http://customthermoelectric.com/tecs_imax.html?gclid=CIK45N6F_KYCFYbb4Aodw3MjFg&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2946" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-09T23:51:16.527" LastActivityDate="2011-03-09T23:51:16.527" CommentCount="3" />
  <row Id="9927" PostTypeId="2" ParentId="9922" CreationDate="2011-02-09T22:47:59.940" Score="0" ViewCount="" Body="&lt;p&gt;Have a chat with these people (disclaimer: I have never used them)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.omega.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.omega.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This enclosure heater claims to have a surface temp of 170C. Not sure if you can get higher temp ones or whether it will heat the load you want:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.omega.com/pptst/RC016_Series.html&quot; rel=&quot;nofollow&quot;&gt;http://www.omega.com/pptst/RC016_Series.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Resistance wire details: &lt;a href=&quot;http://www.omega.com/Temperature/pdf/NI60.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.omega.com/Temperature/pdf/NI60.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2011-02-09T22:47:59.940" />
  <row Id="9928" PostTypeId="2" ParentId="9922" CreationDate="2011-02-09T22:58:12.703" Score="4" ViewCount="" Body="&lt;p&gt;A metal-clad wirewound resistor makes a pretty good ready-made heating element&#xA;&lt;img src=&quot;http://i.imgur.com/ASnTX.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-09T22:58:12.703" CommentCount="3" />
  <row Id="9929" PostTypeId="2" ParentId="2887" CreationDate="2011-02-09T23:05:06.713" Score="0" ViewCount="" Body="&lt;p&gt;I ran across this switcher in my RSS feeds this morning: &lt;a href=&quot;http://www.electronics-lab.com/blog/?p=9159&quot; rel=&quot;nofollow&quot;&gt;LMZ14201H: 1A SIMPLE SWITCHER® Power Module with 42V Maximum Input&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks pretty simple, just a handful of discretes.  It should dissipate quite a bit less power than a 7805, since it's a switching regulator.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-02-09T23:05:06.713" />
  <row Id="9930" PostTypeId="1" AcceptedAnswerId="9934" CreationDate="2011-02-09T23:05:24.477" Score="4" ViewCount="46" Body="&lt;p&gt;Looking for some resources on the design of Integrated Circuit Designs as they can contain a range of components. I am interested in how they can produce diodes and resistors on the dies in the ICs. Are there any free resources available?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-02-09T23:12:02.393" LastActivityDate="2011-02-10T04:08:38.807" Title="IC Design Resources" Tags="&lt;ic&gt;&lt;cmos&gt;" AnswerCount="1" />
  <row Id="9931" PostTypeId="2" ParentId="9922" CreationDate="2011-02-10T00:02:35.513" Score="3" ViewCount="" Body="&lt;p&gt;You want a cartridge heater.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/KdKHT.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fortunately, cartridge heaters are very cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mcmaster.com/#die-cartridge-heaters/=aypket&quot; rel=&quot;nofollow&quot;&gt;McMaster Carr Cartridge Heaters&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.google.com/search?q=heater+cartridge&amp;amp;hl=en&amp;amp;client=opera&amp;amp;hs=K6z&amp;amp;rls=en&amp;amp;prmd=ivns&amp;amp;source=univ&amp;amp;tbs=shop:1&amp;amp;tbo=u&amp;amp;ei=XypTTZSJIo2osAPbq8SrBw&amp;amp;sa=X&amp;amp;oi=product_result_group&amp;amp;ct=title&amp;amp;resnum=11&amp;amp;ved=0CGsQrQQwCg&quot; rel=&quot;nofollow&quot;&gt;Google Shopping&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-02-10T00:02:35.513" />
  <row Id="9932" PostTypeId="2" ParentId="9922" CreationDate="2011-02-10T00:25:50.470" Score="1" ViewCount="" Body="&lt;p&gt;I would recommend looking at silicone heater pads, which take 120VAC.  McMaster is one place that has them.  &lt;a href=&quot;http://www.mcmaster.com/#silicone-heaters/=aypumy&quot; rel=&quot;nofollow&quot;&gt;http://www.mcmaster.com/#silicone-heaters/=aypumy&lt;/a&gt;.  You can pair them with a thermocouple and inexpensive PID controller to regulate the temperature.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-10T00:25:50.470" CommentCount="3" />
  <row Id="9933" PostTypeId="2" ParentId="9922" CreationDate="2011-02-10T02:44:12.927" Score="1" ViewCount="" Body="&lt;p&gt;Any electronic item can dissipate heat.   The temperature achieved depends on the thermal resistance to ambient.  Usually the temperature will rise linearly at a certain number of degrees per watt.  This is determined almost entirely by the load, and not by the element you are using to heat the load.  For further reading look at heatsinking app notes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice that heat rise is above ambient.  If you care about the exact temperature you should plan to have some kind of feedback system to measure the temperature and turn the heating element on / off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;200C is hot!  Most electrical components will be damaged by such heat.  Look for cartridge heaters as mentioned in other answers.  You can buy replacement electric range heating elements in an appliance store.  A complete electric heating plate is about $20 at discount stores.  These wirewound resistors are spec'ed up to 250C: &lt;a href=&quot;http://www.mouser.com/catalog/specsheets/rhnh.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.mouser.com/catalog/specsheets/rhnh.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-10T02:44:12.927" />
  <row Id="9934" PostTypeId="2" ParentId="9930" CreationDate="2011-02-10T04:08:38.807" Score="6" ViewCount="" Body="&lt;p&gt;If you're looking for a free IC design book available on the web, I would recommend Hans Camenzind's book &lt;em&gt;&lt;a href=&quot;http://www.designinganalogchips.com&quot; rel=&quot;nofollow&quot;&gt;Designing Analog Circuits&lt;/a&gt;&lt;/em&gt;. It's a pretty good resource that goes from the device building blocks to the large complicated circuits. It has plenty of drawings and is much more readable than any textbook I have.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;His text is not encyclopedic, but you should be able to get enough examples to understand &lt;strong&gt;A&lt;/strong&gt; way to build a diode so that you wouldn't be shocked by a new method. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-02-10T04:08:38.807" />
  <row Id="9935" PostTypeId="1" AcceptedAnswerId="9936" CreationDate="2011-02-10T06:24:31.517" Score="1" ViewCount="132" Body="&lt;p&gt;I want to  build a FPGA based prototype for uncompressed video over wireless connection with  one box being transmitter and other a receiver (to display). The transceiver speed for HD video (1080) is 3-4Gbps. But it would need an expensive FPGA board. I am thinking of VGA and I guess it needs around 1 Gbps (correct me if I'm wrong). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What type of FPGA board should I use (preferably cheaper)?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I would need to interface the FPGA with an RF module. Are there any RF module available for that could be interfaced with FPGA and support 1Gbps speed?&lt;/p&gt;&#xA;" OwnerUserId="2947" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-09T18:42:27.023" LastActivityDate="2011-03-09T18:42:27.023" Title="FPGA board for implementing wireless video" Tags="&lt;fpga&gt;&lt;wireless&gt;&lt;rf&gt;&lt;video&gt;" AnswerCount="2" />
  <row Id="9936" PostTypeId="2" ParentId="9935" CreationDate="2011-02-10T08:33:44.637" Score="1" ViewCount="" Body="&lt;p&gt;I think reliable 1Gbit RF transmission is the biggest problem here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I would take let's say 5-10x WiFi 11n transcievers in 5Ghz band so that you can have multiple 40Mhz channels there without interference. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I would start from cheapest FPGA board and single transciever, and once you master that, you will see which bigger board you would need, it's totally depend on huw much logic you want to implement there. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to think is compressing video, or going stright to DLNA (which is basically compressed video over WiFi, standardized).&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-10T08:33:44.637" CommentCount="1" />
  <row Id="9937" PostTypeId="2" ParentId="9935" CreationDate="2011-02-10T08:50:33.907" Score="1" ViewCount="" Body="&lt;p&gt;Hi, I usign &lt;a href=&quot;http://www.lyrtech.com/Products/SFF_SDR_development_platforms.php&quot; rel=&quot;nofollow&quot;&gt;A Small Form Factor Software Define Radio of Lyrtech&lt;/a&gt;. You can do many applications for multiples kind of signals, It seems usefull.&#xA;This board has three modules: a Digital signal processing module, a conversion data module and a radio frecuency module.&#xA;The digital signal processing module has a virtex -4 (I would like other anyone with more resources) and a texas instrument Da Vinci DSP.&#xA;As you can see, it has a 1.6–2.2 GHz for high-band RF.&#xA;The only problem I see with this equipment is that could be expensive for your budget.&#xA;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastActivityDate="2011-02-10T08:50:33.907" />
  <row Id="9938" PostTypeId="1" CreationDate="2011-02-10T09:01:44.450" Score="0" ViewCount="123" Body="&lt;p&gt;I am doing a design using System Generator, and I have some doubts if my design could be performed in a Virtex 4 FPGA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know what can I do to check this?&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T21:05:34.777" LastActivityDate="2011-02-12T21:05:34.777" Title="System Generator: How to know if my FPGA could have enough resources to perform a design." Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;xilinx-system-generator&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="9939" PostTypeId="1" CreationDate="2011-02-10T09:20:36.680" Score="0" ViewCount="127" Body="&lt;p&gt;Hi all, I´m working with floating point numbers in System Generator. I need to perform this arithmetic operation &lt;strong&gt;y = x*(-1)&lt;/strong&gt; . I think it could be done by using the mult block, but I don´t like this way because is very expensive in terms of FPGA demanded resources.&#xA;So I was wondering if there is any block to perform some kind of data conversión. The only thing is needed to do is to change one bit.&#xA;&lt;strong&gt;Does anyone know how to change the sign a floating point number using a reasonable way?&lt;/strong&gt;&#xA;Thank you so much.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T21:06:00.593" LastActivityDate="2011-02-15T12:20:41.463" Title="System Generator: a block to change sign of a floating point" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;floating-point&gt;&lt;xilinx-system-generator&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="9940" PostTypeId="1" CreationDate="2011-02-10T09:27:20.117" Score="0" ViewCount="99" Body="&lt;p&gt;Hello, &lt;br&gt;&#xA;I have some issues with getting my internet from my neighbors. &lt;br&gt; &#xA;(don't worry, I got it with permission!) &lt;br&gt;&#xA;Anyways, I can only get a signal from the kitchen, &lt;br&gt;&#xA;and I was wondering, is there an option to use my D-link &lt;br&gt;&#xA;router as a wifi repeater (in order to boost the signal)?&lt;/p&gt;&#xA;" OwnerUserId="2948" LastEditorUserId="2948" LastEditorDisplayName="" LastEditDate="2011-02-10T09:51:48.470" LastActivityDate="2011-02-10T09:51:48.470" ClosedDate="2011-02-10T12:43:31.270" Title="Turning D-link DI 514 to A Wifi Repeater" Tags="&lt;wifi&gt;" CommentCount="8" />
  <row Id="9941" PostTypeId="1" CreationDate="2011-02-10T09:42:05.897" Score="2" ViewCount="194" Body="&lt;p&gt;Hi all, I wonder if the bitwise complement (NOT) of a floating point number's binary representation of a number is the same number but with a change in its sign?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you to all possible references to articles or documentation.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-02-10T23:39:37.557" LastActivityDate="2011-02-11T02:38:38.013" Title="The bitwise complement of a floating point number's binary representation" Tags="&lt;floating-point&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="1" />
  <row Id="9943" PostTypeId="2" ParentId="9938" CreationDate="2011-02-10T09:48:33.993" Score="0" ViewCount="" Body="&lt;p&gt;Well, there was always only 1 universal way to find out: run synthesis of your design for target FPGA and see if it feets in and meet timing constraints.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-10T09:48:33.993" />
  <row Id="9944" PostTypeId="2" ParentId="9941" CreationDate="2011-02-10T09:50:30.343" Score="2" ViewCount="" Body="&lt;p&gt;No, it's garbage.&#xA;floating points have complex internal structure, so you cannot do that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may do some manipulations on mantissa, but not whole number.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-10T09:50:30.343" CommentCount="2" />
  <row Id="9946" PostTypeId="2" ParentId="9824" CreationDate="2011-02-10T10:57:41.860" Score="2" ViewCount="" Body="&lt;p&gt;Custom made boards are nice if you have a budget for this and production big enough to justify the work. Otherwise you stick with products of the shelf, like Arduino, Netduino, Fez Domino, and &lt;a href=&quot;http://en.wikipedia.org/wiki/Single-board_computer&quot; rel=&quot;nofollow&quot;&gt;SBC&lt;/a&gt; boards (like in PC104 and various ITX formats). Making custom AVR/Arduino board is not too complex, but heavy modifications to Netduino or even designing (and later supporting) some linux board (like Gumstix) need a specialist(s) and cost tens of thousands of dollars and more. If you want to have most of the hard work done by someone else, and you want to customize just some parts of it, then &lt;a href=&quot;http://www.xduino.com/hardware/&quot; rel=&quot;nofollow&quot;&gt;module&lt;/a&gt; is the &lt;a href=&quot;http://www.mme-berlin.de/arm9-modul/index.htm&quot; rel=&quot;nofollow&quot;&gt;magic&lt;/a&gt; &lt;a href=&quot;http://www.developmentboard.net/index.php/productdetail/core+boards/ARM9/SAMSUNG/S3C2440/CSKY2440-v2/info/1&quot; rel=&quot;nofollow&quot;&gt;word&lt;/a&gt; for you.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastEditorUserId="1129" LastEditorDisplayName="" LastEditDate="2011-03-13T22:55:31.053" LastActivityDate="2011-03-13T22:55:31.053" CommentCount="2" />
  <row Id="9947" PostTypeId="2" ParentId="9941" CreationDate="2011-02-10T11:05:54.217" Score="14" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Binary32&quot; rel=&quot;nofollow&quot;&gt;IEEE 754&lt;/a&gt; floating point numbers are represented as a sign, a mantissa and an exponent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is possible to work with floats at a bit level, but &lt;A href=&quot;http://en.wikipedia.org/wiki/Fast_inverse_square_root#Overview_of_the_code&quot; rel=&quot;nofollow&quot;&gt;you need to know what you're doing&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/d/d2/Float_example.svg/590px-Float_example.svg.png&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some documents which explain further.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.engrng.pitt.edu/hunsaker/3097/floatingpoint.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.engrng.pitt.edu/hunsaker/3097/floatingpoint.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://floating-point-gui.de/&quot; rel=&quot;nofollow&quot;&gt;http://floating-point-gui.de/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2011-02-11T02:38:38.013" LastActivityDate="2011-02-11T02:38:38.013" CommentCount="2" />
  <row Id="9948" PostTypeId="2" ParentId="9938" CreationDate="2011-02-10T12:46:24.723" Score="4" ViewCount="" Body="&lt;p&gt;Go on Xilinx's DSP course - that'll give you a really good feel for how much resource various dsp-type operations take up, and then you'll be able to estimate in your head.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise, you'll just have to build it and see.  To get a quick idea, generate the NGC from the sysgen block and use &lt;a href=&quot;http://www.conekt.co.uk/capabilities/49-fpga-optim&quot; rel=&quot;nofollow&quot;&gt;FPGAOptim&lt;/a&gt; to show you which blocks are using how much of which resource.  It'll not be the final final answer, but within a few percent of the LUT count. (Full disclosure - I wrote FPGAOptim at work)&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-02-10T12:46:24.723" CommentCount="4" />
  <row Id="9949" PostTypeId="2" ParentId="9939" CreationDate="2011-02-10T12:57:14.513" Score="1" ViewCount="" Body="&lt;p&gt;Negating a floating point number involves inverting the sign bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(For fixed-point numbers there's a Negate block in the sysgen library which should avoid using a multiplier)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be aware though, that sysgen is not designed for use with floating-point - you might find yourself jumping through all sorts of hoops!&lt;/p&gt;&#xA;" OwnerUserId="763" LastEditorUserId="763" LastEditorDisplayName="" LastEditDate="2011-02-15T12:20:41.463" LastActivityDate="2011-02-15T12:20:41.463" CommentCount="5" />
  <row Id="9950" PostTypeId="2" ParentId="9941" CreationDate="2011-02-10T14:13:18.013" Score="4" ViewCount="" Body="&lt;p&gt;I'm not sure what you mean by &quot;the bitwise.&quot;  There are many bitwise operations.  Logical choices are the One's complement/Bitwise NOT (Fake Name's guess) or Two's complement (changes sign for signed integers).  Less logical choices are OR, AND, XOR, and their complements NOR, NAND, XNOR.  None of these will produce the desired result for a floating point number.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see in Joby's nice diagram, the first bit is the sign bit, then the (biased) exponent occupies 8 bits, then the mantissa.  What you want to do is XOR the sign bit:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;FloatingPointNumber ^ 0x80000000 == -(FloatingPointNumber)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;That constant assumes you're using 32-bit floats.  You'll need to add another 8 zeros at the end of the constant for a number of type double.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-10T14:13:18.013" />
  <row Id="9951" PostTypeId="2" ParentId="9915" CreationDate="2011-02-10T15:52:57.357" Score="6" ViewCount="" Body="&lt;p&gt;Any MOSFET outside of a circuit will be extremely ESD sensitive as one spike on the gate that raises its voltage above the maximum and it will be dead.  MOSFETs in circuits very frequently have explicit protection (Zeners on gates or clamping diodes in drivers) and other incidental ESD protections like pulldowns or possibly increased capacitance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More to the point of &quot;are big (and/or) discrete MOSFETs less sensitive&quot;, they are for two reasons:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The gate oxide is likely to be thicker and take more voltage to breakdown (though the input lines on an IC are probably overengineered in this manner as well), and&lt;/li&gt;&#xA;&lt;li&gt;The gate capacitance will be vastly larger, so it will take much more charge to build up a lethal voltage.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In a circuit, the more common failure modes (in my experience) are inductive spikes on the source pin blowing the gate, or those on the drain which can cause a fatal avalanche breakdown.  I don't think I've ever positively identified a dV/dt failure, which is where the voltage rise on the MOSFET is so fast, the parasitic capacitances between drain-gate-source are able to turn on the MOSFET causing bad things to happen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nevertheless, if you ground your source well and blast the gate right at the package with an ESD gun on 11, you might be able to kill it.  Users shouldn't be able to stick their grubby little hands on your gate lines because they could have just shuffled their wool socks along the polyester carpet, but if they can for some reason (???), a Zener should protect nearly everything.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-16T05:02:29.703" LastActivityDate="2011-02-16T05:02:29.703" />
  <row Id="9952" PostTypeId="1" AcceptedAnswerId="9954" CreationDate="2011-02-10T15:56:21.787" Score="1" ViewCount="104" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to stack 2 PCBs together, but the stacking height is extremely critical. In terms of board-to-board connectors, the best I could come up with was SAMTEC GFZ series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone recommend any other solutions to stack 2 different PCBs? I need to have very low stacking height ( &amp;lt; 2mm, the lower the better), and about 100 connections.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards,&lt;/p&gt;&#xA;" OwnerUserId="2893" LastActivityDate="2011-02-10T17:31:41.720" Title="very low stacking height PCB connector" Tags="&lt;pcb&gt;&lt;connector&gt;&lt;pcb-assembly&gt;" AnswerCount="3" />
  <row Id="9953" PostTypeId="1" AcceptedAnswerId="9957" CreationDate="2011-02-10T16:10:54.127" Score="0" ViewCount="219" Body="&lt;p&gt;I want to design a very low frequency (&amp;lt;1Hz) high pass filter.  I was thinking of using a 2 pole sallen-key opamp design with a pair of r's and c's.  Is there anything special I need to consider when choosing component values/types.  It looks as though the caps will need to be in the 100's of µF range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="2952" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-11T16:14:53.347" LastActivityDate="2011-02-11T16:14:53.347" Title="Very low frequency (&lt;1Hz) high pass filter design" Tags="&lt;circuit-design&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="9954" PostTypeId="2" ParentId="9952" CreationDate="2011-02-10T16:12:11.693" Score="3" ViewCount="" Body="&lt;p&gt;The SlimStack and/or PMC connectors might be useful alternatives, it depends a bit on the pin pitch that you can use:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.molex.com/molex/products/group?key=board_to_board_connectors&amp;amp;channel=PRODUCTS&amp;amp;langPref=english&quot; rel=&quot;nofollow&quot;&gt;http://www.molex.com/molex/products/group?key=board_to_board_connectors&amp;amp;channel=PRODUCTS&amp;amp;langPref=english&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a card with the PMC connector, and it is really tiny:&lt;img src=&quot;http://i.imgur.com/JVGan.jpg&quot; alt=&quot;FOXg20 card with Molex PMC connector&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-02-10T16:12:11.693" CommentCount="1" />
  <row Id="9955" PostTypeId="2" ParentId="9952" CreationDate="2011-02-10T16:14:11.770" Score="0" ViewCount="" Body="&lt;p&gt;I don't know how much space you want to take up but you can use standard header pin arrays.  solder them to 1 board, drill through the other board (1 hole per pin) put the female header on the back side of the board (side facing away from the other board) lined up with the holes.  The spacing between the boards could be arbitrarily small, it will only be defined by the thickness of the plastic spacer on the header pins which comes in various sizes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sullinscorp.com/drawings/159_SMH100-LP_E-D___-ST-BK,_11195-A.pdf&quot; rel=&quot;nofollow&quot;&gt;50 Pin header - 1mm molding&lt;/a&gt; (~1mm board to board spacing)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sullinscorp.com/drawings/174_SFM210-LP_E-D___-S_-BK,_11200-A.pdf&quot; rel=&quot;nofollow&quot;&gt;50 Pin Female Socket&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-02-10T16:14:11.770" CommentCount="2" />
  <row Id="9956" PostTypeId="1" AcceptedAnswerId="9958" CreationDate="2011-02-10T16:51:23.080" Score="0" ViewCount="59" Body="&lt;p&gt;I often tend to build a prototype for a project and if I have something that's good enough I find a case that matches the prototype I've built. However, now I'm trying to do more of the design up front and would like to design the casing up front. The latest projects seem to involve more parts as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which tools do you use? I would like something that could give me a 3D view of the assembly. As a hobbyist I'd like something that is free or cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking at &lt;a href=&quot;http://sketchup.google.com/&quot; rel=&quot;nofollow&quot;&gt;Google's SketchUp&lt;/a&gt; now which seem useful but kinda cumbersome for my task.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-02-10T17:07:12.810" Title="What's the best tool to design casings/boxes?" Tags="&lt;cases&gt;&lt;cable-assemblies&gt;&lt;assembly&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="9957" PostTypeId="2" ParentId="9953" CreationDate="2011-02-10T17:00:35.287" Score="2" ViewCount="" Body="&lt;p&gt;It depends on how accurately you are expecting to control your cutoff frequency. A few point come to mind ...&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Tolerance&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;High value electrolytic capacitors have wide tolerances, indeed cheap ones can be as wide as +100%/-50%. You won't get much better than &amp;#177;10% and stability could still be an issue. Solid electrolyte (aluminium/tantalum) have better stability but will be much more expensive.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Leakage&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Electrolytic capacitors will have a finite leakage current which will produce dc offsets given that your resistor values will also be high.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Polarization&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Make sure that your circuit biasing keeps capacitors correcty polarized.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Charge/Discharge&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;High value capacitors will have to charge &amp;amp; discharge somehow if there is a non-zero dc bias (ie single rail). This will cause turn-on 'thumps' as the circuit settles-down which may take a many (tens of) seconds. At turn-off, the capacitors may discharge into the op-amp causing damage although given that your resistor values will also be large, this is less likely to be a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The lowest frequency filter I have ever built was a 5Hz &amp;#177;20% two-stage S&amp;amp;K (4 pole) maximally flat design which worked perfectly well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also want to look at a &lt;a href=&quot;http://en.wikipedia.org/wiki/Gyrator&quot; rel=&quot;nofollow&quot;&gt;Gyrator&lt;/a&gt; circuit to simulate a high value inductor.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-02-10T17:00:35.287" />
  <row Id="9958" PostTypeId="2" ParentId="9956" CreationDate="2011-02-10T17:07:12.810" Score="1" ViewCount="" Body="&lt;p&gt;SketchUp can be a little cumbersome in the beginning. I would urge you to stick with it. There are a lot of really great tutorials out there (start at &lt;a href=&quot;http://sketchup.google.com/support/bin/answer.py?hl=en&amp;amp;answer=36207&quot; rel=&quot;nofollow&quot;&gt;http://sketchup.google.com/support/bin/answer.py?hl=en&amp;amp;answer=36207&lt;/a&gt;). I'd spend just an hour or two really getting familiar with the tools and see how you feel. I'm in the same situation--hobbyist, so free/cheap is the best option. I hated that I could never get things to 'snap' or align properly. A few videos later, I'm fairly competent, and don't feel lost anymore. If nothing else, learn about inference and alignment. That should take some of the frustration out of it and make you more productive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry I don't have any alternatives, but I hope SketchUp works out for you. Good luck! &lt;/p&gt;&#xA;" OwnerUserId="2928" LastActivityDate="2011-02-10T17:07:12.810" CommentCount="3" />
  <row Id="9959" PostTypeId="2" ParentId="9653" CreationDate="2011-02-10T17:29:18.257" Score="0" ViewCount="" Body="&lt;p&gt;You can design a custom enclosure to fit your boards and have &lt;a href=&quot;http://www.ponoko.com/&quot; rel=&quot;nofollow&quot;&gt;Ponoko&lt;/a&gt; make it.  I think it's pretty cheap.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.ponoko.com/2010/10/25/making-enclosures-for-electronics-with-ponoko/&quot; rel=&quot;nofollow&quot;&gt;Making Enclosures for Electronics with Ponoko&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-02-10T17:29:18.257" />
  <row Id="9960" PostTypeId="2" ParentId="9952" CreationDate="2011-02-10T17:31:41.720" Score="0" ViewCount="" Body="&lt;p&gt;Panasonic P4 series, 100 way socket and header parts numbers are AXK700127G and AXK800125WG respecitively.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Total mating height of 1.5 mm&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2011-02-10T17:31:41.720" />
  <row Id="9961" PostTypeId="1" AcceptedAnswerId="9967" CreationDate="2011-02-10T17:34:31.690" Score="2" ViewCount="92" Body="&lt;p&gt;I've got some really tiny leads on a USB port that I need to solder to a board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/iUUZy.jpg&quot; alt=&quot;SMD mini USB port&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The local Hackerspace has a microscope that I'm going to see about using this for, but even a soldering iron is gigantic compared to these tiny leads.  Does anyone have any tips (pun intended and unintended) for soldering these leads to a board?&lt;/p&gt;&#xA;" OwnerUserId="2956" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-10T18:39:29.413" LastActivityDate="2011-02-10T19:01:05.073" Title="Soldering Tiny Leads?" Tags="&lt;soldering&gt;&lt;usb&gt;&lt;components&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="9962" PostTypeId="2" ParentId="9961" CreationDate="2011-02-10T17:42:57.857" Score="0" ViewCount="" Body="&lt;p&gt;I would recommend a hand-held hot air rework tool (like the &lt;a href=&quot;http://www.hakkousa.com/detail.asp?CID=51&amp;amp;PID=1051&amp;amp;Page=1&quot; rel=&quot;nofollow&quot;&gt;Hakko 851&lt;/a&gt;) to gently heat the whole PCB area and allow the part to reflow into place. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may find that using a conventional iron to 'tin' the pads before using the hot air tool will be necessary, if you don't have a stencil and solder paste to properly prep the pads. Just make sure (with the microscope) that there aren't any solder bridges before you introduce the connector. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-10T17:42:57.857" CommentCount="2" />
  <row Id="9963" PostTypeId="2" ParentId="9961" CreationDate="2011-02-10T18:19:19.617" Score="0" ViewCount="" Body="&lt;p&gt;I use a cheap stereo dissecting microscope with a fine tip Metcal cartridge for jobs like that.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-10T18:19:19.617" />
  <row Id="9965" PostTypeId="1" AcceptedAnswerId="10548" CreationDate="2011-02-10T18:32:47.313" Score="5" ViewCount="265" Body="&lt;p&gt;I want to build a &lt;a href=&quot;http://en.wikipedia.org/wiki/Radio_propagation_beacon&quot; rel=&quot;nofollow&quot;&gt;Radio Propagation Beacon&lt;/a&gt; but I would like to find an integrated circuit that does most or all of the work of the transmitter. &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Transmit to 28Mhz (Ham 10-meter band)&lt;/li&gt;&#xA;&lt;li&gt;Allow me to feed it &lt;a href=&quot;http://en.wikipedia.org/wiki/Continuous_wave&quot; rel=&quot;nofollow&quot;&gt;Morse code&lt;/a&gt; audio and for it to transmit that. &lt;/li&gt;&#xA;&lt;li&gt;As cheap and simple as possible, such as a single-chip solution.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I'll write some code on an Arduino to produce the Morse code. It doesn't have to be high power, 200mw range is perfectly fine. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do have an radio amateur license.&lt;/p&gt;&#xA;" OwnerUserId="1033" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-26T12:49:07.097" LastActivityDate="2011-03-26T12:49:07.097" Title="How to build cheap radio propagation beacon?" Tags="&lt;rf&gt;&lt;transmitter&gt;&lt;beacon&gt;&lt;ham-radio&gt;" AnswerCount="3" CommentCount="7" FavoriteCount="1" />
  <row Id="9966" PostTypeId="2" ParentId="9912" CreationDate="2011-02-10T18:52:45.987" Score="2" ViewCount="" Body="&lt;p&gt;Both of those chips are just doing amplification of the thermocouple voltage.  They have some features like temperature compensation, open lead detection, and filtering, but not a whole lot more. They're expensive because they're not commonly required, not because their function is difficult. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could get reasonable results with a single rail-to-rail amplifier.  Using the non-inverting configuration:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/rOiVH.png&quot; alt=&quot;Wikipedia image&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(where Vout ~= Vin(1+R2/R1)), select a large value for R2 and a small value for R1 to get the low-voltage signal into a range that can be read by your microcontroller's ADC pins.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Temperature compensation can be implemented in software, open lead detection can be achieved by a very high value pullup or pulldown resistor (which will cause the amplifier to saturate on one of the rails), but filtering will require some of that analog work you didn't want to do.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-10T18:52:45.987" />
  <row Id="9967" PostTypeId="2" ParentId="9961" CreationDate="2011-02-10T19:01:05.073" Score="6" ViewCount="" Body="&lt;p&gt;Flux! Use plenty of flux and it will magically work.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't need:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;a super-skinny soldering tip&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;hot air station&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;very thin solder&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;solder paste&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;desolder braid (helpful though)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You do need:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Flux&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Magnification (you've got that covered)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Flux up the pads really well, then apply heat and solder.  Try to make a big ball that covers all the pads.  Then remove solder by repeatedly cleaning the tip and touching it to the pads.  This technique is similar to drag soldering.  If in doubt add more flux.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-10T19:01:05.073" CommentCount="1" />
  <row Id="9969" PostTypeId="1" AcceptedAnswerId="9970" CreationDate="2011-02-10T20:00:30.500" Score="0" ViewCount="171" Body="&lt;p&gt;I've seen this &lt;a href=&quot;http://www.vernier.com/probes/probes.html?fp-bta&amp;amp;template=standard.html&quot; rel=&quot;nofollow&quot;&gt;force plate from Vernier&lt;/a&gt; and it requires another USB interface device. They have an SDK that will they allow us to communicate with the force plate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there something that I can create on my own that also measures weight?&#xA;I think that I've seen a &lt;a href=&quot;http://electronics.stackexchange.com/questions/3312/3-wire-digital-scale-strain-gauge-weight-sensor&quot;&gt;strain gauge thread&lt;/a&gt; on this forum.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's this &lt;a href=&quot;http://www.sparkfun.com/products/10245&quot; rel=&quot;nofollow&quot;&gt;load sensor from Sparkfun&lt;/a&gt; (mentioned in thread) but it maxes out at 125lbs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I essentially want to create a plate for someone to step onto and be able to measure their weight.&lt;/p&gt;&#xA;" OwnerUserId="1288" LastActivityDate="2011-02-11T09:48:20.817" Title="I want to be able to measure weight (typical range of human weight), what sensor can I use?" Tags="&lt;sensor&gt;" AnswerCount="4" CommentCount="0" />
  <row Id="9970" PostTypeId="2" ParentId="9969" CreationDate="2011-02-10T20:15:21.780" Score="3" ViewCount="" Body="&lt;p&gt;Like this? &lt;a href=&quot;http://www.walmart.com/catalog/product.do?product_id=5740778&quot; rel=&quot;nofollow&quot;&gt;http://www.walmart.com/catalog/product.do?product_id=5740778&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could buy one and interface to its strain gage.  Or even its measurement electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are making a computer interface to a scale, try to stick to the SMA Serial Communication standard: &lt;a href=&quot;http://www.scalemanufacturers.org/Standards/Standard.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.scalemanufacturers.org/Standards/Standard.htm&lt;/a&gt; Then your scale will be instantly compatible with all software.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-10T20:15:21.780" CommentCount="1" />
  <row Id="9971" PostTypeId="2" ParentId="9969" CreationDate="2011-02-10T20:21:21.573" Score="2" ViewCount="" Body="&lt;p&gt;You could use levers to reduce the load on the sensor. Take apart a typical mechanical/analog bathroom scale and you'll see that your entire weight is being carried by a small spring, with the help of some levers. I have a picture at home that I can upload if you need more explanation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd design a platform that gives you some horizontal stability before looking for a sensor, because the platform may have some mechanical multiplier in it. If this is a one-off project, I'd re-use an existing mechanical scale and replace the spring with a different sensor, or a digital one and piggyback on the sensor or LCD readout.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-10T20:21:21.573" CommentCount="2" />
  <row Id="9972" PostTypeId="2" ParentId="9969" CreationDate="2011-02-10T20:31:47.850" Score="3" ViewCount="" Body="&lt;p&gt;You can use a Nintendo Wii Balance Board. It can be used to calculate weight, as this is what the Wii Fit games do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can connect to the balance board using Bluetooth HID.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://wiibrew.org/wiki/Wii_Balance_Board&quot; rel=&quot;nofollow&quot;&gt;http://wiibrew.org/wiki/Wii_Balance_Board&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-02-10T20:31:47.850" />
  <row Id="9973" PostTypeId="2" ParentId="9833" CreationDate="2011-02-10T21:05:20.663" Score="0" ViewCount="" Body="&lt;p&gt;Depending on the details of your circuit you may be able to use one of these&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1142,C1029,P38400&quot; rel=&quot;nofollow&quot;&gt;http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1142,C1029,P38400&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-02-10T21:05:20.663" />
  <row Id="9974" PostTypeId="1" AcceptedAnswerId="9975" CreationDate="2011-02-10T23:33:08.380" Score="1" ViewCount="68" Body="&lt;p&gt;I have a &lt;a href=&quot;http://www.linear.com/designtools/packaging/foot/DFN10DDB3X2.asc&quot; rel=&quot;nofollow&quot;&gt;.asc PADS file&lt;/a&gt; that defines the footprint for a part I am using. Is there any way I can use this file with Eagle so that I don't have to make the package from scratch?&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-11T00:39:51.450" Title="Importing an asc PADs file into Eagle" Tags="&lt;eagle&gt;&lt;footprint&gt;" AnswerCount="2" />
  <row Id="9975" PostTypeId="2" ParentId="9974" CreationDate="2011-02-10T23:47:20.933" Score="1" ViewCount="" Body="&lt;p&gt;I don't know of any Eagle user scripts for importing files from PADS. I suspect that your best bet is to design your own footprint using Eagle for the part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If money is no object, I found a company who claim to do conversions: &lt;a href=&quot;http://www.logicswap.com/eagle.php&quot; rel=&quot;nofollow&quot;&gt;http://www.logicswap.com/eagle.php&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-02-10T23:47:20.933" />
  <row Id="9976" PostTypeId="2" ParentId="9974" CreationDate="2011-02-11T00:18:03.810" Score="-1" ViewCount="" Body="&lt;p&gt;I imported the file into the Pulsonix software I use without any problems. It's a very simple footprint and it shouldn't take you more than five minutes to create it yourself.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-11T00:39:51.450" LastActivityDate="2011-02-11T00:39:51.450" />
  <row Id="9977" PostTypeId="2" ParentId="9941" CreationDate="2011-02-11T01:54:49.060" Score="1" ViewCount="" Body="&lt;p&gt;No, it's not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can try it here: &lt;a href=&quot;http://babbage.cs.qc.edu/IEEE-754/32bit.html&quot; rel=&quot;nofollow&quot;&gt;http://babbage.cs.qc.edu/IEEE-754/32bit.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can for example enter the number from the &lt;a href=&quot;http://en.wikipedia.org/wiki/Binary32&quot; rel=&quot;nofollow&quot;&gt;binary32 wikipedia page&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;00111110 00100000 00000000 00000000 binary = 3E200000 hex&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;and you will see, that it's really &lt;strong&gt;0.15625&lt;/strong&gt; decimal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you now enter the bitwise NOT (ones' complement) of that binary representation:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;11000001 11011111 11111111 11111111 binary = C1DFFFFF hex&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;you will see that it is &lt;strong&gt;-27.999998092651367&lt;/strong&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1950" LastActivityDate="2011-02-11T01:54:49.060" CommentCount="3" />
  <row Id="9978" PostTypeId="1" CreationDate="2011-02-11T03:57:25.123" Score="4" ViewCount="195" Body="&lt;p&gt;I need to make a bunch of thermocouples but I don't want to spend a ton buying them pre-made. I only need short thermocouples (like 6-8&quot; long) so if i were to buy them it would be wasting a lot of wire too. I know thermocouple wire is pretty cheap but I don't have a good way of connecting the ends. I need to measure temps about 200C so regular solder won't do. I don't have a welder either. Is there any other good way of connecting the ends? Would JB weld work or would that mess up the reading. What about a high temperature epoxy? Can the wire ends be twisted together or can they only touch in one place at the tip?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2011-02-12T00:14:10.133" Title="cheap thermocouples. Homemade?" Tags="&lt;thermocouple&gt;" AnswerCount="6" />
  <row Id="9979" PostTypeId="1" CreationDate="2011-02-11T05:30:39.653" Score="1" ViewCount="43" Body="&lt;p&gt;Hello, I have a Linksys router, two Xbox 360s, a tower PC and television that have recently been screwing up. The xboxes both red-ringed in the last week, on separate days. They each had troubles and needed to be restarted mid game about a month ago.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The router needs to be reset often to allow my three roommates to connect to it on occasion and we tend to lose connection to only certain servers and sites for short periods of time. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My PC freezes to the point where nothing works, no ctrl+alt+delete, nothing, and I have to restart it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After one of these restarts, the TV the PC was using as a monitor, was screwed up. All the colors were correct but instead of showing the correct image, it showed entire vertical lines of those colors on the screen, making it look like a rainbow zebra. I power cycled the TV and it was fixed and hasnt happened since. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now here's my question. Is it possible to have an electrical surge through an ethernet cable? We havent had any thunderstorms recently but I live in an apartment with wiring that I'm sure could use re-doing. All of these items are plugged into the same router (except the TV which is plugged into the PC) and it feels like the only connection. I'm really concerned and wondered if we had any words of wisdom. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2958" LastActivityDate="2011-02-11T05:30:39.653" ClosedDate="2011-02-11T08:03:31.423" Title="Ethernet Surge? Is it possible. Any other ideas?" Tags="&lt;power&gt;&lt;ethernet&gt;" CommentCount="2" />
  <row Id="9980" PostTypeId="2" ParentId="9644" CreationDate="2011-02-11T06:37:49.613" Score="1" ViewCount="" Body="&lt;p&gt;Well, I don´t know if this is the fast way to perform a exponential operation. But you can try to do a LUT. You have to thing in the dynamic range of your signal, the maximun and the minimun value. And depend of the accuracy you want to have in your design.&#xA;For instance, imagine the dinamyc range of the signal is (-1,1) and the accuracy is fo three 3 digits, (0.567,-0.237,0.457...) So there are 2000 possible values. So the LUT will have 2000 files.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastActivityDate="2011-02-11T06:37:49.613" CommentCount="2" />
  <row Id="9981" PostTypeId="1" CreationDate="2011-02-11T06:48:25.283" Score="0" ViewCount="98" Body="&lt;p&gt;With differentiation equation, I mean.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen many books which explains it with quality analysis,but now I'm seeking of a book that can explain it with quantity analysis,which means a lot of math.&lt;/p&gt;&#xA;" OwnerUserId="2959" LastActivityDate="2011-02-15T19:05:50.527" Title="Is there a good book that explains the features of electronics with math?" Tags="&lt;circuit&gt;&lt;transistor&gt;&lt;ic&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="9982" PostTypeId="1" AcceptedAnswerId="10038" CreationDate="2011-02-11T06:57:17.967" Score="1" ViewCount="138" Body="&lt;p&gt;I am trying to implement a &lt;a href=&quot;http://en.wikipedia.org/wiki/Particle_filter&quot; rel=&quot;nofollow&quot;&gt;particle filter&lt;/a&gt; for coupling gyro and electronic compass for better measuring device orientation. &lt;sup&gt;[&lt;a href=&quot;http://electronics.stackexchange.com/q/9894/2118&quot;&gt;related question&lt;/a&gt;]&lt;/sup&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand my &lt;em&gt;state vector&lt;/em&gt; would contain the &lt;em&gt;absolute angle&lt;/em&gt; and &lt;em&gt;turn-rate&lt;/em&gt; and my &lt;em&gt;observation vector&lt;/em&gt; contains the readings for the same from the compass and gyro. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my transition model, I just use the constant &lt;em&gt;turn-rate&lt;/em&gt; assumption plus random noise to move the particles to their next states. Then, &lt;strong&gt;&lt;em&gt;when I get a set of readings (angle and turn-rate from the sensors) in the next time instant, how do I assign weights to the particles?&lt;/em&gt;&lt;/strong&gt; Is there a systematic procedure to assign the weights for a state vector containing multiple variables or should I just calculate it based on the difference between the predicted value and the observed value for both compass and gyro?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i.e.: &lt;code&gt;weight(particle X) = RMS(angle(Particle X) - angle(sensor), rate(Particle X )- rate(sensor))&lt;/code&gt;, and then normalize all the readings?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me explain my problem a little further. I am working on the basis that the electronic compass alone is subjected to magnetic interferences in the indoor environment and hence the gyro should be used along with it to improve the accuracy of orientation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, these magnetic interferences will form the external/environment noise of the process and will definitely be non-Gaussian, since they are bound to be biased towards the side of the metallic structure. That is why I chose the Particle filter over say, the Kalman filter although it is the most preferred method. So when I really don't know the pdf of the noise, then how do I estimate the likelihood that a predicted value is equal to a real value (which would be its weight, right?) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming a normal distribution in this case would not work, because it would give me wrong probabilities for particles. Atleast, this is what I understand; please correct me if I'm wrong.&lt;/p&gt;&#xA;" OwnerUserId="2939" LastEditorUserId="2939" LastEditorDisplayName="" LastEditDate="2011-02-14T06:52:34.657" LastActivityDate="2011-02-14T06:52:34.657" Title="Calculating weights in a particle filter experiment using multiple state variables" Tags="&lt;sensor&gt;&lt;filter&gt;&lt;gyro&gt;&lt;compass&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="9983" PostTypeId="1" AcceptedAnswerId="9992" CreationDate="2011-02-11T07:36:53.557" Score="0" ViewCount="100" Body="&lt;p&gt;Hi all, I want to put in a ROM a vector of values I have in the workspace. Does anyone know how to do it?&#xA;Thank you to all possible references, articles or comments.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T21:01:25.483" LastActivityDate="2011-02-12T21:01:25.483" Title="System Generator: How to make an implementation a mathematical function through a ROM" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;rom&gt;&lt;xilinx-system-generator&gt;&lt;matlab&gt;" AnswerCount="1" />
  <row Id="9984" PostTypeId="1" CreationDate="2011-02-11T08:06:20.270" Score="0" ViewCount="339" Body="&lt;p&gt;Hello, I am looking for a implementation of ROM using VHDL code.&#xA;I´m looking for a piece of code to make this easy example in order to make  a generalization afterwards.&#xA;I want to put in the ROM these values: 14,45,67,32,12,64,89,34,54,22&#xA;so when the for the address 'x' (the input of the system) you get 'y' (the output of the system):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;x  y&#xA;1  14&#xA;2  45&#xA;3  67&#xA;4  32&#xA;5  12&#xA;6  64&#xA;7  89&#xA;8  34&#xA;9  54&#xA;10 22&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Thank you to all possible references, articles or comments.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-11T16:16:17.370" LastActivityDate="2011-02-11T16:16:17.370" Title="Xilinx ISE - VHDL: Code template to make a ROM" Tags="&lt;xilinx&gt;&lt;vhdl&gt;&lt;rom&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="9985" PostTypeId="2" ParentId="9978" CreationDate="2011-02-11T08:36:11.317" Score="5" ViewCount="" Body="&lt;p&gt;Wire ends can be twisted together without any problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I performed an experiment as part of my undergraduate coursework where we used twisted pair of copper and constantan wires (twisted part about 2cm in length) that were held in place mechanically. It worked quite well. The temperature range was about 100-300C, so that should be right in your ballpark.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you twist the wires, you have to make sure they are twisted around each other, not one twisted around the other. The best way I found to achieve this is to bend each wire 45 degrees, so they make a 90 degree angle with respect to each other. Then just hold both wires and twist.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-02-11T08:36:11.317" />
  <row Id="9986" PostTypeId="2" ParentId="9981" CreationDate="2011-02-11T08:50:38.933" Score="0" ViewCount="" Body="&lt;p&gt;It's hard to give a book recommendation without knowing exactly what sub-domain of electronics you are interested in. However, it is my feeling that books that are heavy on math are not particularly hard to come by in this field.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are interested in discrete-component analog electronics, in university we used &lt;a href=&quot;http://www.sedrasmith.org/&quot; rel=&quot;nofollow&quot;&gt;Sedra &amp;amp; Smith&lt;/a&gt;. It's not a particularly good book, but it has enough exercises to help you flex your math muscles a bit.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-02-11T08:50:38.933" />
  <row Id="9987" PostTypeId="2" ParentId="9984" CreationDate="2011-02-11T09:18:22.810" Score="0" ViewCount="" Body="&lt;p&gt;Since FPGAs are programmable devices, you do not want to burn your look-up table into ROM of any kind. Your best bet is to program the lut into the FPGAs Block Memory areas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can do this for example using a tool like Xilinx's &lt;a href=&quot;http://www.xilinx.com/products/ipcenter/dr_dt_data2mem.htm&quot; rel=&quot;nofollow&quot;&gt;Data2Mem&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Consult the datasheet for your part as well as the Data2Mem documentation for the specifics on programming and using block ram.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-02-11T09:18:22.810" CommentCount="1" />
  <row Id="9988" PostTypeId="2" ParentId="9969" CreationDate="2011-02-11T09:48:20.817" Score="1" ViewCount="" Body="&lt;p&gt;Based on the &lt;a href=&quot;http://www.sparkfun.com/products/10245&quot; rel=&quot;nofollow&quot;&gt;discussion on Sparkfun&lt;/a&gt; (as found by following the link you provided) I understand that the general idea is to use more than one of these sensors to support your measuring platform, so that they share the load. For example, you could put one of these sensors at each of the four corners of a plate and you would be able to measure up to 200 kg/500 lbs.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-02-11T09:48:20.817" />
  <row Id="9989" PostTypeId="2" ParentId="9984" CreationDate="2011-02-11T10:07:10.410" Score="1" ViewCount="" Body="&lt;p&gt;here's a VHDL example of doing it in the source code - some data omitted for clarity:                                                                                               &lt;/p&gt;&#xA;&#xA;&lt;p&gt;entity cgrom is&#xA; port (clkin : in std_logic;&#xA;      adr : in std_logic_vector(13 downto 0);&#xA;     data:out std_logic_vector(3 downto 0));&#xA;     end cgrom; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;architecture a_cgrom of cgrom is&lt;/p&gt;&#xA;&#xA;&lt;p&gt;attribute INIT_00 :string;attribute INIT_01 :string;attribute INIT_02 :string;attribute INIT_03 :string; &#xA;attribute INIT_04 :string;attribute INIT_05 :string;attribute INIT_06 :string;attribute INIT_07 :string;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;attribute INIT_00 of chargen0: label is &quot;0000000000000000000000000000000000000000000000000000000000000000&quot;;&#xA;attribute INIT_01 of chargen0: label is &quot;00000000000000E000E00060000000200040006000E000E000E000E000E00000&quot;;&#xA;attribute INIT_02 of chargen0: label is &quot;00000000000000000000000000000000000000000000011C011C011C011C0000&quot;;&#xA;attribute INIT_03 of chargen0: label is &quot;0000000000000048007C005C00CC01D800B800B801B007FC0330017007700260&quot;;&#xA;attribute INIT_04 of chargen0: label is &quot;00000020002000DC03FC01080120035000F0005C0028030C01FC035800200000&quot;;&#xA;attribute INIT_05 of chargen0: label is &quot;00000000000001800600006002C0039C0384038C0398006A0076003600300000&quot;;&#xA;attribute INIT_06 of chargen0: label is &quot;00000000002002F803BA059E03CC03E60654007800700030001C00F800F80020&quot;;&#xA;attribute INIT_07 of chargen0: label is &quot;0000000000000000000000000000000000000000000000600060006000600000&quot;;&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-11T10:07:10.410" CommentCount="1" />
  <row Id="9990" PostTypeId="2" ParentId="9984" CreationDate="2011-02-11T10:16:37.890" Score="1" ViewCount="" Body="&lt;p&gt;This isn't in VHDL, but does provide an answer to the general problem that others may find useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use a Block Memory Generator IP core to do what you want. This is created by adding a coregen type source file to your project and choosing Block Memory Generator from the list of available cores. You can customise the type of memory, you'd want to choose ROM in this case of course, the size and also provide a memory initialisation file. This .coe file is described at &lt;a href=&quot;http://www.xilinx.com/itp/xilinx4/data/docs/cgn/ch3-using20.html&quot; rel=&quot;nofollow&quot;&gt;http://www.xilinx.com/itp/xilinx4/data/docs/cgn/ch3-using20.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'd want something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Memory_Initialization_Radix=16;&#xA;Memory_Initialization_Vector=&#xA;0E,2D,43,20,0C,40,59,22,36,16;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2960" LastActivityDate="2011-02-11T10:16:37.890" />
  <row Id="9991" PostTypeId="2" ParentId="9978" CreationDate="2011-02-11T10:48:23.590" Score="3" ViewCount="" Body="&lt;p&gt;twisted wires will not be reliable long-term unless clamped together to form am airtight joint - yo may be able to use some sort of crimp terminal. I believe real thermocouples are welded in an inert atmosphere.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-11T10:48:23.590" />
  <row Id="9992" PostTypeId="2" ParentId="9983" CreationDate="2011-02-11T11:00:47.740" Score="2" ViewCount="" Body="&lt;p&gt;Use a ROM block (from the memory section of the Xilinx blockset).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has a parameter called &lt;code&gt;Inital value vector&lt;/code&gt; - put the name of the vector in there.  Put &lt;code&gt;length(vector_name)&lt;/code&gt; in the &lt;code&gt;depth&lt;/code&gt; parameter.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Setup the &lt;code&gt;output type&lt;/code&gt; tab to the fixed point representation you want to use.  Bear in mind the sizes of RAM bclock you have available in the target FPGA when selecting the &lt;code&gt;number of bits&lt;/code&gt;. For example, 2k elements of 9 bits fits just as well in a single RAM block as 2k elements of 8 bits (in case you, or other readers, aren't already aware of that).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Job done!&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-02-11T11:00:47.740" CommentCount="1" />
  <row Id="9993" PostTypeId="2" ParentId="9978" CreationDate="2011-02-11T11:21:22.640" Score="0" ViewCount="" Body="&lt;p&gt;A small amount of platimum wire won't cost much, it would be a lot easier to make a platinum resistance thermometer. It will be a lot more reliable and stable.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-11T11:21:22.640" />
  <row Id="9994" PostTypeId="1" AcceptedAnswerId="10000" CreationDate="2011-02-11T11:50:18.887" Score="0" ViewCount="189" Body="&lt;p&gt;Hello stack exchange&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have received some Li-ion batteries which were originally used in Asus A2 Laptop battery original one and I would like to know if it is possible to charge each cells independently with some device or just normal universal charger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I Apologize if i asked in wrong section.&lt;/p&gt;&#xA;" OwnerUserId="2962" LastActivityDate="2011-02-11T12:54:59.187" Title="How to charge Laptop Li-ion Battery cells manualy?" Tags="&lt;battery&gt;&lt;charging&gt;&lt;charger&gt;&lt;lithium-ion&gt;&lt;cell-battery&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="9995" PostTypeId="2" ParentId="9860" CreationDate="2011-02-11T12:01:54.787" Score="2" ViewCount="" Body="&lt;p&gt;With Charlieplexing, you can directly drive n*(n-1) LEDs from n pins. This means 210 LEDs from 15 pins. This can be done with a regular Arduino Uno if you use some of the analog pins as output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need different colors with different resistors, you have to do some smart segmenting. You also have to think about the time multiplex, high pulse current. This is probably easier if you know you will only have a few leds on at each time. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;See application here: &lt;a href=&quot;http://www.evilmadscientist.com/article.php/bulbdial3&quot; rel=&quot;nofollow&quot;&gt;http://www.evilmadscientist.com/article.php/bulbdial3&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1381" LastActivityDate="2011-02-11T12:01:54.787" />
  <row Id="9996" PostTypeId="2" ParentId="9994" CreationDate="2011-02-11T12:07:19.043" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/bq24170.html&quot; rel=&quot;nofollow&quot;&gt;Benchmarq/TI&lt;/a&gt; and &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/1661&quot; rel=&quot;nofollow&quot;&gt;Maxim&lt;/a&gt; make charger chips. Both are very helpful with free samples.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-11T12:07:19.043" />
  <row Id="9997" PostTypeId="2" ParentId="9994" CreationDate="2011-02-11T12:30:51.953" Score="1" ViewCount="" Body="&lt;p&gt;I would warn against it as if you attached imbalanced cells to make a battery (each cell at a slightly different charge), you could suffer from cell failures because of polarity reversal, which, owing to the rather combustable nature of Li-ion cells, it would not be good. It is best to charge all the cells at the same time; per Leon, there are chips which do this too.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-11T12:30:51.953" />
  <row Id="9998" PostTypeId="2" ParentId="9994" CreationDate="2011-02-11T12:46:07.917" Score="4" ViewCount="" Body="&lt;p&gt;From the way that you phrased the question it sounds like you may have some cells from a disassembled battery pack.  If this is the case then &lt;strong&gt;DO NOT TRY TO CHARGE THEM&lt;/strong&gt;.  Battery packs all contain protection electronics to prevent pack overcharging, overheating, fire and explosion.  This protection is not present when you disassemble a battery pack and attempting to charge the cells is highly dangerous. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Individual cells cannot be charged with a typical NiCd or NiMH battery charger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any charger that you use to recharge a battery pack needs to be designed with the particular pack in mind.  They all vary in terms of the number of cells in series (pack voltage) and number of batteries in parallel to give the current capacity required.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the batteries that you have are more than a couple of years old then you may find that there storage capacity is very poor.  Li-ION cells, particularly from laptops, do not have a very long life.  The life of a laptop battery is particularly short as it is highly hostile to the battery chemistry.  The battery does not like being fully charged and/or hot.  Running your laptop from a wall charger ensures that both of these are true. &lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2011-02-11T12:46:07.917" />
  <row Id="9999" PostTypeId="1" AcceptedAnswerId="10018" CreationDate="2011-02-11T12:50:43.387" Score="1" ViewCount="162" Body="&lt;p&gt;I am designing a little class AB amplifier for a small circuit. This circuit is biased such that it has low crossover distortion. Below is a schematic:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/DT8FG.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see, I have inserted 68 ohm resistors in series with the power supply lines.  This is such that when the output is shorted, the current is limited to about +/-200mA. In this demo, I have inserted such a short; a 10m resistor. However, in operation the resistors dissipate 1.5W each and in short circuit conditions about 2.5W, which means I have to use two big and expensive 5W resistors to remain within safe operating boundaries, and it also might cause problems for the power supply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'm looking for some way to limit output current to about +/-100mA before the amplifier begins clipping (which the current solution manages), but without the &quot;hack&quot; of using resistors on the power supply lines. I was considering a comparator measuring the output current across a shunt resistor, but I wasn't sure how to achieve this for short circuits of both polarities. Also, I need the circuit to ideally work up to around 5 MHz, which limits the choice of components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Thanks to russ_hensel and opencircuits.com, I devised the following current limiter (including amplifier), which actually works really well (it clips the output and doesn't make it sag or invert, like some limiting circuits.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/h6rYJ.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-02-12T14:23:08.810" LastActivityDate="2011-02-12T14:23:08.810" Title="Short circuit protecting a class AB amplifier" Tags="&lt;amplifier&gt;&lt;short-circuit&gt;" AnswerCount="2" />
  <row Id="10000" PostTypeId="2" ParentId="9994" CreationDate="2011-02-11T12:54:59.187" Score="2" ViewCount="" Body="&lt;p&gt;So are these loose cells you have?&#xA;You will require a voltage limited and current limited source to charge your li-ion batteries; something such as a lab supply will do nicely but a universal supply will probably do aswell - check its specs tho!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'd probably want to charge the cells to a max of 4.2V (Check datasheets or go lower to be safe with 4-4.1v but you'll be storing less juice tho!).&#xA;Set your current limit conservatively to c/3 or something, c is the capacity of the cells so if you had 2400mAh cells, charge them at 1/3 of that so at a rate of 800mA each. Most cells let you do 1C and few do 10C or other high charge rates but best to be safe and sure when working with these and use low currents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a whole bunch of these cells in series, you'd want to be careful because of the imbalance that may occur as Thomas pointed out. This isn't an issue with single cells however.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also for the battery monitoring chips - they'll disconnect your battery when the voltage / current are beyond safe limits but you will still need proper charging power source as the BMS will not limit current for you.&lt;/p&gt;&#xA;" OwnerUserId="2963" LastActivityDate="2011-02-11T12:54:59.187" CommentCount="3" />
  <row Id="10002" PostTypeId="2" ParentId="9978" CreationDate="2011-02-11T13:24:46.570" Score="1" ViewCount="" Body="&lt;p&gt;It's actually quite easy, get the wires, twist them, then use an acetylene welding torch to melt the joint into a ball.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The excess material will drip off and leave you with a small ball at the tip of the wire pair.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd make up a bunch of twisted wire probes and take them to a mechanic or an other kind of machine shop with a welder and have them meld the ends for me.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-02-11T13:24:46.570" />
  <row Id="10003" PostTypeId="2" ParentId="9953" CreationDate="2011-02-11T13:35:16.720" Score="0" ViewCount="" Body="&lt;p&gt;I would vote for 10-100uF ceramic capacitor with large resistor + temperature controlled chamber OR ceramic cap + programmable resistor to compensate for temperature changes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This should be more stable over time, but less stable over temperature. Also, ceramic caps should have way less leakage.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-11T13:35:16.720" />
  <row Id="10004" PostTypeId="1" CreationDate="2011-02-11T14:41:12.730" Score="4" ViewCount="159" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im planning on buying a useful book for PCB design. Until now, I have these two options:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0133957241&quot; rel=&quot;nofollow&quot;&gt;High Speed Digital Design&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0750663707&quot; rel=&quot;nofollow&quot;&gt;Circuit Designers Companion&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Both books seems OK, but the first one (the older one) is almost 2x more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone with experience with one of two books or both? Would you recommend me another book? If so, why?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks! &lt;/p&gt;&#xA;" OwnerUserId="1074" LastEditorUserId="1074" LastEditorDisplayName="" LastEditDate="2011-02-11T16:03:05.157" LastActivityDate="2011-02-11T16:21:02.737" Title="Useful book for PCB design" Tags="&lt;pcb&gt;&lt;books&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="10005" PostTypeId="1" CreationDate="2011-02-11T14:45:55.940" Score="1" ViewCount="191" Body="&lt;p&gt;My power regulated ac/dc adapter broke the other day and my friend thought it was a good idea to cut the wire from the mains adapter, trim the ends and plug this directly into the mains. he then connected the adapter end to the microcube. the elctricity in the flat tripped out at the circuit breakers. Would the amp be completly wrecked after this happening or is there a part I can replace that will fix it?. I just bought a new ac/dc adapter, plugged it into the amp, but nothing is happening, seems like something has blown(?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;anyone got a suggestion?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE**..i took it apart and saw that next to the dc input socket there is what appears to be a blown fuse. it says next to it &quot;T800mAL&quot; and i saw this &lt;a href=&quot;http://cgi.ebay.co.uk/800mA-Amp-T800mA-T800mAL-Fuse-AntiSurge-20x5mm-x-10-/360325684444&quot; rel=&quot;nofollow&quot;&gt;http://cgi.ebay.co.uk/800mA-Amp-T800mA-T800mAL-Fuse-AntiSurge-20x5mm-x-10-/360325684444&lt;/a&gt;  I dont have time to go and get one, is there another household device I could steal one from? I really need my amp tonight :(&lt;/p&gt;&#xA;" OwnerUserId="2889" LastEditorUserId="2889" LastEditorDisplayName="" LastEditDate="2011-02-11T15:04:06.160" LastActivityDate="2011-02-11T16:42:05.373" Title="Roland Microcube guitar amp damaged beyond repair?" Tags="&lt;circuit&gt;&lt;audio&gt;&lt;speakers&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="10006" PostTypeId="2" ParentId="9999" CreationDate="2011-02-11T14:53:48.780" Score="2" ViewCount="" Body="&lt;p&gt;Generally you have small (but physically large) emitter resistors, like 0.2 ohm, which I believe set the idle current when both output devices are turned on at the same time:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/hRHeo.gif&quot; alt=&quot;schematic showing emitter resistors&quot;&gt; &lt;a href=&quot;http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/part2/page3.html&quot; rel=&quot;nofollow&quot;&gt;source&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The TA7317 is an older IC for protecting amplifier outputs and speakers against a variety of failures.  &lt;a href=&quot;http://www.ic-ts-histo.de/fad/ics/ta7317/ta7317br.htm&quot; rel=&quot;nofollow&quot;&gt;It looks as though&lt;/a&gt; it measures overcurrent (shorting) by measuring the voltage across these resistors.  It also detects overheating, DC on the output, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also measure the current going from each supply line to the output devices: &lt;a href=&quot;http://www.eetimes.com/design/audio-design/4015889/Over-current-protection-in-audio-amplifiers&quot; rel=&quot;nofollow&quot;&gt;Over-current protection in audio amplifiers&lt;/a&gt;  Figure out the maximum current you'd expect to see for a nominal load in clipping, and then put your protect threshold above that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also put a fuse in series with the output. :)&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-02-11T15:13:29.980" LastActivityDate="2011-02-11T15:13:29.980" CommentCount="1" />
  <row Id="10007" PostTypeId="2" ParentId="9953" CreationDate="2011-02-11T14:58:05.400" Score="0" ViewCount="" Body="&lt;p&gt;It's very difficult (or even impossible) to do such filter with a simple 2-pole analog filter, depending on your requirements (fp, fs, As).&#xA;Download and install &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/filterpro.html&quot; rel=&quot;nofollow&quot;&gt;FilterPro&lt;/a&gt; (from Texas Instruments) and test some configurations. That's a very good and simple program. You enter the requirements of your filter, click on a button and then you get the circuit and the values for resistors and capacitors automatically.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Probably, with a digital filter you can achieve much better results. Take a look at IIR filters. &#xA;What's the application of your high pass filter? Maybe DC removal? If so, google for IIR+DC removal, you'll get plenty of results.&lt;/p&gt;&#xA;" OwnerUserId="1074" LastActivityDate="2011-02-11T14:58:05.400" />
  <row Id="10008" PostTypeId="1" CreationDate="2011-02-11T15:06:50.120" Score="1" ViewCount="133" Body="&lt;p&gt;Most of you are probably familiar with exercise machines that have grips for each hand so that you can take your heart rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Imagine one for a skiing type of device...with the metal measuring grips on the 'poles' that you push/pull back and forth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you think that we can retrofit it and replace the metal grips with a larger piece of metal that runs the most of the length of the ski pole without interfering with the measuring electronics?&lt;/p&gt;&#xA;" OwnerUserId="1288" LastEditorUserId="204" LastEditorDisplayName="" LastEditDate="2011-02-11T15:40:24.707" LastActivityDate="2011-02-21T12:47:53.570" Title="Measuring heart rate and hacking an exercise machine to extend the grip area" Tags="&lt;sensor&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="10009" PostTypeId="2" ParentId="10004" CreationDate="2011-02-11T15:25:49.957" Score="4" ViewCount="" Body="&lt;p&gt;My experience learning to lay out PCBs was that books are not helpful at the early stages. I'd start with free layout software like &lt;a href=&quot;http://cadsoftusa.com/&quot; rel=&quot;nofollow&quot;&gt;Eagle&lt;/a&gt; and some good &lt;a href=&quot;http://www.youtube.com/watch?v=qG0O9LKH-_E&quot; rel=&quot;nofollow&quot;&gt;tutorials&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you've laid out a couple of PCBs, the first book you linked to (High Speed Digital Design) is great-- the best reference on high speed design that I know of.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-02-11T15:25:49.957" CommentCount="1" />
  <row Id="10010" PostTypeId="2" ParentId="10004" CreationDate="2011-02-11T16:00:33.060" Score="0" ViewCount="" Body="&lt;p&gt;This should be a good one, judging from the author's articles and experience.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.emcacademy.org/books.asp&quot; rel=&quot;nofollow&quot;&gt;EMC for Printed Circuit Boards by Keith Armstrong.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-02-11T16:00:33.060" />
  <row Id="10011" PostTypeId="2" ParentId="10005" CreationDate="2011-02-11T16:04:48.657" Score="2" ViewCount="" Body="&lt;p&gt;Try going to a radio shack, they should have some fuses, one will probably fit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also find a good fuse at a home improvement store. These fuses should be affordable and easy to access today.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-02-11T16:04:48.657" />
  <row Id="10012" PostTypeId="2" ParentId="10004" CreationDate="2011-02-11T16:21:02.737" Score="2" ViewCount="" Body="&lt;p&gt;plenty of good info here before you splash out on a book : &lt;a href=&quot;http://alternatezone.com/electronics/pcbdesign.htm&quot; rel=&quot;nofollow&quot;&gt;http://alternatezone.com/electronics/pcbdesign.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-11T16:21:02.737" />
  <row Id="10013" PostTypeId="1" CreationDate="2011-02-11T16:22:59.007" Score="3" ViewCount="81" Body="&lt;p&gt;I'm trying to make a wooden table with a touch-sensitive top, made up of a mosaic of small wooden pieces resembling scrabble playing pieces separated by thin glass separations. each wooden piece would be connected to its own sensor(s) and also to LED lights that would glow through the glass around the wooden piece touched. What would be the appropriate sensor to use? I want the table to be as rigid as possible, and i don't want that clicking feel when you press any wooden block...&lt;/p&gt;&#xA;" OwnerUserId="2965" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-11T22:02:08.570" LastActivityDate="2011-02-11T22:02:08.570" Title="what sensors to use in touch sensitive furniture" Tags="&lt;sensor&gt;&lt;led&gt;&lt;hardware&gt;&lt;keyboard&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="10014" PostTypeId="1" CreationDate="2011-02-11T16:29:21.560" Score="1" ViewCount="87" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/10041/how-to-convert-a-floating-point-number-to-integer-using-vhdl&quot;&gt;How to convert a floating point number to integer, using VHDL?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Hi all, I want to pass a from a floating point number to a integer number. Basically I have a floating point number between 1 and 0, with three decimal places and I want to pass it to a integer number as if I  multiply it by 1000. I don´t want to use the mult block because I suspect that there must be a more optimal block for that porpouse.&#xA;Thank you to all possible references, articles or comments.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-11T22:01:25.543" LastActivityDate="2011-02-11T22:01:25.543" ClosedDate="2011-05-11T14:35:04.017" Title="System Generator: a combination of blocks to change a floating point number into a integer number" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;floating-point&gt;" CommentCount="7" />
  <row Id="10015" PostTypeId="2" ParentId="10005" CreationDate="2011-02-11T16:42:05.373" Score="2" ViewCount="" Body="&lt;p&gt;According to the &lt;a href=&quot;http://www.roland.com/products/en/Micro-CUBE/specs.html&quot; rel=&quot;nofollow&quot;&gt;manufacturer&lt;/a&gt; , the Microcube takes 9VDC input. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what you described, your friend took a circuit expecting 9VDC and wired it directly into 120VAC (assuming you're in North America).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is the case, I don't need to rely on my &gt;10 years in power supplies to tell you that this is a VERY BAD THING. Your friend has almost certainly destroyed the low-voltage electronics inside the amplifier by applying line voltage directly to a low-voltage DC circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Properly-sized fuses blow as a consequence of something bad happening. I would expect that the AC application caused a short-circuit which opened the fuse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you intend to replace the fuse and try your luck again, you MUST ensure that you're using a 9VDC supply (preferably current-limited to less than 1A) to power the circuit. Otherwise, you'll simply pop the fuse again.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-11T16:42:05.373" CommentCount="5" />
  <row Id="10016" PostTypeId="2" ParentId="10013" CreationDate="2011-02-11T18:21:28.913" Score="1" ViewCount="" Body="&lt;p&gt;You can use a capacitive touch sensor for this sort of thing -- no pressing of any buttons is required.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to create 3 things for this to work:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A sensor PCB which has two metal pads. Mount this inside each of your wooden pieces &lt;em&gt;near the surface&lt;/em&gt;.  When the user's finger gets close enough, it changes the capacitance between the pads.  See &lt;a href=&quot;http://www.analog.com/static/imported-files/application_notes/AN-925.pdf&quot; rel=&quot;nofollow&quot;&gt;this application note&lt;/a&gt; for some tips on how to design the sensor.&lt;/li&gt;&#xA;&lt;li&gt;A sensor IC wired to these two metal pads which senses the changes in capacitance.  Something like the &lt;a href=&quot;http://www.analog.com/en/analog-to-digital-converters/capacitance-to-digital-converters/ad7147/products/product.html&quot; rel=&quot;nofollow&quot;&gt;AD7147&lt;/a&gt; could work as the measurement chip.  &lt;/li&gt;&#xA;&lt;li&gt;A controller of some sort to communicate with the sensor IC and light up the appropriate LEDs.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2677" LastActivityDate="2011-02-11T18:21:28.913" />
  <row Id="10017" PostTypeId="2" ParentId="9978" CreationDate="2011-02-11T18:43:46.040" Score="0" ViewCount="" Body="&lt;p&gt;Nicrome wire from a heating element can also be used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you can embed in solder, or anything else conductive without changing the reading.  ( assuming the whole joint is isothermal in space ).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Welding is good because it holds until the couple melts, not so with solder.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-02-11T18:43:46.040" />
  <row Id="10018" PostTypeId="2" ParentId="9999" CreationDate="2011-02-11T18:49:07.940" Score="2" ViewCount="" Body="&lt;p&gt;take a look at this circuit.  you would need two one for each &quot;side&quot; of the amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://opencircuits.com/Basic_Circuits_and_Circuit_Building_Blocks#Current_Limit_or_Constant_Current_.28_Transistor_Based_.29&quot; rel=&quot;nofollow&quot;&gt;http://opencircuits.com/Basic_Circuits_and_Circuit_Building_Blocks#Current_Limit_or_Constant_Current_.28_Transistor_Based_.29&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-02-11T18:49:07.940" CommentCount="1" />
  <row Id="10019" PostTypeId="1" CreationDate="2011-02-11T19:13:33.813" Score="1" ViewCount="223" Body="&lt;p&gt;I bought an LG452T-TF monitor about two years ago and the DVI port seems to be busted. The problems first started about a week ago. After waking my computer up from sleep the monitor only showed grey static or flickering. I initially tried different cabling to rule out a bad cable with no success. I gave up frustrated and the tried again the next day and it worked perfectly with the original cables. Then a few days later it died again and it's been about a week with no luck trying different DVI cabels. However, it does work via the VGA input. Since it died, resurrected, died again and given that the VGA port works I've concluded it's probably a loose or broken DVI input port on the monitor. Since LG doesn't seem to want to honor their three year warranty (no word from them) and I don't really want a new monitor (most new affordable 24&quot; monitors are all 16/9 instead of 16/10) I'd like to try to fix it myself, but I'd like some advice before I begin as I've never repaired TV or a monitor before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm hopping someone can pass on some advice about how to fix it. Specifically I'd like to know how difficult it would be, what tools I'd need, and if there are any general how to guides you could point me to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!!&lt;/p&gt;&#xA;" OwnerUserId="2967" LastEditorUserId="2233" LastEditorDisplayName="" LastEditDate="2011-02-11T23:39:18.353" LastActivityDate="2011-02-14T16:42:05.950" Title="How to repair a broken DVI port on my monitor?" Tags="&lt;electronics&gt;&lt;repair&gt;" AnswerCount="1" CommentCount="6" />
  <row Id="10020" PostTypeId="1" CreationDate="2011-02-11T19:49:43.360" Score="2" ViewCount="214" Body="&lt;p&gt;I have a chip that uses SPI for communication and would like to connect it directly to the USB port on my computer. Does anyone have experience with using a USB to SPI converter? Any recommendations? Quick searches on the web revealed&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.robotshop.com/devantec-usb-i2c-spi-serial-interface.html&quot; rel=&quot;nofollow&quot;&gt;http://www.robotshop.com/devantec-usb-i2c-spi-serial-interface.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/9235&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/9235&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2968" LastActivityDate="2011-02-12T03:47:36.767" Title="USB to SPI converter" Tags="&lt;usb&gt;&lt;spi&gt;" AnswerCount="5" />
  <row Id="10021" PostTypeId="2" ParentId="10020" CreationDate="2011-02-11T20:14:48.130" Score="0" ViewCount="" Body="&lt;p&gt;The first unit is the neatest solution, and uses a PIC with USB, SPI and I2C interfaces. It also offers async serial. It also has a bootloader so you can update the code easily, or add your own code.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-11T20:14:48.130" />
  <row Id="10022" PostTypeId="2" ParentId="10020" CreationDate="2011-02-11T20:42:11.233" Score="5" ViewCount="" Body="&lt;p&gt;If you just want to do some experiments, then take a look at the Bus Pirate, it speaks tons of serial protocols at one end and USB on the other.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-02-11T20:42:11.233" CommentCount="1" />
  <row Id="10023" PostTypeId="2" ParentId="5182" CreationDate="2011-02-11T21:12:29.687" Score="0" ViewCount="" Body="&lt;p&gt;Normaly, it work with 2 patchs :&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;tower164.exe for the usb infrared port&lt;/li&gt;&#xA;&lt;li&gt;ris20XPPatch.exe for the automatic runing&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2969" LastActivityDate="2011-02-11T21:12:29.687" />
  <row Id="10024" PostTypeId="1" AcceptedAnswerId="10862" CreationDate="2011-02-11T21:47:04.547" Score="0" ViewCount="152" Body="&lt;p&gt;Would it be safe to use a 1.5 volt motor with the adafruit motor shield? It is rated for 4.5 to 36 volt motors so I am unsure what will happen. Also, what would be a good way to determine the voltage of a motor if you have no information on it at all?&lt;/p&gt;&#xA;" OwnerUserId="2873" LastActivityDate="2011-03-01T06:31:35.970" Title="Low voltage motor with arduino" Tags="&lt;arduino&gt;&lt;motor&gt;&lt;shield&gt;" AnswerCount="2" />
  <row Id="10025" PostTypeId="2" ParentId="10024" CreationDate="2011-02-11T22:03:12.453" Score="0" ViewCount="" Body="&lt;p&gt;It won't drive a motor with a 1.5V supply, you need an H-bridge with very low saturation voltage transistors. The LB1630 driver chip might work, it's OK with 3V motors.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-11T22:03:12.453" CommentCount="10" />
  <row Id="10026" PostTypeId="1" CreationDate="2011-02-11T23:04:57.133" Score="3" ViewCount="86" Body="&lt;p&gt;I am doing a project that requires that I implement a cruise control system on an RC car using a GPS for feedback.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have implemented PID controllers before, but this is a little bit new to me because instead of generating a correction delta like -8 or +6, the controller has to output a value from 0 to 100, 100 being as fast as the car can go, and 0 being a dead stop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At first, I attempted to use a solution where I kept a running tally off the current throttle and I simply added the mv from the PID controller to it. This became a big issue because the &quot;currentThrottle&quot; variable essentially became a second integrator and would frequently windup when the car didn't respond fast enough. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One limitation of this project is that I cannot modify the algorithm used for generating the PID correction delta, but I can do whatever I want with the setpoint and mv before/after the PID correction is generated like so:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;(int)cruiseControl.CalculateCorrection(8, rmc.Speed);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Where 8 is the setpoint (8kts) and rmc.Speed is the current speed. This will return the correction delta calculated from the PidConfig variables (Kp, Ki, Kd, integrator windup control, etc) when I constructed the PidController object.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas?&lt;/p&gt;&#xA;" OwnerUserId="2953" LastActivityDate="2011-02-20T20:59:42.023" Title="Cruise control implementation" Tags="&lt;rc&gt;&lt;pid-controller&gt;&lt;control-system&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="10027" PostTypeId="2" ParentId="9978" CreationDate="2011-02-12T00:14:10.133" Score="1" ViewCount="" Body="&lt;p&gt;You can make a spot welder from a sufficiently large transformer.  I have a transformer out of an old battery charger whose core I wrapped a couple turns of 6-gauge wire around.. It'll heat things up in a hurry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For fine wire, even a few amps should heat the wires to molten temperature.  You could use a 100W soldering gun, which is a basically a low-voltage high-amperage transformer, with the tip removed.&lt;/p&gt;&#xA;" OwnerUserId="2235" LastActivityDate="2011-02-12T00:14:10.133" />
  <row Id="10028" PostTypeId="1" AcceptedAnswerId="10030" CreationDate="2011-02-12T00:24:41.190" Score="1" ViewCount="59" Body="&lt;p&gt;I'm going to be using a microcontroller and SDRAM IC in an enclosure that could, given some environmental variables that I have no control or knowledge of, get too hot for the devices to work properly.  Redesigning the enclosure is not an option.  However, I could notify the operator, if my microcontroller had a means of reading the temperature.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I monitor the temperature of a large IC?  I'm using 54-pin TSOPs and 100-pin TQFPs.  I've considered using a SMD thermistor and an ADC on the microcontroller, or using a prepackaged solution like &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/21942e.pdf&quot; rel=&quot;nofollow&quot;&gt;this SOT-23-3 'active thermistor'&lt;/a&gt;.   However, with either of these methods, I'm not sure how to thermally couple the devices.  I'd like to avoid having components on the back-side of the board if possible. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other possibilities include adhering a device on some long leads to the center of the IC, or monitoring the current used by the device, and extrapolate the power consumed to get an estimate of the temperature.  Both of these seem like hack jobs, while a thermistor or temp sensor seems much cleaner.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What single-sided layout will simultaneously give be the best thermal properties to cool my devices, and allow the sensor to be thermally coupled with the die of the IC?  Or, are there other methods that I'm not considering that would be better?&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-12T00:49:24.080" Title="Measuring temperature of microcontroller and other large ICs" Tags="&lt;temperature&gt;&lt;layout&gt;&lt;heatsink&gt;&lt;thermistor&gt;" AnswerCount="1" />
  <row Id="10029" PostTypeId="2" ParentId="10020" CreationDate="2011-02-12T00:28:42.073" Score="1" ViewCount="" Body="&lt;p&gt;Some of the FTDI USB chips have a MPSSE (multi protocol sync serial engine) mode, which allows all sorts of serial protocols, including SPI, to be implemented very easily (and at high speeds to 30mbit/sec if necessary with FT2232H).&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-12T00:28:42.073" />
  <row Id="10030" PostTypeId="2" ParentId="10028" CreationDate="2011-02-12T00:49:24.080" Score="1" ViewCount="" Body="&lt;p&gt;I guess the cause of overheating is not power dissipation of your uC. That means you can just place thermistor close to uC and you'll get +-2C accurate readings. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some uCs have internal thermistors connected to one of ADC input - check datasheet.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-12T00:49:24.080" CommentCount="2" />
  <row Id="10031" PostTypeId="2" ParentId="9435" CreationDate="2011-02-12T00:51:39.347" Score="4" ViewCount="" Body="&lt;p&gt;For filtering large frequencies I'd recommend the ferrite.  The parasitic capacitance of inductors makes them essentially useless for filtering high frequencies.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-02-12T00:51:39.347" CommentCount="2" />
  <row Id="10032" PostTypeId="1" AcceptedAnswerId="10033" CreationDate="2011-02-12T01:06:33.317" Score="1" ViewCount="118" Body="&lt;p&gt;Hi, in university we had our internal program called HLCCAD - it was very nice, and now I need to do design &amp;amp; debug some digital circuit and wondering what is current state of art software for that kind of things (price is out of consideration for now)? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I.e. I want to visually place components, and then simulate it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Manually writing VHDL code &amp;amp; looking at simulation traceouts of specific nodes is not enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update: Found &lt;strong&gt;Logisim&lt;/strong&gt; - this is exactly what is needed. Are there any commercial alternatives with more horsepower?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/mo0Xw.gif&quot; alt=&quot;http://newit.gsu.by/projects/HLCCAD/webinfo/screenshot_ru.gif&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-02-12T01:44:54.860" LastActivityDate="2011-02-17T05:41:45.043" Title="Visual logic designer + simulation" Tags="&lt;simulation&gt;&lt;vhdl&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="10033" PostTypeId="2" ParentId="10032" CreationDate="2011-02-12T01:38:20.567" Score="2" ViewCount="" Body="&lt;p&gt;I've heard good from Qucs (which has some basic digital logic, including VHDL apparently) and tkgate, which is an event driven logic simulator. Both are free open source software.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-12T01:38:20.567" CommentCount="3" />
  <row Id="10034" PostTypeId="1" AcceptedAnswerId="10035" CreationDate="2011-02-12T02:00:52.977" Score="0" ViewCount="101" Body="&lt;p&gt;I was experimenting with my universal laptop adapter (Meind 100W) and when I switched it to 34V mode (while official max is 24V) the capacitor (25V) popped (the top opened and some white fibers spread over the nearby parts).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The capacitor is glued to the board and is not easy to remove. When using the adaptor it slowly heats now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When under load the output voltage of the adapter drops (and probably recovers after some seconds), so I have to set it to voltage that is higher than needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is it safe to continue using that adaptor? Can it degrage further with time or it will remain stable?&lt;/li&gt;&#xA;&lt;li&gt;How to unglue the damaged capacitor from board?&lt;/li&gt;&#xA;&lt;li&gt;Should I use some additional safety measures (for example, external capacitor connected to output) to reduce the risk? (I'm not going to just buy another adaptor)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2898" LastEditorUserId="2898" LastEditorDisplayName="" LastEditDate="2011-02-12T14:58:19.983" LastActivityDate="2011-02-12T14:58:19.983" Title="Is it safe to keep on using AC adapter with a damaged output capacitor?" Tags="&lt;power-supply&gt;&lt;capacitor&gt;&lt;damage&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="10035" PostTypeId="2" ParentId="10034" CreationDate="2011-02-12T02:16:35.107" Score="2" ViewCount="" Body="&lt;p&gt;Most likely the popped capacitor is causing stability issues (output going up and down as you described).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should be replaced with a part with comparable voltage, ripple current, ESR and life ratings. Failure to choose an appropriate cap will likely result in the cap failing prematurely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A properly protected power supply should not be damaged from a blown output capacitor. I wouldn't recommend operating it until the cap is replaced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems odd to me that the power supply is capable of self-damage. With 25V caps the max output ought to be below 20V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would use a sharp utility knife to cut the part from the glue, then desolder it and replace it. Make sure you note the polarity.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-12T02:16:35.107" CommentCount="3" />
  <row Id="10036" PostTypeId="2" ParentId="10020" CreationDate="2011-02-12T02:27:55.587" Score="2" ViewCount="" Body="&lt;p&gt;I've used Total Phase Aardvark USB/I2C/SPI interfaces in my professional career. They're fairly cheap and work great.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-12T02:27:55.587" />
  <row Id="10037" PostTypeId="2" ParentId="10020" CreationDate="2011-02-12T03:47:36.767" Score="1" ViewCount="" Body="&lt;p&gt;I draw a schematic and posted example code to run  a chain of '595s off of a humble FTDI cable: &lt;a href=&quot;http://electronics.stackexchange.com/questions/7525/how-can-i-control-128-or-more-solenoids#7529&quot;&gt;How can I control 128 (or more) solenoids?&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;'595 are essentially SPI. The code bacomes a bit more complicated if you need to read data as well as write it.  But it is still not bad.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-12T03:47:36.767" />
  <row Id="10038" PostTypeId="2" ParentId="9982" CreationDate="2011-02-12T04:14:29.147" Score="1" ViewCount="" Body="&lt;p&gt;No, it's not a stupid question.  Reweighting (or resampling) particles is non-trivial for any &quot;fun&quot; problem.  Weighting is typically performed by computing the likelihood of the particle fitting the observation.  See page 28 &lt;a href=&quot;http://www.site.uottawa.ca/research/spot/index_fichiers/Theory%20and%20Implementation%20of%20Particle%20Filters.ppt&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  This &lt;a href=&quot;http://students.cs.byu.edu/~cs470ta/goodrich/fall2006/lectures/ParticleFilterTutorial.pdf&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt; and this &lt;a href=&quot;http://www.site.uottawa.ca/~mbolic/Miodrag_Bolic_files/published/bolic_T-SP-2004.pdf&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt; give reasonable discussion on particle resampling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These links assume you can easily compute the likelihood a particle corresponds to the observations.  For ease, we typically assume the likelihood can be expressed as a normal distribution (i.e. with a mean and a variance). Since your observations are comprised multiple dimensions, you might use the multivariate version of the &#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Multivariate_normal_distribution&quot; rel=&quot;nofollow&quot;&gt;normal distribution&lt;/a&gt;.  &lt;/p&gt;&#xA;" OwnerUserId="2632" LastActivityDate="2011-02-12T04:14:29.147" CommentCount="5" />
  <row Id="10039" PostTypeId="2" ParentId="7844" CreationDate="2011-02-12T07:30:41.990" Score="1" ViewCount="" Body="&lt;p&gt;Hello!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought an IMU3000 too, i installed that software that invensense rold me to, and i managed to compile it somehow, and get a libfile out of the whole thing. I am trying to make it work with a pic too...im using pic18f4550..but i dont even know where to start. Are those source codes of some use? or should i forget about it, and try writing my own stuff for this?&lt;/p&gt;&#xA;" OwnerUserId="2974" LastActivityDate="2011-02-12T07:30:41.990" CommentCount="2" />
  <row Id="10041" PostTypeId="1" AcceptedAnswerId="10547" CreationDate="2011-02-12T07:46:04.663" Score="4" ViewCount="351" Body="&lt;p&gt;I want to convert a floating point number to a integer number. Basically I have a floating point number between 1 and 0, with three decimal places, and I want to pass it to a integer number as if multiplied by 1000. I suspect there should be a more optimal way to do it than using the arithmetic multiply operation x1000.&#xA;I'm looking for a piece of code preferably.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-12T18:08:45.857" LastActivityDate="2011-06-05T16:12:31.170" Title="How to convert a floating point number to integer, using VHDL?" Tags="&lt;vhdl&gt;&lt;floating-point&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="2" />
  <row Id="10042" PostTypeId="1" CreationDate="2011-02-12T07:50:45.143" Score="1" ViewCount="122" Body="&lt;p&gt;We are using 12V DC solar power at home, and I want to use it for home appliances. Can you suggest what should I have to use for this? At present we are using 4 (12V) lights and one DC fan. Now we want to use this source for AC fans also.&lt;/p&gt;&#xA;" OwnerUserId="2975" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-12T18:01:55.283" LastActivityDate="2011-02-20T20:43:20.387" Title="How do I convert 12Vdc solar to AC?" Tags="&lt;solar-cell&gt;&lt;inverter&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="10044" PostTypeId="1" CreationDate="2011-02-12T08:20:10.097" Score="0" ViewCount="61" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/10041/how-to-convert-a-floating-point-number-to-integer-using-vhdl&quot;&gt;How to convert a floating point number to integer, using VHDL?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Hi all, I wonder what is the floating point number of floating point numbers that are using in System Generator. I would know I could do something like to design my own custom block to perform arithmetic operations like x100, x1000, x10000. Because the only thing needed to do this is to modify the exponent bit pattern,it doesn´t?&#xA;Thank you to all possible references to documentation, articles or comments.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T20:55:22.840" LastActivityDate="2011-02-12T20:55:22.840" ClosedDate="2011-02-13T14:56:23.820" Title="System Generator: How to know the floating point format of the floating point number you are using." Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;floating-point&gt;&lt;xilinx-system-generator&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="10045" PostTypeId="2" ParentId="10044" CreationDate="2011-02-12T09:28:24.810" Score="1" ViewCount="" Body="&lt;p&gt;If you only want to multiply by a fixed factor as simple as x10, x100 or some other power of ten, then incrementing the exponent should work. Remember to handle degenerate input cases, such as NaN, signed zeros, infinity...&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-12T09:28:24.810" CommentCount="2" />
  <row Id="10046" PostTypeId="2" ParentId="10044" CreationDate="2011-02-12T09:55:55.747" Score="1" ViewCount="" Body="&lt;p&gt;Usually floating-point numbers are encoded as binary, so it won't be that easy to multiply by powers of 10.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are decimal formats in IEEE-754, too, but they are rarely used.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-02-12T09:55:55.747" CommentCount="1" />
  <row Id="10047" PostTypeId="1" CreationDate="2011-02-12T10:00:11.657" Score="2" ViewCount="146" Body="&lt;p&gt;I've read one academic paper on the use of quaternions in IMU's, but it still greatly confuses me. I dont think I've understood anything from it! :( Does anyone know of any good introductions to understanding quaternions?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-02-13T05:28:55.087" ClosedDate="2011-02-13T13:24:13.440" Title="Understanding Quaternions" Tags="&lt;imu&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="10049" PostTypeId="1" CreationDate="2011-02-12T12:03:10.440" Score="1" ViewCount="74" Body="&lt;p&gt;Hi all, does anyone what is the xilinx block for getting a three state logic?&#xA;Thank you so much.&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T18:34:55.333" LastActivityDate="2011-03-02T02:47:13.800" Title="System Generator: a block similar to a three state logic" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;logic&gt;&lt;tri-state&gt;&lt;xilinx-system-generator&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="10050" PostTypeId="1" CreationDate="2011-02-12T12:48:57.027" Score="1" ViewCount="105" Body="&lt;p&gt;I want a system with two inputs,&lt;code&gt;sel&lt;/code&gt; and &lt;code&gt;in&lt;/code&gt;, and at least two outputs &lt;code&gt;channel A&lt;/code&gt; and &lt;code&gt;channel B&lt;/code&gt;. Here's some pseudocode of what I'd like to implement:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if sel == 1 {&#xA;  channel_A = in;&#xA;  float_pin(channel_B); // make high impedance&#xA;}&#xA;&#xA;if sel == 0 {&#xA;  channel_B = in;&#xA;  float_pin(channel_B); // make high impedance&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;How do I do this with Xilinx System Generator?&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-12T18:18:23.070" LastActivityDate="2011-03-02T02:48:28.417" Title="System Generator: How to make a channel selector?" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;hdl&gt;" AnswerCount="2" />
  <row Id="10051" PostTypeId="1" AcceptedAnswerId="10593" CreationDate="2011-02-12T12:20:08.840" Score="1" ViewCount="154" Body="&lt;p&gt;I hope the TVS diode (or something like this) of my HDD's PCB is gone, so I could fix this HDD easily, but I don't know where it is. Can you tell me how to measure it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I &lt;a href=&quot;http://forums.seagate.com/t5/Barracuda-XT-Barracuda-and/Need-PCB-Replacement-for-Momentus-7200-3-ST9320421ASG/m-p/40296&quot; rel=&quot;nofollow&quot;&gt;read this&lt;/a&gt; but I didn't understand, why 3 pins? I'm measuring the circuit resistance since I'm not measuring specifically the diode so I understand that if it's broken the resistance could be different than infinite, so how much should be the resistance?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My broken hdd history is here: &#xA;&lt;a href=&quot;http://superuser.com/questions/242014/is-my-hdd-dead-forever&quot;&gt;http://superuser.com/questions/242014/is-my-hdd-dead-forever&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3133" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-02-12T15:59:41.363" LastActivityDate="2011-02-23T13:52:54.270" Title="How can I measure TVS diode for Seagate Momentus 7200.3?" Tags="&lt;hard-drive&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="10052" PostTypeId="1" AcceptedAnswerId="10059" CreationDate="2011-02-12T14:52:28.120" Score="0" ViewCount="128" Body="&lt;p&gt;I have a circuit board with an oscillator and I'm curious about why there is a capacitor hooked up to the output.  The oscillator is a SWO series HCMOS Square Wave output crystal oscillator.  The schematic of the oscillator connections is as follows.  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;               +3.3V&#xA;                |&#xA;   ---------    |  C=0.01uF&#xA;NC-| 1   4 |---------||-----GND&#xA;   |       |&#xA;GND| 2   3 |----------&amp;gt;Direct to FPGA input pin&#xA;   ---------    |&#xA;                |&#xA;                = C=15pF&#xA;                |&#xA;               GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.mecxtal.com/clock_oscillator.php#XOs&quot; rel=&quot;nofollow&quot;&gt;data sheet&lt;/a&gt; (select H22/H32/H53/SWO) does not reveal much, but there is a &quot;Load&quot; section that says the max load is 15pF.  Specifically, it says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Load |   15 pF  ;  ( 30 pF and 50 pF load are also available for +3.3V and +5.0V VDD) &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;In such a circuit, is the load the capacitor or the FPGA input pin?  If the load is the capacitor, why is the load needed for the oscillator?  What is its purpose?&lt;/p&gt;&#xA;" OwnerUserId="2059" LastActivityDate="2011-02-12T17:15:27.493" Title="Why is a capacitor placed in parallel with oscillator output?" Tags="&lt;capacitor&gt;&lt;oscillator&gt;&lt;cyrstal&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10053" PostTypeId="2" ParentId="10052" CreationDate="2011-02-12T15:11:34.733" Score="1" ViewCount="" Body="&lt;p&gt;The 15 pF load capacitance mentioned in the data sheet is the total load that should be placed on the output - printed circuit track capacitance, input capacitance of the devices it drives, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That capacitor should be removed, it will adversely affect the signal.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-12T15:11:34.733" CommentCount="2" />
  <row Id="10054" PostTypeId="1" CreationDate="2011-02-12T15:15:33.317" Score="4" ViewCount="265" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/oGZoD.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/PvQV5.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone explain it ?&lt;/p&gt;&#xA;" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-02-12T18:38:20.493" LastActivityDate="2011-02-12T18:38:20.493" Title="How does an optical mouse detect movement?" Tags="&lt;mouse&gt;&lt;optoelectronics&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="10055" PostTypeId="2" ParentId="10054" CreationDate="2011-02-12T15:19:53.283" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Mouse_%28computing%29&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Mouse_%28computing%29&lt;/a&gt; check it here&lt;/p&gt;&#xA;" OwnerUserId="2979" LastActivityDate="2011-02-12T15:19:53.283" CommentCount="1" />
  <row Id="10056" PostTypeId="2" ParentId="10054" CreationDate="2011-02-12T15:28:13.577" Score="10" ViewCount="" Body="&lt;p&gt;The optical mouse has a chip that has a lo-res camera in it, with a DSP. The DSP picks off certain high-contrast bits of the image in one frame, and looks at how they've tracked across the field of view in the next image. From this it infers X and Y motion, and reports the position change to the computer through a USB interface. The LED provides illumination to increase contrast on the surface, so there will be more bright spots the DSP can pick off.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-12T15:28:13.577" CommentCount="1" />
  <row Id="10057" PostTypeId="1" CreationDate="2011-02-12T16:11:55.650" Score="0" ViewCount="168" Body="&lt;p&gt;Hey guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What according to you is the biggest challenge facing Electrical and Electronic Engineering in the next decade and why?&lt;/p&gt;&#xA;" OwnerUserId="2981" LastActivityDate="2011-02-12T16:12:56.350" ClosedDate="2011-02-12T17:07:15.363" Title="What are the biggest challenges facing Electrical and Electronic Engineering in the next decade?" Tags="&lt;electronics&gt;&lt;electrical-engineering&gt;" AnswerCount="1" />
  <row Id="10058" PostTypeId="2" ParentId="10057" CreationDate="2011-02-12T16:12:56.350" Score="0" ViewCount="" Body="&lt;p&gt;I would say that the scarcity of some materials, like tantalum, could present a problem. It has already made tantalum capacitors less popular due to increased prices.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-12T16:12:56.350" CommentCount="1" />
  <row Id="10059" PostTypeId="2" ParentId="10052" CreationDate="2011-02-12T17:15:27.493" Score="1" ViewCount="" Body="&lt;p&gt;They have a technote paper on this subject, &quot;Effect of Load Capacitance on the Crystal&quot;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mecxtal.com/pdf/te_notes/tn-021.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.mecxtal.com/pdf/te_notes/tn-021.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="721" LastActivityDate="2011-02-12T17:15:27.493" CommentCount="1" />
  <row Id="10060" PostTypeId="1" AcceptedAnswerId="10066" CreationDate="2011-02-12T17:42:32.303" Score="2" ViewCount="98" Body="&lt;p&gt;I have a schematic for a commerical circuit board, and I was curious about the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;            1.2V&#xA;             |    &#xA;------------------------------------------&#xA;|      |     |      |      |      |      |&#xA;=10uF  =1uF  =.1uF  =.1uF  =.1uF  =.1uF  =.01uF&#xA;|      |     |      |      |      |      |&#xA;------------------------------------------&#xA;             |&#xA;            GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;What is this network for?  I see that for all of the ICs there is a decoupling capacitor on the input voltages near the IC.  The above, however, appears to just be caps connected between the supply and ground.  What purpose does such a network perform, and how does one decide on the value Ctotal of the network?  They all add up to Ctotal=11.41uF for the 1.2V supply.  There is also a 3.3V supply with the same network, except that Ctotal=11.43uF.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also a ground-ground connection I am curious about.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; ------------------&#xA; |                |&#xA;GND              GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;What is the purpose of coupling ground to ground? &lt;/p&gt;&#xA;" OwnerUserId="2059" LastActivityDate="2011-02-12T18:48:49.870" Title="Power and ground configuration in a schematic" Tags="&lt;capacitor&gt;&lt;ground&gt;&lt;supply&gt;" AnswerCount="2" />
  <row Id="10061" PostTypeId="2" ParentId="10042" CreationDate="2011-02-12T17:52:41.937" Score="2" ViewCount="" Body="&lt;p&gt;Normally the way to convert 12v DC to 120v AC is to use a inverter like &lt;a href=&quot;http://www.radioshack.com/product/index.jsp?productId=3537166&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;, designed for automobiles.  I don't know if your solar device would have enough power to run this or not.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-02-12T17:52:41.937" />
  <row Id="10062" PostTypeId="1" AcceptedAnswerId="10065" CreationDate="2011-02-12T18:18:22.353" Score="2" ViewCount="138" Body="&lt;p&gt;I am looking for a darlington array IC like the ULN2803a that can sink up to 1.5A. It needs to be in a DIP. Any recommendations? Its needed because i am driving a stepper motor and requires 1.2A per coil. I am controlling the stepper motor from a PIC. So if you have another solution let me know. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-02-14T09:45:35.367" Title="Darlington Array IC that can sink 1.5A" Tags="&lt;transistor-array&gt;" AnswerCount="3" />
  <row Id="10063" PostTypeId="1" AcceptedAnswerId="10069" CreationDate="2011-02-12T18:20:15.257" Score="1" ViewCount="124" Body="&lt;p&gt;I have seen some kits and boards for a Serial LCD based on the PIC16F648A.&#xA;A have a few of the chips and a few LCDs. I'm not into PIC programming, does anyone have a link to the compiled software I can program my PIC chips with to make my own serial LCD?&lt;/p&gt;&#xA;" OwnerUserId="2319" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-20T22:12:58.960" LastActivityDate="2011-02-20T22:12:58.960" Title="Need bin or hex file for Pic 16F648A Serial LCD" Tags="&lt;lcd&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="10064" PostTypeId="2" ParentId="10060" CreationDate="2011-02-12T18:22:00.943" Score="2" ViewCount="" Body="&lt;p&gt;The capacitors are called decoupling capacitors, they are placed near the power pins of all ICs to smooth out any sudden spikes in the power rails.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any switching that happens in an IC will cause it to put noise out on the power lines, the capacitors try to remove that noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The GND to GND connection is probably a connection between the analog and digital grounds.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-02-12T18:22:00.943" CommentCount="0" />
  <row Id="10065" PostTypeId="2" ParentId="10062" CreationDate="2011-02-12T18:44:26.380" Score="3" ViewCount="" Body="&lt;p&gt;I don't think you will find a Darlington array in DIL that will handle 1.5A per output. The package can't dissipate enough power. You will probably have to use use discrete devices.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-12T18:51:22.693" LastActivityDate="2011-02-12T18:51:22.693" CommentCount="6" />
  <row Id="10066" PostTypeId="2" ParentId="10060" CreationDate="2011-02-12T18:48:49.870" Score="2" ViewCount="" Body="&lt;p&gt;In the schematics they are put next to each other to avoid cluttering the functional part, but on the PCB they are usually spread out as follows:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;100nF are placed across the power supply of each ICs.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;10µF is used for a group of ICs, often only one for the whole circuit, if it is not too big.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I've seen 10nF to decouple the analog supply, I suppose to be able to use a higher quality C0G capacitor without it getting much bigger. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The total capacitance doesn't matter much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the ground connection, there are probably two separate ground networks or planes, which need to be connected by a wire, and for technical reasons the schematic needs to contain that wire (so it is not forgotten).&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-02-12T18:48:49.870" />
  <row Id="10067" PostTypeId="2" ParentId="9922" CreationDate="2011-02-12T20:13:17.890" Score="1" ViewCount="" Body="&lt;p&gt;I've seen a heater design that used fat-ish PCB traces as a resistive heating element.&lt;/p&gt;&#xA;" OwnerUserId="883" LastActivityDate="2011-02-12T20:13:17.890" CommentCount="1" />
  <row Id="10068" PostTypeId="1" AcceptedAnswerId="10070" CreationDate="2011-02-12T20:13:35.300" Score="1" ViewCount="162" Body="&lt;p&gt;Okay, so I was a bit of an idiot while designing my PCB. The specifications of my PCB fab were 6/6 mil trace/space, and the boards did not meet this. So, below is the design for the PCB:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2hNfp.png&quot; alt=&quot;Design file&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The trace going to C16 (a ground) is way too close to the pad which is connected through a trace to an inductor (it's a switch mode buck converter.) This basically connects the +3.3V line next to the filter capacitor to GND, shorting it. I verified this with the continuity test on my multimeter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My PCB:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/RuWb1.jpg&quot; alt=&quot;PCB&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have already bought 10 PCBs, so I'd like to know if it's possible to hack these and repair them. I'm okay with having to provide them with an external 3.3V source; in future, I'd like to get the converter working, but it's the rest of the circuit which is important.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously I won't make this mistake in the next version... I might actually run the DRC. This is only for development.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-13T02:47:35.407" Title="Is it possible to repair a PCB which has suffered a DRC failure?" Tags="&lt;pcb&gt;&lt;hack&gt;&lt;drc&gt;" AnswerCount="3" CommentCount="10" />
  <row Id="10069" PostTypeId="2" ParentId="10063" CreationDate="2011-02-12T20:35:42.350" Score="2" ViewCount="" Body="&lt;p&gt;Compiled bin/hex files are very specific and can not be easily adapted to your specific situation. This means that the bin/hex file would have to be for the exact PIC you have along with all of the exact pins connected as was designed for in the original code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also many companies protect their code and compiled versions of their code very tightly. This means that there is a good chance that they wont just hand it over to you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, likely you wont find an answer to your question. Instead you should look to see if someone has released information on how to build what you are looking for. It will require that you are willing to be open to learning about firmware coding as you will have to touch it to work on a project like this.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-12T20:35:42.350" CommentCount="1" />
  <row Id="10070" PostTypeId="2" ParentId="10068" CreationDate="2011-02-12T20:36:31.927" Score="4" ViewCount="" Body="&lt;p&gt;If I were you, I would try to &lt;em&gt;burn&lt;/em&gt; the small copper bridge with a current surge. Using some cheap probes or solid wire, touch between the two points you don't want connected with a power source current limited to about 5A. If it doesn't work, increase current limit -- I wouldn't go past 50A, though. Note that the points you touch will oxidize immediately, and possibly also release magical smoke, so it'd be best if they were the edges of relatively large pads. Of course, everything between the two wires will be destroyed by 5A-50A, so don't miss any current paths...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, I don't mind blowing stuff up -- kinda' enjoy it, really -- but this method carries quite a bit of product risk. Don't get too mad at me when you burn your fingers, break your PSU, and melt some FR-4 on your desk. (You can get a little bit mad, though -- I understand.)&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-13T02:47:35.407" LastActivityDate="2011-02-13T02:47:35.407" CommentCount="7" />
  <row Id="10071" PostTypeId="2" ParentId="10068" CreationDate="2011-02-12T20:44:36.017" Score="8" ViewCount="" Body="&lt;p&gt;When ever I have PCB errors that cause something to be shorted to something else, I pull out my handy dandy razor blade and go at it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your situation it looks like you might also have an issue with solder causing a short. If this is the case, find anything that you can place to add an insulator. The hard part is going to be finding something that wont melt while soldering. Maybe someone else has a suggestion with this, I would try electrical tape and hot air gun soldering.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-12T20:44:36.017" CommentCount="5" />
  <row Id="10072" PostTypeId="1" CreationDate="2011-02-12T21:35:28.477" Score="5" ViewCount="189" Body="&lt;p&gt;Having trouble getting a &lt;a href=&quot;http://www.national.com/pf/DP/DP83848J.html&quot; rel=&quot;nofollow&quot;&gt;National Semi DP83848J&lt;/a&gt; working in 10BASE-T mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The link partner and local status register agree that the link is in 10Mbps full-duplex mode.  However, instead of receiving 4-bit 2.5Msps data on RXD[3..0] as required by the MII spec, a logic analyzer shows 1-bit 10Msps data.  The only Ethernet standard I can find that describes that type of data is GPSI, which is not part of the DP83848J feature set.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any idea how to configure the DP83848J to output data compliant with the 10 Mb/s MII Timing spec?&lt;/p&gt;&#xA;" OwnerUserId="1743" LastActivityDate="2011-02-25T19:06:06.693" Title="DP83848 (Ethernet PHY) 1-bit serial receive data in 10Base-T" Tags="&lt;ethernet&gt;&lt;mac&gt;&lt;phy&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="10073" PostTypeId="1" AcceptedAnswerId="10075" CreationDate="2011-02-12T21:53:39.423" Score="1" ViewCount="111" Body="&lt;p&gt;I recently obtained DEM 16217 SYH-PY 2x16 character screen. &lt;a href=&quot;http://www.display-elektronik.de/lcd-alphanumeric-table.htm&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;'s the datasheet. As far as I can see, its contrast pin should be connected to voltage source over a potentiometer. How do I pick correct resistance of the potentiometer for this use?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-12T22:04:32.457" LastActivityDate="2011-02-24T20:56:43.590" Title="Which potentiometer to chose for LCD screen contrast?" Tags="&lt;lcd&gt;&lt;potentiometer&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="10074" PostTypeId="1" AcceptedAnswerId="10076" CreationDate="2011-02-12T21:57:44.223" Score="0" ViewCount="84" Body="&lt;p&gt;Hello Everyone,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First post in Electronics and Robotics... I've been trying to order a DIP PIC off of Microchip (first time going directly off the website) for use with the RFM12, but I dont really know what all the variants are. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to get &lt;a href=&quot;http://www.microchipdirect.com/ProductSearch.aspx?keywords=PIC16F873A&quot; rel=&quot;nofollow&quot;&gt;http://www.microchipdirect.com/ProductSearch.aspx?keywords=PIC16F873A&lt;/a&gt; so that it would fit on a non-solder breadboard. Most confusing is E/SP and I/SP, what's the difference? I couldnt find anything online.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!&lt;/p&gt;&#xA;" OwnerUserId="2985" LastActivityDate="2011-02-12T22:04:17.980" Title="Difference between E/SP and I/SP and other variants." Tags="&lt;pic&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10075" PostTypeId="2" ParentId="10073" CreationDate="2011-02-12T21:58:11.800" Score="3" ViewCount="" Body="&lt;p&gt;I don't think it makes a whole lot of difference. I've used a 10K&amp;Omega; linear before which works perfectly well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You're essentially making a potential divider, connecting your pot between your supply and ground, so as long as it's not too low value that it starts to draw more than a negligible amount of current.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-02-13T09:18:29.173" LastActivityDate="2011-02-13T09:18:29.173" CommentCount="1" />
  <row Id="10076" PostTypeId="2" ParentId="10074" CreationDate="2011-02-12T22:04:17.980" Score="2" ViewCount="" Body="&lt;p&gt;If you look at &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010236&quot; rel=&quot;nofollow&quot;&gt;their summary page&lt;/a&gt;, you'll see the difference is in temperature tolerance/range:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;PIC16F873A-E/SP 28  SPDIP   -40C to +125C&#xA;PIC16F873A-I/SP 28  SPDIP   -40C to +85C&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-02-12T22:04:17.980" CommentCount="4" />
  <row Id="10077" PostTypeId="2" ParentId="9922" CreationDate="2011-02-12T22:28:30.877" Score="0" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;I would like to make a circuit that can heat up an object to a very high temperature, similar to an electric griddle or coffee cup warmer.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;If this is a hobby project or other one-off, why don't you repurpose an electric griddle or coffee cup warmer or iron or...? Your local thrift store has a ready-made supply of these.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2011-02-12T22:28:30.877" CommentCount="1" />
  <row Id="10078" PostTypeId="2" ParentId="10068" CreationDate="2011-02-12T22:57:18.247" Score="2" ViewCount="" Body="&lt;p&gt;It's always a good idea to have a rotary tool with a fine tip handy when dealing with PCB rework. I prefer a rotary tool to a utility knife, but have been known to resort to a blade at points (no pun intended).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's quite acceptable to do PCB rework like this on small quantities, even in professional environments. Make your cuts however you can, use your meter to make sure the circuit is OK, then fix the artwork. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-12T22:57:18.247" />
  <row Id="10079" PostTypeId="1" AcceptedAnswerId="10081" CreationDate="2011-02-13T00:01:00.817" Score="3" ViewCount="160" Body="&lt;p&gt;I'm curious as to why dual-slope analog to digital converters are used in most digital voltmeters, &lt;a href=&quot;http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=11023&amp;amp;mid=11&amp;amp;lang=en&amp;amp;pageId=79&quot; rel=&quot;nofollow&quot;&gt;like one of these&lt;/a&gt; when a delta-sigma converter &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en025692&quot; rel=&quot;nofollow&quot;&gt;like one of these&lt;/a&gt; easily exceeds the specifications of any of the other dual-slope converters sold by Microchip, and in fact many other suppliers, especially given the low price point of the chip (about $4 in low quantities.) Is there a reason I am missing?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-06-04T22:28:18.917" Title="Dual slope converter vs. delta-sigma converter?" Tags="&lt;adc&gt;" AnswerCount="3" />
  <row Id="10080" PostTypeId="2" ParentId="10079" CreationDate="2011-02-13T00:29:30.623" Score="1" ViewCount="" Body="&lt;p&gt;It's basically speed, resolution and cost, dual-slope converters are cheaper but a lot slower and offer lower resolution. Speed and high resolution don't matter for something like a DVM, but they are important for, say, sampling speech and music.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-13T00:41:28.003" LastActivityDate="2011-02-13T00:41:28.003" CommentCount="1" />
  <row Id="10081" PostTypeId="2" ParentId="10079" CreationDate="2011-02-13T00:42:35.290" Score="5" ViewCount="" Body="&lt;p&gt;With a dual-slope ADC you effectively get free averaging as the run-up integration phase will have this effect.  The output is also extremely simple, just a pulse that needs to be timed which can be done with even the simplest micro controllers.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;$4 is a really big deal when your making 50,000 of something and trying to sell it for $50.  The dual-slope part you linked is $1.64 in a PDIP for 5000+.  The sigma-delta's cheapest package is $2.88 in its cheapest package.  Saving ~$1.20 on a single part AND being able to use a more basic microcontroller is a big cost win.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you'll find the more expensive multimeters do use higher end ADCs.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-02-13T00:42:35.290" CommentCount="2" />
  <row Id="10082" PostTypeId="1" AcceptedAnswerId="10333" CreationDate="2011-02-13T01:02:42.320" Score="1" ViewCount="266" Body="&lt;p&gt;I need to build supply for ~20 laser diodes (~150 mW each), and the question is why can't we just use a constant current power source for each of them? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A similar question for pulsed mode operation: if I would need, let's say, 50 ns pulses, is it correct that I just need to stabilize the current in these periods or is it again more complex? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can it work this way: We start from, let's say, a 1.5 V supply, use a FET to connect diode to the supply for 50 ns and sense the peak current. Then we slowly increase the supply until we reach the required peak current. Will that work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Any practical experience? Any comments on the last paragraph?&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2011-02-16T21:27:41.167" LastActivityDate="2011-02-17T07:15:20.943" Title="Why is a laser supply so tricky?" Tags="&lt;laser&gt;&lt;constant-current&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="2" />
  <row Id="10083" PostTypeId="2" ParentId="9808" CreationDate="2011-02-13T01:24:10.027" Score="2" ViewCount="" Body="&lt;p&gt;Accurate to a millisecond?  Probably not, and for several reasons:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First the polling loop of whatever you're trying to control is probably nowhere near that fast.  If you're looking at a typical keyboard, the controller may check each key maybe 25 times per second, nowhere near 1000 times.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, variation in the distance from the actuator to the button can give several milliseconds of inaccuracy: if at one time it has to travel 0.5 inches and another time, it has to travel 0.6, even though there's only a tenth of an inch difference, that's still 20% further it would have to travel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Third, the button itself may not switch consistently enough for millisecond accuracy.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're trying to beat the arcade game I'm thinking of, with a ring of light bulbs that shows a circling &quot;pulse&quot; of light and the objective is to hit the button when the pulse is in a target zone, this wouldn't require the millisecond accuracy.  You would need to account for a number of factors which would affect &quot;scoring&quot;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The length of time required from the time the microcontroller says 'go' until the actuator has traveled its distance.  This is on the order of 1/10th second.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The length of time for the game's controller to trigger the leading edge light bulb and that bulb to fully light up (if they're using LED's that's almost instantaneous, but light bulbs would be slower).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;dwell&quot;--how long the light pulse is in the target zone.  You won't want to hit the button too early, so the ideal is to hit it when it's halfway through.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All these timing factors would need to be taken into account with your design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd recommend using a solenoid, since it will take less time to travel the required distance and will make the mechanism simpler.  You'll need a driver circuit to feed the required current through it when the controller commands.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember to cut me in for a share of the prizes!&lt;/p&gt;&#xA;" OwnerUserId="1264" LastActivityDate="2011-02-13T01:24:10.027" CommentCount="1" />
  <row Id="10084" PostTypeId="2" ParentId="10041" CreationDate="2011-02-13T02:59:32.213" Score="0" ViewCount="" Body="&lt;p&gt;From a general programming perspective I would use just multiply by 1000 then cast to an integer. I would only look to optimise &lt;strong&gt;if&lt;/strong&gt; if this solution doesn't perform as fast as you want.&lt;/p&gt;&#xA;" OwnerUserId="25" LastActivityDate="2011-02-13T02:59:32.213" />
  <row Id="10085" PostTypeId="1" CreationDate="2011-02-13T04:08:14.357" Score="0" ViewCount="74" Body="&lt;p&gt;I was wondering how exactly they were made differently which results in DVDs storing a greater amount of data.&lt;/p&gt;&#xA;" OwnerUserId="2989" LastActivityDate="2011-02-13T04:08:14.357" ClosedDate="2011-02-13T14:51:44.593" Title="What is the difference between VCD and DVD?" Tags="&lt;electronics&gt;" CommentCount="1" />
  <row Id="10086" PostTypeId="2" ParentId="10047" CreationDate="2011-02-13T05:28:55.087" Score="0" ViewCount="" Body="&lt;p&gt;I've used them in 3D graphics.  Here are some reasonable discussions in that context: &lt;a href=&quot;http://www.flipcode.com/documents/matrfaq.html#Q47&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;, &lt;a href=&quot;http://www.cprogramming.com/tutorial/3d/quaternions.html&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;, and &lt;a href=&quot;http://en.wikipedia.org/wiki/Slerp&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And, yes, the question is probably better served on math.stackexchange.com, but could also appear in gamedev.stackexchange.com.&lt;/p&gt;&#xA;" OwnerUserId="2632" LastActivityDate="2011-02-13T05:28:55.087" />
  <row Id="10087" PostTypeId="1" AcceptedAnswerId="10097" CreationDate="2011-02-13T05:36:51.053" Score="1" ViewCount="137" Body="&lt;p&gt;The thermal reliefs of my ground polygon to one of the pads of my footprint are just simply weird! I dont know what causes it? It seems to me that the lines leading up from the polygon to the pads are just too thick and are out of proportion to the pad. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kSOEh.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-02-13T14:37:05.487" Title="Weird Thermal Reliefs in Eagle PCB" Tags="&lt;eagle&gt;" AnswerCount="2" />
  <row Id="10088" PostTypeId="2" ParentId="7632" CreationDate="2011-02-13T07:41:32.757" Score="2" ViewCount="" Body="&lt;p&gt;If I were going to do this using a downward facing camera, the first thing i would want is high performance and relatively low resolution (this is a sensor, I'm not interested in the camera's input really) and so the camera i'd use for this would be from an optical mouse: they have very high speed, low resolution cameras.  With a bit of hacking about I'm sure you could come up with a lens arrangement to let it distinguish between features on the ground and then you could use a difference-extracting optical flow algorithm to process this input.&lt;/p&gt;&#xA;" OwnerUserId="2990" LastActivityDate="2011-02-13T07:41:32.757" CommentCount="2" />
  <row Id="10089" PostTypeId="2" ParentId="10087" CreationDate="2011-02-13T08:50:20.490" Score="0" ViewCount="" Body="&lt;p&gt;This may not apply to you because you use Eagle, but in Altium if you have traces going to pads then you pour a plane over it, it can behave badly.  Try removing the (superfluous) traces and repouring it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tangentially related: Did you use an auto-router?  You might want to adjust your neck-down rules so you actually have a neck, or possibly the trace thickness rules.  In any case, because you're using a plane, you should probably do everything manually around those small SMT parts.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-02-13T08:50:20.490" CommentCount="1" />
  <row Id="10091" PostTypeId="1" CreationDate="2011-02-13T12:02:51.420" Score="3" ViewCount="126" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Aj5zL.jpg&quot; alt=&quot;Breadboard&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me say to set the scene, that I am a complete beginner with electronics, not having done anything since my school days.  I can write code, but hardware is another thing entirely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I got myself an Arduino, and bought a breadboard from Maplins. The only thing is, the layout is very different to what I see on most tutorials, and I don't want to risk damaging anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Can anyone link to any tutorial which uses this breadboard layout?&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="2991" LastEditorUserId="1337" LastEditorDisplayName="" LastEditDate="2011-03-09T23:51:08.023" LastActivityDate="2011-03-09T23:51:08.023" Title="I need help with this breadboard..." Tags="&lt;breadboard&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="10092" PostTypeId="1" AcceptedAnswerId="10103" CreationDate="2011-02-13T12:30:11.660" Score="4" ViewCount="329" Body="&lt;p&gt;Rather basic, I'm afraid, but when would you use a relay, and when would you use a transistor?  In a relay the contacts wear out, so why are relays used at all?&lt;/p&gt;&#xA;" OwnerUserId="2992" LastActivityDate="2011-02-15T18:46:55.480" Title="Relay vs. Transistor?" Tags="&lt;transistor&gt;&lt;relay&gt;" AnswerCount="5" CommentCount="1" />
  <row Id="10093" PostTypeId="2" ParentId="10091" CreationDate="2011-02-13T12:41:02.427" Score="3" ViewCount="" Body="&lt;p&gt;I have one of these breadborads. Row 1 A-F are connected(horizontally) this is the same all the way down to 28(not connected vertically). Then 1 G-L are connected. In the picture below I have a 555 AStable. Notice I put it across the gap this is because there not connected. Also the voltage rails are easy to read the length of the line shows the length of the rail. Then the part at the bottom is the same Row A 1-30 are connected and so on to F 1-30. &#xA;&lt;img src=&quot;http://i.imgur.com/8pqWn.jpg&quot; alt=&quot;Similar Breadboard&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-02-13T12:54:48.577" LastActivityDate="2011-02-13T12:54:48.577" />
  <row Id="10094" PostTypeId="2" ParentId="10092" CreationDate="2011-02-13T12:48:26.150" Score="7" ViewCount="" Body="&lt;p&gt;Relays offer complete isolation between the activating circuit and the load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They can switch AC and DC, and be activated by AC or DC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They can be very robust.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also have the advantage that one can often see if the device is actuated, and one can even hear the actuation in many cases.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-13T13:27:35.647" LastActivityDate="2011-02-13T13:27:35.647" CommentCount="2" />
  <row Id="10095" PostTypeId="2" ParentId="10092" CreationDate="2011-02-13T13:19:45.533" Score="1" ViewCount="" Body="&lt;p&gt;Relays are an ok choice for when the load that needs to be controlled draws more than a couple of amps, and when the switching will not be that frequent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you need to break (shut off) a current of several amps, load inductance can cause voltage spikes that will damage a transistor, unless you add a flyback/clamping diode to protect it. Relay contacts, being basically large pieces of metal, have much greater tolerance to this application, but even so, breaking large load currents will eventually burn out relay contacts. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to switch something faster than once every second, a relay would probably have a relatively short life, and it would be worthwhile to go with the transistor option. If you don't need to switch your load faster than once every 10 seconds, you might find the relay more economical. As always, it's a design trade off.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-13T13:19:45.533" CommentCount="1" />
  <row Id="10096" PostTypeId="2" ParentId="10092" CreationDate="2011-02-13T13:37:34.583" Score="1" ViewCount="" Body="&lt;p&gt;Aside from all the correct properties that Leon mentions, relays also have a much lower internal resistance, in fact the switch of a relay looks quite a lot like a straight piece of wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any other kind of solid state switch (bjt, scr, triac, igbt) will have some resistance and drop some voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In many designs where switching is infrequent and the designer of the circuit doesn't know exactly what the user is going to want to switch, a relay is a nice choice as it will switch either ac or dc at a huge voltage and current range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a particular application you can almost always find a solid state component that will do the job cheaper than a relay, if you can do without all the robustness and versatility of a relay.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-02-13T13:37:34.583" CommentCount="2" />
  <row Id="10097" PostTypeId="2" ParentId="10087" CreationDate="2011-02-13T14:37:05.487" Score="2" ViewCount="" Body="&lt;p&gt;You need to change the width of your ground polygon. The polygons are actually made up of many wires drawn to make a continuous surface. If you zoom in on a polygon that is drawn in a non-solid pattern (like an inner layer on a 4 or greater layer board) you can see what I mean.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you draw the polygon you can choose the size of the wires used, just the same as when drawing wires. You can also change it after the fact using change-&gt;width, if I remember correctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You probably want to make the width no greater than the width of your IC pads.&lt;/p&gt;&#xA;" OwnerUserId="2960" LastActivityDate="2011-02-13T14:37:05.487" CommentCount="1" />
  <row Id="10098" PostTypeId="1" AcceptedAnswerId="10100" CreationDate="2011-02-13T15:17:33.977" Score="1" ViewCount="125" Body="&lt;p&gt;I'm soldering through the hole MOSFETs in to a PCB and I don't have a temperature controlled soldering iron. So will I need to heat sink the legs as I solder them to stop internal damage. I as this as bipolar transistors are damaged from heat. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="3411" LastEditorDisplayName="" LastEditDate="2011-04-03T14:45:19.160" LastActivityDate="2011-04-03T14:45:19.160" Title="Are MOSFETs Sensitive to heat while soldering?" Tags="&lt;soldering&gt;&lt;transistor&gt;" AnswerCount="2" />
  <row Id="10099" PostTypeId="2" ParentId="10098" CreationDate="2011-02-13T15:35:33.880" Score="2" ViewCount="" Body="&lt;p&gt;They shouldn't need any special precautions when soldering, in terms of heat, compared to BJTs. They will be a lot more sensitive to ESD, so it might be a good idea to take precautions against that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The data sheet should give you the maximum soldering temperature and time.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-13T15:35:33.880" />
  <row Id="10100" PostTypeId="2" ParentId="10098" CreationDate="2011-02-13T15:36:30.853" Score="3" ViewCount="" Body="&lt;p&gt;The difference in the structure of MOSFETs and BJT is that the former have a thin insulation layer. I don't know if this is easier damaged than the rest of the crystal when heating it. But I would &lt;em&gt;most strongly advise&lt;/em&gt; you to get a temperature controlled soldering station. If you leave your iron unused for a minute the temperature will rise to levels components won't like.&lt;br&gt;&#xA;Also, most likely a temp controlled station will have proper earthing which is even more important than temperature when soldering MOSFETs.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-02-13T16:35:08.060" LastActivityDate="2011-02-13T16:35:08.060" CommentCount="1" />
  <row Id="10101" PostTypeId="1" CreationDate="2011-02-13T16:30:11.500" Score="4" ViewCount="111" Body="&lt;p&gt;Hello there!&#xA;I have four LEDS (Red,Green,Blue,Yellow) and want to use charlieplexing to light them up.&#xA;I'll use an Attiny13V which needs 1.8 to 5.5V. I think one CR2032 with 3V will be suffice for the µC.&#xA;The forward voltages and current of the LEDs are:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;        Min   Typ   Max | Max (mA)&#xA;Red:    1.7   2.1   2.8 | 20&#xA;Green:  1.7   2.1   2.8 | 20 &#xA;Yellow: 1.7   2.1   2.8 | 20&#xA;Blue:   2.9   3.3   3.6 | 10-20&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Will I'm able to light the LEDs with the CR2032 and how can I find the right resistor values?&lt;/p&gt;&#xA;" OwnerUserId="2587" LastActivityDate="2011-02-14T12:48:54.373" Title="Charlieplexing different LEDs" Tags="&lt;led&gt;&lt;charlieplexing&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="2" />
  <row Id="10102" PostTypeId="2" ParentId="10082" CreationDate="2011-02-13T16:38:14.827" Score="2" ViewCount="" Body="&lt;p&gt;The problem with most laser diodes is that there is significant variation from both part to part variation, and also over temperature. This combines with a secondary issue, which doesn't apply to most other semiconductors, in that there is a possible failure mode through optical damage to the mirror surfaces if laser power is too high - this can cause damage way before any thermal damage to the semiconductor material itself.  &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-13T16:38:14.827" CommentCount="1" />
  <row Id="10103" PostTypeId="2" ParentId="10092" CreationDate="2011-02-13T16:41:19.067" Score="4" ViewCount="" Body="&lt;p&gt;Relays are on-off devices. Transistors can have their voltage drop varied.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Relays are far slower than transistors; typically 50ms to switch, and probably more. Some types of transistors can switch in picoseconds (almost 10 orders of magnitude faster.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Relays are isolated. Transistors can be (e.g. SSR), but are often not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Relays are electromagnetic and bring problems with them - for example, try building a relay computer with many relays. You will find that relays will interfere with each other in some cases. Transistors are not very EM sensitive. They do not emit much electromagnetic interference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Relays consume a lot of current in the &quot;on&quot; state, most transistors do not.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-02-13T19:56:32.753" LastActivityDate="2011-02-13T19:56:32.753" CommentCount="2" />
  <row Id="10104" PostTypeId="1" AcceptedAnswerId="10118" CreationDate="2011-02-13T16:43:25.550" Score="0" ViewCount="97" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My brother is a senior in High School. When he visited our college. I've took him to a robotics event (inter college robotics competition). He got to see various bots designed by college students and got mesmerised. Now he too wants to design bots like that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I told him programming is necessary. He already knows little bit and I'm helping him in becoming proficient. But I've no clue regarding this field. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can any one kindly suggest a path &amp;amp; tiny projects to improve his interest.&lt;/p&gt;&#xA;" OwnerUserId="1433" LastActivityDate="2011-02-14T15:33:27.333" Title="Getting started with robotics" Tags="&lt;robotics&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10105" PostTypeId="1" AcceptedAnswerId="10117" CreationDate="2011-02-13T16:44:38.220" Score="3" ViewCount="88" Body="&lt;p&gt;I'm trying to learn more about building RF circuits and I want to buy a spectrum analyzer. I've looked around on ebay, and a lot of them are really expensive. I'm a student, so I don't have a lot of money to spend on it. What's a good model to buy since I'm just starting out? &lt;/p&gt;&#xA;" OwnerUserId="2993" LastEditorUserId="2993" LastEditorDisplayName="" LastEditDate="2011-02-14T04:21:00.797" LastActivityDate="2011-02-14T04:21:00.797" Title="What's a good spectrum analyzer to learn with?" Tags="&lt;spectrum-analyzer&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="10106" PostTypeId="1" AcceptedAnswerId="10111" CreationDate="2011-02-13T16:45:10.670" Score="4" ViewCount="166" Body="&lt;p&gt;I want to amplify a 4 MHz triangle or square wave by 2 using an op-amp. Do I need an ~8 MHz op amp, or a much higher rated (and more expensive) device to handle the harmonics?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-13T20:23:33.777" Title="If I'm amplifying a triangle or square wave, does the GBWP of my op-amp need to be higher?" Tags="&lt;op-amp&gt;" AnswerCount="3" />
  <row Id="10107" PostTypeId="1" AcceptedAnswerId="10112" CreationDate="2011-02-13T17:03:19.293" Score="3" ViewCount="236" Body="&lt;p&gt;This question has two parts:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) How inefficient is it to boost 12V to 120V and then back to 12V as in using a traditional car power inverter to power a laptop (i.e. the 12V car battery power is boosted to 120V by a power inverter and then back to 12V by the laptop's power supply)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Is there any way to power a laptop directly from a 12V car battery? This would be useful not only for use in a car, but also for a solar-powered home that runs on 12V batteries. If there is a significant gain in not going through the boost/buck cycle of power inverters, then it would seem wise to power laptops and other 12V devices directly from battery power. I realize that laptops have different power supply ratings and some require more than 12V, but it seems rather wasteful to boost everything to 120V before bringing it back down.&lt;/p&gt;&#xA;" OwnerUserId="2994" LastActivityDate="2011-02-13T17:56:00.550" Title="Powering laptop from 12V sources without inverter" Tags="&lt;power-supply&gt;&lt;battery&gt;&lt;solar-cell&gt;&lt;inverter&gt;&lt;battery-charging&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="10108" PostTypeId="2" ParentId="10107" CreationDate="2011-02-13T17:18:36.480" Score="0" ViewCount="" Body="&lt;p&gt;An idea is that you could get a plug for the car then run it to a 12V dc regulator so that you could then plug it from that in to your laptop with the same type connector that the mains requires. Something to consider i don't know the answer to is that is it DC coming from the socket or AC. AN educated guess would be DC but if its AC then a rectifier would be needed. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-02-13T17:18:36.480" />
  <row Id="10109" PostTypeId="2" ParentId="10106" CreationDate="2011-02-13T17:27:05.033" Score="0" ViewCount="" Body="&lt;p&gt;You'll need at least 3x for a square wave.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-13T17:27:05.033" CommentCount="2" />
  <row Id="10110" PostTypeId="2" ParentId="10050" CreationDate="2011-02-13T17:43:16.153" Score="1" ViewCount="" Body="&lt;p&gt;Capturing the right signals simply requires an enabled flipflop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Float&quot;ing is more tricky though:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's no way of doing high-impedance internal signals in modern FPGAs, so if your outputs are connected to internal logic, you can't do that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And although the physical pins &lt;em&gt;can&lt;/em&gt; be made to tristate, as far as I can tell there's no way of accessing that from pure system generator.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To do it requires use of some FPGA tools outside of system generator:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;In your system generator model, you have to create three pins: an input, an output and an enable.  &lt;/li&gt;&#xA;&lt;li&gt;Then wrap the system generator model in an HDL block which takes those three pins and wires them up to a suitable &lt;code&gt;IOBUF&lt;/code&gt; block, which will connect to the real pin.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-02-13T17:43:16.153" CommentCount="2" />
  <row Id="10111" PostTypeId="2" ParentId="10106" CreationDate="2011-02-13T17:46:08.583" Score="9" ViewCount="" Body="&lt;p&gt;Short Answer- Yes.  Minimum 3x the fundamental frequency for triangle and 5x for square wave.  (9x gets you pretty good, low ripple answer for both)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Long Answer. Both of these waveforms are the sum of multiple sine waves.  To get a reasonable (and your definition of this may vary) quality square wave, you need at least the first 5 or 6 harmonics (1x,3x,5x,7x,9x, and 11x multiples of the fundamental).  If your opamp doesn't pass these frequencies, then you'll get distortion in the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The links below will show you how to build up triangle and square waves mathematically if you want to see for yourself how much fidelity you get for a given bandwidth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;References: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Triangle_wave&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Triangle_wave&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Square_wave&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Square_wave&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2909" LastActivityDate="2011-02-13T17:46:08.583" CommentCount="3" />
  <row Id="10112" PostTypeId="2" ParentId="10107" CreationDate="2011-02-13T17:56:00.550" Score="6" ViewCount="" Body="&lt;p&gt;Yes, tons of power is wasted going from 12V to 110V, especially when all you do is to stick it into a psu which also loses some power turning it back into low voltage DC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy a DC/DC converter which will deliver a 9-20 V DC adjustable voltage when given 10-24 V DC input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've built a SEPIC style converter before, for just this sort of thing:&#xA;&lt;a href=&quot;http://dren.dk/carpower.html&quot; rel=&quot;nofollow&quot;&gt;http://dren.dk/carpower.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-02-13T17:56:00.550" />
  <row Id="10113" PostTypeId="2" ParentId="10105" CreationDate="2011-02-13T19:39:34.473" Score="1" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;For learning, you are better off with the simulated spectrum analyzer in your simulation software.&lt;/li&gt;&#xA;&lt;li&gt;For use, they are more similar than they are different, so I would worry about what is cheap.&lt;/li&gt;&#xA;&lt;li&gt;Using one at school as @Nick T suggested is certainly cheaper than any one.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-13T19:39:34.473" />
  <row Id="10114" PostTypeId="2" ParentId="9808" CreationDate="2011-02-13T19:54:32.647" Score="0" ViewCount="" Body="&lt;p&gt;If the hardware is pushing a button, there must be wires at the other side of the button. Just take the button out and connect the wires from the input signal to the output(back of the button) with the required electronic logic. Then you can even get the millisecond timing.&lt;/p&gt;&#xA;" OwnerUserId="1927" LastActivityDate="2011-02-13T19:54:32.647" />
  <row Id="10115" PostTypeId="2" ParentId="10106" CreationDate="2011-02-13T20:23:33.777" Score="2" ViewCount="" Body="&lt;p&gt;To perfectly amplify a square wave, you'll need an op-amp with infinite bandwidth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the square wave used for?  You probably don't need to keep all of those harmonics.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-13T20:23:33.777" CommentCount="2" />
  <row Id="10116" PostTypeId="2" ParentId="7675" CreationDate="2011-02-13T21:57:16.310" Score="13" ViewCount="" Body="&lt;p&gt;I found a description of a similar arrangement on p. 333 of &lt;a href=&quot;http://books.google.com/books?id=WiXOAAAAMAAJ&amp;amp;dq=elevator%20control%20schematic&amp;amp;pg=PA333#v=onepage&amp;amp;q&amp;amp;f=false&quot; rel=&quot;nofollow&quot;&gt;Electric Journal, Volume 9&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The relays close in series to gradually accelerate the car and to come to a smooth stop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This truth table shows how each relay is closed as the car accelerates and decelerates up and down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is just for a simple elevator control that does &quot;up&quot;, &quot;down&quot; and &quot;stop&quot;.  Fancy modern elevators have pushbuttons for each floor, so there would be a more complex system, with relays operated by switches on each floor, and relays keeping themselves energized, a form of one-bit memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WonLt.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-13T21:57:16.310" />
  <row Id="10117" PostTypeId="2" ParentId="10105" CreationDate="2011-02-13T22:43:00.893" Score="2" ViewCount="" Body="&lt;p&gt;I use a spectrum analyser made from a &lt;a href=&quot;http://ossmann.blogspot.com/2010/03/16-pocket-spectrum-analyzer.html&quot; rel=&quot;nofollow&quot;&gt;kid's toy&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are £4.99 in my local toy shop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's been handy for determining the operating frequencies of wireless sensors.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-02-13T22:43:00.893" CommentCount="1" />
  <row Id="10118" PostTypeId="2" ParentId="10104" CreationDate="2011-02-14T02:31:30.043" Score="5" ViewCount="" Body="&lt;p&gt;See if there's a FIRST team at his high school. They're a great place to start learning about robotics and he'll get to actually make stuff. If not, something like a &lt;a href=&quot;http://www.amazon.com/LEGO-4544091-Mindstorms-NXT-2-0/dp/B001USHRYI/ref=cm_cr_pr_product_top&quot; rel=&quot;nofollow&quot;&gt;Lego NXT kit&lt;/a&gt; or Vex kit would be a good place to start. They've both got pretty easy methods of programming, and since they have pieces you put together, you don't need to worry about machining your own parts. That way he can concentrate on getting something actually working and driving around instead of designing electronics, fixing tough programming bugs, buying stock and milling parts.&lt;/p&gt;&#xA;" OwnerUserId="2993" LastEditorUserId="1433" LastEditorDisplayName="" LastEditDate="2011-02-14T15:33:27.333" LastActivityDate="2011-02-14T15:33:27.333" CommentCount="2" />
  <row Id="10119" PostTypeId="2" ParentId="10104" CreationDate="2011-02-14T03:56:35.057" Score="1" ViewCount="" Body="&lt;p&gt;The NXT is great - my 10 year-old son loves it.  If the Lego systems are too basic, I recommend the &lt;a href=&quot;http://www.robotshop.com/dfrobotshop-rover-tracked-robot-basic-kit.html&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; robot series.&lt;/p&gt;&#xA;" OwnerUserId="2632" LastActivityDate="2011-02-14T03:56:35.057" />
  <row Id="10120" PostTypeId="2" ParentId="10062" CreationDate="2011-02-14T04:35:34.160" Score="0" ViewCount="" Body="&lt;p&gt;If you're dead-set on DIPs, N/P-channel MOSFET arrays are fairly common, and they still put some of them into 8-DIP packages, e.g. the &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=785-1142-5-ND&quot; rel=&quot;nofollow&quot;&gt;Alpha &amp;amp; Omega Semi AOP609&lt;/a&gt; (or 605, 607, 610).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dropping the thru-hole requirement, it might be cheapest for a low-volume application to just use 4 discrete transistors, plus you have (for better or worse) full control over the specs (aka, you get to figure out which of the millions of MOSFETs to use).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MOSFETs are superior to BJTs in switching applications, as they have no fixed voltage drop (V&lt;sub&gt;ce(sat)&lt;/sub&gt;), just a relatively small R&lt;sub&gt;ds(on)&lt;/sub&gt;, which in low-voltage circuits, will provide much lower losses.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-14T04:41:22.520" LastActivityDate="2011-02-14T04:41:22.520" />
  <row Id="10121" PostTypeId="1" AcceptedAnswerId="10124" CreationDate="2011-02-14T05:21:25.510" Score="2" ViewCount="188" Body="&lt;p&gt;I am considering buying one of the hbridge drivers referenced in the below tutorial, but when I looked at the comments underneath the second hbridges sparkfun page, kickback diodes were referenced and how one of the drivers has internal diodes but the other doesn't. I will be working with motors no more than 8V and much less than 1 A of current. Which of these drivers should I use and should I use kickback diodes with it also?&lt;br&gt;&#xA;&lt;a href=&quot;http://itp.nyu.edu/physcomp/Labs/DCMotorControl&quot; rel=&quot;nofollow&quot;&gt;http://itp.nyu.edu/physcomp/Labs/DCMotorControl&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2873" LastEditorUserId="2873" LastEditorDisplayName="" LastEditDate="2011-02-14T05:57:42.113" LastActivityDate="2011-02-14T07:08:28.633" Title="Motor drivers and kickback diodes" Tags="&lt;arduino&gt;&lt;diode&gt;&lt;driver&gt;" AnswerCount="2" />
  <row Id="10122" PostTypeId="2" ParentId="10121" CreationDate="2011-02-14T06:11:35.987" Score="1" ViewCount="" Body="&lt;p&gt;Always use flyback diodes when driving inductive loads with a transistor. Look for those that can pass at least as much current as the max bridge current and are labeled &quot;flyback&quot; or &quot;fast recovery&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for which one, I leave to someone else...&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-02-14T06:11:35.987" />
  <row Id="10123" PostTypeId="1" CreationDate="2011-02-14T06:21:22.520" Score="3" ViewCount="160" Body="&lt;p&gt;I'm wondering whether anyone has any experience with the &lt;strong&gt;&lt;a href=&quot;http://www.sparkfun.com/products/10126&quot; rel=&quot;nofollow&quot;&gt;SM130 Mifare&lt;/a&gt;&lt;/strong&gt; module. I've managed to get my hands on one, sans antenna of course, and seem to be having a few issues with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got the module connected to an FTDI 5V USB to TTL converter via the UART lines. I've added capacitors over the power rails for good measure. I've got the SM130 module connected to a single wire, a home-brew PCB antenna and a whole 50m roll of thin hookup wire as an antenna. In all cases, I've used the &lt;em&gt;SMRFID&lt;/em&gt; software from &lt;em&gt;SonMicro&lt;/em&gt; directly, which identifies the device correctly and can enable the RF field and disable it just fine. I took out my SSB shortwave receiver and I can hear the field being energized and de-energized.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Here comes the problem:&lt;/em&gt;&lt;br&gt;I've ordered a fair amount of the Mifare transparent and ABS tags, however, when I select seek for tag, SMRFID always reports finding &lt;code&gt;TAG TYPE: 55 SERIAL: 2E31204D&lt;/code&gt;, despite there being no tag in the field. Even with a tag in the field, it refuses to find it and reports the same details. I've tried relocating the device and antenna somewhere else, thinking it's interference, but still it didn't help. I also tried toggling the reset pin a few times; still no change.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet says that it should return an &lt;code&gt;L&lt;/code&gt; representing &lt;em&gt;&quot;Seeking for tag&quot;&lt;/em&gt; right after a seek command and sit there until a tag enters the field. Instead, my module seems to be reporting an &lt;code&gt;L&lt;/code&gt;, then barely 10 seconds later, will report the same data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;At this point a short list of possibilities would be helpful; a total solution is not expected.&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="2998" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-06T00:30:12.503" LastActivityDate="2011-03-06T03:32:33.190" Title="RFID module always finds the same non-existent tag when seeking" Tags="&lt;rfid&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="10124" PostTypeId="2" ParentId="10121" CreationDate="2011-02-14T07:08:28.633" Score="4" ViewCount="" Body="&lt;p&gt;From the &lt;a href=&quot;http://www.sparkfun.com/products/315&quot; rel=&quot;nofollow&quot;&gt;comments @ sparkfun&lt;/a&gt; (Specifically &lt;a href=&quot;http://www.sparkfun.com/users/333&quot; rel=&quot;nofollow&quot;&gt;superbrad&lt;/a&gt;):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The L293D has internal flyback diodes, which catch what would otherwise be high voltage inductive noise (sometimes even in the kilovolts). With the SN754410, you must use external flyback diodes in your H-Bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even though you might feel like you can get away with it, it's a VERY bad idea to use the SN754410 without a flyback diode. It's not just the driver you have to worry about, it's your entire circuit (MCU, accelerometers, expensive XBee, etc.). Eventually, your luck will run out, even if you don't turn it on and off frequently.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-02-14T07:08:28.633" CommentCount="2" />
  <row Id="10125" PostTypeId="2" ParentId="5302" CreationDate="2011-02-14T09:17:30.600" Score="1" ViewCount="" Body="&lt;p&gt;Hackaday had a great write up for AVR programming, it has a lot of great info that could help you&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2010/11/19/avr-programming-04-writing-code-etc/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2010/11/19/avr-programming-04-writing-code-etc/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2010/11/05/avr-programming-03-reading-and-compiling-code/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2010/11/05/avr-programming-03-reading-and-compiling-code/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2010/10/25/avr-programming-02-the-hardware/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2010/10/25/avr-programming-02-the-hardware/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2010/10/23/avr-programming-introduction/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2010/10/23/avr-programming-introduction/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-14T09:17:30.600" />
  <row Id="10126" PostTypeId="2" ParentId="10101" CreationDate="2011-02-14T09:29:25.503" Score="6" ViewCount="" Body="&lt;p&gt;The 3V cell will suffice for the red, green and yellow leds, but not for the blue. Your supply voltage needs to be greater than the forward voltage of the diode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming you can use a larger supply voltage, I'd do:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/CoC6Q.png&quot; alt=&quot;3 pin Charlieplexing circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(taken from the image on &lt;a href=&quot;http://en.wikipedia.org/wiki/Charlieplexing&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Charlieplexing&lt;/a&gt; ) LED1 is the blue led and the others can be placed in any way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R2 is the current limit resistor for LED1, so should be set to about 120 ohms, assuming a supply voltage of 5V and a forward current of 15mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R=(Vsupply-Vforward)/Iforward&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current limit resistors for LED2 is R1+R2 and for LED3,4 is R2+R3. As the LED forward voltages are nominally the same, set R1=R3 and choose R2+R3 to set the current. R2+R3=180 gives a forward current of 16mA at 5V. This means R1=R3=60 ohm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With this circuit, if you set pin 1 low, pin 2 tri-state and pin 3 high, LED2 and LED4 will turn on dimly (again, if you're using a 5V supply). This may be desirable or something to avoid.&lt;/p&gt;&#xA;" OwnerUserId="2960" LastEditorUserId="2960" LastEditorDisplayName="" LastEditDate="2011-02-14T12:48:54.373" LastActivityDate="2011-02-14T12:48:54.373" />
  <row Id="10127" PostTypeId="2" ParentId="10062" CreationDate="2011-02-14T09:45:35.367" Score="2" ViewCount="" Body="&lt;p&gt;At 1.5A you want to be using MOSFETS,not darlingtons. Unfortunately the  best MOSFETS come in SMD packages, but you'll find through-hole parts that will dissipate almost nothing at 1.5A&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-14T09:45:35.367" CommentCount="1" />
  <row Id="10128" PostTypeId="1" CreationDate="2011-02-14T14:18:19.260" Score="0" ViewCount="273" Body="&lt;p&gt;I want to build a 8x8 LED RGB Matrix. I found a couple of projects by other people on the internet and I understand the way they created their stuff. The projects work, but there's always a little information missing - it's just a finished project, with no development detail that beginners could learn from (if you get what I'm saying).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So right now I want to develop my own PCB but I'm not sure how to set up the whole schematics right. Like for example how I have to wire things up. I don't want people telling me specific steps so I can copy and paste it from here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I'd rather like someone pointing me somewhere where I can get information on how to connect stuff x/y to z and what I should consider before doing x / y.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I already know which components I'm going to use, but as I said I'm not sure how to connect those and what stuff I might want to consider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example you have to know to use a resistor for led. or &quot;don't forget to connect all ground pins from the atmega&quot;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that most of this information can be gathered through datasheets, but I'm new to this so I'm not really in the know on how to read those in a right way and get information from it. I come from software so don't bash if my question sounds kinda silly to you.&lt;/p&gt;&#xA;" OwnerUserId="2995" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-12T10:36:33.690" LastActivityDate="2011-05-16T16:06:55.540" Title="Shift Register / LED Matrix / Atmega328" Tags="&lt;led&gt;&lt;atmega328&gt;&lt;shift-register&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="10129" PostTypeId="1" AcceptedAnswerId="10136" CreationDate="2011-02-14T15:28:46.527" Score="11" ViewCount="553" Body="&lt;p&gt;For the sake of not incorrectly connecting my power supply and damaging my board I'm going to ask a relatively dumb question. Is ground on my board the negative terminal on my battery? Explicitly Should I connect the ground to the negative terminal of the battery? Thanks,&lt;/p&gt;&#xA;" OwnerUserId="2617" LastEditorUserId="1633" LastEditorDisplayName="" LastEditDate="2011-02-15T16:35:19.630" LastActivityDate="2011-02-15T16:35:19.630" Title="When a battery is your power source, what is ground?" Tags="&lt;arduino&gt;&lt;power-supply&gt;&lt;battery&gt;&lt;ground&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="3" />
  <row Id="10130" PostTypeId="2" ParentId="10129" CreationDate="2011-02-14T15:33:36.337" Score="0" ViewCount="" Body="&lt;p&gt;I always used - terminal as ground and never had any problems with it, so I think that the answer is yes.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-14T15:33:36.337" />
  <row Id="10131" PostTypeId="1" CreationDate="2011-02-14T15:41:39.777" Score="6" ViewCount="131" Body="&lt;p&gt;I need to decide upon selecting Flash size and RAM for a project. The micro controller I prefer to use is TI MSP430 series. Because of its low power consumption and value line series cost. However I'm a complete newbie to deciding on requirements gathering. Most of my programming experience is on Desktop based systems where generally program size, RAM and processor speed isn't much of a concern for common algorithmic tasks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have the following questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Are there any guidelines or standard practices regarding deciding the RAM and Flash size for a micro controller?&lt;/li&gt;&#xA;&lt;li&gt;How many lines of code (C) translate to what amount of Flash size on the MCU?&lt;/li&gt;&#xA;&lt;li&gt;Is assembly language the only way out if the Flash size needs to kept at a minimum?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Regarding General selection of a Micro controller for a project, how do the professionals in this field go about on deciding the most appropriate micro controller for the task? What resources to they search? What guidelines to they follow?&lt;/p&gt;&#xA;" OwnerUserId="3001" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-14T15:55:55.247" LastActivityDate="2011-02-25T06:05:43.740" Title="Need help in choosing Flash size in a microcontroller" Tags="&lt;flash&gt;&lt;msp&gt;&lt;ram&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="10132" PostTypeId="2" ParentId="10128" CreationDate="2011-02-14T15:45:32.113" Score="0" ViewCount="" Body="&lt;p&gt;I would start with interfacing with the shift register &lt;a href=&quot;http://www.windmeadow.com/node/20&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;and &lt;a href=&quot;http://bildr.org/2011/02/74hc595/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; there are lots of tutorials on interfacing with that chip and then learn how to build an 8x8 led matrix &lt;a href=&quot;http://www.spikenzielabs.com/SpikenzieLabs/8x8.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; Hope this is a good start. Also you should get familiar with reading datasheets, it will be your best source for info for any component.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you starting with a avr programmer and a 328 or are you using an arduino or clone?&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-14T15:45:32.113" CommentCount="5" />
  <row Id="10133" PostTypeId="2" ParentId="10131" CreationDate="2011-02-14T15:53:27.557" Score="7" ViewCount="" Body="&lt;p&gt;The answers for all of your questions will depend of what you wanna do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you said, you are a newbie, so I suggest you use the biggest microcontroller and just try to do the project. After this you can visualize how much code you use and then scale it according to what was used.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-02-14T15:53:27.557" CommentCount="1" />
  <row Id="10134" PostTypeId="2" ParentId="10131" CreationDate="2011-02-14T15:53:55.507" Score="3" ViewCount="" Body="&lt;p&gt;The best way to determine flash/RAM requirements for your project is to build a prototype and measure it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Implement the core algorithms on a PC and calculate the size of object code and RAM usage. This will give you a ballpark figure to work with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget to add more to your budget if you're relying on operating system features such as stdio or memory management.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's no direct way to compare Lines of Code to compiled code size. But, you can compare processor architectures in terms of code density.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-02-14T15:53:55.507" />
  <row Id="10135" PostTypeId="2" ParentId="10131" CreationDate="2011-02-14T15:57:02.697" Score="2" ViewCount="" Body="&lt;p&gt;I think the best way to get a &quot;feeling&quot; of what are your requirements, in this case in terms of memory is to get some samples of an MCU, program it and see how many memory is being used. In fact, it will depend on the compiler used. If it's your first time programming a MCU, don't bother too much with specifications. Just select one with lots of memory, lots of peripherals, etc. That way you can learn a lot from just one MCU. When you make your first project with that MCU you will have a better notion of memory you need for further projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most appropriate MCU for a task? How many ADC channels do you need? What about DAC? What is more important in your application: performance or low power?&#xA;Is that kind of questions you have to answer when selecting a specific MCU.&lt;/p&gt;&#xA;" OwnerUserId="1074" LastActivityDate="2011-02-14T15:57:02.697" />
  <row Id="10136" PostTypeId="2" ParentId="10129" CreationDate="2011-02-14T16:01:52.117" Score="12" ViewCount="" Body="&lt;p&gt;Yes - just remember that your ground in that case will only be relative to the battery.  If you go to connect this to another device (serial interface, etc) you need to link the ground lines so they're a common ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So long as it is isolated, you're fine.&lt;/p&gt;&#xA;" OwnerUserId="3002" LastActivityDate="2011-02-14T16:01:52.117" CommentCount="3" />
  <row Id="10137" PostTypeId="2" ParentId="10131" CreationDate="2011-02-14T16:35:34.490" Score="2" ViewCount="" Body="&lt;p&gt;Choose a microcontroller that has the set of peripherals that you need.  There will probably be a family of micros that have the same/similar peripheral but different amounts of RAM and Flash.  Start with the chip with the largest RAM/Flash.  Once you have a working prototype, you can drop down to a cheaper micro if your program will fit.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-02-14T16:35:34.490" />
  <row Id="10138" PostTypeId="2" ParentId="10019" CreationDate="2011-02-14T16:42:05.950" Score="2" ViewCount="" Body="&lt;p&gt;Good money says it's a loose connector - connectors are the first place to look when nearly anything goes wrong with an electronic system (second is the power supply).  If a couple of pins have come loose things can certainly go south.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way to fix these things is to open up the case (read that as: Step 1 - void your warranty), identify the connector and give it a once over with a magnifying light to see if there are any cracked solder joints.  These are likely fixable with a soldering iron (if you can get everything suitably positioned and braced).  No recommendations from me on what solder or temperature to use exactly but you'll want thin solder, preferably lead-free I think and if your soldering iron supports it start with a low temperature and work your way up until it's easy to work with.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternately, if you have a heat gun or other hot-air rework you can aim it at the connector, heat it up a but and remove the heat to let all of the connections melt and reapply themselves.  I'm not sure if I would do that if it's entirely surface-mount though as it may float slightly off the pads if all of the connections get loose at once.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-14T16:42:05.950" />
  <row Id="10139" PostTypeId="1" CreationDate="2011-02-14T16:56:34.953" Score="0" ViewCount="91" Body="&lt;p&gt;I have a &lt;a href=&quot;http://www.display-elektronik.de/DEM16217SYH-PY.PDF&quot; rel=&quot;nofollow&quot;&gt;DEM 16217 SYH-PY&lt;/a&gt; 2x16 character LCD and I have problems initializing it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using AVR Studio 4. The 8 datalines are connected to port A of the microcontroller while the 3 control lines are connected to port E. Enable is PE2, R/W is PE1 and S is PE0. Port A connections are DBn to PORTAn. As far as I can see from the datasheet, no instructions seem to take more than 2 ms. For some reason, busy flag check isn't working correctly, so I used 2 ms delay instead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At first, I wanted to have an LED blink after each step, but it turned out to be much better to have output at a serial port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;avr/io.h&amp;gt;&#xA;#include&amp;lt;util/delay.h&amp;gt;&#xA;#include &quot;LED.h&quot;&#xA;#include &quot;Terminal.h&quot;&#xA;&#xA;void Screen_Execute(void)&#xA;{&#xA;    _delay_us(2);&#xA;    PORTE=PORTE | 4;&#xA;    _delay_us(2);&#xA;    PORTE=PORTE ^4;&#xA;    _delay_us(2);&#xA;    //_delay_us(2);&#xA;&#xA;}&#xA;&#xA;void Screen_busy(void)&#xA;{&#xA;    _delay_ms(2);&#xA;    //is the screen busy?   &#xA;    //PORTE=PORTE | 2;&#xA;    //DDRA=0x7F;&#xA;    //Screen_Execute();&#xA;    //while ((PINA &amp;amp; 128))&#xA;    //{&#xA;        //Screen_Execute();&#xA;        //BLINK_LED(500);&#xA;    //}// wait until zero&#xA;    //DDRA=0xFF;&#xA;    //PORTE=PORTE ^ 2;&#xA;    //Screen_Execute();&#xA;    //no longer busy&#xA;}&#xA;&#xA;&#xA;&#xA;&#xA;void Screen_init(void)&#xA;{&#xA;&#xA;    //BLINK_LED(1000);&#xA;    SEND_STRING(&quot;Starting initialization\r\n&quot;,0);&#xA;    DDRE=0xFF;&#xA;    PORTE=0x00;&#xA;    DDRA=0xFF;&#xA;    PORTA=0x30;&#xA;    _delay_ms(250);&#xA;    _delay_ms(1000);&#xA;    SEND_STRING(&quot;Step 1 executing.\r\n&quot;,0);&#xA;&#xA;    Screen_Execute();//voltage stabilized&#xA;    _delay_ms(5);//first output complete&#xA;    SEND_STRING(&quot;Step 1 complete.\r\n&quot;,0);&#xA;&#xA;&#xA;    //PORTA=0x30;&#xA;    //Screen_Execute();//second time&#xA;    //_delay_us(110);//end &#xA;&#xA;    //PORTA=0x30;//third time&#xA;    //Screen_Execute();&#xA;&#xA;    SEND_STRING(&quot;Step 2 start.\r\n&quot;,0);&#xA;    //BLINK_LED(1000);&#xA;    Screen_busy();&#xA;    PORTA=0x38;//two lines, 8 bits, 5*7 characters&#xA;    SEND_STRING(&quot;Step 2 execute.\r\n&quot;,0);&#xA;    Screen_Execute();&#xA;    SEND_STRING(&quot;Step 2 complete.\r\n&quot;,0);&#xA;&#xA;    SEND_STRING(&quot;Step 3 start.\r\n&quot;,0);&#xA;    //BLINK_LED(1000);&#xA;    Screen_busy();&#xA;    PORTA=0x08;//screen off&#xA;    SEND_STRING(&quot;Step 3 execute.\r\n&quot;,0);&#xA;    Screen_Execute();&#xA;    SEND_STRING(&quot;Step 3 complete.\r\n&quot;,0);&#xA;&#xA;&#xA;    SEND_STRING(&quot;Step 4 start.\r\n&quot;,0);&#xA;    //BLINK_LED(1000);&#xA;    Screen_busy();&#xA;    PORTA=0x14;//cursor goes to home and screen is cleared&#xA;    SEND_STRING(&quot;Step 4 execute.\r\n&quot;,0);&#xA;    Screen_Execute();&#xA;    SEND_STRING(&quot;Step 4 complete.\r\n&quot;,0);&#xA;&#xA;    //Screen_busy();&#xA;    //PORTA=0x04;//&#xA;    //Screen_Execute();//end of init&#xA;    //Screen_busy();&#xA;    SEND_STRING(&quot;Step 5 start.\r\n&quot;,0);&#xA;    //BLINK_LED(1000);&#xA;    PORTA=0x0F;&#xA;    Screen_Execute();//cursor blinks, screen works&#xA;    SEND_STRING(&quot;Step 5 execute.\r\n&quot;,0);&#xA;    Screen_busy();&#xA;    SEND_STRING(&quot;Step 5 complete.\r\n&quot;,0);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;My problem is that after initialization, cursor appears on a random position on the screen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I try to do initialization as described in the documentation, by sending the &lt;code&gt;PORTA=0x30;&lt;/code&gt; line 3 times, it doesn't work. Also, if I try to use tighter timing, it again doesn't work. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-14T17:08:00.000" LastActivityDate="2011-03-11T19:22:00.030" Title="Need help initializing display on ATmega162." Tags="&lt;avr&gt;&lt;lcd&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="10140" PostTypeId="5" CreationDate="2011-02-14T17:00:54.027" Score="0" ViewCount="" Body="&lt;p&gt;A Field-programmable Gate Array (FPGA) is an integrated circuit designed to be configured by the customer or designer after manufacturing—hence &quot;field-programmable&quot;. The FPGA configuration is generally specified using a hardware description language (HDL), similar to that used for an application-specific integrated circuit (ASIC) -Wikipedia&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-14T17:16:59.200" LastActivityDate="2011-02-14T17:16:59.200" />
  <row Id="10141" PostTypeId="4" CreationDate="2011-02-14T17:00:54.027" Score="0" ViewCount="" Body="A Field-programmable Gate Array (FPGA) is an chip that is configured by the customer after manufacturing—hence &quot;field-programmable&quot;. " OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-14T17:16:56.627" LastActivityDate="2011-02-14T17:16:56.627" />
  <row Id="10142" PostTypeId="1" AcceptedAnswerId="10144" CreationDate="2011-02-14T17:08:02.627" Score="1" ViewCount="86" Body="&lt;p&gt;The powerbrick for my computer emits a high pitched whine. What could be causing the noise? Any way I can stop or reduce it?  &lt;/p&gt;&#xA;" OwnerUserId="3006" LastActivityDate="2011-02-14T17:12:43.897" Title="Power brick with a high pitched whine" Tags="&lt;troubleshooting&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="10144" PostTypeId="2" ParentId="10142" CreationDate="2011-02-14T17:12:43.897" Score="4" ViewCount="" Body="&lt;p&gt;Switching power supplies use an inductor which can emit high-frequency noise. You can't do much about it, apart from replacing it. You could try disassembling the unit and injecting hot-melt glue into the inductor windings. That might dampen the vibration.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-14T17:12:43.897" CommentCount="2" />
  <row Id="10145" PostTypeId="2" ParentId="5302" CreationDate="2011-02-14T17:21:51.783" Score="0" ViewCount="" Body="&lt;p&gt;Something else to consider when dealing with a digital input from a mechanical switch is the contacts bouncing -- changing what should be a single button push into what looks like multiple pushes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For something like turning on an LED when the button is held down, you probably don't have to worry about debouncing. For something a little more complicated (like toggling the LED on the button press), debouncing is a must.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jack Ganssle has a good &lt;a href=&quot;http://www.ganssle.com/debouncing.htm&quot; rel=&quot;nofollow&quot;&gt;Guide to Debouncing&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="2699" LastActivityDate="2011-02-14T17:21:51.783" />
  <row Id="10146" PostTypeId="1" AcceptedAnswerId="11313" CreationDate="2011-02-14T17:56:34.503" Score="2" ViewCount="246" Body="&lt;p&gt;I'm using some QFN devices in a PCB I'm designing using the Eagle PCB software. The QFN packages have a centre pad that is grounded and intended to help with thermal dissipation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When creating the package, if I have the centre pad as an actual pad then I get DRC errors when I come to place vias on the pad to connect it through to the ground plane on the opposite side of the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another possibility would be to leave the centre pad off the package and draw it in on the board, but this is a pretty unsatisfactory solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the best way of dealing with this problem?&lt;/p&gt;&#xA;" OwnerUserId="2960" LastActivityDate="2011-03-11T08:47:11.827" Title="Vias on QFN centre pad in Eagle PCB" Tags="&lt;pcb&gt;&lt;eagle&gt;&lt;qfn&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="10147" PostTypeId="2" ParentId="10146" CreationDate="2011-02-14T17:58:46.353" Score="0" ViewCount="" Body="&lt;p&gt;Just put the vias in the pad and live with the DRC errors. With the Pulsonix software I use I can put vias in pads without DRC errors provided they are assigned to the same net. Perhaps you can do the same with Eagle. I can also create pads of any shape with one or more vias in them.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-14T19:08:30.630" LastActivityDate="2011-02-14T19:08:30.630" CommentCount="2" />
  <row Id="10148" PostTypeId="2" ParentId="10146" CreationDate="2011-02-14T18:15:47.663" Score="1" ViewCount="" Body="&lt;p&gt;When you create the package/schematic for the part assign the center pad to an extra pin on the schematic symbol and tie it to the proper signal (usually GND or occasionally VCC).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't want to confuse the schematic, in most design tools you can hide a pin and internally connect it to another pin.  So you'd just hide the pin for the center pad and tell it that its grouped with a GND pin or whatever signal it should be coupled to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doing that should allow you to pass DRC checks.  Some design tools would treat multiple VIAs as a signal loop and remove them, you may have to set flag for the particular signal to avoid that check.  I've had to do this with Altium in the past but i don't think Eagle does automatic loop removal so you can probably skip this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the center pad is for thermal management, you need to make sure your using enough vias to conduct the heat.  In that situation i usually include the required number/size of vias in the actual package design and only nudge them around in the final PCB layout if I really need to.  I don't recall off the top of my head if eagle allows exploding package footprints for editing on the PCB or not.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-02-14T18:15:47.663" CommentCount="2" />
  <row Id="10149" PostTypeId="1" AcceptedAnswerId="10151" CreationDate="2011-02-14T19:23:04.040" Score="8" ViewCount="190" Body="&lt;p&gt;My multimeter only has one 400mA fuse protecting the µA and mA range (and a 10A fuse protecting the amp range.) Is it possible to damage the microamp range by feeding milliamps through it? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-02-14T19:36:39.747" LastActivityDate="2011-02-14T20:05:17.490" Title="Can I burn out my multimeter's µA range by using a few mA of current?" Tags="&lt;current&gt;&lt;multimeter&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="10150" PostTypeId="1" CreationDate="2011-02-14T19:42:18.587" Score="3" ViewCount="90" Body="&lt;p&gt;I'm in the early stages of planning a MIDI-mapping component that I can plug into my Alesis DM-6 drum kit so I can ultimately play it through Rock Band 3. I know there are commercial options out there, but I'm intrigued about building one (at probably 5x the cost, no doubt :P).  Everything I've read about this talks about requiring an extra set of patch cables to plug into each drum which then plugs into the Arduino black-box. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, my question is this: Is there a specific reason the connector of choice for each drum (not to mention guitars, etc.) is the 1/4&quot; phono?  I could probably get away with a much smaller box if I can use 1/4&quot; on the drum-plug side, but the smaller 1/8&quot; (3.5mm) phono on the box-side. Am I losing anything by using 1/8&quot;(3.5mm) connectors going into my device? Other than being more 'durable' or maybe having a tighter-fit, are there electrical or noise/interference/impedance/other issues using the smaller connectors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="2928" LastActivityDate="2011-05-20T23:59:43.093" Title="Connector Choice for Arduino/MIDI Bridging Interface" Tags="&lt;audio&gt;&lt;connector&gt;&lt;midi&gt;" AnswerCount="2" />
  <row Id="10151" PostTypeId="2" ParentId="10149" CreationDate="2011-02-14T20:05:17.490" Score="13" ViewCount="" Body="&lt;p&gt;Multimeters use a precision shunt resistor to measure current indirectly (known R, measure V, calculate I). Typically a low current range (uA to low mA) will have a larger resistance shunt resistor to generate a larger voltage drop. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a result, this larger resistance is no longer negligible at higher currents and begins to cause a measurable voltage drop. Additionally, the power dissipation can begin to cause resistance change and eventually it will kill the resistor. Typically, a fast-blow fuse protects the shunt resistor from continuous over-current. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're wondering if running 10mA through the meter while in uA mode will damage it, the answer is most likely &quot;no&quot;. If you run 300+ mA through the meter, then you will probably be in danger of blowing the fuse. If you try to use the meter as a volt-meter and forget to switch the leads, and connect it to a supply capable of dumping a lot of instantaneous power, you might be able to blow the shunt resistor before the fuse blows.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-02-14T20:05:17.490" />
  <row Id="10152" PostTypeId="1" CreationDate="2011-02-14T20:34:22.880" Score="3" ViewCount="90" Body="&lt;p&gt;I'm looking for a multiconductor cable with 30-40 conductors, optimized for flexibility and small outer diameter. Unlike say, Litz wire, most wires will carry an independent (microvolt) signal. The application is to transmit data from a tethered, mobile data acquisition device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The multiconductor products carried by the major electronics suppliers tend to be larger diameter; for instance, while &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=MB36S-25-ND&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; one is not bad at 7.4 mm OD for 36 conductors, I'd like something smaller still. For this cable, the individual conductors are 28 AWG, but I'd be happy for them to be 30 or smaller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where might I find such a thing?&lt;/p&gt;&#xA;" OwnerUserId="2796" LastActivityDate="2011-05-05T00:31:12.217" Title="High-density, light multiconductor cable: sources/suppliers/manufacturers?" Tags="&lt;cable-assemblies&gt;&lt;cables&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="10153" PostTypeId="1" AcceptedAnswerId="10155" CreationDate="2011-02-14T20:38:25.947" Score="1" ViewCount="144" Body="&lt;p&gt;I have a decent (equivalent of introductory college level) with circuit design, all on breadboards, as well as programming on a variety of microprocessors and a couple FPGAs. I'm just wondering where would be a good place to go on from here in more advanced and higher level circuit designs, but I'm not sure if I'm at the point where I should make the jump to PCB layouts, or is there an intermediate step that's recommended? I was highly considering making something like Arduino on pcb.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also never actually used a soldering gun, and that's something I know I should learn, but I'm not sure really what kind of devices are good to learn that on, and circuits to do stuff like that.&lt;/p&gt;&#xA;" OwnerUserId="3012" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-18T02:29:12.780" LastActivityDate="2011-02-18T02:29:12.780" Title="I've done breadboards and programming, where is a good place to move on?" Tags="&lt;arduino&gt;&lt;soldering&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="10154" PostTypeId="2" ParentId="10152" CreationDate="2011-02-14T20:40:52.923" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.trinitycablesint.co.uk/telephone-cables.asp&quot; rel=&quot;nofollow&quot;&gt;How about this stuff&lt;/a&gt;... used for connecting telecoms patching frames:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/yQEiX.jpg&quot; alt=&quot;100 core cable&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Available with up to 100 cores from &lt;a href=&quot;http://www.trinitycablesint.co.uk&quot; rel=&quot;nofollow&quot;&gt;www.trinitycablesint.co.uk&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-14T20:40:52.923" CommentCount="3" />
  <row Id="10155" PostTypeId="2" ParentId="10153" CreationDate="2011-02-14T20:53:46.877" Score="4" ViewCount="" Body="&lt;p&gt;Try transferring the circuits you have been working on to stripboard. That will also get you soldering components. Don't get a soldering gun, BTW, get a temperature-controlled soldering station with suitable tips.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-14T20:53:46.877" CommentCount="2" />
  <row Id="10156" PostTypeId="2" ParentId="10153" CreationDate="2011-02-14T21:01:07.447" Score="2" ViewCount="" Body="&lt;p&gt;A great way to learn how to solder is to buy a few electronic project kits (&lt;a href=&quot;http://www.quasarelectronics.com/&quot; rel=&quot;nofollow&quot;&gt;Quasar Electronics&lt;/a&gt; is a great site), and solder these together. You can also find some good &lt;a href=&quot;http://www.epemag.wimborne.co.uk/solderfaq.htm&quot; rel=&quot;nofollow&quot;&gt;soldering tutorials&lt;/a&gt; on the internet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good intermediate step up from breadboards to PCBs is to use &lt;a href=&quot;http://www.maplin.co.uk/components/pcb/stripboard&quot; rel=&quot;nofollow&quot;&gt;stripboard&lt;/a&gt; which is a board pre-drilled with a grid of holes and strips of copper you can solder to.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-14T21:01:07.447" />
  <row Id="10157" PostTypeId="1" AcceptedAnswerId="10198" CreationDate="2011-02-14T21:01:28.990" Score="0" ViewCount="431" Body="&lt;p&gt;I have a &lt;a href=&quot;http://www.hitpoint.com.tw/main.php?product=acoustic&amp;amp;db=ac_pb&amp;amp;type=dc&amp;amp;id=10&quot; rel=&quot;nofollow&quot;&gt;PB-12N23PW-05Q&lt;/a&gt; buzzer and I'm trying to use it with ATmega 162. I can't connect it directly to pin, because from what I've read from 162's datasheet, it can source at most 20 mA. The buzzer takes 50 (or around 25, if we take a look at the graph), so I don't think I can just directly connect it to the microcontroller. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My initial idea was to connect it to a transistor and use the transistor as a switch.  Unfortunately, it didn't work. I used BD237 and my idea was that the microcontroler will pull the pin connected to the base high and the transistor will operate the buzzer. In my setup, I had buzzer connected to Vcc, buzzer's negative port connected to collector, GND connected to the emitter and 162 connected to the base. Transistor is of NPN type. Somewhere I read that this way some problems related to the voltage drop on the transistor can be mitigated, but to me it looks like the voltage drop is the main problem here. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the schematic. The mc is used instead of switch on the real thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/etLrO.png&quot; alt=&quot;buzzer circuit schematic&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right now, I'm looking for other ideas on how to connect the buzzer. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-15T22:54:35.583" LastActivityDate="2011-02-15T22:54:35.583" Title="Control 5 V buzzer using 5 V microcontroller (which can't drive it directly) and a single 5 V power supply?" Tags="&lt;avr&gt;&lt;speakers&gt;" AnswerCount="2" CommentCount="11" />
  <row Id="10158" PostTypeId="1" AcceptedAnswerId="10183" CreationDate="2011-02-14T21:17:22.910" Score="4" ViewCount="112" Body="&lt;p&gt;I am planning on a &lt;strong&gt;1 cubic inch robot&lt;/strong&gt; as my next project in robotics and the biggest challenge I am facing is on the battery. Lithium polymer seems to be the best option in terms of weight and the required current output and rechargeable!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The requirement in circuit is around 400mA with 3.5V, After searching a lot in Internet I could best get to this &lt;a href=&quot;http://www.all-battery.com/polymerli-ionbattery37v240mah602025.aspx&quot; rel=&quot;nofollow&quot;&gt;battery&lt;/a&gt; which fits my dimension and voltage requirements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But its still low on current so I plan on using them in parallel. I read that Li-ion and Lipo batteries are very sensitive and might damage the battery or cause fire if used incorrectly So I need some help on this!&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Can I use them in parallel ? Is that the right and safe thing to do ?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If I use them in parallel then can I charge them to in parallel ? or do I need some special balancer circuit ?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Can somebody help me with a decent charger circuit for this cell ?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Anybody knows a better battery than this one that I can use in my application?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Any other points/suggestions that will help me on this project that I missed out ?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2011-02-15T16:20:01.683" Title="Need help with LiPO batteries" Tags="&lt;batteries&gt;&lt;lipo&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="10159" PostTypeId="2" ParentId="10153" CreationDate="2011-02-14T22:31:42.237" Score="1" ViewCount="" Body="&lt;p&gt;Another way to learn how to solder it to disassemble old electronic devices. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could try to desolder everything on an old radio or DVD player or something similar. This way, you'll be able to see for yourself how different devices behave when being soldered and what kinds of damage they can take. Also, you may be able to get some broken devices for free, if you're lucky. Plus, you'll get a supply of various components which may or may not be useful.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-14T22:31:42.237" CommentCount="1" />
  <row Id="10160" PostTypeId="2" ParentId="10157" CreationDate="2011-02-14T22:46:32.473" Score="0" ViewCount="" Body="&lt;p&gt;Looks like it was my fault in the end. I was poking the wrong pin of the microcontroller. It seems to be working now, but I get a high pitched sound very different from the one I get when the buzzer is directly connected. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-14T22:46:32.473" CommentCount="2" />
  <row Id="10161" PostTypeId="5" CreationDate="2011-02-14T22:58:53.177" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-14T22:58:53.177" LastActivityDate="2011-02-14T22:58:53.177" />
  <row Id="10162" PostTypeId="4" CreationDate="2011-02-14T22:58:53.177" Score="0" ViewCount="" Body="Verilog is a hardware description language (HDL) used to model electronic systems. It is most commonly used in the design, verification, and implementation of digital logic chips." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T02:36:42.420" LastActivityDate="2011-02-15T02:36:42.420" />
  <row Id="10163" PostTypeId="5" CreationDate="2011-02-14T22:59:15.223" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-14T22:59:15.223" LastActivityDate="2011-02-14T22:59:15.223" />
  <row Id="10164" PostTypeId="4" CreationDate="2011-02-14T22:59:15.223" Score="0" ViewCount="" Body="VHDL (VHSIC hardware description language) is a hardware description language used in electronic design automation to describe digital systems such as field-programmable gate arrays and integrated circuits." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T02:38:05.163" LastActivityDate="2011-02-15T02:38:05.163" />
  <row Id="10165" PostTypeId="5" CreationDate="2011-02-14T22:59:43.490" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-14T22:59:43.490" LastActivityDate="2011-02-14T22:59:43.490" />
  <row Id="10166" PostTypeId="4" CreationDate="2011-02-14T22:59:43.490" Score="0" ViewCount="" Body="DxDesigner is a schematic capture package from Mentor Graphics." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T02:36:46.180" LastActivityDate="2011-02-15T02:36:46.180" />
  <row Id="10167" PostTypeId="5" CreationDate="2011-02-14T23:00:20.793" Score="0" ViewCount="" Body="&lt;p&gt;Logic analyzers often include extra features like triggers and signal/protocol analyzers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A trigger will make the analyzer wait with capture until a certain condition is met, typically a rising or falling edge. More advanced logic analyzers often has more advanced trigger configurations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A signal/protocol analyzer will look at one or more signals at a time and display their values. Many logic analyzers have support for asynchronous serial lines, I2C and SPI while the more advanced ones have support for more protocols.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For more information see &lt;a href=&quot;http://en.wikipedia.org/wiki/Logic_analyzer&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-03-21T13:44:41.977" LastActivityDate="2011-03-21T13:44:41.977" />
  <row Id="10168" PostTypeId="4" CreationDate="2011-02-14T23:00:20.793" Score="0" ViewCount="" Body="A logic analyzer is an electronic instrument which displays a set of digital signal across time. It is similar to an oscilloscope which displays analog signals across time.&#xD;&#xA;" OwnerUserId="-1" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-03-21T13:44:35.263" LastActivityDate="2011-03-21T13:44:35.263" />
  <row Id="10169" PostTypeId="5" CreationDate="2011-02-14T23:01:39.700" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-14T23:01:39.700" LastActivityDate="2011-02-14T23:01:39.700" />
  <row Id="10170" PostTypeId="4" CreationDate="2011-02-14T23:01:39.700" Score="0" ViewCount="" Body="A voltage regulator is an analog circuit that produces a stable output voltage that doesn't vary with load current changes." OwnerUserId="-1" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-17T20:39:42.457" LastActivityDate="2011-04-17T20:39:42.457" />
  <row Id="10171" PostTypeId="5" CreationDate="2011-02-14T23:02:02.710" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-14T23:02:02.710" LastActivityDate="2011-02-14T23:02:02.710" />
  <row Id="10172" PostTypeId="4" CreationDate="2011-02-14T23:02:02.710" Score="0" ViewCount="" Body="A relay is an electronic switch." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T02:37:09.440" LastActivityDate="2011-02-15T02:37:09.440" />
  <row Id="10173" PostTypeId="5" CreationDate="2011-02-14T23:02:42.227" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-14T23:02:42.227" LastActivityDate="2011-02-14T23:02:42.227" />
  <row Id="10174" PostTypeId="4" CreationDate="2011-02-14T23:02:42.227" Score="0" ViewCount="" Body="I²C (Inter-Integrated Circuit) is a multi-master serial single-ended computer bus invented by Philips that is used to attach low-speed peripherals to a motherboard, embedded system, or cellphone. -Wikipedia" OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T02:37:16.227" LastActivityDate="2011-02-15T02:37:16.227" />
  <row Id="10175" PostTypeId="5" CreationDate="2011-02-14T23:03:40.527" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Schematic Symbol:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/79R73.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-04T16:22:16.400" LastActivityDate="2011-03-04T16:22:16.400" />
  <row Id="10176" PostTypeId="4" CreationDate="2011-02-14T23:03:40.527" Score="0" ViewCount="" Body="A LED is a light emitting diode.  Most small lights you see on electronics are LEDs." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T02:37:22.620" LastActivityDate="2011-02-15T02:37:22.620" />
  <row Id="10177" PostTypeId="5" CreationDate="2011-02-14T23:04:50.433" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-14T23:04:50.433" LastActivityDate="2011-02-14T23:04:50.433" />
  <row Id="10178" PostTypeId="4" CreationDate="2011-02-14T23:04:50.433" Score="0" ViewCount="" Body="From the main Stack Overflow site &quot;Homework help Questions regarding homework assignments are more than welcome, provided that they: Briefly explain the problem you are trying to solve -- do not post your entire assignment verbatim. Explain what you tried and where you're stuck (preferably with code examples) Don't ask for 'complete' solutions to the problem -- we're not here to do your homework for you.&quot;" OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T02:37:49.673" LastActivityDate="2011-02-15T02:37:49.673" />
  <row Id="10179" PostTypeId="5" CreationDate="2011-02-14T23:26:14.933" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-14T23:26:14.933" LastActivityDate="2011-02-14T23:26:14.933" />
  <row Id="10180" PostTypeId="4" CreationDate="2011-02-14T23:26:14.933" Score="0" ViewCount="" Body="A diode is a device that allows current flow in one direction." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T02:37:38.127" LastActivityDate="2011-02-15T02:37:38.127" />
  <row Id="10181" PostTypeId="5" CreationDate="2011-02-14T23:27:14.713" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-14T23:27:14.713" LastActivityDate="2011-02-14T23:27:14.713" />
  <row Id="10182" PostTypeId="4" CreationDate="2011-02-14T23:27:14.713" Score="0" ViewCount="" Body="JTAG is an interface that allows 1) testing of inter-chip connections 2) programming of Flash, microcontroller and FPGA devices." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T02:37:58.673" LastActivityDate="2011-02-15T02:37:58.673" />
  <row Id="10183" PostTypeId="2" ParentId="10158" CreationDate="2011-02-14T23:30:27.850" Score="1" ViewCount="" Body="&lt;p&gt;We have used LiPo in parallel successfully. Parallel cells must have the same batch #.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When charging, use a voltage regulated source set to (slightly less than) the 4.2 volt cell charging voltage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Look at a DC-DC converter with a current limit at 1C (240mA)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you need a modular DC-DC converter for rated at 400mA, at 4.2V.&#xA;The upright-PCB ones are available from RS etc...&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-02-14T23:30:27.850" CommentCount="2" />
  <row Id="10184" PostTypeId="2" ParentId="10129" CreationDate="2011-02-14T23:31:46.023" Score="3" ViewCount="" Body="&lt;p&gt;The ground pin on the microcontroller is two things: (1) a voltage reference, and (2) a current return.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage Reference: Voltages don't really exist at single points, voltages are differences &lt;em&gt;between&lt;/em&gt; points. This means that to speak sensibly about some single point in a circuit being at a given voltage, it has to be relative to some other point in the circuit. The common convention is to pick one node in the circuit and call it 'ground', and then all voltages are specified relative to that. With a microcontroller, the ground pin is the reference against which the inputs are 'measured' to determine whether they are high or low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current Return: All the current that flows into a micro-controller has to flow back out again somewhere. You're certainly aware that current flows into the +5V pin. Note that some current will flow out various pins as signal outputs, but then some outputs will actually admit current &lt;em&gt;into&lt;/em&gt; the chip. Input pins can also source or sink current. Regardless, whatever current is left over is expected to flow out the ground pin of the micro-controller. In essence, the supply current is &lt;em&gt;returned&lt;/em&gt; to the supply through the ground connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So when your power supply is a battery, it makes perfect sense to connect the (-) side of the battery to your system's ground pin. Notice that this isn't just a voltage reference though; it is also the supply return. In practical terms, what this means that the wire you use to connect (-) to the board's ground should be at the same size as the wire you use to connect (+) to the board's power input.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-14T23:31:46.023" />
  <row Id="10185" PostTypeId="1" AcceptedAnswerId="10360" CreationDate="2011-02-15T01:00:12.603" Score="3" ViewCount="94" Body="&lt;p&gt;I don't see any reference in the &lt;a href=&quot;http://eda.org/pub/ibis/ver5.0/ver5_0.pdf&quot; rel=&quot;nofollow&quot;&gt;specification&lt;/a&gt; that says so, but then I don't see anything that says otherwise.  Other sections do talk about uniqueness, so I'm guessing they don't need to be unique.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: 2/18/11: I'm using Mentor's HyperLynx simulation software.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-18T18:42:15.310" LastActivityDate="2011-02-18T18:42:15.310" Title="Do IBIS signal names need to be unique?" Tags="&lt;ibis&gt;&lt;hyperlynx&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10186" PostTypeId="5" CreationDate="2011-02-15T01:00:47.920" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T01:00:47.920" LastActivityDate="2011-02-15T01:00:47.920" />
  <row Id="10187" PostTypeId="4" CreationDate="2011-02-15T01:00:47.920" Score="0" ViewCount="" Body="IBIS (Input Output Buffer Information Specification) is a method of providing information about the input/output buffers of an integrated circuit to the outside world. -Wikipedia" OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T02:37:33.167" LastActivityDate="2011-02-15T02:37:33.167" />
  <row Id="10188" PostTypeId="2" ParentId="10153" CreationDate="2011-02-15T02:16:56.017" Score="1" ViewCount="" Body="&lt;p&gt;Before you begin designing PCB's, you may want to familiarize yourself with a circuit simulation program such as PSPICE.  I would recommend getting PSPICE version 8 (student edition), which you can easily find for free. It's older, but it has an easier-to-learn interface and does everything. From there, you can design a circuit, and then run simulations on it to ensure proper functionality. There are tons of PSPICE tutorials out there and it is commonly used in college electronics courses. Once you've designed a circuit in PSPICE, it can be exported to a PCB layout program.&lt;/p&gt;&#xA;" OwnerUserId="2895" LastActivityDate="2011-02-15T02:16:56.017" CommentCount="1" />
  <row Id="10189" PostTypeId="1" CreationDate="2011-02-15T04:13:54.633" Score="3" ViewCount="175" Body="&lt;p&gt;In a motor where both the field and armature are wound there are at least two possible control scenarios. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The field winding can be excited with constant current and the armature voltage controlled, this is similar to a common permanent magnet DC motor. There is back EMF generated at the armature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, the armature can be excited with constant current and the field winding controlled. Apparently this configuration allows the torque on the motor to be controlled with a small amount of power at the field winding (and high current at the armature) why does this contrast with the original scenario? Finally, is there any back EMF in the field winding?&lt;/p&gt;&#xA;" OwnerUserId="2656" LastActivityDate="2011-05-17T19:44:12.003" Title="DC motor Armature and Field back emf" Tags="&lt;motor&gt;&lt;dc-motor&gt;&lt;electromagnetism&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="10190" PostTypeId="1" AcceptedAnswerId="10220" CreationDate="2011-02-15T04:46:02.233" Score="1" ViewCount="106" Body="&lt;p&gt;My next robotics project is a &quot;1 cubic inch robot&quot; and I am planning to add a 2 way wireless communication between my robot and a computer. Since for that size Power is a big bottleneck the best I could come up is a IR transceiver. So how can I achieve this ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I use a 38khz receiver then I might end up receiving the same transmit signal ? what Is the best option I can use in my application ??&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2011-02-15T18:17:44.707" Title="2 Way IR communication for my robot." Tags="&lt;wireless&gt;&lt;ir&gt;" AnswerCount="3" />
  <row Id="10191" PostTypeId="2" ParentId="10190" CreationDate="2011-02-15T05:52:57.183" Score="2" ViewCount="" Body="&lt;p&gt;I would disable receiver while transmitting and would implement guaranteed packet delivery - when you are not receiving confirmation with correct crc packet is resent.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-15T05:52:57.183" />
  <row Id="10192" PostTypeId="2" ParentId="1770" CreationDate="2011-02-15T05:56:03.063" Score="1" ViewCount="" Body="&lt;p&gt;You might find some of these articles &lt;a href=&quot;http://tronixstuff.com/tutorials&quot; rel=&quot;nofollow&quot;&gt;interesting&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2011-02-15T05:56:03.063" CommunityOwnedDate="2011-02-17T03:28:35.710" />
  <row Id="10194" PostTypeId="1" CreationDate="2011-02-15T06:10:42.793" Score="4" ViewCount="162" Body="&lt;p&gt;What would it take for me to build something similar to the mockup below?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/t4aby.png&quot; alt=&quot;MIDI Controller Mockup&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3385" LastActivityDate="2011-02-23T18:43:11.737" Title="DIY MIDI knob Controller" Tags="&lt;midi&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="10195" PostTypeId="2" ParentId="10194" CreationDate="2011-02-15T08:19:17.343" Score="4" ViewCount="" Body="&lt;p&gt;Well, not much, really, the biggest problem is making it look nice, if you can handle that, then the electronics and the firmware ought to be relatively easy to handle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd use a small 8bit AVR with a bunch of analog inputs, like an ATmega168, but that's pretty arbitrary and based on what I have in my parts drawer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use one of the new AVRs with built in USB, but as MIDI is so low bandwidth, you should be able to get away with using V-USB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This project looks like a good place to start research:&#xA;&lt;a href=&quot;http://cryptomys.de/horo/V-USB-MIDI/index.html&quot; rel=&quot;nofollow&quot;&gt;http://cryptomys.de/horo/V-USB-MIDI/index.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-02-15T08:19:17.343" CommentCount="1" />
  <row Id="10196" PostTypeId="2" ParentId="10190" CreationDate="2011-02-15T14:27:09.720" Score="0" ViewCount="" Body="&lt;p&gt;You can use a baffle - It's just a piece of something opaque between your receiver and transmitter that should prevent it from be inadvertently picked up.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-15T14:27:09.720" />
  <row Id="10197" PostTypeId="2" ParentId="10129" CreationDate="2011-02-15T15:08:55.963" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;The potential is relative. Ground is an arbitrary designation.&#xA;  &lt;em&gt;—Fake Name&lt;/em&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This is something I worked out recently, only then realising why the &lt;a href=&quot;http://en.wikipedia.org/wiki/Hydraulic_analogy&quot; rel=&quot;nofollow&quot;&gt;hydraulic analogy&lt;/a&gt; was causing me cognitive dissonance. If a &quot;voltage supply&quot; was a waterfall, the image of a 12m top-to-bottom waterfall stuck in the middle of the sky, somewhere above my 5m waterfall which started 5m above the &quot;ground&quot; just didn't make any sense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And then I tied the -ve pin on my Arduino (powered by a 12V wall wart) to the drain on the transistors I was using to switch current to my LED strips and the circuit worked.&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2011-02-15T15:08:55.963" />
  <row Id="10198" PostTypeId="2" ParentId="10157" CreationDate="2011-02-15T15:44:29.680" Score="3" ViewCount="" Body="&lt;p&gt;Thank you for posting and linking to exactly which sound-maker you are trying to use: the &lt;a href=&quot;http://www.hitpoint.com.tw/main.php?product=acoustic&amp;amp;db=ac_pb&amp;amp;type=dc&amp;amp;id=10&quot; rel=&quot;nofollow&quot;&gt;PB-12N23PW-05Q&lt;/a&gt; self-oscillating buzzer.&#xA;(If you had a raw piezo disk, or a coil speaker, we would use a different drive circuit).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you insist on using a NPN such as the BD237, you need to add a external resistor between the MCU and the base of the NPN, as joeforker mentioned: 1 KOhm should be adequate.&#xA;But no matter what resistor or silicon NPN transistor you use, you will end up with (at best) a V_ce_sat voltage drop of around 0.6 V, so the voltage across the buzzer is about 4.4 V -- which is technically outside the &quot;guaranteed-to-work&quot; &quot;4.5 to 5.5 V&quot; operating range in the buzzer datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I were you, I would probably throw out the NPN and replace it with a MOSFET.&#xA;A cheap 2N7000 has an on-resistance of 5 Ohm; at 25 mA that gives a voltage drop of .125 V.&#xA;(More expensive MOSFETs have an order of magnitude less (better) on-resistance).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The MOSFET should work in the circuit you posted -- it doesn't need a resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am surprised that you are getting a different sound.&#xA;The kinds of mistakes I am likely to make (and so the first things I would check) are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Did I put the buzzer in upside down?&#xA;(This doesn't matter much for a raw piezo disk, but it does matter in a self-oscillating buzzer like yours).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Hook the buzzer up to a bench power supply, and see what it sounds like in the 4 V to 5 V voltage range. Perhaps it's supposed to sound like that at that (5V - transistor drop) voltage?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;What is the actual voltage across the buzzer and across the transistor?&#xA;I might check this with an O'scope, since it's quite possible that we have an &lt;em&gt;average&lt;/em&gt; current of 25 mA, as shown on the graph, but peak pulses of much higher current -- perhaps such a high instantaneous current that your so-called &quot;5 V&quot; power supply is briefly pulled down to such a low voltage that your ATmega resets.&#xA;If that is the case, you'll need to add some bypass capacitors and perhaps a ferrite bead or resistor.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-15T15:44:29.680" CommentCount="6" />
  <row Id="10199" PostTypeId="2" ParentId="10158" CreationDate="2011-02-15T16:20:01.683" Score="1" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;you can use it in parallel, and this does make things more complex. And depending on how long your robot is supposed to run for will decide if its right or wrong for your application&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;you can charge them in parallel but you will need a 2 cell charging circuit &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I wish i could help you with this circuit but, but thats over my head&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;here is one from spark fun 1000mAh - &lt;a href=&quot;http://www.sparkfun.com/products/339&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt; this one has the protection included, other places to look would be place that sell micro heli replacement parts &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-15T16:20:01.683" />
  <row Id="10200" PostTypeId="5" CreationDate="2011-02-15T16:27:57.177" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T16:27:57.177" LastActivityDate="2011-02-15T16:27:57.177" />
  <row Id="10201" PostTypeId="4" CreationDate="2011-02-15T16:27:57.177" Score="0" ViewCount="" Body="Eagle is a low-cost PCB design software package." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T16:45:44.190" LastActivityDate="2011-02-15T16:45:44.190" />
  <row Id="10202" PostTypeId="5" CreationDate="2011-02-15T16:28:20.450" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T16:28:20.450" LastActivityDate="2011-02-15T16:28:20.450" />
  <row Id="10203" PostTypeId="4" CreationDate="2011-02-15T16:28:20.450" Score="0" ViewCount="" Body="The MSP430 is a Texas Instruments low-power microcontroller." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T16:45:47.997" LastActivityDate="2011-02-15T16:45:47.997" />
  <row Id="10204" PostTypeId="5" CreationDate="2011-02-15T16:28:45.833" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T16:28:45.833" LastActivityDate="2011-02-15T16:28:45.833" />
  <row Id="10205" PostTypeId="4" CreationDate="2011-02-15T16:28:45.833" Score="0" ViewCount="" Body="RS-232 is the electrical standard used on most serial ports." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T16:45:52.847" LastActivityDate="2011-02-15T16:45:52.847" />
  <row Id="10206" PostTypeId="5" CreationDate="2011-02-15T16:29:12.463" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T16:29:12.463" LastActivityDate="2011-02-15T16:29:12.463" />
  <row Id="10207" PostTypeId="4" CreationDate="2011-02-15T16:29:12.463" Score="0" ViewCount="" Body="Pulse-width modulation, is a very efficient way of providing intermediate amounts of electrical power between fully on and fully off. -Wikipedia" OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T16:46:07.060" LastActivityDate="2011-02-15T16:46:07.060" />
  <row Id="10208" PostTypeId="5" CreationDate="2011-02-15T16:51:05.977" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T16:51:05.977" LastActivityDate="2011-02-15T16:51:05.977" />
  <row Id="10209" PostTypeId="4" CreationDate="2011-02-15T16:51:05.977" Score="0" ViewCount="" Body="System Generator is a Xilinx tool for developing DSP chips." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T17:08:51.700" LastActivityDate="2011-02-15T17:08:51.700" />
  <row Id="10210" PostTypeId="5" CreationDate="2011-02-15T16:51:52.090" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T16:51:52.090" LastActivityDate="2011-02-15T16:51:52.090" />
  <row Id="10211" PostTypeId="4" CreationDate="2011-02-15T16:51:52.090" Score="0" ViewCount="" Body="An IC or Integrated Circuit is a chip.  As opposed to a passive part such as resistor or individual transistor." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T17:08:53.773" LastActivityDate="2011-02-15T17:08:53.773" />
  <row Id="10212" PostTypeId="5" CreationDate="2011-02-15T16:52:49.703" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T16:52:49.703" LastActivityDate="2011-02-15T16:52:49.703" />
  <row Id="10213" PostTypeId="4" CreationDate="2011-02-15T16:52:49.703" Score="0" ViewCount="" Body="A Liquid Crystal Display (LCD) is the type of display used in modern flat montors, for example." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T17:08:55.007" LastActivityDate="2011-02-15T17:08:55.007" />
  <row Id="10214" PostTypeId="5" CreationDate="2011-02-15T16:53:06.660" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T16:53:06.660" LastActivityDate="2011-02-15T16:53:06.660" />
  <row Id="10215" PostTypeId="4" CreationDate="2011-02-15T16:53:06.660" Score="0" ViewCount="" Body="PIC is a brand of 8, 16, and 32 bit RISC microcontrollers manufactured by the company Microchip." OwnerUserId="-1" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-05-12T15:56:49.460" LastActivityDate="2011-05-12T15:56:49.460" />
  <row Id="10216" PostTypeId="5" CreationDate="2011-02-15T16:53:27.580" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T16:53:27.580" LastActivityDate="2011-02-15T16:53:27.580" />
  <row Id="10217" PostTypeId="4" CreationDate="2011-02-15T16:53:27.580" Score="0" ViewCount="" Body="AVR is a series of microcontrollers from Atmel." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T17:08:57.970" LastActivityDate="2011-02-15T17:08:57.970" />
  <row Id="10218" PostTypeId="5" CreationDate="2011-02-15T16:54:06.003" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-15T16:54:06.003" LastActivityDate="2011-02-15T16:54:06.003" />
  <row Id="10219" PostTypeId="4" CreationDate="2011-02-15T16:54:06.003" Score="0" ViewCount="" Body="A microcontroller is similar to a processor, but often with onboard memory (RAM or Flash) and peripherals such as a serial port." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-15T17:08:59.750" LastActivityDate="2011-02-15T17:08:59.750" />
  <row Id="10220" PostTypeId="2" ParentId="10190" CreationDate="2011-02-15T18:17:44.707" Score="2" ViewCount="" Body="&lt;p&gt;The Nordic nRF24L01 RF chips have a 33mW power consumption in Rx mode and much less in Tx. Not really answering your IR question, but I thought I'd mention them because you can buy ready made USB dongles which would speed up your development. It does also mean that line of sight isn't an issue!&lt;/p&gt;&#xA;" OwnerUserId="2770" LastActivityDate="2011-02-15T18:17:44.707" CommentCount="1" />
  <row Id="10221" PostTypeId="2" ParentId="10092" CreationDate="2011-02-15T18:46:55.480" Score="-2" ViewCount="" Body="&lt;p&gt;Relays can be set up to activate so many different voltage levels without adjustment.  This is why they are so often seen in industrial controls.  For instance say I design a controller for a valve that requires switched +15V to work.  Then the company switches the valve to a current controlled style where the output has nothing to do with a fixed voltage level.  This is a simple change for a relay(really no change) and probably a complex one for a MosFET.&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2011-02-15T18:46:55.480" />
  <row Id="10222" PostTypeId="2" ParentId="9981" CreationDate="2011-02-15T18:57:39.833" Score="1" ViewCount="" Body="&lt;p&gt;This is a funny question.  Here is a list of books that are mathy for various sub-domains of electronics.(Not saying best, just mathy)  Also, all the IEEE papers are pretty mathy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Control systems:&#xA;Introductory:&#xA;Linear Systems and Signals (The Oxford Series in Electrical and Computer Engineering) [Hardcover]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More advanced:&#xA;Fundamentals of Linear State Space Systems (McGraw-Hill Series in Electrical Engineering) [Hardcover]&#xA;John S Bay&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Solid state:&#xA;Introductory:&#xA;Semiconductor Physics And Devices Semiconductor Physics And Devices&#xA;Donald Neamen (Author)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;E&amp;amp;M&#xA;Elements of Electromagnetics (The Oxford Series in Electrical and Computer Engineering)&#xA;Matthew N. O. Sadiku&lt;/p&gt;&#xA;" OwnerUserId="72" LastEditorUserId="72" LastEditorDisplayName="" LastEditDate="2011-02-15T19:05:50.527" LastActivityDate="2011-02-15T19:05:50.527" />
  <row Id="10223" PostTypeId="1" AcceptedAnswerId="10224" CreationDate="2011-02-15T19:15:12.853" Score="1" ViewCount="109" Body="&lt;p&gt;I've used small high speed dc motors by just wiring them to a battery and potentiometer, but i've heard a lot of talk in these forums about motor controllers and h-bridges, and I don't fully understand when they are needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is: I want to run a geared motor like one of these:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.surpluscenter.com/item.asp?item=5-1571&amp;amp;catname=electric&quot; rel=&quot;nofollow&quot;&gt;http://www.surpluscenter.com/item.asp?item=5-1571&amp;amp;catname=electric&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.hobbyengineering.com/H2013.html&quot; rel=&quot;nofollow&quot;&gt;http://www.hobbyengineering.com/H2013.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I need a motor controller, arduino motor shield, or h-bridge to do so? Or can I just wire up a 6/12 volt power supply and use a pot to control the speed? I realize I won't be able to run it in reverse this way. Would I be able to just use a switch to reverse the polarity and run it forwards/backwards?&lt;/p&gt;&#xA;" OwnerUserId="2769" LastActivityDate="2011-02-15T23:28:48.360" Title="Controlling a geared motor" Tags="&lt;motor&gt;&lt;dc-motor&gt;" AnswerCount="2" />
  <row Id="10224" PostTypeId="2" ParentId="10223" CreationDate="2011-02-15T19:28:16.807" Score="4" ViewCount="" Body="&lt;p&gt;You can use a potentiometer, but this will give you greatly reduced torque at lower speeds, and you'll probably need a pot with a high power rating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll have much better results using PWM, increasing the duty cycle will increase the speed. The best implementation of this would be to use a microcontroller with a pot on an analogue input, and a MOSFET to power the motor via an output pin. Program the microcontroller to change the duty cycle depending on the value of the voltage divided by the pot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use a switch to control the direction if you're controlling it manually, but if you want your microcontroller to automatically control direction then you'll need an H bridge.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-15T19:28:16.807" CommentCount="2" />
  <row Id="10225" PostTypeId="1" AcceptedAnswerId="10226" CreationDate="2011-02-15T19:32:42.397" Score="3" ViewCount="127" Body="&lt;p&gt;I want to make a fractal antenna to replace an old set of rabbit ears. All the guides I've seen have used a thicker wire (metal coat hangers seem popular). While I don't have any hangers, I do have an absurd amount of cat-5 that I have been harvesting whenever I need wire. If I pull a length of wire out, would the thinness of the wire restrict its ability to pickup a good signal? Thanks and pardon the relative low bar on this question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Note:&lt;/strong&gt; I will be untwisting them and stripping them at the appropriate junctions. I also have a 300-&gt;75ohm transformer already.&lt;/p&gt;&#xA;" OwnerUserId="3034" LastActivityDate="2011-02-15T20:00:07.870" Title="Can a small gauge wire be used in a fractal antenna?" Tags="&lt;wire&gt;&lt;antenna&gt;&lt;tv&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="10226" PostTypeId="2" ParentId="10225" CreationDate="2011-02-15T20:00:07.870" Score="4" ViewCount="" Body="&lt;p&gt;Here are the effects that I would expect from switching between the coat hanger wire and the wire in CAT5:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;(Obvious) The wire in CAT5 will not retain its shape as well as a coat hanger wire. It will also not be as rigid. If you were planning on fastening the whole thing to a board, this wouldn't matter.&lt;/li&gt;&#xA;&lt;li&gt;Thinner wire will have a narrower bandwidth than thicker wire. The closer you get to an ideal wire (zero diameter, zero ohms), the higher the &quot;Q&quot; of the antenna. This is more significant when you are using really thick wire (or a birdcage dipole structure) and really thin wire. Additionally, I don't think your topology is very Q sensitive, so impact should be minimal.&lt;/li&gt;&#xA;&lt;li&gt;Thinner wire will have higher resistance. Since you are receiving, impact will be minimal.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;There are several other very minor effects that you might expect, but ultimately you won't notice an electrical difference, and it would be difficult to measure the difference. The 300-75 ohm transformer is only needed if the antenna is designed to be 300 ohms. Since you didn't post any documentation, I can't comment on that.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-02-15T20:00:07.870" CommentCount="1" />
  <row Id="10227" PostTypeId="2" ParentId="7272" CreationDate="2011-02-15T20:25:26.697" Score="0" ViewCount="" Body="&lt;p&gt;@Kellenjb , thanks for the images -- I think that helped me understand things greatly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;@Sriram , I wish you would say a few more words as to &lt;a href=&quot;http://www.catb.org/~esr/faqs/smart-questions.html#goal&quot; rel=&quot;nofollow&quot;&gt;what you &lt;em&gt;wish&lt;/em&gt; would happen&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm guessing that what you &lt;em&gt;wish&lt;/em&gt; would happen is something like &quot;I want an output that is always as loud as possible -- right on the verge of clipping. But I don't want the volume to radically change from one frame to the next. I want the volume to change more like a human slowly increasing the volume knob during the quiet parts, and somewhat more quickly turning down the volume when it starts to clip. But I don't want an actual human to turn the volume knob -- I want the software to automatically adjust the volume for me.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm also assuming that your system needs to spit out a frame of data within a frame or two of getting in a frame of data, in real time -- so I'm not allowed to analyze the entire song, and then afterward pick the perfect volume level and hold it constant throughout the entire song.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I guess you want to set up a pipeline something like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(1) One interrupt routine collects data into a buffer.&#xA;Often people set up 2 frames worth of storage:&#xA;This routine slowly fills up one frame while the next stages are working with data in the other frame.&#xA;Then when the one frame gets full you ping-ping double-buffer switch to filling up the other frame, while the next stages switch to working with the one frame.&#xA;Some people doing algorithms such as finite (FIR) filters buffer many, many frames worth of storage here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(2) In the &quot;background&quot; main loop, the software runs some DSP algorithm on the latest &quot;full&quot; input buffer and generate some output results in the output buffer.&#xA;Often people set up 2 frames worth of output buffer storage, so this routine quickly fills up one output frame, while the next stages slowly drain data from the other frame, with a ping-pong double-buffer scheme.&#xA;Some people doing algorithms such as infinite (IIR) filters buffer many, many frames worth of storage with these output values.&#xA;Most of the time, the DSP algorithm takes as input the previous outputs of this stage, &lt;em&gt;not&lt;/em&gt; the outputs of the next stages.&#xA;This stage is where most people run into problems with clipping and saturation, so most of the answers I see here focus on this step.&#xA;But from your responses, it sounds like you've already figured out that you need a wide data type with many &quot;extra&quot; bits of precision to calculate these intermediate values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(3) In the main loop, the software multiplies each value of the intermediate frame by some scaling factor V to generate a &quot;scaled value&quot;. (It does &lt;em&gt;not&lt;/em&gt; store this value in any buffer).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(4) In the main loop, the software reduces each &quot;scaled value&quot; to the final output type (8 bits?) required by your output device, and store the result in yet another buffer.&#xA;(The output of this stage should almost certainly &lt;em&gt;not&lt;/em&gt; be fed back into the DSP algorithm in step 2. &lt;a href=&quot;http://www.romanblack.com/picsound.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;The BTC Sound Encoder&quot;&lt;/a&gt; by Roman Black is one of the very few algorithms I know of where such feedback is useful).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(5) One interrupt routine takes one sample at a time from the output buffer from (4), and spits it out to the output device. (This may also use a double-buffered ping-pong arrangement).&#xA;Often the input sample rate and the output sample rate are the same (44100 Samples/s), and the same interrupt routine does (5) and (1).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From your response to Martin, I get the impression that one particular fixed volume setting V1 for V may be adequate for one song, and some other fixed volume setting V2 may be adequate for some other song.&#xA;Imagine that you could listen to the whole song, and calculate a perfect volume for that song -- how would you do that? Is it OK if a &lt;em&gt;few&lt;/em&gt; samples of the song get clipped?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps something like this relatively simple automatic gain control (AGC or VOGAD) would solve your problem:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Every time stage 2 finishes producing a frame, calculate a new V value that will be used to scale the samples in that frame during step 3. One of the simplest ways: find the most positive (maximum) value and most negative value in that frame, and multiply both values by the current V that was used for the previous frame. Check if either sample will clip (i.e., the result is above +127 or below -127) or are close to clipping (i.e., above +63 or below -63), and set the volume multiplier VM appropriately:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;If the volume is too low (none of the samples clip, none of the samples are anywhere close to clipping), set the volume multiplier to some number slightly greater than 1: VM = VM_UP, where VM_UP is something like 1.01 or 1 + 2^(-12).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If the volume is too high (some of the samples clip, or too many of the samples are close too clipping, or both), set the volume multiplier VM to some number slightly less than 1: VM = VM_DOWN, where VM_DOWN is something like 0.98 or 1 - 2^(-8).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If the volume looks OK (not to high, not too low) keep VM = 1.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Periodically (ideally once every sample, but if that eats to much time once per frame or once per millisecond or once every tenth of a second may be adequate), re-adjust the volume with a saturating multiply:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;V := (V * VM).&lt;/li&gt;&#xA;&lt;li&gt;If V is now too small (less than V_min), set V := V_min.&lt;/li&gt;&#xA;&lt;li&gt;If V is now too big (more than V_max), set V := V_max.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You'll want to tweak the compile-time constants VM_UP and VM_DOWN until it subjectively &quot;sounds right&quot;.&#xA;Perhaps set VM_DOWN so that, with very loud inputs, it takes a second or two to crank the volume knob from the maximum volume to the minimum volume.&#xA;Perhaps set VM_UP so that, with absolute silence, it takes ten seconds or so to very slowly crank the volume knob from the minimum volume to the maximum volume.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could guarantee that you'll never saturate by instantly reducing the volume V whenever a frame looks like it might saturate, such that (with the reduced volume V) it just barely hits the peaks of +127 or -127.&#xA;But I suspect that it will sound better to slowly reduce the volume, and allow a few samples to saturate for a few frames.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a wide variety of more complicated ways to (a) envelope/peak/&quot;perceptual loudness&quot; detection: calculate a number that indicates whether a frame of data is too loud or too soft, and by how much.&#xA;There are also a wide variety of more complicated ways for an AGC to (b) use that number from the current frame (and perhaps for the past few frames) and the volume used during the last frame in order to calculate the volume to use for the next frame.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Further reading:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Tony J. Rouphael. &lt;a href=&quot;http://www.eetimes.com/General/DisplayPrintViewContent?contentItemId=4017743&quot; rel=&quot;nofollow&quot;&gt;Wireless 101: Automatic Gain Control (AGC)&lt;/a&gt;. EE Times 2009. Mirror: &lt;a href=&quot;http://vault.embedded.com/columns/technicalinsights/214600265?printable=true&quot; rel=&quot;nofollow&quot;&gt;Wireless 101: Automatic Gain Control (AGC)&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://hawksoft.com/hawkvoice/&quot; rel=&quot;nofollow&quot;&gt;sample AGC code in the open-source HawkVoice software&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.adaptivedigital.com/product/telephony/agc.htm&quot; rel=&quot;nofollow&quot;&gt;AGC code from Adaptive Digital Technologies&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;the &lt;a href=&quot;http://www.analog.com/static/imported-files/data_sheets/AD1954.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet for the AD1954 describes its &quot;compressor/limiter&quot; AGC&lt;/a&gt; that has a &quot;lookahead&quot; feature.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.musicdsp.org/archive.php?classid=4#204&quot; rel=&quot;nofollow&quot;&gt;&quot;Simple Compressor class&quot; for an audio peak compressor&lt;/a&gt; (a kind of AGC) with C++ source code.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-15T20:25:26.697" />
  <row Id="10229" PostTypeId="1" AcceptedAnswerId="10238" CreationDate="2011-02-15T22:15:56.187" Score="4" ViewCount="285" Body="&lt;p&gt;I've asked other questions about having a career in electronics without an EE degree.  I'm wondering specifically about being an analog IC designer.   What would it take to land a position doing that before having that degree?   What would convince an employer to hire me despite lacking that piece of paper?  What kind of employer would I best off sending my resume and other info to?&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2011-02-16T16:18:22.050" Title="Earning a living in analog IC design w/o an EE degree" Tags="&lt;analog&gt;&lt;design&gt;&lt;ic&gt;&lt;career&gt;" AnswerCount="6" CommentCount="6" />
  <row Id="10231" PostTypeId="2" ParentId="10229" CreationDate="2011-02-15T23:18:37.993" Score="4" ViewCount="" Body="&lt;p&gt;Is it possible? Absolutely!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you going to get a job doing full-blown IC design straight off the bat? No.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;The best (and really only reliable) way to get a job doing high-level engineering without a related degree is to work your way up the chain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, get a job doing scut-work at a IC design company. Ask lots of &lt;em&gt;intelligent&lt;/em&gt; questions, do &lt;strong&gt;lots&lt;/strong&gt; of reading, and try to make intelligent suggestions. Assuming the company you work for is at all open to new talent, eventually you should be able to start working on more advanced topics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take your time, work your way up, and learn as much as you can as you go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, the viability of this sort of approach is highly dependent on how rigid the corporate structure at the place you work is. A rigidly structured organization is less willing to consider people without degrees, but a lot of it just depends on the people you are working with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally speaking, it's how I got my current jobs (Consulting/Board layout/CAD).&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-02-15T23:18:37.993" />
  <row Id="10232" PostTypeId="2" ParentId="10229" CreationDate="2011-02-15T23:20:27.773" Score="2" ViewCount="" Body="&lt;p&gt;Experience and track record, especially for analog. You'd probably need to start at the bottom &amp;amp; work your way up. Pubished hobby projects in the area will also be useful to show enthusiasm. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-15T23:20:27.773" />
  <row Id="10233" PostTypeId="2" ParentId="10223" CreationDate="2011-02-15T23:28:48.360" Score="2" ViewCount="" Body="&lt;p&gt;Potentiometers are terribly inefficient for controlling power loads, since significant power is burned up in the potentiometer itself. Under the right load conditions, &lt;em&gt;most&lt;/em&gt; of the power sourced by the power supply will be burnt in the pot. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This doesn't matter too much if you're only dealing with small loads and have a mains supply, and can deal with the heat from the potentiometer. But if your power source is a battery, this inefficiency translates directly to shortened run time between battery charging.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-15T23:28:48.360" />
  <row Id="10234" PostTypeId="2" ParentId="8973" CreationDate="2011-02-15T23:45:23.127" Score="3" ViewCount="" Body="&lt;p&gt;Professor Miriam Leeser's research group at the Reconfigurable Computing Laboratory at Northeastern University has developed an open source floating point library for Xilinx FPGAs in VHDL:&#xA;&lt;a href=&quot;http://www.ece.neu.edu/groups/rcl/projects/floatingpoint/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ece.neu.edu/groups/rcl/projects/floatingpoint/index.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3036" LastActivityDate="2011-02-15T23:45:23.127" CommunityOwnedDate="2011-02-15T23:45:23.127" />
  <row Id="10235" PostTypeId="1" AcceptedAnswerId="10237" CreationDate="2011-02-16T00:53:49.037" Score="1" ViewCount="100" Body="&lt;p&gt;I used to use a breadboard, and it would hold the components put into it. A wire wrap board is different. The components are don't seem to be secured to the board. How are they supposed to be secured to the board?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="906" LastEditorDisplayName="" LastEditDate="2011-02-16T03:19:13.353" LastActivityDate="2011-02-16T04:35:01.450" Title="How to secure components to a wire-wrap board" Tags="&lt;components&gt;&lt;protoboard&gt;&lt;wire-wrap&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="10236" PostTypeId="2" ParentId="10235" CreationDate="2011-02-16T01:08:37.230" Score="2" ViewCount="" Body="&lt;p&gt;I used to solder them to carriers plugged into wire-wrap sockets.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-16T01:08:37.230" />
  <row Id="10237" PostTypeId="2" ParentId="10235" CreationDate="2011-02-16T01:10:17.857" Score="3" ViewCount="" Body="&lt;p&gt;I'm not sure if this is what you're asking, but you are supposed to use sockets specific to wire-wrapping.  The pins in these sockets are square and have very sharp edges.  The mere act of wrapping the wire will hold the socket in place.  Then you press your components into the socket.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-16T01:10:17.857" CommentCount="4" />
  <row Id="10238" PostTypeId="2" ParentId="10229" CreationDate="2011-02-16T01:56:56.320" Score="7" ViewCount="" Body="&lt;p&gt;The fastest route would be to get an EE degree, then a Masters specializing in analog IC design.  I can't imagine how you'd work your way up in less time, or that many companies would give you the opportunity.  Most analog IC designers have advanced degrees, and so there is a high barrier of entry.  A BS in EE actually provides very little in the way of analog IC design, and unlike things like programming, you can't really build an impressive resume hacking away in you're mom's basement.  The amount of money you have to drop for getting your own designs fabricated would be better spent on a degree.  Analog IC design is something where the &quot;piece of paper&quot; really comes in handy.  If you can't devote all your time to schooling, try getting a job at a tech company and go to school part time.  They may help pay for some of your education.  &lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-02-16T01:56:56.320" CommentCount="2" />
  <row Id="10239" PostTypeId="1" AcceptedAnswerId="10240" CreationDate="2011-02-16T02:03:08.417" Score="1" ViewCount="241" Body="&lt;p&gt;I am trying to figure out how to create a combination lock using logic gates, so that a password must be input (let's say pressing numbered buttons) in the correct order.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand logic gates completely, and have some of a grasp on flip-flops and latches, but I'm definitely getting stuck on how to use them in the right combination.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So as an example, if there are 3 buttons (call them 1, 2, &amp;amp; 3), I would like to be able to set a password such as 1 2 3 1 (hardcoded is fine), where they have to be input in that exact order, otherwise you have to start at the beginning again (1 2 3 3 3 3 1 will not work).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any tips, links, hints on this?&lt;/p&gt;&#xA;" OwnerUserId="3037" LastActivityDate="2011-02-16T02:45:02.733" Title="Creating a combination lock using logic gates?" Tags="&lt;logic&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="10240" PostTypeId="2" ParentId="10239" CreationDate="2011-02-16T02:45:02.733" Score="3" ViewCount="" Body="&lt;p&gt;I would probably use two bits to encode the three switches, and the general approach would be to have a string of pairs (one for each bit) of D or JK flip-flops to accept the sequence of input digits, essentially a shift register for pairs of bits. Then there would have to be de-bounce circuitry for the switches, and some way to generate a clock signal from the key presses (probably on release) to shift the digits through the register. Finally, XOR gates between the stages of the shift register and the digits of the key (hardwired to 1231 or use switches, etc) would produce signals to indicate when each digit is a correct match (logic Low on match), and then a multi-input NOR of the XOR outputs would give a final output signal that would indicate when the entire sequence in the shift register matches the key.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-16T02:45:02.733" CommentCount="3" />
  <row Id="10241" PostTypeId="1" CreationDate="2011-02-16T03:15:21.193" Score="2" ViewCount="133" Body="&lt;h2&gt;Old Topic:&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Can I make robot only circuit without microcontroller?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What knowledge should I know, where can I get it?&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;UPDATE:&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;How to learn &lt;a href=&quot;http://en.wikipedia.org/wiki/BEAM_robotics&quot; rel=&quot;nofollow&quot;&gt;BEAM robotics&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="2596" LastEditorUserId="2596" LastEditorDisplayName="" LastEditDate="2011-02-16T04:17:30.493" LastActivityDate="2011-02-16T06:31:33.303" Title="How to learn BEAM robotics?" Tags="&lt;circuit&gt;&lt;robotics&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="10242" PostTypeId="2" ParentId="10235" CreationDate="2011-02-16T03:18:32.700" Score="2" ViewCount="" Body="&lt;p&gt;You can also buy &lt;a href=&quot;http://www.mill-max.com/images/products/pdf/metric/195M.pdf&quot; rel=&quot;nofollow&quot;&gt;dedicated pins&lt;/a&gt; that allow you to solder on one side (usually bifurcated) and wire wrap on the other. The pins have a shoulder that you can jam into the PCB through hole to secure it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, if you want to attach a component to a wire wrap board that component has to be connected to a wire wrap pin. Whether that's a dedicated terminal, a single piece of a strip socket, a repurposed DIP socket, or a component carrier plugged into a DIP socket - that's your choice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an aside, unless you're dealing with exotic components or have a stash of wire wrap stuff, wire wrap components seem pretty expensive. Digikey wants $3 to $7 for a 16 pin DIP socket. You might be better served by doing point-to-point wiring on a Veroboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit to add:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK, given the specific example of a voltage regulator, how would you add that? Let's assume this is a TO-220 or similar package. There are three leads that need to be connected, so you need to connect them to three wire wrap pins. Exactly how you do this depends on what kind of wire wrap pins you have:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Terminal pins (bifurcated or not): I'd solder the pins to the component, then plug the whole thing into the perfboard, then wire-wrap to the pins.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;DIP socket: plug the three leads into 3 adjacent socket pins (bending if necessary), then wire-wrap to those pins.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;SIP or discrete sockets: same as DIP sockets.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If this were a TO-92 with an off-pitch triangular lead layout, you might have to &quot;normalize&quot; the leads to fit the 100 mil pitch of the perfboard. Just use good pliers to make it fit (or cheat and get the 3 leads started into 3 holes, and use the perfboard to leadform it - this is what I'd do).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other tips:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget that you can cut skeletonized wire wrap sockets apart to make discrete socket pins/SIP socket strips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might have to glue the wire wrap sockets in place, especially when using single-pin connections.&lt;/p&gt;&#xA;" OwnerUserId="906" LastEditorUserId="906" LastEditorDisplayName="" LastEditDate="2011-02-16T04:35:01.450" LastActivityDate="2011-02-16T04:35:01.450" CommentCount="2" />
  <row Id="10243" PostTypeId="1" CreationDate="2011-02-16T03:21:41.713" Score="1" ViewCount="125" Body="&lt;p&gt;I want to display  degrees in a seven segment display when rotate multi turn potentiometers.After rotating one round it should be reset to 0 degree.I can use A to D converter ICs.But how I give voltage signal to it when potentiometer rotates after one round. &lt;/p&gt;&#xA;" OwnerUserId="3038" LastActivityDate="2011-02-16T14:44:14.810" Title="multi turn potentiometers to measure degrees" Tags="&lt;potentiometer&gt;&lt;digital&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="10244" PostTypeId="1" AcceptedAnswerId="11767" CreationDate="2011-02-16T03:25:48.830" Score="8" ViewCount="212" Body="&lt;p&gt;Does any of the common circuit simulation software provide the system equations? Deriving a system of 1st-order differential equations for a circuit by hand is kind of a pain. And yes, I know that the simulators will actually run the simulations for me, but there are some cases where I'd really be interested just to see what the equations are. Which, if any, circuit simulators would provide them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT ..&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I am specifically looking for here is, I would like to be able to enter my circuit into the software, just like you would do for simulation, but besides run the simulation, I'd &lt;em&gt;also&lt;/em&gt; like to have the software show me the equations that it has derived and uses to run the simulation - the system of differential equations that says what the rates-of-change of the system state variables are. This could be a system of equations or it could be in matrix form, doesn't matter.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-02-18T00:11:00.833" LastActivityDate="2011-03-25T17:44:23.223" Title="software for obtaining differential equations for circuit simulation" Tags="&lt;software&gt;&lt;simulation&gt;&lt;math&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="4" />
  <row Id="10245" PostTypeId="5" CreationDate="2011-02-16T03:36:02.467" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; can sense the environment by receiving input from a variety of sensors and can affect its surroundings by controlling lights, motors, and other actuators. The microcontroller on the board is programmed using the &lt;a href=&quot;http://arduino.cc/en/Reference/HomePage&quot; rel=&quot;nofollow&quot;&gt;Arduino programming language&lt;/a&gt; (based on &lt;a href=&quot;http://wiring.org.co/&quot; rel=&quot;nofollow&quot;&gt;Wiring&lt;/a&gt;) and the &lt;a href=&quot;http://arduino.cc/en/Main/Software&quot; rel=&quot;nofollow&quot;&gt;Arduino development environment&lt;/a&gt; (based on &lt;a href=&quot;http://processing.org/&quot; rel=&quot;nofollow&quot;&gt;Processing&lt;/a&gt;). Arduino projects can be stand-alone or they can communicate with software on running on a computer (e.g. Flash, Processing, MaxMSP). &lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-04-07T14:52:27.203" LastActivityDate="2011-04-07T14:52:27.203" />
  <row Id="10246" PostTypeId="4" CreationDate="2011-02-16T03:36:02.467" Score="0" ViewCount="" Body="Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments. " OwnerUserId="-1" LastEditorUserId="3531" LastEditorDisplayName="" LastEditDate="2011-03-22T18:45:34.720" LastActivityDate="2011-03-22T18:45:34.720" />
  <row Id="10247" PostTypeId="2" ParentId="10241" CreationDate="2011-02-16T03:51:41.347" Score="1" ViewCount="" Body="&lt;p&gt;Why don't you start by asking yourself, &quot;what do I want my robot to do&quot; and coming up with methods to accomplish the tasks? Then, find the components which have microcontrollers in them, and try to figure out if the microcontroller is a crucial aspect of its function. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, many servos and motors interface through a 3-pin servo connector which interprets a PPM (pulse position modulation) signal on the white wire. A microcontroller is particularly suitable for generating a signal such as this. Now you see why you could benefit greatly from learning how these technologies work. &lt;/p&gt;&#xA;" OwnerUserId="3039" LastActivityDate="2011-02-16T03:51:41.347" CommentCount="2" />
  <row Id="10248" PostTypeId="2" ParentId="10243" CreationDate="2011-02-16T03:59:53.260" Score="1" ViewCount="" Body="&lt;p&gt;You haven't told us what type of potentiometer you're using or what you are using to drive the display, so I'll assume that you're using a linear potentiometer and a microcontroller to drive the display. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I that is so, you could measure the voltage difference for one turn of the potentiometer and use the microcontroller to remove full turns. For linear potentiometer, it's going to be easy. Just measure how big voltage difference is for one turn and then do a module of that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In C that would be something live &lt;code&gt;Voltage= Input_Voltage % Turn_Voltage;&lt;/code&gt; and the  just feed the Voltage into the routine which calculates number of degrees.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the potentiometer is logarithmic, you'll have to record its voltage over whole range of motion and then make a function which will be used by the microcontroller to see where the dial is. Some logarithmic potentiometers have actually two (or more) different linear elements inside, so you'll need to get a graph of voltage and number of turns.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you aren't using a microcontroller, you can do this using discrete components too, but it's going to be more complicated. Also, I haven't done something like that for quite a while, so I can't give you any advice there. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-16T03:59:53.260" />
  <row Id="10249" PostTypeId="1" AcceptedAnswerId="10250" CreationDate="2011-02-16T04:04:54.343" Score="2" ViewCount="275" Body="&lt;p&gt;I just have a few general questions that those with more experience could easily answer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am working with an arduino, and interfacing with various devices such as the PC that I use to write the arduino C code, which is obviously plugged in via USB, and I have had success with a serial link to an iphone by connecting the tx/rx pins. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;What sort of data integrity guarantees are there for the serial link? For example if the cable connecting two devices becomes frayed or damaged, what sort of changes might I expect my data stream to undergo? Could it start receiving garbled data, or will it just cut off? &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Is its functionality fully encapsulated by a byte stream? Suppose I want to relay 16-bit numbers. My first and only instinct is that I must come up with my own protocol (big-endian or little, for example) to pack my data into a byte stream and write to the port? It functions more or less like a network socket (minus the concept of packets) does it not? &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3039" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-02-16T16:16:12.123" LastActivityDate="2011-02-21T13:23:13.237" Title="Serial (UART) communication" Tags="&lt;serial&gt;&lt;uart&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10250" PostTypeId="2" ParentId="10249" CreationDate="2011-02-16T04:32:03.043" Score="13" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Async serial has no data integrity guarantees.  If data integrity is important to your application, add a checksum.  But if everything is connected properly, it should be pretty solid.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You get a series of bytes.  The rest is up to you.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If the serial is connected while transmission is underway, it will not automatically synchronize.  Some garbage will appear on the line.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;One common scheme is to represent data with packets.  Then the packet format is like:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[sync byte][data length byte][data bytes][checksum byte]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a lot of variations on it.  The sync byte lets the receiver synchronize if it gets a partial message.  The sync byte can be escaped if it appears elsewhere in the packet, or not.  Checksum can be a sum of all bytes, or XOR, or CRC16, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative is to only use ASCII for the serial communications.  Then you can synchronize on the '\n' at the end of the message.  This is a nice format for debugging, because you can use your favorite terminal emulator.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-16T04:32:03.043" CommentCount="10" />
  <row Id="10251" PostTypeId="2" ParentId="10229" CreationDate="2011-02-16T05:03:47.580" Score="5" ViewCount="" Body="&lt;p&gt;I have an MSEE and spent around 15 years doing analog IC design for several companies including large multinationals and a few startups (especially around 1999-2000).  I don't do that kind of work anymore because it has largely been outsourced to cheap but highly qualified labor in India (mostly) and China (more recently).  A few years ago, my department head finally told me he had more Phds than products he needed to be designed and since I didn't have a Phd, he could no longer let me do analog design anymore (Phds like to do this kind of work because they can publish papers and eventually most hope to move on to teaching.  But don't worry, there are plenty more coming in the pipe all the time to take their place).  This even though I had a proven track record of high quality design work and many products in production.  Not sure why you would want to go down that path at all and certainly can't imagine anyone hiring someone for that kind of work with no degree.  The field is very mature, highly theoretical (which is why the emphasis on an advanced degree - you're not going to learn that on the job), heavily outsourced and with few entry level openings.  The large US multinational I last worked for hires mostly at their Asia design centers.  Any US based hiring (which has been almost nil for the past 3 years and included huge layoffs of top experienced people in 2009) is highly targeted to specific tasks with solid qualification requirements.  I think you might want to look at a different line of work.  Maybe one hope is if you happen to speak Mandarin and are willing to work in sales and are familiar with Asia, that could be a possible back door way in.  Not kidding.  Good luck.&lt;/p&gt;&#xA;" OwnerUserId="3040" LastActivityDate="2011-02-16T05:03:47.580" CommentCount="2" />
  <row Id="10252" PostTypeId="2" ParentId="10241" CreationDate="2011-02-16T05:15:21.900" Score="-1" ViewCount="" Body="&lt;p&gt;A quick google &lt;a href=&quot;http://lmgtfy.com/?q=BEAM+robotics&quot; rel=&quot;nofollow&quot;&gt;search&lt;/a&gt; will yield lots of information - including a &lt;a href=&quot;http://www.beam-wiki.org/wiki/Main_Page&quot; rel=&quot;nofollow&quot;&gt;wiki&lt;/a&gt;, which happens to have lots of information about BEAM robotics. Next, pick up some electronic components and start hacking away!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-02-16T05:15:21.900" />
  <row Id="10253" PostTypeId="2" ParentId="10241" CreationDate="2011-02-16T06:31:33.303" Score="2" ViewCount="" Body="&lt;p&gt;I really liked &quot;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0072226013&quot; rel=&quot;nofollow&quot;&gt;JunkBots, Bugbots, and Bots on Wheels: Building Simple Robots With BEAM Technology&lt;/a&gt;&quot;. It does a really good job of introducing the BEAM aesthetics, such as they are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you really need to start from the beginning, &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/1430227486&quot; rel=&quot;nofollow&quot;&gt;Robot Building for Beginners (Technology in Action)&lt;/a&gt; might be the best place to start. It's very thorough, and gives what is probably the best advice I've ever read: &quot;Stop being a visionary and start building something.&quot; There's no substitute for experimentation!&lt;/p&gt;&#xA;" OwnerUserId="1269" LastActivityDate="2011-02-16T06:31:33.303" />
  <row Id="10254" PostTypeId="1" AcceptedAnswerId="10430" CreationDate="2011-02-16T09:36:37.753" Score="3" ViewCount="205" Body="&lt;p&gt;I am building clock with ultimate precision.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are few known ways to improve precision: temperature controlled environment and multiple crystals. I am implementing both.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was going to use 5 crystals on separate uC's (2$ each in retail). But then I've thought: maybe I can just build crystal generators on inverters (2 generators per 0.2$ chip), and feed multiple 32khz signals to single uC?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will the precision of inverter-based generators be inferior to uC-based ones?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously inverters look very attractive - in the same budget I can have 2-3 times more crystals.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="1802" LastEditorDisplayName="" LastEditDate="2011-02-16T13:02:46.447" LastActivityDate="2011-02-22T00:16:34.683" Title="Multiple crystals" Tags="&lt;crystal&gt;&lt;generator&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="2" />
  <row Id="10255" PostTypeId="2" ParentId="9114" CreationDate="2011-02-16T10:31:47.303" Score="1" ViewCount="" Body="&lt;p&gt;MES (Miniature Edison Screw) lamp holders are designed for &lt;em&gt;low voltage&lt;/em&gt; lamps and &lt;em&gt;not mains lamps&lt;/em&gt;. You would need a SES (Small Edison Screw) or ES (standard Edison Screw) lamp holder to make this suitable for mains operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, your question doesn't actually mention your intention to use mains voltage. If you want to use a low voltage lamp, you should be perfectly OK. Just don't use mains cable to wire to it otherwise someone will inevitably attach a mains plug to it one day with spectacular consequences.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also repeat tyblu's caveat about safety.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-02-16T10:31:47.303" />
  <row Id="10257" PostTypeId="2" ParentId="10243" CreationDate="2011-02-16T14:41:28.607" Score="1" ViewCount="" Body="&lt;p&gt;First of all, it's kinda bad idea - potentiometers have noise while in movement, and this will distract your readings. Proper solution is to use encoder - they already have digital output and way way more reliable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For multiturn potentiometers you just have to calibrate them: rotate by 90' write down ADC reading, then again and again until you reach the limit. Then you do interpolation to get reading between your calibration marks. In order to reset to 0 - you just add %360 in your code (so that calculated value would 'wrap' after 360').&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-16T14:41:28.607" />
  <row Id="10258" PostTypeId="2" ParentId="10229" CreationDate="2011-02-16T14:42:00.913" Score="1" ViewCount="" Body="&lt;p&gt;Not designing ICs.  The costs are high and the risks of bad ICs are high.  You would be better off with analog board design.  @bt2 is right.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-16T14:42:00.913" />
  <row Id="10259" PostTypeId="2" ParentId="10243" CreationDate="2011-02-16T14:44:14.810" Score="0" ViewCount="" Body="&lt;p&gt;It would be helpful to know more about the background of your project.  The fact that you want the display to reset to 0 after a full rotation is not an issue, and implementation is easy.  However, this implies that you expect the potentiometer to rotate more than one full rotation.  But &lt;em&gt;how many&lt;/em&gt; full rotations do you expect from the user?  5?  10?  infinite?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The issue is that you'd basically need a 1:1 ratio from input rotations (from the knob) to output rotations (connected to the pot) on a multi-turn pot, but this is going to limit your angle resolution.  If you want 5 turns, then you need to buy a 5 turn pot, and the entire resistance over the 5 turns &quot;shares&quot; the ADC range.  In other words, for every N turns, you reduce your angle resolution by 1/N.  It would be disappointing to fiddle with a knob and only see something like 15 degree increments.  Of course this is also a function of your ADC resolution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need high resolution and you have a low resolution ADC, then you'd probably want to &quot;gear down&quot; the knob.  In other words, one rotation of the knob = N rotations of the pot.  This way, the one rotation of the knob gets the full ADC range.  But then you wouldn't get multiple turns of the knob.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need infinite rotations, then you need to put in a rotary incremental encoder.  Something like that from an old mouse could work, and then you'd similarly gear the system down.  Then implement a really simple lookup table in the microcontroller to keep track of where you are.  Of course, this means you'll also need to use an input to set 0 degrees.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-16T14:44:14.810" />
  <row Id="10260" PostTypeId="2" ParentId="10254" CreationDate="2011-02-16T15:56:43.707" Score="3" ViewCount="" Body="&lt;p&gt;Multiple crystals isn't a good way to improve accuracy as they will all be sublect to similar drift mechanisms. There are well-proven ways to get high stability- TXCO's and OCXO's &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-16T15:56:43.707" CommentCount="1" />
  <row Id="10261" PostTypeId="2" ParentId="10229" CreationDate="2011-02-16T16:18:22.050" Score="1" ViewCount="" Body="&lt;p&gt;The only thing I can think of outside of what is mentioned above would be to dive into a program like &lt;a href=&quot;http://en.wikipedia.org/wiki/Electric_%28software%29&quot; rel=&quot;nofollow&quot;&gt;Electric&lt;/a&gt;, teach yourself how to use it (hopefully with guidance from an experienced engineer), make some kind of awesome and before unseen circuit, and finally get it in the hands of someone who matters and has the ability to hire you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://youtube.com/jeriellsworth&quot; rel=&quot;nofollow&quot;&gt;Jeri Ellsworth&lt;/a&gt; took a similar path with digital (granted, which has lower entry costs and less need to be near the process node and device physics) but did not have any education. She stated in &lt;a href=&quot;http://twit.tv/tri3&quot; rel=&quot;nofollow&quot;&gt;a recent interview&lt;/a&gt; that it was all because of mentors. So in the event you think it's something you'd really want to do, that'd be a first step. Even with a MS, a good mentor will get you farther than anything else IMHO.&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2011-02-16T16:18:22.050" CommentCount="2" />
  <row Id="10262" PostTypeId="2" ParentId="10254" CreationDate="2011-02-16T16:55:15.920" Score="2" ViewCount="" Body="&lt;p&gt;The easiest way to get a high-stability clock is to lock it to a suitable radio transmission, such as the &lt;a href=&quot;http://www.qsl.net/pa2ohh/07freqstd.htm&quot; rel=&quot;nofollow&quot;&gt;Droitwich 198 kHz BBC transmitter&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-16T16:55:15.920" CommentCount="2" />
  <row Id="10263" PostTypeId="2" ParentId="10254" CreationDate="2011-02-16T17:12:51.457" Score="0" ViewCount="" Body="&lt;p&gt;I'll flesh out this answer when I have more time but I would look at a clock distribution IC.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They come in various forms but most simply a single crystal drives a programmable (or fixed) PLL in the IC which then provides multiple clock outputs.  These are generally very good at matching each output with very low jitter.  I've used them several times in audio systems that required many devices running off the same clock.  They also come in forms that allow multiple crystals, usually used for multiple clock frequencies, but you could probably use some sort of averaging logic with the same rate and perhaps improve accuracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In terms of an accurate clock, anything you do will become out of sync over time.  Consider an internet connection on the device and periodic syncing with network time servers (NTP protocol).  This should provide accuracy within the milliseconds range synced to global atomic clocks.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-02-16T17:12:51.457" CommentCount="2" />
  <row Id="10264" PostTypeId="1" CreationDate="2011-02-16T17:55:08.863" Score="0" ViewCount="78" Body="&lt;p&gt;I am looking to build a small grip arm for the disabled. My goal is to attach this robotic hand to an arm of a person.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This robotic hand is used to open medicine bottles (like those you get when filling prescription medicine). Thus, the hand needs to be able to grip a cap and rotate it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For rotation, I am thinking of some small servo, but for grip, I don't have an idea yet. Can you please suggest what type of grip I should look for and where I can find them?&lt;/p&gt;&#xA;" OwnerUserId="3044" LastActivityDate="2011-02-17T14:42:29.293" Title="Robot grip hand for the disabled" Tags="&lt;robotics&gt;&lt;servo&gt;" AnswerCount="1" />
  <row Id="10265" PostTypeId="1" CreationDate="2011-02-16T17:46:17.717" Score="3" ViewCount="151" Body="&lt;p&gt;I have an AC/DC power supply (from the UK).  It is labelled 230V/50hz. As far as I know, electric in Mainland britain is 240V/50hz.  Indeed, the unit did correctly power the Korg keyboard in the UK. The DC output is labelled 21V / 1.2A. (The Korg piano is indeed labelled 21V input on the back.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I have the same power supply in France.  As far as I know, France is also 230V/50hz. When I plug the power supply in the wall in france (obviously using a 50 cent plastic plug adaptor - of course NOT using any sort of transformer, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a good multimeter, in France the output from the power supply is 26 volts (around 25.9 to 26). Is that normal?  Why not just 21?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Unfortunately I never tested the output, in the UK.) Now, the electric piano is actually not working.  ie, I did plug the power supply in question in to the Piano and no result, nothing comes on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Why is it showing 26 rather than 21 as labeled?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Do you reckon I may have blown a fuse in the piano, due to the 26 versus 21? Or, perhaps not a fuse, just permanently ruined it?  Conversely, is it likely just some other unrelated problem with the piano?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;To rephrase: If the piano says 21V on the back, would 26 V be too hot, or no problem, typically?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;It's an expensive pro piano and a real nuisance! It is a mystery that it is showing 26V. It's almost impossible to find a replacement power supply, and, that may well not be the problem. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A further question for you experts:&#xA;would an alternate supply, eg,&#xA;&lt;a href=&quot;http://www.webducommerce.com/alimentation-21v/chargeur-alim-secteur-21v-1-7a-36w-p-3485.html&quot; rel=&quot;nofollow&quot;&gt;http://www.webducommerce.com/alimentation-21v/chargeur-alim-secteur-21v-1-7a-36w-p-3485.html&lt;/a&gt;&#xA;with a HIGHER amperage rating, actually be OK??  Should you try to match the amp rating, or us the point that it must be &quot;at least&quot; 1.2A in my example?  Thanks again, pro geniuses!&lt;/p&gt;&#xA;" OwnerUserId="3048" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:08:27.483" LastActivityDate="2011-03-05T16:08:27.483" Title="21V power supply -- 26V output with different mains?" Tags="&lt;power-supply&gt;&lt;line-power&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="10266" PostTypeId="2" ParentId="10265" CreationDate="2011-02-16T17:54:39.393" Score="7" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;That's pretty normal, as it's not regulated. &lt;a href=&quot;http://en.wikipedia.org/wiki/Power_supply&quot; rel=&quot;nofollow&quot;&gt;Voltage drops when load rises&lt;/a&gt;.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Probably just blows fuse, but I think more likely works just fine.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If power supply would be 26V regulated output, then it would be problem, probably.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Many devices tolerate much larger voltages, for example 12V laptop is fine with 16V supply.&lt;/p&gt;&#xA;" OwnerUserId="3064" LastActivityDate="2011-02-16T17:54:39.393" CommentCount="2" />
  <row Id="10268" PostTypeId="2" ParentId="10189" CreationDate="2011-02-16T18:09:34.277" Score="0" ViewCount="" Body="&lt;p&gt;The second scenario is equivalent to a motor with magnets on the rotor. Yes there is counter EMF from field windings. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-02-16T18:09:34.277" CommentCount="1" />
  <row Id="10269" PostTypeId="5" CreationDate="2011-02-16T18:40:03.533" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-16T18:40:03.533" LastActivityDate="2011-02-16T18:40:03.533" />
  <row Id="10270" PostTypeId="4" CreationDate="2011-02-16T18:40:03.533" Score="0" ViewCount="" Body="Sensors in electronicsmonitor the physical world (e.g., temperature, pressure)." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-16T19:50:46.563" LastActivityDate="2011-02-16T19:50:46.563" />
  <row Id="10271" PostTypeId="5" CreationDate="2011-02-16T18:40:15.547" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-16T18:40:15.547" LastActivityDate="2011-02-16T18:40:15.547" />
  <row Id="10272" PostTypeId="4" CreationDate="2011-02-16T18:40:15.547" Score="0" ViewCount="" Body="This tag is for questions on hand and machine soldering." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-16T19:50:48.280" LastActivityDate="2011-02-16T19:50:48.280" />
  <row Id="10273" PostTypeId="5" CreationDate="2011-02-16T18:40:37.887" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-16T18:40:37.887" LastActivityDate="2011-02-16T18:40:37.887" />
  <row Id="10274" PostTypeId="4" CreationDate="2011-02-16T18:40:37.887" Score="0" ViewCount="" Body="Capacitors are energy storage devices.  They are also used for filtering." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-16T19:50:49.387" LastActivityDate="2011-02-16T19:50:49.387" />
  <row Id="10275" PostTypeId="5" CreationDate="2011-02-16T18:41:49.693" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-16T18:41:49.693" LastActivityDate="2011-02-16T18:41:49.693" />
  <row Id="10276" PostTypeId="4" CreationDate="2011-02-16T18:41:49.693" Score="0" ViewCount="" Body="This tag deals with use of surface-mount devices (e.g., 0603 resistors, TQFP ICs) as opposed to through-hole devices (e.g., DIPs)" OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-16T19:50:51.027" LastActivityDate="2011-02-16T19:50:51.027" />
  <row Id="10277" PostTypeId="5" CreationDate="2011-02-16T18:42:25.717" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-16T18:42:25.717" LastActivityDate="2011-02-16T18:42:25.717" />
  <row Id="10278" PostTypeId="4" CreationDate="2011-02-16T18:42:25.717" Score="0" ViewCount="" Body="ARM is a popular series of 32-bit microcontrollers that is in various vendors' ICs." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-16T19:50:52.523" LastActivityDate="2011-02-16T19:50:52.523" />
  <row Id="10279" PostTypeId="5" CreationDate="2011-02-16T18:42:47.883" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-16T18:42:47.883" LastActivityDate="2011-02-16T18:42:47.883" />
  <row Id="10280" PostTypeId="4" CreationDate="2011-02-16T18:42:47.883" Score="0" ViewCount="" Body="If you are asking about a specific protocol, e.g., Bluetooth, please use that tag instead." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-16T19:50:54.317" LastActivityDate="2011-02-16T19:50:54.317" />
  <row Id="10281" PostTypeId="2" ParentId="10265" CreationDate="2011-02-16T18:49:36.237" Score="7" ViewCount="" Body="&lt;p&gt;I'd guess that it's an unregulated power supply, meaning you'll see the 21V under the rated load (1.2A). 26V is its open circuit voltage.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2011-02-16T18:49:36.237" CommentCount="2" />
  <row Id="10282" PostTypeId="1" AcceptedAnswerId="10285" CreationDate="2011-02-16T19:24:29.190" Score="6" ViewCount="180" Body="&lt;p&gt;Is the Microblaze soft cpu better than the Cortex M3 soft cpu in terms of functionality?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given all the buzz about the ARM based processors, I was wondering if to implement an ARM processor on my FPGA or if I should stick to the Microblaze that comes with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any major difference in terms of performance or functionality that I should consider?&lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-02-16T23:49:38.807" Title="Is the Microblaze soft cpu better than the Cortex M3 soft cpu" Tags="&lt;fpga&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="10283" PostTypeId="1" CreationDate="2011-02-16T19:45:36.693" Score="1" ViewCount="92" Body="&lt;p&gt;If the minimum load of a &lt;a href=&quot;http://sensing.honeywell.com/index.cfm/ci_id/155943/la_id/1/document/1/re_id/0&quot; rel=&quot;nofollow&quot;&gt;sensor&lt;/a&gt;(page 7) is 65k Ohm, what does that mean?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does it mean that the sensor needs at least a 65k Ohm resistor, so a 100K Ohm is good?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or does it mean the sensor needs at least a certain amount of current drawn off through the resistor, so a 10K Ohm resistor is good?&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-02-16T20:52:27.837" Title="What is a minimum load?" Tags="&lt;sensor&gt;&lt;resistor&gt;&lt;design&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="10285" PostTypeId="2" ParentId="10282" CreationDate="2011-02-16T19:52:17.857" Score="5" ViewCount="" Body="&lt;p&gt;The two major points are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The Microblaze is a well supported soft core.  Many other IP designs are made to interface with it.  ARM is popular, but you'll have less support available, especially from Xilinx, who designed the Microblaze.&lt;/li&gt;&#xA;&lt;li&gt;Using an ARM core will let you use compilers (and code) designed for the ARM architecture, which is desirable because (according to my totally unbased guess) more code is written for ARM than for Microblaze.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I'm not familiar enough with either processor to make further comparisons without a list of priorities.  What do you value in this processor? &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-16T19:52:17.857" CommentCount="1" />
  <row Id="10286" PostTypeId="2" ParentId="10282" CreationDate="2011-02-16T19:57:54.047" Score="2" ViewCount="" Body="&lt;p&gt;The Microblaze processor has the advantage that it was designed for use on  Xilinx FPGAs and will therefore offer more performance than the ARM. It also has additional features such as hardware floating-point operations.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-16T19:57:54.047" CommentCount="4" />
  <row Id="10287" PostTypeId="2" ParentId="10283" CreationDate="2011-02-16T20:23:49.633" Score="0" ViewCount="" Body="&lt;p&gt;My first guess is that this sensor needs a minimum load to be stable. With a high load the output may not be stable, or the output regulation may provide a significant error. I can recall that a voltage regulator like a LM317 also specifies a minimal load current, which is the minimal load you need to provide for the regulation to be stable. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you could try though is get the sensor and just measure the signal open ended (no load attached except your multimeter voltage probes). If it's all over the place or just not right (like the output voltage is clipping) you may need to add a more significant load (try like 56k first). Your multimeter is typically going to have a load of over 1 M ohm, maybe even more.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-02-16T20:23:49.633" CommentCount="1" />
  <row Id="10288" PostTypeId="1" CreationDate="2011-02-16T20:27:36.933" Score="2" ViewCount="175" Body="&lt;p&gt;I have a task to drive four led's from a 4-20mA loop. I have 24v for the led side so I need to convert the current into something that can drive the LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know I can use a 250r resistor as the converter in the loop which will give me 1-5v from 4-20ma respectively, now I need to get this voltage to drive the LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I simply connect a transistor base to the 1-5v point, ground the emitter and drive the LEDs from the 24v via dropping resistors via the collector??&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It needs to be a variable drive as the brightness of the LEDs must vary with the 4-20ma signal.&lt;/p&gt;&#xA;" OwnerUserId="3047" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-17T16:54:10.393" LastActivityDate="2011-02-18T08:13:02.217" Title="Drive led's from 4-20mA source" Tags="&lt;led&gt;&lt;transistor&gt;&lt;4-20ma&gt;" AnswerCount="2" />
  <row Id="10289" PostTypeId="2" ParentId="10283" CreationDate="2011-02-16T20:52:27.837" Score="3" ViewCount="" Body="&lt;p&gt;Because the diagram on that page:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/hh6GH.png&quot; alt=&quot;Figure 10&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;shows &quot;Voltage Out&quot; (i.e, your ADC input) at the far right, I'm going to assume it's asking for a minimum output current to ensure stability, therefore, you need a resistor of 65k or less resistance (500uA @ 100% humidity) or more current) to get a stable output. To put it another way, 65k is the largest resistor you're allowed to have there.  If the resistor was internal to an ADC block, I would interpret it as the minimum resistance/impedance of the ADC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Typically, power supplies specify a minimum current (or maximum load resistance) to maintain stability, while sensors, opamps, and DACs have a minimum output impedance (or maximum current) required to maintain accuracy.  The way I'm reading it,his one seems to be backwards to the convention.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's interesting that they claim an operating current of 200uA when their minimum load draws 500uA at 3V3.  Perhaps this value doesn't include the output current, or a marketer is specifying the device at 0% humidity and 0V out?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, the only way to really know is to call Honeywell and ask for clarification, or to attach the output to an oscilloscope and pot and see whether it's both stable and accurate at various impedances below, at, and above 65k.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-16T20:52:27.837" />
  <row Id="10290" PostTypeId="2" ParentId="10288" CreationDate="2011-02-16T21:01:30.227" Score="4" ViewCount="" Body="&lt;p&gt;I believe you can simply connect all four LED's in series (observe correct polarity) with the 250 ohm resistor. The 4-20mA transmitter will take care adjusting the current/voltage for you. Just be sure the LED's rated average current is around 20mA, that way the LED's are fully lit at 20mA and dim at 4mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*EDIT - The 4-20mA transmitter should have a specification called &quot;load range&quot;, your resistor should somewhere in this range.&lt;/p&gt;&#xA;" OwnerUserId="2612" LastEditorUserId="2612" LastEditorDisplayName="" LastEditDate="2011-02-16T21:30:43.640" LastActivityDate="2011-02-16T21:30:43.640" CommentCount="7" />
  <row Id="10291" PostTypeId="1" CreationDate="2011-02-16T22:12:15.197" Score="2" ViewCount="255" Body="&lt;p&gt;I've got an issue that appears to be caused by damaged resistors that are either open circuited or of too low a value due to contamination.  The problem is that they're gigaohm resistors, so to a multimeter, they're &lt;em&gt;always&lt;/em&gt; open-circuited.  How can I measure the resistance, or, at least, test the continuity?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-02-17T13:08:34.883" Title="How to measure gigaohm resistors?" Tags="&lt;resistor&gt;&lt;multimeter&gt;&lt;resistance&gt;&lt;production-testing&gt;" AnswerCount="3" />
  <row Id="10292" PostTypeId="1" CreationDate="2011-02-16T22:17:57.477" Score="2" ViewCount="160" Body="&lt;p&gt;Why was 4mA and 20mA picked? Was it an arbitrary choice? I don't see this signalling method used much in hobbyist projects, why's that? What are these current signalling loops best for?&lt;/p&gt;&#xA;" OwnerUserId="1688" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-17T15:19:40.073" LastActivityDate="2011-02-17T15:19:40.073" Title="4-20mA Current Loops" Tags="&lt;4-20ma&gt;&lt;current-signal&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="10293" PostTypeId="2" ParentId="10292" CreationDate="2011-02-16T22:21:39.080" Score="2" ViewCount="" Body="&lt;p&gt;The 20mA current loop goes back to old school teletype, the sort of thing you might have encountered in the 1950s.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-16T22:21:39.080" />
  <row Id="10295" PostTypeId="2" ParentId="10292" CreationDate="2011-02-16T22:53:15.950" Score="0" ViewCount="" Body="&lt;p&gt;I agree with JustJeff - this just sort of happened.  Since it's a signal and not power, you don't want current to be too high (so you can use low gauge wire).  20mA is not too high - comparable to what you might find in a DIO port on a microcontroller if you're lucky.  It's at least a range of values that work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen them used in situations where voltage signaling just doesn't cut it.  Current in one end of a wire is current out at the other.  This isn't true for voltage - especially for long wires.  There will be significant voltage drop over distance which can affect your readings.  The current signal doesn't have this problem.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-16T22:53:15.950" />
  <row Id="10296" PostTypeId="1" AcceptedAnswerId="10521" CreationDate="2011-02-16T22:57:15.690" Score="3" ViewCount="275" Body="&lt;p&gt;I would like to mount a &lt;a href=&quot;http://www.vishay.com/ir-emitting-diodes/list/product-81011/&quot; rel=&quot;nofollow&quot;&gt;TSAL6400 led&lt;/a&gt; on a single AA size battery box, with a simple ON/OFF switch. My problem is that the LED needs exactly 1.35V to function at its rated brightness. At this voltage it uses 100 mA current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to use Sanyo Eneloop batteries. I've measured them and they have 1.405V one day after charging. I think they will drop to about 1.395V @ 100mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've followed the LED tutorials, which all say I have to wire a resistor in serial with the LED. My problem is that if I calculate, that resistor needs to have (1.4-1.35)/0.1 = 0.5 Ohm resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is that what would you recommend me to do this project? I would like to make the box as little as possible, I'm planning on mounting everything directly on a single AA box.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Shell I use two 1 Ohm resistors in parallel, to get a 0.5 Ohm resistor?&lt;/li&gt;&#xA;&lt;li&gt;Can I possibily use some micro turn potentiometers for my problem? It would be the best solution, as then I could just use different batteries, as all I would need to do is to set it after changing batteries. I am mostly interested in this solution. Can someone explain to me what is the best way to get 1.35V from 1.4V-1.6V sources using a simple potentiometer?&lt;/li&gt;&#xA;&lt;li&gt;Maybe it's an overkill, and I really don't know how to use them, but can I use a voltage regulator for this purpose? I mean is there a voltage regulator which is small and can provide as little as 0.4V drop?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;UPDATE:&#xA;I've made some measurements on my LED:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;1.184 V -  12 mA&lt;/li&gt;&#xA;&lt;li&gt;1.315 V -  75 mA&lt;/li&gt;&#xA;&lt;li&gt;1.345 V -  93 mA&lt;/li&gt;&#xA;&lt;li&gt;1.357 V - 100 mA&lt;/li&gt;&#xA;&lt;li&gt;1.380 V - 110 mA&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The last one is when I connected it directly to a Eneloop AA battery. By definition it's overdriving, but I don't know how dangerous it is for the LED.&#xA;&lt;img src=&quot;http://i.imgur.com/XHWDh.png&quot; alt=&quot;LED measurement&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3049" LastEditorUserId="3049" LastEditorDisplayName="" LastEditDate="2011-02-18T03:31:19.793" LastActivityDate="2011-02-21T19:47:42.197" Title="how to drive a 1.35V led with a 1.4V AA battery" Tags="&lt;led&gt;&lt;resistor&gt;&lt;voltage-regulator&gt;&lt;potentiometer&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="1" />
  <row Id="10297" PostTypeId="2" ParentId="10291" CreationDate="2011-02-16T23:03:33.153" Score="2" ViewCount="" Body="&lt;p&gt;Many Fluke meters (e.g. 87,287) have a NanoSiemens conductivity range which will measure up to 100 Gigohms- needs to be manually ranged up from the ohms range. 1 gigohm = 1 nanosiemens 10 gigohms = 0.1 nanosiemens. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, most DMMs have with a 10M input impedance (easily checked with a second meter), so a resistor with value R in series with the millivolt range will form an R+10M/10M voltage divider. So applying 10 volts through a 1 gigohm resistor will read around 99 millivolts. &#xA;A close-enough approximation for high value resistors from a 10V supply would be resistance in gigohms = 100/millivolts.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="1681" LastEditorDisplayName="" LastEditDate="2011-02-16T23:15:36.603" LastActivityDate="2011-02-16T23:15:36.603" CommunityOwnedDate="2011-02-16T23:03:33.153" />
  <row Id="10298" PostTypeId="2" ParentId="10291" CreationDate="2011-02-16T23:05:57.030" Score="1" ViewCount="" Body="&lt;p&gt;I'll assume that you're able to isolate the resistor from the rest of the circuit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You probably need to construct a high-impedance analog buffer.  It doesn't need to be super-fast, but it does need to be high impedance.  A very high impedance amplifier is &lt;a href=&quot;http://www.national.com/pf/LM/LMP7721.html&quot; rel=&quot;nofollow&quot;&gt;National's LMP7721&lt;/a&gt;, requiring only 3 femtoamps of bias current. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have your buffer, get another resistor with a resistance comparable to the one you want to test (a known value).  Connect one side of this resistor to ground, and the other to a probe and to your buffer.  Then, apply a voltage to one side of your resistor, and connect your buffered probe to the other side.  Measure the voltage at the output of your buffer and solve the voltage divider to determine the unknown resistance &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may not need a buffer if your meter has extremely low impedance when measuring voltage.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-17T02:43:29.843" LastActivityDate="2011-02-17T02:43:29.843" CommentCount="3" />
  <row Id="10299" PostTypeId="5" CreationDate="2011-02-16T23:08:38.360" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-16T23:08:38.360" LastActivityDate="2011-02-16T23:08:38.360" />
  <row Id="10300" PostTypeId="4" CreationDate="2011-02-16T23:08:38.360" Score="0" ViewCount="" Body="An op-amp is an analog amplifier or buffer." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-16T23:10:54.723" LastActivityDate="2011-02-16T23:10:54.723" />
  <row Id="10301" PostTypeId="5" CreationDate="2011-02-16T23:09:15.423" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-16T23:09:15.423" LastActivityDate="2011-02-16T23:09:15.423" />
  <row Id="10302" PostTypeId="4" CreationDate="2011-02-16T23:09:15.423" Score="0" ViewCount="" Body="A UART (Universal Asynchronous Receiver Transmitter) is a chip that produces signals for a serial port." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-16T23:11:28.250" LastActivityDate="2011-02-16T23:11:28.250" />
  <row Id="10303" PostTypeId="5" CreationDate="2011-02-16T23:09:36.297" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-16T23:09:36.297" LastActivityDate="2011-02-16T23:09:36.297" />
  <row Id="10304" PostTypeId="4" CreationDate="2011-02-16T23:09:36.297" Score="0" ViewCount="" Body="SPI is a 3-wire serial bus interface." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-16T23:11:18.500" LastActivityDate="2011-02-16T23:11:18.500" />
  <row Id="10305" PostTypeId="5" CreationDate="2011-02-16T23:10:34.377" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-16T23:10:34.377" LastActivityDate="2011-02-16T23:10:34.377" />
  <row Id="10306" PostTypeId="4" CreationDate="2011-02-16T23:10:34.377" Score="0" ViewCount="" Body="DSP stands for Digital Signal Processing.  Use this tag for DSP-related question, but try to select a specific chip or software tag when possible." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-16T23:11:26.737" LastActivityDate="2011-02-16T23:11:26.737" />
  <row Id="10307" PostTypeId="2" ParentId="10296" CreationDate="2011-02-16T23:22:53.897" Score="5" ViewCount="" Body="&lt;p&gt;Use a switching boost converter to, say, 3V. The output will be regulated, so you will be able to get a stable 100 mA through the LED with a suitable resistor, and the battery will last much longer than if you connected it directly to the LED and resistor.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-16T23:22:53.897" CommentCount="5" />
  <row Id="10308" PostTypeId="2" ParentId="10296" CreationDate="2011-02-16T23:26:10.333" Score="1" ViewCount="" Body="&lt;p&gt;LEDs need current, not voltage. When an LED is conducting it imposes a certain voltage at its terminals but the current that flows through is conditioned by a &quot;conditioning circuit&quot; (which can be a simple resistor in series). You are right, you need 0.5Ohm resistance (which, just like you said, you can get with two 1Ohm resistors in parallel) but once is a very small value it probably will work well without it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to turn led ON/OFF maybe the use of a transistor should be a better option. The transistor works as a LED drive. &lt;/p&gt;&#xA;" OwnerUserId="1074" LastActivityDate="2011-02-16T23:26:10.333" CommentCount="3" />
  <row Id="10309" PostTypeId="2" ParentId="10282" CreationDate="2011-02-16T23:49:38.807" Score="3" ViewCount="" Body="&lt;p&gt;A 'standard' CPU core will use a lot more resources in an FPGA than one specifically targetted at a particular FPGA. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-16T23:49:38.807" />
  <row Id="10310" PostTypeId="2" ParentId="10296" CreationDate="2011-02-16T23:53:48.960" Score="1" ViewCount="" Body="&lt;p&gt;As Leon Heller says, you will need to boost the voltage to something higher. The 1.35V forward voltage you mention is &lt;em&gt;not&lt;/em&gt; an accurate reflection of the voltage you will get with 100mA forward current, but a statistical average.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the data sheet, it could be as high as 1.6V and as low as ... who knows, the data sheet doesn't say. If we suppose that the distribution is symmetrical, it could be as low as 1.1V, in which case the current you will get with a 1.4V battery and a 0.5&amp;#937; resistor could be anything between zero and 600mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are only building one of these, you might well get a fairly 'average' LED and get a reasonable brightness - but you can't guarantee it.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-02-16T23:53:48.960" CommentCount="2" />
  <row Id="10311" PostTypeId="2" ParentId="10292" CreationDate="2011-02-17T00:24:47.717" Score="11" ViewCount="" Body="&lt;p&gt;4-20mA loops are used a lot in industrial environments.  The current signal is generally less susceptible to noise and signal loss over long cables.  It's especially popular for things like transducers, where the transducer is actually powered with the signal line.  This allows a 2 wire connection, where one line supplies the power rail (typically 24V) and the current returned is based on the measured value (temp, pressure, etc.).  This can help save money on wire in a large plant, but most hobbyist probably don't care about such things or need to worry about electrically noisy environments.  4mA allows a minimum current draw by the transducer even if there is no signal.  It also provides trouble shooting capability, allowing to distinguish between a signal of 0 and a lost connection or powered down unit.  I don't know where 20mA came from, but 20mA is easily dropped over a 500 Ohm resistor for a 0-10V signal or over a 250 Ohm resistor for a 0-5V signal.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-02-17T00:24:47.717" CommentCount="2" />
  <row Id="10312" PostTypeId="1" CreationDate="2011-02-17T00:30:55.030" Score="1" ViewCount="112" Body="&lt;p&gt;I am working on a circuit that is completly powered by 5VDC from a USB port. The circuit uses SSR's to turn on and off 120VAC from a standard wall plug; the 120VAC powers a high-power heater of sorts. Now it appears as though I am also going to need to add a PC fan into the mix. Most of the PC fans that I have seen run off 12 VDC. So what would be the cheapest and easiest way to get 12VDC to my fan. I am thinking that it doesn't have to be well regulated and smooth becuase the ONLY thing it will be used for is powering this fan. I will likely use another lower power SSR to turn the 12VDC on and off from my MCU.  Extra points for a space saving solution as well!&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2011-04-02T12:33:15.340" Title="Crude/inexpensive AC to DC transformer" Tags="&lt;dc&gt;&lt;transformer&gt;&lt;ac&gt;&lt;fan&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="10313" PostTypeId="2" ParentId="10312" CreationDate="2011-02-17T00:55:45.740" Score="0" ViewCount="" Body="&lt;p&gt;Ok here's my best guess.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can get a transform at Radioshack for $4.49 that will drop the 120VAC down to 12.6VAC. (Suprising I couldn't find a transformer of this type cheaper on digikey or mouser)&#xA;Transformer: &lt;a href=&quot;http://www.radioshack.com/product/index.jsp?productId=2102494#inTheBox&quot; rel=&quot;nofollow&quot;&gt;http://www.radioshack.com/product/index.jsp?productId=2102494#inTheBox&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then I could use four 1N4007 diodes to make a full wave rectifier. Cost of diodes is about a dollar total.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally stick a large capacitor at the output to smooth out the signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This puts the total cost around $7.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know the output won't be prefect and it will be a little higher than 12VDC but I think it should be fine for a PC fan...&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2011-02-17T00:55:45.740" CommentCount="2" />
  <row Id="10314" PostTypeId="1" CreationDate="2011-02-17T00:56:24.867" Score="0" ViewCount="43" Body="&lt;p&gt;For all those out there with solenoid experience I'm looking at a project using them for the &lt;a href=&quot;http://555contest.com&quot; rel=&quot;nofollow&quot;&gt;555 contest&lt;/a&gt;. The spec on most solenoids is ounces of force (at least in the price range I'm looking at). Aside from my disgust at the imperial units, I can fathom what the units mean, but not what kinds of things that amount of force could accomplish.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of actions could 24 oz of force achieve? Is it closer to denting a peach or denting a bowling ball? Is it depended on distance? Drive current? Anything else? Thanks for all your help!&lt;/p&gt;&#xA;" OwnerUserId="404" LastActivityDate="2011-02-17T08:00:52.000" Title="Solenoid Relative Force" Tags="&lt;solenoid&gt;" AnswerCount="2" />
  <row Id="10315" PostTypeId="1" CreationDate="2011-02-17T01:16:27.697" Score="1" ViewCount="70" Body="&lt;p&gt;We have been using the Allegro A6276ELWTR-T. This is a 16 channel LED cathode driver with serial data input and current control. Allegro is shutting their fab and discontinuing this part. Any one have suggestions for a good replacement? 8-16 channels would be ideal and the part must be surface mount. &lt;/p&gt;&#xA;" OwnerUserId="3050" LastActivityDate="2011-02-17T01:38:13.747" Title="Looking for a 7 segment LED Driver" Tags="&lt;led&gt;" AnswerCount="1" />
  <row Id="10316" PostTypeId="2" ParentId="10312" CreationDate="2011-02-17T01:18:50.230" Score="4" ViewCount="" Body="&lt;p&gt;Looks like MPJA.com has 12V, 300mA power supplies for $\$$1.25 and if you buy 50 they're $\$$.99. That is hard to beat! But they aren't the smallest solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mpja.com/prodinfo.asp?number=18295+PD&quot; rel=&quot;nofollow&quot;&gt;http://www.mpja.com/prodinfo.asp?number=18295+PD&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1235" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-04-01T22:42:29.410" LastActivityDate="2011-04-01T22:42:29.410" />
  <row Id="10317" PostTypeId="1" CreationDate="2011-02-17T01:24:52.947" Score="3" ViewCount="109" Body="&lt;p&gt;I have twenty LEDs that I want to light up. I planned out a few possible circuits, which I describe below along with a few questions. Would any of them not work, and why? Anything else I should be taking into consideration but haven't? The LED has the following specs:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Vmin: 2.8V&#xA;Vmax: 3.5V&#xA;If: 20 mA&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;From what I understand, the Vmin is essentially the same as Vd in &lt;a href=&quot;http://upload.wikimedia.org/wikipedia/commons/a/a5/Diode-IV-Curve.svg&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; diagram, so the current will be 0 until it reaches that voltage. Is this correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the LEDs are connected in series, that means that I'll need 20*2.8V=56V in total to get current passing through every LED. I calculated the approximate amount of power necessary (60V*0.02A=1.2W) and compared it to the amount that can be provided by a typical AA battery, which I've been told usually provide around 800mA of current (1.5V*0.8A=1.2W). Seeing as they're the same, I'm pretty sure it'll be possible to step up from a single AA to what's needed to light the LEDs. So far, I know of the SEPIC, which I'm reading up on right now. Is there a better way of accomplishing this? Possibly without needing inductors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another solution I've considered is connecting them in parallel, which I recall reading somewhere that it's a bad idea unless there's a resistor in series with each of the LEDs. Two AA batteries in series would be enough in this case, providing a 3.0V potential across each branch. Since the LED takes 2.8V, the resistor would take up the remaining 0.2V, and to get a 20mA current, I'll need a (0.2V/0.02A=10ohms) 10 Ohm resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could also plug it into an adapter which converts the AC electricity from the outlet to 15V (the current rating on the adapter means the maximum it can give and not the amount it'll always give, right?). In this case, I could separate the LEDs into four groups of five (which is convenient given their layout), each LED in a group of five is connected in parallel to each other, and the four groups are connected in series. That would give a voltage of (15V/4) 3.75V across each group of five, and since the LEDs in the group are in parallel, they'll each get 3.75V too. The current needed would then be (0.02A*5) 100mA. The voltage across the resistor in series with the LEDs is (3.75V-2.8V) 0.95V. The resistance needed would then be (0.95V/0.02A) about 50 ohms.&lt;/p&gt;&#xA;" OwnerUserId="2836" LastActivityDate="2011-02-17T04:57:17.690" Title="Powering twenty high intensity LEDs" Tags="&lt;led&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="10318" PostTypeId="2" ParentId="10296" CreationDate="2011-02-17T01:36:42.773" Score="1" ViewCount="" Body="&lt;p&gt;You don't &lt;em&gt;always&lt;/em&gt; have to have a resistor.  They are there to limit the amount of current going through the LED.  LEDs have a maximum current rating, and can also handle a higher current if you PWM them for short periods of time.  Anyhow, if your battery has a limited output current, you don't even need the resistor.  For example, with LED throwies, you typically use a coin cell.  I can't remember the exact amount, but I think they max out at 20mA, which is well within the rating of most LEDs.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-17T01:36:42.773" CommentCount="3" />
  <row Id="10319" PostTypeId="2" ParentId="10315" CreationDate="2011-02-17T01:38:13.747" Score="1" ViewCount="" Body="&lt;p&gt;Texas Instruments has a good selection &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=480&amp;amp;uiTemplateId=NODE_STRY_PGE_T&quot; rel=&quot;nofollow&quot;&gt;Here.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-17T01:38:13.747" />
  <row Id="10320" PostTypeId="1" CreationDate="2011-02-17T01:54:20.880" Score="3" ViewCount="40" Body="&lt;p&gt;We have been using the Allegro UDQ2559LB. This is a quad (4 channel) low side power driver (used to drive relay and lamp loads) with about 0.5 amp per channel capability and overload, short circuit, and over temperature protection. Allegro is shutting their fab and discontinuing this part. Any one have suggestions for a good replacement? 4 channels would be ideal and the part must be surface mount. &lt;/p&gt;&#xA;" OwnerUserId="3050" LastActivityDate="2011-02-17T21:22:29.137" Title="Looking for a quad low side power driver IC" Tags="&lt;driver&gt;" AnswerCount="1" />
  <row Id="10321" PostTypeId="2" ParentId="10314" CreationDate="2011-02-17T02:36:52.873" Score="2" ViewCount="" Body="&lt;p&gt;The behavior you're describing (denting stuff) is a function of &lt;strong&gt;pressure&lt;/strong&gt; not force. I could dent a bowling ball with a few grams of force if it was in a small enough area.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not just being pedantic, it's a key to thinking of what you want to do. 24oz of force (yes, it is at a specified current) can be increased over small distances using levers, or you can get a smaller force over a longer distance, again using a lever. Force is just part of the equation; you need to consider the Work that Force will do.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-02-17T02:36:52.873" />
  <row Id="10322" PostTypeId="1" CreationDate="2011-02-17T02:40:51.527" Score="9" ViewCount="349" Body="&lt;p&gt;Just a general electronics question: What is negative voltage, like -5 Volt?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From my basic knowledge, power is generated by electrons wandering from the minus to the plus side of the power source (assuming DC power here). Is negative voltage when electrons wander from + to -?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why do some devices even need it, what is so special about it?&lt;/p&gt;&#xA;" OwnerUserId="3051" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-17T16:03:30.800" LastActivityDate="2011-02-17T16:03:30.800" Title="What is negative voltage?" Tags="&lt;electronics&gt;&lt;voltage&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="1" />
  <row Id="10323" PostTypeId="2" ParentId="10322" CreationDate="2011-02-17T02:49:05.923" Score="17" ViewCount="" Body="&lt;p&gt;Someone may have better words to explain this then me, but the big thing you have to remember is voltage is a potential difference. In most cases the &quot;difference&quot; part is a difference between some potential and ground potential. When someone says -5v they are saying that you are below ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also need to keep in mind that voltage is relative. So like I mentioned before most people reference to &quot;ground&quot;, but what is ground? You can say ground is earth ground, but what about the case when you have a battery powered device that has no contact to ground. In this situation we have to treat some arbitrary point as &quot;ground&quot;. Usually the - terminal on the battery is what we consider from this reference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now consider the case that you have 2 batteries in series. If both were 5 volts then you would say you would have 10 volts total. But this assumption is based off of &quot;ground&quot; as being the negative terminal on the battery that isn't touching the other battery and then 10V as being the location of the positive terminal that isn't touching the other battery. In this situation we can make the decision that we want to make the connection between the 2 batteries be our &quot;ground&quot; reference. This would then result in +5v on one end and -5v on the other end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is what I was trying to explain:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;+10v   +++   +5v&#xA;       | |&#xA;       | | &amp;lt; Battery&#xA;       | |&#xA;+5v    ---   0v&#xA;       +++&#xA;       | |&#xA;       | | &amp;lt; Another Battery&#xA;       | |&#xA;0v     ---   -5v&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-02-17T05:07:54.243" LastActivityDate="2011-02-17T05:07:54.243" CommentCount="5" />
  <row Id="10324" PostTypeId="2" ParentId="10322" CreationDate="2011-02-17T04:00:49.600" Score="11" ViewCount="" Body="&lt;p&gt;Imagine you're measuring the height of a car. You could take a tape measure and measure the distance from the ground to the roof of the car. &quot;The roof of this car is 4 feet above the ground.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also stand on the roof of the car and dangle the same tape measure down to the ground. &quot;The ground is 4 feet below the roof of this car.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage works the same way. The negative sign is just a convention, in the same way that the car has the same height, regardless of which way you measure it. Flip your multimeter leads, and the negative sign will disappear.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-02-17T04:00:49.600" CommentCount="4" />
  <row Id="10325" PostTypeId="2" ParentId="10317" CreationDate="2011-02-17T04:11:03.317" Score="2" ViewCount="" Body="&lt;p&gt;56 V is inconveniently high, and in reality, your 20 * 2.8 V will vary as the LEDs heat up. You could do it with a switching voltage converter, but it's not the easiest way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your plan of putting many LEDs in parallel is good as long as you include the resistors you describe. As the battery discharges, the voltage will sag, and the LEDs will dim.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd start with one LED and get the resistor right so you get the brightness you want. Your 10 ohm calculation is a good start. Then add LED/resistor pairs in parallel. If the battery voltage sags, add more batteries in parallel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't quite understand your last plan-- maybe provide a diagram? There is likely a parallel combination of series LED strings that will work. You'll definitely need a resistor in each string.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-02-17T04:11:03.317" />
  <row Id="10326" PostTypeId="2" ParentId="10317" CreationDate="2011-02-17T04:15:46.740" Score="2" ViewCount="" Body="&lt;p&gt;There are &lt;a href=&quot;http://www.marktechopto.com/Engineering-Services/toshiba-constant-current-led-drivers.cfm&quot; rel=&quot;nofollow&quot;&gt;specialized ICs&lt;/a&gt; on the market that act like constant-current sinks, ensuring uniform LED brightness even with varying power supplies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would suggest going with the 15V adapter and driver ICs for the best performance with minimal headache.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your maths seem to make sense at first glance. Also, a boost converter is most likely a better choice than a SEPIC in terms of simplicity. I don't think charge-pump (inductorless) voltage boosting would work well in this sort of application.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-17T04:15:46.740" />
  <row Id="10327" PostTypeId="1" AcceptedAnswerId="10347" CreationDate="2011-02-17T04:17:07.813" Score="4" ViewCount="111" Body="&lt;p&gt;What prefixes should be used on reference designators for components of various types?  I think we can all agree that &quot;R##&quot; refers to a resistor, &quot;C##&quot; refers to a capacitor, and &quot;L##&quot; refers to an inductor.  Beyond that, it appears to be a mishmash of conventions.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen both &quot;IC&quot; and &quot;U&quot; used for chips.   &quot;Q&quot;, &quot;T&quot;, and &quot;M&quot; have been used for transistors and MOSFETs.  Ordinarily, &quot;D##&quot; is used for diodes, but LEDs and Zeners get special treatment on some boards.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What standards are available for reference, and who endorses them?  JEDEC, ISO, IEEE, and other standardization bodies are welcome references (though I'd prefer an inexpensive standard), but I'm also curious to see what's used at various companies other than my own.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:  What I'd really like to see is a list &lt;strong&gt;in an answer here&lt;/strong&gt; which complies with the standard (even if it's just a quote).&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-17T19:32:39.577" LastActivityDate="2011-02-17T19:32:39.577" Title="Standard nomenclature for component types" Tags="&lt;components&gt;&lt;standard&gt;" AnswerCount="2" />
  <row Id="10328" PostTypeId="2" ParentId="10327" CreationDate="2011-02-17T04:40:41.490" Score="3" ViewCount="" Body="&lt;p&gt;I've used the canonical R, C, D, Q, U scheme at both career stops thus far.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first stop would differentiate between 'male' and 'female' connectors by using J for 'jacks' (i.e. female) and P for 'pins' (i.e. male).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I currently use RT for NTC/PTC thermistors and RV for MOVs. Odd that the powers-that-be only opted for such a narrow amount of reference designator innovation.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-17T04:40:41.490" CommentCount="3" />
  <row Id="10329" PostTypeId="1" CreationDate="2011-02-17T04:42:26.530" Score="2" ViewCount="202" Body="&lt;p&gt;I'm currently working with the flyport from OpenPicus, it has 24FJ256GA106 PIC processor in it and I was looking for the best way to send information from the flyport to a server. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to know how can I send this data? In a packet form to the server? Does anyone know where I can find information on accomplishing this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I already have previous experience with .Net programming and was hoping to have it pushed to a SQL server. However, getting the data sent would be enough information to get me started.&lt;/p&gt;&#xA;" OwnerUserId="3054" LastActivityDate="2011-02-18T15:54:57.023" Title="Working with PIC to send data to server" Tags="&lt;pic&gt;&lt;microprocessor&gt;&lt;tcp-ip&gt;&lt;network-interface&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10330" PostTypeId="2" ParentId="10317" CreationDate="2011-02-17T04:57:17.690" Score="2" ViewCount="" Body="&lt;p&gt;The most efficient method to do this would be with a boost converter, preferably one that has current control.  Hundreds of LED drivers which are essentially modified power ICs are available nowadays, including ones that operate from single alkaline cells down to 0.9 V e.g. the &lt;a href=&quot;http://www.micrel.com/_PDF/mic2282.pdf&quot; rel=&quot;nofollow&quot;&gt;Micrel MIC2282&lt;/a&gt; (for more look up &quot;single cell led driver&quot;) which should be able to drive up to 33 V strings (~8 LEDs), though asking it do that from a single cell may be pushing it &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a &lt;a href=&quot;http://electronics.stackexchange.com/questions/7344/led-flashlight-project-need-transistor-ideas/7345#7345&quot;&gt;previous question&lt;/a&gt;, I did actually recommend a power IC, the Linear LT1618 (not outwardly marketed as an LED driver, but an application schematic showed it as one)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whatever you choose, powering (20) 20 mA LEDs from a single alkaline cell is probably not feasible just because the voltage will dip so low with that load it will undervolt most controllers.  If you could use two, you'd probably be in business.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-02-17T04:57:17.690" />
  <row Id="10331" PostTypeId="2" ParentId="10032" CreationDate="2011-02-17T05:41:45.043" Score="1" ViewCount="" Body="&lt;p&gt;Both Xilinx and Altera provide their development environments for free. They are meant for designing the logic for placing on FPGA's and CPLD's, but you can simply use them in simulation mode. They let you place items on a schematic view like the above, and when you need more advanced components that are not built in, you can write their logic in VHDL.&lt;/p&gt;&#xA;" OwnerUserId="131" LastActivityDate="2011-02-17T05:41:45.043" />
  <row Id="10332" PostTypeId="2" ParentId="10288" CreationDate="2011-02-17T07:14:53.387" Score="-2" ViewCount="" Body="&lt;p&gt;Thanks all so far, i will do some tests today on the bench and see what plays best. I have the LDR and leds plus some resitors arriving today so will be able to try the whole setup. Interesting about the 4mA current load to extinguish the leds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Setup tested and works well, i can get a 5k - 40k swing by padding the led with 375R to keep it dim at 4mA, that is plenty enough swing for the application and i have moved on to building the unit now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm amazed that it can be done with only a reseistor, an led and an LDR, very useful stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks to all who helped, this is a great site.&lt;/p&gt;&#xA;" OwnerUserId="3056" LastEditorUserId="3056" LastEditorDisplayName="" LastEditDate="2011-02-17T14:26:55.393" LastActivityDate="2011-02-17T14:26:55.393" CommentCount="1" />
  <row Id="10333" PostTypeId="2" ParentId="10082" CreationDate="2011-02-17T07:15:20.943" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Can it work this way: We start from, let's say, a 1.5 V supply, use a FET to connect diode to the supply for 50 ns and sense the peak current. Then we slowly increase the supply until we reach the required peak current. Will that work?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes it will work, but if it gets too much current you may burn it out, to little current and it will not lase. &#xA;Max current is usually 10 to 15 percent above its min lase current.(depends on laser)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;some good info &lt;a href=&quot;http://www.repairfaq.org/sam/laserdps.htm#dpstoc&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and an interesting chapter &lt;a href=&quot;http://www.repairfaq.org/sam/laserdps.htm#dpsmld&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;&#xA;and &lt;a href=&quot;http://www.repairfaq.org/sam/laserfaq.htm#faqtoc&quot; rel=&quot;nofollow&quot;&gt;full table of contents&lt;/a&gt;they also have some driver references and schematics&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I learned a lot from that site about how to drive some re-purposed red laser diodes that I had laying around. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I personally would start off with the lowest current possible, move it up till it lases and then calculate 10% above lasing current and make that your safe constant current, pulsed current can be higher.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-17T07:15:20.943" />
  <row Id="10334" PostTypeId="1" CreationDate="2011-02-17T07:19:02.040" Score="2" ViewCount="205" Body="&lt;p&gt;My brother in law bought a Prius recently. He's experiencing something strange with his iPod.&#xA;If he has his iPod plugged in via the USB cable to the Prius, everytime he starts up his car, it resets his iPod. If he unplugs his iPod first, starts the car and then plug in the iPod, the iPod is fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What can be the problem? Is there some sort of surge in the Prius circuitry that resets the iPod? Is there an electronic hack for the USB cable to fix this?&lt;/p&gt;&#xA;" OwnerUserId="1288" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-02-17T15:58:28.557" LastActivityDate="2011-02-17T15:58:28.557" Title="Weird Toyota Prius and USB behavior" Tags="&lt;usb&gt;&lt;usb-device&gt;&lt;ipod&gt;" AnswerCount="5" />
  <row Id="10335" PostTypeId="2" ParentId="10334" CreationDate="2011-02-17T07:35:30.067" Score="1" ViewCount="" Body="&lt;p&gt;When the car is started there is either a voltage spike or drop, as for a fix, Create your on DC-DC converter, 12v(car battery) to 5v(usb). you could easily use a simple 7805 regulator and a few caps to even out the signal, and prevent those spikes/drops.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-17T07:35:30.067" CommentCount="3" />
  <row Id="10336" PostTypeId="2" ParentId="1770" CreationDate="2011-02-17T07:53:38.883" Score="0" ViewCount="" Body="&lt;p&gt;Take a look at this answer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/4287/i-understand-arduino-now-what/4331#4331&quot;&gt;I understand Arduino: now what?&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-02-17T07:53:38.883" CommunityOwnedDate="2011-02-17T07:53:38.883" />
  <row Id="10337" PostTypeId="2" ParentId="10314" CreationDate="2011-02-17T08:00:52.000" Score="0" ViewCount="" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your 24oz is not telling us over what area, I'd guess with your odd imerial measurment that per foot or per inch. depending on which will make a big difference on your denting abliity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example if you had a nail on the end you could do some physical damage, but if its pushing a brick then it will do little at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;24oz comes to about 6 Newtons - which is very little BTW.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe posting a datasheet would be good? Little open ended.&lt;/p&gt;&#xA;" OwnerUserId="2649" LastActivityDate="2011-02-17T08:00:52.000" />
  <row Id="10338" PostTypeId="2" ParentId="758" CreationDate="2011-02-17T08:14:28.710" Score="0" ViewCount="" Body="&lt;p&gt;Are you interested in a 64K sampling rate?&#xA;Have a look &lt;a href=&quot;http://didier.longueville.free.fr/arduinoos/?p=1134&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3057" LastActivityDate="2011-02-17T08:14:28.710" />
  <row Id="10340" PostTypeId="1" CreationDate="2011-02-17T08:20:18.033" Score="0" ViewCount="59" Body="&lt;p&gt;Is it safe to use a surge protector which is plugged into a 12VDC mobile power inverter? Or will it damage the surge protector (or the inverter)?&lt;/p&gt;&#xA;" OwnerUserId="3059" LastEditorUserId="3059" LastEditorDisplayName="" LastEditDate="2011-02-17T08:29:22.717" LastActivityDate="2011-02-17T10:42:33.047" Title="safe to use surge protector with 12vDC mobile power inverter?" Tags="&lt;inverter&gt;" AnswerCount="1" />
  <row Id="10341" PostTypeId="2" ParentId="10340" CreationDate="2011-02-17T10:42:33.047" Score="1" ViewCount="" Body="&lt;p&gt;It depends on their implementation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If inverter gives you sine output(unlikely, at least for mid-range models) - you should be fine.&#xA;If inverter give you rectangle output - there is some possibility of damaging protector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would turn it on and see if they overheat. If it's not the case - you should be fine.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-17T10:42:33.047" CommentCount="3" />
  <row Id="10342" PostTypeId="2" ParentId="10334" CreationDate="2011-02-17T10:54:08.467" Score="6" ViewCount="" Body="&lt;p&gt;I would say it is very very dangerous for iPod. Eventually it might die instead of reset.&#xA;This must be the transient spike going through USB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I would take a look at it at oscilloscope.&#xA;And before that I would switch to separate 12v-&gt;USB adaptor, not the bundled one.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-17T10:54:08.467" />
  <row Id="10343" PostTypeId="2" ParentId="10334" CreationDate="2011-02-17T11:03:06.380" Score="3" ViewCount="" Body="&lt;p&gt;How about &lt;a href=&quot;http://en.wikipedia.org/wiki/Decoupling_capacitor&quot; rel=&quot;nofollow&quot;&gt;decoupling capacitors&lt;/a&gt; for the iPod? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Capacitors basically resist voltage change, so you could design a device which will go in between the iPod and USB cable and have some decoupling capacitors which should be strong enough to power the iPod while the car is starting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could have one male and one female USB port on the device and put the capacitors between the GND and +5 V pins. The data pins should be directly connected between two plugs, because iPods may need some circuitry there and since the charger does work, it would be best to use its circuitry for that. &lt;a href=&quot;http://pinouts.ru/Slots/USB_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;'s USB pinout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I've read, if we have 3 V of ripple when the car is starting, 2200µF electrolytic capacitor would probably be enough for full  USB 2.0 load, but I'm not too sure. For voltage rating, I'd take at least 25 V, but more is better in that area. You could also look for low ESR capacitors. They should work a bit better. Some people say that it's a good idea to put in parallel capacitors of several different values, because they all block noise at different frequencies. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option worth considering is to get Toyota's iPod connector, but it's going to be more expensive and defeat the purpose if having a hack.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-17T15:00:55.083" LastActivityDate="2011-02-17T15:00:55.083" CommentCount="2" />
  <row Id="10344" PostTypeId="2" ParentId="10322" CreationDate="2011-02-17T11:31:46.980" Score="0" ViewCount="" Body="&lt;p&gt;oh why not ..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To say you have a voltage of +5V at point A means that point A is 5 volts more positive than your chosen ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To say you have a voltage of -5V at point B means that 'ground' is 5 volts more positive than point B.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sign just tells you the polarity of the voltage, with respect to the ground node.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-17T11:31:46.980" />
  <row Id="10345" PostTypeId="2" ParentId="9325" CreationDate="2011-02-17T12:48:59.550" Score="4" ViewCount="" Body="&lt;p&gt;I'm going to make a few assumptions here, due to what I think is right. If you fill in more information, I can give a more specific answer. I'll try to include the math that shows the general case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first step will be to estimate the small-signal impedance of the diode. Create a piecewise-linear I-V model for your laser diode. The source data would ideally be in a datasheet, but you may need to measure the curve yourself. It should look something like this:&#xA;&lt;img src=&quot;http://i.imgur.com/rl5Ua.jpg&quot; alt=&quot;Figure from Wikipedia Diode Modeling article&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Find the slope of the active region. In this drawing, that would be approximately 100uA/20mV. Take the inverse of that, and for &lt;strong&gt;THIS&lt;/strong&gt; diode the impedance would be 200 Ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Assumption:&lt;/strong&gt; The RF input signal is 10 MHz FM with 25 kHz deviation (f_min is roughly equal to f_max)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/38vsQ.png&quot; alt=&quot;Bias-T circuit. From Wikipedia&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now lets calculate what capacitor value we need for the bias-t circuit. The capacitor provides a low impedance path for the RF signal to load (diode), and a high impedance path for DC. When sizing the capacitor, we need to make it large enough to provide a RF short. I'll shoot for a 1:100 impedence ratio. That means that our capacitor needs an impedance of 2 Ohms at our minimum frequency.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Xc = 1/2*pi*f*C; C=1/(2*pi*f*Xc)&#xA;C = 1 / (2 * 3.14 * 10MHz * 2Ohms) = 8nF&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Our minimum capacitance is 8nF, assuming a 1:100 ratio. You can make the capacitance larger, but larger capacitors may have worse parasitic characteristics. Use a good ceramic (C0G/NP0) capacitor here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, we need to calculate the inductor value. We want the inductor to act like an open circuit at RF frequencies. Let's design the inductor to have a 100:1 impedance ratio to the diode at RF. We then need our inductor to have an impedance of 20,000 Ohms at the minimum frequency.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Xl = 2*pi*f*L;  L = Xl / (2 * pi * f)&#xA;L = 20,000 Ohms / (2 * 3.14 * 10MHz) = 318uH&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;From these calculations, our minimum inductance is 318uH, which is fairly large. At some point, the stray capacitance in the inductor will begin to look like a short circuit. If you purchase an inductor, look for the self-resonant frequency as the upper limit that it can be used. You would need to comprimise the impedance ratio to find a viable inductor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inductors are more complicated to select than capacitors. Taking a Digikey search for &quot;fixed choke&quot;, select and apply the parameters in this order:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Select all saturation currents greater than your maximum diode current. (apply)&lt;/li&gt;&#xA;&lt;li&gt;Select all self-resonant frequencies greater than 2-3 times your maximum frequency. (apply)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;As you decrease your inductor size, less RF power will go to the laser diode. You can compensate this by increasing your input power, but your efficiency will suffer. As with all engineering, you need to decide which trade-offs you make in your design. If you post more information, I can tailor the answer to your data.&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-19T02:02:51.357" LastActivityDate="2011-02-19T02:02:51.357" CommentCount="2" />
  <row Id="10346" PostTypeId="2" ParentId="10291" CreationDate="2011-02-17T13:08:34.883" Score="2" ViewCount="" Body="&lt;p&gt;You need insulation testers. The ones I've seen had 2 GOhm range.&#xA;Not necessary Flukes, there are cheaper ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And for the future, I would try to add some protective insulation on top of such nasty things :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-17T13:08:34.883" CommentCount="1" />
  <row Id="10347" PostTypeId="2" ParentId="10327" CreationDate="2011-02-17T13:12:42.403" Score="3" ViewCount="" Body="&lt;p&gt;There are actually standards to address this, IEC 60617 (also known as British Standard BS 3939), ANSI standard Y32 (also known as IEEE Std 315), Australian Standard AS 1102&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a &lt;a href=&quot;http://en.wikipedia.org/wiki/Electronic_symbol&quot; rel=&quot;nofollow&quot;&gt;link to a Wikipedia article&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-02-17T13:12:42.403" CommentCount="1" />
  <row Id="10348" PostTypeId="2" ParentId="10322" CreationDate="2011-02-17T13:17:30.323" Score="2" ViewCount="" Body="&lt;p&gt;Voltage is a difference in potential. If I connect terminal A of a device to potential of 30 volts and terminal B to a potential 20 volts. The potential from A to B is 10 volts, but the potential from B to A is - 10 volts. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think of it a tall building To go from floor 30 to floor 20 you go down 10 floors. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-02-17T13:17:30.323" />
  <row Id="10349" PostTypeId="2" ParentId="10334" CreationDate="2011-02-17T13:27:44.183" Score="0" ViewCount="" Body="&lt;p&gt;Not sure about the Prius, but normal automotive power surges are a very nasty environment for electronics. You can have low dips and high voltage surges. Special care is required with caps as discussed above as well as diode protection at the input. The car lighter converter is probably a little light for the job. [update] An related article from a vendor &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/760&quot; rel=&quot;nofollow&quot;&gt;http://www.maxim-ic.com/app-notes/index.mvp/id/760&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2157" LastEditorUserId="2157" LastEditorDisplayName="" LastEditDate="2011-02-17T13:40:53.173" LastActivityDate="2011-02-17T13:40:53.173" CommentCount="2" />
  <row Id="10350" PostTypeId="1" CreationDate="2011-02-17T14:11:54.507" Score="5" ViewCount="261" Body="&lt;p&gt;I am looking for a algorithm that can detect the rate of symbols in a base-band signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=221081&quot; rel=&quot;nofollow&quot;&gt;Gardner method&lt;/a&gt; is a way to cancel out the timing drift and synchronize the receiver to sender when the symbol rate (number of samples per symbol) is known. The MATLAB also provides &lt;a href=&quot;http://www.mathworks.com/help/toolbox/commblks/ref/comm.gardnertimingsynchronizerclass.html&quot; rel=&quot;nofollow&quot;&gt;a package&lt;/a&gt; which implements Gardner method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But what if we don't know the symbol rate? I found some proposed methods like using &lt;a href=&quot;http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=831861&quot; rel=&quot;nofollow&quot;&gt;cyclostationary&lt;/a&gt; properties of signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any package/implementation of these methods (or any other method) in MATLAB or C symbol rate estimation?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update #1:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mathworks.com/matlabcentral/fileexchange/16742&quot; rel=&quot;nofollow&quot;&gt;This is&lt;/a&gt; a simple implementation which uses cyclostationary properties to estimate baud rate, but it is not suitable for large inputs like wave files.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update #2:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After demodulating and filtering the received signal I have a basedband signal like:&#xA;&lt;img src=&quot;http://i.imgur.com/Ek9Z4.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Symbols are encoded as different shapes in this signal (e.g. different levels of voltage if the sender uses square shape filter). &#xA;As we can see, the highest frequency in this signal is not the symbol-rate. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not seeking for a new solution/idea to estimate symbol rate. I am looking for an implementation of a known method (like cyclostationary-based or wavelet-based methods) for symbol rate estimation.&lt;/p&gt;&#xA;" OwnerUserId="3061" LastEditorUserId="3061" LastEditorDisplayName="" LastEditDate="2011-02-17T16:42:23.233" LastActivityDate="2011-03-23T22:22:41.020" Title="Symbol rate (baudrate) estimation" Tags="&lt;signal&gt;&lt;detection&gt;&lt;baudrate&gt;&lt;receiver&gt;" AnswerCount="6" CommentCount="17" FavoriteCount="3" />
  <row Id="10351" PostTypeId="2" ParentId="10350" CreationDate="2011-02-17T14:34:24.840" Score="0" ViewCount="" Body="&lt;p&gt;Maybe we're talking at cross purposes here, but automatic baud rate detection for UARTs is a done deal in the microcontroller area - and it doesn't seem to require advanced algorithms.  Of course, your standard 8-N-1 serial connection requires one START bit, so if you can find that and time it you're set (especially considering that there are only certain allowable baud rates - 115200, 38400, etc).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's C code to do autobaud on a serial line for AVRs here (and also a short explanation of the algorithm): &#xA;&lt;a href=&quot;http://mycal.net/?cpath=/Archive/&amp;amp;id=569&amp;amp;action=9&quot; rel=&quot;nofollow&quot;&gt;http://mycal.net/?cpath=/Archive/&amp;amp;id=569&amp;amp;action=9&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I think that you are looking for something more general than this?&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-17T14:34:24.840" CommentCount="1" />
  <row Id="10352" PostTypeId="2" ParentId="10264" CreationDate="2011-02-17T14:42:29.293" Score="1" ViewCount="" Body="&lt;p&gt;There was a lot of talk recently about the coffee-grounds grippers and how well they work at gripping a variety of objects, but I'm not sure how much torque they can provide:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.gizmag.com/universal-robotic-gripper/16729/&quot; rel=&quot;nofollow&quot;&gt;http://www.gizmag.com/universal-robotic-gripper/16729/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-17T14:42:29.293" />
  <row Id="10353" PostTypeId="2" ParentId="10329" CreationDate="2011-02-17T14:47:13.613" Score="1" ViewCount="" Body="&lt;p&gt;It seems that the device already has the Microchip TCP/IP stack compiled up and running so it shouldn't be too hard to implement a HTTP client that POSTs the data to your web server. I think there is at least one example HTTP client with their distribution. If not, there are other implementations available. See Dangerous Prototype's &lt;a href=&quot;http://dangerousprototypes.com/docs/Web_Platform&quot; rel=&quot;nofollow&quot;&gt;web platform&lt;/a&gt;, they have a similar chip with a TCP/IP stack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Making a .NET web application should be quite easy if you've done it before and from there it's also easy to insert the data into an SQL database.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastEditorUserId="2909" LastEditorDisplayName="" LastEditDate="2011-02-18T04:03:19.067" LastActivityDate="2011-02-18T04:03:19.067" />
  <row Id="10354" PostTypeId="2" ParentId="10334" CreationDate="2011-02-17T14:54:24.910" Score="2" ViewCount="" Body="&lt;p&gt;I wouldn't be so sure that it is a voltage spike issue. In a Prius you don't have an engine starting when you first turn on the car so there isn't as high as noise as most standard engine cars. I am going to guess it is 1 of 2 things:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;I believe the Prius is one of the cars that will actually communicate with the iPod and pull off data over USB. If this is the case I could see the negotiation with the iPod getting interrupted on start up causing the iPod to think something funny was going on and resetting itself.&lt;/li&gt;&#xA;&lt;li&gt;There is a large amount of electronics getting turned on at the same time that are all pulling from a battery. This situation could cause a dip in power that could cause the iPod to go in a brownout state that it is smart enough to recover from.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If either of my guesses are true, then most of what has been mentioned before wont work. Ex:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;voltage regulator - the car runs at higher then 5v so they already have to have a voltage regulator of some sort. I don't think regulating again will help at all&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Switching to your own 12v to 5v regulator - If you do this then you will loose the ability to pull data over USB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Decoupling Caps - This might help, the tricky part is figuring out where to put them. If it is a negotiation issue the cap will need to be placed on what ever component handles this negotiation. Probably will be hard to find and will most likely void a warranty. &lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-17T14:54:24.910" />
  <row Id="10355" PostTypeId="1" CreationDate="2011-02-17T15:40:50.330" Score="2" ViewCount="120" Body="&lt;p&gt;I have been looking around all the internet for such a thing, but I haven't found one. Do they exist? All I would need is a neat little plastic battery holder for 1 AA sized battery, which has a switch included. Just like it's common with 2x, 3x, 4x AA sized boxes.&lt;/p&gt;&#xA;" OwnerUserId="3049" LastActivityDate="2011-02-17T15:52:36.693" Title="1 x AA sized battery box with a built in switch?" Tags="&lt;battery&gt;&lt;switch&gt;" AnswerCount="2" />
  <row Id="10356" PostTypeId="2" ParentId="10322" CreationDate="2011-02-17T15:43:19.140" Score="0" ViewCount="" Body="&lt;p&gt;Well, just to chuck in my two cents, let's say you have an ungrounded device. With +10 volts, you're expecting the current to come of the battery, through the widget, and then... where? It's only 10 volts, so arcing through the air to ground isn't really possible, but it could go through the case into the hand of the user, or the charge could simply stay on the far end of the widget. So now you have +10 volts on one side and +8 volts or something on the other, relative to ground. The wiget only sees a 2 volt difference though. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a a +5V and a -5V the current is both pushed into the widget and pulled out of the widget. &lt;/p&gt;&#xA;" OwnerUserId="3062" LastActivityDate="2011-02-17T15:43:19.140" CommentCount="1" />
  <row Id="10357" PostTypeId="2" ParentId="10355" CreationDate="2011-02-17T15:51:56.227" Score="1" ViewCount="" Body="&lt;p&gt;I'd start looking &lt;a href=&quot;http://www.mouser.com/search/refine.aspx?Ntk=P_MarCom&amp;amp;Ntt=106652559&amp;amp;utm_source=supplier&amp;amp;utm_medium=featured+spotlight&amp;amp;utm_campaign=106652559&quot; rel=&quot;nofollow&quot;&gt;here on Mouser&lt;/a&gt;.  I've got a number of enclosed battery holders with switches and wire leads.  I don't have any single-cell holders, but several 2- and 3-cell ones.  It's a place to start, at least…&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-02-17T15:51:56.227" />
  <row Id="10358" PostTypeId="2" ParentId="10355" CreationDate="2011-02-17T15:52:36.693" Score="1" ViewCount="" Body="&lt;p&gt;Use a 2xAA box rewired for a single cell.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-17T15:52:36.693" />
  <row Id="10360" PostTypeId="2" ParentId="10185" CreationDate="2011-02-17T20:49:22.503" Score="3" ViewCount="" Body="&lt;p&gt;I spoke to Mentor support.  They make the HyperLynx family of tools.  They confirmed they need not be unique.  Use the parser to verify your IBIS models; which I did and it didn't complain.  Also they are not shorted even if they have the same name.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-17T20:49:22.503" CommentCount="1" />
  <row Id="10361" PostTypeId="2" ParentId="10350" CreationDate="2011-02-17T20:59:36.703" Score="0" ViewCount="" Body="&lt;p&gt;I don't know of any prebuilt method for doing this, it seems rather unique to me, at least with the experience I currently have. But for academic sake I am going to see if I can write out my approach to a problem like this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this situation a Symbol rate would show up as a shapes being stretched or shrunk. I would take the shapes and &quot;slide&quot; them across the spectrum looking at the correlation. I would then do this many many times with different &quot;stretching&quot; of the shapes, hopefully there are some standard symbol rates that you can use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should then be able to analyze what symbol rates had the best correlation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There may very well be an easier way to do this, but it is all I can come up with right now.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-17T20:59:36.703" />
  <row Id="10362" PostTypeId="2" ParentId="10320" CreationDate="2011-02-17T21:22:29.137" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.irf.com/product-info/datasheets/data/auips2051.pdf&quot; rel=&quot;nofollow&quot;&gt;This part&lt;/a&gt; and &lt;a href=&quot;http://www.irf.com/product-info/datasheets/data/ips1051.pdf&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; from IR are dual channel drivers in an SO-8 package. You maybe could use two of these.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2011-02-17T21:22:29.137" />
  <row Id="10363" PostTypeId="2" ParentId="10244" CreationDate="2011-02-17T21:41:03.623" Score="0" ViewCount="" Body="&lt;p&gt;I don't know of any tool that does this automatically.  It isn't a lot of work though to use a sci-lab script and a set of matrices to do it.  Use ideal Op-amp assumptions for your actives.  You can write one matrix and pull transfer functions for just about any point on the circuit.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Circuit magic seems able to do some of this. &lt;a href=&quot;http://www.circuit-magic.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.circuit-magic.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="72" LastActivityDate="2011-02-17T21:41:03.623" />
  <row Id="10364" PostTypeId="2" ParentId="10350" CreationDate="2011-02-18T00:06:24.290" Score="0" ViewCount="" Body="&lt;p&gt;The generic problem is called &quot;clock recovery&quot;, and many times a phase-locked-loop is used.  Every time a data edge occurs, the PLL compares it to the clock edge from the local VCO.  If the local clock is early or late, the natural PLL action is to adjust the VCO frequency just a bit. Eventually lock is achieved at a multiple of the data edge rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There must be a minimum number of data edges present for the PLL to lock on to them.  This is why bit-stuffing and line encodings such as 8B10B are used to enforce a minimum transition density - otherwise the PLL VCO will drift away from the data clock over a long run of the same bit value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect your RF channel is using some kind of line encoding already, normally DC-biased signals are avoided in RF modulation, and an encoding is employed to eliminate DC bias (a.k.a. long runs).&lt;/p&gt;&#xA;" OwnerUserId="2235" LastActivityDate="2011-02-18T00:06:24.290" CommentCount="2" />
  <row Id="10365" PostTypeId="1" CreationDate="2011-02-18T00:25:09.963" Score="1" ViewCount="67" Body="&lt;p&gt;I've heard that the Vrrm of a diode is a maximum, and the diode should not be continuously exposed to it. I'm using a PMEG4010CEJ diode, a 40V/1A SOD323 diode. Basically, the power input is a 33.6V 8S LiPo battery, which could be reversed. The diode is in series with the power input and protects a buck converter against a reversed supply, which would damage it. To add a bit of a margin, let's say the system has to sustain a maximum -40V input fault. Can this diode (or any 40V diode) handle it, or do I need to use a 50-60V diode (more expensive)?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-18T10:13:15.173" Title="Can I use a 40V schottky on a system which may suffer a 40V reverse fault?" Tags="&lt;schottky&gt;" AnswerCount="2" />
  <row Id="10366" PostTypeId="2" ParentId="10296" CreationDate="2011-02-18T00:50:19.787" Score="3" ViewCount="" Body="&lt;p&gt;The simplest circuit you want is commonly called a &quot;Joule thief&quot;, which consists&#xA;of a resitor, NPN transitor, and a hand-wound inductor. Such a circuit will allow&#xA;you to pull useful current out of a single AA, AAA, etc battery even when the voltage&#xA;is far below the LED's threshold voltage. Not sure this will generate a full 100mA&#xA;though-- this will depend on the inductor and resistor values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Schematic: &#xA;&lt;a href=&quot;http://www.prc68.com/I/JouleThief.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.prc68.com/I/JouleThief.shtml&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;References:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.emanator.demon.co.uk/bigclive/joule.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.emanator.demon.co.uk/bigclive/joule.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/Make-a-Joule-Thief/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Make-a-Joule-Thief/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2909" LastActivityDate="2011-02-18T00:50:19.787" CommentCount="1" />
  <row Id="10367" PostTypeId="2" ParentId="10365" CreationDate="2011-02-18T00:51:36.497" Score="2" ViewCount="" Body="&lt;p&gt;Exceeding the PIV will generally damage the diode, not to mention rapidly allowing current to flow - defeating the point of the protection diode. &lt;/p&gt;&#xA;" OwnerUserId="2235" LastActivityDate="2011-02-18T00:51:36.497" />
  <row Id="10368" PostTypeId="1" AcceptedAnswerId="10387" CreationDate="2011-02-18T03:09:41.270" Score="1" ViewCount="105" Body="&lt;p&gt;I have a &lt;a href=&quot;http://www.interinar.com/vexta-pk266-02a.html&quot; rel=&quot;nofollow&quot;&gt;stepper motor&lt;/a&gt; and it is rated at 2 amps per phase. I also have a &lt;a href=&quot;http://www.sparkfun.com/products/10267&quot; rel=&quot;nofollow&quot;&gt;stepper driver&lt;/a&gt; which is rated at 750 miliamps per phase. To make matters worse I have a wall wart power supply rated as 9V @ 650miliamps. That power is converted by a &lt;a href=&quot;http://www.sparkfun.com/products/114&quot; rel=&quot;nofollow&quot;&gt;voltage regulator PCB&lt;/a&gt; down to a usable 3.3 V at an unknown amperage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, what effect will underpowering the motor have?&lt;br&gt;&#xA;Will it affect the speed of the motor or just holding torque?&lt;/p&gt;&#xA;" OwnerUserId="3045" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-02-18T09:22:17.700" LastActivityDate="2011-02-18T09:24:36.590" Title="Underpowering a stepper motor" Tags="&lt;stepper-motor&gt;" AnswerCount="2" />
  <row Id="10369" PostTypeId="1" AcceptedAnswerId="10412" CreationDate="2011-02-18T03:13:06.773" Score="1" ViewCount="122" Body="&lt;p&gt;How can the required ramp up speed for a stepper motor which is attached to it's drive system be determined?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given that a stepper motor requires ramping up to full velocity, and that ramp speed must be slow enough so that the motor doesn't simply vibrate in place; is there a known method for determining the ramp up speed?&lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-02-19T15:42:35.420" Title="Determining the ramp up speed for a stepper motor with it's drive system" Tags="&lt;stepper-motor&gt;" AnswerCount="3" />
  <row Id="10370" PostTypeId="1" AcceptedAnswerId="10390" CreationDate="2011-02-18T03:23:50.737" Score="2" ViewCount="131" Body="&lt;p&gt;I've done some reading on software defined radios and while the concept is clear I have yet to grasp how the signaling is actually done. I've researched the Analog to Digital IC's that are involved in the process and they say that the support sampling rates of 500Mhz or more (is that even correct?) My question is: How is the modulation and demodulation acheived in a software deined radio?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I was assuming that there was some sort of voltage controlled oscilator involved, however I can't find the literature.&lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-02-18T15:06:14.013" Title="Theory of operation for a software defined radio" Tags="&lt;fpga&gt;&lt;radio&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="10371" PostTypeId="1" AcceptedAnswerId="10388" CreationDate="2011-02-18T03:40:40.437" Score="1" ViewCount="163" Body="&lt;p&gt;I'm trying to find a sound sensor that can give feedback on all the frequencies of sound and their levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sensors I'm finding in my search however only support level of sound it seems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to get the level of individual frequency ranges from one sensor, or does it require multiple senors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm new to this so don't know the exact terminology, but essentially I want to create something that can respond to a set of different frequencies of sound independently, not just how loud the sound is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally the sensor would be made to work with Arduino, but I'm not afraid of something that it is more complicated.&lt;/p&gt;&#xA;" OwnerUserId="3065" LastActivityDate="2011-02-18T09:33:12.803" Title="Sound Sensor that can give feedback on the amplitude of different frequencies?" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;sound&gt;" AnswerCount="2" />
  <row Id="10372" PostTypeId="2" ParentId="10365" CreationDate="2011-02-18T03:50:00.287" Score="1" ViewCount="" Body="&lt;p&gt;Derating guidelines in industry usually allow for no more than 70-80% of the maximum reverse voltage stress for diodes. You'll want a 50V part for 33.6V reverse protection.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-18T03:50:00.287" CommentCount="1" />
  <row Id="10373" PostTypeId="2" ParentId="10350" CreationDate="2011-02-18T04:01:35.293" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;perhaps your demodulator already knows the baud rate&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many wireless communication protocols set the symbol_time to some known integer multiple of the chip-time or carrier cycle time.&#xA;Since you are able to demodulate the signal, your demodulator must already know the chip-time or carrier cycle time.&#xA;Perhaps you can take that time information and multiply it by the &quot;known integer&quot; to get the symbol_time; then you &quot;merely&quot; need to do phase alignment.&#xA;Is there any way to pull that time information out of your demodulator?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;FFT&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The symbol rate is approximately equal to the bandwidth.&#xA;(I hear that the -10 dB bandwidth is 1.19 times the symbol rate for QPSK -- is that true for all signal constellations?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a high enough SNR, you can put your signal through a FFT, and estimate the bandwidth.&#xA;I think this works in almost any format you have handy --&#xA;the raw (&quot;real&quot;) modulated signal, or the demodulated (&quot;complex&quot; I,Q) baseband signal, or I alone, or Q alone -- but I don't think it will work if you feed phase data from the &quot;Update #2&quot; plot above into the FFT.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's usually pretty easy for a human to visually pick out the -3dB bandwidth on a graph.&#xA;Is there a Matlab function for estimating the -3dB bandwidth?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you have pure white noise coming in -- the SNR is too bad -- the -3dB &quot;bandwidth&quot; clearly has nothing to do with any real baud rate, but depends entirely on the filters used in your demodulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;autocorrelation&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find the autocorrelation of a function using the Matlab autocorr() or xcorr() functions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are at least 3 ways of converting that autocorrelation to an estimate of the baud rate:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;With approximately uncorrelated data bits, the autocorrelation at offset time of exactly 1 symbol_time or more are going to be approximately zero, and the normalized autocorrelation at short offset times from 0.0 to 1.0 bit time is approximately linear: 1-(time/symbol_time). Fit a straight line to those short offset times to get a good estimate of the autocorrelation at non-integer offset times, find offset time t_half that gives an estimated autocorrelation of about 1/2 along that fitted line, and your symbol time is about symbol_time ~= 2*t_half.&lt;/li&gt;&#xA;&lt;li&gt;During burst transmissions, some transmitters make every 10th bit a start symbol. Your autocorrelation function, as always, has one peak at 0 offset time; skip past that first peak, and search for the positive time t_positive that gives the next biggest positive peak (with expected amplitude roughly 1/10) in the autocorrelation function, and your symbol time is about symbol_time ~= t_positive/10.&lt;/li&gt;&#xA;&lt;li&gt;Some transmitters use a stop symbol precisely 9 bit-times after every start symbol, and give the stop symbol the negative amplitude of the start symbol. Search for the offset time t_negative that gives the biggest negative peak in the autocorrelation function (with expected amplitude roughly 1/10), and your symbol time is about symbol_time ~= t_negative/9.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;autocorrelation approximation&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many other techniques use some quicker-to-calculate approximation of the autocorrelation function -- in particular, there's really no point computing the autocorrelation amplitude at offset times greater than 10 bit_times.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In particular, let's calculate the autocorrelation function at only one time offset H:&#xA;Delay the signal by some time H, and multiply the delayed signal by the original (non-delayed) signal, and use some perfect or leaky integrator get a long-term average.&#xA;(If your input signal is already clipped to the +1 -1 range, like most FM and PSK receivers, then that long-term average is already normalized.&#xA;Otherwise, normalize by the average of the square of the signal, so your long-term average is guaranteed to be in the range of -1 to +1).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then tweak H to try to get that normalized long-term average to be exactly 1/2 -- make time offset H shorter if the normalized long-term average is less than 1/2; make H longer if the normalized long-term average is more than 1/2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then your symbol time is about symbol_time ~= 2*H.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;other techniques&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The wikibook &lt;a href=&quot;http://en.wikibooks.org/wiki/Clock_and_Data_Recovery&quot; rel=&quot;nofollow&quot;&gt;&quot;Clock and Data Recovery&quot;&lt;/a&gt; sounds promising, although it is still a rough draft. Could you update it to tell what approach worked best for you?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been told that many receivers use a &lt;a href=&quot;http://en.wikipedia.org/wiki/Costas_loop&quot; rel=&quot;nofollow&quot;&gt;Costas loop&lt;/a&gt;&#xA;or some other relatively simple &lt;a href=&quot;http://en.wikipedia.org/wiki/carrier_recovery&quot; rel=&quot;nofollow&quot;&gt;carrier recovery&lt;/a&gt; technique to detect the baud rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://books.google.com/books?id=Tokk5bZxB0MC&quot; rel=&quot;nofollow&quot;&gt;The communications handbook&lt;/a&gt;&#xA;mentions a &quot;early-late gate synchronizer&quot;.&#xA;Could you use something like this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;details&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many wireless communication protocols add many &quot;redundant&quot; features to the signal in order to make it easier for the receiver to lock onto and decode the the signal in spite of noise -- start bit, stop bit, trellis modulation, error detection and correction bits, constant prelude and header bits, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps your signal has one or more of these features that will make your job easier?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-18T04:01:35.293" CommentCount="2" />
  <row Id="10374" PostTypeId="2" ParentId="10371" CreationDate="2011-02-18T04:11:53.840" Score="2" ViewCount="" Body="&lt;p&gt;Would a graphic equalizer sensor do the job you're trying to do?  Sparkfun stocks the &lt;a href=&quot;http://www.sparkfun.com/products/10024&quot; rel=&quot;nofollow&quot;&gt;MSGEQ&lt;/a&gt;, a 7-band filter IC which contains integrated bandpass filters and peak detection.   You'll need to connect one pin of your Arduino to its strobe pin, and an ADC pin to read the amplitude.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bandpass filter and peak detect are, I believe, the building blocks of your desired sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want more customization than that, you're probably looking at doing some DSP work on the Arduino-is there a library for that yet?  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-18T04:11:53.840" CommentCount="4" />
  <row Id="10375" PostTypeId="1" CreationDate="2011-02-18T04:47:23.363" Score="4" ViewCount="411" Body="&lt;p&gt;I am trying to interface my ATmega chips to the computer using a serial interface. I have read that this can be done directly by connecting the appropriate pin between the chips and the serial pin. But it is advised that I use a MAX232 chip. What is the purpose of this chip and do I really need to use it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I ask this because in a project I am making, there is a big size constraint and the chip might take up valuable space.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2011-03-06T18:09:58.133" Title="Do I have to use a MAX232 chip?" Tags="&lt;atmega&gt;&lt;rs232&gt;&lt;max232&gt;" AnswerCount="4" />
  <row Id="10376" PostTypeId="2" ParentId="10254" CreationDate="2011-02-18T04:55:17.723" Score="6" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;I am building clock with ultimate precision.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Are you really talking best precision possible, i.e. a primary time standard (e.g. &lt;a href=&quot;http://www.nrc-cnrc.gc.ca/eng/projects/inms/fountain-clock.html&quot; rel=&quot;nofollow&quot;&gt;Cesium foundation&lt;/a&gt; based time-standard)?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;There are few known ways to improve precision: temperature controlled environment&#xA;  and multiple crystals. I am implementing both.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;There are far more than just those two. It is possible to design temperature compensation circuits, which result in a circuit that is self-adjusting to be independent of (slow) temperature fluctuations, such as used in a Temperature-compensated crystal oscillator (&lt;a href=&quot;http://www.ko4bb.com/ham_radio/FAQ/TCXO.php&quot; rel=&quot;nofollow&quot;&gt;TCXO&lt;/a&gt;). You can use quartz crystals with a different cut, than the most common AT cut, such as the SC-cut quartz crystal, which is typically used in a oven controlled crystal oscillator (&lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Crystal_oven&quot; rel=&quot;nofollow&quot;&gt;OCXO&lt;/a&gt;). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With multiple standard (AT-cut, not temperature compensated or in a thermally stable chamber such as a crystal oven) quartz crystals I don't believe you are going to gain much improvement, because you are not certain which reference is correct. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For long term stability, using an external time standard (such as WWV/WWVH, WWVB (USA), CHU (Canada), DCF77 (Germany), JJY (Japan), etc.) or GPS/GLONASS/Galileo GPS-disciplined oscillators using a timeing GPS receiver (ideally, many common receives produce a high-quality Pulse-Per-Second, PPS, signal with microsecond accuracy). One of the cheapest (and moderate quality) external time sources would be the AC mains, which in the long time will average to the nominal value (e.g. 50/60 Hz) so as to keep AC powered clocks stable. This can be accessed using a diode detector from the AC voltage from the secondary windings of a transformer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I didn't get into Microcomputer/microprocessor Compensated Crystal Oscillator (MCXO) which are cost-effective high-quality oscillators.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;I would strongly recommend reading through the &lt;a href=&quot;https://www.febo.com/mailman/listinfo/time-nuts&quot; rel=&quot;nofollow&quot;&gt;archives&lt;/a&gt; of the &lt;a href=&quot;http://leapsecond.com/time-nuts.htm&quot; rel=&quot;nofollow&quot;&gt;time-nuts&lt;/a&gt;, and their &lt;a href=&quot;http://www.leapsecond.com/&quot; rel=&quot;nofollow&quot;&gt;member&lt;/a&gt;'s &lt;a href=&quot;http://www.febo.com/time-freq/index.html&quot; rel=&quot;nofollow&quot;&gt;web&lt;/a&gt; pages, who were &lt;a href=&quot;http://www.wired.com/science/discoveries/news/2007/12/time_hackers&quot; rel=&quot;nofollow&quot;&gt;profiled&lt;/a&gt; in Wired magazine a &lt;a href=&quot;http://www.leapsecond.com/ptti2003/index.htm&quot; rel=&quot;nofollow&quot;&gt;few years&lt;/a&gt; ago. And a &lt;a href=&quot;http://www.gpstime.com/files/Vig-tutorial_Jan_2007.ppt&quot; rel=&quot;nofollow&quot;&gt;presentation&lt;/a&gt; given by John Vig in 2007.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the cost / budget, and exactly how accurate you want to be, I would suggest as a design starting point, start with considering using a Maxim DS3232, DS3234, DS32B35, or DS32C35 Real-Time-Clock (RTC) IC which includes an integrated TCXO making it trivial to build a low-cost clock with far better than typical accuracy and stability compared to common free running AT-cut quartz crystals. One chip would cost roughly $5 USD, 4 Euros. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next for high quality long term stability, you need to add an external time reference, such as LF/HF time signal from a station such as WWVB, CHU, MSF, DCF77 or a GPS module with a decent PPS output combined with the standard GPS NMEA messages via serial. There are commercially available radio receiver modules for WWVB, and I believe DCF77 and MSF radios, which covers much of North America and Europe. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think these two considerations would be far better gain in time reference quality (accuracy and precision) than messing about with trying to use multiple crystals in Phase-Locked-Loop, PLL, or Frequency-Locked-Loop, FLL, circuits to get marginal improvements.  &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Added:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Will the precision of inverter-based generators be inferior to uC-based ones?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;No. The crystal oscillator built into a microprocessor / microcontroller is often just a single inverter. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a parallel-resonant crystal with thermally stable capacitors (e.g. silver mica, or &lt;code&gt;C0G&lt;/code&gt; / &lt;code&gt;NP0&lt;/code&gt; ceramic) of the correct values would make a bigger difference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think I've seen a FLL circuit based upon several identical frequencies for comparison. I suspect that it would be terribly slow (e.g. days) to determine which signal to lock to that the decision may be invalid before it reaches a lock. And I suspect a digital attempt to compare these signals of the same frequency would just be futile without spending a fortune on high-end ADCs and support circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without a specific (or at least more specific) target for &quot;ultimate precision&quot;, I suggest either buying a used Cesium standard or a GPS-displined oscillator, where the local oscillator is a single high-quality SC-cut quartz OCXO such as the HP/Agilent 10811A oscillator that are readily available on the surplus / second-hand market.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastEditorUserId="2598" LastEditorDisplayName="" LastEditDate="2011-02-22T00:16:34.683" LastActivityDate="2011-02-22T00:16:34.683" />
  <row Id="10377" PostTypeId="2" ParentId="10375" CreationDate="2011-02-18T04:59:51.180" Score="10" ViewCount="" Body="&lt;p&gt;If you need to connect the AVR to the computer using the serial port and a &quot;standard&quot; DB9-DB9 serial cable, yes, you need to use an RS232 transceiver in circuit. The AVR's UART outputs 0-5V signaling. The RS232 spec is +/-15V signaling, and I believe it's also &quot;inverted&quot; with compared to UART signaling. You don't have to use specifically the MAX232, but you do have to use a RS232 transceiver. These chips (plus some external capacitors) handle the voltage level conversions (via charge pumping) in either direction as well as the signal inversion, and act as &quot;line drivers&quot; driving longer lengths of wire allowed by the RS232 standard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you can use a cable that includes such a transceiver circuit embedded in the DB9 shell if you are space constrained on your board. Yet another alternative involving a cable is to use a cable that includes an FTDI FT232 chip in it, which has the advantage of making it look like a COM port over USB to the computer, but you're looking at upwards of $15 for that cable.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-02-18T05:05:10.767" LastActivityDate="2011-02-18T05:05:10.767" CommentCount="3" />
  <row Id="10378" PostTypeId="2" ParentId="10375" CreationDate="2011-02-18T07:02:45.457" Score="0" ViewCount="" Body="&lt;p&gt;I am no AVR expert, but i believe there is a usb 'bitbanging' library to use it as an usb device. You might be able to use that to emulate a serial port. &lt;/p&gt;&#xA;" OwnerUserId="3068" LastActivityDate="2011-02-18T07:02:45.457" />
  <row Id="10379" PostTypeId="1" CreationDate="2011-02-18T07:40:42.397" Score="2" ViewCount="83" Body="&lt;p&gt;I want to  measure degrees using linear potentiometer, so I thought to use the AD 676  analogue to digital converter (ADC) IC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this a good ADC for monitoring a potentiometer?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If so, how can I use it? A schematic of an example implementation would be helpful.&lt;/p&gt;&#xA;" OwnerUserId="3038" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-09T20:32:42.247" LastActivityDate="2011-05-09T20:32:42.247" Title="How to use AD 676 Analogue to Digital IC" Tags="&lt;analog&gt;&lt;potentiometer&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="10380" PostTypeId="1" CreationDate="2011-02-18T07:41:10.773" Score="0" ViewCount="152" Body="&lt;p&gt;I took apart an RC car recently and found 2 sets of motors.  The rear wheels (left) seem to run off an electric DC motor which is understandable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The front wheels (right) I expected to be controlled by a servo motor because it can only make the front wheels face 3 directions (front, steer left, steer right) and no angles in between.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, looking at the insides I can see that there are only 2 wires instead of 3.  And the servo's that I've worked with before needed 3 wires for Vcc, ground and a control wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could somebody confirm whether or not this is a servo?  If not, what's the next best type of motor it could be? And how would I control it (PWM?, etc)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2IlTV.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3070" LastActivityDate="2011-02-18T15:22:01.983" Title="Two Wire Servo in RC Car?" Tags="&lt;motor&gt;&lt;servo&gt;&lt;dc-motor&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="10381" PostTypeId="2" ParentId="10380" CreationDate="2011-02-18T07:50:49.843" Score="2" ViewCount="" Body="&lt;p&gt;Since it can't do angles in between, I would not expect the 3rd control wire.  Perhaps it uses a simple geared brushed DC motor?  It could drive in one direction until it hits a limit switch.  If the user wants to turn in the opposite direction, it just needs to drive current in the opposite direction, so it would only need two wires.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also put an oscilloscope on the wires and see what's going on.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-18T07:50:49.843" CommentCount="9" />
  <row Id="10382" PostTypeId="2" ParentId="10375" CreationDate="2011-02-18T07:53:34.820" Score="0" ViewCount="" Body="&lt;p&gt;As vicatcu said, you do need something to translate the signal levels from the mcu to something the PC's serial port expects.  You don't have to use a MAX232 or similar -- &lt;a href=&quot;http://www.sparkfun.com/products/133&quot; rel=&quot;nofollow&quot;&gt;Sparkfun has something&lt;/a&gt; that would work.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-18T07:53:34.820" />
  <row Id="10383" PostTypeId="2" ParentId="8690" CreationDate="2011-02-18T07:55:14.463" Score="0" ViewCount="" Body="&lt;p&gt;I just saw an article about a stylus by Qualcomm used to write on an Android phone.  The stylus emits an ultrasonic pulse and then software on the phone is able to locate the pen.  Here is a link;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://seat12f.blogspot.com/2011/02/finger-input-just-cant-keep-good-stylus.html&quot; rel=&quot;nofollow&quot;&gt;http://seat12f.blogspot.com/2011/02/finger-input-just-cant-keep-good-stylus.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do also recall reading a few years back about a digitizing pen that used ultrasonics to locate the pen.  A small receiver was connected by USB, and it even had a memory so you could clip the device to any notepad to record your writing for later input into the computer. However, I just looked at some of the office supply stores, and it doesn't seem to be around anymore.&lt;/p&gt;&#xA;" OwnerUserId="3071" LastActivityDate="2011-02-18T07:55:14.463" />
  <row Id="10384" PostTypeId="2" ParentId="10368" CreationDate="2011-02-18T08:06:00.487" Score="0" ViewCount="" Body="&lt;p&gt;According to the product page, it uses an LM317, which has a output rated at 1.5A.  Since your total power input is 9V * 0.65A, hopefully when it is regulated down to 3.3V you will get the maximum current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Driving this stepper with 3.3v will definitely have an effect on your holding torque.  I'd expect it to adversely affect the speed of the motor under load as well.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-18T08:06:00.487" CommentCount="2" />
  <row Id="10386" PostTypeId="2" ParentId="10375" CreationDate="2011-02-18T08:29:31.463" Score="3" ViewCount="" Body="&lt;p&gt;The RS232 specification requires a signal voltage of between -3 and -30V for a logical '1', and a signal voltage of between +3V and +30V for a logical 0, input impedance is around 3k and output impedance should be around 300 ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're going to implement a fully complient interface then yes, you will need something like the MAX232 - or an alternative, like the MAX3221 which does come in a quite small TSSOP package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively you could utilise one of the handshaking lines from the DTE (PC or similar) to supply the negative voltage and use a simple transistor level changer to handle the signal inversion (from the MCU) and level shifting.  This does however require that the DTE is configured such that it's handshaking lines are in a suitable state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to take advantage of the fact that most equipment these days implements RS232 using something like a MAX232 device.  While these are fully complient with the specification they also extend things so that the input levels are basically +2.8 to +30 for a logical '0', +1.4 to -30V for a logical zero (from memory) - in other words the receivers actually include TTL signal levels.  So you can just invert the signal on the UART pins and pass it out directly to the DTE device.  This technique is used on quite a few devices including many handheld GPSes.  I'm not saying you be 100% compatible but you'll find this works more often than not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You still need to invert the UART signals (unless you're bit-banging the pins yourself), two inverters should be smaller than the MAX232 plus associated circuitry, but probably not by much.&lt;/p&gt;&#xA;" OwnerUserId="820" LastActivityDate="2011-02-18T08:29:31.463" CommentCount="2" />
  <row Id="10387" PostTypeId="2" ParentId="10368" CreationDate="2011-02-18T09:19:15.817" Score="6" ViewCount="" Body="&lt;p&gt;Running a stepper motor at under it's rated current will affect &lt;strong&gt;both&lt;/strong&gt; it's maximum speed and torque (both holding and dynamic), though depending on the driver type, it mostly effects the torque.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Firstly, The stepper motor driver you are linking &lt;strong&gt;requires power rails of 7-30V&lt;/strong&gt;. It's &lt;em&gt;logic&lt;/em&gt; interface is 5 or 3.3v.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Furthermore, your stepper motor is 3.6 ohms per winding, so even with 3.3V rails, your motors are going to pull ~900 ma, which will cause power rail brownouts.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Fortunately, in this context, the stepper motor controller IC provides &lt;em&gt;chopped current limiting&lt;/em&gt;, which is a technique which limits the maximum amount of current it runs through the stepper motor. Therefore, you can run the stepper motor you have off the wall-wart you have, a the cost of reduced torque.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a system which uses &lt;em&gt;current chopping&lt;/em&gt;, the voltage largely determines the motors maximum speed, and the current the torque. There is interactions, but they are fairly small in effect size (assuming you are not at extremely low voltage or current), proportionate to the effect of changing the relevant characteristic directly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I urge you to carefully study the &lt;a href=&quot;http://www.sparkfun.com/datasheets/Robotics/A3967.pdf&quot; rel=&quot;nofollow&quot;&gt;A3967 datasheet&lt;/a&gt; (the A3967 is the stepper motor IC the linked driver uses).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Furthermore, the designer of that stepper motor driver provides a fairly decent introduction into the concepts of how the device works &lt;a href=&quot;http://schmalzhaus.com/EasyDriver/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, which, from your question, I don't think you have really read. You should carefully read it before you hook anything up, lest you damage one of your parts.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Additionally, the stepper motor driver you link &lt;em&gt;already has a voltage regulator&lt;/em&gt;, so you do not even need the voltage regulator you included in your post (&lt;a href=&quot;http://www.sparkfun.com/products/114&quot; rel=&quot;nofollow&quot;&gt;SFE sku: PRT-00114&lt;/a&gt;).&lt;br&gt;&#xA;See the schematic for the Stepper Driver &lt;a href=&quot;http://www.sparkfun.com/datasheets/Robotics/EasyDriver_v43.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;. The voltage regulator is IC2.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-02-18T09:24:36.590" LastActivityDate="2011-02-18T09:24:36.590" CommentCount="2" />
  <row Id="10388" PostTypeId="2" ParentId="10371" CreationDate="2011-02-18T09:25:08.757" Score="3" ViewCount="" Body="&lt;p&gt;The best way is to perform &lt;a href=&quot;http://en.wikipedia.org/wiki/Fast_Fourier_transform&quot; rel=&quot;nofollow&quot;&gt;an FFT&lt;/a&gt; on the microphone input. &lt;a href=&quot;http://technology911.com/v/sr0ewZHu9jg,arduino-realtime-fft&quot; rel=&quot;nofollow&quot;&gt;FFT software&lt;/a&gt; is available for the Arduino.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-18T09:33:12.803" LastActivityDate="2011-02-18T09:33:12.803" CommentCount="1" />
  <row Id="10390" PostTypeId="2" ParentId="10370" CreationDate="2011-02-18T10:16:53.867" Score="3" ViewCount="" Body="&lt;p&gt;There is a four part series &quot;Software radio for the masses&quot;, linked from &lt;a href=&quot;http://www.arrl.org/software-defined-radio#f-widget-29624&quot; rel=&quot;nofollow&quot;&gt;the ARRL&lt;/a&gt;, which explains all this basic information, including the different ways of doing software defined radio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once the signal is digitized, it's processed using DSP techniques. You can find more details about them in &quot;Signals, Samples and Stuff: A DSP Tutorial&quot; articles, also linked from above mentioned page.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oscillators in SDR can be of any kind, from crystal, to PLL controlled VCOs, to direct digital synthesis (DDS), to numerically controlled oscillators (NCO, CORDIC) done entirely in software or FPGA.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-02-18T15:06:14.013" LastActivityDate="2011-02-18T15:06:14.013" CommentCount="1" />
  <row Id="10392" PostTypeId="1" CreationDate="2011-02-18T05:59:32.150" Score="-1" ViewCount="268" Body="&lt;p&gt;Hi,&#xA;I have seen Electronic circuit maker (for instance, Circuit maker or electronic work bench)&#xA;can any one tell me if there is any 'electrical' circuit maker?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S: the question is asked by a person who don't use internet.&lt;/p&gt;&#xA;" OwnerUserId="3072" LastActivityDate="2011-03-20T17:08:38.047" ClosedDate="2011-05-13T04:22:31.233" Title="electrical circuit maker" Tags="&lt;software&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="0" />
  <row Id="10393" PostTypeId="2" ParentId="10392" CreationDate="2011-02-18T09:43:13.117" Score="0" ViewCount="" Body="&lt;p&gt;I use 'Labcenter Proteus ISIS' for electronic purposes as a software developer. It is graph based, interactive and animated simulation program. I think it's very nice and strong, to design and test any kind of electrical circuits. It's also well-known in industry. That means you can find lots of learning material and documentation. It has samples, enough to get started, start from basics of electricity.&lt;/p&gt;&#xA;" OwnerUserId="3063" LastActivityDate="2011-02-18T10:39:25.743" CommentCount="1" />
  <row Id="10394" PostTypeId="1" CreationDate="2011-02-18T12:08:51.593" Score="0" ViewCount="381" Body="&lt;p&gt;Hey people, I need to program the ATmega8 chips via serial. I understand that for doing that I would need to install a bootloader on the chip. And to install a bootloader, I would need a parallel port programmer. Am I right? Or can I just hookup the chip with an MAX232 to make a programmer? I am really confused right now. The best answer here would be a circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE&lt;/p&gt;&#xA;&#xA;&lt;p&gt;He people I just found this &lt;a href=&quot;http://www.qubbeks.puslapiai.lt/images/articles/AVR_programmer/avr_programatorius_schema.jpg&quot; rel=&quot;nofollow&quot;&gt;http://www.qubbeks.puslapiai.lt/images/articles/AVR_programmer/avr_programatorius_schema.jpg&lt;/a&gt;. Do you think this is the kind of circuit which won't require any bootloading?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-20T22:09:07.793" LastActivityDate="2011-02-21T13:08:25.010" Title="Programming Atmega with serial port" Tags="&lt;atmega&gt;&lt;programmer&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="10395" PostTypeId="2" ParentId="10394" CreationDate="2011-02-18T12:23:53.547" Score="2" ViewCount="" Body="&lt;p&gt;No need for bootloader.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/drNfc.jpg&quot; alt=&quot;http://forum.cxem.net/index.php?app=core&amp;amp;module=attach&amp;amp;section=attach&amp;amp;attach_rel_module=post&amp;amp;attach_id=77070&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then use uniprof program to flash your AVR. I personally used that.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-18T12:23:53.547" CommentCount="4" />
  <row Id="10396" PostTypeId="1" AcceptedAnswerId="10400" CreationDate="2011-02-18T12:45:37.767" Score="2" ViewCount="227" Body="&lt;p&gt;I'm routing some traces which carry high speed UART at 1.8432 Mbaud. The traces will be routed on the same layer as a power or ground plane (because it's a 2-layer design.) This will introduce capacitance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;How much capacitance on average will a 6 mil trace with 6 mil spacing on each edge have? If there isn't a general rule, is there a way to calculate it?&lt;/li&gt;&#xA;&lt;li&gt;How much capacitance is too much capacitance?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-20T16:08:38.470" Title="Trace-to-plane capacitance?" Tags="&lt;pcb&gt;&lt;capacitance&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="10397" PostTypeId="1" CreationDate="2011-02-18T13:03:26.563" Score="1" ViewCount="117" Body="&lt;p&gt;As in the question title. Is it possible to generate basic dual rail power from two bridge rectifiers? I tried wiring one forwards and one backwards in a simulator, but I found that it did not work. Does anyone know if it's possible? Instincts say no, because it would require doubling the supply voltage, and that's tricky with just diodes.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-18T15:22:56.480" Title="Is it possible to generate basic dual rail power from two bridge rectifiers?" Tags="&lt;rectifier&gt;&lt;bridge&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="10398" PostTypeId="2" ParentId="10397" CreationDate="2011-02-18T13:25:20.207" Score="2" ViewCount="" Body="&lt;p&gt;There's no such thing as a &quot;backwards&quot; bridge rectifier, it's just a regular rectifier with the schematic laid out in the mirror. Therefore, you would get exactly the same voltage levels from both rectifiers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you obviously could do is use a single rectifier, and then split the voltage to make a  virtual ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to use two half-wave rectifiers instead of bridge rectifiers, with large caps to smooth out the blank sections. This would likely yield less voltage overall, but should be workable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yet another option is to use a &lt;a href=&quot;http://en.wikipedia.org/wiki/Rectifier#Voltage-doubling_rectifiers&quot; rel=&quot;nofollow&quot;&gt;voltage doubling rectifier&lt;/a&gt; and tap a virtual ground off the middle of the doubling ladder.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastEditorUserId="1802" LastEditorDisplayName="" LastEditDate="2011-02-18T14:12:50.177" LastActivityDate="2011-02-18T14:12:50.177" CommentCount="2" />
  <row Id="10399" PostTypeId="2" ParentId="10396" CreationDate="2011-02-18T15:09:26.210" Score="1" ViewCount="" Body="&lt;p&gt;Take a look here &#xA;&lt;a href=&quot;http://www.eeweb.com/electronics-quiz/calculate-the-capacitance-of-pcb-planes&quot; rel=&quot;nofollow&quot;&gt;http://www.eeweb.com/electronics-quiz/calculate-the-capacitance-of-pcb-planes&lt;/a&gt; (as you have wrire-to-wire cap, area will be much much lower). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Capacitance will be &amp;lt;1pF per inch, so at 2 Mbaud I wouldn't bother about capacitance.&#xA;But there are also inductance and EM interference. Anyway, under 10Mhz it is not a deadly problem worth simulating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your maximum tolerable capacitance depend on your drive strength. At 1.8 Mboud at some 50 pF you should be fine I believe on most of the chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just check signal quality after assembling first board to be sure that it's ok. And if you have any motors, relays e.t.c in your device - you will have to shield your trace.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-18T15:09:26.210" CommentCount="1" />
  <row Id="10400" PostTypeId="2" ParentId="10396" CreationDate="2011-02-18T15:09:48.780" Score="1" ViewCount="" Body="&lt;p&gt;Calculating the capacitance between two tracks edge to edge is not so easy, because it's not the parallel plate scenario so it's all fringing fields. &lt;a href=&quot;http://chemandy.com/calculators/rectangular-capacitor-calculator.htm&quot; rel=&quot;nofollow&quot;&gt;This calculator&lt;/a&gt; is for tracks over planes, with fringing taken into account. The same site has an inductance calculator which you should also take into account. Obviously both will depend on the length of track.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In terms of how much is too much, it will be clear when your pulses start to show a rounding effect which alter the received width of the pulses. So it depends on the tolerance of the receiver, at what point does it fail to receieve the signal correctly? You end up with a budget: the receiver tolerance has to allow for transmitter tolerance plus the transmission distortions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end, you probably have to prototype it to find out, because it's not just the PCB track-ground capacitance that could affect the signal, there is capacitance between IC pins.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-02-18T15:09:48.780" />
  <row Id="10402" PostTypeId="2" ParentId="10380" CreationDate="2011-02-18T15:22:01.983" Score="3" ViewCount="" Body="&lt;p&gt;It is a DC motor in there, A very simple gear system moves the wheels left and right and a spring centers everything. there is no fine control.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OEP8A.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;to control it you could use PWM and an H-bridge. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-18T15:22:01.983" CommentCount="1" />
  <row Id="10403" PostTypeId="2" ParentId="10397" CreationDate="2011-02-18T15:22:56.480" Score="3" ViewCount="" Body="&lt;p&gt;If the bridge rectifier follows a transformer, and the transformer has a center tap, then the center tap is at the middle (ground) potential.  This is the standard linear power supply fpr hifi amplifiers or to make +/-15V for op-amps.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-18T15:22:56.480" />
  <row Id="10404" PostTypeId="2" ParentId="10329" CreationDate="2011-02-18T15:54:57.023" Score="2" ViewCount="" Body="&lt;p&gt;I've worked a lot with the Microchip TCP/IP Stack and I've found in most cases it's easier to have your server connect to the PIC and request data rather than have the PIC post the data to the server.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-02-18T15:54:57.023" CommentCount="2" />
  <row Id="10405" PostTypeId="1" AcceptedAnswerId="10408" CreationDate="2011-02-18T16:14:42.570" Score="3" ViewCount="250" Body="&lt;p&gt;I am wanting make an embedded device that can communicate with a web-server in a secure fashion. My preference would be for it to use standard SSL so the web-server views my device similar to a web browser.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Are there any prebuit libraries for&#xA;the embedded side to do this?&lt;/li&gt;&#xA;&lt;li&gt;What about an IC that can handle the&#xA;handshaking and decryption for me?&lt;/li&gt;&#xA;&lt;li&gt;If not how would I go about doing&#xA;this myself?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="319" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-18T19:08:35.193" LastActivityDate="2011-02-23T16:19:17.787" Title="SSL from a Microcontroller" Tags="&lt;library&gt;&lt;tcp-ip&gt;&lt;ssl&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="10406" PostTypeId="1" AcceptedAnswerId="10407" CreationDate="2011-02-18T16:14:57.573" Score="2" ViewCount="161" Body="&lt;p&gt;I found myself looking for a low-noise PNP transistor the other day.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I couldn't find any parametric searches that listed noise performance. Even from the transistor manufacturers. You can search by beta, \$V_{ceo}\$, and \$I_{c}MAX\$.  All these searches seem to return a table of every general-purpose part in the manufacturer's portfolio. Not helpful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This circuit needs to have low-noise at audio frequencies.  RF transistors seems to be better characterized for noise, but they aren't necessarily low-noise at audio frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best I have found was &lt;a href=&quot;http://www.diyaudio.com/forums/solid-state/17285-ultra-low-noise-transistors.html&quot; rel=&quot;nofollow&quot;&gt;a forum thread at DIYaudio&lt;/a&gt;, but the recommendations tended to be old-school, even obsolete parts. I'm looking for a mass produced transistor in SOT-23 or smaller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So recommendations are welcome, but I'd really like to see a selection tool or parametric search that includes this information.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-01T11:32:33.807" LastActivityDate="2011-06-01T11:32:33.807" Title="Low-noise audio-frequency BJT?" Tags="&lt;audio&gt;&lt;transistor&gt;&lt;noise&gt;&lt;bjt&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="10407" PostTypeId="2" ParentId="10406" CreationDate="2011-02-18T16:47:57.073" Score="2" ViewCount="" Body="&lt;p&gt;I found &lt;a href=&quot;http://www.nxp.com/#/ps/ps=%5bi=47295%5d|pp=%5bt=pfp,i=47295%5d&quot; rel=&quot;nofollow&quot;&gt;these devices&lt;/a&gt; with a search on the NXP web site. They seem similar to the BC108 which used to be the low-noise device most people used to use.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-18T18:11:24.317" LastActivityDate="2011-02-18T18:11:24.317" CommentCount="1" />
  <row Id="10408" PostTypeId="2" ParentId="10405" CreationDate="2011-02-18T17:05:28.747" Score="3" ViewCount="" Body="&lt;p&gt;I suggest the Microchip &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2680&amp;amp;dDocName=en537041&quot; rel=&quot;nofollow&quot;&gt;TCP stack&lt;/a&gt;. Microchip offers a free licensed TCP/IP stack optimized for the PIC18, PIC24, dsPIC and PIC32.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Microchip’s TCP/IP stack includes the Secure Sockets Layer (SSL) feature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But it's not free. See below:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;To comply with US Export Control&#xA;  restrictions, the encryption portion&#xA;  of the SSL module must be purchased&#xA;  separately from Microchip. The library&#xA;  of Data Encryption Routines (SW300052)&#xA;  is available for a nominal fee from&#xA;  &lt;a href=&quot;http://www.microchipdirect.com/productsearch.aspx?Keywords=SW300052&quot; rel=&quot;nofollow&quot;&gt;http://www.microchipdirect.com/productsearch.aspx?Keywords=SW300052&lt;/a&gt;.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;For better results, you can use &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en541877&quot; rel=&quot;nofollow&quot;&gt;ENCx24J600&lt;/a&gt; that has built-in AES encrypt/decrypt engine and other securities engines.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-23T11:07:45.787" LastActivityDate="2011-02-23T11:07:45.787" CommentCount="4" />
  <row Id="10409" PostTypeId="2" ParentId="10405" CreationDate="2011-02-18T17:06:51.893" Score="2" ViewCount="" Body="&lt;p&gt;If the system can be complicated enough to run an operating system, there are plenty of tools and libraries that can do the job. On an embedded Linux system, you can use wget with SSL. On any system with higher level languages like Python or Ruby, the networking library (&lt;a href=&quot;http://docs.python.org/library/ssl.html&quot; rel=&quot;nofollow&quot;&gt;Python SSL&lt;/a&gt;) will support SSL. If you only have access to C, you could write something using the &lt;a href=&quot;http://www.openssl.org/&quot; rel=&quot;nofollow&quot;&gt;OpenSSL library&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there's no OS, I think you're in for a lot of work. At minimum, you need a TCP/IP stack. I'd build a prototype with an mbed-- there's a &lt;a href=&quot;http://mbed.org/forum/news-announcements/topic/1415/&quot; rel=&quot;nofollow&quot;&gt;forum post&lt;/a&gt; that suggests they might have an SSL library by now.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-02-18T17:06:51.893" CommentCount="2" />
  <row Id="10410" PostTypeId="2" ParentId="10392" CreationDate="2011-02-18T17:06:52.173" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.powersimtech.com/index.php?name=psim&quot; rel=&quot;nofollow&quot;&gt;Powersim&lt;/a&gt; for power electronics and motor control. There are demos online, but I suppose that's not much use if you don't use the internet.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-02-18T17:06:52.173" />
  <row Id="10411" PostTypeId="1" AcceptedAnswerId="11023" CreationDate="2011-02-18T17:09:37.413" Score="3" ViewCount="144" Body="&lt;p&gt;Modular synths have recently piqued my interest, but patch cords are hell. I have been thinking of some intelligent way to route signals - something microcontroller-driven and remembering different presets. I came across analog crosspoint switches - they are used to switch high-frequency signal, television and the like, and have 16 inputs and 16 outputs. They, however have unnecessarily high bandwidths (60+MHz) and prices ($30+/chip) for this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for a 16x16 switch (or a good way to implement one), suitable for modular synth use, and not having dedicated inputs and outputs - just 16 points which can be freely connected to one another.&lt;/p&gt;&#xA;" OwnerUserId="3075" LastEditorUserId="3075" LastEditorDisplayName="" LastEditDate="2011-02-18T19:16:34.850" LastActivityDate="2011-03-04T09:28:20.653" Title="Crosspoint switch matrix for audio frequency signal?" Tags="&lt;audio&gt;&lt;switch&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10412" PostTypeId="2" ParentId="10369" CreationDate="2011-02-18T17:14:22.390" Score="2" ViewCount="" Body="&lt;p&gt;To have the stepper motor ramp up as quickly as possible, but no too quickly so that it stalls requires knowing when the motor shaft has actually turned to the next step.  There is, of course, some amount of lag time between when power is applied and when the shaft actually starts turning.  Perhaps you can get some idea of where your motor is by temporarily attaching a potentiometer to the system.  Note, depending on the package, you may have to break off the little tab to enable it to rotate completely.  There will be a &quot;blank&quot; spot in its rotation but it will still give you at least some idea of where you are at.&lt;img src=&quot;http://i.imgur.com/iqLmG.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apply a voltage across the pot and watch it on a scope relative to the stepper control signals.  If you are ramp is too slow you can see when the stepper starts turning backwards for a bit until it settles in its next step position.  Adjust you ramp speed to make the next step so that the motor does not move backwards at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also note that attaching a pot to your system changes the system by adding at least a tiny amount mechanical load to the stepper motor.  Hopefully this will not be too great and you can still get fairly close to optimum timing on the ramp up and ramp down.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2011-02-18T17:14:22.390" CommentCount="3" />
  <row Id="10413" PostTypeId="1" AcceptedAnswerId="10429" CreationDate="2011-02-18T17:18:02.310" Score="2" ViewCount="123" Body="&lt;p&gt;I have seen patented hardware designs at the level of generic digital block such as shift registers, flip-flops and adders. If a chip maker were to include such a design deep within an ASIC, how can patent holders uncover copyright infringement? Do patent holders really go around planting industry spies to get blueprints, or engage in etching open mass produced chips to deduce internal logic?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On another note, is it ethical to glean ideas from patents and include it within commercial products?&lt;/p&gt;&#xA;" OwnerUserId="2897" LastActivityDate="2011-02-18T19:14:20.227" Title="Patented hardware architectures" Tags="&lt;hardware&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="10414" PostTypeId="5" CreationDate="2011-02-18T17:39:44.973" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-18T17:39:44.973" LastActivityDate="2011-02-18T17:39:44.973" />
  <row Id="10415" PostTypeId="4" CreationDate="2011-02-18T17:39:44.973" Score="0" ViewCount="" Body="SMPS is a Switch Mode Power Supply.  Typically a DC/DC converter." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-18T17:51:05.527" LastActivityDate="2011-02-18T17:51:05.527" />
  <row Id="10416" PostTypeId="1" AcceptedAnswerId="10417" CreationDate="2011-02-18T17:47:53.063" Score="3" ViewCount="302" Body="&lt;p&gt;Hey people, this is just a quick and dirty question. I don't understand the purpose of the caps in the MAX232 circuit. What do they do, exactly? Can they be skipped? Can they be swapped with 10uF caps?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-02-18T19:45:43.470" LastActivityDate="2011-02-18T19:45:43.470" Title="Can I use 10uF caps in a MAX232?" Tags="&lt;rs232&gt;&lt;max232&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="10417" PostTypeId="2" ParentId="10416" CreationDate="2011-02-18T17:56:08.527" Score="3" ViewCount="" Body="&lt;p&gt;I've just seen this schematic on the internet that shows 10&amp;mu;F caps... so assuming this is correct, I guess you can.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WQqWZ.gif&quot; alt=&quot;MAX232 schematic&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-18T17:56:08.527" CommentCount="7" />
  <row Id="10418" PostTypeId="2" ParentId="10416" CreationDate="2011-02-18T18:02:31.617" Score="2" ViewCount="" Body="&lt;p&gt;The purpose of the 4 capacitors is to generate the +/-12 volts needed for RS232 communications. The &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/MAX220-MAX249.pdf&quot; rel=&quot;nofollow&quot;&gt;MAXIM&lt;/a&gt; and &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/max232.pdf&quot; rel=&quot;nofollow&quot;&gt;TI&lt;/a&gt; MAX232 datasheets recommend 1uF capacitors.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-02-18T18:20:13.500" LastActivityDate="2011-02-18T18:20:13.500" />
  <row Id="10419" PostTypeId="5" CreationDate="2011-02-18T18:06:17.667" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-18T18:06:17.667" LastActivityDate="2011-02-18T18:06:17.667" />
  <row Id="10420" PostTypeId="4" CreationDate="2011-02-18T18:06:17.667" Score="0" ViewCount="" Body="FTDI is a popular RS-232 (serial) to USB converter chip." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-18T18:17:15.643" LastActivityDate="2011-02-18T18:17:15.643" />
  <row Id="10421" PostTypeId="2" ParentId="10416" CreationDate="2011-02-18T18:08:30.060" Score="1" ViewCount="" Body="&lt;p&gt;The MAX202 is a better choice, it can use 100n ceramic capacitors.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-18T18:08:30.060" CommentCount="5" />
  <row Id="10422" PostTypeId="5" CreationDate="2011-02-18T18:10:14.027" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-18T18:10:14.027" LastActivityDate="2011-02-18T18:10:14.027" />
  <row Id="10423" PostTypeId="4" CreationDate="2011-02-18T18:10:14.027" Score="0" ViewCount="" Body="An ADC is an Analog to Digital Converter." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-18T18:17:28.610" LastActivityDate="2011-02-18T18:17:28.610" />
  <row Id="10424" PostTypeId="5" CreationDate="2011-02-18T18:10:33.387" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-18T18:10:33.387" LastActivityDate="2011-02-18T18:10:33.387" />
  <row Id="10425" PostTypeId="4" CreationDate="2011-02-18T18:10:33.387" Score="0" ViewCount="" Body="A DAC is a Digital to Analog Converter." OwnerUserId="-1" LastEditorUserId="4480" LastEditorDisplayName="" LastEditDate="2011-05-31T06:36:12.203" LastActivityDate="2011-05-31T06:36:12.203" />
  <row Id="10426" PostTypeId="2" ParentId="10416" CreationDate="2011-02-18T18:22:20.563" Score="1" ViewCount="" Body="&lt;p&gt;They are used for the converter inside to make a negative voltage for the RS232 lines (which is +/-). Honestly, I don't see why you would prefer a bigger cap, as they normally become more expensive and larger..&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-02-18T18:22:20.563" CommentCount="1" />
  <row Id="10427" PostTypeId="5" CreationDate="2011-02-18T18:40:51.067" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-18T18:40:51.067" LastActivityDate="2011-02-18T18:40:51.067" />
  <row Id="10428" PostTypeId="4" CreationDate="2011-02-18T18:40:51.067" Score="0" ViewCount="" Body="A breadboard is a pre-made generic board for prototyping." OwnerUserId="-1" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-18T18:54:54.507" LastActivityDate="2011-02-18T18:54:54.507" />
  <row Id="10429" PostTypeId="2" ParentId="10413" CreationDate="2011-02-18T19:14:20.227" Score="6" ViewCount="" Body="&lt;p&gt;Unless you are a patent lawyer, then stay as far away from patents and patent research as possible, because if someone does slap you or your company with a suit, then you can be hit with triple damages if you are shown to have known about the patent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So rule 1 about patents: Never actively look at patents.&#xA;A good second rule is: Never tell anybody about patents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess it's a &quot;don't ask, don't tell&quot; sort of deal. &lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-02-18T19:14:20.227" CommentCount="1" />
  <row Id="10430" PostTypeId="2" ParentId="10254" CreationDate="2011-02-18T19:15:29.723" Score="1" ViewCount="" Body="&lt;p&gt;Sounds like an interesting project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All microcontroller datasheets I've read so far all have the same crystal oscillator configuration -- a single inverter in the &lt;a href=&quot;http://en.wikipedia.org/wiki/Pierce_oscillator&quot; rel=&quot;nofollow&quot;&gt;Pierce oscillator&lt;/a&gt; configuration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will make no difference to the precision of a Pierce oscillator whether you use such a microcontroller or a SSI discrete logic chip to drive the crystal -- it's a simple inverter either way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While most of the Pierce oscillators I've seen use exactly 2 capacitors, one per crystal pin, some people insist that &lt;a href=&quot;http://techref.massmind.org/techref/clocks.htm&quot; rel=&quot;nofollow&quot;&gt;the right way to built a Pierce oscillator&lt;/a&gt; is with 4 capacitors, one to ground and one to VCC at each crystal pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes I wonder if a &quot;gentle&quot; sine-wave oscillator such as a &lt;a href=&quot;http://en.wikipedia.org/wiki/Wien_bridge_oscillator&quot; rel=&quot;nofollow&quot;&gt;Wien bridge oscillator&lt;/a&gt; would be better at driving a crystal than the digital on/off of a Pierce oscillator.&#xA;Perhaps you could build a couple of each kind of circuit and compare them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wikipedia claims that &lt;a href=&quot;http://en.wikipedia.org/wiki/crystal_oscillator#Stability_and_aging&quot; rel=&quot;nofollow&quot;&gt;thermal noise influences the stability of crystal oscillators&lt;/a&gt;.&#xA;Would putting one of your crystals in a little &lt;a href=&quot;http://en.wikipedia.org/wiki/Thermoelectric_cooling&quot; rel=&quot;nofollow&quot;&gt;Peltier cooler&lt;/a&gt; at a constant cold temperature work any better than the more common approach, putting the crystal in a little oven at a constant hot temperature?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://opencircuits.com/24%22_Wall_Clock&quot; rel=&quot;nofollow&quot;&gt;Spark Fun Wall Clock&lt;/a&gt; has a few pointers on getting a clock to read GPS time.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-18T19:15:29.723" CommentCount="5" />
  <row Id="10431" PostTypeId="1" AcceptedAnswerId="10432" CreationDate="2011-02-18T19:44:28.017" Score="1" ViewCount="160" Body="&lt;p&gt;I'm trying to attach certain components to my prototype board. However they have short pins, so it is hard to wire-wrap to them. Someone showed me something that you can insert the pins into to make them longer. They come in strips which can be divided. He called it something that sounded like &quot;borgstrip&quot;, but that's not what it is. What is it called?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-02-18T20:11:49.173" Title="What is the name of this electronic component" Tags="&lt;electronics&gt;&lt;components&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="10432" PostTypeId="2" ParentId="10431" CreationDate="2011-02-18T20:11:49.173" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.houseofconnectors.com/berg-strip.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.houseofconnectors.com/berg-strip.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-18T20:11:49.173" CommentCount="2" />
  <row Id="10433" PostTypeId="1" AcceptedAnswerId="10434" CreationDate="2011-02-18T22:03:10.547" Score="1" ViewCount="122" Body="&lt;p&gt;I am almost completely new to electronics.  Recently I was reading about an 'analog multiplexer'  I know what a multiplexer does, and how it works, but is there such a thing as a 'digital multiplexer' that would just give +5v when a channel was on?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pardon if my question is malformed, I just started in on electronics two days ago.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;REPHRASE:&lt;br&gt;&#xA;OK, so the difference is that a 'digital' multiplexer will just output +5/0, and an 'analog' multiplexer will just pass the input signal with as little distortion as possible ?&lt;/p&gt;&#xA;" OwnerUserId="3077" LastEditorUserId="3077" LastEditorDisplayName="" LastEditDate="2011-02-19T17:13:17.600" LastActivityDate="2011-02-19T17:13:17.600" Title="Analog Multiplexer ?" Tags="&lt;multiplexing&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="10434" PostTypeId="2" ParentId="10433" CreationDate="2011-02-18T22:57:47.210" Score="2" ViewCount="" Body="&lt;p&gt;Absolutely. Try for example, the 74hc151.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-18T22:57:47.210" />
  <row Id="10435" PostTypeId="1" AcceptedAnswerId="10441" CreationDate="2011-02-19T01:13:59.573" Score="3" ViewCount="159" Body="&lt;p&gt;How to remove that capacitor from the board?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://vi-server.org/vi/_/cap1.jpg&quot; alt=&quot;capacitor&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the &lt;a href=&quot;http://electronics.stackexchange.com/questions/10034/is-it-safe-to-keep-on-using-ac-adapter-with-a-damaged-output-capacitor&quot;&gt;question about damaged power supply&lt;/a&gt; I was told to use &quot;a sharp utility knife&quot;, but it don't cut that thing (is it epoxy?). Also tried old not-so-sharp scalpel (it can punch that things if pressed hard, but not cut).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://vi-server.org/vi/_/cap2.jpg&quot; alt=&quot;knife&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What other methods of removing it can you propose?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;: Mission accomplished:&lt;br&gt;&#xA;&lt;img src=&quot;http://vi-server.org/vi/_/cap3.jpg&quot; alt=&quot;removed capacitor&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2898" LastEditorUserId="2898" LastEditorDisplayName="" LastEditDate="2011-02-19T11:43:10.743" LastActivityDate="2011-02-19T11:43:10.743" Title="How to remove glued capacitor from the board?" Tags="&lt;capacitor&gt;&lt;cutting&gt;&lt;glue&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="10436" PostTypeId="2" ParentId="10435" CreationDate="2011-02-19T01:24:10.600" Score="3" ViewCount="" Body="&lt;p&gt;Do you need to keep the cap intact?  If not, I would cut the leads, desolder them, and get pliers and gently roll the cap side to side to remove it.  I haven't encountered anything yet that has been epoxy-like, so it might come off pretty easily.  Of course, you have to use your judgement, so if it doesn't seem to want to release, don't force it.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-19T01:24:10.600" CommentCount="2" />
  <row Id="10437" PostTypeId="2" ParentId="10435" CreationDate="2011-02-19T01:32:21.727" Score="0" ViewCount="" Body="&lt;p&gt;I'd try to figure out what the substance is - is it softish? That would be either hot-melt or silicone. If it's one of those you can either just cut the leads and pull the thing off (neither one will damage the board in the process), or if it's hot-melt you can heat it up a bit and the thing will come right off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given that you can't cut it easily, I'm guessing it's hard as a rock. That means either epoxy, or superglue, and of the two I'd guess epoxy. If it were superglue, you could get some remover (yea, they make a chemical that will soften superglue!), but if it's epoxy you've no such luck (the only chemical that would work is pretty carcinogenic and thus not readily available). At that point I'd cut the leads and break the cap off - either chiseling it off, or using a thin bladed saw to cut the epoxy above the board (breaking the cap into pieces if need be). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, once you've got the cap off, use silicone or hot melt to attach the new one.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2011-02-19T01:32:21.727" CommentCount="2" />
  <row Id="10438" PostTypeId="1" AcceptedAnswerId="10439" CreationDate="2011-02-19T02:04:39.893" Score="2" ViewCount="83" Body="&lt;p&gt;Years ago, I saw a program on TV about this guy who spent his free time building analog robots that looked and behaved very much like insects.  I've been trying, without success, to find that or similar information.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, I'm just looking for examples of how complex life-like behavior can arise in a system that has no &quot;smarts&quot;, no thoughts, and no stated goals.  It just happens that its component parts cause it to behave in a goal-seeking manner that appears life-like.  Analog robotic insects seem like a great example of that type of phenomenon.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone can point me to information about analog insect-like robots, that would be excellent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone can guess the specific TV program I'm talking about, that would be even cooler!&lt;/p&gt;&#xA;" OwnerUserId="3083" LastActivityDate="2011-02-19T16:17:47.510" Title="Where can I find good examples of analog insect-like robots?" Tags="&lt;robotics&gt;&lt;analog&gt;" AnswerCount="2" />
  <row Id="10439" PostTypeId="2" ParentId="10438" CreationDate="2011-02-19T03:00:50.097" Score="3" ViewCount="" Body="&lt;p&gt;Could that be Mark Tilden? BEAM robotics?&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-19T03:00:50.097" CommentCount="2" />
  <row Id="10440" PostTypeId="2" ParentId="10394" CreationDate="2011-02-19T05:25:39.413" Score="0" ViewCount="" Body="&lt;p&gt;Honestly, and I mean no offense here, but if I were you I would save myself the impending headaches and wasted time, buy an AVRISP mkII for $30, and be done with it!&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-02-19T05:25:39.413" CommentCount="2" />
  <row Id="10441" PostTypeId="2" ParentId="10435" CreationDate="2011-02-19T05:54:01.063" Score="6" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The cap is made of aluminum, wrapped in a plastic jacket.  The jacket is glued down.  Can you slit the plastic and remove the capacitor, leaving the jacket where it is?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Otherwise, try a bit of acetone on the glue and see if it softens any.  (Acetone + perfume =  nail polish remover.)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If it's a hard brittle substance, try using a hammer and punch to dislodge the capacitor.  If that doesn't work, try a bigger hammer!&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Last resort:&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/LczNM.gif&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-19T06:18:19.023" LastActivityDate="2011-02-19T06:18:19.023" CommentCount="2" />
  <row Id="10442" PostTypeId="2" ParentId="10435" CreationDate="2011-02-19T05:59:05.820" Score="6" ViewCount="" Body="&lt;p&gt;I'd smash my beer over my head then start madly hacking at it with the jagged edges 'til it came off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wGDj2.jpg&quot; width=&quot;300&quot;&gt; &lt;img src=&quot;http://i.imgur.com/WTTgX.jpg&quot; width=&quot;300&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-19T06:04:34.320" LastActivityDate="2011-02-19T06:04:34.320" CommentCount="2" />
  <row Id="10443" PostTypeId="2" ParentId="10369" CreationDate="2011-02-19T07:01:18.070" Score="0" ViewCount="" Body="&lt;p&gt;In my experience, stepper motors either run fine, or vibrate. The disconnect between working and too rapid acceleration is VERY obvious.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming you have the whole thing set up, and you can freely run the axes back and forth, determining acceleration rates is therefore easy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, set the system up to cycle one of the axes back and forth, and then gradually increase the acceleration rate until it stops moving. Then back it off about 10-20%&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Repeat for other axes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: The system has to be loaded while testing.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-02-19T07:01:18.070" CommentCount="1" />
  <row Id="10444" PostTypeId="2" ParentId="10438" CreationDate="2011-02-19T08:16:08.563" Score="1" ViewCount="" Body="&lt;p&gt;Theo Jansen builds &lt;a href=&quot;http://www.strandbeest.com/&quot; rel=&quot;nofollow&quot;&gt;wind powered insect-like kinetic robots&lt;/a&gt;. Completely mechanical.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;He got invited to TED and gave &lt;a href=&quot;http://www.ted.com/talks/theo_jansen_creates_new_creatures.html&quot; rel=&quot;nofollow&quot;&gt;a talk on them&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-19T16:17:47.510" LastActivityDate="2011-02-19T16:17:47.510" />
  <row Id="10445" PostTypeId="2" ParentId="10435" CreationDate="2011-02-19T09:18:30.793" Score="0" ViewCount="" Body="&lt;p&gt;If it is epoxy, heat might work. Try going outside (or at least open the window wide), and use an old soldering iron. Remember that you don't want to save the cap, but you want to keep the board in good shape. Cutting the leads before attacking the glue will be a good idea.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-02-19T09:18:30.793" />
  <row Id="10446" PostTypeId="1" CreationDate="2011-02-19T10:07:03.220" Score="5" ViewCount="219" Body="&lt;p&gt;Is there any IC that can be use to convert 9 bit binary code to seven segment display?&#xA;EX:&#xA;100101100-&gt;300&#xA;  I want to display 300 in seven segment display when 100101100 binary code applied to input.I want to do this only using ICs not using microcontrollers.&lt;/p&gt;&#xA;" OwnerUserId="3038" LastActivityDate="2011-03-04T20:11:46.613" Title="Binary coded decimal ICs" Tags="&lt;electronics&gt;&lt;digital&gt;&lt;7segmentdisplay&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="10447" PostTypeId="2" ParentId="10411" CreationDate="2011-02-19T10:10:22.820" Score="0" ViewCount="" Body="&lt;p&gt;I afraid you might not find any cheaper things. It's basically a matrix of 16x16 FET's with control logic. Even in it's simplest implementation it have good bandwidth, so 60Mhz is a basic one :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may be lucky to build that from discreete components (256 FET + 32 shift registers) - but it will probably cost the same.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-19T10:10:22.820" CommentCount="5" />
  <row Id="10448" PostTypeId="2" ParentId="10446" CreationDate="2011-02-19T10:14:44.747" Score="4" ViewCount="" Body="&lt;p&gt;I afraid there are no such standard chips.&#xA;While there are BCD to 7segment chips, it will be hard to extract individual digits, as this would require 'divide by 10' chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, CPLDs are here for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can generate separate digits instead of single 9-bit number, you will be able to use standard chips.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-19T10:14:44.747" CommentCount="1" />
  <row Id="10449" PostTypeId="1" CreationDate="2011-02-19T10:35:22.020" Score="1" ViewCount="116" Body="&lt;p&gt;Can I control my telephone with a computer- things like making and receiving calls? What hardware will I need?&lt;/p&gt;&#xA;" OwnerUserId="2074" LastActivityDate="2011-02-20T22:51:57.443" ClosedDate="2011-02-22T15:48:52.103" Title="Controlling telephone with a computer" Tags="&lt;computers&gt;&lt;telephone&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="10450" PostTypeId="2" ParentId="10446" CreationDate="2011-02-19T11:29:04.460" Score="3" ViewCount="" Body="&lt;p&gt;Perhaps the easiest way would be to make a conversion table and put it into EPROM or FLASH with at least 9 address and 12 data lines. Otherwise CPLD or small FPGA (&lt;a href=&quot;http://opencores.org&quot; rel=&quot;nofollow&quot;&gt;opencores.org&lt;/a&gt; has some HDL for this).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really wanted to do this using discrete ICs, you would have to construct a state machine implementing the algorithm, which would be the most complex solution and not really different from microcontroller except for increased price, size and complexity.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastEditorUserId="2636" LastEditorDisplayName="" LastEditDate="2011-02-19T16:21:33.113" LastActivityDate="2011-02-19T16:21:33.113" CommentCount="1" />
  <row Id="10451" PostTypeId="2" ParentId="10449" CreationDate="2011-02-19T11:49:50.493" Score="3" ViewCount="" Body="&lt;p&gt;It really depends on what you want to do with the call. A basic modem will make and receive calls from a computer, but this will control the phone line, not an actual telephone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can give some more detail on what your trying to achieve, I might be able to elaborate.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-19T11:49:50.493" CommentCount="4" />
  <row Id="10452" PostTypeId="2" ParentId="10449" CreationDate="2011-02-19T14:35:59.803" Score="0" ViewCount="" Body="&lt;p&gt;Could could launch an EC2 instance running Ubuntu and Skype. I outsourced the task of setting up this. You could then use the Skype API to make phone calls and play and record WAV files to have an automated conversation. I believe I got someone to implement all parts of what I described here.&lt;/p&gt;&#xA;" OwnerUserId="1625" LastActivityDate="2011-02-19T14:35:59.803" />
  <row Id="10453" PostTypeId="2" ParentId="10433" CreationDate="2011-02-19T15:09:46.100" Score="0" ViewCount="" Body="&lt;p&gt;Yes, analog and digital multiplexers have been around since the dawn of SSI. &lt;a href=&quot;http://en.wikipedia.org/wiki/Multiplexer&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Multiplexer&lt;/a&gt;. Typically the analog variety are integrated with an A/D device.&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-02-19T15:09:46.100" />
  <row Id="10454" PostTypeId="2" ParentId="10433" CreationDate="2011-02-19T15:34:34.760" Score="0" ViewCount="" Body="&lt;p&gt;You can probably use an analog multiplexer as a digital one.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In actuality, in many cases you can use some types of &quot;digital&quot; multiplexor as an analog one, too.  People build extremely high performance radios using digital bus switches as commutating RF mixers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are basically two ways to do a multiplexor - one is as a choice made of passive switches, basically MOSFET &quot;pass gates&quot; which ideally alter the signal as little as possible when passing through them.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other is to build a multiplexor using logic gates (or PLD LUT's) to implement a truth table.  This would most likely have the usual logic-gate property of non-linear amplification, ie, an input which just barely qualifies as a 1 or a 0 becomes an output which is quite strongly and unambiguously that value, restoring noise margins.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-02-19T15:34:34.760" />
  <row Id="10455" PostTypeId="2" ParentId="10369" CreationDate="2011-02-19T15:42:35.420" Score="0" ViewCount="" Body="&lt;p&gt;If you visit the web sites of companies that manufacturer quality stepper motors, you'll likely find documentation giving the theoretical way to calculate this.  You'll need to know a lot about the mechanical load, and be prepared to do a fair amount of math.  But if you are designing a printer to sell at a loss and make it up on ink... it's worth optimizing these things so you can use the cheapest motor that can meet your ramp speed requirements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But in the more likely case, if you are building a one-off robot or hobby CNC machine or whatever, chances are you are going to buy the biggest motors you can get a good deal on (or you've already extracted them from that ancient printer), and then crank up the ramp-rate until you find it unreliable, then back off whatever safety factor you desire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A well engineered and adjusted high voltage chopping drive amplifier will be necessary to get the maximum performance out of the motor without damaging its magnets.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-02-19T15:42:35.420" CommentCount="2" />
  <row Id="10456" PostTypeId="2" ParentId="10449" CreationDate="2011-02-19T15:42:41.197" Score="1" ViewCount="" Body="&lt;p&gt;If you want to roll your own interface to the telephone line, here are a couple of books:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0750671750&quot; rel=&quot;nofollow&quot;&gt;Understanding Telephone Electronics,&#xA;Fourth Edition&lt;/a&gt; by Joseph Carr,&#xA;Steve Winder, and Stephen Bigelow&#xA;(2001)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0071548440&quot; rel=&quot;nofollow&quot;&gt;Telephone Projects for the Evil&#xA;Genius&lt;/a&gt; by Thomas Petruzzellis&#xA;(2008)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.epanorama.net/circuits/teleinterface.html&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; is a good on-line reference.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-02-19T15:42:41.197" CommentCount="1" />
  <row Id="10457" PostTypeId="1" AcceptedAnswerId="10458" CreationDate="2011-02-19T16:20:57.607" Score="2" ViewCount="78" Body="&lt;p&gt;I have created a wav file (sampling rate of 44.1kHz at 32-bit floating point precision) consisting of 44.1k samples at 0.0 followed by 44.1k at 1.0. After which the file is played out from line-out using Media Player Classic and looped back into line-in. The resulting waveform is captured and inspected using Audacity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output waveform goes from 0.0 to 1.0, holds it there for a number of samples and some how &quot;decays&quot; back to 0.0. What is going on? And how do I recreate the desired step waveform where it will persist at 1.0 for the second half of the waveform?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The brand of the sound card used in question is Realtek, PC is an Acer TravelMate 4720.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS: This may seems like a PC question but I suspect it has more to do with sound electronics used on sound cards.&lt;/p&gt;&#xA;" OwnerUserId="2897" LastActivityDate="2011-02-21T00:40:50.600" Title="PC sound generation of step waveform" Tags="&lt;sound&gt;&lt;pc&gt;" AnswerCount="3" />
  <row Id="10458" PostTypeId="2" ParentId="10457" CreationDate="2011-02-19T16:59:03.780" Score="4" ViewCount="" Body="&lt;p&gt;This sounds like there is some DC Bias removal taking place. In general with audio you want your average voltage should be 0v. This is because of how speakers work. 0v would mean that the speaker is at rest. In order for the speaker to sound normal you want it to be able to go back to its resting position.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to achieve this, sound cards will remove any DC offset in order to set the average voltage to be 0. This can be done both digital and analog. If it is done digitally there may be some settings with your driver to disable DC Bias adjustment. If it is done analog, you will have a tough time getting rid of it.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-19T16:59:03.780" CommentCount="0" />
  <row Id="10459" PostTypeId="2" ParentId="10446" CreationDate="2011-02-19T17:12:01.020" Score="1" ViewCount="" Body="&lt;p&gt;I don't think you can solve this easily with 1 IC. You could look at the MAX7231 chips, but they seem old and very expensive.&#xA;You maybe can use the HEF4511 (or DS8669) if you can find a 10-bit &amp;lt;&gt; BCD encoder of some sort. Also, you'd have a hard time creating it in such a way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may also be able to write down the boolean formulas for the 10-bit code to 3x a BCD output. I wouldn't expect that to be very simple, because 10 inputs to 3x4 outputs seems a lot of work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suppose you're doing this 'just for fun', doing this in the engineering world is not very cost effective. You probably need a 7 segment signal + 3 displays and 10 bits input. This is about 20 I/O. A simple PIC or AVR with 24 or 28 pins can handle that (or a CLPD if you require faster processing - however displays are for human eyes, so they don't have to be ultra fast).&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-02-19T17:12:01.020" />
  <row Id="10460" PostTypeId="2" ParentId="10457" CreationDate="2011-02-19T17:18:52.090" Score="2" ViewCount="" Body="&lt;p&gt;Audio codecs in PCs have digital high pass filters (at least the ones I know) with cutoff at some low frequency like 1 Hz, while your signal is only 0.5 Hz, and this is what deforms it. If you use it for some kind of signaling, you will have to move to higher frequencies. I don't think there is a way to disable the filter unless you write your own driver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As Kellenjb says, the filter is there to remove the DC offset from the signal.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-02-19T17:18:52.090" />
  <row Id="10462" PostTypeId="1" AcceptedAnswerId="10467" CreationDate="2011-02-19T20:36:30.147" Score="1" ViewCount="89" Body="&lt;p&gt;There are some native probabilistic circuits that are being developed by various folks (e.g &lt;a href=&quot;http://smartech.gatech.edu/handle/1853/26706&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt;). I'm wondering if this technology would be classified as mixed-signal, or something else?&lt;/p&gt;&#xA;" OwnerUserId="3085" LastActivityDate="2011-02-19T22:53:04.080" Title="Probabilistic Circuits" Tags="&lt;analog&gt;&lt;logic&gt;&lt;digital&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="10463" PostTypeId="2" ParentId="10446" CreationDate="2011-02-19T21:09:54.110" Score="7" ViewCount="" Body="&lt;p&gt;I can think of three ways to do this. I'll start from the most expensive and complicated and work my way down.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;All Logic IC's: Use a parallel-load 9-bit up/down binary counter (such as 3x 74hc190) and a 3-digit resettable BCD counter (3x 74hc163). Load the binary counter with your 9-bit number, and clear the BCD counter to 0. Clock both counters until the binary counter reaches zero. Load the output of the BCD counter into a latch, and then feed it to a BCD-7seg decoder. Repeat.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Pros: &#xA;&lt;ul&gt;&#xA;&lt;li&gt;Meets requirement of only using standard logic IC's&lt;/li&gt;&#xA;&lt;li&gt;Requires no programming&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Cons:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Expensive (The counter chips are about $1-2 each)&lt;/li&gt;&#xA;&lt;li&gt;Prone to wiring failure&lt;/li&gt;&#xA;&lt;li&gt;Requires a clock signal of 31kHz for 60Hz refresh&lt;/li&gt;&#xA;&lt;li&gt;Requires 8-12 Logic IC's (I'll draw a schematic later)&#xA;&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;ROM Look-Up Table: Use a small parallel asynchronous FLASH memory (such as &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=SST39SF010A-70-4C-PHE-ND&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; one) to take all data inputs as an address, and then program the ROM to generate BCD outputs for 2 digits. Feed the result into a BCD-to-7seg decoder. Alternatively, use one ROM to generate a single decimal digit decoded into 7-segment pins. &#xA;&lt;ul&gt;&#xA;&lt;li&gt;Pros:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Fairly cheap price per digit&lt;/li&gt;&#xA;&lt;li&gt;Scales better&lt;/li&gt;&#xA;&lt;li&gt;Fast (but speed doesn't really matter)&lt;/li&gt;&#xA;&lt;li&gt;Simple to wire/design&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Cons:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Each ROM requires different programming&lt;/li&gt;&#xA;&lt;li&gt;Need to buy a much larger ROM than needed&lt;/li&gt;&#xA;&lt;li&gt;Programming requires computer automation.&#xA;&lt;br&gt;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Microcontroller: A simple microcontroller with enough inputs and outputs can convert the binary number into BCD, and then encode it into 7-segment control signals. The cheapest solution (My digikey search picked out &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=PIC16F57-I/P-ND&quot; rel=&quot;nofollow&quot;&gt;this PIC&lt;/a&gt;) will multiplex the output digits. You may need transistors to drive the common anode/cathode of your 7-segment displays, but those can be cheap transistors.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Pros:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The cheapest solution at $1.50 - $2.00 total&lt;/li&gt;&#xA;&lt;li&gt;Simple Wiring&lt;/li&gt;&#xA;&lt;li&gt;Ease of implementing Binary-&gt;BCD algorithm in software&lt;/li&gt;&#xA;&lt;li&gt;Easy to add more functionality&lt;/li&gt;&#xA;&lt;li&gt;Least expensive system for driving the display&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Cons:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A chip programmer is required&lt;/li&gt;&#xA;&lt;li&gt;You need to write software (not just a hardware problem)&lt;/li&gt;&#xA;&lt;li&gt;The cheapest solution requires digit multiplexing, which is more complicated than direct drive.&#xA;&lt;br&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;I'll draw up some schematics later&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-20T00:57:54.807" LastActivityDate="2011-02-20T00:57:54.807" />
  <row Id="10464" PostTypeId="1" AcceptedAnswerId="10471" CreationDate="2011-02-19T21:55:42.640" Score="2" ViewCount="145" Body="&lt;p&gt;I stripped a DB9 extension cable which I will use to connect to a DB9 connector on one end and an RJ45 on another. I need to make connections to pin 2, 3, and 5 on the DB9 side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I stripped the DB9 wire, I was surprised to find 5 wires, since there are 9 pins in a DB9 connector. Why are there 9 pins but only 5 wires?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the wires is unshielded. Why is that? The other wires are red, brown, orange, and black. Which pins do these go to?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-20T19:36:52.717" LastActivityDate="2011-02-20T19:36:52.717" Title="Questions about wires in a DB9 cable" Tags="&lt;wire&gt;&lt;rs232&gt;&lt;cables&gt;&lt;db9&gt;" AnswerCount="3" />
  <row Id="10465" PostTypeId="1" AcceptedAnswerId="10470" CreationDate="2011-02-19T22:06:33.900" Score="-1" ViewCount="127" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/10464/questions-about-wires-in-a-db9-cable&quot;&gt;Questions about wires in a DB9 cable&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I stripped a DB9 cable. One end of the cable has a DB9 connector with 9 pins. The stripped end of the cable has 5 wires. I want to figure out which wire connects to which pin. I figure the easiest way to do this is to use a multimeter. How can this be done?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-02-19T23:03:46.410" ClosedDate="2011-02-21T21:06:44.333" Title="How to use a multimeter to figure out what is connected to what" Tags="&lt;connector&gt;&lt;wire&gt;&lt;multimeter&gt;&lt;cables&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="10466" PostTypeId="2" ParentId="10464" CreationDate="2011-02-19T22:08:42.417" Score="4" ViewCount="" Body="&lt;p&gt;It's very rare for all nine pins to be connected, &lt;a href=&quot;http://www.aggsoft.com/rs232-pinout-cable/pinout-and-signal.htm&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; are the details. I only use three for anything I design - Ground, TxD and RxD. The other two will depend on the hardware and software.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-19T22:08:42.417" CommentCount="5" />
  <row Id="10467" PostTypeId="2" ParentId="10462" CreationDate="2011-02-19T22:53:04.080" Score="1" ViewCount="" Body="&lt;p&gt;This area has been in development for decades by way of quantum computers, or, more specifically, &lt;a href=&quot;http://en.wikipedia.org/wiki/Qubit&quot; rel=&quot;nofollow&quot;&gt;qubits&lt;/a&gt;*. Papers in the field usually classify the systems as &lt;strong&gt;digital&lt;/strong&gt;, regardless of any superposition. This is similar to classification of busses in digital systems as digital, though they often require &lt;em&gt;analog&lt;/em&gt; matching, reconstruction, and modulation/demodulation techniques in order to go from point A to point B.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These circuits will eventually output a digital value (ok, analog, if we want to read it). I imagine they also have digital inputs, though I guess this is for the researchers to disprove...  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;*&lt;em&gt;They are not scalable to useful ranges, the number of bits, at present due to difficulties in maintaining coherence. See &lt;a href=&quot;http://www.dwavesys.com/&quot; rel=&quot;nofollow&quot;&gt;D-Wave Systems.&lt;/a&gt;&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-02-19T22:53:04.080" CommentCount="2" />
  <row Id="10468" PostTypeId="2" ParentId="10464" CreationDate="2011-02-19T22:56:53.340" Score="3" ViewCount="" Body="&lt;p&gt;There is no standard for the colours used to connect to a DB9 for serial data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get away with using just TX, RX and ground sometimes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other pins are for controlling the flow of data via hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only way to find out what colour goes to which pin is to use a multimeter on continuity or a low ohms range.&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2011-02-19T22:56:53.340" />
  <row Id="10469" PostTypeId="2" ParentId="10465" CreationDate="2011-02-19T22:58:42.643" Score="1" ViewCount="" Body="&lt;p&gt;Even fairly cheap DVMs usually have a continuity test setting, that will sound a tone when the resistance between the probes is less than some small amount. If not, use the ohm-meter setting, and consider anything less than, say, half an ohm to be connected. (The audible type setting is easier b/c you don't have to keep looking at the meter and interpreting the reading there.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use an alligator clip to connect one of the wire ends to one probe of the DVM, and then use the other probe to systematically test the pins in the connector. When one beeps, you know that wire color goes to that pin. Systematically work through each wire this way to get the complete set of color to pin number associations.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-19T22:58:42.643" />
  <row Id="10470" PostTypeId="2" ParentId="10465" CreationDate="2011-02-19T23:03:46.410" Score="1" ViewCount="" Body="&lt;p&gt;How to work out what pin is which.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Switch you meter to a low ohms range or continuity if available (shown with a diode and sound symbol on most meters)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you have to do is check each pin against each coloured wire. - note sometimes a wire can go to more than one pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using a ohms range then you will get a reading of almost zero ohms when there is a connection between the pin and the wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please note that some meters will take a little time to indicate a low value&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(the reading should be almost them same as connecting the two meter probes together) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using the continuity mode, the the reading should be almost zero, and the meter should beep (If it has a buzzer). please note that some meters can take up to 1 second to start to beep.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have fun.&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2011-02-19T23:03:46.410" />
  <row Id="10471" PostTypeId="2" ParentId="10464" CreationDate="2011-02-19T23:06:49.967" Score="2" ViewCount="" Body="&lt;p&gt;I believe you are asking which specific wire goes to which specific pin, based on the wire color. If that is correct, I'll try to give you some guidance, but I must also warn you that although there is an accepted standard for wire colors on DB9 and RJ45 connectors, it is also common to find them with non-standard wire colors. So think of this as more of a rule of thumb, rather than a certainty.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DB9_&lt;strong&gt;Wire&lt;/strong&gt;_RJ45&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1 N/C_&lt;strong&gt;Green&lt;/strong&gt;_5  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;2_&lt;strong&gt;Black&lt;/strong&gt;_3&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3_&lt;strong&gt;Yellow&lt;/strong&gt;_6&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4_&lt;strong&gt;Brown&lt;/strong&gt;_7&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5_&lt;strong&gt;Red&lt;/strong&gt;_4&lt;/p&gt;&#xA;&#xA;&lt;p&gt;6_&lt;strong&gt;Orange&lt;/strong&gt;_2&lt;/p&gt;&#xA;&#xA;&lt;p&gt;7_&lt;strong&gt;White&lt;/strong&gt;_8&lt;/p&gt;&#xA;&#xA;&lt;p&gt;8_&lt;strong&gt;Blue&lt;/strong&gt;_1&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is not what you are looking for, please clarify and I'll try to help you.&lt;/p&gt;&#xA;" OwnerUserId="2904" LastActivityDate="2011-02-19T23:06:49.967" CommentCount="1" />
  <row Id="10472" PostTypeId="2" ParentId="10446" CreationDate="2011-02-20T01:25:49.760" Score="2" ViewCount="" Body="&lt;p&gt;Your example input, 100101100, is raw binary for 300, not binary coded decimal; BCD for 300 would be 0011 0000 0000. If you want to display numbers that are actually BCD, that's relatively straightforward. But if your inputs are really binary, it's a more complex problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get from raw binary to decimal groupings, which will be necessary to drive the display, you effectively have to do base conversion, which entails doing some integer division. While you &lt;em&gt;can&lt;/em&gt; accomplish this with logic IC's, it will take a boat load of them to do it, which implies a LOT of wiring, which means lots of opportunities for debugging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless there's a compelling reason to use logic IC's, this would be an ideal task for an 8-bit microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-20T01:25:49.760" />
  <row Id="10473" PostTypeId="1" AcceptedAnswerId="10477" CreationDate="2011-02-20T02:34:25.643" Score="0" ViewCount="145" Body="&lt;p&gt;I have an AC adapter jack that has three terminals, L(eft), M(iddle), and R(ight). If I plug in the power supply and connect the plug to the jack, these are the readings I get from the multimeter.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;L(red probe) M R(black probe) = +5V&#xA;L(black probe) M R(red probe) = -5V&#xA;L(red probe) M(black probe) R = 0V&#xA;L M(red probe) R(black probe) = 0V&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;So is the middle terminal ground? Or is ground the the right terminal? I heard that I only need to use two of the terminals when supplying power to components. Is this true?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-05-13T00:17:10.370" LastActivityDate="2011-05-13T00:17:10.370" Title="Which one is ground?" Tags="&lt;power-supply&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="10474" PostTypeId="1" CreationDate="2011-02-20T02:44:12.393" Score="-1" ViewCount="170" Body="&lt;p&gt;I have a small brown capacitor. All it says on it is 10. Is that 10uF?&lt;img src=&quot;http://i.imgur.com/xRk2r.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="1657" LastEditorDisplayName="" LastEditDate="2011-02-20T03:56:55.167" LastActivityDate="2011-02-20T18:40:23.037" Title="What kind of capacitor is this?" Tags="&lt;capacitor&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="10475" PostTypeId="2" ParentId="10474" CreationDate="2011-02-20T02:57:27.473" Score="7" ViewCount="" Body="&lt;p&gt;Small and flat and round? Might be 10 pF, but w/o a picture, this is just a shot in the dark.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ceramic caps that are both physically smaller and have only two digits on them are usually marked in pF. On slightly larger ones, if you see three digits, the third digit is a multiplier, like the way resistors work. Thus &quot;22&quot; is 22 pF, while &quot;103&quot; would be 10,000 pF or 0.01 uF.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-02-20T13:54:58.803" LastActivityDate="2011-02-20T13:54:58.803" />
  <row Id="10476" PostTypeId="2" ParentId="10473" CreationDate="2011-02-20T03:33:46.023" Score="1" ViewCount="" Body="&lt;p&gt;It sounds like the middle terminal isn't connected at all, your right terminal is ground and your left terminal is +5v.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is all based off of the assumption that your multimeter has Black as ground and Red as voltage.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-20T03:33:46.023" />
  <row Id="10477" PostTypeId="2" ParentId="10473" CreationDate="2011-02-20T03:37:02.540" Score="5" ViewCount="" Body="&lt;p&gt;From your readings, the middle terminal is isolated from the others, and I would surmise that it's either &lt;em&gt;earth&lt;/em&gt; ground (if your AC adapter has a ground terminal on it) or simply disconnected, so it can be ignored.  For DC power all you need are two terminals, one each positive and negative.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's what most people call &quot;ground&quot; is determined in context of the circuit you're powering, and it's &lt;em&gt;usually&lt;/em&gt; negative--here, the right terminal.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-02-20T03:37:02.540" />
  <row Id="10478" PostTypeId="1" AcceptedAnswerId="10479" CreationDate="2011-02-20T04:03:24.813" Score="3" ViewCount="173" Body="&lt;p&gt;The project I am working on requires a color indicator which shows the current state (either red, green, or yellow).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally the indicator would have a large surface area so you can quickly glance at the device and determine the state. 2&quot; x 2&quot; would be nice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The device is battery powered and would ideally be able to operate for months at a time without recharging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be the best solution to use for this kind of application?&lt;/p&gt;&#xA;" OwnerUserId="3089" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-20T18:05:32.547" LastActivityDate="2011-04-25T14:50:38.263" Title="What is the best low-power color indicator?" Tags="&lt;low-power&gt;&lt;indicator&gt;" AnswerCount="3" />
  <row Id="10479" PostTypeId="2" ParentId="10478" CreationDate="2011-02-20T04:22:33.417" Score="2" ViewCount="" Body="&lt;p&gt;How often does the indicator need to change? If it's only occasionally, then you could place color swatches on a rotor or scroll mechanism and move it mechanically to different positions. The power consumption while not changing would be zero, but it'd be considerable while changing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One option for the motor/mechanism would be to hack an inexpensive clock movement to be controlled by your project rather than the quartz oscillator it comes with, and stick a disc with your color swatches on in place of the second hand. You can often buy them in craft stores for about $5 US.&lt;/p&gt;&#xA;" OwnerUserId="1409" LastEditorUserId="1409" LastEditorDisplayName="" LastEditDate="2011-02-20T21:34:42.890" LastActivityDate="2011-02-20T21:34:42.890" CommentCount="4" />
  <row Id="10480" PostTypeId="2" ParentId="10474" CreationDate="2011-02-20T04:28:19.007" Score="5" ViewCount="" Body="&lt;p&gt;Ceramic capacitor. Likely to be 10pF.&lt;/p&gt;&#xA;" OwnerUserId="1688" LastActivityDate="2011-02-20T04:28:19.007" CommentCount="2" />
  <row Id="10481" PostTypeId="1" CreationDate="2011-02-20T05:42:44.377" Score="1" ViewCount="130" Body="&lt;p&gt;I have been trying to make a serial programmer for AVR chips. I have been using this schematic as reference, &lt;a href=&quot;http://www.elektronika.lt/_sys/storage/2004/05/06/avr_prog.gif&quot; rel=&quot;nofollow&quot;&gt;http://www.elektronika.lt/_sys/storage/2004/05/06/avr_prog.gif&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I made the circuit and have checked that the connections are correct. Here is a picture of it on breadboard&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kZNSg.jpg&quot; alt=&quot;CKT on Breadboard&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is it doesn't even get detected in linux.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;rick2047@Sophiya:~$ setserial -g /dev/ttyS*&#xA;/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4&#xA;/dev/ttyS1, UART: unknown, Port: 0x02f8, IRQ: 3&#xA;/dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4&#xA;/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3&#xA;rick2047@Sophiya:~$ dmesg |grep ttyS&#xA;[    0.220488] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A&#xA;[    0.221036] 00:08: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A&#xA;rick2047@Sophiya:~$ &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;In window there is a com3 and com1 but cannot connect to com3, it says check your port settings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I checked the bios and there is only a Serial Port A in the peripherals section. Does that mean I can use only one serial? My monitor is an old CRT which runs on serial cable. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UPDATE&lt;/strong&gt;&#xA;The monitor is on VGA. So why does this not work?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;rick2047@Sophiya:~$ avrdude -p atmega8 -P /dev/ttyS0 -c ponyser -V -U flash:w:test1.hex &#xA;&#xA;avrdude: AVR device not responding&#xA;avrdude: initialization failed, rc=-1&#xA;         Double check connections and try again, or use -F to override&#xA;         this check.&#xA;&#xA;&#xA;avrdude done.  Thank you.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-20T22:05:55.037" LastActivityDate="2011-02-20T22:05:55.037" Title="Serial programmer not working, what are the possible problem sources?" Tags="&lt;avr&gt;&lt;programmer&gt;" AnswerCount="2" CommentCount="8" />
  <row Id="10482" PostTypeId="2" ParentId="10481" CreationDate="2011-02-20T11:18:38.940" Score="1" ViewCount="" Body="&lt;p&gt;I was recently making a very similar serial programmer too, and had lots of problems with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, check your crystal for the AVR.  I can't see much on the photo, but its ground should be directly connected to power supply's ground. I've read that sometimes breadboards can make problems if the ground is connected through them because of impedance. Still, if you're programming a fresh AVR, it's going to be running on its own internal oscillator, if it has one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next step is to check if the AVR is getting correct voltage when connected to the programmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you power on insert the AVR, check voltages on each pin and see in the datahseet what that pin is supposed to be. Some AVRs may need multiple ground connections and multiple voltage sources, especially if it has analog to digital converters. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure that all your grounds are at same voltage. That may seem to be obvious, but I forgot to connect GND on my ATmega162 and even without GND, it managed to flash LED while running on internal oscillator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I agree with starblue about capacitor. Read the datasheet for the AVR you're using and AVR Hardware Design Considerations document. It should provide some more information on proper decoupling. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next step is to get a program which can tun on and off a pin on the serial port. You should use something like that to check if you have connected the programmer to the port you're attempting to use. Turn on a pin and check voltage on AVR socket. If you're not getting correct voltages, there's something wrong with your setup, so check everything again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;del&gt;Now that I'm talking about setup, I noticed that there's nothing on Vs+ and Vs- pin of your MAX232. From a datasheet I'm reading, they should be connected to +8.5 V and -8.5 V and have 1 µF decoupling capacitors. On my setup, I connected one side of the capacitor to the pins and the other to +5 V and GND, since I didn't have needed voltages. I read that in a on-line tutorial, so I don't know if it's the best setup, but it works for me.&lt;/del&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do not expect the programmer to be detected by your computer. It doesn't communicate with computer at all! Instead, it just converts pulses which computer sends to what AVR can see. Also, there's no plug and play for most serial devices. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're still having problems, you'll need an oscilloscope to see what's happening. I didn't have one, so I took an audio cable, cut off one of its ends, placed a voltage divider there and connected the other end end to microphone input. There are numerous tutorials on the Internet on how to build the probe. &lt;a href=&quot;http://www.ledametrix.com/oscope/index.html&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;'s the one I used.  I used &lt;a href=&quot;http://www.zeitnitz.de/Christian/scope_en&quot; rel=&quot;nofollow&quot;&gt;Soundcard Scope&lt;/a&gt; to see the what kind of signal I'm getting. There should be a clock signal on the SCK and you should be getting signals on MOSI and MISO too. Reset should give you just a few signals, when the AVR needs to be reset.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-20T17:25:17.923" LastActivityDate="2011-02-20T17:25:17.923" CommentCount="2" />
  <row Id="10483" PostTypeId="2" ParentId="10481" CreationDate="2011-02-20T13:47:29.850" Score="0" ViewCount="" Body="&lt;p&gt;If you have a parallel port, try the &lt;a href=&quot;http://www.xs4all.nl/~sbolt/e-spider_prog.html&quot; rel=&quot;nofollow&quot;&gt;SP12 programmer&lt;/a&gt;. I used to use it without any problems, with just three resistors mounted inside a DB-25 shell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I now use an Atmel Dragon, it's only $50 and you get in-circuit debugging as well programming. It also supports all the AVRs.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-20T13:47:29.850" />
  <row Id="10484" PostTypeId="2" ParentId="10474" CreationDate="2011-02-20T18:40:23.037" Score="2" ViewCount="" Body="&lt;p&gt;its ceramic capacitor &#xA;and 10 means 10pf &lt;/p&gt;&#xA;" OwnerUserId="3093" LastActivityDate="2011-02-20T18:40:23.037" />
  <row Id="10485" PostTypeId="1" AcceptedAnswerId="10491" CreationDate="2011-02-20T19:51:41.920" Score="6" ViewCount="101" Body="&lt;p&gt;I have a &lt;a href=&quot;http://www.interinar.com/vexta-pk266-02a.html&quot; rel=&quot;nofollow&quot;&gt;stepper motor&lt;/a&gt; and I've noticed that when I turn the spindle with the motor lead wires touching each other, that the motor strongly resists my efforts to turn it. When the wires are not touching each other the motor turns more freely. I have inferred from this that the current that is induced from my attempts to turn it is so strong that once it is feed back into the motor, it resists the turning motion. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now that I have connected the motor to a &lt;a href=&quot;http://www.sparkfun.com/products/10267&quot; rel=&quot;nofollow&quot;&gt;driver&lt;/a&gt;, it is my expectation that turning the spindle would not cause damaging current to be feedback into the driver to destroy it. I am concerned that turning the spindle would damage the driver because the driver's documentation states that disconnecting the motor while the system is on will damage the driver IC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is: Can turning the spindle while connected to the driver cause damage to the driver?&lt;/p&gt;&#xA;" OwnerUserId="3045" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-20T21:23:40.390" LastActivityDate="2011-02-21T00:09:40.893" Title="Induction voltage from a Stepper Motor" Tags="&lt;stepper-motor&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="2" />
  <row Id="10486" PostTypeId="2" ParentId="10042" CreationDate="2011-02-20T20:43:20.387" Score="0" ViewCount="" Body="&lt;p&gt;You will need to use an Inverter to run AC devices off of your solar panels. There are several kinds of inverters and if you have large panels that you plan to run constantly such as off-grid you will want a pure sine wave inverter. However as tcrosley stated you did not supply us with sufficient information on your setup as to the amount of current your panels output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your panels output 12 Volts at 10 Amps and you used a theoretically perfect inverter (no losses) you will only be able to drive a load at 120 Volts 1 Amp. However there will be conversion losses. Be careful using inductive loads with cheap equipment as you have a possibility of frying your inverter. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps!&lt;/p&gt;&#xA;" OwnerUserId="3095" LastActivityDate="2011-02-20T20:43:20.387" />
  <row Id="10487" PostTypeId="1" AcceptedAnswerId="10517" CreationDate="2011-02-20T20:48:47.583" Score="7" ViewCount="202" Body="&lt;p&gt;I want to make a battery powered, adjustable SMPS for use in situations when I cannot have an outlet near me, so I would like some more information or suggestions about this topic. The SMPS chip I am basing this off is a &lt;a href=&quot;http://www.national.com/profile/snip.cgi/openDS=LM2733&quot; rel=&quot;nofollow&quot;&gt;LM2733&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The power source would be a LiPo, voltage output 3V to 25V, and at most 500mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a few ways I think I can control a SMPS chip digitally: one is a digital pot controlled with a MCU via SPI or I2C. A 1024 step pot would give me 20mV stepping, which is more than enough. What I saw in datasheets is that the pots are only able to go up to 5V for the digital resistor. &lt;em&gt;Would that be a limiting factor in such a design?&lt;/em&gt; This way seems the simplest and least demanding way from what I see.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way would be using a DAC, but I am not sure if it would need to go faster than the switching speed of the SMPS, because in data sheets I always see the voltage dividers before the output capacitor. Problem is that I do not know what the feedback pin wants to see. &lt;em&gt;Does it want the entire ramp up and down from the inductor and compare it to the reference voltage, or does it just find the average voltage of each cycle?&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know it is similar to &lt;a href=&quot;http://electronics.stackexchange.com/questions/6510/using-a-digital-potentiometer-with-a-smps&quot;&gt;{this question}&lt;/a&gt;, but I'm looking for some more information or discussion.&lt;/p&gt;&#xA;" OwnerUserId="2050" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-02-21T20:17:01.237" LastActivityDate="2011-03-27T22:08:17.290" Title="Different ways to digitally control an adjustable SMPS" Tags="&lt;power-supply&gt;&lt;potentiometer&gt;&lt;smps&gt;&lt;dac&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="2" />
  <row Id="10488" PostTypeId="2" ParentId="10026" CreationDate="2011-02-20T20:59:42.023" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;...would frequently windup when the&#xA;  car didn't respond fast enough.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Sounds like your loop gains are outta wack (technically speaking).&#xA;PID loops are bound by the frequency response of the system they are driving.&#xA;I would think the throttle response is violently faster than the GPS velocity information...making high frequency hunting a given.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Start with a small Kp and all other loop gains at zero. Work Kp up until you get a response that is slow and smooth...so you are following an offset of the curve of the set-point. Only when you have something &quot;under-damped&quot; can you start bringing gains up and closing the error. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the GPS is really slow, some interpolation of the velocity data between updates will allow the loop rate to be increased. A rate limit loop around the output would also help. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A PID loop is a model of a system....the system you have....not the system you want :)&lt;/p&gt;&#xA;" OwnerUserId="1419" LastActivityDate="2011-02-20T20:59:42.023" />
  <row Id="10489" PostTypeId="2" ParentId="10449" CreationDate="2011-02-20T22:51:57.443" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.asterisk.org/&quot; rel=&quot;nofollow&quot;&gt;Asterisk&lt;/a&gt; is an open source telephony solution that runs on Linux.  It can use a fairly cheap modem card (requires specific models, however) to use a plain-old telephone (POTS) line, as well as more advanced hardware to connect to T1, ISDN, etc.   There are a lot of layers to the system, but there are a decent number of examples out there.&lt;/p&gt;&#xA;" OwnerUserId="1295" LastActivityDate="2011-02-20T22:51:57.443" />
  <row Id="10490" PostTypeId="1" AcceptedAnswerId="10492" CreationDate="2011-02-20T23:25:23.490" Score="1" ViewCount="64" Body="&lt;p&gt;Hey folks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm building a MindFlex-based EEG. Basically, I'm sniffing a 9600bps bus, analyzing the data with an Arduino*, and sending it to Processing/Java for display. To make it absolutely isolated from mains power, I want to make it wireless, but the only wireless gear I can afford (&lt;a href=&quot;http://www.sparkfun.com/products/8946&quot; rel=&quot;nofollow&quot;&gt;transmitter&lt;/a&gt;, and its matching &lt;a href=&quot;http://www.sparkfun.com/products/8949&quot; rel=&quot;nofollow&quot;&gt;receiver&lt;/a&gt;) transmits at 2400bps. I think that if I move the Arduino into the headset, I can make a SoftSerial connection at 2400bps to operate the transmitter, then use hardware serial at 9600bps to talk to the headset. That way, I can hook up a reciever to a FTDI USB-TTL adaptor and send the data to Processing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will that work? If it helps, new data comes from the headset about once per second, and I plan on implementing a timestamp into the data from the Arduino, so lag shouldn't be too much of an issue. I also cannot afford XBees, Bluetooth, or anything else.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*Before anyone says anything, if wireless works, I will use an Arduino Pro Mini, and if it doesn't I'm going to use a BoArduino - I'm not throwing an entire Uno at this project. &lt;/p&gt;&#xA;" OwnerUserId="3097" LastActivityDate="2011-02-21T00:26:50.697" Title="Wireless UART Speed Shift" Tags="&lt;arduino&gt;&lt;wireless&gt;&lt;sparkfun&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="10491" PostTypeId="2" ParentId="10485" CreationDate="2011-02-21T00:09:40.893" Score="3" ViewCount="" Body="&lt;p&gt;Turning the system while energized will cause high currents to flow, but disconnecting it while operating will cause high voltage as the motor's magnetic field collapses.  The high voltage is probably what will damage the driver.  It is designed to handle high currents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But turning a stepper like that is generally a bad idea.  From &lt;a href=&quot;http://www.cs.uiowa.edu/~jones/step/physics.html&quot; rel=&quot;nofollow&quot;&gt;Jones on Steppers&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;It is also worth noting that the best way to demagnetize something is to expose it to a high frequency-high amplitude magnetic field. Running the control system to spin the rotor at high speed when the rotor is actually stalled, or spinning the rotor at high speed against a control system trying to hold the rotor in a fixed position will both expose the rotor to a high amplitude high-frequency field.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-21T00:09:40.893" CommentCount="1" />
  <row Id="10492" PostTypeId="2" ParentId="10490" CreationDate="2011-02-21T00:26:50.697" Score="1" ViewCount="" Body="&lt;p&gt;If your data is infrequent bursts, then you should be able to resend it at a lower data rate, using any micro controller which has two UARTs and enough memory to store an entire burst.  You could probably even do it with some tiny single-UART parts by bit-banging the slow side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As long as you can resend on the slow side before new data comes on the fast side, I don't think you should have any problem.  And your delays should be deterministic within a few clock cycles so you may not need the timestamp (or does that wireless link do resend on error?)&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-02-21T00:26:50.697" CommentCount="2" />
  <row Id="10493" PostTypeId="2" ParentId="10457" CreationDate="2011-02-21T00:40:50.600" Score="1" ViewCount="" Body="&lt;p&gt;As others have pointed out, you have a high pass filter in the way.  This may be in the DSP logic generating the output, but it's probably also in the form of a DC-blocking capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you trace the circuit from the output jacks back to whatever IC is functioning as the DAC, you maybe be able to find and shunt the capacitor.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on what kind of output you need, another trick might be to build yourself an AM radio...  ie, you could use a diode and a capacitor (from signal to ground) to build an envelope demodulator and lowpass filter.  You then modulate your signal by multiplying your samples by a carrier signal consisting of 1, -1, 1, -1, etc.  There will be some distortion, but you should be able to get low frequencies out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also be aware that in using the audio input as a storage scope, you run the possibility that the problem is on the input instead, or there in addition to on the output.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-02-21T00:40:50.600" CommentCount="1" />
  <row Id="10494" PostTypeId="2" ParentId="7525" CreationDate="2011-02-21T01:47:14.953" Score="0" ViewCount="" Body="&lt;p&gt;Matrix drive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mutiplex both your sources and sinks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connect the solenoids in arrays. ( rows &amp;amp; columns)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;a lot less electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Circuits can be like what's depicted, but you can get by with a lot less if you matrix it.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-02-21T01:47:14.953" CommentCount="6" />
  <row Id="10495" PostTypeId="2" ParentId="7525" CreationDate="2011-02-21T02:55:36.510" Score="0" ViewCount="" Body="&lt;p&gt;For an alternative, if you've got a little funds to burn you could always invest in a &lt;a href=&quot;http://www.tinyclr.com/downloads/Component/Broch_FEZ_IO40.pdf&quot; rel=&quot;nofollow&quot;&gt;Fez Domino&lt;/a&gt; and expand the I2C bus to 320 IOs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.tinyclr.com/downloads/Component/Broch_FEZ_IO40.pdf&quot; rel=&quot;nofollow&quot;&gt;Fez Domino&lt;/a&gt; is and embeded C# device, however the IO board mentioned in the PDF uses a standard I2C bus which is common on most uCs.&lt;/p&gt;&#xA;" OwnerUserId="3045" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-02-25T00:00:21.170" LastActivityDate="2011-02-25T00:00:21.170" />
  <row Id="10496" PostTypeId="2" ParentId="7525" CreationDate="2011-02-21T03:26:27.273" Score="1" ViewCount="" Body="&lt;p&gt;Whichever solution you end up using I would recommend taking a look at the power supply for this beast. You have the potential for really drawing a lot of current by accident (shorting out a transistor due to transient, a clock glitch setting a '1' to many, many outputs, etc.) -- Individual PTCs on each coil protects an individual coil, and I would also suggest either a low-ohm (0.1?) shunt resistor or a hall-effect current sensor which will cut power to the entire driver section if an overload is detected. An op-amp that integrates the overload over time is probably a good hardware trip design, but you can do it in a micro if that's your thing, too.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-02-21T03:26:27.273" />
  <row Id="10498" PostTypeId="1" AcceptedAnswerId="10499" CreationDate="2011-02-21T05:37:35.583" Score="0" ViewCount="190" Body="&lt;p&gt;Can I detect whether bytes are getting dropped by the Arduino Serial driver because of buffer overflow (i.e. if I'm not keeping up with my input stream)? If so, how?&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-02-21T06:43:18.103" Title="Arduino Serial Buffer Overflow" Tags="&lt;arduino&gt;&lt;serial&gt;" AnswerCount="1" />
  <row Id="10499" PostTypeId="2" ParentId="10498" CreationDate="2011-02-21T06:43:18.103" Score="1" ViewCount="" Body="&lt;p&gt;If you're using SoftwareSerial, I think you have no chance of detecting serial overflow, because the docs say you can't use Serial.available.  But even if you were using the hardware serial library, I don't think you can detect if bytes are getting dropped.  The closest thing you could do is use Serial.available to see when you're about to overrun the buffer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But this is really what hardware and XON/XOFF flow control are for.  When the serial driver supports this functionality, you can prevent buffer overflows because the host will tell the client when no more data can be accepted over the serial line, and vice versa.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think Arduino supports any kind of flow control, especially since begin() only takes a serial port speed as a parameter.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-21T06:43:18.103" CommentCount="6" />
  <row Id="10500" PostTypeId="1" AcceptedAnswerId="11321" CreationDate="2011-02-21T11:22:36.857" Score="2" ViewCount="187" Body="&lt;p&gt;I am using an AVR at90usb1286-based &lt;a href=&quot;http://www.pjrc.com/teensy/&quot; rel=&quot;nofollow&quot;&gt;Teensy++ 2.0&lt;/a&gt; to periodically read data from a few sensors. In its final form, my project will act based on the sensor inputs. For now, I log the results to the USB port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because the measurement interval is relatively long I am placing the microcontroller in powersaving sleep between measurements and using the watchdog timer to wake up periodically. This works just fine, but after waking up the USB connection does not work anymore and I have found no way to get it back&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using PJRCs &lt;a href=&quot;http://www.pjrc.com/teensy/usb_debug_only.html&quot; rel=&quot;nofollow&quot;&gt;Debug Only USB library&lt;/a&gt; together with their host-side component &lt;code&gt;hid_listen.exe&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because of its debug function, I would like the solution to impact as little as possible the structure of the code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried three strategies so far:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Entering powersaving sleep (SLEEP_MODE_PWR_SAVE) without any special precautions. I get an &quot;USB Device Not Recognized&quot; error from windows7 and no additional communication is possible.&lt;/li&gt;&#xA;&lt;li&gt;Entering a sleep mode that keeps the USB active (SLEEP_MODE_IDLE). In this mode the USB keeps functioning, but the sleep is interrupted pretty much immediately.&lt;/li&gt;&#xA;&lt;li&gt;Entering powersaving sleep (SLEEP_MODE_PWR_SAVE) and trying to re-initialize the USB afterward by calling &lt;code&gt;usb_init()&lt;/code&gt;. This does not seem to have any effect.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Here is a simplified application that shows the problem, adapted from &lt;a href=&quot;https://www.mainframe.cx/~ckuethe/avr-c-tutorial/#watchdog&quot; rel=&quot;nofollow&quot;&gt;this lesson 13&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;avr/io.h&amp;gt;&#xA;#include &amp;lt;avr/interrupt.h&amp;gt;&#xA;#include &amp;lt;avr/wdt.h&amp;gt;&#xA;#include &amp;lt;avr/power.h&amp;gt;&#xA;#include &amp;lt;avr/sleep.h&amp;gt;&#xA;&#xA;#include &quot;usb_debug_only.h&quot;&#xA;#include &quot;print.h&quot;&#xA;&#xA;ISR(WDT_vect, ISR_NAKED){&#xA;    _WD_CONTROL_REG = _BV(WDIE); // must reset interrupt after trigger&#xA;    /* do other work inside the watchdog interrupt? */&#xA;    PIND = _BV(PD6); /* toggle the pin */&#xA;    reti();&#xA;}&#xA;&#xA;int main(void){&#xA;    DDRD = _BV(PD6);&#xA;    PORTD = _BV(PD6);&#xA;    /* watchdog setup goo */&#xA;    wdt_enable(WDTO_1S);&#xA;    _WD_CONTROL_REG = _BV(WDIE); /* generate watchdog interrupts */&#xA;    usb_init();&#xA;&#xA;    sei(); /* enable interrupts */&#xA;&#xA;    while(1){&#xA;        set_sleep_mode(SLEEP_MODE_PWR_SAVE);&#xA;        sleep_mode();&#xA;        print(&quot;a&quot;);&#xA;        usb_debug_flush_output();&#xA;        /* Do stuff after the watchdog wakes us up */&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Questions&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Considering the given hardware, what are good strategies to put the controller into a sleep state while maintaining some form of debug output capability?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not concerned about power consumption, as the USB will be inactive in battery-powered production mode. However, I do wish to be able to get some debug output while I'm writing the program...&lt;/p&gt;&#xA;" OwnerUserId="1802" LastEditorUserId="1802" LastEditorDisplayName="" LastEditDate="2011-02-21T22:20:06.420" LastActivityDate="2011-03-11T10:11:17.503" Title="AVR (at90usb1286) sleep and USB" Tags="&lt;avr&gt;&lt;usb&gt;&lt;sleep&gt;" AnswerCount="1" />
  <row Id="10501" PostTypeId="2" ParentId="10249" CreationDate="2011-02-21T11:50:21.533" Score="3" ViewCount="" Body="&lt;p&gt;Just to clarify the various comments about synchronisation at the bit level, I have sketched some example bit patterns (not very well!). First, remember that the async bitstream consists of a logic-low start-bit, a number of data-bits (typically 7 or 8), an optional parity-bit and a number of logic-high stop-bits (typically 1 or 2). The data-bits are sent LSB first. Parity is not that often used as the integrity it provides is minimal compared to a vertical checksum as markrages has recommended. The most common format is 8 data-bits, no parity and one stop-bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/zsYMT.png&quot; alt=&quot;Async serial examples&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first trace shows a pair of 0x55 bytes - the green and red rectangles representing the start and stop-bits respectively. As you can see, this is a square wave so the receiver can't tell which low bit is the start bit, since every low bit is preceded by a high bit (which could be a stop bit). Which ever way the receiver looks at it, this represents a pair of 0x55 bytes but only one way has the correct framing. This was the basis of my earlier comment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second trace represents a pair of 0x10 bytes. However, the receiver may see the bits marked by the triangles as framing bits and (incorrectly) decode a pair of 0x04 bytes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The third trace represents a pair of 0xFF bytes. There is no ambiguity here as all the low bits are genuine start-bits - hence JustJeff's earlier comment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A typical sequence is as markrages says in his answer. Traditionally, 0x01 (Start-Of-Header) or 0x02 (Start-Of-Text) have been used as a start byte but a pair of 0xFF bytes is more reliable as JustJeff says. You might also want to put a 'stop-byte' at the end. Traditionally, 0x04 (End-Of-Transmission) and 0x03 (End-Of-Text) have been used for this purpose. Finally, always check your receivers framing-error status!&lt;/p&gt;&#xA;" OwnerUserId="2234" LastEditorUserId="2234" LastEditorDisplayName="" LastEditDate="2011-02-21T13:23:13.237" LastActivityDate="2011-02-21T13:23:13.237" CommentCount="2" />
  <row Id="10502" PostTypeId="2" ParentId="10008" CreationDate="2011-02-21T12:47:53.570" Score="3" ViewCount="" Body="&lt;p&gt;I'm not 100% sure on this but I think the answer is yes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sensor would work by measuring the tiny difference in voltage between the left hand and the right hand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could prove that retrofitting a larger piece of metal to the poles would work by simply wrapping the poles with aluminium foil. If it still works and successfully measures your heart rate from you touching the foil which in turn touches the existing metal pads, then I think you can safely say that the retrofit would work.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-21T12:47:53.570" />
  <row Id="10503" PostTypeId="2" ParentId="10394" CreationDate="2011-02-21T13:00:34.470" Score="0" ViewCount="" Body="&lt;p&gt;First, initial programming of AVR chips can not be done with RS232 serial RX/TX. This means that every chip with boot loader in it was either pre-programmed in the factory, or someone else has used some other way of programming to do it (SPI, JTAG, PDI).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My suggestion is to build a cheap 1$ parallel programmer with just few resistors, and then program some boot loader into the chip with RS232 or FTDI driver. That way programmer is not needed any more.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastEditorUserId="1129" LastEditorDisplayName="" LastEditDate="2011-02-21T13:08:25.010" LastActivityDate="2011-02-21T13:08:25.010" />
  <row Id="10504" PostTypeId="1" AcceptedAnswerId="10509" CreationDate="2011-02-21T13:02:29.840" Score="2" ViewCount="255" Body="&lt;p&gt;I am using an LM35 temperature sensor, which produces an output of 10.0 mV/°C. My circuit will handle temperatures up to around 90C&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What can I do to check the LM35 output, and maybe fine tune it for accuracy? Are there any non hazardous easy to obtain chemicals that boil below 100C?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or if I am forced to change the circuit to handle temperatures up to 100C would sticking the suitably waterproofed sensor in a pan of boiling water be sufficient to calibrate it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Note&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not looking for 0.1C accuracy, 0.5 will do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All interesting answers, thanks, but the simplest solution seems to be changing the circuit to allow 100C as a close enough calibration point&lt;/p&gt;&#xA;" OwnerUserId="1497" LastEditorUserId="1497" LastEditorDisplayName="" LastEditDate="2011-02-23T12:22:10.143" LastActivityDate="2011-02-23T12:22:10.143" Title="How to calibrate a temperature sensor" Tags="&lt;sensor&gt;&lt;temperature&gt;&lt;calibration&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="10505" PostTypeId="2" ParentId="9872" CreationDate="2011-02-21T13:02:34.170" Score="1" ViewCount="" Body="&lt;p&gt;I know you've specified that you want to use solar panels, but have you considered using a &lt;a href=&quot;http://en.wikipedia.org/wiki/Uninterruptible_power_supply&quot; rel=&quot;nofollow&quot;&gt;UPS&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A quick search comes up with a &lt;a href=&quot;http://netsemi.com/p-147675-ups-120v-330w-be550g.aspx&quot; rel=&quot;nofollow&quot;&gt;$115 550VA/330W APC UPS&lt;/a&gt; which should be adequate to supply a router for a few hours at least, possibly more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will also be cheaper than providing the equivalent power in solar panels, be more reliable (doesn't rely on a sunny day), and far easier to set up.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-21T13:02:34.170" CommentCount="1" />
  <row Id="10506" PostTypeId="2" ParentId="10504" CreationDate="2011-02-21T13:33:28.077" Score="2" ViewCount="" Body="&lt;p&gt;Stick a type k &lt;a href=&quot;http://en.wikipedia.org/wiki/Thermocouple&quot; rel=&quot;nofollow&quot;&gt;thermocouple&lt;/a&gt; to the LM35 and compare the result to the reading on the thermocouple meter. Warm the whole assembly slowly in an oven until the reading on the thermocouple meter stabilises. Also put the whole assembly in the fridge to check the low temperature point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While you don't absolutely need a temperature controlled oven, the problem is that the thermal time constants of the thermocouple and the LM35 are different, so while the temperature is changing, one will be ahead of the other. Superglueing the thermocouple to the LM35 will help, rather than letting it poke about in free air, so that they are thermally coupled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Type K thermocouples are cheap and widely available, and can read to reasonable level of accuracy for most purposes. The meter may read to within 0.01C but that would the &lt;a href=&quot;http://en.wikipedia.org/wiki/Accuracy_and_precision&quot; rel=&quot;nofollow&quot;&gt;precision not the accuracy&lt;/a&gt;, so is only usable for relative changes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since all temperature sensors measure their own temperature, be aware that it will change more slowly than an thermocouple due to its higher thermal mass and the coupling to the PCB.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-02-21T13:33:28.077" CommentCount="1" />
  <row Id="10507" PostTypeId="1" CreationDate="2011-02-21T13:37:38.660" Score="1" ViewCount="67" Body="&lt;p&gt;I am going to make &lt;a href=&quot;http://www.der-hammer.info/hvprog/index_en.htm&quot; rel=&quot;nofollow&quot;&gt;HVProg&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I use an ATMEGA8 with it?&#xA;If yes then how, if no them can we use any other microcontroller ?&lt;/p&gt;&#xA;" OwnerUserId="2037" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-02-21T14:10:32.897" LastActivityDate="2011-03-23T15:24:52.540" Title="Microcontroller for HVProg" Tags="&lt;arduino&gt;&lt;atmega8&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10508" PostTypeId="2" ParentId="10507" CreationDate="2011-02-21T14:49:55.170" Score="2" ViewCount="" Body="&lt;p&gt;You should be able to use an Atmega8. The web page you liked to says: &quot;Supports all AVR Controllers&quot;&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-02-21T14:49:55.170" />
  <row Id="10509" PostTypeId="2" ParentId="10504" CreationDate="2011-02-21T14:56:30.000" Score="3" ViewCount="" Body="&lt;p&gt;Physicist's answer ahead:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Prepare a bowl of (melting) ice water on a day where the barometer is near 1013 mbar of pressure. Stick your sensor in it. The reading you get at equilibrium is your 0C reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Prepare a pan of slowly boiling water, also on a day where the barometer is near 1013 mbar of pressure. Stick your sensor in it. The reading you get at equilibrium is your 100C reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Divide the intervening range into 100 equal parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The beauty of this method is that you are not tied to errors made while calibrating the sensor you are using to calibrate with, or errors made when calibrating the sensor they used to calibrate the sensor you are using to calibrate with, or ... (etc).&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-02-21T14:56:30.000" CommentCount="6" />
  <row Id="10510" PostTypeId="1" CreationDate="2011-02-21T15:36:13.463" Score="6" ViewCount="247" Body="&lt;p&gt;I have seen toy remote controlled cars and other toys available for real low prices. How do they implement RF communication?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mean to say when I search for RF units to buy they come at a pretty high prices. So obviously there is some way of implementing RF at lower prices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does any body have information on how toy manufacturers get RF working at such low prices? Of course given the fact that I don't want much communication between the remote and the sensor. &lt;/p&gt;&#xA;" OwnerUserId="3102" LastActivityDate="2011-02-21T21:09:14.300" Title="How do low price toys implement RF communication" Tags="&lt;rf&gt;&lt;remote&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="10511" PostTypeId="2" ParentId="10510" CreationDate="2011-02-21T16:03:53.480" Score="2" ViewCount="" Body="&lt;p&gt;Some of them don't use RF.  They use infrared.  I saw a tear-down at ESC in Boston of a helicopter.  The IR detector is much smaller and lighter than RF parts.  Also, my son has a micro-mini RC car.  It uses IR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also the code to implement the serial IR communication requires much less code, so a smaller micro is needed.&lt;/p&gt;&#xA;" OwnerUserId="204" LastEditorUserId="204" LastEditorDisplayName="" LastEditDate="2011-02-21T16:11:01.137" LastActivityDate="2011-02-21T16:11:01.137" />
  <row Id="10512" PostTypeId="2" ParentId="10510" CreationDate="2011-02-21T16:33:12.950" Score="5" ViewCount="" Body="&lt;p&gt;RF isn't very expensive, the pre-built modules that are sold are generally low volume, high margin devices.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance the ember EM351 is a cortex m-3 microcontroller with a zigbee radio on board and runs around &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=636-1010-2-ND&quot; rel=&quot;nofollow&quot;&gt;$4.50 in volume.&lt;/a&gt;  Chip antennas are only about $0.50 for such a part so the overall cost isn't that high.  There are cheaper SoC's with lower powered microcontrollers out there as well.  For example the &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010386&quot; rel=&quot;nofollow&quot;&gt;rfPIC12F675H&lt;/a&gt; is a PIC microcontroller with a 900Mhz radio on board and runs about $2 in volume.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Part of the reason the modules tend to be expensive is that they get an FCC modular certification with puts the module under test without any sort of enclosure, as a result they require shielding on the PCB and other higher cost controls to pass.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-02-21T16:33:12.950" />
  <row Id="10513" PostTypeId="1" CreationDate="2011-02-21T17:39:51.563" Score="7" ViewCount="322" Body="&lt;p&gt;I've got one of &lt;a href=&quot;http://www.treston.com/index.php?article_id=1826&amp;amp;__from_id__=3072&amp;amp;product_group=5110&quot; rel=&quot;nofollow&quot;&gt;these cabinets&lt;/a&gt;, which I intend to use for storing electronic components:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/PZrV8.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has 24 drawers (each 175 x 69 x 37mm).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Every drawer can be subdivided into up to six compartments by installing dividers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you suggest a good system for organizing resistors, capacitors and suchlike into the limited number of drawers that's available?&lt;/p&gt;&#xA;" OwnerUserId="2096" LastEditorUserId="2096" LastEditorDisplayName="" LastEditDate="2011-02-21T18:06:57.120" LastActivityDate="2011-02-26T11:45:09.517" CommunityOwnedDate="2011-05-04T06:12:46.163" Title="Organizing electronic parts?" Tags="&lt;capacitor&gt;&lt;resistor&gt;&lt;parts&gt;&lt;storage&gt;" AnswerCount="5" CommentCount="8" FavoriteCount="4" />
  <row Id="10514" PostTypeId="2" ParentId="484" CreationDate="2011-02-21T17:52:07.627" Score="0" ViewCount="" Body="&lt;p&gt;Have you considered &lt;a href=&quot;http://www.razorlab.co.uk/&quot; rel=&quot;nofollow&quot;&gt;RazorLAB&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if you're in London, University of the Arts appears &lt;a href=&quot;http://www.csm.arts.ac.uk/37056.htm&quot; rel=&quot;nofollow&quot;&gt;to make its laser cutter available to external clients for a fee.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've not used -- and have no connection to -- either service.&lt;/p&gt;&#xA;" OwnerUserId="2096" LastActivityDate="2011-02-21T17:52:07.627" CommentCount="1" />
  <row Id="10516" PostTypeId="2" ParentId="10296" CreationDate="2011-02-21T18:02:40.360" Score="0" ViewCount="" Body="&lt;p&gt;The 1.35V indicates to me that it is an infrared or IR LED.  Instead of a voltage regulated circuit and a resistor, you should use a current regulated circuit.  In its simplest form this is a chip with a few components such as an inductor, resistors and capacitors.  One maker of these is Maxim.&lt;/p&gt;&#xA;" OwnerUserId="3104" LastActivityDate="2011-02-21T18:02:40.360" CommentCount="1" />
  <row Id="10517" PostTypeId="2" ParentId="10487" CreationDate="2011-02-21T18:07:44.933" Score="1" ViewCount="" Body="&lt;p&gt;Having read the datasheet I'm going to venture a guess.  The chip expects 1.23V at the FB pin when the output is at the desired level.  Usually this is set by a resistive divider, but I don't think it will be too much of a problem to generate it with a D/A.  However, the 13.3K resistor seems to be important, so I'd leave that there but remove the other resistor that connects to the output voltage and basically replace it with your microcontroller/DAC combo.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I &lt;em&gt;think&lt;/em&gt; that all you should have to do is ensure that the output of the DAC is 1.23V when the output voltage is where you want it.  To keep things realistic You'll probably want to make the output of the DAC mimic a resistive divider - just divide the output voltage of the SMPS by a magic number that gives you 1.23V at the FB pin when you have the desired output voltage.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are however right to question how fast you have to update the DAC.  While the switching frequency of the SMPS is either 600KHz or 1.6MHz this is NOT the bandwidth of the control loop in the chip.  I don't see much in the datasheet about what it is, but it does mention using CF to put a zero in the root-locus at 8KHz.  So by wild-guess I'd say try to change your DAC at 10KHz - every 100us if possible.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-02-21T18:07:44.933" CommentCount="4" />
  <row Id="10518" PostTypeId="2" ParentId="10513" CreationDate="2011-02-21T18:34:10.493" Score="1" ViewCount="" Body="&lt;p&gt;I actually opted to not use the drawer dividers, mainly because it just reminds me of BASIC programming.  You number your lines by 10s (10, 20, 30), only to then add more and more lines in between, and then you wish you had gone by 100s instead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The analogy here is that you'll undoubtedly want to label your drawers.  For example, if you label one with 100, 200, and 300 ohm resistors, but then add a 120 ohm resistor, you'll need to relabel a bunch of your drawers.  For some, this is probably fine, but I much prefer to just add a drawer and then shift the rest down as necessary.  So in other words, I just have one resistor type per drawer.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-21T18:34:10.493" CommunityOwnedDate="2011-05-04T06:12:46.163" CommentCount="2" />
  <row Id="10519" PostTypeId="1" CreationDate="2011-02-21T18:59:57.467" Score="1" ViewCount="42" Body="&lt;p&gt;Hi,&#xA;I am going to make &lt;a href=&quot;http://www.der-hammer.info/hvprog/index_en.htm&quot; rel=&quot;nofollow&quot;&gt;HVProg&lt;/a&gt;.&#xA;Can i use 8 MHz crystal rather than 7.3728 MHz ?&lt;/p&gt;&#xA;" OwnerUserId="2037" LastActivityDate="2011-02-21T19:10:40.007" Title="Crystal for HVProg" Tags="&lt;atmega&gt;" AnswerCount="1" />
  <row Id="10520" PostTypeId="2" ParentId="10519" CreationDate="2011-02-21T19:10:40.007" Score="1" ViewCount="" Body="&lt;p&gt;No becuase it affects the transfer rate for the serial connection. You would have to change the source code to change baud rate and things. Here is a &lt;a href=&quot;http://www.wormfood.net/avrbaudcalc.php&quot; rel=&quot;nofollow&quot;&gt;good website&lt;/a&gt; for calculating this. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-02-21T19:10:40.007" />
  <row Id="10521" PostTypeId="2" ParentId="10296" CreationDate="2011-02-21T19:42:21.877" Score="1" ViewCount="" Body="&lt;p&gt;By coincidence I was looking for a bycycle dynamo operated LED lamp. White LEDs require about 3.6V, but because the supply varies from the speed you cycle (6V max, AC) I had to put a bunch of electronics in there for it anyway. Furthermore I wished high effiency, I don't want to be cycling for a resistor converting my power into heat.. So I started looking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also note that if you get a 1.4V battery, if you drain it, the voltage will slowly drop to about 1V. At 0.8V it's completely dead. You may want to consider to have a working product at 1.2V or 1.1V for example, also if you want to support rechargeable batteries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For that you really need a DC/DC converter to boost a voltage up. The LT1932 is probably even more suitable for your purpose. It converts a low voltage to a constant current (which you need for a LED). It's a bit expensive (because 1) it's linear technologies, 2)  you're trying to do something low-voltage), but it is able to drive a single LED from 1V. It also has a SHDN pin so you can control it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Hw4HM.gif&quot; alt=&quot;LT1932 typical circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can drive several white LEDs (they require over 3V drop each) from 2V input. This figure shows 4 white LEDs, so that's why it needs 2.7V minimal. I don't know how it will behave if you put only 1 LED in there, but I think it will work just fine. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;All you need for this driver is shown there. Rset sets the current through the LEDs(in the datasheet is probably a table). It drives the LEDs in this example with 15mA. And as said, LEDs are controlled by current not by voltage. The resistor you normally use only sets a 'fixed' current (for a certain voltage you apply on the system). This regulator is set to a certain current with the resistor Rset, and then you're done. If you put another LED in series, it will adjust the voltage so the current stays the same. Ofcourse, this has limits, but you won't reach that I suppose. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are more of these IC's and are quite handy. You probably find more examples that are cheaper, but might not be able to work from 1V.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastEditorUserId="1476" LastEditorDisplayName="" LastEditDate="2011-02-21T19:47:42.197" LastActivityDate="2011-02-21T19:47:42.197" CommentCount="2" />
  <row Id="10522" PostTypeId="2" ParentId="10513" CreationDate="2011-02-21T19:42:23.293" Score="7" ViewCount="" Body="&lt;p&gt;For one thing, I'd organize them by significant figures and group all different decades together, like 4.7 ohm, 47 ohm, 4.7k, all in the same box. Then they only differ by the multiplier band, which is pretty easy to spot.  Not sure what to do if you have lots of different 5% or 1% values, though.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;E6  (20%): 10    15    22    33    47 &#xA;  68&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;E12 (10%): 10 12 15 18 22 27 33 39 47&#xA;  56 68 82&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;E24 ( 5%): 10 11 12 13 15 16 18 20 22&#xA;  24 27 30&#xA;             33 36 39 43 47 51 56 62 68 75 82 91&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-02-21T19:42:23.293" CommunityOwnedDate="2011-05-04T06:12:46.163" CommentCount="3" />
  <row Id="10523" PostTypeId="1" CreationDate="2011-02-21T20:18:57.420" Score="1" ViewCount="68" Body="&lt;p&gt;I use my computer as a media center and simply love it.  It's an older box running XP and it works better than everything else I've tried turning into a media center (Windows 7, Vista, several Linux distros, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only thing I hate is having to walk to my audio amp to turn the volume up or down.  I can use the Windows volume slider or any keyboard with keys to control volume.  What I'd really love is to have a wireless knob which I can put anywhere when listening to music (e.g. kitchen) which controls the volume.  It seems so simple yet I can't find it anywhere.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having controls for pausing and moving to next song would also be terrific.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.griffintechnology.com/products/powermateQD&quot; rel=&quot;nofollow&quot;&gt;Griffin's Powermate&lt;/a&gt; could do the trick but I'd really want it to be wireless.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you know of something I can buy or build myself to serve this purpose?&lt;/p&gt;&#xA;" LastActivityDate="2011-02-21T20:50:53.420" ClosedDate="2011-02-21T20:56:01.733" Title="How can I obtain/build a wireless volume knob for Windows?" Tags="&lt;windows&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="10524" PostTypeId="2" ParentId="10523" CreationDate="2011-02-21T20:50:53.420" Score="2" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;I can use the Windows volume slider or any keyboard with keys to control volume.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;There's your answer.  You want a wireless keyboard.  Get a bluetooth model for improved range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also look into a &lt;a href=&quot;http://www.google.com/products/catalog?q=media+center+remote&amp;amp;safe=active&amp;amp;um=1&amp;amp;ie=UTF-8&amp;amp;cid=68885883819658559&amp;amp;ei=n89iTYefFIetgQf005TXAg&amp;amp;sa=X&amp;amp;oi=product_catalog_result&amp;amp;ct=result&amp;amp;resnum=3&amp;amp;ved=0CCoQ8wIwAg#&quot; rel=&quot;nofollow&quot;&gt;media center remote&lt;/a&gt; or a &lt;a href=&quot;http://www.logitech.com/remotes?modulename=harmonycategorypage&amp;amp;moduleaction=exploreharmony&quot; rel=&quot;nofollow&quot;&gt;logitech harmony&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="3106" LastActivityDate="2011-02-21T20:50:53.420" />
  <row Id="10525" PostTypeId="2" ParentId="10510" CreationDate="2011-02-21T21:09:14.300" Score="3" ViewCount="" Body="&lt;p&gt;Most of the RF transceivers used in toys (and other wireless devices, like garage door openers and car locks), use proprietary protocols.  Because they are not using one of the standard protocols like Bluetooth or Zigbee, there are no royalties to pay so the RF transceivers can be cheaper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both the proprietary protocols and standard ones like Bluetooth and Zigbee use the unlicensed &lt;a href=&quot;http://en.wikipedia.org/wiki/ISM_band&quot; rel=&quot;nofollow&quot;&gt;ISM&lt;/a&gt; (industrial/scientific/medical) bands. It is the licensing of the protocol that is the cost factor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you buy a module from SparkFun or another supplier, it is more likely to be using on of the standard protocols, and the licensing fee has been factored into the cost.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-02-21T21:09:14.300" />
  <row Id="10526" PostTypeId="2" ParentId="10504" CreationDate="2011-02-21T23:52:14.073" Score="2" ViewCount="" Body="&lt;p&gt;This is really several questions in several realms, almost none of them about electronics. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first part is &lt;a href=&quot;http://en.wikipedia.org/wiki/Metrology&quot; rel=&quot;nofollow&quot;&gt;Metrology&lt;/a&gt;, the study of measurements, and in this case accuracy. Given that the LM35 itself is fairly cheap (roughly $0.65 to $3.00 USD in 1k quantities) and only 0.5°C accuracy (at 25 degrees Celsius) and +/- 1 degree C at the extremes of the scale, it doesn't make sense to spend too much money or time trying to &lt;a href=&quot;http://en.wikipedia.org/wiki/Calibration&quot; rel=&quot;nofollow&quot;&gt;calibrate&lt;/a&gt; or improve its accuracy. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second is about the chemistry question of (safe) substances that have a boiling (or thawing) point below 90 degrees Celsius. The only substance used for standard platinum resistance thermometer (SPRT) calibration under &lt;a href=&quot;http://www.its-90.com/&quot; rel=&quot;nofollow&quot;&gt;ITS-90&lt;/a&gt; is Gallium's melting point (29.7646 C) , and the &lt;a href=&quot;http://en.wikipedia.org/wiki/Triple_point#Triple_point_of_water&quot; rel=&quot;nofollow&quot;&gt;triple point of pure water&lt;/a&gt; (0.010 C). I don't know about the toxicity of Gallium, but I assume that the lack of readily availability of Gallium negates that concern. Again calibrating it against anything other than pure water (&lt;em&gt;deionized&lt;/em&gt; / &lt;em&gt;distilled&lt;/em&gt; water) seems to not be worth the effort. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Distilled / deionized water is typically available in North American and western European grocery stores, combined into the section with bottled water. This isn't analytic laboratory grade, but decent enough for many home lab experiments. I have no clue on its availability globally, but if bottled water is readily available there is a good chance that it is available as well. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also be careful not to assume that any difference is constant or even linear over the entire temperature range. For example SPRT can be calibrated to 5 reference points based upon chemical properties of various elements over their range to help determine the calibration curve. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would &lt;a href=&quot;http://electronics.stackexchange.com/questions/10504/how-to-calibrate-a-temperature-sensor/10506#10506&quot;&gt;agree with Martin&lt;/a&gt;, that the comparison with a thermocouple is likely the best cost-effective and/or affordable approach, my only other suggestion is to compare the LM35 sensor to a known-good calibrated thermometer that is preferably an order of magnitude better than the sensor (i.e. +/- 0.1 degrees at the extremes of the scale, and +/- 0.05 degrees C at 25 C).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because of &lt;a href=&quot;http://en.wikipedia.org/wiki/Combined_gas_law&quot; rel=&quot;nofollow&quot;&gt;Combined gas law&lt;/a&gt;, you also need to factor in barometric pressure as well if referencing to a physical phenomena (e.g. melting, boiling), rather than a relative comparison of two instruments present at the same time/place and thus same atmospheric pressure. Depending on your location, the adjustment  may be small or large, depending on your location's elevation and the current local atmospheric pressure and temperature compared to compared to the &lt;a href=&quot;http://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressure&quot; rel=&quot;nofollow&quot;&gt;standard conditions for temperature and pressure&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;My apologies for what likely seems like overkill, but I don't want you (and others) to be mislead into assuming high-quality calibration / accuracy is easy or quick to achieve.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully this helps to explain what the potential factors are so you can decide how you wish to solve the problem in your case. Good luck.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-02-21T23:52:14.073" />
  <row Id="10527" PostTypeId="2" ParentId="10513" CreationDate="2011-02-21T23:58:26.187" Score="2" ViewCount="" Body="&lt;p&gt;and coin envelopes   &lt;a href=&quot;http://www.opencircuits.com/Component_and_Parts_Storage&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/Component_and_Parts_Storage&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-02-21T23:58:26.187" CommunityOwnedDate="2011-05-04T06:12:46.163" CommentCount="1" />
  <row Id="10528" PostTypeId="1" AcceptedAnswerId="10534" CreationDate="2011-02-22T01:12:31.560" Score="2" ViewCount="121" Body="&lt;p&gt;For my first hardware hack I'm taking a stab at a 'mechanical keyboard from scratch' (where scratch means individual components).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I plan to use a teensy++ board (16MHz) and was wondering about how to scan for key presses, so far I was thinking of using a grid (matrix) for the keys, every row is an out pin and every column is a in pin, the switches connect them (along with a diode for limiting the direction of current to lessen ghosting).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So there would be a scanning cycle, during which a column is set to high (or low, depending) and then every row is tested for this value. My question concerns whether or not this would be accurate enough, it means that the switch has to be closed at the exact moment that row and column are checked otherwise the key wont be registered at all. Is this how it is done or is there some much better approach?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also the issue of key bounce, so either a delay between checking the same key (could be a result of the scanning loop) and/or a counter where a certain key to be activated a number of times.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance :)&lt;/p&gt;&#xA;" OwnerUserId="3108" LastEditorUserId="3108" LastEditorDisplayName="" LastEditDate="2011-02-22T01:24:05.297" LastActivityDate="2011-03-22T15:33:31.390" Title="'keyboard from scratch' registering key presses" Tags="&lt;microcontroller&gt;&lt;avr&gt;&lt;c&gt;&lt;keyboard&gt;&lt;learning&gt;" AnswerCount="2" FavoriteCount="0" />
  <row Id="10530" PostTypeId="2" ParentId="3092" CreationDate="2011-02-22T01:16:42.353" Score="1" ViewCount="" Body="&lt;p&gt;Check out&#xA;&lt;a href=&quot;http://en.wikibooks.org/wiki/Atmel_AVR#Firmware_Programming&quot; rel=&quot;nofollow&quot;&gt;http://en.wikibooks.org/wiki/Atmel_AVR#Firmware_Programming&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It lists many diferent scripting languages for the Atmel AVR including a minimal python call PyMite &lt;a href=&quot;http://wiki.python.org/moin/PyMite&quot; rel=&quot;nofollow&quot;&gt;http://wiki.python.org/moin/PyMite&lt;/a&gt; and &lt;a href=&quot;http://code.google.com/p/python-on-a-chip/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/python-on-a-chip/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3108" LastActivityDate="2011-02-22T01:16:42.353" />
  <row Id="10532" PostTypeId="1" CreationDate="2011-02-22T01:47:24.680" Score="1" ViewCount="122" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to navigate the RC car from point A to point B. The gps module is used to find the current location coordinates i.e point A. The user enters the point B coordinates based on point A. I am wondering what algorithm i should use to move the rc car i.e this algorithm should tell the robot to move forward or turn right until it reaches point B.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been looking at kalman filtering algorithm. Is there a another algorithm out there which i can use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Environment: The robot should navigate indoors. I have to use the GPS because it is a requirement. The GPS is the only navigation sensor present on the robot.&lt;/p&gt;&#xA;" OwnerUserId="3109" LastEditorUserId="1477" LastEditorDisplayName="" LastEditDate="2011-02-22T03:30:03.330" LastActivityDate="2011-02-22T03:30:03.330" Title="How do i navigate RC car with a gps module on it from point A to point B?" Tags="&lt;robotics&gt;&lt;gps&gt;&lt;mobile-robot&gt;&lt;navigation&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="10533" PostTypeId="2" ParentId="10532" CreationDate="2011-02-22T01:54:58.927" Score="1" ViewCount="" Body="&lt;p&gt;GPS indoors is a terrible idea.  Your accuracy will be so poor, and being indoors implies you would need something fairly accurate because the scale of your setup will be relatively small.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally, even if you used it outside, some form of dead-reckoning (e.g. compass) would be of &lt;em&gt;enormous&lt;/em&gt; use so you could determine which direction you were pointed.  It would not strictly be essential, only if you wanted to approach this in an efficient manner.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using some sort of filter with GPS is a good idea, but if you are indoors, the position it will provide will not simply be randomly distributed around the true position, but rather around some chaotic mix of positions of the nearest windows based on what satellites you can get a fix on.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-02-22T01:54:58.927" CommentCount="4" />
  <row Id="10534" PostTypeId="2" ParentId="10528" CreationDate="2011-02-22T02:14:00.377" Score="4" ViewCount="" Body="&lt;p&gt;What you describe is basically the way the 8 bit micros used to do it, before keyboards all got dedicated microcontrollers (which just did the same thing anyway).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Human user keyboard input isn't very fast. If you scan the key matrix once every 20 msec, and make it a rule that you only count the key as being pressed if you see it pressed on two consecutive scans, you will eliminate key-bounce.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-22T02:14:00.377" CommentCount="4" />
  <row Id="10535" PostTypeId="1" AcceptedAnswerId="10536" CreationDate="2011-02-22T02:20:58.537" Score="3" ViewCount="241" Body="&lt;p&gt;Many farms use electric fences to discourage animals breaking through to neighbouring paddocks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These electric fences have regular (say once per second) high-voltage spikes of between around 100 V and 120 kV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would it be possible to &quot;harvest&quot; this as a power supply for remotely-deployed electronics? e.g. a coil wrapped round the electric fence wire, with a high resistance to ground, trickle-charging a battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideas welcome.&lt;/p&gt;&#xA;" OwnerUserId="3112" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-22T10:58:55.003" LastActivityDate="2011-02-23T01:39:08.043" Title="Harvest power from an electric fence." Tags="&lt;high-voltage&gt;&lt;battery-charging&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="10536" PostTypeId="2" ParentId="10535" CreationDate="2011-02-22T02:38:19.513" Score="1" ViewCount="" Body="&lt;p&gt;I'd try connecting a small transformer (one designed for a flyback power-supply) with a high step-down ratio between the energized cable and ground, you could then rectify the output and do whatever with it.  The HV coil impedance should be high enough to avoid a tremendous draw on the cattle killer, but I don't know much about them.  It may take a long while to charge a battery, but possible.  If you just want to power a sensor, I'd use a capacitor.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-02-22T02:38:19.513" CommentCount="2" />
  <row Id="10537" PostTypeId="2" ParentId="5188" CreationDate="2011-02-22T03:19:34.050" Score="0" ViewCount="" Body="&lt;p&gt;Ways for the main CPU to discover how many devices are connected to it -- and the ID of each one -- include:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;daisy chain systems don't require a unique &quot;address&quot; -- each device is implicitly addressed by its distance (hop count) from the main CPU. Once you've figured out there are 7 devices, you can address each on at location 1, 2, 3, 4, 5, 6, and 7.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Systems with a global clock line, such as daisy-chained SPI: the main CPU shifts in a unique pattern followed by lots of &quot;0&quot; bits, and counts how many clocks it takes before that pattern returns to the main CPU: if it clocked out N clock bits, and each device has a 16 bit register, then there must be N/16 devices on the chain.&lt;/li&gt;&#xA;&lt;li&gt;Systems with no global clock line, only local busses, such as token-ring networks: Each message from the main CPU to a peripheral device includes a destination address. When a device gets a message addressed to &quot;1&quot;, it operates on that message. Otherwise, it passes the message to the next device unchanged -- except it decrements the address. When the main CPU sends out a message with an impossibly large destination address, none of the devices claim it, and the main CPU can tell how many devices are on the bus by how many times that address was decremented going all the way around the loop (the hop count).&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;device select systems don't require a unique &quot;address&quot; -- each device is implicitly addressed by which of the device select lines from the main CPU activate it. For each device select line, activate the device select line and send a simple &quot;who are you?&quot; message, and see if there is any device at the end of that line to give a response.&lt;/li&gt;&#xA;&lt;li&gt;bus systems that have only &quot;global&quot; (&quot;common&quot;) signals where every device has a unique hard-wired address.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Some systems, such as CANbus and some RFID protocols, allow the main CPU to detect that there are a hundred devices attached to it, and the unique ID of each one, after only a few hundred commands, even when there are millions of possible addresses -- &lt;a href=&quot;http://en.wikipedia.org/wiki/singulation&quot; rel=&quot;nofollow&quot;&gt;singulation protocols&lt;/a&gt;. This allows every peripheral device to have a unique address, even when millions of them have been manufactured, and still allows the main CPU to rapidly discover the relatively few devices that are actually talking to it.&lt;/li&gt;&#xA;&lt;li&gt;Some protocols, such as I2C, do not support a rapid singulation protocol, but allow scanning: the main CPU can send a &quot;Hello, , can you hear me?&quot; to every possible address. (This may take a very long time if there are millions of possible addresses).&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;bus systems where each device is (eventually) assigned an address, which can be different each time you turn it on: such as DHCP. This is probably unnecessary complexity for your application.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Many people claim that &quot;If you're using SPI, you'll need a chip select line per device.&quot;&#xA;If that is true, then what is a good name for that other protocol that does &lt;em&gt;not&lt;/em&gt; require a chip select line per device, only a fixed 4 pins on the main CPU even with dozens of peripheral devices -- i.e., the protocol used by devices that Wikipedia calls &lt;a href=&quot;http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus#Daisy_chain_SPI_configuration&quot; rel=&quot;nofollow&quot;&gt;&quot;daisy-chain SPI&quot;&lt;/a&gt; ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rather than re-inventing yet another square wheel, you might want to check out the list of &lt;a href=&quot;http://en.wikibooks.org/wiki/Embedded_Systems/Common_Protocols&quot; rel=&quot;nofollow&quot;&gt;common embedded systems protocols&lt;/a&gt;,&#xA;so you avoid most of the gotchas that often bite people who design protocols from scratch.&#xA;Perhaps you are lucky and can use one of those protocols as-is, or with relatively minor tweaking.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-22T03:19:34.050" />
  <row Id="10538" PostTypeId="1" AcceptedAnswerId="10550" CreationDate="2011-02-22T03:53:50.997" Score="4" ViewCount="132" Body="&lt;p&gt;I  have been looking at a lot of different regulators. Generally speaking switching regulators will give me a wide range of input voltages at the out put amps I am looking for with added efficiency. However, the simplicity of a linear regulator is really appealing for the project that I'm looking at. The problem that leaves me with is that most linear regulators will do between 0.5 and 1.5 amps. Is there a way to hook up two regulators so that they provide my 5 volts with their combined amp output like with batteries?&lt;/p&gt;&#xA;" OwnerUserId="2617" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-22T03:57:11.273" LastActivityDate="2011-06-03T16:06:42.663" Title="Regulator solution for 5 volts at +2ish amps" Tags="&lt;voltage-regulator&gt;" AnswerCount="6" CommentCount="2" />
  <row Id="10539" PostTypeId="2" ParentId="10538" CreationDate="2011-02-22T04:01:33.920" Score="1" ViewCount="" Body="&lt;p&gt;Ti's &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/uc385-adj.html&quot; rel=&quot;nofollow&quot;&gt;UC385-ADJ&lt;/a&gt; may do the trick.  You didn't specify the input voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't wish to parallel regulators; it isn't that simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might consider Point of Load (PoL) switching regulators.  They are just about as simple since they have the parts on-board.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-22T04:01:33.920" />
  <row Id="10540" PostTypeId="2" ParentId="10478" CreationDate="2011-02-22T04:01:42.077" Score="1" ViewCount="" Body="&lt;p&gt;Most often found in arrays, &lt;a href=&quot;http://en.wikipedia.org/wiki/Flip-disc_display&quot; rel=&quot;nofollow&quot;&gt;flip-disk&lt;/a&gt; (or flip-dot) indicators only use power while changing.  Finding single dot units may be difficult, though if you're just making a 1-off prototype, you may be able to fabricate your own.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you could use an LCD with a colored reflector you could have either black or the color showing (you may be able to have additional colors besides black).  If you want more than two states, you could flash the LCD.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-02-22T04:01:42.077" />
  <row Id="10541" PostTypeId="5" CreationDate="2011-02-22T04:46:54.733" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-22T04:46:54.733" LastActivityDate="2011-02-22T04:46:54.733" />
  <row Id="10542" PostTypeId="4" CreationDate="2011-02-22T04:46:54.733" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-22T04:46:54.733" LastActivityDate="2011-02-22T04:46:54.733" />
  <row Id="10543" PostTypeId="1" CreationDate="2011-02-22T05:13:51.913" Score="0" ViewCount="117" Body="&lt;p&gt;Any have experience with this device, I have the sensor and the controller for the x band, I test the sensor with a metal device on diferents distances but I did not see significance changes on the fft an on the signal form the controller.&lt;/p&gt;&#xA;" OwnerUserId="3113" LastActivityDate="2011-02-26T13:32:06.693" ClosedDate="2011-02-27T07:25:33.080" Title="Siversima FMCw front end" Tags="&lt;sensor&gt;" AnswerCount="0" CommentCount="2" />
  <row Id="10544" PostTypeId="2" ParentId="5130" CreationDate="2011-02-22T05:17:34.790" Score="2" ViewCount="" Body="&lt;p&gt;The capacitor that Nick T mentions is the most important -- directly across the 2 motor leads, mounted directly on the motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Occasionally that is not enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some people get further improvements by adding one capacitor per motor lead between that motor lead and the metal case of the motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few people go even further, adding ferrite bead &quot;choke&quot; and another capacitor to form a &lt;a href=&quot;http://en.wikipedia.org/wiki/pi_filter&quot; rel=&quot;nofollow&quot;&gt;&quot;pi filter&quot;&lt;/a&gt; -- see&#xA;&lt;a href=&quot;http://reprap.org/wiki/Nophead%27s_Extruder_Tweaks#Interference_suppressor&quot; rel=&quot;nofollow&quot;&gt;&quot;Nophead's inteference suppressor&quot;&lt;/a&gt;&#xA;and the pages it links to&#xA;for the ugly &quot;before&quot; o'scope traces and the pretty &quot;after&quot; o'scope photos.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-22T05:17:34.790" />
  <row Id="10546" PostTypeId="1" AcceptedAnswerId="10549" CreationDate="2011-02-22T07:05:42.093" Score="0" ViewCount="52" Body="&lt;p&gt;I'm using an external power source to power an MBED module. I have the UART transfer and receive ports connected to a MAX232 level switcher in order to make the signals compatible with RS232. From there the wires go to an RJ-45 connector, which goes to a DB9 connector that is connected to a USB-DB9 converter. This is connected to the laptop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With this setup, I should be able to program the CPU to write text which will appear in a terminal program like HyperTerminal in Windows, correct? I've tried several things, but haven't been able to get any input in HyperTerminal. What's a simple program I can use to test my setup?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-02-22T07:46:37.347" Title="Using a laptop to communicate with an MBED module" Tags="&lt;communication&gt;&lt;rs232&gt;&lt;mbed&gt;" AnswerCount="1" />
  <row Id="10547" PostTypeId="2" ParentId="10041" CreationDate="2011-02-22T07:28:28.140" Score="4" ViewCount="" Body="&lt;p&gt;Well, since you don't want to use a power of two for your multiplication, it's going to be a PITA. I'll show you what would be more ideal after answering your question. I'm not going to provide any code - just technique.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The Hard Way (x 1000)&lt;/strong&gt;&#xA;&lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Multiply the mantissa of your 0-1 number with the mantissa of 1000 (Multiply by a Constant)&lt;/li&gt;&#xA;&lt;li&gt;Add the exponent of your 0-1 number with the exponent of 1000 (Add a constant)&lt;/li&gt;&#xA;&lt;li&gt;Normalize the mantissa/exponent to the form 1.XXX*2^Y (variable shift, add)&lt;/li&gt;&#xA;&lt;li&gt;Adjust the mantissa/exponent so that the exponent is 10 (Can be combined with previous step) (shift, add)&lt;/li&gt;&#xA;&lt;li&gt;Take 10 bits of data to the left of the decimal point as your integer&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The Easy Way (x 1024)&lt;/strong&gt; &lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Normalize the mantissa for an exponent of 2^10 (variable shift)&lt;/li&gt;&#xA;&lt;li&gt;Take the 10 most-significant-bits as your integer value&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-02-22T07:28:28.140" />
  <row Id="10548" PostTypeId="2" ParentId="9965" CreationDate="2011-02-22T07:39:26.150" Score="0" ViewCount="" Body="&lt;p&gt;Honestly, there isn't a lot of work to sending Morse Code. All you need is a frequency-stable oscillator that you can turn on and off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The closest I can find to a &quot;single chip&quot; solution is one of these &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=FXO-HC730-28.224-ND&quot; rel=&quot;nofollow&quot;&gt;oscillators&lt;/a&gt;. Add in some low-pass filtering and you're there...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way I'd expect to make a circuit is to use a discrete crystal oscillator (like something you'd find in the ARRL handbook) and add another transistor to be able to switch the oscillator on and off. A simple Morse Code radio is a good place to start. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A straight key can be replaced with a transistor, and that transistor can be driven by your Arduino.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-02-22T07:39:26.150" />
  <row Id="10549" PostTypeId="2" ParentId="10546" CreationDate="2011-02-22T07:46:37.347" Score="1" ViewCount="" Body="&lt;p&gt;If you have the mbed module - &lt;a href=&quot;http://mbed.org/handbook/Serial&quot; rel=&quot;nofollow&quot;&gt;check this page out&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;the easiest code for it to test would be &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;include &quot;mbed.h&quot; &lt;br&gt;&#xA;  Serial device(p9, p10);  // tx, rx&lt;br&gt;&#xA;  int main() {&lt;br&gt;&#xA;      device.baud(19200);&lt;br&gt;&#xA;      device.printf(&quot;Hello World\n&quot;);&lt;br&gt;&#xA;  }&lt;br&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Hope this helps&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-22T07:46:37.347" CommentCount="1" />
  <row Id="10550" PostTypeId="2" ParentId="10538" CreationDate="2011-02-22T09:00:16.860" Score="2" ViewCount="" Body="&lt;p&gt;You can use an external pass transistor with a fixed 7805 regulator, see for example page 14 of National Semiconductor's &lt;a href=&quot;http://www.national.com/ds/LM/LM340.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's also possible to use the LM317 to build tracking regulators that can be connected together so that they share the power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the reason the integrated packages don't go much above 1A is the dissipation due to the product of the difference between input and output voltages times the current. Switching regulators are much better for higher currents than linears because of this thermal problem.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-02-22T09:00:16.860" CommentCount="2" />
  <row Id="10551" PostTypeId="2" ParentId="10538" CreationDate="2011-02-22T09:35:27.783" Score="0" ViewCount="" Body="&lt;p&gt;Depending on the input voltage, a linear regulator is more complex in my opinion due to the cooling. Sometimes it's hard to fit a giant heatsink in your project than it is to add a simple switching supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could try paralleling LM317's to the desired current. However, they are rated at 1.5A max, but that's with a very low input-output difference. If that becomes above 15V, it's degrading quickly (to about 0.4A at 40V difference). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe you should look at a &lt;a href=&quot;http://www.national.com/mpf/LM/LM2596.html#Overview&quot; rel=&quot;nofollow&quot;&gt;LM2596&lt;/a&gt;. You only need a 5pin regulator, an inductor and a diode. If you keep in mind to place the diode and inductor close to the regulator, it's relatively easy. And ofcourse some input/output caps, but you would use them on a LM317 too if you want to drive 2A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Watch out that the On/off pin on the device can't handle &gt;25V inputs, whilst the regulating part can go up to 45V.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-02-22T09:35:27.783" />
  <row Id="10552" PostTypeId="2" ParentId="10538" CreationDate="2011-02-22T09:49:52.320" Score="0" ViewCount="" Body="&lt;p&gt;You could take a look at &lt;a href=&quot;http://www.st.com/internet/analog/product/67043.jsp&quot; rel=&quot;nofollow&quot;&gt;L200&lt;/a&gt; regulators. They should be capable of providing 2A if the difference between input and output voltage is lower than 20 V, if I remember correctly. Control circuit is also relatively easy to build.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will need a big heatsink if you want to run it at full power&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-22T09:49:52.320" />
  <row Id="10554" PostTypeId="2" ParentId="9653" CreationDate="2011-02-22T11:22:36.597" Score="0" ViewCount="" Body="&lt;p&gt;This is another option: &lt;a href=&quot;http://buckeyeshapeform.thomasnet.com/item/bmx-bmu-rackmount-desktop-enclosures/bmu-series-cases/bmu-10-100-13&quot; rel=&quot;nofollow&quot;&gt;http://buckeyeshapeform.thomasnet.com/item/bmx-bmu-rackmount-desktop-enclosures/bmu-series-cases/bmu-10-100-13&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They look very 1980s, but they.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-02-22T11:22:36.597" />
  <row Id="10555" PostTypeId="1" AcceptedAnswerId="10557" CreationDate="2011-02-22T11:31:20.587" Score="1" ViewCount="94" Body="&lt;p&gt;I'm using an external power source to power an MBED module. I have the UART transfer and receive ports connected to a MAX232 level switcher in order to make the signals compatible with RS232. From there the wires go to an RJ-45 connector, which goes to a DB9 connector that is connected to a USB-DB9 converter. This is connected to the laptop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With this setup, I should be able to program the CPU to write text which will appear in a terminal program like HyperTerminal in Windows? I've tried several things, but haven't been able to get any input in HyperTerminal. I can get it to work if I use a USB connection though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've already checked that everything is powered and grounded. I've also checked the connections. What can I do next to figure this out?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-02-22T12:09:11.917" Title="How should I debug my mbed project?" Tags="&lt;communication&gt;&lt;rs232&gt;&lt;projects&gt;&lt;mbed&gt;&lt;debugging&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="10557" PostTypeId="2" ParentId="10555" CreationDate="2011-02-22T12:09:11.917" Score="6" ViewCount="" Body="&lt;p&gt;I'd advise that you check your serial link. Disconnect the serial cable from the mbed and short the TX and RX lines. If it's working, you'll see your data echoing back as you type it from the PC.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-02-22T12:09:11.917" CommentCount="1" />
  <row Id="10558" PostTypeId="1" CreationDate="2011-02-22T12:36:29.697" Score="0" ViewCount="122" Body="&lt;p&gt;How do I compile kernel modules on the beagleboard itself?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems I need the directory /lib/modules/$(uname -r)/build, but this directory is absent, even after installing the kernel headers (opkg install kernel-headers). I know it is possible to build kernel modules using some kind of cross compiling environment, but I'd like to build the modules on the beagleboard itself for simplicity and since compile speed is not really important in this case. Extensive googling didn't provide an answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So,&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is it possible to natively build kernel modules on the beagleboard?&lt;/li&gt;&#xA;&lt;li&gt;If so, how do I obtain the necessary files?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!&lt;/p&gt;&#xA;" OwnerUserId="3115" LastActivityDate="2011-02-22T12:36:29.697" ClosedDate="2011-02-22T18:12:13.773" Title="How do I natively compile kernel modules for the Angstrom linux distribution on the beagleboard?" Tags="&lt;software&gt;&lt;linux&gt;&lt;programmer&gt;&lt;beagleboard&gt;" CommentCount="1" />
  <row Id="10559" PostTypeId="1" AcceptedAnswerId="10560" CreationDate="2011-02-22T12:40:17.810" Score="3" ViewCount="160" Body="&lt;p&gt;Single AC clamp can measure current flowing through a single wire in a non-invasive way. There are AVR/Arduino projects &lt;a href=&quot;http://www.picobay.com/projects/2009/01/real-time-web-based-power-charting.html&quot; rel=&quot;nofollow&quot;&gt;use such a clamp&lt;/a&gt; to measure house power usage. However, they use 3 clamps for 3 main wires that come into house breaker box. Unfortunately, I don't have access to separate wires in my breaker box. I can only access main power cable that comes to my house through the roof, and that cable has all the wires inside itself (is this a good assumption?) without possibility to separate them. If that is so, then the question is &lt;strong&gt;can I use a single clamp on that main cable&lt;/strong&gt; for my own little power usage measurement AVR project, and if I can then &lt;strong&gt;is there some reason for it to be less reliable then 3 clamps solution&lt;/strong&gt;?&lt;/p&gt;&#xA;" OwnerUserId="1129" LastEditorUserId="1129" LastEditorDisplayName="" LastEditDate="2011-02-22T12:45:18.010" LastActivityDate="2011-02-22T12:49:17.430" Title="Can single clamp measure total current from 3 wires?" Tags="&lt;electronics&gt;&lt;power&gt;&lt;transformer&gt;&lt;power-meter&gt;&lt;clamp&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="10560" PostTypeId="2" ParentId="10559" CreationDate="2011-02-22T12:49:17.430" Score="8" ViewCount="" Body="&lt;p&gt;No, you cannot use a clamp meter on both the live and neutral wires at the same time. Current flowing back through the neutral wire will effectively cancel out current flowing through the live wire, and it will read 0 amps (assuming no current is leaking out anywhere).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One clamp around the live wire should give you the reading you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know why you would need 3 clamps though, unless you have 3 phase coming into your building, in which case you'll need to sum the 3 separate currents to get the total current used.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-22T12:49:17.430" CommentCount="4" />
  <row Id="10561" PostTypeId="1" AcceptedAnswerId="10562" CreationDate="2011-02-22T14:57:21.143" Score="1" ViewCount="51" Body="&lt;p&gt;Hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We have to develop a Datalogger. I should get some Data over CAN (1MBit/s), compress this Data and save it to a SD Card. To save time we would prefer to use as much existing Hardware/Software as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I looked into Anrduino (CAN and uSD-Card with a Shield but i'm not sure if it have enough RAM/Speed) and Gumstix (enough speed/RAM but no existing Hardware/Software for CAN, expensive)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has somebody a tip &lt;/p&gt;&#xA;" OwnerUserId="3116" LastActivityDate="2011-02-22T15:25:46.280" Title="Developer/Application Board with CAN/SD-Card" Tags="&lt;embedded&gt;&lt;can&gt;&lt;microsd&gt;" AnswerCount="1" />
  <row Id="10562" PostTypeId="2" ParentId="10561" CreationDate="2011-02-22T15:25:46.280" Score="2" ViewCount="" Body="&lt;p&gt;This is sort of a shopping question, but I'll try to approach it as if you asked about what to look for in a datalogger for CAN networks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll want a way to store the data, and SD/micro-SD cards are great for this.  Most modern dev kits will use a micro SD card to save space.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compressing the data requires that you have enough RAM to record a decent sized buffer of data, and that you have a fast/powerful enough processor for the task.  A 32-bit micro will be good, as most compression algorithms are written for processors which can handle 32-bit words in a single instruction.  You'd have at least a 4x slow-down with an 8-bit controller.  I'm not sure what level of compression you want, so it's hard to say what will be acceptable.  Uncompressed, 1Mbit/s would fill a 2GB SD card (the largest you can go without using SDHC, which is harder) in about 22 minutes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll want a way to get the data off the datalogger.   Unplugging the SD card reader is a possibility, but you'll probably want to use serial, USB, or Ethernet so that you don't wear out (or loose) the card and so that you can read data off of the card while still logging so you can have an unlimited stream of data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd recommend the &lt;a href=&quot;http://www.luminarymicro.com/products/lm3s8962_can_ethernet_evaluation_kit.html&quot; rel=&quot;nofollow&quot;&gt;TI/Stellaris LM3S8962 Evaluation Kit&lt;/a&gt;: it has both integrated CAN and a micro-SD card, and uses a Cortex-M3 (32-bit) microcontroller running at 50MHz. It also has Ethernet and USB connectivity to offload the data.  You might use the daughter board for testing, and you might use the display to indicate how full the card is.  It's $90, which is reasonable for what you get in the package.  You can probably get it cheaper with a board designed for logging, but that will likely take you down to 8-bit microcontrollers (making compression hard) and CAN over an external transceiver that you'll have to add on.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-22T15:25:46.280" />
  <row Id="10563" PostTypeId="1" CreationDate="2011-02-22T15:36:51.467" Score="0" ViewCount="142" Body="&lt;p&gt;I need to slow the rise &amp;amp; fall time or 'average' the output from a process controller, the output is currently 4-20mA but can be 0-10V if desired.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's for a temperature control on a very unstable process, the items respond very quickly to temp changes and the controller (PID) cannot find a steady state, it tends to swing the output too far either way when it really needs a slow and steady rise or fall.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many people have tried PID tuning but the process is too unstable, it has (and needs) a very large heat input and the products have little or no heat mass (sheets of paper), the heat input is large as the process can handle thick card requiring massive heat input or thin paper requiring less input, it is also speed / exposure time dependant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a cost effective way of averaging or smoothing the output in a control loop setup like this? The signal is isolated from the process by an LDR/Led optocoupler. I have had some luck in slowing the fall time by placing a cap across the Led/resistor but this has no effect on the rise time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have not modelled or measured as I am doing this real-time, yes the LDR is a CDS cell and I'm not sure how to check if it is linear or not. I will have a look tomorrow if I get a chance. The system is very unstable and a P only controller was no better.&lt;/p&gt;&#xA;" OwnerUserId="3118" LastEditorUserId="3118" LastEditorDisplayName="" LastEditDate="2011-02-22T19:03:32.773" LastActivityDate="2011-03-26T22:28:22.107" Title="I need to smooth or average the output from a 4-20mA device" Tags="&lt;led&gt;&lt;pid-controller&gt;&lt;4-20ma&gt;" AnswerCount="2" CommentCount="10" />
  <row Id="10564" PostTypeId="1" CreationDate="2011-02-22T17:44:07.273" Score="2" ViewCount="125" Body="&lt;p&gt;I have somewhat successfully installed Cat5e cabling in my home, which works flawlessly for 10 and 100 Mbit/s, but I am experiencing severe packets loss at Gigabit speeds, on &lt;em&gt;all&lt;/em&gt; of the eight cables. So obviously I must have done something wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've already verified that all connections have 1:1 mapping (all jacks are wired as T568A) and all pins are connected, using cheap testing equipment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The obvious next step would be renting the expensive kind of testing device, but I wonder if there is either something obvious that I might have missed here, or that I could try with a modicum of skill and an oscilloscope.&lt;/p&gt;&#xA;" OwnerUserId="3119" LastActivityDate="2011-02-22T21:40:52.323" Title="Verifying Cat5e cabling" Tags="&lt;ethernet&gt;&lt;signal&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="10566" PostTypeId="2" ParentId="10564" CreationDate="2011-02-22T18:08:45.510" Score="3" ViewCount="" Body="&lt;p&gt;As you increase in speed the quality of the construction and length of the cable makes a big difference. CAT5E can support Gigabit speeds, but only when constructed at high quality. While CAT6 can have a slightly poorer construction and still work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main thing I would check is how much of the twisted pair you have untwisted. You should have none except for what is in the slots of the connector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other things to check is to make sure that your connector is actually rated as CAT5e. Just because your cable is CAT5e doesn't mean your plugs are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have access to CAT6 connectors? If so try putting them on your CAT5e cable and see if you get improved performance. The CAT6 connectors are designed for a slightly thicker cable, which is not ideal for your situation, but may help you get the untwisted part to be less.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-22T18:08:45.510" CommentCount="3" />
  <row Id="10568" PostTypeId="2" ParentId="10563" CreationDate="2011-02-22T18:55:50.943" Score="1" ViewCount="" Body="&lt;p&gt;An op amp lossy integrator is a standard way to process this sort of thing. Or other low pass op amp filters.  There are tons.  I would worry about stability.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-02-22T18:55:50.943" CommentCount="1" />
  <row Id="10569" PostTypeId="1" CreationDate="2011-02-22T19:04:17.297" Score="0" ViewCount="66" Body="&lt;p&gt;I have a request to build a speakerphone module that would plug into the handset jack on a phone that is connected to a PBX system. Apparently a phone that already includes this capability for the PBX in question is overly expensive (or not available due to its age).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is whether I should begin such a project, or if a unit already exists that I can simply replace the handset to provide the phone with reasonable speakerphone capability for small conference-room usage. I've not been able to find any such device (so far) with internet searches. I've built small audio devices before, so it doesn't seem overly complicated, but I am concerned about feedback and circuits that deal with room noise.&lt;/p&gt;&#xA;" OwnerUserId="2028" LastActivityDate="2011-05-23T22:46:38.410" Title="Adding speakerphone functionality to PBX-connected phone." Tags="&lt;audio&gt;&lt;telephone&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="10570" PostTypeId="2" ParentId="10564" CreationDate="2011-02-22T20:09:06.517" Score="0" ViewCount="" Body="&lt;p&gt;Outside of a faulty connection or poor quality cable, I have found the most common cause of the types of packet loss you describe, is interference from electrical devices. The most notorious is of course, the fluorescent light. Other common contributors are the ambiguous AC adapters (wall warts) often found powering computer and network gear, including the switch your cable probably connects to. My advice is to trace each cable route and ensure there are no electrical devices near the cables. This doesn't necessarily require any tools, but it is a good step to follow in verifying your Cat5e cable installation.&lt;/p&gt;&#xA;" OwnerUserId="2904" LastActivityDate="2011-02-22T20:09:06.517" CommentCount="2" />
  <row Id="10571" PostTypeId="2" ParentId="10564" CreationDate="2011-02-22T20:41:51.263" Score="1" ViewCount="" Body="&lt;p&gt;Gigabit needs all 4 pairs, 10/100 uses only two. If you hadn't connected all 4 pairs, it wouldn't have worked all. Since yours is working at Gigabit but with a high error rate, this is not your problem.  But others finding this question might have that, so that's why I answered.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="3105" LastEditorDisplayName="" LastEditDate="2011-02-22T21:40:52.323" LastActivityDate="2011-02-22T21:40:52.323" />
  <row Id="10572" PostTypeId="2" ParentId="10513" CreationDate="2011-02-22T20:44:43.070" Score="2" ViewCount="" Body="&lt;p&gt;I organize my small parts by value &lt;em&gt;ranges&lt;/em&gt;. Unlike @endolith (which offers a good suggestion) I use the multiplier band to sort resistors. So for example my first resistor drawer is 0-999 ohm. This makes it easy to find substitutions more readily in case I don't have the 150 ohm resistor needed, but an acceptable 100 ohm is handy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thus the labels on my resistor drawers are &lt;code&gt;0-999 Ω;&lt;/code&gt;, &lt;code&gt;1k-9.9k Ω&lt;/code&gt;, &lt;code&gt;10k-99k Ω&lt;/code&gt; etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do the same for ceramic and electrolytic capacitors. The exceptions to the above are very large electrolytic and power resistors which I put in larger drawers that I have available in the center of my parts storage cabinet.&lt;/p&gt;&#xA;" OwnerUserId="2028" LastActivityDate="2011-02-22T20:44:43.070" CommunityOwnedDate="2011-05-04T06:12:46.163" CommentCount="2" />
  <row Id="10573" PostTypeId="2" ParentId="10569" CreationDate="2011-02-22T21:41:01.080" Score="0" ViewCount="" Body="&lt;p&gt;have you looked at these? &lt;a href=&quot;http://www.polycom.com/products/voice/conferencing_solutions/conference_phones/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.polycom.com/products/voice/conferencing_solutions/conference_phones/index.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3105" LastActivityDate="2011-02-22T21:41:01.080" CommentCount="3" />
  <row Id="10574" PostTypeId="2" ParentId="10535" CreationDate="2011-02-22T22:44:22.717" Score="2" ViewCount="" Body="&lt;p&gt;Possibly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I live on a small horse farm and recently made a fence tester using a resistor and a small neon bulb. Even with 10k resistor, I get a really bright flash from the bulb: clearly visible in broad daylight.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing I'd want to be careful with is how you get power off the line: intuition says wrap a few turns of insulate wire around it, but that will make a step up transformer and give even more voltage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I get a chance tonight I'll try to see if I can power an LED with a single turn around the fence's hot wire.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-02-22T22:44:22.717" />
  <row Id="10575" PostTypeId="1" CreationDate="2011-02-23T00:23:07.010" Score="0" ViewCount="67" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/535/good-tool-for-mac-os-x-to-draw-circuits&quot;&gt;Good tool for Mac OS X to draw circuits.&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Hi I would like to find a program that you can draw up wiring diagrams. For OSX. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please advise of some free ones if possible or ones that cost are ok too. &lt;/p&gt;&#xA;" OwnerUserId="2703" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-23T00:38:57.737" LastActivityDate="2011-02-23T01:51:25.870" ClosedDate="2011-02-23T03:44:14.660" Title="Circuit diagrams" Tags="&lt;schematics&gt;&lt;osx&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="10576" PostTypeId="1" AcceptedAnswerId="10577" CreationDate="2011-02-23T00:47:23.203" Score="1" ViewCount="107" Body="&lt;p&gt;I have a RadioShack 22-812 Digital Multimeter which has a Serial PC Interface.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any sort of adapter that I can use to connect it to a computer's USB port instead of using the Serial Port?&lt;/p&gt;&#xA;" OwnerUserId="2956" LastActivityDate="2011-02-23T01:03:25.850" Title="Is there a USB interface for a RadioShack 22-812 Digital multimeter?" Tags="&lt;usb&gt;&lt;serial&gt;&lt;multimeter&gt;&lt;pc&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10577" PostTypeId="2" ParentId="10576" CreationDate="2011-02-23T00:57:57.887" Score="5" ViewCount="" Body="&lt;p&gt;RS232 to USB is very common. Here is an example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/StarTech-com-RS232-Serial-Adapter-ICUSB232/dp/tags-on-product/B000067SNB&quot; rel=&quot;nofollow&quot;&gt;http://www.amazon.com/StarTech-com-RS232-Serial-Adapter-ICUSB232/dp/tags-on-product/B000067SNB&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Expanding a little, these cables will create a virtual com port on your computer. So when you plug it in, even if there isn't anything connected to the cable, drivers will be installed and a virtual com port will be generated. Because of how it does this it looks like you just plugged the serial cable into the computer directly.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-02-23T01:03:25.850" LastActivityDate="2011-02-23T01:03:25.850" CommentCount="2" />
  <row Id="10578" PostTypeId="2" ParentId="10535" CreationDate="2011-02-23T01:39:08.043" Score="1" ViewCount="" Body="&lt;p&gt;Those fence chargers usually generate a high voltage spike on the wire fence, relative to ground. The wire fence is on insulators to make sure that almost no current flows, unless something touches it. I've heard that wet grass leaning on them can draw enough current to effectively neutralize such a fence.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So here's the take-away: there isn't so much a current &lt;em&gt;through&lt;/em&gt; the wire as there is a voltage &lt;em&gt;on&lt;/em&gt; the wire (capacitive charging currents neglected). So if you connected one end of the high-voltage side of a flyback transformer to the fence, and the other end of same winding to ground, you ought to be able to pick off slugs of current on the low-voltage side of the transformer, at a reduced voltage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Caveat if you try this with a flyback liberated from an old CRT: they often embed a diode in series with the HV winding in those units, and they're usually potted, too.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-23T01:39:08.043" CommentCount="2" />
  <row Id="10579" PostTypeId="2" ParentId="10575" CreationDate="2011-02-23T01:51:25.870" Score="1" ViewCount="" Body="&lt;p&gt;Eagle is quite popular with hobbyist and professionals. The free version has limitations. They have versions for OSX and Linux as well as Windows. &lt;a href=&quot;http://www.cadsoftusa.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.cadsoftusa.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-02-23T01:51:25.870" />
  <row Id="10580" PostTypeId="1" AcceptedAnswerId="10581" CreationDate="2011-02-23T02:05:40.623" Score="2" ViewCount="156" Body="&lt;p&gt;I'm hoping for an IDE of some kind, but I'll take any compiler or assembler! Can't seem to find anything by googling.&lt;/p&gt;&#xA;" OwnerUserId="2520" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-23T03:28:17.760" LastActivityDate="2011-02-25T06:16:18.827" Title="Is there a development system for the MSP430F series microcontrollers?" Tags="&lt;microcontroller&gt;&lt;msp430&gt;&lt;compiler&gt;&lt;ide&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="10581" PostTypeId="2" ParentId="10580" CreationDate="2011-02-23T02:26:09.537" Score="5" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CBsQFjAA&amp;amp;url=http%3A%2F%2Fmspgcc4.sourceforge.net%2F&amp;amp;ei=C3BkTe2lD4Sclgeop6GfBg&amp;amp;usg=AFQjCNE_xrPi85q7V4jki_DXhgPOeivp7Q&quot; rel=&quot;nofollow&quot;&gt;MSPgcc&lt;/a&gt; for msp430 series, &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/iar-kickstart.html&quot; rel=&quot;nofollow&quot;&gt;IAR&lt;/a&gt; is another &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/ccstudio.html&quot; rel=&quot;nofollow&quot;&gt;CSS&lt;/a&gt; The later have restrictions.&#xA;What chip are you trying to program or code for?&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-23T02:26:09.537" CommentCount="1" />
  <row Id="10582" PostTypeId="2" ParentId="10580" CreationDate="2011-02-23T03:23:34.410" Score="8" ViewCount="" Body="&lt;p&gt;Of course there is.  I use &lt;a href=&quot;http://www.gnu.org/software/emacs/&quot; rel=&quot;nofollow&quot;&gt;emacs&lt;/a&gt; + &lt;a href=&quot;http://mspgcc4.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;mspgcc4&lt;/a&gt; + &lt;a href=&quot;http://www.gnu.org/software/make/&quot; rel=&quot;nofollow&quot;&gt;make&lt;/a&gt; + &lt;a href=&quot;http://mspdebug.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;mspdebug&lt;/a&gt; + &lt;a href=&quot;http://www.gnu.org/software/gdb/gdb.html&quot; rel=&quot;nofollow&quot;&gt;gdb&lt;/a&gt;+ &lt;a href=&quot;http://www.gnu.org/software/ddd/&quot; rel=&quot;nofollow&quot;&gt;ddd&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is an IAR compiler for download from TI.  The free one is code-size-limited.  It comes with some kind of IDE as well.  But MSP programs are pretty small by definition, and a simple makefile is all you need to compile and program code.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-23T03:23:34.410" />
  <row Id="10583" PostTypeId="2" ParentId="10580" CreationDate="2011-02-23T03:45:49.203" Score="1" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://www.rowley.co.uk/&quot; rel=&quot;nofollow&quot;&gt;Rowley CrossWorks&lt;/a&gt;. It's very good, with excellent support.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-23T16:53:31.330" LastActivityDate="2011-02-23T16:53:31.330" />
  <row Id="10584" PostTypeId="1" AcceptedAnswerId="11765" CreationDate="2011-02-23T05:49:22.420" Score="0" ViewCount="89" Body="&lt;p&gt;I want to send Ascii codes to an mbed and have it print Ascii characters which can be seen from Hyperterminal. How can this be done? I looked at the mbed website and found nothing about keyboard input or ascii characters.&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-20T20:03:22.207" LastActivityDate="2011-03-21T01:58:32.860" Title="How to make an mbed print text from ascii codes" Tags="&lt;rs232&gt;&lt;mbed&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="10586" PostTypeId="1" AcceptedAnswerId="10592" CreationDate="2011-02-23T06:12:32.987" Score="3" ViewCount="288" Body="&lt;p&gt;I am designing a robot, and need to track the distance and direction of the robot motion, Nothing in 3D, I only need x,y and angle in x y plane.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question :&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is it possible to use gyro and accelerometer with kalman filtering or any other methods to&#xA;track this? (I do not have motor encoders)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;My constraints : I do not have space to include a gps (due to power requirements)&#xA; or motor encoders (due to motor support) &lt;/p&gt;&#xA;" OwnerUserId="1705" LastActivityDate="2011-03-15T13:08:05.983" Title="How to determine relative position using accelerometer and gyro data" Tags="&lt;accelerometer&gt;&lt;gyro&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="4" />
  <row Id="10587" PostTypeId="1" CreationDate="2011-02-23T08:00:34.250" Score="2" ViewCount="554" Body="&lt;p&gt;I've an atmega328 chip (without bootloader), and I want to burn it with my Arduino UNO as ISP, so I can have a spare atmega 328 with UNO bootloader. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to follow the instruction in &lt;a href=&quot;http://arduino.cc/en/Tutorial/ArduinoISP&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Tutorial/ArduinoISP&lt;/a&gt;, but there is a note that said: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Currently, you cannot use an Arduino&#xA;  Uno as an ISP programmer because the&#xA;  optiboot bootloader does not support&#xA;  this sketch. A revision for this is in&#xA;  progress.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So how to do it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone help me ?&lt;/p&gt;&#xA;" OwnerUserId="3124" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-20T16:38:01.343" LastActivityDate="2011-05-20T16:38:01.343" Title="How to burn atmega328 chip via Arduino UNO as ISP ?" Tags="&lt;arduino&gt;&lt;bootloader&gt;&lt;uno&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="10588" PostTypeId="1" AcceptedAnswerId="10590" CreationDate="2011-02-23T08:28:14.247" Score="8" ViewCount="398" Body="&lt;p&gt;Lots of new batteries (for mobile devices, MP3 players, etc) have connectors with 3 pins.&#xA;What is the purpose of this and how should I use these three pins?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are usually marked as (+) plus, (-) minus, and T.&lt;/p&gt;&#xA;" OwnerUserId="3125" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-23T19:02:28.113" LastActivityDate="2011-02-23T19:02:28.113" Title="Why we have 3 pins on some batteries?" Tags="&lt;batteries&gt;&lt;battery-charging&gt;&lt;pins&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="2" />
  <row Id="10590" PostTypeId="2" ParentId="10588" CreationDate="2011-02-23T09:35:43.973" Score="16" ViewCount="" Body="&lt;p&gt;The third pin is usually for an internal temperature sensor, to ensure safety during charging. Cheap knock-off batteries sometimes have a dummy sensor that returns a &quot;temp OK&quot; value regardless of actual temperature.&lt;br&gt;&#xA;Some higher-end batteries have internal intelligence for charge control and status monitoring, in which case the third pin is for communications.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-23T09:35:43.973" CommentCount="2" />
  <row Id="10592" PostTypeId="2" ParentId="10586" CreationDate="2011-02-23T11:52:07.817" Score="4" ViewCount="" Body="&lt;p&gt;You can integrate acceleration to obtain velocity data, and you can further integrate velocity to get position. Integration is just the process where you just cumulatively add something up. For example, if you get a new acceleration reading every 0.1 second, you assume the acceleration was constant over the last 0.1 second; you then find the change in velocity over that same time interval by adding 0.1 seconds * acceleration to the current velocity estimate, and repeat this every time a new acceleration reading comes in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is what's known as 'dead reckoning', and it has some down sides. Most important is that because you basically are just adding up measurements across time, any errors (e.g., noise) in that data also accumulates, so your approximation of where you are, where you're headed, and how fast you're going all degrade over time.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-02-23T11:52:07.817" CommentCount="4" />
  <row Id="10593" PostTypeId="2" ParentId="10051" CreationDate="2011-02-23T13:52:54.270" Score="1" ViewCount="" Body="&lt;p&gt;According to the link to the SATA pinout of the forum page you linked to, pins 7,8,9 are all +5V, so that is just for one end of the diode. Presumably the other end is connected to pins 4/5/6 or 10/11/12 and you could replace it with a TVS diode of the same physical size and a rated voltage &lt;strong&gt;above&lt;/strong&gt; 5V. Given that 5V ICs usually work at least 0.5V above or below the 5V spec, and the 5% tolerance of the TVS threshold, you should be safe with a 6.8V TVS diode. They are usually unipolar so getting it the right way round is important (otherwise you are reducing the 5V rail to 0.7V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can't measure the breakdown voltage of a TVS diode or zener using the resistance range of a meter. They are deliberately non-linear devices, so the resistance you measure depends on the voltage applied. The only way to measure the breakdown voltage with a meter would be to isolate the (working!) device, use a current limited adjustable voltage supply set to 1mA, increase the voltage until 1mA flows, then measure the voltage across the device. For smaller devices rated less than 5 watts, you probably need to use the pulsed version of this method to avoid heating the device up too much.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-02-23T13:52:54.270" CommentCount="2" />
  <row Id="10594" PostTypeId="1" CreationDate="2011-02-23T15:39:20.987" Score="0" ViewCount="72" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/1024/good-tools-for-drawing-schematics&quot;&gt;Good Tools for Drawing Schematics&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I want to keep records of my developments, &lt;strong&gt;what wiring diagram software do you recommend?&lt;/strong&gt;&lt;br&gt;&#xA;Is there also a free circuit diagram software?&lt;/p&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="3130" LastEditorDisplayName="" LastEditDate="2011-02-23T16:00:40.553" LastActivityDate="2011-02-23T16:38:39.353" ClosedDate="2011-02-23T16:48:24.113" Title="Recommendations for schematic capture programs?" Tags="&lt;arduino&gt;&lt;software&gt;&lt;wiring&gt;&lt;diagram&gt;&lt;documentation&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="10595" PostTypeId="2" ParentId="10594" CreationDate="2011-02-23T15:53:24.543" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://geda.seul.org/wiki/geda%3agaf&quot; rel=&quot;nofollow&quot;&gt;gschem&lt;/a&gt; on Linux, or &lt;a href=&quot;http://opencircuitdesign.com/xcircuit/&quot; rel=&quot;nofollow&quot;&gt;xcircuit&lt;/a&gt; on Linux or Windows. I think you are looking for &lt;em&gt;schematic capture&lt;/em&gt; programs.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="3130" LastEditorDisplayName="" LastEditDate="2011-02-23T16:38:39.353" LastActivityDate="2011-02-23T16:38:39.353" />
  <row Id="10596" PostTypeId="1" CreationDate="2011-02-23T16:01:21.193" Score="0" ViewCount="218" Body="&lt;p&gt;On the official Arduino website only the &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoEthernetShield&quot; rel=&quot;nofollow&quot;&gt;Arduino Ethernet Shield&lt;/a&gt; is referenced for Ethernet programming. Are there any other modules for Ethernet on the Arduino?&lt;/p&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-23T18:20:37.100" LastActivityDate="2011-02-23T18:20:37.100" Title="Is there another Arduino ethernet module besides the &quot;Arduino Ethernet Shield&quot;?" Tags="&lt;arduino&gt;&lt;hardware&gt;&lt;ethernet&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="10597" PostTypeId="1" AcceptedAnswerId="10598" CreationDate="2011-02-23T16:01:39.987" Score="0" ViewCount="43" Body="&lt;p&gt;I am looking to get my hands on some Pizeo Buzzers that are as small as possible.  So far I have found &lt;a href=&quot;http://parts.digikey.com/1/parts/338-buzzer-piezo-element-7-0khz-10mm-ab1070b.html&quot; rel=&quot;nofollow&quot;&gt;10mm round&lt;/a&gt;, which is good, but I was wondering if anyone knew of ones that are smaller still?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would prefer to avoid SMD components if at all possible, but I can deal with it if need be.  At the end of the day, as small as 5x5mm would be great.&lt;/p&gt;&#xA;" OwnerUserId="3077" LastActivityDate="2011-02-23T16:17:45.293" Title="Small Piezo Buzzers" Tags="&lt;components&gt;&lt;piezoelectricity&gt;" AnswerCount="1" />
  <row Id="10598" PostTypeId="2" ParentId="10597" CreationDate="2011-02-23T16:08:39.547" Score="3" ViewCount="" Body="&lt;p&gt;I found a Pizeo Buzzer with &lt;strong&gt;6.5 mm&lt;/strong&gt; here:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.produktinfo.conrad.com/datenblaetter/700000-724999/710385-an-01-en-PIEZOELEMENT_EPZ_20MS64W.pdf&quot; rel=&quot;nofollow&quot;&gt;PDF with specifications&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.conrad.de/ce/de/product/710385/PIEZOELEMENT-EPZ-20MS64W/0235311&amp;amp;ref=list&quot; rel=&quot;nofollow&quot;&gt;The item in a shop&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="3130" LastEditorDisplayName="" LastEditDate="2011-02-23T16:17:45.293" LastActivityDate="2011-02-23T16:17:45.293" CommentCount="1" />
  <row Id="10599" PostTypeId="2" ParentId="10596" CreationDate="2011-02-23T16:17:54.637" Score="1" ViewCount="" Body="&lt;p&gt;I can think of two options off the top of my head:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;An &lt;a href=&quot;http://www.lantronix.com/device-networking/embedded-device-servers/xport.html&quot; rel=&quot;nofollow&quot;&gt;Xport&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;A custom solution with an ethernet PHY, a magjack, a SPI connection and a bunch of custom software.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-02-23T16:17:54.637" />
  <row Id="10600" PostTypeId="2" ParentId="10405" CreationDate="2011-02-23T16:19:17.787" Score="1" ViewCount="" Body="&lt;p&gt;This seems to support AES SSL as well: &lt;a href=&quot;http://www.lantronix.com/device-networking/embedded-device-servers/xport.html&quot; rel=&quot;nofollow&quot;&gt;http://www.lantronix.com/device-networking/embedded-device-servers/xport.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3130" LastActivityDate="2011-02-23T16:19:17.787" />
  <row Id="10601" PostTypeId="2" ParentId="6712" CreationDate="2011-02-23T16:27:48.853" Score="3" ViewCount="" Body="&lt;p&gt;The most common form of electrical damage to things is overheating caused by total power dissipation.  In many cases, one can safely get by either limiting voltage to a very low level and not worrying about current, or limiting current to a very low level and not worrying about voltage.  There are some exceptions, though:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;It is possible for excessive voltage to cause a sudden current flow, or for excessive current to cause a sudden voltage drop, and these currents or voltage drops may be sufficiently localized that damage can occur with very small total power dissipation.  In some cases, particularly with overvoltage, it may possible for localized capacitance to hold enough energy to damage the device even if current is externally limited.&#xA;&lt;li&gt;As others have noted, excessive voltage or current applied to a pin of a device which is powered may cause the device to enter a mode (such as latch-up) that converts a lot of supply power into heat.  Even if the power into the over-voltage or over-current pin is limited, the supply may feed enough power to totally destroy the device.&#xA;&lt;li&gt;Overvoltage and overcurrent conditions may accelerate physical or chemical changes in a device sufficiently to cause it to fail prematurely or go out of spec; an electrolytic capacitor which is charged beyond its rated voltage, for example, may have its dielectric gradually get thicker as a result, reducing its capacitance.  Note that such effects can cause damage even if power dissipation is slight and cooling is sufficient to prevent overheating.&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-23T16:27:48.853" />
  <row Id="10602" PostTypeId="2" ParentId="10588" CreationDate="2011-02-23T16:44:02.913" Score="1" ViewCount="" Body="&lt;p&gt;The third pin is usually found on Li-Poly, or Lithium Polymer batteries and is required in order to charge the battery safely. Because these batteries are usually multi-cell, the third pin is used for balancing the charge between each of the cells.&lt;/p&gt;&#xA;" OwnerUserId="3101" LastActivityDate="2011-02-23T16:44:02.913" CommentCount="3" />
  <row Id="10603" PostTypeId="2" ParentId="1154" CreationDate="2011-02-23T16:56:51.920" Score="3" ViewCount="" Body="&lt;p&gt;The torque of a typical motor will vary as it rotates, based upon the motor's position within each commutator &quot;step&quot;.  This varying torque makes it very difficult to turn a motor smoothly at very slow speeds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A common remedy is to hit the motor with short bursts of current, where each burst is long enough to move the motor by at least one commutator step.  The longer the bursts, the more predictable the behavior of the motor will be, but the more 'jerky' the output.  Note that there are two ways of doing this: (1) Let the motor freewheel after each burst of current; (2) dynamic-brake the motor after each burst.  Using approach #1 will require typically much less power to achieve any given speed, but approach #2 offers much finer control of speed.  Note that when using approach #2, the motor will be drawing nearly its full stall current (and dissipating its full stall power) for much of the time that it is on; if a motor would have a 1 amp stall current and a 100mA running current, running the motor at a 1% duty cycle would be safe, but running it at something like 50% could easily cause it to overheat (it could generate nearly 50 times as much heat as it would running normally).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your goal is to make the motor run at a nicely-controllable rate that's about 1% of normal speed, and if power consumption isn't a concern, approach #2 may be good.  If mechanical loading is consistent, approach #1 may be good.  Otherwise you may need some motor-speed feedback.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-23T16:56:51.920" />
  <row Id="10604" PostTypeId="1" AcceptedAnswerId="10629" CreationDate="2011-02-23T17:05:00.930" Score="6" ViewCount="132" Body="&lt;p&gt;What are you capturing the schematic from?  Makes me think of a butterfly net or something.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-02-24T02:55:47.033" Title="Why are they called schematic &quot;capture&quot; programs?" Tags="&lt;software&gt;&lt;schematics&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="10605" PostTypeId="2" ParentId="10596" CreationDate="2011-02-23T17:21:57.303" Score="3" ViewCount="" Body="&lt;p&gt;The official is implemented with a Wiznet 5100 chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is &lt;a href=&quot;http://www.nuelectronics.com/estore/index.php?main_page=project_eth&quot; rel=&quot;nofollow&quot;&gt;another ethernet shield&lt;/a&gt; from NueEletronics implemented with the ENC28J60.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/BVWya.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-02-23T17:21:57.303" />
  <row Id="10606" PostTypeId="1" CreationDate="2011-02-23T17:23:09.483" Score="2" ViewCount="70" Body="&lt;p&gt;What are the the standard &quot;good&quot; capacitors? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, for a 0.1&amp;mu;F ceramic 0603 part 25V seems to be more popular than 6.3 or 10V, so I should go with 25V.  And X5R is only slightly cheaper than the better X7R, so I should go with X7R.  I see that Y5V (F) is really cheap, but doesn't have the temperature rating of X7R so I would avoid those since I'm not in an industry where reliability can be ignored.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-23T17:28:29.307" LastActivityDate="2011-02-23T20:10:25.207" ClosedDate="2011-02-23T20:39:29.443" Title="Standard/recommended/popular capacitor combinations" Tags="&lt;capacitor&gt;&lt;ceramic&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="10607" PostTypeId="2" ParentId="10596" CreationDate="2011-02-23T17:27:10.633" Score="3" ViewCount="" Body="&lt;p&gt;There is also one from &lt;a href=&quot;http://www.freetronics.com/products/ethernet-shield-with-poe&quot; rel=&quot;nofollow&quot;&gt;Freetronics&lt;/a&gt;, which works with Arduino and I have also tested it with Netduino.  You can also get a nice &lt;a href=&quot;http://en.wikipedia.org/wiki/Power_over_Ethernet&quot; rel=&quot;nofollow&quot;&gt;PoE&lt;/a&gt; adapter from them.  Their shield is also based on the Wiznet 5100 chip, and has incorporated the following design features to hopefully help with any issues with the Arduino Ethernet Shield (taken from their website)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;SPI Fixes&lt;/strong&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Combining Ethernet with other SPI&#xA;  devices can be really tricky because&#xA;  the Wiznet chip doesn't relinquish the&#xA;  bus properly when it's deselected. To&#xA;  fix that problem we slaved the&#xA;  Wiznet's SEN (SPI Enable) line to the&#xA;  CS (Chip Select) line, which means&#xA;  that whenever your sketch deselects&#xA;  the Ethernet connection in order to&#xA;  talk to another SPI device it will&#xA;  work exactly the way it should.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;No more messing around with cutting&#xA;  tracks and other nasty hacks you may&#xA;  have seen mentioned on the forums.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Reset Fixes&lt;/strong&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;We've also slaved the Ethernet&#xA;  Shield's reset line to the Arduino&#xA;  reset line, so if your Arduino is&#xA;  reset the Ethernet Shield will&#xA;  automatically reset as well. The&#xA;  Wiznet reset line is also held active&#xA;  for long enough to make it restart&#xA;  reliably each time the Arduino itself&#xA;  restarts.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Power Filtering Fixes&lt;/strong&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Ethernet connections are very&#xA;  susceptible to electrical noise, so&#xA;  the Wiznet chip has multiple ground&#xA;  pins on two separate buses and they&#xA;  need to be individually decoupled and&#xA;  the buses linked by an inductor. We&#xA;  took care of that by implementing&#xA;  proper decoupling on the power and&#xA;  ground rails, ensuring you get maximum&#xA;  reliability even in electrically noisy&#xA;  environments.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-23T17:32:34.310" LastActivityDate="2011-02-23T17:32:34.310" CommentCount="2" />
  <row Id="10608" PostTypeId="2" ParentId="10604" CreationDate="2011-02-23T17:58:15.787" Score="3" ViewCount="" Body="&lt;p&gt;From the mind of the designer.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-02-23T17:58:15.787" CommentCount="1" />
  <row Id="10609" PostTypeId="1" CreationDate="2011-02-23T18:23:05.493" Score="1" ViewCount="130" Body="&lt;p&gt;I'm trying to design an LC low pass filter to attenuate 30-35kHz noise on a 3.3V signal. It's preferable to attenuate higher frequencies as well. So I designed a filter with L=10u, C=1u (which is wrong, but this is just an example) - and I found it boosted frequencies near the cut-off point. Is there any way to avoid this? The boost of 22dB corresponded to an increase in 12.5x the voltage. The filter will be powering a microcontroller, which draws 100mA, so this increase in voltage would likely damage it. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-02-23T18:28:46.203" LastActivityDate="2011-02-24T10:37:18.697" Title="How do I attenuate 30kHz noise?" Tags="&lt;filter&gt;&lt;lc&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="10610" PostTypeId="2" ParentId="10604" CreationDate="2011-02-23T18:25:26.020" Score="4" ViewCount="" Body="&lt;p&gt;They &quot;capture&quot; the netlist from the schematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or &quot;capture&quot; the schematic from paper? (It's still faster to draw the schematic on paper first.)&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-23T18:25:26.020" CommentCount="4" />
  <row Id="10611" PostTypeId="2" ParentId="10194" CreationDate="2011-02-23T18:43:11.737" Score="0" ViewCount="" Body="&lt;p&gt;I have my DIY controller running into Max into an app that generates 8 MIDI CC values and sends them out. I already try it and work perfectly.&lt;/p&gt;&#xA;" OwnerUserId="3132" LastActivityDate="2011-02-23T18:43:11.737" />
  <row Id="10612" PostTypeId="2" ParentId="10609" CreationDate="2011-02-23T19:41:01.410" Score="5" ViewCount="" Body="&lt;p&gt;In simple terms, add a resistor in series with the inductor. But then you could rather use a RC filter because you're decreasing the quality of your inductor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why do you prefer and LC filter? The filters are harder because at a certain frequency, you will get a resonance point. The voltage you put on the filter will be 'amplified'. The amplitude of how much it will shoot up , is called the Q factor. To dampen the Q , you add a series resistance to the coil to dampen it out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A lot of math stored on:&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/RLC_circuit&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/RLC_circuit&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But because you're only operating at 30kHz, I think a RC filter might do the job better/easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&#xA;Sorry your post was confusing because first you were talking about a 3.3V &gt;signal&amp;lt; and then about a power line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The answer still stays similar, add a small resistor, but it will reduce the steepness of the filter. Alternatively you can better add a filter which it's cutoffpoint is way less than your noise. I.e. if you have 30kHz noise, add a filter with a cutoff point at 3kHz or something. You won't get the increase in amplitude at the noisy frequency and a pretty good attenuation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, as mentioned, patching the source is always better.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastEditorUserId="1476" LastEditorDisplayName="" LastEditDate="2011-02-23T20:55:32.897" LastActivityDate="2011-02-23T20:55:32.897" />
  <row Id="10613" PostTypeId="2" ParentId="10606" CreationDate="2011-02-23T20:10:25.207" Score="2" ViewCount="" Body="&lt;p&gt;The cheapest capacitor is the one already loaded in the pick and place machine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Seriously, don't spec things you don't care about.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-23T20:10:25.207" CommunityOwnedDate="2011-02-23T20:10:25.207" CommentCount="1" />
  <row Id="10614" PostTypeId="2" ParentId="7850" CreationDate="2011-02-23T21:00:25.743" Score="3" ViewCount="" Body="&lt;p&gt;In many applications, one will need to allocate memory, but won't need to free anything while keeping something that was allocated after it.  On such a system, all one need do is use the linker to define an array using all available RAM, set a pointer to the start of that array, and then use a nice easy malloc function:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;char *next_alloc;&#xA;void *malloc(int size)&#xA;{&#xA;    char  *this_alloc;&#xA;    this_alloc = next_alloc;&#xA;    if ((END_OF_ALLOC_SPACE - this_alloc) &amp;lt; size)&#xA;      return -1;&#xA;    next_alloc += size;&#xA;    return this_alloc;&#xA;}&#xA;void free(void *ptr)&#xA;{&#xA;    if (ptr)&#xA;        next_alloc = (char*)ptr;&#xA;}&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Nice and easy, and just two bytes total overhead for any number of allocations.  Calling free() on a block will deallocate that block and everything after it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Slightly more complicated allocation patterns can be handled by using two pointers--one which allocates stuff from the bottom of memory moving up, and one of which goes from the top of memory downward.  It's also possible to use a compactifying garbage collector if the data in the heap is homogenous and one knows where all the outside references to it are.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-03-13T17:55:56.810" LastActivityDate="2011-03-13T17:55:56.810" />
  <row Id="10615" PostTypeId="1" AcceptedAnswerId="10617" CreationDate="2011-02-23T21:02:22.340" Score="3" ViewCount="103" Body="&lt;p&gt;I don't know if the power plug should have &lt;code&gt;+&lt;/code&gt; at the inner contact or the outer.&lt;/p&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="3130" LastEditorDisplayName="" LastEditDate="2011-05-26T08:54:27.647" LastActivityDate="2011-05-26T09:14:50.023" Title="Arduino board Power Polarity" Tags="&lt;arduino&gt;&lt;power-supply&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="10616" PostTypeId="2" ParentId="5386" CreationDate="2011-02-23T21:04:43.320" Score="1" ViewCount="" Body="&lt;p&gt;You probably can't allocate from RAM, but for your application you might be able to have a small loader in flash which can then read SD card data into the remainder of flash.  I have used this approach with an SPI-controlled flash chip to allow firmware to be loaded from a wireless link and then installed once it was received completely; I can think of no particular reason it wouldn't work with an SD card, though an SD-compatible bootloader might take up some space.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-23T21:04:43.320" CommentCount="1" />
  <row Id="10617" PostTypeId="2" ParentId="10615" CreationDate="2011-02-23T21:22:38.087" Score="4" ViewCount="" Body="&lt;p&gt;positive is in the center of the plug.  This is a pretty typical way to do it, because having positive on the outside is just inviting shorts if you pull the plug, and then drop it on something that's grounded.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-23T21:22:38.087" CommentCount="1" />
  <row Id="10618" PostTypeId="1" AcceptedAnswerId="10621" CreationDate="2011-02-23T21:36:09.537" Score="4" ViewCount="186" Body="&lt;p&gt;I have a battery pack consisting of 4x1.2V AA Sanyo NiMH Rechargeable batteries used to charge a Beagleboard device. I want their discharge output to not exceed 5V. But when they're fully charged, the voltage output is over 5V (it triggers the overvoltage detector of the Beagleboard). What is a simple (and relatively small) intermediate component I can place between the battery pack and the Beagleboard to limit the voltage to under 5V?&lt;/p&gt;&#xA;" OwnerUserId="2883" LastActivityDate="2011-02-23T23:50:14.730" Title="Keep the voltage under 5V" Tags="&lt;battery&gt;" AnswerCount="3" />
  <row Id="10619" PostTypeId="2" ParentId="5413" CreationDate="2011-02-23T21:37:53.733" Score="2" ViewCount="" Body="&lt;p&gt;My guess would be that you are missing a necessary delay in your initialization sequence.  If the display is busy when you try to send a command, that command will be ignored.  If when you start your procedure, the display is in four bit mode and has just had &quot;0000&quot; clocked in as the first half of a command, then when you clock in &quot;0011&quot; the display will see the whole command as &quot;00000011&quot;, which will cause the display to be busy for up to 1.6ms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incidentally, it is good if possible to wire the low-order data wires from the display in such a way that when a &quot;0011&quot; command is sent to the display, the whole 8 bits seen by the display will form a mode-set command which is correct for the type of display you are using.  That will help avoid any display glitches when resetting a display which is already in use (periodically resetting the display is a good idea, if it can be done glitchlessly, since it will ensure that if the display somehow gets into a bad mode it will fix itself).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-23T21:37:53.733" />
  <row Id="10620" PostTypeId="2" ParentId="10618" CreationDate="2011-02-23T21:40:54.010" Score="1" ViewCount="" Body="&lt;p&gt;Maybe a 5V Zener diode + resistor will be good enough?&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-23T21:40:54.010" CommentCount="2" />
  <row Id="10621" PostTypeId="2" ParentId="10618" CreationDate="2011-02-23T22:56:02.360" Score="5" ViewCount="" Body="&lt;p&gt;You need a voltage regulator.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, you've spec'ed batteries which are awfully close to the operating voltage of your system.  If you can use 5 batteries instead of 4 (giving you 6.something to 5V, instead of 5.something to 4V) , a low-dropout linear regulator will be a simple, easy solution.  The standard 7805 has too high a dropout for this purpose, but there are other pin compatible regulators; you'll want a TO-220 to dissipate the power that the Beagleboard can draw at full charge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you must use 4 batteries, you need to dissipate the excess voltage as heat through a MOSFET when the voltage is greater than 5V, and turn the MOSFET on if the voltage is less than 5V.  You are running slightly out of spec when you're below 5V, though I'm not sure what the absolute minimum voltage is for the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want the best solution possible, a buck-boost regulator would get you optimum efficiency for voltages slightly above and slightly below 5V.  You could even run it off a single battery, or from voltages much higher than 5V.  However, this is an expensive and complicated solution.  I'd recommend just using 5 batteries and an LDO.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-23T22:56:02.360" CommentCount="1" />
  <row Id="10622" PostTypeId="2" ParentId="5540" CreationDate="2011-02-23T23:30:49.223" Score="0" ViewCount="" Body="&lt;p&gt;I've used the hydrochloric acid / peroxide solution known as &quot;super-o&quot; to etch nickel alloy turbine blades for grain structure. I used nine parts hydrochloric and one part peroxide but that's very aggressive... You guys should use one part hydrochloric and two parts peroxide for your application. I use ventilation as well because chlorine gas evolution is a factor. In my experience effective shelf life of the solution is only a few minutes once used. If you dilute the solution to appropriate ph with water you can dump it down the drain.&lt;/p&gt;&#xA;" OwnerUserId="3136" LastActivityDate="2011-02-23T23:30:49.223" CommentCount="2" />
  <row Id="10623" PostTypeId="2" ParentId="10618" CreationDate="2011-02-23T23:50:14.730" Score="4" ViewCount="" Body="&lt;p&gt;You need a &quot;voltage regulator&quot;.  The standard answer to &quot;I just want 5 volts with no hassles&quot; is to use a 7805 voltage regulator chip, but they &quot;eat&quot; 2 volts, so you need at least 7v of batteries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have two good options: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Use a &quot;low dropout&quot; 5v regulator (eg LM117).  The datasheet will contain an example circuit.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Just go to a junk store and buy a car cellphone charger for an obsolete phone.&#xA;These are dirt cheap and typically contain an efficient 5v &quot;switch mode&quot; regulator&#xA;capable of delivering up to 1 amp.  (Motorola 34063 is the usual regulator device&#xA;inside these). &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-02-23T23:50:14.730" CommentCount="2" />
  <row Id="10624" PostTypeId="1" AcceptedAnswerId="10625" CreationDate="2011-02-24T00:25:45.333" Score="1" ViewCount="65" Body="&lt;p&gt;I have a nordic radio module &lt;a href=&quot;http://www.olimex.com/dev/mod-nrf24L.html&quot; rel=&quot;nofollow&quot;&gt;http://www.olimex.com/dev/mod-nrf24L.html&lt;/a&gt; which I am attempting to create a c# driver for (the device is a &lt;a href=&quot;http://www.tinyclr.com/hardware/14/fez-rhino/&quot; rel=&quot;nofollow&quot;&gt;Fez Rhino&lt;/a&gt;). I've been able to initilize the device and been able to send it data however I'm not sure if the device is receiving the information on the SPI bus. Whenever I send a command down the bus I get back hexadecimal &quot;E&quot;. I have been reading the chip specification (&lt;a href=&quot;http://www.nordicsemi.com/files/Product/data_sheet/nRF24L01_Product_Specification_v2_0.pdf&quot; rel=&quot;nofollow&quot;&gt;NRF24L01&lt;/a&gt;) trying to determine if the hexadecimal E response is normal, an error or is an invalid response for this device. All the example code that I've found doesn't seem to care about the response from the device so I don't even know if to expect a response.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is: Does the device respond when commands are sent to it, and if so can you point me in the direction of that literature?&lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-02-24T00:52:57.437" Title="Nordic Radio Responses &quot;E&quot;" Tags="&lt;radio&gt;&lt;spi&gt;&lt;nordic&gt;" AnswerCount="1" />
  <row Id="10625" PostTypeId="2" ParentId="10624" CreationDate="2011-02-24T00:38:04.120" Score="1" ViewCount="" Body="&lt;p&gt;All the information you need is in the &lt;a href=&quot;http://www.nordicsemi.com/files/Product/data_sheet/nRF24L01P_Product_Specification_1_0.pdf&quot; rel=&quot;nofollow&quot;&gt;nRF24L01 documentation&lt;/a&gt;. You should get responses back from the chip, via the SPI link, as most of the registers are Read/Write. There is something wrong if you are getting 0x0E returned for every register. If you read register 06, RF_SETUP, directly after a reset, you should get 0x0E, but the other registers should return different values. For instance, register 03 should return 0x03, after a reset.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used the nRF24L01+ with PIC controllers, without any problems.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-24T00:52:57.437" LastActivityDate="2011-02-24T00:52:57.437" CommentCount="6" />
  <row Id="10626" PostTypeId="1" CreationDate="2011-02-24T01:33:27.323" Score="3" ViewCount="189" Body="&lt;p&gt;My electronic kit-building to date has included pre-drilled kit boxes for mounting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My latest purchase, however, has a plastic project box, and no pre-made cutouts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need a rectangular hole for a small LCD screen - and I don't want to mess it up!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How best to cut the hole?  Tools to use?&lt;/p&gt;&#xA;" OwnerUserId="2117" LastActivityDate="2011-02-24T10:38:58.737" Title="Best way to cut mounting squares out of plastic project boxes?" Tags="&lt;cases&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="10627" PostTypeId="2" ParentId="10626" CreationDate="2011-02-24T01:40:14.870" Score="3" ViewCount="" Body="&lt;p&gt;If the plastic isn't too thick, then you could try this:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Cover the surface of the plastic with masking tape, so you don't scratch it.&lt;/li&gt;&#xA;&lt;li&gt;Mark out the rectangle you want to cut out.&lt;/li&gt;&#xA;&lt;li&gt;Using a very sharp knife, score the edges of the rectangle against the side of a metal ruler.&lt;/li&gt;&#xA;&lt;li&gt;Cut deeper and deeper groves with the knife, until you can eventually push out the rectangle.&lt;/li&gt;&#xA;&lt;li&gt;File any rough edges, and remove the tape.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-24T01:40:14.870" />
  <row Id="10628" PostTypeId="2" ParentId="10626" CreationDate="2011-02-24T02:50:02.673" Score="4" ViewCount="" Body="&lt;p&gt;Drill a 6mm hole and use a step drill to open it out to at least 10mm.   A step drill is the best way to make large holes in thin materials, it doesn't grab as much as a large twist drill will.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then use a 'hand nibbler' (http://en.wikipedia.org/wiki/Nibbler) to open it out to rectangular.  You can drill more large holes with the step drill to reduce the amount of nibbling required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I made the cutouts for this project with a nibbler:&#xA;&lt;img src=&quot;http://i.imgur.com/67orB.jpg&quot; alt=&quot;LCD window cut out with nibbler&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-02-24T02:50:02.673" />
  <row Id="10629" PostTypeId="2" ParentId="10604" CreationDate="2011-02-24T02:55:47.033" Score="5" ViewCount="" Body="&lt;p&gt;The name comes from the days (not necessarily long past) when a circuit would be designed on paper and then entered into computer later.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The electronics design world is strangely conservative, some of these guys still swear by MS-DOS.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-02-24T02:55:47.033" CommentCount="2" />
  <row Id="10630" PostTypeId="2" ParentId="9772" CreationDate="2011-02-24T03:23:27.580" Score="2" ViewCount="" Body="&lt;p&gt;Because of regulator dropout, it will be hard to find an ideal regulator that can deliver &gt;1A from four NiMH cells.   Low dropout regulators typically have modest power, high power regulators typically have larger dropout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recommend you switch to 6 cells (7.2v); however I just don't use NiMH any more, lithium cells are so much better.   Search for &quot;protected 14500&quot; on dealextreme.com, these AA-sized 3.4v laptop cells are awesome.  The larger 18650 size is good too.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For 5v regulation, try the &quot;Battery Eliminator Circuit&quot; from a  model helicopter (search for BEC or battery eliminator on dealextreme.com or a hobby site such as hobbyking.com).   These regulators can handle way more current than you will use. eg &lt;a href=&quot;http://www.dealextreme.com/p/8s-5a-switch-mode-ultimate-bec-ubec-45214&quot; rel=&quot;nofollow&quot;&gt;http://www.dealextreme.com/p/8s-5a-switch-mode-ultimate-bec-ubec-45214&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget you can use your multimeter to measure how much current your beagleboard&#xA;is actually using, which will let you know both how beefy a regulator you will need, and&#xA;how long a battery life you can expect (factoring in the efficiency of your regulator).&lt;/p&gt;&#xA;" OwnerUserId="389" LastEditorUserId="389" LastEditorDisplayName="" LastEditDate="2011-02-24T03:33:26.457" LastActivityDate="2011-02-24T03:33:26.457" CommentCount="2" />
  <row Id="10632" PostTypeId="1" CreationDate="2011-02-24T04:53:21.363" Score="2" ViewCount="271" Body="&lt;p&gt;I'm working on a particle filter experiment for multi-sensor fusion and I just programmed it in MATLAB. However, I get very low accuracies for my final values. Plus, I read a lot of literature where they talk about pdf of state and observations etc. but my practical knowledge is still extremely shaky, since I've had no formal training in filtering/Bayesian estimates etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have devised my algorithm like this:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Initialize particles = I'm doing it as a Gaussian distribution - 10 particles&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Move the 10 particles forward using the state transition equation: X_t+1 = A*X_t + 0.1*rand() (only injecting Gaussian noise so far) &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Using the observation, calculate the weights for the particles. I do this like a root mean square of the difference between predicted state and observation. For example, if my azimuth(a) = 40, pitch(p) = 3, roll(r)=4 in my state and in my observation it is a = 39, p = 3, r = 3, then I do rms = sqrt((40-39)^2 + (3-3)^2 + (4-3)^2). Then my weight is assigned as 1/rms in order for it to be inversely proportional to the 'distance' between the prediction and observation&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Then I normalize these weights to get norm_weight = weight/norm(weight) so that their sum is equal to one. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Then I continue forward for all the observations. I have not included resampling yet because when I run this experiment, I do not experience any degeneracy, which is also very puzzling. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Where am I going wrong? I realized that I haven't 'computed' a lot of the Bayesian equations given in the literature i.e. p(x/z_t) = p(z_t/x)*p(x)/p(z) etc. and I don't know where it fits in here either. Can somebody please help me? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My Matlab code looks like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;function resultx = particlefilter(resultx_1, observationx, A, noiseP)&#xA;&#xA;    for j = 1:length(observationx)&#xA;&#xA;    for i = 1:length(resultx_1)&#xA;&#xA;        apriori_state{i} = A*resultx_1{i} + noiseP;&#xA;&#xA;        rms(i) = sqrt((observationx{j}(1) - apriori_state{i}(1))^2 +(observationx{j}(2) - apriori_state{i}(2))^2);&#xA;&#xA;        weight(i) = 1/rms(i);&#xA;    end;&#xA;&#xA;    norm_weight = weight/norm(weight);&#xA;&#xA;    for i = 1:length(apriori_state)&#xA;        plot(apriori_state{i});&#xA;    end&#xA;&#xA;    disp(rms);&#xA;&#xA;    disp(norm_weight);&#xA;end&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2939" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-24T12:23:21.117" LastActivityDate="2011-04-26T16:29:12.310" Title="MATLAB programming of Particle Filter - what is going wrong?" Tags="&lt;filter&gt;&lt;projects&gt;&lt;matlab&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10633" PostTypeId="2" ParentId="5111" CreationDate="2011-02-24T07:04:25.393" Score="1" ViewCount="" Body="&lt;p&gt;Besides the obvious temperature control application, here is a beautiful project that required PID control.   Make yourself a line-following bot: &lt;a href=&quot;http://elm-chan.org/works/ltc/report.html&quot; rel=&quot;nofollow&quot;&gt;http://elm-chan.org/works/ltc/report.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-02-24T07:04:25.393" CommentCount="1" />
  <row Id="10634" PostTypeId="2" ParentId="10609" CreationDate="2011-02-24T10:37:18.697" Score="2" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Put linear regulator before uC - they will react fast enough to cut low-freq noise. Especially good if you have some margin between power supply voltage &amp;amp; uC voltage.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Just add large(some 10-1000 uF) caps before uC: some electrolytic and some 1uF and 0.01uF ceramic ones all in parallel to prevent resonance. Ceramic ones should be as close as possible to power pins of uC. If it were more powerful uC, I would consider adding ferrite bead, but it might be not needed in this case.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-24T10:37:18.697" />
  <row Id="10635" PostTypeId="2" ParentId="10626" CreationDate="2011-02-24T10:38:58.737" Score="2" ViewCount="" Body="&lt;p&gt;Use a &lt;a href=&quot;http://web.mat.bham.ac.uk/C.J.Sangwin/howroundcom/roundness/applications.html&quot; rel=&quot;nofollow&quot;&gt;square drill bit&lt;/a&gt;!&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-02-24T10:38:58.737" />
  <row Id="10636" PostTypeId="1" AcceptedAnswerId="10638" CreationDate="2011-02-24T12:21:44.830" Score="1" ViewCount="202" Body="&lt;p&gt;Since facebook and all the social media warfare, I have realized that the internet is awesome, but not very scalable to embedded devices: new generation network standards are still expensive to make work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The internet is good for high bandwidth, but the installations are quite static, and I don't really believe that smartphones and tablets will really replace micro-computers in terms of network capabilities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question:&#xA;I'm thinking about a CB-radio-like protocol for P2P data transmission.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you think a low frequency, long distance, peer-to-peer radio network would be possible ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the protocol would provide unencrypted and encrypted mode, do you think people would use it knowing that somebody could try to sniff packets ? Would this kind of physical protocol be possible to integrated on simple phone (does lower frequencies consume more energy ?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Could you redirect me to somewhere I could ask this question if you don't have any idea ?)&lt;/p&gt;&#xA;" OwnerUserId="3141" LastActivityDate="2011-05-19T21:49:20.420" Title="Can a cheap, low bandwidth, long-distance wifi be physically and electronically possible for public use ?" Tags="&lt;radio&gt;&lt;frequency&gt;&lt;wifi&gt;&lt;data&gt;&lt;protocol&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="10637" PostTypeId="2" ParentId="10636" CreationDate="2011-02-24T13:03:44.077" Score="0" ViewCount="" Body="&lt;p&gt;People use public none-ncrypted WiFi hotspots even if anyone can read their traffic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CB indeed require much more power. 10mW for WiFi, 1-2-5W for CB to get few Km of range.&#xA;On CB you can probably transmit some 50-100 kbit over 5km at 1-5W power level. This is deadly slow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And the worst part: lower freq require much larger antennas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is possible to have WiFi working over some 1-2km on openspace provided that you are using directional antenna on 1 side. So you may have funny hotspots having some 20-50 directional antennas covering large area.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But this all is garbage in comparison to coming earth-wide satellite internet - modern satellites have hundreds of beams so there is plenty of bandwidth for everyone. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, these days you have 3G/4G network coverage everywhere, so it's not worth bothering.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-24T13:03:44.077" CommentCount="4" />
  <row Id="10638" PostTypeId="2" ParentId="10636" CreationDate="2011-02-24T13:10:29.640" Score="2" ViewCount="" Body="&lt;p&gt;I'm tempted to say this is a contentious issue for discussion, not something with a &quot;right&quot; answer. However, you could investigate the &lt;a href=&quot;http://wiki.laptop.org/go/Mesh_Network_Details&quot; rel=&quot;nofollow&quot;&gt;OLPC Mesh protocol&lt;/a&gt;. In general, lower carrier frequencies mean lower bandwidth for data on them. It's not so much that they consume more energy (in fact they have greater range for the same transmit power) but that the antenna gets larger or less efficient if size constrained.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are trying to do peer-peer networking on a simple phone, the transmit energy associated with the forwarding of packets could badly affect the battery life.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-02-24T13:10:29.640" CommentCount="2" />
  <row Id="10639" PostTypeId="1" CreationDate="2011-02-24T14:50:17.090" Score="4" ViewCount="272" Body="&lt;p&gt;I have a spray tan machine which I wish to sell in the USA.  I have had the machine tested by a CE test house.  Do I have to have a UL approval as well?&lt;/p&gt;&#xA;" OwnerUserId="3143" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-02-24T14:58:10.077" LastActivityDate="2011-05-24T20:11:58.660" Title="Is UL approval required on all items sold in the USA" Tags="&lt;ul&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="10640" PostTypeId="2" ParentId="10639" CreationDate="2011-02-24T14:57:50.513" Score="3" ViewCount="" Body="&lt;p&gt;No, UL approval is not legally required. It's only common because many large companies will not buy equipment that has not passed UL's safety tests.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-02-24T14:57:50.513" CommentCount="1" />
  <row Id="10641" PostTypeId="2" ParentId="6664" CreationDate="2011-02-24T17:46:52.207" Score="1" ViewCount="" Body="&lt;p&gt;Some capacitors exhibit capacitance which varies with voltage.  As a physical analogy, a &quot;perfect&quot; capacitor will behave as a cylinder filled with liquid (adding a particular volume of liquid will increase the pressure, always at the same rate) while some caps behave more like a point-up code (the amount of liquid required for each unit increase in pressure decreases as the cap fills up).  Note that beyond the fact that one may have to use a higher-rated cap to get the capacitance one wants at the actual working voltage, there's another consequence of this behavior for intermittently-powered devices in battery-operated systems: whereas a normal cap will take 9/16 as much energy to charge to 3 volts as to charge to 4 volts, a cap with whose capacitance decreases with voltage will require more energy for the lower-voltage part of the charge.  If a cap will be charged to 4 volts and needs to supply a certain amount of energy before the voltage drops to 3 volts, the latter cap will effectively waste more energy each time it's switched on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be ideal would be if someone could construct a cap which had the opposite sort of behavior--something electrically equivalent to a cap wired in series with a battery (so that capacitance would be maximized at voltages near the battery voltage).  There would be no net current flow into or out of the battery, but shifting the maximum-capacitance voltage would allow intermittently-powered devices to work more efficiently.  I wonder if using different metals for the anode and cathode of a cap would have such an effect?&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-24T17:46:52.207" />
  <row Id="10642" PostTypeId="2" ParentId="3382" CreationDate="2011-02-24T17:52:51.120" Score="1" ViewCount="" Body="&lt;p&gt;Some items I didn't see mentioned:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A nice vise. I used the cheap &quot;helping hands&quot; from Radio Shack for years and they are OK, but then I got a little 3&quot; Palmer bench vise cheap at an auction of a bankrupt machine shop and it is perfect for holding anything from circuit boards to TO92 packages for soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A magnifier of some sort to check for shorts, or even to read labels on SMT packages. I have a 4&quot; magnifier I paid about $5 for at Northern Tool and a nice Bausch &amp;amp; Lomb loupe I won at the same auction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tweezers, X-Acto knife, Dremel tool with variety of bits and a nibbler for modifying cases. Cheap dial (or digital: they can be around $10 on sale these days) calipers; again for use in making/modifying enclosures.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-02-24T17:52:51.120" CommunityOwnedDate="2011-02-24T17:52:51.120" />
  <row Id="10643" PostTypeId="1" CreationDate="2011-02-24T17:55:43.053" Score="2" ViewCount="133" Body="&lt;p&gt;Most circuits that I have designed in the past deal with low voltages...sensors, communicating with other chips, etc. When would I need to consider the addition of fuses into my designs? Sometimes I need to control higher voltage devices like motors that require 24V for example.&#xA;Fuses protect against shorts and large spikes in current. When should these be introduced?&lt;/p&gt;&#xA;" OwnerUserId="1288" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-01T18:36:26.920" LastActivityDate="2011-03-01T18:36:26.920" Title="Designing with fuses...when to use?" Tags="&lt;microcontroller&gt;&lt;fuses&gt;" AnswerCount="2" CommentCount="0" FavoriteCount="2" />
  <row Id="10644" PostTypeId="2" ParentId="7709" CreationDate="2011-02-24T18:03:12.407" Score="2" ViewCount="" Body="&lt;p&gt;Two more answers: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Adding a resistor to a line may&#xA;limit damaging current flows that&#xA;would otherwise result from short&#xA;high-voltage transients, such as&#xA;those caused by electrostatic&#xA;discharge (ESD).  &lt;/li&gt;&#xA;&lt;li&gt;A low-value&#xA;resistor in line with the&#xA;power-supply input to a chip will&#xA;drop a voltage which is proportional&#xA;to the chip's supply current.  If&#xA;one knows the value of the resistor,&#xA;one can connect a meter, measure the&#xA;voltage, and infer the current,&#xA;without disrupting circuit&#xA;operation.  The circuit will work&#xA;the same with or without the meter&#xA;required.  By contrast, if the board&#xA;had a connection point for an&#xA;ammeter in series with the supply,&#xA;it would be necessary to short that&#xA;connection whenever the mater was&#xA;not present.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-04T16:07:33.130" LastActivityDate="2011-03-04T16:07:33.130" />
  <row Id="10645" PostTypeId="2" ParentId="10643" CreationDate="2011-02-24T18:20:33.507" Score="4" ViewCount="" Body="&lt;p&gt;I tell people to always use a fuse when using a non-current limited source, or a source that can provide more current then you will ever want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 2 main examples that come to mind first are batteries and wall power.  In either situation there is usually enough current available to causing components to actually catch on fire if something went wrong. A fuse is a nice last resort fail safe, but shouldn't be treated as anything more then that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are accepting a digital input I am not sure how you can prevent them from shorting power to ground. They will just be providing you signal that is power or a signal that is ground. There is not much you can do to prevent them from shorting power to ground. If you are providing them with power and ground then you can add some current limiting protection to them, but this is a slightly different case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are providing a dedicated Power that is supposed to be used only for controlling button presses then a simple series resistor will make it so that if they do short power to ground you at least have some resistance to limit the current. However, this situation could cause a voltage divider situation that wouldn't give a true high or low signal. You also wouldn't want to do this on an output that someone actually expects to be able to pull some power from as it will cause it to be very inefficient.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am having a hard time figuring out where you are wanting to put a pull-up or pull-down resistor. All this will do for you is cause your input to be pulled high/low when the external device is leaving it floating.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-24T18:20:33.507" />
  <row Id="10646" PostTypeId="2" ParentId="10643" CreationDate="2011-02-24T18:58:56.283" Score="9" ViewCount="" Body="&lt;p&gt;Fuses protect against fires.  If you have a non-current limited supply (like a connection to mains power or a large battery) and you develop a short on your PCB, it's possible to ignite something.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A fuse won't:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Operate at its rated current indefinitely.&lt;/li&gt;&#xA;&lt;li&gt;Blow at currents above its rating instantly.&lt;/li&gt;&#xA;&lt;li&gt;Protect against very fast current spikes.&lt;/li&gt;&#xA;&lt;li&gt;Protect against overvoltage conditions if the current isn't abnormal.&lt;/li&gt;&#xA;&lt;li&gt;Protect semiconductors or ICs against damage - The fuse is slower than the silicon. &lt;/li&gt;&#xA;&lt;li&gt;Protect a person against damage - You can still be electrocuted by a fused circuit.&lt;/li&gt;&#xA;&lt;li&gt;Protect anything if it's on the wrong side of the short.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;But it will usually prevent large currents from flowing through it long enough to start a fire.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-02-26T21:38:12.000" LastActivityDate="2011-02-26T21:38:12.000" CommentCount="2" />
  <row Id="10647" PostTypeId="1" AcceptedAnswerId="10705" CreationDate="2011-02-24T19:53:13.030" Score="2" ViewCount="115" Body="&lt;p&gt;Hi.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm constructing a power supply based on solar cells backed by batteries. The solar cells deliver between 0 and 4 A, depending on the time of day, while the charger I plan on using, the &lt;a href=&quot;http://cds.linear.com/docs/Datasheet/3652fc.pdf&quot; rel=&quot;nofollow&quot;&gt;LT3652&lt;/a&gt;, has a maximum charging current of 2 A. I've started to consider running two of the chargers in parallel in order to utilize the full 4 A, but I'm very uncertain about how they will behave drawing on the same current source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any hunches, ideas or opinions regarding this setup? A rough sketch of what I'm talking about can be seen below (&lt;strong&gt;note:&lt;/strong&gt; this is &lt;em&gt;not&lt;/em&gt; meant as a circuit diagram, just a sketch of what I mean -- don't let the fact that it's drawn using circuit symbols confuse you, it's more like a flowchart).&lt;img src=&quot;http://i.imgur.com/N3wb5.png&quot; alt=&quot;Circuit sketch&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry about the vagueness/scope of the question, but I don't have much experience with charging circuits and want to avoid doing something stupid.&lt;/p&gt;&#xA;" OwnerUserId="2642" LastEditorUserId="2642" LastEditorDisplayName="" LastEditDate="2011-02-26T12:30:32.270" LastActivityDate="2011-02-26T12:30:32.270" Title="Parallel charger circuits" Tags="&lt;solar-cell&gt;&lt;parallel&gt;&lt;battery-charging&gt;&lt;charger&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10648" PostTypeId="2" ParentId="10639" CreationDate="2011-02-24T20:10:43.830" Score="2" ViewCount="" Body="&lt;p&gt;Maybe...  Assuming this is a mains powered device?  There is US Federal law and there are also local laws.  If you only sell a few you may get away with not getting a Nationally Recognized Testing Laboratories (NRTL) approval (there are many NRTLs, UL is just the most well known).  However, besides pingswept's point, local electrical inspectors may prevent business owners from using your equipment based on local regulations unless they see an NRTL mark (even though the Federal gov may not require it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check with the test house that did your CE approval, if they are big enough they may also grant NRTL marks (we use TUV Rheinland).  Note that not using UL or CSA may cause problems in some jurisdictions that are old fashioned.  We have a $4.5M medical device and the City of Baltimore wanted UL, CSA or MET Labs so we gave MET Labs the TUV test reports and a check for a few thousand dollars and they gave us an approval.  UL is a pain to work with, I would go with CSA before UL (even though CSA is Canadian they can grant US NRTL marks in general).  Also note that as part of getting an NRTL mark, you will be signing up for periodic (typically four times a year) factory inspections where the NRTL will make sure you are still building your product in the approved way.  Of course you pay for that privilege.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.greenexpo365.com/portals/asf0001/resources/intertek/The_Q&amp;amp;A_Guide_for_NA_Product_Certification%28US%29.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.greenexpo365.com/portals/asf0001/resources/intertek/The_Q&amp;amp;A_Guide_for_NA_Product_Certification%28US%29.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the bottom line for mains powered equipment is, if you want the US to be a significant market, you want an NRTL approval.  While getting the NRTL approval, throw in the Canadian approval, there are only small differences in the requirements and you open up both markets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Eric&lt;/p&gt;&#xA;" OwnerUserId="3147" LastActivityDate="2011-02-24T20:10:43.830" />
  <row Id="10649" PostTypeId="2" ParentId="9965" CreationDate="2011-02-24T20:19:32.767" Score="0" ViewCount="" Body="&lt;p&gt;Don't know if this helps but here, have a look at this:&#xA;&lt;a href=&quot;http://www.sparkfun.com/categories/16&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/categories/16&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and this more specifically: &lt;a href=&quot;http://www.sparkfun.com/products/9411&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/9411&lt;/a&gt;&#xA;(This unit is legal without a licence in some countries !!!&lt;/p&gt;&#xA;" OwnerUserId="3140" LastActivityDate="2011-02-24T20:19:32.767" />
  <row Id="10650" PostTypeId="1" AcceptedAnswerId="10707" CreationDate="2011-02-24T20:26:10.250" Score="1" ViewCount="207" Body="&lt;p&gt;I need to convert the output of differential output DAC to single ended. It's a 2 Vpp signal with a 1 V common-mode output. The output is 100 ohms. Should I use a transformer or a instrumentation amp. to do this conversion? The output could be up to 10 MHz (it's a communication signal) and the power is &amp;lt; -10 dBm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update 1&lt;/strong&gt; Since the signal is a RF communications signal, there is no DC component.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update 2&lt;/strong&gt; Avoiding a +/- power supply would be nice, so in that case, a transformer would be better, correct?&lt;/p&gt;&#xA;" OwnerUserId="2454" LastEditorUserId="2454" LastEditorDisplayName="" LastEditDate="2011-02-25T13:01:24.220" LastActivityDate="2011-02-25T20:48:34.477" Title="Differential to single-ended conversion - transformer or instrumentation amp?" Tags="&lt;op-amp&gt;&lt;communication&gt;&lt;transformer&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="10651" PostTypeId="2" ParentId="10639" CreationDate="2011-02-24T20:32:08.380" Score="1" ViewCount="" Body="&lt;p&gt;You cannot be sure about selling in the US without an NRTL mark (it doesn't have to be UL per se, but has to be a recognized mark). You can be sure that if the product has a recognized mark, you can sell it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The CE mark has no weight in North America.  &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-02-24T20:32:08.380" />
  <row Id="10652" PostTypeId="1" AcceptedAnswerId="10694" CreationDate="2011-02-24T20:51:04.073" Score="2" ViewCount="207" Body="&lt;p&gt;I'm using a 7.3728 MHz HC-49 crystal with 22pF disc ceramic load capacitors. I'm doing this on a breadboard, but I've had prior experience with using a breadboard for this and it has worked well, so I'm hoping this is not the problem. On the crystal, the following is written: &quot;ACT Fo 7.3728SCA&quot; and I've tracked the datasheet &lt;a href=&quot;http://www.rapidonline.com/netalogue/specs/90-0305e.pdf&quot; rel=&quot;nofollow&quot;&gt;down to this one&lt;/a&gt;. The load capacitance is correct it seems - well within the specified 12pF to 32pF. I'm using with a PIC24FJ64GA002 microcontroller and the microcontroller is set to HSPLL mode, to generate a 29.4912MHz clock. The clock is a baud multiple, and it's very important it's stable. The expected clock is 7.3728 MHz within 50ppm, but the achieved clock is unstable and I can just about measure 20 MHz using my scope, but even that's tricky because it won't trigger well on such an unstable waveform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the waveform I'm talking about. Notice how unstable it is. Since I tried last night, it changed frequency from 20 MHz down to 10 MHz. What is going on??&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/GA1vJ.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My scope only has a limited sample memory of 1K and doesn't sample nearly as fast as a modern one (it does 10 MS/a real time, 10 GS/a equivalent time), but even so I should still be able see a clock frequency.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-02-25T13:01:29.420" LastActivityDate="2011-02-25T18:37:16.433" Title="What's causing my 7.3728 MHz xtal to be unstable?" Tags="&lt;crystal&gt;" AnswerCount="4" CommentCount="4" />
  <row Id="10653" PostTypeId="2" ParentId="10073" CreationDate="2011-02-24T20:56:43.590" Score="1" ViewCount="" Body="&lt;p&gt;I'm working with RT162-7 based on HD44780 (seems compatible to your DEM 16217 SYH-PY).&lt;br&gt;&#xA;Connecting the contrast pin (V0) directly to 0 gives very reasonable contrast, even without a potentiometer or a potential divider.&lt;/p&gt;&#xA;" OwnerUserId="3149" LastActivityDate="2011-02-24T20:56:43.590" />
  <row Id="10654" PostTypeId="1" AcceptedAnswerId="10655" CreationDate="2011-02-24T21:03:25.130" Score="9" ViewCount="171" Body="&lt;p&gt;Last night I pulled the battery holder out of a toy RC car to test the voltage with my meter.  The pack has 4 AA batteries.  The combined voltage at the terminals of the pack was well under 1 volt, and then I tested each battery individually.  These are ordinary AA alkalines (not rechargables).  They were in good condition, with no leakage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first two batteries showed about 1.2V; the third had a small negative voltage, about -0.2, which I thought was pretty interesting, and the last showed about -1.2v.  I have never come across a negative voltage on a battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now before you ask, yes, I double-checked, and then triple-checked, that my leads were plugged in correctly.  And I was not holding the batteries upside down.  I had all four right in front of me, all pointing the same way.  Two showed a positive voltage, one slightly negative, and one -1.2v.  I did this repeatedly,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is, what the heck?  How does a battery get a negative voltage on it?  The pack had been in the RC car for a couple of weeks, with the car switched on.  I think, but cannot prove now, that they were all inserted the right way in the holder.  But even if one or two were in backward, how could this happen?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now the batteries are Canadian, and my meter was made in the USA, but I don't think that explains it.  [That's just a joke.]&lt;/p&gt;&#xA;" OwnerUserId="2773" LastActivityDate="2011-02-24T22:23:41.643" Title="Negative voltage on AA battery" Tags="&lt;battery&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="10655" PostTypeId="2" ParentId="10654" CreationDate="2011-02-24T21:19:38.583" Score="5" ViewCount="" Body="&lt;p&gt;Batteries when are fully discharged they can reverse their polarity. Sometimes you can carefully discharge this reverse voltage on a single cell and the battery will then successfully charge back up. Other times the cell is ruined and needs to be replaced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used to see this on the large batteries used on aircraft. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-02-24T21:19:38.583" CommentCount="2" />
  <row Id="10656" PostTypeId="2" ParentId="10639" CreationDate="2011-02-24T21:22:02.213" Score="1" ViewCount="" Body="&lt;p&gt;To add to what others have said, anyone who does buy and install a system that is not certified will probably not be able to get insurance coverage.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;UL was created for insurance purposes. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-02-24T21:22:02.213" />
  <row Id="10657" PostTypeId="2" ParentId="10652" CreationDate="2011-02-24T21:22:19.787" Score="1" ViewCount="" Body="&lt;p&gt;I would suspect crack on a crystal. Especially if you get normal freq on different xtal.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-24T21:22:19.787" CommentCount="3" />
  <row Id="10658" PostTypeId="2" ParentId="10652" CreationDate="2011-02-24T21:46:25.637" Score="4" ViewCount="" Body="&lt;p&gt;It might be oscillating on the third harmonic because of the poor layout. I'd avoid those solderless breadboards, especially with those 16-bit PICs.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-24T21:46:25.637" CommentCount="3" />
  <row Id="10659" PostTypeId="2" ParentId="10654" CreationDate="2011-02-24T22:23:41.643" Score="4" ViewCount="" Body="&lt;p&gt;It happens if one cell is somehow &quot;weaker&quot; and gets charged by the other cells. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Rechargeable_battery#Reverse_charging&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Rechargeable_battery#Reverse_charging&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-02-24T22:23:41.643" CommentCount="1" />
  <row Id="10660" PostTypeId="1" AcceptedAnswerId="10663" CreationDate="2011-02-24T22:53:59.213" Score="2" ViewCount="212" Body="&lt;p&gt;I've often seen devices with power requirements specified only in Volts (e.g. 7-12V) but never the amperage. I've wanted to run various embedded devices of wall warts and batteries (the devices have regulators don't worrd) however I've been hesitant because I'm not aware of the amperage requirements for the devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is: Is there a standard amperage that is &quot;understood&quot; for microcontrollers and the like?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been told that amperage doesn't matter however I beg to differ, since I am quite sure that if I supplied a 7-12 volt device with 9 volts at 1 billion, amps that it would explode.&lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-02-25T16:50:21.180" Title="Voltage at what Amperage" Tags="&lt;power-supply&gt;&lt;cmos&gt;" AnswerCount="6" CommentCount="3" />
  <row Id="10661" PostTypeId="2" ParentId="10660" CreationDate="2011-02-24T23:18:48.583" Score="4" ViewCount="" Body="&lt;p&gt;Of course it wouldn't, a device will only take as much current as it requires (Ohm's Law). The maximum current capability of the supply is irrelevant, as long as it is greater than the peak current rating of the device.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-24T23:31:45.853" LastActivityDate="2011-02-24T23:31:45.853" />
  <row Id="10662" PostTypeId="2" ParentId="10660" CreationDate="2011-02-24T23:36:49.260" Score="4" ViewCount="" Body="&lt;p&gt;I agree with Leon.  Just because a power supply can supply some maximum current doesn't mean that the device being powered will draw that much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for your question of an &quot;understood&quot; power rating for microcontrollers and the like, you can find the answer for microcontrollers by looking in the datasheet.  This will, of course, vary greatly with the microcontrollers.  Those typically discussed on this site (PICs, ARM Cortex-Mx, AVR, etc.) are relatively low power consumers (usually a few milliamps or tens of milliamps) compared to what a typical wall wart will supply.  I'd wager you would be hard pressed to find a generic wall wart that supplies less than 100 mA at some retail outlet so, generally speaking, it won't be an issue.&#xA;That being said, I can totally understand your frustration with the lack of good documentation.&lt;/p&gt;&#xA;" OwnerUserId="529" LastActivityDate="2011-02-24T23:36:49.260" CommentCount="2" />
  <row Id="10663" PostTypeId="2" ParentId="10660" CreationDate="2011-02-24T23:37:36.667" Score="4" ViewCount="" Body="&lt;p&gt;Voltage (which is kinda like the strength of the supply), and Current (measured in Amps, which is the quantity of electricity), are two very different things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Voltage:&lt;/strong&gt;&#xA;When trying to match a supply to a device, you need to get the voltage right... if the supply voltage is too high, then it will damage your device. If the supply voltage is too low, then your device just won't work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Current:&lt;/strong&gt;&#xA;When looking at current, you need to ensure that the Amps rating is &lt;em&gt;higher&lt;/em&gt; than the device needs as it will only use as much electricity as it needs. If the rating is too low for the device, it will be trying to get more electricity from the supply than the supply can provide, and so it will get hot and possibly explode. If you had a supply that was rated at 1 billion amps, then it would happily power a tiny bulb... it just means it could also power 1 billion bulbs or more a the same time!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, the possible dangerous situations are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;If the voltage is too high for the device.&lt;/li&gt;&#xA;&lt;li&gt;If the amps are too low for the device.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;As a general rule, devices that produce a lot of heat or light or movement usually need a high current supply. Devices that control things, like a TV remote or some small gadget with maybe a few LEDs on it, won't need a lot of current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To answer your question, the microcontroller itself probably only needs between 0.02 and 0.1 amps. If the microcontroller is controlling something else, and sharing the supply, then the current rating of the supply really depends on the device.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-02-25T10:35:44.850" LastActivityDate="2011-02-25T10:35:44.850" CommentCount="7" />
  <row Id="10664" PostTypeId="2" ParentId="10660" CreationDate="2011-02-25T00:05:48.967" Score="3" ViewCount="" Body="&lt;p&gt;If you connect a 5 V 100 mA device to a 5 V 1 billion amp power supply, the device will draw 100 mA.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-02-25T00:05:48.967" CommentCount="3" />
  <row Id="10665" PostTypeId="2" ParentId="10650" CreationDate="2011-02-25T00:12:07.143" Score="0" ViewCount="" Body="&lt;p&gt;Instrumentation amp.  The transformer won't work if the signal is static.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-25T00:12:07.143" CommentCount="1" />
  <row Id="10666" PostTypeId="2" ParentId="10636" CreationDate="2011-02-25T00:14:36.063" Score="0" ViewCount="" Body="&lt;p&gt;No, FCC limits WiFi and related protocols power. You won't get CB sorts of distance (miles).&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-25T00:14:36.063" CommentCount="2" />
  <row Id="10667" PostTypeId="2" ParentId="10652" CreationDate="2011-02-25T00:36:15.630" Score="3" ViewCount="" Body="&lt;p&gt;I'm guessing the 'scope input capacitance, in addition to the breadboard capacitance, is changing the load capacitance by quite a bit, bumping the generated frequency to a higher harmonic (3&lt;sup&gt;rd&lt;/sup&gt;). If I remember correctly, you have an older analog.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-02-25T00:36:15.630" CommentCount="2" />
  <row Id="10668" PostTypeId="1" CreationDate="2011-02-25T01:29:51.677" Score="3" ViewCount="251" Body="&lt;p&gt;I'm looking for an existing design for a good yet simple class D audio amplifier using discrete semiconductors, no ICs.  The purpose is educational, with a final product that actually could be used.  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;not bad quality (but we don't need top quality, or to compete w audiophile gear)&lt;/li&gt;&#xA;&lt;li&gt;enough power to drive modest size speakers (it's hard to be quantitative about this)&lt;/li&gt;&#xA;&lt;li&gt;no exotic parts.&lt;/li&gt;&#xA;&lt;li&gt;within reach of serious hobbyists, EE students&lt;/li&gt;&#xA;&lt;li&gt;not too simple; not for beginners or kids to make.  &lt;/li&gt;&#xA;&lt;li&gt;need not be commercially viable or survive outside an electronics hacker's home.&lt;/li&gt;&#xA;&lt;li&gt;small transistor count prefered, but no need shave every penny or cut corners.&lt;/li&gt;&#xA;&lt;li&gt;illustrates nicely the operation of class D amplifiers&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2011-05-02T15:41:02.260" Title="Good design for a basic non-IC class D audio amp?" Tags="&lt;audio&gt;&lt;design&gt;&lt;class-d&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="2" />
  <row Id="10669" PostTypeId="2" ParentId="10668" CreationDate="2011-02-25T01:32:51.863" Score="3" ViewCount="" Body="&lt;p&gt;Probably this would too be difficult to do without ICs.  Class D is definitely more complex than traditional ones.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-25T01:32:51.863" CommentCount="1" />
  <row Id="10670" PostTypeId="2" ParentId="10660" CreationDate="2011-02-25T02:38:05.243" Score="2" ViewCount="" Body="&lt;p&gt;The &quot;exploding&quot; misconception, as far as I can see, basically comes from not understanding to what kind of ideal generator commonly used power sources can be approximated to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, we have two types of ideal generators. Ideal &lt;a href=&quot;http://en.wikipedia.org/wiki/Ideal_voltage_source&quot; rel=&quot;nofollow&quot;&gt;voltage generator&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/Ideal_current_source&quot; rel=&quot;nofollow&quot;&gt;ideal current generator&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ideal voltage generator has two contacts and provides constant voltage across them, no matter what kind of load we use. The output current comes from Ohm's law and that's why they mustn't be short-circuited at outputs. It basically makes current available to load connected at its output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ideal current generator provides constant current through its contacts, no matter what kind of load we use. The output voltage comes form Ohm's law and that's why they must always have a load or be short-circuited. It basically pumps current through its outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make yet another overused water analogy, ideal voltage source is like a lake from which you can just pick up as much water as you need, while ideal current source is like a pressurized pipe which will provide steady stream of water until it is closed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In real world we don't have such ideal generators and the real sources which are generally available to common people are much closer to ideal voltage generator than to ideal current generator. So if you have a common power supply which is rated at say 9V and 1 GA, that means that you can approximate it as ideal  9 V voltage generator up to output currents of 1 GA. When output current needs to be higher, it will stop acting as an ideal voltage source and will start showing imperfections such as voltage drop, overheating, current limit and so on. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-25T02:38:05.243" CommentCount="1" />
  <row Id="10671" PostTypeId="2" ParentId="10668" CreationDate="2011-02-25T02:41:37.957" Score="8" ViewCount="" Body="&lt;p&gt;I've done this before (though only in simulations) with a quad high-speed high slew rate op-amp. So there is one IC in it, but if you're really anal about that, you could implement it at the transistor level. Anyway, two op-amps are used as a triangle/ramp wave generator, which is then fed into a third op-amp which compares the audio signal with this ramp - this generates a PWM drive, which is applied to a MOSFET gate driver (a simple transistor driver I found on the 'net) which drives a MOSFET which passes current on request and filtered as required using inductors and capacitors. I don't have schematics, but this is how I would implement it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PWM frequency decides the quality of the audio. Higher frequency PWM will increase MOSFET heating and decrease efficiency due to increased switch rate but it will improve audio quality.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-25T02:41:37.957" CommentCount="1" />
  <row Id="10672" PostTypeId="2" ParentId="6778" CreationDate="2011-02-25T03:31:53.587" Score="2" ViewCount="" Body="&lt;p&gt;Dont know if this topic is still alive, but i have been using a bridge rectivier and a capacitor in between my offline ups and the computer.  This is just to prevent system restart when there is voltage fluctuation. So, the smps can handle input DC voltage... Hope this helps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Kripal &lt;/p&gt;&#xA;" OwnerUserId="3152" LastActivityDate="2011-02-25T03:31:53.587" />
  <row Id="10673" PostTypeId="2" ParentId="10131" CreationDate="2011-02-25T06:05:43.740" Score="1" ViewCount="" Body="&lt;p&gt;As far as the msp430, it is a good architecture, pretty good tools out there mspgcc and mspgcc4 and llvm for that matter.  binutils without patching.  You can get a launchpad for under $5 at that price buy a few (eventually you will brick something or short it out and melt it down, have a spare, esp at this price)...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Download the tools, they are all free, write a few lines of code, learn how to link it, see how big the binary gets, get a feel for embedded, lines of code to rom size, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do pros do it.  Just about every way you can imagine:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some companies the mandate comes down from on high and there is nothing you can do about it other than quit.  And you may never know why that platform was chosen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes the contractor/favorite customer dictates the platform, sometimes you can educate/negotiate, sometimes not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some folks just have a favorite, fear of the unknown, whatever.  Same reason why some folks buy only one brand of car, cause my dad did and his dad did before that, and that could be the whole reason.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some folks focus on the tools.  Here again you have brand loyal folks, limiting themselves to their favorite compiler company and whatever targets they support, or favorite open source tool and what that supports.  Favorite embedded operating system and limit to the targets that supports.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In some cases it is about tools but in a different way, over time you may have invested a lot of money in annual support contracts with a vendor (say arm or xilinx or motorola for example) and it could be that you have liked their support and dont want to change or the devil you know is better than the devil you dont.  Or it could be that because the other 5 active projects in the company use this thing and we already have a support contract and will continue to pay for that year after year you must choose one of those vendors solutions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes it is about saving the millipennies.  This part is 1.5% cheaper than that part, make it work with this part, dont care about the NRE, think about the manufacturing savings in volume.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes it is about the negatives.  One vendor may have screwed your company in one way or another.  Failure to meet the advertised supply of parts causing delays or cancellation of your products.  Bait and switch scams (the $50,000 fee for the software did not include the $1200 fee for the dongle required to unlock the license, that is an extra cost item.  Oh and that was per user for the floating license).  Once you sign the NDA to see the programmers reference manual or reference design guide you find out how dreadful their engineering is and you may choose to blacklist all of their products for life.  Past history with horrible tech support.  Any number of reasons may cause you to never allow their sales folks in the front door, or keep you from ever looking at their website again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes it has to do with performance, interfaces, etc.  Case in point say you have an interface that is wire-ored and needs a pull up, microcontroller brand XYZ for $3 per part has a set of I/O pins that can be used with no other external hardware required, brand ABC has a $3 part that will require an external transistor and resistor to make it work at a minimum.  Your example of the msp430, say it is about power consumption, part A may only require the user to use one AAA battery and run for months, part B might need two AAA batteries and run for weeks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The rarest case of all is to actually do the engineering, survey all the vendors, do the power consumption math, the price per unit of your product math, the how big of a rom do we need and what frequency to run the chip at, glue logic, on and on.  Usually someone (boss/customer/senior engineer) takes their years of experience and shoots from the hip (often using one or more of the above) to choose the path (often a good path saving tons of time in schedule and dollars) and the engineering is done once to fine tune the chosen platform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My personal recommendation is to be flexible.  Most microcontroller brands/families in some form or fashion can be had on an eval board for under $50.  Sparkfun, olimex or direct from the vendor (ti for msp430 or stellaris, etc).  Try one or more of each, get a feel for what is in common and what is different, tools, loaders, how hard to unbrick, etc.  You get two things from this at least, one is that when you are forced down a path from on high or customer you can hit the ground running, second is that when it is your turn to choose the platform you are better educated on what is and isnt out there and can pick the right (loaded word) platform based on the problem to be solved.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if you dont or cant go out and spend that kind of money on the hardware, most have tools that you can download (for free), in cases like microchip you can now get the C compiler (used to be Hi-tech) but have to subscribe (give up your email address).  gcc like it or hate it will be in your future, desktop or embedded, get your hands dirty and learn to use it as a cross compiler.  Try llvm too, it will be around for a while and give gcc some serious competition.  Anyway write or find some emulators, mame has many, gdb has some, etc.  I have written one called the thumbulator at github, ARM thumb mode only, similar to a cortex-m3 except I dont support thumb2 (can still learn quite a bit and have programs run on both before you switch over to hardware only).  I whipped up an msp430 emulator but kinda stalled on that.  The instruction set is so small that the bulk of the work is an evening or perhaps a saturday project.  Same goes for the PIC, a long afternoon and you have an instruction set simulator with which to practice embedded.  If nothing else you can just write the programs compile and link to get a feel for how to do that and how big the programs end up being, how to tune the programs to produce tighter code, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as C vs assembler, some instruction sets are C friendly and some are not.  Some compilers are medium and some are really bad and only a few are really good (and usually cost a few thousand dollars one time or per year to use).  As with performance anywhere if you want to really push it, a mixture of high level language (lets just say C) and assembler may be required.  So the skill is not writing the whole application in assembler, the skill is determining what code is causing you to not meet timing/performance and then knowing how to solve that either through C, compiler options, choosing the right compiler, or writing assembler.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recommend that you know assembler for all of the platforms you choose to use, if nothing else readable knowledge of it as with embedded I recommend you disassemble often (while figuring out where your performance problems are).  Many platforms some assembler is required or desired for the boot up code anyway.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are wanting to save that 10-20% on price per unit and want to buy the cheaper/slower microcontroller or oscillator, or the 32Kb flash part instead of the 64KB flash part and can cover the development cost with volume of sales, and perhaps a long list of other things you may very well choose to write the whole thing in assembler, fast, low power, low cost, happy customers.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your background so far, perhaps you shouldnt worry about writing in all assembler and maybe about the electrical engineering aspects of embedded with microcontrollers, reading schematics, knowing what open collector, tri state, push pull, pwm, adc, dac, and a long list of other terms and how to use them.  bit banging i2c, spi, mdio, dallas one wire, etc.  Using a scope as a software debugger.  Even though scopes can highlight things for you today (an extra cost item), you should be able to eyeball i2c and spi and some other protocols without the highlights.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also recommend that for each of the platforms you play with, get out of someone elses sandbox (the Arduino ide/programming environment for example).  Write the boot code that takes the processor from reset into your main() program, do as much as you can to understand how to load/program the flash to the point that that may involve writing your own loader even though of the shelf ones are there.  It is all about personal education, the more you know and can pull out of your back pocket and use the more control you will have over your career and the more zeros at the end of the number on your paycheck.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whatever you do, DO NOT, try to learn x86 as your first assembler on a desktop, choose pretty much anything else and cross compile and simulate, ARM, THUMB, MSP430, PIC, AVR, even 6502, 8051.  x86 is a horrible instruction set and as a result has been morphed and shaped in so many ways, microcoded, not microcoded, multi core, on and on.  Keep the x86 to high level languages and bulky operating systems.  Use it for your text editor and compilers and target something else.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry for the long answer...hope it was helpful.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-02-25T06:05:43.740" CommentCount="1" />
  <row Id="10674" PostTypeId="2" ParentId="10580" CreationDate="2011-02-25T06:16:18.827" Score="2" ViewCount="" Body="&lt;p&gt;at sourceforge you can find both mspgcc (mspgcc.sf.net) and mspgcc4 (mspgcc4.sf.net).  I had trouble recently building mspgcc on a modern Linux (finally did succeed), but mspgcc4 builds just fine no problem.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If all you need is an assembler and linker for now, it is somewhat trivial to cross compile gnu binutils.    ./configure --target=msp430 --prefix=/opt/msp430  or something like that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, out of the box, llvm includes the various targets, unlike gcc you do not pick one target when compiling the compiler.  The downside is that llvm's msp430 support is considered experimental (as in we probably wont bother with the bug reports).  And you will still need binutils to assemble and/or link.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-02-25T06:16:18.827" CommentCount="1" />
  <row Id="10675" PostTypeId="1" AcceptedAnswerId="10677" CreationDate="2011-02-25T07:05:01.530" Score="4" ViewCount="219" Body="&lt;p&gt;Is it possible to use the 4-pin mode of an SD card when designing an interface with a microcontroller, or must you always use SPI mode? I am particularly thinking of a microcontroller such as a PIC24. The SPI mode is slower, obviously, and I am trying to think of better ways to improve the device's throughput.&lt;/p&gt;&#xA;" OwnerUserId="2895" LastEditorUserId="2895" LastEditorDisplayName="" LastEditDate="2011-02-25T15:24:12.027" LastActivityDate="2011-02-25T15:24:12.027" Title="Is it possible to use 4-pin mode for an SD card with a microcontroller instead of SPI mode?" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;spi&gt;&lt;sd&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10676" PostTypeId="2" ParentId="159" CreationDate="2011-02-25T07:07:01.420" Score="1" ViewCount="" Body="&lt;p&gt;If you have HD44780-compatible LCD and want to use it without consuming too many output pins, you could use a shift register (such as 74VHC164 or 74HC595).&lt;br&gt;&#xA;&lt;a href=&quot;http://www.micahcarrick.com/avr-3-wire-hd44780-lcd-interface-avr-gcc.html&quot; rel=&quot;nofollow&quot;&gt;Here is a link to an example project&lt;/a&gt;.&lt;br&gt;&#xA;Effectively this is very much like a Serial Enabled LCD.&lt;/p&gt;&#xA;" OwnerUserId="3149" LastActivityDate="2011-02-25T07:07:01.420" />
  <row Id="10677" PostTypeId="2" ParentId="10675" CreationDate="2011-02-25T09:30:33.180" Score="3" ViewCount="" Body="&lt;p&gt;That's what I've found:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The SD 1-bit protocol is a synchronous&#xA;  serial protocol with one data line,&#xA;  used for bulk data transfers, one&#xA;  clock line for synchronization, and&#xA;  one command line, used for sending&#xA;  command frames. The SD 1-bit protocol&#xA;  explicitly supports bus sharing. A&#xA;  simple single-master arbitration&#xA;  scheme allows multiple SD cards to&#xA;  share a single clock and DAT0 line.&#xA;  The SD 4-bit protocol is nearly&#xA;  identical to the SD 1-bit protocol.&#xA;  The main dierence is the bus width &#xA;  bulk data transfers occur over a 4-bit&#xA;  parallel bus instead of a single wire.&#xA;  With proper design, this has the&#xA;  potential to quadruple the throughput&#xA;  for bulk data transfers. Both the SD&#xA;  1-bit and 4-bit protocols by default&#xA;  require CRC protection of bulk data&#xA;  transfers. A CRC, or Cyclic Redundancy&#xA;  Check, is a simple method for&#xA;  detecting the presence of simple&#xA;  bit-inversion errors in a transmitted&#xA;  block of data. In SD 4-bit mode, the&#xA;  input data is multiplexed over the&#xA;  four bus (DAT) lines and the 16-bit&#xA;  CRC is calculated independently for&#xA;  each of the four lines. In an&#xA;  all-software implementation,&#xA;  calculating the CRC under these&#xA;  conditions can be so complex that the&#xA;  computational overhead may mitigate&#xA;  the benets of the wider 4-bit bus. A&#xA;  4-bit parallel CRC is trivial to&#xA;  implement in hardware, however, so&#xA;  custom ASIC or programmable-logic&#xA;  solutions are more likely to benet&#xA;  from the wider bus.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://alumni.cs.ucr.edu/~amitra/sdcard/Additional/sdcard_appnote_foust.pdf&quot; rel=&quot;nofollow&quot;&gt;http://alumni.cs.ucr.edu/~amitra/sdcard/Additional/sdcard_appnote_foust.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe you wouldn't have enough power to calculate crc32 in 4-bit mode. But without CRC it might be possible.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-25T09:30:33.180" CommentCount="3" />
  <row Id="10678" PostTypeId="2" ParentId="10584" CreationDate="2011-02-25T11:00:13.927" Score="1" ViewCount="" Body="&lt;p&gt;ASCII printable characters are just bytes with values in the range of 32 to about 127. If your mbed receives ASCII, it should simply pass it to the output unchanged. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it doesn't work, then the problem is in connection between mbed and whatever you want it to send text to.&lt;/p&gt;&#xA;" OwnerUserId="1036" LastActivityDate="2011-02-25T11:00:13.927" />
  <row Id="10679" PostTypeId="2" ParentId="159" CreationDate="2011-02-25T12:02:00.690" Score="0" ViewCount="" Body="&lt;p&gt;You could use the &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=19&amp;amp;products_id=292&quot; rel=&quot;nofollow&quot;&gt;adafruit LCD backpack&lt;/a&gt;. It supports either I2C or SPI. In SPI mode it's really just using a 74HC595 shift register.&lt;/p&gt;&#xA;" OwnerUserId="2654" LastActivityDate="2011-02-25T12:02:00.690" />
  <row Id="10680" PostTypeId="2" ParentId="10650" CreationDate="2011-02-25T14:56:42.323" Score="1" ViewCount="" Body="&lt;p&gt;As a crazy solution you may move ground&amp;amp;supplies of your DAC 1v higher. In this case you will get your shifted signal without any distorsions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Level-converting of digital signals is much easier, does not intoduce analog error, and sometimes is not needed.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-25T14:56:42.323" />
  <row Id="10681" PostTypeId="2" ParentId="10675" CreationDate="2011-02-25T15:00:07.340" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;improving throughput in 1-bit mode&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a huge variation in performance from SD card to another.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(a) All cards give a &quot;busy&quot; response to one command until it is ready to handle the next. A card can still comply with the standards even if it takes a second to write a block of data. Perhaps you could try a few different cards and see which one works the best for you -- the best net throughput, the lowest latency, the least amount of energy to wake up and store the data and go back to sleep, or whatever is most important for your project.&#xA;If throughput is the most important, then you'll want to pick the appropriate&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Secure_Digital#Speeds&quot; rel=&quot;nofollow&quot;&gt;SD Card Speed Class Rating&lt;/a&gt; -- the highest speed you can afford, or at least the lowest class that gives adequate performance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(b) While the standard requires all SD cards to handle communications at up to 25 Mbit/s in 1-bit mode, a few cards seem to work with much higher &lt;a href=&quot;http://en.wikipedia.org/wiki/Talk%3aSerial_Peripheral_Interface_Bus#Baud_rate.3F&quot; rel=&quot;nofollow&quot;&gt;bit rates&lt;/a&gt; -- perhaps you could try a few different cards and bump up your bit rate to something faster that works with that particular card.&#xA;(Is there something like &quot;automatic baud rate detection&quot; to automatically use the maximum speed supported by whatever card is currently plugged in?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;using 4-pin mode&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A microcontroller can support using four-bit SDI transfer mode.&#xA;The 2 options I know about are:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(a)&#xA;Plug the card into a USB SD card adapter that uses four-bit SDI transfer mode.&#xA;Plug the adapter into a USB host connector attached to a microcontroller that can act as a USB host, such as the PIC24FJ32GB002.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(b)&#xA;Plug the card into a SD card slot directly attached to a microcontroller.&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/5628/do-i-need-to-pay-royalties-to-the-sd-card-people-if-my-device-just-happens-to-b&quot;&gt;Do I need to pay royalties to the SD card people if my device “just happens” to be compatible with SD cards?&lt;/a&gt;&#xA;For a long time various patents and trade secrets required a person designing such a host controller interface to sign an NDA and buy a patent licence from the SD Card Association.&#xA;But I hear that &lt;a href=&quot;http://en.wikipedia.org/wiki/Secure_Digital#Openness_of_standards&quot; rel=&quot;nofollow&quot;&gt;the SD interface standard is becoming more open since 2006&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-25T15:00:07.340" />
  <row Id="10682" PostTypeId="2" ParentId="10660" CreationDate="2011-02-25T15:06:27.253" Score="1" ViewCount="" Body="&lt;p&gt;Voltage and resistance is all that matters.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For simple (non-reactive) devices like steppers/speakers/etc, the current is determined by a very simple equation:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;current (amps) = voltage (volts) / resistance (ohms)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, given a fixed voltage and the fixed resistance you can calculate amperage. It's that simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A Power supply with a rating for a certain amperage tells you a few things. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, the power supply is only built to handle that amperage. Wiring, resistors, and other devices heat up based on more or less on much how current you put through them. A thicker wire heats up less, and can therefore handle more current without danger of melting or fire. This is because there's a larger cross-sectional area for the power to be distributed over. (although it's not quite so simple if the voltage has a high frequency AC component to it) So, you don't want the supply to go significantly beyond it's rated range. It may be built with thinner wire and burn up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, many power supplies are fairly dumb devices (unregulated). If they're rated at 12V @ 1A, they may give you 16V at 0.25A, or 10V at 2A (if they don't burn up). You only know that you'll get 12V at exactly the rated voltage. This can give you problems if you put a 12V 5A supply on a device that only draws 100mA (it may end up giving the device 16V+)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Third, supplies also have an internal resistance. So: CURRENT = VOLTAGE / ( RESISTANCE_OF_LOAD + INTERNAL_RESISTANCE_OF_POWER_SUPPLY). So, the current it is able to supply to the load is limited somewhat by this internal resistance. Your 1.2A rated stepper example on a 650mA supply might only be able to draw 900mA for this reason. (For a stepper, that'd usually just mean it operates more slowly and has less torque)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Forth, the supply may have active current limiting. If your mentioned 650mA supply had current limiting, it may limit the maximum current (for safety) to 700mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best power supplies are actively regulated. This means that a microcontroller or some feedback circuit is watching it's output and adjusting to always give you the rated voltage. They usually have current limits, too... so these are the safest type of power supplies. However, many are switching-mode power supplies instead of linear and may add noise, so they may be undesirable for certain devices (high performance audio comes to mind).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So... there's lots of factors that basically mean use a power supply that's close to what your load needs unless you know for sure that it's regulated. Never use a supply rated below what your load needs, unless you have a very good understanding of both the load and the supply and how they'd react to that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reactive devices (like microcontrollers) can dynamically change their resistance to suit their needs. Running these devices with less power than they need would usually mean some sort of incorrect operation.&lt;/p&gt;&#xA;" OwnerUserId="1270" LastEditorUserId="1270" LastEditorDisplayName="" LastEditDate="2011-02-25T16:50:21.180" LastActivityDate="2011-02-25T16:50:21.180" CommentCount="2" />
  <row Id="10683" PostTypeId="2" ParentId="10632" CreationDate="2011-02-25T15:58:13.587" Score="1" ViewCount="" Body="&lt;p&gt;I have a few comments about things to fix.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1st your &lt;code&gt;for j = 1:length(observationx)&lt;/code&gt; doesn't seem to have an end. My guess is you should have this just before the line &lt;code&gt;norm_weight = weight/norm(weight);&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2nd your apriori_state, rms, and weight change size every iteration. This can cause matlab to run very slow. In order to improve this you need to preallocate the variable. This can be done like so: &lt;code&gt;apriori_state = zeros(size(resultx_1));&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as actual functionality I don't see anything that pops at as being wrong. The math and stats site linked to in a comment might be able to find functionality errors faster then I can.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-25T15:58:13.587" CommentCount="1" />
  <row Id="10684" PostTypeId="2" ParentId="8614" CreationDate="2011-02-25T16:05:59.993" Score="0" ViewCount="" Body="&lt;p&gt;The MIDI interface was designed to reliably communicate over 50 feet.&#xA;The hardware required (an optoisolator and a diode and a few resistors and an IC or transistor inverter) costs less and has better performance over long lines than the hardware required for +/- 12 V RS232 communication.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.midi.org/techspecs/electrispec.php&quot; rel=&quot;nofollow&quot;&gt;official MIDI interface schematics&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1187962258/&quot; rel=&quot;nofollow&quot;&gt;beautiful MIDI IN schematic&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-25T16:05:59.993" />
  <row Id="10685" PostTypeId="1" CreationDate="2011-02-25T16:36:52.477" Score="1" ViewCount="127" Body="&lt;p&gt;I bought &lt;a href=&quot;http://www.robotshop.com/seeedstudio-electronic-brick-serial-cmos-camera-2.html&quot; rel=&quot;nofollow&quot;&gt;this serial electronic brick camera&lt;/a&gt; from Robot shop recently. I connected it to a &lt;a href=&quot;http://www.sparkfun.com/products/718&quot; rel=&quot;nofollow&quot;&gt;Spark Fun FT232R&lt;/a&gt; shield. I am able to open my virtual COM port but I am not able to capture any images.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is what I did on the spark fun shield's end:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;I removed the solder jumper and connected 5V to VccIO, and GND to GND.&lt;/li&gt;&#xA;&lt;li&gt;I connected the Rx to Tx and vice versa.&lt;/li&gt;&#xA;&lt;li&gt;When I click on capture, the serial camera client just freezes.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Can anyone throw some light where am I going wrong?&lt;/p&gt;&#xA;" OwnerUserId="3159" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-02-25T23:55:24.560" LastActivityDate="2011-02-28T15:54:31.317" Title="Serial brick camera" Tags="&lt;serial&gt;&lt;camera&gt;&lt;ftdi&gt;" AnswerCount="0" CommentCount="7" FavoriteCount="1" />
  <row Id="10686" PostTypeId="1" AcceptedAnswerId="10781" CreationDate="2011-02-25T16:47:43.400" Score="2" ViewCount="144" Body="&lt;p&gt;The 4-wire SPI bus has a considerable speed advantage over I²C, but unfortunately so far as I know has no standard way to perform handshaking without using extra wires beyond the four (and four wires is already annoying enough as it is).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a recent project where the slave was a CPLD, I implemented a nice approach to provide handshaking in one direction (slave can make master wait) and also incidentally eliminate the need for the /FS line.  The signals are Clock, MOSI (master-out/slave-in) and MISO (master-in slave-out).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Clock idles low; both MISO and MOSI output on the rising edge of Clock and are sampled on the falling edge. Two or more consecutive rising edges on MOSI wire while Clock is low will reset communication.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When Clock is low and MOSI is high, MISO will indicate whether the slave is ready.  When clock and MOSI are both low, MISO will indicate whether the slave wants attention.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While this approach works very nicely when communicating between my CPLD and my controller, it would be nice if the same approach could be used when communicating between two standard microcontrollers.  The biggest features that would be necessary to make this work nicely would be:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;the ability of the slave controller&#xA;to reset itself upon receiving some&#xA;number (probably 2 or 3) of rising&#xA;edges on MOSI while clock is idle;&lt;/li&gt;&#xA;&lt;li&gt;the ability of the slave to control&#xA;the clock-idle state of MISO, and&#xA;preferably load separate values for&#xA;use when MOSI is high or when it is&#xA;low;&lt;/li&gt;&#xA;&lt;li&gt;preferably, the ability for the&#xA;master to control the state of MOSI&#xA;that will be output when the clock&#xA;is idle between bytes (in my&#xA;protocol, the commands which need&#xA;handshaking have the LSB set, but&#xA;that's a bit of a nuisance);&lt;/li&gt;&#xA;&lt;li&gt;for buffered SPI ports, the ability&#xA;for the master to wait on the&#xA;slave's data line.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Do any common controllers or slave devices offer such features, or work in such a way?&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-02-25T16:54:11.473" LastActivityDate="2011-03-08T04:03:10.160" Title="Do any devices support handshaking on SPI-ish bus without extra wires" Tags="&lt;spi&gt;&lt;handshaking&gt;" AnswerCount="3" />
  <row Id="10687" PostTypeId="2" ParentId="6676" CreationDate="2011-02-25T17:07:50.710" Score="2" ViewCount="" Body="&lt;p&gt;I hadn't looked at the 74HC4094, having always used the 74HC595, but the 74HC4094 looks like it has a couple of interesting differences:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The load signal is level-sensitive, rather than edge sensitive, allowing the device to be used in a &quot;transparent&quot; mode, where bits from the input are immediately shown on the output.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;It has a cascading output which triggers on the same clock edge as the input, as well as a cascading output which is delayed by half a clock.  Use of this latter output will greatly improve sample and hold margins when feeding the output of the device into another one; the former may be useful in some situations when feeding a device which is known to receive the clock before the data.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The 74HC4094 does not have the asynchronous clear function of the 74HC595.  There have been times I would have used the 74HC595's asynchronous clear if the load signal was level-sensitive (so that asserting clear and load simultaneously would clear the outputs), and times I would have used a synchronous clear (wire the cascade output to synchronous clear and synchronous load signals, and reduce communications requirement to two wires), but I don't think the signal will be missed on the 74HC4094.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-05T02:34:12.750" LastActivityDate="2011-03-05T02:34:12.750" CommentCount="1" />
  <row Id="10688" PostTypeId="2" ParentId="1299" CreationDate="2011-02-25T17:15:41.740" Score="2" ViewCount="" Body="&lt;p&gt;One advantage not yet mentioned of SPI over I2C is that all SPI wires are unidirectional and are always driven high or low.  This allows much faster communication than is possible with I2C, reduces susceptibility to noise, and allows simple gates to be used as repeaters.  Another useful option is simple async communication (one wire each direction).  The only downside I can see to async communication is that it generally requires both sides to be &quot;awake&quot;, with a stable clock, to exchange data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a project of my own, I used a 3-wire slightly-modified SPI protocol and have found the results satisfactory.  I send display bitmap data (where occasional data corruption would be no big deal) at 10mbps and other data at 2.5mbps without difficulty.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-25T17:15:41.740" />
  <row Id="10689" PostTypeId="1" AcceptedAnswerId="10718" CreationDate="2011-02-25T17:45:14.423" Score="1" ViewCount="129" Body="&lt;p&gt;My company uses Altium Designer for PCB design and the most CPU intensive operation seems to be the autorouting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, when considering a new computer, would it benefit autorouting algorithms more to have multiple cores of a given speed, or fewer cores of a higher speed? Does Altium's autorouting take advantage of multiple CPU cores?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically I am considering laptop processors but this question could easily apply to desktop processors as well.&lt;/p&gt;&#xA;" OwnerUserId="2028" LastActivityDate="2011-02-26T00:45:48.767" Title="CPU considerations for PCB software (routing) when purchasing a new computer." Tags="&lt;computers&gt;&lt;pcb-design&gt;&lt;routing&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="10690" PostTypeId="2" ParentId="5801" CreationDate="2011-02-25T17:49:34.637" Score="3" ViewCount="" Body="&lt;p&gt;I've done video overlay in an application which required polling during the data display.  If you have a spare FSR available, insert:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;  btfsc  INTCONx,RCIF   ; I forget which INTCON it's in&#xA;   movff RCREG,POSTINC2 ; Or whichever FSR is free  &#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;at least once every 16 lines (it may be most convenient to do it every line).  Only three cycles per line.  If you do not have a spare FSR available, but your display code is expanded out rather than looped, then at least once every sixteen lines you need to use:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;  movff  INTCONx,SerStatus+N  ; N=0 for the first one, 1 for the next, etc.&#xA;... and then (not necessarily immediately)&#xA;  btfsc  SerStatus+N&#xA;   movff RCREG,SerData+N&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;at a cost of three cycles on one line and two on another; at the end of the display:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;  lfsr   0,SerData&#xA;  btfsc  SerStatus+0&#xA;   movff SerData+0,POSTINC0&#xA;  btfsc  SerStatus+1&#xA;   movff SerData+1,POSTINC0&#xA;  btfsc  SerStatus+2&#xA;   movff SerData+2,POSTINC0&#xA;  ...&#xA;  movlw  (SerData &amp; 255)&#xA;  subwf  FSR0L,w&#xA;  ; W will now hold number of bytes received&#xA;  ; Data will be in SerData+0 to SerData+(W-1)&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The trick is not to worry about figuring out what to do with data while showing the display.  Just throw it someplace and sort it out later.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-25T17:49:34.637" />
  <row Id="10691" PostTypeId="2" ParentId="4905" CreationDate="2011-02-25T18:15:34.073" Score="1" ViewCount="" Body="&lt;p&gt;My inclination would be to use something to buffer the timing between the processor and the display.  Having hardware that can show an entire frame of video without processor intervention may be nice, but perhaps overkill.  I would suggest that the best compromise between hardware and software complexity would probably be to make something with two or three independent 1024-bit shift registers (two bits per pixel, to allow for black, white, gray, or transparent), and a means of switching between them.  Have the PIC load up a shift register, and then have the hardware start shifting that one out while it sets a flag so the PIC can load the next one.  With two shift registers, the PIC would have have 64us between the time it is told a shift register is available and the time all the data has to be shifted.  With three shift registers, the PIC would have to average one line every 64us, but it could tolerate a delay of up to 64us.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that while a 1024-bit FIFO would be just as good as two 1024-bit shift registers, and in a CPLD a FIFO only costs one macrocell per bit, plus some control logic, in most other types of logic two bits of shift register will be cheaper than one bit of FIFO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative approach would be to connect a CPLD to an SRAM, and make a simple video subsystem with that.  Aesthetically, I like the on-the-fly video generation, and if somebody made nice cheap 1024-bit shift-register chips it's the approach I'd favor, but using an external SRAM may be cheaper than using an FPGA with enough resources to make multiple 1024-bit shift registers.  For your output resolution it will be necessary to clock out data at 12M pixels/sec, or 3MBytes/sec.  It should be possible to arrange things to allow for data to be clocked in at a rate of up to 10mbps without too much difficulty by interleaving memory cycles; the biggest trick would be preventing data corruption if a sync pulse doesn't come at the precise moment expected.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-02-25T20:23:21.763" LastActivityDate="2011-02-25T20:23:21.763" />
  <row Id="10692" PostTypeId="1" AcceptedAnswerId="10695" CreationDate="2011-02-25T18:19:14.070" Score="1" ViewCount="122" Body="&lt;p&gt;So I've been learning AVR assembly in my own time, I rather like it and I understand registers/counters and such.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the problem is...most of the websites I read online/tutorials don't really talk about actually using them with stuff like Servo's/Motors/LEDs/etc&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They more talk about just doing I guess math/logic, but I'm actually wanting to control LEDs/MOTORS/Servos (especially servo's/motors...haven't seen an example yet)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas of where I could find this info?&lt;/p&gt;&#xA;" OwnerUserId="3073" LastEditorUserId="2028" LastEditorDisplayName="" LastEditDate="2011-02-26T03:10:18.653" LastActivityDate="2011-02-26T03:10:18.653" Title="AVR Assembly with Servo/Motors/Etc" Tags="&lt;avr&gt;&lt;led&gt;&lt;motor&gt;&lt;servo&gt;&lt;assembly&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="10693" PostTypeId="1" CreationDate="2011-02-25T18:30:06.423" Score="4" ViewCount="234" Body="&lt;p&gt;I am interested in putting that nice green / red soldermask on the PCBs that I make at home.  The problem is I can't find a lot of information on it, like where to buy it, etc.  Do any hobbyists actually do this, or is it only for the pros?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CLARIFY:&lt;br&gt;&#xA;I am interested in this technique not only to protect my board once it is complete, but also so I can give it a professional look.  I understand fully that I don't 'need' it for hobby type applications, but I am still interested in it.  Is this stuff that can actually be bought in reasonable quantities?  Is it very expensive, etc.  Does anybody know?&lt;/p&gt;&#xA;" OwnerUserId="3077" LastEditorUserId="3077" LastEditorDisplayName="" LastEditDate="2011-02-28T17:21:17.750" LastActivityDate="2011-02-28T17:21:17.750" Title="Soldermask at home?" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;" AnswerCount="2" FavoriteCount="3" />
  <row Id="10694" PostTypeId="2" ParentId="10652" CreationDate="2011-02-25T18:37:16.433" Score="1" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;Is there a short, solid connection between the load capacitors and a GND pin of your MCU?&lt;/li&gt;&#xA;&lt;li&gt;Have you read the errata for your chip?&lt;/li&gt;&#xA;&lt;li&gt;Solderless breadboards are notorious for unwanted parasitic capacitance and inductance.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;You may be overdriving your crystal.&#xA;Have you read &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en020706&quot; rel=&quot;nofollow&quot;&gt;&quot;Microchip AN943: Practical PICmicro® Oscillator Analysis and Design&quot;&lt;/a&gt;?&#xA;In particular, check out Figure 13 and the surrounding text -- it sounds like you need to increase the value of your &quot;Rs&quot; resistor.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-25T18:37:16.433" />
  <row Id="10695" PostTypeId="2" ParentId="10692" CreationDate="2011-02-25T18:45:03.013" Score="2" ViewCount="" Body="&lt;p&gt;Currently, and for good reason, people dont do this in assembly much anymore. Most stuff can easily be done in other programming languages, like C. Maybe you want to look at Arduino (arduino.cc)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To learn more about hardware programming the AVR, you may want to look into any of the excellent books available on the topic, although most literature features C as a language. Most of the C oriented books will give you good hints at the programming. You may then use that in assembler. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, you should also look at the papers at Atmel. They have an extensive library online. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Imho, unless you've proven C is not sufficient for your needs, you sould try that, and see how far you get. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from that, Barrett &quot;Atmel AVR Microcontroller Primer&quot; has a decend description of the registers. &lt;/p&gt;&#xA;" OwnerUserId="3161" LastEditorUserId="3161" LastEditorDisplayName="" LastEditDate="2011-02-25T18:50:57.303" LastActivityDate="2011-02-25T18:50:57.303" CommentCount="3" />
  <row Id="10696" PostTypeId="1" AcceptedAnswerId="10698" CreationDate="2011-02-25T18:47:06.880" Score="1" ViewCount="145" Body="&lt;p&gt;So I understand AVR assembly for the most part, and generally understand the overview of microcontrollers. but when it comes to specific components (besides the obvious stuff like resistors/batterys) I dont understand what they do....and more specifically WHEN to use them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stuff like Capacitors,Regulators,Inductors,Crystals,Etc&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where can I find a generally overview of When and what these components do? to further my knowledge. I can of course wikipedia the definitions....but I more want to know when I should use these specific things because I figure it's probably a good idea to know more than &quot;what&quot; they are and also What to use...&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-02-26T16:06:10.857" Title="Understanding when to use basic Components" Tags="&lt;electronics&gt;&lt;capacitor&gt;&lt;voltage-regulator&gt;&lt;inductor&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="1" />
  <row Id="10697" PostTypeId="2" ParentId="10072" CreationDate="2011-02-25T19:06:06.693" Score="2" ViewCount="" Body="&lt;p&gt;You are probably in RMII (reduce MII mode).  Check this registers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;7.2.5  RMII and Bypass Register (RBR)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And this pin:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MII_MODE (RX_DV) 32 MII MODE SELECT&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-25T19:06:06.693" CommentCount="1" />
  <row Id="10698" PostTypeId="2" ParentId="10696" CreationDate="2011-02-25T19:06:51.137" Score="3" ViewCount="" Body="&lt;p&gt;After some searching, I found this site which seems to have a nice level of explanation: &lt;a href=&quot;http://www.piclist.com/images/www/hobby_elec/e_parts.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.piclist.com/images/www/hobby_elec/e_parts.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I personally dont know of a nice, &lt;em&gt;comprehensive&lt;/em&gt; book to teach the whole topic, but then it is a huge field and hard to condense. But there is Elektors 300 circuit series, which may or may not be still available. Each book contains about 300 circuits to try out. I learned a lot from these books once I had the basics down. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;University of Madras has a lenghty set of lectures on Youtube for that topic. Have a look at &lt;a href=&quot;http://www.youtube.com/watch?v=w8Dq8blTmSA&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=w8Dq8blTmSA&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also a slew of experimental kits out there to teach you. Stuff like &lt;a href=&quot;http://www.makershed.com/productdetails.asp?productcode=mkgk19&quot; rel=&quot;nofollow&quot;&gt;http://www.makershed.com/productdetails.asp?productcode=mkgk19&lt;/a&gt; or so. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bachelor student I am currently responsible for, I introduced to electronics with an arduino experimentation kit. I know I can only teach him very basic stuff, but then he is studying computer sciences, and doesnt need (or have time for) a full blown study in applied electronics. &lt;/p&gt;&#xA;" OwnerUserId="3161" LastEditorUserId="3161" LastEditorDisplayName="" LastEditDate="2011-02-25T19:18:54.090" LastActivityDate="2011-02-25T19:18:54.090" />
  <row Id="10699" PostTypeId="2" ParentId="10696" CreationDate="2011-02-25T19:21:34.477" Score="5" ViewCount="" Body="&lt;p&gt;I recommend the &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0521370957&quot; rel=&quot;nofollow&quot;&gt;Art of Electronics&lt;/a&gt; by Horowitz and Hill.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-25T19:21:34.477" CommentCount="1" />
  <row Id="10700" PostTypeId="2" ParentId="10689" CreationDate="2011-02-25T19:25:05.750" Score="2" ViewCount="" Body="&lt;p&gt;Recommended System Requirements &quot;Intel® Core™2 Duo/Quad 2.66GHz (or faster) processor or equivalent&quot;  If your laptop isn't that fast, I would be concerned regardless of the issue you mention.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-02-25T19:30:25.667" LastActivityDate="2011-02-25T19:30:25.667" CommentCount="4" />
  <row Id="10701" PostTypeId="2" ParentId="10693" CreationDate="2011-02-25T19:33:29.967" Score="3" ViewCount="" Body="&lt;p&gt;Soldermask is a special layer on PCBs that is meant to keep the solder onto the pads. This is only useful if you want to machine solder. I am not aware of a way to do that at home, because you need to have a mask to keep it off the pads. It is usually applied in a screen printing or photoimageable process. If you make your own PCBs, they will not be fine enough to profit from this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to add a shiny protective layer after soldering, you may want to try conformal coating. Perhaps something like &lt;a href=&quot;http://www.electrolube.com/docs/conformalmain.asp?id=76&quot; rel=&quot;nofollow&quot;&gt;http://www.electrolube.com/docs/conformalmain.asp?id=76&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3161" LastEditorUserId="3161" LastEditorDisplayName="" LastEditDate="2011-02-25T19:40:03.090" LastActivityDate="2011-02-25T19:40:03.090" CommentCount="2" />
  <row Id="10702" PostTypeId="1" CreationDate="2011-02-25T19:36:48.757" Score="4" ViewCount="119" Body="&lt;p&gt;I am working on a small wireless sensor platform and trying to figure out power supply options.  My power budget is approximately: .2mA constant, ~15mA for .1s every 2-3s, and 60mA for 10s very intermittently (once or twice per hour).  This works out to about 50mAh for the lifetimes I'm looking for, and ideally it would be rechargeable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found some button cells by Panasonic that fit the bill (&lt;a href=&quot;http://panasonic.com/industrial/includes/pdf/Panasonic_Lithium_VL2330_VL3032.pdf&quot; rel=&quot;nofollow&quot; title=&quot;VL2330&quot;&gt;VL2330&lt;/a&gt; - PDF), but can't find much information on the Lithium Vanadium Pentoxide chemistry.  The data sheet suggests a &quot;continuous standard load&quot; of .1mA, which presumably is just the rate required for the nominal capacity.  Beyond that there's no more information as to maximum pulse currents, derating, or otherwise.  A 1C pulse would be nothing for a regular Lithium chemistry, but I haven't used these before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have experience with these, or know of another direction to look for this kind of application?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&#xA;John&lt;/p&gt;&#xA;" OwnerUserId="3163" LastActivityDate="2011-02-26T06:53:54.603" Title="Lithium Button Cell Characteristics" Tags="&lt;battery&gt;&lt;lithium&gt;&lt;coin-cell&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="10703" PostTypeId="2" ParentId="10702" CreationDate="2011-02-25T19:57:16.867" Score="1" ViewCount="" Body="&lt;p&gt;Lithium cells are reported to have a maximum current that can be drawn from the cell before damaging it.  TI did some tests and were not able to confirm this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=swra349&amp;amp;fileType=pdf&quot; rel=&quot;nofollow&quot;&gt;TI document (pdf)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tinyurl.com/coincell&quot; rel=&quot;nofollow&quot;&gt;Discussion on PIClist&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you may have problems drawing 60mA out of that 50 mAh battery.  While the datasheet doesn't give the resistance, based on my experience with other coin cells, I will guess about 50 ohms.  60 mA * 50 ohms is 3V.  In other words, at 60 mA current draw the output voltage is zero.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-25T19:57:16.867" />
  <row Id="10704" PostTypeId="2" ParentId="4155" CreationDate="2011-02-25T19:59:51.463" Score="1" ViewCount="" Body="&lt;p&gt;A &quot;Charlieplexed&quot; display (Wikipedia lists the concept as having been invented in 1996, but I'm sure the approach was used before that) represents a complete graph of all processor signals (every pair of processor signals has to have an LED on it).  A complete planar graph of N nodes may only be drawn for N less than 4.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the most natural way to visualize a Charlieplexed display would be as a square matrix with the LED's on the primary diagonal replaced with shorting jumpers.  When laying out a board, simply shove the LEDs on either side of the diagonal inward so as to yield an NxN-1 physical configuration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only disadvantages Charlieplexing would have over normal multiplexing would be the fact that Charlieplexing uses a nearly-square square grid, and that one has to in software shift the pixels on one side of the diagonal so as to account for the gap.  Electrically, I would think driving a Charlieplexed display from a tri-state CPU pin should be easy: wire an NPN transistor (e.g. 2N2222) with the collector at VDD, base connected to the CPU pin, and the emitter tied to the Charlieplex line to supply the positive (row-scanned) drive; wire a current-setting resistor between the CPU pin and the column wire.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-25T19:59:51.463" />
  <row Id="10705" PostTypeId="2" ParentId="10647" CreationDate="2011-02-25T20:08:33.690" Score="2" ViewCount="" Body="&lt;p&gt;Short answer: Putting power supplies in parallel is rarely a good idea. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because the power supplies will have slightly different output voltages, one will supply more, and one less. It is next to impossible to determine in advance how the current will be divided. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;About your circuit, clearly, it contradicts the product sheet of the charger. The charger has to be parallel to the battery and the load, not in series. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The charger IC is programmed to a certain charging current, max 2A. This is only indirectly related to the supply current of the solar panels. If they can supply 4A, only 2A will be charged to the battey, the rest should be drawn by the load. If the load doesnt draw &gt;2A at all times, problems may (will) arise. &lt;/p&gt;&#xA;" OwnerUserId="3161" LastActivityDate="2011-02-25T20:08:33.690" CommentCount="1" />
  <row Id="10706" PostTypeId="1" CreationDate="2011-02-25T20:41:23.830" Score="2" ViewCount="168" Body="&lt;p&gt;I understand that most people use a bridge circuit for RTD and possibly thermistor temperature sensing.  I'm trying not to do that for several reasons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to use an opamp in the classic constant current configuration, with the temperature sensing resistor as the load resistor.  I sense the voltage change with an INA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This seems to work so far, on the bench.  Has anyone else had experiance with this? Are there any gotcha's I should be aware of when I put it in the field?&lt;/p&gt;&#xA;" OwnerUserId="3164" LastActivityDate="2011-02-26T16:12:18.087" Title="Any issues with using an opamp as a constant current source for temperature sensing?" Tags="&lt;sensor&gt;&lt;analog&gt;&lt;temperature&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="10707" PostTypeId="2" ParentId="10650" CreationDate="2011-02-25T20:48:34.477" Score="2" ViewCount="" Body="&lt;p&gt;I think, depending on the specifics of the datasheets, that the transformer will give you a better BW, and galvanic isolation, if you like that. I think Analog Devices has some slick isolators based on transformers packaged into normal IC packages. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;INAs could work, but you might want to bias your signal up a bit to get it off the ground power rail (assuming you don't just reference it and use a dual supply), for better performance.  That might not be true so much anymore, but it sure used to be.&lt;/p&gt;&#xA;" OwnerUserId="3164" LastActivityDate="2011-02-25T20:48:34.477" />
  <row Id="10708" PostTypeId="1" CreationDate="2011-02-25T22:14:06.693" Score="1" ViewCount="215" Body="&lt;p&gt;I recently had my ICD3 programmer stop working. I received a replacement today and before returning the old ICD3 wanted to test the new ICD3 out. I connected the new ICD3 to my PC and Windows XP Professional SP3 32-bit prompted me to install the drivers for the device. I selected the drivers located in the MPLAB IDE (v8.63) directory. When the installer reached the NcGen.sys file the computer hung up and I had to force the system to power down using the power button. Has anyone else had and resolved this issue with the Microchip ICD3?&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-04-06T11:56:16.890" Title="Problem installing ICD3 windows driver" Tags="&lt;pic&gt;&lt;programmer&gt;&lt;icd3&gt;&lt;development-tools&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="10709" PostTypeId="2" ParentId="10689" CreationDate="2011-02-25T22:16:06.523" Score="1" ViewCount="" Body="&lt;p&gt;Dual cores will (almost) always help. This is because other processes running at the same time as your auto-route process. Windows is smart enough to assign different processes to different cores. So in the case that the auto-router can only use 1 core, ideally Windows could give the auto-router full use of a core and then give other things that need to be done (like normal overhead OS overhead) to other cores.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Writing a program to be able to use multiple cores is rather simple to do; however, it is usually split up by things like UI vs backend. It is much more difficult to split up computation heavy processes like auto-routing. The way they could do it is by having different routing methods be in different processes and then comparing when each one finishes. If I were to guess, I would be altium hasn't done this much splitting up of their program, but I don't know that for sure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So in summary, will it help to have more cores? Yes. Will it have a huge increase in performance? Maybe. Will more cores be better then less but faster? Even harder to say. My overall recommendation would be to ask Altium. Most companies do extensive performance testing and will know their software better then any of us.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-02-25T22:21:42.677" LastActivityDate="2011-02-25T22:21:42.677" />
  <row Id="10710" PostTypeId="2" ParentId="10693" CreationDate="2011-02-25T22:29:35.863" Score="3" ViewCount="" Body="&lt;p&gt;Surely you can do soldermask, if you already mastered making PCBs using photomasks.&#xA;Material for soldermasks is also UV-sensetive, so you expose &amp;amp; develop it and that's it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But unless you are using reflow soldering at home :-) , there is no much sence. &#xA;You can solder even small-mid size BGA's without soldermask - just flux &amp;amp; practice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or if you badly want soldermask for BGA in small quantity - you can just take capton material, and manually make all required holes and then glue it to PCB.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-02-26T23:19:26.927" LastActivityDate="2011-02-26T23:19:26.927" CommentCount="6" />
  <row Id="10711" PostTypeId="2" ParentId="10706" CreationDate="2011-02-25T22:32:31.103" Score="1" ViewCount="" Body="&lt;p&gt;As you usually need just few mA, the only concern is temperature stability of your opamp &amp;amp; &lt;strong&gt;passive components&lt;/strong&gt; around it. Bridge circuit &amp;amp; precision refV source of ADC usually handle that, but in your case it's much much harder.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-25T22:32:31.103" CommentCount="2" />
  <row Id="10712" PostTypeId="2" ParentId="10692" CreationDate="2011-02-25T22:40:06.723" Score="2" ViewCount="" Body="&lt;p&gt;I wrote quite a lot about AVR assembly with servos here: &lt;a href=&quot;http://www.lhexapod.com&quot; rel=&quot;nofollow&quot;&gt;http://www.lhexapod.com&lt;/a&gt; which was my blog for my 'hexapod robot from scratch' project which was doing well before my baby son arrived and borrowed all my spare time ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's fun to program in assembler. The AVR is an easy platform to get started on. &lt;/p&gt;&#xA;" OwnerUserId="255" LastActivityDate="2011-02-25T22:40:06.723" />
  <row Id="10713" PostTypeId="2" ParentId="9637" CreationDate="2011-02-25T23:29:15.307" Score="1" ViewCount="" Body="&lt;p&gt;I've asked this on rcgroups as well, and it seems there's no way other than experimenting.  If you had a similar bunch of motors and speed controllers that were manufactured identically, then it would be possible to experiment with one motor/esc set and apply the discovered rotation to the other motors and controllers.&lt;/p&gt;&#xA;" OwnerUserId="1756" LastActivityDate="2011-02-25T23:29:15.307" />
  <row Id="10714" PostTypeId="2" ParentId="10702" CreationDate="2011-02-26T00:06:59.377" Score="2" ViewCount="" Body="&lt;p&gt;Button cells perform horribly on large currents.  The 15 mA will be a problem, the 60 mA won't work.  Consider a supercap; they are great in this application.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-26T00:06:59.377" CommentCount="8" />
  <row Id="10715" PostTypeId="2" ParentId="10686" CreationDate="2011-02-26T00:07:41.783" Score="1" ViewCount="" Body="&lt;p&gt;The closest thing I know for what you're asking is UART/RS-232 with RTS/CTS handshaking (4 wires total).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;National Semiconductor's &lt;a href=&quot;http://www.national.com/opf/LM/LMX9838.html&quot; rel=&quot;nofollow&quot; title=&quot;LMX9838&quot;&gt;LMX9838&lt;/a&gt; (it's a Bluetooth module) uses that communication protocol as a slave device.&#xA;And you can implement it with 2 extra GPIOs in any microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ultimately you can implement any type of handshaking with any pair of Master-Slave devices, as long as you have control over a couple of extra GPIOs in both (i.e.: Using uC, FPGA, CPLD...).&lt;/p&gt;&#xA;" OwnerUserId="3078" LastActivityDate="2011-02-26T00:07:41.783" CommentCount="4" />
  <row Id="10716" PostTypeId="2" ParentId="10702" CreationDate="2011-02-26T00:08:27.070" Score="7" ViewCount="" Body="&lt;h3&gt;Quick Rules of Thumb&lt;/h3&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;10mA is your maximum current draw.&lt;/li&gt;&#xA;&lt;li&gt;Buy fresh batteries. Always verify this by running lifetime tests on your batteries when you buy from a new supplier, or a new batch.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;h3&gt;Our General Conclusions&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;When testing with coin cell batteries at my last job we found a number of things:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Surpassing 10mA per cell greatly reduced battery life.&lt;/li&gt;&#xA;&lt;li&gt;20-30mA was normally around your &quot;maximum&quot; current you could draw, but this is not dependable, the 10mA line being the highest current we could pull for deterministic function.&lt;/li&gt;&#xA;&lt;li&gt;1mA was as high as you could go without significantly degrading rated capacity(get nearly the published capacity).&lt;/li&gt;&#xA;&lt;li&gt;Staying below the .1 mA suggested line would normally meet the rating of the capacity.&lt;/li&gt;&#xA;&lt;li&gt;Someone selling you old batteries can do more to harm your tests than almost anything else. The batteries purchased directly from china gave the best results, the nice company in new york had battery cells that performed worse that batteries we had on site in storage for 4 years.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;h3&gt; Capacity Rating &lt;/h3&gt;&#xA;&#xA;&lt;p&gt;These results all seemed relatively consistent across different rated capacities, giving the same results with 50mAh batteries and 400mAh batteries. We chose to use 200mAh batteries on devices that needed to pull 20mA, they would significantly outperform 800mAh coin cells(the big ones you can buy) as passing 10mA hurt the battery life significantly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When we passed the 10mA line the lifetime of the battery had a very large variance, we attributed this to manufacturing differences, but the same batch could have vastly large differences.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;How I know this.&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;We did testing on batches of 20-50 coin cells to choose our rating and package. After this point we ran tests on more than 500 batteries under different conditions to verify results and predict lifetime. We ran tests where the current was pulsed, tests in different temperatures, and tests were we let devices run for months to try to test what our expectation would be. I am sorry I do not have references, as this testing was done at a company and was not published in any form, I have nothing I can reference for this.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-02-26T06:53:54.603" LastActivityDate="2011-02-26T06:53:54.603" CommentCount="2" />
  <row Id="10717" PostTypeId="1" AcceptedAnswerId="10719" CreationDate="2011-02-26T00:27:10.223" Score="4" ViewCount="102" Body="&lt;p&gt;I just bought a cheap function generator and have no test leads for it. I do have 2 pairs of oscilloscope probes with a 1X-10X switch on them. I am curious to know if I will get the same results with them?&lt;/p&gt;&#xA;" OwnerUserId="2143" LastActivityDate="2011-02-26T21:50:21.117" Title="Can you use Oscilloscope probes for a Function Generator?" Tags="&lt;oscilloscope&gt;&lt;function-generator&gt;" AnswerCount="2" />
  <row Id="10718" PostTypeId="2" ParentId="10689" CreationDate="2011-02-26T00:45:48.767" Score="2" ViewCount="" Body="&lt;p&gt;Altium is currently single-threaded, so a quad-core will not benefit you much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've heard Altium talk about multi-threading in the future, but at this point, I'd say go for a really fast dual-core over a slower quad-core.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-02-26T00:45:48.767" CommentCount="2" />
  <row Id="10719" PostTypeId="2" ParentId="10717" CreationDate="2011-02-26T00:48:03.070" Score="7" ViewCount="" Body="&lt;p&gt;As long as they're set to 1x, Sure!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will get some interesting attenuation when set to 10X, and perhaps some interesting signal distortion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use probes set to 1X on a signal generator pretty regularly.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-02-26T02:52:08.707" LastActivityDate="2011-02-26T02:52:08.707" />
  <row Id="10720" PostTypeId="1" CreationDate="2011-02-26T01:30:25.230" Score="1" ViewCount="120" Body="&lt;p&gt;Hello everyone,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know on some MCUs its possible to save data directly on program memory (flash memory). AVRGCC compiler uses &quot;PROGMEM&quot; keyworkd, MPLAB C18 uses a similar one with the same effect.&#xA;However, what's the advantage of having data on program memory?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe because those MCUs have a Harvard arquitecture and so read data from program memory is faster than read it from data memory? Is it &quot;really so much faster&quot; that it's worth to use it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1074" LastActivityDate="2011-02-26T02:51:29.757" Title="MCU: saving data directy on flash. What's the advantage?" Tags="&lt;microcontroller&gt;&lt;flash&gt;&lt;data&gt;" AnswerCount="3" />
  <row Id="10721" PostTypeId="2" ParentId="10720" CreationDate="2011-02-26T01:33:05.467" Score="3" ViewCount="" Body="&lt;p&gt;These microcontrollers have very limited RAM.  So if you want a look-up table, it makes sense to store the large, constant data in program flash instead of the precious RAM.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-02-26T01:33:05.467" CommentCount="1" />
  <row Id="10723" PostTypeId="2" ParentId="10720" CreationDate="2011-02-26T02:51:01.360" Score="1" ViewCount="" Body="&lt;p&gt;If an MCU doesn't have a separate EEPROM area to save data in, then yes, you can save persistent data to an area of the flash memory not used by program code.  This is only good for data that is updated infrequently (such as configuration data or user preferences), since there is a limit to the number of times you can rewrite the flash (typically a minimum of 10,000 erase/write cycles).  The advantage to saving data in this way is that it won't be lost when the MCU loses power.  Without some sort of non-volatile storage, you would need to have a battery-backed up RAM to save data during power shutdown.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second reason for allowing a program to write to the flash, is that it allows programs to be updated remotely in the field.  To do this, you need a portion of the program to be resident all of the time (the part that will write the new code to the updateable portion of the flash memory), and a means to download the updated code (e.g. Bluetooth, cellular, etc.).  You want to make sure the always-resident portion of the code is as bug-free as possible, since it is harder to update that.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-02-26T02:51:01.360" CommentCount="1" />
  <row Id="10724" PostTypeId="2" ParentId="10720" CreationDate="2011-02-26T02:51:29.757" Score="2" ViewCount="" Body="&lt;p&gt;You have two options for constant data on these flash microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Load from flash when needed (PROGMEM)&lt;/li&gt;&#xA;&lt;li&gt;Load from flash into ram on program startup (not PROGMEM). The C compiler does this for you automatically if you forget to use PROGMEM because data is normally read/write in C.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;It is much slower to load data from the program memory compared to loading from ram, but when you only have 128 bytes of ram, and the data has to be stored in the flash anyway,  it pays off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;AVRs also tend to have, say, 128 bytes of EEPROM, and whatever flash memory you didn't need for your program. The microcontroller can then program its own flash memory to save measurements and settings. The flash memory is more plentiful than the EEPROM but, unlike EEPROM which usually appears to be rewritable 1 byte at a time, the Flash must be erased and rewritten in blocks.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastActivityDate="2011-02-26T02:51:29.757" />
  <row Id="10726" PostTypeId="1" AcceptedAnswerId="10728" CreationDate="2011-02-26T05:48:00.063" Score="1" ViewCount="66" Body="&lt;p&gt;What is the point of the NXC &lt;a href=&quot;http://bricxcc.sourceforge.net/nbc/nxcdoc/nxcapi/group__cmath_a_p_i_ga370ecedca3418d42ec3f2a5e38f08411.html#ga370ecedca3418d42ec3f2a5e38f08411&quot; rel=&quot;nofollow&quot;&gt;bcd2dec&lt;/a&gt; API function?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the difference between the &lt;a href=&quot;http://bricxcc.sourceforge.net/nbc/nxcdoc/nxcapi/ex__bcd2dec_8nxc-example.html#a0&quot; rel=&quot;nofollow&quot;&gt;example&lt;/a&gt; code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// convert binary-coded decimal byte to decimal.&#xA;byte dec = bcd2dec(0x3a);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;byte dec = 0x3a;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1940" LastActivityDate="2011-02-26T13:00:06.347" Title="Use of NXC bcd2dec" Tags="&lt;lego-mindstorms&gt;&lt;nxc&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10727" PostTypeId="2" ParentId="10696" CreationDate="2011-02-26T09:49:29.933" Score="5" ViewCount="" Body="&lt;p&gt;The site &lt;a href=&quot;http://www.allaboutcircuits.com/&quot; rel=&quot;nofollow&quot;&gt;All About Circuits&lt;/a&gt; has free textbooks about these.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-02-26T09:49:29.933" />
  <row Id="10728" PostTypeId="2" ParentId="10726" CreationDate="2011-02-26T09:52:56.513" Score="3" ViewCount="" Body="&lt;p&gt;I think the problem is that the example itself is wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A BCD number is a two digit &lt;em&gt;decimal&lt;/em&gt; number stored in a byte with the tens being in the upper 4 bits, and the units being in the lower 4 bits, for example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;dec            binary   hex    bcd&#xA; 01 stored as 00000001 (0x01 =   1)&#xA; 09 stored as 00001001 (0x09 =   9)&#xA; 10 stored as 00010000 (0x10 =  16)&#xA; 18 stored as 00011000 (0x18 =  24)&#xA; 3A &amp;lt;- not a decimal number!!&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;0x3A is &lt;strong&gt;not&lt;/strong&gt; a BCD number, because the units part is 0xA or 10, and although you can store 10 in the lower 4 bits of a byte, it's not BCD because 10 is not a single digit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So how can you convert BCD 0x3A to decimal? You can't, so I think the example you've linked to is a bad example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you plug in a more sensible value, then the two code examples are different:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;byte dec = bcd2dec(0x58);&#xA;// dec = 58&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;But if the code was:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;byte dec = 0x58;&#xA;// dec = 88&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;bcd2dec does this:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Takes a BCD number (in our example 0x58 or 88).&lt;/li&gt;&#xA;&lt;li&gt;Converts it to binary (01011000).&lt;/li&gt;&#xA;&lt;li&gt;Reads the 4 most significant bits (0101 = 5) and multiplies by 10 (to get 50).&lt;/li&gt;&#xA;&lt;li&gt;Reads the 4 least significant bits (1000 = 8).&lt;/li&gt;&#xA;&lt;li&gt;Adds the two values together (to get 58) and returns the result.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The second code example is just converting a hex number (0x58) to decimal (88).&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-02-26T13:00:06.347" LastActivityDate="2011-02-26T13:00:06.347" />
  <row Id="10729" PostTypeId="2" ParentId="10726" CreationDate="2011-02-26T10:04:36.763" Score="1" ViewCount="" Body="&lt;p&gt;BCD is a way of storing numbers that are easier for humans to read...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Binary Coded Decimal - uses 4 bits to store 0 to 9. (Hexadecimal or Hex uses 0 to F)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;         Dec Hex BCD&#xA;0 0 0 0   0   0   0&#xA;0 0 0 1   1   1   1&#xA;0 0 1 0   2   2   2&#xA;0 0 1 1   3   3   3&#xA;0 1 0 0   4   4   4  &#xA;0 1 0 1   5   5   5&#xA;0 1 1 0   6   6   6&#xA;0 1 1 1   7   7   7&#xA;1 0 0 0   8   8   8&#xA;1 0 0 1   9   9   9&#xA;1 0 1 0  10   A   Not Valid&#xA;1 0 1 1  11   B   Not Valid&#xA;1 1 0 0  12   C   Not Valid&#xA;1 1 0 1  13   D   Not Valid&#xA;1 1 1 0  14   E   Not Valid&#xA;1 1 1 1  15   F   Not Valid&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;0x3A from Hex to BCD should give...&#xA;    30 (A is not valid and taken as Zero)&#xA;    40 (A is taken as ten and added to the 30)&#xA;    Error (The routine generates an error because A is not valid)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;0x3A from Hex to decimal gives...&#xA;    58.&lt;/p&gt;&#xA;" OwnerUserId="2280" LastActivityDate="2011-02-26T10:04:36.763" />
  <row Id="10730" PostTypeId="2" ParentId="10513" CreationDate="2011-02-26T11:45:09.517" Score="1" ViewCount="" Body="&lt;p&gt;Just came across &lt;a href=&quot;http://www.davehylands.com/Wood-Working/Electronics-Workbench/&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;, and thought it was pretty awesome.&lt;/p&gt;&#xA;" OwnerUserId="2096" LastActivityDate="2011-02-26T11:45:09.517" CommunityOwnedDate="2011-05-04T06:12:46.163" CommentCount="1" />
  <row Id="10731" PostTypeId="1" AcceptedAnswerId="10737" CreationDate="2011-02-26T12:00:05.640" Score="2" ViewCount="230" Body="&lt;p&gt;I have this DC socket:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/8Xp0E.png&quot; width=&quot;380&quot; height=&quot;300&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which I intend to wire up to a circuit to provide power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a DC power supply which has a positive tip polarity. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm good to go and wire up the socket but I am a little stuck as there are 3 pins on my socket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the look of the socket it's fairly obvious which pin is for the center pin (which I will wire pos) so I assume the other two are for the outside (which I will wire neg).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this assumption correct? And if so why two pins instead of one?&lt;/p&gt;&#xA;" OwnerUserId="2739" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-02-26T18:40:45.920" LastActivityDate="2011-02-27T00:04:04.443" Title="Wiring a DC socket - why three pins?" Tags="&lt;dc&gt;" AnswerCount="3" />
  <row Id="10732" PostTypeId="2" ParentId="10731" CreationDate="2011-02-26T12:10:37.387" Score="4" ViewCount="" Body="&lt;p&gt;It's difficult to tell from this image, and the Maplins website is very poor when it comes to datasheets and specs, so my answer is just a guess...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The two outside pins may act as a switch so that you can build a circuit that is powered by a battery until an external power supply is connected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can test this with a continuity meter, when unplugged these pins should be open circuit, but when something is plugged into it, these pins should be connected together.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-02-26T12:35:29.050" LastActivityDate="2011-02-26T12:35:29.050" />
  <row Id="10733" PostTypeId="5" CreationDate="2011-02-26T12:59:09.857" Score="0" ViewCount="" Body="&lt;p&gt;DC stands for Direct Current which means the flow of electric charge in a single direction, as opposed to Alternating Current which means the flow of electric charge continually switches direction at a particular frequency. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC is generally used in low voltage applications for powering control circuits used in many gadgets and electronic systems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Examples of a DC source are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;batteries&lt;/li&gt;&#xA;&lt;li&gt;solar panels&lt;/li&gt;&#xA;&lt;li&gt;dynamos&lt;/li&gt;&#xA;&lt;li&gt;thermocouples&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-02-26T13:07:09.080" LastActivityDate="2011-02-26T13:07:09.080" />
  <row Id="10734" PostTypeId="4" CreationDate="2011-02-26T12:59:09.857" Score="0" ViewCount="" Body="DC stands for Direct Current, which means the flow of electric charge in a single direction. Examples of a DC source are batteries, solar panels, dynamos." OwnerUserId="-1" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-02-26T13:07:14.837" LastActivityDate="2011-02-26T13:07:14.837" />
  <row Id="10735" PostTypeId="2" ParentId="3578" CreationDate="2011-02-26T13:23:29.577" Score="2" ViewCount="" Body="&lt;p&gt;My favorite is this:&#xA;&lt;img src=&quot;http://i.imgur.com/5vXJU.jpg&quot; alt=&quot;Cubic Configurable Storage Toolboxes&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can view more pictures and videos here: &lt;a href=&quot;http://www.dealextreme.com/p/cubic-configurable-storage-toolboxes-10-pack-4580&quot; rel=&quot;nofollow&quot;&gt;http://www.dealextreme.com/p/cubic-configurable-storage-toolboxes-10-pack-4580&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And there are more options like these:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.dealextreme.com/p/configurable-storage-toolboxes-3-pack-4727&quot; rel=&quot;nofollow&quot;&gt;Configurable Storage Toolboxes&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.dealextreme.com/p/5-section-diy-parts-storage-box-5903&quot; rel=&quot;nofollow&quot;&gt;5-Section DIY Parts Storage Box&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.dealextreme.com/p/14-section-diy-parts-configurable-storage-toolboxes-color-assorted-44542&quot; rel=&quot;nofollow&quot;&gt;14-Section DIY Parts Configurable Storage Toolboxes (Color Assorted)&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-02-26T13:23:29.577" />
  <row Id="10737" PostTypeId="2" ParentId="10731" CreationDate="2011-02-26T13:37:51.720" Score="8" ViewCount="" Body="&lt;p&gt;This might be something similar to the female single channel audio connector where two of the 3 pins will be shorted when unplugged and when its plugged one of those 2 ping will be floating which usually goes to a battery and the remaining 2 pins will be connected to your plug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This diagram might help you understand better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tcQ8n.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here pin 3 will got to  the battery, pin 2 &amp;amp; 1 to the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you plug in the socket pin 1 &amp;amp; 2 would provide the power to the circuit and battery will be disconnected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;when unplugged the battery would be connected back to the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though there are other configuration also in which it can be used but this is a simple example which might help you understand the way these socket works.&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2011-02-26T13:37:51.720" CommentCount="2" />
  <row Id="10738" PostTypeId="2" ParentId="10696" CreationDate="2011-02-26T16:06:10.857" Score="3" ViewCount="" Body="&lt;p&gt;this may help some:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.opencircuits.com/Components&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/Components&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.opencircuits.com/Basic_Circuits_and_Circuit_Building_Blocks&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/Basic_Circuits_and_Circuit_Building_Blocks&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-02-26T16:06:10.857" />
  <row Id="10739" PostTypeId="2" ParentId="10706" CreationDate="2011-02-26T16:12:18.087" Score="0" ViewCount="" Body="&lt;p&gt;a diode can be used a a temp sensor, may get a bigger signal, most resistors, not for temp sensing are designed to not to change resistance with temp.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-02-26T16:12:18.087" />
  <row Id="10740" PostTypeId="1" AcceptedAnswerId="10750" CreationDate="2011-02-26T19:03:54.020" Score="1" ViewCount="98" Body="&lt;p&gt;I want a curcuit with 3.3V and 24V supply. The micro will use the 3.3V supply, which needs to be able to set multiple industrial 24V digital outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My plan was a simple op amp, but as far as I know no op amp will actually achieve an output of 100% of Vcc, no matter the gain. Is there a cheap and simple way to do this? Relays seems expensive and big.&lt;/p&gt;&#xA;" OwnerUserId="941" LastActivityDate="2011-02-26T23:25:57.710" Title="How to set a digital out to 24V Vcc" Tags="&lt;switch&gt;&lt;digital&gt;&lt;24v&gt;" AnswerCount="4" />
  <row Id="10741" PostTypeId="2" ParentId="10740" CreationDate="2011-02-26T19:10:55.263" Score="0" ViewCount="" Body="&lt;p&gt;Use suitable BJTs or MOSFETs. Types will depend on the current to be controlled.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-26T19:10:55.263" />
  <row Id="10742" PostTypeId="2" ParentId="10740" CreationDate="2011-02-26T20:00:12.613" Score="2" ViewCount="" Body="&lt;p&gt;Just to piggy-back on Leon's answer...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use the 3.3V signal to turn on and off a transistor.  The bottom of the transistor is tied to GND.  The top has a pull-up resistor to +24V and a tap go to the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the signal is off, the transistor is off, and the output is pull-up to +24V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the signal is on, the transistor turns on, and the output is shorted to GND.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-02-26T20:00:12.613" />
  <row Id="10743" PostTypeId="2" ParentId="10740" CreationDate="2011-02-26T20:15:46.290" Score="2" ViewCount="" Body="&lt;p&gt;In environments like this you usually want to make sure you have some protection against back flow. One of the easiest ways to deal with this is with an opto-coupler or Opto-isolator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy ICs that are an all in 1 package, but from a functional level it is an LED (something like IR LED) that is turned on by your microcontroller, it then shines on a receiver that acts like a switch based off of the LED shining on it or not. You can then use this in your circuit to turn on or off your 24V output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The big advantage here is that if you have a back flow of current on the 24V side, there is no way for the lower voltage LED side to be affected.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-26T20:15:46.290" CommentCount="1" />
  <row Id="10744" PostTypeId="2" ParentId="3578" CreationDate="2011-02-26T21:06:26.000" Score="3" ViewCount="" Body="&lt;p&gt;I use a Raaco assorter&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i279.photobucket.com/albums/kk134/redgrittybrick/DSC_5448.jpg&quot; alt=&quot;Raaco Assorter&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2191" LastActivityDate="2011-02-26T21:06:26.000" CommentCount="2" />
  <row Id="10745" PostTypeId="1" CreationDate="2011-02-26T21:32:30.223" Score="3" ViewCount="93" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Due to deficit of UART's on my board (LPC3141 based) I have the idea to add external multi-channel UART.&#xA;It has data and address lines, which I'm pretty sure needs to be connected to EBI. Unfortunately surfing the web for several hours didn't made me happy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any links, hints or other info will be highly appreciated :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Parts to be used:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://ics.nxp.com/products/lpc3000/lpc313x.lpc314x.lpc315x/~LPC3141/&quot; rel=&quot;nofollow&quot;&gt;LPC3141&lt;/a&gt; ARM CPU&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.nxp.com/pip/SC16C554_554D.html&quot; rel=&quot;nofollow&quot;&gt;SC16C554&lt;/a&gt; Quad UART&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1603" LastEditorUserId="1603" LastEditorDisplayName="" LastEditDate="2011-02-27T21:49:25.337" LastActivityDate="2011-02-27T22:06:33.930" Title="Interfacing 16C554 UART to ARM based CPU" Tags="&lt;serial&gt;&lt;uart&gt;&lt;rs232&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10746" PostTypeId="2" ParentId="10717" CreationDate="2011-02-26T21:50:21.117" Score="2" ViewCount="" Body="&lt;p&gt;You can use it in 1x mode, but I wouldn't recommend depending on that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oscilloscope probes are expensive, and function generator leads are cheap.  Get a set of leads, a BNC-binding post/banana plug adaptor, or just build some leads out of a BNC jack and some wire, and you'll be fine for the lower speeds that a cheap function generator can reach. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Besides, you're likely to want both oscilloscope probes and your function generator to be operational at the same time someday.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-26T21:50:21.117" />
  <row Id="10747" PostTypeId="2" ParentId="4027" CreationDate="2011-02-26T21:56:27.263" Score="3" ViewCount="" Body="&lt;p&gt;The most significant disadvantage of &quot;Charlieplexing&quot; lights is that it limits the number of LEDs that can be driven with 'n'-way multiplexing to n(n-1).  I don't see the tri-state driver requirement as being much of an issue with the technique as a whole.  Certainly having to use two conventional drivers instead of a tri-state driver will reduce the benefit from CharliePlexing, but in some cases advantages may still remain (e.g. it may reduce the number of interconnect wires between a panel with the drivers and a panel with the lights or switches).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for Charlieplexing switches, the Wikipedia article fails to mention the biggest disadvantage: Charlieplexing does not allow a controller to passively wait for a button push.  On the other hand, it's overly pessimistic about component requirements.  In 1997, I produced a device which scans eight buttons using three I/O pins and one input-only pin on a PIC12C508, without need for any external diodes or other components except IIRC a pull-up for a PIC pin which didn't have one built in; the approach could have handled ten buttons with the addition of another pull-up resistor (for another I/O pin that didn't have one), but the customer only need eight buttons so there was no need.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-26T21:56:27.263" />
  <row Id="10748" PostTypeId="1" CreationDate="2011-02-26T22:15:51.107" Score="5" ViewCount="208" Body="&lt;p&gt;I've used such a technique in a couple of the products I've designed, but I've never seen anyone else do so.  It's possible to drive a 3-way multiplexed LCD using a bunch of 74HC595's to generate an 8-way pattern that gives each &quot;on&quot; segment an RMS excitation of 0.866VDD, and each &quot;off&quot; segment an RMS excitation of 0.5VDD, an RMS excitation ratio of 1.73:1.  By comparison, driving a conventional display with 1/2 bias (requiring that idle rows be driven to half-rail, but active rows and all columns be driven to the rails) yields an RMS &quot;on&quot; voltage of .707VDD and an &quot;off&quot; voltage of 0.408VDD--the same 1.73:1 drive ratio.  Using a 1/3 bias would result in a somewhat better drive ratio, but require all row and column drivers to support four output voltage levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;How have you used purely logic-level signals to drive a multiplexed LCD?&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-06T16:55:09.873" LastActivityDate="2011-03-07T21:13:54.590" Title="Methods to drive a multiplexed LCD with logic-level signals?" Tags="&lt;lcd&gt;&lt;multiplexing&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="10749" PostTypeId="1" AcceptedAnswerId="11367" CreationDate="2011-02-26T22:45:27.327" Score="4" ViewCount="132" Body="&lt;p&gt;I'm trying to learn about interrupts using one of the &lt;a href=&quot;http://www.pjrc.com/teensy/&quot; rel=&quot;nofollow&quot;&gt;Teensy USB&lt;/a&gt; boards. It's got an AVR AT90USB1286 chip on it. I'm using the code below, and I'm expecting my ISR block to get called and periodically flash the LED on pin 6. But nothing is happening. Can anyone see what I'm doing wrong?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;avr/io.h&amp;gt;&#xA;#include &amp;lt;avr/pgmspace.h&amp;gt;&#xA;#include &amp;lt;util/delay.h&amp;gt;&#xA;#include &amp;lt;avr/interrupt.h&amp;gt;&#xA;&#xA;#define PIN_ON(n) (PORTD |= (1&amp;lt;&amp;lt;(n)))&#xA;#define PIN_OFF(n) (PORTD &amp;amp;= ~(1&amp;lt;&amp;lt;(n)))&#xA;&#xA;#define LED_CONFIG  (DDRD |= (1&amp;lt;&amp;lt;6))&#xA;#define CPU_PRESCALE(n) (CLKPR = 0x80, CLKPR = (n))&#xA;&#xA;#define OVERFLOW_INTERRUPT_ENABLE (TIMSK0 |= (1&amp;lt;&amp;lt;TOIE0))&#xA;&#xA;&#xA;volatile unsigned int overflow_count = 0; //Count of overflows&#xA;&#xA;ISR(TIMER0_OVF_vect) {&#xA;  cli(); //Disable Global Interupt&#xA;  if (overflow_count &amp;lt; 0xFFFF) {&#xA;    overflow_count++;&#xA;  }&#xA;  else {&#xA;    PIN_ON(6);&#xA;    _delay_ms(500);&#xA;    PIN_OFF(6);&#xA;    overflow_count = 0;&#xA;  }&#xA;  sei(); //enable global interupt&#xA;&#xA;}&#xA;int main(void)&#xA;{&#xA;&#xA;    // set for 16 MHz clock, and make sure the LED is off&#xA;    CPU_PRESCALE(0);&#xA;    LED_CONFIG;&#xA;    OVERFLOW_INTERRUPT_ENABLE;&#xA;    sei(); //enable global interupts&#xA;&#xA;&#xA;    while (1) {&#xA;      _delay_ms(1000);&#xA;      //analogWrite(6, 10);&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3169" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-12T10:37:35.373" LastActivityDate="2011-03-12T16:28:46.600" Title="Teensy USB Interrupts" Tags="&lt;avr&gt;&lt;c&gt;&lt;interrupt&gt;&lt;teensy&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10750" PostTypeId="2" ParentId="10740" CreationDate="2011-02-26T23:25:57.710" Score="5" ViewCount="" Body="&lt;p&gt;Use a NPN/NFET transistor as an open collector/open drain output. Use a resistor pull-up if your load doesn't have one. Alternatively, opto-isolators will give you the same functionality with the freedom to separate your power and ground domains. I would not recommend using an op-amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, to clear up some misconceptions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;CMOS op-amps will get you pretty close to the power supply rails. For example, the OPA211 from TI will get you within 0.2V of your power supply rails when sinking or sourcing load of 1-3mA, which isn't too bad.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Unless your  load is insanely picky about logic levels, (which makes no sense at all on industrial equipment), you don't actually need exactly 24V and 0V. Most equipment I've seen can tolerate +/- 10%, and logic levels are fairly forgiving. Check your load's datasheet, and you will find input logic high and logic low thresholds. Sparkfun has an excellent writeup on &lt;a href=&quot;http://www.sparkfun.com/tutorials/225&quot; rel=&quot;nofollow&quot;&gt;logic levels&lt;/a&gt;.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-02-26T23:25:57.710" CommentCount="1" />
  <row Id="10751" PostTypeId="2" ParentId="10731" CreationDate="2011-02-27T00:04:04.443" Score="0" ViewCount="" Body="&lt;p&gt;The other possibility is that a 3 pin design is simply to provide a more robust and secure &lt;strong&gt;mechanical&lt;/strong&gt; mounting. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connectors are subjected to mechanical stress when connected and disconnected, so a better connector will have &quot;over-sized&quot; pins that provide a good mechanical connection to the circuit board (or enclosure), beyond the physical connection necessary for the power supply's voltage and current flow. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;While I believe the normally-closed switch (to outer-connector &lt;em&gt;ground&lt;/em&gt;) is the most common make of these DC power connectors (aka barrel or coaxial connectors), personally speaking, I have always just ignored the switch and soldered both switch pins to ground in my own projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe the switching is for the outer connector of the barrel portion of the jack (rather than the center pin), this can be used to drain larger capacitors such as large electrolytic capacitors being used to filter the DC supply from an unregulated power supply, so that after the circuit is disconnected, to reduce the shock (or jolt) risk if you open up the case, the capacitors drain to ground via a bleeder resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In digital circuits, an active low &lt;code&gt;SHUTDOWN*&lt;/code&gt; signal can be used to force a microcontroller off to prevent unstable operation after the power has been disconnected, even if there is a brief residual power such as from large-ish filter capacitors or inductors in a switching mode power supply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Similar connector with better view of the 3 pins in a different layout (and closed frame which fully encases the power jack, something I prefer).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/F1JDK.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(&lt;a href=&quot;http://media.digikey.com/photos/CUI%20Photos/PJ-202AH.jpg&quot; rel=&quot;nofollow&quot;&gt;larger image&lt;/a&gt;) More information is available from Ada Fruit Industries' &lt;a href=&quot;http://www.ladyada.net/wiki/partfinder/powerconn#dc_jacks&quot; rel=&quot;nofollow&quot;&gt;PartFinder&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: Usage of these DC power connectors (or other appropriate types in special uses) is encouraged because the design helps prevent the power supply jack being accidentally shorted out, which could permanently damn many of the cheaper wall-wart style power supplies. &lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-02-27T00:04:04.443" />
  <row Id="10752" PostTypeId="1" AcceptedAnswerId="10753" CreationDate="2011-02-27T00:45:22.617" Score="5" ViewCount="202" Body="&lt;p&gt;Okay, here's the situation: Currently, I am making a small batch of 100 boards of my project. This is a small order, so start up costs are about 10% of the final cost, and the factory charges $50/hour (they say I can get it done in one or two hours.) These will be made in China. Places in the UK or USA won't even talk to me for an order of 100, or if they do, they provide me with outrageous prices (5-10x as much as China.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I know China is cheaper, but to many people, seeing &quot;Made in China&quot; cheapens a product. If I were to make, say 1000 or 2000 boards, would the cost to make them in the USA or UK, or even any European country be competitive with China, even if it was slightly more expensive? I know the Arduino is &quot;Made in Italy&quot;, and the low price point of it makes me consider the possibility that I too could get mine made in a country with higher wages. What are other people's experience with this issue?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-31T19:31:12.917" Title="How much of an extra cost premium is paid for assembly in the USA or UK?" Tags="&lt;assembly&gt;&lt;outsourcing&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="2" />
  <row Id="10753" PostTypeId="2" ParentId="10752" CreationDate="2011-02-27T01:29:06.880" Score="3" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Most of these local companies in fact will outsource your order to China.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You don't need to print 'Made in China' if you just ordered PCB from China. &#xA;'Made in' means place of last significant tech operation, so if Arduino's PCB is from China, but soldering is local - 'Made in Italy' is legitimate.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Premium cost is significant for real local production, maybe not 10x, but more than 2x.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If you can get it done on 2-sided PCB - just make it yourself using popular hobbiest tech. You can hire 1 guy, train him and he'll do you 2000 boards easily :-) This is popular here in Russia - guys who mastered self-made PCB sell products on self-made PCBs and save time &amp;amp; money of PCB production. 100 boards is very easy to do at home.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="1197" LastEditorDisplayName="" LastEditDate="2011-02-27T08:16:16.320" LastActivityDate="2011-02-27T08:16:16.320" CommentCount="11" />
  <row Id="10754" PostTypeId="1" AcceptedAnswerId="10757" CreationDate="2011-02-27T03:20:09.790" Score="1" ViewCount="141" Body="&lt;p&gt;I'm thinking about connecting a micro SD card to my ATmega162 perfboard, but for that I need 3.3 V source which can provide up to 100 mA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most obvious option would be to run the whole board at 3.3 V because all components seem to be working at 3.3 V, but I'd like to keep the 5 V input voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next option and the most obvious one would be to use voltage divider. The downsides of that would be need for high precision resistors, bad stability, space taken and power consumption.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option would be to use a 3.3 V regulator. After checking which regulators I can easily obtain, choice comes down to LF33CV or LP2950CZ-3.0.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LF33CV fits from the electrical side with its dropout voltage of 0.45 V and very low power consumption. It can also provide up to 500 mA, which should be enough for most micro SD cards. I'd need two capacitors, one 0.1 µF on input and one 10 µF at output. On the other hand, the regulator is TO-220 and I'd like to save as much space as possible on the board. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LP2950CZ-3.0 is under just acceptable category from the electrical point of view. It has dropout voltage of 0.38 V and is guaranteed to provide up to 100 mA, which is exactly the amount I expect to need. On the other hand it's much smaller and comes in TO-92 package. It also only needs one 3.3 µF capacitor at its output in order to work properly.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-27T22:47:25.447" Title="Need ideas for 5-&gt;3.3 voltage conversion for micro SD cards" Tags="&lt;voltage-regulator&gt;" AnswerCount="3" />
  <row Id="10755" PostTypeId="2" ParentId="10754" CreationDate="2011-02-27T04:08:21.533" Score="2" ViewCount="" Body="&lt;p&gt;A voltage divider is NOT a solution in this application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Really, a voltage divider is not a solution anywhere you have any variance in the current drawn, or really in any power section of anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, think about the resistor sizes you would need to make a divider without significant droop when 100ma is drawn from it.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Now, a &lt;em&gt;series resistor&lt;/em&gt; will work in cases where the drawn current is extremely fixed, but think about what would happen if you were to change the current load - the voltage would increase when the current decreases, and vice-versa.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You really &lt;strong&gt;HAVE&lt;/strong&gt; to use a voltage regulator here.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-02-27T04:08:21.533" CommentCount="4" />
  <row Id="10756" PostTypeId="1" CreationDate="2011-02-27T04:09:46.477" Score="0" ViewCount="94" Body="&lt;p&gt;Is there a single ic that have both multiplexere and demultiplexere.&lt;/p&gt;&#xA;" OwnerUserId="3172" LastActivityDate="2011-02-27T04:52:41.253" Title="multiplexer and demultiplexer ic" Tags="&lt;multiplexing&gt;&lt;ic&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="10757" PostTypeId="2" ParentId="10754" CreationDate="2011-02-27T04:47:29.183" Score="3" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Why use 5V if you don't need to?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;100 mA * (5-3.3) is 170 mW.  No big deal for TO-92.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;A cheapskate hobbyist approach is three silicon diodes in series.  This will get you in the neighborhood of 3V.  Might need to add a load resistor to set the max voltage with no card.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Have you thought about how you will level-shift the signal lines?  SPI lines are all unidirectional, which should simplify things.  3.3V is a logic &quot;high&quot; for a 5V input.  The outputs should be level-shifted somehow.  A two-resistor divider would work ok.   Use a 1.5k and 3.0 k resistor to get pretty close to 1000 ohms output impedance.  You'll need this on clock, MOSI, chip select at least.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Related: &lt;a href=&quot;http://electronics.stackexchange.com/q/9153/411&quot;&gt;Arduino (5v) and MPR121 (3.3v) how to talk&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-27T06:13:25.257" LastActivityDate="2011-02-27T06:13:25.257" />
  <row Id="10758" PostTypeId="1" AcceptedAnswerId="10767" CreationDate="2011-02-27T04:49:17.873" Score="1" ViewCount="116" Body="&lt;p&gt;Hi, I know guys hanging around here are quite experienced in electronics and robotics. But I am rather new to this area. I have only A/L physics knowledge in electronics. But I am working as a software engineer. Can anybody tell me the best resources that I can follow to become throughly acquainted with the subject. Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="3173" LastActivityDate="2011-02-28T12:32:58.810" Title="Best Electronics and Robotics Resources for a Novice" Tags="&lt;sensor&gt;&lt;electronics&gt;&lt;robotics&gt;&lt;software&gt;" AnswerCount="5" />
  <row Id="10759" PostTypeId="2" ParentId="10756" CreationDate="2011-02-27T04:52:41.253" Score="3" ViewCount="" Body="&lt;p&gt;An analog mux will do this.  It is bidirectional, so the same circuit will work as mux or demux depending on which end is driven.  The classic chip is the &lt;a href=&quot;http://www.datasheetcatalog.org/datasheets/208/109138_DS.pdf&quot; rel=&quot;nofollow&quot;&gt;CD4051&lt;/a&gt; but more modern parts will have better specs.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-02-27T04:52:41.253" CommentCount="2" />
  <row Id="10760" PostTypeId="2" ParentId="5773" CreationDate="2011-02-27T05:33:43.340" Score="0" ViewCount="" Body="&lt;p&gt;After a very long hiatus from electronics and programming, I've gotten back into it because of a project one of my sons is doing at university.  I learned electronics when tubes were the norm and programming with toggle switches (set address, set data, load, store, in binary) and punch cards.  Over the years, I've learned and used each electronic and programming language advancement which took a lot of concentrated effort and time. Consequently, I am so grateful for the advancements in microcontrollers and how incredibly cheap they are, including the development boards such as the Arduino, Netduino, etc.  The arguments about Arduino vs Netduino, etc., remind me of the Microsoft vs Apple battles such as command line vs GUI.  It doesn't matter which platform, programmiing language, etc., is used as long as it is appropriate to the result.    &lt;/p&gt;&#xA;" OwnerUserId="3175" LastActivityDate="2011-02-27T05:33:43.340" CommunityOwnedDate="2011-02-27T07:33:15.000" />
  <row Id="10761" PostTypeId="1" AcceptedAnswerId="10762" CreationDate="2011-02-27T05:51:28.147" Score="4" ViewCount="179" Body="&lt;p&gt;Should an LM317 (specifically a &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/lm317mq.pdf&quot; rel=&quot;nofollow&quot;&gt;TI LM317MQDCYR&lt;/a&gt;) rated for 500ma output current really be getting hot to touch when only pulling 170ma at 5V?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Package is SOT-223, input is 9V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this normal?&lt;/p&gt;&#xA;" OwnerUserId="2654" LastActivityDate="2011-02-27T10:33:41.303" Title="LM317 getting hot" Tags="&lt;voltage-regulator&gt;&lt;temperature&gt;&lt;lm317&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10762" PostTypeId="2" ParentId="10761" CreationDate="2011-02-27T06:05:19.570" Score="15" ViewCount="" Body="&lt;p&gt;Dissipation is (9-5)V*170mA, or 680 mW.  &lt;a href=&quot;http://www.diodes.com/zetex/_pdfs/3.0/pdf/SOT223.pdf&quot; rel=&quot;nofollow&quot;&gt;SOT223 thermal resistance&lt;/a&gt; is 62.5°C/W maximum.  So the junction temperature is 62.5 * 0.680, or 42.5 degrees above ambient.  And the thermal resistance to the case is about 15 °C/W, so the case will be 42.5-(15*0.680) or 32.3 degrees above ambient.  If ambient is 25°C, the case is at 57°C. Does this sound right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(You should look up and substitute your own thermal values, I just grabbed some from the Zetex datasheet.  But I expect all SOT223 will have similar thermal characteristics.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice that the 500 mA rating has nothing at all to do with it.  Temperature is determined by the power dissipated, which is set by the input-output difference and the output current, and the thermal characteristics of the package and surroundings.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-02-27T06:22:51.973" LastActivityDate="2011-02-27T06:22:51.973" CommentCount="3" />
  <row Id="10763" PostTypeId="2" ParentId="10761" CreationDate="2011-02-27T10:33:41.303" Score="3" ViewCount="" Body="&lt;p&gt;markrages is right, it is normal this kind of regulators burn the energy of as heat.&#xA;If the heat is a problem there is two ways to solve it.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;A heatsink, the more current you need the bigger heatsink you need.&lt;/li&gt;&#xA;&lt;li&gt;Use a switched regulator instead.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="689" LastActivityDate="2011-02-27T10:33:41.303" />
  <row Id="10764" PostTypeId="1" CreationDate="2011-02-27T10:39:18.927" Score="4" ViewCount="73" Body="&lt;p&gt;My bathroom lighting consists of recessed down lights and LED pelmet lighting. With everything switched on the light levels are high which is fine but not great for a relaxing bath. I want to be able to dim the lights to create a mood atmosphere. As such I have wired up a single dimmer switch to the supply that feeds all of the lights. The recessed lighting dims fine, but the LED pelmet light comes on pretty much instantly on the dimmed range and lights up the bathroom which ruins the effect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to retain the single switch so am wanting to install some form of relay which only activates the LED lighting at the top of the dimmed range. Does anyone have any ideas? I was wondering whether it was possible to get some form of voltage sensor which would detect voltages over a certain level, say 220v (at the top of the dimmed range) which activates a relay which in turn activates the LED curcuit.&lt;/p&gt;&#xA;" OwnerUserId="3178" LastActivityDate="2011-02-27T11:27:09.890" Title="Lighting Question" Tags="&lt;electronics&gt;" AnswerCount="2" />
  <row Id="10765" PostTypeId="2" ParentId="10764" CreationDate="2011-02-27T10:58:57.663" Score="2" ViewCount="" Body="&lt;p&gt;A simple solution, if you dimmer uses a potentiometer, would be to get a potentiometer with a switch. Have the varistor part control the main lights and have the switch control the LEDs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another more complicated option would be to use a comparator and some optocouplers.&#xA;You could design a circuit which could use a discrete comparator to see if voltages are same on the dimmer output and on the input voltage and then trigger a transistor or a relay, depending on the LED's power consumption.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It could be easier to program a microcontroler with an integrated comparator to trigger a transistor or a relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In both cases, you'd need to provide power supply for the control element of the system, which will take up space and will need to be at a safe location which wouldn't be affected by humidity and water.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-27T10:58:57.663" CommentCount="3" />
  <row Id="10766" PostTypeId="2" ParentId="10764" CreationDate="2011-02-27T11:27:09.890" Score="7" ViewCount="" Body="&lt;p&gt;Don't dim those LEDs!  If they come on full bright at a certain dimmer level or flicker at a certain level then their driver isn't designed to be dimmed and could be damaged or worse.  One solution could be to get a proper dimmable driver and dim the LEDs with the rest of the lights... assuming the LEDs and driver are separate units.&lt;/p&gt;&#xA;" OwnerUserId="2051" LastActivityDate="2011-02-27T11:27:09.890" CommentCount="1" />
  <row Id="10767" PostTypeId="2" ParentId="10758" CreationDate="2011-02-27T11:34:54.810" Score="0" ViewCount="" Body="&lt;p&gt;I have the same background as you, and one of the first things I bought was an &lt;a href=&quot;http://www.mikroe.com/eng/products/view/1/easypic5-development-system/&quot; rel=&quot;nofollow&quot;&gt;EasyPIC5&lt;/a&gt; pic microcontroller development board. It allows you to play around with pics without having to know too much about the electronics side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you want to build a circuit using your newly programmed pic, you can start by prototyping it on a breadboard... and then move on to soldering it on to stripboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get lots of circuit schematic ideas by searching on Google images.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-02-27T11:34:54.810" CommentCount="1" />
  <row Id="10768" PostTypeId="2" ParentId="10752" CreationDate="2011-02-27T12:07:09.200" Score="1" ViewCount="" Body="&lt;p&gt;It is very dependent on the design. For something that is all SMD with minimal manual work, the advantages of going overseas can be minimal - the trick is to find a local asssembler geared to your volumes, who doesn't charge a large 'get out of bed' fee for setting up etc. &#xA;Larger places will be less interested in small jobs, but really small places tend to have a precarious existance and can have disappeared next time you need something done. Even with a 'right size/attitude' place you will generally have to fit inbetween the jobs from their larger customers, so getting stuff turned round quickly is near-impossible unless you're lucky, as even if you offer to pay twice as much it's still small for them and they're always going to prioritise their bigger customers. As mentioned above, successful lower-end assemblers who are ticking along nicely often don't need to advertise, and can be hard to find - recommendations are very useful - maybe ask a few companies making stuff on a similar scale to yours who they use for assembly - people are often happy to reccommend, as once you find a good place, you want them to stay in business.&lt;br&gt;&#xA;You also have to consider that board assembly cost isn't the only cost involved - things like test, optimising for good yield etc. are very dependent on good communication and understanding between client and subcontractor, which can be nonexistent with Chinese suppliers.  For something  made in 100s I wouldn't even think of using China - the time to get things set up and the uncertainty that you're going to get what you want just aren't worth it.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-27T12:07:09.200" />
  <row Id="10769" PostTypeId="2" ParentId="10758" CreationDate="2011-02-27T12:09:32.663" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://hackaday.com/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/&lt;/a&gt; - this will give you the idea of what can possibly be done in limited resources.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then get an Arduino and start playing &lt;a href=&quot;http://arduino.cc/en/Tutorial/HomePage&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Tutorial/HomePage&lt;/a&gt; .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Meanwhile find out local/internet shops where you will be able to buy parts without waiting too long.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-27T12:09:32.663" CommentCount="2" />
  <row Id="10770" PostTypeId="1" CreationDate="2011-02-27T12:27:49.777" Score="5" ViewCount="175" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Could you please explain me about pipelining in FPGA and how is it done in xilinx system generator design by adding registers and delays in a particular system design?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I have a system design in xilinx system generator. That design meets the timing constrain with 20ns (takes 50MHz clock frequency). However, the FPGA board I use is Virtex 4. It offers 100 MHz (10ns) clock at pin B15. I set 20ns as the FPGA clock period and pin B15 in the System generator token. I was able to generate HDL netlist without any error. However, I wasn't able to get any outputs from the FPGA after I downloaded the bitstream from xilinx ISE. I was wondering it would be the issue with the frequency of the FPGA borad and my design as my design meets only 50MHz NOT 100MHz. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;h2&gt;Update with more information&lt;/h2&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;My design: &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I was not able to upload the picture. I designed a system to generate UWB signal.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;For this design I only managed to reached maximum of 50MHz(20 ns) of clock frequency by adding registers and delay blocks in between the inputs and outputs. I was not able to reduced the time constrain below 20 ns. Because when I tried to reduce it to 10 ns (attempting to reach 100MHz) by increasing the amount of delays I ended up with an error &quot;Resource overmapped&quot;, as shown below (&lt;em&gt;Figures are not the same,but similar&lt;/em&gt;).&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;elected Device : 4vfx12ff668-10 &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Number of Slices:                     6690  out of   5472   122% (&lt;em&gt;) &#xA; Number of Slice Flip Flops:          20567  out of  10944   188%&lt;br&gt;&#xA; Number of 4 input LUTs:              10072  out of  10944    92%&lt;br&gt;&#xA;    Number used as logic:              9969&#xA;    Number used as Shift registers:     103&#xA; Number of IOs:                           7&#xA; Number of bonded IOBs:                   6  out of    320     1%&lt;br&gt;&#xA;    IOB Flip Flops:                       2&#xA; Number of GCLKs:                         2  out of     32     6%&lt;br&gt;&#xA; Number of DSP48s:                       33  out of     32   103% (&lt;/em&gt;)&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;However my Virtex 4 FX12FF668 only offers 100MHz clk at pin B15 (i.e. FPGA clock period (ns) = 10 and Clock pin location = B15 ). I'm clueless for how to change it to 50MHz to suite my design and set it in the sys gen token. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3180" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-02-28T23:28:21.337" LastActivityDate="2011-02-28T23:28:21.337" Title="Pipelining and clock frequency issue" Tags="&lt;fpga&gt;&lt;xilinx&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="10771" PostTypeId="2" ParentId="10770" CreationDate="2011-02-27T13:15:39.687" Score="1" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Pipelining can be seen as breaking up an operation that takes a long time (translate - long data path) into a number of smaller operations. Between each operation, you can put in a register to buffer the intermediate data and form pipeline stages. By carefully doing this, you can increase throughput of the operation.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You need to ensure that your design can move the data from input to output within the period - 10ns. Otherwise, there is no guarantee that the design will work correctly. Over-clocking your design may or may not work from time to time. You will need to decrease the data-path of your design.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;One way to do this would be to increase the pipeline stages of your datapath. For example, if your previous design moves input A to output C in 20ns, you can insert a register B in-between. Then, it can move data from intput A to register B in 10ns and move data from register B to output C in 10ns. Effectively, you still move data from A to C in 20ns but your design can now be clocked with a 10ns period (100MHz).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A --------- (20 ns) --------- C&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A -- (10ns) -- B -- (10ns) -- C&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-02-27T13:15:39.687" />
  <row Id="10772" PostTypeId="2" ParentId="10758" CreationDate="2011-02-27T13:29:24.073" Score="1" ViewCount="" Body="&lt;p&gt;My professor last year had us buy a &lt;a href=&quot;http://www.pololu.com/catalog/product/1306&quot; rel=&quot;nofollow&quot; title=&quot;3pi Robot&quot;&gt;3pi Robot&lt;/a&gt;. I thought it was a pretty cool beginners robot. There is a lot of documentation and even a user forum on Pololu's website.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you get an expansion board, you will have more space to add sensors or more sophisticated circuitry.&lt;/p&gt;&#xA;" OwnerUserId="2857" LastActivityDate="2011-02-27T13:29:24.073" CommentCount="1" />
  <row Id="10773" PostTypeId="1" AcceptedAnswerId="10779" CreationDate="2011-02-27T15:02:22.340" Score="6" ViewCount="273" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We know that we have now 50/60Hz in our walls due to mainly historical reasons - back 100 years ago there were no ways to up/down scale DC voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These days we just have problems due to that - every single device sold have to have ~1uF cap per 1W of power before it's PSU to have enough power when we go through 0. (this problem does not exist in 3-phase power, but it available mainly in industrial applications only AFAIK) + caps have to have higher rated voltage to survive sine peaks + all this PFC mess.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is that correct to say that if we were to design modern power grid, we would skip AC, and just have DC everywhere? As far as I see, it would significantly increase reliability &amp;amp; reduce cost of many devices out there.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-02-28T00:06:41.023" LastActivityDate="2011-02-28T01:24:31.033" Title="Power grids : AC vs DC" Tags="&lt;power&gt;&lt;line-power&gt;&lt;grid&gt;" AnswerCount="5" CommentCount="4" FavoriteCount="3" />
  <row Id="10774" PostTypeId="2" ParentId="10773" CreationDate="2011-02-27T15:42:00.267" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Short answer:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Long answer:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The advantage of AC for distributing power over a distance is due to the ease of changing voltages using a transformer. Converting DC power from one voltage to another requires a large spinning rotary converter or motor-generator set, which is difficult, expensive, inefficient, and required maintenance, whereas with AC the voltage can be changed with simple and efficient transformers that have no moving parts and require very little maintenance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Suggested reading:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/War_of_Currents&quot; rel=&quot;nofollow&quot;&gt;War of Currents&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1603" LastActivityDate="2011-02-27T15:42:00.267" CommentCount="9" />
  <row Id="10775" PostTypeId="2" ParentId="10758" CreationDate="2011-02-27T15:45:43.583" Score="1" ViewCount="" Body="&lt;p&gt;Another great place for a beginner is  &lt;a href=&quot;http://letsmakerobots.com/&quot; rel=&quot;nofollow&quot;&gt;Letsmakerobots.com&lt;/a&gt;, the site is geared more toward the hobbyist/hacker crowd.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-02-27T15:45:43.583" CommentCount="1" />
  <row Id="10776" PostTypeId="2" ParentId="4515" CreationDate="2011-02-27T16:28:34.937" Score="1" ViewCount="" Body="&lt;p&gt;Hi Guys,&#xA;Herny Ott discusses this in his book, &quot;Electromagnetic Compatibility Engineering&quot;. You need to look at it from the bigger picture. IE, what is the shield doing?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For low frequency signals, the shield is used to protect the signal being transfered. You want to avoid power line/AM/FM radio signals to couple into your signal because it will interfere with normal operations. Therefore you must not tie the GND on both ends. Ground loops will cause small noises to couple into your signal, therefore the ground loop must be broken. This does not mean that you leave the shield hanging. You should tie the shield of the cable, to your enclosure, and if needed (as in the case of coax), you can tie the ground of your circuit to this same point. You want to use single point grounding as much as possible for low frequency for the above reasons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, for high frequency signals, the opposite is true. They are usually digital signals at very high frequencies. Even if some noise did get coupled, the digital nature of the electronics as well as filtering should easily maintain normal operations. You want to reduce the emissions of the data signals, NOT protect it from radiation. For this reason, the lowest impedance path should be connected to shield at BOTH ends. Yes, there will be ground loops, and noise will get coupled in, but it won't matter. In the case of high frequency, multipoint ground is prefered.&lt;/p&gt;&#xA;" OwnerUserId="3183" LastActivityDate="2011-02-27T16:28:34.937" />
  <row Id="10777" PostTypeId="2" ParentId="10773" CreationDate="2011-02-27T16:40:00.870" Score="0" ViewCount="" Body="&lt;p&gt;Short answer:&#xA;   Not so fast&#xA;Longer:&#xA;   Solid state converters are pretty good.  Long haul transmission has lots of advantages.  Short haul probably still benefits from transformers.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-02-27T16:40:00.870" CommentCount="1" />
  <row Id="10778" PostTypeId="2" ParentId="4515" CreationDate="2011-02-27T17:16:11.160" Score="0" ViewCount="" Body="&lt;p&gt;For the shield to be effective, it requires as low impedance connection as possible to your shield ground.  I think those recommending resistors, or not connecting it to ground at all, or strictly talking about your digital logic ground, and assuming you have a separate shield ground.  If you have a metal enclosure, this will be your shield ground.  At some point, your digital ground must connect to your shield ground.  For EMI reasons, this single point should be close to your I/O area.  This means it's best to place your USB connector with any other I/O connectors around one section of the board and locate your shield to logic ground point at that location.  There are some exceptions to the single point, rule, if you have a solid metal enclosure without any apertures, for example, multiple connection points can be helpful.  In any case, at shield to circuit ground connection, some may recommend using a resistor or capacitor (or both) but rarely is there a reasonable reason to do this.  You want a low inductance connection between the two to provide a path for common mode noise.  Why divert noise though parasitic capacitance (e.g. radiate it out into the environment)?  The only reason usually given for such tactics is to prevent ground loops, but you're talking about USB, ground loops most likely won't be an issue for most USB applications.  Granted, such tactics will prevent ground loops, but they will also rend your shielding all but ineffective. &lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-02-27T17:16:11.160" />
  <row Id="10779" PostTypeId="2" ParentId="10773" CreationDate="2011-02-27T17:39:21.117" Score="4" ViewCount="" Body="&lt;p&gt;Guy Allee at Intel Research wrote about this topic last year -- &lt;a href=&quot;http://blogs.intel.com/research/2010/05/dc_-_an_idea_whose_time_has_co.php&quot; rel=&quot;nofollow&quot;&gt;DC - An idea whose time has come and gone?&lt;/a&gt; -- in support of a 380VDC grid, with the following bullet points:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;7% Energy Savings vs. High-Efficiency 415VAC; 28% vs Current&#xA;  Typical 208VAC&lt;/li&gt;&#xA;  &lt;li&gt;15% Less Capital Cost&lt;/li&gt;&#xA;  &lt;li&gt;15% fewer PSU components&lt;/li&gt;&#xA;  &lt;li&gt;33% Datacenter Space Savings&lt;/li&gt;&#xA;  &lt;li&gt;200% Reliability Improvement, which goes to 1000% if you directly connect&#xA;  the battery bus&lt;/li&gt;&#xA;  &lt;li&gt;Elimination of harmonics and inherently immune to other AC power&#xA;  quality issues&lt;/li&gt;&#xA;  &lt;li&gt;Natural affinity to alternate energy generation (Photovoltaic, and wind are&#xA;  ~400Vdc internally, and you actually&#xA;  lose energy &amp;amp; efficiency when you are&#xA;  forced to convert to AC)&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;He added in the comments:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;We very deliberately picked 380Vdc&#xA;  because you want to get to as high a&#xA;  voltage as you can afford for&#xA;  efficiency. At the same time this&#xA;  standard is targeting Low Voltage&#xA;  applications only (&amp;lt;600V). We would&#xA;  have gone higher, but there are&#xA;  structural cost barriers at 400Vdc and&#xA;  420Vdc. At 380Vdc we stay with the&#xA;  same volume parts ratings that AC is&#xA;  using and get the volume cost benefits&#xA;  of piggybacking on the bulk of current&#xA;  AC power supply component volumes. I’m&#xA;  sure you can also appreciate the&#xA;  significant cost adders that +/-340Vdc&#xA;  has on the personal safety equipment,&#xA;  which is why the standard allows for a&#xA;  cost-effective +/-190Vdc distribution.&#xA;  Thus we have the highest efficiency&#xA;  yet cost effective standard. And with&#xA;  the affinity among other industries,&#xA;  PV, wind, electric vehicles, and&#xA;  lighting, the volume economics seem&#xA;  compelling.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;He also mentions the idea of a mixed distribution of both AC and DC within a building (e.g. data centers). For more on that initiative, see the EMerge Alliance website: &lt;a href=&quot;http://www.emergealliance.org&quot; rel=&quot;nofollow&quot;&gt;http://www.emergealliance.org&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="721" LastActivityDate="2011-02-27T17:39:21.117" CommentCount="4" />
  <row Id="10780" PostTypeId="2" ParentId="10773" CreationDate="2011-02-27T20:37:03.450" Score="4" ViewCount="" Body="&lt;p&gt;Safety.  Having HVDC through the wall outlet is not smart.  Unplug a high current device without first switching it off will pull a huge arc&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-02-27T20:37:03.450" CommentCount="3" />
  <row Id="10781" PostTypeId="2" ParentId="10686" CreationDate="2011-02-27T21:11:57.280" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www1.cs.columbia.edu/async/publications/davis-nowick-intro-tr.pdf&quot; rel=&quot;nofollow&quot;&gt;&quot;An introduction to asynchronous circuit design&quot;&lt;/a&gt; by Davis and Nowick&#xA;(in particular, Figure 1 and Figure 2 and the nearby text)&#xA;describes two handshaking protocols as &quot;pervasive&quot;.&#xA;The 4-cycle protocol, aka RZ (return to zero), 4-phase protocol, and level-signaling.&#xA;And the similar but more complicated to implement 2-cycle protocol, aka transition, 2-phase, or NRZ (non-return to zero) signaling -- which is very similar to the &quot;data strobe encoding&quot; used by SpaceWire and FireWire.&#xA;Either one sounds like it has most of the features you requested --&#xA;it's SPI-like in that there are exactly 4 signals, all 4 signals are one-way (no passive pull-ups), the master can pause the slave indefinitely until it is ready for the next bit from the slave, etc.&#xA;It also has a feature supercat requested that SPI doesn't have: the slave can pause the master indefinitely until it is ready for the next bit from the master.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know of any chips that have the 4-cycle protocol built in, but it looks like it would be easy to bit-bang on a microcontroller or a CPLD.&#xA;In fact, it looks like it would be easier to bit-bang than SPI, since (like SPI) the master has no timing requirements, and (unlike SPI) the slave has no timing requirement either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to use the 4-phase protocol for synchronous bit transfers, and somehow build a higher-level protocol on top of that to get the other things supercat wants -- byte alignment, start-of-command frame alignment, attention/busy/idle states, etc?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-27T21:11:57.280" CommentCount="6" />
  <row Id="10782" PostTypeId="2" ParentId="9497" CreationDate="2011-02-27T22:01:58.933" Score="1" ViewCount="" Body="&lt;p&gt;You may be interested in &lt;a href=&quot;http://www.uclinux.org/&quot; rel=&quot;nofollow&quot;&gt;uClinux&lt;/a&gt; (3S's doesn't have MMU), since &lt;a href=&quot;http://docs.blackfin.uclinux.org/doku.php?id=bluetooth_over_uart&quot; rel=&quot;nofollow&quot;&gt;there is BT support in it&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1603" LastActivityDate="2011-02-27T22:01:58.933" CommentCount="1" />
  <row Id="10783" PostTypeId="2" ParentId="10745" CreationDate="2011-02-27T22:06:33.930" Score="1" ViewCount="" Body="&lt;p&gt;I recently had the same problem and also chose an NXP UART. I picked the &lt;a href=&quot;http://www.nxp.com/documents/data_sheet/SC16IS740_750_760.pdf&quot; rel=&quot;nofollow&quot;&gt;SC16IS740&lt;/a&gt;. It only supports a single channel, but rather than connecting to an external address and data bus it is driven with I2C or SPI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also an interrupt line to alert of incoming data.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-02-27T22:06:33.930" CommentCount="1" />
  <row Id="10784" PostTypeId="1" AcceptedAnswerId="10857" CreationDate="2011-02-27T22:09:06.953" Score="4" ViewCount="114" Body="&lt;p&gt;I am trying to find quotes for low volume displays, Graphic lcd's specifically, but I am interested in touch screen panels too. I found Vishay but cannot see any prices anywhere. I am curious what the big name companies do for their graphic LCD's, and how they determine what lcd to use. Do they fabricate their own displays, or purchase the displays from other companies?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, any opinions on how to choose a display for a low volume product? &#xA;What were your past experiences with choosing a graphic display, and what advice can you give?&lt;/p&gt;&#xA;" OwnerUserId="2050" LastActivityDate="2011-03-01T04:43:43.440" Title="Quotes for Low volume (&gt;500) LCD displays." Tags="&lt;lcd&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="2" />
  <row Id="10785" PostTypeId="1" AcceptedAnswerId="10798" CreationDate="2011-02-27T22:41:13.407" Score="3" ViewCount="198" Body="&lt;p&gt;See &lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CBcQFjAA&amp;amp;url=http%3A%2F%2Fwww.fairchildsemi.com%2Fds%2FMM%2FMM74HC138.pdf&amp;amp;rct=j&amp;amp;q=74HC138&amp;amp;ei=Q9JqTdHaIcWp8QO44sXyBw&amp;amp;usg=AFQjCNHLCxEvNYuuYKTkqvaS5orXoFfJpQ&amp;amp;sig2=HuRGI3GadfBKejtfhW2IGA&amp;amp;cad=rja&quot; rel=&quot;nofollow&quot;&gt;this datasheet&lt;/a&gt;, page 2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The diagram shows logic inverters with bubbles at the input or at the output. Is there an actual difference between them?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-02-28T16:51:48.700" Title="What's the difference between an inverter with a bubble at the input and one with a bubble at the output?" Tags="&lt;logic&gt;&lt;inverter&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="10787" PostTypeId="2" ParentId="10754" CreationDate="2011-02-27T22:47:25.447" Score="3" ViewCount="" Body="&lt;p&gt;Go with all 3v3 if you can.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not, interfacing between 5v and 3v3 can be done with 74LCX series glue chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get 3.3v buffer chips with 5v tolerant input such as the 74LCX244 (the X in the code means 5v tolerant). You can hook these straight to 5v outputs and they give 3v3 outputs. (you'll need a 3v3 regulator to power the chip, a teeny TO92 5v-&gt;3v3 one is fine, and about 20c).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the other direction (3v3 to 5v) you can just use pullup resistors to go from 3v output to 5v input.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-02-27T22:47:25.447" />
  <row Id="10788" PostTypeId="2" ParentId="7092" CreationDate="2011-02-27T22:48:10.923" Score="0" ViewCount="" Body="&lt;p&gt;Here you find a physical explanation which is using maxwells law. &#xA;&lt;a href=&quot;http://physics.stackexchange.com/questions/5628/skin-effect-and-currents&quot;&gt;link to physics.stackoverflow&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1814" LastActivityDate="2011-02-27T22:48:10.923" />
  <row Id="10790" PostTypeId="1" AcceptedAnswerId="10801" CreationDate="2011-02-28T00:05:30.887" Score="1" ViewCount="105" Body="&lt;p&gt;I want to make a remote for &lt;a href=&quot;http://www.google.com/products/catalog?sqi=2&amp;amp;cid=8027797470559825555#p&quot; rel=&quot;nofollow&quot;&gt;Thomas Battery Powered Engine&lt;/a&gt; that will allow it to be turned on and off, but I don't even know where to start. I assume I'll need a receiver that can toggle power on and off to the motor in the engine and an external transmitter. Can I use the AA battery in the engine to power the receiver?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My hope was to be able to control multiple units via bluetooth from a smartphone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What should I read/ask/buy to get started?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not even sure this is on topic for this site.&lt;/p&gt;&#xA;" OwnerUserId="1227" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-03-01T04:55:14.490" LastActivityDate="2011-03-01T14:43:01.760" Title="Modifying AA powered toy engine to be remotely turned on/off" Tags="&lt;remote&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="10791" PostTypeId="1" AcceptedAnswerId="10795" CreationDate="2011-02-28T01:05:20.613" Score="3" ViewCount="137" Body="&lt;p&gt;Hey all -&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm hacking on a board that has an RS232 interface (via a Max232 chip).  My new computer doesn't have a serial port, which leaves me using USB.  I actually have a Serial to USB cord already, but it doesn't appear to work on any modern OS that I run (Windows 7, Linux).  I'm not 100% positive, but I think it's this one:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Cables-Go-26886-Serial-Adapter/dp/B000067RVJ/ref=cm_cr_pr_product_top&quot; rel=&quot;nofollow&quot;&gt;http://www.amazon.com/Cables-Go-26886-Serial-Adapter/dp/B000067RVJ/ref=cm_cr_pr_product_top&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I still have the driver CD too, which worked fine in XP, but Win7 wants nothing to do with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, can anyone recommend a serial to USB cord/converter that they know works?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="3185" LastActivityDate="2011-03-26T16:32:38.963" Title="Recommend a Serial to USB cable/converter that works with modern OSes" Tags="&lt;usb&gt;&lt;serial&gt;&lt;communication&gt;&lt;interface&gt;&lt;cables&gt;" AnswerCount="2" />
  <row Id="10792" PostTypeId="2" ParentId="9059" CreationDate="2011-02-28T01:14:44.707" Score="2" ViewCount="" Body="&lt;p&gt;As someone that started freelancing as a student, I can tell you quite honestly that simply getting started is the hardest part.  For me, and most everyone else that I've talked to, it comes down to networking.  Do you know anyone from school, or otherwise, that is in your field?  Simply getting your foot in the door often leads to future work that you can't possibly foresee.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another common route that I have both seen and used myself is open source communities.  Are you involved with any open source projects?  If not, are there any that interest you?  Get involved, start contributing code and answering questions, and you would be surprised at how quickly you'll get noticed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most people don't get into freelancing without already having a customer or a target customer.  It can be pretty difficult, otherwise.&lt;/p&gt;&#xA;" OwnerUserId="3185" LastActivityDate="2011-02-28T01:14:44.707" CommunityOwnedDate="2011-02-28T04:38:11.237" />
  <row Id="10793" PostTypeId="2" ParentId="10773" CreationDate="2011-02-28T01:24:31.033" Score="1" ViewCount="" Body="&lt;p&gt;You may be right.&#xA;AC once held a huge advantage over DC in the past.&#xA;But as the cost of DC-DC converters has dropped, the relative advantage of AC has dropped and in some cases crossed over.&#xA;If we were designing a new power transmission system today, DC everywhere might reduce total system costs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an equivalent power and current levels and reliability, DC requires slightly stronger parts for circuit breakers and fuses and lightning arrestors; but AC requires slightly more expensive transmission lines and better coordination of power generators to avoid cascading failure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even though (for historical reasons) AC equipment has mass-production economy-of-scale advantages over DC equipment, the designers of &lt;a href=&quot;http://en.wikipedia.org/wiki/List_of_HVDC_projects&quot; rel=&quot;nofollow&quot;&gt;many recent long-distance power&lt;/a&gt; transmission systems have apparently decided that using &lt;a href=&quot;http://en.wikipedia.org/wiki/High-voltage_direct_current&quot; rel=&quot;nofollow&quot;&gt;high-voltage DC&lt;/a&gt; (typically 200,000 VDC) has lower net system costs than using AC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even though (for historical reasons) many airplanes and the Space Shuttle use 400 Hz 120 VAC, early plans for the international space station called for it to use a 20,000 Hz 440 VAC distribution power (!), until program priorities changed and the engineers switched to 120 VDC power.&#xA;(&lt;a href=&quot;http://books.google.com/books?id=V84ZHMmdNmYC&amp;amp;pg=PA538&amp;amp;lpg=PA538&amp;amp;dq=spacecraft+400+Hz&amp;amp;source=bl&amp;amp;ots=9ZyUvxTX42&amp;amp;sig=e_jfCUvOaGYsGxR4r79M4RI0Mqw&amp;amp;hl=en&amp;amp;ei=fONqTdumO4SosQOx7-H5BQ&amp;amp;sa=X&amp;amp;oi=book_result&amp;amp;ct=result&amp;amp;resnum=1&amp;amp;ved=0CBgQ6AEwAA#v=onepage&amp;amp;q=spacecraft%20400%20Hz&amp;amp;f=false&quot; rel=&quot;nofollow&quot;&gt;Mukund R. Patel&lt;/a&gt; p. 543)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;People at Google (&lt;a href=&quot;http://news.cnet.com/8301-1001_3-10209580-92.html&quot; rel=&quot;nofollow&quot;&gt;a&lt;/a&gt;,&lt;a href=&quot;http://www.eetimes.com/design/embedded/4006326/Server-makers-get-Goooogled&quot; rel=&quot;nofollow&quot;&gt;b&lt;/a&gt;) have suggested to desktop and server manufacturers that net cost could go down if we switch to &quot;12V-only supplies&quot; that convert the AC mains power to 12 VDC, and then the computer motherboard requires only 12 VDC, which it steps down to whatever collection of voltages it needs (like most laptops), rather than the current ATX power supply configuration that has a thick bundle of wires with a motley assortment of voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lee Felsenstein and Douglas Adams have gone even further and asked that someone develop a standard 12 VDC distribution system.&#xA;(&lt;a href=&quot;http://www.douglasadams.com/dna/980707-03-a.html&quot; rel=&quot;nofollow&quot;&gt;c&lt;/a&gt;,&lt;a href=&quot;http://www.treehugger.com/files/2006/09/google_pushes_f.php&quot; rel=&quot;nofollow&quot;&gt;d&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-28T01:24:31.033" />
  <row Id="10794" PostTypeId="2" ParentId="10791" CreationDate="2011-02-28T01:27:20.047" Score="2" ViewCount="" Body="&lt;p&gt;I know for a fact that &lt;a href=&quot;http://amzn.to/i6EQvE&quot; rel=&quot;nofollow&quot;&gt;SIIG USB to serial adapters&lt;/a&gt; work in Windows 7, if you get the v2 hardware.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They work on 32 and 64 bit Windows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also can't go wrong with those that are based on the FTDI chipset.  Many aren't, and have caused me troubles in the past by BSODing the OS quite often.   SIIG is not FTDI based, but I have yet to have one BSOD in over 5 years of running multiple of them on several systems.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-02-28T01:27:20.047" />
  <row Id="10795" PostTypeId="2" ParentId="10791" CreationDate="2011-02-28T01:49:22.073" Score="4" ViewCount="" Body="&lt;p&gt;You have 2 chipsets for serial:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.prolific.com.tw/eng/downloads.asp?ID=31&quot; rel=&quot;nofollow&quot;&gt;Prolific&lt;/a&gt; &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ftdichip.com/FTDrivers.htm&quot; rel=&quot;nofollow&quot;&gt;FTDI&lt;/a&gt; &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Both are supported in modern operating systems. Just go tho the websites and download the latest drivers. The one imaged looks like mine(not to say it is) and mine is prolific.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-02-28T01:49:22.073" CommentCount="5" />
  <row Id="10796" PostTypeId="2" ParentId="9059" CreationDate="2011-02-28T02:15:36.470" Score="1" ViewCount="" Body="&lt;p&gt;Your best plan is to find a place that you can work at that allows telecommuniting.  Hardware isn't well suited to only telecommuniting unless you are a contractor with a lab of your own.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also you are the point in your career where you can now really learn from people; you have gotten past the initial &quot;real world&quot; learning that isn't taught in school, it seems.  Long term this learning is more important than the advantage of not having to go to work.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-28T02:15:36.470" CommunityOwnedDate="2011-02-28T04:38:11.237" />
  <row Id="10797" PostTypeId="1" CreationDate="2011-02-28T03:03:06.127" Score="1" ViewCount="286" Body="&lt;p&gt;I have a D-type flip flop (CD4013B) connected to a lithium battery with 240mAh capacity and it is stored for 8years at room temperature. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;May I know how much quiescent current will be drawn from the battery during 8 years storage time?&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Let me expand&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Maybe let me put to you all a better view of my current scenario:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) The quiescent current of this device is ~20uA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) I have 4 batteries connected in 2S and 2P (ie, 2 in series and then parallel with another 2 in series) =&gt; 480mAh @ 8Vdc&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Each battery has a capacity of 240mAh @ 4Vdc and from the graph of Capacity Vs OCV, it will have a capacity loss of 20% after 8 years storage at 55degC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) My circuit can work at min voltage of 5.7Vdc&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hence, i would like to know how much current is consumed from the IC and the self-discharge of the batteries during the 8 years storage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will the batteries be able to operate my circuit after 8 years?&lt;/p&gt;&#xA;" OwnerUserId="3201" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-01T07:50:50.020" LastActivityDate="2011-03-01T07:50:50.020" Title="How to calculate the total quiescent device current draw for 8years if the the device had a 20uA quiescent current?" Tags="&lt;battery&gt;" AnswerCount="2" />
  <row Id="10798" PostTypeId="2" ParentId="10785" CreationDate="2011-02-28T03:26:14.407" Score="6" ViewCount="" Body="&lt;p&gt;Bubbles signify whether a signal is active low or active high. On the digram, signals A, B, C, and G1 are active high. Note that the truth table uses Ls and Hs instead of 0s and 1s. For active-low circuits, a low voltage is logical 1. The operation of a gate depends on how you interpret the signal levels. For example, an AND gate with all active-high signals can be redrawn as an OR gate with all active-low signals, and vice versa.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In mixed logic design, bubbles always pair up. You draw out the basic equation with AND and OR gates, and insert a vertical line with a bubble everywhere there's a signal complement. Then replace all the logic gates with the type you're actually using (e.g. NAND and the equivalent active-low input OR). Finally, insert inverters anywhere that the bubbles don't pair up. This makes it effortless to read the equation right off the schematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I found a professor's page at Georgia Tech with some examples of bubble pairing with mixed logic and a mix of active-low and active-high signals:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://users.ece.gatech.edu/~sudha/academic/class/ece2030/Lectures/gate-design/examples.html&quot; rel=&quot;nofollow&quot;&gt;http://users.ece.gatech.edu/~sudha/academic/class/ece2030/Lectures/gate-design/examples.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Either an input or an output bubble is used on each inverter in order to clearly show the bubble pairs. The bubbles with slashes are just for reading the equation from the schematic. They can be removed (as in example 4), and then anywhere there's a bubble mismatch is a logical inversion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit 2: An inverter is a level inverting buffer. It's not always a logic inverter. In example 2, when Y, B, and D are implemented as active-high signals, the circuit requires inverters even though the logic function doesn't call for the complement. This is because NAND is equivalent to OR with active-low inputs, so the active-high inputs need to first be inverted. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the schematic linked to in the question, note that the inputs and outputs of active-low signals in the schematic on page 2 have matching bubbles in the connection diagram on page 1. I would have repeated those bubbles on the page 2 schematic for completeness.&lt;/p&gt;&#xA;" OwnerUserId="721" LastEditorUserId="721" LastEditorDisplayName="" LastEditDate="2011-02-28T16:51:48.700" LastActivityDate="2011-02-28T16:51:48.700" />
  <row Id="10799" PostTypeId="2" ParentId="10797" CreationDate="2011-02-28T03:43:27.183" Score="1" ViewCount="" Body="&lt;p&gt;The current should not vary with time.  Perhaps your are interested in the charge?  Current times Time.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-02-28T03:43:27.183" />
  <row Id="10800" PostTypeId="2" ParentId="10797" CreationDate="2011-02-28T04:29:39.123" Score="5" ViewCount="" Body="&lt;p&gt;The total discharge caused by your device will be 20uA * (8 years). The issue is you need to convert to mAh to match units.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;.02&lt;/strong&gt; mA * &lt;strong&gt;8&lt;/strong&gt; years * &lt;strong&gt;365.25&lt;/strong&gt; days/year * &lt;strong&gt;24&lt;/strong&gt; hours/day = &lt;strong&gt;1402.56 mAh are required for this&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your battery is only 240mAh capacity, so it will only last a fraction of this time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can approach this with algebra also.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;240mAh / .02 mA = 12000 hours = &lt;strong&gt;500 days of lifetime from your battery&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is actually still not perfect. You need to factor in the self discharge rate of your battery. This will be specific to the battery you have chosen and can be very high, possibly dwarfing your 20uA limit and placing you in the mA range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me know if there is something you need more information on.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-02-28T04:29:39.123" CommentCount="6" />
  <row Id="10801" PostTypeId="2" ParentId="10790" CreationDate="2011-02-28T08:42:43.340" Score="2" ViewCount="" Body="&lt;p&gt;I can't help much on the remote part. You'll most likely want to use radio, but I can't provide anything more specific than that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also can't give good advice right now, but that's because of the low amount of information in the question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So first step would be to carefully disassemble the engine and post some photos of the circuits. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll most likely find one or even two motors inside (they do mention 4x4 drive) and see how they are controlled. Next step would be to decide what you are going to do. The description is a bit vague but I think that they mention multiple buttons on the unit. You'll have to decide if you want to completely switch to remote control, just have remote on-off control and local controls or have full remote and local control.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, if you want remote on/off control, you could accomplish that in two ways: place the extra switch at engine's main power connector or place extra switch on engine's motor power connector.  It could be easier to just switch completely to remote control, but again that depends on internal wiring and available volume. I'd have to think a bit for full remote and local control.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the switch itself, to me a MOSFET in TO-92 package looks like a good idea. If you can afford it, get one of the more expensive ones. They'll most likely be around 1€, but will have much lower internal resistance than cheaper ones which means that they'll consume less power for themselves. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also for the radio power supply could be a problem. Common voltage levels for hobby electronics are 3.3 V and 5 V. On the other hand, AA battery provides between 1.6 V and 0.8 V, so you may have to make or get prefabricated converter. Of course, this will negatively affect power consumption.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-02-28T08:42:43.340" />
  <row Id="10802" PostTypeId="5" CreationDate="2011-02-28T09:14:30.233" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-28T09:14:30.233" LastActivityDate="2011-02-28T09:14:30.233" />
  <row Id="10803" PostTypeId="4" CreationDate="2011-02-28T09:14:30.233" Score="0" ViewCount="" Body="[NXC][1] is a C-like programming language for the [Lego Mindstorms NXT][2] set. &#xD;&#xA;It is built on NBC, an assembler language for the NXT. It runs in a VM mainly designed by LEGO, but an [enhanced version][1] is made by John Hansen    &#xD;&#xA;&#xD;&#xA;&#xD;&#xA;  [1]: http://bricxcc.sourceforge.net/nbc/&#xD;&#xA;  [2]: http://mindstorms.lego.com/" OwnerUserId="-1" LastEditorUserId="3171" LastEditorDisplayName="" LastEditDate="2011-02-28T10:36:55.463" LastActivityDate="2011-02-28T10:36:55.463" />
  <row Id="10804" PostTypeId="1" CreationDate="2011-02-28T09:27:17.560" Score="1" ViewCount="173" Body="&lt;p&gt;I'm working in a project where we are developing a greenhouse control system, to take care of temperature, humidity... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the first step where we only log the parameters to an SD we have been using an Arduino board, but now we want to improve the system and add fans, humidifier, light sensing and control algorithms to maintain the greenhouse at a constant state. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because of the grow of the system we can't use the Arduino anymore, we are looking for a SBC or Microcontroller board, powerful enough to do the job but we don't want a painful migration, we are looking for a easy to use board with RTOS or ever better embedded Linux. And if it is possible it shouldn't be so expensive. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you know some product that fits our needs? or Could you recommend me another solution? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks you all :) &lt;/p&gt;&#xA;" OwnerUserId="2030" LastActivityDate="2011-02-28T14:06:12.270" Title="Controller for greenhouse control system" Tags="&lt;arduino&gt;&lt;pic&gt;&lt;control&gt;&lt;sbc&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="2" />
  <row Id="10805" PostTypeId="1" AcceptedAnswerId="10809" CreationDate="2011-02-28T09:49:31.097" Score="1" ViewCount="205" Body="&lt;p&gt;Hi everyone, i need to regulate the speed of a noisy kitchen FAN from a microcontroller (arduino board), i have been looking around and checked a lot of websites and schematics, and i think the solution should goes to a TRIAC regulator I think... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The point is that i have no knowledge in power electronics and i don't know witch circuit is going to be good and reliable. I have seen some circuits that use only a TRIAC and others that uses a TRIAC and a DIAC... Why is the difference? and the DIAC function? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you provide me with some good schematics or recommendation form my situation? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks you very much :)&lt;/p&gt;&#xA;" OwnerUserId="2030" LastActivityDate="2011-02-28T17:55:55.897" Title="220v AC Fan regulator" Tags="&lt;ac&gt;&lt;control&gt;&lt;fan&gt;&lt;regulator&gt;" AnswerCount="1" />
  <row Id="10806" PostTypeId="2" ParentId="10804" CreationDate="2011-02-28T09:49:44.037" Score="4" ViewCount="" Body="&lt;p&gt;Just take a nettop PC then ;-)&#xA;&amp;lt;200$ and lots of time saved on development &amp;amp; debugging.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-02-28T09:49:44.037" CommentCount="6" />
  <row Id="10807" PostTypeId="2" ParentId="4394" CreationDate="2011-02-28T09:49:49.833" Score="5" ViewCount="" Body="&lt;p&gt;I occasionally do chip design - as mentioned above many chips will intersperse power and grounds within parallel buses so that the drivers will have enough power (lead inductance is an issue - plus you don't want to starve the core when driving external loads).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However there are other issues - you might be constrained for on-die routing resources meaning it makes more sense to push those issues externally - I worked on a PCI interface where we tried hard to push pins to the right places (total system cost means getting to a 4 layer board can be important) but were constrained in some critical timing paths that meant we had to push some of the timing budget off-chip by moving the pads closer to the rest of the logic they drove while assuming longer external traces&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes you design a die but it goes into multiple packages - maybe the BGA package is optimally pinned out but not the QFP - or maybe the package was chosen late in the design cycle after the pads on the die were already chosen &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So there's lots of reasons - sometimes it really is that the chip designer didn't think ahead &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But remember for some buses you don't always have to wire up all pins exactly - if you're wiring up a SRAM/DRAM (or sometimes even flash if it's not being pre-loaded) you can often switch bits within a byte or even (carefully! depends on the chip) address bits&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-02-28T09:49:49.833" />
  <row Id="10808" PostTypeId="2" ParentId="10770" CreationDate="2011-02-28T09:55:54.960" Score="0" ViewCount="" Body="&lt;p&gt;If you're getting absolutely nothing from the FPGA I think you start with something simple - create a simple design that makes a counter and drives some pins with it - you should be able to watch them toggle with a 'scope - that will help you prove that the process of building bitstreams and loading them into the fpga is working - once you have those debugged then try something adventurous &lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-02-28T09:55:54.960" CommentCount="1" />
  <row Id="10809" PostTypeId="2" ParentId="10805" CreationDate="2011-02-28T10:14:49.483" Score="5" ViewCount="" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Word or warning - TRIAC control will generate noise in the windings of the motor (fan) coils. This can be almost as annoying as a fan running fast. The problem is the TRIAC switching on part way though the cycle gives a current surge and the winding will physically move (not damaging) which makes the deep hum.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also you need to check that you fan is a true AC fan and not what we call in the industry a EC fan. These are supplied by AC mains but have a internal PSU and then drive a DC fan - TRIAC control will not work on these fans.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However AC fans run very quiet if you run them of a step down transform, auto transformer which is good if you want a fixed speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would suggest looking at getting a replacement fan if you want quiet operation. DC fans are easy to speed control with either a PWM input or by voltage regulating them (DO NOT voltage chop a fan - its kills them). Or look of a fan with speed control inputs, two speed AC or EC fan.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just worth considering as a option from the start that all.&lt;/p&gt;&#xA;" OwnerUserId="2649" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-02-28T17:55:55.897" LastActivityDate="2011-02-28T17:55:55.897" />
  <row Id="10811" PostTypeId="2" ParentId="5476" CreationDate="2011-02-28T10:41:44.593" Score="0" ViewCount="" Body="&lt;p&gt;Short answer: yes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a few simulators: GHDL is open source and &lt;a href=&quot;http://www.gmvhdl.com/mac-dv.html&quot; rel=&quot;nofollow&quot;&gt;GmVHDL&lt;/a&gt; is commercial. Not as good as the mainstream simulators, but it will get you started.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is &lt;a href=&quot;http://www.sigasi.com&quot; rel=&quot;nofollow&quot;&gt;Sigasi&lt;/a&gt;, a VHDL design entry and code comprehension tool, which works on Mac. This will help you write your code before you send it to the simulator. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for synthesis tools, you should take a look at &lt;a href=&quot;http://www.plunify.com/&quot; rel=&quot;nofollow&quot;&gt;Plunify&lt;/a&gt;. The offer synthesis &quot;in the cloud,&quot; so that's not tied to any platform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will probably end up using VMWare or Parallels sooner or later, but sure you can get started designing VHDL on your Mac.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(disclaimer: I'm on the Sigasi team)&lt;/p&gt;&#xA;" OwnerUserId="3145" LastActivityDate="2011-02-28T10:41:44.593" />
  <row Id="10812" PostTypeId="1" AcceptedAnswerId="10832" CreationDate="2011-02-28T11:04:53.107" Score="2" ViewCount="105" Body="&lt;p&gt;To learn verilog, can anyone recommend any web-page or book?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have never seen such type of a language before, so what you recommend should be for beginner.&lt;/p&gt;&#xA;" OwnerUserId="3192" LastActivityDate="2011-02-28T18:18:01.540" Title="recommendation to learn verilog" Tags="&lt;books&gt;&lt;logic&gt;&lt;verilog&gt;&lt;tutorial&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="10813" PostTypeId="2" ParentId="10770" CreationDate="2011-02-28T11:28:40.853" Score="2" ViewCount="" Body="&lt;p&gt;Your design will not function correctly if it runs at 100 MHz but is only spec'd (by the tools) to run at 50 MHz. If it does, then it's a one-off miracle that wouldn't work when you make a change and rerun the tools. Don't do it. Don't even do it if your clock is 100 MHz and the tools tell you the design can run at 99.5 MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To solve your problem you can either write a simple 'divide by power of 2' clock divider to reduce the clock frequency (something like this in Verilog):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;reg [n:0] count; &#xA;&#xA;always @(posedge CLK_100) begin&#xA;  count &amp;lt;= count + 1;&#xA;end&#xA;&#xA;BUFG bg_0 (.I(count[m]), .O(CLK_DIV));&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(where 'm' &amp;lt;= 'n' and 'bufg' is a global clock buffer, and must be used for synchronous designs) or use a Digital Clock Manager (DCM).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully that solves your pipelining issues as well unless you absolutely have to run the entire design at 100 MHz. Other than pipelining you can consider using FIFOs if you have part of the design running at 50 MHz and the other at 100 MHz, but you'll have to say a bit more about what you're doing to get more meaningful help here. &lt;/p&gt;&#xA;" OwnerUserId="2531" LastActivityDate="2011-02-28T11:28:40.853" />
  <row Id="10814" PostTypeId="2" ParentId="10770" CreationDate="2011-02-28T11:32:25.087" Score="1" ViewCount="" Body="&lt;p&gt;Regarding 2) you should set your clock frequency in the system generator setup to 10ns to match what is incoming.  If you fail to meet timing then your design is not guaranteed to work - you either need to lower the incoming clock or improve the design until it does mpass the timing checks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For early development work in the lab you can often get away with missing timing by a few hundred picoseconds, but not by 10ns!  (And even if you get away with it in the lab, I certainly wouldn't ship a product which missed timing on that sort of constraint!)&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-02-28T11:32:25.087" />
  <row Id="10815" PostTypeId="2" ParentId="10758" CreationDate="2011-02-28T12:32:58.810" Score="0" ViewCount="" Body="&lt;p&gt;Trossen Robotics has some &lt;a href=&quot;http://forums.trossenrobotics.com&quot; rel=&quot;nofollow&quot;&gt;excellent forums&lt;/a&gt; for getting your questions answered. Both &lt;a href=&quot;http://botjunkie.com&quot; rel=&quot;nofollow&quot;&gt;BotJunkie&lt;/a&gt; and &lt;a href=&quot;http://www.robots-dreams.com&quot; rel=&quot;nofollow&quot;&gt;Robots-Dreams&lt;/a&gt; are two good blogs for keeping up with robotics news.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several very good robotics communities which you should check out, &lt;a href=&quot;http://letsmakerobots.com&quot; rel=&quot;nofollow&quot;&gt;Letsmakerobots&lt;/a&gt; and &lt;a href=&quot;http://diydrones.com&quot; rel=&quot;nofollow&quot;&gt;DIY Drones&lt;/a&gt; are two of the best. I've also created a site (&lt;a href=&quot;http://robotbox.net&quot; rel=&quot;nofollow&quot;&gt;RobotBox&lt;/a&gt;) where robot builders post their projects. You might get some inspiration there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For purchasing parts, I recommend &lt;a href=&quot;http://trossenrobotics.com&quot; rel=&quot;nofollow&quot;&gt;Trossen Robotics&lt;/a&gt;, &lt;a href=&quot;http://pololu.com&quot; rel=&quot;nofollow&quot;&gt;Pololu&lt;/a&gt;, &lt;a href=&quot;http://solarbotics.com&quot; rel=&quot;nofollow&quot;&gt;Solarbotics&lt;/a&gt;, or &lt;a href=&quot;http://www.lynxmotion.com&quot; rel=&quot;nofollow&quot;&gt;Lynxmotion&lt;/a&gt;. Those folks have been around for a long time. There are tons of smaller specialty outfits, but you can explore those as you gain knowledge. &lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-02-28T12:32:58.810" CommentCount="1" />
  <row Id="10816" PostTypeId="2" ParentId="10812" CreationDate="2011-02-28T12:36:25.843" Score="1" ViewCount="" Body="&lt;p&gt;When I was learning Verilog I mainly used two resources, the &lt;a href=&quot;http://www.sutherland-hdl.com/online_verilog_ref_guide/vlog_ref_top.html&quot; rel=&quot;nofollow&quot;&gt;Southerland Online Reference Guide&lt;/a&gt; and the &lt;a href=&quot;http://www.fpga4fun.com/&quot; rel=&quot;nofollow&quot;&gt;FPGA4Fun&lt;/a&gt; website. Verilog (for me) required a massive brain shift, so take it slowly. You can do a lot of stuff in simulation, but sometimes it's difficult to create the test waveforms you need. Actually having an FPGA to program helps a lot. You should be able to get a simple board for ~$100. FPGA4Fun sells some useful boards.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-02-28T12:36:25.843" CommentCount="1" />
  <row Id="10817" PostTypeId="5" CreationDate="2011-02-28T14:04:06.843" Score="0" ViewCount="" Body="&lt;p&gt;A Low drop-out voltage regulator is used as a power supply to step down a higher voltage to a lower voltage. eg. 7805 for 12VDC-&gt;5VDC conversion.&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-02-28T14:07:02.957" LastActivityDate="2011-02-28T14:07:02.957" />
  <row Id="10818" PostTypeId="4" CreationDate="2011-02-28T14:04:06.843" Score="0" ViewCount="" Body="A low-dropout or LDO regulator is a DC linear voltage regulator which can operate with a very small input–output differential voltage." OwnerUserId="-1" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-02-28T14:07:05.750" LastActivityDate="2011-02-28T14:07:05.750" />
  <row Id="10819" PostTypeId="2" ParentId="10804" CreationDate="2011-02-28T14:06:12.270" Score="3" ViewCount="" Body="&lt;p&gt;It's difficult to have the right answer for this question. Despite I have some suggestions.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You can use &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;Beagleboard&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wXdhy.png&quot; alt=&quot;Beagleboard&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.friendlyarm.net/products/mini2440&quot; rel=&quot;nofollow&quot;&gt;FriendlyArm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/99z0A.jpg&quot; alt=&quot;FriendlyArm overview&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/EjA9y.jpg&quot; alt=&quot;FriendlyArm running Android&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Or even the &lt;a href=&quot;http://mbed.org/&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/MnjcV.png&quot; alt=&quot;mbed&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-02-28T14:06:12.270" CommentCount="2" />
  <row Id="10820" PostTypeId="1" CreationDate="2011-02-28T14:08:55.663" Score="2" ViewCount="129" Body="&lt;p&gt;I am designing a device that automatically adjusts it's physical position as temperature changes. If the device it shut off or power is disconnected the device needs to remember it's last temperature and position. I have the ability to store these values in EEPROM but the problem is the position and temperature could be changing very rapidly. If I were to write the temp and pos to EEPROM after every time they changed that would (1) slow down the firmware a bit, and (2) likely kill the EEPROM after a year or two. So as I see it my options are as follows...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) use a capacitor/battery to keep the device powered for a short time after power is lost so that I can write the values to EEPROM at that time only. I don't like this because the board is kinda power hungry and this would require a big cap. And I don't have a ton of free space. And I don't want the added cost of a battery and battery holder / or a big cap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) use F-RAM instead of EEPROM so that I can write to it trillions of times without wearing it out. I don't like this option because FRAM is quite a bit more expensive than EEPROM and this is for a production product (not just one).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Only write the position and temperature every 5 minutes or so. That way I always have a fairly recent position/temp recorded but I am not writing every second so my program is not slowed down and the EEPROM won't die as fast. This seems like my best option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone else have any suggestions that I'm not thinking of?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2011-02-28T16:30:05.877" Title="Frequent Write to Non-volatile Memory" Tags="&lt;microcontroller&gt;&lt;eeprom&gt;&lt;non-volatile-memory&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="10821" PostTypeId="2" ParentId="10820" CreationDate="2011-02-28T14:39:30.277" Score="3" ViewCount="" Body="&lt;p&gt;1) Once you've started the write process, you only need to power the MCU/EEPROM and make sure the control lines don't glitch - I2C probably preferable to SPI for this. Only need a few mA for a few milliseconds so shoudn't be a big cap,and you could put the MCU to sleep once the write is initiated.&#xA;3) you can probably apply some intelligence, e.g. a holdoff - once written it always holds a certain time beore another write can happen. Or wait til value is stable for a while before writing.&lt;br&gt;&#xA;You can also increase endurance by spreading the data over a number of locations. &#xA;Microchip have some tools &amp;amp; appnotes to calculate endurance for their eeproms, which may be useful. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-02-28T14:39:30.277" CommentCount="2" />
  <row Id="10822" PostTypeId="2" ParentId="10820" CreationDate="2011-02-28T15:26:45.993" Score="1" ViewCount="" Body="&lt;p&gt;1) Possibly the simplest option, although it might require hardware changes. I've achieved this before without PBC modifications by just increasing the decoupling caps and interrupting on the brown-out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) As you've pointed out, the issue with FRAM is the price!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Depending on the volatility of your temperature and position data, you'll increase the endurance by only writing if the value has changed. You might be sampling the temperature once every second, but if it only changes every 5 minutes, the problem is solved. &lt;/p&gt;&#xA;" OwnerUserId="2770" LastActivityDate="2011-02-28T15:26:45.993" />
  <row Id="10823" PostTypeId="2" ParentId="10820" CreationDate="2011-02-28T15:44:11.970" Score="1" ViewCount="" Body="&lt;p&gt;Here's how I solved this problem in my project:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reserve 1 sector of flash to hold a bitmask of unused slots and a number of slots for the value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bitmask I used was 16 bytes long, so I had 128 slots to put values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bitmask is initialized to all ones, which in flash terms is the erased state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you want to write a new value, read in the bitmask and find the first bit that is a one.  This is the slot number where you will write the value.  Change that bit to a zero to mark it as used and write the bitmask back to flash without first erasing it.  Next, write the value to the slot after the bitmask also without erasing the flash.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This way, you extend the flash write cycles by 128 times by writing the new bitmask with only a change from a one to a zero.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the entire bitmask is 0, then erase the flash sector and start fresh.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-02-28T15:44:11.970" CommentCount="5" />
  <row Id="10824" PostTypeId="1" AcceptedAnswerId="10827" CreationDate="2011-02-28T15:47:16.787" Score="3" ViewCount="285" Body="&lt;p&gt;Basically we're building a simple setup with an Arduino board and some motors. The Arduino with motor shield will control several servo motors and DC motors, and possibly talk to a few sensors. This seems to work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But rather than hook up an XBee, or wifi or something complicated, we'd like to just throw a moto droid into the payload. This would give us A) long range communication through the internet B) a camera we could control via the internet C) realtime video from the droid's camera.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So our question is: the droid has a micro USB port on the side. What's the easiest way to plug that into an arduino (or go-between) and read/write data? I've seen a page where a guy used bluetooth, but I was hoping for a wired connection.&lt;/p&gt;&#xA;" OwnerUserId="2769" LastActivityDate="2011-02-28T17:55:41.557" Title="Control robot with Android phone" Tags="&lt;arduino&gt;&lt;usb&gt;&lt;android&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="10825" PostTypeId="2" ParentId="10824" CreationDate="2011-02-28T15:51:54.160" Score="0" ViewCount="" Body="&lt;p&gt;You probably need USB host mode to interface the phone, the Arduino isn't suitable for that. A controller with USB OTG, such as a suitable ARM device, might work.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-28T15:59:23.967" LastActivityDate="2011-02-28T15:59:23.967" CommentCount="2" />
  <row Id="10827" PostTypeId="2" ParentId="10824" CreationDate="2011-02-28T15:55:24.097" Score="4" ViewCount="" Body="&lt;p&gt;The neatest way I've seen is to drive continuous rotation servos by generating PWM signals as sound from the handset.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are lots of open source examples of cellphone bots at: &lt;a href=&quot;http://www.cellbots.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.cellbots.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://code.google.com/p/cellbots/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/cellbots/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-02-28T15:55:24.097" CommentCount="3" />
  <row Id="10831" PostTypeId="2" ParentId="10820" CreationDate="2011-02-28T16:30:05.877" Score="2" ViewCount="" Body="&lt;p&gt;I would suggest using a block-oriented flash device, and use one byte from each block as a mode flag.  Maintain as an invariant that almost all of the mode flags will be programmed; there will be only one block where the mode flag isn't programmed but the previous block's (wrapping if necessary) is.  That block will be the one with the most recent data.  When that block fills up, erase the following block (note that the block being erased could hold any combination of data during the erase cycle, and the invariant would still hold), then once the erase is done program the mode flag on what used to be the last block.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will be necessary to protect the supply to the flash well enough to ensure that any attempt to program a byte will either succeed or fail its entirety, but it won't matter if an erase cycle is interrupted leaving a block full of arbitrary data, since the next attempt to write a data entry will re-erase that block.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your data are 16 bits, a 64Kx8 chip will hold over 32,000 entries.  Writing one entry per second would fill the chip about 2.7 times.  Even a chip with an endurance of &quot;only&quot; 10K erase cycles would last over 10 years.  Use of a larger chip, or one with 100K endurance, would increase the useful life proportionally.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-28T16:30:05.877" />
  <row Id="10832" PostTypeId="2" ParentId="10812" CreationDate="2011-02-28T16:31:30.913" Score="2" ViewCount="" Body="&lt;p&gt;I've recently embarked on a simmilar journey my self and so far I've found the following useful:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This youtube video blog by Tbird761 (&lt;a href=&quot;http://www.youtube.com/watch?v=gsTpLtEEobE&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=gsTpLtEEobE&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and this book by Pong P. Chu (&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0470185325&quot; rel=&quot;nofollow&quot;&gt;FPGA Prototyping By Verilog Examples: Xilinx Spartan-3 Version [Hardcover])&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-02-28T16:31:30.913" />
  <row Id="10833" PostTypeId="2" ParentId="10790" CreationDate="2011-02-28T17:10:04.123" Score="1" ViewCount="" Body="&lt;p&gt;You might want something like &lt;a href=&quot;http://www.alibaba.com/product-gs/424227989/Mini_1_Channel_DC_12V_RF.html&quot; rel=&quot;nofollow&quot;&gt;this DC Toggle switch&lt;/a&gt;, but to be sure, we'd need more information on how this train works&lt;/p&gt;&#xA;" OwnerUserId="2006" LastActivityDate="2011-02-28T17:10:04.123" />
  <row Id="10835" PostTypeId="2" ParentId="10824" CreationDate="2011-02-28T17:55:41.557" Score="1" ViewCount="" Body="&lt;p&gt;Joby's method is probably the cleanest wired method at the moment. Android is moving toward having USB ports that are called USB On-the-go (OTG) which allows the phone to be a host or a slave. &lt;a href=&quot;http://groups.google.com/group/android-discuss/browse_thread/thread/ca061faaefcf243a&quot; rel=&quot;nofollow&quot;&gt;Here is a forum about it&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are wanting to be a bit more adventurous with bluetooth you should check out the &lt;a href=&quot;http://www.amarino-toolkit.net/&quot; rel=&quot;nofollow&quot;&gt;Amarino&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-02-28T17:55:41.557" />
  <row Id="10836" PostTypeId="5" CreationDate="2011-02-28T18:09:51.890" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-28T18:09:51.890" LastActivityDate="2011-02-28T18:09:51.890" />
  <row Id="10837" PostTypeId="4" CreationDate="2011-02-28T18:09:51.890" Score="0" ViewCount="" Body="C is an imperative (procedural) systems implementation language. It was designed to be compiled using a relatively straightforward compiler, to provide low-level access to memory, to provide language constructs that map efficiently to machine instructions, and to require minimal run-time support. C was therefore useful for many applications that had formerly been coded in assembly language." OwnerUserId="-1" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-02-28T18:17:15.253" LastActivityDate="2011-02-28T18:17:15.253" />
  <row Id="10838" PostTypeId="5" CreationDate="2011-02-28T18:12:55.007" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-02-28T18:12:55.007" LastActivityDate="2011-02-28T18:12:55.007" />
  <row Id="10839" PostTypeId="4" CreationDate="2011-02-28T18:12:55.007" Score="0" ViewCount="" Body="An embedded system is a computer system designed to perform one or a few dedicated functions often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts." OwnerUserId="-1" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-02-28T18:17:04.583" LastActivityDate="2011-02-28T18:17:04.583" />
  <row Id="10840" PostTypeId="2" ParentId="10812" CreationDate="2011-02-28T18:18:01.540" Score="1" ViewCount="" Body="&lt;p&gt;Probably the most important thing to understand about Verilog is that the tools you use to convert verilog (or vhdl) to gates have certain idioms that they use to map verilog to certain types of gates - you need to write using these to get what you want&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a (most simplest) rule:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;always @(posedge clk) &#xA;    q &amp;lt;= d;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;will give you a flop while&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;assign w = a|b;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;will give you a combinatorial (a logic net). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Understanding the differences between '=' and '&amp;lt;=' is important, but more important is simply making sure you use &amp;lt;= for all flops and = elsewhere.&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-02-28T18:18:01.540" />
  <row Id="10841" PostTypeId="1" AcceptedAnswerId="10846" CreationDate="2011-02-28T19:52:22.527" Score="2" ViewCount="131" Body="&lt;p&gt;One thing I do not understand in reading about doing Assembly with the Atmel AVR (or perhaps with Arduino platform) is the actual outputting to devices (like LEDS/motors) and such.&#xA;Most Assembly &quot;tutorials&quot; simply explain counting/numeric stuff with registers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone explain how exactly you send an out signal to a motor or LED under AVR assembly?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess I dont exactly get what each &quot;pin&quot; does for the microcontroller, and which ones can send output signals. (to turn a motor or led)&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-04-09T01:51:30.213" Title="Arduino/Atmel Output Assembly?" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;assembly&gt;" AnswerCount="3" />
  <row Id="10842" PostTypeId="2" ParentId="1689" CreationDate="2011-02-28T20:09:51.310" Score="2" ViewCount="" Body="&lt;p&gt;RS232 voltage-level signaling is becoming less common, as more and more devices are designed to plug into a USB port rather than an RS-232 port.  The common async 8-N-1 signaling protocol, however, allows data to be sent full duplex with predictable timing and no byte stuffing.  A byte can be started at any desired moment when the line is otherwise idle, and there is no danger of data underrun.  Hardware to support 8-N-1 signaling is common and cheap, and while the protocol isn't entirely optimal, many changes that would make it better for some applications would make it worse for others.  The only significant downside to 8-N-1 is that it requires that both sides of the communication have a stable clock which is a known (generally integer) multiple of the desired communications rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incidentally, most async 8-N-1 hardware allows for at least one type of out-of-band signalling: the long break.  While there are certainly times it would be helpful to have a few more types of out-of-band signaling, it's useful to have at least one.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-28T20:09:51.310" />
  <row Id="10843" PostTypeId="2" ParentId="10841" CreationDate="2011-02-28T20:13:09.693" Score="1" ViewCount="" Body="&lt;p&gt;Something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    #define LED PB3&#xA;&#xA;    sbi    DDRB,LED     ;PB3 output (LED)&#xA;&#xA;loop:&#xA;    sbi     PORTB,LED       ;LED on&#xA;    rcall   dly&#xA;    cbi     PORTB,LED       ;LED off&#xA;    rcall   dly&#xA;    rjmp    loop&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I've left out a lot of other stuff that is needed for a working program.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-02-28T21:03:16.313" LastActivityDate="2011-02-28T21:03:16.313" />
  <row Id="10844" PostTypeId="1" AcceptedAnswerId="10845" CreationDate="2011-02-28T20:21:01.780" Score="2" ViewCount="79" Body="&lt;p&gt;I'm looking to build a very basic computer around the Z8180 MCU, I'm looking for a schematics to get a start.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I got a bit experience with fundamental electronics, but I never dabbled with any type of CPU/MCU before. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any tips to get started is very appreciated. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I might add that the choice of processor is purely sentimental and there fore very definitive , Z80 it has to be, even if alternative is both better and simpler :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance !&lt;/p&gt;&#xA;" OwnerUserId="3186" LastActivityDate="2011-02-28T20:25:31.653" Title="Schematics for basic z80180 system" Tags="&lt;schematics&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="10845" PostTypeId="2" ParentId="10844" CreationDate="2011-02-28T20:25:31.653" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.g-photo.net/projects/hwproj3/gcb_manual_a.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is something that should get you started.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-02-28T20:25:31.653" />
  <row Id="10846" PostTypeId="2" ParentId="10841" CreationDate="2011-02-28T21:08:28.320" Score="4" ViewCount="" Body="&lt;p&gt;The AVR, like most microcontrollers, uses &lt;a href=&quot;http://en.wikipedia.org/wiki/Memory-mapped_I/O&quot; rel=&quot;nofollow&quot;&gt;memory-mapped IO&lt;/a&gt;.  In a nutshell, this means that a part of the memory space of the microcontroller is reserved for the peripherals.  When you change a bit in this area of memory, you're not sending a signal to change a bit of memory, you're sending a signal to change the value of a peripheral.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To understand the details of how this works on your AVR, the &lt;a href=&quot;http://www.nongnu.org/avr-libc/user-manual/group__avr__sfr.html&quot; rel=&quot;nofollow&quot;&gt;Special Function Registers&lt;/a&gt; section of AVR-libc (and, more importantly, sfr_defs.h and iom328p.h) are recommended reading.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;[Warning: Technical writing ahead, pay close attention] For example, &lt;code&gt;PORTB&lt;/code&gt; is defined as &lt;code&gt;_SFR_IO8(0x05)&lt;/code&gt; in &lt;code&gt;iom328p.h&lt;/code&gt;.  In &lt;code&gt;sfr_defs.h&lt;/code&gt;, &lt;code&gt;_SFR_IO8(io_addr)&lt;/code&gt; is defined as &lt;code&gt;_MMIO_BYTE((io_addr) + __SFR_OFFSET)&lt;/code&gt;.  &lt;code&gt;__SFR_OFFSET&lt;/code&gt; is &lt;code&gt;0x20&lt;/code&gt;, the location just after the registers.  The space after this address and before &lt;code&gt;RAMSTART (0x100)&lt;/code&gt; is used for the peripherals.  Going back to our example, &lt;code&gt;_MMIO_BYTE(mem_addr)&lt;/code&gt; is defined as &lt;code&gt;(*(volatile uint8_t *)(mem_addr))&lt;/code&gt;.  Therefore, when you write &lt;code&gt;PORTB&lt;/code&gt;, you're really writing &lt;code&gt;*(volatile uint8_t *)(0x25)&lt;/code&gt;, which defines a byte-wide pointer to the location in memory &lt;code&gt;0x25&lt;/code&gt;. [/Warning] &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, when  (in C) you write PORTB |= 0x01, you're really writing the value 1 to the peripheral at byte 0x25, or port B pin 0.  If this pin is configured as output (using DDRB, which is at 0x24), PORTB |= 0x01 will cause port B pin 0 to go high.  Phew!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, if you use the assembly instructions (SBI - Set Bit in I/O Register):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;sbi  0x24,1 ;Data direction set to output&#xA;sbi  0x25,1 ;Set port B pin 0 high&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You'll set the pin high.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, use inline assembler with GCC and &lt;code&gt;#include &amp;lt;avr/io.h&amp;gt;&lt;/code&gt; to get the conventional names and simplify your task.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that &lt;em&gt;all&lt;/em&gt; of the peripherals use this scheme, not just the IO pins.  Read iom328p.h if you're interested in the locations of other peripherals.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-02-28T21:08:28.320" />
  <row Id="10847" PostTypeId="2" ParentId="6534" CreationDate="2011-02-28T21:31:49.783" Score="0" ViewCount="" Body="&lt;p&gt;At such a low current level I would be inclined to pre-regulate down with say a 12v zener and stick a cheap-as-chips LDO on there&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-02-28T21:31:49.783" />
  <row Id="10848" PostTypeId="2" ParentId="10784" CreationDate="2011-02-28T22:00:32.493" Score="3" ViewCount="" Body="&lt;p&gt;Alas, many companies inexplicably neglect to post prices on their website, replacing it with the phrase &quot;call for a quote&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few companies that have prices for LCD displays on their website:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.newhavendisplay.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.newhavendisplay.com/&lt;/a&gt; (prices for 1, call for bulk quantity price)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.crystalfontz.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.crystalfontz.com/&lt;/a&gt; (prices in 1, 10, 500, etc)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/categories/76&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/categories/76&lt;/a&gt; (prices in 1, 10, 100)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.newark.com/graphic&quot; rel=&quot;nofollow&quot;&gt;http://www.newark.com/graphic&lt;/a&gt; (prices in 1, 10, 100)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=524918&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=524918&lt;/a&gt; (prices in 1, 10, 100, etc)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.jameco.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.jameco.com/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.mouser.com/Search/Refine.aspx?Keyword=LCD+graphic+display&quot; rel=&quot;nofollow&quot;&gt;http://www.mouser.com/Search/Refine.aspx?Keyword=LCD+graphic+display&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.alliedelec.com/search/searchresults.aspx?N=0&amp;amp;Ntk=Primary&amp;amp;Ntt=LCD+graphic+display&quot; rel=&quot;nofollow&quot;&gt;http://www.alliedelec.com/search/searchresults.aspx?N=0&amp;amp;Ntk=Primary&amp;amp;Ntt=LCD+graphic+display&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.allelectronics.com/make-a-store/category/365/LCDs-Liquid-Crystal-Displays/1.html&quot; rel=&quot;nofollow&quot;&gt;http://www.allelectronics.com/make-a-store/category/365/LCDs-Liquid-Crystal-Displays/1.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.futurlec.com/LCDDisp.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.futurlec.com/LCDDisp.shtml&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.tvielectronics.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.tvielectronics.com/&lt;/a&gt; (prices in 1, 25)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-02-28T22:00:32.493" CommentCount="2" />
  <row Id="10849" PostTypeId="1" CreationDate="2011-02-28T22:20:51.300" Score="1" ViewCount="159" Body="&lt;p&gt;Right now, I've got:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(x1 and y1)&#xA;(x2 and y2)&#xA;(x3 and y3)&#xA;(x4 and y4)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the outputs from these gates will give me 1 when the bits from both numbers are the same. The issue here is that I will get positive results when they are the same and when each bit is different from each other bit (because 0,0 will still give a 1 in an and gate).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm probably missing something very obvious here.&#xA;Thanks&lt;/p&gt;&#xA;" OwnerUserId="3197" LastActivityDate="2011-03-01T17:03:00.553" Title="Combinational circuit to check if two four bit numbers are equal" Tags="&lt;circuit&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="10850" PostTypeId="2" ParentId="7624" CreationDate="2011-02-28T22:32:17.087" Score="2" ViewCount="" Body="&lt;p&gt;One factor not yet mentioned is metastability.  If a latching circuit is hit with a sequence of input/transitions such that the resulting state would depend upon propagation delays or other unpredictable factors, there is no guarantee that the resulting state will be a clean &quot;high&quot; or &quot;low&quot;.  Consider, for example, an edge-triggered flip flop which is currently outputting a &quot;low&quot;, and has its input change from low to high at almost the same time as a clock edge arrives.  If the clock edge happens long enough before the input change, the output will simply sit low until the next clock edge.  If the clock edge happens long enough after the input change, the output will quickly switch once from low to high and stay there until the next clock edge.  If neither of those conditions applies, the output can do &lt;i&gt;anything&lt;/i&gt;.  It might stay low, or quickly switch once and stay high, but it might stay low for awhile and then switch, or switch and then some time later switch back, or switch back and forth a few times, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a design is fully synchronous, and all the inputs are double-synchronized, it is very unlikely that a timing pulse would hit the first latch of a synchronizer in such a way as to cause it to switch at the perfect time to confuse the second latch.  In general, it is safe to regard such things as &quot;just won't happen&quot;.  In an asynchronous design, however, it is often much harder to reason about such things.  If a timing constraint on a latching circuit (not just flip flops, but any combination of logic that would act as a latch) is violated, there's no telling what the output will do until the next time there's a valid input condition that forces the latch to a known state.  It is entirely possible that delayed outputs will cause the timing constraints of downstream inputs to be violated, leading to unexpected situations, especially if one output is used to compute two or more inputs (some may be computed as though the latch was high, others as though it were low).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The safest way to model an asynchronous circuit would be to have almost every output circuit produce an &quot;X&quot; output for a little while whenever it switches between &quot;0&quot; and &quot;1&quot;.  Unfortunately, this approach often results in nearly all nodes showing &quot;X&quot;, even in cases which would in reality have almost certainly resulted in stable behavior.  If a system can work when simulated as having all outputs become &quot;X&quot; immediately after an input changes, and remain &quot;X&quot; until the inputs are stable, that's a good sign the circuit will work, but getting asynchronous circuits to work under such constraints is often difficult.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-02-28T22:32:17.087" />
  <row Id="10851" PostTypeId="1" AcceptedAnswerId="10855" CreationDate="2011-02-28T22:35:59.967" Score="6" ViewCount="171" Body="&lt;p&gt;It seems common that PBX and other telephone hardware use a positive-ground power supply, where the &quot;hot&quot; line is at -48v.  What's the reason for that?&lt;/p&gt;&#xA;" OwnerUserId="2773" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-01T04:45:38.867" LastActivityDate="2011-03-01T04:45:38.867" Title="Why do PBX systems use -48 V?" Tags="&lt;telephone&gt;" AnswerCount="2" />
  <row Id="10852" PostTypeId="2" ParentId="10849" CreationDate="2011-02-28T22:38:49.093" Score="3" ViewCount="" Body="&lt;p&gt;4 x Xor gate... and 4 input nor gate&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Xor each pair of inputs then use a 4 input nor gate...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Xor gate gives 0 when both inputs are the same.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;a 4 input nor gate gives a logic 1 if all inputs are 0, and 0 if any input is 1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;or&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not((X1 XOR Y1) OR (X2 XOR Y2) OR (X3 XOR Y3) OR (X4 XOR Y4))&lt;/p&gt;&#xA;" OwnerUserId="2280" LastActivityDate="2011-02-28T22:38:49.093" CommentCount="1" />
  <row Id="10854" PostTypeId="2" ParentId="10851" CreationDate="2011-02-28T23:01:22.370" Score="0" ViewCount="" Body="&lt;p&gt;Also they use 48 V (regardless of polarity) because that is lower current so easier to distributed.  Now there are tons of chips and brick for -48 V to 12 V/5 V, etc. conversion.  And for UL and other safety limits it is easier to get approved if it is less than ~60 V.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-02-28T23:01:22.370" />
  <row Id="10855" PostTypeId="2" ParentId="10851" CreationDate="2011-02-28T23:42:28.627" Score="7" ViewCount="" Body="&lt;p&gt;I remember this coming up many years ago in the alt.telecom newsgroup and I managed to find it for you (aint I kind...!):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;https://groups.google.com/group/uk.telecom/browse_thread/thread/3f3f8849ecb69560/6caa52997088d247?hl=en&amp;amp;lnk=gst&amp;amp;q=%22-48v%22+reason#6caa52997088d247&quot; rel=&quot;nofollow&quot;&gt;https://groups.google.com/group/uk.telecom/browse_thread/thread/3f3f8849ecb69560/6caa52997088d247?hl=en&amp;amp;lnk=gst&amp;amp;q=%22-48v%22+reason#6caa52997088d247&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In summary (from the thread):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;&quot;From a book I've been reading lately (Instruction in Army telegraphy&#xA;and telephony, vol 1, 1917), the reason is for fault tracing. An earth&#xA;fault will tend to decrease in resistance, ie, tend towards a dead&#xA;earth, if the earth is positive with respect to the conductor, thus&#xA;enabling it to be located.&quot;&#xA;&#xA;&quot;48v (or in the UK, 50v) seems to be arbitrary, many of the earlier CB&#xA;systems of the Post Office used 22 volts or 40 volts. The automatic&#xA;systems in some early exchanges of the Siemens 17 type used 60 volts&#xA;IIRC.&#xA;&#xA;48 to 50v may have been a happy medium (remembering that years ago,&#xA;telecomms companies were VERY conservative, and standardized across&#xA;their entire network), allowing the use of long thin lines, but not&#xA;risking electrocution of linemen or overheating on short circuits. &quot;&#xA;&#xA;&quot;A negative voltage is really a positive earth potential.&#xA;If your positive conductor i(+) is earth, you can't short it to earth.&#xA;It can be shorted to the exchange earth connection if it comes into contact with&#xA;a suitable conductor in the cable,&#xA;but as this 'earth' is the negative battery terminal (technically) you don't get&#xA;the massive current flow to earth for a conductor to earth.&#xA;The only way you can get massive current flow is if you short the pair together&#xA;or put the positive earth to a foriegn wire connected to the negative battery&#xA;terminal. &quot;&#xA;&#xA;&quot;corrosion reduction - the leakage to earth that would occur if&#xA;insulation were damaged opposes the corrosion. &quot;&#xA;&#xA;&quot;Why negative? AFAIK to reduce electrolytic corrosion of buried cables,&#xA;which were lead-sheathed.&quot; &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1750" LastActivityDate="2011-02-28T23:42:28.627" CommentCount="1" />
  <row Id="10856" PostTypeId="2" ParentId="5764" CreationDate="2011-03-01T00:19:59.637" Score="3" ViewCount="" Body="&lt;p&gt;About 10 years ago, I bought a device called &quot;Party Line&quot; from a company whose name escapes me.  This device has six telephone jacks on it, and simulates the telephone main office.  You could plug in up to six regular phones, and they could call one another.  Think of it as a very simple PBX (with no connection to the real phone network).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any phone can dial any of the other five by dialing a 7-digit number where one of the digits indicates the line to connect to.  It only supports one connection at a time, though.  But for two phones, that's all you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought it as a kit, and assembled it myself.  Inside it has a PIC and some discrete circuitry.  I used it while developing some software that would transfer data over a modem connection.  I had two computers with 56K modems, each connected to the Party Line.  It worked very well, and I made thousands of calls from one system to the other without tying up my real line or incurring any charges.&lt;/p&gt;&#xA;" OwnerUserId="2773" LastActivityDate="2011-03-01T00:19:59.637" CommentCount="2" />
  <row Id="10857" PostTypeId="2" ParentId="10784" CreationDate="2011-03-01T04:43:43.440" Score="3" ViewCount="" Body="&lt;p&gt;If you're looking for ~500-1000 display panels with the intent to buy, I would &lt;em&gt;strongly&lt;/em&gt; suggest speaking with an account manager, sales rep, and/or applications engineer at a distributor.  Such an order will likely generate enough revenue for them to give you a whole lot more than the time of day.  I know the local account managers and FAE's for a few large component distributors in my area (&lt;a href=&quot;http://www.futureelectronics.com/&quot; rel=&quot;nofollow&quot;&gt;Future Electronics&lt;/a&gt; and &lt;a href=&quot;http://www.alliedelec.com/&quot; rel=&quot;nofollow&quot;&gt;Allied Electronics&lt;/a&gt;), and they are usually helpful, though not always prompt.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at Future, they do seem to have a few LCDs quoted on their site, however it is certainly not a comprehensive list.  If you contact a sales rep (there or anywhere) and provide them your requirements, they may come back with additional parts that their manufacturers produce that better fit your need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless your volumes are going to be in the millions, let me dispel any thoughts you have of &quot;Why not just talk to (LCD mfc) directly?&quot;.  Said manufacturers will &lt;em&gt;not&lt;/em&gt; care about you, and the premium they will charge to deal with you (if they bother at all) will be &lt;em&gt;higher&lt;/em&gt; than what a typical distributor would, because, frankly, they &lt;strong&gt;do not want&lt;/strong&gt; your direct business.  Use the middlemen.  They will make specifying, finding, and sourcing LCD panels vastly easier and cheaper.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-01T04:43:43.440" />
  <row Id="10860" PostTypeId="2" ParentId="8112" CreationDate="2011-03-01T05:55:10.920" Score="2" ViewCount="" Body="&lt;p&gt;if you want an efficient solution, using a Buck Converter would be a smart choice. you can build it with discrete components (inductor, diode, capacitor and transistor) or you can use some IC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Buck_converter&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Buck_converter&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="3199" LastActivityDate="2011-03-01T05:55:10.920" />
  <row Id="10861" PostTypeId="1" CreationDate="2011-03-01T06:04:56.220" Score="2" ViewCount="143" Body="&lt;p&gt;I have built a 3V to 5V boost converter with discrete components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;L = 220uH&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vf(Diode) = 0.25V&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ZVN4210A MOSFET&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C = 470uF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;f = 47KHz&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My load is a microcontroller board (M16C QSK62P Plus) that takes upto 90mA of current. I am using the PWM signal from the same microcontroller for the switching pulse for the converter.&#xA;I tested my circuit for a constant load of R = 100Ohm&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I measured average current flowing through the inductor and output voltage. &#xA;From that I calculated powers Pin and Pout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am getting the efficiency of approx. 75%. I know that boost converters can be more efficient (90%). So, I need some suggestion about modifications in my circuit to improve the efficiency.&lt;/p&gt;&#xA;" OwnerUserId="3199" LastActivityDate="2011-03-09T01:15:09.967" Title="How do I improve efficiency of a boost converter?" Tags="&lt;power-supply&gt;&lt;power&gt;&lt;boost&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="3" />
  <row Id="10862" PostTypeId="2" ParentId="10024" CreationDate="2011-03-01T06:31:35.970" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://opencircuits.com/motor_driver&quot; rel=&quot;nofollow&quot;&gt;Many motor drivers&lt;/a&gt; &lt;em&gt;can&lt;/em&gt; directly drive a 1.5 volt motor from a 5 V (or more) power supply,&#xA;because they have built-in current limiters (&quot;chopper circuit&quot;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alas, the &lt;a href=&quot;http://www.ladyada.net/make/mshield/faq.html&quot; rel=&quot;nofollow&quot;&gt;Lady Ada motor shield FAQ&lt;/a&gt; specifically says:&#xA;&quot;Can this shield control small 3V motors? Not really, its meant for larger, 6V+ motors.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It appears to me that you &lt;em&gt;can&lt;/em&gt; add a few power resistors to (inefficiently) drive a 1.5 V motor from the adafruit motor shield using the &quot;L/R driver&quot; system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.stepperworld.com/Tutorials/pgCurrentControl.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;Current Control of Stepper Motors&quot;&lt;/a&gt; document describes the older, less efficient &quot;L/R driver&quot; system, and compares it to the more modern and efficient (but complicated) &quot;chopper circuit&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This motor shield uses the L293D motor driver chip, which simply drives the output high or low, without any limit except its thermal protection limit.&#xA;To convert it to a L/R driver system:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Ir: Find the rated current Ir (if it's not written on the motor and you can't find the datasheet, measure the motionless coil resistance Rcoil with a multimeter and calculate Ir = 1.5 V / Rcoil). If this is more than the 0.6 A that the L293D can provide, do the remaining calculations with Ir = 0.6 A instead. (Example: measure 3 Ohms; Ir = 1.5 V / 3 Ohms so Ir = 0.5 A).&lt;/li&gt;&#xA;&lt;li&gt;Vdd: What is the voltage Vdd of your power supply? (Example: VDD = 5V, but lots of people prefer 12 V.)&lt;/li&gt;&#xA;&lt;li&gt;P: Your power resistors need to dissipate up to P = Ir*(Vdd - 1.5 V)/2. (Example: P = 0.5 A * (5 V - 1.5 V)/2 = 0.88 W)&lt;/li&gt;&#xA;&lt;li&gt;R: Your power resistors need a resistance of R = (Vdd - 1.5 V)/(2*Ir). (Example: R = (5 V - 1.5 V)/(2* 0.5 A) gives R = 3.5 Ohms).&lt;/li&gt;&#xA;&lt;li&gt;Get or make 4 identical power resistors that have approximately the above resistance and at least the above power rating. (Example: a 5 W, 4.7 Ohm resistor will work nicely ... or a series of 4 quarter-watt resistors in series, each one 1 Ohm, produces a 1 W, 4 Ohm resistor, which will also work nicely.)&lt;/li&gt;&#xA;&lt;li&gt;Connect one end of each resistor to one of the 4 halfbridge terminals on one side of the motor shield, the other end to one of the 4 pins of your bipolar stepper motor.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I assumed your motor was a 4 wire (bipolar) stepper motor.&#xA;Does this L/R thing work for DC motors also?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The L293D datasheet says it requires something in the range of 4.5 V to 36 V to function properly, so I wouldn't bother trying to power the adafruit motor shield from anything less than 4.5 V.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-01T06:31:35.970" />
  <row Id="10863" PostTypeId="1" CreationDate="2011-03-01T07:10:25.707" Score="1" ViewCount="178" Body="&lt;p&gt;Articles I read about this tell me to hook up a 1KOhm resistor between the Arduino's TX and the iPhone's RX. I understand this is because Arduino's signal is 5V and I want 3.3V going to the iPhone. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, where did they arrive at this value of 1KOhm? Is it documented somewhere that the serial signals are 1.7mA? &lt;/p&gt;&#xA;" OwnerUserId="3039" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T16:03:47.440" LastActivityDate="2011-03-08T22:50:14.063" Title="Arduino Serial TX to iPhone RX voltage drop?" Tags="&lt;arduino&gt;&lt;serial&gt;&lt;level-shifting&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="10864" PostTypeId="1" CreationDate="2011-03-01T07:22:34.873" Score="3" ViewCount="255" Body="&lt;p&gt;I've found several guides online on how to build a passive ethernet hub, the design is &lt;a href=&quot;http://www.zen22142.zen.co.uk/Circuits/Interface/pethhub.htm&quot; rel=&quot;nofollow&quot;&gt;always the same&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/RhIgF.gif&quot; alt=&quot;passive Ethernet hub by Miroslav Adzic&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wondering what each of the 2 anti-parallel diodes do? For both positive and negative current there's always one diode conducting, so what's the difference to just bridging the wires directly?&lt;/p&gt;&#xA;" OwnerUserId="3203" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-25T21:11:38.007" LastActivityDate="2011-03-25T21:11:38.007" Title="Building a passive ethernet hub with anti-parallel diodes" Tags="&lt;circuit&gt;&lt;ethernet&gt;&lt;diode&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="10866" PostTypeId="1" AcceptedAnswerId="10868" CreationDate="2011-03-01T07:48:20.680" Score="1" ViewCount="144" Body="&lt;p&gt;In my favorite CAD, &lt;a href=&quot;http://cadsoft.de&quot; rel=&quot;nofollow&quot;&gt;Eagle&lt;/a&gt;, there is a function called &quot;ratsnest&quot;, which removes all multisegment airwires and replaces them with one straight airwire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to wiki of &lt;a href=&quot;http://server.ibfriedrich.com/wiki/ibfwikien/index.php?title=Airwires_/_Ratsnest&quot; rel=&quot;nofollow&quot;&gt;some other CAD&lt;/a&gt;, &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;A multitude of airwires are called ratsnest.&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;But why is this feature/object has such a weird name? I was not able to find any reference to its history. (It is also possible that it is a well-known construct which I cannot recognize due to my non-English background. If so, can you point me to any dictionary?)&lt;/p&gt;&#xA;" OwnerUserId="1311" LastActivityDate="2011-03-01T09:24:12.753" Title="Why ratsnest is called so?" Tags="&lt;cad&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="10868" PostTypeId="2" ParentId="10866" CreationDate="2011-03-01T07:57:38.093" Score="10" ViewCount="" Body="&lt;p&gt;Here's what a real ratsnest looks like:&#xA;&lt;a href=&quot;http://www.flickr.com/photos/masneyb/2087687407/&quot; rel=&quot;nofollow&quot;&gt;http://www.flickr.com/photos/masneyb/2087687407/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Rat's nest&quot; is an English idiom meaning &quot;&lt;a href=&quot;http://www.thefreedictionary.com/rat&amp;#39;s+nest&quot; rel=&quot;nofollow&quot;&gt;a place of great clutter or disorder.&#xA;&lt;/a&gt;&quot;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-01T07:57:38.093" CommentCount="1" />
  <row Id="10869" PostTypeId="2" ParentId="10863" CreationDate="2011-03-01T09:07:15.773" Score="1" ViewCount="" Body="&lt;p&gt;someone probably mucked with resistors until the voltage came right, or maybe there's a pullup/down resistor sitting there on the input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or it's a high impedance input and 1.7mA is the most they feel comfortable pushing through the input's protection diodes&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It depends a lot on what the input circuit and impedance is - you might be better off (and safer) building a voltage divider (2 resistors of your own) you really don't want to be pulling inputs above their Vdd - you end up dumping that current into the protection diodes and making stuff hot (or mildy warm) - better off to start with a simple voltage divider and then looking at the signal levels on a 'scope - tweak to get the result near to 3.3v but lower&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-01T09:07:15.773" />
  <row Id="10870" PostTypeId="1" CreationDate="2011-03-01T09:08:48.517" Score="1" ViewCount="89" Body="&lt;p&gt;I would like to learn how to power some house hold appliances from solar energy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't had any experience with electronics but am eager to spent time reading and experimenting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done a little Googling which has been interesting for a start but has also raised some more questions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen a wide range of specifications for small solar systems, batteries, converters and inverters but haven't been able to work out the best combination to use to power say, a TV, a caravan fridge, a laptop and a microwave.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a formula that I can use to calculate the specs required for the solar panel/inverter/batteries and inverter?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A description of a working system with examples of what the system is powering and the sunlight hours required to keep it alive would be very helpful.&lt;/p&gt;&#xA;" OwnerUserId="3204" LastActivityDate="2011-03-31T13:26:23.213" Title="How do I go about powering appliances from solar energy" Tags="&lt;power&gt;&lt;solar-cell&gt;&lt;system&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10871" PostTypeId="2" ParentId="10864" CreationDate="2011-03-01T09:11:14.273" Score="0" ViewCount="" Body="&lt;p&gt;Each diode have a voltage drop, so if you apply voltage between A1, A3 there will be voltage drop across each diode, and both B and C computers will receive signal = voltage drop on 1 diode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why not connect directly? Probably that's about collision detection, no ideas actually...&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-01T09:11:14.273" />
  <row Id="10872" PostTypeId="2" ParentId="10861" CreationDate="2011-03-01T09:18:01.447" Score="4" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Your inductor probably have high serial resistence. You might want to take lower value with thicker wire. Increase frequency if needed (but not too high, switching losses increases).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Use ulta-low ESR caps, tantalum ones. Add some 0.1 + 22-66uF of ceramic cap in parralel. If frequency is high enough just leave ceramic.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Implement synchronious rectification to get rid of that 0.25 vDrop (and I am not sure it's really 0.25, should be higher)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Use proper MOSFET. Why take 100V part? 1.5Ohm Rds? This is not suitable for efficient DCDC. You want some 12-24V logic-level MOSFET with some 0.1 - 0.01 Rds.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-03-01T09:23:51.737" LastActivityDate="2011-03-01T09:23:51.737" />
  <row Id="10873" PostTypeId="2" ParentId="10864" CreationDate="2011-03-01T09:19:22.190" Score="1" ViewCount="" Body="&lt;p&gt;I think the voltage drop over the diodes between xmt and rcv for each leg is high enough so it can't see itself - but can see the others - probably only works for exactly 3 legs&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-01T09:19:22.190" CommentCount="2" />
  <row Id="10874" PostTypeId="2" ParentId="10866" CreationDate="2011-03-01T09:24:12.753" Score="1" ViewCount="" Body="&lt;p&gt;it also looks a lot like the bunch of straw a rat might use to build a nest&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-01T09:24:12.753" />
  <row Id="10875" PostTypeId="2" ParentId="10870" CreationDate="2011-03-01T09:27:17.597" Score="1" ViewCount="" Body="&lt;p&gt;Take for example &lt;a href=&quot;http://www.seeedstudio.com/depot/1w-solar-panel-75x100-p-633.html?cPath=155&amp;amp;zenid=4b1a07633e6e18040020c4399b23bd55&quot; rel=&quot;nofollow&quot;&gt;this solar cell&lt;/a&gt;. It has a maximum peak power output of 1W, and you can fit about 130 of them in on square meter. This would be 130W peak output. &quot;Peak output&quot; would be at the equator at midday on a clear day. You can adjust for latitude and time-of-day using simple trigonometry and add a factor for cloud cover. My feeling is that, depending on your geography and climate, you'd be lucky to get a tenth of that as a peak on any given day under regular circumstances.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All this conspires to require very large surfaces if you need to produce enough power to power appliances.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-03-01T09:27:17.597" />
  <row Id="10876" PostTypeId="1" CreationDate="2011-03-01T10:15:10.817" Score="0" ViewCount="115" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone come across any hardware that we can put out on a remote site (in a field) that uses a sim card to create a gprs connection to a mysql database server.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've looked at the arduino but that protection we'd need to put around it to &quot;industrialise&quot; it is very costly,&lt;/p&gt;&#xA;" OwnerUserId="3205" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-01T10:32:28.993" LastActivityDate="2011-03-01T10:32:28.993" Title="In need of hardware to connect to a mysql server over gprs" Tags="&lt;arduino&gt;&lt;remote&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="10877" PostTypeId="2" ParentId="10876" CreationDate="2011-03-01T10:31:25.620" Score="2" ViewCount="" Body="&lt;p&gt;I think you may want something like &lt;a href=&quot;http://www.sparkfun.com/products/10138&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;. It has a sim card slot and an antenna connector. It supports SMS text messages, GSM/GPRS, TCP/IP etc. To get started I'd get one of these and the corresponding evaluation board, transitioning to a custom PCB with a similar form-factor for the product. Then you can put everything into a neat square enclosure and off you go.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-03-01T10:31:25.620" />
  <row Id="10878" PostTypeId="2" ParentId="10870" CreationDate="2011-03-01T13:13:53.180" Score="1" ViewCount="" Body="&lt;p&gt;Solar cells can't generally be used to power appliances continuously (unless you have very big ones or expensive ones).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, what you can do is use them to charge a battery. You can then use this battery to power your appliances directly if they are 12v (such as a caravan appliance) or via an AC inverter. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the amount of energy hitting the solar cell, the battery will charge very slowly. So after a full day of charging, you might only be able to power your appliances for around 5 to 30 mins at a time, also depending on the power consumed by the appliance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you had datasheets for the solar cells and batteries, and power ratings for the appliances, then it might be possible to more accurately predict how long you can power stuff for.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-01T13:13:53.180" />
  <row Id="10879" PostTypeId="1" AcceptedAnswerId="10931" CreationDate="2011-03-01T13:35:14.113" Score="4" ViewCount="228" Body="&lt;p&gt;So I'm using a PIC32, it's rated for 80 MHz operation. But my crystal might be inaccurate, so it could oscillate at 80.01 MHz. I can presume this is okay, but what if I were to use a 7.3728 MHz crystal and an 11x PLL, would running it at ~81 MHz be okay? I suppose what I'm asking is how far is too far? And why do manufacturers not include a bit of overun (for example rating it at 81 MHz?)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-03-02T13:15:57.283" LastActivityDate="2011-04-10T07:54:42.223" Title="How much overclocking is &quot;okay&quot;?" Tags="&lt;clock&gt;&lt;overclocking&gt;&lt;pic32&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="1" />
  <row Id="10881" PostTypeId="2" ParentId="10879" CreationDate="2011-03-01T13:58:44.330" Score="7" ViewCount="" Body="&lt;p&gt;Manufacturers specify a maximum clock speed for a reason, as it guarantees correct operation under all conditions specified in the data sheet. Operating a device outside its specification might be OK in a hobbyist application, where an occasional failure can be tolerated, but isn't a good idea if reliability is important. You will have to test the system and see if it is sufficiently reliable for your requirements, under all circumstances.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't see 81 MHz causing a problem, but it can't be guaranteed.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-01T13:58:44.330" />
  <row Id="10882" PostTypeId="2" ParentId="10879" CreationDate="2011-03-01T14:14:42.600" Score="5" ViewCount="" Body="&lt;p&gt;In fact, most of these low-speed chips can work on 1.5x frequency in normal conditions, the only problems are at extreme temperatures (like -55 or 125) + flash/EEPROM writing. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if you you are building device which will be operated at 15-40C range, you may test that it works at 120Mhz and leave at 100 permanently.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;:-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Manufacturers underspec devices to increase yeld rates &amp;amp; reduce reclaims.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-01T14:14:42.600" CommentCount="4" />
  <row Id="10883" PostTypeId="1" AcceptedAnswerId="10895" CreationDate="2011-03-01T14:16:46.780" Score="2" ViewCount="90" Body="&lt;p&gt;I am going to try to interface a low-speed 8-bit DDR2 chip with an FPGA, and I've got some questions crucial to make it work:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is that correct that there is on-die termination on both DDR2 memory and controllers (an Altera Cyclone 3 FPGA in my case), so no additional termination resistors are required?&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-01T16:25:32.800" LastActivityDate="2011-03-01T16:25:32.800" Title="Do DDR2 chips and controllers have on-die termination?" Tags="&lt;altera&gt;&lt;ddr2&gt;&lt;sdram&gt;&lt;termination&gt;&lt;cyclone3&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10884" PostTypeId="1" AcceptedAnswerId="10954" CreationDate="2011-03-01T14:17:30.133" Score="5" ViewCount="361" Body="&lt;p&gt;I am going to try to interface low-speed 8bit DDR2 chip to FPGA, and I've got some questions crucial to make it work :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is that correct that the idea of termination resistor is to sink most of the signal to GND, so that only small part of it reflected back? Have anyone tried to put let's say 2-3 resistors of smaller value so that multiple remining reflections will be out of phase &amp;amp; cause less interference?&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-03-02T18:11:54.893" LastActivityDate="2011-04-21T17:32:41.223" Title="How termination resistors work; what happens if I use lower values?" Tags="&lt;signal&gt;&lt;termination&gt;&lt;signal-integrity&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="10885" PostTypeId="1" AcceptedAnswerId="10902" CreationDate="2011-03-01T14:18:15.080" Score="2" ViewCount="163" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am going to try to interface low-speed 8bit DDR2 chip to FPGA, and I've got some questions crucial to make it work :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) What is up with controlled impedance of PCB traces? Why it's important? What will happen if I would just have usual non-controlled 0.15mm traces? (distance between FPGA &amp;amp; DDR2 chips is 5cm).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Aligning trace length (especially on data &amp;amp; clock lines) is pretty clear, shouldn't be a problem as distances &amp;amp; frequency is low. As far as I understand there is still some 5-20cm length difference tolerance on DQ, but no harm making it equal.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-01T15:52:49.647" LastActivityDate="2011-03-01T18:01:10.807" Title="Do I need to control trace impedance for DDR2 memory?" Tags="&lt;pcb&gt;&lt;impedance&gt;&lt;ddr2&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10886" PostTypeId="1" AcceptedAnswerId="10887" CreationDate="2011-03-01T14:27:42.780" Score="3" ViewCount="146" Body="&lt;p&gt;When is it actually practical to use a fuse?&#xA;Like lets say your building a robot using an Arduino.....what area would you want to protect the most with a fuse?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mean do they even make fuses that small (5v's and such) and how do you go about &quot;connecting&quot; them to wires, since the smaller ones seem to be a solid cylinder&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-03-01T15:38:45.303" Title="When should you use a fuse?" Tags="&lt;arduino&gt;&lt;electronics&gt;&lt;fuses&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="10887" PostTypeId="2" ParentId="10886" CreationDate="2011-03-01T14:42:56.473" Score="3" ViewCount="" Body="&lt;p&gt;You need a fuse if you want to limit possible damage if something got shorted. This is defenetly possible with non-protected LiIon batteries for example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For low-voltage applications there are self-healing fuses (often found on motherboards, especially for USB protection).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For non-autonomous robot I would just have 1 fuse on battery, so that it would not burn.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For autonomous one you might need one per each power consumer + sensors to react on shorted engines e.t.c.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-01T14:42:56.473" CommentCount="5" />
  <row Id="10888" PostTypeId="2" ParentId="10790" CreationDate="2011-03-01T14:43:01.760" Score="0" ViewCount="" Body="&lt;p&gt;Are you ok with the remote working in Line of sight ? If yes you can use IR to control it.&#xA;I think there will not be any circuit that drives motor in them and will be rigged directly to the battery. In case it produces some kinda music then there might be a circuit for it in parallel. But you can get this working pretty easily even if it does have a circuit but for any result you will have to open it and see inside :D&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a small circuit you should be able toggle the power to the motor. I would first connect my motors directly to the battery and see how much current it draws and then decide on using either some motor controller or MOSFET for this JOB and the use a simple IR receiver and few electronics component to rig up a small circuit. This should be fairly easy. For having circuit level help you need to post the details as of how much motor it uses (my guess is 1) and how many batteries it is powered with.&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2011-03-01T14:43:01.760" />
  <row Id="10889" PostTypeId="2" ParentId="10849" CreationDate="2011-03-01T15:38:14.650" Score="1" ViewCount="" Body="&lt;p&gt;&quot;0,0 will still give a 1 in an AND gate&quot;. No, it won't. Are you using four 2-input AND gates feeding a 4-input AND? That will only be true when all of the inputs are true (1). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Testing for equivalence needs more than AND. To test A==B, you need to do A AND B OR NOT A AND NOT B, typically written AB + A'B'. This is called an XNOR gate (*), i.e. eXlusive N(egative)OR. In your case you just need to AND together the output from 4 XNOR gates.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(*) I think exclusive NOR is a bad name. It would be better to call it an inclusive AND. That would help with mixed logic design in which you start with all positive logic and slashes for complements. I grabbed this image from a paper on this subject by Mohamad Adnan Al-Alaoui:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ntU1M.png&quot; alt=&quot;Inclusive AND&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Inclusive AND: (A + B') * (A' + B) = (A * B) + (A' * B')&#xA;Exclusive  OR: (A * B') + (A' * B) = (A + B) * (A' + B')&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Edit: The inclusive AND includes the case in which they're both false, and the exclusive OR excludes the case in which they're both true. Much confusion arises when one isn't clear about the exclusivity of a condition. Someone will ask if it's &quot;A or B&quot; (OR) but really mean to ask if it's &quot;Either A or B, but not both&quot; (XOR). Also, I think in this case the question was using AND in an inclusive sense to mean equivalence.&lt;/p&gt;&#xA;" OwnerUserId="721" LastEditorUserId="721" LastEditorDisplayName="" LastEditDate="2011-03-01T17:03:00.553" LastActivityDate="2011-03-01T17:03:00.553" />
  <row Id="10890" PostTypeId="2" ParentId="10886" CreationDate="2011-03-01T15:38:45.303" Score="2" ViewCount="" Body="&lt;p&gt;I would connect the fuses inline, if you can't make your own board with through-hole fuse holders.  Something like this: &lt;a href=&quot;http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_109330_-1&quot; rel=&quot;nofollow&quot;&gt;http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_109330_-1&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/yD9kN.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-03-01T15:38:45.303" />
  <row Id="10891" PostTypeId="2" ParentId="9108" CreationDate="2011-03-01T15:57:16.053" Score="0" ViewCount="" Body="&lt;p&gt;Parity is generally useless with &quot;normal&quot; async-style communication, but it may be useful in some other contexts.  For example, some differential coding schemes require that every character have an even number of line transitions so that the final state of the line will match the initial state.  Code 39 barcodes use parity, sort of(*), to validate individual characters, and generally eliminate the need for a checksum character.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If single-bit errors were much more common and multi-bit errors or framing errors, per-byte parity checking could be a useful adjunct to a checksum or CRC, since locating a byte with an error would allow the error to be corrected.  In most practical situations involving UARTs, however, many line glitches cause framing errors, making data recovery in many cases impossible with or without per-byte parity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(*) A valid Code 39 character must have an odd number of wide spaces (1 or 3) and an even number of wide bars (0 or 2).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-01T15:57:16.053" CommentCount="7" />
  <row Id="10892" PostTypeId="2" ParentId="10884" CreationDate="2011-03-01T15:59:52.727" Score="4" ViewCount="" Body="&lt;p&gt;They match the impedance to the trace impedance.  That's why there isn't a reflection.  The fact that they may sink current is just a side effect.  Their values should be calculated based on the trace impedance and that of the receiver and driver.  High-Speed Digital Design by Johnson &amp;amp; Graham is the book I recommend on this topic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Multiple smaller value resistors will attenuate the signal too much.  It also may be more current than the driver can handle.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-01T15:59:52.727" />
  <row Id="10893" PostTypeId="2" ParentId="10884" CreationDate="2011-03-01T16:04:23.537" Score="2" ViewCount="" Body="&lt;p&gt;The principle behind termination resistors is to match the impedance of your inputs to the impedance of your transmission line (PCB) traces) and your source. Typically, input pins have high input impedance, since they are CMOS. Adding a small value resistor in parallel with the high impedance input pin will effectively set the input impedance to the resistor you added. This is useful, because output impedance is usually fairly low, and it is easy to make a micro strip transmission line with low impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The goal when using a termination resistor is to make it a close to the input pin as possible. Using multiple resistors would be less optimal since the resistor is less like a lumped element. The other thing is that you should know your target impedance. Having a resistance larger or smaller than your impedance will result in mismatch, which causes reflections.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-03-01T16:04:23.537" />
  <row Id="10894" PostTypeId="2" ParentId="10884" CreationDate="2011-03-01T16:04:48.340" Score="1" ViewCount="" Body="&lt;p&gt;I don't fully know the mechanics of it, but the purpose of the termination resistor is to make it appear as though the transmission path carries on forever.  Any change in impedance will cause reflections, such as connectors, damage to the transmission path, or (obviously) transition to a path with different impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a lower value resistor (I'm not sure what you mean by multiple smaller-value resistors&amp;mdash;if you put them in whatever configuration, you'll just get some other effective resistance with worse HF performance as it's spread out) will cause your drivers to source and sink higher powers than normal, which may cause damage.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Reflection_coefficient&quot; rel=&quot;nofollow&quot;&gt;reflection coefficient&lt;/a&gt; would be negative, so the reflected wave would have a 180° phase-shift as a result of transitioning to a lower impedance medium.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-01T16:04:48.340" />
  <row Id="10895" PostTypeId="2" ParentId="10883" CreationDate="2011-03-01T16:20:00.200" Score="2" ViewCount="" Body="&lt;p&gt;Yes, all DDR2 chips have it on-board. It is a required part of the standard.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-01T16:20:00.200" CommentCount="2" />
  <row Id="10896" PostTypeId="2" ParentId="6986" CreationDate="2011-03-01T16:39:24.630" Score="2" ViewCount="" Body="&lt;p&gt;A latch may guarantee that if the clock input has a rising edge and remains high for at least Twidth, and the data input is high at least Tsetup before a rising clock edge and remains high for at least Thold after, then within Tpd the output of the latch will be high and remain so until the next rising clock edge.  That does not mean, however, that the output of the latch will never change at a time more than Tpd removed from a rising clock edge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In an ideal world, if a latching circuit receives a stimulus which may or may not cause it to change state, one of two things would always happen:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The stimulus will visibly change the latch state immediately; the latch will remain in that particular changed state until the next stimulus.&#xA;&lt;li&gt;The stimulus will not change the latch state at all; the latch state will remain unchanged until the next stimulus. &#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, there's another possibility:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The latch state may be changed in a way that is not by immediately or fully apparent for some time; the visible state may change at some arbitrary future time, unless a &quot;clean&quot; stimulus puts the latch into a known state.&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;To use a crude physical analogy, if a standing bowling pin is hit soundly, it will fall over immediately.  If it's hit very weakly, it may be nudged slightly off vertical, but will quickly return to standing firmly.  If it's hit somewhere in the middle, though, it may wobble around awhile before either returning to a steady upright state or toppling over.  It may not be apparent for a over a second what the pin would end up doing if left undisturbed.  The worst-case time to determine if a pin has been hit hard enough to topple it may far exceed the time that would be required to determine a clean hit or miss.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The closer a latch's stimulus is to one which would either almost or barely cause it to permanently change state, the longer it may take the latch to produce a cleanly-resolved output.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would seem like it would be possible to design a latching circuit with a three-phase output, where the three phases were &quot;high&quot;, &quot;low&quot;, and &quot;wobbly&quot;, and have downstream circuitry wait for the latch to produce a clean output before using the output value.  Unfortunately--returning to the bowling analogy--while it may be possible to tell that a pin has fallen over sufficiently that it's not going to right itself, and it may be possible to tell that a pin has sufficiently stabilized that it's not going to fall unless it's hit again, there no clear and unambiguous way of establishing the moment where the pin's outcome becomes certain.  No matter what one does, there will always be a theoretically-possible &quot;trouble case&quot;.  The best one can do, oftentimes, is let the pin sweeper come in and reset the state of the system, and hope there's no disagreement about whether the pin should be counted as having fallen before the pinsweeper got it.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-01T16:39:24.630" />
  <row Id="10897" PostTypeId="1" AcceptedAnswerId="10905" CreationDate="2011-03-01T17:15:27.137" Score="0" ViewCount="135" Body="&lt;p&gt;I'm tinkering with a cheap old alarm clock LCD screen. I think the LCD is multiplexed (there is only one row of connectors along the top of the screen, etched (or something) into the glass, and there doesn't appear to be any common ground or anything from the circuit board the LCD rests against). The clock itself is powered by a single AAA battery. There is no driver circuit board or anything directly attached to the LCD (as many hobbyist purpose-built ones seem to have), so I need to provide the current directly to the LCD. It appears that the screen itself receives about 3 V AC to activate a given region, as measured by a multimeter from the alarm clock circuit board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question: how can I create this AC current from a DC source of around 1.5 V DC? Would it be possible to also do this from 5 V DC (provided by my Arduino)? I would like to avoid (if at all possible) up-converting to 110 V AC first (it seems to be a common recommendation from google searches). I have many basic components (resistors, caps, transistors, pots, diodes, etc) laying around in my 'nerd boxes' which I would prefer to use over specialized components, such as purpose-made inverters or the such, to do this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As may be evident, I am somewhat new to electronics tinkering and as such may be way off with my expectations. I will respond to comments/answers, and can post pictures once I get home if it would help. I appreciate any help I can get on this :)&lt;/p&gt;&#xA;" OwnerUserId="3122" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-01T18:09:33.787" LastActivityDate="2011-03-04T16:19:57.630" Title="Powering an old alarm clock LCD (need to invert DC to 3 V AC)" Tags="&lt;lcd&gt;" AnswerCount="3" />
  <row Id="10898" PostTypeId="1" AcceptedAnswerId="10901" CreationDate="2011-03-01T17:27:54.677" Score="1" ViewCount="182" Body="&lt;p&gt;I am new to Embedded systems. I am starting my learning with AT89C51.&#xA;My first target will be LCD interfacing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a programmer an LCD and a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the program is written in C or assembly language and I need a .HEX file to burn.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I do this?&#xA;I have also heard about Keil IDE but its evaluation version is not working.&#xA;Please help me with any additional information.&lt;/p&gt;&#xA;" OwnerUserId="2951" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-01T17:39:56.230" LastActivityDate="2011-03-01T18:24:58.677" Title="Converting c file to HEX" Tags="&lt;c&gt;" AnswerCount="2" />
  <row Id="10899" PostTypeId="1" AcceptedAnswerId="10907" CreationDate="2011-03-01T17:29:39.703" Score="2" ViewCount="87" Body="&lt;p&gt;I recently bought some 0805 Multicomp PTC/resettable fuses from Farnell. They were MC36213 (500mA) and MC36206 (200mA). I plan to use these in product which may exist in a high humidity (~80-90%) environment, although that is not my main concern: instead, what is written on the package:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;CAUTION: MOISTURE SENSITIVE DEVICES!&#xA;&#xA;The product in this package is a moisture sensitive device.&#xA;&#xA;The package in which it is supplied will offer physical and &#xA;electrical protection but will not offer sufficient protection&#xA;to prevent moisture ingress.&#xA;&#xA;These items should be baked for a minimum of 48 hours at 125C&#xA;prior to reflow.&#xA;&#xA;Moisture sensitivity level: 4&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Now, I have no idea how I will be able to bake them at 125°C for 48 hours. I do not have the ability to do so. Especially not at a reasonable price. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I have to do this, or is it a mistake? How can I prevent damage to these fuses from moisture? What happens if they do get moisture on them? Will they not work properly to protect a power supply against short circuits and over-current? How can I bake them at such a temperature? I plan to reflow them on a hotplate for the initial prototypes, but I'm not sure if that's the &quot;reflow&quot; they talk about.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-02T20:23:58.417" Title="Are PTC/resettable fuses really moisture senstive?" Tags="&lt;reflow&gt;&lt;moisture&gt;&lt;ptc&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="10900" PostTypeId="2" ParentId="10899" CreationDate="2011-03-01T17:34:32.487" Score="4" ViewCount="" Body="&lt;p&gt;The reason for having to pre-bake the parts is to prevent damage during the thermal gradient applied during automated soldering (wave / reflow / whatever) caused by expansion of moisture absorbed by the part during its pre-assembly storage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There isn't an issue once the part is installed in the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's &lt;a href=&quot;http://www.assemblymag.com/Articles/Feature_Article/c8c111024f64a010VgnVCM100000f932a8c0____&quot; rel=&quot;nofollow&quot;&gt;some more information on the subject&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-03-01T18:06:09.370" LastActivityDate="2011-03-01T18:06:09.370" CommentCount="2" />
  <row Id="10901" PostTypeId="2" ParentId="10898" CreationDate="2011-03-01T17:37:36.840" Score="3" ViewCount="" Body="&lt;p&gt;You need a compiler (and an assembler and a linker), also known as a toolchain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The compiler converts your C program source code into executable object code for your target machine. This object code can be represented as a series of hex digits in a .hex file.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Compiler&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Compiler&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://sdcc.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;SDCC&lt;/a&gt; is a free compiler which supports the AT89C51.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-01T17:37:36.840" CommentCount="0" />
  <row Id="10902" PostTypeId="2" ParentId="10885" CreationDate="2011-03-01T17:45:41.487" Score="2" ViewCount="" Body="&lt;p&gt;Since you mentioned that it will be low-speed then you most likely should not bother about impedance. The question is what exactly speed you are planning to go for?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My experience shows that you should think about impedance if the memory speed over 200MHz. If it's less than this number, there shouldn't be any problem, unless you have unusual PCB setup (6 layers, for example). But if you have, let's say, 4 layer PCB with two dedicated power planes, traces up to 3 inches can be even left without any termination at all. Just align the traces and you're done.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, if something went wrong, you always have the possibility to talk with memory on lower speeds.&lt;/p&gt;&#xA;" OwnerUserId="1603" LastActivityDate="2011-03-01T17:45:41.487" CommentCount="11" />
  <row Id="10904" PostTypeId="2" ParentId="10897" CreationDate="2011-03-01T18:04:20.713" Score="1" ViewCount="" Body="&lt;p&gt;Does your LCD look something like &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet/UMC/mXyztwvs.pdf&quot; rel=&quot;nofollow&quot;&gt;what's in this datasheet&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may find that using a micro (to generate PWM) is more practical than inverting DC to AC. I doubt that the LCD will draw much current.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-01T18:04:20.713" CommentCount="2" />
  <row Id="10905" PostTypeId="2" ParentId="10897" CreationDate="2011-03-01T18:16:30.160" Score="2" ViewCount="" Body="&lt;p&gt;You identified the LCD as being multiplexed&amp;mdash;which it very likely is&amp;mdash;so the AC you're seeing is probably just some segment being sequenced.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A microcontroller toggling pins in succession will indeed produce AC, however calling &quot;x V AC&quot; that is an extreme red herring.  It is better described as a multiplexed signal with such a frequency and some voltage (amplitude, not AC voltage as measured by a meter).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Atmel's app note &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc8103.pdf&quot; rel=&quot;nofollow&quot;&gt;AVR340: Direct Driving of LCD Using General &#xA;Purpose IO&lt;/a&gt; may be of use to you.  This portion describes the &quot;AC&quot; that you're seeing and shows why.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tZb7z.png&quot; alt=&quot;LCD PWM waveforms&quot;&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;To energize a segment, the waveform to that segment must be 180 degrees out of phase with its COM waveform.  The voltage difference between the segment and COM signals will therefore be typically 5 Volts AC, which causes the segment to become visible after 300-400 msec of refresh cycles. &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;To de-energize (turn off) a segment, the COM and segment waveforms should be in phase with each other while that segment’s COM is active, that is, not at 2.5 volts.  So, a LCD with all segments OFF will have the segment inputs IN PHASE with each COM input.  (COM3 was omitted from Figure 2-2, since only 4 channels were available.) &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-01T20:34:36.407" LastActivityDate="2011-03-01T20:34:36.407" CommentCount="6" />
  <row Id="10906" PostTypeId="2" ParentId="10898" CreationDate="2011-03-01T18:24:58.677" Score="2" ViewCount="" Body="&lt;p&gt;As Joby said, you need a toolchain.  There are a number of steps which have to happen between the C code you have and loading data onto the device:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The preprocessor converts #include and #define macros, and also processes any conditional compilation (#if) symbols.&lt;/li&gt;&#xA;&lt;li&gt;The compiler converts each .c file into assembly code.&lt;/li&gt;&#xA;&lt;li&gt;The assembler converts those into object files.  These files use relative addressing.&lt;/li&gt;&#xA;&lt;li&gt;The linker puts all the object files together into the series of hex digits in the .hex file, and gives them the addresses required by the device.  It also brings in any external object files for which you don't have the source code (or have already compiled it in a previous iteration).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This is generally referred to as a toolchain, but may be informally referred to as a compiler.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll also need a way to copy the .hex file onto the microcontroller.  The usual way to do this is to use a programmer, though it is often convenient to program the device with a bootloader first, and then use this program to copy the .hex file in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are some of the most basic steps of embedded software development.  You may find native programming a bit easier if you want a slower learning curve.  Also, the AT89C51 (now the AT89S51) uses an older 8051 core, you may find more modern processors like the ATmega, PIC18, or (much more new, but more complex) ARM cores (Cortex-M3/M0, probably) to be more user-friendly and well-supported.  Another way to learn embedded development is through the Arduino (AVR) system, but that gets you out of C and into a beginner language.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-01T18:24:58.677" CommentCount="4" />
  <row Id="10907" PostTypeId="2" ParentId="10899" CreationDate="2011-03-01T18:54:53.623" Score="6" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/Moisture_Sensitivity_Level&quot; rel=&quot;nofollow&quot;&gt;Moisture Sensitivity Level&lt;/a&gt; (MSL) is a measure of how much, how fast, and how sensitive a part is to moisture is when it enters the package.  It has nothing to do with moisture sensitivity &lt;em&gt;after&lt;/em&gt; the board is assembled, for such information you need to consult the datasheet for storage and operating conditions.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If too moisture much enters the part and it vaporizes during reflow, the high pressure can cause sufficient stress to cause the part to explode, causing a &quot;popcorn&quot; noise.  Such failures are usually visible with careful inspection as the package will be fractured, usually near the leadframe.  It may be cracked on the bottom with DFN-type packages, however, though the device may appear to be sitting at an odd angle, canted up from the PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the device, other, more subtle failures may occur.  Internal wire bonds could be broken causing intermittent or no connections, or in the case of a PPTC, an effectively reduced current limit.  Such errors are probably rare, and of course very dependent on the construction of the device, which you don't know.  For prototypes, usually people can deal with it, but for production it's important if you are concerned about reliability and/or manufacturing rejects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can keep moisture-sensitive parts in resealable containers if you control the humidity with desiccants or dehumidifiers, and you can use &lt;a href=&quot;http://en.wikipedia.org/wiki/Humidity_indicator_card&quot; rel=&quot;nofollow&quot;&gt;indicator cards&lt;/a&gt; to monitor that the humidity did not exceed some defined level.  &lt;a href=&quot;http://www.google.com/search?rlz=1C1CHMU_enUS354US377&amp;amp;sourceid=chrome&amp;amp;ie=UTF-8&amp;amp;q=3m+humidity+indicator&quot; rel=&quot;nofollow&quot;&gt;3M makes them&lt;/a&gt;, and there may have been one in the bag from your supplier.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-02T20:23:58.417" LastActivityDate="2011-03-02T20:23:58.417" CommentCount="2" />
  <row Id="10908" PostTypeId="1" AcceptedAnswerId="10915" CreationDate="2011-03-01T19:19:32.593" Score="1" ViewCount="110" Body="&lt;p&gt;Can someone tell me (or link me) the response curve of an LDR. I don't mean the frequency response, just the intensity response; is it linear, or logarithmic?&lt;/p&gt;&#xA;" OwnerUserId="2212" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-01T20:17:43.940" LastActivityDate="2011-03-01T21:28:43.520" Title="Response curve of an LDR?" Tags="&lt;ldr&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10909" PostTypeId="1" AcceptedAnswerId="10912" CreationDate="2011-03-01T20:33:33.417" Score="22" ViewCount="2316" Body="&lt;p&gt;I am trying to decide if the information on the wikipedia page&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Coulomb#In_everyday_terms&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Coulomb#In_everyday_terms&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;is reasonable.  In particular the statements that a lightning bolt has about 15 coulomb, where a battery has 5000.  My first instinct is that this is clearly wrong (a lightning bolt being such an energetic event, and a battery seeming mostly innocent), but then on reflection a lightning bolt does last only an extraordinarily short amount of time.  In the end I am not sure how to check if this makes sense.&lt;/p&gt;&#xA;" OwnerUserId="1773" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-01T23:08:06.540" LastActivityDate="2011-03-21T21:50:09.437" Title="Lightning bolt vs. batteries: a coulomb in everyday terms." Tags="&lt;battery&gt;&lt;energy&gt;" AnswerCount="3" FavoriteCount="3" />
  <row Id="10910" PostTypeId="1" AcceptedAnswerId="11061" CreationDate="2011-03-01T20:35:00.363" Score="2" ViewCount="130" Body="&lt;p&gt;I'm looking for a two servos to power a pointing and tracking gimbal I'm building for some optics. I'm trying to find the highest accuracy servos I can buy in the standard servo package (or close to it). Does anyone have any recommendations? Most hobby servos don't list the positional accuracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt; I'd like &amp;lt;1 degree accuracy (less is better). I've considered using a stepper motor, but then I'd have to incorporate my own feedback. I'd like a COTS (commercial, off-the-shelf) solution.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastEditorUserId="2454" LastEditorDisplayName="" LastEditDate="2011-03-04T19:04:14.093" LastActivityDate="2011-03-04T22:47:22.387" Title="High accuracy servo" Tags="&lt;servo&gt;&lt;angle&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="10911" PostTypeId="2" ParentId="10909" CreationDate="2011-03-01T20:42:46.820" Score="4" ViewCount="" Body="&lt;p&gt;Probably right, keep energy and charge apart ( mentally ) they measure different things.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-01T20:42:46.820" CommentCount="2" />
  <row Id="10912" PostTypeId="2" ParentId="10909" CreationDate="2011-03-01T21:02:39.207" Score="40" ViewCount="" Body="&lt;p&gt;A common source of confusion is the difference between energy and power.  A Snickers bar, for example, has more energy in it than a hand grenade.  One might call a grenade exploding &quot;energetic&quot;, but what's key here is its &lt;em&gt;power&lt;/em&gt; (P), or ability to convert energy (E) &lt;em&gt;extremely&lt;/em&gt; rapidly, in a very short amount of time (t):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$P = \frac{E}{t}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Similarly, there is an analogy in the electrical world, where charge (Q), current (I), voltage (V), power and energy do not always go hand-in-hand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The equations that relate all those are as follows:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$ I = \frac{Q}{t} $$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$ P = I{\cdot}V $$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$ E = P{\cdot}t = I{\cdot}V{\cdot}t $$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$ Q = I{\cdot}t $$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of a lightning bolt, V and I are both &lt;em&gt;extremely&lt;/em&gt; high, so the &lt;em&gt;power&lt;/em&gt; is extreme, but t is fairly low, so the high current and short time mitigate each other somewhat, so there isn't an immense amount of charge.  Of note, all that voltage influences is how much energy that the &lt;em&gt;same amount&lt;/em&gt; of charge carries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Plugging in some numbers, &lt;a href=&quot;http://www.google.com/search?q=120%20kiloamps%20%2a%2030%20microseconds&quot; rel=&quot;nofollow&quot;&gt;120 kA &amp;amp; 30 µs, we get 3.6 coulombs&lt;/a&gt;, close to what you have. The Wikipedia article, however, says there is a fair bit of variability (&quot;up to 350 C&quot;), but they are within a couple orders of magnitude, and having seen a few lightning storms, some strikes are big and meaty, others not so much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a battery, the voltage is pathetic compared to a lighting strike, but that's irrelevant for calculating charge.  What's key is that it's able to provide a current that's several orders of magnitude less for &lt;em&gt;dozens&lt;/em&gt; of orders of magnitude longer.  &lt;a href=&quot;http://www.google.com/search?q=1+milliamp+%2a+1+hour&quot; rel=&quot;nofollow&quot;&gt;One milliamp for one hour (1 mA·h) is equal to 3.6 coulombs&lt;/a&gt; (look, the same as our 120 kA, 30 µs lighting strike), and batteries often have capacities in the thousands of mA·h (2000 mA·h is typical for an AA cell).&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-21T21:50:09.437" LastActivityDate="2011-03-21T21:50:09.437" CommentCount="4" />
  <row Id="10913" PostTypeId="1" AcceptedAnswerId="10924" CreationDate="2011-03-01T21:10:29.747" Score="3" ViewCount="218" Body="&lt;p&gt;Someone gave me this analogy - turning on your TV or radio does not cost the broadcaster more money because the radio waves would otherwise be dissipated by the air or other objects. Is this correct? I find it difficult to believe - surely some energy must be drawn in by the receiver circuit of the radio and the fact that the radio is on or off does not change the properties of said objects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(OK, it may only be milliwatts drawn by said devices, but I'm still curious as to how much it would make a difference.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-02T11:49:07.883" Title="Do radio receivers use any power from a transmitter?" Tags="&lt;radio&gt;" AnswerCount="6" CommentCount="3" FavoriteCount="1" />
  <row Id="10914" PostTypeId="2" ParentId="10913" CreationDate="2011-03-01T21:26:58.577" Score="2" ViewCount="" Body="&lt;p&gt;That is correct; your statement about dissipated is about right.  Or it just keeps radiating out into space or the distance.  Think light: everyone can look at a light or it can hit walls or not, it doesn't draw any more power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some energy is received by the received, but this doesn't effect the transmitter.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-01T21:26:58.577" />
  <row Id="10915" PostTypeId="2" ParentId="10908" CreationDate="2011-03-01T21:28:43.520" Score="1" ViewCount="" Body="&lt;p&gt;For &lt;a href=&quot;http://www.advancedphotonix.com/ap_products/pdfs/PDV-P9004.pdf&quot; rel=&quot;nofollow&quot;&gt;the Advanced Photonix PDV-P9004&lt;/a&gt;, it seems like the illuminance is proportional to the conductance (1/resistance) of the photoresistor.  At some point it probably saturates.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This makes sense as the photons it receives and the applied electric field should be proportional to the electrons that flow.  It might not be purely linear between the field (voltage) and resistance though. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.advancedphotonix.com/ap_products/pdfs/PDV-P9004.pdf&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/OI3iq.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-01T21:28:43.520" CommentCount="1" />
  <row Id="10916" PostTypeId="2" ParentId="10913" CreationDate="2011-03-01T21:34:27.573" Score="0" ViewCount="" Body="&lt;p&gt;Yes i would say they get dissipated some way or other. Any energy dissipated in the devices would be probably in the range of picowatts.&lt;/p&gt;&#xA;" OwnerUserId="3068" LastActivityDate="2011-03-01T21:34:27.573" />
  <row Id="10917" PostTypeId="2" ParentId="10913" CreationDate="2011-03-01T21:41:40.350" Score="10" ViewCount="" Body="&lt;p&gt;Does the Sun create more energy when the cat lies on the windowsill?&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-01T21:41:40.350" CommentCount="2" />
  <row Id="10918" PostTypeId="1" AcceptedAnswerId="10920" CreationDate="2011-03-01T22:10:18.460" Score="1" ViewCount="184" Body="&lt;p&gt;I have a package of 10 inductors, all of which are supposed to be 22µH, but they all have &quot;220&quot; printed on the case. It does not seem right when I compare to an otherwise identical (same type) inductor with an inductance of 3.3µH, which has &quot;3R3&quot; printed on it. Is it just odd ordering or am I missing something? Inductor is an SDR0604 type.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-02T18:05:41.067" Title="Is my inductor really 22µH?" Tags="&lt;inductor&gt;&lt;value&gt;" AnswerCount="4" CommentCount="8" />
  <row Id="10919" PostTypeId="2" ParentId="10918" CreationDate="2011-03-01T22:24:34.703" Score="3" ViewCount="" Body="&lt;p&gt;220 means that the value is 22 times 10^0, or 22uH. It's a similar notation to that used for small value capacitors. If they were really 220uH they would have the value 221.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-01T22:30:02.750" LastActivityDate="2011-03-01T22:30:02.750" />
  <row Id="10920" PostTypeId="2" ParentId="10918" CreationDate="2011-03-01T22:24:51.567" Score="5" ViewCount="" Body="&lt;p&gt;That should be read as 22 × 10&lt;sup&gt;0&lt;/sup&gt; µH and 3.3 µH respectively.  The R is a decimal, the last digit otherwise is an exponent.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-02T16:03:16.450" LastActivityDate="2011-03-02T16:03:16.450" />
  <row Id="10921" PostTypeId="2" ParentId="10913" CreationDate="2011-03-01T22:25:33.183" Score="1" ViewCount="" Body="&lt;p&gt;I am neither physicist nor electrical engineer. I did not know the answer to your question, so read Wikipedia for some background. Caveat Emptor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By definition:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Radio&#xA;  waves are a type of electromagnetic&#xA;  radiation with wavelengths in the&#xA;  electromagnetic spectrum longer than&#xA;  infrared light.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;From Maxwell's Laws: (they seem important, I've heard of them)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&#xA;  Ampère's law with Maxwell's&#xA;  correction states that magnetic&#xA;  fields can be generated in two ways:&#xA;  by electrical current (this was the&#xA;  original &quot;Ampère's law&quot;) and by&#xA;  changing electric fields (this was&#xA;  &quot;Maxwell's correction&quot;).&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Maxwell's correction to Ampère's law&#xA;  is particularly important: It means&#xA;  that a changing magnetic field creates&#xA;  an electric field, and a changing&#xA;  electric field creates a magnetic&#xA;  field.[1][2]&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;strong&gt;Therefore, these equations allow&#xA;  self-sustaining &quot;electromagnetic&#xA;  waves&quot; to travel through empty space&lt;/strong&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Electromagnetic_radiation#Particle_model&quot; rel=&quot;nofollow&quot;&gt;By the Particle Model of Electromagnetic Radiation&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;EM waves are emitted and absorbed as&#xA;  discrete packets of energy, or quanta,&#xA;  called photons. Because photons are&#xA;  emitted and absorbed by charged&#xA;  particles, they act as transporters of&#xA;  energy&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The amount of energy received is defined by the&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Link_Budget#The_Link_Budget_Equation&quot; rel=&quot;nofollow&quot;&gt;Link Budget&lt;/a&gt;. But, it is not coupled to the transmitter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could enough crystal radio sets mute the BBC World Service?&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-02T11:49:07.883" LastActivityDate="2011-03-02T11:49:07.883" />
  <row Id="10922" PostTypeId="2" ParentId="10918" CreationDate="2011-03-01T22:31:08.847" Score="9" ViewCount="" Body="&lt;p&gt;There are two ways of marking parts...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A Three digit code for values from 10 and up&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;X Y Z&#xA;X - First digit&#xA;Y - Second digit&#xA;Z - Power of ten&#xA;&#xA;220 would be 22 = 22 x 10^0 (1)&#xA;221 would be 220 = 22 x 10^1 (10)&#xA;222 would be 2,200 = 22 x 10^2 (100)&#xA;223 would be 22,000 = 22 x 10^3 (1000)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The Minimum for this coding would be &#xA;100 = 10 x 10^0&#xA;and the Maximum would be&#xA;999 = 99,000,000,000 = 99 x 10^9 (1,000,000,000)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For values under 10&lt;/p&gt;&#xA;&#xA;&lt;p&gt;you use a character to replace the decimal point&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e.g. &#xA;3R3 = 3.3&#xA;R33 = 0.33&lt;/p&gt;&#xA;&#xA;&lt;p&gt;R is used for Ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For resistors the value is usually in Ohms&#xA;For Capacitors the value is usually in pico farads&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e.g. a Capacitor marked 103 would be 103 pF = 10 x 10^3 (1000) pF = 10nF = 0.01uF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For Inductors the value is usually in micro henrys&#xA;e.g. a Inductor marked 220 woulf be 22uH = 22 x 10^0 (1) uH&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The part marked 3R3 is a 3.3 ohm resistor as R is used on resistors.&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2011-03-01T22:31:08.847" CommentCount="6" />
  <row Id="10923" PostTypeId="2" ParentId="10863" CreationDate="2011-03-01T22:40:57.880" Score="0" ViewCount="" Body="&lt;p&gt;Don't risk blowing up your iPhone by messing about with series resistors.  Use a proper 5v-3v converter.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 74LVX244 buffer chip will accept 5v input and output a proper, safe, 3.3v logic level.  This requires a source of 3.3v supply.&#xA;A sufficient number of fixed-drop diodes (say 2 diodes in series with 1v drop each) is a better passive solution.&lt;/p&gt;&#xA;" OwnerUserId="389" LastEditorUserId="389" LastEditorDisplayName="" LastEditDate="2011-03-08T22:50:14.063" LastActivityDate="2011-03-08T22:50:14.063" CommentCount="4" />
  <row Id="10924" PostTypeId="2" ParentId="10913" CreationDate="2011-03-02T01:58:16.347" Score="9" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;Turning on your TV or radio does not cost the broadcaster more money, because broadcast transmissions would otherwise be dissipated by some other object.&lt;/li&gt;&#xA;&lt;li&gt;some energy is drawn in by the receiver circuit of the radio.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Both statements are true. Do you think one contradicts the other?&#xA;I think of it as analogous to the big decorative water sprinkler at the local park.&#xA;(I agree that &quot;dissipated in the air&quot; seems unlikely).&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Letting your dog drink water from the sprinkler does not cost the park more money, because the same amount of water comes out of the sprinkler, whether some of the droplets land on the dog's tongue or whether they all falls on the ground.&lt;/li&gt;&#xA;&lt;li&gt;Some water is drawn in by the dog.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Often several dogs catch water drops on their tongues at the same time at the same fountain, and still the vast majority of the water is &quot;wasted&quot; landing on the ground.&#xA;Likewise you can have thousands of people tuning in to the same TV station, and still the vast majority of the photons pouring out of the transmission antennas never hits a receiver antenna, but instead is &quot;wasted&quot; hitting trees or mountains or escaping to outer space.&#xA;There is no way to tell from looking at the park's water meter whether dozens of dogs drink water from this fountain, or no dogs at all -- the same water comes out the sprinkler either way.&#xA;There is no way to tell from looking at the broadcaster's electic meter whether thousands of people are tuned in, or no one is tuned in -- the same electromagnetic power comes out of the transmission tower either way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is very different from the way energy flows &quot;through the air&quot; in a air-core concentric-coil transformer, or &quot;through the air&quot; in an air dielectric capacitor,&#xA;or the way mains powered devices &quot;draw in&quot; only the amount of current and power they need.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Do radio receivers use any power from a transmitter?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;A few crystal radios have no batteries or mains connection -- all the power they have comes from the radio transmitter, and the radio uses power from the transmitter to drive the earphone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could argue that most radios extract only the signal from the station; all the power from the antenna ends up warming the BE junction of the first transistor in the pre-amplifier, and 100% of the power &quot;used&quot; by the radio in later stages and to drive the speakers comes from batteries or mains power or a &lt;a href=&quot;http://www.stepin.org/casestudy.php?id=windupradio&amp;amp;page=2&quot; rel=&quot;nofollow&quot;&gt;clockwork spring&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How much would make a difference?&#xA;Well, if we packed enough radios and their antennas all around the broadcast antenna, eventually we would form a Faraday cage -- those radios would absorb all the broadcast energy, and other radios outside a Faraday cage cannot hear any transmissions from inside it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a few things this analogy does not capture perfectly.&#xA;Although it is tempting to think of the antenna as a &quot;bucket&quot;, since the bigger it is the more photons it catches,&#xA;a tuned antenna can catch far more energy than one might expect from its size and the local energy density -- &lt;a href=&quot;http://amasci.com/tesla/tesceive.html&quot; rel=&quot;nofollow&quot;&gt;'Energy-sucking' Radio Antennas&lt;/a&gt;.&#xA;If a puppy is catching the droplets on his tongue, and then a German Shepherd steps over him and catches the droplets first, then nothing reaches the puppy -- unless the puppy moves a bit to the side to get out of the shadow of the big dog.&#xA;Likewise, if you put one radio antenna close to and immediately &quot;behind&quot; another radio antenna (as seen from the transmission tower), the upstream radio one will receive perfectly, as if the downstream radio is not even there, and the downstream radio will hear nothing -- until the downstream radio moves a bit to the side to get out of the shadow of the big dog.&#xA;However, if you move the downstream radio antenna further away from (and yet still behind) the upstream antenna, it will also start to hear the station -- the power from the station &quot;curves around&quot; the upstream radio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A typical FM broadcast tower puts out 100 kW ERP (+80 dBm) and 300 m high.&#xA;FM radio receivers are expected to work down to a signal strength of 0.5mV/m.&#xA;A typical radio reciever has a sensitivity of -90 dBm with an antenna roughly 1 m long.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-02T01:58:16.347" CommentCount="5" />
  <row Id="10925" PostTypeId="1" CreationDate="2011-03-02T02:06:17.523" Score="-1" ViewCount="108" Body="&lt;p&gt;Hi, Are there any good data rate(~Mbps) RF modules available in market that can be interfaced with &#xA;&lt;a href=&quot;http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,836&amp;amp;Prod=ATLYS&quot; rel=&quot;nofollow&quot;&gt;Digilent Atlys Spartan®-6 FPGA Development Kit&lt;/a&gt; &#xA;? Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="2947" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-03-02T02:45:20.073" LastActivityDate="2011-03-03T00:11:24.200" Title="Rf modules for FPGA board" Tags="&lt;fpga&gt;&lt;rf&gt;&lt;xilinx&gt;&lt;spartan&gt;" AnswerCount="2" />
  <row Id="10926" PostTypeId="2" ParentId="10925" CreationDate="2011-03-02T02:44:53.817" Score="2" ViewCount="" Body="&lt;p&gt;I would ask Digilent.  Also what interfaces it has would help.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-02T02:44:53.817" />
  <row Id="10927" PostTypeId="1" AcceptedAnswerId="10932" CreationDate="2011-03-02T02:46:46.693" Score="1" ViewCount="136" Body="&lt;p&gt;I've acquired some Sanyo Denki 103H5208-1241 stepper motors and I can't find the data sheet for it for the life of me. I've spelunked their catalogs and such looking for them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where can I find them or can I safely use another stepper data sheet interchangeably?&lt;/p&gt;&#xA;" OwnerUserId="3208" LastActivityDate="2011-03-02T05:01:16.110" Title="Where can I find data sheets for a Sanyo Denki 103H5208-1241 Stepper Motor" Tags="&lt;stepper&gt;&lt;datasheet&gt;&lt;stepper-motor&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="10928" PostTypeId="2" ParentId="10049" CreationDate="2011-03-02T02:47:13.800" Score="1" ViewCount="" Body="&lt;p&gt;If you mean 0/1/Z, which I assume from the tags, that's in the IOB.  Internal tri-states aren't in current FPGA families.  See the Xilinx documentation or any VHDL/Verilog book.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-02T02:47:13.800" />
  <row Id="10929" PostTypeId="2" ParentId="10050" CreationDate="2011-03-02T02:48:28.417" Score="1" ViewCount="" Body="&lt;p&gt;Do a mux.  Then tristate its output.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-02T02:48:28.417" />
  <row Id="10931" PostTypeId="2" ParentId="10879" CreationDate="2011-03-02T04:59:40.947" Score="5" ViewCount="" Body="&lt;p&gt;Well the right answer is &quot;you can overclock until it stops working&quot; .... more seriously something like bumping an 80MHz clock to 81MHz is not a big deal&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(puts on chip designer hat) when we tape out a chip we don't have complete control over what happens at the fab - they might put a little too much dopant (or to little) in one step, or under etch a step so that wires are slightly wider (with higher capacitance) - instead we design for the 'worst case corners of the process' and try and make internal timing there - that way any functional chip coming out the other end should work and meet the spec - from you point of view it means that most of what you get from us is somewhere in the middle of the yield curve and happy to run over spec .... but some percentage will be just at spec and will fail if you overclock (and some percentage will go much faster still).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We don't normally test chips for speed (maybe sometimes a test patch on a dies to test the process) - it's way too expensive - we plan on them all working. Some expensive chips (high end processors for example) will get tested and binned because it makes sense for both practical (yield) and marketing reasons to do so&lt;/p&gt;&#xA;" OwnerUserId="3190" LastEditorUserId="3190" LastEditorDisplayName="" LastEditDate="2011-03-02T08:33:39.310" LastActivityDate="2011-03-02T08:33:39.310" CommentCount="1" />
  <row Id="10932" PostTypeId="2" ParentId="10927" CreationDate="2011-03-02T05:01:16.110" Score="3" ViewCount="" Body="&lt;p&gt;If you have a specific part number and don't get a good result with the full thing, start stripping off parts and see if that helps.  For instance, ATMEGA169PA-AU defines an exact part you can order, but searching for &quot;ATMEGA169PA&quot; or &quot;ATMEGA169&quot; probably would give more helpful results.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For your case, &quot;103H5208-1241&quot; seems to provide good results when searched, but &quot;103H5208&quot; does as well, many of them seeming to be whole catalogs or large sections thereof.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason for my example is because most of the additional letters tacked on simply indicate mechanical features or different grades, but the core part is still the same.  Your stepper motor might also differ in some mechanical aspects (threading, mounting, whatever), but even a different part with a similar part number should have closely related features, so you could glean something from that.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-02T05:01:16.110" CommentCount="2" />
  <row Id="10933" PostTypeId="2" ParentId="10913" CreationDate="2011-03-02T08:14:15.193" Score="1" ViewCount="" Body="&lt;p&gt;You can only electrically couple to the evanescent standing waves in the near field (less than a wavelength) where the E/H impedance varies until finally settling to the free space limit of 376.73 Ω. The near field terms decay rapidly in proportion to 1/r^2 and 1/r^3. In contrast, the far field is no longer electrically coupled to the transmitter and decays much more slowly in proportion to 1/r. The energy simply radiates away, whether or not it gets picked up by any receiving antennas, or walls, or whatever. In empty space it would propagate at the speed of light according to the pattern of the antenna design, such as an omni-directional torus for a dipole antenna.&lt;/p&gt;&#xA;" OwnerUserId="721" LastActivityDate="2011-03-02T08:14:15.193" />
  <row Id="10934" PostTypeId="1" CreationDate="2011-03-02T09:26:11.700" Score="0" ViewCount="73" Body="&lt;p&gt;I am searching for a dual full  H-bridge chip with separate load voltage inputs for each bridge and high impedance state for outputs when idle. The TA7279AP is perfect but is being phased out.&#xA;The closest component I have been able to find is SemeLab IP3M10, but it does not have a state with both outputs at high impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Requirements are 8 to 24 volts, and each bridge able to handle up to 100mA. TTL control logic.&#xA;Thanks in advance for suggestions about possible replacement components.&lt;/p&gt;&#xA;" OwnerUserId="3212" LastEditorUserId="3212" LastEditorDisplayName="" LastEditDate="2011-03-03T06:41:43.537" LastActivityDate="2011-03-03T06:41:43.537" Title="Seeking  replacement for TA7279AP dual full H-bridge" Tags="&lt;h-bridge&gt;" AnswerCount="1" />
  <row Id="10935" PostTypeId="1" CreationDate="2011-03-02T09:51:13.637" Score="0" ViewCount="149" Body="&lt;p&gt;I want to monitor a tank's water usage with a &lt;em&gt;Beagleboard&lt;/em&gt;, and develop an interactive, attractive display interface. &lt;strong&gt;&lt;em&gt;How should I approach developing the software?&lt;/em&gt;&lt;/strong&gt; A quick overview of the options available would be helpful.&lt;/p&gt;&#xA;" OwnerUserId="3214" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-02T22:39:45.800" LastActivityDate="2011-03-02T22:39:45.800" ClosedDate="2011-03-02T22:47:11.903" Title="Interactive water usage monitor interface using Beagleboard" Tags="&lt;software&gt;&lt;interface&gt;&lt;display&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="10937" PostTypeId="5" CreationDate="2011-03-02T13:17:40.730" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-03-02T13:17:40.730" LastActivityDate="2011-03-02T13:17:40.730" />
  <row Id="10938" PostTypeId="4" CreationDate="2011-03-02T13:17:40.730" Score="0" ViewCount="" Body="Microchip Technology is an American manufacturer of microcontroller, memory and analog semiconductors." OwnerUserId="-1" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-03-02T13:36:51.023" LastActivityDate="2011-03-02T13:36:51.023" />
  <row Id="10939" PostTypeId="1" AcceptedAnswerId="10940" CreationDate="2011-03-02T15:48:37.957" Score="2" ViewCount="142" Body="&lt;p&gt;After reading some answers on SuperUser, I started thinking: Can EE/E/PROM be damaged by only reading it, with no writing at all? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've read several datasheets for EEPROMS and products that contain them and all I've ever seen were write and erase cycles. I do know that just reading few datasheets does not make me an expert, but up until now I was convinced that you can't wear out EEPROM and relatives just by reading them. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After some searching, I couldn't find a definitive answer which would convince me that reading an EEPROM can wear it out, so I'm asking here.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-02T18:15:32.323" Title="Will reading EE/E/PROM wear it out?" Tags="&lt;eeprom&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10940" PostTypeId="2" ParentId="10939" CreationDate="2011-03-02T15:59:50.900" Score="5" ViewCount="" Body="&lt;p&gt;No, they can't be damaged only by reading.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But keep in mind that a simple read by a &quot;complex&quot; operating system could be followed automatically by one or more write (an example of this behaviour is the change of file last access time)&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-03-02T15:59:50.900" CommentCount="3" />
  <row Id="10941" PostTypeId="2" ParentId="10935" CreationDate="2011-03-02T16:02:42.707" Score="1" ViewCount="" Body="&lt;p&gt;I think that you don't know what you want to do. You are better off to read the documentation that came with the board first.&#xA;The documentation will show you how to build/install your linux kernel and root filesystem. Then after that you will have to write a userspace application to monitor the water usage. I have no experience with this board (only other embedded GNU/Linux platforms) but I guess this application will be build with the Qt toolkit to run in Qtopia.&lt;/p&gt;&#xA;" OwnerUserId="3068" LastActivityDate="2011-03-02T16:02:42.707" CommentCount="1" />
  <row Id="10943" PostTypeId="2" ParentId="10934" CreationDate="2011-03-02T17:28:01.233" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Answering this question for your specific case with parts as they are now will get it closed as being &lt;strong&gt;too localized&lt;/strong&gt;, so this is a more general community wiki answer.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The first thing that you need to determine is why you need the same level of integration that you currently have.  Could you get by with (2) H-bridges, or (4) half-bridges?  This will open up your options immensely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, can you use discrete transistors with drivers?  For low-voltage/low-current applications this isn't really needed, but if you needed higher performance, this is crucial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other related drivers you could look at to replace H-bridge drivers are synchronous-drivers (often used with a half-bridge), which can be much cheaper and offer better performance, but have some limitations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as manufacturers to peruse:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.linear.com/&quot; rel=&quot;nofollow&quot;&gt;Linear Technology&lt;/a&gt;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Half/full/3-phase drivers&lt;/li&gt;&#xA;&lt;li&gt;Good selection of some high-performance parts (low Iq, wide voltage ranges, etc)&lt;/li&gt;&#xA;&lt;li&gt;Some parts can be pricey&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.diodes.com/&quot; rel=&quot;nofollow&quot;&gt;Diodes Inc (Zetex)&lt;/a&gt;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Has a good variety of lower-power transistor packages with various combinations, e.g. Dual N, N/P, 4x N, Dual N/Dual P (H-bridge).&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.irf.com/&quot; rel=&quot;nofollow&quot;&gt;International Rectifier&lt;/a&gt;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;High power transistors&lt;/li&gt;&#xA;&lt;li&gt;High voltage bridge drivers (100-600 V)&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.st.com/&quot; rel=&quot;nofollow&quot;&gt;ST Microelectronics&lt;/a&gt;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;High power transistors&lt;/li&gt;&#xA;&lt;li&gt;Highly integrated motor controllers with drivers and logic, however these are often very specific for door zone applications, so you might get one high-power H-bridge, two lower-power H-bridges, and some high-side drivers, and while they're pretty economical together, you're paying for it all.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-02T17:28:01.233" CommunityOwnedDate="2011-03-02T17:28:01.233" CommentCount="2" />
  <row Id="10944" PostTypeId="1" CreationDate="2011-03-02T17:49:08.553" Score="3" ViewCount="175" Body="&lt;p&gt;Sorry for my previous vague question. I am setting up a heat generator map for my thermal analysis and I was given that one of the ICs will be dissapating 5.2W. Does this mean that 5.2W of heat will be created into my enclosure? This is my first time setting up a thermal simulation for a pcb so bear with me. In my previous experience if 5.2W was put into something the amount of heat generated was based on the effiency of the item.&lt;/p&gt;&#xA;" OwnerUserId="3217" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T22:13:20.030" LastActivityDate="2011-04-27T22:13:20.030" Title="Heat Generation Question" Tags="&lt;power-supply&gt;&lt;electronics&gt;" AnswerCount="2" CommentCount="9" FavoriteCount="1" />
  <row Id="10945" PostTypeId="2" ParentId="10918" CreationDate="2011-03-02T18:05:41.067" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://industrial.panasonic.com/www-data/pdf/AGL0000/AGL0000CE6.pdf&quot; rel=&quot;nofollow&quot;&gt;Panasonic SM inductors&lt;/a&gt; use R in the part marking (for example, 2R6 corresponds to the 2.6 microhenry part on the specified datasheet).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-02T18:05:41.067" />
  <row Id="10946" PostTypeId="2" ParentId="10939" CreationDate="2011-03-02T18:15:32.323" Score="2" ViewCount="" Body="&lt;p&gt;Data will slowly degrade over time (we're talking many years) due to bit rot if the contents of the flash are not periodically rewritten. The memory cells cannot hold their charge indefinitely due to infinitesimally small leakages. Given enough time, bits will decay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reading doesn't cause this issue, or fix this issue. You have to periodically rewrite the contents of the flash card (once a year, maybe).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-02T18:15:32.323" />
  <row Id="10947" PostTypeId="2" ParentId="4942" CreationDate="2011-03-02T18:41:49.173" Score="0" ViewCount="" Body="&lt;p&gt;The most versatile approach, though I don't know if anyone supports this, would be to have a chip programmer read a chip and write it to a file, then run a user-supplied program to update the file with what should be in the chip, program the resulting file into the chip and read it out, and run the user-supplied program to verify it (possibly repeating the program cycle if the verify program wasn't satisfied with the result).  When that isn't practical, I would think the best approach is often to simply have a means of feeding the required data into the target circuit so it can program the memory chip using whatever forms of error-correcting and bad-block memory it uses.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-02T18:41:49.173" />
  <row Id="10948" PostTypeId="2" ParentId="3329" CreationDate="2011-03-02T19:06:18.573" Score="3" ViewCount="" Body="&lt;p&gt;That has since changed, Digikey is included in the results.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[edit]&#xA;Previously, this year even, Octopart did not show search results from Digi-key. It seems they have worked something out with Digi-Key and now Octopart displays results from Digi-key&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am unable to load a picture but here is an example link.&#xA;&lt;a href=&quot;http://octopart.com/partsearch/#search/requestData&amp;amp;q=514&quot; rel=&quot;nofollow&quot;&gt;Octopart Results from Digikey&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3218" LastEditorUserId="3218" LastEditorDisplayName="" LastEditDate="2011-03-07T15:12:53.567" LastActivityDate="2011-03-07T15:12:53.567" CommentCount="4" />
  <row Id="10949" PostTypeId="1" AcceptedAnswerId="10950" CreationDate="2011-03-02T19:58:21.643" Score="3" ViewCount="87" Body="&lt;p&gt;I've selected a MCU in a PLCC packing and is desperate need of tips how to use it when prototyping on a breadboard. There is a DIP version of the MCU but it has some limitation due to a lower pin count, which forces me to use the PLCC packaging.&lt;/p&gt;&#xA;" OwnerUserId="3186" LastActivityDate="2011-03-02T20:09:50.487" Title="Plcc &amp; breadboards" Tags="&lt;prototyping&gt;" AnswerCount="2" />
  <row Id="10950" PostTypeId="2" ParentId="10949" CreationDate="2011-03-02T20:00:55.943" Score="5" ViewCount="" Body="&lt;p&gt;You could use a PLCC to DIP adapter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Searching google for &quot;PLCC DIP adapter&quot; threw up a few. This kind of thing:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.order-bulk.com/images/dip40plcc44.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-02T20:00:55.943" CommentCount="2" />
  <row Id="10951" PostTypeId="2" ParentId="10949" CreationDate="2011-03-02T20:09:50.487" Score="3" ViewCount="" Body="&lt;p&gt;Another option is to solder wires in the pins of the chip.&#xA;&lt;img src=&quot;http://i.imgur.com/avn1I.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-03-02T20:09:50.487" />
  <row Id="10952" PostTypeId="2" ParentId="1911" CreationDate="2011-03-02T20:16:34.067" Score="2" ViewCount="" Body="&lt;p&gt;Many processors are driven by a state machine whose transition sequence is affected by the instructions being executed.  Microcode &quot;instructions&quot; often specify the interactions among various registers and buses in a way which would not be visible to a programmer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, a microcode instruction for an 8-bit CPU in state #1 might specify that output enables for both halves of the program counter should be active (causing the program counter to be output on the upper and lower internal address bus), the program-counter-increment signal should be active, the external address latch signals should be active (so the external address bus will track the internal one) and the RAM-read signal should be active, and the controller should switch to state #2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In state #2, the external data bus should feed to the internal primary data bus, and the instruction register, which reads from that bus, should be loaded.  The program counter should as before be output on both halves of the address bus, and another RAM-read issued.  Bits 5-7 of the instruction register should be loaded into bits 0-2 of the state controller, bit 3 of the state register should be set unless bits 1-7 of the instruction register are all set, and other bits of the state register should be clear, the net result being that the next state will be #7-#15.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that microcode isn't really defined in terms of instructions, but rather in terms of combinations of control signals.  The hardware will not be set up to allow general-purpose instructions in microcode, but rather to load or output various registers from/to the buses on which they sit, or connect different buses to each other, and use various bits or combinations thereof to select different states.  Many aspects of the design will be hard-wired (e.g. opcodes FE and FF might be special-cased in hardware rather than in microcode).  The idea with microcode isn't to run programs, but to replace logic.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-02T20:16:34.067" />
  <row Id="10953" PostTypeId="1" CreationDate="2011-03-02T20:23:14.437" Score="3" ViewCount="119" Body="&lt;p&gt;What techniques do you use for testing/simulating circuits? As at my college we use &lt;a href=&quot;http://www.new-wave-concepts.com/pr/circuit.html&quot; rel=&quot;nofollow&quot;&gt;Circuit Wizard&lt;/a&gt; which we have to simulate our circuit on. I am looking for something a bit more advance. I have tinkered with SPICE but for more sophisticated circuits it gets more complicated and seems lack of documentation for support for microcontrollers. For designing circuits i've used eagle but it is difficult to get used to after coming from circuit wizard. What do engineers use for testing/simulating circuits? Do you use breadboarding, PCB prototype or similar? &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-03T00:51:32.583" CommunityOwnedDate="2011-03-02T20:40:35.897" Title="Testing/Simulating Circuits" Tags="&lt;simulation&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="2" />
  <row Id="10954" PostTypeId="2" ParentId="10884" CreationDate="2011-03-02T20:33:38.523" Score="5" ViewCount="" Body="&lt;p&gt;A transmission line can be modeled as an infinite set of capacitors and inductors(loss-less). You start to use this model as your electrical line becomes large enough that you cannot think of the line as an instant connection.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;General Idea&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;First, an LC circuit is going to have ring, and if it suddenly hits an &quot;open&quot; instead of another LC circuit, it will bounce very high. If you were to make a model using 10 inductors and 10 capacitors this would easily happen. When you place termination on the end you are damping the signal. If you have a perfectly matched resistor at the end you will have 0 overshoot as the resistor will dissipate its power.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Source Termination&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;If you instead place a resistor that matches the transmission line in series between the source and the transmission line you get one of the most effective termination techniques. In this case the line can only be driven to 1/2 of the target voltage, but the signal travels down the line, when it hits the open at the other end(most inputs are almost opens with very high impedances) it bounces, doubling, and giving you a full voltage at the receiver. The signal then travels backwards and when it reaches the source terminates on the resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This may not be instantly clear, I would very much suggest &quot;High Speed Digital Design: A Handbook of Block Magic&quot;, but this means your line does not drive nearly as high at one point, and noise is a function of dV/dt. This only terminates noise on the line at the source, which helps a large amount. I would heavily suggest you tear into my favorite handbook of black magic.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Trace Impedance&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Most people have heard of the simple equation forms of inductance and capacitance. Capacitance goes up with area and down with distance. Inducantance goes up with the size of the loop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you think of of a trace above a ground plane, as your widen the trace, the area increases but distance does not. This means that your capacitance increases while your inductance stays the same. As your distance increases, your area must increase a lot to keep the same impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many many different calculators out there. I found &lt;a href=&quot;http://www.technick.net/public/code/cp_dpage.php?aiocp_dp=util_pcb_imp_calculator&quot; rel=&quot;nofollow&quot;&gt;one&lt;/a&gt; instantly with a &lt;a href=&quot;http://www.google.com/search?q=pcb+trace+impedance+calculator&quot; rel=&quot;nofollow&quot;&gt;google search&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just match your impedance, add some termination, and try to avoid bad practices like bridging across a break in a ground plane(No embedded traces around these signal lines). I hope this also makes the physical affects a little more clear.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Too Small a Termination?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;You will actually get reflections, but instead of bouncing up, it will bounce down. An open will double your voltage, it will all reflect backwards. A short does the opposite, giving you zero voltage. It also greatly increases your power absorption from your driver.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-02T23:48:21.710" LastActivityDate="2011-03-02T23:48:21.710" />
  <row Id="10955" PostTypeId="1" CreationDate="2011-03-02T21:19:25.740" Score="2" ViewCount="132" Body="&lt;p&gt;Hey all - I have an AVR project in mind that will require a 13 by 13 LED matrix of bright white LEDs. I'll be wiring up my own matrix to do this (not using premade 8x8's). I plan on using some shift registers to control the anodes/cathodes (columns/rows).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will be my first project with an LED matrix and my first time working with shift registers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure if my shift registers can handle the current for this many LEDs (if I lit up an entire row for example). I don't know the proper way to wire this up, but I understand that I should control each row (maybe each column?) with a transistor of some kind between my microcontroller/shift register and the LEDs. I'm having trouble finding good explanations of how something like this should be wired up, or how to calculate the current requirements and how that translates to picking the right components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any advice would be appreciated. Thanks!&lt;/p&gt;&#xA;" OwnerUserId="3219" LastActivityDate="2011-03-02T21:34:50.990" Title="How to switch/power a 13x13 LED Matrix?" Tags="&lt;microcontroller&gt;&lt;led&gt;&lt;transistor&gt;&lt;shift-register&gt;" AnswerCount="1" />
  <row Id="10956" PostTypeId="2" ParentId="10955" CreationDate="2011-03-02T21:34:50.990" Score="2" ViewCount="" Body="&lt;p&gt;I would suggest that you should use a shift-register chip that has decent current-sinking capability for the cathodes, and use a shift-register chip to drive discrete transistors for the anodes.  Perhaps wire the matrix as 7x26 and use two TLC5925 chips for the columns, and use a 74HC164 or equivalent to drive seven nice beefy transistors for the rows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually, it may be a good idea to rig up the rows with a counter chip and a 555-timer wired so that they will automatically scan, but the main processor can 'nudge' the timer when it's almost ready for its next count.  Such a circuit could ensure that no matter what the processor did, it would not be possible for a row to be energized much more than 1/5 of the time (the processor could strobe six rows quickly, then linger on the seventh, then six rows quickly, linger on the seventh, etc. but the hardware would limit what fraction of the time would be spent on any one row even in a worst-case situation.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-02T21:34:50.990" />
  <row Id="10957" PostTypeId="2" ParentId="10953" CreationDate="2011-03-02T21:45:09.813" Score="2" ViewCount="" Body="&lt;p&gt;whatever works - I've prototyped, built PCBs for more complex stuff, done extensive verilog simulation for large digital designs (100,000s of gates), thrown that in FPGAs for some testing and then built real silicon&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Really you need to figure out the place on the cost/time to market curve that works for a particular project - for digital circuits it's worth being able to extract net lists for (verilog/vhdl) simulation, for analog stuff you use spice &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting access to digital (verilog/vhdl) models for microcontrolers can get to be expensive - it may be faster and cheaper to just go ahead a build a pcb (or protoboard) so you can hack away - it depends on how much you value your time and your budget&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-02T21:45:09.813" CommunityOwnedDate="2011-03-02T21:45:09.813" />
  <row Id="10958" PostTypeId="2" ParentId="7049" CreationDate="2011-03-02T21:58:30.463" Score="0" ViewCount="" Body="&lt;p&gt;Watch for stack overflows.  Maybe you have too many nested calls to functions.  Try to iron it out by calling them one after another where possible.&#xA;Some functions might as well be replaced by macros.  That might add a bit more weight to your code, but will keep your stack low.&lt;/p&gt;&#xA;" OwnerUserId="3223" LastActivityDate="2011-03-02T21:58:30.463" />
  <row Id="10959" PostTypeId="1" CreationDate="2011-03-02T22:07:41.247" Score="2" ViewCount="103" Body="&lt;p&gt;When I was in High School I used to work with the &lt;a href=&quot;http://spacecats.mit.edu/~6.270/about/&quot; rel=&quot;nofollow&quot; title=&quot;6.270 FTW!!!&quot;&gt;MIT 6.270 Robotics Kits&lt;/a&gt; in a Robotics class I both took and then later was a TA for. I loved those kits, they had an embedded controller you could program in C-code, and you built the robots using legos.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/UertD.jpg&quot; alt=&quot;6.270 Board&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=J5Kdr5f_9dY&quot; rel=&quot;nofollow&quot; title=&quot;Click for 6.270 video goodness&quot;&gt;&lt;img src=&quot;http://i.imgur.com/R4qbZ.png&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there anywhere I can purchase one of these boards? I see that I get one if I &lt;a href=&quot;http://spacecats.mit.edu/sponsors/info.shtml&quot; rel=&quot;nofollow&quot; title=&quot;DO WANT&quot;&gt;become a Gold supporter of the 6.270&lt;/a&gt; but I don't have a spare $10,000 at the moment...&lt;/p&gt;&#xA;" OwnerUserId="3221" LastActivityDate="2011-03-02T22:22:05.087" Title="Can I purchase an MIT 6.270 kit anywhere? If not are there alternatives?" Tags="&lt;robotics&gt;&lt;kit&gt;" AnswerCount="1" />
  <row Id="10960" PostTypeId="2" ParentId="10959" CreationDate="2011-03-02T22:22:05.087" Score="1" ViewCount="" Body="&lt;p&gt;Why don't you just buy a LEGO RCX or NXT set? They're exactly what you're searching... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://mindstorms.lego.com/en-us/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;http://mindstorms.lego.com/en-us/Default.aspx&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Lego_Mindstorms&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Lego_Mindstorms&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-03-02T22:22:05.087" CommentCount="2" />
  <row Id="10961" PostTypeId="2" ParentId="10884" CreationDate="2011-03-02T23:02:27.590" Score="2" ViewCount="" Body="&lt;p&gt;Imagine a transmission line as being a bunch of hanging weights connected by springs.  If everything is uniform, and one gives a weight at the north end of the line a brief southward shove and return it to its original position, a very nice wave will propagate southward down the line; the energy that gets put into each weight from one side will be perfectly delivered to the other, so that once the wave has passed by a weight that weight will be motionless in its original position.  All very good until the wave hits the end of the line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At that point, one of three general things can happen:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&lt;li&gt;If the last weight on the south side has can move freely with nothing connected on its south side, it will accept energy from the second-to-last wave, but won't have anything to push against.  The northward push-back that it didn't receive from the south side won't cancel out the southward push it got from its north side.  The uncanceled momentum of the weight will thus cause it to pull the weight north of it south, and start a wave that propagates to the north.  Note that while the original north-south wave was a compression wave which resulted in waves traveling briefly south from their starting point, the reflected wave will be a tension wave with waves traveling south.&#xA;&lt;li&gt;If the last weight on the south side has its south-side spring attached to an immovable wall, the wall will push back harder than would one of the normal weights.  This harder push-back will cause the weight to send a wave back toward the starting point; this new wave will be a compression wave like the original, but will cause the weights to shift briefly north of their start point.&#xA;&lt;li&gt;If the south spring of the southernmost weight is connected to something that offers just the right amount of resistance, all the energy of the wave will be dumped into that resistance, and there will be no reflection.&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The scenario where the last weight has some resistance, but not the right amount, will behave as a combination of (1) and (3), or (2) and (3) above.  The scenario to shoot for is #3.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-02T23:02:27.590" />
  <row Id="10962" PostTypeId="1" AcceptedAnswerId="10968" CreationDate="2011-03-02T23:05:34.437" Score="2" ViewCount="183" Body="&lt;p&gt;What is the difference between &quot;forward&quot; and &quot;reverse&quot; voltages when working with diodes and LED's?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I realize this question is answered elsewhere on the interwebs such as wikipedia, but I am looking for a short summary that is less of a technical discussion and more a useful tip to someone using diodes in a hobby circuit.&lt;/p&gt;&#xA;" OwnerUserId="2028" LastActivityDate="2011-03-02T23:23:27.317" Title="What is &quot;forward&quot; and &quot;reverse&quot; voltage when working with diodes?" Tags="&lt;diode&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="10963" PostTypeId="2" ParentId="10962" CreationDate="2011-03-02T23:12:02.560" Score="1" ViewCount="" Body="&lt;p&gt;Forward-bias is when the anode (the pointy part of the symbol) is positive and the cathode (the bar) is negative. Reverse-bias is when the anode is negative and the cathode is positive. A lot of current flows when the diode is forward-biased, provided that the voltage is higher than 0.6V or so for a silicon diode or 0.3V or so for a germanium device. A very small amount of current flows if a diode is reverse-biased.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a DVM and some diodes, you can check it for yourself. Diode cathode leads are usually identified with a band, so if you switch the DVM to a low resistance setting, and connect the leads across the diode in both directions, you should see a low resistance in one direction and a high resistance in the other direction, provided that the DVM is supplying a high enough voltage. Some DVMs have a special diode test setting that is easier to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LEDs usually have a flat against the cathode lead.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-02T23:18:36.750" LastActivityDate="2011-03-02T23:18:36.750" />
  <row Id="10964" PostTypeId="2" ParentId="8326" CreationDate="2011-03-02T23:13:31.903" Score="0" ViewCount="" Body="&lt;p&gt;I recall someone telling about some switches he had which sounded like these.  Each switch assembly had an on-off-on momentary SPDT switch and two diodes, so that pushing the switch one way would allow current to flow just that way, and vice versa.  The switches were in turn connected to a latching relay which would open when current flowed one way and close when it flowed the other way.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-02T23:13:31.903" />
  <row Id="10966" PostTypeId="2" ParentId="4528" CreationDate="2011-03-02T23:22:00.193" Score="1" ViewCount="" Body="&lt;p&gt;One approach might be to use a programmable logic device as a gray-code ripple counter with enough stages that you can simply poll the value at a convenient rate and not lose counts.  Note that one advantage of a gray-code ripple counter over some other approaches is that there's no danger of noisy inputs glitching the counter provided that no input changes when the other input isn't stable.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-02T23:22:00.193" />
  <row Id="10967" PostTypeId="2" ParentId="10962" CreationDate="2011-03-02T23:22:13.090" Score="2" ViewCount="" Body="&lt;p&gt;Typically the forward voltage is the voltage at which current starts to flow in the normal conducting direction (as mentioned above it's somewhere in the range 0.3-0.6v)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reverse voltage is sort of the same thing - it's the voltage where current starts to flow when the diode is in the normally non-conducting region - this is also the point where the diode is likely to turn into a charred mess as all the internal semiconductor stuff turns to mush (choose a value somewhat larger than the largest PEAK [not RMS] AC voltage the diode will see)&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-02T23:22:13.090" CommentCount="1" />
  <row Id="10968" PostTypeId="2" ParentId="10962" CreationDate="2011-03-02T23:23:27.317" Score="3" ViewCount="" Body="&lt;p&gt;The &lt;strong&gt;forward voltage&lt;/strong&gt; is the voltage drop across the diode if the voltage at the anode is more positive than the voltage at the cathode (if you connect + to the anode).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will be using this value to calculate the power dissipation of the diode and the voltage after the diode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;strong&gt;reverse voltage&lt;/strong&gt; is the voltage drop across the diode if the voltage at the cathode is more positive than the voltage at the anode (if you connect + to the cathode).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is usually much higher than the forward voltage. As with forward voltage, a current will flow if the connected voltage exceeds this value. This is called a &quot;breakdown&quot;. Common diodes are usually destroyed but with Z and Zener diodes this effect is used deliberately.&lt;/p&gt;&#xA;" OwnerUserId="1950" LastActivityDate="2011-03-02T23:23:27.317" CommentCount="1" />
  <row Id="10969" PostTypeId="2" ParentId="10953" CreationDate="2011-03-02T23:24:45.763" Score="1" ViewCount="" Body="&lt;p&gt;I use SPICE for simulating analogue circuits. For MCUs, I sometimes use the simulators provided with the development tools, but I usually either design a PCB, or use a manufacturer's development board, and do my testing and debugging on actual hardware.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-02T23:24:45.763" CommunityOwnedDate="2011-03-02T23:24:45.763" CommentCount="1" />
  <row Id="10970" PostTypeId="2" ParentId="10925" CreationDate="2011-03-03T00:11:24.200" Score="0" ViewCount="" Body="&lt;p&gt;I'd check out &lt;a href=&quot;http://www.comblock.com&quot; rel=&quot;nofollow&quot;&gt;Comblocks&lt;/a&gt; offerings. We got some of their stuff recently and so far I'm pleased.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-03-03T00:11:24.200" />
  <row Id="10971" PostTypeId="2" ParentId="10953" CreationDate="2011-03-03T00:51:32.583" Score="2" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;Spice for analog&lt;/li&gt;&#xA;&lt;li&gt;VHDL/Verilog for inside FPGAs and with RAMs&lt;/li&gt;&#xA;&lt;li&gt;HyperLynx for signals integrity&lt;/li&gt;&#xA;&lt;li&gt;Vendor's custom tools for power supplies&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-03T00:51:32.583" CommunityOwnedDate="2011-03-03T00:51:32.583" />
  <row Id="10972" PostTypeId="1" AcceptedAnswerId="10974" CreationDate="2011-03-03T01:11:16.430" Score="3" ViewCount="286" Body="&lt;p&gt;This is a question purely out of curiosity. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have several various PCBs, and I'm curious as to how many layers they use, which helps me decide how many layers to use in my project (for example a cheap competing product using 4 layers suggests to me it is possible to do my product with a 4 layer design). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;From looking at the vias (and where they connect to), I can usually determine if they have 2 layers or more, and I can tell apart single layer boards too because they don't have a top or a bottom side, however, I've never been able to actually count the number of layers a more complex board like a motherboard or graphics card uses. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any clues?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-12T19:44:22.653" LastActivityDate="2011-05-12T19:44:22.653" Title="How can you tell how many layers a PCB has?" Tags="&lt;pcb&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="10973" PostTypeId="2" ParentId="10972" CreationDate="2011-03-03T01:34:31.353" Score="4" ViewCount="" Body="&lt;p&gt;Cut the board in half and inspect the copper.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-03T01:34:31.353" CommentCount="7" />
  <row Id="10974" PostTypeId="2" ParentId="10972" CreationDate="2011-03-03T01:56:09.630" Score="4" ViewCount="" Body="&lt;p&gt;As far as non-destructive methods, you may be able to shine a bright light into the edge and through a corner see the copper planes.  Signal traces may be hiding though, and this only works if the copper comes fairly close to the edge, which it may not.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a bright light, it's easy to see if a board has inner layers even if it doesn't have blind vias.  Find some place on the board where there aren't traces/planes on the visible, outer layers and see if you can see light through it.  If it's blocked in some places, that's probably copper.  Even without that, most multi-layer boards I've dealt with using the standard green LPI have a darker appearance than their 2-layer counterparts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the board designer had space to kill or the manufacturing engineer wanted for some reason (not sure why), I've also seen boards with a &quot;stair-step&quot;; each layer labeled with a copper number and cutouts in the other layer to be able to see it.  This might be unique to my old company though, as our layout tech did all sorts of strange things.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-03T01:56:09.630" CommentCount="5" />
  <row Id="10975" PostTypeId="1" AcceptedAnswerId="11031" CreationDate="2011-03-03T03:55:24.193" Score="2" ViewCount="146" Body="&lt;p&gt;I have a pair of small battery-operated self-logging 3-axis accelerometer devices that each use a microSD flash device for storage (the &lt;a href=&quot;http://www.gcdataconcepts.com/x250-2.html&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;GCDC X250-2&lt;/a&gt;&lt;/strong&gt;). Unfortunately, the devices do not buffer microSD writes, so the recorded data has frequent gaps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to find/create a portable device that has a cable that plugs into a microSD slot, and connects to a large ram cache, so writes can proceed without delay. Ideally, this device would spool to an SD card or other permanent storage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many microcontrollers available that can talk to the SPI bus, simulate an SD card, and write data to RAM. It should also be possible to program a small Linux PC to do this, effectively emulating an SD card. The problem is finding a cable or something that can plug into a microSD slot!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas for a complete system, or the components needed to build one?&lt;/p&gt;&#xA;" OwnerUserId="3225" LastActivityDate="2011-03-04T20:03:01.583" Title="RAM device that plugs into microSD slot?" Tags="&lt;hardware&gt;&lt;microsd&gt;&lt;buffer&gt;&lt;ram&gt;" AnswerCount="4" CommentCount="10" />
  <row Id="10980" PostTypeId="1" AcceptedAnswerId="10992" CreationDate="2011-03-03T08:22:47.847" Score="0" ViewCount="145" Body="&lt;p&gt;Hi, I am working with the following IR photodiode &lt;a href=&quot;http://www.mouser.com/catalog/specsheets/bpv22nf.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.mouser.com/catalog/specsheets/bpv22nf.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I am having some trouble figuring out what sort of IR emitter I can use with this. I am trying to setup simple IR data transfer between microcontrollers.  The datasheet makes me think I could use either a 950nm emitter or a 830-880nm emitter but I'm not entirely sure. Also, how closely should I match the rise and fall time? The beam angle? I'd like to use a through hole package, which may limit my choices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for the help.&lt;/p&gt;&#xA;" OwnerUserId="954" LastActivityDate="2011-03-04T08:06:06.967" Title="Choosing The Right IR Emitter for a Photodiode" Tags="&lt;led&gt;&lt;communication&gt;&lt;ir&gt;&lt;infrared&gt;&lt;emitter&gt;" AnswerCount="3" />
  <row Id="10982" PostTypeId="1" AcceptedAnswerId="10987" CreationDate="2011-03-03T10:38:48.897" Score="2" ViewCount="116" Body="&lt;p&gt;My requirement is to transmit a binary form of data from one Road Junction to another road junction which is around 4 to 5 km away.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am going to get the traffic information from each road in the form of binary (4 bits) and transmit this data to the connected junctions of my current traffic measured junction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I want to transmit a binary form (For ex: 1010) to that junction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the other junctions I have a Receiver which receives this binary form of data and manipulates this. So for this requirement which Transmitter and Receiver is good?&#xA;I have an option to use FM transmitter and FM receiver based on my past experience. But I want to explore things and find Transmitter and Receiver other than FM transmitter and Receiver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope you got it right. I don't know If I am overlooking anything here.&lt;/p&gt;&#xA;" OwnerUserId="1731" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-03T10:41:40.810" LastActivityDate="2011-03-03T19:49:25.313" Title="Need suggestion in choosing an effective wireless Transmitter and Receiver." Tags="&lt;wireless&gt;&lt;receiver&gt;&lt;transmitter&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="10983" PostTypeId="2" ParentId="10980" CreationDate="2011-03-03T10:42:20.360" Score="1" ViewCount="" Body="&lt;p&gt;well the data sheet says 'peak sensitivity' is 940nm but it will do 790-1050 - I'd say anything above 70-80% in Figure 6 should be OK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as rise/fall times are concerned look at the signals you want to send: are they faster than signals you can send with the worst of the rise and fall times (and cut off freq) of the sender and receiver? - if so you should be OK&lt;/p&gt;&#xA;&#xA;&lt;p&gt;beam angle depends on how far you want to send the signal and the optics you're using&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-03T10:42:20.360" />
  <row Id="10984" PostTypeId="2" ParentId="10982" CreationDate="2011-03-03T12:04:19.230" Score="1" ViewCount="" Body="&lt;p&gt;I would suggest you use an &lt;a href=&quot;http://www.digi.com/products/wireless-wired-embedded-solutions/zigbee-rf-modules/point-multipoint-rfmodules/xbee-series1-module.jsp#overview&quot; rel=&quot;nofollow&quot;&gt;xbee&lt;/a&gt;. i think this will suit your needs.&lt;/p&gt;&#xA;" OwnerUserId="2995" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-03T19:49:25.313" LastActivityDate="2011-03-03T19:49:25.313" CommentCount="3" />
  <row Id="10985" PostTypeId="2" ParentId="10980" CreationDate="2011-03-03T12:19:40.013" Score="1" ViewCount="" Body="&lt;p&gt;i think you could also improve and broaden the beam angle if you were to use SMD parts, since its not all that hard to DIY.&#xA;as Taniwha pointed out the datasheet says it maxes out at 940, but i would go up to 1.1k maximum before i would start crossing my fingers :)&lt;/p&gt;&#xA;" OwnerUserId="2995" LastActivityDate="2011-03-03T12:19:40.013" CommentCount="2" />
  <row Id="10987" PostTypeId="2" ParentId="10982" CreationDate="2011-03-03T13:21:45.403" Score="2" ViewCount="" Body="&lt;p&gt;XBEE (XBEE Pro to be precise) is a good option if you don't have obstacles in between... XBEE simulates Wired communication over Air. All you need to do is get Two XBEE Modules. It's same like communicating over RS-232. Whatever you'll write in Your Serial Buffer, it will be transmitted over wireless medium. Moreover, there are some Readymade protocol stacks available in market by which you can do Mesh Networking. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But Keep in mind that, XBEE will work for the distance you mentioned only if it is obstacle free or less obstacles. &lt;/p&gt;&#xA;" OwnerUserId="2574" LastActivityDate="2011-03-03T13:21:45.403" CommentCount="6" />
  <row Id="10988" PostTypeId="1" AcceptedAnswerId="11490" CreationDate="2011-03-03T13:31:27.223" Score="0" ViewCount="36" Body="&lt;p&gt;I've been trying to work with the Actel SmartFusion FPGA/MCU SOC boards and their &quot;free&quot; toolchain that includes an Eclipse-based &quot;SoftConsole&quot; IDE that appears to be based on the GNU C/C++ compiler chain.  The &lt;a href=&quot;http://www.actel.com/products/software/softconsole/&quot; rel=&quot;nofollow&quot;&gt;Actel website claims&lt;/a&gt; the compiler supports C and C++ but the &lt;a href=&quot;http://www.actel.com/documents/softconsole_FAQ.pdf&quot; rel=&quot;nofollow&quot;&gt;FAQ says [warning: pdf]&lt;/a&gt; C++ projects are not supported.  Have any of you succeeded in creating simple C++ classes/objects with the tools?&lt;/p&gt;&#xA;" OwnerUserId="923" LastActivityDate="2011-03-15T12:15:23.953" Title="Actel Tools and C++" Tags="&lt;actel&gt;&lt;microsemi&gt;&lt;softconsole&gt;&lt;smartfusion&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="10989" PostTypeId="2" ParentId="10975" CreationDate="2011-03-03T13:45:43.527" Score="0" ViewCount="" Body="&lt;p&gt;An option is to just solder off the connector and add wires instead. You can wire it to another board directly or go through another board that has both the connector and connectors you can connect the buffer to.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-03-03T13:45:43.527" />
  <row Id="10990" PostTypeId="1" AcceptedAnswerId="10991" CreationDate="2011-03-03T14:00:17.447" Score="1" ViewCount="57" Body="&lt;p&gt;I'm kind of new to all this and the choices out there is kind of overwhelming when it comes to selecting a SRAM package and Flash eprom to go with a 10 Mhz Z80180.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for a 128 KB SRAM and a small eprom to contain the boot code, the eprom needs to shadow the the first 512 bytes or so of the SRAM (for the boot up process).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any advice for a good value alternatives is highly appreciated.&lt;/p&gt;&#xA;" OwnerUserId="3186" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-03-03T16:10:15.740" LastActivityDate="2011-03-03T16:10:15.740" Title="Advice on suitable SRAM" Tags="&lt;memory&gt;&lt;eeprom&gt;&lt;sram&gt;" AnswerCount="1" />
  <row Id="10991" PostTypeId="2" ParentId="10990" CreationDate="2011-03-03T14:29:35.247" Score="2" ViewCount="" Body="&lt;p&gt;For the flash I would take parralel flash chip from some 2000-2005 years PC MBs, newer have serial flash usually. They are rated at 70ns, so should work at 10Mhz easily.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the SRAM - not much production left of 'vanilla' SRAM, check out Samsung site, they still have 10ns 3.3 and 5v parts with various widths and sizes, price range - up to 10$ in retail). Most of these are in SOIC package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the 'shadow' functionality you would need some sort of memory controller (they were produced, but probably hard to find these days), but in your simple case you might wire chip select to OR of first bits of address bus, be sure to select fastest logic chips for this circuit.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-03T14:29:35.247" CommentCount="0" />
  <row Id="10992" PostTypeId="2" ParentId="10980" CreationDate="2011-03-03T14:32:06.763" Score="2" ViewCount="" Body="&lt;p&gt;Almost all PIN photodiodes have very similar response curves. Check out figure 6 in the datasheet to see how the diode responds to different wavelengths. For instance, if you use an emitter at 850 nm instead of 950 nm, you'll only lose about 5% of the optical power, as compared to 950 nm. That's not much. If you look under the &quot;Absolute Spectral Sensitivity&quot; field in the Optical Characteristics table, you'll see how much current you get per watt of optical power. The angle in the datasheet should describe from what angles light will fall onto the photodiode. As the angle increases, the power will drop. It has a curved lens, so this will be mitagated a bit, but it's still a factor. Check out Figure 7 to see how this drops off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What type of data will you be sending? You're going to want to hook this diode up to a &lt;a href=&quot;http://en.wikipedia.org/wiki/Current-to-voltage_converter&quot; rel=&quot;nofollow&quot;&gt;transimpedance amplifier&lt;/a&gt; (a current to voltage amp) in order to get decent gain while preserving the bandwidth. As long as your datarate is minimal (&amp;lt; 100 kHz bandwidth, say) then it should be pretty straight forward.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're willing to change your receiver configuration, then I'd recommend looking at this chip: &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/opt101.html&quot; rel=&quot;nofollow&quot;&gt;OPT101&lt;/a&gt;. TI will send you 5 samples for free. I'm using this chip now and it's very nice - has a built in amplifier to make things easy. It also comes in a DIP package.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-03-04T08:06:06.967" LastActivityDate="2011-03-04T08:06:06.967" />
  <row Id="10993" PostTypeId="2" ParentId="10975" CreationDate="2011-03-03T14:46:35.517" Score="0" ViewCount="" Body="&lt;p&gt;I would suggest use a MSP430** to do the buffering. Use something like &lt;a href=&quot;http://www.sparkfun.com/products/544&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; to interface the uC. Depending on how you implement the buffer in the software, this &lt;a href=&quot;http://www.dharmanitech.com/2009/01/sd-card-interfacing-with-atmega8-fat32.html&quot; rel=&quot;nofollow&quot;&gt;article&lt;/a&gt; may be useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;**personal preference but any micro controller could work.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-03T14:46:35.517" />
  <row Id="10994" PostTypeId="1" AcceptedAnswerId="10997" CreationDate="2011-03-03T15:24:47.903" Score="2" ViewCount="121" Body="&lt;p&gt;Hi&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking into designing a badge for a tech conference and we're thinking of creating a small PCB with one or more LEDs on it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Requirements:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Less than $5 per unit for 2500 badges&lt;/li&gt;&#xA;&lt;li&gt;The PCB has to be around the size of a 3.5&quot; floppy with place to add a sticker with the participant's name of it&lt;/li&gt;&#xA;&lt;li&gt;A silk layer would be nice to show of the parts and complete the &quot;geek&quot; feeling&lt;/li&gt;&#xA;&lt;li&gt;Ideally it would run on a &quot;button&quot;/&quot;cell&quot; battery, but a AAA battery might be needed.&lt;/li&gt;&#xA;&lt;li&gt;It would be nice if it would run for up to a year, but the conference is two days so anything that would run for at least three days is doable&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Options we're thinking of:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Blinking a single red LED&lt;/li&gt;&#xA;&lt;li&gt;One &quot;glowing&quot; RGB led that changes between the three different colors of the event's design&lt;/li&gt;&#xA;&lt;li&gt;A strip of RGB LEDs making the whole badge &quot;glow&quot;&lt;/li&gt;&#xA;&lt;li&gt;Using some kind of plastic to use less LEDs to illuminate more of the badge&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The question is: what kind of architectures should I look into?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LM3909 is supposed to be nice, but out of production. Are there any replacement components like that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For stuff that glows I see two possibilities some MCU (MSP430 perhaps?) to do PWM between one or three colors or use a D/A to set the voltage of the LED to an appropriate level.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-03-03T16:12:58.270" Title="Tips on parts for a very low power LED blinker" Tags="&lt;pcb&gt;&lt;battery&gt;&lt;low-power&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="10995" PostTypeId="2" ParentId="10994" CreationDate="2011-03-03T15:34:05.420" Score="0" ViewCount="" Body="&lt;p&gt;The MSP430G2211 is under 50c in 1ku quantities. It could be a good fit.&#xA;Here are a couple of my own flashing LED projects based on it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;A href=&quot;http://blog.hodgepig.org/2010/09/30/jam-jar-lamp/&quot; rel=&quot;nofollow&quot;&gt;RGB Lamp&lt;/a&gt;, &lt;A href=&quot;http://blog.hodgepig.org/2010/09/12/577/&quot; rel=&quot;nofollow&quot;&gt;LED Chaser&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, for a flashing LED, a 555 could be the obvious choice.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-03T15:34:05.420" CommentCount="4" />
  <row Id="10996" PostTypeId="1" CreationDate="2011-03-03T15:45:21.047" Score="2" ViewCount="231" Body="&lt;p&gt;Can someone tell me how the proximity sensor on the Nexus S works or what it is? &lt;/p&gt;&#xA;" OwnerUserId="3230" LastActivityDate="2011-03-03T23:05:59.647" Title="Proximity Sensor Nexus S" Tags="&lt;sensor&gt;&lt;android&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="10997" PostTypeId="2" ParentId="10994" CreationDate="2011-03-03T15:46:14.867" Score="2" ViewCount="" Body="&lt;p&gt;The six-pin SOT-23 &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en019863&quot; rel=&quot;nofollow&quot;&gt;PIC10F200&lt;/a&gt; is $0.32 for 1ku, and can use a supply down to 2V. That would be a good choice. If you need PWM it could be implemented in software, as the device includes a timer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option would be the similar &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?category_id=163&amp;amp;family_id=607&amp;amp;subfamily_id=791&amp;amp;part_id=4605&quot; rel=&quot;nofollow&quot;&gt;ATtiny4&lt;/a&gt; from Atmel. It has more features, including PWM, but is more expensive at over $0.50 for 1ku.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-03T16:00:35.470" LastActivityDate="2011-03-03T16:00:35.470" CommentCount="1" />
  <row Id="10998" PostTypeId="1" AcceptedAnswerId="10999" CreationDate="2011-03-03T15:46:27.723" Score="1" ViewCount="123" Body="&lt;p&gt;I own a &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardUno&quot; rel=&quot;nofollow&quot;&gt;Arduino UNO&lt;/a&gt; with the &lt;strong&gt;ATmega328&lt;/strong&gt; Microcontroller.&lt;br&gt;&#xA;Which other Microcontrollers are compatible to the Arduino system?&lt;/p&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-03T16:00:28.603" LastActivityDate="2011-03-03T16:02:05.843" Title="Which Microcontroller can I use on a Arduino board?" Tags="&lt;arduino&gt;&lt;microcontroller&gt;&lt;atmega&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="10999" PostTypeId="2" ParentId="10998" CreationDate="2011-03-03T15:48:43.447" Score="3" ViewCount="" Body="&lt;p&gt;There are several varieties of Arduino available. All are based on the Atmel AVR 8 bit microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://arduino.cc/en/Main/Hardware&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Main/Hardware&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The UNO has a DIP socket which can support the ATMega8, ATMega168 or the ATMega328. See &lt;a href=&quot;http://arduino.cc/forum/index.php?topic=107.0&quot; rel=&quot;nofollow&quot;&gt;this thread on the Arduino forum&lt;/a&gt; for more detail.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-03T16:02:05.843" LastActivityDate="2011-03-03T16:02:05.843" CommentCount="4" />
  <row Id="11000" PostTypeId="2" ParentId="10998" CreationDate="2011-03-03T15:50:14.617" Score="1" ViewCount="" Body="&lt;p&gt;Generally Arduino (if not all) use Atmel AVR 8-bit MC's.&#xA;Which IMO is a good thing since I find them personally easier to use (and they are usually cheaper too).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not that PICS are bad or anything...&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-03-03T15:50:14.617" />
  <row Id="11002" PostTypeId="2" ParentId="10994" CreationDate="2011-03-03T16:12:58.270" Score="1" ViewCount="" Body="&lt;p&gt;With some RFID components, you can do things like automated people tracking:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/VFpC9.jpg&quot; alt=&quot;http://www.flickr.com/photos/blinkenarea/4800793412/&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://travisgoodspeed.blogspot.com/2010/06/hacking-next-hope-badge.html&quot; rel=&quot;nofollow&quot;&gt;http://travisgoodspeed.blogspot.com/2010/06/hacking-next-hope-badge.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think thats a more interesting use of technology than yet another Blinking Bow Tie: &#xA;&lt;img src=&quot;http://i.imgur.com/ymUVM.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-03T16:12:58.270" CommentCount="3" />
  <row Id="11003" PostTypeId="2" ParentId="10996" CreationDate="2011-03-03T16:18:55.233" Score="4" ViewCount="" Body="&lt;p&gt;I suspect it consists of an IR LED, and an IR phototransistor. When the IR LED's light reflects off your face, it is received by the phototransistor, which either generates an analog or digital (threshold-based) output. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-03-03T16:18:55.233" />
  <row Id="11004" PostTypeId="1" AcceptedAnswerId="11005" CreationDate="2011-03-03T16:43:07.833" Score="3" ViewCount="337" Body="&lt;p&gt;I’m trying to figure out how a step-up transformer works. A step-down transformer is simple and logical enough; you start out with a higher voltage and end with less, the remainder being wasted as heat. But with a step-up transformer, you end up with &lt;em&gt;more&lt;/em&gt; voltage than you start with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried looking it up, but all I can find (whether online or even in some electronics texts) is general information on how transformers work (induction, Faraday’s law, construction, etc.) and explanations of the difference between step-ups and step-downs in terms of the number of turns, but not specifically how step-ups result in &lt;em&gt;more&lt;/em&gt; voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where does that extra voltage come from? Not  magic…&lt;/p&gt;&#xA;" OwnerUserId="2042" LastActivityDate="2011-03-03T17:44:37.873" Title="How do step-up transformers work?" Tags="&lt;transformer&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="11005" PostTypeId="2" ParentId="11004" CreationDate="2011-03-03T16:51:51.160" Score="17" ViewCount="" Body="&lt;p&gt;I think what you're missing is the current...&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Step down transformers change a high voltage/low current, to low voltage/high current.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Step up transformers change a low voltage/high current, to high voltage/low current.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So, in an ideal 100% efficient transformer, the power doesn't change and no heat will be generated by the transformer, i.e. the power in = the power out, because Power = Volts x Amps.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-03T17:12:25.353" LastActivityDate="2011-03-03T17:12:25.353" CommentCount="3" />
  <row Id="11006" PostTypeId="2" ParentId="11004" CreationDate="2011-03-03T16:52:05.200" Score="4" ViewCount="" Body="&lt;p&gt;Think about it this way: magnetic field have no idea how many loops you have on the second half of transformer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, each loop on second side works like a small 'bettery' connected in series, the more loops - the more batteries - the more voltage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But as there is the same amount of magnetic field is divided on all loops, achivable current is less. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same works another way: Less loops - less voltage, but more current as more magnetic field is left for 1 loop.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;In ideal situation no heat is generated. Heat is generated the way you say only in linear regulators.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-03T16:52:05.200" />
  <row Id="11008" PostTypeId="2" ParentId="11004" CreationDate="2011-03-03T17:44:37.873" Score="11" ViewCount="" Body="&lt;p&gt;Think of a transformer as being a like gearbox (or pulley system, or lever, or other such machine).  A 10:1 gearbox can turn a 60rpm rotation into 600rpm, but if the output requires a certain amount of torque to rotate, the input will require at least ten times that much (slightly more, in practice, because of friction in the gearbox itself).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-03T17:44:37.873" CommentCount="1" />
  <row Id="11009" PostTypeId="2" ParentId="5949" CreationDate="2011-03-03T17:59:29.683" Score="2" ViewCount="" Body="&lt;p&gt;Modern semiconductor construction techniques generally require that N transistors be physically above a substrate which is at least as negative as they are(*), P transistors be above a &quot;well&quot; which is as positive as the transistors, and that the wells for P transistors be no more negative than the substrate upon which N transistors sit.  These requirements effectively require a DC voltage potential between the P-transistor wells and the substrate.  While it would be possible to power all the active circuits with AC, and use a minimal-current supply to bias the substrate and P-transistor wells, having such a circuit be able to keep state during the 'off' part of an AC cycle would require that it have internal capacitors whose behavior was predictable.  Given that there are unpredictable parasitic capacitances between transistors and the substrate/wells on which they sit, getting reliable behavior would be difficult.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some interesting techniques for AC-powered counters and things using discrete transistors, but such approaches would be incompatible the design efficiencies of chips sharing substate and wells among many transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(*)added per reminder Actually, one can get away with transistors being about 0.7 volts beyond the substrate voltage.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-03-10T02:29:04.993" LastActivityDate="2011-03-10T02:29:04.993" CommentCount="2" />
  <row Id="11011" PostTypeId="1" AcceptedAnswerId="11016" CreationDate="2011-03-03T19:30:55.263" Score="2" ViewCount="198" Body="&lt;p&gt;I've just got into electronics with an Arduino explorer kit from Oomlout and I have learned a lot about electronics so far, but now I want to start my first proper project. A robotic arm. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should be precise but barely needs to lift any weight at all (a laser pen). I would like it to be 30cm or so long, it would have one servo at the bottom for rotating the whole arm left and right, another up and down, then two more to lift the other segments up and down. Does anyone have any recommendations on servo's I should use? They don't need to be fast or powerful, just precise. And, of course, being cheap will be a bonus.&lt;/p&gt;&#xA;" OwnerUserId="2681" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-10T08:16:18.043" LastActivityDate="2011-03-10T08:16:18.043" Title="Which servo motors for a precise but not powerful robotic arm?" Tags="&lt;arduino&gt;&lt;robotics&gt;&lt;servo&gt;" AnswerCount="3" />
  <row Id="11012" PostTypeId="2" ParentId="10996" CreationDate="2011-03-03T21:02:24.407" Score="0" ViewCount="" Body="&lt;p&gt;It detects when the phone is close to your face during a phone call and turns off the screen and the touch functions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.intomobile.com/2010/01/05/nexus-one-unboxing-googles-first-superphone/&quot; rel=&quot;nofollow&quot;&gt;&quot;the proximity sensor turns off the display when your Nexus One is pressed up to your face during a phone call&quot;&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-03-03T21:02:24.407" />
  <row Id="11013" PostTypeId="2" ParentId="11011" CreationDate="2011-03-03T21:05:14.090" Score="1" ViewCount="" Body="&lt;p&gt;You might start with motors made by the Swiss manufacturer &lt;a href=&quot;http://www.maxonmotorusa.com/product_overview.html&quot; rel=&quot;nofollow&quot;&gt;Maxon&lt;/a&gt;. They're used in high-end robotic arms. They're expensive when bought new, but you might be able to get them cheaper off Ebay if you just need a few.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should also think about how you will measure position and connect the motor to the arm. A lot of your position error will be in the backlash in the mechanism you build, error in the position encoder, and flex in the arm itself. You might also google &quot;harmonic drive&quot; or &quot;anti-backlash gears.&quot;&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-03-03T21:05:14.090" CommentCount="1" />
  <row Id="11014" PostTypeId="2" ParentId="10996" CreationDate="2011-03-03T23:05:59.647" Score="1" ViewCount="" Body="&lt;p&gt;Go to the market and download a program called Elixir (&quot;Phone Explorer&quot; also does this and there's probably a dozen more).  When you run it go to the sensor tab and tap the triangle next to &quot;Proximity&quot;.  The first line should tell you what sensor is being used.  Then you can punch that part number into Google, get the datasheet and know everything about it.&#xA;My HTC 3G Slide uses a &lt;a href=&quot;http://www.capellamicro.com.tw/EN/products_view.php?id=45&amp;amp;mode=16&quot; rel=&quot;nofollow&quot;&gt;CM3602&lt;/a&gt; sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ok, &lt;em&gt;almost&lt;/em&gt; everything about it. Capellamicro wants you to register before you can download a datasheet.  Maybe your sensor manufacturer will be a little more generous.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;None the less, W5VO seems to be correct in his answer.&lt;/p&gt;&#xA;" OwnerUserId="2051" LastActivityDate="2011-03-03T23:05:59.647" />
  <row Id="11015" PostTypeId="2" ParentId="3062" CreationDate="2011-03-03T23:44:01.597" Score="4" ViewCount="" Body="&lt;p&gt;Another reason when done in production designs is to reduce your bill of materials (BOM). If your design has loads of 100 nF caps but needs one ~50 nF, it is often cheaper to use two 100 nF's in series due to the quantity you're buying the 100 nF's in, and also reduces pick/place setup time. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-04T02:20:06.143" LastActivityDate="2011-03-04T02:20:06.143" />
  <row Id="11016" PostTypeId="2" ParentId="11011" CreationDate="2011-03-04T04:41:01.210" Score="1" ViewCount="" Body="&lt;p&gt;I wouldn't necessarily start with motors right off the bat.  You have to look at your entire system.  How are you going to mount the motors, and where?  If you put a motor at every joint, you have to remember that you're increasing the payload requirements for each motor in the chain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think about whether or not your first project &lt;em&gt;really&lt;/em&gt; needs to be so precise.  And how do you define precise?  Within 2mm?  0.5mm?  10 microns?  For gripping, maybe you can get away with a simple RC servo.  Now you've just reduced the payload for the other motors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Antibacklash is very important, and you could use anti-backlash gears and nuts, or you could go a little simpler and cheaper with belts and one or more idler pulleys.  The potential advantage here is that you can move a motor off of a joint and have it somewhere else where the weight of the motor doesn't adversely affect the system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to hear what others think about this, but ultimately your servo's precision is going to boil down to your encoder and the gearing in your system, and the quality of your servo controller.  So perhaps the motor doesn't need to be a Maxon or a MicroMo, but something less expensive that still lets you connect a high-resolution encoder.  While I am not a fan of stepper motors, you could even go with steppers and encoders, which would simplify the system further.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-03-04T04:41:01.210" CommentCount="3" />
  <row Id="11017" PostTypeId="1" AcceptedAnswerId="11019" CreationDate="2011-03-04T04:42:34.853" Score="1" ViewCount="152" Body="&lt;p&gt;I'm plan to interface a atmel avr with my alarm system in home but the issue is DSC has a propriatary protocol between the keypad and the base. So has anyone messed with this before or can give me a few beginners tips on how to reverse engineer this protocol?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The wiring is simple: Vcc, GND, Data, Clock&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Vcc is +12 volts and the data/clk lines are between +8-10 but work just fine through a voltage divider to the logic analyzer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Clock line is confusing tho, its a 1kHz clock at 50% duty but only runs for 41.600ms then it goes high for 5.400ms and then starts over again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Data line appears to change on on either rising or falling edge of the clock&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://oi52.tinypic.com/5tto2w.jpg&quot; rel=&quot;nofollow&quot;&gt;Open Door Data - Picture&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(0 is the Data line, 1 is the Clock line)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ifile.it/25pkd3z/DSC-Keybus-Logic.zip&quot; rel=&quot;nofollow&quot;&gt;OpenLogic Sniffer Files&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3239" LastEditorUserId="3239" LastEditorDisplayName="" LastEditDate="2011-03-05T04:14:54.663" LastActivityDate="2011-04-06T20:49:26.080" Title="DSC Keybus Protocol" Tags="&lt;atmel&gt;&lt;clock&gt;&lt;data&gt;&lt;reverse-engineering&gt;&lt;protocol&gt;" AnswerCount="2" />
  <row Id="11018" PostTypeId="1" CreationDate="2011-03-04T04:59:56.787" Score="-1" ViewCount="124" Body="&lt;p&gt;I have been looking at regulators for some time now, a couple of weeks, and I seem to be looking for something that is fairly non standard. I am taking 9v to 5v and want to out put 5v at a max of 2.5a. I would like the cut off to be as low as possible, like 5v, but I realize I may have to accept a vin cut off of 7v.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think I have found a circuit that will produce the values I want (9-5v in and 5v out at 2.5 amps with drop off at 7vin) I'm just a little curious as to what some of the sub scripts on the equations mean. The diagram is at the top of the page 14 in &lt;a href=&quot;http://www.national.com/ds/LM/LM340.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.national.com/ds/LM/LM340.pdf&lt;/a&gt; . What values should I, how would I find, to plug in to solve for Rsc and R1?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe this is the solution I'm looking for. If there are any glaring reasons that this will not work like I want but am missing, I appreciate the heads up.&lt;/p&gt;&#xA;" OwnerUserId="2617" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-03-04T19:01:26.530" LastActivityDate="2011-03-04T19:09:56.913" Title="Switching regulator question for 9 - 5v in 5v out at 2.5 amps" Tags="&lt;power&gt;&lt;voltage-regulator&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="11019" PostTypeId="2" ParentId="11017" CreationDate="2011-03-04T05:23:19.577" Score="1" ViewCount="" Body="&lt;p&gt;There is no simple answer to decoding a protocol, if they have a good encryption scheme setup then you are probably going to be up &amp;amp;$%* creek. With some work and more questions you might successfully figure out the kind of encryption, and then, if it is poorly implemented, decode it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Chances are that the keypad has a very simple protocol and the controller has some strict constraints on how many button pushes it will accept and such.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the note of the synchronous protocol, chances are that the protocol is a &lt;a href=&quot;http://en.wikipedia.org/wiki/Non-return-to-zero&quot; rel=&quot;nofollow&quot;&gt;NRZ protocol&lt;/a&gt;. That is my best informed guess based on your explanation. I cannot open the files right now, but I hope this helps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fact that it changes on both clock edges is just a sign that both clock edges represent a point that a &quot;bit&quot; of data occurs. With NRZ you are just checking if there was a change or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this helped.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-03-04T05:23:19.577" CommentCount="3" />
  <row Id="11020" PostTypeId="1" CreationDate="2011-03-04T07:54:51.967" Score="1" ViewCount="184" Body="&lt;p&gt;I am lost in loading bootloader for Arduino Single Sided on ATMEGA8-16PU.&#xA;Here is my problem.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;I &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoBoardSerialSingleSided3.&quot; rel=&quot;nofollow&quot;&gt;made the Arduino Single Sided V3&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Placed ATMEGA8-16PU in the board and attached it to the &lt;a href=&quot;http://www.arduino.cc/en/Hacking/ParallelProgrammer&quot; rel=&quot;nofollow&quot;&gt;Parallel Programmer&lt;/a&gt; and attached external 9V battery.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Accessed the controller using &lt;code&gt;avrdude&lt;/code&gt; using command line and it returned correct signature &lt;code&gt;0x1e9307&lt;/code&gt;. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I executed this command &lt;code&gt;avrdude -p atmega8 -c dapa -P lpt1 -U lock:w:0xff:m&lt;/code&gt; it worked well. Everything was fine till this point and controller returning correct signature.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Then this &lt;code&gt;avrdude -p atmega8 -c dapa -P lpt1 -U hfuse:w:0xca:m -U lfuse:w:0xdf:m&lt;/code&gt; and suddenly after execution of this command controller was returning wrong signature &lt;code&gt;0x000012&lt;/code&gt;. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;What is wrong? I cannot go further? Why it is returning the wrong signature?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I noticed something odd, controller was not returning &lt;code&gt;0xffffff&lt;/code&gt; it means it is not bricked, its alive and hence returning signature whatever it is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe the default baud-rate of programmer is not matching anymore with the baud-rate change in controller for different clock source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What should I do ?&lt;/p&gt;&#xA;" OwnerUserId="2037" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-12T10:37:18.637" LastActivityDate="2011-03-12T10:37:18.637" Title="Wrong signature from ATMEGA8-16PU after setting fuses with avrdude" Tags="&lt;arduino&gt;&lt;atmega&gt;&lt;atmega8&gt;&lt;icsp&gt;" AnswerCount="1" />
  <row Id="11022" PostTypeId="2" ParentId="11018" CreationDate="2011-03-04T08:52:26.260" Score="3" ViewCount="" Body="&lt;p&gt;I am not sure you really want this :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(9-5)*2.5 = 10W power dissipation, which is manageble, but way way too hot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would think into DCDC step-down/up-down converters with external switch. 2.5A is easily achivable there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You spend more on chips, save on radiators &amp;amp; electricity bills :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-04T08:52:26.260" CommentCount="1" />
  <row Id="11023" PostTypeId="2" ParentId="10411" CreationDate="2011-03-04T09:28:20.653" Score="2" ViewCount="" Body="&lt;p&gt;Uso 4066 analog switches. These make perfectly good audio analog switches (&lt;a href=&quot;http://www.national.com/ds/CD/CD4066BC.pdf&quot; rel=&quot;nofollow&quot;&gt;See This&lt;/a&gt;) and have been used even in high-end audio (my old Quad 44 preamp uses similarily specced chips). These have been around for a long time and there may be better moderen equivelents. You would need a good few to build up a large matrix but they are easy to drive from ttl/cmos, 5v/3.3v etc.&lt;/p&gt;&#xA;" OwnerUserId="611" LastActivityDate="2011-03-04T09:28:20.653" CommentCount="2" />
  <row Id="11024" PostTypeId="5" CreationDate="2011-03-04T10:33:44.667" Score="0" ViewCount="" Body="&lt;p&gt;A transformer is a device usually used to change the voltage of an AC current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several types of transformer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Step down transformer&lt;/strong&gt;&#xA;The most common type used in electronics to reduce the voltage of a mains supply to a low voltage (typically 12v or 5v), as the first stage in the power supply. This provides isolation of the low voltage circuit from the mains supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Auto transformer&lt;/strong&gt;&#xA;Used if you want to power an appliance designed for use with mains from countries such as the USA with a voltage of 110v in a country that has a higher voltage such as the UK that has a voltage of 230v. This does not provide isolation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Audio transformer&lt;/strong&gt;&#xA;Used for impedance matching in audio circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;3 phase transformer&lt;/strong&gt;&#xA;Used in power transmission systems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transformers have a number of specifications used to identify it for use in a particular circuit:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Primary Voltage - the supply voltage.&lt;/li&gt;&#xA;&lt;li&gt;Secondary Voltage - the output voltage.&lt;/li&gt;&#xA;&lt;li&gt;Power rating - the load the transformer is designed to operate with, measured in VA (in most cases, i.e. resistive loads, this is equivalent to Watts).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Questions tagged with &lt;a href=&quot;/questions/tagged/transformer&quot; class=&quot;post-tag&quot; title=&quot;show questions tagged 'transformer'&quot; rel=&quot;tag&quot;&gt;transformer&lt;/a&gt; will typically be on the subject of power supplies and AC current, but could also include audio circuits and other topics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Schematic Symbol:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/YNjAr.gif&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-04T10:49:15.373" LastActivityDate="2011-03-04T10:49:15.373" />
  <row Id="11025" PostTypeId="4" CreationDate="2011-03-04T10:33:44.667" Score="0" ViewCount="" Body="A transformer is a device usually used to change the voltage of an AC current." OwnerUserId="-1" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-04T10:49:19.383" LastActivityDate="2011-03-04T10:49:19.383" />
  <row Id="11026" PostTypeId="2" ParentId="11020" CreationDate="2011-03-04T10:47:02.940" Score="1" ViewCount="" Body="&lt;p&gt;Looking at:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://frank.circleofcurrent.com/fusecalc/fusecalc.php?chip=atmega8&amp;amp;LOW=DF&amp;amp;HIGH=CA&amp;amp;EXTENDED=FF&amp;amp;LOCKBIT=FF&quot; rel=&quot;nofollow&quot;&gt;http://frank.circleofcurrent.com/fusecalc/fusecalc.php?chip=atmega8&amp;amp;LOW=DF&amp;amp;HIGH=CA&amp;amp;EXTENDED=FF&amp;amp;LOCKBIT=FF&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see that you've turned off all of the CKSEL bits, which seems to select &quot;external clock&quot;. Supplying a square wave to XTAL1 on your AVR might work.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-04T10:47:02.940" CommentCount="3" />
  <row Id="11027" PostTypeId="1" AcceptedAnswerId="11028" CreationDate="2011-03-04T11:42:00.710" Score="3" ViewCount="157" Body="&lt;p&gt;I'm trying to understand this mechanical drawing. (Another one. I asked a question about mechanical drawings a while back.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/QDyvL.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can work out most of the dimensions, but the mount pads are confusing me. They have two numbers (0.7 and 1.2) beside them. They could be any size for what I know...!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The drawing is for an SH type connector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many thanks.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-04T14:29:15.080" Title="Understanding a mechanical drawing" Tags="&lt;connector&gt;&lt;mechanical&gt;&lt;drawing&gt;" AnswerCount="2" />
  <row Id="11028" PostTypeId="2" ParentId="11027" CreationDate="2011-03-04T11:52:42.643" Score="11" ViewCount="" Body="&lt;p&gt;The 0.7 is the distance from the center of the smaller (contact) pads to the edge of the larger (mechanical) pad. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/eecPU.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 1.2 is the width of the larger pad. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/bTi5i.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice the dot both arrows point to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;You'll often see the indication &lt;code&gt;BSC&lt;/code&gt; next to one of the measurements. This means &lt;code&gt;Basic Spacing between Centers&lt;/code&gt; and is a nominal value. Could have been given here next to the 1mm (pitch) value, or next to a 6mm value between centers of first and last pad.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-03-04T14:29:15.080" LastActivityDate="2011-03-04T14:29:15.080" CommentCount="1" />
  <row Id="11029" PostTypeId="2" ParentId="11027" CreationDate="2011-03-04T11:54:53.173" Score="6" ViewCount="" Body="&lt;p&gt;They are actually 1.2 x 1.8.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wCGr4.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The dimensioning could be a lot clearer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wish that they would dimension to the pad centres That is how most PCB packages work.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-04T13:02:19.130" LastActivityDate="2011-03-04T13:02:19.130" CommentCount="5" />
  <row Id="11030" PostTypeId="2" ParentId="11011" CreationDate="2011-03-04T14:19:49.297" Score="0" ViewCount="" Body="&lt;p&gt;I like the idea of building first with cheap imprecise servos ( at less than 10 bucks each )  I think you will learn enough to justify the expense.  Putting the mass at the end of a 30 cm lever will greatly increase the load on the servo.  Consider using different servos in different places.  Using the smallest one at each place ( joint? ) that will do the job, that will lessen the load on the servo that has to move it.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-04T14:19:49.297" />
  <row Id="11031" PostTypeId="2" ParentId="10975" CreationDate="2011-03-04T14:45:21.363" Score="5" ViewCount="" Body="&lt;p&gt;The product has a maximum update rate of 512 Hz, which is really slow.  I understand that it uses a timestamp, takes three readings, buffers for FAT filesystem translation, and writes it all in ASCII/CSV format, which sounds like a lot.  However, an SD card configured for sustained writing should be able to do at least 2 megabytes per second, and class 10 cards can handle 10 megabytes per second.  At 512 Hz, the problem is &lt;em&gt;not&lt;/em&gt; the SD card.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your comment, you mentioned:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The manufacturer knows all about the&#xA;  problem, and is unable to fix it with&#xA;  the available hardware resources (it's&#xA;  only an 8051 that's breathing really&#xA;  hard). All pauses seem to be due to a)&#xA;  FAT overhead, and/or b) flash erase&#xA;  cycles.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Adding a buffer at the SD card is not going to solve this problem.  The bottleneck is up-stream of the SD card.  The &lt;a href=&quot;http://www.gcdataconcepts.com/faq.html#upgrade&quot; rel=&quot;nofollow&quot;&gt;manufacturer's FAQ&lt;/a&gt; reads: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;I have an old accelerometer, can I&#xA;  upgrade the firmware?&lt;/strong&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Yes. Please contact our sales&#xA;  department for instructions on how to&#xA;  return the unit to GCDC. We will&#xA;  upgrade the firmware and return the&#xA;  device promptly.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Unless you've worked out with them that they'll write you a firmware package which doesn't do any buffering/FAT filesystem translation and mutually agreed upon a protocol for a faster, gap-free data stream, adding a RAM device that plugs into an SD slot will not solve your problem. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, just because the task is bringing their 8051 to its knees doesn't mean that this is an un-solveable problem.  A faster, more powerful, more modern microcontroller could handle the data stream.  The on-board RAM on a decent micro should be enough to buffer the data.  Most small micros will run at 20 MHz or more, which is probably plenty fast, especially since they'll have hardware peripherals that can handle the DMA, SPI, and ADC tasks for you.  Of course, there are other people who have tried to solve the same problem - Take a look at &lt;a href=&quot;http://stackoverflow.com/questions/3307428/how-can-i-use-sd-card-for-data-logging-16bit-data-at-48ksps&quot;&gt;this SO question&lt;/a&gt; about logging data at 96kB/s.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have a few options:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Dead-bug a higher-performance microcontroller onto the existing PCB, and write some firmware which will handle the task.  If the 8051 isn't up to it, an ATmega probably is and a Cortex-M3 certainly is.  You might consider ignoring the FAT filesystem and write a simple flat file, and just emulate a USB drive with the microcontroller.&lt;/li&gt;&#xA;&lt;li&gt;Have the original manufacturer do this for you.  I don't see any mention of this problem on the website, so they could probably be motivated to fix the problem. They have all the schematics and drivers already written, so they could probably do this without too much trouble.&lt;/li&gt;&#xA;&lt;li&gt;Build your own.  You can have as fast an uninterrupted logging rate as you want, with as much precision as you want, with as many DOF as you want - You just have to pay for what you want.  The sky is the limit on this sort of project (and the budgets reflect this).  You won't get this nice a package for this much money, but I'm not sure what your requirements are.&lt;/li&gt;&#xA;&lt;li&gt;Buy a different one.  There are plenty of dataloggers that can handle faster serial streams without gaps, and a lot of accelerometers have as fast or faster update rates.  The +/-250 g &lt;em&gt;and&lt;/em&gt; +/-28 g range on this one is unusual, however.  &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-04T14:45:21.363" CommentCount="1" />
  <row Id="11032" PostTypeId="2" ParentId="10863" CreationDate="2011-03-04T15:25:25.527" Score="0" ViewCount="" Body="&lt;p&gt;I've actually brought this into practice and I can tell you 1KOhm works perfect for as long as I use the project. I know that is no guarantee, but it isn't based on hot-air.&lt;/p&gt;&#xA;" OwnerUserId="3241" LastActivityDate="2011-03-04T15:25:25.527" CommentCount="1" />
  <row Id="11033" PostTypeId="1" AcceptedAnswerId="11036" CreationDate="2011-03-04T16:01:37.900" Score="2" ViewCount="149" Body="&lt;p&gt;I used to charge my phone during the day at work with a USB cable (plugged into my workstation). Obviously USB doesn't provide the same amount of juice as an outlet so it took all day to charge but after the charge I noticed that the battery life was very low, maybe 2-3 hours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When charging using an outlet, obviously it only takes about an hour to charge, but afterwards it seems that my battery life is much longer about 5-6 hours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both tests were performed playing MP3s all day, nothing that would cause a serious difference between the two tests.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it just me?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: My question is about charging methods vs battery run time, not the charging methods. &quot;Faster&quot; in this case doesnt mean modified charging, it means using OEM charger with a power outlet.&lt;/p&gt;&#xA;" OwnerUserId="3242" LastEditorUserId="3242" LastEditorDisplayName="" LastEditDate="2011-03-04T16:23:01.280" LastActivityDate="2011-03-04T17:45:19.077" Title="Is it just me, or is charging via usb not as good as using an outlet?" Tags="&lt;power&gt;&lt;battery-charging&gt;&lt;phone&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="11035" PostTypeId="2" ParentId="10897" CreationDate="2011-03-04T16:19:57.630" Score="2" ViewCount="" Body="&lt;p&gt;Incidentally, it's possible to drive a 3-way multiplexed LCD entirely with logic-level signals.  To drive the display, run the common wires through all eight combinations of high and low, and drive each segment wire such that at least two of the three segments it controls will be &quot;correct&quot; (a segment will be &quot;clear&quot; if the state of the segment wire matches the state of its common wire, and &quot;dark&quot; if it differs).  It turns out that no matter what pattern of light and dark segments one wishes to display, every segment that's supposed to be &quot;dark&quot; will be energized 3/4 of the time, and every segment that's supposed to be &quot;light&quot; will be energized 1/4 of the time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a technique I invented myself in the 1990's, and have used in a couple of product designs.  The contrast ratio is the same as what one would get using 1/2-bias (as shown above), but not as good as what would be obtained using 1/3 bias.  In my implementation, I had to clock data through shift registers every frame, which used some current; if the circuitry were built into an ASIC I'm not sure how the efficiency would compare with that of a conventional multi-voltage technique.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note, that Motorola claims a patent on a technique somewhat like this, but they use a six-phase waveform rather than an eight-phase waveform, and they only achieve a 2:1 drive ratio rather than 3:1.  Their patent would cover the use of a four-phase waveform to drive a 2-way multiplex LCD, but explicitly specifies the use of 2n phases rather than 2^n.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-04T16:19:57.630" CommentCount="1" />
  <row Id="11036" PostTypeId="2" ParentId="11033" CreationDate="2011-03-04T16:41:49.967" Score="4" ViewCount="" Body="&lt;p&gt;When charging over a USB port which is also used for communication, you're limited to 2.5W/500mA.   When using a port dedicated for charging (which can be a female USB-A plug), you can use almost 10W/2A.  From these numbers, the dedicated charger is clearly better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, batteries have thermal and chemical properties which often limit the charge rate to something less than these values.  This is especially true for small batteries in confined spaces like your cell phone battery, and the lithium-ion chemistry which is likely used has the added potential of explosive thermal failure, so the charge rate is limited by some circuitry.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would be reasonable to assume that the maximum charge rate for your cell phone battery is a little less than 2A and more than 500mA.  Cell phone batteries are usually charged at about 1C, and the maximum cell voltage of a Li-ion is about 4.2V, so assuming a 1000mAh battery and a 90% efficient charger (which is generous), you'd need 4.6W of power to charge your battery as fast as possible. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Charging more slowly than this (i.e. at 2.5W) shouldn't diminish the charge level of the battery in any noticeable way.  A software power meter could be erroneously reporting a higher battery life due to heating of the battery and the consequent higher voltage, or any number of other errors.  If an accurate test (identical use patterns, signal strength, previous charge levels, etc) indicates that your phone has markedly less battery life after charging by USB, then either your battery is defective or your phone circuitry is poorly designed. &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-04T16:41:49.967" />
  <row Id="11037" PostTypeId="1" CreationDate="2011-03-04T17:23:27.823" Score="4" ViewCount="176" Body="&lt;p&gt;Im working on a project with a lot of external peripherals, so this means lots of wires. Any recommendations on how to keep them tidy while working on it? I don't want to use cable ties just yet as i need to keep moving them so would have to keep cutting them. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-19T00:48:49.310" CommunityOwnedDate="2011-03-04T17:27:40.557" Title="Tips for keeping lots of cables tidy" Tags="&lt;wire&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="2" />
  <row Id="11038" PostTypeId="2" ParentId="11033" CreationDate="2011-03-04T17:45:19.077" Score="1" ViewCount="" Body="&lt;p&gt;I have a few guesses as to what is actually happening.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) It could be an artifact of how the phone is determining how much battery life there is. The more advanced methods of battery life indication will watch the current draw over some sort of moving average. I could see a potential for a programming error that would cause you to have invalid readings after unplugging the power cable. There might actually be more power in the battery, but it would be hard to tell unless you know more about your device and how it is monitoring the voltage. You could always look at the voltage of the battery at 20% after being charged from USB vs wall and seem if the voltages are about the same.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) The lower current limit is able to get the battery up almost to full charge, but can't quite get it there all of the way. This could be checked in a similar manor as I mentioned before where you check the voltage of the battery after USB charge vs wall charge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Some devices do a method of charging and discharging after getting full even though your device is still plugged in. So it will get to 100% and then it will discharged to 90% and then start charging again. This is supposed to help with keeping some types of batteries healthy. I could see the situation where your device has discharged, but since it is on a lower current limit supply it takes it longer to charge.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-04T17:45:19.077" />
  <row Id="11039" PostTypeId="2" ParentId="11037" CreationDate="2011-03-04T17:49:44.220" Score="10" ViewCount="" Body="&lt;p&gt;I like to use &lt;a href=&quot;http://www.google.com/products/catalog?q=velcro+cable+ties&amp;amp;um=1&amp;amp;ie=UTF-8&amp;amp;cid=1877353722848648657&amp;amp;sa=X&amp;amp;ei=lyVxTcKbJ8H7lwe12e2YCQ&amp;amp;ved=0CD8Q8gIwAw#&quot; rel=&quot;nofollow&quot;&gt;Velcro Cable ties&lt;/a&gt;. Basically used the same way as ones you would have to cut, but instead you just have to pull them apart. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on what you are doing a &lt;a href=&quot;http://www.google.com/search?aq=f&amp;amp;sourceid=chrome&amp;amp;ie=UTF-8&amp;amp;q=wire+duct#q=wire+duct&amp;amp;hl=en&amp;amp;prmd=ivns&amp;amp;source=univ&amp;amp;tbs=shop:1&amp;amp;tbo=u&amp;amp;ei=_CVxTaDJD8GAlAfwjJ2FAQ&amp;amp;sa=X&amp;amp;oi=product_result_group&amp;amp;ct=image&amp;amp;resnum=3&amp;amp;ved=0CE0QzAMwAg&amp;amp;biw=1600&amp;amp;bih=1115&amp;amp;bav=on.2,or.&amp;amp;fp=4e757515720d3dfe&quot; rel=&quot;nofollow&quot;&gt;Wire Duct&lt;/a&gt; might benefit you more. They tend to get more messy on the inside, but can produce neater results on the outside.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-04T17:49:44.220" CommunityOwnedDate="2011-03-04T17:49:44.220" />
  <row Id="11040" PostTypeId="1" AcceptedAnswerId="11066" CreationDate="2011-03-04T18:25:28.033" Score="-1" ViewCount="81" Body="&lt;p&gt;I have a PCB with through the hole components on it and its temperamental does this mean that I have a dry joint? As I plug something in to the board and its stops being recognised on the computer(the programming software that is)? I have molex connectors to join every thing together. But these connections don't seem very good. I have read the voltage at my supply and at the pin of the pic and they are the same. So I assumed that this connection is &quot;good&quot;. Some of the joints on my PCB aren't volcano like more balls on the copper tracks. Could this be causing the problem? I don't have a good enough camera to get pictures of my soldering.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-03-04T18:41:31.610" LastActivityDate="2011-03-05T01:29:54.463" Title="Dry Joint and Connection?" Tags="&lt;soldering&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="11041" PostTypeId="2" ParentId="9288" CreationDate="2011-03-04T18:44:54.867" Score="1" ViewCount="" Body="&lt;p&gt;The vast majority of wires on a typical board are connected only to &lt;a href=&quot;http://en.wikipedia.org/wiki/Extra_low_voltage&quot; rel=&quot;nofollow&quot;&gt;extra-low-voltage&lt;/a&gt; power and digital signals -- neighboring traces no more than 30 V apart.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For those components I have only 2 rules for the space between components:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;space equal to height: I try to place components far enough apart so that I can inspect where the pins touch the board at a 45 degree angle. I.e., if I have a 0.5 inch tall component, the closest component is at least 0.5 inch away, so I can peek over the top of the tall component and inspect the side of that other component. (This also helps the fingers of robotic assembly equipment install some tiny SMT component, even if the robot was dumb enough to install tall components all around it first).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;leave space for the PCB traces: with small SMT components, it's really easy to pack the parts together so closely that it's simply impossible to wire them all up with PCB traces, even at 0.006 inch (0.15 mm) minimum trace/space widths. When that happens, you're forced to push the components further apart to leave more room for traces between them.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I snap pin 1 of every though-hole part to a 0.1 inch grid -- i.e., pin 1 is some integer multiple of 0.1 inch away from the 0,0 reference point on this board. This makes it much easier to make a prototype -- and later, a test jig -- out of 0.1 inch grid prototyping board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I snap the &quot;reference point&quot; (usually the centroid) of every surface-mount component to some grid -- perhaps starting out with a relatively coarse 0.05 inch grid (exactly 1.27 mm), but often switching to a finer grid. &lt;a href=&quot;http://alternatezone.com/electronics/pcbdesign.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;PCB Design Tutorial&quot;&lt;/a&gt; by David L. Jones and &lt;a href=&quot;http://www.massmind.org/techref/app/pwb_design_flow.htm#layout&quot; rel=&quot;nofollow&quot;&gt;&quot;PWB design flow layout&quot;&lt;/a&gt; at the Massmind have a few tips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes it's easier to leave twice as much room between components as your first estimate expects you'll need for the wires, just so you get something that's &lt;em&gt;possible&lt;/em&gt; to route, and then afterward pack everything together once -- rather than needing to slightly nudge a quarter of the chips on the board a few dozen times while trying to push through a few hundred wires, getting some really long and winding routes when the &quot;obvious&quot; path is clogged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Space equal to half the height exception: Since I can look &quot;around&quot; tall through-hole cylinder capacitors, I often leave a space only half their height around them (30 degree angle), hoping that the robot is smart enough to install them last.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Zero space exception: some connectors are designed to make a row of connectors each one practically touching the next -- a row of screw terminal connectors, a row of 3-pin hobby servomotor connectors, etc. So I lie to my CAD DRC and claim the whole row is one huge component.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have sensitive analog signals or high-voltage power or high-voltage signal traces, you'll want a little more space -- &lt;a href=&quot;http://en.wikibooks.org/wiki/Practical_Electronics/PCB_Layout&quot; rel=&quot;nofollow&quot;&gt;Wikibooks: Practical Electronics&lt;/a&gt; has a few tips.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-04T18:44:54.867" />
  <row Id="11042" PostTypeId="2" ParentId="11040" CreationDate="2011-03-04T18:50:40.140" Score="2" ViewCount="" Body="&lt;p&gt;'dry' joints have a characteristic sheen (not nice and silvery) - more likely you just have something loose (a non-joint)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fixing this stuff is easy just touch them up with a soldering iron, don;t just let the solder flow make sure the component leads get hot enough to melt solder on their own&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-04T18:50:40.140" CommentCount="2" />
  <row Id="11043" PostTypeId="1" AcceptedAnswerId="11057" CreationDate="2011-03-04T19:04:11.903" Score="1" ViewCount="54" Body="&lt;p&gt;I have a Sharp GP2D120 which is a distance sensor for the range 40mm-300mm. Reading the &lt;a href=&quot;http://www.active-robots.com/products/sensors/sharp/gp2d120.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; the output voltage should change from quite high to very low. I cannot get this change to happen. The most i can get the output voltage to move by is about 0.1V and its averaging about 0.3V at a distance of about 50-60mm. Has anyone got any ideas why this is happening?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-05T12:22:04.740" Title="Sharp Distance Sensor" Tags="&lt;sharp&gt;" AnswerCount="1" CommentCount="13" />
  <row Id="11044" PostTypeId="2" ParentId="11018" CreationDate="2011-03-04T19:09:56.913" Score="1" ViewCount="" Body="&lt;p&gt;Consider a simple switching regulator like the &lt;a href=&quot;http://www.national.com/ds/LM/LM2673.pdf&quot; rel=&quot;nofollow&quot;&gt;LM2673&lt;/a&gt; or &lt;a href=&quot;http://www.linear.com/product/LT1074&quot; rel=&quot;nofollow&quot;&gt;LT1074&lt;/a&gt; to minimize losses and headroom requirements. You should be able to get 5V at 2.5A with both of these parts without too much extra design work.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-04T19:09:56.913" />
  <row Id="11045" PostTypeId="2" ParentId="11040" CreationDate="2011-03-04T19:11:23.217" Score="2" ViewCount="" Body="&lt;p&gt;Try resoldering the suspect joints with a solder with a more active flux, or add some active liquid or jelly flux to the joints. Ensure that you are using the correct soldering temperature and the bit is the correct size, and properly tinned.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-04T19:11:23.217" />
  <row Id="11046" PostTypeId="1" AcceptedAnswerId="11056" CreationDate="2011-03-04T19:12:51.693" Score="4" ViewCount="323" Body="&lt;p&gt;I am using an Atmel ATTINY13 which has a 6-pin I/O. I'd like to control about 15 LED's but am unsure how to connect everything. Without multiplexing of any sort, it seems I'd only be able to control 6 LED's at a time. Am I limited to only 6 LED's because of the size of the microcontroller?&lt;/p&gt;&#xA;" OwnerUserId="2028" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-03-04T21:56:50.380" LastActivityDate="2011-03-19T08:56:06.433" Title="How can I control many LED's with just a few pins on my micro?" Tags="&lt;microcontroller&gt;&lt;led&gt;&lt;multiplexing&gt;" AnswerCount="5" CommentCount="6" FavoriteCount="2" />
  <row Id="11047" PostTypeId="2" ParentId="11046" CreationDate="2011-03-04T19:15:31.237" Score="7" ViewCount="" Body="&lt;p&gt;Use &lt;a href=&quot;http://en.wikipedia.org/wiki/Charlieplexing&quot; rel=&quot;nofollow&quot;&gt;Charlieplexing&lt;/a&gt;, you can directly drive n*(n-1) LEDs from n pins&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Exemple: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Six LED's on 3 Pins&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;PINS        LEDS&#xA;0 1 2   1 2 3 4 5 6&#xA;0 0 0   0 0 0 0 0 0&#xA;0 1 Z   1 0 0 0 0 0&#xA;1 0 Z   0 1 0 0 0 0&#xA;Z 0 1   0 0 1 0 0 0&#xA;Z 1 0   0 0 0 1 0 0&#xA;0 Z 1   0 0 0 0 1 0&#xA;1 Z 0   0 0 0 0 0 1&#xA;0 0 1   0 0 1 0 1 0&#xA;0 1 0   1 0 0 1 0 0&#xA;0 1 1   1 0 0 0 1 0&#xA;1 0 0   0 1 0 0 0 1&#xA;1 0 1   0 1 1 0 0 0&#xA;1 1 0   0 0 0 1 0 1&#xA;1 1 1   0 0 0 0 0 0&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Bq6H5.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-04T19:31:14.097" LastActivityDate="2011-03-04T19:31:14.097" CommentCount="2" />
  <row Id="11048" PostTypeId="1" AcceptedAnswerId="11051" CreationDate="2011-03-04T19:16:07.493" Score="5" ViewCount="180" Body="&lt;p&gt;I've seen that a number of schematics will connect the center (common) pin of a potentiometer to one or the other leg, and it then functions more like a rheostat. Is that how a rheostat is wired internally? What's the difference between a potentiometer and a rheostat? Finally, why connect the common to a leg at all on a potentiometer, instead of just ignoring the unused leg?&lt;/p&gt;&#xA;" OwnerUserId="2028" LastActivityDate="2011-05-18T16:48:43.403" Title="What's the difference between a potentiometer and a rheostat?" Tags="&lt;potentiometer&gt;" AnswerCount="2" />
  <row Id="11049" PostTypeId="2" ParentId="11046" CreationDate="2011-03-04T19:25:12.753" Score="7" ViewCount="" Body="&lt;p&gt;Without multiplexing (direct drive) you are limited to 6 LEDs.&lt;br&gt;&lt;br&gt;&#xA;With charlieplexing you can drive n*(n-1) LEDs from n pins.&lt;br&gt;&lt;br&gt;&#xA;With I/O expanders or shift registers you can drive a virtually unlimited number of LEDs.&lt;br&gt;&#xA;Example: &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en021393&quot; rel=&quot;nofollow&quot;&gt;MCP23008&lt;/a&gt; 8-bit I2C I/O Expander&lt;/p&gt;&#xA;" OwnerUserId="588" LastEditorUserId="588" LastEditorDisplayName="" LastEditDate="2011-03-04T19:32:38.480" LastActivityDate="2011-03-04T19:32:38.480" CommentCount="4" />
  <row Id="11050" PostTypeId="1" AcceptedAnswerId="11052" CreationDate="2011-03-04T19:25:26.970" Score="1" ViewCount="106" Body="&lt;p&gt;I purchased a used 20/100 MHz oscilloscope many years ago. It has always served me well to look at very simple sine and square waves for my hobby projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I have wanted to know if I got a 100% functional o-scope. Is there a way I can test or calibrate it to see if it is operating up to spec? I do not own a function generator.&lt;/p&gt;&#xA;" OwnerUserId="2028" LastEditorUserId="2028" LastEditorDisplayName="" LastEditDate="2011-03-04T21:56:54.280" LastActivityDate="2011-03-04T21:56:54.280" Title="How can I determine if my oscilloscope is operating correctly?" Tags="&lt;oscilloscope&gt;&lt;equipment&gt;" AnswerCount="1" />
  <row Id="11051" PostTypeId="2" ParentId="11048" CreationDate="2011-03-04T19:26:30.737" Score="7" ViewCount="" Body="&lt;p&gt;The correct term for the common terminal of a potentiometer is the slider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A rheostat is simply a variable resistance used to control power to a load and you are correct about the wiring. Only the slider and one other terminal are used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A potentiometer uses all three terminals, enabling a variable voltage or signal to be tapped off from the slider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Potentiometers and rheostats are made the same way, but rheostats are usually much &quot;beefier&quot;, as they are generally used in high-power situations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The slider is often connected to one or other terminal for safety reasons, in case it loses contact with the track.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-04T19:26:30.737" CommentCount="3" />
  <row Id="11052" PostTypeId="2" ParentId="11050" CreationDate="2011-03-04T19:30:56.340" Score="5" ViewCount="" Body="&lt;p&gt;Well, the oscilloscope should have its own internal function generator for calibration purposes. Usually there will be two exposed pins on the from panel where the probe should be connected. It should be explained in the manual what type of waveform you should expect. This is also important for probe calibration too. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know of any other easy way to calibrate it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could always mess with microcontrollers and try to generate some sort of calibration signal, but unless you have another oscilloscope to confirm that the device is producing correct signal, you can't be sure if the oscilloscope or the home made function generator or both are broken.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option would be to get it professionally calibrated, but that could be expensive. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-04T19:30:56.340" CommentCount="5" />
  <row Id="11053" PostTypeId="2" ParentId="10975" CreationDate="2011-03-04T20:03:01.583" Score="1" ViewCount="" Body="&lt;p&gt;There are more accelerometer + SD card fish in the sea:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/products/9814&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/9814&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/products/8755&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/8755&lt;/a&gt;  &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.pcworld.com/appguide/app.html?id=356769&quot; rel=&quot;nofollow&quot;&gt;http://www.pcworld.com/appguide/app.html?id=356769&lt;/a&gt; &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://rossum.posterous.com/microtouch-from-adafruit&quot; rel=&quot;nofollow&quot;&gt;http://rossum.posterous.com/microtouch-from-adafruit&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.radiolocman.com/shem/schematics.html?di=70957&quot; rel=&quot;nofollow&quot;&gt;http://www.radiolocman.com/shem/schematics.html?di=70957&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If yours doesn't work properly, get your money back.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, the SD should buffer writes.  It sounds like their FAT library is flushing the file after every write.  It would be interesting to fix if they provide you the source code to their firmware.  Otherwise, you're starting from scratch and you'd be better off with your own hardware too.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-04T20:03:01.583" />
  <row Id="11054" PostTypeId="1" AcceptedAnswerId="11086" CreationDate="2011-03-04T20:04:10.080" Score="3" ViewCount="217" Body="&lt;p&gt;Can Duemilanove USB interface be used for data transfer/programming when the board itself is connected to an external power source? (say, USB is not powerful enough)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the requirements for the ground in this case? What do you have to do if your external power source is battery?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to connect external power source when USB is already connected?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The following forum post &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1287771433&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1287771433&lt;/a&gt; , seems to suggest the answer to the first question is &quot;yes&quot;, but some official data source would be appreciated.&lt;/p&gt;&#xA;" OwnerUserId="3246" LastEditorUserId="3246" LastEditorDisplayName="" LastEditDate="2011-03-05T20:03:59.953" LastActivityDate="2011-03-05T23:11:25.400" Title="Arduino Duemilanove external power source with USB connected" Tags="&lt;arduino&gt;&lt;power&gt;&lt;usb&gt;&lt;ground&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="11055" PostTypeId="2" ParentId="10446" CreationDate="2011-03-04T20:11:46.613" Score="1" ViewCount="" Body="&lt;p&gt;It's not to hard to set up a CPLD or FPGA to convert binary data shifted MSB-first into decimal data.  The core building block is a module with clock, data, and clear inputs, four latches D0-D3, and a combinatorial next-carry output.  Cascade the blocks as one would a shift register.  After the binary value is shifted in, the registers will hold the equivalent in BCD.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;; Carry if &gt;= 5&#xA;NextCarry = D3 | D2 &amp; D1 | D2 &amp; D0&#xA;&#xA;; Will be 8 or 9 iff input was 4 or 9&#xA;D3 := !D3 &amp; D2 &amp; !D1 &amp; !D0 | D3 &amp; D0&#xA;&#xA;; Will be 4-7 iff input was 2-3 or 7-8&#xA;D2 := !D3 &amp; !D2 &amp; D1 | !D3 &amp; D2 &amp; D1 &amp; D0 | D3 &amp; !D0&#xA;&#xA;; Will be 2-3 or 6-7 iff input was 1, 3, 6, or 8&#xA;D1 := !D3 &amp; !D2 &amp; D0 | !D3 &amp; D2 &amp; D1 &amp; !D0 | D3 &amp; !D0&#xA;&#xA;; Will be odd iff carry-in is set&#xA;D0 := CarryIn&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that it's necessary to clear the register before each use; shifting in zeroes will NOT suffice.  Clearing circuitry is not shown, but should be obvious.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-04T20:11:46.613" />
  <row Id="11056" PostTypeId="2" ParentId="11046" CreationDate="2011-03-04T20:35:02.573" Score="9" ViewCount="" Body="&lt;p&gt;There are several methods which can be used to drive large numbers of LEDs from a few IO pins.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest is standard row/column display multiplexing.  With this technique, you can drive &lt;em&gt;( n / 2 ) &lt;sup&gt;2&lt;/sup&gt;&lt;/em&gt; LEDs with &lt;em&gt;n&lt;/em&gt; IO pins. Mathematically, the duty cycle is &lt;em&gt;1 / minimum(unique row patterns, unique column patterns)&lt;/em&gt;.  This means that this technique has a duty cycle of 100% when all LEDs are lit (or all rows or all columns are identical) and a duty cycle of &lt;em&gt;1 / n&lt;/em&gt; when a diagonal line needs to be lit (or all the rows are different).  You're only guaranteed 100% duty cycle when lighting every LED or one LED (or zero LEDs, but that doesn't really count for much). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Slightly more complex is &lt;a href=&quot;http://en.wikipedia.org/wiki/Charlieplexing&quot; rel=&quot;nofollow&quot;&gt;Charlieplexing&lt;/a&gt;.  With this technique, you can drive &lt;em&gt;n &lt;sup&gt;2&lt;/sup&gt; - n&lt;/em&gt; LEDs with &lt;em&gt;n&lt;/em&gt; IO pins. Only &lt;em&gt;n - 1&lt;/em&gt; LEDs can be lit simultaneously with this technique.  Mathematically, the duty cycle is &lt;em&gt;1/ (minimum simultaneous sets)&lt;/em&gt;, where a simultaneous set is a unique group of LEDs which has a common anode or common cathode.  (This hasn't been proven, it's just what I arrived at after pondering the problem for a minute.  If duty cycle is important to you, you'll want to look into this further.) This is a much more complex calculation both intellectually and computationally than the equivalent calculation for standard multiplexing.  Effectively, you get a duty cycle of &lt;em&gt;1 / n&lt;/em&gt; when all LEDs are lit but some (only some) patterns of n-1 or fewer LEDs can have a duty cycle of 100%.  You're only guaranteed 100% duty cycle when lighting 1 LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The last method I'll mention is to use a &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Shift_register&quot; rel=&quot;nofollow&quot;&gt;shift register&lt;/a&gt; or IO expander.  With two pins (Either the raw data/clock interface, I2C, or unidirectional SPI), you can control an arbitrarily large number of LEDs. The duty cycle for any pattern is 100%, but the update rate is inversely proportional to the number of LEDs.  This is the most costly method.  For 15 LEDs, it will probably be cheaper to just upgrade to a micro with that many IO pins.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-05T19:43:12.913" LastActivityDate="2011-03-05T19:43:12.913" CommentCount="2" />
  <row Id="11057" PostTypeId="2" ParentId="11043" CreationDate="2011-03-04T21:37:04.547" Score="1" ViewCount="" Body="&lt;p&gt;Check the wires are wired correctly from the JST on the sensor to your project. Check the order on that particular model looking at the connector with the sensor facing away from you the output pin is the left one, middle is ground and right is VCC. Check these where you connect them to your project. As having them connected the wrong way round could damage them and will give you this reading.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-03-05T12:22:04.740" LastActivityDate="2011-03-05T12:22:04.740" CommentCount="0" />
  <row Id="11058" PostTypeId="2" ParentId="11046" CreationDate="2011-03-04T21:55:40.740" Score="2" ViewCount="" Body="&lt;p&gt;As @mjh2007 suggested with an I2C expander.  But there are  &lt;a href=&quot;http://parts.digikey.com/1/parts/571111-ic-led-driver-linear-24-tssop-a6279elp-t.html&quot; rel=&quot;nofollow&quot;&gt;ones specifically for driving LEDs&lt;/a&gt; which will avoid the need for external current-limiting resistors.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-04T21:55:40.740" />
  <row Id="11059" PostTypeId="2" ParentId="3741" CreationDate="2011-03-04T22:01:08.223" Score="1" ViewCount="" Body="&lt;p&gt;The biggest single issue for me with Processing/Arduino is the lack of a decent debugger.  I have an AVR dragon, but this doesn't help much because either (a) AVR Studio's debugger is slow and buggy, or (b) debugging in Eclipse is just plain slow and, while less so, still buggy.  I haven't had a chance to try it in WinAVR, but that's next on the list.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There of course is no debugger in the Arduino IDE.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you step outside of simple applications and start building apps that have to do involved stuff at the wired and wireless network level, it's quite frustrating.  This is mainly why I'm taking a serious look at the .NET MF - have been playing with the SDK, and have some hardware turning up soon.&lt;/p&gt;&#xA;" OwnerUserId="3247" LastActivityDate="2011-03-04T22:01:08.223" CommentCount="6" />
  <row Id="11061" PostTypeId="2" ParentId="10910" CreationDate="2011-03-04T22:47:22.387" Score="2" ViewCount="" Body="&lt;p&gt;You may want to check out the &lt;a href=&quot;http://www.trossenrobotics.com/dynamixel-ax-12-robot-actuator.aspx&quot; rel=&quot;nofollow&quot;&gt;Dynamixel AX-12&lt;/a&gt; Digital Hobby Servo, It has a built in 10-bit (1024 position) absolute encoder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is also a highly-customizable servo, and is easily interfaced to via serial.  There are already Arduino and C++ libraries available if you would like to interface through either a microcontroller or computer serial port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe that 300 degrees corresponds to 1023, 150 degrees corresponds to 511, and 0 degrees corresponds to 0.  This would indicate about 1/3 of degree resolution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your torque, speed, and angle requirements, you could also consider gearing this down further to get more accurate resolution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need something more heavy-duty, there are many other servos in the &lt;a href=&quot;http://www.trossenrobotics.com/c/robotis-dynamixel-robot-servos.aspx&quot; rel=&quot;nofollow&quot;&gt;Dynamixel Series&lt;/a&gt;.  The EX-106+ has pointing accuracy of 0.07 degrees, but costs about 500 dollars, as well.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-03-04T22:47:22.387" />
  <row Id="11062" PostTypeId="2" ParentId="9255" CreationDate="2011-03-04T23:25:04.003" Score="3" ViewCount="" Body="&lt;p&gt;Is it possible to hook 2 antennas up to a RFID reader designed to be connected to a single antenna?&#xA;Yes, in 2 ways:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;As BarsMonster suggested, you could alternating between the antennas with a relay or something similar, so only one is connected at a time: As long as one antenna stays on long enough for the complete query-response conversation, it should work fine.&lt;/li&gt;&#xA;&lt;li&gt;Connecting both antennas simultaneously with a matching filter: then it acts just like one larger antenna; with proper matching, it should work fine.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;However, perhaps you don't really need &quot;2 antennas&quot;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible for a single RFID reader to read 2 different RFID chips at once:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Yes, most RFID protocols include &lt;a href=&quot;http://en.wikipedia.org/wiki/Singulation&quot; rel=&quot;nofollow&quot;&gt;singulation&lt;/a&gt; so that if you put dozens of RFID tags in front of it, and then turn on the RFID reader, it can read the correct serial number from each and every tag. (The singulation protocol tells one tag at a time to transmit its serial number, so it's technically not &quot;at once&quot;, but it's quick enough to be practically simultaneous for most purposes).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-04T23:25:04.003" />
  <row Id="11063" PostTypeId="5" CreationDate="2011-03-04T23:43:12.503" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-03-04T23:43:12.503" LastActivityDate="2011-03-04T23:43:12.503" />
  <row Id="11064" PostTypeId="4" CreationDate="2011-03-04T23:43:12.503" Score="0" ViewCount="" Body="NXT-G is a simplified version of LABVIEW co developed by LEGO and NI for Lego Mindstorms NXT robots   " OwnerUserId="-1" LastEditorUserId="3171" LastEditorDisplayName="" LastEditDate="2011-03-05T01:15:26.113" LastActivityDate="2011-03-05T01:15:26.113" />
  <row Id="11065" PostTypeId="2" ParentId="11037" CreationDate="2011-03-04T23:43:55.393" Score="3" ViewCount="" Body="&lt;p&gt;Not sure where you can get it, but I've encountered this stuff that looks like spirally-cut polyethylene tubing. The stuff I've seen comes on a big reel, and you cut off as much or as little as you need. So you lop off a few inches of it, and then wind it around the wires/cables you want to bundle. It's very quick to put to use, it's quick to take off, it's re-usable, and it's neat, too.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-03-04T23:43:55.393" CommunityOwnedDate="2011-03-04T23:43:55.393" CommentCount="2" />
  <row Id="11066" PostTypeId="2" ParentId="11040" CreationDate="2011-03-05T01:29:54.463" Score="1" ViewCount="" Body="&lt;p&gt;On the note of your ball joints, yes, often a really bad joint can show up as a &quot;ball&quot; of solder, instead of the volcano shape.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second note here, when you measure voltage at your pic and at the source, the only sort of verifies one line. The connection could be very resistive or just having temporary contact. I have seen people probe pins and when they place pressure on the pin it causes a contact that was not there, the board works as long as you measure it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lead free solder requires a higher temp to get a good joint on, probably the root of the problem to begin with. Also, just because power makes it, your ground may not, or your crystal may not be properly connected, clean up those bad joints!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Start debugging again once you have them clean. Make sure to use your multimeter for connectivity check but make sure to look at what resistance it is measuring.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-03-05T01:29:54.463" />
  <row Id="11067" PostTypeId="2" ParentId="11037" CreationDate="2011-03-05T02:17:15.140" Score="4" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&quot;flexible plastic conduit&quot;&lt;/li&gt;&#xA;&lt;li&gt;&quot;corrugated flex tubing&quot;&lt;/li&gt;&#xA;&lt;li&gt;&quot;split loom&quot;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'm having trouble finding a good search term for it, but I've used flexible plastic/PVC wire conduit to bundle wires together in text fixtures outside of enclosures.  The stuff is commonly used in wire harnesses, especially in automotive.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's essentially a thin, corrugated plastic hose with a slit running through it so you can shove in or pull out cables and wires, available in a wide range of sizes, from about 1/4&quot; (almost pointless; fits about (3) 16-AWG wires) up to 2&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/HEttv.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T17:34:37.863" LastActivityDate="2011-03-05T17:34:37.863" CommunityOwnedDate="2011-03-05T02:17:15.140" CommentCount="1" />
  <row Id="11068" PostTypeId="1" CreationDate="2011-03-05T04:58:00.883" Score="3" ViewCount="169" Body="&lt;p&gt;I have a project in mind that will involve a lot of moving parts, and I'd like to try using Nitinol wire (which shortens when heated by a current flow) to produce the movement. When the current is stopped, the wire cools, but a force is required to stretch the wire back out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So... I'll produce movement in one direction using electricity through the wire, and movement the other direction by disconnecting the electricity and letting a small spring pull the other direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just need to find a bunch of small, light-duty cheap springs... the kind you'd find in a cheaply made toy, of the same quality as the spring in a retractable pen. I've browsed the industrial supply catalog companies like Grainger, McMaster Carr, etc... but they only seem to have precision (expensive) springs of relatively large sizes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any tips on where I might find something like that?&lt;/p&gt;&#xA;" OwnerUserId="3219" LastActivityDate="2011-03-09T14:51:42.573" Title="Where can I find small cheap springs?" Tags="&lt;mechanical&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="11069" PostTypeId="2" ParentId="9526" CreationDate="2011-03-05T07:49:25.963" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;All four&lt;/strong&gt; pins are Ground, and all four pins should be connected to your circuit ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It &lt;em&gt;may&lt;/em&gt; work if you leave some of the ground connections floating, but you may have reliability issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That GPS module does not have separate ground domains. Basically, to reduce the impedance of the ground connection, and possibly for reliability issues, they are using multiple connections from the same ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is in-fact likely that if you use an ohmmeter to measure the resistance between she separate ground connections, you will find they are coupled together within the GPS module as well. You should still ground them all, however.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-03-05T07:49:25.963" />
  <row Id="11071" PostTypeId="2" ParentId="11068" CreationDate="2011-03-05T12:45:40.887" Score="1" ViewCount="" Body="&lt;p&gt;Try a local hardware store, if you have one. I would expect to find a number of smallish springs, particularly ones designed for tension (short when relaxed, with loops on the ends). However, they might all be too long or large for you, or perhaps you need the compression type.&lt;/p&gt;&#xA;" OwnerUserId="2838" LastActivityDate="2011-03-05T12:45:40.887" />
  <row Id="11073" PostTypeId="1" AcceptedAnswerId="11105" CreationDate="2011-03-05T14:02:34.470" Score="0" ViewCount="113" Body="&lt;p&gt;I'm just starting out building and tinkering with electronics in general and Micro controllers in particular, I considering buying an Oscilloscope pretty soon and some other &quot;lab&quot; items.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be your list of &quot;must-haves&quot; for someone starting out with zero gear and software ? It would be interesting to get a value and a bit more expensive option for each must have item. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm pretty sure that many other beside me would find such list of must-haves for your home lab interesting as well.&lt;/p&gt;&#xA;" OwnerUserId="3186" LastActivityDate="2011-03-06T16:07:48.327" Title="Starting with Electronics, must have software and gear ?" Tags="&lt;tools&gt;&lt;development-tools&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="11074" PostTypeId="1" AcceptedAnswerId="11078" CreationDate="2011-03-05T14:11:21.110" Score="1" ViewCount="140" Body="&lt;p&gt;I have HH100D humidity sensor. It outputs a frequency signal, which I know how to handle. However, it also has a small EEPROM with calibration values that is available via I2C. Those values are necessary to get the actual humidity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is, that I'm very new to I2C. I cannot figure out how to read out those bytes. I've googled for half a day and still got no solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's something I have:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.sparkfun.com/datasheets/Sensors/Temperature/HH10D.pdf&quot; rel=&quot;nofollow&quot;&gt;HH100D datasheet&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://datasheet.octopart.com/M24C02-BN6-STMicroelectronics-datasheet-2222.pdf&quot; rel=&quot;nofollow&quot;&gt;M24C02 EEPROM datasheet&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://translate.google.com/translate?js=n&amp;amp;prev=_t&amp;amp;hl=en&amp;amp;ie=UTF-8&amp;amp;layout=2&amp;amp;eotf=1&amp;amp;sl=de&amp;amp;tl=en&amp;amp;u=http%3A%2F%2Farduino.cc%2Fforum%2Findex.php%2Ftopic%2C29932.0.html&quot; rel=&quot;nofollow&quot;&gt;A topic on this forum (German)&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3253" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-05T15:56:18.167" LastActivityDate="2011-03-05T15:56:18.167" Title="How do I read I2C memory with an Arduino?" Tags="&lt;arduino&gt;&lt;i2c&gt;&lt;eeprom&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="11076" PostTypeId="1" AcceptedAnswerId="11077" CreationDate="2011-03-05T15:21:22.107" Score="1" ViewCount="48" Body="&lt;p&gt;I have a picaxe 28-x1 and a Sharp Distance Sensor. When I try to program the PIC with the sensor plugged in it can't find the PIC but when I unplug the sensor it finds it. Is it possible that the sensor is using all the current and there isn't enough for the PIC? When I test the separate parts they work. Is it another problem, if so what?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-05T15:29:12.583" Title="Effects of not enough current for a microcontroller?" Tags="&lt;sensor&gt;&lt;picaxe&gt;" AnswerCount="1" />
  <row Id="11077" PostTypeId="2" ParentId="11076" CreationDate="2011-03-05T15:29:12.583" Score="1" ViewCount="" Body="&lt;p&gt;It's possible, but I think it's probably more likely that the pin you've connected the sensor to is related to the PIC's programming pins and/or reset function, and that the sensor is interfering with the programming protocol as a result.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, if some component is overloading the power source (drawing too much current), the effect would be that the voltage that the power source was providing would dip. If it dips below the PIC's power-on voltage, you certainly won't be able to program it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PIC might also draw more current during the programming operation than it normally would, and the combination of that and the sensor load might have the same effect of critically dropping the voltage of your source (most likely resulting in an untimely reset of the PIC).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best way to diagnose this is with a multimeter weasuring the source voltage with and without the sensor and with and without programmer attamhed (and with and without programming going on). If you observe a voltage drop, try it with a higher current-rated power source and see if you still get a drop.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-03-05T15:29:12.583" CommentCount="3" />
  <row Id="11078" PostTypeId="2" ParentId="11074" CreationDate="2011-03-05T15:48:11.370" Score="3" ViewCount="" Body="&lt;p&gt;You are going to want to use the Arduino &lt;a href=&quot;http://www.arduino.cc/playground/Learning/I2C&quot; rel=&quot;nofollow&quot;&gt;Wire library&lt;/a&gt; (more details &lt;a href=&quot;http://www.neufeld.newton.ks.us/electronics/?p=241&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) to talk to the device (it comes built in with the IDE).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The I2C lines you will need to connect between your Arduino and your Sensor are SDA, SCL, and GND. Namely:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Arduino Analog Pin 4 = SDA = Sensor Pin SDA (2)&lt;/li&gt;&#xA;&lt;li&gt;Arduino Analog Pin 5 = SCL = Sensor Pin SCL (1)&lt;/li&gt;&#xA;&lt;li&gt;Arduino GND Pin      = GND = Sensor Pin GND (5)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Depending on the distance between the Sensor and the Arduino you might also need external pull up resistors (e.g. 3.3k Ohm) connected between each of SDA and SCL and VCC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a gotcha though. The sensor appears to operate at 3.3V and the Arduino operates at 5V. So to &quot;interface&quot; I2C between them you need to use transistors to level shift the signaling as described &lt;a href=&quot;http://electronics.stackexchange.com/questions/708/i2c-3-3-to-5-0-v-conversion&quot;&gt;in this other post&lt;/a&gt; (with this &lt;a href=&quot;http://ics.nxp.com/support/documents/interface/pdf/an97055.pdf&quot; rel=&quot;nofollow&quot;&gt;key reference&lt;/a&gt;). You're going to want those pull up resistors I mentioned on either side of the level conversion transistors.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-03-05T15:48:11.370" />
  <row Id="11079" PostTypeId="1" AcceptedAnswerId="11083" CreationDate="2011-03-05T15:55:45.007" Score="4" ViewCount="345" Body="&lt;p&gt;I'm driving a 12V 0.11A brushless DC fan with PWM using an MSP430Gxxxx --&gt; TC427CPA FET driver --&gt; BS170 N-FET. The fan is on the low side of the FET.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even with a duty cycle of 90% and a frequency of 10kHz, there's audible buzzing coming from the fan. Lower duty cycle = more noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried to eliminate the noise by adding a 4.7uF cap in parallel with the fan, and it's a little less noisy, but still very audible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I make the noise go away?&lt;/p&gt;&#xA;" OwnerUserId="1124" LastActivityDate="2011-05-22T18:04:59.963" Title="How do I eliminate PWM noise when driving a fan?" Tags="&lt;msp430&gt;&lt;pwm&gt;&lt;noise&gt;&lt;fan&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="11080" PostTypeId="2" ParentId="11079" CreationDate="2011-03-05T15:59:16.900" Score="5" ViewCount="" Body="&lt;p&gt;The easy way is to drive it either at an ultrasonic frequency (&gt;20 kHz) or at a lower frequency (&amp;lt;100-200 Hz).  That low end there isn't really infrasonic, but a &quot;hum&quot; is usually far less objectionable, if it can be heard at all over the noise of the fan itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for &lt;em&gt;why&lt;/em&gt; you see that a lower duty cycle yields more noise, you're essentially increasing the content of the 10 kHz frequency you're sending to the motor until you hit 50%, then it will drop again.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-05T15:59:16.900" />
  <row Id="11081" PostTypeId="2" ParentId="11037" CreationDate="2011-03-05T16:47:50.400" Score="1" ViewCount="" Body="&lt;p&gt;Using twist ties to shorthen cables is a very simple first step, gets rid of long lengths of cable waiting to get tangled.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-05T16:47:50.400" CommunityOwnedDate="2011-03-05T16:47:50.400" />
  <row Id="11082" PostTypeId="1" AcceptedAnswerId="11098" CreationDate="2011-03-05T17:35:19.857" Score="0" ViewCount="205" Body="&lt;p&gt;Is there any practical difference as to how a unity gain buffer using an op-amp might be configured? For example, the input signal can be connected to the noninverting input and the feedback to the inverting input; but it can also be configured the other way, with the inverting input as the signal and the noninverting as the feedback. Practically speaking (noise, stability, frequency response, offset error and so on), is there a difference between these configurations?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-06T10:40:17.653" Title="Difference between configurations of unity gain buffer using op-amp" Tags="&lt;op-amp&gt;&lt;practical&gt;" AnswerCount="2" CommentCount="9" FavoriteCount="1" />
  <row Id="11083" PostTypeId="2" ParentId="11079" CreationDate="2011-03-05T19:10:43.027" Score="4" ViewCount="" Body="&lt;p&gt;In fact I am working on exactly same problem at the moment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Freq &gt; 25Khz - first of all&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) BIG cap at the output, 1-4.7uF ceramic + some 100-1000uF electrolytic would do the trick.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Add some inductance before the cap + diode in reverse to cut negative spikes.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-03-06T16:11:00.080" LastActivityDate="2011-03-06T16:11:00.080" CommentCount="9" />
  <row Id="11084" PostTypeId="2" ParentId="11068" CreationDate="2011-03-05T20:24:02.660" Score="2" ViewCount="" Body="&lt;p&gt;Um, &lt;a href=&quot;http://www.staples.com/BIC-Clic-Stic-Retractable-Ballpoint-Pens/product_SS202028&quot; rel=&quot;nofollow&quot;&gt;Staples&lt;/a&gt;, &lt;a href=&quot;http://www.officedepot.com/a/products/811968/BIC-Clic-Stic-Retractable-Pens-10/&quot; rel=&quot;nofollow&quot;&gt;Office Depot&lt;/a&gt;, &lt;a href=&quot;http://www.amazon.com/Clic-Retractable-Medium-Point-Black/dp/B00006IE7Z&quot; rel=&quot;nofollow&quot;&gt;Amazon&lt;/a&gt;, or &lt;a href=&quot;http://www.newegg.com/Product/Product.aspx?Item=N82E16848000100&quot; rel=&quot;nofollow&quot;&gt;Newegg&lt;/a&gt; (or &lt;a href=&quot;http://www.google.com/search?q=clic+stic&amp;amp;hl=en&amp;amp;tbs=shop%3A1&amp;amp;aq=f&quot; rel=&quot;nofollow&quot;&gt;Google Shopping&lt;/a&gt;)? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/n77Mk.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not a bad option for personal projects.  Shipping from Grainger or McMaster Carr will be more than the cost of the \$5 12-pen box (which puts the springs at \$0.41 apiece).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no idea where to order these for production.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-09T14:51:42.573" LastActivityDate="2011-03-09T14:51:42.573" CommentCount="1" />
  <row Id="11085" PostTypeId="2" ParentId="4350" CreationDate="2011-03-05T20:37:51.597" Score="0" ViewCount="" Body="&lt;p&gt;Why don't you use a router (like a Linksys) ? Some can work on 9V battery and you can run OpenWRT on them.&#xA;Check out www.openwrt.org&lt;/p&gt;&#xA;" OwnerUserId="3255" LastActivityDate="2011-03-05T20:37:51.597" />
  <row Id="11086" PostTypeId="2" ParentId="11054" CreationDate="2011-03-05T23:11:25.400" Score="3" ViewCount="" Body="&lt;p&gt;I'm looking at and interpretting the schematics and here's my take.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;If V_IN (external power minus a protection diode drop of probably about 0.7V) is above 6V, the USB power is cut-off from the 5V rail through a P-channel MOSFET.&lt;/li&gt;&#xA;&lt;li&gt;If V_IN is below 6V then USB power will be connected to +5V through the MOSFET. V_IN will still energize the on-board 5V regulator, but since USB power and the regulator are at the same potential, they shouldn't fight each other , and you should be OK.&lt;/li&gt;&#xA;&lt;li&gt;Looking at GND in the schematics, USB GND is tied to the 5V GND reference on the regulator, so again, you should be all set in terms of USB power not fighting your on-board regulated power.&lt;/li&gt;&#xA;&lt;li&gt;In principle, having both USB and external power connected should allow you to source more draw a higher max current (the sum of the USB and your external power source).&lt;/li&gt;&#xA;&lt;li&gt;Plugging in external power after USB power is already connected shouldn't do any damage, but you might get a transient dipping in +5V while the Op-Amps and MOSFETs settle, which might cause your Arduino to reset. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Anyway, my opinion is that it should be harmless. Not that I'm an &quot;official source&quot; :).&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-03-05T23:11:25.400" />
  <row Id="11087" PostTypeId="2" ParentId="11068" CreationDate="2011-03-05T23:40:12.810" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.amazon.com/Advanced-Tool-Design-ATD-352-Assortment/dp/B000M61J9I/ref=sr_1_1?s=industrial&amp;amp;ie=UTF8&amp;amp;qid=1299368344&amp;amp;sr=1-1&quot; rel=&quot;nofollow&quot;&gt;Amazon: Advanced Tool Design Model ATD-352 200 Piece Spring Assortment&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-05T23:40:12.810" CommentCount="3" />
  <row Id="11088" PostTypeId="2" ParentId="11082" CreationDate="2011-03-06T00:38:37.520" Score="4" ViewCount="" Body="&lt;p&gt;If you use a feedback from the output to the non-inverting input you will find that as the output goes too high it causes the difference to increase and it will rail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have to use the feedback to the inverting input.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;What is really happening?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;An op-amp attempts to take the difference from the non-inverting compared to the inverting and multiply it by infinity. Lets say that the gain is only 10 though(instead of the 10^5 you can reasonable expect) and work through an example. There are two major points to remember here, the feedback from the output to the inverting input is nearly instant, this is not always true, but it is a reasonable approximation for low frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The circuit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/I2yYV.png&quot; alt=&quot;from_http://denethor.wlu.ca/pc300/opamps_lab/opamp_buffer_label.png this circuit was pulled.&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If, lets say, you instantly changed Vi from being 0V to 10V what would happen?&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The instant that the voltage change happens your Vi is 10V, your Vo is 0V.&lt;/li&gt;&#xA;&lt;li&gt;This means that the op-amp has a difference of 0-10 V and will attempt to start swinging towards the -100V mark.&lt;/li&gt;&#xA;&lt;li&gt;As the voltage swings towards 0V the voltage it is targeting will go down. This will happen all the way until it reaches 0V. In a no load circuit with no delay, this will be instant.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In the real world you have delay, this can cause overshoot and ringing. In the real world, you have a load, so a higher gain gate will allow a higher speed transition.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-06T07:46:29.433" LastActivityDate="2011-03-06T07:46:29.433" />
  <row Id="11089" PostTypeId="1" CreationDate="2011-03-06T01:24:45.297" Score="1" ViewCount="188" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am fairly new to electronics and I'd like to connect a thermometer (DS18S20) which generates 9-bit output. I'd like to connect this to my computer through USB and read the data it provides programmatically. Programming is not a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is: how can I connect this to an USB port so my software can read the raw bits?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Simply connecting it to a pin is not the good way I guess…&lt;/p&gt;&#xA;" OwnerUserId="3087" LastActivityDate="2011-05-12T00:15:16.423" Title="Thermometer to USB" Tags="&lt;usb&gt;" AnswerCount="4" />
  <row Id="11091" PostTypeId="2" ParentId="11089" CreationDate="2011-03-06T02:44:54.493" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.leonheller.com/usb/&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; are the details of a simple USB interface I designed around a PIC18F2455, using some software provided by Brad Minch. You could mount the DS18S20 on the PCB prototyping area, interface it to the 18F2455, and modify the software to transmit the temperature to your PC via the USB port. The PCB is available from Olimex.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-06T03:10:41.883" LastActivityDate="2011-03-06T03:10:41.883" CommentCount="3" />
  <row Id="11092" PostTypeId="2" ParentId="11089" CreationDate="2011-03-06T02:51:55.707" Score="2" ViewCount="" Body="&lt;p&gt;You can't connect a DS18S20 directly to a USB port, because they both different protocols. You need something in the middle to translate, like a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done something very similar except I used the RS232 com port on the computer as that allows you to use a much wider range of microcontrollers. Of course thus also required a line driver as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to do this, then you should start by reading the DS18S20 datasheet. It has all the commands you need to get it to take a temperature reading, and send it over its data wire. You'll also need a microcontroller, and write the firmware to talk to the sensor and get back data readings, and send them to the computer.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-06T02:51:55.707" CommentCount="5" />
  <row Id="11093" PostTypeId="2" ParentId="11068" CreationDate="2011-03-06T03:09:04.613" Score="5" ViewCount="" Body="&lt;p&gt;Auto parts stores sometimes have boxes of mixed springs.   Surplus suppliers like the ones on this list are worth checking too: &lt;a href=&quot;http://www.evilmadscientist.com/links/index.php?category=Surplus+Electronics&quot; rel=&quot;nofollow&quot;&gt;http://www.evilmadscientist.com/links/index.php?category=Surplus+Electronics&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Go dumpster diving for discarded inkjet printers (also available from thrift stores).   These are an excellent source of springs, gears, shafts and motors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, search for &quot;assorted springs&quot; on eBay.&lt;/p&gt;&#xA;" OwnerUserId="389" LastEditorUserId="389" LastEditorDisplayName="" LastEditDate="2011-03-08T22:48:22.957" LastActivityDate="2011-03-08T22:48:22.957" CommentCount="5" />
  <row Id="11094" PostTypeId="2" ParentId="10123" CreationDate="2011-03-06T03:32:33.190" Score="2" ViewCount="" Body="&lt;p&gt;I have spent the start of time looking into this, but I need to spend more. This is what I have found so far.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fact that your tag type is 55 is a big deal. The acceptable tag types are:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;0x01 – Mifare Ultralight &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;0x02 – Mifare Standard 1K &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;0x03 – Mifare Classic 4K&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;0xFF – Unknown Tag type&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Now, to continue from here. There are some error codes that you could get querying a tag type.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;0x4E ‘N’ - No Tag present.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;0x55 ‘U’ – Access failed due to RF Field is OFF&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;There are other commands that also get responses of this type, so I need to research the software to find more, but as of right now it seems that it is sending you back an error code as the tag type cannot ever be 0x55, however almost every command has an error option that can return 0x55.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this gives you some direction, either I will find something or you will find more as you debug to make it possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could be helped if you had a debugger and could show me everything being sent over serial to the device, this would allow me to determine the exact state the error is being generated from.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-03-06T03:32:33.190" CommentCount="4" />
  <row Id="11095" PostTypeId="1" AcceptedAnswerId="11096" CreationDate="2011-03-06T06:05:47.150" Score="3" ViewCount="149" Body="&lt;p&gt;I've just got a cheapo &amp;lt; $20 digital multimeter here and was curious if anyone could tell me whether current might still flow through it after i turn the dial so that the power is off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some background: I have a wireless bluetooth mouse that always gave me problems charging because the contacts don't seem to line up properly. The mouse itself doesn't seem to give any indication whether it is charging or not but I am able to watch current start to flow on my multimeter when I move the mouse into just the right position within the cradle to make a proper connection. Now that it is seated correctly I'd like to just leave it charge for a while without disturbing it by disconnecting the leads and reconnecting the +5V wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll probably figure something out for this specific problem (just disconnect the leads from DMM and jumper them together for now) but I'm still kind of curious as to the original question of whether or not current flow is completely shut off when the DMM power is off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It might vary by model but maybe somebody out there with 2 multimeters could test this for me?&lt;/p&gt;&#xA;" OwnerUserId="3261" LastActivityDate="2011-03-06T12:23:07.430" Title="Will current flow through my digital multimeter while it is powered off?" Tags="&lt;multimeter&gt;&lt;current-measurement&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="11096" PostTypeId="2" ParentId="11095" CreationDate="2011-03-06T06:54:22.410" Score="4" ViewCount="" Body="&lt;p&gt;In short, yes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way a digital multimeter measures current (not a loop current meter) is that it measures the voltage drop across a small precision resistor. For reliability, simplicity, and repeatability, no switches or contacts are placed in series with this shunt resistor. Some meters will have a fast-acting fuse to protect the shunt resistor. Basically, the switches will control the electronics hooked up to the shunt resistor, but they won't disconnect it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can perform an experiment with your meter as some degree of proof that this is true. If you configure your meter to read resistance, put the positive probe into the positive current probe socket. You should measure a very small resistance. This shows that the meter doesn't disconnect the shunt resistor while in a separate mode. It would be a small leap of logic to say that if it didn't switch off the shunt resistor then, it probably couldn't when the meter is off. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you could measure the current using a second meter. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-03-06T06:54:22.410" CommentCount="1" />
  <row Id="11097" PostTypeId="2" ParentId="11095" CreationDate="2011-03-06T10:10:36.663" Score="0" ViewCount="" Body="&lt;p&gt;Just hook up a light bulb or LED through the current connections on the meter and observe that it remains lit when the meter is powered off.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or pop the case open and observe the wiring of the current connections.&#xA;Current is inferred by measuring the voltage drop across big hefty resistor (but with quite low resistance). You should see a big thick wire (a low-value resistor called a &quot;shunt&quot;) joining the common and current sockets.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-06T10:10:36.663" />
  <row Id="11098" PostTypeId="2" ParentId="11082" CreationDate="2011-03-06T10:26:51.387" Score="6" ViewCount="" Body="&lt;p&gt;A normal opamp has an infinite gain, practically [factor] x 10^5. The difference between + and - terminal determines its output:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vout = (V+ - V-) * A_ol&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an opamp you will have 2 rules:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;No input current.&lt;/li&gt;&#xA;&lt;li&gt;Input terminals share no voltage difference. This can be explained because A_cl for an ideal opamp is infinite, so (V+ - V-) should be 0V, otherwise Vout would be infinite too.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;When you make a real circuit, you reduce the open loop gain to a closed loop gain. However, the 2 rules stated only work for negative feedback. If you use positive feedback, they do not apply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, if the rule of no input voltage difference doesn't apply, the opamp basically becomes an comperator. An inverting situation would try to get the difference to 0V because of its feedback. Now it will be become a simple comperator with Vout=H if V+ &gt; V-, Vout=L if V+ &amp;lt; V-. In an wrong unity gain buffer, you'll see Vout=L because V+ is lower then the signal you're feeding it with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because I couldn't believe both situations would simulate the same, I did it myself:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/TWXoI.png&quot; alt=&quot;Ideal opamps&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just 2 opamps which are internally fed to +/-15V. They follow a 1kHz 10Vpp source. The results are:&#xA;&lt;img src=&quot;http://i.imgur.com/zIGfW.png&quot; alt=&quot;Simulation 1&quot;&gt;&#xA;(Note: Colors are inverted, so green = purple, cyan = red)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh so they do amplify correctly. But the ideal opamp has an infinite gain, no offset voltages, no input bias currents, no bandwith limitations (however, we wont notice much of that at 1kHz) etc. If we look at a real opamp, I picked one randomly (TL031):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wfLFg.png&quot; alt=&quot;Real opamps&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An now it suddenly clips, because the opamp doesn't have the correct feedback.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OyCzq.png&quot; alt=&quot;Simulation 2&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1476" LastEditorUserId="1476" LastEditorDisplayName="" LastEditDate="2011-03-06T10:40:17.653" LastActivityDate="2011-03-06T10:40:17.653" CommentCount="4" />
  <row Id="11099" PostTypeId="1" AcceptedAnswerId="11101" CreationDate="2011-03-06T11:18:28.707" Score="2" ViewCount="144" Body="&lt;p&gt;I have 2 stepper motors in my micromouse. Every so often one of the stepper motors will turn back one step. My set up is a PICAXE and a ULN2803A and to clock the pulses i just turn the outputs on or off on the picaxe. The stepper motors are back to back so if one is rotating clockwise the other must be going anticlockwise to make it go forwards. This leads me to powering my outputs using the following: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;; Coil 1 of one stepper motor is output 0&#xA;; Coil 4 of one stepper motor is output 3&#xA;; Coil 1 of the other stepper motor is output 4&#xA;; Coil 4 of the other stepper motor is output 7&#xA;let pins = %10000001&#xA;wait 1 ;wait 1 second&#xA;let pins = %01000010&#xA;wait 1 ;wait 1 second&#xA;let pins = %00100100&#xA;wait 1 ;wait 1 second&#xA;let pins = %00011000&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;So why is it rotating backwards after 2 puleses? Have I got the coils the wrong way?&lt;br&gt;&#xA;UPDATE:&lt;br&gt;&#xA;I've just again checked that i have the correct coil numbers and this is correct. So the coils are the correct. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-03-06T11:59:45.323" LastActivityDate="2011-03-07T14:52:05.603" Title="Stepper Motor Pulses Making it reverse" Tags="&lt;stepper-motor&gt;&lt;picaxe&gt;" AnswerCount="2" />
  <row Id="11100" PostTypeId="2" ParentId="1983" CreationDate="2011-03-06T11:50:37.187" Score="2" ViewCount="" Body="&lt;p&gt;I've been looking in to this subject over the last few days as I have the same problem... trying to dim LEDs using PWM in a visibly linear way, but I want full 256 step resolution. Trying to guess 256 numbers to manually create a curve is not an easy task!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not an expert mathematician, but I know enough to generate some basic curves by combining a few functions and formulas without really knowing how they work. I find that using a spreadsheet (I used Excel) you can play around with a set of numbers from 0 to 255, put a few formulas in the next cell, and graph them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using pic assembler to do the fading, and so you can even get the spreadsheet to generate the assembler code with a formula (&lt;code&gt;=&quot;retlw 0x&quot; &amp;amp; DEC2HEX(A2)&lt;/code&gt;). This makes it very quick and easy to try out a new curve.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After a bit of playing around with LOG and SIN functions, the average of the two, and a few other things, I couldn't really get the right curve. What is happening is that the middle part of the fade was happening slower than the lower and higher levels. Also, if a fade-up is immediately followed by a fade-down there was a sharp noticeable spike in the intensity. What is needed (in my opinion) is an S curve.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A quick search on &lt;a href=&quot;http://en.wikipedia.org/wiki/Logistic_function&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt; came up with the formula needed for an S curve. I plugged this into my spreadsheet, and made a few adjustments to make it multiply across my range of values, and came up with this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kpe7K.jpg&quot; alt=&quot;S curve&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tested it on my rig, and it worked beautifully.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Excel formula I used was this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;=1/(1+EXP(((A2/21)-6)*-1))*255&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;where A2 is the first value in column A, which increases A3, A4, ..., A256 for each value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no idea if this is mathematically correct or not, but it produces the desired results.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are the full set of 256 levels that I used:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,&#xA;0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02,&#xA;0x02, 0x02, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04, 0x04, 0x05, 0x05, 0x05,&#xA;0x05, 0x06, 0x06, 0x06, 0x07, 0x07, 0x07, 0x08, 0x08, 0x08, 0x09, 0x09, 0x0A, 0x0A, 0x0B, 0x0B,&#xA;0x0C, 0x0C, 0x0D, 0x0D, 0x0E, 0x0F, 0x0F, 0x10, 0x11, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,&#xA;0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1F, 0x20, 0x21, 0x23, 0x24, 0x26, 0x27, 0x29, 0x2B, 0x2C,&#xA;0x2E, 0x30, 0x32, 0x34, 0x36, 0x38, 0x3A, 0x3C, 0x3E, 0x40, 0x43, 0x45, 0x47, 0x4A, 0x4C, 0x4F,&#xA;0x51, 0x54, 0x57, 0x59, 0x5C, 0x5F, 0x62, 0x64, 0x67, 0x6A, 0x6D, 0x70, 0x73, 0x76, 0x79, 0x7C,&#xA;0x7F, 0x82, 0x85, 0x88, 0x8B, 0x8E, 0x91, 0x94, 0x97, 0x9A, 0x9C, 0x9F, 0xA2, 0xA5, 0xA7, 0xAA,&#xA;0xAD, 0xAF, 0xB2, 0xB4, 0xB7, 0xB9, 0xBB, 0xBE, 0xC0, 0xC2, 0xC4, 0xC6, 0xC8, 0xCA, 0xCC, 0xCE,&#xA;0xD0, 0xD2, 0xD3, 0xD5, 0xD7, 0xD8, 0xDA, 0xDB, 0xDD, 0xDE, 0xDF, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5,&#xA;0xE6, 0xE7, 0xE8, 0xE9, 0xEA, 0xEB, 0xEC, 0xED, 0xED, 0xEE, 0xEF, 0xEF, 0xF0, 0xF1, 0xF1, 0xF2,&#xA;0xF2, 0xF3, 0xF3, 0xF4, 0xF4, 0xF5, 0xF5, 0xF6, 0xF6, 0xF6, 0xF7, 0xF7, 0xF7, 0xF8, 0xF8, 0xF8,&#xA;0xF9, 0xF9, 0xF9, 0xF9, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFB, 0xFB, 0xFB, 0xFB, 0xFB, 0xFB, 0xFC,&#xA;0xFC, 0xFC, 0xFC, 0xFC, 0xFC, 0xFC, 0xFC, 0xFC, 0xFD, 0xFD, 0xFD, 0xFD, 0xFD, 0xFD, 0xFD, 0xFD,&#xA;0xFD, 0xFD, 0xFD, 0xFD, 0xFD, 0xFD, 0xFD, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFF, 0xFF&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-30T12:37:06.573" LastActivityDate="2011-03-30T12:37:06.573" />
  <row Id="11101" PostTypeId="2" ParentId="11099" CreationDate="2011-03-06T12:23:03.147" Score="1" ViewCount="" Body="&lt;p&gt;Have you blown the ULN2803A? As the coils are correct and the pulses also work. Try swapping the stepper motors over if the same happens then you have blown the ULN2803A. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-06T12:23:03.147" />
  <row Id="11102" PostTypeId="2" ParentId="11095" CreationDate="2011-03-06T12:23:07.430" Score="0" ViewCount="" Body="&lt;p&gt;There are multimeters with separate inputs for voltage and for current measurement and there are multimeters that have a single input for both.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With those that have a single input, current will flow through the meter only if it's in current range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With those that have separate inputs, current will always flow when the red lead is plugged into the current measurement plug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, there will flow a very small leakage current even in voltage mode, but that is usually negligible.&lt;/p&gt;&#xA;" OwnerUserId="1950" LastActivityDate="2011-03-06T12:23:07.430" />
  <row Id="11103" PostTypeId="2" ParentId="11073" CreationDate="2011-03-06T13:01:44.943" Score="1" ViewCount="" Body="&lt;p&gt;Find a hackerspace near you, become a member and use the gear at the space.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have gained experience you will know which equipment is the most useful to you and you are better able to figure out how much you are willing to pay for it.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-03-06T13:01:44.943" CommentCount="1" />
  <row Id="11104" PostTypeId="2" ParentId="1983" CreationDate="2011-03-06T14:18:32.090" Score="0" ViewCount="" Body="&lt;p&gt;To get smooth step-less dimming over the full range you need to do PWM at about 12 bits to get enough resolution for a nice correction curve. &#xA;8 bit input to the curve lookup is sufficient.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-03-06T14:18:32.090" CommentCount="1" />
  <row Id="11105" PostTypeId="2" ParentId="11073" CreationDate="2011-03-06T16:07:48.327" Score="0" ViewCount="" Body="&lt;p&gt;Multimeter, power supply and oscilloscope.  For digital logic, a logic analyzer comes next.  The performance of the scope and logic analyzer depends greatly on what you are trying to test.  If you are assembling it yourself, a soldering iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The software depends dramatically on what you are trying to do.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-06T16:07:48.327" />
  <row Id="11106" PostTypeId="2" ParentId="11079" CreationDate="2011-03-06T16:08:42.690" Score="2" ViewCount="" Body="&lt;p&gt;Driving a fan by switching the supply is firstly risky. BLDC fans have electronics in them and your switching these on and off at high speed. Not how they were designed. You risk killing the electronics like this over time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adding the cap helps because you are removing nasty power spikes into the fan. Adding the inductor is a good idea and if you look at what people are suggesting you will see that the best way to speed control a BLDC fan is with a constant current buck regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This way you PWM the FET that is feeding energy into the inductor (energy store) and place a fly back diode to circulate the power when the FET is off. This will keep a steady flow of power in the fan, minimal noise and not risk killing the fan long term.&lt;/p&gt;&#xA;" OwnerUserId="2649" LastActivityDate="2011-03-06T16:08:42.690" />
  <row Id="11108" PostTypeId="2" ParentId="5302" CreationDate="2011-03-06T18:41:58.627" Score="2" ViewCount="" Body="&lt;p&gt;Brazilian greetings!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First of all thanks Joby for your example. Secondly, his example has just a minor error. The number 0x20 is not correct. It should be 0x04. Also, just as a suggestion, I would not use hexadecimal numbers like 0xFB, 0x20, or 0x04 in the code. I would suggest using the PIN port definitions found in the io.h and other ones referenced by header file. I have rewritten Joby's example below, with some comments for the beginners.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;# include &amp;lt;avr/io.h&amp;gt;&#xA;&#xA;int main (void)&#xA;{&#xA;    // set all pins on PORTB for output&#xA;    DDRB = 0xFF;&#xA;&#xA;    // set port pin PORTD2 as input and leave the others pins &#xA;    // in their originally state (inputs or outputs, it doesn't matter)&#xA;    DDRD &amp;amp;= ~(1 &amp;lt;&amp;lt; PD2);        // see comment #1&#xA;&#xA;    while (1) &#xA;    {&#xA;        if (PIND &amp;amp; (1&amp;lt;&amp;lt;PD2))    // see comment #2&#xA;            PORTB |= (1&amp;lt;&amp;lt;PB2);  // see comment #3&#xA;        else&#xA;            PORTB &amp;amp;= ~(1&amp;lt;&amp;lt;PB2); // see comment #4&#xA;    }&#xA;    return 0;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;/*&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;comments for beginners&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;comment #1&lt;/strong&gt;: (1 &amp;lt;&amp;lt; PD2) generates the binary 00000100.&#xA;              The operation &quot;~&quot; flips all the digits, i.e., &#xA;              the binary now is 11111011. Finally the &amp;amp;= &#xA;              applies the logic &quot;AND&quot; between DDRD and 11111011&#xA;              and the result is placed again in DDRD memory. &#xA;              Note: What the operator &quot;AND&quot; does is for each bit &#xA;              in the DDRD memory, it compares with the binary number&#xA;              above. If the bit in DDRD is 0 and the bit in the&#xA;              binary at the same bite position is 1, then the&#xA;              resulting bit is 0, if the DDRD is 1 and the &#xA;              bit in the binary is 1, the resulting bit is 1, &#xA;              and if the bit in the DDRD is 1 or 0 and&#xA;              the bit in the binary is 0 then the resulting &#xA;              bit is always 0. In summary, the command DDRD &amp;amp;= ~(1 &amp;lt;&amp;lt; PD2)&#xA;              changes only the bit PD2 to zero and leave the other ones &#xA;              (zeros or ones) untouched. It seems a little&#xA;              bit complicated, but after you get used to it, it&#xA;              is the best way of changing a bit in a bite without&#xA;              changing the other bits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;comment #2&lt;/strong&gt;: (1 &amp;lt;&amp;lt; PD2) generates the binary 00000100.&#xA;              Using the same logic &quot;AND&quot; described in &#xA;              comment #1, the command &quot;PIND &amp;amp; 0000100&quot; checks&#xA;              only if the PIND2 (our input pin where the push button&#xA;              is connected to) is set to high or not. All the other &#xA;              pins will be FALSE since the binary bits are set to 0, &#xA;              and since the binary bit #2 is set to 1, the IF statement &#xA;              will be TRUE only if the PD2 input is set to high &#xA;              or FALSE if the PD2 input is set to low. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;comment #3&lt;/strong&gt;: Following the logic explained in comment #1, this&#xA;              command sets output pin PINB2 in port PORTB to&#xA;              high voltage. If your LED is correct connected to&#xA;              this pin port with a resistor of ~300 ohms, and that &#xA;              resistor is connected to the ground, the LED should turn on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;comment #4&lt;/strong&gt;: The LED should turn off for the same reasons explained&#xA;              in the previous comments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Final considerations:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;a) &lt;a href=&quot;http://www.edaboard.com/thread193657.html&quot; rel=&quot;nofollow&quot;&gt;To avoid voltage oscillation in the input pin PD2 when the &#xA;   push button is not pressed (open circuit), I strong recommend&#xA;   to place a pull-down resistor (1 kOhm or higher), so that the &#xA;   LED does not light up accidentally due to this random voltage &#xA;   oscillation.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;b) A disclaim note: The ideas described here are to be used as &#xA;   educational only and they should NOT be used in any real system &#xA;   before consulting an expert in electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*/&lt;/p&gt;&#xA;" OwnerUserId="3270" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-03-07T19:23:52.627" LastActivityDate="2011-03-07T19:23:52.627" CommentCount="1" />
  <row Id="11109" PostTypeId="1" CreationDate="2011-03-06T20:33:33.870" Score="6" ViewCount="145" Body="&lt;p&gt;I need to buy a few logic ICs.  Which family should I get?  HC? HCT? Which kind is best to have lying around in a parts box, for maximum compatibility with unpredictable future projects?  Wide supply range, no extreme frequency requirements, etc.  Schmitt inputs?  Open outputs?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-03-06T21:38:13.977" Title="What logic family is best for general-purpose hobbyist stuff?" Tags="&lt;logic&gt;&lt;glue&gt;&lt;74xx&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="11110" PostTypeId="2" ParentId="11109" CreationDate="2011-03-06T20:52:06.877" Score="7" ViewCount="" Body="&lt;p&gt;HC is the most useful. It has a very wide supply voltage range, is easy to interface to most MCUs, has good noise immunity, has plenty of speed, and is widely available. HC is also available as single gates in tiny packages. Forget TTL and LS TTL, no one uses them for new designs these days.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's also worth learning to use CPLDs, Using them often makes a lot more sense than designing with individual logic chips.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-06T21:04:56.580" LastActivityDate="2011-03-06T21:04:56.580" CommentCount="2" />
  <row Id="11111" PostTypeId="2" ParentId="11109" CreationDate="2011-03-06T21:28:53.520" Score="4" ViewCount="" Body="&lt;p&gt;HCT is nice.  All the advantages @Leon Heller mentioned, but also TTL compatible inputs.  If you need speed, consider ACT.  Ti's &lt;a href=&quot;http://focus.ti.com/lit/sg/sdyu001z/sdyu001z.pdf&quot; rel=&quot;nofollow&quot;&gt;Logic Guide&lt;/a&gt; has lots of details.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-03-06T21:38:13.977" LastActivityDate="2011-03-06T21:38:13.977" CommentCount="4" />
  <row Id="11112" PostTypeId="1" AcceptedAnswerId="11113" CreationDate="2011-03-06T21:42:24.107" Score="3" ViewCount="309" Body="&lt;p&gt;When pulling something up or down why is a resistor used and it not just connected straight to the +V or 0V rail?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-07T08:53:07.550" Title="Why the use of resistors when pulling something up or down?" Tags="&lt;resistor&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="11113" PostTypeId="2" ParentId="11112" CreationDate="2011-03-06T21:51:57.917" Score="11" ViewCount="" Body="&lt;p&gt;It limits current to protect the switch (transistor, etc.) and allows signal sources with limited driving capability to change that node's voltage. Rails generally have high drive capability, or low resistance. Think voltage divider, including source impedance of signal and rail, then let the rail impedance be 0-ohms for simplicity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other factors, other than operating current and voltage drops, to determine the pull resistance is charge time and substrate leakage. A 2M-ohm pull-down resistor on a top layer exposed to humidity and salts won't do anything due to sub-1M-ohm electrical resistance of &lt;em&gt;grime&lt;/em&gt; layer.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-03-06T21:51:57.917" CommentCount="4" />
  <row Id="11114" PostTypeId="2" ParentId="11112" CreationDate="2011-03-06T22:01:33.320" Score="2" ViewCount="" Body="&lt;p&gt;Another reason is that it makes it very easy to alter the input - just connect it to the positive supply if it is pulled down, for instance, rather than rewiring the connection. A couple of pins for a jumper are all that is required. A typical example is pin P0.14 on an NXP ARM chip, which determines whether it boots from a serial input or from internal flash memory.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-06T22:29:59.633" LastActivityDate="2011-03-06T22:29:59.633" CommentCount="4" />
  <row Id="11115" PostTypeId="2" ParentId="11112" CreationDate="2011-03-06T23:34:25.533" Score="3" ViewCount="" Body="&lt;p&gt;You can also think of it this way - without a pull-up (or pull-down) resistor in place on an input, the source of the input would have to directly oppose your device's power supply to change the voltage at that input. Depending on the situation, you'd either cause problems for your power supply, or the input source, or both. With the resistor, the input can be controlled by the input source without inordinate currents. The situation for output pull-ups is similar, except that the 'input source' is the device's output transistor.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-03-06T23:34:25.533" />
  <row Id="11116" PostTypeId="1" AcceptedAnswerId="11118" CreationDate="2011-03-07T00:56:44.620" Score="2" ViewCount="123" Body="&lt;p&gt;What screw size should be used to mount a TIP31 in a TO220 package to a bare PCB (no heatsink?) I presume a nut will also be required on the other side, so would appreciate a part number for that too. (I'm not too clued up on mechanical stuff, so go easy on me.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-03-07T01:03:25.160" LastActivityDate="2011-03-08T18:32:01.980" Title="What screw should I use to mount a TO220 package?" Tags="&lt;mount&gt;&lt;to220&gt;" AnswerCount="2" />
  <row Id="11117" PostTypeId="1" AcceptedAnswerId="11384" CreationDate="2011-03-07T01:02:13.927" Score="1" ViewCount="175" Body="&lt;p&gt;I have this crazy idea of mixing Cb and Cr signals (from a YCbCr device outputting 720p video) into a chroma (C) signal, for a side project. Is there a simple drop-in chip solution for each side - both modulation, and demodulation/recovery? I've either only found RF/IF devices (which seem to have a limited span, often not including DC or low frequencies) or digital QAM - neither of which seem to be useful to me, unless I'm missing something. I'm targeting a low cost, low power and hopefully small size system -  but would be okay with some ideas on how to go about implementing a discrete QAM modulation system (using op-amps or other ICs as building blocks.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-13T18:05:18.027" Title="Do chips which do analog modulation/demodulation of QAM exist?" Tags="&lt;video&gt;&lt;modulation&gt;&lt;qam&gt;&lt;demodulation&gt;" AnswerCount="3" CommentCount="7" />
  <row Id="11118" PostTypeId="2" ParentId="11116" CreationDate="2011-03-07T01:34:57.270" Score="5" ViewCount="" Body="&lt;p&gt;I use &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=H743-ND&quot; rel=&quot;nofollow&quot;&gt;a panheaded M3 screw&lt;/a&gt; with &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=H762-ND&quot; rel=&quot;nofollow&quot;&gt;a matching nut&lt;/a&gt; for TO220.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Put the nut on top of the package so that any excess screw length sticks upwards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may be cheaper to buy machine screws (and nuts) of similar thickness at a nearby hardware store. My local screw dealer charges by weight, so I end up paying pennies (cents) for what I need in my hobby projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What matters most is that your screw fits in the mounting hole, which is about 3.5mm in diameter.&lt;/p&gt;&#xA;" OwnerUserId="2545" LastActivityDate="2011-03-07T01:34:57.270" CommentCount="0" />
  <row Id="11119" PostTypeId="2" ParentId="11112" CreationDate="2011-03-07T02:08:08.813" Score="5" ViewCount="" Body="&lt;p&gt;Another point not mentioned is that if it's necessary to alter the board, it's possible to pull off the resistor and replace it with a wire connecting one of the resistor pads to something else.  By comparison, trying to rework a surface-mount pin which connects to a power ground plane using a via which is under the chip can be difficult or impossible (at least difficult enough that scrapping the board would be cheaper).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-07T02:08:08.813" CommentCount="2" />
  <row Id="11120" PostTypeId="1" CreationDate="2011-03-07T02:49:30.043" Score="4" ViewCount="124" Body="&lt;p&gt;In school I have learned in both systems and communication about multiplication blocks. I have been taught that these blocks create a sum and difference frequency and can be filtered to get just the sum or the difference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I am wondering is how to actually implement a block like this in hardware. I first thought about an OPAMP multiplier setup, but I didn't think something like this worked well for high frequencies like 900MHz or 2.4GHz. How do I go about finding a device that will do this block for me?&lt;/p&gt;&#xA;" OwnerUserId="3272" LastActivityDate="2011-03-07T12:35:48.007" Title="Actual Implementation of a Multiplier" Tags="&lt;rf&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="11121" PostTypeId="2" ParentId="11120" CreationDate="2011-03-07T03:48:24.680" Score="3" ViewCount="" Body="&lt;p&gt;Lookup &quot;Gilbert Cell&quot; and &quot;Four quadrant multiplier&quot;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;More generally, look into &quot;translinear circuits&quot; which are more general, the multiplier being a special case.  The key idea is the logarithmic relation between the base-emitter voltage and emitter current.  Some number of transistors are connected with their base-emitter junctions in a loop. By Kirchoff's voltage law, the sums of voltages around this loop is zero, and by the logarithmic relation, you can say something useful about the &lt;strong&gt;product&lt;/strong&gt; of emitter currents.  With cleverness in making use of that fact, you can design a multiplier.   Differential amplifiers are a relevant idea, just not the key idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some articles:&lt;br&gt;&#xA;&lt;a href=&quot;http://www.analog.com/library/analogdialogue/archives/42-11/multipliers.html&quot; rel=&quot;nofollow&quot;&gt;http://www.analog.com/library/analogdialogue/archives/42-11/multipliers.html&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Translinear_circuit&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Translinear_circuit&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and find the paper &quot;Translinear Circuits&quot; by Barrie Gilbert&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and for a good read that covers much more but includes a nice little explanation of translinear circuits, look for the article &quot;The Gears of Genius&quot; in IEEE SOLID-STATE CIRCUITS SOCIETY NEWS, Fall 2007 issue.   This article is followed by one describing a very fast multiplier circuit.  &lt;/p&gt;&#xA;" OwnerUserId="1609" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-03-07T07:15:33.803" LastActivityDate="2011-03-07T07:15:33.803" />
  <row Id="11122" PostTypeId="1" CreationDate="2011-03-07T06:24:02.033" Score="1" ViewCount="157" Body="&lt;p&gt;Hi, I'm looking to measure distances from a submersed robotics project in the range of 1 to 20 feet (around there at least).  However, the only options I seem to come across are rather heavy sonar modules that cost hundreds of dollars.  Are there lighter, cheaper alternatives?  I don't need great resolution or accuracy, just a decent measurement.  Perhaps it's possible to waterproof a normal distance sensor (IR or ultrasonic)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I intend to interface the sensor with a microcontroller so it would be nice to have something that outputs 0-5 V, but that's not a requirement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="954" LastActivityDate="2011-03-07T14:15:18.193" Title="Underwater Distance Sensing" Tags="&lt;sensor&gt;&lt;robotics&gt;&lt;distance&gt;&lt;underwater&gt;&lt;sonar&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="11123" PostTypeId="1" CreationDate="2011-03-07T07:49:10.313" Score="1" ViewCount="221" Body="&lt;p&gt;Hi All,&#xA;i a trying to do is interface the GPS module with my ARM board. &#xA;GPS send RS232 signal from its single pin (say pin Z) .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i want to use the watchdog timer for receiving and parsing the serial stream. Any idea of using watchdog in this context?&lt;/p&gt;&#xA;" OwnerUserId="3276" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-09T19:18:03.997" LastActivityDate="2011-03-09T19:18:03.997" Title="Bit banging a UART" Tags="&lt;arm&gt;&lt;uart&gt;&lt;rs232&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="11124" PostTypeId="2" ParentId="11112" CreationDate="2011-03-07T08:53:07.550" Score="2" ViewCount="" Body="&lt;p&gt;If you only want to supply a defined logical level to a definitely unused input, a direct connection to ground or vcc would be ok in my opinion. BUT: if you do that, it is impossible to drive the input from other sources. (see posts above)&lt;/p&gt;&#xA;" OwnerUserId="495" LastActivityDate="2011-03-07T08:53:07.550" />
  <row Id="11125" PostTypeId="2" ParentId="11123" CreationDate="2011-03-07T10:02:46.393" Score="3" ViewCount="" Body="&lt;p&gt;You cannot use the watchdog timer, as that resets the processor on almost (all?) processors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could insert code in your reset routine, but this would be backwards as the data memory of the chip is usually cleared on reset.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-08T18:32:57.340" LastActivityDate="2011-03-08T18:32:57.340" CommentCount="4" />
  <row Id="11126" PostTypeId="2" ParentId="11122" CreationDate="2011-03-07T11:21:19.613" Score="1" ViewCount="" Body="&lt;p&gt;Fish-finders like &lt;a href=&quot;https://buy.garmin.com/shop/shop.do?pID=85268&amp;amp;ra=true&quot; rel=&quot;nofollow&quot;&gt;this Garmin unit&lt;/a&gt; are quite inexpensive at about $100. Buy one of those and use the transducer. You might even be able to buy the transducer quite cheaply as a spare.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-07T11:21:19.613" CommentCount="4" />
  <row Id="11127" PostTypeId="2" ParentId="11120" CreationDate="2011-03-07T12:27:51.727" Score="0" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.nxp.com/#/pip/pip=%5bpip=SA612A%5d|pp=%5bt=pip,i=SA612A%5d&quot; rel=&quot;nofollow&quot;&gt;SA612&lt;/a&gt; is a popular device using a Gilbert cell multiplier; it's often used by radio amateurs for simple superhet and direct-conversion radio receivers. It won't go up to 900 MHz or 2.4 GHz, but is suitable for experimentation at HF and VHF.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-07T12:35:48.007" LastActivityDate="2011-03-07T12:35:48.007" />
  <row Id="11128" PostTypeId="1" CreationDate="2011-03-07T14:11:10.803" Score="0" ViewCount="156" Body="&lt;p&gt;A question I asked on a mailing list. Thought I'd echo it here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just want to brainstorm something I'd like to exist, and I want a reality check from people who really know about radio / electronics etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to find smaller, more flexible input devices for electronics projects : at first, simple push buttons. The problem is, although buttons themselves are small, there has to be a long wire joining them back to, say, an Arduino. (Let's say, I'm interested in distances of up to a meter.) Or, without that, you need a whole battery powered radio transmitter, which obviously makes things a lot bulkier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OTOH, RFID, as I understand, uses very small chips, which get their power from the field created by a local transceiver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, my question is, are there (or could there be) similar passive input devices. For example, a very small, un-powered, button which can be in one of two states and that can be read via a local radio transceiver?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone make something like this? Or, if not, how would you go about making one?&lt;/p&gt;&#xA;" OwnerUserId="3279" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-20T20:02:19.460" LastActivityDate="2011-03-20T20:02:19.460" ClosedDate="2011-03-10T01:37:17.100" Title="Brainstorm on wireless buttons" Tags="&lt;wireless&gt;" AnswerCount="1" CommentCount="6" />
  <row Id="11129" PostTypeId="2" ParentId="11122" CreationDate="2011-03-07T14:15:18.193" Score="0" ViewCount="" Body="&lt;p&gt;Ultrasound would be your best shot. A quick search on the web tells me that unless you want do do a significant amount of work yourself it's not going to be cheap. Transducers from &lt;a href=&quot;http://www.robotshop.com/world/senix-tspc-30s1-waterproof-ultrasonic-sensor-1.html&quot; rel=&quot;nofollow&quot;&gt;Senix&lt;/a&gt; cost about $500, but if you can get a hold of a waterproof ultrasound sensor for parking aid systems and is able to build the tx-amplifier, the transmit/receive switch, and do the signal processing in a uC you should be done for a lot less than that.&lt;/p&gt;&#xA;" OwnerUserId="1627" LastActivityDate="2011-03-07T14:15:18.193" />
  <row Id="11130" PostTypeId="2" ParentId="11099" CreationDate="2011-03-07T14:44:01.933" Score="2" ViewCount="" Body="&lt;p&gt;You're skipping steps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Full drive mode for a stepper looks like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; Step A  A' B  B'&#xA;  1   1  0  1  0&#xA;  2   1  0  0  1&#xA;  3   0  1  0  1&#xA;  4   0  1  1  0&#xA;  1   1  0  1  0&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;One of the A windings and one of the B windings are always on, and the rotor is resting halfway between the two powered windings.  This gives you maximum torque.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Half stepping sacrifices some torque to give you twice the resolution:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; Step  A  A' B  B'&#xA;  1    1  0  1  0&#xA;  1.5  1  0  0  0&#xA;  2    1  0  0  1&#xA;  2.5  0  0  0  1&#xA;  3    0  1  0  1&#xA;  3.5  0  1  0  0&#xA;  4    0  1  1  0&#xA;  4.5  0  0  1  0&#xA;  1    1  0  1  0&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The half steps don't have as much torque, since only one winding is on part of the time.  But, the half steps are close to a full step, so it doesn't take much to get the rotor there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You're skipping the full steps and just using the half steps.  You might also be sequencing the windings wrong.  I can't tell because your numbering scheme is atypical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See a reference like &lt;a href=&quot;http://zone.ni.com/devzone/cda/ph/p/id/247&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; for more information and pictures.&lt;/p&gt;&#xA;" OwnerUserId="1824" LastEditorUserId="1824" LastEditorDisplayName="" LastEditDate="2011-03-07T14:52:05.603" LastActivityDate="2011-03-07T14:52:05.603" CommentCount="2" />
  <row Id="11131" PostTypeId="1" AcceptedAnswerId="11134" CreationDate="2011-03-07T15:29:03.547" Score="1" ViewCount="106" Body="&lt;p&gt;I was wondering if anyone knew of a simple circuit design that would output &quot;high&quot; only for a certain voltage (within a small degree of error).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!&lt;/p&gt;&#xA;" OwnerUserId="2985" LastActivityDate="2011-03-08T09:29:37.953" Title="A delta function like response for voltage in to voltage out" Tags="&lt;filter&gt;" AnswerCount="2" />
  <row Id="11132" PostTypeId="2" ParentId="3196" CreationDate="2011-03-07T15:53:17.843" Score="0" ViewCount="" Body="&lt;p&gt;There's a detailed description in the STR91xF datasheet - it's complicated, but not as complicated as the ST libraries make it seem. Given the #defines and structs listed at&#xA;the end, to turn on e.g. GPIO4:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;SCU-&amp;gt;PCGR1 |= __GPIO4;                      // switch the port on.&#xA;SCU-&amp;gt;PCGRO &amp;amp;=~ (u32)__GPIO4;                // reset the device&#xA;SCU-&amp;gt;PRR1 |= __GPIO4;                       // peripheral not held in Reset&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then, y'can set up the port using a combination of&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;   GPIO4-&amp;gt;DDR &#xA;   SCU-&amp;gt;GPIOOUT[4]&#xA;   SCU-&amp;gt;GPIOIN[4]&#xA;   SCU-&amp;gt;GPIOTYPE[4]&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(and GPIO4-&gt;DR[n] to set and read the pins)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GPIOn-&gt;DDR    is 8 bits, bits 7:0 corresponding to pins 7:0. any set bit makes its&lt;br&gt;&#xA;              corresponding pin an output, default is zero, all input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The SCU registers are also bit masks, as follows:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GPIOTYPE[port_number] is 8 bits, with bit 7:0 corresponding to pin 7:0. Any set bits&#xA;                      make their corresponding output pins open-collector. Default is all &#xA;                      zero (push-pull)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GPIOIN[port number] is 8 bits. Any set bit has the input routed to some or other &#xA;                    internal peripheral input function, as detailed in a big table in&#xA;                    the data sheet, depends on device. NOTE: Even when connected to &#xA;                    an internal peripheral, you can still also read it as a general input.&#xA;                    Defaul is all zero, plain general purpose input&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GPIOOUT[port number] is 16 bits, each pair of bits corresponding to a pin, so bits&#xA;                     14 and 15 control pin 7, bits 0 and 1 control pin 0. Zero means&#xA;                     ordinary GPIO input, 1 is normal GPIO output, 2 and 3 are alternative&#xA;                     outputs from internal peripherals. (See big table in STR9xx data &#xA;                     sheet) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So to set up GPIO4 so that pins 0 and 1 are outputs, with 0 being open collector, and&#xA;the remaining pins are inputs, do:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;GPIO4-&amp;gt;DDR = 0x03;          //  0  0   0  0   0  0   1  1     pins 0 and 1 are output&#xA;SCU-&amp;gt;GPIOOUT[4] = 0x0005;   // 00 00  00 00  00 00  01 01     pins 0 and 1 are Alt1 output&#xA;SCU-&amp;gt;GPIOTYPE[4] = 0x01;    //  0  0   0  0   0  0   0  1     pin 0 open collector&#xA;SCU-&amp;gt;GPIOIN[4] = 0x00;      // no alternate inputs connected&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;To actually set/read port pins, STR9 has a memory mapped system where you mask pins &#xA;by both address and value, so that you can write to just the pins you want without having&#xA;to do too much ORing of arguments. E.g. &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;GPIO4-&amp;gt;DR[GPIO_Pin_1 &amp;lt;&amp;lt; 2] = GPIO_Pin_1; //sets pin1 output to high.&#xA;x = GPIO4-&amp;gt;DR[GPIO_Pin_3 &amp;lt;&amp;lt; 2];          //reads pin3 &#xA;y = GPIO4-&amp;gt;DR[(GPIO_Pin_3 | GPIO_Pin_4) &amp;lt;&amp;lt; 2];  // reads pins 3 and 4&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The symbols used above boil down to:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define __GPIO0 0x4000&#xA;#define __GPIO1 0x8000&#xA;#define __GPIO2 0x10000&#xA;#define __GPIO3 0x20000&#xA;#define __GPIO4 0x40000&#xA;#define __GPIO5 0x80000&#xA;#define __GPIO6 0x100000&#xA;#define __GPIO7 0x200000&#xA;#define __GPIO8 0x400000&#xA;#define __GPIO9 0x800000&#xA;&#xA;typedef struct&#xA;{&#xA;  vu32 CLKCNTR;    &#xA;  vu32 PLLCONF;    &#xA;  vu32 SYSSTATUS;  &#xA;  vu32 PWRMNG;     &#xA;  vu32 ITCMSK;     &#xA;  vu32 PCGRO;      &#xA;  vu32 PCGR1;      &#xA;  vu32 PRR0;       &#xA;  vu32 PRR1;       &#xA;  vu32 MGR0;       &#xA;  vu32 MGR1;       &#xA;  vu32 PECGR0;     &#xA;  vu32 PECGR1;     &#xA;  vu32 SCR0;       &#xA;  vu32 SCR1;       &#xA;  vu32 SCR2;       &#xA;  u32 EMPTY1;&#xA;  vu32 GPIOOUT[8];   &#xA;  vu32 GPIOIN[8];   &#xA;  vu32 GPIOTYPE[10]; &#xA;  vu32 GPIOEMI;      &#xA;  vu32 WKUPSEL;      &#xA;  u32 EMPTY2[2];&#xA;  vu32 GPIOANA;      &#xA;} SCU_TypeDef;&#xA;&#xA;typedef struct&#xA;{&#xA;  vu8 DR[1021];     /* Data Register                    */&#xA;  vu32 DDR;         /* Data Direction Register          */&#xA;} GPIO_TypeDef;&#xA;&#xA;// #define AHB_BASE   (0x58000000)              // unbuffered&#xA;#define AHB_BASE   (0x48000000)              // buffered&#xA;&#xA;// #define __APB1_BASE          0x5C000000                // unbuffered&#xA;#define __APB1_BASE          0x4C000000                // buffered&#xA;&#xA;#define __SCU_BASE           (__APB1_BASE + 0x2000)&#xA;#define SCU                  ((SCU_TypeDef *)__SCU_BASE)&#xA;&#xA;#define GPIO0_OFFSET     (0x00006000)&#xA;#define GPIO0_OFFSET     (0x00007000)&#xA;// ...&#xA;#define GPIO4_OFFSET     (0x0000A000)&#xA;&#xA;#define GPIO4   (AHB_BASE + GPIO4_OFFSET)&#xA;&#xA;&#xA;#define GPIO_Pin_None 0x00&#xA;#define GPIO_Pin_0    0x01&#xA;#define GPIO_Pin_1    0x02&#xA;#define GPIO_Pin_2    0x04&#xA;#define GPIO_Pin_3    0x08&#xA;#define GPIO_Pin_4    0x10&#xA;#define GPIO_Pin_5    0x20&#xA;#define GPIO_Pin_6    0x40&#xA;#define GPIO_Pin_7    0x80&#xA;#define GPIO_Pin_All  0xFF&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3281" LastActivityDate="2011-03-07T15:53:17.843" />
  <row Id="11133" PostTypeId="2" ParentId="11131" CreationDate="2011-03-07T16:17:26.210" Score="5" ViewCount="" Body="&lt;p&gt;This one simple circuit I could think of. You can set the pot VR1 and VR2 to the lower and upper voltage levels respectively and the output will only be high when your input is in the range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/y4S5X.png&quot; alt=&quot;circuit diagram&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2011-03-07T16:17:26.210" CommentCount="2" />
  <row Id="11134" PostTypeId="2" ParentId="11131" CreationDate="2011-03-07T16:18:55.367" Score="6" ViewCount="" Body="&lt;p&gt;Your question is kind of vague, but a window comparator is what I'm imagining you're asking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ecelab.com/circuit-window-comp.htm&quot; rel=&quot;nofollow&quot;&gt;http://ecelab.com/circuit-window-comp.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OBeZd.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That outputs a low in the middle range, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will give you a high output in the middle, using open-collector comparators:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/vKyed.png&quot; alt=&quot;http://www.aaroncake.net/forum/uploaded/audioguru/2008425111635_window%20comparator%20circuit.PNG&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-07T16:41:46.103" LastActivityDate="2011-03-07T16:41:46.103" />
  <row Id="11135" PostTypeId="1" CreationDate="2011-03-07T19:31:56.417" Score="1" ViewCount="37" Body="&lt;p&gt;Hi,&#xA;i am using Arm project Manager (APM) for writing the firmware in my ARM board. My question is what are the live debugging  feature available in APM. Let say i need to inspect the value at some pin of the CPU?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any tutorial / video is helpful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks&lt;/p&gt;&#xA;" OwnerUserId="3283" LastActivityDate="2011-03-07T20:10:08.060" Title="How to Debug in APM" Tags="&lt;debugging&gt;&lt;arm7&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="11136" PostTypeId="2" ParentId="11135" CreationDate="2011-03-07T19:55:59.857" Score="2" ViewCount="" Body="&lt;p&gt;The APM doesn't include a debugger. You need to use the debugger supplied in the ARM Software Development Toolkit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use the &lt;a href=&quot;http://www.rowley.co.uk/&quot; rel=&quot;nofollow&quot;&gt;Rowley CrossWorks tools&lt;/a&gt; for ARM development. They come with an excellent debugger, which uses many of the more popular JTAG interfaces.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-07T20:10:08.060" LastActivityDate="2011-03-07T20:10:08.060" CommentCount="3" />
  <row Id="11137" PostTypeId="1" AcceptedAnswerId="11139" CreationDate="2011-03-07T21:01:10.753" Score="5" ViewCount="223" Body="&lt;p&gt;Or is the packaging just different?&lt;/p&gt;&#xA;" OwnerUserId="1823" LastActivityDate="2011-03-08T13:34:15.207" Title="Do surface mount components tend to use less power than through hole components?" Tags="&lt;power&gt;&lt;components&gt;" AnswerCount="5" />
  <row Id="11138" PostTypeId="2" ParentId="10748" CreationDate="2011-03-07T21:13:54.590" Score="3" ViewCount="" Body="&lt;p&gt;The technique I use is to drive the common wires through all eight combinations of high and low (I think I used the sequence 000 001 010 100 111 110 101 011, though I don't think it really matters) and, for each common wire phase, drive the segment wires in such a way as to make at least two of the three segments correct.  Which is to say, if C2..C0 are the common wires, and S2..S0 are the desired values of three segments which connect a particular segment wire to C2..C0, the output value should be high if (C2 xor S2)+(C1 xor S1)+(C0 xor S0) is at least 2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an example, suppose that one wants S0 to be dark and S1 and S2 to be light (so S2..S0 == 001).  The eight phases, drive state of the segment wires, and the resulting states of S2..S0, are as follows (for each segment, Y/N indicates whether it's energized; an asterisk will indicate whether it's the correct state):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;Com Drv S2 S1 S0&#xA;000  0  N* N* N&#xA;001  0  N* N* Y*&#xA;010  1  Y  N  Y*&#xA;100  1  N* Y  Y*&#xA;111  1  N* N* N&#xA;110  1  N* N* Y*&#xA;101  0  Y  N  Y*&#xA;011  0  N* Y  Y*&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Notice that each segment will be in the correct state 3/4 of the time.  The logic to generate the correct states is a little irksome, but to avoid bogging down my interrupt handler I compute the first four four output patterns when setting the display content, so my interrupt handler just has to output one of the four patterns, in regular or complemented form.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only annoyance I've observed with this method is that at slower scan rates, changing the display content will sometimes cause 'ghosting' on segments which should be transparent in both the old and new values.  This occurs because the segment may have gone from being incorrectly energized on the fourth 'beat' one frame, to being incorrectly energized on the first beat of the next frame'; the two consecutive energized 'beats' cause the segment to momentarily become visibly opaque.  Avoiding this problem requires using a scan rate twice as fast as would otherwise be necessary to avoid flicker; to minimize power consumption, my application switches to a faster scan rate during active use, or a lower rate when it's showing a static screen.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-07T21:13:54.590" />
  <row Id="11139" PostTypeId="2" ParentId="11137" CreationDate="2011-03-07T21:14:50.097" Score="7" ViewCount="" Body="&lt;p&gt;If it is the same base part number, same power, different packaging.  Heck, its frequently the same die.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-07T21:14:50.097" CommentCount="1" />
  <row Id="11140" PostTypeId="2" ParentId="11137" CreationDate="2011-03-07T21:45:56.003" Score="4" ViewCount="" Body="&lt;p&gt;No.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But through hole components can often handle more power than surface-mount components.  Because they are larger, they have lower junction-to-ambient thermal resistance.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-07T21:45:56.003" CommentCount="5" />
  <row Id="11141" PostTypeId="2" ParentId="11137" CreationDate="2011-03-08T00:32:37.217" Score="0" ViewCount="" Body="&lt;p&gt;Ever so slightly, yes - because the leads are shorter and there is less resistance in those tiny leads which leads to less wasted in these leads ;). (It may well be only a few milliohms and a few milliwatts dissipated (if that), but...)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-08T00:32:37.217" CommentCount="3" />
  <row Id="11142" PostTypeId="2" ParentId="9390" CreationDate="2011-03-08T02:58:29.087" Score="1" ViewCount="" Body="&lt;p&gt;From what I understand, the maximum CAN bus 1Mb data rate can be a challenge even with a short bus.  Have you tried lowering the data rate to 500Kb to see how it affects your error count?&lt;/p&gt;&#xA;" OwnerUserId="3285" LastActivityDate="2011-03-08T02:58:29.087" CommentCount="1" />
  <row Id="11143" PostTypeId="1" CreationDate="2011-03-08T03:57:50.430" Score="3" ViewCount="86" Body="&lt;p&gt;I'm very new to MRDS and I'm trying to simulate a robot driving a car. I have used the Motor Base with Drive in the &lt;code&gt;EntityUI&lt;/code&gt; manifest and would like to insert a GPS sensor to it to get its coordinates and maneuver accordingly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I inserted the GPS sensor in the Visual Simulation Environment and tried to add a Simulated GPS Sensor/Microsoft GPS360 Sensor in VPL. However, when I click on use a Manifest, it does not recognize that my current manifest includes details of the GPS Sensor (i.e. my manifest does not show up)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How do I create and use a GPS Identity in this case?&lt;/strong&gt; This is for a school project and I have to do it in VPL.&lt;/p&gt;&#xA;" OwnerUserId="2939" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-12T10:38:46.980" LastActivityDate="2011-03-12T10:38:46.980" ClosedDate="2011-05-09T23:56:51.527" Title="Inserting a Simulated GPS Entity in Motor Base - Microsoft Robotics Developer Studio" Tags="&lt;sensor&gt;&lt;robotics&gt;&lt;gps&gt;&lt;microsoft&gt;&lt;mrds&gt;" CommentCount="3" />
  <row Id="11145" PostTypeId="2" ParentId="10686" CreationDate="2011-03-08T04:03:10.160" Score="0" ViewCount="" Body="&lt;p&gt;If you're looking for something compatible with off-the-shelf SPI systems, and yet somehow uses fewer wires, you might like the &lt;a href=&quot;http://www.romanblack.com/shift1.htm&quot; rel=&quot;nofollow&quot;&gt;Roman Black Shift1 system for 1-wire shift registers&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-08T04:03:10.160" CommentCount="1" />
  <row Id="11148" PostTypeId="2" ParentId="11137" CreationDate="2011-03-08T09:03:37.130" Score="1" ViewCount="" Body="&lt;p&gt;What they said. Plus:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Power used' is very largely a matter of the circuit parameters rather than the components themselves. Something like a resistor will use exactly the same power for a given task regardless of it's packaging as the designer has complete control over power dissipation.&#xA;Differences that do occur are liable to be due to secondary effects. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) More modern ICs for switch mode power supplies, operating at higher frequencies with potentially improved efficiency may be available only in SM packages, so their &quot;lower power' may not be available in an older package. This is thus a factor of availability rather than inherent difference due to package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) A MOSFET may operate more efficiently at lower junction temperature due to eg increasing  Rdson with temperature. Identical die with different packaging will then produce different results based on thermal resistance from Junction to air. This is made up of Rth_junction_case + Rth_case_sink + Rth_sink_air. Depending on implementation and power level (not to mention phase of the moon) the result may go either way. At high power levels a larger through hole case may have a higher Rth_junction_case, but have better access to gross ambient heat sinking. At power levels below 1 Watt the ease of access to PCB thermal sinking for SM part may encourage a lower temperature design so higher efficiency so lower power overall.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As others have noted, 3rd order effects such as lead lengths, perhaps reduced capacitance and similar will have some effect, but usually minimal&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Summary: Overall neither SM or through hole have an explicit power difference BUT factors specific to each implementation may make a difference either way on a case by case basis.&lt;/p&gt;&#xA;" OwnerUserId="3288" LastActivityDate="2011-03-08T09:03:37.130" />
  <row Id="11149" PostTypeId="1" CreationDate="2011-03-08T09:25:42.753" Score="1" ViewCount="89" Body="&lt;p&gt;I am doing an 8th semester project but I need to use an IR transmitter and receiver to find the wheel direction of car. I would like 8051 assembly level code to find wheel direction. I am using two IR transmitters and receivers to find direction. I am mounting these two IR modules to get following combination of output.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;clockwise direction&#xA;LH-HH-HL-LH&#xA;&#xA;Anti clockwise  direction&#xA;LH-HL-HH-LH&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3289" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-03-08T16:28:06.417" LastActivityDate="2011-03-08T16:28:06.417" Title="wheel encoder to find direction of wheel" Tags="&lt;microcontroller&gt;&lt;encoder&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="11151" PostTypeId="2" ParentId="11149" CreationDate="2011-03-08T12:35:58.913" Score="0" ViewCount="" Body="&lt;p&gt;I noticed that clockwise has a high pulse 4 bits wide and a low pulse 2 bits wide as well as one 1 bit wide. But the anticlockwise pulse has a high pulse 2 bits wide and all the low pulses are 1 bit wide. So if you measured the duration of the pulses and tested the ratio of high to low time using carefully chosen pulses, you could make a decision. But you must use ratio and not absolute times because these will change with the speed of the wheel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(When it is a homework question, people will give you hints and tips but not a complete solution otherwise you do not learn the objective of the course).&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-03-08T12:35:58.913" />
  <row Id="11152" PostTypeId="1" CreationDate="2011-03-08T13:21:06.140" Score="2" ViewCount="111" Body="&lt;p&gt;What &quot;affordable&quot; voltage and current calibrations tools are available? I'm specifically looking for&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Voltage (and preferably current) metering&lt;/li&gt;&#xA;&lt;li&gt;0.05% Accuracy minimum (preferably 0.01%)&lt;/li&gt;&#xA;&lt;li&gt;14 bit+ reading (preferably 16)&lt;/li&gt;&#xA;&lt;li&gt;Preferably 24V tolerant, though if it has a precision resistance meter too, I could scale it down sith some resistors.&lt;/li&gt;&#xA;&lt;li&gt;1k samples pr second&lt;/li&gt;&#xA;&lt;li&gt;Exportable to a PC (preferably real time)&lt;/li&gt;&#xA;&lt;li&gt;Preferably with a DAC with similar performance.&lt;/li&gt;&#xA;&lt;li&gt;Retails for less than 1000$&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Edit:&#xA;Forgot to add what I consider affordable (1000$ max!).&#xA;And by precision I'm really thinking of the ADC max out of the box sample errors. I mean you could theoretically have a 22 bit ADC with 10% off samples. I want to use this to calibrate other ADC/DACs.&lt;/p&gt;&#xA;" OwnerUserId="941" LastEditorUserId="941" LastEditorDisplayName="" LastEditDate="2011-03-08T20:46:36.553" LastActivityDate="2011-05-12T13:19:10.540" Title="Precision calibration tools" Tags="&lt;analog&gt;&lt;current-measurement&gt;&lt;voltage-measurement&gt;&lt;calibration&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="11153" PostTypeId="2" ParentId="11137" CreationDate="2011-03-08T13:34:15.207" Score="0" ViewCount="" Body="&lt;p&gt;Generally no difference between the same part in different packages, the more important difference is that 'better' parts tend to only be available in SMD as that is where the market for efficient parts has gone. &#xA;For example high-efficiency DC-DC converters often operate in the MHz range, which isn't practical in TH due to lead inductance. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-03-08T13:34:15.207" />
  <row Id="11154" PostTypeId="1" AcceptedAnswerId="11157" CreationDate="2011-03-08T14:47:43.477" Score="3" ViewCount="92" Body="&lt;p&gt;I have a TRS232 RS-232 Driver(max232 equivalent). On the &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/trs232e.html&quot; rel=&quot;nofollow&quot;&gt;data sheet&lt;/a&gt;, it shows a capacitor on Vs+ and Vs- (1uF)and they just have arrows saying they go somewhere. Can I omit these connections and capacitors and if I do what are the side effects or issues that may arise from this omission? &lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2060" LastEditorDisplayName="" LastEditDate="2011-03-08T14:57:36.743" LastActivityDate="2011-03-08T15:43:06.207" Title="Does Vs+ and Vs- need to be connected on a TRS232E?" Tags="&lt;max232&gt;" AnswerCount="2" />
  <row Id="11155" PostTypeId="2" ParentId="11154" CreationDate="2011-03-08T14:59:08.590" Score="0" ViewCount="" Body="&lt;p&gt;Those capacitors are essential. If they are omitted the charge pumps won't work properly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The +8.5V and -8.5V outputs can be useful for powering devices that need two supplies, such as op amps. I've used them for that purpose, enabling the whole system to be powered from 5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also need the decoupling capacitor on the Vcc pin.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-08T15:29:50.160" LastActivityDate="2011-03-08T15:29:50.160" CommentCount="1" />
  <row Id="11156" PostTypeId="1" CreationDate="2011-03-08T15:29:38.177" Score="1" ViewCount="51" Body="&lt;p&gt;Does anyone know what a good source for switches, or plugs, or cabling?  In particular I am looking for mini-DPST switches, and DIN5 connectors (male / female).  While I can find some stuff online, the prices are just unreasonable. ($6-10 for a switch, $4-6 for DIN5 females, etc)  It seems like there must be a good source for all of these misc. parts that also give fair prices.  Anybody know of anything?&lt;/p&gt;&#xA;" OwnerUserId="3077" LastActivityDate="2011-03-08T16:02:39.560" ClosedDate="2011-03-08T16:49:15.977" Title="switches, plugs, etc." Tags="&lt;parts&gt;&lt;sourcing&gt;&lt;buying&gt;" AnswerCount="1" CommentCount="7" />
  <row Id="11157" PostTypeId="2" ParentId="11154" CreationDate="2011-03-08T15:43:06.207" Score="5" ViewCount="" Body="&lt;p&gt;This transceiver conveniently includes a &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Charge_pump&quot; rel=&quot;nofollow&quot;&gt;charge pump&lt;/a&gt; to create the proper voltages for RS232 signaling.  All four capacitors  listed (as well as the standard decoupling cap) must be connected for the device to operate.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you omit these capacitors, the charge pump won't work.  Your positive logic level referrence will oscillate at about 400kH between drawing power from 5V through a diode, and getting a boost to about 10V, depleting the charge in C1 or C2 (I don't know which).  The inverting supply will be even worse - I'd guess it will jump between 0V minus a diode drop and -5V until the capacitor is depleted, but I'm not really sure without knowing the topology of the charge pump they're using.   When your logic level reference is jumping around like this, the chip will not be able to determine what is a high voltage and what is a low voltage, and it certainly won't be able to transmit anything.  &lt;strong&gt;Worst case is that a signal on the RX pin will try to power the chip through the ESD protection diodes because the charge pump isn't working, and fuse the diodes into a conducting state, destroying the transceiver.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet says that 0.1uF capacitors may be used, but lists 1uF capacitors as the recommended value.  If you must attempt to transmit or receive immediately on applying power to the chip, you'll want to go with the 0.1uF caps, but if you can wait for a millisecond before doing this, 1uF caps will give you a more stable voltage.  Larger values than that won't help much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 'arrows saying they go somewhere' are just voltage markers.  You don't need to connect these to anything.  If you wanted to test the operation of the charge pump, you would probe these points.  You might also be able to sneak off with a little bit of current from these pins if you had to for some other purpose, like powering devices like opamps that require differential supplies, though you'd need to do some extensive testing to be sure that you didn't draw too much current.  A buffer powered from 5V would be a good thing to have.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-08T15:43:06.207" CommentCount="1" />
  <row Id="11158" PostTypeId="2" ParentId="11156" CreationDate="2011-03-08T16:02:39.560" Score="0" ViewCount="" Body="&lt;p&gt;Digikey.  They have everything.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-08T16:02:39.560" CommentCount="1" />
  <row Id="11159" PostTypeId="2" ParentId="11149" CreationDate="2011-03-08T16:23:39.463" Score="1" ViewCount="" Body="&lt;p&gt;This isn't the usual rotary encoder pattern, but it should still work. See &lt;a href=&quot;http://en.wikipedia.org/wiki/Rotary_encoder#Incremental_rotary_encoder&quot; rel=&quot;nofollow&quot;&gt;this wikipedia section&lt;/a&gt; for the normal gray-code implementation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, you will need to:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Store the current state of the encoders to a register&lt;/li&gt;&#xA;&lt;li&gt;Wait for some length of time. (This must be short enough that only one transition occurs)&lt;/li&gt;&#xA;&lt;li&gt;Compare the new encoder state with the old encoder state to see if they are different. &lt;/li&gt;&#xA;&lt;li&gt;Based on your previous state, and the new state, decode the direction. (This step/algorithm would be easier if you used a typical implementation.)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The disadvantage of your setup is that it takes two transmitters, probably has a more complicated pattern drawn, and there's no way to identify if the encoder has gone 2 steps instead of 1. Additionally, only one bit changes with the gray code count, so the comparison routine is easier and not a look-up table.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-03-08T16:23:39.463" />
  <row Id="11160" PostTypeId="1" CreationDate="2011-03-08T16:44:42.047" Score="3" ViewCount="94" Body="&lt;p&gt;I want to provide my client with a Product Lifecycle Management (PLM) and Product Data Management (PDM) style package of all the documentation related to the project (in house user manual for their technical writers to use as reference, board bring documentation, Test campaign docs, etc...), Hardware files (release verision of schematics, gerbers, etc..), datasheets and parts list (BOM), and finally release binaries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any good software geared towards small design studios (I have a 4 person group...with often only 2 people on a project). So far I have only found enterprise level PLM/PDM software that goes way over board for what I need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And yes, I know, I could just make a folder with all that stuff and just zip it. But there are lots of reasons why that is not the greatest solution. :P&lt;/p&gt;&#xA;" OwnerUserId="3295" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-08T18:11:05.203" LastActivityDate="2011-03-18T06:21:58.593" Title="Software to manage packaging all files related to a product (for hand off to customer)" Tags="&lt;microcontroller&gt;&lt;development&gt;&lt;project-management&gt;" AnswerCount="3" />
  <row Id="11161" PostTypeId="2" ParentId="11068" CreationDate="2011-03-08T16:54:45.707" Score="4" ViewCount="" Body="&lt;p&gt;My go-to place for stuff like this is Small Parts. &#xA;Would this work: &lt;a href=&quot;http://www.smallparts.com/stainless-steel-compression-spring-length/dp/B000FOFG2S/ref=sr_1_11?sr=1-11&amp;amp;qid=1299603198&quot; rel=&quot;nofollow&quot;&gt;http://www.smallparts.com/stainless-steel-compression-spring-length/dp/B000FOFG2S/ref=sr_1_11?sr=1-11&amp;amp;qid=1299603198&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's a box of 10 for $1.97&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-03-08T16:54:45.707" />
  <row Id="11162" PostTypeId="2" ParentId="11068" CreationDate="2011-03-08T18:10:56.157" Score="0" ViewCount="" Body="&lt;p&gt;This might help you...&#xA;&lt;a href=&quot;http://www.hobbytown.com/Shop/mufflers-silencers-tuned-pipes/header-pipe-spring&quot; rel=&quot;nofollow&quot;&gt;http://www.hobbytown.com/Shop/mufflers-silencers-tuned-pipes/header-pipe-spring&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In case you don't get one you can use some &lt;strong&gt;rubber bands&lt;/strong&gt; :D They may not a long life but very cheap...&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2011-03-08T18:10:56.157" />
  <row Id="11163" PostTypeId="2" ParentId="11123" CreationDate="2011-03-08T18:15:51.940" Score="5" ViewCount="" Body="&lt;p&gt;You probably want to use an ordinary timer interrupt and sample at perhaps 8 times the baud rate though four times might possibly work (in hardware implementations 16x is common, but I've personally done it at 8x). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most processors of modern clock speed should be able to fire an interrupt that fast, at least if your code in the ISR is efficient and you don't have much else interrupt-driven running.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will probably want to run a state machine, advancing one state on each interrupt.  Basically you look for the start bit transition and then read each data bit an appropriate number of oversampled cycles later.  There are lots of implementations of this for FPGAs in verilog or VHDL floating around the net, translating back to assembly or C should not be difficult.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, as you can likely reprogram your timers and interrupt modes quickly, there is another option for optimization:   You could start out by having an edge sensitive interrupt on the input pin.  When that fires, you then program a timer interrupt to generate delays of precisely a bit period (not oversampled), and simply read out the state on each interrupt.  When the word is concluded, re-arm the edge interrupt.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But there is a catch with this optimized method: because you are only &quot;paying attention&quot; at the important times, you have to work harder to make sure that the initial transition is a start bit, and that you aren't catching some data word in mid-flight when your code starts up.  Probably you want to do this by using your edge interrupt to make sure that the input has been in a quiescent state long enough (long enough since the last interrupt) - if it hasn't, discard what your get and wait for a clean character.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some googling on &quot;UART state machine&quot; or the like would be informative.  There's always the chance you will find reference code for your particular processor, particularly if it has no hardware UART or only one.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-03-08T18:15:51.940" CommentCount="1" />
  <row Id="11164" PostTypeId="2" ParentId="11160" CreationDate="2011-03-08T18:31:17.183" Score="2" ViewCount="" Body="&lt;p&gt;It sounds like you're more interested in the release packaging than PLM.  Just putting all the files together isn't a bad solution.  It works for a lot of projects!  With a few caveats and policies, it can be a fine solution.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd recommend that it start with a version control system, not a plain folder on disk. It should also have a well-defined, well-planned structure.  This can be changed, but I'd recommend starting every project with the same basic structure.  For four people, doing what sounds like standard embedded system design, I don't think this will get out of hand.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are other things that you'll want to control besides the release, however, and a bug tracking/feature request tool will be required somewhere in the system.  There are plenty of those available. I've used &lt;a href=&quot;http://www.redmine.org/&quot; rel=&quot;nofollow&quot;&gt;Redmine&lt;/a&gt;.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I work at a company with 5000 employees, and while we use the PLM/PDM bundled with various tools as much as we have to, our day-to-day development and product management is done through a combination of a few Subversion repositories and Redmine.   &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-08T18:31:17.183" CommentCount="4" />
  <row Id="11165" PostTypeId="2" ParentId="11116" CreationDate="2011-03-08T18:32:01.980" Score="1" ViewCount="" Body="&lt;p&gt;An M3 bolt is great, but you might also consider soldering the TO220 tab to a wide pad on the PCB. You'll get a little heatsinking (perhaps not necessary) and your project will have fewer parts to rattle loose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do use a mechanical fastener and you're worried about it coming loose over time, you can use a nut with a nylon insert or a drop of Loctite 222 threadlocker for small fasteners. With longer bolts that are made of the same material as the nuts (for example, if you want both to be stainless steel), Loctite is a better choice. When the nut and bolt are the same material, the thread surface tends to gall, and the nylon insert makes it worse.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-03-08T18:32:01.980" />
  <row Id="11166" PostTypeId="2" ParentId="11160" CreationDate="2011-03-08T18:48:52.863" Score="1" ViewCount="" Body="&lt;p&gt;Use a check-list.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;List all the files or documents that your client will need.  At the end of the project, go through the check-list and mark off each item as you move it to the final folder that will be zipped up for the client.&lt;/p&gt;&#xA;" OwnerUserId="204" LastEditorUserId="204" LastEditorDisplayName="" LastEditDate="2011-03-08T20:37:26.250" LastActivityDate="2011-03-08T20:37:26.250" CommentCount="1" />
  <row Id="11168" PostTypeId="1" AcceptedAnswerId="11170" CreationDate="2011-03-08T19:33:20.547" Score="2" ViewCount="246" Body="&lt;p&gt;I have one of these ancient Mentor game stations with the game tennis (Pong). Instead of using the controllers with a poti I'd like to use the Arduino PWM port to set a voltage between 0 and 5 Volt. However, this doesn't work, so there's no movement of the paddle. I tried several possibilities, but now wondering if the PWM and the poti are doing the same thing?&lt;/p&gt;&#xA;" OwnerUserId="1957" LastActivityDate="2011-03-08T20:25:46.687" Title="Arduino PWM vs. Potentiometer" Tags="&lt;arduino&gt;&lt;potentiometer&gt;&lt;pwm&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="11169" PostTypeId="2" ParentId="11168" CreationDate="2011-03-08T19:54:34.840" Score="5" ViewCount="" Body="&lt;p&gt;If the ends of the pot are not 0-5V, then there's no telling what will happen. Did you measure the voltage at both ends of the pot in a running system?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume you're filtering the PWM output with a RC filter?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PWM is a voltage source.  The potentiometer is a passive variable resistor.  It's hard to tell how the rest of the system is reading the pot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your 0-5V PWM would only work the ends are 0-5V, you remove the pot, you connect your RC filtered PWM output to the slider pin, and the measurement circuit doesn't try to draw more current than the PWM output can provide (as reemrevnivek points out).&lt;/p&gt;&#xA;" OwnerUserId="1270" LastEditorUserId="1270" LastEditorDisplayName="" LastEditDate="2011-03-08T20:25:46.687" LastActivityDate="2011-03-08T20:25:46.687" />
  <row Id="11170" PostTypeId="2" ParentId="11168" CreationDate="2011-03-08T19:58:41.337" Score="5" ViewCount="" Body="&lt;p&gt;No, they're not.  The pot sets a constant voltage somewhere between two other voltages, and the PWM drives 0V and 5V pulses in rapid succession, adjusting the time period for which the signal is 0V and 5V to get an average voltage somewhere between the two.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whether this difference is significant (and it appears to be, since the paddle isn't moving) will depend on two things: The sensing circuitry of the hardware which previously used the pot, and the filtering being applied to the PWM signal. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sensing circuitry needs to use the same voltage levels as the PWM.  0V should be equivalent for both circuits (tied together), and the maximum voltage must be less than 5V.  Your Arduino will generate voltages close to 0V and close to 5V, but not precisely those voltages - That should be OK.  The Pong game may draw more current than your Arduino is capable of providing, leading to lower voltages (even constant 0V output) - That would be a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Filtering is usually ignored for systems with a large amount of their own filtering.  Motors have weight, and our eyes provide a high-pass filter for dimming LEDs, but this may not be the case for the input to the PONG game.  Try putting a small resistor in line with the signal, and after the resistor, a small capacitor to ground. This will form a &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Low-pass_filter#Passive_electronic_realization&quot; rel=&quot;nofollow&quot;&gt;passive low-pass filter&lt;/a&gt;.  The values used will depend on the needs of the PONG game and the frequency of your PWM (Higher frequency is better!).  You can start out with a 470 ohm resistor and a 0.1uF cap.  Test the output with an oscilloscope - You should see a sine wave with a small variation about the target voltage, rather than a square wave alternating from 0 to 5V.  The more variation you can tolerate, the faster you can move the paddle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, you should also look at &lt;strong&gt;digital potentiometers&lt;/strong&gt; and DACs.  A digital pot functions electrically very much like a manual pot.  You can move the imaginary wiper in digital steps.  The &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/22060b.pdf&quot; rel=&quot;nofollow&quot;&gt;MCP4131&lt;/a&gt; is an example. A DAC, or Digital-to-Analog Converter, is the opposite of the ADCs available on the microcontroller.  It drives a voltage, rather than averaging two other voltages.  DACs are much more common than digital pots; some microcontrollers include them to complement the ADCs.  I'd suggest using a digital pot in this case, because you want to replace an existing pot and don't have a lot of control over the rest of the system.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-08T19:58:41.337" CommentCount="2" />
  <row Id="11171" PostTypeId="1" CreationDate="2011-03-08T20:12:12.433" Score="0" ViewCount="75" Body="&lt;p&gt;Hello all, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking to Mod a 42V DC brushless fan to work on an 110-AC outlet and incorporate a speed knob into the build. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the info that I have:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fan was originally pulled from a Cisco 7600 Series Router Fan module; it's about 6 inches in diameter and has 4 wires coming from it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tag on the FAN: |&#xA;DC BRUSHLESS |&#xA;MODEL EFC1748DG |&#xA;DC48V 1.84A -4M41R |&#xA;(OPERATE: DC42V) |&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connecting Board Info: |&#xA;Yellow Wire = P |&#xA;Blue Wire = R |&#xA;Black Wire = - |&#xA;Red Wire = + |&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is an Image of the fan:&#xA;&lt;img src=&quot;http://i.imgur.com/tVeoj.png&quot; alt=&quot;Brushless Motor Fan&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3243" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-03-08T22:16:40.137" LastActivityDate="2011-03-14T19:00:39.850" Title="Electronics - ISO 42v DC Brushless Fan to 110AC with Speed Knob MOD HELP" Tags="&lt;dc-motor&gt;&lt;speedcontroller&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11174" PostTypeId="2" ParentId="9390" CreationDate="2011-03-08T22:55:04.230" Score="0" ViewCount="" Body="&lt;p&gt;Well, maybe we need to change your circuits a little.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I've seen done (on RS232/422), and might work for CAN is this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Opto-isolate the CAN transceivers from the boards.&#xA;Power them from fully isolated DC-DC converters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then the transceiver circuits will float, and hopefully nearer each other. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also seen this done on an application note to (not really)&quot;opto-isolate&quot; a USB interface by putting it &quot;outboard&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll watch in interest as my robot servo cards all talk CAN and we get pretty big currents in the chassis, but haven't tried to use the CAN interface in anger ( we've been using them in RS232 with an old proprietary protocol)&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-03-08T22:55:04.230" />
  <row Id="11176" PostTypeId="1" AcceptedAnswerId="11180" CreationDate="2011-03-08T23:34:00.913" Score="0" ViewCount="108" Body="&lt;p&gt;I am trying to get a robotics club started in my school. But I am wondering if I started what could I get the kids to make. They would be aged between 14-18, some with electronics knowledge. So I need some cheap project ideas. I am looking for a project cost of about £3 per device, this only applies to specialised parts such as motors, relays/H-Bridges, sensors and materials for chassises. Other parts such as microcontrollers we have lying around. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-09T02:23:25.780" Title="Simple Robotics to do with teenagers" Tags="&lt;robotics&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11177" PostTypeId="2" ParentId="11171" CreationDate="2011-03-09T00:56:11.160" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Red is +48VDC&lt;/li&gt;&#xA;&lt;li&gt;Black is negative&lt;/li&gt;&#xA;&lt;li&gt;Blue is freq (rotation and lock signals)&lt;/li&gt;&#xA;&lt;li&gt;Yellow is PWM &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;All you need is a 5V PWM signal to control it and a 48v motor driver/power supply. Duty cycle should be 20KHz and to start it you should use a 30% PWM signal. If the yellow line disconnected it will rotate at full speed. everything else is in the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.chipcatalog.com/Delta_Product_Groups/EFC1748DG-TP07.htm&quot; rel=&quot;nofollow&quot;&gt;The Data Sheet&lt;/a&gt; has some good info on how to drive it correctly too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;on a side note you can use a 555 timer and a potentiometer(speed knob) to create the PWM.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2060" LastEditorDisplayName="" LastEditDate="2011-03-14T19:00:39.850" LastActivityDate="2011-03-14T19:00:39.850" />
  <row Id="11178" PostTypeId="2" ParentId="9507" CreationDate="2011-03-09T00:59:33.560" Score="1" ViewCount="" Body="&lt;p&gt;A good solution will be 'not too hard&quot; to provide once the true requirement is fully described :-).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At present your description covers a range of possible requirements. Can you provide more details and/or a circuit diagram with suitable notes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At present the following may describe what is wanted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current from a negative voltage potential of 0 to more than &amp;minus;200V is required to be clamped at a user selectable potential of from 0 to &amp;minus;200V.&#xA;max required current to be clamped = xxx mA&#xA;max power to be clamped is xxx mW&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;A solution to the above is a simple clamp regulator which can be set to a preset voltage.&#xA;Probably a P-channel MOSFET, opamp to drive it, &quot;high side&quot; (high = negative in this case) driver, voltage reference and voltage divider to allow reference and clamp voltage to be compared.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;If the clamp point is to be held constant for driving sources above and below the set point (eg at &amp;minus;150V when driving voltage goes from eg &amp;minus;50V to &amp;minus;200V) then the device may need to actively drive the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on power level the driver could be a driver with drain or collector load, a &quot;totem pole&quot; pair,  or an active switching regulator drive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assume that this is low power and that a single ended driver with resistor will suffice.&#xA;This is identical to the clamp regulator above EXCEPT that a resistor is taken from the P-channel MOSFET drain to a negative source of at least &amp;minus;200 V potential.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Example&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;A current of up to &amp;minus;10 mA is sourced from a potential of 0V to &amp;minus;300 V. (This &lt;em&gt;may&lt;/em&gt; be supplied via a resistor &quot;R1&quot; but this need not matter as long as the maximum current is limited).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current is to be clamped to a user preset voltage of 0 to &amp;minus;200 V.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Solution&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Provide an e.g. &amp;minus;300 V, 10 mA or more supply. This is more negative than &amp;minus;200 V to allow some &quot;headroom&quot; when running at &amp;minus;200V sink. 300 VDC is a convenient value for derivation from rectified 230 V AC mains or from voltage doubled 110 VAC mains.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At &amp;minus;200V and 10 mA, $R_{sink,max} = (300\mbox{ V}-200\mbox{ V})/10\mbox{ mA} = 10\mbox{ k}\Omega$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At $V_{clamp} = 0\mbox{ V}$, power in resistor is $V^2/R = (300\mbox{ V})^2/10\mbox{ k}\Omega = 9\mbox{ W}$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Provide a P-Channel MOSFET &gt; 300V rating. Best &gt;= 400V.&#xA;Source to ground.&#xA;Drain to Rink_10k&#xA;Rsink other end to &amp;minus;300V.&#xA;Monitor Rsin_MOSFET drain junction and use control circuit to drive MOSFET drain to required voltage.&#xA;Connect circuit to be clamped to MOSFET drain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Control circuit is an opamp, probably operating between ground and say &amp;minus;15V.&#xA;Vin is divided by say 50:1 making the 0 to &amp;minus;200 V swing a 0 to &amp;minus;4V.&#xA;Compare this value with a reference voltage.&#xA;Vref = Vclamp/50.&#xA;Use opamp to drive MOSFET gate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;QED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$I_{max}(R_{sink}) = 300 \mbox{ V}/10 \mbox{ k}\Omega = 30\mbox{ mA}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unloaded:&#xA;$$P_{MOSFET,max} = \frac{V_{max}}{2}I = \frac{V_{max}}{2} \times \frac{V_{max}/2}{R_{sink}} &#xA;= \frac{V_{max}{}^2}{4R_{sink}} = \frac{(V_{max}/2)^2}{R_{sink}} $$&#xA;$$ = \frac{(150 \mbox{ V})^2}{4 \times 10\mbox{ k}\Omega} = 9/16 \mbox{ W}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;E&amp;amp;OE.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Loaded is slightly more complex as clamped current gets in on act.&#xA;Easily enough calculated but lets see user true requirement first,\ &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this does not meet the requirement then a better description of the requirement would help.&lt;/p&gt;&#xA;" OwnerUserId="3288" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-09T02:45:18.943" LastActivityDate="2011-03-09T02:45:18.943" CommentCount="1" />
  <row Id="11179" PostTypeId="2" ParentId="10861" CreationDate="2011-03-09T01:15:09.967" Score="2" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;As noted - MOSFET is not very suitable.&#xA;As well as poor Rdson it has marginal gate turnon voltage (Vgth or Vgsth) for use at 3V. &#xA;It will work (and it does) but could be better.&#xA;With your oscilloscope observe the voltage when turned on. If you can measure it its too large :-).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;As noted also, the inductor should have a small enough resistance to drop minimal voltage with FET on and it must have a core designed not to saturate at your operating current. Yu have not said what inductor you are using. Please advise.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Inductor value is possibly a bit high.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Ignore probably: At say 3V available and assuming a current ramp to double I avg it will &#xA;take 220 uH/3V x 0.1A x 2 =~~~ 14 uS to reach required current. with continuous mode operation 220 uH is OK.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Diode drop is suspiciously low.&#xA;What diode are you using?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;At 0.25V as you state the diode loss at 5V is &gt; 0.25V/5V = 5%.&#xA;Done less than properly add MOSFET 5%, Inductor 5%, other 5% = 80% overall. Sound familiar :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ensuring FET and inductor are OK will help.&#xA;90% is hard without synchronous rectification,which has it's own issues. Well over 80% should be possible.&lt;/p&gt;&#xA;" OwnerUserId="3288" LastActivityDate="2011-03-09T01:15:09.967" />
  <row Id="11180" PostTypeId="2" ParentId="11176" CreationDate="2011-03-09T02:23:25.780" Score="2" ViewCount="" Body="&lt;p&gt;You can try &lt;strong&gt;BEAM robots&lt;/strong&gt;, you find tons of them when you google. They should be cheap and easy projects to build and understand. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;some of the link are :&#xA;&lt;a href=&quot;http://www.instructables.com/id/Solar-Powered-Miniball-Wannabe/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Solar-Powered-Miniball-Wannabe/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/How-to-make-a-mini-solar-robot/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/How-to-make-a-mini-solar-robot/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.robotroom.com/Appetizer.html&quot; rel=&quot;nofollow&quot;&gt;http://www.robotroom.com/Appetizer.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.tombot.net/beamrobots.html&quot; rel=&quot;nofollow&quot;&gt;http://www.tombot.net/beamrobots.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from that if you want to include microprocessor then you can do some &lt;strong&gt;light chaser&lt;/strong&gt; or &lt;strong&gt;line follower&lt;/strong&gt; or &lt;strong&gt;obstacle avoidance&lt;/strong&gt; which are fairly easy to understand and build provided you have prior knowledge about micro controllers.&lt;/p&gt;&#xA;" OwnerUserId="1839" LastActivityDate="2011-03-09T02:23:25.780" CommentCount="1" />
  <row Id="11183" PostTypeId="1" AcceptedAnswerId="11185" CreationDate="2011-03-09T03:37:45.593" Score="4" ViewCount="129" Body="&lt;p&gt;I'm coming from a computer science background, and will be writing some software to automate battery testing. I have background in math, but little to none in physics or electronics. Please consider this in your answers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, how would I go about testing the internal resistance of a small lithium polymer cell by hand?&lt;/p&gt;&#xA;" OwnerUserId="3300" LastEditorUserId="3300" LastEditorDisplayName="" LastEditDate="2011-03-09T03:49:13.237" LastActivityDate="2011-03-09T06:21:09.503" Title="How to test internal resistance on small lithium polymer cell?" Tags="&lt;battery&gt;&lt;resistance&gt;&lt;lithium-ion&gt;" AnswerCount="1" />
  <row Id="11185" PostTypeId="2" ParentId="11183" CreationDate="2011-03-09T04:05:54.570" Score="4" ViewCount="" Body="&lt;p&gt;Measure open-circuit voltage $V_{oc}$, then load the battery with resistor $R_{load}$ and measure voltage $V_{loaded}$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$ R_{in} = R_{load} \times \frac{V_{oc}-V_{loaded}}{V_{loaded}} $$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the internal resistance at DC and at your specified load.  Internal resistance varies with load and temperature and battery charge and age, etc.  And you'll need more advanced equipment to measure at higher frequencies.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-09T06:21:09.503" LastActivityDate="2011-03-09T06:21:09.503" />
  <row Id="11186" PostTypeId="1" AcceptedAnswerId="11189" CreationDate="2011-03-09T04:39:22.487" Score="6" ViewCount="205" Body="&lt;p&gt;My question is probably pretty easy to answer for you smart people. But basically I'm building a Segway clone using an Arduino, two Jaguar speed controllers, and two 24 volt batteries (wired in parallel). I want to power my Arduino from the 24 volt batteries and am just wondering if I need any additional circuits to step down the voltage/current, stabilize/condition the power, or anything else that may need to be done before the Arduino can use the power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm fairly new to basic electronic circuits and am more of a programmer. Can someone help me with my question?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="3301" LastActivityDate="2011-03-09T13:51:09.440" Title="Arduino powered by 24 volt battery" Tags="&lt;arduino&gt;&lt;battery&gt;&lt;voltage-regulator&gt;" AnswerCount="3" />
  <row Id="11187" PostTypeId="1" AcceptedAnswerId="11192" CreationDate="2011-03-09T04:40:40.023" Score="4" ViewCount="134" Body="&lt;p&gt;I have a small piezoelectric ultrasonic microphone (receiving signals of around 40 kHz). But the voltages it generates are too small to be read by my micro-controller's ADC. So I want to amplify the voltage created by the microphone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like a solution with a low part count, if possible. I've been trying to use an op-amp + some resistors, but I can't figure it out.&lt;br&gt;&#xA;So, how can I amplify the voltage from the microphone?&lt;/p&gt;&#xA;" OwnerUserId="790" LastEditorUserId="790" LastEditorDisplayName="" LastEditDate="2011-03-10T01:20:29.563" LastActivityDate="2011-03-10T01:20:29.563" Title="Amplifying sound from a microphone" Tags="&lt;piezoelectricity&gt;&lt;microphone&gt;&lt;amplification&gt;" AnswerCount="2" />
  <row Id="11188" PostTypeId="1" CreationDate="2011-03-09T04:47:22.720" Score="1" ViewCount="79" Body="&lt;p&gt;I'm looking for a good guide to design a Colpitts oscillator. Also if you know you can submit your explanation?&lt;br&gt;&#xA;I'm supposed to do one with a 1.63MHz frequency so I'm looking but I want your help too&lt;/p&gt;&#xA;" OwnerUserId="3302" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-03-09T10:10:06.847" LastActivityDate="2011-03-09T10:10:06.847" Title="Guide for bulding a Colpitts Oscillator?" Tags="&lt;oscillator&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="11189" PostTypeId="2" ParentId="11186" CreationDate="2011-03-09T05:02:34.640" Score="3" ViewCount="" Body="&lt;p&gt;You are going to want to use a &lt;a href=&quot;http://en.wikipedia.org/wiki/Linear_regulator&quot; rel=&quot;nofollow&quot;&gt;linear regulator&lt;/a&gt;. This will be very inefficient with respect to power efficiency, but your arduino should not use much power and this should make the power point moot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is an example search for the part you &lt;a href=&quot;http://www2.mouser.com/Semiconductors/Integrated-Circuits-ICs/Power-Management-ICs/Linear-Regulators-Standard/_/N-6j76qZscv7?P=1z0wdj3Z1z0shyuZ1z0wa29Z1yzvduaZ1yzvdtxZ1yzvdtnZ1yzvdtuZ1yzvducZ1yzvdtqZ1yzvdr6&quot; rel=&quot;nofollow&quot;&gt;would need&lt;/a&gt; on mouser. If you are going to pull very much current you are going to need a heatsink, this would probably amount to anything greater than 100mA in your case(just a ballpark so you have a way to estimate your threshhold).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It will require a couple of capacitors, but any good datasheet will tell you exactly what components you need.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="1802" LastEditorDisplayName="" LastEditDate="2011-03-09T13:19:57.787" LastActivityDate="2011-03-09T13:19:57.787" CommentCount="6" />
  <row Id="11190" PostTypeId="1" CreationDate="2011-03-09T05:41:12.017" Score="1" ViewCount="126" Body="&lt;p&gt;I typically shop at &lt;a href=&quot;http://allelectronics.com&quot; rel=&quot;nofollow&quot;&gt;All Electronics&lt;/a&gt; as there is a store (somewhat) nearby, but it is still about a 45 minute drive, and i have looked at a few online retailers (Digikey, Mouser, Jameco) but the shipping is quite expensive considering i typically buy only a few dollars worth of parts and to pay another 3 for shipping is ridiculous. The only other place I can think of nearby is radio shack, but all of their parts are over priced. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what is a cheap place to get electronics, either in the SF valley in LA, CA or online?&lt;/p&gt;&#xA;" OwnerUserId="3210" LastActivityDate="2011-03-09T11:26:43.890" ClosedDate="2011-03-21T00:36:36.290" Title="What is a good place to buy electronic parts?" Tags="&lt;electronics&gt;&lt;components&gt;&lt;distributors&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="11191" PostTypeId="2" ParentId="11186" CreationDate="2011-03-09T06:25:18.800" Score="2" ViewCount="" Body="&lt;p&gt;The hardware documentation for the arduino uno says it can take up to 20v input, so powering it directly off 24v is likely to damage it.  The older NG used a 7805 regulator which is good for up to 40v (but may overheat if drawing a lot of current from a 24v source, since linear regulators are not very efficient).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a newer model Arduino with the 20v limit, definitely use an external regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A convenient way to get an efficient 24v-&gt;5v regulator is to buy a phone charger intended for trucks (which have 24v batteries not 12v as in most cars).   You can get these on ebay and elsewhere for about $7.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-09T06:25:18.800" />
  <row Id="11192" PostTypeId="2" ParentId="11187" CreationDate="2011-03-09T06:36:11.280" Score="4" ViewCount="" Body="&lt;p&gt;Piezos have a high output impedance (capacitive, really), so you need an even higher input impedance on your mic pre or you'll get a &quot;tinny&quot; sound from the low end being rolled off.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A piezo with 1000 pF capacitance would have &lt;a href=&quot;http://www.wolframalpha.com/input/?i=1%2F%282%2api%2a1000+pF%2a50+Hz%29+to+ohm&quot; rel=&quot;nofollow&quot;&gt;a reactance of 3 M&amp;Omega; at 50 Hz&lt;/a&gt;, for instance, so if you wanted to pick up 50 Hz, you'd need an amp with several M&amp;Omega; input impedance.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/lit/an/sloa033a/sloa033a.pdf&quot; rel=&quot;nofollow&quot;&gt;Signal Conditioning Piezoelectric Sensors&lt;/a&gt; from TI shows a circuit with 10 M&amp;Omega; input impedance, for instance.   &lt;a href=&quot;http://www.eng.hmc.edu/NewE80/PDFs/PiezoElectronics.pdf&quot; rel=&quot;nofollow&quot;&gt;Interfacing Piezo Film to&#xA;Electronics&lt;/a&gt; suggests 22 M&amp;Omega; and shows the most basic circuit you could use: one of these big resistors in parallel with a unity-gain buffer op-amp.  If that level is too low, add two resistors and make it into a non-inverting voltage amplifier (figure 9 b):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/CCnMI.gif&quot; alt=&quot;a charge amplifier and non-inverting voltage amplifier for piezo applications&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The major advantage of a charge&#xA;  amplifier, therefore, can be found&#xA;  when a long cable is used between a&#xA;  piezo film sensor and electronics. In&#xA;  addition, it also minimizes charge&#xA;  leakage through the stray capacitance&#xA;  around the sensor. Otherwise, simple&#xA;  voltage amplifiers are sufficient for&#xA;  most applications.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://bmo.tnw.utwente.nl/electronics/Misc/PiezofilmCircuit/interface.stm&quot; rel=&quot;nofollow&quot;&gt;source&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-09T22:46:19.990" LastActivityDate="2011-03-09T22:46:19.990" />
  <row Id="11193" PostTypeId="2" ParentId="11187" CreationDate="2011-03-09T07:08:17.150" Score="0" ViewCount="" Body="&lt;p&gt;Try looking up the LM386 amplifier.  It's a low part count solution!&lt;br&gt;&#xA;Here's a circuit diagram of the &quot;minimum parts&quot; required to use this IC:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/tthvN.gif&quot; alt=&quot;Pic of min part schematic for LM386&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;br&gt;I am sure you could be able to figure out which pieces you can removed depending on your project (the 10k pot for example) Kenny, below, has a link to the digikey page.  I am sure I've seen these at Radioshack too (if you're in the US of A)&lt;/p&gt;&#xA;" OwnerUserId="3304" LastEditorUserId="3304" LastEditorDisplayName="" LastEditDate="2011-03-09T21:21:01.000" LastActivityDate="2011-03-09T21:21:01.000" CommentCount="5" />
  <row Id="11195" PostTypeId="1" AcceptedAnswerId="11200" CreationDate="2011-03-09T08:50:52.670" Score="1" ViewCount="155" Body="&lt;p&gt;I have a Arduino program wich make use of the processing library.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The program code starts with&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;import processing.serial.*;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;When I try to compile it with the Arduino compiler it crashes with&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;'import' does not name a file&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The code I want to execute is &lt;a href=&quot;http://www.instructables.com/id/Controlling-an-RGB-Led-with-Arduino-and-Processing/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Controlling-an-RGB-Led-with-Arduino-and-Processing/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I pasted the serial library folder from processing into the same folder as my code. But it still crashes.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt;&#xA;My assumptions were wrong! The code I tried to use was designed for Java and to be used with the &lt;a href=&quot;http://processing.org/&quot; rel=&quot;nofollow&quot;&gt;Processing IDE&lt;/a&gt; not the Arduino IDE. It works fine now with Processing! And the other part of the code works fine with the Arduino IDE :)&lt;/p&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="3130" LastEditorDisplayName="" LastEditDate="2011-03-09T12:25:07.850" LastActivityDate="2011-03-10T10:37:21.130" Title="How to import a library into a Arduino program?" Tags="&lt;arduino&gt;&lt;programming&gt;&lt;processing&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="11196" PostTypeId="2" ParentId="11190" CreationDate="2011-03-09T09:04:31.640" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.frys.com/ac/storelocator/index.jsp&quot; rel=&quot;nofollow&quot;&gt;Fry's Electronics&lt;/a&gt; has a number of stores in southern California and elsewhere.  They have a number of electronic components; the selection varies somewhat by store.  Pretty good for connectors and cables.  What they have is usually cheaper than RadioShack.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-03-09T09:04:31.640" />
  <row Id="11197" PostTypeId="2" ParentId="11188" CreationDate="2011-03-09T09:33:23.837" Score="1" ViewCount="" Body="&lt;p&gt;You can find a variety of designs on the &lt;a href=&quot;http://en.wikipedia.org/wiki/Colpitts_oscillator&quot; rel=&quot;nofollow&quot;&gt;Colpitt's Oscillator wikipedia page&lt;/a&gt;. This should get you started. Please edit your question if you require more specific advice.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-03-09T09:33:23.837" />
  <row Id="11198" PostTypeId="2" ParentId="11195" CreationDate="2011-03-09T10:19:43.183" Score="1" ViewCount="" Body="&lt;p&gt;Have you tried using a relative path to the library? like ~/proccessing/library/yourfile.* &#xA;another suggestion is add the library to the Arduino library folder and not your project folder. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-09T10:19:43.183" />
  <row Id="11199" PostTypeId="1" AcceptedAnswerId="11209" CreationDate="2011-03-09T10:40:40.227" Score="1" ViewCount="55" Body="&lt;p&gt;Ok so i've got a BTHQ128128 fstn display that i'm tryinf to drive via an ATMEGA128 AVR chip using gnu-c (avrlibc). Found some code on the interweb, but still not able to get the display to show anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The screen driver is a UC1698 (colour although the screen in black&amp;amp;white)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone ever attempted this and succeeded?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also is there an other type of driver that is similar to the uc1698 that a library could be ported from.&lt;/p&gt;&#xA;" OwnerUserId="3309" LastActivityDate="2011-03-09T14:38:30.683" Title="UC1698 based LCD driven by AVR" Tags="&lt;avr&gt;&lt;c&gt;&lt;glcd&gt;" AnswerCount="1" />
  <row Id="11200" PostTypeId="2" ParentId="11195" CreationDate="2011-03-09T10:40:52.667" Score="3" ViewCount="" Body="&lt;p&gt;Your code looks like you are using Java. Or are you using the Arduino IDE.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;import processing.serial.*;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;looks like Java code. If you are using the Arduino IDE it won't accept that command.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To import a library in C, the command is &lt;code&gt;#include&lt;/code&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2995" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-10T10:37:21.130" LastActivityDate="2011-03-10T10:37:21.130" CommentCount="3" />
  <row Id="11201" PostTypeId="2" ParentId="3834" CreationDate="2011-03-09T10:42:18.970" Score="0" ViewCount="" Body="&lt;p&gt;If you're main interest is to get it up and running quickly, there is a bunch of USB-based digital I/O kits which include programming libraries to read/write the states of the pins.  Unlike working with Arduino or other micro-boards, this means you only have to worry about programming the PC (versus having to write and debug the code running on the microcontroller board).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It used to be that wiring inputs and outputs through a PC's joystick or parallel port was the way to go.  But that was in the days of DOS and Windows up to about Windows 95.  Since then, directly accessing the registers to get to the hardware has gotten progressively harder to do. That said, it's still do-able - you just will have to jump through programming hoops to get to those pins from your program.  My ThinkPad's laptop dock, for example, has the legacy style parallel port, and it is still supported by the OS, should I decide to plug in a LaserJet II.  :)&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-03-09T10:42:18.970" />
  <row Id="11202" PostTypeId="2" ParentId="11195" CreationDate="2011-03-09T11:13:38.380" Score="2" ViewCount="" Body="&lt;p&gt;In Arduino language, libraries are included like&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;OneWire.h&amp;gt;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;etc&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And the code you are asking about is for &lt;strong&gt;Processing&lt;/strong&gt;&#xA;You should paste it there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want just to control RGB led, you can use my code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    /*&#xA;  Serial RGB controller&#xA;&#xA; Reads a serial input string looking for three comma-separated&#xA; integers with a newline at the end. Values should be between &#xA; 0 and 255. The sketch uses those values to set the color &#xA; of an RGB LED attached to pins 9 - 11.&#xA;&#xA; The circuit:&#xA; * Common-anode RGB LED cathodes attached to pins 9 - 11&#xA; * LED anode connected to pin 13&#xA;&#xA; To turn on any given channel, set the pin LOW.  &#xA; To turn off, set the pin HIGH. The higher the analogWrite level,&#xA; the lower the brightness.&#xA;&#xA; created 29 Nov 2010&#xA; by Tom Igoe&#xA;&#xA; MODIFIED by Semyon Tushev,&#xA; February 2011&#xA;&#xA; This example code is in the public domain. &#xA; */&#xA;&#xA;String inString = &quot;&quot;;    // string to hold input&#xA;int currentColor = 0;&#xA;int red, green, blue = 0;&#xA;&#xA;void setup() {&#xA;  // Initialize serial communications:&#xA;  Serial.begin(115200);&#xA;  // set LED cathode pins as outputs:&#xA;  pinMode(9, OUTPUT);&#xA;  pinMode(10, OUTPUT);&#xA;  pinMode(11, OUTPUT);&#xA;  // turn on pin 13 to power the LEDs:&#xA;  pinMode(13, OUTPUT);&#xA;  digitalWrite(13, HIGH);&#xA;}&#xA;&#xA;void loop() {&#xA;  int inChar;&#xA;&#xA;  // Read serial input:&#xA;  if (Serial.available() &amp;gt; 0) {&#xA;    inChar = Serial.read();&#xA;  }&#xA;&#xA;  if (isDigit(inChar)) {&#xA;    // convert the incoming byte to a char &#xA;    // and add it to the string:&#xA;    inString += (char)inChar; &#xA;  }&#xA;&#xA;  // if you get a comma, convert to a number,&#xA;  // set the appropriate color, and increment&#xA;  // the color counter:&#xA;  if (inChar == ',') {&#xA;    // do something different for each value of currentColor:&#xA;    switch (currentColor) {&#xA;    case 0:    // 0 = red&#xA;      red = inString.toInt();&#xA;      // clear the string for new input:&#xA;      inString = &quot;&quot;; &#xA;      break;&#xA;    case 1:    // 1 = green:&#xA;      green = inString.toInt();&#xA;      // clear the string for new input:&#xA;      inString = &quot;&quot;; &#xA;      break;&#xA;    }&#xA;    currentColor++;&#xA;  }&#xA;  // if you get a newline, you know you've got&#xA;  // the last color, i.e. blue:&#xA;  if (inChar == '\n') {&#xA;    blue = inString.toInt();&#xA;&#xA;    // set the levels of the LED.&#xA;    // subtract value from 255 because a higher&#xA;    // analogWrite level means a dimmer LED, since&#xA;    // you're raising the level on the anode:&#xA;    analogWrite(11,  blue);&#xA;    analogWrite(9,  red);&#xA;    analogWrite(10, green);&#xA;&#xA;&#xA;&#xA;    // clear the string for new input:&#xA;    inString = &quot;&quot;; &#xA;    // reset the color counter:&#xA;    currentColor = 0;&#xA;&#xA;  }&#xA;&#xA;}&#xA;&#xA;&#xA;/*&#xA;Here's a Processing sketch that will draw a color wheel and send a serial&#xA;string with the color you click on:&#xA;&#xA;// Subtractive Color Wheel with Serial&#xA;// Based on a Processing example by Ira Greenberg. &#xA;// Serial output added by Tom Igoe&#xA;// &#xA;// The primaries are red, yellow, and blue. The secondaries are green, &#xA;// purple, and orange. The tertiaries are  yellow-orange, red-orange, &#xA;// red-purple, blue-purple, blue-green, and yellow-green.&#xA;// &#xA;// Create a shade or tint of the subtractive color wheel using&#xA;// SHADE or TINT parameters.&#xA;&#xA;// Updated 29 November 2010.&#xA;&#xA;&#xA;&#xA;import processing.serial.*;&#xA;&#xA;int segs = 12;&#xA;int steps = 6;&#xA;float rotAdjust = TWO_PI / segs / 2;&#xA;float radius;&#xA;float segWidth;&#xA;float interval = TWO_PI / segs;&#xA;&#xA;Serial myPort;&#xA;&#xA;void setup() {&#xA;  size(200, 200);&#xA;  background(127);&#xA;  smooth();&#xA;  ellipseMode(RADIUS);&#xA;  noStroke();&#xA;  // make the diameter 90% of the sketch area&#xA;  radius = min(width, height) * 0.45;&#xA;  segWidth = radius / steps;&#xA;&#xA;  // swap which line is commented out to draw the other version&#xA;  // drawTintWheel();&#xA;  drawShadeWheel();&#xA;  // open the first serial port in your computer's list&#xA;  myPort = new Serial(this, Serial.list()[0], 9600);&#xA;}&#xA;&#xA;&#xA;void drawShadeWheel() {&#xA;  for (int j = 0; j &amp;lt; steps; j++) {&#xA;    color[] cols = { &#xA;      color(255-(255/steps)*j, 255-(255/steps)*j, 0), &#xA;      color(255-(255/steps)*j, (255/1.5)-((255/1.5)/steps)*j, 0), &#xA;      color(255-(255/steps)*j, (255/2)-((255/2)/steps)*j, 0), &#xA;      color(255-(255/steps)*j, (255/2.5)-((255/2.5)/steps)*j, 0), &#xA;      color(255-(255/steps)*j, 0, 0), &#xA;      color(255-(255/steps)*j, 0, (255/2)-((255/2)/steps)*j), &#xA;      color(255-(255/steps)*j, 0, 255-(255/steps)*j), &#xA;      color((255/2)-((255/2)/steps)*j, 0, 255-(255/steps)*j), &#xA;      color(0, 0, 255-(255/steps)*j),&#xA;      color(0, 255-(255/steps)*j, (255/2.5)-((255/2.5)/steps)*j), &#xA;      color(0, 255-(255/steps)*j, 0), &#xA;      color((255/2)-((255/2)/steps)*j, 255-(255/steps)*j, 0)&#xA;    };&#xA;    for (int i = 0; i &amp;lt; segs; i++) {&#xA;      fill(cols[i]);&#xA;      arc(width/2, height/2, radius, radius, &#xA;      interval*i+rotAdjust, interval*(i+1)+rotAdjust);&#xA;    }&#xA;    radius -= segWidth;&#xA;  }&#xA;}&#xA;&#xA;&#xA;void drawTintWheel() {&#xA;  for (int j = 0; j &amp;lt; steps; j++) {&#xA;    color[] cols = { &#xA;      color((255/steps)*j, (255/steps)*j, 0), &#xA;      color((255/steps)*j, ((255/1.5)/steps)*j, 0), &#xA;      color((255/steps)*j, ((255/2)/steps)*j, 0), &#xA;      color((255/steps)*j, ((255/2.5)/steps)*j, 0), &#xA;      color((255/steps)*j, 0, 0), &#xA;      color((255/steps)*j, 0, ((255/2)/steps)*j), &#xA;      color((255/steps)*j, 0, (255/steps)*j), &#xA;      color(((255/2)/steps)*j, 0, (255/steps)*j), &#xA;      color(0, 0, (255/steps)*j),&#xA;      color(0, (255/steps)*j, ((255/2.5)/steps)*j), &#xA;      color(0, (255/steps)*j, 0), &#xA;      color(((255/2)/steps)*j, (255/steps)*j, 0)&#xA;    };&#xA;    for (int i = 0; i &amp;lt; segs; i++) {&#xA;      fill(cols[i]);&#xA;      arc(width/2, height/2, radius, radius, &#xA;      interval*i+rotAdjust, interval*(i+1)+rotAdjust);&#xA;    }&#xA;    radius -= segWidth;&#xA;  }&#xA;}&#xA;&#xA;void draw() {&#xA;  // nothing happens here&#xA;}&#xA;&#xA;void mouseReleased() {&#xA;  // get the color of the mouse position's pixel:&#xA;  color targetColor = get(mouseX, mouseY);&#xA;  // get the component values:&#xA;  int r = int(red(targetColor));&#xA;  int g = int(green(targetColor));&#xA;  int b = int(blue(targetColor));&#xA;  // make a comma-separated string:&#xA;  String colorString = r + &quot;,&quot; + g + &quot;,&quot; + b + &quot;\n&quot;;&#xA;  // send it out the serial port:&#xA;  myPort.write(colorString );&#xA;}&#xA;&#xA;&#xA;*/&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;It receives string like 100,255,80 via serial and sets the outputs. Don't forget to send newline characters as well&lt;/p&gt;&#xA;" OwnerUserId="3253" LastActivityDate="2011-03-09T11:13:38.380" />
  <row Id="11203" PostTypeId="1" CreationDate="2011-03-09T11:26:34.360" Score="-3" ViewCount="77" Body="&lt;p&gt;robotics&#xA;which specialized univercity in undergrad uation level?&#xA;which subjects like physics,chemistry,maths,mecanical drawing needed for high school level?&#xA;univercities offering robotics with placements and it's fee?&lt;/p&gt;&#xA;" OwnerUserId="3310" LastActivityDate="2011-03-09T12:36:41.193" ClosedDate="2011-03-09T17:58:15.433" Title="robotics and electronics but need to specialize in robotics" Tags="&lt;robotics&gt;" AnswerCount="1" />
  <row Id="11204" PostTypeId="2" ParentId="11190" CreationDate="2011-03-09T11:26:43.890" Score="0" ViewCount="" Body="&lt;p&gt;Take a look at the MightyOhm wiki page on &lt;a href=&quot;http://mightyohm.com/wiki/resources:surplus&quot; rel=&quot;nofollow&quot;&gt;surplus electronics stores&lt;/a&gt;, specifically the section for &lt;a href=&quot;http://mightyohm.com/wiki/resources:surplus#san_francisco_bay_area&quot; rel=&quot;nofollow&quot;&gt;the SF bay area&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-03-09T11:26:43.890" />
  <row Id="11205" PostTypeId="2" ParentId="11203" CreationDate="2011-03-09T12:30:41.807" Score="4" ViewCount="" Body="&lt;p&gt;i really dont understand what you are trying to say, but im assuming you want to get information about robots and electronics stuff which is easy to use and could be done by highschool students. theres a good discussion about this going on, right here: &lt;a href=&quot;http://electronics.stackexchange.com/questions/2028/newbie-friendly-electronics-and-robotics&quot;&gt;Newbie-friendly electronics (and robotics)&lt;/a&gt; and here &#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/11176/simple-robotics-to-do-with-teenagers&quot;&gt;Simple Robotics to do with teenagers&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2995" LastEditorUserId="2995" LastEditorDisplayName="" LastEditDate="2011-03-09T12:36:41.193" LastActivityDate="2011-03-09T12:36:41.193" CommentCount="1" />
  <row Id="11206" PostTypeId="1" AcceptedAnswerId="11222" CreationDate="2011-03-09T13:00:18.787" Score="1" ViewCount="147" Body="&lt;p&gt;I am doing personal project - portable MP3 player.&#xA;Goals are sound quality + power efficiency. Price is not limited to a reasonable amount (100-200$ in parts is ok)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will single-chip DAC+D-class amplifiers give me best possible power efficiency while having excellent audio quality? I've seen 24-bit ones but a little overpowered (like 1.5W per channel). This looks very juicy - No need to design analog part, all sensetive parts are inside the chip. Are there any pitfalls with this approach or with D-class amplifiers with headphones in general?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I afraid that classic op-amp based or AB-class amplifiers will eat too much power + I will need careful design of analog part after DAC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example: &lt;a href=&quot;http://www.cirrus.com/en/products/cs43l22.html&quot; rel=&quot;nofollow&quot;&gt;http://www.cirrus.com/en/products/cs43l22.html&lt;/a&gt;&#xA;Separate output for headphones scares me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Design targets:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;32-50 Ohm headphones support @100mW&lt;/li&gt;&#xA;&lt;li&gt;LiIon power supply, the more play&#xA;hours I get the better :-) &lt;/li&gt;&#xA;&lt;li&gt;Maximum&#xA;quality (as long as I can hear the&#xA;difference) &lt;/li&gt;&#xA;&lt;li&gt;I have 24-bit decoder&#xA;output, so going down to 16 is&#xA;possible to not that fun (extra&#xA;analog filtering and noise shaping).&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-03-09T18:43:34.057" LastActivityDate="2011-03-09T20:04:44.010" Title="24-bit DAC + D-class amplifier in singlechip - good solution for pocket MP3 player?" Tags="&lt;dac&gt;&lt;mp3&gt;&lt;d-class&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="11207" PostTypeId="2" ParentId="1612" CreationDate="2011-03-09T13:25:28.697" Score="0" ViewCount="" Body="&lt;p&gt;Steppers get marked like other motors, but they aren't operated like other motors.  Your motors, depending on size, might have two or three heavy coils in parallel.  This drives the resistance down to 1 or 2 ohms.  At 100% duty, this gives them a nameplate rating of 3 or 4 volts.  But, in actual operation, you don't use 100% duty.  When you are running, the coils are at 50% duty or lower.  When at rest, you usually switch them off or go to a 10% holding current.  So to run them at high speed and/or high acceleration, the packaged drives use a high voltage (somewhere between 24 and 90 volts) and a current limiting resistor.  This overcomes the internal inductance to give a snappy response.  It's not plan B, it's just the way they work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, the critical part of the nameplate is the temperature rating.  It's usually around 120F.  If you can keep your hand on it for a half second or more, then you're fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But acceleration and deceleration is important, too.  You usually can't just jump in a full speed.  So you best bet might be to find a mill control box that has the drives and a control computer that does the profiling that you want. &lt;/p&gt;&#xA;" OwnerUserId="1824" LastActivityDate="2011-03-09T13:25:28.697" CommentCount="3" />
  <row Id="11208" PostTypeId="2" ParentId="11186" CreationDate="2011-03-09T13:51:09.440" Score="0" ViewCount="" Body="&lt;p&gt;I suggest you use a voltage regulator out of the lm series, like this one i.e.&lt;br&gt;&#xA;&lt;a href=&quot;http://www.mercateo.com/p/139N-1640686/VOLTAGE_REGULATOR_Typ_LM317MDCYRG3_.html#texas-instruments-voltage-regulator-typ-lm317mdcyrg3-texas-instruments-lm317mdcyrg3&quot; rel=&quot;nofollow&quot;&gt;http://www.mercateo.com/p/139N-1640686/VOLTAGE_REGULATOR_Typ_LM317MDCYRG3_.html#texas-instruments-voltage-regulator-typ-lm317mdcyrg3-texas-instruments-lm317mdcyrg3&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2995" LastActivityDate="2011-03-09T13:51:09.440" />
  <row Id="11209" PostTypeId="2" ParentId="11199" CreationDate="2011-03-09T14:38:30.683" Score="1" ViewCount="" Body="&lt;p&gt;I wouldn't trust just any display library you find on the internet to drive the display. You might be better off writing your own display library for this display controller. If you do decide to use someone else’s library you will still need to familiarize yourself with the display controller datasheet and the code you are using to make sure it is doing what it's supposed to.&#xA;&lt;p&gt;&#xA;Do you know what communication mode you are using between the AVR and the display? Your display controller supports seven different communication modes using a combination of the BM pins, DB15, and DB13.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-03-09T14:38:30.683" />
  <row Id="11210" PostTypeId="2" ParentId="11123" CreationDate="2011-03-09T15:20:42.303" Score="1" ViewCount="" Body="&lt;p&gt;Another possibly applicable method is to use an external circuit to select one of the two input sources and feed the signal to the UART.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For this to be appropriate you need to know when you're expecting data so that you can switch to the appropriate device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to add an external UART and receive data from that. It's kinda hard to be more specific without knowing more of the platform available.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-03-09T19:16:55.923" LastActivityDate="2011-03-09T19:16:55.923" />
  <row Id="11211" PostTypeId="1" AcceptedAnswerId="11238" CreationDate="2011-03-09T15:41:28.733" Score="0" ViewCount="213" Body="&lt;p&gt;Hey people,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am struggling with making a usb programmer for Atmega. I couldn't get my hands on a proper FT232L or something like that, but I did manage to find a serial to usb converter like &lt;a href=&quot;http://shopping.indiatimes.com/Computer-Peripherals/Computer-Add-Ons/Others/BAFO-USB-to-Serial-Converter/ctl/20376650/pc/960047/cat/963600/pid/1454896&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;. This gets detected like a normal com port and is able to make work modems and printers. Will that do serial programming? There are serial programmers around which I have seen, work with ponyser as the programmer in the makefile. How do I make one?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;&#xA;Through lsusb I have found out that the converter has a pl2303 inside (compatible with ft232r) so how do I do the programming now?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="1200" LastEditorDisplayName="" LastEditDate="2011-03-09T16:25:22.160" LastActivityDate="2011-03-10T01:16:49.650" Title="AVR programmer with serial to USB converter." Tags="&lt;avr&gt;&lt;programmer&gt;&lt;ponyser&gt;" AnswerCount="3" />
  <row Id="11212" PostTypeId="2" ParentId="11211" CreationDate="2011-03-09T15:56:27.950" Score="1" ViewCount="" Body="&lt;p&gt;AVR &quot;serial&quot; programming is in fact done over SPI. It's possible to bit-bang SPI using an FT232, which is why they're often used for this purpose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is an old trick to bit-bang SPI over the flow control lines of a real serial port. You might be able to achieve something similar with your USB converter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ele.uva.es/~jesus/avrprg/powerless.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ele.uva.es/~jesus/avrprg/powerless.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-09T15:56:27.950" CommentCount="3" />
  <row Id="11213" PostTypeId="1" AcceptedAnswerId="11265" CreationDate="2011-03-09T16:09:33.347" Score="2" ViewCount="158" Body="&lt;p&gt;I designed a simple triangle wave oscillator based around a switchable curent soure. It works for a few cycles, then it becomes unstable and finally stops working altogether. Why is this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/FmPYN.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If anyone wants to simulate this - &lt;a href=&quot;http://falstad.com/circuit/#%24+1+5.0E-6+0.3638846248353525+50+5.0+50%0Aa+608+192+720+192+1+15.0+-15.0+1000000.0%0Ar+720+192+720+256+0+100.0%0Aw+720+256+608+256+0%0Aw+608+256+608+208+0%0Ag+720+432+720+448+0%0A172+80+144+48+144+0+6+0.5+0.5+0.0+0.0+0.5+Voltage%0Ar+80+144+144+144+0+10000.0%0Ar+144+112+256+112+0+10000.0%0Aw+256+112+256+160+0%0Aw+144+144+144+112+0%0Aa+144+160+256+160+0+15.0+-15.0+1000000.0%0Ag+144+176+144+192+0%0A160+320+176+256+176+0+20.0+1.0E10%0Aw+256+192+256+224+0%0Aw+256+224+80+224+0%0Aw+80+224+80+144+0%0Ac+720+352+720+432+2+9.999999999999999E-6+-0.49998494835203755%0Aw+592+320+608+320+0%0Aw+592+384+608+384+0%0Aw+608+384+608+352+0%0Aw+608+352+608+320+0%0Aw+720+352+720+256+0%0Aw+720+352+608+352+0%0AR+592+288+624+288+0+0+40.0+0.2+0.0+0.0+0.5%0AR+592+416+624+416+0+0+40.0+-0.2+0.0+0.0+0.5%0Aw+608+176+496+176+0%0Aa+592+400+496+400+0+15.0+-15.0+1000000.0%0Aa+592+304+496+304+0+15.0+-15.0+1000000.0%0A152+496+352+400+352+0+2+5.0%0A155+304+320+336+320+1024+5.0%0Aw+400+320+400+288+0%0Aw+288+288+288+384+0%0Aw+288+384+304+384+0%0Aw+496+176+336+176+0%0Aw+496+336+496+304+0%0Aw+496+400+496+368+0%0Aw+288+288+304+288+0%0Aw+304+288+400+288+0%0Aw+720+352+784+352+0%0Ar+784+352+784+432+0+10000.0%0Ag+784+432+784+448+0%0Aw+320+176+336+176+0%0Aw+288+224+288+192+0%0Aw+288+288+288+224+0%0Ao+22+1+0+35+0.5846006549323611+9.765625E-55+0+-1%0A&quot; rel=&quot;nofollow&quot;&gt;here is the link&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One other thing - occasionally, the osillator will manage 20 cycles, other times it won't complete a single one. Why is the simulation apparently not deterministic?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-12T05:51:08.263" Title="Why is this oscillator unstable?" Tags="&lt;oscillator&gt;&lt;simulator&gt;&lt;stability&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="11214" PostTypeId="2" ParentId="11213" CreationDate="2011-03-09T16:25:31.940" Score="2" ViewCount="" Body="&lt;p&gt;Not giving a full answer, but I remember oscillator simulations as being notoriously difficult to do.  If you don't set the step time correctly you won't see anything at all.  I'm not sure I'd assume the simulation is correct. &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-03-09T16:25:31.940" CommentCount="1" />
  <row Id="11215" PostTypeId="2" ParentId="1714" CreationDate="2011-03-09T16:53:58.960" Score="3" ViewCount="" Body="&lt;p&gt;If you're trying to drive a stepper motor at high speed, you should really use a constant-current driver circuit, since the voltage required to operate at high speeds will be much greater than that required at low speeds, and since driving enough voltage for high-speed operation into a stalled motor would quickly destroy it if the current weren't limited.  If a current-limited supply is used, the motor should continue to supply the expected torque until it's running fast enough that the compliance voltage of the supply is reached.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-09T16:53:58.960" />
  <row Id="11216" PostTypeId="2" ParentId="11213" CreationDate="2011-03-09T17:29:04.540" Score="2" ViewCount="" Body="&lt;p&gt;If you set the voltage slider lower, it seems to simulate fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/BV0Fp.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-09T17:29:04.540" CommentCount="3" />
  <row Id="11217" PostTypeId="2" ParentId="11206" CreationDate="2011-03-09T17:30:11.683" Score="1" ViewCount="" Body="&lt;p&gt;I suggest you use one of the published high quality op-amp headphone driver circuits. The analog design of a class D amplifier is not straightforward.  Class-D amps have approximately 0 dB of PSRR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you figured out your power budget?  I think you will find that the power savings of Class D is minimal over an AB opamp output stage.  You might save more power by using a more appropriate DAC (one with no more bits than your source material.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, a DC/DC converter will waste some power.  With appropriate component choices, I think you should be able to power your circuit directly off a LiIon cell.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-09T17:30:11.683" CommentCount="4" />
  <row Id="11218" PostTypeId="1" AcceptedAnswerId="11221" CreationDate="2011-03-09T17:55:33.890" Score="2" ViewCount="85" Body="&lt;p&gt;Hello all. I had some problems setting up a Opto Coupler today. The data sheet is &lt;a href=&quot;http://www.fairchildsemi.com/ds/H1/H11L1-M.pdf&quot; rel=&quot;nofollow&quot;&gt;HERE&lt;/a&gt;. I set it up putting a 470 ohm resistor to ground from the cathode (pin 2). I am understand the selection of this resistor as it is used to set the current through the LED to about 10mA when he ANODE(pin 1) is given 5 Volts. What I don't understand is why a 270 Ohm resistor(as shown in the test circuit) is needed between pin 4 and 6. From testing I know that with the 270 resistor I get a range of about .2 to 5 volts on the output, and without the outputs range is 0.08 to 1.4 volts. I know its something to do with the baising the circuit and the gains from the internal transistor... Wondering if someone could point me towards a source that actually explains how to bias a opto coupler... its been a few years since I played with transistors.    &lt;/p&gt;&#xA;" OwnerUserId="1337" LastActivityDate="2011-03-09T18:18:27.830" Title="How to properly Bias a Opto Coupler" Tags="&lt;opto-isolator&gt;" AnswerCount="1" />
  <row Id="11219" PostTypeId="1" CreationDate="2011-03-09T18:11:12.307" Score="2" ViewCount="236" Body="&lt;p&gt;So I have a really cheap soldering iron and a dimmer switch meant to be wall-mounted. The soldering iron has a standard, ungrounded cord. The dimmer switch has four wires: a green (for ground), a black and a red, and another red that's &quot;only for use in 3-way switches&quot;. How can I wire this into the soldering iron to allow for variable soldering iron intensities?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried cutting the soldering iron cord, binding neutral back to neutral and binding the positive to the dimmer's red, through the dimmer, and back through the dimemr's black to the other side of the positive. This did not work. I also tried it with the red to red, and the black to the other red, and neither worked.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to insert a wall-mounted dimmer into a standard appliance cord such as a soldering iron?&lt;/p&gt;&#xA;" OwnerUserId="3315" LastActivityDate="2011-03-20T19:40:26.640" Title="Can I wire a dimmer switch into a soldering iron?" Tags="&lt;wiring&gt;" AnswerCount="2" CommentCount="10" />
  <row Id="11220" PostTypeId="1" AcceptedAnswerId="11226" CreationDate="2011-03-09T18:16:42.527" Score="4" ViewCount="119" Body="&lt;p&gt;What's an efficient algorithm for recovering the clock and decoding &lt;a href=&quot;http://en.wikipedia.org/wiki/Manchester_code&quot; rel=&quot;nofollow&quot;&gt;Manchester-encoded&lt;/a&gt; data?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2011-03-09T21:30:18.357" LastActivityDate="2011-03-09T22:58:42.290" Title="Efficient decoding of a Manchester-encoded serial link?" Tags="&lt;serial&gt;&lt;manchester&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="1" />
  <row Id="11221" PostTypeId="2" ParentId="11218" CreationDate="2011-03-09T18:18:27.830" Score="3" ViewCount="" Body="&lt;p&gt;Page 1 of the datasheet clearly says 'open collector output'. Without a pull-up, the voltage is undefined.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The purpose of 270 $\Omega$ on the test circuit is simply to provide a defined amount of current for the output logic to sink during the test. Whatever pull-up value you use is up to you, just don't exceed the sinking capability of the output stage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When it comes to biasing an opto, the best practice is to choose a resistor that will allow the minimum amount of current needed to do the job over the expected current transfer ratio (CTR) distribution of the batch. Generally, the lower the current, the longer the expected life of the part.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-09T18:18:27.830" CommentCount="2" />
  <row Id="11222" PostTypeId="2" ParentId="11206" CreationDate="2011-03-09T18:19:36.970" Score="3" ViewCount="" Body="&lt;p&gt;Your limiting factor is probably voltage swing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your driving higher end headphones your probably looking at a 250-&gt;300 ohm load, 300ohm for higher end sennheiser cans for instance.  But some phones (mostly professional models) can go as high as 600 ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At 300ohms:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For 100mW you need 5.47 Vrms = 15.48 V peak-to-peak ( 18mA RMS)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For 200mW you need 7.75 Vrms = 22 V peak-to-peak ( 25mA RMS )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You probably won't find an integrated part that is specifically designed for portable devices that can achieve those levels of voltage swing.  Your best bet is probably an audio op-amp with a high drive current (TI makes several, as does analog devices) or a purpose built headphone driver, for instance the &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tpa6120a2.html&quot; rel=&quot;nofollow&quot;&gt;TPA6120A2&lt;/a&gt; would fit your needs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your challenge is then to build an efficient power supply to generate the +-12-15V rails needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure what your plan it for batteries but one way to make it easier and more efficient is to use two batteries, maybe two 9V batteries, center tap for ground giving you +-9V rails to start with.  You end up with bigger/more batteries but you don't lose any power boost converting up to your + rail and then using a charge pump or similar to get your negative rail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I'd target 100mW MAX...200mW would explode your head with most phones.  expect 97-102db sensitivity at 1mW for most higher end cans (could be lower for pro models).  meaning at 127mW you'd be looking at SPL in roughly the 115dB to 120db range which is more than enough to cause hearing loss if listening for extended periods.  Targeting ~63mW would put you at 112db -&gt; 117dB which eases your voltage swing constraints and can still cause plenty of ear damage.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2011-03-09T20:04:44.010" LastActivityDate="2011-03-09T20:04:44.010" CommentCount="4" />
  <row Id="11223" PostTypeId="1" CreationDate="2011-03-09T18:43:56.683" Score="1" ViewCount="88" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am interested in taking up robotics as a hobby. I am somewhat familiar with programming (not very advanced) and would like to get some pointers to recommended books / robotic kits that will help me get started. Something that is not too esoteric. I can hopefully get to that level later!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically I am more interested in using WiFi for communications (as opposed to Bluetooth). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did purchase Lego Mindstorm recently....but looking for additional resources.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="3316" LastActivityDate="2011-03-09T21:41:51.113" Title="Pointers to Beginners (Robotics as Hobby)" Tags="&lt;robotics&gt;&lt;beginner&gt;&lt;wifi&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="11224" PostTypeId="2" ParentId="10091" CreationDate="2011-03-09T19:11:39.820" Score="2" ViewCount="" Body="&lt;p&gt;Connections would be wired together as such:&lt;img src=&quot;http://i.imgur.com/iMUBh.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I am not sure about the bottom connections. can someone confirm?&lt;/p&gt;&#xA;" OwnerUserId="1337" LastActivityDate="2011-03-09T19:11:39.820" CommentCount="1" />
  <row Id="11225" PostTypeId="1" CreationDate="2011-03-09T19:37:31.583" Score="0" ViewCount="94" Body="&lt;p&gt;I have a B.S. in Mechanical &amp;amp; Aerospace Engineering and about 3 years experience in the mechanical-electrical-piping construction type field. I am really interested in robotics and would love to make a career transition, but I need some advice on how to do so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most robotics based jobs always seem to be looking for someone who is already experienced in the field, even if it's a fairly entry level position. I have some engineering experience, but not much in the robotics/integrated systems area yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the best way to get into this field? Grad school for robotics, learning a specific programming language, starting a side/pet project? Just somehow meeting the right people...?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My resume can be found at &lt;a href=&quot;http://www.patrick-conley.com/engineering-resume/&quot; rel=&quot;nofollow&quot;&gt;http://www.patrick-conley.com/engineering-resume/&lt;/a&gt; in case it would yield any insights.&lt;/p&gt;&#xA;" OwnerUserId="3317" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-09T19:42:54.373" LastActivityDate="2011-04-04T19:39:59.097" ClosedDate="2011-04-04T20:34:57.953" Title="How to transition to job in robotics" Tags="&lt;robotics&gt;&lt;programming&gt;&lt;mechanical&gt;&lt;career&gt;&lt;engineering&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="11226" PostTypeId="2" ParentId="11220" CreationDate="2011-03-09T20:01:32.127" Score="2" ViewCount="" Body="&lt;p&gt;That depends what you have to work with.  If you're oversampling at a rate of at least 4.1x the bit rate (2.05x the max transition frequency), a simple approach is to use a state machine in which the duration of each high/low time is compared to either 1.5x the previous duration (if the previous one is thought to be 'short') or 0.75x the previous duration (if thought to be 'long').  Note that if you don't know whether you're starting with long or short pulses, you may misidentify a continuous sequence of long pulses as short, or vice versa, but the first pulse of the &quot;other&quot; width will be correctly recognized.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To clarify: suppose the goal is to recognize non-differential manchester-coded data encoded per IEEE 802.3.  If one gets a transition after a &quot;long&quot; time, the state of the communications line following the transition will represent a bit of data.  If one gets a transition after a &quot;short&quot; time, ignore it but look at the next one (which is expected to be short); the state of the line after that next transition will represent a bit of data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For differential coding, a &quot;long&quot; state time represents a zero; two &quot;short&quot; state times represent a 1 (if a short is followed by a long, there's a communications error).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-03-09T22:58:42.290" LastActivityDate="2011-03-09T22:58:42.290" CommentCount="1" />
  <row Id="11227" PostTypeId="1" CreationDate="2011-03-09T20:10:29.250" Score="1" ViewCount="190" Body="&lt;p&gt;I'm planing to build a small 80's &quot;home computer&quot; style computer, something with the following spec:s&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;8-12 Mhz&lt;/li&gt;&#xA;&lt;li&gt;256 / 512 KB external memory &lt;/li&gt;&#xA;&lt;li&gt;128 KB eprom&lt;/li&gt;&#xA;&lt;li&gt;320 x 200 x 32 colors (VGA interface) &lt;/li&gt;&#xA;&lt;li&gt;SD card for storage (cant find any tape hardware ;) )&lt;/li&gt;&#xA;&lt;li&gt;I would prefer a development environment with a live debugger and fast rebuild process, for a stream lined development process.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I havnt found anything that matches this description, AVR is out, Zilog seem to be out since I cant find a reasonable development environ (as described above) and PIC was never an alternative (for the same reason as AVR) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So do you guys have any tips ?&lt;/p&gt;&#xA;" OwnerUserId="3318" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-11T09:56:57.577" LastActivityDate="2011-03-13T01:10:22.930" Title="Looking for microcontroller for computer project" Tags="&lt;microcontroller&gt;&lt;programmer&gt;&lt;development-tools&gt;" AnswerCount="6" CommentCount="8" />
  <row Id="11228" PostTypeId="2" ParentId="9264" CreationDate="2011-03-09T20:14:29.477" Score="1" ViewCount="" Body="&lt;p&gt;For a long time, it has been common to use submultiples of 115,200 for communication--either power-of-two submultiples of 38,400 or else 57,600 or 115,200.  Most PC hardware supports those rates.  Some PC hardware can support 230,400 or 460,800.  Note that many embedded controllers like data rates which are sub-multiples of their own clock speeds, and some USB-to-serial chips can support any integer submultiple of 3,000,000bps, so speeds like 1,000,000bps or 1,500,000bps will probably become more common for devices to connect to PCs via USB chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, one other rate worth mentioning: 31,250bps is the rate used for standard MIDI.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-09T20:14:29.477" CommentCount="1" />
  <row Id="11229" PostTypeId="1" CreationDate="2011-03-09T20:28:41.670" Score="0" ViewCount="189" Body="&lt;p&gt;I have a simple microphone.  How can I send some &quot;volume&quot; or &quot;oscillation&quot; values via serial to the computer?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I built a simple preamp but it does not respond, any hints?&lt;/p&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-09T22:52:13.340" LastActivityDate="2011-03-09T22:52:13.340" Title="Arduino + Microphone how to grab values?" Tags="&lt;arduino&gt;&lt;sound&gt;&lt;microphone&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="11230" PostTypeId="2" ParentId="3067" CreationDate="2011-03-09T20:56:13.407" Score="2" ViewCount="" Body="&lt;p&gt;Many digital signal processors include a variety of functions not found in 'ordinary' processors:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The ability to perform a multiply-accumulate, with both operands fetched from RAM, at a rate of one cycle per pair of operands.&#xA;&lt;li&gt;The ability to perform some form of 'modulo' or 'wrapping' addressing, so as to allow a buffer to be used repeatedly without having to use manual code to ensure pointers wrap.  The 3205x, for example, has a 'buffer start' and 'buffer end' register; if code attempts to incrementing or decrement a pointer register that points to 'buffer start', the processor will load the pointer with 'buffer end'.  The 3205x also has a reverse-carry mode, where address additions propagate carry MSB to LSB, rather than vice versa; this allows for modulo-N addressing if N is a power of 2, though stuff gets stored in jumbled sequence.&#xA;&lt;li&gt;The ability to specify that an instruction be executed 'n' times without needing to be re-fetched.  Some processors like the 8088 include this for a few instructions, but many DSP's allow this on many instructions.&#xA;&lt;li&gt;The ability to specify that a block of code be executed repeatedly, up to 'n' times, without need for branching.  Before each code fetch, the program counter is checked against the 'loop-end' register; if it matches, and looping is enabled, the program counter will be reloaded with 'loop-start' (otherwise it will increment).  If 'loop-count' is zero, looping will be disabled; otherwise 'loop-count' will be decremented.&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Note that many DSPs will have separate buses to allow both operands of a multiply-accumulate to be fetched simultaneously; I've never seen a non-DSP that could do that.  While I'm unaware of any feature that a chip must 'lack' to be a DSP, extra silicon space required to allow double-operand fetching is silicon space that isn't being used for some other more-generally-useful purpose.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-09T20:56:13.407" CommentCount="3" />
  <row Id="11231" PostTypeId="2" ParentId="11229" CreationDate="2011-03-09T21:10:28.677" Score="1" ViewCount="" Body="&lt;p&gt;If you are just trying to sample a microphone, then an Arduino might not be necessary.  The computer has all of the tools required to sample and process data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, if you have the data acquisition toolbox on MATLAB:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ai=analoginput('winsound');&#xA;addchannel(ai,1);&#xA;start(ai);&#xA;data=getdata(ai);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Or if you prefer something a little more free, you could use &lt;a href=&quot;http://people.csail.mit.edu/hubert/pyaudio/&quot; rel=&quot;nofollow&quot;&gt;PyAudio&lt;/a&gt;, which is a simple way of getting audio off of your sound card and into an array of samples.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are dead-set on using the Arduino, you want to make sure that the output of your pre-amp is under 5V peak-to-peak, which you can check on an oscilloscope or multimeter.  You then need to use a DC-block capacitor in series with the output of the pre-amplifier, and then shift the signal up to 2.5V using a simple resistor divider.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The effect that this has is biasing the entire signal up by 2.5V, so that it varies between 0 and 5V (the range of inputs for the Arduino).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that, it is a simple matter of sampling the analog input, and then removing the bias (should be around 512 ticks) from the sampled signal.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-03-09T21:10:28.677" />
  <row Id="11232" PostTypeId="2" ParentId="11227" CreationDate="2011-03-09T21:41:30.997" Score="0" ViewCount="" Body="&lt;p&gt;Have you looked at the &lt;a href=&quot;http://www.ghielectronics.com/catalog/product/131/&quot; rel=&quot;nofollow&quot;&gt;FEZ Cobra&lt;/a&gt;?  If you're not opposed to the &lt;a href=&quot;http://www.microsoft.com/en-us/netmf/about/default.aspx&quot; rel=&quot;nofollow&quot;&gt;.NET Micro Framework&lt;/a&gt;, it looks to be very powerful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has 16BM of RAM, 4.5MB Flash (instead of an EPROM) a 72 MHZ processor, SD card, ethernet and a bunch more.  I haven't worked with this board in particular, but I've worked with the Netduino and developing / debugging is an absolute breeze.  The code is pushed to the device via USB, and debugging takes place over the same USB cable.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The development environment is &lt;a href=&quot;http://msdn.microsoft.com/en-us/vstudio/default&quot; rel=&quot;nofollow&quot;&gt;Visual Studio&lt;/a&gt; (the free version is &lt;a href=&quot;http://www.microsoft.com/express/&quot; rel=&quot;nofollow&quot;&gt;Visual Studio Express&lt;/a&gt;).&lt;/p&gt;&#xA;" OwnerUserId="1823" LastActivityDate="2011-03-09T21:41:30.997" CommentCount="1" />
  <row Id="11233" PostTypeId="2" ParentId="11223" CreationDate="2011-03-09T21:41:51.113" Score="1" ViewCount="" Body="&lt;p&gt;You can't go wrong by reading &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0071741674&quot; rel=&quot;nofollow&quot;&gt;Making Things Move&lt;/a&gt; and &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596510519&quot; rel=&quot;nofollow&quot;&gt;Making Things Talk&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3078" LastActivityDate="2011-03-09T21:41:51.113" />
  <row Id="11234" PostTypeId="1" CreationDate="2011-03-09T22:16:49.527" Score="7" ViewCount="563" Body="&lt;p&gt;I'm a newbie in electronics. I'm trying to build a calculator from scratch as a simple project and side hobby to keep me busy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My goal is to build a simple calculator, not a scientific or graphing calculator, although I don't mind receiving information about how to do that either, just for kicks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Is there a good tutorial for this? How should I start?&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="3249" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-03-28T17:42:04.553" LastActivityDate="2011-03-28T17:42:04.553" Title="How to build a calculator?" Tags="&lt;circuit-design&gt;&lt;calculator&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="1" />
  <row Id="11235" PostTypeId="2" ParentId="23" CreationDate="2011-03-09T22:17:11.653" Score="0" ViewCount="" Body="&lt;p&gt;Have written what is hopefully a &lt;a href=&quot;http://tronixstuff.wordpress.com/2011/03/08/moving-forward-with-arduino-%E2%80%93-chapter-30-%E2%80%93-twitter/&quot; rel=&quot;nofollow&quot;&gt;simple explanation&lt;/a&gt; on how to send a tweet with Arduino and an ethernet shield. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2011-03-09T22:17:11.653" />
  <row Id="11236" PostTypeId="2" ParentId="11234" CreationDate="2011-03-09T22:27:41.317" Score="3" ViewCount="" Body="&lt;p&gt;Well for starters, you should think about the major components that your going to need. You will probably need a microcontroller, a keypad, and an LCD screen. Once you pick out those components, it should be as simple as developing the firmware.&lt;/p&gt;&#xA;" OwnerUserId="2857" LastActivityDate="2011-03-09T22:27:41.317" CommentCount="4" />
  <row Id="11237" PostTypeId="1" AcceptedAnswerId="11271" CreationDate="2011-03-09T22:30:44.700" Score="3" ViewCount="99" Body="&lt;p&gt;Are there any tools or parts that help when soldering a free-floating component to another one, for example a resistor to an LED? Something that will make some kind of mechanical connection instead of just relying on the solder. I imagine someone has to make some kind of little sleeve or collar that you slide both leads into and then crush, but I've never come across anything. &lt;/p&gt;&#xA;" OwnerUserId="1742" LastActivityDate="2011-03-10T11:02:56.293" Title="Is there a crimp tool, or something, for when you're soldering leads to leads." Tags="&lt;soldering&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="11238" PostTypeId="2" ParentId="11211" CreationDate="2011-03-09T22:36:26.017" Score="1" ViewCount="" Body="&lt;p&gt;PC serial port programmers basically use the &quot;handshake&quot; (RTS/CTS DTR/DCD) pins of a serial port as a small parallel port.   It often doesn't work with USB &quot;virtual com port&quot; devices because the USB device distorts the timing.   The conventional wisdom is that USB adaptors &quot;don't work&quot; with PC serial port bitbang software that is expecting a hardware COM port (8250 UART), but I'm not 100% certain that someone hasn't gotten it working with a PL2303.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have an AVR chip preprogrammed with a serial bootloader, you could use your serial adapter (with a rs232-&gt;5v level shifter) to load programmer firmware onto the AVR, then use that AVR as a programmer (with appropriate firmware) to program &lt;em&gt;other&lt;/em&gt; AVRs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy ATmegas with the arduino serial bootloader preloaded, or maybe you know someone with a programmer (or an arduino) who can burn a serial bootloader onto an ATmega for you?&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-09T22:36:26.017" CommentCount="2" />
  <row Id="11239" PostTypeId="2" ParentId="11237" CreationDate="2011-03-09T22:46:25.837" Score="2" ViewCount="" Body="&lt;p&gt;At www.modk.it they do this with ordinary 1/16&quot; or 3/32&quot; aluminium tube from hobby stores, which is crimped with crimping pliers. There was a writeup in the latest issue of Make magazine: &lt;a href=&quot;http://makezine.com/25/modkit/&quot; rel=&quot;nofollow&quot;&gt;http://makezine.com/25/modkit/&lt;/a&gt; or &lt;a href=&quot;http://www.make-digital.com/make/vol25?pg=56#pg56&quot; rel=&quot;nofollow&quot;&gt;http://www.make-digital.com/make/vol25?pg=56#pg56&lt;/a&gt; (not sure if you need to be a subscriber to see that last link).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's modkit's doco:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.modk.it/hardware/knobcard&quot; rel=&quot;nofollow&quot;&gt;http://www.modk.it/hardware/knobcard&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=haN3LBplVu4&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=haN3LBplVu4&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having said that, I always just solder the two leads with about 4mm overlap&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;----------&#xA;      -----------&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And then cover with a 10mm length of heat-shrink tubing.  LEDs with integral resistor&#xA;soldered onto one like like this have withstood all the abuse I've given them.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-09T22:46:25.837" />
  <row Id="11240" PostTypeId="2" ParentId="11237" CreationDate="2011-03-09T22:46:49.553" Score="0" ViewCount="" Body="&lt;p&gt;I always just bend each lead into a hook shape, hook the leads together, and then close the hooks into loops. It makes a pretty good physical connection.&lt;/p&gt;&#xA;" OwnerUserId="2857" LastActivityDate="2011-03-09T22:46:49.553" CommentCount="2" />
  <row Id="11241" PostTypeId="1" CreationDate="2011-03-09T22:46:50.240" Score="1" ViewCount="104" Body="&lt;p&gt;Hello,&#xA;I am looking for a development board (microcontroller based), with reasonably powerful math functionality, for real-time simiulation of oscillation systems (pendulums,SHM,shock absorbers etc.) and other similar systems which can be modelled using differential equations. I hope to represent the solutions graphically on an ossiloscope, so the board should also have analog output with sufficient resolution.&#xA;Thanks,&#xA;Alex&lt;/p&gt;&#xA;" OwnerUserId="3319" LastEditorUserId="3319" LastEditorDisplayName="" LastEditDate="2011-03-09T22:54:25.103" LastActivityDate="2011-03-10T01:28:04.390" Title="Choosing a dev board for physics simulation" Tags="&lt;microcontroller&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="11242" PostTypeId="2" ParentId="11241" CreationDate="2011-03-09T23:04:16.500" Score="2" ViewCount="" Body="&lt;p&gt;It would make more sense to do your simulation on a PC using MATLAB (expensive) or Scilab (free). Output can be plotted graphically, you won't need a scope.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-09T23:04:16.500" CommentCount="2" />
  <row Id="11243" PostTypeId="2" ParentId="11128" CreationDate="2011-03-09T23:46:55.980" Score="1" ViewCount="" Body="&lt;p&gt;A couple of possibilities. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, since RFID tags consist of the electronic circuit and a loop antenna, you could have the switch intermittently connect the circuit to the antenna.  The RFID reader would only get a read for the button when the connection was made.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, a motion-to-electricity converter could power an existing RFID chip, similar to how the exciting coil does.  This could be a piezoelectric crystal, magnet and coil, or some other approach.  The RFID reader can be entirely passive in this case.&lt;/p&gt;&#xA;" OwnerUserId="1264" LastActivityDate="2011-03-09T23:46:55.980" />
  <row Id="11244" PostTypeId="1" AcceptedAnswerId="11246" CreationDate="2011-03-10T00:21:46.277" Score="2" ViewCount="71" Body="&lt;p&gt;I got my hands on a big tube of conductive silicone. I've never heard of it before, but my first thought was, &quot;Is this just basically wire in a tube?&quot; Has anyone ever used this before? Can you just apply it as a low heat solder? The people I got it from said this stuff is kinda expensive, but I got it since they were just going to get rid of it (at cost, so they were glad to let me have it). Plus it is expired (does silicone expire?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, anyone have any experience using the stuff?&lt;/p&gt;&#xA;" OwnerUserId="3080" LastActivityDate="2011-03-10T08:56:11.463" Title="Can I use conductive silicone for anything I could use solder for?" Tags="&lt;conductive&gt;" AnswerCount="2" />
  <row Id="11245" PostTypeId="1" CreationDate="2011-03-10T00:25:29.160" Score="0" ViewCount="59" Body="&lt;p&gt;I'd like to drive an inkjet cartridge, such as an &lt;a href=&quot;http://www.amazon.com/exec/obidos/asin/B001IX1OLM/db73f06059531-20?ref=nosim&quot; rel=&quot;nofollow&quot;&gt;HP 94&lt;/a&gt; using a micro such as an Arduino or MSP 430.  &lt;/p&gt;&#xA;" OwnerUserId="1264" LastActivityDate="2011-03-10T00:58:18.877" Title="Looking for electronics and sample code to drive commodity inkjet cartridge" Tags="&lt;arduino&gt;&lt;electronics&gt;&lt;msp430&gt;" AnswerCount="1" />
  <row Id="11246" PostTypeId="2" ParentId="11244" CreationDate="2011-03-10T00:28:56.470" Score="4" ViewCount="" Body="&lt;p&gt;Well, I had some fun with some conductive paint, which should be similar to your thing.&#xA;First of all, check resistance of the 'wire' of it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main problem is reliability of lines. Also, it should not be able to physically hold elements in place, unlike solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Might be used to repair broken traces on PCB and especially, flexible PCB (cellphones, keyboards). &lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-10T00:28:56.470" CommentCount="1" />
  <row Id="11247" PostTypeId="2" ParentId="11245" CreationDate="2011-03-10T00:58:18.877" Score="1" ViewCount="" Body="&lt;p&gt;I recall that someone already did something like that... searching... .. .. .. oh yes: &lt;a href=&quot;http://spritesmods.com/?art=inker&quot; rel=&quot;nofollow&quot;&gt;http://spritesmods.com/?art=inker&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope that helps.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-10T00:58:18.877" CommentCount="1" />
  <row Id="11248" PostTypeId="2" ParentId="11211" CreationDate="2011-03-10T01:16:49.650" Score="1" ViewCount="" Body="&lt;p&gt;I would suggest starting with a parallel port programmer. They are very easy to make and are&#xA;rock solid. Of course you will need a PC with a parallel port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or if you can find someone with a working programmer (or a PC with a parallel port) you can build yourself an &lt;a href=&quot;http://www.fischl.de/usbasp/&quot; rel=&quot;nofollow&quot;&gt;USBasp&lt;/a&gt;. It is easy to build and works with avrdude.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having a (temporary) programmer you can also make an &lt;a href=&quot;http://www.mikrocontroller-projekte.de/Mikrocontroller/AVR-Prog/AVR-Programmer.html&quot; rel=&quot;nofollow&quot;&gt;AVR910 programmer&lt;/a&gt; but as you can see on the page there is a little mess in the documentation. It takes normal RS232 (5V levels; use a MAX232) on one end and outputs AVR serial programming protocol on the other. There is even AVRospII - a nice Windows GUI for the thing. Some years ago we made several such programmers out of cell phone RS232 cables.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-10T01:16:49.650" CommentCount="1" />
  <row Id="11249" PostTypeId="2" ParentId="11241" CreationDate="2011-03-10T01:28:04.390" Score="1" ViewCount="" Body="&lt;p&gt;You could use a smartphone/PDA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most have serial ports for IO, and you could probably get analog output through the headphone output, if you don't mind a ~20hz highpass filter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, the &lt;a href=&quot;http://beagleboard.org/&quot; rel=&quot;nofollow&quot;&gt;BeagleBoard&lt;/a&gt; is a chunky SOC dev-board, with floating point capabilities, and has parallel IO, so you should be able to attach a DAC to it.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-03-10T01:28:04.390" CommentCount="1" />
  <row Id="11250" PostTypeId="2" ParentId="11237" CreationDate="2011-03-10T01:28:30.473" Score="1" ViewCount="" Body="&lt;p&gt;You might be able to do a &quot;Western Union&quot; ( &lt;a href=&quot;http://www.tpub.com/neets/book4/32NE0334.GIF&quot; rel=&quot;nofollow&quot;&gt;http://www.tpub.com/neets/book4/32NE0334.GIF&lt;/a&gt; ) splice if the wires are flexible enough, I have done them with LEDs to resistors before (I've also made a mess of it before), although I always soldered them as well. I recommend clamping the base of the lead with some pliers before twisting the end lest you break it off the component.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could combine a union splice with the aluminum tubing idea &lt;strong&gt;unixbigot&lt;/strong&gt; mentioned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are butt crimps, but I've never seen one small enough that I would want to use it directly with component leads.&lt;/p&gt;&#xA;" OwnerUserId="3208" LastActivityDate="2011-03-10T01:28:30.473" />
  <row Id="11252" PostTypeId="1" CreationDate="2011-03-10T01:51:54.197" Score="2" ViewCount="183" Body="&lt;p&gt;My Dell laptop comes with an AC adapter with the following specs:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;65 W&#xA;Input AC: 100 - 240 V, ~1.5 A, 50 - 60 Hz&#xA;Output DC: 19.5 V,  3.34 A&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;My HP laptop:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;65 W&#xA;Input AC: 100 - 240 V, ~1.7 A, 50 - 60 Hz&#xA;Output DC: 18.5 V,  3.5 A&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I have 3 questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;On the Input AC, why 1.5 A vs 1.7 A?  I just have one type of power outlet for everything, such as lamp, TV, refrigerator, etc.  So this number is not too significant?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The output DC voltage and current are different.  Would it be safe for me to interchange the adapters, i.e. use the HP laptop with the Dell AC adapter and vice versa.  Which way would be safe and which is not?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If there's another adapter with the same output DC but higher wattage, would I be able to use it as well?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3320" LastActivityDate="2011-03-11T12:16:12.847" Title="Reading and understanding electrical specs on laptop AC adapters" Tags="&lt;voltage&gt;&lt;current&gt;&lt;adapter&gt;&lt;output&gt;" AnswerCount="3" />
  <row Id="11253" PostTypeId="2" ParentId="11252" CreationDate="2011-03-10T02:10:58.647" Score="4" ViewCount="" Body="&lt;p&gt;First, the over arching thing is that if the voltages match and the charger can supply more current the the original you were given, you are fine. If it supplies less, it may still be enough, especially if the battery is already charged.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Your wall socket will general be able to deliver in excess of 15A(depends on your country). The input current they expect is based on how much power their circuit actually uses.&lt;/li&gt;&#xA;&lt;li&gt;Actually, their voltage is different, which is normally a larger issue for the adapters but the reason that interchanging is somewhat safe is for a hidden reason. Let me note first, plugging in a mismatched adapter can damage your device, and easily, if it is not able to handle the voltage you are going to supply. Most adapters user a communication protocol to verify the adapter was purchased from the original equipment manufacturer(OEM). If they do not detect this they often limit their power draw to &quot;protect&quot; the charger. This gives the advantage of protecting the charger if it is underrated.&lt;/li&gt;&#xA;&lt;li&gt;Yes, you should be able to if the computer believes it is acceptable to use(no comm protocol to recognize a mismatched adapter). This voltage output is what primarily determines function. In electronics voltage controlled circuits are much easier to generate and use. This gets a bit too detailed, but I hope this information helps.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-11T12:16:12.847" LastActivityDate="2011-03-11T12:16:12.847" CommentCount="6" />
  <row Id="11254" PostTypeId="1" CreationDate="2011-03-10T03:01:20.160" Score="0" ViewCount="125" Body="&lt;p&gt;I was wondering if anyone had any site or diagram for a cheap (and preferably small) for a circuit for a 60 to 80khz frequency generator.&lt;/p&gt;&#xA;" OwnerUserId="3322" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T21:01:19.137" LastActivityDate="2011-04-29T06:38:26.603" Title="Frequency Transmitter" Tags="&lt;frequency&gt;&lt;generator&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="11255" PostTypeId="2" ParentId="1609" CreationDate="2011-03-10T03:32:42.353" Score="1" ViewCount="" Body="&lt;p&gt;With 17 I/O pins, seventeen NPN transistors (emitter followers to boost current) there should be no particular problem showing 272 LEDs in arbitrary combinations at 1/17 duty cycle, with  average current or 0.7mA (200mA/272), limited by the chip's ability to pull down 200mA at a time.  Adding a diode to get a 0.7-volt drop will allow the addition of another 17 LEDs (reducing duty cycle to 1/18), though the brightness won't quite match the other ones.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-03-19T03:16:13.083" LastActivityDate="2011-03-19T03:16:13.083" CommentCount="2" />
  <row Id="11256" PostTypeId="1" AcceptedAnswerId="11266" CreationDate="2011-03-10T03:51:53.273" Score="2" ViewCount="107" Body="&lt;p&gt;I want to bitbang a Prolific PL-2303HX. There is the library &lt;code&gt;libftdi&lt;/code&gt; which enables bitbanging on the FT232 chip. Can I make it work with PL-2303? When I try using &lt;code&gt;libftdi&lt;/code&gt; it gives in the error &quot;Can't open device&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone knows how to make this work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I try to open the device with the example code in &lt;code&gt;libftdi&lt;/code&gt; (changing the vendor and device id to &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;f = ftdi_usb_open(&amp;amp;ftdic, 0x067b, 0x2303);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I get the following output&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;rick2047@ubuntu:~/work/libftdi$ sudo ./a.out &#xA;[sudo] password for rick2047: &#xA;unable to open ftdi device: -6 (ftdi_usb_reset failed)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-10T08:16:25.890" LastActivityDate="2011-03-10T08:16:25.890" Title="Making libftdi work with PL-2303HX" Tags="&lt;libftdi&gt;&lt;pl2303&gt;" AnswerCount="3" />
  <row Id="11257" PostTypeId="2" ParentId="1609" CreationDate="2011-03-10T03:52:09.377" Score="1" ViewCount="" Body="&lt;p&gt;There's a very nice, detailed tutorial &lt;a href=&quot;http://daid.mine.nu/instructabliss/?url=http://www.instructables.com/id/Led-Cube-8x8x8/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; which includes a section on using an Arduino to run an 8x8x8 LED cube. (Don't miss the YouTube movie they have up)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Du6XF.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2233" LastActivityDate="2011-03-10T03:52:09.377" CommentCount="1" />
  <row Id="11258" PostTypeId="1" AcceptedAnswerId="11259" CreationDate="2011-03-10T02:35:11.280" Score="0" ViewCount="125" Body="&lt;p&gt;I have an old sony universal remote, the rm-v15. I opened it to get to the pcb, and a strange nasty smell came out of it. Is there anything I should be worried about? Any hazards used in old remotes?&lt;/p&gt;&#xA;" OwnerUserId="2873" LastActivityDate="2011-03-11T14:30:53.937" Title="Safe to open old sony remote?" Tags="&lt;remote&gt;&lt;safety&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="11259" PostTypeId="2" ParentId="11258" CreationDate="2011-03-10T02:47:48.350" Score="3" ViewCount="" Body="&lt;p&gt;You could have a leaky battery; you don't want acid all over your skin. There will be trace amounts of the heavy metals found in all electronics manufacturing. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And because remotes are handled so much and are often full of skin cells and food traces, you could be smelling mold spores. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wear gloves, ventilate, and proceed. You should be fine as long as you don't lick anything!&lt;/p&gt;&#xA;" OwnerUserId="3321" LastActivityDate="2011-03-10T02:47:48.350" CommentCount="3" />
  <row Id="11260" PostTypeId="2" ParentId="11256" CreationDate="2011-03-10T04:46:32.243" Score="1" ViewCount="" Body="&lt;p&gt;I have no idea how to do bitbanging with the prolific chips, but the error you're seeing is a result of the vendor identifier (VID) and product identifier (PID) of the Prolific chip being different from FTDI's default&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.intra2net.com/en/developer/libftdi/documentation/&quot; rel=&quot;nofollow&quot;&gt;This sample code&lt;/a&gt; shows an example of where this kind of an error might be thrown: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if ((ret = ftdi_usb_open(&amp;amp;ftdic, 0x0403, 0x6001)) &amp;lt; 0)&#xA;{&#xA;    fprintf(stderr, &quot;unable to open ftdi device: %d (%s)\n&quot;, &#xA;            ret, ftdi_get_error_string(&amp;amp;ftdic));&#xA;    return EXIT_FAILURE;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;ftdi_usb_open()&lt;/code&gt; is an alias for the function:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ftdi_usb_open_desc_index(&#xA;    struct ftdi_context * ftdi,&#xA;    int                   vendor,&#xA;    int                   product,&#xA;    const char *          description,&#xA;    const char *          serial,&#xA;    unsigned int          index  &#xA;)   &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;that just substitutes a null pointer for the description and serial, and '0' for the index.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The source for this function can be found on line 623 of ftdi.c, or it's &lt;a href=&quot;http://www.intra2net.com/en/developer/libftdi/documentation/ftdi_8c_source.html#l00632&quot; rel=&quot;nofollow&quot;&gt;online here&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that every interaction that the FDTI drivers do in this function and beyond assumes that you've got an FTDI chip on the other end.  Fixing this problem is almost certain to lead to further problems, and fixing those problems will get you another. There will be a light at the end of the tunnel, but it may be a long way getting there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adding Prolific support to libftdi (or porting libftdi's API to a new library, call it libprolific) would be pretty neat.  However, you're almost certainly better off using Prolific's drivers: &lt;a href=&quot;http://www.prolific.com.tw/eng/downloads.asp?id=31&quot; rel=&quot;nofollow&quot;&gt;http://www.prolific.com.tw/eng/downloads.asp?id=31&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-10T04:46:32.243" CommentCount="1" />
  <row Id="11261" PostTypeId="2" ParentId="11256" CreationDate="2011-03-10T05:34:53.593" Score="1" ViewCount="" Body="&lt;p&gt;They are two totally different chips inside.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the FTDI Linux driver: &lt;a href=&quot;http://lxr.linux.no/linux+v2.6.37.3/drivers/usb/serial/ftdi_sio.c&quot; rel=&quot;nofollow&quot;&gt;http://lxr.linux.no/linux+v2.6.37.3/drivers/usb/serial/ftdi_sio.c&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And here is the PL230x Linux driver:&#xA;&lt;a href=&quot;http://lxr.linux.no/linux+v2.6.37.3/drivers/usb/serial/pl2303.c&quot; rel=&quot;nofollow&quot;&gt;http://lxr.linux.no/linux+v2.6.37.3/drivers/usb/serial/pl2303.c&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice they are not the same.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet does not mention the PL2303 supporting any bitbang modes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can always use RS232 lines for bitbang: DTR and RTS for output, RI+DCD+DSR+CTS for input.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-10T05:34:53.593" />
  <row Id="11262" PostTypeId="2" ParentId="11234" CreationDate="2011-03-10T05:36:50.203" Score="12" ViewCount="" Body="&lt;p&gt;Here is an example of a calculator that you can build without too much electronics knowledge. It's full featured, although addition is not included. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/sIrB9.jpg&quot; alt=&quot;Yes I'm joking, don't take this too seriously&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-03-10T05:36:50.203" CommentCount="6" />
  <row Id="11263" PostTypeId="1" AcceptedAnswerId="11277" CreationDate="2011-03-10T06:14:19.267" Score="13" ViewCount="391" Body="&lt;p&gt;The traditional logarithmic amplifier circuit is described in &lt;a href=&quot;http://www.national.com/an/AN/AN-311.pdf&quot; rel=&quot;nofollow&quot;&gt;National Appnote 311&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Tu3mE.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This circuit uses the difference of two transistor currents to generate the log of the input over a pretty wide range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The well-matched transistor pair Q1a and Q1b are halves of the LM394 &quot;supermatch&quot; transistor pair.  But National discontinued this part last year with no clear replacement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can use LM3406 array, but the specs are far worse.  There are plenty of arrays of '2222 or &#xA;'3904 available, but there is no mention of matching in the datasheet.  The transistors might be on separate dies for all I know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI still sells some Burr Brown log amps but they are expensive.  LOG101 is $18.37 in onesies.  Analog makes the AD606 for $43.88 each or the AD830x parts for $12 - $20.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I (cheaply) make a logarithm?&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-06-02T04:55:08.183" LastActivityDate="2011-06-02T04:55:08.183" Title="LM394 is obsolete. What is the new standard log amp circuit?" Tags="&lt;amplifier&gt;&lt;lm394&gt;&lt;logarithmic&gt;&lt;long-tailed-pair&gt;&lt;matched&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="6" />
  <row Id="11264" PostTypeId="2" ParentId="11213" CreationDate="2011-03-10T06:14:36.317" Score="3" ViewCount="" Body="&lt;p&gt;What's happening is that the simulation is not deterministic! What an exciting property for a simulator to have! It appears that if it takes too long for an event to occur (computationally) it gets delayed a time-step. If you set the simulation speed too fast, you may get a different result!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At any rate, your flip-flop is getting clocked twice at one of the peaks, and that causes the output to rail or do other silly stuff. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can improve this circuit by using a S-R latch instead of a flip-flop. That way, even if you have glitches out of your comparators, it's the first glitch that counts. Second, there are no possible invalid states. Notice in your image how if the Q_Bar output = 0 and the output wave is below -0.2V, your circuit is permanently stuck.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you really want is something like a Set-Reset latch. That way you don't care about the comparators glitching, because your circuit will still function. Here's a &lt;a href=&quot;http://falstad.com/circuit/#%24+1+1.0E-6+1.1685319768402522+50+5.0+50%0Aa+624+144+736+144+1+15.0+-15.0+1000000.0%0Ar+736+144+736+208+0+100.0%0Aw+736+208+624+208+0%0Aw+624+208+624+160+0%0Ag+736+384+736+400+0%0A172+96+96+64+96+0+6+0.5+0.5+0.0+0.0+0.5+Voltage%0Ar+96+96+160+96+0+10000.0%0Ar+160+64+272+64+0+10000.0%0Aw+272+64+272+112+0%0Aw+160+96+160+64+0%0Aa+160+112+272+112+0+15.0+-15.0+1000000.0%0Ag+160+128+160+144+0%0A160+336+128+272+128+0+20.0+1.0E10%0Aw+272+144+272+176+0%0Aw+272+176+96+176+0%0Aw+96+176+96+96+0%0Ac+736+304+736+384+2+9.999999999999999E-6+0.0676077851660514%0Aw+608+272+624+272+0%0Aw+608+336+624+336+0%0Aw+624+336+624+304+0%0Aw+624+304+624+272+0%0Aw+736+304+736+208+0%0Aw+736+304+624+304+0%0AR+608+240+640+240+0+0+40.0+0.2+0.0+0.0+0.5%0AR+608+368+640+368+0+0+40.0+-0.2+0.0+0.0+0.5%0Aw+624+128+512+128+0%0Aa+608+352+512+352+0+15.0+-15.0+1000000.0%0Aa+608+256+512+256+0+15.0+-15.0+1000000.0%0Aw+512+128+352+128+0%0Aw+736+304+800+304+0%0Ar+800+304+800+384+0+10000.0%0Ag+800+384+800+400+0%0Aw+336+128+352+128+0%0Aw+304+176+304+144+0%0Aw+336+368+304+368+0%0Aw+304+368+368+304+0%0Aw+368+304+448+304+0%0Aw+448+304+448+272+0%0Aw+448+272+432+272+0%0Aw+336+256+304+256+0%0Aw+304+256+368+320+0%0Aw+368+320+448+320+0%0Aw+448+320+448+352+0%0Aw+448+352+432+352+0%0Aw+304+192+304+256+0%0A153+432+368+336+368+0+2+5.0%0A153+432+256+336+256+0+2+0.0%0Aw+304+192+304+176+0%0Aw+432+240+512+240+0%0Aw+512+240+512+256+0%0Aw+432+384+512+384+0%0Aw+512+384+512+352+0%0Ao+22+1+0+35+0.5846006549323611+9.765625E-55+0+-1%0A&quot; rel=&quot;nofollow&quot;&gt;link back to the Farstad simulator&lt;/a&gt;, as well as a screenshot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/D0U3q.png&quot; alt=&quot;Improved state storage&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-03-10T06:14:36.317" CommentCount="4" />
  <row Id="11265" PostTypeId="2" ParentId="11213" CreationDate="2011-03-10T06:54:18.607" Score="1" ViewCount="" Body="&lt;p&gt;Alternatively, instead of the window comparator, simply use a comparator with positive feedback.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://falstad.com/circuit/#%24+1+1.0E-6+1.1685319768402522+59+5.0+50%0Aa+688+144+800+144+1+15.0+-15.0+1000000.0%0Ar+800+144+800+208+0+500.0%0Aw+688+208+688+160+0%0Ag+800+384+800+400+0%0A172+160+96+128+96+0+6+-1.0+-1.0+0.0+0.0+0.5+Voltage%0Ar+160+96+224+96+0+10000.0%0Ar+224+64+336+64+0+10000.0%0Aw+336+64+336+112+0%0Aw+224+96+224+64+0%0Aa+224+112+336+112+0+15.0+-15.0+1000000.0%0Ag+224+128+224+144+0%0A160+400+128+336+128+0+20.0+1.0E10%0Aw+336+144+336+176+0%0Aw+336+176+160+176+0%0Aw+160+176+160+96+0%0Ac+800+304+800+384+2+9.999999999999999E-6+0.20567219669752274%0Aw+688+128+576+128+0%0Aa+576+288+480+288+0+15.0+-15.0+1000000.0%0Aw+576+128+416+128+0%0Ag+592+224+592+240+0%0Aw+400+128+416+128+0%0Aw+368+176+368+144+0%0Aw+368+192+368+256+0%0Aw+368+192+368+176+0%0Ar+608+304+672+304+0+100.0%0Ar+464+352+592+352+0+2000.0%0Aw+576+304+592+304+0%0Aw+592+304+592+352+0%0Aw+592+304+608+304+0%0Aw+464+352+464+288+0%0Aw+464+288+480+288+0%0Aw+464+288+368+288+0%0Aw+368+256+368+288+0%0Aw+688+304+672+304+0%0Aw+592+224+576+224+0%0Aw+576+224+576+272+0%0Aw+688+304+800+304+0%0Aw+688+208+800+208+0%0Aw+800+208+800+304+0%0Ao+36+8+0+35+2.5+0.0125+0+-1%0A&quot; rel=&quot;nofollow&quot;&gt;Sim Link&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kjsrN.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has the advantage of being MUCH simpler, in terms of parts. Also, it should be VERY stable, thanks to the positive feedback on the comparator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can make it even simpler by just getting rid of the analog switch, as well as two of the op-amps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://falstad.com/circuit/#%24+1+1.0E-6+51.8012824668342+39+5.0+50%0Aa+320+160+432+160+1+15.0+-15.0+1000000.0%0Ar+432+160+432+224+0+250.0%0Ag+432+336+432+352+0%0Ac+432+256+432+336+2+9.999999999999999E-6+6.551035378688574%0Ag+208+160+208+176+0%0Ar+336+80+400+80+0+100.0%0Ar+224+144+288+144+0+100.0%0Aw+208+160+208+144+0%0Aw+208+144+224+144+0%0Aw+288+144+304+144+0%0Aw+304+144+304+80+0%0Aw+304+80+336+80+0%0Aw+400+80+432+80+0%0Aw+432+80+432+160+0%0Aw+320+144+304+144+0%0Aw+320+176+304+176+0%0Aw+304+240+432+240+0%0Aw+304+176+304+240+0%0Aw+432+224+432+240+0%0Aw+432+240+432+256+0%0Ao+3+64+0+35+10.0+0.4+0+-1%0A&quot; rel=&quot;nofollow&quot;&gt;Sim Link&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/jWFsq.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Ok, I'm having fun now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, this circuit never makes a perfect triangle wave, because you're charging the capacitor with a voltage through a resistor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make it operate as a true triangle wave generator, we need to do a significant amount of refactoring.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, we need to charge the capacitor with a current source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is simple enough to do, all you have to do is stick the cap in the op-amp feedback.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://falstad.com/circuit/#%24+1+1.0E-6+43.84883893407173+51+5.0+50%0Aa+336+112+448+112+1+50.0+-50.0+1000000.0%0Ar+208+176+320+176+0+1000.0%0Ag+288+96+288+112+0%0Aa+304+288+208+288+0+15.0+-15.0+1000000.0%0Ag+320+224+320+240+0%0Ar+336+304+400+304+0+100000.0%0Ar+192+352+320+352+0+200000.0%0Aw+304+304+320+304+0%0Aw+320+304+320+352+0%0Aw+320+304+336+304+0%0Aw+192+352+192+288+0%0Aw+192+288+208+288+0%0Aw+416+304+400+304+0%0Aw+320+224+304+224+0%0Aw+304+224+304+272+0%0Aw+448+176+448+272+0%0Aw+288+96+336+96+0%0Aw+336+128+336+176+0%0Ac+352+176+416+176+0+1.0E-5+-6.104089742349298%0Aw+336+176+352+176+0%0Aw+416+176+448+176+0%0Aw+192+288+192+176+0%0Aw+208+176+192+176+0%0Aw+320+176+336+176+0%0Aw+448+272+448+304+0%0Aw+448+304+416+304+0%0Aw+448+176+448+112+0%0Ao+18+64+0+35+10.0+0.025+0+-1%0A&quot; rel=&quot;nofollow&quot;&gt;Look at This&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/uPSYB.png&quot; alt=&quot;enter image description here&quot;&gt;&#xA;(Note: this oscillators start-up is a little weird. It basically relies on leakage to charge the capacitor enough that the bottom op-amp output goes to one of the rails. This would &lt;strong&gt;not&lt;/strong&gt; be a problem in the real world, since op-amps always have a little bit of offset, which would drive the output to one of the rails immediately on startup. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, the simulated op-amps are &lt;em&gt;too&lt;/em&gt; perfect.)&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-03-12T05:51:08.263" LastActivityDate="2011-03-12T05:51:08.263" CommentCount="2" />
  <row Id="11266" PostTypeId="2" ParentId="11256" CreationDate="2011-03-10T07:03:07.043" Score="2" ViewCount="" Body="&lt;p&gt;It's not gonna happen.  The chips are /pin/ compatible (the pins do the same things) but the internal behavour is very different.   The FTDI chips are built with bit-bang mode as a design goal, the Prolific chip is not.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-10T07:03:07.043" />
  <row Id="11267" PostTypeId="2" ParentId="2864" CreationDate="2011-03-10T07:48:44.987" Score="1" ViewCount="" Body="&lt;p&gt;I've seen a 1/4-watt 1K resistor explode when one end got connected inadvertently to line voltage while the other end was connected to a ground-referenced circuit.  Interestingly, all the current that went through the resistor also went through an ADC input on a Microchip PIC (16C73 if I recall) but the processor chip suffered no apparent damage.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-10T07:48:44.987" />
  <row Id="11269" PostTypeId="2" ParentId="11244" CreationDate="2011-03-10T08:56:11.463" Score="3" ViewCount="" Body="&lt;p&gt;I would guess that it is normally used as a seal for metal enclosures, to get a very good shield against electromagnetic interference. Since it is silicone it would also be a good seal against water or other substances.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for using it as instant wires I don't think silicone would stick well enough to other electronics to be useful.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-03-10T08:56:11.463" />
  <row Id="11270" PostTypeId="1" AcceptedAnswerId="11291" CreationDate="2011-03-10T10:58:22.063" Score="2" ViewCount="142" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/X10_%28industry_standard%29&quot; rel=&quot;nofollow&quot;&gt;X10&lt;/a&gt; is a protocol for communicating between home automation devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How it is possible to control non-wireless X10 devices (for example &lt;a href=&quot;http://www.x10europe.com/pdf/LM15E.pdf&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;) with Arduino?&lt;/p&gt;&#xA;" OwnerUserId="3064" LastActivityDate="2011-03-10T17:58:25.723" Title="How to control X10 devices with Arduino?" Tags="&lt;arduino&gt;&lt;x10&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11271" PostTypeId="2" ParentId="11237" CreationDate="2011-03-10T11:02:56.293" Score="1" ViewCount="" Body="&lt;p&gt;There are butt splice crimps such as this &lt;a href=&quot;http://www.molex.com/pdm_docs/sd/191640014_sd.pdf&quot; rel=&quot;nofollow&quot;&gt;Molex one&lt;/a&gt; which go down to 22 AWG.&#xA;Or this &lt;a href=&quot;http://uk.farnell.com/tyco-electronics-amp/0-0323994-0/crimp-terminal-butt-pidg-yellow/dp/4217627&quot; rel=&quot;nofollow&quot;&gt;Amp one&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the best way is a &lt;a href=&quot;http://uk.farnell.com/tyco-electronics-raychem/b-155-03/terminal-soldersleeve-3mm-pk100/dp/1292903&quot; rel=&quot;nofollow&quot;&gt;solder sleeve&lt;/a&gt; like this which is heatshrunk onto the pair of wires. The solder melts at the same time as the sleeving shrinks.&#xA;&lt;img src=&quot;http://i.imgur.com/GM0nV.jpg&quot; alt=&quot;Raychem solder sleeve&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-03-10T11:02:56.293" CommentCount="1" />
  <row Id="11272" PostTypeId="2" ParentId="5949" CreationDate="2011-03-10T12:16:31.610" Score="2" ViewCount="" Body="&lt;p&gt;Yes, but it would not be the computer as we know.&#xA;There is already some implementation of these using relays. Its easy to make an digital logic (AND, OR, NOT) using relays in a similar way we use transistors.&#xA;Using relays you're not worried about the flow of current, but only the presence or absence of it. The bits are represented for the relay state: active or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main problem is that with relays there is almost no space for miniaturization, meaning that a simple 4 bit microprocessor would take almost an whole room.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are some academic, but full functional, alternated computers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://web.cecs.pdx.edu/~harry/Relay/&quot; rel=&quot;nofollow&quot;&gt;http://web.cecs.pdx.edu/~harry/Relay/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a DC 3bit relay computer, but easily can me changed to AC relays&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.electronixandmore.com/project/relaycomputertwo/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.electronixandmore.com/project/relaycomputertwo/index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another DC relay computer, with lots of videos&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://nablaman.com/relay/&quot; rel=&quot;nofollow&quot;&gt;http://nablaman.com/relay/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2011-03-10T12:16:31.610" />
  <row Id="11273" PostTypeId="2" ParentId="11234" CreationDate="2011-03-10T12:55:37.410" Score="4" ViewCount="" Body="&lt;p&gt;The simplest electronic calculator your could build would be a four-function binary calculator.  You could build it using switches to input binary numbers, and 7400 family basic logic elements could handle the &lt;a href=&quot;http://en.wikipedia.org/wiki/Adder_%28electronics%29&quot; rel=&quot;nofollow&quot;&gt;adders&lt;/a&gt; that would handle the addition. You could use either individual LEDs to represent each binary number in the output, or you could use several seven-segment displays to display the number in hexadecimal.  Building a binary calculator would allow you to avoid building a decimal-to-binary converter, and would help you familiarize yourself with how digital electronics work.  If you plan to get into digital electronics as a hobby, you might want to consider getting &lt;a href=&quot;http://ozark.hendrix.edu/~burch/logisim/&quot; rel=&quot;nofollow&quot;&gt;Logisim&lt;/a&gt;, a free program that allows you to simulate your circuits before you build them.&lt;/p&gt;&#xA;" OwnerUserId="3323" LastActivityDate="2011-03-10T12:55:37.410" CommentCount="3" />
  <row Id="11274" PostTypeId="1" CreationDate="2011-03-10T12:56:49.843" Score="4" ViewCount="267" Body="&lt;p&gt;Many times we want to kept running low power devices like DSL modems, etc.&#xA;Most of these devices take 12V/9V DC so why to use ordinary UPS which convert AC to DC to AC, lots of conversion lots of power loss lots of money involved.&#xA;I want a DC UPS out put of which can be directly used by these devices.&#xA;&lt;img src=&quot;http://i.imgur.com/uD1NP.png&quot; alt=&quot;DC UPS diagram&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not pro, so I need a circuit diagram for a DC UPS, that:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Tacks 12V input.&lt;/li&gt;&#xA;&lt;li&gt;Gives 12V output to devices.&lt;/li&gt;&#xA;&lt;li&gt;If input current is available it will also charge the battery.&lt;/li&gt;&#xA;&lt;li&gt;If input current is not available, will provide current from battery to attached devices.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2037" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-10T14:34:39.440" LastActivityDate="2011-05-28T07:03:58.803" Title="12V DC UPS for Network Equipment" Tags="&lt;power-supply&gt;&lt;dc&gt;&lt;ups&gt;&lt;dc-dc&gt;" AnswerCount="5" CommentCount="6" FavoriteCount="2" />
  <row Id="11275" PostTypeId="1" AcceptedAnswerId="11901" CreationDate="2011-03-10T13:10:54.550" Score="6" ViewCount="284" Body="&lt;p&gt;I wonder, if that's possible to load lpc3154 at LPCExpresso board with custom firmware?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see that chip supports secure boot, so if AES key was programmed, it is impossible without knowing the key? Or are there any options to boot lpc3154 without knowing the key? (SD, flash, USB, JTAG... Anything?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know if key was indeed loaded?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just buying new lpc3154 is not an option - they are not in stock here anywhere, and wait times are 4 weeks+ (and a price tag &gt; than a price of this board)...&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-10T16:42:43.050" LastActivityDate="2011-03-23T15:10:57.683" Title="Reprogramming LPC3154 at LPCxpresso" Tags="&lt;lpc3154&gt;&lt;lpcxpresso&gt;&lt;secureboot&gt;" AnswerCount="2" CommentCount="8" FavoriteCount="1" />
  <row Id="11276" PostTypeId="2" ParentId="11254" CreationDate="2011-03-10T13:21:46.233" Score="0" ViewCount="" Body="&lt;p&gt;You could probably use a &lt;a href=&quot;http://en.wikipedia.org/wiki/Hartley_oscillator&quot; rel=&quot;nofollow&quot;&gt;Hartley oscillator&lt;/a&gt; or a &lt;a href=&quot;http://en.wikipedia.org/wiki/Colpitts_oscillator&quot; rel=&quot;nofollow&quot;&gt;Colpitts oscillator&lt;/a&gt;.  If you know some basic electronics, you could easily design your own &lt;a href=&quot;http://en.wikipedia.org/wiki/RLC_circuit&quot; rel=&quot;nofollow&quot;&gt;RLC circuit&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="3323" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-22T11:25:35.403" LastActivityDate="2011-03-22T11:25:35.403" CommentCount="1" />
  <row Id="11277" PostTypeId="2" ParentId="11263" CreationDate="2011-03-10T13:27:57.240" Score="1" ViewCount="" Body="&lt;p&gt;I remember some years ago using the Analog Devices MAT02 for this purpose. It seems that this is not recommended for new designs but the replacement is the &lt;a href=&quot;http://www.analog.com/en/other-products/matched-transistors/mat12/products/product.html&quot; rel=&quot;nofollow&quot;&gt;MAT12&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-03-10T13:27:57.240" CommentCount="1" />
  <row Id="11278" PostTypeId="2" ParentId="11274" CreationDate="2011-03-10T13:42:36.550" Score="1" ViewCount="" Body="&lt;p&gt;As a starting point I would research voltage regulators and search for a battery that meets your needs. There are different types that could be used such as linear(cheap but inefficient) and switching(little more pricey but efficient). Making sure that the battery will only output current when there is no input voltage is pretty simple. As long as the input voltage is greater than that of the battery, the battery will act as a power sink, and the input will charge the battery. Otherwise the battery will act as a power source. It might also be useful for you to know that a 12 volt car or deep cycle battery is typically around 12.5 volts when it is fully charged. That means that you could set your input voltage at around 12.5 volts to charge the battery and set the voltage regulator output at 12 volts.. Hope this helps.   &lt;/p&gt;&#xA;" OwnerUserId="1337" LastActivityDate="2011-03-10T13:42:36.550" />
  <row Id="11279" PostTypeId="2" ParentId="11234" CreationDate="2011-03-10T14:33:18.410" Score="2" ViewCount="" Body="&lt;p&gt;You could use a development kit with everything already on the board to enable you to focus on the software.  For example &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en024858&amp;amp;part=DM240001&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en024858&amp;amp;part=DM240001&lt;/a&gt; this kit has PIC, LCD and few buttons.  There are plenty of headers to add additional buttons.  The one drawback is the LCD is bigger then you might want to use initially but it will certainly get you started.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you search around you might be able to find smaller (and cheaper ones) that you can start of on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a kit like this will make it easier to start of writing your code as they will be some examples, and removes the issue of hardware problems as it is all set up correctly.  Another drawback is this kit uses the high end pics which is overkill for a calculator project, but it does give you room to grow and modifiy it in future to do other tasks.  It will also give you schematics to use as starting point for making your own boards in the future.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2011-03-10T14:33:18.410" />
  <row Id="11280" PostTypeId="2" ParentId="11274" CreationDate="2011-03-10T14:40:46.313" Score="3" ViewCount="" Body="&lt;p&gt;First of all you need to realize that a 12V SLA battery is not, ever 12V, if it's charging then it sits around 14.3V (but that's dependent on chemistry and temperature) when it's discharging then it can be as low as 10V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most robust solution is to make sure that all the equipment can tolerate 10-15 V, because that will allow you to get rid of any output regulator which will waste some energy while on battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Almost all electronics that says 12V will easily tolerate 10-15V, much of it will be happy with 8-24V as well, the main exception are computers that feed the 12V input directly to harddisks, those devices really like a regulated 12V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good charger will be needed that regulates the float voltage according to temperature and also limits the charging current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One solution would be:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A beefy AC/DC off-the-shelf mains supply, a 19V power brick for a laptop could do.&lt;/li&gt;&#xA;&lt;li&gt;A Buck DC/DC converter handling charging, but a simple LM317 could also be used.&lt;/li&gt;&#xA;&lt;li&gt;A Buck DC/DC converter handling the on-line output regulation.&lt;/li&gt;&#xA;&lt;li&gt;A switch (2 FETs) which switches over to battery if the output of the online-converter drops out of regulation.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Buck converters tend to be simpler and more efficient than buck/boost converters, so that's a good reason to prefer those in a design, but if you really want a regulated 12V output then there is no way to avoid a buck/boost converter and the plan becomes:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A beefy AC/DC off-the-shelf mains supply, a 19V power brick for a laptop would do nicely.&lt;/li&gt;&#xA;&lt;li&gt;A Buck DC/DC converter handling charging, but a simple LM317 could also be used, especially if the battery is stored at a fixed temperature, (look up &quot;SLA charger lm317).&lt;/li&gt;&#xA;&lt;li&gt;A switch (an opamp controllring two 2 FETs) which switches the input of the output regulator from the primary input DC over to battery if it drops below the battery voltage or simply two diodes.&lt;/li&gt;&#xA;&lt;li&gt;A Buck/boost DC/DC converter handling the output regulation.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;A good buck/boost converter topology is SEPIC, because you only need one FET and a single coil, so it's cheaper than two converters back-to-back: &lt;a href=&quot;http://dren.dk/carpower.html&quot; rel=&quot;nofollow&quot;&gt;http://dren.dk/carpower.html&lt;/a&gt; the linked design will output the same voltage no matter what the input voltage is (8-24 V)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... or, if you are lucky, you can just buy one:&#xA;&lt;a href=&quot;http://www.mini-box.com/micro-UPS-load-sharing&quot; rel=&quot;nofollow&quot;&gt;http://www.mini-box.com/micro-UPS-load-sharing&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastEditorUserId="1675" LastEditorDisplayName="" LastEditDate="2011-03-10T14:48:58.613" LastActivityDate="2011-03-10T14:48:58.613" CommentCount="2" />
  <row Id="11281" PostTypeId="1" CreationDate="2011-03-10T14:54:26.387" Score="0" ViewCount="60" Body="&lt;p&gt;I have a design in Xilinx system generator which meets maximum frequency of &lt;strong&gt;50MHz&lt;/strong&gt; (I found this from &lt;strong&gt;Timing and Power Analyzer&lt;/strong&gt; of &lt;strong&gt;System generator&lt;/strong&gt;). However, my FPGA board offers &lt;strong&gt;100MHz&lt;/strong&gt; clock rate. How could I solve this issue? (is there any way like creating a divided clock which can be assigned to the &lt;strong&gt;FPGA clock period&lt;/strong&gt; of &lt;strong&gt;clocking options&lt;/strong&gt; in &lt;strong&gt;system generator token&lt;/strong&gt;?)&lt;/p&gt;&#xA;" OwnerUserId="3194" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-10T14:57:24.307" LastActivityDate="2011-04-09T15:27:22.723" Title="System generator frequency issue" Tags="&lt;fpga&gt;&lt;xilinx-system-generator&gt;" AnswerCount="1" />
  <row Id="11282" PostTypeId="2" ParentId="11281" CreationDate="2011-03-10T15:08:56.530" Score="1" ViewCount="" Body="&lt;p&gt;Im not an expert on this but a little research (30seconds) on our favorite search enginge brought me to someone who had the exact same problem 5 years ago. I think you can go on from there, eventhough the frequency is a little different.&#xA;&lt;a href=&quot;http://www.velocityreviews.com/forums/t294219-frequency-divider.html&quot; rel=&quot;nofollow&quot;&gt;http://www.velocityreviews.com/forums/t294219-frequency-divider.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2995" LastActivityDate="2011-03-10T15:08:56.530" />
  <row Id="11283" PostTypeId="2" ParentId="11274" CreationDate="2011-03-10T15:41:44.617" Score="2" ViewCount="" Body="&lt;p&gt;My suggestion would be to use an above-voltage battery - like a 24V, 36V or 48V battery. The voltage can be stepped up to charge it, and stepped down to run devices. I'd highly recommend a switching boost regulator for the charging (use a dedicated charging IC) and a buck converter for the discharging. Make sure any converter is rated to handle the maximum voltage of the battery - for example a 48V battery may reach 58V when fully charged! Also, be careful of voltages over about 60V (dc; 30V for ac) - they are generally considered hazardous as they can cause electric shock and require proper wiring standards.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-10T15:41:44.617" />
  <row Id="11284" PostTypeId="2" ParentId="11263" CreationDate="2011-03-10T15:48:05.890" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://falstad.com/circuit/#%24+1+5.0E-6+12.050203812241895+54+5.0+50%0Aa+224+224+320+224+0+15.0+-15.0+1000000.0%0Ad+320+96+224+96+1+0.805904783%0Aw+224+128+224+96+0%0Ac+224+64+320+64+0+1.0E-6+0.5736761776961821%0Aw+320+64+320+96+0%0Aw+224+64+224+96+0%0Aw+224+128+224+208+0%0Ar+224+208+144+208+0+1000.0%0AR+144+208+112+208+0+1+40.0+3.0+3.0+0.0+0.5%0Ag+224+240+224+256+0%0At+336+256+336+224+0+1+0.0+0.6332109005736126+100.0%0Aw+352+224+368+224+0%0Aw+368+224+368+256+0%0Aw+368+256+336+256+0%0Aw+368+224+400+224+0%0Ai+400+160+400+224+0+0.01%0AR+400+160+400+128+0+0+40.0+10.0+0.0+0.0+0.5%0Aa+400+240+496+240+1+15.0+-15.0+1000000.0%0Ar+400+304+496+304+0+15000.0%0Ar+400+304+400+368+0+1000.0%0Aw+400+256+400+304+0%0Aw+496+240+496+304+0%0Ag+400+368+400+384+0%0AO+496+240+544+240+0%0Ap+144+208+144+272+0%0Ag+144+272+144+288+0%0At+272+160+272+128+1+1+-5.736704409917721E-6+0.5736704409917721+100.0%0Aw+224+128+256+128+0%0Aw+288+128+320+128+0%0Aw+320+96+320+128+0%0Aw+320+128+320+224+0%0Ag+272+160+272+176+0%0Ao+8+64+0+34+10.0+0.003125+0+-1+in%0Ao+23+64+0+34+2.5+2.44140625E-5+1+-1+out%0Ao+24+64+0+226+10.0+3.2+2+23+out+vs+in%0A&quot; rel=&quot;nofollow&quot;&gt;This circuit&lt;/a&gt; looks to be a log amplifier using two op-amps, two transistors, a few passives and a current source. However, I'm not sure how suitable it is for your application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Screenshot:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/RF7Iy.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-03-10T17:36:54.310" LastActivityDate="2011-03-10T17:36:54.310" CommentCount="8" />
  <row Id="11285" PostTypeId="2" ParentId="11263" CreationDate="2011-03-10T16:07:05.063" Score="4" ViewCount="" Body="&lt;p&gt;How about the &lt;a href=&quot;http://www.linearsystems.com/datasheets/LS310-3.pdf&quot; rel=&quot;nofollow&quot;&gt;LS312&lt;/a&gt; from Linear Systems? Some people in &lt;a href=&quot;http://www.gearslutz.com/board/geekslutz-forum/451413-lm394-replacement.html&quot; rel=&quot;nofollow&quot;&gt;other forums&lt;/a&gt; claim it's better than the 5% worst-case matching described on the datasheet.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-10T16:07:05.063" CommentCount="1" />
  <row Id="11286" PostTypeId="2" ParentId="11254" CreationDate="2011-03-10T16:07:45.733" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://webspace.webring.com/people/jl/leon_heller/minidds.html&quot; rel=&quot;nofollow&quot;&gt;My version of Jesper's MiniDDS&lt;/a&gt; will give you a variety of waveforms at 60 kHz to 80 kHz. It can be built for about £10.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-10T16:07:45.733" CommentCount="3" />
  <row Id="11287" PostTypeId="1" CreationDate="2011-03-10T16:11:28.553" Score="1" ViewCount="112" Body="&lt;p&gt;I a working on a circuit that has components that need 3.3V and 5V. My power input is 12VDC and can not be changed. The 3.3V components use about 510mA of current and the 5V components use about 155mA.  My first attempt at a circuit used two linear voltage regulators in SOT-223 packages. The 5V reg use 12V as it's input voltage and the 3.3V reg used 5V as it's input. Of course the 5V regulator get's extremly hot and then shuts off (luckily it has thermal protection!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have read some other posts on this forum about how to dissipate the heat with the PCB traces and also to do it using the case (which is a possibility in my case), however it would be much preferable for this design for the enclosure to not get warm. People using it may complain. So I am considering using a switching-mode voltage regulator like this &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=AP1509-50SGDICT-ND&quot; rel=&quot;nofollow&quot;&gt;AD1509&lt;/a&gt;. My concern is with the noise. My board has a WiFi module on it and I am wondering if the performance will be affected by the switching noise. The AD1509 switches at 150kHz and I think WiFi is in the 2.5GHz range so I should be okay right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, do you think the switching voltage regulator will also get hot or if I just a big copper pad under it will it be okay?&lt;/p&gt;&#xA;" OwnerUserId="1235" LastActivityDate="2011-03-11T11:03:09.657" Title="Switching Voltage Regulator with WiFi Ethernet Controller Bad?" Tags="&lt;power-supply&gt;&lt;wifi&gt;&lt;noise&gt;&lt;switching-voltage-reg&gt;" AnswerCount="3" />
  <row Id="11288" PostTypeId="2" ParentId="11287" CreationDate="2011-03-10T16:21:26.290" Score="0" ViewCount="" Body="&lt;p&gt;Don't use traces; use a heat sink instead.  They are cheap and easy to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't use the switching regulator directly, use it for 12 to ~6 V then regulate down.  That saves power and still gets a clean final output.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-10T16:21:26.290" CommentCount="4" />
  <row Id="11289" PostTypeId="1" AcceptedAnswerId="13612" CreationDate="2011-03-10T16:40:12.740" Score="2" ViewCount="101" Body="&lt;p&gt;I know you can stop VHDL code from being compiled by the synthesizer:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;-- pragma translate_off&#xA;assert thisDoesNotGetSynthesized();&#xA;-- pragma translate_on&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;BUT, there are also other ways to write this, including &lt;code&gt;-- synopsys translate_off&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which are all the valid ways to turn off synthesis? Is there a definitive list on which are valid pragmas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally: what are the &lt;em&gt;syntax rules&lt;/em&gt; for these pragmas? Is the whitespace in the pragma important? Can the pragma occur anywhere in any comment, or does it need to be the only thing in that comment? &lt;/p&gt;&#xA;" OwnerUserId="3145" LastEditorUserId="3145" LastEditorDisplayName="" LastEditDate="2011-03-27T20:06:02.833" LastActivityDate="2011-04-28T14:17:33.553" Title="Which are the the valid VHDL compiler pragmas?" Tags="&lt;vhdl&gt;&lt;synthesizer&gt;" AnswerCount="3" />
  <row Id="11290" PostTypeId="1" AcceptedAnswerId="11342" CreationDate="2011-03-10T17:34:43.403" Score="2" ViewCount="116" Body="&lt;p&gt;Does anyone know some ref of high voltage high bandwidth analog multiplexer? I am looking for a mux that can tolerate input voltages up to 10V, but has also a high bandwidth of at least 1Ghz. I am not sure that such component actually exists...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need a high bandwidth because I want to pass very short pulses, typically between 1 to 10 ns, in the multiplexer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Follow-up:&lt;/strong&gt; I just found parts from Analog that look promising: ADG1236 and ADG1213. Both have a 1 GHz bandwidth and can use a power supply of +/-15V. However the bandwidth is given for a load of 50 ohm. Will the bandwidth heavily depend on the load? In that case, what would be the bandwidth for, say, a load of 1 kohm?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="2740" LastEditorUserId="2740" LastEditorDisplayName="" LastEditDate="2011-03-11T14:36:41.857" LastActivityDate="2011-03-11T21:42:26.430" Title="High voltage high bandwidth analog mux" Tags="&lt;analog&gt;&lt;multiplexing&gt;&lt;high-frequency&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="11291" PostTypeId="2" ParentId="11270" CreationDate="2011-03-10T17:58:25.723" Score="2" ViewCount="" Body="&lt;p&gt;here is a good place to start:&#xA;&lt;a href=&quot;http://www.arduino.cc/en/Tutorial/X10&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Tutorial/X10&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3336" LastActivityDate="2011-03-10T17:58:25.723" CommentCount="1" />
  <row Id="11292" PostTypeId="2" ParentId="11287" CreationDate="2011-03-10T18:05:03.100" Score="1" ViewCount="" Body="&lt;p&gt;A switching power supply will be noisier than a linear regulator, no question. The only way to know if it will disturb the wifi is to power it up and see what happens. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any switching regulator will dissipate power as a function of conduction losses and switching losses. These parts with an integrated MOSFET do need PCB cooling - usually a multilayer PCB with relatively large 'islands' of copper interconnected with vias. Again, you'll have to do some math to figure out a loss estimate, and gauge the copper size accordingly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet says that the 5V part at 2A load and 12V in operates at around 83% efficiency. So, for 10W out you're losing just over 2W in the device (and the external diode that completes the buck converter). This will scale down somewhat with your reduced loading (conduction losses will drop, switching losses probably won't). &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-10T18:05:03.100" />
  <row Id="11293" PostTypeId="1" AcceptedAnswerId="11295" CreationDate="2011-03-10T18:25:49.993" Score="4" ViewCount="324" Body="&lt;p&gt;So I often see books/tutorials and references when programming in assembly to a microprocessor.....then I see some refer to it as a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance the Atmel ATtiny2313....i saw some tutorials on, some call it a microprocessor, some call it a microcontroller?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which is it? and is programming them (basically) the same? (in assembly)&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-04-14T13:39:13.740" Title="Programming Differences between a Microcontroller and a Microprocessor?" Tags="&lt;microcontroller&gt;&lt;microprocessor&gt;&lt;assembly&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="11294" PostTypeId="2" ParentId="11293" CreationDate="2011-03-10T18:30:40.817" Score="5" ViewCount="" Body="&lt;p&gt;The difference is that the microcontroller includes on-chip memory like Flash EEPROM and RAM, and peripherals like parallel and serial I/O. With the first microprocessors those were all external devices. Instead of the I/O's microprocessors had an the address and data bus brought to their pins.&lt;br&gt;&#xA;The way you write code for either is the same.  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-03-10T18:30:40.817" CommentCount="1" />
  <row Id="11295" PostTypeId="2" ParentId="11293" CreationDate="2011-03-10T18:46:59.817" Score="8" ViewCount="" Body="&lt;p&gt;This is really two questions in one...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Firstly, what is the difference between a microcontroller and a microprocessor?&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Microprocessor&lt;/strong&gt; is a purely a CPU that follows a set of instructions read from an external memory bus. It controls external peripherals (such as screen, keyboard, mouse, hard drive, etc) via an external communications bus. When you program a microprocessor, your program is external to the device. In a computer, this memory is initially the boot up BIOS ROM which initially reads the operating system from the hard drive into RAM memory, then continues to execute it from there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Microcontroller&lt;/strong&gt; is kinda like an all-in-one CPU + Memory, with some external ports to communicate with the outside world. It's self contained and doesn't use external memory to hold it's program (although if needed it can read and write working data to external memory).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Secondly, is programming a microcontroller and microprocessor the same?&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In some ways yes, and in some ways no.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assembly language is a broad term that describes a set of instructions that the CPU can directly understand. When you 'compile' assembly language, is doesn't really compile anything, all it does it convert it to a sequence of bytes that represent the commands and plugs in some relative memory locations. This is common to both microprocessors and microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, different types of CPU understand a different set of CPU instructions. For example, if you write an assembly language program that works with a pic 16F877 microcontroller, it will be complete nonsense to a microprocessor or any other microcontroller outside of the 16Fxxx family of pic microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, although assembly works in a similar way across all microprocessors and microcontrollers, the actual list of instructions that you write are very different. To write in assembly language, you need to have an in depth knowledge of the devices architecture, which you can normally get from the datasheet in the case of a microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-10T18:46:59.817" CommentCount="5" />
  <row Id="11296" PostTypeId="1" CreationDate="2011-03-10T18:58:58.497" Score="0" ViewCount="93" Body="&lt;p&gt;Hi. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am getting started with robotics and would like to start with some roomba programming. I come from a programmer background so I thought that would be a good starting point and since I already owned a roomba it was a natural choice. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I looked into the how to get it connected to my computer and there are various options out there but I am not sure which is best. Here are my conditions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I don't want to make anything. Not that advanced yet. &lt;/li&gt;&#xA;&lt;li&gt;It needs to be reliably run on a Mac and linux machine. &lt;/li&gt;&#xA;&lt;li&gt;It can be bluetooth but doesn't have to be. I'm planning on mounting my netbook to the top of the roomba. &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'd appreciate help in knowing which way to go. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: A bit more info that is relevant. I am planning on programming it using Pyro, so any solution needs to support pyro (which is why my mounted netbook idea came into being). Also, I own an Arduino and a Teensy although I wasn't planning to use them for this project. Just mentioning them in case they can be useful. &lt;/p&gt;&#xA;" OwnerUserId="3244" LastEditorUserId="3244" LastEditorDisplayName="" LastEditDate="2011-03-10T22:39:51.533" LastActivityDate="2011-04-09T23:27:23.047" Title="Roomba Connector" Tags="&lt;robotics&gt;&lt;connector&gt;&lt;roomba&gt;" AnswerCount="1" />
  <row Id="11297" PostTypeId="2" ParentId="11293" CreationDate="2011-03-10T20:16:02.860" Score="5" ViewCount="" Body="&lt;p&gt;Although this tends to be a grey area, another common difference between microcontrollers and microprocessors is that microcontrollers often use &lt;a href=&quot;http://en.wikipedia.org/wiki/Harvard_architecture&quot; rel=&quot;nofollow&quot;&gt;Harvard architecture&lt;/a&gt; (separate address space for code and data), while micrprocessors almost all use &lt;a href=&quot;http://en.wikipedia.org/wiki/Von_Neumann_architecture&quot; rel=&quot;nofollow&quot;&gt;Von Neumann architecture&lt;/a&gt; (combined address space for code and data).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Examples of microntroller families using Harvard architecture include: AVRs, Intel 8051, PICs (except PIC32, see below), and ARM Cortex-M3.  A notable exception are Freescale processors, like the HCS08, which use Von Neumann architecture, as does the Parallax Propeller. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This affects programming in several ways (examples shown below use C):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There may be several types of RAM, each with their own address space.  For example, the 8051 has external data (xdata) which is addressed separate from the first 256 bytes of RAM, even though both are implemented on the same chip.  So one has to use qualifiers on variables declarations like &lt;code&gt;unsigned int xdata foo;&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If constants are declared in code memory, they may need to be copied to RAM before they can be accessed.  Or, there needs to be a way to access code memory as if it were data -- e.g. the code qualifier for 8051s, or PIC's Program Space Visiblity (PSV) feature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These non-standard ways of accessing code and RAM tend to be the major difference (besides peripherals) when porting C code from one chip family to another.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can't execute code from RAM in a strict Harvard architecture, so there can't be any self-modifying code (unless you count re-flashing program memory on the fly).  However the PIC32 has a modified Harvard architecture that allows code to be executed in RAM.  The Parallax Propeller actually makes use of its ability to modify code to perform subroutine returns, since it has no hardware stack.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-03-10T20:22:02.497" LastActivityDate="2011-03-10T20:22:02.497" />
  <row Id="11298" PostTypeId="2" ParentId="11290" CreationDate="2011-03-10T20:46:14.863" Score="4" ViewCount="" Body="&lt;p&gt;How about a relay? I guess it depends on how fast you want to switch and the impedance of what you're switching&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-10T20:46:14.863" CommentCount="2" />
  <row Id="11299" PostTypeId="2" ParentId="11296" CreationDate="2011-03-10T21:24:30.857" Score="1" ViewCount="" Body="&lt;p&gt;I've added to my roomba 530 a RouterBoard RB411 with a WiFi MiniPCI card and connected the routerboard serial port to the roomba connector using a level adapter (there are many schematics on &quot;hacking roomba&quot; sites, using just diodes and resistors. I've used the common MAX232).&#xA;Routerboard can be powered by unregulated roomba battery voltage thru the connector, and with a driver RFC2217 compliant you can send command to a virtual com port on the local machine. Commands are relayed to the routerboard serial port and to the robot, and the robot answers are relayer to the virtual com port on the local machine. &#xA;The RB411 wired ethernet port can be used to relay an onboard IP camera.&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-03-10T21:24:30.857" />
  <row Id="11300" PostTypeId="2" ParentId="11274" CreationDate="2011-03-10T21:31:50.350" Score="1" ViewCount="" Body="&lt;p&gt;My approach would select a 24 volt battery or two car batteries or similar in series. Then &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=LM2678T-12-ND&quot; rel=&quot;nofollow&quot;&gt;regulate that 24 volts to produce your 12 volt output&lt;/a&gt;. Then buy or build a AC charger for the battery(ies). &lt;a href=&quot;http://www.batterystuff.com/battery-chargers/12-volt/marine-chargers/GEN2.html&quot; rel=&quot;nofollow&quot;&gt;http://www.batterystuff.com/battery-chargers/12-volt/marine-chargers/GEN2.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-03-10T21:31:50.350" />
  <row Id="11301" PostTypeId="2" ParentId="11290" CreationDate="2011-03-10T21:48:01.953" Score="2" ViewCount="" Body="&lt;p&gt;As usual, I can suggest going for discrete FET's controlled from some shift-registers (if you are limited on pins).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While switch speed might be some 10ns, once it's settled, it's like resister, without much bandwidth limiting.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-11T21:03:29.227" LastActivityDate="2011-03-11T21:03:29.227" CommentCount="1" />
  <row Id="11302" PostTypeId="1" AcceptedAnswerId="11682" CreationDate="2011-03-10T22:09:20.273" Score="0" ViewCount="104" Body="&lt;p&gt;I can program LEDs 0 to 3 to light up, but I get an error when I try to assign LEDs 4 to 7. Why is that?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-03-10T23:10:18.393" LastActivityDate="2011-04-17T21:27:53.457" Title="How to light up LEDs 4-7 on a Nexys2 board" Tags="&lt;led&gt;&lt;fpga&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="11304" PostTypeId="2" ParentId="11302" CreationDate="2011-03-10T23:28:51.380" Score="0" ViewCount="" Body="&lt;p&gt;LD4 is connected to both E16 and E17 and LD5 is connected to both P15 and P16, which is rather strange. There is a similar problem with LD6 and LD7. Perhaps you have to enable both outputs in each case. It might be best to contact Digilent support about the anomaly.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-10T23:33:58.690" LastActivityDate="2011-03-10T23:33:58.690" CommentCount="2" />
  <row Id="11305" PostTypeId="2" ParentId="10944" CreationDate="2011-03-11T00:01:08.017" Score="3" ViewCount="" Body="&lt;p&gt;If you're given that 5 W is being &lt;em&gt;dissipated&lt;/em&gt; by a component, than that strongly implies that it will be burning that as heat.  Other components around it will likely also be dissipating some heat as well, but you make it sound like this is some idealized academic question for you learning some thermal sim (FEA?) package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the parts that I've mostly dealt with&amp;mdash;discrete MOSFETs&amp;mdash;the &quot;power rating&quot; is usually given as a current rating under some conditions (easily convertible into watts), and it varies wildly depending on the thermal resistance from the junction (T&lt;sub&gt;J&lt;/sub&gt;, all that really matters) to ambient (T&lt;sub&gt;A&lt;/sub&gt;).  A free standing part with no heat sinking may have several or dozens of times the thermal resistance compared with even modest heatsinks.  Additionally, the figure might be quoted at T&lt;sub&gt;A&lt;/sub&gt; = 25 °C, not the actual maximum temperature your system will operate at, so even if you have a part that &lt;em&gt;can&lt;/em&gt; dissipate 5 W, there might be some caveats.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-11T00:01:08.017" />
  <row Id="11306" PostTypeId="2" ParentId="11289" CreationDate="2011-03-11T00:44:20.877" Score="0" ViewCount="" Body="&lt;p&gt;To my knowledge:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;-- synopsys translate_off&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;-- pragma translate_off&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;-- synthesis translate_off&lt;/code&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the synthesizer tool they might or might not work.&lt;/p&gt;&#xA;" OwnerUserId="3078" LastActivityDate="2011-03-11T00:44:20.877" CommentCount="2" />
  <row Id="11307" PostTypeId="1" AcceptedAnswerId="11360" CreationDate="2011-03-11T02:26:37.397" Score="5" ViewCount="147" Body="&lt;p&gt;Hi, I'm planning to build a table tennis robot using an Arduino controller for the location/placement logistics and control, but I'm stuck on one physical detail and don't know where else to ask. I want to be able to rotate the end of the pipe independently of the base, but I can't find any fixtures that would allow for this. To clarify what I'm looking for, think of joining two pipes together axially - typically the joint will be fixed and they won't be able to rotate in the coupling. I'm looking for a coupling that will allow one end to rotate independently of the other end with minimal friction so a small servo can perform the rotation (obviously being water tight is not a requirement :-) ). Anybody know what the terminology for such a coupling is, or an exact example of one? I'm looking for an opening that can fit a ping pong ball, so 2&quot; inner diameter should be plenty. Thanks for any insight!&lt;/p&gt;&#xA;" OwnerUserId="3339" LastEditorUserId="3339" LastEditorDisplayName="" LastEditDate="2011-03-11T12:19:52.393" LastActivityDate="2011-03-12T07:26:07.593" Title="Join two pipes with independent rotation?" Tags="&lt;arduino&gt;&lt;robotics&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="11308" PostTypeId="2" ParentId="11252" CreationDate="2011-03-11T02:57:43.983" Score="0" ViewCount="" Body="&lt;p&gt;The AC current rating on the power supply label indicates the maximum steady-state current draw at the lowest specified line and the maximum specified load. If both power supplies are delivering 65W on the nose, the one drawing 1.5A may be marginally more efficient than the one drawing 1.7A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's usually not a good idea to use an adapter set to a higher voltage on a piece of equipment expecting a lower voltage. The device being powered could end up dissipating higher than expected power, causing possible thermal issues and/or shortened life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using an adapter with the same voltage and higher current will be OK as long as the device being powered doesn't have a fault. Having more power available to crank into an abnormal condition can lead to bad things like fire. If we're talking a few extra watts, that's one thing. A few hundred more, well, that could be dangerous...&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-11T02:57:43.983" />
  <row Id="11309" PostTypeId="1" AcceptedAnswerId="11314" CreationDate="2011-03-11T04:12:40.473" Score="1" ViewCount="137" Body="&lt;p&gt;I have a project that needs to be in use on saturday (afterwards I'll be able to complete it properly) and my optoisolators haven't come in yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using an arduino to switch mains power (on/off) using a triac, Is there anyway to safely wire the microcontroller to the triac without using an optoisolator?&lt;/p&gt;&#xA;" OwnerUserId="1729" LastActivityDate="2011-03-11T14:31:51.187" Title="Microcontroller + Triac without an optoisolator" Tags="&lt;microcontroller&gt;&lt;triac&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="11310" PostTypeId="2" ParentId="11227" CreationDate="2011-03-11T04:44:36.887" Score="0" ViewCount="" Body="&lt;p&gt;Have you considered using an actual 80's CPU?&#xA;If you're going to build less than 10 items, it should be OK using your favorite 80's CPU, even if it's long been declared obsolete and no longer manufactured -- there's still a bunch of parts kicking around &lt;a href=&quot;http://opencircuits.com/Supplier&quot; rel=&quot;nofollow&quot;&gt;electronics surplus stores&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have fond memories of the 6502, 6802, or the 6809?&#xA;Perhaps you will be interested in the &lt;a href=&quot;http://www.vintage-computer.com/vcforum/showthread.php?23698-homebrew-6809-6802-6502-system&quot; rel=&quot;nofollow&quot;&gt;N8VEM 6x0x homebrew computer project&lt;/a&gt;.&#xA;Perhaps you can pick up a few tips from the &lt;a href=&quot;http://n8vem-sbc.pbworks.com/w/page/4200908/FrontPage&quot; rel=&quot;nofollow&quot;&gt;N8VEM Home Brew Computer Project wiki&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have fond memories of the 68000?&#xA;Perhaps you will be interested in how to &lt;a href=&quot;http://wilcoxengineering.com/68000-microprocessor&quot; rel=&quot;nofollow&quot;&gt;design a wire-wrapped 68000 board that plugged into the S-100 computer bus&lt;/a&gt;.&#xA;Or perhaps you will be more interested picking up tips for working with a surface-mount 68000 in the &lt;a href=&quot;http://en.wikipedia.org/wiki/Minimig&quot; rel=&quot;nofollow&quot;&gt;Minimig project&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-11T04:44:36.887" CommentCount="1" />
  <row Id="11311" PostTypeId="2" ParentId="11227" CreationDate="2011-03-11T05:17:04.643" Score="0" ViewCount="" Body="&lt;p&gt;Have you considered the Parallax Propeller chip?&#xA;As far as I know, it is the only 32-bit CPU (microprocessor or microcontroller) that is currently being manufactured in a DIP package. (It's also available in SMT, like every other 32-bit CPU currently being manufactured).&#xA;I've seen several projects with it that individually meet each of your specs,&#xA;although I haven't seen a single project that does all of them:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;8 Mhz or more -- yes&lt;/li&gt;&#xA;&lt;li&gt;256 / 512 KB external memory; 128 KB eprom -- The &lt;a href=&quot;http://en.wikipedia.org/wiki/HYDRA_Game_Development_Kit&quot; rel=&quot;nofollow&quot;&gt;HYDRA Game Development Kit&lt;/a&gt; Wikipedia article claims that a 512 kB RAM, 128 kB EEPROM expansion card can be plugged into the Hydra, which seems to meet your spec for external memory&lt;/li&gt;&#xA;&lt;li&gt;320 x 200 x 32 colors (VGA interface) -- The Hydra produces 800x600x64 colors VGA.&lt;/li&gt;&#xA;&lt;li&gt;SD card -- the &lt;a href=&quot;http://propeller.wikispaces.com/interface&quot; rel=&quot;nofollow&quot;&gt;Propeller wiki mentions several SD card projects&lt;/a&gt;).&lt;/li&gt;&#xA;&lt;li&gt;development environment -- the &lt;a href=&quot;http://en.wikipedia.org/wiki/Parallax_Propeller&quot; rel=&quot;nofollow&quot;&gt;Parallax Propeller&lt;/a&gt; wikipedia article claims that &quot;The Propeller is known for being easy to program.&quot;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-11T05:17:04.643" />
  <row Id="11312" PostTypeId="1" CreationDate="2011-03-11T05:39:43.110" Score="1" ViewCount="92" Body="&lt;p&gt;I'm looking to be able to build a kind of course location based system where a mobile Arduino will scan for a list of currently visible (discoverable) bluetooth points, and then depending on pattern matching will do work accordingly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody know of how this might be achieved? The bluetooth shields and bluetooth version of Arduino seem to just be endpoints for attaching to the serial of the Arduino itself. Does anyone have experience with this?&lt;/p&gt;&#xA;" OwnerUserId="3340" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-13T06:51:51.603" LastActivityDate="2011-05-12T07:33:29.153" Title="Scanning for discoverable bluetooth devices with Arduino" Tags="&lt;arduino&gt;&lt;bluetooth&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="11313" PostTypeId="2" ParentId="10146" CreationDate="2011-03-11T08:47:11.827" Score="0" ViewCount="" Body="&lt;p&gt;Ok, I've found a solution to this problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The answer is to place the centre pad in the package with &quot;stop&quot; and &quot;cream&quot; turned off, then manually draw in rectangles for the &quot;stop&quot; and &quot;cream&quot; layers over the pad as they would've appeared anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The physical end result is the same, but placing vias on the pad doesn't produce DRC errors.&lt;/p&gt;&#xA;" OwnerUserId="2960" LastActivityDate="2011-03-11T08:47:11.827" />
  <row Id="11314" PostTypeId="2" ParentId="11309" CreationDate="2011-03-11T08:56:00.163" Score="3" ViewCount="" Body="&lt;p&gt;Depends what the micro is powered from and referenced to. You can run the micro on the live side. However, you give yourself a big problem in attaching debuggers and programmers to the micro, because the 0V side of the programmer usually goes to mains earth through the PC power supply. An &lt;a href=&quot;http://bb-europe.com/product.asp?SKU=UISOHUB4&amp;amp;Trail=16&amp;amp;TrailType=Top&quot; rel=&quot;nofollow&quot;&gt;isolated USB hub&lt;/a&gt; can help. Be very careful with this type of circuit - I know of at least one blown up motherboard caused by this type of work, and there is risk of electrocution.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-03-11T08:56:00.163" CommentCount="3" />
  <row Id="11315" PostTypeId="1" CreationDate="2011-03-11T09:15:26.250" Score="2" ViewCount="53" Body="&lt;p&gt;This is the first time I have used &lt;a href=&quot;http://littlebirdelectronics.com/products/4wd-miniq-complete-kit&quot; rel=&quot;nofollow&quot;&gt;this product&lt;/a&gt; (an Arduino-compatible robot) and I'm having some trouble. I've done this on 2 different boards now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I select the serial port, load up the blink sketch....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First time - it loads beautifully and I get the Blink sketch I loaded.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I then change the values for a longer blink....load it and get the error&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;avrdude: stk500_recv(): programmer is not responding&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I get a pause as though its about to start loading the code....but then the error.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="21" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-09T20:36:14.350" LastActivityDate="2011-05-09T20:36:14.350" Title="Problem loading sketch to arduino MiniQ" Tags="&lt;arduino&gt;&lt;error&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="11316" PostTypeId="1" AcceptedAnswerId="11319" CreationDate="2011-03-11T09:20:21.080" Score="1" ViewCount="306" Body="&lt;p&gt;How to measure one or more PT100/1000 (PTC Resistor) with a Arduino/atmega328 over I2C?&#xA;Are there any ready  microchips? Need to constructing my own circuit? If so, are there any ready schematics?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="3341" LastActivityDate="2011-03-11T09:56:45.767" Title="How to measure a PT100/1000 with a Arduino over I2C" Tags="&lt;adc&gt;&lt;temperature&gt;&lt;ptc&gt;" AnswerCount="1" />
  <row Id="11317" PostTypeId="2" ParentId="10944" CreationDate="2011-03-11T09:36:27.697" Score="0" ViewCount="" Body="&lt;p&gt;Sounds like the efficiency has already been taken into account, if you are given a dissipation figure, so you can't use the efficiency factor again. Maybe there is 6W going in, and 0.8W coming out, so 5.2W is dissipated. (In this case efficiency was 0.8/6 = 13%). You couldn't use the 13% again, on top of the 5.2W.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-03-11T09:36:27.697" />
  <row Id="11318" PostTypeId="1" AcceptedAnswerId="11329" CreationDate="2011-03-11T09:50:21.523" Score="2" ViewCount="130" Body="&lt;p&gt;Could anyone suggest, why lifetime of Pb batteries is so short in UPSes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3 years till 0 mAh - I've seen that several times, and some UPSes were not low-end (~250$)...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any ways to make it last longer when designing new device?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same for LiIon - if we rarely charge/discharge them, how long they could last? (I've heard things like '2 years of shelf-life and they are garbage')....&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-03-11T13:06:43.757" LastActivityDate="2011-03-15T15:10:34.613" Title="Pb(Lead acid) &amp; LiIon Battery lifespan" Tags="&lt;battery&gt;&lt;lifetime&gt;" AnswerCount="1" CommentCount="9" />
  <row Id="11319" PostTypeId="2" ParentId="11316" CreationDate="2011-03-11T09:56:45.767" Score="0" ViewCount="" Body="&lt;p&gt;I've seen some ADC's from Analog specifically for RTD sensors with I2C interface - check their parametric table. Other manufacturers probably also have these.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you can use any I2C ADC with differential input for that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Schematics will be in datasheet :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-11T09:56:45.767" />
  <row Id="11320" PostTypeId="2" ParentId="11227" CreationDate="2011-03-11T10:04:45.510" Score="2" ViewCount="" Body="&lt;p&gt;An interesting option for a retro-computer is to use an FPGA; &lt;a href=&quot;http://members.optusnet.com.au/jekent/system09/index.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; 6809 implementation runs on a $99 Digilent Spartan-3 board. I tried it a few years ago - it worked very well with a VGA monitor and PS2 keyboard plugged into the FPGA board. Several similar systems have been designed, including &lt;a href=&quot;http://www.cs.columbia.edu/~sedwards/papers/edwards2009retrocomputing.pdf&quot; rel=&quot;nofollow&quot;&gt;this Apple II&lt;/a&gt; which uses an Altera FPGA board.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-11T10:15:09.450" LastActivityDate="2011-03-11T10:15:09.450" />
  <row Id="11321" PostTypeId="2" ParentId="10500" CreationDate="2011-03-11T10:11:17.503" Score="3" ViewCount="" Body="&lt;p&gt;IIRC electrically you just have to toggle the pull-up resistor connected to D+ (or was it D-) so I would try manually setting and clearing (with a small delay in between) the DETACH bit in the UDCON register.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In both the LUFA and V-USB libraries there were no problems with disconnecting and reconnecting to USB from software. I guess USB_Init did this by itself in those.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-11T10:11:17.503" CommentCount="4" />
  <row Id="11322" PostTypeId="2" ParentId="11227" CreationDate="2011-03-11T10:28:56.193" Score="1" ViewCount="" Body="&lt;p&gt;If you wanted a new and quite powerful chip you could use a LPC1768 chip. You can start with the mBed module which is DIP friendly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Programming and debugging is easy. I cannot comment on IDEs because I prefer Vim + a Makefile but CodeSourcery does offer a free preconfigured toolchain (for Linux and Windows IIRC).&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-11T10:28:56.193" CommentCount="2" />
  <row Id="11323" PostTypeId="2" ParentId="11309" CreationDate="2011-03-11T10:36:40.367" Score="1" ViewCount="" Body="&lt;p&gt;You could test and debug the device at low voltages (use 12V AC instead of 110V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OTOH if you need it to be connected to the PC (or anything having contact with humans, like a button or keyboard) while operating at 110V you should definitely buy a MOC3041 or something similar.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-11T10:36:40.367" />
  <row Id="11324" PostTypeId="2" ParentId="11252" CreationDate="2011-03-11T10:58:16.540" Score="0" ViewCount="" Body="&lt;p&gt;2) I wouldn't do that. Laptops repairs are quite expensive. Aftermarket chargers, not so much. ;]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In any case you could try using the one with lower output voltage with a computer expecting a higher one. But it may not work properly (like powering but not charging and such).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Yes.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-11T10:58:16.540" />
  <row Id="11325" PostTypeId="2" ParentId="11287" CreationDate="2011-03-11T11:03:09.657" Score="0" ViewCount="" Body="&lt;p&gt;If you follow the IC manufacturers tips about component selection and layout you should not have any problems with the WiFi chipset running from a switched power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may consider going for a switcher at 3.3V while using a linear regulator for 5V.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-11T11:03:09.657" />
  <row Id="11326" PostTypeId="2" ParentId="11315" CreationDate="2011-03-11T11:59:04.953" Score="0" ViewCount="" Body="&lt;p&gt;That error usually means that AVRdude missed the window to send something before the bootloader dropped through to the already loaded sketch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some arduino bootloaders have a different wait-for-program delay (or none at all)&#xA;depending on the reset source (poweron, reset pin, or watchdog).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have a schematic (didn't find one on DFR site)?  Are you applying reset the&#xA;same way each time, or differently the first time (power on vs reset-from-serial-DTR maybe?)&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-11T11:59:04.953" />
  <row Id="11327" PostTypeId="2" ParentId="11307" CreationDate="2011-03-11T12:08:39.500" Score="2" ViewCount="" Body="&lt;p&gt;When you say joining two pipes, do you mean at right angles, or axially?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use a ball bearing, with the outer race of the bearing press-fit inside one pipe, and the second pipe press fit inside the inner race.   A large linear bearing would work too (but cost a lot).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have access to a lathe?   A slip fit between two pieces of delrin or metal and delrin might work---all the gearing and linear bearings in some modern printers and scanners work much like this.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-11T12:08:39.500" CommentCount="1" />
  <row Id="11328" PostTypeId="2" ParentId="11315" CreationDate="2011-03-11T13:03:38.580" Score="0" ViewCount="" Body="&lt;p&gt;Try to reset it while holding the button for some time, ive expereienced the same problem. What i found out helps me best when i get errors like those, is that resetting with a long button hold works for me. Eventhough that not be the original source of the problem. but i think it has something to do with how long the mcu takes to initialize before it will accept the flashing process.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does this only come as soon as you try to change something ?&#xA;Your reset button may also be damaged.&#xA;Is your LED Pin13 on ?&#xA;Can you see action on the TX and RX line ?&lt;/p&gt;&#xA;" OwnerUserId="2995" LastActivityDate="2011-03-11T13:03:38.580" />
  <row Id="11329" PostTypeId="2" ParentId="11318" CreationDate="2011-03-11T13:19:25.990" Score="4" ViewCount="" Body="&lt;p&gt;This is due primarily to internal corrosion of the lead frames and the electrodes, short circuits cause the sulfation of the lead.&#xA;  This causes sulfation, that makes the PbSO4 crystals merge into ever larger networks.&#xA;  This reduces the electrochemical active surface of the PbSO4. Due to the now smaller surface, the PbS04 cannot be &quot;come off&quot; that good , as it could before.&#xA;  So it takes very long until a sufficiently high concentration of Pb2+ is present.&#xA;  In addition, the electrical conductivity of the sulfate is lower than that of lead. The resulting increased Internal resistance of the load cell leads to increased voltage drop. &#xA;  Give that process enough time and your at the point where you wont have any cell voltage at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this helped you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S.: i didnt know a good word for &quot;ablösen&quot; in english, since unsolder is not the one i was looking for and peel of is not the right term. but i think youll still get it.&lt;/p&gt;&#xA;" OwnerUserId="2995" LastActivityDate="2011-03-11T13:19:25.990" CommentCount="2" />
  <row Id="11331" PostTypeId="2" ParentId="11258" CreationDate="2011-03-11T14:30:53.937" Score="0" ViewCount="" Body="&lt;p&gt;That was the magic smoke.  It will not come back by itself.  Remote is generally safer than other components that may use high voltage.  Battery could be an issue, also get rid of anything leaking.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-11T14:30:53.937" />
  <row Id="11333" PostTypeId="1" CreationDate="2011-03-11T14:53:04.960" Score="3" ViewCount="332" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/9824/what-makes-a-particular-platform-suitable-or-unsuitable-for-production-use&quot;&gt;What makes a particular platform suitable or unsuitable for production use?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;All the questions I read about Arduino here are almost based on hobby projects. What are the Arduino's commercial applications you have made or heard of? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or What are Arduino's shortcomings precluding it from commercial market.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This question seems relevant to mine though:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/4163/is-arduino-suitable-to-be-a-humanoid-robot-controller&quot;&gt;Is Arduino suitable to be a Humanoid Robot controller?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance&lt;/p&gt;&#xA;" OwnerUserId="3343" LastActivityDate="2011-03-12T00:33:06.090" ClosedDate="2011-03-12T18:50:12.087" Title="Commercial Use of Arduino. Is it suitable?" Tags="&lt;arduino&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="2" />
  <row Id="11334" PostTypeId="1" CreationDate="2011-03-11T15:45:34.587" Score="1" ViewCount="96" Body="&lt;p&gt;I have a composite PAL/NTSC video signal. One problem I am having is getting a reliable sync signal from it; picture brightness causes the sync pulse (normally 0.3V) to vary; so much that my scope won't trigger on it reliably (with the video trigger.) I've heard I need a DC restoration or DC clamp circuit, but I can't find any information on this, except occasional references in books and on the internet, but no detailed information. Does anyone know what circuit I need? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have previously used an LM1881 or LMH1980 to extract sync because they build the DC clamp/restoree parts in. However, the problem with these chips is that they are expensive and often bigger than a discrete solution.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-26T15:00:37.240" Title="DC restoration of a video signal" Tags="&lt;video&gt;&lt;dc&gt;&lt;clamp&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="11335" PostTypeId="2" ParentId="11290" CreationDate="2011-03-11T15:59:09.437" Score="0" ViewCount="" Body="&lt;p&gt;How about an optoisolated solid state relay? What switching speed do you need?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-11T15:59:09.437" CommentCount="2" />
  <row Id="11336" PostTypeId="2" ParentId="11117" CreationDate="2011-03-11T16:09:40.740" Score="1" ViewCount="" Body="&lt;p&gt;This sounds a lot like the PAL and NTSC video formats, which were popular from 1954 until the analog TV switch-off in 2009.&#xA;Both PAL and NTSC transmit the luminance information AM modulated at one frequency,&#xA;and the color information QAM modulated at a frequency a fixed offset above it, and the audio information FM modulated at a frequency a fixed offset even higher above it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I searched for &quot;NTSC decoder&quot; and &quot;NTSC encoder&quot; at a few of my favorite &lt;a href=&quot;http://opencircuits.com/Supplier&quot; rel=&quot;nofollow&quot;&gt;electronic supply websites&lt;/a&gt;&#xA;and found a dozen or so chips in stock that, if I understand what you are asking, seem to meet your requirements.&#xA;3 random chips from that list -- I wouldn't be surprised if some other chip on that might be better for your application:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Analog Devices AD725ARZ RGB To&#xA;NTSC/PAL encoder&lt;/li&gt;&#xA;&lt;li&gt;Analog Devices ADV7171KSUZ video&#xA;encoder 10 bit YCbCr to PAL/NTSC&lt;/li&gt;&#xA;&lt;li&gt;Maxim MAX9526AEI+ Video Decoder&#xA;NTSC/PAL to 10 bit YCbCr component&#xA;video&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-11T16:09:40.740" CommentCount="2" />
  <row Id="11337" PostTypeId="1" CreationDate="2011-03-11T16:42:30.277" Score="0" ViewCount="54" Body="&lt;p&gt;Could anyone explain me how I can use DCM of Virtex 4 fpga to get divided clock-50MHz of the system clock-100MHz?&lt;/p&gt;&#xA;" OwnerUserId="3194" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-03-11T21:27:01.030" LastActivityDate="2011-03-14T16:24:42.233" Title="Virtex 4 fx 12 ff668" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;dcm&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11338" PostTypeId="2" ParentId="11333" CreationDate="2011-03-11T16:50:08.367" Score="4" ViewCount="" Body="&lt;p&gt;It is possible, but not commercially viable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you ditch arduino bootloader and write bare AVR firmware, you can go for much smaller &amp;amp; cheaper uC.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-11T16:50:08.367" CommentCount="1" />
  <row Id="11339" PostTypeId="2" ParentId="11333" CreationDate="2011-03-11T19:11:42.230" Score="6" ViewCount="" Body="&lt;p&gt;As always, it depends.  For this answer I'm assuming that you would be using the bootloader but would be designing your own minimalist board that uses the chip.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Suitability&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will one of the chips used in Arduino boards (ATmega328, etc) be suitable for your application.  In other words, do they chips do everything that you need the product to do.  Also, are you wasting money on a chip that does a lot &lt;em&gt;more&lt;/em&gt; than you need it to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How many units&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're making 5 units, the cost of development is likely much greater than production.  If makes sense to use the least amount of design time (using something like the Arduino bootloader, IDE might make sense in this case).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you're making 1,000 or 10,000, this changes things considerably.  At this scale, saving as much money on each board becomes very important.  At some level, it becomes worth learning how to &quot;write bare AVR firmware&quot; (as BarsMonster pointed out) or paying someone knowledgeable to do it so you can take advantage of least expensive chip to meet your requirements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Customer&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are releasing something as a hackable kit / product, you might get more customers my going with something that is so easy to reprogram.  However, if the product is geared towards the average individual, picking the cheapest hardware that satisfies the requirements is likely the way to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Licensing&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks like the bootloader software &lt;a href=&quot;http://arduino.cc/en/Main/FAQ&quot; rel=&quot;nofollow&quot;&gt;is protected by LGPL&lt;/a&gt; so according to the comments here, you should be fine to use it in a commercial product (but do your own research).  The board itself is protected by the Creative Commons ShareAlike license.  I'm not sure if this applies if you design your own board from scratch (I'm guessing it doesn't, but it's just that - a guess).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There might be some scenarios where using an Arduino for a commercial product is viable, but those are likely edge cases.&lt;/p&gt;&#xA;" OwnerUserId="1823" LastEditorUserId="1823" LastEditorDisplayName="" LastEditDate="2011-03-11T20:35:02.213" LastActivityDate="2011-03-11T20:35:02.213" CommentCount="2" />
  <row Id="11340" PostTypeId="2" ParentId="10139" CreationDate="2011-03-11T19:22:00.030" Score="2" ViewCount="" Body="&lt;p&gt;I like the way you do serial port debugging, and the comments at each stage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It appears that your display, like every other small character &lt;a href=&quot;http://techref.massmind.org/Techref/lcds.htm&quot; rel=&quot;nofollow&quot;&gt;LCD display&lt;/a&gt; I've ever held in my hands, uses the &lt;a href=&quot;http://techref.massmind.org/Techref/io/lcd/44780.htm&quot; rel=&quot;nofollow&quot;&gt;Hitachi 44780 interface&lt;/a&gt; standard.&#xA;May I ask why you aren't using some pre-tested &lt;a href=&quot;http://www.arduino.cc/playground/Code/LCD&quot; rel=&quot;nofollow&quot;&gt;off-the-shelf LCD library code&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would something like the following work for you?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// WARNING: untested code. And therefore riddled with bugs.&#xA;#define SCREEN_ENABLE 4&#xA;#define SCREEN_READ 2&#xA;#define SCREEN_RS 1&#xA;// LCD #defines copied from http://techref.massmind.org/techref/io/lcd/44780.htm&#xA;#define LCDClearDisplay 1&#xA;#define LCDCursorHome   2&#xA;#define LCDOff      8   ;0x08 turn the display (and the cursor) off.&#xA;#define LCDOn       12  ;0x0C Turn on the display, but without a cursor&#xA;#define LCDCursorOn 14  ;0x0E Turn on the cursor (as an underline) as well as the display&#xA;#define LCDCursorBlink  15  ;0x0F Turn on a blinking block cursor as well as the display&#xA;#define LCDCursorLeft   16  ;0x10 Move the cursor left by one character&#xA;#define LCDCursorRight  20  ;0x14 Move the cursor right one letter&#xA;#define LCDShiftLeft    24  ;0x18 Shift the entire display left one character&#xA;#define LCDShiftRight   30  ;0x1C Shift the entire display right one character&#xA;#define LCDGoto     128 ;0x80 Add the location of the character position &#xA;                ;   to which you wish to move the cursor&#xA;&#xA;void screen_enable(void){&#xA;    _delay_us(2);&#xA;    PORTE |= SCREEN_ENABLE;&#xA;    _delay_us(2); // must be at least 140 ns&#xA;}&#xA;void screen_disable(void){&#xA;    PORTE &amp;amp;= ~SCREEN_ENABLE;&#xA;    _delay_us(2);&#xA;}&#xA;void Screen_Execute(void)&#xA;{&#xA;    screen_enable();&#xA;    screen_disable();&#xA;}&#xA;&#xA;/** wait until screen is no longer busy */&#xA;void screen_busywait(void)&#xA;{&#xA;    char busy = 0x80;&#xA;    DDRA=0x00; // all inputs, to avoid fighting the screen outputs&#xA;    while(busy){&#xA;        // read busy flag&#xA;        PORTE |= SCREEN_READ; // read&#xA;        PORTE &amp;amp;= ~SCREEN_RS; // instruction: read busy flag and address&#xA;        screen_enable();&#xA;        // read busy bit while the Enable bit is high&#xA;        busy = PINA &amp;amp; 0x80;&#xA;        screen_disable;&#xA;        //BLINK_LED(500);&#xA;    }// wait until no longer busy&#xA;&#xA;    // switch to &quot;normal&quot; &quot;MCU writes to display&quot; mode.&#xA;    PORTE &amp;amp;= ~SCREEN_READ; // write&#xA;    DDRA=0xFF;&#xA;}&#xA;&#xA;void screen_send_instruction( char instruction ){&#xA;    PORTA=instruction;&#xA;    PORTE=0x00 + SCREEN_RS; // RS high: instruction&#xA;    DDRE=0xFF;&#xA;    DDRA=0xFF;&#xA;    Screen_Execute();&#xA;};&#xA;&#xA;void Screen_init(void)&#xA;{    &#xA;    //BLINK_LED(1000);&#xA;    SEND_STRING(&quot;Starting initialization\r\n&quot;,0);&#xA;    // see http://techref.massmind.org/techref/io/lcd/44780.htm&#xA;&#xA;    _delay_ms(15);&#xA;    SEND_STRING(&quot;Step 1 executing.\r\n&quot;,0);&#xA;    screen_send_instruction( 0x30 );&#xA;    _delay_ms(250);&#xA;    SEND_STRING(&quot;Step 1 complete.\r\n&quot;,0);&#xA;&#xA;    screen_send_instruction( 0x30 );//second time&#xA;    _delay_ms(5);&#xA;    screen_send_instruction( 0x30 );//third time&#xA;    _delay_ms(1);&#xA;&#xA;    SEND_STRING(&quot;Step 2 start.\r\n&quot;,0);&#xA;    screen_send_instruction( 0x38 ); // 8 bit interface, 2 line display, normal font&#xA;    SEND_STRING(&quot;Step 2 complete.\r\n&quot;,0);&#xA;&#xA;    SEND_STRING(&quot;Step 3 start.\r\n&quot;,0);&#xA;    //BLINK_LED(1000);&#xA;    screen_busywait();&#xA;    screen_send_instruction( LCDOff );//screen off&#xA;    SEND_STRING(&quot;Step 3 complete.\r\n&quot;,0);&#xA;&#xA;    screen_busywait();&#xA;    screen_send_instruction( 0x06 );// Entry mode: increment&#xA;&#xA;    screen_busywait();&#xA;    screen_send_instruction( LCDClearDisplay );//cursor goes to home and screen is cleared&#xA;&#xA;    screen_busywait();&#xA;    screen_send_instruction( LCDCursorOn );//screen on and underline cursor on.&#xA;&#xA;    SEND_STRING(&quot;Step 4 start.\r\n&quot;,0);&#xA;    //BLINK_LED(1000);&#xA;    screen_busywait();&#xA;    screen_send_instruction( 0x14 );//Move the cursor right one letter (why????)&#xA;    SEND_STRING(&quot;Step 4 complete.\r\n&quot;,0);&#xA;&#xA;    SEND_STRING(&quot;Step 5 start.\r\n&quot;,0);&#xA;    //BLINK_LED(1000);&#xA;    screen_busywait();&#xA;    screen_send_instruction( LCDCursorBlink );//Turn on a blinking block cursor as well as the display&#xA;    SEND_STRING(&quot;Step 5 complete.\r\n&quot;,0);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;p.s.: Rather than use 11 pins of your MCU to control the display, some people sacrifice a little speed to gain back some of those pins: some control the LCD display with 7 pins of the MCU in 4-bit mode, others &lt;a href=&quot;http://techref.massmind.org/techref/io/lcd/Shift1.htm&quot; rel=&quot;nofollow&quot;&gt;control their LCD display with 1 pin of the MCU&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-11T19:22:00.030" CommentCount="1" />
  <row Id="11341" PostTypeId="1" CreationDate="2011-03-11T20:05:13.743" Score="0" ViewCount="337" Body="&lt;p&gt;Hi.  Has anyone used the IMU-3000 with an attached accelerometer?  I am creating a system which interfaces the IMU-3000 and attached ADXL345 (IMU Fusion board from SparkFun) with an Arduino board to do all the computations about a projectile in motion and output values to an LCD.  I was just looking for how to read the various axis individually since it all comes through the same pin.  Does anyone know the commands for that in Arduino?  I am very new so if I am sounding stupid please just help me understand.  &lt;/p&gt;&#xA;" OwnerUserId="3345" LastActivityDate="2011-03-29T07:30:45.780" Title="IMU - 3000 with ADXL345 and Arduino" Tags="&lt;arduino&gt;&lt;prototyping&gt;&lt;breadboard&gt;&lt;programming&gt;&lt;imu&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11342" PostTypeId="2" ParentId="11290" CreationDate="2011-03-11T21:42:26.430" Score="1" ViewCount="" Body="&lt;p&gt;The ADG1236 and ADG1213 parts from Analog seem to fulfill the requirements. Both have a 1 GHz bandwidth and can use a power supply of +/-15V. They also offer a much higher switching frequency than a relay.&lt;/p&gt;&#xA;" OwnerUserId="2740" LastActivityDate="2011-03-11T21:42:26.430" />
  <row Id="11343" PostTypeId="1" AcceptedAnswerId="11354" CreationDate="2011-03-11T21:50:37.080" Score="1" ViewCount="43" Body="&lt;p&gt;The bandwidth of electronic parts, like analog switches, is usually specified for a specific load, typically 50 ohm and 5 pF for example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now if I have an analog switch with a bandwidth of 1 GHz for a 50 ohm load, how the bandwidth change depending on the load? What appends for, say, a load of 1 kOhm? Is there a way to calculate or estimate the bandwidth for different load values?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(this is a follow-up of &lt;a href=&quot;http://electronics.stackexchange.com/questions/11290/high-voltage-high-bandwidth-analog-mux&quot;&gt;High voltage high bandwidth analog mux&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="2740" LastActivityDate="2011-03-12T00:45:10.697" Title="How the bandwidth is impacted by the load?" Tags="&lt;bandwidth&gt;" AnswerCount="1" />
  <row Id="11344" PostTypeId="1" AcceptedAnswerId="11353" CreationDate="2011-03-11T21:56:06.527" Score="3" ViewCount="117" Body="&lt;p&gt;I'm planning to put together a simple shift-register driven array of LEDs as a first project, something akin to this:&#xA;&lt;img src=&quot;http://i.imgur.com/o6vR1.jpg&quot; alt=&quot;Simple LED array&quot;&gt;&#xA;But using a 74HC595 shift register (two, eventually) and a transistor to drive each individual LED alone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's been twenty years since my (limited) formal electronics education, and I have a few questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;I believe understand why the resistors in line with the LEDs are necessary, because an LED essentially behaves like a short circuit, and will draw a lot of current from the register, right up until either it dies or the register dies. Is this correct?&lt;/li&gt;&#xA;&lt;li&gt;Why the &quot;1K or 2.2K&quot; resistor on the base of the transistor? Will I need one on each of the bases? Is this to limit the current between the base and emitter of the transistors? How do I know what value to use?&lt;/li&gt;&#xA;&lt;li&gt;Should I use 2N2222 transistors or should I use something like a 2N3904? What is the difference, other than the 2N2222 seems to have a much higher collector-emitter capacity? Does that affect the choice of resistor I need?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3240" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T22:13:40.640" LastActivityDate="2011-04-27T22:13:40.640" Title="Building a simple mcu-driven array of LEDs" Tags="&lt;microcontroller&gt;&lt;led&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="11345" PostTypeId="1" CreationDate="2011-03-11T21:59:37.663" Score="2" ViewCount="81" Body="&lt;p&gt;I've seen several electronics devices using MAX3232 or similar devices to generate dual rail power supplies. In my instance, I have 3.3V going in and need regulated ±5V outputs. I have &lt;strike&gt;three&lt;/strike&gt; four questions.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How much output current can they sink or source?&lt;/li&gt;&#xA;&lt;li&gt;Are they regulated or do I need an LDO?&lt;/li&gt;&#xA;&lt;li&gt;What noise do these give? Through an LDO, would any noise be tolerable for high speed (85 MHz) op-amps?&lt;/li&gt;&#xA;&lt;li&gt;What other solutions are there for this problem (dual rail power)?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-03-11T22:26:38.047" LastActivityDate="2011-03-11T22:50:34.500" Title="Generating dual rail power from a MAX3232?" Tags="&lt;power&gt;&lt;max3232&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="11346" PostTypeId="2" ParentId="11345" CreationDate="2011-03-11T22:36:19.880" Score="3" ViewCount="" Body="&lt;p&gt;Charge-pump based voltage generators, like the MAX3232 are generally very limited in terms of output current (it seems that all the MAX3232 datasheet guaranties is a voltage of +/-5V at 2.5 mA load). Beside, they are not very efficient at compensating output transients. If the required output current is higher than a few 10 mA, use a true step-up (boost) DC/DC converter, like the LT1300 from Linear. I even found this part: LT3582-5 (from Linear also), which seems to do exactly what you want. Other similar parts may exist as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your application is noise sensitive, you have no guaranty at all regarding this point in this datasheet... I am afraid that you can't just guess what the output noise would be!&lt;/p&gt;&#xA;" OwnerUserId="2740" LastEditorUserId="2740" LastEditorDisplayName="" LastEditDate="2011-03-11T22:50:34.500" LastActivityDate="2011-03-11T22:50:34.500" />
  <row Id="11347" PostTypeId="2" ParentId="2151" CreationDate="2011-03-11T23:26:17.903" Score="2" ViewCount="" Body="&lt;p&gt;There seems to be a confusion between the size of a (quartz) crystal package, and the crystals' physical properties which include the crystal's size and it's resonant frequency due to its piezoelectric properties.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your photo, the crystal on the left appears to be a very common &lt;code&gt;HC-49/U&lt;/code&gt; package size. The one on the right is most likely an &lt;code&gt;HC-49U/S&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From ICM, a crystal manufacturer, &lt;em&gt;&quot;The frequency is a function of the thickness of the crystal. By carefully polishing or lapping a crystal, it can be made to oscillate at any frequency.&quot;&lt;/em&gt; (&lt;a href=&quot;http://www.icmfg.com/crystals.html&quot; rel=&quot;nofollow&quot;&gt;source&lt;/a&gt;) In fact, amateur radio radio operators (&quot;hams&quot;) historically were known to polish surplus crystals to their desired frequency, back when the cost of manufacturing was much higher. The practice was sometime referred to as &quot;rock grinding.&quot; (&lt;a href=&quot;http://s88932719.onlinehome.us/ham/rokgrind.htm&quot; rel=&quot;nofollow&quot;&gt;ref one&lt;/a&gt; &amp;amp; &lt;a href=&quot;http://www.bliley.net/XTAL/docs/misc/XTAL_grinding/grinding.html&quot; rel=&quot;nofollow&quot;&gt;ref two&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can verify this by looking at a manufacturers' specifications for crystals in different packages. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;E.g. &lt;a href=&quot;http://foxonline.com/thruhole_xtals.htm&quot; rel=&quot;nofollow&quot;&gt;FOX through-hole crystals&lt;/a&gt; and &lt;a href=&quot;http://www.icmfg.com/thruhole_crystals.html&quot; rel=&quot;nofollow&quot;&gt;ICM&lt;/a&gt;, where in fact the larger package includes overtone crystals (&lt;a href=&quot;http://www.foxonline.com/pdfs/osctheoryoper.pdf&quot; rel=&quot;nofollow&quot;&gt;page 3, PDF&lt;/a&gt;) for higher frequencies (looking at HC-49/U and HC-49/S). At fundamental frequencies they are often the same frequency range available.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-03-11T23:26:17.903" />
  <row Id="11348" PostTypeId="1" CreationDate="2011-03-11T23:45:06.393" Score="4" ViewCount="62" Body="&lt;p&gt;I havent used them yet, but I'm getting the impression they will be fine to recharge and use after they dry out.  Is this true?&lt;/p&gt;&#xA;" OwnerUserId="3347" LastActivityDate="2011-03-12T00:32:42.393" Title="My rechargeable Ni-MH AA batteries went through the wash in my pocket! Are they safe to use?" Tags="&lt;batteries&gt;&lt;damage&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="11349" PostTypeId="1" CreationDate="2011-03-12T00:08:11.970" Score="1" ViewCount="37" Body="&lt;p&gt;I know this is a long shot but I thought I would ask while I am waiting for the FAE to get back to me. This is related to Cadence Verilog simulations and regressions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to debug an *.ecom file and I am not sure what language it is written in. Here is a sample of the code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;var vsofs : vm_vsof = vm_manager.read_session(&quot;&amp;lt;1&amp;gt;&quot;);&#xA;&#xA;// create context&#xA;var sessions : list of vm_attribute_container;&#xA;sessions = vm_manager.get_all_sessions().as_a(list of vm_attribute_container);&#xA;var curr_context : vm_context = vm_manager.create_context({sessions}, &quot;session_stats&quot;);&#xA;curr_context.export_to_csv(RUNS, &quot;&amp;lt;2&amp;gt;&quot;);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And this script is invoked like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; &amp;gt; emanager -b -c &quot;setup; @create_csv.ecom \&#xA;   ../vsof/smoke_regr.user.11_03_11_16_15_52_7509/chip_passing.vsof \&#xA;   ../vsof/smoke_regr.user.11_03_11_16_15_52_7509/&quot;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;PS - If there is a better stackexchange place to put this question let me know.&lt;/p&gt;&#xA;" OwnerUserId="3348" LastActivityDate="2011-04-11T04:27:31.187" Title="What language is Cadence's Emanger *.ecom files written in?" Tags="&lt;verilog&gt;&lt;hdl&gt;" AnswerCount="1" />
  <row Id="11350" PostTypeId="2" ParentId="11348" CreationDate="2011-03-12T00:19:01.560" Score="3" ViewCount="" Body="&lt;p&gt;Most batteries and cells are fairly well sealed. They'll be fine. You might want to clean off the terminals to ensure they don't corrode during normal use, but otherwise they should work.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-12T00:19:01.560" />
  <row Id="11351" PostTypeId="2" ParentId="11348" CreationDate="2011-03-12T00:32:42.393" Score="1" ViewCount="" Body="&lt;p&gt;The only answer is probably.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just keep an eye on them while charging and using for the first time.&#xA;That's the only way to be sure.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-12T00:32:42.393" />
  <row Id="11352" PostTypeId="2" ParentId="11333" CreationDate="2011-03-12T00:33:06.090" Score="1" ViewCount="" Body="&lt;p&gt;Using the Arduino for a commercial product is &lt;strong&gt;&lt;em&gt;totally unsuitable&lt;/em&gt;&lt;/strong&gt; for a variety of reasons, with the only exception being if it was branded as &quot;Arduino-compatible&quot; or some such, explicitly meant to be modified by the user (but I wouldn't consider that &quot;commercial&quot;).&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Sourcing Atmel components is notoriously difficult according to a few different sales reps (one of which actually reps Atmel), and they often suggest other manufacturers, e.g. Freescale and occasionally Microchip&lt;/li&gt;&#xA;&lt;li&gt;Virtually any product you design would need an additional PCB, and stacking an Arduino board would on your own would barely give you any net area savings, and absolutely no space savings&lt;/li&gt;&#xA;&lt;li&gt;Most embedded products have no need of a USB/COM bridge.&lt;/li&gt;&#xA;&lt;li&gt;Your power options are: one.  There's a reason that there are thousands of different power regulators, for everything from maximum power rating to minimum power draw when in standby, input and output voltages, ripple output and rejection...&#xA;&lt;ul&gt;&#xA;&lt;li&gt;(either that or you're paying for a regulator you aren't using.)&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Your feature options are extremely limited to about 4(?) different AVRs.  Dozens of AVRs are available, and for whatever you do there is one that will very likely be either a) cheaper, or b) more capable, saving you money from other things (e.g. LCD driver).  You can also go to one of a half-dozen other common manufacturers, mentioned before, and get even more variety.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If we're counting software as well,&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The &quot;Arduino language&quot; or whatever it's called (bastardization of C) and the IDE make C maddeningly difficult for a C developer (at least this one) to work&lt;/li&gt;&#xA;&lt;li&gt;Options provided by &lt;code&gt;avr-gcc&lt;/code&gt;, while extensive, are still eclipsed by some other professional compilers (e.g. IAR).  Granted, the options they provide may not be required in any given project.&lt;/li&gt;&#xA;&lt;li&gt;A bootloader is hardly a compelling reason to bring along the entire baggage of Arduino; there are plenty of alternatives.100.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-12T00:33:06.090" CommentCount="3" />
  <row Id="11353" PostTypeId="2" ParentId="11344" CreationDate="2011-03-12T00:38:45.773" Score="3" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Yes&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Yes. You can calculate the resistor by calculating base required current (you will need to know 'hfe' of your transistor). But you can just try. Working range is quite high, so if you will just use 500 Ohm for example, it should just work.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;For example, if max total current is 100mA, voltage is 5V, and hfe is 150, you need 100/150 = 0.6mA base current, so resistor should be 5V/0.0006 = 8.3kOhm or less.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;There are lots of difference, but yes, it's depend on how much current you will need in the worst case.  If these LED's are usual 10mA ones, almost any BJT will work so you can take what's cheaper or what you already have.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;BTW. Don't see your shift register :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-12T00:38:45.773" CommentCount="1" />
  <row Id="11354" PostTypeId="2" ParentId="11343" CreationDate="2011-03-12T00:45:10.697" Score="3" ViewCount="" Body="&lt;p&gt;In the 1Ghz range the most important is load capacitance. &#xA;The higher capacitance - the less bandwidth. &#xA;With 1nF load you are likely go under 10 MHz bandwidth. So avoid long traces. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Resistive load - if it's too high (like 5Ohm) you can just get signal with lower amplitude or more distortion, but bandwidth is not that much affected. And 1kOhm will not hurt usually (unless there is some fancy load matching, which is unlikely).&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-12T00:45:10.697" />
  <row Id="11355" PostTypeId="1" AcceptedAnswerId="11364" CreationDate="2011-03-12T02:45:23.257" Score="2" ViewCount="214" Body="&lt;p&gt;Before I begin, I'd like to note that I am very unexperienced in the electronics field, so some things that may be obvious are completely unknown to me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recently was dealing with a laptop that would not charge, boot, or show any signs of life. After some discussion over the phone, I learned that the AC adapter's wire was frayed, and so I immediately ordered a new one. When it arrived, there was still no success in getting any power to the laptop. I proceeded to use a multimeter to test both AC adapters, and like I suspected, the old one was reading 0V. The new one, however, was reading only 15.3V on the multimeter. The adapter says it should be outputting at 19V (both on the adapter itself and on the box it came in). Additionally, the battery is labeled at 14.4V, if that matters at all. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question comes down to this: could the fact that the multimeter read 15.3V instead of 19V on the AC adapter be related to why the laptop refuses to show any signs of life? If not, I will probably have to start taking it apart until I get can at the power connector.&lt;/p&gt;&#xA;" OwnerUserId="3352" LastActivityDate="2011-05-18T09:34:59.390" Title="Would a laptop charger at incorrect voltage fail to supply power?" Tags="&lt;power-supply&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="11356" PostTypeId="2" ParentId="11344" CreationDate="2011-03-12T04:10:41.160" Score="1" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;Yes, you need a current-limiting resistor for each LED in this kind of circuit.&lt;/li&gt;&#xA;&lt;li&gt;If, hypothetically, you use BJT transistors, then yes, you will also need a second resistor (per LED) on the base of each and every transistor to limit the current between the base and emitter of the resistor (that base-emitter junction acts like a diode). There is a wide range of resistor values that will work just fine -- BarsMonster shows how to calculate it.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;However, if I didn't already have plenty of BJT transistors, I would consider using something that doesn't need base resistors, perhaps&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;2N7000 or 2N7002 transistors, since FET transistors don't need a base resistor, or&lt;/li&gt;&#xA;&lt;li&gt;transistor arrays such as the SN75468 or ULN2803, which have base resistors built into the IC, or&lt;/li&gt;&#xA;&lt;li&gt;ICs that integrate both the transistor array and the shift register into the same IC. Several of them have the same interface as the 74HC595 (so you can use the same software), but can drive LEDs directly. W5VO kindly mentioned these chips to me at &lt;a href=&quot;http://electronics.stackexchange.com/questions/6676/which-sipo-chip-is-better-74hc4094-or-74hc595-or-something-else&quot;&gt;another question about driving LEDs&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Even the cheapest BJT or FET transistor can handle far more current and far higher frequencies than a single display LED is ever likely to require. So use whatever transistors are easily available to you.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-12T04:10:41.160" />
  <row Id="11357" PostTypeId="2" ParentId="11349" CreationDate="2011-03-12T04:16:54.750" Score="1" ViewCount="" Body="&lt;p&gt;It is the &quot;e&quot; language. and to print:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;out(&quot;Variable foo=&quot;,foo);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3348" LastActivityDate="2011-03-12T04:16:54.750" />
  <row Id="11358" PostTypeId="1" AcceptedAnswerId="11365" CreationDate="2011-03-12T05:03:32.857" Score="2" ViewCount="240" Body="&lt;p&gt;Why can't we light an LED with a single positive wire on the anode, leaving the cathode unconnected?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's suppose I connect a wire with a positive voltage to the anode of the LED.  Now, I think, current will flow past the light emitting diode.  This should, by my understanding, make it glow, even though the cathode isn't connected to anything.  However, experimental evidence and common knowledge show that this isn't the case.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible in any situation(IDEAL) that we calculate current and voltage value so that this circuit will work, and automatically flow to ground after passing through the circuit?  If so, do we need a connection to ground in the real world?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Please point out my mistake if you notice a simple error I've made, and let me know what is right.&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="2951" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-19T02:00:54.780" LastActivityDate="2011-03-19T02:00:54.780" Title="Why we need to complete circuit" Tags="&lt;beginner&gt;&lt;basic&gt;&lt;ideas&gt;" AnswerCount="4" CommentCount="4" />
  <row Id="11359" PostTypeId="2" ParentId="11358" CreationDate="2011-03-12T06:07:46.753" Score="2" ViewCount="" Body="&lt;p&gt;In order for current to flow between two points (in general) the fundamental requirement is that ther must be some potential (voltage) difference between those points. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current is physically the effect of electrons moving through your circuit (as prescribed by electromotive forces given rise to by the aforementioned existent potential difference). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If those electrons have no place to go (i.e. back to ground), and current were somehow flowing into a floating node like the LED situation you described, then you would get a build-up of electrical charge on the on the floating node that would violate energy conservation principles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In response to the comment, think of it like this. Current will only flow from a higher potential to a lower potential (again electromotive force governs this). If a current were able to flow into a floating node, charge would build up there, and the result of this would be that the potential (voltage) at that node would increase. Eventually it would increase to a point where there was no potential difference between that node and the source node, and current would no longer flow.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-03-13T16:05:59.417" LastActivityDate="2011-03-13T16:05:59.417" CommentCount="1" />
  <row Id="11360" PostTypeId="2" ParentId="11307" CreationDate="2011-03-12T07:26:07.593" Score="1" ViewCount="" Body="&lt;p&gt;Sintered bronze bearings (often oil impregnated) can be a useful technology, they are both thinner and cheaper than ball bearings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes a piece of metal or plastic pipe can work as a sleeve bearing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on load and life cycle, a variety of plastics or even hardwood can be used for do it yourself bearings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an old-school approach, if you have a polished shaft, pouring a babbit metal around it may be an option.   A newer take on that idea is epoxy-teflon composites, such as Moglice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are playing around with mechanics, you should have have catalogs from the likes of small parts, msc industrial, mcmaster (probably online only), northern hydraulics, and some of the radio control model outlets kicking around for light reading - it's useful to learn about the range of items that must be manufactured to enable an industrial society, and what sub-varieties thereof are affordable from various sources.  And make a point to browse your discount auto-part store and the dusty corners of anything still resembling a true hardware store in your area.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-03-12T07:26:07.593" CommentCount="4" />
  <row Id="11361" PostTypeId="2" ParentId="11263" CreationDate="2011-03-12T07:34:07.130" Score="1" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/mreM4.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had this idea for a quick and dirty log amp.  If you modulated the reference voltage by 3dB, the output would probably average to about the right value.  That would more-or-less be an interpolation between 3dB values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two LM3915s can be stacked to get 60 dB range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is probably not the way to go unless there is a need for an LED bargraph in the circuit already.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-12T07:34:07.130" />
  <row Id="11362" PostTypeId="1" AcceptedAnswerId="11368" CreationDate="2011-03-12T08:28:05.193" Score="2" ViewCount="122" Body="&lt;p&gt;Hi there, I'm creating a 2-bit alu. It has 8 defined functions (the functions are defined by a 3bit code), AND XOR etc, and these functions act on two, 2-bit binary numbers and produce a 2-bit answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/dZqR2.png&quot; alt=&quot;my circuit diagram&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I have done so far, I have a decoder that decodes what the function is, and the output of that powers/activates the corresponding purpose of that function.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;for example the function code '000' activates the XOR terminal on the decoder and the XOR box spits out its answer, likewise '001' activates the AND box.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem I'm having is, the outputs of the two functions XOR and AND have to go into LSB,MSB and carryOut to indicate the answer, however since the outputs are tied together it causes an error. And I can't have 3 separate LED's defined for each function. I must only use that 3 (LSB,MSB and carryOut).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is how do I not tie the outputs of the AND and XOR and produce a result depending on which function is active?.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;*note on the image*&#xA;&#xA;a - LSB of binary number 1  {these are controlled by switches}&#xA;&#xA;b - MSB of binary number 1&#xA;&#xA;c - LSB of binary number 2&#xA;&#xA;d - MSB of binary number 2&#xA;&#xA;cin - carry in.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Also everything inside the boxes are made using the basic gates and not from simulated blocks.&lt;/p&gt;&#xA;" OwnerUserId="2322" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-20T20:13:11.353" LastActivityDate="2011-03-20T20:13:11.353" Title="Help with a simple two bit Arithmatic Logic Unit?." Tags="&lt;logic&gt;&lt;alu&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="11363" PostTypeId="1" CreationDate="2011-03-12T08:36:08.293" Score="1" ViewCount="166" Body="&lt;p&gt;Is it possible to use an Arduino/Arduino Mega or a Maple (STM32 based board) to perform realtime numerical integration using a Runge Kutta algorithm(for simple physics simulations)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not would the addition of a FPU coprocessor like the uM-FPU v3.1 make it possible?&lt;/p&gt;&#xA;" OwnerUserId="3319" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-12T17:43:27.333" LastActivityDate="2011-03-12T22:15:56.407" Title="Solving differential equations numerically using Arduino" Tags="&lt;arduino&gt;&lt;cortex-m3&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="11364" PostTypeId="2" ParentId="11355" CreationDate="2011-03-12T09:16:19.703" Score="1" ViewCount="" Body="&lt;p&gt;At first, your laptop power source may be really weird one (not likely). Some chargers do provide only lower voltage, until device that's going to be charged requests higher voltage. Good thumb of rule: if there's only two connectors (typically round one, outer one is ground), then it should provide correct voltage all the time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that's not the case, then either your multimeter is showing wrong readings or your power adapter is broken.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can check your multimeter with some known voltage, for example new 9V battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Typically laptop power adapters provide overvoltage without any load. It's not unusual to get for example 23V from 19V AC adapter, when it's not loaded. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your laptop charger circuit regulates whatever is coming from AC adapter to more appropriate voltage for charging battery. In the same way, battery voltage is regulated down to 3.3V, 5V and probably also 12V for computer internals (processor, memory, motherboard, display and so on).&lt;/p&gt;&#xA;" OwnerUserId="3064" LastActivityDate="2011-03-12T09:16:19.703" CommentCount="1" />
  <row Id="11365" PostTypeId="2" ParentId="11358" CreationDate="2011-03-12T09:24:50.037" Score="5" ViewCount="" Body="&lt;p&gt;The idea of a closed circuit works for low frequencies - where the corresponding wavelength is much larger than the components and wires.  Kirchoff's laws hold.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Things get tricky when the frequency is higher. A sudden change in voltage propagates at the speed of light (or some good fraction of it in cables, transmission lines) and there is more current at one point than at another.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In theory, you could put a sharp-edged voltage pulse on one lead of an LED, have nothing connected to the other, and for a tiny instant in time, as the pulse passes through the LED, have enough current for it to glow. But it would be extremely brief.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what if you send a series of pulses?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good rule of thumb to remember is at light speed, one nanosecond is about one foot (30+ cm).  LEDs and the pulse-pushing circuitry I imagine would be a few inches (or cm) and so things happen on a scale of maybe tenths of nanoseconds. You'd have to work with frequencies at several GHz.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another problem - every positive pulse you put on the anode lead will go through the LED and add positive charge to the non-connected cathode lead.  Each positive pulse will add more.  That charge has nowhere to escape to - just a tiny bit can flow back as leakage current, no diode being perfect.   From a physics point of view, so what?  Just let the whole contraption develop a positive charge.  Figure a few milliamps lasting for say 50 ns, times 5 billion times per second (just making up numbers), you quickly get to coulombs of charge, and many volts in just seconds.  At a practical level, it's not very practical at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wonder if it would work better to have two LEDs wired anti-parallel, and feed GHz pulses to one end of the pair and leave the other end disconnected?   (I leave that thought for others to discuss.)&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2011-03-12T09:24:50.037" CommentCount="2" />
  <row Id="11366" PostTypeId="2" ParentId="11334" CreationDate="2011-03-12T09:37:02.837" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://ankythera.com/Projects/video_clamper.htm&quot; rel=&quot;nofollow&quot;&gt;http://ankythera.com/Projects/video_clamper.htm&lt;/a&gt; might be informative.  &lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2011-03-12T09:37:02.837" />
  <row Id="11367" PostTypeId="2" ParentId="10749" CreationDate="2011-03-12T10:57:47.653" Score="1" ViewCount="" Body="&lt;p&gt;Your ISR should not be disabling and re-enabling interrupts and it should not be delaying.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ISR(TIMER0_OVF_vect)&#xA;{&#xA;  PORTD ^= 1&amp;lt;&amp;lt;6;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Or even:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ISR(TIMER0_OVF_vect)&#xA;{&#xA;    if (overflow_count &amp;lt; 0xFFFF)&#xA;        overflow_count++;&#xA;    else&#xA;    {&#xA;        overflow_count = 0;&#xA;        PORTD ^= 1&amp;lt;&amp;lt;6;&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then configure the timer interrupt frequency by changing &lt;code&gt;TCCR0B&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To begin the timer, you may also need to clear the counter:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TCNT0 = 0&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-12T11:03:35.667" LastActivityDate="2011-03-12T11:03:35.667" />
  <row Id="11368" PostTypeId="2" ParentId="11362" CreationDate="2011-03-12T12:02:40.467" Score="3" ViewCount="" Body="&lt;p&gt;You need multiplexers for the outputs. The decoder is not strictly necessary.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-03-12T12:02:40.467" />
  <row Id="11369" PostTypeId="1" AcceptedAnswerId="11403" CreationDate="2011-03-12T12:06:52.287" Score="1" ViewCount="164" Body="&lt;p&gt;Can anyone recommend a hobbist &lt;a href=&quot;http://en.wikipedia.org/wiki/Linear_motor&quot; rel=&quot;nofollow&quot;&gt;linear motor&lt;/a&gt;? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The motors are often described as being a rolled out version of a DC motor (is that true btw). If this is the case then how does one &quot;drive&quot; a linear motor. I'm trying to understand what kind of signals need to be sent to the coils to make it move.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any info welcome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: For clarity, I'm asking about the  &quot;stepper&quot; type linear motor&lt;/p&gt;&#xA;" OwnerUserId="3045" LastEditorUserId="3045" LastEditorDisplayName="" LastEditDate="2011-03-13T23:32:09.367" LastActivityDate="2011-03-16T00:32:39.290" Title="A &quot;hobby&quot; grade linear motor" Tags="&lt;linear-motor&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="11371" PostTypeId="2" ParentId="11363" CreationDate="2011-03-12T14:03:29.580" Score="2" ViewCount="" Body="&lt;p&gt;As @tyblu already noted, yes, it's possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, it depends what you mean by &quot;realtime&quot;, and how accurate results you want. Another possibility - depending on your system - may be offloading calculations to host computer (Arduino reads inputs, writes numbers to serial (or wirelessly with xbee, for example), computer calculates whatever you want to calculate and prints results to Arduino, and then Arduino decides what it'll do (change outputs)).&lt;/p&gt;&#xA;" OwnerUserId="3064" LastActivityDate="2011-03-12T14:03:29.580" CommentCount="3" />
  <row Id="11372" PostTypeId="1" AcceptedAnswerId="11377" CreationDate="2011-03-12T14:13:40.103" Score="1" ViewCount="276" Body="&lt;p&gt;I'm working on a project on the Samsung Galaxy S smartphone. I need to know some additional information on its accelerometer that I can't find. &lt;a href=&quot;http://www.bosch-sensortec.com/content/language1/downloads/SMB380_Flyer_Rev1.3.pdf&quot; rel=&quot;nofollow&quot;&gt;Accelerometer datasheet&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to know following details:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;which type of measurement range they use? +-2g , +-4g or +-8g ?&lt;/li&gt;&#xA;&lt;li&gt;noise depend on the bandpass filter used by the smartphone: how much is the band?&lt;/li&gt;&#xA;&lt;li&gt;there is some way to evaluate from this data sheet the standard deviation of drift process of the sensor?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3360" LastEditorUserId="3064" LastEditorDisplayName="" LastEditDate="2011-03-12T14:49:59.950" LastActivityDate="2011-03-12T16:45:10.280" Title="Samsung Galaxy S accelerometer details" Tags="&lt;sensor&gt;&lt;accelerometer&gt;" AnswerCount="1" />
  <row Id="11373" PostTypeId="2" ParentId="11358" CreationDate="2011-03-12T15:16:02.627" Score="2" ViewCount="" Body="&lt;p&gt;Yes, you could do that.  If you use a high-voltage generator to suck charge out of one metal sphere and deposit it onto another, you would then have a potential without a complete circuit, and you could connect the two spheres together to get a current.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/QBmbC.gif&quot; alt=&quot;charge flow (current) from one charged sphere to another&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would only last for a short time, however, because the charge imbalance would decrease as you discharge them.  If the spheres are oppositely charged at first, they will become neutral after the current flows.  if one sphere was neutral and the other charged, then the equilibrium they reach will be half as much charge on each, instead of becoming neutral.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But what if you want charge to flow continuously from one sphere to the other?  Then you need a conveyor of some type to force the charge back to the other side.  In this case, you've completed the circuit with a voltage or current source.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-03-12T15:16:02.627" CommentCount="10" />
  <row Id="11374" PostTypeId="1" AcceptedAnswerId="11382" CreationDate="2011-03-12T15:32:54.320" Score="3" ViewCount="217" Body="&lt;p&gt;I'm thinking of using a supercapacitor to power a device with low power consumption. I have one 1 F capacitor rated at 5.5 V and I plan to charge it using input voltage of 5 V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What precautions should I take when charging it? I'm afraid that it will overload my power supply if I just connect it directly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any other tips would be appreciated too.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-13T04:36:23.423" Title="How to work with supercapacitors?" Tags="&lt;capacitor&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="1" />
  <row Id="11375" PostTypeId="2" ParentId="11369" CreationDate="2011-03-12T15:38:15.520" Score="1" ViewCount="" Body="&lt;p&gt;Any stepper with a threaded rod and captive nut will make a low speed linear motor with up to about 3 foot reach.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-12T15:38:15.520" CommentCount="1" />
  <row Id="11376" PostTypeId="2" ParentId="10749" CreationDate="2011-03-12T16:28:46.600" Score="0" ViewCount="" Body="&lt;p&gt;Some things to check:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The vector for the interrupt in question points to your ISR&lt;/li&gt;&#xA;&lt;li&gt;The interrupt is enabled&lt;/li&gt;&#xA;&lt;li&gt;The interrupt is actually getting triggered. If the interrupting device is a free-running clock, the clock has been started properly.  If it's a one-shot, the one-shot is being re-started after each interrupt.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3361" LastActivityDate="2011-03-12T16:28:46.600" />
  <row Id="11377" PostTypeId="2" ParentId="11372" CreationDate="2011-03-12T16:45:10.280" Score="2" ViewCount="" Body="&lt;p&gt;All of those details are heavily dependent on the firmware setting up the chip, low level software (Android OS) massaging and delivering the sensor data, and finally the application-level software further massaging and delivering data. At the firmware level, it would be useful to get an SPI/I&lt;sup&gt;2&lt;/sup&gt;C sniffer, like the &lt;a href=&quot;http://dangerousprototypes.com/bus-pirate-manual/&quot; rel=&quot;nofollow&quot;&gt;Bus Pirate&lt;/a&gt; or &lt;a href=&quot;http://dangerousprototypes.com/docs/Open_Bench_Logic_Sniffer&quot; rel=&quot;nofollow&quot;&gt;Open Bench Logic Sniffer&lt;/a&gt;. I wouldn't be surprised if applications were able to access this level, as well. In other words, the initial or default state may change. It will be very difficult to attach probes, however.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Android OS is largely open-source. Check it out and see if you can find the relevant blocks of code and libraries. It would at least set the initial state, and likely define an API to change it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The wrong way to go about this is physical tests while taking measurements with an on-board application. There are at least 3 layers of algorithms fiddling with the sensor data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You cannot determine drift from the datasheet. It is dependent on temperature, age, and batch/wafer.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-03-12T16:45:10.280" CommentCount="3" />
  <row Id="11378" PostTypeId="1" AcceptedAnswerId="11383" CreationDate="2011-03-12T16:55:45.423" Score="2" ViewCount="123" Body="&lt;p&gt;I'm planning to drive multiple RGB LEDs using a TLC5940 with PWM. These LEDs have the following specs:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Voltage Red: 1.8V&lt;/em&gt;&lt;br&gt;&#xA;&lt;em&gt;Voltage Green: 3.0V&lt;/em&gt;&lt;br&gt;&#xA;&lt;em&gt;Voltage Blue: 3.3V&lt;/em&gt;&lt;br&gt;&#xA;&lt;em&gt;Current per color: 20mA&lt;/em&gt;&lt;br&gt;&#xA;&lt;em&gt;Common anode&lt;/em&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the TLC5940 is a current sink, how would I make sure each led gets the correct voltage. Hook up a resistor between each cathode and the TLC5940?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please forgive me for asking such a simple question, I'm still learning :).&lt;/p&gt;&#xA;" OwnerUserId="3362" LastActivityDate="2011-03-12T18:28:02.770" Title="TLC5940 with multiple voltage RGB LEDs" Tags="&lt;led&gt;&lt;voltage&gt;&lt;pwm&gt;" AnswerCount="1" />
  <row Id="11380" PostTypeId="2" ParentId="11374" CreationDate="2011-03-12T18:01:46.473" Score="1" ViewCount="" Body="&lt;p&gt;You are not only going to fry power supply, but also damage your supercap - it's internal connections cannot withstand high peak currents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Charge it with some 0.1A current using current-limiting resistor in the simplest case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same applies for discharging - never short leads.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-12T18:01:46.473" CommentCount="1" />
  <row Id="11381" PostTypeId="2" ParentId="11374" CreationDate="2011-03-12T18:04:37.923" Score="1" ViewCount="" Body="&lt;p&gt;If it were my power supply, I'd have one that can handle dead shorts with some sort current limiting, and not worry about it.   This is inefficient, as power will be dissipated within the power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're worried about inrush current harming the supply, put an inductor in series with the capacitor.  Inductors resist changes in current, but eventually settle into acting like straight wire.  You'll want something like shown here &lt;a href=&quot;http://www.hammondmfg.com/153.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.hammondmfg.com/153.htm&lt;/a&gt; with the laminated core and metal mounting bracket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What size? To get a rough idea...   The fundamental equation for inductors is dI/dt = V/L.  rearrange this for dI = (V/L)dt and imagine capital Greek deltas instead of the infinitesimal lower case 'd's.  The change in current is from zero to the initial inrush current.  Let's put dt at 1 sec, since, although we're not trying to build a resonant circuit, the characteristic frequency for a circuit with 1F and 1H is 1 radians/sec.   Suppose you get a nice hefty 1H coil.  The initial voltage drop across the inductor is 5V.  So we get 5 amps.   In real life, the ESR of the capacitor and the internal resistance of the power supply, as well as its ability to  deliver only so much current, means you probably wont' get that.  To limit the current to say 1A means a 5H coil.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The least efficient way to limit current is with a resistor, or a current regulator such as an LM317.  But this is likely much cheaper than a 5H coil, unless you already have a coil like that in a junk parts box (these were common in old 1960s/1970s TVs)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Supercapacitor charging circuits can get pretty involved for applications that harvest small amounts of energy, where not one microwatt should be wasted, where &gt;90% efficiency in charging is vital.  In some applications, the charging current might be only a small factor greater than leakage current.  A good read with technical details: &lt;a href=&quot;http://www.energyharvestingjournal.com/articles/using-a-supercapacitor-to-manage-your-power-00001921.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.energyharvestingjournal.com/articles/using-a-supercapacitor-to-manage-your-power-00001921.asp&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2011-03-12T18:04:37.923" CommentCount="2" />
  <row Id="11382" PostTypeId="2" ParentId="11374" CreationDate="2011-03-12T18:07:46.083" Score="6" ViewCount="" Body="&lt;p&gt;I have had several students who have used &lt;a href=&quot;http://www.linear.com/product/LTC4425&quot; rel=&quot;nofollow&quot;&gt;super cap chargers&lt;/a&gt;. They provide a lot of nice features like variable current limit on the charging, the particular one that I linked to will also make it so you could use 2 caps with lower voltage on each one and it will make sure you don't over voltage one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only down side is the chips for these are VERY small and can be difficult to solder if you aren't very experienced.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-12T18:07:46.083" CommentCount="1" />
  <row Id="11383" PostTypeId="2" ParentId="11378" CreationDate="2011-03-12T18:28:02.770" Score="4" ViewCount="" Body="&lt;p&gt;Since this is a constant-current sink IC, no resistors are needed in series with the LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current is programmed using a reference resistor connected to one of the pins that sets the reference current used to drive the LEDs, and it is the driver chip's responsibility to make sure the correct voltage and current is applied to the LED. In practice, I have found this works well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could add a resistor in series, but this defeats the purpose of using this chip. It will increase your part count, increase your minimum VDD requirement, and if you need to increase VDD, then you will waste additional power. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Below is the figure used to determine your reference current for each resistor from the &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/tlc5940.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;:&#xA;&lt;img src=&quot;http://i.imgur.com/eTlUM.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-03-12T18:28:02.770" CommentCount="4" />
  <row Id="11384" PostTypeId="2" ParentId="11117" CreationDate="2011-03-12T19:41:12.230" Score="3" ViewCount="" Body="&lt;p&gt;Alas, if highly-specialized and integrated chips don't quite meet your specs, it's impossible to upgrade just that one little section of the chip that is the weak link.&#xA;Some people prefer something &quot;I UNDERSTAND, not a sealed box of unexplained tricks made in the far east using technology I'm unlikely to be able to tweak or repair.&quot; (-- Nick Waterman, G7RZQ).&#xA;You may be one of &lt;em&gt;those people&lt;/em&gt; ;-).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you've already pointed out, a &lt;a href=&quot;http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation&quot; rel=&quot;nofollow&quot;&gt;quadrature amplitude modulation&lt;/a&gt; transmitter has a section that mixes 2 baseband data signals (traditionally called I and Q) into one modulated signal, and the receiver has a surprisingly similar section that decodes the modulated signal into separate I and Q data signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Surely there are ICs that do most or all of the job for me, but searching for &quot;QAM encoder&quot; doesn't give me any ICs.&#xA;Perhaps there is another name for these ICs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Historically the 2 devices in a QAM encoder or the 2 devices in a QAM decoder that &quot;multiply 2 signals together&quot; are each often called a &quot;RF/IF mixer&quot;, even when it is used in a system that doesn't have a radio antenna, in order to distinguish it from &quot;audio mixer&quot; which acts completely differently.&#xA;&lt;a href=&quot;http://www.analog.com/static/imported-files/tutorials/MT-080.pdf&quot; rel=&quot;nofollow&quot;&gt;Analog Devices tutoral &quot;MT-080: Mixers and Modulators&quot;&lt;/a&gt;&#xA;lists a bunch of specific ICs such as the AD8345 QAM encoder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see that at one of my favorite &lt;a href=&quot;http://opencircuits.com/Supplier&quot; rel=&quot;nofollow&quot;&gt;electronic supply websites&lt;/a&gt;, that QAM encoder chip is called a &quot;quadrature modulator&quot;.&#xA;I searched for &quot;quadrature demodulator&quot; and &quot;quadrature modulator&quot; at a few of my favorite electronic supply websites and found list of ICs in stock that, if I understand what you are asking, seem to meet your requirements.&#xA;Analog AD8345,&#xA;Linear LT5502,&#xA;RFMD RF2480SR,&#xA;RFMD RF2713,&#xA;etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The chips I listed contain 2 of the &quot;RF mixer&quot; devices in one IC.&#xA;I suppose you could use a pair of chips that each contain only a single &quot;RF mixer&quot; such as a pair of the popular SA612 chips (the &lt;a href=&quot;http://soldersmoke.blogspot.com/2009/06/na5n-on-ne602.html&quot; rel=&quot;nofollow&quot;&gt;same chip is also called the SA602, the NE602, the NE612&lt;/a&gt;, etc.).&#xA;Or perhaps a person could build each &quot;RF mixer&quot; out of discrete transistors -- perhaps in the &lt;a href=&quot;http://en.wikipedia.org/wiki/Gilbert_cell&quot; rel=&quot;nofollow&quot;&gt;Gilbert cell&lt;/a&gt; configuration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mathematicians often call this device a &quot;multiplier&quot; and feed a sine wave into one and a cosine wave into the other, in order to make the math simpler.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ham radio operators often build IQ decoders that use square waves instead of sine waves, such as the Tayloe decoder, in order to make construction easier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While I agree that it would be nice if a QAM decoder could decode I and Q signals all the way down to DC, many systems fake it. They &lt;em&gt;appear&lt;/em&gt; as if they can produce a constant, solid green color over the entire screen -- apparently a fixed DC level -- while internally they take the I and Q signals and immediately throw away the low-frequency components through &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/3303&quot; rel=&quot;nofollow&quot;&gt;AC-Coupled Video Signals&lt;/a&gt; and somehow magically restore the &quot;right&quot; DC level at a later stage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC restoration, synchronizing the receiver frequency and phase to the transmitter frequency and phase, and restoring amplitude path loss with automatic gain control, are almost always handled in a separate part of the system from the actual modulator and demodulator.&#xA;As you already know, NTSC and PAL hide extra information in the horizontal retrace and vertical retrace time intervals to make the receiver's job possible/easier.&#xA;I suppose you could define a special time where the transmitter sets I to +MAX and Q to 0, and other special times with the 8 other combinations of I and Q with +MAX, 0, and -MAX.&#xA;Then the receiver could use the non-image information it sees at its I and Q outputs at those times to help with frequency synchronization, phase synchronization, automatic gain control, and DC restoration.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-12T19:41:12.230" />
  <row Id="11385" PostTypeId="2" ParentId="11374" CreationDate="2011-03-12T20:14:15.340" Score="2" ViewCount="" Body="&lt;p&gt;Buy a CC/CV power supply, I picked up a 3A one for £40. I've used them before and they won't damage themselves, even with a continuous short. You can set the CV control to about 5 volts and the CC control to the maximum charge current - 1 or 2 amps. Initially, current will stay high, but as the voltage rises the supply will drop the current automatically. Plus, the CV control ensures the cap won't ever be damaged by a high supply voltage.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-12T20:14:15.340" />
  <row Id="11386" PostTypeId="1" CreationDate="2011-03-12T21:21:50.900" Score="1" ViewCount="110" Body="&lt;p&gt;Hello, sometime ago I built an emulator for the 8086 chip and now I'm wanting to actually own one and set one up for some bit banging and such. Note, I'm not interested in all the PC specifics(DMA, PIC, BIOS, etc) only the bare basics to get the 8086 to run some code, which as I understand only requires a power supply, oscillator/clock source, and some RAM(unknown which type?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, for the most part all of the components are easy to find except for the one I need: The 8086 processor itself. I've not been able to find anything but (very pricey) collector's items 8086 chips. So where can I find a reasonably priced replica 8086 chip? Note: The pin out doesn't need to be the exact same, but I'd prefer it to be DIP and expose all of the features of the 8086. Also, don't just say &quot;try buying an old 486 computer&quot; After the 8086, the x86 line of processors got insanely complex. For this reason, I'm sticking to just the 8086. Though possibly an 8186 would be OK. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if there is a system-on-chip type 8086 setup, that'd be awesome. (Note, I'm just talking about a chip that includes the RAM  and possibly some flash ROM on it)&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-03-12T22:27:17.910" Title="Where can I find an 8086 chip?" Tags="&lt;microprocessor&gt;&lt;system-on-chip&gt;&lt;8086&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="11387" PostTypeId="2" ParentId="11386" CreationDate="2011-03-12T21:35:32.627" Score="0" ViewCount="" Body="&lt;p&gt;Try one of &lt;a href=&quot;http://octopart.com/partsearch/#search/requestData&amp;amp;q=8086&amp;amp;filters%5Bmanufacturer%5D%5B%5D=Intel&amp;amp;rangedfilters%5Bavg_avail%5D%5Bmin%5D=1&amp;amp;rangedfilters%5Bavg_avail%5D%5Bmax%5D=null&quot; rel=&quot;nofollow&quot;&gt;these vendors that say they have it in stock&lt;/a&gt;.  The 8186 might be tougher to find.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-12T21:35:32.627" />
  <row Id="11388" PostTypeId="2" ParentId="11386" CreationDate="2011-03-12T21:47:52.920" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://opencores.org/project,zet86&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is an 80186 FPGA emulation, using it might be easier than finding real silicon. It even runs Windows! You can strip out all the stuff you don't need, if you just want to run some 80186 code.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-12T21:55:05.957" LastActivityDate="2011-03-12T21:55:05.957" CommentCount="1" />
  <row Id="11389" PostTypeId="1" CreationDate="2011-03-12T21:50:06.597" Score="1" ViewCount="138" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was checking in some bags at the lab looking for capacitors and found one full (a lot!) of green (ceramic?) capacitors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The capacitors are green, round, flat, with two legs on each side, like so:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  __&#xA; (__)&#xA; /  \&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The package image is:&lt;br&gt;&#xA; &lt;img src=&quot;http://i.imgur.com/CTn4H.jpg&quot; alt=&quot;Capacitor image&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only inscription in the package is: 1/NPO&lt;/p&gt;&#xA;&#xA;&lt;p&gt;None of the multimeters on the lab has capacitance mode. Is there any way to identify what this capacitor is?&lt;/p&gt;&#xA;" OwnerUserId="3365" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-12T23:52:52.413" LastActivityDate="2011-03-14T18:06:11.727" Title="Identify an unknown capacitor" Tags="&lt;capacitor&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="11390" PostTypeId="2" ParentId="11386" CreationDate="2011-03-12T21:51:34.587" Score="0" ViewCount="" Body="&lt;p&gt;I just found КР1810ВМ86 on &lt;a href=&quot;http://cgi.ebay.com/KR1810VM86-Soviet-CPU-Clones-Intel-8086-/180636103907&quot; rel=&quot;nofollow&quot;&gt;e-bay&lt;/a&gt; for sale. It should be pin compatible.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-12T21:51:34.587" CommentCount="2" />
  <row Id="11391" PostTypeId="2" ParentId="11363" CreationDate="2011-03-12T22:15:56.407" Score="0" ViewCount="" Body="&lt;p&gt;What about analog computer? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy discrete integrators and multipliers and have output directly available for oscilloscope in real time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The downside of that is that, as far as I can see, actual analog computer components tend to be expensive and rare these days, so you might be forced to make them yourself using mostly op-amps (which will have negative impact on accuracy) and that you'd have to make a new circuit for each equation you want to solve. Still, they are definitely the fastest solution because they work at speed of propagation of electrical signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A positive side it that on analog computers it is pretty obvious how everything works and how equation gets turned into electrical signal. Plus you get to use lots of really cool potentiometers too!&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-12T22:15:56.407" CommentCount="1" />
  <row Id="11392" PostTypeId="2" ParentId="11386" CreationDate="2011-03-12T22:27:17.910" Score="3" ViewCount="" Body="&lt;p&gt;You can get the 8088 from futurlec.com for about $4.  Its an 8086 with an 8-bit external bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try searching for &quot;NEC v20&quot; which was an 8086 clone that was popular.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 80186 is the embedded system-on-chip equivalent, there's tons of variants of that still in use.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-12T22:27:17.910" CommentCount="1" />
  <row Id="11393" PostTypeId="2" ParentId="11389" CreationDate="2011-03-12T23:12:32.313" Score="6" ViewCount="" Body="&lt;p&gt;I vote for 1pf. NP0 dielectric is the one being used in smallest caps.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-12T23:12:32.313" CommentCount="1" />
  <row Id="11394" PostTypeId="1" CreationDate="2011-03-13T01:01:42.860" Score="1" ViewCount="69" Body="&lt;p&gt;If I have a &lt;a href=&quot;http://support.advantech.com.tw/support/DownloadDatasheet.aspx?Literature_ID=2fcec812-9336-4818-bbc1-a94fc49f8856&amp;amp;utm_source=www.advantech.com&amp;amp;utm_medium=Download&amp;amp;utm_campaign=PCM-9361+Data+Sheet&quot; rel=&quot;nofollow&quot;&gt;PCM-9361 Intel Atom board&lt;/a&gt; that says it uses 12V power supply and under max power consumption it uses 0.09A - does this mean the board uses 1.08 watts per hour?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the board specs says if being powered by 5V, the max power is 2.38A... why does 5V use a lot more power than 12V?&lt;/p&gt;&#xA;" OwnerUserId="3367" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-03-13T08:56:15.373" LastActivityDate="2011-03-13T09:02:15.760" Title="Calculating power requirements" Tags="&lt;power-supply&gt;&lt;12v&gt;&lt;5v&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="11395" PostTypeId="2" ParentId="11227" CreationDate="2011-03-13T01:10:22.930" Score="0" ViewCount="" Body="&lt;p&gt;Your specs are contradictory, something at that low of a clock rate is going to be an embedded microcontroller and not have any external memory, hardly any external pins for that matter.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Really dont understand the desire for external memory, you can find 128K or 256K perhaps even 512K on chip, usually zero wait state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get those features you are going to end up with a considerably faster processor, that doesnt mean you have to run it that fast, but to get those interfaces and features you will end up there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Expanding on the answers already given.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should investigate an fpga solution.  Lattice has a couple of soft cores as does xilinx, eval boards can be had from a number of places knjn.com avnet, etc.  Too bad the $50 spartan3a board I have is no longer available.  Opencores has many cores you can use, the zpu for example, full gcc compiler support.  An fpga solution will allow you the maximum flexibility, perhaps more than one, one for the processor core with a generic memory interface then another for the video support, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the PIC32 series is a mips so there should be tons of support out there, on chip memory sure...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some folks have Atari 2600 solutions out there as well as amiga, you might grab some components from those efforts and mix and match.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;rabbit semi now digi has some with 8/16 bit external memory interfaces.  This is a modified z80 core if I remember right.  Dallas now maxim had the TINI board with an 8051 based deal and I know it supported external flash, they wanted to run java so it may have had external ram.  The sdcc compiler was known for 8051's if I remember right.  I think renesas is another 8051 house, and no doubt you could find or build an 8051 in an fpga.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I highly recommend going with something arm based.  atmel, st, stellaris (ti), a laundry list of others.  Cirrus has an ARM7 with a cache and an external 32 bit memory bus, perhaps the arm9 version has external memory as well.  You can buy boards from embeddedarm.com that use cirrus parts.  Omap and marvell though are the ones to look for, granted you are looking at hundreds of MHz but the parts have what you are interested, external memory interfaces, video, etc.  boards like the hawkboard, beagleboard (I really dislike the beagleboard, big ripoff, go for the chinese knockoff, like my hawkboards better but looks like there was a design issue), there is the open-rd (I like it much better than the plug computers).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could dissect a gameboy advance, gives you a parallel interface, design something around the charmed labs xport.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-03-13T01:10:22.930" CommentCount="1" />
  <row Id="11396" PostTypeId="2" ParentId="11394" CreationDate="2011-03-13T01:24:40.163" Score="1" ViewCount="" Body="&lt;p&gt;watts are already joules &lt;em&gt;per second&lt;/em&gt;.  &quot;watts per hour&quot; is wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it draws 0.09A max, then it uses 1.08 watts max.  Max doesn't necessarily mean average, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know why it would draw 10x as much power at lower voltage.  What kind of board is this?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-03-13T01:24:40.163" CommentCount="3" />
  <row Id="11397" PostTypeId="1" CreationDate="2011-03-13T02:20:26.490" Score="1" ViewCount="117" Body="&lt;p&gt;Greetings,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a 10'x10' shed that gets hot as hades inside, and want some ventilation involving pushing air through a hole I would punch in a wall near the roof peak and screen over so my friends the wasps don't move in.  With a gas-powered mower and weed whacker, gas cans, and spare propane tanks for the bbq and camping lantern, it gets thick with fumes, and I'm uncomfortable with how hot it gets in there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have myself a salvaged solar panel in a weather-proof frame, which in its former life charged a battery that then ran a string of little LEDs at night.  It being March, I don't know what to expect from summer sun in terms of juice production, but I did test with a single 60w incandescent bulb in a reading lamp pointed directly down at the panel.  The multimeter registers 6.5v/1.3a at a distance of about 6&quot;, and with the bulb just about directly over the panel, just barely 9v/2a.  This is direct from the panel; the battery and charging bits have been removed.  They had stopped charging and/or holding a charge, which is how I inherited this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a fan in this vein that came from an old external hard drive enclosure which puts out enough air, I think, to do the job:  en.wikipedia.org/wiki/Centrifugal_fan&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's marked 12v/0.38a.  It would be inside the shed blowing through the opening I make.  Solar shed vents sold for this purpose are $40+ and reviews say they all just plain suck and are worthless.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'd like advice on is how to take this panel's output, which I can't imagine ever getting above the 9v/2a number, and probably hoping for the 6.5v/1.3a is optimistic, stepped up to 12v at sufficient amps to turn this fan.  I found the items below which to my novice eye seem like they might be steps in the right direction:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tinyurl.com/457sr8t&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/457sr8t&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tinyurl.com/4vkqapo&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/4vkqapo&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I out of my mind?  Could a device like one of the above take the panel's output and put out enough to get me 12v/0.38a if I get enough direct light?  Is there some other, better way to go about this based on the panel I have?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for your patience and any advice!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Gene&lt;/p&gt;&#xA;" OwnerUserId="3368" LastActivityDate="2011-03-20T18:55:23.887" Title="Advice making simple solar shed vent from salvaged panel" Tags="&lt;solar-cell&gt;&lt;fan&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="11398" PostTypeId="1" AcceptedAnswerId="11437" CreationDate="2011-03-13T02:28:15.487" Score="4" ViewCount="197" Body="&lt;p&gt;I've been looking for things like the plugs displayed on these orange wires in this photo:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ebc1o.jpg&quot; alt=&quot;mysterious item&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are they called?  I imagine that this is a part that I could buy somewhere.&lt;/p&gt;&#xA;" OwnerUserId="3077" LastEditorUserId="3370" LastEditorDisplayName="" LastEditDate="2011-03-13T10:11:59.017" LastActivityDate="2011-03-14T03:17:24.067" Title="What are these plug-like cable endings called?" Tags="&lt;breadboard&gt;&lt;parts&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="11399" PostTypeId="2" ParentId="11389" CreationDate="2011-03-13T03:05:23.133" Score="0" ViewCount="" Body="&lt;p&gt;Yes; use an LCR meeter or a better multimeter.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-13T03:05:23.133" CommentCount="2" />
  <row Id="11400" PostTypeId="2" ParentId="11398" CreationDate="2011-03-13T04:26:11.580" Score="2" ViewCount="" Body="&lt;p&gt;Patch cords?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless I'm missing something, functionally, they're the same as wires. I wouldn't bother with them and would just use solid-core 22ga wire for solderless breadboard.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-03-13T04:26:11.580" CommentCount="2" />
  <row Id="11401" PostTypeId="2" ParentId="11374" CreationDate="2011-03-13T04:36:23.423" Score="1" ViewCount="" Body="&lt;p&gt;Step 1: Specify the constraints on the charging behavior that you want, based on the characteristics of the capacitor and/or your power supply. (e.g. current limit of not more than 0.2A or 0.5A or 0.1A or whatever)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Step 2: Build a circuit that will meet those characteristics. If the current is low, you can just do this with a resistor. It turns out if you do the math that charging a capacitor through a resistor from 0V to some fixed voltage, always wastes exactly 50% of the energy involved, so it's not hugely efficient, but it's not horribly inefficient either. If you need higher efficiency, you need a switching power supply of some kind. The ones appropriate for this application would produce nearly constant current into the capacitor with a voltage limit.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-03-13T04:36:23.423" />
  <row Id="11402" PostTypeId="1" CreationDate="2011-03-13T04:39:48.280" Score="2" ViewCount="105" Body="&lt;p&gt;I am building my first microcontroller programmer using &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc0265.pdf&quot; rel=&quot;nofollow&quot;&gt;at89c51&lt;/a&gt;. In its documentation I have read that it support 3 level programming lock. But I did not find a simple explanation of this term.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will somebody explain what are memory locks and what is mean by 3 level in this context?&lt;/p&gt;&#xA;" OwnerUserId="2951" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-13T06:51:45.237" LastActivityDate="2011-03-13T09:08:10.980" Title="What is mean by 3 level program memory lock?" Tags="&lt;atmel&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11403" PostTypeId="2" ParentId="11369" CreationDate="2011-03-13T05:44:04.427" Score="0" ViewCount="" Body="&lt;p&gt;There are a number of kinds of linear motor. Which are you referring to?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.baldor.com/products/linear_motors.asp&quot; rel=&quot;nofollow&quot;&gt;Baldor&lt;/a&gt; makes a number of varieties, and their page has an &lt;a href=&quot;http://www.baldor.com/products/linear_motors.asp&quot; rel=&quot;nofollow&quot;&gt;excellent overview&lt;/a&gt; of the different types.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm most familiar with linear stepper motors, which are a &lt;em&gt;type&lt;/em&gt; of linear motor. However, there are Brushless DC and even AC Induction varieties.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I will say that they are generally as or more expensive as a comparable stepper/servo motor and lead-screw arrangement, and are much less common on the surplus market.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given that, I think you would be better off trying to snag a long leadscrew on ebay, rather then find a similar sized linear motor. Then, just add end supports, a motor, and some linear bearings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are you trying to do, anyways?&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-03-13T05:44:04.427" CommentCount="1" />
  <row Id="11404" PostTypeId="2" ParentId="11398" CreationDate="2011-03-13T06:13:57.547" Score="3" ViewCount="" Body="&lt;p&gt;OK, they are known as 'Jumper Wires'  Here is a link to some that SparkFun sells.  I'll bet that they can easily be located in different sizes, etc. elsewhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/9194&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/9194&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This page refers to them as 'leads' and gives some DIY instruction on making them stackable:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/Stackable-Jump-leads-for-BreadBoards/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Stackable-Jump-leads-for-BreadBoards/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And again, for the DIY type person, on page 6 of this catalog is a crimp-style terminal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.molex.com/catalog/web_catalog/pdfs/C.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.molex.com/catalog/web_catalog/pdfs/C.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3077" LastEditorUserId="3077" LastEditorDisplayName="" LastEditDate="2011-03-13T06:32:47.163" LastActivityDate="2011-03-13T06:32:47.163" CommentCount="5" />
  <row Id="11405" PostTypeId="2" ParentId="11312" CreationDate="2011-03-13T06:46:11.880" Score="1" ViewCount="" Body="&lt;p&gt;If you can send &lt;code&gt;AT&lt;/code&gt; commands to your bluetooth module, you can also discover nearby devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See for example &lt;a href=&quot;http://www.cooking-hacks.com/index.php/documentation/tutorials/arduino-bluetooth#step2&quot; rel=&quot;nofollow&quot;&gt;this guide&lt;/a&gt;. In the example they are sending commands from computer, but you can do exactly the same with your Arduino. Sending command&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;AT+JDDS=0&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;should return list of matching devices. Additionally, you can also search for specific services:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;AT+JSDS=0026C3AB5A39,1101&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Where &lt;code&gt;0026C3AB5A39&lt;/code&gt; is MAC address of device and &lt;code&gt;1101&lt;/code&gt; is code for serial port.&lt;/p&gt;&#xA;" OwnerUserId="3064" LastActivityDate="2011-03-13T06:46:11.880" CommentCount="1" />
  <row Id="11406" PostTypeId="2" ParentId="11398" CreationDate="2011-03-13T06:53:10.800" Score="0" ViewCount="" Body="&lt;p&gt;Those look like single row breakaway headers, like these: &lt;a href=&quot;http://rndwarehouse.com/breakaway-headers-1x40-straight-singlerow-extended-height-p-213.html?zenid=83og3qmqjb3g10obpv92sbavo7&quot; rel=&quot;nofollow&quot;&gt;http://rndwarehouse.com/breakaway-headers-1x40-straight-singlerow-extended-height-p-213.html?zenid=83og3qmqjb3g10obpv92sbavo7&lt;/a&gt;.  I've done this in the past as it's the cheapest way to get non-solid core jumper wires for breadboarding.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to make them, you get a 40 pin header like the one I linked to, and then &lt;em&gt;carefully&lt;/em&gt; break them apart, either with clippers or two pairs of pliers.  You want to solder your stranded wire to the short end and then use shrink tube over the connection.  The long end plugs into your breadboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- looking at the picture again, they aren't breakaway headers, but I would still recommend going that route if you're okay with a little soldering.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-03-13T06:53:10.800" />
  <row Id="11407" PostTypeId="2" ParentId="11394" CreationDate="2011-03-13T09:02:15.760" Score="0" ViewCount="" Body="&lt;p&gt;The board is primarily powered from the 5V supply, so that uses most of the power. The 5V supply is required for the board to work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 12V seems just to be needed for some optional stuff, so it is not strictly required (&quot;12V is optional for LCD inverter and add on card&quot;).&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-03-13T09:02:15.760" />
  <row Id="11408" PostTypeId="2" ParentId="11402" CreationDate="2011-03-13T09:08:10.980" Score="1" ViewCount="" Body="&lt;p&gt;Its purpose seems to be to restrict access to the program memory, to prevent reading out the program from a controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are three levels (plus one unprotected level), see the bottom of page 5.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-03-13T09:08:10.980" />
  <row Id="11409" PostTypeId="1" AcceptedAnswerId="11410" CreationDate="2011-03-13T10:20:41.113" Score="0" ViewCount="77" Body="&lt;p&gt;I am doing a project where I need to store information into flash memory and read it back using an mbed. I can't get it to work right, but I noticed that even if there is no connection to power or ground, I can still read non-zero bytes from it. Most of them are 0 but some are 255. Why is that?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="1657" LastEditorDisplayName="" LastEditDate="2011-03-13T10:54:38.557" LastActivityDate="2011-03-13T14:28:32.947" Title="This flash memory works without connection to a power source or gnd?" Tags="&lt;memory&gt;&lt;flash&gt;&lt;mbed&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="11410" PostTypeId="2" ParentId="11409" CreationDate="2011-03-13T10:50:53.540" Score="3" ViewCount="" Body="&lt;p&gt;The inputs are floating and there might be some remaining flux on the board which is slightly conductive, pulling some inputs high or low. If the board was completely clean, you would probably see random values caused by noise.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-13T11:02:58.580" LastActivityDate="2011-03-13T11:02:58.580" />
  <row Id="11411" PostTypeId="1" AcceptedAnswerId="11425" CreationDate="2011-03-13T11:47:07.847" Score="0" ViewCount="152" Body="&lt;p&gt;I am facing this error when try to compile a C program using the SDCC compiler:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The part of programme that is causing error.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;include(reg51.h)&#xA;define cmdport P3&#xA;define dataport P2&#xA;define q 100&#xA;&#xA;(following  3 line are causing error.)&#xA;sbit at  cmdport^0  rs ;  //register select pin&#xA;sbit at  cmdport^1  rw ;  // read write pin&#xA;sbit at  cmdport^6  e ;  //enable pin&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2951" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-13T20:40:17.310" LastActivityDate="2011-03-14T17:24:18.177" Title="sbit definitions with SDCC - Error: &quot;initializer element is not constant&quot;" Tags="&lt;c&gt;&lt;sdcc&gt;&lt;sbit&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="11412" PostTypeId="2" ParentId="4448" CreationDate="2011-03-13T14:00:21.837" Score="0" ViewCount="" Body="&lt;p&gt;I had the same frustrations with RF-magic V4.2 communicating with APC200A-43A (also sold as CM-12111. I finally got it to work by starting RF magic, connecting the APC200A, then applying power to the APC200A. I think the APC200A has a power-on start up routine that senses the &quot;55AA&quot; sequence being sent by RF-Magic and dynamically adapts to the 119k baud rate RF-Magic uses.&lt;/p&gt;&#xA;" OwnerUserId="3371" LastActivityDate="2011-03-13T14:00:21.837" />
  <row Id="11413" PostTypeId="2" ParentId="11409" CreationDate="2011-03-13T14:28:32.947" Score="0" ViewCount="" Body="&lt;p&gt;Assuming that the method of communication with the flash has no pull-up/down on the powered side then the pin is floating and can be influenced by just about anything (stray magnetic fields). Also, there may be internal connection paths on the flash between other pins you are driving (e.g. address or clock) that behave in an undefined manner while power isn't applied.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a commentary roundup from the piclist on the interesting things that float input can do: &lt;a href=&quot;http://www.piclist.com/tecHREF/logic/xtrapins.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.piclist.com/tecHREF/logic/xtrapins.htm&lt;/a&gt; (It's geared toward convincing people not to leave inputs floating on purpose in their designs, but it should provide some insight on what you're experiencing.)&lt;/p&gt;&#xA;" OwnerUserId="3208" LastActivityDate="2011-03-13T14:28:32.947" CommentCount="1" />
  <row Id="11414" PostTypeId="1" AcceptedAnswerId="11415" CreationDate="2011-03-13T14:42:38.677" Score="1" ViewCount="77" Body="&lt;p&gt;Currently I'm working on a DDS based function generator. The idea is to use an AD9834 chip that will generate a triangle/sine or square wave. With some amplification electronics I want a configurable frequency, offset and amplitude. I have no set frequency I want to achieve, but getting more than 10MHz would be nice. I'm trying to get things to work out for the best result.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been looking into ways to switch between several ranges of amplitude resolution. For example, I wish to get 10V amplitude as a maximum but with 1mV step size on the lower amplitudes (&amp;lt;2V). To avoid using a 16-bit DAC I was thinking of using relays to switch between two feedback resistors or two amplification circuits (two different ranges on closed and open contact). The relays would be switched by a microcontroller of somesort that would determine which settings all DAC's and relays should be in for the desired waveform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My main concern is that relays may add additional noise. I think mechanical relays might be OK (is this true?). I was also looking at solid state relays because of their size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I've read on wikipedia that solid state relays have a higher resistance when they are closed and 'increased electrical noise'. How big are the issues with solid-state relays on low-amplitude (100mVpp for example) or high frequency signals (&gt;5MHz). Is it even worth using SSR or use several MOSFETs instead?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I avoid solid-state relays and focus on mechanical switching instead (because I expect they pass through a signal much cleaner)?&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-03-13T16:16:47.457" Title="What kind of effects does a relay have on signals?" Tags="&lt;relay&gt;&lt;noise&gt;&lt;signal-integrity&gt;&lt;solid-state-relay&gt;" AnswerCount="2" />
  <row Id="11415" PostTypeId="2" ParentId="11414" CreationDate="2011-03-13T15:51:17.087" Score="3" ViewCount="" Body="&lt;p&gt;FETs pass signal clean too, as their source&amp;lt;&gt;drain path is like a resistor. &#xA;Especially if you are just at 10Mhz.&#xA;So don't bother and take discrete FETs. If you need resistance &amp;lt;0.1Ohm you can take power FET's which have 12V Gs and Rdson somewhere at 0.01 Ohm, very comparable to relay and reliable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another problem with relays is that their resistance is not consistent, it will change over time and this will cripple your calibration. Anf finally, if you have any mechanical vibration - it will also make things worse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SSR is usually also based on FET's but with additional input&amp;lt;&gt;output insulation (including optocouples for example).&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-13T15:51:17.087" CommentCount="2" />
  <row Id="11416" PostTypeId="2" ParentId="11397" CreationDate="2011-03-13T16:01:48.530" Score="1" ViewCount="" Body="&lt;p&gt;That was a long question :-)&#xA;You are not out of your mind and think in the right direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In fact you can get twice much amps you need for your fan.&#xA;So yes, get one of these modules, and add some extra capacitors on the output (some 10'000 uF) to help it deal with FAN's pulsed current consumption &amp;amp; startup current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can even get way bigger fan, cap will help to start it and it will work even if you have just 30-40% of the power it needs. You just need separate switch for DCDC board and FAN - so that you turn DCDC first, and after 1 second - FAN (so that cap is charged).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And finally, direct sun gives much much more juice than 60 Watt lamp. So you really need more powerful fan &amp;amp; more powerful DCDC.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-13T16:01:48.530" />
  <row Id="11417" PostTypeId="2" ParentId="11414" CreationDate="2011-03-13T16:16:47.457" Score="2" ViewCount="" Body="&lt;p&gt;You can buy relays designed for GHz operation, for example, &lt;a href=&quot;http://uk.farnell.com/panasonic-ew/are1303/relay-coaxial-spdt-3vdc/dp/1448347&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Contact resistance is usually less than 1 ohm, so if you're using kilohm divider resistors, I wouldn't worry about that too much.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-13T16:16:47.457" />
  <row Id="11418" PostTypeId="2" ParentId="11358" CreationDate="2011-03-13T16:59:36.233" Score="2" ViewCount="" Body="&lt;p&gt;There would be some capacitance between the unconnected terminals of the LED and battery, so a little current would have to flow before the unconnected terminals before their potentials was equal to those of the connected terminals.  In practice, however, that level of capacitance would likely be so small as to be impossible to measure much less use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that while a one farad capacitor can accept a whole coulomb of electrons (one amp for one second) before building up a volt of potential difference, that doesn't mean a coulomb of electrons flowing in with none flowing out.  In order for one side of a capacitor to accept a negative charge, the other side must have a balancing positive charge.  Essentially what happens is that as electrons flow into the negative side, their nearby presence makes electrons want to leave the positive side.  Likewise as capacitors leave the positive side, their relative absence makes electrons want to enter the negative side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's possible for substantial AC electric currents to flow without a complete circuit, if there's enough capacitance.  Two leads some distance apart, however, aren't going to have enough electrostatic effect to yield any useful capacitance, though.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-13T16:59:36.233" />
  <row Id="11419" PostTypeId="2" ParentId="2272" CreationDate="2011-03-13T17:06:47.867" Score="1" ViewCount="" Body="&lt;p&gt;Bypass caps are sufficiently cheap that in many cases there's no reason not to put them everywhere.  If space or cost are extreme issues, however, it may be reasonable to leave off a few.  The key is to recognize what may happen if they are left off.  My suggestion would be to assume a worst-case scenario if they're left off: (1) RF radiation at the input switching frequency may be increased, and (2) any time an input switches, assume the device's outputs and internal state may be arbitrarily glitched.  If either of these behaviors would be a problem, bypass caps are required.  If neither would be a problem (e.g. because none of the inputs switch often enough for radiation to be a problem, the device has no internal state, and nothing will care about the state of the outputs at the moments when the inputs are switching) then bypass caps may be omitted.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-13T17:06:47.867" />
  <row Id="11420" PostTypeId="2" ParentId="8685" CreationDate="2011-03-13T17:39:43.670" Score="4" ViewCount="" Body="&lt;p&gt;One early form of read-only memory was a grid where the the address would select a row (pulling it low), and the columns represented data.  Each column would have a pull-up, and each intersection would have a diode soldered in to represent a &quot;zero&quot;, or no diode to represent a &quot;one&quot; [bit levels could be inverted if desired, in cases where that would reduce the number of diodes required].  Any desired pattern of bits could be &quot;programmed&quot; by soldering in the proper diodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This design was brought into the integrated-circuit world in the form of a fuse-PROM.  Essentially a fuse PROM was a circuit just like the above, built onto a chip, except that all diodes were populated, and every diode had a weak fuse in series with it.  As shipped, a PROM would read &quot;0&quot; at all locations.  One could, however, selectively remove diodes by selecting the appropriate address and driving the appropriate data lines &quot;hard&quot; high [note: I think each bit may have had its own transistor, rather than a diode, but the principle is the same].&lt;p&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fuse-programmed PROMs were succeeded by semiconductor memories, which store bits by implanting charges on internal capacitors.  Not only are such memories more compact than fuse-PROMs, but if they are housed in UV-transparent packages they may be erased and reused.  Note that even so-called &quot;one-time programmable&quot; memories almost always use this same design, but are simply housed in UV-opaque packages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/qavEI.jpg&quot; alt=&quot;two men pointing at a large diode matrix&quot;&gt;&#xA;diode-matrix control store of the 1950 &lt;a href=&quot;http://www.cs.clemson.edu/~mark/uprog.html&quot; rel=&quot;nofollow&quot;&gt;MIT Whirlwind Computer&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/S2FLZ.jpg&quot; alt=&quot;transistor-matrix with tiny SMD transistors&quot;&gt;&#xA;transistor-matrix control store of 2005 &lt;a href=&quot;http://www.6502.org/users/dieter/mt15/mt15.htm&quot; rel=&quot;nofollow&quot;&gt;the MT15 CPU&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-04-15T01:13:42.523" LastActivityDate="2011-04-15T01:13:42.523" CommentCount="1" />
  <row Id="11421" PostTypeId="2" ParentId="11117" CreationDate="2011-03-13T18:05:18.027" Score="0" ViewCount="" Body="&lt;p&gt;Consider a A/D plus a FPGA.  Altera has &lt;a href=&quot;http://www.altera.com/literature/wp/wpstxiiqam.pdf&quot; rel=&quot;nofollow&quot;&gt;this app note&lt;/a&gt;.  They may even have an eval board with the A/Ds on board. Since you aren't looking at a particular standard, I fear you will mainly find more highly integrated parts than you are looking for.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-13T18:05:18.027" CommentCount="2" />
  <row Id="11422" PostTypeId="1" AcceptedAnswerId="11465" CreationDate="2011-03-13T18:09:57.453" Score="1" ViewCount="121" Body="&lt;p&gt;I'm currently using a Mastek 1803D (Adjustable Voltage and Current 0-18VDC, 0-3A). When I need an additional voltage I've been breaking out an LM317+Wall Wart supply I got started with. I'd like to move up to something with at least one output good for 30+VDC/5+A and more outputs, preferably adjustable. All that and I'd like to stay under ~$200.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The driver behind this is working with a combination of 3.3V, 5V, and Motors (and I foresee 1.8V eventually being needed to). I deal with it now using linear regulators but I'd like to have the bench supply handle it all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, background out of the way, what would folks recommend? I'm open to a do it all unit, or maybe buying 2 more single supply units and tying all the grounds together. The current limiting features seem to rule out most DIY/ATX Power supply approaches, maybe use those for the fixed voltages and tying it with a standalone? Should I be going with a fixed output supply for the primaries? (I've found lots of 3 supply 5/12/Variable units but no 3.3/5/Variable).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thoughts? (Thanks in advance.)&lt;/p&gt;&#xA;" OwnerUserId="3208" LastActivityDate="2011-03-14T16:57:18.523" Title="Bench Power Supply" Tags="&lt;power-supply&gt;&lt;equipment&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="11423" PostTypeId="2" ParentId="2931" CreationDate="2011-03-13T18:33:55.903" Score="0" ViewCount="" Body="&lt;p&gt;Devices may be designed with one or more of the following types of overload protection:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;When overheated sufficiently, have something melt in such a way as to kill power before things catch on fire.&#xA;&lt;li&gt;When overheated sufficiently, have something shut down before things are damaged.&#xA;&lt;li&gt;When overloaded, cut back on power output sufficiently to prevent the supply from overheating.&#xA;&lt;li&gt;When overloaded, cut back on power output sufficiently to prevent either the supply or the load from overheating.&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Different supplies will do different things when trying to drive a load which behaves as a voltage clamp.  Some supplies will limit the output current, independent of voltage.  Some will limit the output power (so a load which clamps at 3 volts will receive twice the power of one that clamps at 6).  Some will decide something is wrong and shut off completely (until input power is removed and reapplied) or partially (until even the reduced output current will suffice to allow the output voltage to reach its target).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's probably worthwhile to get a supply which won't itself be damaged by an output overload condition.  Depending upon what you're driving, it may or may not be good to have a supply that will attempt to protect the load as well.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-13T18:33:55.903" />
  <row Id="11424" PostTypeId="2" ParentId="11411" CreationDate="2011-03-13T19:26:29.273" Score="0" ViewCount="" Body="&lt;p&gt;My guess is that this is an assembly file - you need to run it through an assembler rather than the C compiler.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many C compilers (especially gcc based ones) will recognise a file with a particular suffix (.s for example) and do the right thing for you - other compilers wont - if you're using a make file that was written for gcc with a different compiler you might find that it makes this mistake&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-13T19:26:29.273" />
  <row Id="11425" PostTypeId="2" ParentId="11411" CreationDate="2011-03-13T20:30:17.493" Score="5" ViewCount="" Body="&lt;p&gt;Your code is not valid C. It should look like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;reg51.h&amp;gt;&#xA;#define cmdport P3&#xA;#define dataport P2&#xA;#define q 100&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;To create &lt;code&gt;sbit&lt;/code&gt; definitions for the individual bits in &lt;code&gt;P3&lt;/code&gt; (address 0xB0), you want:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;__sbit __at (0xB0) rs; // P3.0&#xA;__sbit __at (0xB1) rw; // P3.1&#xA;__sbit __at (0xB6) e;  // P3.6&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Though, if you look in &lt;code&gt;sdcc/includes/mcs51/8051.h&lt;/code&gt; you'll find that there are already generic definitions for &lt;code&gt;P3_0&lt;/code&gt; and so on, allowing you to write:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define rs P3_0&#xA;#define rw P3_1&#xA;#define e  P3_6&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I'd also recommend that you pick more descriptive names for your bit definitions than &lt;code&gt;rs&lt;/code&gt;, &lt;code&gt;rw&lt;/code&gt; and &lt;code&gt;e&lt;/code&gt; as these may clash with variable names.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-14T17:24:18.177" LastActivityDate="2011-03-14T17:24:18.177" CommentCount="3" />
  <row Id="11426" PostTypeId="1" AcceptedAnswerId="11429" CreationDate="2011-03-13T20:49:41.913" Score="1" ViewCount="80" Body="&lt;p&gt;I have a dataflash memory that is too small to fit on a prototype board, so it has been put on a small board. I am having trouble figuring out where pin 1 is on this board. Below is a picture of the setup. The small circle on the chip is where pin 1 is. Underneath the large circles are the pins that connect to the board. Where on the board is pin 1? How do the lines connect to the memory? For the large circles on the right, how can they be connected to the chip if no lines can be seen going to them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/8N5mv.png&quot; alt=&quot;&quot; title=&quot;Hosted by imgur.com&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The pins on the dataflash memory are like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;1. chip select&#xA;2. data output&#xA;3. write protect&#xA;4. ground&#xA;5. data input&#xA;6. clock&#xA;7. hold input&#xA;8. vcc&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If I do a continuity test on pins 4 and 8, I should get continuity, right? What are pin combinations will work?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="1657" LastEditorDisplayName="" LastEditDate="2011-03-13T20:57:47.363" LastActivityDate="2011-03-13T21:13:16.300" Title="How is the board connected to this chip?" Tags="&lt;memory&gt;&lt;pins&gt;&lt;protoboard&gt;" AnswerCount="2" />
  <row Id="11427" PostTypeId="1" CreationDate="2011-03-13T20:50:49.880" Score="0" ViewCount="279" Body="&lt;p&gt;Hi Guys, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to communicate to a PC using an RS 232 interface. I'm using a XLP 16 bit Development Board that has a PIC24F built onto it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't really have much experience with PIC programming, so please clarify a few of my questions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right now, all I want to do is get data, anything even a single character from the PIC to go to my PC. I have it connected using an RS232 cable with DB 9 male/female connectors. All I want my &lt;strong&gt;PIC to do is transmit&lt;/strong&gt; (no receive). I have set up my PC to use Hyperterminal and set the baud rate conifuration and other parameters correctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-Do I need to look at using interrupts to get this single communication working?&#xA;-Is the only thing needed to transmit data to just transmit to the &lt;strong&gt;U1TXREG&lt;/strong&gt; register?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was trying to follow the sample code from: &lt;a href=&quot;http://www.nutsvolts.com/media-files/200711-16_BIT_DRIVER.c_.txt&quot; rel=&quot;nofollow&quot;&gt;http://www.nutsvolts.com/media-files/200711-16_BIT_DRIVER.c_.txt&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And the most relevant code that I have is:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;//&lt;strong&gt;&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;&lt;/strong&gt; //* INITIALIZE UART1 &#xA;  //&lt;strong&gt;&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;&lt;/strong&gt;&lt;br&gt;&#xA;  U1BRG = 0x0019;   // Have clk frq of 8 Mhz, want to use Baud rate of 9600&lt;br&gt;&#xA;  U1MODE = 0x8000; // Reset UART to 8-n-1, alt pins, and enable &#xA;  U1MODEbits.UARTEN = 1; // Enable the UxTX pin as an output.&#xA;  U1STAbits.UTXEN = 1;   // Enable the UxRX pin as an input.&lt;br&gt;&#xA;  U1STA  =0x0400;// Reset status register and enable TX &amp;amp; RX&lt;br&gt;&#xA;  _U1RXIF=0; // Clear UART RX Interrupt Flag&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;In Main code :&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;//&lt;strong&gt;&lt;em&gt;*&lt;/em&gt;***&lt;em&gt;&lt;/strong&gt; //&lt;/em&gt; ECHO CHARACTER CODE&#xA;  //&lt;strong&gt;&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;**&lt;em&gt;*&lt;/em&gt;&lt;/strong&gt;&lt;br&gt;&#xA;  while (_U1RXIF==0); // Wait and Receive One Character&lt;br&gt;&#xA;  U1TXREG = 0x0101; //Random number just for test&#xA;        while(!U1STAbits.TRMT);&#xA;        _U1RXIF=0; // Clear UART RX&gt; Interrupt Flag&lt;br&gt;&#xA;  } }&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;I have probed Pin 3 of the UART output on the development bored with a scope to see if I has any output (since Pin 3 is the standard for transmit). But Unfortunately, I see nothing. So that makes me believe that I'm not correctly programming to transmitting anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help or advice will be greatly appreciated. Sorry if the post is lacking information. Please let me know and I will update it ASAP.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Hi Leon, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks a lot for the reply!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did try your code, changing the baud rate however to &lt;strong&gt;0x0019&lt;/strong&gt;, which I calculated from the datasheet, since I only have access to an onboard clock of 8Mhz (and I want to use 9600 bps). I know the operating freq is 8Mhz/2, so I wrote: &lt;strong&gt;#define FCY 400000&lt;/strong&gt; instead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, I still don't see any output. I tried probing the pin 3 on the board again, but no voltage signal. Does the code automatically configure TX output to pin 3?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you mention that this can be done without Interrupts, but I see ISRs in your code, so I'm slightly confused? :).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm going to keep poking around myself and I do appreciate your reply again! &lt;/p&gt;&#xA;" OwnerUserId="3375" LastEditorUserId="3375" LastEditorDisplayName="" LastEditDate="2011-03-13T21:59:47.717" LastActivityDate="2011-04-12T22:27:40.070" ClosedDate="2011-05-04T06:21:27.970" Title="PIC24F : Communicating with PC via RS232 Connection : Programming in MPLAB" Tags="&lt;pic&gt;&lt;microchip&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="11428" PostTypeId="2" ParentId="11426" CreationDate="2011-03-13T20:53:06.217" Score="1" ViewCount="" Body="&lt;p&gt;The tracks might not be visible under the solder mask. If you don't have any documentation you can work out the connections by checking continuity with a DVM.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-13T20:53:06.217" />
  <row Id="11429" PostTypeId="2" ParentId="11426" CreationDate="2011-03-13T20:53:48.213" Score="2" ViewCount="" Body="&lt;p&gt;The tracks may be running underneath the chip, they may be obscured by soldermask, or they may be running on an inner layer of a multi-layer PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use a multimeter with a continuity checker to &quot;buzz out&quot; the connections. Test each leg of the chip against each pin on the board and draw out a map of what connects where.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, reference the datasheet and label the pins on your board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an Atmel dataflash chip, the legs are almost certainly numbered like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; | | | |&#xA;|4 3 2 1|&#xA;|      .|     &#xA;|       |&#xA;|5 6 7 8|&#xA; | | | |&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Here are the pictures from the AT45DB041D datasheet showing the pin arrangement and marker dot:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/XOI8R.png&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/M3Fx4.png&quot; width=&quot;200&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-13T21:13:16.300" LastActivityDate="2011-03-13T21:13:16.300" CommentCount="6" />
  <row Id="11430" PostTypeId="1" CreationDate="2011-03-13T20:54:29.023" Score="1" ViewCount="150" Body="&lt;p&gt;I have a chip with 8 pins. I think I know which pins are VCC and GND, but I'm not sure. If I use a multimeter, can I do a continuity test to find which pins are VCC and GND?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-03-19T03:34:14.363" ClosedDate="2011-03-19T04:51:53.100" Title="How to find VCC and GND on a chip" Tags="&lt;multimeter&gt;&lt;pins&gt;&lt;ground&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="11431" PostTypeId="2" ParentId="11427" CreationDate="2011-03-13T21:04:53.813" Score="0" ViewCount="" Body="&lt;p&gt;Use the Microchip Peripheral Library. You should find the documentation for it in the C30 directory, in the docs\periph_lib folder. The functions are very easy to use. You don't need to use interrupts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is some code that I think worked OK when I tried it:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define FCY 500000UL&#xA;&#xA;#include &amp;lt;p24Fxxxx.h&amp;gt;&#xA;#include &amp;lt;libpic30.h&amp;gt;&#xA;#include&amp;lt;uart.h&amp;gt; &#xA;#include &amp;lt;i2c.h&amp;gt;&#xA;&#xA;/* Received data is stored in array Buf */&#xA;&#xA;char Buf[80];&#xA;char * Receiveddata = Buf; &#xA;&#xA;/* This is UART1 transmit ISR */&#xA;void __attribute__((__interrupt__)) _U1TXInterrupt(void)&#xA;{&#xA;IFS0bits.U1TXIF = 0;&#xA;}&#xA;&#xA;&#xA;/* This is UART1 receive ISR */&#xA;&#xA;void __attribute__((__interrupt__)) _U1RXInterrupt(void)&#xA;{&#xA;   IFS0bits.U1RXIF = 0;&#xA;   /* Read the receive buffer till atleast one or more character can be read */&#xA;   while( DataRdyUART1())&#xA;   {&#xA;   ( *( Receiveddata)++) = ReadUART1();&#xA;   }&#xA;}&#xA;&#xA;   unsigned int config2, config1;&#xA;&#xA;int main(void)&#xA;{&#xA;&#xA;__delay_ms(10);&#xA;&#xA;&#xA;config1 = (I2C_ON &amp;amp; I2C_IDLE_CON &amp;amp; I2C_CLK_HLD &amp;amp;&#xA;&#xA;             I2C_IPMI_DIS &amp;amp; I2C_7BIT_ADD &amp;amp;&#xA;&#xA;             I2C_SLW_DIS &amp;amp; I2C_SM_DIS &amp;amp;&#xA;&#xA;             I2C_GCALL_DIS &amp;amp; I2C_STR_DIS &amp;amp;&#xA;&#xA;             I2C_NACK &amp;amp; I2C_ACK_DIS &amp;amp; I2C_RCV_DIS &amp;amp;&#xA;&#xA;             I2C_STOP_DIS &amp;amp; I2C_RESTART_DIS &amp;amp;&#xA;&#xA;             I2C_START_DIS);&#xA;&#xA;  OpenI2C1(config1,config2);&#xA;&#xA;&#xA;/* Data to be transmitted using UART communication module */&#xA;&#xA;   char Txdata[] = {'M','i','c','r','o','c','h','i','p',   ' ','I','C','D','2','\0'};&#xA;&#xA;/* Holds the value of baud register */&#xA;&#xA;   unsigned int baudvalue;&#xA;&#xA;/* Holds the value of uart config reg */&#xA;&#xA;   unsigned int U1MODEvalue;&#xA;&#xA;/* Holds the information regarding uart&#xA;&#xA;   TX &amp;amp; RX interrupt modes */&#xA;&#xA;   unsigned int U1STAvalue;&#xA;&#xA;/* Turn off UART1module */&#xA;&#xA;   CloseUART1();&#xA;&#xA;/* Configure uart1 receive and transmit interrupt */&#xA;&#xA;   ConfigIntUART1(UART_RX_INT_EN &amp;amp; UART_RX_INT_PR6 &amp;amp;&#xA;&#xA;                  UART_TX_INT_DIS &amp;amp; UART_TX_INT_PR2);&#xA;&#xA;/* Configure UART1 module to transmit 8 bit data with one stopbit.&#xA;&#xA;   Also Enable loopback mode */&#xA;&#xA;   baudvalue = 5;&#xA;&#xA;   U1MODEvalue = UART_EN &amp;amp; UART_IDLE_CON &amp;amp;&#xA;&#xA;   UART_DIS_WAKE &amp;amp; UART_EN_LOOPBACK &amp;amp;&#xA;&#xA;   UART_EN_ABAUD &amp;amp; UART_NO_PAR_8BIT &amp;amp;&#xA;&#xA;   UART_1STOPBIT;&#xA;&#xA;   U1STAvalue = UART_INT_TX_BUF_EMPTY &amp;amp;&#xA;&#xA;   UART_IrDA_POL_INV_ZERO &amp;amp; UART_SYNC_BREAK_DISABLED &amp;amp;&#xA;&#xA;   UART_TX_ENABLE &amp;amp; UART_INT_RX_3_4_FUL &amp;amp;&#xA;&#xA;   UART_ADR_DETECT_DIS &amp;amp;&#xA;&#xA;   UART_RX_OVERRUN_CLEAR;&#xA;&#xA;   OpenUART1(U1MODEvalue, U1STAvalue, baudvalue);&#xA;&#xA;/* Load transmit buffer and transmit the same till null character is&#xA;&#xA;   encountered */&#xA;&#xA;   putsUART1 ((unsigned int *)Txdata);&#xA;&#xA;/* Wait for transmission to complete */&#xA;&#xA;   while(BusyUART1());&#xA;&#xA;/* Read all the data remaining in receive buffer which are unread */&#xA;&#xA;   while(DataRdyUART1())&#xA;&#xA;{&#xA;&#xA;   (*( Receiveddata)++) = ReadUART1() ;&#xA;&#xA;}&#xA;&#xA;/* Turn off UART1 module */&#xA;&#xA;   CloseUART1();&#xA;&#xA;   return 0;&#xA;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-13T21:33:09.443" LastActivityDate="2011-03-13T21:33:09.443" CommentCount="1" />
  <row Id="11433" PostTypeId="1" CreationDate="2011-03-13T23:09:07.857" Score="0" ViewCount="54" Body="&lt;p&gt;I'm trying to get the device ID out of dataflash memory using an mbed. I'm trying to understand this table that is in the documentation for the memory. I understand that ABh, 90h, and 9Fh are the instructions that have to be sent to the memory to get the ID. What is listed under them? Are those the codes that will be returned? What is (ID7-ID0), (ID15-ID0), and (M7-M0)? What is EFh?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/T3PRl.png&quot; alt=&quot;&quot; title=&quot;Hosted by imgur.com&quot; /&gt;&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="1657" LastEditorDisplayName="" LastEditDate="2011-03-13T23:40:02.343" LastActivityDate="2011-03-14T03:58:25.663" Title="How to read this table in a datasheet" Tags="&lt;memory&gt;&lt;identification&gt;&lt;device&gt;&lt;documentation&gt;" AnswerCount="1" />
  <row Id="11434" PostTypeId="2" ParentId="11430" CreationDate="2011-03-14T00:32:39.533" Score="1" ViewCount="" Body="&lt;p&gt;Power it up and look at signals with a scope.  Check some spec sheets to see what common arrangements are.  Combine two.  When you know so what?&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-14T00:32:39.533" />
  <row Id="11435" PostTypeId="2" ParentId="11430" CreationDate="2011-03-14T01:35:25.220" Score="1" ViewCount="" Body="&lt;p&gt;The chip must have a serial number on it. Could you please provide it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you have it, search for that datasheet and look at it. You can know the orientation based on the little dot on the pin 1 (if DIP) or another sign described on the datasheet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Kind regards&lt;/p&gt;&#xA;" OwnerUserId="3365" LastActivityDate="2011-03-14T01:35:25.220" />
  <row Id="11436" PostTypeId="1" AcceptedAnswerId="11438" CreationDate="2011-03-14T01:53:04.440" Score="1" ViewCount="97" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to control with my Arduino some galvanometers I bought. The galvanometer driver board says it need to have a +-5V asymmetrical analog input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My Arduino is connected to a MCP4922-E/P DAC from Microchip through SPI. The output of the MCP4922-E/P is between 0 and +10V (it can be between 0 and +5V if I don't enable the x2 gain). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I &quot;lower&quot; that signal to be between -5V and +5V? I've read the it could be done with some op-amp, but not sure how. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any other advice about the design is welcome. Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="3365" LastEditorUserId="3365" LastEditorDisplayName="" LastEditDate="2011-03-14T02:28:20.057" LastActivityDate="2011-03-14T03:23:10.183" Title="Interface between DAC and galvanometer board" Tags="&lt;arduino&gt;&lt;dac&gt;" AnswerCount="1" />
  <row Id="11437" PostTypeId="2" ParentId="11398" CreationDate="2011-03-14T03:17:24.067" Score="5" ViewCount="" Body="&lt;p&gt;All they are are stiff peices of wire soldered to stranded Wire with a molded rubber case. &#xA;you can buy them from &lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=33&amp;amp;products_id=153&amp;amp;zenid=8967f547ed39a32b68281ada555ae56e&quot; rel=&quot;nofollow&quot;&gt;adafruit&lt;/a&gt;, also called bread-boarding cables, jumper cables, (premium) wire jumpers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/P9VmE.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-14T03:17:24.067" />
  <row Id="11438" PostTypeId="2" ParentId="11436" CreationDate="2011-03-14T03:23:10.183" Score="1" ViewCount="" Body="&lt;p&gt;opamp is one idea - there are plenty of tutorials in the internets, but it might be easier to connect GND of your galvo to +5V. If you don't have +5V, you can make it from your +10V.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-14T03:23:10.183" CommentCount="3" />
  <row Id="11439" PostTypeId="2" ParentId="11433" CreationDate="2011-03-14T03:58:25.663" Score="1" ViewCount="" Body="&lt;p&gt;in table 10.2.2 states M7-M0 are part of the JEDEC register, same with ID15-ID0. &#xA;so when you send your command to read that register it will return those portions of the Register, (MSB first).&#xA;Ehf is the JEDEC manufacture ID, I believe that is the same for all winbond chips in that family.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-14T03:58:25.663" CommentCount="2" />
  <row Id="11440" PostTypeId="1" AcceptedAnswerId="11442" CreationDate="2011-03-14T04:35:13.667" Score="0" ViewCount="41" Body="&lt;p&gt;It's hard to read what is written on this dataflash memory but it looks like 25p80vg. I searched for datasheets and found some things similar to it, but couldn't find anything that matched it exactly. Are there datasheets for this?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-03-14T04:45:14.387" Title="Are there datasheets for this dataflash memory?" Tags="&lt;memory&gt;&lt;flash&gt;&lt;datasheet&gt;" AnswerCount="1" />
  <row Id="11441" PostTypeId="1" CreationDate="2011-03-14T04:42:17.917" Score="3" ViewCount="159" Body="&lt;p&gt;Hi, I want to build a led wall pretty much like this one: &#xA;&lt;a href=&quot;http://www.youtube.com/watch?v=6xriYUzJ9Ls&quot; rel=&quot;nofollow&quot;&gt;interactive led wall&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the different approaches to detect the people passing by? Looking for an easy - unexpensive way to do it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This led wall can be  mounted indoors, and leds / lights may be smaller as well as the whole led array size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="3377" LastActivityDate="2011-03-15T18:51:17.877" Title="What is the Cheapest way to build a proximity-aware led wall." Tags="&lt;led&gt;" AnswerCount="6" CommentCount="2" />
  <row Id="11442" PostTypeId="2" ParentId="11440" CreationDate="2011-03-14T04:45:14.387" Score="1" ViewCount="" Body="&lt;p&gt;the data sheet i used to answer your other question is &lt;a href=&quot;http://pdf1.alldatasheet.com/datasheet-pdf/view/181475/WINBOND/W25P80VFIG.html&quot; rel=&quot;nofollow&quot;&gt;http://pdf1.alldatasheet.com/datasheet-pdf/view/181475/WINBOND/W25P80VFIG.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The last to letters (VG) are voltages And packaging information&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-14T04:45:14.387" CommentCount="2" />
  <row Id="11443" PostTypeId="1" AcceptedAnswerId="13032" CreationDate="2011-03-14T04:52:20.510" Score="2" ViewCount="144" Body="&lt;p&gt;I am trying to read the device ID of a serial flash memory by using the SPI connections on an mbed. In the datasheet for the serial flash memory W25Q80 there is this figure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/XH42w.png&quot; alt=&quot;&quot; title=&quot;Hosted by imgur.com&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The following is the code I'm using to try to read the device ID.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &quot;mbed.h&quot;&#xA;&#xA;SPI spi(p5, p6, p7); // mosi, miso, sclk&#xA;DigitalOut cs(p8);&#xA;&#xA;Serial pc(p9, p10); // tx, rx&#xA;&#xA;int main() {&#xA;    // Setup the spi for 8 bit data, high steady state clock,&#xA;    // second edge capture, with a 1MHz clock rate&#xA;    spi.format(8,0);&#xA;    spi.frequency(1000000);&#xA;&#xA;    // Select the device by seting chip select low&#xA;    cs = 0;&#xA;&#xA;    wait(1.0);&#xA;&#xA;    pc.printf(&quot;response from sending 90h: %d\r\n&quot;, spi.write(0x90));&#xA;    pc.printf(&quot;response from sending 00h: %d\r\n&quot;, spi.write(0x00));&#xA;    pc.printf(&quot;response from sending 00h: %d\r\n&quot;, spi.write(0x00));&#xA;&#xA;    cs = 1;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;All I read are 0s. Sometimes it reads 128 or 255. That's wrong, right?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="1657" LastEditorDisplayName="" LastEditDate="2011-03-14T05:29:31.930" LastActivityDate="2011-04-14T05:39:14.733" Title="How to read the device ID of a dataflash memory" Tags="&lt;spi&gt;&lt;memory&gt;&lt;flash&gt;&lt;mbed&gt;&lt;device&gt;" AnswerCount="1" CommentCount="8" />
  <row Id="11444" PostTypeId="1" CreationDate="2011-03-14T05:39:52.120" Score="1" ViewCount="80" Body="&lt;p&gt;I'm trying to understand this table in a datasheet:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/FZnLp.png&quot; alt=&quot;&quot; title=&quot;Hosted by imgur.com&quot; /&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next to &quot;Byte 2&quot; there is a (5). What does that mean?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-03-14T06:24:48.897" Title="Trying to understand this table in a datasheet" Tags="&lt;datasheet&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11445" PostTypeId="2" ParentId="11444" CreationDate="2011-03-14T06:24:48.897" Score="7" ViewCount="" Body="&lt;p&gt;I suspect the (5) is a badly typeset footnote. &lt;/p&gt;&#xA;" OwnerUserId="960" LastActivityDate="2011-03-14T06:24:48.897" />
  <row Id="11446" PostTypeId="2" ParentId="11441" CreationDate="2011-03-14T09:01:45.387" Score="1" ViewCount="" Body="&lt;p&gt;A hacked Kinect could make a good, cheap sensor for detecting people walking by.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-14T09:01:45.387" CommentCount="4" />
  <row Id="11447" PostTypeId="1" AcceptedAnswerId="11451" CreationDate="2011-03-14T09:08:40.597" Score="1" ViewCount="103" Body="&lt;p&gt;Dear All,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to store the output of a stand alone comparator (Hittite HMC875LC3C) in computer RAM drive. Currently, I'm using an 8bit 2GHz ADC (an Agilent PCIe - Acquiris U1071A) to bridge between the comparator and the RAM drive. This solution is redundant, slow, and very expensive (the Agilent ADC is almost $10k).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would enjoy a better solution where no ADC is present and the comparator connects directly to the PC. Perhaps through a USB port?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally, I would like the comparator to operate at around 1GHz (it supports operations up to 20 Gbps). I would suspect the maximal throughput essentially depends on the computer's processor and interface i/o characteristics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The comparator outputs pulses are about 60ps long and the Output Voltage High Level is -10mV while the Output Voltage Low Level is about -420 mV. The comparator is emmbeded on a PCB with SMA connectors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Question: Is it possible to connect a high speed (1GHz) comparator into a PC without having to use an ADC? If so would some form of synchronization be required?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Louis&lt;/p&gt;&#xA;" OwnerUserId="3378" LastActivityDate="2011-03-14T19:27:30.630" Title="Connecting a high-speed comparator into a computer" Tags="&lt;adc&gt;&lt;computers&gt;&lt;comparator&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="11448" PostTypeId="2" ParentId="11441" CreationDate="2011-03-14T09:32:01.800" Score="3" ViewCount="" Body="&lt;p&gt;you could use photo-transistors with IR emitters to make a short distance proximity sensor. Instead of photo-transistors you could use PIR sensor or Ultra sonic sensor. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-14T09:32:01.800" CommentCount="5" />
  <row Id="11449" PostTypeId="2" ParentId="11441" CreationDate="2011-03-14T11:09:32.660" Score="1" ViewCount="" Body="&lt;p&gt;You could use a webcam or other video feed and some manner of computer-vision for the tracking- to an extent it looks like thats what the folk in the link did.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One method of doing this would be to have the camera(s) placed at the top of the wall facing down, and then doing edge detection on the image; ignore spots of environmental edges (cracks in concrete); then looking for any dense concentration indicative of a human. You then map that location from screen coordinates to a point along the wall.&lt;/p&gt;&#xA;" OwnerUserId="1507" LastEditorUserId="1507" LastEditorDisplayName="" LastEditDate="2011-03-14T18:02:22.717" LastActivityDate="2011-03-14T18:02:22.717" CommentCount="3" />
  <row Id="11450" PostTypeId="2" ParentId="11441" CreationDate="2011-03-14T11:56:32.360" Score="1" ViewCount="" Body="&lt;p&gt;A tiny, cheap variation could be made with an &lt;a href=&quot;http://www.sparkfun.com/products/760&quot; rel=&quot;nofollow&quot;&gt;8x8 LED matrix&lt;/a&gt;, Arduino and &lt;a href=&quot;http://sophiateam.undrgnd.free.fr/microcontroller/camera/index.html&quot; rel=&quot;nofollow&quot;&gt;Gameboy camera&lt;/a&gt;.&#xA;The Arduino would repeatedly read the camera, scale down the image and present graphics to the matrix.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheap and easy. Not as impressive as the wall in the video though.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-14T11:56:32.360" />
  <row Id="11451" PostTypeId="2" ParentId="11447" CreationDate="2011-03-14T12:19:26.820" Score="1" ViewCount="" Body="&lt;p&gt;If we are talking about custom solutions, one might convert output of comparator to LVDS for example and feed to FPGA, where data is deserialized and pumped into PCI/PCI-E bus. USB is not fast enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if you have long sequences of 0 or 1, FPGA might have RLE-like compressio built in. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;FPGA would cost &amp;lt;500$, which is defenetly less than your ADC, but development costs are not that low. If you need it for just 1 instance, you might want to go with what you have now.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-14T12:19:26.820" CommentCount="2" />
  <row Id="11452" PostTypeId="1" AcceptedAnswerId="11453" CreationDate="2011-03-14T13:27:00.920" Score="6" ViewCount="192" Body="&lt;p&gt;Why don't we measure electrical consumption in joules, instead of kWh? Aren't they the same measurements, but one is more &quot;proper&quot;?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-15T04:46:57.457" LastActivityDate="2011-03-15T12:09:12.633" Title="Why don't we measure electrical consumption in joules, instead of kWh?" Tags="&lt;units&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="11453" PostTypeId="2" ParentId="11452" CreationDate="2011-03-14T13:29:24.107" Score="7" ViewCount="" Body="&lt;p&gt;Yes, they're the same thing, but, an electricity bill stating n * 3.6 megajoules is a bit abstract compared to Watthours when light bulbs are rated in Watts.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-15T12:09:12.633" LastActivityDate="2011-03-15T12:09:12.633" CommentCount="4" />
  <row Id="11454" PostTypeId="2" ParentId="11441" CreationDate="2011-03-14T14:03:22.453" Score="2" ViewCount="" Body="&lt;p&gt;You could use the LEDs as photodiodes, although this may be only a short-range effect. See &lt;a href=&quot;http://www.cs.nyu.edu/~jhan/ledtouch/index.html&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; for an interesting demo video.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-03-14T14:03:22.453" />
  <row Id="11455" PostTypeId="1" AcceptedAnswerId="11459" CreationDate="2011-03-14T14:22:56.060" Score="0" ViewCount="152" Body="&lt;p&gt;Hey,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to operate a lot of RGB LEDs for a project. I came up with a crazy scheme which only works if the RGBs work exactly as three separate LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I want to do is connect the R, G and B lines of all the LEDs with the same source of PWM and connect their grounds to separate pins(which have tri state logic). So when I want to turn on a pin I will give the PWM for the color on the PWM line and drive its ground pin low and ground pins of other RGBs to high impedance (theoretically separating them from the circuit). Will such a circuit work?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-14T14:34:11.507" LastActivityDate="2011-03-14T15:02:56.240" Title="Do RGB LEDs actually behave like three separate LEDs?" Tags="&lt;rgb&gt;&lt;tri-state&gt;" AnswerCount="3" />
  <row Id="11456" PostTypeId="2" ParentId="11455" CreationDate="2011-03-14T14:46:11.527" Score="2" ViewCount="" Body="&lt;p&gt;Yes, RGB leds are usually 3 coloured LEDs in a single package with 4 wires. Sometimes they're common anode, sometimes common cathode.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-14T14:46:11.527" CommentCount="2" />
  <row Id="11457" PostTypeId="1" AcceptedAnswerId="11467" CreationDate="2011-03-14T14:50:26.607" Score="9" ViewCount="175" Body="&lt;p&gt;I'm looking to design a PCB that can reliably survive constant impact. The board will be rigidly mounted to an enclosure that will protect the board from actually hitting anything. The nature of the impact would be similar to a bowling ball, or a hammer head - not what I would consider vibration, but frequent hits from multiple directions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As part of the device functionality, I want to measure the acceleration of the board, so dampening the impact in any way is not preferable. I don't have any measured acceleration values (G's) to provide as a baseline, and I don't really have any experience in this area. As such, I have a few closely related generic questions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;What is the most force that would be OK on a board with no impact hardening measures taken? (Am I worrying too much about a non-issue?)&lt;/li&gt;&#xA;&lt;li&gt;Are there any design practices that should be followed for the PCB?&lt;/li&gt;&#xA;&lt;li&gt;What are the weak points in a design that lead to mechanical failure?&lt;/li&gt;&#xA;&lt;li&gt;Are there parts that should be avoided for a more robust design?&lt;/li&gt;&#xA;&lt;li&gt;At what force levels should I start worrying about the safety of the parts themselves?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-03-14T17:29:32.413" Title="Board Design for High Impact Environments" Tags="&lt;pcb-design&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="4" />
  <row Id="11458" PostTypeId="2" ParentId="11455" CreationDate="2011-03-14T15:02:53.877" Score="1" ViewCount="" Body="&lt;p&gt;RGB leds are common anode of common cathode as Joby has stated. your way will work but will take up 4 pins (R, G, B, PWM) depending on if your pins can sink/source the current. I would use  the below example depending on your specific RGB led, and drive each led line with PWM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Common Cathode example&#xA;&lt;img src=&quot;http://i.imgur.com/BPmNk.png&quot; alt=&quot;RGB pwm schematic&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a side note, you could hook up the example below and drive Vcc with PWM and drive each pin high or low to turn on and off colors&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-14T15:02:53.877" CommentCount="4" />
  <row Id="11459" PostTypeId="2" ParentId="11455" CreationDate="2011-03-14T15:02:56.240" Score="3" ViewCount="" Body="&lt;p&gt;Yes, but they are not full separated LED's, as @Joby Taffey stated they share a common anode or common cathode. In order to use the circuit you said, you'll probably need to get one common anode one and connect the CA pin with the PWM output. The other 3 pins (cathode for R, G and B) will be switched with an transistor for example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use an common cathode, but in this case, with an PWM duty cycle of 100% (turned one) the corresponding led would be turned off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One problem I'd see is the refresh rate. You can't turn on the 3 leds at once because you want to control each color individually. The solution is multiplexing. You should use an enough high PWM frequency and enough low multiplexing frequency, so the multiplexing will not interfere with the color intensity while trying to avoid flicker with multiplexing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And keep in mind that the output luminance will be only one third of the tri-led maximum.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2011-03-14T15:02:56.240" />
  <row Id="11460" PostTypeId="2" ParentId="11457" CreationDate="2011-03-14T15:18:58.410" Score="1" ViewCount="" Body="&lt;p&gt;One point of consideration is the amount and distribution of connect points with the board and the enclosure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using more connect points will better distribute the forces from the enclosure while preventing the board from oscillating. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, the physical contact points are the weakest ones, try to use larger points of contact bigger screw's. Try to use as many holes as possible and as &quot;random&quot; distributed as possible. If they are aligned the board can eventually oscillate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best is to use some kind of epoxy/acrylic coating, as it increase both board resistance and reduce the vibrating effects on the components over the board.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2011-03-14T15:18:58.410" />
  <row Id="11461" PostTypeId="2" ParentId="11457" CreationDate="2011-03-14T15:25:04.427" Score="7" ViewCount="" Body="&lt;p&gt;Have you considered potting your circuit? I haven't had much experience with this myself, but I've seen it before and I understand that you can encase your entire circuit board and components in a non-conductive resin that sets solid. I think this will brace the components relative to any sudden acceleration of the PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't say how effective this would be, but I think it's worth looking into.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-14T15:25:04.427" CommentCount="1" />
  <row Id="11462" PostTypeId="2" ParentId="11422" CreationDate="2011-03-14T15:41:09.007" Score="1" ViewCount="" Body="&lt;p&gt;Hi, i think you can find a ton of information about building one for yourself on the internet. If youre going to use fixed values like 3V,5V,12V, i suggest you use a computer power supply. If you want it adjustable, the approach isnt all that easy as taking a pc supply and wire it up. But since you were asking for commercial ready to buy versions, here are two items that i think will suit your needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Suggestions for commercial versions are: Sako SK-1730SL5A à 90 €, PeakTech P-6005-D à 130 €&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope i've answered your question.&lt;/p&gt;&#xA;" OwnerUserId="2995" LastActivityDate="2011-03-14T15:41:09.007" CommentCount="2" />
  <row Id="11463" PostTypeId="2" ParentId="11457" CreationDate="2011-03-14T16:09:51.777" Score="7" ViewCount="" Body="&lt;p&gt;In the railway industry, the guideline was to support the board at least every 100mm. The best components are those that are light (SMT parts weigh less than TH), close to the PCB (SMT are closer than TH) and have many connections to the PCB (sometimes more pins can be added to divide the weight up over the pins eg custom switched-mode transformers). Larger parts on thin legs with high centers of gravity are going to be the worst eg iron core transformers. Potting will keep everything together but will add weight - so you might end up applying force to the smaller parts from the larger ones. Use all the solder pads you can eg on unused pins of connectors and add local vias to stop the tracks ripping off on SMT connectors. If connectors have additional screw fixing points use them eg 9 pin D sockets.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-03-14T16:09:51.777" />
  <row Id="11464" PostTypeId="2" ParentId="11337" CreationDate="2011-03-14T16:24:42.233" Score="1" ViewCount="" Body="&lt;p&gt;In UG070v2.6 (the V4 userguide), see &lt;code&gt;Fig 2-8: Standard Usage&lt;/code&gt; but use CLKDV instead of CLK0 as the output.  Make sure the Divide by Value is set to 2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or use the Clocking Wizard in Coregen to walk you through the options and generate you an HDL file.&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-03-14T16:24:42.233" />
  <row Id="11465" PostTypeId="2" ParentId="11422" CreationDate="2011-03-14T16:49:00.390" Score="1" ViewCount="" Body="&lt;p&gt;Consider something like &lt;a href=&quot;http://www.apogeekits.com/dual_power_supply_ps23003au.htm&quot; rel=&quot;nofollow&quot;&gt;this kit from Apogee&lt;/a&gt;. It's linear, has adjustable current limit (i.e. important) and meets your budget, as long as you can live with 3A for the time being. If you &lt;a href=&quot;http://www.apogeekits.com/dc_power_supply_ps5005u.htm&quot; rel=&quot;nofollow&quot;&gt;go bigger&lt;/a&gt;, you can get 5A but you're looking at closer to $300.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also keep your eyes open on online auction sites for used industrial equipment like the HP6038A (60V 10A) or the 6Instek GPC-3060D (dual 30V 6A, can be paralleled).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-03-14T16:57:18.523" LastActivityDate="2011-03-14T16:57:18.523" CommentCount="1" />
  <row Id="11466" PostTypeId="2" ParentId="2931" CreationDate="2011-03-14T17:12:27.990" Score="0" ViewCount="" Body="&lt;p&gt;In general, overvoltage protection refers to output protection. The main reason for overvoltage protection is to protect against someone doing something screwy with remote sensing lines (like shorting them) or the voltage feedback loop going open-loop, both of which will generally cause the output voltage to rise above its desired setting and potentially damage downstream devices.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-14T17:12:27.990" CommentCount="1" />
  <row Id="11467" PostTypeId="2" ParentId="11457" CreationDate="2011-03-14T17:29:32.413" Score="12" ViewCount="" Body="&lt;p&gt;This is just general stuff, you should really try to put a bound on the expected acceleration forces, the period and duration of those forces, thermal conditions, and expected angles of impact to get the information you need to make the design robust.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What is the most force that would be OK on a board with no impact hardening measures taken? (Am I worrying too much about a non-issue?)&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is very difficult to put a single number on, it depends on the types of components used and the direction/frequency of the hits.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Are there any design practices that should be followed for the PCB?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lots of attachments to something solid.  One of the most likely failure modes is the PCB flexing which can cause the solder joints on the PCB to crack causing intermittent or complete failure of the connection.  I would try to keep the PCB as compact as you can while providing as much attachment to something that won't flex (steel enclosure) as you can.  The smaller the PCB the smaller the 'overall flex' of the board.  Something like 4+ layer design with solder copper power and ground planes should also add to the rigidity of the PCB but can cause additional thermal flex.  Depending on what your needs are, there are specialized PCB substrates that are more rigid than your stock off the shelf FR-4, such as substrates which employ carbon fiber composites vs fiberglass. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What are the weak points in a design that lead to mechanical failure?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Board Flex as mentioned above can cause solder joint cracking.  Stiffening of the PCB can help.  You could also not use stock solder, but rather a conductive adhesive such as silver conductive epoxy.  You can also use a conformal coating on the PCB which will hold surface mount components in place as well as add some stiffness to the PCB.&lt;/li&gt;&#xA;&lt;li&gt;Large Items: Lite weight surface mount devices are the best parts to use, large heavy items that sit further from the PCB will be the worst parts to use.  Things like large aluminium electrolytic caps, tall inductors, transformers, etc will be the worst.  They will impart the most force on their leads and solder connections to the PCB.  If large devices are needed use additional attachment to the PCB.  Use non-conductive, non-corrosive epoxy or something like that to attach them to the PCB or use a part with an additional PCB support.  Be sure to account for the added thermal resistance when calculating the devices ability to dissipate power if using epoxy or conformal coatings.&lt;/li&gt;&#xA;&lt;li&gt;Connectors.  Any connector going off the board will get beat on, make sure its a solid locking type and rated for the expected G-forces.  Make sure the connector's attachment to the PCB is solid.  Pure surface mount types without a through-hole attachment to the board it probably a bad idea.  These usually require through-holes in the PCB near the edge of the PCB.  Make sure your PCB substrate is strong enough to support the forces on these holes as with being so close to the edge the strength of the PCB is around the hole is much less.  If you need a connector that leaves the enclosure, use a locking panel mount connector and solder leaders to the PCB, this will put the stress on the connector/enclosure and not on the PCB. &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Are there parts that should be avoided for a more robust design?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See the list above but keep all parts as lite and as close to the PCB as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;At what force levels should I start worrying about the safety of the parts themselves?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again this is hard to put a number on.  If the device is getting hit 'edge on' to the PCB than your concern is lateral shear forces.  What force causes a problem there is dependent on the IC.  A large heavy IC with few, small attachments to the PCB is probably the worse case.  Maybe a tall pulse transformer or something like that.  A lite weight, short IC, with many attachments is probably strongest.  Something like a 64pin QFP, even better if it has a large center pad. Some useful reading on this topic: &lt;a href=&quot;http://www.utacgroup.com/library/EPTC2005_B5.3_P0158_FBGA_Drop-Test.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.utacgroup.com/library/EPTC2005_B5.3_P0158_FBGA_Drop-Test.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some parts may be internally damaged by high G-forces, this would be on a part by part basis but would mostly be limited to devices with movable internal parts.  MEMS devices, transformers, mag-jacks, etc, etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Comments&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you considered using 2 boards?  One small board with the accelerometer which is actually stiffly attached to the enclosure and a second board with the rest of the electronics on it which can then be mounted with a shock absorption system.  The shock system could be as simple as rubber supports or as complex as the systems used in hard drives depending on needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your going to need a pretty fast processor and a pretty fast, wide range accelerometer if you want to get accurate measurements of impact events such as getting hit with a hammer. &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-03-14T17:29:32.413" CommentCount="2" />
  <row Id="11468" PostTypeId="1" AcceptedAnswerId="11620" CreationDate="2011-03-14T18:01:37.910" Score="2" ViewCount="126" Body="&lt;p&gt;When debugging a circuit using a micro-controller and triac to control AC current I ran into an issue (the triac wouldn't switch off) that was only resolved by flipping the polarity of the triac. The circuit design had the triac and optoisolator MT1 connected to hot, I accidentally switched the triac and had the polarity reversed. Since I presumed that triacs where symmetrical devices I thought it was no big deal, but apparently it was.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since TRIAC's are supposed to be the equivalent of two Thyristors in reverse-parallel, I couldn't think of any reason for this switching asymmetry, maybe someone can shine light on the situation. &lt;/p&gt;&#xA;" OwnerUserId="1729" LastActivityDate="2011-03-17T17:15:45.123" Title="Are TRIACs symmetrical?" Tags="&lt;microcontroller&gt;&lt;theory&gt;&lt;triac&gt;" AnswerCount="3" />
  <row Id="11469" PostTypeId="2" ParentId="11389" CreationDate="2011-03-14T18:06:11.727" Score="2" ViewCount="" Body="&lt;p&gt;What about putting it in an RC circuit and measuring the charge time using an Oscilloscope? Using a known fixed resistance you can calculate the capacitance.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-03-14T18:06:11.727" CommentCount="1" />
  <row Id="11470" PostTypeId="2" ParentId="11468" CreationDate="2011-03-14T19:08:04.567" Score="3" ViewCount="" Body="&lt;p&gt;No, they are not. Although they work with bidirectional current on MT1 and MT2, they require the gate to have forward current to trigger.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-14T19:08:04.567" CommentCount="1" />
  <row Id="11471" PostTypeId="2" ParentId="11447" CreationDate="2011-03-14T19:27:30.630" Score="1" ViewCount="" Body="&lt;p&gt;If you only need a single board I think the current solution is probably the cheapest given the cost of any form of electronics development.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you need more boards I think the FPGA way is probably the best way to go. Your requirements are kinda vague. You will definitely need &lt;em&gt;an&lt;/em&gt; ADC to sample your signal, but you don't need that &lt;em&gt;particular&lt;/em&gt; ADC. If you want to sample 8 bit at a data rate of 1GHz (8Gbits per second) you will need something like infiniband to give you the required throughput (or at least many ethernet ports). To get those data rates I would probably drop the computer entirely and look for an FPGA board with an Ethernet connector (they're quite common) and either a good enough ADC or buy an external ADC and connect it to the FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a base architecture I would suggest using a synthesizable microcontroller which basically parses the ethernet packets and move bytes from the ADC buffer to ethernet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Possible boards:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.xilinx.com/products/boards_kits/spartan6.htm&quot; rel=&quot;nofollow&quot;&gt;Spartan-6 boards from Xilinx&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.orangetreetech.com/fpga_board_zestsc2.html&quot; rel=&quot;nofollow&quot;&gt;A small board with ethernet and USB connectivity&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Possible microcontrollers:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.xilinx.com/tools/microblaze.htm&quot; rel=&quot;nofollow&quot;&gt;Microblaze&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.altera.com/products/ip/processors/nios2/ni2-index.html&quot; rel=&quot;nofollow&quot;&gt;NIOS II&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Other links&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.xilinx.com/products/design_resources/conn_central/protocols/gigabit_ethernet.htm&quot; rel=&quot;nofollow&quot;&gt;An overview over Xilinx's ethernet IPs&lt;/a&gt; &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-03-14T19:27:30.630" />
  <row Id="11472" PostTypeId="1" AcceptedAnswerId="11476" CreationDate="2011-03-14T21:06:19.273" Score="0" ViewCount="83" Body="&lt;p&gt;I have a project that utilizes two strong digital, coreless servo motors.  Whenever I use DC motors, I usually need to have separate power sources for both the microcontroller and the motors (due to noise and such).  I don't have as much experience with servos, is this still the case?  I'd really like to get away with using just one battery, are there any precautions I can take for this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="954" LastActivityDate="2011-03-14T23:24:29.313" Title="Powering a Servo: Do I need a separate power source?" Tags="&lt;power-supply&gt;&lt;power&gt;&lt;motor&gt;&lt;robotics&gt;&lt;servo&gt;" AnswerCount="2" />
  <row Id="11473" PostTypeId="1" CreationDate="2011-03-14T21:47:01.550" Score="2" ViewCount="101" Body="&lt;p&gt;I have a retired stoplight - with real lightbulbs.  I am looking for a simple way to wire it to have it automatically move RED-GREEN-YELLOW cycle just as the ones on the street.  I have manually switched it but was looking for something more &quot;automatic&quot; that I can put together as a learning project with my 15 year old.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I saw this answer: &lt;a href=&quot;http://electronics.stackexchange.com/questions/5603/most-simple-stoplight-circuit&quot;&gt;Most Simple Stoplight circuit&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I am not sure about the power requirements for the circuts - the bulbs are actual bulbs as used and are 120V and I think 100 watt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideas or suggestions?&lt;/p&gt;&#xA;" OwnerUserId="3381" LastActivityDate="2011-03-15T12:15:09.897" Title="Simple way to wire a stoplight" Tags="&lt;circuit&gt;&lt;circuit-design&gt;&lt;wiring&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="11474" PostTypeId="2" ParentId="11441" CreationDate="2011-03-14T22:01:33.380" Score="1" ViewCount="" Body="&lt;p&gt;Use FETs as electrometers:  &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://amasci.com/electrom/e-field2.html&quot; rel=&quot;nofollow&quot;&gt;Inexpensive FET Electrometer Array&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://amasci.com/electrom/electrom.html&quot; rel=&quot;nofollow&quot;&gt;Array-Electrometer Exhibit: &quot;Visible E-field Panel&quot;&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/0Et8B.gif&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OaxZU.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-15T18:51:17.877" LastActivityDate="2011-03-15T18:51:17.877" />
  <row Id="11475" PostTypeId="2" ParentId="11472" CreationDate="2011-03-14T22:06:07.617" Score="1" ViewCount="" Body="&lt;p&gt;I've used several servo's in combination with a 30W motor on a college project and never had a problem with noise. The servo's took about 1 Amp at 5V when they can't move (but are trying to). Please take note that you should never exceed their voltage specification for too long, neither block them, as they seem to burn out quite quickly (we ran one at 6.5V for 1 hour while it was rated at 6V - it burned a nice hole in it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could try decoupling the engine from the normal supply by using an inductor and some decoupling capacitors. We made some DIY coils: we wrapped some copper wire around some plastic rings and installed them at both motor terminals (the other side of the inductors go to VCC and GND of power pack). In addition we used 10nF and 33nF capacitors at the terminals (10nF between, 33nF to the motor casing I believe). Note that we used high voltages ones because of possible surge voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I heard horror stories of 'dancing servos' from other teams when they fired up their motor. I don't think a servo is that harmful because it uses a rather small motor. If you're using a chunky one, I recommended using decoupling with an inductor. &lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-03-14T22:06:07.617" />
  <row Id="11476" PostTypeId="2" ParentId="11472" CreationDate="2011-03-14T23:24:29.313" Score="1" ViewCount="" Body="&lt;p&gt;Wherever possibe use a seperate power supply.&#xA;(We do in a 4kg robot)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use a proper noise filter if you must share a power source. An isolated DC-DC converter to supply the electronics is very effective (active filter).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Opto-isolate from the MCU to servo power amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's the rule in industrial, where reliability matters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Never share grounds.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-03-14T23:24:29.313" />
  <row Id="11477" PostTypeId="2" ParentId="11473" CreationDate="2011-03-14T23:36:49.317" Score="1" ViewCount="" Body="&lt;p&gt;In order to drive that load, you would need relays or power transistors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You cannot drive relay coils directly from uC, you would need transistors to get more current (uC can supply not more than 20mA). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to use high-voltage BJT/FET transistors, but you also cannot drive them directly from uC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So all you need is 3 power transistors or relays, and 3 low-power transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This way you can switch nearly unlimited load. &lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-14T23:36:49.317" />
  <row Id="11478" PostTypeId="1" CreationDate="2011-03-14T23:50:16.623" Score="3" ViewCount="115" Body="&lt;p&gt;We have a pair of IrDA and its encoder/decoder. After reading the datasheet, we still dont know how to interface IrDA with En/Decoder.&lt;br&gt;&#xA;Here is our current connection: &#xA;&lt;img src=&quot;http://i.imgur.com/jdRJk.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When using BAUD rate 9600, we are not getting any readable data from UART on arduino. The buffer is alway full or 0. We don't know whether it's the en/decoder or IrDA transceiver that is causing the problem.&lt;br&gt;&#xA;Is this the right way to interface? Any advice on how to go about debugging this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Related datasheet and info&lt;br&gt;&#xA;IrDA Vishay TFDT4500 : &lt;a href=&quot;http://www.freeweb.hu/bat21/irda/tfd_4.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.freeweb.hu/bat21/irda/tfd_4.pdf&lt;/a&gt;&lt;br&gt;&#xA;En/Decoder MCP2120 : &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/21618b.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ww1.microchip.com/downloads/en/DeviceDoc/21618b.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3383" LastEditorUserId="3383" LastEditorDisplayName="" LastEditDate="2011-03-17T00:27:06.257" LastActivityDate="2011-04-16T00:27:51.680" Title="interface IrDA with encoder" Tags="&lt;arduino&gt;&lt;interface&gt;&lt;ir&gt;" AnswerCount="1" />
  <row Id="11479" PostTypeId="2" ParentId="11289" CreationDate="2011-03-15T02:09:11.543" Score="1" ViewCount="" Body="&lt;p&gt;See &lt;a href=&quot;http://cseweb.ucsd.edu/~tweng/cse143/VHDLReference/11.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; for details on these:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;–– pragma resolution_method wired_and&#xA;–– pragma resolution_method wired_or&#xA;-– pragma resolution_method three_state &#xA;&#xA;-– pragma map_to_entity entity_name&#xA;–– pragma return_port_name port_name&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-15T02:09:11.543" />
  <row Id="11480" PostTypeId="1" CreationDate="2011-03-15T02:37:45.823" Score="0" ViewCount="41" Body="&lt;p&gt;I'm trying to write data to a &lt;a href=&quot;http://www.winbond-usa.com/products/Nexflash/pdfs/datasheets/W25P80-16-32j.pdf&quot; rel=&quot;nofollow&quot;&gt;W25P80 dataflash memory&lt;/a&gt; using an mbed. The documentation says there is a read data instruction for reading data from a section of memory by sending the opcode 03h followed by the address to read. However, I see no corresponding write data instruction. So how is data written to the flash memory?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="2574" LastEditorDisplayName="" LastEditDate="2011-03-15T06:04:51.557" LastActivityDate="2011-03-15T07:08:03.017" Title="How to write data to this dataflash memory" Tags="&lt;memory&gt;&lt;flash&gt;&lt;mbed&gt;" AnswerCount="1" />
  <row Id="11481" PostTypeId="2" ParentId="11473" CreationDate="2011-03-15T02:55:06.987" Score="2" ViewCount="" Body="&lt;p&gt;Funnily enough, I was just making a stoplight myself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found a microcontroller (see: &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;arduino&lt;/a&gt; for a cheap, premade dev-platform) with a &lt;a href=&quot;http://en.wikipedia.org/wiki/TRIAC&quot; rel=&quot;nofollow&quot;&gt;triac&lt;/a&gt; for each light to be the cheapest, simplest way to achieve what you want. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A triac is a bit like a diode switch that is able of switching mains voltage, and when coupled with an optical isolator, can be driven (safely) by low-level logic voltage (from a microcontroller, ttl, or anything else you like). They cost about 99 cents each (plus $2.15 for a typical optoisolator) so its a very cheap solution. Here is a prototypical TRIAC control circuit, you could require additional capacitors/resistors depending on load type and the characteristics of the particular triac, so see their datasheets. The input resistor is set at the right value for the diode inside the optoisolator to receive the correct current from your logic source&#xA;&lt;img src=&quot;http://i.imgur.com/C47ZM.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The more expensive solution is to use a solid-state relay, which will accomplish approximately the same thing for a bit more. &lt;/p&gt;&#xA;" OwnerUserId="1729" LastActivityDate="2011-03-15T02:55:06.987" CommentCount="1" />
  <row Id="11482" PostTypeId="2" ParentId="9662" CreationDate="2011-03-15T03:17:37.517" Score="1" ViewCount="" Body="&lt;p&gt;There are several open-source ALUs available.&#xA;In particular, there is at least one open-source ALU somewhere in every open-source CPU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://opencores.org/projects&quot; rel=&quot;nofollow&quot;&gt;Open Cores website&lt;/a&gt;, under the &quot;Arithmetic core&quot; tab, has a bunch of projects -- some of them involve floating point.&#xA;It also has a bunch of CPUs under the &quot;Processor&quot; tab,&#xA;some of which apparently include FPUs -- OpenFire, S1 Core (OpenSPARC), Zet (x86), and probably a few others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This &lt;a href=&quot;http://www.1-core.com/library/digital/soft-cpu-cores/&quot; rel=&quot;nofollow&quot;&gt;table of embedded CPU soft cores&lt;/a&gt; has a column that indicates which ones have a FPU and another column that indicates which are open source; several of them are both.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pretty much any ALU &lt;em&gt;can&lt;/em&gt; perform any floating-point operations.&#xA;There are several approaches, including:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;use a CPU with only an integer ALU;&#xA;emulate all floating-point operations&#xA;in software. Perhaps you can&#xA;compile your code with the&#xA;&lt;a href=&quot;http://gcc.gnu.org/onlinedocs/gccint/Soft-float-library-routines.html&quot; rel=&quot;nofollow&quot;&gt;-msoft-float option&lt;/a&gt; or&#xA;--without-fp option. Or perhaps you will want to manually port a&#xA;floating-point library such as&#xA;&lt;a href=&quot;http://gcc.gnu.org/wiki/Software_floating_point&quot; rel=&quot;nofollow&quot;&gt;fp-bit.c, ieeelib, or soft-fp&lt;/a&gt; or&#xA;other &lt;a href=&quot;http://en.wikibooks.org/wiki/Embedded_Systems/Floating_Point_Unit&quot; rel=&quot;nofollow&quot;&gt;floating point emulation&#xA;library&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;use a CPU with a simple&#xA;floating-point ALU (aka FPU) that only does&#xA;add, subtract, multiply, and a few&#xA;utility operations; emulate more&#xA;complicated operations such as divide&#xA;in software.&lt;/li&gt;&#xA;&lt;li&gt;use a CPU with a more complicated&#xA;floating-point ALU (aka FPU); only emulate&#xA;really complicated operations such as&#xA;cosh(), asin(), etc.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As other posters have already pointed out, doing floating-point calculations in a FPGA may not be the be the easiest or lowest-cost way to achieve your goals.&#xA;Many people using FPGAs prefer to use fixed-point calculations if at all possible.&#xA;Often an off-the-shelf microprocessor is a better fit than a FPGA.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-15T03:17:37.517" />
  <row Id="11483" PostTypeId="2" ParentId="11219" CreationDate="2011-03-15T03:32:16.777" Score="2" ViewCount="" Body="&lt;p&gt;The problem is likely the 3-wayness of your dimmer switch. It sounds like you are connecting power and the iron to the &lt;strike&gt;runners&lt;/strike&gt; travelers, instead of through the output &lt;strike&gt;pole&lt;/strike&gt; terminal.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;           ___[traveler]____&#xA;hot _____./                 \.____  switched wire&#xA;           ___[traveler]____      |&#xA;                                  |&#xA;                                  O [light socket (on)]&#xA;                                  |&#xA;                               neutral&#xA;&#xA;           ___[traveler]____&#xA;hot _____.                  \.____  switched wire&#xA;          \___[traveler]____      |&#xA;                                  |&#xA;                                  O [light socket (off)]&#xA;                                  |&#xA;                               neutral&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Make sure you don't have your's set up like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;               ___ pwr&#xA;wirecap _____./       &#xA;               ___ iron&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Also make sure you have clicked over the dimmer to the correct traveler or wire the two travelers together (the switch will always be on then).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;of the &#xA;There are some electronic dimmers that detect the other switch's position and go to full brightness, which would probably not work correctly if only partly wired.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could look at a simpler dimmer switch or cord like this &lt;a href=&quot;http://goo.gl/Mnwbe&quot; rel=&quot;nofollow&quot;&gt;http://goo.gl/Mnwbe&lt;/a&gt;, though as other's mentioned in the comments, it's probably only $20-30 more to get a new variable wattage iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whatever you do, please be careful.&lt;/p&gt;&#xA;" OwnerUserId="3384" LastEditorUserId="3384" LastEditorDisplayName="" LastEditDate="2011-03-20T04:52:18.280" LastActivityDate="2011-03-20T04:52:18.280" CommentCount="2" />
  <row Id="11484" PostTypeId="2" ParentId="11452" CreationDate="2011-03-15T03:41:14.027" Score="1" ViewCount="" Body="&lt;p&gt;Kilowatt-hours makes more sense to the non-physicists.  For instance, business and marketing types who set the prices for pushing electrons to you.&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2011-03-15T03:41:14.027" />
  <row Id="11486" PostTypeId="2" ParentId="11480" CreationDate="2011-03-15T07:08:03.017" Score="3" ViewCount="" Body="&lt;p&gt;send 06h to enable write then send page program (02h) which is the write function. (send 02h -&gt; address 24 bits -&gt; then min 2 bytes and up to 256bytes max) check 9.2.8 in the datasheet. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-15T07:08:03.017" CommentCount="2" />
  <row Id="11487" PostTypeId="2" ParentId="11478" CreationDate="2011-03-15T07:52:08.827" Score="2" ViewCount="" Body="&lt;p&gt;To trouble shoot i would hook up the TXIR RXIR(mcp2120) pins together and make a loop back device. Just to make sure your encoder/decoder works, what you send to the Chip should be echoed back to the uC. Once you confirm that the TX RX lines are working, you would then test to see if your IR sensors are transmitting and receiving by using a digital camera or webcam. The other way to debug this is if you have an oscilloscope on hand to check the data lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;all your connections and pins do look correct, and your clock source is correct for your baud pins for 9600&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2060" LastEditorDisplayName="" LastEditDate="2011-03-16T04:49:09.733" LastActivityDate="2011-03-16T04:49:09.733" CommentCount="1" />
  <row Id="11488" PostTypeId="2" ParentId="10586" CreationDate="2011-03-15T12:09:21.843" Score="0" ViewCount="" Body="&lt;p&gt;for trackin the distance u need position sensors .I hope u have a model in matlab or anyother software for validating ur sensor results.&#xA;As,in u need to simulate a working model and then validate it.&#xA;Give velocity as input and get acceleration as output by means of a DAQ(data aquistion)and then connect the sensors to this daq.the power supplied will not be more than 24-volts ,since the position sensor can be run at low frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this helps/...&lt;/p&gt;&#xA;" OwnerUserId="3388" LastActivityDate="2011-03-15T12:09:21.843" />
  <row Id="11489" PostTypeId="2" ParentId="11473" CreationDate="2011-03-15T12:15:09.897" Score="1" ViewCount="" Body="&lt;p&gt;Well, since your main criteria is simplicity, I'd say use the classic method.  A 1 RPM motor, a plastic shaft and rotor, some un-etched circuit board, and two wipers--one onto the center of the rotor and one off the rotor's edge.  Commutate the mains onto the board with the rotor, leads come off the edge of the board to the lights.  Divide the board into sections: Half of the board goes to the red light, 1/8th to the yellow, and the rest to green.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cut the copper away from any mounting points and cover/box for safety.&lt;/p&gt;&#xA;" OwnerUserId="1824" LastActivityDate="2011-03-15T12:15:09.897" CommentCount="2" />
  <row Id="11490" PostTypeId="2" ParentId="10988" CreationDate="2011-03-15T12:15:23.953" Score="0" ViewCount="" Body="&lt;p&gt;My friendly Actel FAE has shared that the toolchain does not support C++ at this time.&lt;/p&gt;&#xA;" OwnerUserId="923" LastActivityDate="2011-03-15T12:15:23.953" />
  <row Id="11492" PostTypeId="1" CreationDate="2011-03-13T07:17:26.183" Score="1" ViewCount="152" Body="&lt;p&gt;How can I control voltage level on a specific pin in PIC18F? Let's say then I want to send about 0.6V to transistor base. But I cannot use a voltage divider. I need to control output voltage by my PIC18F (PIC18F2525).&lt;/p&gt;&#xA;" OwnerUserId="3409" LastActivityDate="2011-03-15T16:05:31.873" Title="PIC18F various output voltage level" Tags="&lt;pic&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="11493" PostTypeId="2" ParentId="11492" CreationDate="2011-03-15T12:05:20.977" Score="1" ViewCount="" Body="&lt;p&gt;Some PICs have built in low resolution DACs that you can use. Check the datasheet!&lt;/p&gt;&#xA;" LastActivityDate="2011-03-15T12:05:20.977" />
  <row Id="11494" PostTypeId="2" ParentId="11492" CreationDate="2011-03-15T14:19:10.117" Score="1" ViewCount="" Body="&lt;p&gt;If you need to supply a digital signal to a transistor base of 0v or 0.6v, use a resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to provide an analogue output, you need to use an external DAC (Digital to Analogue Converter) (some PICs may provide these internally). You can make a simple DAC with a resistor ladder and several digital output pins. The more pins you use, the more bits of resolution you'll get.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to control the brightness of an LED you can rapidly toggle a digital signal and modulate the width of your pulses. This is called PWM, Pulse Width Modulation. Because we humans cannot see the rapid pulses, we perceive them as a continuous analogue output.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-15T14:19:10.117" />
  <row Id="11495" PostTypeId="1" CreationDate="2011-03-15T14:22:37.640" Score="3" ViewCount="81" Body="&lt;p&gt;Why do most NEMA 5-15P (North America 125V 15A) line and neutral blades have holes in them? I've been wondering this for quite some time and haven't yet found a satisfactory answer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/MoD7O.jpg&quot; alt=&quot;Holes in prongs on a plug&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-15T15:59:15.000" LastActivityDate="2011-03-15T15:59:15.000" Title="NEMA 5-15P blade holes" Tags="&lt;ac&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="2" />
  <row Id="11496" PostTypeId="2" ParentId="11495" CreationDate="2011-03-15T15:05:52.317" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Well, this is rather embarrassing. I totally misread your question.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's worse is that I don't actually know why the blades have holes in them. I suspect it's to help dump crud that wipes off when the blades are inserted into sockets, but that's just a guess. It could just be a result of the manufacturing process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: actually, from what I can tell, there are bumps on the wipers inside of some receptacles. &lt;strong&gt;&lt;em&gt;The bumps fit into the holes, which makes the plug stay in the socket more securely.&lt;/em&gt;&lt;/strong&gt; But, I did a little destructive testing just now on an extra receptacle in my junk drawer, and it definitely had no bumps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Anyway, here's an irrelevant explanation of why the holes in NEMA 5-15P receptacles are different sizes.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of those holes will shock you; the other won't. Normally, this doesn't matter, because you don't stick your finger in either hole.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you wire a light fixture in a lamp, you put the switch on the hot side of the circuit. That way, when you replace the bulb, if you accidentally stick your finger in the bulb socket, you won't get shocked if the lamp is switched off. If you could reverse the blades, this wouldn't be true-- you could get shocked even with the lamp off, because the switch would be on the neutral side, while the hot wire would be unbroken.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More generally, electricians try to minimize the length of wiring that is hot so there's less damage done when something goes wrong. From a functional perspective, it makes no difference, but when we have actual humans interacting with circuits, faulty hardware, and bad luck, it's nice to be able to keep track of which wire is hot.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-03-15T15:41:10.617" LastActivityDate="2011-03-15T15:41:10.617" CommentCount="5" />
  <row Id="11497" PostTypeId="2" ParentId="9321" CreationDate="2011-03-15T15:08:49.100" Score="0" ViewCount="" Body="&lt;p&gt;IC's prefix is used to show their manufacturer's name.&lt;/p&gt;&#xA;" OwnerUserId="3390" LastActivityDate="2011-03-15T15:08:49.100" CommentCount="1" />
  <row Id="11498" PostTypeId="2" ParentId="11468" CreationDate="2011-03-15T15:55:05.720" Score="1" ViewCount="" Body="&lt;p&gt;A triac is switched on when a sufficient potential difference exists between the gate and MT1.  For a triac to be useful, it must be able to have a significant potential between MT1 and MT2 without switching on.  This implies that it must also be able to have a significant potential between the gate and MT2 without switching on, so MT1 and MT2 cannot be symmetrical.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-15T15:55:05.720" />
  <row Id="11499" PostTypeId="2" ParentId="11492" CreationDate="2011-03-15T16:05:31.873" Score="4" ViewCount="" Body="&lt;p&gt;You don't actually want to send 0.6V to the transistor base.  $V_{BE}$ will vary a good deal between various transistors, so you won't get a well defined current through the transistor if you set it to 0.6V.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The standard way to bias a transistor is by sending a small amount of current through it.  Let's assume you're working with a MMBT3904, and want to send 30mA through it.  Get the &lt;a href=&quot;http://www.nxp.com/documents/data_sheet/MMBT3904.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;, and find the graph which relates $h_{FE}$* and $I_C$ (Line 2 is at $25^{\circ}{\rm C}$):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/DWg4Q.png&quot; alt=&quot;Ic vs hFE&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$h_{FE}$ is about 140, so you need to send $214\mbox{ }{\mu}A$ through the base:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$\frac{I_C}{h_{FE}}=\frac{30\mbox{ mA}}{140}=214\mbox{ }{\mu}A$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that this parameter isn't precisely defined (that's why they used a graph), is temperature dependent (that's why there are three lines in this figure), and varies with $V_{CE} (as indicated by Figure 3).  However, it varies a &lt;em&gt;lot&lt;/em&gt; less than $V_{BE}$.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many circuits to perform the task of sending a small current through the base.  Basically, every way you can connect resistors to $V_{CC}$, GND, and $V_{EE} (if a negative supply is used) has a name.  Wikipedia has &lt;a href=&quot;http://en.wikipedia.org/wiki/Bipolar_transistor_biasing&quot; rel=&quot;nofollow&quot;&gt;a good article&lt;/a&gt;, but my college course spent a good two weeks talking about these different modes, so don't be discouraged if you don't get it in the first pass. I'll explain the simplest circuit (fixed bias) here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The schematic looks like this: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/gpo2E.png&quot; alt=&quot;fixed base with microcontroller driving base&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$R_L$ is your load; if you need to connect your load to ground, use a PNP and invert everything. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you drive pin 5 into a low or high-impedance state, only a leakage current will flow through the collector.  According to the datasheet, this value is $I_{CBO}=50\mbox{ }nA$ with $V_{CB} = 30\mbox{ }V$.  When you drive it high (say, $3.3\rm V$), there is a voltage established across $R_B$ and the base-emitter junction of the transistor.  This is an N-P silicon junction, very similar to a diode.  It has a similar voltage characteristic - According to Figure 4 of the datasheet, it will be about $790\rm mV$, but that will vary as we've said before.  But $800\mbox{ }mV$ is close enough for our purposes.  We need to find the value of $R_B$ that gives a current of $30\mbox{ }mA$:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$ I_C = h_{FE} * I_B = 140 * \frac{ 3.3\mbox{ }V - 0.8\mbox{ }V }{R_B} $$&lt;br&gt;&#xA;$$ R_B = \frac{140 * ( 3.3\mbox{ }V - 0.8\mbox{ }V ) }{I_C} $$&lt;br&gt;&#xA;$$ R_B = \frac{350}{I_C} \rightarrow 11.66\mbox{ }k\Omega $$  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An $11\mbox{ }k\Omega$ 5%, 2%, or 1% resistor should do nicely!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;* - $h_{FE}$ is roughly synonymous with $\beta$, so you may see both values in datasheets.  $h_{FE}$ usually refers to the quiescent/DC state of the transistor, while $\beta$ is used when working with small-signal/AC currents.  They both denote the ratio of base current to collector current. &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-15T16:05:31.873" />
  <row Id="11500" PostTypeId="1" CreationDate="2011-03-15T16:12:00.973" Score="1" ViewCount="98" Body="&lt;p&gt;Is there any code based tools for drawing schematics. I only need to draw some simple diagram, including some 16pin Microcontroller, wire, power supply...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to use code to specify the pin and components, and let the software do the layout for me. Kinda like define a graph with graphviz dot format.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some thing I have in mind is:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;define a Microcontroller&lt;br&gt;&#xA;  pin1.label=&quot;Vcc&quot;&lt;br&gt;&#xA;  pin1.goto=other components  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="3383" LastActivityDate="2011-03-15T21:59:54.737" Title="code based tools for drawing schematics" Tags="&lt;schematics&gt;" AnswerCount="4" />
  <row Id="11501" PostTypeId="2" ParentId="11500" CreationDate="2011-03-15T16:55:01.083" Score="1" ViewCount="" Body="&lt;p&gt;You could use TeX &lt;a href=&quot;http://www.ctan.org/tex-archive/graphics/circuit_macros/&quot; rel=&quot;nofollow&quot;&gt;http://www.ctan.org/tex-archive/graphics/circuit_macros/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-15T16:55:01.083" />
  <row Id="11502" PostTypeId="1" AcceptedAnswerId="11503" CreationDate="2011-03-15T17:06:09.420" Score="3" ViewCount="92" Body="&lt;p&gt;Building on &lt;a href=&quot;http://electronics.stackexchange.com/questions/11344/building-a-simple-mcu-driven-array-of-leds&quot;&gt;this&lt;/a&gt; question, I've now got a &lt;a href=&quot;http://3ln.org/Media/Default/Datasheets/DM74LS164.pdf&quot; rel=&quot;nofollow&quot;&gt;shift register&lt;/a&gt; to play with, and I've been trying to work it manually with a couple of switches, like so:&#xA;&lt;img src=&quot;http://i.imgur.com/g5JoE.gif&quot; alt=&quot;shift register LED array&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have resistors (2.2K) between the switches and VCC, even though that's not shown in the schematic. It doesn't work, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I press the clock switch, sometimes an LED will light, and sometimes it won't. Sometimes several LEDs light. Never does it &quot;shift&quot; a zero &quot;bit&quot;. If I just hit the input switch a bunch of times, it shifts in bits, sometimes one at a time, sometimes several at a time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What gives? What have I done wrong here?&lt;/p&gt;&#xA;" OwnerUserId="3240" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T22:14:27.173" LastActivityDate="2011-04-27T22:14:27.173" Title="Playing with a shift register and some LEDs" Tags="&lt;led&gt;&lt;shift-register&gt;" AnswerCount="1" />
  <row Id="11503" PostTypeId="2" ParentId="11502" CreationDate="2011-03-15T17:16:30.597" Score="6" ViewCount="" Body="&lt;p&gt;The switch is &quot;bouncing&quot;:  Each time you open or close it, there is a period where it makes a bit of noise on the clock line.  The chip sees this noise as multiple transitions and clocks in more bits than you intended.  To fix this, you need a &quot;debouncing&quot; circuit.  Google should find you something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can't just switch voltage to an input like that.  Then the input is at +5V when the switch is closed, but floating when the switch is open.  You need at least a pulldown resistor after the switch.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-15T17:16:30.597" CommentCount="6" />
  <row Id="11504" PostTypeId="1" CreationDate="2011-03-15T17:27:14.363" Score="1" ViewCount="117" Body="&lt;p&gt;When plugged into wall warts, &lt;a href=&quot;http://cgi.ebay.com/Dream-color-RGB-5M-5050-Flash-LED-Strip-Light-94-change-/150527564861?pt=LH_DefaultDomain_0&amp;amp;hash=item230c245c3d#ht_3968wt_802&quot; rel=&quot;nofollow&quot;&gt;the flexible LED strips&lt;/a&gt; I want to make into a wearable display draw 3A @ 12V per 5m.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To do a 30 x 15 pixel display that's 15m, or, 9A @ 12V running around my body. Is this prima-facie unsafe? If it's not, am I going to need to carry the batteries around on a trolley?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe the LEDs will light at 9V and just not be as bright (which may be what I want, anyhow) and I'll be running PWM'd patterns so it won't be a 100% duty cycle but I'd at least like to establish a lower bound.&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2011-03-15T18:43:20.880" Title="Is it practical to build a wearable project that draws 9A @ 12V?" Tags="&lt;led&gt;&lt;battery&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="11505" PostTypeId="2" ParentId="11504" CreationDate="2011-03-15T18:42:31.037" Score="0" ViewCount="" Body="&lt;p&gt;As far as I know, 12 V is totally safe.  Shock can't even be felt below dozens of volts.   The current draw of the circuit is irrelevant, unless your wires are too thin and they get hot and burn you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or are you asking how heavy the batteries will be?&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-03-15T18:42:31.037" CommentCount="3" />
  <row Id="11506" PostTypeId="2" ParentId="11504" CreationDate="2011-03-15T18:43:20.880" Score="2" ViewCount="" Body="&lt;p&gt;Expanding on my comment, The ebay page cites 2.2W consumption, with a  12V supply voltage this corresponds to 200mA per 5 meters. Assuming this is correct, 15 meters of lighting will draw approximately 600mA. A high end rechargable NiMh AA battery is rated at around 3000mAh. With this in mind, a battery pack of 9 AA batteries (12 V) will power the display for at most 5 hours (theoretical limit), but likely closer to 2.5. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However this is based on several assumptions, primarily that the rated power consumption is true and represents an &quot;always on state&quot;, because if the power supply is rated with half or less of the LED's on at the same time it could skew your performance (and drive the supply current way up)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that 600mA at 12V corresponds to ~6W make sure that you use fat enough gauge wire for the return current, and that any resistors are beefy enough to handle the power on individual lines.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. $80 dollars for 5 meters is excessive, you might be better off rolling your own&lt;/p&gt;&#xA;" OwnerUserId="1729" LastActivityDate="2011-03-15T18:43:20.880" />
  <row Id="11507" PostTypeId="2" ParentId="597" CreationDate="2011-03-15T18:56:18.670" Score="3" ViewCount="" Body="&lt;p&gt;An 8-row by 16-column, cathode-row driver will at any given time drive exactly one of the 8 row wires low, while driving a program-selectable subset (none, some, or all) of the column drivers high.  An anode-row driver would drive one of eight wires high, while driving selected columns low.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-15T18:56:18.670" />
  <row Id="11508" PostTypeId="2" ParentId="11500" CreationDate="2011-03-15T19:02:45.293" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.geda.seul.org/wiki/geda%3agschem_ug&quot; rel=&quot;nofollow&quot;&gt;gschem&lt;/a&gt; has a simple text-based file format.   But if you want to automatically place the wires making connections on the schematic, then you are asking for autorouting, similar to a pcb layout package.  I don't know any software package that implements this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A schematic is a visual way to represent a netlist.  It is for humans.  The computer (and the electrons) just care about the netlist.  So you could design the pcb from the netlist and skip the schematic step altogether.  Schematics with big FPGAs or processors end up as netlist anyway: each pin is shown connected only to a named net.  If that is what you are planning, there's no need to draw a schematic.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-15T19:02:45.293" />
  <row Id="11509" PostTypeId="1" AcceptedAnswerId="11511" CreationDate="2011-03-15T21:11:35.890" Score="2" ViewCount="130" Body="&lt;p&gt;I have a digital circuit in which I need only one logic inverter, and both PCB size and power consumption are serious constrains. So I thought about using a pair of complementary SMD MOSFETs (the classic coupled gate configuration) instead of an IC with many ready-made inverters. Which MOSFET would be more recommended in this case (both for small size and low gate-drain current)?&lt;/p&gt;&#xA;" OwnerUserId="1078" LastEditorUserId="1078" LastEditorDisplayName="" LastEditDate="2011-03-15T21:41:07.833" LastActivityDate="2011-03-18T15:19:51.677" Title="Recomendation for a digital inverter made of discrete components" Tags="&lt;digital&gt;&lt;low-power&gt;&lt;mosfet&gt;&lt;inverter&gt;&lt;footprint&gt;" AnswerCount="4" />
  <row Id="11510" PostTypeId="2" ParentId="11500" CreationDate="2011-03-15T21:22:55.937" Score="0" ViewCount="" Body="&lt;p&gt;I think that you're going to struggle to find or make such a package.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To represent connections, there are plenty of netlist formats; several EDA packages use text-based formats for internal representation, and almost all can output a text-formatted netlist.  This is probably the easiest third of what you want. I'm not aware of any that have a syntax that's easy to write and keep track of.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The labeling and definition functionality is typically contained in a part library.  Again, there are text-based formats for this.  Some manufacturers publish text-based pinouts of all their components to be used in generating a library.  This functionality should probably be separated from the netlists, i.e. you'll do #import  and then instantiate one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Laying these components out in a sensible way is the last third of the problem, but it would be 99.99% of the effort.  As Mark said, schematics are for humans.  There are some basic rules, like voltages are higher on top and signals/data flows left to right that help make schematics more readable, but there's a lot of information contained in the arrangement of symbols that would be difficult, if not impossible, to represent in a netlist or other code format.  Autorouters are a very high-dollar code project, and autoplace would be, if they could get it to work well.  Those tools are used on PCBs, which don't generally contain semantic information in their placement.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can generate a schematic from code that's almost as readable as a human-designed schematic, then you'll be a millionaire in no time.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-15T21:22:55.937" />
  <row Id="11511" PostTypeId="2" ParentId="11509" CreationDate="2011-03-15T21:47:23.317" Score="6" ViewCount="" Body="&lt;p&gt;You can now get individual SMD inverters &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=296-1112-1-ND&quot; rel=&quot;nofollow&quot;&gt;like this one&lt;/a&gt;, which is just one of the six gates found in a classic 74AHCT04 style package. &lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-03-15T21:47:23.317" CommentCount="1" />
  <row Id="11513" PostTypeId="2" ParentId="11500" CreationDate="2011-03-15T21:59:54.737" Score="1" ViewCount="" Body="&lt;p&gt;Try &lt;a href=&quot;http://fritzing.org/&quot; rel=&quot;nofollow&quot;&gt;Fritzing&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's an all in one simplified schematic and breadboard designer with a straightforward XML format.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://fritzing.org/support-us/developer/fritzing-sketch-file-format/&quot; rel=&quot;nofollow&quot;&gt;http://fritzing.org/support-us/developer/fritzing-sketch-file-format/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-15T21:59:54.737" />
  <row Id="11514" PostTypeId="2" ParentId="8729" CreationDate="2011-03-15T22:05:42.080" Score="3" ViewCount="" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just wanted to follow up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've finally found a device that can do this job.  I just wanted to post in case anyone happens upon this thread, searching for the same thing:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://api-usa.com/pdf/api/apdhvdc.pdf&quot; rel=&quot;nofollow&quot; title=&quot;APD HV-DC spec sheet&quot;&gt;APD HV-DC High Voltage DC to DC Transmitters, Isolated, Field Rangeable&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;which is made by &lt;a href=&quot;http://api-usa.com/&quot; rel=&quot;nofollow&quot; title=&quot;Manufacturer's home page&quot;&gt;API-USA&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2524" LastActivityDate="2011-03-15T22:05:42.080" />
  <row Id="11515" PostTypeId="1" AcceptedAnswerId="11518" CreationDate="2011-03-15T22:15:13.727" Score="3" ViewCount="110" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to construct a simple low-pass filter for the following scenario:  A high-voltage DC signal with lots of noise.  I looked at &lt;a href=&quot;http://en.wikipedia.org/wiki/Low-pass_filter#Passive_electronic_realization&quot; rel=&quot;nofollow&quot; title=&quot;Wikipedia article on a simple passive low-pass filter&quot;&gt;Wikipedia's article on a simple passive low-pass filter&lt;/a&gt;.  I understand how the capacitor &quot;looks like a short&quot; to high-frequency signals and open for DC.  What I don't understand is the role of the resistor.  I read what Wikipedia has to say, but am not quite grasping how the resistor influences the &quot;time for the capacitor to charge up&quot;.  I vaguely grasp the idea of resonant RC circuits, but don't really understand the relevance of that principle in this context.  Any insight would be greatly appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance,&#xA;Brian&lt;/p&gt;&#xA;" OwnerUserId="2524" LastActivityDate="2011-05-29T17:04:22.083" Title="Novice question about low-pass filter" Tags="&lt;circuit&gt;&lt;filter&gt;&lt;noise&gt;&lt;circuit-design&gt;&lt;oscillator&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="11516" PostTypeId="2" ParentId="11509" CreationDate="2011-03-15T22:17:28.897" Score="5" ViewCount="" Body="&lt;p&gt;You'll never beat an IC for size with discrete components; tcrosley's link only draws a few &amp;micro;A and the footprint is a SOT23-5, which is only 2.1x2.4mm. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if simplicity or education is your goal, you can do fairly well with a simple FET inverter.  With a logic-level PNP and NPN, you can make a push-pull totem-pole circuit that will have similar power requirements to an inverter IC.  You can also replace the top transistor with a resistor: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/CCYDM.png&quot; alt=&quot;inverter&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This creates a simple inverter in a small space.  When the input voltage is above $V_{TO}$, the output will be connected to ground through the transistor.  When the input voltage is small, the transistor will be off, and the output will be pulled up to $V_{CC}$ through the resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There will be power dissipation in the resistor when 'driving high' (really a passive operation for this circuit), and current will flow through the resistor when you're driving low, so make the resistor as large as your load capacitance, switching speed, and input impedance allow.  This circuit can sink lots of current, but sourcing current requires a smaller resistor.  If you need to source current, use a PNP and flip the design upside down. For best performance, use two transistors.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-18T15:19:51.677" LastActivityDate="2011-03-18T15:19:51.677" CommentCount="5" />
  <row Id="11517" PostTypeId="2" ParentId="11515" CreationDate="2011-03-15T22:22:04.077" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.wisc-online.com/objects/ViewObject.aspx?ID=ACE2303&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a good explanation, using the RC filter transfer function.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-15T22:22:04.077" CommentCount="3" />
  <row Id="11518" PostTypeId="2" ParentId="11515" CreationDate="2011-03-15T22:42:35.357" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Some Basics&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One way to think about it is the resistor is setting a current limit on the capacitor. In an ideal situation with no resistance, you could potentially have very very large amounts of current being drawn in this &quot;short&quot; situation. Because of this you need to add a resistor. The resistor limits how much current is able to flow which results in the frequency characteristics changing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Non-ideal Case&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now in the not so ideal case, everything has some resistance. This will include the wires/traces and the internal resistance of the capacitor. This allows us to use capacitors between power and ground to filter noise while not having huge spikes of current draw.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Mathematical Point of View&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a mathematical point of view, you can look at the transfer function of the system. The basic ideas of a transfer function comes from the simple electrical science concepts. If you had 2 resistors, you could solve for the voltage between the 2 resistors. In the case of a capacitor or inductor your &quot;resistance&quot; is no longer called a resistance, instead it is called an impedance. Essentially they are the same thing, except impedances typically have imaginary parts to them. In the case of a transfer function, imaginary parts of circuits are frequency dependent. If you solve the math you can find out what you expect the circuit to act like across many frequencies, and then plot it.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-15T22:42:35.357" CommentCount="1" />
  <row Id="11519" PostTypeId="1" AcceptedAnswerId="11520" CreationDate="2011-03-15T22:46:33.073" Score="1" ViewCount="53" Body="&lt;p&gt;The documentation for a chip that I'm trying to use says it needs 2.7 to 3.6V. When I use a multimeter and put on probe on Vin and the other on GND I read 1.7V. Is this the correct way to read supply voltage? Does this mean that it's not getting enough voltage?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-03-15T22:58:26.340" Title="Measuring supply voltage" Tags="&lt;power-supply&gt;&lt;voltage&gt;&lt;voltage-measurement&gt;" AnswerCount="1" />
  <row Id="11520" PostTypeId="2" ParentId="11519" CreationDate="2011-03-15T22:58:26.340" Score="2" ViewCount="" Body="&lt;p&gt;Yes, this is the correct method for reading voltages. You do need to make sure your multimeter is set to DC mode and not AC mode. If it is on DC mode then you are not supply the chip enough voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are you powering it from? Either your voltage source is low (like if it is a battery) and should be replaced, or if you are using a current limited supply you could be hitting a current limit that is causing the voltage to drop.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-15T22:58:26.340" CommentCount="5" />
  <row Id="11521" PostTypeId="1" AcceptedAnswerId="11522" CreationDate="2011-03-15T23:05:18.207" Score="4" ViewCount="146" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have recently come across this #pragma pack(1) preprocessor directive and was wondering why it is being used?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I Googled the usage, and found it has other options such as push,pop etc. Has anyone used this on their embedded application?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to know some examples of how/why you have used this directive and on what kind of processor? What are the pro's/con's of using this directive?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="1785" LastActivityDate="2011-03-16T11:33:06.393" Title="Usage of the #pragma pack(1) compiler directive on embedded applications" Tags="&lt;microcontroller&gt;&lt;embedded&gt;&lt;c&gt;&lt;compiler&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="2" />
  <row Id="11522" PostTypeId="2" ParentId="11521" CreationDate="2011-03-15T23:25:07.860" Score="6" ViewCount="" Body="&lt;p&gt;&lt;code&gt;#pragma pack(1)&lt;/code&gt; ensures that C &lt;code&gt;struct&lt;/code&gt; items are packed in order and on byte boundaries. It may save RAM - which is often precious in a microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Packed structs also allow for casting directly over memory buffers for data interchange:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void f(void *buf)&#xA;{&#xA;  struct ip_header *hdr = (struct ip_header *)buf;&#xA;  hdr-&amp;gt;dst = 0x8000001;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Be careful where you use &lt;code&gt;#pragma pack&lt;/code&gt;. It's globally scoped (as it's in the preprocessor), so forgetting to turn it off will affect any &lt;code&gt;#include&lt;/code&gt; files.&#xA;If you only mean to pack certain structs, consider using GCC's &lt;code&gt;__attribute__ ((packed))&lt;/code&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, due to alignment issues, packed structs can impact performance.&#xA;For example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When packed into bytes:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;struct&#xA;{&#xA;  uint8_t  a;&#xA;  uint32_t b;&#xA;  uint8_t  c;&#xA;  uint8_t  d:&#xA;};&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Will be stored as (not accounting for endianness):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;a, b0, b1, b2, b3, c, d&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, many architectures require 32bit accesses to be aligned to 32bit addresses. With the packed struct, the machine will have to make several byte accesses then stich them together again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Faced with the above &lt;code&gt;struct&lt;/code&gt; without packing enabled, the compiler could reorganise it as:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;b0, b1, b2, b3, a, c, d&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-16T00:43:06.760" LastActivityDate="2011-03-16T00:43:06.760" CommentCount="2" />
  <row Id="11523" PostTypeId="1" AcceptedAnswerId="11593" CreationDate="2011-03-15T23:41:46.130" Score="2" ViewCount="80" Body="&lt;p&gt;Many CPLDs have a handy feature which will weakly drive pins toward their present state, so that a pin which is weakly pulled high will pull high and one which is weakly pulled low will pull low.  Are there any convenient ICs which will perform that function without needing a CPLD or a bunch of resistors?  A possible design for a 14-pin part would be to have eight &quot;bus&quot; pins with &quot;weak&quot; drivers, VDD and VSS, and two pairs of mode pins controlling four bus pins each.  The mode pins would select one of four bus modes:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;00 - Open-circuit (no pull-up or pull-down)&#xA;&lt;li&gt;01 - Unconditional weak pull-down&#xA;&lt;li&gt;10 - Unconditional weak pull-up&#xA;&lt;li&gt;11 - Pull-up or pull-down based upon current pin state&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Such a part could be used for bus-keeper applications, and also for things like low-power polling of switches (with the pull-up/pull-down modes).  Does anything like that exist?&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-16T21:06:15.603" Title="Are there any convenient &quot;bus keeper&quot; or &quot;bus hold&quot; chips?" Tags="&lt;components&gt;&lt;logic&gt;&lt;ic&gt;" AnswerCount="2" />
  <row Id="11524" PostTypeId="2" ParentId="11521" CreationDate="2011-03-16T00:01:17.730" Score="4" ViewCount="" Body="&lt;p&gt;Another reason to pack structures on byte boundaries is to ensure the alignment of the members when transferring data between different processors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I often need to transfer data structures between an MCU and a host PC application. The PC will pack structures on 32bit boundaries unless instructed to pack them on 1 byte boundaries. A PIC24F MCU will pack structures on 16bit boundaries unless instructed to pack them on 1 byte boundaries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By instructing them both to pack their structures on 1 byte boundaries, it ensures the data is in the same place when accessing it on either end. Without it, you would need to pad the structures with reserve bytes so the data members would align properly.&lt;/p&gt;&#xA;" OwnerUserId="2489" LastActivityDate="2011-03-16T00:01:17.730" CommentCount="1" />
  <row Id="11525" PostTypeId="1" CreationDate="2011-03-16T00:23:19.537" Score="0" ViewCount="35" Body="&lt;p&gt;I'm trying to understand this table, which specifies the operating ranges for a dataflash memory I am trying to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Ny5BP.png&quot; alt=&quot;&quot; title=&quot;Hosted by imgur.com&quot; /&gt;&#xA;The one part that I don't understand is where it says Fr under conditions. What does that mean? Why are there two numbers? Can that be measured by a multimeter?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet is &lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CBwQFjAA&amp;amp;url=http://www.winbond-usa.com/products/Nexflash/pdfs/datasheets/W25P80-16-32j.pdf&amp;amp;rct=j&amp;amp;q=w25p80&amp;amp;ei=NQqATey_Jom4sAOv8O2LBg&amp;amp;usg=AFQjCNFT2z5X1gOzmX0E8e4tOy5Yk--7Pg&amp;amp;sig2=moEsAdtGSQcW0DxBkXEDhQ&amp;amp;cad=rja&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="1657" LastEditorDisplayName="" LastEditDate="2011-03-16T00:58:15.180" LastActivityDate="2011-03-16T01:13:15.697" Title="Understanding operating ranges" Tags="&lt;voltage&gt;&lt;datasheet&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="11526" PostTypeId="2" ParentId="11369" CreationDate="2011-03-16T00:32:39.290" Score="0" ViewCount="" Body="&lt;p&gt;I found a 20&quot; one in an old high-end electric typewriter.&#xA;(your requirement for 9' is a little harder to meet.)&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-03-16T00:32:39.290" CommentCount="1" />
  <row Id="11527" PostTypeId="1" CreationDate="2011-03-16T00:35:16.117" Score="2" ViewCount="53" Body="&lt;p&gt;I am trying to use a dataflash memory that requires a voltage of 2.7 to 3.6. Before I was supplying it with too little voltage. Then I supplied it with 5V. Could either of these cause damage to the chip?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The part number is W25P80 and the datasheet is &lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CBwQFjAA&amp;amp;url=http://www.winbond-usa.com/products/Nexflash/pdfs/datasheets/W25P80-16-32j.pdf&amp;amp;rct=j&amp;amp;q=w25p80&amp;amp;ei=NQqATey_Jom4sAOv8O2LBg&amp;amp;usg=AFQjCNFT2z5X1gOzmX0E8e4tOy5Yk--7Pg&amp;amp;sig2=moEsAdtGSQcW0DxBkXEDhQ&amp;amp;cad=rja&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="1657" LastEditorDisplayName="" LastEditDate="2011-03-16T00:55:20.830" LastActivityDate="2011-03-16T00:55:20.830" Title="How likely is it that this chip was damaged?" Tags="&lt;voltage&gt;&lt;memory&gt;&lt;flash&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="11528" PostTypeId="2" ParentId="11527" CreationDate="2011-03-16T00:38:46.173" Score="4" ViewCount="" Body="&lt;p&gt;That's what the &quot;absolute maximum ratings&quot; part of the data sheet is for.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-03-16T00:38:46.173" CommentCount="2" />
  <row Id="11529" PostTypeId="2" ParentId="11527" CreationDate="2011-03-16T00:39:29.600" Score="4" ViewCount="" Body="&lt;p&gt;Yes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5V may have killed the chip. Too little voltage will make the chip's behaviour unpredictable, but won't harm it (though low voltage during write/erase might damage the data).&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-16T00:39:29.600" />
  <row Id="11530" PostTypeId="2" ParentId="11525" CreationDate="2011-03-16T01:12:16.660" Score="2" ViewCount="" Body="&lt;p&gt;Fr and fr are described on page 36 of the datasheet. They are the clock frequencies the data bus is running at. Basically, at the lower rate (33 MHz), the chip can tolerate slightly lower voltages (down to 2.7V), but at the higher rate (50MHz), it needs to be above 3.0V.&lt;/p&gt;&#xA;" OwnerUserId="3382" LastActivityDate="2011-03-16T01:12:16.660" CommentCount="2" />
  <row Id="11531" PostTypeId="2" ParentId="11525" CreationDate="2011-03-16T01:13:15.697" Score="2" ViewCount="" Body="&lt;p&gt;I'd recommend that you read the entire datasheet few times, as it seems that information is scattered around the datasheet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For your question, Fr and fr are two different things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fr is&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Clock frequency, for fast Read (0Bh) and all other instructions except Read Data (03h)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;fr is&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Clock freq. Read data instruction 03h&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-16T01:13:15.697" />
  <row Id="11532" PostTypeId="1" CreationDate="2011-03-16T01:45:12.113" Score="1" ViewCount="35" Body="&lt;p&gt;I'm trying to control a serial dataflash memory through the SPI interface of an mbed. SCK from the mbed is connected to CLK of the dataflash memory. I'm not sure, but I'm starting to suspect that this needs to be running at a certain frequency. Can the frequency be adjusted?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-03-16T02:07:44.253" Title="Can the frequency of the SPI sck on an mbed be adjusted?" Tags="&lt;spi&gt;&lt;frequency&gt;&lt;mbed&gt;&lt;clock&gt;" AnswerCount="1" />
  <row Id="11533" PostTypeId="2" ParentId="11532" CreationDate="2011-03-16T02:07:44.253" Score="1" ViewCount="" Body="&lt;p&gt;Yes you can change the frequency of the clock,&#xA;&lt;a href=&quot;http://mbed.org/projects/libraries/api/mbed/trunk/SPI#SPI.frequency&quot; rel=&quot;nofollow&quot;&gt;http://mbed.org/projects/libraries/api/mbed/trunk/SPI#SPI.frequency&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;frequency&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;void frequency( int     hz   =  1000000 )&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Set the spi bus clock frequency&#xA;  Variables&#xA;  hz  SCLK frequency in hz (default = 1MHz)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-16T02:07:44.253" />
  <row Id="11534" PostTypeId="1" AcceptedAnswerId="11575" CreationDate="2011-03-16T02:21:58.800" Score="3" ViewCount="308" Body="&lt;p&gt;I'm having a lot of trouble finding wifi enabled arduino shields. All the places I've seen them are out of stock for some reason. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would this thing work? How would I hook it up? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.rovingnetworks.com/wifly-gsx.php&quot; rel=&quot;nofollow&quot;&gt;http://www.rovingnetworks.com/wifly-gsx.php&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically I want to build a network enabled (wireless) robot with the arduino. So you can see it's clearly better if I can get a wifi shield. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; To follow up on this post, I did end up getting the Wifly shield from Sparkfun. I was unable to get it working with the Arduino (Duemilanove) I had, and I ordered an Uno on a hunch, and it works on that! Connects to APs and can host an ad-hoc network. Unfortunately no security options exist for ad-hoc. But I'm okay with that. &lt;/p&gt;&#xA;" OwnerUserId="3039" LastEditorUserId="3039" LastEditorDisplayName="" LastEditDate="2011-04-23T02:26:33.733" LastActivityDate="2011-04-23T02:26:33.733" Title="Wifi enabling my Arduino" Tags="&lt;arduino&gt;&lt;wifi&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="3" />
  <row Id="11535" PostTypeId="1" AcceptedAnswerId="11538" CreationDate="2011-03-16T03:33:30.767" Score="1" ViewCount="162" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We have just selected a new processor for our application, and one of the project options available to me is to select the Endian mode: Little endian or Big endian (under Big endian two more choices, BE32 and BE8)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you please tell me what factors I should consider to make this choice?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was under the impression that a processor is either Little endian based or Big Endian. Does this mean that based on the option selected, the compiler would fix the endianess to suit the processor, if required?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks a lot.&lt;/p&gt;&#xA;" OwnerUserId="1785" LastActivityDate="2011-03-16T15:24:52.887" Title="How to choose between little endian or big endian for the processor settings?" Tags="&lt;microcontroller&gt;&lt;embedded&gt;&lt;compiler&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="11536" PostTypeId="2" ParentId="824" CreationDate="2011-03-16T04:06:06.637" Score="2" ViewCount="" Body="&lt;p&gt;One thing I've found useful on a number of machines is a simple stack switcher.  I haven't actually written one for the PIC, but I would expect the approach would work just fine on the PIC18 if both/all threads use a total of 31 or fewer stack levels.  On the 8051, the main routine is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;_taskswitch:&#xA;  xch  a,SP&#xA;  xch  a,_altSP&#xA;  xch  a,SP&#xA;  ret&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;On the PIC, I forget the name of the stack pointer, but the routine would be something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;_taskswitch:&#xA;  movlb _altSP &gt;&gt; 8&#xA;  movf  _altSP ,w,b&#xA;  movff _STKPTR,altSP &#xA;  movwf _STKPTR,c&#xA;  return&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;At the start of your program, call a task2() routine which loads altSP with the address of the alternate stack (16 would probably work well for a PIC18Fxx) and runs the task2 loop; this routine must never return or else things will die a painful death.  Instead, it should call _taskswitch whenever it wants to yield control to the primary task; the primary task should then call _taskswitch whenever it wants to yield to the secondary task.  Often, one will have cute little routines like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;void delay_t1(unsigned short val)&#xA;{&#xA;  do&#xA;    taskswitch();&#xA;  while((unsigned short)(millisecond_clock - val) &gt; 0xFF00);  &#xA;}&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that the task switcher doesn't have any means of doing any 'wait for condition'; all it supports is a spinwait.  On the other hand, the task switch is so fast that a attempting a taskswitch() while the other task is waiting for a timer to expire will switch to the other task, check the timer, and switch back faster than a typical task-switcher would determine that it doesn't need to taskswitch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that cooperative multitasking has some limitations, but it avoids the needs for a lot of locking and other mutex-related code in cases where invariants that are temporarily disturbed can be reestablished quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Edit): A couple caveats regarding automatic variables and such:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&lt;li&gt;if a routine which uses task-switching is called from both threads, it will generally be necessary to compile two copies of the routine (possibly by #including the same source file twice, with different #define statements).  Any given source file will either contain code for only one thread, or else will contain code which will be compiled twice--once for each thread--so I can use macros like &quot;#define delay(x) delay_t1(x)&quot; or #define delay(x) delay_tx(x)&quot; depending upon which thread I'm using.&#xA;&lt;li&gt;I believe that PIC compilers that can't &quot;see&quot; a function being called will assume that such a function may trash any and all CPU registers, thus avoiding the need to save any registers in the task-switch routine [a nice benefit compared with preemptive multitasking].  Anyone considering a similar task switcher for any other CPU needs to be aware of the register conventions in use.  Pushing registers before a task switch and popping them after is an easy way to take care of things, assuming adequate stack space exists.&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Cooperative multitasking doesn't allow one to completely escape issues of locking and such, but it really does greatly simplify things.  In a preemptive RTOS with a compacting garbage collector, for example, it's necessary to allow objects to be pinned.  When using a cooperative switcher, this isn't necessary provided that code assumes GC objects may move any time taskswitch() is called.  A compacting collector which doesn't have to worry about pinned objects can be much simpler than one which does.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-03-16T15:15:26.077" LastActivityDate="2011-03-16T15:15:26.077" CommentCount="1" />
  <row Id="11537" PostTypeId="2" ParentId="11535" CreationDate="2011-03-16T04:23:03.593" Score="1" ViewCount="" Body="&lt;p&gt;What processor is it? It is generally the case that there is a preferred mode that everyone uses. For instance, the Microchip C32 compiler for the MIPS-based PIC32 uses little-endian format.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-16T04:47:44.913" LastActivityDate="2011-03-16T04:47:44.913" CommentCount="3" />
  <row Id="11538" PostTypeId="2" ParentId="11535" CreationDate="2011-03-16T04:24:55.940" Score="3" ViewCount="" Body="&lt;p&gt;It's kind of an overdone argument these days - either works well,  if you're writing code that actually cares and you want it to be portable you're going to code any dependencies out anyway&lt;/p&gt;&#xA;&#xA;&lt;p&gt;so why might you choose?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Big Endian: almost all network protocols are BE - this is probably the main reason to choose these days&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Little Endian: there are a few data tricks (like passing an int and treating it as a char) that are available - but none of them are portable so best avoided&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-16T04:24:55.940" CommentCount="2" />
  <row Id="11539" PostTypeId="2" ParentId="11523" CreationDate="2011-03-16T04:41:31.583" Score="1" ViewCount="" Body="&lt;p&gt;I think a 74HC7541 and eight resistors will get close, modes 00 and 11 at least. &lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-16T04:41:31.583" CommentCount="5" />
  <row Id="11540" PostTypeId="1" AcceptedAnswerId="11631" CreationDate="2011-03-16T04:51:12.077" Score="1" ViewCount="200" Body="&lt;p&gt;Is this possible to load the operating system in the computer's RAM even if there is no BIOS present that can begin the process of loading OS?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If yes, how is this accomplished?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Will it require the use of an external like a programmer to load programme in micro-controller?&lt;/p&gt;&#xA;" OwnerUserId="2951" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-17T09:47:24.093" LastActivityDate="2011-03-17T23:04:27.730" Title="How to load Operating System with out BIOS" Tags="&lt;operating-system&gt;" AnswerCount="6" CommentCount="0" />
  <row Id="11541" PostTypeId="1" CreationDate="2011-03-16T05:22:24.010" Score="3" ViewCount="101" Body="&lt;p&gt;I am looking for a set of digitally usb-controllable potentiometers sample a range of resistances from 1 kilo-ohm up to 1 mega-ohm in ideally both linear and audio (logarithmic) taper.  Here are some sample values:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Linear: 1K, 5K,  10K, 25K, 50K, 100K, 250K, 500K, 1 Meg&lt;br&gt;&#xA;Audio: 10K, 25K, 50K, 100K, 250K, 500K, 1 Meg  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have found this link but they only have 10K, 50K, and 100K values:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.controlanything.com/Relay/Relay/DPOTS&quot; rel=&quot;nofollow&quot;&gt;http://www.controlanything.com/Relay/Relay/DPOTS&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody know of a good source or solution to the problem?  Thanks in advance for your help.&lt;/p&gt;&#xA;" OwnerUserId="3394" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-16T13:59:17.393" LastActivityDate="2011-03-16T16:34:57.180" Title="Where do I find USB controlled digital potentiometers sampling a wide array of values?" Tags="&lt;usb&gt;&lt;potentiometer&gt;&lt;digital&gt;" AnswerCount="2" />
  <row Id="11542" PostTypeId="2" ParentId="11540" CreationDate="2011-03-16T06:11:34.537" Score="3" ViewCount="" Body="&lt;p&gt;The idea behind a BIOS is that it will initialise some of the hardware needed to load an operating system.&#xA;If you can just load your operating system directly from a memory location  there is no need for a BIOS.&lt;/p&gt;&#xA;" OwnerUserId="3068" LastActivityDate="2011-03-16T06:11:34.537" CommentCount="2" />
  <row Id="11543" PostTypeId="1" AcceptedAnswerId="11553" CreationDate="2011-03-16T06:14:14.087" Score="1" ViewCount="53" Body="&lt;p&gt;I'm not sure how best to phrase it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The NXT robot has a program in it and can react to sensors... it is totally autonomous, but ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When it senses something, can it inform a PC based program?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And can that PC based program then issue new commands to the robot?&lt;/p&gt;&#xA;" OwnerUserId="3396" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-16T09:57:41.907" LastActivityDate="2011-03-16T12:46:12.100" Title="Does MindStorms NXT allow 2-way communication with a PC?" Tags="&lt;lego-mindstorms&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11544" PostTypeId="1" CreationDate="2011-03-16T06:18:04.570" Score="3" ViewCount="184" Body="&lt;p&gt;I'm working on a project  that can be powered either by USB or an battery power supply. They can both be plugged in at the same time.I'd like the battery to provide 5V if its plugged in, but fall back to the USB if possible.&#xA;The one solution into my mind is using diodes.But i can't stand the voltage drop.As diodes will definately  drop some voltage.&#xA;other solution i have heard about is by using FETs.But i do not know very much about FETs use.&#xA;Will some body will guide me how to use FETs to switch between supplies in this scenario with explanation.&lt;/p&gt;&#xA;" OwnerUserId="2951" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-03-17T03:34:50.490" LastActivityDate="2011-03-17T03:34:50.490" Title="How to use FETs to switch supplies in circuit" Tags="&lt;fet&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="11545" PostTypeId="1" CreationDate="2011-03-16T07:13:54.387" Score="3" ViewCount="247" Body="&lt;p&gt;Hello all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking to interface a Seeedstudio Bluetooth Bee with an Android phone for a project, and I want to get the Arduino code down pat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specifically, I want to be able to set the time over Bluetooth (which will then interface to a RTC module), then receive RFID strings over the Bluetooth module.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a side issue, and thats whether all my NewSoftSerial stuff will play nicely - an exercise for me later, once I have the Bluetooth working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The code set out by Seeedstudio is helpful, but not complete enough to explain to me. I have a moderate knowledge of Bluetooth, but I'm not afraid to ask questions. Hopefully, I can get the Bluetooth side of things to play &quot;nice&quot; so I can concentrate on the NewSoftSerial issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is some of the code I'm using to initialise the Bluetooth Bee, and I'm hoping I can then pair the Bee with the phone, and transfer data using the serial profile.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Serial.print(“\r\n+STWMOD=1\r\n”);&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Serial.print(“\r\n+STNA=modem”); &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Serial.print(“\r\n+RTPIN=0000\r\n”); &lt;/p&gt;&#xA;&#xA;&lt;p&gt;delay(2000);&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Serial.print(“\r\n+INQ=1\r\n”); &lt;/p&gt;&#xA;&#xA;&lt;p&gt;delay(2000);&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Serial.print(“\r\n+STBD=9600″); &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess, what I'm asking for is the process of connection - on Seeedstudios forum once the +INQ=1 command is issued, then the phone (or computer) can find the Bee. As you can see, I have an RTPIN of &quot;0000&quot; (secure, I know...) so inputing that into the phone will pair the phone and Bee? Or am I way off the mark?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many thanks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Shane.&lt;/p&gt;&#xA;" OwnerUserId="3397" LastEditorUserId="3397" LastEditorDisplayName="" LastEditDate="2011-03-16T13:08:14.383" LastActivityDate="2011-05-07T14:32:00.123" Title="Seeedstudio Bluetooth Bee" Tags="&lt;arduino&gt;&lt;bluetooth&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="11546" PostTypeId="1" CreationDate="2011-03-16T08:24:28.090" Score="1" ViewCount="283" Body="&lt;p&gt;Hello ! i have a arduino Ethernet Shield on top of an arduino MEGA 2560 and have connected the mega through serial to my laptop and through UTP port on the Ethernet Shield to my router . &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried the &quot;search arduino on google&quot; example ( where i corrected google's ip , the example was old ) and it doesn't work ( it doesn't seem to connect to the internet , i get on the serial : &quot;connecting... /connection failed / disconnecting.&quot; )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;my UTP cable is working fine.. i've tested it on my laptop .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The MEGA is connected to my router ( which has everything disabled so that's not the problem ) and when i ping from my laptop the ip address i gave the arduino assembly  , it doesn't ping back .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas why ? Maybe there is something i'm missing .. :-?? Here is my code : &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;SPI.h&amp;gt;&#xA;#include &amp;lt;Ethernet.h&amp;gt;&#xA;&#xA;// Enter a MAC address and IP address for your controller below.&#xA;// The IP address will be dependent on your local network:&#xA;byte mac[] = {  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };&#xA;byte ip[] = { 192,168,1,177 };&#xA;byte server[] = { 209,85,148,147 }; // Google&#xA;&#xA;// Initialize the Ethernet client library&#xA;// with the IP address and port of the server &#xA;// that you want to connect to (port 80 is default for HTTP):&#xA;Client client(server, 80);&#xA;&#xA;void setup() {&#xA;  // start the Ethernet connection:&#xA;  Ethernet.begin(mac, ip);&#xA;  // start the serial library:&#xA;  Serial.begin(9600);&#xA;  // give the Ethernet shield a second to initialize:&#xA;  delay(1000);&#xA;  Serial.println(&quot;connecting...&quot;);&#xA;&#xA;  // if you get a connection, report back via serial:&#xA;  if (client.connect()) {&#xA;    Serial.println(&quot;connected&quot;);&#xA;    // Make a HTTP request:&#xA;    client.println(&quot;GET /search?q=arduino HTTP/1.0&quot;);&#xA;    client.println();&#xA;  } &#xA;  else {&#xA;    // kf you didn't get a connection to the server:&#xA;    Serial.println(&quot;connection failed&quot;);&#xA;  }&#xA;}&#xA;&#xA;void loop()&#xA;{&#xA;  // if there are incoming bytes available &#xA;  // from the server, read them and print them:&#xA;  if (client.available()) {&#xA;    char c = client.read();&#xA;    Serial.print(c);&#xA;  }&#xA;&#xA;  // if the server's disconnected, stop the client:&#xA;  if (!client.connected()) {&#xA;    Serial.println();&#xA;    Serial.println(&quot;disconnecting.&quot;);&#xA;    client.stop();&#xA;&#xA;    // do nothing forevermore:&#xA;    for(;;)&#xA;      ;&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3398" LastActivityDate="2011-03-16T11:31:52.817" Title="problem with Arduino Ethernet Shield : it just won't work !" Tags="&lt;arduino&gt;&lt;ethernet&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="11547" PostTypeId="2" ParentId="11544" CreationDate="2011-03-16T08:25:11.053" Score="1" ViewCount="" Body="&lt;p&gt;What kind of battery?  You can get power controllers for lithium cells that take care of all the problems, charging the cell and switching between USB and battery power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;eg &lt;a href=&quot;http://www.sparkfun.com/products/726&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/726&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you wanted to do it yourself, you could use two MOSFETs (which can be thought of as a transistor with very low resistance when turned on), one controlling each power connection.   Pull the gate input up with a resistor on the battery, so that the power defaults to battery.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;By connecting the mosfet gates to tri-state output ports on a microcontroller, it can it can choose which power supply to use once it has booted, overriding the pull-up/pull-down resistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is likely to be very tricky.  The more usual approach is to have the external power charge the battery, possibly using a step-up converter.&lt;/p&gt;&#xA;" OwnerUserId="389" LastEditorUserId="389" LastEditorDisplayName="" LastEditDate="2011-03-16T08:40:58.100" LastActivityDate="2011-03-16T08:40:58.100" CommentCount="7" />
  <row Id="11549" PostTypeId="1" AcceptedAnswerId="11550" CreationDate="2011-03-16T08:59:09.623" Score="0" ViewCount="67" Body="&lt;p&gt;I have been programming for more years than I care to remember &amp;amp; am familiar with many language &amp;amp; development concepts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to play around with MindStorms NXT and there is a chance that I might end up wanting to do some complicated stuff which could stretch the limits of the graphical programming language.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone recommend a powerful programming language which is well supported and maybe a book or website?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="3396" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-16T09:56:05.823" LastActivityDate="2011-03-16T12:21:37.303" ClosedDate="2011-03-16T12:41:36.770" Title="Which programming language for me? (MindStorms NXT)" Tags="&lt;lego-mindstorms&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="11550" PostTypeId="2" ParentId="11549" CreationDate="2011-03-16T09:54:29.037" Score="0" ViewCount="" Body="&lt;p&gt;There is various options to choose from. Check out &lt;a href=&quot;http://en.wikipedia.org/wiki/Lego_Mindstorms_NXT_2.0#Programming&quot; rel=&quot;nofollow&quot;&gt;this link&lt;/a&gt;.&lt;br&gt;&#xA;I recommend you to go for something C-style, since by using it you will not face any limitations at all.&lt;br&gt;&#xA;&lt;a href=&quot;http://www.hempeldesigngroup.com/lego/pbLua/&quot; rel=&quot;nofollow&quot;&gt;Lua&lt;/a&gt; is a nice well suited option too.&lt;/p&gt;&#xA;" OwnerUserId="1603" LastActivityDate="2011-03-16T09:54:29.037" />
  <row Id="11551" PostTypeId="2" ParentId="11534" CreationDate="2011-03-16T09:55:34.047" Score="2" ViewCount="" Body="&lt;p&gt;Depending on how comfortable you feel with Linux, a really cheep option can be to use a cheep wi-fi router (such as a La Fonera) wit a custom firmware installed.  a google search for &quot;Arduino Fon&quot; will give you some examples.&#xA;Jim&lt;/p&gt;&#xA;" OwnerUserId="2778" LastActivityDate="2011-03-16T09:55:34.047" />
  <row Id="11552" PostTypeId="1" CreationDate="2011-03-16T10:50:30.123" Score="1" ViewCount="112" Body="&lt;p&gt;I am trying to control a serial dataflash memory through an mbed. It is an AT45DB021B and the datasheet is &lt;a href=&quot;http://www.atmel.asia/dyn/resources/prod_documents/doc1937.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. It has a reset pin that I have wired to the mbed so that a software reset can be done. I heard that a software reset makes things easier so that a hardware reset, i.e. shutting off power and turning it back on, is not needed. I noticed that when I do a hardware reset, whatever is in the buffer is overwritten by random values. However, when I do a software reset, the buffer is unaffected. Nothing seems to change on a software reset. Is this normal?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-17T13:23:41.670" LastActivityDate="2011-03-20T03:39:02.917" Title="Does reset do the same thing as shutting off the power to this device and turning it back on?" Tags="&lt;embedded&gt;&lt;memory&gt;&lt;flash&gt;&lt;mbed&gt;&lt;reset&gt;" AnswerCount="5" />
  <row Id="11553" PostTypeId="2" ParentId="11543" CreationDate="2011-03-16T11:02:46.130" Score="1" ViewCount="" Body="&lt;p&gt;Yes this is possible. I came across a &lt;a href=&quot;http://bit.ly/hRRJaU&quot; rel=&quot;nofollow&quot;&gt;project&lt;/a&gt; started by a university in konstanz. The program you'll use is called playerViewer and its part of the player package.&lt;/p&gt;&#xA;" OwnerUserId="2995" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-16T12:46:12.100" LastActivityDate="2011-03-16T12:46:12.100" CommentCount="1" />
  <row Id="11554" PostTypeId="2" ParentId="11552" CreationDate="2011-03-16T11:08:55.437" Score="6" ViewCount="" Body="&lt;p&gt;Yes this is normal. If you do a hard reset(random powerup) you can be pretty sure that the buffer will be some garbage. If you do a soft reset the contents should be the same as before. Sram is designed to behave that way. But it depends on the design of the architecture. If the internal hardware is desinged in such a way that, on receiving a reset signal, the power to the RAM to be removed. Then, in that case, the contents of the RAM will be cleared on the reset.&lt;/p&gt;&#xA;" OwnerUserId="2995" LastActivityDate="2011-03-16T11:08:55.437" />
  <row Id="11555" PostTypeId="2" ParentId="11549" CreationDate="2011-03-16T11:15:20.967" Score="1" ViewCount="" Body="&lt;p&gt;I would suggest Java. Since Java is one of the nicest (personal opinion) programming languages. Theres a Java based replacement framework called Lejos which you can find here: &lt;a href=&quot;http://lejos.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;http://lejos.sourceforge.net/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2995" LastEditorUserId="339" LastEditorDisplayName="" LastEditDate="2011-03-16T12:21:37.303" LastActivityDate="2011-03-16T12:21:37.303" />
  <row Id="11556" PostTypeId="2" ParentId="11534" CreationDate="2011-03-16T11:22:50.270" Score="1" ViewCount="" Body="&lt;p&gt;Watterott sells a nice Wifi shield called &quot;WiFly Shield&quot; its about 80€, get it here: &lt;a href=&quot;http://www.watterott.com/de/Arduino-WiFly-Shield&quot; rel=&quot;nofollow&quot;&gt;http://www.watterott.com/de/Arduino-WiFly-Shield&lt;/a&gt; i looked for it on the sparkfun page, but it says deprecated. Watterott ships internationally so you could order there, eventhough its here in Germany. I hope i could help.&lt;/p&gt;&#xA;" OwnerUserId="2995" LastActivityDate="2011-03-16T11:22:50.270" />
  <row Id="11557" PostTypeId="2" ParentId="11546" CreationDate="2011-03-16T11:31:52.817" Score="1" ViewCount="" Body="&lt;p&gt;The Arduino uses SPI to communicate between the devices and since the design of the Arduino Mega changed and the older pinout relates to older shields, in order to use it with newer shields you have to hack it a little, to workaround the problem. Alot of people had this question before but you can still find the answer here : &lt;a href=&quot;http://mcukits.com/2009/04/06/arduino-ethernet-shield-mega-hack/&quot; rel=&quot;nofollow&quot;&gt;http://mcukits.com/2009/04/06/arduino-ethernet-shield-mega-hack/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2995" LastActivityDate="2011-03-16T11:31:52.817" CommentCount="1" />
  <row Id="11558" PostTypeId="2" ParentId="11521" CreationDate="2011-03-16T11:33:06.393" Score="2" ViewCount="" Body="&lt;p&gt;The traditional use where I've seen this being used is for reading information from files. For example, you can define a struct whose members match those of a BMP file header, and then read all of the header in one swift read operation. OK, so BMP might not be the best example (its header does not have alignment issues on 32-bit systems), but you get the idea. I suppose this is just as useful in the embedded world.&lt;/p&gt;&#xA;" OwnerUserId="2575" LastActivityDate="2011-03-16T11:33:06.393" CommentCount="2" />
  <row Id="11559" PostTypeId="1" AcceptedAnswerId="11560" CreationDate="2011-03-16T11:39:46.343" Score="0" ViewCount="78" Body="&lt;p&gt;I'm looking for a three-state inverting octal buffer for a replacement part for an old microprocessor lab. The package should be DIP. Ucc should be on pin 20. Chip select should be at pins 1 and 19 and active on low, so that the buffer is in high impedance state unless both enables are low. The input/output ports should be next to each other with even pins as input and odd as output. What this would be in practice is a 74540 IC with the described pin configuration or a 74366 with 20 pins. Help would be appreciated.&lt;/p&gt;&#xA;" OwnerUserId="3400" LastActivityDate="2011-03-16T15:43:26.727" Title="Three-state inverting octal buffer" Tags="&lt;ic&gt;&lt;buffer&gt;&lt;74xx&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="11560" PostTypeId="2" ParentId="11559" CreationDate="2011-03-16T12:51:01.703" Score="1" ViewCount="" Body="&lt;p&gt;Consider a &lt;a href=&quot;http://www.fairchildsemi.com/ds/74/74AC540.pdf&quot; rel=&quot;nofollow&quot;&gt;surface-mount version&lt;/a&gt; of the part, and combine it with a &lt;a href=&quot;http://www.sparkfun.com/products/495&quot; rel=&quot;nofollow&quot;&gt;SOIC-to-DIP card&lt;/a&gt; to interface it with the old PCB.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-03-16T14:19:39.707" LastActivityDate="2011-03-16T14:19:39.707" CommentCount="4" />
  <row Id="11561" PostTypeId="2" ParentId="11534" CreationDate="2011-03-16T13:02:18.930" Score="2" ViewCount="" Body="&lt;p&gt;Here's the later version &lt;a href=&quot;http://www.sparkfun.com/products/9954&quot; rel=&quot;nofollow&quot;&gt;WiFly Shield&lt;/a&gt; - US $90.&lt;/p&gt;&#xA;" OwnerUserId="3361" LastActivityDate="2011-03-16T13:02:18.930" CommentCount="2" />
  <row Id="11562" PostTypeId="2" ParentId="9321" CreationDate="2011-03-16T13:57:24.477" Score="0" ViewCount="" Body="&lt;p&gt;There is &lt;em&gt;some&lt;/em&gt; logic to the prefixes.  Whether it's usable or not is a different question entirely.  The problem is that it's only rarely standardized across manufacturers, only occasionally standardized across departments in one department, and only sometimes publicized.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;About the best you can do is look up the datasheet and hope it includes information about what the various sections of the part number mean.  For instance, many microcontrollers have several options for peripheral sets, memory sizes, packages, temperature grades, etc., and you can specify these options by building a part number.  The prefix, however, usually has only one option.  I suppose you could construct a list, but I'm not aware of any standardized format or universal list.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-16T13:57:24.477" />
  <row Id="11563" PostTypeId="2" ParentId="11541" CreationDate="2011-03-16T14:23:21.753" Score="2" ViewCount="" Body="&lt;p&gt;If precise control of resistance is your goal, then digital pots are not a great solution.  Their resistance varies quite a bit, initially and over temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Usually potentiometers are used in a ratiometric way, where the exact pot resistance is not an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The device you linked uses the MCP42xxx digital pots, which only come in 10K, 50K, 100K. (&lt;a href=&quot;http://ww1.microchip.com/downloads/en/devicedoc/11195c.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;)  Notice the initial resistance tolerance is ±30% and the typical drift is 0.8%/°C.  Also notice the high wiper resistance, which is why digital pots at low resistances don't make much sense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you explain what you are trying to do with all these potentiometers?  You may find a different approach to accomplish your goals.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-16T14:23:21.753" CommentCount="3" />
  <row Id="11566" PostTypeId="2" ParentId="11535" CreationDate="2011-03-16T14:46:23.717" Score="2" ViewCount="" Body="&lt;p&gt;Incidentally, I know of an argument that historically favored little-endian format: in a number of CPUs, most notably the 6502, code could run faster using little-endian format than would have been possible with big-endian.  Consider, for example, an instruction:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;$1234:  LDA ($8A),Y ; Load byte from Y register plus the value stored in $008B-$008A&#xA;Assume $008B-$008A hold $5432, and Y holds $10&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The execution sequence is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;$1234 read $B1 - Fetch opcode&#xA;$1235 read $8A - Fetch operand&#xA;$008A read $32 - Fetch LSB of target while adding $01 to $8A&#xA;$008B read $54 - Fetch MSB of target while adding $32 to $10&#xA;$5442 read $XX - Fetch byte from target&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The MSB and LSB of any address to be read or written must be either based on a computation done in the last cycle with values already in the CPU, or else must be the last fetched value verbatum.  The third cycle can read the first byte of the target address (i.e. $8A) without delay; if the processor wanted to read the second byte first, it would have to waste a cycle computing the address.  The fourth cycle can compute the LSB of the target address while fetching the MSB; if there's no carry out of the LSB, the LSB (computed) and MSB (fetched from memory) will be ready simultaneously.  If the 6502 were big-endian, it would be necessary to waste a cycle on every indexed access (instead of only losing a cycle when indexing crosses a 256-byte boundary).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm unaware of any processing advantage to big-endian format beyond the fact that it was arbitrarily chosen as the &quot;standard&quot; network byte order.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-16T14:46:23.717" />
  <row Id="11567" PostTypeId="2" ParentId="11540" CreationDate="2011-03-16T15:01:22.167" Score="0" ViewCount="" Body="&lt;p&gt;In addition to what Erik said, does &lt;a href=&quot;http://en.wikipedia.org/wiki/Coreboot&quot; rel=&quot;nofollow&quot;&gt;LinuxBios/CoreBoot&lt;/a&gt; count?&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-03-16T15:01:22.167" CommentCount="2" />
  <row Id="11568" PostTypeId="2" ParentId="11552" CreationDate="2011-03-16T15:22:12.483" Score="3" ViewCount="" Body="&lt;p&gt;After a power-on reset there's no guarantee as to what's in your buffer.  It may be the same as what was in it before, or all zeroes, or all ones, or a checkerboard, or most of the opening sentence of &quot;A Tale of Two Cities&quot;, or anything else; it may be consistent, or random, or mostly consistent except for the third Tuesday of months containing the letter &quot;a&quot;.  Unless specified otherwise, it's probably wise to figure there's no guarantee of buffer contents after a soft reset.  The proper approach is to assume that the buffer is going to contain whatever data would be most vexing to you, so you should be prepared to accept anything that might be there.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-16T15:22:12.483" />
  <row Id="11569" PostTypeId="2" ParentId="11535" CreationDate="2011-03-16T15:24:52.887" Score="0" ViewCount="" Body="&lt;p&gt;It only matters if you're interfacing with the outside world i.e. if data has to be passed out from the processor or read into the processor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are not careful, you end up with flipped-order bytes. As others have mentioned, networks use big-endian format. So, that is something to consider. Another possible consideration is when you have a multi-processor setup and they need to share data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, some processor &lt;a href=&quot;http://en.wikipedia.org/wiki/Endianness#Bi-endian_hardware&quot; rel=&quot;nofollow&quot;&gt;architectures&lt;/a&gt; can switch endianness in software.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-03-16T15:24:52.887" />
  <row Id="11570" PostTypeId="2" ParentId="11559" CreationDate="2011-03-16T15:43:26.727" Score="0" ViewCount="" Body="&lt;p&gt;Wow. Can't even buy an old buffer in DIP any longer. :( I didn't check, but maybe some type of programmable logic chip will do it (e.g. &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=428-1278-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=428-1278-ND&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;update: possibly &lt;a href=&quot;http://cgi.ebay.com/74HC244B-M74HC244B1-20PIN-DIP-X2-OCTAL-BUS-BUFFER-/370179348158?pt=LH_DefaultDomain_3&amp;amp;hash=item56306896be#ht_500wt_922&quot; rel=&quot;nofollow&quot;&gt;eaby&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-03-16T15:43:26.727" />
  <row Id="11571" PostTypeId="1" CreationDate="2011-03-16T15:47:51.727" Score="3" ViewCount="85" Body="&lt;p&gt;How would you monitor a bank of capacitor to tell if they are fully charged.  I would like to display the precent of they're current charged state using an LED bar graph.&lt;/p&gt;&#xA;" OwnerUserId="2781" LastActivityDate="2011-03-16T20:51:16.740" Title="Capacitor Monitoring" Tags="&lt;capacitor&gt;&lt;circuit&gt;&lt;charging&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="11572" PostTypeId="1" CreationDate="2011-03-16T16:04:39.233" Score="0" ViewCount="60" Body="&lt;p&gt;I am involved with an embedded software development for telecom industry. I have zero experience before with such embedded hardware devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I got a network processor board, which is featured in switching pipeline engines. Besides the board, there is also an accessory board called &quot;piggy&quot; (seems for ethernet connetion), and another serial line connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am completely lost about these boards and serial line connections. what they are used for? I tried to use google to find some useful introduction or materials but failed. Can anyone point out what this piggy board is used for? Any good references or books that explain about this?&lt;/p&gt;&#xA;" OwnerUserId="3402" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-19T13:32:08.147" LastActivityDate="2011-03-19T13:32:08.147" Title="Looking for some references for embedded telecom board" Tags="&lt;embedded&gt;&lt;board&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="11573" PostTypeId="1" CreationDate="2011-03-16T16:08:37.027" Score="8" ViewCount="201" Body="&lt;p&gt;I always assumed that the shape of the antennas was important; a vertical monopole for pitch and a horizontal loop for volume, thinking that this minimized their interference with each other.  But it seems they actually operate more in the range of 200-500 kHz.   At these frequencies a good antenna would be hundreds of meters long, and the use of different frequencies for each antenna is sufficient to prevent interference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, the &lt;a href=&quot;http://www.theremin.info/-/viewpub/tid/10/pid/58&quot; rel=&quot;nofollow&quot;&gt;Moog Etherwave schematic&lt;/a&gt; has a bunch of coils in series with the antennas, which could be &lt;a href=&quot;http://en.wikipedia.org/wiki/Electrical_lengthening&quot; rel=&quot;nofollow&quot;&gt;electrical lengthening&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most descriptions I've read explain that it's just the human's capacitance to ground that detunes the oscillators, so any shape of metal will do, since it's just acting as a capacitor plate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/S8lha.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.oldtemecula.com/theremin/observations.html&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; describes something different, though, which I don't understand:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Beyond 4 inches (10cm) RF heterodyne theremin pitch variations are caused from changes in the &quot;radiation resistance&quot;. This is the total RF electro-magnetic power radiated from the pitch antenna divided by the square of the net current flowing into the pitch antenna. The pitch field is a dual electrical/magnetic equilibrium, not just a capacitive field as so commonly state.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.oldtemecula.com/theremin/mbarton_solution.htm&quot; rel=&quot;nofollow&quot;&gt;Some more explanation here&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this correct?  What's wrong with the capacitance explanation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.thereminworld.com/silicon_chip_theremin_modifications.html&quot; rel=&quot;nofollow&quot;&gt;http://www.thereminworld.com/silicon_chip_theremin_modifications.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Linearizing the pitch sensitivity - I found that the upper octave was much compressed and that the highest notes I wanted to play were so close to the antenna that accurate vibrato wasn't possible. A way to linearize the response is to put an inductor in series with the antenna.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.dogstar.dantimax.dk/theremin/thersens.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.dogstar.dantimax.dk/theremin/thersens.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;This effect is partially offset by the nature of the LC tuned circuit, the frequency of which depends on the inverse square-root of capacitance. This is the main reason, I believe, why oscillators based on a single pole (only one reactive component, i.e. capacitance) never took hold for theremin use. I, and probably many others, have experimented with RC oscillators in an effort to get rid of those pesky coils; even the ordinary NE555 timer can be used for this purpose. However, in such circuits the oscillating frequency is inversely proportional to capacitance, rather than square-root of capacitance, and the &quot;square-law&quot; effect is correspondingly a lot worse. Another way of looking at this is that sensitivity (dF/dC) of the RC circuits is proportional to 1/C2 instead of 1/C1.5 in the case of the LC circuit.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-17T14:29:19.040" LastActivityDate="2011-03-18T17:17:23.710" Title="How does a Theremin &quot;antenna&quot; work?" Tags="&lt;antenna&gt;&lt;electromagnetism&gt;&lt;capacitance&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="4" />
  <row Id="11574" PostTypeId="2" ParentId="11541" CreationDate="2011-03-16T16:34:57.180" Score="0" ViewCount="" Body="&lt;p&gt;As you can see from you example there is no basic component that does this.  The one you point out are expensive.  Basically you need a digital pot and a microcontroller.  Take an arduino and any pot that will talke to it and build your own.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-16T16:34:57.180" />
  <row Id="11575" PostTypeId="2" ParentId="11534" CreationDate="2011-03-16T16:39:53.243" Score="2" ViewCount="" Body="&lt;p&gt;These modules are the basis of most WiFi shields for Arduino.  If you are reasonably comfortable with your soldering ability, you could dead bug a module like this without too much difficulty.  Just connect all the powers and grounds properly, and bring TX/RX to your Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, if you dig a little deeper, you'll find the shields in stock at vendors like SparkFun, Futurlec, Adafruit, etc.  If one vendor is out of stock, others will have it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're just looking at using WiFi for remote control, another option might be ZigBee.  WiFi might be a little overkill for simple remote control, unless you really want the novelty of controlling the thing through the web.&lt;/p&gt;&#xA;" OwnerUserId="3395" LastActivityDate="2011-03-16T16:39:53.243" CommentCount="1" />
  <row Id="11577" PostTypeId="1" AcceptedAnswerId="12041" CreationDate="2011-03-16T16:54:18.800" Score="8" ViewCount="274" Body="&lt;p&gt;&lt;em&gt;&lt;strong&gt;Related&lt;/em&gt;: &lt;a href=&quot;http://electronics.stackexchange.com/q/11978/2118&quot;&gt;High Resolution ADC for Noisy Sensors in Variable Conditions&lt;/a&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;I'm building an interface using resistive textile-based sensors that may have different resistance ranges depending on environmental conditions. In order to best make use of my A/D converters, I'd like to explore using an adaptive amplifier that will help compensate for the unreliable performance of the sensors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are my options here? Or can you point me to some references on the topic?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can think of two general schemes that would be useful:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Auto-calibration by finding min and max values in a given analysis window (~30s-2min)&lt;/li&gt;&#xA;&lt;li&gt;Explicit calibration using a toggle-to-train interface&lt;/li&gt;&#xA;&lt;li&gt;... Are there alternative schemes I'm not thinking of?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Some Constraints&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;It should be a one-chip solution (small) if possible (like capacitive sensing chips)&lt;/li&gt;&#xA;&lt;li&gt;It should be easy to configure and use (I'm not an engineer and I'm not getting paid)&lt;/li&gt;&#xA;&lt;li&gt;There will probably be a microcontroller nearby&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Even better would be a do-it-all chip with Wheatstone bridge / voltage divider, lowpass filter and amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;More About My Particular Setup&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A/D converters will either be the converters built into an Atmel chip (could be ATtiny85 or ATmega32u4) or the converters built into an XBee series 2 radio. I've never used dedicated A/D chips before – I'm not sure if there would be any benefit to doing that.&lt;/li&gt;&#xA;&lt;li&gt;The sensor will be a piece of polymer-doped conductive lycra from Eeonyx. The resistance changes by about 1 order of magnitude at 30% stretch.&lt;/li&gt;&#xA;&lt;li&gt;The whole thing will be mounted on the hand of a performer, so it must be small and physically robust. There's a good chance it will be wireless.&lt;/li&gt;&#xA;&lt;li&gt;Precision is important. The interface will be used to continuously vary realtime audio effects i.e. it's not a switch.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="207" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-25T04:15:54.200" LastActivityDate="2011-03-27T10:42:50.140" Title="Simple Adaptive Amplifier Options for Sensor Interfaces" Tags="&lt;sensor&gt;&lt;interface&gt;&lt;amplifier&gt;&lt;adaptive&gt;" AnswerCount="3" CommentCount="9" FavoriteCount="3" />
  <row Id="11578" PostTypeId="2" ParentId="6301" CreationDate="2011-03-16T17:21:55.157" Score="1" ViewCount="" Body="&lt;p&gt;It's sometimes useful to think of capacitors and batteries as containing charge-storing 'stuff' and charge-carrying 'stuff'.  The material on the surface of each electrode and the dielectric between electrodes work together to hold charge, but are not very effective at moving it around.  The metal interior of each electrode is very effective at moving charge around, but practically useless for holding it.  Some capacitors and batteries are constructed with a lot of metal inside the electrodes, so that charge can be exchanged with any part of the storage surface with minimal resistance.  Others are designed with a lot less metal.  Reducing the amount of metal in a given volume will make more space available for charge-storing surfaces, but it will also increase the effective resistance between those surfaces and the external terminals of the device.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-16T17:21:55.157" />
  <row Id="11579" PostTypeId="2" ParentId="6301" CreationDate="2011-03-16T17:31:21.900" Score="0" ViewCount="" Body="&lt;p&gt;Ceramic capacitors close to their maximum voltage rating lose capacitance. A 6.3V cap may have up to 60% lost in capacitance at the full rated voltage and over the full temperature and tolerance range. Depending on your application, this could cause a lot of intermittent problems.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-16T17:31:21.900" />
  <row Id="11580" PostTypeId="2" ParentId="1150" CreationDate="2011-03-16T17:38:25.657" Score="1" ViewCount="" Body="&lt;p&gt;If you don't want too many bits of PWM control for each LED, and you want to avoid having to have a processor fumble with 500 LED's every PWM cycle, you can control 8 LEDs with N bits of brightness using N 74HC595 or equivalent chips.  Wire the outputs of all N chips together, and wire the enables to some circuitry which will only enable one at a time with suitable timing.  Arrange so the first chip will be enabled half the time, the second will be enabled for half the remainder, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any reload of the shift registers should be synchronized with the PWM rate, so as to minimize aliasing effects (e.g. if a brightness level was switching rapidly between 0111 and 1000, the point in the PWM cycle when the switch occurred could momentarily change the apparent brightness).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While having to use multiple 74HC595 outputs for each LED may be annoying, this approach is probably the simplest one that could maintain different brightness levels without ongoing CPU intervention.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-16T17:38:25.657" />
  <row Id="11582" PostTypeId="2" ParentId="11571" CreationDate="2011-03-16T19:03:11.030" Score="3" ViewCount="" Body="&lt;p&gt;Charge of a cap is CV = Q.  Just measure V.  This is quite different than a battery, much simpler&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-16T19:03:11.030" />
  <row Id="11583" PostTypeId="1" AcceptedAnswerId="11585" CreationDate="2011-03-16T19:15:04.233" Score="5" ViewCount="148" Body="&lt;p&gt;At school our soldering irons don't have grounded tips. I need one as i'm soldering MOSFETs in to my PCB. So what solutions could I use to ground my soldering iron tip?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-21T12:03:06.420" Title="Grounding a soldering iron" Tags="&lt;soldering&gt;" AnswerCount="2" />
  <row Id="11584" PostTypeId="2" ParentId="5424" CreationDate="2011-03-16T19:33:00.147" Score="4" ViewCount="" Body="&lt;p&gt;Several places publish open-source PCB design files:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Olimex sponsors open-source PCB contest every month; all &lt;a href=&quot;http://massmind.org/techref/piclist/pcbcontest.htm&quot; rel=&quot;nofollow&quot;&gt;documentation (including the PCB layout) is posted on the Massmind&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Circuit Cellar magazine hosts design contests a couple times a year; often &lt;a href=&quot;http://www.circuitcellar.com/contests/&quot; rel=&quot;nofollow&quot;&gt;PCB layout and other documentation is posted on the Circuit Cellar &quot;contests&quot; page&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://opencircuits.com/Projects&quot; rel=&quot;nofollow&quot;&gt;Open Circuits wiki has a list of open-source hardware projects&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Sometimes people post open-source hardware design files on one of the popular open-source software places -- Google code, Sourceforge, Launchpad, Github, &lt;a href=&quot;http://programmers.stackexchange.com/questions/237/i-want-to-start-an-open-source-project-wheres-the-best-place-to-host-i&quot;&gt;etc.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few places are trying to make it easy to buy open-source PCBs -- the actual, physical things you hold in your hands, not merely some computer file:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;BatchPCB will sell more copies of your PCBs to anyone else that wants one. And give you money. Why wouldn't you want that? &lt;a href=&quot;http://forum.sparkfun.com/viewforum.php?f=16&quot; rel=&quot;nofollow&quot;&gt;BatchPCB discussion forum at Sparkfun&lt;/a&gt;. A &lt;a href=&quot;http://batchpcb.com/index.php/Products&quot; rel=&quot;nofollow&quot;&gt;database of PCBs other people have designed&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;Open Source Hardware Bank (&lt;a href=&quot;http://antipastohw.blogspot.com/2009/03/introducing-open-source-hardware.html&quot; rel=&quot;nofollow&quot;&gt;early discussion&lt;/a&gt;) has a &lt;a href=&quot;http://www.oshwbank.org/&quot; rel=&quot;nofollow&quot;&gt;library of open-source PCBs&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Seeedstudio has discussed a &lt;a href=&quot;http://www.seeedstudio.com/blog/2008/09/11/an-idea-about-open-source-pcbs/&quot; rel=&quot;nofollow&quot;&gt;library of open-source PCBs&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://shieldlist.org/&quot; rel=&quot;nofollow&quot;&gt;Arduino Shield List&lt;/a&gt; links to the source of many Arduino shield designs. Some of those sources merely publish the PCB layout files; others, in addition, sell the physical hardware -- typically as a kit.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-03-16T19:52:04.700" LastActivityDate="2011-03-16T19:52:04.700" CommentCount="2" />
  <row Id="11585" PostTypeId="2" ParentId="11583" CreationDate="2011-03-16T19:40:04.197" Score="3" ViewCount="" Body="&lt;p&gt;No rocket science there - in the simplest case you just take wire, and mechanically connect(no soldering obviously :-) ) it somewhere to your iron, and make sure you 0Ohm resistance between other end of the wire and the tip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then connect other side to your grounding - if you don't have one, you should call for electrician to make one - there is no universal way to do it yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But personally, I solder FETs without any grounding, and noone ever failed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should only be really worrying about grounding when you work with fragile very high-frequency ones - they indeed are too easy to kill, unlike the majority of FET's and IC's.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-16T19:40:04.197" CommentCount="3" />
  <row Id="11586" PostTypeId="1" CreationDate="2011-03-16T19:58:19.983" Score="4" ViewCount="158" Body="&lt;p&gt;From what I have read it seems that FPAA could provide a way to design a &quot;programmable&quot; analog computer, but are there any online resources on how to implement such a system? &lt;/p&gt;&#xA;" OwnerUserId="3319" LastEditorUserId="3319" LastEditorDisplayName="" LastEditDate="2011-03-16T20:55:31.713" LastActivityDate="2011-03-27T10:15:01.517" Title="Use of Field Programmable Analog Arrays for analog computation" Tags="&lt;analog&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="11587" PostTypeId="1" CreationDate="2011-03-16T20:28:38.600" Score="4" ViewCount="90" Body="&lt;p&gt;How can I select generically re-usable parts for the unique things I build?&#xA;What are good approaches for building unique devices, so that when I no longer need them,&#xA;it's relatively easy to disassemble them into parts I can re-use on the next project?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This question focuses on when I build one or a few physical objects.&#xA;The &lt;a href=&quot;http://blog.makezine.com/archive/2010/02/industrial-designer-advocates-hacka.html&quot; rel=&quot;nofollow&quot;&gt;&quot;design for disassembly&quot;&lt;/a&gt; techniques used in some &lt;a href=&quot;http://en.wikipedia.org/wiki/sustainable_design&quot; rel=&quot;nofollow&quot;&gt;sustainable design&lt;/a&gt;s may also be related, although that focuses more on physical objects built in larger quantities -- is there another question that focuses on that?&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/7382/how-does-your-company-manage-hardware-reuse&quot;&gt;Reusing abstract designs for hardware is already covered in another question.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are lots of items I build exactly one of:&#xA;the first (or the 17th) breadboarded prototype of the electronics of a product;&#xA;various unique templates and jigs used in production;&#xA;test jigs, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When they reach the end of their useful life, they get tossed in the scrap box.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I build them out of&#xA;(a) random scrap still hanging around from previous projects, and&#xA;(b) new stuff we got with (perhaps shortsighted) focus on this particular project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't help but notice that the shiny new stuff ends up in 3 categories:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;a Some things -- solderless breadboards, soldering iron, 1/2 inch (12 mm) socket wrench, pin headers on 1/10 inch centers, alligator clips, velcro cable-ties, etc. -- get re-used over and over again.&lt;/li&gt;&#xA;&lt;li&gt;b Some things that at first glance appear very similar -- 15/16 inch socket wrench, etc. -- only get used for one job, and are never used again. While those things were necessary for that one job, and so perhaps I should think of them as a &quot;sunk cost&quot; that I've already made back the return on their investment. Since they are still functional, it seems wasteful to simply throw them away. So they end up taking up space and collecting dust indefinitely.&lt;/li&gt;&#xA;&lt;li&gt;c Some things can only be used once -- zip ties, solder, etc. Sometimes it seems a little wasteful, but (if I maintain a short-sighted focus on this particular project) these disposable items are the cheapest way to get things done, and at least they don't tend to accumulate and take up space.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Category (b) is the worst.&#xA;If I knew at the time I was buying that part what I know now after watching that part collect dust for years, I would have either saved a little money and bought some disposable category (c) part instead, or else spend a little more money and bought some more generally useful category (a) part instead.&#xA;(Or perhaps not. Sometimes I absolutely need some super-specialized part for some project).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have any tips for recognizing ahead of time that a part I am about to buy is highly likely to end up gathering dust as type (b), so that I can try to substitute something that is more likely to be type (a) or type (c)?&#xA;Any other tips for making it more likely that parts and tools I hope to re-use actually are re-used later?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rather than make one all-singing, all-dancing do-everything hyper-specialized PCB that I'll only use this one time and then toss the whole thing, are there good ways to partition the design so that at least part of it is re-usable later?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are good ways to improve physical hardware reuse?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-17T04:36:29.643" Title="What are good ways to improve physical hardware reuse?" Tags="&lt;design&gt;&lt;connector&gt;&lt;prototyping&gt;&lt;breadboard&gt;&lt;pcb-design&gt;" AnswerCount="2" FavoriteCount="3" />
  <row Id="11588" PostTypeId="1" AcceptedAnswerId="11590" CreationDate="2011-03-16T20:29:55.697" Score="1" ViewCount="52" Body="&lt;p&gt;I am inspired to post this question and answer by &lt;a href=&quot;http://meta.electronics.stackexchange.com/questions/42/seeding-er-with-some-high-level-electronics-questions&quot;&gt;this meta post&lt;/a&gt;.  This problem caused me a lot of problems and took a while to figure out.  I have a partial answer.  Perhaps others can elaborate based on their experiences.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I work for a small business and we have several &lt;a href=&quot;http://www.advanced-energy.com/en/Pinnacle_Series.html&quot; rel=&quot;nofollow&quot; title=&quot;Pinnacle series product page&quot;&gt;Pinnacle power supplies&lt;/a&gt; made by Advanced Energy.  We have recently been making a push to automate a number of our processes.  The hope is to control the power supplies from a computer via RS-232.  Are there any caveats to be aware of?&lt;/p&gt;&#xA;" OwnerUserId="2524" LastActivityDate="2011-03-16T20:47:57.647" Title="RS-232 control for Advance Energy Pinnacle power supply" Tags="&lt;power-supply&gt;&lt;rs232&gt;&lt;automation&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11589" PostTypeId="2" ParentId="11586" CreationDate="2011-03-16T20:47:54.310" Score="1" ViewCount="" Body="&lt;p&gt;I have a Cypress PSoC series 1 programmer w/ 2 chips that I bought for around $50. I haven't gotten around to using them myself, but I know somebody who his using them on the data acquisition side of a prototype digital musical instrument. He uses it to amplify and digitize signals from fiber-optic sensors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also a project in the book iPhone Hacks that uses a series 1 PSoC to make a sensor input to the iPhone using the microphone jack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cypress.com/?id=1573&quot; rel=&quot;nofollow&quot;&gt;http://www.cypress.com/?id=1573&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Last I checked, the companies that used to make pure PGA's went out of business.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; This post at SparkFun has some information: &lt;a href=&quot;http://forum.sparkfun.com/viewtopic.php?f=5&amp;amp;t=577&quot; rel=&quot;nofollow&quot;&gt;http://forum.sparkfun.com/viewtopic.php?f=5&amp;amp;t=577&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;FPAA's are a rare breed. Ther have been three other companies that tried to create these. One went under (they also wanted $20 a chip!), one was reorganized and the FPAA &quot;disappeared&quot; from their product lineup, and the last one, Zetex, still exists, but have one product and it doesn't appear to be all that well supported. &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; Oh, I forgot about this guy: &lt;a href=&quot;http://servenger.com/products/index.htm&quot; rel=&quot;nofollow&quot;&gt;http://servenger.com/products/index.htm&lt;/a&gt; – programmable analog signal processing board.&lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2011-03-27T03:10:24.637" LastActivityDate="2011-03-27T03:10:24.637" CommentCount="2" />
  <row Id="11590" PostTypeId="2" ParentId="11588" CreationDate="2011-03-16T20:47:57.647" Score="1" ViewCount="" Body="&lt;p&gt;Yes!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First:  The supply must be capable of AEBus communication.  You can find out if this is the case via the debug menu from the front panel (if your supply has one), by opening up hyperterminal and trying to communicate with it, or, easiest of all, calling AE and giving them the serial number.  &lt;strong&gt;NOTE:  The presence of a serial port on the back of the device &lt;em&gt;does not&lt;/em&gt; necessarily mean that it is capable of serial communication!&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second:  Even if the supply &lt;em&gt;is&lt;/em&gt; AEBus capable, it may not be able to be set to every mode that one would be able to set from the front panel.  In my experience, the most significant example is:  &lt;strong&gt;If your supply has a DeviceNet port, it will be impossible to set the supply into voltage regulation mode while controlling it with the serial port.&lt;/strong&gt;  In other words, if you have a DeviceNet supply and you want to control it via RS-232 for a voltage-controlled process, you're out of luck.  AE has confirmed that &lt;em&gt;no&lt;/em&gt; DeviceNet enabled supplies support anything other than power-regulation while in host (i.e., RS-232) control mode.  Even though you can set it into this regulation mode while in local control.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Third:  There are several different flavors of serial connector that may be present on the back of the supply.  There's the so-called &quot;standard serial port&quot; which uses an RJ-11 type connector and (possibly present) AEBus ports which may be DB-9 or DB-25.  As far as I can tell, the only difference in communicating via the &quot;standard&quot; port versus the AEBus ports is the baud rate.  The standard port communicates at 19.2 kbaud whereas the AEBus ports communicate at 9200 baud.  The structure of the commands is identical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On a final, semi-related note:  If you do have a DeviceNet supply and wish to not use it, you don't have to supply it with 24V just to avoid an error.  Open the supply up and remove the card.  You then have to switch a jumper (which would otherwise be jumpered on the exterior part of the DeviceNet card), whose identifier depends on the model of your supply.  Call AE and they'll tell you what its label is.  Problem solved! (Unless you also want to use voltage regulation via RS-232!)&lt;/p&gt;&#xA;" OwnerUserId="2524" LastActivityDate="2011-03-16T20:47:57.647" />
  <row Id="11591" PostTypeId="2" ParentId="11571" CreationDate="2011-03-16T20:51:16.740" Score="2" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;Build the &lt;a href=&quot;http://www.national.com/ds/LM/LM3916.pdf&quot; rel=&quot;nofollow&quot;&gt;LM3916 example circuit&lt;/a&gt; and connect the input to your capacitors.&lt;/li&gt;&#xA;&lt;li&gt;Adjust the LM3916 Vref so that the range matches the range you want to measure.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;It already has a high-impedance buffer built-in, so it won't discharge the caps.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-03-16T20:51:16.740" CommentCount="2" />
  <row Id="11592" PostTypeId="2" ParentId="5424" CreationDate="2011-03-16T20:53:56.160" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://bildr.org/&quot; rel=&quot;nofollow&quot;&gt;http://bildr.org/&lt;/a&gt; aims to be a complete open source electronics community (wiki, forum, etc.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.opencircuits.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.opencircuits.com/&lt;/a&gt; aims to be a complete open source electronics wiki&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I found both via SparkFun)&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2011-03-16T20:53:56.160" />
  <row Id="11593" PostTypeId="2" ParentId="11523" CreationDate="2011-03-16T21:06:15.603" Score="1" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;74LCXH2245&lt;/li&gt;&#xA;&lt;li&gt;SN74ACT1071&lt;/li&gt;&#xA;&lt;li&gt;SN74ACT1073&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Would it make any difference if you used a &quot;resistor network&quot; package of 8 resistors that looks like a single IC, to conceal the fact you are using resistors?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-16T21:06:15.603" CommentCount="1" />
  <row Id="11594" PostTypeId="2" ParentId="11587" CreationDate="2011-03-16T21:30:00.593" Score="2" ViewCount="" Body="&lt;p&gt;Forget category c: some things are truly disposable and can't be reused in their current state unless you want to start a recycling company.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Category B is the most interesting. For tools, there's eBay: just resell stuff you don't need. Even then, a lot of what we do is specialty stuff: I have 6805J programmers that no one wants even for the cost of shipping. They've simply outlasted their usefulness.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem with reusing hardware is the documentation has to be perfect, or the time spent trying to reuse a board or other hardware becomes more costly than simply starting from scratch again. I find that for the things I build for other people, I'm pretty good at keeping good documents. But for stuff I build intending to use for few days and then forget about, documentation is pretty much none existent, so boards end up permanently consigned to the junk bin.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-03-16T21:30:00.593" />
  <row Id="11595" PostTypeId="1" CreationDate="2011-03-14T17:47:41.353" Score="1" ViewCount="133" Body="&lt;p&gt;I heard that there is a possibility of IPv4 being implemented on a &lt;a href=&quot;http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=M52259DEMOKIT&quot; rel=&quot;nofollow&quot;&gt;mc52259demo&lt;/a&gt; coldfire board. Can IPv6 be implemented too? It is a Coldfire processor board developed by Freescale and it uses MQX OS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even &lt;a href=&quot;http://www.embedded-access.com/products.html&quot; rel=&quot;nofollow&quot;&gt;Embedded Access Inc&lt;/a&gt; (as seen in &lt;a href=&quot;http://electronics.stackexchange.com/questions/11595/can-ipv6-be-implemented-on-a-mcf52259-demo-board/11618#11618&quot;&gt;Mark's answer&lt;/a&gt;) does not provide IPv6 on the MCF52259demo board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am implementing this myself and not depending on any RTOS vendor's support, so the actual problem in implementation is this: What changes need to occur in the code in IPv6 from IPv4 that is to be loaded onto the board? &lt;/p&gt;&#xA;" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-07T21:02:11.640" LastActivityDate="2011-05-07T21:03:55.960" Title="Can IPv6 be implemented on a mcf52259 demo board?" Tags="&lt;ipv6&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="11596" PostTypeId="1" AcceptedAnswerId="11598" CreationDate="2011-03-16T22:48:40.743" Score="3" ViewCount="61" Body="&lt;p&gt;Hello, I am wanting to mess with the output of my guitar amp. Not actually opening it up, just taking the headphone-output and connecting it to a breadboard and such. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What form of protection, if any, should I use to keep from frying my amplifier (which cost $100) in the case of a short or other problem. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are most amplifiers self-protecting? I'm unsure on how most commercial audio amplifiers work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: My guitar amp is a 60W amplifier, but I of course won't be using it at full power&lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-17T01:55:06.143" LastActivityDate="2011-03-17T01:55:06.143" Title="How can I protect the amplifier behind a headphone jack when interfacing with external circuitry?" Tags="&lt;audio&gt;&lt;amplifier&gt;&lt;fuses&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="11597" PostTypeId="1" AcceptedAnswerId="11600" CreationDate="2011-03-16T23:24:53.693" Score="1" ViewCount="64" Body="&lt;p&gt;Here's a really nice multi-wire splicing connector:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.wago.us/news/5019.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.wago.us/news/5019.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.wago.us/images/222415_PR.jpg&quot; width=&quot;100&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using it for power distribution for a quadcopter:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://eastbay-rc.blogspot.com/2011/03/update-wago-connector-for-power.html&quot; rel=&quot;nofollow&quot;&gt;http://eastbay-rc.blogspot.com/2011/03/update-wago-connector-for-power.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://3.bp.blogspot.com/-r4x3mQi6-Yw/TVnYSinmVXI/AAAAAAAAAXI/8w6eyvWjrSA/s1600/powerdist.jpg&quot; width=&quot;200&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The specs say it has a listed capacity of 600V/20A.  If I am using it for 12V apps, can I go higher on the amperage?  i.e., are these rating in terms of total current flow?&lt;/p&gt;&#xA;" OwnerUserId="1756" LastActivityDate="2011-03-17T00:14:11.700" Title="max amperage of WAGO 222-415 connector?" Tags="&lt;power&gt;&lt;amperage&gt;&lt;power-distribution&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="11598" PostTypeId="2" ParentId="11596" CreationDate="2011-03-16T23:30:10.680" Score="3" ViewCount="" Body="&lt;p&gt;The headphone output is almost certainly protected with output resistors.  It will be extremely hard to damage it by a typical breadboard circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nevertheless, if you would like more protection, put a 1k resistor in series with the signal at the headphone plug.   Now damage is almost impossible.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-16T23:30:10.680" CommentCount="1" />
  <row Id="11599" PostTypeId="2" ParentId="11597" CreationDate="2011-03-16T23:54:30.577" Score="0" ViewCount="" Body="&lt;p&gt;In the absence of any other information, I'd limit it to 20A.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-16T23:54:30.577" />
  <row Id="11600" PostTypeId="2" ParentId="11597" CreationDate="2011-03-17T00:14:11.700" Score="7" ViewCount="" Body="&lt;p&gt;It seems you're hoping that the capacity is a function of power, so that by decreasing the voltage you can increase the current.  Unfortunately, that's not the case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage maximums for connectors are generally a function of the insulating characteristics of the materials.  If you exceed 600V for this connector, you may get arcing or the insulation may break down.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current maximums are due to the resistance of the connector and wire used for insertion.  These connectors don't give a resistance rating, but 20A will generate a lot of heat in the 28AWG wire these things are rated for, and you could exceed the maximum temperature of $85^{o}\mbox{ }C$.  This power dissipation is not due to the voltage present on the wires, but the voltage across the resistance inherent in the connections, so it doesn't matter whether you're using 600V or 12V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, unless it says otherwise, these are generally static ratings: You need to plug everything in before you turn the power on, and turn the power off before you unplug anything.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-17T00:14:11.700" />
  <row Id="11601" PostTypeId="2" ParentId="4972" CreationDate="2011-03-17T00:30:35.070" Score="0" ViewCount="" Body="&lt;p&gt;Repairing electronics is an interesting and sadly disappearing art.  Everything I've learned about it I've learned from one blog: &lt;a href=&quot;http://www.neufeld.newton.ks.us/electronics/&quot; rel=&quot;nofollow&quot;&gt;Keith's Electronics Blog&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apparently it's his job to fix electronics and he has decent writeups on everything he does.  From what I've read, 90% of the time it's the power supply - and he's written up power supply fixing.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would read his blog for no other reason than it's interesting, but also it will probably give you an idea of what fixing your speakers will require and whether it's worth it.  Good luck.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-03-17T00:30:35.070" />
  <row Id="11602" PostTypeId="1" AcceptedAnswerId="11606" CreationDate="2011-03-17T00:51:39.377" Score="0" ViewCount="90" Body="&lt;p&gt;I have been programming for more years than I care to remember &amp;amp; am familiar with many language &amp;amp; development concepts  (c, c++, Pascal, Basic, VB, Ada, Java, JS, PHP, various assemblers, etc. Procedual / OO design, etc, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to play around with MindStorms NXT and there is a chance that I might end up wanting to do some complicated stuff which could stretch the limits of the graphical programming language. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, I woudl like to have a program in my robot which would report sensor inputrs to a prorgram running on aPC and accept commands fromt the PC-based program.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone recommend a powerful programming language which is well supported and maybe a book or website that would be applicab?le to me (as opposed to some general arguemnt about which language is &quot;best&quot;)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="3396" LastActivityDate="2011-03-17T05:44:59.153" Title="Which programming is best language for me? (MindStorms NXT)" Tags="&lt;lego-mindstorms&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="11603" PostTypeId="2" ParentId="11540" CreationDate="2011-03-17T03:11:16.417" Score="0" ViewCount="" Body="&lt;p&gt;find out where boot comes from in booting a computer ( hint bootstrap )  -- look it up &lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-17T03:11:16.417" />
  <row Id="11604" PostTypeId="2" ParentId="11552" CreationDate="2011-03-17T03:21:26.760" Score="3" ViewCount="" Body="&lt;p&gt;The reason memory and other chips have reset lines is not neccessarily to &quot;clear&quot; them, but to to disconnect them from the bus during low power states.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is that, during power-up and shutdown, the strobe, address and data lines are still connected to the bus while power is rising from 0v to Vcc (or draining away), and this may manifest as digital noise that causes random &quot;garbage&quot; to be written to memory during bootup.   This is especially problematic for memory-mapped IO devices, and flash memories.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use a &quot;brown-out reset&quot; chip to ensure that your device is held in RESET state until power has stabilized and the bus values can be trusted.  Many modern microcontrollers have built-in brown-out detectors.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-17T03:21:26.760" />
  <row Id="11605" PostTypeId="2" ParentId="11587" CreationDate="2011-03-17T04:36:29.643" Score="2" ViewCount="" Body="&lt;p&gt;Services like &lt;a href=&quot;http://tgimboej.org/&quot; rel=&quot;nofollow&quot;&gt;Tgimboej&lt;/a&gt;(The Great Internet Migratory Box Of Electronics Junk) are great for trading and getting rid of extra parts. &lt;a href=&quot;http://www.thejunkexchange.com/&quot; rel=&quot;nofollow&quot;&gt;junk exchange&lt;/a&gt; is another place, but its more like a classified ads. Personally I keep things till some one needs it, or I finally found a use for that part, dust and all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;as for one offs on PCBs or perfboards, I Use IC sockets so chips can be re used on other boards, Try to make the power supply on a separate board if possible. leave leads as long as possible when soldering components to boards. I think making things modular is the best way to get the best results for re-usability. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-17T04:36:29.643" CommentCount="2" />
  <row Id="11606" PostTypeId="2" ParentId="11602" CreationDate="2011-03-17T05:44:59.153" Score="0" ViewCount="" Body="&lt;p&gt;The NXT is essentially a 32bit Altera ARM acting as the master controller connected to an 8bit Altera atmega micro (through a 2wire interface) that manages sensors/motors. The sensors themselves are connected via a 2-wire interface, therefore making custom sensors (even intelligent ones) is actually easy. In a general sense its the RCX brick with a ARM slapped on top (with extra goodies like an LCD screen, USB, and bluetooth).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since it is a standard ARM, any language that can compile binaries for the ARM should be able to work (with some effort), and there is an extensive list of languages ported to the NXT platform. Personally I would think that C or some derivative (&lt;a href=&quot;http://bricxcc.sourceforge.net/nbc/&quot; rel=&quot;nofollow&quot;&gt;Not-Exatcly C&lt;/a&gt; - C with a nonstandard library) would be the easiest to get running and get a hang of. AFAIK you can program it to communicate with the PC either through USB or bluetooth, or even through I2C if you want to bang out some real low-level communications. Once your PC gets a hold of the data you can use whatever you want to program the computer-side client, so I can't really help you out there. &lt;/p&gt;&#xA;" OwnerUserId="1729" LastActivityDate="2011-03-17T05:44:59.153" CommentCount="4" />
  <row Id="11607" PostTypeId="2" ParentId="11586" CreationDate="2011-03-17T09:18:41.053" Score="3" ViewCount="" Body="&lt;p&gt;Don't expect to build analog computers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are mainly useful for custom reconfigurable analog filters &amp;amp; some schemes with opamps, that's it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can't suggest any resources except datasheeds on your chips :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-17T09:18:41.053" CommentCount="5" />
  <row Id="11608" PostTypeId="1" AcceptedAnswerId="11611" CreationDate="2011-03-17T11:26:33.407" Score="1" ViewCount="112" Body="&lt;p&gt;I need to receive signal from IR transmitter LED. I am not sure how to program the microcontroler. I am looking for some concept, how to do that. Whether I have to use A/D conversion? How to synchronize transmitter and receiver? What structure will be in coming data? Let's say that I assumed 600us for 0 (binary 0) and 1200 for 1 (binary 1) when I was programming a transmitter. What are the common steps to receive infrared transmission on PIC18F microcontroler?&lt;/p&gt;&#xA;" OwnerUserId="3409" LastActivityDate="2011-03-17T12:48:13.527" Title="How to receive IR signal in PIC18F" Tags="&lt;pic&gt;&lt;ir&gt;" AnswerCount="2" />
  <row Id="11609" PostTypeId="5" CreationDate="2011-03-17T11:58:32.713" Score="0" ViewCount="" Body="&lt;p&gt;Fore more information see &lt;a href=&quot;http://en.wikipedia.org/wiki/TRIAC&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-03-17T12:09:38.797" LastActivityDate="2011-03-17T12:09:38.797" />
  <row Id="11610" PostTypeId="4" CreationDate="2011-03-17T11:58:32.713" Score="0" ViewCount="" Body="A TRIAC is an component often used to control high power currents, both as a switch and as a &quot;dimmer&quot;-like construction for controlling lamps or electric engines. " OwnerUserId="-1" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-03-17T13:11:43.887" LastActivityDate="2011-03-17T13:11:43.887" />
  <row Id="11611" PostTypeId="2" ParentId="11608" CreationDate="2011-03-17T12:12:07.173" Score="2" ViewCount="" Body="&lt;p&gt;Here's a good introduction to IR reception. It's aimed at Arduino, but the concepts are all applicable to any microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ladyada.net/learn/sensors/ir.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/learn/sensors/ir.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-17T12:12:07.173" />
  <row Id="11612" PostTypeId="2" ParentId="5540" CreationDate="2011-03-17T12:27:59.673" Score="0" ViewCount="" Body="&lt;p&gt;I just started etching, and have chosen cupric chloride (CuCl2 - the resulting chemical of etching copper with muriatic acid + peroxide).&#xA;About shelf life:&#xA;The great thing about CuCl2 is that you can REGENERATE the solution by adding a little oxygen (fish tank pump, shake bottle, or add a little H2O2), or acid once in a while.  Which means you almost never have to dispose of the hazardous waste.&#xA;About the previous comment -- the copper in the waste is poisonous even at very small concentrations.  &quot;In Australia the EPA regulates maximum copper in sewage discharge to 5 ppm. If you have etchant containing 150g/L of copper, that means a dilution 1:28000 is necessary to meet regulations&quot; -- from &lt;a href=&quot;http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html&quot; rel=&quot;nofollow&quot;&gt;http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That link has tons of information about using CuCl2 to etch copper.&#xA;Also this link simplifies the process greatly:  &lt;a href=&quot;http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CuCl2 is slower than muriatic + peroxide, but I think it's worth almost never having to buy more etchant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though I haven't tried any very small traces yet.  As I understand it slower etching means more undercutting (etching sideways under your resist).  As noted -- I'm a beginner.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also anyone who wants to do this should read about muriatic acid storage -- according to what I've read, even a little gas slowly escaping from the bottle can rust nearby metal.&#xA;I think I read that the gas is heavier than air, so if I see any rusting, I'm thinking about putting some kind of base chemical in the bottom of a 5-gallon bucket, and storing the acid in there.  Maybe concrete rubble?&lt;/p&gt;&#xA;" OwnerUserId="3410" LastActivityDate="2011-03-17T12:27:59.673" />
  <row Id="11613" PostTypeId="2" ParentId="11608" CreationDate="2011-03-17T12:48:13.527" Score="0" ViewCount="" Body="&lt;p&gt;The signal is digital, no AD for communication uses.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-17T12:48:13.527" />
  <row Id="11614" PostTypeId="1" AcceptedAnswerId="11615" CreationDate="2011-03-17T13:18:19.143" Score="0" ViewCount="128" Body="&lt;p&gt;We are building a robot that will be controlled by mini-ITX PC. The power source for robot will be detached car battery. Question is how to power mini-ITX mother board (and HDD) using this battery? What devices are needed?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; I think I need DC-DC converter that converts from battery voltage and converts it to 12V and stabilizes it. Right?&lt;/p&gt;&#xA;" OwnerUserId="3412" LastActivityDate="2011-03-18T15:07:20.580" Title="Supply power to mini-ITX from car battery" Tags="&lt;power-supply&gt;&lt;robotics&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="11615" PostTypeId="2" ParentId="11614" CreationDate="2011-03-17T14:06:43.647" Score="2" ViewCount="" Body="&lt;p&gt;Mini-ITX does not standardize a power supply.  If your board takes 12V, then yes, you need a DC-DC converter that converts the battery voltage to 12V.  However, according to &lt;a href=&quot;http://en.wikipedia.org/wiki/Mini-ITX#Power&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;, a 20 or 24-pin &lt;a href=&quot;http://pinouts.ru/Power/atx_v2_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;standard ATX power connector&lt;/a&gt; is conventionally used.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This connector has a number of independent supplies for 3.3V, 5V, and 12V.  Here's the &lt;a href=&quot;http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf&quot; rel=&quot;nofollow&quot;&gt;PDF standard&lt;/a&gt; if you want to develop your own - It's not trivial! You'll need to know the power requirements of your mini-ITX board to determine how many amps each supply needs to provide.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, there are a number of ready-made solutions.  If you have an inverter available, a standard ATX power supply will work fine.  mini-box.com has been debugged (good or bad, your choice) on this site before; their &lt;a href=&quot;http://www.mini-box.com/M3-ATX-DC-DC-ATX-Automotive-Computer-car-PC-Power-Supply?sc=8&amp;amp;category=981&quot; rel=&quot;nofollow&quot;&gt;m-series power adapters&lt;/a&gt; are specifically designed for in-car use.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-17T14:06:43.647" CommentCount="2" />
  <row Id="11616" PostTypeId="2" ParentId="11552" CreationDate="2011-03-17T15:40:27.617" Score="2" ViewCount="" Body="&lt;p&gt;Datasheet covers this:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;RESET: A low state on the reset pin&#xA;  (RESET) will terminate the operation&#xA;  in progress and reset the internal&#xA;  state machine to an idle state. The&#xA;  device will remain in the reset&#xA;  condition as long as a low level is&#xA;  present on the RESET pin. Normal&#xA;  operation can resume once the RESET&#xA;  pin is brought back to a high level&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So you don't lose buffer values but any operation in progress is stopped and the state machine is reset.  So the data in the buffer is invalid (does not line up with current state and may not line up with whats actually in flash, it should be treated as garbage).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you trip the software reset while a write or read from flash is occurring the operation stops and upon release of the software reset the chip is in its default state.  This means that the software reset can corrupt flash data without changing the buffer values.  When you write to the flash you have to make sure you allow enough time for the chip to actually write the data to the flash before using the software reset or your data will be not make it to the flash.  These times are listed in section 8.2 of the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Strictly speaking it is also not safe to read from the data buffer as if it were valid after a software reset, you must re-issue a command to copy data from flash to the buffer before you can read it and be assured that it is valid (equivalent to whats actually in flash).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The device incorporates an internal&#xA;  power-on reset circuit, so there are&#xA;  no restrictions on the RESET pin&#xA;  during power-on sequences. If this pin&#xA;  and feature are not utilized it is&#xA;  recommended that the RESET pin be&#xA;  driven high externally&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;and&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;When power is first applied to the&#xA;  device, or when recovering from a&#xA;  reset condition, the device will&#xA;  default to SPI Mode 3. In addition,&#xA;  the SO pin will be in a high-impedance&#xA;  state, and a highto-low transition on&#xA;  the CS pin will be required to start a&#xA;  valid instruction. The SPI mode will&#xA;  be automatically selected on every&#xA;  falling edge of CS by sampling the&#xA;  inactive clock state. After power is&#xA;  applied and VCC is at the minimum&#xA;  datasheet value, the system should&#xA;  wait 20 ms before an operational mode&#xA;  is started&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So there is no need for an external controller to bring the chip online on power up.  Unless your power on operation takes more than 20ms to stabilize supply voltage you shouldn't have any power on garbage issues.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2011-03-17T15:45:41.073" LastActivityDate="2011-03-17T15:45:41.073" />
  <row Id="11617" PostTypeId="2" ParentId="11540" CreationDate="2011-03-17T15:56:40.403" Score="1" ViewCount="" Body="&lt;p&gt;Short answer is no.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An operating system on a computer is loaded in multiple stages but the fundamental reason the BIOS is required in this case is that the BIOS is responsible for finding storage devices and implementing the communication protocol to talk to them.   It then loads the first few bytes into memory (the MBR or Master Boot Record) which contains the initial portion of the boot loader.  What happens from there is OS or bootloader specific.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without BIOS the computer wouldn't know how to find or talk to storage devices and therefore could not load the bootloader which in turn could not load the OS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are lots of other things that the BIOS does that are also required for the operation of a computer.  Much of this is rather complicated, especially on x86 platforms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In microcontrollers or embedded processors the system normally looks to a specified memory address based on how its configured to find the bootloader.  This is normally on chip flash or external flash.  How complicated this process is or what exactly is done is architecture/OS dependent.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You normally need a special programmer to write to the on or off chip flash to load your code to a micro-controller / embedded processor.  &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-03-17T15:56:40.403" CommentCount="3" />
  <row Id="11618" PostTypeId="2" ParentId="11595" CreationDate="2011-03-17T16:18:33.387" Score="1" ViewCount="" Body="&lt;p&gt;Yes, the free RTOS from freescale doesn't support it though (that i know of).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.embedded-access.com/products.html&quot; rel=&quot;nofollow&quot;&gt;Here is one that does&lt;/a&gt;, probably are others as well.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-03-17T16:18:33.387" />
  <row Id="11619" PostTypeId="2" ParentId="11540" CreationDate="2011-03-17T16:28:50.130" Score="2" ViewCount="" Body="&lt;p&gt;Do you mean load Windows on Windows-compatible PC specifically?  Or is this a theoretical question?  Or something else?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the general case, yes.  Look up the DEC PDP-8, for example.  You would use front panel switches to enter an extremely basic paper-tape loader, which would then load your program (or a more capable loader) through a paper tape reader.  No BIOS involved.  People who did it frequently had the loader code memorized (in octal!), and used to compete for who could get the machine started the quickest.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But whether it temporarily maps in a bit of ROM and jumps to it, jumps to a permanent ROM like a BIOS, or allows front-panel entry, as the PDP-8 did, the machine has to have or acquire its initial program from somewhere.&lt;/p&gt;&#xA;" OwnerUserId="3361" LastActivityDate="2011-03-17T16:28:50.130" CommentCount="1" />
  <row Id="11620" PostTypeId="2" ParentId="11468" CreationDate="2011-03-17T17:15:45.123" Score="1" ViewCount="" Body="&lt;p&gt;I am intrigued by your idea of a fully symmetrical AC switch -- how would you keep such a device off, and then later how would you turn it on?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most of the structure of a triac is fairly symmetrical.&#xA;However, as the schematic diagram tries to imply, the gate is attached &quot;closer&quot; to MT1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the triac off, a typical circuit drives the voltage at MT2 up and down hundreds of volts relative to MT1, but as long as the gate voltage stays the same as the MT1 voltage, the triac stays off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One way to turn the triac on is to &quot;pull down&quot; the gate.&#xA;The circuit is the same as with a PNP transistor -- the &quot;+5V&quot; VCC of the microcontroller is connected to MT1; a gate resistor connects a microcontroller output pin to the gate of the triac; and the motor or other load is connected to MT2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As Thomas O mentioned, another way to turn a triac on is to connect the gate resistor to a voltage that pulls away from the MT1 voltage in the same direction as the voltage at MT2 -- positive voltage anytime during the half-cycle when MT2 is positive, negative voltage anytime during the half-cycle when MT2 is negative.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Recently I blew up over a dozen triacs learning that (a) once a triac is on, turning a triac off is a bit more difficult, and (b) hooking the the &quot;GND&quot; pin of the microcontroller to MT1 and pulling the gate through a resistor to +5 V doesn't work right with a logic level triac.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The rough draft of the &lt;a href=&quot;http://en.wikibooks.org/wiki/Power_Electronics#Triacs&quot; rel=&quot;nofollow&quot;&gt;&quot;Power Electronics&quot; book already links to some schematic diagrams illustrating how to use triacs&lt;/a&gt;, and links to &quot;Thyristors &amp;amp; Triacs - Ten Golden Rules for success in your application&quot;. Perhaps you will find those ten rules useful, and perhaps you can help us make that Wikibook better.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-17T17:15:45.123" />
  <row Id="11621" PostTypeId="1" AcceptedAnswerId="11638" CreationDate="2011-03-17T18:33:31.910" Score="2" ViewCount="122" Body="&lt;p&gt;I am trying to do some high time precision work (well not that high, but more than normal) and would need calculate the time delay generated by a small loop. Can anyone help me with that? These are just generic instructions like these&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;for(i=0;i&amp;lt;=100;i++)&#xA;{&#xA;if(i&amp;lt;x)&#xA;&#xA;    PORTA |= (1&amp;lt;&amp;lt;0);&#xA;else&#xA;    PORTA &amp;amp;= ~(1&amp;lt;&amp;lt;0);&#xA;if(i&amp;lt;y)&#xA;    PORTA |= (1&amp;lt;&amp;lt;1);&#xA;else&#xA;    PORTA &amp;amp;= ~(1&amp;lt;&amp;lt;1);&#xA;if(i&amp;lt;z)&#xA;        PORTA |= (1&amp;lt;&amp;lt;2);&#xA;else&#xA;    PORTA &amp;amp;= ~(1&amp;lt;&amp;lt;2);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;}&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is just an example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The controller is an ATmega32 working on the internal 8MHz RC oscillator.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-03-17T19:48:01.550" LastActivityDate="2011-03-18T04:57:57.650" Title="How to calculating loop delay in avr based architectures" Tags="&lt;avr&gt;&lt;timing&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="11622" PostTypeId="2" ParentId="11621" CreationDate="2011-03-17T19:07:27.523" Score="3" ViewCount="" Body="&lt;p&gt;The AVR Studio simulator will tell you how many clock cycles that loop takes for the various conditions, if you set them up properly.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-17T19:07:27.523" CommentCount="1" />
  <row Id="11623" PostTypeId="2" ParentId="11621" CreationDate="2011-03-17T19:18:18.500" Score="2" ViewCount="" Body="&lt;p&gt;You can benchmark the timings using one of the 16 bit timers such as timer1 or timer3.&#xA;Don't forget to time the timing harness as well and correct for it!&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-03-17T19:18:18.500" />
  <row Id="11625" PostTypeId="1" AcceptedAnswerId="11628" CreationDate="2011-03-17T21:09:39.030" Score="2" ViewCount="132" Body="&lt;p&gt;I've designed a simple PWM RGB LED slow fader to be used as a garden lighting effect. My circuit works great, but I under-estimated the amount of heat that is generated by the 7805 linear regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's mains powered, with a 6Vac transformer and a 5V 1A linear regulator. If all the LED's are at full brightness then it draws around 600mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've mounted my circuit board in a plastic enclosure with a transparent lid, and it's rated at IP67 (and I want to keep it that way!).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've put quite a small heatsink on the regulator, and it takes around 3 or 4 hours of continuous use to get to a temperature that is just about too hot to touch, I'm guessing around 70-80&amp;deg;C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My plan is to give this to my Dad for him to use in his garden, but obviously I don't want it to melt or catch fire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is this an acceptable temperature for it to operate at?&lt;/li&gt;&#xA;&lt;li&gt;Is it likely to get any hotter if left on for longer? I didn't want to test this as I didn't want to damage it, but the datasheet says the operating temp is max 125&amp;deg;C so I guess it would be ok.&lt;/li&gt;&#xA;&lt;li&gt;What can I do to make it run cooler, given that I don't want to drill vents into the enclosure and ruin it's IP67 rating?&lt;/li&gt;&#xA;&lt;li&gt;If it does happily operate at a high temperature, do I need to be worried about heat conduction through the PCB tracks into other components that may be damaged? Will it melt the solder?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-21T23:28:16.773" Title="Regulator cooling in a confined space" Tags="&lt;voltage-regulator&gt;&lt;temperature&gt;&lt;heatsink&gt;&lt;heat&gt;&lt;cooling&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="11626" PostTypeId="1" AcceptedAnswerId="11630" CreationDate="2011-03-17T21:54:12.853" Score="2" ViewCount="141" Body="&lt;p&gt;I have a stepper motor rated at 1.8 ohms or resistance per phase, a driver rated at 750mA and a powersupply that gives 12V rated at 1A. This would mean that the motor will draw 6.6A per phase.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I wanted to limit the stepper so that it cannot draw more power at 12V than the driver can tolerate then can I add 14.2 ohms of 1/2 watt resistors (if there is such a thing) to acheive this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is my math correct?&#xA;1.8 Ohms + 14.2 Ohms = 16 Ohms&#xA;12 Volts / 16 Ohms = 0.75 Amps?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that the stepper will not be at full power but it doesn't have to be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Sorry wrong resistance per phase. It supposed to be 3.6 Ohms per phase; would I require 12.4 Ohms of additional resistance per phase?&lt;/p&gt;&#xA;" OwnerUserId="3045" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-03-18T09:36:29.037" LastActivityDate="2011-03-20T01:45:09.143" Title="Will adding 1/2 watt resistors reduce the current load of a stepper motor?" Tags="&lt;resistor&gt;&lt;stepper-motor&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="11627" PostTypeId="2" ParentId="11614" CreationDate="2011-03-17T22:04:40.800" Score="1" ViewCount="" Body="&lt;p&gt;For a DC/DC converter that does exactly what you want see: &lt;a href=&quot;http://dren.dk/carpower.html&quot; rel=&quot;nofollow&quot;&gt;http://dren.dk/carpower.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-03-17T22:04:40.800" />
  <row Id="11628" PostTypeId="2" ParentId="11625" CreationDate="2011-03-17T22:04:50.783" Score="4" ViewCount="" Body="&lt;p&gt;The regulator should have thermal limiting (check the data sheet for details), and will shut down if the temperature gets too high. It won't damage any other parts, and definitely won't melt any solder!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a larger heatsink will reduce the temperature, of course. A switching regulator will be a lot more efficient and will just get slightly warm.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-17T22:04:50.783" CommentCount="4" />
  <row Id="11630" PostTypeId="2" ParentId="11626" CreationDate="2011-03-17T22:58:20.500" Score="5" ViewCount="" Body="&lt;p&gt;well not half watt resistors .... 0.75 amps though a 12.4 ohm resistor P=IIR = 0.75*0.75*12.4 = 7 watts - half watt resistors are going to smoke - maybe some 10 watt wirewounds?&lt;/p&gt;&#xA;" OwnerUserId="3190" LastEditorUserId="3190" LastEditorDisplayName="" LastEditDate="2011-03-17T23:09:11.093" LastActivityDate="2011-03-17T23:09:11.093" CommentCount="2" />
  <row Id="11631" PostTypeId="2" ParentId="11540" CreationDate="2011-03-17T23:04:27.730" Score="3" ViewCount="" Body="&lt;p&gt;Technically yes, but with modern PCs, no. First off, modern PCs require a lot of hardware to be initiated. But anyway. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm going to guess that you are talking about basically a bare x86 and some RAM only. All that must be done is you must somehow(via an external controller/whatever) load your operating system's code into the RAM at address 0xF000:FFF0. The x86 will begin execution at this address, always. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So no, a BIOS is not required, but due to how modern PCs work, it's next to impossible(without major hacks) to &quot;bypass&quot; it and straight load your operating system yourself.&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-03-17T23:04:27.730" />
  <row Id="11632" PostTypeId="1" AcceptedAnswerId="11636" CreationDate="2011-03-18T00:33:58.133" Score="6" ViewCount="160" Body="&lt;p&gt;Why are SMD resistors marked with their value, but SMD ceramic (and similar) capacitors are not? Most SMD resistors, even the very small 0402 and 0603 ones, have their values written on them. Most SMD ceramic caps are not, I haven't to date seen a single one. The &lt;em&gt;only&lt;/em&gt; possible reason I can think of is that resistors are far more likely to fail than capacitors as they natively dissipate heat. Supporting this theory is the fact that tantalum and aluminium electrolytic capacitors generally have a value written on them, because they are less reliable than ceramics. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Out of curiosity.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-03-18T00:42:47.093" LastActivityDate="2011-03-18T10:24:11.790" Title="Why are SMD resistors marked with their value, but SMD capacitors are not?" Tags="&lt;surface-mount&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="11633" PostTypeId="1" AcceptedAnswerId="11683" CreationDate="2011-03-18T01:52:25.017" Score="4" ViewCount="197" Body="&lt;p&gt;Hello &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am planning on creating a &lt;a href=&quot;http://leyanda.de/light/povglobe.php&quot; rel=&quot;nofollow&quot;&gt;RGB LED POV globe&lt;/a&gt; only physically larger then that one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am planning on using 64 RGB LEDs, requiring 3x pins per LED for a total of 192 outputs. Obviously I am going to need some shift registers. I have looked in to &lt;a href=&quot;http://www.arduino.cc/en/Tutorial/ShiftOut&quot; rel=&quot;nofollow&quot;&gt;74HC595&lt;/a&gt; (8bit) and it would require 24 of these chips to handle all of these LEDs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am planning on putting these shift registers in series with 6 per channel from my micro-controller. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 74HC595 has a switching frequency of 100 MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I been told that I will need to spin the Globe at around 1500 RPM (25 per sec) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The plan is to use a &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; for the micro controller but I am open to suggestions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Is there a better suited chip then the 74HC595 for this project? &lt;/li&gt;&#xA;&lt;li&gt;Besides the Arduino is there a better suited micro controller for this project?&lt;/li&gt;&#xA;&lt;li&gt;I don't want to power the LEDs off of the micro-controller So I am going to need external power. How would I go about doing this? &lt;/li&gt;&#xA;&lt;li&gt;With 6x 74HC595 in series, How fast could I switch all of the LEDs colors on this channel?&lt;/li&gt;&#xA;&lt;li&gt;With 12x 74HC595 in series, How fast could I switch all of the LEDs colors on this channel?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="592" LastActivityDate="2011-03-18T21:10:03.963" Title="POV globe speed questions" Tags="&lt;led&gt;&lt;rgb&gt;&lt;74hc595&gt;&lt;shift-register&gt;&lt;pov&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="11634" PostTypeId="5" CreationDate="2011-03-18T01:58:50.020" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-03-18T01:58:50.020" LastActivityDate="2011-03-18T01:58:50.020" />
  <row Id="11635" PostTypeId="4" CreationDate="2011-03-18T01:58:50.020" Score="0" ViewCount="" Body="POV stands for Persistence Of Vision" OwnerUserId="-1" LastEditorUserId="592" LastEditorDisplayName="" LastEditDate="2011-03-19T02:08:11.730" LastActivityDate="2011-03-19T02:08:11.730" />
  <row Id="11636" PostTypeId="2" ParentId="11632" CreationDate="2011-03-18T02:01:43.563" Score="6" ViewCount="" Body="&lt;p&gt;Nice questions, I like to do extensive googling to find answers on tough questions :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason is that 'default' surface material used in resistors is suitable for printing, while on caps(ceramic dielectric) it's not. Extra coating would increase price &amp;amp; reduce cap quality, that's why they don't do it usually. When caps are big enough &amp;amp; plastic, they usually have markings.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-18T02:01:43.563" CommentCount="4" />
  <row Id="11637" PostTypeId="2" ParentId="11625" CreationDate="2011-03-18T02:34:31.197" Score="3" ViewCount="" Body="&lt;p&gt;You probably have too high of an unregulated voltage coming out of your transformer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally, you want to have the VDrop across the linear regulator be pretty much just the regulators drop-out at full load. You can also use a low-drop-out regulator to reduce the dissipated power (the 7805 is &lt;strong&gt;not&lt;/strong&gt; LDO).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the voltage on the input to the linear reg?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, as Leon Heller was mentioning above, there are some pretty easy-to-implement switching voltage regulators, particularly Nation Semiconductor's &lt;a href=&quot;http://www.national.com/analog/power/simple_switcher&quot; rel=&quot;nofollow&quot;&gt;Simple Switcher&lt;/a&gt; Regulators.&lt;br&gt;&#xA;However, for any switching regulator like these, to make them perform properly, you really need either some really tight hand wiring, or a custom PCB. &lt;a href=&quot;http://www.national.com/rap/Story/0,1562,8,00.html&quot; rel=&quot;nofollow&quot;&gt;You can &lt;strong&gt;not&lt;/strong&gt; really breadboard them successfully&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OTOH, if you're willing to spend a little bit more, you can get drop-in switching replacements for something like the 7805. A &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=811-2196-5-ND&quot; rel=&quot;nofollow&quot;&gt;number&lt;/a&gt; of &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=811-1116-ND&quot; rel=&quot;nofollow&quot;&gt;manufacturers&lt;/a&gt; &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=945-1061-ND&quot; rel=&quot;nofollow&quot;&gt;sell&lt;/a&gt; &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=PT78ST105V-ND&quot; rel=&quot;nofollow&quot;&gt;little&lt;/a&gt; 7&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=PT5101N-ND&quot; rel=&quot;nofollow&quot;&gt;805-sized&lt;/a&gt; &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=811-1119-ND&quot; rel=&quot;nofollow&quot;&gt;switching&lt;/a&gt; &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=102-2188-ND&quot; rel=&quot;nofollow&quot;&gt;regulator&lt;/a&gt; &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=945-1053-ND&quot; rel=&quot;nofollow&quot;&gt;modules&lt;/a&gt;, which even have the same footprint. However, they're generally about $\$$10-$\$$15 dollars.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt; - Does anyone know why my dollar sign symbols are vanishing?&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-03-18T03:39:47.223" LastActivityDate="2011-03-18T03:39:47.223" CommentCount="2" />
  <row Id="11638" PostTypeId="2" ParentId="11621" CreationDate="2011-03-18T04:57:57.650" Score="1" ViewCount="" Body="&lt;p&gt;You can have your loop toggle an IO line and measure the frequency of the resulting signal, either with an oscilloscope, or a multimeter with a frequency setting.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2011-03-18T04:57:57.650" />
  <row Id="11639" PostTypeId="2" ParentId="11545" CreationDate="2011-03-18T06:21:46.653" Score="1" ViewCount="" Body="&lt;p&gt;I found some example code on a website, this fellow is doing almost exactly what I'm doing, just the information is going from phone to Arduino, not Arduino to phone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All the code is downloadable, and I've checked it out - I'm going to try the PDE, and see if I can connect from my Mac and U8300.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It also includes constructs for the code I need on the phone side, which was going to be my next question after this one - two for the price of one!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ai.kittywolf.net/index.php/BTArduinoLED1&quot; rel=&quot;nofollow&quot;&gt;http://ai.kittywolf.net/index.php/BTArduinoLED1&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have a look, its said in the description that (paraphrase) &quot;the initialisation sequence must be done right...&quot; so I can now use this code as a guide.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Shane.&lt;/p&gt;&#xA;" OwnerUserId="3397" LastActivityDate="2011-03-18T06:21:46.653" />
  <row Id="11640" PostTypeId="2" ParentId="11160" CreationDate="2011-03-18T06:21:58.593" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.arenasolutions.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.arenasolutions.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not quite what I want, (too BOM oriented and too enterprise) but getting closer.&lt;/p&gt;&#xA;" OwnerUserId="3295" LastActivityDate="2011-03-18T06:21:58.593" />
  <row Id="11641" PostTypeId="2" ParentId="11633" CreationDate="2011-03-18T09:10:24.167" Score="1" ViewCount="" Body="&lt;p&gt;Let's say you need 500 updates per rotation. That's 500*192*25 'shifts' per second - that's just 2.4Mhz shift out frequency, divided by 6 channels = 400kHz shiftout frequency. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is achivable with arduino(20Mhz really preferred), but require careful programming &amp;amp; timing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So for your questions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) I guess not. 8-bit registers would require tricky PCB routing&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) If you would have 24 outputs, it would be easier. Also, for such a large display it would be nice to have enough internal memory to hold framebuffer to make programming easier. On the very minimal you would need 16kb memory which is not something you can find on 8-bit AVRs. mid-range ARM's might be better, but harder to develop for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Well, you are not. You are using power from 595, they are not very powerful, but enough in simplest case (check datasheet for specific model you have).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4,5) Faster than needed :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-18T09:10:24.167" />
  <row Id="11642" PostTypeId="2" ParentId="11632" CreationDate="2011-03-18T10:24:11.790" Score="0" ViewCount="" Body="&lt;p&gt;I think it's simply a case that the material is harder to mark economically. Also there are typically far fewer different value caps than resistors, so the mark being there for inspection purposes is less necessary. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-03-18T10:24:11.790" />
  <row Id="11645" PostTypeId="2" ParentId="5861" CreationDate="2011-03-18T11:22:06.827" Score="1" ViewCount="" Body="&lt;p&gt;I'd strongly second Mr. Hedgehog's suggestion of going with the PIC12f683 and using SourceBoost's compiler free version. It's great chip with lots of features and plenty of program space/ram for such a tiny part.  Not to blow my own trumpet but &lt;a href=&quot;http://catmacey.wordpress.com/tag/12f683/&quot; rel=&quot;nofollow&quot;&gt;here are some things I've done with it&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want something bigger I suggest going direct to the 24f series.  They cost the same or often less than the 18f series with better features. The compiler is free, they are 16bit, can run very fast (16mips) and best of all the majority have Peripheral Pin Select (PPS) which allows you to assign just about all the peripherals (SPI,USART,CCP etc) to pretty much any GPIO pin you like.  This make routing of your circuit boards &lt;strong&gt;so&lt;/strong&gt; much easier. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My favourites would be the &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en536121&quot; rel=&quot;nofollow&quot;&gt;PIC24FJ64GB002&lt;/a&gt; and PIC24FJ64GA102 (&lt;em&gt;I would link but as a newbie I can't have more that 2 hyperlinks&lt;/em&gt;). They're both available in DIP package (28pin) have tons of program memory and ram (64kb,8kb) and have lots of peripherals.  They are pretty much identical except that  GB002 has built in USB hardware at the cost of a couple of GPIOs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;IMHO As a beginner it's not worth bothering with the 16f or 18f series unless you have a very specific need to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And finally, get yourself the USB based PicKit 2 or 3 In circuit Serial Programmer (ISCP).  They're not expensive at around 30USD. It's just not worth bothering with older/cheaper/knockoff/homebuilt programmers, too much hassle.  Sure, you can use a bootloader later if you like, but as a beginner with a new project you want to be sure that any problems you are having are with your circuit and not some random problem with your programmer. It was the best thing I did to make my life easier...&lt;/p&gt;&#xA;" OwnerUserId="3419" LastEditorUserId="3419" LastEditorDisplayName="" LastEditDate="2011-03-18T13:39:06.250" LastActivityDate="2011-03-18T13:39:06.250" CommunityOwnedDate="2011-05-15T04:20:58.030" CommentCount="3" />
  <row Id="11646" PostTypeId="2" ParentId="11046" CreationDate="2011-03-18T13:11:18.110" Score="0" ViewCount="" Body="&lt;p&gt;Here's an example of charlieplexing that I have built.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a lighthouse beam simulator and uses a series of 12 LEDs charlieplexed to 4 GPIOs to sweep a beam of light around a disc. &lt;a href=&quot;http://catmacey.wordpress.com/2008/06/15/finally-got-it-working/&quot; rel=&quot;nofollow&quot;&gt;There's a video of it here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The project is PIC based, I use a PIC12f683 which is also an 8pin uP and could be considered comparable to the 8pin AVRs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LED's intensity is driven by an interupt that provides a 32 step PWM at around 60Hz. Only two LEDs are allowed to be lit at any one time giving a 50% duty for each LED as that was all I needed. It also gives a good trade off of PWM refresh rate against resolution. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The coding for using charlieplexing as actually pretty simple if you stick to the &quot;classic&quot; method of only lighting a single LED at any one point in time at a very fast refresh rate.  I work out the required PORT and TRIS (pic specific registers) first on paper then store the results in a static array.  To light LED x the PIC just has to lookup the value at the array's index[x] and write them directly to the PORT (with a bit of masking to preserve the state of the other pins not used in the charliplex)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My project only has 12 LED not 15 or the maximum 20 the 5 GPIO will allow as I wanted to keep one GPIO spare for future development.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway... I just thought it might be helpfull to have a working example similar to your request.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://catmacey.wordpress.com/tag/lighthouse/&quot; rel=&quot;nofollow&quot;&gt;Full source code and schematics are available&lt;/a&gt; on my blog.&lt;/p&gt;&#xA;" OwnerUserId="3419" LastEditorUserId="3419" LastEditorDisplayName="" LastEditDate="2011-03-19T08:56:06.433" LastActivityDate="2011-03-19T08:56:06.433" />
  <row Id="11647" PostTypeId="2" ParentId="8680" CreationDate="2011-03-18T13:11:35.600" Score="0" ViewCount="" Body="&lt;p&gt;You said:&#xA;&quot;For example the Nexus S's NFC chip is read only and does not offer any card emulation mode.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please take a at &lt;a href=&quot;http://www.nearfieldcommunicationsworld.com/2011/02/13/35913/uncovered-the-hidden-nfc-potential-of-the-google-nexus-s-and-the-nokia-c7/&quot; rel=&quot;nofollow&quot;&gt;http://www.nearfieldcommunicationsworld.com/2011/02/13/35913/uncovered-the-hidden-nfc-potential-of-the-google-nexus-s-and-the-nokia-c7/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They do say &quot;... So the phone comes with everything we do need for card emulation — SWP and even a secure element within the phone.&quot;&lt;/p&gt;&#xA;" OwnerUserId="3421" LastActivityDate="2011-03-18T13:11:35.600" CommentCount="1" />
  <row Id="11648" PostTypeId="1" AcceptedAnswerId="11653" CreationDate="2011-03-18T13:16:18.370" Score="2" ViewCount="98" Body="&lt;p&gt;I've used the PIC assembler and tool kit from gputils with success before, but I noticed that they're lacking support for my new pic12lf1822 chips. How do I go about getting it supported?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After checking out their source code I couldn't find any useful information other than lots of existing .inc and .lkr files which seems to be taken from MPASM. As I don't have a Windows box I can't download MPASM and use their files.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-03-18T13:48:40.420" Title="How do I add support for PIC12LF1822 to gputils" Tags="&lt;pic&gt;&lt;assembly&gt;" AnswerCount="1" />
  <row Id="11653" PostTypeId="2" ParentId="11648" CreationDate="2011-03-18T13:42:16.947" Score="1" ViewCount="" Body="&lt;p&gt;If you can't wait for that device to be added to gputils, and you don't want to use Windows, you could download the beta MPLAB X which runs under Linux and Mac OS. I just checked and it does support the 12F1822, so you could download it and extract the files you need. Or, use MPLAB X for your development, instead of gputils.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-18T13:48:40.420" LastActivityDate="2011-03-18T13:48:40.420" CommentCount="5" />
  <row Id="11654" PostTypeId="1" AcceptedAnswerId="11655" CreationDate="2011-03-18T13:49:51.627" Score="2" ViewCount="349" Body="&lt;p&gt;I want to connect &lt;a href=&quot;http://www.sparkfun.com/datasheets/Robotics/310-101_datasheet.pdf&quot; rel=&quot;nofollow&quot;&gt;this dv motor&lt;/a&gt; to the 5V output of an Arduino board. Of course I need to get the 5V down to 3V in order for the motor to function correctly. I've read that I could use a diode with the correct voltage drop for this, or just use a resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Going the resistor way, I've got some trouble figuring out the correct resistor value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the datasheet I calculated that the resistance of this motor would be 40ohms at 3V (3 / 0.075 = 40). Is this correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ratio between 5V and 3V is 0.6. So I figured I need a (40 * 0.6) = 24ohm resistor to get the correct voltage over the motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are these calculations correct? I'm still an electronics beginner so I'm not quite sure :).&#xA;And even if they are correct, would I be better of using a diode (or maybe even a voltage regulator)?&lt;/p&gt;&#xA;" OwnerUserId="3362" LastActivityDate="2011-03-18T14:23:00.943" Title="5V to 3V, calculate resistor value (or use diode?)" Tags="&lt;voltage-regulator&gt;&lt;voltage&gt;&lt;diode&gt;&lt;resistance&gt;" AnswerCount="2" />
  <row Id="11655" PostTypeId="2" ParentId="11654" CreationDate="2011-03-18T14:08:15.800" Score="4" ViewCount="" Body="&lt;p&gt;It takes 75 mA at 3V, which is far too much for an Arduino output. You need to drive it from a transistor using the following circuit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/qIYJR.gif&quot; alt=&quot;Motor driver&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any similar NPN transistor could be used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use three diodes in series to drop the 5V supply to about 3V, or use a suitable regulator.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-18T14:14:14.687" LastActivityDate="2011-03-18T14:14:14.687" CommentCount="2" />
  <row Id="11656" PostTypeId="2" ParentId="11509" CreationDate="2011-03-18T14:14:14.710" Score="1" ViewCount="" Body="&lt;p&gt;When I have a digital circuit and I discover I need &quot;just one more inverter&quot;, I usually put in an entire chip -- perhaps a 74HC132 -- because usually a few minutes after I get that inverter wired up, I discover that I need yet another &quot;just one more inverter&quot;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-18T14:14:14.710" />
  <row Id="11657" PostTypeId="2" ParentId="11509" CreationDate="2011-03-18T14:14:58.627" Score="1" ViewCount="" Body="&lt;p&gt;A pair of complementary MOSFETs in the standard &lt;a href=&quot;http://en.wikipedia.org/wiki/Inverter_%28logic_gate%29&quot; rel=&quot;nofollow&quot;&gt;static CMOS inverter&lt;/a&gt; arrangement should work fine.&#xA;There are literally hundreds of different kinds of individual transistors and transistor arrays currently on the shelf of &lt;a href=&quot;http://opencircuits.com/Supplier&quot; rel=&quot;nofollow&quot;&gt;my favorite suppliers&lt;/a&gt; that would work.&#xA;(By &quot;work&quot;, I mean &quot;has a threshold Vgs is small enough that you can drive it with digital logic, rather than something that needs 6 V or more to turn on&quot;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Randomly-picked examples:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;BSS84 p-channel FET; and 2N7002 n-channel FET, each in a discrete SOT-23 package&lt;/li&gt;&#xA;&lt;li&gt;Diodes Inc. DMC2004DWK-7 dual complementary MOSFET pair in a single SOT-363 package&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-18T14:14:58.627" />
  <row Id="11658" PostTypeId="2" ParentId="11654" CreationDate="2011-03-18T14:23:00.943" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/00905a.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ww1.microchip.com/downloads/en/AppNotes/00905a.pdf&lt;/a&gt; is a fair description of dc motor control issues. You should look at the Basic Drive Circuits section to see some appropriate circuits. Set VCC across the FET/motor to be 3V and use a FET that can cope with at least 5V gate input and you should be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In particular, you should note the diode placed in parallel with the motor. This is extremely important to prevent the mosfet and your controller from damage. The motor is essentially an inductor and it isn't possible to make an instantaneous change in the current flowing through an inductor. When you turn the motor off, this means that the current flowing through the motor gradually decreases. If there isn't a diode placed as shown, then the voltage at the motor will increase and potentially be high enough to damage other connected devices. With the diode in place, the voltage is limited to its forward voltage and so no damage occurs. This is a well known phenomena called back EMF.&lt;/p&gt;&#xA;" OwnerUserId="2960" LastActivityDate="2011-03-18T14:23:00.943" CommentCount="2" />
  <row Id="11659" PostTypeId="1" AcceptedAnswerId="11660" CreationDate="2011-03-18T14:52:44.163" Score="3" ViewCount="218" Body="&lt;p&gt;I really like the look of &lt;a href=&quot;http://dangerousprototypes.com/docs/Web_Platform&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com/docs/Web_Platform&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone suggest something better/something where I can have my web site on SD card, rather than FTPing them in?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I &lt;em&gt;really&lt;/em&gt; want is soneting like this with PGP &amp;amp; MySql, but small &amp;amp; cheap ...&lt;/p&gt;&#xA;" OwnerUserId="3396" LastActivityDate="2011-03-19T16:24:08.723" ClosedDate="2011-03-22T11:27:46.063" Title="Seeking very small web server" Tags="&lt;hardware&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="11660" PostTypeId="2" ParentId="11659" CreationDate="2011-03-18T15:04:08.903" Score="5" ViewCount="" Body="&lt;p&gt;The link you posted is a truly embedded device. It doesn't run an operating system, but instead runs an IP stack and basic web server &quot;on-the-metal&quot;. There's no SQL database or high level scripting language.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want MySQL and PHP (I assume you didn't mean Pretty Good Privacy - PGP) then you'd be best with a small linux server:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/2191/options-for-a-small-linux-hw-platform&quot;&gt;Options for a small Linux HW platform&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/1967/plug-computer-question&quot;&gt;Plug computer question&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-18T15:04:08.903" />
  <row Id="11661" PostTypeId="2" ParentId="11614" CreationDate="2011-03-18T15:07:20.580" Score="1" ViewCount="" Body="&lt;p&gt;Minibox offers a number of supplies for motherboards, take a look at this and others at the site.&#xA;&lt;a href=&quot;http://www.mini-box.com/M1-ATX-90w-Intelligent-Automotive-DC-DC-Power-Supply&quot; rel=&quot;nofollow&quot;&gt;http://www.mini-box.com/M1-ATX-90w-Intelligent-Automotive-DC-DC-Power-Supply&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-03-18T15:07:20.580" />
  <row Id="11662" PostTypeId="1" CreationDate="2011-03-18T15:14:53.997" Score="2" ViewCount="86" Body="&lt;p&gt;Let's say I have a digital system of basic combinational logic with feedback (I do).  That is, the value of the gates' inputs depend in some way on the value of their outputs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on the system, particular combinations of gate inputs would be unstable, meaning that the outputs of the gates, when they have that particular combination of inputs, would propagate through the feedback path to the inputs and change the set of inputs to a different state.  This is what makes a state unstable: the fact that the system cannot remain in this state any longer than the time it takes for the signals to propagate through the feedback path and back to the inputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, let's say my system has only two stable states, with the only difference being in the state of a single input (let's call it input A).  If A is 0 (and all of the other inputs are in their &quot;proper&quot; configuration to be stable), the system is in stable state 0.  If A is 1 (and all other inputs are properly configured), the system is in stable state 1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I power up the system, is it equally likely to settle in stable state 0 or 1, or is it more likely (or perhaps certain) to be in one or the other due the way the initial power supply curve upward to +5V (and downward to 0V?) affects the logic ICs?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a way to predict which state will be the initial state by just considering the construction of the system?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a way for me to influence the initial state without changing the fundamental structure of the system?  For example, could I possibly use a type of pullup or pulldown resistor on input A, so I could set an initial state of +5V or 0V at A, but then allow the feedback from the other gates to control the state of A at all points after time zero?  (I'm imagining the resistor setting the voltage would happen slightly before the CMOS ICs are powered up and working to set the voltage).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I imagine that dealing with initial states is a pretty common issue, and that there's probably a pretty standard way to do this.&lt;/p&gt;&#xA;" OwnerUserId="3424" LastActivityDate="2011-03-22T17:40:54.563" Title="Initial states in a digital system with more than one stable state" Tags="&lt;logic&gt;&lt;digital&gt;&lt;stability&gt;" AnswerCount="3" />
  <row Id="11663" PostTypeId="2" ParentId="605" CreationDate="2011-03-18T15:30:06.150" Score="0" ViewCount="" Body="&lt;p&gt;You can use 8 of the TLC5947.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/tlc5947.pdf&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/lit/ds/symlink/tlc5947.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TLC5947 is 24 channels of PWM controlled by shifting in 12 bits of brightness data for each channel.  This would give you would give you a nearly continuous spectrum of color for each LED (3 channels per LED -&gt; 8 LEDs per 24-channel IC).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 8 of them could be controlled in series (look at the example on page 1 of the datasheet), so you can essentially treat them as if they are a single IC with 192 registers each of 12 bits.  Though note that this will divide your refresh rate by 8, given any particular clock speed.&lt;/p&gt;&#xA;" OwnerUserId="3424" LastActivityDate="2011-03-18T15:30:06.150" />
  <row Id="11664" PostTypeId="2" ParentId="11633" CreationDate="2011-03-18T15:39:31.117" Score="2" ViewCount="" Body="&lt;p&gt;Note that to get colors other than just off, white, red, green, blue, yellow, cyan, and fuchsia, you'll need to be doing your own PWM if you're just using a shift register bit to control each LED component.  You'll need to be PWMing each bit as you shift each group in, so you'll need to take this into account for your refresh rate, and it will also make your code a little more complex.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, you could use an IC like the TI TLC5947, which will do 24 channels of PWM, based on the bits you shift into it.&#xA;&lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/tlc5947.pdf&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/lit/ds/symlink/tlc5947.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With this solution, you would need to shift in 12 bits (instead of 1) for each channel, but it will take care of the PWM for you, so it may be a worthwhile solution. &lt;/p&gt;&#xA;" OwnerUserId="3424" LastActivityDate="2011-03-18T15:39:31.117" CommentCount="4" />
  <row Id="11665" PostTypeId="2" ParentId="11626" CreationDate="2011-03-18T15:50:29.887" Score="2" ViewCount="" Body="&lt;p&gt;There actually is an advantage of the resistor with a higher than required voltage, it make the drive more like a current drive.  This can improve stepper performance particularly at higher speeds.  Efficiency is not good.  PWM is a more efficient current drive.  If you do not mind the waste, go ahead.  I did not check your math.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-18T15:50:29.887" CommentCount="4" />
  <row Id="11666" PostTypeId="1" AcceptedAnswerId="12236" CreationDate="2011-03-18T15:52:44.860" Score="5" ViewCount="149" Body="&lt;p&gt;[This is a re-post of &lt;a href=&quot;http://stackoverflow.com/q/5346225/69172&quot;&gt;http://stackoverflow.com/q/5346225/69172&lt;/a&gt;]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm new to iMX31 and embedded systems, please help me to understand the translation from SDRAM address to ARM CPU address, especially in &quot;special&quot; command modes of the SDRAM controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the SDRAM initialization code I have problem with:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    ldr r0, ESDCTL_BASE_W&#xA;    mov r2, #SDRAM_BASE_ADDR /* 0x80000000 */&#xA;&#xA;    ldr r1, =0x92100000 /* Precharge */&#xA;    str r1, [r0]&#xA;    ldr r1, =0x0&#xA;    ldr r12, =0x80000F00&#xA;    str r1, [r12]&#xA;&#xA;    ldr r1, =0xA2100000 /* Auto-refresh */&#xA;    str r1, [r0]&#xA;    ldr r1, =0x0&#xA;    str r1, [r2]&#xA;&#xA;    ldr r1, SDRAM_0xB2100000 /* Load Mode Register */&#xA;    str r1, [r0]&#xA;    ldr r1, =0x0&#xA;    strb r1, [r2, #0x33]&#xA;&#xA;    ldr r1, =0xFF&#xA;    ldr r12, =0x81000000&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The RAM I have is &lt;strong&gt;Micron LPDDR MT46H64M32LF&lt;/strong&gt;, and this code follows the initialization procedure nicely, but in &lt;em&gt;PRECHARGE&lt;/em&gt; step, where is the address &lt;code&gt;0x80000F00&lt;/code&gt; coming from?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From iMX31 reference manual I learned that during the &lt;em&gt;PRECHARGE&lt;/em&gt; step, I need to set SDRAM pin &lt;code&gt;A10&lt;/code&gt; to HIGH which will therefore result a &lt;em&gt;PRECHARGE ALL&lt;/em&gt;. Here is the text on &lt;em&gt;PRECHARGE&lt;/em&gt; from RM:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;...While in this mode, an access (either read or write) to the SDRAM/LPDDR address space will generate a precharge command cycle. SDRAM/LPDDR address bit A10 determines whether a single bank, or all banks, are precharged by the command. Accessing an address with the SDRAM/LPDDR address A10 low will precharge only the bank selected by the bank addresses, as illustrated in Figure 19-75. Conversely, accesses with A10 high will precharge all banks regardless of the bank address, ...Note that A10 is the SDRAM pin, not the A10 bit ARM address bus. Translation of the SDRAM A10 to the corresponding ARM address is dependent on the memory configuration.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;And here is another text on multiplexed address bus during “special” mode:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;During “special” mode, for example, precharge mode (SMODE=1) or load mode registers (SMODE=3) there is no address shifting, means that CPU address A0 is mapped on MA0 at all memory width. For example, in order to drive MA10 bit (for the precharge all command) the CPU A10 bit should be set (for both 16 or 32 bit external devices). The same logic is valid for the load mode register command, as can be seen on the initialization routine example on Section 19.5.4.1, “SDRAM Initialization.”&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;According to the text above and assuming A0 is the first bit of &lt;code&gt;0x80000000&lt;/code&gt;, setting A10 to 1 should give address &lt;code&gt;0x80000400&lt;/code&gt;, not the &lt;code&gt;0x80000F00&lt;/code&gt; in the code. Why???&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The code snippet I showed here is supposed to work with DDR. For SDRAM, it actually uses &lt;code&gt;0x80000400&lt;/code&gt; in &lt;em&gt;PRECHARGE&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there anything related to the characteristics of DDR? And how can I get the proper translation between SDRAM pins and ARM CPU address?&lt;/p&gt;&#xA;" OwnerUserId="3425" LastActivityDate="2011-03-29T17:07:31.467" Title="On Freescale iMX31, how can I translate SDRAM address to CPU address?" Tags="&lt;arm&gt;&lt;assembly&gt;&lt;freescale&gt;&lt;imx31&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="11667" PostTypeId="2" ParentId="11662" CreationDate="2011-03-18T15:56:21.023" Score="0" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Pull-ups might work, but they will constantly eat power&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You may use capacitor to VCC - so that during powerup  you'll get a short pulse, but it most cases power rises quite slowly...&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Just make reset signal, which resets everything to required state, and add BOD scheme to autoreset on powerup after vcc reache level of stable operation.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You may design the system so that 0V on all gates is default state - you will have to invert things in many places to do so... This is gonna be tricky :-)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-18T15:56:21.023" CommentCount="4" />
  <row Id="11668" PostTypeId="2" ParentId="11573" CreationDate="2011-03-18T17:17:23.710" Score="3" ViewCount="" Body="&lt;p&gt;While I believe the first explanation is the &quot;simple&quot; one, I think that the second explanation makes a lot of sense.  As @Kortuk stated in his comment, you are operating in the &quot;near-field&quot; region of the antenna.  This is the region that doesn't behave quite like what you would expect if you were basing your calculations on the standard far-field antenna radiation patterns.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the near-field, you have a reactive near-field and a resistive near-field.  The reactive near-field is where E and H fields are constantly being built up and collapsed, without the energy leaving the antenna, it is just alternated between the two different field types.   By putting your hand near the antenna, you are effectively stealing some of the power that are in these fields.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that a good comparison would be a pair of inductors with some mutual inductance.  The mutual inductance of the second inductor makes the measured inductance change on the first.  The same is happening with the antenna.  By putting your hand close to the antenna, you are taking some of the power out of the E and H fields that are alternating in the region, and thus changing the amount of inductance/capacitance that the LC tank circuit is seeing, and detuning the oscillator.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-03-18T17:17:23.710" CommentCount="2" />
  <row Id="11670" PostTypeId="1" AcceptedAnswerId="11676" CreationDate="2011-03-18T17:33:05.203" Score="-1" ViewCount="131" Body="&lt;p&gt;Hello &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking for a Arm development board for a new project I am working on (64 RGB LED POV Globe). &lt;a href=&quot;http://electronics.stackexchange.com/questions/11633/pov-globe-speed-questions&quot;&gt;POV globe speed questions&lt;/a&gt;&#xA;I have lots of experience with the Arduino boards but I would like to take a step up to a more powerful board for this project. Also I have been wanting to play with ARM for a while and this seems like a good project to start on. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Requirements&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Not insanely expensive, &amp;lt;= $250 preferably&lt;/li&gt;&#xA;&lt;li&gt;Lots of PWM outputs at lest 10 idealy 24 &lt;/li&gt;&#xA;&lt;li&gt;Program able by the USB port. &lt;/li&gt;&#xA;&lt;li&gt;32k of chip memory&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Nice to have&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Ethernet, Not that I would need it for this project but most of my other projects require it. &lt;/li&gt;&#xA;&lt;li&gt;SD card or other persistent storage, Logging, loading of settings files, ect... &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The first board I looked in to was the &lt;a href=&quot;http://beagleboard.org/hardware&quot; rel=&quot;nofollow&quot;&gt;beagleboard&lt;/a&gt; as it has a huge community and lots of resources but it does not appear to have any PWM outputs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next I looked in to mbed-NXP-LPC1768 from &lt;a href=&quot;http://www.sparkfun.com/products/9564&quot; rel=&quot;nofollow&quot;&gt;sparkfun&lt;/a&gt; &#xA;But from as far as I can tell from &lt;a href=&quot;http://mbed.org/handbook/mbed-NXP-LPC1768&quot; rel=&quot;nofollow&quot;&gt;the spec&lt;/a&gt; it only has 6 PWM pins, and I was looking for more of a complete board with power supply, ect.. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;My question:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Suggestions on a Arm development board with lots of PWMs?&lt;/li&gt;&#xA;&lt;li&gt;Am i missing something with the PWMs on the beagleboard? It seems strange that the board would not have any I/O &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="592" LastActivityDate="2011-03-19T02:00:43.610" Title="Arm development board with lots of PWMs" Tags="&lt;arm&gt;&lt;pwm&gt;&lt;beagleboard&gt;&lt;dev-kit&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="11671" PostTypeId="1" AcceptedAnswerId="11680" CreationDate="2011-03-18T17:46:04.020" Score="4" ViewCount="142" Body="&lt;p&gt;I was wondering if anyone could recommend a simple, low cost DAC chip that I could use for audio playback.  I am not trying to achieve anything amazing or complicated, just throw some numbers into it and listen to the noises that it makes (I'll probably start by trying to play a sinewave)  I've seen lots of complex SOC solutions, as well as lots of evaluation boards, but I prefer to start with a single IC and go from there.  Any suggestions?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&#xA;My goal is to eventually move into more advanced DSP processing, and possibly synths, so I would prefer a chip based solution.&lt;/p&gt;&#xA;" OwnerUserId="3077" LastEditorUserId="3077" LastEditorDisplayName="" LastEditDate="2011-03-18T19:57:46.917" LastActivityDate="2011-03-19T14:05:42.557" Title="simple audio DAC" Tags="&lt;audio&gt;&lt;ic&gt;&lt;dac&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="11672" PostTypeId="2" ParentId="11671" CreationDate="2011-03-18T18:20:59.497" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.romanblack.com/BTc_alg.htm&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; technique of Roman Black's is quite popular, and is very easy to implement.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-18T18:20:59.497" CommentCount="2" />
  <row Id="11673" PostTypeId="1" AcceptedAnswerId="11684" CreationDate="2011-03-18T18:32:31.043" Score="1" ViewCount="131" Body="&lt;p&gt;So while trying to interface a 5v SPI to a 3.3v SPI device, using the inline resistor method outlined below,&#xA;&lt;a href=&quot;http://www.sparkfun.com/tutorials/65&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/tutorials/65&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I discovered that at high clock speeds (above 200khz), my clock signal was being corrupted by the inductance in the resistor (with an oscilloscope, the clock looks signal looks triangular shaped) I am using carbon film (through hole) resistors for prototyping and I heard that these can have high parasitic inductance and not suitable for high frequency use. Is this information correct? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What types of resistor instead should I be getting (digikey link would be appreciated)? Right now, I'm just working on a protoboard but eventually I would like to manufacture this prototype on a PCB using surface mount components. It seems like from what I read about surface mount resistors, the inductance is not typically a problem for applications under 20Mhz.&lt;/p&gt;&#xA;" OwnerUserId="2968" LastEditorUserId="2968" LastEditorDisplayName="" LastEditDate="2011-03-18T19:35:46.940" LastActivityDate="2011-03-19T14:09:13.310" Title="types of resistors and inductance" Tags="&lt;resistor&gt;&lt;inductance&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="11675" PostTypeId="2" ParentId="11671" CreationDate="2011-03-18T18:36:41.553" Score="3" ViewCount="" Body="&lt;p&gt;If you're looking for &lt;em&gt;simple&lt;/em&gt;, you can use an R-2R resistor ladder.  It takes a fair bit of DIO, but you give it a digital number, it gives you the proper analog level.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Bhxj9.png&quot; alt=&quot;Blockquote&quot;&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;From &lt;a href=&quot;http://en.wikipedia.org/wiki/Resistor_ladder&quot; rel=&quot;nofollow&quot;&gt;Resistor Ladder, Wikipedia&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-18T18:36:41.553" CommentCount="1" />
  <row Id="11676" PostTypeId="2" ParentId="11670" CreationDate="2011-03-18T18:42:19.730" Score="2" ViewCount="" Body="&lt;p&gt;The OMAP chip used on the Beagleboard does actually have PWM capability, but you will have problems implementing it as there don't seem to be any applications using it. The easiest way to implement a large number of PWMs is to forget the ARM and use an &lt;a href=&quot;http://www.xmos.com/&quot; rel=&quot;nofollow&quot;&gt;XMOS chip&lt;/a&gt; - they are often used to control large numbers of LEDs. Low-cost development boards are available that may be controlled via a USB port. &lt;a href=&quot;http://www.youtube.com/watch?v=1JQKtgP5ltU&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is one of their boards being used to control an LED cube. Ethernet support is available on one of their boards.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-18T18:51:28.333" LastActivityDate="2011-03-18T18:51:28.333" />
  <row Id="11677" PostTypeId="2" ParentId="11673" CreationDate="2011-03-18T18:55:42.253" Score="2" ViewCount="" Body="&lt;p&gt;&lt;sub&gt;I'm taking you at your word that inductance is the problem, though I find it dubious at a mere 200 kHz.&lt;/sub&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some axial thru-hole resistors are often created and trimmed by spirally cutting the element over a form which can give it some inductance.  This is usually seen in metal film resistors, though possibly in some other film-type resistors as well.  Carbon composition resistors, however, should possess very low inductances as it's more of a block of material.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps more fool-proof, some parts suppliers (Digi-Key does at least) have filters so you could just select &quot;Non-inductive&quot; and be done with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are quite correct that SMT resistors have very low inductances.  I'm not sure of the trimming patterns, but whatever it is, it's done in a plane, so at most you'll have a turn with an extremely small area.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-18T18:55:42.253" />
  <row Id="11678" PostTypeId="2" ParentId="11670" CreationDate="2011-03-18T19:00:50.907" Score="1" ViewCount="" Body="&lt;p&gt;A LPC2917/LPC2129 has up to 24PWM outputs. It's grouped in 4 segments though, so you'll only be able to choose 4 different frequencies of PWM, but you can control the duty cycle of each individual pin. For the purpose you're trying to achieve, that's all you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Atmel has plenty of PWM too on the AT32UC3L032 chips and are not as expensive as the NXP chip if you would decide to make your own hardware. It also comes in a more friendly package, which is nice. I haven't seen a real development board looking quickly, so USB programming is not possible with Atmel chips without using one of their programmers.&#xA;The XMEGA64 and 128 has the same capabilities, but are 16-bits proccesors.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-03-18T19:00:50.907" />
  <row Id="11680" PostTypeId="2" ParentId="11671" CreationDate="2011-03-18T20:38:16.423" Score="3" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://ww1.microchip.com/downloads/en/devicedoc/21897a.pdf&quot; rel=&quot;nofollow&quot;&gt;MCP4922&lt;/a&gt; is a single chip 12bit DAC with an SPI interface. It's cheap and available in hobbyist quantities. It's very simple to drive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also a mono version, the MCP4921.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's used in the &lt;a href=&quot;http://www.critterandguitari.com/content/arduino-synthesizer-kit&quot; rel=&quot;nofollow&quot;&gt;Critter And Guitari Arduino synthesizer&lt;/a&gt; and there's source code available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can make sounds like &lt;a href=&quot;http://www.critterandguitari.com/sites/default/files/OctaveArp-sample_0.mp3&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; and &lt;a href=&quot;http://www.critterandguitari.com/sites/default/files/FM-sample_0.mp3&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-18T20:38:16.423" CommentCount="1" />
  <row Id="11681" PostTypeId="2" ParentId="11670" CreationDate="2011-03-18T20:43:52.673" Score="0" ViewCount="" Body="&lt;p&gt;Some of the Luminary Micro ARM Cortex-M3 devices have up to 8 PWM outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.luminarymicro.com/products/motion_control_pwm.html&quot; rel=&quot;nofollow&quot;&gt;http://www.luminarymicro.com/products/motion_control_pwm.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-18T20:43:52.673" />
  <row Id="11682" PostTypeId="2" ParentId="11302" CreationDate="2011-03-18T20:53:14.113" Score="0" ViewCount="" Body="&lt;p&gt;The addresses for the LEDs are like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P4,E4,P16,E16,K14,K15,J15,J14&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apparently the following code can be used to test them:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;(* LOC=&quot;P4,E4,P16,E16,K14,K15,J15,J14&quot; *) output reg [7:0] LEDs=0;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-03-18T20:53:14.113" />
  <row Id="11683" PostTypeId="2" ParentId="11633" CreationDate="2011-03-18T21:10:03.963" Score="2" ViewCount="" Body="&lt;p&gt;1.&#xA;A bunch of 74HC595 chips will work great.&#xA;Other chips that would also work just as well and perhaps slightly better are listed at:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/6676/which-sipo-chip-is-better-74hc4094-or-74hc595-or-something-else&quot;&gt;Which SIPO chip is better, 74HC4094 or 74HC595 or something else?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2.&#xA;The Arduino is an excellent choice for prototyping, especially if you are comfortable using gcc.&#xA;Perhaps it would be quicker to use one for now.&#xA;Alas, I suspect you will soon write code for this POV display that needs more RAM than the Arduino has available -- at that time, either (a) use one or more of tricks to reduce the RAM needed, or (b) add some external RAM, or (c) port the code to some other microcontroller with more RAM (perhaps the ATMEGA1284 ?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Parallax Propeller is an excellent choice for a high resolution POV display -- it has an order of magnitude more internal RAM (32 KB RAM) than the ATmega238 in the Arduino.&#xA;(Is there anything I can do to support porting gcc to the Propeller?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some people prefer &quot;square pixels&quot;.&#xA;I'm sure you already know that the distance around the equator of a sphere is twice as long as the distance from pole to pole (Earth's equator is a little more than twice as long).&#xA;Since you have 64 pixels from the south pole to the north pole, you might choose to reload a new vertical &quot;line&quot; of pixels 2*64 = 128 times per revolution in order to get 128 &quot;square pixels&quot; at the equator.&#xA;The simplest way to do that is to store the full frame uncompressed in RAM.&#xA;That requires 64*128 pixels * 3 bits/pixel = 24 576 bits = 3 072 bytes, plus a few bytes of RAM for other program variables.&#xA;Alas, the Atmel ATmega328 in the Arduino only has 2 048 bytes of RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://opencircuits.com/POV_display&quot; rel=&quot;nofollow&quot;&gt;Earlier POV displays&lt;/a&gt; used microcontrollers with an order of magnitude (!) less RAM than this.&#xA;So people have developed a variety of tricks you can use to work around this.&#xA;One trick: Only lighting up the &quot;front&quot; half of the globe turing the time you can see the LEDs, then turning off all the LEDs (or leaving them on some constant color) during the &quot;back&quot; half that you can't directly see the LEDs.&#xA;That halves the amount of RAM you need, so then it fits in the Arduino.&#xA;If you don't like that trick, there are other tricks you can use that are less obvious.&#xA;Another trick: Store the image in the flash program memory.&#xA;The Arduino has enough flash program memory to store several 3 072 byte frames.&#xA;Yet another trick: use ASCII text to store the text you want to display, then use flash program memory to store the &quot;character generator ROM&quot; data.&#xA;I'm pretty sure there are other POV tricks ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3.&#xA;If I were building it, I would power the Arduino and the 74HC595 chips from one big power supply,&#xA;and power the motor that spins the POV from a separate power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Only after I got all that working would I even consider a more complicated separated power supply system.&#xA;(In principle, if you have a separate &quot;red&quot; switching power supply whose +V is only connected to 74HC595 chips which in turn are only connected to red LEDs, you could independently tune its output voltage to minimize the total power and heat production of the system. But it seems unnecessarily complicated.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4.&#xA;and 5.&#xA;Perhaps the simplest way for the Arduino to drive the POV display is to daisy chain all 24 74HC595 chips in one long single string, and then use the &lt;a href=&quot;http://www.arduino.cc/playground/Code/Spi&quot; rel=&quot;nofollow&quot;&gt;Arduino SPI library&lt;/a&gt;.&#xA;That requires 192 clock pulses to clock in the new column of data, and then a pulse on the RCLK (aka framing pulse, SS, etc.) to start displaying that new data.&#xA;According to one &lt;a href=&quot;http://www.arduino.cc/en/Tutorial/SPIEEPROM&quot; rel=&quot;nofollow&quot;&gt;Arduino to SPI interface tutorial&lt;/a&gt;,&#xA;the fastest SPI clock rate is system speed / 4.&#xA;So the 16 MHz Arduino can put out a SPI CLK of 4 MHz.&#xA;If you upgrade it with a 20 MHz crystal, you can get a SPI CLK of 5 MHz.&#xA;If you can get your program fast enough to keep up with the SPI hardware, you can put out a new column, at best, in 5 MHz / 193 pulses, so the maximum theoretically possible speed is 25 907 columns/second.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the standard cartoon film refresh rate of 24 frames/second (which flickers noticeably -- you would like something better), and at 128 columns/frame to get &quot;square&quot; pixels at the equator (you might want more to get better resolution), that gives&#xA;24 frames/second * 128 columns/frame = 3072 columns/second.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's nearly an order of magnitude of breathing room between &quot;the speed you want&quot;: 3072 columns/second, and &quot;the speed that is completely impossible on Arduino hardware&quot;: 25 908 columns/second. Hopefully that gives you enough room.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some people think you can get a faster column refresh rate by re-arranging the 74HC595 chips into 2 or more chains and loading all chains in parallel.&#xA;Some people are like that -- they see unused pins on the Arduino, and they are itching to use them for &lt;em&gt;something&lt;/em&gt;.&#xA;But it may be counter-productive -- the SPI hardware is only connected to one set of pins on the Arduino, and so chains hooked to any other pins must be loading with emulated &quot;bit-banging&quot; software, which will invariably be slower and use more CPU time than the built-in SPI hardware.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-18T21:10:03.963" />
  <row Id="11684" PostTypeId="2" ParentId="11673" CreationDate="2011-03-18T22:21:17.513" Score="5" ViewCount="" Body="&lt;p&gt;In order to observe a clean square wave at 200kHz, the rise-time needs to be around 250ns (about 10% of the pulse width). The sparkfun tutorial shows the clock coupled through a 10k resistor. Now, to get 250ns risetime, you need an RC time constant of 114ns giving a capacitance of about 11pF. So the sum total of the circuit input capacitance, the stray capacitance and critically, your 'scope probe capacitance must be less than 11pF. I reckon this is your problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the waveform looks OK at the driven end of the resistor and the input capacitance of the driven device is low, you might be OK but you won't be able to prove it without a very low capacitance 'scope probe.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-03-18T22:21:17.513" />
  <row Id="11685" PostTypeId="2" ParentId="11037" CreationDate="2011-03-19T00:48:49.310" Score="1" ViewCount="" Body="&lt;p&gt;Insulation tape... cheap, firm hold, easy to remove.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-19T00:48:49.310" CommunityOwnedDate="2011-03-19T00:48:49.310" />
  <row Id="11686" PostTypeId="2" ParentId="11670" CreationDate="2011-03-19T02:00:43.610" Score="2" ViewCount="" Body="&lt;p&gt;TLC5497 has 24 channels of 12bit PWM.  Just shift the data in serially and latch it.&#xA;&lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/tlc5947.pdf&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/lit/ds/symlink/tlc5947.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can control one of them with three Arduino pins (or possibly less, using Roman Black's Shift1 protocol - &lt;a href=&quot;http://www.romanblack.com/shift1.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.romanblack.com/shift1.htm&lt;/a&gt; )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They can also be strung out in series to control as many as you like with the same three Arduino pins (check the example on page 1 of the datasheet).  The only drawback is that as you add more chips in series of the same serial stream it'll take proportionally longer to shift all the bits in for each refresh.  If you don't like this performance cut, you can use another pin as another serial stream and use the same CLK and XLAT pin, and cut your refresh time in half again (by running half the chips off of stream A and the other half on stream B).&lt;/p&gt;&#xA;" OwnerUserId="3424" LastActivityDate="2011-03-19T02:00:43.610" />
  <row Id="11688" PostTypeId="2" ParentId="4972" CreationDate="2011-03-19T02:31:53.630" Score="0" ViewCount="" Body="&lt;p&gt;You state that your &quot;subwoofer/amplifier&quot; is not working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Typically the first step of a troubleshooting like this would be to localize the problem to at least a single device.  That is, you need to determine whether the problem is in the amplifier or the speaker before anything else can be done.  You should try your subwoofer with another amplifier or your amplifier with another subwoofer if possible.  Note that you can probably use a speaker that is not a subwoofer with your amplifier just to check if it's working as long as you restrict yourself to &quot;quiet&quot; levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good (and easy) test to do on any speaker is check its resistance with a multimeter.  It should be roughly 4 or 8 ohms.  This number may be printed somewhere on the speaker, but you probably won't get such a precise value.  Anything in this ballpark, as in not &quot;zero&quot; or &quot;infinite&quot; (read as OL on many multimeters), is probably okay.&lt;/p&gt;&#xA;" OwnerUserId="3424" LastActivityDate="2011-03-19T02:31:53.630" />
  <row Id="11689" PostTypeId="1" CreationDate="2011-03-19T02:40:17.437" Score="-1" ViewCount="130" Body="&lt;p&gt;Hi all,&#xA;I need to hide an pendrive inside an usb mouse.&#xA;So, i need to create an way to use the usb cable for the pen drive, and the mouse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need an simple usb 'hub' for 2 devices. Muse be small =p&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="1539" LastActivityDate="2011-03-19T16:18:15.827" ClosedDate="2011-03-19T23:53:51.260" Title="USB hub? Must be simple and small" Tags="&lt;usb&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="11690" PostTypeId="1" AcceptedAnswerId="11699" CreationDate="2011-03-19T02:48:13.343" Score="1" ViewCount="84" Body="&lt;p&gt;Hey I am trying to make a etchable pdf for a project of mine. It is supposed to be a 2x9inch board. But I cannot find a good software to make this. Eagle's free version will not allow me to make this size and I cannot understand gEDA. Is there other simpler option?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-03-19T12:38:14.847" LastActivityDate="2011-03-19T15:42:34.913" Title="Making Etchable PDFs in linux." Tags="&lt;pcb&gt;&lt;eagle&gt;&lt;eda&gt;&lt;geda&gt;" AnswerCount="3" />
  <row Id="11691" PostTypeId="2" ParentId="11659" CreationDate="2011-03-19T03:00:46.593" Score="4" ViewCount="" Body="&lt;p&gt;You can definitely run PHP and MySQL on any number of small Linux boards. I've run Python and SQLite on a Technologic Systems TS-7260, which stores its filesystem on an SD card, and Python and Django on the TS-7500, which actually uses a microSD card. The performance was decent, but accessing the SD card was definitely slower than I hoped-- total page render times were close to 2 seconds. I suspect that might have been more due to Django than the SD card, as I've used other embedded Linux boards that used also used an object relational mapper like Django and a microSD card, and it was quite fast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.embeddedarm.com/products/arm-sbc.php&quot; rel=&quot;nofollow&quot;&gt;Technologic Systems&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also look at:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://gumstix.com&quot; rel=&quot;nofollow&quot;&gt;Gumstix&lt;/a&gt; (somewhat more expensive, but very small)&lt;/li&gt;&#xA;&lt;li&gt;The [animal]boards: &lt;a href=&quot;http://beagleboard.org&quot; rel=&quot;nofollow&quot;&gt;BeagleBoard&lt;/a&gt;, &lt;a href=&quot;http://hawkboard.org&quot; rel=&quot;nofollow&quot;&gt;HawkBoard&lt;/a&gt;, &lt;a href=&quot;http://pandaboard.org&quot; rel=&quot;nofollow&quot;&gt;PandaBoard&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For ease of use, I'd probably go with a TS-7500 with Debian Linux on a microSD card, with the Beagleboard and Angstrom Linux a close second. Being able to use a package manager (apt-get for Debian and opkg for Angstrom) is great. I'm also interested to try something that runs Poky Linux, like the extremely sexy (but also more expensive) stuff from &lt;a href=&quot;http://www.buglabs.net/&quot; rel=&quot;nofollow&quot;&gt;Bug Labs&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-03-19T15:32:08.930" LastActivityDate="2011-03-19T15:32:08.930" CommentCount="3" />
  <row Id="11692" PostTypeId="1" CreationDate="2011-03-19T03:13:22.370" Score="2" ViewCount="205" Body="&lt;p&gt;I am seeking a very small, cheap, fairly low-spec processor which should have RS232, RJ45, and maybe WiFi.  I want to read measurements using (ModBus) sensors oner serial port, do some processing and pass the results out over RJ45 (TCP/IP) or maybe WiFi.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you may have guessed from my description, I am a software guy, not hardware, so feel free to ask questions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheap and cheerful is what I want ..&lt;/p&gt;&#xA;" OwnerUserId="3396" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-19T04:56:47.000" LastActivityDate="2011-06-06T00:15:38.713" Title="Seeking small, cheap embedded PC" Tags="&lt;hardware&gt;" AnswerCount="5" CommentCount="5" FavoriteCount="1" />
  <row Id="11693" PostTypeId="2" ParentId="11572" CreationDate="2011-03-19T03:25:52.843" Score="3" ViewCount="" Body="&lt;p&gt;The Marvell prestera chips are 10Gbit Ethernet switches used for high throughput telecommunications packet switching.  It is unlikely that you'll be able to use them for anything other than their intended use, which is essentially moving Ethernet packets around a network, very, very quickly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure what the &quot;piggy&quot; is without more information.&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-19T04:59:11.787" LastActivityDate="2011-03-19T04:59:11.787" />
  <row Id="11694" PostTypeId="2" ParentId="11689" CreationDate="2011-03-19T03:33:16.690" Score="0" ViewCount="" Body="&lt;p&gt;Stealing files from industrial PCs? ;-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;just buy 4-port hub, and with some luck you will be able to cut PCB to make it smaller with just 2 ports. Hubs I have can fit inside mouse without USB connectors.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-19T03:33:16.690" CommentCount="4" />
  <row Id="11695" PostTypeId="2" ParentId="11430" CreationDate="2011-03-19T03:34:14.363" Score="3" ViewCount="" Body="&lt;p&gt;Most CMOS chips have input protection diodes on the I/O.  These diodes are reversed, so that current will flow to the vcc if the pin voltage is higher than vcc, and current will flow from ground if the voltage on the pin is lower than ground.  This prevents the chip I/O from seeing voltages outside vcc and ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means that if you put the positive lead of a multimeter on any other pin, and the negative lead on the suspected vcc, you should see current flowing when you use the diode check of e multimeter.  Likewise, if you put the positive lead on the suspected gnd, then the negative lead on any other I/O, then you should see current flowing during the diode check function of your multimeter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't have a diode check mode, use the resistance mode, and you should see a low-ish resistance across those protection diodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a current limited power supply, you can also simply hook it up with the current limited to a few mA, and see if it's drawing a reasonable amount of current, or if something is shorting out.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2011-03-19T03:34:14.363" CommentCount="1" />
  <row Id="11696" PostTypeId="2" ParentId="11692" CreationDate="2011-03-19T03:44:32.170" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.gumstix.com/&quot; rel=&quot;nofollow&quot;&gt;Gumstix&lt;/a&gt; is not what I'd consider fairly cheap, but it delivers what you're looking for.&lt;/p&gt;&#xA;" OwnerUserId="2051" LastActivityDate="2011-03-19T03:44:32.170" />
  <row Id="11697" PostTypeId="2" ParentId="11689" CreationDate="2011-03-19T03:46:40.257" Score="2" ViewCount="" Body="&lt;p&gt;TI sells Hub Controller ICs: &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=366&amp;amp;uiTemplateId=NODE_STRY_PGE_T&amp;amp;paramCriteria=no&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=366&amp;amp;uiTemplateId=NODE_STRY_PGE_T&amp;amp;paramCriteria=no&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are commonly available at digikey and mouser.  LQFP32 is pretty small, but you could etch a board at home capable of interfacing with the thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or you could apart an existing mini-hub and hack it apart.  Seriously, other people have fit hubs inside mice with just this kind of hackery.&lt;/p&gt;&#xA;" OwnerUserId="3395" LastActivityDate="2011-03-19T03:46:40.257" CommentCount="2" />
  <row Id="11698" PostTypeId="2" ParentId="11690" CreationDate="2011-03-19T03:50:33.763" Score="2" ViewCount="" Body="&lt;p&gt;KiCAD is the best you're likely to get: &lt;a href=&quot;http://www.lis.inpg.fr/realise_au_lis/kicad/&quot; rel=&quot;nofollow&quot;&gt;http://www.lis.inpg.fr/realise_au_lis/kicad/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On Linux, gEDA, KiCAD and Eagle are the best games in town.&lt;/p&gt;&#xA;" OwnerUserId="3395" LastActivityDate="2011-03-19T03:50:33.763" CommentCount="1" />
  <row Id="11699" PostTypeId="2" ParentId="11690" CreationDate="2011-03-19T04:24:41.537" Score="4" ViewCount="" Body="&lt;p&gt;Eagle's professional edition layout tool can do 64 x 64 inches.  Since it seems that you know Eagle, that's the simplest option.  It is not the cheapest option, but only because it's not free (as in beer).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like most powerful tools, gEDA has a significant learning curve.  It's not impossible to understand; it's just not as intuitive as Eagle.  Keep trying.  As with many open-source projects, features come before documentation, so many of the tutorials are out of date. I suggest you follow the &lt;a href=&quot;http://www.geda.seul.org/wiki/geda%3amailinglists&quot; rel=&quot;nofollow&quot;&gt;geda-user mailing list&lt;/a&gt; to get the most current information; it's quite active and the devs want to help! &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-19T04:24:41.537" CommentCount="1" />
  <row Id="11700" PostTypeId="2" ParentId="11692" CreationDate="2011-03-19T06:41:51.793" Score="2" ViewCount="" Body="&lt;p&gt;If the processing needed is not very intensive, try an arduino with an ethernet shield. A Modbus library can be found here: &lt;a href=&quot;http://sites.google.com/site/jpmzometa/arduino-mbrt/arduino-modbus-slave&quot; rel=&quot;nofollow&quot;&gt;http://sites.google.com/site/jpmzometa/arduino-mbrt/arduino-modbus-slave&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transfer the data over Ethernet or USB. &lt;/p&gt;&#xA;" OwnerUserId="3438" LastActivityDate="2011-03-19T06:41:51.793" />
  <row Id="11701" PostTypeId="2" ParentId="11689" CreationDate="2011-03-19T10:34:28.393" Score="1" ViewCount="" Body="&lt;p&gt;I've seen this done on &lt;a href=&quot;http://www.thice.nl/hide-your-data-in-plain-sight-usb-hardware-hiding/&quot; rel=&quot;nofollow&quot;&gt;hackaday&lt;/a&gt;(links to the original site which isn't hackaday). It's simple todo. It works by adding a USB hub in to the mouse casing then a keypen. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-19T10:34:28.393" />
  <row Id="11702" PostTypeId="2" ParentId="11671" CreationDate="2011-03-19T14:05:42.557" Score="0" ViewCount="" Body="&lt;p&gt;RB's has enough resistors to make a pain and you need precision.  So I think you can get the circuit in an IC with laser trimed resistors for a few bucks which may be worth it.  If it has some active components ( precision voltage on input to the ladder and buffer on the output ) so much the better &lt;a href=&quot;http://www.national.com/mpf/DA/DAC0800.html#Overview&quot; rel=&quot;nofollow&quot;&gt;http://www.national.com/mpf/DA/DAC0800.html#Overview&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-19T14:05:42.557" />
  <row Id="11703" PostTypeId="2" ParentId="11673" CreationDate="2011-03-19T14:09:13.310" Score="2" ViewCount="" Body="&lt;p&gt;When looking at fast signals it is usually beneficial to use the 10x setting on the probe, for the reasons discussed in the other posts.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-19T14:09:13.310" />
  <row Id="11704" PostTypeId="2" ParentId="11690" CreationDate="2011-03-19T15:42:34.913" Score="0" ViewCount="" Body="&lt;p&gt;Not an ideal solution, but &lt;a href=&quot;http://www.designspark.com/pcb&quot; rel=&quot;nofollow&quot;&gt;DesignSpark PCB&lt;/a&gt; is reported to run fine under Wine. From their site:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;What are the limitations on designs?&lt;/strong&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;There are no intentional limitations&#xA;  on designs. Unlimited schematic sheets&#xA;  per project, up to 1m squared of board&#xA;  size and no limits on layers allow you&#xA;  to get your creativity flowing without&#xA;  restraints.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2960" LastActivityDate="2011-03-19T15:42:34.913" />
  <row Id="11705" PostTypeId="2" ParentId="11689" CreationDate="2011-03-19T15:52:51.183" Score="1" ViewCount="" Body="&lt;p&gt;How about combining this device from FTDI &#xA;&lt;a href=&quot;http://www.ftdichip.com/Support/Documents/DataSheets/Modules/DS_USB_HI-SPEED_SERIAL_HUB_MODULE.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.ftdichip.com/Support/Documents/DataSheets/Modules/DS_USB_HI-SPEED_SERIAL_HUB_MODULE.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;with a device like these&#xA;&lt;a href=&quot;http://www.stec-inc.com/downloads/flash_brochures/usbflashdisk.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.stec-inc.com/downloads/flash_brochures/usbflashdisk.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option&#xA;&lt;a href=&quot;http://www.hy-line.de/fileadmin/hy-line/computer/Marketing/Website/Produkte/Icron/ExtremeUSB%20Core%202100%20Datasheet.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.hy-line.de/fileadmin/hy-line/computer/Marketing/Website/Produkte/Icron/ExtremeUSB%20Core%202100%20Datasheet.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or &lt;a href=&quot;http://www.weichu.net/weichu-E/products/USB%20HUB/HU-500.html&quot; rel=&quot;nofollow&quot;&gt;http://www.weichu.net/weichu-E/products/USB%20HUB/HU-500.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2157" LastEditorUserId="2157" LastEditorDisplayName="" LastEditDate="2011-03-19T16:18:15.827" LastActivityDate="2011-03-19T16:18:15.827" />
  <row Id="11706" PostTypeId="1" CreationDate="2011-03-19T16:10:38.563" Score="8" ViewCount="152" Body="&lt;p&gt;What is the difference between a Programmable Unijunction Transistor and a normal transistor? I am reading the book Make:Electronics and it says I need one of those. Can somebody explain to me in somewhat non-tech terms what it is?&lt;/p&gt;&#xA;" OwnerUserId="3440" LastActivityDate="2011-04-26T11:50:36.510" Title="What is the difference between a PUT and a normal transistor?" Tags="&lt;transistor&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="11707" PostTypeId="2" ParentId="11659" CreationDate="2011-03-19T16:24:08.723" Score="1" ViewCount="" Body="&lt;p&gt;This from CCS may fit the bill. It's pretty small!&#xA;&lt;a href=&quot;http://www.ezweblynx.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.ezweblynx.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-03-19T16:24:08.723" />
  <row Id="11708" PostTypeId="2" ParentId="11275" CreationDate="2011-03-19T17:29:41.000" Score="1" ViewCount="" Body="&lt;p&gt;The question was answered &lt;a href=&quot;http://knowledgebase.nxp.com/showpost.php?p=36&amp;amp;postcount=3&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; on the LPCXpresso forum. The device can only load DFU software from Code Red.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From &lt;a href=&quot;http://knowledgebase.nxp.com/member.php?u=59&quot; rel=&quot;nofollow&quot;&gt;NXP_USA&lt;/a&gt;:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The LPC-LINK boards distributed embedded in LPCXpresso, can only load DFU firmware from our LPCXpresso IDE partner Code Red. However, the LPCXpresso schematics are posted here: &lt;a href=&quot;http://www.embeddedartists.com/products/lpcxpresso/lpc1343_xpr.php?tab=res&quot; rel=&quot;nofollow&quot;&gt;http://www.embeddedartists.com/products/lpcxpresso/lpc1343_xpr.php?tab=res&lt;/a&gt;. They are a useful reference for a more flexible LPC3154 design that could accept arbitrary firmware via DFU.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The LPC3154 is available from &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?site=us&amp;amp;lang=en&amp;amp;keywords=568-5661-ND&quot; rel=&quot;nofollow&quot;&gt;Digi-Key&lt;/a&gt; and &lt;a href=&quot;http://mouser.com/search/ProductDetail.aspx?qs=qr86xXwN5K14epe4k2B5rQ==&quot; rel=&quot;nofollow&quot;&gt;Mouser&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-19T21:56:16.187" LastActivityDate="2011-03-19T21:56:16.187" CommentCount="2" />
  <row Id="11709" PostTypeId="1" CreationDate="2011-03-19T18:35:11.917" Score="3" ViewCount="114" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/10791/recommend-a-serial-to-usb-cable-converter-that-works-with-modern-oses&quot;&gt;Recommend a Serial to USB cable/converter that works with modern OSes&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;My current PC have no COM port. I want to use an RS232 device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an old PC whose motherbord have RS232/COM1 serial port, and also unused COM1 or USB cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a way to build an RS232/USB adapter with these stuff ?&#xA;Or I absolutly need an IC... &lt;/p&gt;&#xA;" LastActivityDate="2011-03-19T18:37:07.213" ClosedDate="2011-03-20T04:13:46.587" Title="Build a RS232/USB adapter" Tags="&lt;usb&gt;&lt;rs232&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11710" PostTypeId="2" ParentId="11709" CreationDate="2011-03-19T18:36:55.690" Score="5" ViewCount="" Body="&lt;p&gt;Too much hastle - just buy one, they're dirt cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While theoretically you could use some custom software on the board to achieve what you want it would be an absolute nightmare.&lt;/p&gt;&#xA;" OwnerUserId="4245" LastActivityDate="2011-03-19T18:36:55.690" />
  <row Id="11711" PostTypeId="1" CreationDate="2011-03-19T19:51:23.420" Score="0" ViewCount="55" Body="&lt;p&gt;How to connect a real external speaker through a classic Jack connecter to the &lt;a href=&quot;http://www.parallax.com/Store/Microcontrollers/BASICStampProgrammingKits/tabid/136/ProductID/294/List/0/Default.aspx?SortField=ProductName,ProductName&quot; rel=&quot;nofollow&quot;&gt;Board of Education&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So that I can send it FREQOUT instructions?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(instead of using the piezo-electric component)&lt;/p&gt;&#xA;" OwnerUserId="3442" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-19T20:33:09.530" LastActivityDate="2011-04-18T21:28:02.220" Title="BASIC Stamp and external speaker" Tags="&lt;microcontroller&gt;&lt;speakers&gt;" AnswerCount="1" />
  <row Id="11712" PostTypeId="2" ParentId="11711" CreationDate="2011-03-19T20:35:39.560" Score="1" ViewCount="" Body="&lt;p&gt;I've not used this board before. But, I assume you could wire the existing piezo sounder to a simple amplifier and onto your speaker. An &lt;a href=&quot;http://web.mit.edu/6.s28/www/schematics/lm386.htm&quot; rel=&quot;nofollow&quot;&gt;LM386&lt;/a&gt; would be ideal.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-19T20:35:39.560" CommentCount="2" />
  <row Id="11714" PostTypeId="1" AcceptedAnswerId="11759" CreationDate="2011-03-19T21:41:52.483" Score="1" ViewCount="166" Body="&lt;p&gt;As in the title. I've noticed several PCBs of mine have vias which are not plated - they do not have a characteristic &quot;gold&quot; shine to them. I suspect this is because I was pushing the limits of drill sizes - my fab specifies 12 mil and I used 15 mil (20 mil including plating.) I've checked a few with a multimeter and they do have continuity, which is good, but I've only checked a few, so have no idea if there might be a few dodgy connections because of this. Is it something to be concerned about? Board passes DRC as specified by fab.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen quite a few high density boards like motherboards and graphics cards without plated vias.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an older board of mine which shows a similar problem to my newer boards. Note that some vias look gold, while others don't look plated at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2hcgU.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-03-21T00:39:49.153" LastActivityDate="2011-03-22T08:12:07.433" Title="Is it important that vias are plated on a PCB?" Tags="&lt;pcb&gt;&lt;drc&gt;&lt;via&gt;" AnswerCount="4" CommentCount="5" />
  <row Id="11715" PostTypeId="2" ParentId="11714" CreationDate="2011-03-19T21:51:21.570" Score="0" ViewCount="" Body="&lt;p&gt;Are you sure they're plating in gold? The boards I get done are plated but with immersion silver only.&lt;/p&gt;&#xA;" OwnerUserId="2960" LastActivityDate="2011-03-19T21:51:21.570" CommentCount="1" />
  <row Id="11716" PostTypeId="2" ParentId="11714" CreationDate="2011-03-19T21:52:51.060" Score="0" ViewCount="" Body="&lt;p&gt;Get your boards tested. It costs a bit more, but it's worth it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You won't be able to see the plating inside the vias unless you use a microscope. Hi-tech boards like motherboards and graphics cards always use PTH.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-19T22:14:53.503" LastActivityDate="2011-03-19T22:14:53.503" CommentCount="1" />
  <row Id="11717" PostTypeId="1" CreationDate="2011-03-19T22:09:02.943" Score="1" ViewCount="51" Body="&lt;p&gt;Hi, I'm currently using a photodiode (found &lt;a href=&quot;http://www.vishay.com/photo-detectors/list/product-81509/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;) along with the appropriate emitter to send data between mobile robots. I'd like to the sensor to optionally be used as an ambient light sensor using a filter with lower sensitivity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My trouble is picking out what this &quot;ambient light&quot; should be. Since the photodiode is only sensitive between 750 and 1150 nm, I imagine I need an IR bulb. However, every IR bulb I look at doesn't seem to specify what wavelengths it outputs. They also seem to all be used as heat sources, which I'm not sure I need. Ideally I'd like a cheap option that I could just stick in a lamp, but I'm open to other ideas. Does anyone know where to buy the correct IR bulb? Or what the correct IR bulb would be?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="954" LastActivityDate="2011-03-19T22:23:33.833" Title="Which infrared bulb should I use with a photodiode?" Tags="&lt;sensor&gt;&lt;light&gt;&lt;infrared&gt;&lt;photodiode&gt;&lt;wavelength&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="11718" PostTypeId="2" ParentId="11717" CreationDate="2011-03-19T22:23:33.833" Score="1" ViewCount="" Body="&lt;p&gt;Would a bunch of high power IR LEDs do? 850nm LEDs are common and easy to get hold of.&lt;/p&gt;&#xA;" OwnerUserId="2960" LastActivityDate="2011-03-19T22:23:33.833" CommentCount="1" />
  <row Id="11719" PostTypeId="2" ParentId="11692" CreationDate="2011-03-19T23:13:29.430" Score="1" ViewCount="" Body="&lt;p&gt;Have a look at &lt;a href=&quot;http://www.embeddedarm.com/index.php&quot; rel=&quot;nofollow&quot;&gt;Technologic Systems&lt;/a&gt;. For well under $200 you can get a full up embedded Linux computer with the hardware basically done for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the Wi-Fi, consider a simple WAP plugged into the thing.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2011-03-19T23:13:29.430" />
  <row Id="11720" PostTypeId="1" AcceptedAnswerId="11721" CreationDate="2011-03-19T23:22:26.467" Score="2" ViewCount="94" Body="&lt;p&gt;I'm thinking about making my own laser security system (think mission impossible). So I was thinking I'd use a laser diode to shine a beam across a doorway into a light dependent resistor that's on the high side of a voltage divider and look for that signal to go low and raise an alarm if it does. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I've done some quick research for parts and I'm surprised at how expensive laser diodes seem to be: &lt;strong&gt;Do I really need to use a &quot;laser diode&quot; to satisfy my requirement to shine focused light across say a 3 foot gap, or is there some other component that is cheaper and gets the same effect?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Does my LDR concept on the &quot;receiver&quot; side of the gap make sense or is there a better way?&lt;/strong&gt; I guess my biggest concern is that it won't respond (resistance won't rise) fast enough when the beam is broken and I'll fail to pick it up as a logic low. If that's the case I imagine what I'll want instead is something like a photo-transistor rather than an LDR.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-20T16:07:04.847" LastActivityDate="2011-03-20T21:27:11.150" Title="Laser Diode Security System" Tags="&lt;laser&gt;&lt;optoelectronics&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="11721" PostTypeId="2" ParentId="11720" CreationDate="2011-03-20T00:41:26.607" Score="1" ViewCount="" Body="&lt;p&gt;Hey, yes its possible and relatively easy, a simple red laser from a dollar store will work fine. Here is a great tutorial on how to do that: &lt;a href=&quot;http://www.youtube.com/watch?v=t0FTzUhdg3w&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=t0FTzUhdg3w&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3444" LastActivityDate="2011-03-20T00:41:26.607" CommentCount="0" />
  <row Id="11722" PostTypeId="2" ParentId="11626" CreationDate="2011-03-20T01:45:09.143" Score="1" ViewCount="" Body="&lt;p&gt;Do you have a choice between (a) a chopper drive that automatically turns everything off when it overheats, and lets you set the maximum current allowed through to the motor to prevent the motor from overheating, or (b) a L/R stepper drive that turns on its internal power transistor between the stepper and the power supply, and if you happen to stop sending step pulses it leaves that transistor on indefinitely, even if it makes the motor or the power transistor melt?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a choice, I recommend the chopper drive.&#xA;Also, I would look at the data sheet for your motor and find the maximum recommended current for that motor, and set the chopper drive to limit its output to that current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your datasheet doesn't say what the rated current is, divide the rated voltage (hopefully at least that is printed on your motor or listed in the datasheet) by the coil resistance (which you can measure with an ohmmeter) to get the rated current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are stuck with the older L/R stepper driver, then resistors in series with the stepper winding are an excellent idea.&#xA;The maximum current before the motor is damaged is different than the maximum current before the L/R stepper driver electronics is damaged -- use the smaller of the two currents in your calculations.&#xA;Is the smaller of the two is &quot;750mA&quot; in your case?&#xA;Russell Laidman's tutorial &lt;a href=&quot;http://www.stepperworld.com/Tutorials/pgCurrentControl.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;Stepper Motors and Control: Part III - Current Control of Stepper Motors&quot;&lt;/a&gt;&#xA;describes how to calculate the appropriate resistor -- it appears that you are doing that calculation correctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may find the&#xA;&lt;a href=&quot;http://reprap.org/wiki/Motor_FAQ&quot; rel=&quot;nofollow&quot;&gt;RepRap Motor FAQ&lt;/a&gt; useful&#xA;and the &lt;a href=&quot;http://reprap.org/wiki/StepperMotor&quot; rel=&quot;nofollow&quot;&gt;RepRep Stepper Motor&lt;/a&gt; page informative.&#xA;The &lt;a href=&quot;http://reprap.org/wiki/Alternative_Electronics&quot; rel=&quot;nofollow&quot;&gt;RepRap alternative electronics&lt;/a&gt; page has a list of many chopping -- or even better, microstepping chopping motor drivers.&#xA;The &lt;a href=&quot;http://opencircuits.com/motor_driver&quot; rel=&quot;nofollow&quot;&gt;Open Circuits motor driver&lt;/a&gt; page has an even longer list.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-20T01:45:09.143" CommentCount="1" />
  <row Id="11723" PostTypeId="2" ParentId="11552" CreationDate="2011-03-20T03:39:02.917" Score="0" ViewCount="" Body="&lt;p&gt;In general, no, a reset is not the same as a power cycle.  You have to analyze the system on a case by case basis to determine what happens on a system wide and/or localized reset.  From Mark's answer it sounds like you are fine for this target, press reset and not have to power cycle.  Saying that before deploying or releasing a version of software though, test it using power cycles as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With sram or dram.  If you dont lose power and the reset is short enough the memory may very well look like nothing changed, but dont rely on that.  Some systems, dram in particular, parity checked, ecc checked memories will go through an initialization process which can include wiping out the memory.  Unless the system was designed to preserve the memory through a reset, do not rely on it being the way you left it.  Programs should always write before they read a memory location (or the location should be written by someone/something before it is read the first time) anyway.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-03-20T03:39:02.917" />
  <row Id="11724" PostTypeId="1" CreationDate="2011-03-20T04:06:52.463" Score="0" ViewCount="30" Body="&lt;p&gt;sir, how to calculate beta of a transistor in multisim10.0,while i calculating using (ic/ib) i obtained 10 but i want it 300 how to change it&lt;/p&gt;&#xA;" OwnerUserId="3446" LastActivityDate="2011-03-20T04:06:52.463" ClosedDate="2011-03-20T08:21:01.627" Title="transistor-multisim10.0" Tags="&lt;software&gt;" CommentCount="1" />
  <row Id="11725" PostTypeId="2" ParentId="11692" CreationDate="2011-03-20T04:14:38.393" Score="2" ViewCount="" Body="&lt;p&gt;I'd have a look at the &lt;a href=&quot;http://mbed.org&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt; platform. It supports ethernet out of the box(though doesn't include an actual RJ-45 port). It runs a modest, but cheap ARM processor. I'd say modbus should've be too hard to implement(if it's not already somewhere).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the arduino solution would work for you, then I'd suggest this instead especially. The processor is much more powerful and it includes more out of the box. Assuming the Arduino is about \$30 and ethernet shield is \$20, an mbed is only \$10 more expensive for a lot more room for expansion. &lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-03-20T04:14:38.393" />
  <row Id="11726" PostTypeId="1" AcceptedAnswerId="11727" CreationDate="2011-03-20T06:56:54.367" Score="0" ViewCount="69" Body="&lt;p&gt;Hello, I have a project requiring very small LEDs. (actually to be put on gloves, sorta). So the common 5mm LED is too big and &quot;pokey&quot; for this kind of thing. So therefore, I'm looking for surface mount infrared LEDs, but 3mm LEDs may work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried searching for surface mount IR LEDs, but all I can find are OEM-only places that have minimum orders of a reel. Where can I find affordable surface mount IR LEDs available in smaller quantities? (I'd like to not order more than 20 at one time, depending on price)&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-03-20T07:12:28.263" ClosedDate="2011-03-20T07:29:06.200" Title="Is there any place to get surface mount IR LEDs?" Tags="&lt;led&gt;&lt;surface-mount&gt;&lt;infrared&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="11727" PostTypeId="2" ParentId="11726" CreationDate="2011-03-20T07:12:28.263" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=475-1459-1-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=475-1459-1-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;187,161 in stock. $0.93 for one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digikey has a &lt;em&gt;lot&lt;/em&gt; of SMT IR LEDs.  I wish there was a way to link a search result. But &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=524328&quot; rel=&quot;nofollow&quot;&gt;start here&lt;/a&gt; and then choose &quot;surface mount&quot; for &quot;Mounting Type&quot;.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-20T07:12:28.263" CommentCount="1" />
  <row Id="11728" PostTypeId="1" AcceptedAnswerId="11803" CreationDate="2011-03-20T07:50:41.563" Score="3" ViewCount="232" Body="&lt;p&gt;I'm carrying out a research project this year at uni, which will include creating small electronic sensory devices for children (under 7) with autism. Obviously, safety has to be taken very seriously.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Only relatively small amounts of current will be used - probably powering simple sensors on an Arduino board - but seeing as my knowledge of all things electronic is pretty limited, I thought I'd try and get some suggestions first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the research I've done, I found PoE at littlebird: &lt;a href=&quot;http://littlebirdelectronics.com/collections/freetronics/products/4-channel-power-over-ethernet-midspan-injector&quot; rel=&quot;nofollow&quot;&gt;http://littlebirdelectronics.com/collections/freetronics/products/4-channel-power-over-ethernet-midspan-injector&lt;/a&gt; - which looks like a pretty good solution, seeing as I want the ability to control the device remotely, over a local network. A benefit also being that I can keep the number of wires poking out of the device to a minimum and also not have a direct lead going to a wall socket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far, I'm really only at the stage of planning the 'core' of these devices, which would be an Arduino board with limited sensors attached, possibly using the internal parts from a Wii remote. Because I don't yet have confirmed participants, I don't know exactly what sensory needs I'll be working with (each autistic child will have specific sensory issues) and therefore exactly how much power I will need for the devices. I will aim to keep it at a minimum though, simply for safety reasons.&lt;/p&gt;&#xA;" OwnerUserId="1855" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-05-02T02:45:19.873" LastActivityDate="2011-05-02T02:45:19.873" Title="Safe Powering Methods - Working with Children" Tags="&lt;arduino&gt;&lt;power&gt;&lt;data&gt;&lt;poe&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="11729" PostTypeId="2" ParentId="11728" CreationDate="2011-03-20T08:20:20.673" Score="2" ViewCount="" Body="&lt;p&gt;A PoE switch is normally used to power IP phones over an Ethernet cable without having to have an additional power adaptor. It sounds like you're doing a something similar with your devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The midspan injector will certainly be a cheap way to add power to an unpowered Ethernet port, with the added advantage of being able to control the supply voltage. You can get PoE switches with everything built in, so I also recommend looking at these as it might be cleaner and easier to use one, but it might cost a bit more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also make your own version of the midspan injector for even less. You'll need some RJ45 sockets and a power supply, and just simply connect the data pins straight through, and the supply to the output sockets to the power pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a table of the pinout for RJ45 ethernet with and without power:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ONqqr.jpg&quot; alt=&quot;PINOUT&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing you need to be careful of is that 'standard' PoE is 48v, which will drop to as much as 32v depending on the length of your ethernet cable. Make sure that when you split out the supply from the ethernet on the Ardunio end you have something to reduce the voltage to 9-12v. If you're using an injector then you can control this and supply a lower voltage, but if you use a standard PoE switch you need to be aware of this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What type of sensory devices are you going to be connecting to your PoE ports?&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-20T09:09:03.517" LastActivityDate="2011-03-20T09:09:03.517" CommentCount="1" />
  <row Id="11730" PostTypeId="2" ParentId="10350" CreationDate="2011-03-20T08:24:39.763" Score="0" ViewCount="" Body="&lt;p&gt;Well if symbols are encoded as different levels of voltage after the filter then looking at your waveform I see 4 levels - that means log2(4) symbols or 2 symbols/baud.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(this is assuming we're not seeing a squished phase modulated signal where the extra phase information is lost)&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-20T08:24:39.763" CommentCount="1" />
  <row Id="11731" PostTypeId="1" CreationDate="2011-03-20T12:58:50.577" Score="0" ViewCount="40" Body="&lt;p&gt;we are planning to manufacture android tablet ( like everybody else ;) ) , and researching options at this stage, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;any recommendation for soc chip we should consider ? more data like , avaibility of debugging tools , price, minimum lot we can order etc is +1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks.&lt;/p&gt;&#xA;" OwnerUserId="1312" LastActivityDate="2011-03-20T12:58:50.577" ClosedDate="2011-03-20T17:20:59.607" Title="soc chip recommendation for android tablet" Tags="&lt;android&gt;&lt;system-on-chip&gt;&lt;soc&gt;" CommentCount="4" />
  <row Id="11732" PostTypeId="1" CreationDate="2011-03-20T13:32:55.593" Score="0" ViewCount="76" Body="&lt;p&gt;I've got a Caltek CM1200 multimeter, which I bought ages ago.&#xA;&lt;a href=&quot;http://www.caltek.com.hk/cm1200.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.caltek.com.hk/cm1200.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can measure voltage perfectly. I'm pretty sure the battery works, as it displays 0 when you go to a voltage with nothing connected to the probes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I move the dial to the resistance measuring area, the display shows nothing. Completely blank (I expect something meaning infinite).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I connect the two probes (plugged into the bottom two sockets, marked V/Ohm/mA and COM) to each other, it is still blank (I expect zero).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is wrong with my multimeter, or am I missing something at how to measure resistance?&lt;/p&gt;&#xA;" OwnerUserId="3448" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-20T17:06:42.607" LastActivityDate="2011-03-20T17:06:42.607" Title="How do I fix my multimeter, which doesn't seem able to measure resistance?" Tags="&lt;multimeter&gt;" AnswerCount="1" />
  <row Id="11733" PostTypeId="2" ParentId="11732" CreationDate="2011-03-20T15:06:43.207" Score="2" ViewCount="" Body="&lt;p&gt;I suspect an internal failure of the meter, which most likely means replace. &lt;/p&gt;&#xA;" OwnerUserId="3443" LastActivityDate="2011-03-20T15:06:43.207" />
  <row Id="11734" PostTypeId="1" CreationDate="2011-03-20T16:43:36.673" Score="10" ViewCount="346" Body="&lt;p&gt;I like this explanation of why there's nothing wrong with &lt;a href=&quot;http://amasci.com/miscon/eleca.html#frkel&quot; rel=&quot;nofollow&quot;&gt;conventional current being the opposite direction from electron current&lt;/a&gt;.  It mentions batteries and fluorescent bulbs as two cases where the current is not a flow of electrons.  (As well as ion flow in human beings and proton flow in water ice, though those are not electrical components.)  What other &lt;em&gt;electrical components&lt;/em&gt; involve flows of charge that are not electrons?  Does this happen in the electrolyte of electrolytic capacitors?  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;From the topic electron theory we know that metals emit electrons easily and semi-conductors and electrolytes emit them with great difficulty. The electrons in the electrolyte are &lt;strong&gt;in fact not free but are bound in ions&lt;/strong&gt;. &lt;a href=&quot;http://www.electronics-tutorials.com/basics/polarization-capacitor.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.electronics-tutorials.com/basics/polarization-capacitor.htm&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Do holes in semiconductors really count, since they're not physical particles?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-21T21:57:33.423" LastActivityDate="2011-03-23T17:11:39.707" Title="Which everyday components involve flows of charge that are not electrons?" Tags="&lt;electronics&gt;&lt;current&gt;&lt;physics&gt;" AnswerCount="7" CommentCount="11" />
  <row Id="11735" PostTypeId="2" ParentId="11734" CreationDate="2011-03-20T17:26:02.237" Score="9" ViewCount="" Body="&lt;p&gt;Now, this does get confusing when you get to semiconductor theory, and I understand your issue. I can name one very important case. When working with &lt;a href=&quot;http://faculty.stcc.edu/AandP/AP/AP1pages/nervssys/unit10/resting.htm&quot; rel=&quot;nofollow&quot;&gt;charge pumps in the human body&lt;/a&gt;. Many places in biology the charge flow is positive. When taking a biomedical modeling class for EE we often had positive charge flow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We can get crazier, what if you have cancer? There are many options, sometimes you pick radiation. Photon radiation exists, what about &lt;a href=&quot;http://en.wikipedia.org/wiki/Proton_therapy&quot; rel=&quot;nofollow&quot;&gt;proton radiation&lt;/a&gt;? The amount of protons they are sending are measured in Amperes. Why? Positively charged particles per second(enjoy the pun).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The important part here your particle makes an issue of. If electrons were positively charged the issue would be swept under the rug by most people. The fact that they are negatively charged makes people &lt;strong&gt;think&lt;/strong&gt; about what it really means. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you really get down to the physics it is just a sign convention and is a menial problem. If you would like to assign them positive charge please do so, be internally consistent and do not publish anything and no one will be the wiser.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most important thing is that if electrons were positively charged we would not have nearly as great of a name for the &lt;a href=&quot;http://en.wikipedia.org/wiki/Positron&quot; rel=&quot;nofollow&quot;&gt;positron&lt;/a&gt;. I personally would not live in a world were the &lt;a href=&quot;http://www.thefreedictionary.com/negatron&quot; rel=&quot;nofollow&quot;&gt;negatron&lt;/a&gt; is a particle.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-03-20T17:26:02.237" CommentCount="5" />
  <row Id="11736" PostTypeId="1" AcceptedAnswerId="11738" CreationDate="2011-03-20T18:17:31.000" Score="0" ViewCount="95" Body="&lt;p&gt;I have a circuit that inputs 24 volts from two 12 volt sla batteries. It has two analog LM317 regulators.One is configured as 5 volts @ 30 ma load, the other @ 3.3 volts @ 250 ma load. The problem is the 3.3 volt regulator gets really hot! The power dissipated on the LM317 measures a heat loss of 200+ deg F! I thought of using a LDO off the 5 volt regulator, but that would just transfer the heat to that regulator. A switching regulator I think would do the job, but is not going to happen due to cost. Trying to keep the cost around $1.&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-03-20T18:27:39.183" Title="Need 3.3V regulator" Tags="&lt;voltage-regulator&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="11737" PostTypeId="2" ParentId="11736" CreationDate="2011-03-20T18:22:17.643" Score="0" ViewCount="" Body="&lt;p&gt;In 1$ you can get bigger heatsink.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are no good ways except getting switching DCDC converter, I believe simplest ones with internal switch should be just a little more than your budget.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-20T18:22:17.643" CommentCount="1" />
  <row Id="11738" PostTypeId="2" ParentId="11736" CreationDate="2011-03-20T18:27:39.183" Score="6" ViewCount="" Body="&lt;p&gt;The MC34063 is the classic choice  for a switching regulator.  Take apart any cell phone car charger, and you're likely to find one of these guys.  It's available in single quantities for about 75 cents (plus a bunch of external components, which might double that cost), and in production quantities for 25-35 cents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a really good design calculator: &lt;a href=&quot;http://dics.voicecontrol.ro/tutorials/mc34063/&quot; rel=&quot;nofollow&quot;&gt;http://dics.voicecontrol.ro/tutorials/mc34063/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the top of that page is a link to Dave Jones' EEVBlog, in which Dave does a pretty good job of explaining the design considerations of a switching regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.eevblog.com/2010/09/10/eevblog-110-lets-design-a-dc-to-dc-switchmode-converter/&quot; rel=&quot;nofollow&quot;&gt;http://www.eevblog.com/2010/09/10/eevblog-110-lets-design-a-dc-to-dc-switchmode-converter/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3395" LastActivityDate="2011-03-20T18:27:39.183" />
  <row Id="11739" PostTypeId="2" ParentId="11397" CreationDate="2011-03-20T18:39:05.787" Score="0" ViewCount="" Body="&lt;p&gt;Hi.  Thank you for taking the time to reply.  That's a big help.  Two questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Could you please clarify what you mean by &quot;&lt;em&gt;You just need separate switch for DCDC board and FAN - so that you turn DCDC first, and after 1 second - FAN (so that cap is charged).&lt;/em&gt;&quot;?  I understand the general idea of charging the capacitor to give the fan the boost it needs to start, and I think you are saying &lt;em&gt;panel -&gt; dc/dc converter -&gt; capacitor -&gt; fan&lt;/em&gt; is the wiring sequence, but I don't understand the &quot;separate switch&quot; part and the &quot;after 1 second&quot; part.&lt;/li&gt;&#xA;&lt;li&gt;I was able to start and run a smaller 12v/0.17a fan directly via the panel's 9v/2a output (see below).  Do you think is there a way with caps that I could start and run the 12v/0.38a fan the same way if the caps gave the fan the initial push?  This might mean not having to buy anything (I have a variety of caps on hand).  I did try to wire it the panel and the bigger fan together, but it wouldn't start, and even with a push (I spun the fan, both directions) I would not run.  I'm confused about how 9v/2a could start and run a smaller 12v fan, but could not run the bigger 12v fan even if I started it manually.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More to add just to contribute the to world of Google search results for someone else at my level that this might help:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;BarsMonster is absolutely correct about the sun versus my lamp... I took the panel outside in moderate sun in March in North America and it generated the same 9v/2a I'd seen with the 60w lamp right on top of the panel.  I take this to be the max the panel can produce.  This is not what I expected as an electronics novice.  I thought sunlight would be faint compared to the 60w bulb practically sitting on the panel.  Go sun! &lt;/li&gt;&#xA;&lt;li&gt;I was able to connect the panel directly to a much smaller fan (cpu fan from the old days) that wants 12v/0.17a, and 9v/2a would start and run that fan w/o a converter or capacitors etc.  So I guess the boost from the capacitor BarsMonster described could get the larger 12v/0.38a fan going, then what the panel puts out could keep it moving, albeit more slowly than full speed.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3454" LastEditorUserId="3454" LastEditorDisplayName="" LastEditDate="2011-03-20T18:55:23.887" LastActivityDate="2011-03-20T18:55:23.887" />
  <row Id="11740" PostTypeId="2" ParentId="11714" CreationDate="2011-03-20T18:39:20.570" Score="0" ViewCount="" Body="&lt;p&gt;You won't be able to see the plating inside the hole without a microscope or some other really good magnification.  If you're talking about the annular ring outside of the via hole-- Check your gerbers.  You might have specified solder mask right up to the hole.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a few of them test good, they're probably &lt;em&gt;all&lt;/em&gt; good, especially at 15 mils (vs. the 12 mil lower limit of the fab).  Of course, if this is a &lt;em&gt;really&lt;/em&gt; critical board, you should have paid for 100% E-testing ;-)&lt;/p&gt;&#xA;" OwnerUserId="3395" LastActivityDate="2011-03-20T18:39:20.570" />
  <row Id="11741" PostTypeId="1" CreationDate="2011-03-20T18:54:06.540" Score="1" ViewCount="152" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/6778/would-this-work-using-a-computer-smps-as-a-dc-dc-converter&quot;&gt;Would this work? Using a computer SMPS as a DC-DC converter.&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I wonder, if that's possible to feed PC hardware PSU's with DC?&#xA;As far as I see, it just might mean higher load on rectifiers (as only 2 diodes out of 4 would be used in case of passive rectification), but average current consumption will be less...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am wondering because I think about rebuilding crappy UPS to make it online with DC output... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;DC will also allow to choose more convenient voltage - safer 100V or lower current at 360. As far as I see most of computer DCDC's can tolerate wide range of input AC voltages...&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-21T21:54:57.763" LastActivityDate="2011-03-21T21:54:57.763" ClosedDate="2011-03-22T11:18:19.053" Title="DC current for computer hardware" Tags="&lt;dc&gt;&lt;dc-dc&gt;" AnswerCount="0" CommentCount="0" FavoriteCount="0" />
  <row Id="11742" PostTypeId="2" ParentId="11734" CreationDate="2011-03-20T19:21:25.403" Score="7" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Neuron&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;Neurons&lt;/strong&gt;&lt;/a&gt;! &lt;a href=&quot;http://electronics.stackexchange.com/questions/11734/which-everyday-components-involve-flows-of-charge-that-are-not-electrons/11735#11735&quot;&gt;@Kortuk touched this&lt;/a&gt; by mentioning biological charge pumps. Charge is transferred in bursts called &lt;em&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Action_potential&quot; rel=&quot;nofollow&quot;&gt;action potentials&lt;/a&gt;&lt;/em&gt;, created by a local chemical reaction that increases ion concentration (Na&lt;sup&gt;+&lt;/sup&gt;) and travels along neurons (ok, it's a bit more complicated than that, but I think we all get the idea).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Electroplating&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;Electroplating&lt;/strong&gt;&lt;/a&gt;! We electronics buffs know a lot about this due to PCB plating (nickel, gold, mixtures, etc.), but it's used in all walks of industry and arts: galvanizing, gold plating, and other metal deposition is done for waterproofing, rust protection, fancy-factor, colouring, anodizing, conductivity, as an intermediate step before other material deposition like polymers, and chemical reactivity changes (other than rust protection). Again, this is the movement of ions. There's also plenty of electrons involved.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Current flow due to ion transfer in piping&lt;/strong&gt;: for example, in our city drinking water pipes there is an ion concentration (chlorine, &lt;a href=&quot;http://www.youtube.com/watch?v=OcHNYenN7OY&quot; rel=&quot;nofollow&quot;&gt;fluoride&lt;/a&gt;, etc.). As it flows through the pipes it is electricity, the movement of charge, and often creates trouble for sensitive magnetic sensors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Photons create charge differentials&lt;/strong&gt;. From radio to gamma rays, we make use of the entire &lt;a href=&quot;http://en.wikipedia.org/wiki/Electromagnetic_spectrum&quot; rel=&quot;nofollow&quot;&gt;electromagnetic spectrum&lt;/a&gt; by turning electrical energy into photons, then back into electrical* at the receiver antenna. Photons excite valence electrons (are absorbed) with enough energy to hit conduction band creating an electron-hole pair. There's other mechanisms, but I'll screw them up if I try to explain them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Many doohickeys and thingamabobs have a non-neutral charge, and their movement relative to a differentially-charged object creates an electromagnetic field. The channeled, group description of this effect is electricity. Electrons are everywhere and really light -- they're easy  -- so we they get abused into doing the grunt electrical work most of the time.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;*&lt;sup&gt;&lt;em&gt;There is work going on to make entirely photonics-based circuitry, but I'm really not the right person to introduce it.&lt;/em&gt;&lt;/sup&gt;&lt;/p&gt;&#xA;" OwnerUserId="2118" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-20T19:47:20.517" LastActivityDate="2011-03-20T19:47:20.517" CommentCount="3" />
  <row Id="11743" PostTypeId="2" ParentId="11219" CreationDate="2011-03-20T19:40:26.640" Score="0" ViewCount="" Body="&lt;p&gt;Yes, you can. I did it with a iron solder sucker. It does reduce the voltage to the iron, however that alone does not control the temperature. The temperature will continue to rise to some maximum. That value will be a lower temperature than with a higher voltage. So yes it does work, only not like a temperature controlled iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mounted the dimmer in a project box, and added an outlet receptacle in the rear to accommodate the iron.&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-03-20T19:40:26.640" />
  <row Id="11745" PostTypeId="1" AcceptedAnswerId="11749" CreationDate="2011-03-20T21:09:15.737" Score="0" ViewCount="86" Body="&lt;p&gt;I'm thinking of buying a pair of &lt;a href=&quot;http://uk.farnell.com/stmicroelectronics/l298n/motor-driver/dp/1589425&quot; rel=&quot;nofollow&quot;&gt;L298N&lt;/a&gt;s, to control a pair of 1.6A motors. I'd like to control each motor with a signal PWM wire and a direction wire. However, I've hit a couple of problems.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;It is unclear whether the chip includes internal diodes or not. Some sources say yes, some say no. There also seems to be general confusion between the 298 and the 293.&lt;/li&gt;&#xA;&lt;li&gt;Looks like I need to invert the direction line so that the two inputs are opposite. However, if that messed up, current could flow through the chip.&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Would pulling the PWM &quot;enable&quot; line low while switching the direction signal solve this?&lt;/li&gt;&#xA;&lt;li&gt;Would a MOSFET be suitable to negate the signal?&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Or would I do better just to buy &lt;a href=&quot;http://www.pololu.com/catalog/product/713&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; complete motor driver?&lt;/p&gt;&#xA;" OwnerUserId="1217" LastActivityDate="2011-03-20T21:49:07.297" Title="What components do I need to build a motor controller from the L298?" Tags="&lt;dc-motor&gt;&lt;h-bridge&gt;&lt;l298n&gt;&lt;diodes&gt;" AnswerCount="2" />
  <row Id="11746" PostTypeId="2" ParentId="6778" CreationDate="2011-03-20T21:16:51.297" Score="0" ViewCount="" Body="&lt;p&gt;If you are going to power it with DC, then why not just get a direct DC-to-DC power supply for your computer? This would be much more efficient as well as much less &quot;risky&quot;.&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-03-20T21:16:51.297" CommentCount="1" />
  <row Id="11747" PostTypeId="2" ParentId="11745" CreationDate="2011-03-20T21:21:37.890" Score="1" ViewCount="" Body="&lt;p&gt;Looked at this the other day for someone -the data sheet's example show the diodes  are external&lt;/p&gt;&#xA;&#xA;&lt;p&gt;yes you invert the direction line - you can't damage it with having both inputs high or low - it ends up with both ends of the motor wired to gnd or VCC (active braking). Just hook up a TTL inverter, or a simple switching transistor (fet or bipolar) with say a 1k resistor between vcc and the collector and if it's a bipolar transistor something to limit base current&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-20T21:21:37.890" CommentCount="1" />
  <row Id="11748" PostTypeId="2" ParentId="11720" CreationDate="2011-03-20T21:27:11.150" Score="1" ViewCount="" Body="&lt;p&gt;You don't need a laser at all, unless you actually want to have a visible beam. If you don't mind it being invisible, then just use an Infrared LED and a matching photodiode.&lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2011-03-20T21:27:11.150" CommentCount="1" />
  <row Id="11749" PostTypeId="2" ParentId="11745" CreationDate="2011-03-20T21:49:07.297" Score="2" ViewCount="" Body="&lt;p&gt;As far as a reference design, Solarbotics has a pretty solid little breakout board for the L298N.  If you don't already have the chips, I would consider purchasing one: &lt;a href=&quot;http://www.solarbotics.com/products/k_cmd/&quot; rel=&quot;nofollow&quot;&gt;Solarbotics L298N&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you already have the parts, then you could probably follow their design, &lt;a href=&quot;http://www.solarbotics.com/assets/schematics/solarbotics_-l298_schematic.pdf&quot; rel=&quot;nofollow&quot;&gt;L298N Schematic&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-03-20T21:49:07.297" CommentCount="3" />
  <row Id="11750" PostTypeId="1" AcceptedAnswerId="11758" CreationDate="2011-03-20T21:50:38.120" Score="9" ViewCount="328" Body="&lt;p&gt;Can someone explain, or provide a good reference to an explanation of Poles and Zeros for say, a power supply compensator, or any control system for that matter.  I'm not really looking for a mathematical explanation, as that seems rather straight forward, but what they mean in a practical sense.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems common, for example, for papers or app-notes to mention something like &quot;a type III error amplifier configuration has three poles (one at the origin) and two zeros&quot; or &quot;adding capacitor C1 introduces an additional zero into the system&quot; as if I'm supposed to take something from that without any further explanation.  In reality, I'm like &quot;ughhh, so what?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what would something like this mean from a practical sense.  Are poles points of instability?  Do the number of zeros and poles indicate something about stability, or lack of it?  Is there a reference about this somewhere written in an understandable manner that would allow me (more of a practical use, not hardcore math for the sake of math type) to join the in-crowd when it came to app-notes referencing Zeros and Poles?&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-03-21T20:37:31.373" Title="Poles and Zeros in English" Tags="&lt;control&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="3" />
  <row Id="11753" PostTypeId="1" CreationDate="2011-03-20T23:07:36.340" Score="2" ViewCount="225" Body="&lt;p&gt;Hello everyone I am new to microcontrollers and electronics in general, and would like to learn how I can control lights within my house via an iOS Application. How would I go about doing this...with the use of an custom arduino board or a pre-built microcontroller. Please understand I really have no idea what to do when it comes to electronics, I know the basics and that is all. I also understand how to program. Any help is appreciated thank you.&lt;/p&gt;&#xA;" OwnerUserId="3206" LastActivityDate="2011-03-21T00:12:51.927" Title="Implementing a Microcontroller with an Iphone App to Control household lights?" Tags="&lt;arduino&gt;&lt;microcontroller&gt;&lt;iphone&gt;" AnswerCount="1" />
  <row Id="11754" PostTypeId="2" ParentId="11753" CreationDate="2011-03-20T23:38:23.423" Score="1" ViewCount="" Body="&lt;p&gt;There are several points that come to mind when thinking about the design for this project.      &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Connecting Arduino to iPhone&lt;/strong&gt;&lt;br&gt;&#xA;There are 2 options for this use bluetooth or have a webserver running on a netduino, so it could be accessed from the web. Here are some tutorials on &lt;a href=&quot;http://www.sparkfun.com/tutorials/152&quot; rel=&quot;nofollow&quot;&gt;iPhone and Arduino&lt;/a&gt;.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Mains/Line Power and Microcontroller&lt;/strong&gt;&lt;br&gt;&#xA;You are going to need some form of isolation between your control system and the lighting system because they both use different current(lighting if mains then is AC, microcontroller is DC) and different voltages(lighting 240v in the UK(120V in the states, while microcontroller uses ~5v). This could be done with a relay or opto-isolator. A relay is a device that is a mechanical switch which has an electro-magnet that pulls the contact instead of pressing it. Primarily used so you can interface different voltage systems. Such as your lighting system and Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Processing Software For Microcontroller&lt;/strong&gt;&lt;br&gt;&#xA;This is trivial basically when it receives a command turn an output on, it is also dependent on how you configure your software. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Software For iPhone&lt;/strong&gt;&lt;br&gt;&#xA;This is the next thing you have to decide on. Remember iPhone development can only be done on a mac so maybe the webserver option is a better approach if you don't have a mac. Also could be accessed on any smartphone(not just iPhone). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Overall I think your best approach is using an Arduino because you don't have to have an extensive electronics knowledge to get this project going, and the majority could be plugging a few wires in with this &lt;a href=&quot;http://www.robotshop.com/seeedstudio-arduino-relay-shield.html&quot; rel=&quot;nofollow&quot;&gt;relay shield&lt;/a&gt;(just quickly googled that), then writing the software which there might be loads of examples around for what you are wanting todo. If I think of anything else I will add more. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-03-21T00:12:51.927" LastActivityDate="2011-03-21T00:12:51.927" />
  <row Id="11755" PostTypeId="1" AcceptedAnswerId="11761" CreationDate="2011-03-21T00:17:02.347" Score="1" ViewCount="93" Body="&lt;p&gt;Are there common sources of 434MHz noise or interference in a residential/household environment? I've been playing with some radios, and they seem to be behaving flakily at my friend's house even at close range, and working flawlessly at my house... I'm a bit stumped. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suppose another possibility is some kind of crazy noise on the wall power at my friend's place, but I'll have to try out a battery power source on the receiver to rule that out, and can post back once I do. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, I don't own or have access to a spectral analyzer either.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-03-22T13:03:15.083" Title="434MHz Noise Sources" Tags="&lt;rf&gt;&lt;radio&gt;&lt;noise&gt;" AnswerCount="2" />
  <row Id="11756" PostTypeId="2" ParentId="11750" CreationDate="2011-03-21T00:53:04.997" Score="16" ViewCount="" Body="&lt;p&gt;In short, poles and zeros are a way of analyzing the stability of a feedback system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll try not to get too math-heavy but I'm not sure how to explain without at least some math.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the basic structure of a feedback system:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/RThKH.png&quot; alt=&quot;Basic feedback system&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this form there is no gain or compensation in the feedback path, it is placed entirely in the forward path, however, the feedback portion of more general systems can be transformed to look like this and analyzed in the same way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The transfer function in the box is called $L(s)$ because the analysis is often done in the Laplace transform space. Laplace transforms are similar to fourier transforms, so you can think of L(s) as a frequency response. For example, a perfect low-pass filter has $L(s) = 1$ for $s$ less than the cutoff frequency, and $L(s) = 0$ above the cutoff frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$L(0)$ is the DC gain of the system. For a feedback control system, a large DC gain is desirable because it reduces the steady-state tracking error of the system. &lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Poles and Zeros&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;$L(s)$ is a complex-valued function. Usually the polar form $A e^{i \theta}$ is used; $A$ is the magnitude and $\theta$ is the phase. The magnitude of $L(s)$ is also called the gain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The poles and zeros provide a convenient, fast way to think about the properties of $L(s)$. When doing a rough plot of $L(s)$, poles contribute -90&amp;deg; of phase above the pole frequency and cause the magnitude to &quot;roll off&quot; (decrease). Zeros do the opposite &amp;mdash; they contribute +90&amp;deg; of phase and the magnitude increases. This will probably make a lot more sense looking at the pictures and the &quot;Rules for hand-made Bode plot&quot; section of &lt;a href=&quot;http://en.wikipedia.org/wiki/Bode_plot&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Bode_plot&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a system to be stable, the magnitude of $L(s)$ needs to drop below unity before (at a lower frequency) the phase reaches -180&amp;deg;. Typically some margin is required here; &quot;gain margin&quot; and &quot;phase margin&quot; are two ways of measuring how far $L(s)$ is from the (1, -180&amp;deg;) point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a simple example, an op-amp might have $L(s) = \frac{10^{6}}{s}$. In this case there is a pole at zero and no zeros. As you would expect for an op-amp, there is a large DC gain. The gain drops off as the frequency increases from DC (due to the pole at zero). According to this model, the system cannot be unstable because the phase is never less than -90&amp;deg;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When reading an app note that talks about poles and zeros, you may need to figure out the general form of $L(s)$ for the system in question, or you may be able to draw some conclusions just from a list of poles and zeros. Adding either a pole or a zero to a system will change both the gain and phase margin; adding a pole and a zero together (at different frequencies, both below the -180&amp;deg; crossover) will change the gain margin but not the phase margin. Adding two zeros and two poles can create a hump in $L(s)$ (think bandpass filter), without changing either the gain or the phase margin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps. In general I would expect datasheets and app notes to suggest values for the compensation components so that the user doesn't need to analyze the stability unless there are special requirements. If you have a specific part in mind that you're having trouble using and you post a link the datasheet, I might be able to offer something.&lt;/p&gt;&#xA;" OwnerUserId="3441" LastEditorUserId="3441" LastEditorDisplayName="" LastEditDate="2011-03-21T04:06:59.090" LastActivityDate="2011-03-21T04:06:59.090" CommentCount="1" />
  <row Id="11757" PostTypeId="1" AcceptedAnswerId="11786" CreationDate="2011-03-21T01:17:13.570" Score="3" ViewCount="162" Body="&lt;p&gt;I'm performing envelope detection in the digital domain. This consists of rectifying the signal (i.e. taking the absolute value) and low pass filtering it to extract the slower varying envelope signal. I've heard that rectification doubles the frequency content in the original signal, therefore this information has to be taken into account when designing the digital low pass filter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to understand the mechanism in which rectification doubles the frequency content of the original signal.&lt;/p&gt;&#xA;" OwnerUserId="2897" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-21T18:00:48.723" LastActivityDate="2011-03-21T19:38:43.843" Title="Why does rectification of a digital signal double the frequency content?" Tags="&lt;dsp&gt;" AnswerCount="2" />
  <row Id="11758" PostTypeId="2" ParentId="11750" CreationDate="2011-03-21T01:30:21.617" Score="5" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;A feedback system (like any other AC circuit) can be described using a complex function $L(s)$. It is called the transfer function of the system and describes all of its linear behavior.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;$L(s)$ can be plotted as two plots: one for magnitude and and one for phase both vs. frequency (the Body plots). These plots let us easily determine the stability of the system. An unstable system gets a $180^\circ$ phase shift (so a negative feedback suddenly starts to be a positive one) while still having some gain.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Every complex function describing an electrical circuit is completely defined by it's poles and zeros. If you write the function as a ratio of two polynomials of $j\omega$ then zeros are points where the numerator equals $0$ and poles are zeros of the denominator.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;It is quite easy to draw Bode plots from poles and zeros so they are the preferred method for specifying control systems. Also if you can ignore output loading (because you separated the various stages with op amps) then you can just multiply transfer functions without doing all the normal circuit calculations. Multiplication of polynomial ratios means you can just concatenate the lists of poles and zeros.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;So back to your question:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Check the &lt;a href=&quot;http://en.wikipedia.org/wiki/Bode_plot&quot; rel=&quot;nofollow&quot;&gt;Wikipedia page&lt;/a&gt; for an introduction and &lt;a href=&quot;http://www.swarthmore.edu/NatSci/echeeve1/Ref/LPSA/Bode/BodeHow.html&quot; rel=&quot;nofollow&quot;&gt;this tutorial&lt;/a&gt; for a reference on how to draw Bode plots from a list of poles and zeros.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Read a little about &lt;a href=&quot;http://en.wikipedia.org/wiki/Laplace_transform#s-Domain_equivalent_circuits_and_impedances&quot; rel=&quot;nofollow&quot;&gt;the practical stuff in the Laplace transform&lt;/a&gt;. Short version: you just calculate the circuit as with complex numbers but substituting $s$ where you would write $j\omega$. Then you find $V_{out} \over V_{in}$ and you have your transfer function.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;From an open loop transfer function (imagine cutting the loop with scissors and putting some kind of frequency response meter in there) you draw Bode plots and verify the stability. The &lt;a href=&quot;http://www.intersil.com/data/an/an9415.pdf&quot; rel=&quot;nofollow&quot;&gt;Feedback, Op Amps and Compensation&lt;/a&gt; application note is short and dense but has all the theory you need for this part. Try at least skimming through it.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-21T10:18:08.843" LastActivityDate="2011-03-21T10:18:08.843" CommentCount="2" />
  <row Id="11759" PostTypeId="2" ParentId="11714" CreationDate="2011-03-21T01:32:59.130" Score="4" ViewCount="" Body="&lt;p&gt;I Think you are using the term plating incorrectly. Plating will &lt;em&gt;decrease&lt;/em&gt; the diameter of the hole, not increase it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The larger dimension (the pad surrounding the via hole) is called the &lt;em&gt;Annular Ring&lt;/em&gt;.&lt;br&gt;&#xA;All the fabs I have worked with generally want a 0.005&quot; per-side annular ring, or the via diameter + 0.010&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You &lt;strong&gt;definitely&lt;/strong&gt; have some really hairy registration issues on the board you posted pics of. It may work, but you're really pushing it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, you never want the via hole to break out through the edge of the annular ring, which is happening a few times in the picture you posted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyways, &lt;strong&gt;Registration&lt;/strong&gt; refers to the accuracy between a fab-house's etching and drilling process.&lt;br&gt;&#xA;Basically, if a fab house etches a circle in the coper of a board, and then drills a hole in the middle of the circle, how close is the drilled hole to the center of the copper circle?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember, drilling a board and etching it are separate processes, and involve the board being unmounted and remounted in different equipment.&lt;br&gt;&#xA;Generally, you can get as good registration as you are willing to pay for, and it looks like your boards are from a pretty budget board-house.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to allow enough annular ring that you never wind up with the via hole too close to the edge of the pad. This is generally specified by the fab house (they should have a minimum annular ring spec on their board requirements). However, it is important to remember that they &lt;em&gt;may&lt;/em&gt; run your boards &lt;em&gt;anyways&lt;/em&gt;, even if it does not meet their minimum required specs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The board house may run the boards anyways, and just refuse to fix any issues if they don't work out.&lt;br&gt;&#xA;This is particularly common in China, where the general philosophy seems to be &quot;Let the Buyer Beware&quot;.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Anyways, I think the reason you are finding your vias a bit odd looking is that you have &lt;strong&gt;&lt;em&gt;tented your vias&lt;/em&gt;&lt;/strong&gt;, which is the practice of covering the annular ring and the hole for the via with soldermask.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With 0.015&quot; vias, you will occasionally get a contiguous layer of soldermask over the hole, and they will look different.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/FO89T.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-03-22T08:12:07.433" LastActivityDate="2011-03-22T08:12:07.433" CommentCount="6" />
  <row Id="11760" PostTypeId="2" ParentId="11757" CreationDate="2011-03-21T01:40:21.260" Score="9" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Rectification is a non-linear process so it can change the spectrum of a signal.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Full-wave rectification gives mostly DC and double the base frequency but not only. There are higher harmonics in this signal as well.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Some hand-waving: Most real life rectifiers have exponential characteristics which can be approximated by their Taylor expansion. The first (and the biggest) non-linear term of this expansion is $Ax^2$ and $\sin^2x$ is $1 - \cos 2x \over 2$.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T01:40:21.260" CommentCount="2" />
  <row Id="11761" PostTypeId="2" ParentId="11755" CreationDate="2011-03-21T01:43:41.037" Score="2" ViewCount="" Body="&lt;p&gt;There can be a lot of devices operating in the 433 MHz band. Many cheap radio devices (like wireless thermometers and stuff) operate on 433 MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The house construction could have something to do with this as well. Did you try testing it outside (with a line-of-sight) near his house?&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T01:43:41.037" CommentCount="1" />
  <row Id="11762" PostTypeId="2" ParentId="3203" CreationDate="2011-03-21T01:49:04.247" Score="1" ViewCount="" Body="&lt;p&gt;I second the RFM12 and JeeNode suggestions and strongly discourage you from rolling your own using a simple on/off transmitter. It is not so easy to make the transmitter/receiver work without RF experience and even if they work then digital modulation and demodulation of a noisy signal are still not trivial.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T01:49:04.247" />
  <row Id="11763" PostTypeId="1" AcceptedAnswerId="11779" CreationDate="2011-03-21T01:51:19.890" Score="4" ViewCount="185" Body="&lt;p&gt;Digital signal processing in radar applications is usually done using finite impulse response filters. Why is that the case? Wouldn't the use of an infinite impulse response filtering be much faster and feasible since we are talking about processing in the gigahertz range?&lt;/p&gt;&#xA;" OwnerUserId="2897" LastActivityDate="2011-03-21T13:17:45.197" Title="Why does radar processing always require FIR filters?" Tags="&lt;dsp&gt;" AnswerCount="3" />
  <row Id="11764" PostTypeId="2" ParentId="6778" CreationDate="2011-03-21T01:55:53.923" Score="4" ViewCount="" Body="&lt;p&gt;For a one-off you could just open it and remove the rectifiers. If you put a high enough voltage on the input then even an active PFC should not complain (it should make the average current proportional to the instantaneous input voltage while maintaining the average output voltage; i don't see a reason for failure here). It it does not have an active PFC then you should be completely safe.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T01:55:53.923" />
  <row Id="11765" PostTypeId="2" ParentId="10584" CreationDate="2011-03-21T01:58:32.860" Score="2" ViewCount="" Body="&lt;p&gt;IIRC you can just use printf and scanf/gets on the serial ports of the mbed.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T01:58:32.860" CommentCount="4" />
  <row Id="11766" PostTypeId="2" ParentId="11734" CreationDate="2011-03-21T02:08:21.523" Score="3" ViewCount="" Body="&lt;p&gt;In plasma (used in various technological processes for depositing thin films and etching stuff) both electrons and ions do the conduction. Ion guns as their name implies use ions accelerated in vacuum using a very string electrical field (in a way similar to how cathode ray tube displays work) to etch away material or implant the ions on a very small scale (nano- to micrometer scale).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Holes in semiconductors are just electrons. It is just that there are so many immobile electrons in p-doped semiconductor that the holes stand out and let us do the theory. In reality the electrons (leaving empty holes behind them) are still the moving parts.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T02:08:21.523" />
  <row Id="11767" PostTypeId="2" ParentId="10244" CreationDate="2011-03-21T02:22:52.660" Score="0" ViewCount="" Body="&lt;p&gt;As far as I remember the SPICE algorithms you do not want its internal matrices dumped on you. Also I believe for transient analysis it converts all capacitors to voltage sources (and inductors to current sources) for every time step and solves the non-linear circuit like a DC one. So there are no true differential equations in SPICE.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, SPICE could output the transfer function of the circuit; IIRC as a list of polynomial coefficients. This sometimes suffers heavily from rounding errors but for simple circuits it may be what you are looking for.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T02:22:52.660" CommentCount="1" />
  <row Id="11768" PostTypeId="1" AcceptedAnswerId="11782" CreationDate="2011-03-21T02:25:08.363" Score="2" ViewCount="232" Body="&lt;p&gt;Apple computers are great. I love my MacBook, however, I haven't been able to find any decent circuit design and simulation software that runs on a Mac. This brings me to a question: If Mac OS X has no professional electronics design software, then Mac electronics are designed on PC's? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would be interesting news for &quot;MacFanaticsPCHaters&quot; and for all of us trying to develop hardware on a Mac.&lt;/p&gt;&#xA;" OwnerUserId="3455" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2011-03-21T21:24:02.090" LastActivityDate="2011-03-21T21:24:02.090" Title="What software is used to design and simulate Mac computers, iPod and iPhone circuits?" Tags="&lt;simulation&gt;&lt;circuit-design&gt;&lt;mac&gt;&lt;osx&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="11769" PostTypeId="2" ParentId="11706" CreationDate="2011-03-21T02:39:07.070" Score="4" ViewCount="" Body="&lt;p&gt;As far as I know these are completely different beasts (and &lt;a href=&quot;http://www.allaboutcircuits.com/vol_3/chpt_7/8.html&quot; rel=&quot;nofollow&quot;&gt;a simple google search&lt;/a&gt; agrees).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The built-in negative resistance of the unijunction transistors is what makes them attractive (or maybe &quot;cute&quot; is a better word) in &quot;simple&quot; oscillators but IMHO you will be better off building a 3xRC ($180^\circ$ phase shift network) oscillator on one normal bipolar transistor or a simple oscillator on an op amp. Almost nobody uses negative resistance devices nowadays.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Negative resistance is fairly common in nature (a humble spark gap has this property) so this may be the reason why historically they were used for intro level oscillators. But there also were times when people notoriously made their own rectifying diodes out of some kind of rock and a piece of wire so they could build a long-wave radio receiver, so... :P&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-04-26T11:50:36.510" LastActivityDate="2011-04-26T11:50:36.510" CommentCount="0" />
  <row Id="11770" PostTypeId="2" ParentId="11768" CreationDate="2011-03-21T02:44:59.277" Score="1" ViewCount="" Body="&lt;p&gt;That is an interesting question but I imagine that Mac hardware developers would rather work on some Sun workstations running some crappy commercial Unix than a PC. :P Chip design is still mostly done on Unix AFAIK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the hobbyist:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can you Eagle for PCB layout and schematics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is (or rather was, but can be still downloaded) &lt;a href=&quot;http://www.kulfx.com/index.php?section=projects&amp;amp;item=misugar&quot; rel=&quot;nofollow&quot;&gt;MiSugar&lt;/a&gt; for simulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have also used ngspice from command line and MacSpice for plotting but they do not offer any schematic capture.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T02:44:59.277" />
  <row Id="11771" PostTypeId="2" ParentId="6263" CreationDate="2011-03-21T02:50:19.207" Score="1" ViewCount="" Body="&lt;p&gt;My experience (I am running a small EE company) is that, just as you are already feeling, the market for electronics is much less flexible if you are an independent freelancer. It may be because there are heavy large scale manufacturing benefits in electronics and that the design and debugging usually takes quite a lot more time.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T02:50:19.207" CommunityOwnedDate="2011-05-16T17:13:11.787" />
  <row Id="11772" PostTypeId="2" ParentId="11763" CreationDate="2011-03-21T03:17:25.040" Score="3" ViewCount="" Body="&lt;p&gt;AFAIK they are not really doing the processing in the gigahertz range (how many chips do you know that can perform several multiplications and additions for each sample at multi gigahertz sample rate). The only way it can work is by up- and downconverting (using mixers) to baseband and operating on that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Returning to your question: IIR filters are fast but their performance is as good (or rather as bad) as their analog counterparts. FIRs on the other hand can have any phase and frequency response if you are willing to pay for lots of taps. OTOH long FIRs can be quite efficiently computed using FFT overlap-add methods. FIRs can also be quite easily tuned on-the-go to get &lt;a href=&quot;http://en.wikipedia.org/wiki/Adaptive_filter&quot; rel=&quot;nofollow&quot;&gt;adaptive filters&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general check &lt;a href=&quot;http://dspguide.com/&quot; rel=&quot;nofollow&quot;&gt;The Scientist and Engineer's Guide to Digital Signal Processing&lt;/a&gt; book. It is a great book about DSP with lots of practice and not too much theory.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T03:17:25.040" CommentCount="2" />
  <row Id="11773" PostTypeId="2" ParentId="11763" CreationDate="2011-03-21T05:17:18.870" Score="3" ViewCount="" Body="&lt;p&gt;Radar often uses phase as part of the signal. After down converting you are going to have a signal that is normally &quot;relatively&quot; low frequency(kHz compared to GHz).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When designing a Digital filter you can get very good &lt;a href=&quot;http://en.wikipedia.org/wiki/Sinc_filter&quot; rel=&quot;nofollow&quot;&gt;brick wall filters&lt;/a&gt;. The major difference is that FIR filters can be symmetric and have linear phase delay. &lt;a href=&quot;http://en.wikipedia.org/wiki/Group_delay_and_phase_delay&quot; rel=&quot;nofollow&quot;&gt;Linear phase delay means a flat group delay&lt;/a&gt; which correlates to the phases being preserved. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When phase is a major part of your signal(in CWFM radar it makes up the position part of the signal) any phase delay can cause a incorrect reading.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-03-21T05:17:18.870" />
  <row Id="11774" PostTypeId="1" AcceptedAnswerId="11776" CreationDate="2011-03-21T05:37:28.400" Score="4" ViewCount="123" Body="&lt;p&gt;I'm a bit confused on if I should be using integers in VHDL for synthesis signals and ports, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use std_logic at top level ports, but internally I &lt;em&gt;was&lt;/em&gt; using ranged integers all over the place. However, I've stumbled across a few references to people saying you should only use signed/unsigned for synthesis-targeted code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've gone and reworked my current project to use unsigned... and, well, it's noticeably uglier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it a bad practice to use integers? What's the problem? Is there some uncertainty on  what width the tool will map integers to?&lt;/p&gt;&#xA;" OwnerUserId="1270" LastActivityDate="2011-03-21T20:33:20.297" Title="VHDL: integers for synthesis?" Tags="&lt;vhdl&gt;&lt;synthesis&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="3" />
  <row Id="11775" PostTypeId="2" ParentId="11583" CreationDate="2011-03-21T12:03:06.420" Score="1" ViewCount="" Body="&lt;p&gt;If the iron is the 120 volt type that does not use a temperature regulator or transformer you could be at risk. Most 120 volt irons I have seen have the neutral leg tied to the irons tip. This makes it grounded already through the service panel. If the outlet is wired wrong, the tip could be at the &quot;hot&quot; leg potential. If you try to ground the tip then the circuit breaker will trip on overload, or worse you could be injured. Also if reversed and ungrounded, you could be putting 120 volts AC into your circuit. I personally never use a ground on the iron and have never blown a chip. Most semiconductors today have adequate esd protection.&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-03-21T12:03:06.420" />
  <row Id="11776" PostTypeId="2" ParentId="11774" CreationDate="2011-03-21T12:10:28.660" Score="5" ViewCount="" Body="&lt;p&gt;Integers are fine in synthesis, I use them all the time. &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I use std_logic at top level ports, but internally I was using ranged integers all over the place&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That's fine!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be aware:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You are simulating first aren't you :) -  Integer types don't automatically &quot;roll-over&quot; in simulation - it's an error to go out of the range you've specified for them.  If you want roll-over behaviour, you have to code it explicitly.&lt;/li&gt;&#xA;&lt;li&gt;They are only specced to go from $-2^{32}-1$ to $+2^{31}-1$ (i.e. not quite the full range of a 32-bit integer, you can't use $-2^{32}$ and remain portable), which is a bit of a pain at times. If you need to use &quot;big&quot; numbers, you'll have to use &lt;code&gt;unsigned&lt;/code&gt; and &lt;code&gt;signed&lt;/code&gt;.  &lt;/li&gt;&#xA;&lt;li&gt;If you don't constrain them, you can &lt;em&gt;sometimes&lt;/em&gt; end up with 32-bit counters where less would do (if the synth and subsequent tools can't &quot;see&quot; that they could optimise bits away).  &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;On the upside:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;They are much faster to simulate than unsigned/signed vectors&lt;/li&gt;&#xA;&lt;li&gt;They don't automatically roll-over in simulation (yes, it's in both lists :).  This is handy - for example you get early warning that your counter is too small.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;When you do use vector types, you are using &lt;code&gt;ieee.numeric_std&lt;/code&gt;, &lt;a href=&quot;http://parallelpoints.com/node/3&quot; rel=&quot;nofollow&quot;&gt;not &lt;code&gt;ieee.std_logic_arith&lt;/code&gt;&lt;/a&gt; aren't you?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use &lt;code&gt;integer&lt;/code&gt;s where I can, but if I explicitly want &quot;roll-over n-bit counters&quot;, I tend to use &lt;code&gt;unsigned&lt;/code&gt;.&lt;/p&gt;&#xA;" OwnerUserId="763" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-21T13:44:00.100" LastActivityDate="2011-03-21T13:44:00.100" CommentCount="2" />
  <row Id="11777" PostTypeId="2" ParentId="4284" CreationDate="2011-03-21T12:50:23.617" Score="4" ViewCount="" Body="&lt;p&gt;I've used &lt;a href=&quot;http://www.saleae.com/logic/&quot; rel=&quot;nofollow&quot;&gt;Saleae's Logic&lt;/a&gt; with success and it works on Linux, OSX and Windows (I've only used the first two). It's cheap, very, very small and has a few useful analyzers built it.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-03-21T12:50:23.617" CommentCount="1" />
  <row Id="11778" PostTypeId="1" CreationDate="2011-03-21T12:57:49.953" Score="0" ViewCount="72" Body="&lt;p&gt;How many Malayalam channels in Airtel DTH?&lt;/p&gt;&#xA;" OwnerUserId="3457" LastActivityDate="2011-03-21T12:57:49.953" ClosedDate="2011-03-21T13:00:07.713" Title="How many Malayalam channels in Airtel DTH?" Tags="&lt;bus&gt;" FavoriteCount="0" />
  <row Id="11779" PostTypeId="2" ParentId="11763" CreationDate="2011-03-21T13:17:45.197" Score="2" ViewCount="" Body="&lt;p&gt;Both answers are very good, but I hope my 2cents and a different perspective will add some value. I am in the middle of having to do essentially the same thing as a radar system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Baseband versus RF&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First off, Radar can be viewed very similar to wireless communication systems in that you have a baseband signal that you modulate, transmit, and then demodulate. Often phase shift keying is used in comm systems. In PSK, you are trying to detect a phase shift, usually between -pi and pi and based off of that phase shift you would determine the bit that was being sent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In radars, the delay/reflection time creates what can be viewed as a phase shift. The only problem is that the delay in a radar is more then likely going to be greater then the 2*pi span that you can detect normally. In order to get a greater range you have to turn off your signal and wait long enough for you to receive the reflected signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In Radars, you could use an &lt;a href=&quot;http://en.wikipedia.org/wiki/Envelope_detector&quot; rel=&quot;nofollow&quot;&gt;envelope detector&lt;/a&gt; and/or an RF mixer. An RF mixer is the same as a multiplier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;DSP&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The key at this point is to remove all noise and determine the time delay between when you transmitted and where your current signal is at. Just like the comm systems, this delay can be viewed as a phase shift. Because of this you want your filter to have a linear phase response otherwise you wouldn't be able to tell (at least not easily) what delay your signal actually had. Here is an example of the frequency response of an FIR filter I just made:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tbudj.png&quot; alt=&quot;FIR&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As I am sure you can see, the phase graph is a straight line, so it is linear.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now here is an example of an IIR with similar passband and stop band specifications:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/iAtPs.png&quot; alt=&quot;IIR&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The phase graph isn't so linear this time. Now it is possible to reverse this phase effect in your delay time calculations, but it usually isn't worth the effort, instead people just use an FIR filter.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-21T13:17:45.197" CommentCount="3" />
  <row Id="11780" PostTypeId="1" CreationDate="2011-03-21T13:33:52.797" Score="1" ViewCount="220" Body="&lt;p&gt;Hi, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm quite new to micro-controller development. However, I wanted to start from someplace. Currently, I wanted to start a project to interface analog signals, do some DSP with it and be able to display these signals in a GUI on a smartphone like Android.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you'll recommend a few micro-controllers I should be looking at that allows easy portability to an Android phone? My criteria for the micro are as follows:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Low Power &lt;/li&gt;&#xA;&lt;li&gt;Great documentation/ sample    code&lt;/li&gt;&#xA;&lt;li&gt;At-least 6 analog input pins     &lt;/li&gt;&#xA;&lt;li&gt;Has Bluetooth/wifi capability  &lt;/li&gt;&#xA;&lt;li&gt;Has an   ADC&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I have looked up a few micros like the &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Arduino&lt;/li&gt;&#xA;&lt;li&gt;Fez Domino&lt;/li&gt;&#xA;&lt;li&gt;Beagle Board&lt;/li&gt;&#xA;&lt;li&gt;Microchips, PIC18, PIC24 etc. series&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;But, I'm not sure which provides the most easy to port to an Android phone?&lt;/p&gt;&#xA;" OwnerUserId="3458" LastActivityDate="2011-03-21T15:29:50.513" Title="Micro-controller to develop application for Android" Tags="&lt;microcontroller&gt;&lt;android&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="11781" PostTypeId="2" ParentId="11780" CreationDate="2011-03-21T13:43:24.740" Score="1" ViewCount="" Body="&lt;p&gt;The easiest way to get to an Android phone is to connect to it using Bluetooth. This can pretty much be as easy or hard as you want to make it. We have plenty of &lt;a href=&quot;http://electronics.stackexchange.com/search?q=bluetooth&quot;&gt;questions&lt;/a&gt; regarding bluetooth, but I think &lt;a href=&quot;http://electronics.stackexchange.com/questions/1404/low-cost-bluetooth&quot;&gt;this one&lt;/a&gt; is probably the best for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as this community goes, we will probably be able to help the most with Arduino and Microchip, but anything that can support bluetooth can interact with Android phones.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-21T13:43:24.740" CommentCount="3" />
  <row Id="11782" PostTypeId="2" ParentId="11768" CreationDate="2011-03-21T13:54:23.640" Score="3" ViewCount="" Body="&lt;p&gt;&lt;em&gt;&quot;What circuit design and simulation software runs on a Mac?&quot;&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://opencircuits.com/software_tool&quot; rel=&quot;nofollow&quot;&gt;list of software tools for electronics design&lt;/a&gt; includes a bunch of tools that run on the Macintosh.&#xA;Some of those tools, such as McCAD, were originally designed to run on a Macintosh.&#xA;After Mac OS switched to a Unix base (starting with Mac OS X), quite a few tools originally designed to run on Unix were ported to the Mac.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&quot;What software is used to design and simulate mac computer, ipod and iphone circuits?&quot;&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I &lt;a href=&quot;http://ask.metafilter.com/177401/What-do-you-use-to-design-an-Apple&quot; rel=&quot;nofollow&quot;&gt;do not know&lt;/a&gt;, but this reminds me of a funny story.&#xA;One story (&lt;a href=&quot;http://www.c2.com/cgi/wiki?AppleCrayComputer&quot; rel=&quot;nofollow&quot;&gt;perhaps apocryphal&lt;/a&gt;) as &lt;a href=&quot;http://research.microsoft.com/en-us/um/people/gbell/craytalk/sld089.htm&quot; rel=&quot;nofollow&quot;&gt;repeated by Gordon Bell&lt;/a&gt; in 1997:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;Seymour Cray ... When asked what kind of CAD tools he&#xA;  used for the CRAY1 he said that he&#xA;  liked #3 pencils with quadrille pads.&#xA;  He recommended using the back sides of&#xA;  the pages so that the lines were not&#xA;  so dominant.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;When he was told that Apple had just&#xA;  bought a Cray to help design the next&#xA;  Mac, Seymour commented that he had&#xA;  just bought a Mac to design the next&#xA;  Cray.&quot;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;According to the &lt;a href=&quot;http://www.faqs.org/faqs/computer/system/cray/faq/&quot; rel=&quot;nofollow&quot;&gt;Cray Supercomputer FAQ&lt;/a&gt;, Apple's Cray did a lot of work in the design of the metal molds used to produce the outer case of Macintosh computers -- the Cray &lt;a href=&quot;http://www.thefreelibrary.com/MOLDFLOW+INJECTION+MOLDING+ANALYSIS+SOFTWARE+AVAILABLE+ON+CRAY...-a012353530&quot; rel=&quot;nofollow&quot;&gt;simulated the 3D flow of plastic&lt;/a&gt; and rendered it as Quicktime movies.&#xA;Although &lt;a href=&quot;http://www.clock.org/~fair/computers/sgi-cray.html&quot; rel=&quot;nofollow&quot;&gt;I hear&lt;/a&gt; that wasn't the original reason Apple bought the Cray.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-21T13:54:23.640" />
  <row Id="11783" PostTypeId="2" ParentId="11780" CreationDate="2011-03-21T13:55:47.620" Score="0" ViewCount="" Body="&lt;p&gt;A (probably Linux based but mbed and Arduino are also doable) board with WiFi and a HTTP server is also an option, given the recent improvements in HTML5, WebSockets and surrounding technologies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In case you are totally new to this I would suggest playing with DSP on a PC using you sound card first and then playing with an Arduino connected to the PC via serial port. You can get boggled down with unimportant stuff and difficult debugging if you just start on the phone.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T13:55:47.620" />
  <row Id="11784" PostTypeId="2" ParentId="11780" CreationDate="2011-03-21T15:29:50.513" Score="1" ViewCount="" Body="&lt;p&gt;One of the quickest ways to get started linking a micro to an Android phone is with the &lt;a href=&quot;http://www.amarino-toolkit.net/&quot; rel=&quot;nofollow&quot;&gt;Amarino toolkit&lt;/a&gt;.  You can use either the basic Android GUI or just the APIs to create some sort of application on the mobile device, then use their very basic libraries for an Arduino directly or port them (as I did) to some other micro.  All they do is send out some ASCII encoded data to the UART, which a basic Bluetooth transceiver sends off to the Android.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can just as well leave it behind and develop your own Bluetooth handler on the Android phone.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-21T15:29:50.513" CommentCount="2" />
  <row Id="11785" PostTypeId="2" ParentId="11768" CreationDate="2011-03-21T15:55:05.397" Score="1" ViewCount="" Body="&lt;p&gt;They (Apple) most likely use PCs and &lt;a href=&quot;http://en.wikipedia.org/wiki/Altium#Products&quot; rel=&quot;nofollow&quot;&gt;Altium&lt;/a&gt;, &lt;a href=&quot;http://en.wikipedia.org/wiki/OrCAD&quot; rel=&quot;nofollow&quot;&gt;OrCAD&lt;/a&gt;, or something of that type.  Given the tight integration with the enclosures in many Apple products I would think that Altium is the best fit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most professionals aren't into the entire 'fan boy' attitude.  You use whatever is the best tool for the job.  Apple doesn't even go after the workstation market from what I've seen outside the graphics/video/content creation fields.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In an example of what I mean, for a very long time www.micosoft.com was hosted on Linux servers.  It wasn't moved to Windows servers until they developed a web server OS that didn't suck (it took them awhile).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For hobby use &lt;a href=&quot;http://en.wikipedia.org/wiki/Eagle_%28program%29&quot; rel=&quot;nofollow&quot;&gt;Eagle&lt;/a&gt; and &lt;a href=&quot;http://www.diptrace.com/&quot; rel=&quot;nofollow&quot;&gt;DipTrace&lt;/a&gt; should be sufficient and run on Macs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can always just boot up a Windows VM and use whatever you want. Also, although Altium doesn't work all that well, it uses &lt;a href=&quot;http://en.wikipedia.org/wiki/Microsoft_Direct3D&quot; rel=&quot;nofollow&quot;&gt;Direct3D&lt;/a&gt; for rendering and VM performance isn't all that great yet. I am not sure if OrCAD is using any 3D rendering nowadays.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2011-03-21T21:23:53.260" LastActivityDate="2011-03-21T21:23:53.260" CommentCount="1" />
  <row Id="11786" PostTypeId="2" ParentId="11757" CreationDate="2011-03-21T16:09:22.523" Score="13" ViewCount="" Body="&lt;p&gt;Just look at the waveform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a sine wave goes through a complete cycle every t, and you full-wave rectify it, there will now be two upward humps in every t.  Since each hump is a complete cycle, you've doubled the frequency:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/x5lFz.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More generally, a perfect rectification means the response function has even symmetry.  This means the output will consist of only even-ordered harmonics, starting at the second harmonic, which is 2&amp;times; the fundamental&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Even_and_odd_functions#Harmonics&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Even_and_odd_functions#Harmonics&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-21T19:38:43.843" LastActivityDate="2011-03-21T19:38:43.843" />
  <row Id="11787" PostTypeId="2" ParentId="7163" CreationDate="2011-03-21T16:16:26.030" Score="2" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;The first book I would start with is &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0120887851&quot; rel=&quot;nofollow&quot;&gt;The Designer's Guide to VHDL&lt;/a&gt; by Peter J. Ashenden. Assuming that you are already familiar with programming, then this book is good reference to the VHDL language.&lt;/li&gt;&#xA;&lt;li&gt;Next I would continue with &lt;a href=&quot;http://www.amazon.com/gp/search?index=books&amp;amp;linkCode=qs&amp;amp;keywords=1402074018&quot; rel=&quot;nofollow&quot;&gt;Writing Testbenches: Functional Verification of HDL Models&lt;/a&gt; by Janick Bergeron. It does not only cover VHDL, but focuses on a number of topics that are important when writing test benches and code for verification. I think it does a better job of emphasizing the difference between VDHL for simulation and VHDL for synthesis than &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0120887851&quot; rel=&quot;nofollow&quot;&gt;The Designer's Guide to VHDL&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;After that I would recommend studying the HDL coding guidelines provided by you FPGA vendor. The provide a lot of useful tips on how to write your VHDL code so that it efficiently maps in to the hardware primitives found in the particular device you are targeting.&lt;/li&gt;&#xA;&lt;li&gt;And finally: Download, read, and understand real-world code. I've found the &lt;a href=&quot;http://www.gaisler.com/cms/index.php?option=com_content&amp;amp;task=section&amp;amp;id=13&amp;amp;Itemid=125&quot; rel=&quot;nofollow&quot;&gt;GRLIB IP Library&lt;/a&gt; a useful source of inspiration. GRLIB is an open-source SoC library based on the SPARC processor from SUN.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1627" LastActivityDate="2011-03-21T16:16:26.030" />
  <row Id="11790" PostTypeId="1" AcceptedAnswerId="11799" CreationDate="2011-03-21T19:32:13.397" Score="12" ViewCount="252" Body="&lt;p&gt;Hello &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking for supplier for RGB LEDs for an upcoming project &lt;a href=&quot;http://www.abluestar.com/blog/rgb-led-pov-globe-research/&quot; rel=&quot;nofollow&quot;&gt;RGB POV LED Globe&lt;/a&gt;. Normally I would go to my local electronics supply story, but this project requires lots (~1000) of LEDs and my local electronics store charges a premium for the LEDs, (@1.50 each) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have done some searching online from a few retailers such as &lt;a href=&quot;http://www.alibaba.com&quot; rel=&quot;nofollow&quot;&gt;http://www.alibaba.com&lt;/a&gt; (~$0.19) or &lt;a href=&quot;http://ledssuperbright.com&quot; rel=&quot;nofollow&quot;&gt;http://ledssuperbright.com&lt;/a&gt; (&lt;a href=&quot;http://www.ledssuperbright.com/100-5mm-4-pin-rgb-led-4000-mcd-p-227&quot; rel=&quot;nofollow&quot;&gt;$0.35&lt;/a&gt;) or &lt;a href=&quot;http://www.adafruit.com&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com&lt;/a&gt; (&lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;products_id=302&amp;amp;zenid=9d36137d8bb2f6da9071f934d4cd405f&quot; rel=&quot;nofollow&quot;&gt;$1.0&lt;/a&gt;) or &lt;a href=&quot;http://www.sparkfun.com&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com&lt;/a&gt; (~&lt;a href=&quot;http://www.sparkfun.com/products/9985&quot; rel=&quot;nofollow&quot;&gt;$0.6&lt;/a&gt;) or &lt;a href=&quot;http://www.digikey.com&quot; rel=&quot;nofollow&quot;&gt;http://www.digikey.com&lt;/a&gt; (&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=754-1492-ND&quot; rel=&quot;nofollow&quot;&gt;~$1.1&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I trust adafruit and sparkfun and have had good experiences from both of them in the past but I am worried that there is a such a huge range in price difference between each of these sites that I might be missing something critical. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also I looked at other POV projects and some use diffuse others use clear LED. I'm not sure what type of LED I should use for this project. The &lt;a href=&quot;http://www.ladyada.net/make/minipov3/parts.html&quot; rel=&quot;nofollow&quot;&gt;MiniPov3&lt;/a&gt; uses diffuse. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;What make a good RGB LED? &lt;/li&gt;&#xA;&lt;li&gt;What features should I be looking for in the data sheet for this type of project.&lt;/li&gt;&#xA;&lt;li&gt;Should I use diffuse or clear LEDs on my &lt;a href=&quot;http://www.abluestar.com/blog/rgb-led-pov-globe-research/&quot; rel=&quot;nofollow&quot;&gt;RGB POV LED Globe&lt;/a&gt; project? &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="592" LastEditorUserId="592" LastEditorDisplayName="" LastEditDate="2011-03-21T19:44:07.520" LastActivityDate="2011-03-21T21:24:15.693" Title="What makes a good RGB LED." Tags="&lt;led&gt;&lt;rgb&gt;&lt;pov&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="6" />
  <row Id="11791" PostTypeId="1" CreationDate="2011-03-21T19:51:54.530" Score="4" ViewCount="311" Body="&lt;p&gt;I want to create a power meter and use arduino to log the info and send to the web. Is there any easy solution to the power meter? I live in Argentina and the power line is 220V. Thanks&lt;/p&gt;&#xA;" OwnerUserId="3479" LastActivityDate="2011-03-22T12:01:28.280" Title="Arduino power meter" Tags="&lt;arduino&gt;&lt;power-meter&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="2" />
  <row Id="11792" PostTypeId="2" ParentId="11791" CreationDate="2011-03-21T19:57:21.660" Score="5" ViewCount="" Body="&lt;p&gt;You might check out &lt;a href=&quot;http://www.ladyada.net/make/tweetawatt/&quot; rel=&quot;nofollow&quot;&gt;Tweet-a-Watt&lt;/a&gt; and see if it will work with your 220V power line.  That project should at least give you an idea of how to get started.&lt;/p&gt;&#xA;" OwnerUserId="2724" LastActivityDate="2011-03-21T19:57:21.660" CommentCount="3" />
  <row Id="11793" PostTypeId="2" ParentId="11791" CreationDate="2011-03-21T20:07:15.370" Score="1" ViewCount="" Body="&lt;p&gt;You could use HAL effect sensor (10-30e maybe?) with arduino board. &lt;a href=&quot;http://en.wikipedia.org/wiki/Hall_effect_sensor&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Hall_effect_sensor&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3483" LastActivityDate="2011-03-21T20:07:15.370" />
  <row Id="11794" PostTypeId="2" ParentId="10909" CreationDate="2011-03-21T20:08:45.493" Score="1" ViewCount="" Body="&lt;p&gt;For more information see &lt;a href=&quot;http://webcast.berkeley.edu/course_details_new.php?seriesid=2009-D-51950|2009-D-69330&amp;amp;semesterid=2009-D&quot; rel=&quot;nofollow&quot;&gt;Physics for Future Presidents&lt;/a&gt; lectures (especially the first one) from Berkeley. There is lots of information about various forms of energy that will surprise even the engineers among us.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-21T20:08:45.493" />
  <row Id="11795" PostTypeId="2" ParentId="11728" CreationDate="2011-03-21T20:27:16.330" Score="3" ViewCount="" Body="&lt;p&gt;You probably have a human research review board to pass you decision thru (at least in the us ).  Batteries are often the simplest safe power supply.  You still need to isolate from any other electrical source, probably including your network.  Check with the review criteria.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-21T20:27:16.330" />
  <row Id="11796" PostTypeId="2" ParentId="11774" CreationDate="2011-03-21T20:33:20.297" Score="1" ViewCount="" Body="&lt;p&gt;Jan Decaluwe wrote an entire white paper on the problems of integers versus bit vectors. I expect his answers would be to &lt;em&gt;use integers whenever possible&lt;/em&gt;.&#xA;&lt;a href=&quot;http://www.jandecaluwe.com/hdldesign/counting.html&quot; rel=&quot;nofollow&quot;&gt;http://www.jandecaluwe.com/hdldesign/counting.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3145" LastActivityDate="2011-03-21T20:33:20.297" />
  <row Id="11797" PostTypeId="2" ParentId="11750" CreationDate="2011-03-21T20:37:31.373" Score="5" ViewCount="" Body="&lt;p&gt;A pole is a frequency where a filter resonates and would, at least mathematically, have infinite gain.   A zero is where it blocks a frequency - zero gain.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A simple DC blocking capacitor, such as for coupling audio amplifiers, has a zero at the origin - it blocks 0Hz signals, that is, blocks constant voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, we're dealing with complex frequencies. We consider not just signals that are sums of sine/cosine waves, like Fourier did; we theorize about exponentially growing or decaying sines/cosines.  Poles and zeros representing such signals can be anywhere in the complex plane.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a pole is close to the real axis, which represents normal steady sine waves, that represents a sharply tuned bandpass filter, like  a high quality LC circuit.  If it's far, it's a mushy soft bandpass filter with a low 'Q' value.  The same kind of intuitive reasoning applies to zeros - sharper notches in the response spectrum occur where zeros are close to the real axis.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The transfer function L(s) describing a filter's response should have equal numbers of poles and zeros.  This is a basic fact in complex analysis, valid because we're dealing with linear lumped components described by simple algebra, derivatives and integrals, and we can describe sines/cosines as complex exponential functions. This kind of math is analytic everywhere.   It is common to not mention poles or zeros at infinity, however.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Either entity, if not on the real axis, will appear in pairs - at a complex frequency and at its complex conjugate.  This relates to the fact that a real signals in result in real signals out.  We don't measure complex number voltages.  (Things get more interesting in the microwave world.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If L(s)= 1/s, that is a pole at the origin and a zero at infinity.  This is the function for an integrator.  Apply a constant voltage, and the gain is infinity - the output climbs without limit (until it reaches the supply voltage or the ciruit smokes).  At the opposite end, putting a very high frequency into an integrator won't have any effect; it gets averaged out to zero over time.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Poles in the &quot;right half plane&quot; represents a resonance at some frequency that makes a signal grow exponentially.  So you want poles in the left half plane, meaning that for any arbitrary signal put into the filter, the output will ultimately decay to zero.   That's for a normal filter.  Of course, oscillators are supposed to oscillate. They maintain a steady signal due to nonlinearities - transistors can't put out more than Vcc or less than 0 volts for output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you look at a frequency response plot, you might guess that every bump corresponds to a pole, and every dip to a zero, but that's not strictly true.  and poles and zeros far from the real axis have effects that aren't apparent in that way.  It would be nice if someone invented a Flash or java web applet that let you move several poles and zeros around anywhere, and plot the response.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;All this is oversimplified, but should give some intuitive idea about what poles and zeros mean.&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2011-03-21T20:37:31.373" />
  <row Id="11798" PostTypeId="2" ParentId="6778" CreationDate="2011-03-21T21:03:47.467" Score="2" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;If the power supply has a range switch on the back (115/230), it most likely does not have PFC and you'll have a better chance of powering it up directly from DC. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Make sure that all fuses are rated for the DC voltage you intend to apply.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Do not exceed the expected RMS AC voltage with the DC input - if it expects 208VAC go with 208VDC. RMS is the 'equivalent' of DC as far as power dissipation goes, after all. This will make it less likely that you're going to damage anything downstream from the input.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Yes, you're only using two rectifiers in the input bridge, so they'll see higher power (since they won't be off half of the time) - you may have to upgrade the bridge rectifier to a higher-rated part, or simply jumper the low-side diode and install a single, large (with heatsink) diode on the HVDC side. I wouldn't recommend &lt;em&gt;not&lt;/em&gt; using a diode.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Make sure you have some sort of switch that can cut off the HVDC if something goes south, and make sure it's rated for the DC voltage you're applying.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;This goes without saying, but: HVDC is VERY effective at killing people. Insulate everything 2-3x more than you think you need to before even considering turning anything on. If the power's on, keep your hands off. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-21T21:03:47.467" CommentCount="8" />
  <row Id="11799" PostTypeId="2" ParentId="11790" CreationDate="2011-03-21T21:24:15.693" Score="12" ViewCount="" Body="&lt;p&gt;Forewarning: You can do this the easy way, or the hard way. &lt;strong&gt;The easy way is to pick an RGB LED that has good stocking at all the major distributors, try it, and be happy.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The hard way is to learn a little bit about &lt;a href=&quot;http://en.wikipedia.org/wiki/Photometry_%28optics%29&quot; rel=&quot;nofollow&quot;&gt;photometry&lt;/a&gt;, which is the study of measuring light, and then make your decision.  No guarantees that the latter will produce better results, though.  But, it's probably best to know a little background, so here we go. Warning: Long post.&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;&lt;strong&gt;Basic Criteria&lt;/strong&gt;&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;The basic criteria for selecting an LED are, ignoring color for now:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Intensity/brightness&lt;/li&gt;&#xA;&lt;li&gt;Viewing angle&lt;/li&gt;&#xA;&lt;li&gt;Lens style (clear/diffuse/external)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;From the top: &lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Intensity/Brightness&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;This is a measurement of how bright you want your LED to be, and is startlingly complex. For an RGB LED, you'll probably find it easiest to first specify the viewing area, and then select the number of lumens you need.  This selection will probably be experimental, especially since you want to do it at Burning Man, which has a really bright environment.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are two ways to measure intensity: Radiometrically and photometrically.  The watt is a radiometric measurement for power, defined by the metric system in terms of electronics as: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;$W = A^2 * \Omega $  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In words, the power dissipated by one amp of current flowing through a one ohm resistance.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Photometric measurements define how bright a source appears to the eye. The candela (or, for LEDs, the millicandela or mcd) measures the intensity in a direction.  The lumen is a measurement of power, and is defined as one candela over one steradian of area (a steradian is a cone about $64^o$ across).  Both are weighted with respect to the radiometric units by the luminosity curve, which looks something like this (dotted black line):  &lt;/p&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://upload.wikimedia.org/wikipedia/commons/a/a0/Luminosity.png&quot; alt=&quot;luminosity curve&quot;&gt;&lt;/p&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Notice that it peaks around 550nm, or the color green.  What this means is that your red and blue colors need to have high wattage ratings to get even coloration.  If you use the millicandella ratings (for a variety of viewing angles) or the lumen ratings (if you've already selected a set of similar viewing angles), you don't have to worry about this curve.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're still paying attention, don't worry, the rest is more straightforward and shorter.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Viewing angle&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;The viewing angle is the maximum inclination that you can have with respect to the LED and still see the color emitted.  This is a function of the lens, and isn't always uniformly distributed.  For a diffused (cloudy) lens, if you can see the lens, you can see the color, if only a little bit.  The viewing angle is not necessarily this number; they're usually more realistic and only define the area which the lens is designed to illuminate.  For a clear lens, optical properties of the lens will define the viewing angle more rigidly.  Hint: It's not 180 degrees for the T 1 3/4 package (the standard 5mm LED you showed in most of your links - that's usually no more than $30^0$).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a POV globe, you probably want a fairly wide viewing angle.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Lens Style&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Lenses can be tinted or colorless. For an RGB LED, you probably want colorless. They can also be water-clear or diffused (cloudy).  Your choice in this selection will depend on the viewing angle of the LEDs.  A diffused lens will help to eliminate bright spots, but will also reduce the effectiveness of any focusing the lens is designed to do.  If you get an LED with a spherical lens, it needs to be diffused, or you'll blind your users as it spins, and it will be hard to see in others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also need to decide whether you want an integrated or external lens.  Some superbright LEDs will have an external lens which allows higher quality optics but costs more and requires more components.  For this project, you almost certainly want an integrated lens.&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;&lt;strong&gt;Electrical Properties&lt;/strong&gt;&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;Next, you need to consider the electrical properties: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Current, both nominal/test and maximum (Will be different for each color of an RGB LED)&lt;/li&gt;&#xA;&lt;li&gt;Forward voltage $V_F$ (will be different for each color of an RGB LED)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;h2&gt;Current&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;An LED creates light by dissipating power across a semiconductor junction.  Below a certain current, the electrons aren't boosted to the next shell, and you get no light.  Above a certain current, you destroy your device.  By modulating the (average) current between these two values, you can get varying degrees of intensity.  This is a non-linear function with respect to light intensity, but you can get a more linear function by using a constant current and rapidly pulsing the LED on and off.  This technique is known as pulse-width modulation, or PWM.  If your PWM never exceeds a given duty cycle, and is sufficiently fast, you can set the constant current at which would, at steady-state, exceed the maximum power rating of your LED.  This doesn't usually get you a brighter average, though. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to select LEDs whose current requirements are within the limits of your drive circuit and whose power requirements are sustainable using your chosen power source.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Forward voltage&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;The forward voltage will be different for each color in the LED.  This just complicates the calculation of the current a bit.  If you're using a resistor to set the current, and the LEDs are common-anode, you should probably select LEDs with similar forward voltages to minimize power losses in the resistors.  Be aware that the forward voltage is a function of the forward current!&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;&lt;strong&gt;Standard stuff&lt;/strong&gt;&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;Then, there are the generic properties that you need to select for any electronic device: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Package&lt;/li&gt;&#xA;&lt;li&gt;Soldering temperature&lt;/li&gt;&#xA;&lt;li&gt;Manufacturer/Supplier&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;h2&gt;Package&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;You may be tempted to use a standard T 1 3/4 5mm dome package.  Don't accept this unless you're sure that it's what you want.  To get 4 leads under this package, you need small, tight holes (soldering and PCB manufacturing will be hard), and the optical properties are less than optimal.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a plethora of surface mount packages which are lower profile and lower weight (which is desirable if you want to spin your project) and which have high viewing angles without using diffused lenses. &lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Soldering temperature&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;LEDs are some of the most sensitive components to heat when soldering because of the optical requirements of their lenses and because of the unique semiconductors used to generate the light.  Be careful if you're using anything but a temperature regulated soldering iron or oven for this.  &lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Manufacturer and distributor&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;For a one-off project or prototype, Adafruit or Sparkfun products are fine, but (1) you'll pay a premium for their selection and endorsement and (2) you're out of luck if they drop the product.  The hobbyist sites are fine if you're making a one-off product, but if you want to distribute plans, make sure a compatible LED is widely available.  Otherwise, contact Cree, Avago, or Lite-On (or your favorite manufacturer) directly, or use a major distributor like Digikey or Mouser.  You'll have better luck and get better prices by buying in bulk and skipping the middleman.&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;&lt;strong&gt;Color&lt;/strong&gt;&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;One of the most important factors to consider is color, but RGB LEDs basically define that for you.  You do need to consider the relationships between each color in your selection, but this can usually be accounted for in software.  For instance, the human eye detects green much better than it detects blue, and red LEDs are usually more efficient than blue.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In addition to the relative power between the colors, you need to consider the spectral information.  Many manufacturers have different definitions of each color - Red might be any light with a wavelength between 629nm (an orangey red) and 660nm, green could be from 515nm to 565nm, and blue could be anywhere from 430nm to 470nm (a greenish blue).  And that's just the nominal peak! This isn't a laser, so not every ray of light coming from it has the same wavelength -there is an irregular distribution of the wavelength for each color.  A red LED will emit a tiny amount of blue light, and vice versa.   &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-21T21:24:15.693" CommentCount="7" />
  <row Id="11800" PostTypeId="2" ParentId="11791" CreationDate="2011-03-21T21:47:09.380" Score="1" ViewCount="" Body="&lt;p&gt;This system from &lt;a href=&quot;http://www.smartenergygroups.com/&quot; rel=&quot;nofollow&quot;&gt;Smart Energy Groups&lt;/a&gt; may be of interest, it is based around Arduino hardware and so on. &lt;/p&gt;&#xA;" OwnerUserId="1307" LastActivityDate="2011-03-21T21:47:09.380" />
  <row Id="11801" PostTypeId="2" ParentId="3345" CreationDate="2011-03-21T21:50:02.297" Score="0" ViewCount="" Body="&lt;p&gt;If you're in Europe (or even if not), then I'd consider the IGEPv2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.igep.es/index.php?option=com_content&amp;amp;view=article&amp;amp;id=46&amp;amp;Itemid=55&quot; rel=&quot;nofollow&quot;&gt;http://www.igep.es/index.php?option=com_content&amp;amp;view=article&amp;amp;id=46&amp;amp;Itemid=55&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's based on the Beagle, but got more built-in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought a Beagle from the US (I was in the UK), and ended up wishing I'd got the IGEPv2. I still love the Beagle, but I think this would have been better!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Europe note: When I received my Beagle from the US, I also received a tax bill from FedEx, which was a nasty surprise.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As it happens, I'm using the Beagle as a part-time desktop, part-time robot brain (and part-time cupboard-dweller). It works well for all these.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;HTH&lt;/p&gt;&#xA;" OwnerUserId="3500" LastActivityDate="2011-03-21T21:50:02.297" />
  <row Id="11802" PostTypeId="2" ParentId="11791" CreationDate="2011-03-21T22:14:15.087" Score="1" ViewCount="" Body="&lt;p&gt;Creating an accurate power meter is not a trivial task. You need a way of sensing the voltage and current with sufficient accuracy and speed that you can detect phase differences between them (power factor) and calculate the real and apparent power. You would almost want a DSP for this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Creating a rudimentary power meter can be done by sensing and DC averaging the voltage and current, ignoring reactive power and the need to sample at high speeds. Accuracy will vary as a function of the quality of the load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are ICs on the market specifically for power metering, like the &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en520376&quot; rel=&quot;nofollow&quot;&gt;Microchip MCP3909&lt;/a&gt; which you may be able to use with your Arduino.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-21T22:14:15.087" />
  <row Id="11803" PostTypeId="2" ParentId="11728" CreationDate="2011-03-21T22:56:58.840" Score="1" ViewCount="" Body="&lt;p&gt;The Power over Ethernet (PoE) is likely most suitable if the devices are network-aware, otherwise one Ethernet cable is pretty much equivalent to a (low current) power cord or a USB cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For any devices that to be &quot;worn&quot; or &quot;attached&quot; by test subjects, I would strongly consider an un-tethered design, powered using rechargeable batteries. For small signal (i.e. sensors, data logging, no motors, very simple LED lighting) this option should be easily economic and practical for up to 24 hour periods or longer. &lt;a href=&quot;http://en.wikipedia.org/wiki/Nickel-metal_hydride_battery&quot; rel=&quot;nofollow&quot;&gt;NiMH&lt;/a&gt; would be my first choice due to low cost and wide availability, with Lithium as a second. Just ensure you use an appropriate charger for the battery type, and things should just work. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Note&lt;/strong&gt; that most rechargeable batteries such as 'AA' size cells, only provide 1.2 rather than 1.5 volts, so 4 of them is not sufficient for 5V needed to stably power an Arduino, while non-rechargeable (i.e. disposable) cells such as alkaline or zinc-carbon would.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With electricity you need to be aware of both voltage and current. The Arduino itself takes an input range of 7-12 DC, up to 500mA (I don't have a reference on average / typically current, but would guess around 100-125mA or less), from an external DC power source. The USB port can also be used to draw 5 volts, up to 500mA from a powered USB hub or powered USB port. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a low-cost low current (e.g. 250-500 mA &lt;em&gt;output&lt;/em&gt;) AC-DC power adapter (&lt;em&gt;wall wart&lt;/em&gt;) would be a default method if there is non-trivial power consumption, or needs to continuously operate for a long period of time. &#xA;A modern switch mode power supply (SMPS) based unit can be had for a modest cost, and is light weight, being able to dispense with the need for a large power transformer encased in it. Combined with the power limiting capabilities already included in the Aruino (UNO) from the &lt;a href=&quot;http://www.littelfuse.com/resettable_fuse.html&quot; rel=&quot;nofollow&quot;&gt;resettable fuse&lt;/a&gt; (PTC, I believe) used for USB power source, and/or the linear voltage regulator used to regulate power from a AC-DC power adapter which also includes over-voltage, current limiting, and short circuit protection unless you need addition power requirements (e.g. motors, high power LEDs) you can use the protection built into the Arduino as sufficient for electrical shock/burn protection. &lt;/p&gt;&#xA;" OwnerUserId="2598" LastEditorUserId="2598" LastEditorDisplayName="" LastEditDate="2011-03-23T21:35:32.730" LastActivityDate="2011-03-23T21:35:32.730" CommentCount="2" />
  <row Id="11804" PostTypeId="2" ParentId="11625" CreationDate="2011-03-21T23:28:16.773" Score="2" ViewCount="" Body="&lt;p&gt;I fixed my overheating linear regulator just by adding a big chunky heatsink. I lifted the regulator out of the PCB, attached hook up wire to the leads, and mounted it on a big chunk of metal I cut from an old power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've run it for about 4 hours and it's only slightly warm... problem solved!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/buXJj.jpg&quot; alt=&quot;circuit with big heatsink&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-21T23:28:16.773" CommentCount="1" />
  <row Id="11805" PostTypeId="1" AcceptedAnswerId="11822" CreationDate="2011-03-22T01:38:17.610" Score="2" ViewCount="162" Body="&lt;p&gt;If you are trying to control memory from a CPU, then if you use two banks instead of one, you can remove the first address line. If you use four banks, then you can also remove the second as well. Why is this?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-03-23T19:54:00.630" Title="Reducing the memory address bus by adding banks" Tags="&lt;memory&gt;&lt;cpu&gt;&lt;addressing&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="11806" PostTypeId="1" AcceptedAnswerId="11809" CreationDate="2011-03-22T01:43:42.363" Score="2" ViewCount="103" Body="&lt;p&gt;Hello guys...I am a neewbie here so don't cush me yet but I have a question concering stepper motors and Microcontrollers (more specificaly PIC16F84A). Does anyone know how to Inteface these two devices? &#xA;Steppers - &lt;a href=&quot;http://www.sparkfun.com/products/9238&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/9238&lt;/a&gt;&#xA;Microcontroller - &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010230&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010230&lt;/a&gt;&#xA;Thanks in advance - James&lt;/p&gt;&#xA;" OwnerUserId="3140" LastActivityDate="2011-03-22T02:54:03.147" Title="Intefacing a PIC Mircocontroller (PIC16F84A) to two stepper motors" Tags="&lt;microcontroller&gt;&lt;stepper&gt;&lt;interface&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="11807" PostTypeId="2" ParentId="11734" CreationDate="2011-03-22T02:30:18.973" Score="3" ViewCount="" Body="&lt;p&gt;Depending on the definition of 'flow of charge':&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your wall outlets and anything else involving AC voltage.  The electron drift velocity is zero at the macro level, at the micro level electrons wobble back and forth and therefore have a non-zero drift velocity at a particular point in time. Energy is transfered via EM waves in AC circuits.  In practice there is always a small DC offset so there is some 'macro scale' electron drift down the wires.  However, its not the primary mechanism of current flow and is very slow, like an inch a day depending on the offset.  You can, correctly, argue that electrons are still the charge carrier here, but i guess i wouldn't describe this as a flow of charge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even thinking about current purely as electron flow under DC voltage isn't a good or accurate way to think of it.  Electron drift velocity is very slow, depending on the voltage and of course the material it can be inches per &lt;em&gt;hour&lt;/em&gt;.  Of course we know that 'electricity' moves much faster than this which is because current is the result of sorta 'bumping' the charge along the conductor rather than requiring a specific electron to 'flow' all the way down the conductor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In electrolytic capacitors the primary charge carriers are ions.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2011-03-22T04:54:08.637" LastActivityDate="2011-03-22T04:54:08.637" />
  <row Id="11808" PostTypeId="2" ParentId="11734" CreationDate="2011-03-22T02:42:30.063" Score="1" ViewCount="" Body="&lt;p&gt;Electrolytic capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dielectric has currents &quot;flowing&quot; in it...&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-03-22T02:42:30.063" CommentCount="1" />
  <row Id="11809" PostTypeId="2" ParentId="11806" CreationDate="2011-03-22T02:54:03.147" Score="3" ViewCount="" Body="&lt;p&gt;This should do what you want:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/10267&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/10267&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will need to connect the Direction and Step pins to I/O pins on the microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="3427" LastActivityDate="2011-03-22T02:54:03.147" CommentCount="1" />
  <row Id="11810" PostTypeId="2" ParentId="11805" CreationDate="2011-03-22T03:01:15.173" Score="3" ViewCount="" Body="&lt;p&gt;I'm going to assume that you're talking about parallel memory, and that when you say &quot;use two banks instead of one&quot; you are using two chips that have the same total memory, but each are half as large.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the thing: you can't actually remove that address line from your CPU. It might not go directly to the memory chip, but if you remove it there is no way to distinguish between the two chips. The missing ingredient is the &quot;chip select&quot; function. Most memory chips will have a pin or set of pins that are used to basically tell that particular memory chip that the processor want to talk to only that chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lets consider a simple example: 256 words of memory. This results in an 8-bit address bus. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;One chip with 256 words: then we are always using only one chip, and it has an 8-bit address. &lt;/li&gt;&#xA;&lt;li&gt;Two chips with 128 words each: Only one memory can be active at the same time, so we will be using the &quot;chip select&quot; pin. The MSB (Most Significant Bit) of the 8-bit address bus will go to the chip select pin on each chip, and the rest of the 7 bits will go to the 7-bit address bus on both chips.&lt;/li&gt;&#xA;&lt;li&gt;Four chips with 64 words each: Only one memory can be active at the same time, so we will be using the &quot;chip select&quot; pin. Some memory chips have multiple chip select pins, but for this example we will assume there is only one. In order to generate the chip select signals for all four chips, we will need a 2-to-4 decoder (also known as a $n\mbox{ }to\mbox{ } 2^{n}$ decoder, row decoder, address decoder - all the same things). This decoder takes the first two MSB from the address bus, and determines which chip select signal should be active. The lower 6 bits of the address go to the 6-bit address bus of all 4 memory chips.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WFJsx.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a really simple example, but it scales fine. This is basically the procedure for making multiple memory chips work together to increase the address space.&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-03-23T09:14:28.430" LastActivityDate="2011-03-23T09:14:28.430" CommentCount="4" />
  <row Id="11811" PostTypeId="1" AcceptedAnswerId="11814" CreationDate="2011-03-22T04:20:59.807" Score="6" ViewCount="214" Body="&lt;p&gt;I'd like to run a stepper motor at a very smooth, constant speed, with minimal vibrations to both the mount holding it and its output. How do I drive the stepper motor so that speed remains constant, even between steps?&lt;/p&gt;&#xA;" OwnerUserId="2240" LastActivityDate="2011-03-22T16:25:46.937" Title="How do you minimize stepper motor vibration?" Tags="&lt;stepper-motor&gt;&lt;speedcontroller&gt;" AnswerCount="5" CommentCount="5" FavoriteCount="4" />
  <row Id="11812" PostTypeId="2" ParentId="11811" CreationDate="2011-03-22T05:15:40.430" Score="1" ViewCount="" Body="&lt;p&gt;I can only suggest reductors, if speed is not a limiting factor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise I would go for brush-less motors with some feedback.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-22T05:15:40.430" CommentCount="3" />
  <row Id="11813" PostTypeId="1" AcceptedAnswerId="12030" CreationDate="2011-03-22T05:47:18.933" Score="2" ViewCount="453" Body="&lt;p&gt;I have an 220V air compressor (30A) in the attic of my garage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has a 110V automatic drain valve connected to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A the breaker box downstairs I want to be able to turn the power off to BOTH. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally I could simply turn off the 220V circuit (the compressor is the only load).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 220V circuit is single phase and the receptacle is a &lt;a href=&quot;http://en.wikipedia.org/wiki/NEMA_connector&quot; rel=&quot;nofollow&quot;&gt;NEMA 14-50&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is my understanding that this is a &lt;a href=&quot;http://en.wikipedia.org/wiki/Split_phase&quot; rel=&quot;nofollow&quot;&gt;split-phase 3-wire system&lt;/a&gt;.  It's really 4-wires:  Ground, Neutral, Leg 1 (110V), Leg 2 (110V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I want to know is if there is any problem with me using one of the two legs (plus ground &amp;amp; neutral) to power a 110V outlet for the automatic drain valve.  I'm 99% sure there's no technical problem.  I just want to double check on any safety issue or something I may not be aware of (as a DIY). &lt;/p&gt;&#xA;" OwnerUserId="2604" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-22T12:46:31.110" LastActivityDate="2011-03-28T02:03:05.197" Title="Have 60A 220V circuit, want to use one 110V leg of it. Can i?" Tags="&lt;line-power&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="11814" PostTypeId="2" ParentId="11811" CreationDate="2011-03-22T05:57:14.213" Score="12" ViewCount="" Body="&lt;p&gt;What you need is sinusoidal current drive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In other words, you have to treat the motor like a traditional brushless motor, rather then a stepper. This requires pretty specialized stepper drivers, and is not simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A simpler alternative might be to try microstepping the stepper motor, but that won't get you perfectly smooth rotation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Really, for situations where you need extremely smooth rotary motion, a stepper is really just the wrong control system. You should use a brushless AC motor, or at least a brushed DC servomotor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.qcontrol.com/SP/WP/QCI-WP003_ServoControlOfMicrostepMotor.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a decent white-paper on stepper drive modalities, with some contrasting to AC synchronous motors.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-03-22T09:33:43.090" LastActivityDate="2011-03-22T09:33:43.090" CommentCount="11" />
  <row Id="11816" PostTypeId="1" AcceptedAnswerId="11817" CreationDate="2011-03-22T07:28:39.407" Score="5" ViewCount="342" Body="&lt;p&gt;I wanted to create a remote fired trigger for a spud gun so I can trigger it remotely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally I'd like to use a spark plug to fire because it should work well for gas mixtures but the trigger is pretty small/simple. Basically it's a a little remote box with a push button trigger that runs off of batteries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has a light, arm switch, and push button that triggers a relay but I currently don't have anything connected on the relay switch end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would it be possible to charge up some caps and get enough juice to bridge a spark plug with a small battery source (4 AAA or AA batteries) or would I need to step it up to something bigger (lipo or lead acid).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Note: I have used caps for filtering before but never for charging/discharging.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Just wanted to clarify. I know that a gas grill push-button igniter is a viable option but I'm looking for something more reliable. Ie, an igniter that I'm 100% positive it'll fire a good spark when I push the button. Check out &lt;a href=&quot;http://www.youtube.com/watch?v=Mr1k4G0T-3U&quot; rel=&quot;nofollow&quot;&gt;&quot;Tater gun Fires a Hunert yards&quot;&lt;/a&gt; to see what I mean by unreliable.&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="1866" LastEditorUserId="1866" LastEditorDisplayName="" LastEditDate="2011-03-23T08:30:20.350" LastActivityDate="2011-03-23T08:30:20.350" Title="Is it possible to fire a spark plug from batteries" Tags="&lt;capacitor&gt;&lt;charging&gt;&lt;discharge&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="11817" PostTypeId="2" ParentId="11816" CreationDate="2011-03-22T08:09:25.053" Score="6" ViewCount="" Body="&lt;p&gt;The answer for automotive spark plugs is no with a normal battery. But with a 9v battery by stepping up the current using a ignition coil (which ramps it up thousands of volts) then you will be able to use a spark plug....Only thing with that though is that your battery (9v) won't last long, as its &quot;Juice&quot; will be all gone in a few shots. Hope this made sense :) just tell me if not....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could make a spark though with your normal everyday disposable camera....Something like this: &lt;a href=&quot;http://www.angelfire.com/80s/sixmhz/camera.html&quot; rel=&quot;nofollow&quot;&gt;http://www.angelfire.com/80s/sixmhz/camera.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S: If you used a larger battery (more volts) then you would have more juice :) &lt;/p&gt;&#xA;" OwnerUserId="3140" LastActivityDate="2011-03-22T08:09:25.053" CommentCount="18" />
  <row Id="11818" PostTypeId="2" ParentId="11816" CreationDate="2011-03-22T08:38:53.317" Score="1" ViewCount="" Body="&lt;p&gt;We have a gas oven. That uses a piezoelectric crystal and a 1.5V battery to light a spark. It's not a spark plug per se, but perhaps you could use a similar setup.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-22T08:38:53.317" CommentCount="4" />
  <row Id="11819" PostTypeId="2" ParentId="11811" CreationDate="2011-03-22T08:46:24.540" Score="4" ViewCount="" Body="&lt;p&gt;Using full step driving, the rotor acts much like a &lt;a href=&quot;http://en.wikipedia.org/wiki/Harmonic_oscillator#Spring.E2.80.93mass_system&quot; rel=&quot;nofollow&quot;&gt;Spring-Mass-System&lt;/a&gt;, with the rotor being the mass and the magnetic force being the spring. When you move from one step to the next, the motion will always be rough. The rotor pretty much jumps from one step to the next and it takes some time until the spring dampens out the rotor's energy, causing a little oscillation (read: &lt;em&gt;rough motion&lt;/em&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can smooth this when you use half-step mode, and you can additionally compensate the torque-nonlinearity, cf. &lt;a href=&quot;http://www.phytron-elektronik.de/antrieb/index.php?Set_ID=349&amp;amp;tl_id=27&amp;amp;PHPSESSID=cc9d1405dfb677f2e3d4bb0f6c5c9f7f&quot; rel=&quot;nofollow&quot;&gt;this link&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Following this logic, you eventually end up using fine-Stepping, micro-stepping and sinusoidal driving. (&lt;a href=&quot;http://www.phytron-elektronik.de/antrieb/index.php?Set_ID=349&amp;amp;tl_id=29&amp;amp;suchbegriff=Micro%20Step&amp;amp;PHPSESSID=cc9d1405dfb677f2e3d4bb0f6c5c9f7f&quot; rel=&quot;nofollow&quot;&gt;See this link for micro-stepping&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Some more details:&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;The resonant frequency of a stepper motor's rotor is usually somewhere around 50 Hz ... 400 Hz. When you drive the motor in full-step mode at its own mechanical resonant frequency, things will get pretty bad and it is likely that you lose (jump over) steps. For slow speeds, it is a good idea to stay below the motor's resonant frequency. For high speeds, try to get beyond the resoncance as fast as you can while accelerating, and don't use full-step driving.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-03-22T08:54:15.373" LastActivityDate="2011-03-22T08:54:15.373" />
  <row Id="11821" PostTypeId="2" ParentId="11811" CreationDate="2011-03-22T10:13:35.243" Score="0" ViewCount="" Body="&lt;p&gt;See &lt;a href=&quot;http://www.geckodrive.com/ark-2/support.html&quot; rel=&quot;nofollow&quot;&gt;the Geckodrive support page&lt;/a&gt;, especially the Application Notes-&gt;Step Drivers-&gt;How Morphing Works (sorry, it seems impossible to link directly). The Step Motor Basics are also useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically if you want to go fast enough then two things happen:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;You do not need microstepping.&lt;/li&gt;&#xA;&lt;li&gt;You lose most of the torque of the motor.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-22T16:25:46.937" LastActivityDate="2011-03-22T16:25:46.937" />
  <row Id="11822" PostTypeId="2" ParentId="11805" CreationDate="2011-03-22T10:27:14.990" Score="3" ViewCount="" Body="&lt;p&gt;I think W5VO's reply is a great description of a modern memory system but does not really describe &lt;a href=&quot;http://en.wikipedia.org/wiki/Bank_switching&quot; rel=&quot;nofollow&quot;&gt;Bank Switching&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You want bank switching when you have a narrow address bus (like 8- or 16-bit) and you want to add more memory. You can then use separate GPIO lines to switch memory chips just like W5VO wrote. You have to be careful because all your pointers are still 8-bit and the switching is manual so you can easily cause a mess.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This technique was/is popular in small micros, but also in 16-bit DOS (it was born on the 80286) and kind of in modern 32-bit  processors to address more than 4GB of memory (but here the trick is done invisibly by the kernel and one program can still only see 4GB).&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-22T10:27:14.990" CommentCount="5" />
  <row Id="11823" PostTypeId="1" AcceptedAnswerId="11824" CreationDate="2011-03-22T11:24:49.187" Score="1" ViewCount="133" Body="&lt;p&gt;Hi, I'm looking for a temperature sensor, that can be connected to a computer over an interface that is ubiquitous, like USB. I'd like to read the temperature data over the command line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions what I could use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All I plan to do, is measure the ambient temperature in the vicinity of the computer, for instance 2m above it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can access internal sensors with &lt;code&gt;sensors&lt;/code&gt;, of the &lt;code&gt;lm_sensors&lt;/code&gt; package. If possible, I'd like a similar interface.&lt;/p&gt;&#xA;" OwnerUserId="2134" LastActivityDate="2011-03-22T22:59:44.400" Title="Temperature sensor for Linux" Tags="&lt;sensor&gt;&lt;temperature&gt;&lt;linux&gt;" AnswerCount="5" CommentCount="1" />
  <row Id="11824" PostTypeId="2" ParentId="11823" CreationDate="2011-03-22T11:30:00.120" Score="4" ViewCount="" Body="&lt;p&gt;One option would be an i2c temperature sensor along with a USB to i2c adapter.&#xA;Plenty of different devices are &lt;A href=&quot;http://www.lm-sensors.org/wiki/Devices&quot; rel=&quot;nofollow&quot;&gt;listed as supported&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.harbaum.org/till/i2c_tiny_usb/index.shtml&quot; rel=&quot;nofollow&quot;&gt;http://www.harbaum.org/till/i2c_tiny_usb/index.shtml&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-22T11:30:00.120" CommentCount="1" />
  <row Id="11825" PostTypeId="1" AcceptedAnswerId="11830" CreationDate="2011-03-22T11:32:04.937" Score="0" ViewCount="56" Body="&lt;p&gt;I have :&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; four outputs :&#xA;  a, b, c, d ( four output pins )&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Assume I have one insect, let us say it jumps one step at a time and I can control its direction.&lt;br&gt;&#xA;If input &lt;code&gt;DW = 1&lt;/code&gt; it goes right to left; else it goes left to right. &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; clock clk :&#xA; DW = 0&#xA; ( clock goes left to right  )&#xA;  0  1  1  0 ( means b,c  = 1, assume rightmost-1 is head of the insect and it goes right ) &#xA;  0  0  1  1 ( now, c and d are  1 )&#xA;  1  0  0  1&#xA;  1  1  0  0  &#xA; after operation on  combinational and sequential  circuit         &#xA; DW = 1 &#xA; clock clk :&#xA;( now, it goes right to left )&#xA;  1  1  0  0 ( a, b = 1 ) ( assume leftmost-1 is now head of the insect and it goes left )&#xA;  1  0  0  1 ( a, d = 1 )&#xA;  0  0  1  1&#xA;  0  1  1  0&#xA;  1  1  0  0&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;How can I construct that circuit ? To construct it, which topic I should (re) read or Can you recommend any web-page?&lt;/p&gt;&#xA;" OwnerUserId="3192" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-22T12:41:21.863" LastActivityDate="2011-03-22T12:48:07.797" Title="manipulation on clock output" Tags="&lt;design&gt;&lt;logic&gt;&lt;circuit-design&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="11826" PostTypeId="2" ParentId="11813" CreationDate="2011-03-22T11:49:34.700" Score="2" ViewCount="" Body="&lt;p&gt;There is really no problem in using only one of the phases in orded to make a lower voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd live in Brazil and most of the residential systems here make use of this split in order to obtain 127(v). Here we have an three-phase system which the voltage between phases is 220 and the voltage between one phase and one neutral is 220/sqrt(3) = 127 ( &lt;a href=&quot;http://en.wikipedia.org/wiki/Three-phase_power#Single-phase_loads&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Three-phase_power#Single-phase_loads&lt;/a&gt; ).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the system is a 2-phase system (as in center tap transformers) the phase-phase voltage is 220 and the phase-neutral voltage is half of the main voltage, in the case 220/2 = 110;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Some warnings before making the connection&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Use an multimeter to assure that your phase-neutral voltage is 110 (v) and not 127. Even if the voltage comes to be 127 (as in Brazil) some equipments are capable to work with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Make sure that the main switch and the wires can hold both equipments current. The info about wires x current can be found here: &lt;a href=&quot;http://www.powerstream.com/Wire_Size.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.powerstream.com/Wire_Size.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2011-03-22T11:49:34.700" CommentCount="1" />
  <row Id="11827" PostTypeId="1" CreationDate="2011-03-22T11:54:17.617" Score="0" ViewCount="64" Body="&lt;p&gt;I'm building a circuit that allows me to blend a guitar effect in and out, based on &lt;a href=&quot;http://www.geofex.com/Article_Folders/panner.pdf&quot; rel=&quot;nofollow&quot;&gt;&gt;this&amp;lt;&lt;/a&gt; (page 2, bottom circuit). I have, however, replaced the 10k pot and the 15k and 51k resistors with 100k, 150k and 510k.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The blending works fine, however the volume is too low, and the blend pot is prone to noise when in the middle position, which makes me think of an impedance problem. Do I have to replace the 1M resistors at FX in and FX out with 10M ones?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the circuit clips quite early. I checked the voltages at the opamp's pins, and, while the second half is OK, the first half has 3.5 at the non-inverting input and 4.5 at the inverting one and at the output. Those should all be within 10mV from each other, right? Try as I might, I couldn't make it right.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm in kind of a hurry, and this pedal has already taken me more time than I could possibly give. I'll be immensely thankful if somebody pointed me in the right direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my schematic. Right click and choose &quot;view image&quot; to see it in full.&#xA;&lt;img src=&quot;http://i.imgur.com/TQ7uX.png&quot; alt=&quot;schematic&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3075" LastEditorUserId="3075" LastEditorDisplayName="" LastEditDate="2011-03-22T18:07:44.657" LastActivityDate="2011-03-23T10:24:42.343" Title="troubleshooting GEOFEX guitar effect panner" Tags="&lt;audio&gt;&lt;op-amp&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="11828" PostTypeId="2" ParentId="11791" CreationDate="2011-03-22T12:01:28.280" Score="1" ViewCount="" Body="&lt;p&gt;Take a look at these projects:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1258971285/all&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1258971285/all&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://pwrusage.codeplex.com&quot; rel=&quot;nofollow&quot;&gt;http://pwrusage.codeplex.com&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.cerebralmeltdown.com/programming_projects/Arduino_Kilowatt_Meter/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.cerebralmeltdown.com/programming_projects/Arduino_Kilowatt_Meter/index.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.alexgirard.com/2009/03/05/powermeter-more-info/&quot; rel=&quot;nofollow&quot;&gt;http://www.alexgirard.com/2009/03/05/powermeter-more-info/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://jarv.org/pwrmon.shtml&quot; rel=&quot;nofollow&quot;&gt;http://jarv.org/pwrmon.shtml&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://openenergymonitor.org/emon/node/58&quot; rel=&quot;nofollow&quot;&gt;http://openenergymonitor.org/emon/node/58&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://openenergymonitor.org/emon/node/27&quot; rel=&quot;nofollow&quot;&gt;http://openenergymonitor.org/emon/node/27&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://openenergymonitor.org/emon/node/79&quot; rel=&quot;nofollow&quot;&gt;http://openenergymonitor.org/emon/node/79&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.billporter.info/not-so-tiny-power-meter/&quot; rel=&quot;nofollow&quot;&gt;http://www.billporter.info/not-so-tiny-power-meter/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Enough? ;-)&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-03-22T12:01:28.280" />
  <row Id="11829" PostTypeId="2" ParentId="11827" CreationDate="2011-03-22T12:12:28.123" Score="1" ViewCount="" Body="&lt;p&gt;This may seem like a simple answer, but use the 10k, 15k and 51k resistors!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would expect that to fix your problem...is there a reason for using the much larger resistors?&lt;/p&gt;&#xA;" OwnerUserId="3525" LastActivityDate="2011-03-22T12:12:28.123" CommentCount="8" />
  <row Id="11830" PostTypeId="2" ParentId="11825" CreationDate="2011-03-22T12:48:07.797" Score="2" ViewCount="" Body="&lt;p&gt;I think what you're asking is for a method to build an reversible/bidirectional circular/ring shift-register. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main concept behind the shift-register is to shift all bits in a direction. You may accomplish it by using some flip-flops as here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/0oxSW.png&quot; alt=&quot;http://en.wikipedia.org/wiki/Shift_register&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may see that the data in is shifted to the right each time the clock ticks. The main concept is that the flip-flop keeps its status while the clock is down and transfers it to its output when the clock is up. In order to make it reversible you need to insert some digital circuitry that choose if the input (D) of the flip-flop will be: 1) the output of the flip-flop before itself or 2) the output of the flip-flop after itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One example of bidirectional shift register is presented in this site&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;http://eelab.usyd.edu.au/digital_tutorial/part2/register06.html&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;In order to make any shift-register circular you just need to connect the output wire to the input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the pattern to be shifted needs to be pre-set to an specif value you may act in the R/S lines, resetting or setting each flip flop to the desired value.&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2011-03-22T12:48:07.797" />
  <row Id="11831" PostTypeId="2" ParentId="11662" CreationDate="2011-03-22T13:01:12.883" Score="1" ViewCount="" Body="&lt;p&gt;In digital electronics, the initial state is usually defined as the &lt;em&gt;reset state&lt;/em&gt;. When the &lt;em&gt;reset signal&lt;/em&gt; is active, the state is forced to a &lt;em&gt;predefined value&lt;/em&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reset signal is active when the device is powered on. Often, '0' (or low voltage) is used to mean an active reset signal. As a capacitor charges, the voltage of the reset signal rises and the reset signal becomes inactive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take a look at the D-flip-flop on the Wikipedia for an example: &lt;a href=&quot;http://en.wikipedia.org/wiki/Flip-flop_(electronics)#D_flip-flop&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Flip-flop_(electronics)#D_flip-flop&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3145" LastActivityDate="2011-03-22T13:01:12.883" CommentCount="1" />
  <row Id="11832" PostTypeId="2" ParentId="11755" CreationDate="2011-03-22T13:03:15.083" Score="2" ViewCount="" Body="&lt;p&gt;PC video cards can generate a lot of hash in the 70cm band.  I've found that to be a problem in my home if the wife is playing video games.&lt;/p&gt;&#xA;" OwnerUserId="1678" LastActivityDate="2011-03-22T13:03:15.083" />
  <row Id="11833" PostTypeId="1" AcceptedAnswerId="11841" CreationDate="2011-03-22T13:09:41.143" Score="4" ViewCount="197" Body="&lt;p&gt;Have you ever encountered an SD card which does not support the SPI mode?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know microSD are not required to but I believe all do support SPI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: The information about optionality of SPI seems to come from Wikipedia and was recently removed (&lt;a href=&quot;http://en.wikipedia.org/w/index.php?title=Secure_Digital&amp;amp;diff=415230469&amp;amp;oldid=415228902&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/w/index.php?title=Secure_Digital&amp;amp;diff=412862593&amp;amp;oldid=412855668&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;).&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-22T15:25:52.050" LastActivityDate="2011-03-22T15:57:03.727" Title="Do all microSD cards support SPI mode?" Tags="&lt;spi&gt;&lt;sd&gt;&lt;microsd&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="11834" PostTypeId="2" ParentId="11813" CreationDate="2011-03-22T13:17:09.153" Score="4" ViewCount="" Body="&lt;p&gt;I broke this up into two different questions.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;1. Is it technically possible to get 110V AC by splitting a three-phase 220V AC system?&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;The answer to question one is &quot;Yes&quot;.  It's perfectly possible.  Every other 110V circuit in your house is powered by splitting this same three-phase 220V AC into sub-circuits.  If you look at your panel, the circuit breakers are arrayed like this (Yay for ASCII art!)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Leg 1       Leg 2&#xA;|-------    |&#xA;|    -------|&#xA;|-------    |&#xA;|    -------|&#xA;|-------    |&#xA;|    -------|&#xA;|-------    |&#xA;|    -------|&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;A 220V circuit simply bridges two of those breaker spaces.  A 110V circuit uses just one of them.  You're proposing to do this in a separate location.  &lt;/p&gt;&#xA;&#xA;&lt;h2&gt;2. Are there any problems with splitting a three-phase 220V AC system?&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;The only safety issue that I can foresee is that a short circuit in your 110V automatic drain valve wiring may not trigger the circuit breaker properly.  I'm not familiar with how a 220V breaker works, but you're using it in a non-standard way: it will be loaded unevenly.  It's entirely possible for one leg of the 220V line to become shorted and not the other, so the designers of the breaker should have planned for this.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other issue which hasn't been mentioned yet is the legal issue. You'll need to talk to an inspector or electrician to verify whether this procedure is legal or not.  My copy of &lt;a href=&quot;http://www.amazon.com/GB-Electrical-Simplified-Reference-ERB-WS/dp/B000E93GA8&quot; rel=&quot;nofollow&quot;&gt;Wiring Simplified&lt;/a&gt; (which is a great resource for a DIY electrician, but doesn't cover edge cases like this very well) doesn't mention it, but you can read the &lt;a href=&quot;http://www.nfpa.org/onlinepreview/online_preview_document.asp?id=7011SB&quot; rel=&quot;nofollow&quot;&gt;National Electrical Code online for free&lt;/a&gt; and see if there's anything about that question.  My guess is that they'll want you to run a sub-panel into your garage, and use separate breakers for your 220V compressor and your 110V automatic drain valve.  That's significantly more expensive than an extra outlet in the attic, but it might be worth it to be compliant with the code and to not have to trek through the house every time you blow a circuit in the garage...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One last thing:  Why do you need to turn the automatic drain valve off when you shut down the compressor?  Depending on the valve you are using, the energy savings will probably be less than the cost of the extra outlet, and it will certainly be less than the cost of a failed inspection! Alternatively, you could use a float-controlled drain valve, which doesn't require electricity.  There are other ways to do this!&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-22T13:17:09.153" CommentCount="6" />
  <row Id="11835" PostTypeId="2" ParentId="11662" CreationDate="2011-03-22T13:46:24.433" Score="2" ViewCount="" Body="&lt;p&gt;Instead of an RC reset circuit, you might want to consider a microprocessor supervisory circuit such as the Micrel &lt;a href=&quot;http://www.micrel.com/_PDF/mic1810.pdf&quot; rel=&quot;nofollow&quot;&gt;MIC1810&lt;/a&gt;.  It generates a 100 ms reset pulse on startup, and whenever VCC falls below a set threshold (so it functions as a BOD also).  Although designed for microprocessors, it may work in your application also.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-03-22T17:40:54.563" LastActivityDate="2011-03-22T17:40:54.563" CommentCount="2" />
  <row Id="11836" PostTypeId="2" ParentId="11823" CreationDate="2011-03-22T13:57:22.097" Score="0" ViewCount="" Body="&lt;p&gt;Use an Arduino to have lots of flexibility on the sensor end.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-22T13:57:22.097" CommentCount="1" />
  <row Id="11837" PostTypeId="2" ParentId="11816" CreationDate="2011-03-22T13:58:46.823" Score="1" ViewCount="" Body="&lt;p&gt;You can get electronics gas grill lighters.  Look for replacement types.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-22T13:58:46.823" CommentCount="1" />
  <row Id="11838" PostTypeId="2" ParentId="11811" CreationDate="2011-03-22T14:00:57.820" Score="0" ViewCount="" Body="&lt;p&gt;Flexible mounting and drive shaft can also help.  &lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-22T14:00:57.820" CommentCount="2" />
  <row Id="11839" PostTypeId="2" ParentId="11816" CreationDate="2011-03-22T14:39:44.433" Score="4" ViewCount="" Body="&lt;p&gt;Capacitors themselves can't step up voltages beyond doubling or inverting, to do anything else you need inductors.  As mentioned previously, automobiles use ignition coils, a transformer (inductors) in an &lt;a href=&quot;http://en.wikipedia.org/wiki/Autotransformer&quot; rel=&quot;nofollow&quot;&gt;autotransformer&lt;/a&gt; configuration like so:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/qvt6y.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Image from &lt;a href=&quot;http://www.sentex.net/~mwandel/cannon/sparky.html&quot; rel=&quot;nofollow&quot;&gt;&quot;How to use an Ignition Coil [in potato cannons]&quot;&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Another possibility, though there are some problems with it, would be to just open up a circuit with some large inductance in it, which will cause high voltages (and sparks) across high resistances (e.g. a spark gap).  To do this, you'd need some switch that had a voltage rating much greater than your spark gap, which may be difficult to find.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I've heard though, pneumatic air cannons are much more controllable, and even better, they can be triggered using sprinkler valves which work at about 24 V (I use (3) 9 V batteries)&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-22T14:39:44.433" CommentCount="7" />
  <row Id="11840" PostTypeId="1" AcceptedAnswerId="11845" CreationDate="2011-03-22T14:50:22.660" Score="1" ViewCount="93" Body="&lt;p&gt;After much experimentation and some &lt;a href=&quot;http://electronics.stackexchange.com/questions/5620/mechanical-connectors-for-flexible-pcbs&quot;&gt;helpful&lt;/a&gt; answers &lt;a href=&quot;http://electronics.stackexchange.com/questions/9147/tips-for-wire-to-pad-and-wire-to-wire-soldering&quot;&gt;here&lt;/a&gt; I've decided that &lt;a href=&quot;http://portal.fciconnect.com/res/en/pdffiles/datasheets/950500-025_FPC-Clincher2.pdf&quot; rel=&quot;nofollow&quot;&gt;FCI &quot;Clincher&quot;&lt;/a&gt; (.pdf link) parts are the right answer for adding connectors to the ends of &lt;a href=&quot;http://www.alibaba.com/product-gs/318410435/ZJ168_Dream_color_strip.html&quot; rel=&quot;nofollow&quot;&gt;flexible ZJ168 RGB LED strip&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The parts themselves are cheap enough (&amp;lt; $2 each) but the crimping tool appears to &lt;a href=&quot;http://parts.digikey.com/1/parts/356767-tool-hand-crimp-clincher-series-ht270.html&quot; rel=&quot;nofollow&quot;&gt;cost almost USD$2500&lt;/a&gt;! I certainly can't afford that and in any case Element 14 here in Singapore (from whom I got the connectors) don't have any crimpers in stock and can't hire/lend me one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've had a modicum of success crushing the crimps down with the tip of my pliers but can someone suggest something more elegant and/or foolproof? Are there any un-obvious flaws with attempting to crimp these without the proper tool?&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2011-03-22T15:51:56.717" Title="Ghetto crimping tool for FCI &quot;Clincher&quot; connectors?" Tags="&lt;connector&gt;&lt;ffc&gt;" AnswerCount="1" />
  <row Id="11841" PostTypeId="2" ParentId="11833" CreationDate="2011-03-22T15:13:55.913" Score="4" ViewCount="" Body="&lt;p&gt;According to the Wikipedia article, all families of SD cards support SPI and furthermore, most MMC cards do as well.  In the &lt;a href=&quot;http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf&quot; rel=&quot;nofollow&quot;&gt;SD 2.00 specification&lt;/a&gt; [PDF], I don't see anything that states that it's optional, though nothing says it's mandatory either.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the specifications seem to keep separate the electrical properties and mechanical form factors (SD, miniSD, microSD), so there should be no electrical difference between any SD card mechanical package unless mentioned separately (e.g. SD vs. SDHC).&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-22T15:57:03.727" LastActivityDate="2011-03-22T15:57:03.727" CommentCount="1" />
  <row Id="11842" PostTypeId="2" ParentId="11823" CreationDate="2011-03-22T15:28:21.957" Score="3" ViewCount="" Body="&lt;p&gt;This is the one we got for monitoring server room temperature with nagios and cacti: &lt;a href=&quot;http://www.dealextreme.com/p/usb-digital-thermometer-dongle-software-displays-temperature-7003&quot; rel=&quot;nofollow&quot;&gt;http://www.dealextreme.com/p/usb-digital-thermometer-dongle-software-displays-temperature-7003&lt;/a&gt; (but from a different supplier).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is an article in linux journal with some software to interface with it using perl to read the temperature, I'll see if I can dig it up.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2011-03-22T15:28:21.957" CommentCount="4" />
  <row Id="11843" PostTypeId="2" ParentId="10528" CreationDate="2011-03-22T15:33:31.390" Score="1" ViewCount="" Body="&lt;p&gt;Yes, a &lt;a href=&quot;http://en.wikipedia.org/wiki/Keyboard_matrix_%28music%29&quot; rel=&quot;nofollow&quot;&gt;matrix with diodes&lt;/a&gt; is exactly how it is done.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm going to assume you select select one column at a time by driving it low, let all the other columns float (open-collector) (or drive all the other columns high),&#xA;and your &lt;a href=&quot;http://geekhack.org/showthread.php?t=9181&quot; rel=&quot;nofollow&quot;&gt;row input pins have pull-up resistors&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In principle, super-brief keytaps would be missed if the MCU doesn't select that column during the entire interval from the time the key is pressed until the time the key is released.&#xA;In practice, humans are so slow that even when they try to quickly tap a key,&#xA;a typical keyboard encoder with a fairly slow MCU will scan through every column dozens of times during that interval.&#xA;The typing speed world-record is 1075 keystrokes over the course of 1 minute.&#xA;That's an average of slightly more than 1 keystroke per millisecond on average.&#xA;Almost certainly some keys were held down longer, and others shorter,&#xA;but as long as you're not trying to beat the world record,&#xA;I suspect that a keyboard scan time of 100 microseconds is more than fast enough.&#xA;A 16 MHz processor should be able to scan every column in 100 microseconds or less fairly easily.&#xA;In fact, some low-quality buttons have &quot;keybounce&quot; for so long that you may get several (false) key-presses and key-releases when a human tries to push the button one time, requiring extra complexity in hardware or software to make sure it is interpreted as a single keypress.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most keyboard encoders simply scan the keyboard over and over (polling), selecting only one column at a time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Low-power keyboard encoders drive &lt;em&gt;all&lt;/em&gt; the columns low,&#xA;set up an interrupt to wake them up if &lt;em&gt;any&lt;/em&gt; row goes low,&#xA;and then go to sleep.&#xA;When they wake up, they scan the keyboard over and over (polling),&#xA;selecting only one column at a time,&#xA;until no keys are being pressed,&#xA;then go back to sleep.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-22T15:33:31.390" CommentCount="1" />
  <row Id="11844" PostTypeId="1" AcceptedAnswerId="12502" CreationDate="2011-03-22T15:45:21.243" Score="6" ViewCount="278" Body="&lt;p&gt;For several years now Don Lancaster is promoting &lt;a href=&quot;http://www.tinaja.com/glib/sinquest.pdf&quot; rel=&quot;nofollow&quot;&gt;magic sinewaves&lt;/a&gt;. They are strings of binary digits (like 420 bits for a full sine cycle) that, when used to drive a digital switch (MOSFET/IGBP), result in quite a clean sinewave (only very high harmonics remaining). For more details, please read the linked article or any other he wrote on that matter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Had anybody actually used these for anything? The idea seems quite useful but I cannot find any information about these (that did not come from Lancaster himself).&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-03T23:21:36.523" Title="Don Lancaster's Magic Sinewaves" Tags="&lt;power&gt;&lt;mosfet&gt;&lt;ups&gt;" AnswerCount="4" CommentCount="5" FavoriteCount="6" />
  <row Id="11845" PostTypeId="2" ParentId="11840" CreationDate="2011-03-22T15:51:56.717" Score="2" ViewCount="" Body="&lt;p&gt;Manufacturers' crimp tools are precision-engineered for their connectors, and actually create a cold weld between the terminal and the wire. It's impossible to make a reliable connection without the correct tool. Distributors will usually make up cables for customers, using the correct tooling, even in prototype quantities.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-22T15:51:56.717" CommentCount="9" />
  <row Id="11847" PostTypeId="1" AcceptedAnswerId="11849" CreationDate="2011-03-22T17:53:51.753" Score="6" ViewCount="153" Body="&lt;p&gt;On some gas grills, there is a button you push which creates a spark to ignite the gas (propane, natural gas etc.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are probably pretty simple:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How does the button create the spark?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What voltage is this spark?&lt;/p&gt;&#xA;" OwnerUserId="3381" LastActivityDate="2011-03-22T18:29:41.770" Title="How does a gas grill starter spark work?" Tags="&lt;voltage&gt;&lt;generator&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="11849" PostTypeId="2" ParentId="11847" CreationDate="2011-03-22T18:29:41.770" Score="11" ViewCount="" Body="&lt;p&gt;Almost all are piezo-electric. Check &lt;a href=&quot;http://en.wikipedia.org/wiki/Piezo_ignition&quot; rel=&quot;nofollow&quot;&gt;this Wikipedia page&lt;/a&gt; for info:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Piezo ignition is a type of ignition that is used in portable camping stoves, gas grills and some lighters. It consists of a small, spring-loaded hammer which, when a button is pressed, hits a crystal of PZT or quartz crystal. Quartz is piezoelectric, which means that it creates a voltage when deformed. This sudden forceful deformation produces a high voltage and subsequent electrical discharge, which ignites the gas.&lt;/p&gt;&#xA;" OwnerUserId="3525" LastActivityDate="2011-03-22T18:29:41.770" CommentCount="1" />
  <row Id="11850" PostTypeId="1" AcceptedAnswerId="11853" CreationDate="2011-03-22T19:18:05.020" Score="2" ViewCount="82" Body="&lt;p&gt;I'd like to build a set of miniature two-way (half-duplex) radios that operate on the FRS band. It seems that transceivers for this band would be widely available. However I've not been able to find any. Ideally they would be controlled digitally (I'm thinking to use a PIC controller) and have analog inputs and outputs for earbuds and a microphone. Where can I find a transceiver?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was planning to use &lt;a href=&quot;http://www.sparkfun.com/products/9582&quot; rel=&quot;nofollow&quot;&gt;this transceiver from Sparkfun&lt;/a&gt; but it doesn't look like there will be an easy way to get an analog output and input. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd actually not mind building a basic transceiver from scratch but I can't find a good tutorial or set of schematics.&lt;/p&gt;&#xA;" OwnerUserId="3427" LastActivityDate="2011-03-22T20:06:27.287" Title="Walkie-talkie transceiver" Tags="&lt;radio&gt;&lt;receiver&gt;&lt;transmitter&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11851" PostTypeId="2" ParentId="11823" CreationDate="2011-03-22T19:24:05.683" Score="5" ViewCount="" Body="&lt;p&gt;Consider getting a &lt;a href=&quot;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_%28MSP-EXP430G2%29&quot; rel=&quot;nofollow&quot;&gt;TI Launchpad&lt;/a&gt;. TI is selling them cheap and one of the micros comes with a built-in temperature sensor. It comes with a board with USB and you can load a firmware that will send the temperature value to the computer.&lt;/p&gt;&#xA;" OwnerUserId="1927" LastActivityDate="2011-03-22T19:24:05.683" CommentCount="2" />
  <row Id="11852" PostTypeId="2" ParentId="11844" CreationDate="2011-03-22T19:52:27.273" Score="2" ViewCount="" Body="&lt;p&gt;I can't load the linked PDF, but from your description it sounds like a specific instance of a &lt;a href=&quot;http://en.wikipedia.org/wiki/Class_D_Amplifier&quot; rel=&quot;nofollow&quot;&gt;Class D Amplifier&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2664" LastActivityDate="2011-03-22T19:52:27.273" CommentCount="10" />
  <row Id="11853" PostTypeId="2" ParentId="11850" CreationDate="2011-03-22T20:06:27.287" Score="3" ViewCount="" Body="&lt;p&gt;Operation of FRS radios might be license-free, but in most countries you are not allowed to build your own equipment. It has to be certified, like anything that transmits RF. If you want to build your own equipment for two-way radio communication, you need to get an amateur radio license and use the amateur radio bands.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-22T20:06:27.287" CommentCount="5" />
  <row Id="11856" PostTypeId="2" ParentId="11844" CreationDate="2011-03-22T21:01:33.747" Score="3" ViewCount="" Body="&lt;p&gt;Yes, this will work. He is switching at a much higher frequency then required and then he is slowly changing what percentage of time he is on 0s to being on 1s. This means that the average of the signal is slowly going to shift up. By matching his rate to the rate change of a Sinusoid he can do this very very well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The issue will probably be the low pass filter, non-ideal components to it will allow odd harmonics though, but a power saving LC filter can probably do the trick by bandpassing for the required frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This could easily be done with DACs and a type D amplifier, he is just cutting out the need of a DAC which is a cost savings.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-03-22T21:01:33.747" CommentCount="4" />
  <row Id="11859" PostTypeId="1" AcceptedAnswerId="12246" CreationDate="2011-03-22T21:45:33.240" Score="4" ViewCount="252" Body="&lt;p&gt;To repair something, I had to disassemble it. Unfortunately, it had an LCD, and that used an &lt;a href=&quot;http://en.wikipedia.org/wiki/Elastomeric_connector&quot; rel=&quot;nofollow&quot;&gt;elastomeric connector&lt;/a&gt; to connect to the LCD. Now I have an LCD, a PCB, and a spare elastomeric connector. I can occasionally get the LCD to work if I put them together, but it will not stay there, and the connection is very dodgy. Is there an easy fix?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/hDKgv.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-03-22T22:25:06.063" LastActivityDate="2011-03-29T19:14:34.633" Title="I took apart an LCD module. How do I fit it back together again?" Tags="&lt;lcd&gt;&lt;repair&gt;" AnswerCount="4" CommentCount="4" />
  <row Id="11860" PostTypeId="2" ParentId="11859" CreationDate="2011-03-22T21:58:38.887" Score="3" ViewCount="" Body="&lt;p&gt;No, there is no easy fix.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I worked on a product with an LCD and two 100+ pin zebra strips. It looked something like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.lctecdisplays.com/bilder/Zebra%20strip%20assembly.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In our design, there was a metal can with tabs poking through holes in the PCB. These tabs were bent to maintain pressure on the zebra strips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This picture shows the idea:&#xA;&lt;img src=&quot;http://farm5.static.flickr.com/4109/5053590566_afd62f005b.jpg&quot; width=&quot;400&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to ensure the strips are clean and dust free, line them up perfectly then maintain pressure. Be careful not to stretch or bend the strips while installing them as the contacts are often very small pitch.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-27T23:19:56.600" LastActivityDate="2011-03-27T23:19:56.600" CommentCount="3" />
  <row Id="11861" PostTypeId="1" AcceptedAnswerId="11865" CreationDate="2011-03-22T22:31:00.063" Score="1" ViewCount="127" Body="&lt;p&gt;How do I easily measure how far apart two objects are in EAGLE 5.11.0 Light? Is the easiest way to record the coordinates and subtract?&lt;/p&gt;&#xA;" OwnerUserId="1256" LastEditorUserId="1256" LastEditorDisplayName="" LastEditDate="2011-03-22T23:45:08.430" LastActivityDate="2011-03-22T23:45:08.430" Title="How to measure component distances in EAGLE PCB" Tags="&lt;eagle&gt;" AnswerCount="1" />
  <row Id="11863" PostTypeId="2" ParentId="11823" CreationDate="2011-03-22T22:59:44.400" Score="2" ViewCount="" Body="&lt;p&gt;Arduino is great for this, and it will give you a chance to learn the basics of microconrollers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looks like the launchpad is a pretty good alternative but the launchpad is not as friendly to beginners as the arduino. &lt;/p&gt;&#xA;" OwnerUserId="2758" LastActivityDate="2011-03-22T22:59:44.400" CommentCount="2" />
  <row Id="11864" PostTypeId="1" CreationDate="2011-03-22T23:02:27.983" Score="0" ViewCount="134" Body="&lt;p&gt;Hi&#xA;I've been asked to construct an lcd usb controller for an art project.  The lcd am using is ST7066. It's spec sheet has told me that the LED. I'm using a 10K pot to adjust the contrast. The 10K pot I have can handle 0.5W power. &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;[power supply (logic)] vdd  0.3(min)&lt;br&gt;&#xA;  7.0(max)&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;[power supply (LCD)]   V0   Vdd - 13.5&#xA;  Vdd + 0.3&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;In my case VDD = 5V&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The led forward current is 240ma. At 5V 240ma equals to 1.2W of power so does that mean my pot needs to be able to withstand 1.2W? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason I ask is the last time I used a pot, it set on fire as soon as I turned on the circuit. There was no bridges in my soldering so I can only assume I overloaded it.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Correspond to high speed MPU bus&#xA;  interface&#xA;  -- 2 MHz (when VCC = 5V)&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Also it's going to be connected to an ATMEGA16-16PU. The spec for the lcd says the logic runs at 2MHZ. So does that mean my avr must also run 2MHZ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&amp;amp;R=720-0235&quot; rel=&quot;nofollow&quot;&gt;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&amp;amp;R=720-0235&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="2824" LastEditorDisplayName="" LastEditDate="2011-03-22T23:10:30.050" LastActivityDate="2011-05-22T00:46:05.723" Title="LCD usb controller design - is my pot suitable" Tags="&lt;lcd&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="0" />
  <row Id="11865" PostTypeId="2" ParentId="11861" CreationDate="2011-03-22T23:12:15.620" Score="2" ViewCount="" Body="&lt;p&gt;Use the &lt;code&gt;mark&lt;/code&gt; command or the Mark button:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/fUixu.png&quot; alt=&quot;screenshot of mark button with freehanded red circle!!!1!&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then click the location you want to measure from.  Unfortunately, the mark command doesn't accept coordinates; you have to click the location manually (and therefore, it must be on the current grid).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will set a reference point, you'll see that a new box appears between the standard coordinates and the command line:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/T0fiE.png&quot; alt=&quot;screenshot of coordinates, no freehanded red circles - sorry.&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first set of parentheses in this new area contains the rectangular offset from the mark to your current cursor location, as indicated by the R. In this example, I'm 0.1&quot; to the right and 0.7&quot; above the mark.  The second set of parentheses is the offset in polar coordinates - I'm 0.71&quot; away at an 81.87&lt;sup&gt;o&lt;/sup&gt; angle above the positive X axis.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This tool is available in both the schematic/symbol/component capture view and the layout/footprint editor. &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;For some repetitive tasks, it's much easier to set your grid to the distance which you want to space things out by and then move that group into place later.  The [alt] key is your friend.  This isn't a generic answer to your question, but it should be considered if you're doing a lot of measurement.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-22T23:12:15.620" />
  <row Id="11866" PostTypeId="2" ParentId="11864" CreationDate="2011-03-22T23:22:46.303" Score="1" ViewCount="" Body="&lt;p&gt;PWM using an output from your MCU would be a much better way of controlling the brightness of the LEDs than using a pot connected directly to them. You could read the pot value with an ADC, and use that to control the PWM. You will need a suitable driver, of course, such as a MOSFET.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The AVR you are using isn't suitable for USB; you need one of the USB AVRs, such as the AT90USB162.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The AVR can run at any speed, but it needs a fast clock to handle USB comms. Use delays to slow things down for the LCD.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-22T23:46:52.630" LastActivityDate="2011-03-22T23:46:52.630" CommentCount="4" />
  <row Id="11867" PostTypeId="2" ParentId="724" CreationDate="2011-03-22T23:42:44.553" Score="0" ViewCount="" Body="&lt;p&gt;Electonic's very own &lt;strong&gt;&lt;a href=&quot;http://electronics.stackexchange.com/users/1307/tronixstuff&quot;&gt;tronixstuff&lt;/a&gt;&lt;/strong&gt; has a huge, very informative &lt;a href=&quot;http://tronixstuff.wordpress.com/tutorials/&quot; rel=&quot;nofollow&quot;&gt;Arduino tutorial at his website&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Jeremy Blum also did a &lt;a href=&quot;http://www.youtube.com/watch?v=fCxzA9_kg6s&amp;amp;feature=list_related&amp;amp;playnext=1&amp;amp;list=SPA567CE235D39FA84&quot; rel=&quot;nofollow&quot;&gt;10-part YouTube series&lt;/a&gt; on the basics of working with Arduino that I found extremely informative, if a little slow-paced at times (but never lacking in detail).&lt;/p&gt;&#xA;" OwnerUserId="693" LastActivityDate="2011-03-22T23:42:44.553" />
  <row Id="11868" PostTypeId="1" AcceptedAnswerId="11876" CreationDate="2011-03-22T23:43:49.263" Score="4" ViewCount="121" Body="&lt;p&gt;Hello Guys, I have a problem concerning GPS units. I have been studying on a project for a weather balloon which will go about 30 - 40km up. Now I do know that some GPS units have a limit on how high they can receive/show you the location whether it is a limitation made by the military to stop random production of cruise missiles and others which just don't work above a certain height. This is a problem as my weather balloon does go to a height which could be considered as a &quot;GPS fail zone&quot;. At the moment I am using a 50 Channel D2523T Helical GPS Receiver - &lt;a href=&quot;http://www.sparkfun.com/products/9566&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/9566&lt;/a&gt; . It’s a great product but I am worried with problems with height etc. Could anyone give me some ideas on GPS units or give me advice....Any help is greatly appreciated....P.S - The unit has to have the standerd GGA protocol.&lt;br&gt;&#xA;Cheers - James Dyson&lt;/p&gt;&#xA;" OwnerUserId="3140" LastActivityDate="2011-03-23T13:57:32.477" Title="GPS Units - Weather Balloon" Tags="&lt;gps&gt;&lt;problem&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="11869" PostTypeId="1" CreationDate="2011-03-22T23:58:46.303" Score="2" ViewCount="236" Body="&lt;p&gt;My dream device is a way to quickly make tea. I can use most of the parts from a Mr. Coffee tea maker but the last part is a way to start the flow of water, measure say, 1/2 a gallon and then stop the flow. It can't be hard . . . ice makers do it all the time. How does an ice maker do it?&lt;/p&gt;&#xA;" OwnerUserId="3534" LastActivityDate="2011-03-24T02:46:35.693" Title="What device can measure the amount of water though a line?" Tags="&lt;arduino&gt;" AnswerCount="7" CommentCount="3" />
  <row Id="11870" PostTypeId="2" ParentId="11869" CreationDate="2011-03-23T00:07:08.313" Score="5" ViewCount="" Body="&lt;p&gt;I'd use a load cell to measure the weight of the container, and turn off the water flow when the contents reach half a gallon.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-23T00:55:57.837" LastActivityDate="2011-03-23T00:55:57.837" CommentCount="2" />
  <row Id="11871" PostTypeId="2" ParentId="11869" CreationDate="2011-03-23T00:09:58.647" Score="2" ViewCount="" Body="&lt;p&gt;You might consider an &lt;a href=&quot;http://en.wikipedia.org/wiki/Ultrasonic_flow_meter&quot; rel=&quot;nofollow&quot;&gt;ultrasonic flow meter&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, I'd either use a calibrated timer or prefill a chamber of known volume on demand (using a sensor to show when it's full), then empty the chamber into the cup.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-23T01:08:02.427" LastActivityDate="2011-03-23T01:08:02.427" CommentCount="2" />
  <row Id="11872" PostTypeId="2" ParentId="11869" CreationDate="2011-03-23T00:38:40.903" Score="1" ViewCount="" Body="&lt;p&gt;Put the vessel that is receiving the hot water on a sprung base, and attach a &lt;a href=&quot;http://en.wikipedia.org/wiki/Miniature_snap-action_switch&quot; rel=&quot;nofollow&quot;&gt;microswitch&lt;/a&gt; to the base that is pressed down as the vessel fills with water that cuts the power to the pump (or heater if your using steam pressure to transfer the water) when the base is pushed down far enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll have to fiddle around with the sprung base and switch to get it to trip at the moment that it has been filled to the desired level.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-23T00:38:40.903" />
  <row Id="11873" PostTypeId="2" ParentId="3433" CreationDate="2011-03-23T00:47:33.513" Score="4" ViewCount="" Body="&lt;p&gt;It's often that it will turn out cheaper to use discrete circuitry to do a simple task. For example, a flashing LED. The cheapest PIC, a PIC10F200, is about US 0.35 in 5ku, and that's before programming costs and taking into account the small size (and associated problems with manufacture.) An NE555 timer, on the other hand, can be picked up for about US 0.10 from TI in 5ku, and a complete solution would probably weigh in at around US 0.20.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing to take into account is that microcontrollers are inherently digital devices. Sure, most have ADCs and some even have DACs, but they still work on discrete units of time and work on individual bits and bytes. An analog circuit can be tuned precisely to do what the designer needs because in theory, analog has infinite resolution**. A digital circuit is limited by its slowest component.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, there is the issue of supply. Going back to my first example, the NE555. That has been around for more than 20 years and will probably be around for another 50 after this. It's such a jellybean part that it will probably be manufactured &lt;em&gt;forever&lt;/em&gt; (or at least until conventional electrons become obsolete in electronics.) Whereas, a PIC10F could be made NRND at any time. With a single supplier like Microchip, there is a significant risk this could ruin a product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;**Okay, this isn't quite true. In reality, we are limited to the resolution of electrons. 1 ampere = 6.24×10^18 electrons/second. So the finest current resolution you can get is the attoampere, or 10^-18 amperes, which is about 6 electrons per second. But for most practical purposes, this is okay. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Note no dollar sign due to broken TeX.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-23T00:47:33.513" CommunityOwnedDate="2011-03-23T01:08:29.540" />
  <row Id="11874" PostTypeId="2" ParentId="11869" CreationDate="2011-03-23T03:16:49.037" Score="4" ViewCount="" Body="&lt;p&gt;Some coffee machines detect water level using a magnetic float inside the glass/plastic tank and a hall-effect sensor outside it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hobbyist supplier futurlec.com has in interesting-looking range of flow sensors, also.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-23T03:16:49.037" />
  <row Id="11875" PostTypeId="1" CreationDate="2011-03-23T04:36:40.697" Score="0" ViewCount="98" Body="&lt;p&gt;If you are using a CPU to address one 2MB memory module, then since 1MB = 2&lt;sup&gt;20&lt;/sup&gt; and 2·2&lt;sup&gt;20&lt;/sup&gt; = 2&lt;sup&gt;21&lt;/sup&gt; = 2MB, you need 21 address lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use a 2MB 16-bit memory module instead, you can remove address line 0. Why is that?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-23T13:35:18.090" LastActivityDate="2011-03-23T15:56:50.787" Title="How does using memory with more bits allow you to reduce the address bus?" Tags="&lt;memory&gt;&lt;bus&gt;&lt;addressing&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="11876" PostTypeId="2" ParentId="11868" CreationDate="2011-03-23T04:42:35.020" Score="6" ViewCount="" Body="&lt;p&gt;GPS Units are typically limited to controlled airspace (60kfeet, 18km), and 1000 knots.  These are commonly known as the COCOM limits.   For anything outside of that, you will probably have to go for a higher-end GPS unit and possibly some additional paperwork.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe that the uBlox module that is on that board implements the COCOM limits correctly.  In the uBlox G5010 datasheet, it gives the operational limits as 972 knots and 50km.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DoD specification (I believe) says that a GPS unit should not operate above 60kfeet and 1000 or knots, but most of the manufacturers don't actually implement it this way.  The commonly cited list of high-altitude capable GPS receivers is &lt;a href=&quot;http://showcase.netins.net/web/wallio/GPSrcvrsvs60kft.htm&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some other companies produce GPS units to spec: most notably &lt;a href=&quot;http://inventeksys.accountsupport.com/store/ISM300F2-C5-V0004.html&quot; rel=&quot;nofollow&quot;&gt;Inventek&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-03-23T04:42:35.020" CommentCount="2" />
  <row Id="11877" PostTypeId="1" CreationDate="2011-03-23T05:34:54.903" Score="0" ViewCount="91" Body="&lt;p&gt;When would you use a Laplace transform to figure something out about a circuit? Does the circuit have to have capacitors?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-03-23T05:58:08.043" Title="Using a Laplace transform to figure something out in a DC circuit" Tags="&lt;circuit&gt;&lt;math&gt;" AnswerCount="1" />
  <row Id="11878" PostTypeId="2" ParentId="4333" CreationDate="2011-03-23T05:50:09.260" Score="3" ViewCount="" Body="&lt;p&gt;My former brother in law made this turtle:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/6H6C0.jpg&quot; alt=&quot;turtle made from PCBs&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can see similar works here:&lt;br&gt;&#xA;&lt;a href=&quot;http://www.pcbcreations.com/work.html&quot; rel=&quot;nofollow&quot;&gt;http://www.pcbcreations.com/work.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just gave him a bunch of TiVos, wireless routers and cell phones.  Can't wait to see what he creates next!&lt;/p&gt;&#xA;" OwnerUserId="3546" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-07T16:03:42.640" LastActivityDate="2011-05-07T16:03:42.640" CommunityOwnedDate="2011-03-23T05:50:09.260" />
  <row Id="11879" PostTypeId="1" AcceptedAnswerId="11891" CreationDate="2011-03-23T05:54:27.407" Score="2" ViewCount="118" Body="&lt;p&gt;I'm expecting a midterm question about the circuit below that involves the equation t=RC and using a Laplace transform. We won't actually be using differential equations. Memorizing a certain equation is all we need, but we're not told what it is. I've found a lot of equations when looking up Laplace transforms. Which equations would be helpful for analyzing this circuit, and where in the circuit could they be applied?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/8YGOB.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="1657" LastEditorDisplayName="" LastEditDate="2011-03-23T07:17:11.130" LastActivityDate="2011-03-23T12:13:44.813" Title="How would a Laplace transform be useful in analyzing this circuit?" Tags="&lt;capacitor&gt;&lt;circuit&gt;&lt;resistor&gt;&lt;math&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="11880" PostTypeId="2" ParentId="11877" CreationDate="2011-03-23T05:58:08.043" Score="3" ViewCount="" Body="&lt;p&gt;The LaPlace transform isn't really used in DC analysis of circuits.  Typically, you would just use your standard &quot;Circuits 101&quot; tools to analyze the DC properties of a circuit.  These are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Kirchhoff's Current Law (Nodal Analysis)&lt;/li&gt;&#xA;&lt;li&gt;Kirchhoff's Voltage Law (Loop Analysis)&lt;/li&gt;&#xA;&lt;li&gt;Thevenin's (or Norton's) Theorem&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In DC, capacitors are treated as open circuits (hence why they are also known &quot;DC blockers&quot;) and inductors are treated as close circuits (or dead shorts).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LaPlace transforms are used in both frequency and transient analysis.  They replace the more complex method of solving differential equations, or using convolution to determine the response of a circuit to an input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transient analysis builds upon the basic DC analysis, but determines what the circuit will do in response to a transient (a step input, an impulse, a ramp, etc).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Frequency analysis then builds upon the transient analysis to determine the response of a circuit to periodic signals (sine wave, square wave, triangle waves, as an example).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LaPlace analysis is frequently used in &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Filter design (creating a circuit with specific frequency responses)&lt;/li&gt;&#xA;&lt;li&gt;Controls (forcing a system or circuit to react with particular transient and frequency responses).&lt;/li&gt;&#xA;&lt;li&gt;Higher level analysis of most electrical engineer (power, communications, electromagnetics,etc).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-03-23T05:58:08.043" CommentCount="10" />
  <row Id="11881" PostTypeId="2" ParentId="11341" CreationDate="2011-03-23T06:29:08.437" Score="1" ViewCount="" Body="&lt;p&gt;The IMU-3000 uses the I2C bus to communicate with the Arduino.  The I2C bus is a simple serial protocol (much like the way you talk to the Arduino from your PC) that utilizes an single line that works in both directions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to use the I2C bus, you need to include the Wire.h library that comes standard with the Arduino.  You can then implement the protocol outlined in the datasheet to get the specific values that you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a rough example of what I'm talking about.  This code is untested, but it should give you the general flow of what you are trying to do on the Arudino.  Once you have the low-level reading done, you can start to implement filters to smooth your data and get it into the format you need for your application.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#define GYRO 0x69 // gyro I2C address&#xA;void setup()&#xA;{&#xA;    Wire.begin();&#xA;    // Do other gyro stuff here, sample rate, max speed, power management&#xA;    // From datasheet, set power management to internal oscillator&#xA;    Wire.beginTransmission(GYRO); //Device Address&#xA;    Wire.send(0x3E); //Register Address&#xA;    Wire.send(0x00); // Value&#xA;    Wire.endTransmission();&#xA;}&#xA;&#xA;void main()&#xA;{&#xA;    // A quick read example, temperature, gyro x,y,z&#xA;    Wire.beginTransmission(GYRO);&#xA;    Wire.send(0x1B); //Register Address TEMP_H&#xA;    Wire.endTransmission();&#xA;&#xA;    Wire.beginTransmission(GYRO);&#xA;    Wire.requestFrom(GYRO,6); // Read 8 bytes&#xA;    int ii = 0;&#xA;    while(Wire.available())&#xA;    {&#xA;        buff[ii] = Wire.receive();&#xA;        ii++;&#xA;    }&#xA;    Wire.endTransmission;&#xA;&#xA;    //Combine bytes into ints&#xA;    int temperature = buff[0] &amp;lt;&amp;lt; 8 | buff[1];&#xA;    int gyro_x = buff[2] &amp;lt;&amp;lt; 8 | buff[3];&#xA;    int gyro_y = buff[4] &amp;lt;&amp;lt; 8 | buff[5];&#xA;    int gyro_z = buff[6] &amp;lt;&amp;lt; 8 | buff[7];&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-03-23T06:29:08.437" />
  <row Id="11882" PostTypeId="2" ParentId="11875" CreationDate="2011-03-23T07:22:30.567" Score="3" ViewCount="" Body="&lt;p&gt;One way to think about this is that the memory module consists of a set of blocks, and that the address identifies a specific block in memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, for memory with an 8 bit block, an address would define 1 byte, and in the 2MB memory case you would need the 21 address lines for 2^21 addressable blocks. An address of '4' points to the 4th byte in memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If instead you have a 16 bit block, an address would define 2 bytes, and there would be only 2^20 addressable blocks. An address of 4 points to bytes 7 and 8 in memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, I would suspect that any decrease in address lines is more then made up for by the doubling of data lines.&lt;/p&gt;&#xA;" OwnerUserId="1507" LastActivityDate="2011-03-23T07:22:30.567" CommentCount="3" />
  <row Id="11883" PostTypeId="1" CreationDate="2011-03-23T08:01:52.583" Score="4" ViewCount="190" Body="&lt;p&gt;I have a AGM deep-cycle battery, 150 Ah, 12V: Banner &quot;Stand By Bull&quot; SBV12-150.&#xA;12V150AhC20.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Up until recently it was working quite OK, I was able many times, for many months, to drain about 170 mA from the battery for a month before recharging it (such a drain should not deplete the battery below 20% full).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But recently the performance suddenly dropped, the last time I tried to charge it, here is what happens: the voltage on the battery without any load before starting to charge was 9.69 V. I don't know why it was so low, because the battery was charged previously only 10 days ago with 16 hours of about 5A charge, at the end of which the voltage on the battery (while still charged) was 14.7 V, and the specifications of CCCV charging of an AGM battery say that an AGM battery is at least 80% full when the voltage reaches 14.1 V, so 14.7 V should be really full. And then the battery was used for 10 days with a load of about 170 mA, so no more then 41 Ah should have been depleted from the battery. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This time (after these 10 days of 170 mA load), I did 20 hours of 2A charge (which should put about 33 Ah back into the battery). The voltage on the battery at the end of charging was 14.0V. Then I disconnected the charger, and the voltage measured on the battery just after disconnecting the charger was 13.0V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And then I placed a 60 mA load on the battery, which is a very tiny load for such a big battery, and it should go for about 40 days like this on an 80% full AGM deep-cycle battery before the voltage should drop below 12V. But in my case, the voltage dropped below 12V after only 10 hours - this is about 100 times less than what it should be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there anything I can do to try to revive this battery? Is there something like a desulfation or equalization charge that I could try to restore this battery, and how to do it to have the highest chance of success?&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-03-23T19:39:04.450" Title="how can I try to revive this AGM deep-cycle battery which started to perform dramatically below specifications?" Tags="&lt;battery&gt;&lt;batteries&gt;&lt;battery-charging&gt;" AnswerCount="1" />
  <row Id="11884" PostTypeId="1" AcceptedAnswerId="11900" CreationDate="2011-03-23T08:25:08.883" Score="12" ViewCount="793" Body="&lt;p&gt;You need 4 channels to determine your position (including elevation), and I can understand that a few extra channels increase accuracy. However, there are maximum 12 satellites in view at any time, so why have receivers with more channels? I've seen receivers with 50 or even &lt;a href=&quot;http://www.amazon.co.uk/Bluenext-BN903S-Channels-GPS-Dongle/dp/B003Q6KZOQ&quot; rel=&quot;nofollow&quot;&gt;65 channels&lt;/a&gt;, that's more than the number of satellites up.&lt;br&gt;&#xA;I don't see any advantages in this explosion of number of channels, while I presume that it does increase the receiver's power consumption.&lt;br&gt;&#xA;So, why do I need 65 channels?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-03-23T09:02:29.540" LastActivityDate="2011-04-05T14:28:26.273" Title="How many GPS channels make sense?" Tags="&lt;gps&gt;" AnswerCount="4" FavoriteCount="4" />
  <row Id="11886" PostTypeId="1" CreationDate="2011-03-23T08:45:30.020" Score="5" ViewCount="198" Body="&lt;p&gt;I often hear of people using Matlab for circuit analysis, but I never actually figured out how it is done. I assume that there is something more to it than just setting up equations by hand and solving them in Matlab.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for a good starting point.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-23T08:58:44.397" LastActivityDate="2011-03-23T12:10:31.650" Title="How to do circuit analysis using Matlab?" Tags="&lt;matlab&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="3" />
  <row Id="11887" PostTypeId="2" ParentId="6066" CreationDate="2011-03-23T09:15:32.160" Score="2" ViewCount="" Body="&lt;p&gt;Maybe its a bit strange to answer my own question, but after a few months, I found an excellent detailed description with schematics how to make one here:&#xA;&lt;a href=&quot;http://www.gorum.ca/lvdisc.html&quot; rel=&quot;nofollow&quot;&gt;http://www.gorum.ca/lvdisc.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Scroll down to about 50% of the page, and there starts a description of a version built using Solid State High Side Switches instead of mechanical relay, because one with a mechanical relay, can drain even about 100 mA from the battery, which would be unacceptable in my situation, that would be a loss of 20 Ah per week!&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-03-23T09:15:32.160" CommentCount="3" />
  <row Id="11888" PostTypeId="2" ParentId="11884" CreationDate="2011-03-23T09:21:59.720" Score="3" ViewCount="" Body="&lt;p&gt;Yes, no need for more than 12. Initially we were limited to 4-5 channels, due to processing limitations, but now it's not the case. So, pure marketing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, these channels are 'software' (as frequency is the same for them all), so it's not really increaseing power consumption while not used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.gpsreview.net/gps-chipset-channels/&quot; rel=&quot;nofollow&quot;&gt;http://www.gpsreview.net/gps-chipset-channels/&lt;/a&gt; &quot;Why More?&quot;&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-23T09:21:59.720" CommentCount="3" />
  <row Id="11889" PostTypeId="2" ParentId="11827" CreationDate="2011-03-23T10:24:42.343" Score="1" ViewCount="" Body="&lt;p&gt;This morning, the device works, as far as I can tell, just as expected. I think it has to do with extensively bathing the PCB in alcohol. I use this flux which is conductive and has proven quite hard to remove, and it's also called &quot;FU&quot;. No, really. The 3.5V at the + input of the opamp is probably due to my DMM's input impedance. Clipping is because of my amp, and the volume is OK. Made a lot of silly mistakes, haven't I? There's still a lot to learn before I can call myself an electronics engineer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks everyone for the advice, you've given me some useful insights. Now, onto the bottom half of the schematic (relays), which I built beforehand, which previously worked, and which is probably going to give me some more hell until I get it to do what it has to...&lt;/p&gt;&#xA;" OwnerUserId="3075" LastActivityDate="2011-03-23T10:24:42.343" />
  <row Id="11890" PostTypeId="2" ParentId="11886" CreationDate="2011-03-23T12:10:31.650" Score="1" ViewCount="" Body="&lt;p&gt;I some time use &lt;a href=&quot;http://www.scipy.org&quot; rel=&quot;nofollow&quot;&gt;scipy&lt;/a&gt; (a numerical toolset for python) to do circuit analysis. And yes, that typically involves solving the circuit equations by hand first. This is mostly helpful when doing tolerance analysis and sensitivity analysis on the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a book on the subject &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0849322766&quot; rel=&quot;nofollow&quot;&gt;&quot;Tolerance Analysis of Electronic Circuits Using MATLAB&quot;&lt;/a&gt; that provides some examples of how to carry out the typical analysis on some common circuits. It's not really a replacement for something like SPICE, but is useful when trying to design for good production yield over all component tolerances, or to account for component drift over time and temperature.&lt;/p&gt;&#xA;" OwnerUserId="328" LastActivityDate="2011-03-23T12:10:31.650" CommentCount="1" />
  <row Id="11891" PostTypeId="2" ParentId="11879" CreationDate="2011-03-23T12:13:44.813" Score="2" ViewCount="" Body="&lt;p&gt;Using the Laplace transform in circuit analysis works just like normal complex analysis. You just plug $s$ instead of $j\omega$ everywhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ze4js.png&quot; alt=&quot;Laplace circuit analysis rules from Wikipedia&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The interesting part comes after you calculate one thing or another since you can use Laplace transfer function to &lt;a href=&quot;http://en.wikipedia.org/wiki/Bode_plot#Rules_for_hand-made_Bode_plot&quot; rel=&quot;nofollow&quot;&gt;draw a Bode (frequency and phase response) plot&lt;/a&gt; or to &lt;a href=&quot;http://en.wikipedia.org/wiki/Laplace_transform#Example_3%3a_Method_of_partial_fraction_expansion&quot; rel=&quot;nofollow&quot;&gt;calculate the circuit's response to any stimulus&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-23T12:13:44.813" />
  <row Id="11892" PostTypeId="2" ParentId="9820" CreationDate="2011-03-23T12:55:23.703" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://parts.digikey.com/1/parts/103789-jack-rt-angl-3-5mm-w-spdt-switch-sj-3568n.html&quot; rel=&quot;nofollow&quot;&gt;http://parts.digikey.com/1/parts/103789-jack-rt-angl-3-5mm-w-spdt-switch-sj-3568n.html&lt;/a&gt; - There is no picture but is this what you want?&lt;/p&gt;&#xA;" OwnerUserId="3140" LastActivityDate="2011-03-23T12:55:23.703" CommentCount="2" />
  <row Id="11893" PostTypeId="2" ParentId="11884" CreationDate="2011-03-23T13:10:31.467" Score="0" ViewCount="" Body="&lt;p&gt;The answer is that you don't.  The latest &lt;a href=&quot;http://www.u-blox.com/en/gps-chips/standard-gps-chips/ubx-g6010-gps-single-chip.html&quot; rel=&quot;nofollow&quot;&gt;u-Blox&lt;/a&gt; family of GPS receivers proudly boasts of &quot;High performance GPS with over 2 million correlators&quot;.  What that means I am not really sure but it makes a good number for the salesman to quote!&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2011-03-23T13:10:31.467" />
  <row Id="11895" PostTypeId="1" AcceptedAnswerId="11898" CreationDate="2011-03-23T13:42:32.013" Score="2" ViewCount="71" Body="&lt;p&gt;I have this wire-wound power resistor that appears to be either ceramic or porcelain in construction with a soft brown plastic or vinyl like coating. I want to find out its power rating. My meter shows about 5.2 ohms. A Google search for 160DR5WL returns nothing. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/CyCct.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/EQMLl.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/B3SZd.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/g3qIB.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2612" LastActivityDate="2011-03-23T14:00:10.510" Title="Need help identifing the power rating for this resistor." Tags="&lt;power&gt;&lt;resistor&gt;&lt;ratings&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="11896" PostTypeId="2" ParentId="11895" CreationDate="2011-03-23T13:57:28.587" Score="1" ViewCount="" Body="&lt;p&gt;Connect it to a suitable power supply and check it for yourself. You will need to judge when the temperature is excessive for your application. You could check against resistors of a similar size and value from the usual suppliers like Digi-Key.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-23T13:57:28.587" />
  <row Id="11897" PostTypeId="2" ParentId="11868" CreationDate="2011-03-23T13:57:32.477" Score="2" ViewCount="" Body="&lt;h1&gt;The Rules:&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;The International Traffic in Arms Regulation law (AKA ITAR) defines as a munition, in section &lt;a href=&quot;http://www.fas.org/spp/starwars/offdocs/itar/p121.htm#P121.16&quot; rel=&quot;nofollow&quot;&gt;§ 121.16 -- Missile Technology Control Regime Annex&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;...The following items constitute all items on the Missile Technology Control Regime Annex which are covered by the U.S. Munitions List: &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Item 11-Category II&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Avionics equipment, &quot;technology&quot; and components as follows; designed or modified for use in the systems in Item 1, and specially designed software therefor:&lt;br&gt;&#xA;  ...&lt;br&gt;&#xA;  (c) Global Positioning System (GPS) or similar satellite receivers;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;(1) Capable of providing navigation information under the following operational conditions:&lt;/p&gt;&#xA;  &#xA;  &lt;blockquote&gt;&#xA;    &lt;p&gt;(i) At speeds in excess of 515 m/sec (1,000 nautical miles/hours); and&lt;/p&gt;&#xA;    &#xA;    &lt;p&gt;(ii) At altitudes in excess of 18 km (60,000 feet), (see § 121.1, Category XV...)&lt;/p&gt;&#xA;  &lt;/blockquote&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.fas.org/spp/starwars/offdocs/itar/p121.htm#C-XV&quot; rel=&quot;nofollow&quot;&gt;Category XV - Spacecraft Systems and Associated Equipment&lt;/a&gt; part C similarly defines as a munition: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;(c) Global Positioning System (GPS) receiving equipment specifically designed, modified or configured for military use; or GPS receiving equipment with any of the following characteristics:&lt;br&gt;&#xA;  ...&lt;/p&gt;&#xA;  &#xA;  &lt;blockquote&gt;&#xA;    &lt;p&gt;(2) Designed for producing navigation results above 60,000 feet altitude and at 1,000 knots velocity or greater;&lt;/p&gt;&#xA;  &lt;/blockquote&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;h1&gt;The Results:&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;Your low-speed balloon should (in theory) be fine, because it's never going to exceed 1,000 knots.  However, many GPS receivers implement conformance by operating neither above 60,000 ft nor at speeds greater than 1000 knots. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/datasheets/GPS/Modules/D2523T%20V1.pdf&quot; rel=&quot;nofollow&quot;&gt;The datasheet&lt;/a&gt; for your module states, on the technical specifications page, under &quot;dynamic conditions&quot; that it's not defined to operate at greater than 1,000 knots.  I don't see any maximum for altitude.  Therefore, you need to call or email them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing that I do see, however, is the GGA specification on page 8, which formats the MSL Altitude as %5.1f - You won't get the right result above 99,999.9 feet.  I'm not sure if this means it overflows, or what happens.  Again, you need to contact the manufacturer.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-23T13:57:32.477" CommentCount="3" />
  <row Id="11898" PostTypeId="2" ParentId="11895" CreationDate="2011-03-23T14:00:10.510" Score="4" ViewCount="" Body="&lt;p&gt;I cannot say for sure who the manufacturer of this part is. I've used many of these sorts of resistors in my career, so my speculation below is made with a fair degree of confidence.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.renfrewelectric.com/prod_resistors_2.html&quot; rel=&quot;nofollow&quot;&gt;Renfrew wire-wound resistors&lt;/a&gt; that are 8&quot; long and 1 1/8&quot; in diameter are rated at 160W, which correlates with the 160D marking on the part. I'd hazard to guess that it's rated 160W (or very close to that). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;R5 on these sorts of parts usually implies 0.5 ohms. The other marks are probably tolerance and packaging codes. If you measure higher, and your meter is OK, the resistor may be somwhat fried.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-23T14:00:10.510" CommentCount="5" />
  <row Id="11899" PostTypeId="1" AcceptedAnswerId="11903" CreationDate="2011-03-23T14:47:25.090" Score="9" ViewCount="315" Body="&lt;p&gt;Each electronic device consumes electric power when it is &quot;idle&quot; unless it has a mechanical switch. I can understand that for example a TV with a remote control needs to &quot;be ready&quot; to receive a command from the remote control. But even a cell phone charger consumes power when it is connected to the outlet and not connected to the phone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, Nokia claims that one of its new chargers &lt;strong&gt;&lt;em&gt;consume less that 30 milliwatts&lt;/em&gt;&lt;/strong&gt; when not connected to the phone and they say it is very cool. I don't understand - the charger is a very simple device, what does it do with those 30 milliwatts?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why can't this standby consumption me made lower when we already have microprocessors with gazillions of transistors fitting onto a plate size of fingernail? What's the fundamental problem here?&lt;/p&gt;&#xA;" OwnerUserId="3552" LastActivityDate="2011-03-24T20:56:43.653" Title="Why is it so problematic to have close to zero standby power consumption?" Tags="&lt;power-supply&gt;&lt;power&gt;&lt;energy&gt;" AnswerCount="4" CommentCount="13" FavoriteCount="2" />
  <row Id="11900" PostTypeId="2" ParentId="11884" CreationDate="2011-03-23T15:05:11.527" Score="28" ViewCount="" Body="&lt;p&gt;The answer is complex due to the way the GPS system operates, so I'm going to simplify a number of things so you understand the principle, but if you are interested in how it's really implemented you'll need to go find a good GPS reference. &lt;strong&gt;In other words, what's written below is meant to give you an idea of how it works, but is technically wrong in some ways.  The below is not correct enough to implement your own GPS software.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Background&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;All the satellites transmit on essentially the same frequency.  They are technically walking all over each others' signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So how does the GPS receiver deal with this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, each satellite transmits a different message every mS.  The message is 1024 bits long, and is generated by a pseudo random number generator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The GPS receiver receives the entire spectrum of all the transmitters, then it performs a process called correlation - it generates the specific sequence of one of the satellites, multiplies it by the signal input, and if its signal matches a satellite's signal exactly then the correlator has found one satellite.  The mixing essentially pulls the satellite's signal out of the noise, and verified that 1) we have the right sequence and 2) we have the right timing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if it hasn't found a match, it has to shift its signal by one bit and try again, until it's gone through all 1023 bit periods and hasn't found a satellite.  &lt;em&gt;Then&lt;/em&gt; it moves on to trying to detect a different satellite at a different period.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Due to the time shifting (1023 bits, 1,000 transmissions per second), in theory it can completely search a code in one second to find (or determine there's nothing) at a particular code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Due to the code shifting (there are currently 32 different PRN codes, one each for each satellite) it can therefore take 30+ seconds to search each satellite.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Further, doppler shift due to the speed of the satellite relative to your ground speed, means that the timebase could be shifted by as much as +/- 10kHz, therefore requiring searching about 40 different frequency shifts for a correlator before it can give up on a particular PRN and timing.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;What this means&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;This leaves us with a possible worst case scenario (one satellite in the air, and we try everything but the exact match first) of a time to first fix off a cold start (ie, no information about the time or location of the receiver, or location of the satellites) of 32 seconds, assuming we don't make any assumptions, or perform any clever tricks, the received signal is good, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if you have two correlators, you've just halved that time because you can search for two satellites at once.  Get 12 correlators on the job and it takes less than a few seconds.  Get a million correlators and in theory it can take a few milliseconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Each correlator is called a &quot;channel&quot; for the sake of marketing.&lt;/strong&gt;  It's not wholly wrong - in a sense, the correlator is demodulating one particular coded frequency at a time, which is essentially what a radio receiver does when you switch channels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a lot of assumptions a GPS receiver can make, though, that simplify the problem space such that a generic 12 channel receiver can get a fix, in the worst case, in about 1-3 minutes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While you can get a 3D fix with a 4 channel GPS, when you lose a GPS signal (goes beyond the horizon, or you go under a bridge, etc) then you lose 3D fix and go to 2D fix with three satellites while one of your channels goes back into correlation mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now your receiver starts to downloaded the ephemeris and almanac, which allows the receiver to very intelligently search for signals.  After 12 minutes or so it knows exactly which satellites &lt;em&gt;should&lt;/em&gt; be in view.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the search goes pretty quickly because you know the position and code for each satellite, but you still only have a 2D fix until you actually find a new satellite.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a 12 channel receiver, though, you can use 4 of the strongest channels to provide your fix, a few channels to lock onto backup satellites so it can switch the calculations to them if needed, and several channels to keep searching for satellites the receiver should be able to see.  In this way you never lose the full 3D fix.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Since you can only see up to 12 satellites, why would you need more than 12 channels?&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;There are 24 or so GPS satellites operating at any given time, which means that on one point on the earth you can really only see half of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But remember - you can only search for one satellite per correlator, so the primary reason to increase correlators past twelve is to improve the time to first fix, and the main reason to improve that is for power consumption.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your GPS chipset has to be powered all the time, it's a 100mW power drain all the time.  If, however, you only need to turn it on once per second for only 10mS each time, then you just cut your power consumption down to 1mW.  This means your cell phone, location beacon, etc can operate for two orders of magnitude longer time on the same set of batteries while still maintaining a full real time fix on their location.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Further, with millions of correlators, one can do more exact searches which can help reduce the effects of radio reflections in urban canyons (tall buildings in big cities used to foul up GPS receivers with fewer correlators).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lastly, while only 4 satellites are needed to get a 3D fix, good receivers use more satellites in its position algorithm to get a more accurate fix.  So only a 4 channel receiver is required, but a 12 channel receiver can get more accuracy.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Conclusion&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;So the millions of correlators:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Speeds up satellite acquisition&lt;/li&gt;&#xA;&lt;li&gt;Reduces power consumption&lt;/li&gt;&#xA;&lt;li&gt;Reduces likelihood of losing a 3D fix even in urban canyons&lt;/li&gt;&#xA;&lt;li&gt;Provide better sensitivity, allowing fixes in dense forests, and even in some tunnels&lt;/li&gt;&#xA;&lt;li&gt;Provides better positioning accuracy&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;sub&gt;&lt;sup&gt;Thanks to borzakk for &lt;a href=&quot;http://www.reddit.com/r/ECE/comments/gavf7/what_do_they_mean_by_gps_channels/c1m81y7&quot; rel=&quot;nofollow&quot;&gt;some corrections&lt;/a&gt;.&lt;/sup&gt;&lt;/sub&gt;&lt;/p&gt;&#xA;" OwnerUserId="161" LastEditorUserId="161" LastEditorDisplayName="" LastEditDate="2011-04-05T14:28:26.273" LastActivityDate="2011-04-05T14:28:26.273" CommentCount="2" />
  <row Id="11901" PostTypeId="2" ParentId="11275" CreationDate="2011-03-23T15:10:57.683" Score="3" ViewCount="" Body="&lt;p&gt;From what i gather the AES key is loaded into the chip. And also there may be a CR232 check on the firmware as well or OTP fuses set&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ics.nxp.com/products/lpc3000/datasheet/lpc3152.lpc3154.pdf&quot; rel=&quot;nofollow&quot;&gt;source&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Supports un-secure boot from UART and USB (DFU class) interfaces during&#xA;  development. Once the AES key is programmed in the OTP, only secure boot is&#xA;  allowed through UART and USB.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This doesn't mean it cant be hacked, if you put the time into it. I would check to see if the JTAG pins have been disabled and start from there. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;some interesting statements from the &lt;a href=&quot;http://ics.nxp.com/support/documents/microcontrollers/pdf/user.manual.lpc315x.pdf&quot; rel=&quot;nofollow&quot;&gt;user guide&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;7.1 Production line use case&#xA;  At the NXP production line the OTP will be tested and programmed using JTAG. In test&#xA;  mode, the fuse block itself will be accessed directly. During programming the VPP will&#xA;  need a higher voltage than in the application use case. Written data is checked afterwards&#xA;  by reading out the fuses (using a low voltage on VPP)&#xA;  The customer will also program the OTP only at the production line, here DFU&#xA;  programming will be used.&#xA;  An image for programming customer-selected bits can be loaded into the device via USB.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;7.2 Application use case&#xA;  nitially it is important to make sure that the data_15 register is updated early during the&#xA;  initialization (by boot-code) this will set the security level. Four levels of security are&#xA;  implemented in the design:&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;• Level 0: nothing is protected.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;• Level 1: password protected. In this level, JTAG can be enabled by software after&#xA;  password sequence (depends on customer application) by setting the sticky bit&#xA;  'JTAG_EN' in OTP_con register.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;• Level 2: In this level, JTAG access can be enabled using special test equipment.&#xA;  Used by NXP for Returned Material Analysis only.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;• Level 3: JTAG is completely disabled and hence the chip is virtually locked.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;The customer can program the security level of the chip. For level 1, fuse-bit 509 should&#xA;  be set. For level 2, fuse-bits 509 and 510 are set. For level 3, fuse-bits 509, 510 and 511&#xA;  are programmed. A special case will be for the customer to disable writing to the fuses,&#xA;  but since in application a low voltage (for reading) will be connected to the VPP, writing will&#xA;  not be possible anyway.&#xA;  During normal application, the fuses will already have been programmed on the&#xA;  production line. So three options remain: copying the fuse data into the data registers,&#xA;  reading this data, and setting the read protection. The boot code will copy the fuse data&#xA;  into the data registers because this is needed for security and DRM. After this, the data&#xA;  can be read from the data registers via the APB0 bus (according to the read protection&#xA;  settings).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Edit: If the key is truly loaded, you will only be able to load custom firmware if you have the key.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-23T15:10:57.683" CommentCount="4" />
  <row Id="11902" PostTypeId="2" ParentId="11899" CreationDate="2011-03-23T15:24:10.337" Score="4" ViewCount="" Body="&lt;p&gt;It is very hard to make a PSU that can efficiently provide a couple of mW for standby as well as several Watts for actual use, so it's not too bad that Nokia managed to get standby consumption down to 30 mW for a charger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only way to be more efficient would be to have a separate PSU just to handle the standby consumption of the main PSU, but that could double the cost of a small charger, so it's unlikely to ever be done.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-03-23T15:24:10.337" />
  <row Id="11903" PostTypeId="2" ParentId="11899" CreationDate="2011-03-23T15:29:17.533" Score="8" ViewCount="" Body="&lt;p&gt;The mobile phone charger is a power conversion circuit which changes your power line voltage (110 or 220V) into something that is useful for your mobile phone (probably 5V). To do this it needs to have some electronic circuity inside which has to be powered and it has to function even if there is not phone around so it can detect one when you connect it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The charger could be merely a mechanical device like the power socket itself but it would then require all the charging circuity to be inside your phone. Unfortunately it is quite big and relatively heavy so it would be inconvenient to carry it around all the time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding the actual 30mW figure: if instead of mW you consider the currents involved you arrive at around 300μA (30mW at 100V). This also means a resistance of $330\,\mathrm{k\Omega}$. It is quite difficult to work using resistances higher than and currents lower than this while still having to sense the moment when somebody plugs the actual load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OTOH 30mW is really, really small. The vampire current draw problems are not as important as many believe. If you want a good review of many aspects of this then I suggest reading &lt;a href=&quot;http://www.withouthotair.com/&quot; rel=&quot;nofollow&quot;&gt;&quot;Sustainable Energy – without the hot air&quot;&lt;/a&gt;, especially the &lt;a href=&quot;http://www.inference.phy.cam.ac.uk/withouthotair/c19/page_114.shtml&quot; rel=&quot;nofollow&quot;&gt;chapter on this topic&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-24T11:35:52.097" LastActivityDate="2011-03-24T11:35:52.097" CommentCount="1" />
  <row Id="11904" PostTypeId="2" ParentId="11875" CreationDate="2011-03-23T15:56:50.787" Score="3" ViewCount="" Body="&lt;p&gt;With 16-bit wide memory a read of address xxx0 gives you two bytes: the byte at address xxx0 and the byte at address xxx1. So the addresses ending in &quot;1&quot; are superfluous; you only read address xxx0, never xxx1. Now, since the last address bit will always be zero, we can drop it, ending up with an address 1 bit shorter.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-03-23T15:56:50.787" />
  <row Id="11905" PostTypeId="2" ParentId="11734" CreationDate="2011-03-23T16:25:40.587" Score="1" ViewCount="" Body="&lt;p&gt;Yes, I also like the ways William Beaty explains&#xA;&lt;a href=&quot;http://amasci.com/amateur/elecdir.html&quot; rel=&quot;nofollow&quot;&gt;&quot;Which way does the &quot;electricity&quot; really flow?&quot;&lt;/a&gt;&#xA;and the distinction between the &lt;a href=&quot;http://amasci.com/miscon/ener1.html&quot; rel=&quot;nofollow&quot;&gt;flow of charged particles&lt;/a&gt; (nearly always very slow) and the &lt;a href=&quot;http://amasci.com/elect/poynt/poynt.html&quot; rel=&quot;nofollow&quot;&gt;flow of electrical energy&lt;/a&gt; (nearly always very fast).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Alas, this isn't really an answer to your question, but a response to some of the responses to it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;The only way you can get positive charges to move (instead of the absence of negative charges, if we're going to differentiate that) is through transporting atom nuclei.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, that is exactly how positive charge does move.&#xA;In a &lt;a href=&quot;http://www.google.com/search?q=proton+conductor&quot; rel=&quot;nofollow&quot;&gt;proton conductor&lt;/a&gt; such as ice, you can think of the moving positive charges as hydrogen nuclei.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&quot;In a solid or crystal structure the flow of positive charges will be extremely slow, and possibly damaging&quot;&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes. Also, the flow of electrons is also surprisingly slow, and often damaging.&#xA;The charged particles that move through solids are typically very small -- electrons in a metal, protons in a proton conductor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, quite large charged particles -- both positive and negative -- flow through battery electrolyte (liquid) and during &lt;a href=&quot;http://en.wikipedia.org/wiki/electric_glow_discharge&quot; rel=&quot;nofollow&quot;&gt;electric glow discharge&lt;/a&gt; (gas).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;fluorescent bulbs&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some people claim that &lt;em&gt;current in fluorescent bulbs is indeed the flow of electrons&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, during the brief fraction of a second when first applying power to a &quot;cold&quot; tube, electrons are the only charged particles available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When first starting a &quot;cold&quot; tube,&#xA;the cathode (because it is metal) has plenty of movable &quot;free&quot; electrons available,&#xA;and yet the tube has a very high resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Later, after striking an electric &quot;arc&quot; (&lt;a href=&quot;http://en.wikipedia.org/wiki/electric_glow_discharge&quot; rel=&quot;nofollow&quot;&gt;electric glow discharge&lt;/a&gt;), during normal operation of a fluorescent bulb or neon light, there are lots of charged ions available.&#xA;Since the tube has a much lower resistance at that time, (a) fluorescent tubes require ballast, and (b) we are led to conclude that most of current involves charged ions rather than electrons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When a fluorescent lamp &quot;operated from DC, the starting switch is often arranged to reverse the polarity of the supply to the lamp each time it is started; otherwise, the mercury accumulates at one end of the tube.&quot; -- &lt;a href=&quot;http://en.wikipedia.org/wiki/Fluorescent_lamp#Electrical_aspects_of_operation&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is evidence that charged mercury ions physically move in a fluorescent lamp.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-23T16:25:40.587" CommentCount="1" />
  <row Id="11906" PostTypeId="1" CreationDate="2011-03-23T16:48:02.440" Score="3" ViewCount="240" Body="&lt;p&gt;Ok, so I need to generate 50 V from 5 V, with a load of 0 to 20 mA, for a mass-produced device.  There are simple boost converter circuits like this &lt;a href=&quot;http://www.linear.com/product/LT3467&quot; rel=&quot;nofollow&quot;&gt;LT3467&lt;/a&gt; example:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/93Ytf.png&quot; alt=&quot;5 V to 50 V boost converter&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but it seems these are limited by the maximum voltage on SW (in this case 42 V).  Are there any that can go directly to 50 V?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not, there seem to be several possibilities:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;external FET with higher voltage rating&lt;/li&gt;&#xA;&lt;li&gt;charge pump after the boost converter &lt;/li&gt;&#xA;&lt;li&gt;autotransformer instead of inductor&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;1: Is adding an external FET sufficient to get up this high?  It seems like it, though I don't know how much current this can supply:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/1U71V.png&quot; alt=&quot;5 V to 50 V converter with external FET&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(&lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/3425&quot; rel=&quot;nofollow&quot;&gt;from here&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2: Can also use a charge pump / voltage doubler after the boost converter, without an external FET, something like this (with the FET built into the boost converter IC):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/FsXa4.jpg&quot; alt=&quot;voltage-doubler boost converter&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(&lt;a href=&quot;http://electronicdesign.com/article/power/Solving-The-Power-Puzzle-For-Edge-Lit-LED-TV-Backlighting.aspx&quot; rel=&quot;nofollow&quot;&gt;from here&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then the SW voltage can be half (or less) of the output voltage.  One advantage of this is that it produces intermediate voltages, which might be useful.  In this case, should the feedback be before or after the voltage doubler?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3: Other examples show an autotransformer replacing the inductor, and no external FET:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/EWSVu.png&quot; alt=&quot;3V to 75 V converter with autotransformer&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(&lt;a href=&quot;http://focus.ti.com.cn/cn/lit/an/slva245/slva245.pdf&quot; rel=&quot;nofollow&quot;&gt;from here&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(&lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/1109&quot; rel=&quot;nofollow&quot;&gt;more here&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, uh, what's the simplest/cheapest/best way to do this?  What are the advantages and disadvantages of each solution?  Which external components cost the most?  Which solution can supply the highest current?  Which has the best output regulation?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-28T15:38:18.000" LastActivityDate="2011-03-28T15:38:18.000" Title="Best way to produce 50 VDC, 20 mA from 5 V" Tags="&lt;power-supply&gt;&lt;boost&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="2" />
  <row Id="11907" PostTypeId="2" ParentId="11734" CreationDate="2011-03-23T17:11:39.707" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Aluminum&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In &lt;a href=&quot;http://en.wikipedia.org/wiki/Hall-H%C3%A9roult_process&quot; rel=&quot;nofollow&quot;&gt;the most common process&lt;/a&gt; of converting naturally occurring aluminum (fully oxidized AL2O3) to the more useful metallic aluminum, workers drop aluminum oxide into molten cryolite, which produces free Al3+ and O2- ions.&#xA;Then a voltage across two carbon electrodes attracts the Al3+ ions to the negative electrode (cathode), where it becomes uncharged pure liquid Al and sinks to the bottom, where it is tapped off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Aluminum is the most abundant metallic atoms in the Earth's crust.&#xA;Metallic aluminum is now a common, everyday household material, used in many electrical components, and the process of making aluminum uses a significant fraction of all the electrical energy produced every day. But does this really qualify as an &quot;everyday component&quot;?)&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-23T17:11:39.707" />
  <row Id="11908" PostTypeId="2" ParentId="11869" CreationDate="2011-03-23T17:27:21.647" Score="0" ViewCount="" Body="&lt;p&gt;Most appliances use timers or level switches as mentioned before. To answer your specific question, you can use one of these: &lt;a href=&quot;http://www.seeedstudio.com/depot/water-flow-sensor-p-635.html?cPath=6&amp;amp;zenid=594b89701c7a2015a13064b67aed4f44&quot; rel=&quot;nofollow&quot;&gt;http://www.seeedstudio.com/depot/water-flow-sensor-p-635.html?cPath=6&amp;amp;zenid=594b89701c7a2015a13064b67aed4f44&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't tried one yet, but the price is so low (flow sensors tend to be expensive!!) I can't resist.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-03-23T17:27:21.647" />
  <row Id="11909" PostTypeId="2" ParentId="11906" CreationDate="2011-03-23T17:31:14.073" Score="3" ViewCount="" Body="&lt;p&gt;Try the Nat Semi Simple Switchers. &lt;a href=&quot;http://webench.national.com/webench5/power/webench5.cgi?lang_chosen=&amp;amp;VinMin=5&amp;amp;VinMax=6&amp;amp;O1V=50&amp;amp;O1I=.050&amp;amp;op_TA=30&quot; rel=&quot;nofollow&quot;&gt;Here are some examples&lt;/a&gt; I found with their interactive selection tool.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used 5V to 6V input, 50V output and a current of 50 mA. You should be able to design a suitable circuit on-line that meets your cost and performance requirements.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-28T12:05:46.640" LastActivityDate="2011-03-28T12:05:46.640" />
  <row Id="11910" PostTypeId="1" CreationDate="2011-03-23T17:55:47.670" Score="4" ViewCount="244" Body="&lt;p&gt;I'm evaluating different processors for a small hoby project. My first choice was the Z80 but it seem to be hard to come by nowdays. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whats left for us that wants an 8/16 bit CPU clocked on 10-20 Mhz with an external memory bus ? &lt;/p&gt;&#xA;" OwnerUserId="3186" LastActivityDate="2011-03-24T06:50:38.860" Title="8/16 bit microprocessor for hobby project" Tags="&lt;memory&gt;&lt;cpu&gt;" AnswerCount="6" CommentCount="5" FavoriteCount="1" />
  <row Id="11911" PostTypeId="2" ParentId="11899" CreationDate="2011-03-23T18:05:10.077" Score="3" ViewCount="" Body="&lt;p&gt;There are several problems. But the most obvious one is that every consumer product has some kind of standby mode. Don't forget, when your PC is off, it will easily draw about 100mA from the +5V. A ATX PSU has a special +5V Standby line, which can deliver up to 2A according to the specification. This is all just circuitry to monitor whether the PC needs to be turned on, wake up LAN, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a charger I could imagine that most of the power is wasted to some monitoring circuit to see if a phone connects. If so, it will probably active a 'bigger' supply to power the whole thing up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, a switching power supply gets a peak effiency closer to it's maximum rating than to it's minimum rating. A controller needs current to operate as well. It needs to have a oscillator (generate a reference signal to PWM from), feedback, etc. Low duty cycles aren't helping neither, because little energy gets powered.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;30mW is not much. If you assume they would use a perfect AC to DC transformation, you will still use only 2.5mA at 12V. &lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-03-23T18:05:10.077" CommentCount="3" />
  <row Id="11912" PostTypeId="2" ParentId="11910" CreationDate="2011-03-23T18:08:54.287" Score="2" ViewCount="" Body="&lt;p&gt;There are some PICs with external memory interfaces that can address up to 2 Mbytes (code or data):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/00869b.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ww1.microchip.com/downloads/en/AppNotes/00869b.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-23T18:49:19.837" LastActivityDate="2011-03-23T18:49:19.837" />
  <row Id="11913" PostTypeId="2" ParentId="11883" CreationDate="2011-03-23T18:23:42.490" Score="1" ViewCount="" Body="&lt;p&gt;I found &lt;a href=&quot;http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries&quot; rel=&quot;nofollow&quot;&gt;an article on deep-cycle batteries&lt;/a&gt;, and they comment that if a battery goes below 10.5V, it's &quot;dead&quot; due to the specific gravity of the acid being too low to be useful any more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It appears that you may need a new battery. : (&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-23T18:23:42.490" />
  <row Id="11914" PostTypeId="1" AcceptedAnswerId="14524" CreationDate="2011-03-23T18:49:33.273" Score="2" ViewCount="89" Body="&lt;p&gt;I have a huge, cheap and dumb battery charger which can charge a 12 V lead-acid battery with 70A, but it only outputs anything near (by &quot;near&quot; I mean over 30A) that value if I give him a completely empty, dead battery. As soon as it starts charging it, the current drops, quite quickly well below 20A, and most of the charging is done at about 10A, in fact it decreases linearly all the time. AFAIK this is called a &quot;taper charger&quot; and is the cheapest, most dumb lead-acid battery charger common on the market.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The battery I want to charge has in the specifications that you can charge it with a maximum of 38A in the &quot;Constant Current&quot; phase of CCCV charging, in which 80% of the battery capacity can be filled. I want to modify my cheap charger to actually do that - to charge with a constant current of 38A up until the voltage at the battery terminals reaches 14.4V, and then just turn-off (I can do this manually, I won't leave it for unattended charging anyway).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any idea how such cheap taper chargers are commonly made, and what could be done to modify one to a constant current charger?&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-05-21T13:29:22.673" Title="how to modify a taper charger of lead-acid batteries to be a constant current charger?" Tags="&lt;battery&gt;&lt;batteries&gt;&lt;battery-charging&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="11915" PostTypeId="2" ParentId="11910" CreationDate="2011-03-23T18:52:33.640" Score="10" ViewCount="" Body="&lt;p&gt;Maybe you should let go of the idea that for small hobby projects 8-bitters are always the best solution. Nowadays 32-bitters, esp. ARM, are everywhere and they have become serious competitors for the often older 8/16-bit parts, both price-wise and toolchain-wise.&lt;br&gt;&#xA;Besides, in your comment you mention 512 KB internal memory, and you won't find that easily on pure 8-bitters; they tend to have a 16-bit address bus which means 64 KB maximum.&lt;br&gt;&#xA;If you think an ARM may suit you, you may have a look at &lt;a href=&quot;http://mbed.org/&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt;:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;This mbed Microcontroller is based on the NXP LPC1768 with an ARM Cortex-M3 Core running at 96MHz, &lt;strong&gt;512KB FLASH&lt;/strong&gt;, 64KB RAM and lots of interfaces including Ethernet, USB Device and Host, CAN, SPI, I2C and other I/O.&quot;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-03-23T18:52:33.640" CommentCount="3" />
  <row Id="11918" PostTypeId="2" ParentId="11805" CreationDate="2011-03-23T19:54:00.630" Score="3" ViewCount="" Body="&lt;p&gt;If one has a half-egabyte of byte-addressable memory, there has to be a way of generating a 19-bit address.  One nice easy approach is to have a CPU whose address bus has 19 or more address lines (e.g. an 8088).  Another approach is to have some of the address lines generated by something other than the CPU's address bus.  For example, suppose one has a CPU with a 16-bit address bus and one wants to construct a system with 32K of RAM and ~512KB of ROM.  One could use a 13-input AND to detect an access to address 0xFFF0-0xFFFF (one input of the AND would be tied to an 'address valid' signal), and a 4-bit latch to grab the bottom 4 bits of such an address.  Fifteen of the ROM address bits would be attached to the CPU's address bus; the other four bits would be connected to latch outputs.  The net effect would be that the ROM would be divided into sixteen banks of 32KB each, all of which would be accessed from 0x8000-0xFFEF.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that such a system wouldn't quite have 512KB of usable ROM, since accessing any of the last 16 bytes of each 32K bank would switch to one particular 32K bank.  Thus, 0xFFF0 would only be available on bank 0, 0xFFF1 from bank 1, etc.  Further, in many cases, one would end up having to duplicate some code in different banks.  Still, such a system would be quite practical and is in fact very close to what was done in many things like 1980's arcade games.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-23T19:54:00.630" CommentCount="5" />
  <row Id="11919" PostTypeId="1" AcceptedAnswerId="11923" CreationDate="2011-03-23T20:35:18.950" Score="5" ViewCount="149" Body="&lt;p&gt;I just built a small 5.1V regulator with LM317, using 220 and 680 ohm resistors. However, I measure 8.6V at the output without a load connected. Is this normal, i.e. under a load (about 120 ohm) it would drop to 5.1V? The input is a 9V/300mA unregulated wall wart, which reads about 13V without a load.&lt;/p&gt;&#xA;" OwnerUserId="3075" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-03-24T00:51:39.470" LastActivityDate="2011-03-24T00:51:39.470" Title="Is it normal for LM317 to give a higher voltage without a load?" Tags="&lt;voltage-regulator&gt;&lt;lm317&gt;" AnswerCount="3" CommentCount="0" FavoriteCount="1" />
  <row Id="11922" PostTypeId="2" ParentId="11910" CreationDate="2011-03-23T20:44:05.150" Score="1" ViewCount="" Body="&lt;p&gt;ez80 series is available both as microprocessor and microcontroller. It can address 24 bits of memory and comes with plenty of peripherals. It's compatible with Z80.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are the microprocessors (but the microcontrollers have memory busses too and are actually cheaper):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556260&amp;amp;k=ez80&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556260&amp;amp;k=ez80&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They also have development boards.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-03-23T20:44:05.150" />
  <row Id="11923" PostTypeId="2" ParentId="11919" CreationDate="2011-03-23T20:51:54.020" Score="14" ViewCount="" Body="&lt;p&gt;You need a minimum load of 10mA for it to be stable. A tip is to add  a LED and run it on 5mA. You'll know whether the supply is on, and it will add additional load to make it stable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that the adjustment resistors of 220+680 ohm also give some load, of about 5.6mA. Together with a LED you get more than the required 10mA.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastEditorUserId="1476" LastEditorDisplayName="" LastEditDate="2011-03-23T21:07:43.727" LastActivityDate="2011-03-23T21:07:43.727" CommentCount="3" />
  <row Id="11924" PostTypeId="2" ParentId="11919" CreationDate="2011-03-23T20:59:50.423" Score="2" ViewCount="" Body="&lt;p&gt;The regulator works mostly like a resistor which is automatically adjusting itself so if there is too little current the voltage drop on the regulator will be too small to regulate the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is possible to make regulators that work without load but they tend to suffer from high quiescent current.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-23T20:59:50.423" CommentCount="2" />
  <row Id="11925" PostTypeId="2" ParentId="10487" CreationDate="2011-03-23T21:07:05.910" Score="1" ViewCount="" Body="&lt;p&gt;What about adding several bottom resistors to the feedback divider and switching one of them (or several at once) to ground with an NPN array to switch the output voltage?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: You should be able to do this with only normal GPIO pins since they really should not see more than 1.23V (the feedback voltage) so they can work as open collector/drain switches.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-23T21:36:37.813" LastActivityDate="2011-03-23T21:36:37.813" CommentCount="1" />
  <row Id="11926" PostTypeId="2" ParentId="11906" CreationDate="2011-03-23T21:15:43.863" Score="0" ViewCount="" Body="&lt;p&gt;From the ideas you provided I think the one with the external switch is the easiest. Obtaining or wiring your own flyback inductors is more difficult than just buying a medium-voltage MOSFET.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just be sure that you use a chip with adequate output since an open drain output of a typical intergrated-switch DC/DC converter will not work with an external MOSFET.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not sure how you want to use the 10V switched capacitor circuit. All these are non-isolated circuits so you cannot just add the 10V to the 40V gnd-to-rail.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-23T21:15:43.863" CommentCount="2" />
  <row Id="11928" PostTypeId="2" ParentId="11910" CreationDate="2011-03-23T21:44:33.363" Score="1" ViewCount="" Body="&lt;p&gt;For that kind of application it boils down to two main product lines: PIC (Microchip) and AVR (Atmel). Both have many models from the very basic (the ATTiny13, for instance, is 10 MHz and costs about $1) to the quite sophisticated (barely overlapping the entry level ARMs). All of them support SPI/I2C via software or hardware, and those with enough interface pins can be connected to external memory. For those who don't, there's also the option of using a SPI memory. Also there are many options of tools for development &amp;amp; debugging, many of them free or low-cost. &lt;/p&gt;&#xA;" OwnerUserId="1078" LastActivityDate="2011-03-23T21:44:33.363" CommentCount="0" />
  <row Id="11929" PostTypeId="2" ParentId="10350" CreationDate="2011-03-23T22:22:41.020" Score="1" ViewCount="" Body="&lt;p&gt;If you know your symbol shape is a square pulse, then you know this will be a sync function in the frequency domain. If you take an FFT of the signal and measure the width of the first lobe of the data (or 2x the lobe at baseband), that will be your symbol rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An early-late gate symbol synchronizer can easily be implemented, but you'll need to first run the data through a matched filter, which will require at least an estimate of the symbol rate.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-03-23T22:22:41.020" />
  <row Id="11931" PostTypeId="2" ParentId="11869" CreationDate="2011-03-23T22:40:40.700" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.proteusind.com/products/flow_meter.html&quot; rel=&quot;nofollow&quot;&gt;Proteus Industries&lt;/a&gt; makes electronic flow meters. They came to mind because I once helped swap one out in a high powered laser exciter; one was used to detect if the flow of water cooling the system was inadequate, and would shut down power.&lt;/p&gt;&#xA;" OwnerUserId="2028" LastActivityDate="2011-03-23T22:40:40.700" />
  <row Id="11932" PostTypeId="1" CreationDate="2011-03-23T22:57:56.303" Score="0" ViewCount="128" Body="&lt;p&gt;I'm after a 12V to 5V voltage regulator. I'm after a more commercial/consumer version with an enclosure rather than a board with doodads on it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only one I can really find is made by Tycon Power and I can only find one online store that acutally stocks the item.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anybody know of any other regulators?&lt;/p&gt;&#xA;" OwnerUserId="3557" LastActivityDate="2011-03-23T23:11:45.720" ClosedDate="2011-03-23T23:30:20.020" Title="12V - 5V step down voltage regulator" Tags="&lt;voltage-regulator&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11933" PostTypeId="2" ParentId="11932" CreationDate="2011-03-23T23:11:45.720" Score="0" ViewCount="" Body="&lt;p&gt;A quick search brings up &lt;a href=&quot;http://cgi.ebay.co.uk/5V-9V-12V-24V-Voltage-Regulator-Stabilizer-Circuit-PCB-/170616920282?pt=UK_BOI_Electrical_Components_Supplies_ET&amp;amp;hash=item27b98f98da&quot; rel=&quot;nofollow&quot;&gt;this production quality board&lt;/a&gt; on eBay for a reasonable price, albeit not in a case. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-23T23:11:45.720" />
  <row Id="11934" PostTypeId="2" ParentId="11910" CreationDate="2011-03-23T23:37:27.130" Score="4" ViewCount="" Body="&lt;p&gt;Interfacing with an external memory module is best done with a hardware peripheral known as an External Memory Interface (tricky, huh?).  An External Bus Interface can also be adapted for the purpose.  These peripherals are abbreviated EMI/EBI on manufacturer and distributor parametric search engines.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using Digikey's parametric search, for example, I note 209 different parts have an EMI or EBI (with a few other distinctions, like onboard Flash, solderable packages, and less-than-reel quantities) .  The following is a selection of the more well-known processors from that set: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;AVR Xmega&lt;/li&gt;&#xA;&lt;li&gt;Arm Cortex-M0&lt;/li&gt;&#xA;&lt;li&gt;Arm Cortex-M3&lt;/li&gt;&#xA;&lt;li&gt;Arm 7&lt;/li&gt;&#xA;&lt;li&gt;Arm 9&lt;/li&gt;&#xA;&lt;li&gt;Coldfire&lt;/li&gt;&#xA;&lt;li&gt;STMicroelectronics   ST9&lt;/li&gt;&#xA;&lt;li&gt;ZNEO (Zilog 16-bit successor to Z80)&lt;/li&gt;&#xA;&lt;li&gt;8051&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="857" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-03-24T06:50:38.860" LastActivityDate="2011-03-24T06:50:38.860" CommentCount="3" />
  <row Id="11935" PostTypeId="2" ParentId="11919" CreationDate="2011-03-24T00:08:48.953" Score="4" ViewCount="" Body="&lt;p&gt;One way to ensure a minimum load is to make sure the feedback network draws the minimum load. For example 240 ohms and 75 ohms gives a 5.25V output and draws 16mA. Tweak the resistors to get it perfect.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-03-24T00:47:31.800" LastActivityDate="2011-03-24T00:47:31.800" />
  <row Id="11937" PostTypeId="2" ParentId="11869" CreationDate="2011-03-24T02:46:35.693" Score="0" ViewCount="" Body="&lt;p&gt;Cheap appliances typically use a water regulator and a timer.  Some water inlet valves include the pressure regulator, so you can buy one part and get both the regulator to give you a consistent flow, and a solenoid to turn the flow on and off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could try one similar to this: &lt;a href=&quot;http://www.repairclinic.com/PartDetail/Water-Inlet-Valve/1259376&quot; rel=&quot;nofollow&quot;&gt;http://www.repairclinic.com/PartDetail/Water-Inlet-Valve/1259376&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2011-03-24T02:46:35.693" />
  <row Id="11938" PostTypeId="1" AcceptedAnswerId="11951" CreationDate="2011-03-24T02:47:38.730" Score="4" ViewCount="128" Body="&lt;p&gt;I have a modern microprocessor (Cortex-M3) with a decent ADC (10-bit 400kSPS or 12-bit 200kSPS).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How to design and build a simple DSSS system for learning purposes? What is the simplest RF front-end that would be needed for this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bandwidth is not very important but the system should demonstrate high noise resistance since this is one of the big selling points of DSSS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hoped I would get more information on how to proceed on the software side. Like should I do blind correlation of the whole buffer at every sample or are there any &quot;magic&quot; tricks. Maybe I should ask another, more focused question.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-26T01:30:09.987" LastActivityDate="2011-03-26T01:30:09.987" Title="How to build a simple DSSS (direct sequence spread spectrum) transceiver?" Tags="&lt;rf&gt;&lt;spread-spectrum&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="11939" PostTypeId="2" ParentId="11910" CreationDate="2011-03-24T03:25:25.330" Score="2" ViewCount="" Body="&lt;p&gt;ARM is the way to go, lots of various sizes of ram vs flash.  Every combination of size speed, power, etc.  Mainstream tools, etc.  For an external memory interface Cirrus has ARM products.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you say 512KB I assume that is just for data and you need flash and/or ram for the program as well.  Depending on the instruction set the amount of program space can/will vary dramatically.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The next question is how fast do you need to get at this memory, you could probably go with some spi or i2c and use pretty much any micro if it doesnt have to be lightnight fast.  Granted if you were looking for a handful of megahertz 8/16 processor then for the same price you can get into a 50-80mhz arm and probably get similar memory speeds to the 8/16 micro with a serial memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the price of an arduino you can get a GameboyAdvance, 17mhz ARM7 256K plus 32M of onboard memory, then for a little over half the price of a second arduino 512KB of ram, plus another 16KB plus 32MB of flash.  You get a display and serial port as a freebie...&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-03-24T03:25:25.330" />
  <row Id="11940" PostTypeId="1" CreationDate="2011-03-24T03:35:05.040" Score="4" ViewCount="145" Body="&lt;p&gt;I was thinking trying to make a little prototype of a wireless mouse that was left-handed or right-handed depending on which side of the keyboard it's on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How might I modify a mouse so that the signals from the button clicks cross if they are on oppisite sides of the keyboard?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking some kind of small component that knows if it's with a keyboards-width-distance of something attached to one side of the keyboard could toggle whatever mechanism does the reversing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this maybe doable?&lt;/p&gt;&#xA;" OwnerUserId="3559" LastActivityDate="2011-03-24T16:01:50.780" Title="how might i make a mouse who's L and R buttons flip depending on what side of the keyboard it's on?" Tags="&lt;mouse&gt;" AnswerCount="6" CommentCount="2" />
  <row Id="11941" PostTypeId="2" ParentId="616" CreationDate="2011-03-24T04:22:19.463" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0945053282&quot; rel=&quot;nofollow&quot;&gt;Getting Started in Electronics [Forrest M. Mims III]&lt;/a&gt; is a very simple book that gives a gentle introduction to a broad range of electrical topics. It is definitely worth a read for anyone starting with electronics.&lt;/p&gt;&#xA;" OwnerUserId="2561" LastActivityDate="2011-03-24T04:22:19.463" CommunityOwnedDate="2011-03-24T07:55:53.500" />
  <row Id="11942" PostTypeId="2" ParentId="11940" CreationDate="2011-03-24T05:08:04.937" Score="5" ViewCount="" Body="&lt;p&gt;a manual switch would be the easiest, but you could use IR LEDs on each side of the key board and 2 IR receivers one on each side of the mouse, then it just detects which side the IR led is lit up on and changes the buttons to the correct configuration.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-24T05:08:04.937" />
  <row Id="11943" PostTypeId="2" ParentId="11940" CreationDate="2011-03-24T06:24:16.587" Score="3" ViewCount="" Body="&lt;p&gt;You could do a hall effect sensor in the mouse with a magnet embedded in the mousepad or desk.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on which side of the mousepad is face-up, the hall effect sensor will return a positive or negative value reflecting the north or south side of the magnetic field.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could then switch the left and right mouse buttons based on the values coming from the hall effect sensor.&lt;/p&gt;&#xA;" OwnerUserId="1477" LastActivityDate="2011-03-24T06:24:16.587" CommentCount="0" />
  <row Id="11944" PostTypeId="2" ParentId="11940" CreationDate="2011-03-24T07:33:35.897" Score="1" ViewCount="" Body="&lt;p&gt;You could put an IR LED mounted on the mouse powered by it's internal battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could then put a IR receiver mounted on &lt;em&gt;one&lt;/em&gt; side of the keyboard facing to the side. Then build a simple IR recieve circuit that detects the presence of the mouse one side, or the non-presence of the mouse meaning it must be on the other side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The IR reciever on the keyboard doesn't have to have any special keyboard interface, as it's the mouse that's wireless and not the keyboard then just have your circuit wired to the serial port on your computer, then perform the button switching in software depending on the signal received on the serial port.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-24T07:33:35.897" CommentCount="7" />
  <row Id="11945" PostTypeId="1" AcceptedAnswerId="11947" CreationDate="2011-03-24T08:37:31.627" Score="1" ViewCount="101" Body="&lt;p&gt;Hi, I found a TV-Set in a dumpster, and checked if it's still working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Indeed it is somewhat functional, but the picture is distorted:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/vRdBo.jpg&quot; /&gt;&lt;em&gt;(screenshot of the TV)&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending how bright the picture is, it get's more or less vertically &quot;compressed&quot;, where the upper half is more compressed than the lower part.&#xA;The brighter the picture, the more compressed it becomes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also a combing effect, and the picture seems horizontally slightly shrunk.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the picture is very bright, as in almost white, the screen flashes, and sound disappears.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the brighter the picture, the more 50Hz noise I can hear from the speakers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect either the V-control IC to be broken (TDA3653B), or one of the capacitors connected to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, some of the AC/DC capacitors might be dried out or otherwise broken.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions?!&lt;/p&gt;&#xA;" OwnerUserId="2134" LastEditorUserId="2134" LastEditorDisplayName="" LastEditDate="2011-03-25T05:18:00.753" LastActivityDate="2011-03-25T05:18:00.753" Title="V-control broken on old (CRT) TV-Set?" Tags="&lt;tv&gt;&lt;repair&gt;&lt;problem&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="11946" PostTypeId="1" AcceptedAnswerId="11950" CreationDate="2011-03-24T08:51:24.470" Score="3" ViewCount="118" Body="&lt;p&gt;I want to build a litle POV display, but I didn't get how the power (and if possible a communication line) are transmited to the spinning part. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've looked at some POV project but they usualy doesn't explain that part a lot...&lt;/p&gt;&#xA;" OwnerUserId="2040" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-05-02T02:54:08.787" LastActivityDate="2011-05-02T02:54:08.787" Title="power for POV display" Tags="&lt;power&gt;&lt;data&gt;&lt;pov&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="11947" PostTypeId="2" ParentId="11945" CreationDate="2011-03-24T09:23:42.970" Score="1" ViewCount="" Body="&lt;p&gt;What makes me curious is the 50 Hz noise whenever the picture is bright. Tow possible reasons come to mind:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Interference from the (broken?) vertical deflection stage or backwards from there to the power supply and then on to the audio amp&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Ripple from the power supply (should be 100 Hz, though.) The total power increases for bright pictures, hence the ripple voltag would increase as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does the TV have a traditional power supply that uses a 50 Hz transformer or does it have a switch-mode power supply?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have a scope? Are you able to probe the various supply rails, especially the one that powers the vertical deflection circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an extremely good app'note with tons of typical oscillograms and ICs that are likely very similar to the ones your TV uses: &lt;a href=&quot;http://www.nxp.com/documents/application_note/APPCHP4.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.nxp.com/documents/application_note/APPCHP4.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some more hints after I have checked my old funny book that has pages after pages with pictures of ill TVs and list their possible causes (ISBN 978-3772350580); parts refer to Fig 4 in the &lt;a href=&quot;http://www.alldatasheet.com/datasheet-pdf/pdf/77335/PHILIPS/TDA3653.html&quot; rel=&quot;nofollow&quot;&gt;TDA3653 data sheet&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Check electrolytic cap in the vertical amp's supply (220 µF). Also check the decouplig resistor (4,7 Ohm)&lt;/li&gt;&#xA;&lt;li&gt;Check electrolytic cap in the vertical oscillator or flyback circuit (100 µF).&lt;/li&gt;&#xA;&lt;li&gt;Check big cap at deflection coil (1500 µF) and 1,2 Ohm resistor.&lt;/li&gt;&#xA;&lt;li&gt;Check feedback circuit (4,7 µF)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-03-24T20:20:44.793" LastActivityDate="2011-03-24T20:20:44.793" CommentCount="4" />
  <row Id="11948" PostTypeId="2" ParentId="11940" CreationDate="2011-03-24T09:32:08.287" Score="1" ViewCount="" Body="&lt;p&gt;I'd suggest a simpler solution: check if the movement sensor of the mouse can detect when the mouse is lifted up (Don't know it that's doable, but I believe it is), if not, add a little sensor to the bottom of the mouse, that checks if the mouse sits on ground. Now, when the mouse is lifted up by, say 15cm, you put the mouse in a 'unset' state, the first button that is pressed, after the mouse lands on a surface, defines button orientation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example: Mouse sits on right of keyboard: Lift mouse, and put it back at left side of keyboard.&#xA;Press &lt;strong&gt;right&lt;/strong&gt; mouse button: Mouse is now a left-hand mouse (right button = Button 1).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the laser - that most mice nowadays have - or the LED led is capable of detecting the distance from the surface (or movement away from those), you could implement the solution completely in software on the driver side. This might even work with standard mice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To minimize accidental button switching and allow &quot;swiping&quot; the mouse several times over the same surface, you's simply activate the 'unset' state after the mouse has been in the air at an altitude of ~15cm and for more than 2sec.&lt;/p&gt;&#xA;" OwnerUserId="2134" LastActivityDate="2011-03-24T09:32:08.287" CommentCount="4" />
  <row Id="11949" PostTypeId="2" ParentId="11938" CreationDate="2011-03-24T10:23:56.513" Score="1" ViewCount="" Body="&lt;p&gt;There are licensing problems associated with operating your own spread spectrum transceiver. A special dispensation was granted to some US radio amateurs several years ago, but it was rescinded:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.tapr.org/ss_tapr_sta.html&quot; rel=&quot;nofollow&quot;&gt;http://www.tapr.org/ss_tapr_sta.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should approach your regulatory authority about the relevant legislation. Unless you are a licensed radio amateur, it is very unlikely that you will get permission to operate such equipment.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-24T10:45:15.653" LastActivityDate="2011-03-24T10:45:15.653" CommentCount="1" />
  <row Id="11950" PostTypeId="2" ParentId="11946" CreationDate="2011-03-24T10:36:26.307" Score="4" ViewCount="" Body="&lt;p&gt;You need to use some form of &lt;a href=&quot;http://en.wikipedia.org/wiki/Slip_ring&quot; rel=&quot;nofollow&quot;&gt;Slip Rings&lt;/a&gt; and carbon brushes. The &lt;a href=&quot;http://en.wikipedia.org/wiki/Slip_ring&quot; rel=&quot;nofollow&quot;&gt;Slip Rings&lt;/a&gt; are mounted on the spinning shaft which are a ring of brass that makes contact with sprung brushes that supply the power. They are similar to a commutator on a DC motor, except they are a continuous ring instead of segmented.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll need two &lt;a href=&quot;http://en.wikipedia.org/wiki/Slip_ring&quot; rel=&quot;nofollow&quot;&gt;Slip Rings&lt;/a&gt; for power and GND unless it's possible to use the shaft itself as GND, then you can get away with just one. But this would mean you'd need to mount all of your control circuitry on the spinning assembly, otherwise you'd also have to have extra rings to supply individual LED circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A neat and cheap alternative to using carbon brushes is to use &lt;a href=&quot;http://www.google.co.uk/search?q=tool%20clips&quot; rel=&quot;nofollow&quot;&gt;Tool Clips&lt;/a&gt; that are mounted on a piece of insulating nylon that surround the rings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Qf3Nh.jpg&quot; alt=&quot;tool clips&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-24T10:58:38.683" LastActivityDate="2011-03-24T10:58:38.683" />
  <row Id="11951" PostTypeId="2" ParentId="11938" CreationDate="2011-03-24T11:05:31.203" Score="1" ViewCount="" Body="&lt;p&gt;The simplest thing to do would be to do all the modulation and carrier shifting in the baseband and then upconvert directly to desired transmitting frequency using one of the many IQ upconverters/downconverters from ADI, TI, Linear Technologies etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will however need much better ADC/DAC then 10 bits (e.g. 24 bits audio codec chip) to get decent SNR, and also low phase noise oscillator for the up/down conversion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another approach would be to do the modulation at some low intermittent frequenty and then heterodyne that up. This approach needs more filtering to get rid of unwanted images that result from mixing.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-03-24T11:05:31.203" CommentCount="2" />
  <row Id="11952" PostTypeId="1" AcceptedAnswerId="11954" CreationDate="2011-03-24T11:42:59.457" Score="7" ViewCount="206" Body="&lt;p&gt;Will a standard home automatic circuit breaker, designed and sold as to work on 230V AC (alternating current), and for example 16A, or 25A etc, will it work (break the circuit if it exceeds the rated amperage) on 12V direct current (DC)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not, are there any automatic circuit breakers for over-current protection, which work on DC? I mean besides fuses which blow, I want the thing to be reusable with a click, not one-time-use.&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-03-24T12:34:18.257" Title="will a circuit breaker designed for 230VAC work for 12VDC?" Tags="&lt;circuit&gt;&lt;current&gt;&lt;safety&gt;&lt;protection&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11953" PostTypeId="1" AcceptedAnswerId="11956" CreationDate="2011-03-24T11:48:03.150" Score="1" ViewCount="91" Body="&lt;p&gt;I have an atmega16 which I need to clock to at least 16MHZ. How do I know what fuses to set? The fuse calculator gives you a choice of low, medium and high frequency. What does that mean?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a limit to how fast the chip can go despite you put a crystal in?&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-03-24T14:33:17.463" Title="AVR and external crystals" Tags="&lt;avr&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="11954" PostTypeId="2" ParentId="11952" CreationDate="2011-03-24T11:58:58.507" Score="11" ViewCount="" Body="&lt;p&gt;Use one designed for low voltage DC such as &lt;a href=&quot;http://uk.farnell.com/eaton/kd1-1/circuit-breaker-1a/dp/1338862&quot; rel=&quot;nofollow&quot;&gt;Eaton KD1&lt;/a&gt; or this &lt;a href=&quot;http://uk.farnell.com/eta/1610-21-6a/circuit-breaker-6a-auto/dp/597697&quot; rel=&quot;nofollow&quot;&gt;automotive type&lt;/a&gt;. A better option is also a &lt;a href=&quot;http://www.circuitprotection.com/polyswitch.asp&quot; rel=&quot;nofollow&quot;&gt;Raychem Polyswitch&lt;/a&gt; which self resets when the current is removed. The problem with the 230V ones is the high trip current, have you really got more than 16 or 25 amps available from your 12V supply?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&#xA;I didn't realise this related to an &lt;a href=&quot;http://electronics.stackexchange.com/questions/6066/how-to-build-a-low-voltage-disconnect-switch-for-dc-12-4v-70a&quot;&gt;earlier question&lt;/a&gt; where you are talking about an automotive battery. In that case, yes, many amps are available (as opposed to a wall wart), and &lt;a href=&quot;http://electronics.stackexchange.com/questions/6066/how-to-build-a-low-voltage-disconnect-switch-for-dc-12-4v-70a/6070#6070&quot;&gt;Andrew's comment&lt;/a&gt; applies - a breaker designed for AC should not be used on DC because it is a harder job to seperate the contacts on a DC current than on AC where the magnetic field falls to zero repeatedly due to the waveform.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MCBs (and fuses) have a characteristic curve showing time to trip against overcurrent. At the rated current, they should last indefinately, but as that is exceeded they trip faster. For a fast trip, you need the source to be capable of many times the rated trip current.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastEditorUserId="2110" LastEditorDisplayName="" LastEditDate="2011-03-24T12:34:18.257" LastActivityDate="2011-03-24T12:34:18.257" CommentCount="1" />
  <row Id="11955" PostTypeId="2" ParentId="11953" CreationDate="2011-03-24T12:09:41.503" Score="2" ViewCount="" Body="&lt;p&gt;The low, medium and high frequencies are explained in the datasheet. For ATmega16 this is in Table 4 on page 26:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/0y20d.png&quot; alt=&quot;crystal oscillator fuses table&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fuse setting descriptions come from Atmel and they sometimes contain the MHz ratings but this depends on the processor model.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general you should read the information about fuse settings in the datasheet since there is a lot of information there that just did not fit into short descriptions shown to you by the fuse calculator (they are more of a quick remainder then a reference).&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-24T12:09:41.503" CommentCount="2" />
  <row Id="11956" PostTypeId="2" ParentId="11953" CreationDate="2011-03-24T12:11:03.597" Score="2" ViewCount="" Body="&lt;p&gt;I'd call 16 MHz high frequency, in terms of setting the AVR fuses. Details are in the data sheet, in the System Clock and Clock Options section. Note the startup time options, you shouldn't use 6 CK for a 16 MHz clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your last question is meaningless. The processor speed is determined by the oscillator frequency, up to the maximum frequency specified (16 MHz).&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-24T12:11:03.597" CommentCount="1" />
  <row Id="11957" PostTypeId="1" AcceptedAnswerId="11967" CreationDate="2011-03-24T12:41:19.710" Score="0" ViewCount="227" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to build RGB led color picker from ladyada.net tutorials.&#xA;&lt;a href=&quot;http://www.ladyada.net/make/eshield/examples.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/make/eshield/examples.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I build ethernet shield, installed on my Arduino Duemilanove with ATMEGA328 and then load the sketch from ladyada web site.&#xA;&lt;a href=&quot;http://www.ladyada.net/make/eshield/LEDcolorpicker.pde&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/make/eshield/LEDcolorpicker.pde&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This code dosent's work for me, until I break line into two separate and re-merge at runtime.&#xA;I need to remove some piece of code to make it works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After burning 3 times this sketch on my Arduino, it seems not to responde anymore.&#xA;On extensive log I see:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;     avrdude: Version 5.4-arduino, compiled on Oct  9 2007 at 11:20:31&#xA;     Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/&#xA;&#xA;     System wide configuration file is &quot;/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/etc/avrdude.conf&quot;&#xA;     User configuration file is &quot;/Users/emaaaa/.avrduderc&quot;&#xA;     User configuration file does not exist or is not a regular file, skipping&#xA;&#xA;     Using Port            : /dev/tty.usbserial-A9007MIy&#xA;     Using Programmer      : stk500v1&#xA;     Overriding Baud Rate  : 115200&#xA;     avrdude: Send: 0 [30]   [20] &#xA;     avrdude: Send: 0 [30]   [20] &#xA;     avrdude: Send: 0 [30]   [20] &#xA;     avrdude: ser_recv(): programmer is not responding&#xA;     avrdude: stk500_recv(): programmer is not responding&#xA;     avrdude: Send: Q [51]   [20] &#xA;     avrdude: ser_recv(): programmer is not responding&#xA;     avrdude: stk500_recv(): programmer is not responding&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Anyone have some ideas ?&#xA;I tryed on 2 different arduino 2009, same results&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="3562" LastActivityDate="2011-03-24T15:31:18.077" Title="Arduino killed trying to load a sketch ?" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;hardware&gt;" AnswerCount="2" />
  <row Id="11958" PostTypeId="2" ParentId="11953" CreationDate="2011-03-24T12:43:42.790" Score="0" ViewCount="" Body="&lt;p&gt;Yes, 16MHz is definitely a &quot;High Frequency&quot; setting. Also If you don't have a good reason not to I usually just pick the longest startup time (SUT fuses) option to give everything time to settle at startup. This would be the should be the 16K CK + 64ms option for the ATMega16.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-03-24T12:43:42.790" />
  <row Id="11959" PostTypeId="2" ParentId="11957" CreationDate="2011-03-24T13:15:10.070" Score="1" ViewCount="" Body="&lt;p&gt;I know after awhile on my arduino that i had to start pressing the reset button before sending the sketch, this may help. Next try just using a simple LED blinky sketch(can be found in the examples on the IDE) If it works your arduino is fine. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;as for the other sketch I don't understand what you mean by this &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;This code [does not] work for me, until I break line into two separate and re-merge at runtime. I need to remove some piece of code to make it works.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;can you explain that a little better?&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-24T13:15:10.070" CommentCount="1" />
  <row Id="11960" PostTypeId="1" AcceptedAnswerId="11962" CreationDate="2011-03-24T13:28:39.470" Score="3" ViewCount="71" Body="&lt;p&gt;I have a huge (28 kg mass) automotive high-current battery charger, and its current delivering capabilities are described like that:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;70A moy/arit 90A eff&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;What do these mysterious abbreviations &quot;moy&quot;, &quot;arit&quot; and &quot;eff&quot; exactly mean, and how much current can this beast really deliver, 70A, 90A, what's the difference between the first and second number?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a photo, so you have an idea what kind of device it is:&#xA;&lt;img src=&quot;http://i.imgur.com/7WIW0.jpg&quot; alt=&quot;http://telto.nazwa.pl/allegro/15.10.2010/d/dscf1313.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-03-24T13:59:53.147" Title="what does &quot;70A moy/arit 90A eff&quot; on a high-current automotive lead-acid battery charger mean?" Tags="&lt;battery&gt;&lt;batteries&gt;&lt;battery-charging&gt;&lt;automotive&gt;" AnswerCount="1" />
  <row Id="11961" PostTypeId="1" CreationDate="2011-03-24T13:44:47.020" Score="2" ViewCount="138" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking for any resources on how to construct a relatively high power (25A, 13.8V) voltage stabilizer (or voltage booster if you like) for my 13.8V powered ham radio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem I try to resolve is powering the radio from both only batteries, and from car battery. So I would like to be protected against both voltage drop especially in first scenario and voltage spikes in the second one. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is still a plenty of charge in a AGM 12 battery when the voltage is around 12,.4 volts but the radio PSU cuts off when the voltage drops that low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that there are ready to buy solutions, but they are not very accessible in my part of the world, and I would like to at least know the principle they operate on :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many thanks in advance!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What about LM2587 in flyback regulation mode in parallel? Is it possible? I have only found a description of boost converter mode parallel application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE2:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Great application note from National about SEPIC design: &lt;a href=&quot;http://www.national.com/an/AN/AN-1484.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.national.com/an/AN/AN-1484.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1562" LastEditorUserId="1562" LastEditorDisplayName="" LastEditDate="2011-03-25T07:38:58.527" LastActivityDate="2011-03-25T07:38:58.527" Title="11-16V DC voltage stabilization for 13.8V powered ham radio." Tags="&lt;voltage-regulator&gt;&lt;dc-dc&gt;&lt;undervoltage&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="11962" PostTypeId="2" ParentId="11960" CreationDate="2011-03-24T13:48:05.060" Score="6" ViewCount="" Body="&lt;p&gt;I think those are French abbreviations. I believe &quot;moy/arit&quot; is an abbreviation of &quot;moyenne arithmétique,&quot; meaning &quot;arithmetic mean,&quot; or average.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure about &quot;eff,&quot; but I bet it's an abbreviation for a French word for &quot;peak.&quot;&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-03-24T13:59:53.147" LastActivityDate="2011-03-24T13:59:53.147" CommentCount="1" />
  <row Id="11963" PostTypeId="2" ParentId="11953" CreationDate="2011-03-24T14:33:17.463" Score="2" ViewCount="" Body="&lt;p&gt;I've had good luck with this online &lt;a href=&quot;http://www.engbedded.com/fusecalc&quot; rel=&quot;nofollow&quot;&gt;AVR Fuse Calculator&lt;/a&gt; in the past. Might be useful for ya.&lt;/p&gt;&#xA;" OwnerUserId="2654" LastActivityDate="2011-03-24T14:33:17.463" />
  <row Id="11964" PostTypeId="2" ParentId="11946" CreationDate="2011-03-24T14:46:07.193" Score="4" ViewCount="" Body="&lt;p&gt;Here's &lt;a href=&quot;http://maybevideodoes.de/howto/slipring.html&quot; rel=&quot;nofollow&quot;&gt;some instructions on building a rather ingenious slip ring&lt;/a&gt; using ball bearings.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/XIelm.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-03-24T14:46:07.193" />
  <row Id="11965" PostTypeId="1" AcceptedAnswerId="11971" CreationDate="2011-03-24T15:02:46.353" Score="2" ViewCount="79" Body="&lt;p&gt;I have in my possession two stepper motors that are clearly marked as 50 ohm, 22V motors. They have six leads each, which I believe makes them unipolar stepper motors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is my understanding (and experience) that unipolar stepper motors can be driven as bipolar stepper motors by ignoring the center lead, and that is what I am doing. When I measure the resistance between leads to determine which lead is the center of each winding, however, I find that the resistance between each &quot;edge&quot; lead and the center lead is 50 ohm, and the resistance between the two &quot;edge&quot; leads is actually 100 ohms. It is my guess that this is because when driven by a unipolar driver, current is never passed between the &quot;edge&quot; leads, and only ever from the center lead to one or the other &quot;edge&quot;. This arrangement would make the 50 ohm rating make sense. Is this correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because I am driving these motors as bipolar motors, however, I see double the resistance that a unipolar driver would see. I am also using a &quot;chopper&quot; driver, or constant-current driver, and I have the ability to select the maximum current for the motor. How do I calculate this? Is it a simple question of ohm's law, using the 100 ohm value I measured between the &quot;edge&quot; leads?&lt;/p&gt;&#xA;" OwnerUserId="3240" LastActivityDate="2011-03-24T16:11:06.997" Title="How do I determine the power rating of a stepper motor?" Tags="&lt;stepper-motor&gt;" AnswerCount="2" />
  <row Id="11966" PostTypeId="2" ParentId="11965" CreationDate="2011-03-24T15:17:01.960" Score="0" ViewCount="" Body="&lt;p&gt;If you are driving motor in non-standard mode, the only reliable way is to increase drive current while monitoring coil temperatures. When it reaches some 60-80C in continious operation - that's your power limit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In any case, going much higher than 22V might cause insulation breakdown, so I would not go higher than 1.5x.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-24T15:17:01.960" CommentCount="2" />
  <row Id="11967" PostTypeId="2" ParentId="11957" CreationDate="2011-03-24T15:31:18.077" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;code&gt;const char javascript[] PROGMEM = &quot;...&quot;&lt;/code&gt; is a &gt;5,000 character string.  It's possible that the Arduino IDE doesn't support line lengths of this size, you can break it up using the continuation character &lt;code&gt;\&lt;/code&gt; at the end of your line: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;const char javascript[] PROGMEM = &quot;&amp;lt;script type=\&quot;text/javascript\&quot;&amp;gt;function&quot; \&#xA;&quot; getScrollY(){var scrOfX = 0,scrOfY=0;if(typeof(window.pageYOffset)=='number')&quot; \&#xA;&quot;{scrOfY=window.pageYOffset;scrOfX=window.pageXOffset;}else if(document.body&amp;amp;&amp;amp;&quot; \&#xA;[Many more lines]&#xA;&quot;setCCbldSty2('colorpicker201','ds','block');&quot; \&#xA;&quot;document.getElementById('colorpicker201').innerHTML=mid;}&amp;lt;/script&amp;gt;&quot;;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that you can't have // comments at the end of these lines.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is what you meant by &quot;broke into 2 parts&quot; you should be fine.  Otherwise, I think your reassembly at runtime is suspicious.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-24T15:31:18.077" CommentCount="1" />
  <row Id="11968" PostTypeId="2" ParentId="11940" CreationDate="2011-03-24T16:00:27.563" Score="2" ViewCount="" Body="&lt;p&gt;I'm guessing that if the mouse is on the other side of the keyboard it's being held by someone who's left handed?  You may be able to get away with having capacitive sensors in key areas - one set where right-handed people might put skin (fingertips, palms, etc) and another where left-handed people would.  If there's not a lot of overlap then you might be able to judge whether a person is left or right handed based on where their hand touches the mouse.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Man that's probably patentable if it works.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-03-24T16:00:27.563" CommentCount="1" />
  <row Id="11969" PostTypeId="2" ParentId="11940" CreationDate="2011-03-24T16:01:50.780" Score="0" ViewCount="" Body="&lt;p&gt;This answer assumes that the important thing is not whether the mouse is on the left or right of the keyboard, but whether the left or right hand is on the mouse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you look at the mouse in your hand, you will see that there is a hole between the thumb and index finger, where there is no hand contact with the mouse.  So put a touch contact in that place on both sides of the mouse.  When the left hand is on the mouse, the palm will rest on the right touch contact, and vice-versa for the right hand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the mouse case is thin enough, you can put the touch contact as a piece of conductive foil inside the case.  Reading of touch contacts is a commonly integrated function into modern microcontrollers.  &lt;a href=&quot;http://www.ti.com/sc/docs/psheets/abstract/apps/slaa363a.htm&quot; rel=&quot;nofollow&quot;&gt;TI app note&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So a small micro can read the two touch sensors and decide which hand is on the mouse, and swap the buttons with a 74hc4053 or similar.  Of course, a commercial design would integrate all functions in the mouse's microcontroller.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-24T16:01:50.780" />
  <row Id="11970" PostTypeId="1" CreationDate="2011-03-24T16:06:35.627" Score="-3" ViewCount="115" Body="&lt;p&gt;I want to know if there is electronics text book with complete rigorous treatment--I mean one that clearly states the assumptions and deduces every statement made from these assumptions.&lt;/p&gt;&#xA;" OwnerUserId="3563" LastActivityDate="2011-03-24T20:42:33.753" ClosedDate="2011-03-24T23:35:04.347" Title="Rigorous Electronics" Tags="&lt;books&gt;" AnswerCount="4" CommentCount="4" />
  <row Id="11971" PostTypeId="2" ParentId="11965" CreationDate="2011-03-24T16:11:06.997" Score="1" ViewCount="" Body="&lt;p&gt;I would suggest driving the motor with 72% of rated current, or about 310mA.  That should yield the same power dissipation as would be expected from unipolar drive at 440mA.  When the motor isn't moving, the voltage would have to be about 31 volts.  I wouldn't expect insulation problems at 31 volts, or even 50, but I don't know how far one could safely go.  Perhaps measure the AC voltage when hand-spinning the motor quickly to see if there seems to be a limit.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-24T16:11:06.997" />
  <row Id="11972" PostTypeId="1" AcceptedAnswerId="12167" CreationDate="2011-03-24T16:38:28.503" Score="1" ViewCount="141" Body="&lt;p&gt;Would you recommend any good book dealing with line codes (i.e. &lt;a href=&quot;http://en.wikipedia.org/wiki/Line_code&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Line_code&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mean a book that goes a little bit deeper into properties of each encoding (e.g. spectrum). I believe this topic is discussed in many digital communications text books, but there are too many of them&lt;/p&gt;&#xA;" OwnerUserId="3564" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-13T16:34:36.300" LastActivityDate="2011-04-13T16:34:36.300" Title="Books on line codes?" Tags="&lt;communication&gt;&lt;books&gt;" AnswerCount="2" />
  <row Id="11973" PostTypeId="1" AcceptedAnswerId="11980" CreationDate="2011-03-24T17:34:25.333" Score="0" ViewCount="42" Body="&lt;p&gt;How can I safely detect output of a car battery charger?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has a OS/MP switch and for output it lists 12 V and 10.1 A. Unfortunately I have no idea what OS/MP means and I of course have no manual. The charger also has a single 5x20 glass slow fuse rated at 2 A and a 10 A standard household circuit breaker. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm hoping to use the charger as a power supply for a project. Either constant current or constant voltage would be OK, but I can't determine right now which one the charger is. It looks low-tech, so I doubt that it has both output types.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the equipment front, I have two multimeters and I could easily obtain various 5 W and 11 W ceramic resistors. I have several 10 $\Omega$ resistors available right now. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-24T22:22:23.733" Title="Safely detecting lead-acid battey charger output?" Tags="&lt;battery-charging&gt;" AnswerCount="1" />
  <row Id="11974" PostTypeId="1" CreationDate="2011-03-24T17:40:04.177" Score="3" ViewCount="152" Body="&lt;p&gt;I'm trying to build a device similar to railgun. It will have two rails and a conductive movable bar in-between. At one side, I'll provide voltage source and a resistor. If I put it in a strong enough magnetic field, it will move. The idea is that the device will work as demonstration of forces behind an electric motor, so I don't require high speed for the bar.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a sketch:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ApYnf.png&quot; alt=&quot;over 9000 hours in paint&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I've got voltage source E, resistor R, bar whose length is A and magnetic field B. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If my calculation are correct, force when bar isn't moving should be  $F_m=IAB$. I don't require much force, so I guess that 5 mN would be more than enough. The power supply could be a problem. I should be able to get up to 1.3 A without much problems, but anything higher will be problematic, since I can't get a good match between resistor power dissipation and limitations of my power supply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since I can't get a perfect constant field, I'm going to have to compromise. I expect the field to drop linearly with A, but on the other hand, force will also get stronger linearly with A, so the differences should cancel themselves out, if I manage to do everything right.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now about the field source itself. Most obvious sources are natural magnets or electric magnets. I can get natural magnets of various sizes but I don't have their magnetic field strengths. I found several types of magnets in local electronics stores. Their compositions are listed as AlNiCo500, NdFeB and SmCo5, so which one would be a good choice? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option would be to make an electrical magnet, but I'm unfamiliar with them, so I don't know where to start.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm also open to other means of generating a magnetic field, if I missed some. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-26T08:40:55.140" LastActivityDate="2011-03-26T08:40:55.140" Title="How to build a constant magnetic field source for a &quot;railgun&quot;?" Tags="&lt;electromagnetism&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="11975" PostTypeId="1" AcceptedAnswerId="11976" CreationDate="2011-03-24T18:17:59.400" Score="3" ViewCount="64" Body="&lt;p&gt;I'm looking at making a universal battery charger. And I am interested in seeing whether I can get it to detect the chemistry so if a non rechargeable had been put in it won't charge. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-24T18:37:30.327" Title="Is it possible to detect battery chemistry?" Tags="&lt;battery-charging&gt;" AnswerCount="1" />
  <row Id="11976" PostTypeId="2" ParentId="11975" CreationDate="2011-03-24T18:31:22.500" Score="2" ViewCount="" Body="&lt;p&gt;Maxim has a &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/666&quot; rel=&quot;nofollow&quot;&gt;good article&lt;/a&gt; on the subject. They also (surprise, surprise) have some ICs available to implement their functions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The article talks mainly about using the Smart Battery System to control charging, but also has good info on how the different chemistries have different charging requirements. It doesn't discuss how to deal with an 'unknown' battery chemistry, so you may be out of luck.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could consider putting a temperature sensor on the cell, but by the time the non-rechargeable cell gets hot it may already be too late. Also, a full alkaline will have a higher float voltage than a NiMH- or NiCd-equivalent (1.5V vs 1.2V) so you may be able to detect this and inhibit charging as well.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-03-24T18:37:30.327" LastActivityDate="2011-03-24T18:37:30.327" CommentCount="1" />
  <row Id="11977" PostTypeId="2" ParentId="11961" CreationDate="2011-03-24T18:52:32.163" Score="3" ViewCount="" Body="&lt;p&gt;Setting up parallel switching regulators is hard. They might not run in sync and start supplying each other. Also, you're saying you want 25A. You would need a ton of those regulators to make it work, if it would work at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My suggestion is to get some big coils and FETs that can handle currents like 30 - 40A and a buck-boost converter. Alternatively, you could begin with a buck converter and regulate to a like 10V, and then boost up to 13.8V again. Don't expect to find these regulators in a package that will supply, you'll have to add external components. Don't forget that a buck converter needs to handle 25*13.8/10 = 34.5A+ (not accounting effiency) , because the voltage is lower.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-03-24T18:52:32.163" />
  <row Id="11978" PostTypeId="1" CreationDate="2011-03-24T19:49:03.757" Score="4" ViewCount="240" Body="&lt;p&gt;&lt;strong&gt;Intro&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In response to &lt;a href=&quot;http://electronics.stackexchange.com/questions/11577/simple-adaptive-amplifier-options-for-sensor-interfaces&quot;&gt;this question about adaptive amplifiers&lt;/a&gt;, It was recommended that in order to deal with variable conditions, it may be more economical to simply use an ADC with higher resolution so that I don't need to worry about amplification and I can do scaling in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Overview&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to design a data acquisition circuit for body mounted textile-based stretch sensors. The textile varies resistance as it's stretched (about 1 order of magnitude, 10k$\Omega$-100k$\Omega$ with 30% stretch). The exact ranges will change depending on how the textile is cut, whether it's soaked with sweat, the temperature, how old the material is, how it's mounted, etc. The entire thing needs to be as small as possible because it's mounted on the hand, so minimizing the number of components is a big plus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Moreover, I'd like the circuit to be reusable for other applications that may have worse performance. For instance, if I use a cheaper version of the textile, my resistance range may be as bad as 100$\Omega$ to 300$\Omega$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Signal Path&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[textile] -&gt; [Wheatstone bridge] -&gt; [lowpass] -&gt; [instrumentation amp] -&gt; [ADC] -&gt; [AVR]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Requirements&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I'm looking for an ADC that will meet my requirements. The ADC should be:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;16bits+&lt;/li&gt;&#xA;&lt;li&gt;As easy to use as possible: much better if there is interface code already written for AVR/Arduino...&lt;/li&gt;&#xA;&lt;li&gt;yet at the same time as comprehensive as possible: I've seen some ADC's with lowpass filters and PGA's built in – all the better as long as it doesn't make configuration a pain&lt;/li&gt;&#xA;&lt;li&gt;8+ channels, or if it's easy enough to implement, 2x 4+ channels. EDIT: If I'm using a Wheatstone bridge, perhaps I want 8 differential input channels (so 16 channels)...&lt;/li&gt;&#xA;&lt;li&gt;I don't think operation voltage matters... (best if not above 5V)&lt;/li&gt;&#xA;&lt;li&gt;surface mount&lt;/li&gt;&#xA;&lt;li&gt;doesn't need to be cheap (it's a one-off)&lt;/li&gt;&#xA;&lt;li&gt;SPI vs. I2C doesn't matter I think...&lt;/li&gt;&#xA;&lt;li&gt;100hz+&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Research&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far through Googling, I've found the following chips:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Linear devices offer various 16-24bit delta sigma ADCs, some of which I've seen recommended: &lt;a href=&quot;http://parametric.linear.com/html/no_latency_delta_sigma_adcs?p=5312974&quot; rel=&quot;nofollow&quot;&gt;http://parametric.linear.com/html/no_latency_delta_sigma_adcs?p=5312974&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Microchip has a range of options, some of which I've seen recommended: &lt;a href=&quot;http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=11022&amp;amp;mid=10&amp;amp;lang=en&amp;amp;pageId=79&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=11022&amp;amp;mid=10&amp;amp;lang=en&amp;amp;pageId=79&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Analog devices have a number of comprehensive data acquisition chips with amplifiers and filters (no need for external signal processing stuff):&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7783/products/product.html&quot; rel=&quot;nofollow&quot;&gt;http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7783/products/product.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7715/products/product.html&quot; rel=&quot;nofollow&quot;&gt;http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7715/products/product.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7709/products/product.html&quot; rel=&quot;nofollow&quot;&gt;http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7709/products/product.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;I haven't looked at the TI chips yet...&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;and the following tutorials:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://arduino.cc/blog/2010/11/29/tired-of-a-10-bit-res-hook-up-a-better-analog-to-digital-converter/&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/blog/2010/11/29/tired-of-a-10-bit-res-hook-up-a-better-analog-to-digital-converter/&lt;/a&gt; (LTC2400)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1275676171&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1275676171&lt;/a&gt; (TI ADS8341)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://forums.adafruit.com/viewtopic.php?f=31&amp;amp;t=12269&quot; rel=&quot;nofollow&quot;&gt;http://forums.adafruit.com/viewtopic.php?f=31&amp;amp;t=12269&lt;/a&gt; (MCP3424)&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1248751435&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1248751435&lt;/a&gt; (LTC2410)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Voltage Reference?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, some people have recommended a precision voltage reference, such as the Analog Devices &lt;a href=&quot;http://www.analog.com/static/imported-files/data_sheets/REF19xSeries.pdf&quot; rel=&quot;nofollow&quot;&gt;REF19x&lt;/a&gt; series. Do you think this is necessary? Resolution is definitely important for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me know if you have any recommendations! I'm also not sure exactly what I'm looking for, so tips on how to decide are also appreciated.&lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2011-03-24T20:45:33.977" LastActivityDate="2011-03-29T18:14:15.923" Title="High Resolution ADC for Noisy Sensors in Variable Conditions" Tags="&lt;sensor&gt;&lt;adc&gt;&lt;acquisition&gt;" AnswerCount="4" CommentCount="11" FavoriteCount="3" />
  <row Id="11979" PostTypeId="2" ParentId="11970" CreationDate="2011-03-24T19:53:33.340" Score="0" ViewCount="" Body="&lt;p&gt;I think that most textbooks on Circuit Theory will be quite rigorous. I cannot recommend anything in particular since I mostly read Polish textbook on this matter.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-24T19:53:33.340" />
  <row Id="11980" PostTypeId="2" ParentId="11973" CreationDate="2011-03-24T19:53:42.117" Score="1" ViewCount="" Body="&lt;p&gt;The charger circuitry is usually not as extensively built as a power supply circuit. Things such as filtering, and well regulated circuits for both current and voltage. I don't know what you are trying to do with it, so it may satisfy your basic needs for devices such as motors, etc...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To test the charger you can connect an ammeter in series with the output, and monitor the voltage output with a dvm. Then apply different loads to the output while monitoring the current and voltage meters. If the voltage deviates a lot, it shows poor or no voltage regulation. You mentioned you have 10 ohm resistors, but you did not say what the power rating in watts were. Using ohms law I=E/R tells you that 12 volts/ 10 ohms = 1.2 amps. Them P = I*E tells us that 1.2*12 = 14.4 watts that the resistor must be rated at. Providing the resistors are 15 watts or greater, you could use these as a load test. Adding other 10 ohm resistors to the load will increase the current additive, so to achieve 10A you could get close with 8 resistors 8*1.2=9.6.&lt;/p&gt;&#xA;" OwnerUserId="3453" LastEditorUserId="3453" LastEditorDisplayName="" LastEditDate="2011-03-24T22:22:23.733" LastActivityDate="2011-03-24T22:22:23.733" CommentCount="3" />
  <row Id="11981" PostTypeId="2" ParentId="11970" CreationDate="2011-03-24T20:02:53.007" Score="0" ViewCount="" Body="&lt;p&gt;A quick search found these books which approach electronic theory from a mathematical perspective.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0521701473&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://ecx.images-amazon.com/images/I/41%2BhQLPYGOL._BO2,204,203,200_PIsitb-sticker-arrow-click,TopRight,35,-76_AA300_SH20_OU02_.jpg&quot;&gt;&lt;/a&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0130268585&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://ecx.images-amazon.com/images/I/51N0EF8P8TL._BO2,204,203,200_PIsitb-sticker-arrow-click,TopRight,35,-76_AA300_SH20_OU02_.jpg&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(disclaimer: I have not read these books)&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-24T20:11:39.773" LastActivityDate="2011-03-24T20:11:39.773" />
  <row Id="11982" PostTypeId="2" ParentId="11961" CreationDate="2011-03-24T20:06:57.343" Score="3" ViewCount="" Body="&lt;p&gt;You can parallel flybacks, if you wanted to, but synchronizing the phases can be messy. Designing flybacks necessitates designing transformers - for an application which doesn't require isolation, there's no need for that level of complexity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could try and design a &lt;a href=&quot;http://en.wikipedia.org/wiki/Single-ended_primary-inductor_converter&quot; rel=&quot;nofollow&quot;&gt;SEPIC&lt;/a&gt; since it works well for inputs both higher and lower than the desired target.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The car battery itself shouldn't have an issue with spikes - the alternator feeding the battery, well, that's another matter. : ) You can put TVS clamps on the input-side to clip any nastiness coming through.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-24T20:06:57.343" CommentCount="1" />
  <row Id="11983" PostTypeId="2" ParentId="6584" CreationDate="2011-03-24T20:29:26.613" Score="1" ViewCount="" Body="&lt;p&gt;Also, cleaning the contacts helps a lot. Don't use tons of alcohol, however, because it might erode the conductive polymer.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-03-24T20:29:26.613" />
  <row Id="11984" PostTypeId="2" ParentId="11970" CreationDate="2011-03-24T20:38:19.647" Score="0" ViewCount="" Body="&lt;p&gt;This book might be what you're looking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://books.google.com/books?id=0zQkXLR5OcIC&amp;amp;printsec=frontcover&amp;amp;dq=classical%20circuit%20theory%20omar%20wing&amp;amp;source=bl&amp;amp;ots=VdgClN9MaH&amp;amp;sig=5NXRls07zVJ03FGraEc0cfpI-6o&amp;amp;hl=en&amp;amp;ei=_aiLTd28J62N0QHqlt3wDQ&amp;amp;sa=X&amp;amp;oi=book_result&amp;amp;ct=result&amp;amp;resnum=1&amp;amp;sqi=2&amp;amp;ved=0CBgQ6AEwAA#v=onepage&amp;amp;q&amp;amp;f=false&quot; rel=&quot;nofollow&quot;&gt;Classical Circuit Theory by Omar Wing&lt;/a&gt; &amp;lt;--- Google Book Preview&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(disclaimer: I have only skimmed this book)&lt;/p&gt;&#xA;" OwnerUserId="2612" LastActivityDate="2011-03-24T20:38:19.647" />
  <row Id="11985" PostTypeId="2" ParentId="11970" CreationDate="2011-03-24T20:42:33.753" Score="0" ViewCount="" Body="&lt;p&gt;Your question is fairly vague, but this comes to mind:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Chua, L. O., C. A. Desoer, E. S. Kuh: Linear and Nonlinear Circuits. &lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-03-24T20:42:33.753" />
  <row Id="11986" PostTypeId="2" ParentId="11859" CreationDate="2011-03-24T20:44:18.203" Score="1" ViewCount="" Body="&lt;p&gt;Once upon a time I took something apart one step too far.  I had situation like that LCD.  To put it back together, I used a very soft graphite pencil - 5B - to coat the contacts on both sides - LCD and PCB.  It actually helped, though the end result was still dodgy, it was quite a bit less dodgy.  This kind of pencil can be found at any artists' supply shop.&lt;/p&gt;&#xA;" OwnerUserId="1609" LastActivityDate="2011-03-24T20:44:18.203" CommentCount="1" />
  <row Id="11987" PostTypeId="2" ParentId="11899" CreationDate="2011-03-24T20:56:43.653" Score="1" ViewCount="" Body="&lt;p&gt;Power Integrations have recently introduced the LinkZero-LP - a range of zero consumption integrated circuits specifically to eliminate AC-DC consumption when the phone is disconnected from the charger - whether the charger is connected to 115Vac or all the way up to 265Vac. &#xA;&lt;a href=&quot;http://www.powerint.com/en/products/linkzero-family/linkzero-lp&quot; rel=&quot;nofollow&quot;&gt;http://www.powerint.com/en/products/linkzero-family/linkzero-lp&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3566" LastActivityDate="2011-03-24T20:56:43.653" CommentCount="1" />
  <row Id="11988" PostTypeId="1" AcceptedAnswerId="11990" CreationDate="2011-03-24T20:57:19.360" Score="1" ViewCount="133" Body="&lt;p&gt;I'm have a project which is using an ATMega 328 which is powered by 5 volts. It is connected to an accelerometer/gyro breakout board through a 3.3 voltage regulator and supplying the 3.3 volts to the ATMega's AREF pin. I want to control a Jaguar speed controller via PWM, which I believe expects a 5 volt signal. My question is, when I set the AREF pin to 3.3 volts, is that going to change the upper limit of my PWM output from 5 volts to 3.3 volts?&lt;/p&gt;&#xA;" OwnerUserId="3301" LastActivityDate="2011-03-24T21:13:37.450" Title="ATMega 328 AREF and PWM/analogWrite()" Tags="&lt;atmega&gt;&lt;pwm&gt;&lt;gyro&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="11989" PostTypeId="2" ParentId="1437" CreationDate="2011-03-24T21:09:38.227" Score="2" ViewCount="" Body="&lt;p&gt;If you have got &lt;a href=&quot;http://www.macports.org/&quot; rel=&quot;nofollow&quot;&gt;Macports&lt;/a&gt; installed you can simply run:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;$ sudo port install avr-binutils avr-gcc avr-libc avrdude &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;and you should be ready to go.&lt;/p&gt;&#xA;" OwnerUserId="1627" LastActivityDate="2011-03-24T21:09:38.227" />
  <row Id="11990" PostTypeId="2" ParentId="11988" CreationDate="2011-03-24T21:12:24.810" Score="4" ViewCount="" Body="&lt;p&gt;AREF is nothing to do with PWM, it's the analogue reference input for the ADC. With a 5V supply, you will get a 5V PWM output.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-24T21:12:24.810" CommentCount="1" />
  <row Id="11991" PostTypeId="2" ParentId="11988" CreationDate="2011-03-24T21:13:37.450" Score="0" ViewCount="" Body="&lt;p&gt;AREF is defined as as the analog input voltage-reference.  I looked in a few places and I can't find any discussion of changing the PWM voltage.  Not a definitive 'no' but that would be my guess.  I'd be reaching for my meter, right about now.&lt;/p&gt;&#xA;" OwnerUserId="3361" LastActivityDate="2011-03-24T21:13:37.450" />
  <row Id="11992" PostTypeId="2" ParentId="11813" CreationDate="2011-03-24T21:31:10.757" Score="0" ViewCount="" Body="&lt;p&gt;Spoke with my electrician and described my plan above. He agreed it would work (with the addition of a 20a breaker for the 110v leg). He thought that if there were  a constant &amp;amp; relatively high load on the 110v leg it might cause an imbalance, but given the infrequent and small load of the auto drain valve it would work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, he had an even better suggestion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Hunter pump-start relay I purchased switches two lines.  It is intended to switch the two legs of a 220v circuit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;His idea is to NOT run the pump start relay off one of the 220v legs, but instead leave it powered by the 110v circuit it is currently on.  ... And to use one of the relay terminals for the 110v to the auto-drain and one for ONE of the legs of the 220v to the compressor!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is brilliant and simple (and works because the compressor does not use neutral, only ground). &lt;/p&gt;&#xA;" OwnerUserId="2604" LastActivityDate="2011-03-24T21:31:10.757" CommentCount="1" />
  <row Id="11993" PostTypeId="1" AcceptedAnswerId="12001" CreationDate="2011-03-24T22:34:00.127" Score="6" ViewCount="240" Body="&lt;p&gt;A good deal of projects I see have their inputs and outputs neatly aligned in to plastic enclosures. I wish to do the same, however, I do not own a drill or anything similar.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is a cheap but effective way to drill neat holes in my cases?&lt;/p&gt;&#xA;" OwnerUserId="2739" LastActivityDate="2011-03-26T19:04:53.333" Title="Cheap method to drill neat holes in plastic casing?" Tags="&lt;projects&gt;&lt;enclosure&gt;" AnswerCount="6" FavoriteCount="3" />
  <row Id="11994" PostTypeId="1" CreationDate="2011-03-24T22:37:43.367" Score="0" ViewCount="76" Body="&lt;p&gt;trying to talk to an accelerometer (LIS3LV02DQ) over SPI, can someone verify that this code is correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This code is taken from the example code on the Atmel website.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int main(void)&#xA;{&#xA;// Init SS pin as output with wired AND and pull-up. &#xA;  PORTC.DIRSET = PIN4_bm;&#xA;  PORTC.PIN4CTRL= PORT_OPC_WIREDANDPULL_gc;&#xA;&#xA;// Instantiate pointer to ssPort. &#xA;  PORT_t *ssPort = &amp;amp;PORTC;&#xA;&#xA;// Initialize SPI master on port C. &#xA;  SPI_MasterInit(&amp;amp;spiMasterC,&#xA;               &amp;amp;SPIE,&#xA;               &amp;amp;PORTC,&#xA;               false,&#xA;               SPI_MODE_2_gc,&#xA;               SPI_INTLVL_OFF_gc,&#xA;               false,&#xA;               SPI_PRESCALER_DIV4_gc);&#xA;&#xA;/* MASTER: Pull SS line low. This has to be done since&#xA; SPI_MasterTransceiveByte() does not control the SS line(s). */ &#xA;  SPI_MasterSSLow(ssPort, PIN4_bm);&#xA;  uint8_t sendData;&#xA;&#xA;  sendData = SPI_MasterTransceiveByte(&amp;amp;spiMasterC, masterData);&#xA;&#xA;// Variable used to send and receive data.&#xA;  SPI_MasterSSHigh(ssPort, PIN4_bm);&#xA;&#xA;/* This PORT setting is only valid to USARTC0 if other USARTs is used a&#xA; different PORT and/or pins is used. */&#xA;// PIN3 (TXD0) as output.&#xA;  PORTD.DIRSET = PIN7_bm;&#xA;&#xA;// PC2 (RXD0) as input.&#xA;  //PORTE.DIRCLR = PIN2_bm;&#xA;&#xA;// USARTC0, 8 Data bits, No Parity, 1 Stop bit.&#xA;  USART_Format_Set(&amp;amp;USART, USART_CHSIZE_8BIT_gc, USART_PMODE_DISABLED_gc, false);&#xA;&#xA;/* Set Baudrate to 9600 bps:&#xA; * Use the default I/O clock frequency that is 2 MHz.&#xA; * Do not use the baudrate scale factor&#xA; *&#xA; * Baudrate select = (1/(16*(((I/O clock frequency)/Baudrate)-1)&#xA; *                 = 12&#xA; */&#xA;  USART_Baudrate_Set(&amp;amp;USART, 12 , 0);&#xA;&#xA;// Enable TX.&#xA;  USART_Tx_Enable(&amp;amp;USART);&#xA;  while(true)&#xA;  {&#xA;    while(!USART_IsTXDataRegisterEmpty(&amp;amp;USART));&#xA;  // Transmit Data */&#xA;    USART_PutChar(&amp;amp;USART, void SPI_MasterInit(SPI_Master_t *spi, USART_PutChar(&amp;amp;USART, sendData);&#xA;  }         &#xA;}&#xA;&#xA;&#xA;uint8_t SPI_MasterTransceiveByte(SPI_Master_t *spi, uint8_t TXdata)&#xA;{&#xA;// Send pattern.&#xA;  spi-&amp;gt;module-&amp;gt;DATA = TXdata;&#xA;&#xA;// Wait for transmission complete. &#xA;  while(!(spi-&amp;gt;module-&amp;gt;STATUS &amp;amp; SPI_IF_bm)){}&#xA;&#xA;// Read received data. &#xA;  uint8_t result = spi-&amp;gt;module-&amp;gt;DATA;&#xA;&#xA;  return(result);&#xA;}&#xA;&#xA;&#xA;void SPI_MasterInit(SPI_Master_t *spi,&#xA;                SPI_t *module,&#xA;                PORT_t *port,&#xA;                bool lsbFirst,&#xA;                SPI_MODE_t mode,&#xA;                SPI_INTLVL_t intLevel,&#xA;                bool clk2x,&#xA;                SPI_PRESCALER_t clockDivision)&#xA;{&#xA;  spi-&amp;gt;module         = module;&#xA;  spi-&amp;gt;port           = port;&#xA;  spi-&amp;gt;interrupted    = false;&#xA;&#xA;  spi-&amp;gt;module-&amp;gt;CTRL   = clockDivision |    /* SPI prescaler. */&#xA;           (clk2x ? SPI_CLK2X_bm : 0) |    /* SPI Clock double. */&#xA;                        SPI_ENABLE_bm |    /* Enable SPI module. */&#xA;        (lsbFirst ? SPI_DORD_bm  : 0) |    /* Data order. */&#xA;                        SPI_MASTER_bm |    /* SPI master. */&#xA;                                 mode;     /* SPI mode. */&#xA;&#xA;/* Interrupt level. */&#xA;  spi-&amp;gt;module-&amp;gt;INTCTRL = intLevel;&#xA;&#xA;/* No assigned data packet. */&#xA;  spi-&amp;gt;dataPacket = NULL;&#xA;&#xA; /* MOSI and SCK as output. */&#xA;  spi-&amp;gt;port-&amp;gt;DIRSET  = SPI_MOSI_bm | SPI_SCK_bm;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3569" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-03-26T14:47:33.207" LastActivityDate="2011-03-26T15:59:23.657" ClosedDate="2011-03-27T10:33:51.350" Title="Atmel ATXmega256A3 spi" Tags="&lt;spi&gt;&lt;atmel&gt;&lt;xmega&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="11995" PostTypeId="2" ParentId="11993" CreationDate="2011-03-24T22:40:50.350" Score="5" ViewCount="" Body="&lt;p&gt;You need a drill, if only to make a pilot hole. I use a hand-held tapered reamer to enlarge the hole to the desired size. It leaves a very neat edge, which is difficult to achieve with a large drill bit. The technique works with aluminium as well as plastic.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-24T22:40:50.350" CommentCount="3" />
  <row Id="11996" PostTypeId="1" AcceptedAnswerId="12002" CreationDate="2011-03-24T23:04:35.943" Score="0" ViewCount="59" Body="&lt;p&gt;I'm wondering if I've blown my lcd by accident. It's supposed to be a 20 * 4 rows lcd however only row 2 and row 4 seem to light up. Should they not all light up&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-03-24T23:46:21.347" Title="LCD rows not all lighting up" Tags="&lt;lcd&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="11997" PostTypeId="2" ParentId="11993" CreationDate="2011-03-24T23:12:07.893" Score="0" ViewCount="" Body="&lt;p&gt;On some softer cases, I've used scissors to make holes. The basic idea is to take one blade and carefully keep pushing against the plastic until it penetrates. After that, start rotating until you get desired hole size. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-24T23:12:07.893" CommentCount="1" />
  <row Id="11998" PostTypeId="2" ParentId="11996" CreationDate="2011-03-24T23:13:48.220" Score="1" ViewCount="" Body="&lt;p&gt;Check your programming and connections. I doubt that you could damage module in such way that only two rows which aren't close together remain functioning. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-24T23:13:48.220" CommentCount="1" />
  <row Id="11999" PostTypeId="2" ParentId="1437" CreationDate="2011-03-24T23:14:07.983" Score="1" ViewCount="" Body="&lt;p&gt;If you ask your package system to install avr-libc, that should give you all you need.  I use emacs as my IDE, cos, well, see username.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want a template makefile, have a look at one of my projects on github, eg &#xA;&lt;a href=&quot;https://github.com/unixbigot/pir-lite&quot; rel=&quot;nofollow&quot;&gt;https://github.com/unixbigot/pir-lite&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In that repo avr-tmpl.mk is an off-the-shelf makefile library (not written by me).  You include it from your main makefile and you only have to define which chip you have, the clock speed, and your files.   I have one copy of it and include it from all my project makefiles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;make program&quot; will call avrdude to download the code.  The makefile also prints out code size at end, so you know how much room you have left.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-24T23:14:07.983" />
  <row Id="12000" PostTypeId="2" ParentId="11946" CreationDate="2011-03-24T23:32:58.250" Score="3" ViewCount="" Body="&lt;p&gt;If you are building a small display, you can also do it with a round circuit board with circular traces that rotates coaxially with your rotating part with two fixed &quot;brushes&quot; (small brass springs) that each drag on one of the circular traces.   Like a flattened out version of how a DC motor commutator works.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-24T23:32:58.250" />
  <row Id="12001" PostTypeId="2" ParentId="11993" CreationDate="2011-03-24T23:41:34.293" Score="8" ViewCount="" Body="&lt;p&gt;A hand-held tapered reamer (&lt;a href=&quot;http://www.google.com/images?q=tapered%20reamer&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/images?q=tapered+reamer&lt;/a&gt;) is a good tool to have for this.  A &quot;step drill&quot; bit is even better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For starting holes, a small hand drill (non electric, &lt;a href=&quot;http://www.google.com/images?q=egg%20beater%20drill&quot; rel=&quot;nofollow&quot;&gt;http://www.google.com/images?q=egg+beater+drill&lt;/a&gt;) gives much better control than an expensive electric drill anyway; try a flea market or junk store.  You can also melt a starting hole for your reamer hole with a hot nail or a worn out soldering iron tip in a pinch.&#xA;A small hex shank drill bit can also be used by hand mounted in a bit-driver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For rectangular holes, a hand nibbler (&lt;a href=&quot;http://en.wikipedia.org/wiki/Nibbler&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Nibbler&lt;/a&gt;) is great, starting from a hole made by your reamer or step drill.&lt;/p&gt;&#xA;" OwnerUserId="389" LastEditorUserId="595" LastEditorDisplayName="" LastEditDate="2011-03-25T09:11:23.343" LastActivityDate="2011-03-25T09:11:23.343" />
  <row Id="12002" PostTypeId="2" ParentId="11996" CreationDate="2011-03-24T23:46:21.347" Score="2" ViewCount="" Body="&lt;p&gt;Some four-row LCDs are actually two controllers with separate enable inputs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try writing to all the locations in the data RAM, the memory-address to character-location in these LCDs is not always what you think it is.   For example I have a weird 16x1 display that is actually laid out as two disjoint 8-column memory ranges.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-24T23:46:21.347" />
  <row Id="12003" PostTypeId="2" ParentId="11993" CreationDate="2011-03-25T00:34:24.643" Score="1" ViewCount="" Body="&lt;p&gt;An old, cheap soldering iron can be used to melt the plastic. Always start to melt from the internal side, so that the displaced plastic stays there. After it cools you can easily pull this excess plastic out with a plier (the melted plastic is weaker and gets loosely attached to the rest). The problem with this, and other cheap solutions, is that you must have a very steady hand. I'd prefer to use a Dremel rotary tool with work station. It's not that expensive these days (about 60 + 40 dollars) and will guarantee much better results; not to mention that such tool has MANY more uses.&lt;/p&gt;&#xA;" OwnerUserId="1078" LastEditorUserId="1078" LastEditorDisplayName="" LastEditDate="2011-03-25T00:39:28.947" LastActivityDate="2011-03-25T00:39:28.947" />
  <row Id="12004" PostTypeId="2" ParentId="11974" CreationDate="2011-03-25T01:09:06.700" Score="1" ViewCount="" Body="&lt;p&gt;There is a configuration of two coils, known as a Helmholtz coil, that is supposed to produce a nearly uniform field. The idea is to have two coils that are separated by a distance about the same as the diameter of the individual coils. Going with this, the coil diameter would obviously have to be about the same as the length of your rails, so would be rather large relative to the rest of the apparatus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But you might not need an exactly uniform field anyway. If you had a field that was non-uniform, but symmetric across a plane that divides the mid-line of your rails, the forces on the movable bar should be in-line. It might be possible to produce a field like that by using two rectangular coils, same width as the rail separation, with one half above the plane of the rails and the other below.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-03-25T01:09:06.700" />
  <row Id="12005" PostTypeId="2" ParentId="11884" CreationDate="2011-03-25T01:47:04.467" Score="7" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;You need one channel, per frequency, per satellite.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most of the cheap receivers (like the one in your phone or car) track only the L1 frequency from only the GPS satellites. If you want accuracy, you need to track two frequencies from each satellite in order to more accurately determine ionospheric delays. If you want better coverage in areas with partial obstructions, you need to track more than just the GPS satellites.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are currently 32 GPS satellites in orbit, 31 of which were healthy as of last week. A receiver will see less than half of them due to the elevation mask, which means that it ignores any satellite less than 5 degrees above the horizon. The elevation mask can be set higher - 8 or 10 degrees is common. Each of those satellites broadcast on both the L1 and L2 frequencies, and one GPS satellite is currently broadcasting on L5 (in test mode). All future GPS satellites will also support L5, and eventually your regular cheap receivers will use L5 instead of L1. It will probably be the year 2020 before you see L5 replace L1 on cheap devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Russia also has a constellation of global positioning satellites known as GLONASS. There are currently 27 GLONASS sats in orbit. As of last week, 23 are healthy, 3 are in maintenance mode, and 1 is in commissioning mode. All of the GLONASS satellites broadcast on two frequencies - L1 and L2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Europe and China are also building constellations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to use WAAS correction data, you need one channel for SBAS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to use OmniStar or Canada's CDGPS, you need a channel for that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The receiver I'm most familiar with tracks the following channels:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;14 GPS L1 channels&lt;/li&gt;&#xA;&lt;li&gt;14 GPS L2 channels&lt;/li&gt;&#xA;&lt;li&gt;6 GPS L5 channels&lt;/li&gt;&#xA;&lt;li&gt;12 GLONASS L1 channels&lt;/li&gt;&#xA;&lt;li&gt;12 GLONASS L2 channels&lt;/li&gt;&#xA;&lt;li&gt;2 SBAS channels (WAAS or EGNOS)&lt;/li&gt;&#xA;&lt;li&gt;1 L-band channel (OmniStar or CDGPS)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The newest generation of high end receivers also have additional channels for the European and Chinese constellations.&lt;/p&gt;&#xA;" OwnerUserId="3573" LastEditorUserId="3573" LastEditorDisplayName="" LastEditDate="2011-03-25T03:48:17.590" LastActivityDate="2011-03-25T03:48:17.590" CommentCount="1" />
  <row Id="12006" PostTypeId="2" ParentId="11938" CreationDate="2011-03-25T05:04:53.847" Score="1" ViewCount="" Body="&lt;p&gt;While having 24-bits would be great lots of useful work can be done with only 14-bits. As an example, see the USRPs from Ettus Research used worldwide by researchers in conjunction with GnuRadio software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ettus.com/downloads/ettus_ds_usrp_n200series_v3.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.ettus.com/downloads/ettus_ds_usrp_n200series_v3.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3574" LastActivityDate="2011-03-25T05:04:53.847" />
  <row Id="12007" PostTypeId="1" CreationDate="2011-03-25T05:21:52.130" Score="0" ViewCount="71" Body="&lt;p&gt;This is &lt;strong&gt;not&lt;/strong&gt; a broad &quot;which system is &lt;em&gt;best&lt;/em&gt;?&quot; question. It will hopefully not be closed as being to vagure or unanswerable. Given my needs, which robotics system for is best &lt;strong&gt;me&lt;/strong&gt;? (sorry about that, but some folks can be alittle over-zealous on closing)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have come to realize that non-techie people don't respond too well to tech descirptions. Even douments and PowerPoints presentations can leave them puzzled, but if you show them something physical then their eyes light up and they see not only what is in front of them but also many further possbilities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I want to make a demo or two.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I develop software. It either works with the customer's existing hardware or I buy them some off the shelf hardware, and then I develop some software to speak to their hardware, an ODBC database (usually MySql) to store data and a browser based application to contol the hardware and analyze the data, generate reports, trigger alarms, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sort of systems we are talking of are all surprisingly similar when viewed at a high level: asset/emplyee/vehicle tracking; stock control; data acqusition (reading of temperature, pressure, voltage, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I coudl go on, but is't basically data acquisition/telemetery/SCADA/process control. At the hardware end can be RDIF tags, GPS sensors, Mobus and the like, etc, etc&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, what's a good system for me to develop some demos? A hard requirement is that the robot should not just load a program and go away and execute it independantly of the PC. The robot should have some sensors and should report values to the PC program (which will add them to the database) and should also accept commands from the PC program (even if I have to develop my own command language and have the robot program interpret it). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And what might be some good demos?&lt;br&gt;&#xA;- a maze runner, where I can show the current location on in a desktop or browser program, with the robot representing an employee or a fork-lift ? (or even a vehicle &amp;amp; I gould show it on google maps)&lt;br&gt;&#xA;- maybe it could pick up RFID tags and scan them (or carry them to a scanner) to identify them to the PC app and then move them form room to room, with new tags appears at goods inwards &amp;amp; disappearing at shipping? That would simualte stock control.&lt;br&gt;&#xA;- maybe stick some bright light or heat source, etc,  soemwhere and have the robot sense it?&lt;br&gt;&#xA;- allow the robot to be controlled from the desktop app or browser  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;any other ideas?&lt;/p&gt;&#xA;" OwnerUserId="3396" LastActivityDate="2011-03-25T05:21:52.130" ClosedDate="2011-03-25T09:26:55.377" Title="Which robotics system for is best me?" Tags="&lt;robotics&gt;&lt;programming&gt;&lt;mobile-robot&gt;" CommentCount="1" FavoriteCount="1" />
  <row Id="12008" PostTypeId="2" ParentId="11978" CreationDate="2011-03-25T07:37:43.700" Score="5" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/ads1256.html&quot; rel=&quot;nofollow&quot;&gt;ADS1256&lt;/a&gt; from TI has eight single-ended 24bit channels with high-impedance input buffer and PGA. OpenEXG project has &lt;a href=&quot;http://sites.google.com/site/openexg/software&quot; rel=&quot;nofollow&quot;&gt;PIC code&lt;/a&gt; to interface it (they use two channel version ADS1255, but it should be the same).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want differential inputs, then there is &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/ads1298.html&quot; rel=&quot;nofollow&quot;&gt;ADS1298&lt;/a&gt;, with 8 channels, PGAs and A/Ds, internal reference, plus ECG/EEG circuitry which you can ignore. I am not sure you can find any example code for this one, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are looking for resolution, then precise, low noise reference is a must.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-03-25T07:37:43.700" CommentCount="2" />
  <row Id="12009" PostTypeId="1" AcceptedAnswerId="12010" CreationDate="2011-03-25T08:34:43.463" Score="0" ViewCount="69" Body="&lt;p&gt;The device is called KY 717 and from what I've been able to find out, it's some sort of rectifier. The solder tab is insulated from the rest of the body.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/4Fe4j.jpg&quot; alt=&quot;KY 717&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was unable to make a better picture. The major division on the paper is 10 mm and the device appears to be 37 mm long. The screw is from what I can see M4 type screw. The soldering hole has diameter of around 3 mm, but is deformed so my measurements could be bad. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-25T08:43:51.067" Title="What's the name of this component's package?" Tags="&lt;rectifier&gt;" AnswerCount="1" />
  <row Id="12010" PostTypeId="2" ParentId="12009" CreationDate="2011-03-25T08:43:51.067" Score="7" ViewCount="" Body="&lt;p&gt;It's a power diode (20A) manufactured in the past by Czech company Tesla, and the package is called DO-5/1.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-03-25T08:43:51.067" CommentCount="1" />
  <row Id="12012" PostTypeId="1" CreationDate="2011-03-25T09:58:19.990" Score="1" ViewCount="142" Body="&lt;p&gt;I need to rotate an object about 20 kg's in weight, 360 degrees.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking of using a stepper motor with some kind of rubber wheel pushing along the rim of a lazy-susan. Geared or belt solutions are probably better, but I don't reckon I need the accuracy. Mostly I am unsure how to spec which stepper motor I need? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the given spec for a stepper motor I can get locally:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;HIGH TORQUE HYBRID STEPPING MOTOR, WITH DUAL / DOUBLE ENDED SHAFT&#xA;12VDC, 0.31A, 38E5/PHASE, 1.6KG-CM TH, 6-WIRE, 120G-CM TD&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any comments welcome.&lt;/p&gt;&#xA;" OwnerUserId="3575" LastActivityDate="2011-04-14T11:20:15.500" Title="Best way to drive a 20 kg object on a turntable?" Tags="&lt;motor&gt;&lt;stepper&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="12013" PostTypeId="2" ParentId="11978" CreationDate="2011-03-25T10:08:18.277" Score="4" ViewCount="" Body="&lt;p&gt;A maybe unconventional idea, I am curious what you guys think about it:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One order of magnitude seems a large enough change to measure it directly in a voltage divider circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could then use a smaller ADC and vary the current through the sensor. A filtered PWM voltage source + a voltage follower (may be one NPN transistor if you are thigh on space) may drastically improve your dynamic range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use one or two of these and switch the voltage when measuring different sensors.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-25T10:08:18.277" CommentCount="3" />
  <row Id="12014" PostTypeId="1" AcceptedAnswerId="12015" CreationDate="2011-03-25T10:43:40.350" Score="6" ViewCount="287" Body="&lt;p&gt;In a car battery charger, I found a strange rectifier. Can someone explain to me how does it work? &#xA;&lt;img src=&quot;http://i.imgur.com/VulyL.png&quot; alt=&quot;Rectifier&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here I have a transformer which is unmarked. By measuring resistance between its output terminals, I determined that the plus cable is connected to the center of the transformer. The two outer connections both have a diode connected as shown on the image. To me it looks similar to this:&lt;br&gt;&#xA; &lt;img src=&quot;http://i.imgur.com/O6aLi.png&quot; alt=&quot;wikipedia rectifier&quot;&gt;&lt;br&gt;&#xA; rectifier, but the diodes are turned backwards. I checked their orientation several times with two different multimeters and I'm sure that I've drawn them correctly.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-25T11:12:43.847" LastActivityDate="2011-03-25T12:58:45.683" Title="How does this rectifier work?" Tags="&lt;rectifier&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="12015" PostTypeId="2" ParentId="12014" CreationDate="2011-03-25T11:13:24.847" Score="7" ViewCount="" Body="&lt;p&gt;By center tapping you have just picked a reference that has two different sides that at any one point will oscillate in reference to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the top side goes negative in reference to the center tap it will conduct from the load. The same applies for the bottom side. The number of turns on each side will determine what voltage peak you can receive. The center tap just makes it like you have 2 transformers each with have of the loops of the larger transformer it could be by ignoring the center tap. With a capacitive load and regulator this is easily turned into a DC voltage.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;Why does diode direction matter?&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;It is just going to change which of the pins is the negative reference. The graph you loaded in shows the rectified hills which are all positive, because of the diode direction they are all negative. They need a negative reference for something in your car.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this helps. Let me know if there is something in this answer I can expand upon to help.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-03-25T11:13:24.847" CommentCount="3" />
  <row Id="12016" PostTypeId="2" ParentId="12014" CreationDate="2011-03-25T11:14:36.437" Score="5" ViewCount="" Body="&lt;p&gt;It's the same, although I've never seen a full-wave rectifier this way round before. Electriclly it makes no difference which way it's done, but it seems more 'natural' to connect the centre-tap of the transformer to the circuit's reference rail - which is usually the negative.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-03-25T11:14:36.437" CommentCount="3" />
  <row Id="12017" PostTypeId="2" ParentId="12014" CreationDate="2011-03-25T11:14:55.290" Score="5" ViewCount="" Body="&lt;p&gt;The diodes conduct on alternate half cycles (the two ends of the secondary winding give a phase reversal), so that the circuit behaves like a full-wave rectifier with four diodes. It's a popular circuit, because it's cheaper to manufacture than one using a single winding secondary with a four diode bridge rectifier.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-25T11:56:22.603" LastActivityDate="2011-03-25T11:56:22.603" CommentCount="3" />
  <row Id="12018" PostTypeId="1" CreationDate="2011-03-25T12:12:46.907" Score="3" ViewCount="156" Body="&lt;p&gt;Is there a way to convert PCM data to PWM impulsion so that I can send it a basic stamp microcontroler in order to play audio on a external speaker ? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(without using an IC)&lt;/p&gt;&#xA;" OwnerUserId="3578" LastActivityDate="2011-03-26T09:03:39.373" Title="Playing a low res WAV/PCM file using a Basic Stamp II microcontroler speaker" Tags="&lt;microcontroller&gt;&lt;pwm&gt;&lt;wave&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="12019" PostTypeId="2" ParentId="12018" CreationDate="2011-03-25T12:43:24.253" Score="3" ViewCount="" Body="&lt;p&gt;Convert your sound file to a WAV file:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;mplayer -ao pcm music.mp3&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Make an unsigned mono 8bit version at the desired sample rate:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;sox audiodump.wav -c 1 -r 8000 -u -1 converted.wav&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Convert the samples to a C header file (get &lt;A href=&quot;http://thieumsweb.free.fr/english/gbacss.html&quot; rel=&quot;nofollow&quot;&gt;wav2c&lt;/a&gt;):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;wav2c converted.wav sounddata.h sounddata&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(For your BASIC Stamp, you'll need to convert this array into some other format).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, in your application you need to read one sample from the array each time the sample rate duration expires and transmit it out of your PWM pin.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-25T12:43:24.253" CommentCount="2" />
  <row Id="12020" PostTypeId="2" ParentId="12014" CreationDate="2011-03-25T12:58:45.683" Score="19" ViewCount="" Body="&lt;p&gt;Maybe these illustrations will help:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/QTyaU.png&quot; alt=&quot;Phase 1&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/IWIY9.png&quot; alt=&quot;Phase 2&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's assume that the start and end of the primary and secondary windings are such that the 'starts' are at the top of the picture and the 'finishes' are at the bottom.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When primary current flows from the top of the picture to the bottom, the top of the primary winding is at higher voltage than the bottom. This will induce a voltage in the secondary winding with the highest potential at the top of the winding and the lowest at at the bottom (and a potential somewhere in between, at the center-tap).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can tell quickly that D1 will be reverse-biased, because the voltage at the top is higher than at the center-tap. Current will flow however it can, which will be out of the center-tap, through D2 and into the bottom of the winding.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When primary current flows from the bottom of the picture to the top, the reverse condition holds true in the secondary: D2 will be reverse-biased, and current will flow from the center-tap through the load and through D1 back to the winding.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-25T12:58:45.683" CommentCount="4" />
  <row Id="12021" PostTypeId="1" CreationDate="2011-03-25T12:58:58.140" Score="1" ViewCount="81" Body="&lt;p&gt;Hello.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to get full list of supported AT commands and other undocumented codes for some cell phone. I found that using &lt;code&gt;strings&lt;/code&gt; command (on linux or win alternative) I can get all ASCII or UTF constant strings from firmware binary file, but it is a junk.&#xA;I don't have any JTAG hardware.&#xA;Maybe I should get fullflash from the device and look for some interrup routines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any other way to get these info?&lt;/p&gt;&#xA;" OwnerUserId="3579" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-25T13:28:16.973" LastActivityDate="2011-03-25T13:45:52.930" Title="How to reverse cellphone firmware" Tags="&lt;reverse-engineering&gt;&lt;firmware&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12023" PostTypeId="1" CreationDate="2011-03-25T13:44:52.210" Score="2" ViewCount="163" Body="&lt;p&gt;I have &lt;a href=&quot;http://www.hzjingce.com/products.asp?id=2&quot; rel=&quot;nofollow&quot;&gt;a Chinese scope&lt;/a&gt; with a two-pin power cord and a plastic body, and measure megaohms between its ground terminals and the actual earth, so I believe it has an internal isolation transformer (I suppose I could open it to confirm...)  I've used it to measure small floating voltages before without problems (connecting the ground to +5V relative to earth, and the probe to a current sensing resistor also around +5 V), but now I want to measure power supply voltages where the ground of my scope will be connected to a rectified wave at maybe 200 VAC relative to Earth.  Any problems?  Does an isolation transformer make everything good?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that what you're supposed to do is use two separate probes and use the Math function to subtract them, but that doesn't work in practice because the common-mode voltages are so much higher than the differential voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;... Oh.  Besides the, um, safety reasons.  The whole scope will then be at 200 VAC relative to Earth ground, so if I touch one of the scope's BNC connectors and a real ground at the same time I'm in trouble.  I guess that's a big problem, but is it the only problem?  Floating the device under test with an isolation transformer would not have this problem?  But that transformer would have to be a lot bigger to handle the high power.  Does it have other problems due to parasitic capacitance, etc.?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any trick to using the differential math function method by reducing the common-mode voltage with a capacitor or large resistor, but not connecting it directly enough to produce a safety hazard?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-25T15:15:06.393" LastActivityDate="2011-03-27T09:59:58.320" Title="Any problems with &quot;floating&quot; an oscilloscope?" Tags="&lt;oscilloscope&gt;&lt;safety&gt;&lt;ground&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="12024" PostTypeId="2" ParentId="12021" CreationDate="2011-03-25T13:45:52.930" Score="4" ViewCount="" Body="&lt;p&gt;In order to get a list of all supported AT commands, you can just run &lt;code&gt;AT+CLAC&lt;/code&gt; which will list just that. It is a &lt;a href=&quot;http://www.3gpp.org/ftp/Specs/html-info/27007.htm&quot; rel=&quot;nofollow&quot;&gt;standardized command&lt;/a&gt; which, although optional, I assume virtuall all manufacturers support. Sony-Ericsson phones (as well as other phones based on platforms from &lt;a href=&quot;http://en.wikipedia.org/wiki/Ericsson_Mobile_Platforms&quot; rel=&quot;nofollow&quot;&gt;Ericsson&lt;/a&gt;/ST-Ericsson) also support &lt;code&gt;AT*&lt;/code&gt; as an alternative command (with an optional numeric parameter for different output formatting (e.g. &lt;code&gt;AT*2&lt;/code&gt;)).&lt;/p&gt;&#xA;" OwnerUserId="568" LastActivityDate="2011-03-25T13:45:52.930" />
  <row Id="12025" PostTypeId="2" ParentId="11234" CreationDate="2011-03-25T14:20:18.593" Score="6" ViewCount="" Body="&lt;p&gt;That is not a trivial project.  There are many educational sub projects to worry about.  One is buttons and debouncing.  Another is writing characters to a display.  There is the decision of how you want to implement this are you interested in making it from a big box of nand gates or want to take a microcontroller or other processor and write software?  Are you interested in using an fpga and doing all of the math in RTL?  You need to break the problem down into those components and work/learn one component at a time and then join them together.  For example if the core math engine is actually software on a microcontroller, one task would include writing some C functions on your desktop computer that you can feed keystrokes and output characters that will ultimately go to the display.  A non-trivial task if you have never programmed before.  If you are choosing to go with an fpga or possibly even discrete logic, you might want to use verilator or icarus verilog or ghdl to work on the core math and interface modules.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an educational project what I would do is get a few msp430 launchapads, under 5 bucks each or The STM32 value line discovery (the stm32/arm based one not the other one) for around 12 bucks each.  A number of folks will steer you toward the arduino, and that is a fine platform as well, it has its pros and cons, i wouldnt go with it as my first microcontroller.  Buy a simple two line lcd panel, earth lcd used to be a good place, perhaps just go to sparkfun.  Take one microcontroller board hook it up to the lcd panel and learn how to put characters on the display.  I would then learn how to use the uart on the microcontroller which often starts with blasting bytes out, then later receiving and echoing.  Use the uart receiver to receive things to put on the display then using a dumb terminal (putty, hyperterm, minicom) from a computer feed stuff in and make sure it works.  Next take another microcontroller, use  your uart in and out experience and work on the core math engine, from your computer feed it 0 - 9, +, -, = at first then add multiply and divide and then floating point if you are brave enough for that (or have a library that fits).  Output from the math module would echo input numbers and print results when = is sent in, etc.  Then figure out what to do with buttons, find an array of buttons, feed those into the third microcontroller somehow, debounce, and have that turn into uart out of 0 - 9, + , - , = to the math microcontroller.   THEN, reduce all of this into a single microcontroller without the uart stuff in the middle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another alternative is to get one of the rs-232 fpga boards from knjn.com or the lattice brevia (is that big enough?) or a number of others, then work on each of the functional blocks using an RTL language.  parts of it will be much easier than the equivalent software solution, some parts will be a bit harder than a software solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can provide more information as to what you are thinking, a box of nand gates or microcontroller based solution or were you thinking about something else?&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-03-25T14:20:18.593" />
  <row Id="12026" PostTypeId="2" ParentId="12023" CreationDate="2011-03-25T14:36:22.863" Score="3" ViewCount="" Body="&lt;p&gt;When we needed to do something like that where I worked many years ago, when testing power controllers that had a direct mains connection (no transformer) under load with a scope I specified a high-power isolation transformer in an &quot;earth free&quot; test area. The setup cost a lot of money, but was necessary for safety reasons, and worked very well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;People sometimes remove the scope ground connection in those circumstances, but it isn't a good idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your case, I'd use an isolation transformer and an earth-free area.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-25T14:44:47.350" LastActivityDate="2011-03-25T14:44:47.350" CommentCount="5" />
  <row Id="12027" PostTypeId="2" ParentId="12012" CreationDate="2011-03-25T14:43:34.043" Score="0" ViewCount="" Body="&lt;p&gt;Provided that you will have good bearings (and very low friction), even the lowest powerful steppers would work, even ones salvaged from DVD-drives. So you would need to focus on mechanical part &amp;amp; bearings, not motor.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-25T14:43:34.043" />
  <row Id="12028" PostTypeId="2" ParentId="11577" CreationDate="2011-03-25T15:14:30.220" Score="3" ViewCount="" Body="&lt;p&gt;If the changes in sensor resistance are large (&gt; 50%) then you could use a  voltage divider circuit instead of the (more complicated) Wheatstone bridge. You can then easily improve the dynamic range by varying the supply voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adjustable supply voltage can easily be made from the PWM in your microcontroller together with a RC filter and a voltage-controlled current source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a rough schematic of my idea:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/0TVxZ.png&quot; alt=&quot;Schematic&quot;&gt;(from &lt;a href=&quot;http://openbookproject.net/books/socratic/output/opamp7.pdf&quot; rel=&quot;nofollow&quot;&gt;Socratic Electronics by Tony R. Kuphaldt&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You then connect the filtered PWM voltage to the non-inverting (+) input of the op amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For fast multiplexing you could make two such current sources. If you connect all even sensors to one and all odd to the other then you can change the voltage on the next sensor while your ADC is still sampling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should use a precision voltage reference for the ADC. You can also gain 1 or 2 bits by using a &lt;a href=&quot;http://www.dspguide.com/ch15.htm&quot; rel=&quot;nofollow&quot;&gt;moving average filter&lt;/a&gt; in your software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. I'd like to thank Jaroslav Cmunt for his vast improvements to this answer.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-26T12:34:28.450" LastActivityDate="2011-03-26T12:34:28.450" CommentCount="0" />
  <row Id="12029" PostTypeId="2" ParentId="12023" CreationDate="2011-03-25T15:27:36.227" Score="2" ViewCount="" Body="&lt;p&gt;Floating the device under test (DUT) is the safe bet, you've mentioned the reasons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your scope appears to be a class II piece of equipment (no protective earth = PE connection). Usually, stuff like that is tested with a high voltage (some 1...2 kV) between mains and secondary, so this is what the scope's mains transformer should be able to take. (Just for clarity, in case it's not obvious: In your case, as seen from the sope's power supply, secondary means everything around the scope inputs and interfaces.) The high voltage is just used for production testing and is by no means meant to be a working voltage that you should continuously apply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, to be sure, there should be something in the manual about this issue. AFAIK, it is mandatory that scopes be grounded even if powered with a power supply that doesn't have a PE connection, or there must be a specification. (The Tek THS7020 battery scope is an example, but this one has isolated inputs that can even be floated with respect to each other).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of all non-battery-powered bench type scopes with ordinary (non-insulated) inputs, this is actually the first one I've seen sold as a class II piece of equipment, i.e. as one that doesn't have a PE connector.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-03-27T09:59:58.320" LastActivityDate="2011-03-27T09:59:58.320" CommentCount="1" />
  <row Id="12030" PostTypeId="2" ParentId="11813" CreationDate="2011-03-25T15:32:56.033" Score="0" ViewCount="" Body="&lt;p&gt;Since I'm loosing confidence in the idea of using the single relay to control both circuits, I now think the right answer is to simply buy ANOTHER RELAY. I can get a less expensive 110v capable relay for the drain-valve circuit and wire them both to the same 24V signal from my digital IO controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This keeps all of the line voltage stuff &quot;clean&quot; and normal. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure why I didn't think of this before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[EDIT: 12pm 3/27] I'm 90% finished with constructing this thing. One more trip to the hardware store and the use of a my toner to find the 24v wire in the attic and it should be up and running. Here's a pic of the two pump-start relays mounted and mostly wired:&#xA;&lt;img src=&quot;http://i.imgur.com/9sRft.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[EDIT: 7pm 3/27] Done! Works like a champ. Here are some pictures of the final result:&#xA;&lt;img src=&quot;http://i.imgur.com/dZFnj.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/F2zoE.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2604" LastEditorUserId="2604" LastEditorDisplayName="" LastEditDate="2011-03-28T02:03:05.197" LastActivityDate="2011-03-28T02:03:05.197" />
  <row Id="12031" PostTypeId="1" AcceptedAnswerId="12034" CreationDate="2011-03-25T15:55:32.047" Score="1" ViewCount="131" Body="&lt;p&gt;I'm not an electrical engineer. I have an unusual need and would like suggestions as to how to proceed. I have an application that needs very high currents at very low voltages. I'm trying to heat a thin strip of aluminum to temperatures near 100C quickly and then control the temperature. My calculations suggest about 150 to 200 amps at less than 0.1 volt. About the only idea I have is using a toroidal transformer with maybe 1000 turns and thick copper bar passing through the center of the toroid connected to the aluminum strip. I can use either AC or DC current and if AC, I'm not necessarily limited to 60hz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any and all good suggestions are welcome.&lt;/p&gt;&#xA;" OwnerUserId="3593" LastActivityDate="2011-03-26T07:33:50.307" Title="Very high current very low voltage application" Tags="&lt;power&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="2" />
  <row Id="12032" PostTypeId="2" ParentId="12023" CreationDate="2011-03-25T16:03:32.927" Score="0" ViewCount="" Body="&lt;p&gt;If the scope has 2 wire supply then it is not earthed and has to have an isolated supply inside.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you describe is sometimes done but you should be extra careful and always verify the polarity of things (a screwdriver-like device with a small incandescent light inside — how do you call it?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also never move (or even touch) the scope probe while the circuit is &quot;live&quot;. Always disconnect the power to the DUT if you want to change your connections.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-25T16:03:32.927" CommentCount="2" />
  <row Id="12033" PostTypeId="2" ParentId="12018" CreationDate="2011-03-25T16:14:42.033" Score="1" ViewCount="" Body="&lt;p&gt;To generate RAW samples from an audio file you could use mplayer&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;mplayer -af resample=48000,channels=2:2:0:1:0:0,format=s16le &#xA;        -ao pcm:nowaveheader:file=outfile.raw&#xA;        infile.mp3&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This outputs raw 16 bit little-endian samples to &lt;code&gt;outfile.raw&lt;/code&gt;. You can then proceed like Joby suggested (just use a bin2c tool, and not wav2c).&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-25T16:14:42.033" />
  <row Id="12034" PostTypeId="2" ParentId="12031" CreationDate="2011-03-25T16:20:15.900" Score="4" ViewCount="" Body="&lt;p&gt;Power supplies from arc welding devices are quite capable of what you describe. You may also try a soldering gun (the kind with a transformer inside) replacing the tip with your stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just be aware that you need really really thick wires for 100A. The problem will be worse with high frequency AC because of the skin effect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as the regulation is concerned you should be able to use a simple PID regulator with a thyristor output for the soldering gun. The arc welding supplies may be more difficult depending on their internal construction.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-26T01:37:03.400" LastActivityDate="2011-03-26T01:37:03.400" />
  <row Id="12035" PostTypeId="2" ParentId="11993" CreationDate="2011-03-25T16:28:07.670" Score="1" ViewCount="" Body="&lt;p&gt;I purchased a toner refill kit once, it came with a cheap soldering iron and a copper fitting cap attached instead of the normal tip, to make the hole in the toner cartridge, to add the toner. &lt;img src=&quot;http://i.imgur.com/f2Zzf.jpg&quot; alt=&quot;copper fitting end cap&quot;&gt;(It would require drilling a small hole through the center end of the cap, and finding a screw that fits in place of the soldering tip.) I have used it many times to make holes in plastic. Some plastics make fumes when melted, use in a well ventilated area.&lt;/p&gt;&#xA;" OwnerUserId="2319" LastActivityDate="2011-03-25T16:28:07.670" CommentCount="1" />
  <row Id="12036" PostTypeId="2" ParentId="10244" CreationDate="2011-03-25T17:44:23.223" Score="1" ViewCount="" Body="&lt;p&gt;SNAP - symbolic, semisymbolic, and numerical analysis of electronic circuits&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://snap.webpark.cz/indexa.html&quot; rel=&quot;nofollow&quot;&gt;http://snap.webpark.cz/indexa.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;very useful&lt;/p&gt;&#xA;" OwnerUserId="3589" LastActivityDate="2011-03-25T17:44:23.223" />
  <row Id="12037" PostTypeId="2" ParentId="12031" CreationDate="2011-03-25T17:56:56.627" Score="2" ViewCount="" Body="&lt;p&gt;How thick is that strip? Aluminium is very reactive and oxidizes instantly when exposed to air, leaving an insulating coating on the aluminium. The resistance of this coating may be much higher than the strip itself, so that the largest part of the power is actually used to heat the contacts, even melt them. Make sure the contact surface is large enough.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-03-26T07:33:50.307" LastActivityDate="2011-03-26T07:33:50.307" CommentCount="1" />
  <row Id="12038" PostTypeId="1" CreationDate="2011-03-25T18:05:27.110" Score="3" ViewCount="275" Body="&lt;p&gt;I have a binary signal, 0V to 1.4V, which I can't change directly. What circuitry, (on a PCB) can I use to increase 1.4V to at least 2.5V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I need a transistor? I guess I'm looking for a switch that will &quot;close&quot; when there's 1.4V? I'm a complete noob at electronics, but I'm alright at physics and understanding the equations&lt;/p&gt;&#xA;" OwnerUserId="1982" LastEditorUserId="2838" LastEditorDisplayName="" LastEditDate="2011-03-26T12:42:57.150" LastActivityDate="2011-05-25T13:53:16.747" Title="Increasing Voltage" Tags="&lt;circuit&gt;&lt;level-shifting&gt;" AnswerCount="5" CommentCount="8" FavoriteCount="3" />
  <row Id="12039" PostTypeId="1" CreationDate="2011-03-25T18:32:24.313" Score="1" ViewCount="59" Body="&lt;p&gt;My company is opening up a visitor center, in which there will be several interactive areas.  We will have 12+ televisions, each having a different video feed of our choosing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are some ways that I can accomplish this, outside of having a DVD player at each TV with a looping video?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some things that we want/need:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;(required) The ability to control all of the video feeds from a central location.&lt;/li&gt;&#xA;&lt;li&gt;(optional) The ability to control all of the TV's from the central location (power off/on, etc).&lt;/li&gt;&#xA;&lt;li&gt;(optional) The ability to feed live video to one of the TV's, from a mounted camera we have.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3590" LastActivityDate="2011-04-24T20:28:41.670" ClosedDate="2011-04-24T23:02:53.100" Title="How can I handle this multiple output video scenario?" Tags="&lt;video&gt;&lt;output&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="12040" PostTypeId="1" CreationDate="2011-03-25T18:34:04.423" Score="3" ViewCount="100" Body="&lt;p&gt;I have a project that requires high quality video and stills to be acquired (almost) live with computer controls. By &quot;almost&quot; live, I mean that a 5 second delay is acceptable, but 5 minutes isn't. (Edit: And by &quot;acquired&quot;, I mean a computer readable file, JPG, h264 or otherwise)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far, I'm using a Sanyo VDC HD 3500 camera, that gives me 4M stills and 1920x1080 30fps video through an IP camera; However, 4M is low resolution for stills, and the optics (for both stills and videos) leaves much to be desired. The HD3500 costs ~$900.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Canon's &lt;a href=&quot;http://www.dpreview.com/news/1002/10020806canoneos550d.asp&quot; rel=&quot;nofollow&quot;&gt;EOS 550D/Rebel T2i&lt;/a&gt; has ridiculously good optics, can do 18MP stills, 1080p that is way better than the Sanyo ... and costs $700 - $800.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A GoPro &lt;a href=&quot;http://gopro.com/cameras/hd-hero-naked-camera/&quot; rel=&quot;nofollow&quot;&gt;HERO HD&lt;/a&gt; Camera can do wide angle 1080p with better optics than the Sanyo ... for $260.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And there are others that optically and sensorly fit the bill much better than the Sanyo. However, neither the Canon nor the GoPro seem to yield to computer control and/or live video streaming - they both write their respective streams to an SD card from which you have to read stuff later, when the camera is not taking pictures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the question is ... Does anyone know how to modify a GoPro, T2i or any other cheap point&amp;amp;shoot / dslr to provide the interface I need? Alternatively, is it possible to construct an SD card which is not actually a card, but rather a computer posing as a card so I can get the streams as they are being written?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any pointers will be highly appreciated.&lt;/p&gt;&#xA;" OwnerUserId="3591" LastEditorUserId="3591" LastEditorDisplayName="" LastEditDate="2011-03-25T21:00:56.013" LastActivityDate="2011-03-26T02:23:12.447" Title="Interface high quality camera to computer in real time?" Tags="&lt;camera&gt;&lt;sd&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="12041" PostTypeId="2" ParentId="11577" CreationDate="2011-03-25T19:17:19.783" Score="5" ViewCount="" Body="&lt;p&gt;Here is the basic idea:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/a6YNQ.png&quot; alt=&quot;sensor&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;V1 is the filtered PWM output and R2 is your sensor. U1 is voltage to current converter, with current through the load R1 being I = V1/R2. This means that voltage across R1 depends on both inputs. U2 and U3 is an instrumentation amplifier with gain 10, which amplifies the voltage across R1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With R1 = 100 Ohms and V1 = 0..5V the circuit works for R2 = 50..5000 e.g. across two orders of magnitude, which from what you say should be enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you do is take out and compare it with reference voltage (4V would be appropriate here for maximum dynamic range) and use &lt;a href=&quot;http://en.wikipedia.org/wiki/Successive_approximation_ADC&quot; rel=&quot;nofollow&quot;&gt;successive approximation&lt;/a&gt; on V1 to get out as close as possible to the reference voltage. From V1 and known voltage drop across R1 (e.g. reference voltage) you can now calculate value of R2, your sensor. This will of course get you result only within the resolution of PWM, but you can use second instrumentation amp to amplify the error (difference between out and reference voltage) to get it within the range of your microcontroller's ADC and this will get you additional bits of resolution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need two opamps (U1 and comparator) and two instrumentation amps. Use real ones instead of making them from opamps, because the imprecisions of resistors and opamps will introduce error.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If two orders of magnitude were not enough, you can replace R1 with digital potentiometer to get another degree of freedom. I have never worked with one, so I don't know how precise they are and whether such solution would need some calibration or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I should mention that it was jpc who came with the idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UPDATE:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ok, I have to agree with OP that this is not really the the answer to his question (though it solves the problem technically). I allowed myself to be carried away by &quot;adaptive amplifier&quot; in the title as an excuse to do some analog design. Forget everything writen above, unless you want to learn something (little) about opamps. Here is, I hope, better answer and much simpler solution: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use resistive divider powered from a voltage regulator (to separate it from other circuitry's noise), with upper resistor set to about the maximum resistance your sensors can have (Rmax), and with the lower resistor being the sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Set the reference voltage for your ADC to half the voltage regulator's output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you sample the voltage on the sensor with your ADC. This way you need only one single-ended channel per sensor. I made ADC recommendation in the other post.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use 10 bit ADC that is integrated in the microcontrollers you mentioned, you will not get much of a dynamic range, though. Enhancing the range using analog circuitry, like the one I originaly posted, would add too many additional parts, which is why I would recommend simply to use some 24 bit ADC, like the ADS1256 I recommended in the other post, because it will give you low noise and high dynamic range, in a single chip (plus the reference, which is tiny, and the voltage regulator, which can be also tiny - you can also try to leave the regulator out and power the resistive divider directly from the reference - this will rob you of 1 bit of resolution, but there are plenty of them anyway). You will have to do some number crunching (&quot;Auto-calibration by finding min and max values in a given analysis window&quot; - is a good idea), but that's easy in this case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this is little more usefull.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UPDATE 2:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the last one: I have been going through MSP430 microcontrollers from TI and I have found that some of them have 16 bit sigma-delta ADC with internal reference. Namely &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?&amp;amp;familyId=912&amp;amp;uiTemplateId=PP-T-GSAT1NU_T&amp;amp;techFamId=null&amp;amp;rootFamilyId=null&amp;amp;sectionId=95&amp;amp;tabId=1528&amp;amp;appId=null&amp;amp;viewDeviceCallingPage=null&amp;amp;totalCount=48&amp;amp;showAdditionalParameters=no&amp;amp;parameter=2443604387&amp;amp;lc=2000062&amp;amp;lc=2001132&amp;amp;lc=2001134&amp;amp;lc=2001227&amp;amp;lc=2001219&amp;amp;lc=2000886&amp;amp;lc=2000121&amp;amp;compare=yes&amp;amp;download=yes&amp;amp;sort=yes&amp;amp;customize=yes&amp;amp;paramResults=yes&amp;amp;paramCriteria=yes&amp;amp;familyTree=yes&amp;amp;military=no&amp;amp;baSystem=yes&amp;amp;paramTable=no&amp;amp;sortOption=PA_SUB_FAMILY_NAME&amp;amp;sortMode=ASC&amp;amp;searchPaths=1000912&amp;amp;pageId=912&amp;amp;templateId=0&amp;amp;navigationId=0&amp;amp;family=mcu&amp;amp;paramTable=no&amp;amp;military=no&amp;amp;&amp;amp;uiTemplateId=PP-T-GSAT1NU_T&amp;amp;techFamId=null&amp;amp;rootFamilyId=null&amp;amp;sectionId=95&amp;amp;tabId=1528&amp;amp;appId=null&amp;amp;viewDeviceCallingPage=null&amp;amp;resetCompare=true#sdp&quot; rel=&quot;nofollow&quot;&gt;MSP430F2003 and MSP430F20013&lt;/a&gt;. That would be your one chip solution if you are willing to give up on Atmels. Very low power too. And they have in queue microcontrollers with 24 ADCs, but these are not in production yet. Than there are also PSoC microcontrollers from Cypress, which have 20 bit sigma-delta ADCs (&lt;a href=&quot;http://www.cypress.com/?id=2232&quot; rel=&quot;nofollow&quot;&gt;PSoC 3&lt;/a&gt; and &lt;a href=&quot;http://www.cypress.com/?id=2233&quot; rel=&quot;nofollow&quot;&gt;PSoC 5&lt;/a&gt; series), also with reference. These would be even better.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastEditorUserId="2636" LastEditorDisplayName="" LastEditDate="2011-03-27T10:42:50.140" LastActivityDate="2011-03-27T10:42:50.140" CommentCount="10" />
  <row Id="12042" PostTypeId="2" ParentId="12039" CreationDate="2011-03-25T19:32:56.540" Score="0" ViewCount="" Body="&lt;p&gt;I'd use a low powered computer streaming video (using something like vlc) from a central server. You can get fair compact boxes nowadays that can handle outputting full HD video, but I'm not sure about the power required to stream/decode an HD stream.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2011-03-25T19:32:56.540" />
  <row Id="12043" PostTypeId="2" ParentId="12038" CreationDate="2011-03-25T19:51:35.517" Score="7" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Note&lt;/strong&gt;: &lt;em&gt;Corrected logic inversion problem.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;2nd Update&lt;/strong&gt;: &lt;em&gt;Fixed output voltage range, using &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/MOSFET&quot; rel=&quot;nofollow&quot;&gt;MOSFET&lt;/a&gt; rather than &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Transistor#Bipolar_junction_transistor&quot; rel=&quot;nofollow&quot;&gt;BJT&lt;/a&gt;&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;The basics of the problem as you have described it, appear to be called either a &quot;logic level shifter&quot; or converter. The essence is that you have a digital logic (binary) signal at a given signal level, and you wish to use adapt it to another signal level. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digital logic signals are normally classified according to the original &lt;a href=&quot;http://www.play-hookey.com/digital/electronics/&quot; rel=&quot;nofollow&quot;&gt;logic family&lt;/a&gt; they belong to. Examples include TTL (low: 0, high: +5V), CMOS (low: 0, high: 5 to 15V), ECL (low: -1.6, high: -0.75) , LowV (low: 0V, high: +3.3).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally, you should also be aware of the switching threshold as well. E.g &lt;a href=&quot;http://www.allaboutcircuits.com/vol_4/chpt_3/10.html&quot; rel=&quot;nofollow&quot;&gt;Logic signal voltage levels&lt;/a&gt; that shows the TTL logic voltage levels in the first two graphics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you wish to amplify a logic signal that is either 0 or 1.4V, then a single transistor can be configured as an electronic switch to act as a level converter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2SOj8.png&quot; alt=&quot;N-channel MOSFET level shifter schematic&quot;&gt; (src: mctylr &lt;img src=&quot;http://i.imgur.com/Ah7j7.png&quot; alt=&quot;CC-BY-SA&quot;&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your application the output is the 5V-level output (0 or 5V depending on low/high status) and &lt;code&gt;M1&lt;/code&gt; could be a common small-signal N-channel enhancement mode MOSFET transistor, the &lt;a href=&quot;http://www.fairchildsemi.com/pf/2N/2N7000.html&quot; rel=&quot;nofollow&quot;&gt;2N7000&lt;/a&gt; in &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/commons/wiki/File%3aTO-92_Package_Four_Different_Projections.jpg&quot; rel=&quot;nofollow&quot;&gt;TO-92&lt;/a&gt; plastic through-hole, and SMT packaging. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistors &lt;code&gt;R2&lt;/code&gt; should be 330Kohms, (additional resistor component details are not critical, e.g. 1 or 5% tolerance, 1/8 to 1/4 Watts rating are fine). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistor's resistance values is not particularly critical, I picked an approximate standard value so that if &lt;code&gt;M1&lt;/code&gt; is not conducting then the output will be below ~0.8 V, while when &lt;code&gt;M1&lt;/code&gt; is conducting (i.e. the input is 1.4V, 'high') then the output will be approximately 5V. I picked the value using a quick SPICE simulation. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;V3&lt;/code&gt; is a +1.4V voltage source, and &lt;code&gt;V2&lt;/code&gt; is a +5V voltage source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other values (tolerance and wattage) are common through-hole component values used to select real-world component, but are not critical in this application. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's a very simple and small circuit, costing about twenty-five cents or less for three common electronic parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you didn't mention any high-speed requirements (i.e. switching speed), so this should work in most simple cases.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've adopted this approach of using a MOSFET rather than a bipolar junction transistor &#xA;as I had trouble making a single BJT give the desired voltage swing when switching. From a design point of view, the nice thing about FETs (and MOSFETs) is that they are voltage controlled devices (in terms of a design model), rather than current-controlled as BJT are. &lt;/p&gt;&#xA;" OwnerUserId="2598" LastEditorUserId="2598" LastEditorDisplayName="" LastEditDate="2011-04-03T04:01:54.093" LastActivityDate="2011-04-03T04:01:54.093" CommentCount="14" />
  <row Id="12044" PostTypeId="2" ParentId="10864" CreationDate="2011-03-25T20:04:08.427" Score="0" ViewCount="" Body="&lt;p&gt;I'm clueless too, but one thing the diodes do is create an hysteresis loop which probably suppress noise under 0.7V. I think it's some sort of security device that has more to do with standard electronic communications and less with Ethernet specifically. But it's just a thought, not something that I know for sure.&lt;/p&gt;&#xA;" OwnerUserId="2175" LastActivityDate="2011-03-25T20:04:08.427" />
  <row Id="12045" PostTypeId="2" ParentId="12040" CreationDate="2011-03-25T20:12:00.343" Score="2" ViewCount="" Body="&lt;p&gt;Several DSLRs lets you control them from a computer. Check out &lt;a href=&quot;http://thephotogeek.com/choosing-nikon-dslr-camera-tethered-shooting-software/&quot; rel=&quot;nofollow&quot;&gt;Choosing Tethered Shooting Software for Nikon DSLR Cameras&lt;/a&gt; for an example on how this can be done with a Nikon DSLR.&lt;/p&gt;&#xA;" OwnerUserId="1627" LastActivityDate="2011-03-25T20:12:00.343" CommentCount="2" />
  <row Id="12046" PostTypeId="2" ParentId="11234" CreationDate="2011-03-25T20:31:28.913" Score="2" ViewCount="" Body="&lt;p&gt;I believe this can be a good first learning project, but it is non-trivial, and you will have to learn quite a bit along the way, as well be patient as the project includes quite a number of sub-projects to tackle along the way. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first design hurdle you need to decide is what technology level do you wish to do this at? With or without a microcontroller (a largely self-sufficient microprocessor), discrete logic (e.g. AND, OR, NOR gates and flip-flops) with/without arithmetic units (ALU), programmable logic (CPLD, FPGA), something else I haven't mentioned or considered. This should be first about the technology used to do the calculations, the input/output controls are secondary decisions (LED seven-segment displays, LCD panel) mostly influenced by aesthetics or cost. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One potentially useful starting places for learning about digital computation is the very accessible book, &lt;a href=&quot;http://www.diycalculator.com/&quot; rel=&quot;nofollow&quot;&gt;How Computers Do Math&lt;/a&gt; (ISBN: 0471732788) by the quirky Clive Maxfield. This is written at the &quot;soft&quot; - programming or logical level, which you will need to understand in order to actually do the calculations. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Someone else mentioned the &lt;a href=&quot;http://opencircuits.com/UWatch&quot; rel=&quot;nofollow&quot;&gt;uWatch&lt;/a&gt; (-- &lt;a href=&quot;http://www.calcwatch.com/index.html&quot; rel=&quot;nofollow&quot;&gt;micro-Watch&lt;/a&gt;) project as an example, and there are references around the Internet to electrical engineers (or EE students) that &lt;a href=&quot;http://www.nixiebunny.com/malmbergcalc/calc.html&quot; rel=&quot;nofollow&quot;&gt;built their own calculator&lt;/a&gt; in the 1970s. Or this &lt;a href=&quot;http://www.edn.com/file/347-click_here.doc?force=true&quot; rel=&quot;nofollow&quot;&gt;TI-59 clone&lt;/a&gt; (MS-Word doc) based on a dsPIC30 microcontroller. There are also some &lt;a href=&quot;http://diycalculator.pcl.at/index.php/Main_Page&quot; rel=&quot;nofollow&quot;&gt;details&lt;/a&gt; on building a FPGA (programmable logic device) based &lt;a href=&quot;http://www.diycalculator.com/popup-m-phyver.shtml&quot; rel=&quot;nofollow&quot;&gt;calculator&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a total novice to electronics (or digital electronics) I would suggest using a micrcontroller as a starting point in your design, look over the mentioned book's web site for a feel of the complexity in programming (not much if you have any programming experience) for the microcontroller and go from there.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-03-25T20:31:28.913" />
  <row Id="12047" PostTypeId="2" ParentId="10864" CreationDate="2011-03-25T21:05:30.050" Score="5" ViewCount="" Body="&lt;p&gt;Ethernet uses $\pm0.85\,\mathrm{V}$ signaling so a signal will only be able to &quot;activate&quot; one diode pair. So any transmission only has a chance to reach the two immediate neighbors (no current will flow more than 1 &quot;hop&quot; round the loop).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you can notice the trick which will work only with 3 devices: both of computer A TX lines' have RX lines from computers B and C in immediate neighborhood and it's own RX lines on the far side of the loop. You really don't want to hear what you are sending since it would trigger the collision detection algorithm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two interesting points:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The diodes will heavily attenuate the signal so it probably won't work over longer distances.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You cannot use resistors since they would linearly attenuate the signal and after going all the way around the loop it would finally reach your own RX line. It would be attenuated but the receiver circuit is very sensitive so it would still be able to detect is as a collision. You need a nonlinear element (like e diode) that provides a sharp cutoff.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;PS. It is a really clever circuit. I cannot imagine inventing something like that on my own. :)&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-25T21:05:30.050" />
  <row Id="12048" PostTypeId="1" AcceptedAnswerId="12049" CreationDate="2011-03-25T21:08:26.660" Score="2" ViewCount="105" Body="&lt;p&gt;I have just become aware that people are using 4017 decade counters and an Arduino to drive relatively large numbers of servos from relatively small numbers of pins. Not being an Arduino connoisseur myself, however, I have not been successful in my attempts to decode the software that makes the magic happen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, in non-code, what exactly is going on &lt;a href=&quot;http://www.auv.co.za/blog/atmega128servocontrol4017&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; that makes this possible?&lt;/p&gt;&#xA;" OwnerUserId="3240" LastActivityDate="2011-03-25T21:25:15.517" Title="How does the 4017 decade counter drive a set of servos?" Tags="&lt;arduino&gt;&lt;servo&gt;" AnswerCount="1" />
  <row Id="12049" PostTypeId="2" ParentId="12048" CreationDate="2011-03-25T21:25:15.517" Score="5" ViewCount="" Body="&lt;p&gt;All servos require a repeating pulse to work&lt;/p&gt;&#xA;&#xA;&lt;p&gt;depending on the servo, they require a 1 to 2ms pulse repeat about 50 times a second.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is done is this...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;a reset pulse sets the counter IC back to 0&#xA;Output 0 on the counter goes high,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A timing loop is run for the first servo (on output 0),&#xA;e.g. 1 ms,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;then a pulse is applied to the clock input, this sets the counter IC to 1&#xA;Output 0 goes low, and output 1 goes high&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A timing loop is run for the second servo (on output 1)&#xA;e.g. 1.5ms&lt;/p&gt;&#xA;&#xA;&lt;p&gt;then a pulse is applied to the clock input, this sets the counter IC to 2&#xA;....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I first came across the method of using a counter IC in &quot;Theory and practice of model radio control&quot; - second edition... (c) around 1975&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A reset pulse, then variable length sequential pulses applied to the clock pin to both control the servo and select the next servo.&lt;/p&gt;&#xA;" OwnerUserId="2192" LastActivityDate="2011-03-25T21:25:15.517" />
  <row Id="12050" PostTypeId="1" AcceptedAnswerId="12052" CreationDate="2011-03-25T21:53:38.640" Score="2" ViewCount="89" Body="&lt;p&gt;Referencing &lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+1.0312258501325766+48+5.0+50%0Aw+304+144+544+144+0%0Aw+544+144+544+160+0%0Ar+544+160+544+224+0+100.0%0Aw+544+224+544+256+0%0Aw+544+256+304+256+0%0Av+304+256+304+144+0+0+40.0+5.0+0.0+0.0+0.5%0Ar+304+144+224+144+0+100.0%0Ag+224+144+192+144+0%0Ag+304+256+304+320+0%0Ar+544+256+544+320+0+100.0%0Ag+544+320+544+336+0%0A&quot; rel=&quot;nofollow&quot;&gt;ground circuit simulator&lt;/a&gt;(link launches a simulator applet)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why doesn't current flow in the resistor in the bottom right? What do I need to read about electric theory to be able to correctly trace current flow and solve problems like this?&lt;/p&gt;&#xA;" OwnerUserId="3594" LastActivityDate="2011-03-26T15:32:29.343" Title="Simple current flow" Tags="&lt;ground&gt;" AnswerCount="2" />
  <row Id="12051" PostTypeId="1" CreationDate="2011-03-25T21:58:09.677" Score="2" ViewCount="149" Body="&lt;p&gt;I need an actuator with a few mm of travel and it has to be very responsive to a very low frequency (DC-10Hz) sine wave generated by a function generator. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking of getting a cheap subwoofer and hooking it up to my function generator via a power amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions: &#xA;a) Can I use a speaker as a pseudo-linear actuator or is the speaker designed to pull back the membrane?&#xA;b) Will the voice coil blow when it's used at very low frequencies with enough power to actually displace the membrane by a few mms?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&#xA;Andrew&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: the load is a PCB assembly weighing around 100 grams. I want to move that assembly up and down in a controlled way at different frequencies which I'm generating with a function generator. I also have linear stages but they are slower and noisy and I've thought about a mechanical contraption with a stepper motor and cam shaft. The actuator solution seems more attractive because I can control the motion more easily and I expect the latency to be better.&lt;/p&gt;&#xA;" OwnerUserId="3603" LastEditorUserId="3603" LastEditorDisplayName="" LastEditDate="2011-03-26T14:22:17.937" LastActivityDate="2011-03-26T19:13:06.403" Title="Can I use a subwoofer as a linear actuator?" Tags="&lt;speakers&gt;&lt;actuator&gt;&lt;function-generator&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="2" />
  <row Id="12052" PostTypeId="2" ParentId="12050" CreationDate="2011-03-25T22:10:32.627" Score="3" ViewCount="" Body="&lt;p&gt;The reason is simple. Current always follows path of least resistance. There is connection to the ground made with no resistor and therefore it will be preferred to one with the resistor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the theory, first make sure that you're familiar with &lt;a href=&quot;http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws&quot; rel=&quot;nofollow&quot;&gt;two Kirchoff's laws&lt;/a&gt; and with &lt;a href=&quot;http://en.wikipedia.org/wiki/Ohm%27s_law&quot; rel=&quot;nofollow&quot;&gt;Ohm's law&lt;/a&gt; as most of the things are derived from them. After that, you should know that you can short-circuit point of same potential in a circuit and nothing will happen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next step is to make an equivalent circuit of the ground points. That is to say that the two grounds are actually shorted together. So this way, you get a &lt;a href=&quot;http://en.wikipedia.org/wiki/Current_divider&quot; rel=&quot;nofollow&quot;&gt;current divider&lt;/a&gt;. If you do the calculations, you'll get currents which  are going through the shorted ground connection (consider it a 0 $\Omega$ resistor for calculation purposes) and the one with the resistor. Numbers will say that the current through the short circuit is infinite and through the resistor is zero. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another point which needs to be mentioned is the circuit itself. Think about what the word circuit means. A meaning that fits best here is &lt;code&gt;a circular journey or one beginning and ending at the same place;&lt;/code&gt;. Current going through the circuit must always move in circles. So in your simulation you have two circles. One is moving from the voltage generator through the left resistor, ground, back up the ground terminal and into the voltage generator. The other is from the generator through the right resistor and back into the generator. It doesn't go through the bottom right resistor because there already is a path back into the generator which has lower resistance. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, here is a circuit which is equivalent to your circuit.&#xA;&lt;img src=&quot;http://i.imgur.com/qEO5n.png&quot; alt=&quot;equivalent circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is now obvious that the resistor R3 is shorted out. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you get the 3 laws I mentioned at the start, go to &lt;a href=&quot;http://en.wikipedia.org/wiki/Thevenin%27s_theorem&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; article and read it. Make sure you pay extra special attention to the See also section! Theorems listed there are the basic theorems of circuit analysis.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-25T22:37:07.620" LastActivityDate="2011-03-25T22:37:07.620" CommentCount="2" />
  <row Id="12053" PostTypeId="1" CreationDate="2011-03-25T22:12:20.020" Score="0" ViewCount="32" Body="&lt;p&gt;With a single phone call to remote equipment, &lt;code&gt;Remote Power Switch&lt;/code&gt; can be used to check current power status, detect past power outages, and reboot on command. Popular applications include rebooting ATM’s, web kiosks, web cams, digital recorders, video equipment, BBS servers, voice mail systems, any type of modem, windows driven pc’s, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Features of this product are:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;* Automatic - Power Down/Up upon Calling&#xA;* Automatic - Reboot upon calling&#xA;* Manual - Power ON or Off&#xA;* Customized Security Code Feature! &#xA;* Fully Configurable&#xA;* A Remote Power Switch activated with a phone call&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;More information about the device can be found on on &lt;a href=&quot;http://www.remotepowerswitch.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.remotepowerswitch.com/&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;I am looking for an alternative device or solution to  Remote Power Switch - RPS II.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Knowing the features of this product, what would be your suggestion for alternatives to this device or any other solution which serves this purpose?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be appreciated. Thanks!&lt;/p&gt;&#xA;" OwnerUserId="2439" LastEditorUserId="2439" LastEditorDisplayName="" LastEditDate="2011-03-25T22:30:49.090" LastActivityDate="2011-03-25T22:30:49.090" ClosedDate="2011-03-25T22:54:26.137" Title="Suggestions for an alternative device or solution to Remote Power Switch" Tags="&lt;power&gt;&lt;switch&gt;&lt;remote&gt;&lt;alternatives&gt;" CommentCount="4" />
  <row Id="12054" PostTypeId="1" AcceptedAnswerId="13589" CreationDate="2011-03-25T22:37:07.757" Score="0" ViewCount="63" Body="&lt;p&gt;IRIG-B is a timecode standard.  Here's &lt;a href=&quot;http://en.wikipedia.org/wiki/IRIG_timecode&quot; rel=&quot;nofollow&quot;&gt;Wikipedia's page&lt;/a&gt;.  I'm mainly looking for the reader. A couple of chips that work together would be fine too.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-03-25T23:00:10.000" LastActivityDate="2011-04-27T20:53:44.077" Title="Is there an IRIG-B IC available" Tags="&lt;irig&gt;&lt;irig-b&gt;&lt;timecode&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="12055" PostTypeId="2" ParentId="12040" CreationDate="2011-03-25T23:49:57.213" Score="1" ViewCount="" Body="&lt;p&gt;You could try libgphoto2 remote control feature. It &lt;a href=&quot;http://www.gphoto.org/doc/remote/&quot; rel=&quot;nofollow&quot;&gt;seems to support the EOS 550D you mentioned&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also &lt;a href=&quot;http://uk.eye.fi/&quot; rel=&quot;nofollow&quot;&gt;Eye-fi&lt;/a&gt; which is an SD card that automatically sends all photos to a PC over WiFi.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-26T02:09:58.003" LastActivityDate="2011-03-26T02:09:58.003" />
  <row Id="12056" PostTypeId="1" CreationDate="2011-03-26T01:09:32.027" Score="0" ViewCount="35" Body="&lt;p&gt;I'm trying to create a lit surface similar to a backlight for an LCD display (I'm replacing an EL panel in an arcade machine). For various reasons I don't want to just replace the EL with more EL. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The biggest constraint is that I only have about 0.2 inch of thickness to work with (the old EL panel and it's PCB are slipped into a very narrow space).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My thought has been to edge-light an acrylic panel (I have some very narrow LEDs from LITE-ON), and then etch it's surface somehow so that the light will exit from the face of the panel. My problem is that I don't have a good way to measure the light output to see if one of my ideas is better than another. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there some simple trick I could do with a digital camera to get an idea of the light output of the panel? I don't really need an absolute measurement, I just need some way to compare relative to my other attempts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, any clues on an optimal pattern for etching the acrylic would be nice - I've so far tried scratching the emitter surface with steel wool and sandpaper to not great effect. I also tried scoring parallel lines with a knife, and that's been interesting, but I'm having trouble figuring out what's my best bet here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I be trying for good light output from the acrylic then adding a diffuser on top of that?&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2011-03-26T02:45:37.763" Title="Flat panel that outputs light - to be used as a replacement for an EL panel" Tags="&lt;led&gt;&lt;backlight&gt;&lt;diffuser&gt;" AnswerCount="1" />
  <row Id="12058" PostTypeId="2" ParentId="12040" CreationDate="2011-03-26T02:02:21.463" Score="0" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://opencircuits.com/Elphel_camera&quot; rel=&quot;nofollow&quot;&gt;open-source software and open-hardware Elphel IP camera&lt;/a&gt; has 5Mpix resolution. It might be easy to re-program to do exactly what you want it to do.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-26T02:02:21.463" />
  <row Id="12059" PostTypeId="2" ParentId="12040" CreationDate="2011-03-26T02:23:12.447" Score="1" ViewCount="" Body="&lt;p&gt;CHDK is an enhanced, free software replacement firmware for many Canon digital cameras; I see at least a couple of those cameras are 10 Mpix.&#xA;There is a &lt;a href=&quot;http://chdk.wikia.com/&quot; rel=&quot;nofollow&quot;&gt;CHDK wiki&lt;/a&gt;.&#xA;Apparently you can write software in C, Lua, or uBasic that runs directly on the camera.&#xA;It might be easy to re-program to do exactly what you want it to do.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-26T02:23:12.447" />
  <row Id="12060" PostTypeId="1" AcceptedAnswerId="12070" CreationDate="2011-03-26T02:24:22.120" Score="5" ViewCount="149" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a general class ham, and am just starting to do my own homebrewing. I was planning on basing a QRP transmitter off of &lt;a href=&quot;http://www.instructables.com/id/Easy-AM-Transmitter/&quot; rel=&quot;nofollow&quot;&gt;this instructables project&lt;/a&gt;,  seeing as I have a veritable plethora of 555 ics in my shack toolbox. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is, this transmitter is designed to operate a bit below the commerical AM band. How is the general operating frequency being set? I'd like to get it set around the 1.8 mhz band (160 meters).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Much help is appreciated, as I'm going to use this to teach the other kids in the ham radio club at my school how to build basic transmitters. Picture of circuit:&#xA;&lt;img src=&quot;http://i.imgur.com/3SUfT.jpg&quot; alt=&quot;Schematic from:http://www.instructables.com/image/FD38QHUGIKL42D3/Schematic.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3597" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-26T12:49:49.203" LastActivityDate="2011-03-28T06:01:35.657" Title="What determines the transmit frequency in this 555-based transmitter?" Tags="&lt;555&gt;&lt;ham-radio&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="2" />
  <row Id="12061" PostTypeId="2" ParentId="12031" CreationDate="2011-03-26T02:29:49.490" Score="0" ViewCount="" Body="&lt;p&gt;Is making a ring of aluminum and putting the ring into a microwave oven an option?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-26T02:29:49.490" />
  <row Id="12062" PostTypeId="2" ParentId="12031" CreationDate="2011-03-26T02:36:25.960" Score="0" ViewCount="" Body="&lt;p&gt;You could build a voltage-divider network going into the strip of metal. Use a few high-current rheostats as resistors. With this, you could drive it with direct current and be able to get very low voltages.&lt;/p&gt;&#xA;" OwnerUserId="3597" LastActivityDate="2011-03-26T02:36:25.960" />
  <row Id="12063" PostTypeId="2" ParentId="12056" CreationDate="2011-03-26T02:45:37.763" Score="1" ViewCount="" Body="&lt;p&gt;At the risk of sounding simplistic, you could &lt;a href=&quot;http://www.tapplastics.com/shop/product.php?pid=324&amp;amp;&quot; rel=&quot;nofollow&quot;&gt;get some faux frosted window film from TAP Plastics&lt;/a&gt;. Then put grid of closely spaced ultra-bright LEDs underneath. It should diffuse nicely. I'm not familiar with this specific product, but it's only $8 a square foot.&lt;/p&gt;&#xA;" OwnerUserId="3597" LastActivityDate="2011-03-26T02:45:37.763" CommentCount="1" />
  <row Id="12064" PostTypeId="2" ParentId="9965" CreationDate="2011-03-26T02:52:33.077" Score="0" ViewCount="" Body="&lt;p&gt;I found a &lt;a href=&quot;http://www.expandedspectrumsystems.com/prod5.html&quot; rel=&quot;nofollow&quot;&gt;ten meter beacon kit&lt;/a&gt; which got a writeup in &lt;a href=&quot;http://www.ogdenarc.org/downloads/Beacon%20by%20N7JS.pdf&quot; rel=&quot;nofollow&quot;&gt;CQ Magazine (PDF)&lt;/a&gt; a while back. It's 30 bucks, and looks like a quality product. Should be a fun build!&lt;/p&gt;&#xA;" OwnerUserId="3597" LastActivityDate="2011-03-26T02:52:33.077" />
  <row Id="12065" PostTypeId="2" ParentId="2653" CreationDate="2011-03-26T02:55:48.487" Score="2" ViewCount="" Body="&lt;p&gt;The Amateur Radio Relay League recommends, as do I, Ham Radio for Dummies. Easily the best guide I ever read to Ham radio. It prepares you on some level for all three exams. I went into my technician knowing more than I needed to, as did I with my General.&lt;/p&gt;&#xA;" OwnerUserId="3597" LastActivityDate="2011-03-26T02:55:48.487" />
  <row Id="12066" PostTypeId="2" ParentId="12038" CreationDate="2011-03-26T03:00:41.993" Score="1" ViewCount="" Body="&lt;p&gt;To change the voltage, you could use a trusty hand-wound transformer. Go to a bookstore and pick up a copy of the ARRL General Class License Manual for ham radio. It teaches you how to do that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the voltage-controlled switch, Panasonic makes an IC called the 1381 voltage-based trigger. It's designed to turn off a switch when voltage drops below a certain level (usually for turning off gadgets when the battery dies). It's available &lt;a href=&quot;http://solarbotics.com/products/1381/&quot; rel=&quot;nofollow&quot;&gt;from Solarbotics&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="3597" LastActivityDate="2011-03-26T03:00:41.993" CommentCount="5" />
  <row Id="12067" PostTypeId="2" ParentId="11974" CreationDate="2011-03-26T03:07:22.360" Score="1" ViewCount="" Body="&lt;p&gt;Perhaps some neodymium permanent magnets (NIB magnets) will be adequate.&#xA;&lt;a href=&quot;http://amasci.com/neodemo.html&quot; rel=&quot;nofollow&quot;&gt;Bill Beaty has posted a list of places that sell neodymium magnets&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-26T03:07:22.360" CommentCount="1" />
  <row Id="12068" PostTypeId="2" ParentId="11946" CreationDate="2011-03-26T04:01:25.403" Score="1" ViewCount="" Body="&lt;p&gt;Please check out the &lt;a href=&quot;http://opencircuits.com/POV_display&quot; rel=&quot;nofollow&quot;&gt;list of POV displays&lt;/a&gt;.&#xA;Many POV displays are &quot;open-hardware&quot; and so should have extensive documentation on exactly how their power and communications work -- if one doesn't have enough detail, try another one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nearly all POV displays that I've seen working use slip rings for power.&#xA;(I've seen one working commercial POV display that uses an alternative to slip rings for power, and I plan to build a spinning POV display without slip rings that transfers power in a completely different way, but it's currently highly experimental).&#xA;Power on the stationary side goes through the slip ring to a large capacitor (to ride out power glitches from bounces and non-conductive dirt in the slip ring) at typically 8 to 12 V, which supplies power to a voltage regulator that powers the microcontroller and the chips that apply power to the LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many POV displays have no communication between the stationary part and the spinning part -- any user-interface buttons are on the spinning part, and you have to stop the motion, push the buttons (with a difficult-to-read linear LED array for feedback), then re-start the motion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some POV displays have a &quot;communications&quot; slip-ring or two for serial communication between the spinning part and the outside world. Alas, the slip ring adds glitches that are difficult to ignore.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many POV displays have a Hall effect sensor on the rotor that passes a fixed magnet, so the spinning microcontroller can compensate for the actual rotational speed.&#xA;In principle, one could send data from a stationary coil to a spinning Hall effect sensor near the rotational axis, but I haven't seen that actually working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of them use infrared communication between the stationary part and the spinning part, much like IrDA or TV remote controls.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-26T04:01:25.403" />
  <row Id="12069" PostTypeId="2" ParentId="12038" CreationDate="2011-03-26T06:55:16.517" Score="6" ViewCount="" Body="&lt;p&gt;You're asking for a logic level shifter. There are many ways to construct such a thing depending on what you're after, and there are packaged chips that do everything for you. I find this schematic, from NXP Semiconductors' &lt;a href=&quot;http://www.nxp.com/documents/application_note/AN10441.pdf&quot; rel=&quot;nofollow&quot; rel=&quot;nofollow&quot;&gt;AN10441&lt;/a&gt; to be a quite elegant way to get that function:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://tangentsoft.net/elec/bitmaps/i2c-level-shifter.png&quot; alt=&quot;bidirectional MOSFET level shifter&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This schematic shows the logic level shifter on an I²C bus, which has two signal lines. If you need only one line shifted, you need only one MOSFET and two pull-up resistors, one on its gate and the other on its drain. Similarly, if you need more lines shifted, you simply add a MOSFET and pair of pull-up resistors to each line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the example shown in the schematic, with 3.3&amp;nbsp;V and 5&amp;nbsp;V logic levels, any small-signal MOSFET will work, such as the ubiquitous 2N7000. Most generic MOSFETs have a V&lt;sub&gt;GS(th)&lt;/sub&gt; maximum too high to work with your 1.4&amp;nbsp;V logic level, however. You'll have to look to something more specialized like a &lt;a href=&quot;http://www.vishay.com/docs/72678/tn0200k.pdf&quot; rel=&quot;nofollow&quot; rel=&quot;nofollow&quot;&gt;Vishay TN0200K&lt;/a&gt; or a &lt;a href=&quot;http://www.diodes.com/datasheets/ZXMN2B14FH.pdf&quot; rel=&quot;nofollow&quot; rel=&quot;nofollow&quot;&gt;Zetex (Diodes, Inc.) ZXMN2B14FH&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The values of the pull-up resistors (R&lt;sub&gt;p&lt;/sub&gt;) depend somewhat on the application, but will have a wide range even then. 10&amp;nbsp;kΩ is a popular value here, giving a good tradeoff between speed, noise, and current draw. I could see using a value as low as 1&amp;nbsp;kΩ in certain circumstances, and values North of 1&amp;nbsp;MΩ in others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The app note describes how the circuit works, but to paraphrase:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;With nothing attached to the data line being shifted, the pull-up resistors bring the data line to the low-voltage logic level (V&lt;sub&gt;DD1)&lt;/sub&gt; on one side and the high-voltage logic level (V&lt;sub&gt;DD2&lt;/sub&gt;) on the other.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;When the low-voltage side brings the signal line down, it drags the MOSFET's source pin down. Since the gate is tied high, this causes the MOSFET to turn on when V&lt;sub&gt;GS&lt;/sub&gt; passes the V&lt;sub&gt;GS(th)&lt;/sub&gt; threshold, so it conducts, dragging the high-voltage side down, too.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;When the high-voltage side wants to do the same, it's more complicated. This circuit scheme relies on the fact that every MOSFET has a parasitic diode built into it, which is shown in the above schematic's MOSFET symbol. (The MOSFET symbol isn't always drawn with the parasitic diode showing, but it's always there.) By dragging the drain pin down, the high-voltage side causes this diode to conduct, which indirectly drags the low-voltage side's source pin down, causing the same thing to happen as in the previous case.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This tendency of the circuit to &quot;ride high&quot; by default may not be appropriate for all applications. If one end can ever become disconnected and the device left connected isn't actively pulling the data line down, the data line will go to the high level. This is fine for I²C, since the high logic level is the normal idle condition. If your data line doesn't work like that but neither end can become unplugged and at least one end is always actively pulling the line down when it wants the line to be low, this circuit will still work.&lt;/p&gt;&#xA;" OwnerUserId="2523" LastEditorUserId="2523" LastEditorDisplayName="" LastEditDate="2011-03-27T07:36:05.073" LastActivityDate="2011-03-27T07:36:05.073" />
  <row Id="12070" PostTypeId="2" ParentId="12060" CreationDate="2011-03-26T08:18:58.693" Score="7" ViewCount="" Body="&lt;p&gt;From what I can see form the circuit, the timer is running in astable mode. The frequency is controlled by the equivalent resistor made by adding resistances of P1 and R3, resistor R1 and capacitor C1. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to experiment, go to &lt;a href=&quot;http://freespace.virgin.net/matt.waite/resource/handy/pinouts/555/&quot; rel=&quot;nofollow&quot;&gt;555 calculator&lt;/a&gt; and take a look at bottom schematic. Your P1+R3 are its R1, your R1 is its R2 and your C1 is its C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE:&#xA;I'll try to make it a bit clearer how this transmitter gets its frequency. First, read through the whole instructable. There is a nice explanation related to harmonics in it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This transmitter controls antenna output using the Q1 transistor.  The transistor is triggered by the output of the 555 timer. Therefore there is direct relation between 555 frequency and transmission frequency. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The timer itself is controlled by two resistors and a capacitor. Timer monitors situation on the C1 capacitor. When it is $\frac {2}{3}$ full, timer will emit high output and start discharging the capacitor. When it is $\frac {1}{3}$ full, timer will start emitting low output and start charging the capacitor. When the capacitor is charging, current is going through resistors (P1+R3) and R1. They limit the charging current and modify the time it takes to charge the capacitor. When the capacitor is being discharged, current goes from C1 through resistor R1 into discharge pin which is connected to ground during discharge. This way, R1 controls the discharge time. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now about the 1.8 MHz band. You may be able to directly transmit at that band by using proper timer settings. For example TS555 timers made by STmicroelectroncs can provide up to 2.7 MHz  frequency in astable mode. To get the 1.8 MHz frequency, you can use formulas from the 555 timer. Basically, you should pick the resistors, potentiometer and capacitor so that $((R3+P1)+R1)*C1=8.05*10^{-7}$. If you for example take a 22 pF capacitor (they are commonly used for microcontroller crystals oscillators), resistors added together should be around 37 $k\Omega$. You can take for example R1 to be 8.2 $k\Omega$ and then set the P1+R3 to be 20 $k\Omega$. After that, you can calculate exactly what kind of potentiometer and resistor you need for the transmitter to work correctly using the calculator. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recommend that you do some more research before making the circuit with the values I recommended. Capacitors usually have high tolerances, so its impact on the circuit should be minimized. Resistors with 1% can be very cheaply obtained, but precise potentiometers or rheostats may be expensive. For example at local stores here, a good multi-turn potentiometer costs between 10€ and 20€, while cheap single turn one costs about 2€. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The point of the above paragraph is that there may be other set of values which could make it much easier and cheaper to set the correct frequency and provide higher precision. I unfortunately don't have enough experience to provide a better set of values.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-28T06:01:35.657" LastActivityDate="2011-03-28T06:01:35.657" CommentCount="4" />
  <row Id="12071" PostTypeId="2" ParentId="12038" CreationDate="2011-03-26T08:25:21.397" Score="4" ViewCount="" Body="&lt;p&gt;You can build a &lt;em&gt;logic level shifter&lt;/em&gt; (that's what it's called) with a few discrete components (transistors and resistors) or you can go for a one-component solution, i.e. an IC. Most ICs won't accept input voltages as low as 1.4 V, but I found Fairchild's &lt;a href=&quot;http://www.fairchildsemi.com/ds/FX/FXLP34.pdf&quot; rel=&quot;nofollow&quot;&gt;FXLP34&lt;/a&gt; which does. (You want the FXLP34P5X, the other versions have leadless packages and are therefore more difficult to solder)&lt;br&gt;&#xA;Connection diagram:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/Aj4lu.png&quot; alt=&quot;FXLP34&quot;&gt;&lt;br&gt;&#xA;&lt;strong&gt;A&lt;/strong&gt; is where you supply the low-level input signal, &lt;strong&gt;Y&lt;/strong&gt; is your &quot;high&quot;-level output signal. &lt;strong&gt;Vcc1&lt;/strong&gt; is your 1.4 V connection, connect the required output voltage to &lt;strong&gt;Vcc&lt;/strong&gt; (up to 3.6 V).&lt;br&gt;&#xA;The device may be hard to get in low quantities, maybe a distributor can supply with a few samples.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS: yes, that tiny cursor is also present in the image in &lt;a href=&quot;http://www.fairchildsemi.com/ds/FX/FXLP34.pdf&quot; rel=&quot;nofollow&quot;&gt;the datasheet&lt;/a&gt; :-)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-25T13:53:16.747" LastActivityDate="2011-05-25T13:53:16.747" CommentCount="2" />
  <row Id="12072" PostTypeId="1" CreationDate="2011-03-26T08:51:07.270" Score="1" ViewCount="78" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/mT7xo.jpg&quot; alt=&quot;From the &amp;quot;Half the battle is knowing what to search for on DigiKey&amp;quot; deptartment&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are these connectors commonly called, and what would I search for if I wanted to buy sets of male/female pairs with a specific gauge of wire pre-attached?&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2011-03-26T11:27:13.190" Title="What are these wires with pre-attached connectors called?" Tags="&lt;connector&gt;&lt;wire&gt;&lt;identification&gt;" AnswerCount="1" />
  <row Id="12073" PostTypeId="2" ParentId="12018" CreationDate="2011-03-26T09:03:39.373" Score="0" ViewCount="" Body="&lt;p&gt;I've tried to do such procedure before (I read &lt;a href=&quot;http://www.enide.net/webcms/index.php?page=pcm2pwm&quot; rel=&quot;nofollow&quot;&gt;http://www.enide.net/webcms/index.php?page=pcm2pwm&lt;/a&gt; )&#xA;but I didn't regonized the original sound.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I called the statement : PWM pin, duty, cycles&#xA;which &quot;converts a digital value to analog output via pulse-width modulation.&#xA;where Cycles is a variable/constant (0-65535) specifying an approximate&#xA;number of milliseconds of PWM output.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means : I can send only one sample per millisecond.&#xA;So my sample rate shoud be : 1000 hz.&#xA;Is it true?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wondering why I didn't recognized the sound. Maybe it comes from the way I converted the WAV file on my computer.&lt;/p&gt;&#xA;" OwnerUserId="3601" LastActivityDate="2011-03-26T09:03:39.373" CommentCount="3" />
  <row Id="12074" PostTypeId="2" ParentId="12072" CreationDate="2011-03-26T11:27:13.190" Score="1" ViewCount="" Body="&lt;p&gt;Generically these are just polarized header connectors. Sometime they are referred to as Molex connectors, but this is just one manufacturer. (I think the Molex SPOX range seems to be the closest match)&lt;/p&gt;&#xA;" OwnerUserId="2595" LastActivityDate="2011-03-26T11:27:13.190" CommentCount="2" />
  <row Id="12075" PostTypeId="2" ParentId="12051" CreationDate="2011-03-26T11:32:57.600" Score="4" ViewCount="" Body="&lt;p&gt;The actuator used to position a hard-drive would match those attributes. Funnily enough they are called voice-coil actuators!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess with any solenoid type of actuator that needs to operate at very low frequencies you probably need to design your drive circuit to not overheat the windings even with a DC current.&lt;/p&gt;&#xA;" OwnerUserId="2595" LastActivityDate="2011-03-26T11:32:57.600" CommentCount="1" />
  <row Id="12076" PostTypeId="1" CreationDate="2011-03-26T12:02:04.547" Score="0" ViewCount="42" Body="&lt;p&gt;Hi  guys,&#xA;I'm new to electronics. I'm trying to interface my lcd with an avr but I don't think my code is initialising the lcd properly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the top of header file for the library am using, I have this&lt;/p&gt;&#xA;&#xA;&lt;p&gt;define LCD_LINE_LENGTH   0x40&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am told by the manual that this might need to be changed. It's not blindingly ovious in the data sheet for beginners.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the link to the datasheet:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&amp;amp;R=7200235&quot; rel=&quot;nofollow&quot;&gt;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&amp;amp;R=7200235&lt;/a&gt;&#xA;What does it mean and where is it stated in ds&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-03-27T01:14:20.010" Title="What does line width mean for LCD" Tags="&lt;lcd&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="12077" PostTypeId="2" ParentId="11972" CreationDate="2011-03-26T12:59:55.340" Score="1" ViewCount="" Body="&lt;p&gt;Answering my own question - after reviewing all the books I could find around, it seems that the classic &quot;Digital Communications&quot; by Glover &amp;amp; Grant was enough for what I was looking for (Chapter 6: Baseband transmission and line codes, 6.4. Line coding).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also found this great PDF:&#xA;&lt;a href=&quot;http://gemini.udistrital.edu.co/comunidad/profesores/hjeslavab/Downloads/Codigos%20de%20linea.pdf&quot; rel=&quot;nofollow&quot;&gt;http://gemini.udistrital.edu.co/comunidad/profesores/hjeslavab/Downloads/Codigos%20de%20linea.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-03-26T12:59:55.340" CommentCount="2" />
  <row Id="12078" PostTypeId="1" AcceptedAnswerId="12115" CreationDate="2011-03-26T13:48:33.693" Score="4" ViewCount="175" Body="&lt;p&gt;I have a hex file with a size of 42 kB.  Does the size matter while loading it in a microcontroller?  Can I load 42 kB hex file in a ATMEGA32 chip which has a memory of 32 kB?&lt;/p&gt;&#xA;" OwnerUserId="3602" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-26T14:56:11.403" LastActivityDate="2011-03-27T14:31:18.617" Title="Will my HEX file fit in my microcontroller?" Tags="&lt;microcontroller&gt;&lt;programming&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="2" />
  <row Id="12079" PostTypeId="2" ParentId="12076" CreationDate="2011-03-26T13:58:28.520" Score="1" ViewCount="" Body="&lt;p&gt;Line width is the number of characters that can be displayed on one line. In the description section, the datasheet says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The maximum display size can be either 80 characters in 1-line display or 40 characters in 2-line display.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2857" LastActivityDate="2011-03-26T13:58:28.520" CommentCount="1" />
  <row Id="12080" PostTypeId="2" ParentId="12078" CreationDate="2011-03-26T14:35:40.137" Score="3" ViewCount="" Body="&lt;p&gt;Each byte in a hex file takes two hex digits, plus a few characters per record. Your hex file should fit in the device's flash memory.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-26T14:35:40.137" />
  <row Id="12081" PostTypeId="2" ParentId="12078" CreationDate="2011-03-26T14:54:40.670" Score="9" ViewCount="" Body="&lt;p&gt;The hex file generated is often somewhat human-readable and includes checksum data, both of which inflate the size a few times.  I believe that AVRs use the &lt;a href=&quot;http://en.wikipedia.org/wiki/Intel_Hex&quot; rel=&quot;nofollow&quot;&gt;Intel HEX format&lt;/a&gt;, while other micro toolchains use other formats; e.g. Codewarrior for Freescale HCS08 provides &lt;a href=&quot;http://en.wikipedia.org/wiki/S19_%28file_format%29&quot; rel=&quot;nofollow&quot;&gt;Motorola S-records&lt;/a&gt;, which is extremely similar.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you open the .hex file with a text editor (Notepad), it should look similar to this, though much longer:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;:10010000214601360121470136007EFE09D2190140&#xA;:100110002146017EB7C20001FF5F16002148011988&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;where the various fields are described in the &lt;a href=&quot;http://en.wikipedia.org/wiki/Intel_Hex#Example&quot; rel=&quot;nofollow&quot;&gt;example on Wikipedia&lt;/a&gt;.  There are only 16 bytes in each of those lines that denote data that will be stored in the micro, the rest is checksum and control data that is just used by the flasher program.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-26T14:54:40.670" CommentCount="1" />
  <row Id="12082" PostTypeId="2" ParentId="12050" CreationDate="2011-03-26T15:32:29.343" Score="2" ViewCount="" Body="&lt;p&gt;Both sides of the resistor are connected to the same point: ground.  Since there is no voltage across the resistor, no current will flow through it.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-03-26T15:32:29.343" />
  <row Id="12083" PostTypeId="2" ParentId="11994" CreationDate="2011-03-26T15:59:23.657" Score="0" ViewCount="" Body="&lt;p&gt;Compile and test it. Look at the datasheet to check to see how the accelerometer behaves in situations then test for those.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-26T15:59:23.657" />
  <row Id="12085" PostTypeId="1" AcceptedAnswerId="12096" CreationDate="2011-03-26T17:37:31.550" Score="8" ViewCount="202" Body="&lt;p&gt;I'm an electronics beginner and I find myself often needing to pick an IC for an analog application with no prior knowledge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the domain of microcontrollers, it's very clear that I should use Atmel AVR since many hobbyists use the ATMega8/128/168/32u4 etc. due to Arduino + I've got the toolchain setup for that now. I've familiarized myself with the line at this point and I don't bother looking elsewhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But when I'm researching something like signal conditioning, I'm always finding myself asking: so do I get an IC from Analog, Linear, TI or Microchip? Especially these three companies have a lot of overlap in the signal conditioning domain, but I'm sure you can find other groups of companies with similar overlaps in other domains.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you're picking an IC, do you have a favorite or &quot;go to&quot; company that you'll start with? Or do you compare the specs from all the main companies and go with the &quot;best&quot; one? Do you leave it up to chance and go with the first thing you find that satisfies the requirements?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do things like the general quality of datasheets, customer service, website UX and marketing influence your decisions?&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2011-03-28T00:43:45.937" Title="How Do You Decide Between Analog Chip Manufacturers?" Tags="&lt;ic&gt;&lt;buying&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="4" />
  <row Id="12086" PostTypeId="2" ParentId="12085" CreationDate="2011-03-26T18:20:27.550" Score="4" ViewCount="" Body="&lt;p&gt;Completely depends on the application as 'analog IC' is a massively broad term.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It comes down to price, performance, package, environmental rating, required external components, availability(location, volume, distributor), etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your coming at it from the hobbyist perspective then your choice is usually driven by low unit count availability (e.g. can I buy just 1 from digikey?), easy to breadboard package, example usage from some other source, is the thing stable with minimal breadboard-able external components?, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can't just look at the numbers on a datasheet and expect it to 'just work' when tossed into a design.  Some devices will work like this, some will work poorly, some won't work at all.  I've seen/heard of lots of hobbyists go to digikey and buy some 50Mhz high end super duper opamp and toss it in a breadboard only to spend the next 2 weeks trying to figure out why their circuit oscillates.  Another example is going out and buying what looks like a similarly specced part at first glance but the part has a different mode of operation which causes small, but significant changes in the required implementation that are often overlooked. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So one important metric is how resilient a part is to 'poor' designs.  I don't mean to sound insulting, but there really is a lot more to analog design than copying an opamp topology off wikipedia.  Simple, highly stable parts will allow such an approach but generally have limited performance envelopes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen production designs have this issue as well.  e.g. It worked on the prototype but no one looked at the circuit stability and it was teetering on the edge such that in the first test run 5 out of 100 failed or there are intermittent failures that seems to happen completely randomly.  Another example is a prototype run was done but someone didn't properly consider input/output impedance, input current, quiescent current, required decoupling, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In summary the metrics used vary widely by application and needed performance.  For hobbyist use its best to stick with simple, stable and resilient ICs that come in easy to hand work packages which have been used in other designs you've seen on the internet.  Even so you may run into troubles just copying the design.  I've seen the contact capacitance in breadboards throw all sorts of seemingly simple op amp circuits into oscillation.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-03-26T18:20:27.550" CommentCount="1" />
  <row Id="12087" PostTypeId="1" AcceptedAnswerId="12104" CreationDate="2011-03-26T18:50:19.970" Score="0" ViewCount="70" Body="&lt;p&gt;It's not responding to the programmer at all in avr studio.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;avrisp     attiny44&#xA;mosi  -- - mosi&#xA;miso  ---- miso&#xA;sck   ---- usck&#xA;reset ----  reset&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Or can it not be programmed by an mk2? I assumed all chips can be programmed by it&lt;/p&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-03-27T03:01:45.903" LastActivityDate="2011-03-27T03:01:45.903" Title="ATtiny44 not responding to AVRISP mkII programmer" Tags="&lt;avr&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12088" PostTypeId="2" ParentId="12051" CreationDate="2011-03-26T18:50:36.350" Score="1" ViewCount="" Body="&lt;p&gt;Woofers have been used to move mirrors for simple laser light displays, but you probably won't get much displacement out of a cheap woofer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A better idea might be a solenoid with a weak spring attached.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-03-26T18:50:36.350" />
  <row Id="12089" PostTypeId="2" ParentId="11577" CreationDate="2011-03-26T18:59:57.237" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.kobakant.at/DIY/&quot; rel=&quot;nofollow&quot;&gt;Have you read this site?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are lots of examples of wearable electronics including some with Eeonyx fabrics.  The site has examples of sensing circuits (ardunio and xbee).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't need many components to build a Wheatstone bridge and your likely best off with 1 sensing circuit multiplexed to the 8 sensors, you can still get 100 samples a second or more quite easily on each input.  Use a fabric PCB (again check the site above) to create the bridge.  Or just run sensor wires to the glove and put all the sensing electronics in a belt mounted pack.  Most fabric 'sensors' i've seen have relatively high resistance, the 0.1 ohms you can get from the wire between the belt unit and gloves doesn't matter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Put a temperature sensor in each glove and use the result to make a correction in the software if needed to adapt for environmental changes.  Maybe calibrate the gloves before each use, may not be needed depending on the intelligence of the interpreter.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume the Xbee module transmits to a computer, build the calibration function into the computer, in fact do as much processing as you can, such as temperature correction, on the computer.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bonus points if you just use a neural network to convert the sensor input to an action.  This will make training it easy and adapt for different people's hand motions.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-03-26T18:59:57.237" />
  <row Id="12090" PostTypeId="2" ParentId="11993" CreationDate="2011-03-26T19:04:53.333" Score="0" ViewCount="" Body="&lt;p&gt;The simple answer is to buy a really cheap drill on eBay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could make your own hand drill by purchasing drill bits and a tap handle to turn them. It would work, but seeing that there are electric drills on eBay Buy It Now for less than $10, it's really not worth it. The local used goods place (e.g., Goodwill in the US) often has used power tools even cheaper than this.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-03-26T19:04:53.333" />
  <row Id="12091" PostTypeId="2" ParentId="12051" CreationDate="2011-03-26T19:13:06.403" Score="2" ViewCount="" Body="&lt;p&gt;A subwoofer will work just fine.  &lt;a href=&quot;http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-486&quot; rel=&quot;nofollow&quot;&gt;Something like this would work&lt;/a&gt;, you'd get about 12mm of approximately linear travel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll have to adapt for the response down to DC.  I don't mean just the woofer itself which will have some roll off under fs but amplifiers will roll off at a couple hz (cheap amplifier will be higher) and just the interconnects used in the system generally form a HPF at 5-7hz.  Basically you'll need some equalization to keep the excursion response flat.  Most off the self EQ will not work at these frequencies so you'll probably have to deal with it by just adjusting the magnitude of your input signal, i.e. pre filter the source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't send the woofer DC if you can avoid it but when operating in free air it doesn't take much power at all to move cone a few mm, i doubt you'd have heating issues with the voice coil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most subwoofers you see used as such are in enclosures.  Its the job of the enclosure to provide spring resistance to the driver.  It takes a lot more power to move the cone with its in a sealed enclosure than it does when its just sitting on the table.  A 9V battery will move a subwoofer cone a millimeter or two.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-03-26T19:13:06.403" CommentCount="1" />
  <row Id="12092" PostTypeId="2" ParentId="11263" CreationDate="2011-03-26T20:10:24.190" Score="0" ViewCount="" Body="&lt;p&gt;Maxim-IC has a &lt;a href=&quot;http://para.maxim-ic.com/en/search.mvp?fam=logamps&amp;amp;tree=amps&quot; rel=&quot;nofollow&quot;&gt;couple of log amps&lt;/a&gt;, and so does &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=522&amp;amp;uiTemplateId=NODE_STRY_PGE_T&quot; rel=&quot;nofollow&quot;&gt;TI&lt;/a&gt;, but Analog Devices makes I think the &lt;a href=&quot;http://www.analog.com/en/amplifiers-and-comparators/log-ampsdetectors/products/index.html&quot; rel=&quot;nofollow&quot;&gt;biggest selection&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Intersil makes a &lt;a href=&quot;http://www.intersil.com/products/pt/parametric_table_17981.asp&quot; rel=&quot;nofollow&quot;&gt;number of transistor arrays&lt;/a&gt; some are certainly single die and well matched. &lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-03-26T20:10:24.190" CommentCount="5" />
  <row Id="12093" PostTypeId="1" AcceptedAnswerId="12099" CreationDate="2011-03-26T20:13:12.147" Score="0" ViewCount="49" Body="&lt;p&gt;I'd like to be able to put something small on items (eg glasses, car keys, etc) and have an Android or iPhone app that will tell me the direction or proximity of a certain item. Current phones usually just communicate via cell, wifi, and bluetooth, but for these the other end of the communication has to be powered, which increases the size of what I attach to my items. Is passive RFID what I'm looking for? (In which case I'd have to wait for phones to come out with better RFID readers.) If yes, what size passive tags have what ranges? For range I'd like to be able to find a device a couple floors away, but even just within a room would be useful. For size, the smaller the better, with maybe a quarter the size of a dime as the minimum practical/usable size. Do you think that the RFID readers in phones will be able to take advantage of those maximum ranges? (Currently the ones I've looked at, eg Nexus S, have to be inches away.) And finally, where do you recommend I buy such tags?&lt;/p&gt;&#xA;" OwnerUserId="3605" LastEditorUserId="3605" LastEditorDisplayName="" LastEditDate="2011-03-26T20:33:32.550" LastActivityDate="2011-03-27T00:21:45.523" Title="How can I locate items from a phone? RFID?" Tags="&lt;rfid&gt;&lt;phone&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="12095" PostTypeId="1" CreationDate="2011-03-26T22:14:42.590" Score="0" ViewCount="186" Body="&lt;p&gt;I have a very tiny LCD ripped from a piece of electronic scrap. The LCD is about 1 inch by .25 inches. It does not include a backlight(it had an external LED functioning as the backlight) and is basically just a flat piece of glass. There are 16 wires coming from the board it's on. (it is just a plain &quot;breakout&quot; board for the small SMD connector)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LCD board says &quot;LCD:91-42959-B01&quot; which does not pull up any relevant results with google.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried my best to test it with a multimeter, but nothing seems to even be connected. I'm not sure how most simple LCDs work, so what can I do to try and get this to work (hopefully) without ruining it in the process?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, because this is a flat piece of glass, I do not believe there will be a command type of interface, because as far as I can tell, there is no actual logic connected to it. It's just 16 wires going into clear glass. Also on the breakout board they are bundled into 4 bundles with 4 wires each(with brown, orange, orange, yellow being the colors in each bundle). I have no idea if this matters, but I figured maybe it could help&lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="708" LastEditorDisplayName="" LastEditDate="2011-03-26T22:22:45.703" LastActivityDate="2011-05-26T15:47:25.827" Title="How to figure out the pin out of this undocumented LCD?" Tags="&lt;led&gt;&lt;lcd&gt;&lt;datasheet&gt;" AnswerCount="3" />
  <row Id="12096" PostTypeId="2" ParentId="12085" CreationDate="2011-03-26T22:27:58.410" Score="11" ViewCount="" Body="&lt;p&gt;There is no single rule that drives you to just one analog chip manufacturer's parts. (Not in microcontrollers, either, despite your claim that only Atmel makes sense for you. But that's a separate question.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A really good component engineer could probably fill books about how to choose a chip and/or manufacturer. I am not a component engineer, but I can lay out a bunch of cases where I've been forced to one manufacturer or another:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Unique chip&lt;/strong&gt;: TI's &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/tle2426.html&quot; rel=&quot;nofollow&quot;&gt;TLE2426&lt;/a&gt; is truly unique. There are numerous ways to build something similar out of generic components, but if you need that function and it has to fit in a TO-92 footprint, you're stuck with TI's chip.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;No standard pinout&lt;/strong&gt;: Unlike with op-amps, analog buffers never really settled on a common pinout, and there are few enough of them available that it's rare for more than a few to be really suitable for a given circuit. Say you pick NatSemi's &lt;a href=&quot;http://www.national.com/pf/LM/LMH6321.html&quot; rel=&quot;nofollow&quot;&gt;LMH6321&lt;/a&gt; for some reason. Even though another chip may be an acceptable alternative, no other analog buffer on the market shares that particular pinout, so as soon as you make a PCB with the LMH6321 in mind, you cannot change to another chip without re-spinning the board.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Subjective matters&lt;/strong&gt;: In high-end audio circuits, a good ear can distinguish the sound of op-amps, or at least, op-amp families. If you happen to like the Burr-Brown sound, you will be looking only at their chips, while another will swear by Analog Devices chips, and you may both wish to ignore the Linear fanbois.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Price&lt;/strong&gt;: Maybe you need an LM324 but aren't too picky about quality. In that case, you're going to be looking at one of the second-source suppliers for this chip like Fairchild or ST, rather than the chip's creator, NatSemi.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Durability&lt;/strong&gt;: This is the inverse of the previous point. I'll bet anyone in the industry for more than a few years could tell you stories where the design engineer chose something widely second-sourced (an &lt;a href=&quot;http://www.national.com/mpf/LM/LM317.html&quot; rel=&quot;nofollow&quot;&gt;LM317&lt;/a&gt; for example), did all their prototyping with a high-quality implementation of that chip design, sent it off to the manufacturing folk who substituted a far cheaper generic, and then had to deal with field failures because the replacement, though claiming equivalent performance in its datasheet, turned out less durable when abused in ways you cannot control from your clean lab. (ESD in winter in North Dakota, idiot end users unplugging connectors the manual says not to unplug while power is applied, etc.) It is often cheaper to go back to using the more expensive first-source version than re-spin the board with protection components scattered around the cheap knockoff.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Obsolescence&lt;/strong&gt;: You're tasked with stuffing boards you can't re-spin for a design made 20 years ago, and some of the chips aren't available from their original manufacturers any more, or at least aren't available in the packages the design engineer chose 20 years ago. You might be forced into the arms of a company like NTE or Central Semiconductor, who specialize in offering old designs that all the tier 1 companies have abandoned.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Higher performance&lt;/strong&gt;: A highly popular IC like the LM317 often inspires pin-compatible follow-ons with higher performance. Linear Technology specializes in this. If you find yourself needing better performance, it is often worth paying the higher price for a less common pin-compatible replacement than redesigning your circuit to give better performance with the original chip you selected.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;strong&gt;Availability&lt;/strong&gt;: Once you've run the gauntlet above, you might still seem to have a few choices of sources for a given part, but one of the sources has burned you in the past on availability. That sort of thing can force you to another manufacturer all by itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A more extreme variant of this situation is that you've whittled away your choices until you end up looking at just one part, but it's made by a manufacturer that doesn't always have ready stock. That might force you to abandon that choice, desirable though it may be on paper, simply to switch to a more reliable source. You might even end up reinventing that perfectly good wheel with generics just to get better control of parts availability.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2523" LastEditorUserId="2523" LastEditorDisplayName="" LastEditDate="2011-03-28T00:07:30.943" LastActivityDate="2011-03-28T00:07:30.943" CommentCount="5" />
  <row Id="12097" PostTypeId="2" ParentId="12095" CreationDate="2011-03-26T22:28:10.417" Score="2" ViewCount="" Body="&lt;p&gt;Driving raw LCDs is a complex business. Microchip have a good appnote on &lt;A href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/00563c.pdf&quot; rel=&quot;nofollow&quot;&gt;how to create an LCD driver with a PIC microcontroller&lt;/a&gt;, the ideas are all transferrable to other devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When reverse engineering devices, it's best to gain as much information as possible from a still working unit with a &lt;a href=&quot;http://electronics.stackexchange.com/questions/2036/beginners-logic-analyzer&quot;&gt;logic analzyer&lt;/a&gt;. If you have two units, you can then keep one working while you clone the driver hardware/software for your new system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are lucky, your LCD may be a chip-on-glass module with a driver chip built in. By sniffing the data transactions with this, it might be possible to guess at the device.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-26T22:28:10.417" CommentCount="1" />
  <row Id="12098" PostTypeId="2" ParentId="10563" CreationDate="2011-03-26T22:28:22.107" Score="0" ViewCount="" Body="&lt;p&gt;So you have an arrangement something like&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PID_outputs --&gt; heater --&gt; paper --&gt; temperature sensor --&gt; PID_inputs&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adding something to electrically &quot;smooth&quot; or &quot;filter&quot; between the output of the temperature sensor and the PID inputs may make things worse -- it adds some latency, which often makes oscillation worse, and you never really know the &quot;real&quot; temperature of the paper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps it would be better to physically &quot;smooth&quot; the actual temperature at the paper, by adding some insulation around the heater-paper-sensor system. (This makes the paper take longer to cool down).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps it would be better to physically &quot;smooth&quot; the actual temperature at the paper, using a larger thermal mass (perhaps a sheet of metal) between the heater and the paper. (This makes the paper take longer to heat up and cool down).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do any of the tips listed at&#xA;&lt;a href=&quot;http://reprap.org/wiki/Temperature_control&quot; rel=&quot;nofollow&quot;&gt;http://reprap.org/wiki/Temperature_control&lt;/a&gt;&#xA;work for you?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-26T22:28:22.107" CommentCount="1" />
  <row Id="12099" PostTypeId="2" ParentId="12093" CreationDate="2011-03-27T00:21:45.523" Score="1" ViewCount="" Body="&lt;p&gt;Don't expect phones to have the hardware built in to ever be able to do what you are wanting. RFID in the Nexus S is designed for &lt;a href=&quot;http://en.wikipedia.org/wiki/Near_field_communication&quot; rel=&quot;nofollow&quot;&gt;near field communication&lt;/a&gt; and is mostly centered around the idea of being able to walk up to a product and find out more information about it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a very interesting design problem though. Passive RFID can work from decently long distances, like what is used in many toll booths, but requires the active side to be rather high power, have a large antenna, and have a very sensitive receiver, all of which you will have a hard time getting to be portable.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-27T00:21:45.523" />
  <row Id="12100" PostTypeId="2" ParentId="12076" CreationDate="2011-03-27T01:14:20.010" Score="0" ViewCount="" Body="&lt;p&gt;LCD modules that are compatible with HD44780 (which the datasheet says it is) have 80 bytes of display RAM.   The same controller can be used to drive displays anywhere from 8x1 up to 20x4 (and even larger if two or more controller chips are present).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On different sized multi-line displays, the memory address of the start of each line is different.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 16x2 display typically has line 0 at 0, and line 1 at address 40.  The extra&#xA;RAM addresses that are not visible on screen can be used for scrolling, by changing the memory address that corresponds to the first column.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 20x4 display probably has the lines starting at 0,20,40,60 but consult the datasheet to be sure.   You'd probably need to set the line length to 20 in your driver, therefore.  (Hard to say without seeing source code to the library).&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-03-27T01:14:20.010" />
  <row Id="12101" PostTypeId="2" ParentId="12085" CreationDate="2011-03-27T01:39:01.853" Score="2" ViewCount="" Body="&lt;p&gt;Where possible, choose ICs that are available from multiple vendors. This means pin- and function-compatible. Most manufacturers ensure that all part numbers used on mass-produced BOMs (bills of material) are multiple-vendor parts unless specifically approved. There are situations in which unique parts are needed, but minimizing the number of parts like this is an important supply chain management function.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This puts more work upfront, qualifying multiple parts during the design cycle, but it's better to do this early rather than once something is being mass-produced  and the line is down due to a parts shortage.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-27T01:39:01.853" />
  <row Id="12102" PostTypeId="1" AcceptedAnswerId="12105" CreationDate="2011-03-27T02:40:43.067" Score="0" ViewCount="78" Body="&lt;p&gt;Hello, I'm wanting to buy this &lt;a href=&quot;http://www.sparkfun.com/products/8773&quot; rel=&quot;nofollow&quot;&gt;IR camera&lt;/a&gt; but it says it has RCA output. Is it possible to read this into an mbed without external components(aside from a 12v power source)? If so, how?&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-03-27T03:25:16.803" Title="How to read RCA output from an mbed?" Tags="&lt;microcontroller&gt;&lt;video&gt;&lt;mbed&gt;&lt;rca&gt;" AnswerCount="2" />
  <row Id="12103" PostTypeId="2" ParentId="12102" CreationDate="2011-03-27T02:49:50.027" Score="0" ViewCount="" Body="&lt;p&gt;It's got a video output so you won't be able to use it with the mbed. It isn't fast enough and doesn't have enough memory.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-27T02:49:50.027" />
  <row Id="12104" PostTypeId="2" ParentId="12087" CreationDate="2011-03-27T02:59:42.893" Score="0" ViewCount="" Body="&lt;p&gt;The AVRISP mkII can program the tiny44 in the latest version of AVR Studio (4.18 SP3 or 5 beta).  Make sure your version is either up-to-date or check the help files/release notes that came with it to verify.  Also allow AVR Studio to update the firmware in your AVRISP mkII if it needs to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Verify the following conditions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Programmer is connected to PCB (GND, RESET, MOSI, MISO, and SCK)&lt;/li&gt;&#xA;&lt;li&gt;Target is powered. &#xA;&lt;ul&gt;&#xA;&lt;li&gt;Not sure how much power the AVRISP MKII can provide, but don't rely on it if your board takes more than 50 mA.&lt;/li&gt;&#xA;&lt;li&gt;You do &lt;em&gt;not&lt;/em&gt; need to connect the programmer's VCC line to the chip power if you provide it externally.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;MOSI, MISO, SCK have pullups to GND/VCC no stronger than 820 Ω.&lt;/li&gt;&#xA;&lt;li&gt;RESET pullup should be no stronger than 4.7 kΩ and have a decoupling capacitor less than 10 µF.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Follow the troubleshooting guide in the &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/AVRISPmkII_UG.pdf&quot; rel=&quot;nofollow&quot;&gt;AVRISP mkII user guide&lt;/a&gt; [PDF] if you experience problems as a first step:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/stJQx.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-27T02:59:42.893" CommentCount="1" />
  <row Id="12105" PostTypeId="2" ParentId="12102" CreationDate="2011-03-27T03:25:16.803" Score="2" ViewCount="" Body="&lt;p&gt;By &quot;RCA output&quot; I assume they mean a composite video output.  In order to convert that into some sort of digital image that a microcontroller can use, you would need an extremely fast ADC, or simply a video decoder (i.e. one from &lt;a href=&quot;http://www.maxim-ic.com/products/video/decoders.cfm&quot; rel=&quot;nofollow&quot;&gt;Maxim IC&lt;/a&gt;, &lt;a href=&quot;http://www.analog.com/en/audiovideo-products/video-decoders/products/index.html&quot; rel=&quot;nofollow&quot;&gt;Analog Devices&lt;/a&gt;, &lt;a href=&quot;http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&amp;amp;familyId=375&amp;amp;uiTemplateId=NODE_STRY_PGE_T&quot; rel=&quot;nofollow&quot;&gt;TI&lt;/a&gt;) to tease out the image data.  Better yet, just get a camera with a digital output, as the digital-to-analog-to-digital path is a waste, as it's costly and performs worse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NTSC scanlines are transmitted at 15.734 kHz with frequency content up to 4.2 MHz, impossible to handle with a standard microcontroller ADC which have sample rates of 1 Msps at the high end (NXP LPC1768 only has 200 ksps).  Furthermore, as Leon points out, your memory is extremely limited.  If you read just &lt;em&gt;one&lt;/em&gt; QVGA (320 x 240) frame into memory at 8 bits/pixel, that's 76.8 kB, which exceeds the mbed's (NXP LPC1768's) on-board 64 kB RAM.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-27T03:25:16.803" CommentCount="1" />
  <row Id="12107" PostTypeId="2" ParentId="2653" CreationDate="2011-03-27T06:25:53.497" Score="3" ViewCount="" Body="&lt;p&gt;Look at free &lt;a href=&quot;http://www.qsl.net/k3pd/book.html&quot; rel=&quot;nofollow&quot;&gt;Crystal Sets To Sideband&lt;/a&gt; book, which gets you through building your own equipment. For more advanced stuff there is excellent &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0872598799&quot; rel=&quot;nofollow&quot;&gt;Experimental Methods in RF design&lt;/a&gt; book, which does the same with a lot more sophistication.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-03-27T06:25:53.497" />
  <row Id="12108" PostTypeId="2" ParentId="11586" CreationDate="2011-03-27T10:15:01.517" Score="0" ViewCount="" Body="&lt;p&gt;As someone who actually worked on designing a programmable analogue computer in the first year of my PhD, I'd say that there are interesting applications for such machines. However, like what some of the others have said, it's rather niche.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to start to think of analogue as &lt;strong&gt;analogous&lt;/strong&gt; instead of continuous. Once you do that, you should be able to design analogue computation circuits with FPAA. However, there is limited modern literature on this matter. You would need to go further back to the 1950s or so to find books on the fundamentals of designing analogue computers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find some newer papers from &lt;a href=&quot;http://www.eecg.toronto.edu/~gulak/publications.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; academic.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-03-27T10:15:01.517" />
  <row Id="12109" PostTypeId="1" CreationDate="2011-03-27T10:26:55.567" Score="1" ViewCount="74" Body="&lt;p&gt;What are the &lt;strong&gt;quality&lt;/strong&gt; hand tool (wire cutters, wire strippers, pliers etc) brands for electronics? I am looking for alternatives to cheap chinese tools which render themselves unusable after two years of use.&lt;/p&gt;&#xA;" OwnerUserId="94" LastActivityDate="2011-03-27T12:20:17.557" ClosedDate="2011-03-27T13:27:04.840" Title="Quality hand tool brands for electronics?" Tags="&lt;tools&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="1" />
  <row Id="12111" PostTypeId="2" ParentId="12109" CreationDate="2011-03-27T12:09:50.653" Score="2" ViewCount="" Body="&lt;p&gt;I have a set of Cooper Xcelite tools I acquired in 1981 and they're still as good as new - but they're not cheap. I also have a set of own-brand tools from RS Components from 1995 which are showing no signs of wear and are a lot cheaper.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-03-27T12:09:50.653" />
  <row Id="12112" PostTypeId="2" ParentId="12109" CreationDate="2011-03-27T12:20:17.557" Score="2" ViewCount="" Body="&lt;p&gt;I like Lindstrom tools. They are expensive, but I've been using the same pliers and cutters for over 20 years, making them very good value. The same models are still available.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-27T12:20:17.557" />
  <row Id="12113" PostTypeId="1" CreationDate="2011-03-27T13:01:12.187" Score="1" ViewCount="105" Body="&lt;p&gt;Does anyone know of a tool that can make jumper wires to fit standard spacings for breadboards?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I have in mind is a jig where you dial in the number of rows you want the jumper to span, insert your chosen single-core wire, and the tool cuts a piece of wire to length, strips the ends and maybe even bends them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've bought jumper lead kits before, but I'm not a fan of them because they always seem to have one colour per length. I'd prefer to keep my 'traces' the same colour, which is hard to do with such a kit.&lt;/p&gt;&#xA;" OwnerUserId="814" LastActivityDate="2011-03-28T17:40:39.257" Title="Jig for making jumper leads?" Tags="&lt;jumper&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="12114" PostTypeId="1" CreationDate="2011-03-27T14:21:25.483" Score="1" ViewCount="91" Body="&lt;p&gt;I am trying to investigate the RST5.5, RST6.5, and RST7.5 interrupts on the 8085 microprocessor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to find information about the to the type of interrupting signal used and the built in hardwired priority scheme,but finding resources explained in a plain and simple way is next to impossible...even the Intel documents are very hard to understand!!&lt;/p&gt;&#xA;" OwnerUserId="3617" LastActivityDate="2011-03-29T21:20:14.967" Title="Learning about the Interrupt system of the 8085 processor." Tags="&lt;interrupts&gt;&lt;processor&gt;&lt;8085&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="12115" PostTypeId="2" ParentId="12078" CreationDate="2011-03-27T14:31:18.617" Score="1" ViewCount="" Body="&lt;p&gt;You can use &lt;code&gt;avr-size&lt;/code&gt; to check the real size of your program:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;[jpc@jpc sepack] avr-size sepack.elf &#xA;   text    data     bss     dec     hex filename&#xA;   4396       6     277    4679    1247 sepack.elf&#xA;[jpc@jpc sepack] avr-size sepack.hex &#xA;   text    data     bss     dec     hex filename&#xA;      0    4402       0    4402    1132 sepack.hex&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;As you can see it works better with &lt;code&gt;.elf&lt;/code&gt; files since it can also show you both how much ram you need (&lt;code&gt;data&lt;/code&gt;+&lt;code&gt;bss&lt;/code&gt;) and how much flash will be used (&lt;code&gt;text&lt;/code&gt;+&lt;code&gt;data&lt;/code&gt;). With the &lt;code&gt;.hex&lt;/code&gt; file only shows you the second figure (labeling it &lt;code&gt;data&lt;/code&gt;)&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-27T14:31:18.617" CommentCount="4" />
  <row Id="12116" PostTypeId="1" CreationDate="2011-03-27T14:57:25.213" Score="1" ViewCount="178" Body="&lt;p&gt;I'm using the pic 18F4550 with microchip v8.63 and with the C compiler C18. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to trigger port RB3, RB4 and RB5. when, I press on respectively S1 (switch 1), S2 switch (S2) and S3 (switch 3). on these ports (RB3, RB4 and RB5) there are leds connected to, the should burn when I press S1 or S2 or S2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first question is, How do I stream from my S1 and S2 and S3 to the gates (RB3, RB4, RB5).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And second how can I enable port RB6, there is a light dependent resistor connected to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wrote this program: but, nothing is happening. only led 1 goes on.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &quot;p18cxxx.h&quot;  &#xA;void main(void) &#xA;{ &#xA;    // turn off all LED latches &#xA;    LATDbits.LATD0 = 0; &#xA;    LATDbits.LATD1 = 0; &#xA;    LATDbits.LATD2 = 0; &#xA;    LATDbits.LATD3 = 0; &#xA;    // make port d bits which drive LEDs outputs &#xA;    TRISDbits.TRISD0 = 0; &#xA;    TRISDbits.TRISD1 = 0; &#xA;    TRISDbits.TRISD2 = 0; &#xA;    TRISDbits.TRISD3 = 0; &#xA;&#xA;    if(PORTBbits.RB3 == 0) {&#xA;        LATDbits.LATD0 = 1;     &#xA;    }&#xA;    if(PORTBbits.RB4 == 0) {&#xA;        LATDbits.LATD1 = 1;&#xA;    }&#xA;    if(PORTBbits.RB5 == 0) {&#xA;        LATDbits.LATD2 = 1;&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3618" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-03-27T19:02:13.847" LastActivityDate="2011-03-29T10:41:46.530" Title="burn a led with the switchs on pic 18F4550." Tags="&lt;microcontroller&gt;&lt;pic&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="12117" PostTypeId="2" ParentId="12116" CreationDate="2011-03-27T15:02:45.333" Score="2" ViewCount="" Body="&lt;p&gt;Several of the pins you are using also have an analogue input function, which is enabled by default on reset. For instance, RB3 will be the AN9 ADC input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See the data sheet (page 116) for details of how to enable them for digital I/O. You need to set some bits in your C program; I use  this for PORTA on the 18F4520:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ADCON1 = 0x0F;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="305" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-29T10:41:46.530" LastActivityDate="2011-03-29T10:41:46.530" CommentCount="2" />
  <row Id="12118" PostTypeId="2" ParentId="12113" CreationDate="2011-03-27T15:13:28.780" Score="0" ViewCount="" Body="&lt;p&gt;Well, you can buy the individual parts to make the connectors, and crimp them onto any wire you like. &lt;a href=&quot;http://www.pololu.com/&quot; rel=&quot;nofollow&quot;&gt;Pololu&lt;/a&gt; sells the parts to do this (&lt;a href=&quot;http://www.pololu.com/catalog/product/1930&quot; rel=&quot;nofollow&quot;&gt;sockets&lt;/a&gt;,&#xA;&lt;a href=&quot;http://www.pololu.com/catalog/product/1931&quot; rel=&quot;nofollow&quot;&gt;pins&lt;/a&gt;, and&#xA;&lt;a href=&quot;http://www.pololu.com/catalog/category/70&quot; rel=&quot;nofollow&quot;&gt;housings&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In terms of crimping the connectors, you can go anywhere from a $\$$200 tool for crimping an entire housing in one go, to a $\$$30 single crimper, to an effectively free pliers and patience approach.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, they also sell &lt;a href=&quot;http://www.pololu.com/catalog/category/71&quot; rel=&quot;nofollow&quot;&gt;pre-crimped connectors&lt;/a&gt;, in a random selection of colors.&lt;/p&gt;&#xA;&#xA;&lt;h3&gt;EDIT:&lt;/h3&gt;&#xA;&#xA;&lt;p&gt;Oops, I seem to be thinking about the wrong type of jumper cable. Oh well.&lt;/p&gt;&#xA;" OwnerUserId="1217" LastEditorUserId="1217" LastEditorDisplayName="" LastEditDate="2011-03-28T17:40:39.257" LastActivityDate="2011-03-28T17:40:39.257" CommentCount="4" />
  <row Id="12119" PostTypeId="2" ParentId="12085" CreationDate="2011-03-27T15:21:19.553" Score="3" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;&lt;strong&gt;Second Source Available:&lt;/strong&gt; When you use parts available from multiple manufacturers, you have a pretty good way to get ICs that are industry standards. In mass production, as Madmanguruman has said, this means less trouble when certain manufacturers tell you amazingly long lead times; for the hobbyist, it means that your chances to get the part from small-volume distributors are far better.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Package options:&lt;/strong&gt; Another way to find good mainstream parts is looking for package options. If an op amp is available in CERDIP-8, DIP-8, SO-8, MSOP-8 and whatnot (maybe even metal can TO-99), you can be sure it is a widely available part used successfully in plenty of different applications and likely far from being obsoleted within the next couple of years.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Good and detailed data sheet available:&lt;/strong&gt; Read the data sheet &lt;em&gt;in detail&lt;/em&gt; and compare data sheets published by different manufacturers. Buy the part from the manufacturer whose data sheet you trust most. I've come across many data sheets that even have conflicting information within themselves, and those were the parts I've often had trouble with.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Cost:&lt;/strong&gt; Not that the difference between 20 and 50 Ct. will kill you when you only need four or five ICs for your project, but if you find similar parts at different prices, the cheaper one is usually the one closer to mainstream. You can also look for the &quot;product status&quot; category on the manufacturer's website: If they tell you a part is &quot;active&quot; that equals good and if they tell you it's &quot;not recommended for new designs&quot; it means that you should not buy it unless you need it to repair stuff.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-03-27T15:26:22.997" LastActivityDate="2011-03-27T15:26:22.997" />
  <row Id="12120" PostTypeId="1" AcceptedAnswerId="12121" CreationDate="2011-03-27T16:00:03.940" Score="0" ViewCount="93" Body="&lt;p&gt;If I understand correctly, the state diagram of a sequential circuit simply shows  the different states the circuit goes through. However, if I'm trying to build a 2's complementer using a shift register and a flip-flop, how does the state diagram look? Seeing as what goes through the flip-flop depends on the digit put in the register, I'm not sure how to draw it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="3619" LastActivityDate="2011-03-27T17:53:19.400" Title="Problems deriving state diagrams" Tags="&lt;circuit-design&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="12121" PostTypeId="2" ParentId="12120" CreationDate="2011-03-27T17:53:19.400" Score="1" ViewCount="" Body="&lt;p&gt;You should only consider drawing the state machine for the actual 2-complementer with serial input, and forget about the shift register (drawing a state diagram for a shift register of a given length is perfectly possible, but makes hardly any sense). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Said that, the task boils down to a single-input/single-output state machine with 2 states. Look here: &lt;a href=&quot;http://k5rec.blogspot.com/2006/12/digital-electronics-serial-twos.html&quot; rel=&quot;nofollow&quot;&gt;http://k5rec.blogspot.com/2006/12/digital-electronics-serial-twos.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-03-27T17:53:19.400" CommentCount="4" />
  <row Id="12122" PostTypeId="1" CreationDate="2011-03-27T18:34:00.953" Score="0" ViewCount="108" Body="&lt;p&gt;I'm using the picdem 18F4550 with microchip v8.63 and the c compiler. components that i'm use are: - 3 leds (red, green, blue); - a LDR (327700 NORPS-12 farnell).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have connected 3 leds (red, green and blue), on RB4, RB5 and RB6 as output. I also connect the LDR on RB1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, when the green of another led lights up, how can I retrieve the value in my code that the LDR measures?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I included my code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &quot;p18cxxx.h&quot;&#xA;#pragma config WDT = OFF &#xA;void main(void) {     &#xA;    // turn off all LED latches     &#xA;    LATDbits.LATD0 = 0;     &#xA;    LATDbits.LATD1 = 0;     &#xA;    LATDbits.LATD2 = 0;     &#xA;    // make port d bits which drive LEDs outputs     &#xA;    TRISDbits.TRISD0 = 0;     &#xA;    TRISDbits.TRISD1 = 0;     &#xA;    TRISDbits.TRISD2 = 0;    &#xA;    TRISB = 0;    &#xA;    // RB port output.    &#xA;    PORTB = 0;    &#xA;    PORTB = 0b10001111; &#xA;    // 0b01011010    &#xA;    if(PORTBbits.RB4 == 0) {        &#xA;        LATDbits.LATD0 = 1;         &#xA;    }    &#xA;    else if(PORTBbits.RB5 == 0) {        &#xA;        LATDbits.LATD1 = 1;    &#xA;    }    &#xA;    else if(PORTBbits.RB6 == 0) {        &#xA;        LATDbits.LATD2 = 1;    &#xA;    }       &#xA;    if(PORTBbits.RB1 == 1) {    &#xA;    }         &#xA;    while(1) {        ;    }   &#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3618" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T21:00:59.747" LastActivityDate="2011-04-27T21:00:59.747" Title="Get value from LDR." Tags="&lt;microcontroller&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="12123" PostTypeId="2" ParentId="12122" CreationDate="2011-03-27T19:10:01.250" Score="1" ViewCount="" Body="&lt;p&gt;As in your other question, a couple of those pins are analogue inputs by default, and should be enabled for digital I/O. The code won't work, otherwise.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-27T19:10:01.250" CommentCount="1" />
  <row Id="12124" PostTypeId="1" CreationDate="2011-03-27T19:17:23.290" Score="0" ViewCount="92" Body="&lt;p&gt;I'm looking for recommendations for solar cell &lt;a href=&quot;http://pvcdrom.pveducation.org/MODULE/Bypass.htm&quot; rel=&quot;nofollow&quot;&gt;bypass diodes&lt;/a&gt;. In essence, I'm looking for a Schottky diode with a low as possible voltage drop at 5A, and a reasonable price. Any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="3148" LastActivityDate="2011-03-27T19:17:23.290" ClosedDate="2011-03-27T21:34:11.687" Title="Recommendation for solar cell bypass Schottky diode" Tags="&lt;diode&gt;&lt;solar-cell&gt;&lt;schottky&gt;" CommentCount="2" />
  <row Id="12125" PostTypeId="1" AcceptedAnswerId="12126" CreationDate="2011-03-27T19:35:23.307" Score="5" ViewCount="208" Body="&lt;p&gt;I'm starting to design a circuit that includes a QFP-38 component. I'm accustomed to using DIP components and prototyping on a breadboard, but in this case I won't be able to acquire a DIP version of the component.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it normal practice for electrical engineers to have a PCB fabricated without prototyping? Or do you always acquire breakout boards for small components at first?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(In my case, I would just go ahead and order a QFP-38 to DIP adapter, but it will cost me $20 including shipping. It seems like I may as well just have a PCB made and hope for the best.)&lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2011-03-27T19:43:57.000" LastActivityDate="2011-03-28T22:31:35.193" Title="How Do You Prototype with QFP-Only Components?" Tags="&lt;pcb&gt;&lt;prototyping&gt;&lt;qfp&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="2" />
  <row Id="12126" PostTypeId="2" ParentId="12125" CreationDate="2011-03-27T19:39:50.010" Score="6" ViewCount="" Body="&lt;p&gt;I make my own PCBs at home, it's very easy and doesn't cost much. I can make a board in 30 minutes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to use a breakout board for the QFP, like &lt;a href=&quot;http://www.schmartboard.com/&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; Schmartboards.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-27T19:39:50.010" CommentCount="5" />
  <row Id="12127" PostTypeId="2" ParentId="12122" CreationDate="2011-03-27T19:41:25.970" Score="4" ViewCount="" Body="&lt;p&gt;You cannot read a resistance (directly) from a PIC input port.  There are a few different ways to go here:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;If you connect another resistor to Vdd you can make a voltage divider, which has an output voltage determined by the two resistances.  The ADC will give you the voltage, and some algebra will get you the resistance.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You could build a constant-current source, and pass this current through the LDR.  Then the voltage across the LDR will be exactly proportional to the resistance.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You could use a capacitor from the LDR and connect it to another pin.  When the capacitor pin is set high, you can watch the rise time on the capacitor-LDR connection.  This technique does not require an ADC.  (For more accuracy, charge the capacitor through a known resistance and discharge through the LDR, then use the charge time / discharge time ratio.)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-27T19:41:25.970" />
  <row Id="12128" PostTypeId="2" ParentId="12125" CreationDate="2011-03-27T20:21:23.777" Score="3" ViewCount="" Body="&lt;p&gt;I've used dead-bug style prototyping for such parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic idea is that you start out with a copper-clad board which is all copper, then glue down the parts with their pads sticking up, using cyano.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This way you can easily solder to the pads and pins of small parts using wirewrap wire or other fine wire and you will have a good solid ground plane anywhere you want it, which is good for noise immunity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Islands of non-ground connections are made by cutting out some small (like 3x3 mm) bits of PCB and gluing those down with the copper facing up, I've even mounted some SMD parts this way.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-03-27T20:21:23.777" />
  <row Id="12129" PostTypeId="2" ParentId="12125" CreationDate="2011-03-27T20:31:31.610" Score="6" ViewCount="" Body="&lt;p&gt;I just have a PCB fabbed.  Its incredibly cheap to do so nowadays unless you need exotic materials or construction parameters.    &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Making your own PCB is reasonable for hobby work but when contracting for $150-200+ an hour as most design houses do, having a 4 board 4 day turn done is just cheaper than screwing around with adapters or etching your own copper.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-03-27T20:31:31.610" />
  <row Id="12130" PostTypeId="1" AcceptedAnswerId="12146" CreationDate="2011-03-27T21:25:41.007" Score="0" ViewCount="74" Body="&lt;p&gt;Anyone familiar with the SMD1 Stepper Motor Driver Kit ? &#xA;I am trying to figure out how to connect external control to the lugs on the switch assembly (DPDT push switches). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The lugs already have the leads soldered so leads for the following &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;run/hold&lt;/li&gt;&#xA;&lt;li&gt;Counter and Clockwise&lt;/li&gt;&#xA;&lt;li&gt;Power&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Really new to the electronic stuff though (Two months in). It could be that I am not understanding how to control the leads so that they behave in a similar fashion to the switches. The kit has already been pre-built the only missing piece is the external controls.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Li3Km.png&quot; alt=&quot;Illustration of the SMD1&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Interestingly (at least for me... still grasping), a lead is soldered to the right end of Resistor 3. The &lt;a href=&quot;http://www.ramseyelectronics.com/downloads/manuals/SMD1.pdf&quot; rel=&quot;nofollow&quot;&gt;manual&lt;/a&gt; says the only requirement is that the control's state is equal to 5 vdc when energized. So ... in simple (new to electronics) layman terms how does one connect it say to a breadboard with a 5V supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wcXGb.png&quot; alt=&quot;Switch&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3623" LastEditorUserId="3623" LastEditorDisplayName="" LastEditDate="2011-03-28T02:07:40.077" LastActivityDate="2011-03-28T06:14:11.937" Title="Connecting an external control to a DPDT switch" Tags="&lt;switch&gt;&lt;stepper-motor&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="12131" PostTypeId="2" ParentId="10487" CreationDate="2011-03-27T21:28:41.690" Score="1" ViewCount="" Body="&lt;p&gt;I'm not sure how committed you are to the LM2733. You may want to look for a chip that provides output voltage control separate from the main feedback path. For example, &lt;a href=&quot;http://www.linear.com/product/LT3495&quot; rel=&quot;nofollow&quot;&gt;LT3495&lt;/a&gt;. This will let you adjust the voltage without worrying about what you're doing to the stability of the regulator. &lt;/p&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-03-27T21:28:41.690" />
  <row Id="12132" PostTypeId="1" CreationDate="2011-03-27T21:58:47.093" Score="5" ViewCount="243" Body="&lt;p&gt;Some people enjoy &lt;a href=&quot;http://en.wikibooks.org/wiki/Microprocessor_Design/Wire_Wrap&quot; rel=&quot;nofollow&quot;&gt;building &quot;homebrew&quot; CPUs out of simpler ICs.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a name for &quot;chips out of which one can build a CPU, if you have enough of them&quot;?&#xA;Is there a name for the other chips, &quot;chips that one cannot build a CPU out of, no matter how many of them you have&quot;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One can build a CPU out of sufficiently large quantities of 4:1 mux chips&#xA;( &lt;a href=&quot;http://www.6502.org/users/dieter/a1/a1_4.htm&quot; rel=&quot;nofollow&quot;&gt;multiplexers are the tactical Nuke of Logic Design&lt;/a&gt; ).&#xA;One can build a CPU out of (somewhat larger) quantities of 2-in NAND gates. Or from 2-in NOR gates. Or from a few (perhaps one) CPLD or FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One cannot build a CPU out of 2-in XOR gates alone.&#xA;One cannot build a CPU entirely out of &lt;a href=&quot;http://en.wikipedia.org/wiki/diode-resistor_logic&quot; rel=&quot;nofollow&quot;&gt;diode-resistor logic&lt;/a&gt; alone.&#xA;One cannot build a CPU entirely out of D-type flip-flops alone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there some term or phrase for distinguishing these two categories of chips that is less awkward than &quot;chips out of which one can build a CPU&quot;?&lt;/p&gt;&#xA;" OwnerUserId="813" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-05-13T02:39:56.353" LastActivityDate="2011-05-13T02:39:56.353" Title="Is there a name for &quot;chips out of which one can build a CPU&quot;?" Tags="&lt;digital&gt;&lt;cpu&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="12133" PostTypeId="2" ParentId="2653" CreationDate="2011-03-27T21:59:44.530" Score="3" ViewCount="" Body="&lt;p&gt;The range and variety of interests within amateur radio is quite large, enough so that in a local club there may be a number of members each with their own unique interests, but as it has been a global hobby for over a century, there is large community of amateurs how may share an common sub-interest as yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two &quot;sub-interests&quot; that spring to mind are the QRP (low power) groups and members, including the &lt;a href=&quot;http://mailman.qth.net/mailman/listinfo/qrp-l/&quot; rel=&quot;nofollow&quot;&gt;QRP-L&lt;/a&gt; and &lt;a href=&quot;http://www.qrp-l.org/&quot; rel=&quot;nofollow&quot;&gt;qrp-l.org&lt;/a&gt; mailing lists, &lt;a href=&quot;http://www.norcalqrp.org/&quot; rel=&quot;nofollow&quot;&gt;Northern California QRP&lt;/a&gt; Club, &lt;a href=&quot;http://www.gqrp.com/&quot; rel=&quot;nofollow&quot;&gt;G-QRP&lt;/a&gt; club, and numerous others including &lt;a href=&quot;http://www.phonestack.com/farhan/&quot; rel=&quot;nofollow&quot;&gt;Ashhar Farhan VU2ESE&lt;/a&gt;, who became a mini-celebrity with his &lt;a href=&quot;http://www.phonestack.com/farhan/xcvr1.html&quot; rel=&quot;nofollow&quot;&gt;BitX20&lt;/a&gt; (affordable home made 20/40 meter dual band SSB transceiver). There are also numerous clubs and small to medium businesses selling QRP oriented kits. Because of the simplicity of not having large and complex power amplifiers, they often design and build simple CW (Morse code encoded on a &lt;strong&gt;C&lt;/strong&gt;-ontinuous &lt;strong&gt;W&lt;/strong&gt;-ave signal) transceivers, or even separate transmitter and receiver pairs. Many affordable (and a few not so affordable) QRP kits are available. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other major area is in microwave frequency operation, as less amateur oriented equipment is available, so many adapt surplus commercial equipment or build their own gear to operate above &lt;a href=&quot;http://www.w1ghz.org/&quot; rel=&quot;nofollow&quot;&gt;1GHz&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few &quot;big&quot; references for amateur radio building are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arrl.org/arrl-handbook-2011&quot; rel=&quot;nofollow&quot;&gt;ARRL Handbook&lt;/a&gt;, published annually by the US national amateur radio group, ARRL, and with a major revision every 5-10 years&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arrl.org/shop/The-ARRL-Antenna-Book/&quot; rel=&quot;nofollow&quot;&gt;ARRL Antenna book&lt;/a&gt;, an fairly encyclopedic reference on antenna design and construction&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.rsgbshop.org/acatalog/Online_Catalogue_Technical_6.html&quot; rel=&quot;nofollow&quot;&gt;RSGB Radio Communication Handbook&lt;/a&gt;, published by the Great Britain national society, RSGB&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.arrl.org/shop/Experimental-Methods-in-RF-Design/&quot; rel=&quot;nofollow&quot;&gt;Experimental Methods in RF Design&lt;/a&gt; (aka &lt;a href=&quot;http://groups.yahoo.com/group/emrfd/&quot; rel=&quot;nofollow&quot;&gt;EMRFD&lt;/a&gt;), is an &lt;a href=&quot;http://www.qrp.pops.net/emrfd.asp&quot; rel=&quot;nofollow&quot;&gt;excellent RF guide&lt;/a&gt; once you understand basic electricity and electronics.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Keep an eye out for used copies of the ARRL or RSGB Handbooks, either one make an great technical (RF oriented) reference about many aspects in ham radio including learning electronics and building things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Informally, I find that UK and India hams are more likely to build some or all of their equipment than US/Canadian hams. So they tend to have affordable approaches to getting on their air, and operating. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a decent understanding of basic electronics (i.e. the basics of diodes, transistors, ICs, digital logic) then the EMRFD is an excellent starting point, which starts off in chapter 1 with a couple of simple and small projects to start with. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another interesting reference is the ARRL published &lt;a href=&quot;http://www.arrl.org/shop/ARRL-s-Hands-On-Radio-Experiments&quot; rel=&quot;nofollow&quot;&gt;book&lt;/a&gt; and &lt;a href=&quot;http://www.arrl.org/Hands-On-Radio&quot; rel=&quot;nofollow&quot;&gt;column&lt;/a&gt; in their monthly magazine, QST, both by Ward Silver. (I don't know if the second link will work, the column information use to be freely accessible I thought, but I don't know) The book chapters, or magazine columns form a series of very short treatment of a single topic, typically 1-4 pages with a simple and quick experiment or two.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-03-27T21:59:44.530" />
  <row Id="12134" PostTypeId="2" ParentId="10487" CreationDate="2011-03-27T22:08:17.290" Score="3" ViewCount="" Body="&lt;p&gt;The feedback pin is expecting a DC error voltage, with some usual stuff (ripple, noise, etc.) riding on it. The analog voltage loop is bandwidth-limited so that only useful information is used to determine the duty cycle of the converter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The easiest way is to use a DAC output and a series resistor to either sink or source amount of current out of / into the FB node. The size of the injection resistor will determine the adjustment range. The FB reference voltage is 1.23V, so as long as the DAC can go above and below that reference, you can control the voltage both up and down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the digital equivalent of having the bottom resistor adjustable.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-03-27T22:08:17.290" />
  <row Id="12135" PostTypeId="2" ParentId="12132" CreationDate="2011-03-27T23:33:34.503" Score="2" ViewCount="" Body="&lt;p&gt;The set of &lt;em&gt;&quot;chips you can build a computer out of&quot;&lt;/em&gt; can be assembled into &lt;a href=&quot;http://en.wikipedia.org/wiki/Turing_completeness&quot; rel=&quot;nofollow&quot;&gt;Turing complete&lt;/a&gt; machines. The rest are cannot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Functional_completeness&quot; rel=&quot;nofollow&quot;&gt;All logic gates can be assembled from sets of either only NAND or only NOR gates.&lt;/a&gt; If your IC in question can act as either or of these, it can be made into a Turing machine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know of a specific term to describe such a set.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These questions may also help:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://stackoverflow.com/questions/4908893/what-logic-gates-are-required-for-turing-completeness&quot;&gt;http://stackoverflow.com/questions/4908893/what-logic-gates-are-required-for-turing-completeness&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://stackoverflow.com/questions/7284/what-is-turing-complete&quot;&gt;http://stackoverflow.com/questions/7284/what-is-turing-complete&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-03-27T23:38:59.727" LastActivityDate="2011-03-27T23:38:59.727" CommentCount="1" />
  <row Id="12136" PostTypeId="1" AcceptedAnswerId="12143" CreationDate="2011-03-27T23:52:27.353" Score="0" ViewCount="73" Body="&lt;p&gt;At college we have to use a colophony-free solder, but over heating the solder leaves the flux residue on the boards(light amber in colour). Multicore recommend there own &lt;a href=&quot;http://www.prime-electronics.com.au/datasheets/data/Multicore/Wave%20Soldering/Solvents/Prozone/Tech%20Data%20Sheets.pdf&quot; rel=&quot;nofollow&quot;&gt;Multicore Prozone cleaner&lt;/a&gt;(this is some datasheet on what it is) to remove this residue from the board, but I can't find it on RS, Farnell or Rapid Electronics. Is there another alternative? Is there another industrial alternative as it looks like a generic PCB cleaner. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-03-28T04:35:13.257" Title="Multicore Prozone Alternative" Tags="&lt;soldering&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="12137" PostTypeId="2" ParentId="12136" CreationDate="2011-03-28T00:14:00.253" Score="1" ViewCount="" Body="&lt;p&gt;I use 99% iso-propyl alcohol, it works very well.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-28T00:14:00.253" CommentCount="5" />
  <row Id="12138" PostTypeId="2" ParentId="12085" CreationDate="2011-03-28T00:43:45.937" Score="2" ViewCount="" Body="&lt;p&gt;All of the other answers are fairly good, but you all forgot one important thing:  simulation!  Analog circuits are often somewhat tweaky, and spending a little bit of time with a simulator can often save hours or days of headaches later on.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many of the manufacturers have some level of support for simulations, but they all have issues.  In my opinion, Linear Tech's LTSpice (http://www.linear.com/designtools/software/#LTspice) is probably the best free tool available for simulations. &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-28T00:43:45.937" CommentCount="1" />
  <row Id="12139" PostTypeId="2" ParentId="11906" CreationDate="2011-03-28T01:02:15.047" Score="2" ViewCount="" Body="&lt;p&gt;The best solution, but not the easiest, is to use a flyback converter topology.  This will give you the most current, good efficiency, and the least issues.  Other solutions, like a typical boost topology in your first two diagrams can work, but you have to watch out for any duty-cycle limitations on the converter chip.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Switched capacitor converters can work for currents of 20 mA, but are noisy and don't regulate&#xA;well with a 10:1 increase in voltage.  I've seen these used for generating +48v in commercial products, but I wouldn't recommend them.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-28T01:02:15.047" CommentCount="2" />
  <row Id="12140" PostTypeId="2" ParentId="12132" CreationDate="2011-03-28T01:40:44.670" Score="8" ViewCount="" Body="&lt;p&gt;You need to be able to do NOT and one of AND and OR. Using Demorgan's laws, either of these functions can be transformed into the other, and thence into all other logical functions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is known as functional completeness or expressive adequacy.  The components or functions which create such a system are known as Sheffer functions (after Henry Sheffer, who published a proof on the topic) or sole sufficient operators.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also of interest is the fact that you can combine a quartet of NAND gates to make a D-type flip flop, and from there a memory cell, which is also required to create Turing completeness.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.proofwiki.org/wiki/Functionally_Complete_Logical_Connectives&quot; rel=&quot;nofollow&quot;&gt;ProofWiki's article&lt;/a&gt; on the topic is good reading.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-28T01:40:44.670" CommentCount="8" />
  <row Id="12141" PostTypeId="2" ParentId="12136" CreationDate="2011-03-28T03:09:06.140" Score="2" ViewCount="" Body="&lt;p&gt;The trick to clean soldering is to figure out the proper solvent for the flux you're using-- or even if you should clean it up at all.  For example, in my lab I only use water soluble flux.  It cleans up well with, you guessed it, water!  I just rinse the PCB's off in the sink with hot water and my boards are nice and clean.  Just make sure that's it's good and dry before powering it up.  But it turns out that isopropyl alcohol doesn't work well at all on it, and leaves a weird residue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other fluxes will clean up with isopropyl, but some require things like acetone (yuck!).  But keep in mind that some fluxes will never clean up well, and that's just the way it is.  For example, the &quot;no clean fluxes&quot; will often leave a residue that is unsightly but harmless.  Standard rosin core flux is the worst for residue, in my opinion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative to 99% isopropyl is the 97% stuff that you can get at most corner drug stores or pharmacies.  It costs a lot less than the 99% stuff, and does almost as good of a job.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-28T03:09:06.140" CommentCount="2" />
  <row Id="12142" PostTypeId="2" ParentId="12113" CreationDate="2011-03-28T03:34:45.900" Score="2" ViewCount="" Body="&lt;p&gt;What you're looking for is a sort of &lt;em&gt;lead forming tool&lt;/em&gt;. The most common such tools don't strip wire, as they're usually used for components such as resistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The usual hobbyist version I've seen is &lt;a href=&quot;http://www.flickr.com/photos/lenore-m/857277446/&quot; rel=&quot;nofollow&quot;&gt;a plastic device having a series of grooves in 0.1&quot; increments&lt;/a&gt;. Perhaps you could use one of those as a cutting-and-stripping guide before bending.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Googling around, &lt;a href=&quot;http://www.controlsignals.net/component-preparation.html&quot; rel=&quot;nofollow&quot;&gt;the CM-01 on this page&lt;/a&gt; claims to be able to form insulated jumpers and isn't obviously overkill, but I didn't find a price.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also found various hand tools which automatically cut and bend, or just bend, to an adjustable width, but that would probably make stripping the short ends difficult. I also found high-priced fully-automatic jumper forming machines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps a little more research starting with these keywords might turn up something useful.&lt;/p&gt;&#xA;" OwnerUserId="2838" LastEditorUserId="2838" LastEditorDisplayName="" LastEditDate="2011-03-28T03:44:28.900" LastActivityDate="2011-03-28T03:44:28.900" CommentCount="2" />
  <row Id="12143" PostTypeId="2" ParentId="12136" CreationDate="2011-03-28T04:35:13.257" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://hazard.com/msds/f2/bwl/bwlzd.html&quot; rel=&quot;nofollow&quot;&gt;MSDS for Prozone&lt;/a&gt; tells us that it is basically entirely &quot;GLYCOL ETHERS&quot;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I use %50 Acetone, %50 Methanol for cleaning PCBs, because it is very effective at dissolving the Kester solderpaste flux that I use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would recommend trying a few spray-can flux cleaners, then look up the MSDS for the one that works best. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, for safety reasons, the manufacturer &lt;em&gt;has&lt;/em&gt; to disclose the volatile/dangerous ingredients in the product, and you can probably mix your own from that.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-03-28T04:35:13.257" />
  <row Id="12144" PostTypeId="1" CreationDate="2011-03-28T04:36:53.910" Score="0" ViewCount="65" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using Microsoft Robotics Studio for a school project and I am getting a strange error when I try to run the Visual Simulation Environment. It was working fine until yesterday and then suddenly it gave me a runtime error saying &quot;Illegal command line arguments... do not use VPLHost directly, use dsshost instead to run a manifest&quot; But I am only clicking on Run in VPL/DSS Manifest editor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am running MRDS as administrator and I even tried re-installing MRDS but it is still showing the same MS VPL Runtime error. I tried to search online, but cannot find any suitable solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I already tried running the existing samples, i.e. Urban Environment, Multiple Simulated Robots etc. but it still gives me the same error. The strange thing is that it was working perfectly one minute, and then started giving me this error message the next minute, when I had not changed anything in between. In fact, I had wanted to change something in my manifest, so I closed the running VPL application, closed VPL and opened DSS manifest editor, and ran my manifest and that is when I got this error.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is going wrong? Is some MRDS script using vplhost32.exe instead of dsshost? If so, then where and how do I change it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried running the urban envrionment manifest from the command prompt and Using DSSHost32 directly. This time, it didn't give me a runtime error but an intiialization error. I tried changing port numbers but it still doesn't work. I have deleted many files from my computer to free space (JIC) and it still doesn't work. The window just doesn't open even when I hover over it in Windows 7.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The error message looks like this: Only one usage of each socket address (protocol/network address/port) is normally permitted.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This was even after I checked netstat for free ports and tried but I get this error message. Its either this one or the &quot;Don't use VPLHost directly&quot; if I run it through VPL or DSS Manifest Editor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could it be that some external services are interfering with DSSHost/VPLHost? Are there any such services which I could try killing? ANY help/suggestion would help right now as my project is due Thursday and this is a really unfortunate time for it to be acting up like this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks very much!&lt;/p&gt;&#xA;" OwnerUserId="2939" LastEditorUserId="1200" LastEditorDisplayName="" LastEditDate="2011-03-28T11:12:21.573" LastActivityDate="2011-03-28T11:12:21.573" ClosedDate="2011-03-28T11:50:50.873" Title="Runtime Error in Visual Simulation Environment - Microsoft Robotics Studio" Tags="&lt;robotics&gt;&lt;projects&gt;&lt;microsoft&gt;&lt;error&gt;&lt;mrds&gt;" CommentCount="2" />
  <row Id="12145" PostTypeId="1" AcceptedAnswerId="12147" CreationDate="2011-03-28T05:57:17.273" Score="0" ViewCount="124" Body="&lt;p&gt;I recently purchased an Arduino Uno and I've had lots of fun tinkering with it. I'm now interested in measuring the amount of water that flows into my house from through the water line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm have trouble finding an appropriate device that will let me measure the flow of water from my well and capture it with my Arduino. Can you guys please recommend a specific component or some general search terms so I can start looking?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!&lt;/p&gt;&#xA;" OwnerUserId="3353" LastActivityDate="2011-03-28T08:24:11.603" Title="Measuring Home Water Flow" Tags="&lt;arduino&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="12146" PostTypeId="2" ParentId="12130" CreationDate="2011-03-28T06:14:11.937" Score="1" ViewCount="" Body="&lt;p&gt;Looking at th PCB those 2 DPDT switches are being used as SPST ones - one pin (the middle one) is wired to +V, the other is connected to an input on a chip with a pulldown resistor to ground (R6/10).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the switches are off then the pin furthest from the panel will be pulled down by the resistor to ground - you could then drive it externally (run that pin and ground to the external controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some caveats: if you accidentally turn the switch on bad stuff could happen - best to drive the signal through a small diode for protection - you also need to be careful about voltages - don't drive the circuit from something with a higher voltage than expected (perhaps snarf the power from that other pin assuming it's 5v)&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-28T06:14:11.937" CommentCount="2" />
  <row Id="12147" PostTypeId="2" ParentId="12145" CreationDate="2011-03-28T07:01:56.003" Score="1" ViewCount="" Body="&lt;p&gt;Seeedstudio sells a flow sensor: &lt;a href=&quot;http://www.seeedstudio.com/depot/g12-water-flow-sensor-p-635.html?cPath=144_151&amp;amp;zenid=2550fe072947d974a46772da306b7a46&quot; rel=&quot;nofollow&quot;&gt;http://www.seeedstudio.com/depot/g12-water-flow-sensor-p-635.html?cPath=144_151&amp;amp;zenid=2550fe072947d974a46772da306b7a46&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's probably too small for your application, but it could be a place to start.&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2011-03-28T07:01:56.003" CommentCount="3" />
  <row Id="12148" PostTypeId="2" ParentId="12116" CreationDate="2011-03-28T07:58:09.020" Score="5" ViewCount="" Body="&lt;p&gt;Your &lt;code&gt;main&lt;/code&gt; routine runs once only. You need a loop, probably starting after the ports are initiallised, around the &lt;code&gt;if&lt;/code&gt; statements.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-03-28T07:58:09.020" />
  <row Id="12149" PostTypeId="2" ParentId="12145" CreationDate="2011-03-28T08:24:11.603" Score="0" ViewCount="" Body="&lt;p&gt;Wikipedia &lt;a href=&quot;http://en.wikipedia.org/wiki/Water_meter&quot; rel=&quot;nofollow&quot;&gt;has a page&lt;/a&gt; on different methods of measuring water flow. If you wanted to build the sensor yourself, then the &lt;a href=&quot;http://en.wikipedia.org/wiki/Ultrasonic_flow_meter&quot; rel=&quot;nofollow&quot;&gt;ultrasonic flow meter&lt;/a&gt; would be probably the easiest.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-03-28T08:24:11.603" />
  <row Id="12150" PostTypeId="1" AcceptedAnswerId="12152" CreationDate="2011-03-28T08:45:32.270" Score="1" ViewCount="139" Body="&lt;p&gt;Is there anything I need to he aware of when using K-type thermocouples?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I got the idea by touching the probe. I can get a reading when measuring temperature for 30 seconds using a DMM. A commercial electronic thermometer needs around  minutes for the same result. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This gave me an idea to make a device which will use K-type thermocouple to quickly measure temperature. On the other hand if it was so simple to measure temperature, why don't the commercial thermometers produce their result faster.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a feeling that I'm missing something important here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is: Are there any non-obvious problems I could face when using a K-type thermocouple to measure  measure human body temperature?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-28T10:54:33.393" Title="Using K-type thermocouple to measure human body temperature" Tags="&lt;temperature&gt;&lt;measurement&gt;" AnswerCount="3" />
  <row Id="12151" PostTypeId="2" ParentId="12150" CreationDate="2011-03-28T09:49:25.647" Score="1" ViewCount="" Body="&lt;p&gt;The use of thermocouples is not an easy task if you want to achieve high accurracy (that you need to measure the human body temperature). You also have to measure the temperature of the plug that connects the thermo couple to the DMM because this plug also generates a thermo voltage. To get the right temperature that you measure with the thermo couple you have to consider the thermo valtage generated by the plug. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you would go better with a PT-100 or PT-1000.&lt;/p&gt;&#xA;" OwnerUserId="495" LastEditorUserId="495" LastEditorDisplayName="" LastEditDate="2011-03-28T10:54:33.393" LastActivityDate="2011-03-28T10:54:33.393" />
  <row Id="12152" PostTypeId="2" ParentId="12150" CreationDate="2011-03-28T10:02:20.457" Score="4" ViewCount="" Body="&lt;p&gt;These themocouples have a tiny spot weld between two thin wires to make the active sensor element, which results in a very low thermal mass. Hence they change temperature quickly, which is the same thing as reacting to temperature changes quickly. As soon as you mount them in a larger substrate or coating (eg to provide a sterile insulation, to prevent breakage, to electrically isolate) you increase the thermal mass, so you have to wait longer for stabilisation.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-03-28T10:02:20.457" />
  <row Id="12153" PostTypeId="2" ParentId="12150" CreationDate="2011-03-28T10:50:23.790" Score="4" ViewCount="" Body="&lt;p&gt;Thermocouples are not stable enough to measure human body temperature (you want 0.05C accuracy there). It only gives about 1-2C long-term stability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Platinum PT100/1000 RTD ones are much more suitable and way way more procise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you have this extra-accuracy, you can measure target temperature while ovserving how it's rising by extrapolating... This would allow some 1-5sec measurement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only way to be faster - IR sensors.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-28T10:50:23.790" />
  <row Id="12154" PostTypeId="1" CreationDate="2011-03-28T12:52:35.553" Score="1" ViewCount="75" Body="&lt;p&gt;Could someone suggest a voltage follower with thermal protection (thermal shutdown)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see possible solutions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;An LDO with external reference. I found only few of them, seems they are called tracking LDO and they are very rare and are hard to buy. Maybe I did a wrong search?&lt;/li&gt;&#xA;&lt;li&gt;Use a transistor with thermal shutdown. I found only one transistor in the entire internet and it's seem obsolete. Does such transistors exist?&lt;/li&gt;&#xA;&lt;li&gt;High current op-amp with thermal shutdown. I found only big expensive specialized devices of this type. Are there small, like SOT-23-6, and cheap op-amps of this type?&lt;/li&gt;&#xA;&lt;li&gt;Maybe it's possible to create a voltage follower using an op-amp and a regular adjustable LDO? How?&lt;/li&gt;&#xA;&lt;li&gt;Something else?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Please share your ideas. Thank you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;i&gt;Just if you want a specific details: I need a voltage follower buffering 1.2-3.3V signal and powered from 5V supply. I want it to be able to provide up to 200mA of current at least for short period of time, typical consumption is about 30-50mA. Since my device is small and fitted in 10 x 8 x 3cm plastic box, I think, there is a possibility that under long lasting worst condition (200mA at 1.2V (i.e. 3.8V dropout)) the transistor of classic voltage follower could overheat. That is why I would like to have a solution with thermal shutdown.&lt;/i&gt;&lt;/p&gt;&#xA;" OwnerUserId="1932" LastActivityDate="2011-03-28T17:16:31.057" Title="Voltage follower with thermal protection" Tags="&lt;heat-protection&gt;" AnswerCount="1" />
  <row Id="12155" PostTypeId="1" AcceptedAnswerId="12157" CreationDate="2011-03-28T13:38:20.653" Score="0" ViewCount="82" Body="&lt;p&gt;Hi all,&lt;br&gt;&#xA;as experimental project, I want to create Arduino circuit with a lot of sensors for &lt;strong&gt;ping pong table&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need two controls:&lt;br&gt;&#xA; - first one is related to the net. &lt;em&gt;If the ball touches the net&lt;/em&gt;, the controller light on a led or beep.&lt;br&gt;&#xA; - second one is related to the table. &lt;em&gt;If the ball is out of range&lt;/em&gt;, a 7-segment display increases the score.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the components that I need to start developing this project?&lt;br&gt;&#xA;What type of sensors I need?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any sensor to control bounds of surface or something similar?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks,&lt;br&gt;&#xA;A&lt;/p&gt;&#xA;" OwnerUserId="3359" LastActivityDate="2011-03-28T13:50:04.490" ClosedDate="2011-03-28T14:34:20.580" Title="Arduino sensors for the Ping Pong table" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;boundary-scan&gt;" AnswerCount="1" CommentCount="7" />
  <row Id="12156" PostTypeId="1" CreationDate="2011-03-28T13:46:05.610" Score="2" ViewCount="111" Body="&lt;p&gt;First of all, I do not have an electronics background. I have recently been experimenting with software radio using GNU Radio and a USRP1. I came here in hopes that some people outside of GNU Radio could lend some insight into my problem. I am not sure if I'll get any answers from here, but it's worth a shot.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;We are experimenting with tunnelling a known communications protocol inside our GNU Radio transmissions. Within GNU Radio's modulators a packet_encoder class takes the incoming data stream, divides it into packets, and then sends it along to the modulator. The modulated data is then sent to the USRP for transmission.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Our problems seem to revolve around very short burst transmissions. For example, we are trying to perform a sort of hand-shaking process where one radio transmits a 'hello' packet and waits for a response. We are unable to reliably transmit single packets, but it seems we can get some throughput if we spam the same packet a few hundred times. Similar setups which continuously stream data from an input file seem to work fine in the same setup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We have two USRP1 devices with suitable antennas located in the same room. As I have said continuous transmissions seem to work ok, but very short burst transmissions are a problem and we are not able to successfully transmit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;SO, my question is what are the various implications/issues surrounding short burst transmissions in radio? I am having a hard time finding the problem on the software side of things, and was curious if some insight into the hardware could help me. For example, are issues like this common in 'cheap' hardware like the USRP1?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Universal_Software_Radio_Peripheral&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Universal_Software_Radio_Peripheral&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for looking!&lt;/p&gt;&#xA;" OwnerUserId="3630" LastActivityDate="2011-03-28T20:35:13.547" Title="Implications of short burst transmissions in radio? (SDR/gnu-radio)" Tags="&lt;radio&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="12157" PostTypeId="2" ParentId="12155" CreationDate="2011-03-28T13:50:04.490" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Net Sensor&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This sounds pretty do-able.  I would imagine that there is some sort of vibration sensor that should work for you here... One idea is attaching a wire to the net that disturbs some sort of magnetic field and you could use that do know when the net has been hit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Out of range&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So by this do you mean if the ball completely misses the table your controller should know about it?  This seems like a big challenge.  The first thing that comes to mind here is embedding some sensors in the paddles and the table.  The idea here would be after every hit on a paddle, if there isn't a hit on the table, the ball is out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some huge challenges making this robust though (really no matter what approach you end up using).  Dealing with ambient noise and incidental table knocks might be tricky.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can figure this out, it would be pretty slick!&lt;/p&gt;&#xA;" OwnerUserId="1823" LastActivityDate="2011-03-28T13:50:04.490" CommentCount="2" />
  <row Id="12159" PostTypeId="2" ParentId="12156" CreationDate="2011-03-28T14:57:31.153" Score="0" ViewCount="" Body="&lt;p&gt;Interesting that you are having this problem. My lab mate is working with a GNU radio (USRP1) right now and found that very short packets tended to be all garbage. He was able to narrow it down to a couple things, but ultimately hasn't figured out why it is happening and is just focusing on longer packets now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1st off, every time the radios start a broadcast, the receiver has to re-sync itself with the transmitter. Usually there is a preamble on the packet that allows for this to happen, but there is a chance that the radios aren't able to get a full sync on very short packets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2nd, he was pulling all of his data from a file. He believed the system may have started to transmit before getting the data out of the file and the setup time for a harddrive to retrieve the file caused some &quot;jitter&quot; on the transmission.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-28T14:57:31.153" CommentCount="6" />
  <row Id="12160" PostTypeId="2" ParentId="12156" CreationDate="2011-03-28T15:00:59.170" Score="0" ViewCount="" Body="&lt;p&gt;If the packet gets eventually through, it means that you have some interference issue. Some possibilities, based on assumption that your continuous transfers are not actually all that continuous (droping data, as you indicate):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Strong source of interference on the same frequency you are using for transmission. This can be resolved by moving to another frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Mismatched antenna. In this case the antenna can't pass enough of the received signal into USRP (or from USRP). Needs better antenna design or better matching.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Not receiving enough signal. In this case the signal will be burried in the noise. Can be resolved using more power on the transmitting side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) Not enough filtering on receiving side. Signal can be swamped by other signals received by the antenna, even if they are on other frequencies. Signal to noise/interference ratio can be increased by filtering the signal through bandpass filter that will select the signal and suppress the other signals you are not interested in. Ideally such filter will be placed between the antenna and USRP. Like in 2) the filter has to be impedance matched to the antenna on one side, and to the USRP on the other side. Another, narrowband filter should be used on the software side to further narrow down the selection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That you are transmitting in bursts plays no role - unless you are having some timing issue with switching between transmission and receiving. The quality of USRP hardware also should not be an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can try experimenting with 1) and 3), and if it does not work, than you will need somebody with backgroung in RF design to do 2) or 4) for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given Kellenjb's friend analysis, this really looks like a problem with GNU Radio software. Look at what other possibilities it gives you both on transmit and receive, and try to use other modulations, methods of feeding it the data and so on to go around the issue. Another possibility is to debug the software.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastEditorUserId="2636" LastEditorDisplayName="" LastEditDate="2011-03-28T17:51:48.883" LastActivityDate="2011-03-28T17:51:48.883" CommentCount="1" />
  <row Id="12161" PostTypeId="1" CreationDate="2011-03-28T15:15:54.740" Score="0" ViewCount="69" Body="&lt;p&gt;We're looking for a decent hot air SMD rework station to help us fix up our prototypes. In the past, I've used one of the low-end Aoyue models, and found it lacking (the interface had problems, and the air pump got gummed up after a while). What should I be looking for in a rework station? Any model recommendations?&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2011-03-28T17:49:48.830" Title="Rework station recommendations?" Tags="&lt;surface-mount&gt;&lt;hot-air&gt;&lt;rework&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="12162" PostTypeId="2" ParentId="2653" CreationDate="2011-03-28T15:34:47.070" Score="0" ViewCount="" Body="&lt;p&gt;You might want to look into the ARRL QEX publication (http://www.arrl.org/qex).  Aimed more at experimenters/builders.  QST is also good, but is a balance between building and operating.&lt;/p&gt;&#xA;" OwnerUserId="1678" LastActivityDate="2011-03-28T15:34:47.070" />
  <row Id="12163" PostTypeId="1" CreationDate="2011-03-28T15:53:33.547" Score="0" ViewCount="70" Body="&lt;p&gt;Hello fella's&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am having a problem in trying to build pierce oscillator to work with my SMART Card reader design. I am using 3.58MHz oscillator, 74HCU04 gate IC for the NOT gate, and the 22pf capacitor and 1M resistor. But still, I was unable to get any clock pulse. I tried but I cant really figure out where things might have gone wrong in not been able to get the pulse. Thanks&lt;/p&gt;&#xA;" OwnerUserId="3632" LastActivityDate="2011-03-28T16:01:10.787" Title="Pierce Oscillator issues" Tags="&lt;oscillator&gt;" AnswerCount="2" />
  <row Id="12164" PostTypeId="2" ParentId="12163" CreationDate="2011-03-28T15:57:19.493" Score="1" ViewCount="" Body="&lt;p&gt;The Pierce oscillator requires two capacitors! See &lt;a href=&quot;http://en.wikipedia.org/wiki/Pierce_oscillator&quot; rel=&quot;nofollow&quot;&gt;this circuit&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The capacitor values depend on the crystal load capacitance; they are effectively in series so you need roughly twice the value of the load capacitance. You need to allow for stray capacitance.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-28T15:57:19.493" CommentCount="2" />
  <row Id="12165" PostTypeId="2" ParentId="12163" CreationDate="2011-03-28T16:01:10.787" Score="0" ViewCount="" Body="&lt;p&gt;Aren't you missing one capacitor? Also, you should separate the oscillator from other circuits by another inverter, otherwise you may be overloading it.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-03-28T16:01:10.787" CommentCount="1" />
  <row Id="12166" PostTypeId="2" ParentId="5294" CreationDate="2011-03-28T16:02:55.153" Score="0" ViewCount="" Body="&lt;p&gt;I keep CFLs out of my 'shack and antenna areas, but use them elsewhere.  They do seem to generate some ugly RF, but it's relatively low power so can be insulated with distance.  :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Still using incandescents in the shack at the moment as I happen to have them laying around.  Might as well use them.  Once I run out, I plan on LED lighting.  I don't like the limitations of the LED lighting, but I don't really see any viable options at this time.&lt;/p&gt;&#xA;" OwnerUserId="1678" LastActivityDate="2011-03-28T16:02:55.153" CommunityOwnedDate="2011-03-28T16:02:55.153" />
  <row Id="12167" PostTypeId="2" ParentId="11972" CreationDate="2011-03-28T16:15:41.353" Score="0" ViewCount="" Body="&lt;p&gt;On my shelf I have&#xA;B. P. Lathi. &quot;Modern Digital and Analog Communication Systems&quot;. 1983. (Should I upgrade to a later edition?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In section &quot;3.2: Line Coding&quot;, it has a description and frequency spectrum for a few line codes: on-off, polar, bipolar (pseudoternary), duobinary, split-phase (Manchester), high-density bipolar (HDB3). It mentions &quot;A list of codes ... can be found in Bylanski and Ingram.&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P. Bylanski and D. G. W. Ingram, &quot;Digital Transmission Systems&quot;, Peter Peregrinus Ltd., Herts., England, 1976&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-28T16:15:41.353" />
  <row Id="12168" PostTypeId="2" ParentId="12161" CreationDate="2011-03-28T16:47:51.107" Score="0" ViewCount="" Body="&lt;p&gt;I use the &lt;a href=&quot;http://www.hakkousa.com/AHPDirect/download/um/851e199903.pdf&quot; rel=&quot;nofollow&quot;&gt;Hakko 851&lt;/a&gt; station at my workbench and have had good success with it. I find that I can deal with chip resistors / capacitors and small ICs (SOICs, MSOPs) easily with it.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-03-28T16:55:26.283" LastActivityDate="2011-03-28T16:55:26.283" CommentCount="4" />
  <row Id="12169" PostTypeId="2" ParentId="12154" CreationDate="2011-03-28T17:16:31.057" Score="1" ViewCount="" Body="&lt;p&gt;It seems to me that it would be easier to create a solution that can withstand the 0.8 watts of heat, worst case continuous conditions than it would be to create a thermal shutdown.  0.8 watts isn't a lot in that size of case.  It's mainly a matter of spreading the heat out so it's not concentrated.  If the heat is spread out, it will more effectively dissipate through the plastic box.  For that amount of heat, you could use a small heat sink, or simply put about 1 or 2 square inches of copper plane on the PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if you must have a thermal shutdown, I would go with option 4:  An adjustable LDO with an Op-Amp.  Have the output of the op-amp go through an RC filter then to the ADJ pin of the LDO.  The RC filter would have to be tweaked to keep the whole thing stable while giving you the frequency response that you need.  The inputs to the op-amp are the input and output voltages.  This whole circuit is going to need tweaking depending on the op-amp, LDO, acceptable noise, etc.  I highly recommend simulating it first.  I don't see an option for attaching a file to this answer, otherwise I'd whip up a quick simulation and put the file here.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-28T17:16:31.057" />
  <row Id="12170" PostTypeId="2" ParentId="11234" CreationDate="2011-03-28T17:30:18.307" Score="2" ViewCount="" Body="&lt;p&gt;On my shelf I have &quot;Electronic Calculators&quot; by H. Edward Roberts, edited by Forrest M. Mims III. 1974.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's pretty educational about how people &lt;em&gt;used&lt;/em&gt; to build calculators in 1974. Many photos are of the complete life cycle of a mass-produced MITS calculator -- photos of the prototyping (a big spaghetti mess of wires), the PCB design (laying Rubylith on a drafting table), individual parts, assembly line, wave solder machine, and troubleshooting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ah, many things have changed since then.&#xA;Today's books usually avoid showing big spaghetti mess of wires.&#xA;Today's calculators avoid applying mains voltage directly to the calculator PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many things are still the same.&#xA;People still usually make a big spaghetti mess of wires while prototyping.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-28T17:30:18.307" />
  <row Id="12171" PostTypeId="2" ParentId="12161" CreationDate="2011-03-28T17:34:32.097" Score="0" ViewCount="" Body="&lt;p&gt;I would buy mid-top end Aoyue again ;-)&#xA;At least you can buy 5 of them for the price of Hakko ;-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally I use KADA 858D (even cheaper Aoyue clone) and it's perfect.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-28T17:34:32.097" />
  <row Id="12172" PostTypeId="2" ParentId="12161" CreationDate="2011-03-28T17:37:21.910" Score="0" ViewCount="" Body="&lt;p&gt;I use an Aoyue 968. Cheap and has a few issues, but for its price there isn't going to be too much to complain about. Temperature controlled soldering iron, temperature controlled hot air (with adjustable flow rate) and fume extractor.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-28T17:37:21.910" />
  <row Id="12173" PostTypeId="2" ParentId="12161" CreationDate="2011-03-28T17:49:48.830" Score="1" ViewCount="" Body="&lt;p&gt;I'll put a vote in for the &lt;a href=&quot;http://www.newark.com/metcal/hct-900-11/hand-held-convection-hot-air-tool/dp/66K6681?whydiditmatch=rel_default&amp;amp;matchedProduct=HCT-900&quot; rel=&quot;nofollow&quot;&gt;Metcal (now Oki) HCT-900&lt;/a&gt; Its basically the same price as the Hakko units but has a much better selection of tips, specifically for QFP/BQFP packages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, probably the best thing you can buy to ease rework is a convection pre-heater, if your not using one already.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-03-28T17:49:48.830" CommentCount="1" />
  <row Id="12174" PostTypeId="1" CreationDate="2011-03-28T18:43:24.070" Score="0" ViewCount="110" Body="&lt;p&gt;I have made temperature indicator using microcontroller P89V51. My temperature sensing IC is DS1621. I'm using LCD for the display..n ckt is working very fine,&#xA;Do I have to calibrate this IC?&#xA;If yes, then how can I?   &lt;/p&gt;&#xA;" OwnerUserId="3633" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-28T20:18:39.380" LastActivityDate="2011-03-28T20:18:39.380" Title="how to calibrate temperature sensor IC DS1621?" Tags="&lt;temperature&gt;" AnswerCount="2" />
  <row Id="12175" PostTypeId="1" AcceptedAnswerId="12184" CreationDate="2011-03-28T19:03:15.813" Score="5" ViewCount="107" Body="&lt;p&gt;My mother runs a small veterinary clinic. She is getting a new X-Ray machine that will need a network connection to send digital copies of the X-Ray to the server. I will be installing a wall plate with a few Ethernet jacks in the X-Ray room. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I need to do anything special like shielded cabling for this install? I am not worried about transmission errors that may occur during the split second the X-Ray is active, TCP can fix those, I am concerned about damaging the NIC card on the computer or router in the wiring closet due to some form of current induction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The cable will not be running in the direct path of the X-Ray beam just be in wall leading to the room. Am I being overly cautious or is this a legitimate concern? Also if I need to route under the path of the beam for some reason are there any consequences for that?&lt;/p&gt;&#xA;" OwnerUserId="1655" LastActivityDate="2011-03-28T21:03:05.897" Title="Runing network cable near X-Ray equipment" Tags="&lt;ethernet&gt;&lt;interface&gt;&lt;cables&gt;&lt;shielding&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12176" PostTypeId="1" AcceptedAnswerId="12430" CreationDate="2011-03-28T19:31:16.130" Score="3" ViewCount="115" Body="&lt;p&gt;I'm using the picdem 18F4550 with microchip v8.63 with the C18 compiler.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will enable PortA to set as input, I will connect a LDR on port RA0. Which is as following (I think):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TRISAbits.TRISA0 = 1; //&amp;lt;= set RA0 as input.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Now I want the value of the LDR (voltage/value if a led is on), can I say: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int colorLed = PortAbits.RA0;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And now in the variable of type int there is the value/voltage of my Led.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Correct me if I'm wrong.&lt;/p&gt;&#xA;" OwnerUserId="3618" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T21:00:47.203" LastActivityDate="2011-04-27T21:00:47.203" Title="Enable port RA0 as input and retrieve value LDR from led." Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;c&gt;&lt;microprocessor&gt;" AnswerCount="2" />
  <row Id="12177" PostTypeId="2" ParentId="12174" CreationDate="2011-03-28T19:45:31.690" Score="1" ViewCount="" Body="&lt;p&gt;In general the best way to find out if you need calibration is to check manufacturer's website. There you will probably be able to find product datasheet which will probably contain needed information. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the datasheet isn't available on manufacturer's website (or there isn't any website), search for &lt;code&gt;model_number datasheet&lt;/code&gt;. There are several sites on the Internet which catalog datasheets, so you may be able to obtain it even manufacturer isn't providing it anymore.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For your specific case, &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/2737&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; is the product site. Under technical documents, you will find &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/DS1621.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the second page, under OPERATION it is said that the sensor is already calibrated for measuring temperature in Celsius degrees, so no further calibration should be needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Furthermore is you read the command set part of the datasheet, you will find out that there is no command for calibration, so it should be impossible for user to calibrate the sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are having accuracy problems, take a look at page 13 of the datasheet. Accuracy is related to voltage, as show in the DC electrical characteristics table.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-28T19:55:31.890" LastActivityDate="2011-03-28T19:55:31.890" CommentCount="3" />
  <row Id="12178" PostTypeId="2" ParentId="12174" CreationDate="2011-03-28T20:03:52.337" Score="0" ViewCount="" Body="&lt;p&gt;You may consider the physical way. Go boil some water and make some ice. Two good calibration points for a sensor. You can use these to compensate for the error, assuming that it is linear.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-28T20:03:52.337" CommentCount="4" />
  <row Id="12179" PostTypeId="1" AcceptedAnswerId="12399" CreationDate="2011-03-28T20:16:31.880" Score="3" ViewCount="139" Body="&lt;p&gt;I am doing a space constrained board layout, in terms of surface area. So I found an inductor which is $15\mbox{ }\mu H$, $2.3\mbox{ }A_{RMS}$. I need about $3.5\mbox{ }A_{RMS}$, so I was thinking of paralleling two $8.2\mbox{ }\mu H$ ($2.7\mbox{ }A_{RMS}$) to get $16.4\mbox{ }\mu H$ at $5.4\mbox{ }A_{RMS}\mbox{ (max)}$, with each inductor on opposite sides of the board. Is this a viable solution?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-04-01T14:14:56.113" LastActivityDate="2011-04-01T14:14:56.113" Title="Is parallelling inductors a viable solution?" Tags="&lt;pcb&gt;&lt;inductor&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="12180" PostTypeId="2" ParentId="12179" CreationDate="2011-03-28T20:28:54.177" Score="3" ViewCount="" Body="&lt;p&gt;Parallel inductors don't add, that's capacitors. Inductors work like resistors in this respect. But yes, you should not have a problem with such solution.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-03-28T20:28:54.177" />
  <row Id="12181" PostTypeId="2" ParentId="12156" CreationDate="2011-03-28T20:35:13.547" Score="2" ViewCount="" Body="&lt;p&gt;&lt;em&gt;We are unable to reliably transmit single packets&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yeah, me either.&#xA;If you can find any wireless protocol anywhere that never drops a packet, please let us know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm guessing that you're working pretty &quot;close to the metal&quot; with this SDR, running simple experiments rather than using some tried-and-tested protocol. Here are a bunch of things that I often see go wrong. Perhaps if you're lucky you're only seeing one of these problems, and it's one of the easier-to-fix problems. Pretty much everyone building a wireless protocol from scratch bangs into several of these problems.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Perhaps bit-slicer is incorrectly slicing bits. The simplest on-off protocols need to discriminate between &quot;on&quot; and &quot;off&quot;. Most bit-slicers assume that a simple leaky average of the signal over the past N bits is approximately halfway between &quot;on&quot; and &quot;off&quot; and makes a good reference point. Halfway through a packet, that's a pretty good assumption. When you haven't transmitted anything for a few seconds, you need to transmit some dummy data -- a preamble -- with a good balance of 1 and 0 bits (often 01010101 &quot;UUUU&quot; in the simplest protocols). That data in the preamble will be incorrectly received, but it pushes the reference of the bit-slicer to a point where the important data in the packet can be sliced properly.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Perhaps the gain the the AGC is not set correctly. With ASK or more complex IQ modulation, the gain in the AGC needs to be set properly to decode symbols properly. If you haven't transmitted anything for a few seconds, the AGC cranks the gain all the way up, and most symbols (except the maximum-amplitude symbols) will be received incorrectly. Again, dummy data -- a preamble -- to push the gain of the AGC to a point where the important data in the packet can be decoded properly.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Perhaps the center frequency is not exactly right, or the I and Q phases are &quot;rotated&quot;. There are ways to detect and compensate for this -- typically using the known patterns near the end of the preamble.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Perhaps the symbol/bit timing is a fraction of a symbol/bit off. For very short packets, one of the 7 known &lt;a href=&quot;http://en.wikipedia.org/wiki/Barker_code&quot; rel=&quot;nofollow&quot;&gt;Barker codes&lt;/a&gt; is useful for re-aligning the bit timing.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Perhaps your bit timing is good, but your byte alignment is off by some integer number of bits. Many people use 10 bits -- a start bit, 8 data bits, and a stop bit -- even on synchronous communication systems, because it makes debugging and byte-alignment ever so much easier.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Perhaps your bit and byte alignment is fine, but the packet framing is off -- the software is picking up some random bytes in the middle of a packet, an interpreting them as the &quot;destination&quot; and &quot;length&quot; fields of the packet header. Some people reserve the &quot;newline character&quot; for the start-of-packet character (the last byte in the preamble, or the first byte of the packet header, depending on your point of view), and forbid that character from ever occurring inside the packet, in order to make it easier to properly frame each packet, and debug when things go wrong.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;All of the above issues occur even when there is practically no external noise.&#xA;With the above issues, if you send a packet enough times, sometimes the packet will happen to line up and get through just fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you occasionally get a little noise, there are simple techniques to work around it: CRC, acknowledgment, retry-on-timeout.&#xA;In cases where I accidentally unplugged the antenna, or I rebooted the receiver, the transmitter may re-try transmitting the same packet hundreds of times before it gets a good acknowledgment in return.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you get a lot of noise, there are terribly complicated techniques to work around it -- trellis coded modulation, iterative Viterbi decoding, forward error correction, frequency-hopping, noise detection and avoidance, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikibooks.org/wiki/Serial_Programming/Forming_Data_Packets&quot; rel=&quot;nofollow&quot;&gt;Serial Programming/Forming Data Packets&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-28T20:35:13.547" />
  <row Id="12182" PostTypeId="2" ParentId="12176" CreationDate="2011-03-28T20:57:19.567" Score="4" ViewCount="" Body="&lt;p&gt;To read an analogue voltage you need to use the PIC's ADC (Analogue to Digital Converter).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a tutorial: &lt;a href=&quot;http://www.roboticsguy.com/tutorials/pic-microcontrollers/configuring-the-pic18f4550-10-bit-adc-module&quot; rel=&quot;nofollow&quot;&gt;http://www.roboticsguy.com/tutorials/pic-microcontrollers/configuring-the-pic18f4550-10-bit-adc-module&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-28T20:57:19.567" CommentCount="1" />
  <row Id="12183" PostTypeId="2" ParentId="12179" CreationDate="2011-03-28T20:58:03.357" Score="2" ViewCount="" Body="&lt;p&gt;Paralleling will give you 4.1uH @5.4Arms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Series will give you 16.4uH @2.7Arms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll need four of those inductors to meet your specs.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-03-28T20:58:03.357" CommentCount="8" />
  <row Id="12184" PostTypeId="2" ParentId="12175" CreationDate="2011-03-28T21:03:05.897" Score="4" ViewCount="" Body="&lt;p&gt;No, you do not need to do anything special. We have X-ray generators and Digital Imaging devices everywhere at my place of work, we run cable around them, in front of them sometimes(tie comes loose) and all around them. We have never had issues.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other forms of radiation can have very negative affects on materials and electronics, but on ethernet cable we do not see negative affects from these either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;X-Rays are not that terrible, it is just not a good idea to get a dose from them repeatedly throughout the day. This is why the therapist is placed behind a bit of lead.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-03-28T21:03:05.897" CommentCount="6" />
  <row Id="12185" PostTypeId="2" ParentId="12125" CreationDate="2011-03-28T21:40:33.513" Score="1" ViewCount="" Body="&lt;p&gt;If I want to tiker with one isolated component that has not too much pins (let's say less than 40), I use a breakout board. When more is involved it becomes impractical, because you have to hook so many wires from the breakouts to the breadboard that the mess turns it highly probable that you'll make a mistake.&#xA;What I do sometimes is make a &quot;partial&quot; board, in which I have the high-density components interconnected and hook just their ends (usually one or two SPI ports) to the breadboard.&#xA;I do the boards myself on the first design round, and have it fabbed when I arrive to the final design - or sometimes when the prototype board is too complex and I'm unable to make it myself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know two good ways to make PCB at home. One is with toner transfer paper and the other is with photosensitive PCBs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the first you print your PCB to that special paper using a laser printer, and then press this paper against the board using a heat source (can be an old iron). After that you use water to wash out the paper and the toner is attached to the copper, ready to etch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the photosensitive board you print the circuit to a transparent sheet, place it on the board and expose it to UV light; then you apply a developer and again it's ready to etch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first method is cheaper (assuming you already have a laser printer) but I found the limit for vias to be about 0.5 mm. With the second you can have 0.3 mm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some links:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.pulsarprofx.com&quot; rel=&quot;nofollow&quot;&gt;http://www.pulsarprofx.com&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.injectorall.com&quot; rel=&quot;nofollow&quot;&gt;http://www.injectorall.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1078" LastActivityDate="2011-03-28T21:40:33.513" />
  <row Id="12186" PostTypeId="1" CreationDate="2011-03-28T21:54:18.383" Score="3" ViewCount="255" Body="&lt;p&gt;I would like to build a switched-mode DC-to-DC converter which should support up to 4000 W of power. It should be able to act as a CCCV power-supply, so supply a constant current Imax up to the point where voltage Vmax is required to have that current, and then supply a constant voltage Vmax with a diminishing current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like it to be modular, to be able to swap-out a few components to change the Imax and Vmax. I do not want to have knobs to change the Imax and Vmax like on a general-purpose lab power supply, as these parameters will be changed very rarely, when I change the battery configurations, maybe every few months, and I do not want the risk of me or someone else accidentally turning the knobs, and then connecting it to the batteries with wrong parameters which could kill very costly batteries - as I want this to support up to 4kW, you can imagine the batteries will be large. No, I don't have batteries supporting such current yet, but within years I could have, so I want this device to be easily expandable as my battery park grows.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT - I modified my expectations, which I hope will make it easier to build:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The configuration I would like to have:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Input: rectified 230VAC mains (that will be something around 325VDC?)&lt;/li&gt;&#xA;&lt;li&gt;Output: CCCV with exactly Imax=15.0A, Vmax=230.4VDC&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Parameters:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;input and output electrically isolated&lt;/li&gt;&#xA;&lt;li&gt;low ripple (1% is OK, 2.5% is too much)&lt;/li&gt;&#xA;&lt;li&gt;efficiency at least 90%, I am willing to spend up to 10% more for every extra 1% efficiency that I gain over 90%.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In the future I would like to be able to install modules to be able to accept a different voltage input, for example from solar panels, so a design that will accept a wide voltage input range (say 100-400VDC) would be a plus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would be grateful for some basic pointers into how to build such a beast, possibly using some ready-made blocks, but I don't want to buy the whole device, as I want it to be modular and expandable (unless some DIY kit is available). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could take four Chinese 48V (adjustable to 58.8V) 15A CCCV supplies for less then 200$ each and connect them in series to do the job, but then I have &quot;black boxes&quot; which if a single component inside brakes, not having the schematic will be difficult to fix. So I would prefer to spend even twice as much for a modular, self-made design, so if something breaks I can easily exchange the faulty element, and if my desired voltages change I can just rebuild part of the device without buying a whole new one.&lt;/p&gt;&#xA;" OwnerUserId="1691" LastEditorUserId="1691" LastEditorDisplayName="" LastEditDate="2011-04-05T13:04:08.073" LastActivityDate="2011-04-05T13:04:08.073" Title="how to build a high-power (4kW) switched-mode DC-DC converter?" Tags="&lt;power-supply&gt;&lt;power&gt;&lt;dc&gt;&lt;dc-dc&gt;&lt;conversion&gt;" AnswerCount="5" CommentCount="7" FavoriteCount="1" />
  <row Id="12187" PostTypeId="1" AcceptedAnswerId="12205" CreationDate="2011-03-28T22:06:01.550" Score="1" ViewCount="96" Body="&lt;p&gt;Here's a diagram of what I'm working with:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/nNCIo.png&quot; alt=&quot;http://i.imgur.com/nNCIo.png&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ground... I can't figure out where I should ground it to. Chassis ground? Input ground? No ground? This is for a stereo, to bring the 10v outputs down to a reasonable level. &lt;/p&gt;&#xA;" OwnerUserId="3634" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-28T23:09:29.050" LastActivityDate="2011-03-29T02:28:00.080" Title="Stereo line-level converter: Odd grounding?" Tags="&lt;capacitor&gt;&lt;resistor&gt;&lt;ground&gt;" AnswerCount="2" CommentCount="8" FavoriteCount="2" />
  <row Id="12189" PostTypeId="2" ParentId="12179" CreationDate="2011-03-28T22:13:18.913" Score="6" ViewCount="" Body="&lt;p&gt;That is not a viable solution. You are correct that paralleling would allow you to pass more total current, but the effective inductance would be decreased.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The equivalent inductance for parallel inductors is $$L_{equiv}=\Bigl( \frac 1 L_1 + \frac 1 L_2 + ... + \frac 1 L_n  \Bigr) ^{-1}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The equivalent inductance for series inductors is $$L_{equiv}=L_1+L_2+...+L_n$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For series inductors, the equivalent current rating would basically be equal to the lowest rated inductor in the circuit. For example, for a 2Arms inductor in series with a 1Arms inductor, the equivalent current rating would be 1Arms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For parallel inductors, the (DC) current would be split evenly between them so the total current through the network could be $I_{total}=nI_{rated}$ where $n$ is the number of inductors paralleled and $I_{rated}$ is again the lowest of the current ratings. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For $8.2\mu\text{H}=L$ you would need eight of those inductors to meet your spec. That's two parallel branches each with four series inductors. This would split the 3.5Arms current evenly between each branch (1.75Arms in each) and yield an effective inductance of $(1/2)(4)(8.2\mu\text{H})=(2)(8.2\mu\text{H})=16.2\mu \text{H}$. I would guess that this approach would not save board space.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your best bet is probably to find another inductor with a higher current rating. Or as suggested in the comments to Markrages's answer, you could parallel two larger valued inductors. Whichever uses the least space sounds like it would be the best solution.&lt;/p&gt;&#xA;" OwnerUserId="3635" LastActivityDate="2011-03-28T22:13:18.913" CommentCount="0" />
  <row Id="12190" PostTypeId="2" ParentId="12187" CreationDate="2011-03-28T22:26:48.770" Score="1" ViewCount="" Body="&lt;p&gt;Put a capacitor between the input return ground and your system ground, and also put a high value resistor (1 Mohm probably) as well.   That way, each ground can stay at their respective ground potential, but the high-ohm resistor will &quot;pull down&quot; either grounds that might be floating.   The capacitor will allow signal current to flow on the ground line as needed.  Make sure you have a high enough voltage capacitor to accomodate the signal voltage AND the likely ground voltage differential.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-03-28T22:26:48.770" />
  <row Id="12191" PostTypeId="2" ParentId="12125" CreationDate="2011-03-28T22:31:35.193" Score="0" ViewCount="" Body="&lt;p&gt;Sometimes, such a QFP device will have either a demo board that you can buy with headers broken out, or have a family equivalent device in a smaller/bigger package (which either is available in DIP or have an easy to prototype demo board).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will let you get started in a hurry and validate your design, and let you get on the software while you are still working on designing/building the &quot;real&quot; PCB.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-03-28T22:31:35.193" />
  <row Id="12192" PostTypeId="2" ParentId="11859" CreationDate="2011-03-28T22:48:50.623" Score="0" ViewCount="" Body="&lt;p&gt;Make sure both the PCB and the strips are clean of any debris - so that there are no gap irregularities.  Also, you need to make sure you have the right amount of clamping pressure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you need to let the trapped micro air gap get squeezed out -- if you're lucky, the elastomeric strip will &quot;seat&quot; with time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for graphite -- graphite lubricating powder is available at home depot -- it's a dirty dusty mess, but takes the squeak out of door hinges -- and perhaps might work for this application, as suggested by others.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-03-28T22:48:50.623" />
  <row Id="12193" PostTypeId="2" ParentId="11978" CreationDate="2011-03-28T22:55:59.790" Score="2" ViewCount="" Body="&lt;p&gt;If your main worry is to have a wide dynamic range for any given &quot;sensor&quot;, you might consider using DAC's (or even just MPU-pin controlled voltage sources) to adjust the amplifier offset/gain to alter the system performance for different materials.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also follow this variable gain stage with a charge integration circuit so that you can gain fine tune signal sensitivity by adjusting the &quot;exposure&quot; period.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-03-28T22:55:59.790" CommentCount="1" />
  <row Id="12194" PostTypeId="2" ParentId="12038" CreationDate="2011-03-28T23:01:04.450" Score="0" ViewCount="" Body="&lt;p&gt;Do you have control over the waveform from the low-voltage side?  If so, maybe a rectifier voltage double circuit can be used to charge pump to the higher voltage.  The only gotcha with this approach is that you need to have the low-voltage side output go from a &quot;high/low&quot; signaling to a &quot;carrier/no carrier&quot; signaling.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-03-28T23:01:04.450" />
  <row Id="12195" PostTypeId="1" AcceptedAnswerId="12838" CreationDate="2011-03-28T23:16:14.900" Score="1" ViewCount="93" Body="&lt;p&gt;Is it possible/practical to use a heat gun instead of an iron to transfer toner when making your own PCBs?  Can you get a uniform heat pattern without for a small board?  Is enough heat applied from the heat gun to actually transfer the toner?&lt;/p&gt;&#xA;" OwnerUserId="3424" LastActivityDate="2011-04-10T18:47:56.590" Title="Using a heat gun to transfer toner onto DIY PCB?" Tags="&lt;pcb-fabrication&gt;&lt;heat&gt;" AnswerCount="3" />
  <row Id="12196" PostTypeId="2" ParentId="12186" CreationDate="2011-03-28T23:21:17.593" Score="0" ViewCount="" Body="&lt;p&gt;You won't do it for a few hundred $&#xA;200VDC input would be OK for most universal-input mains SMPS units (if it doesn't confuse the PFC circuitry) so you might luck out on a surplus unit.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-03-28T23:21:17.593" />
  <row Id="12197" PostTypeId="2" ParentId="12195" CreationDate="2011-03-28T23:28:19.443" Score="2" ViewCount="" Body="&lt;p&gt;From my experience with iron-based toner transfer you really need to apply lots of pressure to get the toner to transfer properly. I tried lots of different techniques (&gt;10 tries) before finding the correct paper, correct/sufficient pressure across the board was important.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suggest you try with an iron first and then move on to heat guns. I'm interested in your findings.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-03-28T23:28:19.443" />
  <row Id="12198" PostTypeId="1" AcceptedAnswerId="12206" CreationDate="2011-03-29T00:26:07.347" Score="2" ViewCount="158" Body="&lt;p&gt;I've got a 1 F electrolytic capacitor and it seems to have developed a short. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I never used it before and its brand new. It reads zero resistance only when I connect positive lead of my DMM to its negative lead and negative lead of my DMM to its positive lead. In the other direction, there's no short. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-30T03:52:20.217" Title="Is it possible for electrolytic capacitor to develop a short in one way only?" Tags="&lt;capacitor&gt;" AnswerCount="3" CommentCount="10" />
  <row Id="12200" PostTypeId="1" AcceptedAnswerId="12201" CreationDate="2011-03-29T00:58:05.633" Score="-1" ViewCount="67" Body="&lt;p&gt;Do you have some source code of an example of a cognitive radio?.&lt;/p&gt;&#xA;" OwnerUserId="3628" LastActivityDate="2011-03-29T01:13:00.897" ClosedDate="2011-03-29T04:02:52.963" Title="cognitive radios" Tags="&lt;radio&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12201" PostTypeId="2" ParentId="12200" CreationDate="2011-03-29T01:13:00.897" Score="0" ViewCount="" Body="&lt;p&gt;Exercising my google-fu:  the &lt;a href=&quot;http://www.ltsnet.net/oscr/&quot; rel=&quot;nofollow&quot;&gt;Open Source Cognitive Radio project&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="3597" LastActivityDate="2011-03-29T01:13:00.897" CommentCount="3" />
  <row Id="12202" PostTypeId="1" AcceptedAnswerId="12212" CreationDate="2011-03-29T01:16:19.757" Score="1" ViewCount="89" Body="&lt;p&gt;I have set up a circuit similar to the one &lt;a href=&quot;http://luckylarry.co.uk/arduino-projects/control-a-dc-motor-with-arduino-and-l293d-chip/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. I was wondering instead of the 10 uf 50V capacitor, would A 100 uf 16 V or a 47 uf 6.3V capacitor work? I am asking because I don't know how much kickback into the hbridge there is. I know there can be enough to damage it, but how much is that? Also, how would I determine the amount of current used by a 4v motor?&lt;/p&gt;&#xA;" OwnerUserId="2873" LastEditorUserId="2873" LastEditorDisplayName="" LastEditDate="2011-03-29T03:17:09.260" LastActivityDate="2011-03-29T08:53:29.843" Title="Amount of kickback from dc motor" Tags="&lt;voltage-regulator&gt;&lt;dc-motor&gt;" AnswerCount="1" />
  <row Id="12203" PostTypeId="2" ParentId="12198" CreationDate="2011-03-29T01:16:24.670" Score="2" ViewCount="" Body="&lt;p&gt;The design of electrolytic capacitors requires them to be polarized. With an electrolytic, the end with the stripe on the body is negative.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you connect your DMM to it in that way, the current flows correctly.&lt;/p&gt;&#xA;" OwnerUserId="3597" LastEditorUserId="3597" LastEditorDisplayName="" LastEditDate="2011-03-29T17:14:24.913" LastActivityDate="2011-03-29T17:14:24.913" CommentCount="3" />
  <row Id="12204" PostTypeId="2" ParentId="12186" CreationDate="2011-03-29T02:13:06.390" Score="4" ViewCount="" Body="&lt;p&gt;Sadly, what you are asking for is impractical for a one-off design. Someone may possibly offer you a complete DIY design, but you overall specification is so high that you would find it hard to build unless you are already expert in such matters. More on that below, but your most likely chance of success is to look for top quality surplus units that either suit your need exactly or which can be adapted relatively easily. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doing it yourself, one mistake could lead to the destruction of electronics (say main MOSFET switches) worth most of your budget.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;95% efficiency at 2 kW means 100 Watts total losses.&#xA;At 65 A output, for resistive losses alone to be less that 100 Watts requires &#xA;I^2.R &amp;lt;= 100 or resistance to be under about 20 milliohm. This includes winding resistance, tracks, connector resistance and more. This is doable but with vast difficulty. But, that doesn't leave any margin for any other losses. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At 28V out, 0.5 volt rectification loss will by itself result in 0.5/28 ~= 1.8% losses. A large Shottky diode MAY get down to 0.5V in that application - but probably will drop a larger voltage so lose even more than 1.8%. Synchronous rectification is about the only superior option - but even to equal a 0.5 V Schottky performance requires a genuine on resistance in your synchronous switch of R= V/I = 0.5/65 = about 7 milliohms.  Again, that is doable, but you require top specification parts and vast amounts of skill and care.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And reasonable quality batteries (presumably deep cycle and presumably rated for some hours of operation at this power level) will cost you far more than your inverter budget. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Overall, a more realistic approach is to gain some experience by buying the best surplus equipment that you can get for your budget and seeing how well it works, and investigating where the main losses are and what may be able to be done to reduce them. You should be able to buy surplus equipment for far less than you can build something equivalent yourself. If you are capable of building something like this and adequately understanding what needs to be done, then you could buy surplus equipment that has been damaged and rebuild or repair it. If that sounds too hard then doing it yourself from the start is liable to be harder. &lt;/p&gt;&#xA;" OwnerUserId="3288" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-29T14:59:20.083" LastActivityDate="2011-03-29T14:59:20.083" CommunityOwnedDate="2011-03-29T02:13:06.390" CommentCount="4" />
  <row Id="12205" PostTypeId="2" ParentId="12187" CreationDate="2011-03-29T02:28:00.080" Score="3" ViewCount="" Body="&lt;p&gt;Ok, so here's the deal.  First you need to determine if the output of the head unit is balanced or unbalanced.  This is fairly easy to figure out.  First, find a GND connection.  This could be a signal on another connector, or use the chassis ground.  With the unit off, measure the resistance from GND to the negative output (left or right channel, doesn't matter).  If the resistance is nothing (less than 1 ohm) then you have an unbalanced output, more than 1 ohm and you have a balanced output.  Next, look at the diagrams I've included here (you might have to enlarge them to make all the lines show up, right click on the image and select &quot;View Image&quot; or something similar):&#xA;&lt;img src=&quot;http://i.imgur.com/ygGsm.png&quot; alt=&quot;Audio Adapters&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;From those diagrams, pick the one that matches what you need.  You'll probably need the balanced to unbalanced, or unbalanced to unbalanced.  I've included the other two for completeness sake, and for the sake of explanation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first, balanced to balanced, has three sections.  The first is a balanced voltage divider made from R1-R3.  It is important to note that R1 and R2 must have the same value.  C1 and C2 are the DC blocking caps.  The higher the cap value used, the lower the frequency response.  1 uF will work for some things, but 10 uF is better.  Values up to 68 uF is not unreasonable.  Then finally R4 is used to make the output tend to settle to zero volts when the thing is turned off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the unbalanced out versions you'll notice that R2 and R3 are connected in series.  These could (and should) be replaced with a single resistor, but I left them separate to show that their functionality has not gone away when compared to balanced in-balanced out. &#xA;These unbalanced out versions are also similar to your diagram.  To make the similarities more obvious, R1=4.7K and R2+R3=680 ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ultimate way to do this is with an transformer.  I show this only for amusement, as a good quality audio transformer will run about US$100.  Not worth it for most applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should also point out that I drew the caps as a polarized cap.  For this application it's better that the + terminal be on the input side, but this isn't true for other applications.  I recommend using a simple aluminum electrolytic cap.  There is the chance the cap will be reverse biased (a.k.a. reverse polarity), but that's OK in this application.  There are better caps to use, but they are going to be expensive and have little audible benefit over the aluminum electrolytic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this is useful!&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-29T02:28:00.080" CommentCount="9" />
  <row Id="12206" PostTypeId="2" ParentId="12198" CreationDate="2011-03-29T03:33:36.427" Score="7" ViewCount="" Body="&lt;p&gt;It sounds like the capacitor is functioning correctly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Large capacitors are normally polarised with positive/negative terminals, so they only work one way which is why you not getting a short in one direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason you appear to have a short in the other direction is because the capacitor is not charged, and your multimeter is charging the capacitor as it reads the resistance. If you held your multimeter on the capacitor for long enough it will become fully charged and your meter would change to read an open circuit. Don't bother trying this with a 1 farad though, it will likely take a long time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it sounds like everything is good with your capacitor.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-29T03:33:36.427" CommentCount="5" />
  <row Id="12207" PostTypeId="1" AcceptedAnswerId="12208" CreationDate="2011-03-29T04:00:13.013" Score="0" ViewCount="73" Body="&lt;p&gt;I'm trying to create a circuit that will pulse out (short pulse) whenever it passes a certain threshold going upwards and another one to detect going downwards. I was thinking of using delay to achieve this... but I dont know how to really go about it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be appreciated, thanks in advance!&lt;/p&gt;&#xA;" OwnerUserId="2985" LastActivityDate="2011-03-29T12:43:03.070" Title="Threshold activated circuit" Tags="&lt;filter&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="12208" PostTypeId="2" ParentId="12207" CreationDate="2011-03-29T06:31:09.047" Score="2" ViewCount="" Body="&lt;p&gt;Use a comparator to detect the treshold crossing. Apply this signal to both inputs of an XOR-gate, one directly, the other delayed. You can use a few gates to create the delay. The output of the XOR-gate will give a short positive pulse each time you cross the treshold. The width of this pulse is determined by the delay introduced by the gates. If you use slow logic like standard CMOS (CD4000 series) you'll get a few tens of nanoseconds per gate. If you need much longer pulses, then use this short pulse to trigger an MMV (monostable multivibrator).&lt;br&gt;&#xA;Use an XNOR instead of an XOR-gate if you want negative pulses.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-03-29T06:31:09.047" CommentCount="3" />
  <row Id="12210" PostTypeId="1" AcceptedAnswerId="12231" CreationDate="2011-03-29T07:43:13.417" Score="1" ViewCount="144" Body="&lt;p&gt;I am designing a board with Ethernet input, but would like to have the Ethernet re-routed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the board should have two RJ-45 connectors, one which is the main Ethernet (board is using this port for accessing the network), and another which is just re-routing of Ethernet signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Ethernet) --&gt; My Board --&gt; (Ethernet) --&gt; PC(or another board).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have looked around for a description, circuit or chip for doing this, but with no luck.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have found the passive 3-port Ethernet hub, but I'm not sure whether that circuit is any good for my application.&lt;/p&gt;&#xA;" OwnerUserId="3041" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-29T11:53:36.357" LastActivityDate="2011-03-29T15:33:28.420" Title="Ethernet two-port hub (re-routing)" Tags="&lt;ethernet&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="12211" PostTypeId="2" ParentId="5294" CreationDate="2011-03-29T08:15:26.857" Score="0" ViewCount="" Body="&lt;p&gt;I noticed that EMC test labs do not use CFLs in the chamber but stick to mains tungsten.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-03-29T08:15:26.857" CommunityOwnedDate="2011-03-29T08:15:26.857" />
  <row Id="12212" PostTypeId="2" ParentId="12202" CreationDate="2011-03-29T08:47:34.977" Score="2" ViewCount="" Body="&lt;p&gt;The 10 uf 50V capacitor you are talking about looks like its connected to the Power rails, and it is used to smooth out the power lines. Depending on your power supply and voltage you are using you can switch out the cap for another value, I would suggest at least double the voltage and a similar capacity. Check out this question for a better explanation.&#xA; &lt;a href=&quot;http://electronics.stackexchange.com/questions/2262/smoothing-capacitors-what-size-and-how-many&quot;&gt;Smoothing capacitors: what size and how many?&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the kickback that you are talking about is usually quite high and is taken care of by the motor driver, not something you need to worry about in this example,but double check the datasheet to be sure. when creating your own motor driver you will need to consider these conditions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;as for your 4V motor, best way to measure is hook it up to a 4V source with an multimeter in series and turn it to measure milli amps and run it for a few seconds and get the running current, next if possible stall the motor for no more then 2 secs and read the current. That will tell you your running current and stall current. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2060" LastEditorDisplayName="" LastEditDate="2011-03-29T08:53:29.843" LastActivityDate="2011-03-29T08:53:29.843" CommentCount="3" />
  <row Id="12213" PostTypeId="1" AcceptedAnswerId="12278" CreationDate="2011-03-29T10:17:45.870" Score="1" ViewCount="108" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a project, I want to measure weight with the resolution of 1 gram. Things I want to weigh, are max of 6 grams and I need to diffrentiate between a 5 gram thing and a 6 gram thing.... So I would require a Load cell with resolution of 1 gram.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I searched in Local Market as well as online but I couldn't find a good one.... Can anybody have suggestions what can I do?? Or Links where such load cells are available will be way good....If anyone used such load cells then...then I would be the happiest person on earth! :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. I been to  &lt;a href=&quot;http://www.omega.com/guides/loadcells.html&quot; rel=&quot;nofollow&quot;&gt;omega.com&lt;/a&gt; but these are very costly.... If no other alternative.... I have to choose them or close the project.... Second option would be easy for me! :(&lt;/p&gt;&#xA;" OwnerUserId="2574" LastActivityDate="2011-05-24T04:46:01.273" Title="Load cell required with resolution of 1 gram" Tags="&lt;sensor&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="12214" PostTypeId="2" ParentId="12210" CreationDate="2011-03-29T10:49:37.213" Score="1" ViewCount="" Body="&lt;p&gt;The obvious answer is the 3-port passive ethernet hub as seen previously in the question &lt;a href=&quot;http://electronics.stackexchange.com/questions/10864/building-a-passive-ethernet-hub-with-anti-parallel-diodes&quot;&gt;&quot;Building a passive ethernet hub with anti-parallel diodes&quot;&lt;/a&gt;. Giving you a more specific answer is hard as you don't give any requirements for your application. The passive version is &quot;usually sufficient if you know its limitations&quot;.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-03-29T10:49:37.213" CommentCount="3" />
  <row Id="12215" PostTypeId="1" CreationDate="2011-03-29T11:05:49.587" Score="1" ViewCount="150" Body="&lt;p&gt;I need to save space on PCB and have to convert voltage from +48 to +9, -9 and virtual ground. Is there a single IC that could do that?&lt;/p&gt;&#xA;" OwnerUserId="3641" LastActivityDate="2011-05-02T22:13:56.340" Title="Voltage regulator IC with positive and negative voltage output" Tags="&lt;voltage-regulator&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="12216" PostTypeId="2" ParentId="12207" CreationDate="2011-03-29T11:38:44.810" Score="1" ViewCount="" Body="&lt;p&gt;Here is the circuit made out of two opamps:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/fFNFY.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the simulation for Vthreshold = 1V&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2JQ2I.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The width of the pulse can be set by value of C1 (the bigger, the longer). Output should be followed by something with high input impedance (CMOS logic, or another opamp), otherwise it will distort the pulse.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-03-29T11:38:44.810" />
  <row Id="12217" PostTypeId="1" CreationDate="2011-03-29T11:55:18.323" Score="6" ViewCount="360" Body="&lt;p&gt;I'm looking for a simple electronic &lt;a href=&quot;http://en.wikipedia.org/wiki/Geiger_counter&quot; rel=&quot;nofollow&quot;&gt;Geiger counter&lt;/a&gt; element. In my design I need to detect radiation and did not know what my options were for components to detect radiation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What components exist for my need and what kind of complexity is associated with them?&lt;/p&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-29T14:38:57.233" LastActivityDate="2011-05-27T15:57:10.407" Title="Is there a simple Geiger counter component?" Tags="&lt;sensor&gt;&lt;radiation&gt;&lt;radiation-sensor&gt;" AnswerCount="6" CommentCount="12" FavoriteCount="2" />
  <row Id="12218" PostTypeId="2" ParentId="12207" CreationDate="2011-03-29T12:17:05.683" Score="1" ViewCount="" Body="&lt;p&gt;I'd use a small MCU, like a PIC, which has a comparator. The software will be quite trivial. It has the advantage that it's a one-chip (and two resistors) solution, and should be cheaper than the other proposed techniques. It would also be a lot more compact, if one of the tiny PIC10F200 six-lead devices was used.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-29T12:43:03.070" LastActivityDate="2011-03-29T12:43:03.070" CommentCount="5" />
  <row Id="12219" PostTypeId="1" AcceptedAnswerId="12221" CreationDate="2011-03-29T12:24:13.750" Score="1" ViewCount="140" Body="&lt;p&gt;What's the cheapest way to detect vibration with Arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the vibration sensor that I need?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to detect PING PONG NET vibration and light on led if touched.&lt;/p&gt;&#xA;" OwnerUserId="3359" LastEditorUserId="3359" LastEditorDisplayName="" LastEditDate="2011-03-29T12:45:02.200" LastActivityDate="2011-03-29T13:34:26.277" Title="What's the cheapest way to detect vibration with Arduino?" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;components&gt;&lt;piezoelectricity&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="12220" PostTypeId="1" CreationDate="2011-03-29T12:29:03.410" Score="0" ViewCount="70" Body="&lt;p&gt;Ok, so I reinstalled my development enviroment on the mac using the latest build of avr-gcc (4.4.2), avr-libc and avrdude from the Fink project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Problem is when compiling I keep on getting a linker issue &quot;multiple definition of ...&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have narrowed it down to a floating point issue associated with &quot;libm.a&quot; (using strtod()). All indications says to just include this library, but i'm unsure of how to do this in my Make file (below).&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;DEVICE     = atmega128&#xA;CLOCK      = 8000000&#xA;PROGRAMMER = -c stk600 -P usb&#xA;OBJECTS    = main.o a2d.o buffer.o gps.o nmea.o uart2.o vt100.o rprintf.o timer128.o tsip.o&#xA;FUSES      = -U hfuse:w:0x99:m -U lfuse:w:0xC2:m&#xA;&#xA;AVRDUDE = avrdude $(PROGRAMMER) -p $(DEVICE)&#xA;COMPILE = avr-gcc -std=gnu99 -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE)&#xA;&#xA;all:    main.hex&#xA;&#xA;.c.o:&#xA;    $(COMPILE) -c $&amp;lt; -lm -o $@&#xA;&#xA;.S.o:&#xA;    $(COMPILE) -c $&amp;lt; -lm -o $@&#xA;&#xA;.c.s:&#xA;    $(COMPILE) -S $&amp;lt; -lm -o $@&#xA;&#xA;flash:  all&#xA;    $(AVRDUDE) -U flash:w:main.hex:i&#xA;&#xA;fuse:&#xA;    $(AVRDUDE) $(FUSES)&#xA;&#xA;install: flash fuse&#xA;&#xA;load: all&#xA;    bootloadHID main.hex&#xA;&#xA;clean:&#xA;    rm -f main.hex main.elf $(OBJECTS)&#xA;&#xA;main.elf: $(OBJECTS)&#xA;    $(COMPILE) -lm -o main.elf $(OBJECTS)&#xA;&#xA;main.hex: main.elf&#xA;    rm -f main.hex&#xA;    avr-objcopy -j .text -j .data -O ihex main.elf main.hex&#xA;&#xA;disasm: main.elf&#xA;    avr-objdump -d main.elf&#xA;&#xA;cpp:&#xA;    $(COMPILE) -E main.c&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3309" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-04-28T18:58:09.800" LastActivityDate="2011-04-28T18:58:09.800" Title="Mac based AVR development issue" Tags="&lt;c&gt;&lt;compiler&gt;&lt;osx&gt;&lt;avr-gcc&gt;" AnswerCount="1" />
  <row Id="12221" PostTypeId="2" ParentId="12219" CreationDate="2011-03-29T12:35:49.477" Score="1" ViewCount="" Body="&lt;p&gt;Piezo sensors are cheap, reliable and designed for the purpose you suggest - &lt;a href=&quot;http://www.arduino.cc/en/Tutorial/Knock&quot; rel=&quot;nofollow&quot;&gt;arduino tutorial&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the uk, &lt;a href=&quot;http://www.bitsbox.co.uk/sensors.html#sound&quot; rel=&quot;nofollow&quot;&gt;bitsbox&lt;/a&gt; has one for 75p. You can probably find others cheaper, or salvage from electronic toys.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT following poster's clarification of use:&#xA;Sound is vibration through the air, I see no reason why a piezo sensor cannot accomplish what you suggest, but the form factor may not be ideal for fixing to ping pong nets! I think &lt;a href=&quot;http://www.sparkfun.com/products/8606&quot; rel=&quot;nofollow&quot;&gt;a flex sensor&lt;/a&gt; would be more suitable, sewn into the top of the net.&lt;/p&gt;&#xA;" OwnerUserId="623" LastEditorUserId="623" LastEditorDisplayName="" LastEditDate="2011-03-29T13:34:26.277" LastActivityDate="2011-03-29T13:34:26.277" CommentCount="1" />
  <row Id="12222" PostTypeId="2" ParentId="12220" CreationDate="2011-03-29T13:00:43.200" Score="2" ViewCount="" Body="&lt;p&gt;Your makefile should compile each C file into object code, then use the linker to combine the objects with libraries. You don't need &lt;code&gt;-lm&lt;/code&gt; for each compiled file.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your makefile, you are using &lt;code&gt;$(COMPILE)&lt;/code&gt; as both compiler and linker, which is fine for GCC, but is probably confusing matters.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;all:    main.hex&#xA;&#xA;.c.o:&#xA;    $(COMPILE) -c $&amp;lt; -o $@&#xA;&#xA;.S.o:&#xA;    $(COMPILE) -c $&amp;lt; -o $@&#xA;&#xA;.c.s:&#xA;    $(COMPILE) -S $&amp;lt; -o $@&#xA;&#xA;main.elf: $(OBJECTS)&#xA;    $(COMPILE) -lm -o main.elf $(OBJECTS)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-29T13:00:43.200" />
  <row Id="12223" PostTypeId="2" ParentId="12219" CreationDate="2011-03-29T13:13:57.130" Score="1" ViewCount="" Body="&lt;p&gt;An optical or magnetic sensor mounted mid net, bottom edge might be a good way to acomplish this.  Might also detect vibrations in the table, as might any sensor.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-29T13:13:57.130" />
  <row Id="12225" PostTypeId="2" ParentId="12210" CreationDate="2011-03-29T13:36:02.927" Score="0" ViewCount="" Body="&lt;p&gt;With the passive version (for reasons explained in the other thread) you will not be able to chain more then one such device (and you seem to want this).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately I don't think you can buy cheap Ethernet hub or switch chips in small quantities. Maybe you could get some cheap COTS switches and recycle them into your project.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-29T13:36:02.927" CommentCount="2" />
  <row Id="12226" PostTypeId="1" CreationDate="2011-03-29T13:41:05.827" Score="1" ViewCount="165" Body="&lt;p&gt;How can I generate a frequency of 5 GHZ with a crystal&lt;/p&gt;&#xA;" OwnerUserId="3642" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-03-29T14:53:33.543" LastActivityDate="2011-03-29T14:53:33.543" Title="How can I generate a frequency of 5 GHZ with a crystal" Tags="&lt;pll&gt;&lt;microwave&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="12227" PostTypeId="2" ParentId="12226" CreationDate="2011-03-29T14:16:49.293" Score="4" ViewCount="" Body="&lt;p&gt;Use one of &lt;a href=&quot;http://www.analog.com/en/rfif-components/pll-synthesizersvcos/adf4108/products/product.html&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; PLL chips with a suitable crystal oscillator for the reference signal and one of &lt;a href=&quot;http://www.crystek.com/microwave/?gclid=CN-N2p7786cCFYFB4Qodt1G7ZA&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; VCOs. You will need a suitable MCU to configure the PLL chip. It's a standard microwave PLL synthesiser approach.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-29T14:16:49.293" />
  <row Id="12228" PostTypeId="2" ParentId="12226" CreationDate="2011-03-29T14:19:08.963" Score="6" ViewCount="" Body="&lt;p&gt;Through frequency multiplication, e.g. 50x100MHz, or 100x50MHz etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This can be done either directly using &lt;a href=&quot;http://www.qsl.net/va3iul/Frequency_Multipliers/Frequency_Multipliers.pdf&quot; rel=&quot;nofollow&quot;&gt;frequency multipliers&lt;/a&gt;, or indirectly using phase locked loop, and locking 5 GHz oscillator to crystal reference oscillator.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-03-29T14:19:08.963" />
  <row Id="12229" PostTypeId="2" ParentId="12226" CreationDate="2011-03-29T14:25:27.730" Score="3" ViewCount="" Body="&lt;p&gt;If you are using the 5 GHz for wireless application you will need to check to see if exactly 5 GHz is required, many times stuff is said to be a certain frequency, but it is actually a slightly different frequency needed. For example, &lt;a href=&quot;http://parts.digikey.com/1/parts/1390828-osc-vco-5256-5356mhz-smd-5x-5-cvco55bh-5256-5356.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; is a Voltage Control Oscillator (VCO) that can vary between 5.256 and 5.356GHz. These are very useful when trying to get locks on to communication systems.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-29T14:25:27.730" />
  <row Id="12230" PostTypeId="1" AcceptedAnswerId="12232" CreationDate="2011-03-29T15:20:36.683" Score="3" ViewCount="101" Body="&lt;p&gt;I can't post a picture, since I don't have a good camera.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've noticed white powder on leads of some components. What could it be?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm sure that it isn't just dust, because there isn't any on the component bodies and was on some components which were stored in their own sealed bags. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen it on all types of components, but not all components have it. I was unable to find any mention of it in any datasheets. I've seen in on for example Fairchild DB237 transistors, Piher potentiometers, various no name resistors and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did notice that most components which have the powder have flat leads. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-03-29T15:36:32.937" Title="What is white powder on component leads?" Tags="&lt;components&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="12231" PostTypeId="2" ParentId="12210" CreationDate="2011-03-29T15:33:28.420" Score="1" ViewCount="" Body="&lt;p&gt;As Ranieri pointed out, we don't know if you need 10/100/1gig or half/full duplex.  We also don't know what kind of CPU you are using.   And we don't know how many of these you want to make (I'm assuming 50+, for various reasons).  So this answer is sort of a stab in the dark, but...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are four different approaches you can take.  1.  Use a passive hub.  2.  Use a 3-port switch chip.  3. Use a CPU that has two Ethernet ports on it.  Or 4. forget the 2-port requirement and use commercially available Ethernet switches instead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done enough PCB's with Ethernet to tell you that a passive hub isn't all that great. It might work in some one-off situations, but for a real product they stink.  They will limit network bandwidth in weird ways, limit your max cable length, etc.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several companies that make Ethernet switch chips.  Micrel is one of them, and more importantly Digikey has them in stock.  I haven't read the datasheets to know now suitable they are, but it looks promising.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a CPU with two embedded Ethernet controllers can be a good option, and would be the option that most companies would choose.  But for this to work well, the CPU should be at least a 32-bits, like an ARM or PowerPC.  The CPU needs to be running a reasonable TCP/IP stack and be setup to route packets between the two Ethernet controllers.  Companies like AMCC and Freescale make these.  TI has one on their roadmap, although I don't know if it's available yet.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I don't know which one will be a good solution for you.  My guess is that you'll have to choose between the lesser of three evils, but that's frequently the way engineering works.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-29T15:33:28.420" CommentCount="1" />
  <row Id="12232" PostTypeId="2" ParentId="12230" CreationDate="2011-03-29T15:36:32.937" Score="2" ViewCount="" Body="&lt;p&gt;When tin, a common plating on components, is left exposed to the air, it will oxidize over time, forming tin oxide, a white powder that is insoluble in water.  I believe that if your components are bright tin, the oxide layer will be fairly smooth and not &quot;powdery&quot;, which may be the case if you have components plated with matte tin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The flux in your solder (paste or rosin-core wire) should be able to remove a fair bit of the oxides, but if they are extremely oxidized you may have to add additional flux, or clean the parts somehow.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-29T15:36:32.937" CommentCount="2" />
  <row Id="12233" PostTypeId="1" CreationDate="2011-03-29T16:29:30.380" Score="0" ViewCount="124" Body="&lt;p&gt;After I download a KiCad schematic library or footprint library --&#xA;such as the ones from &lt;a href=&quot;http://kicadlib.org/&quot; rel=&quot;nofollow&quot;&gt;http://kicadlib.org/&lt;/a&gt; --&#xA;how do I use it in my schematic and layout?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I install that KiCad library file somewhere in the KiCad program folders ( C:\Program Files\KiCad\ ), or a copy of that file in each and every project that uses anything out of that file?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then what do I do to get the things in the library to show up on my schematic or my layout?&#xA;I don't see &quot;using 3rd party libraries&quot; in the &lt;a href=&quot;http://kicad.sourceforge.net/wiki/Frequently-asked-questions&quot; rel=&quot;nofollow&quot;&gt;KiCad FAQ&lt;/a&gt; or the tutorials it mentions. Is there a &quot;using 3rd party libraries&quot; tutorial on the KiCad wiki that I'm overlooking?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-10T05:01:24.547" Title="How do I install a KiCad schematic or footprint library?" Tags="&lt;schematics&gt;&lt;layout&gt;&lt;cad&gt;&lt;tutorial&gt;&lt;kicad&gt;" AnswerCount="2" />
  <row Id="12234" PostTypeId="2" ParentId="12186" CreationDate="2011-03-29T16:49:07.857" Score="3" ViewCount="" Body="&lt;p&gt;I'd tie four &gt;1000W computer power supplies together, and add a PIC or (insert-favourite-microcontroller-here) to control the CC/CV stuff. A computer power supply can &lt;a href=&quot;http://electronics.stackexchange.com/questions/6778/would-this-work-using-a-computer-smps-as-a-dc-dc-converter&quot;&gt;run off high voltage DC&lt;/a&gt;, and it can be &lt;a href=&quot;http://www.youtube.com/watch?v=mK_rIs7uFlo&quot; rel=&quot;nofollow&quot;&gt;made adjustable by modifying the feedback loop&lt;/a&gt;. A microcontroller could modify the feedback resistors by using a digital potentiometer and it could monitor the current through a hall effect current sensor. However, 95% efficiency is going to be next to impossible to achieve.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-29T16:49:07.857" CommentCount="1" />
  <row Id="12235" PostTypeId="2" ParentId="12217" CreationDate="2011-03-29T16:52:46.437" Score="3" ViewCount="" Body="&lt;p&gt;Sparkfun has a couple of &lt;a href=&quot;http://www.sparkfun.com/search/results?term=geiger%20counter&amp;amp;what=products&quot; rel=&quot;nofollow&quot;&gt;things&lt;/a&gt; available: one is just the tube, the other is a module that takes care of all the analog bits. Be aware that all the sensor suppliers are pretty backed up right now, so availability may be limited.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2011-03-29T16:52:46.437" CommentCount="2" />
  <row Id="12236" PostTypeId="2" ParentId="11666" CreationDate="2011-03-29T17:07:31.467" Score="2" ViewCount="" Body="&lt;p&gt;To answer your base question, to get to the address of pin A10 of the memory you need to look at the memory map for the ARM device...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this case it looking at the memory map:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;0x8000 0000 -&gt; 0x8FFF FFFF  is mapped to CSD0 (SDRAM/DDR)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and &lt;/p&gt;&#xA;&#xA;&lt;p&gt;0x9000 0000 -&gt; 0x9FFF FFFF  is mapped to CSD1 (SDRAM/DDR)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'd need to know what chip select was used in the PCB design to determine your answer as to which bank your DDR is attached to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This implies that A10 is located as either 0x8000 0400 (as you mentioned) or 0x9000 0400.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As to why 0x8000 0F00 was used in place of 0x8000 0400...reading the datasheet for that memory implies, but does not state that the other address pins, A(n) are don't cares for this operation so the coder probably just tossed in an F there instead of figuring out that it was only a 4 that was needed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also don't find those 2 sections of the datasheet to contradict each other.  The first is basically just saying that you need to reference the device's memory map to locate the real address where the memory is mapped so you can use that address as a base.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second quotes tells you that bit 0 of the address corresponds to address pin 0 on the memory in this mode, which may not always be the case in normal operation.  It may depend on the data/address width of the memory combined with alignment issues for the core.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-03-29T17:07:31.467" CommentCount="1" />
  <row Id="12237" PostTypeId="1" AcceptedAnswerId="12282" CreationDate="2011-03-29T17:31:39.690" Score="2" ViewCount="120" Body="&lt;p&gt;I have a cell phone that has a 1500 mAh 3.7 V battery.  It comes with a 700 mA charger but I've sucessfully used a 1 A charger with no problems.  I'm now trying to make my own multi-device charging station and my first problem if figuring out the maximum amount of current I can use at 5V?&lt;/p&gt;&#xA;" OwnerUserId="2809" LastActivityDate="2011-03-30T11:33:45.950" Title="How do I determine the maximum current for charging a li-ion battery?" Tags="&lt;battery-charging&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="3" />
  <row Id="12238" PostTypeId="2" ParentId="12233" CreationDate="2011-03-29T17:41:18.353" Score="2" ViewCount="" Body="&lt;p&gt;I found &lt;a href=&quot;http://code.google.com/p/opendous/wiki/KiCADTutorialAddingLibraries&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; in a few seconds with Google. Search term was &quot;KiCAD adding libraries&quot;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-29T17:41:18.353" />
  <row Id="12239" PostTypeId="1" AcceptedAnswerId="12296" CreationDate="2011-03-29T17:55:19.073" Score="2" ViewCount="87" Body="&lt;p&gt;I'm thinking about getting a bunch of &lt;a href=&quot;http://www.sparkfun.com/categories/84&quot; rel=&quot;nofollow&quot;&gt;Maxbotix Ultrasonic rangefinders&lt;/a&gt;. I'd like to use as few pins on my controller as possible. Since I don't think you can have multiple devices on an RS232 serial connection, I'd quite like to interface their PWM output with the controller using I²C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there some I²C device I can buy that accepts around 8 PWM inputs, and stores a representation of $\frac{\text{pulse width}}{\text{period}}$ in its registers?&lt;/p&gt;&#xA;" OwnerUserId="1217" LastActivityDate="2011-03-30T15:27:08.643" Title="Is there an I²C device out there for reading a set of PWM inputs?" Tags="&lt;i2c&gt;&lt;pwm&gt;&lt;ultrasound&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="12240" PostTypeId="2" ParentId="12237" CreationDate="2011-03-29T18:00:16.357" Score="2" ViewCount="" Body="&lt;p&gt;It's probably 1C, which means 1xcapacity, or 1500mA. However, there is a reason the manufacturer chose 700mA. It's best to keep to that to preserve battery lifetime and for safety. Overcharging a lipo can damage it. It may, in rare circumstances, become &quot;puffy&quot;, or even overheat or burn. So be careful!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Never charge a lipo battery without a proper charger. They must not be exposed to a charging voltage exceeding 4.2V. They should be charged with a constant current and monitored for voltage. Never connect a lipo directly to a supply.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-29T18:00:16.357" CommentCount="8" />
  <row Id="12241" PostTypeId="2" ParentId="11978" CreationDate="2011-03-29T18:14:15.923" Score="0" ViewCount="" Body="&lt;p&gt;If you have enough compute power for the sample rate you need, consider digital filtering. A &lt;a href=&quot;http://en.wikipedia.org/wiki/Savitzky%E2%80%93Golay_smoothing_filter&quot; rel=&quot;nofollow&quot;&gt;Savitzky-Golay&lt;/a&gt; filter, f/ex.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You can change algorithms easier than you can change parts;&lt;/li&gt;&#xA;&lt;li&gt;By pushing some of the filtering onto the software, you can probably use a lower spec part than if the part itself had to be more noise tolerant or do all the filtering;&lt;/li&gt;&#xA;&lt;li&gt;You'll learn a bunch more about your inputs and and what you need from them and can make a better informed parts choice, if you do, in fact, need a higher spec part.&lt;/li&gt;&#xA;&lt;li&gt;Software and skills are readily transferred to your other applications!&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3361" LastActivityDate="2011-03-29T18:14:15.923" CommentCount="1" />
  <row Id="12242" PostTypeId="1" CreationDate="2011-03-29T18:16:55.927" Score="0" ViewCount="284" Body="&lt;p&gt;If I would like to use a piece of copper wire as a 150A fuse, what size of wire should I use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It doesn't have to be 150A very accurately, the parameters I need the wire to meet are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;it needs to conduct continuously 70A 10V-30V DC without getting red or overheating&lt;/li&gt;&#xA;&lt;li&gt;it needs to conduct 120A sometimes for 15 seconds without melting&lt;/li&gt;&#xA;&lt;li&gt;it needs to surely be melted before the current reaches 200A&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Easily available wires over here are: 0.5 mm^2, 0.75 mm^2, 1.0 mm^2, 1.5 mm^2, 2.5 mm^2, 4 mm^2, 6 mm^2, 10 mm^2. Will any of these do the job? I can combine a few if the required value is not in the above series.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Edit: now I read more into the specifications of the device, and it is in fact rated to be fine with 600A for 5 seconds. Besides that I will be only ever using it continuously with 50A. Is that gap (50A - 600A) large enough to make a fuse out of copper? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/American_wire_gauge#Table_of_AWG_wire_sizes&quot; rel=&quot;nofollow&quot;&gt;This table of AWG wire sizes&lt;/a&gt; suggests that a 2.5mm^2 copper wire will melt with about 750A in 1s, and with a little under 200A in 10s, so it looks like it will melt in time for the device not to be damaged. The device itself is wired with 10mm^2 insulated wire, and I mostly worry about that wire not to be damaged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I only need to find out to what temperature will a short piece of uninsulated 2.5mm^2 copper wire heat-up with 50A continuous current flow, and will it not melt the thing it is secured in at that temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By &quot;continuous&quot; use I mean max 1 hour at a time, with full attendance of me, so it will not run unattended like this.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;More info: The machine came originally with two 50A fuses wired in parallel. In fact I want to use a wire, because the fuses blow so often it starts to get expensive, on average I need 1 fuse per 1 hour of charging, so the fuses cost more then the electricity to power this. I don't know why they blow, because I have an ammeter wired in series with the fuse, and I never seen anything over 60A on the ammeter! The fuses don't blow randomly, I just can see the fuse slowly get red, it stays red for some time, and at one point it just melts. I've been watching this process and I didn't see over 60A while the fuse was melting, I was watching the ammeter all the time in the slow process of the fuse being melted. So if I need 1 fuse per hour, so be it, but I need some cheaper option then 50 cents a fuse if I am to use them at that rate.&lt;/p&gt;&#xA;" OwnerUserId="1691" LastEditorUserId="1691" LastEditorDisplayName="" LastEditDate="2011-03-30T15:58:49.700" LastActivityDate="2011-03-30T17:06:50.680" Title="what size of copper wire can act as a 150A fuse?" Tags="&lt;current&gt;&lt;wire&gt;&lt;wiring&gt;&lt;fuses&gt;" AnswerCount="3" CommentCount="10" FavoriteCount="2" />
  <row Id="12244" PostTypeId="2" ParentId="12239" CreationDate="2011-03-29T18:25:18.063" Score="2" ViewCount="" Body="&lt;p&gt;Will an 8 channel ADC that supports I2C cut it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.linear.com/product/LTC2309&quot; rel=&quot;nofollow&quot;&gt;http://www.linear.com/product/LTC2309&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1823" LastActivityDate="2011-03-29T18:25:18.063" CommentCount="2" />
  <row Id="12245" PostTypeId="2" ParentId="12242" CreationDate="2011-03-29T18:42:35.070" Score="4" ViewCount="" Body="&lt;p&gt;Finding a fuse with those characteristics is going to be difficult. I'd use a current shunt with a suitable MCU and circuit breaker and monitor the current taken by the device, shutting off the current if it rises above 120A for 15 seconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two fuses in parallel can cause problems unless they are well-matched and the holders are properly designed. Any difference between them can cause one fuse to take more current than the other one, and fail.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-30T17:06:50.680" LastActivityDate="2011-03-30T17:06:50.680" CommentCount="4" />
  <row Id="12246" PostTypeId="2" ParentId="11859" CreationDate="2011-03-29T19:14:34.633" Score="4" ViewCount="" Body="&lt;p&gt;As Joby Taffey said in his post:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;You need to ensure the strips are clean and dust free, line them up perfectly then maintain pressure. Be careful not to stretch or bend the strips while installing them as the contacts are often very small pitch.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This is probably the way to go. I would comment that in the picture it does not look like the contacts are very small pitch. I disagree with the other posters who have suggested using graphite to enhance the connection. I would not put graphite or any other conductive powder/substance on the pwb or connector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order for electrical contact to be made, pressure must be continuously applied to the LCD/elasto/PCB &quot;sandwich&quot;. This is normally accomplished by the case, which is screwed together, pressing in on the structure from both sides.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The following procedure should work if you can pull it off. You might need help from a friend or some kind of jig...&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Sandwich the elastomeric connector between the LCD connector and the board pads. You will need to keep enough pressure on the sandwich to keep the connector from wiggling around.&lt;/li&gt;&#xA;&lt;li&gt;Screw the case back together while making sure the LCD/elasto/PCB sandwich doesn't come apart. This is assuming that you still have the case, and you will be reassembling it...&lt;/li&gt;&#xA;&lt;li&gt;Test it&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Note: the LCD connector is not visually distinctive. Referring to the photo you have attached, I would guess that it is the translucent region at the bottom of the LCD module. You can just make out the &quot;ghosted&quot; strips which are possibly electrically conductive. Or maybe the clear strips are. You will figure it out. You probably could use an ohmmeter to test continuity if you are very careful and gentle. Anyway, the black squares on the connector edges are the conductive parts of the elasto connector, and should be lined up with the PCB pads and the conductive LCD &quot;pads&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I once took apart an electronic guitar tuner which was having display problems, and to my great surprise encountered one of those elastomeric connectors. I had never seen one before. It totally freaked me out when it fell off and I could not see any adhesive or other fastening agent to reattach it with... but using the above procedure I put it back together and it's working, once again...&lt;/p&gt;&#xA;" OwnerUserId="3635" LastActivityDate="2011-03-29T19:14:34.633" />
  <row Id="12247" PostTypeId="2" ParentId="12237" CreationDate="2011-03-29T19:41:34.507" Score="2" ViewCount="" Body="&lt;p&gt;Current is not limited as long as battery does not overheat internally &amp;amp; externally.&#xA;You can have higher currents with active cooling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Going above 1C is possible (i.e. 1.5A in your case) but it will reduce lifespan of your battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Under no conditions you should connect unregulated 5V to LiIon - current will be &gt;10A and something would explode (PSU or battery). You need regulated current circuit.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-03-29T19:41:34.507" />
  <row Id="12248" PostTypeId="1" AcceptedAnswerId="12250" CreationDate="2011-03-29T19:46:48.723" Score="4" ViewCount="144" Body="&lt;p&gt;If you have a common fuse is there way quantify the power consumption which is flowing through this fuse. Or could you replace the fuse with something that measures the power consumption but still works as a fuse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or am I completely stupid? Could you explain me why it is impossible?&lt;/p&gt;&#xA;" OwnerUserId="3648" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T21:00:27.907" LastActivityDate="2011-04-27T21:00:27.907" Title="Is it possible to quantify electric power consumption on a fuse?" Tags="&lt;energy&gt;&lt;fuses&gt;" AnswerCount="5" CommentCount="7" FavoriteCount="1" />
  <row Id="12249" PostTypeId="1" CreationDate="2011-03-29T19:48:38.930" Score="0" ViewCount="141" Body="&lt;p&gt;I am trying to do my first Arduino project, and I would like to drive a 5x5 matrix of IR leds. I would only like to have one switched on at a time. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand that in an array I can do it with 5 lines for anodes and 5 lines for cathodes. &lt;strong&gt;My problem is that I cannot supply 100 mA with an Arduino.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;What would be the easiest way for me to supply 100 mA for these leds?&lt;/strong&gt; I think they don't need current limiting, if I could drive them with 1.35 V voltage, it would work perfectly. I've measured a couple of my LEDs and they used exactly 100 mA at 1.35V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that I can use a transistor for supplying a higher current power source, but I don't understand that how could I do it with a 5x5 LED matrix. &lt;strong&gt;How many transistors do I need?&lt;/strong&gt; 5 or 10? And if I need 10 transistors, then I understand the 5 which supply 1.35 V, but what are the other 5 doing? How can a transistor supply 0 V?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, as an ugly trick, I was thinking about using a Mega, and for each line, &lt;strong&gt;using 3 pins in parallel&lt;/strong&gt;. I mean one pin has a current limit of 40 mA, so 3 pins would be enough for 100 mA. That way I wouldn't need to care about an other power source, and transistors. I could just run the whole thing from USB. All I would need would be 5 resistors. Is that a good option?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, as an alternative, I was thinking about using &lt;strong&gt;Rainbowduino&lt;/strong&gt; in itself. It has current limiting, and in theory I could possibly run the whole thing from 5V USB. But it seems really complicated to just control 5x5 LEDs. I don't understand the whole idea about source driving the anode and current driving the cathode! Isn't it a &lt;em&gt;circuit&lt;/em&gt;, I mean we either set the source, or the current? And why does the anode has 500 mA current limit, while the cathode has 120 mA? So while it looks good on paper, I think I'm really not on a level to understand how it works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All I would need is to control 5x5 LEDs, where each of them would require 100 mA @ 1.35 V. &lt;strong&gt;What would be the best way you’d recommend me doing it?&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="3049" LastActivityDate="2011-03-29T21:39:04.070" Title="how to drive 5x5 IR LEDs with 100 mA, using Arduino" Tags="&lt;arduino&gt;&lt;led&gt;&lt;transistor&gt;&lt;current&gt;&lt;matrix&gt;" AnswerCount="2" />
  <row Id="12250" PostTypeId="2" ParentId="12248" CreationDate="2011-03-29T20:23:26.027" Score="8" ViewCount="" Body="&lt;p&gt;A fuse is basically a resistor where resistance varies from almost zero to infinity.  So just like a resistor, measure the voltage drop across the fuse, and the current through it.  Calculate the Volts times Amps and you'll get Watts.  Since the resistance is almost zero, the voltage drop will also be almost zero.  And so the watts will be almost zero.  Not exactly zero, but close. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the fuse is blown, the resistance is near infinity.  This will make the current basically zero.  And thus the watts will be basically zero.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The interesting part is when measuring the power while the fuse is blowing.  It's not impossible, but not easy either.  Basically you work out a system where you can graph the current and voltage on an o-scope then do some tricky math to work out the amount of energy required during the fuse-blowing event.  I've never done this, so I couldn't tell you what it looks like.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-29T20:23:26.027" CommentCount="1" />
  <row Id="12251" PostTypeId="2" ParentId="12242" CreationDate="2011-03-29T20:30:50.793" Score="2" ViewCount="" Body="&lt;p&gt;It sounds to me like like you're about to violate some NEC/NFPA* fire and safety regulations. Replacing a fuse like this with bare copper wire is &lt;strong&gt;ILLEGAL&lt;/strong&gt; period. Machine downtime is always preferable to property damage, injury or loss of life. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT * Assuming you're in the USA.&lt;/p&gt;&#xA;" OwnerUserId="2612" LastActivityDate="2011-03-29T20:30:50.793" CommentCount="6" />
  <row Id="12252" PostTypeId="2" ParentId="12249" CreationDate="2011-03-29T20:32:10.063" Score="1" ViewCount="" Body="&lt;p&gt;How did you measure the led current? An led will act as a diode while in forward conduction and will take as much current as you can supply, or will destruct at its current limit. Sounds as if your 1.35 volt supply might have been limited to 100ma. Also if they are IR led's does your circuit need to pulse modulate them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In any case, you could use a current limiter on the high side which could be anything from a single resistor (only one led on at a time) to a current regulator. See LM317 datasheet for how to make a current limiter with only one resistor. You will need 10 switching devices. Five to switch the high side (positive) and five to switch the low side (negative).&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-03-29T20:32:10.063" CommentCount="3" />
  <row Id="12253" PostTypeId="2" ParentId="12217" CreationDate="2011-03-29T20:53:22.233" Score="1" ViewCount="" Body="&lt;p&gt;The only direct &quot;sensor&quot; of ionizing radiation I know if the &lt;a href=&quot;http://en.wikipedia.org/wiki/Geiger%E2%80%93M%C3%BCller_tube&quot; rel=&quot;nofollow&quot;&gt;Geiger-Müller tube&lt;/a&gt;. These are generally only available used or NOS (New, Old Stock) parts on the surplus electronic market. The tubes are often designed to only measure beta and/or gamma particles. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;GM tubes are powered by a high voltage (low current) power source which makes them modestly complex if you do not have experience working with HV supplies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only other &quot;sensor&quot; I can imagine would be to adapt the &lt;a href=&quot;http://en.wikipedia.org/wiki/Smoke_detector#Ionization&quot; rel=&quot;nofollow&quot;&gt;ionizing smoke detector&lt;/a&gt;'s ionization &lt;a href=&quot;http://en.wikipedia.org/wiki/Gaseous_ionization_detectors&quot; rel=&quot;nofollow&quot;&gt;chamber&lt;/a&gt;, but as it is designed to detect a disruption of alpha particles (emitted from &lt;a href=&quot;http://en.wikipedia.org/wiki/Americium-241&quot; rel=&quot;nofollow&quot;&gt;americium-241&lt;/a&gt;) caused by smoke absorbing the alpha particles, I don't know is such an approach is very feasible to detect all but high levels of ambient radiation (assuming you removed the Am-241). &lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-03-29T20:53:22.233" />
  <row Id="12255" PostTypeId="1" AcceptedAnswerId="12263" CreationDate="2011-03-29T21:07:11.763" Score="3" ViewCount="225" Body="&lt;p&gt;Hi everybody,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my story:  I got my electrical engineering degree BUT I do not have a lot of experience with circuits (OMG, right? O_O).  Most of my education was about communication theory, so I really feel incomplete and want to apply my knowledge somewhere and start making something on a microprocessor.  It would also be a good skill to develop for the workforce.  Do you folks have any recommendations as to what type of microprocessor I should be working with?  PIC?  Arduino?  Others?  What is used most in the market and for production purposes? Does it matter?  I hear Arduino has a very good community for help, but I hear it is more for &quot;hobbyists&quot;?  Is that necessarily a bad thing?  Any insight is much appreciated.  Thanks!!&lt;/p&gt;&#xA;" OwnerUserId="3649" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-03-29T21:10:46.253" LastActivityDate="2011-03-30T16:51:30.367" Title="Want to apply EE knowledge -- which microprocessor would you recommend?" Tags="&lt;arduino&gt;&lt;pic&gt;" AnswerCount="9" CommentCount="2" FavoriteCount="1" />
  <row Id="12256" PostTypeId="2" ParentId="12255" CreationDate="2011-03-29T21:18:59.430" Score="4" ViewCount="" Body="&lt;p&gt;Every microcontroller has its realm where it is really able to thrive well. For example, the MSP430 is very good for low power. If you really want to prepare yourself for all of industry you would need to learn everything you can get your hands and so when you have a situation that you come across you know the best microcontroller to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ardunios are not microcontrollers, they essentially are a development board built around Atmel AVR as their microcontroller. Ardunios are very hobbyist orientated, which is not a bad thing for starting off, but you will need to learn more in depth about the Atmel that is being used if you want to do anything with them in industry.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-29T21:18:59.430" CommentCount="7" />
  <row Id="12257" PostTypeId="2" ParentId="12255" CreationDate="2011-03-29T21:20:03.687" Score="2" ViewCount="" Body="&lt;p&gt;Microchip is the market leader in 8-bit MCUs so you won't go wrong if you learn on them. ARM Cortex devices are replacing 16-bit and 8-bit devices in many applications, so familiarity with them will also be useful.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-29T21:20:03.687" />
  <row Id="12258" PostTypeId="2" ParentId="12114" CreationDate="2011-03-29T21:20:14.967" Score="1" ViewCount="" Body="&lt;p&gt;If you want to learn about interrupt-driven programming by studying old processors, the Z-80 might be a better bet... one of its features was a better interrupt system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I learned a lot of hard-won lessons by writing an interrupt-driven serial I/O handler for the thing!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if you're really wanting to learn about interrupts, it might be better to use a CPU where you have easy access to a system for development and test.&lt;/p&gt;&#xA;" OwnerUserId="1756" LastActivityDate="2011-03-29T21:20:14.967" />
  <row Id="12259" PostTypeId="2" ParentId="12255" CreationDate="2011-03-29T21:23:09.813" Score="1" ViewCount="" Body="&lt;p&gt;Select a common microcontroller and use it for a project. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a lot on this topic on this forum, I think I would recommend the avr:s.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;pic &lt;/li&gt;&#xA;&lt;li&gt;avr &lt;/li&gt;&#xA;&lt;li&gt;arm&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="689" LastActivityDate="2011-03-29T21:23:09.813" />
  <row Id="12260" PostTypeId="1" AcceptedAnswerId="12273" CreationDate="2011-03-29T21:26:40.500" Score="0" ViewCount="127" Body="&lt;pre&gt;&lt;code&gt;ar 29 22:12:14 stevendesktop kernel: [ 4265.290019] usb 5-1: device descriptor read/64, error -62&#xA;Mar 29 22:12:15 stevendesktop kernel: [ 4265.572782] usb 5-1: new low speed USB device using ohci_hcd and address 52&#xA;Mar 29 22:12:15 stevendesktop kernel: [ 4265.990018] usb 5-1: device not accepting address 52, error -62&#xA;Mar 29 22:12:15 stevendesktop kernel: [ 4266.160020] usb 5-1: new low speed USB device using ohci_hcd and address 53&#xA;Mar 29 22:12:16 stevendesktop kernel: [ 4266.580018] usb 5-1: device not accepting address 53, error -62&#xA;Mar 29 22:12:16 stevendesktop kernel: [ 4266.580032] hub 5-0:1.0: unable to enumerate USB device on port 1&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;These are the messages that appear in the logs when I connect my avr. What could of caused these errors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;pin D-&#xA;I  have D- connected to a 68R resistor in series. The other end goes to my avr. I wired a 1.5K pull in parallel to the 68ohm resistor. A zener 0.5w 3.6v parallel to pin 2 of the type A socket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;pin D+&#xA;Wires in series to a 68ohm resistor. The other end to avr. A zener in parallel to the D+ pin. Also wired to int0 pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's self powered at the moment so therefore I don't need to connect the 5v and gnd pins right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I connected the D+ pin to my scope I could see a square wave being generated. I tested the frequency it's bang on 16MHZ. Though I did notice occasionally it went down to 15.98.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what could be wrong?&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-03-30T08:25:25.453" Title="USB connection not working VUSB" Tags="&lt;avr&gt;&lt;usb&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="12261" PostTypeId="2" ParentId="12248" CreationDate="2011-03-29T21:26:50.373" Score="3" ViewCount="" Body="&lt;p&gt;I don't think you can count on the fuse's resistance to be stable or repeatable.  Put a small, but known, resistance in series with the fuse (0.1 Ω), and measure the voltage across it.  The voltage divided by the resistance will tell you the current. V / R = I&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe there are special components that act both as current-sensing resistors and as fuses, but I don't know of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simultaneously, measure the voltage across the thing that's supplying this current (like the voltage from the fuse to your circuit's ground, if the fuse is on the high side).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Multiply current by voltage to get power.  P = V · I&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-03-29T21:26:50.373" CommentCount="2" />
  <row Id="12262" PostTypeId="2" ParentId="12255" CreationDate="2011-03-29T21:29:24.930" Score="3" ViewCount="" Body="&lt;p&gt;I have programmed on atmel, pic, microchip and TI and I personally like TI's IDE the best. They have put a lot of effort into making their microcontrollers as easy it use as possible. Not to mention their documentation and tutorials are well above par. Try getting an msp430 dev kit. Its a microcontroller with a decent amount of memory and processing power, it has multi-channel a/d and d/a converters, and even comes with an onboard 2.4 ghz tranciever for experimenting with wireless networks. The devkit comes with 2 msp430 modules, a usb probrammer and a battery pack, and its less that $100.&lt;/p&gt;&#xA;" OwnerUserId="3906" LastActivityDate="2011-03-29T21:29:24.930" CommentCount="1" />
  <row Id="12263" PostTypeId="2" ParentId="12255" CreationDate="2011-03-29T21:30:57.870" Score="7" ViewCount="" Body="&lt;p&gt;Hey, great timing!  This week I've been interviewing E.E. students for an intern position.  Here's what I can say with 100% certainty:  Students from the big schools, even Juniors working on their Bachelors, have almost ZERO useful knowledge.  One guy I interviewed couldn't calculate the value for a current limiting resistor for an LED.  Yup, that's what $30k/year will get you for an education.   The point is, any practical experience or knowledge you have will put you above your classmates when it comes to landing a job!  Seriously, it's that bad out there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ok, on to your question.  From an employers perspective it doesn't matter which uC you use.  Odds are that whatever you choose, it'll be wrong.  What's more important is the experience and knowledge you gain will apply to most uC's.  That being said, stick to the common ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Microchip PIC's are my least favorite.  The hardware is fine, but writing software for them is a super pain in the you-know-what.  I've used them in the past, and never again.  I've also used the Cypress pSoC 1.  It was nice at first, but their software is buggy and documentation is very lacking.  A current project of mine uses an MSP430, but it's too early to say how well it works.  The TI ARM based uC's are also nice, but might be too much for you at this early stage.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-29T21:30:57.870" CommentCount="4" />
  <row Id="12264" PostTypeId="2" ParentId="12255" CreationDate="2011-03-29T21:31:18.190" Score="2" ViewCount="" Body="&lt;p&gt;You should use the right microcontroller/microprocessor for the task at hand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pick a project, then pick your processor.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-29T21:31:18.190" />
  <row Id="12265" PostTypeId="2" ParentId="12249" CreationDate="2011-03-29T21:39:04.070" Score="3" ViewCount="" Body="&lt;h2&gt;&lt;strong&gt;First, a safety warning&lt;/strong&gt;&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;25 IR LEDs at 100 mA each will be a &lt;strong&gt;LOT&lt;/strong&gt; of IR radiation.  If they're close together, your pupils are dilated (indoors, this is often true), and/or you're close to the matrix, you could really hurt your eyes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The image of the matrix will be focused to a tiny area on your retina, and you'll hear/feel a little &lt;em&gt;pop&lt;/em&gt; as the blood and fluid there boils.  You'll have a permanent blind spot.  Not fun.  BTW, it's your job to make sure that you understand what you're doing and don't hurt yourself, not mine.  I'll help you begin understanding, but I won't be held responsible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My advice:  For development (and production if possible), put bright green LEDs in series and physically close to the IR LEDs so that your blink reflex is activated at a bare minimum.  Use hardware (in addition to software) techniques to limit the number of LEDs lit and/or the power delivered to the matrix to help ensure that only one LED is on at a time.  &lt;/p&gt;&#xA;&#xA;&lt;h2&gt;&lt;strong&gt;Techniques&lt;/strong&gt;&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;There are many LED driving techniques.  None of them hinge on delivering 1.35V; that will change between LED batches, over time, and with temperature.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're just interested in current limiting, a few transistors will be sufficient.  The total transistor count will depend on your choice of a current limiting circuit topology, which is dependent on your heat sinking capabilities, routing area, and other contstraints.  There are also voltage/current regulation ICs and linear LED drivers which would simplify your job.  If you're interested in power conservation, many buck converters can be configured for current limiting, which would maximize your battery life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may want to have unlimited sink and limited source (or vice versa).  Alternatively, you might have just one current source, and mux it between the various LEDs.  Because of the safety issues inherent in this project, I'd recommend the latter option.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-29T21:39:04.070" />
  <row Id="12266" PostTypeId="2" ParentId="12242" CreationDate="2011-03-29T21:39:45.260" Score="2" ViewCount="" Body="&lt;p&gt;Sounds like you're planning ahead for a tragedy.  Kinda like, &quot;If a robber comes through the door should I shoot him, or stab him?&quot;  Forget that and just lock the door!  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you should do with all your planning is simply buy extra fuses and keep them handy.  If on the odd chance that you run out of fuses, then kludge something up however the situation calls for it (keeping in mind the safety and legal aspects of it).  But at that point, you're not worrying about what amperage the copper wire is going to melt.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-29T21:39:45.260" CommentCount="1" />
  <row Id="12267" PostTypeId="2" ParentId="12198" CreationDate="2011-03-29T21:39:57.550" Score="0" ViewCount="" Body="&lt;p&gt;AFAIK electrolytic capacitors (like any other capacitors) will work in both polarizations, but DC voltage of the wrong direction will degrade (like in electrolysis) the oxide layer. After being degraded for a while the oxide layer will cause short and a violent explosion.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-30T03:52:20.217" LastActivityDate="2011-03-30T03:52:20.217" />
  <row Id="12268" PostTypeId="2" ParentId="12239" CreationDate="2011-03-29T22:09:19.103" Score="1" ViewCount="" Body="&lt;p&gt;The microchip &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en546891&quot; rel=&quot;nofollow&quot;&gt;PIC18F87K22&lt;/a&gt; has 10 capture compare modules that can handle this function and of course you can talk to it through I2C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also do this will a really simple FPGA. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Cypress PSoC family could probably also handle measurement of a bunch of PWM inputs.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-03-29T22:09:19.103" />
  <row Id="12269" PostTypeId="1" CreationDate="2011-03-29T22:41:39.367" Score="8" ViewCount="198" Body="&lt;p&gt;I made transmitter from &lt;a href=&quot;http://electronics.stackexchange.com/q/12060/1240&quot;&gt;this&lt;/a&gt; question with some minor modifications (100 K pot for resistor between 8 and 7 and 22K for resistor between 7 and 6. 22 pF for the capacitor). &#xA;Here's the picture:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/nlidI.png&quot; alt=&quot;Transmitter&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When transmitting &lt;a href=&quot;http://remix.kwed.org/?search_id=3956&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; song, it is almost normally transmitted. On the other hand, when transmitting &lt;a href=&quot;http://remix.kwed.org/?search_id=4078&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; song, almost nothing is audible. For example from 2:15 to 2:50 noting can be heard.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My home-brewed sound card oscilloscope (96 kHz, 16 bit) sees first song like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/0wTmO.png&quot; alt=&quot;scope 1&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and the second like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/PnKoI.png&quot; alt=&quot;scope 2&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I'm right, on the second image only artifacts from the carrier wave can be seen (I'm running radio at 612 kHz. I guess that's OK, since it has range of about 5 cm).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've heard such effects on radios with bad antennas before. What could be the technical explanation, or at least where could I start looking for it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just to be clear, the my question isn't about improving the transmitter, its about the effect I'm describing. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-03-29T22:53:06.490" LastActivityDate="2011-05-05T23:54:55.180" Title="Why doesn't this radio transmitter correctly transmit some songs?" Tags="&lt;radio&gt;" AnswerCount="2" CommentCount="18" FavoriteCount="1" />
  <row Id="12270" PostTypeId="2" ParentId="12260" CreationDate="2011-03-29T23:09:08.123" Score="0" ViewCount="" Body="&lt;p&gt;Do you use a 16MHz quartz crystal or a ceramic oscillator? The accuracy required by the USB standard is far higher then what your scope (or most simple frequency counters) could measure.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-29T23:09:08.123" CommentCount="3" />
  <row Id="12271" PostTypeId="1" CreationDate="2011-03-30T00:38:44.343" Score="-2" ViewCount="81" Body="&lt;p&gt;Hi.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im trying to find a cool looking &quot;switch&quot;.  can anyone point me in the right direction?  I tried to surf digikey to find something interesting, but realistically I can barely tell what is pictured in their images...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any advice would be appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="3653" LastActivityDate="2011-03-30T12:37:44.717" ClosedDate="2011-03-30T14:16:27.537" Title="Where to find a simply stylish touch button" Tags="&lt;switch&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12273" PostTypeId="2" ParentId="12260" CreationDate="2011-03-30T01:25:18.510" Score="2" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;pin D- I have D- connected to a 68R&#xA;  resistor in series. The other end goes&#xA;  to my avr. I wired a 1.5K pull in&#xA;  parallel to the 68ohm resistor. A&#xA;  zener 0.5w 3.6v parallel to pin 2 of&#xA;  the type A socket.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;sounds like your pulling D- up to your board's supply (it should be pulled up to 3.3V), at least i think thats what your trying to say.  If the 1.5k is actually in parallel with the 68 ohm resistor, that is a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you haven't connected the ground from the USB link, the other end has no reference at all for what you've pulled that pin up to.  Nor is your controller seeing the pull downs on the host side of the link.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connect the ground from the USB link to your board ground.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2011-03-30T01:36:24.637" LastActivityDate="2011-03-30T01:36:24.637" />
  <row Id="12274" PostTypeId="1" CreationDate="2011-03-30T03:25:07.177" Score="5" ViewCount="181" Body="&lt;p&gt;How would you solve for \$V_x\$ using node voltage method. I can solve this using \$Q_{initial}=Q_{final}\$, but I can't solve it using node voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using node voltage I get \$v(t)-v(0)=\frac{k}{170\mbox{ aF}}\$. I'm not sure how to solve for the k constant or if this is even correct.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/2ORxv.png&quot; alt=&quot;Homework Problem Image&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3657" LastEditorUserId="1950" LastEditorDisplayName="" LastEditDate="2011-06-06T01:42:21.217" LastActivityDate="2011-06-06T01:42:21.217" Title="How to solve for voltage using node voltage method?" Tags="&lt;capacitor&gt;&lt;voltage&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="1" />
  <row Id="12275" PostTypeId="2" ParentId="12255" CreationDate="2011-03-30T03:28:52.760" Score="4" ViewCount="" Body="&lt;p&gt;The msp430 has a very nice instruction set.  And you can currently get an msp430 board to play with for about five bucks.   ARM dominates the processor world, nobody is even close, almost everything you use is arm based.  Also a good instruction set, many variations can be had for under $50, goto sparkfun.  the reduced arm instruction set is called thumb and the expanded thumb instruction set is called thumb2 and there is now a core that is thumb2 only (each thumb instruction mapped one to one with arm instructions so it was easy to just insert the arm instruction in the pipe when a thumb instruction was found, but thumb2 changed that they made a new core).  ST, who I like more than LPC and perhaps the other arm based micros, now has a value line discovery board for about 12 bucks (you want the 12 dollar stm32s not the 7 dollar stm8s or whatever that is a completely different processor, has a 6502 feel, I bought the wrong ones but have not played with it yet).  The PIC instruction set, the old/real one (not the mips PIC32) is very educational, and actually elegant, but dreadful for compilers, wont ever touch msp430 or arm from that perspective.  Microchip and pic was the Atmel AVR (butterfly and now Arduino) of its day but just doesnt really &quot;get it&quot;.  Atmel &quot;gets it&quot; and their customers are very happy and very loyal.  I do like my sam7 arm boards, quite a bit.  The AVR instruction set is dreadful, but that has not stopped it from being insanely popular with hobbyists.  Depends on if you want to learn to program or not have to worry about it.  If you dont want to get into programming very much the arduino is probably your first choice.  If you want to get into programming, I have a couple of emulators at github, thumbulator a thumb emulator and an msp430.  You can get a feel for what is going on.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My recommendation is get a few, many different ones can be had for under 50 bucks.  sparkfun.com for many of them, direct from TI for the ezusb (the 5 dollar launchpad is cheaper, but the ezusb has additional boards, 3 for $10).  Also direct from TI (or do you have to go to digikey/mouser?) the stellaris boards, packed with stuff so much that you cant really get at the I/O without cutting traces.  but at the same time lots of datasheets to read and understand as well as a lot more schematics to read and understand.  The stellaris boards are more in the sub 100 dollar category.  the 811 is super easy to brick, be careful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;knjn.com has some affordable fpga boards, pluto I think.  I think everything you need for that after the hardware is free (from xilinx or altera).  At one point altera had a modelsim version, but I prefer verilator and icarus verilog.  Would like to spend more time on ghdl but I dont know enough to connect it to a C test bench.  With verilator it is somewhat trivial to build a test bench using C with which you can write code/drivers that can later talk to the hardware or run on the hardware depending on what you are making...here again assumes you have some programming interest...I am a big fan of cyclicity-cdl.sf.net a hardware design language that I feel is verilog done right.  It has its own, free, simulation environment as well.  Basically, you can do logic designs for $50 bucks or so, whatever the board costs.  Or if you dont want to buy the hardware can do tons of designs with all free tools.  gtkwave is your friend when it comes to looking at the vcd waveforms, even with modelsim now I simply create a .vcd and use gtkwave's viewer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found things like decoding IR remotes using an IR receiver (Radio Shack used to have them, now digikey or mouser or sparkfun), bit banging rs232, i2c, spi, dallas one wire (dallas semi is now maxim). x10, etc.  if there is a hobby/hacker space where you can hang out and solder and use an oscilloscope that would be really useful.  Learning to read protocols like these and debug your logic/software with a scope is very useful (dont use the software package that lets the scope decode it for you, learn it the old fashioned way). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Learning to program the various peripherals in the various microcontrollers (timers, pwm's, etc) is very educational.  lcd and oled displays, etc.  (stellaris or arduino is good for this).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the mbed is not a bad platform other than the painful blue leds. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;lattice has the brevia for not much money and the mico8 I believe will fit in there and is in source form so you can simulate it.   The lattice tools are not as bad as the others.  So you can get a little microcontroller and logic and electronics if that is what you are after.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the primary problem with Arduino and the ST primers lxpresso and some others is the strong desire to hold you in their sandbox.  The Arduino is easy to erase and reprogram and take over the board and abandon the sandbox, the other two are not.  dont buy them.  Where this may help or hurt what you are trying to do is that by wrapping up all the &quot;hard&quot; stuff into a package or api or whatever basically hides it from you.  And if you are interested in learning this protocol (spi, i2c, etc) or how to wiggle the signals on an lcd to make it work, or pwm a motor the easy way or hard way.  You might want to not be tied to the sandbox.  At the same time using the Arduino sandbox you dont have to get too much into the programming side and can spend more time wiring electronics up to the board and debugging or playing with those circuits, not having to worry about the Arduino itself.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are places that sell 2 or 3 pcboards for like $50, and use the eagle I think it is layout software which you can download and use for free.  Probably worth downloading and trying to do some layouts even if you arent ready to purchase any boards or even have an idea of something you want to build.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Granted you may still be on a college budget, and I understand that, but I would say try as many of these different platforms you can get your hands on.  You probably have more time than money right now so you can certainly go with free software that simulates much of this stuff, also you can research the datasheets and schematics and software and hardware tools for the various boards before you pull the trigger to purchase.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The real education that you need to know here is reading datasheets and schematics.  And you dont want to read only datasheets from one vendor, some are good, some are horrible, and in the real world with a real job in this area you have to deal with the good and the bad.  The other skills are soldering and using the oscilloscope, soldering you can afford (well a good iron, probably not just yet), a scope, the kind you would really use at a job, not affordable.  When you get that first job, get as much scope time as you can.  Watch how other engineers use it as they all have their own way to navigate through the menus and features.  Debugging is critical to your career.  If you lean toward logic, get some hours on the xilinx and altera tools as well as the others I mentioned and get real comfortable looking at waveforms on modelsim or gtkwave.  The pay-for tools are all horrible, about the worst software you could imagine, and for some reason cost tens of thousands.  (and the software gets worse every year/version).  But that pain is the key to that career path, &quot;know your tools&quot;.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-03-30T03:28:52.760" CommentCount="1" />
  <row Id="12276" PostTypeId="2" ParentId="12274" CreationDate="2011-03-30T06:10:02.460" Score="0" ViewCount="" Body="&lt;p&gt;Not sure if this is node voltage method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But you can replace the capacitors with a voltage source $V_c$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With this you can use the differential equation: ${dV_c\over dt} = i_C \cdot {1\over C}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current $i_C$ is calculated by shorting all voltage sources one by one, and calculate the currents $i_C$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will end up with four first-order differential equations, which then easily can be solved.&lt;/p&gt;&#xA;" OwnerUserId="3041" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-30T13:57:32.153" LastActivityDate="2011-03-30T13:57:32.153" />
  <row Id="12277" PostTypeId="1" CreationDate="2011-03-30T06:36:07.653" Score="0" ViewCount="87" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully this is the right place to ask for suggestions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a 720p 32-inch LCD TV. I have connected my laptop to the TV via VGA channel, but for some reason the laptop screen is centered on the TV with wide vertical black stripes. I want to get rid of those so that the laptop screen covers the entire TV area. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have several different screen resolution options on Windows, but only 1024x768 works. The operating system will let me increase my resolution, but the TV will output a &quot;mode not supported&quot; message. I have tried everything I can think of but came up empty handed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that the laptop has VGA, HDMI, and DisplayPort outputs. I tried using a HDMI-to-HDMI cable. I was able to use a higher resolution with no black stripes, but then colors were all washed out. I tried changing color settings on the TV with no ultimate satisfaction. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would a DP-to-HDMI cable fix the problem? Is there a way to use the VGA cable and still achieve full screen display? I want to use all of the TV real estate instead of a partial area.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. I noticed that the TV name is not recognized on the computer if the VGA cable is used. Rather there is a generic &quot;display 2&quot; name for it. If the HDMI cable is used, the OS will recognize the name. I also have the latest graphics driver.&lt;/p&gt;&#xA;" OwnerUserId="3660" LastEditorUserId="3660" LastEditorDisplayName="" LastEditDate="2011-03-30T06:52:55.300" LastActivityDate="2011-03-30T06:52:55.300" ClosedDate="2011-03-30T09:33:08.250" Title="How to display VGA output in fullscreen on the TV?" Tags="&lt;tv&gt;&lt;vga&gt;" />
  <row Id="12278" PostTypeId="2" ParentId="12213" CreationDate="2011-03-30T07:24:56.067" Score="2" ViewCount="" Body="&lt;p&gt;have you considered finding a cheap gram scale and taking out the load cell out? usually I see them accurate down to +-.1 grams&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As stevenh pointed out, cheap scales may not be that accurate, compared to there &quot;box values&quot; If you are just using a load cell from it you should be able to get at least the same and or better accuracy if you have a sufficient design for your ADC and cell combo. &#xA;To get even better results i would suggest getting a small set of standard weights to calibrate your device.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-03-30T07:24:56.067" CommentCount="3" />
  <row Id="12279" PostTypeId="2" ParentId="12260" CreationDate="2011-03-30T08:25:25.453" Score="0" ViewCount="" Body="&lt;p&gt;If I were you I would study the reference project for using the internal clock with a 5v design carefully. It's the &lt;a href=&quot;http://www.obdev.at/products/vusb/easylogger.html&quot; rel=&quot;nofollow&quot;&gt;EasyLogger&lt;/a&gt;.&#xA;You can download the schematic from the archives at the bottom.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-03-30T08:25:25.453" CommentCount="2" />
  <row Id="12280" PostTypeId="1" AcceptedAnswerId="12281" CreationDate="2011-03-30T10:46:21.930" Score="0" ViewCount="68" Body="&lt;p&gt;How exact is the velocity that is showing in a GPS Navigation System like Navigon or TomTom?&lt;/p&gt;&#xA;" OwnerUserId="3662" LastActivityDate="2011-03-30T15:54:40.493" Title="Velocity showing in GPS-Navigation Systems" Tags="&lt;gps&gt;&lt;navigation&gt;" AnswerCount="2" />
  <row Id="12281" PostTypeId="2" ParentId="12280" CreationDate="2011-03-30T11:20:58.730" Score="3" ViewCount="" Body="&lt;p&gt;This depends upon a large number of variables that are imposed by the GPS navigation system in use and by the processing of the data by the SAT-NAV following the determination of the position fix.  These include&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The interval between position fix solutions.  This is normally 1 second.&lt;/li&gt;&#xA;&lt;li&gt;The position accuracy of each of the positions used to determine the velocity.  This depends upon the quality of the sky view and, to a certain extent, the length of time that the GPS has had a sky view.&lt;/li&gt;&#xA;&lt;li&gt;The number of positions used to calculate the velocity&lt;/li&gt;&#xA;&lt;li&gt;The acceleration of the unit &lt;/li&gt;&#xA;&lt;li&gt;Filtering algorithm used to smooth the velocity value &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The velocity value from the GPS receiver is calculated from the difference between position fixes.  As these are typically generated at a 1Hz rate you are measuring a distance travelled in 1 second.  The position fixes can have an error of a number of metres, with successive positions wandering from the true position, sometimes by a metre or more for a static unit.  I have had static units using high end GPS chipsets that have apparently had a velocity of up to 2 m/s while fixed to my office building.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some units may filter the velocity value or use more than 2 position fixes to calculate the antenna velocity.  This will add a lag to the velocity value shown as the antenna accelerates.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Providing a definitive answer is not possible in just the same way that defining position accuracy has to be bounded by many caveats around the sky view and number of satellites visible.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2011-03-30T11:20:58.730" CommentCount="2" />
  <row Id="12282" PostTypeId="2" ParentId="12237" CreationDate="2011-03-30T11:33:45.950" Score="2" ViewCount="" Body="&lt;p&gt;If you are charging the battery through the phone then this will have the charge controller circuitry between the 5V charge supply and the battery.  You CANNOT/MUST NOT just connect a battery pack to a power supply and expect it to charge without fire and or explosion.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The charge controller in the phone will limit the current supplied to the battery pack to be within the limits specified by the battery manufacturer to ensure that the battery is not damaged.  Supplying the phone from a 5V source that has a higher current capability will not make the battery charge any faster.  If it did then you would run the risk of damaging the connector on the phone or even melting the tracks on the PCB within the phone.  Small USB connectors that I have used have a contact rating of up to 1A on the power lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to build a charging station to charge multiple phones at a time then you need to have a power source that can supply up to the maximum charge current taken by the phone down each of the charging leads.  These can all be in parallel but I would place a diode in each of the positive supply lines to prevent the possibility of any current flowing from the battery back to the charger.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2011-03-30T11:33:45.950" />
  <row Id="12283" PostTypeId="1" AcceptedAnswerId="12284" CreationDate="2011-03-30T11:42:20.837" Score="4" ViewCount="348" Body="&lt;p&gt;I am beginner to electronics. I come to know about oscillator using RC circuits (Capacitor charge and discharge and time constant tells the behavior of circuit).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then I saw following circuit that blinks 2 LEDs timely in sequence.&#xA;Will somebody explain its working? I know that capacitor will charge and during the charging the LED will off and when they discharge they will on the LED.&#xA;But why transistor are there?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/G6Bx6.png&quot; alt=&quot;This Circuit will blink LEDs timely&quot;&gt; &lt;/p&gt;&#xA;" OwnerUserId="2951" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-30T13:59:47.953" LastActivityDate="2011-04-09T23:59:55.423" Title="How does an astable multivibrator LED blinking circuit work?" Tags="&lt;led&gt;&lt;transistor&gt;&lt;basic&gt;&lt;learning&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="12284" PostTypeId="2" ParentId="12283" CreationDate="2011-03-30T11:58:31.973" Score="10" ViewCount="" Body="&lt;p&gt;This circuit is called an astable multivibrator, and the reason this circuit works is a little difficult to put into words.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take a look at this &lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+8.63434833026695+50+5.0+50%0Aw+160+16+240+16+0%0Aw+240+16+320+16+0%0Aw+320+16+400+16+0%0Ar+160+16+160+144+0+330.0%0Ar+240+16+240+144+0+1020.0%0Ar+320+16+320+144+0+1020.0%0Ar+400+16+400+144+0+320.0%0Ac+160+224+240+224+0+1.8E-5+1.355691174861903%0Ac+320+224+400+224+0+1.8E-5+0.08243596569797973%0Aw+400+224+400+288+0%0At+320+304+400+304+0+1+-1.9284584808844805+-1.342790864916931+100.0%0Aw+240+224+320+304+0%0Aw+320+224+240+304+0%0At+240+304+160+304+0+1+0.6552032717205571+0.6681035816655293+100.0%0Aw+160+224+160+288+0%0AR+160+16+112+16+0+0+40.0+5.0+0.0+0.0+0.5%0Ag+160+320+160+352+0%0Ag+400+320+400+352+0%0Ax+191+260+212+264+0+16+C1%0Ax+349+261+370+265+0+16+C2%0Ax+128+308+149+312+0+16+Q1%0Ax+414+310+435+314+0+16+Q2%0A162+160+144+160+224+1+2.1024259+1.0+0.0+0.0%0A162+400+144+400+224+1+2.1024259+1.0+0.0+0.0%0Aw+240+144+240+224+0%0Aw+320+144+320+224+0%0Ao+13+64+6+35+5.0+9.765625E-5+0+-1%0Ao+10+64+6+35+5.0+9.765625E-5+1+-1%0A&quot; rel=&quot;nofollow&quot;&gt;circuit simulation&lt;/a&gt; that shows visually what is happening. You can slow the speed right down and look carefully at how the current is flowing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While one of the capacitors is charging, current flows to the base of the alternate transistor, making the emitter-collector path conduct, making one of the LEDs light. When the capacitor is charged, it stops conducting and switches off the transistor, and then the other capacitor begins to charge switching on the other transistor, at the same time the first capacitor discharges, then the cycle repeats. &lt;/p&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-30T12:03:50.443" LastActivityDate="2011-03-30T12:03:50.443" CommentCount="2" />
  <row Id="12285" PostTypeId="2" ParentId="12271" CreationDate="2011-03-30T12:37:44.717" Score="1" ViewCount="" Body="&lt;p&gt;You might consider SparkFun buttons to be cool-looking and stylish:&#xA;&lt;a href=&quot;http://www.sparkfun.com/categories/145&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/categories/145&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3424" LastActivityDate="2011-03-30T12:37:44.717" />
  <row Id="12286" PostTypeId="1" AcceptedAnswerId="12288" CreationDate="2011-03-30T12:57:35.560" Score="4" ViewCount="192" Body="&lt;p&gt;I know it's good practice to use bypass capacitors near the power pins of your ICs, but I'm now moving on from the breadboarding stage to the PCB-design stage, and I'd like to know if there are any good rules of thumb for when the caps are actually needed (I don't want to waste any PCB real-estate).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, what if I have a simple counter IC fed by a 250KHz clock signal?  31.25 kHz?  If all input and output signals of an IC are changing at sufficiently low frequencies &lt;em&gt;and if the IC doesn't draw much current&lt;/em&gt;, can I leave off the bypass caps? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Edit: inserted text in italic.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="3424" LastEditorUserId="3424" LastEditorDisplayName="" LastEditDate="2011-03-30T13:08:49.153" LastActivityDate="2011-03-31T01:08:43.570" Title="Bypass capacitors needed in low-frequency digital logic systems?" Tags="&lt;pcb-design&gt;&lt;decoupling-capacitor&gt;" AnswerCount="7" CommentCount="1" FavoriteCount="1" />
  <row Id="12287" PostTypeId="2" ParentId="12286" CreationDate="2011-03-30T13:01:57.233" Score="1" ViewCount="" Body="&lt;p&gt;I do not think so. 250kHz is not low frequency as far as PCB layout and decoupling is concerned. You do not need electrolytics on every chip, a $1\,\mathrm{\mu F}$ SMD ceramic should have you covered.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-30T13:01:57.233" />
  <row Id="12288" PostTypeId="2" ParentId="12286" CreationDate="2011-03-30T13:11:48.137" Score="7" ViewCount="" Body="&lt;p&gt;The relevant factor is the rise/fall times, not the clock rate. &lt;a href=&quot;http://www.cdnusers.org/community/allegro/Resources/resources_pcbsi/si/tp_zhen_capacitors.pdf&quot; rel=&quot;nofollow&quot;&gt;Here is a relevant paper&lt;/a&gt;.&#xA;Conventionally, designers stick to 100nF cap per IC. Bear in mind that they serve multiple purposes: signal integrity, power supply noise, internal IC operation, radiated EMI, susceptability to EMI. Using an SMT 0805 or smaller (smaller is better) shouldn't take too much board space.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastEditorUserId="2110" LastEditorDisplayName="" LastEditDate="2011-03-30T14:56:52.743" LastActivityDate="2011-03-30T14:56:52.743" />
  <row Id="12289" PostTypeId="2" ParentId="12286" CreationDate="2011-03-30T13:12:01.487" Score="3" ViewCount="" Body="&lt;p&gt;When, in the distant past, I used to do discrete logic designs, the rule was to put a 100nF ceramic by each chip and one 47uF electrolytic for every 6/8 devices.  This was in the days of 74LS ttl and 16MHz 80386 processors.&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2011-03-30T13:12:01.487" CommentCount="1" />
  <row Id="12290" PostTypeId="2" ParentId="12286" CreationDate="2011-03-30T13:13:45.280" Score="3" ViewCount="" Body="&lt;p&gt;When it comes to decoupling, clock frequency is rarely what determines how to do it.  The primary determination on simple chips (like quad-gates, buffers, etc.) is the edge rate (or slew rate) of the output signals.  The faster that signal transitions from 0 to 1 and 1 to 0 is the edge rate.  The faster the edge rate the more decoupling caps are required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edge rate is still very important for complex chips, but the logic inside the chip becomes a significant factor too.  Essentially, there are signals inside the chip that are transitioning too, and although you can't see or probe them they are important.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Decoupling caps are important, don't skimp on them-- especially when your power distribution wiring has more impedance than you'd like, as in a breadboard.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-30T13:13:45.280" />
  <row Id="12291" PostTypeId="1" CreationDate="2011-03-30T13:53:07.040" Score="4" ViewCount="187" Body="&lt;p&gt;Hey, yesterday I saw a demo (which was actually meant for my seniors) of a PSoC 5 board by cypress at my college. They demonstrated how to use the capsense built into the board and one of the PSoC chips to turn an LED on and off. This is basic Hello World stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although I thought it was cool and all, I really couldn't figure out in what way could I use those boards. Yes they eliminate all the need for making my own hardware, but how would I use this capability?&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2011-04-05T22:10:38.403" Title="What exactly is the use of PSoC?" Tags="&lt;projects&gt;&lt;psoc&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="3" />
  <row Id="12292" PostTypeId="2" ParentId="12291" CreationDate="2011-03-30T14:41:23.520" Score="4" ViewCount="" Body="&lt;p&gt;Cypress PSoC devices have blocks (PWM modules, counters, timers, UARTs, ADC, DAC, etc.) that can be configured easily by a GUI, which can speed up the development time of a project. (no need to design external circuitry, lay it out, etc.) Also, the PCB real estate reduction is a nice plus (no need for external chips for all of these functions).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since these blocks are actual hardware modules, you also don't need to spend time writing software to emulate these functions. They can be configured to trigger interrupts, so your state machine can easily interact with the blocks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PSoC 5, for example, has the following blocks: 20-bit sigma-delta ADC, 8-bit IDAC, 8-bit VDAC, 12-bit 1 Msps SAR ADC, PGA, Op-amp, TIA, frequency mixer, comparator, reference, cap-sense block. This sort of hardware is above and beyond what is provided in most microcontrollers.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-05T20:59:08.303" LastActivityDate="2011-04-05T20:59:08.303" CommentCount="4" />
  <row Id="12293" PostTypeId="2" ParentId="12291" CreationDate="2011-03-30T14:41:27.950" Score="6" ViewCount="" Body="&lt;p&gt;Those development boards are just a way for someone to quickly get up to speed in using the PSoC.  The intention is for an engineer to become familiar with that chip and then go and design it into your own custom PCB (and build millions of them and make everybody fist-fulls of money).  They also use those boards at college as sort of a &quot;gateway drug&quot;.  They get you hooked on the PSoC early, so when you go out into the real world you will tend to use them, ship millions, and make everybody fist-fulls of money.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cypress is by no means unique in this.  TI, Atmel, STMicro, Freescale, etc. all do this.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, if those boards work for you then great, use them.  Otherwise, um, don't.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an aside...  I used a PSoC when making the capacitive touch keypad for this &lt;a href=&quot;http://www.qscaudio.com/products/network/QSys/pagestation.php&quot; rel=&quot;nofollow&quot; title=&quot;QSC Q-Sys Paging Station&quot;&gt;paging station&lt;/a&gt;.  It turned out to be cheaper, more reliable, and better looking to make our own than buy a mechanical keypad.  We started out by evaluating one of the Cypress development boards, then quickly made our own PCB.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-30T14:41:27.950" CommentCount="2" />
  <row Id="12294" PostTypeId="1" AcceptedAnswerId="12354" CreationDate="2011-03-30T14:41:38.293" Score="0" ViewCount="102" Body="&lt;p&gt;So this seems to be a generic issue. &quot;libc.a&quot; is associate with some sort of incompatibility with floating point math and/or the correct library used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've added the &quot;-lm&quot; as suggested on the forums, but still unable to link/compile correctly?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any other suggestions? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;code&gt;&#xA;/opt/local/lib/gcc/avr/4.0.2/../../../../avr/lib/avr5/libc.a(cmpsf2.o):../../../libm/fplib/cmpsf2.S:58: multiple definition of &lt;code&gt;__ltsf2'&#xA;/opt/local/lib/gcc/avr/4.0.2/avr5/libgcc.a(_lt_sf.o):/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_cross_avr-gcc/work/build/gcc/fp-bit.c:1272: first defined here&#xA;/opt/local/lib/gcc/avr/4.0.2/../../../../avr/lib/avr5/libc.a(floatsisf.o):../../../libm/fplib/floatsisf.S:44: multiple definition of&lt;/code&gt;__floatsisf'&#xA;/opt/local/lib/gcc/avr/4.0.2/avr5/libgcc.a(_si_to_sf.o):/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_cross_avr-gcc/work/build/gcc/fp-bit.c:1334: first defined here&#xA;/opt/local/lib/gcc/avr/4.0.2/../../../../avr/lib/avr5/libc.a(modf.o):../../../libm/fplib/modf.S:88: relocation truncated to fit: R_AVR_13_PCREL against symbol `__subsf3' defined in .text section in /opt/local/lib/gcc/avr/4.0.2/avr5/libgcc.a(_addsub_sf.o)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;/code&gt;&lt;/p&gt;&#xA;" OwnerUserId="3309" LastActivityDate="2011-05-30T11:49:03.783" Title="avr-gcc(4.4.2)/avr-libc linker issues" Tags="&lt;avr&gt;&lt;compiler&gt;&lt;avr-gcc&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="12295" PostTypeId="2" ParentId="12132" CreationDate="2011-03-30T15:27:05.323" Score="0" ViewCount="" Body="&lt;p&gt;I agree with the view that 4:1 multiplexers are wonderful.  A couple years ago, I implemented an 8K bank-switched memory controller for an Atari 2600 using a single 74xx153/74xx253 and an RC de-glitching circuit.  The controller has to both provide an output which is the inverse of the A12 input, and it has to latch A6 when A11 is high and A12 low.  &quot;Back in the day&quot; (early 1980's), bank-switching cartridges would either use custom silicon or three TTL chips; using an off-the-shelf 74xx153, however (which was available back then) the job can be done in one chip.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-30T15:27:05.323" />
  <row Id="12296" PostTypeId="2" ParentId="12239" CreationDate="2011-03-30T15:27:08.643" Score="2" ViewCount="" Body="&lt;p&gt;Thank you for linking to exactly what you are talking about -- it makes it much easier to get to the data sheets.&#xA;The question &lt;a href=&quot;http://www.maxbotix.com/MaxSonar-EZ1__FAQ.html#How_can_I_use_more_than_one_MaxSonar_EZ1_in_the_same_system&quot; rel=&quot;nofollow&quot;&gt;&quot;How can I use more than one MaxSonar®-EZ1™ in the same system?&quot; in the MaxBotix MaxSonar FAQ&lt;/a&gt; lists several ways of using a bunch of them at one time (and some pitfalls to avoid).&#xA;Some of them use 2 pins of the MCU -- the same number of pins as I2C, but a completely different protocol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I understand &lt;a href=&quot;http://www.sparkfun.com/products/9491&quot; rel=&quot;nofollow&quot;&gt;the data sheet&lt;/a&gt; correctly, one of those 2-pin methods is:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;wire pin 1 low the MaxSonar to enable chaining&lt;/li&gt;&#xA;&lt;li&gt;Wire an output pin from your MCU to the RX pin of the first MaxSonar in the chain.&lt;/li&gt;&#xA;&lt;li&gt;Wire TX of each MaxSonar to RX of the next in the chain&lt;/li&gt;&#xA;&lt;li&gt;Combine the signals from all the MaxSonar PW pins (AND? OR? NAND? diodes?).&lt;/li&gt;&#xA;&lt;li&gt;Wire that combined signal to a timer input pin on the CPU.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Then software on the MCU&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;pulse the RX pin of the first MaxSonar&lt;/li&gt;&#xA;&lt;li&gt;Time the first pulse width to give the distance the first MaxSonar sees&lt;/li&gt;&#xA;&lt;li&gt;Time the second pulse width to give the distance the second MaxSonar sees&lt;/li&gt;&#xA;&lt;li&gt;...&lt;/li&gt;&#xA;&lt;li&gt;After getting the pulse from every sonar (or timing out at 49 ms per sonar), do something with the data.&lt;/li&gt;&#xA;&lt;li&gt;repeat.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Perhaps one of the other methods listed in the FAQ would work just as well or better for you.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-30T15:27:08.643" />
  <row Id="12297" PostTypeId="2" ParentId="12280" CreationDate="2011-03-30T15:54:40.493" Score="2" ViewCount="" Body="&lt;p&gt;With no filter at all the most error you should ever see is 30 meters/second, but this will only last for 1 sample. In my past experiences, you should expect to see an error more around less than 1 meter a second, but with 0 mean. This equates to about +/- 2.25 miles per hour. However, for consumer GPS modules you will never see an error like this. There are several reasons for this, but it all comes down to filtering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;GPS systems like the Garmin and Tom Tom employ filtering algorithms to give you the most accurate position it can. One of the things that these systems do is they assume you stay on the road until they are very sure that you didn't. With the filtering on the position, it forces the velocity calculations to already be much more accurate then using the raw data. Then with the filtering on the velocity calculations you get a very accurate measurement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NOTE: I should probably quantify what I mean by &quot;very accurate&quot;. I thinking about the situation of you having a GPS in a car and comparing its accuracy to what the car says it is at.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-03-30T15:54:40.493" CommentCount="2" />
  <row Id="12298" PostTypeId="2" ParentId="12255" CreationDate="2011-03-30T16:02:54.887" Score="1" ViewCount="" Body="&lt;p&gt;I would strongly argue that you should start you experience in C not asm.  It has many advantages, amoung them that it is much easier to take your experience to a new processor.  If you choose asm you should have a good reason for taking on the additional pain ( and in some cases it may be reasonable )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should be able to get your hands on free software tools to start, if not move to a different processor.  It is hard to see how you could go wrong starting with an arduino and use that experience to consider other enviroments.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-30T16:02:54.887" />
  <row Id="12299" PostTypeId="2" ParentId="12217" CreationDate="2011-03-30T16:17:00.113" Score="3" ViewCount="" Body="&lt;p&gt;Here is a technique for detecting gamma radiation using a PIN photodiode:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/2236&quot; rel=&quot;nofollow&quot;&gt;http://www.maxim-ic.com/app-notes/index.mvp/id/2236&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-30T16:17:00.113" />
  <row Id="12300" PostTypeId="1" AcceptedAnswerId="12377" CreationDate="2011-03-30T16:40:24.540" Score="2" ViewCount="145" Body="&lt;p&gt;Hi there,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got a big problem with my new Arduino. I made a big mistake, and now I can't anymore connect to my arduino. Is there any possibility to recover the Arduino, or to &lt;strong&gt;stop&lt;/strong&gt; the execution of code definitly?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here my code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void setup () {&#xA;  Serial.begin(9600);&#xA;}&#xA;&#xA;void loop () {&#xA;  Serial.write(&quot;Hello World!&quot;);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;My problem is, that this code is executed so immediatly after booting the Arduino, and I can't upload something different to the Arduino...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please help me. &lt;/p&gt;&#xA;" OwnerUserId="3451" LastActivityDate="2011-03-31T20:00:25.720" Title="Arduino - Stop execution of code definitly." Tags="&lt;arduino&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="12301" PostTypeId="2" ParentId="12255" CreationDate="2011-03-30T16:51:30.367" Score="1" ViewCount="" Body="&lt;p&gt;I would recommend getting started with Arduino, doing a few projects, then teaching yourself how to program the AVR ATMega. The two reasons to use AVR are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;huge online support network between AVR Freaks, Arduino Forums, SparkFun forums and Adafruit forums&lt;/li&gt;&#xA;&lt;li&gt;Free, open source tool-chain (unlike PIC AFAIK)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I good device to get is the Bus Pirate, which works as an ISP programmer for AVR chips + does lots of other things: &lt;a href=&quot;http://dangerousprototypes.com/bus-pirate-manual/&quot; rel=&quot;nofollow&quot;&gt;http://dangerousprototypes.com/bus-pirate-manual/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A great first project is to build an LED array. Start with an Arduino prototype, then re-do it with an AVR ATtiny chip (plenty of tutorials available).&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2011-03-30T16:51:30.367" />
  <row Id="12302" PostTypeId="1" AcceptedAnswerId="12309" CreationDate="2011-03-30T17:36:49.390" Score="4" ViewCount="207" Body="&lt;p&gt;So im wanting to learn Assembly first on a MP, then move onto C (since it seems like thats what most of them use)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im wanting to get into Embedded Programming, I really love low level C stuff (Kernals/Modules for Linux is mainly what i've done) but I love the idea of being able to program even lower level than that (Microcontrollers/Microprocessors)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know about Arduino....and thats great and all, but I can't find many resources for using Assembly with them. Atmel AVR's seem to be very popular (and cheap)....but when it comes to the actual hardware portion (hooking them up on a breadboard/etc) Im not finding much info.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ANY suggestions/Infomation or Resources that you guys/gals know about please let me know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: Another thing:&#xA;It seems like all the Microprocessor books I read (Usually AVR's) talk about the microprocessor itself, and programming it....but I have YET to see a book that actually talks about installing all the components yourself (Microprocessor+Memory+Power+etc) If I could find something that walks me through that i'd be in business. (I want to learn from the ground up) Not to mention I have no idea how'd you communicate between them.&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-03-31T14:39:40.170" Title="Whats a Good Starter Microprocessor to learn ASM?" Tags="&lt;microcontroller&gt;&lt;microprocessor&gt;&lt;assembly&gt;" AnswerCount="8" CommentCount="5" FavoriteCount="2" />
  <row Id="12303" PostTypeId="2" ParentId="12302" CreationDate="2011-03-30T18:09:13.263" Score="0" ViewCount="" Body="&lt;p&gt;You are confusing microcontrollers and microprocessors here. AVR is a microcontroller line by Atmel, not a microprocessor.&#xA;I suggest you first search on wikipedia to get a better understanding of what the differences are between these. Basically a microcontroller is a more or less complete system, whereas a microprocessor is only the cpu (hence a microcontroller has a microprocessor inside).&lt;/p&gt;&#xA;" OwnerUserId="3068" LastActivityDate="2011-03-30T18:09:13.263" CommentCount="3" />
  <row Id="12304" PostTypeId="1" AcceptedAnswerId="12307" CreationDate="2011-03-30T18:16:48.590" Score="2" ViewCount="190" Body="&lt;p&gt;I asked this question on programmers.exchange, but this seems like a better place to get a.....better idea if this is possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyways I graduated with a B.S. in CS at a pretty high ranked engineering college. Anyways.....I really love low level C stuff, Im trying to learn Assembly on various Microprocessors and such...but Im wondering if it's all a waste.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've really been advancing my knowledge in circuits (slowly but surely) Im investing in a Development kit to further my knowledge (still researching to find out which one I want to go with, but im thinking the MPS430 from T.I.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyways....do any of you professional Embedded Programmers have C.S. degrees instead of a C.E. or E.E. degree and ended up with a job? I realize E.E/C.E is probably more aimed at Embedded Programming.....but I figure a C.S. degree i mean your still writing C/Assembly which is still programming, and if I had Circuits knowledge would I still be able to get a job? I really really hope so.....because I didn't really realize I loved low level stuff until I ended college.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: I DO have a job btw, but it's not in embedded. it's a typical QA position but I do some development too, it's for a large fortune 500 company so maybe I could move sideways within the company....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="3073" LastEditorUserId="3073" LastEditorDisplayName="" LastEditDate="2011-03-30T22:23:16.043" LastActivityDate="2011-03-31T05:26:03.387" Title="Any Embedded Programmers with CS degrees here?" Tags="&lt;embedded&gt;&lt;programming&gt;&lt;careers&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="2" />
  <row Id="12305" PostTypeId="1" AcceptedAnswerId="12351" CreationDate="2011-03-30T18:16:54.080" Score="1" ViewCount="93" Body="&lt;p&gt;Normally in a car's DC installation the negative is on the car's body. Is it just to make it cheaper by not having to provide two wires everywhere, but just one and use the car body as negative, or is there another more important reason it is done that way?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I ask, because I want to make a secondary DC installation in the car, with another battery, different voltage, to be used for my electronics, computers, etc. The second installation will have a separate battery, but that battery will be charged off the main installation - not directly, but through a charge controller, basically a DC-to-DC converter with current limit, which will have separate positive and negative terminals for both input and output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you recommend to wire the negative of this secondary DC circuit, should I keep it separate, isolated from the car body, or should I also connect its negative wire to the car body, so use a common ground for both installations?&lt;/p&gt;&#xA;" OwnerUserId="1691" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-03-30T19:27:30.020" LastActivityDate="2011-03-31T10:50:18.247" Title="Is it a good idea to make a second DC installation in a car with its negative separate from the car body?" Tags="&lt;wiring&gt;&lt;car&gt;&lt;negative&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="12306" PostTypeId="2" ParentId="12304" CreationDate="2011-03-30T18:40:33.990" Score="3" ViewCount="" Body="&lt;p&gt;I have a BSc in Computer Science. My year group was the first to be taught wholly in Java. But, I did lots of hobby stuff and contributed to open source projects. That gave me something to put on my CV/resume.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first job, straight after graduation, was C programming for embedded Linux. From there I've moved further down the stack and now mostly work with microcontrollers, still in C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My advice: Do lots of what you enjoy. In my experience, employers are more impressed by completed hobby projects than qualifications.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-30T18:40:33.990" CommentCount="2" />
  <row Id="12307" PostTypeId="2" ParentId="12304" CreationDate="2011-03-30T18:50:58.453" Score="6" ViewCount="" Body="&lt;p&gt;I don't have an engineering degree, but in my experience working with engineers and reading answers to questions like these on the web, I've learned that you really shouldn't worry about what degree you have. What's much more important is what you can do, how efficiently you can solve problems and how well you can work with others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Engineering school gives you a theoretical background, but doesn't provide most of the practical knowledge needed for engineering. Since you have a &lt;em&gt;different&lt;/em&gt; theoretical background, it only makes you a more 'exotic' employee. &lt;/li&gt;&#xA;&lt;li&gt;IMO your undergraduate education is more about learning how to think in a structured way than it is about learning particular skills – engineering degrees are interchangeable in this sense.&lt;/li&gt;&#xA;&lt;li&gt;Other factors like your ability to work in teams, communication skills and general problem solving ability are more important than your undergraduate education.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Have a look at this article about when Richard Feynman was hired to work at an innovative computer hardware startup in the mid 80's: &lt;a href=&quot;http://longnow.org/essays/richard-feynman-connection-machine/&quot; rel=&quot;nofollow&quot; rel=&quot;nofollow&quot;&gt;http://longnow.org/essays/richard-feynman-connection-machine/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So keep hacking away at circuits and microcontrollers and you'll be fine. You're already way ahead of most engineering graduates.&lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2011-03-31T05:26:03.387" LastActivityDate="2011-03-31T05:26:03.387" CommentCount="2" />
  <row Id="12308" PostTypeId="2" ParentId="12305" CreationDate="2011-03-30T19:03:02.157" Score="3" ViewCount="" Body="&lt;p&gt;The battery negative being attached the the body is for a &lt;a href=&quot;http://en.wikipedia.org/wiki/Ground_%28electricity%29&quot; rel=&quot;nofollow&quot;&gt;common ground&lt;/a&gt;.  If you add a second battery it would probably be best to add it's negative to the body as well.  If not you could have issue with a &lt;a href=&quot;http://en.wikipedia.org/wiki/Floating_ground&quot; rel=&quot;nofollow&quot;&gt;floating ground&lt;/a&gt;.  This can cause circuit noise and shocks/discharges. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.zbattery.com/Connecting-Batteries-in-Series-or-Parallel&quot; rel=&quot;nofollow&quot;&gt;Connecting Batteries in series/parallel&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2412" LastEditorUserId="2412" LastEditorDisplayName="" LastEditDate="2011-03-30T20:20:34.040" LastActivityDate="2011-03-30T20:20:34.040" CommentCount="14" />
  <row Id="12309" PostTypeId="2" ParentId="12302" CreationDate="2011-03-30T19:03:41.763" Score="4" ViewCount="" Body="&lt;p&gt;I learned on a 68HC11 in college.  They are very simple to work with but honestly most low powered microcontrollers will be similar (AVR, 8051, PIC, MSP430).  The biggest thing that will add complexity to ASM programming for microcontrollers is the number and type of supported memory &lt;a href=&quot;http://en.wikipedia.org/wiki/Addressing_mode&quot; rel=&quot;nofollow&quot;&gt;addressing modes&lt;/a&gt;.  You should avoid more complicated devices at first such as higher end ARM processors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd probably recommend the MSP430 as a good starting point.  Maybe write a program in C and learn by replacing various functions with inline assembly.  Start simple, x + y = z, etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After you've replaced a function or algorithm with assembly, compare and contrast how you coded it and what the C compiler generated.  This is probably one of the better ways to learn assembly in my opinion and at the same time learn about how a compiler works which is incredibly valuable as an embedded programmer.  Just make sure you turn off optimizations in the C compiler at first or you'll likely be very confused by the compiler's generated code.  Gradually turn on optimizations and note what the compiler does.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;RISC vs CISC&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RISC means 'Reduced Instruction Set Computing' it doesn't refer to a particular instruction set but just a design strategy that says that the CPU has a minimal instruction set.  Few instructions that each do something basic.  The is no stringently technical definition of what it takes 'to be RISC'.  On the other hand CISC architectures have lots of instructions but each 'does more'.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The purposed advantages of RISC are that your CPU design needs fewer transistors which means less power usage (big for microcontrollers), cheaper to make and higher clock rates leading to greater performance.  Lower power usage and cheaper manufacturing are generally true, greater performance hasn't really lived up to the goal as a result of design improvements in CISC architectures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Almost all CPU cores are RISC or 'middle ground' designs today.  Even with the most famous (or infamous) CISC architecture, x86.  Modern x86 CPUs are internally RISC like cores with a decoder bolted on the front end that breaks down x86 instructions to multiple RISC like instructions.  I think Intel calls these 'micro-ops'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As to which (RISC vs CISC) is easier to learn in assembly, I think its a toss up.  Doing something with a RISC instruction set generally requires more lines of assembly than doing the same thing with a CISC instruction set.  On the other hand CISC instruction sets are more complicated to learn due to the greater number of available instructions.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most of the reason CISC gets a bad name is that x86 is by and far the most common example and is a bit of a mess to work with.  I think thats mostly a result of the x86 instructions set being very old and having been expanded half a dozen or more times while maintaining backward compatibility.  Even your 4.5Ghz core i7 can run in 286 mode (and does at boot).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for ARM being a RISC architecture, I'd consider that moderately debatable.  Its certainly a load-store architecture.  The base instruction set is RISC like, but in recent revisions the instruction set has grown quite a bit to the point where I'd personally consider it more of a middle ground between RISC and CISC.  The thumb instructions set is really the most 'RISCish' of the ARM instruction sets.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2011-03-31T06:08:34.353" LastActivityDate="2011-03-31T06:08:34.353" CommentCount="6" />
  <row Id="12310" PostTypeId="2" ParentId="12300" CreationDate="2011-03-30T19:34:21.140" Score="0" ViewCount="" Body="&lt;p&gt;Looking at the &lt;a href=&quot;https://github.com/arduino/Arduino/blob/master/hardware/arduino/bootloaders/atmega8/ATmegaBOOT.c&quot; rel=&quot;nofollow&quot;&gt;bootloader code&lt;/a&gt;. It seems that sending '0' to the Arduino as early as possible might hold it in bootloader mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try sending &quot;0000000000&quot; to the Arduino, followed quickly by uploading your code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Failing that, use another Arduino to program yours via the ISP pins.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-03-30T19:34:21.140" />
  <row Id="12311" PostTypeId="2" ParentId="12300" CreationDate="2011-03-30T19:39:31.873" Score="1" ViewCount="" Body="&lt;p&gt;Try &lt;a href=&quot;http://www.arduino.cc/en/Guide/Troubleshooting#upload&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; troubleshooting guide. The Auto-reset section may help.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-03-30T19:47:12.150" LastActivityDate="2011-03-30T19:47:12.150" CommentCount="1" />
  <row Id="12312" PostTypeId="1" AcceptedAnswerId="12314" CreationDate="2011-03-30T19:41:56.583" Score="5" ViewCount="168" Body="&lt;p&gt;I'm looking at a datasheet for a digital circuit and it specifies that the typical input hysteresis is 100 mV. What does this mean exactly? &lt;/p&gt;&#xA;" OwnerUserId="2968" LastActivityDate="2011-05-31T18:40:38.023" Title="what is &quot;input hysteresis&quot;?" Tags="&lt;datasheet&gt;" AnswerCount="6" />
  <row Id="12313" PostTypeId="2" ParentId="12312" CreationDate="2011-03-30T19:58:53.983" Score="3" ViewCount="" Body="&lt;p&gt;Hysteresis in a circuit arises when an input above a certain level triggers an output, but the output isn't reset until the input reaches a lower level. With an input between those values, the output remains the same (high or low). The difference between the two input values is the hysteresis. It typically occurs in circuits with positive feedback. An example of a circuit with hysteresis is a Schmitt trigger.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-03-30T19:58:53.983" />
  <row Id="12314" PostTypeId="2" ParentId="12312" CreationDate="2011-03-30T20:04:22.803" Score="8" ViewCount="" Body="&lt;p&gt;Let's say you detect a low-to-high transition at 2.5 V. A 100 mV hysteresis would mean that the low-to-high transition is detected at 2.55 V and the high-to-low transition is detected at 2.45 V, a 100 mV difference.&lt;br&gt;&#xA;Hysteresis is used to prevent several quickly successive changes if the input signal would contain some noise, for example. The noise could mean you cross the treshold of 2.5 V more than just once, which you don't want. A 100 mV hysteresis means that noise levels less than 100 mV won't influence the treshold passing.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-03-30T20:04:22.803" CommentCount="1" />
  <row Id="12315" PostTypeId="2" ParentId="12302" CreationDate="2011-03-30T20:08:53.707" Score="5" ViewCount="" Body="&lt;p&gt;I think 8 bits PIC microcontrollers are the best choice because of the reduced number of instructions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The side effect of the reduced number of instructions is that you have to reinvent the wheel compared with other microcontrollers with more instructions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But after learn with PIC, you can migrate to other microcontrollers and see whats fits better for you.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-03-30T20:08:53.707" />
  <row Id="12316" PostTypeId="1" AcceptedAnswerId="12317" CreationDate="2011-03-30T20:43:08.473" Score="1" ViewCount="39" Body="&lt;p&gt;I'd like to create a small device that can tell when it's near another created device or sensor.  When it detects the other device, it lights up an LED.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe maximum detection range of a few feet.  No need for any unique ID values or complex data exchange, just a simple &quot;Yes I detect one, no I don't&quot; sort of control.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions on how this could be done in a low power, portable sort of way? Because its requirements are so simple, something like RFID seems overkill (even if it could be made to work).&lt;/p&gt;&#xA;" OwnerUserId="3666" LastActivityDate="2011-03-30T20:49:48.063" Title="WTB (Build): Low power &quot;proximity to a device&quot; detector" Tags="&lt;sensor&gt;&lt;wireless&gt;" AnswerCount="1" />
  <row Id="12317" PostTypeId="2" ParentId="12316" CreationDate="2011-03-30T20:49:48.063" Score="1" ViewCount="" Body="&lt;p&gt;You could use a simple Infra-red LED, and a photo diode. You may have to adjust the LED intensity with a potentiometer to calibrate the range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will sense proximity providing there is line-of-sight.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-03-30T20:49:48.063" CommentCount="3" />
  <row Id="12319" PostTypeId="2" ParentId="12302" CreationDate="2011-03-30T21:08:28.180" Score="1" ViewCount="" Body="&lt;p&gt;I learnt 16-bit PIC assembly with a dsPIC33F. The processor's assembly is quite C like, in that it supports pointers and three variable operations (A = B + C, for example), which makes learning and adapting to it much easier.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-30T21:08:28.180" />
  <row Id="12320" PostTypeId="2" ParentId="12302" CreationDate="2011-03-30T21:21:02.853" Score="3" ViewCount="" Body="&lt;p&gt;Similar to Mark's suggestion of the 68HC11, The instruction set of the &lt;a href=&quot;http://www.freescale.com/webapp/sps/site/taxonomy.jsp?nodeId=01624684491437&quot; rel=&quot;nofollow&quot;&gt;Freescale 68HCS08 family&lt;/a&gt;  is a slimmed-down version of the Motorola 6809, which I thought had one of the cleanest 8-bit instructions sets of its time.  You can get a development board with switches, LED's, 3-axis accelerometer and piezo buzzer for $79 &lt;a href=&quot;http://www.mouser.com/ProductDetail/Freescale-Semiconductor/DEMO9S08JS16/?qs=sGAEpiMZZMsjLMBIknjmkoA5JE3wl8ndzJI33CHOPqI=&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-03-30T21:21:02.853" CommentCount="3" />
  <row Id="12321" PostTypeId="2" ParentId="12217" CreationDate="2011-03-30T21:24:08.203" Score="1" ViewCount="" Body="&lt;p&gt;For some reason, the &lt;a href=&quot;http://www.electronickitsbychaneyelectronics.com/?utm_source=Electronic%20Goldmine%20Newsletter&amp;amp;utm_campaign=eb06d451de-Mar18&amp;amp;utm_medium=email&quot; rel=&quot;nofollow&quot;&gt;Electronics Goldmine weekly sales sheet&lt;/a&gt; featured radiation detectors a couple of weeks ago.  There's a lot of interesting and informative material on the links.  Most of the items are cold war salvage.&lt;/p&gt;&#xA;" OwnerUserId="1756" LastActivityDate="2011-03-30T21:24:08.203" />
  <row Id="12322" PostTypeId="2" ParentId="12302" CreationDate="2011-03-30T21:25:14.333" Score="3" ViewCount="" Body="&lt;p&gt;The msp430 instruction set is a good one for learning assembler on.  Avoid x86.  Arm is another good one but has a lot more instructions and options and may not be best suited as a first instruction set.  Thumb is a subset of the arm instruction set and not bad, on github I have both a thumb emulator (thumbulator) and an msp430 emulator (not tested as much as the thumb one) that are barebones, just the processor and memory and little more, so you can get good visibility into what is going on.  An alternative would be qemu for example where the visibility is there but much harder to get at, likewise with a qemu like solution it takes a lot more work before you figure out if you have anything working.&lt;br&gt;&#xA;goto mspgcc4.sf.net to build a toolchain, and/or a stock binutils (./configure --target=msp430 --prefix=/something) in combination with a stock llvm.  Once you are ready for hardware an msp430 development board costs under 5 dollars.&#xA;For arm/thumb tools just get the lite version from codesourcery.  A cortex-m3 (thumb/thumb2) board is about 12 bucks right now.&#xA;I would avoid x86 and avr and others as a first instruction set, you will want to learn others to be well rounded.  The old/original pic instruction set is something worth looking at as well.  You could write a simulator yourself in an afternoon for it as well as learn the assembler.  I wouldnt learn it first necessarily, it does teach some interesting things, but at the same time doesnt scale and isnt necessarily representative of common features you find in most instruction sets.  The msp430 gave me the feel of the pdp11 which is the first instruction set I really learned, both have well rounded, mostly orthogonal features.  Both the msp430 and microchip pic instruction sets are documented at wikipedia, at least as a reference, to get the whole picture get the datasheets/manuals from the vendors which will describe each register and addressing mode, reset/boot, etc.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-03-30T21:25:14.333" CommentCount="1" />
  <row Id="12323" PostTypeId="2" ParentId="12304" CreationDate="2011-03-30T21:43:44.090" Score="1" ViewCount="" Body="&lt;p&gt;I have both a BSEE and an MSCS, and have been doing embedded microcontroller projects for 30 years.  You don't need a EE degree to be able to do embedded programming, but some knowledge of electronics certainly helps.  (I also design the hardware and layout the PCB's, where my EE is more relevant).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In almost any embedded project, you will be dealing with lots of I/O and register layouts, so you need to be able to read datasheets and understand bit-twiddling.  This is particularly the case when you are working with smaller 8 and 16-bit microcontrollers with embedded I/O and memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are working with embedded Linux, unless you are writing device drivers you will be less involved in the hardware, since you will probably be dealing with a 32-bit microprocessor, which is not that much different than writing code for desktop Linux.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In any kind of embedded system, you sometimes need to look at various signals, where the ability to use an oscilloscope or logic analyzer, and be able to read a schematic will come in very useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting a development board and learning how to use its various features will give you a good start.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-03-30T21:43:44.090" CommentCount="2" />
  <row Id="12324" PostTypeId="2" ParentId="12304" CreationDate="2011-03-30T22:02:28.637" Score="1" ViewCount="" Body="&lt;p&gt;I have a BSc(Hons) in Computer Science  ( that's a commonwealth degree).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done embedded realtime since about 1999, soft realtime before that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also do JEE ( client-server stuff).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've written C, Assembly, ADA, .... embedded realtime Java&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can be done.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-03-30T22:02:28.637" />
  <row Id="12325" PostTypeId="2" ParentId="12302" CreationDate="2011-03-30T22:11:25.320" Score="2" ViewCount="" Body="&lt;p&gt;I too learned on a 68HC11 in college. Rather they suggest this over any other MPU/MCU, I just wanted to point out the the development board we used had a monitor program on it. So from a dumb terminal we could step through the code and examine the registers... I'd suggest when you know which processor fits your requirements you also check into what development boards are available with a monitor program.&lt;/p&gt;&#xA;" OwnerUserId="2319" LastEditorUserId="2319" LastEditorDisplayName="" LastEditDate="2011-03-31T14:39:40.170" LastActivityDate="2011-03-31T14:39:40.170" CommentCount="1" />
  <row Id="12326" PostTypeId="2" ParentId="12286" CreationDate="2011-03-30T22:14:10.733" Score="1" ViewCount="" Body="&lt;p&gt;The reason that capacitors are placed between IC supply pin(s) and power return (ground) is usually to filter out noise produced as current pulses are sucked into the IC (sorry if I'm stating the obvious). This is mostly a consideration with digital ICs, not so much with say linear amplifiers. CMOS digital circuits, for example, generally only draw current when they switch. Thus, the supply current tends to go in pulses. These current pulses create voltage noise as they flow through the finite interconnect resistance between the power supply and the IC. Additionally, the power supply (or battery) will generally have a finite output resistance which will have a voltage drop across it as current is pulled from the power supply. And since many circuits usually share a supply, everybody sees this noise -- not a good thing for sensitive circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, with a &quot;local&quot; filter (decoupling) capacitor placed right at the IC supply pin, most of the current pulse will be pulled out of the local capacitor and will not need to come from all the way from the power supply. And since the pulse is brief, the total charge taken out of the cap will be small enough that the capacitor voltage will droop only a little bit--so not much current will need to come from the supply to charge it back up over each switching cycle. Upshot: noise on the supply rail is greatly reduced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As others have suggested, the clock frequency is not so much the problem. The amplitude of the current spikes is the problem. The more transistors switching, the more current will be drawn. And since the transistors switch very quickly, the current pulses will be very brief (this is sort of what is meant when talking about edge rate or slew rate). You could imagine a situation where many many transistors switch synchronously at 10Hz and draw gigantic current spikes. So indeed, clock rate does play a large part, but not the only part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Decoupling is primarily an issue with digital ICs, but you do generally want to use decoupling caps on the rails of say an opamp as well, since it will help filter out noise produced by other circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Updated: generally the rule of thumb would be to stick a 0.1uF on each power pin. Shouldn't take up too much space. Even if the RMS current is low, the pulsed current could be higher. But if you have a noise-robust system (all digital, few components, low power, low current), it may not really matter much...&lt;/p&gt;&#xA;" OwnerUserId="3635" LastEditorUserId="3635" LastEditorDisplayName="" LastEditDate="2011-03-31T00:50:51.360" LastActivityDate="2011-03-31T00:50:51.360" />
  <row Id="12328" PostTypeId="2" ParentId="12286" CreationDate="2011-03-30T23:05:09.387" Score="1" ViewCount="" Body="&lt;p&gt;My inclination would be to assume that if a chip does not have a bypass cap, the outputs and internal state may be arbitrarily randomized for a few nanoseconds any time any of the inputs or internal state changes.  If this would cause adverse effects, use a bypass cap.  If this would not cause any adverse effects (e.g. because the outputs of the chip will only be sampled at a time long after the inputs have changed, and because the input changes are sufficiently far apart that output noise would not cause unwanted RF emissions) then the bypass caps may probably be omitted.  Note that by this definition almost any part with any sort of latching will need a bypass cap; if the state of a device's output pins will always either be irrelevant to any downstream circuitry or else be determined unambiguously by the inputs, any latching will be irrelevant.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-30T23:05:09.387" />
  <row Id="12329" PostTypeId="2" ParentId="12304" CreationDate="2011-03-31T00:50:21.273" Score="2" ViewCount="" Body="&lt;p&gt;&quot;Embedded&quot; spans a broad spectrum. I have a BSEE and an MS in Software Engineering and work on embedded systems, but they are Pentium-class CPU based. My co-workers have degrees ranging from CS to EE to Physics and Math. Some of us have traditional embedded microcontroller background, but many of the others have never fired up a cross compiler or an ICE. But it's all still &quot;embedded.&quot; When the customer hits the power button, the only thing they can identify as a computer would be the UI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The guys doing the microcontroller level work all have EE degrees. The products we build have literally dozens of CPUs, programmed in everything from Assembly to C++ (and sometimes a scripting language for in house debugging tools). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a lot of work available at different system levels and where you fit depends less on the specific degree you have and more on what you can bring to the table in terms of experience. Embedded systems have become large and complex enough that simply hacking together a few lines of C doesn't cut it anymore for a large class of product.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-03-31T00:50:21.273" />
  <row Id="12331" PostTypeId="2" ParentId="12286" CreationDate="2011-03-31T01:08:43.570" Score="1" ViewCount="" Body="&lt;p&gt;What drives your concern about PCB real-estate?  0.1 uF and 1 uF caps are physically small, and usually adds only small routing complication. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doing surface mount devices?  Try adding the caps on the back side of the board.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doing socketed-DIP's?  You can get sockets with built-in capacitors, so you could design without the caps, and change your socket if you find that you need them.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-03-31T01:08:43.570" />
  <row Id="12332" PostTypeId="1" CreationDate="2011-03-31T01:55:11.400" Score="3" ViewCount="62" Body="&lt;p&gt;Can I effectively take a 3 ft standard cell phone charger (AC to microUSB, 750 mA at 5V) and lengthen the cord to 6 ft by splicing the cord or am I going to lose something in the mix?  Do I need to account for the length of the cord when they are such short lengths?&lt;/p&gt;&#xA;" OwnerUserId="2809" LastActivityDate="2011-03-31T03:44:17.120" Title="Lengthen a AC to microUSB phone charger cord?" Tags="&lt;wire&gt;&lt;battery-charging&gt;&lt;resistance&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="12333" PostTypeId="2" ParentId="12332" CreationDate="2011-03-31T02:15:48.223" Score="3" ViewCount="" Body="&lt;p&gt;Adding 3 feet shouldn't be any problems at all.  The USB power spec allows for some voltage variation, and the added 3 feet isn't going to exceed that spec at all.  In fact, it will hardly be noticeable.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-31T02:15:48.223" />
  <row Id="12334" PostTypeId="2" ParentId="12332" CreationDate="2011-03-31T02:17:16.087" Score="4" ViewCount="" Body="&lt;p&gt;A couple things.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Charging cables run up to &lt;a href=&quot;http://www.usb.org/developers/devclass_docs/batt_charging_1_1.zip&quot; rel=&quot;nofollow&quot;&gt;1.8 amps under the usb spec&lt;/a&gt;. I have an &lt;a href=&quot;http://electronics.stackexchange.com/q/5498/230&quot;&gt;answer about it here&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.ehow.com/how_5770966_splice-two-usb-cables-together.html&quot; rel=&quot;nofollow&quot;&gt;Yes&lt;/a&gt;, it will work. Please make sure to use heat-shrink or electrical tap to avoid shorts.&lt;/li&gt;&#xA;&lt;li&gt;USB runs relatively high speed and 6 feet is further then you might think, this can significantly degrade performance on the communication, not an issue for just charging. There are cables out there that come &lt;a href=&quot;http://www.amazon.com/USB-Male-Micro-Cable-Feet/dp/B002HMWQE2&quot; rel=&quot;nofollow&quot;&gt;6 foot&lt;/a&gt; or &lt;a href=&quot;http://www.amazon.com/Cable-Type-Male-Micro-Feet/dp/B002I8MUJG/ref=sr_1_2?s=electronics&amp;amp;ie=UTF8&amp;amp;qid=1301537758&amp;amp;sr=1-2&quot; rel=&quot;nofollow&quot;&gt;more&lt;/a&gt;.&lt;em&gt;(ignore this if it is a wall outlet to USB charge adapter)&lt;/em&gt;&lt;/li&gt;&#xA;&lt;li&gt;If you are using a wall charger and it is only giving you 750mA you are getting half of the capacity you could be getting. If you phone can handle it, higher end phones will, you will be able to charge in less than half the time. (ignoring the charging characteristics of the last 10% of a lithium battery)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Just a quick list of things that might help. Your splicing the data cables will hurt the data quality and probably radiate some noise. I do not think there are any communication protocols on a harmonic of USB, so it should not matter one bit.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-03-31T03:44:17.120" LastActivityDate="2011-03-31T03:44:17.120" CommentCount="2" />
  <row Id="12335" PostTypeId="2" ParentId="12312" CreationDate="2011-03-31T02:20:04.420" Score="2" ViewCount="" Body="&lt;p&gt;The other two answers give an example of what hysteresis means in a particular case where there is a discrete trigger, but hysteresis has a more general meaning in the continuous domain, which is the following:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A system is said to exhibit hysteresis when measurements taken in one &quot;direction&quot; are not necessarily equal to measurements of the &quot;same thing&quot; taken in the other &quot;direction&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, imagine you have a potentiometer with markings from 0 to 9. The potentiometer could be said to exhibit hysteresis if when turned to &quot;5&quot; in the clockwise direction, the actual resistance were 5.1kΩ while when turned to &quot;5&quot; in the counter-clockwise direction, the actual resistance were 4.9kΩ. Unlike the discrete example, the same effect might be present when the knob is turned to &quot;4&quot;. Or the effect could be the opposite at &quot;4&quot;!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's a 1-dimensonal case. You can imagine 2-dimensional hysteresis in the case of, for instance, a sensor consisting of a sheet of material that can sense stretch or strain in two nearly orthogonal directions.&lt;/p&gt;&#xA;" OwnerUserId="207" LastEditorUserId="207" LastEditorDisplayName="" LastEditDate="2011-03-31T05:27:47.473" LastActivityDate="2011-03-31T05:27:47.473" />
  <row Id="12336" PostTypeId="2" ParentId="12312" CreationDate="2011-03-31T02:55:45.583" Score="0" ViewCount="" Body="&lt;p&gt;This is tangentially related, but it is a mechanism by which ICs can provide input hysteresis; some chip inputs have &quot;pin keeper&quot; circuits.  They generate a weak positive feedback out the pin which aids in preserving state.  However, the hysteresis range varies depending on the input impedance.  Providing the pin-keeper a signal with no impedance would have no hysteresis, while giving it a signal with impedance higher than the feedback resistor would mean it's unable to change the state at all.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WnGKQ.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Adapted from an &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc0776.pdf&quot; rel=&quot;nofollow&quot;&gt;Atmel CPLD datasheet&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-03-31T02:55:45.583" />
  <row Id="12337" PostTypeId="2" ParentId="12302" CreationDate="2011-03-31T02:56:59.313" Score="2" ViewCount="" Body="&lt;p&gt;Are you sure you want to learn Assembly?  Can you say why?  It is quite a task, and is less and less relavent or useful now a days.  This is from a person who has written in it and even hand assembled programs ( no assembler, linker, just a card with the instruction set ).&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-03-31T02:56:59.313" />
  <row Id="12338" PostTypeId="2" ParentId="12312" CreationDate="2011-03-31T03:30:45.943" Score="1" ViewCount="" Body="&lt;p&gt;If you have ever had one of those nightlight hall light things you plug in a wall socket that has a light sensor, when it gets dark it turns the light on, but its own light turns the light off, then it is dark and it turns the light on.  But it is so fast that it just flickers, can be headache inducing for some folks. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now think about a digital thermostat for your house.  Imagine if it were poorly placed right in line with an air conditioner vent.  You have it set for some temp like 72 degrees.  Imagine that when it reads 73 it turns the A/C on, but as soon as the A/C turns on it cools it back down into the 72 range and turns it off.  Not as fast as the light sensor nightlight but not a great design.  Instead what you will see is a well placed or at least better placed thermostat, that when it switches from 72 to 73 it kicks the A/C on, but wont turn it off until it drops down into 72 then down below 72 into 71.  Being well placed the mass of warm air has to push through the house until the mass of cooler air reaches the thermostat to the point that it turns the A/C off.  Instead of a quick on and off the on, off, to on cycle can be half an hour or more.  Much more efficient.  In this case the hysteresis is a whole degree, the switch on temperature is on the boundary between 72 and 73 degrees and the switch off temperature is on the boundary between 72 and 71 degrees.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a number of problems that either by design want to have hysteresis, the switch on is at one level and the switch off at another level.  Specifically to avoid some sort of oscillation about a single switch point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes you end up with hysteresis when you dont necessarily want it, like the steering on an older vehicle, from mechanical wear you may have to turn the wheel a inch or two to the left of center to make the wheels start to turn left and then travel through the dead spot an inch or two to the right of center to get the wheels to turn to the right.  you can wiggle the wheel in between these two points and have nothing happen.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-03-31T03:30:45.943" />
  <row Id="12339" PostTypeId="2" ParentId="12304" CreationDate="2011-03-31T04:40:17.600" Score="1" ViewCount="" Body="&lt;p&gt;Not a waste, my degree is EE, but my day job has almost always been on the low level embedded software side of the line between hardware and software (although I do walk the line and step over from time to time).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been doing this for over 25 years and have worked with folks with no degrees at all, CS degrees, EE degrees, folks that started out as technicians.  It has more to do with being motivated and going after what you want than taking a class or waiting for the company to send you to some training thing.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The low level embedded stuff is not all about assembler.  Assembler is a language, load and stores, alu operations, add, and, or, not, xor, etc.  No matter what you do, some assembler experience will make you a better high level language programmer.  What is more important is reading the datasheets and programmers reference manuals and at least seeing where things are hooked up on a schematic.  You dont necessarily need to understand the resistors and capacitors and such but it helps if you get someone to show you.  So the bigger problem is learning to program the peripherals, start with I/O pins and timers and perhaps uarts and work your way up from there.  Getting a microcontroller eval board like the msp430 boards is a good thing.  Just the act of learning to boot the thing using your software.  from the schematic knowing what I/O pin the led is on.  Enabling the I/O as an output and writing a 1 and 0 to the right bits to change the voltage on that I/O pin to turn the led off.  Then slowing that down from megahertz down to something slow enough a human can see that it is turning on and off.  Every few seconds perhaps.  That activity will teach you volumes.  Do it in assembler then re-do it in C likely with assembler as your startup code.   Manipulating the compiler/assembler/linker tools is a big part of the knowledge you will need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Get a microcontroller board or a few, expect to melt some parts down from time to time (you are not trying hard enough if you never let any smoke out of the parts)(careful not to blow your computer/motherboard in the process) so buy spares. And have at it, I think you will find out for yourself if this is the kind of thing you want to keep doing and where your skills are lacking.  I bet you can use the home projects as watercooler talk in the engineering wing of the company, both learning what you really need to know from the engineers (which is not necessarily what you would learn if you took a class) and at the same time getting familiar with those engineers to find out what they do and get your foot in the door with their department group in case you want to try to transfer over and work there.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-03-31T04:40:17.600" CommentCount="1" />
  <row Id="12340" PostTypeId="2" ParentId="5435" CreationDate="2011-03-31T06:01:08.427" Score="0" ViewCount="" Body="&lt;p&gt;I'm not sure about Digilent boards, but the Altera boards have full documentation as well as code demonstrations for every peripheral. its pretty easy to get started.&lt;/p&gt;&#xA;" OwnerUserId="3668" LastEditorUserId="3668" LastEditorDisplayName="" LastEditDate="2011-03-31T06:09:30.250" LastActivityDate="2011-03-31T06:09:30.250" />
  <row Id="12341" PostTypeId="1" CreationDate="2011-03-31T06:39:30.717" Score="2" ViewCount="145" Body="&lt;p&gt;My lab partner and I are really stumped. We are given a circuit that has a FET with a $V_{DD} = -V_{SS} = 15\mbox{ }V$. We are told $A_V = 20$ and $I_{DS} = 1\mbox{ }mA$. The DC circuit is straightforward, containing an $R_D$ and $R_S$ between $V_{DD}$ and $V_{SS}$, respectively, and the FET drain and source terminals. There is a resistor $R_G = 1.5\mbox{ }M\Omega$ on the gate terminal of the transistor, connected to ground on the other end. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are asked what the DC current through this resistor ($R_G$?) is. We are then asked what $V_{OV}$ is. It seems to imply that we only need values that I have outlined so far, but maybe it would require values from a data sheet too, I'm not sure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then it says, using $V_{GS}$, which I would know how to calculate if I knew $V_{OV}$, to calculate $R_S$. It also says we don't know $V_{DS}$ nor $R_D$ yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be appreciated. I have tried reading the notes and textbook, but I can't find what I need. I would also appreciate any sort of good sources/guides to this, if you don't want to just give me the answer. I too, would like to understand so I feel less like a cheater, haha.&lt;/p&gt;&#xA;" OwnerUserId="3669" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-31T17:31:48.900" LastActivityDate="2011-04-04T03:31:10.613" Title="Solving DC Operating Point of Common Source Amp" Tags="&lt;circuit&gt;&lt;transistor&gt;&lt;amplifier&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="2" />
  <row Id="12342" PostTypeId="2" ParentId="12248" CreationDate="2011-03-31T06:54:47.013" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;The power consumption of the fuse itself:&lt;/strong&gt; $P_{FUSE} = R_{FUSE} * I^2$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The contribution of a fuse's power dissipation becomes significant when you count all the watts and milliwatts on the way to finding out about the efficiency of a device on the component level, e.g. in a switch-mode power supply. This is often done to cross-check the efficiency you measured on a black-box level ($P_{OUT}$ vs. $P_{IN}$).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The power consumption of the device connected to the fuse:&lt;/strong&gt; Not measurable when just the two pins of the fuse are available. You can measure the current flowing to the circuit, but you don't know the exact voltage.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-31T20:05:43.710" LastActivityDate="2011-03-31T20:05:43.710" />
  <row Id="12343" PostTypeId="1" CreationDate="2011-03-31T07:37:42.017" Score="2" ViewCount="102" Body="&lt;p&gt;Hey Stack!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After receiving a ton of feedback from &lt;a href=&quot;http://electronics.stackexchange.com/questions/7003/best-one-off-diy-pcb-creation-technique&quot;&gt;this post&lt;/a&gt;, I decided to give the old toner method a try once again. I grabbed a GBC Creative 9 laminator off of &lt;a href=&quot;http://www.amazon.com/GBC-9-Creative-Laminator/dp/B000MBLW90&quot; rel=&quot;nofollow&quot;&gt;Amazon&lt;/a&gt; for $23 and am now looking to modify it to produce more heat for the transfer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I ran across &lt;a href=&quot;http://ultrakeet.com.au/index.php?id=article&amp;amp;name=fritzHack&quot; rel=&quot;nofollow&quot;&gt;UltraKeet Australia&lt;/a&gt; where PodeCoet modified a similar GBC laminator for the same purpose. I got the laminator in the other day and quickly took it apart only to realize that my model was slightly different. Unlike his model, I only have one thermal switch in my unit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a picture of the thermal switch and thermal fuse that comes with the Creative 9 laminator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/LnSUL.jpg&quot; alt=&quot;Thermal Switch (left) and Thermal Fuse (right)&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing that I noticed on PodeCoet's laminator, he has a switch on the front of his unit which allows 3mm and 5mm items to be inserted. He also labeled the two thermal switches noting that one was for 3mm and one for 5mm. This may explain the missing component on my system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am wondering if and how I can safely modify my unit to produce more heat for the Toner Transfer method. Also, if anyone can point me in the direction of a component that will put out around 200-220 celcius, I would be much appreciated as I have not found anything cheaper than $35 (on Mouser).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help is appreciated. Thank you in advance.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastEditorUserId="1575" LastEditorDisplayName="" LastEditDate="2011-03-31T07:44:26.833" LastActivityDate="2011-03-31T07:44:26.833" Title="Toner Transfer + GBC Creative 9 Laminator: GBC Mod Question" Tags="&lt;pcb&gt;&lt;pcb-fabrication&gt;&lt;toner-transfer&gt;" />
  <row Id="12344" PostTypeId="2" ParentId="5435" CreationDate="2011-03-31T08:16:46.430" Score="0" ViewCount="" Body="&lt;p&gt;Something worth considering is the range of boards offered by Opal Kelly. There isn't much of a difference in price between their entry level Spartan 3 and Spartan 6 boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The big advantage we find with them is the on board USB support with associated HDL blocks for the FPGA and library code for your computer that makes it very easy to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.opalkelly.com/products/&quot; rel=&quot;nofollow&quot;&gt;http://www.opalkelly.com/products/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2960" LastActivityDate="2011-03-31T08:16:46.430" />
  <row Id="12345" PostTypeId="1" CreationDate="2011-03-31T08:57:46.253" Score="2" ViewCount="215" Body="&lt;p&gt;I'm trying to think of the best way to convert a PWM signal into an analog signal. I &lt;em&gt;could&lt;/em&gt; use an RC filter, but that requires a very high PWM frequency to create a faithful reproduction of the signal. In my case I'm dealing with audio frequencies for the analog signal - up to 20 kHz. So, what other options are there?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-31T22:11:24.680" Title="Converting PWM into an analog signal" Tags="&lt;analog&gt;&lt;pwm&gt;" AnswerCount="3" CommentCount="6" FavoriteCount="4" />
  <row Id="12346" PostTypeId="1" AcceptedAnswerId="12348" CreationDate="2011-03-31T09:00:30.447" Score="1" ViewCount="90" Body="&lt;p&gt;I have multiple generators that are producing a variable DC voltage between 0 and 18volts each that are being sent to an inverter for an AC output used to power various devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really need to be able to transmit an audio signal back to each of the generators, and would really like to avoid having to add additional wires. Would it be possible to piggyback an audio signal of a usable quality over these variable DC lines?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've searched around and suspect &lt;a href=&quot;http://electronics.stackexchange.com/questions/1654/injecting-a-communication-signal-over-dc-power-supply-lines/1661#1661&quot;&gt;this answer&lt;/a&gt; might be appropriate, but they're mostly talking about communication signals, and I'm not sure if the required fidelity for an audio signal would be possible. I'm also not sure the effect a highly variable DC voltage would cause.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="3670" LastActivityDate="2011-03-31T09:12:08.643" Title="Transmitting audio over variable voltage DC power line?" Tags="&lt;power&gt;&lt;audio&gt;&lt;dc-dc&gt;" AnswerCount="1" />
  <row Id="12347" PostTypeId="1" CreationDate="2011-03-31T09:05:27.527" Score="0" ViewCount="93" Body="&lt;p&gt;Can any one recommend / compare performance of digital inverter and analogue inverter for home UPS application? Which one is better, Analaogue or digital ? and why?&lt;/p&gt;&#xA;" OwnerUserId="3671" LastActivityDate="2011-03-31T09:58:03.487" Title="Digital Inverter or Analogue Inverter?" Tags="&lt;inverter&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12348" PostTypeId="2" ParentId="12346" CreationDate="2011-03-31T09:12:08.643" Score="4" ViewCount="" Body="&lt;p&gt;You would need to use a modulated signal, not the baseband audio because the low frequencies will be heavily attenuated by capacitance on the d.c. voltage, and because of the rate of change of your d.c. voltage could be at low audio frequencies (rumble). I'm sure you could get reasonable audio quality if you use a suitable modulation that could be seperated out from the d.c./low frequency signal.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-03-31T09:12:08.643" CommentCount="5" />
  <row Id="12349" PostTypeId="2" ParentId="12347" CreationDate="2011-03-31T09:58:03.487" Score="6" ViewCount="" Body="&lt;p&gt;I think you have been confused by the &lt;a href=&quot;http://en.wikipedia.org/wiki/Polymorphism_in_object-oriented_programming&quot; rel=&quot;nofollow&quot;&gt;overloading&lt;/a&gt; of the term &quot;inverter&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A UPS (&lt;a href=&quot;http://en.wikipedia.org/wiki/Uninterruptible_power_supply&quot; rel=&quot;nofollow&quot;&gt;uninterruptable power supply&lt;/a&gt;) converts a low d.c. battery voltage to an approximation of a sinusoidal mains (high) voltage. Since it is the opposite of the common power supply design which converts high voltage mains to low voltage d.c., it can be called an inverter. But it has nothing to do with analogue and digital inverters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A digital inverter is also called a &lt;a href=&quot;http://en.wikipedia.org/wiki/Inverter_%28logic_gate%29&quot; rel=&quot;nofollow&quot;&gt;NOT gate&lt;/a&gt; and simply outputs the boolean opposite of the input. Voltage levels are defined by the logic family and supply rails.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An &lt;a href=&quot;http://en.wikipedia.org/wiki/Operational_amplifier#Inverting_amplifier&quot; rel=&quot;nofollow&quot;&gt;analogue inverter&lt;/a&gt; is an amplifier which produces opposite phase signals to the input, so as the input goes up, the output goes down.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-03-31T09:58:03.487" />
  <row Id="12351" PostTypeId="2" ParentId="12305" CreationDate="2011-03-31T10:50:18.247" Score="2" ViewCount="" Body="&lt;p&gt;You can connect the grounds in one point or leave them separate. As long as the only common point between the two circuits is the isolated power supply you are free to do as you wish.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If OTOH you want to connect them somewhere (to use the car antenna or sth.) then you should carefully choose the connection point (or even points) to avoid ground loops and ground noise.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-31T10:50:18.247" CommentCount="2" />
  <row Id="12352" PostTypeId="2" ParentId="5435" CreationDate="2011-03-31T10:51:07.077" Score="0" ViewCount="" Body="&lt;p&gt;If you'd like to do some breadboarding and hookup your own I/O devices (LEDs, 7-segs, buttons/switches, etc), while figuring things out for yourself (doesn't come with docs) you can get a &lt;a href=&quot;http://shop.ebay.com/i.html?_nkw=Altera%20EP2C5T144&quot; rel=&quot;nofollow&quot;&gt;'barebones' mini FPGA board on eBay&lt;/a&gt; for around $50.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I picked up one of those and have been reasonably happy with it. I'll probably still end up getting a more full-featured board or make my own custom one someday, but for now this 'mini board' is fine for learning purposes.&lt;/p&gt;&#xA;" OwnerUserId="2654" LastActivityDate="2011-03-31T10:51:07.077" />
  <row Id="12353" PostTypeId="2" ParentId="12248" CreationDate="2011-03-31T10:57:45.500" Score="1" ViewCount="" Body="&lt;p&gt;@Zebonaut has a valid sidepoint. To correctly measure AC power you will need to capture both the current and the voltage waveforms (synchronized). This allows you to account for voltage variations and, more importantly, for the phase relationships between the current and the voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is especially important if you want to measure power usage of switch-mode power supplies (like phone chargers or computers) and motors (like the one in you blender or washing machine). You can on the other hand measure the power of resistive heaters (most electric heaters are resistive) using just the current without correcting for the voltage.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-31T10:57:45.500" />
  <row Id="12354" PostTypeId="2" ParentId="12294" CreationDate="2011-03-31T11:11:23.277" Score="0" ViewCount="" Body="&lt;p&gt;A little explanation of what's really going on:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;code&gt;-l&lt;/code&gt; argument order does not normally matter on computers since most libraries are dynamically loaded (.dll, .dylib or .so) and are truly &lt;em&gt;linked&lt;/em&gt; only at program startup time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OTOH on the AVR all libraries are static. When linking with static libraries the linker adds to the program only the functions he currently needs from the library. &#xA;If you pass &lt;code&gt;-lm&lt;/code&gt; on the command line before a file that needs a particular function you will get unresolved symbols errors.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-31T11:11:23.277" CommentCount="2" />
  <row Id="12355" PostTypeId="2" ParentId="5498" CreationDate="2011-03-31T11:23:57.467" Score="0" ViewCount="" Body="&lt;p&gt;Adding to the excellent advice from Kortuk:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;You should really use a powered hub or a &quot;USB charger&quot; for debugging since you do not want to fry your computer by accidentally shorting something.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;All computers I had pleasure with do not bother with limiting current draw below 500mA. (with or without enumeration)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-31T11:23:57.467" />
  <row Id="12356" PostTypeId="5" CreationDate="2011-03-31T12:49:13.277" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-31T12:49:13.277" LastActivityDate="2011-03-31T12:49:13.277" />
  <row Id="12357" PostTypeId="4" CreationDate="2011-03-31T12:49:13.277" Score="0" ViewCount="" Body="PCB is the acronym to Printed Circuit Board. It is a place to mount the components and it provides the means of electrical connection between the components." OwnerUserId="-1" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-31T12:49:13.277" LastActivityDate="2011-03-31T12:49:13.277" />
  <row Id="12358" PostTypeId="2" ParentId="12345" CreationDate="2011-03-31T13:16:15.510" Score="4" ViewCount="" Body="&lt;p&gt;The simple answer is that you can't.  There are several things going against you:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;would be that for good audio quality you'd need to be very precise in your PWM generation.  This is fairly difficult, as your master clock frequency (the freq that the logic used to generate the PWM from) would have to be around 100 MHz just to get the equivalent of an 11-Bit DAC.  There are ways to generate PWM that good without that, but then you'd be starting with an analog signal and thus wouldn't have this problem.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;as noted you would need a super steep rolloff of a filter.  Just to match your 11-bit DAC equivalent you'd need something like 60 dB/octave-- which is unreasonable even for the pro's.  There is a lot of difficultly in doing this kind of filter which is why everyone went to Delta-Sigma DAC's for their audio, which require about a 6 db/octave filter.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If your filter is not 60 db/octave then you'll need the PWM frequency to be super high.  If you have 60 db/octave then you could have a PWM freq of 40KHz.  At 54 db/octave then maybe 80 KHz will work.  48 db/octave = 160 KHz.  Etc.  Very quickly you get into the high MHz range-- and then your master clock frequency would have to be into the GHz.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;All is not lost, however.  Do you really need to filter out the high frequency stuff?  In many applications (not all) you can either not filter it or use a simple RC filter at 1-5 MHz.  There will still be high frequency stuff getting though but either the speaker or your ear will filter it all out.  But the audio will still sound bad.  AM Radio on a bad day quality.  That's just the way it is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update:&#xA;My numbers for #3, above, are somewhat wrong.  But before I get to that, let me explain where I got all the numbers from.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Let's say that you are generating the PWM using digital logic (FPGA, Microcontroller, etc.).  And then let's say that your audio sample rate and thus your PWM frequency is 48 KHz.  And you want 8-bit resolution.  That means that your master clock frequency should be 12.288 MHz.  I calculated that this way:  Master_Clk_Freq = Sample_Rate * 2^n_bits.  Doing that again for an 11 bit resolution is 98.304 MHz.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The theoretical best noise level of an ideal DAC is about -6dB/Bit.  So a 24-bit DAC has no better than -144 db noise.  (Note:  I'm playing a little loose with the terms here, lumping SNR, THD+N, and dynamic range all together.)  Of course, no real 24-bit DAC can do this, but we're talking theoretical here.  What this means is that an 11-bit DAC has about a -66 db noise level, so there is little point in making a filter that works better than this.  AM Radio has approximately 60-ish dB signal to noise ratio, for comparison.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Ok, here's where I royally messed up the numbers.  Assume that the PWM Rate = 48 KHz, and filter Cutoff=24 KHz (to make the math easy).  With a -60dB/Oct filter we'll be -63dB @ 48KHz.  If our filter were changed to -54dB/Oct then we'd be -57dB @ 48 KHz and -62.4dB @ 50.4KHz.  What this means is that by changing our filter from -60db/oct -54db/oct we would have to change the PWM rate from 48 KHz to 50.4KHz to achieve the same filter blocking performance.  Not a doubling of PWM frequency as I mentioned before.  In the same way, if the filter were changed to -18dB/Oct (which is a manageable design) then the PWM frequency would have to be 104 KHz to still have -63dB filter attenuation at the PWM frequency.  I calculated this by making a small spreadsheet and playing with the numbers.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="3078" LastEditorDisplayName="" LastEditDate="2011-03-31T22:11:24.680" LastActivityDate="2011-03-31T22:11:24.680" CommentCount="4" />
  <row Id="12360" PostTypeId="1" AcceptedAnswerId="12365" CreationDate="2011-03-31T13:58:36.723" Score="3" ViewCount="253" Body="&lt;p&gt;I have a dewalt 18V cordless drill. I am wondering if it is feasible to build an adapter that can power the drill from a standard US wall socket?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A typical DeWalt drill needs 2.6 amps with no-load. I am assuming this jumps significantly higher under load. Most DeWalt motors have a stall current over 250 amps...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any insight would be greatly appreciated!!&lt;/p&gt;&#xA;" OwnerUserId="3089" LastActivityDate="2011-03-31T17:26:37.607" Title="Is it possible to power a cordless drill from wall socket adapter?" Tags="&lt;power&gt;&lt;adapter&gt;&lt;supply&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="0" />
  <row Id="12361" PostTypeId="2" ParentId="12345" CreationDate="2011-03-31T14:34:02.173" Score="1" ViewCount="" Body="&lt;p&gt;The RC Low-pass filter would be the natural solution, but you can also use a microcontroller to measure the duty cycle and use that value to control a DAC. To measure duty cycle you need a timer with input-capture capability. The higher your timer clock, the more accurate your measurement. If the microcontroller doesn't have on on-chip DAC you can use an external one.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-31T15:37:36.363" LastActivityDate="2011-03-31T15:37:36.363" />
  <row Id="12362" PostTypeId="1" AcceptedAnswerId="12364" CreationDate="2011-03-31T14:44:35.483" Score="5" ViewCount="165" Body="&lt;p&gt;When reading/writing/talking about electronics, I like to understand the acronyms and mneumonics for abbreviations used for registers, functions, filenames, pin names, etc.  Usually, the first time the abbreviation is used, either the context or a parenthetical note sets it off, or it's blatantly obvious.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the Microchip dsPIC parts, the TRIS register controls the data direction. I can't find a note which uses the full word/phrase that would be abbreviated or have the acronym TRIS. ('The Register Input/output Settting' is about the best I can come up with, although 'TRIS Really Is a Silly abbreviation' is a close second guess).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you remember this?  I've heard it pronounced as a word, but I'd like to know what it means to make it easier to remember, read, and write.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-31T21:36:43.143" Title="What is the meaning of Microchip's acronym TRIS for data direction registers?" Tags="&lt;microchip&gt;" AnswerCount="2" />
  <row Id="12363" PostTypeId="2" ParentId="12341" CreationDate="2011-03-31T14:46:52.257" Score="0" ViewCount="" Body="&lt;p&gt;If I understand correctly, there is a resistor connected between the gate of an FET and ground.  In order to figure out the exact (very small) current through this gate resistor, you'd need a datasheet, and to get a datasheet, you'd need a part number.  Did they give you one?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For practical purposes, you don't need one, since this is an FET, and the gate resistance will be extremely high, making the current extremely low, essentially 0.  (But since this is a homework assignment, it might not be very practical.)&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-03-31T20:53:49.327" LastActivityDate="2011-03-31T20:53:49.327" CommentCount="2" />
  <row Id="12364" PostTypeId="2" ParentId="12362" CreationDate="2011-03-31T14:46:54.407" Score="12" ViewCount="" Body="&lt;p&gt;TRIS stands for TRIState. It means the port is waiting for an input rather than output a high or low signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's named as such because a port can have 3 states:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Output High&lt;/li&gt;&#xA;&lt;li&gt;Output Low&lt;/li&gt;&#xA;&lt;li&gt;Input (High Impedance)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-03-31T14:50:32.550" LastActivityDate="2011-03-31T14:50:32.550" CommentCount="4" />
  <row Id="12365" PostTypeId="2" ParentId="12360" CreationDate="2011-03-31T14:49:37.887" Score="1" ViewCount="" Body="&lt;p&gt;It would be possible to build such and adapter.  It would depend on the rating of your drills and how you want to plug in the power.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Either way a cordless drill has a DC motor so it will require a step down transformer and a full wave bridge rectifier.  Probably also need a regulator and a few capacitors.    You might be able to use the power transformer from a laptop or some other device.  But the voltage must match the drill and the ampere requirement must be very similar (more you can fry the drill less you can fry the power supply.)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for how you attach the power supply I would recommend building the interface out of an old battery pack so you don’t have to modify the drill.  But it should be possible to add an auxiliary power jack to the drill as well.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.aircraftdynamics.com/71.htm&quot; rel=&quot;nofollow&quot;&gt;DeWalt Tool Adapter (longer life battery packs)&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2412" LastEditorUserId="2412" LastEditorDisplayName="" LastEditDate="2011-03-31T15:05:41.230" LastActivityDate="2011-03-31T15:05:41.230" CommentCount="7" />
  <row Id="12367" PostTypeId="2" ParentId="12360" CreationDate="2011-03-31T15:27:21.813" Score="1" ViewCount="" Body="&lt;p&gt;The aforementioned corded drills work from 110V which means 1/6 of the current.&#xA;I think it is easier to get a 18V battery with very high discharge current rating than it is to make a cheap high current 18V supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to do this then a toroidal power transformer + a bridge rectifier should work well. I don't think you will need to stabilize the voltage but a quick inspection of the internal circuity may prove me wrong.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-03-31T15:41:52.197" LastActivityDate="2011-03-31T15:41:52.197" CommentCount="2" />
  <row Id="12368" PostTypeId="1" CreationDate="2011-03-31T15:35:08.127" Score="4" ViewCount="150" Body="&lt;p&gt;Many manufacturers apply licenses to the header files they publish for their products.  These files usually consist of a long list of #defines which are a correlation between the names and adjacent numbers in the datasheets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I want to produce a driver or other software solution which is free of these license restrictions, will using the same names in my header file be valid?  Am I allowed to copy the #defines straight out of the license file?  Does it matter whether I type it out by hand from the datasheet or programmatically access the .pdf file or other data structure containing this information?  (the datasheet isn't covered by the license.)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll assume that I need to leave licensed macros, functions, comments, and all other information outside of the #defines behind, but do I need to do more, like use a common prefix for these names (which I might do anyways to avoid namespace conflicts) or come up with my own acronyms/abbreviations?  Do I have to reverse-engineer the registers without looking at the datasheet?  Or is it completely impossible to produce a copyleft header file?&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-03-31T16:56:24.220" Title="Avoiding copyright violations when writing header files" Tags="&lt;legal&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="12369" PostTypeId="2" ParentId="12368" CreationDate="2011-03-31T15:49:20.913" Score="4" ViewCount="" Body="&lt;p&gt;The defines for things like hardware addresses are fundamentally facts and facts can't be copyrighted.  I might like to change the format of the defines for my own purposes but there's absolutely no way you can get by without using those values.  The only thing you can do is change the name of the define which would be a simple search and replace - not much effort if you do plan to do it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Chip manufacturers generally want you to use their chips and do a lot to ensure that you can.  If they prevented you from using the register definitions in any reasonable way then no one would use their chips. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: After discussion I don't believe that I actually answered the question with regards to license-free implementations of header files.  I decided to do some digging and the MSPGCC project seemed to be a good place to start.  Turns out they (basically) use the TI-provided headers for each device (rewritten to their formatting and maintainability standards).  The headers don't seem to have a license included or stated in the header file, nor could I find any licensing information.  The only documentation I found was a description of where the headers came from and how/why they were modified.  They do say that the files are created such that the register definitions match the names in the datasheet, so theoretically you could recreate it from the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I took a look at one TI datasheet I have an didn't find any licensing info - just a copyright notice which applies to the document as a whole (so I assume).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thus, I've come to the conclusion that it is NOT permissible to take a licensed file, strip out parts and release it under a different license.  You should start from a blank file and implement a header as per the description in the chip datasheet (after ensuring there's no license attached to it, but if TI doesn't do it I doubt others will).  Alternately, if there's no license attached to the released chip-specific header files, use the hell out of them instead :) &lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="249" LastEditorDisplayName="" LastEditDate="2011-03-31T16:56:24.220" LastActivityDate="2011-03-31T16:56:24.220" CommentCount="8" />
  <row Id="12370" PostTypeId="2" ParentId="12360" CreationDate="2011-03-31T15:51:15.163" Score="8" ViewCount="" Body="&lt;p&gt;The answer is simple:  Don't.  If you did, odds are that you'd spend lots of money on high-current step-down transformers or other kind of power supply and run the risk of destroying your cordless drill.  Corded drills, new from Home Depot, start at thirty dollars  and will have as good or better performance than a $150 cordless.  You'd be time and money ahead by just buying one-- and not have the headaches or risk of electrocution.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-03-31T15:51:15.163" CommentCount="2" />
  <row Id="12371" PostTypeId="2" ParentId="12368" CreationDate="2011-03-31T15:56:09.273" Score="2" ViewCount="" Body="&lt;p&gt;Reverse engineering clauses could apply here but for this you would most likely need to change all the names.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To be fully covered you should manually or automatically rewrite the header file from the datasheet or ask the manufacturer to release an unlicensed header file.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. Also (at least in Poland) there is a provision in the copyright law that databases are not covered under copyright.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS2. This remind me of an unrelated thing with fonts. Font files fall under copyright but the font design itself does not. So you can print the font and legally make a new one from the printout.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-03-31T15:56:09.273" CommentCount="1" />
  <row Id="12372" PostTypeId="2" ParentId="12345" CreationDate="2011-03-31T15:56:36.823" Score="0" ViewCount="" Body="&lt;p&gt;I'm integrating the PWM ramp up, capturing the voltage with a sample and hold circuit and then resetting the ramp. This seems to get a relatively faithful representation of the signal, but it still has some issues, like PWM noise on the peaks, and it's slightly nonlinear. But, it does work fairly well, and it allows me to use a 100kHz PWM signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/EUMLu.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simulate it &lt;a href=&quot;http://falstad.com/circuit/#%24+1+5.0000000000000004E-8+7.308818067910767+66+15.0+50%0Ar+448+80+448+16+0+39000.0%0Ar+400+96+400+16+0+27000.0%0Ar+400+96+400+176+0+120000.0%0Aw+400+16+448+16+0%0Aw+448+112+448+176+1%0Ag+400+176+400+192+0%0Aw+448+176+448+240+0%0Aw+448+240+448+272+0%0Aw+448+272+448+336+0%0Ac+448+336+448+368+0+5.6E-11+0.19545534388978755%0Ag+448+368+448+384+0%0Ar+448+176+496+176+0+10.0%0Aw+496+240+448+240+0%0Aw+448+272+496+272+0%0At+400+96+448+96+0+-1+3.4375276117559017+-0.45828510457812+100.0%0A165+496+144+512+144+2+5.0%0AR+560+96+560+80+0+0+40.0+5.0+0.0+0.0+0.5%0Aw+560+112+624+112+0%0Aw+624+112+624+176+0%0Aw+560+96+560+112+0%0Ad+320+16+400+16+1+0.805904783%0Aw+624+208+672+208+0%0At+336+352+368+352+0+1+-0.19545534239035178+4.998119189280962E-10+100.0%0Ag+368+368+368+384+0%0Aw+336+352+320+352+0%0Ar+448+336+368+336+0+10000.0%0Ar+320+16+320+80+0+10000.0%0Ac+320+80+256+80+2+1.0E-10+3.902186941725084%0Ag+256+80+240+80+0%0AI+320+80+320+160+0+0.5%0Ar+320+352+320+272+0+10000.0%0Aw+320+272+320+160+0%0Aa+608+352+704+352+1+15.0+-15.0+1000000.0%0Aw+608+368+608+400+0%0Aw+704+352+704+400+0%0Aw+704+400+608+400+0%0Aw+608+336+448+336+0%0Aw+704+352+704+336+0%0Aw+320+80+352+80+0%0A159+752+352+816+352+0+20.0+1.0E10%0Ac+832+352+832+432+0+1.0E-8+0.5509771995917925%0Ag+832+432+832+448+0%0Aw+960+368+960+352+0%0Aw+960+416+864+416+0%0Aw+960+368+960+416+0%0Aw+864+384+864+416+0%0Aa+864+368+960+368+1+15.0+-15.0+1000000.0%0Aw+832+352+832+320+0%0Aw+192+16+320+16+0%0Ar+192+448+272+448+0+10000.0%0Ac+272+448+272+528+0+4.7E-11+4.78407107952905%0Aw+192+416+192+448+0%0Aw+192+416+272+416+0%0Aw+368+432+400+432+0%0A150+272+432+368+432+0+2+5.0%0Ac+624+112+688+112+2+1.0000000000000001E-7+5.0%0Ag+688+112+704+112+0%0Aw+864+352+832+352+0%0Ar+752+352+704+352+0+100.0%0Aw+832+352+816+352+0%0Aw+784+432+400+432+0%0Aa+96+96+96+16+1+5.0+0.0+1000000.0%0AR+80+96+48+96+0+1+10000.0+3.5+0.0+0.0+0.5%0AR+112+96+144+96+0+3+100000.0+5.0+0.0+0.0+0.5%0Aw+96+16+192+16+0%0Aw+784+432+784+368+0%0Ag+272+528+272+544+0%0Aw+192+416+192+16+0%0Ar+960+464+896+464+0+1000.0%0Ac+896+464+896+512+0+1.0E-8+0.8778897023245152%0Ag+896+512+896+528+0%0Aw+960+464+960+416+0%0Aw+896+464+864+464+0%0Ao+62+16+0+35+5.0+9.765625E-5+0+-1%0Ao+64+16+0+34+8.749002899132048+6.835158514946913E-4+0+-1%0Ao+72+16+0+35+1.1692013098647223+9.765625E-55+1+-1%0A&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-03-31T15:56:36.823" CommentCount="1" />
  <row Id="12373" PostTypeId="2" ParentId="12341" CreationDate="2011-03-31T17:10:48.527" Score="1" ViewCount="" Body="&lt;p&gt;You're not saying what kind of FET you're using, a JFET or a MOSFET. In the latter case the gate is isolated from the channel and there will flow no current through the resistor. If it's a JFET it's different. Depending on the type the gate is either the N- or the P-part of a diode formed by the gate-channel junction. This diode is reversely polarized, but there will be a leakage current which may generate a small voltage over a large enough resistor.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-03-31T17:10:48.527" />
  <row Id="12374" PostTypeId="2" ParentId="12360" CreationDate="2011-03-31T17:26:37.607" Score="1" ViewCount="" Body="&lt;p&gt;It's possible but by no means straightforward.  An irreversible change is shown here: &lt;a href=&quot;http://www.instructables.com/id/Convert-a-battery-drill-to-wall-power/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Convert-a-battery-drill-to-wall-power/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could have sworn that I saw plug adapters for cordless drills before but for the life of me I can't find them now.  I suppose it would be difficult - batteries are high-current beast and fitting a power supply that could manage that sort of current into a manageable size on the drill might be difficult.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-03-31T17:26:37.607" CommentCount="4" />
  <row Id="12375" PostTypeId="2" ParentId="5666" CreationDate="2011-03-31T17:44:42.060" Score="1" ViewCount="" Body="&lt;p&gt;This isn't a direct answer to your question, but it's related. I assume you're using multiple AA batteries in series (in order to achieve a higher voltage for your circuit to operate). In that case, you might consider using a buck/boost circuit to boost the voltage from one AA battery. You'll pay a penalty in terms of how much current you can supply, but compared to a coin cell, it will be better.&#xA;&lt;a href=&quot;http://www.sparkfun.com/products/10255&quot; rel=&quot;nofollow&quot;&gt;Sparkfun sells a kit that will take in down to 0.3v and output 5v at 500 mA&lt;/a&gt;, for example.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-03-31T17:44:42.060" />
  <row Id="12376" PostTypeId="2" ParentId="12341" CreationDate="2011-03-31T18:38:04.507" Score="3" ViewCount="" Body="&lt;p&gt;I will try to help without giving too much away. I just took an analog IC design course last semester, so I'm all psyched up about this stuff. I hope that this does not come off as too academic...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a common source FET amplifier, the input (gate) resistance is really really high, so the gate current is usually assumed to be zero. So the current through $R_G$ should be zero. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, you should know that the drain current in a FET operating in the saturation region is given by&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$I_D = \frac {k&amp;#39;} 2 \frac W L (V_{GS} - V_t)^2$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where $k&amp;#39;=\mu_n C_{ox}$ and is related to process parameters. $\mu_n$ is electron mobility (in NMOS) and $C_{ox}$ is gate oxide capacitance. W and L are the width and length of the channel, respectively. So you have an expression relating drain current to gate-source voltage. And $V_{ov}$ as well, since $V_{ov}=V_{GS}-V_t$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You already know the drain current, $I_D=1m\text{A}$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also should know that in a common source amplifier, the open circuit voltage gain $A_v$ is related to the drain and source resistances, $R_D$ and $R_S$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And you know that $V_{GS}$ should be equal to the voltage across $R_S$. (And you know the current through $R_S$, which is $I_D$. &lt;em&gt;Correction: $V_{GS}$ is not the drop across $R_S$! But you should be able to determine the relationship from the information you have.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without having a circuit drawing in front of me, and without having thought about it too much (please check my work!), I think that should give you enough info to make these calculations. You may have to leave in a &quot;transconductance&quot; parameter in the expressions for things if you do not know $k&amp;#39;$ or $\frac W L$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0470245999&quot; rel=&quot;nofollow&quot;&gt;Analysis and Design of Analog Integrated Circuits&lt;/a&gt; by Paul R. Gray and Robert G. Meyer et. al is my go-to reference for transistor circuits. I have the 5th edition. It's been around forever. You would probably be okay with a 4th edition. I would highly recommend this if you are interested in linear transistor amplifiers (op amps).&lt;/p&gt;&#xA;" OwnerUserId="3635" LastEditorUserId="3635" LastEditorDisplayName="" LastEditDate="2011-04-04T03:31:10.613" LastActivityDate="2011-04-04T03:31:10.613" CommentCount="2" />
  <row Id="12377" PostTypeId="2" ParentId="12300" CreationDate="2011-03-31T20:00:25.720" Score="5" ViewCount="" Body="&lt;p&gt;Ok thanks, I found the soloution yesterday:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Unplug the USB cable&lt;/li&gt;&#xA;&lt;li&gt;Hold down Reset&lt;/li&gt;&#xA;&lt;li&gt;Plug in the USB cable&lt;/li&gt;&#xA;&lt;li&gt;Upload Code from IDE&lt;/li&gt;&#xA;&lt;li&gt;Release the Reset Button after seeing the compile done message&lt;/li&gt;&#xA;&lt;li&gt;AND IT NOW IT DOES IT'S JOB GOOD AGAIN.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3451" LastActivityDate="2011-03-31T20:00:25.720" CommentCount="1" />
  <row Id="12378" PostTypeId="2" ParentId="12248" CreationDate="2011-03-31T20:44:27.573" Score="0" ViewCount="" Body="&lt;p&gt;Traditionally, to measure the power consumed by a circuit powered by a common input (which may be fused), a shunt resistor and shunt current monitor is used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an example, here's a diagram of TI's INA193:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/SEHsb.gif&quot; alt=&quot;ti ina 193 diagram&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic functionality is that current across the shunt resistor $R_S$ creates a proportionally related voltage at the output.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are available in three-pin and five-pin layouts; the three-pin devices (often SOT23-3) set an output current from $V_{IN+}$ to ground through a resistor attached to out (eliminating the ground and $V+$ nodes, but externalizing the $R_L$ resistor shown in the block diagram) or a five-pin device which creates a voltage somewhere between $V+$ and ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously, you'd like to eliminate the $R_S$ component if possible, but there are three major disadvantages to this approach:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The voltage across the fuse may be wrong for your application.  Most shunt monitors are designed for voltages less than (and sometimes much less than) 500mV.  The plane-jane Bussman S500 glass tube series fuses have  voltage drops over 1V for currents less than 500mA.  Higher current fuses will usually be able to use the power in the current to blow faster, and will therefore have voltage drops less than 200 mV, which is perfect for this application.&lt;/li&gt;&#xA;&lt;li&gt;The resistance of the fuse will vary a lot.  For example, the 1A fuse in the S500 series has a cold resistance of 0.125 $\Omega$, but a maximum voltage drop of 200mV at 1A.  $V = I * R$, so you'd expect the voltage drop to be 125mV.  In fact, the fuse functions as a PTC/resettable fuse that goes out of control (but that's another topic), and almost doubles its resistance between the cold and rated current states.  I'm not sure (but I doubt) that this is a linear function, and it's also a function of the ambient temperature/cooling rate.  &lt;/li&gt;&#xA;&lt;li&gt;The direct connection of $V_{IN+}$ to the shunt monitor represents an unfused connection in your system.  This will be a very low current path; you can give it some protection with a very thin trace or a small resistor without affecting your signal much, but the former probably won't pass inspection and the latter defeats the purpose of using the fuse as the sensing element.  If you're using the fuse to protect equipment from damage (which might not be prudent - see &lt;a href=&quot;http://electronics.stackexchange.com/questions/10643/designing-with-fuses-when-to-use&quot;&gt;Designing with fuses...when to use?&lt;/a&gt;), you might be able to get away with it.  However, in general, you want a sharp disconnect of fused and unfused portions of your circuit.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;You &lt;em&gt;could&lt;/em&gt; do some calibration of your fuses, and come up with an equation to translate the input voltage to your current.  This would work best if you were primarily interested in the steady-state currents and the device was in an enclosure at a constant temperature.  However, you're only saving a few pennies apiece.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-03-31T21:00:23.650" LastActivityDate="2011-03-31T21:00:23.650" CommentCount="2" />
  <row Id="12379" PostTypeId="1" CreationDate="2011-03-31T20:46:27.220" Score="0" ViewCount="36" Body="&lt;p&gt;I want to design a simple circuit with a timer, forward and reverse interlocking relays to operate a 480VAC 1/2 horse motor.I would like the system to start with a 120 vac source to activate a 700 series bulliton relay witch closes contacts to feed a new source 120 vac from a xfrm. Energize forward motor starter, then automatically stop, time out for 1 minute, then proceed in the opposite direction. continuous auto untill 120 vac main source is turned off.&lt;/p&gt;&#xA;" OwnerUserId="3683" LastActivityDate="2011-03-31T20:46:27.220" ClosedDate="2011-04-01T16:01:38.793" Title="Motor controls/for-rev" Tags="&lt;circuit-design&gt;" CommentCount="3" />
  <row Id="12380" PostTypeId="2" ParentId="8164" CreationDate="2011-03-31T20:56:47.233" Score="1" ViewCount="" Body="&lt;p&gt;Does William Beaty answer your question in&#xA;&lt;a href=&quot;http://amasci.com/elect/mcoils.html&quot; rel=&quot;nofollow&quot;&gt;&quot;RIGHT ANGLE CIRCUITRY - or - AC Electronics for Alien Minds&quot;&lt;/a&gt;&#xA;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A transformer is often drawn as a coil of copper wire on the left, a coil of copper wire on the right, and a ferrite ring in the middle going through the center of each.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That article suggests the possibility of ferrite &quot;coil&quot;on the left, a ferrite &quot;coil&quot;on the right, and a copper ring in the middle going through the center of each.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-03-31T20:56:47.233" CommentCount="1" />
  <row Id="12381" PostTypeId="2" ParentId="8164" CreationDate="2011-03-31T21:17:29.570" Score="2" ViewCount="" Body="&lt;p&gt;yes, you can step down at least, you can uses caps just like a resistive bridge - put two in series say in a 10:1 ratio (10nF and 1nf) across 110v AC and measure the AC voltage across the 10nF - you'll see roughly 11v AC - it's a rather inefficient way to make a lower voltage - but it's a cheap way if you only need a mA or so - but the more energy you need to tap (you need larger caps) the more inefficient it gets (just like a resistive divider)&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-03-31T21:17:29.570" CommentCount="2" />
  <row Id="12382" PostTypeId="2" ParentId="12362" CreationDate="2011-03-31T21:36:43.143" Score="2" ViewCount="" Body="&lt;p&gt;The term &quot;tri-state&quot; is often used informally to refer to the act of floating a pin; I know that National Semiconductor used to have a trademark on the term, though its widespread usage as a common term may have rendered it unenforceable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incidentally, in case anyone's curious why the OPTION instruction is so called, and the settings aren't controlled via a register, on the original General Instruments PIC devices, there were no TRIS or OPTION instructions; instead, the selection of which pins should be floating, as well as the settings for the timer/watchdog prescalar and modes, were part of the factory specification (the devices used mask ROM, so the whole program would be a factory spec).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-03-31T21:36:43.143" CommentCount="2" />
  <row Id="12383" PostTypeId="1" AcceptedAnswerId="12384" CreationDate="2011-04-01T00:46:57.587" Score="1" ViewCount="142" Body="&lt;p&gt;I'm a beginner to FPGA programming. I just started programming an Atlys Spartan 6 board and so far have written one program to blink LEDs in a counter pattern.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I'm trying to send the clock signal down-sampled to audio frequencies to the AC97 codec. Here is the Verilog program I've written:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;module music(&#xA;    input clk,&#xA;    output ac97_sdo&#xA;    );&#xA;reg [25:0] count_aud;&#xA;reg clk_aud;&#xA;&#xA;assign ac97_sdo = clk_aud;&#xA;&#xA;/* down-sample the 100MHz system clock to 1kHz */&#xA;always @(posedge clk)&#xA;begin&#xA;    count_aud &amp;lt;= count_aud + 1;&#xA;    if (50000 == count_aud)&#xA;    begin&#xA;        clk_aud &amp;lt;= !clk_aud;&#xA;        count_aud &amp;lt;= 0;&#xA;    end&#xA;end&#xA;&#xA;endmodule&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The bit-file generation is fine, but the code doesn't seem to work - I don't hear anything either on Line Out or on HP Out (I don't know how to control the output, either), and I don't have enough experience with the AC97 specification to figure this out. The audio part of the UCF is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;NET ac97_bitclk LOC = L13;&#xA;NET ac97_sdi LOC = T18;&#xA;NET ac97_sdo LOC = N16;&#xA;NET ac97_sync LOC = U17;&#xA;NET ac97_reset LOC = T17;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Do I need to use the bit clock, sync, reset, etc. to make this work? If yes, how can I go about it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I couldn't find any detailed information on the Atlys Reference Manual.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please help!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you.&lt;/p&gt;&#xA;" OwnerUserId="3684" LastActivityDate="2011-04-01T01:39:28.603" Title="Using the AC97 Codec on an Atlys Spartan 6 Board" Tags="&lt;audio&gt;&lt;fpga&gt;&lt;verilog&gt;&lt;spartan&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="2" />
  <row Id="12384" PostTypeId="2" ParentId="12383" CreationDate="2011-04-01T01:39:28.603" Score="2" ViewCount="" Body="&lt;p&gt;The interface to an AC97 codec is a bit more complicated than straight digital audio. The serial data consists of 256-bit data frames; each frame contains several channels of 20-bit samples. The overall data rate is 12.288 MHz; dividing by 256 gives the sample rate of 48 kHz. Part of the 256-bit frame is dedicated to control messages, e.g. to set mixer registers. You may need to do this once after power up/reset to set the volume.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The AC97 spec is available &lt;a href=&quot;http://download.intel.com/support/motherboards/desktop/sb/ac97_r23.pdf&quot; rel=&quot;nofollow&quot;&gt;from Intel&lt;/a&gt;. Writing your own master is not unreasonable but it will take some time. You may also be able to find one you can reuse. &lt;a href=&quot;http://opencores.org/project,ac97&quot; rel=&quot;nofollow&quot;&gt;OpenCores has one&lt;/a&gt;. There's a very barebones AC97 controller and some general information about the protocol &lt;a href=&quot;http://www-mtl.mit.edu/Courses/6.111/labkit/audio.shtml&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't remember how many of the AC97 registers are standardized. The manual I found online for your board says it has an LM4550 codec. Assuming that's right, you may want to refer to the &lt;a href=&quot;http://www.national.com/opf/LM/LM4550.html&quot; rel=&quot;nofollow&quot;&gt;LM4550 datasheet&lt;/a&gt; for a complete list of configuration registers.&lt;/p&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-04-01T01:39:28.603" CommentCount="2" />
  <row Id="12385" PostTypeId="1" AcceptedAnswerId="12742" CreationDate="2011-04-01T01:42:50.597" Score="5" ViewCount="221" Body="&lt;p&gt;How can I send data to the arduino from the computer? I'm thinking sort of a prompt on the command line and some commands like &quot;led1 on&quot;. Then, the arduino would process that and light up a certain led.&lt;/p&gt;&#xA;" OwnerUserId="3440" LastActivityDate="2011-04-08T13:58:38.057" Title="How can I send data to the arduino from the computer?" Tags="&lt;arduino&gt;&lt;serial&gt;&lt;computers&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="3" />
  <row Id="12386" PostTypeId="2" ParentId="12385" CreationDate="2011-04-01T02:19:41.360" Score="1" ViewCount="" Body="&lt;p&gt;Your plan should work fine. You do not say what computer you have (PC Mac Linux etc.) but obviously you will need a program running on the computer that acts as a terminal emulator and allows you to send the command to the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the Arduino side you need to parse or decode the command, so best to keep the commands as simple as possible. For example instead of &quot;Led 1 on&quot; perhaps &quot;L1+&quot; and &quot;L1-&quot; to turn it on and off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many other people have done this sort of thing with Arduinos so if you Google you should find ots of samples.&lt;/p&gt;&#xA;" OwnerUserId="3514" LastActivityDate="2011-04-01T02:19:41.360" />
  <row Id="12388" PostTypeId="1" AcceptedAnswerId="12389" CreationDate="2011-04-01T07:43:11.360" Score="2" ViewCount="67" Body="&lt;p&gt;I want to generate a precise frequency in the 500MHz range, and have therefore purchased a VCO (200MHz to 400MHz).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To measure the VCO output frequency, I'm trying to build a high frequency counter up to 500MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way I have been trying to do it, is using the MC100E016 (ECL Synchronous Binary Up Counter). Take the Q6 (/64) output and feed this into my oscilloscope (and later MCU). But this seems hard to get to work, because the PECL logic sets high demands on the input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have any good and easy way to build a frequency counter, or even just a divider would be fine (my 100MHz oscilloscope can measure the output from the divider).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or even better, generate a 200MHz to 400MHz range frequency, who's frequency can be set (digital or what ever).&lt;/p&gt;&#xA;" OwnerUserId="3041" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-01T10:56:02.007" LastActivityDate="2011-04-01T10:56:02.007" Title="frequency generator / counter" Tags="&lt;frequency&gt;&lt;generator&gt;&lt;counter&gt;" AnswerCount="1" />
  <row Id="12389" PostTypeId="2" ParentId="12388" CreationDate="2011-04-01T10:33:55.350" Score="1" ViewCount="" Body="&lt;p&gt;You can use several methods:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) PLL - for example &lt;a href=&quot;http://www.analog.com/en/rfif-components/pll-synthesizersvcos/adf4002/products/product.html&quot; rel=&quot;nofollow&quot;&gt;ADF4002&lt;/a&gt; works up to 400 MHz. The resolution is limited, because it works by multiplying reference frequency. This chip will work with your VCO.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Integrated PLL synthesizer - &lt;a href=&quot;http://www.analog.com/en/rfif-components/timing-ics-clocks/adf4350/products/product.html&quot; rel=&quot;nofollow&quot;&gt;ADF4350&lt;/a&gt; can generated frequencies within 137-4400 MHz range with fairly good resolution. However, within your range the result will be more square wave rather than sine. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) DDS - direct digital synthesis - &lt;a href=&quot;http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad9910/products/product.html&quot; rel=&quot;nofollow&quot;&gt;AD9910&lt;/a&gt; can generate frequencies up to 400 MHz with resolution under 1 Hz. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Trying to tune wideband VCO without any stabilization and measuring the result will not provide stable frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.analog.com/en/rfif-components/pll-synthesizersvcos/products/index.html&quot; rel=&quot;nofollow&quot;&gt;Here is a list&lt;/a&gt; of PLL chips and PLL synthesizers made by ADI. Other vendors have some too, but usually working within GHz range. &lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-04-01T10:33:55.350" CommentCount="2" />
  <row Id="12390" PostTypeId="1" AcceptedAnswerId="12393" CreationDate="2011-04-01T10:38:48.683" Score="4" ViewCount="324" Body="&lt;p&gt;My circuit uses main electricity in parts of the circuit. However my AVR and other components only need 5V. So I'm using a step down transformer to generate 12V. It's then regulated to 5V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The transformer won't convert it to dc for me will it? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It just steps it down then outputs a certain voltage depending on it's coils. So I would need to convert it to dc myself right?&lt;/p&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-01T13:02:41.817" LastActivityDate="2011-04-02T04:00:27.840" Title="Using a transformer to step down 230V to 12V" Tags="&lt;transformer&gt;" AnswerCount="4" CommentCount="4" />
  <row Id="12391" PostTypeId="2" ParentId="12390" CreationDate="2011-04-01T10:44:44.780" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;The transformer won't convert it to dc&#xA;  for me will it?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Correct!&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;AFAIK it just steps it down then&#xA;  outputs a certain voltage depending on&#xA;  it's coils. So I would need to convert&#xA;  it to dc myself right?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Correct again!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your transformer will convert 120$V_{ac}$ to 12$V_{ac}$. So you'll need to regulate it to 5$V_{dc}$.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-01T10:50:08.517" LastActivityDate="2011-04-01T10:50:08.517" />
  <row Id="12392" PostTypeId="2" ParentId="12390" CreationDate="2011-04-01T11:24:41.607" Score="6" ViewCount="" Body="&lt;p&gt;The transformer is the first part of the power supply, but you need more to get DC.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The varying input voltage of the transformer creates an equally varying magnetic field in the metal core. This magnetic field in turn creates an, again varying, voltage on the output. Both input and output voltage are sine waves. It's called AC (alternating current) because the sign of the output voltage changes continuously, 100 or 120 times per second, depending on the country you live in.&lt;br&gt;&#xA;You rectify this AC voltage to get rid of the sign changes; one pin will always be positive with respect to the other one.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/YtcMc.png&quot; alt=&quot;enter image description here&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The one thing which remains to be done now is to flatten the curve, get rid of the bumps. This is done by a capacitor. You now have a DC (direct current) voltage which is already usable for a number of situations. This voltage, however, may still show slight variations, which may be unwanted. To get rid of those you follow the capacitor by a voltage regulator.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-01T11:24:41.607" />
  <row Id="12393" PostTypeId="2" ParentId="12390" CreationDate="2011-04-01T12:01:09.397" Score="12" ViewCount="" Body="&lt;p&gt;You are correct. The transformer will only reduce the voltage (and increase the available current), so you need to add additional circuitry to rectify, smooth and regulate your 12$V_{ac}$ transformer output to 5$V_{dc}$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the type of circuit you should be looking to build:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WscTo.jpg&quot; alt=&quot;AC to DC PSU&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The transformer reduces the voltage from mains to 12$V_{ac}$ (rms).&lt;/li&gt;&#xA;&lt;li&gt;The Diode Bridge (known as a bridge rectifier) will convert 12$V_{ac}$ to 17$V_{dc}$. The voltage is $\sqrt{2}$ times higher than the input voltage because the rectifier output is the peak AC voltage, not the rms AC voltage.&lt;/li&gt;&#xA;&lt;li&gt;The first capacitor will smooth out the ripples that come from the output of the AC to DC bridge rectifier.&lt;/li&gt;&#xA;&lt;li&gt;The 7805 regulator will maintain a constant voltage as the load varies. For example if you are switching a light bulb on and off, the current will go up and down, and if you didn't have a regulator then the voltage would drop as the bulb is switched on. The regulator keeps it at the 5$V_{dc}$ your microcontroller needs.&lt;/li&gt;&#xA;&lt;li&gt;The final small capacitor filters out any noise or interference on the regulated side of the circuit.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-04-01T13:48:24.580" LastActivityDate="2011-04-01T13:48:24.580" CommentCount="10" />
  <row Id="12394" PostTypeId="2" ParentId="12385" CreationDate="2011-04-01T13:18:24.303" Score="2" ViewCount="" Body="&lt;p&gt;One of my favorite features I added to a project years ago was to implement a &lt;a href=&quot;http://wiki.bash-hackers.org/scripting/terminalcodes&quot; rel=&quot;nofollow&quot;&gt;VT100 terminal&lt;/a&gt;.  It was a pretty simple and flexible way to allow users to configure our Ethernet-based devices over an RS-232 connection.  It had a tabbed interface, status updates, and could also accept commands.  You can get surprisingly fancy with this simple approach.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-01T13:18:24.303" />
  <row Id="12395" PostTypeId="1" AcceptedAnswerId="12450" CreationDate="2011-04-01T13:51:50.687" Score="6" ViewCount="138" Body="&lt;p&gt;I was reading an electronics book and came upon this circuit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ZguAL.jpg&quot; alt=&quot;enter link description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am having a difficult time understanding why the voltage across D1 is 0.6V. I understand that that the reason is because the input signal's pp voltage is lower than 0.6v C and R1 make a differentiator then D2 rectifies that but none of that would work if the signal is less than 0.6v. I just don't understand why D1 is at 0.6V and how that makes D2 be higher than 0.6V. I was going to post a diagram but I don't have enough reputation.&lt;/p&gt;&#xA;" OwnerUserId="3688" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-01T13:54:04.677" LastActivityDate="2011-04-02T19:27:19.550" Title="Help Understanding a signal rectifier" Tags="&lt;signal&gt;&lt;rectifier&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="2" />
  <row Id="12396" PostTypeId="1" AcceptedAnswerId="12417" CreationDate="2011-04-01T13:55:52.487" Score="3" ViewCount="36" Body="&lt;p&gt;This is in regards to digital communications. I have a link I've set up using &lt;a href=&quot;http://www.gnuradio.org&quot; rel=&quot;nofollow&quot;&gt;GNURadio&lt;/a&gt; that's sending BPSK modulated data through water via a LED. I can control the roll-off factor, $\beta$, of the &lt;a href=&quot;http://en.wikipedia.org/wiki/Raised-cosine_filter&quot; rel=&quot;nofollow&quot;&gt;root-raise cosine filter&lt;/a&gt;. What are the practical implications of this number? It seems that any value should work fine, since it fulfills the nyquist criteria (adjacent symbols have zero energy at the current symbol's sample point) and the energy/frequency is constrained. Is it mostly just a way to control the affects of jitter vs. slight savings in bandwidth?&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-04-01T17:39:02.417" Title="What are the practical implications of changing the rolloff factor of a root-raise cosine filter?" Tags="&lt;communication&gt;&lt;filter&gt;&lt;digital&gt;" AnswerCount="1" />
  <row Id="12397" PostTypeId="2" ParentId="12395" CreationDate="2011-04-01T13:58:25.657" Score="3" ViewCount="" Body="&lt;p&gt;The voltage across D1 is 0.6V because of the &lt;a href=&quot;http://en.wikipedia.org/wiki/Diode&quot; rel=&quot;nofollow&quot;&gt;diode forward voltage drop&lt;/a&gt; ($V_{d}$). The forward voltage drop of a diode is almost constant whatever the current passing through the diode so they have a very steep characteristic:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/KhyAb.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Volt across D2 is about 0.6V or 0.7V too.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-01T14:05:22.047" LastActivityDate="2011-04-01T14:05:22.047" CommentCount="1" />
  <row Id="12398" PostTypeId="2" ParentId="12395" CreationDate="2011-04-01T14:03:18.663" Score="3" ViewCount="" Body="&lt;p&gt;I'd say your confusion is justified. When the input signal is constant or varying near ground or above, D1 is forward biased, so it's at 0.6 V. However, if the input signal spikes massively downward, such that the voltage between C and R1 is below -5 V, D1 will be reverse biased, so it will act like an open circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For large negative spikes, R1 and R3 act like a voltage divider. With a large enough spike, the voltage across D1 could be as large a negative voltage as you like (until R1 and/or R3 burn out or C explodes).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, I'd assume that the point of the circuit is to handle small positive signals, so in normal operation, you'd just assume the diode was forward biased and thus at 0.6 V.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-04-01T14:03:18.663" />
  <row Id="12399" PostTypeId="2" ParentId="12179" CreationDate="2011-04-01T14:03:43.937" Score="3" ViewCount="" Body="&lt;p&gt;If build a &quot;super-component&quot; out of 4 identical inductors (or 4 identical resistors) in 2 chains of 2 components each,&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;   +--X1--X2--+--&#xA;   |          |&#xA;---+--X3--X4--+&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(assuming negligible mutual inductance, which is true for many common &quot;shielded&quot; inductors),&#xA;then if each of the four components has identical impedance X, all 4 of them considered as a whole as a single super-component also have the same net impedance X and can handle twice as much current and dissipate 4 times as much power.&#xA;(This is related to the idea of measuring &lt;a href=&quot;http://en.wikipedia.org/wiki/Sheet_resistance#Units&quot; rel=&quot;nofollow&quot;&gt;sheet resistance in &quot;Ohms per square&quot;.&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There may have been times ;-) ;-) where I've already bought a bulk bag of exactly the impedance I need, and then discover it can't handle the power. The square arrangement allows me to continue prototyping with the components I have on hand, where each component has exactly the desired net impedance X, while I'm waiting for the &quot;right&quot; component(s) to ship.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes the current rating is limited by thermal considerations -- higher currents will make the wires overheat and something will melt and cause permanent damage or melt the solder.&#xA;In those cases, the power dissipated is proportional to the surface area. Using N components rather than one big component makes it easier to cool and can save net space.&#xA;(Sometimes N components in parallel, each with N times the desired impedance X, uses the least space. N components in series, each with 1/N of the desired impedance X, has the least parasitic capacitance).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes the current rating is limited by core saturation -- higher currents will saturate the ferrite core, causing the inductance to drop out of spec.&#xA;In those cases, the maximum energy (temporarily) stored in the core is proportional to the volume of the core. Using one big component that holds all the necessary volume usually uses less board area than using the same volume of core divided up into a bunch of smaller components.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-01T14:03:43.937" />
  <row Id="12400" PostTypeId="1" CreationDate="2011-04-01T14:04:48.100" Score="3" ViewCount="113" Body="&lt;p&gt;Do you know any program that works on linux and can simulate complex circuits?&lt;/p&gt;&#xA;" OwnerUserId="1392" LastActivityDate="2011-04-01T14:33:10.597" CommunityOwnedDate="2011-04-01T15:08:11.097" Title="Program for simulating circuits on linux" Tags="&lt;linux&gt;&lt;simulator&gt;" AnswerCount="2" CommentCount="10" FavoriteCount="1" />
  <row Id="12401" PostTypeId="2" ParentId="12400" CreationDate="2011-04-01T14:15:16.923" Score="2" ViewCount="" Body="&lt;p&gt;There are several SPICE implementations for Linux, such as &lt;a href=&quot;http://www.spiceopus.si/&quot; rel=&quot;nofollow&quot;&gt;SPICE OPUS&lt;/a&gt; (it's free). I used the Windows version some years ago, and found it quite good. It can use Eagle schematics, which is a plus.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-01T14:15:16.923" CommunityOwnedDate="2011-04-01T15:08:11.097" />
  <row Id="12402" PostTypeId="2" ParentId="12395" CreationDate="2011-04-01T14:24:40.237" Score="1" ViewCount="" Body="&lt;p&gt;R3 and D1 form a voltage divider with 0.6V in the midpoint. The 0.6V is given by forward voltage of the diode and R3 is there to limit the current through the diode. This voltage is then applied through resistor R1 in between C and D2 as a biasing voltage to make sure that D2 will stay always open, given that input voltage is smaller that the bias.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-04-01T14:24:40.237" />
  <row Id="12403" PostTypeId="2" ParentId="12400" CreationDate="2011-04-01T14:27:40.943" Score="2" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.gpleda.org/index.html&quot; rel=&quot;nofollow&quot;&gt;gEDA project&lt;/a&gt; supports the &lt;a href=&quot;http://www.icarus.com/eda/verilog/&quot; rel=&quot;nofollow&quot;&gt;Icarus Verilog&lt;/a&gt; (digital only, though &lt;a href=&quot;http://iverilog.wikia.com/wiki/Development_Time_Line#Verilog_A.2FMS&quot; rel=&quot;nofollow&quot;&gt;Verilog-AMS support is planned&lt;/a&gt;), &lt;a href=&quot;http://gtkwave.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;GTK Wave&lt;/a&gt;, &lt;a href=&quot;http://ngspice.sourceforge.net/index.html&quot; rel=&quot;nofollow&quot;&gt;ngSpice&lt;/a&gt;, and &lt;a href=&quot;http://www.gnu.org/software/gnucap/&quot; rel=&quot;nofollow&quot;&gt;Gnucap&lt;/a&gt; simulators.  It has the advantage that you can compose your schematics, simulations, and PCBs in the same flow, instead of having to manually copy everything from your schematic editor into the simulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to evaluate more options, the Wikipedia &lt;a href=&quot;http://en.wikipedia.org/wiki/Comparison_of_EDA_software&quot; rel=&quot;nofollow&quot;&gt;comparison of EDA software&lt;/a&gt;, &lt;a href=&quot;http://en.wikipedia.org/wiki/Electronic_circuit_simulation&quot; rel=&quot;nofollow&quot;&gt;Electronic circuit simulation&lt;/a&gt;, and &lt;a href=&quot;http://en.wikipedia.org/wiki/List_of_free_electronics_circuit_simulators&quot; rel=&quot;nofollow&quot;&gt;list of free (as in freedom) simulators&lt;/a&gt; pages all contain useful links.&lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-04-01T14:33:10.597" LastActivityDate="2011-04-01T14:33:10.597" CommunityOwnedDate="2011-04-01T15:08:11.097" />
  <row Id="12404" PostTypeId="1" AcceptedAnswerId="12609" CreationDate="2011-04-01T14:38:58.410" Score="2" ViewCount="128" Body="&lt;p&gt;I would like run daily builds, or check-in/commit triggered builds of Keil MDK-ARM based projects.  So far I've gotten things going with the batch file feature of the IDE.  This does require you to build the project at least once with the IDE, then check-in the batch file and associated .__i and ._ia files created by the IDE.  Additionally, the IDE puts lots of user specific things into the batch file like the windows PATH variable.  This could become a problem with multiple developers, because the batch file for building could be changed at each commit from a different developer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ultimately, one just needs to keep track of the various switches for armcc, armasm, and ArmLink.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a way to use a more standard makefile to build Keil uVision Projects?  Does anyone have a method of translating a uVision project file into a more maintainable build script?&lt;/p&gt;&#xA;" OwnerUserId="3346" LastActivityDate="2011-04-05T17:50:02.273" Title="How can I use a build server with Keil uVision4 (MDK-ARM), script a build, use a makefile?" Tags="&lt;arm&gt;&lt;compiler&gt;&lt;keil&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="12405" PostTypeId="1" AcceptedAnswerId="12413" CreationDate="2011-04-01T14:40:47.180" Score="5" ViewCount="98" Body="&lt;p&gt;I'm doing my second ATX-to-bench supply conversion, and this time, I've decided to follow the &quot;book&quot; and place the correct minimum loads on all the rails instead of merely the 5V rail. This involves fairly small loads on the 3.3V rail and 5V rail (under 2W each), but a fairly sizable load on the 12V rail (12W). I've sourced very cheap cement resistors to provide the loads, but I understand that they are inductive loads, and I would like to know, will that cause a problem?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume it will not, because many of the loads in a normal computer are already inductive (HDD motors etc), but I would like confirmation from someone who knows a lot more about switching power supply design than I do.&lt;/p&gt;&#xA;" OwnerUserId="3240" LastActivityDate="2011-04-01T18:29:49.517" Title="Can I use an inductive load in an ATX-to-bench supply project?" Tags="&lt;power-supply&gt;&lt;resistance&gt;&lt;inductive&gt;" AnswerCount="3" />
  <row Id="12406" PostTypeId="2" ParentId="12385" CreationDate="2011-04-01T14:40:50.627" Score="2" ViewCount="" Body="&lt;p&gt;Something that you can take advantage of is the &lt;a href=&quot;http://firmata.org/wiki/Main_Page&quot; rel=&quot;nofollow&quot;&gt;Firmata&lt;/a&gt; approach.  It's basically a way to control ports / read inputs on a microcontroller using serial commands (which sounds like what you're trying to do).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is already a Firmata library for Arduino &lt;a href=&quot;http://www.arduino.cc/en/Reference/Firmata&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  There are also a number of programs that implement the PC end of the conversation.&lt;/p&gt;&#xA;" OwnerUserId="1823" LastActivityDate="2011-04-01T14:40:50.627" />
  <row Id="12407" PostTypeId="1" AcceptedAnswerId="12412" CreationDate="2011-04-01T15:23:02.963" Score="9" ViewCount="345" Body="&lt;p&gt;If I have sampled a signal using proper sampling methods (Nyquist, filtering, etc) how do I relate the length of my FFT to the resulting frequency resolution I can obtain?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like if I have a 2,000 Hz and 1,999 Hz sine wave, how would I determine the length of FFT needed to accurately tell the difference between those two waves?&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-27T13:49:00.083" Title="What is the relation between FFT length and frequency resolution?" Tags="&lt;dsp&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="12408" PostTypeId="2" ParentId="12407" CreationDate="2011-04-01T15:53:09.327" Score="3" ViewCount="" Body="&lt;p&gt;Basic FFT resolution is $f_s \over N$, where $f_s$ is the sampling frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ability to differentiate two very closely spaced signals depends strongly on relative amplitudes and the windowing function used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may find that playing with the &lt;a href=&quot;http://www.baudline.com/&quot; rel=&quot;nofollow&quot;&gt;Baudline signal analyzer&lt;/a&gt; is a good way to develop some intuition on this matter (and no, running some FFTs and plotting one spectrum at a time in Matlab or Python/Numpy is really not the same).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: There is also a trick to pad the input with zeros and taking a bigger FFT. It will not improve your differentiation ability but may make the spectrum more readable. It is basically a trick similar to antialiasing in vector graphics.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-01T15:53:09.327" CommentCount="3" />
  <row Id="12409" PostTypeId="1" CreationDate="2011-04-01T15:55:36.003" Score="6" ViewCount="275" Body="&lt;p&gt;So I need design a prototype PCB circuit and need to decide on using what kind of surface mount resistors and capacitors to use. But looking at digikey, there are so many types with many variations in size, manufacturers, etc.! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since there is not really any strict requirements for my project, I'm assuming most of them would work fine. Cost and precision is not a huge issue for my case. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But what are some deciding factor on choosing which size/packaging/manufacturers to use? &lt;/p&gt;&#xA;" OwnerUserId="2968" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-01T16:02:53.877" LastActivityDate="2011-04-02T00:10:21.960" Title="choosing surface mount resistor/capacitors" Tags="&lt;capacitor&gt;&lt;resistor&gt;&lt;surface-mount&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="3" />
  <row Id="12410" PostTypeId="2" ParentId="12409" CreationDate="2011-04-01T16:11:28.977" Score="3" ViewCount="" Body="&lt;p&gt;The main consideration is whether you are assembling the board yourself or not. 0805 Rs and Cs are best in the former case, being relatively easy to hand-solder and not taking up much room. If the latter, the assembly company will usually supply the passive components. It would be a good idea to check what they are using but a reputable company selects appropriate parts, in my experience.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another important thing to consider is RoHS vs non-RoHS.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-01T16:55:32.807" LastActivityDate="2011-04-01T16:55:32.807" CommentCount="1" />
  <row Id="12411" PostTypeId="2" ParentId="12409" CreationDate="2011-04-01T16:13:40.593" Score="6" ViewCount="" Body="&lt;p&gt;In the past I've often used parts from Yageo and AVX. There was not really a preference, most of the time the choice was determined by lead time.&lt;br&gt;&#xA;As for size, last time I ordered parts 0603 were the cheapest, but you say that price is not an issue. If space is a premium it's obvious that you'd rather choose 0402 parts, that is if power consumption is not a problem. If you have plenty of room you may want to use the older 0805 parts as they're easier to work with, measuring-wise and rework-wise.&lt;br&gt;&#xA;1% parts are only slightly more expensive than their 5% counterparts, but they have the advantage of better reproducibility; individual devices (assemblies, not only components) are more likely to behave exactly the same.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-01T16:25:40.070" LastActivityDate="2011-04-01T16:25:40.070" CommentCount="1" />
  <row Id="12412" PostTypeId="2" ParentId="12407" CreationDate="2011-04-01T16:33:03.147" Score="10" ViewCount="" Body="&lt;p&gt;The frequency resolution is dependent on the relationship between the FFT length and the sampling rate of the input signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the sampling rate of the signal is 10khz and we collect 8192 samples for the FFT then we will have:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;8192 / 2 = 4096 FFT bins&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Since, via nyquist, our signal contains content up to 5khz our bin resolution is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;5000Hz / 4096 bins = 1.22 Hz/bin&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This is may be the easier way to explain it conceptually but simplified, your bin resolution is just: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;$Fs/N$ &lt;/p&gt;&#xA;&#xA;&lt;p&gt;where Fs is the input signal's sampling rate and N is the number of FFT points used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We can see from the above that to get smaller FFT bins we can either run a longer FFT or decrease our sampling rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The Catch:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is always a trade off between temporal resolution and frequency resolution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the example above, we need to collect 8192 samples before we can run the FFT, which when sampling at 10khz takes 0.82 seconds.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If we tried to get smaller FFT bins by running a longer FFT it would take even longer to collect the needed samples. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That may be OK, it may not be.  The important point is that at a fixed sampling rate, increasing frequency resolution decreases temporal resolution.  That is the more accurate your measurement in the frequency domain, the less accurate you can be in the time domain.  You effectively lose all time information inside the FFT length.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this example, if a 1999Hz tone starts and stops in the first half of the 8192 sample FFT and a 2002Hz tone plays in the second half of the window, we would see both, but they would appear to have occurred at the same time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also have to consider processing time.  A 8192 point FFT takes some decent processing power.  A way to reduce this need is to reduce the sampling rate, which is the second way to increase frequency resolution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your example, if you drop your sampling rate to something like 4096 Hz, then you only need a 4096 point FFT to achieve 1hz bins and can still resolve a 2khz signal.  This reduces the FFT bin size but also reduces the bandwidth of the signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ultimately with an FFT there will always be a trade off between frequency resolution and time resolution.  You have to perform a bit of a balancing act to reach all goals.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2011-05-27T13:49:00.083" LastActivityDate="2011-05-27T13:49:00.083" CommentCount="3" />
  <row Id="12413" PostTypeId="2" ParentId="12405" CreationDate="2011-04-01T17:04:32.517" Score="5" ViewCount="" Body="&lt;p&gt;In this case, you're fine.  Of course there are already a bunch of inductive loads already in the system, but also the inductive loads only play a part when the supply turns on or off.  Inductive loads only show their &quot;inductiveness&quot; when the current changes, and since the load is going to have a constant current then you're all right.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to be extra careful, you could put a diode between your output and GND (oriented so it's not normally drawing a current).  That would protect your power supply during turn on/off from any inductive kickback.  Even if your &quot;minimum loads&quot; were not inductive, this would be a good idea just in case you want to connect motors or whatever to your benchtop supply.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-01T17:04:32.517" />
  <row Id="12414" PostTypeId="2" ParentId="12405" CreationDate="2011-04-01T17:06:09.637" Score="2" ViewCount="" Body="&lt;p&gt;If you examine the typical circuit used in such regulators, you will see that the load is outside the control loop, so an inductive load should not really matter. This is confirmed by the data sheets of switching regulator devices, such as the Simple Switchers made by National Semiconductor; no requirements are mentioned for the type of load.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-01T17:06:09.637" />
  <row Id="12415" PostTypeId="2" ParentId="12409" CreationDate="2011-04-01T17:20:58.020" Score="1" ViewCount="" Body="&lt;p&gt;Here is a summary table describing various types of capacitors. This is from &lt;em&gt;The Art of Electronics&lt;/em&gt; by Horowitz &amp;amp; Hill. Reprinted without permission. This may help you to choose the best type of capacitor for your application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another factor to consider is capacitor frequency &quot;response&quot;. I should be clear that this is not referring to frequency response in the usual sense (i.e. $X_C=\frac 1 {j\omega C}$). Different dielectrics are generally only usable over a certain frequency range. &lt;a href=&quot;http://sites.google.com/site/interfacebus/Home/capacitor-frequency-response&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; has a chart and a short description. I believe this is why two different types of caps are often paralleled even though one may have a much smaller capacitance than the other, such as a 0.1uF ceramic cap in parallel with a 1uF electrolytic or tantalum.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/lNpbS.gif&quot; alt=&quot;Capacitor summary from The Art of Electronics by Horowitz &amp;amp; Hill&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3635" LastEditorUserId="3635" LastEditorDisplayName="" LastEditDate="2011-04-01T17:31:28.960" LastActivityDate="2011-04-01T17:31:28.960" CommentCount="7" />
  <row Id="12416" PostTypeId="2" ParentId="12409" CreationDate="2011-04-01T17:25:37.317" Score="5" ViewCount="" Body="&lt;p&gt;You do have to do some due diligence before choosing parts, namely:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;are the parts rated for the expected power dissipation?&lt;/li&gt;&#xA;&lt;li&gt;are the parts rated for the expected voltage?&lt;/li&gt;&#xA;&lt;li&gt;is the design manufacturable?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Some generalizations:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;1206 resistors: 0.25W maximum dissipation, 200V maximum&lt;/li&gt;&#xA;&lt;li&gt;0805 resistors: 0.125W maximum dissipation, 150V maximum&lt;/li&gt;&#xA;&lt;li&gt;0603 resistors: 100mW maximum dissipation, 75V maximum&lt;/li&gt;&#xA;&lt;li&gt;0402 resistors: 62.5mW maximum dissipation, 50V maximum&lt;/li&gt;&#xA;&lt;li&gt;1% resistor tolerance is good enough for most applications, select 0.1% Nichrome resistors if accuracy is needed&lt;/li&gt;&#xA;&lt;li&gt;Go with X7R or X5R dielectric material for the surface-mount caps, for a good compromise between thermal drift and cost. NP0 or C0G is good where less drift is desired&lt;/li&gt;&#xA;&lt;li&gt;Many surface-mount MLCCs are good for 50V (down to 0402)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-01T17:25:37.317" />
  <row Id="12417" PostTypeId="2" ParentId="12396" CreationDate="2011-04-01T17:39:02.417" Score="1" ViewCount="" Body="&lt;p&gt;It's a bandwidth-saving measure.  Consider if instead of raised-cosine waveforms you used square waves (the beta = 1 case) - lots more harmonics, more bandwidth required.  The raised-cosine limits the bandwidth at the expense of making the baseband signal more difficult to produce and detect.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-01T17:39:02.417" CommentCount="3" />
  <row Id="12418" PostTypeId="1" CreationDate="2011-04-01T17:41:21.517" Score="2" ViewCount="73" Body="&lt;p&gt;My stepper rating is 0.33A per phase, 23.9&amp;Omega; phase resistance and 29.8mH inductance/phase.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What voltage should I use to drive this motor so that it provides holding torque around 13.7Ncm (rated on motor)?&lt;/p&gt;&#xA;" OwnerUserId="3691" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-04-01T18:54:28.553" LastActivityDate="2011-04-02T01:14:34.780" Title="Stepper Motor Supply Voltage" Tags="&lt;stepper&gt;&lt;stepper-motor&gt;&lt;ratings&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12419" PostTypeId="2" ParentId="12405" CreationDate="2011-04-01T18:29:49.517" Score="5" ViewCount="" Body="&lt;p&gt;I would venture that any inductance in the resistors would be swamped by the output inductance of the power supply, so the likelihood that they'd cause any disturbance would be low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a hard time believing that the inductance in a small cement wire-wound resistor could store enough energy to do any damage to the output of a power supply, especially one that doesn't have ORing (i.e. an ATX computer supply, which isn't intended to operate in parallel with another supply) - the output capacitors will do their best to absorb any energy kicked back from the inductance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Imagine that you have 1 microhenry of inductance, and 1A of current. The energy is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$E = \frac{1}{2} \mbox LI^2 = 0.5 \mu J $&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that 1A were to dissipate in 1 microsecond, the voltage would be:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$V = L \frac{di}{dt} \mbox = 1V $&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The risks are minimal. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-01T18:29:49.517" CommentCount="1" />
  <row Id="12420" PostTypeId="2" ParentId="12385" CreationDate="2011-04-01T18:45:04.360" Score="0" ViewCount="" Body="&lt;p&gt;The way I do it is with &lt;a href=&quot;http://cycling74.com/&quot; rel=&quot;nofollow&quot;&gt;Max&lt;/a&gt; and the [serial] object. You can implement a simple terminal using the text editor GUI object. &lt;a href=&quot;http://puredata.info/&quot; rel=&quot;nofollow&quot;&gt;PureData&lt;/a&gt; is a free alternative, which has a similar solution, though I'm not sure what the object for serial communication is called.&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2011-04-01T18:45:04.360" />
  <row Id="12421" PostTypeId="2" ParentId="7888" CreationDate="2011-04-01T18:59:19.613" Score="3" ViewCount="" Body="&lt;p&gt;The terms &quot;set low&quot; and &quot;set high&quot;, applied to an output pin, mean to drive the output voltage to VSS or VDD, respectively, regardless of whether the pin's value will be interpreted as an active-low signal.  The terms &quot;release&quot; or &quot;float the pin&quot; means to set an output to high-impedance mode.  The term &quot;assert&quot;, applied to an output pin which has clearly-defined active and inactive states, means to drive the pin to the active state (which may in some cases be low and in other cases be high).  The term &quot;deassert&quot; means to either drive such a pin to in inactive state, or float it and allow an external resistor to do so.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-01T18:59:19.613" />
  <row Id="12422" PostTypeId="1" CreationDate="2011-04-01T19:26:30.317" Score="6" ViewCount="173" Body="&lt;p&gt;Does anyone know of any old-school function generator ICs (similar to the ICL8038 or XR2206) that are still on the market? (i.e. not obsolete / NFFD - I'm not interested in scouring the globe for old inventory)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm aware of digitally-programmable parts that use I2C / SPI, but am looking for something that won't involve adding a micro to a legacy design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking primarily for an IC that will output a triangular waveform at low frequency (640Hz). The XR2206 was the original part in the application which is now obsolete. The frequency can be adjusted a small amount from an external input (+/- 50Hz or so).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Exar has obsoleted most (all?) of their function generator parts:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/GtadC.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-04T16:24:09.497" LastActivityDate="2011-04-05T07:48:43.143" Title="Analog function generator ICs?" Tags="&lt;ic&gt;&lt;function-generator&gt;&lt;obsolete&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="2" />
  <row Id="12423" PostTypeId="1" AcceptedAnswerId="12426" CreationDate="2011-04-01T19:58:01.617" Score="2" ViewCount="125" Body="&lt;p&gt;I have a DB25 I/O connector, thru-hole.  The pins connect to an SMT MCU, which I want to protect from ESD, specifically IEC 61000-4-2.  I want to use SMT Zener diodes to protect the pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am considering various layouts.  I imagine the optimal layout would have the diodes between the DB25 and the MCU.  In this way, an ESD event can be shunted to ground before it gets to the MCU&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MCU &amp;lt;-&gt; Diodes &amp;lt;-&gt; DB25&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I would like to take advantage of the thru-holes in the DB25 to simplify routing and reduce the number of vias that I would need.  However, in doing so, the diodes will end up on the &quot;other side&quot; of the DB25.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MCU &amp;lt;-&gt; DB25 &amp;lt;-&gt; Diodes&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this a bad idea?  I'm slightly concerned about whether a sufficiently fast ESD strike could &quot;split up&quot; and reach the MCU before the diodes begin fully conducting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is the case, would it be mitigated if the MCU &amp;lt;-&gt; DB25 traces were run on bottom-layer, while DB25 &amp;lt;-&gt; Diodes traces were on the top layer?  Would the added vias between the MCU and DB25 encourage the ESD current to go through the diode instead?&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-04-01T20:20:30.400" Title="ESD Diode layout recommendations" Tags="&lt;pcb-design&gt;&lt;esd&gt;" AnswerCount="1" />
  <row Id="12424" PostTypeId="5" CreationDate="2011-04-01T19:59:45.780" Score="0" ViewCount="" Body="&lt;p&gt;A buck converter is a non-isolated DC-DC converter topology used to step down voltage. It is one of the most fundamental converter topologies in existence.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic buck converter power train is comprised of a switch (usually a MOSFET or transistor), an inductor, a diode, and a capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/UpSA6.png&quot; alt=&quot;Public-domain buck converter image from Wikipedia&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The duty cycle of the switch determines the ratio of load voltage to supply voltage:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$ \frac{V_{out}}{V_{in}} \mbox = D $&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An improvement on the buck converter is the synchronous buck converter, where the diode is replaced with another switch. This increases the efficiency of the converter but requires more complicated control.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Buck_converter&quot; rel=&quot;nofollow&quot;&gt;Wikipedia: Buck converter&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-01T21:25:26.050" LastActivityDate="2011-04-01T21:25:26.050" />
  <row Id="12425" PostTypeId="4" CreationDate="2011-04-01T19:59:45.780" Score="0" ViewCount="" Body="A non-isolated DC-DC converter topology." OwnerUserId="-1" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-01T21:25:29.620" LastActivityDate="2011-04-01T21:25:29.620" />
  <row Id="12426" PostTypeId="2" ParentId="12423" CreationDate="2011-04-01T20:20:30.400" Score="3" ViewCount="" Body="&lt;p&gt;ESD is difficult to deal with, and solutions are more black magic than science.  That being said, what you want is for the impedance to ground to be higher than the impedance to the chip you're protecting.  There are several ways to do this, and the most practical solution will probably involve several of these things at once.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Placement and routing of traces is a good start.  As you noted, MCU &amp;lt;-&gt; Diodes &amp;lt;-&gt; DB25 is probably the best, although MCU &amp;lt;-&gt; DB25 &amp;lt;-&gt; Diodes can work.  To make it work, the traces to the diodes should be thick and short.  The traces to the MCU should be long-ish and thin.  But, IMHO, just doing this is not enough for a commercial product.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Put some sort of of resistor or ferrite bead between the DB25/Diodes and the MCU.  I prefer resistors for this because their impedance is more predictable at high frequencies, but a bead could work too.  A resistor of around 10 to 50 ohms is good, depending on the nature of the signals you're running.  This resistor/bead will increase the impedance to the MCU, guiding the ESD to ground through a different way.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Put a capacitor in parallel with the diodes.  A value of 3 nF is ideal for ESD protection.  But depending on your signal you might have to use a smaller or larger one., or none at all.  The largest you can get away with will also reduce your EMI problems.  The basic function of the cap is to quickly absorb the ESD shock and re-emit it more slowly and with a smaller voltage.  If the cap is large enough then the diode is not required.  This cap also forms an RC filter with #2 above and prevents EMI from going in or out of the box.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Connect the shield of the DB25 to chassis ground, and make sure your chassis make a good shield.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Recently I had an issue with a USB device that would crash whenever an ESD zap happened within 8 feet of the box.  In the end I had to connect the USB shell to Chassis, add 33 ohm resistors to the USB data lines, add caps, and diodes.  Until I did all that I still experienced failures.  If I left off one of those, any one, it would fail.  Now it runs solid, even with 1 inch long sparks right to the chassis.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-01T20:20:30.400" CommentCount="6" />
  <row Id="12427" PostTypeId="2" ParentId="12409" CreationDate="2011-04-01T20:22:37.840" Score="6" ViewCount="" Body="&lt;p&gt;For assembling by hand I offer the following suggestions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Capacitors:  For the ubiquitous 0.1uF ceramic decoupling caps go with 0603.  They're nonpolar and unlabelled so the small size is not that much of an issue.  You could buy a whole reel and be set for life.  Every tantalum and electrolytic SMT cap is big enough that handling is not an issue.  If you are following a datasheet recommendation to put down 2 or 3 decades of caps near a pin of a high-density package even 0805 will feel very big.&lt;/li&gt;&#xA;&lt;li&gt;Resistors:  They are labelled down to 0603 (usually).  If you care about reading the markings it's worth checking a few with your own eyes to see what you can read.  I find 0805 much more readable than 0603.  A nice tradeoff for density vs handling is 4 resistor arrays.  A 1206 array is basically 4 0603 resistors side-by-side.  The package is much bigger and the label is much easier to read but the density is even better than 0603 (because there is no gap) and the soldering is only slightly trickier.  These are great for pullups, series/stub terminations, LED arrays, etc.&lt;/li&gt;&#xA;&lt;li&gt;Jumping over tracks:  It's easy to home-etch a board with a trace going under (between the pads) of a 1206 or 805.  You can manage nearly 10/10 rules cutting under 0603 but you will probably have to make your own land pattern for 0603 to do it (otherwise the pads will be too close).&lt;/li&gt;&#xA;&lt;li&gt;LEDs:  I find the ones in the tantalum-capacitor style A, B, C, D cases the easiest to orient and solder.  Ones sized like resistors (0603) can be quite hard to orient without magnification.  I usually use a setup where I can probe the LED to light it up to verify which way it's going in.&lt;/li&gt;&#xA;&lt;li&gt;Other ICs:  SOT-223 and SO-89 are nice for voltage regulators.  SOT-23 is fairly easy to work with in 3-lead packages and slightly trickier in 5 or 6 lead.  SO-8 is easy to work with.  QFP with pitch 0.8 or 1.0mm is pretty easy but fine-pitch QFP (0.65, 0.5mm)  requires a lot of flux and good technique.  QFN, MLF, BGA and the like are very tricky to work with at home and can be difficult to route on 2-layer boards (especially without plated through-holes).  I avoid PLCC when I can because it's neither small nor that easy to solder (it's very easy to bridge pins under the chip and very hard to desolder them).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Mind your ground relief when connecting to surface mount pads.  If you let your plane simply merge with a pad it can be very hard to solder even with a very good iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember that putting SMT components in your PCB &lt;em&gt;design&lt;/em&gt; is almost free.  There's no hole to drill and it's just a modification of the copper and silk masks.  It won't affect the cost of the PCB at all.  If you think you might need another cap or an indicator LED or a pullup resistor just put them all in the design.  You can always DNI them.&lt;/p&gt;&#xA;" OwnerUserId="2664" LastEditorUserId="2664" LastEditorDisplayName="" LastEditDate="2011-04-02T00:10:21.960" LastActivityDate="2011-04-02T00:10:21.960" CommentCount="2" />
  <row Id="12428" PostTypeId="2" ParentId="9066" CreationDate="2011-04-01T20:31:18.977" Score="0" ViewCount="" Body="&lt;p&gt;I don't think you can multiplex like this.  You are using all those pins as outputs i.e. digitalWrite(X, HIGH) makes the output of pin X +5 volts.  To use two outputs together you need some kind of switch (e.g. an AND gate or some configuration of transistors).  I'd say you'd be better off using a shift register (3 inputs to 8) of just use 9 output lines from the board, one for each LED, then write the code for controlling the matrix.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps :)&lt;/p&gt;&#xA;" OwnerUserId="3694" LastActivityDate="2011-04-01T20:31:18.977" />
  <row Id="12429" PostTypeId="2" ParentId="12422" CreationDate="2011-04-01T20:36:50.787" Score="7" ViewCount="" Body="&lt;p&gt;This would seem to be similar to the XR2206 :)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;a href=&quot;http://www.exar.com/Common/Content/ProductDetails.aspx?ID=10418&amp;amp;ParentID=257&quot; rel=&quot;nofollow&quot;&gt;The XR2209&lt;/a&gt; is a monolithic voltage-controlled oscillator (VCO) integrated circuit featuring excellent frequency stability and a wide tuning range. The circuit provides simultaneous triangle and squarewave outputs over a frequency range of 0.01Hz to 1MHz. It is ideally suited for FM, FSK and sweep or tone generation, as well as for phase-locked loop applications.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Applications&lt;/p&gt;&#xA;  &#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;Waveform Generation Triangle, Sawtooth, Pulse, Squarewave&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-04-01T20:36:50.787" CommentCount="4" />
  <row Id="12430" PostTypeId="2" ParentId="12176" CreationDate="2011-04-01T22:03:00.997" Score="7" ViewCount="" Body="&lt;p&gt;Firstly, lets check that you have connected your LDR up correctly, it should be something like this...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/YW0B3.gif&quot; alt=&quot;LDR wiring&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To read the value of PIN RA0/AN0, you need to do some initialisation to make sure the port is setup correctly. The &lt;a href=&quot;http://ww1.microchip.com/downloads/en/devicedoc/39632c.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; explains how all this works, but these values should work:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;TRISAbits.TRISA0 = 1;           // Set RA0/AN0 to input&#xA;ADCON0           = 0b00000000;  // Set channel select to AN0&#xA;ADCON1           = 0b00001110;  // Configure RA0/AN0 as analogue&#xA;ADCON2           = 0b10101010;  // Right justified result&#xA;                                // TAD 12 and FOSC 32 - may need to adjust this&#xA;                                // depending on your clock frequency (see datasheet)&#xA;ADCON0.ADON      = 1;           // Enable ADC&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Now the port should be set up, you can now read the LDR value:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ADCON0bits.GO    = 1;           // Set the GO bit of the ADCON0 register to start&#xA;                                // the conversion.&#xA;&#xA;while (ADCON0bits.GO);          // Wait until the conversion is complete.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You can now read the result of the LDR as a 10-bit value in &lt;code&gt;ADRESH:ADRESL&lt;/code&gt;. If you only need 8-bit resolution, then set &lt;code&gt;ADCON2.ADFM = 0&lt;/code&gt; for left justification of the result, then you only need to read the &lt;code&gt;ADRESH&lt;/code&gt; to get your result.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-04-01T22:03:00.997" CommentCount="1" />
  <row Id="12432" PostTypeId="1" AcceptedAnswerId="12433" CreationDate="2011-04-01T22:58:57.100" Score="4" ViewCount="117" Body="&lt;p&gt;Hello, I'm struggling with WebPack's bloat and random broken pieces when running in Linux. So, I'm thinking it may just be easier to use a different compiler/simulator. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to use something different? Note, all I need to do is get a &lt;code&gt;.bit&lt;/code&gt; file. I have the &lt;a href=&quot;http://gadgetforge.gadgetfactory.net/gf/project/butterfly_one/&quot; rel=&quot;nofollow&quot;&gt;Butterfly One&lt;/a&gt; which has an external programming application. (which only requires a .bit file)&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-04-12T11:37:48.337" Title="Can I use ghdl or some other VHDL compiler/simulator than WebPack with a Spartan 3E?" Tags="&lt;fpga&gt;&lt;xilinx&gt;&lt;vhdl&gt;&lt;spartan&gt;" AnswerCount="3" />
  <row Id="12433" PostTypeId="2" ParentId="12432" CreationDate="2011-04-01T23:10:13.853" Score="2" ViewCount="" Body="&lt;p&gt;No. Only the vendor's tools produce .bit. But you can use many for simulation. You may just need a Xilinx library for it.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-04-01T23:10:13.853" CommentCount="2" />
  <row Id="12435" PostTypeId="1" CreationDate="2011-04-01T23:43:20.223" Score="1" ViewCount="234" Body="&lt;p&gt;This sounds really very easy, but I'm afraid to try it because I don't want to fry my microcontroller. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll use an Arduino for an example, but it should be the same for all microcontrollers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, say you have a switch and you want for when you press the switch to bring a digital pin to high(1) and when it's not pressed, to low(0). Would this require resistors? Or would you just straight wire from 3.3v into the input pin?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or to further simplify what I'm asking. If for some reason you wanted a certain digital input pin to always be high, would you just stick a wire from 3.3v into the digital pin? Or would you need a resistor somewhere in there?&lt;/p&gt;&#xA;" OwnerUserId="708" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-04-02T00:36:34.983" LastActivityDate="2011-04-02T00:57:30.333" Title="How to bring a digital input pin to high state?" Tags="&lt;arduino&gt;&lt;microcontroller&gt;&lt;circuit&gt;&lt;digital&gt;&lt;mbed&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="12436" PostTypeId="2" ParentId="12435" CreationDate="2011-04-02T00:14:05.793" Score="1" ViewCount="" Body="&lt;p&gt;You need to use either a pullup to Vdd or a pulldown to GND.  If you don't, when you press your switch, you will effectively short Vdd to GND.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- I should have drawn a picture, but instead found a &lt;a href=&quot;http://www.seattlerobotics.org/encoder/mar97/basics.html&quot; rel=&quot;nofollow&quot;&gt;site with an explanation&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-02T00:14:05.793" CommentCount="2" />
  <row Id="12437" PostTypeId="2" ParentId="12395" CreationDate="2011-04-02T00:17:37.957" Score="3" ViewCount="" Body="&lt;p&gt;This kind of circuit is used in amplitude detectors which (assuming appropriate diodes) can work with signals from kilohertz up to several gigahertz. They give output voltage that is proportional to the amplitude of the input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you wire this circuit without $R_1$, $D_1$ and $R_3$ you will get a detector with the nice property that the output current is proportional to the &lt;a href=&quot;http://www.phys.hawaii.edu/~anita/new/papers/militaryHandbook/detector.pdf&quot; rel=&quot;nofollow&quot;&gt;square of the input voltage&lt;/a&gt;. This means that if you know the load resistance (which is most likely $50\,\Omega$) you can make a direct power measurement with just a linear scale ($P = {V^2 \over R}). Unfortunately this only holds if the input is below 0.6 V (or 0.3 V for Schottky diodes which are frequently used in such circuits) and the output current is very low (see the diode I-V characteristics below and the pictures in &lt;a href=&quot;http://www.phys.hawaii.edu/~anita/new/papers/militaryHandbook/detector.pdf&quot; rel=&quot;nofollow&quot;&gt;this document&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/TqtsE.gif&quot; alt=&quot;Diode I-V characteristics&quot;&gt;(picture by &lt;a href=&quot;http://engphys.mcmaster.ca/~elmer101/sqlaw/sqlaw.html&quot; rel=&quot;nofollow&quot;&gt;Glen Leinweber&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$C$ is very small (100pF) so you can treat is as a open circuit when considering DC voltages and as a short at high frequencies (it works like a $100\,\Omega$ resistor at 15MHz). This means that adding $R_1$, $D_1$ and $R_3$ will add some polarizing voltage (and current) to the $D_2$ diode. $R_3$ and $D_1$ form a so called shunt voltage regulator. Because of the highly nonlinear characteristics of the diode it's output voltage is largely independent of both the supply voltage and the current through $R_3$ (within some limits).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output from this regulator is fed through $R_1$ (a small inductor would be even better here) to get some current flowing through $D_2$. This (thanks to $C$) shifts the average input voltage and that results in a change in the operating conditions of $D_2$. At higher voltages a diode permits more current to flow. Also the rate of change of the current with applied voltage is higher (recall the characteristics). This improves the sensitivity and makes it easy to measure thanks to the higher overall output current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could do this with a normal resistive divider but this would make the circuit sensitive to temperature and diode parameter variation. OTOH making $D_1$ and $D_2$ the same (in fact two diodes made from one silicon die are the best) will make the output from the shunt regulator follow any changes in the characteristics of $D_2$ (because of temperature, humidity or other stuff) protecting you from over- or under-polarizing.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-02T10:18:56.090" LastActivityDate="2011-04-02T10:18:56.090" CommentCount="4" />
  <row Id="12438" PostTypeId="2" ParentId="12435" CreationDate="2011-04-02T00:57:30.333" Score="1" ViewCount="" Body="&lt;p&gt;To get at your question about if you can plug power directly to the pin with no resistor and have it always be high... yes, that does work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you have your microcontroller set to input mode you can treat the pin like there is a very large resistor inside. So using ohms law, V/R=I with V=3.3 and R=very large, lets say 10megohm gives you a current of 0.33 micro amps. The inputs are designed to act like such a high impedance so that it has a very small effect on anything externally.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-02T00:57:30.333" CommentCount="2" />
  <row Id="12439" PostTypeId="2" ParentId="12418" CreationDate="2011-04-02T01:14:34.780" Score="1" ViewCount="" Body="&lt;p&gt;You need the motor torque constant. It's sometimes called Kt and/or Ke. This parameter will let you relate current to torque. Then you can work backwards, starting with the torque you want, figure out what the current must be, and then ohms law will tell you what voltage will push that current.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-02T01:14:34.780" />
  <row Id="12440" PostTypeId="2" ParentId="12390" CreationDate="2011-04-02T04:00:27.840" Score="1" ViewCount="" Body="&lt;p&gt;If you need 12 VDC, it may be simpler to use an off-the-shelf wall wart with a 12 VDC output. Such devices &lt;em&gt;do&lt;/em&gt; convert to DC for you. A few of them use exactly the circuit BG100 shows, but nowadays many of them use a switching regulator technique that requires &lt;em&gt;more&lt;/em&gt; parts, but has a lower net cost.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-02T04:00:27.840" />
  <row Id="12441" PostTypeId="1" CreationDate="2011-04-02T08:14:49.987" Score="1" ViewCount="61" Body="&lt;p&gt;I'm looking into getting a TinyCLR microcontroller. The two that I've found that seem most suitable are the &lt;a href=&quot;http://proto-pic.co.uk/products/FEZ-Panda.html&quot; rel=&quot;nofollow&quot;&gt;FEZ Panda&lt;/a&gt; and the &lt;a href=&quot;http://netduino.com/&quot; rel=&quot;nofollow&quot;&gt;Netduino&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hardware-wise, the FEZ Panda appears to come out on top. However, I was wondering what the API, support, and other software side of things was like.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any advice over which one to go with (assuming hardware specs are irrelevant)?&lt;/p&gt;&#xA;" OwnerUserId="1217" LastActivityDate="2011-04-02T08:14:49.987" ClosedDate="2011-05-16T16:23:48.830" Title="From a software and support point of view, which is better: Netduino or FEZ Panda?" Tags="&lt;microcontroller&gt;&lt;netduino&gt;" CommentCount="1" />
  <row Id="12442" PostTypeId="2" ParentId="12385" CreationDate="2011-04-02T09:30:56.927" Score="0" ViewCount="" Body="&lt;p&gt;How about Arduino Explorer: &lt;a href=&quot;http://www.avr-developers.com/arduino_exp.html&quot; rel=&quot;nofollow&quot;&gt;http://www.avr-developers.com/arduino_exp.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From the site:&#xA;&quot;... allows you to examine memory, examine and toggle I/O pins, explore the mapping of Arduino pin numbers to AVR port names and bit numbers, scan I2C bus, look at interrupt vectors and much more. &quot;&lt;/p&gt;&#xA;" OwnerUserId="1504" LastActivityDate="2011-04-02T09:30:56.927" />
  <row Id="12444" PostTypeId="1" CreationDate="2011-04-02T12:32:15.093" Score="2" ViewCount="88" Body="&lt;p&gt;I have only 1 pulse as input and I use qubic-spline to reshape the pulse. The user plot manually the signal inputs from a flow-image and then the signal is imported to Matlab in a ASCII form. That means that the sampling period is not uniform. Then I have a pressure pulse that are sampled at 128 Hz. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I use same samplig period (128Hz) using qubic spline on the flow signal. If I increase the sampling to 4-8 times what will it effects of the FFT analysis?&#xA;I can see in Matlab that the amplitude changes at different up-sampling rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I multiply the input signal (pulse train) e.g. 2-6 times it will also effect the FFT analysis. The bins are the same at higher pulse train but not at just one single pulse. &#xA;One pulse or many should not impact the FFT analysis?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right know I have no filter on the signal (before and after resampling)&lt;/p&gt;&#xA;" OwnerUserId="3699" LastEditorUserId="3699" LastEditorDisplayName="" LastEditDate="2011-04-03T10:46:06.437" LastActivityDate="2011-04-03T10:46:06.437" Title="Up-sampling input signal" Tags="&lt;dsp&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="0" />
  <row Id="12445" PostTypeId="2" ParentId="10312" CreationDate="2011-04-02T12:33:15.340" Score="1" ViewCount="" Body="&lt;p&gt;You could just get a 12VDC wall supply. Has the transformer, rectifier, filter and regulator built in. can get fans cheap also. Check these links, $8.50 for all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.allelectronics.com/index.php?page=search&amp;amp;search_query=dctx-1227&amp;amp;x=39&amp;amp;y=7&quot; rel=&quot;nofollow&quot;&gt;http://www.allelectronics.com/index.php?page=search&amp;amp;search_query=dctx-1227&amp;amp;x=39&amp;amp;y=7&lt;/a&gt;&#xA;&lt;a href=&quot;http://www.allelectronics.com/index.php?page=search&amp;amp;search_query=CF-387&amp;amp;x=29&amp;amp;y=12&quot; rel=&quot;nofollow&quot;&gt;http://www.allelectronics.com/index.php?page=search&amp;amp;search_query=CF-387&amp;amp;x=29&amp;amp;y=12&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-04-02T12:33:15.340" />
  <row Id="12446" PostTypeId="2" ParentId="9066" CreationDate="2011-04-02T12:47:20.487" Score="1" ViewCount="" Body="&lt;p&gt;Without current limiting, you are counting on the micro to limit the current. By turning on several outputs at one time it is consuming a lot of current. I would add 3 resistors to the high bus, 330-560 ohms to the outputs on 8, 9, 10. Turn on only one led at a time. If you need the appearance of several led's on at one instance you can clock the outputs faster in succession.&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-04-02T12:47:20.487" />
  <row Id="12447" PostTypeId="2" ParentId="12444" CreationDate="2011-04-02T16:08:06.380" Score="1" ViewCount="" Body="&lt;p&gt;why do you want to upsample?  upsampling comes at a cost in the digital domain, and can save expense in the analogue domain.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example if you have a signal with content that you are interested in the range of 0-3 kHz you can sample using inexpensive a/d at 64 ksps using a one pole passive lower pass anti alias filter.  Once in the digital domain you can pass it through a IIR/FIR multipole low pass and perform decimation (drop seven out of eight samples) so you have 8 KS/s with no aliasing issue and ALL the signal information with no spectral overlap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand up sampling a 8 KS/s to 64 KS/s signal will not give you any benefit.  It will reduce the resolution of information you are interested within the 0-3 kHz range, increase memory requirements, and increase processor usage.  Of course you can define smaller frequency bins, but this comes at a computational and memory cost. &lt;/p&gt;&#xA;" OwnerUserId="1397" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-02T16:17:12.643" LastActivityDate="2011-04-02T16:17:12.643" CommentCount="1" />
  <row Id="12449" PostTypeId="2" ParentId="3957" CreationDate="2011-04-02T16:50:54.497" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0945053282&quot; rel=&quot;nofollow&quot;&gt;Forrest Mims' books&lt;/a&gt; on electronics are great for understanding the basics. For the digital stuff, I find the internet (Google, AVR Freaks, this site, Arduino forums) and the &lt;a href=&quot;http://www.google.com/search?q=atmega328&amp;amp;ie=utf-8&amp;amp;oe=utf-8&quot; rel=&quot;nofollow&quot;&gt;datasheet for your microcontroller&lt;/a&gt; to be the best guides.&lt;/p&gt;&#xA;" OwnerUserId="207" LastActivityDate="2011-04-02T16:50:54.497" CommunityOwnedDate="2011-04-02T16:50:54.497" />
  <row Id="12450" PostTypeId="2" ParentId="12395" CreationDate="2011-04-02T17:36:09.553" Score="4" ViewCount="" Body="&lt;p&gt;The short answer is that this is the &quot;magic&quot; of capacitive coupling. The signal voltage is superimposed on top of the node &quot;bias&quot; voltage (which is 0.6V). Therefore the voltage at C,D2,R1 is 0.6V + Vin, not just Vin. And therefore the diode D2 must turn on, have a 0.6V drop across it (assuming D2 and D1 identical), and the output voltage must then be basically equal to Vin. It is important to note that just the AC part of Vin gets through the cap. The DC part is blocked, if there is a DC part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The longer answer goes like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In your response to my comment, you wrote &quot;C, D1, R1&quot; but I think you meant &quot;C, &lt;strong&gt;D2&lt;/strong&gt;, R1&quot;. So I will continue with that assumption. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, note the node D1, R1, R3 will basically be clamped to 0.6V at all times. This will not change no matter what the input signal is. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, remember that the I-V relationship for a capacitor is &lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$i_c = C\frac {dV} {dt}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What does this mean? It means that if your input voltage source changes, then the voltage across the cap changes. Therefore you have a nonzero $\frac {dV} {dt}$. Therefore you will have a nonzero current. (It's easy to get confused about signs at this point... bear with me) This is the differentiator action that you mentioned in your question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So let's assume an increase in input voltage which would cause a current to flow &quot;through&quot; the cap into the circuit (to the right). Where does the current go? It can either go through R1 or  D2 or both.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We started with the assumption that D2 is off, so let's first assume that the current flows only through the resistor R1. That causes a voltage to be developed across R1. So the voltage at C,D2,R1 becomes 0.6V + I*R1. &lt;strong&gt;Here is kind of the key part&lt;/strong&gt; for you to see, I think... see that the voltage at that node must have an 0.6V offset? That is because the change in input voltage causes a current to flow through the capacitor, not a voltage. So the current causes an additional voltage to be developed across the resistor R1, which adds to the voltage at that node due to the diode D1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Okay, so continuing on, this means that the voltage across D2 would be greater than 0.6V, since the cathode (&quot;line side&quot;) of the diode is presently at 0V. If the diode forward voltage is 0.6V, then we have an extra voltage (equal to I*R1) that would cause the diode D2 to turn on--which would mean that the diode would present a very low resistance compared to R1, which means current would flow through the diode D2, also. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, our initial assumption that the current flows &lt;strong&gt;only&lt;/strong&gt; downward through R1 must be incorrect--instead, the current must also flow through D2 and then through R2. Note that the current that flows through D2 is then limited by the 10K resistance R2, so it will indeed be small compared to the current that flows through R1 (by a factor of about 1/10, in fact). But regardless of the amount of current that flows, the output voltage still effectively &quot;follows&quot; the voltage at C,D2,R1, just shifted down by one diode drop (0.6V). &lt;em&gt;EDIT: except of course for negative input swings, in which case D2 blocks. But I think that part is already understood.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That came out pretty lengthy. I hope it was clear. It's tough to talk about circuits without a chalkboard or something to draw on...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;EDIT: I reread your comment, and you mention a square wave input. In the case of the square wave, the voltage at C,D2,R1 is not going to look like a square wave. It is going to look like a series of positive and negative spikes. This is due to the differentiating action of the capacitor. The square wave signal is &quot;constant in the short term&quot;. It just switches polarity periodically. It is during those switching times that a signal will appear at the C,D2,R1 node, because only during switching is $\frac{dV}{dt}$ nonzero. This is all assuming several &quot;idealities&quot; which I will not list out at this time, in order to keep it simple. It's easier to think about if the input signal were a sine wave (easier for me, anyway).&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="3635" LastEditorUserId="3635" LastEditorDisplayName="" LastEditDate="2011-04-02T19:27:19.550" LastActivityDate="2011-04-02T19:27:19.550" CommentCount="2" />
  <row Id="12451" PostTypeId="5" CreationDate="2011-04-02T17:54:10.617" Score="0" ViewCount="" Body="&lt;p&gt;A boost converter is a non-isolated DC-DC converter topology used to step up voltage. It is one of the most fundamental converter topologies in existence.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic boost converter power train is comprised of an inductor, a diode, a switch (usually a MOSFET or transistor), and a capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/rMpgr.png&quot; alt=&quot;From Wikipedia: &amp;quot;http://upload.wikimedia.org/wikipedia/commons/thumb/3/39/Boost_conventions.svg/500px-Boost_conventions.svg.png&amp;quot;&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The duty cycle of the switch determines the ratio of load voltage to supply voltage:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$ \frac {V_{out}} {V_{in}} \mbox = \frac {1}{1-D} $&lt;/p&gt;&#xA;&#xA;&lt;p&gt;or&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$ D = 1 - \frac {V_{in}}{V_{out}} $&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Boost_converter&quot; rel=&quot;nofollow&quot;&gt;Wikipedia: Boost converter&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-02T21:32:45.903" LastActivityDate="2011-04-02T21:32:45.903" />
  <row Id="12452" PostTypeId="4" CreationDate="2011-04-02T17:54:10.617" Score="0" ViewCount="" Body="A non-isolated DC/DC converter topology." OwnerUserId="-1" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-02T21:32:49.147" LastActivityDate="2011-04-02T21:32:49.147" />
  <row Id="12453" PostTypeId="1" AcceptedAnswerId="12456" CreationDate="2011-04-02T18:08:41.357" Score="3" ViewCount="225" Body="&lt;p&gt;If a standard (in Europe and a large part of the world except North America and Japan) three-phase 400V AC (three lines having 230V RMS voltage if measured to neutral each) mains supply is rectified with a standard 6-diode rectifier like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/w7RYk.png&quot; alt=&quot;Three-phase, full-wave bridge rectifier circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What DC voltage value will come out of the rectifier? How to calculate it having the RMS AC source voltage given?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any other ways to wire diodes to get a different voltage (without using any transformers or anything else then just diodes), what are they and what DC voltage will come out then?&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-04-02T23:07:33.690" Title="if a standard three-phase 400V AC connection is rectified what DC voltage comes out of it?" Tags="&lt;voltage&gt;&lt;diode&gt;&lt;high-voltage&gt;&lt;rectifier&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="12454" PostTypeId="2" ParentId="12453" CreationDate="2011-04-02T19:41:16.070" Score="4" ViewCount="" Body="&lt;p&gt;This configuration is commonly known as a star, or WYE configuration. Its easier to see if you break it down into two halves. Phase to neutral is 230 vrms. Three phases each connected to a diode anode and all three of the cathodes tied together. If measured from neutral to the cathode connections, you would expect to see 230 * 1.414 = 325 vdc. This represents the &quot;peak&quot; voltage of the waveform. Now do the same with the other half of the bridge, which will create a negative voltage of equal value in respect to the neutral. The pulses interweave with each other affectively filing in the gaps of the positive pulses, resulting in 6 pulses creating a smoother dc voltage.  The voltage unfiltered would be slightly less than 325 volts. If a filter were added such as a capacitor, the voltage would average close to the calculated value minus the &quot;ripple&quot; value which is always present in a filter. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;CAUTION:These voltages are lethal and the proper precautions need to be taken to prevent injury or death! The explanation is for illustration purposes only. In real practices this circuit would be built with an isolation transformer and circuit protection, such as fuses. &lt;/p&gt;&#xA;" OwnerUserId="3453" LastEditorUserId="3453" LastEditorDisplayName="" LastEditDate="2011-04-02T21:15:05.220" LastActivityDate="2011-04-02T21:15:05.220" CommentCount="6" />
  <row Id="12455" PostTypeId="2" ParentId="12215" CreationDate="2011-04-02T20:31:53.903" Score="-1" ViewCount="" Body="&lt;p&gt;You need a DC/DC converter.  I suggest browsing the following websites where you should find something suitable&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mornsun-power.com/cn/Index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.mornsun-power.com/cn/Index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xppower.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.xppower.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.murata-ps.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.murata-ps.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-04-02T20:31:53.903" CommentCount="5" />
  <row Id="12456" PostTypeId="2" ParentId="12453" CreationDate="2011-04-02T23:07:33.690" Score="2" ViewCount="" Body="&lt;p&gt;If you measure across the load shown in your figure, the peak voltage will be ~565V; the DC voltage will depend on your load and filtering as others have noted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you measure from the + of the load in your figure to the neutral of your AC supply, the peak voltage will be ~325V. If you hook up a load like that, you aren't actually using a full-wave rectifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest way to get 565V is to start from 400V and apply the standard $\sqrt{2}$ scaling from $V_{rms}$ to $V_{p-p}$. However, starting from 400V is skipping part of the calculation. The more thorough way to derive 565V is to calculate it as:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$(325 \text{V}) * \max_{\theta} \left\{ \sin (\theta + \frac{2 \pi}{3}) - \sin (\theta)  \right\}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The expression is maximized when $\theta$ is $\frac{5 \pi}{3}$, and the maximum value is $325 \sqrt{3} = 563$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a detailed analysis including some java applets &lt;a href=&quot;http://services.eng.uts.edu.au/~venkat/pe_html/ch05s1/ch05s1p1.htm&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-04-02T23:07:33.690" />
  <row Id="12457" PostTypeId="1" AcceptedAnswerId="12460" CreationDate="2011-04-02T23:35:18.140" Score="1" ViewCount="85" Body="&lt;p&gt;I'm looking for a generic version of this part: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.onsetcomp.com/products/sensors/cable-25-stereo&quot; rel=&quot;nofollow&quot;&gt;http://www.onsetcomp.com/products/sensors/cable-25-stereo&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks like a 3.5mm tip-ring-sleeve connector. I'd buy it, except I'm allergic to paying $9 + shipping for a 25 cent connector. I looked around but I can't find it cheaply anywhere. Most places that sell it only sell the connector by itself, with no wires attached. I'd like to buy a part that doesn't require me to solder anything, like the one in the url.&lt;/p&gt;&#xA;" OwnerUserId="2183" LastActivityDate="2011-04-03T01:13:11.603" ClosedDate="2011-04-20T12:08:30.507" Title="Where can I buy a 3.5mm TRS connector with wires soldered to it?" Tags="&lt;connector&gt;&lt;shopping&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="12458" PostTypeId="2" ParentId="11844" CreationDate="2011-04-02T23:46:49.773" Score="1" ViewCount="" Body="&lt;p&gt;I've read Don's articles in magazines etc for over 20 years, he always has excellent information and seems to know what he's talking about. But, I've been in touch with him a number of times about Magic Sinewaves over the years and never seem to get a straight answer out of him, regarding if anyone is using them, any actual implementations, efficiency numbers, etc. My own research has found no real implmentations in existence either. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best I can tell, they should work well for a fixed freq output or perhaps through a range of fixed output freq., but I'm not sure they could work well for a complex output like the comparisons to a Class D amplifier state. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thus I think things likebrushless motor controls could possibly benefit from them, in that you could reduce the number of switching &quot;events&quot; necessary when compared to something like a normal PWM output. This comes at the expense of requiring very accurate switching timing. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If they add even 5% efficiency to motor drive systems, I could see them being worthwhile for things like increasing efficiency of electric car drive systems or other similar AE systems using battery power. Just tough to determine on paper if the benefits would outweigh the additional expense of implementation. &lt;/p&gt;&#xA;" OwnerUserId="3705" LastActivityDate="2011-04-02T23:46:49.773" CommentCount="2" />
  <row Id="12459" PostTypeId="1" AcceptedAnswerId="12471" CreationDate="2011-04-02T23:57:16.757" Score="1" ViewCount="90" Body="&lt;p&gt;I don't know if this is the best place, but it seems the best out of the exchanges. How do you attach a plastic (or metal) gear to the little pole/nub that sticks out of a dc hobby motor? I have come up with 3 ideas: gluing, it doesn't seem like it would hold well; soldering, maybe but what about plastic gears; and making the hole on the gear slightly smaller so there is enough friction to hold it well, the most likely solution. Has anyone tried these or any other?&lt;/p&gt;&#xA;" OwnerUserId="2873" LastActivityDate="2011-04-03T13:10:12.987" Title="Attach a gear to dc motor pole" Tags="&lt;soldering&gt;&lt;dc-motor&gt;&lt;glue&gt;" AnswerCount="2" />
  <row Id="12460" PostTypeId="2" ParentId="12457" CreationDate="2011-04-03T00:05:45.763" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.allelectronics.com/make-a-store/item/CB-389/12-CABLE-3.5-MM-STEREO-PLUGS-BOTH-ENDS//1.html&quot; rel=&quot;nofollow&quot;&gt;http://www.allelectronics.com/make-a-store/item/CB-389/12-CABLE-3.5-MM-STEREO-PLUGS-BOTH-ENDS//1.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cut it in half: $2 for two cables.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-03T00:05:45.763" CommentCount="2" />
  <row Id="12461" PostTypeId="2" ParentId="12457" CreationDate="2011-04-03T00:10:21.680" Score="0" ViewCount="" Body="&lt;p&gt;Acquire something that uses the connector, and cut off the connector with cable. There are several options available. Good things to try include:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Headphones (they don't need to work)&lt;/li&gt;&#xA;&lt;li&gt;A Male-Male extension cable (cut it in half, you get two)&lt;/li&gt;&#xA;&lt;li&gt;Computer speakers&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that you can go dumpster diving for dead headphones, etc... and you don't care if they work - just cut off the cable.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-04-03T00:10:21.680" CommentCount="2" />
  <row Id="12462" PostTypeId="1" AcceptedAnswerId="12469" CreationDate="2011-04-03T00:36:28.323" Score="1" ViewCount="156" Body="&lt;p&gt;I want to design a simple LED audio spectrum analyzer kinda like &lt;a href=&quot;http://www.youtube.com/watch?v=LIOUXr9v2RI&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which method would be less expensive to do:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Use many filters for each frequency band, depending on how much bands and LEDS I want to use&lt;/li&gt;&#xA;&lt;li&gt;Use a microprocessor to do FFTs&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Clearly, doing FFTs will have a certain lag, but would that lag be significant enough to overcome the expensive of the many filters of the first bullet?  Which method would be most power efficient?  Or is this extremely dependent on the hardware?  Any input is much appreciated.  This is the first time I am taking on such a project, and I want to get as much feedback as possible.  Thank you!!&lt;/p&gt;&#xA;" OwnerUserId="3649" LastActivityDate="2011-04-03T15:08:21.287" Title="Designing a Audio Spectrum Analyzer" Tags="&lt;led&gt;&lt;spectrum-analyzer&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="2" />
  <row Id="12464" PostTypeId="1" AcceptedAnswerId="12470" CreationDate="2011-04-03T02:32:57.327" Score="4" ViewCount="166" Body="&lt;p&gt;Hello, I'm designing a very simplistic microprocessor as a project to help learn VHDL. So I'm needing something to increment the 8 bit program counter. I will need to increment it by two. Is there a better (either faster or less logic required for equal speed) design than using an 8 bit full adder? I'm also interested for the same thing for if you only needed to increment the PC by 1. &lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-04-04T01:07:16.907" Title="Is there a more optimized way of making an incrementer than a full adder?" Tags="&lt;design&gt;&lt;logic&gt;&lt;vhdl&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="12465" PostTypeId="2" ParentId="12464" CreationDate="2011-04-03T02:51:54.953" Score="3" ViewCount="" Body="&lt;p&gt;You don't actually need a full adder for increment by 1; using half adders where the first input is set to 1, and carry bits are daisy chained to the next bit would do. I'm not sure if there's a still better way to do it, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incrementing by two could be done by ignoring the first bit of a number, and using the same method above.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NOTE: not a VHDL expert, can't state if this could actually be faster, but should be less logic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Also, there's an expired patent for a simple binary incrementer that might be of interest: &lt;a href=&quot;http://www.freepatentsonline.com/3989940.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.freepatentsonline.com/3989940.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1507" LastEditorUserId="1507" LastEditorDisplayName="" LastEditDate="2011-04-03T02:57:04.763" LastActivityDate="2011-04-03T02:57:04.763" CommentCount="2" />
  <row Id="12466" PostTypeId="2" ParentId="12462" CreationDate="2011-04-03T02:57:25.137" Score="3" ViewCount="" Body="&lt;p&gt;Microchip supplies an FFT library with their C compiler for the dsPIC 16-bit digital signal controllers. The free version of the compiler is suitable, and the chips are quite inexpensive. The on-chip ADC could be used for this application, all that needs to be added are the drivers for the LED array. The Microchip Explorer 16 board has an audio spectrum analyser using the LCD display, it's supplied as part of the demo software. You should be able to use the low-cost &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en548414&quot; rel=&quot;nofollow&quot;&gt;Microstick&lt;/a&gt; for this; the dsPIC33FJ128 that can be used with it should have enough memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't have any DSP experience you are likely to find this a challenging project, however.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-03T03:31:14.420" LastActivityDate="2011-04-03T03:31:14.420" />
  <row Id="12468" PostTypeId="1" AcceptedAnswerId="12475" CreationDate="2011-04-03T04:43:23.553" Score="1" ViewCount="118" Body="&lt;p&gt;I'm currently working on a project that involves hooking up an arduino, a cellular shield, and an electromagnet (in this case, one of those old fashioned ringer boxes with a bell powered by electromagnets). I need the arduino to be able to power the ringer - presumably via a relay, and the power supply for the arduino and the ringer electromagnet will be the same 9v wall wart.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know the arduino and the cellular shield have their own regulators, but should I be concerned about effects the inductive load of the electromagnet might have when it's turned on and off? What precautions should I take besides the obvious reverse-biased diodes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Further, in order to use the ringer effectively, I need to be able to pass current through the electromagnet in both directions (each polarity moves the striker in a corresponding direction). Can anyone suggest a simple circuit that will achieve this with a minimum of external componentry?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Does this look like a reasonable interface circuit? It seems involved to use two relays to control a third electromagnet, but I can't think of another way to achieve what I need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ECVRV.png&quot; alt=&quot;Ringer interface circuit&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3707" LastEditorUserId="3707" LastEditorDisplayName="" LastEditDate="2011-04-03T06:10:58.237" LastActivityDate="2011-04-04T14:46:42.897" Title="Safely connecting an solenoid/electromagnet to a switch-mode supply" Tags="&lt;arduino&gt;&lt;power&gt;&lt;electromagnetism&gt;&lt;inductive&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12469" PostTypeId="2" ParentId="12462" CreationDate="2011-04-03T05:18:51.147" Score="4" ViewCount="" Body="&lt;p&gt;Well, most people are good at analog circuits, or MCU/DSP stuff.  Not many people are good enough at both.  So...  Do what you know better.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DSP approach will be more flexible, and would allow you to do cool things like: change the decay time, do both a peak and RMS reading at the same time, etc.  The response time will be slower than an analog approach, but still faster than what your eye could perceive.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As Ben Jackson pointed out, the LEDs will draw more current than the rest of the circuit.  Assuming that you're driving each LED with 20 mA, and you have 31 bands with one LED on for each band then you're pulling 620 mA just for the LED's.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for which approach would be less expensive, that all depends.  If this were a commercial product then the DSP based approach is by far the cheaper one.  But the economics of working in your basement changes the whole equation.  For example, if you need to spend $100-500 on DSP/MCU development tools then that's an issue.  So in the end, we can't say which is cheaper-- only you can.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So this brings me back to my original point:  do whatever you do better.  Do whatever one makes sense for you-- and just know that might not be what makes sense to others.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-03T05:18:51.147" CommentCount="1" />
  <row Id="12470" PostTypeId="2" ParentId="12464" CreationDate="2011-04-03T05:27:06.947" Score="9" ViewCount="" Body="&lt;p&gt;Hmmm,  this all depends on what exactly you are trying to learn.  A counter or adder in VHDL is super easy:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  signal count  :std_logic_vector (7 downto 0) := (others=&amp;gt;'0');&#xA;  . . .&#xA;  process (clk)&#xA;  begin&#xA;    if rising_edge(clk) then&#xA;      if count_enable='1' then&#xA;        count &amp;lt;= count + 1;  -- could be +2 also&#xA;      end if;&#xA;    end if;&#xA;  end process;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And that's it!  The VHDL compiler will normally synthesize a full-adder for this, and them optimize out everything that isn't needed-- ending up with some sort of half-adder.  The nice thing about doing it this way is that your code is readable and easily understood and the compiler deals with figuring out the best way to implement it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, if you are trying to learn about adders and counters and such then my little code snippet isn't going to help you much.  In that case you should implement a half-adder the manual and hard way.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-03T05:27:06.947" CommentCount="2" />
  <row Id="12471" PostTypeId="2" ParentId="12459" CreationDate="2011-04-03T09:14:38.840" Score="2" ViewCount="" Body="&lt;p&gt;a grub screw? - file one side of the motor shaft a little flat, drill and tap a hole in the hub of a metal gear, cut off the end of a bolt with the right thread, then cut a slot in one end so you can turn it with screwdriver&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-04-03T09:14:38.840" CommentCount="1" />
  <row Id="12472" PostTypeId="2" ParentId="12464" CreationDate="2011-04-03T11:01:50.963" Score="2" ViewCount="" Body="&lt;p&gt;Maybe you can use a &lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/bincount.html&quot; rel=&quot;nofollow&quot;&gt;binary counter built from JK flip-flops&lt;/a&gt;, one where you can load the bit value into each flip-flop, then just toggle the clock. Counting by 2 would mean loading everything but the least significant bit into the counter since that bit never changes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This probably won't be better than a half-adder implementation, but perhaps it is easier to understand :)&lt;/p&gt;&#xA;" OwnerUserId="2340" LastActivityDate="2011-04-03T11:01:50.963" />
  <row Id="12473" PostTypeId="2" ParentId="9480" CreationDate="2011-04-03T12:02:54.533" Score="3" ViewCount="" Body="&lt;p&gt;I've compiled a list of books, with brief descriptions of their coverage and intended readership, relating to spice simulation at&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.macspice.com/books&quot; rel=&quot;nofollow&quot;&gt;http://www.macspice.com/books&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;several of these may be useful to you. They include: &lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Elementary SPICE&lt;/h1&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;&lt;em&gt;The SPICE Book&lt;/em&gt;  By Andrei Vladimirescu.&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;h1&gt;Intermediate SPICE&lt;/h1&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;&lt;em&gt;Inside Spice&lt;/em&gt;  By Ron M. Kielkowski.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;The Designer's Guide to SPICE and Spectre&lt;/em&gt;  By Ken Kundert.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;High Speed A/D Converters - Understanding Data Converters Through SPICE&lt;/em&gt; By Alfi Moscovici.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;SPICE Circuit Handbook&lt;/em&gt; By Steven M. Sandler.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;Circuit Simulation with SPICE OPUS&lt;/em&gt; By Tadej Tuma and Árpád Bürmen.&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;h1&gt;Advanced Spice&lt;/h1&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;&lt;em&gt;Switch-Mode Power Supplies - Spice Simulations and Practical Designs&lt;/em&gt; By Christophe P. Basso.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;Switch-Mode Power Supply SPICE Cookbook&lt;/em&gt; By Christopher Basso.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;VLSI Circuit Simulation and Optimization&lt;/em&gt; By V. Litovski and M. Zwolinski.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;Semiconductor Modeling&lt;/em&gt; By Roy G. Leventhal, Lynne Green, et al.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;Node List Tolerance Analysis&lt;/em&gt; By Robert R. Boyd.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;MOSFET Modelling with SPICE&lt;/em&gt; By Daniel P. Foty.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;Transistor Level Modeling for Analog/RF IC Design&lt;/em&gt; By Wladyslaw Grabinski et al. &lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;SPICE: Practical Device Modeling&lt;/em&gt; By Ron M. Kielkowski.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;Mosfet Models for Spice Simulation, Including BSIM3v3 and BSIM4&lt;/em&gt; By William Liu.&lt;/li&gt;&#xA;  &lt;li&gt;&lt;em&gt;Semiconductor Device Modeling with SPICE&lt;/em&gt; By Giuseppe Massobrio and Paolo Antognetti.&lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Descriptive reviews for many of these books are available at the linked site, as well as a number of uncategorized/unreviewed books.&lt;/p&gt;&#xA;" OwnerUserId="3708" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-09T20:27:21.520" LastActivityDate="2011-05-09T20:27:21.520" CommentCount="5" />
  <row Id="12474" PostTypeId="1" AcceptedAnswerId="12951" CreationDate="2011-04-03T12:03:12.893" Score="2" ViewCount="99" Body="&lt;p&gt;I am designing a portable device meant to be connected to multiple computers and able to recognize them. I am thinking of a qrcode, different for every computer and displayed on their screen, that my device can detect.&#xA;What do I need for such an application? can a cheap camera (less than VGA) do the job? Do you know any IC that can do the job without writing a proper algorithm on my MCU (XMEGA).&lt;/p&gt;&#xA;" OwnerUserId="2285" LastActivityDate="2011-04-12T19:35:28.253" Title="QRCode electronics" Tags="&lt;camera&gt;&lt;detection&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="12475" PostTypeId="2" ParentId="12468" CreationDate="2011-04-03T12:08:54.023" Score="2" ViewCount="" Body="&lt;p&gt;I would consider using four MOSFETs in an H-bridge configuration. Connect the top of the bridge to the 9V supply, the bottom to return, and drive the diagonally-opposite MOSFETs with PWM to alternate the current flow through the ringer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The body diodes of the MOSFETs will clamp any kickback, so ensure that you choose robust-enough parts for the task. Trying to use discrete diodes is tricky when MOSFET body-diodes are in parallel with them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will need to generate high-side drive for the upper bridge FETs, perhaps with another wall-wart supply having it's return referenced to the 9V high side. (You need to bring the top MOSFETs several volts above +9 in order for them to turn on.)&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-04T14:46:42.897" LastActivityDate="2011-04-04T14:46:42.897" CommentCount="6" />
  <row Id="12476" PostTypeId="2" ParentId="12459" CreationDate="2011-04-03T13:10:12.987" Score="2" ViewCount="" Body="&lt;p&gt;With really small hobby motors, the usual scheme is to go for an 'interference fit', which is basically the 3rd option you mentioned. Even when the shaft is completely round and smooth, this works b/c the power and torques are so low. You will find this done in inexpensive toys, for example.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-03T13:10:12.987" />
  <row Id="12477" PostTypeId="1" CreationDate="2011-04-03T14:15:13.217" Score="1" ViewCount="164" Body="&lt;p&gt;This is what I know about NPN BJTs (Bipolar Junction Transistors):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The Base-Emitter current is amplified HFE times at Collector-Emitter, so that &lt;code&gt;Ice = Ibe * HFE&lt;/code&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;code&gt;Vbe&lt;/code&gt; is the voltage between Base-Emitter, and, like any diode, is usually around 0,65V. I don't remember about &lt;code&gt;Vec&lt;/code&gt;, though.&lt;/li&gt;&#xA;&lt;li&gt;If &lt;code&gt;Vbe&lt;/code&gt; is lower than the minimum threshold, then the transistor is open and no current passes through any of its contacts. (okay, maybe a few µA of leak current, but that's not relevant)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;But I still have some questions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;How the transistor works when it is &lt;em&gt;saturated&lt;/em&gt;?&lt;/li&gt;&#xA;&lt;li&gt;Is it possible to have the transistor in open state, under some condition other than having &lt;code&gt;Vbe&lt;/code&gt; lower than the threshold?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In addition, feel free to point (in answers) any mistakes I made in this question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Related question:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/5336/i-dont-care-how-a-transistor-works-how-do-i-get-one-to-work&quot;&gt;I don't care how a transistor works, how do I get one to work?&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3411" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-03T15:19:43.543" LastActivityDate="2011-04-04T18:41:25.797" Title="How do BJT transistors work in a saturated state?" Tags="&lt;transistor&gt;&lt;bjt&gt;&lt;physics&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="12478" PostTypeId="2" ParentId="12477" CreationDate="2011-04-03T14:27:10.923" Score="2" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;When it's saturated, the collector current is not HFE times the base current anymore. It's less, how much, it depends on the rest of the circuit (I'm talking about the simplest model you can think of). In saturation, the VCE voltage can be considered more or less constant and you can call it VCEsat, let's say around 0.2V.&#xA;TYour BJT is saturated when both its BE and BC junctions are active. That limits the Ic current to less than Ib*HFE and pins the VCE voltage drop to VCEsat.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Why do you care of having your BJT in open state if there's no current going thru it? it's like having your tap open with no water in the pipe :D&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2285" LastActivityDate="2011-04-03T14:27:10.923" CommentCount="2" />
  <row Id="12479" PostTypeId="2" ParentId="12477" CreationDate="2011-04-03T14:32:01.570" Score="2" ViewCount="" Body="&lt;p&gt;Saturation simply means that an increase in base current results in no (or very little) increase in collector current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Saturation occurs when both the B-E and C-B junctions are forward biased, it's the low-resistance &quot;On&quot; state of the device. The properties of the transistor in all modes, including saturation, can be predicted from the Ebers-Moll model.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-04T18:41:25.797" LastActivityDate="2011-04-04T18:41:25.797" CommentCount="1" />
  <row Id="12480" PostTypeId="1" CreationDate="2011-04-03T14:41:45.007" Score="3" ViewCount="126" Body="&lt;p&gt;Suppose that I know &lt;a href=&quot;http://electronics.stackexchange.com/questions/12477/how-bjt-transistors-work-in-saturated-state&quot;&gt;how a NPN transistor works&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How different is a PNP transistor? What are the differences between a PNP and a NPN?&lt;/p&gt;&#xA;" OwnerUserId="3411" LastActivityDate="2011-04-03T15:27:14.773" Title="What's the difference between NPN and PNP transistors?" Tags="&lt;transistor&gt;&lt;bjt&gt;&lt;pnp&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="12481" PostTypeId="2" ParentId="12462" CreationDate="2011-04-03T15:08:21.287" Score="3" ViewCount="" Body="&lt;p&gt;Since FFT is linear in frequency and you most probably want a logarithmic display you may also check the &lt;a href=&quot;http://en.wikipedia.org/wiki/Goertzel_algorithm&quot; rel=&quot;nofollow&quot;&gt;Goertzel filter algorithm&lt;/a&gt;. It may be faster if you only need the values of several frequency bins.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-03T15:08:21.287" CommentCount="2" />
  <row Id="12483" PostTypeId="2" ParentId="12480" CreationDate="2011-04-03T15:27:14.773" Score="4" ViewCount="" Body="&lt;p&gt;They work the same but all voltages and currents are reversed. You connect the emitter to the higher potential, source current from the base and the main current flows into the emitter and through the collector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$V_\rm{BE}$ will be $-0.7\,\rm{V}$ but it's magnitude should be the same in both PNP and NPN if you use complementary parts.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-03T15:27:14.773" />
  <row Id="12484" PostTypeId="1" AcceptedAnswerId="12488" CreationDate="2011-04-03T15:31:10.827" Score="1" ViewCount="120" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im trying to implement a simple first order IIR filter on a MCU (PIC24FJ32GA002), without success until now.&#xA;The filter is a DC tracking filter (low pass filter) whose purpose is to track DC component of a 1.5Hz signal. The difference equation was taken from a TI application note:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;y(n)=K*x(n)+y(n-1)*(1-K)&lt;br&gt;&#xA;with K = 1/2^8&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I made a MATLAB script to test it and it works well in the simulation.&#xA;Code used:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;K=1/2^8&#xA;b = K&#xA;a = [1 -(1-K)]&#xA;&#xA;Fs=200; // sampling frequency&#xA;Ts=1/Fs;&#xA;Nx=5000; // number of samples&#xA;nT=Ts*(0:Nx-1);&#xA;fin=1.5; // signal frequency&#xA;&#xA;randn('state',sum(100*clock));&#xA;noise=randn(1,Nx);&#xA;noise=noise-mean(noise);&#xA;&#xA;xin=200+9*(cos(2*pi*fin*nT));&#xA;xin=xin+noise;&#xA;&#xA;out = filter(b,a,xin);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kDOgG.png&quot; alt=&quot;Simulation&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/NykUn.png&quot; alt=&quot;Frequence response&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However I can't implement it on a PIC24F microcontroller. i'm representing the coefficients in Q15 (1.15) format, storing them in short variables and using a long one for multiplications. Here it is the code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;short xn;&#xA;short y;&#xA;short b0 = 128, a1 = 32640; // Q15&#xA;long aux1, aux2;&#xA;&#xA;// (...)&#xA;&#xA;while(1){&#xA;&#xA;    xn = readADC(adc_ch);&#xA;&#xA;    aux1 = ((long)b0*xn) &amp;lt;&amp;lt; 1;&#xA;    aux2 = ((long)a1*y) &amp;lt;&amp;lt; 1;&#xA;    y = ((aux1 + aux2) &amp;gt;&amp;gt; 16);&#xA;&#xA;    delay_ms(5);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Long cast is used to extend the signal so the multiplying operation is done correctly. After each multiplication I shift left one bit to remove the extended signal bit. When summing I shift right 16 bits to get y in Q15 format.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im debugging the MCU with Pickit2 and &quot;View-&gt;Watch&quot; window (MPLAB IDE 8.53) and testing the filter with a DC signal (I change the DC signal with a potenciometer to test different values). The ADC has 10bit resolution and the MCU is supplied with 3.3V.&#xA;Some results:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1V --&gt; xn = 312 (correct), yn = 226 (incorrect)&lt;br&gt;&#xA;1.5V --&gt; xn = 470 (correct), yn = 228 (completely wrong)&lt;br&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What am I doing wrong?&#xA;Any suggestions on how to implement this IIR filter on a 16bit MCU?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many thanks in advance :)&lt;/p&gt;&#xA;" OwnerUserId="1074" LastEditorUserId="1074" LastEditorDisplayName="" LastEditDate="2011-04-03T15:53:26.387" LastActivityDate="2011-04-29T01:33:00.857" Title="IIR filter on a 16bit MCU (PIC24F)" Tags="&lt;filter&gt;&lt;digital&gt;" AnswerCount="5" />
  <row Id="12485" PostTypeId="2" ParentId="12474" CreationDate="2011-04-03T15:31:12.430" Score="5" ViewCount="" Body="&lt;p&gt;If you want to connect them to the computers (as you wrote) then maybe a software-based detection method would be easier?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use Ethernet (no very expensive anymore) you can get the MAC address which is globally unique (a USB solution would require some drivers since there are no unique computer identifiers used in the enumeration).&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-03T15:31:12.430" CommentCount="5" />
  <row Id="12486" PostTypeId="2" ParentId="12484" CreationDate="2011-04-03T16:10:12.380" Score="1" ViewCount="" Body="&lt;p&gt;Using a dsPIC instead of the PIC24 might make things much easier (they are pin-compatible). The dsPIC compiler comes with a DSP library that includes IIR filters and the hardware supports fixed-point arithmetic directly.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-03T16:29:54.383" LastActivityDate="2011-04-03T16:29:54.383" CommentCount="2" />
  <row Id="12487" PostTypeId="1" AcceptedAnswerId="12489" CreationDate="2011-04-03T17:30:06.797" Score="2" ViewCount="122" Body="&lt;p&gt;I already have a transformer 2x 6V outputs. I was wondering can I these in series to produce 12V? Similar to how you would wire two 1.5v batteries to produce 3V.&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-04-04T12:48:47.807" Title="Wiring transformer output in series to get twice the voltage possible?" Tags="&lt;transformer&gt;" AnswerCount="1" />
  <row Id="12488" PostTypeId="2" ParentId="12484" CreationDate="2011-04-03T17:32:25.883" Score="5" ViewCount="" Body="&lt;p&gt;I didn't dive super far into your filter design, but just looking at the source code brings a couple of things up.  For example, these lines:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;aux1 = ((long)b0*xn) &amp;lt;&amp;lt; 1;&#xA;aux2 = ((long)a1*y) &amp;lt;&amp;lt; 1;&#xA;y = ((aux1 + aux2) &amp;gt;&amp;gt; 16);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The first issue I see is the ((long)b0*xn).  I have ran across compilers that would compile this incorrectly as ((long)(b0*xn)), which is entirely wrong.  Just to be on the safe side, I would write this as (((long)b0)*((long)xn)).  To be sure, this is paranoid programming, but...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, when you do the &quot;&amp;lt;&amp;lt;1&quot;, this is &lt;em&gt;NOT&lt;/em&gt; the same as &quot;*2&quot;.  For most things, it's close, but not for DSP.  It has to do with how the MCU/DSP handles overflow conditions and sign extensions, etc.  But even if it did work as a *2, you are removing one bit of resolution that you don't need to remove.  If you really have to do a *2, then do a *2 and let the compiler figure out if it could substitute a &amp;lt;&amp;lt;1 instead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &gt;&gt;16 is also problematic.  Off the top of my head, I don't know if it's going to do a logical or arithmetic shift.  You want an arithmetic shift.  Arithmetic shifts will handle the sign bit correctly where a logical shift will insert zeros for the new bits.  Besides, you can save bits of resolution by getting rid of the &amp;lt;&amp;lt;1 and changing the &gt;&gt;16 to &gt;&gt;15.  Well, and changing all of these to normal multiplies and divides.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So here's the code I would use:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;aux1 = ((long)b0) * ((long)xn);&#xA;aux2 = ((long)a1) * ((long)y);&#xA;y = (short)((aux1+aux2) / 32768);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Now, I don't claim that this will solve your problem.  It may or may not, but it does improve your code. &lt;/p&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="3624" LastEditorDisplayName="" LastEditDate="2011-04-03T18:37:37.570" LastActivityDate="2011-04-03T18:37:37.570" CommentCount="1" />
  <row Id="12489" PostTypeId="2" ParentId="12487" CreationDate="2011-04-03T17:40:10.950" Score="5" ViewCount="" Body="&lt;p&gt;Yes, transformers with this configuration are designed to be used in this way if required. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;You can wire the secondary coils in series to get twice the voltage.&lt;/li&gt;&#xA;&lt;li&gt;You can wire the secondary coils in parallel to get twice the current.&lt;/li&gt;&#xA;&lt;li&gt;You can use each secondary independently to get two power supplies.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2426" LastEditorUserId="2426" LastEditorDisplayName="" LastEditDate="2011-04-04T12:48:47.807" LastActivityDate="2011-04-04T12:48:47.807" CommentCount="6" />
  <row Id="12490" PostTypeId="1" CreationDate="2011-04-03T17:41:14.910" Score="4" ViewCount="100" Body="&lt;p&gt;I'm trying to get a circuit to work (linistepper driver) and I suspect I may have fried the drive transistors (tip122's in this case).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there common behaviors of broken transistors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;does c-&gt;e short? b-&gt;e? open? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I measure with my multimeter to get any meaningful information?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;is it possible for devices to half break with degraded performance?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for generalities. I also have an old stereo which has a broken channel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not particularly good at desoldering, so it'd be good to have some confidence that I'm looking at the right component.&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2011-04-03T19:16:24.963" Title="how does a transistor behave when it's broken?" Tags="&lt;transistor&gt;&lt;repair&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="12491" PostTypeId="1" CreationDate="2011-04-03T17:46:50.723" Score="0" ViewCount="113" Body="&lt;p&gt;As I've dorked around in electronics, I've found that the cheap (often chinese) suppliers are a great resource. Resisters, headers, terminal blocks, chip sockets, pic programmer...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an example, I bought some desolder braid. Doesn't work for me. Am I not doing it right? do I need flux? If I buy flux (which I probably should; I'm thinking about trying SMT) is that another good ebay item?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What should I avoid? For which items should I get the good stuff.&lt;/p&gt;&#xA;" OwnerUserId="550" LastActivityDate="2011-04-03T19:29:13.287" ClosedDate="2011-04-04T02:56:19.783" Title="What items should I NOT by from cheap ebay suppliers?" Tags="&lt;parts&gt;&lt;supplier&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="12492" PostTypeId="2" ParentId="12491" CreationDate="2011-04-03T18:24:54.427" Score="3" ViewCount="" Body="&lt;p&gt;Avoid:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Expensive power transistors.  These can easily be fakes.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Giant, expensive electrolytic caps.  Again, easily faked.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;ZIF sockets.  There were a bunch of fake ones floating around&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Consumer electronics that you will use regularly.  The noname stuff is generally of shockingly poor quality.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;On the other hand, anything with a brand name is likely to be a fake.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I've noticed that good desoldering braid works much better than the cheap stuff; it's all in the flux used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several different kinds of flux.  Basic rosin flux from an ebay vendor should be fine, as it is not a high-tech product.   Applying your own flux to a desolder braid is a good trick.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-04-03T19:29:13.287" LastActivityDate="2011-04-03T19:29:13.287" CommentCount="1" />
  <row Id="12493" PostTypeId="2" ParentId="12490" CreationDate="2011-04-03T18:30:35.983" Score="5" ViewCount="" Body="&lt;p&gt;In my experience, power transistors fail shorted.  All the pins will measure low resistance to each other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TIP122 is in TO-220 case.  All three leads are in a row, at least in the linistepper.  The way to desolder this part is to add solder until all three joints are bridged in a big solder blob.  Melt the blob, then pull the part out.  Then clean the solder blob up with a solder sucker, then braid.  Do not attempt to desolder one pin at a time.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-04-03T19:16:24.963" LastActivityDate="2011-04-03T19:16:24.963" CommentCount="2" />
  <row Id="12494" PostTypeId="2" ParentId="12484" CreationDate="2011-04-03T19:25:35.707" Score="3" ViewCount="" Body="&lt;p&gt;I suggest you replace &quot;short&quot; with &quot;int16_t&quot; and &quot;long&quot; with &quot;int32_t&quot;.  Save &quot;short&quot;, &quot;int&quot;, &quot;long&quot; etc. for places where the size doesn't really matter, such as loop indexes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then the algorithm will work the same if you compile on your desktop computer.  It will be a lot easier to debug on the desktop.  When it is working satisfactorily on the desktop, then move it to the microprocessor.  To make this easier, factor the tricky routine into its own file.  You will probably want to write a simple main() function for the desktop that exercises the routine and exits zero (for success) or nonzero (for fail).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then integrate building and running the test into the build system for your project.  Any development system worth considering will let you do this, but you might have to read the manual.  I like &lt;a href=&quot;http://www.gnu.org/software/make/&quot; rel=&quot;nofollow&quot;&gt;GNU Make&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-04-03T19:33:06.063" LastActivityDate="2011-04-03T19:33:06.063" />
  <row Id="12495" PostTypeId="1" AcceptedAnswerId="12497" CreationDate="2011-04-03T21:28:03.583" Score="2" ViewCount="143" Body="&lt;p&gt;Hello, I'm needing to create a 4 bit, 16 input multiplexer. I know I could describe this as a long list of &lt;code&gt;S =&amp;gt; when &quot;0000&quot;&lt;/code&gt; etc.. but I think that's not very clean, and I'd like to opt for a generic n-bit multiplexer so I can reuse it later for more inputs or whatever. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would you do this?&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-04-03T23:09:07.670" Title="How to create an n-bit multiplexer?" Tags="&lt;vhdl&gt;&lt;multiplexing&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="12496" PostTypeId="2" ParentId="12484" CreationDate="2011-04-03T21:35:56.900" Score="0" ViewCount="" Body="&lt;p&gt;It looks like you aren't ever giving y a value before you use it. You use y in the computation for aux2, which is correct because it is the filtered previous sample, but you have no idea what it is going to start as in this situation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would suggest you take an ADC sample before you enter your while(1) loop. Assign that value to y, delay 5 ms, then enter your loop. This will allow your filter to act normally.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also recommend that you go ahead and change your shorts to be longer variables. Unless you are running low on space, you will have much simpler code if you aren't having to type cast in every loop.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-03T21:35:56.900" />
  <row Id="12497" PostTypeId="2" ParentId="12495" CreationDate="2011-04-03T21:37:09.747" Score="3" ViewCount="" Body="&lt;p&gt;It's like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;use ieee.numeric_std.all;&#xA;...&#xA;signal din :std_logic_vector (15 downto 0);  -- must be &quot;downto 0&quot;&#xA;signal sel :std_logic_vector (3 downto 0);&#xA;...&#xA;dout &amp;lt;= din(conv_integer(sel));&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Hope that helps!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Addition:&#xA;If you'd need a multiple bit wide mux then...&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;type data_bus_array is array(7 downto 0) of std_logic_vector (31 downto 0);&#xA;signal din :data_bus_array;&#xA;signal dout :std_logic_vector (31 downto 0);&#xA;signal sel :std_logic_vector (3 downto 0);&#xA;...&#xA;dout &amp;lt;= din(conv_integer(sel));&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This is where VHDL gets a little bit wordy, since sometimes it's not &quot;compact&quot; to fill in that data bus array just to do a simple mux.  But, there you have it...&lt;/p&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="3624" LastEditorDisplayName="" LastEditDate="2011-04-03T23:09:07.670" LastActivityDate="2011-04-03T23:09:07.670" CommentCount="4" />
  <row Id="12498" PostTypeId="1" CreationDate="2011-04-03T21:54:38.957" Score="5" ViewCount="349" Body="&lt;p&gt;Hello,&#xA;I have 2 questions.  One is simple, the other may be not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;1.&lt;/strong&gt; What's the official name for the standard headphone jack?  It's universal for all brands of phones, so it must have a name (when you want to go shopping for components).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;2.&lt;/strong&gt; Is it using some sort of a communication protocol?  I know for a fact that it's not only for headphones.  There is a device for scanning credit cards that plugs into the same jack.  I believe Nexus also has a TV-out support from the same jack.  Basically, can it be used for other I/O applications?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you&lt;/p&gt;&#xA;" OwnerUserId="3710" LastActivityDate="2011-04-04T14:45:08.830" Title="What protocol does a headphone jack use?" Tags="&lt;android&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="12499" PostTypeId="2" ParentId="12498" CreationDate="2011-04-03T22:11:48.603" Score="3" ViewCount="" Body="&lt;p&gt;Phones tend to have 2.5mm TRRS (tip-ring-ring-sleeve) jacks. A normal stereo jack with just 3 connections is called a TRS jack; the fourth connection is of course used for the microphone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a &lt;a href=&quot;http://www.sparkfun.com/products/10331&quot; rel=&quot;nofollow&quot;&gt;device&lt;/a&gt; that lets you use the headphone jack as a modem. It is just a frequency shift keying modem that you'd attach to a UART. The gadgets probably don't use any standard communication protocol; it's all done by recording and playing back audio with the sound device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TV-out over a headphone jack has nothing to do with the sound card. It is just NTSC or PAL composite video.&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-03T23:02:56.127" LastActivityDate="2011-04-03T23:02:56.127" CommentCount="1" />
  <row Id="12500" PostTypeId="2" ParentId="12498" CreationDate="2011-04-03T22:37:18.860" Score="2" ViewCount="" Body="&lt;p&gt;Headphones outputs are just pure analog outputs. The fact that some other kinds of ports happen to use the same connector is just coincidental.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-03T22:37:18.860" />
  <row Id="12501" PostTypeId="1" AcceptedAnswerId="12505" CreationDate="2011-04-03T22:57:57.147" Score="1" ViewCount="85" Body="&lt;p&gt;I've been reading the document &lt;a href=&quot;http://www.xilinx.com/support/documentation/application_notes/xapp452.pdf&quot; rel=&quot;nofollow&quot;&gt;Spartan-3 FPGA Family Advanced Configuration Architecture&lt;/a&gt; and I'm having trouble figuring out what the address of the first LUT is. Can anyone point me in the right direction?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I'm trying to setup a Spartan 3E. In order to configure the first LUT as a NOT gate and connect it to outside world, I need to know what value to send to the configuration so that LUT becomes a not gate connected to the pins on the IC that I want. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am learning about FPGAs and I need to know how they work from the transistor up.&lt;/p&gt;&#xA;" OwnerUserId="3045" LastEditorUserId="3045" LastEditorDisplayName="" LastEditDate="2011-04-04T00:00:52.357" LastActivityDate="2011-04-04T06:35:23.790" Title="What is the Address of the first LUT in a Spartan 3E?" Tags="&lt;fpga&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="12502" PostTypeId="2" ParentId="11844" CreationDate="2011-04-03T23:21:36.523" Score="2" ViewCount="" Body="&lt;p&gt;I think Magic Sinewaves is essentially the sames as &quot;selective harmonic elimination&quot;, a well known method in Power Electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://web.eecs.utk.edu/~tolbert/publications/trans_pe_mar_2004_complete.pdf&quot; rel=&quot;nofollow&quot;&gt;This paper&lt;/a&gt; has a description of the theory and some experimental results.&lt;/p&gt;&#xA;" OwnerUserId="2544" LastActivityDate="2011-04-03T23:21:36.523" CommentCount="3" />
  <row Id="12503" PostTypeId="1" AcceptedAnswerId="12513" CreationDate="2011-04-04T00:04:03.600" Score="7" ViewCount="137" Body="&lt;p&gt;I'm creating a simple effect for musical instruments and I'm wondering how I will package it when it'll be ready. I mean, I can create some kind of stomb box with my own hands but if I'm ever going to sell it I need to find a way to create some small batch of them. The problem is it's hard (impossible?) to find some manifacturer who cares of building, say, 100 boxes. On the other hand I cannot order thousends of them because I'm not sure I'll sell the out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So has anyone faced/solved this problem in the past?&#xA;Thank you very much ;)&lt;/p&gt;&#xA;" OwnerUserId="2316" LastActivityDate="2011-04-05T00:12:31.350" Title="Where to order small batches (say, 100 units) of custom boxes for your projects" Tags="&lt;pcb&gt;&lt;electronics&gt;&lt;hardware&gt;" AnswerCount="6" CommentCount="3" FavoriteCount="3" />
  <row Id="12504" PostTypeId="2" ParentId="12498" CreationDate="2011-04-04T00:18:18.223" Score="14" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Background on the Jack&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;It's universal for all brands of phones, so it must have a name&quot; it actually isn't. There have been many phones over the years that have used various connectors. The &quot;standard&quot; technology is not a formal standard like what you consider things like any of the IEEE standards. The industry has just evolved over time to tend to use what we all know as a audio jack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The typical audio only jack has 3 rings, usually call Tip, Ring, Sleeve (TRS). These typically map to Left, Right, and Ground. Phone manufactures wanted to make this jack work with existing headphone so they used a connector with 4 rings, called Tip, Ring, Ring, Sleeve (TRRS). These map to Left, Right, and ground just like the 3 ring, but the final connector maps to a microphone. This makes it so that if you plug an audio only cable into it, the microphone input gets connected to ground so nothing is hurt. It also means that if a headset with microphone is connected to an audio only device, the microphone is connected to ground, also hurting nothing. There are similar connectors in 2.5mm (used on some phones to save space), 3.5mm (for phones, mp3 player, etc) and .25&quot; (for larger headphones, guitars, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Data on the Jack&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as what &quot;data&quot; travels over this, it is purely analog. Some people have reused these cables to pass serial data over them, but they are very application specific. For the case of devices using the jack for other purposes, they can do whatever they want as long as the signal on the line is band-limited, meaning that there isn't any high frequencies being used. The reason for this is that there are filter on the input that block frequencies too high. This frequency will change depending on the device itself but is usually around 12 KHz or so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The method that people send data over this are usually all pretty similar to how phone line modems work. The general concept is that there is a mapping between the frequencies being transmitted and serial data. If you wanted to reverse engineer a system, you would need to record the line and look at what frequencies there are. The hard part is to figure out what the resulting data is supposed to mean.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;2 Way Communication&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also like to note that 2 way communication is possibly in these systems. The microphone line is used to send information to the phone and the audio out lines are used to send information back to your external device. If you are trying to reverse engineer a device, you will want to look at Mic, Left, and Right to see if there appears to be any bi-directional communication.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Reverse Engineering&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mentioned that reverse engineering would be the difficult part. Here is the method I would go about doing this:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Check to see what lines have data on them. You can use a computers audio jack to capture your data with. This will probably be the easiest method to look at the data.&lt;/li&gt;&#xA;&lt;li&gt;Determine the symbol rate. Basically when you look at your captured data you should see very specific points that the frequencies change. &lt;/li&gt;&#xA;&lt;li&gt;Look to see if there are discreet frequencies being used, and how many are used at the same time. For example, there could be 6 KHz, 8 KHz, 10 KHz, and 12 KHz. These could map to 4 bits per symbol. So if you see 6 and 8 at once it may mean 1100 (or maybe 0011). Look a the next symbol and it could be 6, 8, and 12 and could mean 1101. Of course if it is a custom protocol, it could really mean anything they want it to. But this will at least give you a start.&lt;/li&gt;&#xA;&lt;li&gt;Assuming you collected the data running a card that you know the data for, you can look for patterns. &lt;a href=&quot;http://en.wikipedia.org/wiki/Magnetic_stripe_card&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is the information included on the cards. You could do things like if your card has a short sequence that repeats look to see if your symbols have a similar repeating pattern. Once you get some of these patterns worked out, you should be able to do a 1 to 1 comparison for the rest of the numbers, You should eventually be able to get a pretty good idea of what is being sent.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;There may be some data sent that has nothing to do with your card and you may never know what it means, but as long as you know the position of the data you care about, that is all that is needed. You just have to hope that the hardware manufacture didn't put any &quot;anti-hacking&quot; or &quot;anti-reuse&quot; measures in place. Potentially the designer could have used bi-directional communication to provide encryption. It is also possible for them to just mix all of the data up so it is hard to figure out what is what. I would say it is unlikely that they have done any of this though.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-04-04T14:45:08.830" LastActivityDate="2011-04-04T14:45:08.830" CommentCount="2" />
  <row Id="12505" PostTypeId="2" ParentId="12501" CreationDate="2011-04-04T00:31:02.060" Score="3" ViewCount="" Body="&lt;p&gt;Learning how FPGA's work from the transistor up is very ambitious.  There's a lot of stuff inside an FPGA, and for the most part you never have to understand it to the level of detail that you are seeking.  In fact, it's probably better if you ignore that stuff at first and learn some practical FPGA stuff instead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason why you don't need to know those fine details is because the FPGA compiler will do it for you.  Using VHDL or Verilog, you tell the FPGA compiler what you want, and it figures out how to do it for you.  You don't need to know what gets programmed into the LUT's, where that LUT is located, or how to route the signals to/from the LUT.  This also helps when you move from one FPGA to another.  A Spartan-6 has a different LUT architecture than the Spartan-3's, and you don't want to have to learn a completely new architecture for each chip you use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, as you get into it more you will learn more of the internal workings of the FPGA.  Not down to the transistor level, but you will learn about the different kinds of signal routing resources, RAMs, I/O Blocks, carry logic, etc.  Knowing about this kind of logic will help you make better use of the FPGA-- making your logic smaller and faster.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One really cool way to find out about the internals of a Xilinx FPGA is to write some VHDL/Verilog code and compile it.  Then using the Xilinx FPGA Editor to go in and examine what the compiler did, looking at signal routing, slice usage, LUTs, and Flip-flops.  This is most useful for me in understanding why my logic was bigger than I thought it should be.  I would guess that 95% of the time you don't have to understand the inner working of an FPGA in more detail than what FPGA Editor will give you.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-04T00:31:02.060" CommentCount="7" />
  <row Id="12506" PostTypeId="2" ParentId="12503" CreationDate="2011-04-04T01:02:32.357" Score="1" ViewCount="" Body="&lt;p&gt;I would find a local guy with laser cutter - this way you can quickly make cases out of wood or metal(harder to do, obviously). Personally, I love wooden cases, no production items can have them :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ordering 100 non-standard plastic cases on a factory is not possible, production preparation will eat your money for such a small series.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-04T01:02:32.357" CommentCount="2" />
  <row Id="12507" PostTypeId="2" ParentId="12503" CreationDate="2011-04-04T01:02:47.950" Score="3" ViewCount="" Body="&lt;p&gt;Some enclosures on Digikey have notices that the company will do custom drilling and cutouts on their stock enclosures (in sufficient quantities).  This is one such enclosure: notice the 'Customize your Enclosure' link: &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=SCR4B-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=SCR4B-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a link to a presentation on the custom capabilities of Bud Industries:  &lt;a href=&quot;http://dkc1.digikey.com/us/en/tod/BUD/ModifiedEnclosures_NoAudio/ModifiedEnclosures_NoAudio.html&quot; rel=&quot;nofollow&quot;&gt;http://dkc1.digikey.com/us/en/tod/BUD/ModifiedEnclosures_NoAudio/ModifiedEnclosures_NoAudio.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if you can find an enclosure on Digikey that gets close, some of the suppliers may be able to help you. &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-04T01:02:47.950" CommentCount="2" />
  <row Id="12508" PostTypeId="2" ParentId="12464" CreationDate="2011-04-04T01:07:16.907" Score="1" ViewCount="" Body="&lt;p&gt;What specifically you need is series of T-triggers + a bunch of AND gates. You should pass 'toggle' signal to bit n only if all previous bits were 1. This is much faster than full adder, does not require carry look ahead and eats way less transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS. Some time ago I was wondering exactly the same question ;-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-04T01:07:16.907" CommentCount="3" />
  <row Id="12509" PostTypeId="1" AcceptedAnswerId="12510" CreationDate="2011-04-04T02:02:54.217" Score="4" ViewCount="238" Body="&lt;p&gt;Hi, I've just calculated trace parameters so that it would have 50 Ohm impedance on PCB.&#xA;Then I've noticed, that its impedance does not change when I make line longer or shorter as long as I leave trace width &amp;amp; distance to ground plane intact. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is that correct and why is that? &lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-04T08:38:52.103" LastActivityDate="2011-04-04T08:38:52.103" Title="50-ohm trace impedance" Tags="&lt;impedance&gt;" AnswerCount="1" />
  <row Id="12510" PostTypeId="2" ParentId="12509" CreationDate="2011-04-04T02:43:43.493" Score="15" ViewCount="" Body="&lt;p&gt;That is correct. The 50 ohm impedance refers to the &quot;characteristic impedance&quot; of the &quot;transmission line&quot;. This comes from electromagnetic theory and is usually applicable to RF and high frequency applications. At DC your trace will still be very low impedance (resistance). If you were to take an ohmmeter to it you would probably measure maybe 1 ohm or 0.5 ohm, and that is only because the probe resistances would dominate over the actual trace resistance (which should be in maybe the tens of milliohms range).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Characteristic impedance has (mostly) to do with the capacitance and inductance per unit length of the transmission line. The capacitance and inductance are not that important at low frequencies, but as your signal frequency increases they will cause effects that can no longer be ignored. This is why you often will see coaxial cables advertised as 50 ohm or 75 ohm. This refers to the characteristic impedance (applicable to higher frequencies, like upper MHz range and GHz), not the DC resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the characteristic impedance depends on C and L per unit length, as long as you do not change the distance between trace and ground plane (affects capacitance) nor do you change the trace width (affects inductance) your characteristic impedance should not change, no matter how long the trace is (Note: this is a simplified explanation, but captures the basic idea).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that often the word &quot;characteristic&quot; is dropped from the term, and it's just called &quot;impedance&quot;. It sounds like this is the case in your layout program.&lt;/p&gt;&#xA;" OwnerUserId="3635" LastActivityDate="2011-04-04T02:43:43.493" CommentCount="3" />
  <row Id="12511" PostTypeId="2" ParentId="12503" CreationDate="2011-04-04T06:34:42.043" Score="4" ViewCount="" Body="&lt;p&gt;Looks like &lt;a href=&quot;http://pedalpartsplus.com/&quot; rel=&quot;nofollow&quot;&gt;Pedal Parts Plus&lt;/a&gt; has a variety of pre-drilled cases and will do custom drilling for you. This looks like your best bet, if you ask me.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2011-04-04T06:34:42.043" />
  <row Id="12512" PostTypeId="2" ParentId="12501" CreationDate="2011-04-04T06:35:23.790" Score="1" ViewCount="" Body="&lt;p&gt;To program FPGAs you need to use the tools provided by the manufacturer, in this case Xilinx. IIRC Free Webpack ISE tools support Spartan3Es.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You write your code in Verilog, VHDL, or use their schematic capture tool to generate the logic you want. Connect the top level of the logic to the desired input or output pin. Compile. You'll have a bitstream that you can program into the chip.&lt;/p&gt;&#xA;" OwnerUserId="3712" LastActivityDate="2011-04-04T06:35:23.790" />
  <row Id="12513" PostTypeId="2" ParentId="12503" CreationDate="2011-04-04T06:36:21.557" Score="3" ViewCount="" Body="&lt;p&gt;One option would be to use a service like &lt;a href=&quot;http://www.ponoko.com/&quot; rel=&quot;nofollow&quot;&gt;Ponoko&lt;/a&gt;, who do custom laser-cutting on a variety of materials. You can do the assembly and finishing yourself.&lt;/p&gt;&#xA;" OwnerUserId="3707" LastActivityDate="2011-04-04T06:36:21.557" CommentCount="2" />
  <row Id="12515" PostTypeId="1" AcceptedAnswerId="12518" CreationDate="2011-04-04T11:39:06.130" Score="4" ViewCount="388" Body="&lt;p&gt;The supply cable that came with my PSU has a 13A fuse fitted inside it's plug.  However on the side of the PSU it says it's cable of producing 30A of current at 5V. How is that possible when it only has 13A to play with?&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-04-05T05:46:59.317" Title="How can a PSU be capable of providing more current than it draws from the mains" Tags="&lt;power-supply&gt;" AnswerCount="4" />
  <row Id="12516" PostTypeId="2" ParentId="12515" CreationDate="2011-04-04T11:44:46.243" Score="-2" ViewCount="" Body="&lt;p&gt;It presumably has a transformer - 1 amp at 240 volts on the input equates to 240 amps at 1 volt on the output, ignoring losses.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-04T11:44:46.243" CommentCount="7" />
  <row Id="12517" PostTypeId="2" ParentId="12515" CreationDate="2011-04-04T11:48:47.073" Score="6" ViewCount="" Body="&lt;p&gt;Look at the power.  It can take 230 * 13 = 3kW from your outlet, but is only giving you 5 * 30 = 150w out.&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-04-04T11:48:47.073" />
  <row Id="12518" PostTypeId="2" ParentId="12515" CreationDate="2011-04-04T12:25:36.853" Score="10" ViewCount="" Body="&lt;p&gt;What power supplies do is a conversion of power, not current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means you take primary power ($P_{pri} = V_{pri} I_{pri}$) from the mains network and you get secondary power ($P_{sec} = V_{sec} I_{sec}$) at the output. The power at the output can never be greater than the power at the input:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$P_{pri} &amp;gt; P_{sec}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Substituting the above equations, we get:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$V_{pri} I_{pri} &amp;gt; V_{sec} I_{sec}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's solve for $I_{sec}$:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$I_{sec} &amp;lt; \frac{V_{pri}}{V_{sec}} I_{pri}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You see that the &quot;trick&quot; is hidden within the relationship of the input and output voltages. If the output voltage is lower than the input voltage, the output current may well be higher than the input current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the numbers you give (and assuming you live in the UK because this is where fuses are often found in mains plugs):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$I_{sec} &amp;lt; \frac{240V}{5V} 13A$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$I_{sec} &amp;lt; 624A$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is just meant to prove the point. The number is very (!) much theoretical and way beyond the real numbers, because (i) the fuse has a rating much higher than the RMS current used by your power supply, usually around a factor of 5...10, because it must not blow during inrush events at turn-on, (ii) the power supply's output current may be limited by other factors and (iii) the power supply has some losses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This relationship can also be explained using the waterfall model, where voltage equals height and current equals the size of the stream. On the input side, you can imagine having a very high waterfall with not that much water, on the output you have a big river with a lot of water but not much height that pushes the water towards the ocean.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-05T05:46:59.317" LastActivityDate="2011-04-05T05:46:59.317" />
  <row Id="12519" PostTypeId="2" ParentId="9645" CreationDate="2011-04-04T12:49:37.993" Score="1" ViewCount="" Body="&lt;p&gt;This is probably off-topic, because the easiest way to achieve this is to use the tools already provided by your graphics card. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mirror your display, adjust the resolution of your screen to that of the window, and pan the screen until the desired area is displayed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to be able to select an arbitrary window to be mirrored, you need to add this functionality to your window manager, which is impossible on Windows (but should be doable for most Linux window managers).  If you want to do this with an app you're developing (or an open-source terminal), just use a second display.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-04-04T12:49:37.993" />
  <row Id="12520" PostTypeId="2" ParentId="12432" CreationDate="2011-04-04T13:16:48.353" Score="3" ViewCount="" Body="&lt;p&gt;There is an alternative to installing and running the Xilinx tools yourself. &lt;a href=&quot;http://www.plunify.com&quot; rel=&quot;nofollow&quot;&gt;Plunify.com&lt;/a&gt; offers these tools &quot;in the cloud&quot;. It might be easier to operate the tools through the Plunify interface.&lt;/p&gt;&#xA;" OwnerUserId="3145" LastActivityDate="2011-04-04T13:16:48.353" CommentCount="1" />
  <row Id="12521" PostTypeId="2" ParentId="12515" CreationDate="2011-04-04T13:33:39.093" Score="6" ViewCount="" Body="&lt;p&gt;There are a couple answers posted that point out the limit between the input and output of a PSU is actually power, not current. This is true; you can't get more power out than you put in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But maybe you're still puzzled by the current. An amp is a large number of electrons per second. If you have only 13 amps coming into the box and 30 amps going out, it seems like you'd run out of electrons in the box pretty quick.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a diagram with 3 PSUs that might clear up what's actually happening.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Imaginary PSU-- what you might think was happening in a PSU. How can 13 A turn into 30 A?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;A PSU with a transformer, vastly simplified. There are two separate loops of current with no conductors connecting them.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;A switchmode PSU, also vastly simplified. The current flows in two overlapping loops. How exactly the electrons are persuaded to flow in this path involves a very fast switch and an inductor, but I've left those out to make the current paths clear.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tGozB.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-04-04T13:59:47.110" LastActivityDate="2011-04-04T13:59:47.110" CommentCount="3" />
  <row Id="12522" PostTypeId="1" CreationDate="2011-04-04T13:37:00.447" Score="0" ViewCount="53" Body="&lt;p&gt;I have an ISP which gives me a triple-play subscription. For telephony I have to plug in an 'old skool' analog phone. However, I am very much underwhelmed with most DECT sets and would like a VoIP solution, while still using my triple-play telephony.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know I need to set up an Asterisk server (or something equal to that) to provide VoIP. To connect to the outside world I would use a FXO card, I believe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I know that there is an Asterisk package for OpenWRT and I am wondering if it is possible to use a *DSL modem instead of a whole server.&lt;/p&gt;&#xA;" OwnerUserId="3718" LastActivityDate="2011-04-04T13:37:00.447" ClosedDate="2011-04-04T15:24:05.087" Title="Is it possible to use an *DSL modem as FXO?" Tags="&lt;hack&gt;&lt;modem&gt;" />
  <row Id="12523" PostTypeId="1" AcceptedAnswerId="12595" CreationDate="2011-04-04T14:52:54.733" Score="5" ViewCount="184" Body="&lt;p&gt;I'm just starting to mess with the MSP430 and have some simple apps working fine.  However, now I want to use it with an LCD and am trying to determine if I'm short on I/O.  For sure, I'll need to use the 4-bit interface, and I also need 3 outputs for E, RW, and RS.  On top of that, I need to talk to my computer over RS232, but &lt;strong&gt;not&lt;/strong&gt; via the built-in COM port-over-USB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been looking over the documentation and can't figure out which lines the onboard FET is using.  The situation I'm in is, I'd like to debug my application, but then need the FET.  If the FET uses the TX/RX lines, then I can't test my serial code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the questions I have are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What's the best documentation to look at to figure out the answer to my question?  I've been googling and reading slau144f.pdf.&lt;/li&gt;&#xA;&lt;li&gt;Do people typically break up applications on the MSP430 into more logical groups to get around I/O shortages, and then combine at the end and hope for the best?  This is the approach I would typically use.  For example, I could use a different set of lines for TX/RX to test the software serial feature in one application, then test the LCD w/o serial support in another application.  Then at the end, I could reassign the TX/RX lines and combine the features.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-06T07:58:52.527" Title="Trying to figure out available resources on MSP430 LaunchPad" Tags="&lt;serial&gt;&lt;rs232&gt;&lt;msp430&gt;&lt;fet&gt;" AnswerCount="4" FavoriteCount="3" />
  <row Id="12524" PostTypeId="2" ParentId="12503" CreationDate="2011-04-04T15:01:25.777" Score="2" ViewCount="" Body="&lt;p&gt;Like the others said, manufacturers will often mod small quantities. However, for stuff like guitar stompboxes, some builders go the other way and make the hand-modification of the cases a reason to charge extra.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't have my links anymore, but I have seen a lot of boxes that were just off the shelf aluminum cases then hand painted, stained, corroded, or just polished with high quality hardware then sold for upwards of $300 each with about fifty cents in electronics inside. Some of these are truly works of art!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another poster pointed out that the electronics is usually trivial, the real work is in the enclosure.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-04-04T15:01:25.777" />
  <row Id="12525" PostTypeId="2" ParentId="12523" CreationDate="2011-04-04T15:06:45.603" Score="3" ViewCount="" Body="&lt;p&gt;One reason why the Launchpad is so cheap is because the chip it uses is a very low-end device, which is missing many useful peripherals such as a UART. You will find things much easier if you use one of the other, more capable, devices You will need a FET, of course, but they aren't all that expensive, and it is a very useful tool.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pins 16 and 17 on the target device are used for debugging. It might be possible to use them in your application if they are isolated with resistors, Microchip recommends that solution for debugging their devices when the ICSP pins are in use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most people build software like that starting from a simple application using one peripheral, and then add the additional functionality to the same program. Combining programs can cause problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A useful resource for MSP430 development is &lt;a href=&quot;http://tech.groups.yahoo.com/group/msp430/&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; Yahoo MSP430 group.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-04T15:29:42.657" LastActivityDate="2011-04-04T15:29:42.657" CommentCount="1" />
  <row Id="12526" PostTypeId="1" AcceptedAnswerId="12527" CreationDate="2011-04-04T15:51:00.170" Score="2" ViewCount="151" Body="&lt;p&gt;Hi &#xA;I want my circuit to be able to switch on and off several 230V AC circuits. I was wondering if relays are my only option. It starts to get a bit expensive if you need a few. Originally I was going to use a 5V dc relay to switch the devices on and off&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-04-06T10:35:56.710" Title="Alternative to relay" Tags="&lt;circuit-design&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="12527" PostTypeId="2" ParentId="12526" CreationDate="2011-04-04T16:01:56.840" Score="4" ViewCount="" Body="&lt;p&gt;You may find relays with a 12 or 24V coil cheaper. You may consider triacs (thyristors) but it is hard to beat the price (and simplicity) of a relay.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-05T10:56:13.820" LastActivityDate="2011-04-05T10:56:13.820" CommentCount="7" />
  <row Id="12528" PostTypeId="2" ParentId="12523" CreationDate="2011-04-04T16:19:40.617" Score="1" ViewCount="" Body="&lt;p&gt;If you need some extra slow IO, you can add some 74HC595 or 2 which can give you some 8-16 extra IO lines for 2 lines on uC(1 line with tricks). It will cost you some 0.2$ each.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-04T16:19:40.617" CommentCount="1" />
  <row Id="12529" PostTypeId="1" AcceptedAnswerId="12532" CreationDate="2011-04-04T16:31:24.923" Score="3" ViewCount="110" Body="&lt;p&gt;This is what I found in PIC16F1947 data sheet:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Reading the PORTB register reads the status of the pins,&#xA;  whereas writing to it will write to&#xA;  the PORT latch. All write operations&#xA;  are read-modify-write operations.&#xA;  Therefore, a write to a port implies&#xA;  that the port pins are read, this&#xA;  value is modified and then written to&#xA;  the PORT data latch (LATB).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I'm a firmware developer and my background is Computer Science. I still struggle to understand electronics and logic in hardware level. I only have the basic knowledge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I want to understand what happens when data is written to latch in hardware level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you.&lt;/p&gt;&#xA;" OwnerUserId="3720" LastActivityDate="2011-04-04T17:12:58.440" Title="What happens when data is written to LATCH?" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;hardware&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="12531" PostTypeId="2" ParentId="12529" CreationDate="2011-04-04T16:57:54.397" Score="4" ViewCount="" Body="&lt;p&gt;To avoid read-modify-write problems you should write to the port as a whole, rather than setting or resetting individual bits in the port. An R-M-W problem might result in a bit not being set, or another output going high, especially if output pins are sourcing or sinking a lot of current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A &quot;shadow register&quot; is typically used. Set or reset bits in that, and output it to the port, to avoid R-M-W problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is avoided with 18F PICs by the use of a separate latch, individual bits in that can be set and reset with impunity.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-04T17:06:03.640" LastActivityDate="2011-04-04T17:06:03.640" CommentCount="4" />
  <row Id="12532" PostTypeId="2" ParentId="12529" CreationDate="2011-04-04T17:12:58.440" Score="10" ViewCount="" Body="&lt;p&gt;Latch is a kind of memory of one bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's use the picture in manual:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/iCogk.png&quot; alt=&quot;Generic I/O Port Operation&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you write a bit in a I/O pin, you're storing this bit from Data Bus to the Data Register (&lt;a href=&quot;http://en.wikipedia.org/wiki/Flip-flop_%28electronics%29&quot; rel=&quot;nofollow&quot;&gt;D-FlipFlop&lt;/a&gt;). If TRISx of this bit is 0, so data from Q of the Data Register will be in the I/O pin. Write in LATx or PORTx is the same. See below in red:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/E2xz3.png&quot; alt=&quot;Generic I/O Port Operation Write&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, read from LATx is different of read from PORTx.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you're reading from LATx, you're reading what is in the Data Register (&lt;a href=&quot;http://en.wikipedia.org/wiki/Flip-flop_%28electronics%29&quot; rel=&quot;nofollow&quot;&gt;D-FlipFlop&lt;/a&gt;). See picture below in green:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Qluvl.png&quot; alt=&quot;Generic I/O Port Operation Read LATx&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And when you read from PORTx, you're reading the actual I/O pin value. See below in blue:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wdvIE.png&quot; alt=&quot;Generic I/O Port Operation Read PORTx&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PIC uses read-modify-write to write operations and this can be a &lt;a href=&quot;http://marcansoft.com/uploads/readmodifywrite.pdf&quot; rel=&quot;nofollow&quot;&gt;problem&lt;/a&gt;, so they use this shadow register to avoid it.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-04-04T17:12:58.440" CommentCount="1" />
  <row Id="12533" PostTypeId="1" AcceptedAnswerId="12544" CreationDate="2011-04-04T17:59:17.640" Score="4" ViewCount="166" Body="&lt;p&gt;This is probably the dumbest question ever, but I am an electronics nublet.&#xA;Like I understand what Capacitors do, and i've been reading beginner Electronics books and such.....but I dont quite understand &quot;when&quot; to use them? Sometimes in these books they just seem kinda thrown in, I understand they are meant to &quot;smoothen&quot; out current........but.....I still am not sure I understand &quot;when&quot; to use them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like I said.....prolly nublet question to the max. But most information I find is more about 'what' they are rather than 'when' to use them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: For clarity I mean in SMALL electronic applications. Think simple circuits and such.&lt;/p&gt;&#xA;" OwnerUserId="3073" LastEditorUserId="3073" LastEditorDisplayName="" LastEditDate="2011-04-04T18:56:18.497" LastActivityDate="2011-04-04T20:09:42.760" Title="When to use Capacitors?" Tags="&lt;capacitor&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="12534" PostTypeId="2" ParentId="8669" CreationDate="2011-04-04T18:01:01.733" Score="0" ViewCount="" Body="&lt;p&gt;Is this a one-off project or a product that will be shipped to customers?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For one-offs, there are a bunch of ethernet-capable MCU's with vendor-supplied TCP/IP stacks - go with those.  Off the top of my head, I know Microchip and Zilog had such parts; and there are plenty others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the wireless features -- you could buy a WiFi module - Google for M2M wifi modules.  They are expensive, though, and if you're focusing on one-off's, you might be better off just buying an ethernet-to-wifi bridge adapter.  Heck, the DD-WRT that Jay Kominek mentioned would probably do the job nicely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to directly connect the ethernet MAC from your MCU to the MAC in the bridge/router, you can bypass the magnetics (isolation transformers) and just capacitively couple the MAC's together.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-04T18:01:01.733" />
  <row Id="12535" PostTypeId="1" AcceptedAnswerId="12542" CreationDate="2011-04-04T18:09:34.047" Score="2" ViewCount="73" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to measure Mains AC voltage of 230V RMS/50Hz with the ADC of a MCU.&#xA;Therefore I need some isolation and voltage division (+/-325Vp down to +/- 1V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The voltage division is easy to solve, but for the isolation I was thinking about using a Common mode Choke.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea is to use the Common mode choke as a small transformer, by connecting it to the Mains power (230V RMS), in series with a resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the secondary side I would place a resistor, and hopefully the voltage across this resistor would be dependent on the 230V RMS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But can I use a Common mode choke in this way (at 50Hz)? &#xA;These chokes are normally for RF.&lt;/p&gt;&#xA;" OwnerUserId="3041" LastActivityDate="2011-04-04T19:53:57.693" Title="Common mode Choke for AC voltage measurement" Tags="&lt;ac&gt;" AnswerCount="1" />
  <row Id="12538" PostTypeId="2" ParentId="12533" CreationDate="2011-04-04T18:48:48.737" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://electronics.howstuffworks.com/capacitor.htm&quot; rel=&quot;nofollow&quot;&gt;How Stuff Works&lt;/a&gt; says&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes, capacitors are used to store charge for high-speed use. That's what a flash does. Big lasers use this technique as well to get very bright, instantaneous flashes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Capacitors can also eliminate ripples. If a line carrying DC voltage has ripples or spikes in it, a big capacitor can even out the voltage by absorbing the peaks and filling in the valleys.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A capacitor can block DC voltage. If you hook a small capacitor to a battery, then no current will flow between the poles of the battery once the capacitor charges. However, any alternating current (AC) signal flows through a capacitor unimpeded. That's because the capacitor will charge and discharge as the alternating current fluctuates, making it appear that the alternating current is flowing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Capacitor#Applications&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt; lists the following applications:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;energy storage&lt;/li&gt;&#xA;&lt;li&gt;pulsed power&lt;/li&gt;&#xA;&lt;li&gt;power conditioning&lt;/li&gt;&#xA;&lt;li&gt;power factor correction&lt;/li&gt;&#xA;&lt;li&gt;signal coupling&lt;/li&gt;&#xA;&lt;li&gt;decoupling&lt;/li&gt;&#xA;&lt;li&gt;noise filters and snubbers&lt;/li&gt;&#xA;&lt;li&gt;motor starters&lt;/li&gt;&#xA;&lt;li&gt;signal processing&lt;/li&gt;&#xA;&lt;li&gt;tuned circuits&lt;/li&gt;&#xA;&lt;li&gt;sensing&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2191" LastActivityDate="2011-04-04T18:48:48.737" CommentCount="6" />
  <row Id="12539" PostTypeId="2" ParentId="12533" CreationDate="2011-04-04T18:51:46.133" Score="6" ViewCount="" Body="&lt;p&gt;Uses: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;ac coupling –- blocking -- isolation &lt;/p&gt;&#xA;&#xA;&lt;p&gt;timing -- Time for a capacitor to charge or discharge is very roughly RC where R is the     resistor in series with the capacitor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Filter ( often power supply filter ) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;decoupling &lt;/p&gt;&#xA;&#xA;&lt;p&gt;tuned circuits&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://opencircuits.com/Capacitors&quot; rel=&quot;nofollow&quot;&gt;http://opencircuits.com/Capacitors&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-04-04T18:51:46.133" />
  <row Id="12540" PostTypeId="2" ParentId="12404" CreationDate="2011-04-04T19:29:13.723" Score="1" ViewCount="" Body="&lt;p&gt;I call the Keil IDE via command line to build (not a generated batch file) from within a Makefile. Usually it works out better to lock down the project files via the scm, or take a reference build copy renaming the relevant project names when doing this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The IDE is perfectly happy to work with read-only project files, so if you lock them down, the irritant is that you need to unlock them to change settings, save, and check them back in. If you're at a fairly stable point in the project this is pretty minor - even desirable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you take a reference copy, then the build tends to break as project settings change - especially as project files are added or dropped from the compilation. Explictly capturing those changes isn't necessarily bad, but is an extra step needed to maintain builds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Either way, redirecting the output to a log file via the &quot;-o&quot; option lets you access the full output log. The log doesn't come out a line at a time, but it seem to all be there. (I actually parse the Keil error format to GNU fmt for integration with the eclipse CDT environment. This lets me jump directly to errors/warnings after the build)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The command-line build also generates the __i, __ia files so those don't need to go into version control for the build server either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="960" LastActivityDate="2011-04-04T19:29:13.723" />
  <row Id="12541" PostTypeId="2" ParentId="11225" CreationDate="2011-04-04T19:39:59.097" Score="0" ViewCount="" Body="&lt;p&gt;Build some kit robots and volunteer for a &lt;a href=&quot;http://usfirst.org/&quot; rel=&quot;nofollow&quot;&gt;First Robotics&lt;/a&gt; team near you. You might meet some others in the field.&lt;/p&gt;&#xA;" OwnerUserId="960" LastActivityDate="2011-04-04T19:39:59.097" />
  <row Id="12542" PostTypeId="2" ParentId="12535" CreationDate="2011-04-04T19:53:57.693" Score="5" ViewCount="" Body="&lt;p&gt;Not a good idea. It is not designed to carry much magnetic flux in the core at 50 Hz nor have the isolation between windings that you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think about how the common mode choke is used. With live and neutral running through it in opposite phase, there would normally be very little resultant magnetic flux at 50Hz and all other frequencies. The core is only designed for the small induced RF currents which come in common mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The easiest solution is a mains to low voltage transformer, with safety agency approval (kilovolts of dielectric strength between windings). Other solutions are also possible eg voltage divider into an ADC on the live side, and pass the digital signal through an opto coupler to the rest of the circuit (low side micro). But then you have to make a small power supply for the ADC.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-04-04T19:53:57.693" CommentCount="1" />
  <row Id="12543" PostTypeId="1" CreationDate="2011-04-04T20:04:02.280" Score="4" ViewCount="209" Body="&lt;p&gt;I have a couple years of experience with computers - I can program, and I know computers really well. But I don't understand them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This leads to a broader scope - I don't understand electronics in general. I have read some internet articles, like howstuffworks.com, that kind of thing. I understand the basics, but about 90%  of it is beyond me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where do I learn? What books can I read? What websites can I go to? I'm especially interested in knowing what books I can read to understand more about electronics.&lt;/p&gt;&#xA;" OwnerUserId="3725" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-05T14:39:01.753" LastActivityDate="2011-04-05T15:40:34.987" Title="What good resources are there for a high school student to start learning electronics?" Tags="&lt;electronics&gt;&lt;learning&gt;" AnswerCount="8" FavoriteCount="2" />
  <row Id="12544" PostTypeId="2" ParentId="12533" CreationDate="2011-04-04T20:09:42.760" Score="8" ViewCount="" Body="&lt;p&gt;When I first started out in electronics I struggled with the same question. The problem is that capacitors are used in a vast number of different ways.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, as your just starting out in electronics you probably only need to know about a few of these to start with. The most widely used and basic of these are:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+10.20027730826997+50+5.0+48%0Av+144+368+144+80+0+1+40.0+5.0+0.0+0.0+0.5%0Aw+144+80+272+80+0%0Aw+272+80+272+144+0%0Ad+272+144+336+208+1+0.805904783%0Ad+272+272+336+208+1+0.805904783%0Ad+208+208+272+144+1+0.805904783%0Ad+208+208+272+272+1+0.805904783%0Aw+272+272+272+368+0%0Aw+272+368+144+368+0%0Aw+208+208+208+304+0%0Aw+336+208+384+208+0%0Aw+208+304+384+304+0%0Ac+384+208+384+304+0+1.02E-4+3.3850691902835575%0Aw+384+208+464+208+0%0Aw+384+304+464+304+0%0Ar+464+208+464+304+0+430.0%0Ax+499+264+529+268+0+16+load%0Ao+0+32+0+34+5.0+0.05+0+-1%0Ao+15+32+0+35+5.0+0.0125+1+-1%0A&quot; rel=&quot;nofollow&quot;&gt;Power Supply Smoothing&lt;/a&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the easiest and very widely used application of a capacitor. If you stick a big beefy electrolytic capacitor (the bigger the better), it will fill in all the gaps created by rectifying an AC waveform, to create a relatively smooth DC. It works be repeatedly charging during the peaks, and discharging during the gaps. However, the more load you put on it, the quicker it will drain the capacitor and the more ripple you'll get.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+10.20027730826997+50+5.0+50%0Ac+336+224+336+320+0+1.9999999999999998E-4+0.0010%0Ar+336+224+336+144+0+100.0%0As+240+144+336+144+0+1+false%0Aw+240+224+240+144+0%0As+416+320+416+224+0+1+true%0A162+336+320+240+320+1+2.1024259+1.0+0.0+0.0%0Aw+336+224+416+224+0%0Aw+336+320+416+320+0%0Av+240+320+240+224+0+0+40.0+5.0+0.0+0.0+0.5%0Ax+431+282+484+288+0+24+reset%0Ax+264+115+311+121+0+24+start%0A&quot; rel=&quot;nofollow&quot;&gt;Timing&lt;/a&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you supply power to a capacitor through a resistor, it will take time to charge. If you connect a resistive load to a capacitor, it will take time to discharge. The key thing to understand here about timing circuits is that capacitors appear as though they are short circuit &lt;em&gt;while&lt;/em&gt; they are charging, but as soon as they are charged, they appear to be open circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+6.450009306485578+50+5.0+50%0Ac+208+144+368+144+0+1.0E-5+-1.5422100174719175%0Ar+368+144+368+272+0+35.0%0AO+368+144+480+144+0%0Ag+368+272+368+304+0%0A170+208+144+176+144+3+20.0+1000.0+5.0+0.1%0Ao+4+16+0+34+5.0+0.025+0+-1+in%0Ao+2+16+0+34+5.0+9.765625E-5+1+-1+out%0Ah+3+1+0%0A&quot; rel=&quot;nofollow&quot;&gt;Filtering&lt;/a&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you pass DC through a capacitor, it will charge and then block any further current from flowing. However, if you pass AC through a capacitor, it will flow. How much current flows depends on the frequency of the AC, and the value of the capacitor.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-04-04T20:09:42.760" CommentCount="2" />
  <row Id="12545" PostTypeId="2" ParentId="12543" CreationDate="2011-04-04T20:16:56.297" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/&quot; rel=&quot;nofollow&quot;&gt;MIT's Free Online Courses&lt;/a&gt; are a good place to start. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to just grab an &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; and start hacking from there.  They have a pretty large and helpful online following.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for books, hopefully someone else can provide some good starter references, my only experience with intro books are the ones I had to use in college which were...meh... &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-04-04T20:16:56.297" />
  <row Id="12546" PostTypeId="2" ParentId="12543" CreationDate="2011-04-04T20:31:36.600" Score="7" ViewCount="" Body="&lt;p&gt;Considering you're of 'high school age', I think the MIT courses are maybe very difficult (from Mark's post) They generally require a lot of math and previous knowhow from highschool. Or am I only able to pick out the courses that handle circuit theory and maths?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may find this very interesting:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.allaboutcircuits.com/vol_1/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.allaboutcircuits.com/vol_1/index.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Start at chapter 1 and read through. You may find some parts that you think is familiar, but read through it anyway. You may already know what a Volt and an Amp is, but it might also be nice to read through some literature so you can conform your previous knowledge. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This website is focussed on analog electronics. It's about understanding how electricity and electronic components work. This doesn't have a particular big focus on digital electronics, which you may want to know more about considering you're interested in writing computer programs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As Mark said, Arduino is a great platform to start from for digital electronics. It contains a small microcontroller with an easy to pick up language to start with programming embedded systems. Out of the box you won't be that concerned with configuring registers of microcontrollers. You can get a ton of addons created by 'the community' for it. You can get a ton of stuff from &lt;a href=&quot;http://www.sparkfun.com/&quot; rel=&quot;nofollow&quot;&gt;Sparkfun&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-04-04T20:31:36.600" CommentCount="3" />
  <row Id="12547" PostTypeId="2" ParentId="12186" CreationDate="2011-04-04T20:47:14.770" Score="0" ViewCount="" Body="&lt;p&gt;I would be interested to see how you draw 4kw from a single mains socket&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-04-04T20:47:14.770" CommentCount="5" />
  <row Id="12548" PostTypeId="2" ParentId="12543" CreationDate="2011-04-04T21:07:39.223" Score="4" ViewCount="" Body="&lt;p&gt;Get yourself some basic components (either individually or just get a starter kit from a &lt;a href=&quot;http://www.richquackenbush.com/2011/01/electronics-vendors.html&quot; rel=&quot;nofollow&quot;&gt;supplier&lt;/a&gt;):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Components&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Wire / alligator clips&lt;/li&gt;&#xA;&lt;li&gt;LEDs, Lamps, buzzers, motors, etc&lt;/li&gt;&#xA;&lt;li&gt;Resistors, Capacitors, Some transistors (TIP120 are a great start for learning about switching)&lt;/li&gt;&#xA;&lt;li&gt;Switches, pressure sensors, etc&lt;/li&gt;&#xA;&lt;li&gt;Breadboard&lt;/li&gt;&#xA;&lt;li&gt;Battery holders (can be scavenged from consumer electronics / toys).  Batteries are a good way to start out playing with electronics because there typically isn't enough juice to hurt yourself.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Tools&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And some very basic tools (if you don't already have them):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Multimeter (so you can get an idea what is happening at various points in your circuit).&lt;/li&gt;&#xA;&lt;li&gt;Some alligator clips&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Note that I left out a soldering iron.  You don't need one to start out with (but you'll likely want one if electronics holds your interest).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Start Hacking!&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best way to learn is by playing with circuits.  Try making buzzers buzz, LEDs light (without burning them out).  There are a tremendous number of resources available on the web, and some great starter kits available from many vendors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="1823" LastActivityDate="2011-04-04T21:07:39.223" CommentCount="2" />
  <row Id="12549" PostTypeId="2" ParentId="12186" CreationDate="2011-04-04T21:26:25.810" Score="1" ViewCount="" Body="&lt;p&gt;Designing a power supply is not a trivial task. I've spent more than 10 years in the employ of professional companies which do this sort of work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some thoughts:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Input-side - that's huge power you'll be drawing from the mains. I'd estimate that you'll need at least 20A service. You'll also need some hefty EMI filtering to avoid polluting the mains with the switching noise from the converter. Don't forget about inrush limiting, surge suppression, fuse sizing and X-capacitor discharge circuitry.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;PFC - Most designs need some sort of power-factor correction to ensure that sinusoidal current is being drawn from the mains. You'll most likely need a multiphase PFC to handle this sort of current effectively.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;DC/DC converter: You'll definitely need a soft-switching topology to achieve any reasonable sort of efficiency on the primary side. Look into the zero-voltage-transition full-bridge converter, aka phase-shift full-bridge (Intersil, Texas Instruments and others make controllers for this sort of topology) and look into really rugged MOSFETS (I've used IRFPS40N50Ls for 3kW designs). You'll need really good transformer core material (consider Ferroxcube or Nicera) to keep the losses low. You may want to even consider running two 2kW converters, and sum the currents on the secondary-side with a current sharing circuit.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Rectification: There isn't an efficient way to rectify such high voltage. You won't be able to take advantage of synchronous rectifiation (in my estimation) so you'll be burning power in Schottky diodes.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Thermal management: You need to ensure that your magnetics and switching devices are all in their safe operating areas, and design heatsinks / install fans to ensure that they all stay out of any potential thermal runaway conditions.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Protections: Over voltage, over current, over temperature, short-circuit, line surge, ESD, EFT ... all things that you need to design protection against.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Regulatory / Safety: You'll need to ensure that you meet proper creepages and clearences, that your touch current is safe, that all the critical magnetics and power train devices do not result in the power supply becoming unsafe during any single abnormal event, that your thermal management is keeping the parts within their safe operating areas, that you're using regulatory-approved parts for safety-critical functions (X- and Y-caps, MOVs, optoisolators, etc.)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Are you sure you really want to try and design such a thing yourself? There are books out there that explain how to design, but becoming proficient is a life's work in itself.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-04T21:26:25.810" CommentCount="2" />
  <row Id="12550" PostTypeId="1" CreationDate="2011-04-04T21:29:56.777" Score="5" ViewCount="215" Body="&lt;p&gt;I'm designing a project that controls 110VAC (plug in, socket out), and also has a microprocessor inside.  I'd really like this project to not need a wall wart to get it's 5V, so I want to include a small DC power supply inside.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apple's USB power adapter looks like a great small design that I can fit inside my case.  I'm guessing this is a switching power supply but I can't find any teardowns or schematics anywhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know how this thing works?  I know I could make my own 110V-&gt;5VDC supply from a bridge rectifier and some caps, but I'd like to also be super safe.  What's in the Apple brick?&lt;/p&gt;&#xA;" OwnerUserId="3726" LastActivityDate="2011-04-05T16:34:15.320" Title="How can I duplicate Apple's tiny USB power adapter?" Tags="&lt;power&gt;&lt;usb&gt;&lt;supply&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="12551" PostTypeId="1" AcceptedAnswerId="12558" CreationDate="2011-04-04T21:30:59.537" Score="1" ViewCount="87" Body="&lt;p&gt;Is using a relay and some switches a standard way to reverse a motor or is the preferred method to use a H-Bridge? The circuit for reversing a motor with a relay looks like this:&#xA;&lt;img src=&quot;http://i.imgur.com/t0Vmg.jpg&quot; alt=&quot;Circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that this circuit is just to show the relay and motor connections. The main control would be the coming from a PIC not an op-amp. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Me and my teacher are having disagreements about the best way/standard/preferred way to reverse motors, so what would engineers do?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-04-04T22:44:30.187" Title="Standard way to reverse a motor?" Tags="&lt;dc-motor&gt;" AnswerCount="4" />
  <row Id="12552" PostTypeId="2" ParentId="12543" CreationDate="2011-04-04T21:37:07.997" Score="0" ViewCount="" Body="&lt;p&gt;If books is what you want, you might want to look at this thread:&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/616/basic-electronics-book&quot;&gt;Basic Electronics Book&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3078" LastActivityDate="2011-04-04T21:37:07.997" />
  <row Id="12553" PostTypeId="2" ParentId="12551" CreationDate="2011-04-04T21:37:37.537" Score="0" ViewCount="" Body="&lt;p&gt;You can also get speed control with an H-bridge. They are popular because of that.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-04T21:37:37.537" CommentCount="1" />
  <row Id="12554" PostTypeId="2" ParentId="12551" CreationDate="2011-04-04T21:50:33.303" Score="1" ViewCount="" Body="&lt;p&gt;How about the best of both, use a relay to switch the motor direction and a power device to control the speed of the motor (It's how early speed controllers worked - it was a lot cheaper to just have a single power stage, and a relay could switch easily - you just need to make sure the motor is going slowly when switching to avoid arcing in the relay)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So 1 pin would control the motor and 1 PWM output run a power stage to control the speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(A power stage could be a simple as a resistor, a transistor and a reverse protection diode)&lt;/p&gt;&#xA;" OwnerUserId="2280" LastActivityDate="2011-04-04T21:50:33.303" CommentCount="1" />
  <row Id="12555" PostTypeId="1" AcceptedAnswerId="12557" CreationDate="2011-04-04T21:58:07.200" Score="1" ViewCount="68" Body="&lt;p&gt;In &lt;a href=&quot;http://www.scienceprog.com/wp-content/uploads/2008i/DDS2/AVR_DDS_2_0_circuit.png&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; circuit &lt;a href=&quot;http://www.datasheetcatalog.org/datasheets/166/49945_DS.pdf&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;LM358N&lt;/strong&gt;&lt;/a&gt; 1MHz 32V dual op amp is used (+12V and -12V). The question is, can I simply replace it with &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet/philips/NE5532FE.pdf&quot; rel=&quot;nofollow&quot;&gt;&lt;strong&gt;NE5532N&lt;/strong&gt;&lt;/a&gt; 10MHz +-22V dual op amp for up to 8MHz DDS signal source?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, this circuit has DDS output generated via R2R resistor network and adjusted via LM358N offset and amplitude regulating circuits. Offset can be regulated in range +5V..-5V while amplitude in range 0..10V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/c6a5y.png&quot; alt=&quot;DUAL OP AMP LM358N&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-04-04T22:32:59.820" Title="Can I replace LM358N with NE5532N dual op amp?" Tags="&lt;electronics&gt;&lt;circuit&gt;&lt;op-amp&gt;&lt;amplifier&gt;&lt;amplification&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="12556" PostTypeId="1" AcceptedAnswerId="12559" CreationDate="2011-04-04T21:59:53.937" Score="1" ViewCount="114" Body="&lt;p&gt;Two of the pins on the l293d are labeled VS and VSS. Apparently they are both power. &lt;a href=&quot;http://www.8051projects.net/dc-motor-interfacing/l293d-interfacing-with-microcontroller.php&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; it shows VS being supplied with 12V, while vss is receiving 5V. &lt;a href=&quot;http://luckylarry.co.uk/arduino-projects/control-a-dc-motor-with-arduino-and-l293d-chip/comment-page-1/#comment-5829&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;, it shows both receiving 6V from the same source of 4AAs. What are each of these for? Also, in the second link, he shows wiring to the ground on the arduino, why is that? Wouldn't he be able to do the same by wiring to the negative terminals on the batteries?&lt;/p&gt;&#xA;" OwnerUserId="2873" LastActivityDate="2011-04-05T00:34:22.463" Title="Power input on l293d motor driver" Tags="&lt;power&gt;&lt;h-bridge&gt;" AnswerCount="1" />
  <row Id="12557" PostTypeId="2" ParentId="12555" CreationDate="2011-04-04T22:17:02.637" Score="2" ViewCount="" Body="&lt;p&gt;Given that you won't be able to get much more than a 250 kHz sine wave with a software DDS running on an AVR, it doesn't matter much what op amp you use.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-04T22:32:59.820" LastActivityDate="2011-04-04T22:32:59.820" CommentCount="3" />
  <row Id="12558" PostTypeId="2" ParentId="12551" CreationDate="2011-04-04T22:29:17.283" Score="4" ViewCount="" Body="&lt;p&gt;Whenever I have done motor control it has been with an H-Bridge.  But the ideal solution depends on several factors:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the voltage/current required?  For &amp;lt;24 volts and &amp;lt;5 amps, an H-Bridge is normally the preferred solution.  The reason for this is the MOSFET's that can handle those voltages/currents are easy to get, easy to design with, and fairly inexpensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is speed control, dynamic breaking, or regenerative breaking required?  If so, an H-Bridge is again usually the best.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But in the case where there is no speed control, and the frequency of &quot;direction reversals&quot; is low, and/or the voltage/current is very high then a relay could be a good choice.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main selling point of the relay is its simplicity and ease of use.  An H-Bridge will always perform better but it is harder to design, sometimes can be more expensive, and adds complexity that is not always required.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-04T22:29:17.283" />
  <row Id="12559" PostTypeId="2" ParentId="12556" CreationDate="2011-04-04T22:39:42.327" Score="2" ViewCount="" Body="&lt;p&gt;One is logic power (pin 16 (20 for SMD) at top right,should be 5v or whatever your logic level is), the other  is motor power (pin 8 (10 for SMD), bottom left, can be from 4-36v and should be whatever your&#xA;motor needs).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means you can run your motors at different voltage, and also isolates &#xA;power spikes from the motor supply from the logic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have a look at the bipolar stepper motor example circuit here: &lt;a href=&quot;http://www.tigoe.net/pcomp/code/circuits/motors/stepper-motors&quot; rel=&quot;nofollow&quot;&gt;http://www.tigoe.net/pcomp/code/circuits/motors/stepper-motors&lt;/a&gt;  (The circuit says SN754410NE, that device is just a higher power version of the L293).&lt;/p&gt;&#xA;" OwnerUserId="389" LastEditorUserId="389" LastEditorDisplayName="" LastEditDate="2011-04-05T00:34:22.463" LastActivityDate="2011-04-05T00:34:22.463" CommentCount="10" />
  <row Id="12560" PostTypeId="2" ParentId="12551" CreationDate="2011-04-04T22:44:30.187" Score="1" ViewCount="" Body="&lt;p&gt;If you are switching a lot of current, a relay is cheaper (especially in the old days when high power transistors cost a lot more!), a H-bridge has the advantage of PWM speed control, and  instant reversal.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For small currents, (&amp;lt;2A) a single chip H-bridge is economical and more compact.   For heavy duty high current motors, the reverse is true, a relay will be cheaper and smaller than a high-power H-bridge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't need electronic speed control, and aren't changing direction zillions of times an hour, a relay is a fine solution, and a heckload easier to debug.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-04-04T22:44:30.187" />
  <row Id="12561" PostTypeId="2" ParentId="10152" CreationDate="2011-04-04T23:55:05.553" Score="1" ViewCount="" Body="&lt;p&gt;I might be barking up the wrong tree here, but if you've got any extra space at all at the far end of the cable, you'd probably do better to digitize the data there. You can then use a robust signaling method over a single conductor pair to deliver the data upstream. Coaxial antenna cable can be gotten in really tiny diameters, it's very noise-resistant, and can be quite strong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most of the major analog IC manufacturers sell multi-channel serial ADC chips that you could trivially integrate (again, assuming you have space).&lt;/p&gt;&#xA;" OwnerUserId="3588" LastActivityDate="2011-04-04T23:55:05.553" />
  <row Id="12562" PostTypeId="2" ParentId="12550" CreationDate="2011-04-04T23:58:03.163" Score="3" ViewCount="" Body="&lt;p&gt;Looks like MAX 611 couldn't make it any easier:  &lt;a href=&quot;http://www.selectronic.fr/includes_selectronic/pdf/Maxim/MAX_611.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.selectronic.fr/includes_selectronic/pdf/Maxim/MAX_611.pdf&lt;/a&gt; (sorry about the random site, not turning up a link on Maxim's site).&lt;/p&gt;&#xA;" OwnerUserId="2664" LastActivityDate="2011-04-04T23:58:03.163" CommentCount="9" />
  <row Id="12563" PostTypeId="2" ParentId="12503" CreationDate="2011-04-05T00:12:31.350" Score="0" ViewCount="" Body="&lt;p&gt;Check out Polycase, PacTec, Hammond, Bud for off-the-shelf enclosures that you can get custom cutouts done either turnkey from the manufacturer, or shopped out to a machine shop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, check out ToolLess  - &lt;a href=&quot;http://toolless.com&quot; rel=&quot;nofollow&quot;&gt;www.toolless.com&lt;/a&gt; - they claim to have a tool-less no-mold capability for unique shapes.  I haven't personally used them, but heard about them from a friend-of-a-friend, and it sounded pretty impressive.  The idea is that they &#xA;&quot;build up&quot; the case by fusing/joining together sub-panels made up of cut sheets or hogged-out stock.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-05T00:12:31.350" />
  <row Id="12564" PostTypeId="2" ParentId="12543" CreationDate="2011-04-05T02:03:01.650" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596153740&quot; rel=&quot;nofollow&quot;&gt;Make - Electronics Discovery&lt;/a&gt;. This starts at a very basic level explaining resistors, capacitors and transistors. It is more a small taste in the different areas of electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0945053282&quot; rel=&quot;nofollow&quot;&gt;Getting Started in Electronics&lt;/a&gt;. This is also an introductory text. It is an older book but many of the principles still apply. The author Forest Mims is well known. He published a few small books which you were able to purchase from radio shack they dealt with different areas of electronics. It would be great if you could get your hands on them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally at a more advanced level&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0521370957&quot; rel=&quot;nofollow&quot;&gt;Art of Electronics&lt;/a&gt; This book is considered the standard text on electronics in some circles. It is still considered an introductory text but it is a little more advance. There is some math sometimes but you can still get the general ideas without fully understanding the math. I am currently studying this book.&lt;/p&gt;&#xA;" OwnerUserId="3688" LastActivityDate="2011-04-05T02:03:01.650" CommunityOwnedDate="2011-04-05T02:03:01.650" />
  <row Id="12565" PostTypeId="1" AcceptedAnswerId="12567" CreationDate="2011-04-05T02:20:49.593" Score="4" ViewCount="128" Body="&lt;p&gt;I have &lt;a href=&quot;http://www.sparkfun.com/datasheets/Wireless/Bluetooth/rn-42-ds.pdf&quot; rel=&quot;nofollow&quot;&gt;contacts&lt;/a&gt; that are so close together I'm either bridging them, or melting the neighboring one. What am I missing?&#xA;&lt;img src=&quot;http://i.imgur.com/rzrkV.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1227" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-04-05T15:20:28.693" LastActivityDate="2011-04-05T15:20:28.693" Title="Solder very close together contacts" Tags="&lt;soldering&gt;" AnswerCount="4" CommentCount="4" FavoriteCount="3" />
  <row Id="12566" PostTypeId="2" ParentId="12565" CreationDate="2011-04-05T02:52:41.730" Score="1" ViewCount="" Body="&lt;p&gt;To solder an item like that you need to:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Use flux&lt;/li&gt;&#xA;&lt;li&gt;Make sure your iron is clean and tinned&lt;/li&gt;&#xA;&lt;li&gt;Have your soldering iron hot enough that your solder will melt as soon as you touch it to it&lt;/li&gt;&#xA;&lt;li&gt;Use a solder diameter that is rather narrow&lt;/li&gt;&#xA;&lt;li&gt;Heat up your trace and pad and then slide the solder into it&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I think I have everything covered, am I missing anything?&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-05T02:52:41.730" />
  <row Id="12567" PostTypeId="2" ParentId="12565" CreationDate="2011-04-05T02:53:47.623" Score="12" ViewCount="" Body="&lt;p&gt;Flux.  You're missing flux, and lots of experience.  I regularly solder with a tip that easily covers 10 or more pins at a time, but by carefully controlling how much solder is on the tip and using lots of flux I can get perfect solder joints.  When soldering a TQFP or TSSOP package here's what I do:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;If the pads on the PCB are not super flat, then use some solder braid and suck up some of the solder on the pads to make them flat.&lt;/li&gt;&#xA;&lt;li&gt;Put the part on the PCB and carefully align the part.  Don't rush this step, because if you mess this one up then nothing else will work correctly.&lt;/li&gt;&#xA;&lt;li&gt;Put a drop or two of liquid flux on the part.  I use water soluble liquid flux, but others are successful with other liquid fluxes.&lt;/li&gt;&#xA;&lt;li&gt;Clean the iron tip and put a little bit of solder on it.  &lt;/li&gt;&#xA;&lt;li&gt;Carefully touch a corner pad (&lt;em&gt;NOT&lt;/em&gt; the pin itself) and let the solder wick up and tack down that pin.&lt;/li&gt;&#xA;&lt;li&gt;Repeat 4 &amp;amp; 5 for 2 to 4 corner pins.  Reapply flux as required. &lt;/li&gt;&#xA;&lt;li&gt;Put some solder on the tip and run the tip down one complete side of the chip.  Ideally you won't have bridges, but if the last 2 or 3 pins are bridged then you did good.  Ignore the bridges.&lt;/li&gt;&#xA;&lt;li&gt;Add more flux (you can never have too much flux).&lt;/li&gt;&#xA;&lt;li&gt;Repeat 7 and 8 for all sides of the chip.&lt;/li&gt;&#xA;&lt;li&gt;Add flux, clean the tip on the sponge, and touch the tip to the bridge.  Solder should stick to the tip.  Repeat until bridges are gone.&lt;/li&gt;&#xA;&lt;li&gt;In bad cases, careful use of a solder wick can help.  But be careful because it is easy to bend the pins and then you're, um, hosed.&lt;/li&gt;&#xA;&lt;li&gt;Clean the flux off.  Some flux can be conductive, like the water soluble flux, so make sure it's clean (and dry) before powering up.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I should mention that my soldering iron has a straight, but angled tip.  It's often called a chisel tip.  This tip makes it easy to do everything from 1206's, 0402's, TQFP's, TSSOP's, etc.  It just doesn't work for BGA's, QFN's, and some of the weirder things.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-05T02:53:47.623" CommentCount="2" />
  <row Id="12568" PostTypeId="2" ParentId="12565" CreationDate="2011-04-05T02:59:36.263" Score="7" ViewCount="" Body="&lt;p&gt;Use less solder, lots of flux, and practice.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Consider pre-soldering the pads on the PCB. Cover the area with some flux, and use your iron to push a bead of solder over the necessary pads. It is surprising (or was to me) how little solder was necessary.  After the small amount of extra solder you have added to the pads have cooled, add a little more flux, place your device, and use just your iron to attach.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It takes practice, and it seems everybody prefers something a little different.  I learned by watching and reading some of the superb sparkfun tutorials and other random youtube videos.  I think watching other people in action is the best way to learn. &lt;/p&gt;&#xA;" OwnerUserId="3729" LastActivityDate="2011-04-05T02:59:36.263" />
  <row Id="12569" PostTypeId="2" ParentId="12543" CreationDate="2011-04-05T03:09:01.357" Score="1" ViewCount="" Body="&lt;p&gt;I'm a high school student. A good basic introduction is the &lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=9780596153748&quot; rel=&quot;nofollow&quot;&gt;MAKE: Electronics&lt;/a&gt; book. It teaches you hands-on. The handbook I use for my Electronics class is Teach Yourself Electricity and Electronics by Stan Gibilisco. It's good, if not dry. Another good way to learn it is to become a Ham Radio operator. That's how I learned the meat of my electronics.&lt;/p&gt;&#xA;" OwnerUserId="3597" LastActivityDate="2011-04-05T03:09:01.357" />
  <row Id="12571" PostTypeId="2" ParentId="12565" CreationDate="2011-04-05T03:59:46.697" Score="0" ViewCount="" Body="&lt;p&gt;You can try to wrap some steel wire around the shaft of your iron, and use that as a makeshift extension. Clamping a sewing needle to the shaft worked for me, too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need lots of flux, less solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If even that fails, and you need to solder some really tricky stuff like BGAs, I have some other tricks in the box, like stove-soldering, etc. Those tricks are likely to break your hardware, so I'm not gonna advice them before suggesting the needle-trick.&lt;/p&gt;&#xA;" OwnerUserId="2134" LastActivityDate="2011-04-05T03:59:46.697" CommentCount="1" />
  <row Id="12572" PostTypeId="2" ParentId="3821" CreationDate="2011-04-05T04:15:48.563" Score="1" ViewCount="" Body="&lt;p&gt;dude,u can use 1N5822 schottky diode they r rated at 3Amp and as they are schottky diode they do not have a stage from where they have to return.&lt;/p&gt;&#xA;" OwnerUserId="3731" LastActivityDate="2011-04-05T04:15:48.563" />
  <row Id="12573" PostTypeId="2" ParentId="12269" CreationDate="2011-04-05T04:48:24.783" Score="1" ViewCount="" Body="&lt;p&gt;It's possible that the frequency that you're trying to produce is out of the range of the 555.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm also not entirely sure that this signal as actually pure AM. I may be wrong, though. I've been trying to figure it out for myself. It might be a form of direct modulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. Nice use of LabVIEW.&lt;/p&gt;&#xA;" OwnerUserId="3597" LastActivityDate="2011-04-05T04:48:24.783" CommentCount="1" />
  <row Id="12574" PostTypeId="2" ParentId="12543" CreationDate="2011-04-05T06:53:05.063" Score="0" ViewCount="" Body="&lt;p&gt;Fix stuff. Get all kinds of broken electronic things and figure out how to fix them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.edn.com/archives/1995/020295/03df4.htm&quot; rel=&quot;nofollow&quot;&gt;&quot;Oh boy, it's broken! Life doesn't get any better than this.&quot;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure you don't do unsafe things (mains voltage is deadly, for example, and microwave ovens are no toys and present numerous safety issues when the cover is removed), but otherwise, go and fix whatever you can.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-05T07:21:58.020" LastActivityDate="2011-04-05T07:21:58.020" />
  <row Id="12575" PostTypeId="2" ParentId="12422" CreationDate="2011-04-05T07:02:53.307" Score="1" ViewCount="" Body="&lt;p&gt;If you can't find a proper part in your area, then you might end up with a micro and software based DDS like &lt;a href=&quot;http://www.myplace.nu/avr/minidds/index.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;. Small AVR and resistor ladder is all it takes.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-04-05T07:02:53.307" />
  <row Id="12576" PostTypeId="1" CreationDate="2011-04-05T07:04:31.607" Score="3" ViewCount="117" Body="&lt;p&gt;I am interested in buying a micro controller to start playing around with electronics this summer. So far i have learned about the Arduino. Are there any other options? What do you suggest as a good first micro controller? Or it doesn't really matter for a beginner which board to get?&lt;/p&gt;&#xA;" OwnerUserId="3689" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-05T13:29:14.790" LastActivityDate="2011-04-06T10:29:02.430" Title="Need advice on which micro controller to get for a total newbie." Tags="&lt;arduino&gt;" AnswerCount="3" FavoriteCount="0" />
  <row Id="12577" PostTypeId="2" ParentId="12526" CreationDate="2011-04-05T07:10:35.190" Score="1" ViewCount="" Body="&lt;p&gt;If you need fast switching (up to 50-60Hz), you can take a look at solid state relays. They don't produce a &quot;click&quot; like mechanical ones, but this feature comes with a price...&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-04-05T07:10:35.190" />
  <row Id="12578" PostTypeId="2" ParentId="9645" CreationDate="2011-04-05T07:20:24.250" Score="0" ViewCount="" Body="&lt;p&gt;Your graphics card driver can put windowed video played in a video player to some external monitor or TV in full screen. If we are not talking about video, but just a window of some software application running on your pc, then you can use &lt;a href=&quot;http://www.uvnc.com&quot; rel=&quot;nofollow&quot;&gt;UltraVNC&lt;/a&gt; and share just that single window for displaying on remote pc.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-04-05T07:20:24.250" />
  <row Id="12579" PostTypeId="2" ParentId="12576" CreationDate="2011-04-05T07:35:24.350" Score="6" ViewCount="" Body="&lt;p&gt;As far as a &quot;starter&quot; system goes, it's hard to beat Arduino. It has a nice programming environment. You can also get many useful circuits that connect to it (called &quot;shields&quot;), meaning that you can start doing something useful right away instead of getting stranded in the electronics tar-pit. There is also a large community of enthusiasts that can function as a support mechanism.&#xA;If you are just sarting out, with little experience in electronics or embedded programming, I would definitely get my feet wet with an Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are other options of course. If you want a more hands-on approach, I really like &lt;a href=&quot;http://www.nerdkits.com/&quot; rel=&quot;nofollow&quot;&gt;Nerdkits&lt;/a&gt;. Their kits will guide you as you assemble a complete microcontroller system yourself from basic components, with no magic circuit boards or software. They also have lots of tutorials.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both Arduino and the Nerdkits are AVR-based. If you need your microcontrollers with a bit more punch, there is also &lt;a href=&quot;http://www.mbed.org/&quot; rel=&quot;nofollow&quot;&gt;MBED&lt;/a&gt;. MBED is a small but very full-featured board with an ARM processor that can be programmed using an on-line programming environment. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you give me a better idea of your aims (what project you want to be able to do with it) and your skill level, I can fine-tune the recommendations a bit more.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-04-05T07:35:24.350" />
  <row Id="12580" PostTypeId="2" ParentId="12422" CreationDate="2011-04-05T07:48:43.143" Score="0" ViewCount="" Body="&lt;p&gt;I encounted this issue about one year ago trying to source an analogue function generator and noticed that they are generally obsolete or not for new design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also had a restriction that prevented the use of a microcontroller for the design.  In the end I settled on 555 timer with supporting components and was able to obtain a reasonably precise sawtooth generator.  It worked well, and took a few attempts to get my calculations correct, in the end the result was ideal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a 555 timer you can use it to generate various waveforms and it does not require any digital components.&lt;/p&gt;&#xA;" OwnerUserId="1397" LastActivityDate="2011-04-05T07:48:43.143" />
  <row Id="12581" PostTypeId="1" AcceptedAnswerId="12585" CreationDate="2011-04-05T08:10:15.707" Score="0" ViewCount="49" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I read in a datasheet that the Input sensitivity of the AD4002 (RFin) is -10dBm to 0dBm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know how to convert this to a voltage drop over a resistor, say 50ohm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I got myself confused over the exact definition of input sensitivity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it the power that should flow into the pin of the chip?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or is it the power delivered to a 50ohm termination resistor on the input?&lt;/p&gt;&#xA;" OwnerUserId="3041" LastActivityDate="2011-04-05T09:41:47.117" Title="RF Input Sensitivity" Tags="&lt;rf&gt;" AnswerCount="1" />
  <row Id="12582" PostTypeId="1" CreationDate="2011-04-05T08:40:11.433" Score="0" ViewCount="72" Body="&lt;p&gt;I am implementing the DQPSK modulator and Demodulator. I was successful in implementing the DQPSK modulator. But, unfortunately, I could not recover the samples from the modulated signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the help indicates and I quote, &quot;If the Output type parameter is set to Integer, then the block maps a phase difference of&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Theta + pi*m/2&lt;/p&gt;&#xA;&#xA;&lt;p&gt;to m, where Theta is the Phase rotation parameter and m is 0, 1, 2, or 3.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you please suggest me the steps to recover the samples.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is what I am doing,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Code&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Data =[2 0 0 1 2 3 2 3 2 0 3 1 1 1 ];&#xA;&#xA;Theta=pi/4;&#xA;&#xA;for i=1:length(Data)&#xA;&#xA;if(i==1) &#xA;      DQPSK_Sig(i)=exp(1j*Theta+1j*pi*Data(i)/2);&#xA;else&#xA;      DQPSK_Sig(i)=DQPSK_Sig(i-1)*exp(1j*Theta+1j*pi*Data(i)/2);&#xA;end &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;end&lt;/p&gt;&#xA;&#xA;&lt;p&gt;%%%Demodulation&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;for i=1:length(DQPSK_Sig)&#xA;&#xA;if(i==1) &#xA;  theta(i)=angle(DQPSK_Sig(i));&#xA;else&#xA;  theta(i)=angle(DQPSK_Sig(i))-theta(i-1);&#xA;end&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;end&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;" OwnerUserId="3733" LastActivityDate="2011-04-05T08:40:11.433" ClosedDate="2011-04-26T00:59:42.007" Title="QPSK Demodulation" Tags="&lt;communication&gt;&lt;matlab&gt;&lt;modulation&gt;&lt;demodulation&gt;" CommentCount="2" />
  <row Id="12583" PostTypeId="1" CreationDate="2011-04-05T09:17:44.317" Score="1" ViewCount="76" Body="&lt;p&gt;I wand to make a simple stereo 4-band EQ for a mid-fi amp I'm building. I draw my knowledge from &lt;a href=&quot;http://www.geofex.com/article_folders/eqs/paramet.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; excellent article - however, it only seems to talk about peak/notch bands and not low and high pass filtering in the context of a graphic EQ.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Could anyone clue me up on circuits for a low-pass and a high-pass band which would fit well in a design such as &lt;a href=&quot;http://www.geofex.com/article_folders/eqs/greq.gif&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;?&lt;/li&gt;&#xA;&lt;li&gt;How can I adapt the schematic to work with 20k pots instead of 100k?&lt;/li&gt;&#xA;&lt;li&gt;What are some good center frequencies for my EQ?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3075" LastActivityDate="2011-04-05T10:12:05.470" Title="Schematic for 4-band stereo equalizer?" Tags="&lt;audio&gt;&lt;filter&gt;&lt;frequency&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="12584" PostTypeId="2" ParentId="12576" CreationDate="2011-04-05T09:27:28.907" Score="2" ViewCount="" Body="&lt;p&gt;Check this article out, it covers most of the development boards on the market.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2011/02/01/what-development-board-to-use/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2011/02/01/what-development-board-to-use/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that it is proper to call &quot;microcontroller&quot; only the chip (AVR, PIC, Cortex, Propeller, 8051, what have you). Otherwise, bad things happen.&lt;/p&gt;&#xA;" OwnerUserId="3075" LastActivityDate="2011-04-05T09:27:28.907" />
  <row Id="12585" PostTypeId="2" ParentId="12581" CreationDate="2011-04-05T09:36:33.623" Score="3" ViewCount="" Body="&lt;p&gt;dBm is power relative to 1 mW , so 0 dBM is 1 mW of input power to the device. You need to know the input impedance of the device to calculate the voltage level of the input signal. If it is 50 ohms, you don't put a 50 ohm resistor across the input.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-05T09:41:47.117" LastActivityDate="2011-04-05T09:41:47.117" CommentCount="4" />
  <row Id="12586" PostTypeId="1" AcceptedAnswerId="12587" CreationDate="2011-04-05T09:44:57.740" Score="1" ViewCount="53" Body="&lt;p&gt;Say I have a 16-bit DAC which outputs a range from 0-5V. My application only requires an output from 4-5V. I am interested in the effective precision of the DAC due to this range restriction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the formula 16 - log((5 - 0)/(5 - 4))/log(2) = 13.68 bits valid?&lt;/p&gt;&#xA;" OwnerUserId="2897" LastActivityDate="2011-04-05T10:03:23.450" Title="Calculating effective bit precision of DAC due to range restriction" Tags="&lt;dac&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12587" PostTypeId="2" ParentId="12586" CreationDate="2011-04-05T10:03:23.450" Score="3" ViewCount="" Body="&lt;p&gt;I think your result is correct. A 16 bit DAC has 2^16 = 65536 steps, but over 5V range. You are only using 1/5 of the range, so are using 13107 steps. Since 2^14 = 16384 it is clearly a bit less than 14 bits. &lt;a href=&quot;http://en.wikipedia.org/wiki/Binary_logarithm&quot; rel=&quot;nofollow&quot;&gt;Log base 2 (n) = log (n)/ log (2)&lt;/a&gt; so log base 2(13107) = 13.68 bits.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-04-05T10:03:23.450" CommentCount="1" />
  <row Id="12588" PostTypeId="2" ParentId="12583" CreationDate="2011-04-05T10:12:05.470" Score="1" ViewCount="" Body="&lt;p&gt;A graphic EQ doesn't usually have LP &amp;amp; HP sections (otherwise it wouldn't be graphic). The schematic in your link is a 7 section EQ with sections from about 60Hz to 15kHz. To maintain these extremes with a four-section EQ, you would need two intermediate sections with frequencies of about 400Hz and 2.4kHz to maintain equal logarithmic spacing. These would need these capacitors :-&lt;/p&gt;&#xA;&#xA;&lt;p&gt;400Hz  -&gt; C1=15nF, C2=150nF&lt;br /&gt;&#xA;2400Hz -&gt; C1=2n7,  C2=27nF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(These are the nearest E24 preferred values and are approximate).&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-04-05T10:12:05.470" CommentCount="3" />
  <row Id="12589" PostTypeId="1" AcceptedAnswerId="12590" CreationDate="2011-04-05T10:21:08.813" Score="4" ViewCount="54" Body="&lt;p&gt;I'm new to this area and know very little about electrons and how electrical components work. I'm always curious about Inverter/UPS usage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm from India and we have a &lt;a href=&quot;http://www.microtekdirect.com/upseb_1400va.php&quot; rel=&quot;nofollow&quot;&gt;inverter&lt;/a&gt; at home. It is attached with two batteries which will supply the power for my home for 8 hours (TV, 4 ceiling fans, 4 lights). When there is interruption in power supply I drain out the inverter completely and when power comes back it gets charged fully in 2 hours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was always thinking that if it can charge up fully in 2 hours and supply power for 8 hours then I can save electricity for 6 hours which I'm paying to supplier by disconnecting power supply after my inverter charge up completely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this is silly thinking but I want to have some explanation from experts saying that my thinking is incorrect, because if that happens then everyone in this world can save lot of power.&lt;/p&gt;&#xA;" OwnerUserId="3734" LastActivityDate="2011-04-05T10:39:53.047" Title="Voltage used to charge a UPS-Inverter and its usage" Tags="&lt;voltage-measurement&gt;&lt;inverter&gt;&lt;ups&gt;&lt;charge&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12590" PostTypeId="2" ParentId="12589" CreationDate="2011-04-05T10:39:53.047" Score="4" ViewCount="" Body="&lt;p&gt;Electricity isn't simply on or off... you're missing the quantity of electricity which is measured in Amperes (Amps for short).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, while your UPS is charging, it's using lots of electricity to charge your UPS storing a large amount of power as well as the relativity small quantity of electricity powering your house.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the power is switched off, your UPS is just providing the relativity small quantity of electricity for your home appliances.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, in the space of time it takes to charge your UPS, your electric company will charge you the cost of 8 hours worth of electricity, plus 2 hours of normal use, plus a tiny bit extra for the inefficiency of your UPS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do this, it will likely cost slightly more than you are paying now, due to the UPS inefficiencies.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-04-05T10:39:53.047" CommentCount="2" />
  <row Id="12591" PostTypeId="2" ParentId="12550" CreationDate="2011-04-05T11:04:21.483" Score="6" ViewCount="" Body="&lt;p&gt;The simplest way would be probably to buy a USB power adapter (probably not from Apple but a cheap replacement) and use this (preferably without removing it from the casing to avoid any electric shock hazards).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are not experienced with electronics I would suggest against making you own power line switched-mode power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also easily do a small transformer based supply but it will be quite a lot heavier and larger than the USB &quot;chargers&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For mass-market solutions you may check &lt;a href=&quot;http://www.powerint.com/products/product-archive/linkswitch&quot; rel=&quot;nofollow&quot;&gt;LinkSwitch&lt;/a&gt; chips. They are quite cheap and require almost no external components. I am afraid that in small runs you will have a problem with obtaining cheap ferrite power transformers but I would love to be proved wrong on this one.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-05T16:34:15.320" LastActivityDate="2011-04-05T16:34:15.320" CommentCount="3" />
  <row Id="12592" PostTypeId="1" AcceptedAnswerId="12596" CreationDate="2011-04-05T13:38:10.270" Score="6" ViewCount="196" Body="&lt;p&gt;Imagine I have a single-IC switching DC-DC converter which supports input voltage up to 16V, for example a &lt;a href=&quot;http://www.google.com/search?q=LM2727&quot; rel=&quot;nofollow&quot;&gt;LM2727&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I stack the inputs of such converter in series, for example 64 of them, and be able to apply up to 1024V across the combined input?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need lots of stable 3.6V outputs anyway (for charging each cell in a multi-cell battery separately).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And on the output side, can I put a 3.6V cell between the outputs of each DC-DC converter and then connect all the batteries in series - will that be fine, or everything will blow-up?&lt;/p&gt;&#xA;" OwnerUserId="1691" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-05-13T00:03:38.687" LastActivityDate="2011-05-13T00:03:38.687" Title="is it OK to stack several DC-DC converters with their inputs connected in series to support a larger input voltage?" Tags="&lt;power-supply&gt;&lt;dc-dc&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="12594" PostTypeId="1" AcceptedAnswerId="12693" CreationDate="2011-04-05T13:56:30.963" Score="4" ViewCount="96" Body="&lt;p&gt;I have large amounts of inductors and transformers from power supplies or other undocumented sources. They are of course completely unmarked and I have no idea what kind of ferrite material they are made of but sometimes I would like to use them in one-off power supplies or other experiments since ferrite cores are quite expensive to buy in low quantities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you know of any good methods to determine the important characteristics of the cores?&#xA;$A_L$ is quite easy (I just wind $N = 10$ turns and measure the inductance using $L = N² * A_L$) but what about $B_\rm{max}$ or maximum useful frequency? Are there other parameters I should have in mind?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically I like to know all the good tricks you know for determining suitability of cores of unknown origin. :)&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-06T20:08:58.370" LastActivityDate="2011-04-06T20:08:58.370" Title="Measuring ferrite core parameters" Tags="&lt;power-supply&gt;&lt;measurement&gt;&lt;inductor&gt;&lt;ferrite&gt;&lt;metrology&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="12595" PostTypeId="2" ParentId="12523" CreationDate="2011-04-05T14:26:37.103" Score="1" ViewCount="" Body="&lt;p&gt;I'm not positive, but I'm offering what I think is another potential answer to my question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, I'm not sure why I had such a hard time finding the correct datasheet initially, but the MSP430G2231 datasheet is &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/msp430g2231.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/zeCRf.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From this datasheet, page 6 clearly lists the functions of each pin.  It turns out that while XIN and XOUT are the default functions for pins 13 and 12, respectively, they can also be configured as GPIO.  Sweet!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So TX and RX can be used for the software serial UART, where sample code is found &lt;a href=&quot;http://e2e.ti.com/cfs-file.ashx/__key/CommunityServer-Components-PostAttachments/00-00-28-69-22/msp430g2xx1_5F00_ta_5F00_uart9600.c&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  I can bitbang the 4 bit bus on the LCD using P1.4,P1.5,P1.6, and P1.7, which are conveniently contiguous.  E, RS, and RW can be controlled by P1.3, P2.6, and P2.7.  I even end up with an extra I/O, so I can just keep P1.0 connected to the LaunchPad's LED for extra debugging info!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd be interested to hear some comments about this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- on another note, it looks like the TEST and RST pins are used for Spy-Bi-Wire.  Isn't that what TI uses on the LaunchPad for communication with the FET?&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-05T14:26:37.103" />
  <row Id="12596" PostTypeId="2" ParentId="12592" CreationDate="2011-04-05T14:57:12.480" Score="5" ViewCount="" Body="&lt;h1&gt;Connecting the chargers in series&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;Connecting several such switchers in series will be a problem since they would have to share the same supply current (all would have to draw the same current all the time). All the chargers have some input resistance which vary according to their immediate needs. If one of the chargers draws less current then:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;It's input resistance rises so it will get less current.&lt;/li&gt;&#xA;&lt;li&gt;This causes the voltage on this charger to rise.&lt;/li&gt;&#xA;&lt;li&gt;Other chargers get lower a little lower voltage and when they &quot;notice&quot; it they lower their input resistances to get the required current.&lt;/li&gt;&#xA;&lt;li&gt;This effect is highly unstable. Eventually only one charger (unfortunately the one that requires the least power) will get all the input voltage and (most probably) be destroyed.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;To verify this logic assume that one charger finished charging and does not need any current at all. The same thing happens.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only way out is to dissipate excess (unneeded at the moment) power but that is probably not something you would like to do. :)&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;High input voltage SMPS&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;A single SMPS supply working from 1000V input is also quite difficult to do since most MOSFETs and IGBTs are only rated up to 1200V. A 600V supply should be doable.&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Output current regulation in multiple-output SMPS&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;You could do a multi-output transformer based switched supply and regulate the output voltages and currents with a &lt;a href=&quot;http://sparkbangbuzz.com/mag-amp/mag-amp.htm&quot; rel=&quot;nofollow&quot;&gt;magnetic amplifier&lt;/a&gt; (this &lt;a href=&quot;http://www.ferroxcube.com/appl/info/square.pdf&quot; rel=&quot;nofollow&quot;&gt;Ferroxcube flyer&lt;/a&gt; is a proof that this is used in real circuits)&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-05T15:27:46.490" LastActivityDate="2011-04-05T15:27:46.490" CommentCount="2" />
  <row Id="12597" PostTypeId="1" AcceptedAnswerId="12638" CreationDate="2011-04-05T15:09:52.177" Score="0" ViewCount="58" Body="&lt;p&gt;hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;could anyone please explain to me what are the CTRL and PROG pins in &lt;a href=&quot;http://www.xilinx.com/itp/3_1i/data/common/jtg/dppb/appb.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; schematic good for? with CTRL i know what does it do but i don't much get the purpose, so far i would say it's there just to make the schematic look nice..&lt;/p&gt;&#xA;" OwnerUserId="3736" LastEditorUserId="3736" LastEditorDisplayName="" LastEditDate="2011-04-05T15:21:49.327" LastActivityDate="2011-04-06T00:06:17.460" Title="xilinx jtag cable" Tags="&lt;schematics&gt;&lt;jtag&gt;" AnswerCount="1" />
  <row Id="12598" PostTypeId="2" ParentId="12543" CreationDate="2011-04-05T15:40:34.987" Score="0" ViewCount="" Body="&lt;p&gt;When I was in high school my understanding of electricity was very flawed.  I eventually worked out my misunderstandings in college, but if I had done it sooner I could have built actually working circuits earlier, instead of just being confused.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think this list of &lt;a href=&quot;http://amasci.com/miscon/elect.html&quot; rel=&quot;nofollow&quot;&gt;Electricity misconceptions&lt;/a&gt; is really helpful to read.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-04-05T15:40:34.987" />
  <row Id="12599" PostTypeId="2" ParentId="12291" CreationDate="2011-04-05T16:21:14.780" Score="0" ViewCount="" Body="&lt;p&gt;An additional advantage of a device like the PSoC is that you can reconfigure the digital and analog blocks during runtime.  This lets you get a lot more functionality out of the chip with fewer pins.&lt;/p&gt;&#xA;" OwnerUserId="3726" LastActivityDate="2011-04-05T16:21:14.780" />
  <row Id="12600" PostTypeId="1" AcceptedAnswerId="12696" CreationDate="2011-04-05T16:29:03.450" Score="5" ViewCount="242" Body="&lt;p&gt;I see recommendations of 2-4 mils for solder mask expansion.  But why is it necessary?&lt;/p&gt;&#xA;" OwnerUserId="1278" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T20:32:03.340" LastActivityDate="2011-04-27T20:32:03.340" Title="What is the purpose of solder mask expansion?" Tags="&lt;pcb&gt;&lt;solder-mask&gt;" AnswerCount="5" FavoriteCount="1" />
  <row Id="12601" PostTypeId="1" AcceptedAnswerId="12608" CreationDate="2011-04-05T16:35:43.480" Score="2" ViewCount="148" Body="&lt;p&gt;I'm looking into developing battery-powered software using the EFM Gekko controllers (http://energymicro.com/) and would like the controller to be asleep whenever there's nothing useful for it to be doing.  The WFI (Wait For Interrupt) instruction is used for this purpose; it will put the processor to sleep until an interrupt occurs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If sleep were engaged by storing something someplace, one could use load-exclusive/store-exclusive operations to do something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;  // dont_sleep gets loaded with 2 any time something happens that&#xA;  // should force the main loop to cycle at least once.  If an interrupt&#xA;  // occurs that causes it to be reset to 2 during the following statement,&#xA;  // behavior will be as though the interrupt happened after it.&#xA;&#xA;  store_exclusive(load_exclusive(dont_sleep) &gt;&gt; 1);&#xA;&#xA;  while(!dont_sleep)&#xA;  {&#xA;    // If interrupt occurs between next statement and store_exclusive, don't sleep&#xA;    load_exclusive(SLEEP_TRIGGER);&#xA;    if (!dont_sleep)             &#xA;      store_exclusive(SLEEP_TRIGGER);&#xA;  }&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If an interrupt were to occur between the load_exclusive and store_exclusive operations,&#xA;the effect would be to skip the store_exclusive, thus causing the system to run through the loop one more time (to see if the interrupt had set dont_sleep).  Unfortunately, the Gekko uses a WFI instruction rather than a write address to trigger sleep mode; writing code like&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;  if (!dont_sleep)&#xA;    WFI();&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;would run the risk that an interrupt could occur between the 'if' and the 'wfi' and set dont_sleep, but the wfi would go ahead and execute anyway.  What's the best pattern to prevent that?  Set PRIMASK to 1 to prevent interrupts from interrupting the processor just before executing the WFI, and clear it immediately after?  Or is there some better trick?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;B&gt;EDIT&lt;/b&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wondering about the Event bit.  By the general description, it woulds like it's intended for multi-processor support, but was wondering whether something like the following might work:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;  if (dont_sleep)&#xA;    SEV();  /* Will make following WFE clear event flag but not sleep */&#xA;  WFE();&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Every interrupt that sets don't_sleep should also execute an SEV instruction, so if the interrupt happens after the &quot;if&quot; test, the WFE would clear the event flag but not go to sleep.  Does that sound like a good paradigm?&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-04-05T19:45:34.553" LastActivityDate="2011-04-05T19:45:34.553" Title="Best pattern for WFI (wait-for-interrupt) on Cortex (ARM) microcontrolers" Tags="&lt;arm&gt;&lt;cortex-m3&gt;&lt;sleep&gt;" AnswerCount="1" CommentCount="7" FavoriteCount="1" />
  <row Id="12602" PostTypeId="1" CreationDate="2011-04-05T16:37:13.213" Score="0" ViewCount="166" Body="&lt;p&gt;The power rating on the bulb is the amount of power the PSU has to deliver in order for the bulb to light up the brightest right? Hence if it's a 40w bulb I need 40watts of power for it to light up properly right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If so then my dilema is I have 15 or so light bulbs which need to be switched on and off invididually. The only way I can think of is using a relay but that means 15 relays!! It's turn on and off by a microcontroller which switches the relay on and off. I need to use bulbs because the person am doing it for insists on bulbs&lt;/p&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-05T23:08:28.163" LastActivityDate="2011-04-06T15:08:05.947" Title="How to switch many (15) low power (40W) lightbulbs from a microcontroller?" Tags="&lt;microcontroller&gt;&lt;switch&gt;&lt;circuit-design&gt;&lt;line-power&gt;" AnswerCount="5" CommentCount="4" />
  <row Id="12603" PostTypeId="2" ParentId="12600" CreationDate="2011-04-05T16:38:35.647" Score="4" ViewCount="" Body="&lt;p&gt;Solder resist masks are plotted oversize to allow for mask shrinkage, movement and inaccuracies, according to the manual for the Pulsonix PCB software I use. The default value is 5 mil.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-05T16:38:35.647" />
  <row Id="12604" PostTypeId="2" ParentId="12602" CreationDate="2011-04-05T16:46:55.877" Score="3" ViewCount="" Body="&lt;p&gt;You can use either relays or triacs (with optoisolation). There are no easier or cheaper ways around this.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-05T16:46:55.877" />
  <row Id="12605" PostTypeId="2" ParentId="12602" CreationDate="2011-04-05T16:47:21.443" Score="5" ViewCount="" Body="&lt;p&gt;You seem to be asking two different questions here...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Do I need 40w of power to light up a 40w bulb?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Answer: yes you do, if it's less then the bulb will be dim or not light at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;How do I switch 15 bulbs independently using a microcontroller?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Answer: yes, you can either use relays as a nice simple solution. But if you need to switch them quickly, or many times over a long period of time then you should use solid state relays or triacs.&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-04-05T16:47:21.443" CommentCount="0" />
  <row Id="12606" PostTypeId="1" AcceptedAnswerId="12631" CreationDate="2011-04-05T16:48:57.783" Score="6" ViewCount="302" Body="&lt;p&gt;I have seen dozens of different real-time clock chips on the market, as well as a number of processors with a built-in separately-powered real-time clock module.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nearly all of them not only store time as year-month-day-hours-minutes-seconds, but even the individual fields are stored in BCD rather than binary format.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there some underlying reason for this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any microprocessor applications that do anything more sophisticated than simply display a clock where the BCD format is more useful than binary, or where year-month-day-hour-minutes-seconds format would be more useful than a straight 47-bit count of oscillator state changes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I can tell, it seems RTCC makers add a lot of extra circuitry to make their chips less useful; the only reason I can figure for RTCC modules in processors to behave that way is that the processor vendors use some pre-existing BCD implementation rather than producing their own.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-05T16:53:33.723" LastActivityDate="2011-04-08T21:05:23.970" Title="Why do real-time clock chips use BCD" Tags="&lt;rtc&gt;" AnswerCount="6" CommentCount="2" FavoriteCount="3" />
  <row Id="12607" PostTypeId="2" ParentId="12606" CreationDate="2011-04-05T17:14:36.560" Score="2" ViewCount="" Body="&lt;p&gt;When using clocks in the end you're more likely to be interested in minutes and tens of seconds(towards displaying them) than just the total of seconds, minutes and so on. In case you're not interested in separate digits chances are that you don't care about separate minutes or seconds values either, and that you might as well use a long binary counter like you suggested.&lt;br&gt;&#xA;It's easier to convert from BCD to binary in software than the other way around. And since BCD counters don't require that much extra real estate over binary counters it makes sense to choose for BCD.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-05T17:14:36.560" CommentCount="7" />
  <row Id="12608" PostTypeId="2" ParentId="12601" CreationDate="2011-04-05T17:38:16.523" Score="1" ViewCount="" Body="&lt;p&gt;If you disable interrupts before going into WFI, who will enable them while the CPU is sleeping? I don't think it's a good idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did not fully understand the dont_sleep thing, but one thing you could try is do the &quot;main work&quot; in the PendSV handler, set to the lowest priority. Then just schedule a PendSV from other handlers each time you need something done. &lt;a href=&quot;http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0395b/CIHJHFJD.html&quot; rel=&quot;nofollow&quot;&gt;See here&lt;/a&gt; how to do it (it's for M1 but M3 is not too different).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing you could use (maybe together with the previous approach) is the Sleep-on-exit feature. If you enable it, the processor will go to sleep after exiting the last ISR handler, without you having to call WFI. See some examples &lt;a href=&quot;http://infocenter.arm.com/help/topic/com.arm.doc.ddi0337e/ch05s09s02.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1082" LastActivityDate="2011-04-05T17:38:16.523" CommentCount="4" />
  <row Id="12609" PostTypeId="2" ParentId="12404" CreationDate="2011-04-05T17:50:02.273" Score="2" ViewCount="" Body="&lt;p&gt;This is the best method I have come up with recently:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the build options, select create batch file.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you initiate a build from the IDE, a batch file along with several text files are created based on the options set in the IDE.  You need to track these IDE generated files in source control:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;*.bat&lt;/li&gt;&#xA;&lt;li&gt;*.ini&lt;/li&gt;&#xA;&lt;li&gt;*.__i&lt;/li&gt;&#xA;&lt;li&gt;*._ia&lt;/li&gt;&#xA;&lt;li&gt;*.lnp&lt;/li&gt;&#xA;&lt;li&gt;*.sct&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Then foo.bat can be launched from a build script.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While this does create extra files that need to tracked in source control if you want to build reliably from the generated batch file, it does remove the need to rely on the Keil project file (foo.uvproj) and the IDE.  I find it easier to compare differences, and thus track changes, to the generated text files (*.__i) that contain compiler flags than to the .uvproj file.  Additionally, the batch file calls the various tools, armasm, armcc, armlink, directly.  This gives you the direct output of each of those steps as well as a seemingly better potential for migrating a project to a different tool chain in the future if necessary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I realize this answer sounds a lot like my original question, but I genuinely don't know of a better way of running a scripted build with Keil's tools.  I asked to see what might come up from others.  I don't completely disagree with the answer from @digikata, but I prefer to have compiler flags and the memory map in an easier format for tracking and to use more unix-style tools for compilation rather than launching an all-in-one compilation with the IDE.  I think the all-in-one compilation from the IDE works well at my workstation, but not for the build server.&lt;/p&gt;&#xA;" OwnerUserId="3346" LastActivityDate="2011-04-05T17:50:02.273" />
  <row Id="12610" PostTypeId="2" ParentId="12606" CreationDate="2011-04-05T18:07:00.150" Score="3" ViewCount="" Body="&lt;p&gt;I suspect several reasons:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Historical - they've been doing it this way for some time now. If you want your new part to replace some other part, then it has to more-or-less work the same. So you keep with the BCD.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Application - if someone is using an RTC from a small micro (something in the 8 bit range, like a low-end PIC), then dealing with a large number (such as your 47 bit counter) is a big pain in the neck. It's MUCH easier to deal with the BCD digits, as you don't have to work at breaking things up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not that hard - Doing the BCD counters isn't that hard, and in fact I think it isn't many more gates than doing them binary. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One can imagine a system where you get separate hour, minute, etc counters in binary instead of BCD (thus avoiding the 'breaking down the 47 bit number' issue), but it's not that much easier, and you're going to do some conversions when displaying the thing anyway.&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2011-04-05T18:07:00.150" CommentCount="12" />
  <row Id="12611" PostTypeId="2" ParentId="12600" CreationDate="2011-04-05T18:16:18.003" Score="2" ViewCount="" Body="&lt;p&gt;With some designs, you want to make sure that the solder mask is never on top of SMD pads. This is especially critical with QFN or LGA packages where the contacts of the parts don't stick out over the plastic molding or with parts that have a very fine pitch: Even small registration issues would cause the solderable areas of the tiny pads to become even more tiny.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-04-05T18:16:18.003" />
  <row Id="12612" PostTypeId="1" AcceptedAnswerId="12617" CreationDate="2011-04-05T18:23:52.740" Score="3" ViewCount="93" Body="&lt;p&gt;It is easy to make a meter which will show the engine RPM, many cars have one installed. But to know the power in kW that the engine is providing right now, I also need to know the torque, because:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$power = RPM * torque/9548.8$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Besides RPM all in metric units (kW, Nm). BTW, does anyone know how the 9548.8 number is derived?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But back to my main question: is it possible to install some measuring device which will measure and show in real time the torque my diesel engine is providing at the moment? I want to know how many kW is used to move the car in real-time. I want to do something like this with Arduino.&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-04-05T19:45:24.807" Title="is it possible to install some device which will measure in real time the torque my diesel engine is providing at the moment?" Tags="&lt;power&gt;&lt;measurement&gt;&lt;automotive&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="12613" PostTypeId="2" ParentId="12612" CreationDate="2011-04-05T18:44:02.507" Score="2" ViewCount="" Body="&lt;p&gt;I'm guessing that it would be difficult to install a torque sensor in most cars without disassembling the thing.  I imagine that you'd have to place load cells in the most awkward locations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But...  There are devices out there that can measure horsepower, speed, etc by using accelerometers.  You can even get an iPhone app to do it.  You can't get RPM from that, but connecting to the OBDII port or doing something like &lt;a href=&quot;http://www.proamauto.com/gtech.htm&quot; rel=&quot;nofollow&quot;&gt;what this device does&lt;/a&gt; could work.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-05T18:44:02.507" CommentCount="3" />
  <row Id="12615" PostTypeId="2" ParentId="12592" CreationDate="2011-04-05T18:55:47.800" Score="1" ViewCount="" Body="&lt;p&gt;&lt;em&gt;Edit: I completely misread your question. I think this is still applicable, though:&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, it sounds like you want to &quot;stack&quot; the inputs/outputs of these converter IC's, which I would describe as more of a parallel combination rather than a series combination, although I do not think that either term really describes this arrangement perfectly. From what I know about the various popular DC-DC converter topologies, my intuition tells me that this would fail, although to fully explain why would take a bit of digging and explanation and circuit theory (probably). Maybe someone else can provide a concise answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Edit: I am not actually sure all of the following would apply to the proposed arrangement, since your switches may share the combined 1kV and therefore no one switch would have the full magnitude of the input voltage across it.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A final note: 1kV is really high and generally super dangerous. In order to deal with this kind of voltage, all your switches (probably most of your other components as well) would need to be rated to this voltage, as would your PCB, etc. I'm guessing you were exaggerating on that number in order to get your point across.&lt;/p&gt;&#xA;" OwnerUserId="3635" LastEditorUserId="3635" LastEditorDisplayName="" LastEditDate="2011-04-05T19:03:13.270" LastActivityDate="2011-04-05T19:03:13.270" CommentCount="2" />
  <row Id="12616" PostTypeId="1" AcceptedAnswerId="12635" CreationDate="2011-04-05T19:16:13.887" Score="2" ViewCount="114" Body="&lt;p&gt;My friend has asked me to do some marketing for his student targeted company. The hope is to create a good animation/flash video and project this (at night) inside the student campus onto the building. I saw a decent instructable here &lt;a href=&quot;http://www.instructables.com/id/PROJECTION-BOMBING/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/PROJECTION-BOMBING/&lt;/a&gt; but this method involves a car/car battery. We need something more mobile as we will be situated inside the campus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could someone please suggest what power source I could use that would allow me to plug in the laptop and projector. Also could anyone suggest a good affordable projector?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;THanks in advance&lt;/p&gt;&#xA;" OwnerUserId="2889" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-05T23:30:48.560" LastActivityDate="2011-04-06T18:49:01.097" Title="A mobile power source for a laptop and a projector" Tags="&lt;power-supply&gt;&lt;power&gt;&lt;video&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="1" />
  <row Id="12617" PostTypeId="2" ParentId="12612" CreationDate="2011-04-05T19:45:24.807" Score="1" ViewCount="" Body="&lt;p&gt;The power the engine outputs at any given time will vary with the load on the engine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The load on the engine when in normal operation depends on the drive-train efficiency, gear ratio, wheels slippage, the weight of the car, inclines in the road surface, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Real Dynos put a known constant load on the wheels which allows them to calculate horsepower at the wheels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doing this just for the engine would require putting a constant load on the engine, which would mean removing the engine from the car and applying a constant load to the flywheel or having a good estimate for the drive-train efficiency, but that tends to vary over various parameters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best your going to get for a car on the road is an estimation of wheel horsepower.  You can make a decent guess based on the weight of the car and its acceleration.  You could try to make some sort of correction for inclines/declines based on another accelerometer axis.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you wanted to get a guestimate of the flywheel horsepower you can include a factor for drive-train efficiency and adjust for the current transmission gearing.  Alternatively you can estimate based on drive-train efficiency and engine RPM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you wanted to contrast that with the actual energy released in the engine, you can calculate that from fuel flow, amount of air taken in, and measuring residual oxygen in the exhaust using a wideband O2 sensor.  You'd find that a LOT of energy goes straight out the tailpipe.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-04-05T19:45:24.807" CommentCount="6" />
  <row Id="12618" PostTypeId="1" AcceptedAnswerId="12630" CreationDate="2011-04-05T20:38:44.850" Score="6" ViewCount="367" Body="&lt;p&gt;If a hardware doesn't support modulus or division operations, it takes many more CPU cycles to simulate modulus/division by software. &lt;strong&gt;Is there any faster way to calculate division and modulus if the operand is 10?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my project I frequently need to calculate integer modulus 10. In particular, I'm working on PIC16F and need to show a number on an LCD. There are 4 digits to support, so there are 4 calls to modulus and division function (software implementation). That is, like the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;digit = number % 10;    // call to an expensive function&#xA;number /= 10;           // call to an expensive function&#xA;somehow_lit_segments();&#xA;&#xA;digit = number % 10;    // call to an expensive function&#xA;number /= 10;           // call to an expensive function&#xA;somehow_lit_segments();&#xA;&#xA;digit = number % 10;    // call to an expensive function&#xA;number /= 10;           // call to an expensive function&#xA;somehow_lit_segments();&#xA;&#xA;digit = number % 10;    // call to an expensive function&#xA;number /= 10;           // call to an expensive function&#xA;somehow_lit_segments();&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;There are other areas that uses similar code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you.&lt;/p&gt;&#xA;" OwnerUserId="3720" LastActivityDate="2011-04-06T18:48:59.657" Title="Fastest way to get integer mod 10 and integer divide 10?" Tags="&lt;microcontroller&gt;&lt;simulation&gt;&lt;math&gt;&lt;divide&gt;&lt;optimization&gt;" AnswerCount="9" CommentCount="5" FavoriteCount="0" />
  <row Id="12619" PostTypeId="2" ParentId="12618" CreationDate="2011-04-05T21:03:24.010" Score="4" ViewCount="" Body="&lt;p&gt;Assuming unsigned integers, division and multiplication can be formed from bit shifts. And from (integer) division and multiplication, modulo can be derived.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To multiply by 10:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;y = (x &amp;lt;&amp;lt; 3) + (x &amp;lt;&amp;lt; 1);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;To divide by 10 is more difficult. I know of several division algorithms. If I recall correctly, there is a way to divide by 10 quickly using bit shifts and subtraction, but I can't remember the exact method. If that's not true, then &lt;a href=&quot;http://www.piclist.com/techref/microchip/math/div/16by8lz.htm&quot; rel=&quot;nofollow&quot;&gt;this is a divide algorithm which manages &amp;lt;130 cycles&lt;/a&gt;. I'm not sure what micro you're using, but you can use that in some way, even if you have to port it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Somebody &lt;a href=&quot;http://stackoverflow.com/questions/5558492/divide-by-10-using-bit-shifts/5558598#5558598&quot;&gt;says over at Stack Overflow&lt;/a&gt;, if you can tolerate a bit of error and have a large temporary register, this will work:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;temp = (ms * 205) &amp;gt;&amp;gt; 11;  // 205/2048 is nearly the same as /10&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Assuming you have division and multiplication, modulo is simple:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;mod = x - ((x / z) * z)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-04-05T21:46:41.227" LastActivityDate="2011-04-05T21:46:41.227" />
  <row Id="12621" PostTypeId="2" ParentId="12618" CreationDate="2011-04-05T21:07:10.563" Score="1" ViewCount="" Body="&lt;p&gt;I don't have a good answer, but there's a &lt;a href=&quot;http://stackoverflow.com/questions/48053/is-there-an-alternative-to-using-modulus-in-c-c&quot;&gt;great discussion&lt;/a&gt; on our sister site Stack Overflow on the exact same subject of division and modulo optimization.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have enough memory to implement a lookup table?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hackers Delight has &lt;a href=&quot;http://www.hackersdelight.org/divcMore.pdf&quot; rel=&quot;nofollow&quot;&gt;a paper&lt;/a&gt; on optimal division algorithms.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-06T13:20:47.723" LastActivityDate="2011-04-06T13:20:47.723" CommentCount="1" />
  <row Id="12622" PostTypeId="2" ParentId="12291" CreationDate="2011-04-05T21:15:25.040" Score="2" ViewCount="" Body="&lt;p&gt;The beauty of PSoC is that they have a number of useful analog blocks already baked into the chip, so that in many cases, you can just use the processor with very few (and mostly passive) components to have a working product when other MCU's would require a bunch of external parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PSoC also comes with a large library of pre-canned solutions (in the form of software plus wiring diagrams) that allows you to quickly mix-and-match the solutions into a completed product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, just as an example - one PSoC design I made had a 2-axis accelerometer, a TFT LCD, and 8 capacitive sensing input buttons (four used as an iPod style &quot;jog dial&quot;, and 4 other general button presses), an iButton port, and a audio speaker output.  The non-passives on that board consisted only of the accelerometer chip, the FET to drive the speaker, and a 5V-to-3.3V level shifter to interface to the TFT (because we couldn't source a 5V TFT display with the features we wanted).   The opamp circuitry for the accelerometer, the cap sense circuitry, and the various digital blocks were all contained within the PSoC.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-04-05T22:10:38.403" LastActivityDate="2011-04-05T22:10:38.403" />
  <row Id="12623" PostTypeId="2" ParentId="12618" CreationDate="2011-04-05T21:23:58.307" Score="0" ViewCount="" Body="&lt;p&gt;Why optimize? The user can't see the numbers if they update faster than ~10 Hz.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-04-05T21:23:58.307" CommentCount="1" />
  <row Id="12624" PostTypeId="1" AcceptedAnswerId="12625" CreationDate="2011-04-05T21:26:14.260" Score="0" ViewCount="245" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm experiencing a lot of noise in an RS485 network I've put together using ST485 chips. The cable lengths are very short (&amp;lt;1m total cable length), I'm properly biasing the A and B signals and I've tried both with and without a terminator (seems to make no difference), and I'm only running at 19200 baud. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect the problem is ground noise, as I'm using the RS485 input signals to set PWM levels for high-power LEDs (up to 1000mA momentarily at 3.8V). I'm using a four-wire connection between each node (+12V, GND, RS485-A, RS485-B, with the RS485-A &amp;amp; -B a self-twisted pair of hookup wire).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although it's not suggested in the ST485 datasheet, would it be enough to add a signal ground wire between the RS485 device ground inputs, with 100Ω resistors in series between the RS485 device ground and the signal ground wire? Or should I think about adding full isolation to the RS485 device, including a transformer for floating power supply and opto-isolators on the A and B signal lines? Or is this excessive?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt; I know I'm getting noise because in order to get the desired effect (particular brightnesses of particular LED lights), I have to use a CRC-8 on each packet (to drop bad packets at the receiving end) and send every message twice (to make up for dropped bad packets), and even then I'm still getting incorrect packets showing up on the receiving end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt; Removed baud-rate error comments, as baud rate is in fact very accurate.&lt;/p&gt;&#xA;" OwnerUserId="3741" LastEditorUserId="3741" LastEditorDisplayName="" LastEditDate="2011-04-16T22:53:48.107" LastActivityDate="2011-04-16T22:53:48.107" Title="RS485 noise problems: signal ground / common ground / isolation?" Tags="&lt;noise&gt;&lt;rs485&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="12625" PostTypeId="2" ParentId="12624" CreationDate="2011-04-05T21:45:55.100" Score="4" ViewCount="" Body="&lt;p&gt;I'm guessing that the pulsed current draw on the +12v supply is what is putting the noise into the RS-485 signals.  For debugging purposes, try disconnecting the LEDs.  If your noise issues go away then you know that it's that pulsed 1 amp current.  Assuming that's the case, then your job will be to reduce the current spikes on the +12v wire (which are also on the GND wire).  A filter using an inductor+large_cap would help.  Using a different cable where the power is isolated from the data could help too.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-05T21:45:55.100" CommentCount="2" />
  <row Id="12626" PostTypeId="2" ParentId="12624" CreationDate="2011-04-05T21:47:47.797" Score="0" ViewCount="" Body="&lt;p&gt;A 3.8%  error is too high, change your crystal or use a baud rate that has a smaller error. It won't be causing your noise problem, although noise will have more effect than if the error was smaller.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-05T22:09:57.617" LastActivityDate="2011-04-05T22:09:57.617" CommentCount="4" />
  <row Id="12627" PostTypeId="2" ParentId="12600" CreationDate="2011-04-05T21:52:51.813" Score="4" ViewCount="" Body="&lt;p&gt;There are various sources of errors in the plotting and placement of different layers (and holes!) that go into the board.  The board house knows their capabilities/yields, and will tell you the allowance that you have to make for that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That is why they have things like minimum annulus (when the drilled holes end up so off center that it might end up not plating to the pads).  And the solder mask clearance ensures that the worst-case mask placement offset does not end up covering the pad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For simple prototypes, it's usually not a big deal, and you can just use &quot;default numbers&quot; and then tell the board house to accept the clearance violations.  However, for very expensive boards, large runs, et cetra, you should get the exact numbers for all the various clearances to meet the board house's capabilities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that board houses can also have different classes of ever increasing tolerances, and charge different amounts of money.  Unless your product really requires super tight registrations, use as &quot;sloppy&quot; a clearance number as you can afford.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-05T21:52:51.813" CommentCount="2" />
  <row Id="12628" PostTypeId="2" ParentId="12624" CreationDate="2011-04-05T21:53:24.183" Score="0" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;my actual baud is 19966, out by 3.8% - could that be my problem?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I'd tent to say yes, especially if you use 9-Bit master/slave mode. With start and stop makes this 11 Bits that have to come through. Even with &quot;normal&quot; 8 Bit (resulting in 10 Bit transferred) the error should be much smaller than 5%.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;my F_CPU at 8MHz &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;How do you generate this 8 MHz? An &quot;internal clock&quot; usually has 1% or more error.&#xA;With that 1% added, your 3.8% drops &quot;out of the window&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that you also must consider the clock errors of the receiving side. This is why most people use a so called &quot;baud rate quarz&quot;. &lt;/p&gt;&#xA;" OwnerUserId="1472" LastActivityDate="2011-04-05T21:53:24.183" CommentCount="4" />
  <row Id="12629" PostTypeId="2" ParentId="12606" CreationDate="2011-04-05T21:59:50.540" Score="0" ViewCount="" Body="&lt;p&gt;I agree with Michael Kohne that there's a lot of historical momentum.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Early MCU's also had much less space for code and data (think 128 BYTES of RAM, for example).  Since time information is often used for human-interfacing purposes, it made more sense to keep the data closest to the format used to display to/input from humans.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some newer MCU's with more code and data space sometimes implement hardware real time counters -- these devices often keep binary counts of 32kHz ticks.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-05T21:59:50.540" CommentCount="21" />
  <row Id="12630" PostTypeId="2" ParentId="12618" CreationDate="2011-04-05T22:01:56.310" Score="7" ViewCount="" Body="&lt;p&gt;Heres a binary to BCD algorithm I used several years ago based on one found &lt;a href=&quot;http://www.piclist.com/techref/language/ccpp/convertbase.htm&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  I was using an external BCD to 7 seg display driver so the result could be written to the proper ports directly as packed BCD for output.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is fairly fast if you have a hardware multiplier in the PIC, i was using a PIC18F97J60.  If you don't have a hardware multiplier on your PIC, consider using shift + add for the multiplication.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This takes in an unsigned 16bit int and returns packed BCD with 5 digits, it could be modified and made faster for 4 digits.  It uses shift + additions to approximate division by 10 but given the limited input range it is exact for this use.  You may want to pack the result differently as well to line up with how your using the result.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void intToPackedBCD( uint16_t n, uint8_t *digits ) {&#xA;&#xA;    uint8_t d4, d3, d2, d1, d0, q;  //d4 MSD, d0 LSD&#xA;&#xA;    d1 = (n&amp;gt;&amp;gt;4)  &amp;amp; 0xF;&#xA;    d2 = (n&amp;gt;&amp;gt;8)  &amp;amp; 0xF;&#xA;    d3 = (n&amp;gt;&amp;gt;12) &amp;amp; 0xF;&#xA;&#xA;    d0 = 6*(d3 + d2 + d1) + (n &amp;amp; 0xF);&#xA;    q = (d0 * 0xCD) &amp;gt;&amp;gt; 11;&#xA;    d0 = d0 - 10*q;&#xA;&#xA;    d1 = q + 9*d3 + 5*d2 + d1;&#xA;    q = (d1 * 0xCD) &amp;gt;&amp;gt; 11;&#xA;    d1 = d1 - 10*q;&#xA;&#xA;    d2 = q + 2*d2;&#xA;    q = (d2 * 0x1A) &amp;gt;&amp;gt; 8;&#xA;    d2 = d2 - 10*q;&#xA;&#xA;    d3 = q + 4*d3;&#xA;    d4 = (d3 * 0x1A) &amp;gt;&amp;gt; 8;&#xA;    d3 = d3 - 10*d4;&#xA;&#xA;    digits[0] = (d4&amp;lt;&amp;lt;4) | (d3);&#xA;    digits[1] = (d2&amp;lt;&amp;lt;4) | (d1);&#xA;    digits[2] = (d0&amp;lt;&amp;lt;4);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-04-05T22:01:56.310" CommentCount="1" />
  <row Id="12631" PostTypeId="2" ParentId="12606" CreationDate="2011-04-05T22:46:48.207" Score="4" ViewCount="" Body="&lt;h1&gt;Do all RTCs use BCD encoding?&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;RTCs from Philips/NXP (both standalone and integrated into ARM7 or Cortex-M3 chips) do not use BCD encoding.&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;What's wrong with a BCD RTC?&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;When compared to flat counter the only operations which are more difficult with a split BCD clock are time difference calculations (adding seconds or calculating elapsed time). Time comparisons like: &quot;is current time greater than the alarm time set by the user&quot; are just as easy.&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;What's nice about BCD (and generally split-field) RTCs?&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;Splitting the fields is really nice when you care for the calendar date. Human calendars have funny things like months of different lengths and on top of that leap years. Try to do that in a single counter (you can get a bonus point for using almost no power). Oh and try supporting week days (quite useful in all kinds of devices meant for humans: from alarm clocks to heater controllers) with this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The BCD approach has one additional feature: you get &quot;every second&quot; or &quot;every ten seconds&quot; interrupts for free, without having to do any calculations on times or dates.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the record leap year calculation is a little off in the NXP RTCs since it only cares for the divisible by 4 rule and does not check the division by 100 and 400. If it kept the year counter in BCD this would be trivial and most probably done right.&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Summary&lt;/h1&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;If you want a monotonic clock then use one. You can buy a PIC or AVR with the &quot;RTC counter&quot; (which is just an asynchronous counter with an autonomous 32kHz oscillator). Just keep in mind that simply displaying the date will be difficult. :)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;When you need to display the time and date and set alarms based on user input of times and dates then use an RTC. And remember that when the user changes the current time and date your RTC based interrupts may be inaccurate.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-06T02:28:37.273" LastActivityDate="2011-04-06T02:28:37.273" CommentCount="7" />
  <row Id="12632" PostTypeId="2" ParentId="12600" CreationDate="2011-04-05T22:48:29.477" Score="4" ViewCount="" Body="&lt;p&gt;Perhaps this scan of a (rather poorly) commercially made board will illustrate the tolerance issues involved:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://ad7gd.net/flex/custompcb-detail.jpg&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2664" LastActivityDate="2011-04-05T22:48:29.477" />
  <row Id="12633" PostTypeId="2" ParentId="12618" CreationDate="2011-04-05T22:59:33.363" Score="3" ViewCount="" Body="&lt;p&gt;Depending on the amount of digits you need you may be able to use the brute force method (&lt;code&gt;d&lt;/code&gt; - input number, &lt;code&gt;t&lt;/code&gt; - output ASCII string):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;t--;&#xA;if (d &amp;gt;= 1000) t++; *t = '0'; while (d &amp;gt;= 1000) { d -= 1000; *t += 1; }&#xA;if (d &amp;gt;= 100) t++; *t = '0'; while (d &amp;gt;= 100) { d -= 100; *t += 1;}&#xA;if (d &amp;gt;= 10) t++; *t = '0'; while (d &amp;gt;= 10) { d -= 10; *t += 1;}&#xA;t++; *t = '0' + d;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You can also change the multiple ifs into a loop, with powers of ten obtained by multiplication or a lookup table.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-05T22:59:33.363" />
  <row Id="12634" PostTypeId="1" AcceptedAnswerId="12642" CreationDate="2011-04-05T23:09:05.123" Score="5" ViewCount="40" Body="&lt;p&gt;I have come across a project which used this &lt;a href=&quot;http://www.dealextreme.com/p/100mw-532nm-green-laser-module-3v-11-9mm-26890&quot; rel=&quot;nofollow&quot;&gt;Chinese laser module&lt;/a&gt;. Apparently from someone who worked with the mentioned laser, it emits IR light (noise) even though it's a green laser. While I was browsing for &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&amp;amp;site=CA&amp;amp;WT.z_homepage_link=hp_go_button&amp;amp;KeyWords=532%20nm%20laser%20module&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;alternatives on Digikey&lt;/a&gt;, I have a hard time finding an alternative that has an IR filter built in to get rid of the noise. Here are my questions.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;From your experiences working with the laser modules ordered from Digikey, have you encountered any issues with IR noise?&lt;/li&gt;&#xA;&lt;li&gt;Should I be looking at lasers with similar wattage to ensure similar brightness?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance for your help!&lt;/p&gt;&#xA;" OwnerUserId="1944" LastActivityDate="2011-04-06T15:45:21.750" Title="Infrared Filtering from Laser Modules and Wattage Considerations" Tags="&lt;filter&gt;&lt;parts&gt;&lt;laser&gt;" AnswerCount="2" />
  <row Id="12635" PostTypeId="2" ParentId="12616" CreationDate="2011-04-05T23:17:42.763" Score="5" ViewCount="" Body="&lt;p&gt;The cheapest way to carry a lot of power around without cords is probably going to be lead acid batteries. Let's figure out your power usage, and then go from there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic system is going to look like this: &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Battery -&amp;gt; DC-AC Inverter -&amp;gt; Projector&#xA;                          L&amp;gt; Laptop&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;We need to identify the load on the battery before we can estimate run time, so let's start with our loads. I was able to find a page that lists the &lt;a href=&quot;http://www.google.com/products/catalog?q=Acer%20X1261-3D&amp;amp;oe=utf-8&amp;amp;client=firefox-a&amp;amp;cid=12202693343710365518&amp;amp;os=tech-specs&quot; rel=&quot;nofollow&quot;&gt;operating power consumption&lt;/a&gt; of the projector as 224W. I'll estimate that you don't have a power-hungry laptop, and estimate power consumption at 40W. (You didn't include any current figures for the power supply, so I'm guessing.) This gives a load of 265W for the inverter. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found an &lt;a href=&quot;http://www.tripplite.com/en/products/model.cfm?txtSeriesID=815&amp;amp;txtModelID=2552&quot; rel=&quot;nofollow&quot;&gt;inverter&lt;/a&gt; that meets your continuous load requirements, and I calculate that it has a full-load efficiency of 78%. With a load of 265W, that results in an input power of 340W. This is effectively an average current of 29A at 12V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The final step is to select the right battery. Battery capacity is measured in Amp-hours, and for every 30 Amp-hours you will get about 1 hour use. This &lt;a href=&quot;http://www.batterymart.com/p-12v-75ah-sealed-lead-acid-battery.html&quot; rel=&quot;nofollow&quot;&gt;sealed lead acid battery&lt;/a&gt; is 75 Ah, and it will last you for about 2.5 hours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to increase your run-time, you can:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Find a more efficient / lower power projector&lt;/li&gt;&#xA;&lt;li&gt;Use a lower-power laptop&lt;/li&gt;&#xA;&lt;li&gt;Consider using a 12V laptop power supply&lt;/li&gt;&#xA;&lt;li&gt;Run your laptop off it's internal battery (thanks @jpc)&lt;/li&gt;&#xA;&lt;li&gt;Find a more efficient inverter (The one I linked to was the first I found)&lt;/li&gt;&#xA;&lt;li&gt;Buy a larger (Ah) battery&lt;/li&gt;&#xA;&lt;li&gt;Put multiple 12V batteries in parallel&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;All this should fit reasonably well on a hand cart of some kind. The battery will be heavy - the one I listed was 60 pounds. If this sounds like too much work/danger/weight, invest in a really long extension cord.&lt;/p&gt;&#xA;" OwnerUserId="638" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-04-06T18:49:01.097" LastActivityDate="2011-04-06T18:49:01.097" CommentCount="7" />
  <row Id="12636" PostTypeId="1" AcceptedAnswerId="12637" CreationDate="2011-04-05T23:36:30.187" Score="2" ViewCount="109" Body="&lt;p&gt;I am considering using a KZE series (by United Chemi-Con) electrolytic capacitor, which has a specified lifespan of 5,000 hours at 105°C with rated ripple current. Now, for an example assume I am using it at room temperature (25°C) with half the rated ripple current and half the applied working voltage. How long would the capacitor last? In future, how would I calculate it?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-06T00:03:42.367" Title="How do I compute the lifetime of an electrolytic capacitor?" Tags="&lt;capacitor&gt;&lt;lifetime&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="12637" PostTypeId="2" ParentId="12636" CreationDate="2011-04-06T00:03:42.367" Score="7" ViewCount="" Body="&lt;p&gt;The general rule used is that usable lifetime doubles for every 10C reduction in operating temperature.  This should be considered an upper bound on expected life.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As the capacitor ages its capacitance will decrease and ESR will increase.  The increase in ESR can result in a temperature increase if running high ripple currents which in turn increases the rate of aging. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also make sure that the increase in ESR / decrease in capacitance over the caps life span is acceptable.  For instance make sure that the circuit still operates when the cap hits -20% of baseline capacitance (or whatever its end of life rating is).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other factors can increase the rate of aging as well.  For instance the more air flow over the cap the shorter its life expectancy (although a reduction in temperature from the air flow can more than offset this issue if the cap is running warm).&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-04-06T00:03:42.367" CommentCount="3" />
  <row Id="12638" PostTypeId="2" ParentId="12597" CreationDate="2011-04-06T00:06:17.460" Score="2" ViewCount="" Body="&lt;p&gt;The CTRL pin enables the DIN, TMS_IN and CLK signals so that they &quot;reach&quot; TDI, TMS and CCLK on the JTAG and FPGA headers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PROG pin is similar, it will pull down the line that goes to TDO and D/P.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not exactly sure why it is wired as it is, but I'm sure that they're not just there to make the schematics look nice. I couldn't find any links that referenced the link you gave so I can't find any more information on the exact device you're looking at.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-04-06T00:06:17.460" CommentCount="5" />
  <row Id="12639" PostTypeId="2" ParentId="10379" CreationDate="2011-04-06T00:10:35.130" Score="2" ViewCount="" Body="&lt;p&gt;This &lt;a href=&quot;http://www.analog.com/static/imported-files/data_sheets/AD676.pdf&quot; rel=&quot;nofollow&quot;&gt;data sheet&lt;/a&gt; contains one example circuit. You will need to specify a bit more on your requirements to get a better answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that particular chip is a bit overkill if you just want a simple measurement of a potentiometer. I would go for a chip with 1) a breakout board and 2) sample code if this is your first chip you're talking to. It's just easier to get started and will save your potential problems the your first time around.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-04-06T00:10:35.130" />
  <row Id="12640" PostTypeId="1" AcceptedAnswerId="12671" CreationDate="2011-04-06T00:24:46.583" Score="1" ViewCount="145" Body="&lt;p&gt;Recently, I purchased a FEZ Panda and I've done some pretty cool stuff with it. Well, cool to me anyway. I recently had some ideas for things to do with LEDs and wanted to share them as kits. I see a lot of such kits utilizing small, cheap processors like the ATTiny13 or ATTiny85. Makes sense if it's just doing one thing with a small circuit that's simple. But I'm now hooked on using the .Net Micro Framework and love the fact that I can do everything from Visual Studio. For these little kits, I'm not opposed to using an AVR chip and writing in C, but was wondering if there was a .Net-enabled alternative. I've found some ARM7/ARM9 processors for around $5, but their package is rather difficult to solder onto a PCB for something as basic as a learning kit. Arent there any other form factors or other cheap alternatives that can be programmed using .NET MF?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I'll also point out that there exist AVRs that come preloaded with the Arduino bootloader and they're cheap. These are also good chips to program with a single purpose and ship them with kits. I can't find a .Net MF enabled chip that I can do the same with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance...&lt;/p&gt;&#xA;" OwnerUserId="3344" LastEditorUserId="3344" LastEditorDisplayName="" LastEditDate="2011-04-06T00:45:11.427" LastActivityDate="2011-04-06T13:12:13.780" Title="Is there a cheap alternative to AVRs that can run the .Net Micro Framework?" Tags="&lt;microcontroller&gt;&lt;.net-micro-framework&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="12641" PostTypeId="1" CreationDate="2011-04-06T01:04:56.973" Score="3" ViewCount="85" Body="&lt;p&gt;Voltage output DACs are usually specified by a settling time. If a DAC converter has a settling time of T, can it be used to faithfully reproduce a signal which has been sampled at a frequency of 1/T? Or does this frequency has to be lower since there may be substantial ringing in the output signal if one changes the signal before the output has fully settled?&lt;/p&gt;&#xA;" OwnerUserId="2897" LastActivityDate="2011-05-01T18:35:19.917" Title="DAC settling time and output signal bandwidth" Tags="&lt;dac&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="12642" PostTypeId="2" ParentId="12634" CreationDate="2011-04-06T01:37:42.530" Score="3" ViewCount="" Body="&lt;p&gt;Chemistry dictates that lasers often produce light in the infrared spectrum.  Popular neodymium-doped lasers produce light at 1064 nm, which is well into the infrared range.  To get around this, &lt;a href=&quot;http://en.wikipedia.org/wiki/Second_harmonic_generation#Other_uses&quot; rel=&quot;nofollow&quot;&gt;frequency doublers&lt;/a&gt; are employed, which halve the wavelength to 532 nm, which is a green light.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For this reason, it's unsurprising that your laser emits IR light.  The frequency doublers aren't perfect; a significant amount of IR gets through.  Good lasers will filter this out, cheap ones won't bother.  If this is important to you, use a reputable manufacturer (like the ones on Digikey) and verify that they at least claim to use IR filters.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-04-06T01:37:42.530" CommentCount="0" />
  <row Id="12643" PostTypeId="2" ParentId="1332" CreationDate="2011-04-06T02:40:47.087" Score="1" ViewCount="" Body="&lt;p&gt;You can use the M5451 chip to economically drive constant-current outputs.  My board uses them to directly drive 70 constant-current &quot;sinks&quot;, and provides 16 500mA &quot;sources&quot; for people who want to do large LED matrices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.toastedcircuits.com/html/product/Lightuino_5.0.html&quot; rel=&quot;nofollow&quot;&gt;http://www.toastedcircuits.com/html/product/Lightuino_5.0.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3743" LastActivityDate="2011-04-06T02:40:47.087" />
  <row Id="12644" PostTypeId="2" ParentId="12640" CreationDate="2011-04-06T02:51:59.500" Score="1" ViewCount="" Body="&lt;p&gt;Why are you wanting to use something other than the Panda? If you need more power, you might have a look at the other .Net FEZ line of products: &lt;a href=&quot;http://www.ghielectronics.com/catalog/category/7/&quot; rel=&quot;nofollow&quot;&gt;http://www.ghielectronics.com/catalog/category/7/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="708" LastActivityDate="2011-04-06T02:51:59.500" CommentCount="5" />
  <row Id="12645" PostTypeId="2" ParentId="12602" CreationDate="2011-04-06T03:18:11.180" Score="5" ViewCount="" Body="&lt;p&gt;Are these large DC (eg automotive) bulbs, or small mains bulbs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're fuzzy on what a Watt means, you're not ready to be tackling high voltage circuits.&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-04-06T03:18:11.180" />
  <row Id="12646" PostTypeId="1" AcceptedAnswerId="12659" CreationDate="2011-04-06T04:51:02.257" Score="5" ViewCount="151" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/vT9tt.jpg&quot; alt=&quot;Voltage Doubler Circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a little lost as to what is going on in this circuit. The book I am reading mentions that the load would see double the voltage of the input voltage. How does this work?&lt;/p&gt;&#xA;" OwnerUserId="3688" LastActivityDate="2011-04-06T11:03:33.983" Title="Voltage doubler" Tags="&lt;circuit&gt;&lt;analog&gt;&lt;voltage&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="2" />
  <row Id="12648" PostTypeId="1" AcceptedAnswerId="12755" CreationDate="2011-04-06T06:36:04.047" Score="1" ViewCount="89" Body="&lt;p&gt;I.e. &lt;img src=&quot;http://i.imgur.com/xgbJl.png&quot; alt=&quot;enter image description here&quot;&gt; vs. &lt;img src=&quot;http://i.imgur.com/wMXVA.jpg&quot; alt=&quot;Custom-Patterned PCB&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would the reasons be similar to those answered &lt;a href=&quot;http://electronics.stackexchange.com/questions/2103/when-to-avoid-using-a-breadboard&quot;&gt;here&lt;/a&gt;, but emphasized on unwanted capacitance, noise, and power issues?&lt;/p&gt;&#xA;" OwnerUserId="1944" LastActivityDate="2011-04-08T19:46:59.483" Title="When to Use a Etched Prototyping PCB vs. Custom-Patterned PCB" Tags="&lt;circuit&gt;" AnswerCount="2" />
  <row Id="12649" PostTypeId="2" ParentId="12602" CreationDate="2011-04-06T06:51:11.913" Score="3" ViewCount="" Body="&lt;p&gt;You can use mechanical or solid-state relays (SSR).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A mechanical relay offers the advantage that when off there's a complete separation between the bulb and the mains. You'll need a transistor to drive the relay.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy SSRs which you can drive directly from your microcontroller, but they're not cheap. No problem, because you can create the same functionality cheap with just a few components.&#xA;You start with an opto-triac like the &lt;a href=&quot;http://www.fairchildsemi.com/ds/MO/MOC3041-M.pdf&quot; rel=&quot;nofollow&quot;&gt;MOC3041&lt;/a&gt; (that's for 230V applications, use MOC3031 for 115V). It's like an ordinary opto-coupler but with a triac as the switch instead of a transistor (a triac can switch AC, which a transitor can't). If you don't use this opto-triac your whole circuit will be connected to the mains!&lt;br&gt;&#xA;The MOC3041 has the additional feature of switching on the zero-crossing of the mains' sine. Incandescent bulbs tend to fail when being switched on, and when the mains voltage is near a maximum. Zero-crossing switching prolongs the bulb's life.&lt;br&gt;&#xA;The MOC3041 can't drive large currents directly, therefore we use it to drive a power triac.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/2h1Gn.png&quot; alt=&quot;MOC3041 application circuit&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-06T06:51:11.913" />
  <row Id="12650" PostTypeId="1" AcceptedAnswerId="12681" CreationDate="2011-04-06T06:55:15.723" Score="1" ViewCount="145" Body="&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; &lt;em&gt;Additional Information below original post...&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;PRE&gt;Looking for a 360 degree servo motor that has adjustable control for timing of steps&#xA;(or at the least timing per full oscillation) and can support (via vertical shaft) at&#xA;least 30 pounds of weight overhead (imagine a oscillating tower fan where the base is&#xA;the motor and the fan is the 30 pound weight with a vertical shaft at least 4 feet in&#xA;length). Any suggestions for where to look for a baseline to mod or an off-the-shelf&#xA;solution?&lt;/PRE&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for assisting in directing my ongoing efforts to build my prototype, peeps :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I still have some primary concerns and questions unanswered in regards to the gearing, controls, etc for the oscillating motor and will continue those in more specific &quot;Questions&quot; posted as I think of them. I will post some google sketchup images of examples, as well. Thanks again and looking forward to hacking this project to completion :D&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Google Sketchup Prototype:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess I'll fill out the images once I have 10 frickin points. :P&lt;/p&gt;&#xA;&#xA;&lt;p&gt;img src=&quot;http://goo.gl/fZykD&quot; width=&quot;912&quot; height=&quot;445&quot; title=&quot;Google sketchup prototype Revision 1&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;img src=&quot;http://goo.gl/kVBAi&quot; width=&quot;1024&quot; height=&quot;498&quot; title=&quot;Revision 2&quot;&lt;/p&gt;&#xA;" OwnerUserId="3744" LastEditorUserId="3744" LastEditorDisplayName="" LastEditDate="2011-04-07T07:27:27.587" LastActivityDate="2011-04-08T20:56:22.303" Title="Need oscillating servo/stepper motor guidance" Tags="&lt;motor&gt;&lt;robotics&gt;&lt;servo&gt;&lt;stepper-motor&gt;&lt;oscillator&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="1" />
  <row Id="12651" PostTypeId="2" ParentId="12648" CreationDate="2011-04-06T07:24:24.600" Score="1" ViewCount="" Body="&lt;p&gt;More and more components, a.o. microcontrollers, are only available in SMT (Surface Mount Technology), which don't have a 0.1&quot; pitch. Adapter boards to go from, say, TQFP to breadboard exist, but become very inefficient if you need several of them, real estate-wise.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-06T07:24:24.600" CommentCount="4" />
  <row Id="12657" PostTypeId="2" ParentId="12523" CreationDate="2011-04-06T07:58:52.527" Score="1" ViewCount="" Body="&lt;p&gt;I would use the newer 20pin Pdip or favorite package &#xA;msp430G23xx or msp430g24xx&#xA;They have expanded ports 2x 8bit ports = 16outputs &#xA;more timers and built in hardware UART &lt;/p&gt;&#xA;&#xA;&lt;p&gt;but for your current conundrum, You can use the tx and rx on the FET- just disconnect the jumpers and connect the pins to your level converter(max232) You do not need the rx tx to program it from my experience. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;second question, is yes i break it up into smaller chunks and once i know all my code works i start putting it all together. so far it works great for smaller projects for me.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-04-06T07:58:52.527" CommentCount="9" />
  <row Id="12658" PostTypeId="2" ParentId="10379" CreationDate="2011-04-06T08:45:19.333" Score="2" ViewCount="" Body="&lt;p&gt;Why did you choose the AD676 in particular? It's a 16-bit ADC, which is much more than you need. A potmeter rotates over about 270°, so an 8-bit ADC would give you a resolution of about 1°. Nowadays it's often easier to find a 10-bit ADC, and they don't cost much more.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally you should also look at the ADC's speed, but for reading a potmeter 10 samples per second should do and any SAR (Successive Approximation) ADC will do here (most will easily be a thousand times faster).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you want to interface it to your microcontroller? I2C, SPI?&lt;br&gt;&#xA;A standard serial protocol makes it ridiculously easy to interface your ADC with your microcontroller. As an example the following &quot;schematic&quot; from the &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/21805a.pdf&quot; rel=&quot;nofollow&quot;&gt;Microchip MCP3021 datasheet&lt;/a&gt;:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ppSN1.png&quot; alt=&quot;MCP3021 Application&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The MCP3021 is a 10-bit ADC which interfaces through I2C. It comes in a 5 pin SOT23 package:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;2 x power (Vdd, Gnd)&lt;br&gt;&#xA;  2 x I2C (SDA, SCL)&lt;br&gt;&#xA;  1 x Analog input  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That's all you need.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-06T08:52:52.963" LastActivityDate="2011-04-06T08:52:52.963" />
  <row Id="12659" PostTypeId="2" ParentId="12646" CreationDate="2011-04-06T09:31:59.563" Score="9" ViewCount="" Body="&lt;p&gt;I've made a little GIF animation explaining what happens during the negative and positive voltage swing of the output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The big thing to understand is that the first (left) capacitor is not fixed to ground on either side, but relative to the transformer output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This allows it to first be charged at the negative part of the cycle, then be &quot;lifted&quot; above +x V at the positive swing. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The diodes restrict the flow of current such that none of the capacitors get discharged when the transformer swings to the opposite polarity voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/pm1Xh.gif&quot; alt=&quot;Voltage doubler animation&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3745" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-06T10:31:15.563" LastActivityDate="2011-04-06T10:31:15.563" />
  <row Id="12660" PostTypeId="2" ParentId="11545" CreationDate="2011-04-06T09:52:36.360" Score="0" ViewCount="" Body="&lt;p&gt;Are you by chance using a Nexus S? If so, you already have both read and write NFC/RFID functionality.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Write function news release: &lt;a href=&quot;http://www.nearfieldcommunicationsworld.com/2011/01/25/35758/nexus-s-video-androids-hidden-nfc-tag-writing-abilities-revealed/&quot; rel=&quot;nofollow&quot;&gt;NFC World Article&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More from Android: &lt;a href=&quot;http://developer.android.com/sdk/android-2.3.3.html&quot; rel=&quot;nofollow&quot;&gt;Android SDK&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise, using a bluetooth RFID reader to transfer the RFID info to android &lt;a href=&quot;http://www.youtube.com/watch?v=kEp0a5PQrKY&quot; rel=&quot;nofollow&quot;&gt;has been accomplished without the need for arduino&lt;/a&gt;, but if you're just dead-set on using arduino as a third device middle-man... here's some links that might help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://iloapp.marcboon.com/blog/rfid&quot; rel=&quot;nofollow&quot;&gt;Arduino RFID Sniffer&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://amarino-toolkit.net&quot; rel=&quot;nofollow&quot;&gt;Amarino (Android + Arduino Toolkit)&lt;/a&gt; This uses the bluetooth uart module for communications between phone and arduino just as you're wanting&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-- Daerk&lt;/p&gt;&#xA;" OwnerUserId="3744" LastEditorUserId="3744" LastEditorDisplayName="" LastEditDate="2011-04-07T13:36:57.670" LastActivityDate="2011-04-07T13:36:57.670" CommentCount="1" />
  <row Id="12661" PostTypeId="2" ParentId="10379" CreationDate="2011-04-06T10:27:01.510" Score="1" ViewCount="" Body="&lt;p&gt;A AD676 ADC is way too extreme for your purpose of reading an analog potentiometer signal. If you'd use the full scale of your ADC (so if it can read 0 - 5V, you would use min 0V and max 5V), you have over 65000 positions.. and a lot of noise to deal with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 10 bit ADC has about 1024 positions. If you want to encode 360 degrees , you could get up to 0.36 degrees resolution. However, potentiometers don't turn full 360 degrees or circles, so you will likely be limited to about 270 degrees.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stevenvh showed a simple example of how to connect the ADC. Connect the SDA and SCL signals on your microcontroller on the appriotate pins. Look up the datasheet for your devices to see what pin that is, that's different for every chip. The analog input would just be the middle tapoff from the potentionmeter, and just apply +5V and 0 to it (if your potentiometer can read up to +5V)&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-04-06T10:27:01.510" />
  <row Id="12662" PostTypeId="2" ParentId="12576" CreationDate="2011-04-06T10:29:02.430" Score="0" ViewCount="" Body="&lt;p&gt;If you're on a Windows computer and have some experience working with Visual Studio, you can always look at working with a .Net Micro Framework device, such as one of the &lt;a href=&quot;http://www.tinyclr.com/compare/&quot; rel=&quot;nofollow&quot;&gt;Fez devices&lt;/a&gt;. I just bought a Fez Panda and it's been fun to play around with. The upside to this is that they are built to be parts/shields-compatible with the Arduino. The downside, as I discovered, is that it is not &lt;em&gt;nearly&lt;/em&gt; as plug-and-play as the Arduino is. It took me about 20 minutes of downloading and installing SDKs and drivers before I got to the programming part, and then I was running into the issue of their example code not being up to date. I did finally get it working, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino is super easy to learn, and you can go to hundreds of different websites for tutorials and examples. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Maker's Shed has an &lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MSAPK&quot; rel=&quot;nofollow&quot;&gt;Arduino Project Pack for $99&lt;/a&gt; that comes with an Arduino and a whole bunch of parts and sensors. SparkFun, my personal favorite (and local, if you live in Colorado!) parts store has a similar kit called the &lt;a href=&quot;http://www.sparkfun.com/products/10173&quot; rel=&quot;nofollow&quot;&gt;Arduino Inventor's Kit&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The nice thing about Arduinos is that it's open source, so people can create their own types of Arduinos. For example, SparkFun worked with Leah Buechley to create the &lt;a href=&quot;http://www.sparkfun.com/products/9266&quot; rel=&quot;nofollow&quot;&gt;LilyPad Arduino&lt;/a&gt;, which is a sewable arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And finally, if you do decide you want an Arduino, &lt;a href=&quot;http://www.sparkfun.com/tutorials/148&quot; rel=&quot;nofollow&quot;&gt;SparkFun also has a buying guide&lt;/a&gt; to help you decide which version you'd like.&lt;/p&gt;&#xA;" OwnerUserId="693" LastActivityDate="2011-04-06T10:29:02.430" />
  <row Id="12663" PostTypeId="2" ParentId="12526" CreationDate="2011-04-06T10:35:56.710" Score="1" ViewCount="" Body="&lt;p&gt;I just purchased several &lt;a href=&quot;http://www.sparkfun.com/products/100&quot; rel=&quot;nofollow&quot;&gt;SPDT 5V relays from SparkFun&lt;/a&gt; the other day, and they're working very well for me. They're rated for a maximum of 5A at 250VAC or 30VDC and only cost $1.95/relay. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/9XY1U.jpg&quot; alt=&quot;5V relay&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the devices you're switching are pulling more than 5A, they also have &lt;a href=&quot;http://www.sparkfun.com/products/101&quot; rel=&quot;nofollow&quot;&gt;30A SPST relays&lt;/a&gt; for $4 each.&lt;/p&gt;&#xA;" OwnerUserId="693" LastActivityDate="2011-04-06T10:35:56.710" />
  <row Id="12664" PostTypeId="2" ParentId="12646" CreationDate="2011-04-06T11:03:33.983" Score="1" ViewCount="" Body="&lt;p&gt;One way to think about voltage doublers like this one is to think about what happens with the voltages in a simpler, one-diode, one-capacitor type of circuit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With one diode and one cap, the cap charges up to the peak voltage of the transformer secondary, but think about the voltage on the diode; when it is conducting, the voltage across the diode is just the forward drop, usually on the order of no more than a volt, but when it is non-conducting, it has to block the combined series voltages of the capacitor (charged to peak) &lt;em&gt;and&lt;/em&gt; the transformer secondary, in the worst case also at peak. In other words, the voltage across the diode would be half-wave AC but with twice the peak voltage as the transformer secondary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By adding a second diode and capacitor, using the voltage of the first diode as input, you can then get the peak voltage of the first diode to appear across the second cap, and there you are, twice the peak voltage of the transformer secondary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, there are other ways to think about the circuit, equally valid, but hopefully this lets you make some intuitive sense of what's going on.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-06T11:03:33.983" />
  <row Id="12666" PostTypeId="1" AcceptedAnswerId="12667" CreationDate="2011-04-06T11:20:58.683" Score="4" ViewCount="114" Body="&lt;p&gt;hello&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am new to hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the first object, I want to connect my rc car controller with my computer&lt;/p&gt;&#xA;&#xA;&lt;p&gt;so I can control my rc car in my pc&lt;/p&gt;&#xA;&#xA;&lt;p&gt;what kind of things do I need to acheive it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(knowledges, cables, etc..)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;is it useful if I have a BreadBoard?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks&lt;/p&gt;&#xA;" OwnerUserId="3746" LastActivityDate="2011-05-16T04:30:04.550" Title="connect my rc car controller with my computer" Tags="&lt;hardware&gt;&lt;communication&gt;" AnswerCount="1" FavoriteCount="3" />
  <row Id="12667" PostTypeId="2" ParentId="12666" CreationDate="2011-04-06T11:41:59.743" Score="8" ViewCount="" Body="&lt;p&gt;I did this a couple of years ago with a cheap (£5) RC Lamborghini I bought from a supermarket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To start with, I dismantled the remote control and located the switches that made it go forward/backward/left/right.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I then soldered wires onto each side of each switch, the other end of these wires I connected to octocouplers in a breadboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other side of the octocouplers were wired into an Arduino - the octocouplers simply separate the two electronic circuits (Arduino and Remote) so you can control the switches on the remote from the Arduino without mixing the two circuits and all of the complications that go with that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, I wrote a small Arduino program that could receive commands over the serial port (USB) from the computer and control the appropriate switch depending upon the command received.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This enabled me to write simple Python scripts to send the required commands to the Arduino, meaning I didn't have to compile and upload new code to the Arduino every time I tweaked what I wanted the car to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can see the result here:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=KDM_f_t8TL8&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=KDM_f_t8TL8&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did this with very basic electronics knowledge, though if you don't have any experience in programming, you'll likely struggle with the software side of things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anthony&lt;/p&gt;&#xA;" OwnerUserId="2573" LastActivityDate="2011-04-06T11:41:59.743" CommentCount="3" />
  <row Id="12668" PostTypeId="2" ParentId="12634" CreationDate="2011-04-06T11:47:51.717" Score="0" ViewCount="" Body="&lt;p&gt;I have 2 green lasers from DX, and both are without IR filter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I don't think it's a problem as IR is way less collimated, so at a distance, only green dot is in focus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Extra IR filter would reduce usable output power &amp;amp; will increase it's cost. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's critical to you - you can pass your beam through prism, so that 532nm beam would be split from 808nm/1064nm IR light, then you can put an obstacle on the path of IR beams. &lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-04-06T15:45:21.750" LastActivityDate="2011-04-06T15:45:21.750" CommentCount="3" />
  <row Id="12669" PostTypeId="2" ParentId="10708" CreationDate="2011-04-06T11:56:16.890" Score="1" ViewCount="" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Boot up in Safe Mode, goto c:\windows\system32\driver and remove NcGen.sys&#xA;  Then connect the USB cable of ICD 3, install the driver then reboot your system. Now here you go!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good Luck&lt;/p&gt;&#xA;" OwnerUserId="3747" LastActivityDate="2011-04-06T11:56:16.890" />
  <row Id="12671" PostTypeId="2" ParentId="12640" CreationDate="2011-04-06T13:12:13.780" Score="1" ViewCount="" Body="&lt;p&gt;No.  The price of a microcontroller running the .NET framework will always be greater than the price for a microcontroller with equivalent performance (or equivalent to the price of a micro with greater performance) which is programmed in assembly, C, or even using the Arduino tools.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When buying a microcontroller for the .NET framework, you pay for small transistors, you pay for more transistors, you pay for complexity, you probably pay for licensing a core developed somewhere else, and, since you're paying for all that, most manufacturers imagine that you'll want to pay for higher pin-count packages since your die budget supports them.  If you did this in assembly or C, you could get equivalent performance and pay a lot less.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See also the following questions:   &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/3741/arduino-processing-versus-net-micro-framework-best-language-best-hardware&quot;&gt;Arduino / Processing versus .Net Micro Framework? Best language? Best hardware?&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/7901/microcontroller-with-java-api&quot;&gt;Microcontroller with Java API&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/4604/what-are-the-net-micro-framework-ready-systems-available&quot;&gt;What are the .NET Micro Framework ready systems available?&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/3027/is-c-suitable-for-embedded-systems&quot;&gt;Is C++ suitable for embedded systems?&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The first question in the list is very applicable to this question, it just discusses the suitability of the .NET micro framework as opposed to the pricing and programming which we're discussing here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you still want to use .NET, you think you can get acceptable performance out and you're going to be buying a significant number of parts (at least 1k, probably easier at 10k), you can do the same thing that the vendors of the FEZ parts do: Have it loaded at the factory. It costs somewhere in the region of a quarter apiece  to program large files like the one you'll be working with.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-04-06T13:12:13.780" CommentCount="3" />
  <row Id="12673" PostTypeId="1" CreationDate="2011-04-06T13:28:02.290" Score="1" ViewCount="87" Body="&lt;p&gt;I want to use two batteries rated 6v, 4A with a 9v,1A device. I figured that connecting the batteries in parallel would give 12v and connecting a 3ohm resistor in series with the device would give the device 9v(law of potential dividers). Now, to get the required current, do I connect a resistor(~8 ohm) in parallel to the device? Would that do the trick?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, how do I set up the circuit to charge these batteries up?&lt;/p&gt;&#xA;" OwnerUserId="2074" LastActivityDate="2011-04-06T13:54:05.167" Title="Beginner question regarding batteries' voltage/amperage" Tags="&lt;beginner&gt;&lt;batteries&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="12674" PostTypeId="2" ParentId="12618" CreationDate="2011-04-06T13:28:28.210" Score="1" ViewCount="" Body="&lt;p&gt;Have you considered holding that value as BCD all the time (using simple special &quot;BCD increment&quot; and &quot;BCD add&quot; subroutines), rather than holding that value in binary form and converting to BCD as needed (using a more difficult to understand &quot;convert from binary to BCD&quot; subroutine)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At one time, all computers stored all data as decimal digits (ten-position gears, two-out-of-five code vacuum tubes, BCD, etc.), and that legacy still lingers on today. (see &lt;a href=&quot;http://electronics.stackexchange.com/questions/12606/why-do-real-time-clock-chips-use-bcd&quot;&gt;Why do real-time clock chips use BCD&lt;/a&gt; ).&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-06T13:28:28.210" CommentCount="1" />
  <row Id="12675" PostTypeId="2" ParentId="12618" CreationDate="2011-04-06T13:33:17.010" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc0938.pdf&quot; rel=&quot;nofollow&quot;&gt;This application note&lt;/a&gt; describes algorithms for BCD arithmetic, including conversion from binary to BCD and vice versa. The appnote is by Atmel, which is AVR, but the described algorithms are processor-independent.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-06T13:33:17.010" />
  <row Id="12676" PostTypeId="2" ParentId="12673" CreationDate="2011-04-06T13:45:37.907" Score="9" ViewCount="" Body="&lt;p&gt;To get 12V you have to put them &lt;strong&gt;in series&lt;/strong&gt;. This gives you 12V @ 4A. Placing them &lt;strong&gt;in parallel&lt;/strong&gt; would give you double the current, i.e. 6V @ 8A. This is a bit tricky, however, because voltages of the two batteries have to be exact the same, otherwise a large current will run from one battery to the other. As safety measure you place small resistors in series with each battery.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you place them in series. A series resistor to get a defined lower voltage is never a good idea, because the voltage drop over the resistor will vary with the load. Use a voltage regulator, like &lt;a href=&quot;http://www.fairchildsemi.com/ds/LM/LM7809.pdf&quot; rel=&quot;nofollow&quot;&gt;LM7809&lt;/a&gt; or &lt;a href=&quot;http://www.national.com/profile/snip.cgi/openDS=LM317&quot; rel=&quot;nofollow&quot;&gt;LM317&lt;/a&gt;. This converts the 12V in to 9V out. If you connect the 9V, 1A device you'll have this 1A current automatically.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/MAznN.png&quot; alt=&quot;typical application&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-06T13:54:05.167" LastActivityDate="2011-04-06T13:54:05.167" CommentCount="9" />
  <row Id="12677" PostTypeId="2" ParentId="12641" CreationDate="2011-04-06T13:59:23.713" Score="1" ViewCount="" Body="&lt;p&gt;From what I've seen in datasheets, it looks like the ringing will usually be a few octaves above the bandwidth implied by the settling time (1/T).  If that's what's really going on, a low-pass filter should help to dampen that ringing out.  On the other hand, I rather suspect that the actual bandwidth and ringing are influenced more by the impedance of the load the DAC is connected to, and the settling time listed on the datasheet is going to be the optimal case caused only by the parasitic capacitance of the DAC itself.&lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2011-04-06T13:59:23.713" />
  <row Id="12678" PostTypeId="2" ParentId="12618" CreationDate="2011-04-06T14:28:30.863" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.piclist.com/&quot; rel=&quot;nofollow&quot;&gt;PICList&lt;/a&gt; is an amazing resource for people programming PIC processors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;BCD conversion&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have you considered using an off-the-shelf tried-and-tested binary-to-BCD subroutine specifically optimized for the PIC16F?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In particular, people on the PICList have spent a lot of time optimizing binary-to-BCD conversions on a PIC16F.&#xA;Those routines (each one hand-optimized for a specific size) are summarized at&#xA;&quot;PIC Microcontoller Radix Conversion Math Methods&quot;&#xA;&lt;a href=&quot;http://www.piclist.com/techref/microchip/math/radix/index.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.piclist.com/techref/microchip/math/radix/index.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;integer division and mod&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On a CPU like the PIC16F, a subroutine specialized to divide by a constant is often much faster than a general-purpose &quot;divide variable A by variable B&quot; routine.&#xA;You may want to put your constant (in this case, &quot;0.1&quot;) in the&#xA;&quot;Code Generation for Constant Multiplication/Division&quot; &lt;a href=&quot;http://www.piclist.com/techref/piclist/codegen/constdivmul.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.piclist.com/techref/piclist/codegen/constdivmul.htm&lt;/a&gt;&#xA;or check out the canned routines near &lt;a href=&quot;http://www.piclist.com/techref/microchip/math/basic.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.piclist.com/techref/microchip/math/basic.htm&lt;/a&gt; .&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-06T14:28:30.863" CommentCount="1" />
  <row Id="12679" PostTypeId="1" AcceptedAnswerId="12727" CreationDate="2011-04-06T14:59:19.100" Score="3" ViewCount="156" Body="&lt;p&gt;I've been experimenting running my &lt;a href=&quot;http://electronics.stackexchange.com/questions/11504/is-it-practical-to-build-a-wearable-project-that-draws-9a-12v&quot;&gt;3A LED strips&lt;/a&gt; off battery power and the results are disappointing. I'm only getting a few minutes (&amp;lt; 10) out of a &lt;a href=&quot;http://www.inesun.com/Brand-New-Super-1800mA-Rechargeable-Lithium-Battery-for-Security-CCTV-Camera--8269.html&quot; rel=&quot;nofollow&quot;&gt;YSD-168 1800mAh lithium ion&lt;/a&gt;. How can I find the &quot;C rating&quot; of this battery? Is it something mainly dependent on battery chemistry (as &lt;a href=&quot;http://www.dansdata.com/batterylife.htm&quot; rel=&quot;nofollow&quot;&gt;this Dan's Data article I just remembered implies&lt;/a&gt;, search for &quot;[space]C[space]&quot; on the page) or something mainly dependent on manufacturing quality/technique? Macho RC battery packs always quote C-ratings, other battery types not so much. And it's difficult to google.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, what are typical maximum &quot;discharge C ratings&quot; of AA and AAA NiMH batteries?&lt;/p&gt;&#xA;" OwnerUserId="1633" LastEditorUserId="1633" LastEditorDisplayName="" LastEditDate="2011-04-07T09:40:02.700" LastActivityDate="2011-06-03T12:12:56.193" Title="How do I find the maximum &quot;discharge C rating&quot; of a battery?" Tags="&lt;battery&gt;&lt;discharge&gt;&lt;capacity&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="12680" PostTypeId="1" CreationDate="2011-04-06T15:01:29.213" Score="0" ViewCount="143" Body="&lt;p&gt;hi, I m very new to fpga.I got a spartan6 from digilent. As my final year project I want to do image processing through it.How matlab/simulink can be used fo this? How should the camera be connected to d board? through HDMI or USB ?plz help..&lt;/p&gt;&#xA;" OwnerUserId="3749" LastActivityDate="2011-04-08T10:41:15.443" Title="video/image processing in spartan 6 fpga" Tags="&lt;fpga&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="12681" PostTypeId="2" ParentId="12650" CreationDate="2011-04-06T15:02:29.443" Score="4" ViewCount="" Body="&lt;p&gt;Unless you go with something &lt;strong&gt;big&lt;/strong&gt; like a 1/2hp motor, you're going to have to build this yourself. The bearings on a small servo or stepper won't support that kind of load. You have to deal with the vertical thrust load of 30 lbs and then any torque caused by the load - motor axis not being perfectly vertical! You will need to build a base and a vertical support with bearings to carry the shaft. A couple of 2x4's would do it just fine. Or you could start with a floor lamp and toss the lamp head part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having said that, once the load is properly supported, it shouldn't be too hard to turn so a size 23 stepper motor will probably do it just fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How thick is the axis you want to turn? Maybe I can offer some suggestions on where to get the parts you need.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-04-06T15:02:29.443" CommentCount="3" />
  <row Id="12682" PostTypeId="2" ParentId="12602" CreationDate="2011-04-06T15:08:05.947" Score="3" ViewCount="" Body="&lt;p&gt;What is the objection to relays? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If they are DC bulbs you can use 15 transistors. Or you could build a 3x5 matrix and switch them that way with just 8 transistors and a lot more complexity...&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-04-06T15:08:05.947" CommentCount="1" />
  <row Id="12683" PostTypeId="2" ParentId="12679" CreationDate="2011-04-06T15:48:33.197" Score="1" ViewCount="" Body="&lt;p&gt;The best bet is to check datasheet and/or run an experiment :-)&#xA;And yes, it depends on chimestry AND quality.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But for Lithium &amp;amp; NiMh batteries you usually can get more than 1C reliably.&#xA;The more current you get - the more looses &amp;amp; heat generated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wouldn't got over 3C in any case. &lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-06T15:48:33.197" />
  <row Id="12684" PostTypeId="1" AcceptedAnswerId="12685" CreationDate="2011-04-06T15:49:55.730" Score="1" ViewCount="107" Body="&lt;p&gt;I'm a Microchip guy, but I'm helping a customer out with an Atmel project using the ATmega88PA project they inherited from another division. I'm using AVR Studio 5 and I would like to compile the fuse selections into the source code and eventually hex file. How do I do this? &lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-04-06T18:38:03.443" Title="How to set ATmega88PA fuses in code or HEX file" Tags="&lt;avr&gt;&lt;atmel&gt;" AnswerCount="1" />
  <row Id="12685" PostTypeId="2" ParentId="12684" CreationDate="2011-04-06T16:20:28.157" Score="3" ViewCount="" Body="&lt;p&gt;You can't, they have to be set in AVR Studio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use the AVRdude utility, programming and fuse settings can be automated with makefiles.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-06T18:38:03.443" LastActivityDate="2011-04-06T18:38:03.443" CommentCount="6" />
  <row Id="12686" PostTypeId="1" AcceptedAnswerId="12689" CreationDate="2011-04-06T17:30:59.560" Score="4" ViewCount="197" Body="&lt;p&gt;I have a simple 12V 10 A power supply with just a transformer and a rectifier. After doing some research and simulations, I've added 3 10 mF capacitors in parallel to smooth out the output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My problem is that after turning the supply off, capacitors remain charged for quite some time. I can get small sparks after shorting the output even 5 minutes after turning the supply off. Right now I only have a single LED connected to the capacitors and it takes more than 10 minutes for it to turn off completely after powering the supply down and the capacitors still aren't fully discharged when it turns off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most obvious way to solve the problem would be to put a resistor and a switch on the output and connect the resistor to the capacitors after turning off the supply by hand, but I'm hoping to get something a bit smarter and a bit safer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another point is that I want to use the supply's original case which has very little free volume now that I've added the capacitors, so just putting a ceramic 11 W resistor could be a problem because there would be very little free space around it for safe cooling.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-04-06T17:51:12.310" LastActivityDate="2011-04-08T12:18:14.487" Title="How to discharge smoothing capacitors?" Tags="&lt;power-supply&gt;&lt;capacitor&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="12687" PostTypeId="2" ParentId="12679" CreationDate="2011-04-06T17:32:53.840" Score="0" ViewCount="" Body="&lt;p&gt;Many RC aircraft batteries can be run at 20 or 30C continuously, but those are specifically designed to do so. I wouldn't imagine a C rating exceeding 1C for a consumer battery, like the CCTV camera.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-06T17:32:53.840" />
  <row Id="12688" PostTypeId="2" ParentId="12618" CreationDate="2011-04-06T17:38:58.153" Score="1" ViewCount="" Body="&lt;p&gt;Given an 8x8 hardware multiply, one can compute a divmod-10 of an arbitrary-size number by using a routine which computes it for 12-bit number in the range 0-2559 via the procedure:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Assume original number in OrigH:OrigL&#xA;&lt;li&gt;Divide the original number by two and store that in TempH:TempL&#xA;&lt;li&gt;Add the MSB of TempL*51 to the LSB of TempH*51.  That is the approximate quotient&#xA;&lt;li&gt;Multiply the approximate quotient by 10, discarding the MSB of the value.&#xA;&lt;li&gt;Subtract the LSB of that result from the LSB of the original number.&#xA;&lt;li&gt;If that value is 10 or greater (max will be 19), subtract 10 and add 1 to the approximate quotient&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I would suggest writing a divmod routine which the MSB of the number will be in W, and the LSB pointed to by FSR; the routine should store the quotient in FSR with post-decrement and leave the remainder in W.  To divide a 32-bit long by 10, one would then use something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;  movlw 0&#xA;  lfsr 0,_number + 3   ; Point to MSB&#xA;  call _divmod10_step&#xA;  call _divmod10_step&#xA;  call _divmod10_step&#xA;  call _divmod10_step&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;A divmod-6 step would be very similar, except using constants of 85 and 6 rather than 51 and 10.  In either case, I would expect the divmod10_step would be 20 cycles (plus four for the call/return) so a short divmod10 would be about 50 cycles and a long divmod10 would be about 100 (if one special-cases the first step, one could save a few cycles).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-04-06T18:48:59.657" LastActivityDate="2011-04-06T18:48:59.657" />
  <row Id="12689" PostTypeId="2" ParentId="12686" CreationDate="2011-04-06T17:51:40.803" Score="8" ViewCount="" Body="&lt;p&gt;Appropriate bleeder resistors are the usual solution. They aren't usually switched, although they can be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The value depends on the time you require to discharge the capacitors. The formula is&lt;/p&gt;&#xA;&#xA;&lt;p&gt;V(t) = V(0)Exp(-t/RC)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;where V(t) is the voltage at time t and V(0) is the initial voltage at time 0. It's an exponential function, so I'd just assume 1/10 of the initial voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It isn't a power function, as someone edited it!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should find that the power taken by the bleeder resistors is negligible compared to the 120W capability of the supply.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-08T12:18:14.487" LastActivityDate="2011-04-08T12:18:14.487" CommentCount="2" />
  <row Id="12690" PostTypeId="2" ParentId="12686" CreationDate="2011-04-06T17:51:58.067" Score="3" ViewCount="" Body="&lt;p&gt;What you want is a switch which is open when the circuit is powered, and closed when it is switched off. When closed it should discharge the capacitor over a resistor. You don't want to short the capacitor; they don't like that. Two approaches I can think of (from the top of my head):  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Use a depletion MOSFET as the switch. Depletion MOSFETs conduct when there's no voltage applied to the gate. Apply a voltage to switch it off. This voltage can not be derived from the capacitor you want to discharge! Otherwise the MOSFET would never be switched off. (You think about this, if you don't get it tell me, and I'll try to explain.)  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Use an ordinary NPN transitor which you drive from the capacitor's voltage. As long as there's a voltage present, it will discharge. Pull the transistor's base to ground if the circuit is switched on. Again, the voltage to do this is from a separate power supply.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-06T17:51:58.067" />
  <row Id="12691" PostTypeId="2" ParentId="5951" CreationDate="2011-04-06T18:09:15.400" Score="0" ViewCount="" Body="&lt;p&gt;If your drawing calls out +/- mil tolerances for PTH's and via's, your board house can select appropriate hole sizes that match their &quot;standard&quot; without upcharging for custom hole sizes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, you might have something like:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;+2/-0 PTH for &amp;lt; 50 mil&#xA;+4/-2 PTH &gt;= 50 mil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;+2/-2 for all via's.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-06T18:09:15.400" />
  <row Id="12692" PostTypeId="1" AcceptedAnswerId="12694" CreationDate="2011-04-06T19:45:17.027" Score="2" ViewCount="120" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to design a circuit to measure power of 230VAC (MAINS), with the ADC of a small MCU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have designed the part of the circuit to measure current, but my solution to measure voltage is getting a bit messy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If have come up with a solution using an opto-coupler, but I'm not sure, it is the best way to do it.&#xA;I have also looked at transformers, but the seem expensive and kinda big.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please come with some good suggestions?&lt;/p&gt;&#xA;" OwnerUserId="3041" LastActivityDate="2011-04-07T14:30:37.417" Title="Best way to measure 230VAC" Tags="&lt;adc&gt;&lt;isolation&gt;" AnswerCount="1" CommentCount="0" FavoriteCount="2" />
  <row Id="12693" PostTypeId="2" ParentId="12594" CreationDate="2011-04-06T19:45:33.377" Score="3" ViewCount="" Body="&lt;p&gt;$B_\rm{max}$: There is no universal definition about the exact point above which an inductor is called saturated. Many modern ferrites saturate around 300 mT. Useful values tend to vary between the points when the inductor has lost 10 % to 33 % of its original inductance. Here's a practical test useful for finding a reasonable $I_\rm{max}$ for a given inductor: You apply a square voltage across the inductor and monitor the current while doing so. You will observe a current waveform that starts from zero in a linear way as soon as the voltage is applied. You can calculate the inductance using $L = U * \frac{dt}{dI}$. You will observe an increased rate of rise once you get to the point of saturation. $I_\rm{max}$ is reached when the rate of rise just starts to get bigger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Maximum useful frequency and other parameters:&lt;/strong&gt; Most interesting parameters (including frequency) have to do with core losses. It's quite hard to find out about them without being able to compare an unknown core to a known sample. When I was designing transformers for switching power supplies, we would test different cores and just see how hot they behaved at different currents, with or without being driven into saturation, at different temperatures and at different frequencies. It was a lot of experimentation and trial and error, and we made samples with different numbers of windings, different air gaps and various ways of layer construction.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-04-06T19:45:33.377" CommentCount="3" />
  <row Id="12694" PostTypeId="2" ParentId="12692" CreationDate="2011-04-06T19:59:39.707" Score="9" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.vishay.com/docs/83622/il300.pdf&quot; rel=&quot;nofollow&quot; rel=&quot;nofollow&quot;&gt;Vishay IL300&lt;/a&gt; is an &lt;strong&gt;analog optocoupler&lt;/strong&gt; with excellent linearity. It contains 2 identical photodiodes, one of which you use in a feedback loop.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/7RLD4.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously the Vcc on the left hand side (power of U1 and the optocoupler's pin 3) is different and isolated from the Vcc at the right.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-07T14:30:37.417" LastActivityDate="2011-04-07T14:30:37.417" CommentCount="3" />
  <row Id="12695" PostTypeId="2" ParentId="11017" CreationDate="2011-04-06T20:49:26.080" Score="1" ViewCount="" Body="&lt;p&gt;I went down this path, and found it was &lt;strong&gt;far, far easier&lt;/strong&gt; to just buy one of the supported serial interface cards, such as the DSC 5401 or the newer IT-100.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For more info, see: &lt;a href=&quot;http://www.payne.org/index.php/Product:DSC_5401&quot; rel=&quot;nofollow&quot;&gt;http://www.payne.org/index.php/Product:DSC_5401&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: if you had your alarm installed, your installer will have to come over and &quot;register&quot; the interface card on your KEYBUS network.  I suspect the protocol may have some security features (I'd hope so), and that will make reverse engineering even harder.&lt;/p&gt;&#xA;" OwnerUserId="2718" LastActivityDate="2011-04-06T20:49:26.080" />
  <row Id="12696" PostTypeId="2" ParentId="12600" CreationDate="2011-04-06T21:45:29.217" Score="5" ViewCount="" Body="&lt;p&gt;If the solder mask expansion were 0, in theory -- assuming everything aligned perfectly -- the board would work fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In practice, things never align perfectly.&#xA;The actual hole punched in the solder mask may be slightly less than what you specified (&quot;shrinkage&quot;), and that hole is &lt;em&gt;always&lt;/em&gt; be placed in a slightly different location than what you specified (&quot;movement&quot;).&#xA;If your solder mask expansion is too small, then these misalignments cause the solder mask to partially or completely overlap SMT pads and through-hole pads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the solder mask completely covers most or all of the pad, the SMT part will be completely disconnected from that pad.&#xA;Then the board will immediately fail the end-of-line go-nogo test.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many people specifically design the pads of a footprint to comply with IPC's fillet recommendations.&#xA;If the solder mask even partially covers some of that pad,&#xA;then the fillet of solder will be smaller than a person looking only at the copper might expect.&#xA;If the fillet of solder is too small, then the (SMT or through-hole) part will not be mechanically attached as well.&#xA;After a few thousand cycles of vibration, the solder may eventually crack, and the part will be completely disconnected from that pad or hole.&#xA;Then your customer will notice the problem.&#xA;(This is much worse than a board failing the end-of-line go-nogo test).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Daniel Grillo gives an excellent explanation of what happens if the solder mask is too big.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-06T21:45:29.217" />
  <row Id="12697" PostTypeId="1" AcceptedAnswerId="12700" CreationDate="2011-04-06T21:56:54.893" Score="1" ViewCount="82" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am going to use a DPST relay to pass a 1A 1000V DC signal through it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have see many relays, they share a property like maximum DC switching for example 200V (and it is generally higher for AC like 400).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now my question is, If I get a relay that has 200V DC switching property what kind of problems I will get?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or can I do like this: I will control the signal and also the relay using a micro controler, so I can be sure that I first turn ON the relay then start the signal. I beleive the relay should just work like a shorting wire and cause no problems? Same case also for switching the relay OFF that is I first stop the signal and then turn OFF the relay. is this approach going to work?&lt;/p&gt;&#xA;" OwnerUserId="3757" LastEditorUserId="3757" LastEditorDisplayName="" LastEditDate="2011-04-06T22:59:47.490" LastActivityDate="2011-04-07T02:00:27.833" Title="Need clearification about relay properties" Tags="&lt;relay&gt;&lt;switching-voltage-reg&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="12698" PostTypeId="2" ParentId="12697" CreationDate="2011-04-06T23:09:45.993" Score="4" ViewCount="" Body="&lt;p&gt;First I would NOT try to pass a 1000V signal through a relay rated for 200V.  When closed you &lt;em&gt;may&lt;/em&gt; not have a problem (absolutely no guarantees), but when OPEN it may arc and, well, that would be bad.  Suffice it to say it would not exactly act as an open in that circumstance. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, I realize you said that the signal wouldn't be there when the relay is open - you'd turn it on after the relay is closed and off after the signal is turned off.  If you already have that control over the signal why use a relay?  To switch between two different destinations?  In that case you'll still have the arcing problem.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A datasheet would help if you want a better answer.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-06T23:09:45.993" />
  <row Id="12699" PostTypeId="2" ParentId="12680" CreationDate="2011-04-06T23:17:58.060" Score="2" ViewCount="" Body="&lt;p&gt;You're very new to FPGAs and you want to do image processing?  I'm no expert but that sounds like biting off a lot more than you can chew.  Can you answer any of these questions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;What image processing algorithm do&#xA;you want to implement?  Can you&#xA;express the algorithm in pseudocode?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;What format is the image you want to&#xA;process?  Bitmap?  JPEG?  What color&#xA;depth?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;What image sensor have you chosen? &#xA;What resolution is it?  Is it&#xA;grayscale or color?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Do you have a basic block diagram of&#xA;the system?  Can you show us?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you haven't thought about any of these questions or don't understand the terms I'm using then this project probably isn't for you.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-06T23:17:58.060" CommentCount="4" />
  <row Id="12700" PostTypeId="2" ParentId="12697" CreationDate="2011-04-07T02:00:27.833" Score="10" ViewCount="" Body="&lt;p&gt;Here is what happens when you try to disconnect a relay at a high voltage relative to the dielectric strength of the medium (air)/open air gap.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;During the brief period when the gap is opening, but not yet fully open, the air gap looks like a capacitor.  The dielectric strength of air, that is, the amount of voltage needed to turn it from an insulator into a conductor, isn't terribly great.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there is any inductance in the circuit, current will continue to flow into the gap, momentarily charging the capacitor up far past the dielectric strength of the air.  Almost all contact style switches produce some amount of spark.  You may have noticed the wall switches in your house flash when you turn off large loads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That spark is cause by the ionization of the air, turned into a plasma, that happened to carry a few electrons across the gap.  Though air is a decent insulator, plasma is a very good conductor.  As current flows through the plasma, more plasma is produced.  The rate of plasma production will basically be determined by the voltage across the gap (more voltage is more current is more plasma), and the resistance of the plasma (less resistance is more current is more plasma).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the gap is large compared to the voltage, the plasma will quickly dissipate, and the switch will do it's job of opening the circuit.  If the voltage is large, compared to the gap, the volume plasma will increase faster than it can dissapate, until the whole gap is filled with plasma, and conducting electricity in a run-away reaction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're lucky, that's the worst of it.  If the contacts are metallic (and they usually are at modest voltages), the intense heat of the plasma can cause the contacts to melt and ultimately &lt;em&gt;weld closed&lt;/em&gt;, putting the switch in a perminantly on state, even after current is removed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A similar process can occur even in solid state switches;  This is not a phenomenon limited to mechanical relays.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should &lt;em&gt;NEVER&lt;/em&gt; use a switch to open a circuit at a voltage higher than the value it is rated to block.  Fortunately, high voltage, &lt;a href=&quot;http://www.mouser.com/ProductDetail/STMicroelectronics/STGF3NC120HD/?qs=sGAEpiMZZMtvcUztdGSumGWBIWhLr08tF8O2aJQLh70=&quot; rel=&quot;nofollow&quot;&gt;solid state&lt;/a&gt; switches are perfectly capable and available at reasonable cost.&lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2011-04-07T02:00:27.833" CommentCount="1" />
  <row Id="12701" PostTypeId="1" AcceptedAnswerId="12709" CreationDate="2011-04-07T02:34:20.830" Score="0" ViewCount="161" Body="&lt;p&gt;So, I decided I wanted to make my very first foray into some basic electronics. I decided I was going to attempt to make a laser mag-lite, as per &lt;a href=&quot;http://www.liveleak.com/view?i=85d_1186747374&quot; rel=&quot;nofollow&quot;&gt;this hack here&lt;/a&gt;. The steps seem pretty straight forward, so I figured it would make a good first project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wound up getting (not thinking about possible differences) the laser diode mount for the DVD reader in the XBox 360. I'm now in post-mortem mode. I extracted the diode with no issue, and through some trial and error I figured out the correct 2 pins (out of four on this diode). Once I got those extended and plugged into the mag-lite, it glowed red for a few seconds, then I started to smell some ozoney-smelling &quot;burning&quot; and then it went out, and now it is apparently dead, and will not light again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I'm looking for confirmation/input why it failed, as I have my theory. My working theory is that since this was a &quot;reader&quot; diode as opposed to a writer, it has a much lower energy usage... and so the 3V of the mag-lite batteries were way too much for the poor little diode, burning it out. Is this a likely theory? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If so, would the speed of the burner (16x, etc.) being used make a difference? I don't know if the laser is any different based on the speed or if that just indicates differences in the speed of the spindle and the lens actuators in the laser assembly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As one related question, in project directions for this kind of project, most of them talk about &quot;finishing&quot; the end project with a laser control circuit. What exactly does the LCC do?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. If someone with the rep could maybe create and tag this Q with the following tags: &lt;code&gt;dvd&lt;/code&gt;, &lt;code&gt;mag-lite&lt;/code&gt;, &lt;code&gt;post-mortem&lt;/code&gt; I'd appreciate it.&lt;/p&gt;&#xA;" OwnerUserId="3758" LastActivityDate="2011-04-07T18:26:13.053" Title="Using a DVD diode to create a mag-lite laser" Tags="&lt;laser&gt;" AnswerCount="4" CommentCount="6" />
  <row Id="12702" PostTypeId="2" ParentId="12701" CreationDate="2011-04-07T03:08:46.613" Score="2" ViewCount="" Body="&lt;p&gt;This may be way off the mark because a laser diode I-V characteristic may be very different from the ordinary p-n junction diode, but if a regular semiconductor diode is forward biased with nothing to limit the current (such as a resistor) it's generally going to act like a short circuit. The current is going to become very large, and therefore the power dissipation is going to be very high, and the diode will probably burn out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have connected &lt;s&gt;3.3V&lt;/s&gt; 3V across the diode's terminals with no series resistance, then the scenario described above may be what has happened...&lt;/p&gt;&#xA;" OwnerUserId="3635" LastEditorUserId="3635" LastEditorDisplayName="" LastEditDate="2011-04-07T18:26:13.053" LastActivityDate="2011-04-07T18:26:13.053" />
  <row Id="12703" PostTypeId="2" ParentId="12701" CreationDate="2011-04-07T06:43:33.927" Score="3" ViewCount="" Body="&lt;p&gt;From what I've read, most lasers have a light sensor built into them and require it for reliable operation.  There is a very fine line between putting in too little current and getting no output, or putting in too much and destroying the laser.  This amount of current required will vary depending upon temperature, phase of the moon, etc. and so the only way to consistently find it is to vary the current so the laser is right at the threshold.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-07T06:43:33.927" CommentCount="1" />
  <row Id="12704" PostTypeId="1" AcceptedAnswerId="12722" CreationDate="2011-04-07T07:53:57.147" Score="1" ViewCount="117" Body="&lt;p&gt;Hey all, continuing my PhotoBioReactor project. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Need some assistance determining not only what kind of rotary slip ring I need to use but where to get it as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basic overview:&#xA;I plan on oscillating a vertical shaft 360 degrees over a varied timeframe. This shaft has some aquarium lights vertically mounted to it. I need to power these lights without the cords getting tangled up, hence the idea to use a rotary slip ring to pass the electricity needed through the rotating shaft's axle housing and have a stationary cord to the base unit and an automagical electrified light pole. Of doom.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Needless to say, finding a slip ring supplier (or even someone who knows WTF I'm talking about) has been... challenging. Help?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need the rotating joint to be able to attach to 1/2&quot; thick transparent lexan, support at least 30 pounds of weight on it (likely need ball bearings), pass enough electric-juice through to power (at full peak power) four fluorescent 24&quot; T8 light fixtures that suck down 120v~277v 50/60Hz each, allow a geared servo or stepper motor to effortlessly rotate the shaft, and preferably not be a pain in the arse or wallet. :P&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A work-in-progress Google Sketchup shot of the light-shaft:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/YL7bp.png&quot; alt=&quot;http://goo.gl/kVBAi&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Eagerly awaiting enlightenment,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-- Daerk&lt;/p&gt;&#xA;" OwnerUserId="3744" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-04-07T12:20:20.373" LastActivityDate="2011-04-07T19:40:50.470" Title="Electrified Vertical mounted rotary joint questions" Tags="&lt;power&gt;&lt;robotics&gt;&lt;hardware&gt;&lt;interconnect&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="12705" PostTypeId="1" CreationDate="2011-04-07T08:42:59.820" Score="0" ViewCount="82" Body="&lt;p&gt;I'm looking into various gate level (NAND, NOR, AND, INV) designs for low energy arithmetic/logic blocks, especially adders. Low energy indicates the use of minimal energy per operation executed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Holding $V_{dd}$, technology and clock speed constant, which of the following adder designs are more energy efficient: Ripple, carry lookahead, carry-select, prefix adders? And why is that so?&lt;/p&gt;&#xA;" OwnerUserId="2897" LastActivityDate="2011-04-07T21:58:58.710" Title="Low energy arithmetic/logic gate level design" Tags="&lt;low-power&gt;&lt;vlsi&gt;" AnswerCount="2" />
  <row Id="12706" PostTypeId="2" ParentId="12705" CreationDate="2011-04-07T09:02:34.330" Score="0" ViewCount="" Body="&lt;p&gt;It's not that simple. There are lots of variants of fulladder itself, with different number of transistors. This is very popular subject, and on IEEE you can easily find many papers with specific benchmark results you are interested in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can also add, that going for carry-lookahead added allow you to go for much lower voltage with the same performance level =&gt; less total consumption at the same performance level. &lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-07T09:02:34.330" />
  <row Id="12707" PostTypeId="2" ParentId="12701" CreationDate="2011-04-07T09:06:22.920" Score="4" ViewCount="" Body="&lt;p&gt;In the simplest (acceptable) case you need stabilised current source - for example built from LM317/1117. For a diode from DVD-RW, you can start from 100ma. If it's from reader - not more than 3-5ma. Yes, reader diodes are 100x weaker.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without any regulation any diode would die immidiately.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-07T09:06:22.920" />
  <row Id="12708" PostTypeId="2" ParentId="12686" CreationDate="2011-04-07T09:09:01.280" Score="2" ViewCount="" Body="&lt;p&gt;Such huge caps seems to be an overkill... If it's regulated (linear/pulse) you would need to tune it till ripple would be acceptable with much less output capacitor. If you have alot of high-freq noise - you would need to add several ceramic caps. Also, make sure that your inductor at the output is calculated correctly.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-07T09:09:01.280" CommentCount="3" />
  <row Id="12709" PostTypeId="2" ParentId="12701" CreationDate="2011-04-07T09:30:40.083" Score="4" ViewCount="" Body="&lt;p&gt;Laser diodes are like LEDs in that the more current you put through them, the hotter they get, and the hotter they get, the more current will go through them, which makes them get hotter... and then &lt;em&gt;fzzt&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So yes, as BarsMonster says, without anything to regulate the current (in the simplest case, a &lt;a href=&quot;http://ledcalc.com/&quot; rel=&quot;nofollow&quot;&gt;current limiting resistor&lt;/a&gt;) the laser diode will die immediately.&lt;/p&gt;&#xA;" OwnerUserId="1633" LastActivityDate="2011-04-07T09:30:40.083" />
  <row Id="12710" PostTypeId="1" CreationDate="2011-04-07T09:41:33.830" Score="0" ViewCount="58" Body="&lt;p&gt;Looking for a design that can convert GSM mobile phone into a two-in-one to act as a cordless phone to receive or make calls from/to landline at home as well as to use as GSM cellular phone to receive/make calls via cellular network.&lt;/p&gt;&#xA;" OwnerUserId="3762" LastActivityDate="2011-04-07T09:41:33.830" ClosedDate="2011-04-07T12:07:01.227" Title="Do you have a design that converts mobile phone in to a mobile phone cum cordless phone for use at home?" Tags="&lt;phone&gt;&lt;mobile&gt;" CommentCount="2" />
  <row Id="12711" PostTypeId="2" ParentId="9553" CreationDate="2011-04-07T09:57:51.240" Score="1" ViewCount="" Body="&lt;p&gt;As I know, Inductor and capacitor is combined to get the frequency resonance when $X_C =X_L$, Inductor and capacitor also can be used as filter $X_L= 2{\pi}fL$, $X_{C}=\frac{1}{2{\pi}f C}$ , with Band stop or Band pass when $V=0.707V_{max}$&lt;/p&gt;&#xA;" OwnerUserId="3763" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-07T13:07:03.570" LastActivityDate="2011-04-07T13:07:03.570" />
  <row Id="12712" PostTypeId="2" ParentId="9553" CreationDate="2011-04-07T11:28:12.727" Score="2" ViewCount="" Body="&lt;p&gt;The basic electrical property of a capacitor is that the voltage across a capacitor cannot change instantaneously, whereas the basic property of inductance is that the current through an inductor cannot change instantaneously. Capacitors preserve voltage by storing energy in an electric field, whereas inductors preserve current by storing energy in a magnetic field. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One result of this is that while capacitors conduct best at higher frequencies, inductors conduct best at lower frequencies. Another result is that if you put an AC current through&#xA;a capacitor, the voltage will lag behind the current by some phase angle that depends on the capacitance and the frequency - capacitors inhibit changes in voltage. Meanwhile if you put an AC voltage across an inductor, the current will lag behind the voltage by a phase angle that depends on the inductance and the frequency - inductors inhibit changes in current.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-07T11:28:12.727" />
  <row Id="12713" PostTypeId="1" CreationDate="2011-04-07T13:13:11.007" Score="1" ViewCount="45" Body="&lt;p&gt;Asked the question here : &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to understand Complementary Code Keying. How modulation and demodulation is done ? &#xA;How higher data rate is achieved using CCK modulation in IEEE 802.11b ? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is Hadamard transform encoding specified in IEEE 802.11b spec ? How demodulation can be performed on the received samples. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://stackoverflow.com/q/5551869/630661&quot;&gt;http://stackoverflow.com/q/5551869/630661&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3733" LastActivityDate="2011-04-07T13:13:11.007" Title="Complementary Code Keying" Tags="&lt;wireless&gt;&lt;matlab&gt;&lt;modulation&gt;&lt;demodulation&gt;" CommentCount="1" />
  <row Id="12714" PostTypeId="1" AcceptedAnswerId="12721" CreationDate="2011-04-07T13:20:46.107" Score="1" ViewCount="76" Body="&lt;p&gt;I'm using PIC16F1947 for a project. The project requires real time tracking so a stable 32768 Hz crystal is connected with the Timer1 oscillator. The Timer1 oscillator circuit and the crystal will provide stable clock for our project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Timer1 can only provide interrupt when the timer counter overflows. It is a 16 bit counter so interrupt will be given each time the counter rolls over to 0x0000 from 0xFFFF.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the timer will be used for time keeping purpose from the beginning to the end of the product, Timer1 can't be stopped. Also, it has to be run while the processor is sleeping. So we need to use it in asynchronous mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In our project we also need interrupts every 0.5 second. So we plan to initialize Timer1 counter to 0xC000 and then start it. Each time an interrupt will be given, we plan to bitwise OR 0xC0 to the high byte of the register.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to the datasheet:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Reading TMR1H or TMR1L while the timer&#xA;  is running from an external&#xA;  asynchronous clock will ensure a valid&#xA;  read (taken care of in hardware).&#xA;  However, the user should keep in mind&#xA;  that reading the 16-bit timer in two&#xA;  8-bit values itself, poses certain&#xA;  problems, since the timer may overflow&#xA;  between the reads.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;For writes, it is&#xA;  recommended that the user simply stop&#xA;  the timer and write the desired&#xA;  values. A write contention may occur&#xA;  by writing to the timer registers,&#xA;  while the register is incrementing.&#xA;  This may produce an unpredictable&#xA;  value in the TMR1H:TMR1L register&#xA;  pair.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Is it OK to bitwise OR 0xC0 with the high byte while the timer is running? Or should we use another Timer for 0.5 second interrupt?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="3720" LastActivityDate="2011-04-07T17:11:47.810" Title="Writing to timer counter while timer is running" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;timer&gt;&lt;best-practice&gt;&lt;interrupt&gt;" AnswerCount="1" />
  <row Id="12715" PostTypeId="1" AcceptedAnswerId="12717" CreationDate="2011-04-07T14:18:07.900" Score="3" ViewCount="177" Body="&lt;p&gt;I am trying to wire up a LED matrix using a FET transistor as a switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The AVR will be connected to the gate. To turn the LEDs on I have drive the pin connected to the transistor gate low, right?&lt;/p&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-08T12:21:51.503" LastActivityDate="2011-04-08T12:21:51.503" Title="Driving a LED Matrix with a N-channel MOSFET (2N3819) using an AVR" Tags="&lt;avr&gt;&lt;led&gt;&lt;switch&gt;&lt;mosfet&gt;&lt;matrix&gt;" AnswerCount="2" />
  <row Id="12716" PostTypeId="2" ParentId="12715" CreationDate="2011-04-07T14:24:22.253" Score="1" ViewCount="" Body="&lt;p&gt;The 2N3819 is a poor choice because of its limited current-handling capability and because it needs a negative voltage on the gate to turn it off. A BJT would be more suitable.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-07T16:06:55.230" LastActivityDate="2011-04-07T16:06:55.230" CommentCount="3" />
  <row Id="12717" PostTypeId="2" ParentId="12715" CreationDate="2011-04-07T14:52:19.643" Score="3" ViewCount="" Body="&lt;p&gt;The 2N3819 is an RF 'N' channel depletion mode JFET and is not really suitable for LED switching. Depletion mode means that the gate needs to be driven abut 7 volts &lt;em&gt;more negative&lt;/em&gt; than the source to turn it off, and driven to the source voltage &lt;em&gt;but no higher&lt;/em&gt; to turn it on. The maximum drain current is probably not high enough for your needs either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Look for an N channel enhacement mode MOSFET instead.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-04-07T14:52:19.643" CommentCount="3" />
  <row Id="12718" PostTypeId="1" AcceptedAnswerId="12719" CreationDate="2011-04-07T14:52:24.610" Score="2" ViewCount="121" Body="&lt;p&gt;I need to cut the voltage going through a 1/4&quot; &lt;a href=&quot;http://en.wikipedia.org/wiki/TRS_connector&quot; rel=&quot;nofollow&quot;&gt;TRS cable&lt;/a&gt; (at the connector) by 1/2 (and I need to do this to about 14 cables). I understand that this can be accomplished with two 4.7 kohm resistors per cable; however, I have never soldered before (although I've always been interested in soldering and this seems like a simple enough project -- the need happens to have presented itself). I was wondering if anybody could give me some pointers. I've managed to find a reference schematic but it doesn't really make sense to me (there seem to be more than two resistors -- that is two R1s and two R2s):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/8eU8o.png&quot; alt=&quot;TRS Voltage Divider Schematic&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other than help understanding exactly what needs to be done, I was wondering if anybody could recommend any soldering irons and other equipment or supplies (shrink tubing, etc) for a newbie to buy. What exactly will I need to make this appear clean (not as if the cable was never tampered with, but at least semi-professional looking)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&#xA;- KP&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. If I could use two 4.7 kohm resitors to multiply the voltage by 1/2 what resistors could I use to multiply the voltage by 2/3 (remove a third voltage) -- I imagine based on the information I've gathered that the two resistors would have to be different values. I am doing this to cut the voltage coming from electronic drum pads, and from what I've read the tom pads don't need to be cut down as much as snare, kick, and cymbal pads.&lt;/p&gt;&#xA;" OwnerUserId="3765" LastActivityDate="2011-04-08T01:43:08.090" Title="Voltage Divider" Tags="&lt;voltage-regulator&gt;&lt;resistor&gt;&lt;voltage&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="12719" PostTypeId="2" ParentId="12718" CreationDate="2011-04-07T15:14:30.497" Score="4" ViewCount="" Body="&lt;p&gt;A voltage divider follows the equation of Vout=Vin*(R2/(R1+R2)). So in your case 4.7kohm/(4.7+4.7) = 1/2. You can adjust your R1 and R2 values however you want in order to get the ratio you want. For ease I would recommend you keep R2 as 4.7 KOhm and just change the R1 value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now as far as your schematic and having 2 sets of R1s and R2s, this is because you essentially have 2 inputs. The connector you are using has 3 pins, ground, left, and right. There are different variances to drum kits, but the one I used in the past would put one instrument on left and a different on right. You need 1 set of R1/R2 per input signal which results in you having 2 per plug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a side note, I would suggest you consider NOT doing this voltage divider method and instead go with an actual sound board that lets you adjust the levels.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-07T15:14:30.497" CommentCount="4" />
  <row Id="12720" PostTypeId="2" ParentId="12718" CreationDate="2011-04-07T15:18:38.107" Score="3" ViewCount="" Body="&lt;p&gt;There are four resistors because there are two signals (left and right on a stereo jack) and a voltage divider needs two resistors. For half the voltage, the resistors are the same. For 2/3 the voltage, the resistor to ground is twice the resistance to the source. Therefore replacing R2 with 10k would give you close to 2/3.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-04-07T15:18:38.107" />
  <row Id="12721" PostTypeId="2" ParentId="12714" CreationDate="2011-04-07T17:11:47.810" Score="2" ViewCount="" Body="&lt;p&gt;On the PICs with two 32KHz timers (TMR1 and TMR3) my recommendation would be to use one of the timers 'free-running' (never write to it) and use the other to generate wakeup events.  If you only have one timer available, getting reliable operation without cumulative errors is going to be very difficult.  Different part revisions have different behaviors when it comes to writing timer 1, and so an approach that would work with one revision may be broken by a future revision.  What would have been nice would have been if Microchip had allowed the timer to switch between synchronous and asynchronous modes without losing a count (simple to do: instead of using a multiplexer to switch between sync and async mode, add asynchronous set/clear to the synchronizing latch, and when in async mode use those to force the output to follow the input).  None of their parts are, so far as I know, documented as doing any such thing.  Consequently, I would expect that switching between synchronous and async mode may randomly gain or lose a count.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-07T17:11:47.810" />
  <row Id="12722" PostTypeId="2" ParentId="12704" CreationDate="2011-04-07T18:40:31.770" Score="1" ViewCount="" Body="&lt;p&gt;You didn't say how large the shaft is, but...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thrust bearing or lazy susans can support the load. Search for those at AS&amp;amp;S: www.sciplus.com&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Slip rings are expen$$ive. If you're oscillating, can you just use flexible cable that can wrap and unwrap around the shaft?&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-04-07T18:40:31.770" CommentCount="4" />
  <row Id="12723" PostTypeId="2" ParentId="12704" CreationDate="2011-04-07T19:40:50.470" Score="1" ViewCount="" Body="&lt;p&gt;Can you arrange a stationary vertical lights and rotate mirrors / slits around them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you absolutely must use a slip ring, look at the brushes and commutator of a DC motor for ideas.  Or just save up a little money and buy a Mercotac connector (mercury inside, not RoHS).  Or save up a big pile of money and buy a slip ring connector.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-07T19:40:50.470" CommentCount="2" />
  <row Id="12724" PostTypeId="1" CreationDate="2011-04-07T21:54:13.253" Score="2" ViewCount="91" Body="&lt;p&gt;Is there a way to develop some Verilog designs on mac?&lt;/p&gt;&#xA;" OwnerUserId="2404" LastActivityDate="2011-05-08T03:23:14.363" Title="Verilog simulator or development environment on Mac OS" Tags="&lt;simulation&gt;&lt;mac&gt;&lt;verilog&gt;&lt;development-tools&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="12725" PostTypeId="2" ParentId="12705" CreationDate="2011-04-07T21:58:58.710" Score="1" ViewCount="" Body="&lt;p&gt;Independently of full-adder design (which is very important as BarsMonster says), objectively, the most power efficient adder would be the one with the least number of transistors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using the same kind of full-adder unit (same quantity of transistors in each FA) in the Adders that you mention, the &quot;smallest&quot; would be the Ripple Carry Adder. All other adders have some sort of extra circuitry to lower the critical propagation delay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out this link: &lt;a href=&quot;http://users.encs.concordia.ca/~asim/COEN_6501/Lecture_Notes/Lecture_2_Slides.pdf&quot; rel=&quot;nofollow&quot;&gt;http://users.encs.concordia.ca/~asim/COEN_6501/Lecture_Notes/Lecture_2_Slides.pdf&lt;/a&gt; @ pages 40 - 48.&lt;/p&gt;&#xA;" OwnerUserId="3078" LastActivityDate="2011-04-07T21:58:58.710" />
  <row Id="12727" PostTypeId="2" ParentId="12679" CreationDate="2011-04-07T22:34:37.283" Score="2" ViewCount="" Body="&lt;p&gt;You're not really looking for the C rating (maximum discharge current in multiples of nominal capacity), you're looking for the adjusted capacity at your nominated discharge current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 1.8Ah lithium battery can &lt;em&gt;theoretically&lt;/em&gt; give 1.8A for 1hour, or 3A for 1.8/3h = 36 minutes.   &lt;em&gt;HOWEVER&lt;/em&gt; the capacity for a battery is traditionally quoted for a 20 hour discharge.   That is, a capacity rating of 1.8Ah means the battery delivered 90mA for 20 hours in testing. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The relationship between continuous current and time-to-full-discharge is NOT linear.    You have discovered that when discharged at 3A, your 1.8Ah battery is delivering much less capacity (only about a quarter!) than a linear interpolation of the amp-hour rating would suggest.    This is not unusual.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The better batteries will give rated capacity at several discharge time samples, or even a graph of current vs capacity.   A battery intended for remote control uses will probably give better performance, as quick discharge is the intended application of these batteries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I use a 1500mAh 3-cell (11.1v) 25C lithium pack to power a 3A LED bike light, and I get around an hour, which is close to rated capacity given a reasonably efficient buck regulator).&lt;/p&gt;&#xA;" OwnerUserId="389" LastActivityDate="2011-04-07T22:34:37.283" CommentCount="2" />
  <row Id="12728" PostTypeId="2" ParentId="12724" CreationDate="2011-04-07T22:43:37.653" Score="1" ViewCount="" Body="&lt;p&gt;I hear that&#xA;&lt;a href=&quot;http://www.icarus.com/eda/verilog/&quot; rel=&quot;nofollow&quot;&gt;Icarus Verilog&lt;/a&gt;&#xA;supports&#xA;&lt;a href=&quot;http://iverilog.wikia.com/wiki/Installation_Guide#Macintosh_OS_X&quot; rel=&quot;nofollow&quot;&gt;Macintosh OS X&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-07T22:43:37.653" />
  <row Id="12730" PostTypeId="2" ParentId="6321" CreationDate="2011-04-07T23:48:01.207" Score="2" ViewCount="" Body="&lt;p&gt;Most off-the-shelf inductors are &quot;shielded&quot; specifically to &lt;em&gt;prevent&lt;/em&gt; one inductor from coupling with another inductor (or anything else).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use &quot;unshielded&quot; inductors, or wind your own coils without shielding, or break the shielding off some inductors, all too often you &lt;em&gt;do&lt;/em&gt; get unwanted coupling between inductors -- enough to be annoying, but usually not enough to do anything useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To get good coupling between coils, you pretty much have to wind them both on the same bobbin -- producing a transformer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some examples of coupled inductors made from 2 coils that are different from standard wire-wound transformers (and therefore have worse coupling than a standard transformer):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Transformer_types#Planar_transformer&quot; rel=&quot;nofollow&quot;&gt;planar transformer&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.afrotechmods.com/cheap/arnoldpad/arnold.htm&quot; rel=&quot;nofollow&quot;&gt;Arnold fixed my mousepad charger&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://web.mit.edu/newsoffice/2007/wireless-0607.html&quot; rel=&quot;nofollow&quot;&gt;WiTricity&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-07T23:48:01.207" />
  <row Id="12731" PostTypeId="1" AcceptedAnswerId="12732" CreationDate="2011-04-07T23:54:29.430" Score="2" ViewCount="188" Body="&lt;p&gt;I am using &lt;a href=&quot;http://www.8051projects.net/dc-motor-interfacing/l293d.gif&quot; rel=&quot;nofollow&quot;&gt;this(also below in question)&lt;/a&gt; circuit to drive a motor, and I heard I should put a decoupling cap in there to smooth out voltage spikes. I have been told to put it close to the ic, and I have also been told not to put it in front of the ic, but between the battery terminals. Where should it go? Here's an image of how I have it worked out on the breadboard:  &lt;img src=&quot;http://i.imgur.com/3usFR.jpg&quot; alt=&quot;http://dl.dropbox.com/u/10949404/P1010135.JPG&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;circuit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ypW0K.gif&quot; alt=&quot;schematic for motor driver IC&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2873" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-08T01:45:37.020" LastActivityDate="2011-04-12T16:32:29.043" Title="Where to place decoupling capacitor" Tags="&lt;h-bridge&gt;&lt;decoupling-capacitor&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="12732" PostTypeId="2" ParentId="12731" CreationDate="2011-04-08T01:18:09.990" Score="2" ViewCount="" Body="&lt;p&gt;You probably want the cap on (or near) the motor.  The main purpose of the cap, there, is not to protect anything from ripple current, since neither the motor nor (probably) the output side of the IC, is particularly sensitive to it, but rather to reduce the stray rf caused by the commutation of the motor.  Placing the capacitor near the motor means only a short region of the leads between the driver source and the motor is experiencing much ripple, and so there's less rf interference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for other places to use smoothing capacitors, the best option is to just hook everything up, turn it all on, and probe around sensitive areas (IC signal and power inputs, mainly) with an Oscilliscope and add enough capacitance to drop undesirable ripple to a few millivolts (or whatever the circuit requires).&lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2011-04-08T01:18:09.990" CommentCount="11" />
  <row Id="12734" PostTypeId="2" ParentId="10668" CreationDate="2011-04-08T03:49:09.067" Score="1" ViewCount="" Body="&lt;p&gt;This doesn't satisfy your &quot;no-IC&quot; constraint, but may be is a good starting point:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://tinyurl.com/3oce3oz&quot; rel=&quot;nofollow&quot;&gt;International Rectifiers Audio Reference Designs &lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can get the schematics or buy one of the kits (~US$300).&lt;/p&gt;&#xA;" OwnerUserId="2544" LastActivityDate="2011-04-08T03:49:09.067" />
  <row Id="12735" PostTypeId="1" CreationDate="2011-04-08T08:20:32.543" Score="3" ViewCount="123" Body="&lt;p&gt;There is a DMM (not a cheap one, so its worth to repair it), whose leads where put into a 230V AC socket on the frequency measuring range. The meter did &quot;bzzzt&quot; sound and stopped showing anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Neither of its two fuses (1A and 10A) got blown (I checked with a resistance meter, both of them have less then an ohm).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What element would usually get fried in such situation? Is there any chance to repair it, by replacing some elements? Maybe its a common accident, so someone might know what usually gets burnt in such situation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It was an auto-ranging DMM, the setting it had when in contact with 230V AC was:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Frequency: 100Hz - 10MHz ±0.05%&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;EDIT, more details:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I opened it, and it looks like there are three transistors (or maybe something else with 3 legs?) on the board fried, and nothing else looks like fried. They are however fried to the extent that it is not possible to find out what markings where on them, so I don't know with what kind of transistors (or whatever this is) I can try to replace them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All the three fried elements are about 2.9 x 1.3 mm in size, are SMD with three legs, look exactly like &lt;a href=&quot;http://www.fairchildsemi.com/products/discrete/packaging/sot23_1.html&quot; rel=&quot;nofollow&quot;&gt;SOT-23&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/1yLDw.gif&quot; alt=&quot;SOT-23&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two of them are next to each other, and their descriptions on the PCB are: TP1 and TP2. The third element is in a different region of the board, and is described TC on the board. These are the only discrete transistor-looking-like elements on the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would be very grateful for some wild guesses with what elements, with what parameters to replace them. Are they transistors or maybe voltage reference? Its worth to do it, even if it takes me several tries to find the right one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DMM was a &lt;a href=&quot;http://www.digitek.com.cn/en/cpxx.php?id=661&quot; rel=&quot;nofollow&quot;&gt;Digitek DT80000&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1691" LastEditorUserId="1691" LastEditorDisplayName="" LastEditDate="2011-04-08T11:48:38.543" LastActivityDate="2011-04-08T13:28:17.230" Title="is it possible to repair a DMM which was burned by putting the leads into 230V on a frequency-measuring setting?" Tags="&lt;multimeter&gt;&lt;repair&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="12736" PostTypeId="2" ParentId="12735" CreationDate="2011-04-08T10:23:11.703" Score="3" ViewCount="" Body="&lt;p&gt;If the display isn't working, it's probably damaged beyond repair as the chip will have been zapped as well as the other devices on the input. It's a bit surprising that it failed if it is a good quality instrument, it should have been protected against such mishaps. A typical Fluke DMM will take 1000V on all ranges, IIRC.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-08T12:24:00.800" LastActivityDate="2011-04-08T12:24:00.800" />
  <row Id="12737" PostTypeId="2" ParentId="12680" CreationDate="2011-04-08T10:41:15.443" Score="0" ViewCount="" Body="&lt;p&gt;Big question - I've &lt;a href=&quot;http://parallelpoints.com/taxonomy/term/21&quot; rel=&quot;nofollow&quot;&gt;started a series of articles&lt;/a&gt; about developing image processing systems in FPGAs.  It's not complete yet, but it may give you some ideas. &lt;a href=&quot;http://parallelpoints.com/node/46&quot; rel=&quot;nofollow&quot;&gt;The first one is here&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can get a sensor which directly connects to the FPGA pins (ie a clock, couple of sync pins and some data pins) you'll get going much quicker than having to pull data over USB/Firewire/etc.&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-04-08T10:41:15.443" />
  <row Id="12738" PostTypeId="2" ParentId="12735" CreationDate="2011-04-08T13:28:17.230" Score="2" ViewCount="" Body="&lt;p&gt;Small parts like transistors don't stop the 230V. It's very probable that most of the 230V went into the controller and that that is fried as well. This would explain why the meter doesn't do nothing anymore. Having the controller replaced may cost you more than a new DMM (&lt;em&gt;if&lt;/em&gt; they replace it at all, you'll probably get a replacement DMM). This is a custom IC which you won't find to do it yourself.&lt;br&gt;&#xA;It's impossible to identify the fried parts without a schematic if they don't have readable markings anymore. (It's even impossible to identify good parts without marking with absolute certainty.)&lt;br&gt;&#xA;TP1 and TP2 probably refer to test points rather than components; &lt;code&gt;TP&lt;/code&gt; is normally not used as a prefix for components.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-08T13:28:17.230" />
  <row Id="12739" PostTypeId="1" AcceptedAnswerId="12741" CreationDate="2011-04-08T13:30:06.537" Score="3" ViewCount="102" Body="&lt;p&gt;Is it possible to measure the amount of water in a rubber water tank by using sound waves?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to make a non intrusive measuring device that attaches to the outside of a tank, and is able to approximate the amount of water in the tank however I don't know how to calculate what sound of a specific frequency will &quot;sound&quot; like given different mediums (e.g. sound travels faster in water than air).&lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-04-10T01:18:39.830" Title="Acoustic Measurement of water level" Tags="&lt;sensor&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="12740" PostTypeId="2" ParentId="12739" CreationDate="2011-04-08T13:33:28.507" Score="7" ViewCount="" Body="&lt;p&gt;You could place an ultrasonic transducer (transmitter-receiver pair) in the top of the tank, sending its signal down to the water, and measure the time between sending a pulse and receiving its reflection.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-08T13:33:28.507" CommentCount="3" />
  <row Id="12741" PostTypeId="2" ParentId="12739" CreationDate="2011-04-08T13:52:48.927" Score="4" ViewCount="" Body="&lt;p&gt;Also consider using a capacitive sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you glue two plates side-by-side on the outside of the tank, they will act as a capacitor with the water (or air) in the tank as the dielectric. Because water has a dielectric constant that is 100x that of air, you can easily and accurately relate the capacity of the plates to the water level in the tank. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;See &lt;a href=&quot;http://mechanical.poly.edu/faculty/vkapila/ME3484/Readings/NV27-Measuring%20Water%20Level.pdf&quot; rel=&quot;nofollow&quot;&gt;Measuring Water Level Without Getting Wet&lt;/a&gt; for more information.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-04-08T13:52:48.927" CommentCount="1" />
  <row Id="12742" PostTypeId="2" ParentId="12385" CreationDate="2011-04-08T13:58:38.057" Score="1" ViewCount="" Body="&lt;p&gt;You can use &lt;code&gt;Serial.print(&quot;DATA&quot;)&lt;/code&gt; and on your pc build a program that listen on serial port.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if (Serial.value == &quot;DATA&quot;) {&#xA; doWork()&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;When you get correct value, do anythink.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like &lt;a href=&quot;http://www.albertopasca.it/whiletrue/2011/03/arduino-mail-notifier-cs/&quot; rel=&quot;nofollow&quot;&gt;gMail notifier&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;hope this helps.&lt;/p&gt;&#xA;" OwnerUserId="3359" LastActivityDate="2011-04-08T13:58:38.057" />
  <row Id="12743" PostTypeId="1" AcceptedAnswerId="12744" CreationDate="2011-04-08T14:13:11.840" Score="3" ViewCount="66" Body="&lt;p&gt;I need to calculate the elapsed time between the rising edge of one pulse to the rising edge of the next pulse. This needs to be in a mobile environment, but I am not attached to any solution as long as its mobile. I have 3 questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What is the best way of calculating this time? I have thought about using PICs capture module, is there anything better out there?&lt;/li&gt;&#xA;&lt;li&gt;How do I determine the fastest delta between rising edges that I can measure?&lt;/li&gt;&#xA;&lt;li&gt;How do I determine the resolution (ie. 1 second compared to 1.0001 seconds between edges) that can be obtained, is it related to point 2?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-08T14:37:03.990" Title="How do I determine the fastest time between pulses I can measure?" Tags="&lt;timer&gt;&lt;counter&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="12744" PostTypeId="2" ParentId="12743" CreationDate="2011-04-08T14:37:03.990" Score="5" ViewCount="" Body="&lt;p&gt;Well, I'll take a stab at your questions...&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The best way of measuring the time between edges greatly depends on what accuracy and overall elapsed time you need.  For example, if the edges can be 2 to 4 hours apart with an accuracy of 10 seconds then you might use just about any simple microcontroller.  If the edges are milliseconds apart then a more advanced microcontroller would work-- maybe something like the PIC with some sort of capture module.  If you're talking &amp;lt;1 ms then maybe a carefully selected micro could work, or an FPGA.  &amp;lt;100 ns and you're talking FPGA or some very dedicated circuits.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Very related to #3, below.  Normally, but not always, the fastest delta will be whatever is required to get you past your basic accuracy.  Typically 1 clock period.  Note:  some measurement methods will have a larger &quot;minimum delta&quot; than others.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Typically (but not always) your logic will run off of some sort of clock.  The frequency of that clock will determine the accuracy delta.  With a typical microcontroller it would be in the 1 to 50 MHz range.  With an FPGA it could be up around 2.5 GHz if you did something fancy with the built-in SERDES's.  Without thinking too hard about it, your accuracy is going to be about +/- 1 clock periods.  But this could change depending on exactly how you do the measurement.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;There are lots of other things to consider, however.  What I wrote above assumes that you have a simple digital signals without noise or anything else.  But if this is hooked up to some sort of sensor system (Radar, Sonar, Lidar, etc.) then the sensors you're using could greatly impact the minimum delta, accuracy, and measurement method.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-08T14:37:03.990" />
  <row Id="12745" PostTypeId="2" ParentId="12606" CreationDate="2011-04-08T14:54:52.237" Score="0" ViewCount="" Body="&lt;p&gt;In case anyone is interested, I just looking at ST's 32F series and it seems that while the newer 32L series uses a BCD RTC, the 32F uses a straight 32-bit counter with configurable prescalar and provides a separate battery input for it (hooray!).  I would have rather had a longer straight counter without a configurable prescalar (so I could get 1/256sec accuracy but keep time for years without having to worry about wrapping) but if I were to set the prescale for 1/64sec the timer could run two years without overflowing.  Not ideal, but not too bad.  A little unaesthetic that if someone powers the machine on after it's been off for too long (2.1+ years), the time/date would undetectably slip back by 2.1 years, but hardly a major problem (the counter has an overflow flag, but in many cases that wouldn't be terribly helpful.  If the machine was on for two years prior to being powered off, and was powered on three months later, the timer would be expected to overflow; the question would be whether it had overflowed twice, and I don't know of any flag for that.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-04-08T19:29:14.233" LastActivityDate="2011-04-08T19:29:14.233" />
  <row Id="12746" PostTypeId="1" AcceptedAnswerId="12748" CreationDate="2011-04-08T16:07:55.113" Score="2" ViewCount="80" Body="&lt;p&gt;I'm wanting to nicely balance some unbalanced inputs to a power amp for good CMRR, and because I'm feeling too lazy to start trying to closely match pairs of resistors, I'm looking at using a hi-fi balanced line driver IC like &lt;a href=&quot;http://www.thatcorp.com/1600-series_Balanced_Line_Driver_ICs.shtml&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this can do the job for me, but is it appropriate or overkill?  It's designed to drive balanced outputs of a device, including long cable runs, and this is obviously not needed because I'm using it to buffer / balance the input of a device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a more appropriate monolithic IC for me? (again, ignoring the obvious op amp solution that requires matched resistors)&lt;/p&gt;&#xA;" OwnerUserId="3424" LastActivityDate="2011-04-09T23:45:10.573" Title="Balancing Unbalanced Audio Inputs" Tags="&lt;audio&gt;&lt;input&gt;&lt;asic&gt;&lt;common-mode&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="12747" PostTypeId="1" CreationDate="2011-04-08T16:17:05.270" Score="2" ViewCount="128" Body="&lt;p&gt;The Hitachi HD44780 LCD controller is an extremely common character-mode LCD controller. Though I believe it is now discontinued, compatible controllers are used in many hobbyist and commercial grade LCD displays that are very widely and cheaply available. Interfacing instructions are also widely available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to know what an equivalent controller might be for graphical LCD displays, such as a 128x64 pixel display. Something widely and cheaply available to the hobbyist, that is reasonable to interface with from a MCU, either parallel or serial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Possibilities include the KS0108 (parallel) and ST7565 (serial), but neither seem to be as popular as the HD44780.&lt;/p&gt;&#xA;" OwnerUserId="3240" LastEditorUserId="3240" LastEditorDisplayName="" LastEditDate="2011-04-08T20:12:00.560" LastActivityDate="2011-04-17T22:12:48.550" Title="Graphical equivalent to HD44780 LCD controller" Tags="&lt;lcd&gt;&lt;display&gt;" AnswerCount="3" />
  <row Id="12748" PostTypeId="2" ParentId="12746" CreationDate="2011-04-08T16:24:21.790" Score="3" ViewCount="" Body="&lt;p&gt;The simplest way to balance an unbalanced signal is with an isolation transformer.  Unfortunately, a transformer that works well across the entire audio frequency range is going to be expensive ($&gt;100 from Jensen).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to do it is to use a chip similar to the one you found from THAT Corp.  Is it overkill, probably.  But it'll be cheaper and perform better than a transformer (assuming that you don't really need the isolation that a transformer will give you).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;typical&quot; way would be to use two op-amps.  One is set as a mostly-unity gain non-inverting buffer and drives the + input of the amp.  The other opamp is set as a unity-gain inverting buffer and takes it's input from the other op-amp and drives the - input on the amp.  Vary the gain on the first op-amp if you need to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, the real question for this is:  do you need to use a balanced signal or can you get away with going unbalanced straight into the amp?  Of course, a balanced input will give you better audio quality but the op-amps or THAT chip will degrade quality.  If you don't do a good job, the net effect could be a decrease in quality.  And then you have to wonder if the change in quality (for good or bad) is even noticeable to your ears.  It's very likely that simply going unbalanced into the amp is going to be the better choice.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-08T16:24:21.790" CommentCount="3" />
  <row Id="12749" PostTypeId="2" ParentId="12747" CreationDate="2011-04-08T17:03:05.690" Score="0" ViewCount="" Body="&lt;p&gt;I found this &lt;a href=&quot;http://www.byvac.co.uk/downloads/datasheets/BV4512%20DataSheet.pdf&quot; rel=&quot;nofollow&quot;&gt;BV4512 controller&lt;/a&gt; via Google. It looks to be reasonably easy to control via I2C.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-08T17:03:05.690" CommentCount="1" />
  <row Id="12750" PostTypeId="1" AcceptedAnswerId="12752" CreationDate="2011-04-08T18:20:25.403" Score="1" ViewCount="183" Body="&lt;p&gt;Since for my venture into Microprocessing I decided to go with Atmel AVR due to the vast resources available. And Arduino seems to has alot as well, not to mention their starter kits seem more &quot;at my level&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is I want to learn it in Assembly first, and then go to C/C++ or w/e Arduino uses, but ive heard Arduino won't take AVR assembly? Is this true? is their any way around that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: I would go with the ATMEL STK500 but..for a first timer it looks VERY complicated? Is there any reason why I can't just get a 8 bit AVR and put it on a breadboard and experiment that way? (i guess i'd have to figure out how to interface them as such....)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit2: This is what I was thinkin&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=17&amp;amp;products_id=193&quot; rel=&quot;nofollow&quot;&gt;http://www.adafruit.com/index.php?main_page=product_info&amp;amp;cPath=17&amp;amp;products_id=193&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3073" LastEditorUserId="3073" LastEditorDisplayName="" LastEditDate="2011-04-08T18:27:10.047" LastActivityDate="2011-04-22T20:59:14.063" Title="Arduino With Assembly?" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;assembly&gt;" AnswerCount="6" FavoriteCount="1" />
  <row Id="12751" PostTypeId="2" ParentId="12750" CreationDate="2011-04-08T19:03:33.043" Score="1" ViewCount="" Body="&lt;p&gt;Arduino boards (Uno and Duemilanove at any rate) have a standard AVR programming connector which is supported by Atmel programmers and debuggers via AVR Studio. Studio supports assembler and C. A suitable programmer is the AVRISP MkII, and the AVR Dragon offers both programming and debugging. I'd get the latter, it's more expensive at $50, but the debugging facility is invaluable. You can also use those tools with a standard AVR chip (not Arduino) plugged into a breadboard or a PCB.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-08T19:03:33.043" />
  <row Id="12752" PostTypeId="2" ParentId="12750" CreationDate="2011-04-08T19:04:17.427" Score="1" ViewCount="" Body="&lt;p&gt;The Arduino boards can be programmed in assembly.  All you need is an ICSP Cable (In Circuit Serial Programmer) cable and the AVR toolchain (free from ATMEL) to write to the board.  You then get the advantage of on board debugging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you suggested, you can just slap an ATMEL chip on a breadboard and go to town.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The kit you referenced looks like a great starting point.  You can take the chip right off the board and stick it on your own breadboard (as long as it has correctly regulated power and you account for the clock).&lt;/p&gt;&#xA;" OwnerUserId="1823" LastActivityDate="2011-04-08T19:04:17.427" CommentCount="2" />
  <row Id="12753" PostTypeId="2" ParentId="12750" CreationDate="2011-04-08T19:38:43.167" Score="1" ViewCount="" Body="&lt;p&gt;The Arduino is comprised of two pieces: the hardware and the IDE. The IDE mainly (if not completely) restricts you to C and C++ (with some syntactical sugar the developers have thrown in to make it a little more like Processing/Java).  There's a chance that the IDE will recognize .s or .S files in the same directory as a standard sketch (.pde), but I wouldn't hang my hat on that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's nothing special about the hardware.  It's a nice, friendly board with lots of nifty features that µC neophytes will appreciate, but if you want to just program the AVR via the ISP header, you can do that, too.  You'll need something like the &lt;a href=&quot;http://www.atmel.com/dyn/products/tools_card.asp?tool_id=3808&quot; rel=&quot;nofollow&quot;&gt;Atmel AVRISP mkII&lt;/a&gt;, or any other programmer that works with the 2x3 row connector on the Arduino board.  Look for ones that are compatible with the avrdude program that you'll use to upload your applications.  Stay away from Adafruit's USBtinyISP; I've had horrible luck with it and ended up buying the Atmel one I linked for less than $40 from Mouser.&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-04-08T19:38:43.167" CommentCount="1" />
  <row Id="12754" PostTypeId="2" ParentId="12747" CreationDate="2011-04-08T19:39:56.873" Score="1" ViewCount="" Body="&lt;p&gt;The wonderful thing about standards is that there are so many of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The closest thing to a standard is, unfortunately, for LCD panels that have controllers but no drivers.  IIRC, a typical interface will have signals for phase polarity, frame clock, line clock, data clock and 4 data bits.  Every line of pixels one should clock in enough groups of four pixels to fill the width of the display (extra bits will be ignored), driving the data clock high and low for each group.  The drive the line clock high and low to strobe the line.  The first line of each frame should have the frame clock high, and the phase polarity signal should toggle every frame.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The line clock signals, and those derived from them, must be sent at a uniform rate.  The precise timing of the data clock signals, however, doesn't matter provided that all the clocks happen for a line happen within the proper window.  If you don't have DMA, it may be possible to keep a small display happy and still have time to do something else, but refreshing the display will be a pain.  If you do have DMA, however, and can manage a small CPLD to handle a few aspects of the timing, implementing the display that way may be very rewarding.  I've done a display panel like that and achieved display-update performance superior to anything I could have done with a conventional display controller.  I even achieved 4-level gray-scale by running the display at 100 frames/second and, every three frames, driving the display twice using one buffer and once with another.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-08T19:39:56.873" />
  <row Id="12755" PostTypeId="2" ParentId="12648" CreationDate="2011-04-08T19:46:59.483" Score="1" ViewCount="" Body="&lt;p&gt;My rule of thumb is something like:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(a) Am I putting together something that is highly sensitive to parasitic induction and capacitance, such as a switching power supply or GHz radio transmitter or receiver; or do I need some IC that only comes in a fine-pitch SMT package? I don't have a choice. I am forced to use a custom PCB. (Sometimes you can get an off-the-shelf demo board or adapter board for just that one section, or make a custom PCB for just that one section, and prototype the rest of the system using a quicker and lower-cost technique).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(b) Am I rigging up a single quick experiment to test something for a few minutes? Use a solderless breadboard: it's the quickest. Alas, for longer-term use, or if you try to ship it any significant distance, wires and components inevitably work loose, causing frustration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(c) Am I rigging up want to rig up one or two devices and expect to use it (sporadically or continuously) for over a month? Or do I expect it to still work after shipping it to another location? Use wire-wrap or soldered wires (or both) on some prototyping board (stripboard, perfboard, etc.). Alas, even though any one wire connection can be placed and soldered (or placed and wire-wrapped) in a few seconds, it seems to take a long time build each board (compared to custom PCB or solderless breadboard), and any human placing lots of wires will inevitably put some wires in the wrong place, causing frustration.&#xA;(Many SMT devices can be used on such a board).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(d) Do I want dozens of identical devices, at minimum the total time and cost? Use a custom PCB. Alas, a custom PCB has much higher up-front costs, which eat up your savings in assembly time and in some cases part costs unless you make lots of them. Alas, a custom PCB usually takes longer to get the first functioning prototype than other methods -- often requiring 2 or more &quot;spins&quot; -- although, once production is set up, it's much faster and less error-prone per device.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-08T19:46:59.483" />
  <row Id="12756" PostTypeId="1" AcceptedAnswerId="12758" CreationDate="2011-04-08T19:48:34.007" Score="1" ViewCount="116" Body="&lt;p&gt;Inspired by &lt;a href=&quot;http://electronics.stackexchange.com/questions/12606/why-do-real-time-clock-chips-use-bcd&quot;&gt;this question&lt;/a&gt; I would like to know how low power you could go with a counter + 32kHz oscillator (possibly made by yourself).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found &lt;a href=&quot;http://www.discovercircuits.com/DJ-Circuits/ultralowpwrxtlosc1.htm&quot; rel=&quot;nofollow&quot;&gt;a nice oscillator circuit on a BJT&lt;/a&gt; reportedly drawing less than $1.2\,\rm{μA}$ from 3V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately the counter and/or prescaler parts are a little more tricky. I do not believe you can make low power flip-flops from discrete transistors but most normal logic ICs are not very efficient either (standard counter ICs all draw around $80\,\rm{μA}$ at room temperature).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do not want a counter that is integrated into a microcontroller (PIC or AVR or ARM).&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-09T22:48:50.147" Title="How to build an ultra-low power time counter?" Tags="&lt;circuit-design&gt;&lt;clock&gt;&lt;low-power&gt;&lt;learning&gt;" AnswerCount="4" />
  <row Id="12757" PostTypeId="1" CreationDate="2011-04-08T19:53:05.263" Score="-1" ViewCount="74" Body="&lt;p&gt;Hello sir,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am working with 32 bit ifx uc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i have seen bit field errors in registers, ram errors, pflash errors as very common..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;can you please tell me some more issue where a high end 32-bit uC coulld have errors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or resources to find such info?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have to create test programs to catch it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Awaiting your reply, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;best regards...&lt;/p&gt;&#xA;" OwnerUserId="3777" LastActivityDate="2011-04-08T22:55:59.917" Title="32-bit uC failures and catching the failure as an user" Tags="&lt;microcontroller&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="12758" PostTypeId="2" ParentId="12756" CreationDate="2011-04-08T20:13:14.837" Score="3" ViewCount="" Body="&lt;p&gt;There are several issues here... &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The oscillator circuit on a BJT doesn't quite spit out +3.3v logic levels.  Fortunately, you want to use a lower voltage to get lower power consumption.  +1.8v logic levels would be compatible with that oscillator-- but then you'd need +1.8 and +3.3v power rails (and probably loose all benefits in your voltage conversion inefficiency.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Dynamic power consumption (the power used when things switch) is mostly from charging and discharging the parasitic caps on the various signal lines.  The way to reduce that is to use shorter, thinner wires.  And by shorter &amp;amp; thinner I mean don't use wires and instead use a chip.  Building this from a collection of chips and transistors instead of one chip that does everything will drive your power consumption up.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You said no microcontroller, but honestly that's the best way to do this.  TI has an &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/msp430c091.html&quot; rel=&quot;nofollow&quot;&gt;ultra low power MSP430&lt;/a&gt; that would run at 32.768 KHz at less than 1.5 uW.  As you've already seen, this type of performance is really hard to beat.  After a microcontroller, my next choice would be a Xilinx Coolrunner-II CPLD-- but I doubt that meets your requirements either.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;To summarize, an MCU will give you the lowest total power consumption.  Otherwise your best choice is to use standard logic parts and suffer with something in the several hundred micro-watt range.  Making something out of discrete transistors isn't going to be better.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-08T20:13:14.837" CommentCount="12" />
  <row Id="12759" PostTypeId="2" ParentId="12757" CreationDate="2011-04-08T20:28:10.253" Score="5" ViewCount="" Body="&lt;p&gt;This sort of error is very hard to catch using software.  Essentially you're taking something that is unstable when running software and running software on it to catch the error.  And if you do catch the error, then what?  If a register is getting corrupted then you'll have a hard time probing the signals inside the CPU.  This could be a futile effort.  Instead, I would focus on the basics of electrical engineering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's what I'd be looking at:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Power.  If power is questionable then you could have issues.  Other than the average DC level, you have to look at noise.  This can be hard to probe, because you need to look at the noise directly at the CPU's power pins using a good scope with careful o-scope probe considerations so you don't pick up other noise.  Check external memories too.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Power pins.  I have actually seen chips work with some or all power pins unconnected.  In one case the PLL power pins for a chip were not powered, but the chip operated mostly fine except in one or two specific cases.  Check external memories too.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Clocks.  Make sure the clocks have good signal integrity.  Like power, this needs to be probed at the CPU's pins with a good probe setup.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Reset.  Make sure there are no glitches or noise on the reset line(s).  A momentary glitch could cause only part of the CPU to reset, causing no end of issues.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;JTAG/Debug connectors.  Are the pins pulled high or low, or are they left floating.  Noise on these pins can cause really strange behavior.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Floating &quot;unused&quot; pins.  In some cases, CPU's can have large numbers of unused I/O pins that need to be pulled, driven, or tied to a valid logic level.  Even if the pin is not used, a floating pin can cause lots of noise inside the part.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Bad signal integrity on the PCB can cause noise places that you don't want.  One board I saw had long traces on a memory bus, and nothing was terminated properly.  There was 2 volts of overshoot/undershoot on those signals that would occasionally cause something &quot;unrelated&quot; to fail.  On not-rare-enough occasions it would cause latchup and some chips would literally blow up.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-08T20:28:10.253" />
  <row Id="12760" PostTypeId="2" ParentId="6016" CreationDate="2011-04-08T20:28:42.037" Score="2" ViewCount="" Body="&lt;p&gt;Excellent question. I like the analogy to reading English text -- no matter how much someone (verbally) explains reading to you, the only way to get good at it is to actually read stuff, with at least some excruciatingly simple stuff.&#xA;I hear that &lt;em&gt;writing&lt;/em&gt; (starting with simple stuff) is also helpful in learning to read.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you know what each electrical component does -- transistors, diodes, caps, etc. -- you can eventually work out the results of some connected set of components (or write a simulator that simulates it, like SPICE), much like knowing how each letter sounds, you can eventually sound out words in written text.&#xA;Alas, just because you can read the words &quot;Eppur Si Muove&quot; or &quot;Jedenfalls bin ich überzeugt, dass der Alte nicht würfelt.&quot; with perfect diction does not mean you really understand it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The vast majority of circuits can be divided into small, relatively independent clumps of components. Often we quickly (after only a few hours :-) recognize &lt;em&gt;roughly&lt;/em&gt; what each clump does -- we have a mains-to-DC converter here, we have an oscillator there, we have a power amplifier over there, there's some kind of power-up reset (perhaps a soft-start?) circuit over there, there's a microprocessor with its standard caps and pull-ups over there, there's a keyboard matrix here and a LED matrix there, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When &lt;em&gt;designing&lt;/em&gt; electronics, recognizing these groupings is even more important.&#xA;Often some prototype does something that's a little annoying -- say, rapidly drains the batteries, or the particular parts chosen are now unavailable -- and the best way to fix it is to tear out a section (or, more often, completely disconnect, isolate, and bypass that section), and replace it with a functionally equivalent section that is faster, cheaper, lower-power, or better in some other way, although implemented completely differently.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few people are really good at drawing schematics.&#xA;In theory, it shouldn't matter where each component is drawn on the schematic, as long as it is connected to the right pins of the other components -- in theory, it shouldn't matter how you spell words on paper, as long as it sounds OK when you sound it out.&#xA;In practice, there are certain common ways of arranging things (idioms) that help people remember where they've seen this particular group of parts arranged in that way before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many schematic diagrams look like a big spaghetti ball of interconnections where you pretty much have to figure out what everything is doing all at once.&#xA;But extremely rarely is it &lt;em&gt;really&lt;/em&gt; a circuit where everything depends on everything else -- most of the time, it's merely poorly drawn.&#xA;Most people, when trying to figure out such a big mess of seemingly randomly-connected components,&#xA;get a pencil and a big piece of paper and re-draw sections in their preferred style.&#xA;Nearly always a schematic can be re-drawn more clearly -- we have input power, we have an oscillator over here, etc. -- and then we can draw a big box around each section and label it &quot;oscillator&quot;, &quot;signal amplifier&quot;, &quot;power amplifier&quot;, etc., and label what the connections between sections mean.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I imagine that the original designer rigged up a quick prototype with an oscillator here, with its output connected to a power amp there.&#xA;In order to reduce net parts cost, sometimes (even though it makes things more confusing) we overlap sections. For example, using much more expensive transistors in the oscillator than we really need just to oscillate, so that its output can directly drive a heavy load -- the &quot;oscillator&quot; section overlaps the &quot;power amplifier&quot; section.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-08T20:28:42.037" />
  <row Id="12761" PostTypeId="2" ParentId="12750" CreationDate="2011-04-08T20:49:50.607" Score="1" ViewCount="" Body="&lt;p&gt;As far as I know there should be nothing specific about the Arduino bootloader that could prevent you from using assembly instead of C. The Arduino IDE may make it difficult to upload you own .hex files but it looks like the Arduino bootloader &lt;a href=&quot;http://www.ladyada.net/library/arduino/bootloader.html&quot; rel=&quot;nofollow&quot;&gt;is STK500 compatible&lt;/a&gt; so you should be able to use it with avrdude.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-08T20:49:50.607" />
  <row Id="12762" PostTypeId="2" ParentId="12650" CreationDate="2011-04-08T20:56:22.303" Score="1" ViewCount="" Body="&lt;p&gt;As lyndon said -- the bearings &lt;em&gt;inside&lt;/em&gt; a typical motor won't support that kind of axial thrust.&#xA;Not to worry though -- the bearings inside the motor don't need to support &lt;em&gt;any&lt;/em&gt; axial thrust if you set up your system with a separate &lt;a href=&quot;http://en.wikipedia.org/wiki/thrust_bearing&quot; rel=&quot;nofollow&quot;&gt;thrust bearing&lt;/a&gt; at the bottom and possibly the top of the shaft.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps the simplest approach is to use a motor where the shaft exits both ends of the motor something like this one:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/zkomz.jpg&quot; alt=&quot;motor with axis through and extending from both ends&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A thrust bearing holding up the shaft exiting the bottom of the motor can hold up the full weight of all the stuff you have rigidly attached to the shaft exiting the top of the motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps the next-simplest approach is to put a thrust bearing at the bottom and a skate bearing (or another thrust bearing) at the top, with a concentric wheel somewhere between, and use a V-belt between that wheel and the motor mounted next to your rotating assembly.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-08T20:56:22.303" CommentCount="3" />
  <row Id="12763" PostTypeId="2" ParentId="12756" CreationDate="2011-04-08T21:03:12.027" Score="0" ViewCount="" Body="&lt;p&gt;Technically, the method to make the most power efficient (and fastest) circuit (anything) would be a &lt;a href=&quot;http://en.wikipedia.org/wiki/Full_custom&quot; rel=&quot;nofollow&quot;&gt;Full Custom IC&lt;/a&gt; using the tiniest technology you can find. You'd have to design your own &lt;a href=&quot;http://en.wikipedia.org/wiki/Integrated_circuit_layout&quot; rel=&quot;nofollow&quot;&gt;IC layout&lt;/a&gt; and have a foundry build a wafer for you. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are universities that have agreements with some foundries, maybe you could research your local schools for information on that. If they are willing to help you then it would be free.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.staticfreesoft.com/electric.html&quot; rel=&quot;nofollow&quot;&gt;Static Free's Electric&lt;/a&gt; is a great free software to start building your own custom ICs.&lt;/p&gt;&#xA;" OwnerUserId="3078" LastActivityDate="2011-04-08T21:03:12.027" CommentCount="2" />
  <row Id="12764" PostTypeId="2" ParentId="12606" CreationDate="2011-04-08T21:05:23.970" Score="0" ViewCount="" Body="&lt;p&gt;Maxim seems to be doing just what you want with &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/DS1372.pdf&quot; rel=&quot;nofollow&quot;&gt;DS1372U&lt;/a&gt;. It needs less than 1μA, costs 1.7 USD and is available(!) on DigiKey and Mouser. The only problem is that it does not seem to offer alarms with more than 1 second precision and the lowest output clock rate is $\approx$4kHz.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-08T21:05:23.970" CommentCount="1" />
  <row Id="12765" PostTypeId="1" AcceptedAnswerId="12768" CreationDate="2011-04-08T21:26:18.750" Score="2" ViewCount="70" Body="&lt;p&gt;I purchased &lt;a href=&quot;http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&amp;amp;_trksid=p4340.l2557&amp;amp;rt=nc&amp;amp;nma=true&amp;amp;item=120702651462&amp;amp;si=3gsUkig29Quejyid2uHntNf4gxc%253D&amp;amp;viewitem=&amp;amp;sspagename=STRK%3aMEWNX%3aIT#ht_636wt_1139&quot; rel=&quot;nofollow&quot;&gt;some steppers motors&lt;/a&gt; with relatively little known about the specs.  I'm hoping to drive them with a &lt;a href=&quot;http://arduino.cc/en/Reference/StepperBipolarCircuit&quot; rel=&quot;nofollow&quot;&gt;L293DNE wired up like this&lt;/a&gt;.  I've got it working and it all seems to be going well - except the L293DNE is getting quite hot.  It would burn my finger quite quickly if I left it running long.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand they can run quite hot, but I'd rather not have it that hot if I can reduce it.  I require minimal torque for my application, so I was hoping to be able to run it off a 5v 700ma wall wart.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm pretty new to all this, but I thought increasing the resistance would lower the current and solve my problem, but it didn't didn't seem to help (or very possibly I did it wrong).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What should I do to reduce the heat?  &lt;/p&gt;&#xA;" OwnerUserId="3778" LastActivityDate="2011-04-09T04:18:12.887" Title="Stepper motor and L293dne getting hot" Tags="&lt;stepper-motor&gt;" AnswerCount="2" />
  <row Id="12766" PostTypeId="2" ParentId="6016" CreationDate="2011-04-08T21:32:33.783" Score="1" ViewCount="" Body="&lt;p&gt;I'll try to put together the building blocks of your circuit diagram:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;L2, F1, RECT1, C4: Mains rectifier.   &lt;/li&gt;&#xA;&lt;li&gt;R6, C2, D1, C1, R4, DIAC: Start-up circuit.   &lt;/li&gt;&#xA;&lt;li&gt;Rest: &lt;a href=&quot;http://electronics.stackexchange.com/questions/6811/what-is-the-use-of-transformers-with-3-pairs-of-wires/6812#6812&quot;&gt;See this thread.&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-04-08T21:32:33.783" />
  <row Id="12767" PostTypeId="2" ParentId="12757" CreationDate="2011-04-08T21:35:26.277" Score="0" ViewCount="" Body="&lt;p&gt;As far as I remember there are some standard test procedures for microcontrollers in the IEC 60730 Class B standard. The best thing that I could find in a quick search was &lt;a href=&quot;http://www.freescale.com/files/microcontrollers/doc/app_note/AN3257.pdf&quot; rel=&quot;nofollow&quot;&gt;a Freescale Application Note&lt;/a&gt;. OTOH I cannot tell if these things improve reliability at all (standards sometimes are stupid).&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-08T21:35:26.277" CommentCount="2" />
  <row Id="12768" PostTypeId="2" ParentId="12765" CreationDate="2011-04-08T21:52:12.400" Score="2" ViewCount="" Body="&lt;p&gt;Use L298s with heat sinks. They can handle a lot more current and are intended for use with heat sinks, unlike the DIL L293D.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-08T21:57:33.923" LastActivityDate="2011-04-08T21:57:33.923" CommentCount="1" />
  <row Id="12769" PostTypeId="1" AcceptedAnswerId="12772" CreationDate="2011-04-08T22:38:10.143" Score="0" ViewCount="54" Body="&lt;p&gt;Well, it seems that static electricity has fried my LiPo balance plug adapter.&#xA;When I was plugging in my LiPo battery to it, which was plugged into my Thunder AC6 LiPo charger, a short wisp of smoke was created and the copper trace for the ground balance connection was damaged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pictures:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://i.imgur.com/gf5Ru.jpg&quot; rel=&quot;nofollow&quot;&gt;http://i.imgur.com/gf5Ru.jpg&lt;/a&gt;&#xA;An overview of the balance adapter plug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://i.imgur.com/waGTD.jpg&quot; rel=&quot;nofollow&quot;&gt;http://i.imgur.com/waGTD.jpg&lt;/a&gt;&#xA;A closeup of the damaged connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;br /&gt;&lt;br/&gt;&#xA;Can I fix this, or would I have to buy another balance plug? If so, where should I buy one?&lt;/p&gt;&#xA;" OwnerUserId="3780" LastEditorUserId="3780" LastEditorDisplayName="" LastEditDate="2011-04-08T23:26:30.033" LastActivityDate="2011-04-08T23:26:30.033" Title="LiPo charger balance plug is kaput" Tags="&lt;battery&gt;&lt;charger&gt;&lt;lipo&gt;" AnswerCount="1" />
  <row Id="12770" PostTypeId="1" CreationDate="2011-04-08T22:43:32.477" Score="1" ViewCount="52" Body="&lt;p&gt;I have a circuit like:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/fPF1C.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you get Thevenin ( $V_x = I_x  * R$) circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have these formulas, but I am a little stucked...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$\ I_0 + Ix = (\frac{V\pi}{r\pi}) + gmV\pi $   &lt;code&gt;--- 1&lt;/code&gt;&lt;br&gt;&#xA;$VR_1 - VR_2 = Vx$                  &lt;code&gt;--- 2&lt;/code&gt;&lt;br&gt;&#xA;$\ I_0 = (\frac{VR_2}{R_2})$                  &lt;code&gt;--- 3&lt;/code&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you get $V_{R1}$?&lt;/p&gt;&#xA;" OwnerUserId="3628" LastActivityDate="2011-04-08T22:43:32.477" Title="computing Impedance related with Voltage Vx" Tags="&lt;voltage&gt;&lt;impedance&gt;" CommentCount="4" />
  <row Id="12771" PostTypeId="2" ParentId="12757" CreationDate="2011-04-08T22:55:59.917" Score="1" ViewCount="" Body="&lt;p&gt;I've written some code for applications that required extreme resistance to failing in an unsafe manner.  The code was written entirely in assembly language, and kept two copies of many important variables, with a fixed delta between them.  Rather than computing and storing the value for the second variable based upon the first one, the code would be something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;' Code to add reg1a to reg2a and maintain delta invariants&#xA;  if reg1b  reg1a + REG1_DELTA then error&#xA;  if reg2b  reg2a + REG2_DELTA then error&#xA;  reg2b += reg1b - REG1_DELTA&#xA;  reg2a += reg1a&#xA;  if reg2b  reg2a + REG2_DELTA then error&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Any register that got corrupted would immediately get flagged as an error.  It would be unlikely for multiple registers to get corrupted in such a way as to coincidentally avoid causing an error.  Because the 'b' registers aren't computed based upon the 'a' registers, a glitch which hits an 'a' register won't cause the proper corresponding change in a 'b' register, no matter when it occurs.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-08T22:55:59.917" CommentCount="2" />
  <row Id="12772" PostTypeId="2" ParentId="12769" CreationDate="2011-04-08T23:14:22.500" Score="0" ViewCount="" Body="&lt;p&gt;That's a pretty big fault there and I doubt that static electricity could have caused that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I recommend that you check the whole circuit for any other strange problems, just in case the cause isn't static electricity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the broken trace, you can always fix it with a wire. Try soldering a wire between damaged ends of the trace and that should fix it. It may be easier to solder the wire on the other side directly between two connectors, since there is very little space left between trace breakage and the connector. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you decide to work on the trace side, you'll need to carefully scratch off the coating on the trace without damaging the trace itself first. You might be able to solver through the coating, but in my opinion it would be best to remove in on the trace. Later you can cover the joints with insulation tape or buy conformal coating spray and carefully apply it over joints.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you decide to work on the other side, you'll need to be careful not to use too much heat so as not to damage the connectors. The joints on the other side may be covered by some sort of coating, so test them out with a multimeter first. If you don't get continuity, try scratching or filing the coating off. You may be able to solder through it, but there's no guarantee that you will and you need to be extra careful not to damage the plastic connectors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for wire size, there isn't a clear reference there, but I guess that something like standard&lt;br&gt;&#xA;0.75 $mm^2$ would be strong enough for the current. To be 100% safe, measure the size of the wires coming to the connector on the left and use such wire or larger to fix the open circuit.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-04-08T23:14:22.500" CommentCount="4" />
  <row Id="12773" PostTypeId="1" CreationDate="2011-04-09T00:04:15.430" Score="-1" ViewCount="49" Body="&lt;p&gt;Hello. I'm trying to hunt down a supplier for connectors for the Nokia 6101 LCD. These are 22-pin connectors similar to the Hirose DF36 series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1990" LastActivityDate="2011-05-11T18:33:15.757" ClosedDate="2011-05-11T19:32:08.773" Title="Supplier for Nokia 6101 LCD connector" Tags="&lt;lcd&gt;&lt;connector&gt;" AnswerCount="1" />
  <row Id="12774" PostTypeId="1" AcceptedAnswerId="12775" CreationDate="2011-04-09T00:46:39.857" Score="1" ViewCount="149" Body="&lt;p&gt;I have a huge led matrix which will draw 3.1Amps of current. However I only have a 15v 1A psu&gt; Would it be possible to use a transistor to amplify the current after I've lowered the voltage? Could you recommend such a transistor.&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-04-11T12:23:48.923" Title="Creating a 12V @ 3.5A out of 15 volt 1A" Tags="&lt;transistor&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="12775" PostTypeId="2" ParentId="12774" CreationDate="2011-04-09T00:56:58.863" Score="22" ViewCount="" Body="&lt;p&gt;15V * 1A is 15 watts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;12V * 3.5A is 42 watts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You cannot create power out of nothing.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-09T00:56:58.863" />
  <row Id="12777" PostTypeId="2" ParentId="12774" CreationDate="2011-04-09T01:02:32.853" Score="4" ViewCount="" Body="&lt;p&gt;A transistor does not create current (and power) out of thin air. Transistors can amplify voltage or current but only if you provide them with an adequate supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A transistor is not magic at all. It works like a valve: it can pass more or less current (water) but if there is none available in the hose (supply) it will not be able to &quot;create&quot; it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The amplification part comes from the ability to take small current or voltage and use it to control the transistor (valve) which can pass or block much higher currents and voltages.&lt;/p&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-10T22:39:18.133" LastActivityDate="2011-04-10T22:39:18.133" CommentCount="2" />
  <row Id="12778" PostTypeId="2" ParentId="12750" CreationDate="2011-04-09T01:49:27.313" Score="1" ViewCount="" Body="&lt;p&gt;Not difficult at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.dwelch.com/arduino/&quot; rel=&quot;nofollow&quot;&gt;http://www.dwelch.com/arduino/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to look at I think ser.c on my page to pick which card.  some use different serial port speeds by default, and different reset schemes to get into the programming mode.  If you look at the arduino firmware you find that hardly any of the avr programming commands are really supported.  Dont really need them anyway.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-04-09T01:49:27.313" />
  <row Id="12779" PostTypeId="2" ParentId="10841" CreationDate="2011-04-09T01:51:30.213" Score="0" ViewCount="" Body="&lt;pre&gt;&lt;code&gt;.device ATmega168&#xA;.equ  DDRB       = 0x04&#xA;.equ  PORTB      = 0x05&#xA;&#xA;.org 0x0000&#xA;    rjmp RESET&#xA;&#xA;RESET:&#xA;    ldi R16,0x20&#xA;    out DDRB,R16&#xA;&#xA;    ldi R18,0x00&#xA;    ldi R17,0x00&#xA;    ldi R20,0x20&#xA;Loop:&#xA;&#xA;    ldi R19,0xE8&#xA;aloop:&#xA;    inc R17&#xA;    cpi R17,0x00&#xA;    brne aloop&#xA;&#xA;    inc R18&#xA;    cpi R18,0x00&#xA;    brne aloop&#xA;&#xA;    inc R19&#xA;    cpi R19,0x00&#xA;    brne aloop&#xA;&#xA;    eor R16,R20&#xA;    out PORTB, R16&#xA;    rjmp Loop&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-04-09T01:51:30.213" />
  <row Id="12780" PostTypeId="1" AcceptedAnswerId="12830" CreationDate="2011-04-09T03:03:27.410" Score="1" ViewCount="143" Body="&lt;p&gt;I am designing a simple programmable LED screen system as an exercise, and I need a non-standard type of SRAM (16x5) so I am designing the memory circuits. I have looked everywhere (Digikey, TI, National Semiconductor, etc.) for a chip that is just a sense amplifier for SRAM and I haven't found anything. I called TI and they said they didn't make anything like that, but I may be able to use a comparator for that. My question is, is it possible to wire up, say, a LM339 as a sense amplifer? And if so, how?&lt;br&gt;&#xA;Thanks&lt;/p&gt;&#xA;" OwnerUserId="3782" LastActivityDate="2011-04-10T13:38:00.723" Title="How to implement SRAM sense amplifier?" Tags="&lt;led&gt;&lt;memory&gt;&lt;amplifier&gt;&lt;sram&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="12781" PostTypeId="1" AcceptedAnswerId="12787" CreationDate="2011-04-09T03:26:29.773" Score="0" ViewCount="99" Body="&lt;p&gt;I've got a Sansa Clip that recharges via USB. Problem is that it &quot;connects&quot; to the PC whenever I plug it in. I learned a trick where you pull the cable out of the PC partially such that the data leads are no longer connected but the power leads are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However I am looking for a more permanent solution. How can I modify the cable itself such that only the power leads remain and it never transfers data?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I have an extra cable, so it's OK.)&lt;/p&gt;&#xA;" OwnerUserId="3783" LastActivityDate="2011-04-09T09:02:36.133" Title="Disable data leads of USB cable" Tags="&lt;usb&gt;&lt;cable-assemblies&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="12782" PostTypeId="2" ParentId="12781" CreationDate="2011-04-09T03:50:29.870" Score="2" ViewCount="" Body="&lt;p&gt;Much as I like hacking things, I think the simple answer here is a dedicated charger with a USB port.&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2011-04-09T03:50:29.870" CommentCount="2" />
  <row Id="12783" PostTypeId="2" ParentId="12765" CreationDate="2011-04-09T04:18:12.887" Score="0" ViewCount="" Body="&lt;p&gt;Open loop drivers of this sort work best when the back EMF of the load does the work of limiting current; i.e. there is very little load.  In the case of a stepper motor, this generally means that the motor is moving a light load quickly, with only rare 'hold' operations.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Higher loads normally require current sensing, or at least some form of current limiting.  Some drivers, for example the &lt;a href=&quot;http://www.st.com/stonline/books/pdf/docs/1773.pdf&quot; rel=&quot;nofollow&quot;&gt;L298&lt;/a&gt;, can do this by measuring the voltage across a resistor in series with the outputs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, if you have a good idea about what your load will look like, you can use the same L293 with a reduced duty cycle during periods of high load, just estimating how much current the motor will draw.&lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2011-04-09T04:18:12.887" />
  <row Id="12784" PostTypeId="2" ParentId="12781" CreationDate="2011-04-09T04:47:06.450" Score="-1" ViewCount="" Body="&lt;p&gt;The pinout of USB is the following:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;pin1 (usually red) is Vcc&lt;/li&gt;&#xA;&lt;li&gt;pin2 (usually white) is D-&lt;/li&gt;&#xA;&lt;li&gt;pin3 (usually green) is D+&lt;/li&gt;&#xA;&lt;li&gt;pin4 (usually black) is Gnd&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;What you want is an cable where pin2 and pin3 are disconnected.&#xA;Just cut the cable and only reconnect pin1 (red) and pin4 (black).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt; the following &lt;a href=&quot;http://pinouts.ru/Slots/USB_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;page&lt;/a&gt; says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;simple USB charger should short the 2 data lines together. The device will then not attempt to transmit or receive data, but can draw up to 1.8A, if the supply can provide it.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So if simply disconnecting pin2 and pin3 does not work you might try to short them.&lt;/p&gt;&#xA;" OwnerUserId="595" LastEditorUserId="595" LastEditorDisplayName="" LastEditDate="2011-04-09T04:54:11.250" LastActivityDate="2011-04-09T04:54:11.250" CommentCount="2" />
  <row Id="12785" PostTypeId="1" CreationDate="2011-04-01T06:48:56.517" Score="1" ViewCount="140" Body="&lt;p&gt;I need to display the characters and numbers on a &lt;code&gt;2x16&lt;/code&gt; LCD on the Altera DE2 board using a Verilog program. Any advice?&lt;/p&gt;&#xA;" LastActivityDate="2011-04-09T07:39:01.820" Title="LCD driver program in Verilog for Altera DE2 board" Tags="&lt;verilog&gt;&lt;fpga&gt;" AnswerCount="2" />
  <row Id="12786" PostTypeId="2" ParentId="12785" CreationDate="2011-04-01T13:37:39.303" Score="1" ViewCount="" Body="&lt;p&gt;This should get you started!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://groups.google.com/group/comp.arch.fpga/msg/f4ef5805dbafbcc9&quot; rel=&quot;nofollow&quot;&gt;http://groups.google.com/group/comp.arch.fpga/msg/f4ef5805dbafbcc9&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2531" LastActivityDate="2011-04-01T13:37:39.303" CommentCount="0" />
  <row Id="12787" PostTypeId="2" ParentId="12781" CreationDate="2011-04-09T05:40:05.000" Score="2" ViewCount="" Body="&lt;p&gt;my first attempt at solving your problem would be to get some kapton (or other non-conductive) tape and just stick it on top of the traces in your USB plug.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-09T05:40:05.000" CommentCount="3" />
  <row Id="12788" PostTypeId="2" ParentId="12785" CreationDate="2011-04-09T07:39:01.820" Score="1" ViewCount="" Body="&lt;p&gt;This project will probably get you 90% of the way... &lt;a href=&quot;http://opencores.org/project,wb_lcd&quot; rel=&quot;nofollow&quot;&gt;http://opencores.org/project,wb_lcd&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-09T07:39:01.820" />
  <row Id="12789" PostTypeId="1" AcceptedAnswerId="12790" CreationDate="2011-04-09T08:18:49.577" Score="2" ViewCount="88" Body="&lt;p&gt;hello &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am new to hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My breadboard just arrived and I am trying to light up my LED. I used computer power supply for power (red wire for + black for -) and used strands of LAN cable for connect LED and power supply. It works! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the both of two stands of power supply side cable jacket melted and computer slowly shutted down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just use old computer power supply's FDD power cable's strands (red for plus &#xA;and black for minus).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could somebody let me know why this happened and how to use power supply safely?&lt;/p&gt;&#xA;" OwnerUserId="3746" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-09T11:44:48.443" LastActivityDate="2011-04-09T11:44:48.443" Title="cable jacket melts" Tags="&lt;power-supply&gt;&lt;power&gt;&lt;led&gt;&lt;safety&gt;&lt;cables&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="12790" PostTypeId="2" ParentId="12789" CreationDate="2011-04-09T08:27:33.293" Score="1" ViewCount="" Body="&lt;p&gt;Hi, seems like somewhere in your setup, there is a short circuit. Computer power supplies deliver a very high current easily capable of heating up wires. Can You try to draw a circuit diagram or upload a picture that shows the details of how your setup is wired? Are you using a resistor in series with the LED?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might want to try your first experiments with a power supply not as strong as a PC power supply (old wall wart with something 5V / 1A, ...).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I recommend not using the power of your running PC for experimentation. You risk damaging your entire PC, not just the power supply.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-04-09T08:27:33.293" CommentCount="4" />
  <row Id="12791" PostTypeId="1" AcceptedAnswerId="12796" CreationDate="2011-04-09T08:55:58.843" Score="0" ViewCount="44" Body="&lt;p&gt;hello I am new to hardware&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I opened old rc car controller up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;with some anticipation such as control rc car by computer, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;by smart phone, embed old phone's camera, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;send data to computer, processing it and rc car drive by it self!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but I don't understand how it works at all-_-;;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;what kind of thing should I learn to do that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know it is long way to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but I want to understand circuits and how computer works in very low level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;could somebody suggest me series of book or document for my learning?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ah! and is there any alternative way to connect wire to soldered PCB other than &#xA;dangerous soldering?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks&lt;/p&gt;&#xA;" OwnerUserId="3746" LastActivityDate="2011-04-09T12:13:56.093" Title="book and document suggestion" Tags="&lt;circuit&gt;&lt;books&gt;&lt;data&gt;" AnswerCount="1" />
  <row Id="12792" PostTypeId="2" ParentId="12789" CreationDate="2011-04-09T08:57:34.863" Score="8" ViewCount="" Body="&lt;p&gt;An LED acts like a &lt;a href=&quot;http://en.wikipedia.org/wiki/Diode&quot; rel=&quot;nofollow&quot;&gt;diode&lt;/a&gt;, and in the forward bias (when the voltage is applied in the correct direction), the diode will have a small voltage drop. &#xA;The voltage drop for LED can be found in &lt;a href=&quot;http://en.wikipedia.org/wiki/Light-emitting_diode&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice that diode does not behave like a resistor (does not obey Ohm's law): once a diode is in forward bias, its voltage drop will remain fairly constant for a large range of currents. That is, until the diode melts or overheats due to overcurrent. Other electrical elements may also melt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your voltage source is much larger than 0.7V, this will lead to a very large electrical current flowing, and the heat caused by the electrical current will be dissipated along various places in the circuit (because the remaining voltage drop will have to be distributed along the rest of the circuit, which consists of mostly good conductors and therefore has a very low resistance).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To prevent this from happening, please connect a resistor in series with the LED, or use a voltage source that is about the same as the LED's voltage drop.&lt;/p&gt;&#xA;" OwnerUserId="1450" LastEditorUserId="1450" LastEditorDisplayName="" LastEditDate="2011-04-09T09:05:52.433" LastActivityDate="2011-04-09T09:05:52.433" />
  <row Id="12793" PostTypeId="2" ParentId="12781" CreationDate="2011-04-09T09:02:36.133" Score="1" ViewCount="" Body="&lt;p&gt;how about covering the two middle pins on the type A side of the cable with electrical tape? simple, reversible, and if you get it wrong, its a matter of removing the tape ;p&lt;/p&gt;&#xA;" OwnerUserId="1870" LastActivityDate="2011-04-09T09:02:36.133" />
  <row Id="12794" PostTypeId="1" CreationDate="2011-04-09T10:51:33.477" Score="0" ViewCount="90" Body="&lt;p&gt;i just want to now the name of a temperature sensor that can send its reading to a wireless hub and from there my pda can read data. Name of temperature sensor?&lt;/p&gt;&#xA;" OwnerUserId="3784" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-09T15:29:56.780" LastActivityDate="2011-04-09T15:29:56.780" ClosedDate="2011-04-10T14:11:10.230" Title="Temperature sensor" Tags="&lt;sensor&gt;&lt;wireless&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12795" PostTypeId="2" ParentId="12794" CreationDate="2011-04-09T11:17:30.460" Score="0" ViewCount="" Body="&lt;p&gt;Ehrm...&#xA;Is this about DIY or buying it straight from the market? (Psst this forum is only about the first section)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would get a temperature sensor of any kind (like a LM60, but that heavily depends on your desired accuracy, and what you want to measure) and hook it up to a zigbee module. You can probably get one of those that have analog inputs and that can send those values straight into the air. You probably have to get some kind of server that is hooked up to the web that also contains a zigbee module to receive and process the data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From there it's just a matter of connecting everything together from your zigbee host machine and your PDA.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-04-09T11:17:30.460" CommentCount="2" />
  <row Id="12796" PostTypeId="2" ParentId="12791" CreationDate="2011-04-09T12:13:56.093" Score="0" ViewCount="" Body="&lt;p&gt;Soldering is a pretty essential skill to have if you intend to do projects like these, and it isn't so dangerous when you get the hang of it.  Unless you mean the lead fumes you're likely to inhale, in which case you can get lead-free solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But yes, you probably will have to do some soldering, and possibly some scratching-off of PCB traces as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In terms of a path of learning to do these things, I recommend getting started with an &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt;.  With an Arduino, it's fairly easy for a beginner to either load a program on the microcontroller to do the controlling or send data to or from a computer over USB (or Wifi, but that's extra hardware you have to buy).  You can do these things without an Arduino, obviously, but it's very convenient for a beginner because it does a lot of the work for you (handling the microcontroller's needs, data communication to and from a computer, getting the program written to the microcontroller).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are plenty of beginner and advanced Arduino tutorials floating around the internet, and they'll probably all be beneficial to you if you're just getting started.&lt;/p&gt;&#xA;" OwnerUserId="3424" LastActivityDate="2011-04-09T12:13:56.093" />
  <row Id="12797" PostTypeId="1" AcceptedAnswerId="12816" CreationDate="2011-04-09T15:27:00.413" Score="1" ViewCount="73" Body="&lt;p&gt;I'm trying to get my bluetooth module into &lt;a href=&quot;http://www.sparkfun.com/datasheets/Wireless/Bluetooth/rn-bluetooth-um.pdf&quot; rel=&quot;nofollow&quot;&gt;command mode&lt;/a&gt;. I have &lt;a href=&quot;http://www.sparkfun.com/datasheets/Wireless/Bluetooth/rn-42-ds.pdf&quot; rel=&quot;nofollow&quot;&gt;pin 0(RX)&lt;/a&gt; on the Uno connected to the &lt;a href=&quot;http://www.sparkfun.com/datasheets/Wireless/Bluetooth/rn-42-ds.pdf&quot; rel=&quot;nofollow&quot;&gt;UART_TX pin&lt;/a&gt; on the bluetooth module, and pin 1(TX) on the Uno connected to the UART_RX pin on the bluetooth module.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Heres the sketch thats running on the Uno.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int incomingByte = 0;   // for incoming serial data&#xA;&#xA;void setup() {&#xA;  // put your setup code here, to run once:&#xA;  Serial.begin(9600);   // opens serial port, sets data rate to 9600 bps&#xA;  Serial.flush();&#xA;  //enter command mode&#xA;  Serial.println(&quot;$$$&quot;);&#xA;}&#xA;&#xA;void loop() {&#xA;  // send data only when you receive data:&#xA;  if (Serial.available() &amp;gt; 0) {&#xA;    //read the incoming byte:&#xA;    incomingByte = Serial.read();&#xA;&#xA;    //say what you got:&#xA;    Serial.print(&quot;I received: &quot;);&#xA;    Serial.println(incomingByte, DEC);&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This is what I see on the Serial Monitor&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;$$$&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I expected to see&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;$$$&lt;br&gt;&#xA;  I received: C&lt;br&gt;&#xA;  I received: M&lt;br&gt;&#xA;  I received: D&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;What am I doing wrong? Or if its not supposed to do what I expected, what am I not understanding correctly?&lt;/p&gt;&#xA;" OwnerUserId="1227" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-09T15:28:06.673" LastActivityDate="2011-04-10T15:10:07.693" Title="Communicate with bluetooth module from Arduino Uno" Tags="&lt;arduino&gt;&lt;bluetooth&gt;" AnswerCount="1" />
  <row Id="12798" PostTypeId="2" ParentId="12756" CreationDate="2011-04-09T16:17:25.367" Score="1" ViewCount="" Body="&lt;p&gt;For the oscillator I'd use an RTC like &lt;a href=&quot;http://www.nxp.com/documents/data_sheet/PCF8563.pdf&quot; rel=&quot;nofollow&quot;&gt;NXP PCF8563&lt;/a&gt;, which provides a buffered 32kHz output and only consumes about 300nA @ 2V.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the counter/divider I looked at HCMOS. According to &lt;a href=&quot;http://ics.nxp.com/support/documents/logic/pdf/family.hcmos.specification.pdf&quot; rel=&quot;nofollow&quot;&gt;NXP's HCMOS family specification&lt;/a&gt; quiescent current for a flip-flop is 4uA maximum, but that's @ Vdd=6V, so it should be lower at 3V.&#xA;If you use &lt;a href=&quot;http://ics.nxp.com/products/hc/datasheet/74hc93.74hct93.pdf&quot; rel=&quot;nofollow&quot;&gt;74HC93&lt;/a&gt;s (4 FF per device, you'll need 4 of those to get 1Hz) total quiescent current is 64uA maximum, which agrees with the 80uA you mentioned.&lt;br&gt;&#xA;The good news is that at this low frequency dynamic power is far less than that.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Minimum supply voltage for HCMOS is 2V, so working at this voltage should also reduce the current. The PCF8563 even operates at Vdd=1V (since you don't need the interface).&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-09T16:17:25.367" CommentCount="3" />
  <row Id="12799" PostTypeId="2" ParentId="1069" CreationDate="2011-04-09T17:11:49.193" Score="3" ViewCount="" Body="&lt;p&gt;Most modern microcontroller designs will work with any pattern on their clock input, provided only that no high pulse is below a certain minimum length, no low pulse is below a certain minimum length, and no low-high-low or high-low-high pulse pair is below a certain length.  Essentially what happens is that after the chip does all of the actions associated with a particular clock edge, the chip will be in a state where it is doing nothing but waiting for the next clock edge.  If the next clock edge doesn't arrive for ten days then (unless the chip has some external watchdog) the chip will be in the same state as if the edge had arrived the moment the chip was ready for it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that in general, pausing the clock on a microcontroller will reduce current consumption substantially, but not as much as using the &quot;sleep&quot; feature.  Most microcontrollers' current consumption in &quot;run&quot; mode can be pretty well estimated as a constant quiescent current plus a certain amount of current per cycle per second (which might be more 'naturally' expressed as charge per cycle).  For example, a chip might have a quiescent current of 10uA, plus a current of 0.1mA/MHz (100pC/cycle).  Running such a chip at 10MHz would yield a current of 1.01mA.  Running it at 1MHz would yield 0.11mA.  Running it at 100KHz would yield 0.02mA.  Running it at 1Hz woudl yield 0.0100001mA.  On the other hand, the chip might offer a sleep current of 1uA.  Generally, entering sleep mode will completely power off areas of the chip that aren't going to do anything useful while the chip is sleeping, thereby avoiding any leakage current such areas might have.  It will in some cases also reduce the voltage to areas like register files to a level where the register files can hold their contents, but not access them very quickly (since they won't be accessed at all, access speed doesn't matter).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some older microprocessors, microcontrollers, and other devices had maximum clock-high and/or clock-low times.  Such processors made use of dynamic logic to save circuitry.  As an example of dynamic logic, consider a shift register: a typical static register bit requires a two-transistor circuit to hold the value, while a dynamic register bit holds the value on the gate of a readout transistor.  A two-phase-clocked dynamic shift register may be realized in NMOS using four NFETs and two resistors per bit.  A static shift register would require eight NFETs and four resistors per bit.  Dynamic logic approaches are not nearly so common today.  Back in the 1970's, gate capacitance was substantial and there wasn't any getting rid of it.  There was thus no particular reason not to take advantage of it.  Today, gate capacitance is generally much lower, and chip makers are actively trying to reduce it further.  Making dynamic logic work reliably would often require deliberately working to increase gate capacitance.  In most cases, the extra chip area needed to increase capacitance could be just as effectively used to add more transistors so as to make the capacitance unnecessary.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-09T17:11:49.193" CommentCount="3" />
  <row Id="12800" PostTypeId="2" ParentId="4868" CreationDate="2011-04-09T17:17:47.250" Score="0" ViewCount="" Body="&lt;p&gt;Incidentally, another approach would be to simply feed audio into the USB port using an off-the-shelf product, and then have the computer perform the DTMF recognition.  Depending upon the exact application, a computer may be able to do a better job of DTMF recognition than a simple IC could manage.  For example, a computer could take advantage of the fact that DTMF is generally gated on and off relatively cleanly.  If the computer sees something that starts out looking like a DTMF tone but the frequencies change after 100ms, it might be able to (depending upon the application) retroactively determine that the tones weren't really DTMF after all.  There's no way a DTMF chip could do that.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-09T17:17:47.250" />
  <row Id="12801" PostTypeId="1" AcceptedAnswerId="12803" CreationDate="2011-04-09T18:15:52.327" Score="8" ViewCount="105" Body="&lt;p&gt;I need a 12V 2.56A regulator. I happened to have 2x 2A 12V linear regulators I brought and did nothing with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was wondering could I wire them together and get 12V 4A or would I have divide my circuit amongst the two regulators? A schematic of how I would wire them would be much appriciated.&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-04-09T18:50:23.813" Title="2 Voltage regulator wired together to produce higher amperage possible?" Tags="&lt;voltage-regulator&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12802" PostTypeId="2" ParentId="12780" CreationDate="2011-04-09T18:28:52.247" Score="1" ViewCount="" Body="&lt;p&gt;Unless you're trying to use the smallest transistors you can get away with to hold data, I'm not clear why you would need sense amplifiers.  Wouldn't the data latches and passgates themselves provide enough strength to drive a normal logic input?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually, I would expect that the simplest way to get a 16x5 RAM would be to simply use a 32Kx8 SRAM and ignore the upper part.  Otherwise depending upon your you might be able to use something like a dual 64-bit shift register chip which has taps every 16 bits.  Combining that with a 74LS374 or equivalent along with suitable clocking logic you should be able to store 80 bits fairly nicely and access them five at a time.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-09T18:28:52.247" CommentCount="5" />
  <row Id="12803" PostTypeId="2" ParentId="12801" CreationDate="2011-04-09T18:50:23.813" Score="12" ViewCount="" Body="&lt;p&gt;It all depends on the regulator, and how &quot;balanced&quot; the two should be.  And by &quot;balanced&quot; I mean should each regulator be supplying exactly 50% of the current, or can it be more like 20%/80%?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The normal method is to simply run the output of the two regulators through a diode (one each), and then connect the outputs of the diodes together.  In this case, this is called a &quot;Wired OR&quot; and the diodes referred to as &quot;OR-ing Diodes&quot;.  The diodes are there mainly to isolate one regulator from the other.  While simple, this method doesn't always work well.  First, you have the voltage drop of the diodes to contend with.  And second, the regulators are not well balanced.  In practice, it is in the 80%/20% range.  As the load increases, the balancing gets better but it's never perfect.  Because of this balancing issue, the max load is not quite double what one regulator can do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The better method is called &quot;active load balancing&quot;.  It still uses the OR-ing diodes, but this time a small circuit dynamically adjusts the output voltage of the regulators to keep the load balanced.  In this case, the regulators can be kept very close to 50% of the total load.  And thus, the max current can be double what any one regulator can achieve by itself.  Doing this kind of circuit is tricky and challenging, but not beyond an experienced hobbyist.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A third method requires the use of regulators with an isolated output.  In this case, you set up the regulators to provide all the current, but half the voltage (6v @ 2.56A in your case).  Then wire the regulators in series to give you the proper voltage.  When you do this the regulators will be balanced fairly close to 50%/50% without any tricky balancing circuit.  Of course, this isn't appropriate for every situation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fourth method is simple.  Just wire up the two regulators in parallel.  Without knowing a great deal about the regulators and their behavior in this situation I wouldn't even attempt this, since if it doesn't work then it'll probably fail catastrophically.  But some regulators are designed with this in mind and have it documented in the datasheets.  If your regulator is one of these, then go for it.  The danger here is that the combination of the two regulators could cause a control loop instability, forcing the output to be very noisy and one regulator to take most of the load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I'd either buy a single regulator with the current you require, or partition up your circuit so one regulator powers half and the other regulator powers the other half.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-09T18:50:23.813" CommentCount="4" />
  <row Id="12804" PostTypeId="1" CreationDate="2011-04-09T21:08:15.023" Score="3" ViewCount="151" Body="&lt;p&gt;I m newbie.I don't want to ruin my board.I searched and found crysal soldering to launchpad.But there is msp430 launchpad pins too.Can I solder pins directly or should I use male header or female header.I said that pins like 1.6 1.7..... Can i solder them directly&lt;/p&gt;&#xA;" OwnerUserId="3788" LastEditorUserId="3788" LastEditorDisplayName="" LastEditDate="2011-04-10T07:57:03.513" LastActivityDate="2011-04-10T09:49:14.880" Title="Msp430 Launchpad Soldering" Tags="&lt;beginner&gt;&lt;msp430&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="12805" PostTypeId="2" ParentId="12804" CreationDate="2011-04-09T21:11:44.130" Score="8" ViewCount="" Body="&lt;p&gt;The crystal should be close to the chip - use the pads provided.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For most applications a crystal isn't necessary as it's got a very stable on-chip oscillator.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-09T21:11:44.130" CommentCount="1" />
  <row Id="12806" PostTypeId="2" ParentId="2377" CreationDate="2011-04-09T21:20:40.237" Score="1" ViewCount="" Body="&lt;p&gt;Devices like that are often programmed in assembler, resulting in smaller executables. It's worth making the effort and learning to use it.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-09T21:20:40.237" CommentCount="1" />
  <row Id="12807" PostTypeId="2" ParentId="12780" CreationDate="2011-04-09T22:45:24.113" Score="0" ViewCount="" Body="&lt;p&gt;If you are not shooting for top speed(&gt;1Mhz), you don't need any sense amplifiers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Standard 2T trigger  (plus some Ts for accessing the data) would give you close to 0 and VCC voltages.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-09T22:45:24.113" />
  <row Id="12808" PostTypeId="2" ParentId="12756" CreationDate="2011-04-09T22:48:50.147" Score="0" ViewCount="" Body="&lt;p&gt;If you think about simple ICs, you can get decent power consumption on CMOS chips.&#xA;You may take single inverter in a chip, and a counter. Run it at some 1.8V, and hopefully it will eat very little :-)&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-09T22:48:50.147" />
  <row Id="12809" PostTypeId="2" ParentId="12780" CreationDate="2011-04-09T22:55:34.540" Score="0" ViewCount="" Body="&lt;p&gt;(a) Are you using an off-the-shelf SRAM IC chip? If so, it already includes the &lt;a href=&quot;http://en.wikipedia.org/wiki/Register_file&quot; rel=&quot;nofollow&quot;&gt;sense amplifier&lt;/a&gt; -- the bitlines cannot be accessed from the outside, even if you wanted to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(b) Are you not using an SRAM IC chip? I.e., are you storing a few bits in a D latch or a shift register IC chip or are you building something out of &lt;a href=&quot;http://www.6502.org/users/dieter/mt15/mt15.htm&quot; rel=&quot;nofollow&quot;&gt;3 000 discrete transistors&lt;/a&gt;? If so, then you don't need a sense amplifier. As supercat mentioned, the output transistors of those devices is much larger than the tiny transistors inside a chip, and so that output can directly feed a digital input -- at worst you might need some digital inverter/tristate/line-driver/buffer to give you better fanout.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you actually have something -- such as, say, magnetic core memory -- that &lt;em&gt;needs&lt;/em&gt; a sense amplifier? While I doubt that is actually the case, if so, the LM339 may work fine for you -- please tell use what you are actually building.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-09T22:55:34.540" CommentCount="1" />
  <row Id="12810" PostTypeId="2" ParentId="12746" CreationDate="2011-04-09T23:45:10.573" Score="0" ViewCount="" Body="&lt;p&gt;Oh, ok.  The TDA8920 has a differential input.  This is good for two things: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Cancelling out interference in the cable&lt;/li&gt;&#xA;&lt;li&gt;Cancelling out common-mode ground loop voltages&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;For #1, you'd need a balanced line feeding it.  This means the source impedance for the positive and negative signal pins needs to be equal, so that any interference creates identical voltages on each, which can then be cancelled out by the diff amp.  (The signals do &lt;strong&gt;not&lt;/strong&gt; need to be equal and opposite, despite popular opinion.)  But since your signal is already unbalanced, you won't get this benefit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The #2 case only matters if the source is grounded through the third prong on the power cord.  If the amp and source are grounded through different outlets, there can be significant differences in their reference voltages.  Then you can get 60 Hz power line hum in your amp, because ground loop currents flowing through the cable's shield will cause the amp to measure relative to a fluctuating ground.  If so, you want to keep the power amp's ground disconnected from the source's ground, except the unavoidable connection through the wall.  The ground from your source should connect to the - input of the amp, and nothing else.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, if the source is floating, this will cause problems because the common mode voltage will be too great to cancel.  To handle both cases (floating source and grounded source), you can use a ground lift switch on the input, or compromise with a smallish resistor (100 Ω) between the amp's ground and the source ground:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/e05Im.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And follow the NXP schematic and PCB layout as closely as possible, including all the filter components shown above, or you'll get distortion, noise, EMI, etc.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-04-09T23:45:10.573" />
  <row Id="12811" PostTypeId="2" ParentId="12283" CreationDate="2011-04-09T23:59:55.423" Score="1" ViewCount="" Body="&lt;p&gt;Imagine that R2 were omitted, and suppose the left side transistor (which I'll call Q1) started out being turned on.  Then the right side transistor (Q2) would have nothing to turn it on, and the left side transistor would be held on by current through R3, while the R4 and the LED would charge C2.  The effect would be that the left LED would come on and stay on, while the right LED would never light.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now add R2.  This will cause C1 to charge to -0.7 volts, until Q2 turns on.  Once that happens, the charge on C2 would cause the base of Q1 to go negative, turning it off.  When that happens, left-side LED current will start flowing through C1 and the base of Q2, turning it on even harder.  Once Q2 has turned on, it will keep Q1 off until C2 charges to -0.7 volts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that while the circuit would have a stable state with both transistors on and both capacitors reverse-biased by 0.7 volts, in practice the winky-blink circuit always starts oscillating rather than entering such a state.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-09T23:59:55.423" />
  <row Id="12812" PostTypeId="2" ParentId="9757" CreationDate="2011-04-10T00:42:04.990" Score="0" ViewCount="" Body="&lt;p&gt;It's possible to design a T flip-flop using two transistors, some capacitors, and some resistors.  Start by wiring the transistors in a classic bistable multivibrator.  Next, put small capacitors in parallel with the feedback resistors.  The effect will be that if the circuit is sitting with one transistor on it will remain that way (the capacitors will enter a steady state where the cap that's in parallel with the feedback resistor that's passing current will be charged, and the cap in parallel with the other one won't be).  If the circuit is disturbed slightly (e.g. by reducing the supply voltage by a volt) the charged cap will render its associated feedback resistor momentarily ineffective, causing its transistor to turn off.  This will in turn cause the output of that transistor to float to its rail, turning on the other transistor.  Depending upon the exact requirements, there are many variations of the circuit which may be used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your goal is to divide down a known frequency, another approach you could use would be to use some relaxation oscillators which can be &quot;nudged&quot;, and then have each stage nudge the succeeding one.  For example, suppose one wanted to output one high-going pulse every 3600 high-going pulses of a 60Hz signal (3600 counts).  One could design a two-transistor circuit which would output a high pulse and discharge a cap every time the cap voltage reached 3.0 volts, or any time an input pulse was received and the cap voltage was over 2.0 volts.  One could then cascade six such circuits which would cycle when fed pulses after delays of 75ms, 208ms, 875ms, 4.5s, 12.5s, and 52.5s (effectively yielding divide ratios of 5, 3, 4, 3, 5, 4).  This approach might require some tweaking to ensure reliable operation, but it would a divide-by-3600 using twelve transistors rather than using twenty-four or more.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-10T00:42:04.990" />
  <row Id="12813" PostTypeId="2" ParentId="12739" CreationDate="2011-04-10T01:18:39.830" Score="0" ViewCount="" Body="&lt;p&gt;This is not a method I've tested myself, I am just offering a potential solution. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can place a speaker on top of the tank that outputs at a tone at a certain frequency, and place a waterproof mic on the bottom of the tank. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there is more water in the tank, the mic will pick up less volume from the speaker. To determine the amount of water, you just need to calibrate the device by recording the mic level at each water level. &lt;/p&gt;&#xA;" OwnerUserId="2968" LastActivityDate="2011-04-10T01:18:39.830" />
  <row Id="12814" PostTypeId="2" ParentId="10879" CreationDate="2011-04-10T01:37:42.987" Score="0" ViewCount="" Body="&lt;p&gt;Back in the 1970's, it was pretty common to run 6502 microprocessors at above the rated speed, even though the data sheet gave a minimum cycle time of 1000ns for the 1MHz part.  The popular Atari 2600 Video Computer System ran its processor at 1.1932MHz; the Apple II, Commodore VIC-20, and Commodore 64, all ran at 1.0227MHz.  Since there were no speed grades between 1MHz and 2MHz, I would expect all of those machines were overclocked (by almost 20% in the case of the Atari 2600 Video Computer System).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-10T01:37:42.987" />
  <row Id="12815" PostTypeId="1" AcceptedAnswerId="12817" CreationDate="2011-04-10T03:53:24.360" Score="0" ViewCount="67" Body="&lt;p&gt;I'm experimenting with a linear-mode fast-charge circuit for NiMH batteries. I was surprised to find that the voltage measured across the battery terminals while fast-charging is higher than the theoretical series cell voltage. By that, I mean rechargeable cells are theoretically 1.2V each (as opposed to non-rechargeable cells that are 1.5V each).  Charging four AA NiMH cells in series I measured a voltage of around 6V across the pack, rather than 4.8V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the explanation for this higher voltage while charging? Can I predict the maximum voltage, V, I will measure while charging N cells in series with a current of J mA?&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-04-10T05:00:25.257" Title="Battery Voltage While Charging" Tags="&lt;battery&gt;&lt;battery-charging&gt;&lt;measurement&gt;" AnswerCount="1" />
  <row Id="12816" PostTypeId="2" ParentId="12797" CreationDate="2011-04-10T04:33:17.917" Score="1" ViewCount="" Body="&lt;p&gt;I think the problem you're having is that you can't both talk to a device on the UART and talk to a terminal (your computer) at the same time using the same pins (0 and 1) of the Arduino. If you want to talk to your computer as well as a device you have to use a &lt;a href=&quot;http://arduino.cc/en/Reference/SoftwareSerial&quot; rel=&quot;nofollow&quot;&gt;SoftSerial&lt;/a&gt; library (or &lt;a href=&quot;http://sundial.org/arduino/index.php/newsoftserial/&quot; rel=&quot;nofollow&quot;&gt;NewSoftSerial&lt;/a&gt;) and wire the device to use different pins rather than the hardware UART... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strike&gt;That being said, it seems plausible that the bluetooth module is prompting your for a command with the message &quot;CMD&quot;.&lt;/strike&gt; (misread question, this was what you expected, not what actually happened)&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-04-10T15:10:07.693" LastActivityDate="2011-04-10T15:10:07.693" CommentCount="1" />
  <row Id="12817" PostTypeId="2" ParentId="12815" CreationDate="2011-04-10T04:52:01.787" Score="1" ViewCount="" Body="&lt;p&gt;The charging voltage will be 1.4 V -1.6 V per cell. They must be charged at constant current, not 1.2 V per cell.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-10T05:00:25.257" LastActivityDate="2011-04-10T05:00:25.257" CommentCount="2" />
  <row Id="12818" PostTypeId="2" ParentId="12233" CreationDate="2011-04-10T05:01:24.547" Score="0" ViewCount="" Body="&lt;p&gt;Leon's link is right on the mark as far as importing downloaded libraries into KiCad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I highly recommend all of the posts from curiousinventor.com.  Start &lt;a href=&quot;http://store.curiousinventor.com/guides/kicad&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and go through all of the posts.  There aren't that many, and they are quick and easy reads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a nutshell, the icons in the toolbar are your friends, so learn them right away.  You'll put parts into you schematic with the &quot;Place a Component&quot; function in the right toolbar.  You can pick the part you want by using &quot;Select by Browser&quot;, or you can do a keyword search.  The problem with the keyword search is that if you've modified a component and saved it into your own custom library, when you search for the keyword you'll get multiple instances, and you won't be able to tell which library the instance is from!  So in this case, &quot;Select by Browser&quot; is the way to go.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-10T05:01:24.547" />
  <row Id="12819" PostTypeId="1" CreationDate="2011-04-10T05:14:55.507" Score="0" ViewCount="96" Body="&lt;p&gt;Hi,&#xA;I'm trying to solve AC equivalence of small signal BJT circuits. I'm confused wether to use Hybrid-Pi or T-model&lt;/p&gt;&#xA;" OwnerUserId="3789" LastActivityDate="2011-04-11T19:49:07.043" Title="BJT's Small signal Models" Tags="&lt;transistor&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="12820" PostTypeId="2" ParentId="10879" CreationDate="2011-04-10T07:54:42.223" Score="0" ViewCount="" Body="&lt;p&gt;If you're working with a single device you can just try and see what frequency still works. 81 MHz will still work, no doubt about it.&lt;br&gt;&#xA;It's a bit different if you're working with production quantities. You can't make a production run and hope everything will be all right.  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;In the early 90's I worked for Philips Audio and we had a design which used a Motorola 56002 DSP running at 27 MHz. This was an audio application, and the 4th harmonic of 27 MHz is 108 MHz, just at the edge of the FM band. Because we feared interference we wanted to run the DSP at 27.1 MHz. Would this work? Yes. For sure? No. Motorola guaranteed it for 27 MHz, no more. We requested and got a custom version of the specification which stated 27.1 MHz as the maximum frequency.  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Did we get different, selected devices, or was there a die redesign? Of course not, but in unlikely the event that a DSP would not work Motorola would be liable.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-10T07:54:42.223" />
  <row Id="12821" PostTypeId="1" CreationDate="2011-04-10T08:22:46.430" Score="2" ViewCount="109" Body="&lt;p&gt;I want to put some solar cells on the roof of my van to powerup some stuff while the van is off. I would like to know how much area of blue solar cells (they look like cracked blue glass) I need to generate 12V 30-40amps in clear sky at noon?&lt;/p&gt;&#xA;" OwnerUserId="3792" LastEditorUserId="1691" LastEditorDisplayName="" LastEditDate="2011-04-10T14:08:10.470" LastActivityDate="2011-04-10T18:49:57.507" Title="solar cell area to gain 12V 40amps?" Tags="&lt;solar-cell&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="12822" PostTypeId="2" ParentId="4571" CreationDate="2011-04-10T08:38:23.947" Score="3" ViewCount="" Body="&lt;p&gt;How about the &quot;STM32/ARM Cortex-M3 HOWTO: Development under Ubuntu.&quot; &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://fun-tech.se/stm32/&quot; rel=&quot;nofollow&quot;&gt;http://fun-tech.se/stm32/&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://fun-tech.se/stm32/gcc/index.php&quot; rel=&quot;nofollow&quot;&gt;http://fun-tech.se/stm32/gcc/index.php&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The build scripts can also be found over at github&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;https://github.com/jsiei97/FunTechCortexMX_gcc&quot; rel=&quot;nofollow&quot;&gt;https://github.com/jsiei97/FunTechCortexMX_gcc&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;It should be working for the other Cortex M3 based MCU:s as well, &#xA;even thou this is tested  on the stm32.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2011-04-10T08:38:23.947" />
  <row Id="12823" PostTypeId="1" AcceptedAnswerId="12824" CreationDate="2011-04-10T08:44:13.610" Score="0" ViewCount="38" Body="&lt;p&gt;hello&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used lan cable for light LED up on my bread board&#xA;power source is PC's power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;without any resistor, the lan cable melt!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I reallize I have to keep OHM's law in my mind &#xA;and use proper resistor for safety.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;on lan cable's jacket, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;it says &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;0270M LS Cable UTP 4PR 24AWG CM CAT . 5E 75C KS Verified KS C 3342 HDPE 2009 V8&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;how much current do this 24AWG cable tolerate?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and&lt;br&gt;&#xA;could somebody tell me the relationship between temperture, current, thickness, and material?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;linking website, simple hint also welcome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks.&lt;/p&gt;&#xA;" OwnerUserId="3746" LastActivityDate="2011-04-10T09:33:43.733" Title="relationship between temperture, current, thickness, and material" Tags="&lt;power-supply&gt;&lt;resistor&gt;&lt;wire&gt;&lt;safety&gt;" AnswerCount="1" />
  <row Id="12824" PostTypeId="2" ParentId="12823" CreationDate="2011-04-10T09:12:00.963" Score="2" ViewCount="" Body="&lt;p&gt;You must have a short somewhere.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;24AWG is 0.511 mm in diameter and has a resistance of 84 mOhm/m. That means that a 1 A current will generate 84 mW in heat loss per meter.&lt;br&gt;&#xA;Copper has a specific heat of 0.385 J/g, this means you have to 0.385 Watt-second to heat 1 g of copper 1 °C.&lt;br&gt;&#xA;Specific mass of copper is 8.93 g/cm^3, or 1 m of 24AWG weighs 1.83 g. So you need 0.705 Watt-second to heat 1 m of 24AWG 1°C, provided it can't loose this heat. Now we're generating 84 mW, this means that having 1 A for 1 second will heat -- well, warm -- your cable up by 0.12 °C.&lt;br&gt;&#xA;In 1 minute your cable will be 7 °C warmer, in practice less, because the cable can conduct/convect/radiate part of this heat.&lt;br&gt;&#xA;The insulation is HDPE (High Density PolyEthylene), which has a melting point around 120 °C.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In conclusion: even 1 A will not melt your cable, and a LED uses far less than that.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-10T09:33:43.733" LastActivityDate="2011-04-10T09:33:43.733" CommentCount="1" />
  <row Id="12825" PostTypeId="2" ParentId="12821" CreationDate="2011-04-10T09:23:33.753" Score="9" ViewCount="" Body="&lt;p&gt;I do not know what &quot;blue cell which looks like cracked glass&quot; you are talking about, but I have seen cells on sale rated up to 173 W/m&lt;sup&gt;2&lt;/sup&gt; nominal power - these where best quality, selected cells. The ratings are however usually given as open circuit voltage times short circuit current, and even with the best cells, the most power you are ever going to get even with the cell facing directly the sun, is 70% of that, which is about 120 W/m&lt;sup&gt;2&lt;/sup&gt;. But that nominal power you are only going to get at full sunlight with the cell facing exactly in the direction of the sun. Yesterday I was making tests with some small cell around 14:00, and when the cell was in horizontal position, I was able to get about 67% of the maximum power it had facing the sun. However when the cell was in shade, the output was only about 6% of the maximum power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are interested in getting 12 V &amp;amp; 40 A only at clear sky, if you buy the best quality cell of rated nominal power 173 W/m&lt;sup&gt;2&lt;/sup&gt; (real maximum power 120 W/m&lt;sup&gt;2&lt;/sup&gt;), the rough calculation would be:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$12 \mbox{ V} \times 40 \mbox{ A} = 480 \mbox{ W}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$\frac{480 \mbox{ W}}{120 \mbox{ W}/\mbox{ m}^2 \times 67\%} \approx 6 \mbox{ m}^2$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That might fit on a van if it is a moderately large one, but if you want it to provide that power also when there are clouds, or any shade, you will need a panel at least 10 times as large. If you don't buy the highest quality selected cells, but go for most common panels, they have only 114 W/m&lt;sup&gt;2&lt;/sup&gt; nominal rated power, the required area will be 50% more. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you would want to supply that 480 W round the clock, you will need batteries, account for the loss of power while charging (10% - 50% depending on what batteries and charge controllers you use), and take into account that sun only shines a small part of the day. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I read that from a panel in horizontal position, in London, UK, in December, you get on average 0.434 Wh of energy per each nominal W of panel power per day. In July the value is about 10 times as much Wh per day. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That means to provide 480 W continuously even in December, you would need a panel of nominal power 26544 W, which would be at least 154 m&lt;sup&gt;2&lt;/sup&gt; in size. And that's not taking into account loss on charging the battery.&lt;/p&gt;&#xA;" OwnerUserId="1691" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-04-10T18:49:57.507" LastActivityDate="2011-04-10T18:49:57.507" CommentCount="1" />
  <row Id="12826" PostTypeId="2" ParentId="12804" CreationDate="2011-04-10T09:49:14.880" Score="0" ViewCount="" Body="&lt;p&gt;The crystal location is placed there because it's a critical thing for a clock reference, as Leon said. Place the crystal at that location. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;An alternative is, what I've seen very similar on some of the olimex microcontroller boards, is to use &lt;strong&gt;female&lt;/strong&gt; pin headers at the location. You can slide a crystal in there and swap it with another one whenever necessary. However, this might not be the best and reliable connection, as it might not be a perfect fit (and make very poor contact).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, if you want to use the board occasionally, take 1 crystal you think you'll use most often and place it right in there. I also believe the boards very sold for a very very low price, so you may as well get another one and place another crystal on there, if you're a bit anxious with desoldering and soldering.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-04-10T09:49:14.880" CommentCount="3" />
  <row Id="12827" PostTypeId="1" AcceptedAnswerId="13098" CreationDate="2011-04-10T10:42:39.650" Score="5" ViewCount="71" Body="&lt;p&gt;I'd like to build a 4-wheel skid steer robot. I have selected &lt;a href=&quot;http://www.superdroidrobots.com/shop/item.aspx?itemid=840&quot; rel=&quot;nofollow&quot;&gt;this motor&lt;/a&gt; and &lt;a href=&quot;http://www.basicmicro.com/Robo-Claw-2x10A_p_45.html&quot; rel=&quot;nofollow&quot;&gt;this motor controller&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The motor controller can handle a 10A draw and has the ability to operate over serial TTL and give me encoder feedback (which is what I want).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The motor controller is designed to drive two motors (not four). I know that I can link two motor controllers together (one for left wheels and one for right)... but is that necessary? I mean the motors are rated at 2300mA max and the motor controller is 10A. Would it be a bad idea to simply connect two motors to channel A and the other two to channel B?&lt;/p&gt;&#xA;" OwnerUserId="3793" LastActivityDate="2011-04-15T03:47:36.497" Title="Drive 4 DC motors off a dual drive motor controller." Tags="&lt;robotics&gt;&lt;dc-motor&gt;&lt;controller&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="12828" PostTypeId="1" AcceptedAnswerId="12829" CreationDate="2011-04-10T11:25:35.900" Score="1" ViewCount="96" Body="&lt;p&gt;how can I construct a d flip flop from jk ?&lt;/p&gt;&#xA;" OwnerUserId="3192" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-05-13T02:38:56.447" LastActivityDate="2011-05-13T02:38:56.447" Title="Constructing a D flip flop from JK" Tags="&lt;logic&gt;&lt;homework&gt;" AnswerCount="2" />
  <row Id="12829" PostTypeId="2" ParentId="12828" CreationDate="2011-04-10T12:29:18.857" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Flip-flop_%28electronics%29#JK_latch&quot; rel=&quot;nofollow&quot;&gt;As per wikipedia&lt;/a&gt;, all you need to do is connect &lt;code&gt;K&lt;/code&gt; to the inverse of &lt;code&gt;J&lt;/code&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Doing this effectively removes the possibility of &lt;code&gt;00&lt;/code&gt; and &lt;code&gt;11&lt;/code&gt; inputs. If the &lt;code&gt;J&lt;/code&gt; is treated as &lt;code&gt;D&lt;/code&gt; then:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;code&gt;D&lt;/code&gt; = 1 sets &lt;code&gt;Q&lt;/code&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;code&gt;D&lt;/code&gt; = 0 resets &lt;code&gt;Q&lt;/code&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This behaviour is then identical to the &lt;code&gt;D&lt;/code&gt; flip-flop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For this reason the &lt;code&gt;JK&lt;/code&gt; flip-flop is called the universal flip-flop, because you can construct all other flip-flop types with it. &lt;/p&gt;&#xA;" OwnerUserId="2340" LastActivityDate="2011-04-10T12:29:18.857" />
  <row Id="12830" PostTypeId="2" ParentId="12780" CreationDate="2011-04-10T13:38:00.723" Score="2" ViewCount="" Body="&lt;p&gt;To answer your question, yes you can use a LM339 as a sense amp, and all you need to do is wire the + input to the non-inverting bit-line, and the - input to the inverting bit-line. BUT...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since we're talking about reading a SRAM, the basic sequence of events during a READ is: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Pre-charge both bit-lines to VDD.&lt;/li&gt;&#xA;&lt;li&gt;Assert the desired word-line&lt;/li&gt;&#xA;&lt;li&gt;The selected bits will now pull one of each complimentary bit-line pair towards VSS&lt;/li&gt;&#xA;&lt;li&gt;The sense amplifier will sense a difference between the bit-line voltages (one will stay at VDD, the other will be falling towards VSS)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If you look at the schematic for a 4T or 6T bit-cell, then you can see that the falling bit-line will eventually reach VSS. In typical IC designs, where density is very important, the bit-cells have very small transistors. Additionally, they are typically built into large arrays, which have very large bit-line capacitances. This results in a very slow (relatively) discharge of the bit-line by the bit-cell. This is the motivation for the speed aspect of a sense amplifier. It probably doesn't apply to you because you can use large transistors (since they're discrete, or in an array), and your array is small.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The isolation aspect of the sense amp is also very important. If you don't use a sense amp, your bit-line will have an unknown load based on whatever you hook up. Also, any noise on the signal will be broadcast to all your bit-cells. Some isolation is always a good idea here. Something as simple as a CMOS buffer/inverter will work just fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't think you're going to see a major benefit from using a comparator to sense the bit-lines. Instead, I would recommend that you use a CMOS inverter or buffer. It will be simpler, just as fast, and denser.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-04-10T13:38:00.723" />
  <row Id="12831" PostTypeId="1" AcceptedAnswerId="12834" CreationDate="2011-04-10T14:23:22.337" Score="15" ViewCount="426" Body="&lt;p&gt;I have seen one inverter rated at 300W, and another at 300VA. What is the practical difference between them, if any? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-11T05:36:40.310" Title="What is the practical difference between watts and VA (volt-amps)?" Tags="&lt;power&gt;&lt;va&gt;&lt;watts&gt;" AnswerCount="1" FavoriteCount="3" />
  <row Id="12832" PostTypeId="1" AcceptedAnswerId="13478" CreationDate="2011-04-10T14:56:27.257" Score="4" ViewCount="158" Body="&lt;p&gt;Hi! I want to use some metal halide lamps (5-7*150W) to get some decent lighting in my room.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, inductors for these lamps have weight about 2kg each. I cannot accept 10kg of metal hanging near the ceiling :-) So I must go with electronic ballast, but their cost is about 100 bucks per lamp. Forking out 500 bucks does not sounds good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I am thinking about making 5-channel electronic ballast for these lamps. While basic idea looks simple (just make constant current supply), the main problem is ignition.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to avoid HV ignition by feeding RF signal into lamp, so that discharge would start just like in induction lamps, and after some time turn on the current?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And finally, do I still need alternating current direction in the lamp? If yes, how fast it should change?&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-25T21:42:48.157" Title="Lighting metal halide lamp" Tags="&lt;ballast&gt;&lt;lamp&gt;&lt;metal-halide&gt;" AnswerCount="2" CommentCount="5" FavoriteCount="1" />
  <row Id="12834" PostTypeId="2" ParentId="12831" CreationDate="2011-04-10T15:17:50.067" Score="18" ViewCount="" Body="&lt;p&gt;For resistive loads they're equivalent. For reactive (inductive/capacitive) loads however, voltage and current are not in phase, and you have to take this phase difference (phi) into account.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Effective power = Voltage * Current * cos(phi), in Watt&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apparent power = Voltage * Current, in VA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apparent power is higher for non-resistive loads, but that's because it contains a part of blind power; power the utility has to provide but also gets back during part of the cycle (in the graph the part where the power is negative, purple line under the X-axis).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/L77fH.png&quot; alt=&quot;enter image description here&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because they have to provide it, but can't invoice it (after all they get it back) the utilities are not too happy with reactive loads, and industries have to pay fines if their cos(phi) becomes too low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt; (re jpc's comment):&lt;br&gt;&#xA;The 300W PSU will consume 300 W of effective power, for the other PSU the apparent power is given, effective power for this PSU will be lower, e.g. if the cos(phi) = 0.9, effective power will be 270W.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-11T05:36:40.310" LastActivityDate="2011-04-11T05:36:40.310" CommentCount="16" />
  <row Id="12836" PostTypeId="1" CreationDate="2011-04-10T16:19:46.997" Score="3" ViewCount="52" Body="&lt;p&gt;Could anyone please explain the working of so called 'peaking inductors'? I know they are used to enhance the bandwidth but how do they do this?&lt;/p&gt;&#xA;" OwnerUserId="3794" LastActivityDate="2011-04-10T22:25:01.260" Title="Peaking Inductance" Tags="&lt;inductor&gt;&lt;inductance&gt;&lt;bandwidth&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="12837" PostTypeId="2" ParentId="12832" CreationDate="2011-04-10T16:26:41.090" Score="4" ViewCount="" Body="&lt;p&gt;Microchip has a &lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/01372A.pdf&quot; rel=&quot;nofollow&quot;&gt;dsPIC app note&lt;/a&gt; on electronic ballasts for automotive (not so different from what you have). They use an HV igniter to get the lamp fired. You will also see that AC is used once the lamp is fired. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A little research showed me that &lt;a href=&quot;http://knol.google.com/k/how-induction-lamps-work#&quot; rel=&quot;nofollow&quot;&gt;induction lamps don't have electrodes&lt;/a&gt;, and need HF applied constantly to excite mercury amalgam into emitting UV, whereas a &lt;a href=&quot;http://en.wikipedia.org/wiki/Metal_halide_lamp&quot; rel=&quot;nofollow&quot;&gt;metal halide lamp&lt;/a&gt; relies on an arc to be the UV source, and doesn't appear to have a mercury amalgam pellet at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It appears that the induction lamp is specially constructed so that the external electromagnet is close to the amalgam pellet. If there is no pellet in the HID lamp, game over. Even if there were, I don't know if you'd be able to excite it given the dimensions of the glass around it.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-25T14:59:21.967" LastActivityDate="2011-04-25T14:59:21.967" CommentCount="1" />
  <row Id="12838" PostTypeId="2" ParentId="12195" CreationDate="2011-04-10T17:07:53.473" Score="0" ViewCount="" Body="&lt;p&gt;Yep, so for anyone else looking at this, I tried it and it seems like you do need the pressure of the iron.  Heat gun is a no go.&lt;/p&gt;&#xA;" OwnerUserId="3424" LastActivityDate="2011-04-10T17:07:53.473" />
  <row Id="12839" PostTypeId="1" AcceptedAnswerId="12898" CreationDate="2011-04-10T18:33:13.227" Score="3" ViewCount="237" Body="&lt;p&gt;I've been working on designing an ALU that calculates various functions but I don't really know how to separate each function from one another.  The inputs are 4-bit numbers A and B.  I have a decoder that selects which function to use, but I don't know how to implement the functions from the decoder.  The ALU needs to do arithmetic operations and also logical operations.  If anyone knows how to go about structuring an ALU that has 2 4-bit inputs and 1 4-bit output, any guidance would be appreciated.  Thanks.&lt;/p&gt;&#xA;" OwnerUserId="3796" LastActivityDate="2011-04-12T00:57:05.250" Title="Designing a 4-bit ALU to compute various functions" Tags="&lt;logic&gt;&lt;circuit-design&gt;&lt;homework&gt;&lt;alu&gt;&lt;asic&gt;" AnswerCount="4" />
  <row Id="12840" PostTypeId="2" ParentId="12839" CreationDate="2011-04-10T18:42:14.903" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/File:2-bit_ALU.png&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is an example of a 2-bit ALU. As you can see XOR, and, or are computer by the first 3 logic gates. Then two XOR gate are used to determine the sum value. Then two AND and an OR gate are used to determine the carry on value. You can work out the truth table and see that it works. The carry is then fed to the logic for the second bit which works the same way. The decoder then selects the operation. You just have to continue the same pattern and extend it to 4 bits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For adding three bits (C is the carry over) the truth table is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;A B C  (A+B) Carry&#xA;0 0 0    0     0&#xA;0 0 1    1     0&#xA;0 1 0    1     0&#xA;0 1 1    0     1&#xA;1 0 0    1     0&#xA;1 0 1    0     1&#xA;1 1 0    0     1&#xA;1 1 1    1     1&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You can find out how to implement these two logic functions using a &lt;a href=&quot;http://en.wikipedia.org/wiki/Karnaugh_map&quot; rel=&quot;nofollow&quot;&gt;Karnaugh map&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3688" LastEditorUserId="3688" LastEditorDisplayName="" LastEditDate="2011-04-10T18:55:23.330" LastActivityDate="2011-04-10T18:55:23.330" CommentCount="2" />
  <row Id="12841" PostTypeId="2" ParentId="12195" CreationDate="2011-04-10T18:47:56.590" Score="0" ViewCount="" Body="&lt;p&gt;This is just a crazy idea I got, but...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Build your own little contraption consisting of two sheet of metal, say aluminum, and drill 4 wholes in the corners. Add some nuts and bolts through said wholes to apply pressure, and lastly apply heat. This could be with a big-ass heat gun, or even a (domestic) oven. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Report back with the results if you try it. :)&lt;/p&gt;&#xA;" OwnerUserId="3745" LastActivityDate="2011-04-10T18:47:56.590" CommentCount="2" />
  <row Id="12842" PostTypeId="1" CreationDate="2011-04-10T20:22:37.793" Score="0" ViewCount="103" Body="&lt;p&gt;When I program my Atmega816au, I lose communication with the microcontroller after I program the fuses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can write and read the Flash memory with no problems, but only before I program the fuses. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I program the fuses, the microcontroller becomes &quot;useless&quot; and I don't have access to it anymore.&lt;/p&gt;&#xA;" OwnerUserId="3798" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-12T12:03:57.813" LastActivityDate="2011-04-12T12:03:57.813" Title="AVRISP mkII. No comunication betwen programmer and device, after programing fuses" Tags="&lt;avr&gt;" AnswerCount="1" CommentCount="8" />
  <row Id="12843" PostTypeId="2" ParentId="12842" CreationDate="2011-04-10T20:53:31.810" Score="1" ViewCount="" Body="&lt;p&gt;Did you program the fuse correctly? An AVRISP mkII uses the SPI serial programming protocol, which can be disabled by fuses. Make sure SPIEN is programmed (0).&#xA;Also, you need to select a valid clock to use the SPI serial programming protocol.&#xA;Use &lt;a href=&quot;http://www.engbedded.com/fusecalc/&quot; rel=&quot;nofollow&quot;&gt;http://www.engbedded.com/fusecalc/&lt;/a&gt; to calculate your fuses.&lt;/p&gt;&#xA;" OwnerUserId="3800" LastActivityDate="2011-04-10T20:53:31.810" CommentCount="1" />
  <row Id="12845" PostTypeId="1" AcceptedAnswerId="12850" CreationDate="2011-04-10T21:20:54.880" Score="3" ViewCount="266" Body="&lt;p&gt;I have 6 high resoloution encoders (10k lines) that I want to interface with a micro controller. I have written code to do the quadrature decoding for all the encoders but there is just no way that a poor Arduino can handle that that many encoders at any reasonable speed, let alone do anything else while keeping track of the encoders.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What should I do in such a situation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately I don't have much of a background in electronics, just in programming (just a little bit).&lt;/p&gt;&#xA;" OwnerUserId="1319" LastEditorUserId="1319" LastEditorDisplayName="" LastEditDate="2011-04-11T20:29:57.570" LastActivityDate="2011-04-12T15:24:43.347" Title="Quadrature decoding" Tags="&lt;arduino&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="12846" PostTypeId="2" ParentId="12845" CreationDate="2011-04-10T21:39:10.087" Score="2" ViewCount="" Body="&lt;p&gt;Use a $7.50 XMOS XS1-L1 chip, with six threads doing the decoding - one thread for each encoder:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xmos.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.xmos.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That leaves two threads for doing other stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The XK-1A board available from Digi-Key only costs 99, and comes with the XTAG-2 debugger. It's got everything you need on it Development software is free, and I think I've seen encoder software on the users forum. The 1600 MIPS XC-1A board is another option, and also costs 99.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is probably the easiest and cheapest way to do it.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-11T20:59:38.013" LastActivityDate="2011-04-11T20:59:38.013" CommentCount="14" />
  <row Id="12847" PostTypeId="2" ParentId="12839" CreationDate="2011-04-10T22:02:16.900" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikibooks.org/wiki/VHDL_for_FPGA_Design/4-Bit_ALU&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a 4-bit ALU in VHDL. If actual hardware is required the code could be implemented in a suitable CPLD.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-10T22:02:16.900" CommentCount="3" />
  <row Id="12848" PostTypeId="2" ParentId="12845" CreationDate="2011-04-10T22:07:52.033" Score="2" ViewCount="" Body="&lt;p&gt;My suggestion would be to have the Arduino execute user application code, and simply talk to 3 or 6 other very low cost microcontrollers that do the quadrature decoding.  The number of external micros depends on how capable they are of decoding such a high-resolution encoder at a given speed.  The external micros would behave like those in mice -- they keep track of the encoder count delta since the last position query.  Assuming that you're not trying to do realtime position feedback for closed loop motor control, and just want to know where each motor is at an arbitrary point in time, this could work out for you.  Use SPI or I2C to talk to all of the external micros, and of course you'll need to deal with counter rollover in the event that the main controller (Arduino) doesn't request a position update at regular, guaranteed intervals.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-10T22:07:52.033" CommentCount="5" />
  <row Id="12849" PostTypeId="2" ParentId="12836" CreationDate="2011-04-10T22:25:01.260" Score="1" ViewCount="" Body="&lt;p&gt;This seems to be a way of improving the performance of analog high-frequency (GHz range) integrated circuits. Too bad that all the articles I found about this topic are behind a IEEE paywall. I think I could download them at my former University if there is interest in more details about this technique.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic bandwidth limitation of many circuits is the low pass RC filter formed by the resistance of the signal source (which may be a transmission line which &quot;looks&quot; like a resistance) and the input capacitance of an amplifier circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By adding some inductance the input capacitance can be brought to resonance and &quot;neutralized&quot;. If you choose the right inductance value you can place the resonant frequency (and the peak of the LC characteristic from which this technique takes its name) near the low pass frequency limit of the original circuit to boost the signal amplitude a little and therefore improve the bandwidth.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-10T22:25:01.260" CommentCount="1" />
  <row Id="12850" PostTypeId="2" ParentId="12845" CreationDate="2011-04-10T22:29:03.350" Score="8" ViewCount="" Body="&lt;p&gt;My pet peeve is when quadrature decoding is done in software.  When done in software, the decoder frequency can't keep up, especially when the pulse rate is fast or the MCU is doing a lot of other things.  I have seen many devices that use quadrature encoders on a data-entry knob, and it works fine most of the time.  But the decoder would skip pulses whenever the MCU had to do something, like refresh the screen or talk over RS-232.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do quadrature decoding in an FPGA.  A 50K Gate Xilinx Spartan-3A costs less than $10 and can decode more channels than it has pins.  And it'll do it with a quadrature pulse rate over 1 MHz.  There are no MCUs for similar or cheaper cost that can do that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:  What follows below is a summary of lots of comments, and some further elaboration on my part.  Enjoy!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's true that you can do a software approach if the pulse rate is slow enough.  But when this is done, you have to make sure that the &quot;corner cases&quot; are covered.  Things like interrupts for other peripherals (like UARTs, ADCs, etc.) can effect how often you sample the quadrature data causing the quadrature decoding process to occasionally miss pulses.  These missed pulses are &quot;ok&quot; for some applications, like a data-entry knob, but are still annoying to me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;@Leon Heller really likes the &lt;a href=&quot;http://www.xmos.com/&quot; rel=&quot;nofollow&quot;&gt;XMOS processors&lt;/a&gt; for something like that.  For those who don't know, the XMOS stuff is basically a simple but super fast MCU.  Where most MCU's run in the &amp;lt;25 MIPS range, the XMOS stuff is pushing 500 MIPS.  XMOS doesn't do a lot of hardware based peripherals, like UARTs.  Instead they &quot;bit-bang&quot; it and do the UART in software.  They also bit-bang things like USB and 10mbps Ethernet.  Ok, I'm super-over-simplifying this, but you get the point.  Here's my opinion:  there are FPGA guys and there are CPU guys.  If you're a CPU type of guy and don't like FPGAs then the XMOS processor might be right for you.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The topic of &lt;a href=&quot;http://en.wikipedia.org/wiki/Gray_code&quot; rel=&quot;nofollow&quot;&gt;Gray-codes&lt;/a&gt; in an FPGA implementation was brought up, and implementing the up/down position counters in gray code.  There are typically two reasons to use Gray-codes:  if you have some asynchronous logic going on (2 or more clocks), or if you want the counters to take up less logic.  Normally you wouldn't have async logic in the FPGA (other than sampling the quadrature data at the input pins), and the FPGA already has super-fast carry chains (a.k.a. binary adders).  So really, under normal circumstances there isn't any need for gray-code counters for this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use a CPLD for this, instead of an FPGA.  This would work for 1 or 2 quadrature decoders, but as you add more decoders the interfacing to a MCU gets more complex.  FPGAs are nice for this because the MCU interface could be SPI or other simple thing that doesn't take up dozens of pins on the MCU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;correct&quot; way to do this in an FPGA is where the FPGA has a simple 8-16 bit counter that tracks the position.  This counter is never reset after initialization, and sometimes not even then.  Software (SW) would poll this position every so often, and would keep a record of the &quot;previous position&quot;.  Taking the current position and subtracting the previous position would tell the software how far the position changed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason the position counter is never reset is because we're trying to avoid a &quot;destructive read&quot;.  That's when the CPU reads a register which causes something irreversible to happen-- like clearing a position counter.  Sometimes destructive reads are unavoidable, like when reading a FIFO, but generally you want to avoid them.  The thinking behind this is beyond this post.  I tried to find a good web page that discusses them, but I failed.  Sorry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When talking about the count-rate, below, I mean how fast the position counter can go up or down.  Because of the quadrature nature of the thing, the &quot;pulse rate&quot; is one quarter of the count rate.  I'm assuming that for every full pulse we can count up/down 4 times.  I know there are other ways to count (one count per full pulse), but I'm ignoring it out of principal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ignoring the XMOS processor (which is more like an FPGA, in the context of the next few paragraphs), MCU's are going to be limited to a max count rate of less than 500 Hz and in many cases less than 100 Hz max.  Of course there might be some outliers that get higher than 1 KHz, but for most people that's hard to do.  For your typical MCU you're doing good to get above 100 Hz, assuming that the MCU is not dedicated to quadrature decoding.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A typical data-entry knob has 12 to 20 pulses per revolution, or 48 to 80 counts per revolution.  Assuming the knob is 1 inch in diameter, a typical but over-zealous person could get about 4 turns per second when trying to scroll through lots of data.  That works out to a count rate of 192 to 320 Hz.  Still within the capability of an MCU, but just barely and only with careful programming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An FPGA, depending on exactly how the logic is written, could handle a count rates of more than 100 MHz.  I've written my logic to handle count rates of up to about 50 KHz, but it can do many quadrature decoders in a very small amount of logic.  In a Xilinx Spartan-3 FPGA it takes about 50 slices and 1 Block-RAM to do 32 to 512 decoders (you'll run out of pins before you run out of logic).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, which is better, FPGA, MCU, or XMOS?  As usual, it depends.  It depends not only on the usual things like count rate and number of decoders, but also on what the designer is comfortable using and what else is in the system.  My preference is FPGA, but that's just the kind of guy I am!  :)&lt;/p&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="3624" LastEditorDisplayName="" LastEditDate="2011-04-12T15:24:43.347" LastActivityDate="2011-04-12T15:24:43.347" CommentCount="1" />
  <row Id="12851" PostTypeId="1" AcceptedAnswerId="12855" CreationDate="2011-04-10T23:17:50.633" Score="4" ViewCount="262" Body="&lt;p&gt;For three phase electricity the wave is offset by 120 degrees(2$\pi/3$ Rad). Why aren't the phases closer together? Is it because it will affect the frequency of the phases? How was this 120 degrees chosen?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Eb4Mc.jpg&quot; alt=&quot;3 Phase Wave Form&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-04-11T16:05:25.830" Title="Why is three-phase offset by 120 degrees?" Tags="&lt;line-power&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="2" />
  <row Id="12852" PostTypeId="1" CreationDate="2011-04-10T23:29:13.953" Score="0" ViewCount="72" Body="&lt;p&gt;Can someone suggest for me a good course (preferably video) on satellite communication? &lt;/p&gt;&#xA;" OwnerUserId="3802" LastActivityDate="2011-04-16T14:11:51.897" ClosedDate="2011-04-16T19:10:31.637" Title="Satellite Communication course" Tags="&lt;communication&gt;&lt;electrical-engineering&gt;" AnswerCount="1" />
  <row Id="12853" PostTypeId="2" ParentId="12851" CreationDate="2011-04-10T23:51:41.000" Score="11" ViewCount="" Body="&lt;p&gt;Being 120 degrees apart makes the phases balanced such that power transfer at any instant is a constant.  If you had phases 'closer together' as you suggest, there wouldn't be any real advantage over single phase power.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-10T23:51:41.000" CommentCount="2" />
  <row Id="12854" PostTypeId="2" ParentId="12851" CreationDate="2011-04-11T05:48:25.747" Score="3" ViewCount="" Body="&lt;p&gt;By separating the phases by 120° one keeps the voltage peaks (for instance) evenly spaced.  For example, 60 Hz has peaks every 16.66 msec, so phase A, B, C peaks would come one third of that time apart, in this pattern: A-5.55ms-B-5.55ms-C-5.55ms-A.  If one separated phases A &amp;amp; C from B by, say 100° then phases C and A would be separated by 160°, and the pattern of peaks would be A-4.63ms-B-4.63ms-C-7.40ms-A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Such a stuttering set of phases (with, say, 100°, 100°, 160° separation) would entail many inefficient, unnecessary consequences, not least of which would be designing an AC motor which could effectively use the staggering impulses of such syncopated voltage peaks.&lt;/p&gt;&#xA;" OwnerUserId="3769" LastActivityDate="2011-04-11T05:48:25.747" />
  <row Id="12855" PostTypeId="2" ParentId="12851" CreationDate="2011-04-11T06:14:18.407" Score="12" ViewCount="" Body="&lt;p&gt;When there's 120° between phases the sum of the voltages at any time will be zero.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/3PQJx.gif&quot; alt=&quot;3-phase vector diagram&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This means that with a balanced load no current flows in the return line (neutral).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/pZRD7.gif&quot; alt=&quot;3 current vectors added&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if each phase is 230V with respect to the neutral (star operation), then there will be 400V between any two phases (triangle operation), and they're also equally spaced, i.e. at 120° angles.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(images from &lt;a href=&quot;http://www.electrician2.com/electa1/electa3htm.htm&quot; rel=&quot;nofollow&quot; rel=&quot;nofollow&quot;&gt;http://www.electrician2.com/electa1/electa3htm.htm&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="131" LastEditorDisplayName="" LastEditDate="2011-04-11T16:05:25.830" LastActivityDate="2011-04-11T16:05:25.830" />
  <row Id="12856" PostTypeId="1" AcceptedAnswerId="13669" CreationDate="2011-04-11T06:50:19.760" Score="5" ViewCount="222" Body="&lt;p&gt;Hi there, while 555 contest is long gone, I am still debugging my device, where I already abandoned 555 itself :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the moment, I am driving PC fan from an PWM (30kHz) signal from atmel uC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am powering P-MOSFET with a simple 1-BJT-transistor-&quot;driver&quot;. Output is filtered with an 22uH inductor + 330uF cap. Surely I have kickback diode in place. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem I have is while I have 256 &quot;levels&quot; of PWM, I am getting most of output difference somewhere in the 1-20 range. It looks like even short pulses have the &quot;power&quot; to drive the fan at full power. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) How can I make it &quot;less&quot; powerful? Will I have more powerful fans underpowered then?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) On the drain of the mosfet I see some 1-3Mhz ringing with some 5V amplitude, and while it all works, I don't like it (no ringing on the source or gate). What causes it and how should I fight it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt;&#xA;R1 - 1kOhm&#xA;R2 - 47Ohm&#xA;MOSFET - is PMOSFET from motherboard&#xA;Diode is some medium-size Schottky one, with 0.2V drop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/QVTSN.gif&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-04-30T08:10:24.673" LastActivityDate="2011-04-30T08:37:06.333" Title="PWM &amp; output voltage" Tags="&lt;driver&gt;&lt;pwm&gt;&lt;mosfet&gt;" AnswerCount="5" CommentCount="4" />
  <row Id="12857" PostTypeId="1" AcceptedAnswerId="12859" CreationDate="2011-04-11T07:08:18.623" Score="2" ViewCount="156" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/J9hjP.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am reading a book called getting started with arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;in that book, I don't understand why there is no resistor between pin number 7 and switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(see picture above)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;if there is no resistor between power source and ground, wouldn't it be dangerous short-circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;does pin 7 contain built-in resistor or something?&lt;/p&gt;&#xA;" OwnerUserId="3746" LastActivityDate="2011-04-11T09:01:16.657" Title="arduino's pin number 7, isn't it dangerous without resistor?" Tags="&lt;arduino&gt;&lt;ground&gt;&lt;short-circuit&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="12858" PostTypeId="1" AcceptedAnswerId="12861" CreationDate="2011-04-11T08:05:25.557" Score="2" ViewCount="100" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to figure out what the input impedance of the &lt;a href=&quot;http://www.analog.com/static/imported-files/data_sheets/ADF4110_4111_4112_4113.pdf&quot; rel=&quot;nofollow&quot;&gt;ADF4113&lt;/a&gt; is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking a figure 15, I'm not sure how to read that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my setup input is on RFinA and RFinB if connected to GND via a 100pF capacitor (HF to GND).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the Bias generator is a current source it is HF open, and then the impedance would be 1k ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the figure says there is 1.6V at the generator out, which made me think it probably works more as a voltage source, and therefore is HF short, which makes the impedance 500 ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So to figure this out, I tried to measure the impedance, by connecting a generator with a known source resistor, and from that my guess is 1k ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But could some one help me on how get the impedance from the datasheet?&lt;/p&gt;&#xA;" OwnerUserId="3041" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-11T08:13:39.083" LastActivityDate="2011-04-12T10:40:41.147" Title="Input impedance" Tags="&lt;impedance&gt;&lt;input&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="12859" PostTypeId="2" ParentId="12857" CreationDate="2011-04-11T08:48:49.723" Score="4" ViewCount="" Body="&lt;p&gt;Your hypothesis is correct: in input mode, the pins have very high impedance, somewhere along the range of 10s of mega ohms. So there will be little current flowing into pin 7, and it is OK to use it as is. Note that pin 7 is NOT ground so there is no short circuit between power source and ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you press the switch, current will flow primarily through the resistor. The voltage will rise and will be seen by pin 7 as a digital high. &lt;/p&gt;&#xA;" OwnerUserId="2340" LastActivityDate="2011-04-11T08:48:49.723" />
  <row Id="12860" PostTypeId="2" ParentId="12857" CreationDate="2011-04-11T09:01:16.657" Score="2" ViewCount="" Body="&lt;p&gt;It's not exactly a built-in resistor. The input pin is internally connected to the gate of a MOSFET. Now a MOSFET's gate is floating as they call it; it's insulated from the FET's channel. This means that an incoming voltage has no way to go, so there will be no current, (apart from a negligible leakage current). This means that you can make voltage and current calculations for the switch-resistor circuit as if it's not connected to the input pin at all.  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-11T09:01:16.657" />
  <row Id="12861" PostTypeId="2" ParentId="12858" CreationDate="2011-04-11T09:18:58.827" Score="3" ViewCount="" Body="&lt;p&gt;Figure 5 has S-parameters for ADF4113 RF input. You can calculate input impedance from these.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$R=\frac{Z_0(1-\rm{MAG}^2)}{1+\rm{MAG}^2-2\cdot\rm{MAG}\cdot\cos(\frac{\rm{ANG}}{360}\cdot 2\pi)}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$X=\frac{2\cdot\rm{MAG}\cdot\sin(\frac{\rm{ANG}}{360}\cdot 2\pi)\cdot 50}{1+\rm{MAG}^2-2\cdot\rm{MAG}\cdot\cos(\frac{\rm{ANG}}{360}\cdot 2\pi)}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$Z = \sqrt{R^2 + X^2}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where $Z_0 = 50$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope I latexed the formulas correctly, just in case they are from &lt;a href=&quot;http://www.microwaves101.com/encyclopedia/Sparameterspreadsheet.cfm&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-12T10:40:41.147" LastActivityDate="2011-04-12T10:40:41.147" CommentCount="8" />
  <row Id="12862" PostTypeId="2" ParentId="12851" CreationDate="2011-04-11T11:08:11.187" Score="0" ViewCount="" Body="&lt;p&gt;In principle Any Power Generator has a rotar with magents and coil on the periphery,one rotation of rotor is is one cycle and it is 360 degree,suppose the has generator one magnet and one coil then as the magent /rotor rotate one turn ,the voltage generated in the coil gradually rise and reaches peak(max)when the coil comes closest to the magnet and  reduces gradulay as the magnet moves away suppose we connect the  bulb  then the filcker rate is clearly visble This is called 360 deg single phase Ac,&#xA;now say generator has two magents and two coils placed equidistant then the flicker rate is increased, it is 2phase , 360/2=180deg Ac&#xA;Say generator has 3 magents and 3coils placed equidistant then the flicker rate much is increased(not visible),then it is 3phase with 360/2=120deg AC.&#xA;if we have  magents and 4coils placed equidistant then the flicker rate much much increased(not visible),then it is 4phase with 360/4=81deg, 4Pase AC.&#xA;Practically 3phase much suitable for design handling etc etc with no mouch advanages over 3phase Ac so is..&lt;/p&gt;&#xA;" OwnerUserId="3805" LastActivityDate="2011-04-11T11:08:11.187" />
  <row Id="12863" PostTypeId="2" ParentId="12774" CreationDate="2011-04-11T12:23:48.923" Score="1" ViewCount="" Body="&lt;p&gt;If you only have 15W available, then the best switched mode power supply will get you between 1.1 and 1.25 amps at 12V, because switched mode power supplies can be 90% or more efficient. But not over 100% efficient, so for 12V at 3.5A you would need an initial supply of 15V at 2.8A at least. Alternatively, your 15W supply could be converted to a 3.5A at just less than 4V supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A transistor on its own will not perform this conversion but will be an important part of a &lt;a href=&quot;http://en.wikipedia.org/wiki/Switched_mode_power_supply&quot; rel=&quot;nofollow&quot;&gt;switched mode power supply&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-04-11T12:23:48.923" />
  <row Id="12864" PostTypeId="2" ParentId="12856" CreationDate="2011-04-11T12:59:09.147" Score="1" ViewCount="" Body="&lt;p&gt;Edited based on the schematic:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You essentially have a buck converter there. The P-channel is sort of acting like the high-side N-channel that you usually have in a buck. I doubt that the FET is turning on as solidly as a N-channel with high-side drive would, but it still is acting buck-ish.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't have good speed control, you probably have a fan that only operates over a limited DC input range (10-12V), or the high-side P-channel is dissipating some of the input voltage, limiting the maximum DC that the fan can see.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or, &lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+4.9999999999999996E-6+2.4737822143832555+53+5.0+50%0Ac+624+272+624+304+0+3.3E-4+6.61619064997705%0Ar+720+256+720+336+0+24.0%0Al+576+336+496+336+0+2.2E-5+1.0206699341264169E-7%0Af+384+416+448+416+0+1.5%0Aw+448+336+496+336+0%0Aw+576+336+624+336+0%0Aw+624+336+624+304+0%0Aw+624+336+720+336+0%0Aw+720+256+624+256+0%0Aw+624+256+624+272+0%0Ad+448+320+448+272+1+0.805904783%0Ag+448+480+448+496+0%0AR+336+416+288+416+0+2+25000.0+10.0+5.0+0.0+0.3%0Av+352+320+352+272+0+0+40.0+12.0+0.0+0.0+0.5%0Aw+352+272+352+256+0%0Aw+352+320+352+336+0%0Aw+448+336+448+400+0%0Aw+448+432+448+480+0%0Aw+448+336+448+320+0%0Aw+448+272+448+256+0%0Ag+352+352+352+368+0%0Aw+352+336+352+352+0%0Ar+336+416+384+416+0+100.0%0Aw+624+256+448+256+0%0Aw+448+256+352+256+0%0Ao+1+64+0+35+10.0+0.4+0+-1%0Ao+22+64+0+35+7.62939453125E-5+9.765625E-5+1+-1%0Ao+2+16+0+35+10.0+1.6+2+-1%0A&quot; rel=&quot;nofollow&quot;&gt;rearrange the buck so the FET is in the low side&lt;/a&gt; and use a N-channel there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have HF ringing on the MOSFET, you can try to slow down the switching by increasing the series gate resistance, or add a high-frequency RC snubber circuit across the gate-source to suppress the rings.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-12T16:16:50.890" LastActivityDate="2011-04-12T16:16:50.890" CommentCount="1" />
  <row Id="12865" PostTypeId="1" AcceptedAnswerId="12866" CreationDate="2011-04-11T13:26:05.697" Score="5" ViewCount="232" Body="&lt;p&gt;For blue LEDs with a forward voltage of 3.3 V and supply voltage of 3.3 V, is a series resistor still needed to limit current?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ohm's Law in this case says 0 &amp;Omega;, but is this correct in practice?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps just a small value like 1 or 10 &amp;Omega; just to be safe?&lt;/p&gt;&#xA;" OwnerUserId="2654" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-05-03T21:42:52.390" LastActivityDate="2011-05-03T21:42:52.390" Title="Is a current-limiting resistor required for LEDs if the forward voltage and supply voltage are equal?" Tags="&lt;led&gt;&lt;resistor&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="12866" PostTypeId="2" ParentId="12865" CreationDate="2011-04-11T13:39:26.630" Score="13" ViewCount="" Body="&lt;p&gt;You always need a current limiting device. When using a voltage source, you should always have a resistor, think about what happens when the voltage changes by a small amount. With no resistor, the LED current would shoot up (until you hit a thermal based limit due to the LED materials). If you had a current source, then you would not need a series resistor because the LED would run at the current source level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is also unlikely that the forward voltage of the LED is always exactly the same as the supply. There will be a range mentioned in the datasheet. So even if your supply exactly matched the typical forward voltage, different LEDs would run at vastly different currents, and hence brightnesses.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastEditorUserId="2110" LastEditorDisplayName="" LastEditDate="2011-04-11T14:00:24.060" LastActivityDate="2011-04-11T14:00:24.060" CommentCount="1" />
  <row Id="12867" PostTypeId="2" ParentId="12865" CreationDate="2011-04-11T13:42:29.387" Score="4" ViewCount="" Body="&lt;p&gt;You need a voltage drop over the current limiting resistor for it to work. And that voltage drop should be substantial to avoid high currents when your 3.3V is a bit off (maybe 3.45V for a while). If you would drive a LED with 1V voltage drop across a resistor and the supply is 1V higher, you would have approx. the double current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A LED needs a constant current to shine. However, a constant current source probably needs more than 3.3V for a blue LED, unless you're using a buck-boost version.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-04-11T13:42:29.387" />
  <row Id="12868" PostTypeId="2" ParentId="12856" CreationDate="2011-04-11T14:32:25.450" Score="1" ViewCount="" Body="&lt;p&gt;A while back I did a similar circuit, basically a PWM with an LC filter on the output.  This is, in essence, a switching buck DC/DC converter.  I'll cut to the chase:  It didn't work.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main problem is that the cap was completely charging when the PWM was on and not fully discharging when the PWM was off-- thus basically powering the fan 100% of the time.  Also, keep in mind that most 12v fans will spin when powered off of only 4v.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My suggestion is to remove the LC filter and see if that improves things (it should).  If you're not trying to pass FCC tests then you're done.  If you are trying to pass tests, then simply adding a small cap (1 uF or less) should work.  Other than EMI emissions, there isn't much reason to filter things to a fan.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, if you leave the LC filter in there then what you're really doing is not PWMing the fan, but controlling the speed by varying the voltage.  For this to work, you should either increase the size of the inductor and/or increase the PWM frequency.  Basically, you want to make this switching buck DC/DC converter work properly.  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-04-30T00:01:19.110" LastActivityDate="2011-04-30T00:01:19.110" CommentCount="3" />
  <row Id="12869" PostTypeId="1" CreationDate="2011-04-11T14:54:13.713" Score="1" ViewCount="77" Body="&lt;p&gt;We are currently using the &lt;a href=&quot;http://www.saelig.com/BRD/BRD018.htm&quot; rel=&quot;nofollow&quot;&gt;Wiz108SR&lt;/a&gt; device and need to provide this as a consumer ready component with a power supply. We would rather not build and package the powersupply but instead purchase something that is already done and packaged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody know of a similar product that we can buy, rather than this DIY component?&lt;/p&gt;&#xA;" OwnerUserId="1960" LastEditorUserId="1960" LastEditorDisplayName="" LastEditDate="2011-04-11T15:17:25.400" LastActivityDate="2011-04-11T19:05:47.117" Title="Looking for TCP/IP Ethernet &lt;-&gt; RS-485, Half Duplex Device" Tags="&lt;ethernet&gt;&lt;rs485&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="12870" PostTypeId="1" AcceptedAnswerId="12873" CreationDate="2011-04-11T15:00:22.320" Score="2" ViewCount="70" Body="&lt;p&gt;I'm working on a project where I'm going to drive 2 x 8-ohm loudspeakers using 1 (or more) car batteries and a Class-D amplifier. The setup is going to be used at a festival, so I need maximum efficiency from my system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, how does the amplifier draw power? Does it keep a constant load on the battery or does it vary according to the power needed from the loudspeakers? If I simply hook the amplifier up and simply vary the amplitude of the audio-signal, will it use power accordingly, or?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm considering this amplifier at the moment:&#xA;&lt;a href=&quot;http://classdaudio.com/products/600w-class-d-power-amplifier.html&quot; rel=&quot;nofollow&quot;&gt;http://classdaudio.com/products/600w-class-d-power-amplifier.html&lt;/a&gt; since I should be able to drive it with 2-batteries in serial. Anything I should notice?&lt;/p&gt;&#xA;" OwnerUserId="3807" LastActivityDate="2011-04-13T09:11:11.337" Title="Amplifier power draw" Tags="&lt;battery&gt;&lt;amplifier&gt;&lt;class-d&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="12871" PostTypeId="2" ParentId="3941" CreationDate="2011-04-11T15:24:39.353" Score="0" ViewCount="" Body="&lt;p&gt;The mechanical analogy I like for impedance is a vertically-hanging spring with a collection of weights hanging on it.  If the system is initially motionless and one gives a brief upward jerk to the weight at the top, returning it quickly to its original position, the disturbance will travel down the spring.  Each weight will be pulled upward by the weight above, then push upward on the weight above (and be pushed downward by it) while it pulls upward on the weight below (and is pulled downward by it), and finally be pushed upward by the weight below.  Once all these things have happened, the weight will return to its original position and (zero) velocity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that the behavior of the downward-propagating wave does not depend upon anything below it.  Once the wave reaches the bottom, however, one of three things may happen depending upon whether the end of the spring is dangling, rigidly fixed to something, or fixed to something that can move with some resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the end of the spring is dangling, the bottom weight won't have anything below it to pull down on it when it jerks upward.  The effect of this will be that the weight will jerk upward more than it otherwise would, and more than the weight above would be expecting to cancel out its energy.  This in turn will cause the weight to push upward on the weight above, and generate an upward-traveling wave which will be (absent frictional losses) be equal in magnitude to the initial downward wave.  The displacement direction will be the same as the original wave (i.e. upward) but the stress will be opposite (the original wave was a tension wave; the rebound will be compression).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By contrast, if the end of the spring is fixed, the bottom weight will find that the spring below it resists more strongly than expected.  The bottom weight will thus not move up as much as the weight above it was expecting, and the net effect will be as though the bottom gave an extra &quot;tug&quot;, sending a wave upward.  The displacement direction of this wave will be the opposite of the original wave (i.e. downward) but the stress will be the same (compression).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the bottom of the spring is attached to something which moves somewhat, but not as much as a dangling spring, the two behaviors above may cancel out to some degree.  If the bottom of the spring is allowed to move just the right amount, the behaviors will cancel and the wave will disappear.  Otherwise one or other type of wave will rebound, but the magnitude will generally be less than it would with a dangling or fixed end.  The amount of resistance required is effectively defined by the impedance, which is in turn a function of the mass of the weights and the spring constant of the springs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that many impedance-related behaviors are captured by this model.  For example, if all the weights above a certain point weight 100g while those below weigh 200g, and all springs are equal, the transition from the lighter weights to the heavier weights will cause some of the wave energy to be reflected upward (in a manner similar to the fixed bottom end) since the heavier weights won't move as much as expected.  The key notion is that for things which are pushed to return to zero velocity, they must transfer both their kinetic energy and their momentum.  If the they can transfer their energy and momentum to something with the same characteristics as whatever pushed them, they will accept all the energy and momentum and pass them on.  Otherwise they will have to send back some of the energy and/or momentum.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-11T15:24:39.353" CommunityOwnedDate="2011-04-11T15:24:39.353" />
  <row Id="12872" PostTypeId="2" ParentId="12865" CreationDate="2011-04-11T16:09:54.540" Score="4" ViewCount="" Body="&lt;p&gt;The I-V relationship in a diode is exponential, so applying a voltage difference of 3.3 V +/- 5% to an LED with a nominal 3.3V drop is not going to result in a 5% variation in intensity. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the voltage is too low, the LED may be dim; if the voltage is too high, the LED may be damaged. As Hans says, a 3.3V supply is probably not enough for a 3.3V LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When driving an LED, it is better to set the current, not the voltage, since the current has a more linear correlation with the light intensity. Using a series resistor is a good approximation of setting the current through the LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't use a supply with enough headroom to allow a current-setting resistor, you might be able to use a &lt;a href=&quot;http://en.wikipedia.org/wiki/Current_mirror&quot; rel=&quot;nofollow&quot;&gt;current mirror&lt;/a&gt;. That still requires some voltage drop, but possibly not as much as you'd need for a resistor.&lt;/p&gt;&#xA;" OwnerUserId="3441" LastEditorUserId="3441" LastEditorDisplayName="" LastEditDate="2011-04-11T17:23:13.820" LastActivityDate="2011-04-11T17:23:13.820" CommentCount="2" />
  <row Id="12873" PostTypeId="2" ParentId="12870" CreationDate="2011-04-11T16:21:30.720" Score="4" ViewCount="" Body="&lt;p&gt;At 100% efficiency, the power drawn from the battery will be exactly the same as the power output to the speaker.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Real amplifiers are never 100% efficient, but a class D amplifier can be pretty efficient.  TI claims &gt; 88% for the chip used in the amplifier you are looking at.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should really look at the &lt;a href=&quot;http://focus.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=tas5630&amp;amp;fileType=pdf&quot; rel=&quot;nofollow&quot;&gt;tas5630 datasheet&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is power wasted vs. power output.  It is nearly a straight line.  Notice a few watts are drawn all the time, even with zero output:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/AFgJq.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another graph to study carefully is this one.  Maybe two car batteries in series (for 24V) is not enough voltage to get your desired power output:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tup0w.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-04-11T23:38:20.573" LastActivityDate="2011-04-11T23:38:20.573" CommentCount="2" />
  <row Id="12874" PostTypeId="1" AcceptedAnswerId="12897" CreationDate="2011-04-11T16:21:44.883" Score="5" ViewCount="70" Body="&lt;p&gt;I'm looking at triac datasheets, in particular this &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet/stmicroelectronics/7471.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet for BTA16 series triac&lt;/a&gt;. The &quot;electrical characteristics&quot; section is split into two parts: snubberless/logic level (3 quadrants) and standard (4 quadrants).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no idea what this is referring to. Are they different devices, as suggested by the column titles? Are they different operating modes? What is the difference?&lt;/p&gt;&#xA;" OwnerUserId="1951" LastEditorUserId="1951" LastEditorDisplayName="" LastEditDate="2011-04-12T09:30:00.930" LastActivityDate="2011-04-12T09:30:00.930" Title="What's the difference between 3 and 4 quadrant triacs?" Tags="&lt;triac&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="12875" PostTypeId="1" AcceptedAnswerId="13055" CreationDate="2011-04-11T16:27:08.247" Score="1" ViewCount="112" Body="&lt;p&gt;Coming from a programming background, I'm used to user guides telling me how to use something, rather than how it's implemented. In the world of electronics, when it comes to discretes like, say, a MOSFET, all I can usually find is inventor, history, an overview of the theory and some implementation details.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's quite hard to find answers to basic questions, like &quot;does a fully turned-on MOSFET conduct more current from source to drain or from drain to source?&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I just looking in the wrong places? Or is the best thing to do actually understand the underlying implementation details so that I can deduce the answer from that? It always feels like a bit of an overkill trying to learn how to make MOSFETs when all I want is find out how to use them in a most conventional way.&lt;/p&gt;&#xA;" OwnerUserId="1951" LastActivityDate="2011-04-14T15:20:29.427" Title="Are there any generic &quot;how to use this part&quot; guides for basic discretes?" Tags="&lt;components&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="12876" PostTypeId="2" ParentId="12869" CreationDate="2011-04-11T16:30:14.897" Score="2" ViewCount="" Body="&lt;p&gt;Digi makes an entire &lt;a href=&quot;http://www.digi.com/products/serialservers/&quot; rel=&quot;nofollow&quot;&gt;product line&lt;/a&gt; of ethernet to serial (RS-485 included) gateways / bridges / servers with various capabilities/levels of hardening.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-04-11T16:30:14.897" />
  <row Id="12877" PostTypeId="2" ParentId="12875" CreationDate="2011-04-11T16:30:28.783" Score="6" ViewCount="" Body="&lt;p&gt;Get a good book, like The Art of Electronics, if you want things explained properly.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-11T16:30:28.783" CommentCount="1" />
  <row Id="12878" PostTypeId="1" AcceptedAnswerId="12879" CreationDate="2011-04-11T16:49:25.703" Score="0" ViewCount="215" Body="&lt;p&gt;This is a newbie question. Can someone confirm: a resistor on its own is useless. True or false? I mean, I can't do anything with a resistor alone, or is there something that can be done with it? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry, I know the question is too newbie. &lt;/p&gt;&#xA;" OwnerUserId="3802" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T20:59:42.180" LastActivityDate="2011-04-27T20:59:42.180" Title="Can a resistor on its own do anything" Tags="&lt;resistor&gt;&lt;electrical-engineering&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="12879" PostTypeId="2" ParentId="12878" CreationDate="2011-04-11T16:52:30.680" Score="1" ViewCount="" Body="&lt;p&gt;Yes, a resistor by itself is useless. It plays an important part in circuits though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Resistors limit current in your circuit. For example, if you want to light up an LED, you typically can't just connect an LED to a battery because the current is not limited. With a resistor in series with the LED, you can control the current going through the LED. Also, different values of resistors will give you different currents, which also gives you different LED brightnesses.&lt;/p&gt;&#xA;" OwnerUserId="935" LastActivityDate="2011-04-11T16:52:30.680" />
  <row Id="12880" PostTypeId="2" ParentId="8551" CreationDate="2011-04-11T16:56:38.460" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.precisionmicrodrives.com/&quot; rel=&quot;nofollow&quot;&gt;Precision Microdrives&lt;/a&gt; are fantastic for small quantities of tiny motors.&lt;/p&gt;&#xA;" OwnerUserId="1951" LastActivityDate="2011-04-11T16:56:38.460" />
  <row Id="12881" PostTypeId="2" ParentId="12878" CreationDate="2011-04-11T17:01:26.050" Score="7" ViewCount="" Body="&lt;p&gt;Almost everything we have in electronics is useless on its own. What good is a light bulb by itself? With no power source you can't light it. Even with a power source, it is still not all that helpful with out a switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even the more complex things, like a microcontroller, are pretty useless on there own. Even if you have a power source there isn't much purpose of them unless they are connected to other things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for focusing on the resistor itself, there are things that it can be useful for when combined with a power source. For example, creating heat. If your goal is to create heat with a very simple component, using a resistor with a power source is a very simple way of doing it.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-11T17:01:26.050" />
  <row Id="12882" PostTypeId="2" ParentId="12878" CreationDate="2011-04-11T17:02:13.353" Score="1" ViewCount="" Body="&lt;p&gt;It doesn't do exactly nothing: it will generate heat, depending on the current flowing through it -- this is why resistors have a wattage rating.&lt;/p&gt;&#xA;" OwnerUserId="3741" LastActivityDate="2011-04-11T17:02:13.353" CommentCount="2" />
  <row Id="12883" PostTypeId="2" ParentId="3578" CreationDate="2011-04-11T17:06:06.590" Score="0" ViewCount="" Body="&lt;p&gt;I just love &lt;a href=&quot;http://uk.farnell.com/duratool/d00413/box-compartment-230x125x35mm/dp/1447377&quot; rel=&quot;nofollow&quot;&gt;these Duratool boxes&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/LubEt.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The horizontal dividers are removable, and the bottoms are curved so it's easy to pull out small components; they don't get stuck in corners.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are cheap too! 10 boxes for £14 and I couldn't be happier. Messing around with the breadboard is now more fun than ever before:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/jE5IR.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They do have some of the most difficult to peel stickers right across the front though...&lt;/p&gt;&#xA;" OwnerUserId="1951" LastActivityDate="2011-04-11T17:06:06.590" />
  <row Id="12884" PostTypeId="2" ParentId="4571" CreationDate="2011-04-11T17:07:40.277" Score="1" ViewCount="" Body="&lt;p&gt;A bit dated now, I can/have built the latest gcc (on linux) as a cross compiler, but just use code sourcery&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://lpcstuff.blogspot.com/2008/09/roll-your-own-gcc.html&quot; rel=&quot;nofollow&quot;&gt;http://lpcstuff.blogspot.com/2008/09/roll-your-own-gcc.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have little or no desire for a C library nor a gcc library so I am content with what the above produces.  If you want a C library and/or gcc library you should look here, this is the most recent (meaning 4.x) gcc that I can find that builds with newlib and works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cowlark.com/2009-07-04-building-gcc/&quot; rel=&quot;nofollow&quot;&gt;http://www.cowlark.com/2009-07-04-building-gcc/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or you can take the llvm path, out of the box llvm can be used as a cross compiler, arm/thumb in particular.  I mix llvm with gnu binutils as my assembler/linker.  I prefer clang to llvm-gcc.  Very easy to build llvm from sources (takes an eternity though) if you want to be cutting edge on fixes, etc.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-04-11T17:07:40.277" />
  <row Id="12885" PostTypeId="2" ParentId="12878" CreationDate="2011-04-11T17:26:29.353" Score="2" ViewCount="" Body="&lt;p&gt;A resistor on its own may be useless, but that doesn't mean that it doesn't do anything!&#xA;Resistors produce &lt;em&gt;thermal noise&lt;/em&gt;. This noise occurs because of the random movement of charge carriers (mainly electrons). It depends on temperature (the higher the temperature, the higher the noise) and on the resistance value (again, the higher the resistance, the higher the noise). This noise, however, is too small to be useful; you can't power a circuit from a resistor, and the variable nature of the voltage doesn't help either.&lt;br&gt;&#xA;While not useful as a power source, this thermal noise often plays a role in circuits. It may be amplified with the signal and deteriorate it.&lt;br&gt;&#xA;But even in a circuit the resistor generates this noise voltage all by itself.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-11T17:26:29.353" CommentCount="2" />
  <row Id="12886" PostTypeId="1" AcceptedAnswerId="12895" CreationDate="2011-04-11T17:34:26.913" Score="6" ViewCount="184" Body="&lt;p&gt;We recently came across this video:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://blog.makezine.com/archive/2011/04/the-awesome-button.html&quot; rel=&quot;nofollow&quot;&gt;http://blog.makezine.com/archive/2011/04/the-awesome-button.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and both my six year old and 13 year old thought it was pretty cool.  I am a computer programmer, but never did much with electronics, so I am looking for some suggestions on how to introduce electronics to myself and my kids in a fun lab/project oriented way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its a little challenging b/c of the age gap between my kids, but I'm ok if the younger doesn't understand everything.  As long as he can participate in the lab and be involved in what we are doing, he will pick things up along the way.  Likewise, I wouldn't want something so simple that my older son is bored.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few preferences:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I would prefer to stay away from robotics initially, maybe we can graduate to that, but I am looking for something not quite as involved.&lt;/li&gt;&#xA;&lt;li&gt;I would prefer that we can bring a programming component into the mix relatively soon, like in the example I linked to above, but that's not a requirement.  That also is something we can graduate into.&lt;/li&gt;&#xA;&lt;li&gt;I would prefer not to shell out a whole lot of money initially.  Maybe a couple hundred dollars at most, but hopefully less.&lt;/li&gt;&#xA;&lt;li&gt;I'm ok with learning stuff from a book or videos but my main goal is to give us projects to work on together.  This is mostly about trying to find something to do with Dad time that is fun for us all, learning electronics is kind of a bonus.  The labs or projects are my focus.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So, can you suggest books, kits, websites, or other resources that would facilitate what I have outlined above?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;update&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;@AndrejaKo: I know basically nothing about electronics.  I understand that it involves things like resistors and logic gates, etc. but as to what those things are and how they are used, I know nothing.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a multi-meter I bought at Lowes, but that is about it.  If I have to spend the money to get some basic tools &amp;amp; components, thats ok.  I just want to keep the cost down until I found out if this is really something they we are interested in doing together or if its going to die after a few projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;solution&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I began trying to put together an order for the electronic components for the &lt;a href=&quot;http://www.allaboutcircuits.com/vol_6/index.html&quot; rel=&quot;nofollow&quot;&gt;All About Electronics experiments section&lt;/a&gt; as well as the first chapter of &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596153740&quot; rel=&quot;nofollow&quot;&gt;Make: Electronics&lt;/a&gt;.  I had a couple hours into it, wasn't sure I was ordering the right components, and was somewhat discouraged when I happened across a &lt;a href=&quot;http://handsonelectronics.blogspot.com/&quot; rel=&quot;nofollow&quot;&gt;blog that is walking through the Make: Electronics book&lt;/a&gt; that mentioned MakerShed's &lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MECP1&amp;amp;CartID=1&quot; rel=&quot;nofollow&quot;&gt;component&lt;/a&gt; &lt;a href=&quot;http://www.makershed.com/ProductDetails.asp?ProductCode=MECP2&quot; rel=&quot;nofollow&quot;&gt;packs&lt;/a&gt; for the Make: Electronics book.  That sealed the deal for me!  I went ahead and ordered the first component pack and the book (which was only $10 if you buy the component pack).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are going to start out with this book.  If we make it past chapter two, I will go ahead and order the second component pack.  The price has to beat RadioShack and even if its more expensive than ordering the components individually, I'm way sold on the time its saving me.&lt;/p&gt;&#xA;" OwnerUserId="3810" LastEditorUserId="3810" LastEditorDisplayName="" LastEditDate="2011-04-28T02:15:02.827" LastActivityDate="2011-04-28T02:15:02.827" Title="Looking for a *fun* way to introduce basic electronics to my kids" Tags="&lt;electronics&gt;&lt;books&gt;&lt;kit&gt;" AnswerCount="4" CommentCount="7" FavoriteCount="1" />
  <row Id="12887" PostTypeId="2" ParentId="12773" CreationDate="2011-04-11T17:45:01.930" Score="0" ViewCount="" Body="&lt;p&gt;Ok, the part is made by Hirose, and it is DF23C-22DS-0.5V(53).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Arrow and DigiKey don't list it. Mouser does, but only as a full reel.&lt;/p&gt;&#xA;" OwnerUserId="1990" LastActivityDate="2011-04-11T17:45:01.930" />
  <row Id="12888" PostTypeId="2" ParentId="12819" CreationDate="2011-04-11T17:47:31.110" Score="1" ViewCount="" Body="&lt;p&gt;You can use either model to analyze a small signal BJT circuit, but the hybrid-pi model is most commonly used. The T-model is supposedly easier to use in certain situations, but I've always used the hybrid-pi model without a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main difference between the two models is that the hybrid-pi model uses $r_{\pi}$ and the T-model uses $r_e$. Here's the relationship between the two:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$r_{\pi} = \left( \beta + 1 \right) r_e$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;where beta is the gain of the transistor. On datasheets this may be $h_{fe}$.&lt;/p&gt;&#xA;" OwnerUserId="935" LastEditorUserId="935" LastEditorDisplayName="" LastEditDate="2011-04-11T19:49:07.043" LastActivityDate="2011-04-11T19:49:07.043" />
  <row Id="12889" PostTypeId="2" ParentId="12886" CreationDate="2011-04-11T18:00:23.117" Score="2" ViewCount="" Body="&lt;p&gt;I would stay away from anything so complicated that you only can use it as a black box, like in the video a USB interface. Instead I would use very basic components, preferably things which generate a sound or display something, these will appeal to your youngest too.&lt;br&gt;&#xA;One possible project is an electronic die. You can do this with a few HCMOS ICs, like a 7-segment LED driver. It has the advantage that you don't have to introduce transistors yet (transistors are Really Complicated Devices!!) and they &lt;em&gt;see&lt;/em&gt; something happen.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt; (re OP's comment)&lt;br&gt;&#xA;HCMOS is a family of digital ICs, it comprises basic logical functions like gates (AND, OR, NOR, inverter,...), but also more functional blocks, like counters and the 7-segment driver I mentioned. For the die I was thinking of an oscillator you can start-stop, which makes the counter loop from 1 to 6. (Note to chief engineer: that's a presetable counter, a normal counter would start counting at 0.) The 7-segment driver converts its binary input to a pattern for the 7-segments digit display.&lt;br&gt;&#xA;Alternatively, you can create a die-like LED pattern and use logic ICs to determine which LEDs have to light up for which counter value. (chief engineer: you can use a Johnson counter, like the 74HC4017. Count from zero to 5.) For instance, the center LED only lights up when you roll a 1, 3 or 5. Then you OR outputs 0, 2, and 4 of the counter (remember, zero-based)&lt;br&gt;&#xA;The advantage of working with logic ICs is that you don't need to explain about electrons right away, and that they can get acquainted with voltage levels first.&lt;br&gt;&#xA;If you create the oscillator with a NAND gate like the 74HC132, you can explain its working with the &lt;em&gt;water model&lt;/em&gt;: voltage = water level, capacitor = water tank, resistor = thin water tube.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a concrete example see &lt;a href=&quot;http://www.tech.plym.ac.uk/dcee/staff/paulfilmore/teaching/undrgrad/DiceProject00.pdf&quot; rel=&quot;nofollow&quot;&gt;this googled document&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-12T07:08:10.623" LastActivityDate="2011-04-12T07:08:10.623" CommentCount="3" />
  <row Id="12890" PostTypeId="2" ParentId="12886" CreationDate="2011-04-11T18:37:27.850" Score="4" ViewCount="" Body="&lt;p&gt;I recommend the &lt;a href=&quot;http://www.elenco.com/snapcircuits.html&quot; rel=&quot;nofollow&quot;&gt;Snap Circuits&lt;/a&gt; sets for basic electronics.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-12T02:46:51.647" LastActivityDate="2011-04-12T02:46:51.647" CommentCount="1" />
  <row Id="12891" PostTypeId="1" AcceptedAnswerId="12896" CreationDate="2011-04-11T18:45:20.617" Score="3" ViewCount="99" Body="&lt;p&gt;I asked Xilinx for such a list but they don't have a complete list. I wish to make sure all input files are in source control and all output files aren't. This is with 13.1 and I am not using the EDK.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of the information they have provide is the list of PAR Output Files and the ISE Design Suite Files in the Command Line Tools User Guide, the source files list from &lt;a href=&quot;http://www.xilinx.com/support/documentation/sw_manuals/xilinx13_1/ise_r_source_types.htm&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. &lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-04-27T20:43:21.173" Title="List of Xilinx file suffixes" Tags="&lt;xilinx&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="12892" PostTypeId="2" ParentId="12869" CreationDate="2011-04-11T19:05:47.117" Score="2" ViewCount="" Body="&lt;p&gt;Easysync do such a device, bit more pricey though!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.easysync-ltd.com/category/126/rs232-422-485-servers.html&quot; rel=&quot;nofollow&quot;&gt;http://www.easysync-ltd.com/category/126/rs232-422-485-servers.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-04-11T19:05:47.117" />
  <row Id="12894" PostTypeId="2" ParentId="12891" CreationDate="2011-04-11T20:26:14.597" Score="2" ViewCount="" Body="&lt;p&gt;Quick answer:  No such list exists, anywhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Long answer:  I could tell you, but then I'd be wrong.  I've been using Xilinx tools for the past 15+ years and every time they come out with a new version (or even a new service pack) things change.  Sometimes even just changing various XST/MAP/PAR options will cause new files to be generated.  So even if I did give you a list it would likely be out of date or just wrong.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've created my own makefiles for building my FPGA's (I'm not using ISE's GUI environment), and it's fairly well documented what the input files to the various tools are (XST, MAP, etc).  Everything else is not required and thus doesn't need to be checked into the source control system.  My makefiles have a &quot;make clean&quot; option that removes all of the extra files.  So when Xilinx releases a new version I simply recompile and the &quot;make clean&quot;.  Any file that remains (and isn't obviously something I need) is considered to be junk, and I add those files to the &quot;make clean&quot; list of things to delete.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-11T20:26:14.597" />
  <row Id="12895" PostTypeId="2" ParentId="12886" CreationDate="2011-04-11T20:35:16.527" Score="2" ViewCount="" Body="&lt;p&gt;You're probably looking for a book like these: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596153740&quot; rel=&quot;nofollow&quot;&gt;Make: Electronics (Learning by Discovery)&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0071452818&quot; rel=&quot;nofollow&quot;&gt;Practical Electronics for Inventors&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/159200346X&quot; rel=&quot;nofollow&quot;&gt;Physical Computing: Sensing and Controlling the Physical World with Computers&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0596510519&quot; rel=&quot;nofollow&quot;&gt;Making Things Talk: Practical Methods for Connecting Physical Objects&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Which are introductory, but practical, books on electronics.&lt;/p&gt;&#xA;" OwnerUserId="3078" LastActivityDate="2011-04-11T20:35:16.527" CommentCount="1" />
  <row Id="12896" PostTypeId="2" ParentId="12891" CreationDate="2011-04-11T20:47:23.507" Score="1" ViewCount="" Body="&lt;p&gt;Here's the start of a community wiki for the suffixes. I agree with @David Kessner.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;File Suffix,Input or output,description&#xA;bat,input,batch file&#xA;cfi,,&#xA;cgc,,C&#xA;cgp,,Coregen project file&#xA;cmd,,&#xA;css,output,HTML file&#xA;csv,output,pin list&#xA;do,input,simulation script&#xA;drc,,&#xA;f,,&#xA;gise,,an version of ise file&#xA;ipf,input,impact (programmer) project&#xA;log,output,log file&#xA;lso,input ,library serach order input  to XST.&#xA;lst,,&#xA;map,output,&#xA;ncd,output,after map process&#xA;ngc,output,&#xA;ngc_xst,output&#xA;ngr,output,RTL schematic generated from XST&#xA;nlf,output,ASCII NetGen NetGen log file that contains information on the NetGen run&#xA;pad,output,list of I/O pads/pins&#xA;par,output,Place and route log&#xA;pdf,output,Documental file for core.&#xA;prj,input,project file&#xA;prm,output,PROM file&#xA;ptxw,,twx file which project navigator uses for parsing &#xA;sdbl,,&#xA;sdbx,,Installation files&#xA;sdc,output,timing report&#xA;sh,input,Linux shell script&#xA;txt,output,log file&#xA;twr,output,timing report&#xA;twx,output,&#xA;v,input,Verilog file&#xA;vhd,input,VHDL file&#xA;wcfg,input,ISim waveform configuration file&#xA;xrpt,output,report file&#xA;unroutes,output&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="206" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T20:43:21.173" LastActivityDate="2011-04-27T20:43:21.173" />
  <row Id="12897" PostTypeId="2" ParentId="12874" CreationDate="2011-04-11T20:58:43.257" Score="3" ViewCount="" Body="&lt;p&gt;NXP has &lt;a href=&quot;http://www.nxp.com/documents/application_note/AN_3Q_TRIACS.pdf&quot; rel=&quot;nofollow&quot;&gt;a good explanation&lt;/a&gt; as to what the differences between 3-quadrant and 4-quadrant triacs are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Summary: a 3-quadrant triac cannot be turned on in the fourth quadrant (T2 negative, G positive) which is beneficial when dealing with inductive loads - ringing caused by sudden turn-off could potentially turn on a 4-quadrant triac, necessitating snubbers and other protection means to prevent spurious conduction.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-11T20:58:43.257" />
  <row Id="12898" PostTypeId="2" ParentId="12839" CreationDate="2011-04-11T21:35:52.647" Score="4" ViewCount="" Body="&lt;p&gt;In terms of &quot;separating&quot; the functions, that's not really how digital logic works.  Digital logic is &quot;always doing everything&quot;.  You need a mux (multiplexer) in there.  The multiplexer is used to pick the right output from all of those generated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assume inputs A and B, output Q.  Assume the ALU does two different things: Q=A+B, or Q=A&amp;amp;B.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ALU will have an adder.  It will also have a big AND gate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A and B both go to the adder, and the AND gate.  Always.  Every moment of every day, the adder is adding A and B, and the gate is ANDing A and B.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The mux is used to select which one of the outputs we want to pass to Q.  If the control signals to the ALU say &quot;add&quot;, then the mux will select the output of the adder and pass it to Q; the output of the AND gate is unused.  If the control says &quot;and&quot;, the mux will select the output of the AND gate and pass it to Q instead, while the output of the adder is unused.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Imagine A = 0b0001 and B = 0b0010 on the inputs of the ALU.  The adder is always producing 0b0011, and the AND gate is always producing 0b0000.  If you provide the &quot;add&quot; control signal, the 0b0011 is passed to Q.  You can leave A and B alone, and change the control signal to &quot;and&quot;, then 0b0000 is passed to Q.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-04-11T21:35:52.647" CommentCount="1" />
  <row Id="12899" PostTypeId="1" CreationDate="2011-04-11T22:33:12.813" Score="1" ViewCount="78" Body="&lt;p&gt;Hi everyone,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it easy to layout a PCB with this kind of connectors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.1632bit.com/tools/Shop/UploadPhotos/201005/AC164124.jpg&quot; alt=&quot;http://www.1632bit.com/tools/Shop/UploadPhotos/201005/AC164124.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And what's the name of the female part of this type of connection?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Honestly, Im just lost in the interconnections world. What are the most common names for SMD and/or trough-hole connectors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="1074" LastActivityDate="2011-04-11T23:21:35.690" Title="Types of (pcb) connectors" Tags="&lt;connector&gt;&lt;interconnect&gt;" AnswerCount="1" />
  <row Id="12900" PostTypeId="2" ParentId="12899" CreationDate="2011-04-11T22:52:44.783" Score="5" ViewCount="" Body="&lt;p&gt;It's a card edge connector, &lt;a href=&quot;http://uk.farnell.com/3m/3358-0001/card-edge-connector-socket-10pos/dp/1369088&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; is a typical example. PCB design using them is quite straightforward. They can be single-sided or double-sided. It's an example of a direct connector; there are also indirect connectors, such as the DIN41612.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-11T23:21:35.690" LastActivityDate="2011-04-11T23:21:35.690" />
  <row Id="12901" PostTypeId="1" CreationDate="2011-04-11T23:25:08.873" Score="2" ViewCount="58" Body="&lt;p&gt;What I want to do is measure the bandwidth of a wireless video transmitter. I know for a fact that this is going to be at least 8 MHz if not much more as it gives a good video image with an OSD which has a pixel clock exceeding 4 MHz. (I'm trying to repurpose the transmitter to send other analog data.) Since I have no access to a high frequency signal generator (10 MHz+) to directly verify the -3dB point, is it possible to measure, say, the -1dB point and derive the frequency of the -3dB point from this?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-12T10:02:57.060" Title="Can I measure the -3dB point of a wireless link with a lower frequency?" Tags="&lt;frequency&gt;&lt;3db&gt;" AnswerCount="2" />
  <row Id="12903" PostTypeId="1" CreationDate="2011-04-12T00:35:34.127" Score="3" ViewCount="90" Body="&lt;p&gt;Hi, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wanted to use a micro-controller with a camera module to be able to do some processing on the captured images. The Arduino was my choice, but since it has only 256K of Flash memory, it clearly is not a good candidate, I scoured Google to find relevant posts, but decided the Arduino is not the best tool. The closest Arduino came was with &lt;a href=&quot;http://jarv.org/sdcam.shtml&quot; rel=&quot;nofollow&quot;&gt;http://jarv.org/sdcam.shtml&lt;/a&gt;, using an SD card to store the images.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I stumbled across Leapord Board: &lt;a href=&quot;http://designsomething.org/leopardboard/default.aspx&quot; rel=&quot;nofollow&quot;&gt;http://designsomething.org/leopardboard/default.aspx&lt;/a&gt;, it has an onboard camera, unfortunately documentation and sample code is really scare for this. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone recommend a good micro-controller that can allow me to use a standalone camera and perform simple processing on it? And more importantly has an active community, sample codes already available?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would appreciate any thoughts!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT: The ability to use a regular camera and process those images would be great if possible. I would assume this would be done via a USB interface, so the micro-controller has to be able to act as a USB host.&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="3458" LastEditorUserId="3458" LastEditorDisplayName="" LastEditDate="2011-04-12T00:58:59.677" LastActivityDate="2011-05-08T01:54:49.603" Title="Development Board / Micro-controller with an onboard camera or external addon" Tags="&lt;microcontroller&gt;&lt;dsp&gt;&lt;camera&gt;&lt;imageprocessing&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="12904" PostTypeId="2" ParentId="12839" CreationDate="2011-04-12T00:57:05.250" Score="2" ViewCount="" Body="&lt;p&gt;Perfect ALU design articles are here : &lt;a href=&quot;http://www.6502.org/users/dieter/&quot; rel=&quot;nofollow&quot;&gt;http://www.6502.org/users/dieter/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-12T00:57:05.250" />
  <row Id="12905" PostTypeId="2" ParentId="12901" CreationDate="2011-04-12T01:53:27.033" Score="1" ViewCount="" Body="&lt;p&gt;No you cannot, as it's all nonlinear and hardly predictable. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But you can build signal generator by yourself, 10Mhz or even 50Mhz is not deadly complex.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can do rough estimations on square wave generator if you have osciloscope, which is deadly simple - just 1 digital invertor chip (F or LV/LVC series).&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-12T01:53:27.033" CommentCount="5" />
  <row Id="12906" PostTypeId="1" AcceptedAnswerId="12908" CreationDate="2011-04-12T02:41:20.767" Score="2" ViewCount="107" Body="&lt;p&gt;I am currently in the process of designing a custom arcade-style&#xA;joystick console for use with emulators on my PC.  My design separates&#xA;each joystick console from a single keyboard-encoder &quot;hub&quot; such that I&#xA;may add additional joysticks or upgrade the encoder circuit without&#xA;modifying existing joystick consoles.  The connection to the hub  may span&#xA;several feet, much like existing joysticks connect to their game&#xA;systems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While designing, I became puzzled as to which cable and connectors to use for&#xA;connecting a console to the hub. I need at least 12 signal wires for&#xA;each console (joystick directions, buttons, and ground) and so I&#xA;thought of using a standard HD-15 VGA cable and terminals.  I am now&#xA;dubious that this will work in general as I've read that some VGA&#xA;cables don't wire all the pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the use of HD-15 cables suitable for my design and usage?  It is&#xA;definitely attractive as it is inexpensive and generally available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What other cable and connector options are available to me and&#xA;suitable for this project?  Jumper cables are appealing as they&#xA;connect without soldering, but they don't appear to be available in&#xA;long lengths or as resistant to tangling as a VGA cable.&lt;/p&gt;&#xA;" OwnerUserId="3814" LastActivityDate="2011-04-13T04:00:18.043" Title="Is it safe to assume that all pins in a standard VGA cable are wired?" Tags="&lt;connector&gt;&lt;cables&gt;&lt;vga&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="12907" PostTypeId="2" ParentId="12906" CreationDate="2011-04-12T02:47:33.910" Score="2" ViewCount="" Body="&lt;p&gt;You should not assume it, get out an ohm meter and check it out.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-04-12T02:47:33.910" />
  <row Id="12908" PostTypeId="2" ParentId="12906" CreationDate="2011-04-12T02:51:09.377" Score="5" ViewCount="" Body="&lt;p&gt;Don't assume.  Most VGA cables use some sort of coax or individually shielded conductors for the Red, Green, Blue, and sync signals.  The shields for these signals, which have their own pins, are commonly tied together inside the cable.  Additionally, some older VGA cables might not connect the &quot;unused&quot; pins-- which are used on more modern devices.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-12T02:51:09.377" CommentCount="1" />
  <row Id="12909" PostTypeId="1" AcceptedAnswerId="12911" CreationDate="2011-04-12T03:42:48.990" Score="3" ViewCount="126" Body="&lt;p&gt;Whats a good circuit/design that will generate a very stable 4Hz signal  (to feed into a counter) that won't drift with temp / time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not so important that its exactly any particular frequency, just around 4Hz, it's just important for it to stay at that frequency ( it's to be used as a test signal )&lt;/p&gt;&#xA;" OwnerUserId="1260" LastActivityDate="2011-04-12T05:32:46.793" Title="4 Hz Stable Frequency generator" Tags="&lt;frequency&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="12910" PostTypeId="2" ParentId="12909" CreationDate="2011-04-12T04:07:48.983" Score="4" ViewCount="" Body="&lt;p&gt;Standard crystal oscillator circuits have an accuracy of +/- 20ppm to 200ppm accuracy (ppm=pulses per million) depending on the crystal used.  4 Hz +/- 0.01 Hz is an accuracy of 2500ppm.  So...  just about any crystal oscillator circuit will give you the accuracy you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem that you'll find is that a crystal oscillator will run at much higher than 4 Hz.  32.768 KHz is about the lowest you'll find, with the upper end in the hundreds of MHz (or maybe a GHz or so).  So what you'd do is use a higher clock frequency and divide it down to get the 4 Hz you desire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Exactly how you do it all depends on what you're comfortable designing and building.  You can use a metal-can type oscillator and then divide it down with simple counter chips.  Or you could use a CPLD or FPGA (overkill).  Or even a small microcontroller for both the crystal oscillator and the divider.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would use the microcontroller approach.  If you have never done a microcontroller approach, it is probably more difficult to do.  But it's fairly flexible, low power, and small size.  Although I'll be the first to admit that this approach isn't for everyone.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-12T04:07:48.983" CommentCount="5" />
  <row Id="12911" PostTypeId="2" ParentId="12909" CreationDate="2011-04-12T05:32:46.793" Score="9" ViewCount="" Body="&lt;p&gt;$\frac{32768}{8192} = 4$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Crystals are available that oscillate at 32786 Hz and you can divide this frequency down by 8192 using CMOS IC 4060, which also contains an oscillator circuit. Images are taken from &lt;a href=&quot;http://www.kpsec.freeuk.com/components/cmos.htm#4060&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. Stability will be better than you are asking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Bs4wH.gif&quot; alt=&quot;enter image description here&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/f67op.gif&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-04-12T05:32:46.793" CommentCount="3" />
  <row Id="12912" PostTypeId="2" ParentId="12906" CreationDate="2011-04-12T05:51:53.930" Score="2" ViewCount="" Body="&lt;p&gt;As stated earlier, some cables may not connect everything. Instead, try using a 25-pin parallel port cable instead, pins 1-17 are guaranteed to be connected. From my experiences so far, all 25 wires seem to be connected individually.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've opened up a few VGA splitter/switchers before. I was surprised to see that those switchers only switch 4 wires. I assume they were 3 color components and 1 ground.&lt;/p&gt;&#xA;" OwnerUserId="1319" LastEditorUserId="1319" LastEditorDisplayName="" LastEditDate="2011-04-13T00:29:00.763" LastActivityDate="2011-04-13T00:29:00.763" CommentCount="2" />
  <row Id="12913" PostTypeId="1" CreationDate="2011-04-12T06:22:42.160" Score="2" ViewCount="117" Body="&lt;p&gt;I've got a project I want to work on, which involves an LCD, MAX232, and MSP430.  The LCD requires 5V for logic and 3V for the backlight.  The MAX232 will work from 3VDC to 5.5VDC.  The MSP430G2231 will handle 1.8VDC to 3.6VDC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main power source is going to be the 12V accessory power circuit in a car.  It seems logical to regulate the ~12VDC to 5VDC, and then use the regulated 5V to create the 3.3V needed for the MSP430.  I was thinking about trying 3.3V on the backlight -- the specs state 3V typical, but don't specify a min or max value.  I plan to see if I can just measure Vf of the backlight and add a current-limiting resistor to the circuit so I can safely use the 3.3V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyhow, since I need two voltage regulators, does anyone have any recommendations for an ideal configuration?  It looks like the LCD uses a max of 1.5mA @ 5V, and the backlight takes a max of 45mA.  The MAX232 clone uses a max of 1mA @ 3.3V with no load (I have no idea what it would be under load), and the MSP430 looks like it uses about 4.2mA @ 3.3V and 16MHz.  I think these are worst-case conditions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would you use a switching regulator to go from 12V to 5V, and then a linear regulator to go from 5V to 3.3V?  Or one of the really low-count options as in the 3V Tips 'n Tricks from Microchip like a single zener or multiple diodes?  I picked up some MC34063s to play with, but am open to anything else with a lower / smaller part count.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LCD specs I used:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/6n1ws.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MSP430 specs:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/g9Ixd.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MAX232 specs:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/MEDX0.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would sure appreciate any comments, like recommended approaches, or if I have flaws in my interpretation of the specs.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-04-12T13:23:38.347" LastActivityDate="2011-04-12T13:23:38.347" Title="Tips for multiple voltage regulators?" Tags="&lt;voltage-regulator&gt;&lt;lcd&gt;&lt;rs232&gt;&lt;msp430&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="12914" PostTypeId="2" ParentId="12913" CreationDate="2011-04-12T06:38:53.387" Score="0" ViewCount="" Body="&lt;p&gt;One red LED will drop you from 5 to 3.3 for applications &amp;lt; 20mA.  Its super-cheap AND tells you if the power is on.&lt;/p&gt;&#xA;" OwnerUserId="3743" LastActivityDate="2011-04-12T06:38:53.387" CommentCount="2" />
  <row Id="12915" PostTypeId="2" ParentId="12913" CreationDate="2011-04-12T06:44:27.413" Score="1" ViewCount="" Body="&lt;p&gt;Use +5V for the backlight.  Select a resistor to drop 2V at 30 mA. (67 ohms).  The backlight will get a nicely regulated current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the 3.3V, use a three-pin LDO.  They are not expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be safe when connecting the LCD's output to the MSP430 input.  Use a resistor divider or such.  &lt;a href=&quot;http://focus.ti.com.cn/cn/general/docs/lit/getliterature.tsp?literatureNumber=slaa148&amp;amp;fileType=pdf&quot; rel=&quot;nofollow&quot;&gt;TI appnote&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-12T06:44:27.413" CommentCount="8" />
  <row Id="12916" PostTypeId="2" ParentId="12913" CreationDate="2011-04-12T06:49:53.737" Score="2" ViewCount="" Body="&lt;p&gt;If power requirements are low (tens of millamps) I tend to use linear regulators. It doesn't matter whether you go from 12V to 3.3V immediately, or via 5V. Make sure, however, if you use a regulator to go from 5V to 3.3V to use an LDO; the voltage difference is too small for standard regulators.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to use SMPSs you'll have to look at the efficiency. This is in general lower for lower output voltages, and also if the Vin/Vout ratio gets higher. Let's say you go from 12V to 5V at 90%, from 12V to 3.3V at 80% and from 5V to 3.3V at 95%. So going from 12V to 3.3V in 1 step will be 80% efficient, if you do this in 2 steps (via 5V) your overall efficiency will be 90% * 95% = 85.5%. You'll have to make the calculation for your specific regulator.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-12T06:49:53.737" CommentCount="1" />
  <row Id="12917" PostTypeId="1" AcceptedAnswerId="12919" CreationDate="2011-04-12T07:41:26.620" Score="4" ViewCount="113" Body="&lt;p&gt;I got myself a spartan-3an evaluation board in order to learn fpga programming and some verilog. It's taken a little while to stop seeing it in terms of a sequential programming language and to start seeing it in terms of connections between blocks of hardware but I'm getting there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've made a small &quot;program&quot; that takes a image defined in &quot;ram&quot; and displays it on the vga port. The ram is just a set of reg's like this&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;reg ram[4095:0]; // Video memory for 64x64 pixel display&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I used the patterns in the help and the compiler has inferred that it should put this into a blockmem and it all works nicely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My doubt is about timing though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have one &quot;always&quot; block incrementing a counter for the vga horizontal position, and one incrementing a counter for the vga vertical position. Then I have another always block that uses that counter to generate an address into a &quot;reg&quot; that indxes the memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is then another &quot;always&quot; block triggered by a clock that reads that memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My doubt is this - I'm generating the sync pulses based on the counters. That's fine, but I'm generating the address in the video memory too from those counters to read the pixel. However that read will occur on the &lt;em&gt;next&lt;/em&gt; clock pulse so my pixel data will be output one clock cycle later than I'm expecting. I'll calculate the address on one clock cycle but not have the pixel data available until the next one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have I understood that situation correctly? And if so, what do I do about it? Ignore it because it won't be visible? I could probably buffer the sync pulses too and delay them in the same way. Or I could pre adjust the calculated memory address to compensate in advance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What do people generally do in this kind of situation? Or is every case different?&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2011-04-13T12:55:07.913" Title="Beginner with fpga and timing issues" Tags="&lt;fpga&gt;&lt;verilog&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="12918" PostTypeId="2" ParentId="12917" CreationDate="2011-04-12T09:20:27.197" Score="1" ViewCount="" Body="&lt;p&gt;Generic way to deal with things that take more than one clock cycle is pipelining, e.g. in your case you could create two stage pipeline, in first stage you generate the address and read signals for the memory, and in second stage you process the result and generate the sync pulses when appropriate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However because in your simple case you only need to deal with the synchronicity of sync pulses, the simplest thing to do would be to delay them by one clock cycle by a flip-flop.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-04-12T09:20:27.197" CommentCount="1" />
  <row Id="12919" PostTypeId="2" ParentId="12917" CreationDate="2011-04-12T09:59:33.420" Score="2" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Have I understood that situation&#xA;  correctly?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes - if some part of your output data is available later than other parts, you have to delay the other parts so they line up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not a fudge, or a &quot;bad&quot; thing to do - it's just what has to be done to make the outputs right.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;I could probably buffer the sync pulses too and delay them in the same way. &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That's what I'd do.  (EDIT: And as Yann reminded me, delaying signals can be very cheap in Xilinx FPGAs - 16 ticks can fit in a single look-up table + 1 more in the flipflop that's next to the LUT)&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Or I could pre adjust the calculated memory address to compensate in advance.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That's another option, but will probably take more logic.&lt;/p&gt;&#xA;" OwnerUserId="763" LastEditorUserId="763" LastEditorDisplayName="" LastEditDate="2011-04-13T12:55:07.913" LastActivityDate="2011-04-13T12:55:07.913" CommentCount="1" />
  <row Id="12920" PostTypeId="2" ParentId="12901" CreationDate="2011-04-12T10:02:57.060" Score="1" ViewCount="" Body="&lt;p&gt;Assuming your transmitter is NTSC, you have 4.2MHz to play with, &lt;a href=&quot;http://en.wikipedia.org/wiki/NTSC#Transmission_modulation_scheme&quot; rel=&quot;nofollow&quot;&gt;according to Wikipedia&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To answer the original question, yes, it is possible to measure a signal at a lower frequency (using aliasing), but you must be able to sample at atleast twice the bandwidth of interest, &lt;em&gt;and&lt;/em&gt; the signal band must start at a multiple of your sampling rate.&lt;/p&gt;&#xA;" OwnerUserId="3823" LastActivityDate="2011-04-12T10:02:57.060" CommentCount="1" />
  <row Id="12921" PostTypeId="2" ParentId="12886" CreationDate="2011-04-12T11:25:29.793" Score="1" ViewCount="" Body="&lt;p&gt;At that sort of age you can definitely get them soldering and even designing circuits - there is a regular show that comes to the Edinburgh festival that my kids went to and got to do the full build (not design) of solar powered audio circuits and stylophone equivalents, including the soldering at age 4. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They can certainly cope mentally - it's just like building with lego or meccano - but be aware it will probably take one instance of dropping a soldering iron on a hand or leg for them to really believe you that it hurts a lot :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would also recommend kits such as &lt;a href=&quot;http://www.sciencekits.com/electron.html&quot; rel=&quot;nofollow&quot;&gt;these ones from sciencekits.com&lt;/a&gt; as they do help you pick up the basics without really needing much in the way of tools.&lt;/p&gt;&#xA;" OwnerUserId="3525" LastActivityDate="2011-04-12T11:25:29.793" />
  <row Id="12922" PostTypeId="2" ParentId="12432" CreationDate="2011-04-12T11:37:48.337" Score="3" ViewCount="" Body="&lt;p&gt;Sorry to have to be contradictory here, but I must say &lt;strong&gt;yes&lt;/strong&gt; - you can use other tools, or at least work around the bloated parts. Simulation and logic synthesis are in fact separate targets. However, you're much more limited when it comes to bitstream generation. There have been a few tools, like Jbits, but for the most part you're restricted to vendor supported tools. Xilinx tools for this are XST (Xilinx Synthesis Technology), par (place and route) then bitgen (to make the bit file). They are what ISE uses as its backend, so you get them in WebPack. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a workable toolchain, it's often much quicker to enter your designs in Emacs, simulate them with Verilator, Icarus Verilog or GHDL, inspect simulation results with gtkwave.. and finally, synthesize to logic with XST etc. XST can be run without using ISE, but it's a somewhat more complicated procedure you'll want to use make for. Check the &lt;a href=&quot;http://www.xilinx.com/support/documentation/dt_ise13-1_userguides.htm&quot; rel=&quot;nofollow&quot;&gt;ISE user guides&lt;/a&gt;; XST manual chapter Command Line Mode, and the Command Line Tools chapters on PAR and BitGen. If you want post-synthesis simulation, that's also technology (and thus vendor) specific. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a rule, you can write all your logic without vendor specific instantiations (the ISE snippets show examples which infer usage correctly), but the DCMs can't be described that way. You'll thus have to make your simulation benches without them, which shouldn't be hard as you can just add the required clocks there.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2011-04-12T11:37:48.337" CommentCount="1" />
  <row Id="12923" PostTypeId="1" AcceptedAnswerId="12928" CreationDate="2011-04-12T11:50:03.453" Score="3" ViewCount="130" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm currently testing a design, and using two small wires to connect an oscillator with a frequency counter (both are small circuits I have build).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So here is a question, when designing RF and connecting different circuits, when is something to be considered a transmission line?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mean, when do I have to think about transmission line impedance matching (and to start worrying about reflection and ect.).&lt;/p&gt;&#xA;" OwnerUserId="3041" LastEditorUserId="3041" LastEditorDisplayName="" LastEditDate="2011-04-12T11:55:17.880" LastActivityDate="2011-04-12T14:57:05.383" Title="Transmission line" Tags="&lt;transmission-line&gt;" AnswerCount="3" />
  <row Id="12924" PostTypeId="2" ParentId="12923" CreationDate="2011-04-12T12:32:38.097" Score="5" ViewCount="" Body="&lt;p&gt;As a rule, a transmission line isn't required if the length of the connection is under 1/10 of a wavelength.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A low-impedance source can generally drive a high-impedance load without any problems. Loss of signal results if they are the other way round, and a buffer stage is usually the answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Impedances should be matched when using transmission lines.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-12T13:00:32.513" LastActivityDate="2011-04-12T13:00:32.513" CommentCount="5" />
  <row Id="12925" PostTypeId="2" ParentId="12923" CreationDate="2011-04-12T12:50:18.543" Score="3" ViewCount="" Body="&lt;p&gt;Every line is a transmission line, however different situations require different level of rigour.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At low frequencies - from DC to few hundred MHz, short transmission lines have only very small inductance and capacitance and can be usually ignored because they don't contribute much to input of output impedance of what they are connecting. The situation with them is similar to the case when the stages are connected directly. Once you start moving into GHz range, impedance of the line becomes significant and you have to treat it as separate stage of your device and match it. When the line is long, like in the case of cable, impedance also goes up and becomes significant, and you have to match it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At high power levels reflected wave can destroy previous stage and you have to care about matching even at low frequencies. For example if you try to transmit 100W with disconnected antenna, you are likely going to fry your power amplifier (unless it has protection against such situation).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example: short PCB trace is going to have say 10 nH inductance, which at 10 MHz would give it reactance 0.63 ohm (open circuit), shunt capacitance 1 pF, or capacitive reactance 15783 ohm (high impedance), and resistance under 1 ohm - all values insignificant if the input and output impedance of the stages is 50 ohm. At 2 GHz it would be reactance 125 ohm and shunt capacitance 79.6 ohm - significant values that would require redesign into transmission line.&lt;/p&gt;&#xA;" OwnerUserId="2636" LastActivityDate="2011-04-12T12:50:18.543" CommentCount="1" />
  <row Id="12926" PostTypeId="5" CreationDate="2011-04-12T13:59:39.770" Score="0" ViewCount="" Body="&lt;p&gt;The term &quot;power supply&quot; is extremely broad, and covers a large variety of devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some examples of common power supplies:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;em&gt;AC adapters&lt;/em&gt;, which convert AC from the mains to low-power DC loads (commonly referred to as 'wall-warts')&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;ATX PC power supplies&lt;/em&gt;, which convert AC from the mains to several regulated DC outputs to power computers and their peripherals&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;battery chargers&lt;/em&gt;, which vary the output voltage and current to safely charge batteries&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;inverters&lt;/em&gt;, which convert DC into mains-equivalent AC to power devices usually connected to the mains&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;DC-DC converters&lt;/em&gt;, which convert DC into higher (or lower) voltage DC&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;Linear regulators&lt;/em&gt;, which regulates DC into lower voltage DC without conversion&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Commonly used definitions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;em&gt;load&lt;/em&gt;: a circuit which draws electrical power from a power supply (a computer, a light bulb, etc.)&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;mains&lt;/em&gt;: (generally) AC power provided by an electrical utility&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;rectification&lt;/em&gt;: conversion of AC to DC&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;converter&lt;/em&gt;: a circuit which changes voltage from one form to another (AC to DC) or converts DC to DC using a switching stage (DC -&gt; AC -&gt; DC)&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;PFC&lt;/em&gt;: &lt;strong&gt;power factor correction&lt;/strong&gt;, which generally refers to a circuit that converts the mains AC into DC while keeping the input current sinusoidal and in-phase with the voltage (making the power supply load appear resistive to the mains)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Power_supply&quot; rel=&quot;nofollow&quot;&gt;Wikipedia power supply article&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-12T14:19:00.167" LastActivityDate="2011-04-12T14:19:00.167" />
  <row Id="12927" PostTypeId="4" CreationDate="2011-04-12T13:59:39.770" Score="0" ViewCount="" Body="An electronic device which supplies electrical energy to a load." OwnerUserId="-1" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-12T14:19:03.210" LastActivityDate="2011-04-12T14:19:03.210" />
  <row Id="12928" PostTypeId="2" ParentId="12923" CreationDate="2011-04-12T14:57:05.383" Score="1" ViewCount="" Body="&lt;p&gt;An interconnection should be considered a transmission line if reflections are detrimental to your application. As Leon Heller says, 1/10th wavelength is a good rule-of-thumb.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, all this depends on the nature of the signal (1/10th of what wavelength?). With sine waves, the wavelength in the cable will be about $\frac{2 X 10^8}{f}$ where f is the frequency, but will vary according to the cable type. The effect of reflections on sine waves is to cause &lt;a href=&quot;http://en.wikipedia.org/wiki/Standing_waves&quot; rel=&quot;nofollow&quot;&gt;standing waves&lt;/a&gt;, so the amplitude will vary along the length of the cable but will always be sinusoidal. With square waves the situation is complicated by harmonics. Although the square-wave may have a low fundamental frequency, the harmonics introduced by the edges will be significant. The effect of reflections in this case is undershoot, overshoot or ringing depending on where the mismatches are (if both $R_S$ &amp;amp; $R_L$ are lower than $Z_0$ for example, you will get ringing).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So do you need to match the source? No. As long as the load is perfectly matched, the wavefront will travel down the transmission line and be fully absorbed by the load. Consider a digital system with 3.3V logic for example. If you terminated both source &lt;em&gt;and&lt;/em&gt; load you would only get 1.65V swing at the load. Terminating only at the load is termed &lt;em&gt;parallel termination&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also a technique known as &lt;em&gt;series termination&lt;/em&gt; in which the source is terminated but the load is left open circuit. In this case, a half-amplitude edge propagates down the line and is reflected back to the source, lifting the voltage to full amplitude as it returns until it is absorbed by the source termination. Along the line, you would see a 'stepped' signal except right at the load where you would see a clean waveform.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-04-12T14:57:05.383" CommentCount="4" />
  <row Id="12929" PostTypeId="1" CreationDate="2011-04-12T16:06:01.330" Score="-3" ViewCount="80" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my hardware class, we have been assigned papers on random topics of computer hardware. Mine is &quot;optical chips.&quot; I'm having trouble finding sufficient information (print or online) about what exactly they are, and how they work. Can anyone give me tips on where to find information about optical chips?&lt;/p&gt;&#xA;" OwnerUserId="3831" LastActivityDate="2011-04-14T10:40:04.817" ClosedDate="2011-04-15T17:43:35.383" Title="What is an Optical Chip? Where can I find information on it?" Tags="&lt;hardware&gt;" AnswerCount="1" CommentCount="7" />
  <row Id="12930" PostTypeId="1" AcceptedAnswerId="12934" CreationDate="2011-04-12T16:13:02.010" Score="2" ViewCount="140" Body="&lt;p&gt;So I know what they both do......but yet I don't know when you'd choose to use one over the other? There was a similar question on here, but the answer didn't really make sense to me (who is an electronics newb)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know Caps are alot of times used for smoothing, but then what are inductors mainly used for?&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-04-12T18:28:31.037" Title="Capacitors or Inductors?" Tags="&lt;capacitor&gt;&lt;inductor&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="12932" PostTypeId="2" ParentId="12930" CreationDate="2011-04-12T16:32:11.210" Score="2" ViewCount="" Body="&lt;p&gt;Inductors are used for a lot, but if I had to pick something I'd say they're used in buck and/or boost converters to help produce the output voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The inductor is an energy storage element - it stores energy in a magnetic field that is produced when current is run through the inductor.  Inductors resist changes in the current flowing through them by changing the voltage across themselves.  This produces a couple of effects:  if there is constant current flowing through an inductor then the voltage across it is zero.  If you try to change the current flowing through it (by turning off a power supply for instance) then the voltage across it becomes non-zero.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second effect is used to produce high voltages:  if you put lots of current through an inductor then try to remove it very quickly you get a very high voltage.  This is what boost converters do: create an output voltage that's higher than the input voltage.  Buck converters do the opposite: produce lower voltage from higher voltage input.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-12T16:32:11.210" />
  <row Id="12933" PostTypeId="2" ParentId="12731" CreationDate="2011-04-12T16:32:29.043" Score="1" ViewCount="" Body="&lt;p&gt;It depends on what you're trying to do with the caps.  It sounds like you've just been told to use them, but not why or how.  Generally you want to have a capacitor (or several, probably one's fine for you) to decouple the supply pins from the chip the supply is powering (the load).  This &quot;smooths&quot; out the voltage response of the supply.  This is why some people refer to them as smoothing capacitors.  You do this because the supply voltage will change based on the demand the circuit is putting on it.  When your circuit tries to draw more current, the supply cannot react immediately to the extra demand so the voltage it is supplying drops.  A decoupling capacitor will charge when you turn the circuit on and will discharge during these load changes to counteract the supply's drop in voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're trying to reduce noise from the motor, then do as TokenMacGuy says.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best thing to do is to scope the voltage between your supply pins (8 &amp;amp; 16) and between each supply pin and ground as you operate the circuit and see if you're getting more than a few tens of mV of ripple.  If you are, place a 0.1uF cap across the offending pins as close to the pins as you can, and re-measure to confirm the reduction in noise/ripple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't have a scope and can't borrow one, just put one 0.1uF cap across the supply pins (so between pins 8 &amp;amp; 16), and one each between pin 8 and ground and between pin 16 and ground.  Again, try to get them close to the pins on the chip.  The supply header on the edge of the board might be a good place to make those connections.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure that in any case you pay attention to the voltage ratings of your caps and what voltage you're placing it across.&lt;/p&gt;&#xA;" OwnerUserId="3830" LastActivityDate="2011-04-12T16:32:29.043" />
  <row Id="12934" PostTypeId="2" ParentId="12930" CreationDate="2011-04-12T16:46:44.697" Score="8" ViewCount="" Body="&lt;p&gt;There are many ways to answer this question.  I'm going to answer it one way, and you'll just have to keep in mind that you're not getting the whole story.  Also, I'm over-simplifying it for the sake of discussion.  Here goes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Impedance is the &quot;effective resistance at a given frequency&quot;.  The impedance will be measured in ohms, and depending on the device the impedance will change depending on frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Resistor:  The &quot;impedance&quot; of the ideal resistor is the same regardless of frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Capacitor:  The impedance of the cap goes DOWN as the frequency goes UP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inductor:  The impedance of the inductor goes UP as the frequency goes UP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, imagine a normal &lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage_divider&quot; rel=&quot;nofollow&quot;&gt;voltage divider&lt;/a&gt; made from a couple of resistors.  Because the resistor has a constant impedance over frequency it will divide down the voltage evenly for all frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you replace the lower resistor with a cap (figure 3 from the web page previously linked to) then you have something different.  This will reduce the amplitude of high frequencies more than low frequencies.  Effectively making a &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/Low-pass_filter&quot; rel=&quot;nofollow&quot;&gt;low pass filter&lt;/a&gt;&quot;,  which lets the low frequencies pass through, but attenuates the high frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, if you put the cap on top, and the resistor on the bottom, you get a &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/High-pass_filter&quot; rel=&quot;nofollow&quot;&gt;high pass filter&lt;/a&gt;&quot;.   This will allow the high frequencies to pass through, but block the low frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The high and low pass filters mentioned are variations of an &quot;RC filter&quot;-- a filter made up from resistors and caps.  There are such things as &quot;LC filters&quot;, with are made up from inductors and caps.  Don't ask me why &quot;L&quot; stands for inductor, but it does.  And I'm sure somewhere there is an LR filter that uses inductors and resistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The basic concepts of LC and LR filters are similar to the RC filters-- using the various impedance vs. frequency characteristics of the components to create the type of circuit that you want.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inductors tend to be used instead of resistors in situations where the current of the &quot;pass frequency&quot; is high.  But this isn't always the case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I intentionally ignored one aspect of inductors and caps:  They can both be used to store energy.  That could be a lesson for a later time, since it can get rather complex.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-12T16:46:44.697" CommentCount="1" />
  <row Id="12935" PostTypeId="1" AcceptedAnswerId="12936" CreationDate="2011-04-12T16:55:19.687" Score="1" ViewCount="91" Body="&lt;p&gt;So i am designing a device that is supposed to connect to the PC via USB and draw power from the VBUS (+5v) of the USB. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am wondering if I need to put a voltage regulator in between the +5v from the USB and the microcontroller on my device. I've tested this device on my own laptop and it works fine. But I'm not sure if I can make any assumption regarding the stability of the VBUS on other computers. I looked at some Arduino designs and they don't seem to place any voltage regulator when it is powered through the USB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So is it safe to assume that the +5v coming from a PC USB connection is fairly stable? &lt;/p&gt;&#xA;" OwnerUserId="2968" LastActivityDate="2011-04-12T18:51:31.027" Title="Stability of USB +5V output" Tags="&lt;usb&gt;&lt;usb-device&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="12936" PostTypeId="2" ParentId="12935" CreationDate="2011-04-12T17:05:07.323" Score="6" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.usb.org/developers/docs&quot; rel=&quot;nofollow&quot;&gt;USB specification&lt;/a&gt; states that the 5v is supposed to be +-5% under load, which translates to 4.75v to 5.25v.  A simple power connection will provide up to 100 ma.  (Up to 500 ma can be drawn, but you have to negotiate for it.).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most IC's designed for 5v should accommodate the +-5% variation also.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-04-12T17:05:07.323" />
  <row Id="12937" PostTypeId="2" ParentId="12935" CreationDate="2011-04-12T17:05:32.600" Score="1" ViewCount="" Body="&lt;p&gt;Provided you are using a computer as a source, then yes you can assume that the 5V is stable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You cannot assume this if you use a mains power supply adaptor with a USB output, like the one that comes with an Apple iPhone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, to use a regulator effectively, you should supply the regulator with a slightly higher voltage than the regulator output, otherwise as soon as you put a load on it there won't be enough 'spare voltage' for it to draw from to maintain +5V. (I know that's a bad way of saying it but it kinda makes it easier to understand!).&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-04-12T17:05:32.600" CommentCount="1" />
  <row Id="12938" PostTypeId="2" ParentId="7133" CreationDate="2011-04-12T17:12:14.707" Score="2" ViewCount="" Body="&lt;p&gt;Play music. You don't need to spend one cent extra money.&#xA;&lt;a href=&quot;http://franktu.com/playing_music.htm&quot; rel=&quot;nofollow&quot;&gt;http://franktu.com/playing_music.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3832" LastActivityDate="2011-04-12T17:12:14.707" />
  <row Id="12939" PostTypeId="1" CreationDate="2011-04-12T18:09:05.207" Score="4" ViewCount="89" Body="&lt;p&gt;A while ago I upgraded my TV antenna in preparation for Digital Switch-Over here in the UK. It's a high-gain &quot;Triple Boom&quot; design, the same as &lt;a href=&quot;http://www.aerialshack.com/magician-element-triple-boom-aerial-p-1327.html&quot; rel=&quot;nofollow&quot;&gt;this antenna&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other day I started thinking... what is the benefit of the 'triple-boom' design and how does it work?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The booms are clearly angled, how does this effect things? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It also appears the elements are evenly spaced, in contrast to single-boom antennas, so I infer from this that the angling, and thus vertical distance between elements, leads to sensitivity at different frequencies. But why doesn't the horizontal spacing matter too (as in single boom designs)? or does it? And why do &lt;a href=&quot;http://www.aerialshack.com/televes-boss-ultra-high-gain-aerial-p-272.html&quot; rel=&quot;nofollow&quot;&gt;higher-gain antennas with more elements&lt;/a&gt; just keep extending outwards but at the same angle? So a longer 'boom' means the furthest most elements are even further apart than normal. Doesn't this just mean they are resonant at even lower frequencies?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Comparing the performance of this antenna with traditional single-boom design shows it has a higher gain but also a wider acceptance angle. I can see how a triple boom array would increase gain, but why/how does it broaden the angle?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lots of questions I know, but I've got a feeling there is one answer to answer them all!&lt;/p&gt;&#xA;" OwnerUserId="3833" LastActivityDate="2011-05-19T11:38:02.733" Title="Please explain this High-Gain Yagi UHF antenna design" Tags="&lt;rf&gt;&lt;antenna&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="12940" PostTypeId="1" AcceptedAnswerId="13006" CreationDate="2011-04-12T18:11:46.107" Score="1" ViewCount="125" Body="&lt;p&gt;I'm working on a project where I have to communicate different lengths command from my PC to a microcontroller. (using usb to uart bridge)&#xA;I already make a litle protocol (start byte, some data, checksum ...) but I need to adapt it for my new need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm wondering if there is already a standard or a common way to do that.&lt;/p&gt;&#xA;" OwnerUserId="2040" LastActivityDate="2011-04-13T15:01:13.153" Title="uart communication protocol" Tags="&lt;uart&gt;&lt;communication&gt;&lt;protocol&gt;&lt;standard&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="12941" PostTypeId="1" CreationDate="2011-04-12T18:25:04.120" Score="0" ViewCount="59" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I dont normally purchase capacitors of this type and have no idea where to look - if someone could point me in the right direction on where to buy a compatible one (or the same one) then that would be EXCELLENT!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the part number is: &lt;strong&gt;PME261JC6100KR30&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the specifications are: http://www.kemet.com/kemet/web/homepage/kechome.nsf/weben/52B4230E2F4A329F8525771B004F6999/$file/F3294_PME261.pdf&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(its the last one on the last page)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PLEASE HELP I need this ASAP so if there is any supplier in the UK that would be excellent!&lt;/p&gt;&#xA;" OwnerUserId="3834" LastActivityDate="2011-04-12T19:13:37.390" ClosedDate="2011-04-12T20:16:58.707" Title="HELP! replacement capacitor needed" Tags="&lt;capacitor&gt;&lt;circuit-design&gt;&lt;decoupling-capacitor&gt;" AnswerCount="1" />
  <row Id="12942" PostTypeId="2" ParentId="12930" CreationDate="2011-04-12T18:28:31.037" Score="-2" ViewCount="" Body="&lt;p&gt;In electronics, inductors are to be avoided. They tend to take up a lot of area, they are prone to impulses (voltage spikes due to switching), and produce more noise than other components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One appealing property of the inductor is that it can create a zero in your transfer function. However, this can also be achieved with a &lt;a href=&quot;http://en.wikipedia.org/wiki/Operational_amplifier_applications#Inverting_differentiator&quot; rel=&quot;nofollow&quot;&gt;capacitor, resistor and opamp&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="3823" LastActivityDate="2011-04-12T18:28:31.037" CommentCount="4" />
  <row Id="12943" PostTypeId="2" ParentId="12940" CreationDate="2011-04-12T18:39:02.167" Score="4" ViewCount="" Body="&lt;p&gt;There are many protocols available. One of my favorites is the Modbus.&#xA;&lt;a href=&quot;http://www.modbus.org/docs/PI_MBUS_300.pdf&quot; rel=&quot;nofollow&quot;&gt;Modbus protocol&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-04-12T18:39:02.167" CommentCount="1" />
  <row Id="12944" PostTypeId="2" ParentId="12940" CreationDate="2011-04-12T18:40:04.363" Score="0" ViewCount="" Body="&lt;p&gt;xmodem, ymodem, zmodem, kermit solved those problems a couple of decades ago.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-04-12T18:40:04.363" CommentCount="1" />
  <row Id="12945" PostTypeId="2" ParentId="12940" CreationDate="2011-04-12T18:50:36.927" Score="3" ViewCount="" Body="&lt;p&gt;If there is only one master-slave connection, it sounds like you've done all you need to do. Use a standard CRC checksum algorithm, but that's all there is to meaningfully standardize. Don't worry about having an official ISO/IEEE protocol.&lt;/p&gt;&#xA;" OwnerUserId="3835" LastActivityDate="2011-04-12T18:50:36.927" />
  <row Id="12946" PostTypeId="2" ParentId="12935" CreationDate="2011-04-12T18:51:31.027" Score="2" ViewCount="" Body="&lt;p&gt;The 5 V VBUS is definitely not stable, and will usually vary with the computer's load.  In USB audio products, this creates all kinds of noise, presumably from audio frequency fluctuations caused by video cards, hard drives, etc.  For these applications, a regulator is necessary.  With your micro, it probably doesn't matter, but if you're doing any kind of analog to digital conversion, I'd also recommend a regulator.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The USB spec lists a worst-case drop of 4.375 V at the device, after a bus-powered hub, with transient drops to 4.07 V.  Keep in mind that not every USB host follows the USB spec, so it could be even worse.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-04-12T18:51:31.027" />
  <row Id="12947" PostTypeId="1" AcceptedAnswerId="12948" CreationDate="2011-04-12T18:57:10.677" Score="1" ViewCount="76" Body="&lt;p&gt;Hi&#xA;I need to know what is the L200C maximum current. The datasheet says it's internally limited. Am not quite sure what this means.&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-04-12T21:16:18.970" Title="L200C regulated power supply - maximum current" Tags="&lt;voltage-regulator&gt;" AnswerCount="2" />
  <row Id="12948" PostTypeId="2" ParentId="12947" CreationDate="2011-04-12T19:04:32.027" Score="1" ViewCount="" Body="&lt;p&gt;It's in the data sheet (page 4) - peak short circuit current is 3.6 A, with pins 2 and 5 shorted. It'll probably go into thermal shutdown if you try it, unless it has a large heatsink.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-12T19:20:04.250" LastActivityDate="2011-04-12T19:20:04.250" CommentCount="2" />
  <row Id="12949" PostTypeId="2" ParentId="12941" CreationDate="2011-04-12T19:13:37.390" Score="1" ViewCount="" Body="&lt;p&gt;RS stocks PME261 capacitors, they probably have that one. Farnell stocks similar ones.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-12T19:13:37.390" CommentCount="3" />
  <row Id="12950" PostTypeId="1" CreationDate="2011-04-12T19:30:15.057" Score="1" ViewCount="166" Body="&lt;p&gt;I want to build a 500 cell shift register using the TI SN74AUP1G79 flip flop.How much current must my power supply put out to drive this many flip flops and how much current must my clock buffer put out to drive all the clocks? I am running the register at 1.54mhz. Thank you.&lt;/p&gt;&#xA;" OwnerUserId="3836" LastActivityDate="2011-04-14T16:23:03.430" Title="building large shift registers" Tags="&lt;logic&gt;" AnswerCount="3" CommentCount="8" />
  <row Id="12951" PostTypeId="2" ParentId="12474" CreationDate="2011-04-12T19:35:28.253" Score="3" ViewCount="" Body="&lt;p&gt;Depending on your exact application a simpler method might be to flicker the screen in a certain pattern and recognize it with one or more photo diodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, the german &quot;chipTAN comfort&quot; TAN generator for online banking uses such an approach. There are five flickering fields on the bank's web page which transfer data to the TAN generator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The data includes the account number and the amount, which both are displayed and used in the computation of the TAN, so checking this data is a very effective countermeasure against phishing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately I didn't find any web page in English describing the system, so here is one in german: &lt;a href=&quot;http://6xq.net/html/00/20.html&quot; rel=&quot;nofollow&quot;&gt;http://6xq.net/html/00/20.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-04-12T19:35:28.253" CommentCount="2" />
  <row Id="12953" PostTypeId="1" CreationDate="2011-04-12T20:02:04.840" Score="5" ViewCount="114" Body="&lt;p&gt;I am considering whether to replace the commercial differential temperature controller on my solar water heater with a Arduino based controller of my own design.  I know just enough to be dangerous about such things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First question: will the classic 5V/10Kohm thermistor voltage splitter circuit blow something during a lightning storm?  The thermistor is located 60 ft away on the roof mounted solar panel.  The cable is shielded and grounded.  What's needed - surge protector on the thermistor circuit, some RC connection to the thermistor leads, reduce the base resistor for more current flow to the thermistor ....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second question: does the Arduino Atmega microprocessor auto-reboot and resume software execution after a loss of power?  Put another way, does the reset button have to be pressed after a loss of power?&lt;/p&gt;&#xA;" OwnerUserId="3837" LastActivityDate="2011-05-20T21:09:39.653" Title="Lightning/surge protection for a Arduino monitored thermistor circuit" Tags="&lt;arduino&gt;&lt;solar-cell&gt;&lt;protection&gt;&lt;thermistor&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="12954" PostTypeId="1" CreationDate="2011-04-12T20:30:59.823" Score="0" ViewCount="73" Body="&lt;p&gt;Hi! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been wondering about Beagleboard and it's possibilities of supporting many embedded OSes &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I was wondering was:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Using a SSD as a SD Card? Does it depend on the OS?&lt;/li&gt;&#xA;&lt;li&gt;Relocation of the Usb ports?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3838" LastActivityDate="2011-05-13T16:43:03.233" Title="Expansion of Beagleboard?" Tags="&lt;beagleboard&gt;" AnswerCount="1" />
  <row Id="12955" PostTypeId="1" CreationDate="2011-04-12T20:35:45.157" Score="0" ViewCount="69" Body="&lt;p&gt;Is it possible to conceive of a system that would use a stationary camera with a fish-eye lens to effectively provide the same images as a camera that was actually panning and tilting. &lt;/p&gt;&#xA;" OwnerUserId="3839" LastActivityDate="2011-04-13T22:53:32.940" Title="Electronic pan/tilt camera" Tags="&lt;sensor&gt;&lt;interface&gt;&lt;camera&gt;&lt;imageprocessing&gt;&lt;ideas&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="12956" PostTypeId="2" ParentId="12955" CreationDate="2011-04-12T21:08:38.470" Score="1" ViewCount="" Body="&lt;p&gt;The results would be pretty awful.  The distortion from a fish eye lens would result in images that look ridiculous compared to image stitching.  Although your results of the stitched images vary based on the quality of your lens, all fisheye images I've ever seen result in vertical lines looking bowed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://wiki.panotools.org/Fisheyes&quot; rel=&quot;nofollow&quot;&gt;http://wiki.panotools.org/Fisheyes&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-12T21:08:38.470" CommentCount="2" />
  <row Id="12957" PostTypeId="1" CreationDate="2011-04-12T21:14:58.167" Score="3" ViewCount="105" Body="&lt;p&gt;When I replaced my water heater, the installer was telling me how cool the Bradford White unit I got was because the electronics are powered by the same heat used to heat the water in the tank.  I thought it was a cool idea, but didn't give it much more thought after that, until now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there good resources for designing circuits that can be powered with heat?  I couldn't find any information on Bradford White's website, but google turned up &lt;a href=&quot;http://inhabitat.com/mit-developing-body-heat-powered-electronics/&quot; rel=&quot;nofollow&quot;&gt;this one article&lt;/a&gt; about how MIT is researching the use of body heat to power electronics.  I think it's pretty fascinating and would like to play with the concepts, if possible.  I assume that if MIT is currently working on it, then it's way past the ability of my pea brain to put something together, but hopefully someone here can prove me wrong.  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- I should have thought of Peltiers immediately, but it just occurred to me.  I haven't ever tried applying a heat differential to one and measuring the voltage, but it's worth a shot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- I had to revise the title for this question.  I found a thermoelectric generator, and if its price is any indication, this technology is insanely expensive.  Does anyone know of an &lt;em&gt;inexpensive&lt;/em&gt; way to implement powered circuits with a temperature differential?&lt;/p&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T20:59:26.783" LastActivityDate="2011-04-27T20:59:26.783" Title="Powering electronics with a low-cost thermoelectric generator?" Tags="&lt;thermal&gt;&lt;thermoelectric&gt;&lt;heat-powered&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="12958" PostTypeId="2" ParentId="12947" CreationDate="2011-04-12T21:16:18.970" Score="1" ViewCount="" Body="&lt;p&gt;On the first page of the data sheet, it is said that it has adjustable current up to 2 A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another very important thing is note 1 on the page 4. It says that up to 2 A can be provided if the difference between input and output is less than 20 V (this came back and bit me couple of times).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Figure 3 on page 4 also provides interesting information. It shows relation between voltage difference, junction temperature and output current.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-04-12T21:16:18.970" CommentCount="1" />
  <row Id="12959" PostTypeId="2" ParentId="1842" CreationDate="2011-04-12T21:48:47.440" Score="1" ViewCount="" Body="&lt;p&gt;I have two issues for you:&#xA;(1) the AD590 should be strobed to a moderately low duty cycle to prevent self-heating.  Check out the AD apnotes.&#xA;(2) When you go underwater with wide temp swings especially if you go very deep you will probably get water intrusion.  The sneakiest way water gets to the leads ( and screws the reading ) is by capillary action along the leads right through the silicon caulk or casting acrylic.  Maybe there are potting compounds that could prevent that but the only way I found way to put the sensor at the end of a pipe through which the leads run to the surface.  In case of condensation I even put a little sump branch below the sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck.&lt;/p&gt;&#xA;" OwnerUserId="3840" LastActivityDate="2011-04-12T21:48:47.440" />
  <row Id="12960" PostTypeId="1" CreationDate="2011-04-12T21:58:38.703" Score="2" ViewCount="111" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im doing a project with a PIC18F452 and I will have to use USART. Thus, I bought a FTDI Basic breakout board (from Sparkfun) to make debugging easier. The board is the 5V version.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I already tested FT232R with a loopback circuit and Putty (on Windows) and it works well. I also tested PIC with a loopback circuit and it also works well.&#xA;However I can't get FT232R to work with PIC. In the microcontroller I have USART configured with 9600kbaud, 8bit, no parity (same as PC side), RX with interrupt. Im just sending data from PC to PIC. When PIC receives something prints it on LCD. The problem is PIC isn't receiveing anything.&#xA;So I picked up a osciloscope probe and the results are these:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/hcmmd.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The signal doesn't touch the GND!&#xA;Thats why PIC doesn't detect data arriving at RX pin, right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However if I disconnect FT232 TX pin from PIC RX pin, I get:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Gp0S1.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have both GND (ft232 and PIC) connected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions on how to solve this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks! &lt;/p&gt;&#xA;" OwnerUserId="1074" LastEditorUserId="1074" LastEditorDisplayName="" LastEditDate="2011-04-12T22:04:31.553" LastActivityDate="2011-05-13T18:04:01.733" Title="FTDI basic breakboard + PIC18F452" Tags="&lt;pic&gt;&lt;ftdi&gt;" AnswerCount="4" />
  <row Id="12961" PostTypeId="2" ParentId="12950" CreationDate="2011-04-12T22:10:07.957" Score="0" ViewCount="" Body="&lt;p&gt;If trying to minimize the current used by a shift register implemented in a CPLD, and if all you need is an output delayed by some number of clocks, you can minimize the number of latch transitions by keeping a count of the number of shifts and storing and accessing them round-robin fashion.  Depending upon the CPLD family used, this may allow one to store two or three bits per macrocell (at the cost of a few macrocells of overhead).  If, for example, each macrocell could, when used in register mode, have a combinatorial feedback term as well as an I/O pin input, one could hold one bit in the combinatorial output (used as a transparent latch), one in the latch, and one on the I/O pin (using a pin-keeper circuit).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the first cycle, sample the I/O pin from macrocell 3 (as the shift-register output), enable the driver on macrocell 2 (causing the registered value to be copied to the pin), and latch the input data into macrocell 1.  On the next cycle, sample macrocell 4, enable macrocell 3, and latch macrocell 2.  Then macrocell 5, 4, and 3, etc. wrapping when one reaches the end.  The result will be 3N-3 bits stored in N macrocells.  Note that some lower-pin-count CPLDs have internal pin drivers which are not brought out to the package; these can be used for holding data, but the only way I've found to program them is to claim to be using a larger-pin-count package.  I'm not sure whether the behavior of such non-bounded pins is guaranteed.  On the other hand, being able to store 3 bits per macrocell can be a lot nicer than storing one per.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-12T22:10:07.957" CommentCount="4" />
  <row Id="12962" PostTypeId="1" CreationDate="2011-04-12T22:19:49.653" Score="1" ViewCount="81" Body="&lt;p&gt;Hello! I'm really new to this electronics thing, but I was curious how to connect this &lt;a href=&quot;http://www.sparkfun.com/products/9944&quot; rel=&quot;nofollow&quot;&gt;High Altitude Balloon sensor board&lt;/a&gt; to &lt;a href=&quot;http://www.sparkfun.com/products/559&quot; rel=&quot;nofollow&quot;&gt;this modem&lt;/a&gt;. I want to think that it will connect easily and that the hardest part will be connecting the battery to both?&lt;/p&gt;&#xA;" OwnerUserId="3654" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-04-13T05:54:33.813" LastActivityDate="2011-04-13T07:59:04.220" Title="New to Electronics: How to connect these sparkfun sensors to this radio?" Tags="&lt;sensor&gt;&lt;radio&gt;&lt;modem&gt;" AnswerCount="1" />
  <row Id="12963" PostTypeId="2" ParentId="1842" CreationDate="2011-04-12T22:27:28.277" Score="0" ViewCount="" Body="&lt;p&gt;A friend in college stuck a standard temperature sensing IC into a metal tube, encapsulated it with epoxy, and then sealed the immersion end with high temperature gasket sealant.  Worked fine for his purposes, but he only needed it for a semester.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are industry standard thermocouples that are made for immersion.  You can buy them from industrial warehouses like &lt;a href=&quot;http://www.mcmaster.com/#thermocouples/=bukf6i&quot; rel=&quot;nofollow&quot;&gt;McMaster Carr&lt;/a&gt;.  If you plan on immersion for long-term use, that's probably the way to go.  The only drawback is that thermocouples don't give you a digital (or even linear analog) output like temperature IC's.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-04-12T22:33:41.560" LastActivityDate="2011-04-12T22:33:41.560" />
  <row Id="12964" PostTypeId="1" CreationDate="2011-04-05T22:00:40.840" Score="0" ViewCount="64" Body="&lt;p&gt;Hi good people,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a question regarding the programming of printing text on the screen after an LED lights up on a breadboard. Should we plug in the LED into the Arduino board or a regular breadboard? How do I get the Arduino to recognize that the LED has lit up? I am doing a physical game where if you touch the wire with a wand, a buzzer and a LED lights up, which is currently connected as a parallel circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you very much in advance!&lt;/p&gt;&#xA;" LastActivityDate="2011-04-13T02:47:43.797" Title="Using Arduino/Processing to print text on screen when an LED light up." Tags="&lt;java&gt;&lt;python&gt;&lt;processing&gt;&lt;arduino&gt;&lt;led&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="12965" PostTypeId="1" CreationDate="2011-04-12T23:05:03.987" Score="5" ViewCount="168" Body="&lt;p&gt;I have a large 2600W 230V -&gt; 28V transformer, and it makes a constant quite loud bzzzzzz sound while it works. Is there any way to make it more silent (other then buying an equivalent SMPS which I don't have money for now)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking for some quick and cheap ways to make it less loud. Wrapping the whole thing in a large towel might not be the best idea as it will probably prevent the transformer from cooling properly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why does it make that annoying sound anyway?&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-04-15T06:20:42.440" Title="how can I make a large transformer less loud?" Tags="&lt;transformer&gt;&lt;ac&gt;" AnswerCount="5" />
  <row Id="12966" PostTypeId="2" ParentId="12957" CreationDate="2011-04-12T23:24:03.637" Score="1" ViewCount="" Body="&lt;p&gt;Here's a development kit that looks interesting.  It includes everything needed to conduct thermoelectric generation experiments.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.customthermoelectric.com/powergen.html&quot; rel=&quot;nofollow&quot;&gt;http://www.customthermoelectric.com/powergen.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a little on the pricey side, so I'm going to keep looking for other options.  I wonder if I can just get the thermoelectric generator and pair it with a boost regulator to get a more useful voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- even the thermoelectric generator &lt;strong&gt;alone&lt;/strong&gt; is way too pricey.  I think I need to reword my question.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-12T23:24:03.637" CommentCount="3" />
  <row Id="12968" PostTypeId="2" ParentId="12965" CreationDate="2011-04-12T23:28:45.473" Score="10" ViewCount="" Body="&lt;p&gt;The sound is a result of the system creating large magnetic fields as a function of how it operates.  These fields are fluctuating, probably at 50Hz based on your input voltage but maybe 60Hz if your in the US.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These magnetic fields push and pull on components in the system, since perfect dampening isn't possible these components vibrate.  Some of what you hear isn't at 50/60Hz though, it is also harmonics of that frequency and interactions with other components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You definitely shouldn't do anything that will limit air flow or otherwise create a situation where the transformer could overheat.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can poke around a bit (carefully) and see if you can find a particular components or panel that is vibrating and try to use something to dampen the vibration.  High Temp Dampening material may be an option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, transformers of that power are basically impossible to silence.  The transformer core or the windings are probably vibrating and causing most of the noise.  At high enough power levels the iron core itself actually stretches and contracts as well causing vibration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some designs try to isolate the core to prevent vibrations transferring to other components but its not something you can likely fix in an after-market fashion.     &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-04-12T23:28:45.473" />
  <row Id="12969" PostTypeId="2" ParentId="12960" CreationDate="2011-04-12T23:35:20.647" Score="1" ViewCount="" Body="&lt;p&gt;Do you have the output driver enabled on the PIC UART RX pin? If it is driving a high level out, the voltage will go to 5V when the FTDI drives high, and something in the middle due to contention when the FTDI drives low.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(This may be a silly suggestion, depending on how the PIC UART configuration works, in which case I'm sorry.)&lt;/p&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-04-12T23:35:20.647" CommentCount="1" />
  <row Id="12970" PostTypeId="2" ParentId="12960" CreationDate="2011-04-12T23:46:05.527" Score="0" ViewCount="" Body="&lt;p&gt;Do you have the FT232 configured for TTL I/O?&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-04-12T23:46:05.527" CommentCount="1" />
  <row Id="12971" PostTypeId="2" ParentId="12965" CreationDate="2011-04-13T00:22:21.500" Score="4" ViewCount="" Body="&lt;p&gt;The explanation I've usually heard is 'loose laminations'; at least one of the laminations has room to vibrate with the time-varying magnetic field. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure what can be done about it. Some transformers have bolts through them to hold the laminations together, and it might be that tightening them would mitigate the buzzing somewhat. If there's an obvious gap somewhere, there might be some way to get some epoxy or something into the gap that would limit the freedom of movement of the adjacent laminations.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-13T00:22:21.500" />
  <row Id="12972" PostTypeId="1" AcceptedAnswerId="12998" CreationDate="2011-04-13T00:43:56.627" Score="2" ViewCount="153" Body="&lt;p&gt;Let's say I have a signal where 1v is digital 0, and 4v is digital 1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am a little lost how can I use PNP+NPN transistor to have +11..12(for 1) or -11..12V(for 0) output, provided that I have +12/-12 PSU? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE: This is for low-power MOSFET driver, which has to be done in discreet transistors.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="2062" LastEditorDisplayName="" LastEditDate="2011-04-14T04:27:04.330" LastActivityDate="2011-04-29T17:51:11.390" Title="Level shift + amplify" Tags="&lt;level-shifting&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="12973" PostTypeId="1" AcceptedAnswerId="12983" CreationDate="2011-04-13T00:55:51.103" Score="1" ViewCount="103" Body="&lt;p&gt;Just to be fair, this is a previous exam question and was an assignment question. I've already handed in the assignment and now I'm trying to see why I got it wrong -- to study for my final.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I fully understand how to find the 2's complement of a binary number, however, implementing a circuit to find the complement is driving me crazy. I'm given a shift register (that stores my binary number) and a flip flop (using D for simplicity). The process I follow for building sequential circuits is this:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I look at the question and derive a state diagram.&lt;/li&gt;&#xA;&lt;li&gt;From the state diagram, I draw a state table and find the input of my flip flops&lt;/li&gt;&#xA;&lt;li&gt;I use maps and stuff to finally build the circuit.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'm trying to visualize how to actually draw the state diagram for this complementer. I know it depends on the previous value and stuff, but if someone could take the time to explain in plain english how he/she would go about building the state diagram, I would be vey grateful.&lt;/p&gt;&#xA;" OwnerUserId="3619" LastEditorUserId="3619" LastEditorDisplayName="" LastEditDate="2011-04-13T01:33:09.537" LastActivityDate="2011-04-13T03:39:48.380" Title="Building a 2's complementer (need help visualising how to make a state diagram and table)" Tags="&lt;logic&gt;&lt;circuit-design&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="12974" PostTypeId="1" CreationDate="2011-04-13T01:08:40.397" Score="0" ViewCount="42" Body="&lt;p&gt;The SDram contain 8 Mbytes . This IC have 12 address (A0 - A11) all the 12 address bit are latched into the row address register by RAS. The IC has two input pin( spereate from the memory bytes  ) to select banks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;a) how many bank are in this IC? &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;(MY ANS : 4 banks) &lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;b) how many bytes are in each Bank?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;(MY ANS :2  bytes)&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;c) How many Row must be refresed on this SDRAM?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;(MY ANS : 1)&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;d)How many bits must be latched into the columen address register to select one of the memory bytes stored in the selected banks?&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;( MY ANS : 6 bits)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;any help would be appericated as i am flying blind here ( the book doesnt really explain it))&lt;/p&gt;&#xA;" OwnerUserId="3842" LastActivityDate="2011-04-13T01:08:40.397" ClosedDate="2011-04-13T01:58:18.257" Title="Question on memory" Tags="&lt;memory&gt;&lt;homework&gt;&lt;ram&gt;" CommentCount="3" FavoriteCount="1" />
  <row Id="12975" PostTypeId="2" ParentId="12973" CreationDate="2011-04-13T01:12:01.680" Score="-2" ViewCount="" Body="&lt;p&gt;state diagram is just the output to next &lt;/p&gt;&#xA;&#xA;&lt;p&gt;for a mod 3 count up counter the state diagram would be &lt;/p&gt;&#xA;&#xA;&lt;p&gt;000 -&gt; 001 -&gt; 010 -&gt; back to 000 &lt;/p&gt;&#xA;&#xA;&lt;p&gt;since it counts from 0 to 2 and reset on 3&lt;/p&gt;&#xA;" OwnerUserId="3842" LastActivityDate="2011-04-13T01:12:01.680" CommentCount="1" />
  <row Id="12976" PostTypeId="2" ParentId="12828" CreationDate="2011-04-13T01:15:33.083" Score="0" ViewCount="" Body="&lt;p&gt;connect J to high and a also a not gate whos input is connected to the J's input and output connect to K and leave the rest un touch or disable you get a D flip flop from JK flip flop&lt;/p&gt;&#xA;" OwnerUserId="3842" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-13T10:59:05.270" LastActivityDate="2011-04-13T10:59:05.270" CommentCount="1" />
  <row Id="12977" PostTypeId="2" ParentId="12973" CreationDate="2011-04-13T01:54:33.723" Score="0" ViewCount="" Body="&lt;p&gt;You know the 2's complement of each of the binary values 0000, 0001, 0010, 0011, ... 1111, right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are at least 2 ways to get the 2's complement of a number in a SIPO shift register:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;direct combinatorial logic. Take the 4 bits of the value, (simultaneously) invert all the bits and (simultaneously) add one. (I think a bunch of half-adder circuits are adequate here -- you can copy those out of your textbook, right?) There is no flip-flop or other internal state with this approach.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Serial incrementer. Starting with the least-significant bit, shift one bit at a time into a serial incrementer (a single half-adder and a single D flip flop). The serial incrementer generates (one bit at a time), from the current bit from the shift register and a Carry_in bit, the Carry_out bit and the Sum bit. Every clock cycle, the old Carry_out bit is latched into your D flip flop and becomes the new Carry_in bit, and the next bit comes out of the shift register. Then the half-adder combinational logic combines them to produce another Carry_out bit and Sum bit. (The flip-flop also needs some way to reset the carry bit it holds to &quot;1&quot; when starting over with the least-significant bit of a new number).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;When adding 2 bits, the Carry_out is 1 only when both bits are 1; otherwise the Carry_out is zero.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-13T01:54:33.723" CommentCount="1" />
  <row Id="12978" PostTypeId="1" AcceptedAnswerId="12981" CreationDate="2011-04-13T01:56:50.570" Score="1" ViewCount="40" Body="&lt;p&gt;I have NewSoftSerial.h and NewSoftSerial.cpp in the same folder as my sketch.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sketch is thus.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;NewSoftSerial.h&amp;gt;&#xA;&#xA;int incomingByte = 0;   // for incoming serial data&#xA;NewSoftSerial bluetooth(2, 3);&#xA;&#xA;void setup() {&#xA;  // put your setup code here, to run once:&#xA;  Serial.begin(9600);   // opens serial port, sets data rate to 9600 bps&#xA;  Serial.flush();&#xA;  //enter command mode&#xA;  Serial.println(&quot;$$$&quot;);&#xA;}&#xA;&#xA;void loop() {&#xA;  // send data only when you receive data:&#xA;  if (Serial.available() &amp;gt; 0) {&#xA;    //read the incoming byte:&#xA;    incomingByte = Serial.read();&#xA;&#xA;    //say what you got:&#xA;    Serial.print(&quot;I received: &quot;);&#xA;    Serial.println(incomingByte, BYTE);&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;What am I doing wrong that I get these errors?&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;trainremotesketch.cpp:1:27: error:&#xA;  NewSoftSerial.h: No such file or&#xA;  directory trainremotesketch:3: error:&#xA;  'NewSoftSerial' does not name a type&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="1227" LastActivityDate="2011-04-13T02:55:34.833" Title="Correct location of header file for arduino sketches" Tags="&lt;arduino&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="12979" PostTypeId="1" CreationDate="2011-04-13T02:32:33.660" Score="8" ViewCount="314" Body="&lt;p&gt;Way &lt;a href=&quot;http://www.eetimes.com/discussion/other/4024488/The-Two-Percent-Solution&quot; rel=&quot;nofollow&quot;&gt;back in 2002, Jim Turley&lt;/a&gt; mentioned that about 14% of all CPUs sold were &lt;a href=&quot;http://en.wikipedia.org/wiki/4-bit&quot; rel=&quot;nofollow&quot;&gt;4-bit&lt;/a&gt; CPUs, while about 8% of all CPUs sold were 32-bit CPUs.&#xA;(Most people I know were surprised that &lt;em&gt;any&lt;/em&gt; 4-bit CPUs were still being made, much less that they were doing so well).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's 2011 now -- Do 4-bit CPUs still outsell 32-bit CPUs and 64-bit CPUs combined in unit volume?&#xA;Where could I go to look up the latest numbers for sales by unit volume?&#xA;What are the top websites and magazines to learn more about modern 4-bit CPUs and their development tools?&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-14T13:28:07.383" Title="Do 4-bit CPUs still outsell 32-bit CPUs in unit volume?" Tags="&lt;microprocessor&gt;&lt;cpu&gt;&lt;development-tools&gt;" AnswerCount="4" CommentCount="5" FavoriteCount="1" />
  <row Id="12980" PostTypeId="2" ParentId="12964" CreationDate="2011-04-13T02:47:43.797" Score="1" ViewCount="" Body="&lt;p&gt;You don't want your Processing sketch to detect when the LED lights up.  Per your description, you are touching a wire with a wand.  This wire, which I will assume is some kind of switch, has to go into one of the pins on the Arduino that has been configured as an input.  Your Arduino code is then responsible for detecting a change on this input, and then will set the output bit high (or low, if that's how your circuit is set up) to turn on the LED and buzzer.  It is this change in the input that you will &lt;em&gt;also&lt;/em&gt; use to make the text appear on the screen.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-13T02:47:43.797" />
  <row Id="12981" PostTypeId="2" ParentId="12978" CreationDate="2011-04-13T02:55:34.833" Score="1" ViewCount="" Body="&lt;p&gt;The short answer is that library files go in the libraries folder in the Arduino root folder. A library should be in a sub-folder named for the class, and should contain a c++ implementation and header file.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;-Arduino&#xA;  |&#xA;  +--libraries  &#xA;       |&#xA;       +--NewSoftSerial&#xA;           |&#xA;           +--NewSoftSerial.cpp&#xA;           |&#xA;           +--NewSoftSerial.h           &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-04-13T02:55:34.833" />
  <row Id="12982" PostTypeId="1" AcceptedAnswerId="12984" CreationDate="2011-04-13T03:02:51.977" Score="5" ViewCount="62" Body="&lt;p&gt;I am trying to get a pushbutton working with the &lt;a href=&quot;http://www.arduino.cc/en/Tutorial/button&quot; rel=&quot;nofollow&quot;&gt;Arduino Button tutorial&lt;/a&gt; (and the example sketch). Unfortunately, I was not able to find a button like the one in the example and, instead, have a button with two pins from the bottom. (I don't know if this makes a difference - just trying to provide the information).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Below are pictures of my wiring of my breadboard and Arduino board. Am I doing something wrong here?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/xbc3e.jpg&quot; alt=&quot;Full View&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/lEsCh.jpg&quot; alt=&quot;Close-Up Arduino&quot;&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/bfhP5.jpg&quot; alt=&quot;Close-Up Breadboard&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3844" LastActivityDate="2011-04-13T03:33:38.843" Title="Pushbutton Not Working with Arduino" Tags="&lt;arduino&gt;&lt;breadboard&gt;&lt;wiring&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="12983" PostTypeId="2" ParentId="12973" CreationDate="2011-04-13T03:15:10.907" Score="4" ViewCount="" Body="&lt;p&gt;That link you gave says it all:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Hint: - 2’s complement of a number can&#xA;  be obtained by keeping the least&#xA;  significant bits as such until the&#xA;  first 1, and then complementing all&#xA;  bits&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&quot;example 001010 → 110110&quot; that is to say&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;   001010 -&amp;gt; flip bits -&amp;gt; 110101 -&amp;gt; add 1 -&amp;gt; 110110&#xA;msb     lsb             msb    lsb         msb    lsb&#xA;&#xA;&#xA;      msb    lsb&#xA;input   001010&#xA;output  110110&#xA;         &amp;lt;--- time&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;So there are two states - &quot;I haven't seen a one yet&quot; and &quot;I have seen a one previously&quot;. Given my state and my current input, my output and next state are fully determined.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If my current state is &quot;I haven't seen a one yet&quot; and my input is a 0, my output is a 0 and my next state is (still) &quot;I haven't seen a one yet&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If my current state is &quot;I haven't seen a one yet&quot; and my input is a 1, my output is a 1 and my next state is (changes to) &quot;I have seen a one previously&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If my current state is &quot;I have seen a one previously&quot; and my input is a 0, my output is a 1 and my next state is (still) &quot;I have seen a one previously&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If my current state is &quot;I have seen a one previously&quot; and my input is a 1, my output is a 0 and my next state is (still) &quot;I have seen a one previously&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Write that out as a truth table encoding &quot;I haven't seen a one yet&quot; as 0 and &quot;I have seen a one previously&quot; as 1, and you should be home free.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To &quot;wire it up&quot; the current data input bit and the current state go into logic that feeds the input to the D-flip flop and separate logic that feeds the input to the shift register, the D-flip-flop holds the &quot;state variable&quot;, and both are clocked by the data clock. And to be complete you need some kind of reset logic - left as an exercise to the reader. The &quot;current state&quot; is the output of the D-flip-flop, and next state is the input to it...&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;       +----------------------------+&#xA;       |                            |&#xA;       |  +---------+     +-----+   |&#xA;       +--+ Logic A +-----+ DFF +---+&#xA;Data-+-|--+         |     |     |&#xA;     | |  +---------+     | CLK |&#xA;     | |                  +--+--+&#xA;     | |                     |&#xA;     | |                     +--------Clock &#xA;     | |                  +--+--+&#xA;     | |  +---------+     | CLK |&#xA;     | +--+ Logic B +-----+     |&#xA;     +----+         |     | S R |&#xA;          +---------+     +-----+&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-04-13T03:39:48.380" LastActivityDate="2011-04-13T03:39:48.380" CommentCount="1" />
  <row Id="12984" PostTypeId="2" ParentId="12982" CreationDate="2011-04-13T03:33:38.843" Score="3" ViewCount="" Body="&lt;p&gt;[facepalm]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, in case it wasn't obvious from the above question, I am new to the electronics side of the house. In fact, one reason I bought an Arduino breadboard, so I could learn about hardware and become more comfortable with it. (As a software developer, I tend to avoid hardware altogether other than understanding the basics of what is going on in my computer. With the level of abstraction in software these days, that is fairly easy to do.) While I was first going to just delete the question (mostly out of embarrassment), I figured I would share what I just learned so it may help others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, the reason the above wasn't working is explained in &lt;a href=&quot;http://www.ladyada.net/learn/arduino/lesson3.html&quot; rel=&quot;nofollow&quot;&gt;this tutorial&lt;/a&gt; by Lady Ada (image reposted below):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/chaiY.jpg&quot; alt=&quot;Breadboard Broken Down&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the image, you can see that there is a series of metal strips underneath the board. The long ones (called rails) connect the outside rows. Because of their length, they can connect 25 (or more) column holes at a time. By doing this, it makes it easy to provide power and ground to an entire column and to eventually feed off of for the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The shorter strips (called rows) connect strips of 5 holes. This is where I went wrong. I made the (wrong) mistake of thinking the rows were longer and ran all the way across the row. However, if you look at the image below, you can see that strips only run halfway across the board. Because of this, in the setup I had above, anything connected on the A-E side was not &quot;talking to&quot; anything on the F-J side. So, I moved everything over to one side, and it all works well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope my newbie mistake helps someone else. Good luck!&lt;/p&gt;&#xA;" OwnerUserId="3844" LastActivityDate="2011-04-13T03:33:38.843" CommentCount="2" />
  <row Id="12985" PostTypeId="2" ParentId="12972" CreationDate="2011-04-13T03:47:23.053" Score="0" ViewCount="" Body="&lt;p&gt;That sounds like a TTL-to-RS232 level shifter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a &lt;a href=&quot;http://opencircuits.com/RS232#Level_Shifters&quot; rel=&quot;nofollow&quot;&gt;list of TTL-to-RS232 level shifters at Open Circuits&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In particular, you might be interested in 2 cheap MOSFETs and 2 resistors using the &lt;a href=&quot;http://www.botkin.org/dale/rs232_interface.htm&quot; rel=&quot;nofollow&quot;&gt;Dale N0XAS configuration&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-13T03:47:23.053" CommentCount="4" />
  <row Id="12986" PostTypeId="2" ParentId="12906" CreationDate="2011-04-13T04:00:18.043" Score="1" ViewCount="" Body="&lt;p&gt;Not directly the answer you were looking for, but some consoles, like the SNES, use a simple shift register system to pass data with fewer connectors.  Something like this may be easier than a N-conductor cable to each controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Info on pinning, etc: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://hackaday.com/2011/01/30/snes-arcade-controller/&quot; rel=&quot;nofollow&quot;&gt;http://hackaday.com/2011/01/30/snes-arcade-controller/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://pinouts.ru/Game/snescontroller_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;http://pinouts.ru/Game/snescontroller_pinout.shtml&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3002" LastActivityDate="2011-04-13T04:00:18.043" />
  <row Id="12987" PostTypeId="2" ParentId="12979" CreationDate="2011-04-13T04:09:07.970" Score="6" ViewCount="" Body="&lt;p&gt;The reason that 4 bit CPUs beat out the high end processors at the time was primarily due to their use in watches and clocks.  A 4 bit CPU, running in BCD mode (ie, each 4 bits was one 0-9 digit), is very optimal for clock and timing applications, and in volume they are nearly as cheap as transistors.  They are used in many other very low cost, very high volume applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know whether they still beat 32 bit CPUs, however the trend has been going up steeply for 32 bit processors due to cell phones and portable computing devices. I can't imagine that 4 bit CPUs are going up at the same rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;64 bit CPUs are still largely related to computers, and are probably still low volume enough that they have not yet eclipsed 4 bit CPU volume.&lt;/p&gt;&#xA;" OwnerUserId="161" LastActivityDate="2011-04-13T04:09:07.970" CommentCount="4" />
  <row Id="12988" PostTypeId="2" ParentId="12878" CreationDate="2011-04-13T04:26:59.790" Score="0" ViewCount="" Body="&lt;p&gt;Resistors by themselves are perfectly useful in debugging situations.  Ever not have a jumper wire handy so you can beep out a serial cable, or use it as a test lead?  I plug a resistor into the cable or breadboard and that becomes the means for connecting my multimeter.  Yes, I read on the same end of the wire, not from the other lead.  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this was a bit of a silly answer and it doesn't answer the OP's question in an EE/circuit analysis sense, but in all practicality, I have used resistors like this very often.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-13T04:26:59.790" />
  <row Id="12989" PostTypeId="2" ParentId="1842" CreationDate="2011-04-13T04:45:21.597" Score="0" ViewCount="" Body="&lt;p&gt;If you don't need too much precision and aren't dealing with very high temperatures, you can just use a thermistor instead. I recently did something similar: soldered a thermistor to a length of insulated wire, and covered the junction with silicone. Works great, and costs pennies.&lt;/p&gt;&#xA;" OwnerUserId="70" LastActivityDate="2011-04-13T04:45:21.597" />
  <row Id="12990" PostTypeId="1" CreationDate="2011-04-13T04:57:15.543" Score="5" ViewCount="164" Body="&lt;p&gt;The title says it all: &lt;strong&gt;&lt;em&gt;How many layers are there in a typical, current motherboard PCB?&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;" OwnerUserId="3845" LastEditorUserId="2118" LastEditorDisplayName="" LastEditDate="2011-04-13T06:38:05.913" LastActivityDate="2011-04-13T09:38:13.943" ClosedDate="2011-04-13T13:56:46.370" Title="How many layers are there in a typical, current motherboard PCB?" Tags="&lt;pcb-design&gt;" AnswerCount="2" />
  <row Id="12991" PostTypeId="2" ParentId="12955" CreationDate="2011-04-13T05:50:13.897" Score="1" ViewCount="" Body="&lt;p&gt;It is a matter of recalculating the image projection, and has been done in software, so the short answer is yes - it's possible. Whether it's worth it would require some more knowledge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An example is &lt;a href=&quot;http://hugin.sourceforge.net/tutorials/enfuse-360/en.shtml&quot; rel=&quot;nofollow&quot;&gt;using Hugin to remap fisheye images&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1181" LastActivityDate="2011-04-13T05:50:13.897" CommentCount="1" />
  <row Id="12992" PostTypeId="2" ParentId="12950" CreationDate="2011-04-13T05:51:51.040" Score="5" ViewCount="" Body="&lt;p&gt;Usually, it's best to assume the worst case switching pattern, and in this case it will be the easiest. I will define worst case as the input to the shift register changing every clock cycle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll break the power consumption down into several categories. This datasheet isn't exactly crystal clear, so I'm open to any corrections. These are also designed for very small capacitances, so if you have a very large load or long wires, you may be &quot;swamping&quot; these numbers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Assumptions:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;No current consuming load, like LEDs&lt;/li&gt;&#xA;&lt;li&gt;$V_{DD}$ is not given, so it will be kept as a variable, and the maximum value will be calculated.&lt;/li&gt;&#xA;&lt;li&gt;All traces are small enough to minimize capacitance&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Leakage/Quiescent Power&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Listed as 0.9uA at worst case, this power comes out to:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$500\times0.9\mu A \times V_{DD}=450\mu A\times V_{DD}$ (0.36mW to 1.49mW)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Internal (no load) Switching Power&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You won't find a figure for this in the datasheet. Instead, they give you the value of something called $C_{pd}$, which is the equivalent of the load capacitance for a given switching event. Depending on your $V_{DD}$, you will have different values of effective $C_{pd}$. &lt;a href=&quot;http://e2e.ti.com/support/logic/f/150/p/15632/60166.aspx&quot; rel=&quot;nofollow&quot;&gt;Texas Instruments describes&lt;/a&gt; $C_{pd}$ as:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The equivalent capacitance used to&#xA;  determine the no-load dynamic power&#xA;  dissipation per logic function for&#xA;  CMOS devices.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I find this to be somewhat ambiguous for a flip-flop since it isn't clear whether the Data input transitions count. I will assume that they do not. The values would increase by 50% if the D input should be included.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$500\times C_{pd}\times V_{DD}{}^2\times f=500\times 3.0pF \times V_{DD}{}^2\times 1.52MHz$ (1.46mW to 24.83mW)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Output Load Switching Power&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The next item is how much power is used to make all the output pins switch. At the bare minimum, each output will be driving one D input to the next flip-flop stage. Also, any board capacitance or additional loads will contribute to this power figure. Try to account for as much capacitance as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$C_{load}=\sum{Capacitance}=C_{Pin.D}+C_{wire}+?$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$C_{load}=1.5pF+3.5pF=5.0pF$ (For the sake of calculation)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then the output switching power is fairly easy to compute. If you have any appreciable capacitive load, your output switching power can skyrocket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$500\times C_{load}\times V_{DD}{}^2 \times f=500 \times 5.0pF \times V_{DD}{}^2 \times 760kHz$ (1.22mW to 20.69mW)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Total Power&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again, this depends on your load and power supply voltage. For a worst-case switching pattern, we can simply add the three power losses listed, and get the result. The minimum value uses a $V_{DD}$ of 0.8V, and the maximum value uses a $V_{DD}$ of 3.3V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$\sum{power}=P_{leak}+P_{internal}+P_{load}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For $V_{DD}=3.3V:\mbox{ }P_{total}=47.01mW\mbox{;    }I_{avg}=14.24mA$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For $V_{DD}=0.8V:\mbox{ }P_{total}=3.04mW\mbox{;    }I_{avg}=3.8mA$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Clocking Considerations&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is difficult to determine the peak clock current without knowing more variables, including the board layout and clock tree structure and clock buffer behavior and the power supply voltage. However, delivering a clock pulse simultaneously to 500 clock sinks will be difficult. To make it even harder, the gate you have chosen is fast, so that reduces your margin. After you build your device, test it at the coldest operational temperature with the highest power supply voltage allowed and see if the data makes it through ok. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The capacitance of all the clock pins is 750pF, but that doesn't account for any wiring load. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-04-13T05:51:51.040" CommentCount="7" />
  <row Id="12993" PostTypeId="2" ParentId="12979" CreationDate="2011-04-13T06:44:33.063" Score="4" ViewCount="" Body="&lt;p&gt;I doubt it. 32-bit has gained enormously in market share the last 5 years. More and more designs that in the past would have been done in 8-bit are now being done by 32-bitters, mainly ARM. Due to technological progression a 32-bit RISC controller doesn't need more real estate than an 8-bit CISC. That translates in lower cost.&lt;br&gt;&#xA;Same for 4-bitters. Most 4-bit controllers are older designs being produced in an older process (larger feature size). &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-13T06:44:33.063" CommentCount="3" />
  <row Id="12994" PostTypeId="2" ParentId="12990" CreationDate="2011-04-13T07:39:43.073" Score="1" ViewCount="" Body="&lt;p&gt;6 to 8 layers.........................&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-04-13T07:39:43.073" />
  <row Id="12995" PostTypeId="2" ParentId="12962" CreationDate="2011-04-13T07:59:04.220" Score="3" ViewCount="" Body="&lt;p&gt;Sparkfun has a &lt;a href=&quot;http://www.sparkfun.com/tutorials/185&quot; rel=&quot;nofollow&quot;&gt;tutorial&lt;/a&gt; that explains in greater detail how to use the High Altitude Sensing Board. Pay special attention to the section called &quot;Radio System&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the tutorial they use the &lt;a href=&quot;http://www.sparkfun.com/products/9411&quot; rel=&quot;nofollow&quot;&gt;XTend 900 1W RPSMA&lt;/a&gt; radio module instead of the one you selected. A brief look tells me they both speak UART to the uC (please verify before committing to either module), so it should be relatively straightforward to substitute one for the other. Keep in mind that:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;There might be things like differences in supply voltage -- be sure to check the design and read the datasheet for the parts in detail.&lt;/li&gt;&#xA;&lt;li&gt;It's possible/likely that they are controlled differently over that serial link, so firmware modifications might be in order.&lt;/li&gt;&#xA;&lt;li&gt;The part you chose is out of stock.&lt;/li&gt;&#xA;&lt;li&gt;The part you chose is less well-suited to this application because of issues of range and interference.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Happy flying!&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-04-13T07:59:04.220" CommentCount="1" />
  <row Id="12996" PostTypeId="2" ParentId="12870" CreationDate="2011-04-13T09:11:11.337" Score="0" ViewCount="" Body="&lt;p&gt;What you need to worry about is peak current draw.&lt;br&gt;&#xA;Car type batteries should be pretty good for this application, because they are rated to start a car, which needs a lot of current.&lt;br&gt;&#xA;Just make sure you have some nice fat wires between the battery and the amplifier.&lt;br&gt;&#xA;Also try not to discharge your car batteries all the way, it reduces their lifespan.&lt;/p&gt;&#xA;" OwnerUserId="3846" LastActivityDate="2011-04-13T09:11:11.337" />
  <row Id="12997" PostTypeId="2" ParentId="12990" CreationDate="2011-04-13T09:38:13.943" Score="4" ViewCount="" Body="&lt;p&gt;A low end motherboard may use 6 but the higher end ones I've seen 8 and 10 layers. &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-13T09:38:13.943" />
  <row Id="12998" PostTypeId="2" ParentId="12972" CreationDate="2011-04-13T10:01:59.703" Score="6" ViewCount="" Body="&lt;p&gt;Is this what you mean?&#xA;&lt;img src=&quot;http://i.imgur.com/QUA47.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-04-13T10:01:59.703" CommentCount="6" />
  <row Id="13000" PostTypeId="1" AcceptedAnswerId="13007" CreationDate="2011-04-13T12:19:26.243" Score="2" ViewCount="31" Body="&lt;p&gt;I have a ticketing device with an ARM9 CPU, more specifically a NS9750 module.&#xA;In the &lt;a href=&quot;http://www.digi.com/pdf/prd_mp_ns9750_ds.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;, its operating grades/ambient temperatures are listed as follows:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;125 MHz: 0 to 70ºC&lt;/li&gt;&#xA;&lt;li&gt;162 MHz: -40 to +85ºC&lt;/li&gt;&#xA;&lt;li&gt;200 MHz: 0 to 70ºC&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Why is the operating range much wider at 162MHz?&#xA;If it were linear, I would guess it has to do with the frequency of the crystal changing according to temperature. But this? No clue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, (this is important) what would happen if I were to run it at 200MHz in sub-zero ambient temperatures (up to -10ºC)? Worst case scenario. &lt;/p&gt;&#xA;" OwnerUserId="1124" LastActivityDate="2011-04-13T14:27:38.213" Title="NS9750 operating temperatures" Tags="&lt;temperature&gt;&lt;arm9&gt;" AnswerCount="1" CommentCount="7" />
  <row Id="13001" PostTypeId="1" AcceptedAnswerId="13002" CreationDate="2011-04-13T12:21:05.307" Score="0" ViewCount="123" Body="&lt;p&gt;Hello Folks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am getting some strange character displays on hyper terminal, after establishing communication with my GSM modem using the appropriate baud rate. When I type &quot;AT&quot;, it appears to get repeated  or display strange characters (as though the baud rate were not correct) on the hyper terminal screen as &quot;AATT&quot;. And all other AT commands get repeated as well, but what surprises me is that they all respond to the command. &quot;AATT&quot;(having typed &quot;AT&quot;) give me &quot;OK&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What could possibly be the problem? I am connecting the Modem to the DB9 using a MAX232. Below is the response&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;øatt&lt;br&gt;&#xA;OK&lt;br&gt;&#xA;aaütø&lt;br&gt;&#xA;OK&lt;br&gt;&#xA;aatt++ücnnmmiiþ?ø&lt;br&gt;&#xA;+CNMI: 1,0,0,0,0                &lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK&lt;br&gt;&#xA;aattþ+ccssccss??ø&lt;br&gt;&#xA;+CSCS: &quot;UCS2&quot;             &lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RING&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RING&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RING&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NO CARRIER&lt;/p&gt;&#xA;&#xA;&lt;p&gt;øat++ücnnmmii==11&amp;lt;,22&amp;lt;,00,,00,,00ø&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK&lt;/p&gt;&#xA;&#xA;&lt;p&gt;aattþ+ccssccss==&quot;&quot;GGêSMM&quot;&quot;ø&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Øaüt++ccmmögæf==11ø&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK&lt;/p&gt;&#xA;&#xA;&lt;p&gt;aatt&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK&lt;/p&gt;&#xA;&#xA;&lt;p&gt;aaüt++ccþnmii??&lt;/p&gt;&#xA;&#xA;&lt;p&gt;+CNMI: 1,2,0,0,0&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="3632" LastActivityDate="2011-04-15T11:04:48.347" Title="DB9 Serial communication" Tags="&lt;serial&gt;&lt;communication&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13002" PostTypeId="2" ParentId="13001" CreationDate="2011-04-13T12:25:54.210" Score="5" ViewCount="" Body="&lt;p&gt;You have local echo turned on in your terminal emulator. Turn it off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, turn off echo on your modem:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ATE0&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-04-13T12:25:54.210" CommentCount="4" />
  <row Id="13003" PostTypeId="1" CreationDate="2011-04-13T13:33:02.530" Score="2" ViewCount="64" Body="&lt;p&gt;I would like to build an electronic device that periodically checks some web internet API giving the result through a display.&#xA;This device should have:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Wireless shield to connect to the internet through some available connection (wep, wpa)&lt;/li&gt;&#xA;&lt;li&gt;LCD display to show the API call results to the user &lt;/li&gt;&#xA;&lt;li&gt;Some way to configure it remotely via http&lt;/li&gt;&#xA;&lt;li&gt;A speaker to alert the user with some rudimental bell sound (Optional)&lt;/li&gt;&#xA;&lt;li&gt;A second LED display to visually alert the user of some new fetched result (Optional)&lt;/li&gt;&#xA;&lt;li&gt;Battery operated (Optional)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I have found &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1295621061&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; project that looks good but does not give any insight about the used components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm just looking for some general input since I'm really a newbie in this field; is this project too complex or is it possible to realize it?&lt;br&gt;&#xA;Do you have any suggestion on which components do I need to realize something like this?&lt;/p&gt;&#xA;" OwnerUserId="2313" LastEditorUserId="2313" LastEditorDisplayName="" LastEditDate="2011-04-14T12:23:44.273" LastActivityDate="2011-04-14T12:23:44.273" Title="Device that fetches a web API call via wifi showing the result through a display" Tags="&lt;projects&gt;&lt;wifi&gt;&lt;display&gt;&lt;website&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13005" PostTypeId="1" AcceptedAnswerId="13012" CreationDate="2011-04-13T14:13:55.913" Score="3" ViewCount="101" Body="&lt;p&gt;Hi &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the licenses on &lt;a href=&quot;http://www.arm.com/products/processors/cortex-m/cortex-microcontroller-software-interface-standard.php&quot; rel=&quot;nofollow&quot;&gt;CMSIS&lt;/a&gt; is unclear when it comes to open source, &#xA;it is probably a violation to include the CMSIS is a open source project regardless if it using a GPL or BSD style license.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any CMSIS alternative out there for the Cortex M based MCU:s out there that is compatible with a BSD or Apache2.0 license?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or does anyone know if it is ok to include the CMSIS in a open source project?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2011-04-13T15:42:09.530" LastActivityDate="2011-04-13T17:04:48.867" Title="BSD style Open Source alternatives to CMSIS?" Tags="&lt;arm&gt;&lt;cortex-m3&gt;&lt;open-source&gt;&lt;cmsis&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="13006" PostTypeId="2" ParentId="12940" CreationDate="2011-04-13T14:17:02.460" Score="5" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;variable-length commands&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many people highly prefer fixed-length commands.&#xA;If you need to have variable-length commands, you need to think about:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Is it possible for accidental noise (or malicious pranksters) to generate something that will overflow my receive buffer?&lt;/li&gt;&#xA;&lt;li&gt;If a little bit of noise flips the high bit of the &quot;length&quot; field of a short packet (making it appear to be a long packet), does my system properly recover?&#xA;&lt;ul&gt;&#xA;&lt;li&gt;bad: the microcontroller stops everything, waiting for the rest of what it thinks is a &quot;long&quot; packet. Several days later, after many frantic attempts to send it messages saying &quot;deploy the airbags&quot;, &quot;lower the control rods&quot;, &quot;Open the pod bay doors, HAL&quot;, etc., it eventually gets all the bytes it expected, sees that the checksum fails, throws away this &quot;long packet&quot;, and starts working normally again.&lt;/li&gt;&#xA;&lt;li&gt;good: after a minute or some other reasonable time, the microcontroller times-out, erases everything in the command buffer (possibly discarding a few &quot;deploy the airbags&quot; messages after the length-corrupted message), and starts working normally again.&lt;/li&gt;&#xA;&lt;li&gt;good: The microcontroller immediately recognizes there is some error in the header (which includes the start byte, the length field, and the header's checksum), and immediately throws away that header and begins searching for the start byte again. The microcontroller immediately starts working normally again, recognizing the first valid command (the header's checksum is good, and also the data's checksum is good) after the corrupted command.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;li&gt;Does the microcontroller immediately send one ACK after it sees that the (final) checksum of the packet is good, and then execute the command, and finally send back a response to that command? Or is it better to send only the ACK or only the response? Which one makes it easier to debug?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;general protocol design tips&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many more or less simple &lt;a href=&quot;http://en.wikibooks.org/wiki/Serial_Programming/Forming_Data_Packets&quot; rel=&quot;nofollow&quot;&gt;protocols listed in the &quot;Serial Programming&quot; Wikibook&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're lucky, perhaps one of them is already perfect for your application.&#xA;Or at least close enough that it only requires a little tweaking to fit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pretty much everyone who successfully develops a new protocol goes through these phases:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;1 I may not know much, but reading other people's protocols gives me a headache. It looks like a bunch of unnecessary complexity. Let's dump all that stuff and build a nice, simple protocol.&lt;/li&gt;&#xA;&lt;li&gt;2 It's not working. Maybe if I add [feature 1] then it will work.&lt;/li&gt;&#xA;&lt;li&gt;3 Better, but still not working very well. Perhaps add [feature 2]?&#xA;...&lt;/li&gt;&#xA;&lt;li&gt;98 Finally it's working. I better write down who does what in my simple protocol so that if I need to switch to a different microcontroller or want to write a better program on the PC, I'll remember how it goes.&lt;/li&gt;&#xA;&lt;li&gt;99 Funny how my simple protocol takes so many pages to describe.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastEditorUserId="813" LastEditorDisplayName="" LastEditDate="2011-04-13T15:01:13.153" LastActivityDate="2011-04-13T15:01:13.153" CommentCount="1" />
  <row Id="13007" PostTypeId="2" ParentId="13000" CreationDate="2011-04-13T14:27:38.213" Score="2" ViewCount="" Body="&lt;p&gt;The first thing to mention is that these grades are all manufactured identically, and their performance is measured so that they can be put into one of these three bins. There might only be two real bins, but at this point it's speculation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The temperature plays a part in the speed as well - the higher the temperature, the lower the maximum clock frequency. At cold temperatures, the chip will run faster. Cold temperature failures are usually hard failures, in the sense that reducing clock frequency won't fix things. &quot;Worst case&quot; depends on your application. Here are a few scenarios that could happen. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The PLL could fail, and the chip would not operate.&lt;/li&gt;&#xA;&lt;li&gt;The memory could enter a failure mode (can't write or can't read reliably)&lt;/li&gt;&#xA;&lt;li&gt;Data corruption due to datapath hold-time violations&lt;/li&gt;&#xA;&lt;li&gt;Improper behavior due to hold-time violations&lt;/li&gt;&#xA;&lt;li&gt;Excessive EMI due to uncontrolled transitions in the output busses&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;There is a distinct possibility that they only qualified the industrial temperature range part because a wider specification means more time and money. In that case, all grades will probably work down to -40C. There may also be more durable packaging with the industrial range part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using this part for a hobby project, you may be comfortable &quot;risking it&quot;. You may also be able to qualify individual parts, but any manufactured device will be a tough sell without the wide temperature range chips.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-04-13T14:27:38.213" CommentCount="3" />
  <row Id="13008" PostTypeId="2" ParentId="13005" CreationDate="2011-04-13T14:36:11.703" Score="3" ViewCount="" Body="&lt;p&gt;I don't think there is a problem. The individual files have this statement:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;* ARM Limited (ARM) is supplying this software for use with Cortex-M &#xA; * processor based microcontrollers.  This file can be freely distributed &#xA; * within development tools that are supporting such ARM based processors.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and I don't see anything in the license that precludes it, either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a gcc directory in the CMSIS distribution, which implies that it can be supplied with open-source tools.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This statement:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(i) use and copy the CMSIS Specification for the purpose of developing, having developed, manufacturing,&#xA;having manufactured, offering to sell, selling, supplying or otherwise distributing products that comply with the&#xA;CMSIS Specification, provided that you preserve any copyright notices which are included with, or in, the CMSIS&#xA;Specification and provided that you do not use ARM's name, logo or trademarks to market such products;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;implies that you can incorporate CMSIS in your open source project.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-13T16:16:25.277" LastActivityDate="2011-04-13T16:16:25.277" CommentCount="3" />
  <row Id="13009" PostTypeId="1" AcceptedAnswerId="13056" CreationDate="2011-04-13T14:56:53.893" Score="0" ViewCount="164" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to measure a power device's voltage using TI's MSP430. The voltage source is connected to A1 (i.e. P4) and ground (i.e. P1) on the target board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the relevant code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ADC10CTL1 = INCH_1 + CONSEQ_0; //A1, single measurement&#xA;ADC10CTL0 = SREF_1 + ADC10SHT_3 + REFON + ADC10ON + ADC10IE + ADC10SR; //same as sample temperature sensor code&#xA;ADC10CTL1 &amp;amp;= ~ADC10DF; //setting binary format for ADC10MEM&#xA;ADC10CTL0 |= ENC + ADC10SC; //Sampling and conversion start&#xA; __bis_SR_register(CPUOFF + GIE);        // LPM0 with interrupts enabled&#xA;//read result in a uint8_t[2]&#xA;incomingVoltage[0] = ((uint8_t *)&amp;amp;ADC10MEM)[0]; //this is Least-significant-byte&#xA;incomingVoltage[1] = ((uint8_t *)&amp;amp;ADC10MEM)[1]; //this is most-significant-byte&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I am having following problems:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;I am printing the ADC10MEM contents on the AP, and I see that the leading 6 bits of ADC10MEM are all 1, instead of 0. I am unable to get the reason for the same.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If I consider only the last 10 bits of ADC10MEM, I can see that the value increases and decreases with rise and fall in voltage, but if I obtain Vin using the formula:&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;N = 1023 * ((Vin - VR- ) / (VR+ - VR-)), I do not get the correct value. (VR+ = 1.5V, VR- = 0V, as batteries power the target board) &#xA;N: the value in ADC10MEM, in decimal&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am unable to find where I am going wrong. Do I have to enable the pin for analog input (ADC10AE0 |= 0x02), and set direction (P4DIR &amp;amp;= 0x00) as well?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT 1: Vin Values:&lt;/strong&gt;&#xA;These are the ADC10MEM values I am getting, considering last 10 bits. &#xA;Following calculations use Vr+ = 1.5, Vr- = 0. &#xA;For input voltage 0.38V, N=1100000010 i.e. 770, and Vin=1.12. &#xA;For input voltage 0.5V, N=1101010110 i.e. 854, and Vin=1.25. &#xA;For input voltage 1V, N=1110101001 i.e. 937, and Vin = 1.37. &#xA;For input voltage 1.45V, N=1111011000 i.e. 984, and Vin = 1.44. &#xA;As I said, the value is increasing/decreasing with increase/decrease in input, but it isn't correct.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT 2: Interrupts:&lt;/strong&gt;&#xA;I am modifying the sample temperature sensor code. I see &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;__bis_SR_register(LPM3_bits+GIE);  // LPM3 with interrupts enabled &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;at the start of while(1) loop in linkTo()/main_ED.c, and there's &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; __bis_SR_register(CPUOFF + GIE);        // LPM0 with interrupts enabled&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;after 'sampling and conversion start' and before 'read results'&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT 3: Code based on msp430x22x4_adc_10_02.c from &lt;a href=&quot;http://focus.ti.com/mcu/docs/mcuflashtools.tsp?sectionId=95&amp;amp;tabId=1538&amp;amp;familyId=342&quot; rel=&quot;nofollow&quot; title=&quot;TI's code samples&quot;&gt;TI's code samples&lt;/a&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ADC10CTL1 = INCH_1 + CONSEQ_0;&#xA;ADC10CTL0 = SREF_1 + ADC10SHT_2 + REFON + ADC10ON + ADC10IE;&#xA;ADC10AE0 |= 0x02;&#xA;P4DIR |= 0x00;&#xA;ADC10CTL0 |= ENC + ADC10SC; //Sampling and conversion start&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I am getting similar values even with this code.&lt;/p&gt;&#xA;" OwnerUserId="3852" LastEditorUserId="3852" LastEditorDisplayName="" LastEditDate="2011-04-13T16:21:11.637" LastActivityDate="2011-04-14T15:35:05.193" Title="reading voltage using TI's MSP430 FF22x4" Tags="&lt;adc&gt;&lt;msp430&gt;&lt;voltage-measurement&gt;" AnswerCount="1" CommentCount="14" />
  <row Id="13010" PostTypeId="2" ParentId="12954" CreationDate="2011-04-13T16:03:18.693" Score="0" ViewCount="" Body="&lt;p&gt;You can run a lot of different OS on the Beagleboard, but set it up to do Multiboot is probably a little bit tricky.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the easiest is to have a couple of different SD cards and switch the card when you need another OS on the board.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2011-04-13T16:03:18.693" />
  <row Id="13011" PostTypeId="2" ParentId="2425" CreationDate="2011-04-13T16:05:20.543" Score="0" ViewCount="" Body="&lt;p&gt;Yes, I would recommend using a common mode choke.  It helps with EMI but as everyone has said, you will have a degraded signal.  If you don't need the choke, just add jumper wires.&lt;/p&gt;&#xA;" OwnerUserId="3853" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-04-13T16:29:39.923" LastActivityDate="2011-04-13T16:29:39.923" CommentCount="1" />
  <row Id="13012" PostTypeId="2" ParentId="13005" CreationDate="2011-04-13T17:04:48.867" Score="3" ViewCount="" Body="&lt;p&gt;From the reading the current &lt;a href=&quot;http://usbarm.googlecode.com/svn/trunk/Libraries/CMSIS/License.doc&quot; rel=&quot;nofollow&quot;&gt;CMSIS 2.0 license&lt;/a&gt;, it &lt;em&gt;seems&lt;/em&gt; the intention is not to prevent you from developing your software as open-source or otherwise, but more about covering ARM's ass. I.e. they want to make sure that you don't claim ownership of the code itself or any IP that might be in it, and also that it's used to develop code complying to CMSIS and not for some other purpose.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;&lt;p&gt;Subject to the provisions of Clauses 2, 3, 4 and 5, ARM hereby&#xA;  grants to you under any intellectual&#xA;  property that is (a) owned or freely&#xA;  licensable by ARM without payment to&#xA;  unaffiliated third parties and (b)&#xA;  either embodied in either or both the&#xA;  Source Code and Specification, as&#xA;  applicable, or Necessary (defined in&#xA;  Clause 4 below) to copy or implement&#xA;  an applications binary interface&#xA;  compliant with the Specification, a&#xA;  perpetual, non-exclusive,&#xA;  non-transferable, royalty free,&#xA;  worldwide licence to:&lt;br&gt;&#xA;  (i)       use and copy&#xA;  the Specification for the purpose of&#xA;  developing, having developed,&#xA;  manufacturing, having manufactured,&#xA;  offering to sell, selling, supplying&#xA;  or otherwise distributing products&#xA;  which comply with the Specification;&lt;br&gt;&#xA;  (ii)       use, copy, modify and&#xA;  sublicence the Source Code (in source&#xA;  or object code form) solely for the&#xA;  purpose of developing, having&#xA;  developed, manufacturing, having&#xA;  manufactured, offering to sell,&#xA;  selling, supplying or otherwise&#xA;  distributing products which comply&#xA;  with the Specification, provided that&#xA;  you preserve all copyright notices&#xA;  included in the Source Code.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;li&gt;&lt;p&gt;The Source Code and Specification are owned by ARM or its licensors and&#xA;  are protected by copyright laws and&#xA;  international copyright treaties as&#xA;  well as other intellectual property&#xA;  laws and treaties. The Source Code and&#xA;  Specification are licensed not sold.&#xA;  Except as specifically licensed in&#xA;  accordance with Clause 1, you acquire&#xA;  no right, title or interest in the&#xA;  Source Code and Specification or any&#xA;  intellectual property embodied&#xA;  therein. In no event shall the&#xA;  licences granted in accordance with&#xA;  Clause 1 be construed as granting you,&#xA;  expressly or by implication, estoppel&#xA;  or otherwise, a licence to use any ARM&#xA;  technology except the Source Code and&#xA;  Specification.  Except as provided in&#xA;  Clause 1, no right is granted to you&#xA;  to sublicense the rights granted to&#xA;  you under this Licence.&lt;/p&gt;&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That said, if you're still uncomfortable with those terms, you can just take the datasheet and make the headers yourself. Guys from &lt;a href=&quot;http://microbuilder.eu&quot; rel=&quot;nofollow&quot;&gt;microbuilder.eu&lt;/a&gt; has done just that, and released their &lt;a href=&quot;http://code.google.com/p/lpc1114codebase/&quot; rel=&quot;nofollow&quot;&gt;LPC1114 codebase&lt;/a&gt; under BSD.&lt;/p&gt;&#xA;" OwnerUserId="1082" LastActivityDate="2011-04-13T17:04:48.867" CommentCount="2" />
  <row Id="13013" PostTypeId="1" CreationDate="2011-04-13T19:32:45.300" Score="0" ViewCount="72" Body="&lt;p&gt;Is anybody familiar with manufacturers of GaN in Russia or Eastern Europe?&#xA;Also are there any MMIC Amplifiers made there (not necessarily GaN)?&lt;/p&gt;&#xA;" OwnerUserId="3854" LastActivityDate="2011-04-13T19:32:45.300" ClosedDate="2011-04-14T01:06:32.563" Title="GaN Transistors made in Russia" Tags="&lt;rf&gt;" CommentCount="11" FavoriteCount="1" />
  <row Id="13014" PostTypeId="1" AcceptedAnswerId="13016" CreationDate="2011-04-13T19:41:39.927" Score="0" ViewCount="74" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have constructed a half-wave dipole antenna for the 433MHz frequency.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using the antenna to receive in a simple setup, where I measure the output power of a transmitter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Everywhere I read about the antenna is stated that the impedance is about 75 ohms, so if the antenna was used to transmit, I can be seen as a 75 ohms load, and therefore is simple to match. Ok, I got this... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I cannot find how to match the antenna, when using it as a receiver?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it just a source with 75 ohms output impedance, or is a dipole not good for receiving?&lt;/p&gt;&#xA;" OwnerUserId="3041" LastActivityDate="2011-04-13T22:11:10.450" Title="Dipole Antenna as Receiver" Tags="&lt;antenna&gt;" AnswerCount="1" />
  <row Id="13015" PostTypeId="1" AcceptedAnswerId="13028" CreationDate="2011-04-13T21:03:21.603" Score="1" ViewCount="67" Body="&lt;p&gt;Hi all,&#xA;I'm working on a project about electricity pricing, and need to understand the following: to keep the room at confortable temperature (70 degree, for example), does the amount of energy consumed by the AC grow linearly as the outside air temperature rises over the same length of time (a day, say)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="3855" LastActivityDate="2011-04-14T13:15:21.177" Title="Temperature vs AC energy consumption" Tags="&lt;power&gt;&lt;energy&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="13016" PostTypeId="2" ParentId="13014" CreationDate="2011-04-13T22:11:10.450" Score="2" ViewCount="" Body="&lt;p&gt;Dipoles are excellent for receiving. It would appear as a 75 ohm source, as you guessed. Impedance matching is usually more important for transmitters because of the levels of power involved. Mismatched impedance with receivers doesn't tend to melt anything, because there are only micro-watts of power involved, but you may get more signal into your receiver's front end if you match the antenna.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-13T22:11:10.450" CommentCount="2" />
  <row Id="13017" PostTypeId="2" ParentId="12955" CreationDate="2011-04-13T22:53:32.940" Score="0" ViewCount="" Body="&lt;p&gt;You might want to email Garrett Brown, the inventor of Steady-Cam and Acadamy Award winner. He knows everything there is to know about cameras and he super nice guy to boot!&lt;/p&gt;&#xA;" OwnerUserId="3836" LastActivityDate="2011-04-13T22:53:32.940" />
  <row Id="13018" PostTypeId="2" ParentId="13003" CreationDate="2011-04-13T23:00:46.383" Score="1" ViewCount="" Body="&lt;p&gt;Take a look at the &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en548037&quot; rel=&quot;nofollow&quot;&gt;Microchip Mutimedia Expansion Board&lt;/a&gt;. It has a &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Integrated 802.11 module&lt;/li&gt;&#xA;&lt;li&gt;a 3.2 inch QVGA touchscreen&lt;/li&gt;&#xA;&lt;li&gt;Full TCP/IP stack and lots of examples, including GET/POST, SNMP, etc.&lt;/li&gt;&#xA;&lt;li&gt;Headphone and Line out jacks with 24-bit audio codec&lt;/li&gt;&#xA;&lt;li&gt;5 user-controlled LEDs&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;It has many other features, but those are the ones you requested. You also need to get a &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2637#hardware&quot; rel=&quot;nofollow&quot;&gt;PIC32 Starter Kit&lt;/a&gt;. There are 3 types available, a basic (50 dollars US), one with USB (55 dollars US) and one with Ethernet and USB (72 dollars US). They plug into the multimedia board, which is $250.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are only building 1, this is probably the easiest route, even if it is over $300.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are planning on building lots, then maybe you can get some ideas on how to create your device from this setup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Microchip TCP/IP stack is very easy to use and the demo programs they have can be easily modified to do what you are interested in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using an Arduino and necessary shields is a good way to go, but this is another option.&lt;/p&gt;&#xA;" OwnerUserId="2150" LastEditorUserId="2150" LastEditorDisplayName="" LastEditDate="2011-04-13T23:08:11.900" LastActivityDate="2011-04-13T23:08:11.900" CommentCount="1" />
  <row Id="13019" PostTypeId="1" AcceptedAnswerId="13029" CreationDate="2011-04-13T23:40:06.730" Score="1" ViewCount="140" Body="&lt;p&gt;I have an &lt;a href=&quot;http://www.sparkfun.com/products/9950&quot; rel=&quot;nofollow&quot;&gt;Arduino Uno&lt;/a&gt;. Pins 2 and 3 are connected to pins UART_TX and UART_RX, respectively, on &lt;a href=&quot;http://www.sparkfun.com/products/10253&quot; rel=&quot;nofollow&quot;&gt;a bluetooth SMD module&lt;/a&gt;. I have the following sketch running on the Uno.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;NewSoftSerial.h&amp;gt;&#xA;&#xA;NewSoftSerial bluetooth(2, 3);&#xA;byte b;&#xA;&#xA;void setup() {&#xA;  // put your setup code here, to run once:&#xA;  Serial.begin(9600);   // opens serial port, sets data rate to 9600 bps&#xA;  Serial.flush();&#xA;  bluetooth.begin(9600);&#xA;  //enter command mode&#xA;  bluetooth.println(&quot;$$$&quot;);&#xA;  Serial.println(&quot;setup complete.&quot;);&#xA;}&#xA;&#xA;void loop() {&#xA;  // if theres data from the bluetooth module&#xA;  if (bluetooth.available()) {&#xA;    //echo it to the serial monitor&#xA;    Serial.print(&quot;bt module said:&quot;);&#xA;    Serial.println((char)bluetooth.read(),BYTE);&#xA;  }&#xA;  //if theres data from the serial monitor&#xA;  if (Serial.available()&amp;gt;0) {&#xA;    b=Serial.read();&#xA;    //echo it back to the serial monitor&#xA;    Serial.print(&quot;serial said:&quot;);&#xA;&#xA;    Serial.println(b,BYTE);&#xA;    //send it to the bluetooth module&#xA;    bluetooth.print(b,BYTE);&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I see the following on the serial monitor.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;setup complete.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I expected to see&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;setup complete.&lt;br&gt;&#xA;  bt module said:C&lt;br&gt;&#xA;  bt module said:M&lt;br&gt;&#xA;  bt module said:D&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Why am I not getting a response from the bluetooth module? Am I using &lt;a href=&quot;http://arduiniana.org/libraries/newsoftserial/&quot; rel=&quot;nofollow&quot;&gt;NewSoftSerial&lt;/a&gt; incorrectly? Is the bluetooth module wired backwards? Are there examples communicating with a bluetooth module from an Arduino board?&lt;/p&gt;&#xA;" OwnerUserId="1227" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-04-14T00:42:31.847" LastActivityDate="2011-04-14T04:01:41.973" Title="Communicate with bluetooth module from Arduino Uno - Take Two" Tags="&lt;arduino&gt;&lt;serial&gt;&lt;bluetooth&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13020" PostTypeId="2" ParentId="13015" CreationDate="2011-04-14T00:03:37.157" Score="1" ViewCount="" Body="&lt;p&gt;I am not an expert on this at all, but my assumption would be that it is not linear at all. There are many factors that are going to determine a relation between outside air and energy consumption. Here are a few items to think about:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;There is a large amount of energy required to start up AC units. Ideally you would start up less often, but this means either running longer resulting in larger temperature swings or running the motor at a slower speed.&lt;/li&gt;&#xA;&lt;li&gt;The energy efficiently for the motor for the fans is non-linear. (Like if you were to run it at a slower speed)&lt;/li&gt;&#xA;&lt;li&gt;The energy passed through the walls may be non-linear, and different per material. Like sheetrock, plaster, brick, wood, insulation, etc.&lt;/li&gt;&#xA;&lt;li&gt;Psychological aspects. What I mean by this is people tend to allow the temperature in the house to be higher when it is warmer outside. This is due to the act of the air blowing (which it will be doing more often when its hot outside) makes people more comfortable regardless of temperature. This causes the &quot;comfortable&quot; temperature to change.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-04-14T00:10:01.037" LastActivityDate="2011-04-14T00:10:01.037" />
  <row Id="13021" PostTypeId="2" ParentId="2425" CreationDate="2011-04-14T00:12:23.333" Score="1" ViewCount="" Body="&lt;p&gt;If your product sits &quot;floating&quot; on the USB cable, the common-mode choke is probably not necessary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if your device is electrically attached through any other paths that could form a loop back to where your USB cable originates, you will have a potential for inductively picking up or generating noise that can affect the performance of your product, or other product attached to it.  At that point, you will need the choke.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-14T00:12:23.333" />
  <row Id="13022" PostTypeId="2" ParentId="12965" CreationDate="2011-04-14T00:20:41.530" Score="2" ViewCount="" Body="&lt;p&gt;Is the transformer mounted? If you temporarily unmount it, is it still noisy?  It could be that what it is mounted to is acting as a sounding board -- you might be able to use rubber insulators or otherwise modify the mount to reduce noisy generation.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-14T00:20:41.530" CommentCount="1" />
  <row Id="13023" PostTypeId="1" CreationDate="2011-04-14T00:36:29.077" Score="3" ViewCount="98" Body="&lt;p&gt;Hi folks,&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Summary&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;I'm trying to find a light that can be connected straight into a network via WIFI or LAN Cable (cat5, etc..).&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Details&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;We have a server which handles automated builds and deployment for our website development. If the automated build (aka our continuous integration) failed, we would like to be told.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So - traditionally, people have been using lights or monitors to visually display the status of their builds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;green - last build worked 100% fine.&#xA;yellow - in progress&#xA;red - last build failed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I was hoping to find a light (bulb/lava lamp/whatever) that can be connected to the network and I can hack up a program to then tell that light to display as red/yellow/green, depending on the state of the build.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So - are there any lights that can be connected to a network, preferably via WIFI but via cable is fine. I'm assuming they will also need a power plug to get power .. unless maybe the lan cable can supply power, if the light doesn't require too much?&lt;/p&gt;&#xA;" OwnerUserId="3858" LastActivityDate="2011-04-16T09:40:40.723" Title="Are there any Wifi/Networked Lights available to purchase?" Tags="&lt;light&gt;&lt;wifi&gt;&lt;network-interface&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="13024" PostTypeId="1" AcceptedAnswerId="13026" CreationDate="2011-04-14T00:39:24.707" Score="2" ViewCount="107" Body="&lt;p&gt;Is there a device which acts like an accelerometer but only measures absolute velocity? I could integrate the accelerometer's output but errors quickly accumulate and cause problems. Preferably the device is available in a MEMS based chip and is low cost. I could use a GPS device (and am currently, with success), but this is expensive, bulky, and requires a GPS link, which is not available in all circumstances.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-14T08:39:14.737" Title="A speedometer like chip" Tags="&lt;accelerometer&gt;&lt;velocity&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="13025" PostTypeId="2" ParentId="12965" CreationDate="2011-04-14T01:22:57.113" Score="3" ViewCount="" Body="&lt;p&gt;You might not be able to do much about the noise directly but you can always redirect the noise such that you hear less of it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lower frequency noises are more difficult to absorb, they tend to travel right through the material. Thus wrapping a towel around it won't do much. They are however easily reflected by a dense hard material. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Build a sturdy sound wall around one side and that should redirect the noise somewhere else while keeping good airflow to the transformer. &lt;/p&gt;&#xA;" OwnerUserId="1319" LastEditorUserId="1319" LastEditorDisplayName="" LastEditDate="2011-04-14T01:30:11.413" LastActivityDate="2011-04-14T01:30:11.413" />
  <row Id="13026" PostTypeId="2" ParentId="13024" CreationDate="2011-04-14T01:35:02.707" Score="10" ViewCount="" Body="&lt;p&gt;There is no such thing as absolute velocity; velocity is always relative to something.  Velocity cannot be measured internally to a chip (as can acceleration).  You must have external input, such as radio references a la GPS or sensors detecting changes in other phenomena external to the chip and its vehicle.&lt;/p&gt;&#xA;" OwnerUserId="3769" LastActivityDate="2011-04-14T01:35:02.707" />
  <row Id="13027" PostTypeId="2" ParentId="12875" CreationDate="2011-04-14T02:00:17.540" Score="1" ViewCount="" Body="&lt;p&gt;I never liked the Art of Electronics myself; it's encyclopaedic for sure, but getting knowledge out of it has always been rough for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I was learning this stuff, Forrest M. Mims III and Robert Grossblatt were two authors whose works I devoured. Mims' Getting Started In Electronics is geared toward younger people, but it's very approachable and easy to understand.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-04-14T02:00:17.540" CommentCount="0" />
  <row Id="13028" PostTypeId="2" ParentId="13015" CreationDate="2011-04-14T03:36:23.703" Score="2" ViewCount="" Body="&lt;p&gt;The short answer is no. It's not linear.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the long answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are three kinds of heat transfer: conduction, convection, and radiation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Conduction&lt;/strong&gt; means heat transfer due to physical contact. In the case of a building, the conduction &lt;em&gt;is&lt;/em&gt; linear-- the amount of energy that leaks into a building is linearly proportional to the difference between the temperature outside and the temperature inside. The constant of proportionality is called the thermal conductivity of the material the heat is passing through. For well-insulated buildings, a great deal of the heat comes in through the windows, as glass is a poor insulator. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Convection&lt;/strong&gt; means heat transfer due to bulk fluid flow, like wind. Unfortunately, this is hard to model accurately for buildings. It's safe to say that in most places on Earth, for most buildings, convection heats up your building, but not as much as conduction. Still, it screws up your model. It's particularly a problem with cold winds in the winter, where the temperature difference can be higher than in the summer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For buildings, &lt;strong&gt;radiation&lt;/strong&gt; means the sun. The effects of radiation are roughly proportional to the projected area of your windows over the course of the day. Unfortunately, the contribution to heating from radiation can be greater than that from conduction, especially for a well-insulated house with a lot of windows facing toward the equator. This is where the real nonlinearity comes in-- total irradiance is difficult to measure without considering the geometry of the windows and modeling cloud cover as a function of time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To add a few numbers-- on a hot night (say, 80 F), you can cool a two-car garage with 1000 W air conditioner (which is actually providing you around 3000 W of cooling, see &lt;a href=&quot;http://en.wikipedia.org/wiki/Heat_pump&quot; rel=&quot;nofollow&quot;&gt;heat pumps&lt;/a&gt;). At noon, the sun averages around 1000 W per square meter, so if your garage has some large windows pointed toward the sun (say, skylights on a roof angled toward the equator), your AC unit can easily be overwhelmed by radiation alone.&lt;/p&gt;&#xA;" OwnerUserId="712" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-04-14T03:45:39.230" LastActivityDate="2011-04-14T03:45:39.230" />
  <row Id="13029" PostTypeId="2" ParentId="13019" CreationDate="2011-04-14T04:01:41.973" Score="1" ViewCount="" Body="&lt;p&gt;Did you see in the datasheet page 5 that you need some resistors on the RX line in the note &quot;R1, R2 required if MCU logic=5V&quot; the maximum rating on inputs to the devide is 3.4V. It's not inconceivable you fried the receiver... the Arduino is a 5V logic device.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-04-14T04:01:41.973" CommentCount="1" />
  <row Id="13030" PostTypeId="2" ParentId="13023" CreationDate="2011-04-14T04:07:51.277" Score="1" ViewCount="" Body="&lt;p&gt;I assume that you're ready to write code to make such a device.  Even if there was something as simple as a networkable LED, you'd have to write custom code to parse the build output file so you could choose a color to display.  And since you want this for a build server, I'm already assuming that you can write code.  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first product that came to mind was a thing I remember from a couple of years ago -- it looked like a rabbit and the ears would go up or down, and change color.  I think it was supposed to report the general mood of the internet, at least for things that interest you, like stocks and sports.  Stocks up == good == green == ears up.  Favorite team loses == bad == red == ears down.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I couldn't find that product anymore, so the next most logical, hackable, open &quot;network LED&quot; is the Chumby / Chumby One.  You can &lt;a href=&quot;http://www.chumby.com/pages/chumby_one&quot; rel=&quot;nofollow&quot;&gt;read about it here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, why don't you use the free network LED, which is basically a monitor hooked up to a cheap PC that meta refreshes the results page from your integration server?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- so my joke about a &quot;free network LED&quot; wasn't well received.  :)  If you want to keep development of this to a minimum, then two good options are Arduino / Netduino and mbed.  Arduino + ethernet shield make it super simple to get your embedded device on the network and is outlined &lt;a href=&quot;http://arduino.cc/en/Tutorial/WebClient&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  mbed is another candidate and looks pretty easy to get hooked up to your network.  There are examples like &lt;a href=&quot;http://mbed.org/users/no2chem/notebook/ethernet-testing/&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; and &lt;a href=&quot;http://www.youtube.com/watch?v=CQm2B6BqU1I&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; for getting the networking going.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-04-14T13:13:34.783" LastActivityDate="2011-04-14T13:13:34.783" CommentCount="4" />
  <row Id="13031" PostTypeId="2" ParentId="12979" CreationDate="2011-04-14T04:31:30.297" Score="0" ViewCount="" Body="&lt;p&gt;The size of the chip has less to do with its word-length than it has to do with its architecture. For example, an 8-bit CISC-like machine would probably suck up more real-estate than a 32-bit RISC-like machine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As others have commented, 4-bit CPUs are still being sold and still find application in all kinds of things from air-conditioning units through to microwave ovens and maybe some toasters. However, they will be slowly phased out as the cost of 32-bit machines are now as low as the smaller machines (due to economies of scale).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, if you are working on a new design, it would be a good idea to build it on a newer chip. The slight difference in cost today, may well disappear in a few years time.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-04-14T04:31:30.297" />
  <row Id="13032" PostTypeId="2" ParentId="11443" CreationDate="2011-04-14T05:39:14.733" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.winbond-usa.com/products/Nexflash/pdfs/datasheets/W25Q80_16_32a.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; for the part you listed states that a 24-bit address should be written after the 0x90 code. Then the 2-byte Manufacturer and Device codes can be read. So insert 3 write instructions and it should work.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;pc.printf(&quot;response from sending 90h: %d\r\n&quot;, spi.write(0x90));&#xA;pc.printf(&quot;response from sending 00h: %d\r\n&quot;, spi.write(0x00)); //Address 23..16&#xA;pc.printf(&quot;response from sending 00h: %d\r\n&quot;, spi.write(0x00)); //Address 15..8&#xA;pc.printf(&quot;response from sending 00h: %d\r\n&quot;, spi.write(0x00)); //Address 7..0&#xA;pc.printf(&quot;response from sending 00h: %d\r\n&quot;, spi.write(0x00)); //Manufacturer ID&#xA;pc.printf(&quot;response from sending 00h: %d\r\n&quot;, spi.write(0x00)); //Device ID&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If you get inconsistent results, you may want to do your writes in a loop, then print when finished. I'm not sure how the printf IO affects the mbed SPI implementation timing, but if you get gaps between byte writes, that may affect how the flash part responds.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;unsigned char command[6] = {0x90, 0x00, 0x00, 0x00, 0x00, 0x00};&#xA;unsigned char response[6];&#xA;&#xA;for(int i=0; i&amp;lt;6; i++)&#xA;{&#xA;    response[i] = spi.write(command[i]);&#xA;}&#xA;&#xA;pc.printf(&quot;Manufacturer ID: %d\r\n&quot;, command[4]);&#xA;pc.printf(&quot;Device ID: %d:\r\n&quot;, command[5]);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;You also have instruction 90h in your source, but your diagram is for instruction 9Fh. Just changing the instruction may allow your original code to work.&lt;/p&gt;&#xA;" OwnerUserId="2150" LastActivityDate="2011-04-14T05:39:14.733" />
  <row Id="13033" PostTypeId="1" CreationDate="2011-04-14T08:12:04.647" Score="0" ViewCount="91" Body="&lt;p&gt;I know that stepper motor structure is more diffrent.I have msp430 launchpad.&#xA;I know that i m guessing that i can't solder it to pins.Can I use it with breadboard,uln2003a and a potentiometer.This stuff is suitable with launchpad&#xA;I m going to use unipolar stepper motor.&lt;/p&gt;&#xA;" OwnerUserId="3426" LastActivityDate="2011-04-14T14:34:12.113" Title="Msp430 Stepper Motor" Tags="&lt;msp430&gt;&lt;stepper-motor&gt;" AnswerCount="1" />
  <row Id="13034" PostTypeId="2" ParentId="13024" CreationDate="2011-04-14T08:39:14.737" Score="1" ViewCount="" Body="&lt;p&gt;As has already been said, there is no such thing as absolute velocity, however STM make a 3D motion sensing chipset (iNEMO). &lt;a href=&quot;http://www.st.com/internet/evalboard/product/250367.jsp&quot; rel=&quot;nofollow&quot;&gt;Details of the evaluation kit here&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="400" LastActivityDate="2011-04-14T08:39:14.737" />
  <row Id="13035" PostTypeId="1" AcceptedAnswerId="13049" CreationDate="2011-04-14T09:25:43.693" Score="3" ViewCount="115" Body="&lt;p&gt;I have a testbench and a verilog modules. I want to write ouput of the testbench to a file anmed as output.txt. While doing this job, I want to use $monitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible ? If yes, can you give me pseudo code of that segment ?&lt;/p&gt;&#xA;" OwnerUserId="3192" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-05-13T02:39:04.340" LastActivityDate="2011-05-13T02:39:04.340" Title="how to write output of the monitor to a file" Tags="&lt;verilog&gt;&lt;hdl&gt;" AnswerCount="2" />
  <row Id="13036" PostTypeId="2" ParentId="9915" CreationDate="2011-04-14T10:33:44.153" Score="0" ViewCount="" Body="&lt;p&gt;There is a second source of 2n7000 whith &quot; KL &quot; at the end of the reference made from VISHAY and is totally protected.&lt;/p&gt;&#xA;" OwnerUserId="3863" LastActivityDate="2011-04-14T10:33:44.153" CommentCount="1" />
  <row Id="13037" PostTypeId="2" ParentId="12929" CreationDate="2011-04-14T10:40:04.817" Score="1" ViewCount="" Body="&lt;p&gt;Off the top of my head, the following could be classed as 'Optical Chips':&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;strong&gt;CCD&lt;/strong&gt; (&lt;a href=&quot;http://en.wikipedia.org/wiki/Charge-coupled_device&quot; rel=&quot;nofollow&quot;&gt;Charge-Coupled Device&lt;/a&gt;) - sensor used in modern still/video cameras.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;DMD/DLP&lt;/strong&gt; (&lt;a href=&quot;http://en.wikipedia.org/wiki/Digital_Micromirror_Device&quot; rel=&quot;nofollow&quot;&gt;Digital Micromirror Device&lt;/a&gt;/Digital Light Processor) - chip used in modern high-brightness video projectors.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;Opto Isolators&lt;/strong&gt; - for communicating information whilst providing complete electrical isolation.&lt;/li&gt;&#xA;&lt;li&gt;Even perhaps some &lt;strong&gt;LED&lt;/strong&gt; (Light Emitting Diode) packages, particularly the higher powered ones, could be considered 'chips'.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Wikipedia gives you a starting point for all of these (a couple of links included, search wikipedia for the rest).&lt;/p&gt;&#xA;" OwnerUserId="3861" LastActivityDate="2011-04-14T10:40:04.817" CommentCount="1" />
  <row Id="13038" PostTypeId="1" CreationDate="2011-04-14T11:05:34.480" Score="5" ViewCount="100" Body="&lt;p&gt;Hello, I am trying to modify a SWR meter (&lt;a href=&quot;http://www.mondoplast.ro/Reflectometru-powermetru-Performer-DF2469-pg_ft-3597&quot; rel=&quot;nofollow&quot;&gt;http://www.mondoplast.ro/Reflectometru-powermetru-Performer-DF2469-pg_ft-3597&lt;/a&gt;) and add a new scale (now it has 200W/50W and 20W/5W) for 2W/0.5W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have made some measurements and it does not work exactly how I expected so I am stuck...&#xA;The SWR meter is a cross needle Ampere meter (100uA) with 1,8k ohms internal resistor. In the directional coupler is only 1 shunt resistor of 150Ohms.(the schematic for the coupler is similar with the one in the left (&lt;a href=&quot;http://f1frv.free.fr/main3h_SWR_Bridges_fichiers/DET_bridge_R2.png&quot; rel=&quot;nofollow&quot;&gt;http://f1frv.free.fr/main3h_SWR_Bridges_fichiers/DET_bridge_R2.png&lt;/a&gt;))&#xA;The scale selector adds a capacitor between the FWD/REF line to the ground in the peak position:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FWD:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;200W 220uF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;20W 100uF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;REF:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;50W 100uF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5W 47uF&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(here I expect this to be for the average not for peak... )&#xA;And also adds in the FWD/REF line a series resistor:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FWD:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;200W - 145,5K&lt;/p&gt;&#xA;&#xA;&lt;p&gt;20W - 33,4K&lt;/p&gt;&#xA;&#xA;&lt;p&gt;REF:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;50W - 54,5k&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5W - 12,5k&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Actually in the schematic there is a fixed resistor an a variable one in series, here is the measured value of the resulted resistor)&#xA;What values of resistors should I put for 2W/0,5W. (I expected  that the resistor to variate linear eg. 200W 145,5K 20W 14,55k)&#xA;Can you please help me or at least send me to a documentation of how a SWR circuit/bruene bridge works.&#xA;Thank you,&#xA;Bogdan&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/n4uNm.png&quot; alt=&quot;schematic image at stated URL&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3864" LastEditorUserId="1609" LastEditorDisplayName="" LastEditDate="2011-04-14T17:52:19.793" LastActivityDate="2011-05-24T15:28:24.670" Title="Modify SWR meter" Tags="&lt;swr-meter&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="13039" PostTypeId="2" ParentId="13035" CreationDate="2011-04-14T11:17:31.620" Score="4" ViewCount="" Body="&lt;p&gt;use $fmonitor:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;integer f;&#xA;initial begin&#xA;  f = $fopen(&quot;output.txt&quot;);&#xA;  $fmonitor(f, &quot;time=%5d, v=%h\n&quot;, $time, vv);&#xA;  #1000 &#xA;  $fclose(f);&#xA;  $finish;&#xA;end&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3190" LastEditorUserId="3192" LastEditorDisplayName="" LastEditDate="2011-04-14T14:20:48.067" LastActivityDate="2011-04-14T14:20:48.067" />
  <row Id="13040" PostTypeId="2" ParentId="12012" CreationDate="2011-04-14T11:20:15.500" Score="2" ViewCount="" Body="&lt;p&gt;If you are not trying to be accurate (as you allude to) but just continuously rotate something you could probably just use a normal DC motor with rubber drive wheel (have you considered using the belt/motor from an old vinyl record player turntable?).  If you need slow rotation you may need a gearbox (model shop, old toy, meccanno, lego?), or need to PWM (Pulse Width Modulation) drive the motor (remote control car motor controller?).  Another idea is an old variable speed electric drill/powertool, you could rig the trigger to a specific speed fairly easily (cable tie?).  This will all depend on how quick-and-dirty vs robust/reliable/long-term you are aiming for and whether you need variable speed and/or direction control (things you don't specify).  Stepper will give you the most control, but is probably the most complicated.  Match the complexity of your solution to the complexity of your problem. :)&lt;/p&gt;&#xA;" OwnerUserId="3861" LastActivityDate="2011-04-14T11:20:15.500" />
  <row Id="13041" PostTypeId="1" CreationDate="2011-04-14T11:57:24.037" Score="9" ViewCount="280" Body="&lt;p&gt;Hi, this is a bit of a long shot but I'm hoping someone has access to the full data sheet for one of the chips listed in the title, and can tell me what combination of VBUS_IN and resistors on ID_CON will make it trigger the BOOT pin on the chip. Unfortunately Fairchild will not release the full data sheet for these chips (I have asked), and only &lt;a href=&quot;http://www.fairchildsemi.com/ds/FS%2FFSA9280A.pdf&quot; rel=&quot;nofollow&quot;&gt;an abbreviated version&lt;/a&gt; (PDF link) is available on the web. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Long story: the FSA9480 chip is used on some Samsung phones to detect various accessories using sensing resistors on the ID pin of the USB port. We've already made a lot of progress through info from the phone's Android kernel source. Now we're &lt;a href=&quot;http://forum.xda-developers.com/showthread.php?t=1018862&quot; rel=&quot;nofollow&quot;&gt;trying to force the phone's CPU into a boot recovery mode&lt;/a&gt; that will make it load an external bootloader from the serial port, and it looks like the BOOT pin on the FSA9480 might do this, but we can't figure out how to trigger it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far I've tried &lt;a href=&quot;http://forum.xda-developers.com/showthread.php?t=820275&quot; rel=&quot;nofollow&quot;&gt;all the resistors on the known list&lt;/a&gt; without power connected to the USB port, and all of the resistor values that produced serial output again with power on the USB port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt; We're working on the theory that &lt;a href=&quot;http://forum.xda-developers.com/attachment.php?attachmentid=433248&amp;amp;d=1288824267&quot; rel=&quot;nofollow&quot;&gt;this schematic&lt;/a&gt; from the service manual shows a signal going from the FSA9480 BOOT pin to a signal named BOOT_MODE, which in any sane world would go the the application processor chip's OM5 pin. But we don't have the full schematic to prove it, and we don't have the internal details of the FSA9480 to show how that pin gets triggered. You would think it would be the resistors with BOOT_ON in their names (like RID_FM_BOOT_ON_UART), but apparently not. Or maybe it is, but the BOOT_MODE signal doesn't go to the right place. Either way the FSAx80 data sheet would confirm it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've &lt;a href=&quot;http://forum.xda-developers.com/showthread.php?t=1018862&amp;amp;page=3#23&quot; rel=&quot;nofollow&quot;&gt;reverse-engineered the startup and bootloader download code&lt;/a&gt; in the application processor's (Samsung S5PC110) internal ROM, and worked out that if we succeed we should see the first byte of the bootloader download protocol on the serial port. Instead we are getting the output of the primary bootloader which is being loaded from NAND, which indicates a normal boot.&lt;/p&gt;&#xA;" OwnerUserId="3862" LastEditorUserId="3862" LastEditorDisplayName="" LastEditDate="2011-04-14T22:56:21.950" LastActivityDate="2011-05-02T17:24:57.170" Title="How do I make the Fairchild FSA9280/FSA9480/FSA880 BOOT pin trigger? (Samsung Galaxy S)" Tags="&lt;usb&gt;&lt;serial&gt;&lt;usb-device&gt;&lt;mobile&gt;" AnswerCount="0" CommentCount="13" FavoriteCount="3" />
  <row Id="13042" PostTypeId="1" AcceptedAnswerId="13057" CreationDate="2011-04-14T13:11:08.887" Score="2" ViewCount="114" Body="&lt;p&gt;I am thinking of the issue that &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;the TEPCO electric transmission&#xA;  networks cannot be taken over by other&#xA;  electric companies because of&#xA;  frequency difference.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;TEPCO is the electric company having the nuclear crisis.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why cannot generators having different frequencies supply in the same transmission line?&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Edit&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;I think most electric equipments can work at either 50 OR 60 Hz. So what is the problem?&lt;/p&gt;&#xA;" OwnerUserId="3866" LastEditorUserId="3866" LastEditorDisplayName="" LastEditDate="2011-04-14T15:11:21.133" LastActivityDate="2011-04-14T22:00:57.927" Title="why cannot generators having different frequencies supply in the same transmission line?" Tags="&lt;frequency&gt;&lt;transformer&gt;&lt;generator&gt;" AnswerCount="5" />
  <row Id="13043" PostTypeId="2" ParentId="13015" CreationDate="2011-04-14T13:15:21.177" Score="0" ViewCount="" Body="&lt;p&gt;I go with linear for first order.  Cooling must make up the heat gain, for conduction heat is like current and temperature difference like voltage.  And there is a ohm's law.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The efficiency of air conditioners depends on temperature difference because it is a heat engine and this falls as the temperature difference increases, since this is on top of the linear demand above it is a diviation from linear.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that the effect of start up currents, overall, is small.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just my opinion with out running any calculations.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-04-14T13:15:21.177" />
  <row Id="13044" PostTypeId="2" ParentId="12979" CreationDate="2011-04-14T13:22:31.670" Score="2" ViewCount="" Body="&lt;p&gt;That 2002 statistic might have been a bit surprising, but it wasn't some two bit factoid from USAToday.  The author was once an editor for the Microprocessor Report.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you think back to the technology and prices of the mid-1990's (when many design decisions affecting volumes in the early 2000's were made), a lot of embedded applications were simple and well-suited to 4-bit and 8-bit processors.  (Heck, it's still true today for most of the &quot;invisible&quot; processors in use - like the LCD thermostat, or the microwave, or the smart dimming dome light in your car.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem with 16-bit and 32-bit processors back then was that it was needlessly more expensive to provide memory for them.  RAM was not cheap back then.  And wider RAM was much more expensive for the same capacity. (In fact, the early PC's were quasi-16-bit machines.  They had an 8-bit external memory bus.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fast forward to this decade, and one key change is that the newer embedded processors have plenty of embedded RAM on-board; thanks in large part to improved semiconductor processes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without the external RAM penalty, it's just as easy to grab a 32-bit processors for a new design.  And the volumes are there that you don't pay much more for the 32-bit.  In fact, for bang-per-buck, the older 8-bit processors are awful for new designs.  And, I can't even imagine anyone today would even bother with datasheets for a 4-bit processor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, have 4-bit processors died?  Given that even soft core processors are 8-bits, I'd say yes.  The fun question today is what the split is between 8-bits, 32-bits, and 64-bits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Circling back to the original question - I used to see &quot;processor yearbooks&quot; that detailed processor offerings from different manufacturers - and they were broken into groups by processor bit size, and whether they were MCU or CPU's.  I haven't seen one of those things lately -- I think there's far more players in the market today, many of them from Asia-centric companies that have little or no sales presence in the U.S.  Additionally, &quot;processors&quot; may be hidden inside FPGA's so that it would be hard to count them.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-04-14T13:28:07.383" LastActivityDate="2011-04-14T13:28:07.383" />
  <row Id="13045" PostTypeId="2" ParentId="11293" CreationDate="2011-04-14T13:39:13.740" Score="0" ViewCount="" Body="&lt;p&gt;A microcontroller is generally a single-chip solution to provide computation and peripheral functions.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A microprocessor provides the computation functions but not the peripheral functions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Peripheral functions can be as simple as having a few bits of simple I/O; or might include sophisticated counters and timers, video display, ethernet, motor control, audio and video codec, et cetra.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a given architecture (say the x86-based CPU's and MCU's), the &quot;computational&quot; coding will be identical.  But how you access peripheral functions will vary, and so you will have very different hardware-specific coding to do, based on how the peripheral functionality is implemented on your target hardware.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-14T13:39:13.740" />
  <row Id="13046" PostTypeId="2" ParentId="13042" CreationDate="2011-04-14T13:41:21.183" Score="2" ViewCount="" Body="&lt;p&gt;It's a lot more than just the transformers. It's turbines, control systems, meters, loads... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;TEPCO's sole generating source isn't Fukushima - there's &lt;a href=&quot;http://en.wikipedia.org/wiki/TEPCO&quot; rel=&quot;nofollow&quot;&gt;additional nuclear in Niigata&lt;/a&gt; as well as fossil fuel generation. You can't mix frequencies unless the whole system is changed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also according to Wikipedia, &lt;a href=&quot;http://en.wikipedia.org/wiki/Mains_electricity&quot; rel=&quot;nofollow&quot;&gt;there are several HVDC stations&lt;/a&gt; that interconnect between the 50Hz and 60Hz grids through an intermediary conversion to HVDC. Inefficient, sure, but at least there is some interconnection. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-14T13:41:21.183" CommentCount="2" />
  <row Id="13047" PostTypeId="1" AcceptedAnswerId="13052" CreationDate="2011-04-14T13:53:33.803" Score="2" ViewCount="155" Body="&lt;p&gt;How to find out what is the internal resistance of a voltmeter? I imagine the higher the better - it'll have less influence on the measured circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the approximate internal resistance of cheap DMM on the voltmeter setting? Do more expensive multimeters have better (higher) internal resistance? Is there a significant difference in internal resistance of the voltmeter between a Fluke and a 5$ DMM?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the best method to measure the internal resistance of a voltmeter?&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-04-27T17:56:50.230" Title="how to measure the internal resistance of a voltmeter?" Tags="&lt;multimeter&gt;&lt;voltage-measurement&gt;&lt;internal-resistance&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="13048" PostTypeId="2" ParentId="13042" CreationDate="2011-04-14T14:08:25.423" Score="3" ViewCount="" Body="&lt;p&gt;A voltage phase mismatch from one generator and the power grid would mean a voltage difference between the grid and the generator during different parts of the phase(s). This voltage difference means current would flow to/from the grid and the generator, causing resistive heating in the lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I don't know all the mechanical and electrical consequences of trying to run a spinning turbine in reverse, but I don't think it would be good.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2011-04-14T14:08:25.423" CommentCount="2" />
  <row Id="13049" PostTypeId="2" ParentId="13035" CreationDate="2011-04-14T14:09:06.733" Score="2" ViewCount="" Body="&lt;p&gt;I have wrote Makefile to meet that desire ;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;default :&#xA;iverilog -o verilog_testbench lab_work.v test_bench.v &#xA;odt  :&#xA;./verilog_testbench &amp;gt; simulation.odt&#xA;txt  :&#xA;./verilog_testbench &amp;gt; simulation.txt&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I have tried  Taniwha 's answer before, but It did not work. So, I have wrote Makefile. &lt;/p&gt;&#xA;" OwnerUserId="3192" LastEditorUserId="3192" LastEditorDisplayName="" LastEditDate="2011-04-15T06:36:21.747" LastActivityDate="2011-04-15T06:36:21.747" />
  <row Id="13050" PostTypeId="1" AcceptedAnswerId="13059" CreationDate="2011-04-14T14:17:26.720" Score="1" ViewCount="73" Body="&lt;p&gt;I am developing a portable device embedding sensors, Bluetooth, MCUs etc.. At present I'm at a prototype stage and I'm starting thinking about production.&#xA;What kind of certification steps do I need to follow in order to produce and sell it?&lt;/p&gt;&#xA;" OwnerUserId="2285" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-04-14T14:39:57.287" LastActivityDate="2011-04-14T17:18:02.647" Title="Certifications and requirements" Tags="&lt;bluetooth&gt;&lt;prototyping&gt;&lt;certification&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="13051" PostTypeId="2" ParentId="13033" CreationDate="2011-04-14T14:34:12.113" Score="1" ViewCount="" Body="&lt;p&gt;I wouldn't solder a motor directly to the output pins of a Launchpad.  You won't be able to source enough current for the stepper -- at least not any hobbyist stepper I've used before.  You can use it with a breadboard, but you won't be able to use the male header because the pins rows are spaced too far apart on the Launchpad to be used with a normal breadboard, unless you use &lt;em&gt;two&lt;/em&gt; separate breadboards, one for each side of the Launchpad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my project, I'm using the female header option with jumper wires to hook up the Launchpad to peripherals.  So far it seems to work just fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ULN2003A should work fine for now if you don't exceed its current rating, so check the datasheet.  I vaguely recall that it has provisions for external flyback diodes as well, and I feel you'll want to add those if possible.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-14T14:34:12.113" CommentCount="2" />
  <row Id="13052" PostTypeId="2" ParentId="13047" CreationDate="2011-04-14T14:50:24.443" Score="7" ViewCount="" Body="&lt;p&gt;Apply a known voltage over a series resistor. This resistor in combination with the internal resistance will form a voltage divider. Say you apply 5V over a 1M series resistor, and the DMM shows it as 2.5V, then the internal resistance is 1M.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Now that I reread it, I guess it's not completely unambiguous. By &quot;applying a voltage over a series resistor&quot; I meant you connect the + to the resistor and the - to the ref. input of the DMM.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-14T17:40:22.707" LastActivityDate="2011-04-14T17:40:22.707" CommentCount="1" />
  <row Id="13053" PostTypeId="2" ParentId="13042" CreationDate="2011-04-14T14:51:25.883" Score="2" ViewCount="" Body="&lt;p&gt;All power line components should work fine at both 50 and 60Hz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand the whole electrical grid has to be precisely synchronized so there is no easy way to suddenly connect several circuits together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is no difference between connecting:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;two out-of-phase generators&lt;/li&gt;&#xA;&lt;li&gt;24V DC to 12V DC&lt;/li&gt;&#xA;&lt;li&gt;a supply directly to the ground (a short circuit).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="659" LastEditorUserId="659" LastEditorDisplayName="" LastEditDate="2011-04-14T14:59:26.347" LastActivityDate="2011-04-14T14:59:26.347" />
  <row Id="13054" PostTypeId="2" ParentId="13050" CreationDate="2011-04-14T15:18:01.097" Score="2" ViewCount="" Body="&lt;p&gt;It depends where in the world you are trying to sell your device. In Europe for example, there are numerous EEC directives affecting the sale of electronic goods, the most well known being :-&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Electromagnetic Compatability Directive (EMC)&lt;/li&gt;&#xA;&lt;li&gt;Low Voltage Directive (LVD)&lt;/li&gt;&#xA;&lt;li&gt;Waste Electrical and Electronic Equipment (WEEE)&lt;/li&gt;&#xA;&lt;li&gt;Restriction of Hazardous Substances Directive (RoHS)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="2234" LastEditorUserId="2234" LastEditorDisplayName="" LastEditDate="2011-04-14T15:26:35.113" LastActivityDate="2011-04-14T15:26:35.113" CommentCount="2" />
  <row Id="13055" PostTypeId="2" ParentId="12875" CreationDate="2011-04-14T15:20:29.427" Score="2" ViewCount="" Body="&lt;p&gt;I don't think there is any such guide. At least if there is one, it will be limited to a few basic uses of the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The difference is that if you are using, e.g., a programming library, all you really need to understand is the API. The library is designed to do a few well-constrained things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, a component like a transistor is also designed to do a single thing: a bipolar transistor controls the output (Collector) current by varying the base current. However, that single &quot;feature&quot; has huge amounts of leverage and hides a lot of complexity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The same transistor can act like a switch: give it plenty of base current and it will saturate and conduct a lot of current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a proportional valve: give it varying, small amounts of base current, and you will get a varying, larger amount of current conducted at collector-emitter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a temperature sensor: give it a small, fixed amount of base current and the voltage from base-emitter will vary depending on the temperature. As a result, the current at the collector-emitter junction will also vary according to temperature.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My point is that the only useful &quot;user guide&quot; to a transistor requires knowing its fundamental properties. You may not need to remember the complete Ebers-Moll model, but you do need to understand the fundamental properties if you're going to use the device to its fullest.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Failing that, if you have a specific question, just ask. Lots of smart people here: someone will be able to help you.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-04-14T15:20:29.427" CommentCount="1" />
  <row Id="13056" PostTypeId="2" ParentId="13009" CreationDate="2011-04-14T15:35:05.193" Score="0" ViewCount="" Body="&lt;p&gt;This is the code that worked:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ADC10CTL1 = INCH_1 + CONSEQ_0;&#xA;ADC10CTL0 = SREF_1 + ADC10SHT_2 + REFON + ADC10ON + ADC10IE;&#xA;for (countDown = 240; countDown &amp;gt; 0; countDown--); //delay to allow references to settle&#xA;ADC10AE0 |= 0x02;&#xA;ADC10CTL0 |= ENC + ADC10SC; //Sampling and conversion start&#xA;__bis_SR_register(CPUOFF + GIE);        // LPM0 with interrupts enabled&#xA;result = ADC10MEM; //result is a int&#xA;incomingVoltage[0] = result&amp;amp;0xFF; //incoming voltage is an array of uint8_t, send it to AP&#xA;incomingVoltage[1] = (result&amp;gt;&amp;gt;8)&amp;amp;0xFF; //this and previous line is similar to temperature sensing code sample&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Thanks for the help!&lt;/p&gt;&#xA;" OwnerUserId="3852" LastActivityDate="2011-04-14T15:35:05.193" />
  <row Id="13057" PostTypeId="2" ParentId="13042" CreationDate="2011-04-14T15:44:39.633" Score="6" ViewCount="" Body="&lt;p&gt;Equipment designed to work with one frequency power will not necessarily work with another frequency. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Transformers designed to work with 60Hz will have lower ratings when working at 50Hz (Important for power distribution and individual devices)&lt;/li&gt;&#xA;&lt;li&gt;The speed (RPM) of AC motors is tied directly to the power line frequency.&lt;/li&gt;&#xA;&lt;li&gt;AC Wall clocks wouldn't work :)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The combination of 50Hz and 60Hz would cause generators to fight eachother&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;See the plot of both 50Hz and 60Hz superimposed from &lt;a href=&quot;http://www.wolframalpha.com/input/?i=sin%2850x%29-sin%2860x%29%2C+sin%2850x%29%2C+sin%2860x%29&quot; rel=&quot;nofollow&quot;&gt;Wolfram&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;The blue plot shows the difference. Where the function is large, the generators are fighting eachother (Big Boom!)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-04-14T15:44:39.633" />
  <row Id="13058" PostTypeId="2" ParentId="13047" CreationDate="2011-04-14T15:46:12.473" Score="0" ViewCount="" Body="&lt;p&gt;This value should be stated in the manual of the DMM. My UT-60 is specified to have $&amp;gt; 10\,\rm{M\Omega}$.&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-04-14T15:46:12.473" CommentCount="2" />
  <row Id="13059" PostTypeId="2" ParentId="13050" CreationDate="2011-04-14T15:54:27.993" Score="7" ViewCount="" Body="&lt;p&gt;The more I learn about regulatory compliance, the more I'm convinced that I don't know anything.  This is a giant maze of international laws that is difficult to navigate.  What I wrote below is just a rough guide, to be taken with a grain of salt.  But my last paragraph is very important:  You need professional help (not mental help, that I know of anyway).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a variety of regulatory standards that you must adhere to.  Most of them are going to center around EMI, Electrical Safety, and Materials Safety. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;EMI, or Electro-Magnetic-Interference, is concerned with what interference your box is spitting out and receiving either through the air or through the AC power cable.  Spitting out would be EMI Emissions, and receiving would be EMI Susceptibility.  Emissions is how your box effects other boxes, and susceptibility is more like will your box work when someone is on their cell phone near by.  A somewhat related aspect of this is your boxes tolerance to static electricity zaps.  In the USA, this falls under the domain of FCC compliance testing.  In the EU, it's part of the &quot;CE&quot; approval process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Electrical Safety is concerned with things like:  will your box burst into flames or electrocute the user.  In the USA, this is normally certified by an independent lab, like UL or TUV-- I'm not sure about other countries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Materials Safety is mostly about the use of lead, but does involve a whole list of bad things.  In the USA, I'm not even sure there is anyone who cares what's in the device (as long as it isn't medical or food related).  In other countries it's referred to as RoHS or other names, but I'm not sure if that falls under &quot;CE approval&quot; or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The important thing to know is this:  In the practical sense, you cannot self-certify.  Doing this compliance testing involves lots of expensive equipment and knowledge and it's simply not practical to do it yourself.  Fortunately, there are companies that specialize in this.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Find such a company, and use their expertise to not only perform the tests, but to give you solid information on the whole regulatory compliance testing/reporting process.  In many cases these companies will also file all the paperwork with the various government groups, etc.  These companies are often well versed in not only your countries regulations, but also international regulations.  I'll warn you that this process is not cheap, and not fast.  But that's the cost of doing business.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-14T15:54:27.993" CommentCount="1" />
  <row Id="13060" PostTypeId="2" ParentId="13050" CreationDate="2011-04-14T16:22:29.913" Score="1" ViewCount="" Body="&lt;p&gt;There are also the ETSI requirements. I think they are required for Bluetooth in the EU.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-14T16:22:29.913" />
  <row Id="13061" PostTypeId="2" ParentId="12950" CreationDate="2011-04-14T16:23:03.430" Score="1" ViewCount="" Body="&lt;p&gt;W5VO gave an excellent answer covering exactly what you asked.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, because I'm obsessed with driving LEDs and usually plan to drive them with a large shift register, let's see where that goes:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Driving 500 LEDs fairly dimly at 2 mA, requires 1000 mA = 1 A of current from your power supply; at 3.0 V that's 3 W of power (3000 mW) -- the power required by all of your shift registers and clock drivers combined is insignificant compared to that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alas, the output voltage appears to be inadequate to turn on blue or white LEDs.&#xA;But many LED displays only use red and green LEDs, and it's perfectly adequate for that.&#xA;Alas, the maximum &quot;recommended&quot; output current at is only 4 mA (either sink or source) -- enough to get a red or green LED to turn on, but not enough to give full brightness.&#xA;Sometimes other kinds of chips can drive an LED brighter, but allow the output voltage to drift into the range where it is no longer guaranteed to be recognized as a &quot;1&quot; or &quot;0&quot;.&#xA;At Vcc = 3 V, this chip has an input range of Vih_min of 2.0 V and Vil_max of 0.9 V, so it can properly recognize the output of another identical chip even when that other chip is fully loaded with 4 mA, since that other chip gives a &quot;high&quot; output Voh of at least 2.55 V, and a &quot;low&quot; output Vol of less than 0.45 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;The&quot; clock signal in many systems, including yours, drives hundreds of devices.&#xA;While I suppose one could use one really strong buffer to drive all of them,&#xA;many designers limit their fanout to a much smaller number.&#xA;I generally limit my fanout to around 20 gate inputs connected to any gate output.&#xA;When everything is together on one compact PCB, we make a &lt;a href=&quot;http://en.wikipedia.org/wiki/clock_tree&quot; rel=&quot;nofollow&quot;&gt;clock tree&lt;/a&gt; --&#xA;but it makes no sense to use 500 of that chip on a compact PCB rather than driving those 500 LEDs with 8 bit shift registers such as 74AHC595 or one of the other alternatives mentioned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm assuming you are driving these LEDs in a very long, narrow strip,&#xA;each LED driven by its own flip-flop.&#xA;So for something like this I would buffer the clock signal every 19 flip-flops (or perhaps some more convenient number like 16 or 10 or 8),&#xA;so the main clock that drives the string drives only the first buffer&#xA;(which requires insignificant amounts of power),&#xA;and each buffer drives 19 or fewer flip-flops and the next buffer in the chain&#xA;(which also requires insignificant amounts of power per gate, but over the course of all 500 flip-flops and roughly 50 buffers, it adds up).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At 1.5 pF of input capacitance per gate that's 500*1.5 = 750 pF of gate capacitance for the flip-flops, and roughly 1/10 of that for the clock buffers. At guestimated (?) 4 pF of trace capacitance per gate we have 2,000 pF of trace capacitance.&#xA;The (dynamic) power drawn charging and discharging those capacitances is P = fCV^2, so at 1.54 MHz and 3.0 V we require (estimated) (1.54 MHz)(2825 pF)(3.0 V)^2 = 39 mW.&#xA;That's still insignificant compared to those LEDs.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-14T16:23:03.430" CommentCount="2" />
  <row Id="13062" PostTypeId="2" ParentId="13050" CreationDate="2011-04-14T17:18:02.647" Score="1" ViewCount="" Body="&lt;p&gt;If you establish that the device is going to have sufficient sales to cover costs, you should approach a certification agency (UL, CSA, TUV, ETL, MET...) and get a quotation for certification. Certification could easily run into the tens of thousands of dollars.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Bluetooth part of the circuit will need FCC approval for the USA, Industry Canada approval for Canada (obviously), etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pretty well everything sold (officially) in the China market needs a CCC mark.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are including some sort of power supply in the design, you will need it approved by UL or an NRTL for the USA, CSA or a recognized equivalent for Canada, TUV or a recognized equivalent for Europe, etc. - it may be best to require use of an agency-recognized off-the-shelf power supply with the design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stuff for sale in Europe and China (and other areas) must be RoHS compliant. This is another external approval.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-14T17:18:02.647" />
  <row Id="13063" PostTypeId="1" AcceptedAnswerId="13080" CreationDate="2011-04-14T17:54:00.943" Score="3" ViewCount="204" Body="&lt;p&gt;I understand that in &quot;saturation mode&quot;, a BJT functions as a simple switch. I've used this before driving LEDs, but I'm not sure I understand clearly how I got the transistor into that state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does a BJT become saturated by raising Vbe above a certain threshold? I doubt this, because BJTs, as I understand them, are current-controlled, not voltage-controlled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does a BJT become saturated by allowing Ib to go over a certain threshold? If so, does this threshold depend on the &quot;load&quot; that is connected to the collector? Is a transistor saturated simply because Ib is high enough that the beta of the transistor is no longer the limiting factor in Ic?&lt;/p&gt;&#xA;" OwnerUserId="3240" LastActivityDate="2011-04-15T02:18:19.823" Title="How do I saturate an NPN transistor?" Tags="&lt;transistor&gt;" AnswerCount="3" CommentCount="8" FavoriteCount="4" />
  <row Id="13064" PostTypeId="2" ParentId="13023" CreationDate="2011-04-14T18:00:25.320" Score="1" ViewCount="" Body="&lt;p&gt;I think you want the &lt;a href=&quot;http://www.ambientdevices.com/cat/orb/orborder.html&quot; rel=&quot;nofollow&quot;&gt;Ambient Orb&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, I think they're not being manufactured any more. Might find one on Ebay.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-04-14T18:00:25.320" />
  <row Id="13065" PostTypeId="2" ParentId="12878" CreationDate="2011-04-14T18:14:50.497" Score="0" ViewCount="" Body="&lt;p&gt;You have to define what is usefull and what is useless first. Resistor on it's own (assuming it is connected to a power supply) can only dissipate power and heat up. If that is what you whant then it is usefull on its own.&lt;/p&gt;&#xA;" OwnerUserId="2088" LastActivityDate="2011-04-14T18:14:50.497" />
  <row Id="13067" PostTypeId="2" ParentId="13063" CreationDate="2011-04-14T18:48:11.463" Score="-2" ViewCount="" Body="&lt;p&gt;The NPN BJT will enter the saturation mode when Vcb will below some value. Sedra&amp;amp;Smith use value of 0.4V, but this will be device dependent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though I have no idea why you would whant to use BJT as a switch. MOSFETS are better suited for this task.&lt;/p&gt;&#xA;" OwnerUserId="2088" LastActivityDate="2011-04-14T18:48:11.463" CommentCount="2" />
  <row Id="13068" PostTypeId="2" ParentId="616" CreationDate="2011-04-14T18:58:24.347" Score="0" ViewCount="" Body="&lt;p&gt;I am supprised to see that noone has mentioned &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0195116631&quot; rel=&quot;nofollow&quot;&gt;Sedra &amp;amp; Smith Microelectronic Circuits&lt;/a&gt;. It starts from very basic consepts in the first few chapers, but then covers pretty much everything. The book contains a lot of circuit analysis and design examples. I got it for the sencond year electronics class and ended up returning to it over and over again for different classes as well as for work related stuff.&lt;/p&gt;&#xA;" OwnerUserId="2088" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T19:16:45.440" LastActivityDate="2011-05-13T19:16:45.440" CommunityOwnedDate="2011-04-14T18:58:24.347" />
  <row Id="13069" PostTypeId="1" AcceptedAnswerId="13074" CreationDate="2011-04-14T19:48:55.857" Score="4" ViewCount="166" Body="&lt;p&gt;Ok.....i've been trying to understand something (and trust me, to most people it's a VERY newbish question)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I see people all the time &quot;multiplexing&quot; LEDS. using just a few Pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lets say for an Arduino that has..... 5 I/O pins for example, apparently this can control 20 LEDS (or so i've been told) using Multiplexing...but.....what Im confused about is that this is all controlled by 5 pins. Maybe im getting Multiplexing wrong but how exactly does this happen?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also as iv'e been reading assembly tutorials for the AVR I notice that each Port has 3 registers, PORTB, DDRB and PINB, do these correspond with LOW/HIGH/OFF.....or is this entirely unrelated?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess I don't understand the whole idea of Multiplexing, I've read tutorials.....but I don't understand exactly how/why you hook them up, and for that matter where (and how much) to use resistors for, I know using certain combinations of High/Low/Input you can achieve a pretty awesome LED matrix. but How do I determine this. Im sure you would have to use transitors though right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry for the confusing question, it's even harder to ASk the question when Im not very sure about it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: Also I understand Shift Registers/Multiplexing (at least somewhat) in terms of &quot;Truth tables&quot; but I dont understand actually how to implement it. Maybe anyone could recommend a book on using Transistors and the like with Electronics, since some of the basic books really only go over Capacitors/Resistors&lt;/p&gt;&#xA;" OwnerUserId="3073" LastEditorUserId="3073" LastEditorDisplayName="" LastEditDate="2011-04-14T19:56:54.587" LastActivityDate="2011-04-18T03:36:55.260" Title="Multiplexing LEDS and Multiple Output Pins" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;led&gt;&lt;multiplexing&gt;" AnswerCount="3" />
  <row Id="13070" PostTypeId="1" AcceptedAnswerId="13076" CreationDate="2011-04-14T19:57:01.540" Score="0" ViewCount="76" Body="&lt;p&gt;I'm not sure if this one is on-topic here, but I'll give it a shot anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that if I have some sort of signal, like for example $y(t)=x(t)$, and I want a signal with twice the frequency, I can write that as $z(t)=x(2t)$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also know that if I have signal $y(t)=x(t)$ and I want to shift it to right, I can write the shifted signal as $z(t)=x(t-1)$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also know that if I have signal $y(t)=x(t)$ and I want to time-reverse it, I can write the time-reversed signal as $z(t)=x(-t)$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What confuses me is if I have a signal which has already been shifted, time-reversed or scaled and I need to shift it or scale it again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example I have a signal which is $y(t)=x(2t-1)$ and I need a signal which has been time-reversed, should that be $z(t)=x(-2t-1)$ or $z(t)=x(-2t+1)$?  Same thing for scaling: If I have $y(t)=x(2t-1)$ and want to scale it by a factor of 2, should the result be $z(t)=x(4t-1)$ or $z(t)=x(4t-2)$?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that this is a homework question, so I'm looking for an answer which will explain the principle behind the transformations.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-04-14T21:02:19.187" LastActivityDate="2011-04-14T21:02:19.187" Title="How to properly scale, time-reverse and shift a signal?" Tags="&lt;signal&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="13071" PostTypeId="1" CreationDate="2011-04-14T19:59:28.187" Score="0" ViewCount="57" Body="&lt;p&gt;I'm planning out a very simple circuit using an LED, capacitor, switch and a battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Idea is that the LED is off until something &quot;bumps into&quot; the circuit. At this point it should light up and slowly dim out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could use a microcontroller, but it would be nicer to be able to solve it with just a large capacitor and something that can trigger it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there such a thing as a switch that triggers (like a reed?) on impact?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm grateful for any other ideas or pointers on the circuit!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks&lt;/p&gt;&#xA;" OwnerUserId="2920" LastActivityDate="2011-04-14T20:37:59.887" Title="Accelerometer switch to trigger LED fade" Tags="&lt;capacitor&gt;&lt;switch&gt;&lt;accelerometer&gt;" AnswerCount="1" />
  <row Id="13072" PostTypeId="1" AcceptedAnswerId="13088" CreationDate="2011-04-14T20:12:18.163" Score="4" ViewCount="167" Body="&lt;p&gt;My PCB design software comes with some libraries that include some common components, like chip resistors and capacitors.  I have noticed, however, that the footprint land pattern for the 0805 resistor is not identical to the 0805 capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I then did some googling, and discovered multiple IPC standards that don't seem to quite agree with each other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a reason an 0805 resistor would have a different land pattern than an 0805 capacitor?  Is there a &quot;best standard&quot;?  IPC-7351, IPC-SM-782, or what?&lt;/p&gt;&#xA;" OwnerUserId="1278" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T20:33:31.607" LastActivityDate="2011-04-27T20:33:31.607" Title="The &quot;right&quot; 0805 footprint land pattern" Tags="&lt;pcb&gt;&lt;surface-mount&gt;&lt;footprint&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13073" PostTypeId="2" ParentId="13071" CreationDate="2011-04-14T20:16:07.253" Score="7" ViewCount="" Body="&lt;p&gt;There is a form of accelerometer that is commonly seen on kids toys, is super cheap, and works reasonably well when calibration isn't critical.  It's made from a spring and a metal post...  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Imagine this:  start with a simple spring like what you'd find in a ball-point pen.  Inside the spring is a simple metal post (or a piece of solid-core wire without insulation).  The post and spring are mounted together on one end and the other end flops in the breeze.  Normally, the spring and post do not make electrical contact.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When this is struck (or, what it's mounted to is struck) the spring with deflect and contact the post, thus making electrical contact.  It only responds to force perpendicular to the post, so you might need a second one to get &quot;3d response&quot;.  Vary the spring and post to change the sensitivity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a photo of one I just whipped up in the lab:  &lt;img src=&quot;http://i.imgur.com/coiqC.jpg&quot; alt=&quot;Simple accelerometer&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ignore the other stuff on the PCB.  I took a stiff piece of wire (not stiff enough, IMHO) and soldered it down.  Then I took a spring from a pen, unwound a little bit of it and soldered it down.  Then bend whatever you need to in order to get the wire centered on the spring.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="3624" LastEditorDisplayName="" LastEditDate="2011-04-14T20:37:59.887" LastActivityDate="2011-04-14T20:37:59.887" CommentCount="4" />
  <row Id="13074" PostTypeId="2" ParentId="13069" CreationDate="2011-04-14T20:25:10.967" Score="4" ViewCount="" Body="&lt;p&gt;I started writing about demultiplexers and calling the multiplexers, so the error should now be fixed. What you need to easily control multiple LEDs are demultiplexers, or use of multiplexers in reverse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a simple version: Imagine you have a telephone. The telephone is (in our simple world) connected to a switchboard and the board is connected to other telephones. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you dial a number, the board recognizes it and connects your telephone to another telephone and that's how connection is made. You only need one telephone and one switchboard to connect that one telephone to multiple other telephones. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Demultiplexers work in a similar way, except here the data and address lines are separated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So you have a hardware demultiplexer. It has address pins, input pin and output pins. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your microcontroller also has output pins. In the LED example, you can connect one output of the microcontroller to input of the demultiplexer. Using that one pin, you can control one LED at a time. If you connect the other output pins of the microcontroler to the demultiplexer, you can set the address. To get back to out telephone example, you use the microcontroller output pins connected to demultiplexer address pins to dial a number. So you send a signal to the demultiplexer and the signal is actually a binary number. The output pin of the demultiplexer with that number is then connected to the demultiplexer's input pin and you can send data from the microcontroller to the device connected to demultiplexer's output. This itself isn't very useful, because the demultiplexer is then a fifth wheel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here comes the interesting part: When you're done using the device connected to that particular output, you can the use address pins to select another output pin with another device connected to it. This way, we get a simple switch, so we can select the device to which the microcontroller will communicate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now let's get to the LED example. You have a microcontroller with 5 output pins. Let's say that you have a demultiplexer with 4 address pins, one input pin and 16 output pins (Mo0 to Mo15). Let's also say that you want to control 16 LEDs. So you connect each LED to the output pin of the demultiplexer and you connect 4 output pins (Here called A0-A3) of the Arduino to the address pins of the demultiplexer. That leaves one pin for the demultiplexer input pin (here called Ao) . &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now let's say that you want to light up a LED. You can just power up the Ao pin. In this case, the demultiplexer will read the signal sent by the A0-A3 pins. Since they are low, it will interpret that as 0000. That is the number of pin Mo0, so it will connect Mo0 to Ao. Now let's say you want to turn on another diode. You can do that by setting A0 pin to high, so you'll get 0001 and demultiplexer will connect pins Ao and Mo1. This way, you can connect Ao to any of the Mo pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK, that's nice, but how do you control all LEDs at the same time? Well, you don't. Instead, you'll exploit limits of human perception. If you turn an LED on and off fast enough, people won't notice. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For that you'll need a program which will cycle through selected output pins at a certain rate. The program should count up the A pins like binary numbers and that way you'll select which LED to control at each particular moment. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the registers you mentioned. Well, they are related, but at a different level. My advice is to learn first how to control one LED. After that learn how to control several LEDs connected to same port. When you learn that, you'll know how to set address pins for a demultiplexer high or low (it's same as turning on or off an LED) and since you already know how to control an LED, you'll be able to control the currently selected LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a picture of a demultiplexer. The GEN on the left is input signal. The GEN on the top controls if the multiplexer is on or off. In a real world project, you'd do this using power connectors. The 3 GENs on the bottom control address pins and on the right are output signals. When the address lines are low, output number 0 is selected.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tClLl.png&quot; alt=&quot;pin 0&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here we have pin 1 selected:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/qPTpH.png&quot; alt=&quot;pin 1&quot;&gt;   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here we have pin 2 selected:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/FQtLK.png&quot; alt=&quot;pin 2&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And finally here we have pin 3 selected:   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/PJOlB.png&quot; alt=&quot;pin 3&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same results should be obtainable using a  multiplexer and connecting the  microcontroller's output to multiplexer's output and using multiplexer's input pins as output. Of course, before doing that datasheet should be checked to see if such thing is possible. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just now noticed that you mentioned resistors. As I mentioned, before controlling large number of LEDs, first learn to control a single LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This one depends on microcontroller, but for AVR, when you set a pin to high state, it will be set to 5 V. Also maximum current through each pin should be limited. I used for example ATmega 162 and it can provide up to 200 mA for all pins and up to 20 mA for each pin. Another important thing is the LED current use. Different types of LEDs need different amounts of current to achieve maximum brightness. The second important characteristic of a LED is it's voltage drop. I used for example a 20 mA, 3.6 V LED. In this case, I need to limit current to under 20 mA. To do that, I used a resistor. There's a nice calculator &lt;a href=&quot;http://ledcalc.com/#calc&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, which will tell you what type of resistor to get for the LED. Also, when choosing the LED current, keep in mind that you're looking for the lower of the two supplied currents. You shouldn't exceed current of microcontroller pin and you shouldn't exceed current of the LED itself.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-04-14T22:09:43.710" LastActivityDate="2011-04-14T22:09:43.710" CommentCount="4" />
  <row Id="13075" PostTypeId="1" AcceptedAnswerId="13077" CreationDate="2011-04-14T20:32:42.073" Score="5" ViewCount="144" Body="&lt;p&gt;I have used commonly-available BJTs such as the 2N2222 and 2N3904 as switches by operating them in &quot;saturation mode&quot; from my MCU. I believe, however, that for these sorts of applications, a MOSFET is a more appropriate device. I have a few questions, however.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Does a MOSFET have a &quot;saturation mode&quot; like the BJT does? Is this &quot;saturation&quot; achieved by simply providing a high enough voltage on the base that the MOSFET is completely &quot;on&quot;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Is it safe to drive the MOSFET directly from the MCU? I understand that the gate of the MOSFET behaves like a capacitor, and therefore draws some current while &quot;charging&quot;, and then none thereafter. Is this charging current high enough to damage the MCU pin? By placing a resistor in series with the gate, I can protect the pin, but this will slow down the switch, possibly resulting in high heat dissipation by the MOSFET?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) What is a common &quot;hobbyist&quot; MOSFET suitable for various low-power situation? I.E., what's the MOSFET equivalent to a 2N2222 or 2N3904?&lt;/p&gt;&#xA;" OwnerUserId="3240" LastActivityDate="2011-04-14T21:10:10.290" Title="Is it safe to drive a MOSFET from an output pin of a microcontroller?" Tags="&lt;microcontroller&gt;&lt;mosfet&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="4" />
  <row Id="13076" PostTypeId="2" ParentId="13070" CreationDate="2011-04-14T20:39:50.413" Score="2" ViewCount="" Body="&lt;p&gt;I think what might help is if we start to use different symbols to avoid confusion.  When you're doing this shifts, inverts and so on what's happening is that the variable t is being replaced by some transform of t (t = -1*t for mirroring, t=(t-2) for shifting, etc).  You can see how ungainly and confusing the equations above are: there's t's on both sides.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So when you do these transforms, figure out how t is being affected.  If we're doing a right shift of x(t), then we're replacing t with (t-n).  Define a new variable (a temporary one, to keep things straight) tau and the relationship with t: tau = t-2.  So now the transformed equation is x(tau) and tau = t-2, so to simplify, the transformed equation is x(t-2).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One step is plain and simple, but applying another shift, invert or scale makes the reasoning behind the approach more clear.  To shift x(tau) all we do is treat tau like t was treated before.  So this time, y(tau) = x(tau-1) (right shift by one).  Then substitute t for tau from the above equation and you get this: y(t) = x( (t-2) -1 ) == x(t-3)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If instead we mirrored it, y(tau) = x(-tau) then we simplify again and get this: y(t) = x(-1 * (t-2) ) == x( -t + 2 )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Taking it in small steps and using substitution will help keep things straight and prevent what basically boils down to algebra mistakes.  The trick is that &lt;em&gt;you're always replacing t and &lt;strong&gt;only&lt;/strong&gt; t with something else.&lt;/em&gt; Good luck!&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-14T20:39:50.413" />
  <row Id="13077" PostTypeId="2" ParentId="13075" CreationDate="2011-04-14T20:44:32.500" Score="3" ViewCount="" Body="&lt;p&gt;Many power MOSFETs require a high gate voltage for high-current loads, to ensure that they are fully turned on. There are some with logic-level inputs, though. The data sheets can be misleading, they often give the gate voltage for 250 mA current on the front page, and you find that they need 12V for 5A, say.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a good idea to put a resistor to ground on the gate if a MOSFET is driven by an MCU output. MCU pins are usually inputs on reset, and this could cause the gate to float momentarily, perhaps turning the device on, until the program starts running. You won't damage the MCU output by connecting it directly to a MOSFET gate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The BS170 and 2N7000 are roughly equivalent to the BJTs you mentioned. The Zetex ZVN4206ASTZ has a maximum drain current of 600 mA. I don't think that you will find a small MOSFET that can be driven from 3.3V, though.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-14T21:10:10.290" LastActivityDate="2011-04-14T21:10:10.290" CommentCount="6" />
  <row Id="13078" PostTypeId="1" CreationDate="2011-04-14T21:23:37.677" Score="2" ViewCount="72" Body="&lt;p&gt;Can anyone recommend a book on wireless protocol design?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to find books with a thorough treatment of MAC and network layers without just being a guide to one specific protocol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The kinds of topics I'm looking for include: frequency hopping, time slicing, cryptography, low power design and routing.&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-04-15T08:52:34.107" LastActivityDate="2011-04-15T14:21:01.230" Title="Can you recommend a book on wireless protocol design?" Tags="&lt;rf&gt;&lt;radio&gt;&lt;books&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="2" />
  <row Id="13079" PostTypeId="1" AcceptedAnswerId="13081" CreationDate="2011-04-14T21:45:21.467" Score="7" ViewCount="232" Body="&lt;p&gt;In my experimentation, I've used only BJTs as switches (for turning on and off things like LEDs and such) for my MCU outputs. I've been repeatedly told, however, that N-channel enhancement-mode MOSFETs are a better choice for switches (see &lt;a href=&quot;http://electronics.stackexchange.com/questions/13063/how-do-i-saturate-an-npn-transistor/13067#13067&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://electronics.stackexchange.com/questions/11344/building-a-simple-mcu-driven-array-of-leds/11356#11356&quot;&gt;here&lt;/a&gt;, for examples), but I'm not sure I understand why. I do know that a MOSFET wastes no current on the gate, where a BJT's base does, but this is not an issue for me, as I'm not running on batteries. A MOSFET also requires no resistor in series with the gate, but generally DOES require a pulldown resistor so the gate doesn't float when the MCU is rebooted (right?). No reduction in parts count, then.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There doesn't seem to be a great surplus of logic-level MOSFETs that can switch the current that cheap BJTs can (~600-800mA for a 2N2222, for example), and the ones that do exist (TN0702, for example) are hard to find and significantly more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When is a MOSFET more appropriate than a BJT? Why am I continually being told that I should be using MOSFETs?&lt;/p&gt;&#xA;" OwnerUserId="3240" LastActivityDate="2011-04-15T14:51:20.870" Title="When is a MOSFET more appropriate as a switch than a BJT?" Tags="&lt;microcontroller&gt;&lt;transistor&gt;&lt;mosfet&gt;&lt;bjt&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="3" />
  <row Id="13080" PostTypeId="2" ParentId="13063" CreationDate="2011-04-14T21:49:31.393" Score="1" ViewCount="" Body="&lt;p&gt;Drive enough current into the base so that the base-collector junction becomes forward biased. How much current will depend on the type of transistor. 'saturation' has to do with how many of the charge carriers in the base region can make it into the collector region. Some will come from the base terminal, but many more will come into the base region from the emitter region. Beyond a certain amount of base current, there just won't be an increase in the available charge carriers that can cross the B-C junction. &lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-14T21:49:31.393" CommentCount="1" />
  <row Id="13081" PostTypeId="2" ParentId="13079" CreationDate="2011-04-14T21:52:59.457" Score="4" ViewCount="" Body="&lt;p&gt;BJTs are much more suitable than MOSFETs for driving low-power LEDs and similar devices from MCUs. MOSFETs are better for high-power applications because they can switch faster than BJTs, enabling them to use smaller inductors in switch-mode supplies, which increases efficiency.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-15T14:51:20.870" LastActivityDate="2011-04-15T14:51:20.870" CommentCount="9" />
  <row Id="13082" PostTypeId="2" ParentId="13063" CreationDate="2011-04-14T22:00:25.103" Score="8" ViewCount="" Body="&lt;p&gt;A transistor goes into saturation when both the base-emitter and base-collector junctions are forward biased, basically. So if the collector voltage drops below the base voltage, and the emitter voltage is below the base voltage, then the transistor is in saturation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Consider this Common Emitter Amplifier circuit. If the collector current is high enough, then the voltage drop across the resistor will be big enough to lower the collector voltage below the base voltage. But note that the collector voltage can't go too low, because the base-collector junction will then be like a forward-biased diode! So, you will have a voltage drop across the base-collector junction but it will not be the usual 0.7V, it will be more like 0.4V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/MOrLo.png&quot; alt=&quot;Common Emitter Amplifier&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do you bring it out of saturation? You could reduce the amount of base drive to the transistor (either reduce the voltage $V_{be}$ or reduce the current $I_b$), which will then reduce the collector current, which means the voltage drop across the collector resistor will be decreased also. This should increase the voltage at the collector and act to bring the transistor out of saturation. In the &quot;extreme&quot; case, this is what is done when you switch off the transistor. The base drive is removed completely. $V_{be}$ is zero and so is $I_b$. Therefore, $I_c$ is zero too, and the collector resistor is like a pull-up, bringing the collector voltage up to $V_{CC}$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A follow-up comment on your statement &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Does a BJT become saturated by&#xA;  raising Vbe above a certain threshold?&#xA;  I doubt this, because BJTs, as I&#xA;  understand them, are&#xA;  current-controlled, not&#xA;  voltage-controlled.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;There are a number of different ways to describe transistor operation. One is to describe the relationship between currents in the different terminals:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$I_c = \beta I_b$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$I_c = \alpha I_e$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$I_e = I_b + I_c$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;etc. Looking at it this way, you could say that the collector current is controlled by the base &lt;em&gt;current&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way of looking at it would be to describe the relationship between base-emitter voltage and collector current, which is&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$I_c = I_s e^{\frac{V_{be}} {V_T}}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at it this way, the collector current is controlled by the base &lt;em&gt;voltage&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is definitely confusing. It confused me for a long time. The truth is that you cannot really separate the base-emitter voltage from the base current, because they are interrelated. So both views are correct. When trying to understand a particular circuit or transistor configuration, I find it is usually best just to pick whichever model makes it easiest to analyze.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Edit:&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Does a BJT become saturated by&#xA;  allowing Ib to go over a certain&#xA;  threshold? &lt;strong&gt;If so, does this threshold&#xA;  depend on the &quot;load&quot; that is connected&#xA;  to the collector? Is a transistor&#xA;  saturated simply because Ib is high&#xA;  enough that the beta of the transistor&#xA;  is no longer the limiting factor in&#xA;  Ic?&lt;/strong&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The bold part is basically exactly right. But the $I_b$ threshold is not intrinsic to a particular transistor. It will depend not only on the transistor itself but on the configuration: $V_{CC}$, $R_C$, $R_E$, etc.&lt;/p&gt;&#xA;" OwnerUserId="3635" LastEditorUserId="3635" LastEditorDisplayName="" LastEditDate="2011-04-15T02:18:19.823" LastActivityDate="2011-04-15T02:18:19.823" CommentCount="2" />
  <row Id="13083" PostTypeId="2" ParentId="13042" CreationDate="2011-04-14T22:00:57.927" Score="1" ViewCount="" Body="&lt;p&gt;Loads notwithstanding, if you just connect a 50Hz source and a 60Hz source together, they will alternate between being in-phase and out-of-phase 10 times per second. So half the time, things would be fine, but the other half the time, the sources would be trying to burn one another out. This might not be such a big deal except that when the sources can supple megawatts, there would definitely be smoke.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-14T22:00:57.927" />
  <row Id="13084" PostTypeId="2" ParentId="13079" CreationDate="2011-04-14T22:50:27.287" Score="5" ViewCount="" Body="&lt;p&gt;BJT's waste some current whenever they're switched on, regardless of whether the load is drawing anything.  In a battery-powered device, using a BJT to power something whose load is highly variable but is often low will end up wasting a lot of energy.  If a BJT is used to power something with a predictable current draw, though (like a LED), this problem isn't as bad; one can simply set the base-emitter current to be a small fraction of the LED current.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-14T22:50:27.287" />
  <row Id="13085" PostTypeId="2" ParentId="13079" CreationDate="2011-04-14T23:36:04.283" Score="4" ViewCount="" Body="&lt;p&gt;BJT's are more suitable in some situations because they are often cheaper. I can buy TO92 BJT's for 0.8p each but MOSFET's don't start until 2p each - it might not sound like much but it can make a big difference if you're dealing with a cost sensitive product with many of these.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-14T23:36:04.283" />
  <row Id="13086" PostTypeId="1" CreationDate="2011-04-14T23:44:33.573" Score="1" ViewCount="138" Body="&lt;p&gt;A servo interprets a 1ms pulse as far left, a 1.5ms pulse as centre and a 2ms pulse as far right, usually. But what if there is no pulse? Will a servo hold its position if it is just commanded once and never commanded again for a few minutes? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-15T21:59:04.037" Title="Will a servo hold its position without a signal?" Tags="&lt;servo&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13087" PostTypeId="1" CreationDate="2011-04-15T00:04:29.033" Score="7" ViewCount="1301" Body="&lt;p&gt;Dyson keep going on about their new &quot;digital&quot; motor. What is a digital motor? How can a motor be digital, it is inherently analog? Is it just marketing doublespeak?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-16T04:42:42.323" Title="What is a &quot;digital&quot; motor?" Tags="&lt;motor&gt;" AnswerCount="3" CommentCount="7" />
  <row Id="13088" PostTypeId="2" ParentId="13072" CreationDate="2011-04-15T00:34:41.520" Score="4" ViewCount="" Body="&lt;p&gt;The current standard is IPC-7351B, which replaced IPC-7351A, IPC-7351 and IPC-SM-782 (in that order).  Mentor graphics have a free &lt;a href=&quot;http://www.mentor.com/products/pcb-system-design/library-tools/lp-wizard/lp-viewer-download&quot; rel=&quot;nofollow&quot;&gt;PCB footprint viewer for Windows&lt;/a&gt; for all of the standard parts using this standard.  Each part also includes a &quot;courtyard&quot; layer which defines how much space needs to be left around the component for manufacturing; useful when you are designing high density boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The standard itself consists of three versions but for most boards it is recommended that the &quot;N&quot; suffix (Nominal) footprints are used.  Note that most parts do differ slightly from manufacturer recommended patterns but in my experience (and the experiences of my board loader these footprints do tend to meet manufacturing requirements very well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for you query about the 0805 resistor vs 0805 capacitor, I suspect that the footprints have been designed to best attach the parts; while they are fairly similar in the horizontal plane, capacitors do tend to be slightly higher so maybe the differences in the footprints take this into account.&lt;/p&gt;&#xA;" OwnerUserId="820" LastActivityDate="2011-04-15T00:34:41.520" CommentCount="2" />
  <row Id="13089" PostTypeId="2" ParentId="13087" CreationDate="2011-04-15T00:37:51.687" Score="10" ViewCount="" Body="&lt;p&gt;Unfortunately the term digital seems to be applied inappropriately to all sorts of things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a good video &lt;a href=&quot;http://www.eevblog.com/2010/12/13/eevblog-132-delusional-dyson-marketing/&quot; rel=&quot;nofollow&quot;&gt;http://www.eevblog.com/2010/12/13/eevblog-132-delusional-dyson-marketing/&lt;/a&gt;&#xA;from the EEV blog taking Dyson to task for their &quot;Dyson digital motor&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is Dyson's take: &lt;a href=&quot;http://www.dyson.com/technology/ddmtabbed.asp&quot; rel=&quot;nofollow&quot;&gt;http://www.dyson.com/technology/ddmtabbed.asp&lt;/a&gt;&#xA;where they say &quot;Dyson digital motors use digital pulse technology, spinning at up to 104,000 times a minute&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then again most switched to turn a motor on or off are digital, binary in fact ;-)&lt;/p&gt;&#xA;" OwnerUserId="3869" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-04-15T03:21:36.820" LastActivityDate="2011-04-15T03:21:36.820" CommentCount="4" />
  <row Id="13090" PostTypeId="2" ParentId="13086" CreationDate="2011-04-15T00:45:29.793" Score="2" ViewCount="" Body="&lt;p&gt;It all depends. If no external forces are applied, then yes. This might be if only a pointer were attached to the servo and nobody touched it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most servo applications do have external forces, and most servos are not capable of resisting them when not powered.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, there are some servo motors that are better at resisting external torque than others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See also: &lt;a href=&quot;http://www.servocity.com/html/how_do_servos_work_.html&quot; rel=&quot;nofollow&quot;&gt;http://www.servocity.com/html/how_do_servos_work_.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3869" LastActivityDate="2011-04-15T00:45:29.793" CommentCount="1" />
  <row Id="13091" PostTypeId="1" AcceptedAnswerId="13103" CreationDate="2011-04-15T00:58:24.040" Score="1" ViewCount="166" Body="&lt;p&gt;Quick question, is using a Capacitor rated for High Voltage (lets say 35v) in a System that lets say supplies 5v (like for LEDS.....or what have you) Dangerous?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since it can store UP to 35v, will it like somehow store a bunch then release it at once damaging the system? or it is ok to use a higher rated capacitor than the voltage being supplied?&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-04-15T08:23:15.737" Title="High Voltage Capacitor, in a low voltage system?" Tags="&lt;capacitor&gt;&lt;voltage&gt;" AnswerCount="5" />
  <row Id="13093" PostTypeId="2" ParentId="13091" CreationDate="2011-04-15T01:12:25.160" Score="12" ViewCount="" Body="&lt;p&gt;No, having a higher rated cap will not somehow store up more voltage than is available in the circuit. You actually want a cap with a slightly higher voltage rating than the highest voltage you expect to put across it. In fact, if you put more voltage on a cap than it is rated for, it is apt to catastrophically fail, i.e., pop or explode.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-15T01:12:25.160" CommentCount="1" />
  <row Id="13094" PostTypeId="2" ParentId="8973" CreationDate="2011-04-15T01:48:48.877" Score="1" ViewCount="" Body="&lt;p&gt;I would avoid IEEE floating point format, go with the format the TI DSP uses.  Ti has some good doc that goes along with one of the older DSPs that holds your hand through the operations.  From there you can start on your logic.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-04-15T01:48:48.877" CommunityOwnedDate="2011-04-15T01:48:48.877" CommentCount="2" />
  <row Id="13095" PostTypeId="1" AcceptedAnswerId="13096" CreationDate="2011-04-15T01:51:08.747" Score="0" ViewCount="84" Body="&lt;p&gt;Today I purchased a USB memory card reader. I cracked it open and saw that it basically only has an AU6477CL IC, which is based on the AU6370, which is a chip which takes SD/MMC/etc pins as input and acts as a USB driver for a computer to do i/o on the card. &lt;a href=&quot;http://pdf1.alldatasheet.com/datasheet-pdf/view/218991/ETC2/AU6370.html&quot; rel=&quot;nofollow&quot;&gt;Here is the datasheet for the AU6370&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where can I buy one of these things? It seems like every card reader in the universe is driven by one of these ICs, but short of buying 50,000 from alibaba (maybe), I can't find them anywhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternately, does anyone know of equivalent ICs which perform similar functions? Generically, what would I be searching for?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For hobbyists, is the best option really to use an AVR/PIC to write our own code (or existing libraries) if we were to create our own memory card reader?&lt;/p&gt;&#xA;" OwnerUserId="1021" LastActivityDate="2011-04-15T02:05:20.370" Title="Memory Card to USB IC?" Tags="&lt;usb&gt;&lt;ic&gt;&lt;sd&gt;&lt;microsd&gt;" AnswerCount="1" />
  <row Id="13096" PostTypeId="2" ParentId="13095" CreationDate="2011-04-15T02:05:20.370" Score="2" ViewCount="" Body="&lt;p&gt;The cheapest way of getting the part is by buying a card reader from your favorite eBay Hong Kong vendor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was involved in purchasing AU6350s for a project.  The process involved lots of transcontinental communications, purchase orders, international wire transfers, and shipping accounts.  The developer board was about $150 if I remember correctly.  The Alcor people are nice, but there is just a lot of bureaucracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Microchip USB stack has a card reader as one of their example projects.  It works fine, but is very slow compared to the dedicated chip.  About 50 times slower by my memory.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-15T02:05:20.370" CommentCount="4" />
  <row Id="13097" PostTypeId="2" ParentId="13086" CreationDate="2011-04-15T03:44:38.437" Score="2" ViewCount="" Body="&lt;p&gt;It is very doubtful that it would stay in the same location.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way I understand servo motors to work is that there is a constant feedback loop that is comparing the position to your pulse. Something like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/bfGde.png&quot; alt=&quot;Control System&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To explain a bit more, the pulse is feed into what I called a low pass filter. It turns your pulse into a voltage that is in the range that the position sensor should also be outputting. It is also designed so that the voltage is maintained during your pulses 20ish ms off time. This voltage is then compared to the position sensor output. If they are equal then the motor doesn't need to run, but if they are different then the motor will run forward or backward to attempt to make the error be 0.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now this is a very simplistic way of looking at a servo as most have more complicated control systems to insure stability with fast response, low overshoot, and high position accuracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a chance that there are servos out there that have &quot;memory&quot; of the last pulse so you don't have to keep sending it a pulse train, but none of the ones I have used do this.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-15T03:44:38.437" />
  <row Id="13098" PostTypeId="2" ParentId="12827" CreationDate="2011-04-15T03:47:36.497" Score="1" ViewCount="" Body="&lt;p&gt;Since nobody better qualified has answered, I'll take a crack at this one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simply looking at the current draw, it looks OK.  But it's close enough that you might want to verify the current draw just in case the motor makers took a little &quot;creative license&quot; with the specs.  Check the current under both no load and max load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, what I would be most concerned with is the speed of the motors.  It's almost certain that two motors will not be matched in speed.  And even if they are, they won't stay that way due to age, wear, and differences in weight distribution and terrain. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This difference in speed, especially with a geared motor that won't tend to slip, will manifest itself as stearing problems, increased wear on the wheels, and other bad things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, assuming that the current spec is correct, I don't see any harm in just trying it.  There is a chance that I'm wrong and they will be matched enough that it'll work just fine.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-15T03:47:36.497" />
  <row Id="13099" PostTypeId="2" ParentId="13091" CreationDate="2011-04-15T04:08:57.047" Score="5" ViewCount="" Body="&lt;p&gt;I have a staircase with 35 steps.  I am standing on the fifth step.  What if I fall down?  Is it dangerous?  Falling down 35 steps can hurt!&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-15T04:08:57.047" CommentCount="2" />
  <row Id="13100" PostTypeId="1" AcceptedAnswerId="13109" CreationDate="2011-04-15T05:10:45.077" Score="8" ViewCount="138" Body="&lt;p&gt;Hi All,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For Inter-task communication or to share data between two tasks of RTOS, We use Queues.&#xA;But Problem with Queues is that they are slow.... They copy data in Buffer then Mutex Handling and then Data Transfer. It's irritatingly slow if you have to transfer large data.&#xA;Another problem is if same queue is accessed by Multiple tasks. Then Picture becomes like this:- First Wait to get access to The Queue then Queue internal Mutex Handling then Data Transfer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This increases overhead on the system. What could be the &lt;strong&gt;Efficient replacement&lt;/strong&gt; for Queues?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I guess this question is Independant of RTOS we use. Most of the RTOS handle Queues in this way only) &lt;/p&gt;&#xA;" OwnerUserId="2574" LastEditorUserId="2574" LastEditorDisplayName="" LastEditDate="2011-04-18T04:02:43.953" LastActivityDate="2011-04-18T16:12:47.197" Title="Replacement for Queues in RTOS" Tags="&lt;rtos&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="3" />
  <row Id="13101" PostTypeId="2" ParentId="12965" CreationDate="2011-04-15T06:20:42.440" Score="0" ViewCount="" Body="&lt;p&gt;Can't really help you with your problem, but I might be able to give you some insight into the cause:&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Magnetostriction&quot; rel=&quot;nofollow&quot;&gt;Magnetostriction -- sounds cool, huh?&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3872" LastActivityDate="2011-04-15T06:20:42.440" />
  <row Id="13102" PostTypeId="2" ParentId="13100" CreationDate="2011-04-15T06:58:57.880" Score="4" ViewCount="" Body="&lt;p&gt;One easy way is to put a pointer to the data on the queue and consume the data using the pointer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that you're trading safety for performance this way as you have to make sure that:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;the buffer remains valid until the consumer has consumed the data&lt;/li&gt;&#xA;&lt;li&gt;someone deallocates the buffer&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If you're not using dynamically allocated memory you don't have to deallocate it, but you still have to make sure that the memory area is not reused before the data has been consumed.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-04-15T06:58:57.880" />
  <row Id="13103" PostTypeId="2" ParentId="13091" CreationDate="2011-04-15T07:06:42.740" Score="5" ViewCount="" Body="&lt;p&gt;While not a perfect analogy, think of the voltage on the capacitor similar to the liter capacity of a tank. It will hold &quot;35 V&quot; but you needn't fill it completely. But like @JustJeff said, you'd be wise to ensure the container can hold more than necessary to prevent spills (and in an electrolytic capacitor's case, the electrolyte can expand and quite literally &quot;spill&quot; out).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Note that a better analogy to capacity would be the farad unit, since that's a measure of a capacitor's charge capacity, so don't get that confused with voltage, which is the potential to do work.&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2028" LastActivityDate="2011-04-15T07:06:42.740" CommentCount="2" />
  <row Id="13104" PostTypeId="2" ParentId="13091" CreationDate="2011-04-15T07:36:51.900" Score="5" ViewCount="" Body="&lt;p&gt;The voltage rating of a capacitor is a measure of how strong its insulation is.  A 35V cap can withstand at least 35 volts applied across it (a higher voltage may cause bad things like a short through the cap and burnup).  It has nothing to do with how much voltage the capacitor will store; it can store nothing higher than is input to it.  The voltage rating is describing how high its barrier is; electricity shall not pass through it as long as it does not get that high.  &lt;/p&gt;&#xA;" OwnerUserId="3769" LastActivityDate="2011-04-15T07:36:51.900" />
  <row Id="13105" PostTypeId="2" ParentId="13091" CreationDate="2011-04-15T08:23:15.737" Score="5" ViewCount="" Body="&lt;p&gt;If a high-voltage electrolytic is used at low-voltage, the actual capacitance might be a lot lower than the stated value.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-15T08:23:15.737" CommentCount="2" />
  <row Id="13107" PostTypeId="2" ParentId="13001" CreationDate="2011-04-15T11:04:48.347" Score="0" ViewCount="" Body="&lt;p&gt;I was able to rectify the problem and totally avoided the repetitions.&#xA;Simply use a 1k pull-up both at the TXD and RXD pins of the UART, to VCC. So all work with any baud rate. The problem was simply an issue with voltage levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks to all who contributed!&lt;/p&gt;&#xA;" OwnerUserId="3632" LastActivityDate="2011-04-15T11:04:48.347" />
  <row Id="13108" PostTypeId="2" ParentId="13078" CreationDate="2011-04-15T12:00:08.080" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.comsoc.org/content/algorithms-and-protocols-wireless-and-mobile-ad-hoc-networks&quot; rel=&quot;nofollow&quot;&gt;Algorithms and Protocols for Wireless and Mobile Ad Hoc Networks&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-04-15T12:00:08.080" />
  <row Id="13109" PostTypeId="2" ParentId="13100" CreationDate="2011-04-15T12:14:33.613" Score="4" ViewCount="" Body="&lt;p&gt;Queues operate that way because that is a thread-safe transaction model for inter-task communication.  You risk data corruption and/or ownership issues in any less-stringent scheme.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you copying the data into a buffer in memory then passing a pointer with the queue elements, or trying to pass all the data in the queue elements themselves?  If you're not passing pointers then you'll get an increase in performance doing that instead of passing one byte at a time through queue elements.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-15T12:14:33.613" CommentCount="4" />
  <row Id="13110" PostTypeId="2" ParentId="3348" CreationDate="2011-04-15T12:17:49.807" Score="0" ViewCount="" Body="&lt;p&gt;If you want to calculate the gate current during switching you can use this formula:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ig = Q/t&lt;/p&gt;&#xA;&#xA;&lt;p&gt;where Q is the gate charge in Coulomb (nC from the data sheet) and t is the switching time (in ns if you use nC).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to switch in 20 ns, a typical FET with a total gate charge of 50 nC will need 2.5A. You can find nimbler parts with gate charge below 10 nC. I prefer to use 2 BJTs in a totem configuration for driving MOSFETs instead of the expensive driver ICs.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastActivityDate="2011-04-15T12:17:49.807" CommunityOwnedDate="2011-04-15T12:17:49.807" CommentCount="2" />
  <row Id="13111" PostTypeId="2" ParentId="13087" CreationDate="2011-04-15T12:18:40.070" Score="1" ViewCount="" Body="&lt;p&gt;They could be referring to the control method as well.  Most motors are controlled with PWM from an external source, but if there's a built-in driver then you might command it with serial protocols or DIO instead of voltage.  I've seen 'smart motors' like that.  It looks like there's electronics integrated on to the Dyson motor, so that might be it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But yeah, marketspeak.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-15T12:18:40.070" />
  <row Id="13112" PostTypeId="1" CreationDate="2011-02-14T12:19:06.313" Score="3" ViewCount="173" Body="&lt;p&gt;I am working on an NEC v850ES/JH3 controller for testing SD card driver in SPI mode.&#xA;&lt;strong&gt;We interfaced SD card slot directly to v850ES/JH3 controller without any pullup resistors&lt;/strong&gt;.&#xA;Is it gives any negative effect?&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;I am able to initialize SD card in SPI mode. I am getting 0x00 response for CMD16 also.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;After SD card initialization I am changing clock frequency to 4 MHz.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I am checking SD card busy or not (if response is 0xFF then SD card is not busy).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Sending read command (CMD17) and dummy data. Getting response of 0xc1, after that, next byte is 0x3f. That means read command is failed.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If we don't send dummy data after read command then i am getting response 0x04 means illegal command. In this case also read is failing.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If we won't check SD card is busy or not then I am getting response 0x00 for read command, which means read command is accepted. And also I am getting start token (0xFE) also. Means SD card will send block of data. If I read 512 bytes of block data then I am getting all zeros. I am trying to read boot record. That means some data is there other than zeros. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I am facing same issue with SD card block write also.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Can you please tell me what is the problem? I am struggling with this issue since 2 weeks.&lt;/p&gt;&#xA;" LastEditorUserId="536" LastEditorDisplayName="" LastEditDate="2011-04-15T12:41:41.307" LastActivityDate="2011-04-27T17:05:31.480" Title="SD card read/write problems in SPI mode" Tags="&lt;spi&gt;&lt;sd&gt;" AnswerCount="1" FavoriteCount="2" />
  <row Id="13114" PostTypeId="1" CreationDate="2011-04-15T12:58:16.063" Score="1" ViewCount="178" Body="&lt;p&gt;Does anyone know if a 5v battery exists? I'm looking for a small battery - N size is perfect - that puts out between 5v and 5.5v. A coin cell 2032 or similar would be fine too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can use a 9v N and regulate it, but that seems such a waste.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The application is a remote control.&lt;/p&gt;&#xA;" OwnerUserId="1402" LastEditorUserId="2465" LastEditorDisplayName="" LastEditDate="2011-04-17T20:39:36.277" LastActivityDate="2011-04-17T20:39:36.277" Title="5v Battery - smaller is better" Tags="&lt;power&gt;&lt;battery&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="13115" PostTypeId="2" ParentId="13114" CreationDate="2011-04-15T13:03:31.740" Score="4" ViewCount="" Body="&lt;p&gt;Depending on technology cell voltage is either 1.2V (NiCd), 1.5V (Alkaline, NīMH), 2V (Lead), or 3V (Lithium). You can get higher voltages by combining multiple cells. AFAIK there are no 5V batteries.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regulating down from 9V doesn't have to be a waste, if you use a switching regulator (SMPS). For this in/out ratio efficiencies over 90% are attainable.&lt;br&gt;&#xA;Alternatively you can regulate down from 2x CR2032 (in &lt;a href=&quot;http://parts.digikey.com/1/parts/1808465-holder-batt-stack-2-cr2032-smd-bhx2-2032-sm.html&quot; rel=&quot;nofollow&quot;&gt;space-saving stacking holder&lt;/a&gt;) using an LDO.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;I read in your comment to another answer that the application is a remote control. In that case I'd go for the 2x CR2032 + LDO. Firstly, Lithium cells have a low self-discharge. I take it that the device is in low-power mode when not in use. You'll want an LDO with a &amp;lt; 1uA ground current, like Seiko &lt;a href=&quot;http://www.glyn.de/data/glyn/media/doc/S812C_E.pdf&quot; rel=&quot;nofollow&quot;&gt;S-812C50&lt;/a&gt;. The S-812C is available in SOT-23.&lt;br&gt;&#xA;In a typical remote control application your batteries should last several years with this setup.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-16T11:32:16.213" LastActivityDate="2011-04-16T11:32:16.213" CommentCount="2" />
  <row Id="13116" PostTypeId="2" ParentId="13114" CreationDate="2011-04-15T13:03:36.553" Score="0" ViewCount="" Body="&lt;p&gt;Not sure why you're targeting 5 to 5.5V - what kind of application do you have in mind? Depending on what it is you might be able to step outside this range. Four NiCd cells will get you to 4.8V, or a pair of 2032 cells will get you 6V.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-04-15T13:09:26.613" LastActivityDate="2011-04-15T13:09:26.613" CommentCount="4" />
  <row Id="13117" PostTypeId="2" ParentId="13079" CreationDate="2011-04-15T13:41:26.847" Score="3" ViewCount="" Body="&lt;p&gt;A good N-channel MOSFET will have a very low $R_{ds(on)}$ (drain-source equivalent resistance) when properly biased, which means that it behaves very much like an actual switch when turned on. You will find that the voltage across the MOSFET when on will be lower than the $V_{ce(sat)}$(collector-emitter saturation voltage) of a BJT.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A 2N2222 has $V_{ce(sat)}$ from $ 0.4V - 1V $ depending on biasing current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A VN2222 MOSFET has a maximum $R_{ds(on)}$ of $ 1.25 \Omega$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can see that the VN2222 will dissipate much less across the drain-source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, as previously explained, the MOSFET is a transconductance device - voltage on the gate allows current through the device. Since the gate is high-impedance to the source, you do not require constant gate current to bias the device on - you need only overcome the inherent capacitance to get the gate charged up then the gate consumption becomes miniscule.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-15T13:41:26.847" CommentCount="1" />
  <row Id="13118" PostTypeId="2" ParentId="13100" CreationDate="2011-04-15T13:44:02.587" Score="3" ViewCount="" Body="&lt;p&gt;Lock-free queues can be implemented for the single-producer/single-consumer case, and often you can architect your software to minimize the number of multiple-producer or multiple-consumer queues. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A lock-free queue can be constructed like so: Allocate an array of the elements to be communicated, and also two integers, call them Head and Tail. Head is an index into the array, where the next item will be added. Tail is an index into the array, where the next item is available to be removed. The producer task reads H and T to determine if there is room to add an item; writes the item in at the H index, then updates H. The consumer tasks reads H and T to determine if there is data available, reads data from index T, then updates T. Basically it's a ring buffer accessed by two tasks, and the order of operations (insert, then update H; remove, then update T) ensures that data corruption doesn't occur.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a situation with multiple producers and a single consumer, or a single producer and multiple consumers, you effectively have a resource limitation of some kind, and there's nothing else for it but to use synchronization, since the performance limiter is more likely to be the lone producer/consumer than an OS overhead with the locking mechanism. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if you have multiple producers AND consumers, it's worth spending the time (in design-space) to see whether you can't get a more coordinated communication mechanism; in a case like this, serializing everything through a single queue definitely makes the efficiency of the queue the central determinant of performance.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-15T13:44:02.587" />
  <row Id="13119" PostTypeId="2" ParentId="13114" CreationDate="2011-04-15T14:01:49.117" Score="3" ViewCount="" Body="&lt;p&gt;Use a single Li-ion cell with a boost converter to 5V. Microchip makes the MCP1640 boost converter chip, and other manufacturers make similar devices. &lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/01311a.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is an app note describing the technique. One of the examples delivers 5V at 200 mA. The circuit could be made very small, to go with a coin cell. It has a big advantage over two cells and an LDO - it will start with a voltage as low as 0.65V, and still work with the cell discharged to 0.35V, giving a very long cell life.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-16T12:21:08.587" LastActivityDate="2011-04-16T12:21:08.587" />
  <row Id="13120" PostTypeId="2" ParentId="13078" CreationDate="2011-04-15T14:21:01.230" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0133499456&quot; rel=&quot;nofollow&quot;&gt;Computer Networking&lt;/a&gt; by Tannenbaum is a good guide to networking. It covers all the layers, but has plenty of info on the lower levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0072957166&quot; rel=&quot;nofollow&quot;&gt;Digital Communications&lt;/a&gt; by Proakis is a great general guide to digital comms. Not sure it will be as specific as you'd like though.&lt;/p&gt;&#xA;" OwnerUserId="2454" LastActivityDate="2011-04-15T14:21:01.230" />
  <row Id="13121" PostTypeId="1" AcceptedAnswerId="13122" CreationDate="2011-04-15T14:49:26.550" Score="0" ViewCount="69" Body="&lt;p&gt;Hi all, I don´t get to get the bitstream file. I have an several errors when I try to generate the bitstream file.&#xA;The error&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/OVwdq.jpg&quot; alt=&quot;&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/kTan7.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have this error message from the file call 'xflow.results':&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ERROR:Par:228 - At least one timing constraint is impossible to meet because component delays alone exceed the&#xA;   constraint.  A physical timing constraint summary follows. This summary will show a MINIMUM net delay for the paths.&#xA;   The &quot;Actual&quot; delays listed in this summary are the UNROUTED delays with a 100 ps timing budget for each route, NOT&#xA;   the achieved timing.  Any constraint in the summary showing a failure (&quot;*&quot; in the first column) has a constraint that&#xA;   is too tight.  These constraints must be relaxed before PAR can continue.&#xA;     Please use the Timing Analyzer (GUI) or TRCE (command line) with the Mapped NCD and PCF files to identify the&#xA;   problem paths.  For more information about the Timing Analyzer, consult the Xilinx Timing Analyzer Reference manual;&#xA;   for more information on TRCE, consult the Xilinx Development System Reference Guide &quot;TRACE&quot; chapter. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is strange to me because I have never had a constraint problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anybody know what I could do, to avoid constraint problems in system Generator?&#xA;Thank you so much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The link for my .mdl file:&#xA;&lt;a href=&quot;https://www.dropbox.com/s/h15ns3p55wlbuc2/singledivider_exampleconceptlatencyandsimtime.mdl&quot; rel=&quot;nofollow&quot;&gt;https://www.dropbox.com/s/h15ns3p55wlbuc2/singledivider_exampleconceptlatencyandsimtime.mdl&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The link for my xflow. file:&#xA; &lt;a href=&quot;https://www.dropbox.com/s/odqoakbrs21ngbx/xflow.results&quot; rel=&quot;nofollow&quot;&gt;https://www.dropbox.com/s/odqoakbrs21ngbx/xflow.results&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2597" LastEditorUserId="2597" LastEditorDisplayName="" LastEditDate="2011-04-16T05:34:23.670" LastActivityDate="2011-04-16T05:34:23.670" Title="System Generator: Problems with CORDIC block at getting the bitstream file" Tags="&lt;xilinx-system-generator&gt;&lt;problem&gt;&lt;cordic&gt;&lt;error&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13122" PostTypeId="2" ParentId="13121" CreationDate="2011-04-15T15:43:41.437" Score="2" ViewCount="" Body="&lt;p&gt;The error means that your design can not run as fast as you are telling the tools it needs to. There are a few possible strategies:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;If you are doing this as an experiment without specific requirements, you could try a smaller divider, that is more likely to work at the clock frequency you have.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If your board allows you to select a different clock frequency for the FPGA, you can do that, and update the constraints with the lower frequency.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You can add registers to your design to reduce the length of the critical path, as described &lt;a href=&quot;http://electronics.stackexchange.com/questions/9642/system-generator-how-to-configure-the-cordic-divider-block-understanding-the-bl/9650#9650&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;You can add a clock divider to your design. There is an example in &lt;a href=&quot;http://electronics.stackexchange.com/questions/10770/pipelining-and-clock-frequency-issue/10813#10813&quot;&gt;Pipelining and clock frequency issue&lt;/a&gt;.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-04-15T15:43:41.437" CommentCount="1" />
  <row Id="13123" PostTypeId="2" ParentId="13087" CreationDate="2011-04-15T15:57:33.023" Score="4" ViewCount="" Body="&lt;p&gt;Turning something on and off does not make it &quot;digital&quot;.  Switch-mode power supplies are not digital.  Class D amplifiers are not digital.  Just because something outputs square waves doesn't mean it's digital.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Digital&quot; means data or information being transferred in the form of discrete symbols.  As long as a symbol is received without error, the signal suffers zero degradation, unlike analog which is incrementally corrupted by noise and distortion.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Those symbols can be represented by on and off pulses, like in digital logic, but also by any other scheme you can think of, like &lt;a href=&quot;http://en.wikipedia.org/wiki/Phase-shift_keying&quot; rel=&quot;nofollow&quot;&gt;phase shifts of a sine wave&lt;/a&gt;, or by &lt;a href=&quot;http://en.wikipedia.org/wiki/Frequency-shift_keying&quot; rel=&quot;nofollow&quot;&gt;frequency shifts of a sine wave&lt;/a&gt;, or whatever.  They're all digital.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-16T04:42:42.323" LastActivityDate="2011-04-16T04:42:42.323" CommentCount="2" />
  <row Id="13124" PostTypeId="1" CreationDate="2011-04-15T16:02:59.430" Score="3" ViewCount="179" Body="&lt;p&gt;I've been trying to get my LCD initialized for about a week now, and am quite embarrassed to say that I've been unsuccessful thus far.  I've done this in the past, and I remember it being a little tricky getting the initialization sequence just right, but at this point I think I've fully vetted the implementation and it's just not working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Setup:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;NHT-C0220AZ-FSW-FTW LCD with an NT7605 driver&lt;/li&gt;&#xA;&lt;li&gt;TI Launchpad w/ MSP430G2231&lt;/li&gt;&#xA;&lt;li&gt;single-turn 10k pot for contrast control&lt;/li&gt;&#xA;&lt;li&gt;LCD powered with 3.3V&lt;/li&gt;&#xA;&lt;li&gt;Launchpad powered with USB&lt;/li&gt;&#xA;&lt;li&gt;Grounds for each component tied together&lt;/li&gt;&#xA;&lt;li&gt;using the LCD's 4bit interface&lt;/li&gt;&#xA;&lt;li&gt;LCD backlight connected to Vcc (3.3V) from Launchpad&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WkMcd.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are things I have done so far for testing:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Double checked connections&#xA;&lt;ol&gt;&#xA;&lt;li&gt;LCD pins D4-D7, RS, R/W, and E&lt;/li&gt;&#xA;&lt;li&gt;Potentiometer hooked up to contrast control pin, and I have verified that the voltage goes from 0 - Vdd.&lt;/li&gt;&#xA;&lt;li&gt;LCD Vdd hooked up to 3.4V, which is at about the minimum voltage spec&lt;/li&gt;&#xA;&lt;/ol&gt;&lt;/li&gt;&#xA;&lt;li&gt;Double checked I/O routines on MSP430&#xA;&lt;ol&gt;&#xA;&lt;li&gt;LCD pins are reset/set as expected as I step through my code&lt;/li&gt;&#xA;&lt;li&gt;Timing routines are semi &quot;calibrated&quot; &lt;code&gt;for&lt;/code&gt; loops&lt;/li&gt;&#xA;&lt;/ol&gt;&lt;/li&gt;&#xA;&lt;li&gt;Cross checked documentation for initialization routines against others' routines that I have found online&#xA;&lt;ol&gt;&#xA;1. &#xA;&lt;/ol&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Yet after all of this, I can't get anything to display on the LCD!  So here are my questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The manufacturer has verified that there is a bug in the NT7605 where the busy bit isn't asserted properly.  So I have been using fixed delays (fine with me), but wanted to use the busy flag to see if the driver is even responding to commands.  Is there another way for me to do a low-level diagnostic to see what the LCD is thinking as I send initialization commands?&lt;/li&gt;&#xA;&lt;li&gt;Has anyone else here used the same LCD?  All other standard LCDs I've used (2x20 character types) darken noticeably when I turn the contrast adjustment, and IIRC they do this even when not initialized properly.  However, when I turn the pot on mine, the LCD doesn't darken at all.  Perhaps this is because it's not initialized, but I'm not sure.&lt;/li&gt;&#xA;&lt;li&gt;Can anyone find something screwy with this initialization routine?&#xA;&lt;ol&gt;&#xA;&lt;li&gt;delay &gt; 30ms&lt;/li&gt;&#xA;&lt;li&gt;send 0x20, upper nibble only&lt;/li&gt;&#xA;&lt;li&gt;send 0x28 (set 4 bit interface)&lt;/li&gt;&#xA;&lt;li&gt;wait 10ms&lt;/li&gt;&#xA;&lt;li&gt;send 0x0C (display on, cursor off, blink off)&lt;/li&gt;&#xA;&lt;li&gt;wait 10ms&lt;/li&gt;&#xA;&lt;li&gt;send 0x01 (clear display)&lt;/li&gt;&#xA;&lt;li&gt;wait 10ms&lt;/li&gt;&#xA;&lt;li&gt;send 0x02 (increment cursor, no display shift)&lt;/li&gt;&#xA;&lt;li&gt;wait 10ms&lt;/li&gt;&#xA;&lt;li&gt;set RS high to start sending character data&lt;/li&gt;&#xA;&lt;li&gt;send 0x48 (display 'H')&lt;/li&gt;&#xA;&lt;/ol&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/02EHN.png&quot; alt=&quot;Initialization routine from the manufacturer&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My code looks like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void InitializeLcd()&#xA;{&#xA;    DelayTicks( 10000);&#xA;    // 4 bit interface, 2 lines, 5x8 characters&#xA;    // the spec sheet shows the 0x20 part of 0x28 getting sent an extra time&#xA;    // so I used a special function to deal with this case.  This just sends&#xA;    // the 0x20 part and ignores the 0x08 part.&#xA;    SendLcdUpperNibble( COMMAND, 0x28);&#xA;    SendLcdByte( COMMAND, 0x28);&#xA;    DelayTicks( 1000);&#xA;    // Display on, cursor off, blink off&#xA;    SendLcdByte( COMMAND, 0x0C);&#xA;    DelayTicks( 1000);&#xA;    // clear display&#xA;    ClearLcd();&#xA;    // Entry mode set - increment cursor, no display shift&#xA;    SendLcdByte( COMMAND, 0x02);&#xA;    DelayTicks( 1000);&#xA;    // Set write to DDRAM mode since we'll just be sending data from now on&#xA;    SendLcdByte( DATA, 0x48);&#xA;    SendLcdByte( DATA, 0x65);&#xA;    SendLcdByte( DATA, 0x6C);&#xA;    SendLcdByte( DATA, 0x6C);&#xA;    SendLcdByte( DATA, 0x6F);&#xA;}&#xA;&#xA;void ClearLcd()&#xA;{&#xA;    // Clear display&#xA;    SendLcdByte( COMMAND, 0x01);&#xA;    DelayTicks( 1000);  &#xA;}&#xA;&#xA;void SetRS( int value)&#xA;{&#xA;    if( value == 0)&#xA;        P2OUT &amp;amp;= ~RS;&#xA;    else&#xA;        P2OUT |= RS;&#xA;}&#xA;&#xA;void SetRW( int value)&#xA;{&#xA;    if( value == 0)&#xA;        P2OUT &amp;amp;= ~RW;&#xA;    else&#xA;        P2OUT |= RW;    &#xA;}&#xA;&#xA;void SetE( int value)&#xA;{&#xA;    if( value == 0)&#xA;        P1OUT &amp;amp;= ~E;&#xA;    else&#xA;        P1OUT |= E;&#xA;}&#xA;&#xA;void DelayMs( int delay)&#xA;{&#xA;    int ctr;&#xA;    int ms = delay * 100;&#xA;    for( ctr=0; ctr&amp;lt;ms; ctr++);&#xA;}&#xA;&#xA;void DelayTicks( int ticks)&#xA;{&#xA;    int ctr;&#xA;    for( ctr=0; ctr&amp;lt;ticks; ctr++);&#xA;}&#xA;&#xA;void SendLcdByte( unsigned char command_0_or_data_1, unsigned char command)&#xA;{&#xA;    SendLcdUpperNibble( command_0_or_data_1, command);&#xA;    // send the lower nibble next&#xA;    // special thank you to ToyBuilder for catching my missed bit-shift in the following line&#xA;    // I also had the mask on P1OUT incorrect, presumably because I messed up the command mask and just made it match that.&#xA;    P1OUT = ((command &amp;amp; 0x0F) &amp;lt;&amp;lt; 4) | (P1OUT &amp;amp; 0x0F);&#xA;    Strobe( command_0_or_data_1);&#xA;}&#xA;&#xA;void SendLcdUpperNibble( unsigned char command_0_or_data_1, unsigned char upper_nibble)&#xA;{&#xA;    P1OUT = (upper_nibble &amp;amp; 0xF0) | (P1OUT &amp;amp; 0x0F);&#xA;    Strobe( command_0_or_data_1);&#xA;}&#xA;&#xA;void Strobe( unsigned char command_0_or_data_1)&#xA;{&#xA;    SetRS( command_0_or_data_1);&#xA;    SetRW( 0);&#xA;    DelayTicks( 1000);&#xA;    SetE( 1);&#xA;    DelayTicks( 1000);&#xA;    SetE( 0);       &#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The only thing I can say is that the LCD looks like it flickers when I step over SendLcdByte and am sending it character data.  When I scope everything, it sure looks like I'm flipping bits properly...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- I soldered up a new LCD, and this time I tried leaving the unused data pins (D0-D3) disconnected (i.e. floating).  There was no difference.  The LCD still flickers when I initialize.  I am now waiting 100ms for all delays, including a delay when strobing E.  I have also disconnected Vcc coming from the Launchpad FET section and am now just powering the MSP430 and LCD from my lab power supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT #2 -- I went to a 3.3V LCD and everything magically started working.  Thanks to ToyBuilder for catching a stupid code bug when I was debugging with the 5V LCD.  After the swap the LCD initialized properly.  I'm currently displaying garbage instead of &quot;Hello&quot;, but that's unrelated to this question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT #3 -- found my display bug -- I was sending 0x06 for entry mode instead of 0x02.  Not sure why I did that, must have been a typo.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-04-27T14:54:46.417" LastActivityDate="2011-04-27T14:54:46.417" Title="Debugging initialization of LCD with NT7605 driver" Tags="&lt;lcd&gt;&lt;msp430&gt;&lt;launchpad&gt;&lt;initialization&gt;&lt;nt7605&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="13125" PostTypeId="1" CreationDate="2011-04-15T16:23:47.517" Score="3" ViewCount="131" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using the following circuit (from &lt;a href=&quot;http://luckylarry.co.uk/arduino-projects/arduino-control-a-dc-motor-with-potentiometer-and-multiple-power-supplies/&quot; rel=&quot;nofollow&quot;&gt;http://luckylarry.co.uk/arduino-projects/arduino-control-a-dc-motor-with-potentiometer-and-multiple-power-supplies/&lt;/a&gt;) to control the speed of a 6V DC motor powered by a separate power supply:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tX6n0.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I put a heavy load on the motor or stall it, serial communication between my Arduino Uno and my PC (over USB) fails.  Data stops coming over and I need to disconnect the Uno, close the IDE, connect the Uno again, and then start the IDE in order to get the link back up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not sure if this is a grounding problem (I took care to make sure all grounds go to the same rail), a load problem (even though the Uno and the motor have separate power supplies) or a back-emf problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-Rob&lt;/p&gt;&#xA;" OwnerUserId="3881" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-04-16T03:19:21.690" LastActivityDate="2011-04-19T18:45:39.397" Title="Arduino serial communication fails when stalling/loading a DC motor controlled by PWM" Tags="&lt;arduino&gt;&lt;pwm&gt;&lt;dc-motor&gt;&lt;troubleshooting&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="13128" PostTypeId="2" ParentId="7791" CreationDate="2011-04-15T19:11:21.920" Score="3" ViewCount="" Body="&lt;p&gt;We provide equipment that will bring the GPS signal indoors.  Yes, you need a passive antenna and an active antenna - you have to be able to calculate the correct amount of cable and possibly the use of an amplifier.  All of this is regulated by the FCC.  Unless you are a Federal agency, part of the military or using this in an anechoic chamber, you have to apply for a license from the FCC.&lt;/p&gt;&#xA;" OwnerUserId="3885" LastActivityDate="2011-04-15T19:11:21.920" />
  <row Id="13132" PostTypeId="2" ParentId="13125" CreationDate="2011-04-16T00:12:53.933" Score="2" ViewCount="" Body="&lt;p&gt;It seems like it might be a ground issue of some kind. What are your power supplies, and how are they connected? Did you do the circuit on a breadboard like the picture in the link?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you heavily load or stall the motor, it will pass significant current. Assuming you built it like the picture, a large current in your motor power return lead could cause the (-) rail on the breadboard to ride up. If the motor p.s. is referenced back to the PC's ground (beware the 'sneak path'!), this could cause the apparent voltage levels at the USB interface to be out of spec. You might even get some kind of latch-up effect that would require removal of power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your motor p.s. isn't a battery, you might want to try using a battery, and see if the condition persists.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-16T00:12:53.933" CommentCount="2" />
  <row Id="13134" PostTypeId="1" AcceptedAnswerId="13144" CreationDate="2011-04-16T07:40:29.220" Score="1" ViewCount="71" Body="&lt;p&gt;&lt;strong&gt;Hello everyone&lt;/strong&gt;&lt;br&gt;&#xA;This is my first question on the ED site. I have been on SO and programmers. stackexchange before.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm writing a C program that will access a flash AT45DB041B from the controller ATmega169. I'm using a Butterfly development kit.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have succeeded to read the status register and get correct data so I'm quite sure that the flash works and can communicate. But I haven't been able to write and read to flash, the only thing that I can read from it is zeros.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I unfortunately I don't have any possibility to snoop the traffic either.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;init:  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; void init_flash_as_master(void)&#xA; {&#xA;&#xA;// double speed, p 150 mega169 manual&#xA;SPSR = 0x01; // the other bits are don't care or set by hardware&#xA;&#xA;//      MOSI        SCK         !SS    are outputs&#xA;DDRB |= _BV(PB2) | _BV(PB1) | _BV(PB0);&#xA;&#xA;&#xA;// p 148 in mega169 manual&#xA;/* bit 7, 0 interrupt not enabled&#xA; * bit 6, 1 SPI enable,&#xA; * bit 5, 0, MSB first, ch 5 flash datasheet&#xA; * bit 4, 1, Master&#xA; * bit 3,2, 00, CPOL,CPHA, SPI mode 0, p 5 flash datasheet&#xA; * bit 1,0, 10, /32, flash max operating frequency 20 MHz p 1 flash datasheet&#xA; */&#xA;&#xA;SPCR = 0x52;&#xA;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;send:  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;inline void send_byte(uint8_t byte)&#xA;{&#xA;    SPDR = byte;&#xA;    while (!(SPSR &amp;amp; _BV(SPIF))) {;}&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;recive:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;inline uint8_t recieve_byte(void) &#xA;{&#xA;SPDR = 'A'; //load SPDR to start clock generation&#xA;while (!(SPSR &amp;amp; _BV(SPIF))) {;}&#xA;return SPDR;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;start transmission:  &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;inline void start_transmission(void) &#xA;{&#xA;    // set chip select for sending data&#xA;    PORTB &amp;amp;= 0xFE; // setting bit 0 on port B low&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;stop transmission:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;inline void stop_transmission(void) &#xA;{&#xA;    // finish transmission&#xA;    PORTB |= 0x01;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;clear flag:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;inline void clear_SPIF(void)&#xA;{&#xA;    uint8_t temp = 0;&#xA;&#xA;    // clear SPIF&#xA;    if(SPSR &amp;amp; _BV(SPIF)) { temp = SPDR; }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;write operation:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// write a struct song_t to specified page in the flash memory&#xA;void flash_write_song(uint16_t page, const song_t * song)&#xA;{&#xA;    if (direction != master) init_flash_as_master();&#xA;&#xA;    clear_SPIF();&#xA;    start_transmission();&#xA;    // ch. 12.2 flash datasheet &#xA;    send_byte(0x84); // write to buffer 1, 84h&#xA;    send_byte(0x00); // three address bytes, starting at byte 0&#xA;    send_byte(0x00); // table 7, flash application note&#xA;    send_byte(0x00);&#xA;&#xA;    // push name&#xA;    for (int i = 0; i != NAME_LEN; i++)&#xA;    {&#xA;        send_byte(song-&amp;gt;name[i]);&#xA;    }&#xA;    int j = 0;&#xA;    while (j &amp;lt; TUNE_LEN) &#xA;    {&#xA;        send_byte(song-&amp;gt;tune[j]);&#xA;        j++;&#xA;}&#xA;stop_transmission();&#xA;&#xA;flash_ready();&#xA;&#xA;start_transmission();&#xA;// ch. 12.3 flash datasheet&#xA;&#xA;    // Buffer 1 to Main Memory Page Program with Built-in Erase&#xA;send_byte(0x83); &#xA;&#xA;    // first byte contains the 4 uppermost bits&#xA;send_byte(get_high_byte(page));&#xA;&#xA;    // second byte contains the 7 lowest bits, starting at bit 1&#xA;send_byte(get_low_byte(page)); &#xA;send_byte(0x00); // table 7, flash application note&#xA;&#xA;stop_transmission();&#xA;flash_ready();&#xA;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;read operation:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// read a struct song_t from specified page in the flash memory&#xA;void flash_read_song(uint16_t page, song_t * song)&#xA;{&#xA;&#xA;if (direction != master) init_flash_as_master();&#xA;&#xA;clear_SPIF();&#xA;&#xA;// flash datasheet 16.2&#xA;start_transmission();&#xA;&#xA;// table 7, flash application note&#xA;send_byte(0xD2); // read page from main memory,&#xA;// first byte contains the 4 uppermost bits&#xA;send_byte(get_high_byte(page)); &#xA;// second byte contains the 7 lowest bits, starting at bit 1&#xA;send_byte(get_low_byte(page)); &#xA;send_byte(0x00); // controller says, read from byte 0&#xA;&#xA;send_byte(0x00); // 4 don't care bytes&#xA;send_byte(0x00);&#xA;send_byte(0x00);&#xA;send_byte(0x00);&#xA;&#xA;// read name&#xA;for (int i = 0; i != NAME_LEN; i++)&#xA;{&#xA;    song-&amp;gt;name[i] = recieve_byte(); &#xA;}&#xA;/*  // and now we will read the data until we find a 0&#xA;int j = 0;&#xA;uint8_t byte_popped = recieve_byte();&#xA;while (j &amp;lt; 4) //TODO&#xA;{&#xA;    song-&amp;gt;tune[j] = byte_popped;&#xA;    j++;&#xA;    byte_popped = recieve_byte();&#xA;}&#xA;*/&#xA;stop_transmission();&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;}&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The question&lt;/strong&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am quite sure that the error is in my code, as I can read the status register. But I can't see any problems in my code. Am I pulling the right signals in the right time?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want any clarifications or more descriptions, please tell.&lt;br&gt;&#xA;&lt;em&gt;Regards&lt;/em&gt;&lt;br&gt;&#xA;Gorgen&lt;/p&gt;&#xA;" OwnerUserId="3882" LastEditorUserId="3882" LastEditorDisplayName="" LastEditDate="2011-04-18T07:07:40.957" LastActivityDate="2011-04-18T07:07:40.957" Title="problems while trying to communicate between ATMEL mega169 and ATMEL flash" Tags="&lt;avr&gt;&lt;spi&gt;&lt;flash&gt;&lt;homework&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="13135" PostTypeId="1" CreationDate="2011-04-16T07:50:05.837" Score="-1" ViewCount="63" Body="&lt;p&gt;Hi&#xA;I'm trying to interface this transceiver chip with my avr. I understand the databits should be connected to my avr. However am unsure of what to do with the rest of the pins. Also how would you get the chip to dial a number.&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-05-16T10:43:53.860" Title="DTMF transceiver MT8889CE - trying to make dtmf dialler" Tags="&lt;circuit-design&gt;" AnswerCount="2" />
  <row Id="13136" PostTypeId="1" CreationDate="2011-04-16T08:20:09.747" Score="2" ViewCount="128" Body="&lt;p&gt;What's the best way to remove this???  I have tried alcohol and simple solvents to no&lt;/p&gt;&#xA;" OwnerUserId="3887" LastActivityDate="2011-04-18T00:42:24.293" Title="conformal coating" Tags="&lt;beginner&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="13137" PostTypeId="2" ParentId="13135" CreationDate="2011-04-16T08:45:19.990" Score="0" ViewCount="" Body="&lt;p&gt;I'd forget about that chip and implement DTMF transmission in software. &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc1982.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is an Atmel app. note describing DTMF generation. It's cheaper than using an external chip, and the frequencies may be fine-tuned if necessary. Given the complexity of the MT8889CE interface, using the Atmel software will save a lot of time.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-16T10:38:23.883" LastActivityDate="2011-04-16T10:38:23.883" CommentCount="4" />
  <row Id="13139" PostTypeId="2" ParentId="13023" CreationDate="2011-04-16T09:31:39.283" Score="1" ViewCount="" Body="&lt;p&gt;I've searched long and hard for this before and the best I've come up with are networked power switches from &lt;a href=&quot;http://www.leunig.de/_en/_pro/remote_power_switches.html&quot; rel=&quot;nofollow&quot;&gt;this manufacturer&lt;/a&gt;. They have an embedded web server, so you could easily hack together a plugin for your CI server to switch lava lamps on and off after a build.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note they're Ethernet only and &lt;strong&gt;very&lt;/strong&gt; expensive as from what I can tell these type of products are intended for data centre operations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Upon further googling, I also find &lt;a href=&quot;http://www.digital-loggers.com/lpc.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;, which is wifi and cheaper, but apparently on backorder. They say they have similar products available now though.)&lt;/p&gt;&#xA;" OwnerUserId="1633" LastEditorUserId="1633" LastEditorDisplayName="" LastEditDate="2011-04-16T09:40:40.723" LastActivityDate="2011-04-16T09:40:40.723" />
  <row Id="13140" PostTypeId="2" ParentId="13135" CreationDate="2011-04-16T10:28:28.563" Score="1" ViewCount="" Body="&lt;p&gt;The datasheet doesn't give a timing diagram for writing to the MT8889, but it contains a number of connection diagrams for different processors, like this one:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/wxmjB.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would consult write timing diagram in the microprocessor's datasheet to see how the different signals relate.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-16T10:28:28.563" CommentCount="1" />
  <row Id="13141" PostTypeId="2" ParentId="12852" CreationDate="2011-04-16T14:11:51.897" Score="0" ViewCount="" Body="&lt;p&gt;What in particular do you want to learn? If you just want to learn more about RF Communications I'd look into your Amateur Radio License. The ARRL handbook has tons of information on RF Propagation, Digital Modes, and so forth. There are several satellite you can communicate with that are currently in space given the proper license.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise your question is a bit vague, If you specify a bit more I may be able to direct you better.&lt;/p&gt;&#xA;" OwnerUserId="3095" LastActivityDate="2011-04-16T14:11:51.897" />
  <row Id="13142" PostTypeId="1" AcceptedAnswerId="13152" CreationDate="2011-04-16T14:57:41.733" Score="2" ViewCount="32" Body="&lt;p&gt;I'm currently building a triangulation-based laser rangefinder with a camera and a number of laser pointers.  Something that I'm interested in doing is using the strobe output from my Point Grey FireflyMV to trigger the laser, so that it is only on when the shutter of the camera is open.  I want  to do this primarily for eye safety.  In addition, I'm curious as to whether I can then run the laser at a higher power level for this very short period of time.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The camera is gathering images at 60 FPS.  This means it is collecting an image every 16.6 ms.  The shutter time is adjustable between .12 and 512 ms.  In this case, let's say that the shutter is open for .3 ms.  I might keep the laser on for .1 ms on either side of the shuttering, just to ensure that the laser is at full brightness for the entirety of image capture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I'm looking for a .5 ms pulse every 17 ms.  First of all, is  a diode laser (like &lt;a href=&quot;http://aixiz.com/store/product_info.php?cPath=44_26&amp;amp;products_id=56&quot; rel=&quot;nofollow&quot; title=&quot;5 mW Line Laser&quot;&gt;this one&lt;/a&gt;) even capable of pulsing this quickly?  Also, could I run the laser at say, 50mW for that short period of time, given that I'm running it at a 3% duty cycle?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lastly, any circuits capable of doing this would be awesome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="3889" LastActivityDate="2011-04-16T21:29:05.607" Title="Laser strobe for Point Grey camera" Tags="&lt;pwm&gt;&lt;camera&gt;&lt;laser&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="2" />
  <row Id="13143" PostTypeId="1" CreationDate="2011-04-16T15:27:23.647" Score="2" ViewCount="100" Body="&lt;p&gt;I am planning to purchase a good inverter, and pure sine wave inverters cost about 3 times as much as modified sine wave ones of the same power. I am thinking about a 2000W continuous/4000W peak inverter 12/24VDC -&gt; 230VAC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which commonly used equipment requires a pure sine wave, and what kind of equipment will be equally fine with a modified sine wave?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am especially wondering about compressor and absorption refrigerators, dehumidifiers, electric drills, fans, microwave ovens, common power tools and kitchen tools. Purely electronic, computer and lighting equipment will not be used through this inverter, as these will have dedicated low-voltage DC-DC converters straight from the battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are pure sine wave inverters any more efficient then much cheaper modified sine wave ones, in terms of input battery consumption per 230VAC output power?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do there exist inverters which can accept a wide range of input DC voltage, for example will work on all of: 12V, 24V and 48V DC?&lt;/p&gt;&#xA;" OwnerUserId="1691" LastActivityDate="2011-04-17T05:00:17.387" Title="which kinds of electrical equipment need a pure sine wave inverter to work correctly?" Tags="&lt;inverter&gt;&lt;efficiency&gt;&lt;pure-sine-wave&gt;&lt;modified-sine-wave&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="13144" PostTypeId="2" ParentId="13134" CreationDate="2011-04-16T17:27:33.783" Score="1" ViewCount="" Body="&lt;p&gt;The only thing I can spot is that &lt;code&gt;stop_transmission()&lt;/code&gt; is missing from &lt;code&gt;flash_ready()&lt;/code&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your programming sequence is:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;fill buffer&lt;/li&gt;&#xA;&lt;li&gt;wait for ready&lt;/li&gt;&#xA;&lt;li&gt;program&lt;/li&gt;&#xA;&lt;li&gt;wait for ready&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The program command may be lost since it is not preceded by a falling edge of $\overline{\text{CS}}$.&lt;/p&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-04-16T17:27:33.783" CommentCount="1" />
  <row Id="13145" PostTypeId="2" ParentId="13143" CreationDate="2011-04-16T18:35:17.627" Score="3" ViewCount="" Body="&lt;p&gt;The modified sine wave inverters generally cause more power loss in your products' power supplies.  So the inverter itself may not be any more efficient, but the equipment running on a pure sine wave inverter will most likely run more efficiently.  This is especially true for inductive loads, such as all the equipment you listed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd guess that most of your equipment with linear AC/DC power supplies will work, but perhaps not as efficiently or with reduced performance and increased heat.  Many radios, for example, will sound worse when run off a modified sine wave converter.  Other products that use switching supplies may not work.  I'd recommend ponying up the extra money for the pure sine wave inverter for anything other than an emergency power supply you need to use temporarily when power is lost, for example.  Especially as you are looking to drive inductive loads.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not an expert on inverters, but I know there are plenty that run on 12V designed for the RV community.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastEditorUserId="2377" LastEditorDisplayName="" LastEditDate="2011-04-16T18:43:48.870" LastActivityDate="2011-04-16T18:43:48.870" />
  <row Id="13146" PostTypeId="2" ParentId="13069" CreationDate="2011-04-16T18:44:11.380" Score="1" ViewCount="" Body="&lt;p&gt;The act of multiplexing consists of taking a number of signals and combining them into one.  The act of demultiplexing consists of taking one multiplexed signal and reconstituting the multiple outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a simple mechanical analogy, suppose there are sixteen switches that need to control sixteen lights some distance away, but one doesn't want to run sixteen wires.  One approach would be to rig a motor/commutator arrangement that would connect one wire (the &quot;data&quot; wire) to one of the sixteen switches, and output on four other wires a 1/0 pattern indicating which of the sixteen switches was selected.  At the other end, one could use the four &quot;counting&quot; wires along with some relays to connect the &quot;data&quot; wire to one of sixteen lightbulbs.  Sixteen wires have now been reduced to five.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that the signal sent on the &quot;counting&quot; wires doesn't change with what switches are enabled and disabled.  One could omit the four wires between the sender and receiver if there were other ways of keeping them in sync.  For example, one could arrange the commutator wheel so that it would always have a gap between the lights, but would send a long &quot;fixed&quot; pulse every revolution.  The receiving end could have a mechanism to look for that long pulse and make sure its motor was positioned suitably.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When lights are multiplexed in this fashion, it's possible for the sender to communicate any combination of lights to the receiver, but multiplexing effectively delays transmission.  When a light is switched on, the receiver won't know about it until the multiplexing wheel comes around.  In some situations, speed is essential but it's not important to communicate the state of all the switches--just the highest-numbered one that's enabled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To handle that scenario, one could have one wire which indicates whether any of the switches have been turned on, and four wires to indicate which of the sixteen switches is the highest-numbered one that's turned on.  At the receiving end, relays could light one of sixteen lamps based upon the combination of signals on the incoming wires.  This system is not called &quot;multiplexing&quot;, but &quot;encoding&quot;.  The device to detect which of the sixteen inputs is the highest one turned on and set the outputs accordingly is an &quot;encoder&quot;; the device to light the appropriate lamp is a &quot;decoder&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that the decoder is in fact identical to the original relay-based demultiplexer; what differs is how it's used.  In the original system the pattern sent on the selector wires was fixed and the real information was sent in on the &quot;data&quot; wire.  Here, the data wire simply serves as a master enable, and the real information is sent on the selector wires (actually, if there were fifteen switches rather than sixteen, one could omit the selector wire, but in many cases a master enable is a very useful thing to have; among other things, it may be hard to ensure that signals on all the other wires are processed identically, but it would be much easier to ensure that the master-enable would arrive last).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's one other scenario that's worth mentioning: the intended receiver of the data might want to be able to find out the status of any particular switch instantly, but only be interested in one at a time.  In this scenario, the receiver of the data would supply four select wires to the sender, and the sender would use some relays to connect one of the sixteen switches to the return data wire.  The sender is a effectively multiplexer (combining many independent signals into one); the receiver can do with the information what he wants.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The multiplxer (take a number of data inputs, plus a selector input) is so called because that is by far its most common use.  Whether the selection of inputs is occurring at some regular interval, or if in practice the recipient of the data is interested in one particular input far more than any other, the multiplexer combines many inputs into one.  If a microprocessor is used to poll multiple inputs and store the results in different places, the microprocessor would be acting as a demultiplexer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the flip side, a device to enable one of some number of outputs based upon a selector and master-enable input could be used as a demultiplexer, but such devices are far more often used for decoding a binary-coded selector signal into a one-hot output.  The processor outputs on the select wires an indicator of which signal it wants to be active, and the decoder's job is to make that happen.  In a processor-controlled multiplexed grid of LEDs, the CPU effectively multiplexes the LED data and the LEDs themselves serve as demultiplexers (if 16 LEDs have a processor pin wired as a common cathode, and the anodes of the LEDs are wired to a decoder, each LED will individually either convey or not convey the state of the processor line, based upon whether its row wire is active).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only time one typically sees the term &quot;demultiplexer&quot; used is with analog signals.  If a device connects an analog signal to one of sixteen outputs, it's usually clear that the signal itself is what's interesting, rather than the selection of the output.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-16T18:44:11.380" />
  <row Id="13147" PostTypeId="1" AcceptedAnswerId="13153" CreationDate="2011-04-16T18:51:46.570" Score="0" ViewCount="126" Body="&lt;p&gt;Hi all,&#xA;i bought from web &lt;strong&gt;one of this matrix&lt;/strong&gt;: &lt;a href=&quot;http://tinyurl.com/3zjhuk7&quot; rel=&quot;nofollow&quot;&gt;http://tinyurl.com/3zjhuk7&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I followed all instructions and i connected it to my arduino uno &lt;strong&gt;without sensor shield&lt;/strong&gt; (it's necessary?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used &lt;strong&gt;IN pins&lt;/strong&gt; of the matrix in this way:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Arduino digital pin 4,5,6,7 to input pin OIA,OIB,OIC,OID of LED screen&lt;br&gt;&#xA;  Arduino digital pin 8,9,10 to pin SER,SCK,RCK of LED screen LED screen&lt;br&gt;&#xA;  GND to Arduino ground and VCC of LED screen to Arduino power  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I've also uploaded code.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, using the code (as show in link) my matrix &lt;strong&gt;show me only lines without characters&lt;/strong&gt;!!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also changed &lt;code&gt;#define ScreenNO 4&lt;/code&gt; to &lt;code&gt;#define ScreenNO 1&lt;/code&gt; because i've only one 16x16 matrix.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Screenshots:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/TUJ3i.jpg&quot; alt=&quot;http://tinyurl.com/3drepwx&quot;&gt;&lt;br&gt;&#xA;&lt;img src=&quot;http://tinyurl.com/3qlk95u&quot; alt=&quot;http://tinyurl.com/3qlk95u&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What could be the cause?&lt;br&gt;&#xA;What's wrong in wires or code?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks all!&lt;/p&gt;&#xA;" OwnerUserId="3359" LastActivityDate="2011-04-16T21:37:46.923" Title="Why my 16x16 LED matrix show only lines?" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;led&gt;&lt;matrix&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="13148" PostTypeId="2" ParentId="13143" CreationDate="2011-04-16T19:56:19.210" Score="3" ViewCount="" Body="&lt;p&gt;Generally speaking, anything with an inductive or motor load, pure sine wave is better.&#xA;A load that first rectifies the input (PC power supply, phone charger etc) a modified output would be sufficient&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-04-16T19:56:19.210" />
  <row Id="13149" PostTypeId="2" ParentId="13136" CreationDate="2011-04-16T19:57:36.217" Score="1" ViewCount="" Body="&lt;p&gt;If its just a small area I find the best thing is to burn it off with a soldering iron&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-04-16T19:57:36.217" />
  <row Id="13150" PostTypeId="1" CreationDate="2011-04-16T20:49:48.497" Score="0" ViewCount="115" Body="&lt;p&gt;I'm constructing a LED matrix using tricolour LEDs. I was wondering - will I be able to wire these in series?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was told to mount the LEDs in series using stripboard, then wire each stripboard in parallel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the &lt;a href=&quot;http://docs-europe.electrocomponents.com/webdocs/01ff/0900766b801ff521.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; for the tricolour LEDs.&lt;/p&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="3028" LastEditorDisplayName="" LastEditDate="2011-06-01T14:50:31.143" LastActivityDate="2011-06-01T14:50:31.143" Title="Can tricolour LEDs be connected in series?" Tags="&lt;led&gt;" AnswerCount="1" />
  <row Id="13151" PostTypeId="2" ParentId="13150" CreationDate="2011-04-16T21:29:01.117" Score="1" ViewCount="" Body="&lt;p&gt;The LED described would these days more commonly be called a bi-color LED (the term tri-color refers to LED assemblies with red, green, and blue diodes); it does not allow for series connection since the two diodes are wired cathode-to-cathode.  Some other bicolor diodes are wired anode-to-cathode, thus allowing series or reverse-parallel operation, but the one you linked isn't one of them.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-16T21:29:01.117" CommentCount="7" />
  <row Id="13152" PostTypeId="2" ParentId="13142" CreationDate="2011-04-16T21:29:05.607" Score="1" ViewCount="" Body="&lt;p&gt;Laser diodes themselves can pulse as fast as you like - down to nanosecs - actual speed depends on the driver.&#xA;It is not generally practical to increase power at lower duty cycles as the limiting factor tends to be optical damage rather then purely thermal. &#xA;Bear in mind that unless you need the coherence or tight beam of a laser, normal power LEDs will typically give you more output power then lasers, and are more amenable to increasing power for short durations.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-04-16T21:29:05.607" CommentCount="2" />
  <row Id="13153" PostTypeId="2" ParentId="13147" CreationDate="2011-04-16T21:37:46.923" Score="0" ViewCount="" Body="&lt;p&gt;Since the display is square, it's not clear which way is &quot;up&quot;.  One would expect the top row to be nearest the top of the picture, but sometimes things can be surprising.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My guess would be that rows are indeed horizontal, and the LSB of the OIA/B/C/D wires is not connected properly or is otherwise not working and the display is always seeing it as &quot;high&quot;.  This causes only the odd-numbered rows to be illuminated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without knowing exactly what you're trying to display, it's hard to determine what problems there might be beyond that; seeing what patterns are displayed when the row-select pin is fixed may reveal other issues.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-16T21:37:46.923" CommentCount="2" />
  <row Id="13156" PostTypeId="2" ParentId="13136" CreationDate="2011-04-17T00:22:23.660" Score="1" ViewCount="" Body="&lt;p&gt;That depends on wether you want to remove just a small area (like eddie mentioned) or the entire board. If you just want to solder a component on a coated copper terminal, a bit of solder flux followed by a normal soldering procedure will do the job for most coatings. If not, heat it with the soldering iron and it will loosen from the copper so you can scrap it off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to remove all the coating, in general you'll need a specific solvent, from the same manufacturer that provides the coating (one well known is Electrolube). Look for their products in major stores like Digikey, Mouser, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One more simple approach I use (not feasible for bigger boards) is to scrap the coating off with the abrasive side of a kitchen sponge. The downside is that if you have plated surfaces they can be damaged by this. &lt;/p&gt;&#xA;" OwnerUserId="1078" LastEditorUserId="1078" LastEditorDisplayName="" LastEditDate="2011-04-18T00:42:24.293" LastActivityDate="2011-04-18T00:42:24.293" />
  <row Id="13157" PostTypeId="1" CreationDate="2011-04-17T01:07:06.703" Score="6" ViewCount="172" Body="&lt;p&gt;I really want to develop on a gumstix with an e-ink display, but &lt;a href=&quot;http://store.nexternal.com/eink/am350-prototyping-kit-c5.aspx&quot; rel=&quot;nofollow&quot;&gt;$3000 for a development board&lt;/a&gt; is a bit steep for me right now, especially since I just want to get a prototype out so I can see what the market is like.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a work-around, this is what I have in mind:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Buy a &lt;a href=&quot;http://www.amazon.com/Kindle-Wireless-Reader-Wifi-Graphite/dp/B002Y27P3M&quot; rel=&quot;nofollow&quot;&gt;Kindle&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Buy a gumstix with a dev board&lt;/li&gt;&#xA;&lt;li&gt;Hook up the Kindle display to dev board using clever soldering&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This is what I want in the end:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Low-power, easy to read screen (text viewing)&lt;/li&gt;&#xA;&lt;li&gt;Wifi-enabled device&lt;/li&gt;&#xA;&lt;li&gt;More than 4 GB of persistent storage&lt;/li&gt;&#xA;&lt;li&gt;Touch enabled device (I can get by without this)&lt;/li&gt;&#xA;&lt;li&gt;Preferably color, but monochrome is ok&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I am really intrigued by the persistence of the e-ink display without using battery...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Is it possible to use the e-ink screen with the gumstix?&lt;/strong&gt; If not, is there anything else I should be looking into?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think I can root the Kindle and install my own OS on it, but I won't be able to easily add parts to it (say USB ports, audio ports, etc).  The gumstix is really the way to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Legal:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I read in the &lt;a href=&quot;http://www.amazon.com/gp/help/customer/display.html?nodeId=200505590&amp;amp;&quot; rel=&quot;nofollow&quot;&gt;EULA&lt;/a&gt;, it is a violation to disassemble the Kindle, but the only thing they can do is revoke access to the Kindle Store and revoke use of any eBooks or services downloaded.  There is no mention of penalties or fines for violating the EULA with respect to hardware.  Since I am not developing this as part of a company, I don't think there is anything they can do legally.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even so, I just want to know if it can be done with existing hardware and software. If I plan to market something with Kindle hardware components (which I won't), I'll definitely talk to a lawyer first.&lt;/p&gt;&#xA;" OwnerUserId="3895" LastEditorUserId="3895" LastEditorDisplayName="" LastEditDate="2011-04-18T16:53:36.040" LastActivityDate="2011-04-18T16:53:36.040" Title="Gumstix with an e-ink screen" Tags="&lt;arm&gt;&lt;display&gt;&lt;e-ink&gt;&lt;gumstix&gt;" CommentCount="12" FavoriteCount="2" />
  <row Id="13159" PostTypeId="1" AcceptedAnswerId="13162" CreationDate="2011-04-17T02:19:36.290" Score="1" ViewCount="148" Body="&lt;p&gt;I'd like to remove all the ICs from the below PCB, hopefully preserving them for future use:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/NPKwa.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This was a failed (ish) reflow attempt using paste and a hot plate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a hot plate, a hot air machine and a soldering iron, plus soldering stuff: wick, solder sucker, and lead-free solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I do it?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-04-17T02:30:12.700" LastActivityDate="2011-04-19T16:04:38.393" Title="Reworking a PCB - remove these components" Tags="&lt;pcb&gt;&lt;rework&gt;" AnswerCount="6" />
  <row Id="13160" PostTypeId="2" ParentId="13159" CreationDate="2011-04-17T02:39:01.057" Score="1" ViewCount="" Body="&lt;p&gt;I would try using the hot plate to warm the board, combined with the hot air tool to heat up the ICs and the solder joints. With patience (and some luck) you'll get the ICs off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tweezers and/or a utility knife can be helpful getting the parts off once the solder is flowing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does your air tool have nozzles that line up with the IC packages? They help with the larger parts.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-17T02:39:01.057" />
  <row Id="13161" PostTypeId="2" ParentId="13136" CreationDate="2011-04-17T02:42:47.947" Score="2" ViewCount="" Body="&lt;p&gt;At my workplace, small amounts of conformal coating are removed with a rotary tool and a fine tip. Make sure you have respiratory protection if you're removing CC.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-17T02:42:47.947" />
  <row Id="13162" PostTypeId="2" ParentId="13159" CreationDate="2011-04-17T04:00:28.897" Score="4" ViewCount="" Body="&lt;p&gt;Here's what I'd do...  To start with, read my answer to the question of &quot;&lt;a href=&quot;http://electronics.stackexchange.com/questions/12565/solder-very-close-together-contacts/12567#12567&quot;&gt;Solder very close together contacts&lt;/a&gt;&quot;.  That answer won't tell you what to do to remove these parts, but it will tell you the type of soldering iron tip to use and what to do once the parts are off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, as for getting the parts off... I would use a pair of curved fine-tip tweezers, and a super pointy dental pick with a 60-70 degree bend in the end.  Most dental picks are not sharp enough for this.  You need one that's narrow enough to get at least a little bit of the tip under the part.  You might be able to use an X-Acto knife instead of a dental pick.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, let's separate this into chips with two rows of pins (SOIC's, TSSOP's, etc).  We'll tackle the chips with 2-rows first...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Start with lots of flux on the chip.  Clean off the soldering iron tip and then put on a good amount of solder.   Touch one row of pins and run the soldering iron back and forth across the entire row of pins.  The idea here is that you get the solder on the entire row melted and keep it melted.  You need to use enough solder so that there is enough thermal mass to keep it molten as you move the tip back and forth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While that one side is melted, put the dental pick under the chip and pry it up.  You are not going to get it up very much, maybe 1 mm.  You shouldn't need much pressure (or you could damage things).  When you're done, one row of pins should be about 1 mm higher than the other row.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let me be clear here.  With one hand, you are running the iron across the pins, keeping the solder molten.  With the other hand, you're gently prying up that row of pins.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Repeat this process for the other row.  Now both rows should be about 1 mm higher.  Repeat again, alternately jacking up each side until one side comes completely loose.  Now, grab the chip with the tweezers and heat up the remaining row.  The chip should be loose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Clean up the chip's pins, and the pads on the PCB with some flux and solder braid.  It's important to get the pins back as straight as possible before trying to solder it down again.  If it's a cheap chip, and you have more of them, then consider throwing it away and starting with a fresh chip-- it's that important that they are all straight and even.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, on to chips with 4 rows of pins (QFP, TQFP, PLCC, etc).  I hate to say it, but you can't use the previous method with those chips.  The only way I have been able to remove a QFP and not destroy the chip in the process is to use a hot-air rework station with a nozzle that is made for the chip package that I'm removing.  You might be able to kludge something together using a standard heat gun or toaster oven or whatever, but I have never had luck with that.  Whatever you do, practice, practice, practice.  Actually, that goes for everything else too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, here's how you remove a QFP/PLCC by destroying the chip (and not destroying the PCB):  Get an X-Acto knife.  You might consider putting a fresh blade in it.  And run the blade across each row of pins where the pin enters the plastic/ceramic body of the chip.  You'll have to go across 10-20 times, each time scoring the pin a little bit deeper.  Eventually you will cut through the pins.  Do that for each row.  Remove the plastic/ceramic part of the chip.  Then use a soldering iron with a gob of solder on it to remove the pins from the pads.  Clean up the PCB as before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The danger with any type of PCB rework is that you could damage the PCB-- lifting pads and traces off of the board.  Mostly this comes from applying too much heat for too long, or prying things off when the solder is not completely melted.  I recommend that you practice any of this before working on a PCB that you actually care about.  Get some old piece of gear and start unsoldering things.  This will save you much frustration and broken PCB's.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-17T04:00:28.897" CommentCount="0" />
  <row Id="13163" PostTypeId="2" ParentId="13143" CreationDate="2011-04-17T05:00:17.387" Score="2" ViewCount="" Body="&lt;p&gt;Some people claim that certain loads &quot;may&quot; not work as well, or &lt;a href=&quot;http://en.wikibooks.org/wiki/Talk%3aBasic_Electrical_Generation_and_Distribution#damage&quot; rel=&quot;nofollow&quot;&gt;&quot;may&quot; be damaged&lt;/a&gt;, with anything other than a pure sine wave.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since the power coming out of my wall sockets is significantly different from a pure sinewave, I suspect these sincere and well-meaning people are merely repeating propaganda from the manufacturer of a pure sinewave inverter manufacturer,&#xA;much like people repeat urban legends.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is only one kind of device that I &lt;em&gt;know&lt;/em&gt; doesn't work as well with a non-sine-wave inverter: devices that use a &quot;capacitive power supply&quot;&#xA;-- see &#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/5572/how-efficient-is-a-capacitive-power-supply&quot;&gt;How efficient is a capacitive power supply?&lt;/a&gt;&#xA;for details.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since a &quot;capacitive power supply&quot; has a power factor near 0, it is questionable whether any &quot;capacitive power supply&quot; meets EU-mandated power factor laws, such as EN61000-3-2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect that all products -- as long as they were designed after EU-mandated power factor laws went into effect -- should work just as well on &quot;modified sine wave&quot; as with &quot;pure sine wave&quot; inverters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, I can't possibly know about every product ever designed -- if there is any specific product (that was designed after those EU-mandated power factor laws went into effect) that can't work or doesn't work as well with &quot;modified sine wave&quot; power, I would be interested. If anyone can explain &lt;em&gt;why&lt;/em&gt; it doesn't work, in enough detail that I can try to avoid that kind of failure, I would be fascinated and grateful.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-17T05:00:17.387" CommentCount="2" />
  <row Id="13164" PostTypeId="2" ParentId="13159" CreationDate="2011-04-17T09:28:35.213" Score="3" ViewCount="" Body="&lt;p&gt;I would use &lt;a href=&quot;http://www.chipquikinc.com/&quot; rel=&quot;nofollow&quot;&gt;Chip Quik&lt;/a&gt;. It works very well, in my experience, and is very fast. The board and parts aren't damaged in any way, and the removed devices can be reused if necessary. Ideally, it's used with a temperature-controlled soldering station on a low temperature setting. They will send you a free sample kit if you want to try it out, which will remove a couple of QFP parts.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-17T09:59:56.600" LastActivityDate="2011-04-17T09:59:56.600" CommentCount="3" />
  <row Id="13165" PostTypeId="2" ParentId="13125" CreationDate="2011-04-17T09:42:44.673" Score="2" ViewCount="" Body="&lt;p&gt;I think the problem is the solderless breadboard. The motor connections will be taking a lot of current, which is unsuitable for the spring contacts in the breadboard, and introduces noise into the Arduino supply via the common ground when the motor stalls. The motor could be taking 1A or so under a heavy load or stall condition and those solderless breadboards are only rated for a few mA, IIRC. Wire the circuit up properly on a PCB or a prototyping board, with a single-point ground, and your problem will probably go away. Or, avoid stalling the motor and subjecting it to a heavy load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could monitor the motor current with a sense resistor and ADC input on the Arduino, turn off the drive when the current becomes excessive, and light an LED to indicate a fault condition.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-17T12:07:23.437" LastActivityDate="2011-04-17T12:07:23.437" />
  <row Id="13166" PostTypeId="1" AcceptedAnswerId="13170" CreationDate="2011-04-17T10:37:53.337" Score="0" ViewCount="52" Body="&lt;p&gt;I've set up an old fridge with a custom thermostat to finely control the cooling levels of the contents but would like to provide heating to the unit if the temperature drops below the thermostat's defined temp. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thermostat has 2 modes, heating &amp;amp; cooling, as described in the wiring diagram below.  I've got it running the fridge over the &quot;2-C&quot; configuration but would like to hook up a heating device as well.  Can I use the one thermostat to control a heating and cooling device simultaneously?  Can I just split the active line to each device or is there some other technique I need to use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/obhxW.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3898" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-04-17T14:46:51.617" LastActivityDate="2011-04-17T14:46:51.617" Title="Wiring an SPDT thermostat to simultaneously control heating and cooling devices" Tags="&lt;heating&gt;&lt;cooling&gt;" AnswerCount="1" />
  <row Id="13167" PostTypeId="2" ParentId="13125" CreationDate="2011-04-17T11:05:50.750" Score="0" ViewCount="" Body="&lt;p&gt;I have a Makerbot - one of the boards drives a DC motor and also has a thermistor input - I was seeing similar issues - solved them by &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) routing the wires away from each other&#xA;2) dropping a 100nF cap over the analog input &#xA;3) putting a ferrite bead on that input lead&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would worry about grounds too - are the grounds connected elsewhere? (a ground loop)&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-04-17T11:05:50.750" />
  <row Id="13168" PostTypeId="1" CreationDate="2011-04-17T12:45:37.443" Score="-3" ViewCount="67" Body="&lt;p&gt;I'm switching some RGB leds. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was wondering if will I have to use a transistor for each colour.&lt;/p&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T13:12:38.900" LastActivityDate="2011-05-16T13:14:31.193" Title="fet transistor - spdt switch possible" Tags="&lt;led&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="0" />
  <row Id="13169" PostTypeId="2" ParentId="13168" CreationDate="2011-04-17T13:26:33.800" Score="1" ViewCount="" Body="&lt;p&gt;Yes. RGB LEDs come in 4-pin packages (common anode or common cathode) or 6-pin packages (separate anode/cathode for each colour). For common anode (or common cathode) packages you connect the anode to $V_{cc}$ (or cathode to GND), and connect a transistor via a current-limiting resistor to each of the colour pins.  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T13:14:31.193" LastActivityDate="2011-05-16T13:14:31.193" />
  <row Id="13170" PostTypeId="2" ParentId="13166" CreationDate="2011-04-17T13:45:34.997" Score="0" ViewCount="" Body="&lt;p&gt;The wiring diagram you linked to is too &quot;dummed down&quot; to seriously trust.  &lt;em&gt;If&lt;/em&gt; it is correct then the answer to your question is Yes, you can use one thermostat to both heat and cool by rewiring it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To rewire it, I would swap the extension cord connectors, so that the male connector is on the right and you have &lt;em&gt;two&lt;/em&gt; female connectors on the left.  Plug the heater into one, and plug the cooler into the other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But as I said before, this assumes that the wiring diagram is correct:  namely that there is a SPDT relay of sorts in there, and that nothing else in the unit takes power from the AC lines.  Some digital units run off of AC power, while others will take a battery.  So figure things out before attempting this or you might blow up your thermostat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are some other important issues to keep in mind here:  This thermostat, if rewired like this, will be always cooling or heating.  Most thermostats have a sort of dead-band where it is doing nothing, right around the temperature it's set for.  This is for an energy savings and to reduce &quot;wear and tear&quot; on the heater/cooler.  Also, in most cases either the heater or cooler is not required so the dead-band acts to keep the unrequired part from turning on.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, there is a large chance that you don't actually need to have both a cooler and heater running.  Normally when fermenting beer &quot;at room temp&quot; you only need to cool it.  If your &quot;room temp&quot; is lower than your desired fermentation temp then you need a heater.  If your &quot;room temp&quot; is fluctuating so much that you need both a cooler and heater then you should probably re-evaluate where you are fermenting.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And lastly, the wiring diagram implies that you can use a light-bulb as a heater.  Don't do this.  Exposing your brew to light will cause all sorts of problems:  mainly &lt;a href=&quot;http://beeradvocate.com/articles/527&quot; rel=&quot;nofollow&quot;&gt;&quot;light struck&quot; or &quot;skunked&quot; beer&lt;/a&gt;.  Instead, use some sort of heater belt, like &lt;a href=&quot;http://www.northernbrewer.com/brewing/brewing-equipment/fermenting-equipment/fermentation-temperature-control/brew-belt.html&quot; rel=&quot;nofollow&quot;&gt;this one sold by Northern Brewer&lt;/a&gt;.  Although light struck beer happens quickly with UV light, I have seen it happen with incandescent light too, it just takes longer.  Also, a normal incandescent light won't last long in a fridge (I've had them die within a week or two) so you'll run the risk of your brew getting too cold when it fails.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-17T13:45:34.997" CommentCount="1" />
  <row Id="13171" PostTypeId="2" ParentId="13159" CreationDate="2011-04-17T14:09:47.833" Score="0" ViewCount="" Body="&lt;p&gt;For SOIC it can be done with normal tin, by using 'a whole lot' of it and getting both sides liquid so you can get the chip off. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally I don't use flux with this, because if I desolder chips I am 100% sure I'm not reusing them. You have putten them through &gt;3 times their heat cycle, by soldering/desoldering/soldering. For TSSOP, TQFP etc that's probably even more the case with certain soldering tricks. If a chip is broken in the process but you're unaware of , it can be a very time consuming mistake to figure out why. And then you have the desolder the chip again if you want to use the same PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also 'special desoldering' tin that stays liquid at a lower temperature. By using that you can possibly get all sides liquid for long enough to desolder it.  I haven't tried this myself on QFP, so I don't know if the chip survives. I know for a fact that the PCB does, because they did this a couple of times to an ARM development board at my internship where the chip was already broken (blown up). As always, heat is the danger of destruction, so desoldering QFPs is always a pain.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-04-17T14:09:47.833" CommentCount="1" />
  <row Id="13172" PostTypeId="1" CreationDate="2011-04-17T15:22:03.397" Score="2" ViewCount="58" Body="&lt;p&gt;I’m working on a VHDL project which is a small SDRAM test. I have these entities:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;top&lt;/li&gt;&#xA;&lt;li&gt;sdramwrapper&lt;/li&gt;&#xA;&lt;li&gt;sdram &amp;lt;– generated IP core sdrampkg &amp;lt;– contains a package containing constants used several places and a couple of type's to bundle signals&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;ISE usually organizes the implementation files in a tree and automatically determines the required compilation order. However, in this project it refuses to include the sdram_pkg package when building and thus I have to use manual compliation order. In itself it is silly but works. When I try to simulate the project it refuses to include the sdram_pkg package at all, even if I’ve specified the compilation order.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to know both how (figure out how) to solve this problem, but also know the rules ISE uses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Update: By marking the sdram_pkg.vhd file as &quot;global source&quot; it was included and I can use the automatic compliation order.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-04-17T15:46:28.837" LastActivityDate="2011-04-17T15:46:28.837" Title="How does Xilinx ISE determine compilation order?" Tags="&lt;xilinx&gt;&lt;vhdl&gt;&lt;hdl&gt;&lt;ise&gt;" CommentCount="2" />
  <row Id="13173" PostTypeId="1" AcceptedAnswerId="13187" CreationDate="2011-04-17T19:35:04.357" Score="1" ViewCount="130" Body="&lt;p&gt;The canonical breadboard layout consists of two strips of five contact points for every column, separated by a divider that allows you to accommodate DIP-style ICs. Is there a special reason why the strips are five contacts each? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is wiring up five different components a common occurrence? My experience indicates this is actually quite rare. Is it perhaps related to the fact that five contact make up 0.5&quot;, allowing you to lay out 1&quot;+ DIP packages?&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-04-17T23:53:40.420" Title="Why are breadboards laid out in strips of five?" Tags="&lt;breadboard&gt;&lt;layout&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13174" PostTypeId="1" AcceptedAnswerId="13175" CreationDate="2011-04-17T19:53:01.463" Score="5" ViewCount="123" Body="&lt;p&gt;I would like to make a board which can be plugged directly into the USB port of a computer, instead of using a separate male &quot;USB-A&quot; connector. I have seen this system used for very small USB memory keys, such as &lt;a href=&quot;http://www.engadget.com/2007/03/15/kingmax-unveils-worlds-smallest-usb-flash-drive/&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;. How would I lay out a PCB with such a &quot;connector&quot; built in?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using Eagle. Does anyone have a library for it? Can anyone suggest another way to do this?&lt;/p&gt;&#xA;" OwnerUserId="1802" LastEditorUserId="1802" LastEditorDisplayName="" LastEditDate="2011-04-17T23:20:26.450" LastActivityDate="2011-04-17T23:20:26.450" Title="Connectorless USB on a PCB" Tags="&lt;pcb&gt;&lt;usb&gt;&lt;connector&gt;&lt;eagle&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="13175" PostTypeId="2" ParentId="13174" CreationDate="2011-04-17T20:10:12.187" Score="6" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;https://github.com/sparkfun/SparkFun-Eagle-Library&quot; rel=&quot;nofollow&quot;&gt;Sparkfun Eagle Library&lt;/a&gt; has one. It's called &quot;USBPCB&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's &lt;a href=&quot;http://goodfet.sourceforge.net/hardware/goodfet31/&quot; rel=&quot;nofollow&quot;&gt;a project using it&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-04-17T20:10:12.187" CommentCount="4" />
  <row Id="13176" PostTypeId="1" AcceptedAnswerId="13184" CreationDate="2011-04-17T20:56:30.123" Score="4" ViewCount="115" Body="&lt;p&gt;Since im just starting out in Electronics, when looking for a Soldering Iron (obviously it would make no sense since im starting to get a SUPER expensive iron)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But what kind of wattage should I be looking for? 30-40 watts?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen the name Weller thrown around alot. Are they a good reliable brand?&#xA;edit: Also side question, when looking for multimeters I see alot of &quot;ranges&quot; like 29 range.....39 range etc...How do I know exactly which one to get....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I saw something like this: &lt;a href=&quot;http://www.sparkfun.com/products/9672&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/9672&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but I dunno if thats like &quot;good&quot;. But I wouldn't figure i'd need a HUGELY expensive kit just to do small electronics/robotics.&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-04-18T11:05:22.133" Title="What kind of Wattage for Small Electronics? (For Soldering)" Tags="&lt;soldering&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="13177" PostTypeId="1" CreationDate="2011-04-17T20:58:09.110" Score="1" ViewCount="77" Body="&lt;p&gt;The numbers I can see are&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FLE 62635&#xA;VE 527762N35&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help is greatly appreciated&lt;/p&gt;&#xA;" OwnerUserId="3904" LastActivityDate="2011-04-17T20:58:09.110" ClosedDate="2011-04-20T12:06:28.587" Title="How can I find a data sheet on this IC" Tags="&lt;ic&gt;" CommentCount="5" FavoriteCount="1" />
  <row Id="13178" PostTypeId="1" AcceptedAnswerId="13182" CreationDate="2011-04-17T21:11:47.977" Score="1" ViewCount="81" Body="&lt;p&gt;Is it a good practice to put polygon pours on the top layer underneath a BGA?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've occasionally got several GND or VCC pins in a row/column, and I'd like to pour around them all.  I've got the same vias I would otherwise, this is just in my mind lowering the inductance between the pins and the vias.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The soldermask would then define the pad shapes.  Is that safe?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any SI reason not to do this?  I can't think of a negative... it may even add a little more buried capacitance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any reason I shouldn't go nuts with pouring over everything?  (Being careful not to leave islands or little antenna structures)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't see this in the few reference designs I've checked...  so I'm curious why not...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would this somehow prevent the ground plane from being as effective?  (If there's a large VCC pour between it and the BGA)&lt;/p&gt;&#xA;" OwnerUserId="1270" LastEditorUserId="1270" LastEditorDisplayName="" LastEditDate="2011-04-17T21:21:16.113" LastActivityDate="2011-04-17T22:43:32.410" Title="Polygons pours under BGAs?" Tags="&lt;layout&gt;&lt;signal-integrity&gt;&lt;bga&gt;" AnswerCount="1" />
  <row Id="13179" PostTypeId="2" ParentId="12747" CreationDate="2011-04-17T22:12:48.550" Score="0" ViewCount="" Body="&lt;p&gt;If you're interested in using an HD44780 display, I have a short tutorial here: &lt;a href=&quot;http://www.roboticsguy.com/tutorials/pic-microcontrollers/hd44780-lcd&quot; rel=&quot;nofollow&quot;&gt;http://www.roboticsguy.com/tutorials/pic-microcontrollers/hd44780-lcd&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for a graphic LCD, check out this Graphic 128x64 LCD at SparkFun: &lt;a href=&quot;http://www.sparkfun.com/products/710&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/710&lt;/a&gt;. It seems to be pretty popular and uses the KS0108B parallel interface.&lt;/p&gt;&#xA;" OwnerUserId="3905" LastActivityDate="2011-04-17T22:12:48.550" CommentCount="1" />
  <row Id="13180" PostTypeId="1" AcceptedAnswerId="13186" CreationDate="2011-04-17T22:13:59.103" Score="0" ViewCount="100" Body="&lt;p&gt;Ok I've been looking at a few tutorials and such, and i've done my reading on getting started with an AVR on a breadboard (flashing a few LEDS and such)&#xA;I know i'll need an AVR 8bit ATtiny&#xA;and a USB AVR programmer + Breadboard and whatever those wires are called for testing (I forget what they all called, they are like prestripped testing wires....)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyways....is there anything else I need? to just get started. I worry because I see these Arduino's and AVR prototype boards and they have TONS of extra stuff on them (that im not even sure what they are)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I missing something....Like do I need FLASH memory or anything additional to just do basic stuff?&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-04-17T23:59:58.017" Title="Getting Started with AVR On Breadboard, few questions" Tags="&lt;microcontroller&gt;&lt;avr&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="13181" PostTypeId="2" ParentId="13180" CreationDate="2011-04-17T22:40:04.677" Score="1" ViewCount="" Body="&lt;p&gt;no there's flash inside the chip, sounds like you're  - make sure you have current limiting resistors for the leds&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-04-17T22:40:04.677" />
  <row Id="13182" PostTypeId="2" ParentId="13178" CreationDate="2011-04-17T22:43:32.410" Score="4" ViewCount="" Body="&lt;p&gt;I would not put a copper pour on the top layer of the PCB directly under a BGA.  Not because of any signal integrity issue, but because of a manufacturability issue.  There are two main reasons:  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The increased copper could (and I emphasize the &quot;could&quot;) suck too much heat away from the pads causing bad solder joints.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Normally the soldermask is pulled back a small amount from the pads.  If your copper plane had a direct connect to the pads (which it should) then the effective area for the pad would be increased.  And the increased pad size could cause solder issues where the amount of solder required for this ball is more than the solder required for a ball not connected to the plane.  The &quot;unevenness&quot; of the solder per ball could cause solder issues.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I'll be the first to admit that both issues could be solved by changing the oven temperature profile, changing the solder mask pullback, and/or changing the size or thickness of the solder paste screen.  But why?  Unless you have a very specific requirement (RF maybe), I don't see the advantage.  I've lost track of how many multi-GHz BGA's I've used and I have never needed a plane on the top layer of the PCB.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-17T22:43:32.410" CommentCount="11" />
  <row Id="13183" PostTypeId="2" ParentId="13176" CreationDate="2011-04-17T22:51:51.853" Score="6" ViewCount="" Body="&lt;p&gt;Get a soldering iron with a thermostat.  This is much more important than the wattage.  Without a good temperature control, you run the risk of putting too much heat into the PCB and damaging it (or the chips).  It's easy enough to do that with temp control, but without it you're really at a disadvantage.  Once you have a good temperature control, then something in the 20 to 50 watt range is good.  If for some reason you can't get good temp control then stick with an iron that is less than 25 watts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The soldering iron I use at my office is the Weller WESD51, and &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=WESD51-ND&quot; rel=&quot;nofollow&quot;&gt;costs US$129 from Digikey&lt;/a&gt;.  This thing will last 10-15 years.  While that might sound expensive, it is well worth the money when you think of all the frustration it saves.  It could even save you real money since you have less risk of damaging PCB's.  Besides, $129 isn't a lot of money in the grand scheme of an electronics hobby that could easily cost 10x of that per year.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="3624" LastEditorDisplayName="" LastEditDate="2011-04-17T23:22:37.890" LastActivityDate="2011-04-17T23:22:37.890" CommentCount="4" />
  <row Id="13184" PostTypeId="2" ParentId="13176" CreationDate="2011-04-17T23:35:54.543" Score="3" ViewCount="" Body="&lt;p&gt;A 30-40 watt fixed-temperature iron will be on the hot side for electronics work. It will melt solder very quickly and make it really easy to heat up large component leads quickly, such as those on connectors. However, it also risks exceeding the heat limits on more delicate components. If you have good technique so that you can make a joint quickly, you avoid the risk and get the benefit, but by the same token, I don't know that I would recommend an iron that hot to a newbie.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you only want a simple pencil iron and are going to be using it primarily for relatively delicate parts &amp;mdash; ICs, small-signal transistors, film capacitors... &amp;mdash; you may want to start with something more in the 15 to 25 W range. Again, the hotter it is, the faster it is to make the joint, but also the quicker it can damage something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a tradeoff, where the iron is too cool to heat the component lead and solder quickly so you also burn the board because it simply takes too long to make the joint. Some may argue that 15 W is below this limit, others may say it's just above the limit. I haven't used an iron that cool in so long that I couldn't really say.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The high road is to avoid all this and get a good temperature-controlled iron. With such a tool, you can trust that when you set the iron to 300°C to solder a component whose datasheet says it should be soldered at no more than 300°C for 5 seconds, that it won't die if you complete the joint in less than 5 seconds. With a fixed-temperature iron, you not only probably won't know the idle temp of the iron, you won't know how far its temp dips when loaded or how long it takes to recover. With a cheap adjustable iron, it probably won't be properly calibrated to give the rated temp at the tip with every combination of tip type, and you also get the &quot;loading and recovery&quot; problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know you say you don't want a &quot;super expensive&quot; iron, but the one you pointed to is downright cheap, relatively speaking. It may be that it's a poor clone of the famous Hakko 936, and its bad value is signalled by being in that no-mans land between a basic pencil iron and the low-end of good temp-controlled irons. (I'd put that low end border at around $90 US, by the way.) It may also be that it's an outstanding value. I couldn't say, having not used it. Its price does make me wary, however, as does the fact that it's cloning a well-known design. Some clones are nearly as good as the original, a rare few are better, but most are worse. If you buy it, I'd say you'd want to be prepared to replace it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually, for someone in that position, I'd say start with a $9 pencil iron and then later step up to a good temperature-controlled iron and skip over the no-mans land of cheapies you're looking at now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for &quot;Weller&quot; as a brand, they have a good reputation, but I've never used one, having never found one with the combination of features and price that made me happy. I've only ever used one name-brand iron, and it's way outside your price range. Everything else I've used successfully has been no-name house brand stuff. The point is that while quality matters, brand names aren't the best way to find it in this particular market. I suppose that's due to the fact that soldering irons are fundamentally not that complicated, and they're used worldwide, including in the same cheap Chinese factories we all love/hate. The poor Chinese laborer needs good irons, too, so they make their way out to the rest of us.&lt;/p&gt;&#xA;" OwnerUserId="2523" LastActivityDate="2011-04-17T23:35:54.543" CommentCount="2" />
  <row Id="13185" PostTypeId="2" ParentId="13180" CreationDate="2011-04-17T23:37:32.640" Score="1" ViewCount="" Body="&lt;p&gt;To work with bare AVR chips you will need some way to put your code into the on-chip flash. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The arduino really doesn't have much else on it besides an AVR. The thing with the AVR on the arduino is that it's pre-flashed with a boot loader that can use the AVR's serial port to accept code and reflash &lt;em&gt;itself&lt;/em&gt;. As far as hardware goes, it basically just has some power conditioning, an oscillator, and a USB-to-serial interface. It's better to think of the on-board USB interface as part of the PC rather than part of the arduino. I think you can get the AVRs with the arduino boot-loader pre-flashed, in which case you should be able to program it on a breadboard with the arduino PC support s/w, as long as you have an appropriate serial connection.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-17T23:37:32.640" CommentCount="2" />
  <row Id="13186" PostTypeId="2" ParentId="13180" CreationDate="2011-04-17T23:46:11.297" Score="4" ViewCount="" Body="&lt;p&gt;In my opinion, first step should be to get four basic documents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First one you should get is the short version of the datasheet for your microcontroller. It shouldn't be more than 20-30 pages, so do read it whole before touching the microcontroller. Don't panic if you don't understand everything (or anything!). Just read it a couple of times. While reading it, there are few thing you should pay attention to. The page you'll probably use the most is the pin configurations page. It will probably be one of the first pages. It may be a good idea to print it and keep it close to the microcontroller. There you'll find out what each pin does. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After that, it would be a good idea to get the whole datasheet. It will probably have several hundred pages, but you don't need to read it whole at once. Instead just read the bookmarks list and if you're having any problems with a specific feature, read the part of datasheet which describes it. It would be a good idea to take a look at electrical characteristics page. There you'll find relationship between voltages and frequencies, voltages for high and low, maximum output currents and other important information without which your microcontroller can die. That part may just be few pages long, so do read it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next two documents are a bit more complicated, but they focus on some things that are very important. They are &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc2521.pdf&quot; rel=&quot;nofollow&quot;&gt;Atmel AVR042: AVR Hardware Design Considerations&lt;/a&gt; and &lt;a href=&quot;http://www.atmel.com/dyn/resources/prod_documents/doc1619.pdf&quot; rel=&quot;nofollow&quot;&gt;AVR040: EMC Design Considerations&lt;/a&gt;. They're a bit scary at first, but do read them, since they're only around 17-18 pages each. In them you'll find ways how to correctly connect the reset pin, what types of decoupling capacitors to use (you didn't mention these on your parts list for example), how to set them up and so on. As with other manuals, you don't have to worry if you don't understand everything at first. Since you're a beginner, just focus on parts which explain how to connect reset pin and how to use decoupling capacitors. For the rest, it's good read, because at one point your microcontroller board probably won't work and you'll need to figure out why. You'll be able to find some pitfalls there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I made an AVR board few months ago and had some beginner questions about it. For example &lt;a href=&quot;http://electronics.stackexchange.com/q/9888/1240&quot;&gt;how to connect decoupling capacitors when pins aren't close&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also take a look &lt;a href=&quot;http://electronics.stackexchange.com/q/9692/1240&quot;&gt;here&lt;/a&gt;. Similar situation, except that guy had ATmega 16. I wrote a bit about setting up the toolchain and getting a programmer there.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-04-17T23:54:37.567" LastActivityDate="2011-04-17T23:54:37.567" />
  <row Id="13187" PostTypeId="2" ParentId="13173" CreationDate="2011-04-17T23:53:40.420" Score="2" ViewCount="" Body="&lt;p&gt;Considering the contact group size, unused points represent wasted real estate, so there's a reason to make the group size as small as possible. In some parts of a circuit, you'll only need to connect two component leads together, but just as commonly you'll need to connect three or four. Sometimes more. Only two points per group would not allow you to connect three or more leads. You could make the group size 3 points, which would be the minimum that would allow you to bridge groups and connect more leads, but to connect four or more components you'd be using 1/3 to 2/3 of your available contacts just to bridge groups. Obviously if the group is big enough, you don't have to bridge groups at all. So, five per group just seems like the best compromise between unused contact points and points tied up bridging groups.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-17T23:53:40.420" />
  <row Id="13188" PostTypeId="2" ParentId="13180" CreationDate="2011-04-17T23:59:58.017" Score="2" ViewCount="" Body="&lt;p&gt;Sounds like you have everything you NEED in order to make this thing work in a hardware sense. You will definitely want the data sheets for your processor, which will be downloadable from the manufacturer's website. Another very useful thing is example code. There should be some (again) on the manufacturer's website as well as other various places online and in books. Once you get everything hooked up to your computer, you are going to want to spend some significant time learning how to use your IDE. I recommend using an IDE that is supported by the manufacturer when you are a beginner. Another thing you might want to keep in mind is that learning how to program this thing is going to be a lot easier if you have a USB dongle that supports in system debugging. In other words, a mode in which you can write your program to the chip, begin execution, pause execution, set breakpoints and examine memory. Hope this helps!&lt;/p&gt;&#xA;" OwnerUserId="3906" LastActivityDate="2011-04-17T23:59:58.017" CommentCount="1" />
  <row Id="13189" PostTypeId="2" ParentId="13069" CreationDate="2011-04-18T03:36:55.260" Score="1" ViewCount="" Body="&lt;p&gt;I suppose a person &lt;em&gt;could&lt;/em&gt; drive a bunch of LEDs using multiplexer or demultiplexer or address decoder chips, but that arrangement seems pretty rare.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;People with big square grids of LEDs generally drive then in a &quot;LED matrix&quot; arrangement.&#xA;Alas, the &quot;LED matrix&quot; arrangement is a bit difficult to explain -- perhaps the pictures will help at&#xA;&lt;a href=&quot;http://electronics.stackexchange.com/questions/9066/arduino-3x3-led-matrix&quot;&gt;arduino 3x3 LED matrix&lt;/a&gt;&#xA;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;People with one long line of LEDs often drive them using &lt;a href=&quot;http://electronics.stackexchange.com/questions/6676/which-sipo-chip-is-better-74hc4094-or-74hc595-or-something-else&quot;&gt;shift registers&lt;/a&gt;.&#xA;Those are much easier to understand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, DDRB and PORTB are used to drive LOW/HIGH/OFF of the 8 pins of port B.&#xA;The PINB is used to &lt;em&gt;read&lt;/em&gt; the current state of those pins.&#xA;If you are using Arduino, you may find it simpler to use the&#xA;&lt;a href=&quot;http://arduino.cc/en/Reference/PinMode&quot; rel=&quot;nofollow&quot;&gt;pinMode()&lt;/a&gt; and &lt;a href=&quot;http://arduino.cc/en/Reference/DigitalWrite&quot; rel=&quot;nofollow&quot;&gt;digitalWrite()&lt;/a&gt; library functions.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-18T03:36:55.260" />
  <row Id="13190" PostTypeId="1" CreationDate="2011-04-18T06:18:36.617" Score="0" ViewCount="118" Body="&lt;p&gt;I've been wondering. How hard is it to craft a (digital) watch from scratch?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm currently thinking that (with a lot of assumptions) you can buy/import quartz chips or something like that from overseas, and then after putting them on a case, stick them to some circuits, batteries, some LCD display etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So yeah, what other considerations could there be, besides manufacturing (cases, straps etc)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;disclaimer: I'm a complete newbie when it comes to electronics, so you probably cringed just by reading that. I'm just curious about this because after trying to shop for a good watch, it seems that there's almost too many choices, and I can't help but wonder how hard is it to get to the watchmaking business.&lt;/p&gt;&#xA;" OwnerUserId="2817" LastActivityDate="2011-05-20T00:40:35.560" Title="Crafting a digital watch" Tags="&lt;hardware&gt;&lt;clock&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="13191" PostTypeId="2" ParentId="5139" CreationDate="2011-04-18T07:12:23.293" Score="1" ViewCount="" Body="&lt;p&gt;Another reason to use hatched planes is for a flexible PCB. There are a number of benifits of a hatched plane vs a solid plane. A solid plane has the potential for cracking along a bend line, this is far less likely with a hatched plane. More importantly for a flexible PCB a hatched plane allows for more flexibility in the bends.&lt;/p&gt;&#xA;" OwnerUserId="3914" LastActivityDate="2011-04-18T07:12:23.293" />
  <row Id="13192" PostTypeId="2" ParentId="13190" CreationDate="2011-04-18T07:45:57.970" Score="5" ViewCount="" Body="&lt;p&gt;The quartz crystal should be the least of your problems. You can find them in miniature dimensions (2mm diameter x 6mm length) at any distributor. You may have some trouble to find the LCD, though. Microcontrollers in small packages are readily available, but they usually don't have enough I/O pins to control the LCD + some buttons. In common watches you'll see that they solved this by bonding the die (with sufficient I/Os) directly to the PCB. Standard components are never used for the battery holder and the push buttons, because they wouldn't fit. Instead, custom made metal metal strips are used.&lt;br&gt;&#xA;Frankly I think this will be a difficult to do. If you really want to build a clock I'd suggest to make it a table top clock.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main difference between you and the watchmakers business is that you want to build 1 (one) watch, while they build them in large quantities, which allows them to use custom components at a low cost.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-18T08:26:55.043" LastActivityDate="2011-04-18T08:26:55.043" />
  <row Id="13193" PostTypeId="2" ParentId="13190" CreationDate="2011-04-18T08:44:39.203" Score="1" ViewCount="" Body="&lt;p&gt;Not at all difficult - the most expensive part would be making a nice case. &#xA;For minimum cost you'd be constrained to a small selection of off-the-shelf LCDs (which also constrains choice of case), but if you;re serious you can get a batch of small custom-design LCDs for something like $1000-2000 for several  hundred units including tooling.   &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-04-18T08:44:39.203" />
  <row Id="13194" PostTypeId="2" ParentId="5139" CreationDate="2011-04-18T09:03:22.027" Score="1" ViewCount="" Body="&lt;p&gt;One more reason why hatched planes should be preferred for flexible PCBs is the drying process needed with the flexible material (Polyimide) prior to soldering. With a hatched plane, the moisture can exit the flexible carrier material, whereas it is trapped under solid planes.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-04-18T09:03:22.027" />
  <row Id="13195" PostTypeId="1" AcceptedAnswerId="13196" CreationDate="2011-04-18T09:23:14.617" Score="4" ViewCount="152" Body="&lt;p&gt;How will temperature affect the output of a semiconductor diode?&lt;/p&gt;&#xA;" OwnerUserId="3916" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-16T18:37:20.930" LastActivityDate="2011-05-16T18:37:20.930" Title="Diode Temperature effect" Tags="&lt;diode&gt;&lt;temperature&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="1" />
  <row Id="13196" PostTypeId="2" ParentId="13195" CreationDate="2011-04-18T09:27:51.583" Score="7" ViewCount="" Body="&lt;p&gt;The forward voltage of a Si diode will drop by about 2.1 mV/°C (negative temperature coefficient).&lt;br&gt;&#xA;The effect is almost perfectly linear, so if you want you can make the diode a temperature sensor by supplying it with a constant current.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-05T11:17:45.373" LastActivityDate="2011-05-05T11:17:45.373" CommentCount="8" />
  <row Id="13197" PostTypeId="2" ParentId="13176" CreationDate="2011-04-18T11:05:22.133" Score="0" ViewCount="" Body="&lt;p&gt;I have that exact iron (Hakko clone) and it works great.  It's one of the best deals out there for soldering irons in my opinion.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-18T11:05:22.133" />
  <row Id="13198" PostTypeId="1" AcceptedAnswerId="13199" CreationDate="2011-04-18T14:07:41.047" Score="8" ViewCount="202" Body="&lt;p&gt;In the answer to another question, I read that it's bad to short-circuit electrolytic capacitors. Why is that? What happens if I do?&lt;/p&gt;&#xA;" OwnerUserId="3920" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-04-18T15:54:25.993" LastActivityDate="2011-04-18T15:54:25.993" Title="Why shouldn't electrolytic capacitors be short-circuited?" Tags="&lt;capacitor&gt;&lt;components&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="13199" PostTypeId="2" ParentId="13198" CreationDate="2011-04-18T14:20:37.947" Score="14" ViewCount="" Body="&lt;p&gt;Electrolytic capacitors may become permanently damaged by excessive peak currents, which will definitely occur during short-circuit events. The reason is that (a) the internal resistance will cause a momentary, but large power dissipation (heat!) and (b) the distribution of the current spike inside the capacitor will not be formed evenly across the large area of the aluminum foil and hot spots may occur. The electrolyte may vaporize along these small zones and damage to the insulating aluminum oxide layer may occur as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're lucky, the capacitance will decrease just a bit or the top of the can may change its shape into something like a dome. If you're very unlucky, the cap may fail and heat up quite a bit (and eventually blow).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With very large currents, e.g. during inrush events into the primary caps of switching power supplies, you can actually feel how the caps heat up in an unhealthy way (don't touch live circuits or charged caps!!!). Such inrush events may be viewed as the opposite of a short circuit condition, just that the current flows in the opposite direction (&quot;into the cap&quot;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW: Also true for other capacitors like ceramics. I've seen ceramics explode, too, when they were subjected to rapid discharge events. The ceramic dielectric material changes its shape just a tiny bit when the electric field varies. If this happens fast, enough force may be created for the capacitor to blow. Disc capacitors will withstand some abuse, ceramic multilayer capacitors (MLCCs) are quite sensitive.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-18T14:28:15.303" LastActivityDate="2011-04-18T14:28:15.303" CommentCount="2" />
  <row Id="13200" PostTypeId="1" AcceptedAnswerId="13210" CreationDate="2011-04-18T14:44:29.757" Score="0" ViewCount="76" Body="&lt;p&gt;So Im about to set up my first AVR MC experiment (the typical LED Blink)&#xA;Im going to be ordering an ATmega328 and a Serial and Breadboard and such.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However i've heard it's a good idea to use some Capacitors to help smoothen out some specific lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've &quot;heard&quot; it's a good idea to use smaller caps CLOSER to the Microcontroller, and then Larger caps near other components. is this true? And what kind (size) caps should I look for? Do I need these for every output pins, or just the VCC?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="3073" LastActivityDate="2011-04-18T16:34:52.630" Title="AVR Power Conditioning" Tags="&lt;microcontroller&gt;&lt;avr&gt;&lt;capacitor&gt;" AnswerCount="2" />
  <row Id="13201" PostTypeId="1" CreationDate="2011-04-18T14:51:26.673" Score="7" ViewCount="103" Body="&lt;p&gt;I have a vague recollection that while off, a LED can actually receive light and generate a small current (in uA).&#xA;Is that correct? How does that work? What is the best way to prevent this?&lt;/p&gt;&#xA;" OwnerUserId="3922" LastActivityDate="2011-04-18T15:01:30.580" Title="LED current while off" Tags="&lt;led&gt;&lt;current&gt;&lt;light&gt;&lt;low-power&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="13202" PostTypeId="1" CreationDate="2011-04-18T14:58:57.103" Score="1" ViewCount="75" Body="&lt;p&gt;The values for resistors in a typical series, like E12, follow an exponential series (hence the &quot;E&quot;?). 10, 12, 15, 18, 22, etc., everybody knows them by heart (at least E12). But often you want simple ratios in dividers, where a series like 10, 20, 30, 40, etc. would be more convenient. The problem with the exponential series is that, if 15/10 is the wrong ratio, so will 22/15 be, or 33/22. They'll all produce the same result.&lt;br&gt;&#xA;Are there resistors with values 10, 20, 30,... ?&lt;/p&gt;&#xA;" OwnerUserId="3920" LastActivityDate="2011-04-18T16:36:11.847" Title="linear resistor values series?" Tags="&lt;resistor&gt;&lt;components&gt;" AnswerCount="3" />
  <row Id="13203" PostTypeId="2" ParentId="13201" CreationDate="2011-04-18T15:01:30.580" Score="6" ViewCount="" Body="&lt;p&gt;A LED can work as a (not very good) photodiode, and produce a small current when it receives light. You have to connect it like a photodiode, though, that is reversed polarised. In a normal circuit you won't have trouble with it.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-18T15:01:30.580" CommentCount="6" />
  <row Id="13204" PostTypeId="2" ParentId="13202" CreationDate="2011-04-18T15:28:29.263" Score="3" ViewCount="" Body="&lt;p&gt;The E12 series isn't quite evenly spaced from an exponential standpoint.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1.0 1.2 1.5 2.2 2.7 3.3 3.9 4.7 5.1 5.6 6.8 8.2&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, 10/3.3 is much closer to 3 than to 3.3.  It is admittedly curious that the 12-per-decade series offers two ways of getting a 3:1 ratio within 1.3% (one is 10/3.3; the other is 8.2/2.7) but the best 2:1 ratios it offers are off by 3% or more (5.6/2.7 is 3.7% off; 6.8/3.3 is 3.03% off).  On the other hand, since the E12 series is typically used with 10%-tolerance parts, the sloppiness of the ratios doesn't really matter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The E24 series (5% parts) offers values of 2.0 and 3.0; the E96 and E192 series offer 2.00, but the closest they offer to 3.0 is 3.01.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-18T15:28:29.263" />
  <row Id="13205" PostTypeId="1" AcceptedAnswerId="13212" CreationDate="2011-04-18T15:28:43.833" Score="17" ViewCount="627" Body="&lt;p&gt;What's the use of teardrops on PCB pads?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Mr3y7.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3920" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-18T15:58:54.413" LastActivityDate="2011-04-19T00:39:44.180" Title="why teardrops on PCB?" Tags="&lt;pcb&gt;" AnswerCount="4" CommentCount="5" FavoriteCount="2" />
  <row Id="13206" PostTypeId="2" ParentId="13202" CreationDate="2011-04-18T15:33:46.200" Score="1" ViewCount="" Body="&lt;p&gt;The exponential series ensures that on average, you get minimum error when you choose the nearest preferred value to a calculated value &lt;em&gt;see &lt;a href=&quot;http://en.wikipedia.org/wiki/Preferred_number#E_series%3a_Capacitors_and_resistors&quot; rel=&quot;nofollow&quot;&gt;Preferred Number&lt;/a&gt;&lt;/em&gt;. If you go to E192 you will get close as supercat says but some manufacturers make special non-preferred values (eg 600 Ohms).&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-04-18T15:33:46.200" CommentCount="2" />
  <row Id="13207" PostTypeId="2" ParentId="13205" CreationDate="2011-04-18T16:05:22.007" Score="7" ViewCount="" Body="&lt;p&gt;They are mainly used on single-sided boards, to increase reliability. I often use them on my home-made PCBs.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-18T16:29:17.227" LastActivityDate="2011-04-18T16:29:17.227" CommentCount="5" />
  <row Id="13208" PostTypeId="2" ParentId="13100" CreationDate="2011-04-18T16:12:47.197" Score="1" ViewCount="" Body="&lt;p&gt;One can get efficient operation in a lock-free multi-producer single-consumer queue if the queue itself holds items that are small enough to work with a load-store-exclusive, compare-exchange, or similar primitive, and one can use a reserved value or reserved values for an empty queue slots.  When writing to the queue, the writer does a compare-exchange to try to store his data into the next empty slot; if that fails, the writer tries the following slot.  Although the queue maintains a pointer to the next empty slot, the pointer value is &quot;advisory&quot;.  Note that if a system uses compare-exchange rather than load-store-exclusive, it may be necessary to have a 'family' of different 'empty slot' values.  Otherwise, if between the time the writer finds an empty queue slot and attempts to write to it, another writer writes the slot and the reader reads it, the first writer would unknowingly put his data in a spot where the reader wouldn't see it.  This problem does not occur in systems that use load-store-exclusive, since the store-exclusive would detect that the data had been written even though it was written back to the old value.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-18T16:12:47.197" />
  <row Id="13209" PostTypeId="2" ParentId="13200" CreationDate="2011-04-18T16:13:05.043" Score="4" ViewCount="" Body="&lt;p&gt;AVR has an app note exactly for this!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/atmel/acrobat/doc2521.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/atmel/acrobat/doc2521.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Advice on page 14 for layout considerations.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-18T16:13:05.043" />
  <row Id="13210" PostTypeId="2" ParentId="13200" CreationDate="2011-04-18T16:29:17.610" Score="3" ViewCount="" Body="&lt;p&gt;Each supply pin (including AVdd) must be decoupled close to the pins, I use 100 nF on each one. A 10 uF is a good idea across the supply to the whole circuit. If you are using the ADC, the AVdd pin should have a filter; details are in the data sheet.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-18T16:34:52.630" LastActivityDate="2011-04-18T16:34:52.630" />
  <row Id="13211" PostTypeId="2" ParentId="13202" CreationDate="2011-04-18T16:36:11.847" Score="0" ViewCount="" Body="&lt;p&gt;Digikey reports &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=P30ATR-ND&quot; rel=&quot;nofollow&quot;&gt;this Panasonic 30 ohm part&lt;/a&gt;, among others. $0.003 US, 0805.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-04-18T16:36:11.847" />
  <row Id="13212" PostTypeId="2" ParentId="13205" CreationDate="2011-04-18T16:43:35.420" Score="14" ViewCount="" Body="&lt;p&gt;There are primarily two reasons to use teardrops:  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;It avoids a pocket (where the trace meets the pad) that could collect acid from the PCB etching process which would later do bad things.&lt;/li&gt;&#xA;&lt;li&gt;It reduces mechanical &amp;amp; thermal stress resulting in less hairline cracks in the trace.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;That being said, in professionally made PCB's teardrops are rarely needed. It's almost more of an aesthetic thing than a solution to a real problem. I've done many boards with and without teardrops and I have yet to notice a difference. In my opinion, they are more trouble than they are worth.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-18T17:22:55.643" LastActivityDate="2011-04-18T17:22:55.643" CommentCount="3" />
  <row Id="13213" PostTypeId="2" ParentId="13205" CreationDate="2011-04-18T17:22:26.593" Score="5" ViewCount="" Body="&lt;p&gt;The teardrop is to help the drilling process. It prevents drill breakout where the trace joins the via or through hole. Sometimes it's not necessary do it because the manufacturer can do it for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where I work, our repair department recommend us do it because it increase the strengthening of connections between pads and tracks.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-04-18T17:22:26.593" CommentCount="2" />
  <row Id="13214" PostTypeId="1" AcceptedAnswerId="13525" CreationDate="2011-04-18T18:28:49.293" Score="6" ViewCount="107" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have designed a common-emitter RF amplifier, with input and output impedance matched for my load and source impedance. I have used Smith Chart for the matching.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The matching is good for the designed frequency, but when using other frequencies the matching is poor (I get large reflections in my spice simulation).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that wideband matching (one that works for all frequencies) is not possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if I want to make a fair matching in a frequency band, say 200 MHz to 600 MHz, is there any good technique for this? &#xA;(Except just trial and error with the Smith Chart).&lt;/p&gt;&#xA;" OwnerUserId="3041" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-26T14:43:01.577" LastActivityDate="2011-04-26T23:32:13.660" Title="Wideband Impedance Matching" Tags="&lt;impedance&gt;&lt;matching&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="2" />
  <row Id="13215" PostTypeId="1" AcceptedAnswerId="13235" CreationDate="2011-04-18T21:42:50.580" Score="1" ViewCount="117" Body="&lt;p&gt;Im going to be working on a project where I will need 2 nodes and one base station. To communicate with each other. I am going to be using an Atmel AVR for the processing on the base station. I have thought about playing with the Atmel raven stuff(for development) and then building my own circuit for the project. Just need to transmit data from the nodes to the base station when some inputs go off. Range is an issue about 100m needed(note this is a maximum Minimum that might be needed is only 2 or 3m). Due to the unknown length each time these will be used I don't want to wire them in. I would like low power with the possibility of the nodes being run of a coin cell.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Is this a good way to go?&lt;/li&gt;&#xA;&lt;li&gt;Are there any alternatives to the Atmel Raven technology(Do microchip have an alternative)? &lt;/li&gt;&#xA;&lt;li&gt;Should I consider bluetooth or anything else for the wireless communications?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-04-19T08:14:52.483" LastActivityDate="2011-04-19T14:03:52.357" Title="Wireless Communication Ideas" Tags="&lt;wireless&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="13216" PostTypeId="2" ParentId="13215" CreationDate="2011-04-18T22:37:36.970" Score="0" ViewCount="" Body="&lt;p&gt;I haven't used ATMEL AVR but you probably want to go with something where Wireless etc. has good built in support already.. look up NESC.. it is like C and has a lot of built in API's for you to use to make your life simpler. &lt;/p&gt;&#xA;" OwnerUserId="3925" LastActivityDate="2011-04-18T22:37:36.970" />
  <row Id="13217" PostTypeId="1" AcceptedAnswerId="13261" CreationDate="2011-04-18T22:37:49.873" Score="2" ViewCount="190" Body="&lt;p&gt;I'm currently laying out a PCB in eagle for a circuit that will form the basis for some experimentation. Instead of adding a row of headers so that I can plug it into a breadboard, I figured I would try and layout a small protoboard directly onto the PCB itself. I have room to spare on the board and the resulting creations will be somewhat more resilient. &lt;a href=&quot;http://www.seeedstudio.com/depot/electronic-brick-protoshield-kit-p-599.html&quot; rel=&quot;nofollow&quot;&gt;This PCB&lt;/a&gt; is a good example of what I'm shooting for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have considered using vias, but I seem to recall they are usually sealed off with a chemical to prevent solder from bonding. This is obviously not what I'm going for. Adding hundreds of single-pad components to my schematic does not seem very appealing either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the best way of achieving this using Eagle?&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-04-19T19:16:29.243" Title="Adding a small protoboard-like area to a PCB" Tags="&lt;pcb&gt;&lt;layout&gt;&lt;eagle&gt;&lt;protoboard&gt;&lt;stripboard&gt;" AnswerCount="6" CommentCount="2" />
  <row Id="13218" PostTypeId="1" AcceptedAnswerId="13245" CreationDate="2011-04-18T22:59:48.490" Score="2" ViewCount="98" Body="&lt;p&gt;I'm developing a fully graphical on screen display (OSD) for RC aircraft and other RC things. The project is almost complete, with a working prototype and PCBs made. The OSD is based around a dsPIC33F clocked at 36.85 MHz and works with PAL and NTSC video sources. The video sync is sliced by an LM1881 sync separator. On the CSYNC rising edge, an interrupt fires, checks VSYNC, checks ODDEVEN, and then outputs a scan line if required. The output stage is assembler code, and it works by controlling an IO port. Making a black pixel is accomplished by setting the output low, making a white pixel is accomplished by setting the output high, and no pixel is handled by tristating the pin. Everything about this is open sourced here: &lt;a href=&quot;http://code.google.com/p/super-osd/&quot; rel=&quot;nofollow&quot;&gt;http://code.google.com/p/super-osd/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, as it stands, there is one minor problem with this. The image has ringing on it. The resolution of the OSD is 208 pixels horizontally and the ringing can sometimes extend to two or three pixels, which is quite a lot! It doesn't make the OSD look as good as it should and reduces visibility. (Which is very important on an RC aircraft. If you are miles from home, you need to know exactly where you are, in case your plane goes down or you get lost.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Below is an image capture of the OSD. Look near the edges of the test lines, and near the text. Ignore the chroma noise, that is an unavoidable effect of composite video. (The OSD firmware still has some bugs, and I'm still squashing them, like the horizontal lines being one pixel too long and wrapping to the next line. Ignore them for now...)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/h15aa.jpg&quot; alt=&quot;OSD&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, I have few ideas why the image has so much ringing on it. I suspect it might be due to poorly terminated video signals but I have no idea on how to terminate them correctly, as my video card has already got a built in 75 ohm termination and my camera has matching termination (I hope.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can see how much ringing the video has in the scope trace below (bottom trace, 70mV/div):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Mdfwd.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suspect the ringing comes down to the capacitance of the IO pin, the termination resistance, and reflections in my... uh... transmission line which is currently a small piece of wire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ringing matches the image - about 2-3 pixel clocks. (One pixel clock is 40µs / 208 = 192 ns.) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, any ideas?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-20T00:09:34.307" Title="Ringing on my OSD project" Tags="&lt;video&gt;&lt;high-frequency&gt;&lt;ringing&gt;" AnswerCount="4" />
  <row Id="13219" PostTypeId="2" ParentId="13217" CreationDate="2011-04-18T23:24:28.120" Score="4" ViewCount="" Body="&lt;p&gt;You could use the 1x25 package in the &lt;a href=&quot;http://www.sparkfun.com/tutorial/SparkFunEagle-04-13-10.zip&quot; rel=&quot;nofollow&quot;&gt;SparkFun Eagle library&lt;/a&gt; as a starting point.  It gives you 25 pins spaced 0.1&quot; apart (used for single row headers).  Modify to taste.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/woDn8.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1322" LastActivityDate="2011-04-18T23:24:28.120" CommentCount="4" />
  <row Id="13220" PostTypeId="2" ParentId="13217" CreationDate="2011-04-18T23:48:44.333" Score="2" ViewCount="" Body="&lt;p&gt;What you are talking about with regards to the vias is solder mask capping them. In most good PCB programs you can get rid of the solder mask over a via by expanding the hole cut in the mask. &lt;a href=&quot;http://forum.sparkfun.com/viewtopic.php?f=20&amp;amp;t=7349&quot; rel=&quot;nofollow&quot;&gt;This thread&lt;/a&gt; seems to be useful.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-18T23:48:44.333" CommentCount="2" />
  <row Id="13222" PostTypeId="1" CreationDate="2011-04-19T00:12:44.860" Score="0" ViewCount="67" Body="&lt;p&gt;I also posted this at All About Circuits but I thought I would get some more opinions as I'm quite worried.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was using my power supply to power an electronics project (Super OSD.) The power supply is a TM035-3/GM035-3 0-3A 0-35V CC/CV power supply. When I turned the supply off, then on again, it made a little pop sound from inside and the RCD for the sockets tripped. (Lights remained.) It also blew the 5A mains input fuse. Obviously both safety features helped protect against a bad failure. After untripping the RCD and replacing the fuse, all is well - it still works perfectly fine. I am now a little concerned about how the power supply blew both the fuse and tripped the RCD! I have turned the supply on and off many times before. I am thinking inrush current but why only this time? &lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-04-19T12:02:15.873" Title="My power supply tripped the RCD" Tags="&lt;protection&gt;&lt;fuse&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="13223" PostTypeId="1" CreationDate="2011-04-19T00:22:31.697" Score="4" ViewCount="115" Body="&lt;p&gt;My cows keep getting out and i have a solar powered 6volt fence charger.  I have seen one that was hacked and it was very powerful.  I would like to know how to do it.  I could do it with one that plugs into an electrical outlet also.  Any help appreciated.&lt;/p&gt;&#xA;" OwnerUserId="3927" LastActivityDate="2011-04-19T02:45:00.900" Title="I want to increase the voltage on my electric fence charger" Tags="&lt;voltage&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="13224" PostTypeId="2" ParentId="13205" CreationDate="2011-04-19T00:39:44.180" Score="3" ViewCount="" Body="&lt;p&gt;If you look at the picture the Ben Jackson posted &lt;a href=&quot;http://electronics.stackexchange.com/questions/12600/what-is-the-purpose-of-solder-mask-expansion/12627&quot;&gt;in answer to a question about solder mask expansion&lt;/a&gt;, you'll see that the drilled holes can be significantly off-center from the pad centers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In extreme cases, you could actually end up with holes that leaves no or very little annulus to make the connection to outgoing traces.  The tear drop ensures that there's enough pad material left over to have a solid connection to the pad.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-19T00:39:44.180" CommentCount="2" />
  <row Id="13225" PostTypeId="2" ParentId="13223" CreationDate="2011-04-19T01:53:29.953" Score="11" ViewCount="" Body="&lt;p&gt;Don't do it.  What you're wanting to do is dangerous from a safety point of view, but also it would make you much more liable in the case of an accident.  Instead, buy an electric fence that does want you want.  Here's some articles that demonstrate what I'm talking about:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://jonathanturley.org/2009/01/02/six-year-old-girl-killed-on-electric-fence-of-neighbor-in-texas/&quot; rel=&quot;nofollow&quot;&gt;6-Year Old Girl Killed on Electric Fence&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.darwinawards.com/darwin/darwin2000-30.html&quot; rel=&quot;nofollow&quot;&gt;2000 Darwin Award Winner Kills Self with DIY electric fence&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.nytimes.com/1988/05/16/us/electric-fence-kills-woman.html&quot; rel=&quot;nofollow&quot;&gt;Electric Fence Kills 77 Year Old Woman&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ehow.com/facts_6108738_electric-fence-laws.html&quot; rel=&quot;nofollow&quot;&gt;Electric Fence Laws&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, you might be saying to yourself, &quot;I wouldn't be as stupid as those people&quot;.  But do you want to take that risk?  At least if you buy a commercially made one then they have to go through all the safety testing and they assume some or most of the liability in case of a fatality.  Just my opinion.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-19T01:53:29.953" CommentCount="1" />
  <row Id="13226" PostTypeId="1" CreationDate="2011-04-19T02:36:00.227" Score="0" ViewCount="71" Body="&lt;p&gt;I'm trying to use a 276-640 instead of a tsop 1236. I heard that it will still work. I can't find any datasheets for the 276-640. In the tsop 1236 datasheet, is the picture below. Does this apply to the 276-640 as well? I'm guessing that the 276-640 is newer and maybe better designed so that it doesn't need the capacitor and resistor shown in that picture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ZKLJb.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-04-19T15:06:28.880" Title="Using a 276-640 instead of a tsop 1236" Tags="&lt;capacitor&gt;&lt;resistor&gt;&lt;infrared&gt;&lt;wiring&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="13227" PostTypeId="2" ParentId="13223" CreationDate="2011-04-19T02:45:00.900" Score="5" ViewCount="" Body="&lt;p&gt;The AC powered ones are usually better. Also, check that you don't have weeds or tall grass touching the wire as that will reduce the voltage unless you have a current-controlled charger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But before you do that, is your ground good? If you're in a dry desert-like climate, the ground is pretty poor and the cows are perhaps not being zapped hard enough, if at all. Even around here, when it's summer, the ground often dries out enough to provide a pretty weak charge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We had a problem with a young colt getting out because he hadn't learned to respect the fence. What I ended up doing was stringing a ground wire a foot below the hot wire, so even on dry ground he would touch both and be hit hard enough to learn to stay away.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just don't do what I did and absent-mindedly hold the hot wire in one hand while holding the ground in the other -- wakes you up in a hurry :-) That's a pretty good reason for not rolling your own right there: a buggy design could have killed me right there.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-04-19T02:45:00.900" />
  <row Id="13228" PostTypeId="2" ParentId="13218" CreationDate="2011-04-19T04:32:46.673" Score="0" ViewCount="" Body="&lt;p&gt;Perhaps you can try buffering the IO pin and move the buffer as close to the video input as possible. You would still get the ringing on the input of the buffer, but hopefully the buffer will restore the signal and isolate the ringing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would need a tristate buffer for the high-impedance state.&lt;/p&gt;&#xA;" OwnerUserId="2340" LastActivityDate="2011-04-19T04:32:46.673" />
  <row Id="13229" PostTypeId="2" ParentId="13218" CreationDate="2011-04-19T05:14:05.313" Score="0" ViewCount="" Body="&lt;p&gt;From the look of it, you have an analog buffer for the composite video, and are overriding the composite video signal in some way, probably a summing network and an IO pin, or a pull-up transistor, etc... to produce the white text sections, correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Afterwards, I presume there is another buffer before the video output to the capture card you are using.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks like the recovery from the white-signal override is messy. You either need a faster output buffer, or need to stop driving the output buffer as far into clipping. If you clip the output buffer hard, many op-amps have nasty recovery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing you could try is putting a 75 ohm resistor as close to the output pin as possible on the OSD pcb. This will serve to properly impedance-match the driven end of the video transmission line.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-04-19T05:14:05.313" CommentCount="10" />
  <row Id="13230" PostTypeId="2" ParentId="13226" CreationDate="2011-04-19T06:08:14.923" Score="3" ViewCount="" Body="&lt;p&gt;You won't find a datasheet for a &lt;code&gt;276-640&lt;/code&gt; because it's not a manufacturer's part number, it's a Radio Shack catalog number. I find components without datasheet pretty useless.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wouldn't call Radio Shack &lt;em&gt;avant garde&lt;/em&gt; when it comes to offering newer parts. I think Vishay's parts are well up-to-date. For instance, all recent parts work with voltages down to 2.5V.&lt;br&gt;&#xA;Even so, the capacitor is always recommended, no matter how new the receiver is. If you don't place it the receiver will cause minor spikes on Vcc.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another note on the &lt;code&gt;276-640&lt;/code&gt;: keep in mind it has a carrier frequency of 38kHz, whereas for the TSOP1236 this is 36kHz. Things you'll find in the datasheet... (at least for the TSOP1236, for the &lt;code&gt;276-640&lt;/code&gt; you can find this information on Radio Shack's webpage, but there's no other info than that...)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-19T15:06:28.880" LastActivityDate="2011-04-19T15:06:28.880" CommentCount="6" />
  <row Id="13231" PostTypeId="2" ParentId="13217" CreationDate="2011-04-19T06:52:10.440" Score="1" ViewCount="" Body="&lt;p&gt;I'm not acquainted with Eagle, but I guess it has copy/paste like any EDA program. Set your grid to 0.1&quot;, place a free pad, copy and paste. Select both pads, copy/paste. Select all four pads, copy/paste. You can do the whole area in less than a minute.&lt;br&gt;&#xA;Vias are a bad choice because 1) they're too small, or you'd have to make a custom one, and 2) the pad of a via usually has a solder mask, which you would have to remove.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-19T06:52:10.440" />
  <row Id="13232" PostTypeId="1" CreationDate="2011-04-19T07:13:19.733" Score="0" ViewCount="138" Body="&lt;p&gt;Is it possible to use a microcontroller to read an input frequency? Please explain how?&lt;/p&gt;&#xA;" OwnerUserId="2480" LastActivityDate="2011-04-19T07:23:53.017" Title="How do you measure frequency using a microcontroller?" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;dspic&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13233" PostTypeId="2" ParentId="13232" CreationDate="2011-04-19T07:23:53.017" Score="5" ViewCount="" Body="&lt;p&gt;You can use a timer capture to detect edges. If the selected edge of the signal occurs the timer value will be latched and the controller will get an interrupt. Read and store the timer value and wait for the next interrupt. Read the new timer value and subtract the previous one. You now have the signal's period. Calculate 1/period to find frequency.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notes:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;I'm assuming that you have a decent digital signal  &lt;/li&gt;&#xA;  &lt;li&gt;You'll have to take the timer's overflow(s) into account  &lt;/li&gt;&#xA;  &lt;li&gt;Also make sure that the timer is clocked by an appropriate clock&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-19T07:23:53.017" />
  <row Id="13234" PostTypeId="2" ParentId="13217" CreationDate="2011-04-19T08:02:19.330" Score="2" ViewCount="" Body="&lt;p&gt;There is a &lt;a href=&quot;http://www.eaglecentral.ca/forums/index.php?t=msg&amp;amp;th=34853&quot; rel=&quot;nofollow&quot;&gt;thread&lt;/a&gt; on the Eagle Support forums that deals with this issue in detail. &lt;a href=&quot;http://www.eaglecentral.ca/forums/index.php?t=msg&amp;amp;th=34853&amp;amp;goto=120151#msg_120151&quot; rel=&quot;nofollow&quot;&gt;One of the replies&lt;/a&gt; includes a link to a &lt;a href=&quot;http://www.eaglecentral.ca/forums/index.php?t=getfile&amp;amp;id=3084&quot; rel=&quot;nofollow&quot;&gt;library of prototyping components&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-04-19T08:02:19.330" CommentCount="1" />
  <row Id="13235" PostTypeId="2" ParentId="13215" CreationDate="2011-04-19T08:23:40.283" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.digi.com/products/wireless-wired-embedded-solutions/zigbee-rf-modules/zigbee-mesh-module/&quot; rel=&quot;nofollow&quot;&gt;Digi&lt;/a&gt; has XBee modules which have the ZigBee protocol built-in and present themselves to your AVR as a simple UART, easy to interface. Digi has point-to-multipoint and mesh solutions. Modules are compact and reasonably priced.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Running off a coin cell may not be possible; RF transceivers are rather power-hungry (10s of milliAmps). Unless you have a very small power duty cycle. If for instance the device is switched on for 1 second every ten minutes you have a duty cycle of 0.17%.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-19T12:59:28.117" LastActivityDate="2011-04-19T12:59:28.117" CommentCount="0" />
  <row Id="13236" PostTypeId="2" ParentId="13217" CreationDate="2011-04-19T09:50:46.403" Score="3" ViewCount="" Body="&lt;p&gt;EAGLE trains you to add schematic parts for everything that appears on the PCB, but in this particular case, you really want to just add the holes, traces and silkscreen elements directly to the PCB. Think of it more as technical drawing than building a circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did this in the spare space in the upper left corner of my &lt;a href=&quot;http://tangentsoft.net/audio/pimeta2/&quot; rel=&quot;nofollow&quot;&gt;PIMETA v2&lt;/a&gt; board:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://tangentsoft.net/audio/pimeta2/bitmaps/brd-2.01.png&quot; alt=&quot;PIMETA v2 board layout&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The holes are 40 mil drill with 70 mil pads, and the traces are 40 mil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I highly recommend adding silkscreen outlines, as you see above. This makes clear which pads are connected to which. That was particularly helpful on this board, since the traces were on the bottom, but even if they were on top, I'd add the outlines. The contrast of silk on solder mask is simply a lot better than for the copper under the mask.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most of the pattern is intended to support DIP chips. The bits at the leftmost edge deviate from that partly due to lack of space but also to support an optional switch. (That's the translucent yellow overlay you see.) It's not important, here, to discuss what those switch pads are good for. The point is that you may not want to make your prototyping area completely generic. You should think through the scenarios of how the prototyping area will be used, and if there are special features you can add that will make it more useful than a generic protoboard pattern, do so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another example where I deviated from generic patterns is that some of the pads connect to the board's existing power and ground rails: V+, V-, B+ and IG. Doing that is one of the major advantages of having a prototyping areas on a special-purpose PCB, as opposed to using generic off-the-shelf protoboard: it means that things built up in the prototyping area can be run directly off the board's existing power supply and you don't have to run hookup wires across the board to get back to power points elsewhere. I recommend that you do the same.&lt;/p&gt;&#xA;" OwnerUserId="2523" LastEditorUserId="2523" LastEditorDisplayName="" LastEditDate="2011-04-19T19:16:29.243" LastActivityDate="2011-04-19T19:16:29.243" CommentCount="2" />
  <row Id="13237" PostTypeId="1" AcceptedAnswerId="13246" CreationDate="2011-04-19T11:28:42.647" Score="1" ViewCount="77" Body="&lt;p&gt;I've decided to conquer my fear of switched-mode power supplies and build one. Right now, I have a &lt;a href=&quot;http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000075.pdf&quot; rel=&quot;nofollow&quot;&gt;L4960&lt;/a&gt; regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its datasheet recommends use of a 150 $\mu H$ inductor rated at 5 A. My problem is that I can't find such an inductor. I can either get inductors with lower current rating (for example 150 $\mu H$ at 1 A) or inductors with smaller or higher inductance (for example 100 $\mu H$ at 10 A). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question is: How is it calculated that 150 $\mu H$ 5 A inductor is needed?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-19T14:03:11.883" LastActivityDate="2011-04-19T14:03:11.883" Title="Building SMPS using L4960: How does the choice of inductor affect circuit operation?" Tags="&lt;inductor&gt;&lt;smps&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="13238" PostTypeId="2" ParentId="13215" CreationDate="2011-04-19T11:31:13.787" Score="3" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.nordicsemi.com/&quot; rel=&quot;nofollow&quot;&gt;Nordic nRF24L01+&lt;/a&gt; is an ideal chip for this application, used with small MCUs. They are widely used in wireless keyboards and mice, due to the very low cost. A range of 100m is feasible with decent antennas, out of doors. I've used the nRF24L01+ Spark Fun modules with PICs, &lt;a href=&quot;http://www.leonheller.com/MiRF%20V2/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; is some information on my hardware and software. They are very low power, and the operating voltage is ideal for use with a coin cell. I'm powering my hardware with two NiMH cells - about 2.5V. I know someone who is using the Nordic chips with an MSP430 device who is getting a battery life of a couple of years from coin cells in the remote nodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've just ordered some very low-cost modules from &lt;a href=&quot;http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&amp;amp;item=320674876163&amp;amp;ssPageName=STRK%3aMEWNX%3aIT&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Several people have used them with AVRs, you should be able to find some source code you can use.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-19T11:53:55.813" LastActivityDate="2011-04-19T11:53:55.813" CommentCount="3" />
  <row Id="13239" PostTypeId="1" AcceptedAnswerId="13247" CreationDate="2011-04-19T11:35:37.653" Score="0" ViewCount="107" Body="&lt;p&gt;The drilled holes aren't always perfectly centered. For single sides boards this doesn't make much difference, but for plated through holes having a hole in the pads copper could mean that the pad only partly connects to the through-hole metalization if the drill doesn't match the hole perfectly.&lt;br&gt;&#xA;Are through-hole pads without hole in the copper allowed?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;About the larger annular ring (re Leon's comment): it's not the outside I'm worried about. I've never had an annular ring so small that the drill comes outside of it. If the drill goes a little bit to the west, then possibly on the east side the copper of my pad doesn't connect to the through-hole metalization. This wouldn't be noticed when the board is tested, since there's still a (partial) connection, but it may have a higher resistance.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-19T12:07:40.533" LastActivityDate="2011-04-19T16:31:51.653" Title="Should I always have holes in my PCB pads?" Tags="&lt;pcb&gt;" AnswerCount="3" />
  <row Id="13240" PostTypeId="2" ParentId="13239" CreationDate="2011-04-19T11:52:48.197" Score="1" ViewCount="" Body="&lt;p&gt;If you are getting problems with off-centre holes in your pads, you should change your PCB supplier, or use a larger annular ring. It sounds as though your supplier has problems with his PTH process as the copper is deposited after the holes have been drilled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You must have holes in your vias, it's the only way to get connectivity through the board. Holes can be filled, but it's a very expensive process and only used on high-end boards with vias in pads for BGA devices.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-19T13:45:29.493" LastActivityDate="2011-04-19T13:45:29.493" CommentCount="2" />
  <row Id="13241" PostTypeId="2" ParentId="13237" CreationDate="2011-04-19T11:57:56.290" Score="3" ViewCount="" Body="&lt;p&gt;If you can't find one, it's quite easy to wind your own with a suitable toroidal ferrite core. 150 uH is quite a low value and won't require many turns. You need to ensure that you use a wire gauge that can handle 5A, of course. Suitable cores are available from most component suppliers, and the manufacturer's web site will have design details. I've wound larger inductors using a pot core for an MCU-controlled switching power supply without any problems.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-19T11:57:56.290" CommentCount="2" />
  <row Id="13242" PostTypeId="2" ParentId="13222" CreationDate="2011-04-19T12:02:15.873" Score="1" ViewCount="" Body="&lt;p&gt;Probably an elctrolytic cap inside the PSU has blown open circuit, can you open it up to check?  If there is not any noticable ripple on your output I would not be too concerned.&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-04-19T12:02:15.873" CommentCount="1" />
  <row Id="13243" PostTypeId="2" ParentId="10668" CreationDate="2011-04-19T12:08:53.060" Score="3" ViewCount="" Body="&lt;p&gt;I've just found a reference design for a class D design using &lt;em&gt;discrete components only&lt;/em&gt;. It is published and patented by NXP (TCFKA Philips).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have not built it to verify the design, but they seem to use a very clever idea of making the differential amplifier and switsching power stage self-oscillating by adding a capacitive feedback path.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here are the links to...&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://www.nxp.com/documents/user_manual/UM10155.pdf&quot; rel=&quot;nofollow&quot;&gt;the application report&lt;/a&gt; and  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;&lt;a href=&quot;http://worldwide.espacenet.com/publicationDetails/biblio?FT=D&amp;amp;date=20031030&amp;amp;DB=EPODOC&amp;amp;locale=en_EP&amp;amp;CC=WO&amp;amp;NR=03090343A2&amp;amp;KC=A2&quot; rel=&quot;nofollow&quot;&gt;the patent document&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I found it while looking for other stuff at nxp.com, but &lt;em&gt;dames en heren&lt;/em&gt;, the design looks so cool I wish I had the time to start hacking it on a breadboard right away...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For educational purposes, I believe it is o.k. to build a patented circuit without trouble, but I'm not a lawyer. Other than that, it seems to be an absolutely perfect match for the requirements you mentioned.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-05-02T15:41:02.260" LastActivityDate="2011-05-02T15:41:02.260" />
  <row Id="13244" PostTypeId="2" ParentId="13237" CreationDate="2011-04-19T12:42:00.673" Score="1" ViewCount="" Body="&lt;p&gt;The inductance determines how much energy you put in the magnetic field. Lower switching frequencies require larger inductance. The wire diameter is determined by the maximum current the coil will see. Too thin a wire will have a higher resistance and reduce efficiency.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;I don't think the coil's value is found experimentally, but rather that it's a complex calculation that the manufacturer has done for us. Same, by the way, for the other components. Take &lt;a href=&quot;http://www.national.com/analog/webench&quot; rel=&quot;nofollow&quot;&gt;National's Webench&lt;/a&gt;, for instance. You supply the SMPS's black box parameters, and it returns a full schematic including BOM. If you're interested in the details of the calculation, however, have a look at a &lt;a href=&quot;http://www.linear.com/products/switching_regulator&quot; rel=&quot;nofollow&quot;&gt;Linear Technology&lt;/a&gt; datasheet.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-19T13:59:42.993" LastActivityDate="2011-04-19T13:59:42.993" CommentCount="1" />
  <row Id="13245" PostTypeId="2" ParentId="13218" CreationDate="2011-04-19T13:19:21.753" Score="3" ViewCount="" Body="&lt;p&gt;If you're just trying to overpower a video signal without gating it, your effective source impedance is going to vary every time your video is switched on and off.  Not good.  You need to ensure that both sides of your video connection see a uniform 75-ohm impedance whether you are passing through the signal or supplying your own.  The easiest way to do that would be to use a pair of video amplifiers and put your circuit in the middle.  The input amplifier should probably have 1:1 gain and a low-impedance output; use something like a 4066 to switch that and a white signal.  The output amplifier should have a 2:1 gain and a 75 ohm resistor in series.  BTW, are you doing anything for DC restoration?  That could be an issue as well.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-19T13:19:21.753" />
  <row Id="13246" PostTypeId="2" ParentId="13237" CreationDate="2011-04-19T13:23:36.527" Score="2" ViewCount="" Body="&lt;p&gt;I'm not totally clear on the question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the question is: why was $150 \mu H$ and $ 5A $ chosen, it's a matter of preference. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, the size of the inductor in a buck regulator is chosen to achieve a certain ripple voltage in the output capacitors at a given load, or to set the discontinuous-continuous threshold at a given load. The $ 5A $ saturation current threshold is most likely to ensure that the regulator itself will go into over-current protection before the inductor saturates out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the question is: how are the inductance and saturation current properties of an inductor calculated, then it's a matter of physics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The inductance and saturation current of an inductor are primarily properties of numerous characteristics, the most important of which are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;the construction geometry (shape, number of turns, etc.)&lt;/li&gt;&#xA;&lt;li&gt;the core material (air, ferrite, etc.)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Different numbers of turns will change the inductance for a given core. The core material (and air gap, if applicable) will determine how much DC current the inductor can carry before the permeability rolls off, which is generally what saturates out an inductor in a buck design (it carries more DC than ripple current, generally speaking).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-19T13:23:36.527" CommentCount="2" />
  <row Id="13247" PostTypeId="2" ParentId="13239" CreationDate="2011-04-19T13:36:51.923" Score="2" ViewCount="" Body="&lt;p&gt;I understand what you want, but it doesn't make sense: the drill diameter is determined by the hole diameter in your pad. No hole in the pad = no hole drilled.&lt;/p&gt;&#xA;" OwnerUserId="3920" LastActivityDate="2011-04-19T13:36:51.923" CommentCount="2" />
  <row Id="13248" PostTypeId="2" ParentId="13215" CreationDate="2011-04-19T14:03:52.357" Score="1" ViewCount="" Body="&lt;p&gt;Based off your need for wanting it to be able to run off a coin cell, very low power is going to be much desired. This will probably have more to do with how well you code your micro (going to sleep when you aren't doing anything), but the MSP430 line is very good for low power. They also have the CC430 which is combination MSP430 and CC1100. The CC1100 is a sub 1 GHz wireless IC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having the two devices in a single IC makes it very nice to implement features like Wake on Radio since the device that is being woken is the same device that has wireless in it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a few downsides to go with this method. Unless you want to make your own board with matching network and all your other option will be to buy a dev board that has that all done for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, by going with something like the XBee you can have the communication layer obscured to you. Meaning that you just throw data to it and it deals with getting it to the other end. This can be a good thing and a bad thing.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-19T14:03:52.357" CommentCount="3" />
  <row Id="13249" PostTypeId="1" AcceptedAnswerId="13272" CreationDate="2011-04-19T14:38:50.390" Score="3" ViewCount="134" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm just trying to layout a PCB with CY7C68013A (100-pin TQFP) on it. It's a sort of experiment, so I'd like to use 2-layer PCB, 4 layer PCBs are just too expensive. This leads to some interesting layout issues (note, that I'm more concerned with signal integrity than EMI).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I decided to use bottom layer as a ground plane, yet I have a really hard time choosing the best way to route the VCC trace. There are a few high-speed signals routed from the left and bottom edges of the chip to the connector on the left side of the board (carrying up to ~30MHz signals). There are 3 VCC/GND pairs on the left side, and 3 more on the bottom of the chip, to make things complex - I need to route VCC away from between those fast signals..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This makes it necessary to either:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;a) route parts of these signals on the bottom layer and keep most VCC on top &lt;/p&gt;&#xA;&#xA;&lt;p&gt;b) route these signals on top of the board and route some segments of VCC on the bottom layer (but this introduces holes in the bottom layer's ground plane, exactly underneath the signal traces, making the return path's loop bigger)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any advice? Is it OK to route the VCC underneath the chip on the bottom layer? &#xA;This would let me leave the ground solid under my fast signals. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How about top layer? (this would require a power track connected to the pin from one side, and decoupling capacitor stub track from the other side - that doesn't sound good to me). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps I'm overestimating the potential issues, but it's interesting problem on its own - I can imagine many projects choosing 2-layer PCBs to lower the costs. &lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-04-19T22:02:14.633" Title="VCC trace routing on a two-layer board with TQFP chip" Tags="&lt;pcb&gt;&lt;layout&gt;&lt;pcb-design&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="13250" PostTypeId="2" ParentId="13249" CreationDate="2011-04-19T14:49:40.940" Score="2" ViewCount="" Body="&lt;p&gt;If your Vcc is properly decoupled it's as good as ground. (There is no such thing as too much decoupling!) I would have no problem routing it underneath the chip. Make sure you have capacitors on it close to the chip's pins, and keep the Vcc traces as short as possible.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you get into trouble routing the thing you could use zero ohm chip resistors as jumpers to keep traces as short as possible.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-19T15:00:15.250" LastActivityDate="2011-04-19T15:00:15.250" />
  <row Id="13251" PostTypeId="2" ParentId="13159" CreationDate="2011-04-19T15:42:11.590" Score="0" ViewCount="" Body="&lt;p&gt;Use flux + solder wick to gently remove the majority of the solder from the part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Run the board through the reflow process again, on a hot plate.  When you hit the molten solder point, remove the parts with tweezers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most reflow profiles call for 60-150 seconds in a liquidous state, you should be able to remove the components at this time with tweezers and thats plenty of time to remove a couple parts.  You'll also have 10-30 seconds within 5C of the peak temperature where you can definitely just remove the parts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't want to do this just pre-heat the board to 100-150C and use a hot air gun.  Trying to remove a package as large as that PIC with a regular old solder gun is a meticulous hit or miss process and not really worth it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The SOIC 8 you can lift with just a pair of tweezers and a wide chisel tip, just lift one side then the other.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just keep in mind using any method other than heating the entire package and lifting it straight off the board will require a fair bit of clean up and bending of pins to get the package back into a state that it will reliably reflow.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-04-19T15:42:11.590" />
  <row Id="13252" PostTypeId="2" ParentId="13159" CreationDate="2011-04-19T16:04:38.393" Score="0" ViewCount="" Body="&lt;p&gt;Here's what I've done: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Put the board in a toaster oven.  Cut off a few mm of wire solder and place it on top of the black QFP part.  Set to &quot;dark brown&quot; and begin toasting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the solder goes from wire-shaped to ball-shaped, quickl&#xA;y open the toaster oven, grab the edge of the board with pliers, hold it vertically over your desk and knock the edge on the desk a couple times.  The parts will fall off.  You might need to clean the parts and board up with braid before reuse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also pick the part up with tweezers, but just letting the part slide off the board is better in my opinion, because there is no way it can put significant stress on the pads or pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you overheat the board this way it will discolor the silkscreen (the white browns a bit) but will be perfectly functional.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-19T16:04:38.393" CommentCount="1" />
  <row Id="13253" PostTypeId="1" AcceptedAnswerId="13257" CreationDate="2011-04-19T16:24:25.320" Score="2" ViewCount="164" Body="&lt;p&gt;The standard 9 pins RS232 connector has 9 pins. Those are:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1 -- DCD -- Data Carrier Detected&lt;br&gt;&#xA;2 -- RxD -- Receive Data&lt;br&gt;&#xA;3 -- TxD -- Transmit Data&lt;br&gt;&#xA;4 -- DTR -- Data Terminal Ready&lt;br&gt;&#xA;5 -- GND -- Signal Ground&lt;br&gt;&#xA;6 -- DSR -- Data Set Ready&lt;br&gt;&#xA;7 -- RTS -- Request to Send Data&lt;br&gt;&#xA;8 -- CTS -- Clear to Send Data&lt;br&gt;&#xA;9 -- RI  -- Ring Indicator&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A) If I need bi-directional communication it is obvious that I should connect RxD and TxD. What should I do with other signals/pins - connect to ground, left open, need to drive them with appropriate signals according to protocol?   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;B) If I care only about uni-directional connection can I connect only RxD or TxD?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C) What are the consequences of not using/connecting certain signals. What software on PC side expect to have those signals? What functionality will be lost? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;NOTE 1: I am using here word &quot;connect&quot; in sense of logical connection -&gt; for electrical connection I would require level shifter circuitry such as MAX232)&lt;br&gt;&#xA;NOTE 2: I am pin limited on uC - I do not mind connecting any signals on the board (like pulling them up/down).&lt;/p&gt;&#xA;" OwnerUserId="1471" LastActivityDate="2011-04-20T08:07:34.770" Title="How to connect uC to PC using RS232 with minimum number of signals?" Tags="&lt;rs232&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="13254" PostTypeId="2" ParentId="13239" CreationDate="2011-04-19T16:31:51.653" Score="1" ViewCount="" Body="&lt;p&gt;The only time I know of when it's useful to have holes in the copper design is when boards are being hand-drilled.  In such cases, a &lt;i&gt;much-smaller-than-actual-size&lt;/i&gt; hole will help show where the drill should go and keep it centered.  Otherwise, it's often nice to have holes shown actual size in paper plots but it's a very bad idea for production.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-19T16:31:51.653" />
  <row Id="13255" PostTypeId="2" ParentId="13253" CreationDate="2011-04-19T16:34:14.407" Score="5" ViewCount="" Body="&lt;p&gt;You only have to connect RxD and TxD, and Ground, of course. (If you're using unidirectional communication only Ground and RxD or TxD is required.) The other signals are used for communication with a modem. Most UARTs on microcontrollers don't provide these control signals. I do remember I've seen it on 1 or 2 UARTs of a uC with several more UARTs (though I don't remember which uC it was).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;more on the modem thing (FYI):&lt;/strong&gt;&lt;br&gt;&#xA;EIA-232 defines DTE (Data Terminal Equipment, in this case your PC or SBC) and DCE (Data Communication Equipment, often a modem).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/vJiPR.jpg&quot; alt=&quot;DTE-DCE configuration&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have several ways to connect the PCs.  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;ol&gt;&#xA;  &lt;li&gt;A direct connection, without the modems, uses a crossover cable (RxD on one side is connected to TxD on the other side, and vice versa). You only need those two signals + ground. &lt;strong&gt;That's what you use to connect a PC to a SBC.&lt;/strong&gt;  &lt;/li&gt;&#xA;  &lt;li&gt;A modem connection uses the extra signals too, the PC and the modem are connected via a straight through cable (pin 1 connected to pin 1, etc.)  &lt;/li&gt;&#xA;  &lt;li&gt;You can set up a connection between two DTEs as if there are modems present, in that case you use a null-modem to connect control signals between DTEs, like RTS from 1 DTE is connected to CTS on the other. This uses a complete wired crossover cable.  &lt;/li&gt;&#xA;  &lt;li&gt;A null-modem setup, where the control signals aren't connected between PCs, but you cheat and don't connect RTS to CTS on the other PC, but on your own PC. Other signals are also locally looped back. The result is that like in case 1) only RxD, TxD and Ground are connected between PCs.&lt;/li&gt;&#xA;  &lt;/ol&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-20T08:07:34.770" LastActivityDate="2011-04-20T08:07:34.770" CommentCount="2" />
  <row Id="13256" PostTypeId="1" CreationDate="2011-04-19T16:51:39.857" Score="1" ViewCount="84" Body="&lt;p&gt;I am looking for a block diagram  for Transmitter and Receiever for IEEE 802.11a/b/g/n ( or or Transceiver Architecture )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any useful pointers would be helpful for my work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I would like to understand the order in which the following blocks are implemented in the 802.11b Transmitter.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Scrambling&lt;/li&gt;&#xA;&lt;li&gt;Spreading&lt;/li&gt;&#xA;&lt;li&gt;Modulation&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I would like to understand the way the Packet are formed in the PHY Layer till it is transmitted and how the reverse process works in the Receiver as well. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="3733" LastEditorUserId="3733" LastEditorDisplayName="" LastEditDate="2011-04-20T08:49:24.703" LastActivityDate="2011-04-20T08:49:24.703" Title="Receiver Architecture for wlan" Tags="&lt;wireless&gt;&lt;wifi&gt;&lt;receiver&gt;&lt;transmitter&gt;" CommentCount="6" FavoriteCount="1" />
  <row Id="13257" PostTypeId="2" ParentId="13253" CreationDate="2011-04-19T17:10:30.170" Score="9" ViewCount="" Body="&lt;p&gt;It will depend of the software that you're using. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A) In my case, as I develop my own PC software, I've never used other pins, only RxD, TxD and GND. So, in this case you can left other pins open. This is called as &lt;strong&gt;null modem without handshaking&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/S7Fh3.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;B) Yes (assuming GND is being considered)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C) Again, it will depend of the software on PC side. Some softwares you can configure to not take care of hardware control. Others will require RTS/CTS handshaking, so you can do a &lt;strong&gt;null modem with loop back handshaking&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/rN4Kv.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Source of the pictures: &lt;a href=&quot;http://www.lammertbies.nl/comm/info/RS-232_null_modem.html&quot; rel=&quot;nofollow&quot;&gt;http://www.lammertbies.nl/comm/info/RS-232_null_modem.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-19T18:00:59.403" LastActivityDate="2011-04-19T18:00:59.403" CommentCount="4" />
  <row Id="13258" PostTypeId="1" CreationDate="2011-04-19T17:23:17.143" Score="0" ViewCount="65" Body="&lt;p&gt;I remember from reading on a website that Radio Shack parts are known by another name. For example the 276-038 is a 1458 and a 900-6298 is a 353. I would like to know what the 276-640 is so that I can find a datasheet on it, since there is no datasheet for th 276-640.&lt;/p&gt;&#xA;" OwnerUserId="1657" LastEditorUserId="1657" LastEditorDisplayName="" LastEditDate="2011-04-19T17:37:35.470" LastActivityDate="2011-04-19T18:14:10.637" Title="What is the other name for the 276-640?" Tags="&lt;datasheet&gt;&lt;infrared&gt;" AnswerCount="1" />
  <row Id="13259" PostTypeId="2" ParentId="1024" CreationDate="2011-04-19T17:33:35.100" Score="1" ViewCount="" Body="&lt;p&gt;I use DipTrace and I'm very satisfied. It's not free, but is quite inexpensive. I tried Eagle, which seems to be the most widely used, but was horrified about its unfriendliness. To me, it's not only a thing about learning curve, but simply making things harder to do thant it should be. Made me remember a traumatic experience with AutoCAD during the late 80s. I tried many other low-cost and free alternatives, but they either were also a bad-UI, unstable, or had a poor component library. The only under-100s package that worked well was DipTrace. Its weakness is that the PCB router is not very efficient (it was unable to route some boards that I was able to route manually without much effort), in particular when you have few layers, but to my use this was a minor limitation in comparision.&lt;/p&gt;&#xA;" OwnerUserId="1078" LastEditorUserId="1078" LastEditorDisplayName="" LastEditDate="2011-04-20T00:48:05.383" LastActivityDate="2011-04-20T00:48:05.383" CommunityOwnedDate="2011-04-19T17:33:35.100" />
  <row Id="13260" PostTypeId="2" ParentId="13124" CreationDate="2011-04-19T17:43:38.163" Score="0" ViewCount="" Body="&lt;p&gt;Newhaven Display tech support has recommended that I replace the LCD and try again.  It's possible that I damaged it during the initial setup, so we'll see how that goes.  I'll post up the results here.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-19T17:43:38.163" CommentCount="2" />
  <row Id="13261" PostTypeId="2" ParentId="13217" CreationDate="2011-04-19T17:51:39.550" Score="1" ViewCount="" Body="&lt;p&gt;At some point, with any EDA tool, you're probably going to have to create a custom part for something; so you might as well dive in and create a proto-area part with an array of pads the way you want.  You need to make the schematic component for that as well and place it on your schematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a good technique also for design-specific holes, especially if the holes have to align to some externally defined dimensions.   Having a pseudo-component in your schematic to call out those features would make those features &quot;official&quot; parts of your design.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-19T17:51:39.550" CommentCount="4" />
  <row Id="13262" PostTypeId="2" ParentId="13124" CreationDate="2011-04-19T18:04:00.697" Score="1" ViewCount="" Body="&lt;p&gt;Double check the signal high/low output voltages from the MSP430, and the minimums for the inputs on the LCD.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One other thing is whether you are bit banging too fast -- your source listing doesn't show how you're twiddling the data and E signals.  If you twiddle E too soon after loading the data bits, it won't work.  If you are not holding E long enough for the LCD to latch the incoming data, it won't work.  Try adding a time delay between writing D0-D7, and then between asserting and then deasserting the E line.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm assuming the lines are used strictly for the LCD's, so that there's no hold-time issue.  If you are using the lines as a bus to other devices as well, you'll need to make sure your data is held long enough before the bus is used for other things.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-19T18:04:00.697" CommentCount="3" />
  <row Id="13263" PostTypeId="2" ParentId="13249" CreationDate="2011-04-19T18:07:01.430" Score="2" ViewCount="" Body="&lt;p&gt;Here's how I've routed 2 layer boards...&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Top layer is to move signals&#xA;north-south. &lt;/li&gt;&#xA;&lt;li&gt;Bottom layer is to move signals east-west. &lt;/li&gt;&#xA;&lt;li&gt;Fill the bottom with a GND plane. &lt;/li&gt;&#xA;&lt;li&gt;Route any high speed or special traces.&lt;/li&gt;&#xA;&lt;li&gt;Route a single Vcc power bus along the outside edge of the board on the bottom layer.  This violates rule 2, but that's OK.&lt;/li&gt;&#xA;&lt;li&gt;All Vcc traces come off the power bus and run east-west until it reaches close to the chip.  Then use a via to get to the top layer and connect normally.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;This usually keeps all the tracks spaced out that you can route everything, even if it means a couple extra vias to hop over other traces.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-04-19T18:07:01.430" />
  <row Id="13265" PostTypeId="2" ParentId="13253" CreationDate="2011-04-19T18:12:37.470" Score="5" ViewCount="" Body="&lt;p&gt;You must have Tx, Rx, and signal ground at a minimum. While in theory you don't need to Tx if you are only receiving, as a practical matter in many situations, you will need to acknowledge receiving the message. The other pins are used for &quot;hardware handshaking&quot; a permission system where the sending device verifies the receiving device is ready. You can use Xon / Xoff instead (software handshaking). Some devices, serial mice for example, also used the hardware handshaking lines for power. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-04-19T18:12:37.470" />
  <row Id="13266" PostTypeId="2" ParentId="13258" CreationDate="2011-04-19T18:14:10.637" Score="1" ViewCount="" Body="&lt;p&gt;I'm not sure it has a fixed part number.  The catalog page &lt;a href=&quot;http://www.radioshack.com/product/index.jsp?productId=2049727&quot; rel=&quot;nofollow&quot;&gt;http://www.radioshack.com/product/index.jsp?productId=2049727&lt;/a&gt; gives the description &quot;38kHz Infrared (IR) Receiver Module&quot; but I'm not sure how precisely RS defines the part beyond that.  Radio Shack probably selected some particular manufacturer's receiver unit, but I don't know that they'll always use that same one.  Unless you need to precisely match a particular component, I'd suggest going to digikey.com, search for &quot;remote receiver&quot;, select &quot;38KHz&quot;, and go from there.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-19T18:14:10.637" CommentCount="3" />
  <row Id="13267" PostTypeId="2" ParentId="13125" CreationDate="2011-04-19T18:45:39.397" Score="0" ViewCount="" Body="&lt;p&gt;I added a 0.1 µF capacitor across the leads of the motor, and a 470µF capacitor across the power and ground rails on the breadboard, right next to the Uno's ground lead insertion point.  I no longer lose serial communication to the Uno when the motor comes under load or stalls.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was coming close to building an isolator circuit in order to completely decouple the motor side from the Arduino/PC side, using an ADUM1402 (http://www.analog.com/en/interface/digital-isolators/adum1402/products/product.html), but I figured that this couldn't be the only solution.  I did some more research and found that it's good practice to filter out the noise and spikes from DC motors by using capacitors as shown at &lt;a href=&quot;http://www.pololu.com/docs/0J15/9&quot; rel=&quot;nofollow&quot;&gt;http://www.pololu.com/docs/0J15/9&lt;/a&gt; and in many other sites.  A glaring display of ignorance on my part, but now I know better.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure how (i.e. what's the theory behind it) this fixes the problem, because I'm still not sure what the cause of the problem was.&#xA;If any one can shed some light on this, I'd be grateful.  I don't like doing things without having and understanding of why I'm doing them.  I'll keep reading until I figure out how this actually fixes things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In any case, thanks to everyone that tried to help out!&lt;/p&gt;&#xA;" OwnerUserId="3881" LastActivityDate="2011-04-19T18:45:39.397" />
  <row Id="13268" PostTypeId="1" AcceptedAnswerId="13289" CreationDate="2011-04-19T20:36:28.650" Score="7" ViewCount="232" Body="&lt;p&gt;I am not a specialist in electronics. I'm just a programmer. I ask this question just for fun.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question: How the frequency for a design of a digital circuit is chosen?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the frequency chosen &quot;before-hand&quot; before doing actual design, &quot;as the last choice&quot; after the circuit is already designed, or &quot;in-middle&quot; adjusting it several times during design?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What if it turns out that different parts of a big circuit require different optimal frequencies? Isn't it a reason for redesign of some parts of the circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you describe the stages of choosing frequency during design?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How it has happened that many of &quot;Core&quot; series CPUs had lesser frequency than Pentium-4 having indeed greater speed?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also heard that lesser frequency leads to lesser power consumption. But aren't Core CPU having lesser frequency having nevertheless not lesser number of logical gates changing their state per second? Isn't the number of gates changing their state not frequency the factor which defines power consumption?&lt;/p&gt;&#xA;" OwnerUserId="3932" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-20T06:04:29.540" LastActivityDate="2011-04-20T06:50:55.757" Title="How is frequency chosen?" Tags="&lt;power&gt;&lt;circuit-design&gt;&lt;digital&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="2" />
  <row Id="13269" PostTypeId="2" ParentId="13218" CreationDate="2011-04-19T20:39:32.057" Score="0" ViewCount="" Body="&lt;p&gt;A schematic would be helpful.  I suspect that when you are driving the video line, you're causing your camera's output stage to be quite unhappy.  Supercat has already pointed that out...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT after seeing schematic:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whooo, yeah - if I read that correctly, you're just pulling the video signal straight down via an 18 ohm resistor.  That would make the output buffer on your camera unhappy, and puts an 18 ohm stub in the video signal line that would cause ringing.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-04-20T00:09:34.307" LastActivityDate="2011-04-20T00:09:34.307" CommentCount="1" />
  <row Id="13270" PostTypeId="1" AcceptedAnswerId="13273" CreationDate="2011-04-19T20:57:27.613" Score="1" ViewCount="93" Body="&lt;p&gt;I have an ESD mat and wrist strap.  The wrist strap plugs into a little box that beeps when either the mat or the wrist strap do not have a good connection to ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also have a standard Phihong 5V wall wart.  I have noticed that when the wall-wart is plugged into a device, and the device is sitting on the mat, the box indicates a fault with the mat.  If I touch an exposed ground pad on the device, I get another fault indicator for the operator, as if my wrist strap is improperly grounded.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I attach a serial cable to the device, this problem vanishes.  I assume this is because the serial cable somehow provides a proper ground to the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This happens even if the device is off.  However, the wall-wart is still active; if I turn the wall wart off by flipping the switch on the surge protector, the problem vanishes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem also appears sometimes when I merely approach my mat with the device connected, without even necessarily touching it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there an explanation for this odd behavior?&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-04-19T22:17:05.483" Title="Why does my ESD wrist strap beep?" Tags="&lt;ground&gt;" AnswerCount="1" />
  <row Id="13271" PostTypeId="2" ParentId="13268" CreationDate="2011-04-19T20:58:18.560" Score="5" ViewCount="" Body="&lt;p&gt;Actually, power dissipated by a CMOS circuit is a sum of static power consumption (caused by leakage currents) and dynamic power consumption (consumed only when the transistors are changing the logic state). The latter is a function of the switching frequency. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an excellent TI's application note which describes it in more details:&#xA;&lt;a href=&quot;http://focus.ti.com/lit/an/scaa035b/scaa035b.pdf&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/lit/an/scaa035b/scaa035b.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Said that, it's usually the best idea to select lower clock frequency. However, sometimes it makes more sense to use higher clock frequency so e.g. interrupt handler can finish its task faster, and switch the CPU into power saving mode between interrupts.&lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-04-19T20:58:18.560" />
  <row Id="13272" PostTypeId="2" ParentId="13249" CreationDate="2011-04-19T22:02:14.633" Score="1" ViewCount="" Body="&lt;p&gt;That's the Cypress FX2LP USB microcontroller (I recognize it because I use it myself).  If you're using the Hi-Speed USB transceiver, then you should really go with a 4-layer board.  Without that ground plane right below the top layer, it will be near impossible to get the 90 ohm differential impedance that you want for the USB D+/D- lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cypress.com/?id=4&amp;amp;rID=34128&quot; rel=&quot;nofollow&quot;&gt;http://www.cypress.com/?id=4&amp;amp;rID=34128&lt;/a&gt; flat out states that 4 layers is &lt;strong&gt;required&lt;/strong&gt;.  It also states that controlled impedance is required, but in my experience you can usually get away without it, so long as you carefully research your fab's typical stack-up and work out the right width, space, and height.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.cypress.com/?docID=25406&quot; rel=&quot;nofollow&quot;&gt;http://www.cypress.com/?docID=25406&lt;/a&gt; also provides more info on calculating the width, space, and height for the D+ and D- lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4-layers isn't that much more expensive; Advanced Circuits has a 66 each deal for 4 layer boards that I use quite often for projects that use that very chip, as opposed to the 33 each deal for 2 layers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In regards to your actual question...use plenty of bypass caps, as close to the pins as possible.  If you split the bottom layer to have VCC and GND, don't have a trace cross the split on the top layer.  Keep all high-speed signals on the top layer because the via inductance can kill what fragile signal integrity a 2-layer board has.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-04-19T22:02:14.633" CommentCount="2" />
  <row Id="13273" PostTypeId="2" ParentId="13270" CreationDate="2011-04-19T22:17:05.483" Score="3" ViewCount="" Body="&lt;p&gt;A fault is registered when a threshold voltage differential is measured between the banana plug of the mat or wrist strap and the provided ground. &lt;a href=&quot;http://www.trcelectronics.com/Phihong/pdf/psa15r.pdf&quot; rel=&quot;nofollow&quot;&gt;The datasheet&lt;/a&gt; states no more than 50mV ripple, at whatever frequency it switches (assuming it is a switcher, as a linear regulator would be hard-pressed to claim &lt;em&gt;&quot;High Efficiency&quot;&lt;/em&gt;). If the connections are long enough, the magic ESD box may be registering up to 100mV or 0.1V differential.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hook up your oscilloscope in differential probe mode between the ESD box ground and banana plugs to see if it's an issue.&lt;/p&gt;&#xA;" OwnerUserId="2118" LastActivityDate="2011-04-19T22:17:05.483" />
  <row Id="13274" PostTypeId="2" ParentId="13268" CreationDate="2011-04-19T22:19:42.457" Score="5" ViewCount="" Body="&lt;p&gt;In the embedded arena, often a specific frequency is chosen because of constraints with the peripherals of the microcontroller.  For example, a 1.8432 MHz crystal (or multiple of this frequency such as 18.432 MHz) might be used because this base frequency divided by 16 results in a 115,200 baud rate for a UART.  32768 Hz is often used for low-power microcontroller applications because it is easily divided down to 1 Hz for time-keeping.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Crystal_oscillator_frequencies&quot; rel=&quot;nofollow&quot;&gt;Here is a list&lt;/a&gt; of various crystal frequencies and the reason they exist.  The ones listed &quot;UART clock&quot; are often picked for microcontrollers for the reason given earlier; the specific one chosen depends on the circuitry of the BRG (baud rate generator) and desired baud rate(s).&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-04-20T00:10:09.923" LastActivityDate="2011-04-20T00:10:09.923" />
  <row Id="13275" PostTypeId="1" AcceptedAnswerId="13378" CreationDate="2011-04-19T23:00:09.190" Score="11" ViewCount="378" Body="&lt;p&gt;Can anyone recommend a small, free implementation of AES-128 Rijndael for microcontrollers. Ideally, for the PIC18, though a general implementation in C would be useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compiling the &lt;a href=&quot;http://codesearch.google.com/codesearch/p?hl=en#RGCD84x9Jg0/trunk/xbmc/lib/libUPnP/Neptune/ThirdParty/axTLS/crypto/aes.c&quot; rel=&quot;nofollow&quot;&gt;axTLS implementation&lt;/a&gt; for PIC18 and encrypting/decrypting a block requires 6KB ROM and 750b of RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compiling &lt;a href=&quot;http://fastcrypto.org/front/misc/rijndael-alg-fst.c&quot; rel=&quot;nofollow&quot;&gt;rijndael-alg-fst.c&lt;/a&gt; for PIC18 and encrypting/decrypting a block requires 28KB ROM and 0.5KB RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compiling &lt;a href=&quot;http://gladman.plushost.co.uk/oldsite/AES/aes-byte-29-08-08.zip&quot; rel=&quot;nofollow&quot;&gt;Brian Gladman's 8-bit AES&lt;/a&gt; for PIC18 and encrypting/decrypting a block requires 19KB of ROM and 190 bytes of RAM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there better optimised PIC specific variants available?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(updated RAM requirements for axTLS version)&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-04-23T18:42:34.957" LastActivityDate="2011-04-23T18:42:34.957" Title="Smallest AES implementation for microcontrollers?" Tags="&lt;pic&gt;&lt;aes&gt;&lt;cryptography&gt;" AnswerCount="1" CommentCount="9" FavoriteCount="3" />
  <row Id="13276" PostTypeId="1" CreationDate="2011-04-19T23:16:55.767" Score="2" ViewCount="106" Body="&lt;p&gt;I'm having trouble finding the equation for Vx. I keep getting close, but it's always off. Can anyone help me out with this?&#xA;&lt;img src=&quot;http://i.imgur.com/9TLWd.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3657" LastActivityDate="2011-04-19T23:16:55.767" ClosedDate="2011-05-13T03:29:19.660" Title="How to solve this RLC circuit equation" Tags="&lt;homework&gt;" CommentCount="3" />
  <row Id="13277" PostTypeId="1" CreationDate="2011-04-19T23:20:22.840" Score="0" ViewCount="75" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/1024/good-tools-for-drawing-schematics&quot;&gt;Good Tools for Drawing Schematics&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I tried using Visio to draw schematics of a project but the problem is I can't make customized chips with pin connections. Is there a better program for this?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-04-19T23:49:45.703" ClosedDate="2011-04-20T02:15:49.000" Title="How to draw schematics" Tags="&lt;software&gt;&lt;schematics&gt;" AnswerCount="0" CommentCount="1" />
  <row Id="13278" PostTypeId="2" ParentId="13268" CreationDate="2011-04-19T23:46:04.193" Score="1" ViewCount="" Body="&lt;p&gt;As mentioned above people make speed vs. power trade offs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the high performance end of the market it's more complex - in the Intel case there are competing issues - how fast can I make the silicon go? depends - to execute an instruction takes several clocks - As a (very) simple example I might be able to build a 4 clock/instruction pipeline that clocks at 1GHz and a 6 clock/instruction pipeline that clocks at 1.25GHz I'll still retire 1 instruction on every clock and the 6 clock/instruction pipe will be faster&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the real world though things like pipeline bubbles occur, the more pipeline stages you have the more clocks you waste when you have to refill the pipeline - the 4 clock pipe will fill faster than the 6 clock pipe and on average (over a large bunch of benchmarks) the 6 clock pipe might take 2 clocks to retire every instruction compared with the 1.5 clocks for the 4 pipe stage design - the 4 stage design will out perform the 6 stage one (1gHz/1.5 &gt; 1.25GHz/2).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course it's hard for the marketing guys to sell things like this - people are so used to &quot;more GHz means faster&quot; &lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-04-19T23:46:04.193" />
  <row Id="13280" PostTypeId="2" ParentId="13124" CreationDate="2011-04-20T00:01:06.620" Score="0" ViewCount="" Body="&lt;p&gt;Could it be possible that you have the pins wired in reverse?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Every once in a while, I would come across LCD's with the pin numbers reversed either on the part itself or on the datasheet or both.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know this might seem like an &quot;is it plugged in?&quot; question - but I've personally been caught by surprise with this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;* EDIT *&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ugh, in my earlier comment, I said to write 0x80 -- what I intended was for you to try and holding the value 0x40 or 0x60 to the data lines.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it turns out the pins are reversed, writing 0x40 would apply power and ground via the data pins to the LCD, giving it a chance to do its self-reset.  This is possible because a typical character LCD module only draws like 1 to 5 mA of current, well within the driving ability of most outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I suspect may be happening is that you are writing some 0x6X and 0x4X values to your LCD for a brief period of time while you're initializing the LCD -- and that the LCD is powering up during that brief period; but when you start writing other values, you are effectively turning it off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;* EDIT 2 *&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While looking up the datasheet of another LCD to verify the current requirements, I noticed that you may have your Vcc and Vcontrast pins swapped.  Make sure you check that as well!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just looked and saw in the NHT-C0220AZ-FWS-FTW datasheet (where you got your schematic drawing above) that the contrast is pin 2, and supply voltage is pin 3.  Which is the reverse of the Vishay and Optrex parts where contrast is pin 3, and supply voltage is pin 2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Well, heck, even NewHaven's NHD-0420DZ-FSW-FBW has contrast on pin 3 and supply on pin 2.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-04-23T15:56:18.863" LastActivityDate="2011-04-23T15:56:18.863" CommentCount="3" />
  <row Id="13281" PostTypeId="1" AcceptedAnswerId="13283" CreationDate="2011-04-20T00:09:07.473" Score="5" ViewCount="132" Body="&lt;p&gt;I am going to need a large length of wire from my microcontroller analogue input to a &lt;a href=&quot;http://www.rapidonline.com/netalogue/specs/58-0128.pdf&quot; rel=&quot;nofollow&quot;&gt;LDR&lt;/a&gt; or similar sensor. The length of wire is likely to be about 100m so will it have any affects on the reading the ADC? Is there anyway I can reduce the effects?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-04-21T21:47:01.867" Title="Will there be any effects on a signal in a long wire?" Tags="&lt;ldr&gt;" AnswerCount="5" CommentCount="3" />
  <row Id="13282" PostTypeId="2" ParentId="13281" CreationDate="2011-04-20T00:40:38.277" Score="2" ViewCount="" Body="&lt;p&gt;It will probably pick up interference.  Maybe you can use the same circuit design as a microphone, with the two LDR wires inside a shielded cable and equal loads and a diff amp at the other end.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you're going to an ADC, I'm guessing your LDR signal changes slowly relative to the time it takes for a signal to travel 100 m (500 ns), so you &lt;a href=&quot;http://en.wikipedia.org/wiki/Transmission_line#Applicability&quot; rel=&quot;nofollow&quot;&gt;don't need to worry about transmission line effects&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistance of the wire probably won't affect it, either, if the sensor's resistance is in the kiloohms.  The wire &lt;a href=&quot;http://www.wolframalpha.com/input/?i=200%20m%20AWG%2028&quot; rel=&quot;nofollow&quot;&gt;might be 50 ohm&lt;/a&gt; or so by itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually, if your LDR signal changes slowly relative to the interference, the diff amp could be overkill and you could just filter the interference out with a low-pass filter.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-20T01:01:13.167" LastActivityDate="2011-04-20T01:01:13.167" />
  <row Id="13283" PostTypeId="2" ParentId="13281" CreationDate="2011-04-20T04:43:34.177" Score="1" ViewCount="" Body="&lt;p&gt;Yes, normally you would &lt;strong&gt;not&lt;/strong&gt; put a sensor 100 meters from the ADC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why? Because that length of wire will experience voltage drop due to the resistance of the copper wire, doing a quick estimate to demonstrate, using 24 AWG (&lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/tables/wirega.html&quot; rel=&quot;nofollow&quot;&gt;wire gauge chart&lt;/a&gt;) the resistance would be in about 8 ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using Ohm's Law and say 10mA of current (my guess, small signal level) that would equal about 0.1 volts drop. &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;V = I * R&#xA;voltage drop = 10mA times 8 ohms&#xA;V = 0.010 * 8 = 0.08&#xA;or approximately 0.1 V. &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If it's a 5V signal that's 2%, enough to lose accuracy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally for a signal to be transmitted reliably over a longer distance, and resist interference as well as handle the wire resistance, you can do a few things. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first is to increase the voltage, say use a 24 Volt signal rather than 5V (or 3.3V) or whatever the limit of your ADC input is. This can be useful, and is what &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/RS-232#Voltage_levels&quot; rel=&quot;nofollow&quot;&gt;RS-232&lt;/a&gt; (EIA-232) serial protocol does to improve communication reliability over a distance. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second is to use a &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Current_loop&quot; rel=&quot;nofollow&quot;&gt;current loop&lt;/a&gt;, where the information is encoded as current differences, such that LDR value is encoded near the sensor, and the current loop spans the 100 meter distance. This would require a current loop transceiver at either end of the distance, and at least one end of the loop should have a robust power supply to provide the necessary power for the loop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A third way would be to use a &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Differential_signaling&quot; rel=&quot;nofollow&quot;&gt;differential signal&lt;/a&gt;, where two wires (&lt;em&gt;balanced transmission lines)&lt;/em&gt; span between the LDR sensor and the ADC. The difference between the two values is the actual &lt;strong&gt;signal&lt;/strong&gt;. This has very good &lt;a href=&quot;https://secure.wikimedia.org/wikipedia/en/wiki/Common-mode_interference&quot; rel=&quot;nofollow&quot;&gt;common mode interference&lt;/a&gt; rejection (filtering). Examples include &lt;a href=&quot;http://www.bb-elec.com/tech_articles/rs422_485_app_note/overview.asp&quot; rel=&quot;nofollow&quot;&gt;RS-422&lt;/a&gt;, and most Ethernet modes. There are line-drivers ICs for RS-422, similar to the popular MAX232 transceiver / driver for RS-232 serial communications.&lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-04-20T04:43:34.177" />
  <row Id="13284" PostTypeId="2" ParentId="13268" CreationDate="2011-04-20T04:59:01.173" Score="0" ViewCount="" Body="&lt;p&gt;Another consideration is EMC / EMI - electromagnetic compatibility / electromagnetic interference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, high speed digital signals can create unintended RF (radio frequency - from long-wave to microwave) radiation that can be a source of interference for licensed RF usage. This includes broadcast AM (MW) radio, television broadcast, cellular phones, to GPS receivers and other electronic circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In fact at high speeds, long (copper) traces on a printed circuit board (PCB) can act as antennas, for both transmitting and receiving. For example, a poorly laid out circuit could easily receive enough interference if a mobile phone is place too close to the circuit board to crash a system. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Satellites have to also consider ionizing radiation (i.e. gamma particles), one solution requires using radiation hardened ICs which may only operate at limited speeds due to the manufacturing process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because of this commercial products have to go through EMC / EMI testing before being allowed to be sold to the general market. &lt;/p&gt;&#xA;" OwnerUserId="2598" LastActivityDate="2011-04-20T04:59:01.173" />
  <row Id="13286" PostTypeId="1" AcceptedAnswerId="13288" CreationDate="2011-04-20T05:31:17.443" Score="2" ViewCount="129" Body="&lt;p&gt;I am trying to interface a pair of Chinese calipers with my Arduino. Due to the calipers running at 1.5v, I've used a TPQ-2222 (quad 2N2222 transistors I think, please let me know if I'm mistaken) to step up the voltage to 5v. However, on power up, the Arduino fires voltage down it's pins randomly and I'm worried that that voltage may damage my calipers. Unfortunately I don't have any diodes on hand (they are on order from china, ETA 2 weeks...but they were cheap! And I'm not paying $3 for 10 diodes at my local electronics shop!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I use the transistors on the TPQ-2222 as a signal diode and is it necessary because the transistor amplifying the voltage will already work as one?&lt;/p&gt;&#xA;" OwnerUserId="1319" LastActivityDate="2011-04-20T06:46:23.203" Title="Using a transistor as a diode?" Tags="&lt;transistor&gt;&lt;diode&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="13287" PostTypeId="2" ParentId="13281" CreationDate="2011-04-20T06:00:41.273" Score="1" ViewCount="" Body="&lt;p&gt;Your 100 m of wire will act as 1 big antenna an pick up all kinds of EMI (ElectroMagnetic Interference). You could use a shielded cable, as endolith suggests, or a decent twisted pair (decent = enough twists per meter).&lt;br&gt;&#xA;A lower impedance at the end of the wire also reduces EMI, but the lower this impedance, the more the wire's resistor comes into play. You may have to adjust your ADC reading for the loss.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-20T06:00:41.273" />
  <row Id="13288" PostTypeId="2" ParentId="13286" CreationDate="2011-04-20T06:25:37.747" Score="8" ViewCount="" Body="&lt;p&gt;From your question, I can't really figure out how your circuit works. But I can answer the question if you can use transistors as diodes with &quot;yes&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One example where this is often done is when you want to have a diode with a very low leakage current: A diode-connected transistor (C and B terminals shorted together in order to use its B-E-diode) has much lower leakage than most regular diodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just make sure you pay attention to the absolute maximum ratings of your transistors for the &quot;blocking direction&quot;: The maximum allowed negative B-E-voltage is quite low compared to diodes.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-20T06:46:23.203" LastActivityDate="2011-04-20T06:46:23.203" />
  <row Id="13289" PostTypeId="2" ParentId="13268" CreationDate="2011-04-20T06:50:55.757" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;I.&lt;/strong&gt; Most of the time chip will use different frequencies for different part of the chip. Now days even most basic 0.5$ mikrocontrollers have fairly complicated clocking scheme (well at least deserving separate chapter in datasheet). So clock frequency will be chosen on block by block bases.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;II.&lt;/strong&gt; At whats stage of design frequency is chosen:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;a) I would claim that most of the  time it is at the early stage. One would get requirements (example: have to decode HD Video). Based on that one would chose architecture taking into account power/technology/cost(area) tradeoffs. One of the output of the architecture decision is clock frequency.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;b) But some times the early decision is sub-optimal/wrong. So modification are being made. However this can be costly as usually different parts of the chip are designed in parallel. Changing one clock may trigger re-design of other block (due to interface and clock source itself). I would say that for this reason this is avoided. Of course it is easier for some block to change clock frequency then for other so &quot;your millage may vary&quot;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;c) At the last stage of place and route (this is one of the last stages before sending chip to factory) sometimes one can have troubles closing on timing/power budget (ie. making design work at targeted frequency/power) so decision is made to lower clock frequency. This is definitely avoided as this means not meeting some of the marketing specs. But some times it is wiser to be faster on the market then doing redesign which at this stage will be really costly and time consuming.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But there is more:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;d) Some times clock frequency decision is made after fabrication (if certain provision in the design are made beforehand). Due to manufacturing variability some chips turn out better then other. Than one can perform binning - sort the chips based on what maximum frequency those can work reliably and sell those faster at premium. I would say this is mostly used by PC processor vendors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;e) Sometimes ready chips are under clocked in the final equipment to save power (popular in the uC) if required processing power is lower then maximum allowed from the chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;f) In some modern design clock can be adjusted dynamically. Then clock is changed in the field based on the load in order to save power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;III.&lt;/strong&gt; So how the frequency is chosen and why it is some times design working at lower clock will have bigger processing capability:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh boy there are so many variables so this is engineering discipline on itself. You have take into marketing requirements, technology, cost, EMI, power, supported standard, IO requirements  etc etc ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But basically one can dumb down this to following - in order to achieve given performance one can have faster clock (do things in series one after another) or do things in parallel at lower clock at the cost of using more transistors. Due to some factors - mainly pipeline stall/memory latency it is sometimes better to use more transistor then faster clock.&lt;/p&gt;&#xA;" OwnerUserId="1471" LastActivityDate="2011-04-20T06:50:55.757" CommentCount="2" />
  <row Id="13290" PostTypeId="1" CreationDate="2011-04-20T09:06:38.710" Score="0" ViewCount="98" Body="&lt;p&gt;Firstly, I am new to CAN. I bought microchip's Can Bus Monitor Demo Board that includes a mcp2515 and a pic18f4550..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here the mcp is a stand alone Can controller and all the instructions, data to be moved from the 4550 to it through SPI..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am looking for guidance from people who are used to this or if you can please help me with the best ways to learn controller area networks..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance..&lt;/p&gt;&#xA;" OwnerUserId="1484" LastActivityDate="2011-04-26T17:11:13.487" ClosedDate="2011-05-17T11:32:36.280" Title="CAN through SPI - Mcp 2515 - Guidance" Tags="&lt;pic&gt;&lt;spi&gt;&lt;can&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="13291" PostTypeId="1" AcceptedAnswerId="13292" CreationDate="2011-04-20T12:16:01.063" Score="4" ViewCount="112" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why don't they use zener diodes in high frequencies?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="3916" LastActivityDate="2011-04-20T12:42:47.093" Title="Zener diodes in high frequencies" Tags="&lt;high-frequency&gt;&lt;zener&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="13292" PostTypeId="2" ParentId="13291" CreationDate="2011-04-20T12:24:22.113" Score="6" ViewCount="" Body="&lt;p&gt;In reverse biased mode, which is how you would normally use a zener, the capacitance is tens to hundreds of picofarads. This could be enough to attenuate your signal significantly, depending on the frequency and source impedance.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-04-20T12:24:22.113" CommentCount="4" />
  <row Id="13293" PostTypeId="1" CreationDate="2011-04-20T12:28:18.310" Score="0" ViewCount="89" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This question is specifically targeted to a RTOS -- ThreadX.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are using it for our project. Problem with this is default RTOS tick time is 10ms which is very high. We need to change it to 1ms. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone used this RTOS? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(For Ref:&lt;a href=&quot;http://ftp1.digi.com/support/training/SW_APIS/ThreadXKernelAPIs.ppt&quot; rel=&quot;nofollow&quot;&gt;ThreadX PPT&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2574" LastActivityDate="2011-05-20T21:45:28.583" Title="Change Timer Tick of RTOS - ThreadX" Tags="&lt;rtos&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13294" PostTypeId="2" ParentId="13291" CreationDate="2011-04-20T12:42:47.093" Score="3" ViewCount="" Body="&lt;p&gt;Zener diodes aren't typically used in a signal path. You won't find them easily in lower frequency paths either. They're used mostly to control DC voltages.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-20T12:42:47.093" />
  <row Id="13295" PostTypeId="1" AcceptedAnswerId="13296" CreationDate="2011-04-20T12:57:06.457" Score="2" ViewCount="111" Body="&lt;p&gt;I have a &lt;a href=&quot;http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000075.pdf&quot; rel=&quot;nofollow&quot;&gt;L4960&lt;/a&gt; regulator. In its datasheet on page 9 there is a typical application circuit. Under notes, it says C1, C6, C7: EKR(ROE). What does that mean?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-04-20T13:38:38.760" Title="What does EKR(ROE) mean in capacitor markings?" Tags="&lt;capacitor&gt;" AnswerCount="3" />
  <row Id="13296" PostTypeId="2" ParentId="13295" CreationDate="2011-04-20T13:15:09.367" Score="2" ViewCount="" Body="&lt;p&gt;ROE (Roederstein) was a German capacitor manufacturer, they made EKR-type capacitors. They are now owned by Vishay:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.vishay.com/company/brands/roederstein/&quot; rel=&quot;nofollow&quot;&gt;http://www.vishay.com/company/brands/roederstein/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It doesn't look as though the EKR devices are still available. If you contact ST they should be able to suggest an alternative device. Switchers can be fussy about things like capacitor types, you probably need to use devices with similar characteristics.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-20T13:28:40.333" LastActivityDate="2011-04-20T13:28:40.333" />
  <row Id="13297" PostTypeId="1" AcceptedAnswerId="13916" CreationDate="2011-04-20T13:27:06.450" Score="7" ViewCount="205" Body="&lt;p&gt;While routing my CY7C68013A based PCB I just realized that regular USB B receptacle and mini USB equivalent have D+ and D- effectively swapped.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems that the chip was prepared for regular size receptacle (DP is on the left if looking towards the chip), while for mini USB I have to route one of the tracks under the receptacle. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it really like this, or did I mess something up? How am I suppose to keep the tracks impedance and length constraints, while one of the tracks needs to go a different way, around the receptacle pads?&lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-05-08T20:50:41.820" Title="Mini USB receptacle versus proper PCB layout" Tags="&lt;pcb&gt;&lt;usb&gt;&lt;pcb-design&gt;" AnswerCount="2" CommentCount="7" FavoriteCount="2" />
  <row Id="13298" PostTypeId="2" ParentId="13295" CreationDate="2011-04-20T13:36:09.123" Score="3" ViewCount="" Body="&lt;p&gt;Like Leon said, EKR devices were made by Roederstein. But I also found them at &lt;a href=&quot;http://www.frolyt.de/en/&quot; rel=&quot;nofollow&quot;&gt;Frolyt&lt;/a&gt;, a manufacturer I never heard of before, frankly.&lt;br&gt;&#xA;&lt;a href=&quot;http://www.frolyt.de/x-ohne_VDA6.1-EKR_S1-5_10_97_1_.pdf&quot; rel=&quot;nofollow&quot;&gt;This datasheet&lt;/a&gt; suggests that it's a series of low-impedance elcos, which indeed is what you want for SMPSs. Other than that the document doesn't mention what EKR means, materials-wise or process-wise.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-20T13:36:09.123" />
  <row Id="13299" PostTypeId="2" ParentId="13295" CreationDate="2011-04-20T13:38:38.760" Score="2" ViewCount="" Body="&lt;p&gt;As stated, Mfg. is Roederstein (ROE), type is EKR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's a &lt;a href=&quot;http://www.vishay.com/docs/28398/replace.pdf&quot; rel=&quot;nofollow&quot;&gt;replacement list&lt;/a&gt; saying that the type is replaced by the EKE series, &lt;a href=&quot;http://www.vishay.com/docs/25008/25008.pdf&quot; rel=&quot;nofollow&quot;&gt;the data sheet of which is linked here.&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-04-20T13:38:38.760" />
  <row Id="13300" PostTypeId="2" ParentId="13297" CreationDate="2011-04-20T14:39:10.067" Score="1" ViewCount="" Body="&lt;p&gt;Are you sure that D- and D+ are swapped? I checked the &lt;a href=&quot;http://www.usb.org/developers/docs/usb_20_021411.zip&quot; rel=&quot;nofollow&quot;&gt;USB2 specification&lt;/a&gt;. ECN 1 describes the miniB connector, and I see the same order for the regular and the mini: Vbus, D-, D+, Ground.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the connections &lt;em&gt;are&lt;/em&gt; swapped, can't you add a few zigzags in the shorter trace to make it as long as the other? (I don't think it is really necessary, but it might give you some rest :-))  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ZQyqU.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-20T14:46:07.517" LastActivityDate="2011-04-20T14:46:07.517" CommentCount="3" />
  <row Id="13302" PostTypeId="1" CreationDate="2011-04-20T17:00:22.040" Score="1" ViewCount="62" Body="&lt;p&gt;I am wondering how to send values to a 104 PC I/O board. There are several on the market that use a similar approach. Information surrounding the one I have in my possession can be found &lt;a href=&quot;http://www.dpie.com/pc104/r104.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. I have the R104-88 model(8 inputs and 8 outputs). From my understanding I have to select which base address I want to use with the jumpers. Using the jumpers I have selected the base address to be 300H.  So if I were to read 302H I would be getting the inputs from pins 0, 1 , 2, and 3. The problem is that not matter what the inputs are, I always read FFH from address 302H. I am using &lt;a href=&quot;http://logix4u.net/Legacy_Ports/Parallel_Port/Inpout32.dll_for_Windows_98/2000/NT/XP.html&quot; rel=&quot;nofollow&quot;&gt;inpout32.dll&lt;/a&gt; to read the addresses. The code I am using to do this using python is below. I am running Windows XP as my OS. &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;import ctypes&#xA;print ctypes.windll.inpout32.Inp32(0x302)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Is there a better way do this? What am I missing? Do I have to configure the Hardware some how? I am at a loss of what to try next. Apologies if this is not the correct forum to ask. The question kinda falls under electronics, stackover flow and super user. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The setup I am using is a 104 PC. The I/O board just fits on top of the 104pc and power supply.&lt;/p&gt;&#xA;" OwnerUserId="1337" LastEditorUserId="1337" LastEditorDisplayName="" LastEditDate="2011-04-21T13:29:16.557" LastActivityDate="2011-05-23T01:44:25.040" Title="Reading and Sending Values to a 104 pc I/O relay board." Tags="&lt;hardware&gt;&lt;input&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="13304" PostTypeId="1" CreationDate="2011-04-20T19:06:05.477" Score="3" ViewCount="54" Body="&lt;p&gt;I have TVS diode in parallel with circuitry for ESD/lightening/transient voltage protection.  Say I receive an over-voltage condition which is beyond the specifications of the part, what happens internally?  I assume that the part is unable to dissipate the heat generated internally fast enough which causes a break down in the junction doping resulting in an open circuit (like a blown fuse).  Is this an accurate assessment of what happens? Could an out of spec transient condition ever cause a permanent short instead?&lt;/p&gt;&#xA;" OwnerUserId="1571" LastActivityDate="2011-04-21T01:43:25.693" Title="How does a high voltage condition break down a semiconductor?" Tags="&lt;high-voltage&gt;&lt;transient-suppression&gt;&lt;tvs&gt;&lt;thermal&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="13305" PostTypeId="1" CreationDate="2011-04-20T19:22:38.113" Score="3" ViewCount="60" Body="&lt;p&gt;I have two air coils. They both have diameter &lt;strong&gt;d&lt;/strong&gt;. There is a distance &lt;strong&gt;D&lt;/strong&gt; between their centres.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;D&lt;/strong&gt; is much greater than &lt;strong&gt;d&lt;/strong&gt; (more than 10x greater)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both coils are at different angles, &lt;strong&gt;a&lt;/strong&gt; and &lt;strong&gt;b&lt;/strong&gt;, relative to the line between their centers. There is an alternating current in one coil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there some simple function which estimates the current induced in the second coil?  I would be happy if the form of the function was:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;k * f(D, a, b)   (where k had to be measured)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example: k * cos(a) * cos(b) * D^-2&lt;/p&gt;&#xA;" OwnerUserId="1024" LastActivityDate="2011-04-20T19:22:38.113" Title="How to estimate inductive coupling between distant air coils" Tags="&lt;inductance&gt;&lt;solenoid&gt;" CommentCount="3" FavoriteCount="1" />
  <row Id="13306" PostTypeId="1" AcceptedAnswerId="13308" CreationDate="2011-04-20T19:57:37.963" Score="1" ViewCount="128" Body="&lt;p&gt;Hi &#xA;I'm using an atmega 16 chip to drive a BS170 N channel enhancement mosfet. I'm unsure how would I go about this. Having read the datasheet, I'm guessing  I set the pin the fet is connected to as a output pin. I would then set the PORTxn to high for on and low for off. Yes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would have eight of these connected to the same chip. Is that ok?&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-04-21T05:54:21.583" Title="how to drive a N channel Mosfet transistor" Tags="&lt;avr&gt;" AnswerCount="2" />
  <row Id="13307" PostTypeId="2" ParentId="13124" CreationDate="2011-04-20T20:00:28.720" Score="0" ViewCount="" Body="&lt;p&gt;Also one thing that tricked me one time was the backlight being so low I couldn't see that it was working.&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-04-20T20:00:28.720" CommentCount="3" />
  <row Id="13308" PostTypeId="2" ParentId="13306" CreationDate="2011-04-20T20:03:32.170" Score="0" ViewCount="" Body="&lt;p&gt;Yes that would work. Connecting 8 to the 8 outputs should be fine. Just remember MOSFETs are ESD sensitive.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-04-20T20:03:32.170" CommentCount="3" />
  <row Id="13309" PostTypeId="2" ParentId="2178" CreationDate="2011-04-20T20:11:35.380" Score="0" ViewCount="" Body="&lt;p&gt;The guys over at seeedstudio sell a &lt;a href=&quot;http://www.seeedstudio.com/depot/wireless-power-supply-p-701.html?cPath=155&quot; rel=&quot;nofollow&quot;&gt;ready-made inductive transmitter/receiver pair&lt;/a&gt;, designed specifically for charging batteries. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have no experience with it, but at $\$$9.50 it might be worth a shot.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-04-20T20:11:35.380" />
  <row Id="13310" PostTypeId="2" ParentId="13293" CreationDate="2011-04-20T21:27:41.757" Score="1" ViewCount="" Body="&lt;p&gt;From what I can tell from the PPT you linked, you are responsible for setting up the hardware timer that generates the tick interrupt and therefore you can set it to whatever value you like.  My primary reference is slide 66 in the PPT which says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The System Tick Rate is set with #define&lt;br&gt;&#xA;          BSP_TICKS_PER_SECOND which defaults to 100&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;But chaning the #define won't change the period - altering the period register for the timer you're using will.  Once you do that you'll have to change the #define to keep it consisten with the new period.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-20T21:27:41.757" />
  <row Id="13311" PostTypeId="2" ParentId="13304" CreationDate="2011-04-21T01:43:25.693" Score="1" ViewCount="" Body="&lt;p&gt;There's no heat until there's current. Of course, when device features are very small, it doesn't take very much current; localized heating is proportional to localized current density. When there's enough current density and enough heating, the dopant atoms begin to diffuse through the substrate. This destroys the integrity of the structure of the affected PN junction region, so that you no longer have the desired electrical properties.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-21T01:43:25.693" />
  <row Id="13312" PostTypeId="2" ParentId="13281" CreationDate="2011-04-21T01:54:17.467" Score="1" ViewCount="" Body="&lt;p&gt;This would be an ideal application for an AT-tiny, which is an 8 pin AVR. Flash the Tiny to just loop doing the ADC conversion, and transmit your information over the 100m of wire by bit-banging the digitized signal. Given that the signal will be changing only very slowly, you could send back single bytes, say once per second, at a low baud rate (e.g., 2400bps). Running the signal back as analog over 100m of wire, you're apt to collect a bunch of unwanted noise, to which a digital signal should be immune.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-04-21T21:47:01.867" LastActivityDate="2011-04-21T21:47:01.867" />
  <row Id="13313" PostTypeId="1" AcceptedAnswerId="13323" CreationDate="2011-04-21T03:52:07.360" Score="2" ViewCount="129" Body="&lt;p&gt;I have a cheap multimeter, which gives me different readings between the two inputs. I would like to set 100 mA using a potentiometer in a circuit, which runs from two AA batteries. If I measure the circuit using the standard slot which works up to 200 mA, it shows about 80-90 mA. In the same circuit, if I plug the cable into the 10 A slot, and switch the multimeter to the 10 A mode, it shows 0.11 A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you tell me why is it happening and how should I know that:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;is my multimeter actually modifying&#xA;the current, or just showing it? &lt;/li&gt;&#xA;&lt;li&gt;if not, then which measurement is the&#xA;correct?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;As a small question: if I buy a new multimeter, what should I look for if I want to buy a better one? Should I buy one from a known brand? Is there any way to identify the ones I should avoid?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt;&#xA;I think I should tell you what is my circuit:&#xA;2xAA batteries ---- 10 Ohm ----- IR LED (specified at 1.35V/100mA) --- multimeter ---- batteries&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you for all the detailed answers! Based on markrages' answer, I think in my case the multimeter is indeed modifying the current, because &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;without the multimeter its 10 Ohms&lt;/li&gt;&#xA;&lt;li&gt;with the multimeter in 10 A mode its 10.1 Ohms in total.&lt;/li&gt;&#xA;&lt;li&gt;with the multimeter in 100 mA mode its 12.5 Ohms in total.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Which would prove the fact why am I seeing 80-90 mA vs. 110 mA in the two modes, as thats the same 25% difference as the difference in resistance between 2. and 3.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even more extreme was when I tried to run the 1.35V LED from a single AA battery. In that case I used a 1 Ohm resistor, and the two readings in the multimeter were 35 mA vs. 100 mA. Now I understand why, because the multimeter + 1 Ohm acted as a 3.5 Ohm resistor.&lt;/p&gt;&#xA;" OwnerUserId="3049" LastEditorUserId="3049" LastEditorDisplayName="" LastEditDate="2011-04-21T14:25:18.313" LastActivityDate="2011-04-21T14:25:18.313" Title="different current readings with a multimeter between the 200 mA and the 10 A slots" Tags="&lt;voltage&gt;&lt;current&gt;&lt;multimeter&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="13314" PostTypeId="2" ParentId="13313" CreationDate="2011-04-21T04:04:23.493" Score="1" ViewCount="" Body="&lt;p&gt;The different measurement ranges will have different accuracies.  Generally, the cheaper the multimeter the more the two ranges will give different measurement values.   But, to more directly address your questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;You're multimeter is not modifying the current, what it's showing is off.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Generally, the lower range (200 mA in this case) will &lt;em&gt;probably&lt;/em&gt; give you the more accurate reading.  This isn't 100% true, but maybe 95% true.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;It's hard to go wrong with a Tek or Fluke.  Other major brands are probably fine.  I'd stay clear of the no-name brands, but I'm sure someone will disagree with me on this one.  My experience is that you get what you pay for on this one.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-21T04:04:23.493" />
  <row Id="13315" PostTypeId="2" ParentId="13313" CreationDate="2011-04-21T05:17:01.037" Score="2" ViewCount="" Body="&lt;p&gt;On the 10A scale, you are asking it to read a current value at about 1% of full scale. To get a difference at that level of only about 20% is pretty good if you think about. Having a perfectly linear circuit is always fairly difficult to do. Most components will only have at best 0.5% to 1% tolerance and will also vary with temperature (which is usually compensated for). A better-brand will probably give a closer result but I would still expect a 5% - 10% error when you are working at the bottom of the scale.&lt;/p&gt;&#xA;" OwnerUserId="2595" LastActivityDate="2011-04-21T05:17:01.037" />
  <row Id="13316" PostTypeId="2" ParentId="13281" CreationDate="2011-04-21T05:24:37.910" Score="0" ViewCount="" Body="&lt;p&gt;If you don't want to program an AVR as per JustJef's suggestion you could try a one-wire analog-to-digital converter like DS2450 from Maxim. This is a quad ADC. It should be able to send data up to 500m if you follow their guidelines. (I was easily able to get a DS18B20 temperature sensor work at 30m on basic alarm cable).&lt;/p&gt;&#xA;" OwnerUserId="2595" LastActivityDate="2011-04-21T05:24:37.910" />
  <row Id="13317" PostTypeId="1" CreationDate="2011-04-21T05:48:05.157" Score="0" ViewCount="68" Body="&lt;p&gt;I will try to design an inductive charger which will run by using cigar lighter of the car. Does anybody have any suggestions on my project? Taking the power from cigar lighter is easy but how should I choose my circuit components for best ergonomy &amp;amp; efficiency?&lt;/p&gt;&#xA;" OwnerUserId="3935" LastActivityDate="2011-05-21T07:45:47.873" Title="Car Inductive Charger Module?" Tags="&lt;car&gt;&lt;charger&gt;&lt;inductive&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="13318" PostTypeId="2" ParentId="13306" CreationDate="2011-04-21T05:54:21.583" Score="3" ViewCount="" Body="&lt;p&gt;Yes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Did you also read the &lt;a href=&quot;http://www.fairchildsemi.com/ds/BS/BS170.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet for the BS170&lt;/a&gt;? Datasheets are documents you have to learn how to read. In case of the BS170 Vgs (page 2) is important. It's the minimum gate voltage at which the MOSFET starts conducting. For the BS170 this Vgs can be anything between 0.8V and 3V. This wide range is typical of MOSFETs. It means that in a worst-case scenario you only get 1mA of drain current when driven from a 3V microcontroller, which isn't enough to drive a LED! If you're using the ATmega16 (and not the ATmega16L) you won't have this problem.&lt;br&gt;&#xA;Most important graph for the BS170 is figure 1 on page 3. This shows that at Vgs = 5V you can have 800mA of drain current.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;MOSFET's gates are extremely ESD sensitive; you can zap them just by looking at them, so to speak. Make sure you're properly grounded when handling them (antistatic wrist strap), this also goes for your soldering iron.&lt;br&gt;&#xA;I also make it a habit to have a resistor from the gate to the source, this ensures that the BS170 remains off when for one reason or another the gate should be floating. This can be a 1M resistor.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-21T05:54:21.583" CommentCount="0" />
  <row Id="13319" PostTypeId="1" CreationDate="2011-04-21T05:55:24.420" Score="2" ViewCount="127" Body="&lt;p&gt;I don't understand these sentences from Razavi's book, &lt;em&gt;Design of CMOS Integrated Analog Circuit&lt;/em&gt;, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;'the gate polysilicon and the source and drian terminals are typically tied to metal(aluminum) that serve as interconnects with low resistance and capacitance. To accomplish this, &lt;strong&gt;one more &quot;contact window&quot;&lt;/strong&gt; must be opened in each reigon, filled with metal, and connected to the upper metal wires'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does this mean that one and more &quot;contact window&quot; could lead to low resistance and capacitance, if it is, how could it be?&lt;/p&gt;&#xA;" OwnerUserId="493" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T20:59:14.490" LastActivityDate="2011-04-27T20:59:14.490" Title="Why do MOFET need so many contact windows?" Tags="&lt;mosfet&gt;&lt;cmos&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="13320" PostTypeId="2" ParentId="13313" CreationDate="2011-04-21T07:01:42.413" Score="3" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Screen Error&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to keep in mind that a larger range will result in less resolution. Auto-ranging multimeters help you get around this issue by automatically switching to the highest resolution range that it can use for your signal. But without auto-ranging, you are just stuck with rounding error that has to be in place in order to display the value on the screen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lets say you have 4 positions for numbers to go, on a 0 to 200mA scale this means you can display at most a resolution of .1 mA. Ex, 199.9mA is 4 digits, and unless you change the screen, theres no way to add more digits. Now if you switch to the 10A mode, you have the same 4 digits that now have to represent 0 to 10,000 mA. This means you can display 9.999A or 9.998A but you can't show 9.9985. This makes your step size 10 mA where as before your step size was 0.1mA. That is a factor of 100 difference in resolution!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So purely by design of the LCD screen you will be able to get more accurate data at a lower range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I have seen cheap multimeter that have the first digit be either a '1' or turned off. This might be the case here. Even though it says it can go up to 200 mA, it could mean that it can go up to 199.9mA&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Measurement Error&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First of all, 0.1mA resolution can be pretty hard to measure, especially on cheaper meters. Some might show you something that might make you think it is reading that exactly, but I wouldn't trust it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Second, 80-90mA is a pretty significant swing in readings at that range. This makes me think you either have a very crappy meter or there is something else going on. I have found that when you are at a range like that, how well your connections are between multimeter and circuit start to show up as variability. For example, I have seen people try to stick the pointy end of a DMM probe into a breadboard and just barely make contact internally. In this situation, as you move the probes around making more and less contact, the resistance between the probe and breadboard changes which then of course causes the current to change.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally you should be able to set up your measurement such that you can take your hands off of the project and just look at the measurement. Hopefully if you set yourself up to be able to do this you will find a reading that is pretty steady.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Range Differences&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On DMMs, as you change your range, it is changing what components are being used to take the measurement. Every component is going to have some chance or error associated with it. There is a chance that by luck of the draw your meter ended up with higher accuracy components for the 10A range while it had much worse in the 200mA range. But at the same time it is just as likely to happen in any configuration you can imagine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is also a possibility that the manufacture was willing to spend a bit extra to get nicer components for the 200mA range (like 1% or .5% tolerance) while allowed for 5%-20% tolerance to be allowed in the 10A range in order to save money. But even in this situation it is possible that a 20% tolerance component ended up being exactly correct while a .5% could be its full .5% off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now nicer meters will generally use components that have higher accuracy and thus will yield more accurate results.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Moral to the story&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think David's answer pretty well sums it up.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-21T07:01:42.413" CommentCount="1" />
  <row Id="13321" PostTypeId="2" ParentId="13317" CreationDate="2011-04-21T07:15:56.670" Score="0" ViewCount="" Body="&lt;p&gt;The guys over at seeedstudio sell a &lt;a href=&quot;http://www.seeedstudio.com/depot/wireless-power-supply-p-701.html?cPath=155&quot; rel=&quot;nofollow&quot;&gt;ready-made inductive transmitter/receiver pair&lt;/a&gt;, designed specifically for charging batteries. Input voltage is 12V, so it would be an excellent fit for automotive applications. I have no experience with it, but at $\$$9.50 it might be worth a shot. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both the transmitter and the receiver should fit in a flat 50x60mm housing, so i suggest you design your product on a similar footprint. It is hard to comment on ergonomics without knowing at least the shape of what you are planning to charge, the approximate interior arrangement of the vehicle and whether it's intended to be operated by the driver or the passengers.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-04-21T07:15:56.670" CommentCount="1" />
  <row Id="13322" PostTypeId="2" ParentId="13319" CreationDate="2011-04-21T07:53:56.263" Score="1" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/frKyG.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A &quot;contact window&quot; is a loop that connects two materials (usually a metal and a semiconductor) together. Since they are square frames, they look like windows. The picture above is a two-gate mosfet with metal gates. For each of the three source/drains you can clearly see the contact windows, connecting the semiconductor islands to the metal pads. The gates do not need a contact windows in this particular design, as they are already made out of metal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What leads to lower resistance and capacitance is not so much the contact window itself, but the fact that the signal travels the distance through metal instead of semiconductor.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-04-21T07:53:56.263" />
  <row Id="13323" PostTypeId="2" ParentId="13313" CreationDate="2011-04-21T08:34:34.720" Score="2" ViewCount="" Body="&lt;p&gt;Measuring the cheap meter on my desk, the 10A range uses a 0.1 ohm shunt resistor and the 400 mA range uses a 2.5 ohm shunt resistor and the 4mA range uses a 100 ohm shunt resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;100 mA through 0.1 ohms is 10 mV drop and 100 mA though 2.5 ohms is 250 mV drop. So depending on the impedance of your circuit, the current could be lower in the lower range just because of the increased series resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can measure the voltage drop across the ammeter with another voltmeter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you can't tolerate voltage drop, try a feedback ammeter: &lt;a href=&quot;http://www.keithley.com/data?asset=6169&quot; rel=&quot;nofollow&quot;&gt;http://www.keithley.com/data?asset=6169&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-21T08:34:34.720" CommentCount="5" />
  <row Id="13325" PostTypeId="1" CreationDate="2011-04-21T09:00:12.997" Score="3" ViewCount="121" Body="&lt;p&gt;What are the different tinning techniques for PCBs, and what are the advantages of one technique over the other?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-21T18:01:37.870" Title="What are current PCB surface protection techniques?" Tags="&lt;pcb&gt;" AnswerCount="3" />
  <row Id="13326" PostTypeId="2" ParentId="13325" CreationDate="2011-04-21T09:47:57.690" Score="1" ViewCount="" Body="&lt;p&gt;Immersion silver seems to be getting popular for RoHS boards. It gives a very flat surface, and is fine if boards are soldered quickly. Some companies use immersion gold, even on low-cost boards. Silver can oxidise over time, which apparently can affect solderability, so gold might be better if boards are to be stored. I've had no problems hand-soldering boards finished with both immersion silver and immersion gold (lead solder), and neither has the company I use sometimes for surface-mount board assembly, using lead-free solder paste.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Gold plating has been used on connector pins for years, and has never caused soldering problems.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-21T18:01:37.870" LastActivityDate="2011-04-21T18:01:37.870" CommentCount="8" />
  <row Id="13327" PostTypeId="1" AcceptedAnswerId="13328" CreationDate="2011-04-21T11:29:01.227" Score="2" ViewCount="78" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to make a simple 8 chanel relay multiplexer. My choice for driver IC at the moment is ULN2803A and for relays it is a 12v DC DPST relay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I read in ULN2803A datasheet that it contains Suppression Diodes. Does this means I should not be worried about adding a diode in the return path of relay coil?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="3757" LastActivityDate="2011-04-21T14:21:28.957" Title="Suppression diode for relays in ULN2803A" Tags="&lt;diode&gt;&lt;relay&gt;&lt;driver&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13328" PostTypeId="2" ParentId="13327" CreationDate="2011-04-21T11:42:58.937" Score="5" ViewCount="" Body="&lt;p&gt;You need to connect the common cathode (pin 10) of the ULN2803A to the positive supply of the relay, then all outputs will be protected from the counter emf produced by the relays. There is no need to add an additional diode.&lt;/p&gt;&#xA;" OwnerUserId="3453" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-21T14:21:28.957" LastActivityDate="2011-04-21T14:21:28.957" CommentCount="2" />
  <row Id="13329" PostTypeId="2" ParentId="13325" CreationDate="2011-04-21T11:50:57.527" Score="2" ViewCount="" Body="&lt;p&gt;The easy answer is that you should look at the options your board house offers and then research that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Common options I've seen are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;HASL, Hot Air Solder Leveling: They bascially coat the entire board in solder and use a air knife to blow the excess off, it's cheap but it can leave a slightly uneven surface, which might mean something if you are doing BGAs.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;OSP, Organic Solderability Preservatives: A very thin coating that keeps oxygen away and evaporates when soldering, it looks as though there is just bare copper on the board.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This page has a good description of these and other finishings:&#xA;&lt;a href=&quot;http://www.multicircuits.com/pcb/tech/surface_finishes.html&quot; rel=&quot;nofollow&quot;&gt;http://www.multicircuits.com/pcb/tech/surface_finishes.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-04-21T11:50:57.527" CommentCount="0" />
  <row Id="13330" PostTypeId="1" AcceptedAnswerId="13331" CreationDate="2011-04-21T12:00:50.107" Score="3" ViewCount="110" Body="&lt;p&gt;I recently got a small &lt;a href=&quot;http://www.national.com/mpf/LM/LM386.html#Overview&quot; rel=&quot;nofollow&quot;&gt;LM386 M-1&lt;/a&gt; based amplifier kit, mainly to practice my SMD soldering. I managed to solder it, but it's giving me unexpected results. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the schematic:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ELnXD.png&quot; alt=&quot;LM386M-1&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The input signal is supposed to be connected to NF (for positive) and GND connectors. ZV is obviously a speaker. Pin 1 is not connected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now about the results: When I power on the device and sent a 1 kHz sine wave to it, I get this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/MavWX.jpg&quot; alt=&quot;sine wave&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The peak to peak voltage here is around 190 mV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I turn it off, I get this:&#xA;&lt;img src=&quot;http://i.imgur.com/GPVMs.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and the peak to peak voltage is around 1.46 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it works much better when it's off than when it's on. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also after reading the LM386 datasheet, the circuit looks a bit strange to me. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the pinout of LM386 form the datasheet:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/Ua5SJ.png&quot; alt=&quot;LM386 pinout&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So is the PCB I got plain wrong or should I start checking out each individual component?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-04-21T17:14:41.207" Title="How do I start debugging this circuit?" Tags="&lt;op-amp&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="13331" PostTypeId="2" ParentId="13330" CreationDate="2011-04-21T12:26:30.927" Score="6" ViewCount="" Body="&lt;p&gt;Where to start?&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Your input signal is being applied to pin 4 which should be 0V&lt;/li&gt;&#xA;&lt;li&gt;Your speaker is connected between $V_{OUT}$ &amp;amp; Gain instead of between $V_{OUT}$ &amp;amp; 0V&lt;/li&gt;&#xA;&lt;li&gt;Both inverting &amp;amp; non-inverting inputs (pins 2 &amp;amp; 3)are connected to 0V&lt;/li&gt;&#xA;&lt;li&gt;Bypass (Pin 7) is connected directly to 0V instead of through a capacitor (as per the data sheet)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The schematic is clearly wrong. Where did you get the kit from?&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-04-21T12:26:30.927" CommentCount="1" />
  <row Id="13332" PostTypeId="1" AcceptedAnswerId="13337" CreationDate="2011-04-21T12:35:28.580" Score="1" ViewCount="128" Body="&lt;p&gt;Today I found Texas Instruments &lt;a href=&quot;http://www.semiconductorrelease.com/tis-bq51013-receiver-ic-next-generation-of-wireless-power-technology/&quot; rel=&quot;nofollow&quot;&gt;announced a circuit for wireless charging&lt;/a&gt; - all the materials emphasis how tiny, lightweight, portable, efficient and otherwise cool it is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While I of course like the idea I don't get one thing. What's so hard in implementing such circuit in just all cell phones allready? Every other company introduces so-called &quot;charging mats&quot; that also require en extra gadget attached to the wireless device to make it receive power from the &quot;charging mat&quot; and I guess different systems are incompatible with each other, but there're almost no devices with built-in wireless charging (except maybe shavers and toothbrushes).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's year 2011 and we have microchips with millions of transistors on them - why don't we have such simple thing as wireless charging in every applicable device yet? What's the technical difficulty here?&lt;/p&gt;&#xA;" OwnerUserId="3552" LastActivityDate="2011-04-21T16:14:12.933" Title="Why don't we have wireless charger in every portable device yet?" Tags="&lt;power-supply&gt;&lt;power&gt;&lt;wireless&gt;&lt;transformer&gt;&lt;inductive&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="13333" PostTypeId="2" ParentId="13332" CreationDate="2011-04-21T12:45:12.597" Score="2" ViewCount="" Body="&lt;p&gt;Give it some time. There are surely advantages to it (space saving: not needing an external power connector, with all the protection that comes with it), so I expect we'll see this in mobile phones in the near future. An attention point may be the size of the antenna.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;There's also the issue of electromagnetic pollution. If you want to charge your device in a reasonable time you'll have to generate a rather strong HF EM field.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-21T13:55:23.830" LastActivityDate="2011-04-21T13:55:23.830" CommentCount="2" />
  <row Id="13334" PostTypeId="1" AcceptedAnswerId="13335" CreationDate="2011-04-21T13:17:01.197" Score="6" ViewCount="193" Body="&lt;p&gt;Every time I hear the description of a wireless charging system it goes like this: &quot;remember a transformer? It's the same here - one coil is in the base and another is in the device and when you put the device onto the base the transformer gets assembled and starts transmitting power&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One problem with this description is there's no magnetic core in the system. AFAIK each transformer has a magnetic core in its design. A magnetic core is a huge set of steel plates that goes though both coils and this set of plates in fact conducts energy - the alternating current in the primary coil induces alternating electromagnetic field in the core and that field induces current in the secondary coil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So looks like the core is a key component and a transformer can't possibly work without a core. Yet I don't see a magnetic core in a wireless charging system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How does it work without a magnetic core?&lt;/p&gt;&#xA;" OwnerUserId="3552" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-21T14:42:20.637" LastActivityDate="2011-04-21T22:46:31.870" Title="How does a wireless charger work without a magnetic core passing through both &quot;coils&quot;?" Tags="&lt;power-supply&gt;&lt;power&gt;&lt;transformer&gt;&lt;inductive&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="3" />
  <row Id="13335" PostTypeId="2" ParentId="13334" CreationDate="2011-04-21T13:24:29.147" Score="4" ViewCount="" Body="&lt;p&gt;A metal core is advisable because it concentrates the magnetic field. This makes magnetic coupling between coils more effective, but you can do it without the core too, especially if both coils are tightly coupled (mechanically close to each other). If you don't have a core and the two coils are some distance apart, part of the generated field will pass outside of the other coil.&lt;br&gt;&#xA;(In a transformer the outside metal &quot;shortcuts&quot; the field, increasing it. Without this outside metal the field would fill a large volume around the core.)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-21T13:47:21.077" LastActivityDate="2011-04-21T13:47:21.077" />
  <row Id="13336" PostTypeId="2" ParentId="13330" CreationDate="2011-04-21T13:42:14.077" Score="1" ViewCount="" Body="&lt;p&gt;Also, the speaker should be connected to Vout via a capacitor (250 uF).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Forget about that kit and wire the chip according to one of the schematics in the data sheet.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-21T17:14:41.207" LastActivityDate="2011-04-21T17:14:41.207" CommentCount="2" />
  <row Id="13337" PostTypeId="2" ParentId="13332" CreationDate="2011-04-21T14:22:27.083" Score="5" ViewCount="" Body="&lt;p&gt;It is still fairly expensive to add to devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have development time and cost since cell phone companies have never added this feature before. I would have to imagine the cost to do this is fairly significant. Cell phone companies will have to do a fair amount of testing to insure that the charging doesn't have any adverse effects on the phone. You can argue that there are already people using these types of chargers on phones, but you have to keep in mind that these systems are still outside of the phone for the most part. When you bring it in to the phone itself there are potentially areas of issue, like inductively coupling to data lines that are already pushing the limits of speed, any extra unwanted noise can be very bad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have the cost of the IC and board space. The IC is about $3.50 each. And even though the ICs biggest claim is how small it is, you seem to be forgetting that this IC is new so no one has had a chance to use it yet. But even with how small it is, board space is limited. Figuring out how to fit it all in is extra engineering time and the extra component is slightly additional fabrication cost, maybe only less then a cent more, but these companies are already counting every penny. As @stevenvh mentioned, if you have wireless charging you can remove the external power connector which will save lots of space. However, people still want a USB port. It will be a little while before people are &quot;ok&quot; with the idea of just using bluetooth to transfer data between the phone and computer. In fact there are still phones out there now that have their bluetooth so locked down that you just have to use a USB cable in some situations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Public view still is not great. There is a large amount of people who are very much against the idea of wireless power. Reasons behind it range from it being less efficient to it causing cancer. You can try to debate these points all you want, but it isn't going to change the minds of people in the general population. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So overall, extra cost that just results in not much gain (at least as of now).&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-21T14:22:27.083" />
  <row Id="13338" PostTypeId="2" ParentId="13334" CreationDate="2011-04-21T14:26:44.783" Score="5" ViewCount="" Body="&lt;p&gt;A good example of electromagnetic induction without a metal core is a passive RFID tag, which has no battery. Instead, its draws power from the reader, which sends out electromagnetic waves that induce a current in the tag's antenna.  The distance between the tag and the reader can be several inches.  Obviously at this distance, very little power can be transmitted, but it illustrates the principle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ml25m.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-04-21T14:40:20.197" LastActivityDate="2011-04-21T14:40:20.197" />
  <row Id="13339" PostTypeId="2" ParentId="13334" CreationDate="2011-04-21T14:44:01.057" Score="6" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;the alternating current in the primary&#xA;  coil induces alternating&#xA;  electromagnetic field in the core and&#xA;  that field induces current in the&#xA;  secondary coil&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes, but &quot;in the core&quot; is not necessary.  A coil creates a magnetic field all around it, whether there's a core there or not.  The core just confines the magnetic field so that less of it &quot;leaks&quot;, which makes the transformer more efficient.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also make the transmission more efficient by putting a capacitor in series with both coils so that they resonate at the same frequency:  &lt;a href=&quot;http://en.wikipedia.org/wiki/Resonant_inductive_coupling&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Resonant_inductive_coupling&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-04-21T14:44:01.057" />
  <row Id="13340" PostTypeId="1" CreationDate="2011-04-21T14:57:29.033" Score="0" ViewCount="100" Body="&lt;p&gt;I'm using the pic18F4550 with microchip v8.63 and with the C 18 compiler. I'm using a LDR that retrieve the value of the led (not on my picdem board) (red, green and blue) these values are stored in a variable after each conversion. Afther that when I press the button S2, I come into the method ISR: this part works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But now: I try to compare the variable red, green and blue in the if's: but I think that it not happen, he just go to my 'else' (led RB3 on my picdem board burns).&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;p18f4550.h&amp;gt;  &#xA;&#xA;/** V E C T O R  R E M A P P I N G *******************************************/&#xA;&#xA;extern void _startup (void);        // See c018i.c in your C18 compiler dir&#xA;#pragma code _RESET_INTERRUPT_VECTOR = 0x001000&#xA;void _reset (void)&#xA;{&#xA;    _asm goto _startup _endasm&#xA;}&#xA;#pragma code&#xA;void ISR (void);&#xA;#pragma code _HIGH_INTERRUPT_VECTOR = 0x001008&#xA;void _high_ISR (void)&#xA;{&#xA;      _asm goto ISR _endasm&#xA;}&#xA;&#xA;#pragma code _LOW_INTERRUPT_VECTOR = 0x001018&#xA;void _low_ISR (void)&#xA;{&#xA;    ;&#xA;}&#xA;#pragma code&#xA;/******************************************************************************/&#xA;&#xA;// global variable, value off LDR.&#xA;unsigned int var1ADRESH = 0x00;&#xA;unsigned int color_red = 0;&#xA;unsigned int color_green = 0;&#xA;unsigned int color_blue = 0;&#xA;&#xA;void main (void)&#xA;{   &#xA;    TRISD = 0x00;               // PORTD  als uitgang&#xA;&#xA;    RCONbits.IPEN = 0;          // prioriteit uit&#xA;    INTCONbits.GIE = 1;         // enable interrupt&#xA;    INTCONbits.RBIE = 1;        // interrupt portB aan&#xA;&#xA;    //= set up port =&#xA;    TRISAbits.TRISA0 = 1;           // Set RA0/AN0 to input&#xA;    //leds&#xA;    TRISAbits.TRISA3 = 0;&#xA;    TRISAbits.TRISA4 = 0;&#xA;    TRISAbits.TRISA5 = 0;&#xA;    LATAbits.LATA3 = 1;&#xA;    LATAbits.LATA4 = 1;&#xA;    LATAbits.LATA5 = 1;&#xA;&#xA;    ADCON0 = 0b00000000;            // Set channel select to AN0&#xA;    ADCON1 = 0b00001110;            // Configure RA0/AN0 as analogue&#xA;    ADCON2 = 0b10101010;            // Right justified result&#xA;                                    // TAD 12 and FOSC 32 - may need to adjust this&#xA;                                    // depending on your clock frequency (see datasheet)&#xA;&#xA;    while(1)&#xA;    {   &#xA;        _asm sleep _endasm  &#xA;    }&#xA;}&#xA;&#xA;#pragma interrupt ISR&#xA;void ISR (void)&#xA;{&#xA;    if (INTCONbits.RBIF==1) {&#xA;&#xA;        //conversie blauw&#xA;        LATAbits.LATA3 = 0;&#xA;        ADCON0bits.ADON = 1;            // Enable ADC   &#xA;        // read LDR value.&#xA;        ADCON0bits.GO = 1;              // Set the GO bit of the ADCON0 register to start the conversion.&#xA;        while (ADCON0bits.GO);          // Wait until the conversion is complete.&#xA;        ADCON2bits.ADFM = 0;            // read result as 8-bit. (dus data in ADRESH) ! &#xA;        //= read data in ADRESH =&#xA;        var1ADRESH = ADRESH;    // reading value from LDR&#xA;&#xA;        color_blue = ADRESH; //waarde in blauw&#xA;&#xA;        //conversie rood&#xA;        LATAbits.LATA3 = 1;&#xA;        LATAbits.LATA4 = 0;&#xA;&#xA;        ADCON0bits.ADON = 1;            // Enable ADC   &#xA;        // read LDR value.&#xA;        ADCON0bits.GO = 1;              // Set the GO bit of the ADCON0 register to start the conversion.&#xA;        while (ADCON0bits.GO);          // Wait until the conversion is complete.&#xA;        ADCON2bits.ADFM = 0;            // read result as 8-bit. (dus data in ADRESH) ! &#xA;        //= read data in ADRESH =&#xA;        var1ADRESH = ADRESH;    // reading value from LDR&#xA;&#xA;        color_red = ADRESH; //waarde in blauwe steken&#xA;&#xA;        //conversie groen&#xA;        LATAbits.LATA4 = 1;&#xA;        LATAbits.LATA5 = 0;&#xA;&#xA;        ADCON0bits.ADON = 1;            // Enable ADC   &#xA;        // read LDR value.&#xA;        ADCON0bits.GO = 1;              // Set the GO bit of the ADCON0 register to start the conversion.&#xA;        while (ADCON0bits.GO);          // Wait until the conversion is complete.&#xA;        ADCON2bits.ADFM = 0;            // read result as 8-bit. (dus data in ADRESH) ! &#xA;        //= read data in ADRESH =&#xA;        var1ADRESH = ADRESH;    // reading value from LDR&#xA;&#xA;        color_green = ADRESH; //waarde in blauwe steken&#xA;&#xA;        // alles uitzetten&#xA;        //PORTB = 0b1111111;&#xA;        LATAbits.LATA5 = 1;&#xA;&#xA;        if(color_blue &amp;gt; color_red &amp;amp;&amp;amp; color_blue &amp;gt; color_green){&#xA;            //blauw&#xA;            LATDbits.LATD0 = 1;&#xA;        }&#xA;        if(color_red &amp;gt; color_blue &amp;amp;&amp;amp; color_red &amp;gt; color_green){&#xA;            //rood&#xA;            LATDbits.LATD1 = 1;&#xA;        }&#xA;        if(color_green &amp;gt; color_red &amp;amp;&amp;amp; color_green &amp;gt; color_blue){&#xA;            //groen&#xA;            LATDbits.LATD2 = 1;&#xA;        } &#xA;        else {&#xA;            LATDbits.LATD3 = 1;&#xA;        }   &#xA;    }&#xA;    INTCONbits.RBIF = 0;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3940" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-04-21T15:18:43.410" LastActivityDate="2011-04-21T17:01:59.130" Title="pic 18F4550: local variable problem:" Tags="&lt;microcontroller&gt;&lt;c&gt;&lt;microchip&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="13341" PostTypeId="2" ParentId="13332" CreationDate="2011-04-21T16:14:12.933" Score="1" ViewCount="" Body="&lt;p&gt;Size is an issue - people want phones to be smaller-&gt;less antenna area-&gt;less coupling-&gt;less power transfer-&gt;longer charge time.  As I said above, heat may be an issue, RF blocking materials could be an issue, EMI as well, charge rate, blah blah blah.  Theoretically it works, but practically not yet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI's chip may be good, but if only TI is making it it's expensive.  We need Fairchild, Linear, National and all the others to roll out their own solutions as well before this party gets started.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Technology tends to take off when there are large amounts of cheap, effective chips available for a purpose.  That's why it took a bit for MP3 to take off after it was created - application-specific integrated circuits that could decode it easily had to license the standard, be created, refined, made smaller, integrate more features (ie, on-chip amplifier, mono/stereo output selection, digital communication bus, etc) and become easier to use before you can have a USB pen that plays MP3s.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wireless charging will come - I've got one of those wireless charging pads for my Wii-motes and it rocks.  Of course, the battery and antenna are integrated together, so it acts just as a battery replacement.  You may not be able to do such a thing with phones.  Just give it some time.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-21T16:14:12.933" />
  <row Id="13342" PostTypeId="2" ParentId="13340" CreationDate="2011-04-21T16:28:20.623" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;code&gt;else&lt;/code&gt; only ties to the last &lt;code&gt;if&lt;/code&gt;, not to all the preceeding &lt;code&gt;if&lt;/code&gt;s. If you want that it ties to all the preceeding &lt;code&gt;if&lt;/code&gt;s, use an &lt;code&gt;if/else if/else if/else&lt;/code&gt; structure.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-04-21T16:28:20.623" />
  <row Id="13343" PostTypeId="2" ParentId="13340" CreationDate="2011-04-21T17:01:59.130" Score="2" ViewCount="" Body="&lt;p&gt;Just to mak Martin's response clearer:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if(color_blue &amp;gt; color_red &amp;amp;&amp;amp; color_blue &amp;gt; color_green){&#xA;    //blauw&#xA;    LATDbits.LATD0 = 1;&#xA;}&#xA;if(color_red &amp;gt; color_blue &amp;amp;&amp;amp; color_red &amp;gt; color_green){&#xA;    //rood&#xA;    LATDbits.LATD1 = 1;&#xA;}&#xA;if(color_green &amp;gt; color_red &amp;amp;&amp;amp; color_green &amp;gt; color_blue){&#xA;    //groen&#xA;    LATDbits.LATD2 = 1;&#xA;} &#xA;else {&#xA;    LATDbits.LATD3 = 1;&#xA;}   &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;should become&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    if(color_blue &amp;gt; color_red &amp;amp;&amp;amp; color_blue &amp;gt; color_green){&#xA;        //blauw&#xA;        LATDbits.LATD0 = 1;&#xA;    }&#xA;    else if(color_red &amp;gt; color_blue &amp;amp;&amp;amp; color_red &amp;gt; color_green){&#xA;        //rood&#xA;        LATDbits.LATD1 = 1;&#xA;    }&#xA;    else if(color_green &amp;gt; color_red &amp;amp;&amp;amp; color_green &amp;gt; color_blue){&#xA;        //groen&#xA;        LATDbits.LATD2 = 1;&#xA;    } &#xA;    else {&#xA;        LATDbits.LATD3 = 1;&#xA;    }   &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-04-21T17:01:59.130" CommentCount="1" />
  <row Id="13344" PostTypeId="1" AcceptedAnswerId="13347" CreationDate="2011-04-21T17:23:56.677" Score="1" ViewCount="114" Body="&lt;p&gt;I'd like to make a voltage doubler, I've read up on &lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage_doubler&quot; rel=&quot;nofollow&quot;&gt;wikipedia&lt;/a&gt; and also &lt;a href=&quot;http://www.play-hookey.com/ac_theory/ps_v_multipliers.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. My issue is that I have DC input and I need DC output, first is this even possible, second, if so the problem I'm having, is that I think I'm in over my head. I don't really understand the diagrams or how to read them (what the symbols mean etc). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My experience with electronics is quite limited, suffice it to say I've put a capacitor over an electric motor to evan out the power on an RC car and used variable resisters to control the speed of a motor. And much of this was cargo-culted from forum posts where individuals made some suggestions and I tried them till something worked.&lt;/p&gt;&#xA;" OwnerUserId="3942" LastActivityDate="2011-04-21T18:26:13.223" Title="How would I create a voltage doubler and what parts would I need?" Tags="&lt;voltage&gt;&lt;dc&gt;" AnswerCount="2" />
  <row Id="13347" PostTypeId="2" ParentId="13344" CreationDate="2011-04-21T17:39:54.293" Score="5" ViewCount="" Body="&lt;p&gt;For small currents (tens of ma), you can use a charge pump, which use ceramic or electrolytic capacitors to store energy.  You can &lt;a href=&quot;http://www.reconnsworld.com/power_voltdoubler.html&quot; rel=&quot;nofollow&quot;&gt;build your own&lt;/a&gt;, or use an IC like the Maxim &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/1785&quot; rel=&quot;nofollow&quot;&gt;MAX1682&lt;/a&gt;.  Many more Maxim charge pumps are listed in &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/725&quot; rel=&quot;nofollow&quot;&gt;this article&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For larger currents (up to a couple amps), you need an inductive DC-DC boost converter, such as the &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/5747&quot; rel=&quot;nofollow&quot;&gt;Maxim 17067&lt;/a&gt;.  Lots more &lt;a href=&quot;http://para.maxim-ic.com/en/search.mvp?fam=stepup&amp;amp;tree=powersupplies&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.  Most are not limited to just voltage doubling.&lt;/p&gt;&#xA;" OwnerUserId="1322" LastEditorUserId="1322" LastEditorDisplayName="" LastEditDate="2011-04-21T17:47:35.517" LastActivityDate="2011-04-21T17:47:35.517" CommentCount="1" />
  <row Id="13348" PostTypeId="2" ParentId="13325" CreationDate="2011-04-21T17:42:48.267" Score="0" ViewCount="" Body="&lt;p&gt;Most of the work that I did in recent years have called for &lt;a href=&quot;http://en.wikipedia.org/wiki/Electroless_nickel_immersion_gold&quot; rel=&quot;nofollow&quot;&gt;ENIG - Electroless nickel immersion gold.&lt;/a&gt;  The plating comes out nice and flat, which is not the case with HASL.  It also looks pretty, but that's a subjective thing.  :)&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-21T17:42:48.267" />
  <row Id="13349" PostTypeId="2" ParentId="13344" CreationDate="2011-04-21T18:26:13.223" Score="3" ViewCount="" Body="&lt;p&gt;If you've got a PWM source (a µC or 555 timer), you can roll your own boost converter with a MOSFET or transistor and an inductor (plus a few other discretes you've probably already got lying around).  &lt;a href=&quot;http://www.ladyada.net/library/diyboostcalc.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/library/diyboostcalc.html&lt;/a&gt;  I'm planning on using this arrangement for boosting 3.3v to 40v to drive an antique analog volt meter that doesn't have an external resistor.  The duty cycle and frequency of the PWM source control the final voltage.  This probably wouldn't be sufficient for a motor with any kind of variable load, as the output voltage is dependent on the load, but I think it's kind of cool and hope it'll work for my purposes. :-)&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-04-21T18:26:13.223" CommentCount="1" />
  <row Id="13350" PostTypeId="1" AcceptedAnswerId="13351" CreationDate="2011-04-21T19:34:37.310" Score="0" ViewCount="56" Body="&lt;p&gt;I want to run a printer in another room in my house WITHOUT networking.  My needs require a direction USB connection.  Will I have trouble running a USB beyond a certain length of cabling?&lt;/p&gt;&#xA;" OwnerUserId="2090" LastActivityDate="2011-04-21T20:49:03.863" Title="Maximum USB 2 length (printer in another room)" Tags="&lt;usb&gt;&lt;wiring&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13351" PostTypeId="2" ParentId="13350" CreationDate="2011-04-21T20:01:29.400" Score="1" ViewCount="" Body="&lt;p&gt;I have used a 15'  USB extension cable successfully to bring my printer to the oposite side of my office. Beyond that you can get a &lt;a href=&quot;http://www.usbcables.com/Extension_cable_USB_15ft/&quot; rel=&quot;nofollow&quot;&gt;USB repeater cable&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-04-21T20:01:29.400" />
  <row Id="13352" PostTypeId="1" CreationDate="2011-04-21T20:03:30.230" Score="1" ViewCount="75" Body="&lt;p&gt;Hello, I want to turn an LED indicator on when current is flowing through a path. If there's no current the LED will be off, and when there's current, the LED would turn on. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been experimenting with placing a shunt resistor in series with the measured load, and the voltage reading indeed relates to the current load, on the mV scale around 6 to 60 mV's. I'd like to turn a LED on when there's any voltage on either side of the shunt resistor. For this I've unsuccessfully tried to amplify the voltage with a 741 op-amp by &quot;supposedly&quot; measuring the difference between the voltage and setting a gain of 1000's so that the output saturates the maximum voltage available for the op-amp. Here's an overview of what's going into the op-amp according to pinout:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;V+  :   +5v&lt;/li&gt;&#xA;&lt;li&gt;V-  :   -5v&lt;/li&gt;&#xA;&lt;li&gt;+op :   One side of the shunt resistor  &lt;/li&gt;&#xA;&lt;li&gt;-op :   The other side of the shunt resistor&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Output: Always 4.5v no mater what load the line with the shunt resistor has.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what would I need to do for the 741 to return 4.5v when pins across the shunt resistor measures &quot;any&quot; voltage and 0v when there's no voltage across the shunt resistor. In programming style:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;if (shuntdifferential &amp;gt; 0)&#xA;    output = 4.5v (anything that would emit light from LED)&#xA;else&#xA;   output = 0v (anything less than what would emit light from a LED)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The question is: How can I set up the amplifier to do this? I've got +12, +5, 3.3, 0v -5v, -12v from my power supply available. Note that I'd like to know if it's possible to read current from any rail from the psu with the same circuit.  Also, maybe I'm looking into some weird solution when there could be a simpler solution for my purpose, recommendations?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please don't be harsh on me if I'm doing something wrong, the reason I'm asking for help is because i want to learn. Thanks for your time and help :)&lt;/p&gt;&#xA;" OwnerUserId="3945" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-21T21:38:12.297" LastActivityDate="2011-04-21T22:33:46.507" Title="Current Indicator" Tags="&lt;resistor&gt;&lt;current&gt;&lt;op-amp&gt;&lt;indicator&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="13353" PostTypeId="1" CreationDate="2011-04-21T20:14:31.057" Score="0" ViewCount="139" Body="&lt;p&gt;Is there a name for feedback amplifier topologies which include an opamp and transistor in the feed-forward path?. I need to design an amplifier with high bandwidth (almost 100 MHz) and high gain (50) and I think that I am better off getting most of my gain from a transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for literature on how to properly bias the transistor.&lt;/p&gt;&#xA;" OwnerUserId="2656" LastActivityDate="2011-06-02T21:02:13.347" Title="Operation Amplifier with Transistor output" Tags="&lt;transistor&gt;&lt;op-amp&gt;&lt;amplifier&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="13354" PostTypeId="2" ParentId="13352" CreationDate="2011-04-21T20:34:00.637" Score="-1" ViewCount="" Body="&lt;p&gt;Here's another idea which may be simpler if you have needed tool-chain or would be good to consider when you do get it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Get a simple microcontroler with analog comparator. Connect one side of the comparator to the ground and the other to the shunt resistor. After that you could keep comparing the voltages and have the microcontroller turn on the LED when there's voltage on the pin. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't recommend any specific microcontroller right now, but I'm sure that your favorite manufacturer would have one. Also small microcontrollers are very cheap and you might be able to find one which could replace the op-amp and not increase the price of the project considerably. Also don' forget that there are tons of other stuff a microcontroller could do, so with some planning, you could replace two or more devices and make up the cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, if you never worked with microcontrollers and don't have needed tools, the introduction into that area could get expensive or troublesome. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-04-21T20:34:00.637" />
  <row Id="13355" PostTypeId="2" ParentId="13350" CreationDate="2011-04-21T20:49:03.863" Score="2" ViewCount="" Body="&lt;p&gt;5m is the maximum officially supported cable length, and you can chain several cables using at most five hubs, which gets you at most 30m.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.usb.org/developers/usbfaq#cab_sol&quot; rel=&quot;nofollow&quot;&gt;http://www.usb.org/developers/usbfaq#cab_sol&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-04-21T20:49:03.863" CommentCount="2" />
  <row Id="13356" PostTypeId="2" ParentId="12217" CreationDate="2011-04-21T20:59:04.337" Score="1" ViewCount="" Body="&lt;p&gt;It is getting comercial: &lt;a href=&quot;http://www.cooking-hacks.com/index.php/documentation/tutorials/geiger-counter-arduino-radiation-sensor-board&quot; rel=&quot;nofollow&quot;&gt;http://www.cooking-hacks.com/index.php/documentation/tutorials/geiger-counter-arduino-radiation-sensor-board&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3130" LastActivityDate="2011-04-21T20:59:04.337" />
  <row Id="13357" PostTypeId="2" ParentId="13352" CreationDate="2011-04-21T21:19:22.140" Score="2" ViewCount="" Body="&lt;p&gt;If you want a simple solution, you could look for &quot;current sense amplifier&quot; ICs, which are designed specifically for this purpose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The approach you describe is using the op-amp as a comparator, which is a viable strategy, but it will behave unpredictably when the input voltage difference is around 0V, so somehow you need to introduce an offset in the comparison.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a sample current sense circuit in figure 27 of &lt;a href=&quot;http://www.analog.com/static/imported-files/application_notes/28080533AN106.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.analog.com/static/imported-files/application_notes/28080533AN106.pdf&lt;/a&gt;. The quick way to analyze that circuit is to use the rule of thumb that an op-amp in a negative feedback configuration (meaning with a connection from the output back to the $-$ terminal) will make the voltages at its inputs equal. I can explain in more detail if it would be useful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To create a current threshold detector from that circuit, you could add a comparator on $V_{OUT}$, or you could remove the $R_3$ / $R_5$ divider and connect the $-$ terminal directly to the low side of the sense resistor $R_1$. The $R_2$ / $R_4$ divider would then set the trip point of the detector.&lt;/p&gt;&#xA;" OwnerUserId="3441" LastEditorUserId="3441" LastEditorDisplayName="" LastEditDate="2011-04-21T22:33:46.507" LastActivityDate="2011-04-21T22:33:46.507" />
  <row Id="13358" PostTypeId="1" AcceptedAnswerId="13371" CreationDate="2011-04-21T22:29:02.990" Score="0" ViewCount="130" Body="&lt;p&gt;I have successfully counted the rotary encoders on the wheel of my robot so this is not a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My problem is what to do with this number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, the bigger problem is that I need my robot to go straight and I want to do it using only two encoders (one on every wheel).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even if I send the same amount of power to both motors the robot does not go straight. This is why I decided to use encoders, so no matter the power on the batteries, or the conditions of the motors; the robot will go straight.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, now that I have successfully counted the &quot;clicks&quot; on the encoder I need to know what to do with the number to make sure the tow wheels are synchronized.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the code I am using (Arduino):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  digitalWrite(dirMotO, HIGH);&#xA;  digitalWrite(dirMotE, HIGH);&#xA;  //digitalWrite(motO, HIGH);&#xA;  analogWrite(motO, 150);&#xA;  //digitalWrite(motE, HIGH);&#xA;  analogWrite(motE, 150);&#xA;&#xA;  PololuWheelEncoders::getCountsAndResetM1();&#xA;  PololuWheelEncoders::getCountsAndResetM2();&#xA;&#xA;  while(PololuWheelEncoders::getCountsM1()&amp;lt;clicks &amp;amp;&amp;amp; PololuWheelEncoders::getCountsM1()&amp;lt;clicks){&#xA;    if(PololuWheelEncoders::getCountsM1()&amp;gt;=clicks){&#xA;      digitalWrite(motO, LOW);&#xA;    }&#xA;    if(PololuWheelEncoders::getCountsM2()&amp;gt;=clicks){&#xA;      digitalWrite(motE, LOW);&#xA;    }&#xA;  }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I thought this code would make sure that if one wheel gets to counts before the other it would stop and wait for the other wheel but the robot does not go straight.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would really appreciate some help on this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you!&lt;/p&gt;&#xA;" OwnerUserId="3949" LastActivityDate="2011-04-22T04:33:18.067" Title="Rotary encoders to ensure 2 wheel robot goes straight!" Tags="&lt;arduino&gt;&lt;robotics&gt;&lt;encoder&gt;&lt;speed&gt;&lt;wheel&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="13359" PostTypeId="1" AcceptedAnswerId="13361" CreationDate="2011-04-21T22:30:45.767" Score="2" ViewCount="139" Body="&lt;p&gt;Is there a specific purpose for jumper wires like &lt;a href=&quot;http://spacetinkerer.blogspot.com/2011/03/how-to-make-your-own-breadboard-jumper.html&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; where they have female pins at the ends?  I'm assuming they are mainly useful when you want to chop a wire into something like a breadboard, but the wire is too thin or flimsy.  If the wire is thick enough, I'm assuming a wire with the insulation cut off on both sides is equivalent, right?  Seems like a common sense question, but I haven't really seen wires with female pins attached on both sides before.. :)&lt;/p&gt;&#xA;" OwnerUserId="3649" LastActivityDate="2011-04-23T03:51:27.793" Title="Are jumper wires just wires with insulation cut off on both ends?" Tags="&lt;wire&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="13360" PostTypeId="2" ParentId="13334" CreationDate="2011-04-21T22:46:31.870" Score="2" ViewCount="" Body="&lt;p&gt;All that's required for a transformer is that the magnetic fields of the two coils are linked. Iron cores make this more effective at power and audio frequencies, but at radio frequencies (more than a few 100kHz) cores actually become a liability.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-21T22:46:31.870" />
  <row Id="13361" PostTypeId="2" ParentId="13359" CreationDate="2011-04-21T22:50:47.187" Score="5" ViewCount="" Body="&lt;p&gt;If you are connecting to actual female pins, it does help to have the right sized male pin crimped onto your jumper wires. But if you're just using them on a breadboard, bare wire ends are fine. Just make sure to cut the wire with diagonal cutters, not scissor-type cutters, so that you get a nice pointy end. The shearing action of scissor type cutters can sometimes roll the wire end enough to make it snag in the breadboard.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-21T22:50:47.187" />
  <row Id="13362" PostTypeId="2" ParentId="13359" CreationDate="2011-04-21T22:53:48.463" Score="4" ViewCount="" Body="&lt;p&gt;Only potential reasons for &lt;em&gt;maybe&lt;/em&gt; soldering male header pins on the end would be if using stranded core wires or a really small gauge solid core (like 24 or 26 gauge).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A lot of in-wall cat5/cat6 cable is going to be 24 gauge solid core which &lt;em&gt;should&lt;/em&gt; work as-is in most breadboards. 22 or 20 would give a firmer/more-confident connection though.&lt;/p&gt;&#xA;" OwnerUserId="2654" LastActivityDate="2011-04-21T22:53:48.463" />
  <row Id="13363" PostTypeId="1" AcceptedAnswerId="13383" CreationDate="2011-04-21T23:08:29.527" Score="4" ViewCount="149" Body="&lt;p&gt;This has been floating in my mind for a while, everything has a frequency. Like a dc-dc converter, my scope is 100 MHz(i know that's a bandwidth but it has the unit of frequency). I understand that an Astable 555 has a frequency which is the mark and space time based on the values of the cap and resistors. And then you have the use of band-pass filter which can filter different frequencies so what is this all about? How does a direct current have a frequency? And the relationship between bandwidth and frequency as they have the same units. &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-22T00:40:34.680" LastActivityDate="2011-04-27T18:39:38.883" Title="What is Frequency in electronics?" Tags="&lt;frequency&gt;" AnswerCount="4" />
  <row Id="13364" PostTypeId="2" ParentId="13363" CreationDate="2011-04-21T23:37:43.550" Score="7" ViewCount="" Body="&lt;p&gt;Frequency, in the generic sense, is the rate at which something repeats.  Usually measured in &quot;repetitions per second&quot;, or Hertz (Hz).  My watch ticks at 1 Hz.  I water my lawn at a rate of 0.00000386 Hz. And my car blinkers blink at about 0.5 Hz.  That's it!  Of course things get a little more complex when you consider what exactly is repeating.  But &quot;frequency&quot; really is that simple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A scope, or band pass filter, is usually rated in Hz and refers to the frequency of a signal that can (or can't) go through it.  In this context, it is talking about a &lt;a href=&quot;http://en.wikipedia.org/wiki/Sine_wave&quot; rel=&quot;nofollow&quot;&gt;sine wave&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something like a 555, or other clock signal type circuit, is talking about how often the signal switches.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The term &quot;DC&quot; is often abused, so don't take it too seriously.  Most of the time it refers to a power supply that outputs a steady voltage.  But it could also refer to anything that outputs a signal that is only a positive voltage.  Or, it could refer to a signal that is a &quot;mostly constant&quot; voltage.  But, if the signal is truly unchanging then it has a frequency of zero.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bandwidth and frequency do have a relationship-- in much the way that a car and a baseball are related (they are both measured in miles per hour). &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-21T23:37:43.550" CommentCount="5" />
  <row Id="13365" PostTypeId="1" AcceptedAnswerId="13366" CreationDate="2011-04-22T01:44:39.893" Score="0" ViewCount="78" Body="&lt;p&gt;I thought that hooking the same wire into two pins(2 and 3, on an Uno) would work, but it doesn't appear to be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sketch looks like such.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;byte b;&#xA;&#xA;NewSoftSerial nss(2,3);&#xA;&#xA;void setup()&#xA;{&#xA;  nss.begin(9600);&#xA;  Serial.begin(9600);&#xA;}&#xA;&#xA;void loop() {&#xA;  // if theres data from the bluetooth module&#xA;  if (nss.available()&amp;gt;0) {//this is never true&#xA;    //echo it to the serial monitor&#xA;    Serial.print(&quot;nss echo:&quot;);&#xA;    Serial.println((char)nss.read(),BYTE);&#xA;  }&#xA;  if (Serial.available()&amp;gt;0) {&#xA;    b=Serial.read();&#xA;    //echo it back to the serial monitor&#xA;    Serial.print(&quot;serial echo:&quot;);&#xA;&#xA;    Serial.println(b,BYTE);&#xA;    //send it to the bluetooth module&#xA;    nss.print(b,BYTE);&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I expected to see pairs of outputs for every input.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;serial echo:g&lt;br&gt;&#xA;  nss echo:g&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;What am I doing wrong?&lt;/p&gt;&#xA;" OwnerUserId="1227" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-04-22T01:58:19.563" LastActivityDate="2011-04-22T02:58:08.410" Title="How do I test NewSoftSerial?" Tags="&lt;arduino&gt;" AnswerCount="1" />
  <row Id="13366" PostTypeId="2" ParentId="13365" CreationDate="2011-04-22T02:42:00.447" Score="1" ViewCount="" Body="&lt;p&gt;You're probably not doing anything wrong, but you are hitting a limitation of the library.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NewSoftSerial disables interupts on transmission, to ensure clean timing of the transmitted byte. As NSS receives data by picking up an interrupt on the receive pin, that interupt isn't fired, meaning nothing is received. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For reference, the write(byte) function of NSS&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void NewSoftSerial::write(uint8_t b)&#xA;{&#xA;      //irrelevant code&#xA;&#xA;  uint8_t oldSREG = SREG;&#xA;  cli();  // turn off interrupts for a clean txmit&#xA;&#xA;  // Write the start bit&#xA;  tx_pin_write(_inverse_logic ? HIGH : LOW);&#xA;  tunedDelay(_tx_delay + XMIT_START_ADJUSTMENT);&#xA;&#xA;      //code to send a byte, omitted for brevity&#xA;&#xA;  SREG = oldSREG; // turn interrupts back on&#xA;  tunedDelay(_tx_delay);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;And the recv function:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void NewSoftSerial::recv()&#xA;{&#xA;  uint8_t d = 0;&#xA;&#xA;  // If RX line is high, then we don't see any start bit&#xA;  // so interrupt is probably not for us&#xA;  if (_inverse_logic ? rx_pin_read() : !rx_pin_read())&#xA;  {&#xA;    // Wait approximately 1/2 of a bit width to &quot;center&quot; the sample&#xA;    tunedDelay(_rx_delay_centering);&#xA;&#xA;    // Read each of the 8 bits&#xA;    for (uint8_t i=0x1; i; i &amp;lt;&amp;lt;= 1)&#xA;    {&#xA;      tunedDelay(_rx_delay_intrabit);&#xA;      uint8_t noti = ~i;&#xA;      if (rx_pin_read())&#xA;        d |= i;&#xA;      else // else clause added to ensure function timing is ~balanced&#xA;        d &amp;amp;= noti;&#xA;    }&#xA;&#xA;    // skip the stop bit&#xA;    tunedDelay(_rx_delay_stopbit);&#xA;&#xA;            //buffer code omitted&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Two things to note: both routines assume they'll have control while sending/receiving. Basically, NSS is half duplex, no simultaneous read and write.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to test it, what you could do is tie the RX pin from the arduino (pin 0 &lt;em&gt;I think&lt;/em&gt;; will be TX of the USB serial chip) to RX of NSS. What this will do is any data coming down from USB serial will be sent to both Serial and NSS. You can then transmit the NSS received data using Serial. Should work, but has not been tested.&lt;/p&gt;&#xA;" OwnerUserId="1507" LastEditorUserId="1507" LastEditorDisplayName="" LastEditDate="2011-04-22T02:58:08.410" LastActivityDate="2011-04-22T02:58:08.410" CommentCount="1" />
  <row Id="13367" PostTypeId="1" CreationDate="2011-04-22T03:10:43.613" Score="0" ViewCount="81" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/5759/is-it-normal-for-dc-wall-adapter-power-supplies-to-provide-voltages-above-the-nom&quot;&gt;Is it normal for DC wall adapter power supplies to provide voltages above the nominal ones?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;I am selling some Transformers on eBAY and I sold one of the Plantronics with 7.5 VDC output. The one I sold didn't work for the person who purchased it. I took out a volt meter and read the voltage with a volt meter. The volt meter read 10. volts out under lite load. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do these AC Adapters work the way they need to?&lt;/p&gt;&#xA;" OwnerUserId="3950" LastEditorUserId="1802" LastEditorDisplayName="" LastEditDate="2011-04-22T11:21:31.287" LastActivityDate="2011-04-22T11:21:31.287" ClosedDate="2011-04-22T17:50:33.567" Title="Adapter reads 3 volts higher than label indicates" Tags="&lt;ac&gt;&lt;adapter&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="13368" PostTypeId="2" ParentId="13358" CreationDate="2011-04-22T03:15:53.673" Score="1" ViewCount="" Body="&lt;p&gt;I assume clicks is the number of encoder ticks you want to go forward. This answer depends on clicks being slightly large- more then a few multiples of the wheel tick count- below that I'm not sure of the performance of this method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Part of the problem is that you're correcting by completely turning off one motor. That means that those wheels are effectively stuck, and start to act as a pivot. You want to make corrections with both wheels moving. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you need to do is try and keep the difference between ticks of the two motors as small as possible while running. As an example, if you have 16 ticks per rev, and want to go 100 ticks, you want to keep the difference in ticks as near to 0 as possible, by applying more power to the slower motor, and less to the faster one. Code left as an exercise to the reader (it depends on how you want to manage the variability: update the analogWrite's 10 times a second? 20? 5?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This probably wont work as well for a small number of ticks (1 rev), and the various laws of accumulating error mean it probably won't be perfectly straight for large numbers of ticks either; but it should give better results then what you have now.&lt;/p&gt;&#xA;" OwnerUserId="1507" LastEditorUserId="1507" LastEditorDisplayName="" LastEditDate="2011-04-22T03:23:32.733" LastActivityDate="2011-04-22T03:23:32.733" />
  <row Id="13369" PostTypeId="2" ParentId="13358" CreationDate="2011-04-22T04:20:17.220" Score="1" ViewCount="" Body="&lt;p&gt;Have you considered closing a velocity loop instead of a position loop?  Initially, accelerate at a reasonably slow rate so there's less of a chance of the two wheels getting out of sync.  If both wheels are moving at the same velocity, then your robot must be moving straight, barring any sort of coupling slippage or slipping between the wheels and the surface your robot is riding on.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-04-22T04:20:17.220" />
  <row Id="13370" PostTypeId="2" ParentId="13367" CreationDate="2011-04-22T04:28:54.623" Score="8" ViewCount="" Body="&lt;p&gt;Simple unregulated DC and AC adapters will only supply the stated voltage when they are delivering the current stated on the label. With a light load the voltage will be a lot higher. There is nothing wrong with that unit.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-22T04:28:54.623" />
  <row Id="13371" PostTypeId="2" ParentId="13358" CreationDate="2011-04-22T04:33:18.067" Score="3" ViewCount="" Body="&lt;p&gt;Your while loop logic is incompatible with the conditions inside it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your while loop is saying:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;as long as BOTH wheel encoders read&#xA;  less than clicks, execute the code&#xA;  inside&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;and your if statements are saying: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;if any of the wheel encoders is greater or equal to clicks, stop &#xA;  the corresponding motor&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;This is generally false except for the rare condition where one of the encoders happen to increment between the arduino evaluating the while and the if statements. In order words just about never.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the first thing you need to do is fix your logic. Then you need to investigate more sophisticated means of keeping the wheels in sync, such as computing an error term from the different in ticks, and employing a &lt;a href=&quot;http://en.wikipedia.org/wiki/PID_controller&quot; rel=&quot;nofollow&quot;&gt;PID&lt;/a&gt; controller algorithm to adjust the speed of both motors via &lt;code&gt;analogWrite&lt;/code&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2340" LastActivityDate="2011-04-22T04:33:18.067" />
  <row Id="13372" PostTypeId="1" CreationDate="2011-04-22T04:56:12.193" Score="0" ViewCount="168" Body="&lt;p&gt;I'm interested in building a custom laptop computer with the hope of being able to sell it and make a profit. The only problem is I have no idea where to start. I have an idea for a laptop chassis which is very different than what you're used to seeing. I'm looking to design it in a CAD program. I will also need to be able to design the keyboard, which will also be of an unusual shape, the monitor, and the rest of the hardware. I will need to be able to manufacture it, or find somebody who can take my designs and build it for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I go about getting started? Any suggestions? I need suggestions for:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Possible manufactures&lt;/li&gt;&#xA;&lt;li&gt;CAD software&lt;/li&gt;&#xA;&lt;li&gt;How to do computer engineering using off the shelf components &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'm a software engineer by profession, so all this hardware stuff is alien to me. Thanks!&lt;/p&gt;&#xA;" OwnerUserId="3952" LastEditorUserId="1802" LastEditorDisplayName="" LastEditDate="2011-04-22T11:20:37.077" LastActivityDate="2011-04-22T11:20:37.077" Title="How to build a custom laptop computer with original chassis, keyboard, etc?" Tags="&lt;hardware&gt;&lt;design&gt;&lt;computers&gt;&lt;keyboard&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="13374" PostTypeId="2" ParentId="13372" CreationDate="2011-04-22T06:18:52.703" Score="4" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;mechanics&lt;/strong&gt;&lt;br&gt;&#xA;I agree with @Faken; plastic injection molds are way too expensive for DIY. You can make first prototypes in SL (StereoLithography), but they don't compare with molded ABS or PC.&lt;br&gt;&#xA;For a CAD program there's a number of options, Pro Engineer or Solid Designer to name a few. 3D CAD is expensive, and be prepared for a long learning curve. SolidWorks and AutoDesk Inventor should get you up and running more quickly (sic @Faken).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;electronics&lt;/strong&gt;&lt;br&gt;&#xA;You can use components for COTS laptops, like display, HDD/SSD and optical drives. However, designing a motherboard is not an easy task. You'll need another CAD program (expensive, learning curve) and a lab to do primarily testing. Laying out a PCB is not connect-the-dots. Keywords: EMC, transmission lines, power.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;software&lt;/strong&gt;&lt;br&gt;&#xA;Since you're a software engineer you should have some idea of the difficulties here. Do you want to run Linux? Can you write the drivers? Can you test your software?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;all in all&lt;/strong&gt;&lt;br&gt;&#xA;Designing a new product and hoping someone will be interested is a risky thing, at least. A manufacturer will want to have his say about the design, and ultimately may want to do most of it, if not all, himself. Why do you think your unusual keyboard design will appeal?&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-22T08:24:06.337" LastActivityDate="2011-04-22T08:24:06.337" CommentCount="4" />
  <row Id="13375" PostTypeId="2" ParentId="13372" CreationDate="2011-04-22T06:53:40.940" Score="2" ViewCount="" Body="&lt;p&gt;A short rundown on what steps are involved:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First you decide on the requirements like computing and graphics power, memory, storage, runtime, ports and interfaces.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From this you work out the battery size and cooling requirements, and the size of all the required parts. You may want to rip apart a few laptops to see how cooling is accomplished. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You check the application notes and reference designs of the vendor to see how a mainboard may be set up. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Step by step you move towards a frame of spatial requirements. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once that is finished, you move on to the actual design part, where the real work starts. Faken's comment is absolutely correct. On a professional level notebook, each design step is done by a team of experienced specialists who have full command of a set of expensive tools. This should be a few manyears of training with the tools and learning the tech, and a few manyears of applying those skills to produce a good notebook. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In short: it cant be done alone, at least not to make a profit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your idea is truly novel, you may want to learn how to use a 3d-modeling program, set up a good model and presentation, and go hunt for venture capital. If you are lucky, you get bought :-)&lt;/p&gt;&#xA;" OwnerUserId="3438" LastEditorUserId="3438" LastEditorDisplayName="" LastEditDate="2011-04-22T07:10:11.457" LastActivityDate="2011-04-22T07:10:11.457" />
  <row Id="13377" PostTypeId="2" ParentId="13353" CreationDate="2011-04-22T09:48:28.360" Score="1" ViewCount="" Body="&lt;p&gt;What you can try is this: Connect a push-pull transistor pair to the output of an opamp and connect the feedback path to the output of the push-pull pair instead of the opamp's output. This way, you have the opamp do all the voltage amplification, and you can use the transistors for additional current amplification. The trainsistor pair's non-linearity will be compensated by the opamp because it's inside of the feedback loop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ecircuitcenter.com/circuits/pushpull/pushpull.htm&quot; rel=&quot;nofollow&quot;&gt;This is an example I found after a quick search&lt;/a&gt; illustrating the general idea.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-22T10:04:10.523" LastActivityDate="2011-04-22T10:04:10.523" CommentCount="5" />
  <row Id="13378" PostTypeId="2" ParentId="13275" CreationDate="2011-04-22T09:59:29.783" Score="5" ViewCount="" Body="&lt;p&gt;I'm wondering how did you get 7.5kB of RAM usage with axTLS. Looking at the code, all the context is stored in this structure:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;typedef struct aes_key_st &#xA;{&#xA;    uint16_t rounds;&#xA;    uint16_t key_size;&#xA;    uint32_t ks[(AES_MAXROUNDS+1)*8];&#xA;    uint8_t iv[AES_IV_SIZE];&#xA;} AES_CTX;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Size of this structure is 2 + 2 + 4 * 15 * 8 + 16 = 504. I see no global variables in aes.c, automatic variables are all small, so stack usage is also reasonable. So where does 7.5kB go? Perhaps you're trying to use the whole library instead of just extracting AES implementation from it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyway, this implementation looks pretty simple, I'd rather stick to this code and try to optimize it. I know it can be tricky, but learning the AES details can help you at least to estimate the absolute minimum RAM usage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update:&lt;/strong&gt; I've just tried to compile this library on IA-32 Linux and write a simple CBC AES-128 encryption test. Got the following results (first number is the section length hex):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; 22 .data         00000028  0804a010  0804a010  00001010  2**2&#xA;                  CONTENTS, ALLOC, LOAD, DATA&#xA; 23 .bss          00000294  0804a040  0804a040  00001038  2**5&#xA;                  ALLOC&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;That's just 660 bytes of .bss (I've declared AES_CTX as a global variable). Most of .data is occupied by IV and key. I don't include .text here, as you'll get totally different result on PIC (data sections should be nearly the same size on both architectures). &lt;/p&gt;&#xA;" OwnerUserId="3564" LastEditorUserId="3564" LastEditorDisplayName="" LastEditDate="2011-04-22T11:18:02.150" LastActivityDate="2011-04-22T11:18:02.150" CommentCount="3" />
  <row Id="13379" PostTypeId="1" AcceptedAnswerId="13381" CreationDate="2011-04-22T11:04:44.043" Score="4" ViewCount="133" Body="&lt;p&gt;I'm still just beginning my adventure into electronics and IC chips and datasheets have me confused so I'm going to ask a series of beginner questions will help me and hopefully others as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many different IC and IC manufactures out there. Specifically for the 74 line, are these chips standard across the different manufacturers? If not, what are generally the differences between them? Will it matter if I mix and match different ICs from different manufactures?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Datasheets, for some reason these tend to be horribly thought out and rather difficult for a beginner like me to decipher (I've noticed TI is notorious for this, giving abbreviations to all their pins without any explanation. What the heck is OE?). Is there a company (assuming that all chips are standard between different manufacturers) that provides clear and concise datasheets for all of the 74 IC chip line?&lt;/p&gt;&#xA;" OwnerUserId="1319" LastActivityDate="2011-04-22T19:12:09.907" Title="IC chips and datasheets" Tags="&lt;datasheet&gt;&lt;ic&gt;&lt;74xx&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="13380" PostTypeId="2" ParentId="13379" CreationDate="2011-04-22T11:16:39.407" Score="4" ViewCount="" Body="&lt;p&gt;Most chips of a certain type will have nearly the same specifications. You have to be careful how you define 'type' here though; those letters in the middle (e.g. LS, HCT, and so on) &lt;em&gt;will&lt;/em&gt; result in different speeds, current capability, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Better data sheets will have a 'pin description' section, which will tell you what things like 'OE' actually do. For example, OE is almost always 'output enable'.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-04-22T11:37:35.493" LastActivityDate="2011-04-22T11:37:35.493" />
  <row Id="13381" PostTypeId="2" ParentId="13379" CreationDate="2011-04-22T11:18:17.450" Score="6" ViewCount="" Body="&lt;p&gt;OE is Output Enable. :-)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Logic ICs with the same number have the same functionality and pinout across manufacturers. A 74xx32 is always a quad 2-input OR gate. The technology used may be different though; a 74LS32 is low-power Schottky, while a 74HC32 is high speed CMOS. These families have their particular properties, which you'll find in a &quot;Logic Family Guide&quot;.&lt;br&gt;&#xA;Sometimes there are small differences in the details. I remember a Schmitt-Trigger inverter I once use for an oscillator, which generated a complete different frequency when using make Y instead of X. Reason: different trigger levels, these are not standardized.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I never realized this before, but you're right: the datasheets have many terms and abbreviations which are not clearly explained. At least not in the datasheet. The datasheet often refers to the Logic Family Guide, which contains information concerning the whole series. That way they avoid datasheets becoming twice as long because they contain all this information time and again.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;I checked with a few datasheets from different manufacturers, and I must say, it might have been worse. For many parameters there are tables with a column &quot;symbol&quot;, and next to it a column &quot;parameter&quot;, which describes it briefly. The &quot;OE&quot; appears as abbreviation in truth tables, but for what it stands for you'll have to read the ICs description.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-22T12:05:30.453" LastActivityDate="2011-04-22T12:05:30.453" CommentCount="2" />
  <row Id="13382" PostTypeId="2" ParentId="13363" CreationDate="2011-04-22T12:05:45.490" Score="0" ViewCount="" Body="&lt;p&gt;Inside that DC-DC converter the current is switched at a certain frequency to transform it to a different voltage.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-04-22T12:05:45.490" CommentCount="1" />
  <row Id="13383" PostTypeId="2" ParentId="13363" CreationDate="2011-04-22T13:19:31.147" Score="2" ViewCount="" Body="&lt;p&gt;Frequency is the inverse of time for repeating events. If a single cycle of your mains is 1/50 of a second in duration (0.02 seconds), then there will be 50 cycles in a second (1 / 0.02). We say the frequency is 50 Hz.&lt;br&gt;&#xA;The unit for frequency is the Hertz (Hz). 1 Hz is equal to 1 cycle per second, an older name for it (cps). It's a convenient unit, even for very short cycles we use, with a prefix: MHz, GHz. For longer cycles (near or longer than 1 Hz) we sometimes use the minute as unit: a heart rate of 70 beats per minute (BPM), a metronome setting of 100 BPM.&lt;br&gt;&#xA;Still longer cycles are often expressed as a period of time (1 / frequency).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Every system has its typical (range of) frequencies. A heartbeat will be around 1-2 Hz, and the resonance frequency of a trampoline is also in the order of 1 Hz. Radio waves have a broad range of frequencies: 30 kHz (for a corresponding wavelength of 10 km) is VLF (very low frequency), while the magnetron of a microwave oven &quot;transmits&quot; at 2.45 GHz. And while 30 kHz is low for radio, it's already well beyond what we acoustically can perceive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;Direct current&quot; (DC) as a constant voltage has a frequency of 0 Hz.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bandwidth indicates a range of frequencies, going from the lower limit to the higher. If your scope can handle signals from DC (0 Hz) up to 100 MHz, its bandwidth is 100 MHz - 0 Hz = 100 MHz.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-22T14:09:59.637" LastActivityDate="2011-04-22T14:09:59.637" />
  <row Id="13384" PostTypeId="2" ParentId="9820" CreationDate="2011-04-22T14:23:21.823" Score="2" ViewCount="" Body="&lt;p&gt;Most jacks have only 1 SPST contact, because you can always create any combination of switching by having the SPST contact control a relay.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-22T14:23:21.823" CommentCount="1" />
  <row Id="13386" PostTypeId="1" CreationDate="2011-04-22T16:58:21.553" Score="0" ViewCount="123" Body="&lt;pre&gt;&lt;code&gt;library IEEE;  &#xA;use IEEE.STD_LOGIC_1164.ALL;  &#xA;use IEEE.STD_LOGIC_ARITH.ALL;  &#xA;use IEEE.STD_LOGIC_UNSIGNED.ALL;  &#xA;&#xA;entity fifo is  &#xA;port (  clk : in std_logic;  &#xA;        enr : in std_logic;   --enable read,should be '0' when not in use.  &#xA;        enw : in std_logic;    --enable write,should be '0' when not in use.  &#xA;        dataout : out std_logic_vector(7 downto 0);    --output data  &#xA;        datain : in std_logic_vector (7 downto 0);     --input data  &#xA;        empty : out std_logic;     --set as '1' when the queue is empty  &#xA;        full : out std_logic     --set as '1' when the queue is full  &#xA;     );  &#xA;end fifo;  &#xA;&#xA;architecture Behavioral of fifo is  &#xA;type memory_type is array (0 to 255) of std_logic_vector(7 downto 0);  &#xA;signal memory : memory_type :=(others =&amp;gt; (others =&amp;gt; '0')); --memory for queue.  &#xA;signal readptr,writeptr : std_logic_vector(7 downto 0) :=&quot;00000000&quot;; --read/write pointers.  &#xA;begin  &#xA;  process(clk)  &#xA;  begin   &#xA;    if(clk'event and clk='1' and enr ='1') then  &#xA;      dataout &amp;lt;= memory(conv_integer(readptr));  &#xA;      error &amp;lt;= '0';  &#xA;      readptr &amp;lt;= readptr + '1';      --points to next address.  &#xA;    end if;  &#xA;    if(clk'event and clk='1' and enw ='1') then  &#xA;      memory(conv_integer(writeptr)) &amp;lt;= datain;  &#xA;      writeptr &amp;lt;= writeptr + '1';   --points to next address.  &#xA;    end if;  &#xA;    if(readptr = &quot;11111111&quot;) then      --resetting read pointer.  &#xA;      readptr &amp;lt;= &quot;00000000&quot;;  &#xA;    end if;  &#xA;    if(writeptr = &quot;11111111&quot;) then        --checking whether queue is full or not&#xA;      full &amp;lt;='1';  &#xA;      writeptr &amp;lt;= &quot;00000000&quot;;  &#xA;    else  &#xA;      full &amp;lt;='0';  &#xA;    end if;  &#xA;    if(writeptr = &quot;00000000&quot;) then   --checking whether queue is empty or not  &#xA;      empty &amp;lt;='1';  &#xA;    else  &#xA;      empty &amp;lt;='0';  &#xA;    end if;  &#xA;  end process;  &#xA;end Behavioral; &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;In the above code I want to know whether the read function is also acting to delete the particular element which is being read?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not can some one please provide a small vhdl code for delete function?&lt;/p&gt;&#xA;" OwnerUserId="3957" LastEditorUserId="3441" LastEditorDisplayName="" LastEditDate="2011-04-23T04:30:32.330" LastActivityDate="2011-04-23T04:30:32.330" Title="FIFO implementation in VHDL: is read function deleting the element of the FIFO ?" Tags="&lt;vhdl&gt;&lt;fifo&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="13387" PostTypeId="2" ParentId="13319" CreationDate="2011-04-22T17:22:22.200" Score="0" ViewCount="" Body="&lt;p&gt;Each window has a significant resistance (may go as high as 10 Ohm). So in order to minimize losses on the contanct windows, many of them are put in parallel. There is a trade-off here though: each contact also has a capacitance and when you put them in parallel you add the capacitances.&lt;/p&gt;&#xA;" OwnerUserId="2088" LastActivityDate="2011-04-22T17:22:22.200" />
  <row Id="13388" PostTypeId="2" ParentId="13386" CreationDate="2011-04-22T19:00:42.133" Score="5" ViewCount="" Body="&lt;p&gt;The first problem is that he code, even when formatted so you can read it, is not very good.  You'd be lucky if it synthesizes at all, and if it does then it won't work very well.  The main problem is that there are multiple clocked and not-clocked chunks of logic inside the process.  If it did synthesize then there are still D-Flip-Flops that have nasty asynchronous set/resets.  It might be find for simulations, but I wouldn't want to use it &quot;for real&quot;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second problem is that it's hard to know what you actually mean by &quot;delete&quot;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given those issues, here's my best attempt at an answer...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most FIFO's (including this one to a brain-dead extent) use what we refer to as a &lt;a href=&quot;http://en.wikipedia.org/wiki/Circular_buffer&quot; rel=&quot;nofollow&quot;&gt;circular buffer&lt;/a&gt;.   In a FIFO it's just a chunk of RAM that holds the data, plus a read and write pointer.  The pointers are used to keep track of which ram locations are being used.  Once a piece of data has been read, it is still in the ram but the pointers indicate that it's not used.  As more and more data flow through the FIFO, that ram location will eventually get overwritten with new data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, there is no concept of deleting data.  Only ram locations that are being used and not used.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-22T19:00:42.133" />
  <row Id="13389" PostTypeId="2" ParentId="13379" CreationDate="2011-04-22T19:12:09.907" Score="1" ViewCount="" Body="&lt;p&gt;Typically, one manufacturer will develop a part and offer it for sale.  If that part is successful, other manufacturers will develop substitute parts to match, either because there's a market-wide demand for the product, and/or because the original manufacturer licensed the design to others to assure a second-source supply of the part.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In most cases, the secondary producers will use similar technologies to achieve similar performance specs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's the technology that generally drives the performance of the part.  That is why for the smaller IC's (74xx and 40xx), there's a &quot;family&quot; of parts.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 74 series actually have many different families - the original 7400 family, the 74S, 74LS, 74F, 74HC, 74HCT, and so on (look at &lt;a href=&quot;http://en.wikipedia.org/wiki/7400_series&quot; rel=&quot;nofollow&quot;&gt;the Wikipedia entry on the 7400 series&lt;/a&gt;) -- some of the technologies within the overall 7400-series varients are quite different from each other, and the main reason why they're named 74xx is because the naming of the devices are kept the same for the same functionality.  So you know that a 74(foo)00 is a quad-NAND, 74(foo)373 is an octal transparent latch, and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As stevenvh pointed out, there's usually a &quot;family guide&quot;.  Actually, there used to be dataBOOKS that had the family technology information in the front, followed by the per-device data.  As these big encyclopedic books have fallen out of favor, you now mostly see individual datasheets, and a separate guide to the technology.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-22T19:12:09.907" />
  <row Id="13390" PostTypeId="1" AcceptedAnswerId="13411" CreationDate="2011-04-22T19:59:16.257" Score="0" ViewCount="81" Body="&lt;p&gt;I have in my box of parts a phototriac coupler, namely a Sharp PC3SD21NTZ (&lt;a href=&quot;http://www.farnell.com/datasheets/73765.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;), which is a zero cross type. I don't know how to use it, but I've been meaning to learn for a while.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This part is specifically intended for triggering a main triac in load control applications and &quot;are ideal isolated drivers for medium to high current triacs&quot;. Typical application from the datasheet:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/C9u6F.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When triggering the main triac directly, one would typically have a zero-cross detection circuit which a microcontroller can use as an input to decide when to trigger the triac. However, this part does not appear to offer any way for the microcontroller to detect zero crossing, which leaves me wondering what its purpose is in the first place.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of input would one typically drive onto the diode side when using this part? Is it intended for on/off control only?&lt;/p&gt;&#xA;" OwnerUserId="1951" LastActivityDate="2011-04-23T09:12:39.363" Title="How to use a phototriac coupler to trigger the main triac?" Tags="&lt;triac&gt;&lt;how-does-it-work&gt;" AnswerCount="2" />
  <row Id="13391" PostTypeId="1" CreationDate="2011-04-22T20:42:53.167" Score="1" ViewCount="108" Body="&lt;p&gt;I am working on a remote-controlled (IR) lightswitch. This is pretty easy with an Arduino; you just do serial I/O with an IR receiver/transmitter to read &quot;ON&quot; and &quot;OFF&quot; signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to know if this kind of thing is possible without a microcontroller. Do there exist IC's that send/receive a pre-defined pattern (and then activate a pin if one of those patterns is recognized?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want something similar to a multiplexer; if I activate a set of pins, how can I output that pattern, like morse code, to my LED? Similarly, how could I read in such a pattern?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a category of IC's, pertaining to logic or communication, that I might want to be aware of?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason I ask is:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;I am a software guy. So &quot;just programming it&quot; is really easy, and I would like to learn more about ICs and using them.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;I plan to make a few of these, to give to my buddies and put in different rooms of the house. It would be cool if I could use standard parts, rather than having to program a chip every time I wanted a new one!&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1021" LastActivityDate="2011-04-23T16:15:53.287" Title="Transmit data without microcontroller?" Tags="&lt;serial&gt;&lt;ic&gt;&lt;ir&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="13392" PostTypeId="2" ParentId="12750" CreationDate="2011-04-22T20:59:14.063" Score="0" ViewCount="" Body="&lt;p&gt;The Aruduino can absolutely be programmed in assembly. And you don't even need an ICSP cable to do it!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Okay, in fairness, this is &lt;em&gt;not&lt;/em&gt; the same as programming it in pure assembly from the ground up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But you can inline assembly in C. Which means that you can load code onto your Arduino that has inline assembly, which will then execute. Consider the &lt;a href=&quot;http://code.google.com/p/arduino-tvout&quot; rel=&quot;nofollow&quot;&gt;TVOut library&lt;/a&gt;, which allows the Arduino to output NTSC/PAL to a TV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That library is very time-sensitive (since it is outputting to a TV, each scanline has to be written at the right time.) So it uses inline assembly to speed up the process. Looking at &lt;a href=&quot;http://code.google.com/p/arduino-tvout/source/browse/video_gen.cpp?r=59c833abde4555cecc9cc09167ef55d82d3985f3&quot; rel=&quot;nofollow&quot;&gt;line 89 of this file&lt;/a&gt; from the library, the author is using some of the &lt;a href=&quot;http://code.google.com/p/arduino-tvout/source/browse/spec/asm_macros.h&quot; rel=&quot;nofollow&quot;&gt;assembly macros&lt;/a&gt; that he wrote.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now. I suspect that he did not write them using the default Arduino IDE. But this library calls upon his inline asm code, which anyone can import, compile, and execute via their interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best of luck!&lt;/p&gt;&#xA;" OwnerUserId="1021" LastActivityDate="2011-04-22T20:59:14.063" />
  <row Id="13395" PostTypeId="1" CreationDate="2011-04-22T21:21:01.947" Score="1" ViewCount="101" Body="&lt;p&gt;I have a circuit that takes two analog inputs and positions a stepper motor accordingly. The problem I have ran into is the ground has a lot of noise and in turn makes my a/d inputs noisy and then the motor starts to get shaky and all kinds of strange stuff. I have tried isolating the grounds and also a star ground. I am sure the noise is coming from the stepper motor driver and the high speed switching. The board has both 12V(for motor) and 5V(for microcontroller and a/d's) regulated supplies and the noise is also coming through on them. The only thing that I have found to eliminate this is when I attach the ground lead from the oscilloscope to the ground on the board and it goes away. Why is this? What can I do to try and solve this problem. I am completely out of ideas TIA.&lt;/p&gt;&#xA;" OwnerUserId="3960" LastActivityDate="2011-04-24T13:36:07.587" Title="Grounding problems" Tags="&lt;noise&gt;&lt;ground&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="13396" PostTypeId="2" ParentId="13395" CreationDate="2011-04-22T21:31:16.500" Score="0" ViewCount="" Body="&lt;p&gt;Sounds as if its grounding through the O'scope back to earth ground. Can you connect your pcb ground to the line cord ground?&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-04-22T21:31:16.500" CommentCount="4" />
  <row Id="13397" PostTypeId="2" ParentId="13390" CreationDate="2011-04-22T21:42:10.387" Score="1" ViewCount="" Body="&lt;p&gt;As its shown, looks like it is for on-off control. It could be proportionality controlled if you were to synchronize pulse width modulation of the led. That would require proper timing from something such as a microprocessor.&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-04-22T21:42:10.387" CommentCount="3" />
  <row Id="13398" PostTypeId="1" AcceptedAnswerId="13400" CreationDate="2011-04-22T22:22:35.737" Score="0" ViewCount="60" Body="&lt;p&gt;Suppose I have a FIFO code written in vhdl for FIFO. I want to delete an element from the FIFO. Here would the FIFO be acting the same as a linked list where I check each and every element of the FIFO and then match it with the data_in and then finally delete it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OR it is the case that I should always delete the first element of the FIFO ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please give me some valuable suggestions .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regards to all.&lt;/p&gt;&#xA;" OwnerUserId="3957" LastActivityDate="2011-04-22T23:07:39.113" Title="FIFO(vhdl) : Delete Operation" Tags="&lt;vhdl&gt;&lt;verilog&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13399" PostTypeId="1" AcceptedAnswerId="13401" CreationDate="2011-04-22T23:03:04.127" Score="0" ViewCount="78" Body="&lt;p&gt;I own a couple of PS/2 to USB adaptor/converter connectors that look like the following:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://img.tomshardware.com/us/2005/11/23/pc_interfaces_101/ps2_usb.jpg&quot;/&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there anyway to test if these adapters are passive without disassembling them (or risking damage by disassembly)?  In all likelihood, they are passive as the active converters usually have a chip of some kind embedded in a cable to actively convert the protocol.&lt;/p&gt;&#xA;" OwnerUserId="3814" LastActivityDate="2011-04-23T00:34:47.307" Title="Is there an easy way to test if my PS/2 -&gt; USB adapter is passive?" Tags="&lt;usb&gt;&lt;adapter&gt;&lt;keyboard&gt;&lt;mouse&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13400" PostTypeId="2" ParentId="13398" CreationDate="2011-04-22T23:07:39.113" Score="0" ViewCount="" Body="&lt;p&gt;I have done a type of fifo with had four extra inputs:  rd_cancel and rd_commit, and wr_cancel and wr_commit.  The idea is that you can do a bunch of writes and then either cancel the writes you did (erase the data you just wrote) or commit that data (make it available to the read port).  The same thing for reading:  rd_cancel would &quot;unread&quot; what you just read, rd_commit would commit your reads.  The cancel/commit operation would cancel or commit only the data since the last cancel/commit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is done by having a temporary copy of the write and read pointers.  These temp pointers are copied back and forth with the real pointers depending on the cancel/commit inputs.  Also, when calculating if the FIFO is full or not, sometimes the temp pointers or the real pointers are used.  It's a bit complicated, and beyond this kind of forum, but if this sounds like what you want then let me know and I'll see what I can come up with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just FYI:  I have never seen this type of FIFO done before, but it seems like an obvious solution to several FIFO related problems.  The last time I googled for a FIFO like this I came up empty, but I'd be surprised if nobody else have ever dreamed up something like this.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-22T23:07:39.113" CommentCount="2" />
  <row Id="13401" PostTypeId="2" ParentId="13399" CreationDate="2011-04-22T23:08:02.313" Score="3" ViewCount="" Body="&lt;p&gt;We pulled apart one of those and it's all wire or passive. The mouse that they come with must detect what it's plugged into USB or PS2 and do the right thing. &lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-04-22T23:08:02.313" CommentCount="1" />
  <row Id="13402" PostTypeId="2" ParentId="13395" CreationDate="2011-04-23T00:20:06.780" Score="1" ViewCount="" Body="&lt;p&gt;The actual topology of your ground system is important in cases like this. Currents don't just go away when they reach a ground node, they return to their source. What you want to do is to minimize the amount of conductor that the motor return currents share with the return current for the A/D section. For instance, the 12V return wire should go quite near the stepper driver, and for the 0V reference you can tie the logic ground and stepper-driver ground (12V return) together at just that point.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-23T00:20:06.780" CommentCount="5" />
  <row Id="13403" PostTypeId="2" ParentId="13399" CreationDate="2011-04-23T00:34:47.307" Score="0" ViewCount="" Body="&lt;p&gt;All USB mice are capable of sending to a PS/2 port. This was by design because there are still many people who need to use PS/2 (for KVM's and such), but it is not reasonable for companies to continue to manufacture 2 separate items. Because of this, adapters like those are purely passive as the mouse itself is the one that figures out what it is connected to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, it doesn't work the other way around since PS/2 devices never had any idea of what USB was.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I did come across something interesting though, it &lt;a href=&quot;http://superuser.com/questions/189465/usb-ps2-usb-thumb-drive-wtf&quot;&gt;looks as though&lt;/a&gt; you can plug a flash drive into a USB-&gt;PS/2 converter and then plug that into a PS/2-&gt;USB converter. Not really sure how that actually works though.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-23T00:34:47.307" CommentCount="1" />
  <row Id="13404" PostTypeId="1" AcceptedAnswerId="13417" CreationDate="2011-04-23T01:20:15.053" Score="1" ViewCount="102" Body="&lt;p&gt;How hot can a dremel get during normal operation and what happens if it stalls? I use a dremel 200 at home and when it's been running for longer periods of time (5 min continious) I notice that it get's hot and seems to run faster. &lt;/p&gt;&#xA;" OwnerUserId="3045" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-04-23T02:09:58.760" LastActivityDate="2011-04-23T16:41:10.627" Title="How hot can a dremel 200 get?" Tags="&lt;tools&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="13405" PostTypeId="1" AcceptedAnswerId="13408" CreationDate="2011-04-23T02:44:24.200" Score="0" ViewCount="99" Body="&lt;p&gt;I have an Arduino Duemilanove that I have used for various tasks (including signaling servos). When I got &lt;a href=&quot;http://www.sparkfun.com/products/9367&quot; rel=&quot;nofollow&quot;&gt;Sparkfun's Wifly shield&lt;/a&gt; I was unable to get it working. I then got an Arduino Uno which (surprise) did work with the shield. This leads me to believe that somehow I have damaged my original Arduino.  I suspect that it may have been due to controlling a servo.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am aware of the Servo library and have successfully used it in the past. I am controlling a regular servo (steering servo) and a brushless motor (from a 35A ESC, which the servo plug is attached to) on &lt;a href=&quot;http://www.redcatracing.com/RC-Cars/1-10-Scale-Electric-Brushless/CALDERA-10E_3&quot; rel=&quot;nofollow&quot;&gt;this R/C car&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However I'm wondering if there is potential for damage to the hardware under certain situations. Of course I won't be powering any motors off of the Arduino itself, but do I have any guarantees that the signal pin of a servo won't draw too much power or do something else that may be a problem? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I could come up with a voltage follower circuit, which might be safer. I'd need to find some op-amps for that, though. &lt;/p&gt;&#xA;" OwnerUserId="3039" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-16T13:41:49.607" LastActivityDate="2011-05-16T13:41:49.607" Title="Controlling servos with an arduino" Tags="&lt;arduino&gt;&lt;servo&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13407" PostTypeId="2" ParentId="13359" CreationDate="2011-04-23T03:51:27.793" Score="1" ViewCount="" Body="&lt;p&gt;Looks like you're wondering if having female ended wires available is useful?BTW The ones in the link look like double male ended wires. (which yea generically you could get by with a wire). As far as female I think a useful aspect would be if you have two sets of components with headers connected, then you can just connect the &quot;male headers&quot; to male headers and you're golden.&lt;/p&gt;&#xA;" OwnerUserId="982" LastActivityDate="2011-04-23T03:51:27.793" />
  <row Id="13408" PostTypeId="2" ParentId="13405" CreationDate="2011-04-23T04:32:03.983" Score="2" ViewCount="" Body="&lt;p&gt;From what I have read, the signal line should only draw a few milliamps at most. However, as Arduino can safely sink or source up to 40mA on it's pins, if you want to limit the draw to say half that just use say a 270 ohm resistor in series with the signal pin to provide a current limit. On a 5V line no more than 18mA should be able to flow in or out per pin.&lt;/p&gt;&#xA;" OwnerUserId="2595" LastActivityDate="2011-04-23T04:32:03.983" />
  <row Id="13409" PostTypeId="1" AcceptedAnswerId="13419" CreationDate="2011-04-23T06:15:31.117" Score="1" ViewCount="136" Body="&lt;p&gt;Here is a question that I stumbled upon:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://asicdigitaldesign.wordpress.com/2007/06/08/puzzle-4-the-min-max-question/&quot; rel=&quot;nofollow&quot;&gt;http://asicdigitaldesign.wordpress.com/2007/06/08/puzzle-4-the-min-max-question/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;MinMax2 is a component with 2 inputs, A and B, and 2 outputs, Max and Min. You guessed it, you connect 2 numbers at the inputs and the component drives the Max output with the bigger of the two and the Min output with the smaller of the two.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your job is to design a component MinMax4, with 4 inputs and 4 outputs, which sorts the 4 numbers using only MinMax2 components. Try to use as few MinMax2 components as possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the solution:&#xA;&lt;a href=&quot;http://asicdigitaldesign.wordpress.com/2007/06/24/puzzle-4-solution/&quot; rel=&quot;nofollow&quot;&gt;http://asicdigitaldesign.wordpress.com/2007/06/24/puzzle-4-solution/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I succeeded in solving it, but what I didn't successfully answer is: how many different input sequences are needed to verify the logical behavior of MinMax4?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The obvious answer is $4!$, but as I understand there is a more minimal solution.&lt;/p&gt;&#xA;" OwnerUserId="3963" LastEditorUserId="3441" LastEditorDisplayName="" LastEditDate="2011-04-23T18:50:59.350" LastActivityDate="2011-04-23T18:50:59.350" Title="Interview question, testing a sorting network" Tags="&lt;logic&gt;&lt;vlsi&gt;&lt;interview-questions&gt;" AnswerCount="1" CommentCount="8" />
  <row Id="13410" PostTypeId="1" CreationDate="2011-04-23T07:01:07.587" Score="0" ViewCount="129" Body="&lt;pre&gt;&lt;code&gt;library IEEE;  &#xA;use IEEE.STD_LOGIC_1164.ALL;  &#xA;use IEEE.STD_LOGIC_ARITH.ALL;  &#xA;--use IEEE.STD_LOGIC_UNSIGNED.ALL;  &#xA;use ieee.std_logic_signed.all;  &#xA;&#xA;entity fifo is  &#xA;    port (  clk : in std_logic;  &#xA;          read_data : in   std_logic;                                       --enable read,should be '0' when not in use.  &#xA;          insert : in   std_logic;                                          --enable write,should be '0' when not in use.  &#xA;          delete : in std_logic;  &#xA;          datain : in std_logic_vector (7 downto   0);                      --input data  &#xA;          dataout : out std_logic_vector(7 downto   0);                 --output data           &#xA;          empty : out std_logic :=   '1';                                   --set   as '1' when the queue is empty  &#xA;          full : out std_logic  :=   '0';                                       --set as '1' when the queue is full  &#xA;          no_insert : out std_logic;  &#xA;          no_delete : out std_logic  &#xA;         );  &#xA;end fifo;  &#xA;&#xA;architecture Behavioral of fifo is  &#xA;    type memory_type is array (0 to 255) of std_logic_vector(7 downto 0);  &#xA;    signal memory : memory_type :=(others =&amp;gt; (others =&amp;gt;   '0'));            --memory for queue.  &#xA;    signal rp,wp,tmp_ptr : std_logic_vector(7 downto 0) :=&quot;00000000&quot;;       --read and write pointers.  &#xA;    signal isfull : std_logic := '0';  &#xA;    signal isempty : std_logic := '1';  &#xA;    begin  &#xA;        --dataout &amp;lt;= &quot;00000000&quot;;  &#xA;        process(clk)  &#xA;        begin  &#xA;            -- Reading Process                     &#xA;                -- Read when not empty  &#xA;                -- empty when Write_ptr = Read_ptr  &#xA;                -- increment as 0 1 2....255 0 1 2....255  &#xA;                -- If Last_wrt is high set low Last_rd,  &#xA;                -- overwrite Last_rd as high if actually   reading take place  &#xA;            if(clk'event and clk='1' and read_data ='1')   then                         --read the tail of FIFO  &#xA;                --if(isempty = '1') then  &#xA;                --  dataout &amp;lt;= &quot;00000000&quot;;  &#xA;                --else   &#xA;                    dataout &amp;lt;= memory(conv_integer(rp));  &#xA;                --end if;  &#xA;            end if;  &#xA;            if(clk'event and clk='1' and insert ='1')   then                                --insert on the   top/head of FIFO  &#xA;                --if(isfull = '1') then   &#xA;                    --no_insert &amp;lt;= '1 ;  &#xA;                    --dataout &amp;lt;= &quot;00000000&quot;;  &#xA;                --else  &#xA;                    no_insert &amp;lt;= '0';  &#xA;                    memory(conv_integer(wp)) &amp;lt;= datain;  &#xA;                    dataout &amp;lt;= datain;  &#xA;                    --if(wp = &quot;11111111&quot;) then  &#xA;                    --  wp &amp;lt;= &quot;00000000&quot;;  &#xA;                    --else   &#xA;                    --  wp &amp;lt;= wp + 1;  &#xA;                    --end if;  &#xA;                --end if;  &#xA;                --if(wp = rp) then  &#xA;                --      full &amp;lt;= '1';  &#xA;                --      isfull &amp;lt;= '1';  &#xA;                --  else   &#xA;                --      full &amp;lt;= '0';  &#xA;                --      isfull &amp;lt;= '0';  &#xA;                --end if;  &#xA;            end if;  &#xA;&#xA;            if(clk'event and clk='1' and delete ='1')   then                            --pop/delete the tail   of FIFO  &#xA;                --if(isempty = '1') then  &#xA;                --  no_delete &amp;lt;='1';  &#xA;                --  dataout &amp;lt;= &quot;00000000&quot;;  &#xA;                --else   &#xA;                    no_delete &amp;lt;= '0';  &#xA;                    dataout &amp;lt;= memory(conv_integer(rp));  &#xA;                --  if(rp = &quot;11111111&quot;) then  &#xA;                --      rp &amp;lt;= &quot;00000000&quot;;  &#xA;                --  else   &#xA;                        rp &amp;lt;= rp + 1;  &#xA;                --  end if;  &#xA;                --  if(rp = wp) then  &#xA;                --      empty &amp;lt;= '1';  &#xA;                --      isempty &amp;lt;= '1';  &#xA;                --  else  &#xA;                --      empty &amp;lt;= '0';  &#xA;                --      isempty &amp;lt;= '0';  &#xA;                --  end if;  &#xA;                --end if;  &#xA;            end if;  &#xA;            if(rp = &quot;11111111&quot;)   then                                          --resetting read pointer.  &#xA;                rp &amp;lt;= &quot;00000000&quot;;  &#xA;            end if;  &#xA;            if(wp = &quot;11111111&quot;)   then                                          --resetting read pointer.  &#xA;                wp &amp;lt;= &quot;00000000&quot;;  &#xA;            end if;  &#xA;&#xA;            if(wp = rp and insert = '1')   then                                         --checking whether queue is full or not  &#xA;                full &amp;lt;='1';               &#xA;            else  &#xA;                full &amp;lt;='0';  &#xA;            end if;  &#xA;&#xA;            if(wp = rp and delete = '1')   then                                     --checking whether queue is empty or not  &#xA;                empty &amp;lt;='1';  &#xA;            else  &#xA;                empty &amp;lt;='0';  &#xA;            end if;       &#xA;        end process;  &#xA;&#xA;end Behavioral;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;In the above vhdl code for FIFO I am not actually getting the write testbench simulation. Even though the FIFO buffer is not full then also full becomes equal to 1. Can some1 please help me sort out the error ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;when the process(clk) is run everytime on the clk tick then what exactly happens .... are all the ifs called simultaneously ?I mean all the different functions in the process(clk) block rum at the same time in parallel ?&lt;/p&gt;&#xA;" OwnerUserId="3957" LastEditorUserId="3145" LastEditorDisplayName="" LastEditDate="2011-05-11T09:17:43.990" LastActivityDate="2011-05-11T09:17:43.990" Title="FIFO : doubt in process(clk)." Tags="&lt;vhdl&gt;&lt;verilog&gt;&lt;fifo&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="13411" PostTypeId="2" ParentId="13390" CreationDate="2011-04-23T08:19:12.217" Score="2" ViewCount="" Body="&lt;p&gt;It's for on/off control only. After the opto-coupler sees the LED going on it waits for the next zero-crossing of the mains voltage, at which point it switches on. After switching off, like any triac it remains on until the current goes below a hold-value. The circuit doesn't need to tell te microcontroller; it takes care of it all by itself.&lt;br&gt;&#xA;Opto-couplers with zero-crossing switch are useful for switching resistive loads, like incandescent bulbs. They don't offer advantages for switching reactive loads.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that with typical PCB pads there may be not sufficient creepage distance between the pins on the control side (1, 2) and the load side (4, 5, 6). In Europe this should be 6 mm. The NVZ version may offer a solution.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PC3SD21NTZ sounds like a somewhat exotic part. If you need more of them, you may consider the compatible MOC3031/3041 (3031 for 115 V, 3041 for 230 V).&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-23T09:12:39.363" LastActivityDate="2011-04-23T09:12:39.363" />
  <row Id="13412" PostTypeId="2" ParentId="13410" CreationDate="2011-04-23T09:15:22.947" Score="1" ViewCount="" Body="&lt;p&gt;For your specific question on the &lt;em&gt;full&lt;/em&gt; signal, it will definitely be full since both &lt;em&gt;wp&lt;/em&gt; and &lt;em&gt;rp&lt;/em&gt; are 0 at the start. Plus, you are not using a register to clock the &lt;em&gt;full&lt;/em&gt; signal. This can potentially result in glitches in your output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My advice to you would be to stop thinking of this in terms of code but to think of it in terms of hardware i.e. instead of asking if the 'ifs are called simultaneously' think of how the signals are wired up through multiplexers, registers and memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, code according to the hardware that you would like to generate, and not the other way around. There is a reason why it is a 'Hardware Description Language'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a start, there are any number of example FIFO designs around that you might want to study first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-04-23T09:15:22.947" />
  <row Id="13413" PostTypeId="2" ParentId="13404" CreationDate="2011-04-23T10:47:34.260" Score="1" ViewCount="" Body="&lt;p&gt;Hobbyist tools like Dremels aren't intended for long periods of heavy-duty operation which causes them to stall, which can damage them. You need to get a professional tool with more power.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-23T10:47:34.260" CommentCount="2" />
  <row Id="13416" PostTypeId="2" ParentId="13391" CreationDate="2011-04-23T16:15:53.287" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.holtek.com/&quot; rel=&quot;nofollow&quot;&gt;Holtek&lt;/a&gt; produces a &lt;a href=&quot;http://www.holtek.com/english/products/encoder_decoder.htm&quot; rel=&quot;nofollow&quot;&gt;series of encoder/decoders&lt;/a&gt;, which are often used in cheap (China made) remote controlled wall outlet kits.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-23T16:15:53.287" CommentCount="1" />
  <row Id="13417" PostTypeId="2" ParentId="13404" CreationDate="2011-04-23T16:41:10.627" Score="2" ViewCount="" Body="&lt;p&gt;It's pretty hard to break a Dremel. From their &lt;a href=&quot;http://www.dremel.com/en-us/customerservice/faq/rotarytools/pages/demel4000.aspx&quot; rel=&quot;nofollow&quot;&gt;FAQ&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Q: What are some tips to allow the tool to run cooler?&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;A: Allowing the tool to run by itself for one minute after use, actually helps cool the tool compared to turning the tool off immediately after use.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Additionally, make sure to avoid covering the vents on the side of the tool with your hands while using it because airflow to the motor is blocked.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Let the speed do the work. Do not bare down on the tool causing the motor to stall. If the motor stall the fan will run slower and therefore not cool the motor as efficiently.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;Q: How do I know if the tool is running too hot?&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;A: A heat sensitive fuse prevents the tool from overheating at a critical level.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="906" LastActivityDate="2011-04-23T16:41:10.627" />
  <row Id="13419" PostTypeId="2" ParentId="13409" CreationDate="2011-04-23T17:23:37.370" Score="1" ViewCount="" Body="&lt;p&gt;The question is ambiguous, although sometimes interview questions are intentionally ambiguous to prompt a discussion of the ambiguities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One way to look at it is, if you are verifying a design for a 4-input sorting network, how many input sequences are needed to be sure the implementation is correct. If you don't know anything about how it's implemented, then you need to test all $4!$ permutations of four values to be absolutely certain the implementation is correct.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to look at it is, if you manufacture the circuit, how many input sequences do you need to apply to each device during testing to be sure the circuit was manufactured correctly. In this case you would usually take the design as a given, so you don't need to cover all $4!$ permutations, you just need enough inputs to cover the interesting cases for each element of the circuit. I'm guessing this was the intention of the question, and I'm guessing that only two cases are considered interesting for each MinMax2 component (A&amp;gt;B and A&amp;lt;B). There's also the A=B case, but you can argue the behavior of the MinMax2 is a don't-care when A=B. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This isn't realistic, since in practice you would need more than two cases to make sure all of the transistors and wires inside the MinMax2 component were manufactured correctly. But I'll assume that we're just trying to cover two cases for each MinMax2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In that case, if the inputs are A through D where A &amp;lt; B &amp;lt; C &amp;lt; D, then only two inputs are necessary to cover both cases for each MinMax2: A, C, B, D and D, C, B, A. The first covers the &quot;no-swap&quot; case for each MinMax2, and the second covers the &quot;swap&quot; case for each MinMax2.&lt;/p&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-04-23T17:23:37.370" />
  <row Id="13421" PostTypeId="1" AcceptedAnswerId="13433" CreationDate="2011-04-23T19:22:48.120" Score="5" ViewCount="146" Body="&lt;p&gt;I'm interested in making myself a 12V power supply. I need one because I often go out to places with little or no power and need some electricity to power my gear (which is basically a telescope, a camera and some accessories - all run on 12V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't want it to be powered by mains and would instead use a 12V deep cycle battery. For regulation, I'm going to be using 7812. I need about 6 outputs, each capable of 4A. My question is this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it better to regulate each output separately with a 7812 (with a power transistor for increased current capability) or use single 7812 with several power transistors, for a current rating of, say, 25A, and then split this into 6 outputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Secondly, since I'm using a 12V battery I understand that regulation is not going to be good as Vout is also 12V. Unfortunately, I can't get a new battery so I was thinking, perhaps, stepping the voltage with a DC-DC Converter to about 14V and then feeding this voltage into the regulator will help with regulation. Is this a good idea?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I require some decent regulation as my telescope is quite sensitive to the power's quality. I apologize if these are boneheaded questions, but searching the web did not return good results.&lt;/p&gt;&#xA;" OwnerUserId="3966" LastEditorUserId="1951" LastEditorDisplayName="" LastEditDate="2011-04-24T20:02:31.853" LastActivityDate="2011-04-24T20:02:31.853" Title="Some Power Supply Questions - Multiple Rails or Single Rail w/ multiple Outputs?" Tags="&lt;power-supply&gt;&lt;voltage-regulator&gt;" AnswerCount="3" />
  <row Id="13422" PostTypeId="2" ParentId="13421" CreationDate="2011-04-23T20:40:03.793" Score="3" ViewCount="" Body="&lt;p&gt;You won't be able to get a good 12V output from a 12V input using a linear regulator like the 7812. Linear regulators need at least a couple of volts more on the input, so they have margin to regulate in, and they aren't very efficient, because that excess voltage, multiplied by whatever current is delivered into your load, is just wasted as heat. Better to use some kind of switching regulator, such as (yep) a DC-DC converter. Don't bother with the follow-on regulation, just select a DC-DC converter that gives you your desired output voltage with suitable regulation, and you're done.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-23T20:40:03.793" CommentCount="4" />
  <row Id="13423" PostTypeId="2" ParentId="13421" CreationDate="2011-04-23T20:57:54.280" Score="1" ViewCount="" Body="&lt;p&gt;You have several issues here, so let me try to address them all:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Most versions of the 7812 are limited to 1 to 2 amps.  So you're not going to get 4 amps out of them.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Most versions of the 7812 have a dropout voltage of about 2 volts, meaning that the input needs to be 2 volts higher than the output.  Again, for most 7812 type regulators, if the input is not at least 14 volts, then the output will be the Input Voltage - 2.  So if the input is 12 volts, then the output will be 10 volts.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If Vin-Vout=2 volts at 4 amps then you're dissipating 8 watts of heat at the regulator.  Times 6 outputs and you're spitting out 48 watts of heat.  That's a heck of a lot of heat to deal with.  You'll need a fan, at least, and it still probably wouldn't work.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;A standard 12v lead-acid battery is going to output anything but 12v.  Depending on the state of charge, temperature, phase of the moon, and if you've phoned your mother recently it could have up to 15 volts on the output.  More typically it is around 13.2 volts, but you must design for the range from 12-15 volts (10-15 would be better).  Keep in mind that if it is outputting 15 volts, then your power dissipation goes from 48 watts to 72 watts.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In short, it won't work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's what I recommend:  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;If you can avoid using a regulator then don't!  Many &quot;+12v devices&quot; will work just fine on 10-15 volts.  Anything that is designed to operate from a cigarette lighter in a car will work to up 15v (because cars have the same issues).  For other devices you might have to read the manual or talk with tech support.   But odds are that it'll work just fine.  Odds are very good that your telescope will work directly from the battery, as that's what most of their customers are going to do.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For the devices that require a regulator, they are going to need something better than what a simple 7812 is going to do.  The 7812 isn't going to handle the current demands, or regulate very well with a 12-14v input.  Running a boost DC/DC converter to get 14v and then using a linear regulator like the 7812 doesn't really buy you anything since you're still burning a lot of power needlessly.  What you'd want to do then is take a Boost DC/DC converter and follow it with a Buck DC/DC converter-- or use a SEPIC converter (which is like a boost and buck combined into a single converter).&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-23T20:57:54.280" CommentCount="6" />
  <row Id="13424" PostTypeId="2" ParentId="514" CreationDate="2011-04-23T22:39:41.893" Score="0" ViewCount="" Body="&lt;p&gt;I would probably start here at Microchip... but I'm familiar with PICs and they usually have cost sensitive options. &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en551867&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1406&amp;amp;dDocName=en551867&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-04-23T22:39:41.893" />
  <row Id="13425" PostTypeId="1" CreationDate="2011-04-20T21:00:47.957" Score="0" ViewCount="111" Body="&lt;p&gt;I felt for getting a new hobby. I was thinking about controlling an Arduino through the Internet, and I'm not really sure yet how I'm supposed to do that. I was thinking about connecting it to a computer and then have a program on the computer and then communicate to the Arduino through another computer, but it feels very chunky and big.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To give you some more simple understanding ( &amp;lt;--&gt; = communication):&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Keyboard --&gt; Computer A --&gt; Internet --&gt; Computer B --&gt; Arduino --&gt; Electrical Engine. This does sound chunky.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So I wondered if maybe it would be possible to do this:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Keyboard --&gt; Computer A --&gt; Internet --&gt; Arduino --&gt; Electrical Engine.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;But yeah, I hope you get my idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what I do want is this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make an Internet controlled car (same as radiocontrolled, same size, etc.) with a camera with live streaming. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why do I want to do it? - I figured that I'm very bored most of the time so I felt for making a new fun project. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've ordered an &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardNano&quot; rel=&quot;nofollow&quot;&gt;Arduino Nano&lt;/a&gt; AND a laptop AND a GPS transmitter for an Arduino in case you're curious.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my question to YOU is, what exactly do I need? I'm not asking you to do everything for me. I'm asking you as an amateur what I should get in order for my project to go as smooth and best as possible.&lt;/p&gt;&#xA;" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2011-05-02T16:53:38.613" LastActivityDate="2011-05-02T16:54:03.777" Title="Arduino Nano usage" Tags="&lt;control&gt;&lt;communication&gt;&lt;arduino&gt;" AnswerCount="2" />
  <row Id="13426" PostTypeId="2" ParentId="13425" CreationDate="2011-04-20T21:44:40.463" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Short answer&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to avoid a computer connected directly to an Arduino over USB or Ethernet, I recommend using a wireless option like 802.11, Bluetooth, &lt;a href=&quot;http://en.wikipedia.org/wiki/ZigBee&quot; rel=&quot;nofollow&quot;&gt;ZigBee&lt;/a&gt;, or RF. I'll warn you right now, an Arduino cannot process video. It doesn't even have enough memory to store a higher resolution video frame. I recommend starting without the camera and just sending basic navigation commands using the wireless option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Long Answer&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Arduino has a concept of &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoShields&quot; rel=&quot;nofollow&quot;&gt;shields&lt;/a&gt;. These are modules you can add on to the Arduino for extra functionality. To get the Arduino to communicate over a wireless connection, options include the &lt;a href=&quot;http://www.sparkfun.com/products/9954&quot; rel=&quot;nofollow&quot;&gt;WiFly shield&lt;/a&gt; for 802.11B, XBee shields and adapters to connect over the ZigBee protocol (a low bandwidth, energy efficient protocol), Bluetooth Arduinos for Bluetooth connections and even straight up RF options (see &lt;a href=&quot;http://jeelabs.com/products/jeenode&quot; rel=&quot;nofollow&quot;&gt;JeeNode&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most shields are not directly compatible with the Arduino Nano however. That doesn't mean you can't use them, just that you may have extra work related to wiring up the pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a programming perspective, the easiest way to communicate is over the Tx/Rx lines of the Arduino. This is a basic serial connection that's easier to understand. See the &lt;a href=&quot;http://www.arduino.cc/en/Serial/Begin&quot; rel=&quot;nofollow&quot;&gt;Serial page&lt;/a&gt; for more details.&lt;/p&gt;&#xA;" OwnerUserId="2542" LastEditorUserId="804" LastEditorDisplayName="" LastEditDate="2011-05-02T16:54:03.777" LastActivityDate="2011-05-02T16:54:03.777" />
  <row Id="13427" PostTypeId="2" ParentId="13425" CreationDate="2011-04-20T22:09:03.520" Score="0" ViewCount="" Body="&lt;p&gt;If you had a regular Arduino I would simply suggest that you get a WiFi shield to let your &quot;Computer A&quot; communicate with the Arduino via WiFi.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since you have a nano, and nano's are designed to plug into breadboards and don't support shields the way a regular Arduino does, you may want to either design your own WiFi interface or simply get a regular Arduino depending on your goals and skill level.&lt;/p&gt;&#xA;" OwnerUserId="3869" LastActivityDate="2011-04-20T22:09:03.520" CommentCount="2" />
  <row Id="13429" PostTypeId="1" CreationDate="2011-04-24T03:41:28.140" Score="0" ViewCount="112" Body="&lt;p&gt;Can I use an AC solid state relay to control a DC current as long as the DC voltage doesn't exceed the rated AC voltages?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to control a solenoid but I'm concerned about the inductance problem of the device. Will a solid state relay survive the back EMF of the solenoid when turned off by  itself?&lt;/p&gt;&#xA;" OwnerUserId="1319" LastEditorUserId="1319" LastEditorDisplayName="" LastEditDate="2011-04-25T14:49:11.897" LastActivityDate="2011-04-25T14:49:11.897" Title="Can I use a solid state relay to control a DC current?" Tags="&lt;solenoid&gt;&lt;solid-state-relay&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13430" PostTypeId="2" ParentId="13429" CreationDate="2011-04-24T04:45:47.830" Score="3" ViewCount="" Body="&lt;p&gt;It depends on the relay. Many solid state relays use a thyristor as their main switching component, and a thyristor can't be turned off simply by removing the trigger voltage. They rely on the reverse-bias portion of the AC cycle to switch off. Other solid state relays use FETs as their switching component and those relays may work with DC. It all depends on what the specific relay is rated for, and the only way to know is to carefully read the relay's data sheet. &lt;/p&gt;&#xA;" OwnerUserId="1409" LastActivityDate="2011-04-24T04:45:47.830" />
  <row Id="13431" PostTypeId="1" CreationDate="2011-04-24T08:33:27.047" Score="0" ViewCount="96" Body="&lt;p&gt;I watched some diy synthesizer vids on youtube, mostly APC's, and I thought since most use the 556/555's, what if we used something different. As fun as buying kits are, sometimes, we are broke, but still inspired. So, I went into my closet and found 7+ modems(mostly ISA) and 6 sound cards (all SB; vibra16 ISA, awe64 value, SB16Pro2, Live value, live platinum and audigy 2 platinum). A little research suggested the vibra 16 was the most outdated and pretty much useless, so it's now wearing a red jumper.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I couldn't find any schematics for any of the boards or IC's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I totally off base thinking I can salvage an IC to use as a simple tone generator like an APC type synthesizer? I included modems in my search because I recall the sounds they made when dialing up, and I thought, hmmm, if that were modulated and probably slowed down it might work as a tone generator. I admit I am new to this, so identifying the correct chip to use and well, which pins do what is a little confusing. Oh, and modems and soundcards are also a good source for jacks (the sbpro2 actually has a volume pot, ha).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ps- this all started last wednesday when my Roland D2 arrived from a stint on ebay and the left channel is out, after running it thru test mode, I don't think it's more serious, theoretically than cold spots that will go away after being reflowed, but wanted to warm up to possibly ruining the piece of gear with a distraction.&lt;/p&gt;&#xA;" OwnerUserId="3967" LastActivityDate="2011-04-24T19:45:51.333" Title="Are there any viable sound IC's in older consumer PC sound cards/modems for diy/circuitbending?" Tags="&lt;synthesizer&gt;" AnswerCount="2" />
  <row Id="13432" PostTypeId="2" ParentId="13431" CreationDate="2011-04-24T08:45:08.177" Score="1" ViewCount="" Body="&lt;p&gt;The modem ICs are rather limited in the sound they can generate. You have FSK (Frequency Shift Keying), which switches between two frequencies depending on the input bit's value. More advanced modulation methods include PM (Phase modulation), but that doesn't add more frequencies.&lt;br&gt;&#xA;The dialler will be a DTMF (Dual Tone Multiple Frequency) generator, which generates a pair of frequencies from a limited set of eight. So that's out as well.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Creative Labs used custom chips on its SoundBlaster boards. They may be very versatile, but unless you can find a datasheet they're useless.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I looked around a bit and found the &lt;a href=&quot;http://www.speechchips.com/shop/item.aspx?itemid=2&quot; rel=&quot;nofollow&quot;&gt;SSG01 Sound Coprocessor IC&lt;/a&gt;, which may also be interesting. (Yes, I know you're broke.) It has a simple interface: it's controlled via EIA232 and outputs a mono audio signal. Unfortunately the link to the datasheet on the page is dead.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-24T09:38:01.313" LastActivityDate="2011-04-24T09:38:01.313" CommentCount="1" />
  <row Id="13433" PostTypeId="2" ParentId="13421" CreationDate="2011-04-24T09:51:49.927" Score="5" ViewCount="" Body="&lt;p&gt;Forget the 7812. If you're going to use a switcher to create a higher voltage first and then use the 7812 to go to 12V, you might as well use the switcher to go to 12V directly.&lt;br&gt;&#xA;If the output voltage is close to the input voltage (sometimes below, sometimes above), you want a &lt;strong&gt;buck-boost regulator&lt;/strong&gt;, like &lt;a href=&quot;http://www.national.com/pf/LM/LM5118.html#Overview&quot; rel=&quot;nofollow&quot;&gt;National's LM5118&lt;/a&gt;. The Webench Designer creates a design to your parameters.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-24T09:51:49.927" />
  <row Id="13434" PostTypeId="1" AcceptedAnswerId="13435" CreationDate="2011-04-24T10:23:33.380" Score="2" ViewCount="99" Body="&lt;p&gt;I wonder if solder paste might work as a good substitute for soldering wire for through-hole soldering. I imagine that it could make soldering a bit easier in some cases, for example by providing a better contact between the part, the pad and the soldering iron for heat transfer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone tried this and was it any more convenient than wire?&lt;/p&gt;&#xA;" OwnerUserId="1951" LastActivityDate="2011-04-24T17:44:53.120" Title="Using solder paste instead of soldering wire for through-hole parts" Tags="&lt;soldering&gt;" AnswerCount="2" />
  <row Id="13435" PostTypeId="2" ParentId="13434" CreationDate="2011-04-24T10:27:37.043" Score="2" ViewCount="" Body="&lt;p&gt;I've done it, and it is far messier than wire solder, with negligible advantages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, through hole soldering requires a lot more solder then surface mount. Therefore, you wind up building huge mounds of solderpaste on every component hole, which then gets pushed around as the rosin in the paste boils off during soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The end result is solderpaste/solderballs all over your PCB, with little of it where you want, on the component leads.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-04-24T10:27:37.043" CommentCount="8" />
  <row Id="13436" PostTypeId="1" CreationDate="2011-04-24T10:58:10.047" Score="0" ViewCount="168" Body="&lt;p&gt;Can someone suggest me any embedded platforms that would be capable of streaming video from an USB webcam (pref. HD) over wlan and run some flavor of linux? The platform should be as small as possible. I already know about gumstix and beagleboard, but gumstix are a tad expensive and beagleboard is a tad big.&lt;/p&gt;&#xA;" OwnerUserId="140" LastActivityDate="2011-06-05T18:06:17.217" Title="Smallest embedded platform capable of streaming video over wlan?" Tags="&lt;embedded&gt;&lt;video&gt;&lt;beagleboard&gt;&lt;gumstix&gt;&lt;wlan&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="13438" PostTypeId="2" ParentId="13395" CreationDate="2011-04-24T13:36:07.587" Score="1" ViewCount="" Body="&lt;p&gt;Just try a few decently sized shunt capacitors from the 5V to gnd and/or 12V to gnd. Make sure of the polarity and voltage rating.&lt;/p&gt;&#xA;" OwnerUserId="3970" LastActivityDate="2011-04-24T13:36:07.587" CommentCount="1" />
  <row Id="13439" PostTypeId="1" AcceptedAnswerId="13443" CreationDate="2011-04-24T14:56:08.940" Score="0" ViewCount="106" Body="&lt;p&gt;I'm developing a portable device embedding inertial sensor, bluetooth, a small camera (for qrcode detection), flash memory (like a usb key).&#xA;I'm thinking of 2 solutions:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;one XMEGA-based, in which I need to implement/adapt/develop the bluetooth stack, the filesystem, the qrcode detection algorithm, etc..&lt;/li&gt;&#xA;&lt;li&gt;one based on linux on an ARM9, where I can find these things already developed or easy to implement and I just need to write my applications in C on Linux. Furthermore, this way I have an easily expandable solution, in the sense that if I want to add something, I just need write its application and there's no need of rethinking the firmware architecture as with the first solution.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Is there anything I'm missing? I'm afraid I'm making things too easy..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Talking about the last solution, what board would you suggest to start with? I though about &lt;a href=&quot;http://www.embeddedartists.com/products/kits/lpc3141_kit.php&quot; rel=&quot;nofollow&quot;&gt;http://www.embeddedartists.com/products/kits/lpc3141_kit.php&lt;/a&gt;, &lt;a href=&quot;http://beagleboard.org&quot; rel=&quot;nofollow&quot;&gt;http://beagleboard.org&lt;/a&gt;, &#xA;&lt;a href=&quot;http://www.gumstix.com&quot; rel=&quot;nofollow&quot;&gt;http://www.gumstix.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2285" LastActivityDate="2011-04-24T18:49:34.420" ClosedDate="2011-04-24T20:26:25.700" Title="Linux on a MCU, boards and examples" Tags="&lt;arm&gt;&lt;bluetooth&gt;&lt;linux&gt;&lt;xmega&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="13440" PostTypeId="1" AcceptedAnswerId="13466" CreationDate="2011-04-24T16:05:04.487" Score="3" ViewCount="179" Body="&lt;p&gt;I'm looking for an introductory book to CPU / microcontroller /microprocessor design. Any ideas? ARM or x86 are both great. I have a great assembler language book, but I'm looking for something more on the engineering level. Or maybe they're the same? Maybe it doesn't exist, or maybe I need to refine my question but anything would help. Thanks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: migrated from Superuser&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I'm coming from a basic programming background, but I'm looking for something on a more electrical-engineering level.&lt;/p&gt;&#xA;" OwnerUserId="3972" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-05T21:21:05.893" LastActivityDate="2011-05-05T21:21:05.893" Title="microcontroller / cpu design book?" Tags="&lt;microcontroller&gt;&lt;arm&gt;&lt;books&gt;&lt;microprocessor&gt;&lt;cpu&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="1" />
  <row Id="13441" PostTypeId="2" ParentId="13440" CreationDate="2011-04-24T17:11:58.313" Score="1" ViewCount="" Body="&lt;p&gt;For ARM I'd recommend &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0201675196&quot; rel=&quot;nofollow&quot;&gt;ARM System-on-chip Architecture&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-24T17:11:58.313" />
  <row Id="13442" PostTypeId="2" ParentId="13440" CreationDate="2011-04-24T17:14:16.583" Score="1" ViewCount="" Body="&lt;p&gt;In the textbook domain, &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0123744938&quot; rel=&quot;nofollow&quot;&gt;Computer Organization and Design&lt;/a&gt; is one of the classics. I'm not sure how well it works for self-study, though.&lt;/p&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-04-24T17:14:16.583" />
  <row Id="13443" PostTypeId="2" ParentId="13439" CreationDate="2011-04-24T17:40:41.027" Score="0" ViewCount="" Body="&lt;p&gt;You've left out another possible solution which is a micro-controller running an RTOS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm also not sure an xmega is a capable solution for the camera processing you'll need.  I don't know what your qrcode algorithm looks like but image processing is something that generally requires more processing power and memory than the xmega series supplies, you could use external memory to help that issue but the processing time may still be too slow.  Especially with a bluetooth stack running and other sensor acquisition capabilities required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to collect sensor data from the camera and the inertial sensor at the same time and/or close to real time then you will almost certainly need a more advanced device than the xmega as well as some sort of multiple process support via an operating system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a linux board I would recommend starting with the beagleboard as its probably the cheapest, most complete solution for what your trying to do and provides more than enough processing power to prototype your design.  After you've coded a solution you can make the determination as to how much power you really need as the beagleboard is definitely overkill.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a down side to going the linux route, you may need to be comfortable with coding drivers for your sensors / external devices unless you use devices that already have available drivers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Bluetooth:&lt;/strong&gt; You can likely use an off the shelf USB based bluetooth device which already has linux drivers.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Camera:&lt;/strong&gt; You can also probably use an off the shelf camera that plugs into the camera port on the beagleboard which I believe there are multiple choices for with ready to go drivers.  USB cameras are also an option.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Inertial Sensor:&lt;/strong&gt; This will probably end up being connected to the beagleboard expansion header via SPI/UART/I2C and will likely require you to develop a driver to expose the device via some sort of com port.  If you go the simple pass through com port route you probably don't need to do much driver coding other than to adapt an existing driver for your device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Flash:&lt;/strong&gt; All set here, the beagleboard has on board flash and an SD card slot and it can boot from either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Linux probably is drastic overkill for what your building but its probably the cheapest / fastest way to prototype your design.  A mass production version would probably use a much lower powered (cheaper) processor than the beagleboard offers and use a cut down RTOS in place of the full linux kernel.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-04-24T17:40:41.027" CommentCount="5" />
  <row Id="13444" PostTypeId="2" ParentId="13434" CreationDate="2011-04-24T17:44:53.120" Score="2" ViewCount="" Body="&lt;p&gt;This is called &lt;a href=&quot;http://www.phoenixcontact.com/global/pcb-connection/226_6950.htm&quot; rel=&quot;nofollow&quot;&gt;pin in paste&lt;/a&gt;. &#xA;It seems to be useful when reflow soldering is done anyway for surface mounted components.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-04-24T17:44:53.120" />
  <row Id="13445" PostTypeId="2" ParentId="13439" CreationDate="2011-04-24T18:49:34.420" Score="0" ViewCount="" Body="&lt;p&gt;check out &lt;a href=&quot;http://bifferos.bizhat.com/&quot; rel=&quot;nofollow&quot;&gt;bifferboard&lt;/a&gt; a nice small low power linux system. runs Openwrt, slackware or debian so you have a lot of software support.&lt;/p&gt;&#xA;" OwnerUserId="3974" LastActivityDate="2011-04-24T18:49:34.420" />
  <row Id="13446" PostTypeId="2" ParentId="13431" CreationDate="2011-04-24T19:45:51.333" Score="0" ViewCount="" Body="&lt;p&gt;Nowadays the best bet for DIY sound is probably something like an ARM chip with built-in DACs.  I'm not sure they're available in convenient packages for DIY work, but someone may make homebrewing modules with the parts pre-soldered and the DAC output pins exposed on a header.  An ARM should be able to do a decent job of generating multi-voice FM or wave-table synthesis, and probably throw in some FIR or IIR filtering as well.  FYI, I'm not familiar with the particular &quot;sound coprocessor IC&quot; mentioned, but I strongly suspect it's something like a PIC 18Fxx.  An ARM chip would be far more capable than that, probably for comparable cost.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-24T19:45:51.333" CommentCount="3" />
  <row Id="13447" PostTypeId="1" AcceptedAnswerId="13454" CreationDate="2011-04-24T21:26:30.807" Score="2" ViewCount="137" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for a capacitor to use as the output cap with this regulator: &lt;a href=&quot;http://uk.farnell.com/exar/sp6205em5-l-3-3/ic-v-reg-ldo-0-5a-3-3v-smd-6205/dp/9388338&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/exar/sp6205em5-l-3-3/ic-v-reg-ldo-0-5a-3-3v-smd-6205/dp/9388338&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It says it requires a 2.2uF capacitor, with an ESR less than 0.5 Ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've found this type of tantalum capactior which would suffice: &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=478-3127-1-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=478-3127-1-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However these are quite expensive, almost half the cost of the regulator... I wondered if these ceramics (it says ceramics are allowed in the spec) would have the low esr required (they say 'Low ESR' - but do not have a value specified.)&#xA;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=445-4585-1-ND&quot; rel=&quot;nofollow&quot;&gt;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=445-4585-1-ND&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone say what Low ESR would mean, at the frequencies involved with this regulator?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you very much for any help!&lt;/p&gt;&#xA;" OwnerUserId="3975" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-04-24T22:04:31.240" LastActivityDate="2011-04-26T18:29:27.210" Title="How is ESR specified on ceramic capacitors?" Tags="&lt;capacitor&gt;&lt;voltage-regulator&gt;&lt;ceramic&gt;&lt;esr&gt;" AnswerCount="3" />
  <row Id="13448" PostTypeId="1" CreationDate="2011-04-24T21:44:22.247" Score="1" ViewCount="47" Body="&lt;p&gt;I have an inmotion speaker set with embedded ipod dock circa 2006. I love it and it sounds great. But the dock does not work with the newer model ipods / iphone etc. I'd like to try my hand at hacking it to upgrade the dock. Any thoughts on how to do this? Seems to me that somehow I could replace the old connector with the part of the new one. &lt;/p&gt;&#xA;" OwnerUserId="2619" LastActivityDate="2011-04-25T14:00:12.630" Title="ipod dock upgrade for inmotion speakers unit" Tags="&lt;speakers&gt;&lt;ipod&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13449" PostTypeId="2" ParentId="13447" CreationDate="2011-04-25T00:34:44.287" Score="1" ViewCount="" Body="&lt;p&gt;The linked page does specify ESR, 300 milliOhm&lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2011-04-25T00:34:44.287" CommentCount="3" />
  <row Id="13450" PostTypeId="1" CreationDate="2011-04-25T00:56:29.357" Score="1" ViewCount="78" Body="&lt;p&gt;I'm looking at a few different stepper motors for an engineering project im working on ... and im attempting to tease out any correlations that a stepper motors stats would have with its max speed...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage, current, micro stepping on or off .. as well as the chip and driver all have an effect ( i believe ) ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;so is there a way i could take a datasheet from something like :&#xA;&lt;a href=&quot;http://www.anaheimautomation.com/manuals/stepper/L010469%20-%2017YPG%20Series%20Product%20Sheet.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.anaheimautomation.com/manuals/stepper/L010469%20-%2017YPG%20Series%20Product%20Sheet.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and calc the max torque and speed?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;the sheet says:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Speed of the output shaft (after gearbox) = (Motor Speed)/(Gear Ratio&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;but im unable to find a &quot;motor speed&quot; on the sheet.&lt;/p&gt;&#xA;" OwnerUserId="4067" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-27T20:58:51.840" LastActivityDate="2011-04-27T20:58:51.840" Title="With the case of stepper motors ... what correlates to the max RPM of the individual unit" Tags="&lt;motor&gt;&lt;driver&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="13452" PostTypeId="2" ParentId="13436" CreationDate="2011-04-25T01:34:24.577" Score="0" ViewCount="" Body="&lt;p&gt;Try a wireless router that can run DD-WRT/Openwrt - there are many with USB host capabilities and obviously wireless networking.  A compatibility list for OpenWRT is here: &lt;a href=&quot;http://wiki.openwrt.org/toh/start&quot; rel=&quot;nofollow&quot;&gt;http://wiki.openwrt.org/toh/start&lt;/a&gt; and for DD-WRT here: &lt;a href=&quot;http://www.dd-wrt.com/wiki/index.php/Supported_Devices&quot; rel=&quot;nofollow&quot;&gt;http://www.dd-wrt.com/wiki/index.php/Supported_Devices&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-25T01:34:24.577" CommentCount="3" />
  <row Id="13453" PostTypeId="2" ParentId="13450" CreationDate="2011-04-25T03:16:50.217" Score="5" ViewCount="" Body="&lt;p&gt;This particular datasheet doesn't provide much information about the power curve of the motor it describes.  A better example is &lt;a href=&quot;http://www.nmbtc.com/pdf/motors/standard_hybrid/17PM-K.pdf&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; (not endorsing the particular motor, just picked at random for the information it presents).   The important bit is the graph at the bottom of the second page, which shows, for each of the motors the datasheet describes, a curve relating frequency to torque, at a particular voltage-current.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reading that graph for the detail you need to know is basically straitforward.  You will need to know the torque you expect to need for your application, and find the corresponding frequency.  Each oscillation of input represents four full steps of motion, and since these motors are 1.8 deg/step, you can take that frequency and divide by 50 to get the RPM.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, supposing you needed about 0.2 Newton meters of torque, and went with the biggest motor on that datasheet, you would find that it could operate at about 2500 Hz, which equates to about 50 RPM.  However, it's usually wise to derate stepper motors in an open loop configuration to minimize the likelyhood of missing steps, so it might be best to run that motor at around 30 RPM so that you can have around 0.30 Nm at hand.&lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2011-04-25T03:16:50.217" />
  <row Id="13454" PostTypeId="2" ParentId="13447" CreationDate="2011-04-25T04:13:09.593" Score="2" ViewCount="" Body="&lt;p&gt;The part's datasheet says &quot;Unconditionally Stable with 2.2μF Ceramic&quot;, so I think you're good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Ceramics have lower ESR than tantalum or aluminum electrolytics.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Notice the note about increasing the capacitance if you decouple the BYP pin.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-25T04:13:09.593" CommentCount="1" />
  <row Id="13455" PostTypeId="2" ParentId="13124" CreationDate="2011-04-25T06:52:41.613" Score="1" ViewCount="" Body="&lt;p&gt;Oh, duh, I didn't read your code carefully -- your send SendLcdByte is wrong:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    void SendLcdByte( unsigned char command_0_or_data_1, unsigned char command)&#xA;{&#xA;    SendLcdUpperNibble( command_0_or_data_1, command);&#xA;    // send the lower nibble next&#xA; // AS WRITTEN:&#xA;    P1OUT = (command &amp;amp; 0x0F) | (P1OUT &amp;amp; 0xF0);&#xA; // SHOULD BE:&#xA;    P1OUT = ((command &amp;amp; 0x0F) &amp;lt;&amp;lt; 4) | (P1OUT &amp;amp; 0xF0);&#xA;    Strobe( command_0_or_data_1);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-25T06:52:41.613" CommentCount="6" />
  <row Id="13456" PostTypeId="1" AcceptedAnswerId="13457" CreationDate="2011-04-25T11:57:39.710" Score="1" ViewCount="79" Body="&lt;p&gt;Hello folks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am working on a design, but still in the prototype stage. In any case, I am using a straight Vero board and hence quite a lot of Jumper cables are involved even to its bearest minimum. I want to know the effect of the Jumpers when they are much? Actually my design is not actually behaving well as it ought to, so I am kind of thinking it my be as a result of this. It involves using MAx232 to transmit data's between a GSM module and microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And if there is possible an effect of jumpers, then how can I reduce it to a bearable minimum. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="3632" LastActivityDate="2011-04-25T13:15:39.620" Title="Using Jumpers wires in an Electronic design" Tags="&lt;jumper&gt;" AnswerCount="1" />
  <row Id="13457" PostTypeId="2" ParentId="13456" CreationDate="2011-04-25T12:13:35.173" Score="3" ViewCount="" Body="&lt;p&gt;RS-232 will be running comparatively slowly. Provided the MAX232 is properly decoupled and the connections are kept short the number of jumpers shouldn't matter. You probably have a wiring error with the capacitors; I prefer the MAX202 to the MAX232 as the former uses 100 nF ceramic capacitors. I never use Veroboard and often make my own prototype PCBs at home, I have a useful little board with a MAX202 on it that I can connect to anything that needs RS-232 conversion.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-25T13:15:39.620" LastActivityDate="2011-04-25T13:15:39.620" />
  <row Id="13458" PostTypeId="2" ParentId="13448" CreationDate="2011-04-25T14:00:12.630" Score="1" ViewCount="" Body="&lt;p&gt;Does it just not work at all, or does it just not charge?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to get audio out of the dock connector you have to have an apple security chip that authenticates with the iDevice before the iDevice will output any audio. It may be that the older devices that you talk about do not require this chip while newer do, or that the chip has changed. Either way, it is beyond hobbyist level to hack it if the security chip is the issue. In fact it is difficult for even the experience cryptographers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if it is an issue of it just not charging, then there is a hack that can be done with resistors on the data lines of the connector. I am pretty sure there is a question around here going over that, but I can not find a link to it at the moment.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-25T14:00:12.630" CommentCount="4" />
  <row Id="13459" PostTypeId="1" AcceptedAnswerId="13463" CreationDate="2011-04-25T14:49:38.967" Score="0" ViewCount="77" Body="&lt;p&gt;I have some carbon film resistors out of an electronics kit I got given and for a project I need 1/2 Watt of 4k7. Is there anyway I can test to see the power rating? I don't have any other resistors in stock atm so can't use 2 2k2 with 1/4 Watt.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-04-25T15:53:27.873" Title="Calculating power rating for resistors" Tags="&lt;resistor&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="13460" PostTypeId="2" ParentId="10478" CreationDate="2011-04-25T14:50:38.263" Score="0" ViewCount="" Body="&lt;p&gt;If you want red, green, yellow, and black, you could perhaps get a set of automotive door-lock actuators, and mount them at right angles to each other.  Have a yellow square that's always visible, and have the actuators slide red and green filters to either cover or uncover the square (both filters uncovering the square would yield yellow; red and green both covering would yield black; one or the other alone would yield that color).  Automotive door-lock actuators are designed to operate off twelve volts, but they would probably work acceptably at lower voltages; they would simply take longer to switch colors.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-25T14:50:38.263" CommentCount="1" />
  <row Id="13461" PostTypeId="2" ParentId="13459" CreationDate="2011-04-25T15:01:09.077" Score="1" ViewCount="" Body="&lt;p&gt;If you have a variable power supply, increase the voltage across it until it is dissipating 1/2W, and see if it is getting hot. About 17V will be required. You should be able to judge the power rating by the temperature rise at a given voltage (W = V^2/R)).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise, put it in the circuit, switch on for a short while and see if it gets hot. If the ones you have are about 10 mm long, they are probably 1/4W devices. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you test one and it doesn't have a high enough power rating, you could put four in series-parallel, if you have them, to increase the wattage.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-25T15:48:38.160" LastActivityDate="2011-04-25T15:48:38.160" CommentCount="4" />
  <row Id="13462" PostTypeId="1" AcceptedAnswerId="13464" CreationDate="2011-04-25T15:20:43.047" Score="2" ViewCount="71" Body="&lt;p&gt;I'm working on a product with a specified -40 to 85 degC temperature range, and I'd like to have a RTC with a coin cell or similar battery backup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Beyond that temperature range, damage to the battery is acceptable... as long as it doesn't explode under 125 degC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also believe that my initial client's industry has an aversion to the word &quot;lithium&quot;, so lithium-anything is potentially problematic.  (Unless I can point to something very authoritative saying it's perfectly safe and that it adds no hassles in shipping requirements)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It doesn't need to be rechargeable, really. It'd be a bonus, but not a requirement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What reasonably attainable battery fits these criteria?&lt;/p&gt;&#xA;" OwnerUserId="1270" LastActivityDate="2011-06-02T00:55:36.643" Title="Low current, long life batteries with an extended temperature range?" Tags="&lt;battery&gt;" AnswerCount="3" />
  <row Id="13463" PostTypeId="2" ParentId="13459" CreationDate="2011-04-25T15:31:18.277" Score="2" ViewCount="" Body="&lt;p&gt;Unfortunately answer is no.  There is no quick test you can perform to figure out the wattage of the resistor.  Based on the appearance you can make an educated guess, but that's all it is, a guess.  The only way to be 100% sure is if it's marked or you happen to have the manufacturer's part number and can look it up in the datasheets.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-25T15:31:18.277" CommentCount="1" />
  <row Id="13464" PostTypeId="2" ParentId="13462" CreationDate="2011-04-25T15:52:31.860" Score="2" ViewCount="" Body="&lt;p&gt;You'll have to do some searching to find exactly what you want, but it's out there.  For example, here's a link to some Panasonic batteries that work from -40 to +125 deg C:  &lt;a href=&quot;http://www.panasonic.com/industrial/batteries-oem/oem/primary-coin-cylindrical/high-operating-temperature.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.panasonic.com/industrial/batteries-oem/oem/primary-coin-cylindrical/high-operating-temperature.aspx&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That web page doesn't say it's lithium, but odds are that it is.  That might be one thing that your client will just have to deal with.  Lithium is no less reliable than other chemistries.  That being said, there are other battery chemistries like Silver Oxide, Zinc Air, and Alkaline Manganese that might work for you-- but a quick search of the Duracell web site didn't return any temperature data for those.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other option is to do some out of the box thinking.  Maybe a small solar cell plus supercap.  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-25T15:52:31.860" CommentCount="3" />
  <row Id="13466" PostTypeId="2" ParentId="13440" CreationDate="2011-04-25T17:06:45.760" Score="3" ViewCount="" Body="&lt;p&gt;I happen to be working on something like this but am not ready to release any of it yet. (at least not publicly) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think you need to edit/refine your question though.  Taking a general stab at the question.  I would start with something simpler than both the ARM and x86, and would avoid x86 all together.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having an assembler book implies you are a programmer or have some programming skills.  I dont know if your question is more from the programming side or digital design side.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are coming from the programmer side, I would start by learning assembler for the msp430, and arm or thumb (dont mess with x86 just yet, it is not a good architecture), maybe PIC (older pic, not the dspic nor the pic32).  Then write a disassembler and/or an instruction set simulator.  if it is just a dissassembler choose a non-variable word length instruction set like the ARM or thumb (yes if you think about it you can handle that branch instruction) or the PIC.  Eventually write an instruction set simulator, at least enough of one to implement a handful of instructions and a branch, make a loop see it execute.  Then go study up on state machines and re-write the simulator using state machines.   I have an instruction set simulator, not necessarily, completely, state machine based, but might give you the feel for what I am talking about.  search for thumbulator at github.  My username is dwelch67 there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;if you are approaching this from an electrical engineer perspective, you might want to look at opencores.  The readability and other features of the hdl may be difficult but it is out there to be consumed.  verilator and icarus verilog are good verilog simulators.  I like verilator more partly because it is so rigid with the verilog parsing and second it is super easy to cross the C/C++ and HDL boundary for writing software to talk to the hardware being simulated, and other reusable type things.  There is a tiny one called mcpu or something like that that the whole thing fits on about a page of paper if printed.  You really have to wrap your head around how to write a program with only one or two real operations (I think it only has a NOR).  If you are an electrical engineer and need a crash course in digital, the transistors are always saturated, basically they are used as electrically controlled switches.  Take a pair of them with some wiring and other components and you can make AND, and OR gates, add an inverting transistor and make a NOT gate allowing NAND and NOR.  You will want to learn about state machines if you dont already know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general you need to understand basic logic AND, OR, NOT, etc.  Learn about state machines which work just fine either with software or hardware, the concept is the same.  Reset and clocking are actually part of the state machine learning, getting the state machine going and thinking in terms of each pass through the logic/code is a clock cycle in the cpu and you state variables are used on each pass to indicate what to do during that clock cycle, what is the current state, and based on the current state and inputs what is the next state going to be, etc.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-04-25T17:06:45.760" CommentCount="1" />
  <row Id="13467" PostTypeId="2" ParentId="13462" CreationDate="2011-04-25T17:16:14.877" Score="0" ViewCount="" Body="&lt;p&gt;What kind of battery capacity and RTC duration do you need?  If your duration is short enough, a super-capacitor might be the better way to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, double check the regulations on lithium batteries.  The rules keep changing around - I don't know the exact state of things today, as I haven't looked at making a new RTC circuit in a few years - but many batteries are sufficiently low-energy that they are allowed for air shipment.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Coin batteries, IIRC, are ok. I believe your first step is to e-mail your battery supplier (in my case, it was Panasonic, via Digikey) to ask for their latest document on safety and transportability.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-25T17:16:14.877" />
  <row Id="13468" PostTypeId="1" CreationDate="2011-04-25T17:30:21.153" Score="3" ViewCount="73" Body="&lt;p&gt;I have been looking into using &lt;a href=&quot;http://en.wikipedia.org/wiki/Low-density_parity-check_code&quot; rel=&quot;nofollow&quot;&gt;LDPC's&lt;/a&gt; in some of my projects and have had some questions come up. Currently my structure looks something like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/gABpq.png&quot; alt=&quot;Message&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am then able to have hardware wake when it sees the preamble, read the length byte, and even check CRC for me before my processor has to handle the packet at all. This takes a lot of load off of processing time as well as code writing time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I am wondering is if there is any hardware out there that can use LDPC or any other correction code in a similar manner to what I am currently doing. Preferably it would be included with the wireless module, especially if it is able to do some soft decoding, but I am starting to think there isn't anything out there that does that currently. Because of this I am also open to &quot;in-line&quot; hardware that can assist with this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, know of anything?&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-25T18:03:44.730" Title="How can I add ECC to my packets?" Tags="&lt;communication&gt;&lt;error-correction&gt;" AnswerCount="1" />
  <row Id="13469" PostTypeId="2" ParentId="13410" CreationDate="2011-04-25T17:50:22.483" Score="3" ViewCount="" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your problem is that you are &lt;em&gt;mixing combinational and sequential logic&lt;/em&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each process should either be combinational, or sequential. Sequential processes have everything (except the reset statements inside a clock detection (&lt;code&gt;if rising_edge(clk)&lt;/code&gt; or &lt;code&gt;if clk'event and clk='1'&lt;/code&gt;). Combinational processes have a sensitivity list that contains all signals that you read.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While your code is perfectly &lt;em&gt;legal&lt;/em&gt; and even &lt;em&gt;deterministic&lt;/em&gt;, there is no easy way to predict how it will be synthesized, so it is &lt;em&gt;not suited for RTL code&lt;/em&gt;.&lt;/p&gt;&#xA;" OwnerUserId="3145" LastActivityDate="2011-04-25T17:50:22.483" CommentCount="1" />
  <row Id="13470" PostTypeId="2" ParentId="13468" CreationDate="2011-04-25T18:03:44.730" Score="1" ViewCount="" Body="&lt;p&gt;What is the physical representation of bits being sent?  In many cases, intra-packet error-correcting codes will be useless because even a transient glitch will cause many bits to be misinterpreted--quite possibly all bits until the next synchronization mark.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If forward error correction is needed, and packets are of uniform size, the simplest approach may be to send n packets worth of data using n+1 packets--each labeled with a packet number--where the (n+1)th packet contains the xor of the other ones.  If the first n packets are read successfully, ignore the extra one.  Otherwise, if one packet is missing or corrupted, infer its value by xor'ing the remaining n packets together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A slight improvement of this approach would be to send 2n packets worth of data using 2n+2 packets, interleaving two sets of n+1 packets, each set being formulated as above.  That would guarantee recovery from any single communications glitch which was no longer than the time required to send a single packet (a short glitch might hit the end of one packet and the start of the next, but the two packets would be in different xor-groups).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The biggest limitation with this approach is that packets must be assembled into groups (or, putting it another way, what could otherwise be larger packets must be subdivided into smaller ones).  On the other hand, it is robust against glitches that would cause synchronization loss render large amounts of data unreadable.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-25T18:03:44.730" CommentCount="7" />
  <row Id="13471" PostTypeId="1" AcceptedAnswerId="13473" CreationDate="2011-04-25T18:19:08.783" Score="3" ViewCount="117" Body="&lt;p&gt;I've noticed that if there's not a good connection between my jack and the port, like if it's dirty or half plugged in, then the sound is different, but there is still sound, and sometimes twisting it around makes it sound better. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why is that? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was looking at some schematics of a 3.5mm headphone jack, but it doesn't look like there's a &quot;this part of the jack gets the treble&quot; thing going on. You'd think that if there's a signal at all, it doesn't matter which way the jack is twisted since it's a ring inside a ring anyway. &lt;/p&gt;&#xA;" OwnerUserId="3981" LastActivityDate="2011-04-25T18:45:47.890" Title="Why do speakers sound different when they're not fully plugged in?" Tags="&lt;audio&gt;&lt;signal&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="13472" PostTypeId="1" AcceptedAnswerId="13477" CreationDate="2011-04-25T18:45:01.480" Score="5" ViewCount="207" Body="&lt;p&gt;Can we make something like chip reader, which can understand chip design and generate blueprint of it?&lt;/p&gt;&#xA;" OwnerUserId="3982" LastActivityDate="2011-04-25T21:47:42.720" Title="Is there possible to reverse engineer a chip design?" Tags="&lt;reverse-engineering&gt;&lt;chip&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="2" />
  <row Id="13473" PostTypeId="2" ParentId="13471" CreationDate="2011-04-25T18:45:46.627" Score="4" ViewCount="" Body="&lt;p&gt;The simple answer is:  Changes in resistance/impedance at the connector or cable can change the actual or perceived frequency response that you hear from the speaker.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of the actual frequency response:  The connector and stuff inside the speaker form an &lt;a href=&quot;http://en.wikipedia.org/wiki/Low-pass_filter&quot; rel=&quot;nofollow&quot;&gt;RC filter&lt;/a&gt; (a low-pass filter).  The connector is the R and the stuff inside the speaker is the C.  As R goes up, the cutoff frequency of the low-pass filter goes up.  Normally, the R is less than 1 ohm, so the cutoff frequency is very low (less than 5 Hz).  But if the connector is bad or dirty then the R could be several hundred ohms, which could increase the cutoff frequency by several hundred times.  The net effect is that the bass is all cut out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And for perceived frequency response:  Human hearing is very weird.  &lt;a href=&quot;http://en.wikipedia.org/wiki/Loudness&quot; rel=&quot;nofollow&quot;&gt;At low volume levels, our ears simply don't pick up some frequencies very well&lt;/a&gt;-- usually the low and high frequencies.  We're more sensitive to mid frequencies.  So, as you reduce the volume level we perceive that the low and high frequencies are being cut out more than the middle frequencies.  The &quot;Loudness&quot; button of a stereo attempts to compensate for this by boosting those frequencies and therefore making us hear a more balanced sound at low listening levels.  If the connector is bad or dirty, less power will be making it to the speaker and causing a lower volume level.  But due to human hearing, we would also hear less low and high frequencies-- making it sound like we're listening through a phone or something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is an over-simplified answer, but reasonably accurate for your purposes.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-25T18:45:46.627" CommentCount="4" />
  <row Id="13474" PostTypeId="2" ParentId="13471" CreationDate="2011-04-25T18:45:47.890" Score="3" ViewCount="" Body="&lt;p&gt;For the case of it being dirty, turning the jack will many times help get a better connection. The reason it actually sounds poor is that the dirtiness causes noise to be added, signal to be cut, and a filter to be generated. There are different types of filters like low pass, band pass, high pass, etc. Depending on how the poor connection is made it can cause an effective filter. Also depending on how you have the jack turned there will be different characteristics of noise and signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the case of it being half plugged in, you end up with things connecting to places they shouldn't be. Many times the Left and Right channel will get shorted together which can cause some phase cancellation, you can also end up with ground shorting the channels, but it can be a light short, which in turn will cause an effective filter as well.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-25T18:45:47.890" />
  <row Id="13475" PostTypeId="2" ParentId="13472" CreationDate="2011-04-25T18:50:40.850" Score="3" ViewCount="" Body="&lt;p&gt;Yes.  There are companies out there that specialize in this.  This is done all the time, although it's more of an art than a science.  Usually they do some wacky chemical and mechanical etching process to progressively strips off the layers of the chip (like the layers of a PCB)-- taking detailed photos of each layer.   Normally, these companies do it to help people like T.I. and Intel figure out why their own chips are failing, but you can bet that there is some illegal uses of this too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an interesting and relevant article that I just ran across:  &lt;a href=&quot;http://www.forbes.com/forbes/2005/0328/068.html&quot; rel=&quot;nofollow&quot;&gt;http://www.forbes.com/forbes/2005/0328/068.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And another link:  &lt;a href=&quot;http://www.siliconinvestigations.com/ref/ref.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.siliconinvestigations.com/ref/ref.htm&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="3624" LastEditorDisplayName="" LastEditDate="2011-04-25T18:56:55.057" LastActivityDate="2011-04-25T18:56:55.057" CommentCount="3" />
  <row Id="13476" PostTypeId="2" ParentId="13472" CreationDate="2011-04-25T19:39:56.637" Score="0" ViewCount="" Body="&lt;p&gt;Another way to copy a chip design is to emulate its functionality using an FPGA. Many emulations of older chips like the Z80 and 6502 are available. Some students  even produced their own version of an ARM device and made it available via the Web, but had to delete it when ARM threatened legal action.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-25T19:39:56.637" CommentCount="2" />
  <row Id="13477" PostTypeId="2" ParentId="13472" CreationDate="2011-04-25T21:40:22.340" Score="6" ViewCount="" Body="&lt;p&gt;ChipWorks has an excellent blog about doing exactly this, with lots of great pictures &lt;a href=&quot;http://www.chipworks.com/en/technical-competitive-analysis/resources/technology-blog/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;FlyLogic also has an excellent blog. It is &lt;a href=&quot;http://www.flylogic.net/blog/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The short answer is it is absolutely possible. IC DIEs are basically really small circuit boards. You can reverse engineer them pretty easily, it just takes a different tool set.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to particularly call attention to some posts flylogic did on reverse-engineering ICs (how topical!) &lt;a href=&quot;http://www.flylogic.net/blog/?p=63&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://www.flylogic.net/blog/?p=32&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.flylogic.net/blog/?p=63&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.imgur.com/IV7iR.jpg&quot; alt=&quot;Image borrowed from flylogic&quot;&gt;&lt;/a&gt;&lt;br&gt;&#xA;&lt;sup&gt;Image from flylogic website&lt;/sup&gt;&lt;/p&gt;&#xA;" OwnerUserId="1374" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-04-25T21:47:42.720" LastActivityDate="2011-04-25T21:47:42.720" CommentCount="1" />
  <row Id="13478" PostTypeId="2" ParentId="12832" CreationDate="2011-04-25T21:42:48.157" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://members.misty.com/don/light.html&quot; rel=&quot;nofollow&quot;&gt;Don's Lighting Page&lt;/a&gt; has a lot of information on lamps from a DIY perspective.  If there isn't a driver circuit listed in this site, you probably can't do it as a hobby.&lt;/p&gt;&#xA;" OwnerUserId="3983" LastActivityDate="2011-04-25T21:42:48.157" CommunityOwnedDate="2011-04-25T21:42:48.157" CommentCount="1" />
  <row Id="13481" PostTypeId="2" ParentId="12095" CreationDate="2011-04-25T23:36:32.423" Score="0" ViewCount="" Body="&lt;p&gt;Very likely the display is driven directly from an MCU with an LCD-drive output.  The resistance of an LCD segment is typically in the meg-ohms range.  As a quick test, you can try applying about 3V to various pin pairs until you get a segment to change.  If that fails, try 12V.  You will have to then experiment with the voltage until you get the correct excitation voltage.  Then, you'll need to modulate the drive waveform so that the LCD will get a 0-DC average voltage across it - otherwise, it will eventually die.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-25T23:36:32.423" />
  <row Id="13482" PostTypeId="1" AcceptedAnswerId="13487" CreationDate="2011-04-26T00:22:27.250" Score="2" ViewCount="178" Body="&lt;p&gt;Hello,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I work in a research lab where we occasionally need to develop electronic driver boards for quantum cascade lasers. The type of signal these handle are digital data streams up to around 10 MHz and output drive current up to 100 ma or so. The board needs to interface with Altera development boards using their proprietary hsmc connector. We have some preliminary designs that work on a soldered breadboard, but the lack of a proper PCB is causing ringing and overshoot, etc. (there are some SMDs involved). Since I'm primarily a software engineer, I'm looking for a basic how-to on spining prototype PCBs using modern tools. Any help appreciated.&lt;/p&gt;&#xA;" OwnerUserId="3985" LastActivityDate="2011-04-26T10:24:04.543" Title="Low-cost PCB prototyping" Tags="&lt;pcb-fabrication&gt;&lt;pcb-design&gt;&lt;eda&gt;" AnswerCount="2" CommentCount="11" />
  <row Id="13483" PostTypeId="2" ParentId="11706" CreationDate="2011-04-26T07:53:52.093" Score="-1" ViewCount="" Body="&lt;p&gt;According to &lt;a href=&quot;http://en.wikipedia.org/wiki/Unijunction_transistor&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Unijunction transistor circuits were popular in hobbyist electronics circuits in the 1960s and 1970s because they allowed simple oscillators to be built using just one active device. … Later, as integrated circuits became more popular, oscillators such as the 555 timer IC became more commonly used.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://en.wikipedia.org/wiki/555_timer_IC&quot; rel=&quot;nofollow&quot;&gt;555 Timer&lt;/a&gt; is probably the easiest way to build an oscillator, programmable or not. It can be bought at Radio Shack, or anywhere chips are sold. Instructions can be found in Wikipedia, various datasheets published by its many manufacturers, or hobbyist websites. It's old as rocks. Calculate the waveform and frequency you want and smooth with a resistor + capacitor if necessary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I remember when I was a 10-year-old electronic hobbyist and Mac programmer. I guess some things don't change! Have tons of fun.&lt;/p&gt;&#xA;" OwnerUserId="3835" LastActivityDate="2011-04-26T07:53:52.093" CommentCount="3" />
  <row Id="13484" PostTypeId="2" ParentId="13482" CreationDate="2011-04-26T09:10:58.227" Score="4" ViewCount="" Body="&lt;p&gt;For the software side take a look at KiCAD, it's Free and runs on Linux, OSX and even Windows, it's about as clunky as any other EDA package, but you can't beat the cost and it has no artificial limitations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the fabrication side take a look at ITead, they do really cheap double sideded PCBs in about two to three weeks including shipping:&#xA;&lt;a href=&quot;https://github.com/dren-dk/HAL900/wiki/Quirks-of-PCB-manufacturing-at-ITead&quot; rel=&quot;nofollow&quot;&gt;https://github.com/dren-dk/HAL900/wiki/Quirks-of-PCB-manufacturing-at-ITead&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-04-26T09:10:58.227" />
  <row Id="13485" PostTypeId="1" AcceptedAnswerId="13486" CreationDate="2011-04-26T09:43:49.480" Score="2" ViewCount="75" Body="&lt;p&gt;I have a board which has these holes in them for interfacing with other components. I would like to reuse this board in the future for other uses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is soldering breakaway headers onto these holes the standard for prototyping? If not, what other options do I have and where can i buy it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/117&quot; rel=&quot;nofollow&quot;&gt;Breakaway headers&lt;/a&gt; sold at SparkFun.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/oKwmm.jpg&quot; alt=&quot;Breakout holes&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3926" LastActivityDate="2011-04-26T12:38:44.533" Title="Are breakaway headers the standard for interfacing when prototyping with these holes?" Tags="&lt;pcb&gt;" AnswerCount="1" />
  <row Id="13486" PostTypeId="2" ParentId="13485" CreationDate="2011-04-26T09:59:51.237" Score="3" ViewCount="" Body="&lt;p&gt;Those connectors will probably be a loose fit in the holes, and they aren't very robust. &#xA;Headers like &lt;a href=&quot;http://www.rapidonline.com/Cables-Connectors/Connectors-Multipole/PCB-Interconnect/Double-row-PCB-header-plug-2.54mm-pitch./28945&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; are probably intended for use with that board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They have 0.64 mm square pins. Check the hole size with the board supplier to make sure. I use 0.9 mm holes for those connectors on my PCBs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They are available from other suppliers as 2x20, or use shorter lengths as they are end-stackable. You can attach ribbon cable, or use double-row sockets like &lt;a href=&quot;http://www.rapidonline.com/Cables-Connectors/Connectors-Multipole/PCB-Interconnect/Double-row-sockets/76076&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; on a mating PCB.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-26T12:38:44.533" LastActivityDate="2011-04-26T12:38:44.533" CommentCount="1" />
  <row Id="13487" PostTypeId="2" ParentId="13482" CreationDate="2011-04-26T10:15:51.263" Score="3" ViewCount="" Body="&lt;p&gt;Try &lt;a href=&quot;http://uk.rs-online.com/web/generalDisplay.html?id=DesignSpark-Jan11&amp;amp;cm_sp=Homepage-uk-_-RightColumnBanner-_-DesignSpark&quot; rel=&quot;nofollow&quot;&gt;DesignSpark &lt;/a&gt; (it's free) from RS. It's based on Number One Systems' Easy-PC, which I used for many years. It generates standard Gerber and Excellon drill files which can be sent to any PCB supplier. You need to set it up for your supplier's design rules (track widths, hole sizes, etc.) of course, as with any PCB software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For your PCBs, I recommend &lt;a href=&quot;http://www.pcb-pool.com/&quot; rel=&quot;nofollow&quot;&gt;PCB Pool&lt;/a&gt;. They aren't the cheapest, but their boards are very high quality, and their customer service is superb if there are any problems.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-26T10:24:04.543" LastActivityDate="2011-04-26T10:24:04.543" CommentCount="1" />
  <row Id="13488" PostTypeId="1" CreationDate="2011-04-26T12:16:35.387" Score="3" ViewCount="101" Body="&lt;p&gt;I wanted to use a tiny Linux computer to read data from I²C bus. I knew there was Picotux, and I was thingking about buying one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/36dgs.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the website is down, so I guess there's no Picotux anymore. :(&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since Picotux is gone, are there alternatives around, that house a Linux computer in a tiny package, such as Picotux?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need a tiny package, it should run on batteries and consume little power, and have a I²C or USB bus available. Bonus points if it has WLAN (which Picotux had as an option).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should be able to run a webserver (a tiny one, not a behemoth as Apache) and RRDtool if possible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Picotux was available at the now defunct website: &lt;a href=&quot;http://www.picotux.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.picotux.com/&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2134" LastActivityDate="2011-04-26T21:58:03.023" Title="Picotux alternatives available?" Tags="&lt;microcontroller&gt;&lt;ethernet&gt;&lt;i2c&gt;&lt;linux&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="2" />
  <row Id="13489" PostTypeId="1" AcceptedAnswerId="13490" CreationDate="2011-04-26T12:39:36.927" Score="0" ViewCount="76" Body="&lt;p&gt;Capacitor-input filters are a common thing. However, what is the theory behind this and can someone show me some evidence of before and after using them? I read the &lt;a href=&quot;http://en.wikipedia.org/wiki/Capacitor-input_filter&quot; rel=&quot;nofollow&quot;&gt;wikipedia&lt;/a&gt; page on this and it seems a bit technical for a new comer - too many concepts at once. Can anyone care to explain more simply?&lt;/p&gt;&#xA;" OwnerUserId="3926" LastActivityDate="2011-04-26T13:01:40.700" Title="Evidence for using capacitor-input filters?" Tags="&lt;capacitor&gt;&lt;filter&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13490" PostTypeId="2" ParentId="13489" CreationDate="2011-04-26T12:45:55.817" Score="1" ViewCount="" Body="&lt;p&gt;It's a low-pass filter which attenuates high-frequency signals and allows low-frequency signals to pass through it. Basically, the capacitors pass high frequencies better than low frequencies so high frequencies are shunted to ground, and don't appear on the output. The inductor works in the opposite fashion, and passes low-frequency signals much better than high-frequency ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you find the theory behind that type of filter difficult, make one for yourself and try it out with a suitable signal generator and oscilloscope.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where I once worked, I designed a system that met all the EMC requirements in our preliminary testing, apart from a VHF emission from the RS-232 cables that connected it to the host PC. An additional little PCB by the RS-232 connector with Pi filters as in that article solved the problem and the system passed the formal tests without any problems.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-26T12:53:38.757" LastActivityDate="2011-04-26T12:53:38.757" />
  <row Id="13491" PostTypeId="2" ParentId="13489" CreationDate="2011-04-26T13:01:40.700" Score="2" ViewCount="" Body="&lt;p&gt;I'm not going to explain the pi configuration, but you can understand much of its function when you look at the individual components.&lt;br&gt;&#xA;The impedance of a capacitor is inversely proportional with frequency: the higher the frequency, the more it conducts. So high frequency disturbances are shortcut to ground. Also, the impedance of the coil is proportional with frequency: the higher the frequency the less it conducts. So the high frequency disturbances which haven't been filtered away by the capacitor will be blocked by the coil.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-26T13:01:40.700" />
  <row Id="13492" PostTypeId="2" ParentId="13488" CreationDate="2011-04-26T13:06:55.343" Score="3" ViewCount="" Body="&lt;p&gt;The &lt;A href=&quot;http://en.wikipedia.org/wiki/Digi_Connect_ME&quot; rel=&quot;nofollow&quot;&gt;Digi Connect ME&lt;/a&gt; is a similar device.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;With respect to software development&#xA;  options, in addition to NET+OS, the&#xA;  Digi Connect ME 9210 now also provides&#xA;  a complete Embedded Linux development&#xA;  environment with an Eclipse based IDE.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://www.newark.com/productimages/nio/standard/4734618.jpg&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.newark.com/jsp/search/productdetail.jsp?SKU=94M6849&amp;amp;CMP=AFC-GB100000001&quot; rel=&quot;nofollow&quot;&gt;http://www.newark.com/jsp/search/productdetail.jsp?SKU=94M6849&amp;amp;CMP=AFC-GB100000001&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-04-26T21:58:03.023" LastActivityDate="2011-04-26T21:58:03.023" CommentCount="3" />
  <row Id="13493" PostTypeId="1" CreationDate="2011-04-26T14:30:34.390" Score="2" ViewCount="92" Body="&lt;p&gt;I'm familiar with using ground planes when designing circuit boards.  I've started used power planes for the predominant voltage in a couple of my designs, and I'm wondering if that's a bad idea.  I'm only working with 2-layer boards, and I've found that putting a ground plane on one layer and a power plane on the other layer makes placing components much simpler.  I've been building low-density boards with only low-frequency digital signals, and very few (if any) analog signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the pros and cons?&lt;/p&gt;&#xA;" OwnerUserId="51" LastActivityDate="2011-04-26T14:57:19.087" Title="What are the drawbacks to a Vcc (positive voltage) plane?" Tags="&lt;layout&gt;&lt;pcb-design&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13494" PostTypeId="2" ParentId="13493" CreationDate="2011-04-26T14:46:29.937" Score="2" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;Supply nets:&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Pro:&lt;/strong&gt; For supplying nets on your PCB (as opposed to signals that are routed with respect to GND), a supply plane is just as important as a ground (return) plane. Remember that currents always flow in loops, and in the case of copper planes, the loops include both the supply plane and the ground plane. In this case, think of the two planes for VCC and GND as a capacitor that stabilizes your supply rails for all the ICs and everything else.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Con:&lt;/strong&gt; Polygons (planes) for VCC and GND need a lot of space and may not be necessary when you're just doing low speed stuff.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Signal nets:&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The reason for planes with signal nets is that they act as a shield, or they form a strip line with the signal lines, creating a defined impedance. In these cases, you don't use planes that also carry supplying current for other parts of your board because these currents will influence your precious and sensitive analog signals; instead, you connect the planes in a way that returns nothing but the return current of any field the planes &quot;catch&quot;. A &quot;star grounding&quot; technique might be one option to accomplish this. Theoretically, a plane connected to VCC will act just as well as a plane connected to GND, it just needs a good (low impedance) path to &lt;em&gt;any&lt;/em&gt; stable voltage. In practice, it will often be much easier to use GND for this purpose.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-26T14:57:19.087" LastActivityDate="2011-04-26T14:57:19.087" />
  <row Id="13495" PostTypeId="1" CreationDate="2011-04-26T14:47:56.893" Score="0" ViewCount="103" Body="&lt;p&gt;I am planning to buy a netduino or FEZ Panda for an embedded project. In your experience using both which do you prefer between the two?&lt;/p&gt;&#xA;" OwnerUserId="2480" LastActivityDate="2011-04-26T14:47:56.893" ClosedDate="2011-04-26T15:50:57.193" Title="Which do you prefer, netduino or FEZ Panda?" Tags="&lt;embedded&gt;&lt;netduino&gt;&lt;.net-micro-framework&gt;" FavoriteCount="0" />
  <row Id="13496" PostTypeId="2" ParentId="13493" CreationDate="2011-04-26T14:51:30.417" Score="0" ViewCount="" Body="&lt;p&gt;With proper decoupling Vcc is as good as ground as far as EMI is concerned. So an extra plane is a good thing. However, if you're working on only two layers the plane may be cut into several islands. Try to keep connections as short as possible.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-26T14:51:30.417" />
  <row Id="13497" PostTypeId="2" ParentId="11334" CreationDate="2011-04-26T15:00:37.240" Score="0" ViewCount="" Body="&lt;p&gt;Many video devices are AC coupled on the inputs and outputs; it might be nice if that weren't the case, but in practice unless one knows one will only be accepting signals from devices with DC-coupled inputs, one has to accept AC-coupled signals.  Further, in many cases, if one will have to deal with AC-coupled signals, it's often helpful to AC-couple one's own input stage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If one has positive and negative supply rails available, the easiest approach is probably to have the input (past the coupling capacitor) pulled weakly to the negative supply and have a clamp diode to a point about 0.35 volts above ground.  The effect will be a signal where the lowest parts of the signal are at -0.35 volts.  This will make it easy to detect sync signals, and will provide a usable (though not wonderful) black reference for superimposing opaque video.  If negative supply isn't available, one could use a pulldown to VSS and clamp to 3 volts or so and expect all levels to be shifted.  The sync detection from this approach is fine; the biggest weaknesses are:&#xA;&lt;ol&gt;If the pulldown sinks much current, the end of each line will be made a little darker than it should be; if it doesn't, the circuit may be slow to deal with shifts in the input DC bias;&lt;/p&gt;&#xA;&#xA;One has to 'guess' the difference between the input signal's sync level and black level.  Ideally the sync voltage will be 0.34 volts below the black level, but not all video output devices are perfectly &quot;to spec&quot;.&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If one wants broadcast-quality video, one should decode the sync signals in a way that won't disrupt the original video (e.g. by passing it through a buffer and then AC coupling it to the described clamp circuit), and then ground an AC coupled output briefly after each rising edge of the sync signal (about 500ns if one doesn't have a 3.579MHz notch-reject filter, or 4.5us if one does).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-26T15:00:37.240" />
  <row Id="13498" PostTypeId="2" ParentId="12095" CreationDate="2011-04-26T15:30:20.107" Score="1" ViewCount="" Body="&lt;p&gt;If the display was a segmented display, and it has less than 64 segments total, you could try connecting pairs of pins through a 1K resistor to a function generator outputting +/- 5 volts.  If you hit a row and a column, you should see one segment become somewhat dark, and possibly some other segments become less dark.  If you hit a row and a row or a column and a column you may or may not see two or more segments become somewhat dark.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the display is a dot matrix, it probably has a driver or controller.  Without a working device to examine it in, I'd regard it as junk.  If you had a working device, you could easily determine which pins are for power, and probing the other pins would let you see whether the waveforms look like those of a driver or controller, and what pins seem to be doing what.  Without that, it might be possible to experiment with the device and figure things out, but if you guess wrong about things you could unknowingly damage the device, rendering further experimentation useless, and consequently waste a lot of time.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-26T15:30:20.107" />
  <row Id="13499" PostTypeId="2" ParentId="13290" CreationDate="2011-04-26T17:11:13.487" Score="1" ViewCount="" Body="&lt;p&gt;Checkout this Microchip application note (AN873) for the MCP2515.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en012112&quot; rel=&quot;nofollow&quot;&gt;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=1824&amp;amp;appnote=en012112&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-04-26T17:11:13.487" />
  <row Id="13500" PostTypeId="1" AcceptedAnswerId="13527" CreationDate="2011-04-26T17:53:05.523" Score="7" ViewCount="145" Body="&lt;p&gt;If there's any EMI/SI lesson I've taken in, it's to minimize return loops as much as possible. You can work lots of EMI/SI guidelines from that one simple statement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, not having or ever even seen Hyperlynx or any sort of full RF simulation tool... it's somewhat hard to imagine what specifically I need to concentrate on.  My knowledge is also entirely book/internet based...  not formal or based on too many discussions with experts so I likely have weird conceptions or gaps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As I imagine it, I have two main components to a return signal. The first is a low frequency (DC-ish) return signal that follows generally as you'd expect...  along the lowest resistance path through the power network/plane. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second component is a high frequency return signal which tries to follow the signal trace on the ground plane. If you switch layers from say the top layer through to the bottom layer on a 4 layer board (signal, ground, power, signal) the HF return signal will as I understand it try to jump from the ground plane to the power plane by detouring through nearest available path (nearest decoupling cap, hopefully... which to HF might as well be a short).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suppose if you put these two components into terms of inductance, then it's all the same thing really (near DC resistance is all that matters, at HF lower inductance means following along underneath the trace)..  but it's easier for me to imagine them separately as two different modes to deal with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I'm okay so far, then how does that work on internal signal layers with two adjacent planes?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a 6 layer board (signal, ground, power, signal, ground, signal).  Every signal layer has an adjacent ground plane that is entirely unbroken (except for vias/holes, obviously).  The middle signal layer also has an adjacent power plane.  The power plane is split up into several regions.  I tried to keep that to a minimum, but my 5V split for instance takes the form of a large thick &quot;C&quot; shape around the outside of the board. Most of the rest is 3.3V, with a 1.8V region under most of a large BGA, with a very small 1.2V region near the center of that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;(1)&lt;/strong&gt; Will my split power plane cause me issues even if I focus on ensuring the signals have good return paths through the ground planes? &lt;strong&gt;(2)&lt;/strong&gt; Will the low frequency return path taking a wide detour on my &quot;C&quot; shaped 5V plane split cause trouble? (I'd generally think no... ?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can imagine that two unbroken planes with nearly equal inductance would possibly induce return current to flow in both... but my wild guess is that any significant detour required on the power plane would make the return signal heavily bias itself towards the ground plane. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;(3)&lt;/strong&gt; Also, the middle and bottom layers share the same ground plane. How big a problem is that?  I'd intuitively guess that traces directly over eachother sharing the same ground return would interfere with eachother more than simple adjacent trace coupling on the same layer. Do I need to work extra hard there to make sure that doesn't happen?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd suspect there may be a &quot;yeah generally, but you can't know without simulating it&quot; comment coming...  let's just assume I'm talking generally.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; Oh, I just thought of something. Would crossing a power plane split screw up trace impedance for stripline?  I can sort of see how the ideal trace impedance is lower based partly on having two planes...  and if one is broken up could that be a problem...  ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT EDIT:&lt;/strong&gt; Okay, I've partially answered my question on sharing a plane between signal layers. Skin effect depth probably mostly limits the signals to their own side of the plane.  (1/2 Oz copper = 0.7 mils, skin depth @ 50MHz is 0.4 mil, 0.2 mil @ 200MHz..  so anything over 65MHz should stick on it's side of the plane. I'm mostly worried about 200MHz DDR2 signals, but &amp;lt; 65MHz components of that could still be a problem)&lt;/p&gt;&#xA;" OwnerUserId="1270" LastEditorUserId="1270" LastEditorDisplayName="" LastEditDate="2011-04-26T20:47:35.610" LastActivityDate="2011-04-27T02:40:58.653" Title="PCB routing: EMI and signal integrity, return current questions" Tags="&lt;pcb&gt;&lt;pcb-design&gt;&lt;emi&gt;&lt;signal-integrity&gt;" AnswerCount="2" />
  <row Id="13502" PostTypeId="2" ParentId="13447" CreationDate="2011-04-26T18:29:27.210" Score="1" ViewCount="" Body="&lt;p&gt;The ESR of a ceramic capacitor is so low it is fairly common to disregard it altogether for practical purposes in DC regulators. The main reason I find to use tantalum instead of ceramics as output caps is if you have problems with piezoelectric ringing in the ceramic caps.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastActivityDate="2011-04-26T18:29:27.210" CommentCount="3" />
  <row Id="13503" PostTypeId="1" AcceptedAnswerId="13506" CreationDate="2011-04-26T18:39:41.027" Score="1" ViewCount="85" Body="&lt;p&gt;It seems to me like a huge waste of electricity for a vending machine to cool all of the sodas. That being said, I have no idea how vending machines work or how many of the sodas they refrigerate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it were my design, I would probably have a front cooling section plus 2-3 additional sections that were controlled by a sensor. The sensor would basically try to estimate the rate that sodas are coming out and cut the additional sections on as needed so as to minimize the electricity consumed. That way if you have a machine in the basement of a department store, it keeps the extra sections off all the time; if it's in a theme park in July, they're running full-blast all day.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm fairly certain that the machines aren't that sophisticated, but I'm wondering if there's anything more to it than being a big refrigerator.&lt;/p&gt;&#xA;" OwnerUserId="3995" LastActivityDate="2011-04-26T19:08:12.793" ClosedDate="2011-04-26T19:15:33.423" Title="Do soda vending machines cool the entire collection or just the last few rows?" Tags="&lt;sensor&gt;&lt;hardware&gt;&lt;temperature&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="13504" PostTypeId="2" ParentId="13503" CreationDate="2011-04-26T18:54:29.663" Score="0" ViewCount="" Body="&lt;p&gt;Most things aren't as efficient as they could be simply because there's no economic incentive to make them so.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Electricity costs a tiny bit more to cool more sodas vs. the added complexity (read: more stuff to break) that you want to add? Simple solution: jack up the price of the soda!&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-04-26T18:54:29.663" CommentCount="1" />
  <row Id="13505" PostTypeId="1" AcceptedAnswerId="13517" CreationDate="2011-04-26T19:04:26.167" Score="1" ViewCount="97" Body="&lt;p&gt;I need to figure out if an LLC half-bridge resonant SMPS is designed (more or less) correctly.  I am not an SMPS designer, and neither is the manufacturer, so I'm just reading a bunch of app notes and learning what I can.  It's producing ±35 V 400 W from a constant 400 VDC PFC output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As I understand from my reading: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The resonant frequency is a property of the LLC transformer network, increasing with load from f&lt;sub&gt;p&lt;/sub&gt; (unloaded resonant frequency) towards f&lt;sub&gt;0&lt;/sub&gt; (shorted resonant frequency).&lt;/li&gt;&#xA;&lt;li&gt;The switching frequency is controlled by the driver IC, and &lt;em&gt;decreases&lt;/em&gt; with load to regulate the output by riding up the resonant gain peak, getting closer to resonance and increasing the output as the load increases.  &lt;/li&gt;&#xA;&lt;li&gt;The switching frequency must never drop below the resonant frequency at any given load, or it will enter capacitive ZCS mode, which is Bad.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Is this all correct?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They've set the switching frequency to always be below f&lt;sub&gt;0&lt;/sub&gt;.  They claim this is ok, because &lt;a href=&quot;http://www.fairchildsemi.com/an/AN/AN-4151.pdf#page=5&quot; rel=&quot;nofollow&quot;&gt;Fairchild AN-4151&lt;/a&gt; says you can do above or below resonant operation:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;Below resonance operation is preferred for high output voltage applications, such as Plasma Display Panel (PDP) TV ... above resonant operation ... can show better efficiency for low output voltage applications, such as Liquid Crystal Display (LCD) TV or laptop adapter&quot;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Would 70 V out be considered low or high voltage in this case?  I'm guessing high voltage means hundreds of volts, so this is low voltage.  So does that mean it would ideally be operating always above f&lt;sub&gt;0&lt;/sub&gt;?  Maybe as long as point 3 is met (ZVS mode), it's not too important?  &lt;a href=&quot;http://electronicdesign.com/article/services/Use-The-LLC-Half-Bridge-In-Your-Offline-Converters.aspx&quot; rel=&quot;nofollow&quot;&gt;This article&lt;/a&gt; says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Most of these converters are operated above resonance so that at light-load conditions the switching frequency is higher than the resonant design points (region 1) [f&lt;sub&gt;s&lt;/sub&gt; &gt; f&lt;sub&gt;0&lt;/sub&gt;]. As load increases, the switching frequency droops. At maximum load, the converter operates slightly below the LlkCr resonant point [f&lt;sub&gt;s&lt;/sub&gt; &amp;lt; f&lt;sub&gt;0&lt;/sub&gt;] in region 2 [but should never enter region 3].&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-26T21:17:09.080" LastActivityDate="2011-04-28T19:48:28.490" Title="Setting correct operating frequency for LLC resonant SMPS" Tags="&lt;frequency&gt;&lt;smps&gt;&lt;resonant-converter&gt;" AnswerCount="1" />
  <row Id="13506" PostTypeId="2" ParentId="13503" CreationDate="2011-04-26T19:08:12.793" Score="2" ViewCount="" Body="&lt;p&gt;(Your question isn't about electronics, so it will probably be closed shortly. In any case, it's an interesting topic.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The rate at which the machine uses energy for cooling scales with the surface area and conductivity of the insulation, not the amount of soda inside. By trying to make some kind of internal wall that opens and closes to let sodas move inside the insulated volume, you would win on reduced surface area, but lose on conductivity-- heat would leak in at the seams and through the hatch whenever you opened it to move more sodas to the cold zone. You could solve that, but it would likely cost more than the savings you'd get from the reduced surface area.&lt;/p&gt;&#xA;" OwnerUserId="712" LastActivityDate="2011-04-26T19:08:12.793" CommentCount="2" />
  <row Id="13508" PostTypeId="1" AcceptedAnswerId="13514" CreationDate="2011-04-26T19:40:53.710" Score="0" ViewCount="76" Body="&lt;p&gt;The chain on my toilet often gets tangled, causing it to run indefinitely. The standard solution is to simply jiggle the handle which untangles the chain. Since my roommates are not as keen to keep an eye on this as I am, the toilet occasionally runs all night.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to build a simple sensor for my toilet that will automatically jiggle the chain if it detects that the tank is not refilling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What parts would I need to build such a device? Is it cost-effective?&lt;/p&gt;&#xA;" OwnerUserId="3995" LastActivityDate="2011-04-27T15:19:37.410" Title="What would it take to make a handle-jiggle sensor for my toilet?" Tags="&lt;sensor&gt;&lt;hardware&gt;&lt;hack&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="13509" PostTypeId="1" CreationDate="2011-04-26T19:41:27.960" Score="1" ViewCount="60" Body="&lt;p&gt;why common emitter configuration is used more than common base configuration of transistor for amplification purpose? &#xA; when common base configuration provides more stability than of common emitter configuration &lt;/p&gt;&#xA;" OwnerUserId="3998" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-27T11:10:02.523" LastActivityDate="2011-04-27T13:47:25.487" Title="configuration of transistor for amplification" Tags="&lt;transistor&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="13510" PostTypeId="1" AcceptedAnswerId="13515" CreationDate="2011-04-26T19:45:13.120" Score="0" ViewCount="60" Body="&lt;p&gt;if someone is generating frequency, can receiver detect from where exactly it's emitting? If someone is emitting on illegal frequency band, how it can be caught?&lt;/p&gt;&#xA;" OwnerUserId="3982" LastActivityDate="2011-04-26T20:15:45.937" Title="How can we detect the source of the radio emission ?" Tags="&lt;frequency&gt;" AnswerCount="2" />
  <row Id="13511" PostTypeId="2" ParentId="13509" CreationDate="2011-04-26T19:46:40.527" Score="1" ViewCount="" Body="&lt;p&gt;Compared to other configurations, common emitter (CE) amplifiers tend to have higher input impedance and lower output impedance, and better-than-unity gain, which makes them very useful for both input buffering and voltage gain applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By contrast, common base (CB) amplifiers have low input impedance and higher output impedance. CB amps aren't so much for voltage gain as they are for power gain; with a CB configuration, any power sourced by the input is passed through to the load, in addition to the power added by the transistor itself, but this shows up as current gain.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-26T19:46:40.527" CommentCount="2" />
  <row Id="13512" PostTypeId="2" ParentId="13510" CreationDate="2011-04-26T19:52:00.163" Score="0" ViewCount="" Body="&lt;p&gt;The standard approach is 'triangulation' - you use a directional receiving antenna, and determine the direction to the source from two different locations. Draw the lines on a map and you have a pretty good idea of where the signal originates from.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-26T19:52:00.163" />
  <row Id="13513" PostTypeId="1" CreationDate="2011-04-26T19:55:46.153" Score="1" ViewCount="77" Body="&lt;p&gt;Is it possible to detect when a device is consuming stand-by or phantom power?&#xA;For example if I leave my charger plugged in, detect that a small amount of current is being drawn and stop the flow. What about turning it back on. For example, plugging in my phone it could detect the demand and turn the flow back on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How could you create a device which could turn an outlet on or off depending on the load?&lt;/p&gt;&#xA;" OwnerUserId="3089" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-26T21:05:51.237" LastActivityDate="2011-04-26T23:28:17.640" Title="How would you detect phantom power?" Tags="&lt;power-supply&gt;&lt;low-power&gt;" AnswerCount="2" CommentCount="13" FavoriteCount="1" />
  <row Id="13514" PostTypeId="2" ParentId="13508" CreationDate="2011-04-26T19:58:18.837" Score="2" ViewCount="" Body="&lt;p&gt;Cost effective? Probably not, unless this thing wastes a LOT of water, or if water is extremely expensive. (If it puts you over some local water ordinance quota, it could cost a bunch). Anyway, it's a fun exercise..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A microphone clamped to the cold-water supply line should do the trick. Amplify the signal, then LPF it and use a comparator to give you a digital signal that represents the sound level exceeding a threshold. This would then give you a signal that says when the water's running or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, from there, you have to allow that it's &lt;em&gt;normal&lt;/em&gt; for the water to run for a certain length of time, so you'd either want a microcontroller, or resort to some analog pulse-width circuitry. Personally, I'd throw an extremely minimal AVR or PIC at it, as it's easier (for me, anyway) to deal with code than reconfiguring analog pulse-width threshold circuits. So, if the water has been running for more than the maximum allowed 'normal' time, then you know you have a problem to act on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, the 'jiggle the handle' part isn't a sensor, that's an actuator. You could try any number of things here; a servo motor or a solenoid would probably be the easiest to work with, but controlling &lt;em&gt;this&lt;/em&gt; part would probably be the most complex part of your device. &lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-26T19:58:18.837" CommentCount="1" />
  <row Id="13515" PostTypeId="2" ParentId="13510" CreationDate="2011-04-26T20:15:45.937" Score="5" ViewCount="" Body="&lt;p&gt;Every Government does things slightly different, but the way most organizations look for illegal wireless use is to use directional antennas. This is usually an array of antennas to cover a decently large frequency range and direction. They will then stick this array on top of a van and drive around. If an antenna shows a strong signal then they can know to travel in the direction that the &quot;hot&quot; antenna is pointed. They can then just play a game of Hot and Cold until they find where it is coming from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most likely if you are using a frequency that is allowed, but at slightly higher radiated powers, they probably wont notice. There is enough variations that can be caused by various objects in its path that it would be hard to tell if you were radiating too much or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are using a frequency that is not allowed, but keep the power low enough that it would just look like noise at the street then you will also most likely be fine.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-26T20:15:45.937" CommentCount="6" />
  <row Id="13516" PostTypeId="2" ParentId="13508" CreationDate="2011-04-26T20:48:14.693" Score="2" ViewCount="" Body="&lt;p&gt;Not an electrical solution, but change or modify the chain so it doesn't get caught.  Simple. Easy. Effective. And doesn't combine electronics with water. &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-26T20:48:14.693" CommentCount="1" />
  <row Id="13517" PostTypeId="2" ParentId="13505" CreationDate="2011-04-26T20:54:39.107" Score="3" ViewCount="" Body="&lt;p&gt;The Q and M curves show that the resonant frequency is a property of the transformer, the load &lt;em&gt;and&lt;/em&gt; the series capacitor. $f_o$ isn't necessarily a 'shorted' resonant frequency but a mostly-load-independent second resonant point predominantly controlled by the leakage inductance and series capacitor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The switching frequency is indeed controlled by the some form of control IC (usually a PWM). The frequency of operation will vary as a function of input line and load, and should stay above the worst-case (minimum load) resonant peak to ensure ZVS over the whole range. You are correct in that operation below the worst-case peak gain forces the converter into an uncontrolled region and should be avoided.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LCD TV and laptop adapters are usually &amp;lt; 24V. If the designer was able to use a schottky diode for the output rectifier, you don't have to rely on forced commutation from the primary to reduce losses. The best way to tell if you're suffering from excessive reverse recovery loss is to put a current probe in the secondary and measure the reverse recovery current. Operating this 70V converter above resonance means they're not soft-commutating the secondary (which isn't necessarily bad) to reduce conduction losses (less circulating current in the primary).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-26T20:54:39.107" CommentCount="8" />
  <row Id="13518" PostTypeId="6" CreationDate="2011-04-26T21:04:25.857" Score="0" ViewCount="" Body="&lt;p&gt;I've been a regular on this site for 7 months now, since the commitment phase. With the time I'm able to spend here (between work and family life) I have strived not only to answer questions to the best of my knowledge but to improve things in general - by editing questions to add equations, voting up/down as necessary, flagging posts, and contributing to tag wikis.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Being close to 40 (yikes!) gives me a great deal of life experience to draw upon when considering how to deal with people. I enjoy spending time on this site and would appreciate the trust of the community to participate in a more active role here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Adam (madmanguruman)&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-26T21:04:25.857" LastActivityDate="2011-04-26T21:04:25.857" CommunityOwnedDate="2011-04-26T21:04:25.857" CommentCount="2" />
  <row Id="13519" PostTypeId="2" ParentId="13513" CreationDate="2011-04-26T21:14:32.327" Score="2" ViewCount="" Body="&lt;p&gt;You wouldn't be able to totally isolate the flow, because once you did that, there'd be nothing to detect: plugging something in to an 'off' power bar doesn't lead to any power flow that could be detected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There'd have to be some sort of cycle-on, cycle-off mode of operation - turn the AC on, measure the power, make a decision to stay on or shut off, and repeat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Measurement is tricky as well - you may well need instrumentation-grade current metering to detect the low current flow, which can also withstand the 15A of a usual circuit without frying.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some components may draw larger amounts of initial power to get going, before they settle into a quiescent state. Many components hiccup on and off by themselves. The detector will have to deal with all of these variables as part of its logic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the control circuitry (and AC controls) will themselves consume power. You have to figure if what you can potentially save is worth the power budget needed to save it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Finally, whatever you have plugged into this power bar will need to be able to withstand numerous perpetual turn-on and turn-off cycles. This is quite stressful for power supplies in general (due to inrush current).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-26T21:14:32.327" CommentCount="1" />
  <row Id="13520" PostTypeId="1" CreationDate="2011-04-26T22:26:25.027" Score="1" ViewCount="56" Body="&lt;p&gt;I'm looking to build a home automation system which uses the powerline to carry the data between nodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an old design based on a combination of LM1893, HC123 and 8748, but the slave board is just too big to fit inside a standard UK light switch backbox, so I'm thinking of trying to shrink the design. A PIC should be a suitable replacement for the 8748 and HC123, but I wonder if there is a better option for the powerline comms side than the existing LM1893.&lt;/p&gt;&#xA;" OwnerUserId="3774" LastActivityDate="2011-04-26T22:26:25.027" Title="What better options are there than the LM1893 for powerline communications?" Tags="&lt;pic&gt;&lt;communication&gt;&lt;powerline&gt;" />
  <row Id="13521" PostTypeId="2" ParentId="13410" CreationDate="2011-04-26T22:26:36.550" Score="1" ViewCount="" Body="&lt;p&gt;The problem is that your full and empty flags are being enabled by the insert and delete control signals.  The full flag will only be asserted when wp = rp and insert = '1'.  If insert /= '1', then your full flag won't be asserted.  So, unless you're actively inserting an item into the FIFO, it won't tell you that it's full.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the full flag should be when the write pointer + 1 = read pointer (i.e. if adding an item would then make the write pointer equal the read pointer).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should get rid of the &quot;insert = '1'&quot; and &quot;delete = '1'&quot; checks, so that your full and empty flags will be asserted regardless of the control signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Directly inside your Process block should be only a single if statement, which is clk'event or rising_edge (I prefer rising_edge).  This represents the clock input of all the flops.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of your other if statements are nested inside the rising_edge if.  These would be like the enable input of the flops.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the flags are outside of the rising_edge if, they will be combinational; i.e. they will be set regardless of the clock signal.  To register the flags, include them inside the rising_edge if, and they will only change when the clock changes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding your question about the Process block, all if statements in a given Process block will execute simultaneously.  HOWEVER, when mulitple if statements assign a value to the same signal, the last if statement will &quot;win&quot;, because the statements inside the Process block are executed sequentially, despite occurring simultaneously.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should have only one line of code with clk'event (though I prefer rising_edge myself).  Nested inside this if (which kinda represents the clock inputs of all the flops in the process block), there are more ifs (which kinda represent the enable inputs for all the flops).&lt;/p&gt;&#xA;" OwnerUserId="1278" LastEditorUserId="1278" LastEditorDisplayName="" LastEditDate="2011-04-27T15:54:43.960" LastActivityDate="2011-04-27T15:54:43.960" CommentCount="2" />
  <row Id="13522" PostTypeId="2" ParentId="13500" CreationDate="2011-04-26T22:40:45.623" Score="1" ViewCount="" Body="&lt;p&gt;Yeah, you pretty much answer your own questions.  For what it's worth, everything you state is exactly as I have learned it (disclosure: I am also book/Internet educated on EMI/SI).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm pretty sure crossing split planes would ruin the stripline's impedance.  However, for non-stripline, as long as one neighboring plane provides an unbroken return current path, you should be okay with EMI.  Although I would check the stack-up to make sure that the unbroken plane is physically closer to the signal layer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wouldn't worry about low-frequency return currents on your 5V split.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-04-26T22:40:45.623" CommentCount="1" />
  <row Id="13523" PostTypeId="1" AcceptedAnswerId="13535" CreationDate="2011-04-26T22:53:07.583" Score="1" ViewCount="67" Body="&lt;p&gt;I have this &lt;a href=&quot;http://www.rapidonline.com/sku/Electrical-Power/Transformers/Lighting-Transformers/60W-Lighting-transformer/72743/88-3667&quot; rel=&quot;nofollow&quot;&gt;transformer&lt;/a&gt; which is 240VAC to 11.4VAC. But when I hook up my multimeter I am only reading about 1.2V. I have my multimeter configured to read AC and the scale is also correct. However my multimeter isn't true RMS. Could this be causing a problem? If not what else could be the problem?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-27T11:24:53.617" LastActivityDate="2011-04-27T14:15:02.347" Title="Transformer Output Problem" Tags="&lt;transformer&gt;&lt;line-power&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13524" PostTypeId="2" ParentId="13513" CreationDate="2011-04-26T23:28:17.640" Score="4" ViewCount="" Body="&lt;p&gt;I think you're laboring under a false assumption. Where there are power strips that turn outlets off to save power based on a 'control' outlet, the 'control' outlet is always live.  It will always be consuming its 'phantom power'/'vampire power' (cue the Twilight fangirls!).  All of the outlets that are slaved to the 'control' outlet will be off until the 'control' outlet has enough current flowing through it to trip the circuit.  As others have suggested, this is the only reasonable way to do it - you can't be continually switching something on and off just to test whether it's on.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have such a power strip for my home entertainment system - older solutions were to run power through your receiver via a built-in pass through.  When the receiver is off, the passthrough is off, when on, it's on.  I can't say for certain whether it's saving me any money but it definitely means fewer absurd 'off' lights on the electronics (seriously, a light that's on when the device is off?  Crazy).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to measure this 'phantom'/'vampire' power, get a &lt;a href=&quot;http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU/ref=sr_1_1?ie=UTF8&amp;amp;qid=1303860377&amp;amp;sr=8-1&quot; rel=&quot;nofollow&quot;&gt;Kill-a-watt&lt;/a&gt;.  It measures power draw of whatever is plugged into it.  I haven't used one yet but many people rave about them, and Lady Ada hacked one to put a bluetooth unit in it for datalogging purposes, so they're at least popular.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-26T23:28:17.640" CommentCount="1" />
  <row Id="13525" PostTypeId="2" ParentId="13214" CreationDate="2011-04-26T23:32:13.660" Score="1" ViewCount="" Body="&lt;p&gt;That's a relatively wide bandwidth to match a circuit over. The Bode-Fano equation governs bandwidth/return loss for reactive circuits, and google has some articles that will help with this.  As long as the impedances you are working with don't vary much, you can do a decent job of matching. Resistive matches are pretty broadband, but lossy. &lt;/p&gt;&#xA;" OwnerUserId="2148" LastActivityDate="2011-04-26T23:32:13.660" CommentCount="3" />
  <row Id="13526" PostTypeId="2" ParentId="4611" CreationDate="2011-04-27T00:30:08.663" Score="2" ViewCount="" Body="&lt;p&gt;One point not yet mentioned: a 60 watt bulb will use 60 watt-hours per hour, or 60 watt-seconds per second, or 60 watt-microseconds per microsecond, or 60 watt-centuries per century.  In other words, the &quot;watts&quot; part of the bulb's power usage has nothing to do with hours or any other unit of time.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-04-27T00:44:10.650" LastActivityDate="2011-04-27T00:44:10.650" />
  <row Id="13527" PostTypeId="2" ParentId="13500" CreationDate="2011-04-27T01:04:44.093" Score="2" ViewCount="" Body="&lt;p&gt;I think you're on the right path, a couple of notes,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) With a signal trace between two planes, the return current will split between the two planes, even if one of the planes is split.  The return current cannot &quot;see the future&quot; and decide ahead of time which plane to return on.  It will return above and below the trace until it sees the split at which point is says &quot;oh crap!&quot; and pays you back by possibly causing you to fail FCC testing.  So you want to avoid running traces over plane splits even if another adjacent plane is not split.  You can deal with splits with capacitors and such but this type of solution is less than ideal.  I'd focus on always avoiding running a trace over a plane split on an adjacent plane.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) Wide return paths on DC signals don't really matter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) You asked about two signal layers sharing the same plane.  Usually, this is not a big deal if done properly.  What many people do is use one of the layers as a &quot;horizontal&quot; signal layer and the other as a &quot;vertical&quot; signal layer so the return currents are orthogonal to each other.  It is very common to route two signal layers for each plane, and use this horizontal/vertical technique.  The most important thing to remember is to not change reference planes.  Your setup could be a little tricky because going from the bottom layer to the 4th layer adds another return plane.  More typical 6 layer boards are &lt;/p&gt;&#xA;&#xA;&lt;p&gt;1)ASignalHor   2)GND   3)ASignalVer   4)BSignalHor   5)POWER   6)BSignalVer&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need smaller additional planes, like under the micro, these would usually be placed as an island on one of the signal layers.  If you need to use more power planes, you might want to think about going to 10+ layers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4) Plane spacing is important, and can have huge impact on performance, so you should specify this to the board house.  If you take the example 6 layer stackup I mentioned above, spacing of .005 .005 .040 .005 .005 (instead of standard stackup with equal distance between layers) can make an order of magnitude improvement.  It keeps the signal layers close to their reference plane (smaller loops).&lt;/p&gt;&#xA;" OwnerUserId="2377" LastEditorUserId="2377" LastEditorDisplayName="" LastEditDate="2011-04-27T02:40:58.653" LastActivityDate="2011-04-27T02:40:58.653" CommentCount="10" />
  <row Id="13529" PostTypeId="1" CreationDate="2011-04-27T03:06:44.233" Score="-1" ViewCount="152" Body="&lt;p&gt;Hey all,&#xA;I need a little help on an assignment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We need to design a logic circuit for an elevator with 3 floors. Our professor was unbelievably vague about the requirements, but basically each floor has an up/down button, and the elevator has buttons to Floor 1, Floor 2, and Floor 3. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm assuming it would be similar to this &lt;a href=&quot;http://apcentral.collegeboard.com/apc/public/repository/ap08_cs_BoolAlgApps_problems.pdf&quot; rel=&quot;nofollow&quot;&gt;two floor elevator&lt;/a&gt; (example 3). Any help would be appreciated!&lt;/p&gt;&#xA;" OwnerUserId="4002" LastEditorUserId="4002" LastEditorDisplayName="" LastEditDate="2011-04-27T03:17:00.500" LastActivityDate="2011-04-27T08:17:59.640" ClosedDate="2011-04-27T10:31:32.093" Title="Three level elevator circuit" Tags="&lt;logic&gt;&lt;circuit-design&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13530" PostTypeId="1" AcceptedAnswerId="13532" CreationDate="2011-04-27T05:19:28.007" Score="0" ViewCount="41" Body="&lt;p&gt;I am using 'pickit2' through Mplab to burn my code. Suddenly none of the codes(even blinking led) that i fuse through it gets executed. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I confirmed whether it writes the hex code properly using 'Read Memory' feature.On comparison,I found no change in the hex.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I changed lot of IC's(16f/18f) ,I tried other boards too, but nothing worked.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whats going wrong with my setup?? please help me to figure it out..&lt;/p&gt;&#xA;" OwnerUserId="1484" LastActivityDate="2011-04-27T07:06:31.913" Title="PIC mcu gets programmed but doesnt get executed" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;programming&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="13531" PostTypeId="1" CreationDate="2011-04-27T07:01:07.647" Score="-1" ViewCount="101" Body="&lt;p&gt;Hi, I'm a complete newbie to electronics and I'd like to take on the chalenge of building some pretty intricate hardware. Basically, I have a laser meter that gives me distance, I'd like to find the inverse tan of that distance x 10 so that's:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;tan-1(distance x 10).&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I then want to take the angle obtained and mechanically (with a motor and some sort of robotic setup) move a cylindrical object to that angle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any insight on how I could get started and how I could achieve my goal would be strongly appreciated, remember I'm a complete newbie so please recommend books, tutorials and anything that you find suitable.&lt;/p&gt;&#xA;" OwnerUserId="4004" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-04-28T11:33:49.223" LastActivityDate="2011-04-28T11:33:49.223" ClosedDate="2011-04-28T11:39:53.057" Title="Basic robotics and math for a newbie" Tags="&lt;robotics&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="13532" PostTypeId="2" ParentId="13530" CreationDate="2011-04-27T07:06:31.913" Score="1" ViewCount="" Body="&lt;p&gt;Check the configuration fuse options, that you are using the correct ones for your hardware. Specifically the clock type (internal rc, external crystal) etc matches your hardware because it sounds like the chip is not running.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-04-27T07:06:31.913" CommentCount="2" />
  <row Id="13533" PostTypeId="2" ParentId="13529" CreationDate="2011-04-27T08:17:59.640" Score="0" ViewCount="" Body="&lt;p&gt;I believe the procedure in the PDF you linked to generalizes to all these kinds of questions (and quite a bit more too!). I will now outline a solution strategy to get you started.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your first step should be compiling the truth table. Then you simplify it and express it as a logical statement. Then you figure out how to represent it with gates.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way I see it you have 7 inputs (one button on the first and last floor, two on the middle floor, as well as 3 &quot;elevator on this floor&quot;) and you will need two outputs (go up, go down. Both false to stay). Compile the truth table for all possible values (which is a good deal less than all the combinations -- the elevator can only be at one floor at the same time!) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that you might have to resolve ambiguity while compiling the truth table: if the elevator is on the middle floor and both top and bottom floor press the button, what happens then? How you resolve this will be crucial for the performance (i.e. average wait time) of the elevator. The canonical solution (so canonical that it's actually called an &quot;elevator algorithm&quot;) is to keep the elevator moving in the same direction as long as possible. What do you need to add to the truth table to make this happen?&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-04-27T08:17:59.640" />
  <row Id="13534" PostTypeId="1" CreationDate="2011-04-27T09:18:51.837" Score="-1" ViewCount="126" Body="&lt;p&gt;My pic-kit is not working properly, i have decided to fuse tiny pic boot-loader into all my ic's.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are 8 hex files(the so called boot-loader) as listed: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;notinybid16f88.asm&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f.asm&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f88.asm&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f870.asm&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f873.asm&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f873a.asm&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f886.asm&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f887.asm&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f887_8MHz_int.asm&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f88&lt;/li&gt;&#xA;&lt;li&gt;tinybid_16f876A_04MHz&lt;/li&gt;&#xA;&lt;li&gt;tinybid_16f876A_20MHz&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f88_20MHz_115200&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f88_i8MHz_19200&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f886_int4MHz_19200&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f887&lt;/li&gt;&#xA;&lt;li&gt;tinybid16f887_8MHz_int&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The controller I prefer the most is 16f877a. Though the hex file for this device is not given directly, I came to know that I can load the hex of 16f876a which belongs to the same family.(i.e., 16f876a~16f877a)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a  11.059200Mhz Crystal Oscillator placed in the board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are 2 hex files available for 16f876a, one corresponding to 4Mhz and the other one is 20Mhz(last file of the 1st row and the first file of 2nd row, resp).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since my crystal is none of those two, which file should I choose and why??&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!!&lt;/p&gt;&#xA;" OwnerUserId="1484" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-12T23:50:47.330" LastActivityDate="2011-05-12T23:50:47.330" Title="Burning a BOOTLOADER into pic mcu - which file should i choose??" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;bootloader&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13535" PostTypeId="2" ParentId="13523" CreationDate="2011-04-27T11:04:33.823" Score="4" ViewCount="" Body="&lt;p&gt;Your link points to the description of a device marketed as a &quot;transformer&quot;, but obviously containing much more. It seems like this device is designed specifically for the use with 12 V halogen lamps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it was a true transformer (and nothing more), it would work at mains frequency (50 or 60 Hz), and you would have this frequency at the input (primary) and at the output (secondary). In this case, a cheapo multimeter would likely give you an acceptable reading when you were measuring the output voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your &quot;transformer&quot; seems to be a switching device. I assume it works like this: The AC input voltage is rectified to DC and fed to an internal electronic switch (likely MOSFET). This electronic switch chops the input current to an AC current with a frequency of 40 kHz (cf. your link, see output frequency specification!). This AC current at 40 kHz is fed into a transformer, and the secondary side of this transformer seems to directly accessible at the output wires.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume your multimeter uses a low-pass filter when it measures AC voltages, and this filter blocks most of the voltage at 40 kHz, giving you a reading of only 1.2 V when you should actually see &gt; 11 V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To be really sure, you could measure the output voltage with an oscilloscope. I am fairly sure you would see a somewhat rectangular waveform at 40 kHz = 40000 Hz, and not a somewhat sinusoidal waveform at 50 or 60 Hz like you would with an ordinary transformer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a voltage with a frequency and waveform like this, I would even carefully check the manual of a good RMS multimeter because even one of those might have a low pass filter around 1 kHz.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-04-27T14:15:02.347" LastActivityDate="2011-04-27T14:15:02.347" CommentCount="4" />
  <row Id="13536" PostTypeId="1" AcceptedAnswerId="13537" CreationDate="2011-04-27T11:23:59.317" Score="2" ViewCount="79" Body="&lt;p&gt;My BIOS died (&lt;em&gt;ASUS M2N SLI&lt;/em&gt; Deluxe motherboard) on me and I would like to remove it from its place. But I cannot figure out whether it is socketed or soldered. Here is a picture of it: &lt;a href=&quot;http://i.imgur.com/KjzPm.jpg&quot; rel=&quot;nofollow&quot;&gt;http://i.imgur.com/KjzPm.jpg&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I will not try to desolder, don't have the skills. Hope it is socketed. )&lt;/p&gt;&#xA;" OwnerUserId="2296" LastActivityDate="2011-04-27T15:07:50.583" Title="Socketed or Soldered BIOS?" Tags="&lt;soldering&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="13537" PostTypeId="2" ParentId="13536" CreationDate="2011-04-27T11:40:31.027" Score="4" ViewCount="" Body="&lt;p&gt;That is soldered direct on to the PCB. The package is a &lt;a href=&quot;http://en.wikipedia.org/wiki/Plastic_leaded_chip_carrier&quot; rel=&quot;nofollow&quot;&gt;PLCC with J lead pins&lt;/a&gt;. It is best removed with a hot air desoldering station with the right nozzle to go around the chip and a sucker to hold it when removed. But it could possibly be desoldered with braid and enough heat from an iron, with a high risk of lifting pads and tracks from the board, depending on your experience. In your case, I think you need to look at a new motherboard.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastEditorUserId="2110" LastEditorDisplayName="" LastEditDate="2011-04-27T11:46:11.457" LastActivityDate="2011-04-27T11:46:11.457" />
  <row Id="13538" PostTypeId="2" ParentId="13534" CreationDate="2011-04-27T12:12:19.520" Score="1" ViewCount="" Body="&lt;p&gt;You need to use a hex file compiled for your specific pic. Also the part number must be the same. A pic16F877 is not the same as a pic16f877a. The pic oscillator frequency must be the same in the hex files as your hardware is. Either change your crystal to match the hex file, or modify the assembly program written for the boot loader hex file. There is documentation on Microchips web site regarding boot loaders. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A Google search turned up this &lt;a href=&quot;http://www.microchipc.com/PIC16bootload/&quot; rel=&quot;nofollow&quot;&gt;PIC16 bootloader&lt;/a&gt;. Use the assembly program included for your pic16f877(a).The instructions within the assembly will guide you to change the oscillating frequency. Then simply build the new hex file with your new osc. freq..&lt;/p&gt;&#xA;" OwnerUserId="3453" LastEditorUserId="3453" LastEditorDisplayName="" LastEditDate="2011-04-27T15:55:33.157" LastActivityDate="2011-04-27T15:55:33.157" CommentCount="4" />
  <row Id="13539" PostTypeId="2" ParentId="4611" CreationDate="2011-04-27T12:50:48.200" Score="1" ViewCount="" Body="&lt;p&gt;The concept of 'Watt-hours' as Watt x Hours will be confusing to someone who cannot conceptualize Watt - being 'enegergy used per amount of time'.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I sometimes try to explain this using more familiar concepts: If we use the term 'Keem' in stead of 'km/hour', one could use 'Keem-Hour' to describe distance travelled - going 60 Keem for half an hour means you've travelled 30km as 60 x 0.5=30&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just like a rental company that's interested in the distance your travelled in their car, the energy company is interested in the energy used - they will charge you per Watt-hour. If a Watt-hour costs 1c, it will cost you 60c if you leave a 60 Watt lamp on for one hour.&lt;/p&gt;&#xA;" OwnerUserId="1612" LastActivityDate="2011-04-27T12:50:48.200" />
  <row Id="13540" PostTypeId="1" CreationDate="2011-04-27T13:39:13.890" Score="3" ViewCount="126" Body="&lt;p&gt;Hi ,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wanted know what should be the optimum distance between a microntroller(AT89C51ED2) and a crystal of frequency 11.0592MHz?&lt;/p&gt;&#xA;" OwnerUserId="4006" LastActivityDate="2011-04-27T20:12:54.417" Title="What is the optimum distance between a micro-controller and a crystal on a PCB?" Tags="&lt;microcontroller&gt;&lt;pcb-design&gt;&lt;crystal&gt;" AnswerCount="6" CommentCount="1" FavoriteCount="0" />
  <row Id="13541" PostTypeId="2" ParentId="13540" CreationDate="2011-04-27T13:44:13.337" Score="0" ViewCount="" Body="&lt;p&gt;You have to put the crystal as closed as possible of the AT89C51ED2.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-04-27T13:44:13.337" />
  <row Id="13542" PostTypeId="2" ParentId="13509" CreationDate="2011-04-27T13:47:25.487" Score="0" ViewCount="" Body="&lt;p&gt;Common collector: Current gain but no voltage gain&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Common base: Voltage gain but no current gain&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Common emitter: Some voltage and some current gain, depending on the impedances in the basis and collector circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've never used the common basis configuration, I understand it is used mostly for the input stages of high frequency amplifiers.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-04-27T13:47:25.487" />
  <row Id="13543" PostTypeId="1" CreationDate="2011-04-27T13:55:59.400" Score="1" ViewCount="84" Body="&lt;p&gt;Hi, I like to interface a humidity sensor over the I²C bus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should come in a small package, and consume little power. Accuracy isn't that important. I'm using the &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/2737&quot; rel=&quot;nofollow&quot;&gt;DS1621&lt;/a&gt; as temperature sensor, I'd like something similar, but for a humidity sensor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After looking for modules with my criteria, I came across the &lt;a href=&quot;http://www.hygrosens.com/en/products/sensor-elements/digital-humidity-sensors/hyt-271-allround-talent.html&quot; rel=&quot;nofollow&quot;&gt;HYT271&lt;/a&gt;, but that thing is ridiculously expensive. The low-cost version &lt;a href=&quot;http://www.hygrosens.com/en/products/sensor-elements/digital-humidity-sensors/hyt-371-inexpensive.html&quot; rel=&quot;nofollow&quot;&gt;HYT371&lt;/a&gt; has about the characteristics I'd need, but it's currently not available from my dealer of choice...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need something reasonable accurate for ambient temperature measuring, and at the same time not too expensive. Should be in the range of a few euros.&#xA;&lt;em&gt;(Bonus points if those chips can be sampled)&lt;/em&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2134" LastEditorUserId="2134" LastEditorDisplayName="" LastEditDate="2011-04-28T21:56:46.890" LastActivityDate="2011-04-28T21:56:46.890" Title="Advice a humidity sensor with I²C interface" Tags="&lt;sensor&gt;&lt;i2c&gt;&lt;humidity&gt;" AnswerCount="1" />
  <row Id="13544" PostTypeId="2" ParentId="13543" CreationDate="2011-04-27T14:05:24.087" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.sensirion.com/&quot; rel=&quot;nofollow&quot;&gt;Sensirion&lt;/a&gt; has combined temperature/humidity sensors. Their &lt;a href=&quot;http://www.sensirion.com/en/01_humidity_sensors/05_humidity_sensor_sht21/00_humidity_sensor_sht21.htm&quot; rel=&quot;nofollow&quot;&gt;SHT21&lt;/a&gt; and &lt;a href=&quot;http://www.sensirion.com/en/01_humidity_sensors/05_humidity_sensor_sht25.htm&quot; rel=&quot;nofollow&quot;&gt;SHT25&lt;/a&gt; have an I2C interface. Both come in a small DFN-6 package.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-27T14:12:34.707" LastActivityDate="2011-04-27T14:12:34.707" CommentCount="3" />
  <row Id="13545" PostTypeId="2" ParentId="13540" CreationDate="2011-04-27T14:19:26.057" Score="1" ViewCount="" Body="&lt;p&gt;As close as possible. Provide a ground plane around the oscillator components (crystal + capacitors). &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-27T14:19:26.057" />
  <row Id="13546" PostTypeId="2" ParentId="13540" CreationDate="2011-04-27T14:23:33.880" Score="5" ViewCount="" Body="&lt;p&gt;Once again, Atmel app notes to the rescue:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.atmel.com/atmel/acrobat/doc2521.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.atmel.com/atmel/acrobat/doc2521.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Crystal/oscillator advice starts on page 9 and on page 15 it recommends the distance between crystal and MCU be 'very short'.  Also, an example layout on page 16 shows how they laid-out the crystal circuit.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-27T14:23:33.880" CommentCount="1" />
  <row Id="13547" PostTypeId="2" ParentId="13540" CreationDate="2011-04-27T14:31:16.467" Score="2" ViewCount="" Body="&lt;p&gt;Microchip recommends &amp;lt;0.5&quot; for their PIC18FxxJxx devices.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-27T15:47:39.337" LastActivityDate="2011-04-27T15:47:39.337" />
  <row Id="13548" PostTypeId="1" CreationDate="2011-04-27T14:40:17.153" Score="0" ViewCount="52" Body="&lt;p&gt;This is not really a hardware-hacking question, but there is no stack-exchange website more appropriate for this topic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other day my cellphone (LG KP500) ran out of battery power and turned itself off during the night. When I woke up, I noticed that the cellphone was making a very distinct humming sound. I took the battery out obviously.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This has never happened before, and it bothers me, since I think I recall reading that the rare cellphone battery explosions were preceded by the battery making a humming or hissing noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What could make the battery do this? Is it safe to use the battery again? Is there any chance that the phone is faulty and will &quot;break&quot; a new battery in the same way, when I put it in?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance for any insight on this.&lt;/p&gt;&#xA;" OwnerUserId="4007" LastActivityDate="2011-04-27T15:05:12.860" Title="cellphone battery makes a humming noise" Tags="&lt;battery&gt;&lt;cellphone&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13549" PostTypeId="2" ParentId="13540" CreationDate="2011-04-27T14:50:06.560" Score="0" ViewCount="" Body="&lt;p&gt;Ensure that your crystal is close to the Micro controller, in fact it should be  closer to the Pins of the controller where it will be connected to. And with the capacitors connected, it should work just fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far i know for 8051, there is no distance specified, but closeness is well adviced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All the best.&lt;/p&gt;&#xA;" OwnerUserId="3632" LastActivityDate="2011-04-27T14:50:06.560" />
  <row Id="13550" PostTypeId="2" ParentId="13548" CreationDate="2011-04-27T15:05:12.860" Score="1" ViewCount="" Body="&lt;p&gt;The cellphone may have been malfunctioning due to the voltage being too low. The cellphone could also be damaged which led to the battery discharge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can try to operate the phone (with the battery) while plugged into a charger or a USB connection to a PC to see if the behaviour changes. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-27T15:05:12.860" CommentCount="2" />
  <row Id="13551" PostTypeId="2" ParentId="13536" CreationDate="2011-04-27T15:07:50.583" Score="2" ViewCount="" Body="&lt;p&gt;Don't throw it out yet!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This motherboard has the &lt;a href=&quot;http://www.asus.com/Motherboards/AMD_AM2/M2NSLI_Deluxe/&quot; rel=&quot;nofollow&quot;&gt;CrashFree BIOS 3&lt;/a&gt; feature which allows for reflash from a USB drive even if the main BIOS is corrupted.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-27T15:07:50.583" CommentCount="3" />
  <row Id="13552" PostTypeId="2" ParentId="13508" CreationDate="2011-04-27T15:19:37.410" Score="0" ViewCount="" Body="&lt;p&gt;Cost effective? No, it's simpler to adjust the chain: it's probably stretched with age and was too long to begin with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But since what you're proposing is a short step away from building a pushbutton-operated toilet, I suggest you do that instead. Much cooler than a &quot;tangled chain&quot; detector.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-04-27T15:19:37.410" />
  <row Id="13553" PostTypeId="1" CreationDate="2011-04-27T06:15:43.177" Score="1" ViewCount="142" Body="&lt;p&gt;I know what a diode can do in a AC circuit, but what can a diode do in a DC circuit?&lt;/p&gt;&#xA;" LastEditorUserId="536" LastEditorDisplayName="" LastEditDate="2011-04-27T15:49:05.740" LastActivityDate="2011-04-28T08:50:51.513" ClosedDate="2011-04-28T10:12:39.577" Title="What are Diodes For?" Tags="&lt;diode&gt;&lt;dc&gt;" AnswerCount="6" CommentCount="1" />
  <row Id="13554" PostTypeId="2" ParentId="13553" CreationDate="2011-04-27T08:17:13.277" Score="0" ViewCount="" Body="&lt;p&gt;1st, a diode can be used as a .7 V bias in forward direction. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;2nd I doubt that You can really differentiate AC, DC and &#xA;mixed circuits. The way You ask, You still have a lot to learn &#xA;in electronics. &lt;/p&gt;&#xA;" LastActivityDate="2011-04-27T08:17:13.277" CommentCount="1" />
  <row Id="13555" PostTypeId="2" ParentId="13553" CreationDate="2011-04-27T11:15:50.537" Score="1" ViewCount="" Body="&lt;p&gt;Flyback diodes (I think that's the term) are placed in reverse across relay coils in 24 VDC control circuits to allow the inductive current to circulate after the relay is turned off. Otherwise the switching contacts would burn out.&lt;/p&gt;&#xA;" LastActivityDate="2011-04-27T11:15:50.537" CommentCount="1" />
  <row Id="13557" PostTypeId="2" ParentId="13553" CreationDate="2011-04-27T15:53:45.130" Score="1" ViewCount="" Body="&lt;p&gt;It can conduct when forward-biased, and block when reverse-biased, exactly the same as in an AC circuit.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-27T15:53:45.130" />
  <row Id="13558" PostTypeId="1" AcceptedAnswerId="13597" CreationDate="2011-04-27T16:14:48.093" Score="2" ViewCount="130" Body="&lt;p&gt;I am interested to remote control something (sorry for the vagueness) over a distance of several hundred kilometers to a place where there are no internet cables. Therefore, I am interested to know how the US Military remote controlls their drones. My best guess is via satelite communicatation, but wouldn't there be too much lag to make this a feasible option, at least when considering the speed these drones fly with? I also wonder whether such satelite communication is available for civil purposes at a reasonably affordable price?&lt;/p&gt;&#xA;" OwnerUserId="1625" LastActivityDate="2011-04-29T01:03:26.350" Title="How do they remote control the military drones?" Tags="&lt;remote&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="13559" PostTypeId="2" ParentId="13558" CreationDate="2011-04-27T16:21:29.647" Score="1" ViewCount="" Body="&lt;p&gt;I remember reading an article about how the older drones used an unencrypted wireless signal (apparently they've all now been retrofitted with newer hardware that can support real-time encryption of video).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My guess is they just use a high powered transmitter to send a signal to a base station that can then relay the data with a more traditional network anywhere they need it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, I don't know where I read this article.&lt;/p&gt;&#xA;" OwnerUserId="536" LastActivityDate="2011-04-27T16:21:29.647" CommentCount="2" />
  <row Id="13560" PostTypeId="1" CreationDate="2011-04-27T16:25:00.223" Score="0" ViewCount="51" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have multiple RFID cards that I use to get into parking garages at the office, client site, home, parents place, etc, etc, etc.....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to either &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A) combine all of these into 1 card or device (perhaps pressing a button to send the right signal?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or even better B) Have a way to transmit the proper signal from a device mounted in my car with a dash button. &lt;/p&gt;&#xA;" OwnerUserId="4011" LastActivityDate="2011-05-27T16:47:48.563" Title="Combining RFID badges" Tags="&lt;arduino&gt;&lt;rfid&gt;&lt;automotive&gt;" AnswerCount="1" />
  <row Id="13561" PostTypeId="2" ParentId="13531" CreationDate="2011-04-27T16:34:24.333" Score="0" ViewCount="" Body="&lt;p&gt;As far as your question on starting robotics, I started with the &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0071468935&quot; rel=&quot;nofollow&quot;&gt;Robot Builder's Bonanza&lt;/a&gt;.  For me, it was the quintessential robot book and it's targeted at those with little or no background knowledge.  It has also been continually updated, but I haven't checked out the newest versions.  If they're anything like the original then it's indispensible.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-27T16:34:24.333" />
  <row Id="13562" PostTypeId="1" CreationDate="2011-04-27T16:38:00.960" Score="0" ViewCount="35" Body="&lt;p&gt;If I were to print a image on a transparency and hold it really close to my eyes (the same distance as glasses on my spectacles) the image would become blur and I would be able to see the background environment. Is there a way so that I can transform the image such that the image is viewable as an overlay to the background.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2011-04-27T17:04:09.473" Title="Transforming image for close eye viewing." Tags="&lt;imageprocessing&gt;" AnswerCount="2" />
  <row Id="13563" PostTypeId="2" ParentId="13560" CreationDate="2011-04-27T16:44:50.397" Score="0" ViewCount="" Body="&lt;p&gt;They are passive, so b) isn't realistic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind the antenna is also in the card. If they use different frequencies, they will need different antennas.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-04-27T16:44:50.397" />
  <row Id="13564" PostTypeId="2" ParentId="3760" CreationDate="2011-04-27T16:54:23.787" Score="0" ViewCount="" Body="&lt;p&gt;SpiritCircuits sell 6 layer fabrication on their ebay store:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://stores.ebay.co.uk/Spirit-Electronics/_i.html?_nkw=printed&amp;amp;submit=Search&amp;amp;_sid=429897585&quot; rel=&quot;nofollow&quot;&gt;http://stores.ebay.co.uk/Spirit-Electronics/_i.html?_nkw=printed&amp;amp;submit=Search&amp;amp;_sid=429897585&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your order in multiples of 1 sq foot (approx 30cm x 30cm), at £45 per square foot. If your board is smaller than 1 sq foot, they'll panelise it and route to individual circuits for free (but only one design is allowed per square foot).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure, but they may only deliver to the UK - you can always ask them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've recently ordered a couple of 2 layer boards from them, the service has been very good and the boards look good.&lt;/p&gt;&#xA;" OwnerUserId="4012" LastActivityDate="2011-04-27T16:54:23.787" CommunityOwnedDate="2011-05-20T11:44:01.827" />
  <row Id="13565" PostTypeId="2" ParentId="13562" CreationDate="2011-04-27T17:00:53.733" Score="0" ViewCount="" Body="&lt;p&gt;If You insist on this: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If I were to print a image on a&#xA;  transparency and hold it really close&#xA;  to my eyes&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;it is impossible. How that can be done look for the &#xA;3d headsets sold in the nineties as a gadget for computers. &#xA;This were small CRTs fastened on the side of ones head, the &#xA;CRT image side forward. This image was &quot;mirrored&quot; in the &#xA;eye with the aid of lenses, mirrors an a prism. &#xA;I assume that similar things are available still for &#xA;PC games &lt;/p&gt;&#xA;" OwnerUserId="4013" LastActivityDate="2011-04-27T17:00:53.733" />
  <row Id="13566" PostTypeId="2" ParentId="13562" CreationDate="2011-04-27T17:04:09.473" Score="2" ViewCount="" Body="&lt;p&gt;That would be an optics question, and not an image processing question.  Basically you need lenses to make the apparent image appear farther away where the eye can focus on it better.  This is how all head worn heads-up-displays work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can't &quot;un-fuzzyfy&quot; the image in software, print it on a transparency, look through it, and expect it to somehow be in focus.  Physics doesn't work that way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for how to use lenses to make it work-- I don't know.  I'm not that good with optics.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-27T17:04:09.473" CommentCount="3" />
  <row Id="13567" PostTypeId="2" ParentId="13112" CreationDate="2011-04-27T17:05:31.480" Score="1" ViewCount="" Body="&lt;p&gt;The &quot;checkbusy&quot; must send 0xFF to the SD card (that is not clear in your question). Is this SD or SDHC? The latter have some differences in initialization and operation sequences.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If we don't send dummy data after read ...&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;In SPI, you have to send data to be able to read from the client. Remember that the master always drives the clock line. The dummy data I send when reading SD cards is 0xFF, too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 512 zero bytes may be actual data from the device. Are you sure that you sent the address bytes in the correct order? &lt;a href=&quot;http://www.sdcard.org/developers/tech/pls/&quot; rel=&quot;nofollow&quot;&gt;Specs&lt;/a&gt; can be found on &lt;a href=&quot;http://www.sdcard.org/developers/tech/pls/&quot; rel=&quot;nofollow&quot;&gt;www.sdcard.org&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1472" LastActivityDate="2011-04-27T17:05:31.480" />
  <row Id="13568" PostTypeId="1" AcceptedAnswerId="13569" CreationDate="2011-04-27T07:50:30.550" Score="2" ViewCount="102" Body="&lt;p&gt;I just received my first Arduino kit today - it wasn't hard to make my first LCD chaser - woot!  Already I am on to better things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to mess with the &lt;a href=&quot;http://www.emartee.com/product/41872/Arduino%20Serial%20LCD%201602%20Shield&quot; rel=&quot;nofollow&quot;&gt;EL1602A LCD&lt;/a&gt; screen next.  What's the best way to connect to the pins?  They look enticingly solderable so that I end up with jumper leads hanging permanently off, but is that a good idea?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not, what do people suggest?&lt;/p&gt;&#xA;" OwnerUserId="4017" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-04T09:29:31.423" LastActivityDate="2011-05-04T09:29:31.423" Title="Arduino beginner LCD question - best way to connect to pins?" Tags="&lt;arduino&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="13569" PostTypeId="2" ParentId="13568" CreationDate="2011-04-27T15:12:39.823" Score="1" ViewCount="" Body="&lt;p&gt;Didn't find pictures of this part of yours (didn't look too hard). But if there are holes in it (that's what comes to my mind when I hear &quot;enticingly solderable&quot; :)) - through hole soldering ready - what I usually do is solder it with break away header pins (&lt;a href=&quot;http://www.sparkfun.com/products/10158&quot; rel=&quot;nofollow&quot;&gt;like this&lt;/a&gt;) so it can be easily seated on a breadboard.&lt;/p&gt;&#xA;" OwnerUserId="4028" LastActivityDate="2011-04-27T15:12:39.823" CommentCount="5" />
  <row Id="13570" PostTypeId="1" AcceptedAnswerId="13576" CreationDate="2011-04-27T17:32:21.163" Score="0" ViewCount="48" Body="&lt;p&gt;How 3-D TVs work? some comes with glasses and some without glasses? Doesn't seem to be very successful, any idea why and how ?&lt;/p&gt;&#xA;" OwnerUserId="3982" LastActivityDate="2011-04-27T18:53:43.027" ClosedDate="2011-04-27T19:36:29.423" Title="How 3-D televisions works?" Tags="&lt;tv&gt;" AnswerCount="1" />
  <row Id="13571" PostTypeId="1" CreationDate="2011-04-27T17:45:03.177" Score="1" ViewCount="25" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am working on a research project that involves implementing a dynamic voltage and frequency scaling for Renesas M16C microcontroller based system. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am working on BNS QSK62P+ development board. The microcontroller M16C can run at some discrete frequencies starting from 32KHz to 24MHz.  I want to change the operating frequency of this controller at runtime depending on the power and performance needs of the system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have worked on this kind of problem before?&lt;/p&gt;&#xA;" OwnerUserId="3199" LastActivityDate="2011-04-27T17:45:03.177" Title="Dynamic Frequency Scaling in Renesas M16C" Tags="&lt;microcontroller&gt;&lt;frequency&gt;&lt;low-power&gt;" CommentCount="1" />
  <row Id="13572" PostTypeId="2" ParentId="13047" CreationDate="2011-04-27T17:56:50.230" Score="2" ViewCount="" Body="&lt;p&gt;This is quite easy, you only need a 1.5 volts battery and a 1 megaohms resistor.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;First measure the voltage battery with the DMM. Let say it reads 1.609 volts&lt;/li&gt;&#xA;&lt;li&gt;Second measure the resistor. Let say the DMM reads 1.008 megaohms&lt;/li&gt;&#xA;&lt;li&gt;Then measure the voltage again but this time use the 1 megaohms resitor in the positive pole of the battery so you take the measure in the resistor leg.&lt;/li&gt;&#xA;&lt;li&gt;If the DMM reads 0.801 volts the DMM has a internal resistance of 1 megaohms, if it reads 1.461 volts then the internal resistance is 10 megaohms&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The formula for using different input voltages or resistors is: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;DMM internal resistance in megaohms= (&quot;DMM voltage measured &quot; x &quot;value of resistance used in megaohms&quot;) / (&quot;input voltage&quot; - &quot;DMM voltage measured &quot;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use this simple Excel file for the calculations: &lt;a href=&quot;http://www.qsl.net/ea2bsn/DMM_IR.xls&quot; rel=&quot;nofollow&quot;&gt;DMM_IR calculator&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4014" LastActivityDate="2011-04-27T17:56:50.230" />
  <row Id="13573" PostTypeId="1" CreationDate="2011-04-27T18:27:33.020" Score="4" ViewCount="37" Body="&lt;p&gt;what is the difference between frequency modulation and phase modulation?&lt;/p&gt;&#xA;" OwnerUserId="3998" LastActivityDate="2011-04-27T19:12:06.710" Title="modulation in phase and frequency" Tags="&lt;modulation&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="13574" PostTypeId="1" AcceptedAnswerId="13577" CreationDate="2011-04-27T18:36:40.343" Score="1" ViewCount="80" Body="&lt;p&gt;I saw quite a few custom computer units and laptops that are powered by adapters/batteries totalling 18 to 24 V. What's the significance of this design choice?&lt;/p&gt;&#xA;" OwnerUserId="1944" LastActivityDate="2011-04-27T20:24:23.677" Title="Significance of 24 Volts Power Supply" Tags="&lt;power-supply&gt;&lt;design&gt;" AnswerCount="3" />
  <row Id="13575" PostTypeId="2" ParentId="13363" CreationDate="2011-04-27T18:39:38.883" Score="1" ViewCount="" Body="&lt;p&gt;As it stated in above answer the frequency is the measure for repetition of an event. As you asked more than one questions about frequency, let me describe what it means in different contexts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Sine Wave&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this case,  frequency is the number of positive (or negative) peaks in the signal in one second. Sine wave is an example of the waves associated with AC power supply. So, an AC supply with 60Hz frequency means that the sine wave of its voltage repeats itself 60 times per second. A DC signal (it does not change over time) is said to have frequency of 0 Hz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sine wave is a lot more useful and meaningful outside the AC power domain. Actually we can classify signals in two parts namely periodic (signals that repeat some pattern over time) and aperiodic (signals that do not repeat in time). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A sine wave is the most fundamental periodic signal. That is because it has only one frequency associated with it. We can represent all periodic and aperiodic signals using some combination of sine waves of different frequencies. A periodic signal is made of a fundamental frequency and harmonic frequencies. For example a square-wave with 100Hz frequency actually means it has a fundamental frequency of 100Hz and the harmonic frequencies (always integer multiple of fundamental freq) are 200Hz, 300Hz, 400Hz ... etc.&#xA;The frequencies associated with aperiodic signals require bit more involved discussion, so I won't include it here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Filters&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An (electronic) filter is a device which literally &quot;filters&quot; frequencies. For example if a filter says it is a low pass filter (LPF) with cutoff freq of 1KHz, it means that any sine-wave coming at its input will reach the output if and only if it has frequency less than 1 KHz.&#xA;So if we pass a square wave of 10Hz through this LPF, at the output we will only see the harmonics of square-wave which are less than 1000hz (100 harmonics).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If we do not include all (infinite for square wave) the harmonics (sine waves) and add them together with fundamental frequency sine-wave, we will not get a square wave. But, the resulting wave would be an approximation of square-wave. So, producing an accurate square wave of any frequency is practically impossible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;DC-DC converter&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think this your main topic of question, how a DC &quot;thing&quot; can have a frequency. Actually a DC-DC converter uses a square wave (essentially a switch turning on and off repeatedly) to convert one DC voltage (ex. 5V ) to another DC voltage (ex. 20 V). So, the frequency of switch which is used to perform this function (DC-DC conversion) is known as the frequency of DC-DC converter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Bandwidth and frequency&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let us go back to the filter again. We just saw what an LPF does. there are other type of filters; high pass filter (HPF), band pass filter (BPF) and many more. Let us think about BPF. A BPF has a property that it allows only the frequencies (sine-waves) which are in a fixed range of values. A BPF with cutoff frequencies 100Hz and 5KHz, will pass only the frequencies in that range -i.e. band. So we can say that &quot;bandwidth&quot; of our filter is (5000 - 100 = 4900 Hz. Even an LPF can have bandwidth which is equal to cutoff frequency itself. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bandwidth is a term used in lot more context other than filters. A more general and loose explanation is how fast a device can work (so if that device is a filter what is the upper cutoff of that filter, assuming we do not care about the lower cutoff). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Frequency in computers&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know you did not ask for this, but this is a right place to cover this topic also. What does it mean when you say I have a 3 GHz computer?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A computer has a CPU which performs all mathematical and logical operations using digital circuits. Each operation in CPU is divided into one or more instructions. These instructions are then processed into multiple stages. each stage in instruction processing takes some time and the stage that takes maximum time decides the frequency of CPU. so if a CPU stage that takes maximum time = 1ns (nano second = 0.000000001 second), then then we can run that CPU at 1GHz (1 / 1ns). This is a very basic explanation of a very complex concept, so it is not too accurate and differs across different CPUs.&lt;/p&gt;&#xA;" OwnerUserId="3199" LastActivityDate="2011-04-27T18:39:38.883" CommunityOwnedDate="2011-04-27T18:39:38.883" />
  <row Id="13576" PostTypeId="2" ParentId="13570" CreationDate="2011-04-27T18:42:30.010" Score="2" ViewCount="" Body="&lt;p&gt;3-D imaging is all based off of how human vision works. Our brain is able to interpret depth by using the differences in what each eye sees. If for some reason you were to go blind in 1 eye you would actually loose your sense of depth. Now, the brain is smart enough to be able to &quot;make up&quot; what it believes the depth actually is even with just 1 eye, but this mostly comes from referencing past knowledge, things like &quot;i know that table is about 5 feet from me because i have run into it before&quot; or &quot;the way the shadow is being cast makes it seem like it is so far from me&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a little visualization to think about:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/VTpOq.jpg&quot; alt=&quot;Eyes&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When it comes to trying to make the brain perceive something as being 3d when it is truly just flat, you have to figure out tricks. One old trick is to wear glass where each eye has a different color. The video then can be produced such that each eye receives a slightly different image and the brain automatically processes the differences into what we perceive as depth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another trick is to use shutter glasses, essentially the idea of these is to flicker each lens so fast that you cant tell anything is even happening. So your left eye will be blocked while your right eye can see and then it switches. When synchronized with a TV, the TV can show you different images based off of what eye can currently see.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One method I have seen attempted with out glasses is to use the angle at which you are viewing the screen to create images that appear to have depth. The problem with this method is that you are very tightly limited on the angle that you can be looking at the screen, and you also can't have multiple viewers at once.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another method I have seen with out glasses is to have 2 physical image layers on the screen. They may only be a slight by apart from each other, but developers can take advantage of the human visual system being able to notice this slight depth difference and so they can again put different images on each layer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem with all of these methods is that they are attempts to trick the brain. The brain is so difficult to understand that it is virtually impossible to trick it so well that it doesn't know the difference. Even things like the spacing between your eyes can effect how well this tricks work for you.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-04-27T18:53:43.027" LastActivityDate="2011-04-27T18:53:43.027" />
  <row Id="13577" PostTypeId="2" ParentId="13574" CreationDate="2011-04-27T19:01:16.720" Score="6" ViewCount="" Body="&lt;p&gt;There are a few things that come into consideration with this voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One item is the voltage required by LCD backlights. A higher voltage makes it much easier to power them instead of having to go into some variable voltage boosting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another item is the chemical make up of batteries and the number of battery cells inside. I know 6 cell batteries seem to be pretty common in laptops. I believe LiPo's usable voltage range is about 2.7-4.2v per cell. So for a 6 cell battery, you are looking at about 24 V. It makes it easier for equipment designers to have their charger voltages to be about the same as the battery voltage. &lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-27T19:01:16.720" />
  <row Id="13578" PostTypeId="2" ParentId="13573" CreationDate="2011-04-27T19:11:27.827" Score="3" ViewCount="" Body="&lt;p&gt;Modulation in radio communication means, changing a parameter of the carrier wave according to the amplitude of the modulating signal. Generally modulating signal (often audio or video) signal is of a lower frequency and known as baseband signal. While a carrier signal (much higher in frequency, able to be transmitted with feasible antenna) is known as passband signal. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;After this background, lets jump directly into the question. &#xA;Frequency and phase are two different parameters of carrier signal. if we represent the carrier signal as c(t) = A sin (w(t)t + p(t)), w(t) is the (angular) frequency and p(t) is the phase. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Modulation means, we can vary either w or p or both in time according to the amplitude value of the modulating signal. Lets represent modulating signal as m(t). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Frequency Modulation&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;c(t) = A sin (w(t)t + p)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;w(t) = some_function(m(t))&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Phase Modulation&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;c(t) = A sin (wt + p(t))&lt;/p&gt;&#xA;&#xA;&lt;p&gt;p(t) = some_function(m(t))&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, although the modulated signals resulting from FM and PM look very similar, they are fundamentally different. &lt;/p&gt;&#xA;" OwnerUserId="3199" LastActivityDate="2011-04-27T19:11:27.827" CommentCount="2" />
  <row Id="13579" PostTypeId="2" ParentId="13573" CreationDate="2011-04-27T19:12:06.710" Score="2" ViewCount="" Body="&lt;p&gt;Frequency modulation is using different frequencies to represent different pieces of data. The binary cases is probably the easiest to understand, in this case Frequency X would correspond to a binary 1 while Frequency Y might correspond to a binary 0. So from a receivers perspective, if you see power at frequency y then you put a 0 down, while if you see power at frequency x then you put a 1 down. More complicated FM modulators can use different frequencies and combinations of frequencies to mean different symbols. For example, you could have it set up such that if you see frequency x but not y then your symbol is 10, if you see y but not x then it is 01, if you see both then it is 11, if you see neither then it is 00.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Phase modulation on the other hand uses a fixed frequency. It is then the change of phase that tells the demodulator what data to output. It usually makes most sense to look at what is called a constellation:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/eou9P.jpg&quot; alt=&quot;constellation&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you think of this as each point on the circle being a different phase change, you can see how each dot could represent different data.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-27T19:12:06.710" CommentCount="2" />
  <row Id="13580" PostTypeId="1" AcceptedAnswerId="13630" CreationDate="2011-04-27T19:14:54.757" Score="3" ViewCount="53" Body="&lt;p&gt;I've never used stencils before, but now I'm going to have to (BGAs, lots of 0402 caps and resistors, etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How close together can the paste holes for say adjacent 0402 caps be for a stencil to work properly?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tried calling my stencil manufacturer, and they basically said &quot;I dunno, send us your board files and we'll let you know if it's too close&quot;...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One person I know says 5 mils between paste holes, but that seems like an awfully awfully thin wall in the stencil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's a reasonable clearance value? Would that number be different for using a stencil by hand?  (vs. a more controlled automated unit)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; I'm currently aiming for a 10 mil clearance between paste holes. It appears that should be perfectly doable (since providers like Pololu say they can do approximately 0.5mm pitch, which works out to a ~10 mil gap between pads) However, what's a good clearance value assuming a nice laser cut metal stencil?&lt;/p&gt;&#xA;" OwnerUserId="1270" LastEditorUserId="1270" LastEditorDisplayName="" LastEditDate="2011-04-28T16:57:28.673" LastActivityDate="2011-04-28T17:53:48.587" Title="Component clearance for stencils and solder paste" Tags="&lt;solder-paste&gt;&lt;stencil&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="13581" PostTypeId="1" AcceptedAnswerId="13949" CreationDate="2011-04-27T19:18:34.097" Score="4" ViewCount="133" Body="&lt;p&gt;I have a clock.  It generates ticks.  I want to know the error in PPM relative to another clock, so I count the ticks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's say the oscillator is 1 MHz (for simplicity).  I should count 1,000,000 ticks per second.  I plot the (expected_tick_count - actual_tick_count) per other-clock-second.  I get a nice line which represents the accumulating error, in microseconds.  Linear regression results in R^2 = 0.9999 (i.e. a perfect line), and a slope of 27.  To me, this implies 27 PPM error in the oscillator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume this means I actually get 999,973 ticks per second instead of 1,000,000.  So I tune the oscillator frequency so that it includes an extra 27 ticks per second.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I re-run my test.  I expect to see negligible error.  Instead, I find another line, with a slope of about 3.  So it appears as if my initial regression analysis was off by 3 PPM, despite an R^2 that is the envy of statisticians everywhere.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I missing something?&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-05-05T20:48:45.440" Title="Calculating error between two clocks?" Tags="&lt;clock&gt;&lt;drift&gt;" AnswerCount="4" />
  <row Id="13582" PostTypeId="2" ParentId="13574" CreationDate="2011-04-27T19:35:44.210" Score="6" ViewCount="" Body="&lt;p&gt;Absolutely nothing inside the system works directly on the main DC voltage, there is always a DC/DC converter in between, so designers tend to choose the voltage high enough to get the current down to something the connectors and wires will take as long as it's not chosen so high that it becomes a risk and components get more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's generally much easier and more efficient to do a step-down converter than a step-up converter, so that also drives up the voltage until you can get rid of most of the step-up converters, the backlight converter being the obvious exception.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-04-27T19:35:44.210" />
  <row Id="13583" PostTypeId="2" ParentId="13581" CreationDate="2011-04-27T19:41:47.130" Score="4" ViewCount="" Body="&lt;p&gt;What accuracy does the datasheet for your oscillator claim? Typically, a crystal oscillator will only guarantee to be within 25ppm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Perhaps the act of measuring the frequency is having an effect also.&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-04-27T19:41:47.130" CommentCount="3" />
  <row Id="13584" PostTypeId="2" ParentId="13581" CreationDate="2011-04-27T20:11:44.570" Score="2" ViewCount="" Body="&lt;p&gt;How are you tuning the oscillator to get the 27 more ticks/sec, that is different from the way you are measuring the difference?  Are you are using two different references that could be slightly off, by say, 3 ppm?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Then, from our comments below, and despite the error having been determined by the more accurate device, I'd suggest that the secondary error is due, at least in part, to having tweaked your OUT against itself, known to have been out by 27ppm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen this happen when I've calibrated a new bicycle odometer by riding an independently measured distance, and compensating the device for the %-age error in its reading.  A second trial will come really close but it's not perfect.  After the second tweak, the device will be good to within the 0.01 mile (53') limit of the display.&lt;/p&gt;&#xA;" OwnerUserId="3361" LastEditorUserId="3361" LastEditorDisplayName="" LastEditDate="2011-04-29T17:59:10.480" LastActivityDate="2011-04-29T17:59:10.480" CommentCount="4" />
  <row Id="13585" PostTypeId="2" ParentId="13540" CreationDate="2011-04-27T20:12:54.417" Score="2" ViewCount="" Body="&lt;p&gt;As short as possible, but don't stress out about it for hobby work.  &lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-27T20:12:54.417" />
  <row Id="13587" PostTypeId="2" ParentId="13574" CreationDate="2011-04-27T20:24:23.677" Score="1" ViewCount="" Body="&lt;ul&gt;&#xA;&lt;li&gt;Low enough to make it easy to meet safety requirements (so should be &amp;lt;60 V)&lt;/li&gt;&#xA;&lt;li&gt;High enough to make the current not much, cutting connector size&lt;/li&gt;&#xA;&lt;li&gt;Common parts available.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-04-27T20:24:23.677" />
  <row Id="13588" PostTypeId="1" CreationDate="2011-04-27T20:28:22.033" Score="1" ViewCount="72" Body="&lt;p&gt;I am looking for something to log the read and writes on an AXI 4 bus to a file. And similar for AXI4-Stream. For what it is worth, this is for Xilinx. I could roll my own, but I hoped someone else had already solved this problem.&lt;/p&gt;&#xA;" OwnerUserId="206" LastEditorUserId="763" LastEditorDisplayName="" LastEditDate="2011-04-28T10:10:41.233" LastActivityDate="2011-04-28T10:10:41.233" Title="Is there a free/low-cost bus monitor in VHDL/Verilog for ARM AXI/AXI4 and/or AXI4-Stream protocols?" Tags="&lt;arm&gt;&lt;hdl&gt;&lt;axi4&gt;&lt;axi4-stream&gt;&lt;axi&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13589" PostTypeId="2" ParentId="12054" CreationDate="2011-04-27T20:53:44.077" Score="0" ViewCount="" Body="&lt;p&gt;After checking online, with other engineers who use the standard and with an IC distributor, there is no such discrete IC.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-04-27T20:53:44.077" />
  <row Id="13590" PostTypeId="1" CreationDate="2011-04-27T21:34:16.307" Score="2" ViewCount="93" Body="&lt;p&gt;I have a common base amplifier with a source resistance and a load resistor.  I am trying to solve for the system gain including the source resistor with both the hybrid-pi and T model but seem to be getting different answers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When solving the hybrid-pi model for Vbe by looking at the currents at the emitter I end up with an extra gm term due to the voltage controlled current source.  I do not get this term when I solve for the same circuit with the T-model.  Any help?  Its probably something simple I am missing.&lt;/p&gt;&#xA;" OwnerUserId="4018" LastActivityDate="2011-04-27T22:12:23.800" Title="Common Base Amplifier - Hybrid-Pi vs. T Model" Tags="&lt;bjt&gt;" AnswerCount="1" />
  <row Id="13591" PostTypeId="1" CreationDate="2011-04-27T21:35:41.900" Score="5" ViewCount="127" Body="&lt;p&gt;What is a Fourier Series?  What it is used for?&lt;/p&gt;&#xA;" OwnerUserId="3998" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-28T00:53:00.127" LastActivityDate="2011-04-28T00:53:00.127" Title="What is the function of a Fourier Series?" Tags="&lt;math&gt;&lt;fourier&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13592" PostTypeId="1" AcceptedAnswerId="13598" CreationDate="2011-04-27T21:47:05.540" Score="2" ViewCount="37" Body="&lt;p&gt;I'm trying to remember the approximation for the value of the diffusion capacitance for a bipolar power transistor.  I think it might have been gm/Ft?  Can anyone confirm this and/or give a reference? Thanks!&lt;/p&gt;&#xA;" OwnerUserId="4019" LastActivityDate="2011-04-28T10:11:05.833" Title="Diffusion capacitance approximation for bipolar power transistor" Tags="&lt;transistor&gt;&lt;capacitance&gt;" AnswerCount="1" />
  <row Id="13594" PostTypeId="2" ParentId="13590" CreationDate="2011-04-27T22:12:23.800" Score="1" ViewCount="" Body="&lt;p&gt;Without the equations you get it's hard to know exactly what's going on, but you wouldn't expect to get a &quot;gm&quot; term when you solve for the gain T model, as the model consists of a current controlled current source Beta*ib in series with the dynamic emitter resistance.  The two are related, however, as Beta*ib = (Beta/r_pi)*v_pi = gm*v_pi.  For the T model of a common base amplifier with source resistance Rs and load resistance RL, one should get the gain as being (alpha*RL)/(Rs + Re), with Re being the dynamic emitter resistance.&lt;/p&gt;&#xA;" OwnerUserId="4019" LastActivityDate="2011-04-27T22:12:23.800" CommentCount="1" />
  <row Id="13595" PostTypeId="2" ParentId="13591" CreationDate="2011-04-27T22:33:04.970" Score="3" ViewCount="" Body="&lt;p&gt;Every realizable analog signal, anything you can think of or draw legitimately on a voltage vs. time graph can be expressed in mathematical terms as the sum of an infinite number of sine waves of different frequencies - something of this form:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;any_signal(t) = A*sin(f1*t) + B*sin(f2*t) + C*sin(f3*t) ....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Different signals are constructed by changing the values of A, B, C etc and f1, f2 and others.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When someone refers to a Fourier series they refer to expressing the waveform as a series of addition operations like above.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Realistically every analog signal has SOME content at every frequency - even if the amplitude is .1e-67 it's still there.  Ideally this isn't so - if I construct a pure square wave then I know for a fact it consists ONLY of frequencies that are an odd multiple of its period.  Thus 1Hz square wave is the sum of a 1Hz sine wave plus a 3Hz sine wave and so on down the line.  For other well-known waveforms such as triangle waves, and ramps people have done the calculations as to what frequencies are present and at what content.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-04-27T22:33:04.970" CommentCount="5" />
  <row Id="13596" PostTypeId="2" ParentId="13581" CreationDate="2011-04-28T01:34:31.240" Score="2" ViewCount="" Body="&lt;p&gt;I don't have any potential solutions, just a couple of further questions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen oscillators drift for a couple of minutes after tuning, so there may be a post adjustment issue you're dealing with. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you take data over a longer time, does it change the results? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are you using as a reference clock? How accurate is that? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other thing that comes to mind, and I'm not going to explain it correctly because it's still something I'm struggling with is this. As you are plotting the accumulated error, your operating in the phase domain, as you've measuring accumulated error in time. However, you're measuring the frequency, so there may be a phase/frequency thing going on. I'll try to dig up some more references. &lt;/p&gt;&#xA;" OwnerUserId="2148" LastActivityDate="2011-04-28T01:34:31.240" CommentCount="3" />
  <row Id="13597" PostTypeId="2" ParentId="13558" CreationDate="2011-04-28T01:36:01.597" Score="5" ViewCount="" Body="&lt;p&gt;Try checking out &lt;a href=&quot;http://www.diydrones.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.diydrones.com/&lt;/a&gt; it may answer a lot of your questions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for multi-km links RF waves travel at the speed of light which is 299,792,458 meters per second that's more than fast enough for realtime control. The problem with long distance links is that for a frequency high enough to support realtime high-quality video such as microwave frequencies are line of sight for the most part. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In order to get past free space attenuation you'll also need some power over FCC legal limits I'd assume, but you can get past that by getting an amateur radio license. There are ways around this, directional antennas but thats a whole story by itself.&#xA;(I am not a lawyer, I am however an Amateur Radio Operator)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Free space attenuation of signals (path loss) can be calculated as follows: Lfs = 32.45 + 20 log d + 20 log f&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lfs = Free space loss in dB&lt;/p&gt;&#xA;&#xA;&lt;p&gt;d = distance in km&lt;/p&gt;&#xA;&#xA;&lt;p&gt;f = frequency in Mhz&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hope this helps!&lt;/p&gt;&#xA;" OwnerUserId="3095" LastActivityDate="2011-04-28T01:36:01.597" />
  <row Id="13598" PostTypeId="2" ParentId="13592" CreationDate="2011-04-28T01:46:09.687" Score="2" ViewCount="" Body="&lt;p&gt;Good old Sedra and Smith fourth edition, pg 322 has the formula as $C_{de} = \mathrm{T}_{f}*g_m$ and has a note that $\mathrm{T}_f$ is usually in the 10 to 100 picosecond range.  It looks like your formula is equivalent.&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="1802" LastEditorDisplayName="" LastEditDate="2011-04-28T10:11:05.833" LastActivityDate="2011-04-28T10:11:05.833" CommentCount="2" />
  <row Id="13599" PostTypeId="1" AcceptedAnswerId="13600" CreationDate="2011-04-28T01:19:42.627" Score="1" ViewCount="96" Body="&lt;p&gt;I have an HTC Incredible phone which eats a lot of battery, and a cy-fi speaker which I use with the phone.  I'd like to charge them both while riding my bicycle, and I think the best choice is a solar charger, so I can avoid carrying along tons of AA batteries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I go about building a solar charger?  I've soldered in the past, but have no specific electronics knowledge.&lt;/p&gt;&#xA;" OwnerUserId="4174" LastEditorUserId="4023" LastEditorDisplayName="" LastEditDate="2011-04-28T04:26:33.467" LastActivityDate="2011-04-28T13:33:34.177" Title="How do I build a solar charger for my phone / other devices?" Tags="&lt;solar-cell&gt;&lt;charger&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="2" />
  <row Id="13600" PostTypeId="2" ParentId="13599" CreationDate="2011-04-28T01:43:31.967" Score="4" ViewCount="" Body="&lt;p&gt;I think it's unlikely you'll be able to do better than the cheap systems off eBay without spending a huge amount of time. Those systems are relatively rugged, weatherproof and have fairly smart charging systems. Building something equivalent means spending a lot of time finding cheap parts and making the bits you can't buy. If you have a 3D printer that will make it easier, but it will still take time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found a ~$40 one that folds and has a 10Wh battery that seemed like the best of the lot on eBay but don't have the link handy. Will edit the link in here tonight.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given that $40 budget for a DIY system you'll need to start with some scrounged parts. If you can find a LiIon USB battery that will make your life a lot easier - all you need to do is add some scrounged solar panels. But I suggest trying to find all the small solar panels you can to start with. Test them to find which ones still work and what their output is. Work out how to stitch them together to get a single source (both mechanically and electrically). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then spend most of your money on a smart LiIon charger and voltage regulator to feed 5.1V out the USB port you'll use to get power out of the device. I suggest a battery inside it to buffer the erratic solar input as some smart devices don't like that (my phone, for one). Even a smallish battery will do, a couple of Wh, as long as it can handle the max power you get out of your panels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would probably go with either a small 12V SLA or ideally scrounge a complete LiIon booster battery system that has a working charge/protection circuit. Then add a 5V regulated output you're good to go.&lt;/p&gt;&#xA;" OwnerUserId="4023" LastActivityDate="2011-04-28T01:43:31.967" />
  <row Id="13601" PostTypeId="2" ParentId="13553" CreationDate="2011-04-28T01:55:48.117" Score="1" ViewCount="" Body="&lt;p&gt;Diodes are used in DC-DC switching supplies and can also be used as variable capacitors when reverse biased!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.skyworksinc.com/uploads/documents/200824A.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.skyworksinc.com/uploads/documents/200824A.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.electronics-tutorials.ws/diode/diode_1.html&quot; rel=&quot;nofollow&quot;&gt;http://www.electronics-tutorials.ws/diode/diode_1.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3095" LastActivityDate="2011-04-28T01:55:48.117" />
  <row Id="13603" PostTypeId="2" ParentId="13599" CreationDate="2011-04-28T03:19:32.350" Score="3" ViewCount="" Body="&lt;p&gt;Another solution is to wire in a power adapter connected to your motocycle's battery that can charge them via a 12v&gt;5v USB adapter. It would be by far the simplest approach and probably a cheaper one than buying batteries and such. Make sure to add a fuse and a cutoff switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unless you're in an area that gets lots of sun, a solar panel probably won't be able to pay for itself with short term use as they are relatively expensive. You can also look at projects like the Mintybuck:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.nycresistor.com/2010/05/04/mintybuck/&quot; rel=&quot;nofollow&quot;&gt;http://www.nycresistor.com/2010/05/04/mintybuck/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Mintybuck is a DC-DC Switching converter (Higher Efficiency than a Linear Regulator) that runs off Li-Ion batteries based off of Ladyada's Mintyboost project. You can pick up Li-Ion batteries from plenty of vendors and even laptop batteries. 18650's are between $3-8 each and pack plenty of power if connected together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your mind is set and you want a solar charger I suggest just buying one pre-made from a company such as Brunton. You will need to have a smart charger for the battery as well as a proper DC-DC converter as the voltage can drop in the solar panels which means you'll need a SEPIC configuration converter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A great generic DC-DC converter IC you can use to get your hands dirty would probably be the 34063, or the LT1302 if you only want 5v output. Lots of information on these particular chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Something to keep in mind is that USB powered devices can draw more current than the standard 500ma upwards of 1A. These devices usually sense the device they are attached to by shorting the data leads or applying a voltage/resistor to them. You can find more out about that here: &lt;a href=&quot;http://www.ladyada.net/make/mintyboost/&quot; rel=&quot;nofollow&quot;&gt;http://www.ladyada.net/make/mintyboost/&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="3095" LastEditorUserId="1836" LastEditorDisplayName="" LastEditDate="2011-04-28T13:33:34.177" LastActivityDate="2011-04-28T13:33:34.177" CommentCount="3" />
  <row Id="13605" PostTypeId="2" ParentId="13553" CreationDate="2011-04-28T07:35:00.527" Score="0" ViewCount="" Body="&lt;p&gt;One of many uses, and a true DC application, is this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use a diode to measure temperatures. The voltage acorss a forward-biased diode will decrease with increasing temperature. It's not very accurate, but sometimes, it's good enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the temperature dependency of a diode forward voltage can be used to compensate for temperature dependencies in other elements of your circuit.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-04-28T07:35:00.527" />
  <row Id="13606" PostTypeId="2" ParentId="13588" CreationDate="2011-04-28T07:57:47.593" Score="1" ViewCount="" Body="&lt;p&gt;Does the Xilinx AXI Bus functional model help? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xilinx.com/ipcenter/axi4.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.xilinx.com/ipcenter/axi4.htm&lt;/a&gt; has a link to an &lt;a href=&quot;http://www.xilinx.com/support/documentation/ip_documentation/pb001_axi_bfm.pdf&quot; rel=&quot;nofollow&quot;&gt;AXI BFM Product Brief&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-04-28T07:57:47.593" CommentCount="2" />
  <row Id="13607" PostTypeId="1" AcceptedAnswerId="13609" CreationDate="2011-04-28T08:23:54.740" Score="2" ViewCount="47" Body="&lt;p&gt;Morning all, I've built the Velleman IR Light Barrier kit:&#xA;&lt;a href=&quot;http://www.vellemanusa.com/us/enu/product/view/?id=350693&quot; rel=&quot;nofollow&quot;&gt;http://www.vellemanusa.com/us/enu/product/view/?id=350693&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It currently beeps when the light barrier is broken, but I'd like to remove the speaker and replace it with a reed relay to trigger another circuit. I imagine I'll also need to add some resistors in order to stop it from blowing the rest of the board, but am unsure how to work out what to add.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got a reasonable multi-meter, which can measure DC &amp;amp; AC current/voltage, resistance and capacitance. If I can measure what I need to using it, could you please describe how - I'm not sure whether I should be bridging the contacts on the speaker, or introducing the meter into the circuit in series...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please let me know if any of the above makes no sense, I usually keep these projects inside my head, and don't know how many of the terms I've used are correct and how many I've made up.&lt;/p&gt;&#xA;" OwnerUserId="4029" LastActivityDate="2011-04-28T09:11:43.000" Title="I'd like to swap the speaker on an electronics kit for a reed relay" Tags="&lt;kit&gt;" AnswerCount="1" />
  <row Id="13608" PostTypeId="2" ParentId="13553" CreationDate="2011-04-28T08:40:48.210" Score="0" ViewCount="" Body="&lt;p&gt;Diodes have a very convenient feature in that their forward drop is almost the same as a transistor's Vbe drop. These can be used to bias an amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And although you distinguish AC and DC by the fact that one reverses in a predictable fashion, it is possible for DC to reverse, if, for example, the user plugs the battery in backwards and almost lets the magic smoke out.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-04-28T08:50:51.513" LastActivityDate="2011-04-28T08:50:51.513" />
  <row Id="13609" PostTypeId="2" ParentId="13607" CreationDate="2011-04-28T08:42:04.553" Score="1" ViewCount="" Body="&lt;p&gt;This looks straight-forward. From the receiver schematic, the &quot;speaker&quot; is in fact a piezo sounder and is DC driven so you can wire a relay coil in it's place. You will need to add a small general purpose diode (1N4148 or 1N914 etc) across the relay coil with the cathode connected to +V and the anode connected to the &quot;speaker&quot; output (T2 collector). You will need a small 9V relay with a coil resistance of at least 500 Ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;EDIT:- I've attached a (badly drawn) sketch ...&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/gYT8g.png&quot; alt=&quot;Relay replacing sounder&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2234" LastEditorUserId="2234" LastEditorDisplayName="" LastEditDate="2011-04-28T09:11:43.000" LastActivityDate="2011-04-28T09:11:43.000" CommentCount="3" />
  <row Id="13610" PostTypeId="1" CreationDate="2011-04-28T11:40:55.993" Score="0" ViewCount="145" Body="&lt;p&gt;What is a feedback resistor and capacitor?  Why are they are used in amplifier circuits? &lt;/p&gt;&#xA;" OwnerUserId="3998" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-28T16:20:55.147" LastActivityDate="2011-04-30T03:11:34.353" Title="Feedback Resistor and Capacitor in amplifier" Tags="&lt;capacitor&gt;&lt;resistor&gt;&lt;op-amp&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="13611" PostTypeId="2" ParentId="13610" CreationDate="2011-04-28T13:40:36.077" Score="3" ViewCount="" Body="&lt;p&gt;To understand why they are needed you first need to understand the basics of the opamp. There are a few simplified rules that you can use to help you solve any opamp circuit:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;The opamp will adjust Vout in attempt to make the + input equal to the - input. So when trying to solve for the voltage out, you should set the voltage at the + terminal equal to the voltage at the minus terminal. You don't actually know what this voltage is, so you just have to assign it a variable.&lt;/li&gt;&#xA;&lt;li&gt;No current flows in or out of the + or - terminals.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;If you apply these two rules to your circuit you will find that you can use any other standard circuit analysis method to solve your circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It turns out that you can get some very basic equations for specific configurations, but they all are derived from circuit analysis combined with the rules I mentioned.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a specific configuration that you are having a hard time understanding how it operates, feel free to post a schematic of it and we can help explain it.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-04-28T13:40:36.077" />
  <row Id="13612" PostTypeId="2" ParentId="11289" CreationDate="2011-04-28T14:17:33.553" Score="2" ViewCount="" Body="&lt;p&gt;Since there does not seem to be a single list of all the pragma's accepted by all the different tools, I made an attempt to compose such a list myself. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sigasi.com/content/list-know-vhdl-metacomment-pragmas&quot; rel=&quot;nofollow&quot;&gt;http://www.sigasi.com/content/list-know-vhdl-metacomment-pragmas&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Feel free to post comments if you find any omissions or inaccuracies.&lt;/p&gt;&#xA;" OwnerUserId="3145" LastActivityDate="2011-04-28T14:17:33.553" />
  <row Id="13613" PostTypeId="1" CreationDate="2011-04-28T14:25:15.813" Score="2" ViewCount="181" Body="&lt;p&gt;I'm trying to wire up 6 RGB LEDs in parallel, all controlled from a single source (well, three sources, one for each colour). The LEDs came supplied with resistors to limit the current of 270 Ohm for a 5v supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is, 6 LEDs x 3 colours = 18 resistors, which is a lot, and means I need a much bigger board and a lot more soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, can I instead wire the LEDs in parallel with each other, with a single resistor protecting all six? (3 resistors in total, one for each colour). How do I calculate the value of that resistor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More details:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LEDs are being driven from a &lt;a href=&quot;http://oomlout.co.uk/octal-transistor-array-uln2803a-x2-p-213.html&quot; rel=&quot;nofollow&quot;&gt;ULN2803A&lt;/a&gt; to supply a bit of current, which is in turn controlled by a Netduino providing a PWM signal on the three channels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://oomlout.co.uk/5mm-rgb-leds-super-flux-x3-p-203.html&quot; rel=&quot;nofollow&quot;&gt;These are the RGB leds in question&lt;/a&gt;. If I've correctly understood the data sheet they want 20mA of current, and forward voltages of 2, 3, 3 volts (for R,G and B respectively?). The supplied resistors were all 270 Ohm, so the channels may not be balanced quite right.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For extra credit: I'm only using 3 of the transistors in my driver chip, which has 8 in total. could I wire the PWM from the netduino to a second trio of transistors, and split the LEDs into two groups of three? Is it worth the effort?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS I don't have any diagramming tools to hand, but I can provide a diagram (drawn in paint) if it would help clarify my question. (see also &lt;a href=&quot;http://meta.electronics.stackexchange.com/questions/547/simple-online-tool-to-draw-circuit-diagram-schematics&quot;&gt;this meta question&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="4031" LastActivityDate="2011-06-03T10:37:56.993" Title="6 LEDs in parallel with a single resistor to simplify soldering" Tags="&lt;led&gt;&lt;resistor&gt;&lt;netduino&gt;&lt;parallel&gt;" AnswerCount="6" />
  <row Id="13614" PostTypeId="2" ParentId="13613" CreationDate="2011-04-28T14:33:39.597" Score="10" ViewCount="" Body="&lt;p&gt;Using only one resistor for 6 LEDs is not a good idea: if there's a slight difference in forward voltage between two LEDs one will light brighter than the other one.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Splitting the 6 LEDs in two groups of 3 and using additional inputs of the ULN2803A would only help if you would exceed the maximum current for one driver. But each driver of the ULN2803A can sink 500 mA, while 6 LEDs will need only 120 mA.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-06-03T10:37:56.993" LastActivityDate="2011-06-03T10:37:56.993" />
  <row Id="13615" PostTypeId="2" ParentId="13613" CreationDate="2011-04-28T14:35:43.810" Score="5" ViewCount="" Body="&lt;p&gt;No, you should not put LEDs in parallel. They will not share the current very well, one will dominate so the brightnesses will be different. Only once you have a series resistor or several LEDs in series (from a high enough voltage supply) can you successfully parallel up the strings of LEDs.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-04-28T14:35:43.810" />
  <row Id="13616" PostTypeId="1" AcceptedAnswerId="13621" CreationDate="2011-04-28T14:42:26.377" Score="1" ViewCount="92" Body="&lt;p&gt;I would like to start to play with Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've read that C and C++ are the official languages but I've also found other way to communicate using &lt;a href=&quot;http://www.arduino.cc/playground/Interfacing/Python&quot; rel=&quot;nofollow&quot;&gt;Python&lt;/a&gt; or &lt;a href=&quot;http://www.arduino.cc/playground/Interfacing/Java&quot; rel=&quot;nofollow&quot;&gt;Java&lt;/a&gt; for example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which programming languages are supported to program Arduino?&lt;br&gt;&#xA;Are there any limitations using Python or Java?&lt;/p&gt;&#xA;" OwnerUserId="2313" LastEditorUserId="2313" LastEditorDisplayName="" LastEditDate="2011-04-28T15:01:15.340" LastActivityDate="2011-04-28T15:51:54.600" Title="Which programming languages are supported to program Arduino? " Tags="&lt;arduino&gt;&lt;programming&gt;" AnswerCount="2" />
  <row Id="13617" PostTypeId="2" ParentId="4441" CreationDate="2011-04-28T14:49:33.100" Score="1" ViewCount="" Body="&lt;p&gt;I've tried to do this before and the problem is the shape of the exponential RC curve. Your eyes are very sensitive to changes at low light levels, so going from OFF to low current, it immediately looks  bright because that part of the curve is rising quickly. I think that an inverted curve (logarithmic) would give you what you want, but it's harder to do with just analog components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I ended up throwing a microcontroller at the problem since it was simpler to do that than build a log amplifier. Even then, I found that I had to increase the current very very slowly at the low end (was trying to simulate sunrise).&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-04-28T14:49:33.100" />
  <row Id="13618" PostTypeId="1" AcceptedAnswerId="13627" CreationDate="2011-04-28T15:05:18.333" Score="5" ViewCount="167" Body="&lt;p&gt;I'm going to buy an Arduino Uno/Duemilanove and I would like to add a couple of shields like an LCD and a WIFI shiled. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do I know if I can plug them both to Arduino?&lt;/p&gt;&#xA;" OwnerUserId="2313" LastActivityDate="2011-04-29T18:46:55.103" Title="How many shields can I plug into Arduino?" Tags="&lt;arduino&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="13620" PostTypeId="2" ParentId="13613" CreationDate="2011-04-28T15:31:33.247" Score="2" ViewCount="" Body="&lt;p&gt;From the figures you have given, the LED currents will be less than you expect.&#xA;For the red LED :-&lt;br /&gt; \$I_F=\frac{5.0-2.0}{270\Omega}=11.1\mathrm{mA}\$&lt;br /&gt;&#xA;For the green &amp;amp; blue LEDs :-&lt;br /&gt; \$I_F=\frac{5.0-3.0}{270\Omega}=7.4\mathrm{mA}\$&lt;br /&gt;&#xA;... which seem like they might be rather dim, especially the green &amp;amp; blue - and I haven't even taken into account the voltage drop across the driver (\$V_{CE(sat)}\$)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a 12V supply available, you could string the LEDs together in groups of three in series with a single resistor for each group (6 resistors). Assuming the currents are correct, you would need :-&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$R_{RED}=\frac{12.0-(3X2.0)}{11.1\mathrm{mA}}=541\Omega\$ (say 470)&lt;br /&gt;&#xA;\$R_{GREEN}=R_{BLUE}=\frac{12.0-(3X3.0)}{7.4\mathrm{mA}}=405\Omega\$ (say 390)&lt;/p&gt;&#xA;" OwnerUserId="2234" LastEditorUserId="2234" LastEditorDisplayName="" LastEditDate="2011-06-02T12:12:07.930" LastActivityDate="2011-06-02T12:12:07.930" />
  <row Id="13621" PostTypeId="2" ParentId="13616" CreationDate="2011-04-28T15:34:32.317" Score="3" ViewCount="" Body="&lt;p&gt;You are a bit confused.  I would stick with the c/c++ arduino enviroment for the arduino.  Java, Python, Processing are used on the pc to run communications with the arduino, they are not laguages for the arduino.  One limitation for them is that they do not run on the arduino.&lt;/p&gt;&#xA;" OwnerUserId="1498" LastActivityDate="2011-04-28T15:34:32.317" CommentCount="0" />
  <row Id="13622" PostTypeId="1" AcceptedAnswerId="13625" CreationDate="2011-04-28T15:42:18.470" Score="2" ViewCount="147" Body="&lt;p&gt;We have some big resistor test loads, like 8 Ω 250 W loads for simulating speakers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ukN1O.gif&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there also big variable load resistors for testing power supplies?  What are they called?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If not, what do people use instead?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-28T19:30:55.907" LastActivityDate="2011-04-29T12:50:32.473" Title="Variable resistor that can handle hundreds of watts?" Tags="&lt;power-supply&gt;&lt;resistor&gt;&lt;smps&gt;&lt;electronic-load&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="13623" PostTypeId="2" ParentId="13616" CreationDate="2011-04-28T15:51:54.600" Score="1" ViewCount="" Body="&lt;p&gt;My advice, stick with the C++ derived Arduino language or use raw C/C++. It's ideally suited to microcontrollers. But, if you like esoteric languages:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Occam via &lt;A href=&quot;http://concurrency.cc/&quot; rel=&quot;nofollow&quot;&gt;concurrency.cc&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;BASIC via &lt;a href=&quot;http://code.google.com/p/dk-basic/&quot; rel=&quot;nofollow&quot;&gt;DK-Basic&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Java via &lt;a href=&quot;http://www.harbaum.org/till/nanovm/index.shtml&quot; rel=&quot;nofollow&quot;&gt;NanoVM&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Forth via &lt;a href=&quot;http://amforth.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;amforth&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-04-28T15:51:54.600" CommentCount="2" />
  <row Id="13624" PostTypeId="2" ParentId="13622" CreationDate="2011-04-28T15:52:16.487" Score="3" ViewCount="" Body="&lt;p&gt;Large open-frame wirewound potentiometers are called &lt;em&gt;rheostats&lt;/em&gt;. You have to be careful when using these to test power supplies as it's too easy to burn them out! A fixed series padding resistor is a good idea.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-04-28T15:52:16.487" CommentCount="1" />
  <row Id="13625" PostTypeId="2" ParentId="13622" CreationDate="2011-04-28T16:12:06.893" Score="4" ViewCount="" Body="&lt;p&gt;As MikeJ-UK mentioned, there are rheostats.  I personally don't like them for the same reasons what Mike mentions.  But there are two more options:  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Build a a resistor box and use switches to change the load.  Or if you're fancy you can use MOSFET's and a MCU to do the job as well.  Careful selection of the resistor values could give you a very wide range of resistances with fairly fine control.  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Buy an &quot;electronic load&quot;.  Just google the term (in quotes) and you'll come up with a lot of pages.  Basically it's the opposite of a benchtop power supply.  Most will work in 3 modes:  Constant Current, Constant Voltage, and Constant Resistance.  My employer has one that's rated for 30 KWatts!  Of course they make smaller ones.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-04-28T16:12:06.893" />
  <row Id="13626" PostTypeId="1" AcceptedAnswerId="13637" CreationDate="2011-04-28T16:29:18.597" Score="0" ViewCount="96" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to make high-power LED Flasher circuit with Pic Microcontroller by using  15 pieces 3-Watt power LED.&#xA;We will have two pieces Switch Push Button.when it pressed the first button,it will blinking 4 times per second and will wait one second.&#xA;when it pressed the second button,it will blinking 2 times per second and will wait one second.&#xA;By the way, it will working  with battery of auto.(12 volt/72 Amp).Lastly, we will used in ambulance this circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I do that circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="3916" LastActivityDate="2011-04-28T20:24:44.670" ClosedDate="2011-05-24T16:05:09.400" Title="High-power LED Flasher circuit with Pic Microcontroller" Tags="&lt;microcontroller&gt;&lt;pic&gt;&lt;led&gt;&lt;circuit-design&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="13627" PostTypeId="2" ParentId="13618" CreationDate="2011-04-28T16:40:00.847" Score="8" ViewCount="" Body="&lt;p&gt;Go to &lt;a href=&quot;http://shieldlist.org/&quot; rel=&quot;nofollow&quot;&gt;shiedlist.org&lt;/a&gt; and look up the shields you are going to use. Then see if they both want to use the same pins. If your shield is not on &lt;a href=&quot;http://shieldlist.org/&quot; rel=&quot;nofollow&quot;&gt;shieldlist.org&lt;/a&gt; then look up their schematic/datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally if multiple shields need to use the one pin, you can't use them together, &lt;em&gt;unless&lt;/em&gt; those pins happen to be SPI or I2C pins. Both of these protocols use a master-slave model, with one master and many slaves. In these cases you may be able to use shields that share some or all pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The SPI pins are digital 10, 11, 12, an 13 by default. Pin 10 is the &lt;strong&gt;Slave Select&lt;/strong&gt; pin, which is used to specify which slave you want to talk to. You will need a &lt;em&gt;different&lt;/em&gt; SS pin for each SPI slave you want to talk to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The I2C pins are analog 4 and 5. I2C uses device addressing to differentiate between slave devices, so there is no equivalent of Slave Select. The same two pins can be shared by all I2C devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that stacking many shields introduces various issues like increased capacitance, which may start to deteriorate the signals, including those for SPI/I2C, and cause communication failures. &lt;/p&gt;&#xA;" OwnerUserId="2340" LastActivityDate="2011-04-28T16:40:00.847" />
  <row Id="13628" PostTypeId="2" ParentId="13622" CreationDate="2011-04-28T17:16:15.290" Score="2" ViewCount="" Body="&lt;p&gt;I've used large arrays of parallel carbon plates in a vise-like structure for testing power supply overload. You close the vise tight to compress the plates and lower the resistance, and see what the power supply does.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use active loads in my day-to-day work, mind you.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-04-29T12:50:32.473" LastActivityDate="2011-04-29T12:50:32.473" CommentCount="3" />
  <row Id="13629" PostTypeId="2" ParentId="13613" CreationDate="2011-04-28T17:45:44.400" Score="2" ViewCount="" Body="&lt;p&gt;The forward voltage (Vf) of the LED's is characterized for a given current; but if you look at the datasheets, you'll see that the Vf will increased with current (If).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you wire the LED's in parallel, the two common nodes of the LED's will have to have the same voltage drop.  That is, the Vf's of all the LED's will have to match.  Consequently, the If's of the LED's will vary until the Vf's are matched amongst the LED's - and hence you will have very different currents in the LED's, and very different brightness as a result.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even when you have &quot;identical&quot; LED's, when you wire them in parallel, the subtle variations between each piece may cause different currents to flow through them.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having an external resistor minimizes the Vf/If variance.  That is why in most simple designs, the LED current is controlled by a resistor.  For more sophisticated designs, you control the current with a current source.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-28T17:45:44.400" />
  <row Id="13630" PostTypeId="2" ParentId="13580" CreationDate="2011-04-28T17:53:48.587" Score="1" ViewCount="" Body="&lt;p&gt;For laser-cutting, it seems like a few mils is enough precision to ensure you create the necessary &quot;mask wire&quot; for the paste.  As long as your stencil is framed well and you are gentle with it, I doubt the application of paste would stress the stencil much...&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-28T17:53:48.587" />
  <row Id="13631" PostTypeId="1" CreationDate="2011-04-28T18:56:56.970" Score="2" ViewCount="120" Body="&lt;p&gt;What is impedance matching? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why it is used?&lt;/p&gt;&#xA;" OwnerUserId="3998" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T13:15:33.303" LastActivityDate="2011-05-16T13:15:33.303" Title="Impedance matching" Tags="&lt;impedance&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13632" PostTypeId="2" ParentId="13622" CreationDate="2011-04-28T19:09:19.163" Score="1" ViewCount="" Body="&lt;p&gt;The limiting factor on any given rheostat is generally RMS current rather than power, though within a family the current limit is usually, up to a certain point, roughly inversely proportional to &lt;i&gt;full-scale&lt;/i&gt; resistance; many families have a specified power rating, and the allowable RMS current will be that power divided by full-scale resistance.&lt;p&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to generate a continuous range of resistances in the range 50-1000 ohms, you could use a 1,000-ohm rheostat, but you could probably much more cheaply use a 100-ohm rheostat plus fixed 50, 100, 200, 200, and 500-ohm resistors (many other combinations would work).  Since you'd be using a 100-ohm rheostat instead of a 1K rheostat, you could use one that was rated for 1/10 the power that you'd otherwise need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incidentally, before the advent of triac-controlled dimmers, theatrical lighting used to use rheostats.  Certainly many of those rheostats have been junked over the years; people who keep them for sale would might charge a fair bit for them, but if you asked at the right places you might be able to get them for practically nothing.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-04-28T19:09:19.163" CommentCount="4" />
  <row Id="13633" PostTypeId="2" ParentId="13631" CreationDate="2011-04-28T19:27:38.627" Score="2" ViewCount="" Body="&lt;p&gt;To maximize power transfer to the load.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-04-28T19:27:38.627" CommentCount="4" />
  <row Id="13634" PostTypeId="2" ParentId="13622" CreationDate="2011-04-28T19:52:08.143" Score="2" ViewCount="" Body="&lt;p&gt;If you are going for cheap, get a large metal bucket and a bag of rock salt.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Liquid_rheostat&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Liquid_rheostat&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-28T19:52:08.143" CommentCount="2" />
  <row Id="13635" PostTypeId="1" AcceptedAnswerId="13636" CreationDate="2011-04-28T19:57:19.807" Score="4" ViewCount="137" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/7042/how-much-does-it-cost-to-have-a-custom-asic-made&quot;&gt;How much does it cost to have a custom ASIC made?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;A company used to exist, that I cannot locate anymore, to provide low cost ($2K USD)fabbing of microchip designs for students and other low count components. Last I can recall is that they group multiple small orders into large bulk ones that are sent to professional foundries (like IBM) for fabbing. They also took credit card and in some cases would assist students with the costs of doing their chip runs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know the name of that company and if they still exist?&lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-04-28T20:12:05.887" ClosedDate="2011-04-30T01:06:56.833" Title="Microchip Fabbing Not for Profit" Tags="&lt;ic&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="3" />
  <row Id="13636" PostTypeId="2" ParentId="13635" CreationDate="2011-04-28T20:12:05.887" Score="5" ViewCount="" Body="&lt;p&gt;For academic/research use, there's &lt;a href=&quot;http://www.mosis.com/orders/customer_accounts/academic-accounts.html&quot; rel=&quot;nofollow&quot;&gt;MOSIS&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The guy at Satre Electronics &lt;a href=&quot;http://www.satre-electronics.com/home/personal-projects&quot; rel=&quot;nofollow&quot;&gt;used MOSIS for his own personal projects&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-04-28T20:12:05.887" CommentCount="4" />
  <row Id="13637" PostTypeId="2" ParentId="13626" CreationDate="2011-04-28T20:24:44.670" Score="1" ViewCount="" Body="&lt;p&gt;I really suggest against using this in something as critical as in an ambulance, especially if (I am guessing) you are using this for an alarm or siren. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you can do is connect each switch to an external interrupt pin. You can do the coding easily, such as use the timer in the pic for the blinking and stopping. You can use a voltage regulator such as the LM7805 to get the voltage to run the pic from the 12v battery. For powering the actual leds, I recommend using a mosfet to switch enough current for the leds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.instructables.com/id/Power-LED-s---simplest-light-with-constant-current/step2/Specs-Function/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/Power-LED-s---simplest-light-with-constant-current/step2/Specs-Function/&lt;/a&gt; That is an example for a LED driver, you can buy a IC designed for this, or use the provided example I just gave.&lt;/p&gt;&#xA;" OwnerUserId="2050" LastActivityDate="2011-04-28T20:24:44.670" CommentCount="2" />
  <row Id="13639" PostTypeId="2" ParentId="13631" CreationDate="2011-04-28T23:03:35.937" Score="3" ViewCount="" Body="&lt;p&gt;Any kind of electrical power transfer has a typical ratio of voltage to current. For example, you can deliver 100 watts by 1 amp at 100 volts, or 10 amps at 10 volts, or any other product that comes to 100. It's convenient to express the ratio of volts to amps as a number of ohms (since dimensionally that's all ohms are anyway). Power sources, loads, and even transmission lines all have characteristic impedance, which tells you something about what will happen when things are connected together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Impedance &lt;em&gt;matching&lt;/em&gt; is the selection of components with identical impedance, or the addition of impedance transforming components to cause a component with an undesired impedance to appear as though it has a more desirable one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As Brian Carlton pointed out, when you have matched impedance, you achieve maximal power transfer. This is often desirable, but not always. The thing to remember is that maximal power transfer is achieved at the cost of dissipating equal power in the source and the load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So for example, a case for &lt;em&gt;not&lt;/em&gt; matching impedance is when you want to efficiently use the energy from a source. A 0.1 ohm load would get optimal &lt;em&gt;power&lt;/em&gt; out of a battery with a 0.1 ohm internal resistance, but half the energy would be dissipated in the battery itself, which would be rather wasteful of the stored energy. (Not to mention that the terminal voltage would fall to half!) By purposely using a load much with much higher resistance than the battery, most of the stored energy ends up doing work in the load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, you DO want to match impedance when, for example, you have an audio amplifier stage that ideally wants to drive a 600 ohm load, but you only have a 3.2 ohm speaker. An ordinary transformer, having a 1:N voltage ratio, will conveniently give you a 1:N^2 impedance ratio. Another common case is in RF work, where as volting pointed out, you need to minimize reflections, because reflected energy can cause excessive power dissipation in your source.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-04-28T23:11:18.960" LastActivityDate="2011-04-28T23:11:18.960" />
  <row Id="13640" PostTypeId="1" CreationDate="2011-04-29T00:00:43.030" Score="2" ViewCount="114" Body="&lt;p&gt;For a test of a filter and video transmitter gear, I need a variable frequency (potentiometer adjusted) sine or square wave oscillator, adjustable from about 1 to 10 MHz. Output about 1Vp-p okay, but I could reduce a higher output. I don't have many parts at the moment; so I need the cheapest way to do this. I have a lot of NOR gates lying around and I'm thinking of a ring oscillator but when I try to make them adjustable they become unstable.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-04-29T00:09:27.200" LastActivityDate="2011-04-29T06:31:02.943" Title="Cheap simple way to make an adjustable 1-10 MHz square or sine wave oscillator" Tags="&lt;filter&gt;&lt;oscillator&gt;&lt;test&gt;" AnswerCount="1" CommentCount="0" FavoriteCount="1" />
  <row Id="13641" PostTypeId="2" ParentId="13558" CreationDate="2011-04-29T01:03:26.350" Score="2" ViewCount="" Body="&lt;p&gt;Microhard &lt;a href=&quot;http://www.microhardcorp.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.microhardcorp.com/&lt;/a&gt;  make nice tiny, light 900Mhz (ISM band) radio modules that bridge ethernet (and serial and USB) &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;1.5Mbps over 90-100km without a repeater. &lt;/li&gt;&#xA;&lt;li&gt;Add a repeater every 90-100km, or put the repeater on a tall hill every 300km&lt;/li&gt;&#xA;&lt;li&gt;The export restricted versions do 128 bit encryption as well. &lt;/li&gt;&#xA;&lt;li&gt;We use the unrestricted module  on our robots, which are a lot like US military drones. &lt;/li&gt;&#xA;&lt;li&gt;Our old military UAV had an older Microhard radio module (lower bit rates). &lt;/li&gt;&#xA;&lt;li&gt;I'm pretty sure most of the short range ( 1-200km) stuff is using the 900Mhz band.&lt;/li&gt;&#xA;&lt;li&gt;The module the size of a big matchbox and lightweight.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Why use the 900Mhz ISM band?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Because it works well, even in built up areas. &lt;/li&gt;&#xA;&lt;li&gt;Doesn't need a special radio license to use.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-04-29T01:03:26.350" />
  <row Id="13642" PostTypeId="1" CreationDate="2011-04-29T01:08:35.707" Score="0" ViewCount="109" Body="&lt;p&gt;Hi I'm driving some leds using bs170 mosfet. The led's are lighting up however I would like to be able to turn it off after 30 seconds say.  I tried using the following code but it didn't work. I think it's turning off and on faster than I notice. I seem to be getting a square wave on the scope on the pin that the fet is connected to.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/*&#xA; * AVRGCC1.c&#xA; * &#xA; * Created: 21/04/2011 21:38:56&#xA; *  Author: steven&#xA; */ &#xA;&#xA;#define F_CPU 20000000UL  // 1 MHz &#xA;&#xA;#include &amp;lt;util/delay.h&amp;gt;&#xA;#include &amp;lt;avr/io.h&amp;gt;&#xA;&#xA;int main(void)&#xA;{ &#xA;        //TODO:: Please write your application code &#xA;        DDRA=0b00000001; //Make PDA0 as output  &#xA;        PORTA =0b00000001; // turn on fet  &#xA;        _delay_ms(30000);&#xA;        DDRA=0b00000000;&#xA;} &#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="568" LastEditorDisplayName="" LastEditDate="2011-04-29T01:54:09.803" LastActivityDate="2011-04-30T19:44:43.200" Title="Turning led off after 30 seconds" Tags="&lt;avr&gt;" AnswerCount="2" CommentCount="5" />
  <row Id="13643" PostTypeId="2" ParentId="13640" CreationDate="2011-04-29T01:08:51.817" Score="3" ViewCount="" Body="&lt;p&gt;How about an oscillator around a Schmitt-Trigger inverter? Capacitor on input, resistor from output to capacitor, done.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ODosK.png&quot; alt=&quot;relaxation oscillator&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-04-29T06:31:02.943" LastActivityDate="2011-04-29T06:31:02.943" CommentCount="6" />
  <row Id="13644" PostTypeId="2" ParentId="13610" CreationDate="2011-04-29T01:26:15.153" Score="1" ViewCount="" Body="&lt;p&gt;Feedback can be used in any kind of amplifier circuit, not just in op-amp circuits. Feedback can be achieved by any component or network that will deliver a portion of the output signal back to the input; resistors and capacitors and networks built from them just happen to be common choices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Feedback can be either positive or negative. Positive feedback adds to the input in such a way that an increase in the output signal will reinforce the input signal, producing in turn still more output. Negative feedback has the opposite effect, tending to cancel out the input and reducing the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Negative feedback decreases the gain of an amplifier, so what good is it? The usual reason for using negative feedback is to improve the frequency response of an amplifier. Suppose that, without the feedback network, the amplifier does a better job at amplifying some frequencies than others. By adding negative feedback, the stronger response to these favored frequencies results in more negative feedback, which reduces the output at those frequencies. The overall gain is lowered, but the payoff is that it essentially levels the amplifier's frequency response over a wide range of frequencies.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Positive feedback is less common, but has uses. Positive feedback increases the gain of the amplifier, and an old (early 20th century) radio design employed positive feedback for just that purpose. The problem with positive feedback, however, is that when the gain of the amplifier combined with the loss in the feedback network gives you a 'loop gain' of 1 or more, your amplifier turns into an oscillator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Feedback can exist in an amplifier whether it's intentional or not. Parasitic capacitance can couple outputs back to inputs, as can magnetic coupling. If there happens to be a frequency at which these un-intentional feedback paths can result in a loop gain over 1, a circuit that is intended as an amplifier can quickly turn into an oscillator at that frequency. It's often the case that a feedback network is added to the amplifier just to counteract the effects of parasitic feedback.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-29T01:26:15.153" />
  <row Id="13645" PostTypeId="2" ParentId="12484" CreationDate="2011-04-29T01:33:00.857" Score="0" ViewCount="" Body="&lt;p&gt;Many early MCUs don't even have a multiply instruction, much less a divide.&#xA;The IIR filter with the magic value&#xA;with K = 1/2^8&#xA;was specifically designed for such MCUs.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// filter implements&#xA;// y(n)=K*x(n)+y(n-1)*(1-K)&#xA;// with K = 1/2^8.&#xA;// based on ideas from&#xA;// http://techref.massmind.org/techref/microchip/math/filter.htm&#xA;// WARNING: untested code.&#xA;// Uses no multiplies or divides.&#xA;// Eventually y converges to a kind of &quot;average&quot; of the x values.&#xA;short average; // global variable&#xA;// (...)&#xA;while(1){&#xA;    short xn = readADC(adc_ch);&#xA;    // hope that we don't overflow the subtract --&#xA;    // -- perhaps use saturating arithmetic here?&#xA;    short aux1 = xn - average;&#xA;    short aux2 = aux1 / 256;&#xA;    // compiler should use an arithmetic shift,&#xA;    // or perhaps an unaligned byte read, not an actual divide&#xA;    average += aux2;&#xA;    delay_ms(5);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-04-29T01:33:00.857" />
  <row Id="13646" PostTypeId="2" ParentId="13642" CreationDate="2011-04-29T01:42:48.860" Score="5" ViewCount="" Body="&lt;p&gt;This part ..&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;PORTA =0b00000001; // turn on fet &#xA;_delay_ms(30000);&#xA;DDRA=0b00000000;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;should probably look like this ..&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;PORTA =0b00000001; // turn on fet &#xA;_delay_ms(30000);&#xA;PORTA=0b00000000;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;i.e., you don't want to redefine the direction of the pin, you want to change its state.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-29T01:42:48.860" CommentCount="3" />
  <row Id="13647" PostTypeId="1" CreationDate="2011-04-29T02:15:39.980" Score="0" ViewCount="99" Body="&lt;p&gt;What is your favorite micro controller, what micro-controller was the most pleasant to work with, what was the easiest micro controller you ever used?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, what in your opinion is the best micro controller out there, and if you had the possibility to tell others what micro controller they should learn or use, what would you tell them?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For me, it would be the RX62N. I just started playing around with it a few weeks ago, and I saw the online renesas interactive presentation for the chip, and well, I feel like I am working on some fantastic technology. Sure this is the quickest and most complicated MCU I ever worked with (I never got to work with any OS capable chips yet), but thanks to it, I have a better idea on how mcu's work in general. The HEW IDE is alright, I cannot get eclipse working with it yet, and I am still messing around with getting GNURX working for it. The interrupts are pretty cool, with all the possible interrupt sources such as the ADC, comparator, the usual external interrupts, and timer. The best thing about it in my opinion is the ease of access to resources. The renesas interactive online course thing is fantastic, and it seems to give a massive amount of explanation for each function of the chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've worked with the PIC18f family, as they were my introductory into digital electronics, and they are most certainly quite fun and cheap, but they do not seem to have enough &quot;omph&quot; for me. I was about to work with the PIC32 family, but I unfortunately made a mistake in the land pattern for the QFN chip, so it did not work for me, but I still do want to work with them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All in all, if I were to recommend for anyone to try out a new micro controller, it would be the RX62N.&lt;/p&gt;&#xA;" OwnerUserId="2050" LastActivityDate="2011-04-29T03:15:54.190" ClosedDate="2011-04-29T09:28:03.863" Title="What is your favorite or most enjoyable micro controller you ever used?" Tags="&lt;microcontroller&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="13648" PostTypeId="2" ParentId="13647" CreationDate="2011-04-29T02:45:58.000" Score="0" ViewCount="" Body="&lt;p&gt;Which ever one best fits the design challenge at hand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know that sounds like a cop-out answer but really the most enjoyable microcontroller to work with is the one that best fits the problem.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is not enjoyable (for me) is spending massive amounts of time shoe-horning a solution into a device it was never designed for.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm sure that is not the same for everyone, some may enjoy the challenge of shoe-horning the most.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For me the joy is truly in the system design phase so whatever results in the best and quickest implementation is what i'm after so I can move on to the next design.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-04-29T02:45:58.000" />
  <row Id="13649" PostTypeId="2" ParentId="13647" CreationDate="2011-04-29T03:15:54.190" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.parallax.com/propeller/&quot; rel=&quot;nofollow&quot;&gt;Parallax Propeller&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The multi-core shared-ram architecture is &lt;em&gt;so&lt;/em&gt; much easier then interrupts. It much more closely matches how I think about approaching a task. This means I have to spend FAR less time on software design, which is a good thing, because I am not a great programmer (I am a hardware guy who does a little programming, not vice-versa).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, the interpreted language uses tab-indentation, which puts it far above every language but python in my book (to hell with semicolons).&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-04-29T03:15:54.190" />
  <row Id="13650" PostTypeId="1" CreationDate="2011-04-29T03:27:06.050" Score="0" ViewCount="44" Body="&lt;p&gt;i had been using it a lot for a month or so, and then the cpu usage started to go through the roof all of a sudden. i spoke to people who are certified for repairing this equipment and they've never heard of the issue before. i just turned it on after a couple of months of it just laying around, it worked for like 10 minutes fine, and then the cpu usage started going through the roof again. every operation it does lags (ie: switching menus, etc). is the mobo fried?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;it's an Akai MPC 4000&lt;/p&gt;&#xA;" OwnerUserId="4038" LastActivityDate="2011-04-29T03:27:06.050" ClosedDate="2011-04-29T09:30:12.480" Title="electronic music sampler cpu usage spikes" Tags="&lt;cpu&gt;&lt;heat&gt;" CommentCount="2" />
  <row Id="13651" PostTypeId="1" CreationDate="2011-04-29T05:18:47.867" Score="1" ViewCount="46" Body="&lt;p&gt;I have a 1:24 scale remote control flatebed towtruck. The only function that it is missing is that i would like the flatebed to slide back slow. i am in need of a very small slow moving motor so it will look even more realistic. The motor that i have turn to fast. Can someone help me and where can i purchase the motor at?&lt;/p&gt;&#xA;" OwnerUserId="4039" LastEditorUserId="4039" LastEditorDisplayName="" LastEditDate="2011-04-29T05:29:13.587" LastActivityDate="2011-04-29T10:51:20.297" ClosedDate="2011-04-30T00:40:29.980" Title="Remote Control 47 Rollback" Tags="&lt;dc-motor&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13652" PostTypeId="1" CreationDate="2011-04-29T05:51:29.457" Score="0" ViewCount="60" Body="&lt;p&gt;I have had a htc sense rom on my htc hd2 phone, and I noticed that I can update facebook/twitter, send and receive email, etc, basically like a data plan but limited.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I have a vanilla rom and that free data thing is gone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does tmobile have some special apn settings that can give you free data plan with maybe limited speed or something?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. I am sure I didnt have wifi on and I am sure that I do not have data plan nor been charged extra&lt;/p&gt;&#xA;" OwnerUserId="4040" LastActivityDate="2011-04-29T05:51:29.457" ClosedDate="2011-04-29T09:26:08.147" Title="Free DataPlan on TMobile US" Tags="&lt;cellphone&gt;&lt;data&gt;" />
  <row Id="13653" PostTypeId="2" ParentId="11254" CreationDate="2011-04-29T06:38:26.603" Score="3" ViewCount="" Body="&lt;p&gt;This relaxation oscillator must be the most simple you can find:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/tFgNj.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-29T06:38:26.603" CommentCount="1" />
  <row Id="13654" PostTypeId="1" AcceptedAnswerId="13655" CreationDate="2011-04-29T08:45:35.910" Score="1" ViewCount="134" Body="&lt;p&gt;I would like to buy an LCD screen fom Arduino to display some results from a web http call; the Web API returns a JSON text encoded in UTF-8.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've read that &lt;a href=&quot;http://userguide.icu-project.org/strings/utf-8&quot; rel=&quot;nofollow&quot;&gt;UCI&lt;/a&gt; is the way to go to handle unicode in C/C++ program for Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions:&lt;br&gt;&#xA;Will I be able to display UTF-8 characters to &lt;a href=&quot;http://www.nuelectronics.com/estore/index.php?main_page=product_info&amp;amp;cPath=1&amp;amp;products_id=2&quot; rel=&quot;nofollow&quot;&gt;this kind of screen&lt;/a&gt;?&lt;br&gt;&#xA;Are there (affordable) character LCD screens able to display UTF-8 characters?&lt;/p&gt;&#xA;" OwnerUserId="2313" LastEditorUserId="2313" LastEditorDisplayName="" LastEditDate="2011-04-29T12:51:11.340" LastActivityDate="2011-04-29T17:53:15.480" Title="How to deal with unicode characters with character LCD displays?" Tags="&lt;arduino&gt;&lt;display&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13655" PostTypeId="2" ParentId="13654" CreationDate="2011-04-29T10:33:29.963" Score="4" ViewCount="" Body="&lt;p&gt;I'm not that much familiar with Arduino, but let's look at it from the LCD perspective.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Virtually all popular character LCDs use &lt;a href=&quot;http://en.wikipedia.org/wiki/HD44780_Character_LCD&quot; rel=&quot;nofollow&quot;&gt;HD44780&lt;/a&gt; controller these days (that's what &lt;a href=&quot;http://arduino.cc/en/Reference/LiquidCrystal&quot; rel=&quot;nofollow&quot;&gt;LiquidCrystal&lt;/a&gt; library supports). This controller doesn't support UTF-8 directly, each character is represented by a single byte.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thus you need to convert UTF-8 to 8-bit characters manually. The controller has a built-in character generator with 208 5x8 and 32 5x10 characters, plus up to 8 user-defined characters (see &lt;a href=&quot;http://arduino.cc/en/Reference/LiquidCrystalCreateChar&quot; rel=&quot;nofollow&quot;&gt;createChar&lt;/a&gt;). You need to map every input character to one of the predefined/custom characters - obviously you can only display a subset of UTF8 characters, you need to decide which characters you want/can to display.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The conversion itself should be pretty straightforward - you just need to iterate over the UTF8 string, mapping every character to a single byte. Most likely you'll want to use a lookup tables to keep it simple. Let me know if this needs further explanation.&lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-04-29T10:33:29.963" CommentCount="2" />
  <row Id="13656" PostTypeId="2" ParentId="13651" CreationDate="2011-04-29T10:51:20.297" Score="1" ViewCount="" Body="&lt;p&gt;Not sure what classifies as 'small' - but it seems to me you're looking for a geared motor - strong but slow.&#xA;Something like &lt;a href=&quot;http://www.sparkfun.com/products/8910&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/8910&lt;/a&gt; - 120rpm (2 revolutons per second).&lt;/p&gt;&#xA;" OwnerUserId="1612" LastActivityDate="2011-04-29T10:51:20.297" CommentCount="1" />
  <row Id="13658" PostTypeId="2" ParentId="13610" CreationDate="2011-04-29T13:01:48.893" Score="0" ViewCount="" Body="&lt;p&gt;Resistors and capacitors are used with amplifier circuits to shape the bandwidth of the response to ensure stability. Most amplifier circuits have large bandwidth capabilities, necessitating external limitation to guarantee a predictable response.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Control_Theory&quot; rel=&quot;nofollow&quot;&gt;Control theory&lt;/a&gt; dictates that a closed-loop system (which an amplifier with feedback can be considered to be) needs to have certain gain and phase criteria to be considered unconditionally stable (i.e. never oscillating).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Generally, in a negative feedback system, if there is positive gain with no phase shift, you end up with an oscillatory response. This is generally bad news for amplifier circuits.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-04-29T13:01:48.893" />
  <row Id="13659" PostTypeId="2" ParentId="12972" CreationDate="2011-04-29T17:45:39.040" Score="1" ViewCount="" Body="&lt;p&gt;My attempt at a solution. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;R5 and R6 are only there to model source resistance and are not part of the circuit. C1 and R4 are used as load for simulation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;V4: input source (10MHz 0.5 duty ratio 0-to-5V square wave for simulation)&lt;br&gt;&#xA;V3: reference source (2.5V for simulation)&lt;br&gt;&#xA;V1: +12V supply&lt;br&gt;&#xA;V2: -12V supply&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's basically an op amp or comparator. I only did some transient simulations to check it out. It might suit your needs. Main drawbacks are complexity, 1:1 output level sensitivity to the supply levels, no output short circuit protection. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would need to trim up the supplies a little bit if you need to get closer to +/-12V output. I would recommend increasing R1 and R3 to 5k or 10k or 20k. This would lower quiescent power consumption but would decrease output current capability--but you probably would not need to drive a lot of current with this, right? You would want to play with the values to get it right for your needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;V3 sets the switching threshold. There is no hysteresis. You might be able to set up a positive feedback loop from output to input to make schmitt trigger to add hysteresis.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output stage could probably also be changed to push-pull common emitter amplifiers instead of followers to get a wider output swing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Schematic:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/e8yBG.gif&quot; alt=&quot;shifter schematic&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simulation:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/F8xTC.gif&quot; alt=&quot;shifter simulation&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3635" LastEditorUserId="3635" LastEditorDisplayName="" LastEditDate="2011-04-29T17:51:11.390" LastActivityDate="2011-04-29T17:51:11.390" CommentCount="1" />
  <row Id="13660" PostTypeId="2" ParentId="13654" CreationDate="2011-04-29T17:53:15.480" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://unicode.org/&quot; rel=&quot;nofollow&quot;&gt;Unicode&lt;/a&gt; is complicated and big, in its entirety it is too big for an Arduino. In the current version there are in total over 100000 characters, including cuneiform, hieroglyphics, Klingon, and not to mention many thousands of chinese characters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if you really want to show some Unicode characters on an Arduino:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Get a graphic display. The one you mention is a character display, it can only show a mostly fixed set of 256 characters.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Define a small subset of characters you want to handle. There are some predefined subsets, for example the &lt;a href=&quot;http://www.cen.eu/cen/Sectors/Sectors/ISSS/CEN%20Workshop%20Agreements/Pages/Multilingual%20Eur%20Subsets.aspx&quot; rel=&quot;nofollow&quot;&gt;Multilingual European Subsets&lt;/a&gt; look nice.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Get some fonts and strip them down to the set you need. Note that even displaying can be much more complicated than what you are used to from ASCII, due to combining characters, bidirectional writing and such. Best is probably to stick to latin characters without any combining accents. Cyrillic and greek should be ok, too, as should anything that is a simple left-to-right sequence of characters.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Maybe you could use some external memory to store the fonts.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Then there's a whole lot of other topics you probably don't need, for example sorting and searching, see the Unicode standard and its annexes (it's big!).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Forget ICU, it needs megabytes of memory.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-04-29T17:53:15.480" />
  <row Id="13661" PostTypeId="2" ParentId="13618" CreationDate="2011-04-29T18:46:55.103" Score="3" ViewCount="" Body="&lt;p&gt;Freetronics have a &lt;a href=&quot;http://www.freetronics.com/pages/stacking-arduino-shields&quot; rel=&quot;nofollow&quot;&gt;guide&lt;/a&gt; on stacking various shields covering issues like:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Stacking Headers&lt;/li&gt;&#xA;&lt;li&gt;Physical Clearance&lt;/li&gt;&#xA;&lt;li&gt;Pin Contention&lt;/li&gt;&#xA;&lt;li&gt;Software Interaction&lt;/li&gt;&#xA;&lt;li&gt;Power Requirements&lt;/li&gt;&#xA;&lt;li&gt;Radio/Electrical Interference&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-04-29T18:46:55.103" />
  <row Id="13662" PostTypeId="1" CreationDate="2011-04-29T19:36:16.667" Score="3" ViewCount="134" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am trying to read voltage values on two channels on eZ430-RF2500T, and transfer the result to the AP connected to a PC. Although I can successfully read from single channel, I am unable to do so using two channels. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is my code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int * readPtr = (int *)0x200;&#xA;ADC10CTL1 = INCH_2 + CONSEQ_1;&#xA;ADC10CTL0 = REF2_5V + SREF_1 + ADC10SHT_2 + REFON + ADC10ON + ADC10IE;&#xA;for (countDown = 240; countDown &amp;gt; 0; countDown--); //delay to allow references to settle&#xA;&#xA;ADC10AE0 |= 0x06; //110&#xA;&#xA;ADC10DTC1 = 0x02;                         // 2 conversions&#xA;ADC10SA = 0x200;                        // Data buffer start, same as readPtr above&#xA;&#xA;ADC10CTL0 |= ENC + ADC10SC; //Sampling and conversion start&#xA;while(!(ADC10CTL0 &amp;amp; ADC10IFG)); // wait till the block conversion is complete&#xA;ADC10CTL0 &amp;amp;= ~ADC10IFG; //reset ADC10IFG&#xA;//code for reading from readPtr&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Please note that no interrupts are being used; results are read after the ADC10IFG bit is set. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not getting ANY results with this code. The 'reading from readPtr' part is never reached.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, if I set ADC10DTC1 to 0x01, I can read from the highest ordered pin. I.e. given that ADC10DTC1 is 0x01, I can read from A2 if INCH_2 is selected, and from A1 if INCH_1 is selected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am unable to get conversions for &lt;strong&gt;both&lt;/strong&gt; A2 and A1, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help will be greatly appreciated.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I am now trying to make this interrupt based. Not sure how to code it, though.&lt;/p&gt;&#xA;" OwnerUserId="3852" LastEditorUserId="3852" LastEditorDisplayName="" LastEditDate="2011-05-05T14:16:45.387" LastActivityDate="2011-05-11T21:23:00.090" Title="Reading from multiple channels using ADC10 and DTC" Tags="&lt;adc&gt;&lt;msp430&gt;" AnswerCount="1" CommentCount="9" />
  <row Id="13663" PostTypeId="1" AcceptedAnswerId="13664" CreationDate="2011-04-29T20:32:39.163" Score="0" ViewCount="73" Body="&lt;p&gt;I'm building just a basic 12v regulator circuit with a LM7812 (it will be knocking a 15v wall wart down to 12v) and pretty much every example I see online uses 100uF caps in the circuit.  How critical is that 100uF value?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have some a little lower and some a little higher on hand but I'm not clear on &lt;em&gt;why&lt;/em&gt; its 100uF or if that can change. (Generally, I'm not clear on when to use what value cap yet in circuits...)&lt;/p&gt;&#xA;" OwnerUserId="3778" LastActivityDate="2011-04-29T20:53:54.587" Title="Capacitors in a voltage regulation circuit" Tags="&lt;power-supply&gt;&lt;voltage-regulator&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="13664" PostTypeId="2" ParentId="13663" CreationDate="2011-04-29T20:48:20.660" Score="2" ViewCount="" Body="&lt;p&gt;If you look at the data sheet you will see that the minimum requirement is a 330 nF capacitor on the input if the regulator is situated some way from the rectifier reservoir capacitor and a 100 nF capacitor on the output to improve stability and transient response. Those are the minimum requirements for the regulator itself. Additional capacitance is often provided for the circuit that is being powered; it depends on the characteristics of the load, and 100 uF is a popular value for most applications. I wouldn't worry much about the value, and use whatever you have.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-29T20:53:54.587" LastActivityDate="2011-04-29T20:53:54.587" CommentCount="3" />
  <row Id="13665" PostTypeId="1" CreationDate="2011-04-29T22:42:17.757" Score="5" ViewCount="236" Body="&lt;p&gt;If I wanted to make a simple device that communicates with my computer, say maybe a switch that could mute my computer when turned on and off and plug it in via USB, what would be the cheapest and easiest way to accomplish this?&lt;/p&gt;&#xA;" OwnerUserId="3210" LastActivityDate="2011-04-30T16:42:36.617" Title="What is the simplest and cheapest way to interface with USB?" Tags="&lt;microcontroller&gt;&lt;usb&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="4" />
  <row Id="13666" PostTypeId="2" ParentId="13665" CreationDate="2011-04-29T22:55:59.817" Score="5" ViewCount="" Body="&lt;p&gt;Build a USB Human Interface Device Class device. That is the same class used by keyboards, mice, joysticks, game pads, and the like. Your PC already has full device driver support for HID devices, so software access is easy. Lots of pointers and even sample code can be found at Jan Axelson's &lt;a href=&quot;http://www.lvr.com/hidpage.htm&quot; rel=&quot;nofollow&quot;&gt;HID page&lt;/a&gt;. Browse around her site for lots of good information related to USB device development.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many of the small microprocessor families can do HIDs. I've even &lt;a href=&quot;http://www.sparkfun.com/products/9147&quot; rel=&quot;nofollow&quot;&gt;seen it done&lt;/a&gt; at USB Low Speed with an ATtiny 8-pin AVR entirely in software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pick your preferred chip, then search its &quot;usual resources&quot; for HID samples.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another approach is to make a serial communications device. Several single chip solution from &lt;a href=&quot;http://ftdichip.com/&quot; rel=&quot;nofollow&quot;&gt;FTDI&lt;/a&gt; exist. The &lt;a href=&quot;http://www.ftdichip.com/Products/ICs/FT232R.htm&quot; rel=&quot;nofollow&quot;&gt;FT232R&lt;/a&gt; is a popular choice. Drivers are required, but Windows Certified drivers are known to the Found New Hardware wizard so installation isn't hard. Once installed, you have a device that looks like a COM port. Alternate drivers are available that will let you access its GPIO pins and use it in more advanced modes.&lt;/p&gt;&#xA;" OwnerUserId="1494" LastActivityDate="2011-04-29T22:55:59.817" />
  <row Id="13667" PostTypeId="2" ParentId="13665" CreationDate="2011-04-29T23:12:34.473" Score="0" ViewCount="" Body="&lt;p&gt;If you don't mind Cortex-M3 based microcontroller, take a look at NXP's &lt;a href=&quot;http://www.nxp.com/#/pip/pip=%5Bpip=LPC1342FHN33%5D%7Cpp=%5Bt=pip,i=LPC1342FHN33%5D&quot; rel=&quot;nofollow&quot;&gt;LPC1343&lt;/a&gt;. It's only $6.30 at Digikey (1 piece). There's one very cool feature - firmware for storage and HID devices in chip's ROM!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Compared to a solution with FTDI chip + microcontroller, there's one chip less :)&lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-04-29T23:12:34.473" />
  <row Id="13669" PostTypeId="2" ParentId="12856" CreationDate="2011-04-30T00:21:57.930" Score="5" ViewCount="" Body="&lt;p&gt;I think you're being bitten by the physics of the fan.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The power in a stream of moving air is proportional to the cube of the air velocity, and the rotational speed of a fixed pitch propeller (i.e., fan) is directly proportional to the air speed. This means that to double the air speed from your fan (or its rotation rate), you have to put in eight times as much power. Or conversely, to cut speed in half, you only need an eighth of the power. If you call the air speed you get at 100% duty cycle 'full speed', then 'half speed' will occur at 1/8th the power level; at 12.5% duty cycle. Even more dramatically, quarter speed would be at 1/8th of &lt;em&gt;that&lt;/em&gt;, at just 1.5625% duty cycle. In other words, whatever speed you get at the very lowest duty cycles is nearly all you're going to get, because power in moving air is so non-linear.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-30T00:21:57.930" />
  <row Id="13671" PostTypeId="2" ParentId="12856" CreationDate="2011-04-30T01:00:33.013" Score="0" ViewCount="" Body="&lt;p&gt;Varying PWM duty-cycle in an attempt to gain linear (or near-linear) voltage output works when you're smoothing charge and discharge from an &quot;output&quot; which sources and sinks current at the same rate.  Typically, you would see this with a bipolar (by this I mean both polarity, not BJT) output feeding a R/C filter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you've built, instead, is a variable-duty cycle charge injection circuit (a sort of buck converter) -- you're not controlling voltage because the discharge rate of your filter is controlled by the load, not the PWM circuit.   You're operating at an open loop here - and so beyond a small window, you'll either not have enough current and the voltage goes to zero, or you'll have too much current and you get full voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suppose one quick hack to get the result you want is to have a FET totem-pole that would pull the left side of L1 to ground.   I'm not sure your 12V power supply is going to thank you for that, though.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-04-30T01:11:21.293" LastActivityDate="2011-04-30T01:11:21.293" CommentCount="1" />
  <row Id="13672" PostTypeId="6" CreationDate="2011-04-30T01:07:56.987" Score="0" ViewCount="" Body="&lt;p&gt;Hello, I am Kortuk. I have been with the site for 1 year and 5 months. As a few others probably have, I started with the SE1.0 system and had no prior experience with stack overflow or the stack exchange system. I slowly picked things up on chiphacker and was promoted to moderator there with about 25 others before moving to Electronics.stackexchange.com&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been a pro temp moderator with ED for a while now and hope to continue. I try to help steer the site in the right direction and with a large amount of help from &quot;the teachers lounge.&quot; I have learned a large amount about moderation since, many decisions that go unnoticed, quite a few that at least a few members have shared their dislike of on meta. I only note this to say that I stand by my decisions but I am also open to criticism. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I stand behind my decisions and attempt to share when I think I have made a mistake. If I am unsure of a decision I ask other moderators. There are normally points we reach were a new problem comes to light, or an old problem is approached, at these points I seek advice. This forms what I consider a core part of moderation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Patience for new and old users is key. I try to be both kind and heavy handed. I give warnings, I share when there is an issue, but I also fix the issue. I will close a bad question, but I attempt to leave a kind message for the user explaining the issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am just taking a moment of my day and trying to give some basic background of my stances. I have been a mod already, I know many of the ins and outs already, and I feel that my wisdom will be valuable to any fresh blood that joins the ranks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not great at just listing the many reasons I feel I am qualified and hope those with questions will just ask me. I am in chat and I check meta, just let me know.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-30T06:49:35.713" LastActivityDate="2011-04-30T06:49:35.713" CommunityOwnedDate="2011-04-30T01:07:56.987" CommentCount="2" />
  <row Id="13673" PostTypeId="6" CreationDate="2011-04-30T01:28:02.403" Score="0" ViewCount="" Body="&lt;p&gt;Greetings.  I am Nick.  You may know me from places such as Stack Overflow, Gaming at StackExchange, or community-access radio in the Flint area.  I'm an electrical engineer from Michigan (&lt;a href=&quot;http://redwings.nhl.com/index.html&quot; rel=&quot;nofollow&quot;&gt;go Red Wings&lt;/a&gt;) who's been around on this site for a couple of months working to both add content by answering plenty of questions and perform some janitorial duties by waging small personal wars on tags that I find useless.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to be your moderator so I can derive personal satisfaction by helping this site maintain a high level of quality and fostering a positive community.  As a moderator I would take great care to avoid imposing my will on the site, but rather encourage and facilitate discussion on what to direction to take; moderators should take a moderate point of view.  I like to think of myself as extremely pragmatic, open to whatever works.  My goal would be to treat all users equally, but taking care to help new users (They Are Our Future&lt;sup&gt;TM&lt;/sup&gt; after all) along with nudges and/or turning their posts that may not fit our particular model into something more constructive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If elected, I would probably be guilted into listening to the SE podcast regularly in order to keep up on the latest from Atwood &amp;amp; Co.  I would also continue to work cleaning up useless tags, preferably without cluttering the entire front page with edits when I do so.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-04-30T01:28:02.403" LastActivityDate="2011-04-30T01:28:02.403" CommunityOwnedDate="2011-04-30T01:28:02.403" CommentCount="2" />
  <row Id="13674" PostTypeId="1" AcceptedAnswerId="13681" CreationDate="2011-04-30T02:09:44.330" Score="2" ViewCount="72" Body="&lt;p&gt;How do you tell the difference between speakers and microphones?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I pulled the following two components out of an old cell phone&#xA;and cannot tell them apart.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/hVpyl.jpg&quot; alt=&quot;microphone and speaker&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each have two metal contacts on the back.&lt;/p&gt;&#xA;" OwnerUserId="3392" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-30T02:16:47.033" LastActivityDate="2011-04-30T08:20:00.357" Title="How do you tell the difference between speakers and microphones?" Tags="&lt;speakers&gt;&lt;microphone&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="13675" PostTypeId="2" ParentId="13610" CreationDate="2011-04-30T03:11:34.353" Score="0" ViewCount="" Body="&lt;p&gt;Traditionally in both tube and transistor amplifiers negative feedback is used to prevent the amplifier from oscillating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Similarly an oscillator stage can be built from a basic amplifier circuit by simply adding some positive feedback and having a tuned output circuit.&lt;/p&gt;&#xA;" OwnerUserId="3869" LastActivityDate="2011-04-30T03:11:34.353" />
  <row Id="13676" PostTypeId="2" ParentId="13674" CreationDate="2011-04-30T03:16:27.080" Score="1" ViewCount="" Body="&lt;p&gt;You can measure the impedance.  Speakers generally have lower impedance than microphones.  Otherwise they are really the same thing, a transformer between sound and electrical energy.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-04-30T03:16:27.080" CommentCount="1" />
  <row Id="13677" PostTypeId="2" ParentId="13665" CreationDate="2011-04-30T03:35:10.723" Score="2" ViewCount="" Body="&lt;p&gt;Here is a very detailed blog post &lt;a href=&quot;http://www.waitingforfriday.com/index.php/Building_a_PIC18F_USB_device&quot; rel=&quot;nofollow&quot;&gt;http://msdn.microsoft.com/en-us/devlabs/dd491992&lt;/a&gt; with software to use an under $5 PIC18F4550 to interface via USB as a standard HID device. The software provided can be used to interface to any HID device, so if you want an alternate chip the software will still work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An added plus is that the blog post shows you how to do bi-directional communication so not only can you interface a switch you can turn an LED on and off.&lt;/p&gt;&#xA;" OwnerUserId="3869" LastActivityDate="2011-04-30T03:35:10.723" />
  <row Id="13678" PostTypeId="2" ParentId="13665" CreationDate="2011-04-30T05:04:17.357" Score="3" ViewCount="" Body="&lt;p&gt;Easiest? Grab an &lt;a href=&quot;http://www.arduino.cc&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; and write a couple of lines of Python. Arduino's are incredibly easy to program, don't require any additional hardware to work with, and are &lt;a href=&quot;http://www.sparkfun.com/products/9950&quot; rel=&quot;nofollow&quot;&gt;quite popula&lt;/a&gt;r. &lt;a href=&quot;http://www.python.org&quot; rel=&quot;nofollow&quot;&gt;Python&lt;/a&gt; has a very &lt;a href=&quot;http://pyserial.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;straightforward serial library&lt;/a&gt; and is a breeze to write in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Example Code&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Python:&#xA;Run this script as a service. I'm using Ubuntu, so this script will pop up a notification telling you when a button has been pressed on the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#! /usr/bin/python&#xA;&#xA;import serial&#xA;import pynotify&#xA;&#xA;ser = serial.Serial('/dev/ttyUSB0', 9600)&#xA;while True:&#xA;  x = ser.read()&#xA;  if x == 'b':&#xA;    # Show notification&#xA;    n = pynotify.Notification(&quot;Arduino&quot;, &quot;The button was pressed.&quot;)&#xA;    n.show()&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Arduino:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void setup(){&#xA;  // Assuming button is active low and on pin 4&#xA;  pinMode(4, INPUT);&#xA;  Serial.begin(9600);&#xA;}&#xA;&#xA;void loop(){&#xA;  if(digitalRead(4) == LOW){&#xA;    Serial.print('b');&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="2762" LastEditorUserId="2762" LastEditorDisplayName="" LastEditDate="2011-04-30T16:42:36.617" LastActivityDate="2011-04-30T16:42:36.617" CommentCount="3" />
  <row Id="13679" PostTypeId="1" AcceptedAnswerId="13680" CreationDate="2011-04-30T05:16:52.847" Score="1" ViewCount="63" Body="&lt;p&gt;Where can I buy a USB to I2c bridge? Cheaper the better!&lt;/p&gt;&#xA;" OwnerUserId="3926" LastActivityDate="2011-04-30T06:16:03.980" ClosedDate="2011-04-30T06:38:38.123" Title="Where can I buy a USB to I2c bridge?" Tags="&lt;usb&gt;&lt;i2c&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="13680" PostTypeId="2" ParentId="13679" CreationDate="2011-04-30T06:16:03.980" Score="1" ViewCount="" Body="&lt;p&gt;Try &lt;a href=&quot;http://www.cypress.com&quot; rel=&quot;nofollow&quot;&gt;Cypress&lt;/a&gt;. Their &lt;a href=&quot;http://www.cypress.com/?rID=3421&quot; rel=&quot;nofollow&quot;&gt;CY3240&lt;/a&gt; is a USB-I2C bridge built around a PSOC controller.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-04-30T06:16:03.980" CommentCount="1" />
  <row Id="13681" PostTypeId="2" ParentId="13674" CreationDate="2011-04-30T08:20:00.357" Score="1" ViewCount="" Body="&lt;p&gt;The speaker is the yellow device on the right-hand side, the microphone is the device on the left, with blue plastic/metal visible.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The speaker will almost inevitably be larger then the microphone. Also, you can actually see the &lt;a href=&quot;http://en.wikipedia.org/wiki/Voice_coil&quot; rel=&quot;nofollow&quot;&gt;voice-coil&lt;/a&gt; in the speaker - it is the copper colored oval.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;@markrages - is somewhat correct about measuring impedance, but not correct about the internals. The speaker should read as a fairly low impedance - less than 100 ohms.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, in all likelyhood, the microphone is a &lt;a href=&quot;http://en.wikipedia.org/wiki/Electret_microphone&quot; rel=&quot;nofollow&quot;&gt;Electret Microphone&lt;/a&gt;, which uses a capacitor which varies in capacitance in response to air pressure waves, e.g. sound.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Getting a meaningful signal out of an electret microphone is pretty simple, but they do not produce an output without being &lt;em&gt;biased&lt;/em&gt; with a power supply. Basically, they need a little bit of power to run, and you have to supply them with that.&lt;br&gt;&#xA;Fortunately, &lt;a href=&quot;http://www.scroogle.org/cgi-bin/nbbw.cgi?Gw=electret%20microphone%20preamp&quot; rel=&quot;nofollow&quot;&gt;there are lots of schematics freely available&lt;/a&gt;, and they're generally pretty simple.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-04-30T08:20:00.357" />
  <row Id="13682" PostTypeId="2" ParentId="12856" CreationDate="2011-04-30T08:37:06.333" Score="0" ViewCount="" Body="&lt;p&gt;&quot;Bitten by the physics of the fan&quot; sounds likely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could recalculate your scale according to the inverse square law p/4πr^2.&#xA;But you will need more than 8 bit of PWM resolution to make that work.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastActivityDate="2011-04-30T08:37:06.333" />
  <row Id="13683" PostTypeId="2" ParentId="13665" CreationDate="2011-04-30T09:38:47.393" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.leonheller.com/usb/&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a simple project of mine using a PIC18F2455, based on Brad Minch's USB software. PCBs are available from Olimex.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-04-30T09:38:47.393" />
  <row Id="13684" PostTypeId="1" AcceptedAnswerId="13694" CreationDate="2011-04-30T11:17:18.217" Score="1" ViewCount="73" Body="&lt;p&gt;Suppose I have a 20,000 counts multimeter, and I am measuring a 220k resistance with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The multimeter can only display a resistance below 200k as &lt;code&gt;200.00k&lt;/code&gt; - supposedly because of the counts. For higher resistances, it has to switch the range and starts displaying the result as &lt;code&gt;0.2200M&lt;/code&gt;. But this makes no sense to me: switching range doesn't &lt;em&gt;require&lt;/em&gt; the display to change in a major way like that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Granted, by switching range the meter loses one digit of precision, and conjuring it up would be wrong. But why not simply hide that non-existent digit, and display &lt;code&gt;220.0 k&lt;/code&gt; (see how the last digit is missing) instead of the less readable &lt;code&gt;0.2200M&lt;/code&gt; - they both have the exact same precision!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why don't multimeters do this seemingly very sane thing, not even the very expensive ones? Am I missing something important?&lt;/p&gt;&#xA;" OwnerUserId="1951" LastActivityDate="2011-04-30T15:41:00.670" Title="Why do multimeters show values at the lower parts of a given range the way they do?" Tags="&lt;multimeter&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13685" PostTypeId="1" CreationDate="2011-04-30T11:55:05.527" Score="3" ViewCount="91" Body="&lt;p&gt;I made a little windmill which is turning a small generator to light up an LED, but the voltage is too low even with high wind speed for the LED to glow. I thought maybe the electricity could be stored somehow maybe by a capacitor and released when the voltage is high enough, making the LED blink according to the wind speed.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know little about electronics so I'm asking for help.&#xA;Thank You.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit:&#xA;What I want to know is how to make a circuit that charges up electricity from a low power source and discharge when the voltage is high enough. The frequency of discharges should increase when the power (wind speed) is increased.&#xA;About the generator. It's actually a small electric motor. I tested it with another motor, connected their rotating heads together, applied 5V to one of them and measured about 4V coming from the other, so I thought it's not a bad idea to use it as a generator. This is a really small project and it shouldn't be taken too seriously.&lt;/p&gt;&#xA;" OwnerUserId="4052" LastEditorUserId="4052" LastEditorDisplayName="" LastEditDate="2011-04-30T18:53:01.000" LastActivityDate="2011-04-30T19:11:23.730" Title="Blinking an LED using a generator as the source of electricity." Tags="&lt;led&gt;&lt;generator&gt;&lt;blink&gt;" AnswerCount="4" CommentCount="1" FavoriteCount="1" />
  <row Id="13687" PostTypeId="2" ParentId="8493" CreationDate="2011-04-30T12:47:01.703" Score="7" ViewCount="" Body="&lt;p&gt;Your question can be easily answered with a continuity tester (which most voltmeters have).&#xA;The below pinout is for an i3-540 (LGA1156). I connected one voltmeter probe to the jtag pad on the underside of the processor. Then I swept the other voltmeter probe across the top side of the processor until the voltmeter registered a continuity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TOP SIDE OF PROCESSOR:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;| 1 |    2 |   3 |   4 |   5 |   6 |    7 |   8 |   9 |  10 |     11 |  12 | 13 |&#xA;|   |AL31* |BPM4 |BPM1 |BPM0 |     |AL31* |TDO  |TRST |PRDY |TAPPWRGD|AL31 |    |&#xA;|   |      |BPM6 |BPM7 |AL31 |     |TCK   |TDI  |PREQ |     |        |     |    |&#xA;|   |      |BPM5 |BPM3 |BPM2 |TMS  |      |     |     |     |        |     |    |&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;*Connected to BLCK_ITP# (useless since shorted)&#xA;AL31 refers to Vss&lt;/p&gt;&#xA;&#xA;&lt;p&gt;CPU IS UPSIDE DOWN&#xA;(ie Intel Made in Malaysia and S/n Upside down)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will be interested if you could find the pinout for the i7 or perhaps we could reverse engineer the Intel JTAG protocol.&lt;/p&gt;&#xA;" OwnerUserId="4053" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-09T06:49:16.147" LastActivityDate="2011-05-09T06:49:16.147" CommentCount="1" />
  <row Id="13688" PostTypeId="2" ParentId="13685" CreationDate="2011-04-30T13:09:03.840" Score="0" ViewCount="" Body="&lt;p&gt;Without thinking about it much I would have the generator charge a CAP and regulate that voltage to a low-power micro (perhaps a PIC12F615 or similar). The micro would mostly sleep but wake on a edge transition that is created every rotation. I would use the TIMER1 count between rotation interrupts to calculate the speed. I would turn on the LED proportional to the speed and go to SLEEP. The slower the speed the more the uP would be asleep and take less power.&lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-04-30T13:09:03.840" />
  <row Id="13689" PostTypeId="2" ParentId="13685" CreationDate="2011-04-30T13:15:37.640" Score="0" ViewCount="" Body="&lt;p&gt;To store small amounts of generated electrical energy and get it to do something useful you need to use &quot;energy harvesting&quot; (EH) techniques. Suitable hardware is available from several sources and this company's &lt;a href=&quot;http://www.aldinc.com/pdf/EH300Brochure.pdf&quot; rel=&quot;nofollow&quot;&gt;EH300 kit&lt;/a&gt; might be suitable for your application. Farnell stocks the EH300; I bought one some time ago but haven't got round to trying it. The EH300 can deliver 25 mA for 68 ms at 1.8V - 3.6V, which is more than enough for an MCU and LED. &lt;a href=&quot;http://www.cymbet.com/content/products-energy-harvesting.a&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is another company making EH hardware. Their technology is used with wireless transceivers and MCUs, taking a lot more power than an LED, powered by small solar cells.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could power a suitable low-power MCU such as an XLP PIC or an MSP430 from the EH device, measure the voltage provided by the EH unit, and flash the LED at a rate proportional to the wind speed when there was sufficient stored power. The RPM of the windmill could be ascertained by measuring the voltage generated using an ADC input on the ADC. XLP PICs typically take under 20 nA in deep sleep mode, and can operate down to 1.8V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I just tested the EH300 with input from my bench supply, varying it from 1.1V to 2V to represent the varying output from a generator. After a few minutes, it was delivering a stable 1.8V from a 1.1V input, so the EH technique will definitely work. Once the capacitors are charged, it should function indefinitely, provided that there is enough wind to turn the windmill at a reasonable speed from time to time. A battery could also be charged with the EH300 output.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-30T19:11:23.730" LastActivityDate="2011-04-30T19:11:23.730" CommunityOwnedDate="2011-04-30T17:17:04.857" CommentCount="0" />
  <row Id="13690" PostTypeId="1" CreationDate="2011-04-30T13:32:32.117" Score="1" ViewCount="74" Body="&lt;p&gt;I have a smart UPS 1500, which requires an RBC7 battery (12v lead-acid).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The cheapest I have found it for is $92.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see that it has a funky cable, but was wondering whether, if I am willing to hack, I can attach a cable to a car battery, which is a) cheaper b) has more capacity.  I don't mind the car battery being external to the UPS, but I don't want to do anything that won't work well.  Are the charging characteristics of the RBC7 radically different? Does it have internal electronics in addition to being a battery?  It's obscene what they get away with charging for these things -- and Amazon wants $150+&lt;/p&gt;&#xA;" OwnerUserId="4054" LastActivityDate="2011-05-02T01:07:13.787" Title="substituting batteries on a UPS" Tags="&lt;battery&gt;&lt;hack&gt;&lt;ups&gt;" AnswerCount="3" CommentCount="5" />
  <row Id="13692" PostTypeId="2" ParentId="13685" CreationDate="2011-04-30T15:18:42.280" Score="1" ViewCount="" Body="&lt;p&gt;Technical Explanation:  The open circuit voltage produced by your generator is too low to drive any current through the LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Straightforward Explanation:  Your problem is probably that there aren't enough volts produced by the generator, even when the LED isn't connected.  You can measure this with a simple multimeter when spinning the generator.  Set the multimeter to 20V AC or DC and see what voltage you measure.  To get the LED working you should see at least 1.4 volts for a RED LED, 2.5 volts for blue, or 3 volts for a white LED.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Others have suggested a resistor is necessary to prevent damage to the LED.  Normally, this would be true, but in this case as the LED starts to light up, it will slow down the wind turbine, protecting itself in all but the strongest winds.  Additionally, most generators have the equivalent of a resistor inside them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One suggestion is to use a microcontroller/capacitor.  The problem with this solution is you will not be able to get a high enough voltage to power up the microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My solution:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Use a Red rather than white/blue LED.&#xA;Use no resistor (or if you do, choose&#xA;something below 300 ohms)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Spin the generator faster - use gears&#xA;to up the speed and lower the torque&#xA;if necessary&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Get a different type of generator&#xA;designed for slow speed use.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If you have multiple LED's, connect&#xA;them all in parallel (ie. every LED&#xA;connects direct to the generator)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Make sure you're spinning the&#xA;generator the right way - test&#xA;spinning it backwards, or connect the&#xA;LED the other way round.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Note:  Human eyes are very sensitive - if the output voltage of the generator is high enough, even a tiny current flow will cause the LED to visibly light up in the dark.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally, there are many types of generator, AC/DC, brushed and brushless etc.  In this situation, it doesn't really matter which you choose.&lt;/p&gt;&#xA;" OwnerUserId="4055" LastActivityDate="2011-04-30T15:18:42.280" CommentCount="1" />
  <row Id="13693" PostTypeId="1" AcceptedAnswerId="13696" CreationDate="2011-04-30T15:39:10.840" Score="1" ViewCount="103" Body="&lt;p&gt;I need a voltage regulator for a project which will handle a voltage on its output pin with no input. (The GND pin may still be connected.) Most devices don't seem to be able to handle this. Are there any which can?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-04-30T21:25:56.373" LastActivityDate="2011-05-02T20:42:54.167" Title="Regulator that can handle voltage on its output" Tags="&lt;voltage-regulator&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="13694" PostTypeId="2" ParentId="13684" CreationDate="2011-04-30T15:41:00.670" Score="3" ViewCount="" Body="&lt;p&gt;The display is not the limiting factor (as you point out). Fundamentally, there is a cut-off. If the display was the most expensive part in the meter, then most meters would probably read up to 9999 on all digits. However, there's a couple factors that make the meter ranges what they are.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is a limit to how high a range goes - the count is a design decision for the meter maker. A 20... meter isn't the only type available either, I personally have a 6000 count meter. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Logarithmically, you get the most bang for your buck by having 2000 counts. See the image of the number line below. By doubling the counts from 1000 to 2000, you get a bigger bang for your buck, and you also get to use one more digit (better for marketing). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ch0R1.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;There's another reason for not dropping the least significant digit. Part of the gotcha with auto-ranging meters is that you can easily forget that the meter has different measurement ranges, and that the measurement accuracy changes with each range. For example, compare the following displays:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;193.00 k&#xA; .1930 M&#xA;193.0  k &amp;lt;----- Would you notice the missing digit as easily?&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Personally, I see it as a more obvious way of conveying information about the measurement. It doesn't detract much from the readability in my opinion. &lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-04-30T15:41:00.670" CommentCount="1" />
  <row Id="13695" PostTypeId="2" ParentId="13693" CreationDate="2011-04-30T15:45:34.140" Score="3" ViewCount="" Body="&lt;p&gt;Which regulators have you seen that don't allow that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's actually a requirement of voltage regulators that they can handle a voltage on the output with no input voltage! Suppose that you have a 12V regulator with a large capacitor on the output, which is generally the case. As soon as the input supply to the regulator is removed, the capacitor on the output will discharge into the regulator output, starting at 12V.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-30T18:19:56.393" LastActivityDate="2011-04-30T18:19:56.393" CommentCount="4" />
  <row Id="13696" PostTypeId="2" ParentId="13693" CreationDate="2011-04-30T15:57:22.800" Score="4" ViewCount="" Body="&lt;p&gt;You sometimes see a diode connected from the output of a regulator back to the input, such that under normal powered operation, the diode is reverse biased. If you remove the input power, the diode can conduct, and clamps the regulator input voltage to not more than a diode drop below the output voltage.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-04-30T15:57:22.800" />
  <row Id="13697" PostTypeId="1" AcceptedAnswerId="13703" CreationDate="2011-04-30T16:44:51.313" Score="4" ViewCount="166" Body="&lt;p&gt;Is there any reason for an electronics engineer to go for a professional engineering (PE) license?  My understanding is that becoming a PE is only useful/necessary for architectural electrical engineering, due to government regulations.  Is this correct, or is there any reason that an embedded electronics hardware/software engineer should become a PE?  Also, would this even be possible, as getting a PE usually means years of experience under an existing PE, whom only seem to be working for architectural firms?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the main reasons I'm asking is because I was thinking of registering a company name for contract electrical engineering work and I'm wondering if I can even call myself an engineer (legally).  Maybe I should call myself an electronic product designer?  Anyone own a contracting business have any insight here?&lt;/p&gt;&#xA;" OwnerUserId="2377" LastActivityDate="2011-05-01T13:15:00.090" Title="Is there any reason for an electronics engineer to go for a professional engineering (PE) license?" Tags="&lt;legal&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="13698" PostTypeId="2" ParentId="13685" CreationDate="2011-04-30T16:55:06.250" Score="0" ViewCount="" Body="&lt;p&gt;Charge an electrolytic capacitor in your generator's output an use a &lt;a href=&quot;http://en.wikipedia.org/wiki/Joule_thief&quot; rel=&quot;nofollow&quot;&gt;Joule Thief&lt;/a&gt; to drive the LED. You can light up any LED as long as the input voltage is at least 0.6 volts I think. &lt;/p&gt;&#xA;" OwnerUserId="2639" LastActivityDate="2011-04-30T16:55:06.250" CommentCount="5" />
  <row Id="13699" PostTypeId="1" AcceptedAnswerId="13701" CreationDate="2011-04-30T17:06:58.533" Score="2" ViewCount="117" Body="&lt;p&gt;I've never done contract work before so I'm a bit lost here.  Hopefully this is the correct place to ask such a question, if not.. let me know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have the experience necessary to come up with an accurate quote for the development of the electronic product in question, but I'm not sure how it should be presented (email, legal document...) or how payment should be specified.  A lump payment upon completion of the design and delivery of a prototype scares me a bit.  What if the customer decides to back out after all my work and investment in prototype development?  I also think it would be unreasonable for me to ask for total payment up front.  I was thinking of specifying partial payment up front, with the remaining payment upon approval of the delivered prototypes.  Is this reasonable or standard practice?  If so, what would be a reasonable up front percentage?  Does anyone with experience with this type of thing have more knowledge on standard contract engineering quoting practice?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, If anyone knows of a good resource for information regarding the business side of things related to contract engineering, that would be greatly appreciated.&lt;/p&gt;&#xA;" OwnerUserId="2377" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-04-30T19:38:51.757" LastActivityDate="2011-05-01T02:41:48.507" Title="Contract Engineering Quoting - HowTo" Tags="&lt;electrical-engineering&gt;&lt;contract&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="13700" PostTypeId="2" ParentId="13699" CreationDate="2011-04-30T18:34:13.310" Score="3" ViewCount="" Body="&lt;p&gt;I have always worked on 33% initially, 33% on first design milestone and 34% on a final product.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-04-30T19:47:26.537" LastActivityDate="2011-04-30T19:47:26.537" CommentCount="2" />
  <row Id="13701" PostTypeId="2" ParentId="13699" CreationDate="2011-04-30T19:26:23.327" Score="2" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Pricing&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I break mine down into steps or milestones, I then charge for each step based off of what the step includes. I essentially have the person pay up front for what the bare minimum of the next step would be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if you have a step of designing a PCB, and you think at minimum it will take 10 hours of work at $\$50$ an hour, then ask for $\$500$ up front. Make note that I said minimum, not expected. You can charge what you expect for that step to cost, but a lot of times it is just far too much to be asking for upfront.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your next step is fabrication, find out how much you will be paying for parts and PCB and labor and what not,  charge them for all of the &quot;minimum&quot; required for this step.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you finish with the entire project, you will have already been paid for the minimum of everything, so make your final payment be compensating for all of the minimums that you charged before.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I like this method because it keeps you safe from someone ripping you off, since you will at least have the minimum covered. It also makes the person paying feel like you aren't trying to rip them off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Legal&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are going to be doing this in any sort of full time sense, I would highly recommend you find a lawyer. They can help you make sure you have everything in tip top shape so that you don't get caught and end up loosing your livelihood.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are doing this as something just here and there then it may not be cost effective you get a lawyer. If this is the case my biggest recommendation to you is to be very clear on the work that will be performed and the amount that you will be liable for the product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Ease of Invoicing&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I tend to shy away from recommending service on this site, but I would highly recommend you go look at &lt;a href=&quot;https://butlertc.freshbooks.com/refer/www&quot; rel=&quot;nofollow&quot;&gt;freshbooks.com&lt;/a&gt;. They let you generate estimates, track time, and send invoices. It makes life very easy if you plan on doing more and might be able to cover yourself more if you have issues arise with someone not paying.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-05-01T02:41:48.507" LastActivityDate="2011-05-01T02:41:48.507" />
  <row Id="13702" PostTypeId="2" ParentId="13642" CreationDate="2011-04-30T19:44:43.200" Score="2" ViewCount="" Body="&lt;p&gt;Plus, instead of overwriting the whole Port, it is generally better to modify only the affected bit (pin). This can be done by&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Set Pin x to &quot;high&quot;:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;PORTA |= (1 &amp;lt;&amp;lt; x);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Set Pin x to &quot;low&quot;:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;PORTA &amp;amp;= ~(1 &amp;lt;&amp;lt; x);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Especially if mutliple parts are connected to the port, this method is way safer. The same can be done with the DDRx register, if you only want to modify the direction of single Pins.&lt;/p&gt;&#xA;" OwnerUserId="4058" LastActivityDate="2011-04-30T19:44:43.200" CommentCount="1" />
  <row Id="13703" PostTypeId="2" ParentId="13697" CreationDate="2011-04-30T20:21:41.640" Score="3" ViewCount="" Body="&lt;p&gt;In Florida it is illegal to use the term 'Engineer' or derivatives in a business name if there are no licensed professional engineers working there.  There may be restrictions on using the term even if the number of licensed engineers working there is not zero, but if there are zero you can't use it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Realistically, there's no reason to call yourself an 'engineer'.  At least in the US, because of restrictions similar to the one above the term 'Engineering Services' or similar is limited mainly to the architectural firms you mentioned.  The term is co-opted.  Just call yourself a consumer electronics designer, embedded software developer, analog electronics designer, digital designer or whatever is more specific to your case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for whether it would ever be worth it for an electronics engineer I've found the answer is generally no.  I've worked for several different companies in different fields and no one even gave it a thought.  It wasn't expected, it wasn't sought and there wouldn't be talk of a raise or anything if you did get one.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I only ever really hear of two types of electrical/electronics/embedded engineers getting the PE: engineers who have years of experience in a variety of areas and had a specific need in mind when getting it and confused new graduates who have been talking to their uncle who's a civil engineer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: After skulking around on Wikipedia for a bit I've unearthed some information that is interesting but doesn't change my original answer.  That is, this information applies only to other circumstances. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It seems that the restriction on using the term 'engineer' is more directed towards not being allowed to offer the public 'engineering services' unless you or your company is licensed.  Thus saying 'Hi Bill, I'm Fred and I'd like to offer you engineering services in exchange for money - here's my card' means you need to be a professional engineer. If you're just a shmo who works for a company you can put 'engineer' on your business card because you're not offering any services to the public - your company is doing the offering and hopefully they have this mess sorted out for themselves.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="249" LastEditorDisplayName="" LastEditDate="2011-05-01T13:15:00.090" LastActivityDate="2011-05-01T13:15:00.090" CommentCount="3" />
  <row Id="13704" PostTypeId="1" CreationDate="2011-04-30T21:41:31.720" Score="1" ViewCount="85" Body="&lt;p&gt;I have code like this in IAR Embedded Workbench. At least Led0 should blink?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;io430.h&amp;gt;&#xA;#include&amp;lt;signal.h&amp;gt;&#xA;&#xA;void main(void)&#xA;{&#xA;  WDTCTL = WDTHOLD + WDTPW; &#xA;  P1DIR = BIT6 + BIT4 + BIT3 + BIT7 + BIT0;&#xA;  P1OUT |= BIT6 + BIT4 + BIT3 + BIT7+ BIT0;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="3426" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-05-01T03:55:59.490" LastActivityDate="2011-05-01T03:55:59.490" Title="Msp430 Launchpad Programming" Tags="&lt;msp430&gt;" AnswerCount="1" />
  <row Id="13705" PostTypeId="2" ParentId="13704" CreationDate="2011-04-30T22:10:54.787" Score="5" ViewCount="" Body="&lt;p&gt;That won't do anything. You need an infinite loop, a delay, and some way of toggling the output. Something like this should work:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;&#xA;void main(void)&#xA;{&#xA;  WDTCTL = WDTPW + WDTHOLD;             // Stop watchdog timer&#xA;  P1DIR |= 0x01;                        // Set P1.0 to output direction&#xA;&#xA;  for (;;)&#xA;  {&#xA;    volatile unsigned int i;&#xA;&#xA;    P1OUT ^= 0x01;                      // Toggle P1.0 using exclusive-OR&#xA;&#xA;    i = 50000;                          // Delay&#xA;    do (i--);&#xA;    while (i != 0);&#xA;  }&#xA;}&#xA;&lt;/pre&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-04-30T23:01:30.127" LastActivityDate="2011-04-30T23:01:30.127" CommentCount="9" />
  <row Id="13706" PostTypeId="2" ParentId="13690" CreationDate="2011-04-30T22:26:18.217" Score="1" ViewCount="" Body="&lt;p&gt;Every UPS I have seen just uses generic SLA (&lt;a href=&quot;http://en.wikipedia.org/wiki/VRLA_battery&quot; rel=&quot;nofollow&quot;&gt;Sealed Lead-Acid, also called gel-cell &lt;/a&gt;) batteries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In this case, the &quot;RBC7&quot; is a 12V, 17 AH (Amp-Hour) battery (&lt;a href=&quot;http://rbc7.net/&quot; rel=&quot;nofollow&quot;&gt;ref&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, any 12V ~15-20 AH gel-cell battery will probably work.&lt;br&gt;&#xA;&lt;a href=&quot;http://www.allelectronics.com/index.php&quot; rel=&quot;nofollow&quot;&gt;AllElectronics&lt;/a&gt; has pretty &lt;a href=&quot;http://www.allelectronics.com/make-a-store/category/160300/Batteries-Rechargeable/Sealed-Lead-Acid/1.html&quot; rel=&quot;nofollow&quot;&gt;good selection&lt;/a&gt; of gel-cells. &lt;a href=&quot;http://www.allelectronics.com/make-a-store/item/GC-217/12V-18AH-SEALED-LEAD-ACID-BATTERY//1.html&quot; rel=&quot;nofollow&quot;&gt;This one&lt;/a&gt; would probably work in your application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would need to cut or unscrew the connector cables from the current battery, and move them across, though.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-04-30T22:26:18.217" />
  <row Id="13707" PostTypeId="1" CreationDate="2011-04-30T23:29:24.593" Score="1" ViewCount="174" Body="&lt;p&gt;Is there something special about high bandwidth oscilloscopes that make them so insanely expensive?&lt;/p&gt;&#xA;" OwnerUserId="4059" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-04-30T23:37:07.487" LastActivityDate="2011-05-01T00:06:59.260" ClosedDate="2011-05-01T04:10:03.927" Title="Why are oscilloscopes so expensive?" Tags="&lt;oscilloscope&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="13708" PostTypeId="2" ParentId="13707" CreationDate="2011-04-30T23:44:57.340" Score="4" ViewCount="" Body="&lt;p&gt;20+ GS/s A/D's are expensive. The memory subsystem needed to store that data isn't trivial either.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-04-30T23:44:57.340" />
  <row Id="13709" PostTypeId="2" ParentId="13707" CreationDate="2011-05-01T00:06:59.260" Score="5" ViewCount="" Body="&lt;p&gt;..and they don't sell many so  development costs are a major proportion of the price.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-05-01T00:06:59.260" />
  <row Id="13710" PostTypeId="2" ParentId="13690" CreationDate="2011-05-01T00:09:34.373" Score="1" ViewCount="" Body="&lt;p&gt;Be aware that low-end UPSs may not b ethermally designed to run for longer than their battery's expected lifetime at full power- adding an external battery may cause overheating. You may also find that the charge circuitry may be expecting a particular capacity, and may cut out before a larger capacity battery is fully charged.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-05-01T00:09:34.373" />
  <row Id="13711" PostTypeId="1" CreationDate="2011-05-01T00:33:26.857" Score="1" ViewCount="175" Body="&lt;p&gt;I can blink the led but the time of it's very 1 second or 2 second.I try to increase but it did not.But my question I'm using L293D motor driver to control motors.I want to Dc motors turn when button switched 15 second.This my code but I can't find a solution.I m asking how to increase the time&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;#include &quot;io430.h&quot;&#xA;void delay(unsigned long int d)&#xA;{&#xA;  d*=9999999999999999;&#xA;  for(;d&gt;0;d--);&#xA;}&#xA;void main(void)&#xA;{&#xA;&#xA;  WDTCTL = WDTPW + WDTHOLD;             // Stop watchdog timer&#xA;&#xA;P1DIR = BIT6 + BIT4  + BIT7 + BIT0;          // Toggle P1.0 using exclusive-OR&#xA;P1DIR &amp;= ~BIT3;&#xA;if((P1IN&amp;BIT3) == 0){ &#xA;P1OUT |= BIT6 + BIT4  + BIT7;&#xA;}&#xA;else&#xA;{&#xA; P1OUT |= BIT0;&#xA;delay(9000);&#xA;}&#xA;}&#xA;&lt;/pre&gt;&#xA;" OwnerUserId="3426" LastActivityDate="2011-05-02T13:56:52.047" Title="Msp430 Launchpad Using Motor to Control Motor" Tags="&lt;msp430&gt;" AnswerCount="3" CommentCount="2" FavoriteCount="1" />
  <row Id="13712" PostTypeId="1" CreationDate="2011-05-01T05:27:26.977" Score="0" ViewCount="92" Body="&lt;p&gt;For the design of digital CMOS circuits, there is a need to ratio the PMOS and NMOS transistors so that the worst case rise time and fall time on the output are equal. Why is this a crucial requirement?&lt;/p&gt;&#xA;" OwnerUserId="2897" LastActivityDate="2011-05-01T20:21:43.980" Title="Equal rise time and fall time in CMOS circuits" Tags="&lt;cmos&gt;&lt;vlsi&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="13713" PostTypeId="2" ParentId="13711" CreationDate="2011-05-01T05:41:03.763" Score="0" ViewCount="" Body="&lt;p&gt;If you're using the built in oscillator, you don't need to delay that long for 15 seconds.  In a tight &lt;code&gt;for&lt;/code&gt; loop, I think a 15 second delay is closer to 1500000 loops.  Plus, you can't multiply by such a large number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the other problem is with your &lt;code&gt;if/else&lt;/code&gt; statement.  You're using |= in both cases, so when you push the button, you aren't toggling the bits -- BIT0, BIT4, BIT6, and BIT7 eventually will all be high.  If you can provide more information about what you're doing with all of the bits, and maybe a circuit diagram, that will help me help you more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- To address the delay implementation part of your question, jsolarski certainly has the best solution for the timer.  I looked into it some more since I haven't used timers with the MSP430, and ended up with some questions of my own.  I'm going to put my findings here just for discussion's sake, and hopefully jsolarski can add comments where appropriate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You've got a several core clock sources, which include LFXT1CLK, XT2CLK, DCOCLK, and VLOCLK.  I'm personally going to be using an internal clock source for my application, and am going to try VLOCLK first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have a clock source selected, now you have to determine where three other internally-generated clock sources will originate from.  These other three clocks are ACLK, MCLK, and SMCLK.  Conveniently enough, VLOCLK is a valid clock source for all three.  You can also set a prescaler for these clocks, in case you don't need high-speed timing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will want to configure the WDT to use interval mode via WDTTMSEL.  This also requires you to set WDTIE bit in IE1.  You'll also want to set your clock source via WDTSSEL and prescaler via WDTISx.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I couldn't figure out what &lt;code&gt;WDT_MDLY_64&lt;/code&gt; equates to, based on his numbers, but that's expected because you haven't specified what clock source you intend to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully this edit to my answer has given you some more information on how to set up the WDT for intervals, should you decide to try it.  However, I think your problem is more fundamental as my original answer stated, regarding your use of &lt;code&gt;|=&lt;/code&gt;, and whether you use a tight &lt;code&gt;for&lt;/code&gt; loop or intervals, it just wouldn't work.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-05-02T13:56:52.047" LastActivityDate="2011-05-02T13:56:52.047" CommentCount="5" />
  <row Id="13715" PostTypeId="1" CreationDate="2011-05-01T11:42:45.970" Score="0" ViewCount="53" Body="&lt;p&gt;I have searched so many website to take background about how asm chart is used in verilog code.However, I could not find any web cite with sufficient examples to learn asm chart. Can anyone give or recommend any website/book which I can be similar with asm chart implemented over using verilog?&lt;/p&gt;&#xA;" OwnerUserId="3192" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-05-01T12:27:26.197" LastActivityDate="2011-06-01T04:13:24.987" Title="recommandation webpage/book  to learn asmd chart over using verilog" Tags="&lt;homework&gt;&lt;verilog&gt;&lt;hdl&gt;&lt;digital-logic&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13716" PostTypeId="2" ParentId="13715" CreationDate="2011-05-01T12:09:13.363" Score="0" ViewCount="" Body="&lt;p&gt;I have found a book and in it there are so many example about how asmd char can be implemented over using Verilog HDL: &lt;em&gt;FPGA Prototyping By Verilog Examples: Xilinx Spartan-3 Version&lt;/em&gt; by Pong P. Chu (&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0470185325&quot; rel=&quot;nofollow&quot;&gt;Amazon link&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA; &#xA;" OwnerUserId="3192" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-06-01T04:13:24.987" LastActivityDate="2011-06-01T04:13:24.987" />
  <row Id="13717" PostTypeId="1" CreationDate="2011-05-01T12:31:38.847" Score="1" ViewCount="77" Body="&lt;p&gt;Microchip have a free but non-distributable &lt;a href=&quot;http://www.microchip.com/usb/&quot; rel=&quot;nofollow&quot;&gt;USB stack source code&lt;/a&gt; available. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, what open source virtual serial port code exist? And which one should I invest my time in using?&lt;/p&gt;&#xA;" OwnerUserId="3926" LastActivityDate="2011-05-01T15:46:43.080" Title="What open source virtual serial port code exist which can run on a Microchip IC?" Tags="&lt;usb&gt;&lt;microchip&gt;" AnswerCount="0" CommentCount="7" />
  <row Id="13718" PostTypeId="1" AcceptedAnswerId="13768" CreationDate="2011-05-01T13:37:40.710" Score="1" ViewCount="140" Body="&lt;p&gt;I don't know if this belongs here or stackoverflow. I assume here as although verilog looks like software it's actually describing hardware connections?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a Spartan-3AN evaluation board and I'm trying to implement a simple rs232 port interface on it which I can't get to work. I'm an experienced software developer but new to verilog and digital design. I want to move up from flashing a single LED to the next step.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried to implement it like this - &#xA;1) Generate a clock pulse &quot;serclock&quot; at the baud rate, so at the start of each bit.&#xA;2) Implement a state machine that once it's told to start steps through the states at the correct speed.&#xA;3) Implement a lookup to output the correct data bit depending on the state that 2) is in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there is a better way I'd appreciate any help. However I would expect this to work but I get nothing at all. Can anyone spot anything stupid that I've done? I'd appreciate any advice.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// Serial port demo program&#xA;// &#xA;// Assumptions: 50Mhz clock rate&#xA;&#xA;module SerDemo(input clk, output ser);&#xA;&#xA;&#xA;// Start signal tells it to start sending bits&#xA;reg start;&#xA;&#xA;//The bits of data to send&#xA;reg [7:0] data;&#xA;&#xA;/////////////////////////////////////////////////////////////////////////////&#xA;// Serial port clock generator&#xA;// Generate a 9600 baud clock signal for the serial port by dividing the&#xA;// 50Mhz clock by 5208&#xA;&#xA;reg [14:0] clockdiv;&#xA;&#xA;// Count from 0..5207 then reset back to zero&#xA;always @(posedge clk) &#xA;begin&#xA;    if (clockdiv == 5207) &#xA;        clockdiv &amp;lt;= 0;&#xA;    else&#xA;        clockdiv &amp;lt;= clockdiv + 1;&#xA;end&#xA;&#xA;// The serclock is a short pulse each time we are reset&#xA;wire serclock = (clockdiv == 0);&#xA;&#xA;/////////////////////////////////////////////////////////////////////////////&#xA;// Serial port state machine&#xA;// Only start the state machine when &quot;start&quot; is set. Only advance to the&#xA;// next state when serclock is set.&#xA;&#xA;reg [3:0] state;&#xA;&#xA;always @(posedge clk)&#xA;begin&#xA;   case (state)&#xA;        4'b0000: if (start) state &amp;lt;= 4'b0001;&#xA;        4'b0001: if (serclock) state &amp;lt;= 4'b0010;    // Start bit&#xA;        4'b0010: if (serclock) state &amp;lt;= 4'b0011;    // Bit 0&#xA;        4'b0011: if (serclock) state &amp;lt;= 4'b0100;    // Bit 1&#xA;        4'b0100: if (serclock) state &amp;lt;= 4'b0101;    // Bit 2&#xA;        4'b0101: if (serclock) state &amp;lt;= 4'b0110;    // Bit 3&#xA;        4'b0110: if (serclock) state &amp;lt;= 4'b0111;    // Bit 4&#xA;        4'b0111: if (serclock) state &amp;lt;= 4'b1000;    // Bit 5&#xA;        4'b1000: if (serclock) state &amp;lt;= 4'b1001;    // Bit 6&#xA;         4'b1001: if (serclock) state &amp;lt;= 4'b1010;   // Bit 7&#xA;        4'b1010: if (serclock) state &amp;lt;= 4'b0000;    // Stop bit&#xA;        default: state &amp;lt;= 4'b0000;                  // Undefined, skip to stop&#xA;    endcase&#xA;end&#xA;&#xA;&#xA;///////////////////////////////////////////////////////////////////////////////&#xA;// Serial port data&#xA;// Ensure that the serial port has the correct data on it in each state&#xA;&#xA;reg outbit;&#xA;&#xA;always @(posedge clk)&#xA;begin&#xA;    case (state)&#xA;         4'b0000: outbit &amp;lt;= 1;              // idle&#xA;         4'b0001: outbit &amp;lt;= 0;              // Start bit&#xA;         4'b0010: outbit &amp;lt;= data[0];        // Bit 0&#xA;         4'b0011: outbit &amp;lt;= data[1];        // Bit 1&#xA;         4'b0100: outbit &amp;lt;= data[2];        // Bit 2&#xA;         4'b0101: outbit &amp;lt;= data[3];        // Bit 3&#xA;         4'b0110: outbit &amp;lt;= data[4];        // Bit 4&#xA;         4'b0111: outbit &amp;lt;= data[5];        // Bit 5&#xA;         4'b1000: outbit &amp;lt;= data[6];        // Bit 6&#xA;         4'b1001: outbit &amp;lt;= data[7];        // Bit 7&#xA;         4'b1010: outbit &amp;lt;= 0;          // Stop bit&#xA;         default: outbit &amp;lt;= 1;          // Bad state output idle&#xA;    endcase&#xA;end&#xA;&#xA;// Output register to pin&#xA;assign ser = outbit;&#xA;&#xA;///////////////////////////////////////////////////////////////////////////////&#xA;// Test by outputting a letter 'd'&#xA;&#xA;always @(posedge clk)&#xA;begin&#xA;    data = 100;&#xA;     start = 1;&#xA;end&#xA;&#xA;endmodule&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="710" LastActivityDate="2011-05-02T14:49:35.937" Title="Implement serial port on fpga (verilog)" Tags="&lt;fpga&gt;&lt;rs232&gt;&lt;verilog&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="13719" PostTypeId="2" ParentId="13712" CreationDate="2011-05-01T13:55:48.380" Score="0" ViewCount="" Body="&lt;p&gt;IIRC, the reason why we tune the PMOS/NMOS W/L ratios (which affects the rise-time and fall-time) is so that we can have a symmetrical switching point at VDD/2.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastEditorUserId="1938" LastEditorDisplayName="" LastEditDate="2011-05-01T14:06:27.447" LastActivityDate="2011-05-01T14:06:27.447" />
  <row Id="13720" PostTypeId="2" ParentId="13718" CreationDate="2011-05-01T14:46:06.570" Score="3" ViewCount="" Body="&lt;p&gt;You did not &lt;strong&gt;reset&lt;/strong&gt; the system to a known state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, I assume that you are doing this to learn Verilog? Otherwise, there are many freely available cores that you can find on the Internet that does this. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;// Count from 0..5207 then reset back to zero&#xA;always @(posedge clk) &#xA;begin&#xA;  if (rst) begin&#xA;    clockdiv &amp;lt;= 0;&#xA;  end else begin&#xA;    if (clockdiv == 5207) &#xA;        clockdiv &amp;lt;= 0;&#xA;    else&#xA;        clockdiv &amp;lt;= clockdiv + 1;&#xA;  end&#xA;end&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1938" LastEditorUserId="1938" LastEditorDisplayName="" LastEditDate="2011-05-01T14:52:19.293" LastActivityDate="2011-05-01T14:52:19.293" CommentCount="6" />
  <row Id="13721" PostTypeId="1" CreationDate="2011-05-01T15:19:37.727" Score="0" ViewCount="50" Body="&lt;p&gt;I connected Msp430 Launchpad to the PC but when i click download and debug it shows this error&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fatal error: Failed to initialize.  Check if hardware is connected. Check if drivers are installed. Try to restart the computer. Tools using the parallel port are not supported on Windows  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ok I solved it.I connected to the another USB port.I wish I would not ask these question :D&lt;/p&gt;&#xA;" OwnerUserId="4063" LastEditorUserId="4063" LastEditorDisplayName="" LastEditDate="2011-05-02T16:11:19.290" LastActivityDate="2011-05-02T16:11:19.290" Title="IAR Embedded WorkbenchDebbuging" Tags="&lt;msp430&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="13722" PostTypeId="2" ParentId="13712" CreationDate="2011-05-01T15:23:17.997" Score="1" ViewCount="" Body="&lt;p&gt;If they were different there would be problems designing transmission lines for high-speed systems. A transmission line that was optimal for one edge would be unsuitable for the other edge.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-01T15:23:17.997" />
  <row Id="13724" PostTypeId="1" CreationDate="2011-05-01T15:46:35.683" Score="-1" ViewCount="75" Body="&lt;p&gt;I have an l293d motor driver, should I give the 5 to 36 volts for motor power to 9th pin of it?&lt;/p&gt;&#xA;" OwnerUserId="4064" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-05-02T02:36:16.923" LastActivityDate="2011-05-02T02:36:16.923" Title="l293d motor driver problem" Tags="&lt;msp430&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="13726" PostTypeId="2" ParentId="13711" CreationDate="2011-05-01T15:51:35.400" Score="0" ViewCount="" Body="&lt;p&gt;That &quot;d *= 9999...&quot; looks suspicious. That many nines times 9000 is 0xE100 3B28 D927 DCD8 hex - 64 bits. I don't know what &lt;code&gt;sizeof(unsigned long int) * CHAR_BIT&lt;/code&gt; evaluates to on MSP430 but on most systems it's 32. In other words it would be overflowing the variable. &#xA;So assuming an unsigned long int is 32 bits, the value your code is using is D927 DCD8.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you getting a compiler warning about truncation?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good way to experiment with delay loops is with a binary search. Start the value off at 0x1. That won't work (of course), so move to 0x2, 0x4, 0x6, 0x10... each value double the prior. If it's too slow, back off and start setting lower order bits but from the top down. Once you hit 0x8000 0000 (again assuming a 32-bit long) you only get one more doubling if you set every lower-order bit, so unless you are close you need to think about using two delays (nested loop).&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2011-05-01T15:51:35.400" />
  <row Id="13727" PostTypeId="2" ParentId="13724" CreationDate="2011-05-01T15:56:34.897" Score="2" ViewCount="" Body="&lt;p&gt;Have you read the data sheet? Pin 9 of the L293D in the N or NE package is an enable pin for drivers 3 and 4 and is a logic input. Connecting it to anything over 6V is liable to damage the device.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-01T15:56:34.897" />
  <row Id="13728" PostTypeId="2" ParentId="13721" CreationDate="2011-05-01T15:57:13.703" Score="1" ViewCount="" Body="&lt;p&gt;On Windows &quot;Device Manager&quot;, under the node &quot;Ports (COM &amp;amp; LPT)&quot; check there is a &quot;MSP430 Application UART (COMx)&quot; (x should be a number depends on your pc). Then on IAR, open your project options, under &quot;General Options&quot; category, make sure you selected Device as MSP430G2231 or MSP430G2001 (which you use), under &quot;Debugger&quot; category select Driver as FET Debugger, under &quot;FET Debugger&quot; category select Connection as Texas Instruments USB-IF.&lt;/p&gt;&#xA;" OwnerUserId="3063" LastActivityDate="2011-05-01T15:57:13.703" />
  <row Id="13730" PostTypeId="1" AcceptedAnswerId="13740" CreationDate="2011-05-01T17:47:51.913" Score="1" ViewCount="86" Body="&lt;p&gt;What is the difference between Spi and framed Spi?&lt;/p&gt;&#xA;" OwnerUserId="1484" LastEditorUserId="1484" LastEditorDisplayName="" LastEditDate="2011-05-02T03:15:11.507" LastActivityDate="2011-05-02T03:15:11.507" Title="Spi and Framed Spi" Tags="&lt;pic&gt;&lt;spi&gt;" AnswerCount="3" />
  <row Id="13731" PostTypeId="1" AcceptedAnswerId="13733" CreationDate="2011-05-01T17:50:16.467" Score="1" ViewCount="77" Body="&lt;p&gt;I've been thinking about getting into using some pic microcontrollers, and I found the below two things to help get me started. But, on the product page for the microcontroller, it says 20 mhz, but then in the description it says it has an 8mhz internal oscillator. Which is right? Also, with the programmer below, it says usb to serial adapters don't work, but I don't have any serial ports on my computer, is there anything I can do about that?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/8&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/8&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.sparkfun.com/products/228&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/228&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2873" LastActivityDate="2011-05-01T19:21:00.243" Title="Internal oscilator vs external and Serial port question" Tags="&lt;pic&gt;&lt;serial&gt;&lt;oscillator&gt;" AnswerCount="2" />
  <row Id="13732" PostTypeId="2" ParentId="13730" CreationDate="2011-05-01T18:05:29.970" Score="1" ViewCount="" Body="&lt;p&gt;I haven't heard the term &quot;framed SPI&quot;, but would suggest that there are two says in which I've seen SPI devices handle the chip-select wire.  On some devices, any time the CS wire is deasserted and reasserted, the following byte will be interested as the first byte of a command sequence; on some other devices, any byte which is received while CS is asserted will be interpreted identically regardless of whether CS has been deasserted since the previous byte.  On some such systems it would be normal practice to deassert CS between bytes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I had my druthers, the CS wire would be optional and SPI devices would assume the start of a new command if there were two rising edges on the data wire while the clock wire was low (if SPI were unused, it would have to be strapped low).  I'm unaware of any SPI devices that actually work that way, though, other than a CPLD I designed myself.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-01T18:05:29.970" />
  <row Id="13733" PostTypeId="2" ParentId="13731" CreationDate="2011-05-01T18:09:01.930" Score="3" ViewCount="" Body="&lt;p&gt;The pic 16F88 can run up to 20 MHz with an external oscillator. Then up to 8 MHz with the internal oscillator selected. This is usually done by setting the fuse bits(I use AVR not PICs so not completely sure on how to do that usually in the IDE). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for the programmer I would look at just getting a PICKIT 2 or 3 for programming easy to use also made my microchip. And forgot to mention USB :). &lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-05-01T18:09:01.930" CommentCount="4" />
  <row Id="13734" PostTypeId="2" ParentId="9324" CreationDate="2011-05-01T18:21:44.723" Score="2" ViewCount="" Body="&lt;p&gt;In the days of &quot;classical&quot; analog video, one could meaningfully count the number of transistors (or vacuum tubes) between the video camera tube and the video display tube, since there would generally be a single path for the signal to take.  Even if a video was captured by a CCD or had to undergo something like analog or digital NTSC/PAL conversion, one could still produce a meaningful figure since every portion of the video image would gone through an identifiable path (even though different portions of the video image would go through different paths).  A video signal might get converted to video, but all the digital stages it went through were purely combinatorial (sequential circuits would be used to keep track of horizontal and vertical scanning, but the picture data would be handled by combinatorial circuits) and, at any given time, one could point to a circuit and identify that it was handling some particular portion of the original picture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With compressed digital video, it's impossible to meaningfully count how many transistors the signal goes through, since it goes through a many sequential circuits which munge and reconstitute it.  Often times some of these circuits will be running in parallel.  If the data from 64 pixels are munged together so as to yield 64 numbers, and then those numbers are processed in parallel, and the results are then reconstituted so as to yield 64 pixels, how many transistors did the pixel data go through?  I don't think any particular answer is really &quot;right&quot;.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-01T18:21:44.723" />
  <row Id="13735" PostTypeId="2" ParentId="12641" CreationDate="2011-05-01T18:35:19.917" Score="0" ViewCount="" Body="&lt;p&gt;One thing it would be helpful to know, but many DAC data sheets don't make it clear, is whether the DAC will always have its output value between the minimum and maximum value from among those received within the sampling time.  On some DACs, if the input changes from 0x7F to 0x80, the ouput may momentarily swing to a voltage which is below the steady-state voltage for 0x7F or above the steady-state voltage for 0x80.  On some other DACs, that won't happen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If one has a DAC whose output voltage may go 'wonky' when its value changes, one must either use a sample/hold circuit to ensure that the voltage from the DAC won't be output when it's 'wonky', or else one must operate the DAC sufficiently below the rate implied by its settling time that the glitches will represent a small portion of the signal and one can filter them out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If one has a DAC that won't go wonky, then one may output data at whatever rate one wants (subject to any express maximum limits in the data sheet) but the output may have artifacts related to the settling time.  If the settling behavior mimics that of an RC filter, there won't be any problem, but if the DAC settles to some values faster than others, or if it behaves differently with large swings than small ones, the output may be regarded as having timing jitter equal to the settling time.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-01T18:35:19.917" />
  <row Id="13736" PostTypeId="2" ParentId="13731" CreationDate="2011-05-01T18:53:27.520" Score="5" ViewCount="" Body="&lt;p&gt;Forget about those serial port programmers sold by Sparkfun and other suppliers, they aren't supported by MPLAB, they don't program the latest chips, they don't work very well, and you won't get in-circuit debugging. If you don't believe me, look at the posts about them on the Sparkfun forums. &lt;a href=&quot;http://forum.sparkfun.com/viewtopic.php?f=4&amp;amp;t=8742&amp;amp;hilit=PG1&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a typical tale of woe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Get a Microchip PICkit 2 or 3, they plug straight into a USB port and the PICkit 3 supports all current devices, and works with the new MPLAB-X IDE.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-01T19:21:00.243" LastActivityDate="2011-05-01T19:21:00.243" CommentCount="4" />
  <row Id="13737" PostTypeId="2" ParentId="8428" CreationDate="2011-05-01T18:54:55.463" Score="0" ViewCount="" Body="&lt;p&gt;If you want accurate timing, you can't go to separate serial ports.  You need a microcontroller that can capture the data from both sources and output it to the PC at a data rate which is more than twice as fast as the data rate for the devices that are communicating.  Suppose the devices communicate at 115,200 baud and the PC connection is at 500,000 baud (a rate supported by the FTDI).  One could then, 12,500 times/second (every 80us), have the microcontroller output a 1-3 byte record, consisting of a header, and the lower 7 bits of transmit and receive data bytes (the latter only being included if present)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;Header formats:&#xA;10rrRttT - Both bytes are present; &#xA;             RX byte received rr*20us after start of frame; MSB is R&#xA;             TX byte received xx*20us after start of frame; MSB is T&#xA;11000rrR - RX byte only is present; data as above&#xA;11001ttT - TX byte only is present; data as above&#xA;11111111 - Neither RX nor TX data is present; &#xA;           Next one or two bytes may provide a long timestamp&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Including a timestamp in the case neither byte of data is present would avoid having to send 12,500 records/second at times when nothing was being sent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using an approach like this would allow far more accurate evaluation of data timing than would be possible using two separate serial ports (where timing resolution would be 1ms at best).  PC software would have to be prepared to parse out the data, of course.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-01T18:54:55.463" />
  <row Id="13738" PostTypeId="2" ParentId="13712" CreationDate="2011-05-01T20:21:43.980" Score="1" ViewCount="" Body="&lt;p&gt;Balanced rise/fall is not a crucial requirement, except in certain situations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a digital logic circuit, most data signal paths will be in one of these categories:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;fast paths, with a risk of violating a hold constraint, but little risk of violating a setup constraint&lt;/li&gt;&#xA;&lt;li&gt;slow paths, with a risk of violating a setup constraint, but little risk of violating a hold constraint&lt;/li&gt;&#xA;&lt;li&gt;paths somewhere in between, with little risk of violating either setup or hold constraints&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;It is important that timing analysis consider all the possible combinations of rising and falling edges, but it's not important that the rise and fall time be matched for any of those categories. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In cases where a path is simultaneously at risk of violating a setup or a hold constraint, anything that increases the variation between maximum and minimum propagation delay along the path is undesirable, as it reduces the timing margin. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This would typically be a concern for high-speed interconnects attempting to communicate information from one place to another, for example, PCI express. The timing of such interconnects is often analyzed using an &quot;eye diagram&quot;: [*]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/dlvVi.png&quot; alt=&quot;Sample eye diagram, from wikipedia&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The eye diagram shows many overlayed oscilloscope traces of the voltage at the receiver. The bigger the &quot;eye&quot; in the center of the diagram, the more timing margin the system has. Variation between maximum and minimum propagation delay through transistors and across the wire increases the width of the X-shaped clusters of traces to the left and the right of the eye, and reduces the size of the eye opening.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another case where balanced rise/fall is important is clock distribution. Mismatched rise/fall through cells in the clock tree will distort the duty cycle of the clock. Clocks are generally expected to have a duty cycle close to 50%. A moderately imbalanced clock distribution could be a problem:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;if there are falling-edge-triggered flops in the circuit&lt;/li&gt;&#xA;&lt;li&gt;if there are memories in use that use the falling edge of the clock to generate internal timing signals&lt;/li&gt;&#xA;&lt;li&gt;if the clock is being forwarded to other devices&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;A severely imbalanced clock distribution could result in clock pulses that are too short to reliably propagate, i.e. cell inputs that transition again before the output has completely responded to the previous input transition.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;sub&gt;[*]: image from wikipedia: &lt;a href=&quot;http://en.wikipedia.org/wiki/File:Multipath_system_eye_diagram.svg&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/File:Multipath_system_eye_diagram.svg&lt;/a&gt;&lt;/sub&gt;&lt;/p&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-05-01T20:21:43.980" />
  <row Id="13739" PostTypeId="2" ParentId="8428" CreationDate="2011-05-01T20:41:45.817" Score="0" ViewCount="" Body="&lt;p&gt;This may be a time when scrounging the resources to buy an inexpensive USB-based logic analyzer is the right answer. I recently acquired a &lt;a href=&quot;http://www.usbee.com/sx.html&quot; rel=&quot;nofollow&quot;&gt;USBee SX&lt;/a&gt; and have been very pleased. Out of the box, it can decode serial on multiple (TTL level only) lines, and keep it all synchronized to well better than single bit time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It has no internal RAM, so it pushes all the data it samples up the USB. That has a couple of advantages, and at least one disadvantage. A big advantage is price. There's hardly anything inside the USBee SX between your signals and the USB, so it doesn't have to cost many arms and legs. The biggest advantage is capture depth. You are limited only by the storage on the PC. If you need a one hour capture to catch an elusive timing window bug, it can do that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A disadvantage is that the top sample rate is limited so that all sample can be fed up the USB. This makes it less useful for high-end digital logic, but for serial communications protocols that really isn't a big deal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The SX lists for about US$170. At that price it doesn't have to save your company very many hours to pay off....&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It certainly isn't the only example of the breed, but it is the only one I've personally used.&lt;/p&gt;&#xA;" OwnerUserId="1494" LastActivityDate="2011-05-01T20:41:45.817" />
  <row Id="13740" PostTypeId="2" ParentId="13730" CreationDate="2011-05-01T21:40:41.557" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.eecs.wsu.edu/~aofallon/cpts466/handouts/refMaual/PIC32%20Family%20Reference%20Manual,%20Sect.%2023%20Serial%20Peripheral%20Interface.pdf&quot; rel=&quot;nofollow&quot;&gt;Here are the details&lt;/a&gt; of how normal SPI and framed SPI are implemented on a PIC32.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;In Normal mode operation, the SPI Master controls the generation of the serial clock. The&#xA;number of output clock pulses corresponds to the transfer data width: 8, 16, or 32 bits.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;In Framed mode operation, the Frame Master controls the generation of the frame&#xA;synchronization pulse. The SPI clock is still generated by the SPI Master and is continuously running.&quot;&lt;/p&gt;&#xA;" OwnerUserId="3869" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-01T21:49:20.067" LastActivityDate="2011-05-01T21:49:20.067" />
  <row Id="13741" PostTypeId="1" AcceptedAnswerId="13783" CreationDate="2011-05-01T21:41:54.990" Score="0" ViewCount="82" Body="&lt;p&gt;I'm trying to use a bluetooth module, but I'm stuck at connecting/configuring it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When powered, the &lt;a href=&quot;http://www.sparkfun.com/datasheets/Wireless/Bluetooth/rn-42-ds.pdf&quot; rel=&quot;nofollow&quot;&gt;module&lt;/a&gt; blinks an led connected to PIO5 once per second, so it is in Discoverable/Inquiring/Idle according to &quot;7.3 LED Status&quot; of the &lt;a href=&quot;http://www.sparkfun.com/datasheets/Wireless/Bluetooth/rn-bluetooth-um.pdf&quot; rel=&quot;nofollow&quot;&gt;user manual&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I view the properties of the device on my laptop, it shows its using COM6.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/x3aMv.png&quot; alt=&quot;properties&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bluetooth Settings shows the device using two ports: COM6 and COM7.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/O3jbv.png&quot; alt=&quot;bluetooth settings&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Device Manager shows COM6 and 7 for serial over bluetooth.&#xA;&lt;img src=&quot;http://i.imgur.com/Rnsru.png&quot; alt=&quot;device manager&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first question is why there are two ports being used; one for outgoing and one for incoming. I did not expect to see separate ports for incoming and outgoing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I attempt to connect to the device from my laptop with PuTTY over COM6 using the settings documented in 3.2 and 3.3 of the user manual.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/mM6i7.png&quot; alt=&quot;PuTTY configuration&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LED stops blinking, but that behavior isn't documented.&lt;br&gt;&#xA;PuTTY 's session window is empty and doesn't allow me to type/send characters, even after hitting enter a dozen times.&lt;br&gt;&#xA;&lt;img src=&quot;http://i.imgur.com/FtnUq.png&quot; alt=&quot;PuTTY session&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I doing something wrong?&lt;br&gt;&#xA;Should I have a second session open on COM7?&lt;/p&gt;&#xA;" OwnerUserId="1227" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-02T19:30:02.970" LastActivityDate="2011-05-02T19:30:02.970" Title="Bluetooth module" Tags="&lt;bluetooth&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="13742" PostTypeId="2" ParentId="13730" CreationDate="2011-05-01T22:29:46.670" Score="2" ViewCount="" Body="&lt;p&gt;&quot;Framed SPI&quot; is basically just a term microchip made up and is supported on some of their chips (dsPIC and PIC32 I think).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally the chip select is held low by the master to talk to a slave and the master just sends out however many clock pulses it wants to define the data width (8,16,32bit).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the SPI unit is in framed mode the chip select doesn't do this, rather it can function as an output or an input which either generates or accepts a 1bit pulse called the 'frame sync'.  This indicates the beginning of a data 'word'.  In this mode the clock is continuously generated by the clock master.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This also means the link is now point to point, you can only communicate to one device in this mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This mostly exists to allow the microcontroller to communicate to low speed audio codecs.  You can approximate I2S/TDM communication with this setup (for some devices, not all).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Its not really something you would use for high quality or high sampling rate audio as there isn't support for the extra features needed for such operation (real I2S support, deep buffers, robust sampling rate control, etc). &lt;/p&gt;&#xA;" OwnerUserId="1438" LastActivityDate="2011-05-01T22:29:46.670" CommentCount="1" />
  <row Id="13743" PostTypeId="1" CreationDate="2011-05-02T00:09:31.567" Score="3" ViewCount="118" Body="&lt;p&gt;I would like to play around with this servo motor but I'm not sure what the feedback mechanism on it is or what the interface is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The mechanism has 3 wires leading to it (yellow, orange, brown). It consists of a hard black disc (I think the disc is metal or possibly a ceramic?), a PCB behind it that has a square wave pattern around the circumference of the board, and on the board itself there are a couple resistors, ceramic capacitors and a single 8 pin IC (I can't see what is on the IC, I don't want to take the mechanism apart).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The motor came from an old photocopier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My best guess is that it might be a magnetic resolver but I've never had any experience with them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the question is: What is the mechanism in the picture and how would I go about interfacing it (ie, if it was an encoder, I'd do quadrature decoding ect).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/WlzRb.jpg&quot; alt=&quot;motor&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1319" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-05-02T10:31:16.127" LastActivityDate="2011-06-01T11:50:02.830" Title="What is the feedback mechanism behind this motor?" Tags="&lt;dc-motor&gt;" AnswerCount="1" CommentCount="8" />
  <row Id="13744" PostTypeId="2" ParentId="13690" CreationDate="2011-05-02T01:07:13.787" Score="1" ViewCount="" Body="&lt;p&gt;The other posts all seem like sound advice.  Having performed similar hacks on similar UPSes, it generally Just Works&amp;trade;.  You can put a larger battery on most any UPS and be successful.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you should never do, and the reason why I'm offering an posting in addition to the fine answers already given, is use a smaller battery than the size rated for the particular UPS.  The UPS assumes that it may charge the battery safely by supplying it with a given ammount of current.  Smaller batteries can tolerate only smaller charging currents.  If you supply too much current, the battery will fail.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The precise mode of failure depends on the battery, but ranges from swelling, overheating, outgassing or even catching fire or exploding.   &lt;/p&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2011-05-02T01:07:13.787" />
  <row Id="13745" PostTypeId="1" AcceptedAnswerId="13750" CreationDate="2011-05-02T02:06:28.587" Score="1" ViewCount="96" Body="&lt;p&gt;I need to get the higest possible precision from an analog to digital convertor (and by high I mean 24bits or more), 10 times per second. To this end I've decided to investigate using an ADC that is designed for audio. Unfortunately, after vast amounts of reading and research the only way that I can interface it with my microcontroller, which I can't connect directly to it because of timing concerns. The only way that I can interface it is with an FPGA, which is alot of work for such a seemly simple task. I refuse to believe that nobody has wanted 24bit ADC precision on a simple non DSP microcontroller such as the Adurino or Fez. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know of an IC that can interface the I2S bus to either SPI, I2C, CAN, Serial, etc for the purpose of obtaining the 24bit value of the analog signal. Note: The data is not being using for high speed Digital Signal Processing. &lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-05-02T15:50:28.153" Title="I2S to SPI or some other normal interface" Tags="&lt;adc&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="13746" PostTypeId="1" AcceptedAnswerId="13749" CreationDate="2011-05-02T02:34:34.197" Score="11" ViewCount="476" Body="&lt;p&gt;Please be kind, I am an electronics nub.  This is in reference to getting an LED to emit photons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I read (Getting Started in Electronics - Forrest Mims III and Make: Electronics) electrons flow from the more negative side to the more positive side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In an example experiment (involving a primary dry cell, a SPDT switch, a resistor and an LED) it states that the resistor MUST be connected to the anode of the LED.  In my mind, if the electrons flow from negative to positive, wouldn't the electron flow run through the LED before the resistor; thereby making the resistor pointless?&lt;/p&gt;&#xA;" OwnerUserId="4070" LastActivityDate="2011-05-02T12:01:25.397" Title="Why does a resistor need to be on the anode?" Tags="&lt;led&gt;&lt;resistor&gt;&lt;current&gt;&lt;switch&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="13747" PostTypeId="2" ParentId="13711" CreationDate="2011-05-02T02:41:23.690" Score="2" ViewCount="" Body="&lt;p&gt;My suggestion would be get rid of the delay function and use the built in if you are using IAR or CCS.&quot;__delay_cycles (cycles);&quot; using the built ins, will give you more predicable results and better timing. You could probably just replace your delay for the built in, to get closer to the results you are looking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;personally I would go about the whole thing using interrupts and timers to pull  the whole thing off and use the peripherals that the msp430 has.&#xA;I would suggest using the WDT as an interval timer, doing this would leave the other timer for your motor control. p1.3 is used as the wake up pin and p1.0 is the led pin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;example code&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;volatile int counter;&#xA;void main(void) {&#xA;    WDTCTL = WDTPW + WDTHOLD;                 // Stop watchdog timer&#xA;    P1DIR = 0x01;                             // P1.0 output, else input&#xA;    P1OUT =  BIT3;                            // P1.3 set, else reset&#xA;    P1REN |= BIT3;                            // P1.3 pullup&#xA;    P1IE |= BIT3;                             // P1.3 interrupt enabled&#xA;    P1IES |= BIT3;                            // P1.3 Hi/lo edge&#xA;    P1IFG &amp;amp;= ~BIT3;                           // P1.3 IFG cleared&#xA;    _BIS_SR(GIE);&#xA;}&#xA;// Port 1 interrupt service routine&#xA;#pragma vector=PORT1_VECTOR&#xA;__interrupt void Port_1(void)&#xA;{&#xA;    WDTCTL = WDT_MDLY_64; //enables intervals of 64mS&#xA;    IE1 |= WDTIE;  // set WDT interrupt&#xA;}&#xA;#pragma vector=WDT_VECTOR&#xA;__interrupt void watchdog_timer (void)&#xA;{&#xA;    ++counter;&#xA;    P1OUT |= BIT0;&#xA;    if (counter == 245) {  //245 x 64mS = 15.6 seconds&#xA;        P1OUT &amp;amp;= ~BIT0;&#xA;        WDTCTL = WDTPW + WDTHOLD; &#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Not complete nor has this code been tested, but it should turn the led on for 15 seconds every time the P1.3 button is pushed. &lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-05-02T02:41:23.690" CommentCount="1" />
  <row Id="13748" PostTypeId="2" ParentId="13746" CreationDate="2011-05-02T02:59:20.367" Score="7" ViewCount="" Body="&lt;p&gt;Regardless of what side the resistor is placed on, it limits the amount of current that flows through the LED. It is usually a lot simpler to not think about what the electrons are doing and instead just think about it in sense of Resistance, Current, Voltage, and sometimes power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of an LED, if you connect a constant voltage source across the LED, the LED will act like almost 0 resistance, which will based off of V=IR (or V/R=I), will result in very large current, which causes the LED to &quot;pop&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have to connect a resistor in order to set the current that your LED is expecting.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-02T02:59:20.367" />
  <row Id="13749" PostTypeId="2" ParentId="13746" CreationDate="2011-05-02T03:07:38.893" Score="25" ViewCount="" Body="&lt;p&gt;The resistor can be on either side of the LED, but it must be present.  When two or more components are in series, the current will be the same through all of them, and so it doesn't matter which order they are in.  I think the way to read &quot;the resistor must be connected to the anode&quot; as &quot;the resistor cannot be omitted from the circuit.&quot;&lt;/p&gt;&#xA;" OwnerUserId="2773" LastActivityDate="2011-05-02T03:07:38.893" />
  <row Id="13750" PostTypeId="2" ParentId="13745" CreationDate="2011-05-02T03:15:18.420" Score="2" ViewCount="" Body="&lt;p&gt;If you only need 10 Hz sampling then an audio ADC seems like overkill. I would bet most Audio ADCs that are 24 bit would be at least 48 or 96 KHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Instead I would recommend going with something like &lt;a href=&quot;http://www.cirrus.com/en/pubs/proDatasheet/CS5530_F3.pdf&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; that provides you with SPI like you want and has a selectable sample rate between 6.25 SPs to 3840 SPs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am also not sure why a microcontroller would be unable to handle reading that data. &lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-02T03:15:18.420" CommentCount="1" />
  <row Id="13751" PostTypeId="1" AcceptedAnswerId="13752" CreationDate="2011-05-02T03:15:23.660" Score="1" ViewCount="79" Body="&lt;p&gt;I found that I can control one dc motor with PWM from P1.2.What how i'm going to wire it?&#xA;How I am going to divide voltage in this picture.In physical way.&#xA;&lt;img src=&quot;http://i.imgur.com/vuCqP.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="4063" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-05-02T03:17:29.277" LastActivityDate="2011-05-02T03:31:29.123" Title="Controlling Dc Motor With Pwm" Tags="&lt;dc-motor&gt;&lt;pwm&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="13752" PostTypeId="2" ParentId="13751" CreationDate="2011-05-02T03:31:29.123" Score="1" ViewCount="" Body="&lt;p&gt;This setup will almost work. The pin outputs on the MSP430 are not capable of driving a motor directly, this is due to the current limits on the output pins. You will need to place &quot;something&quot; between the pin and the motor. There are many things that can fill the &quot;something&quot;, but in all cases they will basically act as a switch. A simple mosfet is probably the easiest to go with, you just need to make sure you get one big enough to power the motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far how a PWM change the speed across the motor, what you will be doing is adjusting the duty cycle of the PWM. This is essentially adjusting the On/Off time of the motor. The PWM will be running so fast that you wont actually be able to notice the Ons and Offs unless you look at it on a scope, but the effective voltage across the motor will change which results in a change of speed.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-02T03:31:29.123" CommentCount="3" />
  <row Id="13753" PostTypeId="2" ParentId="13746" CreationDate="2011-05-02T05:52:17.453" Score="12" ViewCount="" Body="&lt;p&gt;No it would not make the resistor pointless.  Imagine if the resistor were so large it completely prevented electrons from flowing.  Does it matter which side of the LED it's on?  Either way, it will break the circuit and prevent current from flowing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't think about individual particles traveling through the circuit.  The charged particles are not &quot;used up&quot; by the LED.  They go through it, and their motion is what carries energy from one place to another.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Think about all the particles moving at all points in the circuit at once, like a belt or chain.  If you slow down the chain at one point, it slows down at every other point, too, due to the links pushing and pulling against each other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I read &lt;em&gt;Getting Started in Electronics&lt;/em&gt; as a kid, and I think it teaches ideas like this poorly.  I had to unlearn everything in college and don't recommend it.  Try this instead:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://amasci.com/miscon/eleca.html#electron&quot; rel=&quot;nofollow&quot;&gt;http://amasci.com/miscon/eleca.html#electron&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://amasci.com/miscon/eleca.html#circle&quot; rel=&quot;nofollow&quot;&gt;http://amasci.com/miscon/eleca.html#circle&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://amasci.com/amateur/elecdir.html&quot; rel=&quot;nofollow&quot;&gt;http://amasci.com/amateur/elecdir.html&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Try out &lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+10.20027730826997+50+5.0+50%0Av+160+304+160+144+0+0+40.0+5.0+0.0+0.0+0.5%0Aw+160+144+208+144+0%0A174+208+144+272+112+0+1000.0+0.5792+Resistance%0Aw+240+112+208+112+0%0Aw+208+112+208+144+0%0Aw+272+144+320+144+0%0A162+320+144+320+304+1+2.1024259+1.0+0.0+0.0%0Aw+160+304+320+304+0%0A&quot; rel=&quot;nofollow&quot;&gt;this circuit&lt;/a&gt;.  When you adjust the resistance, does it only slow down the charges before the resistor, or does it change the speed of all the charges in the entire circuit?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-02T06:00:15.530" LastActivityDate="2011-05-02T06:00:15.530" CommentCount="5" />
  <row Id="13754" PostTypeId="2" ParentId="13745" CreationDate="2011-05-02T06:55:26.357" Score="4" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://tinyurl.com/3m8ur5r&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; on the TI website lists a dozen 24 bit ADCs interfacing with SPI. Speeds start at 15 sps.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A thought on resolution:&lt;br&gt;&#xA;24 bits &lt;em&gt;or more&lt;/em&gt;! You do realize that 20 bit offers 1 ppm resolution, and that 1 LSB in 24 bit is 0.06 ppm of FS? Just looking at the circuit will give you several LSB of error, so to speak. For one thing, you'll need temperature control to within tenths of a degree to take advantage of the full measurement range.&lt;br&gt;&#xA;If you really need more than 24 bits, TI has the &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/ads1281.pdf&quot; rel=&quot;nofollow&quot;&gt;ADS1281&lt;/a&gt; which offers 31 bits. &lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-02T07:17:36.370" LastActivityDate="2011-05-02T07:17:36.370" CommentCount="1" />
  <row Id="13755" PostTypeId="1" AcceptedAnswerId="13852" CreationDate="2011-05-02T07:35:34.580" Score="0" ViewCount="84" Body="&lt;p&gt;I know the exact values depend on the specific battery used, but is there a general rule for the maximum charge current (as a function of the battery capacity) for each of the mainstream battery technologies (NiCd, NiMH, Li-ion, Li-Polymer, lead-acid), for normal and fast charging? The typical capacity I'm going to use is 10 - 40 Ah.&lt;/p&gt;&#xA;" OwnerUserId="897" LastActivityDate="2011-05-04T02:28:15.567" Title="Maximum battery charge current by technology" Tags="&lt;battery&gt;&lt;battery-charging&gt;" AnswerCount="2" />
  <row Id="13756" PostTypeId="1" CreationDate="2011-05-02T08:37:02.990" Score="0" ViewCount="81" Body="&lt;p&gt;when Pi Filter should be used and how to choose its L an C value ?&lt;/p&gt;&#xA;" OwnerUserId="199" LastActivityDate="2011-05-04T02:20:17.773" Title="Pi Filter details" Tags="&lt;filter&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13757" PostTypeId="2" ParentId="13756" CreationDate="2011-05-02T09:47:23.813" Score="4" ViewCount="" Body="&lt;p&gt;It's used when a low-pass filter is required. They are often used to filter noise from power supplies and in radio transmitters and receivers. In the latter applications it needs to be designed to match the impedances on the input and output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use &lt;a href=&quot;http://tonnesoftware.com/elsie.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; software for LC filter design, it's very good. The ARRL Handbook has design tables for the amateur radio bands.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A simulator (I use SPICE) is useful for checking a filter's characteristics.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-02T10:01:08.557" LastActivityDate="2011-05-02T10:01:08.557" CommentCount="1" />
  <row Id="13758" PostTypeId="2" ParentId="13743" CreationDate="2011-05-02T11:26:43.430" Score="1" ViewCount="" Body="&lt;p&gt;With just three wires, I don't see how it can supply a quadrature output. For that, a supply for the IC, ground, and two wires for the quadrature outputs would be required. It's probably just a tacho.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-02T11:26:43.430" CommentCount="2" />
  <row Id="13759" PostTypeId="2" ParentId="13746" CreationDate="2011-05-02T12:01:25.397" Score="5" ViewCount="" Body="&lt;p&gt;The resistor doesn't need to be on the anode side, but it needs to be there (unless the voltage of the power supply is equal to or less than the voltage drop of the LED.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After all, if you have a 9 volt power source, and an LED that drops 2 volts, then the other 7 volts have to get dropped someplace.&lt;/p&gt;&#xA;" OwnerUserId="4075" LastActivityDate="2011-05-02T12:01:25.397" />
  <row Id="13760" PostTypeId="1" CreationDate="2011-05-02T12:30:53.933" Score="1" ViewCount="143" Body="&lt;p&gt;I know how to work with AVRs on Windows but I want to know how to do this on my Mac.  Can I use Xcode?&lt;/p&gt;&#xA;" OwnerUserId="4076" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-05-03T14:46:28.563" LastActivityDate="2011-05-03T14:46:28.563" ClosedDate="2011-05-03T12:04:10.627" Title="How do I program AVRs on MacOS X?" Tags="&lt;microcontroller&gt;&lt;avr&gt;&lt;mac&gt;" AnswerCount="2" CommentCount="10" FavoriteCount="1" />
  <row Id="13762" PostTypeId="2" ParentId="13760" CreationDate="2011-05-02T12:39:13.243" Score="0" ViewCount="" Body="&lt;p&gt;I thought that Xcode was for running Mac applications, I don't think it is relevant for running code on an AVR. It might be useful for writing AVR development software that runs on a Mac, of course, including a downloader to an AVR target.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Google turned up &lt;a href=&quot;http://www.obdev.at/products/crosspack/index.html&quot; rel=&quot;nofollow&quot;&gt;CrossPack&lt;/a&gt;, which looks as though it will allow you to do AVR development on the Mac. It doesn't require Xcode, which might be useful to you.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-02T13:39:30.787" LastActivityDate="2011-05-02T13:39:30.787" CommentCount="6" />
  <row Id="13763" PostTypeId="2" ParentId="13755" CreationDate="2011-05-02T12:53:45.553" Score="1" ViewCount="" Body="&lt;p&gt;This site has a whealth of battery information - including some indication of charge time: &lt;a href=&quot;http://www.batteryspace.com/batteryknowledge.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.batteryspace.com/batteryknowledge.aspx&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Interestingly, although load is specified in Amps, a charge indication is given in hours, not amps. I guess that has to do that larger batteries (im Ah) will generally allow for higher charge current - charge time therefore staying constant.&lt;/p&gt;&#xA;" OwnerUserId="1612" LastActivityDate="2011-05-02T12:53:45.553" CommentCount="1" />
  <row Id="13764" PostTypeId="1" AcceptedAnswerId="13767" CreationDate="2011-05-02T13:50:46.103" Score="5" ViewCount="75" Body="&lt;p&gt;I'm building a motor driver circuit, and am looking at diodes to clamp the output voltage between the supply rails. Apparenly, I should use schottky diodes for this purpose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, are there ICs out there than contain a pair of diodes arranged as shown below?&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;┌───►|──┬──►|───┐&#xA;│       │       │&#xA;0V      S       V+&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Or should I just buy a pair of single diodes?&lt;/p&gt;&#xA;" OwnerUserId="1217" LastActivityDate="2011-05-02T14:17:14.623" Title="Can I get a pair of schottky diodes in a single chip?" Tags="&lt;motor&gt;&lt;diodes&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="13766" PostTypeId="2" ParentId="13764" CreationDate="2011-05-02T14:15:24.750" Score="1" ViewCount="" Body="&lt;p&gt;Yes, such devices do exist; they are known as dual Schottky or dual diodes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The most common arrangement is two diodes with a common cathode; these are used in switch mode power supplies to boost the allowable current from a typical single diode in package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, dual series diodes do exist; here is one example of a power device: &lt;a href=&quot;http://www.vishay.com/docs/94554/8sth06.pdf&quot; rel=&quot;nofollow&quot;&gt;VS-8STH06FP&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another example of a device not intended for high power applications is &lt;a href=&quot;http://www.nxp.com/acrobat_download/datasheets/BAV99_SER_5.pdf&quot; rel=&quot;nofollow&quot;&gt;BAV99W&lt;/a&gt;, which is a very popular device.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-02T14:15:24.750" />
  <row Id="13767" PostTypeId="2" ParentId="13764" CreationDate="2011-05-02T14:17:14.623" Score="8" ViewCount="" Body="&lt;p&gt;They're simply called &quot;double Schottky diodes&quot; :-). They often come in different configurations, like for instance the &lt;a href=&quot;http://www.fairchildsemi.com/ds/BA%2FBAT54.pdf&quot; rel=&quot;nofollow&quot;&gt;BAT54&lt;/a&gt;:  &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;BAT54A: common anode&lt;br&gt;&#xA;  BAT54C: common cathode&lt;br&gt;&#xA;  BAT54S: in series, one diode's cathode connects to the other's anode&lt;br&gt;&#xA;  BAT54: is the single diode version&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/8hEJw.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-02T14:17:14.623" CommentCount="2" />
  <row Id="13768" PostTypeId="2" ParentId="13718" CreationDate="2011-05-02T14:49:35.937" Score="4" ViewCount="" Body="&lt;p&gt;I don't speak Verilog, but I noticed that your stopbit is zero, which should be 1. Are you reading the port on a scope, or are you reading on a UART? In the latter case you may not have a character received if it doesn't see the stopbit.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-02T14:49:35.937" CommentCount="1" />
  <row Id="13769" PostTypeId="1" AcceptedAnswerId="13771" CreationDate="2011-05-02T14:50:36.203" Score="2" ViewCount="126" Body="&lt;h2&gt;The Problem:&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;I want to be able to detect if a garage door is opened or closed with my Arduino. I don't know what kind of sensor would be suitable for this task. The Arduino and the unknown sensor will be placed approximately 4 meters from the garage door.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Some Context:&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;I live at the second floor of a house and last weekend the garage door left opened the whole night by mistake. I want a method to detect the door is opened. My first thought (I'm newbie in electronics) has been to place the Arduino I own in the garage, and putting some sensor detect the door is opened and then send via wireless to another Arduino place at the second floor that the door is opened and reproduce some sound to warn the garage door is opened.&lt;/p&gt;&#xA;" OwnerUserId="4079" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-05-04T16:01:02.170" LastActivityDate="2011-05-04T16:01:02.170" Title="How can I detect if a garage door is opened or closed?" Tags="&lt;arduino&gt;&lt;sensor&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="2" />
  <row Id="13770" PostTypeId="2" ParentId="13769" CreationDate="2011-05-02T15:09:41.333" Score="2" ViewCount="" Body="&lt;p&gt;If you really don't want the sensor on the door itself, you could opt for a Sharp GP2DXX IR sensor. There are different versions depending on the range, &lt;a href=&quot;http://www.acroname.com/robotics/info/articles/sharp/sharp_compare.pdf&quot; rel=&quot;nofollow&quot;&gt;this document&lt;/a&gt; gives you an overview.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the sensor can be on the door, there's microswitches like  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/XgCke.jpg&quot; alt=&quot;microswitch&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Despite their name they're often not really micro, but rather for heavy duty industrial use. I guess the name derives from a Honeywell trade mark.)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-02T15:09:41.333" CommentCount="1" />
  <row Id="13771" PostTypeId="2" ParentId="13769" CreationDate="2011-05-02T15:10:59.457" Score="5" ViewCount="" Body="&lt;p&gt;In many home security systems they use magnet switches to detect the state of the door.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also use something like IR to see if a certain part of the door frame is blocking the light.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And one more option is to sense if the door is horizontal or vertical, basically you would mount it to the inside of the door, when it opens it would be horizontal and closed would be vertical. This is actually how most of the off-the-shelve generic sensors work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a particular method that you prefer I can give some specific sensor recommendations as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I missed that you said you wanted it 4 meters from the door. I am not sure if you just want this because you don't want to deal with wireless, but the IR method can also work in which you put something that reflects IR on the door and then have your sensor look to see if your IR beam has been reflected or not.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Some more additions:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it were me, I would get something like &lt;a href=&quot;http://www.homesecuritystore.com/p-500-gm-318-skylink-garage-door-monitor.aspx&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;, there are lots of other brands and methods that are used. Buying sensors and wireless modules can be pretty expensive when bought in quantity 1 and probably wont be worth the cost over just buying the off the shelf method.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now if it were me wanting to tackle a fun project, I would use an accelerometer attached to the inside of the door (could even be a board just Velcro'd to the inside of the door). The accelerometer doesn't need to be anything special, just something that when attached can detect acceleration in the down direction when the door is vertical and the down direction when the door is horizontal. It so happens that the force of gravity will show up on an accelerometer. I would then use an Xbee module to transmit the status to an xbee that is inside.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Realistically you don't need to transmit very much very often, you could put everything into sleep mode when ever you aren't reading and then once every minute or so wake up and transmit the current state. Because of how little the device is on it could easily run off of a battery for a decently long time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There may be other, better, methods of detection, but when ever I do a &quot;for fun&quot; project I like using parts that I might use in other projects. It helps to grow the intellectual property that I have, which is useful for the future.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-05-02T15:50:02.873" LastActivityDate="2011-05-02T15:50:02.873" CommentCount="2" />
  <row Id="13772" PostTypeId="2" ParentId="13769" CreationDate="2011-05-02T15:13:41.470" Score="0" ViewCount="" Body="&lt;p&gt;Why would you need to place the sensor 4 meters from the door? a simple limit switch or even a photo-eye placed by the door would be much simpler. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-05-02T15:13:41.470" CommentCount="1" />
  <row Id="13773" PostTypeId="1" AcceptedAnswerId="13776" CreationDate="2011-05-02T15:50:12.413" Score="2" ViewCount="147" Body="&lt;p&gt;I have a pair of &lt;a href=&quot;http://shop.lego.com/ByTheme/Product.aspx?p=9693&amp;amp;cn=17&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt; Li-ion batteries. I'd like to couple them so that I get double the current. However, I realize that this could be a Bad Idea™, as the charge could flow in a loop through both batteries.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the best way to prevent this?&lt;br&gt;&#xA;Should I add diodes in series with each battery? (if so, what type and value?)&lt;br&gt;&#xA;Should I put a resistor in series with one of the batteries?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or is there a better way?&lt;/p&gt;&#xA;" OwnerUserId="1217" LastActivityDate="2011-05-04T02:16:23.627" Title="How should I connect batteries in parallel?" Tags="&lt;battery&gt;&lt;parallel&gt;" AnswerCount="4" FavoriteCount="1" />
  <row Id="13774" PostTypeId="2" ParentId="13745" CreationDate="2011-05-02T15:50:28.153" Score="2" ViewCount="" Body="&lt;p&gt;You could use a CPLD instead of an FPGA in order to get a more cost effective digital hardware solution.  However, there are a number of reasons you shouldn't use an audio ADC for certain applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Audio ADCs tend to be sigma-delta architecture.  You can't just sample them whenever you like by asserting some input.  You are required to pump the data from them at a constant rate, and there's only a limited number of specific frequencies that they can use for operation.  In addition, if you need to phase-lock onto the signal, that will be almost impossible without careful manipulation of the ADC's oscillator, and such manipulation is almost certainly going to cause artifacts that could be detected at 24-bits, and that's assuming that you aren't overwhelmed with all kinds of other noise already.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another problem with audio ADCs is that they make a lot of assumptions based on the typical audio frequency range of the human ear.  These assumptions may interfere with your sampling, particularly if it is outside of typical audio frequency range.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-05-02T15:50:28.153" CommentCount="1" />
  <row Id="13776" PostTypeId="2" ParentId="13773" CreationDate="2011-05-02T16:32:23.527" Score="4" ViewCount="" Body="&lt;p&gt;The resistor solution has the main disadvantage that there can flow a (rather large) current from one battery to the other. This may reduce the life of the battery receiving the current (you're not properly &quot;charging&quot; it).&lt;br&gt;&#xA;I would go for the diodes. If one battery's voltage is higher than the other this battery will be the only one supplying current, until both voltages are the same. From that moment both batteries will supply current.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-02T16:32:23.527" CommentCount="1" />
  <row Id="13777" PostTypeId="2" ParentId="13773" CreationDate="2011-05-02T16:40:23.683" Score="1" ViewCount="" Body="&lt;p&gt;If the load power isn't too low, you could connect the batteries in series then use a converter (i.e. a buck) to convert the power to  lower voltage / higher current. You'll need to implement some sort of undervoltage protection to shut the converter down if the input voltage gets too low. You'll lose some power in control as well as conversion.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-02T16:40:23.683" />
  <row Id="13779" PostTypeId="1" CreationDate="2011-05-02T17:06:53.013" Score="0" ViewCount="35" Body="&lt;p&gt;Hello!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my device i need to use flash memory chip like one used in this device - &lt;a href=&quot;http://www.supertalent.com/products/stt_usb_detail.php?type=Pico&quot; rel=&quot;nofollow&quot;&gt;http://www.supertalent.com/products/stt_usb_detail.php?type=Pico&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In other words, a single-chip solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The question is where i can get such chips?&#xA;Thanks very much!&lt;/p&gt;&#xA;" OwnerUserId="4083" LastActivityDate="2011-05-02T17:06:53.013" ClosedDate="2011-05-02T19:02:16.497" Title="Pico Flash Memory" Tags="&lt;memory&gt;&lt;flash&gt;" CommentCount="1" />
  <row Id="13780" PostTypeId="1" CreationDate="2011-05-02T17:19:47.830" Score="0" ViewCount="39" Body="&lt;p&gt;I'm looking for a single board computer with the following capabilities. &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;can run linux &lt;/li&gt;&#xA;&lt;li&gt;has usb otg interface so I can plug a commercial, off the&#xA;shelf camera into it&lt;/li&gt;&#xA;&lt;li&gt;wifi&lt;/li&gt;&#xA;&lt;li&gt;powerful enough to stream video from camera to wifi&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The goal is to end up with a device that can stream video from a camera and broadcast it over wifi. The problem I'm trying to solve is losing video when the police decide it's within their rights to confiscate my camera or the person being recorded decides to attack and break my camera. If I could stream the camera output to one or more friends while I'm recording then they would have a much harder time destroying the evidence. It would be really nice if there was a reasonably cheap commercial solution I could just buy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I may be over thinking this and you all will have a really simple solution to my problem. &lt;/p&gt;&#xA;" OwnerUserId="4084" LastActivityDate="2011-05-02T17:19:47.830" ClosedDate="2011-05-02T17:22:38.250" Title="Hardware to stream usb video from camera to other wifi devices." Tags="&lt;camera&gt;&lt;wifi&gt;&lt;usb-host&gt;" CommentCount="2" />
  <row Id="13783" PostTypeId="2" ParentId="13741" CreationDate="2011-05-02T18:14:11.000" Score="1" ViewCount="" Body="&lt;p&gt;A bit of background first: the distinction between incoming and outgoing RFCOMM (Bluetooth stack protocol for virtual COMs) ports is necessary because it's always one of the communicating devices that initiates the connection (a bit similar to TCP sockets - where you have server and client).&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The outgoing COM port is used when the PC initiates the connection to the&#xA;remote device (opening the port initiates RFCOMM connection to the remote device).&lt;/li&gt;&#xA;&lt;li&gt;The incoming COM port is used when the remote device initiates the&#xA;connection.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Once the connection is opened it is bidirectional, regardless of the type. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, this Bluetooth module supports both master and slave mode (see manual chapter 2), that's why it advertises 2 RFCOMM/SPP ports, I guess. If you want PC to initiate the connection, use COM6, otherwise use COM7.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why you see no echo in PuTTY? By default there's no local echo, and you actually shouldn't see any characters you type (unless you short UART_RX to UART_TX, or have some real device attached there to communicate with). The module itself is transparent (in the data mode, that is).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, baud rate etc. shouldn't really matter for Blueooth connection - note, that chapter 3.2 refers to configuring the device via physical serial port (UART_RX/TX pins, i.e. from the device side), while 3.3 describes configuring over virtual port (i.e. from the PC side). I somehow feel you're confusing the module sides ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This excerpt from the manual is quite important:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;To connect to FireFly, browse for&#xA;  services, you should see: “SPP”&#xA;  profile with a virtual COM port. Open&#xA;  this virtual COM port to create a&#xA;  Bluetooth connection. Once connected,&#xA;  the device will be in data mode&#xA;  allowing data to flow in both&#xA;  directions as if the serial port were&#xA;  locally attached to the PC. The device&#xA;  must be in command mode for&#xA;  configuration and programming. To&#xA;  enter command mode type “$$$” (three&#xA;  dollar signs) from either the remote&#xA;  Bluetooth connection or the local&#xA;  serial port connection. You must enter&#xA;  command mode within 60 seconds&#xA;  (configurable by setting the config&#xA;  timer).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Cool module, btw!&lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-05-02T18:14:11.000" CommentCount="5" />
  <row Id="13784" PostTypeId="1" CreationDate="2011-05-02T18:37:55.903" Score="0" ViewCount="75" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/6108/small-sot-23-transistor-markings&quot;&gt;Small SOT-23 transistor markings&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Hello does anyone know what component has &quot;B6PP&quot; in a SOT23-5. &#xA;How about &quot;H102B&quot; also in a SOT23-5.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="4085" LastActivityDate="2011-05-02T21:27:33.723" ClosedDate="2011-05-03T01:07:50.690" Title="SMD Markings for SOT23-5 Package" Tags="&lt;sot23&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13785" PostTypeId="6" CreationDate="2011-05-02T19:09:38.127" Score="0" ViewCount="" Body="&lt;p&gt;I am not much of one to &quot;toot my own horn&quot;, because of that I am not going to go into much detail here. I think I have been around the community and expressed my opinions through comments, questions, answers, and chats long enough that you will either think I am suitable for the job or not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to know more about me go read my profile or @me in chat.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-05-02T19:09:38.127" LastActivityDate="2011-05-02T19:09:38.127" CommunityOwnedDate="2011-05-02T19:09:38.127" CommentCount="2" />
  <row Id="13786" PostTypeId="2" ParentId="13784" CreationDate="2011-05-02T19:22:52.523" Score="1" ViewCount="" Body="&lt;p&gt;Without knowing the manufacturer, it's almost impossible to figure it out.  As parts get smaller and smaller, there is less room to mark what they are.  Manufacturers started putting proprietary codes on them that as shorthand.  They bare no relationship to the actual part number.  Most manufacturer web sites have some search feature that lets you enter that code and get the real part #, but you must know the manufacturer first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should point out that some parts have no markings on them what-so-ever.  On one PCB, I'm using a quad-diode thing in a 4-pin BGA package.  That thing is so small that even if the part was marked, you'd need a microscope to read it.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-02T19:22:52.523" />
  <row Id="13787" PostTypeId="6" CreationDate="2011-05-02T20:21:06.160" Score="0" ViewCount="" Body="&lt;p&gt;Hello, I am Kevin Vermeer. As my &lt;a href=&quot;http://electronics.stackexchange.com/users/857/reemrevnivek&quot;&gt;profile page&lt;/a&gt; says, I'm a university engineering student in electrical and computer engineering. I've been a member for 10 months, which includes the entire transition from Chiphacker to the graduated StackExchange site. In that time, I've been active in enhancing the site by creating content (primarily answers, not questions) and by improving the quality of the site through prolific editing, commenting, chatting, and participation on Meta.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My philosophy of moderation would have a primary goal of enhancing the community to be the best place on the Web for expert questions and answers on electronics engineering and computer engineering.  Since I've not been an official moderator before, I would seek guidance from the community, the podcast, and other, more experienced moderators.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want some stats or name-drops, here you go:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I was offered a pro-tempore moderation position by Robert Caratino &quot;because of your [my] outstanding contribution to the community&quot; at the start of the Beta period in September.&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://blog.stackoverflow.com/2010/07/our-designer-in-residence-jin-yang/&quot; rel=&quot;nofollow&quot;&gt;Jin&lt;/a&gt; &lt;a href=&quot;http://chat.stackexchange.com/transcript/message/704625#704625&quot;&gt;personally thanked me&lt;/a&gt; for my contributions during the design phase.&lt;/li&gt;&#xA;&lt;li&gt;In the past year, I've been the &lt;a href=&quot;http://meta.electronics.stackexchange.com/users?tab=editors&quot;&gt;2nd most prolific editor on Meta&lt;/a&gt;, the &lt;a href=&quot;http://meta.electronics.stackexchange.com/users?tab=voters&quot;&gt;3rd most prolific voter on Meta, &lt;/a&gt;, the &lt;a href=&quot;http://electronics.stackexchange.com/users?tab=editors&amp;amp;filter=year&quot;&gt;7th most prolific editor on the main site&lt;/a&gt;, and the &lt;a href=&quot;http://electronics.stackexchange.com/users?tab=voters&amp;amp;filter=year&quot;&gt;6th most prolific editor on the main site&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;li&gt;If you want more stats, please feel free to gather them yourself.  I don't put too much stock in them.  Instead of trying to rank through the stats, read through the site's history and see what I and the other candidates have actually done and said.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;As moderator, I would continue to use the tools which I previously used during the beta and during Chiphacker to improve the site. If I'm not elected, well, I'll keep doing that. &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-02T20:21:06.160" LastActivityDate="2011-05-02T20:21:06.160" CommunityOwnedDate="2011-05-02T20:21:06.160" CommentCount="4" />
  <row Id="13788" PostTypeId="1" CreationDate="2011-05-02T20:23:32.800" Score="1" ViewCount="88" Body="&lt;p&gt;Is there any way to make a switch that uses a 5V input to open a -5V or 10V connection? (so i can switch between making a line -5 and 10V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance!&lt;/p&gt;&#xA;" OwnerUserId="2985" LastActivityDate="2011-05-03T10:19:56.460" Title="CMOS Switch for -5, 10, and 5V" Tags="&lt;switch&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="13789" PostTypeId="2" ParentId="4206" CreationDate="2011-05-02T20:25:26.050" Score="0" ViewCount="" Body="&lt;p&gt;To get precise timing with timer 0, the divide ratio must either be less than about 259, or else must be a power of two.  Because of Microchip's unfortunate decision not to allow TMR0 to be written without clearing the prescalar, it is impossible to get precise timings when adjusting TMR0 with the prescalar enabled.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To achieve precise timings with 'short' timer intervals, one need only add&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;  TMR0 += (259-interval);&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Provided the code generates an &quot;ADDWF _TMR0,f&quot; instruction (as it should with any typical compiler) it should yield a precise timer rate of 'interval' clock cycles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If one needs an interrupt action to be performed at some rate slower than once every 259 cycles that isn't a power of two, and if the interrupt action might take more than 256 cycles, adding a little assembly-language before the standard interrupt handler may be 'just the ticket'.  For best efficiency, this approach requires a non-banked variable to hold the execution counter.  Before the interrupt handler, insert:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;; Example assumes code should run once every thousand cycles&#xA;  decfsz _intCounter,f  ; Must be in unbanked RAM!&#xA;   retfie&#xA;  ... Proveed to normal interrupt handler.  Then in C code:&#xA;  TMR0 += (3+24); /* Three cycles for RTCC 'loss'; advance 24 cycles;&#xA;                     so we execute main interrupt once every 1000 cycles&#xA;                     rather than once every 1024 */&#xA;  GIE = 1;  /* Interrupts are okay now */&#xA;  ... Do main interrupt code; at end of interrupt:&#xA;  intCounter += 4;&#xA;  /* Note that if the timer tick interrupt triggers more than three times while&#xA;     running the main interrupt routine, intCounter will be zero or will be greater&#xA;     than four.  This code ignores that possibility. */&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Note that this code allows nested interrupts, but the &quot;quick&quot; interrupts don't disturb the flags, nor do they disturb any registers other than _intCounter.  Consequently, there's no need to save/restore registers, and no re-entrancy problems if the &quot;quick&quot; timer-tick interrupts happen while the main timer-tick routine is running.  Problems only occur if four or more timer-tick interrupts occur while the main timer-tick code is running.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-02T20:25:26.050" />
  <row Id="13790" PostTypeId="2" ParentId="13693" CreationDate="2011-05-02T20:42:54.167" Score="0" ViewCount="" Body="&lt;p&gt;An elegant solution to this problem would be to use a regulator with a shutdown pin, and have some sort of undervoltage limit derived from the input voltage controlling this shutdown pin.&lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-05-02T20:42:54.167" />
  <row Id="13791" PostTypeId="2" ParentId="13773" CreationDate="2011-05-02T20:45:37.003" Score="1" ViewCount="" Body="&lt;p&gt;Connecting 2 batteries of similar charge in parallel should not be an issue, your charger may struggle though and you may have to charge them seperately.  &lt;/p&gt;&#xA;" OwnerUserId="1827" LastActivityDate="2011-05-02T20:45:37.003" />
  <row Id="13792" PostTypeId="1" CreationDate="2011-05-02T20:54:24.223" Score="-1" ViewCount="86" Body="&lt;p&gt;I want to learn CAD on my MAC.  Can anyone suggest websites or books that I should start with?  I have a degree in Electrical Engineering and I have been working in the field for 6 years.  I was mostly doing analog design and DC-DC converter designs.  I would like to start doing CAD and want to know where to start.  Thanks.&lt;/p&gt;&#xA;" OwnerUserId="4086" LastEditorUserId="4086" LastEditorDisplayName="" LastEditDate="2011-05-02T21:02:23.173" LastActivityDate="2011-05-03T00:09:15.490" ClosedDate="2011-05-03T01:10:35.587" Title="cheapest way to learn CAD" Tags="&lt;cad&gt;" AnswerCount="1" CommentCount="6" />
  <row Id="13795" PostTypeId="6" CreationDate="2011-05-02T21:26:25.523" Score="0" ViewCount="" Body="&lt;p&gt;Hi,   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been a member of Electronics Design for about 6 months now with daily(sometimes hourly) visits to the site to see what new interesting questions have come up. I am always interested in helping new members get an understanding of how the site works as its different from a forum site. Over the past couple of months my interest in electronics has grown from a hobby to something I can see myself doing as a job. This has largely been due to this community(Electronics Design).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I read a question that is inappropriate I flag it. If I see a question that i'm unsure about then I also flag it to get someone else's opinion on what should happen with the question. I'm fair and don't judge people over the internet. If I have no knowledge on a subject then I will go research it and comment on the question if I have discovered anything that might be considered useful to the user asking the question as well as the community.   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Being a moderator would allow me to put something back in to this community after I have taken so much out of it(check my questions against answers). If there is anything else you would like to know about me ask me in chat(just start your message @Dean and it will appear in my inbox). &lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-05-02T21:26:25.523" LastActivityDate="2011-05-02T21:26:25.523" CommunityOwnedDate="2011-05-02T21:26:25.523" CommentCount="2" />
  <row Id="13796" PostTypeId="2" ParentId="13784" CreationDate="2011-05-02T21:27:33.723" Score="1" ViewCount="" Body="&lt;p&gt;I've found this website useful previously: &lt;a href=&quot;http://www.marsport.org.uk/smd/mainframe.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.marsport.org.uk/smd/mainframe.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, Digi-Key has a listing of &lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CB8QFjAA&amp;amp;url=http://www.digikey.es/Web%2520Export/Supplier%2520Content/MCC_353/PDF/MCC_SMD_Marking_Codes.pdf&amp;amp;rct=j&amp;amp;q=digikey%20surface%20mount%20codes&amp;amp;ei=cyG_TdyXL42LhQfFiaHUBQ&amp;amp;usg=AFQjCNGcnLPOrtumX5s7YXUzeeT1X0O8qQ&amp;amp;sig2=UJK8ZKqz4d2ARBzrBkUytw&amp;amp;cad=rja&quot; rel=&quot;nofollow&quot;&gt;one manufacturer's codes&lt;/a&gt;, which could be shared across manufacturers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I couldn't find your codes in either of these lists, although the SMD list does have some of your prefixes (&quot;B6&quot; and &quot;H1&quot;) which could be starting points.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Apart from that though, echoing David, it is next to impossible to decode a part number. Sometimes you might just break out the multimeter or trace the circuit and make an educated guess.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-02T21:27:33.723" CommentCount="1" />
  <row Id="13797" PostTypeId="2" ParentId="13788" CreationDate="2011-05-02T21:33:39.197" Score="1" ViewCount="" Body="&lt;p&gt;Some switches like ADG733 have a separate Vss pin which can be at a lower potential than the logic GND; this means you could have a -10V supply on the Vss pin which would allow the gate to control up to a -10V signal whilst still having a 0-Vdd logic input. Unfortunately the ADG733 is limited to a 5.5V supply; but there are probably other parts that will do the same job (numbers escape me at the moment.)&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-02T21:33:39.197" CommentCount="6" />
  <row Id="13798" PostTypeId="2" ParentId="2679" CreationDate="2011-05-02T21:48:14.680" Score="0" ViewCount="" Body="&lt;p&gt;I had the same need and went with SpaceClaim.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alibre, Autodesk Inventor and SolidWorks share the same basic philosophy with increasing capabilities and cost. They are all in my opinion old-fashioned, clunky and takes a lot of time and effort to learn.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason we went with SpaceClaim is that it is much easier to use, you can work entirely in 3D if you want, you don't have to go back and forth between 2D and 3D. It is not history-based, meaning it &quot;understands&quot; most geometry better. Most other modellers rely on history and without the history you often have to recreate a model from scratch if you need to edit it.&#xA;SpaceClaim also includes IDF support so you may be able to import your PCB and design around it. SpaceClaim is less expensive that SolidWorks or Inventor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Before SpaceClaim we used SketchUp, which is similar in terms of ease of use. I like SketchUp a lot, but it is not a solid modeller and is lacking in precision and features. But it's great for its price if you are ok with a surface modeller.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastActivityDate="2011-05-02T21:48:14.680" CommentCount="1" />
  <row Id="13799" PostTypeId="2" ParentId="12215" CreationDate="2011-05-02T22:13:56.340" Score="2" ViewCount="" Body="&lt;p&gt;You could do it, for just a few milliamps, with two zeners and a resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you did it this way you could probably get away with a 1206 SMD resistor (0.5W) and a dual series SOT23 zener, in total smaller than most linear regulator packages. Here is a possible circuit (output is 9.1V per rail):&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;      ____&#xA;48V -|10k_|-+-- 9V&#xA;            |&#xA;         |__|__&#xA;           / \ |  9.1V&#xA;          /___\&#xA;            |&#xA;            |&#xA;            +-- GND&#xA;            |&#xA;         |__|__&#xA;           / \ |  9.1V&#xA;          /___\&#xA;            |&#xA;Source COM -+-- -9V&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-02T22:13:56.340" CommentCount="0" />
  <row Id="13800" PostTypeId="1" AcceptedAnswerId="13801" CreationDate="2011-05-02T22:14:14.217" Score="3" ViewCount="83" Body="&lt;p&gt;I want to use this clock oscillator&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ecsxtal.com/store/pdf/ecs-2100x.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.ecsxtal.com/store/pdf/ecs-2100x.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It does not require loading capacitance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, it says &quot;3.3V operation (optional)&quot;, yet on the same page it says &quot;Supply Voltage: 5VDC +/- 0.25&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was considering just throwing it in a breadboard, giving it 3.3V, and scoping the output pin to see if it worked.  But I was wondering if I would have any problems since the output pin would be unloaded, except for the scope.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-05-02T22:31:38.133" Title="Does a clock oscillator require a load?" Tags="&lt;oscillator&gt;" AnswerCount="1" />
  <row Id="13801" PostTypeId="2" ParentId="13800" CreationDate="2011-05-02T22:26:35.893" Score="1" ViewCount="" Body="&lt;p&gt;I often check oscillators like that without a load. You might notice some ringing on the edges.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The optional 3.3V means that they can supply a low-voltage version.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've occasionally used a 5V CMOS oscillator at 3.3V in a prototype when I haven't had a suitable 3.3V device, they've always worked.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-02T22:31:38.133" LastActivityDate="2011-05-02T22:31:38.133" CommentCount="3" />
  <row Id="13802" PostTypeId="1" AcceptedAnswerId="13809" CreationDate="2011-05-02T22:39:07.573" Score="13" ViewCount="373" Body="&lt;p&gt;You get your PCB back from the manufacturer. It is a new design, you have of course bread-boarded all the major parts, but you know there are going to be problems. There are just too many things that can cause problems, e.g.:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Errors in the schematic&lt;/li&gt;&#xA;&lt;li&gt;Errors in the layout, not found by the ERC/DRC&lt;/li&gt;&#xA;&lt;li&gt;Misplaced parts during soldering&lt;/li&gt;&#xA;&lt;li&gt;Shorts and the like during soldering&lt;/li&gt;&#xA;&lt;li&gt;any combination of the above&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I've had two relatively complex boards lately where I've basically had to de-populate the entire boards after assembly in order to locate the error. I found the errors, but the boards were scrap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've tried to start with the bare minimum of parts and the parts that can't be hand-soldered (I'm using paste, stencil and toaster). Typically this would be the MCU, the JTAG connector and a few capacitors. Then I'm gradually populating other areas while checking them for problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This approach works, but is really slow. I also have to comment out/comment in any code that assumes the presence of some particular hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have tips/suggestions on how to approach newly designed PCBs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: I'm mainly thinking about the kind of problems that leaves your board dead, like hidden power rail shorts, or anything that bricks the MCU.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastEditorUserId="1407" LastEditorDisplayName="" LastEditDate="2011-05-04T02:49:42.500" LastActivityDate="2011-05-04T14:14:48.573" CommunityOwnedDate="2011-05-04T06:17:46.380" Title="How do you attack a new board?" Tags="&lt;pcb&gt;&lt;pcb-assembly&gt;&lt;debugging&gt;" AnswerCount="8" CommentCount="13" FavoriteCount="3" />
  <row Id="13803" PostTypeId="2" ParentId="13802" CreationDate="2011-05-02T22:46:45.107" Score="7" ViewCount="" Body="&lt;p&gt;With boards of any complexity, it's nearly as important to develop a test plan as it is to develop the board itself. Even at the outset of designing the board, it's a good idea to know what you will test, even though the implementation doesn't exist yet; &quot;design for test&quot; as they say. Be sure to bring key signals to test-point pads. Try to partition the design so that individual subsystems can be brought up independently, or as nearly as independently as possible.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-02T22:46:45.107" CommunityOwnedDate="2011-05-04T06:17:46.380" CommentCount="2" />
  <row Id="13804" PostTypeId="2" ParentId="13802" CreationDate="2011-05-02T22:56:41.233" Score="15" ViewCount="" Body="&lt;p&gt;I do it by populating the board with the bare minimum initially, getting the supply working first, then the MCU, then adding the various sub-systems one at a time, and testing them before continuing, writing test software as necessary. I don't find the process at all slow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have boards of any complexity bare-board tested. It costs extra but it's worth it.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-02T23:07:30.320" LastActivityDate="2011-05-02T23:07:30.320" CommunityOwnedDate="2011-05-04T06:17:46.380" CommentCount="1" />
  <row Id="13805" PostTypeId="2" ParentId="13802" CreationDate="2011-05-02T23:13:34.547" Score="7" ViewCount="" Body="&lt;p&gt;I only breadboard very small circuits.  Then I solder the small circuits onto proto-boards.  If working with SMD chips, it helps to get the SMD-&gt;Thru-hole adapters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This basically gives you &quot;building blocks&quot;.  I then solder these circuit blocks onto a dev kit, or an old PCB with the MCU that I'm trying to use.  It looks atrocious, with four or five different small PCBs hanging off of a larger one, but it works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once I have the building blocks working on a dev board, I move to a PCB.  If the schematic changes &lt;em&gt;at all&lt;/em&gt; while making the PCB, I go back and rework the building blocks and test them on the dev board again.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;On a side note, instead of commenting out code, you should look into using #define and #ifdef preprocessor directives.  It makes it significantly easier to add and remove functional blocks of code in an MCU.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-05-02T23:13:34.547" CommunityOwnedDate="2011-05-04T06:17:46.380" CommentCount="1" />
  <row Id="13806" PostTypeId="2" ParentId="13792" CreationDate="2011-05-03T00:09:15.490" Score="0" ViewCount="" Body="&lt;p&gt;Cheapest way? Ok:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Acquire/Pirate/Buy (easier if you have School/University connections, they often get licenses for dirt cheap that you can borrow) CAD software you are interested in.  &lt;/li&gt;&#xA;&lt;li&gt;Install&lt;/li&gt;&#xA;&lt;li&gt;Experiment with software until you understand how it works.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;It worked for me with solidworks, but you need to be very self-motivated. I went from not knowing anything to designing cases for injection molding in about 1.5 years.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-05-03T00:09:15.490" />
  <row Id="13807" PostTypeId="2" ParentId="13802" CreationDate="2011-05-03T00:56:44.107" Score="2" ViewCount="" Body="&lt;p&gt;Well, one of the first steps to prevent shorted nets from happening in the first place is to make good use of the design rule checks in your board software.  Both at the schematic level to make sure nets aren't inadvertently tied together when they shouldn't be; and at the PCB level to make sure sufficient clearances between nets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there are any design elements that are untested, rather than tackling a whole new design on one board, I try to build proof-of-concept and proof-of-performance test boards on cheap proto PCB's (like Advanced Circuit's BareBonesPCB service - two layers, no solder mask, about $80 for a 24 hour turn).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even when I do a complete board, on the first generation boards, I like putting in plenty of breakout headers.  In some cases, you can populate two identical PCB's, one with the &quot;stable&quot; portion, with header pins exiting to the top; and another with the &quot;testing&quot; portion, with bottom entry pin receptacles.  If everything tests ok, you can then finish populating both boards.  Or, you can spin new versions of the &quot;testing&quot; circuit that you can swap into place.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-03T00:56:44.107" CommunityOwnedDate="2011-05-04T06:17:46.380" CommentCount="1" />
  <row Id="13808" PostTypeId="1" CreationDate="2011-05-03T02:25:52.457" Score="-2" ViewCount="117" Body="&lt;p&gt;I am designing a cordless LED lamp to be recharged by USB cable from the pc. Though I dont have any idea where to start. Any leads?&lt;/p&gt;&#xA;" OwnerUserId="4088" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T13:17:20.387" LastActivityDate="2011-05-16T13:17:20.387" ClosedDate="2011-05-16T14:21:41.960" Title="Lamp design requiring assistance" Tags="&lt;led&gt;&lt;power&gt;&lt;usb&gt;&lt;supply&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="13809" PostTypeId="2" ParentId="13802" CreationDate="2011-05-03T03:54:45.993" Score="3" ViewCount="" Body="&lt;p&gt;I've decided that breadboarding ahead of time is a waste of time unless there are aspects of a part's performance that you need to measure yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I even think building the board in pieces is a waste of time.  The initial hardware debug just takes a day or two.  Any subtle issues won't show up until software integration anyway.  I'd rather debug one circuit (the complete one) than several ad-hoc reductions of the circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just build the thing!  Assemble the whole board and power it up.  Look at the supply voltage. How many mA does it draw?  Which part is burning hot?  Which part is warm?  Then try to burn firmware on to whatever microcontroller is on the board.  Then start writing firmware.  Get the clock going and toggle a pin.  Get serial (or whatever) communication up.  Now write test programs for each peripheral.  Then build the production test fixture and start writing the &quot;real&quot; firmware.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Edit:  &lt;/p&gt;&#xA;&#xA;&lt;h2&gt;On finding stuck rails&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;If a supply rail is stuck to ground, (measures 0 ohms with an ohmmeter), power it up on a bench supply.  Set the voltage normally and the current limit to a few hundred mA.  Print out the PCB design on paper, and find a DMM that measures microvolts.  Measure microvolts starting at the supply terminals, and write down the voltage drops on the PCB printout.  By looking at microvolt differences, you can trace exactly where the current is going without depopulating or chopping up the PCB.  This technique is a better than using an ohmmeter because you can pump a lot of current through the circuit, more than any normal ohmmeter will supply. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A similar technique works for finding shorted traces on an otherwise populated board.  Run the board a use a scope to find &quot;digital&quot; traces that are in an in-between voltage range.  &lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-05-04T14:14:48.573" LastActivityDate="2011-05-04T14:14:48.573" CommunityOwnedDate="2011-05-04T06:17:46.380" CommentCount="4" />
  <row Id="13810" PostTypeId="2" ParentId="13808" CreationDate="2011-05-03T06:38:26.400" Score="2" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Though i dont have any idea where to start. Any leads&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Divide and conquer is always the first step.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't understand the big picture, divide it into smaller building blocks.&#xA;If you don't understand those smaller building blocks, then divide those into even smaller blocks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you have a full set of small but understandable building blocks, then you put them together and you have your project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So the answer to your question is &quot;Divide and conquer&quot;, and then come back and ask questions about the small building blocks.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2011-05-03T06:38:26.400" CommentCount="1" />
  <row Id="13811" PostTypeId="2" ParentId="13808" CreationDate="2011-05-03T06:50:01.907" Score="2" ViewCount="" Body="&lt;p&gt;As Johan has said divide the project into smaller projects. So for your project:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Output - How many LEDs, what luminosity, what colour?&lt;/li&gt;&#xA;&lt;li&gt;Turning on and off - Is there a need for a microcontroller or can it just be done with a switch?&lt;/li&gt;&#xA;&lt;li&gt;Charging mechanism - What batteries are you going to use? Ni-Cad NiMH constant current(can be done with an LM317), LIPO need a proper charger.&lt;/li&gt;&#xA;&lt;li&gt;Casing does it matter? &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Also here are some great videos on Product Design from the EEVBlog. &lt;a href=&quot;http://www.eevblog.com/2009/05/27/eevblog-11-part-1-of-2-diy-product-design/&quot; rel=&quot;nofollow&quot;&gt;Part 1&lt;/a&gt;, &lt;a href=&quot;http://www.eevblog.com/2009/05/27/eevblog-11-part-2-of-2-diy-product-design/&quot; rel=&quot;nofollow&quot;&gt;Part 2&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-05-03T06:50:01.907" />
  <row Id="13812" PostTypeId="2" ParentId="13788" CreationDate="2011-05-03T10:19:56.460" Score="0" ViewCount="" Body="&lt;p&gt;I'm not sure if you're asking for an analogue switch that can handle signals in the range -5V to +10V or a digital interface to convert a 0 to 5V level into a -5v to +10V level. If it is the latter, my answer to &lt;a href=&quot;http://electronics.stackexchange.com/questions/12972/level-shift-amplify/12998#12998&quot; title=&quot;level shift &amp;amp; amplify&quot;&gt;this question&lt;/a&gt; might help. This arrangement would work with N &amp;amp; P channel FETs with little modification.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-05-03T10:19:56.460" CommentCount="1" />
  <row Id="13813" PostTypeId="1" AcceptedAnswerId="13815" CreationDate="2011-05-03T10:37:48.320" Score="2" ViewCount="52" Body="&lt;p&gt;One of the answers to &lt;a href=&quot;http://electronics.stackexchange.com/questions/13718/implement-serial-port-on-fpga-verilog&quot;&gt;this&lt;/a&gt; question advised I used a reset signal for my fpga design. I agree, it's good advice and I'm adding it. Is there any way for me to ensure that this signal gets asserted on startup though withoug adding additional hardware? This is on a spartan-3an evaluation board.... I can't find anything in the documentation anywhere&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2011-05-03T12:06:28.260" Title="Reset signal for fpga evaluation board" Tags="&lt;fpga&gt;&lt;verilog&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13814" PostTypeId="2" ParentId="13760" CreationDate="2011-05-03T12:02:29.743" Score="1" ViewCount="" Body="&lt;p&gt;I do Arduino development on my Mac.  I started in the Arduino IDE, but felt it was too restrictive, so did a bit of googling and discovered how to do it in Eclipse, which is a much better IDE and should be suitable for your needs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Check out this article on setting up Eclipse to work with Arduino, you should be able to ignore the Arduino specific stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.arduino.cc/playground/Code/Eclipse&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/Code/Eclipse&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2573" LastActivityDate="2011-05-03T12:02:29.743" />
  <row Id="13815" PostTypeId="2" ParentId="13813" CreationDate="2011-05-03T12:06:28.260" Score="3" ViewCount="" Body="&lt;p&gt;With an FPGA you can make use of the fact that your flipflops &lt;em&gt;will&lt;/em&gt; initialise to a known state and create an internal synchronous reset signal which you can &quot;and&quot; with the external one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When using an external reset, make sure that you synchronise it to the internal clock (with a different synchroniser for each clock if you have more than one) otherwise you may find that your logic comes out of reset in weird ways.  This is because the signal will have different delays to different parts of your circuit and if the reset button is released just before a clock edge, some parts of the FPGA will see it (as the reset signal made it to them before the clock signal) and other parts will see it one clock cycle later (as the reset was slightly delayed and therefore missed the clock edge).&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-05-03T12:06:28.260" CommentCount="1" />
  <row Id="13816" PostTypeId="1" AcceptedAnswerId="14872" CreationDate="2011-05-03T12:50:33.373" Score="2" ViewCount="180" Body="&lt;p&gt;I've designed the following circuit for a battery charger. With the PIC just turning the output on and off when it is charged. For the program design what would be better, to have the analogue input constantly checked? Or to have the output on for the charge time then to move to the second?&#xA;&lt;img src=&quot;http://i.imgur.com/upMn6.jpg&quot; alt=&quot;Battery Charger&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-06-02T12:02:49.357" Title="Designing a Battery Charger With a PIC" Tags="&lt;battery-charging&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="13817" PostTypeId="2" ParentId="13816" CreationDate="2011-05-03T13:19:20.993" Score="6" ViewCount="" Body="&lt;p&gt;Depending on the chemistry of the battery you'll want to be very careful about overcharging.  Here is a page describing attributes of various batteries: &lt;a href=&quot;http://www.batteryspace.com/batteryknowledge.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.batteryspace.com/batteryknowledge.aspx&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Down near the bottom is the overcharging tolerance information.  You have to be very careful with... well, everything except lead-acid batteries.  Deciding when to stop charging or how to moderate the charging rate is very important in battery chargers.  &lt;a href=&quot;http://www.angelfire.com/electronic/hayles/charge1.html&quot; rel=&quot;nofollow&quot;&gt;This page&lt;/a&gt; describes designing a PIC-based a NiCd/NiMH charger and discusses the important aspects of the charging method.  Quickly though:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;There are a variety of methods to charge: quick, slow, trickle, etc.  Different strategies are required for each. Obviously faster charging methods get it charged faster but might cause excess heat, your battery to explode, etc.&lt;/li&gt;&#xA;&lt;li&gt;Overheating is bad - you ideally would monitor it if you were attempting to do a very quick charge.&lt;/li&gt;&#xA;&lt;li&gt;Overcharging is bad - you have to monitor the NiCd/NiMH voltage and watch for a slight (very slight) drop in voltage that tells you when it's done, or monitor change in temperature over change in voltage and cut off charging when it reaches a specific value.&lt;/li&gt;&#xA;&lt;li&gt;Desired charged voltage varies depending on the number of cells in the battery, the chemistry, etc.  &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;There's a lot to keep track of and bad things can happen if you try to charge the battery the wrong way.  In general your schematic is good but it's the internals of the PIC that are going to be the important part here. Good luck.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Followup question: is that really a 5V NiMH battery?  If so, that's nominally 1.25V/cell and four cells = 5V.  Okay, good deal, but you'll want to charge the cells up to about 1.4-1.6V.  With four cells, that turns out to roughly 6V.  You can't measure 6V with the A/D of the PIC and it may be dangerous for the PIC to have those voltages on its pins- check the absolute maximum voltage rating of that pin.  It's usually VCC + something.  In any case, you'll need a voltage divider to read the full range of the battery so you know when it's done charging.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bottom line: that circuit won't work unless I'm mistaken.  And I have been known to be.  Anyone confirm?&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="249" LastEditorDisplayName="" LastEditDate="2011-05-03T20:41:21.547" LastActivityDate="2011-05-03T20:41:21.547" CommentCount="3" />
  <row Id="13818" PostTypeId="1" AcceptedAnswerId="13819" CreationDate="2011-05-03T13:48:29.307" Score="3" ViewCount="135" Body="&lt;p&gt;So, I have these garden lights powered by solar cells. I also happen to have a power-LED over from a broken flashlight, I think its a Cree R2 or Q5 or similar. These lights charge a 1.5V 600mah Nimh battery during the day, and then light up these rectangular low-power leds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I would want to experiment with simply driving a high-power LED at similar, or slightly lower power levels, meaning a very very low current. I have not measured the drive current for these, but I imagine its well below 50ma. The theory being that it will be brighter still because of the excellent efficiency of power LEDs in this power band.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know power leds generally require current limiting or control, and that the battery voltage is not enough so I will need some sort of boost circuit if not already present. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I am wondering is what is the most efficient way of doing this, without being overly complicated? Is it possible to do this with just a resistor, or am I still prone to current run-away at these low levels?&lt;/p&gt;&#xA;" OwnerUserId="4094" LastEditorUserId="4094" LastEditorDisplayName="" LastEditDate="2011-05-03T18:41:30.937" LastActivityDate="2011-05-03T18:41:30.937" Title="Driving a high-power LED at very low levels *efficiently*" Tags="&lt;led&gt;&lt;efficiency&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="13819" PostTypeId="2" ParentId="13818" CreationDate="2011-05-03T14:14:29.430" Score="7" ViewCount="" Body="&lt;p&gt;The amount of light LEDs put out has a very linear relationship with the current they are driven with, and the voltage to current graph is &lt;em&gt;relatively&lt;/em&gt; constant as they are diodes with a characteristic junction voltage.  Taken together, this means that the efficiency can rise about 25% if an LED is driven at 10% of rated brightness (in &lt;a href=&quot;http://www.kingbrightusa.com/images/catalog/SPEC/WP1503EC.pdf&quot; rel=&quot;nofollow&quot;&gt;this LED&lt;/a&gt;, but others should be fairly similar).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In any case, regardless of the level you choose to drive the LED at, what you want is a &quot;single cell LED driver&quot;.  These are usually current-regulated, eliminating the need for any resistors which do nothing for your efficiency, and also have the ability to step-up the voltage, so you can drive a 3 V nominal LED with one or two 1.2 V NiMH cells.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.linear.com/product/LTC3490&quot; rel=&quot;nofollow&quot;&gt;Linear&lt;/a&gt;, &lt;a href=&quot;http://www.micrel.com/page.do?page=/product-info/products/mic2282.jsp&quot; rel=&quot;nofollow&quot;&gt;Micrel&lt;/a&gt;, and &lt;a href=&quot;http://www.diodes.com/zetex/?ztx=3.0/product_portfolio@pno~ZXSC380&quot; rel=&quot;nofollow&quot;&gt;Diodes Inc&lt;/a&gt; all make drivers for this purpose, and you can find many more in a search for &quot;&lt;a href=&quot;http://www.google.com/search?rlz=1C1CHMU_enUS354US377&amp;amp;sourceid=chrome&amp;amp;ie=UTF-8&amp;amp;q=single%20cell%20led%20driver&quot; rel=&quot;nofollow&quot;&gt;single cell LED driver&lt;/a&gt;&quot;.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-05-03T14:14:29.430" CommentCount="1" />
  <row Id="13820" PostTypeId="1" CreationDate="2011-05-03T14:39:31.537" Score="10" ViewCount="188" Body="&lt;p&gt;I have made many designs that I would consider &quot;professional grade&quot;, but in reality they are still just prototypes. I have used professional board fabs and professional population, but what I haven't had the ability to go through is actually turning that product into a commercial product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is needed in order to take the product across this large last step? I can think of obvious things like FCC/CE testing, case design, marketing, distributors, etc. but I am sure there are other things that aren't thought of until going through the process a time or two, as an engineer, what are these things that would come up?&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-05-03T15:30:49.807" LastActivityDate="2011-05-05T07:46:59.093" Title="How can I go from prototype to commercial product?" Tags="&lt;design&gt;&lt;manufacturing&gt;" AnswerCount="4" FavoriteCount="4" />
  <row Id="13822" PostTypeId="2" ParentId="13820" CreationDate="2011-05-03T15:32:09.463" Score="4" ViewCount="" Body="&lt;p&gt;In my industrial experience, the way things generally go in terms of a design cycle follow this sort of flow (condensed version):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Market research/contact with a customer (identification of the what the basics of the product should be)&lt;/li&gt;&#xA;&lt;li&gt;Establishment of a specification (or &quot;spec&quot; as it's often abbreviated)&lt;/li&gt;&#xA;&lt;li&gt;A formal quotation and business agreement between the parties (or between engineering and marketing for a 'standard' product)&lt;/li&gt;&#xA;&lt;li&gt;Initial design / calculation / simulation / debugging&lt;/li&gt;&#xA;&lt;li&gt;Design validation testing, or DVT (you making sure the product meets the spec)&lt;/li&gt;&#xA;&lt;li&gt;Bugfix implementation / regression test&lt;/li&gt;&#xA;&lt;li&gt;Independent DVT (&lt;em&gt;someone else&lt;/em&gt; making sure the product meets the spec)&lt;/li&gt;&#xA;&lt;li&gt;Safety and regulatory approvals&lt;/li&gt;&#xA;&lt;li&gt;Design for manufacturability review (DFM)&lt;/li&gt;&#xA;&lt;li&gt;Production release / marketing release&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If you have a project that you've developed, and you feel you're ready to market it, you may want to consider some or all of the following points:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Write a spec if one doesn't exist. Characterize the typical performance of the product and put this in the spec, as well as any absolute maximums or minimums in terms of 'externals' (volts / amps / degrees) that should be avoided.&lt;/li&gt;&#xA;&lt;li&gt;Make sure that your product meets your spec. Do a formal DVT and make a report of the results. Also, test a quantity of boards against the spec and use statistical analysis (Cp/Cpk) to prove that over tolerances and normal variation, you product can do what you say it can do.&lt;/li&gt;&#xA;&lt;li&gt;Come up with a reduced number of tests to perform per-unit as a manufacturing reliability test. Bad builds, bad parts, new operators, bad equipment can all lead to problems.&lt;/li&gt;&#xA;&lt;li&gt;Make sure that your PCB has in-circuit test pads on as many nets as possible to facilitate in-circuit test (ICT) or manufacturing defect analysis (MDA) - finding problems earlier rather than later is always beneficial.&lt;/li&gt;&#xA;&lt;li&gt;If this product is intended to be high reliability, you may want to perform a life test. Run a quantity of units perpetually until something fails. There are industry standards on life testing (acceleration factors, lot size, etc.) which fall beyond the scope of casual advice.&lt;/li&gt;&#xA;&lt;li&gt;Consider HALT (highly-accelerated reliability testing) as well - testing the product under thermal and mechanical vibration stress can show weaknesses in the design as well as its construction.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Many of these sorts of tests are big bucks. (Tens of thousands of dollars per test). The cheapest things you can do are those that you can do yourself - the spec, the DVT test and statistical analysis, test pads on the PCB, for instance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may wish to consult with an experienced manufacturing engineer to figure out what you really need to do, given your budget and the expected revenue of the product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-03T15:32:09.463" />
  <row Id="13823" PostTypeId="2" ParentId="13820" CreationDate="2011-05-03T15:38:40.723" Score="1" ViewCount="" Body="&lt;p&gt;In addition to FCC interference testing there's also potentially Underwriters Labs (UL) testing to consider if you think it appropriate.  Unfortunately I can't parse the mess of marketing on their website to figure out what a manufacturer is supposed to do.  If anyone can parse it maybe we should write a guide.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-03T15:38:40.723" />
  <row Id="13824" PostTypeId="2" ParentId="13820" CreationDate="2011-05-03T15:55:12.187" Score="3" ViewCount="" Body="&lt;p&gt;You already covered some of the things needed, but here's my list:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Great Product Design (on the inside). &lt;/li&gt;&#xA;&lt;li&gt;Great Product Design (on the outside).  I'm talking about the parts that the user would care about.  The &quot;Look and Feel&quot;.&lt;/li&gt;&#xA;&lt;li&gt;Proper legal and governmental approvals:  FCC, CE, RoHS, UL, TUV, ETC.&lt;/li&gt;&#xA;&lt;li&gt;Proper &quot;environmental&quot; design:  ESD, EMI, shock &amp;amp; vibration, temperature, &lt;/li&gt;&#xA;&lt;li&gt;Great support.  This includes the manual, web site resources, and phone/email support.&lt;/li&gt;&#xA;&lt;li&gt;Reliable manufacturing.  Not just electrical here, but chassis, packaging, etc.&lt;/li&gt;&#xA;&lt;li&gt;Good sales department.  Responsive.  Much of this can be done online, so a good web site design is an alternative to having a large staff.&lt;/li&gt;&#xA;&lt;li&gt;International stuff:  this includes regulatory, monetary, shipping, etc.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;There are thousands or millions of designs that were great products, but failed because of one or more of the other items above.  I've also seen companies skimp too much on these things, thinking that they are &quot;just starting&quot; and will &quot;correct it once a revenue stream starts coming in&quot;-- only to find that the revenue never comes in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It just goes to show you that you need much more than a good product design to be successful.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-03T15:55:12.187" CommentCount="0" />
  <row Id="13825" PostTypeId="1" AcceptedAnswerId="13917" CreationDate="2011-05-03T16:30:09.367" Score="6" ViewCount="146" Body="&lt;p&gt;I am prototyping a potential future product and I am struggling to get my head around the complexities of using wifi components in it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand that wifi (or 802.11x) is primarily just a 2.4GHz signal modulated in a specific way, as is bluetooth and zigbee. Is it possible therefor to just use a basic 2.4GHz transceiver in my project and configure it for the 802.11 protocol rather than having to use some expensive branded one that comes pre determined? Or is it not as simple as that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I presume in industry when doing design for large production runs something similar takes place? Or do they indeed have to use a transceiver that is preconfigured to be wifi? All the pre configured components I have found so far seem quite expensive (even when purchased in volume) to make a commercial design viable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have looked at devices such as the Lantronix WiPort and the Roving Network WiFly GSX and comparing them to devices such as the Microchip MRF24J40 - is it possible to use a Microchip MRF24J40 and then configure the rest of the hardware and software to enable the device to work on a WiFi network?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For further detail here is what I want to do at the most basic level:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Part 1: I want to make a patch that contains a small buzzer, an accelerometer, a pic and a wifi transceiver that can be stuck to an object. This patch would be able to communicate with &quot;The Cloud&quot; though the users home WiFi network. When the accelerometer detects movement the pic will send a message, via the wifi link, to a server in the cloud to register that movement along with a time stamp. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Part 2: Through a web interface I want to be able to send a message to the patch setting the buzzer to make a sound next time the accelerometer detects a movement.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have already made a rudimentary version of the system which works over a 433MHz RF link and a laptop serial port with a local piece of software running on my laptop. I know how to do the web coding (PHP &amp;amp; MYSQL) but it's the replacing the RF link with the internet that is causing the issue.&lt;/p&gt;&#xA;" OwnerUserId="4096" LastEditorUserId="4096" LastEditorDisplayName="" LastEditDate="2011-05-05T15:25:43.070" LastActivityDate="2011-06-02T04:31:32.040" Title="Can a generic 2.4GHz transceiver be used on an 802.11x network?" Tags="&lt;components&gt;&lt;design&gt;&lt;wifi&gt;&lt;production&gt;" AnswerCount="3" CommentCount="9" FavoriteCount="1" />
  <row Id="13826" PostTypeId="2" ParentId="13802" CreationDate="2011-05-03T16:50:12.217" Score="1" ViewCount="" Body="&lt;p&gt;On a totally fresh design, I generally go with a divide-and-conquer approach.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I try and isolate major architectural blocks and power up each section independently using switches / DC supplies / potentiometers etc. to simulate the dependencies needed to get the circuit to run.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This approach generally isn't hard when you're dealing with power supplies - most converters need only input and perhaps a few logic signals to start switching away (and hopefully &lt;em&gt;not&lt;/em&gt; releasing the magic smoke of failure). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Boards that are second/third spins (clean-ups) don't usually need such diligence. I may only isolate parts of the circuit that were changed, test them independently and save testing the rest of the circuitry for the all-in power up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget your personal protective equipment. I'm very uncomfortable powering anything with exposed components up without my safety goggles (and sometimes earplugs...)&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-03T16:50:12.217" CommunityOwnedDate="2011-05-04T06:17:46.380" CommentCount="1" />
  <row Id="13827" PostTypeId="2" ParentId="13802" CreationDate="2011-05-03T17:36:21.383" Score="3" ViewCount="" Body="&lt;p&gt;What the other guys said is all valid, but I'd like to add my 2 cents worth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The absolute best thing to do is not make the mistakes in the first place.  It seems silly to mention this, but all too often this is overlooked.  Do a schematic and PCB design review.  Have several people look at your design-- even beginner engineers.  Use the design rule checks in your software.  Use any resource available to make sure your design is good.  Have good engineering practices to improve your odds of catching a bug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the past 20 years, and having designed dozens and dozens of PCB's (some with 14 layers and 2,000 components) I have only had TWO pcb's that were unusable on the first round of prototypes.  Of course I've had bugs, but only two boards were &quot;bricked&quot;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In every case, the prototypes were fully populated before I ever started debugging them.  I'd ohm out the power rails to make sure there were no shorts.  Then do a visual inspection using a microscope.  Then power it up.  After that I'd start on a methodical test and debug session-- working on small sections of the circuit at a time until everything is tested and working.  In most cases, I'd make a couple of changes and go into volume production with the next revision of the PCB.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;None of this would have been possible without major efforts to reduce the bugs up front.  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-03T17:36:21.383" CommunityOwnedDate="2011-05-04T06:17:46.380" CommentCount="1" />
  <row Id="13828" PostTypeId="6" CreationDate="2011-05-03T18:31:20.047" Score="0" ViewCount="" Body="&lt;p&gt;First and foremost, and I hope you forgive me for using this space, I would like to congratulate everybody on our graduation. I'd like to thanks also @RobertCartaino for the opportunity of being a pro term moderator. It was really fun and rewarding. I've learned a lot during these months.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And my special thanks is to @Kortuk for being a fellow patient and generous. There could be no better moderator.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;I was a poor user here and didn't know right the philosophy of the Stack Exchange.&#xA;Since I became a moderator, I have studied a lot the guidelines and whenever there is any doubt, I look for help from other moderators trying to avoid my decision being wrong.&#xA;At the beggining I've committed some mistakes, but nowadays I like to think that I'm doing a good job.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My philosophy is that the moderator has to do the minimum possible, and whenever possible leave the community to be self-moderated. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We have to treat everyone with respect and patience.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And we have to keep in mind that this should be the best resource available for professionals in electronics in the world.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would be honored to serve again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please, consider use &lt;a href=&quot;http://se.awio.com/election.html&quot; rel=&quot;nofollow&quot;&gt;Stack Exchange Elections Statistics Page&lt;/a&gt; to help you choose the best three.&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-03T19:02:02.317" LastActivityDate="2011-05-03T19:02:02.317" CommunityOwnedDate="2011-05-03T18:31:20.047" CommentCount="1" />
  <row Id="13829" PostTypeId="2" ParentId="4962" CreationDate="2011-05-03T18:56:56.837" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://knjn.com&quot; rel=&quot;nofollow&quot;&gt;knjn.com&lt;/a&gt; has some boards, Altera and Xilinx, starting with the &lt;a href=&quot;http://www.knjn.com/FPGA-RS232.html&quot; rel=&quot;nofollow&quot;&gt;Pluto RS232&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="985" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T13:23:24.110" LastActivityDate="2011-05-16T13:23:24.110" CommentCount="2" />
  <row Id="13830" PostTypeId="6" CreationDate="2011-05-03T19:02:39.990" Score="0" ViewCount="" Body="&lt;p&gt;Hi.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm markrages -- Change you can believe in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vote for me to change the direction of the stack exchange site.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I believe:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Questions about selecting and sourcing electronic components should be considered on-topic and encouraged.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Questions about non-design but related items (how to solder, etc.) should be allowed.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Lazy, &quot;send me the codez&quot; questions should be closed quickly.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Respect the Electropus&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Only vote for me if you agree with the above ideas.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;About me:  I have an engineering degree and have been doing electronics design professionally for fifteen years.  I still type &quot;chiphacker.com&quot; to visit this site.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-05-03T19:02:39.990" LastActivityDate="2011-05-03T19:02:39.990" CommunityOwnedDate="2011-05-03T19:02:39.990" CommentCount="1" />
  <row Id="13831" PostTypeId="2" ParentId="12865" CreationDate="2011-05-03T19:45:04.817" Score="0" ViewCount="" Body="&lt;p&gt;If the power source was exactly 3.3V and the voltage drop across the LED was 3.3V then you would not need a current limiting resistor. However, the world is not perfect and there are imperfections in everything!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You only can calculate an appropriate safety resistor value after accounting for the power supply configuration and variation in the LED forward voltage.  If you think $V_{SOURCE}-V_{LED}$ may have an error/variation up to $0.5 \mbox{ }V$, then you would calculate the resistor value for that. As an example the case of $ \pm 0.5\mbox{ }V$, which isn't unreasonable for a 10% 5V source:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$\frac{V}{I} = \frac{0.5\mbox{ }V}{20 \mbox{ mA}} = 25\mbox{ }\Omega $$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just note that this is probably not a good idea in practice, but it is possible.&lt;/p&gt;&#xA;" OwnerUserId="4034" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-03T20:15:58.687" LastActivityDate="2011-05-03T20:15:58.687" />
  <row Id="13832" PostTypeId="1" AcceptedAnswerId="13833" CreationDate="2011-05-03T20:33:16.947" Score="1" ViewCount="87" Body="&lt;p&gt;Tradition says that electricity and water do not mix well, but sooner or later some electronic components are going to come into contact with water. I noticed that datasheets don't mention anything about that for regular components so I'm looking for a source of information on that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example I noticed that some resistors with copper tin plated leads will release tin and copper when submerged in water and powered on (looks like electrolysis is taking place). I also noticed that some electric motors work just fine when submerged in water and that for example AA alkaline batteries don't seem to have any problems working under water. I also heard that some types of mineral oils can remove insulation from cables and that some people who used mineral oils to cool computers had problems with that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Books are acceptable, but bonus points if the source if freely available on the Internet. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-05-03T22:18:41.523" LastActivityDate="2011-05-04T00:56:14.957" Title="Looking for information about how well standard electronic components function when submerged in liquids, especially water." Tags="&lt;components&gt;&lt;underwater&gt;" AnswerCount="3" CommentCount="6" FavoriteCount="0" />
  <row Id="13833" PostTypeId="2" ParentId="13832" CreationDate="2011-05-03T20:55:22.523" Score="6" ViewCount="" Body="&lt;p&gt;The easy answer is, things don't work underwater.  Although technically water is not conductive (a circuit will run fine when submerged in &lt;em&gt;pure&lt;/em&gt; water), it's all the impurities in the water that make bad things happen.  And water will pick up lots of impurities.  Take a container of pure water and just let it sit there, uncovered.  Over time it will begin to absorb stuff from the air and its electrical conductivity will go up.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To make matters worse, water is a mild solvent so things tend to dissolve in it.  And there's your real problem.  You cannot predict what will be dissolved in the water.  Is the pH acidic, or alkaline?  What else is on your PCB that could get dissolved in the water that then effects other things?  Maybe the ink on the labels of those caps could turn the pH slightly acidic, causing more corrosion on something else.  Since you don't know what's in the water, you can't predict what will happen-- but only bad things can happen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's unlikely that you'll ever see an electrical component that is spec'd for operation underwater.  The only spec that I've ever seen is in the temperature spec of some chips, that's listed as &quot;+120 to -40 deg C, non-condensing&quot;.  Underwater is considered &quot;condensing&quot;, by the way.  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The normal way of protecting electronics from water or high humidity is to use a conformal coating on them.  That's basically a way to cover the PCB with a protective coating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are people who cool PCB's by submerging them in some sort of liquid.  Normally mineral oil or some sort of inert chemical (the name escapes me right now).  I have only seen anecdotal evidence for this, although maybe the supercomputer guys from 10-20 years ago would have done a study.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And somewhat off topic, but...  While a standard motor might work underwater, it wouldn't work for long.  The water, and motion of the motor, would tend to remove the lubrication.  Followed by corrosion.  Then the thing would seize up.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="3624" LastEditorDisplayName="" LastEditDate="2011-05-03T21:50:47.113" LastActivityDate="2011-05-03T21:50:47.113" CommentCount="6" />
  <row Id="13834" PostTypeId="1" CreationDate="2011-05-03T21:57:02.253" Score="0" ViewCount="53" Body="&lt;p&gt;Anyone familiar with connectors that have large enough spacing to support the creepage/clearance requirements for 400-600V, but that don't need to carry much current (only a few milliamps at most)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We're presently using Molex Sabre connectors which are rated at 600V 18A but it's silly to need such a large contact. The spacing is what I need, not the contact size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit:&lt;/strong&gt; I am looking for multipin systems with between 4 and 8 contacts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any suggestions? (besides buying smaller connectors and leaving out every other pin -- that's not very manufacturable unless the manufacturer offers this as a standard option)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am offering an &quot;honor system bounty&quot; of 100 points: if I get an answer that is an improvement over the Sabre connector, I'll accept the best one and add an after-the-fact 100 point bounty.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-06-02T23:17:37.560" Title="signal/sense connectors rated for 400-600V, a few milliamps" Tags="&lt;connector&gt;&lt;high-voltage&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="13835" PostTypeId="2" ParentId="13834" CreationDate="2011-05-03T22:21:22.943" Score="0" ViewCount="" Body="&lt;p&gt;I know that Samtec can readily modify their connectors to omit pins (they do that to make differential pair variants of their QST/QSH line, for example) - that might be enough to give you the necessary creepage distance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bigger worry, though, is the flashing of the connector surface if the connector make/break under voltage.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-03T22:21:22.943" />
  <row Id="13836" PostTypeId="2" ParentId="13832" CreationDate="2011-05-03T22:26:54.637" Score="3" ViewCount="" Body="&lt;p&gt;Unless a part is &lt;em&gt;explicitly&lt;/em&gt; designed to work underwater, a manufacturer would just laugh in your face if you asked them about it.  Sure, they may work for a time, but you would need to test and certify them yourself.  The manufacturer's specifications and guarantees will not apply if you use them outside of their normal conditions, plus the water would give you all sorts of problems with high-speed and/or high-impedance circuits before it's done eating through traces.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only environmental conditions electronic components are expected to survive are temperature swings (and occasionally, &lt;a href=&quot;http://www.atmel.com/products/radhard/default.asp&quot; rel=&quot;nofollow&quot;&gt;radiation&lt;/a&gt;).  Water, given enough time, is extremely corrosive and will destroy unprotected, exposed circuitry.  It is the job of enclosures and coatings to protect parts and PCBs from moisture and other potentially corrosive chemicals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An enclosure would be best if you want to survive underwater for mechanical reasons, but if you're trying to cut down on space/weight, you may be able to get away with just a conformal coating&amp;mdash;essentially a thin layer of potting. A company I used to work for would get warranty returns for vehicle data computers that were half filled with water but still fine electrically as the board was conformal coated with a silicone resin.&lt;/p&gt;&#xA;" OwnerUserId="1407" LastActivityDate="2011-05-03T22:26:54.637" />
  <row Id="13837" PostTypeId="1" AcceptedAnswerId="13842" CreationDate="2011-05-03T23:26:23.377" Score="4" ViewCount="175" Body="&lt;p&gt;I've always was wondering why they chose 9v, well really 9-12v.. Why not 5v or 3.3v or 12v? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Surely there was some good thought put into this. Does anyone know or have sources? &lt;/p&gt;&#xA;" OwnerUserId="3926" LastActivityDate="2011-05-04T00:29:05.917" Title="What is the reasoning behind Arduino choosing 9v?" Tags="&lt;arduino&gt;" AnswerCount="3" />
  <row Id="13838" PostTypeId="1" CreationDate="2011-05-03T23:30:13.173" Score="3" ViewCount="117" Body="&lt;p&gt;I'm working on a device with a 4-digit 7-segment counter and wondering what is the best way to drive all the LEDs. Right now I have a custom PCB that's driving them all from an Atmega168, using most of the I/O pins. The problem is that some of the numbers appear brighter than others. For example, a &quot;1&quot; is brighter than an &quot;8888&quot;.&lt;br&gt;&#xA;Someone suggested that should be using an LED driver such as the TLC5940. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this necessary? Since it's for a wearable device, I'm trying to keep the size and power to a minimum. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current prototype works well, but I want to make sure the digits are equally bright and as bright as they can safely be, to increase it's visibility.&lt;/p&gt;&#xA;" OwnerUserId="4101" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-04T13:08:34.660" LastActivityDate="2011-05-06T16:35:53.930" Title="What's the best way to connect a 4-digit 7-Segment LED to Atmega168" Tags="&lt;arduino&gt;&lt;7segmentdisplay&gt;&lt;atmega168&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="13839" PostTypeId="2" ParentId="13838" CreationDate="2011-05-03T23:44:48.843" Score="1" ViewCount="" Body="&lt;p&gt;You can reduce the number of pins you are using on the AVR by multiplexing the displays. Connect all the segments together and connect them to seven output pins via resistors, and connect the four common cathodes to another four output pins. This should give you consistent brightness. The software will be more complex, but it's a much better solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Because the human eye responds to peak brightness, multiplexing can provide more brightness than is possible with non-multiplexed displays, and uses less power, especially if the duty cycle is reduced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need to ensure that the current limits of the AVR pins aren't exceeded, of course. Driver devices will be needed if greater currents than the 25 mA limit for the AVR pins are required. I use them on a PCB I designed for a similar application.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-04T08:29:26.213" LastActivityDate="2011-05-04T08:29:26.213" CommentCount="11" />
  <row Id="13841" PostTypeId="2" ParentId="13837" CreationDate="2011-05-03T23:57:29.783" Score="2" ViewCount="" Body="&lt;p&gt;A common supply voltage for the AVR chips used in the Arduino boards is 5v. The supply needs to be regulated, and regulator chips generally need to be supplied from at least 2V  more than the output voltage. A 9V supply ensures that the regulator will always function properly, and is a very common value for the mains supplies that are available.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-03T23:57:29.783" />
  <row Id="13842" PostTypeId="2" ParentId="13837" CreationDate="2011-05-03T23:58:36.030" Score="12" ViewCount="" Body="&lt;p&gt;You can actually supply 6-20 min-max (they don't recommend it though) and Arduino's recommendation is 7-12v.  One reason for this is because with the linear voltage regulator the arduino uses will have a voltage drop of around 2V and since the avr micro controllers the arduino uses need 5V there is a ~7V minimum. The reason the max recommended voltage is 12v is probably because any excess voltage will be let off as heat and the voltage regulator can only dissipate so much heat! You can operate the arduino from 5v, but you need to go around the voltage regulator.  That's how the arduino is powered from USB, which has a 5v line.&lt;/p&gt;&#xA;" OwnerUserId="4034" LastActivityDate="2011-05-03T23:58:36.030" CommentCount="2" />
  <row Id="13843" PostTypeId="2" ParentId="13837" CreationDate="2011-05-04T00:29:05.917" Score="1" ViewCount="" Body="&lt;p&gt;As the others have said the input voltage to the Arduino needs to be greater than the 5V it runs off of to allow for the regulator to work, so why not 9V to allow it to run off of a 9V battery?  And you can still run it off of a 12V battery as well as the others also pointed out.  It's kind of a win-win.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-04T00:29:05.917" />
  <row Id="13845" PostTypeId="2" ParentId="13832" CreationDate="2011-05-04T00:56:14.957" Score="3" ViewCount="" Body="&lt;p&gt;The prudent answer to insuring that your project will survive in a harsh environment (rain, underwater, whatever) is to properly protect it. You can put it in a waterproof box or potting it in epoxy will do an excellent job of protecting it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of greater concern perhaps is safety, operating any sort of energized electrical/electronic device in the open (rain or not) where someone could accidentally touch it is not a good idea. Would you want to step into a bathtub that had a live electrical wire in it?&lt;/p&gt;&#xA;" OwnerUserId="3869" LastActivityDate="2011-05-04T00:56:14.957" />
  <row Id="13846" PostTypeId="1" CreationDate="2011-05-04T01:46:17.400" Score="6" ViewCount="289" Body="&lt;p&gt;I have two leftover 2GB RAM modules that I removed from my MacBook Pro when doing an upgrade. I was just wondering if these were usable with, for example, an Arduino. I'd be too much of a beginner to actually try to do this now anyway, but I'm curious if it is at all possible, or if that's just way too much memory for a microcontroller to address.&lt;/p&gt;&#xA;" OwnerUserId="4103" LastActivityDate="2011-05-09T17:23:26.390" Title="Is it possible to use multi gigabyte DRAM modules with a microcontroller?" Tags="&lt;arduino&gt;&lt;microcontroller&gt;&lt;memory&gt;" AnswerCount="6" CommentCount="3" />
  <row Id="13847" PostTypeId="2" ParentId="13846" CreationDate="2011-05-04T01:57:03.300" Score="2" ViewCount="" Body="&lt;p&gt;The short answer is no.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino can't drive the DDR or DDR2 memory interface. You could make a DDR/DDR2 controller with a SPI interface with an FPGA, but that's a significant undertaking.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-05-04T01:57:03.300" />
  <row Id="13848" PostTypeId="2" ParentId="13846" CreationDate="2011-05-04T01:59:24.107" Score="14" ViewCount="" Body="&lt;p&gt;I'm going to say no: the most basic incompatibility is that there's way too many pins on those modules even be able to interface it physically to an Arduino.  Ditto for similar small microcontrollers.  An ARM Cortex M3 is getting closer, but few of those actually have the external bus necessary to interface RAM in such a fashion (I think).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I'll play along an go further.  Assuming you could interface the chip to the Arduino somehow another basic electrical compatibility problem is the voltages required.  I think these RAM modules use something odd like 2.2V - not present on a vanilla Arduino board or really, any other basic hobbyist microcontroller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming that was taken care of then the chip would pretty much work like any other external memory to the Arduino.  This is really done all the time - people add external EEPROM to store important constants or SD/MMC cards for storage of webserver logs and such.  Of course, within this context the RAM modules presents no real benefit to the Arduino.  Its main feature is speed and the Arduino (and yes, other hobbyist microcontrolers) typically don't break 25MHz in clock speed.  They're too slow to care about speed.  And storage size isn't a big issue since interfacing to an SD/MMC card is distinctly easier and provides as much space to play with.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So even if it were possible it wouldn't really be advisable.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-04T01:59:24.107" CommentCount="4" />
  <row Id="13849" PostTypeId="2" ParentId="13846" CreationDate="2011-05-04T02:00:31.840" Score="5" ViewCount="" Body="&lt;p&gt;You could conceivably use a system of latches to allow something like an arduino to generate 32 bits of address, and you could probably devise some scheme to generate the refresh cycles, but there'd be almost no point in doing so, except as a technical exercise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The interface circuitry would probably be the most complex part of the resulting system, and there'd be little practical value in the result; the arduino would not be able to execute code out of the RAM, the storage would be volatile, and would probably consume more power than the arduino as well. If you want to store data, an SPI EEPROM is probably a much better solution.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-04T02:00:31.840" CommentCount="4" />
  <row Id="13850" PostTypeId="2" ParentId="13773" CreationDate="2011-05-04T02:16:23.627" Score="1" ViewCount="" Body="&lt;p&gt;Two batteries in parallel will work fine &lt;em&gt;if&lt;/em&gt; the following are true:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;the batteries are of identical types&lt;/li&gt;&#xA;&lt;li&gt;the number of cells in each string is low (1 is best, 2-4 OK, I wouldn't do this for &gt;4)&lt;/li&gt;&#xA;&lt;li&gt;the cells are matched (same age, charged + discharged together)&lt;/li&gt;&#xA;&lt;li&gt;the cells are in thermally similar environments -- if they're next to each other but one is next to a heat sink and the other is on top of a hot component, you'll reduce life.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-05-04T02:16:23.627" />
  <row Id="13851" PostTypeId="2" ParentId="13756" CreationDate="2011-05-04T02:20:17.773" Score="1" ViewCount="" Body="&lt;p&gt;Pi filters (shunt capacitor + series inductor + shunt capacitor) present very low high-frequency input impedance at each end due to the capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;T filters (two series inductors with a shunt capacitor in the middle -- the dual of a pi filter) present very high high-frequency input impedance at each end due to the inductors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For 50-ohm source and load, it doesn't matter much, and you can just pay attention to the transfer function between input and output. But in other situations, one may be better than the other because of impedance characteristics.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-05-04T02:20:17.773" />
  <row Id="13852" PostTypeId="2" ParentId="13755" CreationDate="2011-05-04T02:28:15.567" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;is there a general rule for the maximum charge current (as a function of the battery capacity) for each of the mainstream battery technologies (NiCd, NiMH, Li-ion, Li-Polymer, lead-acid), for normal and fast charging?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I don't think so. It depends on a number of factors besides the chemistry, including:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;what charge algorithm is being used&lt;/li&gt;&#xA;&lt;li&gt;voltage accuracy of the charger (to prevent overvoltage on each cell)&lt;/li&gt;&#xA;&lt;li&gt;temperature sensing ability (faster charge = potential to overheat individual cells)&lt;/li&gt;&#xA;&lt;li&gt;# of cells in series (more cells in series = harder to keep cells balanced and charged safely)&lt;/li&gt;&#xA;&lt;li&gt;manufacturer tradeoffs&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;This last point is important: maximum charge current is very highly dependent on how the manufacturer has made tradeoffs for energy density vs. power density vs. cycle life. Battery manufacturers such as Sanyo and Panasonic will often sell several different types of batteries, some with high power density, some with high energy density.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a general rule of thumb, C/10-C/5 is probably safe for most chemistries without taking any precautions. Beyond that, you have to manage the temperature and voltage of the cells carefully in order to implement fast charging in the 1C / 2C / 5C / 10C range. 10C is iffy and I'd be surprised to see any battery of any type that could be charged at higher currents without sacrificing cycle life and safety.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-05-04T02:28:15.567" CommentCount="1" />
  <row Id="13853" PostTypeId="2" ParentId="13802" CreationDate="2011-05-04T03:12:15.403" Score="3" ViewCount="" Body="&lt;p&gt;I suppose one key question is: What is the pre-flight checklist before you release a board to production.  My pre-flight list is:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Schematic design review&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Net names and off-sheet ports&lt;/li&gt;&#xA;&lt;li&gt;Power supply pins connected&lt;/li&gt;&#xA;&lt;/ol&gt;&lt;/li&gt;&#xA;&lt;li&gt;Schematic DRC&lt;/li&gt;&#xA;&lt;li&gt;Footprint scrub&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Complete manufacturer part number&lt;/li&gt;&#xA;&lt;li&gt;Part number matches footprint on PCB and pinout in schematic&lt;/li&gt;&#xA;&lt;li&gt;Footprint pin number is &quot;right-side-up&quot; and correct&lt;/li&gt;&#xA;&lt;li&gt;Footprint dimensions double checked for hole sizes, clearance, keepouts, etc.&lt;/li&gt;&#xA;&lt;li&gt;Mating connectors are oriented correctly; pins 1-to-1, 2-to-2, etc.&lt;/li&gt;&#xA;&lt;/ol&gt;&lt;/li&gt;&#xA;&lt;li&gt;PCB Dimensions and holes&lt;/li&gt;&#xA;&lt;li&gt;PCB DRC&lt;/li&gt;&#xA;&lt;li&gt;Fab Drawings has all layers and call outs.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;This answer community wiki'd.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-04T03:12:15.403" CommunityOwnedDate="2011-05-04T03:12:15.403" />
  <row Id="13854" PostTypeId="1" CreationDate="2011-05-04T03:27:32.890" Score="7" ViewCount="196" Body="&lt;p&gt;There was recently an article in the Christian Science Monitor about the launch of a &lt;a href=&quot;http://www.csmonitor.com/Science/2011/0429/Cracker-size-satellites-to-launch-with-Space-Shuttle-Endeavour&quot; rel=&quot;nofollow&quot;&gt;cracker-size satellite&lt;/a&gt;. The article says that the satellite has, &quot;power storage in capacitors, and switching circuitry to turn on the microprocessor when the stored energy is enough to create a single radio-frequency emission — a digital beep.&quot; The power is collected from a solar cell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm interested in creating an earth-based device which would do just that, collect power from a solar cell and only turn on the device to transmit when it's got enough power. I recently purchased an &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;arduino&lt;/a&gt;, but have little experience with this kind of engineering. Any suggestions about how to get started? Thanks!&lt;/p&gt;&#xA;" OwnerUserId="4105" LastActivityDate="2011-05-09T05:41:47.820" Title="How to have arduino only turn on when enough power has been collected?" Tags="&lt;arduino&gt;&lt;capacitor&gt;&lt;switch&gt;&lt;solar-cell&gt;" AnswerCount="5" CommentCount="2" FavoriteCount="3" />
  <row Id="13855" PostTypeId="1" AcceptedAnswerId="13859" CreationDate="2011-05-04T04:05:01.630" Score="1" ViewCount="97" Body="&lt;p&gt;I am using Eagle5.11 to prepare schematic diagram. I need the .lbr file for &#xA;&lt;img src=&quot;http://i.imgur.com/A7yMX.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;img src=&quot;http://i.imgur.com/AH5Ry.jpg&quot; alt=&quot;enter image description here&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Breakaway-Male Header,CAT9532 SOIC 28 pin package&lt;/em&gt;..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So where can i find a bulk of .lbr files for these small but necessary components?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What other .lbr's you would suggest for a guy preparing schematics for his projects that includes things like interfacing pic mcu(16f/32mx) with driver ic's(uln2003) and lots of sensors?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I got one from &lt;em&gt;sparkfun&lt;/em&gt; but that doesnt contain what I am looking for&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance..&lt;/p&gt;&#xA;" OwnerUserId="1484" LastEditorUserId="1484" LastEditorDisplayName="" LastEditDate="2011-05-05T21:03:47.187" LastActivityDate="2011-05-05T21:03:47.187" Title="Schematic Editor - Library files" Tags="&lt;pcb&gt;&lt;schematics&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13856" PostTypeId="2" ParentId="13854" CreationDate="2011-05-04T04:11:44.473" Score="3" ViewCount="" Body="&lt;p&gt;You will want to look at how to put the avr into sleep mode. When in sleep mode the micro controller will turn off as much as possible to increase power savings. What you can do is hook whatever you are storing the energy from the solar panel in up to one of the ADC pins on the arduino and when that reaches a certain threshold you can wake the micro controller up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a few different levels of sleep though, and the more power you want to save the more stuff gets turned off. I think ADC pins are only on with the highest/least power saving level. You could also use the avrs internal comparator, with the capacitor/battery you are storing the energy in and a voltage source for whatever voltage threshold you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One last thing is that using an arduino for this may not be the best.  Even in the lowest sleep state the arduino will use ~15mA, which an avr chip only uses 0.05mA in this state. The arduino has a linear voltage regulator on it that will always use up about 10mA, plus a few other extra chips. It would probably be worth it to make your own avr setup for this reason. &lt;/p&gt;&#xA;" OwnerUserId="4034" LastEditorUserId="4034" LastEditorDisplayName="" LastEditDate="2011-05-04T20:28:38.103" LastActivityDate="2011-05-04T20:28:38.103" CommentCount="2" />
  <row Id="13857" PostTypeId="2" ParentId="13846" CreationDate="2011-05-04T04:11:55.750" Score="4" ViewCount="" Body="&lt;p&gt;I would say no, not without sticking a good sized (pin count) fpga in between, the fpga talks to the memory and the microcontroller talks to the fpga using a paging scheme.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-05-04T04:11:55.750" CommentCount="2" />
  <row Id="13858" PostTypeId="2" ParentId="3934" CreationDate="2011-05-04T04:40:01.170" Score="1" ViewCount="" Body="&lt;p&gt;You didn't specify the frequency (100Hz or 100MHz?) or how much the frequency had to be varied (0.01% or 1000% ?) or whether the frequency had to be varied by a voltage or a physical knob. Purity of sine wave and stability matters too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A one-transistor FET Hartley oscillator is hard to beat for cheap.&lt;/p&gt;&#xA;" OwnerUserId="4106" LastActivityDate="2011-05-04T04:40:01.170" />
  <row Id="13859" PostTypeId="2" ParentId="13855" CreationDate="2011-05-04T05:33:04.843" Score="4" ViewCount="" Body="&lt;p&gt;The microbuilder library &lt;a href=&quot;http://www.microbuilder.eu/Projects/EagleFootprintLibrary.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.microbuilder.eu/Projects/EagleFootprintLibrary.aspx&lt;/a&gt; is pretty good and is maintained by the all around nice guy Kevin Townsend.&#xA;There is also the adafruit library &lt;a href=&quot;https://github.com/adafruit/Adafruit-Eagle-Library&quot; rel=&quot;nofollow&quot;&gt;https://github.com/adafruit/Adafruit-Eagle-Library&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, it would probably take no more than 5 minutes to draw that 100 mil header. In my experience Eagle footprints, even the standard ones, are of varying quality and it pays to learn to draw your own.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastActivityDate="2011-05-04T05:33:04.843" />
  <row Id="13860" PostTypeId="2" ParentId="3934" CreationDate="2011-05-04T06:50:41.843" Score="1" ViewCount="" Body="&lt;p&gt;Triangle oscillator with a &lt;a href=&quot;http://falstad.com/circuit/e-sinediode.html&quot; rel=&quot;nofollow&quot;&gt;triangle to sine converter&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-04T06:50:41.843" CommentCount="2" />
  <row Id="13861" PostTypeId="2" ParentId="13838" CreationDate="2011-05-04T07:11:48.617" Score="1" ViewCount="" Body="&lt;p&gt;You don't &lt;em&gt;need&lt;/em&gt; a LED driver, but it has its advantages. You save a lot on your microcontroller's I/O, you only need a couple of lines for the serial interface (SPI or I2C). It may also save board space, since you don't need a bunch of discrete components for the multiplexing.&lt;br&gt;&#xA;Personally I like the &lt;a href=&quot;http://datasheets.maxim-ic.com/en/ds/MAX6950-MAX6951.pdf&quot; rel=&quot;nofollow&quot;&gt;Maxim MAX6950/51&lt;/a&gt; for five and eight 7-segment digits resp. It comes in a small 16 pin package. It has digital brightness control and hexadecimal-to-7-segment decoder. Interfaces to your uC with 3 lines.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-04T07:11:48.617" CommentCount="2" />
  <row Id="13862" PostTypeId="1" AcceptedAnswerId="13868" CreationDate="2011-05-04T07:17:32.293" Score="0" ViewCount="49" Body="&lt;p&gt;As far as i can tell they are both Arduino shields. Is that correct?&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://www.seeedstudio.com/depot/electronic-brick-shield-v4-p-458.html?cPath=132_134&quot; rel=&quot;nofollow&quot;&gt;electronic brick shield&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;The &lt;a href=&quot;http://www.seeedstudio.com/depot/electronic-brick-chassis-v11-p-460.html?cPath=132_134&quot; rel=&quot;nofollow&quot;&gt;electronic brick chassis&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;If they are indeed both shields, what's the difference between them and why would someone buy one over the other? Their wiki is incomplete.&lt;/p&gt;&#xA;" OwnerUserId="3926" LastActivityDate="2011-05-04T11:05:54.270" Title="What is the difference between the Seeduino Electronic Brick shield vs the chassis?" Tags="&lt;arduino&gt;" AnswerCount="1" />
  <row Id="13863" PostTypeId="2" ParentId="13846" CreationDate="2011-05-04T07:43:53.567" Score="2" ViewCount="" Body="&lt;p&gt;You'd need a low voltage driver (SSTL), and some way to control about 100 channels (each differential, so about 200 pins. Think BGA.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most DRAM has to be refreshed at at least 1kHz and probably more to have a low bit error rate. This will then form a major background task and use up most of the prcoessing power of the Arduino, if it's even possible to refresh memory at such a rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you can look at though is with some microcontrollers, e.g. PIC24F/H/dsPIC33F, they support a parallel master bus interface, which allows some types of parallel SRAM to be accessed. There's even support with C, as this external memory can be mapped onto several in code variables and even blocks which combine both internal and external memories. The external memory requires you to write some PMB code. You'd only be able to address up to about 1 MB with this though.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-05-09T17:23:26.390" LastActivityDate="2011-05-09T17:23:26.390" CommentCount="4" />
  <row Id="13864" PostTypeId="2" ParentId="13854" CreationDate="2011-05-04T08:10:10.963" Score="7" ViewCount="" Body="&lt;p&gt;That satellite will presumably use &quot;energy harvesting&quot; (EH) to store the energy provided by the solar cell in a super capacitor. Both TI and Microchip have just started suppling evaluation kits using EH with a solar cell to power an MCU and a wireless transceiver. Advanced Linear Devices makes the &lt;a href=&quot;http://www.aldinc.com/pdf/EH300Brochure.pdf&quot; rel=&quot;nofollow&quot;&gt;EH300 energy harvesting module&lt;/a&gt;, which can charge a pair of super capacitors from a variety of sources, including solar cells. I've been experimenting with one, and it can provide 1.8V - 3.3V from very low voltage sources, and is capable of delivering 25 mA for 68 ms, which is more than  enough for an MCU such as an MSP430 or XLP PIC and a low-power transmitter. The EH300 has two super capacitors. They cost about £34, I bought mine from Farnell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Arduino isn't suitable for this application, as it won't work from such low voltages, and takes too much power. XLP PICs typically use 20 nA in deep sleep mode, and  50 uA/Mhz when active.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-04T08:41:08.210" LastActivityDate="2011-05-04T08:41:08.210" />
  <row Id="13865" PostTypeId="1" CreationDate="2011-05-04T08:27:59.737" Score="3" ViewCount="130" Body="&lt;p&gt;With the amazing amount of devices available to anyone, each one usually comes with it's own power requirements!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right at this moment, on my work table i have these adapters which I have at arms length for various things (and many more which I shall not list):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;9v dc 500ma (Arduino)&lt;/li&gt;&#xA;&lt;li&gt;12v dc 1a&lt;/li&gt;&#xA;&lt;li&gt;5v dc 700ma&lt;/li&gt;&#xA;&lt;li&gt;5v dc 2a&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;How can I simplify my DC power requirements? Does a device exist where it's a power supply and can output any combination of voltage and current? And also have flexible adapter plugs?&lt;/p&gt;&#xA;" OwnerUserId="3926" LastActivityDate="2011-05-05T19:34:05.097" Title="How can I simplify my DC power requirements?" Tags="&lt;power-supply&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="13866" PostTypeId="1" CreationDate="2011-05-04T08:33:30.200" Score="1" ViewCount="112" Body="&lt;p&gt;I need to know what the value of TH1 and TL1 should to set the baudrate of an 8051 controller to 115200 Hz. I'm using an oscillator frequency of 11.0952 MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, is there any software that calculate baudrate values?&lt;/p&gt;&#xA;" OwnerUserId="3632" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-04T13:06:24.970" LastActivityDate="2011-05-04T15:26:53.593" Title="Baudrate Calulator" Tags="&lt;baudrate&gt;" AnswerCount="3" />
  <row Id="13867" PostTypeId="2" ParentId="13865" CreationDate="2011-05-04T08:33:43.710" Score="5" ViewCount="" Body="&lt;p&gt;Get a bench power supply. I use one of &lt;a href=&quot;http://uk.rs-online.com/web/search/searchBrowseAction.html?method=retrieveTfg&amp;amp;binCount=1&amp;amp;Nty=1&amp;amp;Ntx=mode%2bmatchallpartial&amp;amp;Ntk=I18NBrand&amp;amp;Ne=4294957561&amp;amp;Nr=AND%28avl%3auk,searchDiscon_uk%3aN%29&amp;amp;N=4294957460&amp;amp;Ntt=Lascar&quot; rel=&quot;nofollow&quot;&gt;these&lt;/a&gt;, it won't cost much more than your selection of mains adapters, and is a lot more convenient. I've made up a variety of leads that plug into it for powering various boards. Having voltage and current displayed is very useful, as I can see immediately if there is a short on a prototype.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-04T10:55:37.903" LastActivityDate="2011-05-04T10:55:37.903" CommentCount="1" />
  <row Id="13868" PostTypeId="2" ParentId="13862" CreationDate="2011-05-04T08:48:46.780" Score="2" ViewCount="" Body="&lt;p&gt;The Shield is intended only for Arduino boards, whereas the Brick Chassis can be used with any system with compatible connectors. It could be used with an Arduino, of course, with suitable connectors and cables. It isn't a Shield, it looks as though they put it in the wrong category. You could email them to make sure.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-04T11:05:54.270" LastActivityDate="2011-05-04T11:05:54.270" />
  <row Id="13869" PostTypeId="2" ParentId="13866" CreationDate="2011-05-04T08:50:13.830" Score="2" ViewCount="" Body="&lt;p&gt;Is &lt;a href=&quot;http://www.keil.com/products/c51/baudrate.asp&quot; rel=&quot;nofollow&quot;&gt;on-line baud rate calculator&lt;/a&gt; OK? Timer 1 used as baud-rate generator works in auto-reload 8-bit mode, so you only have to set TH1, TL1 is loaded from TH1 at the beginning of each cycle. Check this &lt;a href=&quot;http://www.8052.com/tuttimer.phtml&quot; rel=&quot;nofollow&quot;&gt;tutorial&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-05-04T08:50:13.830" CommentCount="1" />
  <row Id="13870" PostTypeId="2" ParentId="13865" CreationDate="2011-05-04T08:52:24.533" Score="4" ViewCount="" Body="&lt;p&gt;You can get multi-output adapters with a selection of reversible tips. Typically, these provide switchable 3V, 4.5V, 6V, 9V &amp;amp; 12V (No 5V) with half a dozen or so tips (1.6mm, 2.1mm, 2.5mm etc) which can be reversed for centre-negative/centre-positive applications.&lt;br /&gt;&lt;br /&gt; The only problem is that you have to be very careful to check the voltage &amp;amp; polarity settings before plugging them into your expensive gadgets!.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-05-04T08:52:24.533" CommentCount="4" />
  <row Id="13871" PostTypeId="2" ParentId="13866" CreationDate="2011-05-04T09:16:26.590" Score="1" ViewCount="" Body="&lt;p&gt;Which variant are you using? A standard 8051 (12 clocks per machine cycle and a 16X serial clock) has a maximum baud rate of 57600 with a 11.0592MHz crystal.&lt;br /&gt;&lt;br /&gt;&#xA;For instance with timer 1 set to 8 bit auto-reload mode, to get 9600 baud you take 11.0592MHz, divide by 12 then 16 to get 57600. Now 57600/9600 = 6 so we need a further division by 6 which we get by setting the timer register TH1 to the two's complement of 6 which is 0xFA.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastEditorUserId="2234" LastEditorDisplayName="" LastEditDate="2011-05-04T14:19:25.907" LastActivityDate="2011-05-04T14:19:25.907" CommentCount="3" />
  <row Id="13872" PostTypeId="2" ParentId="13865" CreationDate="2011-05-04T09:49:07.250" Score="3" ViewCount="" Body="&lt;p&gt;First of all, the current rating on the power supply is a maximum current the psu can deliver, so if you have a 5V / 700mA and a 5V / 2A supply, then a single 5V / 2.7A supply will do the job of both of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, what you need to figure out is what voltages you really need and sum up the current for each of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The voltages you need might not even be all the once you have now.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lots of devices will be able to work fine on a much higher voltage than the supplied PSU, I have several network switches that come with 9V supplies, but they are built for and works perfectly on everything from 6V to 24V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That Arduino will be happy with 12V, though the regulator might get a little hot if you are loading it down a lot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only way to know for sure which voltage a device will work with is to open it up and look at the regulator section of the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your 5V devices will probably not be happy with 12V, perhaps a 12V powered USB hub would be a good idea there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All my on-always gear is powered by a single 12V / 5A power brick, which is much more efficient and compact than the 8 separate wallwarts that the devices came with originally.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I made a small box with a load of 5.5mm barrel DC connectors, then I bought a good hand full of DC connectors that fit them and then I either cut the original power cables and fitted my new DC connectors or I simply made all new power cables for things.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-05-04T09:49:07.250" CommentCount="4" />
  <row Id="13873" PostTypeId="1" AcceptedAnswerId="13876" CreationDate="2011-05-04T10:12:46.447" Score="11" ViewCount="356" Body="&lt;p&gt;Once a chip overheats it can start malfunctioning - for example many programs may start failing once some or all parts in a computer overheat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What exactly happens that makes chips malfunction when they overheat?&lt;/p&gt;&#xA;" OwnerUserId="3552" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-04T10:43:37.847" LastActivityDate="2011-05-05T07:07:24.633" Title="Why exactly do chips start malfunctioning once they overheat?" Tags="&lt;microchip&gt;&lt;heat&gt;&lt;reliability&gt;" AnswerCount="4" />
  <row Id="13874" PostTypeId="2" ParentId="13873" CreationDate="2011-05-04T10:41:07.797" Score="12" ViewCount="" Body="&lt;p&gt;The main problem with IC operation at high temperatures is the greatly increased leakage current of individual transistors. The leakage current can increase to such an extent that the switching voltage levels of the devices is affected, so that signals can't propagate properly within the chip, and it stops functioning. They usually recover when allowed to cool down, but that is not always the case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Manufacturing processes for high-temperature operation (up to 300C) employ silicon-on-insulator CMOS technology because of the low leakage over a very wide temperature range.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-04T10:49:42.933" LastActivityDate="2011-05-04T10:49:42.933" />
  <row Id="13875" PostTypeId="1" AcceptedAnswerId="13877" CreationDate="2011-05-04T10:46:33.593" Score="1" ViewCount="103" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is sort of a follow up to my previous question regarding power supply for my telescope. The general advice I got was that I should just ditch regulation and connect the lead-acid battery directly to the telescope and camera. I have read the manuals for both these devices and both state that is is safe to do so as they both have internal regulators anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I almost always connect my telescope to the computer via RS232. My computer does not have a RS232 port, so I'm using a Keyspan USB to RS232 adapter. I don't think the adapter is isolated because I checked with my DVM and there is continuity between the grounds of both (that is the USB and RS232).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem is my telescope's electronics are known to be problematic when it comes to ground loops. Some people have outright blown the RS232 chip due to this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is, since the computer is going to be connected to the mains and the telescope + camera to the 12V battery, there is no common ground. Am I going to need an RS232 opto-isolater for the telescope-&gt;computer connection?&lt;/p&gt;&#xA;" OwnerUserId="3966" LastActivityDate="2011-05-04T19:50:32.630" Title="Connecting Different Devices via RS232 - Worried about Ground Loops" Tags="&lt;power-supply&gt;&lt;groundloops&gt;" AnswerCount="2" />
  <row Id="13876" PostTypeId="2" ParentId="13873" CreationDate="2011-05-04T10:54:16.297" Score="17" ViewCount="" Body="&lt;p&gt;To expand on other answers.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Higher leakage currents: this can lead to more heating issues and can easily result in thermal runaway.&lt;/li&gt;&#xA;&lt;li&gt;Signal to noise ration will decrease as &lt;a href=&quot;http://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise&quot; rel=&quot;nofollow&quot;&gt;thermal noise increases&lt;/a&gt;: This can result in a higher bit error rate, this will cause a program to be misread and commands to be misinterpreted. This can cause &quot;random&quot; operation.&lt;/li&gt;&#xA;&lt;li&gt;Dopants become more mobile with heat. When you have a fully overheated chip the transistor can cease being transistors.&lt;strong&gt;This is irreversible.&lt;/strong&gt;&lt;/li&gt;&#xA;&lt;li&gt;Uneven heating can make the crystalline structure of Si break down. A normal person can experience by putting glass through temperature shock. It will shatter, a bit extreme, but it illustrates the point. &lt;strong&gt;This is irreversible.&lt;/strong&gt;&lt;/li&gt;&#xA;&lt;li&gt;ROM memories that depend on a charged isolated plate will be able to lose memory as temperature increases. The thermal energy, if high enough, can allow electronics to escape the charged conductor. This can corrupt program memory. This regularly happens to me during soldering of ICs that are already programmed when someone overheats the chip.&lt;/li&gt;&#xA;&lt;li&gt;Loss of transistor control: With enough thermal energy your electrons can jump the bandgap. A semiconductor is a material that has a small bandgap so that it is easily bridged with dopants but large enough that the required operating temperature does not turn it into a conductor where the gap is smaller then the thermal energy of the material. &lt;em&gt;This is an oversimplification and is the basis of another post, but I wanted to add it and put it in my own words.&lt;/em&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;There are more reasons, but these make an important few.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-05T07:07:24.633" LastActivityDate="2011-05-05T07:07:24.633" />
  <row Id="13877" PostTypeId="2" ParentId="13875" CreationDate="2011-05-04T11:21:39.997" Score="5" ViewCount="" Body="&lt;p&gt;If your telescope supply is from a battery, &lt;em&gt;it&lt;/em&gt; is already isolated from ground; when you connect the 232 cable, its system will become referenced to &lt;em&gt;that&lt;/em&gt; ground.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-04T11:21:39.997" CommentCount="3" />
  <row Id="13878" PostTypeId="1" CreationDate="2011-05-04T12:07:22.930" Score="2" ViewCount="61" Body="&lt;p&gt;The basic principle of RFID tags in cars for toll collection is the same as the hand held tags we use to open doors. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How exactly are they different? How come my door RFID reader does not read my tag at 10 meters away while i run at 100km/hr :) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone elaborate on the differences in the two systems for them to work the way they do? Am i being blasted with high powered radio frequencies when i pass a toll RFID reader?&lt;/p&gt;&#xA;" OwnerUserId="3926" LastActivityDate="2011-05-04T13:38:51.060" Title="RFID car tags vs hand held tags, how exactly are they different?" Tags="&lt;rfid&gt;" AnswerCount="1" />
  <row Id="13879" PostTypeId="1" AcceptedAnswerId="13880" CreationDate="2011-05-04T12:40:01.647" Score="0" ViewCount="59" Body="&lt;p&gt;I decided to try etching my own PCBs and I got some blue press and peel transfer foil. It has shiny and matte side. I'm supposed to print on one side and iron the other, but the procedure of transferring isn't too clear to me and the only site which Google provides appears to be infested with malware, so I'm asking here for advice. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-05-04T12:55:27.753" Title="How to use blue press and peel transfer foil for PCB etching?" Tags="&lt;pcb-fabrication&gt;" AnswerCount="1" />
  <row Id="13880" PostTypeId="2" ParentId="13879" CreationDate="2011-05-04T12:43:57.127" Score="2" ViewCount="" Body="&lt;p&gt;You transfer the image onto the dull side, place that in contact with the copper, and iron on the other side placing a plain sheet of paper between the iron and the P&amp;amp;P stuff. &lt;a href=&quot;http://www.eidusa.com/Theory_PnP.htm&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a non-hacked web page.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Members of the &lt;a href=&quot;http://tech.groups.yahoo.com/group/Homebrew_PCBs/&quot; rel=&quot;nofollow&quot;&gt;Homebrew PCB Yahoo group&lt;/a&gt; have found that shiny magazine paper works just as well as that expensive Press and Peel material, and costs nothing, just use sheets from an old magazine. I've tried both, and can confirm that. Moreover, you don't have to worry about which side is which! :) I get much better results using transparencies printed on an inkjet printer with the conventional photo-etch process using precoated positive resist boards.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-04T12:55:27.753" LastActivityDate="2011-05-04T12:55:27.753" CommentCount="4" />
  <row Id="13881" PostTypeId="2" ParentId="13436" CreationDate="2011-05-04T12:51:27.667" Score="0" ViewCount="" Body="&lt;p&gt;I would use the &lt;a href=&quot;http://www.gumstix.com/store/catalog/product_info.php?products_id=256&quot; rel=&quot;nofollow&quot;&gt;Gumstix FE COM&lt;/a&gt;. I don't believe there is a more mature linux based product which could do wifi and video streaming at the moment.&lt;/p&gt;&#xA;" OwnerUserId="3926" LastActivityDate="2011-05-04T12:51:27.667" CommentCount="1" />
  <row Id="13882" PostTypeId="2" ParentId="13878" CreationDate="2011-05-04T13:38:51.060" Score="2" ViewCount="" Body="&lt;p&gt;In the toll roads you have a few things that help out:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bigger antennas. The antenna over head is decently large compared to anything you would put to read someones badge walking into a building. The size of the antenna helps it to get better receive signal strength.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Inside the car, I have seen both active and passive tags, the active tags have longer range just because they have a battery in them, but they take up more space which you don't want to be carnying around. I have been told, by a letter sent out by my transit authority to all customers, that they take advantage of the windshield to help as an antenna. I am not exactly sure how this happens, but they say it does. It could also be that they use the metal of the car to help reflect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Larger power. Yes, they do also send larger power down at you. But relative to the speed that you are driving through compared to walking through the door, you probably don't have much energy actually make it to you anyways.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most car RFID stations don't actually care to get 100% of the reads so they are able to push the limits a little bit. The reason they don't care is that they can just take a picture of your license plate and realize what account it is and charge it. This process takes more computational power and many times includes a human so they try to limit it, but they can still fall back to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One thing you should also think about throwing into your thought process loop, the sensors that some stores use to but in items and then have an alarm go off if you try to steal them, those are all forms of RFID as well. In that situation they are able to take advantage of antennas that can be 4-5 feet tall and stick one on both sides of you.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-04T13:38:51.060" CommentCount="1" />
  <row Id="13883" PostTypeId="2" ParentId="13866" CreationDate="2011-05-04T15:26:53.593" Score="1" ViewCount="" Body="&lt;p&gt;The best calculator for baudrates is the preprocessor of the assembler or compiler you are using.  Let the computer do the work.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-05-04T15:26:53.593" CommentCount="1" />
  <row Id="13884" PostTypeId="2" ParentId="13873" CreationDate="2011-05-04T15:45:48.947" Score="7" ViewCount="" Body="&lt;p&gt;Although leakage currents increase, I would expect a bigger issue for many MOS-based devices is that the amount of current passed through a MOS transistor in the &quot;on&quot; state will decrease as the device gets hot.  For a device to operate correctly, a transistor which is switching a node must be able to charge or discharge any latent capacitance in that part of the circuit before anything else relies upon that node having been switched.  Reducing the current-passing ability of transistors will reduce the rate at which they can charge or discharge nodes.  If a transistor is unable to charge or discharge a node sufficiently before another part of the circuit relies upon that node having been switched, the circuit will malfunction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that for NMOS devices, there was a design trade-off when sizing passive pull-up transistors; the bigger a passive pull-up, the more quickly the node could switch from low to high, but the more power would be wasted whenever the node was low.  Many such devices were therefore operated somewhat near the edge of correct operation and heat-based malfunctions were (and for vintage electronics, remain) fairly common.  For common CMOS electronics, such issues are generally less severe; I have no idea in practice the extent to which they play a part in things like multi-GHZ processors.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-04T15:45:48.947" CommentCount="4" />
  <row Id="13885" PostTypeId="1" AcceptedAnswerId="13887" CreationDate="2011-05-04T16:21:17.107" Score="2" ViewCount="124" Body="&lt;p&gt;I'm assembling a new computer from components. It's something I've done quite a few times, but now I would like to skip the case. Except for some structural integrity and LEDs, the only technical necessity the case supplies is the power button that tells the motherboard to start.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know I can buy generic power switches, but I have no idea which, exactly, to get, and how they should be interfaced with the motherboard. Can anyone help out?&lt;/p&gt;&#xA;" OwnerUserId="4111" LastActivityDate="2011-05-04T22:10:41.957" Title="How to make my own atx power switch?" Tags="&lt;switch&gt;&lt;computers&gt;&lt;atx&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="13886" PostTypeId="1" AcceptedAnswerId="13891" CreationDate="2011-05-04T16:39:34.600" Score="1" ViewCount="106" Body="&lt;p&gt;I must be blind... I'm trying to decide which of the '165, '166, and '597 shift registers is appropriate/inappropriate for a SPI input shift register. All are 8-bit parallel in.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;HC165: &lt;a href=&quot;http://www.nxp.com/documents/data_sheet/74HC_HCT165.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.nxp.com/documents/data_sheet/74HC_HCT165.pdf&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;HC166: &lt;a href=&quot;http://www.nxp.com/documents/data_sheet/74HC_HCT166pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.nxp.com/documents/data_sheet/74HC_HCT166pdf&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;HC597: &lt;a href=&quot;http://www.nxp.com/documents/data_sheet/74HC_HCT597_CNV.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.nxp.com/documents/data_sheet/74HC_HCT597_CNV.pdf&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;It looks like the HC165 has a latching asynchronous load input (parallel load triggered by a pulse), the HC166 has a clocked synchronous load input (parallel load triggered by the same clock edge as the serial shift, when load enable is asserted), and the 597 has a separate set of load registers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone add anything to the differences, or suggest which might be the most appropriate for SPI? (my gut call is the HC165, with the parallel load triggered by the inverted SPI CS line, and I'd have to add a 1-gate tristate driver for the MOSI signal)&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-05-04T19:33:23.633" Title="shift registers: differences between the standard parallel-in serial-out ICs" Tags="&lt;logic&gt;&lt;spi&gt;&lt;shift-register&gt;" AnswerCount="2" />
  <row Id="13887" PostTypeId="2" ParentId="13885" CreationDate="2011-05-04T16:50:55.983" Score="8" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://case-mods.linear1.org/case-mod-101-the-atx-power-switch-demystified/&quot; rel=&quot;nofollow&quot;&gt;requirements for the switch&lt;/a&gt; are not severe. The switch will be pulling down a current-limited 5V signal. It should be normally-open and momentary (non-latching).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The motherboard manual will have diagrams of the pin headers; two of those pins will be for the power switch (one side for the signal, the other for signal return / ground).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A reset switch is always a good idea too - the same sort of switch will do (momentary, normally-open).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-04T16:50:55.983" />
  <row Id="13888" PostTypeId="2" ParentId="13886" CreationDate="2011-05-04T17:05:46.750" Score="2" ViewCount="" Body="&lt;p&gt;Motorola, who invented SPI, designed the 74HC595 and the 74HC597 (they would have been LS parts then) to be SPI-compatible. The original data sheets for them had the pins identified with the standard SPI signal names, but this seems to have changed over the years. The 74HC597 has an additional non-SPI pin which loads data from the inputs to the shift register. I've used the 74HC595 with an SPI port on an MCU, but not the 74HC597.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've heard that the 74HC165 is not fully SPI-compatible because the output remains active when the device is disabled, instead of being tri-stated, and there are one or two other differences.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-04T17:31:25.113" LastActivityDate="2011-05-04T17:31:25.113" CommentCount="1" />
  <row Id="13889" PostTypeId="1" AcceptedAnswerId="13890" CreationDate="2011-05-04T18:20:06.783" Score="1" ViewCount="114" Body="&lt;p&gt;I'd like to buy or build a UV exposure unit for the photoresist method of making my own PCBs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Nice-to-haves:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;adjustable timer knob&lt;/li&gt;&#xA;&lt;li&gt;works for double-sided PCBs&lt;/li&gt;&#xA;&lt;li&gt;US$50 budget&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;What are my options?&lt;/p&gt;&#xA;" OwnerUserId="2172" LastActivityDate="2011-05-04T19:43:09.300" Title="DIY UV Exposure Unit for Making PCBs" Tags="&lt;pcb&gt;&lt;uv&gt;" AnswerCount="1" />
  <row Id="13890" PostTypeId="2" ParentId="13889" CreationDate="2011-05-04T18:42:51.497" Score="8" ViewCount="" Body="&lt;p&gt;Making one for $50 with those features is going to be difficult. Here is my very simple one:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/gN4GI.jpg&quot; alt=&quot;Here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's made from MDF and some strips of wood, held together with some glue and wood screws. A sheet of ordinary window glass rests on the upper wood strips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used standard 12&quot; fluorescent light fittings, disassembled, with the tubes replaced by UV tubes. They are connected to a piece of mains cable and a mains plug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I time the exposure (11 minutes) with the kitchen timer on my Dell Streak tablet. Although it's very crude, I get excellent results - 8/8 mil tracks if necessary - with transparencies printed on my cheap inkjet printer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It cost me the equivalent of about $40.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could build a basic unit like mine, and add the bells and whistles later.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some members of the Homebrew PCB Yahoo group are using UV LEDs, but they are far more expensive than a couple of UV tubes. Enough LEDs for a small board could cost over $100, IIRC.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-04T19:43:09.300" LastActivityDate="2011-05-04T19:43:09.300" CommentCount="2" />
  <row Id="13891" PostTypeId="2" ParentId="13886" CreationDate="2011-05-04T19:28:14.983" Score="2" ViewCount="" Body="&lt;p&gt;The 74xx165 is the more typical choice.  The 74HC597 is only better if it will be necessary to sample the input during a byte transition (and then make the sample available for the following transmission).  Because the front-edge latch is rising-edge sensitive but the parallel-load latch is level sensitive, there will often not be any good signal anywhere to clock the parallel-load latch.  The part would be much nicer if either both latches were level-sensitive, but otherwise the front-end latch is more likely to be a nuisance than to serve any functional purpose.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, the similar timing issues exist with the 74HC595's asynchronous clear.  If the parallel-load pin were level-sensitive, one could asynchronously drive the clear pin and the parallel load, so as to force all outputs to a known state.  Unfortunately, the edge-triggered parallel-load pin gets in the way of such a design; one could asynchronously drive the clear pin, but one would have to then drive the parallel-load pin some time after the clear signal had registered.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-05-04T19:33:23.633" LastActivityDate="2011-05-04T19:33:23.633" />
  <row Id="13892" PostTypeId="2" ParentId="13875" CreationDate="2011-05-04T19:50:32.630" Score="0" ViewCount="" Body="&lt;p&gt;I would have not guessed this would be a problem (and the issue probably would not be ground loops per se) but if other people have blown connected electronics, I suppose it pays to be careful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your baud rate isn't too high you should be able to make your own RS232 opto isolation pretty simply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option would be to use an embedded Ethernet to rs232 gateway, since UTP (ie CAT 5) Ethernet interfaces are usually transformer isolated (at least if you aren't doing power-over-ethernet).  I'm seeing these in the neighborhood of $30, and they'd let you run cat 5 cable out to the telescope.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option would be to go wireless...  &lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-05-04T19:50:32.630" />
  <row Id="13894" PostTypeId="2" ParentId="13885" CreationDate="2011-05-04T22:10:41.957" Score="0" ViewCount="" Body="&lt;p&gt;Okay you can use any push button to power the board, yes. I used a screwdriver more than once while testing a board just to short the pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the hacker solution is to use a capacitor (some µF). For electrolytic type: Minus (-) goes to GND (ground). This will switch on the board once the ATX power supply is connected to mains. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Modern BIOSes should have that functionality too (full on on power connect).&lt;/p&gt;&#xA;" OwnerUserId="1472" LastActivityDate="2011-05-04T22:10:41.957" CommentCount="3" />
  <row Id="13895" PostTypeId="1" AcceptedAnswerId="13897" CreationDate="2011-05-05T01:59:36.340" Score="3" ViewCount="65" Body="&lt;p&gt;I would like to track the movement of a persons hands and feet in relation to their waist.  I imagine them wearing something around their waist that can measure how far away a sensor attached to each hand and foot is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What kind of sensor would I be looking for to do this?  Everything needs to be attached to the person so can't be a done via a stationary camera.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I thought IR or some kind of sound sensor but would those work when not in line of sight such as when they are walking/running and their feet are behind the front of their waist?&lt;/p&gt;&#xA;" OwnerUserId="4117" LastEditorUserId="4117" LastEditorDisplayName="" LastEditDate="2011-05-05T02:12:48.970" LastActivityDate="2011-05-06T05:13:26.057" Title="Sensor for hand/foot location in relation to a persons body" Tags="&lt;sensor&gt;" AnswerCount="3" CommentCount="0" FavoriteCount="2" />
  <row Id="13896" PostTypeId="2" ParentId="13854" CreationDate="2011-05-05T02:15:30.173" Score="2" ViewCount="" Body="&lt;p&gt;You can try the techniques used by &lt;a href=&quot;http://www.solarbotics.net/library/circuits/se_t1.html&quot; rel=&quot;nofollow&quot;&gt;voltage triggered (Type I) BEAM solar engines&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Essentially you charge a big capacitor until voltage across it crosses some threshold, and you power your circuit by discharging it. With a big enough capacitors you should be able to power up an arduino cold. But you are going to need some &lt;em&gt;big&lt;/em&gt; capacitors to feed it for &gt;1s.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These circuits can be quite small. For example &lt;a href=&quot;http://www.solarbotics.net/library/circuits/se_t1_1381.html&quot; rel=&quot;nofollow&quot;&gt;this circuit&lt;/a&gt;, shown below, uses 2 transistors and a Panasonic &lt;a href=&quot;http://library.solarbotics.net/pieces/parts_elect_ic.html#1381&quot; rel=&quot;nofollow&quot;&gt;1381x&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/zgBqn.gif&quot; alt=&quot;Simple type I solar engine using 1381x&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Solar engines use other techniques, e.g. slope triggering. You can find out more about them &lt;a href=&quot;http://www.solarbotics.net/library/circuits/se.html&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2340" LastActivityDate="2011-05-05T02:15:30.173" />
  <row Id="13897" PostTypeId="2" ParentId="13895" CreationDate="2011-05-05T03:41:17.070" Score="3" ViewCount="" Body="&lt;p&gt;That's a very interesting problem!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think it could be done with transmitting and receiving transducers on a belt. An ultrasonic pulse, generated by an MCU, which resets a timer, is transmitted. An MCU with receiving and transmitting transducers, on, say, the right wrist, detects the pulse, and immediately retransmits it. The belt MCU detects the retransmitted pulse, and stops the timer. From the speed of sound, and the time for the outward and return journey, the total distance can be calculated. Halving the distance gives the distance from the wrist to the waist.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The distances are relatively small, so enough signal should be present, even if the transmitter and receiver are not line-of-sight. Amplification will be needed for reception.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll leave you to work out the details for all four wrists and ankles. :) Some form of encoding will be needed so that the four remote units can be distinguished from each other.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A Google search for similar techniques turned up &lt;a href=&quot;http://www.idmil.org/projects/the_soundcatcher&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;, which uses a passive reflector on the hand, with the transmitter and receiver on a microphone stand. I can't see that simpler technique working for Glen's application.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-05T12:59:53.840" LastActivityDate="2011-05-05T12:59:53.840" />
  <row Id="13898" PostTypeId="1" CreationDate="2011-05-05T03:58:16.737" Score="-1" ViewCount="33" Body="&lt;p&gt;Hey all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Im looking for something along the lines of some type of showcase of mechanical movements, applications, forces, rotations .. .. ..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;something like an extended &quot; how its made &quot; .. that is gone through in painstaking detail ... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;double points if there are labels for the different types of actuators .. gears  and sibling machinery &lt;/p&gt;&#xA;" OwnerUserId="4067" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-05T04:22:15.103" LastActivityDate="2011-05-05T04:22:15.103" ClosedDate="2011-05-05T04:19:25.993" Title="mechanical standards guide for automated movements" Tags="&lt;robotics&gt;&lt;mechanical&gt;&lt;mechanical-assembly&gt;" CommentCount="13" />
  <row Id="13899" PostTypeId="1" AcceptedAnswerId="14087" CreationDate="2011-05-05T04:36:26.977" Score="2" ViewCount="98" Body="&lt;p&gt;The LPC11C24 has a on-chip CAN transceiver and a section of ROM with CAN driver software. I am trying to run the can_onchip sample project on the LPCXpresso board. The CAN-HI and CAN-LO lines are connected to an MCP2551 (because you need at least 2 nodes to test a CAN bus). I don't see any change on the CAN-HI and LO lines and the CAN Error callback function is called with error code 0x82, which is a BIT_0 error, meaning the bus is always in the HIGH state and it could not be pulled LOW/Dominant. This makes me think there is a problem with the on-chip transceiver because any CAN node should be able to pull the bus LOW for a Dominant bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The linker files used are the CAN version provided that reserve the ROM memory mapping for the CAN driver. The init and callback functions are being called, so I am relatively certain the drivers are working correctly. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any other settings that need to be used to enable the on-chip transceiver?&lt;/p&gt;&#xA;" OwnerUserId="2150" LastEditorUserId="2150" LastEditorDisplayName="" LastEditDate="2011-05-10T06:23:26.150" LastActivityDate="2011-05-10T06:23:26.150" Title="Running CAN sample project on LPCXpresso LPC11C24" Tags="&lt;can&gt;&lt;lpcxpresso&gt;&lt;nxp&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="13900" PostTypeId="1" AcceptedAnswerId="14152" CreationDate="2011-05-05T05:43:40.133" Score="2" ViewCount="91" Body="&lt;p&gt;Hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I needed 2N3904 transistors so I went to the few crappy electronics shops we find in my country. They didn't have those, but they gave me 2N9013 and stated that those were equivalent NPN transistors. Both in TO-92 packages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've searched for a datasheet and found one from Promax-Johnton (who?) with &quot;1W OUTPUT AMPLIFIER OF POTABLE RADIOS IN CLASS B PUSH-PULL OPERATION&quot; which is worst than Chinese to me :(&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are: &#xA;1. Is if this part is a good replacement for my 2n3904? &#xA;2. What additional considerations I need to be aware? &#xA;3. Recommendations?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="3365" LastActivityDate="2011-05-11T01:59:35.623" Title="Is 2N9013 a good replacement for 2N3904" Tags="&lt;transistor&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13901" PostTypeId="1" CreationDate="2011-05-05T05:52:42.663" Score="-1" ViewCount="46" Body="&lt;p&gt;what is the size of a raw yuv frame&lt;/p&gt;&#xA;" OwnerUserId="4120" LastActivityDate="2011-05-05T05:52:42.663" ClosedDate="2011-05-05T07:30:02.813" Title="what is the size of a raw yuv frame" Tags="&lt;video&gt;" CommentCount="2" />
  <row Id="13902" PostTypeId="2" ParentId="13900" CreationDate="2011-05-05T06:22:30.850" Score="1" ViewCount="" Body="&lt;p&gt;It is a little more powerful than the 2n3904. Most likely the current gain is less, and and maybe also the maximal voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your application that may be OK, which is quite likely if it is not too demanding. The correct thing would for you to check the numbers in the data sheet.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-05-05T06:22:30.850" />
  <row Id="13903" PostTypeId="2" ParentId="13873" CreationDate="2011-05-05T06:31:13.400" Score="6" ViewCount="" Body="&lt;p&gt;Just one addition to some excellent answers: Technically it isn't the dopants that get more mobile it is an increase in intrinsic carrier concentration. If anything the dopants/carriers get less mobile as the silicon crystal lattice starts to &quot;vibrate&quot; due to the increase thermal energy making it harder for the electrons and holes to flow through the device - optical phonon scattering I believe phsyics calls it but I may be wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the intrinsic carrier concentration increases beyond the doping level you loose electrical control of the device. Intrinsic carriers are the ones that are there before we dope the silicon, the idea of semiconductors is that we add our own carriers in to generate pn junctions and the other interesting things that transistors do. Silicon tops out about 150degC so heat sinking RF and high speed processors is very important as 150degC is not too difficult achieve in practice. There is a direct link between intrinsic carrier concentration and the off leakage current of a device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like the other chaps have shown, this is just one of the reasons chips fail - it can even get down to something as simple as a wire bond getting too hot and popping off it's pad, there's a huge list of things.&lt;/p&gt;&#xA;" OwnerUserId="4096" LastActivityDate="2011-05-05T06:31:13.400" CommentCount="3" />
  <row Id="13904" PostTypeId="2" ParentId="13820" CreationDate="2011-05-05T07:46:59.093" Score="4" ViewCount="" Body="&lt;p&gt;This may be somewhat tangential to what you are asking. But it sounds like you are thinking about setting up your own business?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My advice is to forget about government approvals, writing business plans, printed letterheads and all that. Get your prototype into the hands of users, find people that are need your product, that are enthusiastic about it and who is willing to pay you money for it. Until you have something that people are willing to pay you real money for, you don't have a product.&#xA;Yes, the typical big customer requires approvals, documentation, independent testing, steaks&amp;amp;strippers, etc. etc. etc. You can spend a year or two getting that done, but in the end they won't buy from you anyway. You are a small player. Big Dumb Corporations buy from other Big Dumb Corporations, period.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have to do the one thing that most engineers hate intensely, and that is getting out of the house and find potential customers. If you don't, your business will go nowhere. Long to-do lists are a trap, a comfortable excuse. Worry about the approvals and all that &lt;em&gt;after&lt;/em&gt; you have a product that people are willing to fork over real money for.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastActivityDate="2011-05-05T07:46:59.093" />
  <row Id="13905" PostTypeId="1" AcceptedAnswerId="13909" CreationDate="2011-05-05T08:24:56.780" Score="3" ViewCount="141" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;for my exam i need to calculate the apparent power, active power and reactive power.&#xA;I know i get the active power from the real part and reactive power from imaginary part of the apparent power. But i can't find any formulas for my specific problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have \$ U = 82.58 e^{j31.89°} \$ and \$ I = 1.65 e^{j31.89°} \$ &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The formula i found is \$ S = \frac{1}{2} UI^* \$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But it starts with the problem that i don't know how to get from for example \$68e^{j30°}\$ to something like \$68.19 - j42.45\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Used Euler.&#xA;But know i don't get the correct solution.&lt;br&gt;&#xA;I have \$S= 0.5* 82.58 e^{j31.89°} 1.65 e^{j31.89°}\$&lt;br&gt;&#xA;That would be \$S=68.13cos(63.78)+j68.13sin(63.78)\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tried to conjugate &quot;I&quot; like that: \$I=1.65 e^{-j31.89°}\$&lt;br&gt;&#xA;But then \$\Phi = 0\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But the solution is \$S=68.19 - j42.45\$&lt;/p&gt;&#xA;" OwnerUserId="3817" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T03:00:04.587" LastActivityDate="2011-06-02T15:04:16.063" Title="How to calculate apparent power?" Tags="&lt;power&gt;&lt;homework&gt;" AnswerCount="3" CommentCount="0" />
  <row Id="13906" PostTypeId="2" ParentId="13905" CreationDate="2011-05-05T08:27:42.253" Score="4" ViewCount="" Body="&lt;p&gt;Euler's Formula: \$ e^{j  \theta} = cos(\theta) + j * sin(\theta) \$  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Euler helps you to separate the complex power of \$e\$ into its real and imaginary parts. These agree with your active and reactive power resp.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-06-02T15:04:16.063" LastActivityDate="2011-06-02T15:04:16.063" CommentCount="4" />
  <row Id="13908" PostTypeId="2" ParentId="13905" CreationDate="2011-05-05T09:19:54.587" Score="3" ViewCount="" Body="&lt;p&gt;It's easier to multiply complex numbers in polar form, so find your UI* product that way. The conjugate in polar form is easy too, just negate the angle. Apply Euler's formula at the end to separate out real and imaginary components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The relation between polar and rectangular forms can be illustrated like so:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/hXJ0E.png&quot; alt=&quot;relation of polar and rectangular coordinates&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-05-06T01:02:47.517" LastActivityDate="2011-05-06T01:02:47.517" CommentCount="9" />
  <row Id="13909" PostTypeId="2" ParentId="13905" CreationDate="2011-05-05T09:20:18.370" Score="7" ViewCount="" Body="&lt;p&gt;Use these identities :-&lt;br /&gt;&lt;br /&gt;&#xA;\$z = R.e^{j\theta}\$&lt;br /&gt;&#xA;\$Re(z) = R\cos(\theta) = a\$&lt;br /&gt;&#xA;\$Im(z) = R\sin(\theta) = b\$&lt;br /&gt;&#xA;\$z = a + jb\$&lt;br /&gt;&#xA;\$R = |z| = \sqrt{a^2 + b^2}\$&lt;br /&gt;&#xA;\$\theta = Arg(z) = \arctan(\frac{b}{a})\$&lt;br /&gt;&lt;br /&gt;&#xA;For example:&lt;br /&gt; \$56.e^{j40} = 56\cos(40) + 56j\sin(40) = 42.9 + 36.0j\$&lt;br /&gt;&#xA;\$75 - j22 = \sqrt{75^2 + 22^2}.e^\arctan(\frac{-22}{75}) = 78.16.e^{-16.3j}\$&lt;/p&gt;&#xA;" OwnerUserId="2234" LastEditorUserId="2234" LastEditorDisplayName="" LastEditDate="2011-06-02T12:07:34.100" LastActivityDate="2011-06-02T12:07:34.100" CommentCount="10" />
  <row Id="13910" PostTypeId="1" AcceptedAnswerId="13911" CreationDate="2011-05-05T09:24:17.970" Score="3" ViewCount="118" Body="&lt;p&gt;What's the easiest way to regulate a 12 V battery to a regulated 12 V power source?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Preferably, I'd like a ready-made product so that I could avoid having to show my lack of skill with the soldering iron. :-) More complex answers are fine, too, as long as they are insightful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking of powering a 12 V / 600 mA stage piano/synth by replacing its AC/DC converter with a small car battery for portable use. Because the device is not designed for in-car use, I understand that regulation is the safest bet. (Of course, I could buy an inverter, but I'd like to &quot;do it right&quot; and get rid of the DC/AC AC/DC conversion.)&lt;/p&gt;&#xA;" OwnerUserId="4122" LastActivityDate="2011-05-05T19:51:58.243" Title="Easiest way to regulate a 12 V battery to regulated 12 V?" Tags="&lt;power-supply&gt;&lt;voltage-regulator&gt;&lt;beginner&gt;" AnswerCount="5" CommentCount="4" />
  <row Id="13911" PostTypeId="2" ParentId="13910" CreationDate="2011-05-05T09:34:31.943" Score="5" ViewCount="" Body="&lt;p&gt;What a regulator actually does is to smooth out variations in voltage to make a source look more like a battery. In a case like this, you don't have to worry about the source voltage changing much, so the main advantage of regulation is moot. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Often equipment that's designed for low-voltage DC will actually accept a range of voltages. Sometimes it isn't, and really does expect a regulated supply. The problem here is, what's the range that the synth will find acceptable? Admittedly, applying regulation solves &lt;em&gt;that&lt;/em&gt; problem by nailing the voltage down to something that's supposed to work, but the thing is, voltage regulation gets complicated when the source and the output voltages are closer than about 2 volts, because regulators need some headroom to work with. Automotive batteries nominally sit around 13.8V; worryingly high if your device wants a regulated 12V input, annoyingly low if you want to regulate it to 12V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can measure the voltage from your present AC/DC converter, &lt;em&gt;while it's connected to the synth, with the synth turned on&lt;/em&gt;, and that voltage is with say, half a volt of the battery's open-circuit voltage, you would probably be able to directly connect the battery, without a regulator. &lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-05-05T09:43:42.983" LastActivityDate="2011-05-05T09:43:42.983" CommentCount="1" />
  <row Id="13912" PostTypeId="1" AcceptedAnswerId="14597" CreationDate="2011-05-05T13:36:23.327" Score="1" ViewCount="119" Body="&lt;p&gt;What is the reverse recovery time in diode?&lt;/p&gt;&#xA;" OwnerUserId="3916" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-05T13:46:23.700" LastActivityDate="2011-05-23T20:20:21.740" Title="What is the reverse recovery time in diode?" Tags="&lt;diode&gt;" AnswerCount="1" CommentCount="11" FavoriteCount="1" />
  <row Id="13913" PostTypeId="1" AcceptedAnswerId="13915" CreationDate="2011-05-05T13:55:14.180" Score="6" ViewCount="188" Body="&lt;p&gt;When shopping for components it's common to find a lead-free or RoHS-compliant version of the part along side one that is not. Under what circumstances does it matter that I chose exclusively lead-free or RoHS (or whatever other lead-free designation is out there) parts? What would motivate me to pick a lead-free part over a cheaper non-lead free part?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On a side note, some explanation of what all this lead-free business is about would be interesting to me.&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-05-11T08:43:43.713" Title="When Does Lead-Free Matter?" Tags="&lt;manufacturing&gt;&lt;rohs&gt;&lt;lead-free&gt;" AnswerCount="4" CommentCount="6" />
  <row Id="13914" PostTypeId="2" ParentId="13913" CreationDate="2011-05-05T14:09:35.653" Score="4" ViewCount="" Body="&lt;p&gt;RoHS (Restriction of Hazardous Substances Directive) covers a number of hazardous substances, not just lead. Google RoHS for a list.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can not sell an electronic product in Europe if it contains any of the listed toxins. It seems likely that other parts of the world will follow suit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main challenge with RoHS is that you can not use solder that contains lead. Lead-free solder has a higher melting point and is generally a bit more tricky to work with. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the bright side, you are less likely to cause lead poisoning to yourself or anyone else manufacturing or recycling your product :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;hr&gt;&#xA;EDIT: The general idea is that these toxins tend to concentrate in places like landfills. Sooner or later this stuff returns to bite you through fires, leaks etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The RoHS directive is not an absolute ban, it specifies the max concentration. You can for example have 0.1% lead in your product. Industrial products may not require RoHS compliance, you can for example use NiCd batteries in medical equipment even if it is banned for consumer use. But the batteries have to be brought in to recycling stations after use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an individual you are welcome to lick lead all day long or to import non-compliant products for your own use. You can use solder containing lead as long as you don't sell what you make.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastEditorUserId="3876" LastEditorDisplayName="" LastEditDate="2011-05-05T15:55:40.923" LastActivityDate="2011-05-05T15:55:40.923" CommentCount="4" />
  <row Id="13915" PostTypeId="2" ParentId="13913" CreationDate="2011-05-05T14:20:24.280" Score="6" ViewCount="" Body="&lt;p&gt;Aside from the RoHS stuff mentioned, in our lab we use lead free solder for high temperature circuit work, we tend to operate diodes and JFETs up to around 450degC and we've found leaded solder can't take the heat. Of course without the lead the solder is harder to work with but the result is that we can test circuits at high temperature without having to make mechanical joins between components, which is the alternative.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh, and although you can't use leaded solder in Europe for commercial products you can in military stuff - I think the theory is that military people don't tend to lick circuit boards but there is always the risk that a toddler will in consumer stuff :-)&lt;/p&gt;&#xA;" OwnerUserId="4096" LastEditorUserId="4096" LastEditorDisplayName="" LastEditDate="2011-05-11T08:43:43.713" LastActivityDate="2011-05-11T08:43:43.713" CommentCount="5" />
  <row Id="13916" PostTypeId="2" ParentId="13297" CreationDate="2011-05-05T14:35:25.547" Score="3" ViewCount="" Body="&lt;p&gt;I've noticed the same problem when routing boards with the FTDI FT232 chips. Here's what the CY7C68013A datasheet says about routing those signals:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;em&gt;DPLUS and DMINUS trace lengths should be kept to within &#xA;2 mm of each other in length, with preferred length of 20 to &#xA;30 mm.&lt;/em&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;Maintain a solid ground plane under the DPLUS and DMINUS &#xA;traces. Do not allow the plane to split under these traces.&lt;/em&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;Do not place vias on the DPLUS or DMINUS trace routing.&lt;/em&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;em&gt;Isolate the DPLUS and DMINUS traces from all other signal &#xA;traces by no less than 10 mm.&lt;/em&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I would suggest the zig-zag method, but only if it that little detour around the pin added more than 2 mm to the trace length.&lt;/p&gt;&#xA;" OwnerUserId="2827" LastEditorUserId="2827" LastEditorDisplayName="" LastEditDate="2011-05-08T20:50:41.820" LastActivityDate="2011-05-08T20:50:41.820" CommentCount="2" />
  <row Id="13917" PostTypeId="2" ParentId="13825" CreationDate="2011-05-05T14:35:53.537" Score="3" ViewCount="" Body="&lt;p&gt;802.11x is significantly more complicated than Zigbee, and the TCP/IP stack you need to make it work on top of all that is similarly complex.  If you purchase something like the &lt;a href=&quot;http://www.lantronix.com/device-networking/embedded-device-servers/wiport.html&quot; rel=&quot;nofollow&quot;&gt;Lantronix WiPort&lt;/a&gt; or &lt;a href=&quot;http://www.digi.com/products/wireless-wired-embedded-solutions/solutions-on-module/digi-connect/digiconnectwime.jsp#overview&quot; rel=&quot;nofollow&quot;&gt;Digi Connect WiMe&lt;/a&gt; to make 802.11x networking as easy as communicating over a serial port, you're paying for a lot of stuff (there's a whole ARM based server in those modules!) that you don't need if you're willing to do a lot of RF hardware design and software integration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're interested in taking that path, you should get some background understanding of the IEEE 802.11x network architecture.  This is one of just a couple IEEE standards available for free through the &lt;a href=&quot;http://standards.ieee.org/about/get/&quot; rel=&quot;nofollow&quot;&gt;IEEE-Get&lt;/a&gt; program. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you've got an overview of the networking system, look up the &lt;a href=&quot;http://para.maxim-ic.com/en/search.mvp?fam=wlan_tcr&amp;amp;tree=master&quot; rel=&quot;nofollow&quot;&gt;Maxim MAX283X&lt;/a&gt; line of transcievers.   From the datasheet, &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The fully integrated transceivers&#xA;  include a receive path, transmit path,&#xA;  voltage-controlled oscillator (VCO),&#xA;  sigma-delta fractional-N synthesizer,&#xA;  crystal oscillator, RSSI, PA power&#xA;  detector (MAX2831), temperature&#xA;  sensor, Rx and Tx I/Q error-detection&#xA;  circuitry, basebandcontrol interface&#xA;  and linear power amplifier (MAX2831).&#xA;  The only additional components&#xA;  required to implement a complete radio&#xA;  front-end solution are a crystal, a&#xA;  pair of baluns, a BPF, a switch, and a&#xA;  small number of passive components&#xA;  (RCs, no inductors required).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That's about as close as you'll get to a generic 2.4GHz transceiver that can be sanely integrated into an 802.11x network.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They cost about $5 in small quatities at the moment. As you requested, these chips only implement the PHY layer of the protocol.  You still need to handle the data link layer (MAC and LLC), network layer, and transport layer on top of that before you can begin communicating at the application layer level.  &lt;/p&gt;&#xA;" OwnerUserId="857" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:59:10.297" LastActivityDate="2011-06-02T02:59:10.297" CommentCount="1" />
  <row Id="13918" PostTypeId="2" ParentId="13825" CreationDate="2011-05-05T14:37:28.197" Score="2" ViewCount="" Body="&lt;p&gt;Well, since no one else came forward with an answer, I'll give it a shot.  (Hey, someone else came forward! :(  )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main problem with the question is that you don't say what exactly you want to do with WiFi.  You use the word &quot;transceiver&quot;, but I've learned that people use that term somewhat generically.  Thus, forgive me if the rest of the answer isn't quite what you were looking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To directly answer your question (paraphrased), &quot;Can the Microchip MRF24J40 be made to do IEEE 802.11a/b/n?&quot;, the answer is no.  It's made to do IEEE 802.15.4, or Zigbee, and cannot be forced through software or hardware to do WiFi.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But to address the bigger issue:  Unless you're an expert in 802.11 there is little or no chance that you'll be able to use generic chips and make it do 802.11.  The RF modulation and software protocols alone are quite challenging-- enough for people to make just that into a career.  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-05T14:37:28.197" CommentCount="1" />
  <row Id="13919" PostTypeId="2" ParentId="13913" CreationDate="2011-05-05T14:37:41.503" Score="-1" ViewCount="" Body="&lt;p&gt;These are the substances prohibited by the RoHS legislation (copied from the UK Government leaflet):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;RoHS restricts the use of mercury, lead, hexavalent chromium, cadmium and a range of flame retardants notably polybrominated biphenyls and polybrominated diphenyl ethers.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-05T14:37:41.503" CommentCount="1" />
  <row Id="13920" PostTypeId="2" ParentId="13913" CreationDate="2011-05-05T15:37:58.123" Score="1" ViewCount="" Body="&lt;p&gt;As others have already pointed out, RoHS requirements generally forbids the use of components with hazardous materials (with some exceptions made for batteries and other specialty components where alternatives do not exist). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;As a manufacturer of your product, you'll need to certify your product is RoHS compliant (amongst many other regulatory and industry requirements like emissions, safety, recyclability) in order to satisfy your customers and (in increasing number of markets) to be legally sold.  Because of this, the entire &quot;supply chain&quot; from the components, to the printed circuit board, to the board assembly (i.e. soldering) will need to be documented as being RoHS.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not being &quot;RoHS&quot; doesn't necessarily mean that the item contains a hazardous substance.  Sometimes, the products are given the RoHS designation to confirm their process compatibility with no-lead manufacturing.  Because lead-free solder has a higher melting point, the components must also withstand higher temperatures during board assembly.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-05T15:37:58.123" CommentCount="4" />
  <row Id="13921" PostTypeId="2" ParentId="9641" CreationDate="2011-05-05T15:39:27.763" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.mikmo.dk/gobetwino.html&quot; rel=&quot;nofollow&quot;&gt;gobetwino&lt;/a&gt; is software for the PC that responds to various serial requests from the Arduino such as &quot;open file on the PC&quot;, &quot;open internet web file&quot; etc&lt;/p&gt;&#xA;" OwnerUserId="4119" LastActivityDate="2011-05-05T15:39:27.763" />
  <row Id="13922" PostTypeId="2" ParentId="7744" CreationDate="2011-05-05T15:41:25.020" Score="3" ViewCount="" Body="&lt;p&gt;If you want to charge a cap in a very simple manner you can just run the piezo output into a rectifier (or doubler if you want the extra voltage and don't mind the reduced charge rate) and then connect the DC output straight across a capacitor. As the piezo vibrates you will see the voltage on the cap slowly increase - if you have a high enough input impedance volt meter that is - there are some good papers by Ferrari et al that cover the basics. Shad Roundy's PhD thesis also covered this rather well I think but it is a trifle long.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to get really fancy with the inductance you could look into a technique called SSHI (synchronized switch harvesting on inductor) the maths is heinous but it is clever.&lt;/p&gt;&#xA;" OwnerUserId="4096" LastActivityDate="2011-05-05T15:41:25.020" CommentCount="4" />
  <row Id="13923" PostTypeId="2" ParentId="13910" CreationDate="2011-05-05T15:45:13.550" Score="0" ViewCount="" Body="&lt;p&gt;I've done it often in the past (and precisely with some synthesizer) without any problem.&#xA;A fully charged 12V car battery measures about 13V, and with that voltage I've never damaged anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also used 6V Lead batteries to replace 6V supply of my old Atari Lynx&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-05-05T15:45:13.550" />
  <row Id="13924" PostTypeId="1" AcceptedAnswerId="13927" CreationDate="2011-05-05T15:52:49.957" Score="1" ViewCount="159" Body="&lt;p&gt;After reading &lt;a href=&quot;http://skeptics.stackexchange.com/q/2849/43&quot;&gt;this question about ultra-expensive audio cables&lt;/a&gt;, I was reminded of a product that we sold at a company I used to work for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.mitcables.com/&quot; rel=&quot;nofollow&quot;&gt;MIT Cables&lt;/a&gt; makes these &quot;audio interfaces&quot; which go a step beyond mere audio cables, adding little electronic circuits that are claimed to transform (for lack of a better word) the audio signal. Primarily, &quot;&lt;a href=&quot;http://www.mitcables.com/reference-library/multipole-technology.html&quot; rel=&quot;nofollow&quot;&gt;Multipole&lt;/a&gt;&quot; technology.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any truth behind these claims whatsoever?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I'm looking for either a debunking or validation of the claims, from an electrical and audio stance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Related question: &lt;a href=&quot;http://electronics.stackexchange.com/q/9671/2028&quot;&gt;Whats the best cable to transfer audio signal?&lt;/a&gt;)&lt;/p&gt;&#xA;" OwnerUserId="2028" LastEditorUserId="2028" LastEditorDisplayName="" LastEditDate="2011-05-05T16:13:23.317" LastActivityDate="2011-06-02T02:58:44.557" Title="Any truth behind &quot;multipole&quot; technology in audio signal transmission?" Tags="&lt;audio&gt;&lt;cables&gt;&lt;speakers&gt;" AnswerCount="4" CommentCount="9" />
  <row Id="13925" PostTypeId="2" ParentId="13924" CreationDate="2011-05-05T16:18:23.897" Score="2" ViewCount="" Body="&lt;p&gt;Does it have some truth? Eh, well maybe. It is true that audio will sound different based off of the response of the channel that the signal travels through. However, I doubt that the effective inductances and capacitances that the wires have are truly noticeable to the human ear (if even seen by scopes).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It could be that they have actually placed some passive filters on the ends of the cable in order to produce a better sound. But, if you are willing to pay for higher quality cables, you probably have already paid for higher quality electronics. More then likely the electronics you are using already have methods to tune the response (EQ), this will have more of an effect then the cables can have.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-05-05T16:26:31.377" LastActivityDate="2011-05-05T16:26:31.377" CommentCount="1" />
  <row Id="13926" PostTypeId="2" ParentId="13924" CreationDate="2011-05-05T16:18:38.780" Score="4" ViewCount="" Body="&lt;p&gt;This is hogwash, and belongs in the same (fairy) realm as oxygen free copper cables (OFC, strange that I haven't seen questions about this). What you do is &lt;em&gt;impression management&lt;/em&gt;: you tell a story which the average user doesn't understand but accepts because it sounds scientific. The hole in the theory here is that this capacitance/inductance matching occurs for just 1 frequency, while it should work for for (at least a subband of) the audio range.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The wavelength of audio signals is (for 100kHz) 3000m. Transmission line effects show as a rule of thumb from 1/10 this distance, or 300m. Below this length the important parameter is resistance. As low as possible. That's it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In double-blind listening tests for OFC test persons can't tell any difference in sound quality. I'm sure the results for these tests on the &quot;Multipole&quot; cables would be the same.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-05T16:18:38.780" CommentCount="2" />
  <row Id="13927" PostTypeId="2" ParentId="13924" CreationDate="2011-05-05T16:20:59.510" Score="12" ViewCount="" Body="&lt;p&gt;First, let me give you a little background on myself, so you can &quot;know the source&quot;...  I'm a Sr. Electrical Engineer working in the Professional Audio field. I design high end pro-audio equipment.  You've heard my stuff, as it's been used all over.  I have also designed stuff for a small &quot;audiophile&quot; company.  I'd also call myself a Skeptic, and a practical person.  My pet peeve is worthless pieces of expensive audiophile junk.  That being said:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are two ways to approach this:  Does it work? and Is it worth it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does it work:  Yes!  Um, no.  Well, maybe.  It depends on what you define as &quot;work&quot;.  If you define &quot;work&quot; as &quot;can it, in theory, make a positive difference when compared to normal speaker cable&quot; then it does work.  But if you define work as &quot;makes a positive difference that an expensive piece of gear can measure, or that can be determined by multiple listeners in a double-blind test&quot; then the answer is no.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it worth it:  These things cost US $8500 and make such a small improvement that no one can really hear it (or can prove that they hear it).  A good pair of practical speaker cables will cost about $30.  For the $8470 price difference, what could you buy that would make more of a difference in your life/happiness?  A vacation to a remote tropical island?  A semester in a University?  The ultimate man-cave?  With these speaker cables all you get is bragging rights that you can blow lots of money.  Get spinners for your car, they'll attract more attention that speaker cables.  So, um, no.  They aren't worth it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://consumerist.com/2008/03/do-coat-hangers-sound-as-good-monster-cables.html&quot; rel=&quot;nofollow&quot;&gt;Here's an interesting article&lt;/a&gt; about comparing expensive Monster speaker cables to a wire coat hanger.  Spoiler:  The coat hangers work quite well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The ideal speaker cable is short-ish, reasonably large (but not absurdly large) gauge, and set up as a twisted pair.  Nothing else really matters.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:58:44.557" LastActivityDate="2011-06-02T02:58:44.557" CommentCount="11" />
  <row Id="13928" PostTypeId="1" CreationDate="2011-05-05T16:22:11.040" Score="-1" ViewCount="79" Body="&lt;p&gt;I'm thinking about putting together as a pet project a keyboard with e-ink keys. So I will need tens of ~1cm e-ink displays, and (preferably significantly fewer) display controllers :D&lt;/p&gt;&#xA;&#xA;&lt;p&gt;any ideas how to go about this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;strong&gt;edit to be a &quot;good shopping-type question&quot;&lt;/strong&gt;: what are the cheapest possible 1cm e-ink displays I can get from a supply store?.. even at $10 a pop, that's a grand for a pet project and basically a non-starter. what are the cheapest and smallest display controllers I can get? are there alternatives to one-to-one controllers (ie, any way to mate many e-ink displays to a single controller)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;strong&gt;edit #2&lt;/strong&gt; sample: &lt;a href=&quot;http://www.avesodisplays.com/products/custom_displays.html&quot; rel=&quot;nofollow&quot;&gt;http://www.avesodisplays.com/products/custom_displays.html&lt;/a&gt; Aveso custom displays are immutable, but otherwise quite in keeping with the design specifications (thin, tiny, cheap -- in fact disposable). But as they are not general pixel-based displays they are not suitable for general display applications. I would like to be able to show any Unicode character, so I am going to need a general-purpose pixel display.&lt;/p&gt;&#xA;" OwnerUserId="4125" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-05T18:53:12.633" LastActivityDate="2011-05-05T18:53:12.633" ClosedDate="2011-05-05T18:10:24.107" Title="where can I find dirt cheap, tiny, eink displays and controllers" Tags="&lt;e-ink&gt;&lt;shopping&gt;" CommentCount="9" />
  <row Id="13929" PostTypeId="2" ParentId="13910" CreationDate="2011-05-05T16:48:58.017" Score="2" ViewCount="" Body="&lt;p&gt;Many musical keyboards don't particularly care about exactly what voltage they get, because they have internal regulation.  Unfortunately, devices rarely specify the exact range of voltages they'll tolerate, in some measure because few wall bricks specify the exact range of voltages they might put out.  A keyboard which nominally accepts 9-12 volts may be perfectly happy with anything from 6 to 15, especially if the voltage only goes up to 15 at times when the synth's current draw happens to be minimal, but if the manufacturer labeled the unit as accepting 6-15, someone might expect it to work with a so-called 15-volt wall brick that actually puts out 18.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many devices with a 12-volt nominal input would be perfectly happy if driven directly by a car battery that was not connected a charger (or worse, something like a starter motor--starting a car can cause its +12 rail to swing up and down by dozens of volts).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-05T16:48:58.017" />
  <row Id="13930" PostTypeId="2" ParentId="13924" CreationDate="2011-05-05T17:31:41.347" Score="7" ViewCount="" Body="&lt;p&gt;Ah, Multipole Articulation - of course.  I think I'll for my next EE new grad job interview I'll ask him/her about Multipole Articulation and watch the confused, scared look on his/her face as he/she tries to decide whether that's a real thing or just something I made up. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the record, it's something that's entirely made up. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So let's digress a bit and talk about your stereo setup, you, and sound in general.&#xA;Sound is pressure waves traveling through the air (obviously).  When I say waves I mean like a sine wave - ups, downs, periods, frequencies etc.  Just about the only truly interesting thing about how people think about sound is that it doesn't 'look' like a sine wave looks - The perturbations in the don't travel 'up and down' like a sine wave looks, but instead 'back and forth' like a piston.  The 'up and down' waves are called 'transverse waves' and the 'back and forth' are 'longitudinal'.  Sound is a longitudinal wave.  Neat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But we don't listen to sine waves (unless you love Electronica, haha, I jest) - we listen to voices and instruments.  Well, luckily because of our good friend Fourier we know that all sound is a sum of many many sine waves.  Just a bunch of sine waves with different frequencies, different amplitudes and phases (but also note well: we can't hear phase unless some very particular canceling out is happening - like with noise canceling headphones).  So to have great reproduction of sound in a mathematical and engineering sense we need immaculate reproduction of sine waves.  The measure of how well a sine wave is reproduced is called total harmonic distortion.  If a sine wave is distorted it... looks funny.  Odd edges, flat tops, etc.  This introduces extra sine waves that weren't there originally and produces a sound that isn't the sound you're looking for.  It is undesirable.  THD (acronym for Total Harmonic Distortion) is generally considered good when it is much less than 1% (I think) &lt;em&gt;across all frequencies&lt;/em&gt;.  THD can vary for different frequencies, so watch out.  The only other bad thing that can happen to your sine wave is to have its amplitude changed - and in general it only gets lower.  This is called being attenuated.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So to accurately reproduce sound, don't attenuate your sine waves and don't introduce new frequencies that weren't there before. That's it - if you can accomplish this then you have the perfect stereo.  What kind of sine waves are we playing with when we listen to our stereo?  To answer that question we have to look at our ears and their limits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Humans can hear &lt;em&gt;in general&lt;/em&gt; sound within a range of frequency of 20Hz to 20KHz.  Now at the low end you can certainly &lt;em&gt;feel&lt;/em&gt; sound lower than 20Hz - if it's loud enough anyway - and some people can hear some sounds below 20Hz as well.  As a side note, let no one tell you you can 'hear' 0Hz.  0Hz is nothing - at best a constant pressure on your eardrums.  You might feel it but it's merely uncomfortable and not in any way enjoyable or a sound.  And yes, it's also true that some people can hear sounds higher than 20KHz - especially so if they're very loud and particularly when the person is younger rather than older.  Let me point out at this point that I seriously doubt the ability to hear high/low pitched sounds correlates to people who call themselves audiophiles (I'm betting the main correlation to people calling themselves audiophiles is the willingness to spend significant amounts of money on audio equipment).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So your cables connect your amplifier to the speakers - out of which you hear sound.  Ignoring the rest of the stereo system, how do cables introduce harmonic distortion and attenuation?  Let's find out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your cable is a wire.  Wires are electrical devices with real electrical values.  The ones we care about are resistance, inductance and capacitance.  As EEs know, R's, L's and C's form the basis of filters.  Filters attenuate sine waves and add phase (but remember we don't hear phase, so it doesn't matter), thus, your cable may attenuate your sine wave.  Bad cable!  To prevent this you generally need to lower the resistance.  The capacitance and inductance of your basic wire is typically negligible so don't worry.  We need a big honkin' thick cable to ensure our signal isn't attenuated.  Big cable like... power cord.  Yep, it can handle 15A, so it can handle speakers.  Done! No attenuation! success!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Right?  Maybe.  There are other effects.  Remember how I said there's capacitance in your cable?  Yep, it exists.  You know what else is basically a capacitor?  An antenna.  Yep, you cable will act like an antenna and pick up stray electrical signals.  Those stray electrical signals will cause harmonic distortion in your sine waves.  That's bad.  How can we stop this?  Actually it often doesn't matter if we stop it.  Antennas operate with electromagnetic waves which follow the equation speed of light = frequency * wavelength.  The wavelengths an antenna picks up are related to the length.  From &lt;a href=&quot;http://www.csgnetwork.com/antennagenericfreqlencalc.html&quot; rel=&quot;nofollow&quot;&gt;this site&lt;/a&gt; I can tell that to pick up 20KHz noise, the length of my cable would have to be about 12,000ft long.  It gets worse if you want to pick up noise with a lower frequency.  So you're not going to pick up anything harmful with that 20ft cable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But let's say you want to get rid of it anyway.  Fine.  Get shielded cable.  Shielded cable has a wire mesh around the conductor.  The mesh gets grounded at some point and makes it hard for stray EM fields to work their way into your cable.  This is how very expensive, highly engineered cables for very important applications are engineered, so it's overkill for a stereo setup, but hey, whatever.  You can still do this fairly cheap even if you go overboard and shield each conductor.  Still not made of gold, still not expensive, still no buzzwords.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what are these cables doing with all the talk about Articulated Multipole bullsh*t?  What they're saying is that they will sell you three different cables, each tuned to a different frequency range.  When you tune something you set the frequency response in a specific range.  Since the cable is passive &lt;em&gt;all it can do is attenuate the signal&lt;/em&gt;.  So they're selling you a cable that attenuates certain sine waves.  Isn't the goal to get all the sine waves through the cable without doing that kind of thing to them?  Yes! &lt;em&gt;I&lt;/em&gt; thought so anyhow.  The frequency response of your basic wire is flat up to 20KHz - it doesn't attenuate anything, it just passes everything without interference.  Isn't &lt;em&gt;that&lt;/em&gt; the desirable thing?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not for the people who want to sell you things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mean, it was bad enough that you can buy a lamp cord that does the job of their premium cables, but hey, they got some people to buy a set anyhow.  If only they could figure out a way to get people to buy more cables to do the same thing.  So they convince you that certain cables work better for certain frequency ranges.  Then instead of buying one ALL-PASS cable (ie, lamp cord) you'll buy THREE PREMIUM TUNED CABLES: one high-pass cable, one mid-pass and one low-pass.  Only $3995 each! Your ears will thank you! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But wait, doesn't it matter what the cable is made of?  No, material mainly affects resistance.  So as long as your resistance is okay it doesn't matter why.  Gold?  Sure, but copper is also very acceptable.  Don't waste your money - measure the resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wait! Don't I need to be concerned about the poles designed into my cable?  No!  Poles mean filters, filters mean ACTIVE components - op amps, power supplies, etc.  Are those in your cable?  No!  There's no room!  A cable is entirely passive and shouldn't include any filtering.  Filtering should be performed either in software or hardware in your amplifier.  Your cable is the wrong place to be doing it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll reiterate for everyone:  You want a big fat dumb cable - as fat and big and dumb as possible.  Luckily for you this also means &lt;em&gt;cheap&lt;/em&gt;!  Buy lamp cord at Radio Shack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem with 'audiophiles' and the raft of premium audio equipment is that they're not trying to accurately reproduce sine waves.  They talk about sounds being 'warm', 'bright', 'muddied' or 'veiled'.  They want bright sounds and such. This means they &lt;em&gt;want&lt;/em&gt; harmonic distortion and attenuation.  After all, they buy equalizers - an instrument whose only purpose is to modify the frequency response of their entire stereo system - because they don't want their music to sound like it was recorded but instead &lt;em&gt;how they like it&lt;/em&gt;.  And since you can't measure preference, audiophile companies can sell them anything by promising various adjectives.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's what's going on here.  Snake oil pure and simple. &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-05T17:31:41.347" CommentCount="3" />
  <row Id="13931" PostTypeId="1" AcceptedAnswerId="13936" CreationDate="2011-05-05T17:33:02.750" Score="1" ViewCount="61" Body="&lt;p&gt;When wiring speakers to a 100W consumer-grade amplifier, how do I select an appropriate gauge cable (for 8-ohm speakers)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, if 14 gauge cable is sufficient, what harm is there in using a heavier cable such as 12 or 10 (other than inconvenience and cost)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Related: &lt;a href=&quot;http://electronics.stackexchange.com/q/9671/2028&quot;&gt;Whats the best cable to transfer audio signal?&lt;/a&gt;&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Semi-related: &lt;a href=&quot;http://electronics.stackexchange.com/q/13924/2028&quot;&gt;Any truth behind &amp;quot;multipole&amp;quot; technology in audio signal transmission?&lt;/a&gt;&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2028" LastEditorUserId="2028" LastEditorDisplayName="" LastEditDate="2011-05-05T17:43:27.167" LastActivityDate="2011-05-05T18:04:12.073" Title="How to determine appropriate speaker cable gauge?" Tags="&lt;audio&gt;&lt;cables&gt;&lt;speakers&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="13932" PostTypeId="2" ParentId="13895" CreationDate="2011-05-05T17:38:32.663" Score="0" ViewCount="" Body="&lt;p&gt;The distance from a person's foot to their waist won't change much while they're walking (as opposed to, say, standing up from sitting).  Except when they bend their knee, their foot will always be about a leg's length away from their waist.  If you're using a distance sensor, it will need to be further from the leg's center of rotation (hip).  To look at it another way, the foot behind that you're stepping off of, and the foot ahead that you're stepping on to are about the same distance from your hip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To be totally mobile (without protruding booms to aid distance measurement, f/ex), you'll probably need angle sensors at each joint between your reference point (the person's CofG, f/ex) and the body part you want to locate.  Some joints will need 2 angles to describe them; the shoulder and wrist would need 3.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might use more sensors in different combinations to reduce ambiguities or improve accuracy, or to reduce the math if you're tracking the parts in real-time.  Eg., if I reach over my head, the distance from my waist to my hand has most of the position information, but distinguishing between my hand on either shoulder wouldn't be helped at all by its distance from a sensor in front or in back of my waist.&lt;/p&gt;&#xA;" OwnerUserId="3361" LastEditorUserId="3361" LastEditorDisplayName="" LastEditDate="2011-05-05T17:46:54.370" LastActivityDate="2011-05-05T17:46:54.370" />
  <row Id="13933" PostTypeId="2" ParentId="13931" CreationDate="2011-05-05T17:42:01.563" Score="2" ViewCount="" Body="&lt;p&gt;&lt;em&gt;Damping factor&lt;/em&gt; is the ratio of the impedance of the speakers over the output impedance of your amplifier, including cabling. For instance, for 8 Ohm speakers and an impedance of 0.1 Ohm you have a damping factor of 80.&lt;br&gt;&#xA;You want the damping factor as high as possible, and thus the resistance of your cable as low as possible. A bigger cable is better. It also helps to keep its length as short as possible.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-05T17:42:01.563" />
  <row Id="13934" PostTypeId="2" ParentId="13910" CreationDate="2011-05-05T17:52:17.903" Score="0" ViewCount="" Body="&lt;p&gt;If you do this with a single battery, you will probably be fine. But if you decide to move it to a car, you must be very careful of load dumps. If you are using your synth in your car and you turn the headlamps off while the alternator is running, the energy in the alternator doesn't go away instantly. Instead, it appears as a high voltage spike - in some cases as high as 60V! I'd &lt;em&gt;highly&lt;/em&gt; recommend a TVS and at least an LC filter to get rid of the noise which other systems in the car produce. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, don't forget an &quot;idiot diode&quot;, to stop you reversing the polarity. Many manufacturers omit input polarity protection diodes.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-05T17:52:17.903" />
  <row Id="13935" PostTypeId="1" CreationDate="2011-05-05T17:57:08.383" Score="2" ViewCount="153" Body="&lt;p&gt;When designing an ARM-based device that should display simple graphics on a color LCD, how should one best go about designing things to allow fast updates, preferably without being tied to a particular ARM or LCD vendor?  My current project uses a black-and-white display which can be driven lightning-fast by a the SPI port on a PIC (redrawing a complex display in 1/60 second).  It seems common color LCD displays have an SPI port, but even filling a 160x120 LCD with a solid color would take 30ms, and a 320x240 would take 120ms best-case (10MHz shift clock).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If one could spare the controller pins, parallel mode could be better, but I don't know of any family-independent means of hooking up the parallel interface without requiring three separate memory-store instructions for each pixel (one to set the data, one to set the clock output high, and one to clock it low).  Some ARM chips have memory-bus interfaces, but those often want to do things like multiplex address and data, or commit a lot of pins to outputting irrelevant address bits (the LCD would just need one address bit).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Looking at the ILI9320 by ILITEK, or the HD66789 by Renesas, one approach that would seem interesting would be to use a CPLD to convert SPI to parallel data, and include a mode which would output a pixel per bit.  Looking at the Renesas data sheet, it might be possible to get pixel-per-bit writes with minimal hardware (no CPLD required) by making all the parallel-port data bits track the serial-data pin, using serial mode for everything but pixel writes, and using the compare/mask functions so that either all-zeroes pixels would be transparent and all-ones pixels would set selected bits in GRAM, or all-ones pixels would be transparent and all-zeroes pixels would clear selected bits.  The &quot;features&quot; section of the IKITEK data sheet suggests that it has similar functionality, but the register maps don't seem to include the appropriate registers (most of the appropriate register addresses don't appear in the IKITEK, but one of them--register 4, is used for a different purpose).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming the code will mainly be showing solid-color text and graphics, the ideal approach would seem to be to use a CPLD to interface the ARM's SPI port to the display's parallel port, and allow the CPLD to be loaded with foreground/background colors.  This would be especially nice if one had a means of writing &quot;transparent&quot; pixels.  Given a font as a two-color bitmap, one could simply load the font data directly into the SPI port; this would allow font data to be shown at a rate of one pixel every two ARM clocks.  On the other hand, a CPLD sufficient to handle such a display-control task would cost about $2.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the best way to interface an ARM with a color LCD, if the objective is to mainly to show solid-color text or simple (e.g. 16-color or 64-color) graphics?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;b&gt;Edit&lt;/b&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've done many LCD display projects, with many types of LCDs, including character-mode LCDs, custom 3:1 multiplexed segment-based using my own drive method, black and white graphic LCDs with built-in controllers, and black-and-white LCDs for which I designed my own CPLD-based controller to interface with a microcontroller's general-purpose DMA (providing four-level grayscale even).  I pride myself on making displays zippy.  One of the graphic controllers was a bit of a dog that required about 1/10 second for a full screen refresh even when writing constant data, but most of my displays can render even a fairly complex image in under 1/50 second.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many of the projects I do are battery-powered, so current draw is an issue.  The DMA-based display controller I did worked nicely, but it was for a line-powered project.  I believe the only way to get reasonable current draw from a graphics LCD is to use a controller which combines the display buffer and the column drivers.  Sending lots of display between chips every frame would waste a lot of energy even on a single bit-per-pixel display; on a color display with sixteen bits per pixel, it would be far worse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've only started looking at color LCD data sheets; many displays seem to use a controller similar to the ILITEK ILI9320, though all of the data sheets I've found for controllers based on that general design have been marked &quot;preliminary&quot;.  Some like the ILITEK one claim to have masking and transparency features but don't list any registers for them; I don't know whether the real chips have such features but the &quot;preliminary&quot; data sheets neglected to include them, or whether they omitted the features but forgot to strike the mention of them.  If in practice all such chips have transparency features, it would seem reasonable to design for them; if not, not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would expect that for most projects a typical screen would consist of arbitrarily-placed text in moderate number of arbitrarily-sized solid-color fonts.  Fonts would most likely be stored as bit-per-pixel data.  Using a Cortex-M3, if I wanted to write the display with parallel data, the code's &quot;inner loop&quot; to write two pixels would probably end up something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;  rol r0,r0,#2 ; Get one bit in C, the other in N&#xA;  itcs&#xA;  strhcs r1,[r3,#DATA_OFS]      ; Write data&#xA;  strhcc r2,[r3,#DATA_OFS]      ; Write data&#xA;  strb   r4,[r3,#CLOCK_SET_OFS] ; Set clock high&#xA;  strb   r4,[r3,#CLOCK_CLR_OFS] ; Set clock low&#xA;  itmi&#xA;  strhmi r1,[r3,#DATA_OFS]      ; Write data&#xA;  strhpl r2,[r3,#DATA_OFS]      ; Write data&#xA;  strb   r4,[r3,#CLOCK_SET_OFS] ; Set clock high&#xA;  strb   r4,[r3,#CLOCK_CLR_OFS] ; Set clock low&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Not exactly the fastest thing in the world.  Eliminating the writes to the set/clear clock instructions would help.  My guess would be that there's no nice architecture-independent way to eliminate both clock writes, but there may be a pretty common way that would allow for eliminating one (e.g. many chips may have a counter/PWM that could be made to pulse an output briefly in response to a single memory store operation).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using the SPI port and adding hardware to clock one pixel per bit would greatly speed up display access.  If using a display without masking and transparency, the CPLD would have to include an address counter, and for each pixel either clock a word of pixel data or else a set-address command for the following pixel's position (for which it would need a counter).  By contrast, if a display had masking and transparency, all I would need to do would be to have the CPLD support a mode where after it had clocked in 16 bits, each additional bit would clock a word of data out to the display with the LSB tracking the SDI pin (it might not even be necessary to use a CPLD--just a few normal logic chips).  I would set the transparency color to the be color I want to write but with the LSB flipped.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't want to come up with a beautiful design that relies upon masking and transparency and then discover that the only displays with such features have a 30-week lead time.  On the other hand, if such displays are apt to be and remain widely available from many vendors, I don't want to let paranoia about availability drive me to use an inferior design.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-05-06T15:29:38.137" LastActivityDate="2011-06-05T15:52:00.020" Title="Efficient display of simple text/graphics on color LCD by ARM" Tags="&lt;arm&gt;&lt;lcd&gt;" AnswerCount="1" CommentCount="6" />
  <row Id="13936" PostTypeId="2" ParentId="13931" CreationDate="2011-05-05T18:04:12.073" Score="8" ViewCount="" Body="&lt;p&gt;The #1 issue with speaker cables is that they have a fixed resistance, and the speaker has a impedance that varies with frequency.  (Note:  you can almost use the terms resistance and impedance interchangeably in this context.)  When you combine the wires resistance with the speakers impedance you'll get, basically, a voltage divider.  The net effect of this is that the resistance of the wire will change the frequency response of the speaker.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a &lt;a href=&quot;http://www.qscaudio.com/products/speakers/acoustic_design/ad_s52/ads52_freq.htm&quot; rel=&quot;nofollow&quot;&gt;graph that shows the speaker impedance and frequency response&lt;/a&gt;.  Notice that the average impedance is 8 ohms, but really varies between 4 and 33 ohms.  Now, let's say that your wire has a resistance of 10 ohms (that's super high, but I'm illustrating a point).  At 500 Hz the speaker has a 5 ohm impedance.  This effectively makes a voltage divider that cuts the power going to the speaker by 5:15, or 1:3.  So if the amp is spitting out 100 watts, only 33 watts is making it to the speaker.  But at 2 KHz the speaker impedance is about 30 ohms.  That means that the voltage divider is more like 30:40, or 75 watts from the 100 watt amp output is making it to the speaker.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The end result of this is that the higher the resistance of the cable, the more the frequency response of the cable is going to be effected.  When you size the gauge of the cable to minimize this resistance, odds are that the cable is going to work fine for whatever current you actually need to move-- unless you're doing pro-audio and have several kilowatt amps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A really rough rule of thumb is that you want the cable resistance to be less than 10% of the nominal speaker impedance.  So for an 8 ohm speaker you'd want less than 0.8 ohms in the cable.  Of course, if you want to know for sure then you have to look up the impedance graph on the speaker and start calculating.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When this is all distilled down, you'll find that 16 gauge wire works for most home applications unless you have your amp a long way from the speakers (which you shouldn't do anyway).  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-05T18:04:12.073" CommentCount="2" />
  <row Id="13937" PostTypeId="1" AcceptedAnswerId="13952" CreationDate="2011-05-05T18:29:00.587" Score="3" ViewCount="190" Body="&lt;p&gt;I'm looking for an e-ink display (pixel-based) that is as cheap as humanly possible, and tiny, yet still a fully pixel-based display that can refresh within a hundred milliseconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;custom display&quot; products from Aveso are &lt;em&gt;almost&lt;/em&gt; what I am referring to. But they are immutable displays, ie, &lt;strong&gt;not&lt;/strong&gt; pixel based.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The displays must be very small — 1cm, and ideally they would work with a multi-head controller.&lt;/p&gt;&#xA;" OwnerUserId="4125" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-06T18:12:01.180" LastActivityDate="2011-05-06T18:12:01.180" Title="what are some dirt cheap, small e-ink displays?" Tags="&lt;e-ink&gt;" AnswerCount="1" CommentCount="7" FavoriteCount="1" />
  <row Id="13938" PostTypeId="1" AcceptedAnswerId="13943" CreationDate="2011-05-05T18:47:03.190" Score="3" ViewCount="83" Body="&lt;p&gt;I was told it was possible to get a negative voltage from a ring oscillator (that doesnt go negative), I was wondering how is that possible?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you in advance.&lt;/p&gt;&#xA;" OwnerUserId="2985" LastActivityDate="2011-05-05T19:46:16.593" Title="Negative Charge Pump with Ring Oscillator" Tags="&lt;oscillator&gt;&lt;negative&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13939" PostTypeId="1" CreationDate="2011-05-05T18:56:59.447" Score="3" ViewCount="125" Body="&lt;p&gt;The university I study at has a special elevators for masters, and masters have somthing like a coin that they can use the elevator. As I know it's an rfid tag and  it is a 125khz one. and have a 100 turn coil.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My masters know that I want to do that, and there is no problem with doing this. Its something like a university project. I know that the tags have a special serial, and I can find one of that tags serial by using a RFID reader. However the current tags are not writable. Can I do this project by using a microcontroller? If so how? Also one of my friends is a specialist can he help me?&lt;/p&gt;&#xA;" OwnerUserId="4127" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-05-07T12:29:44.330" LastActivityDate="2011-05-07T15:57:49.370" Title="coin shaped rfid tag " Tags="&lt;rfid&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="13940" PostTypeId="1" AcceptedAnswerId="13945" CreationDate="2011-05-05T19:17:16.710" Score="1" ViewCount="76" Body="&lt;p&gt;I recently bought a car with an iPod dock. When I plug in the iPod disables and I am forced to control it with the car's audio controls. I want to get around this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I simply yank pin 21 from an Dock Connector cable to disable the car's control of the iPod?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reference: &lt;a href=&quot;http://pinouts.ru/PortableDevices/ipod_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;http://pinouts.ru/PortableDevices/ipod_pinout.shtml&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4128" LastActivityDate="2011-05-06T13:28:48.727" Title="iPod connector car control" Tags="&lt;audio&gt;&lt;wiring&gt;&lt;car&gt;&lt;ipod&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="13941" PostTypeId="2" ParentId="13865" CreationDate="2011-05-05T19:34:05.097" Score="1" ViewCount="" Body="&lt;p&gt;Consider an adjustable dual-power supply such as this &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/tps55386.pdf&quot; rel=&quot;nofollow&quot;&gt;3-A one from TI&lt;/a&gt;. Its &lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/tps55386evm-363.html&quot; rel=&quot;nofollow&quot;&gt;eval board&lt;/a&gt; is US$25.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-05-05T19:34:05.097" />
  <row Id="13942" PostTypeId="2" ParentId="13939" CreationDate="2011-05-05T19:34:26.240" Score="5" ViewCount="" Body="&lt;p&gt;Won't help - RFID tags all have a unique number on them.  And when I say unique I mean 64 bits unique, maybe more.  This is 'more atoms than the universe has' unique.  They keep a list of the people who are allowed to use the elevator and know what numbers they have.  So if your tag hasn't been entered into the system you can't use it.  Unless you could get your hands on one of the 'masters' tags and copy the number.  But if you can do that just use that tag.  Theft, sure, but you're already asking how to elegantly trespass so I'd assume you're okay with theft?&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-05T19:34:26.240" CommentCount="3" />
  <row Id="13943" PostTypeId="2" ParentId="13938" CreationDate="2011-05-05T19:46:16.593" Score="4" ViewCount="" Body="&lt;p&gt;Have a look at this charge pump circuit using a 555 that produces a negative voltage:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.eleccircuit.com/wp-content/uploads/2007/09/nagative-voltage-generation-using-555-timer.gif&quot; rel=&quot;nofollow&quot;&gt;http://www.eleccircuit.com/wp-content/uploads/2007/09/nagative-voltage-generation-using-555-timer.gif&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In principle, the square wave oscillator doesn't have to be a 555 timer, it could be a ring oscillator using inverters as you propose.  In practice, using 4000 series CMOS logic for example, the negative output voltage produced would not be able to provide a great deal of current due to the current sourcing limitations of the IC.  If the amount of current required from the negative output created is small, maybe half a mA depending upon the supply voltage, I don't see why using CMOS inverters for the oscillator wouldn't work.&lt;/p&gt;&#xA;" OwnerUserId="4129" LastActivityDate="2011-05-05T19:46:16.593" CommentCount="2" />
  <row Id="13944" PostTypeId="2" ParentId="13910" CreationDate="2011-05-05T19:51:58.243" Score="1" ViewCount="" Body="&lt;p&gt;How about &lt;a href=&quot;http://www.powerstream.com/DC-UPS-1212.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; from PowerStream? It's 12 V to 12 V for a UPS when used with an external battery. 3A, ready-made, rugged.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-05-05T19:51:58.243" />
  <row Id="13945" PostTypeId="2" ParentId="13940" CreationDate="2011-05-05T19:59:04.147" Score="2" ViewCount="" Body="&lt;p&gt;The iPod normally uses USB, Firewire, or serial when talking to other devices, like your car.  Pin 21 is used by the iPod to detect what it's plugged into, not by the car to detect when the iPod is connected.  We simply don't know what will happen when Pin 21 is disconnected, but I'll make an educated guess and say that it won't make a bit of difference.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Odds are that your car uses the USB port to talk with your iPod, and detect that the iPod is present.  If you disable the USB port (by clipping the wires, for example) the car won't detect that the iPod is present, and thus not enable the iPod as a valid audio input.  In short, it probably won't work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used to have a car with an iPod dock.  When connected, the iPod controls were disabled, like yours, and the car's controls were absolutely terrible to the point of being unusable.  So I feel your pain.  Now, I won't ever buy a car or car stereo with a device specific MP3 player connection-- just a standard &quot;AUX In&quot; for me.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-05T19:59:04.147" CommentCount="2" />
  <row Id="13946" PostTypeId="2" ParentId="13935" CreationDate="2011-05-05T20:01:38.787" Score="0" ViewCount="" Body="&lt;p&gt;The problem with using a microcontroller to drive an LCD is that an LCD requires constant attention.  This can be mitigated with a CPLD driven over SPI (using DMA, of course), but then you run into the other problem: Color LCDs require a &lt;em&gt;lot&lt;/em&gt; of data.  320x240 in black and white is marginal at 9.6KB, but make it 24 bit color and suddenly you need to deliver 230KB of data in 1/60th of a second.  (Don't forget, though, that you can get 4-bit, 16-color control just by tieing the low 20 bits to one setting). A 24-bit frame buffer no longer fits in onboard RAM on most microcontrollers, and you probably don't have time to read from an external RAM chip, clock the data out, and still do other processing.  Trying to do this with a CPLD (or an FPGA) and a RAM chip gets you well over the $2 price that caused you to balk in your question. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The traditional solution to interfacing a microcontroller with a color LCD is a display controller like an SSD1963.  Here's a very simple block diagram:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/ijZ46.png&quot; alt=&quot;MCU to RAM buffer and registers, and thence to LCD interface&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Parallel input to a big RAM frame buffer (Translation: More than $2) interfaced with a register-configurable parallel LCD interface. The parallel input is usually compatible with a memory bus interface.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The color LCD market is not always easy to find on the web, usually being the domain of OEMs only, with the rest buying displays from companies who integrate the controller with the display.  The best resource I've found has been Crystal Fontz, specifically &lt;a href=&quot;http://www.crystalfontz.com/products/graphic_lcd_and_oled_displays.html&quot; rel=&quot;nofollow&quot;&gt;this page on choosing graphic LCDs&lt;/a&gt;.  Scroll to the bottom for the controllers, which include the following options (note: Not all are color controllers):&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Epson S1D13521B01 E Ink Broadsheet (1 module)&lt;/li&gt;&#xA;&lt;li&gt;Epson S1D13700 (11 modules)&lt;/li&gt;&#xA;&lt;li&gt;Epson SED1520 Compatible (8 modules)&lt;/li&gt;&#xA;&lt;li&gt;Himax HX8345 Compatible (1 module)&lt;/li&gt;&#xA;&lt;li&gt;ILITek ILI9325 Compatible (3 modules)&lt;/li&gt;&#xA;&lt;li&gt;KS0107/KS0108 Compatible (26 modules)&lt;/li&gt;&#xA;&lt;li&gt;Novatek NT7534 (14 modules)&lt;/li&gt;&#xA;&lt;li&gt;Orise Technology OTM2201A (1 module)&lt;/li&gt;&#xA;&lt;li&gt;Orise Technology SPFD5420A (1 module)&lt;/li&gt;&#xA;&lt;li&gt;RAiO RA8835 (1 module)&lt;/li&gt;&#xA;&lt;li&gt;Sanyo LC7981 (13 modules)&lt;/li&gt;&#xA;&lt;li&gt;Sino Wealth SH1101A (2 modules)&lt;/li&gt;&#xA;&lt;li&gt;Sitronix ST7920 (29 modules)&lt;/li&gt;&#xA;&lt;li&gt;Solomon SSD1303 (1 module)&lt;/li&gt;&#xA;&lt;li&gt;Solomon SSD1305 (9 modules)&lt;/li&gt;&#xA;&lt;li&gt;Solomon SSD1325 (2 modules)&lt;/li&gt;&#xA;&lt;li&gt;Solomon SSD1332 (1 module)&lt;/li&gt;&#xA;&lt;li&gt;Solomon SSD2119 (2 modules)&lt;/li&gt;&#xA;&lt;li&gt;ST STV8105 (1 module)&lt;/li&gt;&#xA;&lt;li&gt;Toshiba T6963 (23 modules)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-05-05T20:01:38.787" CommentCount="11" />
  <row Id="13947" PostTypeId="2" ParentId="13940" CreationDate="2011-05-05T20:06:30.873" Score="0" ViewCount="" Body="&lt;p&gt;My Kenwood deck has the ability to turn the iPod hands-free mode off and on via the front panel. If your deck doesn't have this ability, you could try and ask the vendor if they can support this with a future firmware upgrade.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-05T20:06:30.873" />
  <row Id="13948" PostTypeId="2" ParentId="13440" CreationDate="2011-05-05T20:44:02.820" Score="3" ViewCount="" Body="&lt;p&gt;I would suggest &lt;a href=&quot;http://www1.idc.ac.il/tecs/&quot; rel=&quot;nofollow&quot;&gt;Building a Modern Computer from First Principles&lt;/a&gt;. As the title suggests, it goes through the process of building a computer from the fundamental logic gates on up. Check out the reviews on amazon &lt;a href=&quot;http://amzn.com/0262640686&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The author's website actually has quite a lot of info on it, so you can decide for yourself if it looks like it would meet your needs.&lt;/p&gt;&#xA;" OwnerUserId="4130" LastActivityDate="2011-05-05T20:44:02.820" />
  <row Id="13949" PostTypeId="2" ParentId="13581" CreationDate="2011-05-05T20:48:45.440" Score="0" ViewCount="" Body="&lt;p&gt;I was unable to determine what the problem is.  I even went to the math stackexchange to see if the math types had any input, but all I got was &quot;your residuals aren't randomly distributed so linear regression is inappropriate&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ultimately, iterative application of linear regression manages to narrow in on the true value given enough time.  Why the iteration is required is a mystery.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-05-05T20:48:45.440" />
  <row Id="13950" PostTypeId="2" ParentId="12269" CreationDate="2011-05-05T23:54:55.180" Score="1" ViewCount="" Body="&lt;p&gt;Three observations&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(1) With &lt;em&gt;any&lt;/em&gt; kind of transmitter, to get consistent output, you need consistent input levels, so that's the first thing to check. If the level in the second file are significantly different, it would be worthwhile to adjust it. This transmitter doesn't appear to have any way to accommodate variations in input level, so the easiest thing to do is try adjusting the output level from the PC playing the file. Commercial broadcasters use special hardware to automatically adjust levels into the transmitter, a technique called &lt;em&gt;compression&lt;/em&gt; in the audio world. If you play a signal with a lot of dynamic range into this transmitter, you may find that the level setting that makes one part of the song sound better will make louder/quieter sections sound worse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(2) That's definitely not amplitude modulation. It's essentially pulse width modulation. If you LPF pulse width modulation, you can recover an approximation of the input signal. An AM receiver will respond to the fundamental component, so apparently the fundamental's envelope closely approximates the input, but I'd be surprised if there wasn't significant distortion. You wouldn't call it high fidelity, but you could probably recognize voice through it. Using the 555 to do pulse width modulation is going to be especially sensitive to input levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(3) Transistor Q1 is probably not doing anything helpful. As shown, Q1 will be either completely off or .. completely off. The only signal getting to the antenna will be from capacitive coupling between the base and emitter. Two alternatives to try - you could just connect your antenna directly to pin 3, i.e., omit Q1 altogether, and get more signal onto the antenna that way, OR - leave Q1 where it is, but connect a 75 ohm resistor from its emitter to ground. This would make Q1 into an emitter follower (common collector) amplifier, and might give you some power gain, but pin 3 of the 555 is already a push-pull output, so just wiring pin 3 to the antenna would probably work just as well.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-05T23:54:55.180" CommentCount="1" />
  <row Id="13951" PostTypeId="1" CreationDate="2011-05-06T00:39:16.873" Score="4" ViewCount="65" Body="&lt;p&gt;I have just bought a whole bunch of Xbee Pro S2Bs and Freetronics Eleven boards.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I set up the XBees in AT mode, the Arduino constantly resets.  At least that's what I think it is doing - the D13 LED keeps flashing (3 times in quick succession, once per second) and the sketch won't run.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In API Mode it seems fine, but I want to use AT mode for simplicity - anyone have any ideas why AT mode would be causing the Arduino to reset?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have already asked this question on the Arduino forum but haven't got anywhere yet ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://arduino.cc/forum/index.php/topic,60285.0.html&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/forum/index.php/topic,60285.0.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4133" LastActivityDate="2011-05-07T05:43:31.947" Title="XBee Pro S2B in AT mode keeps resetting the Arduino" Tags="&lt;arduino&gt;&lt;xbee&gt;" AnswerCount="2" />
  <row Id="13952" PostTypeId="2" ParentId="13937" CreationDate="2011-05-06T01:08:48.143" Score="4" ViewCount="" Body="&lt;p&gt;I had, for a brief period of time, considered the idea of tinkering with the eink displays; and followed up with e-Ink Corporation.  They are the folks holding the eInk IP.  They referred me to PrimeView, which is a well established LCD manufacturing company.  (And as I googled to do some fact-checking, it turns out PVI has now acquired EInk.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was able to talk my way into some datasheets and pricing data.  I'm afraid it doesn't look good for the average tinkerer.  They were quoting $ 200.00 per piece for the display.  and 4.50 per piece for the controller (in sample quantities).  The panels were quoted at  60.00/pc for production volumes. Of course, that latter quote would depend on the volume - and I suspect Amazon gets much better pricing!  (BTW, this was for the 6&quot; panel, quoted around December 2007)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are really serious about it, they did offer their development kit for around $3,000.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given that the technology is still relatively new and much of the key technology (versus the enabling technology) is under a lot of patent protection, it'll be a while before we'll see commodity (generic) e-ink displays.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-05-06T17:37:52.090" LastActivityDate="2011-05-06T17:37:52.090" CommentCount="2" />
  <row Id="13953" PostTypeId="1" CreationDate="2011-05-06T01:48:41.193" Score="0" ViewCount="83" Body="&lt;p&gt;hi. i'm using a peltier device to cool my equipment but it seems not to be effective cause it dissipates too much heat. do you know any other effective cooling device which is very small like peltier.&#xA;or can you guys help me with the best power supply for my peltier it's power rating is 25W. &lt;/p&gt;&#xA;" OwnerUserId="4134" LastActivityDate="2011-05-06T10:49:05.490" Title="cooling devices" Tags="&lt;power-supply&gt;&lt;cooling&gt;&lt;peltier&gt;&lt;thermoelectric&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="13954" PostTypeId="2" ParentId="13953" CreationDate="2011-05-06T01:53:37.820" Score="3" ViewCount="" Body="&lt;p&gt;Are you cooling the other side with a heat sink/fan combo?  That's kinda fundamental.  It won't cool very well if you aren't drawing heat away from the other side in some way.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-06T01:53:37.820" CommentCount="3" />
  <row Id="13955" PostTypeId="1" AcceptedAnswerId="13962" CreationDate="2011-05-06T02:08:47.813" Score="5" ViewCount="133" Body="&lt;p&gt;I'm doing a bit of RF PCB design, and one of the things that caught my eye is the &quot;Controlled Impedance&quot; option. Checking more boxes always costs more, so I want to know if this is worth the extra money to ensure functionality on arrival. For the RF portion, I'm using 50 ohm microstrip-line on a 4 layer board. (Top layer [1] is signal, top inner layer [2] is a ground plane)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most board vendors have made their laminate stack-up contents and thicknesses available on their website, and I have been able to calculate the width of the transmission line to my satisfaction using their numbers. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;What is the benefit of using&#xA;&quot;controlled impedance&quot; or &quot;controlled&#xA;dielectric&quot;?&lt;/li&gt;&#xA;&lt;li&gt;At small distances (about 1/10 wavelength), would the impedance bump matter? (I get about 2 ohms difference in Zo from changing the dielectric constant by +-0.4)&lt;/li&gt;&#xA;&lt;li&gt;Is this something that should be done for production boards but isn't necessary for one-off prototypes?&lt;/li&gt;&#xA;&lt;li&gt;Have you ever used this feature?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-05-10T15:59:55.527" Title="Is paying extra for &quot;Controlled Impedance&quot; boards necessary?" Tags="&lt;pcb&gt;&lt;impedance&gt;&lt;transmission-line&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="13956" PostTypeId="1" CreationDate="2011-05-06T02:18:27.963" Score="1" ViewCount="39" Body="&lt;p&gt;We are trying to read analog voltage supplied to two channels simultaneously using ADC10 and DTC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are not getting the results of conversions. Our code is as follows:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;ADC10CTL1 = INCH_2 + CONSEQ_1;&#xA;ADC10CTL0 = REF2_5V + SREF_1 + ADC10SHT_2 + REFON + ADC10ON + ADC10IE;&#xA;ADC10AE0 |= 0x06;&#xA;ADC10DTC1 = 0x02;&#xA;ADC10SA = 0x200;                        // Data buffer start&#xA;&#xA;while (1)&#xA;{&#xA;    ADC10CTL0 &amp;amp;= ~ENC;&#xA;    while (ADC10CTL1 &amp;amp; BUSY);&#xA;    ADC10SA = 0x200;&#xA;    ADC10CTL0 |= ENC + ADC10SC; //Sampling and conversion start&#xA;     __bis_SR_register(CPUOFF + GIE);        // LPM0 with interrupts enabled&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;and, the ISR is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#pragma vector=TIMERA0_VECTOR&#xA;__interrupt void Timer_A (void)&#xA;{ int * read = 0x200;&#xA;//code that reads from the location 'read'&#xA; __bic_SR_register_on_exit(LPM3_bits);        // Clear LPM3 bit from 0(SR)&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;While we are getting the results back at AP, they do not show the correct value, and the value doesn't change if the supplied voltage changes.&#xA;How do we make sure that an interrupt is generated only when the conversion is complete?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks a lot for your time.&lt;/p&gt;&#xA;" OwnerUserId="4132" LastActivityDate="2011-05-06T13:02:42.680" Title="ADC10 and DTC (MSP430 F2xx) - problems in reading analog input on multiple channels" Tags="&lt;adc&gt;" AnswerCount="1" />
  <row Id="13957" PostTypeId="2" ParentId="13955" CreationDate="2011-05-06T03:07:16.633" Score="4" ViewCount="" Body="&lt;p&gt;For a controlled dielectric board, they probably take more care in doing the stackup, as well as using better materials. I'm currently using controlled impedance boards, but have skipped it in the past at 1.8 GHz for Cell phones. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For short runs, you likely won't see much of an issue for an impedance bump. If you're going to do it in production, then you should prototype with it as well. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're doing small boards and short traces, then you probably can skip the controlled impedance and live with what you get. You may see some slightly higher trace insertion losses with an uncontrolled board, but that might not matter. &lt;/p&gt;&#xA;" OwnerUserId="2148" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-10T15:59:55.527" LastActivityDate="2011-05-10T15:59:55.527" CommentCount="3" />
  <row Id="13958" PostTypeId="2" ParentId="13953" CreationDate="2011-05-06T03:43:13.077" Score="3" ViewCount="" Body="&lt;p&gt;A peltier device does not remove heat. It moves heat from one side of the device to the other side while adding its own power consumption in heat. Therefore, the hot side of a peltier will be hotter than the equipment you want to cool in the first place. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, no matter what, you will still have to do effective cooling on the warm side of the peltier element. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;They only make sense if you did a proper thermal analysis of the situation, and you know the thermodynamic effect. If you do not know usage of a peltier makes sense, it very probably doesn't.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, they are mostly used in applications to produce a chill (as in for beverages), if a mechanical heat pump would be to big - in full knowledge of the added power, low efficiency etc - and including proper cooling for the warm side. For cooling electronics - not so much. &lt;/p&gt;&#xA;" OwnerUserId="3438" LastActivityDate="2011-05-06T03:43:13.077" CommentCount="2" />
  <row Id="13959" PostTypeId="2" ParentId="13895" CreationDate="2011-05-06T05:13:26.057" Score="0" ViewCount="" Body="&lt;p&gt;Use 3 axis accelerometers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Put two on the torso ( top, bottom)&#xA;Two on lower leg ( one at knee, one at ankle)&#xA;Two on forearm ( one at elbow,one at wrist)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That gets you quaternions for the ends of the limbs, and it all acts like a Wii controller, only more accurate as the &quot;bar&quot; is longer.&lt;/p&gt;&#xA;" OwnerUserId="1481" LastActivityDate="2011-05-06T05:13:26.057" />
  <row Id="13960" PostTypeId="2" ParentId="13951" CreationDate="2011-05-06T05:46:14.003" Score="0" ViewCount="" Body="&lt;p&gt;Is this a full serial interface? If so, you might need a pull-up resistor to keep the DTR high - Arduino will reset if it's pulled low (used by the IDE for programming).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;More details here: &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1213719666/28#28&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1213719666/28#28&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1612" LastActivityDate="2011-05-06T05:46:14.003" CommentCount="4" />
  <row Id="13961" PostTypeId="1" CreationDate="2011-05-06T07:03:11.920" Score="1" ViewCount="131" Body="&lt;p&gt;I am trying to make a start in Robotics and my guess is that Arduino platform might be a good platform because of its programming interface and also its scalability due to different shields available in the market. However, I come from the software world and have very little experience with circuit design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would like to gather some opinions and experiences from you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="2709" LastActivityDate="2011-05-06T19:57:57.927" CommunityOwnedDate="2011-05-07T01:30:29.050" Title="Is Arduino suitable to begin with robotics?" Tags="&lt;arduino&gt;&lt;robotics&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="13962" PostTypeId="2" ParentId="13955" CreationDate="2011-05-06T07:09:06.687" Score="4" ViewCount="" Body="&lt;p&gt;If you specify controlled impedance/controlled dielectric, they will test your board to ensure that the traces are at the specified impedance.  In your fabrication notes on your PCB printout, specify the nets and their targeted impedance (with tolerance, e.g., 50 ohms +/- 2 ohms).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;They will either test a small test strip that is manufactured on the same panel as your boards; or they will test all nets as needed.  This will help catch boards that do not meet spec, before they end up being stuffed with components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, the &quot;weave&quot; of the board may affect the actual impedance of any particular trace, even when the traces are built to spec (see &lt;a href=&quot;http://www.altera.com/literature/an/an528.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.altera.com/literature/an/an528.pdf&lt;/a&gt;).&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-06T07:09:06.687" CommentCount="1" />
  <row Id="13963" PostTypeId="2" ParentId="13939" CreationDate="2011-05-06T08:57:17.913" Score="1" ViewCount="" Body="&lt;p&gt;125kHz tags have about 32 bits of data, in practice less because all tags used at a certainl location will share the same prefix, see &lt;a href=&quot;http://www.priority1design.com.au/em4100_protocol.html&quot; rel=&quot;nofollow&quot;&gt;this link&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will never guess the ID, but you could easily clone it using something like this: &lt;a href=&quot;http://www.youtube.com/watch?v=fDimlEdeGjM&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=fDimlEdeGjM&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can buy cloners, but it's much more educational to build one yourself, so have at it!&lt;/p&gt;&#xA;" OwnerUserId="1675" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-07T15:57:49.370" LastActivityDate="2011-05-07T15:57:49.370" CommentCount="1" />
  <row Id="13964" PostTypeId="2" ParentId="13961" CreationDate="2011-05-06T09:03:31.313" Score="0" ViewCount="" Body="&lt;p&gt;I have a software developer background as well and just starting with electronics, my advice would be to stick with Arduino, their library is good and gives you the abstraction you need to start programming electrons :)) &#xA;There is a huge friendly community to help you, and a lot of shared libraries and projects.&lt;/p&gt;&#xA;" OwnerUserId="4138" LastActivityDate="2011-05-06T09:03:31.313" CommunityOwnedDate="2011-05-07T01:30:29.050" CommentCount="1" />
  <row Id="13965" PostTypeId="1" AcceptedAnswerId="13975" CreationDate="2011-05-06T09:49:48.757" Score="1" ViewCount="111" Body="&lt;p&gt;For a personal hobby project I'm looking to make a small vga display using an fpga. I was thinking of making the display  640x480 pixels with one byte colour per pixel at 60hz (I believe those timings should work on any monitor?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By my calculation that means I need to read 640*480*60 bytes from the ram every second which is 18432000 bytes per second giving a time per byte of a little over 54ns per pixel.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking at a device something like this for my memory.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://uk.farnell.com/cypress-semiconductor/cy62128ell-45sxi/ic-sram-1mb-128kx8-5v-soic32/dp/1650060&quot; rel=&quot;nofollow&quot;&gt;http://uk.farnell.com/cypress-semiconductor/cy62128ell-45sxi/ic-sram-1mb-128kx8-5v-soic32/dp/1650060&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet indicates that it has an access time of 45ns so by my understanding it should be fast enough for my fpga to read the data from it. But I'd have to update it during the period when no data is being displayed as it's not fast enough to complete a read and write in that time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are my calculations correct, and would such a device be suitable for using in this way? Or did I miss something?&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2011-05-06T17:52:09.160" Title="RAM device / timings for small VGA project" Tags="&lt;fpga&gt;&lt;memory&gt;&lt;vga&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="13966" PostTypeId="2" ParentId="13965" CreationDate="2011-05-06T09:54:18.510" Score="4" ViewCount="" Body="&lt;p&gt;You might be better with using the block RAM in a good FPGA as it will easily outperform the performance of external SRAM; also, if you want to make a PCB, routing will be crucial with 54ns clock times. Also, it looks to be only 5V; what FPGAs work on 5V? You'd need logic level translation, introducing delay into the processing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I figure you need 300KB and FPGAs can have this amount of memory onboard.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-06T09:54:18.510" CommentCount="6" />
  <row Id="13967" PostTypeId="2" ParentId="13961" CreationDate="2011-05-06T10:38:10.287" Score="3" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://www.parallax.com/propeller/&quot; rel=&quot;nofollow&quot;&gt;Parallax Propeller&lt;/a&gt; would be a much better choice, the multi-core architecture is a lot more suitable for robotics than that of the AVR. Lots of Propeller-heads are using them for robotics, so you will find plenty of source code for driving servos and other motors, and get all the assistance you need on the Parallax forum. Parallax even sells complete robot systems, if you don't want to build your own. They aren't expensive.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-06T19:57:57.927" LastActivityDate="2011-05-06T19:57:57.927" CommunityOwnedDate="2011-05-07T01:30:29.050" CommentCount="3" />
  <row Id="13968" PostTypeId="2" ParentId="13961" CreationDate="2011-05-06T10:39:09.707" Score="3" ViewCount="" Body="&lt;p&gt;Compare it to what Lego put in the mindstorms kit a couple of years ago - the RCX brick only had three inputs and three outputs, and had an 8 bit micro with a simple programming interface. The arduino programming interface is decidedly more technical than the Lego's, but if you come from a software background that's actually a plus. As I see it, the arduino is sufficient for robotics projects in exactly the same way as the Lego system - it's an inexpensive controller with a gentle learning curve that will let you get things moving quickly. Once you have things moving, you're in a better position to decide how you want to proceed with more serious projects. &lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-06T10:39:09.707" CommunityOwnedDate="2011-05-07T01:30:29.050" CommentCount="1" />
  <row Id="13969" PostTypeId="2" ParentId="13953" CreationDate="2011-05-06T10:49:05.490" Score="2" ViewCount="" Body="&lt;p&gt;If you are trying to cool something that's &lt;em&gt;hot&lt;/em&gt;, like a chip, you do not need a Peltier; the temperature gradient from the hot device to the cooler environment will naturally cause heat to flow out of the device. To increase the cooling effect, you only need to prevent the heat from the device from warming up the environment around it, which would reduce the gradient. Fortunately, this is easily accomplished with a good thermally bonded heat sink and fan. The Peltier device will actually only increase the amount of heat that must be removed from the system, as it dissipates energy (as heat!) in order to move heat.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-06T10:49:05.490" />
  <row Id="13970" PostTypeId="2" ParentId="13956" CreationDate="2011-05-06T12:57:22.907" Score="2" ViewCount="" Body="&lt;p&gt;... you could start by using the ADC10 interrupt vector instead of the timer0 interrupt vector ... it also looks like you're going into LPM0 at startup then switching to LPM3 after the first interrupt wakes you up (just reading comments here) ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See section 22.2.10 of &lt;a href=&quot;http://www.ti.com/litv/pdf/slau144h&quot; rel=&quot;nofollow&quot;&gt;the manual&lt;/a&gt;, excerpted here for convenience.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;One interrupt and one interrupt vector&#xA;  are associated with the ADC10 as shown&#xA;  in Figure 22-16. When the DTC is not&#xA;  used (ADC10DTC1 = 0) ADC10IFG is set&#xA;  when conversion results are loaded&#xA;  into ADC10MEM. When DTC is used&#xA;  (ADC10DTC1 &gt; 0) ADC10IFG is set when a&#xA;  block transfer completes and the&#xA;  internal transfer counter 'n' = 0. If&#xA;  both the ADC10IE and the GIE bits are&#xA;  set, then the ADC10IFG flag generates&#xA;  an interrupt request. The ADC10IFG&#xA;  flag is automatically reset when the&#xA;  interrupt request is serviced or may&#xA;  be reset by software&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I would also consider perusing the TI-provided &lt;a href=&quot;http://focus.ti.com/mcu/docs/mcuprodcodeexamples.tsp?sectionId=96&amp;amp;tabId=1468&quot; rel=&quot;nofollow&quot;&gt;code examples&lt;/a&gt; for your particular chip variant.&lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-05-06T13:02:42.680" LastActivityDate="2011-05-06T13:02:42.680" />
  <row Id="13971" PostTypeId="2" ParentId="13940" CreationDate="2011-05-06T13:28:48.727" Score="0" ViewCount="" Body="&lt;p&gt;If you jailbreak your iDevice you can get rid of this restriction with NoAccessorySpash which is available from the Cydia repo. I had this same frustration and while it's not an electronics answer, it does work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I didn't write the util, nor am I affiliated with it in any way. I'm just someone happy to have this idiotic restriction removed.&lt;/p&gt;&#xA;" OwnerUserId="974" LastActivityDate="2011-05-06T13:28:48.727" />
  <row Id="13972" PostTypeId="1" AcceptedAnswerId="13986" CreationDate="2011-05-06T15:10:38.400" Score="11" ViewCount="150" Body="&lt;p&gt;So I've used the popular linear regulators (7805, LM317, LD1117, etc), but I'd like to learn more about switching regulators.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any &quot;must have&quot; switching regulators out there that are as popular, as ubiquitous as those common linear ones?&lt;/p&gt;&#xA;" OwnerUserId="2654" LastActivityDate="2011-05-06T20:22:49.947" Title="What are some common/popular/go-to switching voltage regulators?" Tags="&lt;power-supply&gt;&lt;voltage-regulator&gt;&lt;switching-voltage-reg&gt;" AnswerCount="4" FavoriteCount="2" />
  <row Id="13973" PostTypeId="2" ParentId="13972" CreationDate="2011-05-06T15:22:26.913" Score="4" ViewCount="" Body="&lt;p&gt;There are no &quot;must have&quot; switching regulators, a.la. the 78xx or LM317.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the &quot;electronics hobbyist&quot; I recommend looking at Linear Tech's switching regulators.  They are slightly more expensive than others, but that doesn't matter so much when just buying a few.  Also, they have an awesome simulator, LTSpice, that makes it much easier to get something up and running on your first try-- and they have an example circuit/simulation for just about every chip they make.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-06T15:22:26.913" CommentCount="3" />
  <row Id="13974" PostTypeId="2" ParentId="13972" CreationDate="2011-05-06T15:32:54.263" Score="3" ViewCount="" Body="&lt;p&gt;Consider the PoL (Point of Load) Alliance parts. Multiple sourced, includes inductors in the part so about as easy to use as a linear regulator. Parts with crosses &lt;a href=&quot;http://www.murata.com/products/power/selection_guide/converter/pdf/pola_e.pdf&quot; rel=&quot;nofollow&quot;&gt;here from MuRata&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-05-06T15:32:54.263" />
  <row Id="13975" PostTypeId="2" ParentId="13965" CreationDate="2011-05-06T15:33:49.460" Score="2" ViewCount="" Body="&lt;p&gt;Here's how I'd do it...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would start with a Xilinx Spartan-6 FPGA.  The reason I'd go with this is because they have &quot;hard cores&quot; for a DDR-SDRAM interface.  By hard core, I mean that the circuitry for this memory interface is a dedicated chunk of logic and not in the normal &quot;user programmed fabric of logic&quot;.  This means that you're going to meet timing, and you don't have to write this logic on your own.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, I'd hook up some DDR2 SDRAM to the part.  DDR2 SDRAM is fairly inexpensive, easy to get, and certainly fast and large enough for what you want to do.  I'd start with a 16-bit wide data bus, and increase that if you need more speed.  You can use the Xilinx CoreGen or Memory Interface Generator to get your DDR2 interface core.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The rest is &quot;relatively easy&quot;, in that it's just moving data around and generating the proper sync pulses.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One major down-side to this approach is that you're basically limited to using BGA's for both the memory and FPGA.  One plus side is that there are FPGA development boards that already have this circuitry on it.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-06T15:33:49.460" />
  <row Id="13976" PostTypeId="2" ParentId="13838" CreationDate="2011-05-06T15:45:28.040" Score="1" ViewCount="" Body="&lt;p&gt;You're saying that this is a wearable device. It is possible that the brightness problems you're seeing have nothing to do with the chip(s) involved, but is a result of the internal resistance of the battery, especially if you're using button cells. I.e., when you're trying to turn on all LEDs (in a segment) at once, you hit the limit of how much current the battery can deliver, regardless of the microcontroller's drivers.&lt;/p&gt;&#xA;" OwnerUserId="3745" LastActivityDate="2011-05-06T15:45:28.040" />
  <row Id="13977" PostTypeId="1" CreationDate="2011-05-06T16:07:54.783" Score="0" ViewCount="42" Body="&lt;p&gt;Hi all, I am trying to generate a bitstream file from a the FFTv4 block, but I get errors, one of the errors is about a file called 'fftv4_cw.ise'&#xA;This is the error message I get:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;standard exception: XNetlistEngine: An&#xA;  exception was raised:&#xA;  com.xilinx.sysgen.netlist.NetlistInternal:&#xA;  Could not copy 'C:/My Dropbox/Archivos&#xA;  sobre mi PFC/Files_Matlab/System&#xA;  Generator/Mis&#xA;  pruebas/bitstream/FFTv4/sysgen/fftv4_cw.ise'&#xA;  to 'C:\My Dropbox\Archivos sobre mi&#xA;  PFC\Files_Matlab\System Generator\Mis&#xA;  pruebas\bitstream\FFTv4/fftv4_cw.ise':&#xA;  No such file or directory at&#xA;  C:/Xilinx/dsptools/9.2.01.1028/sysgen/scripts/SgPass2Netlist.pm&#xA;  line 150&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any idea of what to do?&#xA;Does anyone could me give the file called 'fftv4_cw.ise?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By the way the link to my file is:&#xA;&lt;a href=&quot;https://www.dropbox.com/s/gpoeuefmbrpg5n9/FFTv4.mdl&quot; rel=&quot;nofollow&quot;&gt;https://www.dropbox.com/s/gpoeuefmbrpg5n9/FFTv4.mdl&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you for your help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.imgur.com/9ZUDQ.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2597" LastActivityDate="2011-05-06T17:36:27.550" Title="System Generator. Estandard exception in FFT block" Tags="&lt;xilinx-system-generator&gt;&lt;error&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="13978" PostTypeId="2" ParentId="13838" CreationDate="2011-05-06T16:22:56.137" Score="0" ViewCount="" Body="&lt;p&gt;A viable approach is to use a chain of four 8-bit shift registers (e.g. 74HC595) to drive all the segments, and use the same size current limiting resistor for each segment (important - each segment gets its own resistor). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then just shift in the appropriate 32-bit pattern from the AVR for the value you are trying to depict. That will decouple the power requirements of the LCD from the AVR pin current sourcing constraints. It will also reduce your AVR pin utilization to three pins (data, clock, latch).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In terms of software complexity, all you need is a table to map digit values to bit patterns. If you keep the wiring consistent among digits, that's just a 10-entry lookup table (if you are just displaying plain-old base-10 numbers). The shift register communication protocol couldn't really be much simpler - open the latch, clock in the data bits, close the latch, and they are capable of reliable operation at speeds far greater than you can achieve with AVRs, so you can just wiggle the wires as fast as possible in software. If you want to reduce power, you can conceivably achieve PWM by shifting in 0x0000 during the off cycle as well and using timer interrupts to ensure duty cycle consistency for example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Last thing, these things are cheap and come in DIP packages if that is important to you. &lt;/p&gt;&#xA;" OwnerUserId="771" LastEditorUserId="771" LastEditorDisplayName="" LastEditDate="2011-05-06T16:35:53.930" LastActivityDate="2011-05-06T16:35:53.930" />
  <row Id="13979" PostTypeId="2" ParentId="13972" CreationDate="2011-05-06T16:34:49.257" Score="2" ViewCount="" Body="&lt;p&gt;Switchers are usually designed for a specific application. National Semiconductor has &lt;a href=&quot;http://www.national.com/analog/power/simple_switcher&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; on-line software for their Simple Switcher devices that helps one select a suitable device, and designs a supply using it. They also have modules that are very easy to use.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-06T16:34:49.257" />
  <row Id="13981" PostTypeId="2" ParentId="2170" CreationDate="2011-05-06T17:21:01.770" Score="0" ViewCount="" Body="&lt;p&gt;I just wanted to note that varicaps are not an &quot;alternative&quot; to variable capacitors:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Your typical variable capacitors require the user to turn a screwdriver and are still used in trimming HF filters.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Varicaps OTOH change capacitance as a function of reverse DC voltage so they are electronically adjustable.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-05-06T17:21:01.770" />
  <row Id="13982" PostTypeId="2" ParentId="13977" CreationDate="2011-05-06T17:27:31.643" Score="2" ViewCount="" Body="&lt;p&gt;Just a guess but looking at:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;'C:\My Dropbox\Archivos sobre mi PFC\Files_Matlab\System Generator\Mis pruebas\bitstream\FFTv4*&lt;em&gt;/&lt;/em&gt;*fftv4_cw.ise'&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that '\' used in the majority of this line is the proper windows directory separator.  The '/' used in the rest of the error and the stared bit above is not the correct directory separator for windows.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;'C:/My Dropbox/Archivos sobre mi PFC/Files_Matlab/System Generator/Mis pruebas/bitstream/FFTv4/sysgen/fftv4_cw.ise'&lt;/p&gt;&#xA;&#xA;&lt;p&gt;is using the forward slash which isn't the windows directory separator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As such I would venture a guess that there is an error somewhere in your project that set the directories incorrectly which is resulting in this exception.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is possible that whatever library is doing this would accept either forward or backward but I doubt it, and very much doubt it would allow both versions in one path.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Got that backwards fixed...&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2011-05-06T17:36:27.550" LastActivityDate="2011-05-06T17:36:27.550" />
  <row Id="13983" PostTypeId="2" ParentId="13965" CreationDate="2011-05-06T17:52:09.160" Score="2" ViewCount="" Body="&lt;p&gt;I'd suggest using a 64Kx16 chip or two 128Kx8 chips; that would cut the required data rate in half, allowing alternating 40ns accesses between the display and the CPU.  If you don't want to use a 16-bit data bus, and you don't mind limiting the speed of external CPU accesses slightly, you could still get the desired speed with a 40ns access time if the OE time is 20ns.  Every twelve half-cycles of a 25MHz clock:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Output pixel 0-1 address.&#xA;&lt;li&gt;Enable low-byte OE.&#xA;&lt;li&gt;Latch pixel 0 data, disable low-byte OE, and enable high-byte OE.&#xA;&lt;li&gt;Latch pixel 1 data and output pixel 2-3 address.&#xA;&lt;li&gt;Enable low-byte OE.&#xA;&lt;li&gt;Latch pixel 2 data, disable low-byte OE, and enable high-byte OE.&#xA;&lt;li&gt;Latch pixel 3 data and output pixel 4-5 address.&#xA;&lt;li&gt;Enable low-byte OE.&#xA;&lt;li&gt;Latch pixel 4 data, disable low-byte OE, and enable high-byte OE.&#xA;&lt;li&gt;Latch pixel 5 data and output CPU address.&#xA;&lt;li&gt;Enable high or low-byte OE or WE.&#xA;&lt;li&gt;Output data on bus (if write) or latch data at end of cycle.&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;This would allow remote CPU access at a rate of about 4MHz.  Not instant, but not too bad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, if scrolling will be needed, it might be useful to have 960 bytes of memory hold the start address for each of 480 lines of display data.  This would allow regions of the screen to be scrolled without having to move around lots of data.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-06T17:52:09.160" />
  <row Id="13984" PostTypeId="1" CreationDate="2011-05-06T19:35:02.857" Score="3" ViewCount="94" Body="&lt;p&gt;Was looking over at Sparkfun and trying to figure out if any of the temperature sensors support or distinguish between wet and dry temperature -- potential application is in a freezer or refrigerated storage.  I'm also not 100% sure what the difference of wet vs dry temperature is and if you can derive that with a humidity sensor?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="4143" LastActivityDate="2011-05-23T15:18:07.777" Title="Temperature Sensors" Tags="&lt;sensor&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="13985" PostTypeId="1" AcceptedAnswerId="13988" CreationDate="2011-05-06T20:17:07.220" Score="7" ViewCount="280" Body="&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/bp7Z4.jpg&quot; alt=&quot;palm tree island electrical storm&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This symbol is stenciled on the circuit board for Compaq PS2021 ATX power supplies. I spent almost half an hour on Google trying to identify it, and I haven't even gotten close. I thought it might be an old company logo, but nothing came up on that search either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone seen this symbol before? If not, can you hazard a guess as to what it might represent?&lt;/p&gt;&#xA;" OwnerUserId="4144" LastEditorUserId="4144" LastEditorDisplayName="" LastEditDate="2011-05-07T02:03:58.597" LastActivityDate="2011-05-17T21:59:47.683" Title="Is this &quot;lightning storm over a tropical island&quot; a valid electrical symbol?" Tags="&lt;identification&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="13986" PostTypeId="2" ParentId="13972" CreationDate="2011-05-06T20:22:49.947" Score="5" ViewCount="" Body="&lt;p&gt;That's easy, MC34063 is a very common part that has been around for quite a while so there are several manufacturers and many applications.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the buck configuration it will output up to 700 mA without dissipating very much power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It comes in dip8 and soic8, so it's small enough for many products and still easy to prototype with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can find lots on ebay for very little money:&#xA; &lt;a href=&quot;http://cgi.ebay.com/50-PCS-MC34063S-SMD-MC34063-34063-converted-Controller-/120710050179?pt=LH_DefaultDomain_0&amp;amp;hash=item1c1ae13183&quot; rel=&quot;nofollow&quot;&gt;http://cgi.ebay.com/50-PCS-MC34063S-SMD-MC34063-34063-converted-Controller-/120710050179?pt=LH_DefaultDomain_0&amp;amp;hash=item1c1ae13183&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only disadvantage is that it's an older part with a lower switch frequency than newer parts, so the inductor will have to be a bit larger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For space-critical applications you will probably need a newer part with a higher switching frequency, so the inductor can be smaller, but those parts are quite a bit more expensive. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;With an external switch transistor you can get higher currents.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The MC34063 is so popular there's even a Youtube video about it:&#xA;&lt;a href=&quot;http://www.youtube.com/watch?v=qGp82xhybs4&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=qGp82xhybs4&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-05-06T20:22:49.947" />
  <row Id="13987" PostTypeId="1" CreationDate="2011-05-06T20:36:43.450" Score="6" ViewCount="167" Body="&lt;p&gt;Hi folks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the general protocol to send information from one system to another?  For example, let's say we have some information collected from microcontroller over a length of time that we want to send to another microcontroller.  I've heard of SPI and I2C interfaces, but I am unclear when you use one method over another and how you implement it.  Are there other methods besides SPI and I2C that are common?  Is the implementation process similar for different microcontrollers?  Is it basically parsing bytes of data that I am doing on the receiving microcontroller? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!!!&lt;/p&gt;&#xA;" OwnerUserId="3649" LastActivityDate="2011-05-09T23:50:24.947" Title="General protocol for data transfer from one system to another?" Tags="&lt;i2c&gt;&lt;spi&gt;&lt;data&gt;" AnswerCount="5" CommentCount="5" FavoriteCount="1" />
  <row Id="13988" PostTypeId="2" ParentId="13985" CreationDate="2011-05-06T20:42:00.007" Score="12" ViewCount="" Body="&lt;p&gt;It's not an official symbol.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Often times PCB designers will add in some of their own artwork.  It appears to me that the lightning bolt was there to indicate that there is high voltage present.  The clouds and island was some &quot;artistic liberties&quot; the PCB designer took.  That kind of thing is not uncommon.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-06T20:42:00.007" CommentCount="4" />
  <row Id="13989" PostTypeId="2" ParentId="13987" CreationDate="2011-05-06T21:00:36.360" Score="5" ViewCount="" Body="&lt;p&gt;SPI and I2C are kind of similar, in that they're really used more for attaching peripheral devices to a controller or cpu, than for actually transferring data between systems. USB is another interface that people seem to want to treat as a communication system, which is in fact a peripheral attachment bus. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Communication between systems isn't exactly like attaching a device to a bus. Bus attachment allows the processor to directly bang on registers in a device, whereas a communication interface allows you to send/receive streams of data. A device connected on a bus generally needs a device driver, whereas with communications, it really doesn't matter &lt;em&gt;what&lt;/em&gt; is connected on the other end, as far as the host computer is concerned. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, this is getting to be a hazier boundary all the time. Things like PCI and ISA are indisputably buses; I2C, SPI, USB are arguably buses; whereas RS232, RS485, and ethernet are definitely communications interfaces. But then there are things like CAN bus and 1553, which are definitely about moving data around, but in a very involved kind of way.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-06T21:00:36.360" CommentCount="4" />
  <row Id="13990" PostTypeId="2" ParentId="13987" CreationDate="2011-05-06T21:16:47.290" Score="5" ViewCount="" Body="&lt;p&gt;A simple serial &lt;a href=&quot;http://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter&quot; rel=&quot;nofollow&quot;&gt;UART&lt;/a&gt; can be used (one Tx and one Rx line with no discrete clock) and can be easily adapted to cross between different potentials (even primary and secondary circuits) with optoisolators or &lt;a href=&quot;http://www.analog.com/en/interface/digital-isolators/adum2201/products/product.html&quot; rel=&quot;nofollow&quot;&gt;magnetic isolators&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as protocols go, anything with defined command bytes and some sort of checksum scheme will work well. There really isn't a cover-all standard protocol that suits all types of communications. I2C has a signalling standards (defining addressing, stops, starts, etc.) but the protocol of what's actually being communicated is solely up to the developer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Power_Management_Bus&quot; rel=&quot;nofollow&quot;&gt;PMBus&lt;/a&gt;, for example, is a power supply communication protocol that uses I2C as its physical medium. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-05-06T21:21:54.230" LastActivityDate="2011-05-06T21:21:54.230" />
  <row Id="13991" PostTypeId="1" AcceptedAnswerId="13992" CreationDate="2011-05-06T21:18:34.950" Score="1" ViewCount="67" Body="&lt;p&gt;I want to make a device that measures absolute small scale 3D speed. Small scale as in 10-150cm movements, and absolute as relative to ground and not relative to the device (the device will turn, roll, etc). Most use cases are indoors, so a GPS won't help. The range 0-5m/s would be the most interesting. Is this possible to realize? Preferably in a watch like footprint. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought the TI chronos watch thinking that would be decent candidate with its accelerometer and easy prototyping through python. However I met some problems.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;I can't seperate gravity. Can this even be done if the device turns? I guess at least a gyro calibrated to ground would be needed?&lt;/li&gt;&#xA;&lt;li&gt;Accuracy. The chronos had only 8 bit accuracy, and even then has quite a lot of noise. Even after removing gravity I suspect from simply integrating acceleration I could end up with crazy speeds. &lt;/li&gt;&#xA;&lt;li&gt;Detecting zero movement. Closely related to the 2 above.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Hopefully my question is not too open ended.&lt;/p&gt;&#xA;" OwnerUserId="941" LastActivityDate="2011-05-06T21:44:41.880" Title="How to get 3D speed vectors?" Tags="&lt;sensor&gt;&lt;accelerometer&gt;&lt;speed&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="13992" PostTypeId="2" ParentId="13991" CreationDate="2011-05-06T21:44:41.880" Score="3" ViewCount="" Body="&lt;p&gt;I don't think you can reliably do it from just using measurements from the device's frame of reference.  I think your best bet is to capture the position of the device externally.  Basically motion-capturing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Depending on your measurement resolution, it might be possible to use non-GPS triangulation methods.  Acoustic beacons, probably.   Radio time-to-distance probably won't work in such a small volume.  And I suspect radio time-to-angle (VOR) probably would not work in an indoor environment.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-06T21:44:41.880" CommentCount="3" />
  <row Id="13993" PostTypeId="2" ParentId="13939" CreationDate="2011-05-06T22:48:36.097" Score="1" ViewCount="" Body="&lt;p&gt;RFID tags work with &quot;near-field&quot; radio signalling. The elevator (RFID master) emits a low-power radio signal which is only strong enough to extend a small distance away before being lost to noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When an RRFID tag is placed within range of the low-power master signal, it powers up (using power from the transmitted signal, which is cool) and transmits a unique identification number. In the case of the elevator, this ID number will be checked against a list of approved IDs before granting or denying access to the elevator controls.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To gain access without a tag, you would have to record the radio signal sent from a valid tag to the elevator, and then reproduce the same signal. If that proves difficult, you could make or modify an RFID master with a directional gain antenna. The trick would then be to aim that antenna at a valid RFID tag from farther away, and record its ID number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Important Note:&lt;/strong&gt; If you get caught pointing a directional antenna at a masters student, be prepared to answer a &lt;em&gt;lot&lt;/em&gt; of questions. Security is a serious matter these days.&lt;/p&gt;&#xA;" OwnerUserId="4144" LastActivityDate="2011-05-06T22:48:36.097" />
  <row Id="13994" PostTypeId="1" CreationDate="2011-05-06T23:28:05.270" Score="1" ViewCount="66" Body="&lt;p&gt;I have come across a Program &amp;amp; Verify technique. But I am unsure if that's how data is written to Flash memories in practice. I need a detailed specific protocol, preferably with the relevant numbers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="4146" LastActivityDate="2011-05-06T23:49:36.460" Title="What is the exact industry-standard programming protocol used for writing bits to a Flash memory device?" Tags="&lt;flash&gt;&lt;non-volatile-memory&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="13995" PostTypeId="1" CreationDate="2011-05-06T23:36:09.513" Score="1" ViewCount="72" Body="&lt;p&gt;I want to create a schematic of a specific verilog module hierarchy showing which blocks are connected to which other blocks.  Much like &lt;a href=&quot;http://www.springsoft.com/&quot; rel=&quot;nofollow&quot;&gt;Novas'/Springsoft's Debussy/Verdi&lt;/a&gt; nschema tool, or any of a number of EDA tools that provide a graphical design browser for your RTL.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What tools area available to draw schematics programmatically either from a verilog or vhdl definition, or from some other text-based input format?&lt;/p&gt;&#xA;" OwnerUserId="1708" LastActivityDate="2011-05-07T15:30:17.443" Title="How can I generate a schematic block diagram image file from verilog?" Tags="&lt;vhdl&gt;&lt;verilog&gt;" AnswerCount="2" />
  <row Id="13996" PostTypeId="2" ParentId="13994" CreationDate="2011-05-06T23:48:28.647" Score="2" ViewCount="" Body="&lt;p&gt;The process is slightly different depending in the flash device. You can find that info in the datasheet for the part you're trying to program.  Beyond that there is no &quot;industry standard&quot;. &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-06T23:48:28.647" CommentCount="1" />
  <row Id="13997" PostTypeId="2" ParentId="13995" CreationDate="2011-05-06T23:48:56.993" Score="0" ViewCount="" Body="&lt;p&gt;What do you have? These ones have that feature, with various qualities of output.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Synplicity&lt;/li&gt;&#xA;&lt;li&gt;Synopsys Design Compiler&lt;/li&gt;&#xA;&lt;li&gt;Altera Quartus II&lt;/li&gt;&#xA;&lt;li&gt;Xilinx ISE&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-05-06T23:48:56.993" CommentCount="1" />
  <row Id="13998" PostTypeId="2" ParentId="13994" CreationDate="2011-05-06T23:49:36.460" Score="1" ViewCount="" Body="&lt;p&gt;Read the datasheet of the device in question.  There are some JEDEC standard Flash device ID and programming methods for NAND FLASH devices - those are documented in the databooks as well.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-06T23:49:36.460" />
  <row Id="13999" PostTypeId="2" ParentId="4282" CreationDate="2011-05-07T00:42:22.057" Score="2" ViewCount="" Body="&lt;p&gt;There is no need to use a IDE like arduino, to use avr's. look at avr-gcc + isp. you can program the avr in c like arduino, but without the overhead and need for a bootloader.&lt;/p&gt;&#xA;" OwnerUserId="2906" LastActivityDate="2011-05-07T00:42:22.057" />
  <row Id="14000" PostTypeId="1" AcceptedAnswerId="14004" CreationDate="2011-05-07T02:20:37.387" Score="1" ViewCount="172" Body="&lt;p&gt;How can I put power to some wires [possibly connected via Serial Port?], by using a script? I use Ubuntu. I want to schedule a time [using cron] to automate turning on something, say, an LED, a small motor, anything like that. I just need the power to go on when I run the command, and I can use a transistor or whatever for more power. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I do it? My laptop doesn't have a serial port, but I can get a usb-to-serial adapter.&lt;/p&gt;&#xA;" OwnerUserId="4148" LastEditorUserId="4148" LastEditorDisplayName="" LastEditDate="2011-05-07T12:56:50.353" LastActivityDate="2011-05-09T03:34:35.493" Title="turn on power to physical wire from linux?" Tags="&lt;serial&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="14001" PostTypeId="1" AcceptedAnswerId="14002" CreationDate="2011-05-07T04:17:43.853" Score="1" ViewCount="62" Body="&lt;p&gt;Hey all,&#xA;I'm fiddling with a breadboard to make some logic gates and instead of buying spst switches, I bought dpdt switches because they were the only ones that would fit in the board.  :/&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I somehow use these dpdt switches as inputs in my logic gate?&lt;/p&gt;&#xA;" OwnerUserId="3796" LastActivityDate="2011-05-07T07:23:18.470" Title="DPDT switch for on/off" Tags="&lt;logic&gt;&lt;switch&gt;&lt;breadboard&gt;&lt;input&gt;" AnswerCount="2" />
  <row Id="14002" PostTypeId="2" ParentId="14001" CreationDate="2011-05-07T04:39:29.160" Score="3" ViewCount="" Body="&lt;p&gt;I don't see why not -- just hook up one of the poles.  If you have a NO SPST switch, you can just use one &quot;half&quot; of the DPDT switch.  You should check the resistance between two of the pins on your DPDT switch so that when you throw it, it makes contact.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-05-07T04:39:29.160" CommentCount="7" />
  <row Id="14003" PostTypeId="2" ParentId="14000" CreationDate="2011-05-07T04:52:38.547" Score="2" ViewCount="" Body="&lt;p&gt;Connect a suitable MCU with USB, such as a PIC18F2455, to the laptop via the USB port. Interface an LED to the PIC, and write some software to control it via a Linux program running on the laptop. I've done something like it which works with a Windows program, based on Brad Minch's work. &lt;a href=&quot;http://www.leonheller.com/usb/&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; are details of how to compile the code for the PIC and Windows, and details of the PIC hardware, including where to buy the PCB that I designed. You just need to write some Linux software similar to the Windows code. A lot more can be done with this hardware than simply toggling an LED, of course, as a sizeable prototyping area is provided.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest and cheapest way to do it is to emit a tone from the headphone port on the laptop, amplify it (a single transistor) and rectify the amplified signal, and use that to control an LED via another transistor. This should cost under $1 to build. By generating different frequencies and detecting them more complex control is feasible.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-07T13:37:16.587" LastActivityDate="2011-05-07T13:37:16.587" />
  <row Id="14004" PostTypeId="2" ParentId="14000" CreationDate="2011-05-07T05:22:35.163" Score="4" ViewCount="" Body="&lt;p&gt;What is the &lt;em&gt;something&lt;/em&gt; that you want to turn on?  You said LED in your question, but then said &lt;em&gt;something&lt;/em&gt; in the question.  :)  I only ask because an LED vs. a solenoid can have very different power requirements.  Is there a budget in mind?  Do you want something turnkey?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was going to recommend trying the &lt;a href=&quot;http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_%28MSP-EXP430G2%29?DCMP=launchpad&amp;amp;HQS=Other%20OT%20launchpadwiki&quot; rel=&quot;nofollow&quot;&gt;TI Launchpad&lt;/a&gt;, which gives you a micro with a handful of I/O, plus a built-in USB-to-serial adapter, and is Linux-compatible, for a reasonable &lt;strong&gt;&lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&amp;amp;site=US&amp;amp;KeyWords=launchpad&amp;amp;x=0&amp;amp;y=0&quot; rel=&quot;nofollow&quot;&gt;$5&lt;/a&gt;&lt;/strong&gt;.  The price is so good, it's unbelievable.  And the tools are free.  But if you want to make anything that requires more current than an LED turn on with a serial command sent via cron through Linux, then you'll have to wire up additional components to make it work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't have much of a budget, and want something that looks like it would work out of the box, take a look at &lt;a href=&quot;http://www.phidgets.com/products.php?category=0&amp;amp;product_id=1012&quot; rel=&quot;nofollow&quot;&gt;this module from Phidgets&lt;/a&gt; to see if it's easy enough to get working in Linux.  They provide plenty of source code, and have Linux drivers available.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also the obvious other option, Arduino, which from what I've read works on Linux.  I'm just not a fan of the tools, nor the price when compared to the Launchpad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT -- a totally unrelated comment that I just had to share -- today I wanted to get more of the female headers for the Launchpad from Digikey.  Well, the two headers cost $1 apiece.  I ended up buying another Launchpad, because I would get &lt;strong&gt;both&lt;/strong&gt; headers, as well as a USB cable, the dev board, and an extra MSP430G2 for an extra 3 bucks!  Seriously, TI?  :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT (regarding USB-to-serial adapter) -- I am actually having a hard time getting information that this works on the Launchpad.  From &lt;a href=&quot;http://www.43oh.com/forum/viewtopic.php?f=8&amp;amp;t=498&quot; rel=&quot;nofollow&quot;&gt;this post&lt;/a&gt;, it sounds like it's possible, but I'm a little confused because some responses talk about the ez430, instead of the Launchpad.  I definitely have the MSP430 application UART appear in my Device Manager, but haven't tried to use it in any way.  I'll try to play with this next week to see if it really does work.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-05-07T06:37:45.580" LastActivityDate="2011-05-07T06:37:45.580" CommentCount="8" />
  <row Id="14005" PostTypeId="2" ParentId="14000" CreationDate="2011-05-07T05:28:09.830" Score="4" ViewCount="" Body="&lt;p&gt;If you only want to switch a single LED, programming a microcontroller is overkill.  Use a USB-&gt;serial adapter, and toggle DTR or RTS pin using the serial API of your scripting language. (I recommend Python + pySerial, but every mainstream language will have some way of addressing serial ports.)  This will only supply a few mA, probably enough to dimly light an LED.  You can get more current by adding a transistor. The details of that are out of scope for this question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit:  For ubuntu, first install pyserial:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;sudo apt-get install python-serial&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then try something like the following:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#!/usr/bin/python&#xA;&#xA;import serial&#xA;&#xA;s=serial.Serial('/dev/ttyUSB0')&#xA;s.setDTR(1)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-05-09T03:34:35.493" LastActivityDate="2011-05-09T03:34:35.493" CommentCount="3" />
  <row Id="14006" PostTypeId="2" ParentId="13951" CreationDate="2011-05-07T05:43:31.947" Score="1" ViewCount="" Body="&lt;p&gt;Is the Aruduino board's regulators rated for the XBee Pro's current draw?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know sparkfun had some issues with this, where their XBee -&gt; computer interface bard had a 150ma 3.3v regulator, and the XBee Pro needs ~ 215mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the 3.3V regulator is too small, the XBee could be browning-out the local power supply as it tries to power on.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;How are you connecting the XBee to the Aruduino board anyways? From what I could see looking up the Freetronics board you mentioned, it doesn't have an XBee socket.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-05-07T05:43:31.947" CommentCount="1" />
  <row Id="14007" PostTypeId="2" ParentId="13987" CreationDate="2011-05-07T06:05:31.693" Score="5" ViewCount="" Body="&lt;p&gt;There is no one way to send data, there are many different ways to communicate depending on the distance, the data rate, the environment, the application ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The lowest layer is the &lt;em&gt;physical layer&lt;/em&gt;, which actually moves the bits around.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;SPI and I²C are for short distances inside a device, where there is not much noise that could disturb the transmission.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For not too fast communication over distances up to some tens of meters serial communication via RS-232 is a good choice.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If there is more noise or longer distance differential signals are used, for example in RS-485. For faster data transmission there is Ethernet, which is becoming more and more popular.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Then there are also various wireless standards.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;On top of the physical layer there are more layers organizing how the data is sent, for detecting and correcting errors in transmission, routing in a network, and many other things. For example, the internet protocol is a rather complex stack of several layers, typically on top of the Ethernet protocol.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-05-07T06:05:31.693" CommentCount="1" />
  <row Id="14008" PostTypeId="2" ParentId="14001" CreationDate="2011-05-07T07:23:18.470" Score="6" ViewCount="" Body="&lt;p&gt;Use of a double-throw switch can be very good for debouncing.  Wire one throw to VDD and the other to VSS; wire the pole to an input, adding a small cap to ground.  Even if there's some bounce on the contacts, the switch signal won't go high until the high-side contact is closed, and once it's gone high it won't go low until the low-side contact is closed.  There are some slightly more robust approaches feeding the signal through logic gates, but the capacitor-hold approach is nice and simple.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-07T07:23:18.470" CommentCount="2" />
  <row Id="14009" PostTypeId="2" ParentId="13985" CreationDate="2011-05-07T08:00:20.407" Score="3" ViewCount="" Body="&lt;p&gt;It's not a symbol. Looks like the layout person just had fun one night before sending off the PCB production data to the manufacturer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This example seems to have been created just for the purpose of fun. On the boards of &lt;a href=&quot;http://www.dynacord.com/en/products/7/4/24/176_pm2600.html&quot; rel=&quot;nofollow&quot;&gt;an audio power amp&lt;/a&gt; I have &lt;a href=&quot;http://electronics.stackexchange.com/questions/8610/testing-an-audio-power-amp-with-paralleled-transistors&quot;&gt;fixed recently&lt;/a&gt;, I found the letters &quot;MORE POWER TO YOU!&quot; printed in the silkscreen layer. This could even have been a requirement by product management to impress reviewers of audio magazines who would test and take apart the amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Related: &lt;a href=&quot;http://en.wikipedia.org/wiki/Chip_art&quot; rel=&quot;nofollow&quot;&gt;chip art&lt;/a&gt; and &lt;a href=&quot;http://electronics.stackexchange.com/questions/4333/what-is-the-most-amazing-pcb-artwork-youve-ever-seen&quot;&gt;this question&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-05-07T08:00:20.407" />
  <row Id="14010" PostTypeId="1" CreationDate="2011-05-07T08:32:00.130" Score="2" ViewCount="84" Body="&lt;p&gt;I would like some advice on what digital signal frequencies I'd be able to work with for hobby projects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I asked &lt;a href=&quot;http://electronics.stackexchange.com/questions/13965/ram-device-timings-for-small-vga-project&quot;&gt;this&lt;/a&gt; question recently about interfacing to a memory chip from an fpga as a hobby project. The answers are all very good but have made me realise that I have a little more to learn before attempting some a project. I feel I could probably build the design I want in verilog but I have a lot to learn about physical design first.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I realise this question is rather vague, but all I'm looking for is an order of magnitude answer to get some idea what projects might be viable for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can buy an fpga on a breakout board so that I can connect plug in wires to a breadboard for experimenting. I imagine that for flashing an LED there would be no issues with this. I imagine that I could likely get I2C working (as I've done similar things with microcontrollers). I could likely get an interface to a static memory chip working at a Mhz or so maybe? I imagine that interfacing to a memory chip at 133MHz would have zero chance of working. Assuming I take some care with connections, wiring etc, what is the highest frequency that it's even worth my time trying to make work for a hobby project on such a setup?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I presume that if I make a home made pcb I could work with somewhat higher frequencies. What sort of frequencies would I likely have to go beyond before I'd &lt;em&gt;really&lt;/em&gt; have to know what I'm doing to design high frequency boards?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I got a professionally made board I imagine I could likely get it to work a little faster still, but beyond that I'd need to educate myself a lot more to know how to make it work reliably with high speed signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again, I'm not looking for exact figures, just order of magnitude figures to prevent me from wasting my time on something that's never going to work.&lt;/p&gt;&#xA;" OwnerUserId="710" LastActivityDate="2011-06-02T02:57:40.720" Title="Speed of various prototype systems for digital electronics" Tags="&lt;fpga&gt;&lt;frequency&gt;&lt;prototyping&gt;&lt;reliability&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="14011" PostTypeId="2" ParentId="14010" CreationDate="2011-05-07T09:16:20.147" Score="0" ViewCount="" Body="&lt;p&gt;Why don't you try how far you can get as a challenge?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would guess that with careful termination and short twisted pair wires of equal length you could get up to at most about 100MHz, though it won't be easy. A GHz oscilloscope will help to see how the signals are doing (ringing and such).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've not tried this myself on a breadboard, but seen 80MHz signals go over more than half a meter of twisted pair with several connectors in between. It was ugly, but made to work with series resistors to dampen the ringing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A nice project would be a fast JTAG adapter, the faster the better but useful already at lower speeds.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-05-07T09:16:20.147" CommentCount="2" />
  <row Id="14012" PostTypeId="1" CreationDate="2011-05-07T10:03:31.813" Score="-2" ViewCount="74" Body="&lt;p&gt;How can we initialze memory declared in verilog code segment ? &lt;/p&gt;&#xA;" OwnerUserId="3192" LastEditorUserId="3192" LastEditorDisplayName="" LastEditDate="2011-05-07T10:36:45.220" LastActivityDate="2011-05-07T16:37:19.173" ClosedDate="2011-05-11T06:14:57.783" Title="initializing memory | how ?" Tags="&lt;logic&gt;&lt;verilog&gt;&lt;homework&gt;&lt;hdl&gt;&lt;digital-logic&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="14013" PostTypeId="2" ParentId="14010" CreationDate="2011-05-07T12:28:55.300" Score="2" ViewCount="" Body="&lt;p&gt;Okay, Here is how you decide. From a basic level, you just need to determine if you are dealing with &lt;a href=&quot;http://en.wikipedia.org/wiki/Transmission_line&quot; rel=&quot;nofollow&quot;&gt;Transmission lines&lt;/a&gt;. As the article states, as long as the wire is less then 1/10th the wavelength of the signal, you do not have to take into account transmission line affects.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The speed of light is \$10^8\$ meters per second. For example, at 100MHz, which roughly equates to a rise time of 1nS, you would have termination to worry about around \$\frac{10^8}{(10*10^8)}\$ meters. This means 10 centimeters. Not that far, but far enough.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This does not mean you can just treat wires as ideal as long as they are below that point. You still need to determine their inductance and capacitance and determine if they will ring. With a simple LC circuit a resistor in parallel with the capacitor will stop oscillations. This is a lower level theory, but for many also complicated, which is why higher frequency boards become an issue before the lines become transmission lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In short, I think you can do 100MHz, use a solid ground plane, try not to embed traces in it and keep the lines short. When you are ready, read &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0133957241&quot; rel=&quot;nofollow&quot;&gt;High Speed Digital Design&lt;/a&gt;. I do not promise it is an easy read, but it is one of the best books I have ever read.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:57:40.720" LastActivityDate="2011-06-02T02:57:40.720" />
  <row Id="14014" PostTypeId="2" ParentId="14010" CreationDate="2011-05-07T13:21:42.813" Score="5" ViewCount="" Body="&lt;p&gt;Now that question will open a can of worms!  Basically, there is no way to accurately answer that question because there are so many factors involved.  That being said...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;quick&quot; answer is that I wouldn't be concerned until the signal frequencies get near 1 MHz.  Between 1 and 10 MHz I would be extra careful.  And above 10 MHz I would have a PCB made.  Of course there are exceptions, and this is what &lt;em&gt;I&lt;/em&gt; would do, etc.  But as a rough order of magnitude place to start, it works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many issues involved with this, and I'll try to cover them here...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As others have stated, it's not the signal frequency but the rise/fall time of the signal edges.  If you can slow down the edges (but not too much) then you'll have an easier time.  FPGA's are great for this because you can change the slew rate and drive strength of the I/O Pins.  In a synchronous system, this is more important on the clock lines than the data lines (I'm not saying that data isn't important, however.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While doing proper signal termination is important, you can't do signal termination without knowing the characteristic impedance of the wire.  And in a breadboard type system you won't know what the impedance is, no matter how hard you try.  In this case, you'll simply end up twiddling with it until it just happens to work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pay attention to the signal return paths and loop currents.  This is going to play the biggest part in making the system run fast.  Of course, this is damn near impossible to do correctly with a breadboard, but those are the breaks.  This is why people use power/gnd planes and 4+ layer PCB's.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've ran PCIe (2.5 GHz) over wire-wrap-wire for about 5 inches.  And I've ran PCIe over a &quot;commercially available&quot; wire for 12 inches.  So you can get good performance from wire.  It's all in how you use it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A good breadboard can probably run faster than a bad 2-layer PCB.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, most modern parts are in packages that require a PCB.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-07T13:21:42.813" CommentCount="3" />
  <row Id="14015" PostTypeId="1" CreationDate="2011-05-07T14:31:09.117" Score="2" ViewCount="82" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/8121/capacitor-sizes-for-7805-regulator&quot;&gt;Capacitor Sizes for 7805 Regulator&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;i aquired a tachometer that operates on 12v d.c. however the l.e.d.backlight operates on 5v d.c.,the control unit is missing so i need to power the backlight by other means (make a voltage regulator of my own) i have it down i think but capacitor values i am unsure of,i dont have any info regarding current draw from the light circuit.what value caps do i need on either side of the I.C. 7805&lt;/p&gt;&#xA;" OwnerUserId="4151" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-07T14:47:15.517" LastActivityDate="2011-05-07T15:42:44.713" ClosedDate="2011-05-07T17:19:00.253" Title="voltage regulator capacitors" Tags="&lt;capacitor&gt;&lt;7805&gt;" AnswerCount="1" CommentCount="0" />
  <row Id="14016" PostTypeId="2" ParentId="14015" CreationDate="2011-05-07T14:48:24.407" Score="0" ViewCount="" Body="&lt;p&gt;The backlight is unlikely to require much current, and you shouldn't have any problems with an LM7805.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need a 0.22 uF on the input and a 0.1 uF on the output according to National Semiconductor (they invented it), they should be close to the leads. &lt;a href=&quot;http://www.national.com/ds/LM/LM340.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is the data sheet. Fairchild recommends 0.1 uF on the input only &lt;a href=&quot;http://www.fairchildsemi.com/ds/LM/LM7805.pdf&quot; rel=&quot;nofollow&quot;&gt;for their version&lt;/a&gt; of the LM7805, it might be an error as they suggest 0.33 uF and 0.1 uF for all the other voltage versions in the data sheet, and have both 0.33 uF and 0.1 uF on the input and output in the diagram on page 22. I use 0.33 uF on the input and 0.1 uF on the output (monolithic ceramic) for any version on my PCBs and they work OK.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-07T15:42:44.713" LastActivityDate="2011-05-07T15:42:44.713" CommentCount="1" />
  <row Id="14017" PostTypeId="2" ParentId="13995" CreationDate="2011-05-07T15:30:17.443" Score="0" ViewCount="" Body="&lt;p&gt;Altera Quartus should be able to do it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I was studying VHDL, I've done the reverse conversion sometimes (starting from schematic to obtain the VHDL equivalent) with Quartus Web Edition, and it worked. &lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-05-07T15:30:17.443" />
  <row Id="14018" PostTypeId="1" AcceptedAnswerId="14022" CreationDate="2011-05-07T15:33:56.723" Score="1" ViewCount="144" Body="&lt;p&gt;If I use a &lt;a href=&quot;http://www.mini-box.com/DC-DC&quot; rel=&quot;nofollow&quot;&gt;PicoPSU&lt;/a&gt;, the computer is connected to an external 12V adapter (power brick) by a simple two pole +/- connector. The protective earth is not connected to the PC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does this situation involve any life-threatening risk in case of electric failure?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Normally the computers are powered with standard ATX power supplies, which are connected to the power system by a three wire cable. One of the wires is the protective earth (PE) which is connected to all exposed metallic parts of the computer (case, backplate, audio jacks, etc.)&lt;/p&gt;&#xA;" OwnerUserId="1514" LastEditorUserId="1514" LastEditorDisplayName="" LastEditDate="2011-05-07T16:33:52.490" LastActivityDate="2011-05-07T17:31:45.920" Title="Is PicoPSU hazardous?" Tags="&lt;power-supply&gt;&lt;picopsu&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="14019" PostTypeId="2" ParentId="9495" CreationDate="2011-05-07T15:42:23.390" Score="1" ViewCount="" Body="&lt;p&gt;I've got a &lt;a href=&quot;http://www.mcumall.com/comersus/store/comersus_viewItem.asp?idProduct=4282&quot; rel=&quot;nofollow&quot;&gt;True-USB PRO GQ-4X Willem Programmer&lt;/a&gt; with SMD adapters about 150 USD. It can do everything I need:)&lt;/p&gt;&#xA;" OwnerUserId="1514" LastActivityDate="2011-05-07T15:42:23.390" />
  <row Id="14020" PostTypeId="2" ParentId="14018" CreationDate="2011-05-07T15:45:15.727" Score="1" ViewCount="" Body="&lt;p&gt;If the adapter has been designed properly it should meet all the relevant safety standards and no ground connection needs to be made.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use &lt;a href=&quot;http://www.stontronics.co.uk/&quot; rel=&quot;nofollow&quot;&gt;Stontronics&lt;/a&gt; mains adapters. They are UL/CUL and GS approved.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-07T15:59:19.857" LastActivityDate="2011-05-07T15:59:19.857" CommentCount="2" />
  <row Id="14021" PostTypeId="2" ParentId="14012" CreationDate="2011-05-07T16:37:19.173" Score="1" ViewCount="" Body="&lt;p&gt;With Xilinx FPGAs RAM is initialized with Memory Initialization Files, for both VHDL and Verilog designs. A special CORE generator utility can be used, which makes it very easy.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-07T16:37:19.173" />
  <row Id="14022" PostTypeId="2" ParentId="14018" CreationDate="2011-05-07T17:31:45.920" Score="2" ViewCount="" Body="&lt;p&gt;The rationale behind grounding the cases of mains powered equipment has to do with the fact that one side (the 'neutral') of the AC mains is typically already tied to ground, by the utility company. If a piece of equipment had an un-grounded case, and a physical failure inside the unit caused the other leg of the mains (the 'hot' side) to contact the exposed surface, a potentially lethal hazard would be created; anyone coming into contact with the case and a ground at the same time would be directly across the full mains voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now consider running from a 12V supply. Some low voltage DC supplies do tie one side of their output to ground, some don't, it depends on the supply. Obviously if one side is grounded, the same possibility exists that an internal failure could energize the case with respect to ground, albeit at only 12V. If you have the output-not-grounded kind, even if the case comes into contact with one of the 12V supply leads, and you touch that case, you aren't likely to come into contact with the other side of the 12V supply, unless you really work at it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Personally, I wouldn't worry too much about the lack of an earth-ground in a 12V system. The odds of a multi-point failure that would result in getting one's person across the 12V supply are low, and even if it happens, it's only 12V. But a parting word about 'only 12V' - if your skin is dry, and you apply 12V to it, chances are you won't even feel it, but if you have significant moisture on your skin, especially salty moisture, you definitely can feel it. I wouldn't recommend the experience. Also, even though the voltage is low, you can often get enough current from low voltage supplies to turn rings, metal watch straps, etc. red hot, also un-fun.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-07T17:31:45.920" />
  <row Id="14023" PostTypeId="1" CreationDate="2011-05-07T18:12:58.257" Score="2" ViewCount="101" Body="&lt;p&gt;I'm going to Africa this summer for a veterinary mission and need an egg incubator. Considering I will not have a steady supply of power I need to find an efficient way to power an incubator continuously off of a battery and solar power. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to run this incubator:&#xA;&lt;a href=&quot;http://www.flemingoutdoors.com/little-giant--10200-circulated-air-incu.html&quot; rel=&quot;nofollow&quot;&gt;http://www.flemingoutdoors.com/little-giant--10200-circulated-air-incu.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this battery/solar setup:&#xA;&lt;a href=&quot;http://www.goalzero.com/shop/p/59/Sherpa-120-Explorer-Kit/1:1/&quot; rel=&quot;nofollow&quot;&gt;http://www.goalzero.com/shop/p/59/Sherpa-120-Explorer-Kit/1:1/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though I don't think the setup  is going to be powerful enough to power it continuously, any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="4153" LastActivityDate="2011-05-16T16:01:31.020" Title="Solar power egg incubator" Tags="&lt;power-supply&gt;&lt;battery&gt;&lt;components&gt;&lt;solar-cell&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="14024" PostTypeId="1" AcceptedAnswerId="14025" CreationDate="2011-05-07T18:22:32.713" Score="1" ViewCount="139" Body="&lt;p&gt;I'm trying to make a NOT gate, but with a PNP transistor instead of NPN.  What would a wire diagram look like for a NOT gate with a PNP transistor? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/wtg1t.jpg&quot; alt=&quot;NOT GATE&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3796" LastEditorUserId="3796" LastEditorDisplayName="" LastEditDate="2011-05-08T14:17:34.850" LastActivityDate="2011-05-08T15:21:46.267" Title="NOT gate with PNP transistor" Tags="&lt;transistor&gt;&lt;logic&gt;" AnswerCount="2" />
  <row Id="14025" PostTypeId="2" ParentId="14024" CreationDate="2011-05-07T18:31:14.953" Score="6" ViewCount="" Body="&lt;p&gt;It's the mirror image of the NPN solution: emitter to Vcc instead of ground, load resistor between collector and ground instead of between collector and Vcc.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Like JustJeff says, make sure your input high voltage is high enough. If it is less than Vcc - 0.6V the transistor will be always on, or at least conduct partially, which shows when your LED isn't completely off. You can make the base voltage higher by adding a resistor from base to Vcc. Together with the base resistor it will form a divider. Example: say Vcc = 5V and your input high voltage is 4.2V. That's too low, the transistor will always be off. If you place a resistor between base and Vcc the same value as your input resistor, the base will be at 4.6V and the transistor will be off.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-07T22:31:39.583" LastActivityDate="2011-05-07T22:31:39.583" CommentCount="8" />
  <row Id="14026" PostTypeId="1" AcceptedAnswerId="14128" CreationDate="2011-05-07T18:50:04.797" Score="7" ViewCount="106" Body="&lt;p&gt;I have a system arm that free-ranges within a certain area.  The arm swings, translates and rotates about a vertical axis which sits atop a mobile base.  The mobile base can move any direction in the X-Y plane.  It's movements are strictly programmed but I would like to start a new version that is semi-autonomous.  This new version would need to receive feedback on 3-axis positioning, speed and rotation relative to a fixed point at the edge of the enclosed system (or relative to the position at which it is initialized).&#xA;Sensor feedback is completely new to me but I am willing to dive in.  Could someone recommend a great starting point for me?  Thanks!&lt;/p&gt;&#xA;" OwnerUserId="4155" LastActivityDate="2011-05-10T15:26:58.793" Title="accelerometer/gyro combo question" Tags="&lt;sensor&gt;&lt;accelerometer&gt;&lt;gyro&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="4" />
  <row Id="14027" PostTypeId="1" AcceptedAnswerId="14034" CreationDate="2011-05-07T19:47:20.050" Score="2" ViewCount="77" Body="&lt;p&gt;I recently learnt about the existence of PTC fuses, and I'd like to use one for an USB power supply I'm building. I guess there are PTC fuses on the PC side, but you never know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I went happily to buy some at my local electronic supply store, but unfortunately they said they don't have resettable fuses (weird, they've got almost anything.) Since I'm spanish I didn't ask for PTC fuses, but asked for resettable fuses and explained how they worked, in case they're called something else here at Spain. They didn't have the fuses or knew where I could find them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've read PTC fuses are essentially thermistors, is it possible that they know them as thermistor or some other name, instead of resettable fuse?&lt;/p&gt;&#xA;" OwnerUserId="4156" LastActivityDate="2011-05-08T00:01:26.837" Title="Are PTC fuses called some other way?" Tags="&lt;ptc&gt;&lt;fuse&gt;" AnswerCount="3" />
  <row Id="14029" PostTypeId="2" ParentId="14000" CreationDate="2011-05-07T20:23:54.120" Score="1" ViewCount="" Body="&lt;p&gt;Is &lt;a href=&quot;http://www.cedarlakeinstruments.com/SharedFiles/io.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; what you're looking for? Uses handshake line from serial port. Also has code in C for Linux &amp;amp; Windows to control it.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-05-07T20:23:54.120" CommentCount="1" />
  <row Id="14030" PostTypeId="2" ParentId="14024" CreationDate="2011-05-07T20:27:24.353" Score="2" ViewCount="" Body="&lt;p&gt;It seems that you want an inverter in the sense that you want to drive an LED on when you input a logic low, and off when you input a logic high. Something like this would do that:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/xvr8A.png&quot; alt=&quot;RTL PNP Inverting LED Driver&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Values for the resistors depend on your supply voltage, and on what you're driving the input with. Assuming Vcc of 5V, R1 in the range of 470 ohm to 1K would be a fair choice, regardless of the input device. For a CMOS stage (or a switch between Vcc/Gnd) driving the input, R2 and R3 about equal and about 1K to 5K ought to do. For a TTL input, R2 should probably be about 3 or 4 times the value of R3, e.g., R3=680 ohm and R2=2.2K, because TTL doesn't guarantee anything more than 2.4V for a logic high, and you'll need to get the base to at least Vcc-0.7V, or higher, to shut the transistor off.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-05-08T15:21:46.267" LastActivityDate="2011-05-08T15:21:46.267" CommentCount="4" />
  <row Id="14031" PostTypeId="2" ParentId="14027" CreationDate="2011-05-07T20:32:43.663" Score="-1" ViewCount="" Body="&lt;p&gt;Not a ton of experience with this, but the thermistors that I've used were dead once they had been triggered. As in, one time use. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without knowing what you're trying to use it for, I can't say too much, but &lt;strong&gt;circuit breakers&lt;/strong&gt; are basically resettable fuses. Maybe thats what you were looking for?&lt;/p&gt;&#xA;" OwnerUserId="4159" LastActivityDate="2011-05-07T20:32:43.663" CommentCount="7" />
  <row Id="14032" PostTypeId="2" ParentId="14027" CreationDate="2011-05-07T20:45:46.877" Score="3" ViewCount="" Body="&lt;p&gt;Just a thought the PTC could mean Positive Temperature Coefficent, which would make sense with thermistors as you get 2 basic types PTC and NTC(Negative Temperature Coefficient). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is what Wikipedia says are some trademark names for PTC Fuses:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;These devices are sold by different companies under various trademarks, including PolySwitch (Tyco Electronics),[3] OptiReset (OptiFuse), Everfuse (Polytronics), Polyfuse (Littelfuse) and Multifuse (Bourns, Inc.).&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Here is the link to the &lt;a href=&quot;http://en.wikipedia.org/wiki/Resettable_fuse&quot; rel=&quot;nofollow&quot;&gt;wikipedia article&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-05-07T20:45:46.877" CommentCount="1" />
  <row Id="14033" PostTypeId="2" ParentId="14023" CreationDate="2011-05-07T21:35:07.580" Score="1" ViewCount="" Body="&lt;p&gt;Assuming the night is 12 hours near the equator you have about 10W of power for the incubator before the sun starts to shine again. Depending on the insulation and the ambient temperature this might be enough, or it might not. Unfortunately there is no specification how much power the incubator will need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To reduce power consumption you could try to improve the insulation by packing it in styrofoam.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-05-07T21:35:07.580" CommentCount="1" />
  <row Id="14034" PostTypeId="2" ParentId="14027" CreationDate="2011-05-08T00:01:26.837" Score="4" ViewCount="" Body="&lt;p&gt;I've heard them called polyswitches, polyfuses, multifuses and self-resetting fuses.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-08T00:01:26.837" />
  <row Id="14035" PostTypeId="1" CreationDate="2011-05-08T01:26:24.547" Score="10" ViewCount="109" Body="&lt;p&gt;Butterworth, Bessel, Chebychev, and sinc low-pass filters are used in various cases where there are different tradeoffs between having a uniformly-decreasing frequency response, a uniform phase response, a steep cutoff, or &quot;brick-wall&quot; response.  I believe all such filters can, in some cases, can have overshoot on their step response, meaning their impulse response is in some places negative.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be the optimal frequency response, or what types of frequency responses would be available, in a filter whose only constraint was that the impulse response could not be negative anyplace?  Certainly it's possible to have a low-pass filter meeting such a constraint, since a basic RC filter will do so (though the response of such a filter is a bit crummy).  Would the optimal impulse response be a normal distribution curve, or something else?&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-10T07:25:06.340" Title="What's the sharpest frequency response for a non-causal low-pass filter whose step response doesn't overshoot?" Tags="&lt;filter&gt;&lt;dsp&gt;" AnswerCount="1" CommentCount="17" FavoriteCount="1" />
  <row Id="14036" PostTypeId="1" AcceptedAnswerId="14045" CreationDate="2011-05-08T01:49:20.197" Score="4" ViewCount="107" Body="&lt;p&gt;I think I read somewhere on the internet that an LED could be used as a wavelength-sensitive photodetector. Could any of you point me to a electronics beginner-friendly article or tutorial on how to do this?&lt;/p&gt;&#xA;" OwnerUserId="4161" LastActivityDate="2011-05-08T10:07:41.553" Title="How do I use an LED as a photodetector?" Tags="&lt;led&gt;" AnswerCount="1" CommentCount="17" />
  <row Id="14037" PostTypeId="2" ParentId="12903" CreationDate="2011-05-08T01:54:49.603" Score="0" ViewCount="" Body="&lt;p&gt;This is one thing I could find.... &lt;a href=&quot;http://www.sparkfun.com/products/10549&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/10549&lt;/a&gt; It might not be exactly what you want, but Sparkfun is glad to help and answers quite quickly. The community will also help you if you need much help. Most of what you need in that kit is already included (From what I can see). If I find any more I will edit this answer.&lt;/p&gt;&#xA;" OwnerUserId="3140" LastActivityDate="2011-05-08T01:54:49.603" />
  <row Id="14038" PostTypeId="1" CreationDate="2011-05-08T02:18:11.507" Score="2" ViewCount="234" Body="&lt;p&gt;So a few weeks ago, my boyfriend's 32&quot; flat-screen TV popped like a firecracker while I was watching it (and scared the hell out of me!), followed by a burning smell. This is the third device of his to fail on my watch (the first and second being his hard drive and a lightbulb, which I recovered and replaced respectively)... It's just a string of bad luck, but I couldn't help feeling guilty, even though they failed through sheer coincidence and no fault of my own (honestly!).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I unscrewed the back panel and took a look inside. At first, I thought that it was just a popped resistor and some damage to the nearby connector. Upon further inspection, however, I noticed there's another spot on the bottom of the PCB that's popped and burned through. Also note the puffy capacitors, which probably caused the cascade of failures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/VaKIX.jpg&quot; alt=&quot;Popped resistor&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/TLr2g.jpg&quot; alt=&quot;Damage underneath&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My primary question to you guys is: Can an average electronics specialist with standard soldering tools fix/replace all of the components that are damaged on this board? Or is it too far gone to attempt a repair without highly specialized equipment? Also, I've heard that some companies can make you a PCB given a schematic diagram... Think I could just ship this to one of them and have them make me a new one? :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If so, my secondary question is: What kind of connector do I need to replace the damaged one? It's a linear 10-pin connector (as you can see in the picture), with a spacing of 2.25mm. Can I use any connector matching the shape and pitch requirements as long as I have a matching socket piece? And what kind of crimping tool do I need for the pins? I'll probably have to cut that whole end off since it's damaged.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Forgive my ignorance, as I'm a computer scientist and not an electrical engineer, but I'd just like to know whether it would be worth my time learning how to fix it, or if the whole thing should just be trashed.&lt;/p&gt;&#xA;" OwnerUserId="4162" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-05-08T12:24:09.207" LastActivityDate="2011-05-09T15:53:03.417" Title="Is the damage on this circuit board too much to be fixed? (pics inside!)" Tags="&lt;pcb&gt;&lt;capacitor&gt;&lt;resistor&gt;&lt;damage&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="14039" PostTypeId="2" ParentId="12724" CreationDate="2011-05-08T02:39:10.593" Score="1" ViewCount="" Body="&lt;p&gt;You might try &lt;a href=&quot;http://www.veripool.org&quot; rel=&quot;nofollow&quot;&gt;verilator&lt;/a&gt; if icarus verilog doesnt work for you.  Or perhaps even if it does.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-05-08T02:39:10.593" />
  <row Id="14040" PostTypeId="2" ParentId="12724" CreationDate="2011-05-08T03:23:14.363" Score="0" ViewCount="" Body="&lt;p&gt;Going with what @Sergio Campama and @jpc mentioned, consider virtualization. If you wish to avoid Windows, various vendors including Model Sim support Linux. RHEL 5 is the most commonly supported one.&lt;/p&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-05-08T03:23:14.363" />
  <row Id="14041" PostTypeId="2" ParentId="14038" CreationDate="2011-05-08T03:31:01.673" Score="3" ViewCount="" Body="&lt;p&gt;First off, I'm going to presume that the TV is out of warranty. If it is still covered, your best bet is to call the warranty line and get it fixed that way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's hard to tell from your popped resistor photo, but is there a heat sink to the left of it in the image that is black? There might be something under there that blew out too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for DIYing the repair, you could try swapping out that through hole resistor that blew. However, while it's common for low quality capacitor to give out, resistors don't usually pop unless there is an over current situation, so there might be a larger issue at hand here. It also looks like there are 0 ohm and a 47K (? hard to read) ohm surface mount resistors in the damaged area on the back of the PCB that might need replacing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it's currently broken, there's no harm in attempting a repair. Find a friend who does electronics to help you source the parts, especially if you think you'll need to replace those surface mount resistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for getting a replacement board, rather than having it replicated from scratch, you should be able to get a replacement board. The various boards in TVs are usually modular (power, tuner, etc), and that appears to be the power supply board. Try searching for &quot;TVMAKE TVMODEL Replacement Power Supply Board&quot; and see what comes up. I know the Vizio 50&quot; plasmas have a nasty habit of blowing power supplies and thus they're pretty easy to find replacements for online.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck and stay away from your boyfriend's books lest they burst into flames. ;)&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2011-05-08T03:31:01.673" CommentCount="1" />
  <row Id="14042" PostTypeId="1" CreationDate="2011-05-08T03:42:42.957" Score="2" ViewCount="105" Body="&lt;p&gt;Are there any kinds of standards or common practice dimensions which define what BGA escape vias and routing trace/space should look like at 0.8mm pitch? If not, what's the most economical set of dimensions to use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Several documents I found when searching online discuss vias and routing dimensions on the top and bottom layers, but not inner layers.  As I understand it, the inner layers require antipad which makes them more restrictive than the outer layers. Therefore these should be the driving dimensions, but I can't find much on that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found a document &lt;a href=&quot;http://www.pcb.ddiglobal.com/Press/Technical_Bulletins/BGA_Guidelines.pdf&quot; rel=&quot;nofollow&quot;&gt;BGA/PCB Interconnect Design Guidelines&lt;/a&gt; that discussed 0.8mm pitch (search for &quot;0.8-mm&quot;). It says that with a hole/antipad of 10/28 mil, only 3.5 mils remain on the planes and that isn't good. It goes on to say that using 8/26 for hole/antipad still leaves only 5.5 mil, and so you should just use microvias. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I see some manufacturers offer 8 mil inner clearance (antipad?), so couldn't you use 8 mil holes with a 24 mil antipad and have plenty of ground plane copper left?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found this NXP document: &lt;a href=&quot;http://www.nxp.com/documents/application_note/AN10778.pdf&quot; rel=&quot;nofollow&quot;&gt;PCB layout guidelines for NXP MCUs in BGA packages&lt;/a&gt;. It has a nice but very confusing table in it.  It shows generally standard hole sizes like you'd see from PCB manufacturers (12 mil, 8 mil, in mm) as drill size, and finished sizes way way too small.  The pad to drill size for 1mm pitch in particular would be an entirely normal sounding 12/21 via but the 'finished size' is 7 mil!  My understanding is that PCB manufacturers operate on finished hole size, not drill size.  What's wrong here?  (or with my understanding?)&lt;/p&gt;&#xA;" OwnerUserId="1270" LastActivityDate="2011-05-08T11:40:03.143" Title="BGA escape via dimensions at 0.8mm pitch?" Tags="&lt;pcb-design&gt;&lt;pcb-fabrication&gt;&lt;via&gt;" AnswerCount="1" />
  <row Id="14043" PostTypeId="2" ParentId="9817" CreationDate="2011-05-08T03:52:12.030" Score="1" ViewCount="" Body="&lt;p&gt;It is in a minimum/Sum of Products [SOP] and maximum/Product of Sums [POS] terms, so we can use a Karnaugh map (K map) for it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For SOP, we pair 1 and write the equation of pairing in SOP while that can be converted into POS by pairing 0 in it and writing the equation in POS form.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, for SOP if we write \$x \cdot y \cdot z\$ then for pos we write \$x+y+z\$.&lt;/p&gt;&#xA;" OwnerUserId="4164" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:56:12.423" LastActivityDate="2011-06-02T02:56:12.423" />
  <row Id="14045" PostTypeId="2" ParentId="14036" CreationDate="2011-05-08T06:32:48.390" Score="3" ViewCount="" Body="&lt;p&gt;I'm not sure what you mean by &lt;em&gt;wavelength-sensitive&lt;/em&gt;. But you can use the LED to respond to light, like a photodiode, albeit a rather inefficient one, which means that it generates only a small current.&lt;br&gt;&#xA;Cathode to Vcc, anode via a resistor to ground. If light falls on the LED it will create a current that results in a voltage over the resistor. Like I said, it's not very efficient, so you need a rather large resistance, 1~10 MOhm.&lt;br&gt;&#xA;Keep in mind that maximum allowable reverse voltage for LEDs is limited, usually around 5V.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-08T10:07:41.553" LastActivityDate="2011-05-08T10:07:41.553" CommentCount="1" />
  <row Id="14046" PostTypeId="2" ParentId="14038" CreationDate="2011-05-08T09:24:22.300" Score="2" ViewCount="" Body="&lt;p&gt;Assuming you can diagnose and fix the underlying fault, the  physical damage is entirely repairable - where the PCB has carbonized, you need to dremel off all the black stuff and dig down to clean material. Once fixed, a coat of PCB laquer or conformal coating over the demelled area is a good idea to prevent long-term moisture absorbtion into the rough surface left from the digging.   &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-05-08T09:24:22.300" />
  <row Id="14047" PostTypeId="2" ParentId="14042" CreationDate="2011-05-08T11:40:03.143" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.hunterpcb.com/files/SeminarPresentations/37095BGA_092304.pdf&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; is a useful document. It references IPC7095B, which can be purchased &lt;a href=&quot;https://portal.ipc.org/Purchase/ProductDetail.aspx?Product_code=a9815fda-c900-dd11-91f9-001422202d38&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; for $103. It's worth buying a copy, the price is negligible compared to what you will be spending on your board design and PCB manufacture.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-08T11:40:03.143" />
  <row Id="14048" PostTypeId="1" CreationDate="2011-05-08T13:45:59.227" Score="-1" ViewCount="13" Body="&lt;p&gt;Hi Guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First of all, apologies for the novice and dumb question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am buying a 15&quot; laptop and I need to have a desktop replacement, therefore I will buy monitor, keyboard and mouse as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is no docking station designed specifically for this model, so the only option I have is to buy one of these Stream-Video-Via-USB and Pray-Photoshop-Will-Work things. So I prefer to connect two cables to laptop instead of one to get video streamed separately.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My Questions are:&#xA;1. Is it possible to do so?&#xA;2. The monitor has built-in speakers and HDMI port. Will the dual screen Windows 7 mode work if I connect it via HDMI rather than D-Sub or DVI port? The laptop has dedicated GeForce graphics card&lt;/p&gt;&#xA;" OwnerUserId="4167" LastActivityDate="2011-05-08T13:45:59.227" ClosedDate="2011-05-08T18:22:33.830" Title="Docking station vs USB ports in the back of the monitor" Tags="&lt;usb&gt;&lt;monitor&gt;" CommentCount="1" />
  <row Id="14049" PostTypeId="1" CreationDate="2011-05-08T13:49:13.700" Score="1" ViewCount="33" Body="&lt;p&gt;Hoping someone might be able to point me in the right direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am currently trying to create a wireless accelerometer using two x-bees (series 1). The accelerometer module is set up so that the x,y,z channels are connected to the DIO0, DIO1 and DIO2 channels on an x-bee explorer. The device is all powered through the 3.3V input on the explorer by a 3.7V (110mAh) li-po battery which is also connected to a usb li-po charger. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have setup the x-bees within X-CTU and there is no problem communicating between them. DIO0, DIO1 and DIO2 are all set to ADC and i have set it using several different sampling frequencies. I have noticed within the terminal window that when moving the device both DIO0 and DIO1 appear to remain constant (FF 03 from memory) and only DIO2 seems to vary within each data packet. If i change the setup at any one time to only transmit the data from one of the three channels at a time, they all change with movement. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any chance you might be able to guess where ive managed to mess it up. I am assuming that the wiring and power between the accelerometer and the explorer is fine given it works when only displaying one channel at a time but my experience with these things is limited so im stumped with where to go with it now... Just wondering if the x-bee requires more power for the ADC for all three channels and the it might just need more power to the device to work?&lt;/p&gt;&#xA;" OwnerUserId="4168" LastActivityDate="2011-05-08T13:49:13.700" Title="X-bee and accelerometer: problem streaming data" Tags="&lt;accelerometer&gt;&lt;xbee&gt;" />
  <row Id="14050" PostTypeId="1" CreationDate="2011-05-08T13:55:14.407" Score="0" ViewCount="48" Body="&lt;p&gt;Hi&#xA;I'm using eagle 5.11 for linux. I have a regulator at the bottom of my pcb. The vin and vout pins are fine. For some reason the gnd pin always gets masked over . &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The traces then disappear when I run a script to generate the tool path for the modella MDX20. Zooming in confirms the gnd pin has a trace connected to it's pad.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or is that normal? so the gnd and gnd plane for the board meant to be seperate.&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-05-08T13:55:14.407" ClosedDate="2011-05-10T05:16:24.227" Title="Gnd plane masking over traces causing them to disappear when generating toolpath" Tags="&lt;eagle&gt;" AnswerCount="0" CommentCount="7" />
  <row Id="14051" PostTypeId="1" CreationDate="2011-05-08T14:41:07.620" Score="4" ViewCount="91" Body="&lt;p&gt;I know almost nothing about electronics, but I'd like to intercept the power going to a small speaker and use a relay switch to close a speaker connection on a completely different, but more powerful device (a home outdoor sound system).  I used a multi meter to discover that the original speaker works with a voltage of 1.4 VDC but I can't figure out how to get the amperage.  Is there a generic relay switch that would work in a situation like this? &lt;/p&gt;&#xA;" OwnerUserId="4169" LastActivityDate="2011-06-02T10:54:18.143" Title="relay switch selection" Tags="&lt;switch&gt;&lt;relay&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="14052" PostTypeId="2" ParentId="14051" CreationDate="2011-05-08T15:10:22.743" Score="3" ViewCount="" Body="&lt;p&gt;I'm not sure what your proposing to switch here, but I can address the speaker current question.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Suppose you have 8 ohm speakers, and want to drive 100W into them. Power is impedance times the square of the current, so the current will be the square root of power over impedance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$P = I^2 * R\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$I = \sqrt{\frac{P}{R}}\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So in the example, current would be \$\sqrt{\frac{100}{8}}\$ = 3.5A . Similarly, power is voltage squared over impedance,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$P = \frac{V^2}{R}\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$V = \sqrt{P * R}\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;so in this example, the voltage is \$\sqrt{100*8}\$ = 28.3V . &lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, these would be RMS values; the peaks would be \$\sqrt{2}\$ times as great, so you'd want to size your relay accordingly. A relay that could handle 5A and 50V would just suffice for the example. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would actually want a safety margin, so using these example numbers, 10A and 100V would be a better choice. Finally, you might want to size the relay in anticipation of future upgrades. If you thought you might replace the 100W source with say, 500W, you'd definitely want a heavier device.&lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-06-02T10:54:18.143" LastActivityDate="2011-06-02T10:54:18.143" CommentCount="9" />
  <row Id="14053" PostTypeId="1" CreationDate="2011-05-08T16:43:08.600" Score="2" ViewCount="149" Body="&lt;p&gt;I came across this cable and I don't really understand what it does. Notice that the 1/4'connector has 4 conductors. There isn't any room along the cable (i.e. no box) which allows embedding of a large circuit.&#xA;&lt;img src=&quot;http://i.stack.imgur.com/j0Fyf.jpg&quot; alt=&quot;esoteric&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2656" LastActivityDate="2011-05-08T17:07:35.183" Title="What does this cable do?" Tags="&lt;connector&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="14054" PostTypeId="2" ParentId="14053" CreationDate="2011-05-08T16:52:18.970" Score="7" ViewCount="" Body="&lt;p&gt;It's an alternative cable for connecting devices to your PC. Some manufacturers of portable equipment try to save space in their devices by using an alternative connector for the standard USB B-type. A bit silly, because there's a mini B-type for this purpose.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-08T17:07:35.183" LastActivityDate="2011-05-08T17:07:35.183" CommentCount="6" />
  <row Id="14055" PostTypeId="1" AcceptedAnswerId="14057" CreationDate="2011-05-08T17:01:11.903" Score="4" ViewCount="135" Body="&lt;p&gt;I just wondered, when I saw my new MicroSd memory card , how the hell can 32GB fit in that space? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Simple math: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;it's around \$\frac{1}{2}cm^2\$ (my estimate, most of it is controllers anyway)&#xA;and it contains 32GB cells. So \$\frac{5*10^{-5}}{2^{(5+30)}} = 1.45*10^{-15} m^2\$ space for one cell. Since atoms are in area about \$10^{-12} m^2\$ , how come the memory cells are smaller than atoms?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is an image of what a microSD card looks like:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/NnKW4.jpg&quot; alt=&quot;MircoSD Card&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="4170" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:53:56.590" LastActivityDate="2011-06-02T02:55:04.060" Title="How can so many memory cells fit on MicroSd card?" Tags="&lt;microsd&gt;" AnswerCount="1" CommentCount="5" />
  <row Id="14057" PostTypeId="2" ParentId="14055" CreationDate="2011-05-08T18:34:09.713" Score="6" ViewCount="" Body="&lt;p&gt;Flash memory is currently made in a \$19nm = 1.9 * 10^8\$ m process. Since a cell is basically just one transistor, this leads to a minimum of \$3.6 * 10^{-16} m^2\$per cell. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In silicon, the inter-atomic distance is about \$2.35 *10^{-10}m\$. Making the area that an atom occupies about \$5 * 10^{-20} m^2\$. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you have to see that each cell is a three-dimensional object, leading to about 10^6 atoms per cell. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fits easily...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mind you, the above numbers are estimates, ignoring material mix etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now lets look at the area size of a 64 Gbit chip. Thats about \$7 * 10^{10}\$ cells. If it were square-ish, it would have about \$2.5 * 10^5\$ cells per row. Whoops, thats \$2 * 2.5 * 10^{-8} * 10^5 = 5 * 10^{-3} m = 5mm\$ square at least.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a 32GB card, we'd need 4 of those. So yes, they probably are stacked.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With the expected higher integration, maybe down to a 10nm process, and threedimensional stacking of transistors within the chip, it looks like the volumetric size will be reduced by about a factor of ten within a year or two. &lt;/p&gt;&#xA;" OwnerUserId="3438" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:55:04.060" LastActivityDate="2011-06-02T02:55:04.060" CommentCount="1" />
  <row Id="14058" PostTypeId="2" ParentId="14051" CreationDate="2011-05-08T19:14:32.310" Score="3" ViewCount="" Body="&lt;p&gt;This isn't really an answer for the question, but the comment field is too small. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Speakers don't actually use DC currents. Instead they use AC currents, so it could be that your measurement is incorrect. Sometimes some multimeters will detect some AC voltages as DC, so it's best to be sure when measuring. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So a good way to test this would be to generate a signal which would be easier for multimeter to read. A nice program is Two channels frequency generator  which can be obtained &lt;a href=&quot;http://www.cognaxon.com/index.php?page=download_educational&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next check the output characteristics of your speaker. If it can make 50 Hz or 60 Hz sounds, open the generator, set left and right frequency to 50 Hz or 60 Hz and click start (or if you can't connect the system to a computer, record the sound and then play it on the speaker) and be sure to set the volume to maximum both on the device and in program and on computer output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So why 50 Hz or 60 Hz? Well those frequencies are commonly used for mains power and most multimeters are made so that they can easy and correctly read voltages at those frequencies. A good quality multimeter should be able to read voltages at other frequencies too, but this way you'll be sure that you get the correct reading. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the speaker can't produce those frequencies, then try with whole number multiples of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, why frequency generator? Well, normal music produces complicated waveforms which change very quickly and are quite complicated. A single tone which is made by the frequency generator will be much easier for multimeter to read. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the end check available settings on your multimeter. Good meters will have AC+DC voltage measurement option which will give you the real voltage at the speaker. If yours doesn't have such setting, try measuring both AC and DC voltage. Somewhere I read that you should calculate the actual voltage using following formula: \$V_r=\sqrt{V_{DC}^2+V_{AC}^2}\$. That should give you the real effective voltage. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-02T02:51:58.247" LastActivityDate="2011-06-02T02:51:58.247" />
  <row Id="14059" PostTypeId="2" ParentId="13987" CreationDate="2011-05-08T19:36:18.333" Score="4" ViewCount="" Body="&lt;p&gt;There really isn't a &quot;general&quot; protocol, what you end up using depends highly on the application.  In order for us to give you a better answer, we need to understand your requirements a little better.  You mention that you would like to have separate micro-controllers talking to each other as subsystems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some questions about this application:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Will there be more than 2 micro-controllers in this project?&lt;/li&gt;&#xA;&lt;li&gt;What are your speed and throughput requirements?  How fast does the information need get there and how often are you sending/receiving data?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;If you answered NO to question 1:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there are only 2 micrco-controllers in this project, you can definitely use UART between them.  If they both need to initiate communication, use flow control, otherwise it should be trivial to send data in one direction.  For the most part it should be &quot;fast enough&quot; given that you select one of the higher baud rates.  I2C and SPI are typically only good for master/slave architecture.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;If you answered YES (more than 2 controllers) to question 1:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;If there are more than 2 micro-controllers in your project, which one initiates communications?  Will it only be one master controller (ie master-slave architecture)?  Or would any of the subsystems be able to speak at any time?  &lt;/li&gt;&#xA;&lt;li&gt;Is there a need for any of the subsystems to talk to each other? eg: for devices A, B and C: A can send to B and C, and B can send to both A and C, etc.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So now you need something more scalable where you can drop addressable devices onto a common bus.  The answer to these follow up questions will help you decide between I2C and SPI (master-slave) or something like CAN (multi-master).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your micro-controller most likely has a UART peripheral, the others (especially CAN) may only be available on more higher end chips.  In either case, there should be plenty of documentation on how to use these peripherals to move bytes around.&lt;/p&gt;&#xA;" OwnerUserId="4172" LastEditorUserId="4172" LastEditorDisplayName="" LastEditDate="2011-05-09T23:50:24.947" LastActivityDate="2011-05-09T23:50:24.947" />
  <row Id="14060" PostTypeId="2" ParentId="8946" CreationDate="2011-05-08T20:01:21.387" Score="1" ViewCount="" Body="&lt;p&gt;An ARM might be able to do a good job of estimating the energy in each frequency component, at least if one uses a little assembly language and is using a nice ARM variant (e.g. Cortex-M3 or ARM7-TDMI, rather than a Cortex-M0).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming the original data and reference wave are 16 bits, and one has separate copies of the reference waveform for each frequency of interest (probably not too hard if there are only twelve of them) the inner loop might look something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;; R0 - Data source pointer&#xA;; R1 - Reference wave pointer&#xA;; R2 - Data source end, plus one&#xA;; R3 - Reference wave end&#xA;; R4 - Reference wave length&#xA;; R5 - Reference wave cosine delta&#xA;; R8 - Sine total L&#xA;; R9 - Sine total H&#xA;; R10 - Cosine total L&#xA;; R11 - Cosine total H&#xA;&#xA;lp:&#xA;  ldrsh r6,[r0],#2  ; I forget the syntax for post-increment&#xA;  ldrsh r7,[r2,r5]  ; Fetch cosine reference&#xA;  smlal r10,r11,r6,r7&#xA;  ldrsh r7,[r2],#2&#xA;  smlal r8,r9,r6,r7&#xA;  ; Repeat the above a few times if desired, if wave length will always be&#xA;  ; a multiple of the number of repetitions.  Note that the reference wave&#xA;  ; may need to be extended a bit to accommodate this (it must be extended&#xA;  ; be a quarter-wavelength to accommodate the cosine term).&#xA;  cmp r1,r3 ; Carry set if r1 has gotten as bit as r3&#xA;  subcs r1,r4 ; If passed end of wave, wrap&#xA;  cmp r0,r2 ; See if at end of wave&#xA;  bcc lp&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I think that inner loop would take about 20 cycles to process the sine and cosine terms for one same of one frequency.  So for twelve frequencies, you'd have to spend 240 cycles of front-line processing.  Even a 16MHz ARM should have no trouble handling that.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-08T20:01:21.387" />
  <row Id="14061" PostTypeId="2" ParentId="13987" CreationDate="2011-05-08T20:15:57.580" Score="3" ViewCount="" Body="&lt;p&gt;As @Jon noted, one issue in selecting a communications interface is whether one entity will always be responsible for initiating communications, or whether more than one entity may be so responsible.  A related matter is whether one entity will always be ready to receive unsolicited communications.  SPI is frequently used in applications where one side will always be ready to receive communication.  Something like a 74HC595 shift register, for example, is never &quot;busy&quot;.  While SPI is good for communication between a microcontroller and hardware which the micro is supposed to control, it is really not good for communication between two microcontrollers.  When two processors with I2C hardware are using it to communicate, software can take as long as it wants (within very generous constraints) to deal with what's going on, without causing data loss.  If a processor were to take a 100 microseconds to process each incoming byte, that would severely limit throughput, but the sender would slow down enough for the receiver to keep up.  The only way that can generally happen with SPI is if one has a separate wire for handshaking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I2C is really a wonderful protocol.  The biggest limitations that stop it from being the most perfect protocol imaginable are&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&lt;li&gt;Its speed is somewhat limited; SPI can go much faster, and even UARTs can sometimes go a little faster&#xA;&lt;li&gt;(2) While it's very convenient that I2C only needs two wires, both wires must be capable of bidirectional open-collector communication.  This makes it difficult to send I2C via repeaters.&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Personally, I'd like to see controller venders support a three-wire variant of SPI which included handshaking.  I'm unaware of any controller that does so, though.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-08T20:15:57.580" CommentCount="5" />
  <row Id="14062" PostTypeId="1" CreationDate="2011-05-08T21:03:46.223" Score="2" ViewCount="135" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/9137/what-kind-of-components-are-black-blobs-on-a-pcb&quot;&gt;What kind of components are black blobs on a PCB?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Here's a pic (sorry for the quality), what I'm asking about is the black blob in the middle:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/6YeRZ.jpg&quot; alt=&quot;IC under a dome&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As far as I can tell its some kind of surface mount IC.  What is this black blob called and is there a way to get it off without damaging the board/ic?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's from the controller board of a USB keyboard.&lt;/p&gt;&#xA;" OwnerUserId="4173" LastActivityDate="2011-05-08T21:55:33.170" ClosedDate="2011-05-08T23:30:35.917" Title="What is this kind of IC mount called?" Tags="&lt;pcb&gt;&lt;ic&gt;" AnswerCount="0" CommentCount="7" />
  <row Id="14065" PostTypeId="2" ParentId="13854" CreationDate="2011-05-08T21:30:18.803" Score="1" ViewCount="" Body="&lt;p&gt;I'll second the suggestion to look into the concepts behind BEAM robotics and solar engines. I think the solar engine based on the MAX8212 chip (which maxim will give you free samples of) would be the most suitable SE for you as it's the most (easily) configurable.  The arduino is a brilliant platform for learning about microcontrollers, but it's a bit power hungry for solar power. once you understand Arduino, start looking into working with at Atmel AVR chips directly. ATtiny45 is a great fun little platform to work with, and can be powered from a solar engine quite well. &lt;a href=&quot;http://jimblackhurst.com/wiki/index.php?title=SolarTherm&quot; rel=&quot;nofollow&quot;&gt;Check out what I've been doing with them here&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2778" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-09T03:14:50.233" LastActivityDate="2011-05-09T03:14:50.233" />
  <row Id="14067" PostTypeId="1" CreationDate="2011-05-08T22:10:13.997" Score="0" ViewCount="89" Body="&lt;p&gt;USB standard says voltage should be 5.0 +/- 0.25.&#xA;I have a car charger that specifies its output as 5.6v DC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How safe it is to use this charger to charge battery of HTC phone, that comes with a 5.0v-output home-charger?&#xA;Can this difference in voltage harm battery in any way or shorten its life?&lt;/p&gt;&#xA;" OwnerUserId="4175" LastActivityDate="2011-05-09T00:46:13.253" ClosedDate="2011-05-09T05:00:42.293" Title="Is USB car-charger with output 5.6v DC safe to use with battery-powered device designed for standard USB input" Tags="&lt;usb&gt;&lt;battery-charging&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="14068" PostTypeId="2" ParentId="14067" CreationDate="2011-05-08T22:30:08.120" Score="-1" ViewCount="" Body="&lt;p&gt;I would say &lt;em&gt;not&lt;/em&gt; safe.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have seen a lot of linear voltage regulators with an absolute maximum limit of 5.5V or 6V, which is very close to the limit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, with the 5.6V output, you can't be certain of other issues. It seems likely that it is using a step down converter. What about the ripple on the converter output? Could this damage the phone?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Bottom line is: don't risk it. The phone is expensive. Spend a few more on a decent charger.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-08T22:30:08.120" CommentCount="1" />
  <row Id="14069" PostTypeId="2" ParentId="14067" CreationDate="2011-05-08T23:05:56.597" Score="0" ViewCount="" Body="&lt;p&gt;Just put a diode in series with the supply. 8-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It should be OK with 5.6V.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-09T00:46:13.253" LastActivityDate="2011-05-09T00:46:13.253" />
  <row Id="14070" PostTypeId="1" CreationDate="2011-05-08T23:28:56.403" Score="0" ViewCount="37" Body="&lt;p&gt;I have few gears in 1 location: modem, router and switches. All of them use adaptors. But now, I have 3 separate adaptors for each of them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to buy/use 1 adaptor and branch out to supply power to 3 of them?&lt;/p&gt;&#xA;" OwnerUserId="4177" LastActivityDate="2011-05-08T23:35:22.840" ClosedDate="2011-05-09T00:03:05.237" Title="Combine Few Equipments Adaptor" Tags="&lt;adapter&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="14071" PostTypeId="2" ParentId="14070" CreationDate="2011-05-08T23:35:22.840" Score="0" ViewCount="" Body="&lt;p&gt;If they all use the same voltage, and the new adapter can supply the total current, you should be OK.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-08T23:35:22.840" />
  <row Id="14072" PostTypeId="1" CreationDate="2011-05-09T04:46:29.653" Score="0" ViewCount="65" Body="&lt;p&gt;I have been updating the embedded code on a set of &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardMega&quot; rel=&quot;nofollow&quot;&gt;Arduino Mega&lt;/a&gt; chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have been performing the upload via USB. Unfortunately, this is extremely unreliable. I get an error along the lines of&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;avrdude: stk500_getsync(): not in sync: resp=0x00 &#xA;avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I simply get another board (we have a whole shelf full of them) and work with that one until it stops working as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;According to &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1248528012/all&quot; rel=&quot;nofollow&quot;&gt;this forum&lt;/a&gt;, I'm not the only one who's having this problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've heard (somebody telling me he heard from somebody else) that the USB transfer is unreliable, and that there's some other way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone tell me if I'm hearing correctly, and if so, what the upload method is?&lt;/p&gt;&#xA;" OwnerUserId="4069" LastEditorUserId="4069" LastEditorDisplayName="" LastEditDate="2011-05-09T04:59:53.900" LastActivityDate="2011-05-09T07:28:33.273" Title="What possible ways can I upload sketches to Arduiono Mega chips?" Tags="&lt;arduino&gt;&lt;avrdude&gt;" AnswerCount="2" />
  <row Id="14073" PostTypeId="1" CreationDate="2011-05-09T04:52:21.557" Score="9" ViewCount="127" Body="&lt;p&gt;Hello&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is a cheap way to receive and record on PC several (tens) of fm-radios (public, e.g. news, music, etc)? Such radios uses frequencies like 90.4 MHz or 102.7 MHz, sends a stereo (sometimes with digital text subchannel).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I want to record tens of radios, I need to cover a spectrum of tens of MHz. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first way is to buy two or three dozen usual radiorecievers and try to connect them all to PC (e.g. with half-dozen of multichannel external usb soundcards). I think, that this is not very cheap.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second way is to build a single radio, which will downsample entire band 88-105 MHz into 3-20 MHz, then feed it into high-speed ADC, and do a software detection of each station.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the second way possible? cheap? How mush will it cost? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What hardware can be used, if I have no skills of making PCBs and using ADCs &amp;amp; FPGAs?&lt;/p&gt;&#xA;" OwnerUserId="1994" LastActivityDate="2011-05-09T10:21:51.493" Title="Receive several fm-radio stations at the same time (~10-20 MHz wide summary at 90MHz radiofrequency)" Tags="&lt;fpga&gt;&lt;adc&gt;&lt;radio&gt;&lt;fm&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="14074" PostTypeId="2" ParentId="13846" CreationDate="2011-05-09T05:00:14.410" Score="3" ViewCount="" Body="&lt;p&gt;If you ever look at DRAM chip datasheets there's a minimum clock speed of something like 50MHz+ for DDR2. So no, you will not be able to interface with them with a microcontroller (unless it has built-in hardware support).&lt;/p&gt;&#xA;" OwnerUserId="3953" LastActivityDate="2011-05-09T05:00:14.410" CommentCount="1" />
  <row Id="14075" PostTypeId="2" ParentId="13854" CreationDate="2011-05-09T05:41:47.820" Score="0" ViewCount="" Body="&lt;p&gt;I have no experience with arduino and it seems from the current crop of answers to be that it draws to much power and probably doesn't have a low enough sleep current draw to make it a viable option. A nanowatt xlp PIC would be the place to start, however you still need to deal with the interface between energy harvester (solar cell in this case) and microchip. The output of the solar cell is low voltage in comparison to other forms of energy harvesters and the requirements of a PIC + circuitry, linear technology do a range of self starting dcdc converters targetted at energy harvesting applications (LTC3105 for instance) which can act as your power converter. From that point you would attach the pic across the capacitor/battery and then run it in sleep mode when the solar cell is charging the battery/capacitor. Make sure that the battery/capacitor has a full charge (or at least isn't empty) when you first run the system as the PIC will have a fairly high cold-start current draw and could stop your stored voltage every reaching beyond 0.7V - you can solve this with a 1.9V low voltage comparator if need be. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Although people have stated the arduino is too power hungry for this type of thing you can solve that problem by just using more solar cells until you are able move on to PICs etc which would allow you to make a more sophisticated system.&lt;/p&gt;&#xA;" OwnerUserId="4096" LastActivityDate="2011-05-09T05:41:47.820" />
  <row Id="14076" PostTypeId="2" ParentId="14072" CreationDate="2011-05-09T06:00:31.253" Score="1" ViewCount="" Body="&lt;p&gt;The other way is to program is via the In Circuit Serial Progamming (ICSP) connector - with an appropriate interface like the STK-500 or &lt;a href=&quot;http://www.sparkfun.com/products/9825&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1612" LastActivityDate="2011-05-09T06:00:31.253" />
  <row Id="14077" PostTypeId="1" CreationDate="2011-05-09T07:23:39.410" Score="4" ViewCount="229" Body="&lt;p&gt;The drywall is just starting to go up in my family’s basement project. I’ve been looking into residential light control systems. Some of the ones I’ve seen have been an upwards of $2,000. I’m thinking it'd be much more fun (and cost effective!) to implement my own Arduino-based system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The real problem lies in the actual control of the lights. Each group of lights will need to be controlled by a switch-based dimmer system. It would be much simpler if the microcontroller was the only point of control. Alas, this is not the case. I’m assuming I need to use a dimmer switch that lets an outside device interface with it. That would avoid the problem completely as the switch and Arduino could both control the lights.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anybody recommend a better solution/approach or suggest a dimmer switch that has some kind of “remote” interface?&lt;/p&gt;&#xA;" OwnerUserId="3353" LastActivityDate="2011-05-10T17:18:26.613" Title="Arduino Home Light Dimming" Tags="&lt;arduino&gt;&lt;light&gt;&lt;home-automation&gt;&lt;dimming&gt;" AnswerCount="4" />
  <row Id="14078" PostTypeId="2" ParentId="14072" CreationDate="2011-05-09T07:28:33.273" Score="1" ViewCount="" Body="&lt;p&gt;As long as it has the boot loader you could use your serial port, as a work around. On another arduino, I used a max232 chip hooked up to the TX and RX bypassing the USB to serial connection and pointed the arduino SW to that comm port, worked like a charm except you have to hit reset before you send the new firmware, no automatic reset.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I notice is that if i leave my arduino connected to the PC/USB line(linux), after awhile(30mins+) I try and program it and it gets a similar message.&lt;/p&gt;&#xA;" OwnerUserId="2060" LastActivityDate="2011-05-09T07:28:33.273" />
  <row Id="14079" PostTypeId="2" ParentId="14073" CreationDate="2011-05-09T07:40:32.943" Score="8" ViewCount="" Body="&lt;p&gt;The second technique you mention is the way to do it, using what is called a &quot;Software Defined Radio&quot; or SDR. Many radio amateurs are using SDRs, and the simple ones are very cheap, about 30 dollars for a kit that down-converts the input into in-phase and quadrature baseband audio output which is fed into the stereo inputs of a PC sound card for digital signal processing. However, they are using relatively low-frequency signals on the HF amateur radio bands, and the hardware doesn't use any exotic components. Digitising VHF signals as you require and receiving several channels simultaneously is going to be rather expensive, the ADC alone is going to cost about 50 dollars and you will also need an FPGA and a DSP, unless you convert down to baseband and do the DSP on a PC. You will need a lot of high-frequency design experience, be able to develop code for the FPGA, write DSP code and be able to design a high-speed multilayer PCB, so you should start studying. :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for cost, I'd estimate 500 dollars for the hardware, including the PCB, assuming you designed it yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Linear Technology makes suitable ADCs that can downsample at 750 MHz! They were good enough to give me a couple as free samples. I have suitable FPGA and DSP boards, so it's just a question of putting them together. :)&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-09T10:21:51.493" LastActivityDate="2011-05-09T10:21:51.493" CommentCount="12" />
  <row Id="14080" PostTypeId="2" ParentId="14077" CreationDate="2011-05-09T11:27:43.407" Score="1" ViewCount="" Body="&lt;p&gt;DMX512 is widely used for controlling stage lighting. Since it uses EIA-485 the hardware and software should be quite easy to implement on an Arduino with a suitable shield. &lt;a href=&quot;http://www.arduino.cc/playground/Learning/DMX&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is an Arduino DMX project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Low-cost DIY remote DMX dimmer controllers are available, &lt;a href=&quot;http://www.hoelscher-hi.de/hendrik/english/dimmer.htm&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; is one which uses an ATmega8515 AVR, a similar device to that used on the Arduino. I'd be inclined to use a much smaller, cheaper controller. The dimmer interface to the lamps, the &quot;power unit&quot;, is also described. It's a rather nice project.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-09T12:12:49.143" LastActivityDate="2011-05-09T12:12:49.143" CommentCount="3" />
  <row Id="14081" PostTypeId="1" CreationDate="2011-05-09T13:06:36.877" Score="1" ViewCount="75" Body="&lt;p&gt;I am trying to connect three nodes(A,B,C) through RF cables in the following manner :&#xA;A can communicate with both B and C(and vice versa), but B and C cannot communicate directly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Somebody suggested using a splitter for this work, but when I tested one I found that all three nodes could communicate with each other. Now, somebody is telling me to use a coupler. Can a coupler achieve what I want? What is the difference between splitter and coupler?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS: I am working in the 2.4GHz band(wifi), if that makes a difference.&lt;/p&gt;&#xA;" OwnerUserId="4183" LastActivityDate="2011-05-09T13:37:37.800" Title="Difference between RF splitter and coupler?" Tags="&lt;rf&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="14082" PostTypeId="2" ParentId="14081" CreationDate="2011-05-09T13:15:55.607" Score="2" ViewCount="" Body="&lt;p&gt;A splitter definitely won't work. It's a device that accepts an input signal and delivers multiple output signals.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think that you need a directional coupler. It has an input, an output, a coupled port, and a load. It's a device that operates on an input so that two output signals are available, on the output port (larger signal) and the coupled port (smaller signal). However, when the input is applied to the opposite port of a terminated coupler, only one output signal is produced. MCL makes suitable devices.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-09T13:37:37.800" LastActivityDate="2011-05-09T13:37:37.800" />
  <row Id="14083" PostTypeId="2" ParentId="14077" CreationDate="2011-05-09T14:04:14.120" Score="1" ViewCount="" Body="&lt;p&gt;You might want to look at &lt;a href=&quot;http://en.wikipedia.org/wiki/X10_%28industry_standard%29&quot; rel=&quot;nofollow&quot;&gt;X10&lt;/a&gt; I have not used it in a while but since I used it last I know that there has at least been a serial port interface, perhaps even wireless, so that you dont have to actually get on the power lines with your hardware.  There are (were) modules where you closed a relay and could get an all on or all off.  For dim or bright you will need more control.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-05-09T14:04:14.120" CommentCount="1" />
  <row Id="14084" PostTypeId="2" ParentId="14077" CreationDate="2011-05-09T14:25:55.623" Score="3" ViewCount="" Body="&lt;p&gt;I setup a whole house with X10 about 10 years ago, and while it worked, it could be kind of flaky. If I were going to do it again, I would look at more modern products like &lt;a href=&quot;http://www.insteon.net/products-home.html&quot; rel=&quot;nofollow&quot;&gt;Insteon&lt;/a&gt;. Insteon is supposed to resolve a lot of the flakiness that X10 has.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I wouldn't bother trying to build the device AC control modules (dimmers, remote switches, etc) yourself as working with mains voltages is very dangerous unless you really know what you're doing.&lt;/p&gt;&#xA;" OwnerUserId="746" LastEditorUserId="746" LastEditorDisplayName="" LastEditDate="2011-05-09T14:33:55.193" LastActivityDate="2011-05-09T14:33:55.193" CommentCount="5" />
  <row Id="14085" PostTypeId="2" ParentId="14038" CreationDate="2011-05-09T15:53:03.417" Score="0" ViewCount="" Body="&lt;p&gt;As ducksauz noted if it currently isn't working you are not going to make it any worse. Having said that, while you can find and replace the damaged components, it might be more difficult to find out what caused the damage. It is very possible that after spending time and money to fix what you see, as soon as power it back up, everything you just replaced will burn up again. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to try to fix for the experience of fixing it, go ahead. If you want to get a working TV, you might want to price a new one. &lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-05-09T15:53:03.417" CommentCount="1" />
  <row Id="14086" PostTypeId="1" CreationDate="2011-05-09T16:04:01.223" Score="3" ViewCount="68" Body="&lt;p&gt;Hi All,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an issue with DC motor and Bluetooth.&#xA;I'm using PIC PIC18F, TIP 31 NPN transistor as motor driver and 4 x AA rechargeable battery. Each battery is about 1500mAh.&#xA;The board has 2 modes, 1.Simple Run and 2.Bluetooh&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have 3 motors and all are in good condition:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Motor A: 2.1 mAh&lt;/li&gt;&#xA;&lt;li&gt;Motor B: 20 mAh&lt;/li&gt;&#xA;&lt;li&gt;Motor C: 70 mAh&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In &quot;Simple Run&quot; mode, the 3 motors run without an issue.&#xA;But when in &quot;Bluetooth&quot; mode with PWM, Motor B had difficulty in running and Motor C had a slight issue. Motor A is perfectly fine.&#xA;I have an android app to control the motor using bluetooh.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks like the current issue. But I already use 1500mAh battery.Somehow Motor C is run better than Motor B.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What may be the issue? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks like the Motor draw away the current from Bluetooth module and the microprocessor. This cause the signal send from the Android App break.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or could it be the current from the motor fall back / kick back to the board?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I should Motor Driver IC instead of using TIP 31?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/dfRP8.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="4185" LastEditorUserId="4185" LastEditorDisplayName="" LastEditDate="2011-05-10T16:56:50.143" LastActivityDate="2011-05-10T16:56:50.143" Title="Different types of DC Motor with PIC + Bluetooth" Tags="&lt;dc-motor&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="14087" PostTypeId="2" ParentId="13899" CreationDate="2011-05-09T16:59:51.817" Score="4" ViewCount="" Body="&lt;p&gt;The LPC11C24 requires an additional 5V supply to operate the on-chip CAN transceiver. When powering the LPCXpresso board through the USB debug port only, the transceiver does not receive the full 5V. The +5VIN pin only reads 1.3V, so the transceiver does not operate correctly. I have found 2 ways to resolve this:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Use an external 5V regulated supply, connected through the +5VIN pin.&lt;/li&gt;&#xA;&lt;li&gt;Connect the LPCXpresso to the &lt;a href=&quot;http://www.embeddedartists.com/products/lpcxpresso/xpr_base.php&quot; rel=&quot;nofollow&quot; title=&quot;Embedded Artists LPCXpresso Base Board&quot;&gt;Embedded Artists LPCXpresso Base Board&lt;/a&gt;.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The Base Board requires that the +5V is supplied through the USB-to-UART main power source port in addition to the debug port.&lt;/p&gt;&#xA;" OwnerUserId="2150" LastActivityDate="2011-05-09T16:59:51.817" />
  <row Id="14088" PostTypeId="2" ParentId="14086" CreationDate="2011-05-09T17:16:54.003" Score="1" ViewCount="" Body="&lt;p&gt;Driving the PIC, Bluetooth and the motor from the same battery is asking for problems. Try using a separate supply for the motor.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-09T17:16:54.003" CommentCount="3" />
  <row Id="14089" PostTypeId="1" CreationDate="2011-05-09T17:22:45.370" Score="4" ViewCount="108" Body="&lt;p&gt;Hello Folks,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will like to know if a baud-rate of 9600 is so fast for an 8051 MCU using an 11.0952Mhz crystal. Why? I have observed some inconsistency in the behavior of my MCU, in that when I send a set of characters looking for a particular character to perform certain operations, I discover that my MCU does not perform the required operation. Meaning that there was a misplacement along the line during receiving.&#xA;Then I did some serial routine. I sent a &quot;ABC&quot; from terminal to the MCU, which should transmit back to the terminal an increment of each character sent, hence it should give &quot;BCD&quot;. But this is what i got consistently - &quot;BD&quot; missing &quot;C&quot;. Meaning that the MCU missed &quot;B&quot;. I also send other set of characters and discovered that some characters get missed by the MCU. What could be the cause of this. Could it be the Baud-rate or in my code. How can I possibly rectify this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the code.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void initUART()&#xA;{&#xA;  SCON = 0x50;&#xA;  TMOD = 0x20;&#xA;  TH1 = TL1 =-3;&#xA;  TR1 = 1;&#xA;}&#xA;&#xA;void sendCHAR()&#xA;{&#xA;  SBUF = uartBUFF[s];&#xA;  while(!TI);&#xA;  TI=0;&#xA;}&#xA;&#xA;void serial_isr(void) interrupt 4  &#xA;{&#xA;  if (RI)&#xA;  {&#xA;    RI = 0;&#xA;    tmpBUFF = SBUF;&#xA;    charFLAG=1;&#xA;  }&#xA;}&#xA;&#xA;main()&#xA;{&#xA;  IE= 0x91;&#xA;  initUART();&#xA;  while (1)&#xA;  {&#xA;    if(charFLAG)&#xA;    {&#xA;      SBUF = (tmpBUFF+1);&#xA;      while(!TI);&#xA;      TI=0;&#xA;      charFLAG = 0;&#xA;    }&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="3632" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-05-10T09:28:37.720" LastActivityDate="2011-05-11T14:31:10.573" Title="Baud-rate for 8051 Microcontroller" Tags="&lt;microcontroller&gt;&lt;8051&gt;&lt;baudrate&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="14090" PostTypeId="1" AcceptedAnswerId="14092" CreationDate="2011-05-09T17:25:44.517" Score="2" ViewCount="70" Body="&lt;p&gt;I am designing a board, which has a high current (~2A) buck-topology switch mode power supply on it, which uses an unshielded SDR0805 inductor. About 4cm from it, there is a magnetometer (combined mag/acc LSM303DLH.) Would problems be encountered with this setup? Would I need to shield the inductor?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-09T18:00:40.907" Title="Should I avoid placing a SMPS inductor close to a magnetometer?" Tags="&lt;inductor&gt;&lt;electromagnetism&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="14091" PostTypeId="2" ParentId="14089" CreationDate="2011-05-09T17:48:52.023" Score="2" ViewCount="" Body="&lt;p&gt;With a 11.0952 MHz crystal the maximum bitrate for the 8051 is 57600 bps, so that should not be the problem. Besides, you do seem to receive some characters OK. You may want to check the answers  to &lt;a href=&quot;http://electronics.stackexchange.com/questions/13866/baudrate-calulator&quot;&gt;this question&lt;/a&gt; if you're not sure about the bitrate.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-09T17:48:52.023" CommentCount="3" />
  <row Id="14092" PostTypeId="2" ParentId="14090" CreationDate="2011-05-09T18:00:40.907" Score="3" ViewCount="" Body="&lt;p&gt;The datasheet says this in the application hints.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;h2&gt;High current wiring effects&lt;/h2&gt;&#xA;  &#xA;  &lt;p&gt;High current in wiring and printed circuit traces can be the cause of errors in magnetic field measurements for compassing.&#xA;  Conducto-generated magnetic fields add to earth’s magnetic field, creating errors in compass heading computation.&#xA;  Keep currents that are higher than 10 mA a few millimeters further away from the sensor IC.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;2 A is way more than 10 mA,  and an inductor is a obviously going to create a stronger magnetic field than a straight wire. A good guesstimate is that you're going to have interference problems even if you shield the inductor.&lt;/p&gt;&#xA;" OwnerUserId="3745" LastActivityDate="2011-05-09T18:00:40.907" CommentCount="5" />
  <row Id="14093" PostTypeId="1" CreationDate="2011-05-09T18:17:15.837" Score="2" ViewCount="117" Body="&lt;p&gt;I would like to goof around with some CPLD stuff and I see I have a couple options out there. I don't have a particular application in mind; it just seems like there a lot of possibilities, some of which are easier to use than others.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main manufactures have development boards, some more expensive than others. They also have programmer cables that generally seem... not cheap. Doing some digging, I've come across several options and I'm looking to understand the pros/cons of each.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is it fair to say that CPLDs with X Macrocells are more or less the same?&lt;/li&gt;&#xA;&lt;li&gt;Although the JTAG interface is standard, for the purposes of programming the part, there is no standard &lt;a href=&quot;http://electronics.stackexchange.com/questions/9595/very-basic-question-about-jtag&quot;&gt;previous JTAG Question&lt;/a&gt;. Is this a matter of the vendor software talking to the programmer? Do things become more standard if I use some other utility to dump a binary file?&lt;/li&gt;&#xA;&lt;li&gt;Some of the platforms have cheaper alternatives. I'm wondering what the catches are with these in terms of USB/parallel port, Linux/Windows.&lt;/li&gt;&#xA;&lt;li&gt;Assuming I get comfortable with a development board, how difficult is the transition to &#xA;just using one of the base parts directly? My impression is that in the major options, it's just a matter of some header pins and a couple diodes/resistors. Am I far off on this?&lt;/li&gt;&#xA;&lt;li&gt;How would I program the devices in my own designs? If I have a development board or starter kit, will I then have to go back and buy an expensive programmer? Why does a dev board sell for cheap but the programmer runs hundreds of dollars? Presumably the dev board comes with the ability to program.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Here are some of the options that stand out for me. I list the prices only to differentiate them from the multi-hundred-dollar options. All of them are in the ballpark for me. I'm looking for the hiden costs in terms of ease of use, software issues and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Xilinx is a popular path. I could do:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Digilent C-Mod board for $\$$17:&#xA;&lt;a href=&quot;http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,798&amp;amp;Prod=CMOD&quot; rel=&quot;nofollow&quot;&gt;http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,798&amp;amp;Prod=CMOD&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;and one of their programming cables (parallel for $\$$12 or USB  for $\$$48)&#xA;&lt;a href=&quot;http://www.digilentinc.com/Products/Catalog.cfm?NavPath=2,395&amp;amp;Cat=5&quot; rel=&quot;nofollow&quot;&gt;http://www.digilentinc.com/Products/Catalog.cfm?NavPath=2,395&amp;amp;Cat=5&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The Digilent cable requires using their software which is currently windows only, so I'd need to go the $\$$48 USB route.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another Xilinx possibility is &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;a Bus Pirate board ($\$$28)&#xA;&lt;a href=&quot;http://www.seeedstudio.com/depot/bus-pirate-v3-assembled-p-609.html?cPath=61_68&quot; rel=&quot;nofollow&quot;&gt;http://www.seeedstudio.com/depot/bus-pirate-v3-assembled-p-609.html?cPath=61_68&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;and a Coolrunner development board ($\$$15)&#xA;&lt;a href=&quot;http://www.seeedstudio.com/depot/xc9572xl-cpld-development-board-p-799.html?cPath=174&quot; rel=&quot;nofollow&quot;&gt;http://www.seeedstudio.com/depot/xc9572xl-cpld-development-board-p-799.html?cPath=174&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Switching companies to Lattice: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;they have a breakout board development kit ($\$$29)&#xA;&lt;a href=&quot;http://www.latticesemi.com/products/developmenthardware/breakoutboardevalkits.cfm&quot; rel=&quot;nofollow&quot;&gt;http://www.latticesemi.com/products/developmenthardware/breakoutboardevalkits.cfm&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I like the idea of using Lattice parts as Mouser.com carries them (I don't see much Xilinx there). I tend to order more from them. Once I get comfortable with their stuff, I'm guessing that I could hack up a programmer cable based on the schematics of this board. It looks really straight forward. Could I use the eval board as a programmer? The do expose the JTAG header?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Lattice MachXO2 Pico kit ($\$$29) also looks to be a great value, though the part that it's showcasing is more expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Altera also has good offerings.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A programmer can be had from EBay for ($\$$15)&lt;/li&gt;&#xA;&lt;li&gt;A demo board can be had from EBay for ($\$$28)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Alternately, Altera has&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A starter kit for ($\$$50) &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Which of these is the better route for a beginner that is easier to get working (drivers and such), has some staying power, and perhaps offers the most flexibility?&lt;/p&gt;&#xA;" OwnerUserId="550" LastEditorUserId="550" LastEditorDisplayName="" LastEditDate="2011-05-09T22:39:11.833" LastActivityDate="2011-05-09T22:39:11.833" Title="What are my less expensive options for getting started with CPLDs" Tags="&lt;programmable-logic&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="14094" PostTypeId="2" ParentId="14093" CreationDate="2011-05-09T18:31:15.760" Score="2" ViewCount="" Body="&lt;p&gt;I much prefer the Altera MAX II CPLDs to those from Xilinx. They are actually small FPGAs, but Altera keeps quiet about that. I've designed my own PCBs for Xilinx and Altera CPLDs, it's quite easy. Low-cost programming cables for both Xilinx and Altera devices are available on Ebay, I use them with FPGAs and don't have any problems with both Xilinx and Altera parts. At the prices asked it isn't worth making your own any more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Altera's software is much easier to use than Xilinx's. I'd download the software for the devices you are thinking of using and try it before making a final decision.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-09T18:31:15.760" CommentCount="3" />
  <row Id="14095" PostTypeId="2" ParentId="14089" CreationDate="2011-05-09T19:56:08.543" Score="3" ViewCount="" Body="&lt;p&gt;How do you get the characters from the serial port buffer register? If you simply read them in a loop like&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void main() {       &#xA;  char c;&#xA;  while (1) {&#xA;    c=SBUF;&#xA;    do_something(c);&#xA;  }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Then you will miss characters once the execution time of do_something() gets longer. Note that this includes time spend in intterrupts. The 8051 serial port has no hardware fifos, a character will be overwritten by the next one if it was not read in time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Our solution was to read the characters into a Ringbuffer during the serial Intterupt, and to use the FIFO in the main loop. Works (with high priority interrupt) for 460800 Baud with 7,3728 MHz crystal on a Silabs 80C51FXXX.&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Update&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;As we now see the source coude, the bug is now clear: You wait in the main loop for your character to be sent. But that means you wait a whole &quot;character time&quot; without being able to read your interrupt character buffer, and another few cyles to detect and read the next. This is too long if the sender sends characters fast, as a PC does.&lt;/p&gt;&#xA;" OwnerUserId="1472" LastEditorUserId="1472" LastEditorDisplayName="" LastEditDate="2011-05-10T13:53:38.313" LastActivityDate="2011-05-10T13:53:38.313" CommentCount="3" />
  <row Id="14096" PostTypeId="1" CreationDate="2011-05-09T20:12:47.110" Score="3" ViewCount="110" Body="&lt;p&gt;Hi Everyone -- I don't know much about electronics... but wanted to know if someone could give some advice on LED screens --&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Is it possible to make/buy a circular LED screen about 12 inch in diameter? What would this cost?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;How much battery power would be needed to run such a device? Would it last say 6 months of continuous use?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Am I right to think that these LEDs could be switched to different colors? eg, Red, Yellow, Green?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Just to make it clear it is low resolution, ie. I am not talking about a TV screen type display, literally 100x100 pixels or similar (I hope this is making some sense) maybe LED is not the best solution?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="4189" LastActivityDate="2011-05-10T00:24:23.413" Title="LED screen (cost, size, power)" Tags="&lt;led&gt;&lt;display&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="14097" PostTypeId="2" ParentId="14096" CreationDate="2011-05-09T20:37:47.513" Score="7" ViewCount="" Body="&lt;p&gt;This question is very, very vague.  So here are my vague answers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) Yes, it is possible.  You'll want an RGB LED to produce the most colors.  A surface mount part would make a 12-inch 100x100 possible I'd wager.  &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=511-1624-1-ND&quot; rel=&quot;nofollow&quot;&gt;Something like this is a good bet&lt;/a&gt;. For a volume of 2500 they're $\$$1627.50, so multiply by 4 for 10,000 and get it's roughly $\$$6500 and this doesn't include the cost of the boards or the controller which will be significant.  Also, I make no claims about the refresh rate, brightness, clarity, etc.  This is just a Rough Order of Magnitude number.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) The current draw is ~5mA on these LEDs and assuming they were all on at the same time they would use 50A altogether.  This is insane and there's no way to have a reasonably-sized battery large enough to power it for an hour let alone months.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) Yes, RGB LEDs can make pretty much any color.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is not the best solution - you'll probably have better luck using an LCD instead.&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-10T00:24:23.413" LastActivityDate="2011-05-10T00:24:23.413" CommentCount="6" />
  <row Id="14098" PostTypeId="1" AcceptedAnswerId="14104" CreationDate="2011-05-09T21:11:13.933" Score="5" ViewCount="129" Body="&lt;p&gt;I'm putting together an ALU, that I want to synthesize on an FPGA. The carry-look-ahead adder is the one many choose to use as opposed to the ripple-carry adder. However, a thought crossed my mind. The ripple-carry adders I have put together before simply has a series of one bit full-adders connected to each other. My though is, what if I were to design a 4-bit full-adder? I'm not talking about an an adder made up of four one bit full-adders. I'm talking about a single components with 9 inputs (x3,x2,x1,x0,y3,y2,y1,y0,cin). I'm aware this would have 512 possible states (2^(9 inputs)).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'm wondering is:  &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;There is obviously going to be a massive number of gates used, is it worth it?&lt;/li&gt;&#xA;&lt;li&gt;If I were implementing all my components using NAND gates with a certain delay or all of this, how much of an improvement in speed would a see in a 32-bit using a.) 4-bit full adders b.) CLA adder c.) 1-bit full adders&lt;/li&gt;&#xA;&lt;li&gt;Is there some other implementation of an adder I'm not aware of.&lt;/li&gt;&#xA;&lt;li&gt;Although an adder is a very menial part of an ALU, what do most digital designers actual go for? Or do they simply use &lt;code&gt;assign Sum = X+Y+cin;&lt;/code&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="4191" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-05-10T00:06:49.670" LastActivityDate="2011-05-10T14:39:24.720" Title="Different Adder Implementations" Tags="&lt;fpga&gt;&lt;verilog&gt;&lt;speed&gt;&lt;optimization&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="14099" PostTypeId="2" ParentId="14026" CreationDate="2011-05-09T21:35:58.723" Score="3" ViewCount="" Body="&lt;p&gt;Accelerometers and Gyroscopes are going to be good, but not perfect. Depending on what your goal of the feedback is, you might want to consider using something like stepper motors. They will give you more of an absolute position of the current rotation of each motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to use accelerometers and gyroscopes you should go take a look at this question: &lt;a href=&quot;http://electronics.stackexchange.com/questions/4983/how-to-determine-position-from-gyroscope-and-accelerometer-input&quot;&gt;How to determine position from gyroscope and accelerometer input?&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-09T21:35:58.723" CommentCount="4" />
  <row Id="14100" PostTypeId="2" ParentId="14035" CreationDate="2011-05-09T21:48:51.827" Score="2" ViewCount="" Body="&lt;p&gt;Most of the filters used in the digital world are just sampled version of the analog counterpart. A large reason for this is that there was lots of work done in analog filtering before digital came along, so rather then reinventing the wheel, most just used prior designs. The advantage to digital though is that a higher order filter can be achieved much easier then in the analog world. Just imagine of complex a circuit get every time you add another order to the design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are going for a brick wall type filter the Gaussian curve is a pretty good place to start. If you know about Time Domain &amp;lt;-&gt; Frequency Domain; a Gaussian transforms into a Gaussian in the other domain. As it gets winder in one, it gets narrower in the other. So in order to get a perfect spike in frequency domain you would need an infinite amount of samples.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you happen to have Matlab available for use, you should check out some of the built in filter design tools. Here is a link talking about &lt;a href=&quot;http://www.mathworks.com/help/toolbox/signal/butter.html&quot; rel=&quot;nofollow&quot;&gt;Butterworth&lt;/a&gt; and &lt;a href=&quot;http://www.mathworks.com/help/toolbox/signal/besself.html&quot; rel=&quot;nofollow&quot;&gt;Bessel&lt;/a&gt;. The design tools allows you to specify certain aspects of the filter. These aspects changes for each filter type, but some examples are Passband, stopband, ripple, etc. If you give the designer the constraints you want, it will either give you an error (meaning it can't make that filter with that filter type) or it will give you a filter with the minimum order required to meet spec.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-09T21:48:51.827" CommentCount="2" />
  <row Id="14101" PostTypeId="5" CreationDate="2011-05-09T21:54:33.007" Score="0" ViewCount="" Body="&lt;p&gt;See also&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Intel_MCS-51&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-05-09T23:47:27.403" LastActivityDate="2011-05-09T23:47:27.403" />
  <row Id="14102" PostTypeId="4" CreationDate="2011-05-09T21:54:33.007" Score="0" ViewCount="" Body="The &quot;8051&quot; is a (still) very popular chip in the Intel MCS-51 micro controller series." OwnerUserId="-1" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-05-09T23:47:31.303" LastActivityDate="2011-05-09T23:47:31.303" />
  <row Id="14103" PostTypeId="2" ParentId="14098" CreationDate="2011-05-09T22:06:06.540" Score="5" ViewCount="" Body="&lt;p&gt;What you &lt;em&gt;&lt;strong&gt;don't&lt;/strong&gt;&lt;/em&gt; want to do is implement the adder yourself out of gates.  Use the features that VHDL/Verilog give you for adding numbers.  Any adder you create is going to be larger and slower than anything the VHDL/Verilog compiler can do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason for this is simple:  FPGA's have dedicated logic in them for doing adders with a minimum amount of logic and as fast as possible.  This includes special carry chain logic and routing.  If you let the compiler utilize these then you'll benefit from the stuff that's already in the FPGA.  In other words, just do Sum=X+Y+cin, where X and Y are multi-bit numbers.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-09T22:06:06.540" CommentCount="4" />
  <row Id="14104" PostTypeId="2" ParentId="14098" CreationDate="2011-05-09T23:06:31.900" Score="3" ViewCount="" Body="&lt;p&gt;To answer #4, at least in code targeted for synthesis, an adder will usually be coded as &lt;code&gt;assign sum = x + y&lt;/code&gt;. This leaves the choice of how to implement the adder up to the synthesis tool. There is a cost/performance tradeoff. If there is a minimal performance constraint, the tool will implement a ripple carry adder, as that has the lowest cost. If there are more aggressive performance requirements, the tool will implement a more sophisticated structure, at some added cost. Another possibility for FPGA synthesis is that the adder will be mapped to a special-purpose DSP component, if available in the target device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When maximum performance is desired, the logic will be designed by hand rather than implemented with a synthesis tool. In this case, in addition to a high-level reference model with the form &lt;code&gt;sum = x + y&lt;/code&gt;, there would also be a lower-level description describing the individual gates or transistors (this might be done in an HDL, or in a schematic tool). This &quot;maximum performance&quot; scenario would almost certainly be an ASIC implementation rather than an FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To (not really) answer #3, for more than you ever wanted to know about adder architectures, I found this thesis linked from a thread on edaboard: &lt;a href=&quot;http://www.iis.ee.ethz.ch/~zimmi/publications/adder_arch.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.iis.ee.ethz.ch/~zimmi/publications/adder_arch.pdf&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To answer #1 and #2, the best way to figure things like this out is to do some experiments, anything else is speculation. What you will get for the &quot;4-bit full adder&quot; design depends how you code it. If you code it as an adder, the tool will likely do what it would have done anyways, although it may fail to figure out that the 4-bit adders go together to form a larger adder. If you code it as a logic function, you may get something faster than the ripple-carry implementation, but you may not. If I have time later I will update this with some specific results.&lt;/p&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-05-09T23:06:31.900" CommentCount="1" />
  <row Id="14105" PostTypeId="2" ParentId="1404" CreationDate="2011-05-10T00:14:01.277" Score="0" ViewCount="" Body="&lt;p&gt;The $2 option:&lt;br&gt;&#xA;&lt;a href=&quot;http://scanlime.org/2010/04/embedded-bluetooth-for-2/&quot; rel=&quot;nofollow&quot;&gt;Stick a $2 USB-Bluetooth adapter on your propller MCU&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It depends on you already using a &lt;a href=&quot;http://www.parallax.com/propeller/&quot; rel=&quot;nofollow&quot;&gt;Parallax Propeller&lt;/a&gt; for your local Microprocessor, but you could probably bang-together a USB-Host driver for another microprocessor, if you really know the microprocessor well.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-05-10T00:14:01.277" />
  <row Id="14106" PostTypeId="1" AcceptedAnswerId="14112" CreationDate="2011-05-10T01:14:05.717" Score="1" ViewCount="135" Body="&lt;p&gt;Hello &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am making a POV RGB LED Globe that plays animations on its surface. Currently I am using a Arduino Mega 2560 with 256k of Flash Memory. My program and the boot loader take up 20k of memory leaving me with 236k. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are 64 RGB LEDs using 8 bits of brightness that change color 64 times a revolution. $\left( 64 \cdot 64 \cdot 3 \cdot 8 \right) \div 1024 = 12\mbox{ kB}$ == 12288 BYTES &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each frame of animation takes up 12288 BYTES (12k) of memory. That only leaves me with 19 Frames of animation. Good but not great, at 10 frames a sec thats only 2 secs of animations. I was hoping for ~64 frames of animation or 768k RAM. (768+20=788k total)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried a few load 'on the fly' and steaming methods (SD, Wireless) but they can't keep up with the data required while streaming the data to the LEDs. I am going to try using a simple compression method next but I don't have high hopes that the system will be able to uncompress the data while steaming the color information out to the LEDs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have currently tested 10 frames of animation using the Arduino Mega 2560 and it works. Kind of, there are still some bugs. But I don't really want to switch off an Arduino board if I can help it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Are there pre-built Arduino boards with more ram?&lt;/li&gt;&#xA;&lt;li&gt;Can I add RAM to an existing Arduino board?&lt;/li&gt;&#xA;&lt;li&gt;Suggest a different Dev board thats is VERY similar to the Arduino with a c++ compiler. &lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Thank you for your time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: &#xA;I am using the &quot;PROGMEM&quot; keyword to store my animations in the Flash memory not the SRAM. &#xA;&lt;a href=&quot;http://www.arduino.cc/playground/Learning/Memory&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/playground/Learning/Memory&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3407" LastEditorUserId="3407" LastEditorDisplayName="" LastEditDate="2011-05-11T04:32:01.593" LastActivityDate="2011-05-11T04:32:01.593" Title="Arduino Mega 2560 like board but with more ram" Tags="&lt;arduino&gt;&lt;led&gt;&lt;ram&gt;&lt;pov&gt;" AnswerCount="4" CommentCount="6" />
  <row Id="14107" PostTypeId="2" ParentId="14106" CreationDate="2011-05-10T01:39:09.973" Score="0" ViewCount="" Body="&lt;p&gt;You can't really expand the addressable RAM; the chip has whatever it has inside it and doesn't present a memory bus outside.  You could add an SD shield such as &lt;a href=&quot;http://www.adafruit.com/products/243&amp;amp;zenid=82a8dfa1fe8b54f4da934e4885e6fa17&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; and use it as a solid-state disk, much as you're doing now with the on-board flash.  &lt;/p&gt;&#xA;" OwnerUserId="3361" LastEditorUserId="3361" LastEditorDisplayName="" LastEditDate="2011-05-10T12:22:06.837" LastActivityDate="2011-05-10T12:22:06.837" />
  <row Id="14108" PostTypeId="1" AcceptedAnswerId="14111" CreationDate="2011-05-10T02:29:32.200" Score="0" ViewCount="77" Body="&lt;h1&gt;TL;DR&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;How is phase in a delay system represented by the equation of a straight line with slope equal to -n?&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;Background:&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;There is delay system concept given in this &lt;a href=&quot;http://imm.io/5xEH&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/8CrXa.jpg&quot; alt=&quot;Definition of delay system&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, I did not understand the phase response of this dely system by diagram.&lt;br&gt;&#xA;Diagram details are given in this &lt;a href=&quot;http://imm.io/5xEN&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt; (crop shown below) as  figure 6.2:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/gfxYM.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;h1&gt;The problem restated:&lt;/h1&gt;&#xA;&#xA;&lt;p&gt;I tried to understand phase of a delay system by this diagram but I failed to understand how the phase is represented by the equation of a straight line with slope equal to -n in figure 6.2.&lt;/p&gt;&#xA;" OwnerUserId="4180" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-10T02:40:35.330" LastActivityDate="2011-05-10T05:41:47.667" Title="delay system ==&gt; graphical representation of the frequency response" Tags="&lt;electronics&gt;&lt;homework&gt;&lt;signal&gt;" AnswerCount="1" CommentCount="8" />
  <row Id="14109" PostTypeId="1" CreationDate="2011-05-10T02:54:24.837" Score="-2" ViewCount="82" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/14123/how-dc-component-is-removed&quot;&gt;how DC component is removed?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;hi all,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i have the concept of &lt;strong&gt;first different system&lt;/strong&gt; given in the  &lt;a href=&quot;http://imm.io/5xHu&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt; &#xA;and the real ,maginary,phase and magnitude are  plotted in this &lt;a href=&quot;http://imm.io/5xFy&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt; .&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i understand that  DC component is removed from system but i did not understand from  6.4 figure.&#xA;Any one please help me thanks ..&lt;/p&gt;&#xA;" OwnerUserId="4180" LastEditorUserId="4180" LastEditorDisplayName="" LastEditDate="2011-05-10T11:41:10.447" LastActivityDate="2011-05-10T11:41:10.447" ClosedDate="2011-05-10T13:49:39.133" Title="first difference system" Tags="&lt;electronics&gt;" CommentCount="4" />
  <row Id="14110" PostTypeId="2" ParentId="10150" CreationDate="2011-05-10T03:28:06.443" Score="1" ViewCount="" Body="&lt;p&gt;I don't see how there could be any difference between the two plugs, other than size.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is some discussion of this issue on &lt;a href=&quot;http://www.reddit.com/r/audioengineering/comments/fl6jf/differences_between_18_and_14_inch_adapter/&quot; rel=&quot;nofollow&quot;&gt;Reddit&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To summarize that discussion, the consensus is that the 1/4&quot; plug would be more durable, but otherwise exactly the same.&lt;/p&gt;&#xA;" OwnerUserId="2827" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-10T05:37:56.927" LastActivityDate="2011-05-10T05:37:56.927" />
  <row Id="14111" PostTypeId="2" ParentId="14108" CreationDate="2011-05-10T05:41:47.667" Score="4" ViewCount="" Body="&lt;p&gt;It is important to understand what phase is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Consider a 1 Hz sine wave.  This means it goes through 360 degrees in one second. If you delay this wave by 1/2 second, that's 180 degrees phase shift.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now consider a 2 Hz sine wave.  This means it goes through 720 degrees in one second. If you delay this wave by 1/2 second, that's 360 degrees phase shift.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By these examples, see how the phase at a constant time delay depends on frequency?&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-05-10T05:41:47.667" CommentCount="3" />
  <row Id="14112" PostTypeId="2" ParentId="14106" CreationDate="2011-05-10T05:57:59.417" Score="3" ViewCount="" Body="&lt;p&gt;Try using an I2C SRAM chip. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe a 256 kbit N256S0830HDA @ 3V from AMI fits the bill:  &lt;a href=&quot;http://www.modtronix.com/products/components/ram/n256s0830hda.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.modtronix.com/products/components/ram/n256s0830hda.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See &lt;a href=&quot;http://arduino_related.livejournal.com/1414.html&quot; rel=&quot;nofollow&quot;&gt;http://arduino_related.livejournal.com/1414.html&lt;/a&gt; for a tutorial.&lt;/p&gt;&#xA;" OwnerUserId="3438" LastActivityDate="2011-05-10T05:57:59.417" CommentCount="1" />
  <row Id="14114" PostTypeId="2" ParentId="6047" CreationDate="2011-05-10T08:02:06.690" Score="1" ViewCount="" Body="&lt;p&gt;You can &lt;a href=&quot;http://psychoul.com/electronics/xbee-dropping-bytes-my-solution&quot; rel=&quot;nofollow&quot;&gt;reduce to zero the dropped packages&lt;/a&gt; by assigning the correct destination address before starting transmission. &lt;/p&gt;&#xA;" OwnerUserId="4194" LastActivityDate="2011-05-10T08:02:06.690" />
  <row Id="14115" PostTypeId="2" ParentId="14106" CreationDate="2011-05-10T09:16:41.613" Score="1" ViewCount="" Body="&lt;p&gt;If there's enough I/O pins left, you may try to connect the SRAM chip and manually control it. You could try to use extra latches to store the address, to reuse the same set of pins for both data and address busses (e.g. MCS-51 based systems used to use 74HCT373 to latch the lower part of the address bus, see &lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/57&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;). This approach should allow for faster data transfers compared to I2C SRAM chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note, that the memory of the size you need will most likely come in a TSOP package or similar.&lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-05-10T09:16:41.613" />
  <row Id="14116" PostTypeId="1" CreationDate="2011-05-10T11:27:59.183" Score="1" ViewCount="103" Body="&lt;p&gt;This might sound a bit weird, but does anybody here know of a bicycle ergometer that is hackable? What I would like to do is to connect it to a PC (don't care how, usb, parallel port, serial...) to transfer the current speed in real time. My ultimate goal would be to modify an open source racing game in such a way that the speed on the bike determines the speed of a bike/car in the racing game.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: By &quot;bicycle ergometer&quot; I mean something that you would find in a fitness center. It is not a real bicycle at all and it usually already comes with an integrated computer. The problem is getting the information out of that computer. Sorry if I caused any confusion, but English is not my native language and &quot;bicycle ergometer&quot; is what my dictionary told me.&lt;/p&gt;&#xA;" OwnerUserId="4197" LastEditorUserId="4197" LastEditorDisplayName="" LastEditDate="2011-05-10T15:03:30.613" LastActivityDate="2011-05-10T15:03:30.613" Title="Hackable exercise bicycle computer?" Tags="&lt;interface&gt;&lt;pc&gt;" AnswerCount="3" CommentCount="5" FavoriteCount="1" />
  <row Id="14117" PostTypeId="2" ParentId="14116" CreationDate="2011-05-10T12:04:56.730" Score="0" ViewCount="" Body="&lt;p&gt;Since I've worked on embedded systems for yonks I'd find it easier to develop something from scratch using a suitable small MCU that took input from a sensor on the bike and input it to the PC. The only suitable interface on modern PCs is a USB port. I have designed &lt;a href=&quot;http://www.leonheller.com/usb/index.html&quot; rel=&quot;nofollow&quot;&gt;this small prototyping board&lt;/a&gt; with a USB PIC to go with Brad Minch's USB software, that would be suitable. It costs about $10 to build.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bike is on rollers, presumably, so you will need to compute the &quot;road speed&quot; from the wheel RPM, knowing the diameter of the wheel.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-10T12:48:23.980" LastActivityDate="2011-05-10T12:48:23.980" CommentCount="1" />
  <row Id="14118" PostTypeId="1" AcceptedAnswerId="14122" CreationDate="2011-05-10T12:10:23.430" Score="2" ViewCount="49" Body="&lt;p&gt;In my understanding, the polarity of the magnetic field of a bipolar stepper motor does not matter. You can hook it up to the biploar driver either way and it would still work correctly. However, is there a drawback to reversing the polarity of the magnetic field by hoooking it up incorrectly?&lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-05-10T22:52:27.533" Title="BiPolar Stepper Motor Polarity" Tags="&lt;stepper-motor&gt;" AnswerCount="2" />
  <row Id="14119" PostTypeId="1" CreationDate="2011-05-10T12:25:31.517" Score="2" ViewCount="69" Body="&lt;p&gt;I need help on what resistor (if any) I need for this set up.&#xA;12v car power as signal power to DPDT relay switch. What do I need on the deadend side of relay signal?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/2SPM8.png&quot; alt=&quot;http://i.stack.imgur.com/5t0Oa.png&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="4198" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-05-10T12:37:46.803" LastActivityDate="2011-05-10T12:44:58.007" Title="Resistor selection" Tags="&lt;resistor&gt;&lt;relay&gt;&lt;current-signal&gt;" AnswerCount="1" />
  <row Id="14120" PostTypeId="2" ParentId="14116" CreationDate="2011-05-10T12:33:32.737" Score="1" ViewCount="" Body="&lt;p&gt;Most bicycle speedometers I've seen use a magnet on the wheel and a hall effect mounted to the fork. The microprocessor would then measure the time between the magnet rotating passed the sensor on the wheel. You can use this time measurement to calculate RPMs.&lt;/p&gt;&#xA;" OwnerUserId="588" LastActivityDate="2011-05-10T12:33:32.737" CommentCount="6" />
  <row Id="14121" PostTypeId="2" ParentId="14119" CreationDate="2011-05-10T12:44:58.007" Score="4" ViewCount="" Body="&lt;p&gt;If it's a 12V DC relay you don't need a resistor!&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-10T12:44:58.007" />
  <row Id="14122" PostTypeId="2" ParentId="14118" CreationDate="2011-05-10T13:09:34.587" Score="0" ViewCount="" Body="&lt;p&gt;It &lt;em&gt;technically&lt;/em&gt; doesn't matter.  Bipolar stepper motor drivers need to be able to drive current in either direction through the coils.  However, I assume that you'll be using some off the shelf stepper driver, and if it just takes DIR and STEP inputs, by wiring it up in an arbitrary matter your motor might not step properly, that's all.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-05-10T13:09:34.587" />
  <row Id="14123" PostTypeId="1" AcceptedAnswerId="14124" CreationDate="2011-05-10T13:28:57.767" Score="0" ViewCount="118" Body="&lt;p&gt;Given these waveforms:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/vCru5.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and the first difference system:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/c6r9h.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;there are discontinuities at omega = 0 ,2pi, ...  I know that there is a DC component, but how is the DC component at omega=0 removed from the system?  Can anyone please help me?&lt;/p&gt;&#xA;" OwnerUserId="4180" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-05-10T13:39:19.643" LastActivityDate="2011-05-11T18:06:16.320" Title="how DC component is removed?" Tags="&lt;electronics&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="1" />
  <row Id="14124" PostTypeId="2" ParentId="14123" CreationDate="2011-05-10T13:47:04.020" Score="1" ViewCount="" Body="&lt;p&gt;Just try it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A pure DC signal, for example would be:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$x[n] = 1_{\mbox{for all n}}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now try solving for $y[n]$ for any value of n. What is it?&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-11T18:06:16.320" LastActivityDate="2011-05-11T18:06:16.320" CommentCount="15" />
  <row Id="14125" PostTypeId="2" ParentId="14098" CreationDate="2011-05-10T14:39:24.720" Score="2" ViewCount="" Body="&lt;p&gt;Write code that is easy to read (for others, or for yourself in two week's time :)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; a &amp;lt;= b+c;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Trust the synthesiser until it is proven that&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;it's not doing what you want&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;and&lt;/strong&gt; you are not meeting your area, timing or power targets.  &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;To do anything else is premature optimisation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, and only then, mess around trying to improve things.  But at least by this point you already have a full-coverage testbench of the &quot;simple&quot; option (you do have that before starting optimising, don't you? :).&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-05-10T14:39:24.720" />
  <row Id="14126" PostTypeId="2" ParentId="14116" CreationDate="2011-05-10T15:03:14.263" Score="0" ViewCount="" Body="&lt;p&gt;You can sign up to read the ANT+ spec at &lt;a href=&quot;http://thisisant.com&quot; rel=&quot;nofollow&quot;&gt;http://thisisant.com&lt;/a&gt;.  Then you can use off-the-shelf sensors for speed, cadence, or power.  Buy an ANT receiver USB stick from Garmin and you have a wireless link to your computer.  One stick can receive from multiple sensors as well, so you can receive from several bikes for a competition scenario.  Recent builds of Golden Cheetah ( &lt;a href=&quot;http://goldencheetah.org&quot; rel=&quot;nofollow&quot;&gt;http://goldencheetah.org&lt;/a&gt; ) also have real-time ANT receiving built-in.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-05-10T15:03:14.263" CommentCount="1" />
  <row Id="14127" PostTypeId="1" CreationDate="2011-05-10T15:05:46.887" Score="1" ViewCount="61" Body="&lt;p&gt;Why do I get analog reading to the non connected ports, by taping the piezo in channel 1 ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The piezo element is only connected to Channel 1 (Arduino A[0] port).&#xA;The channels Ch 1 – Ch 6 are connected to female mono jacks and the ground(GND)      wiring is in series from jack 1, 2 and 3 so on... till the Ch 6 end to the Arduino GND port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The channels Ch2 – Ch6 have no piezo connected, but still connected to the arduino board. A&lt;a href=&quot;http://i.stack.imgur.com/2HzEM.jpg&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt;-A[5]&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the serial read... first column is Ch1 … Ch 6.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Taped 3 times&#xA;&#xA;787 0 0 0 0 0 &#xA;191 0 0 0 0 0 &#xA;19 0 0 0 0 0 &#xA;937 123 63 5 0 0 &amp;lt; ch2, ch3 ch4 ERROR !&amp;gt; &#xA;86 0 0 0 0 0 &#xA;13 0 0 0 0 0 &#xA;507 83 126 16 8 0 &amp;lt; ch2, ch3, ch4 ch5 ERROR !&amp;gt;&#xA;21 1 1 0 0 0  &amp;lt; ch2, ch3 ERROR !&amp;gt;&#xA;0 0 18 0 0 0 &amp;lt; ch3 ERROR !&amp;gt;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This is the arduino code:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;const int singnalLevel = 10;  &#xA;boolean treshold = false;&#xA;&#xA;int sensorReading[6];&#xA;&#xA;void setup() {&#xA;  Serial.begin(9600);          &#xA;}&#xA;&#xA;void loop() {&#xA;   int sensorReading[6] = {0, 0, 0, 0, 0, 0}; &#xA;   boolean treshold = false;&#xA;   sensorReading[0] = analogRead(A0);&#xA;   sensorReading[1] = analogRead(A1);&#xA;   sensorReading[2] = analogRead(A2);&#xA;   sensorReading[3] = analogRead(A3);&#xA;   sensorReading[4] = analogRead(A4);&#xA;   sensorReading[5] = analogRead(A5);&#xA;&#xA;  for (int index = 0; index &amp;lt;= 5 ; index++) {        &#xA;    if(sensorReading[index] &amp;gt; singnalLevel){&#xA;      treshold = true;&#xA;    }&#xA;  }&#xA;    if(treshold){  &#xA;        for (int index = 0; index &amp;lt;= 5 ; index++) {        &#xA;          Serial.print(sensorReading[index]);   &#xA;          Serial.print(&quot; &quot;);  &#xA;        }&#xA;    Serial.println();  &#xA;  }    &#xA;  delay(1);  &#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This is the circuit schematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/2HzEM.jpg&quot; alt=&quot;schematic&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="4199" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-05-10T15:16:10.770" LastActivityDate="2011-05-10T15:44:09.487" Title="Arduino analog signal read problem ?" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;serial&gt;&lt;noise&gt;&lt;piezoelectricity&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="14128" PostTypeId="2" ParentId="14026" CreationDate="2011-05-10T15:26:58.793" Score="0" ViewCount="" Body="&lt;p&gt;What kind of range and accuracy are you looking for?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a repeated position accuracy standpoint, using a accelerometers and gyroscopes would accumulate errors and drift over time.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rotary and linear position encoders would probably be the way to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you've opened up a more recent mechanical mouse, you've probably seen the slotted plastic wheel running through the gap of a caliper-like component &lt;a href=&quot;http://www.avagotech.com/pages/en/motion_control_encoder_products/incremental_encoders/transmissive_encoders/heds-9730a50/&quot; rel=&quot;nofollow&quot;&gt;like this one&lt;/a&gt;.  You count pulses to keep track of where you are.   These are pretty cheap, as long as you have a way of easily making/obtaining the necessary rotary or linear code strip.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are nicer encoders that &lt;a href=&quot;http://www.avagotech.com/pages/en/motion_control_encoder_products/incremental_encoders/transmissive_encoders/aeda-3300-te1/&quot; rel=&quot;nofollow&quot;&gt;cost a bit more&lt;/a&gt;.  Avago seems to have a bunch of position sensing and motion sensing technologies (&lt;a href=&quot;http://www.avagotech.com/pages/en/navigation_interface_devices/navigation_sensors/led-based_sensors/adns-5030/&quot; rel=&quot;nofollow&quot;&gt;led/laser mouse motion detectors&lt;/a&gt;, for example).&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-10T15:26:58.793" />
  <row Id="14129" PostTypeId="2" ParentId="14127" CreationDate="2011-05-10T15:44:09.487" Score="2" ViewCount="" Body="&lt;p&gt;I'm not sure if this is a valid answer or not, but I'm going to submit it anyway since there is a remote chance that it's helpful.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In other microcontrollers that I've used before, you need to have a settling time between ADC channel reads, or the previous reading is likely to affect subsequent reads.  I haven't used the ADC on the Arduino yet, but perhaps there is either a library function you can call so that there will be a processor-dependent sleep / delay that is used when reading ADC channels.  In either case, you can easily test this theory out by delaying between ADC channel reads to see if the problem goes away.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-05-10T15:44:09.487" CommentCount="1" />
  <row Id="14130" PostTypeId="2" ParentId="12407" CreationDate="2011-05-10T16:11:35.583" Score="0" ViewCount="" Body="&lt;p&gt;It's worth noting that an FFT is an alternative to computing a number of separate pairs of sums (k=0..sample_length-1) of Sample[k]*SineRefWave[j][k] and Sample[j]*CosRefWave[j][k], for all j up to half the sample length.  If one needs amplitude readouts at all those frequencies, an FFT will compute them all in O(NlgN) time, whereas computing them individually would take O(N^2) time.  On the other hand, if one only needs amplitude readouts at a few frequencies, one will often be better off simply computing them individually, especially if one is using a processor or DSP which can efficiently compute that style of sum.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-10T16:11:35.583" />
  <row Id="14131" PostTypeId="2" ParentId="4172" CreationDate="2011-05-10T16:55:10.687" Score="0" ViewCount="" Body="&lt;p&gt;The IBM Portable PC behaved as though internal monitor was wired to the composite output of a stock CGA card.  One of the side-effects of this was that when the mode was set to &quot;color&quot; 80 columns, colors would appear as gray stripe patterns rather than as shades of gray.  This in turn would render many foreground-background combinations (e.g. blue on black) almost completely illegible.  This was rather irksome given that (1) the internal monitor was monochrome, and thus chroma information would be useless to it; (2) even when using an external composite monitor, the colorburst signal was mistimed in 80-column mode, so one couldn't get color anyway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incidentally, the Compaq's internal monitor seems to be unique; it uses the NTSC horizontal scan rate, but the vertical scan can be either 60Hz or 30Hz.  I'm not sure why Compaq decided to use non-interlaced 30Hz, rather than jinxing the vertical circuit of the monitor to work nicely with the 6485's not-quite-right interlaced output, but it's the only machine I've ever seen with a 30Hz display scan.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-10T16:55:10.687" />
  <row Id="14132" PostTypeId="2" ParentId="14077" CreationDate="2011-05-10T17:13:26.430" Score="1" ViewCount="" Body="&lt;p&gt;If are going to be installing wiring and new lights anyways, I would consider installing LED light fixtures. Not only will you save money in the long run due to lower electricity costs, but you will save money in the installation on wiring. Because LEDs use voltages under 24V, the electrical code is very lax. You do not have to install thick (expensive) copper wires to each outlet but rather much cheaper 20-18 AWG wiring (I even used 23AWG in a CAT6 cable) There are many options for high power LED driving from an arduino. My favourite would be &lt;a href=&quot;http://neuroelec.com/2011/05/high-power-rgb-led-shield-2-0/&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;. Up to 128 can be controlled from a single arduino. The code to control them is very easy. After you have done that, add a ethernet shield to the arduino and some basic javascript and then controlling your lights will be as simple as visiting a webpage on a computer or smartphone. You could even forward incoming port 80 requests to the shield and allow you to control it while you are away (perhaps to scare off crooks). Additionally you would have independent dimming control over every light in the basement (so for example if you were watching a movie you could only turn on two lights in the back and leave them really dim). &lt;/p&gt;&#xA;" OwnerUserId="4201" LastEditorUserId="4201" LastEditorDisplayName="" LastEditDate="2011-05-10T17:18:26.613" LastActivityDate="2011-05-10T17:18:26.613" CommentCount="5" />
  <row Id="14133" PostTypeId="1" CreationDate="2011-05-10T17:36:18.570" Score="7" ViewCount="122" Body="&lt;p&gt;For software, the book &lt;a href=&quot;http://en.wikipedia.org/wiki/Design_Patterns&quot; rel=&quot;nofollow&quot;&gt;Design Patterns&lt;/a&gt; is a set of patterns for doing common things in software and it gives software practitioners common terminology to describe some of the components they need to create.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does such a book or resource exist for synthesizable RTL or RTL in general?  Things like common pitfalls, design trade-offs, deadlock considerations, and interface design.&lt;/p&gt;&#xA;" OwnerUserId="1708" LastActivityDate="2011-05-11T16:04:09.587" Title="Is there a &quot;Design Patterns&quot; for synthesizable RTL?" Tags="&lt;vhdl&gt;&lt;verilog&gt;&lt;best-practice&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="14134" PostTypeId="2" ParentId="14106" CreationDate="2011-05-10T17:40:54.637" Score="1" ViewCount="" Body="&lt;p&gt;Data compression may be an option. You probably don't NEED every iteration of the 255/255/255 data set. Even sticking with 256 colors would be more than enough for what you are trying to do.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then each LED only needs 1 byte of information to store it's brightness setting, increasing the amount of frames available to 57, which would be pretty close to the 64 you were looking for. &lt;/p&gt;&#xA;" OwnerUserId="4201" LastActivityDate="2011-05-10T17:40:54.637" />
  <row Id="14135" PostTypeId="1" CreationDate="2011-05-10T17:53:51.510" Score="-3" ViewCount="115" Body="&lt;p&gt;Low pass Filter==&gt;image: &lt;a href=&quot;http://imm.io/5yBL&quot; rel=&quot;nofollow&quot;&gt;http://imm.io/5yBL&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;phase  of system response: &lt;a href=&quot;http://imm.io/5yC2&quot; rel=&quot;nofollow&quot;&gt;http://imm.io/5yC2&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;in the above figure .. how this system has dely by 1 sample.. and how is  this  system  is low pass filter/....]&#xA;I tried to understand this figure &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any one can please help me..  &lt;/p&gt;&#xA;" OwnerUserId="4180" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-05-10T21:42:03.127" LastActivityDate="2011-05-10T21:42:03.127" ClosedDate="2011-05-10T22:22:32.857" Title="how this is low pass filter" Tags="&lt;electronics&gt;&lt;homework&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="14136" PostTypeId="1" CreationDate="2011-05-10T18:53:19.070" Score="3" ViewCount="74" Body="&lt;p&gt;In one of the answers to &lt;a href=&quot;http://electronics.stackexchange.com/questions/14118/bipolar-stepper-motor-polarity&quot;&gt;this question&lt;/a&gt;, it is stated that wiring one of the coils on a bipolar stepper backwards can cause the motor to step improperly, or not at all. I've salvaged several steppers from discarded electronics (printers, scanners, typewriters), and I'm curious, is there a better method than trial and error for determining the proper polarity of the coils?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I reverse both coils, does the motor simply run in reverse?&lt;/p&gt;&#xA;" OwnerUserId="3240" LastActivityDate="2011-05-11T17:56:26.307" Title="How to determine proper stepper polarity?" Tags="&lt;stepper-motor&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="14137" PostTypeId="2" ParentId="12953" CreationDate="2011-05-10T19:34:27.967" Score="1" ViewCount="" Body="&lt;p&gt;The second question is easy to answer. The ATmega is a microcontroller, which is hard-wired to reboot and resume after a loss of power.  In fact, that's what the reset button actually does on some boards.  Many voltage regulators have an enable pin, and it's very easy to wire it up in such a way that the reset button actually cuts power to the board. Every time you apply power, the controller reads the content at 0x00 (usually a jump instruction), and begins executing code.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The first question, not so much.  Lightning strikes are pretty serious events, and (especially without a schematic), it's hard to say what will happen.  I'd suggest that you first provide some isolation for your circuitry.  A little optoisolator is likely to provide the isolation you need, but you'll need to provide power on the high-voltage side.  An easier method would be to make the temp sensor completely independent.  A little MSP430 + MRF24J40 system could run for months on a couple batteries and cost less than $10, transmitting the current temperature every couple minutes.  Then, when lighting strikes, there won't be an easy path to ground through the sensing wire, which means that lightning is likely to strike elsewhere instead.  The easiest method (also the least likely to survive a strike) would be to place a zener diode across the thermistor.  You'll want to be careful about compensating your measurements for leakage currents through the zener, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't accept the possibility that the temp sensor would be destroyed by a lightning strike (which is an interesting requirement to design for), you should research transient voltage suppression diodes and be prepared for some much higher system costs.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-05-10T19:34:27.967" />
  <row Id="14138" PostTypeId="2" ParentId="14135" CreationDate="2011-05-10T20:07:39.110" Score="-1" ViewCount="" Body="&lt;p&gt;The simplest low-pass digital filter is one with a delay of 1 sample time:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;https://ccrma.stanford.edu/~jos/filters/Definition_Simplest_Low_Pass.html&quot; rel=&quot;nofollow&quot;&gt;https://ccrma.stanford.edu/~jos/filters/Definition_Simplest_Low_Pass.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could have found that out for yourself!&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-10T20:07:39.110" CommentCount="1" />
  <row Id="14139" PostTypeId="2" ParentId="14133" CreationDate="2011-05-10T20:52:27.387" Score="2" ViewCount="" Body="&lt;p&gt;My experience has been that you need to read the docs on one or more of the popular synthesis tools to see which design patterns they accept and what they translate to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mostly you need to know:&#xA;- how to make flops&#xA;- how to make wires (and not latches) &#xA;- how to handle reset (sync and/or async)&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-05-10T20:52:27.387" CommentCount="2" />
  <row Id="14140" PostTypeId="1" AcceptedAnswerId="14141" CreationDate="2011-05-10T21:23:41.117" Score="2" ViewCount="71" Body="&lt;p&gt;I'm working on a project where I need to model the voltage/current relationship of various LEDs.  I'm wondering what values I would need to use for the saturation current in the Shockley diode equation for various colors - I know the proper thing to do would be to take the LEDs in question and measure the forward voltage at various currents and fit a curve, but at the moment for my rough calculations I don't need that level of accuracy.  Anyone have any &quot;ballpark figures&quot;?&lt;/p&gt;&#xA;" OwnerUserId="4129" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-05-10T21:39:50.850" LastActivityDate="2011-05-10T21:51:31.697" Title="LED modeling with Shockley diode equation" Tags="&lt;led&gt;&lt;diode&gt;&lt;math&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="14141" PostTypeId="2" ParentId="14140" CreationDate="2011-05-10T21:51:31.697" Score="2" ViewCount="" Body="&lt;p&gt;There's a few things that you can do:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Find a SPICE model for your particular LED. SPICE uses the Shockley diode model, so you can just pull &lt;strong&gt;Is&lt;/strong&gt; and &lt;strong&gt;N&lt;/strong&gt; from the model card.&lt;/li&gt;&#xA;&lt;li&gt;Find a datasheet for the LED in question (with a graph indicating a voltage-current relationship) and model only &lt;strong&gt;Is&lt;/strong&gt; and &lt;strong&gt;N&lt;/strong&gt;, which is actually not very difficult. See my answer on &quot;&lt;a href=&quot;http://electronics.stackexchange.com/questions/9510/how-do-i-model-an-led-with-spice/9543#9543&quot;&gt;How to model a LED&lt;/a&gt;&quot; for most of what you need to get started. Only solving for &lt;strong&gt;Is&lt;/strong&gt; and &lt;strong&gt;N&lt;/strong&gt; will work well until you start trying to use the equation for peak currents (high current, low duty cycle).&lt;/li&gt;&#xA;&lt;li&gt;Take the forward threshold voltage of the diode, and solve the diode equation for &lt;strong&gt;Is&lt;/strong&gt;. Guess about 1.8-2.0 for &lt;strong&gt;N&lt;/strong&gt; and just be satisfied with the result. It won't track reality very well, but it will behave like a diode.&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Take the values for this red LED and hope that they mostly work for your LED. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;IS=1a RS=3.3 N=1.8&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Keep in mind that different color LEDs have different forward voltage drops, and that even diodes with the same color can have different voltages. Also, the diode equation neglects series resistance, which can have a significant effect at high currents. It is up to you to understand your accuracy requirements, and to know the limitations of your calculations.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-05-10T21:51:31.697" CommentCount="1" />
  <row Id="14142" PostTypeId="2" ParentId="14118" CreationDate="2011-05-10T22:52:27.533" Score="1" ViewCount="" Body="&lt;p&gt;If it's the four-wire kind, you can't really hook it up backwards. Both coils are designed and intended for current to pass in each direction. In fact, to get rotation at all requires periodically reversing the direction of the current first in one coil, then in the other.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-10T22:52:27.533" />
  <row Id="14143" PostTypeId="2" ParentId="14136" CreationDate="2011-05-10T23:08:52.667" Score="1" ViewCount="" Body="&lt;p&gt;If you think of the phases of the stepper, it would go from [--] to [-+] to [++] to [+-], and then repeat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If we label those phases as:&#xA;[--] J&#xA;[-+] K&#xA;[++] L&#xA;[+-] M&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you go &quot;forward&quot; by stepping JKLMJLKMJLKM... and &quot;backwards&quot; by stepping MKLJMKLJMKLJ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you flip the bit on both, we now have:&#xA;[++] J'&#xA;[+-] K'&#xA;[--] L'&#xA;[-+] M'&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So when you drive, you get J'K'L'M'J'K'L'M'...  But J' is really L, K' is really M, L' is really J and M' is really K on the motor, so you are moving LMJKLMJKLMJK... which is the same sequence of the &quot;forward&quot; stepping, but with the cycle starting half-way in the middle of the original cycle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, yes, if you reversed the polarity on BOTH coil sets, you would still move in the same direction.  However, you will be off by half a stepper revolution.  Depending on the gearing, the difference would probably not make a difference.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;EDIT&lt;/em&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I updated to indicate polarity as +/- (versus 1/0 in my original posting).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is easier to visualize graphically -- if you treat each winding 1 as the X coordinate, and winding 2 as the Y coordinate, then you are stepping between four quadrants.  If you then half- or quarter- step, you are just increasing the number of points that define your loop.  Taken to the limit, if you have the X=sin(wt) and Y=cos(wt), you'll have a smooth circle; and if you reverse the sign of one (say X=-sin(wt)), you'll just go through the circle in reverse direction.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-05-11T17:56:26.307" LastActivityDate="2011-05-11T17:56:26.307" CommentCount="1" />
  <row Id="14144" PostTypeId="1" CreationDate="2011-05-11T00:10:58.807" Score="4" ViewCount="91" Body="&lt;p&gt;I am driving a &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet/stmicroelectronics/7471.pdf&quot; rel=&quot;nofollow&quot;&gt;BTB16-600BW&lt;/a&gt; triac using a &lt;a href=&quot;http://www.farnell.com/datasheets/301912.pdf&quot; rel=&quot;nofollow&quot;&gt;MOC3052&lt;/a&gt; exactly as suggested in the MOC3052 datasheet:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/Oedhh.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The current into the power triac gate is limited using the highlighted resistor. My triac requires at least 50 mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistor gets fairly hot during actual operation and no surprise: $I^2R$ (RMS) with the 10k resistor I'm using is about 1.2W if my calculations are correct.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a better way to limit the current here, especially one that doesn't involve generating much extra heat? I don't mind spending a few more pennies on a solution that requires less tweaking - in particular, I'd love to just grab a purpose-built DIP6/8 IC that requires only a single additional passive to set the current limit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've seen a few circuits using transistors, but I don't have any with a high enough voltage rating, and if I'm going to buy something I'd prefer to buy the most suitable part for the job.&lt;/p&gt;&#xA;" OwnerUserId="1951" LastActivityDate="2011-05-11T08:27:36.117" Title="Current limiting at mains voltage" Tags="&lt;current&gt;&lt;ac&gt;&lt;triac&gt;" AnswerCount="1" />
  <row Id="14145" PostTypeId="2" ParentId="8515" CreationDate="2011-05-11T00:24:45.327" Score="-1" ViewCount="" Body="&lt;p&gt;If you make the power supply large enough, I think you can. You might just need to attach a few kg of meat to it though...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The idea is to use the large chunk of meat as the reference. I believe the live wire w.r.t meat will look quite different to neutral w.r.t. meat - sufficiently so to reliably distinguish the two.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the simplest conceivable scheme, two simple live/neutral testers are attached to a volunteer and the AC inputs. The system uses the light from the two testers to decide whether to flip the wires or not using a DPDT relay. It doesn't need to be quite this crude, though, of course.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I do wonder though: what is it about the large chunk of meat that makes this possible (capacitance?) and thus can it be packed into a smaller form factor?&lt;/p&gt;&#xA;" OwnerUserId="1951" LastActivityDate="2011-05-11T00:24:45.327" />
  <row Id="14146" PostTypeId="1" CreationDate="2011-05-11T00:35:54.600" Score="11" ViewCount="224" Body="&lt;p&gt;Hey there,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My first arduino project, I have made a headlight sensor that will activate an outside light when car headlights hit it.  I know I could go buy one, but where is the fun in that?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I would like to make a &quot;real&quot; one to mount outside my  house so I can reuse my arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I really have no idea where or how to start.  I have had a look but can't find any info on this...I am sure someone here will be able to suggest something.&lt;/p&gt;&#xA;" OwnerUserId="4017" LastActivityDate="2011-05-20T15:16:35.093" Title="How do I go from arduino breadboard to creating a real device" Tags="&lt;arduino&gt;" AnswerCount="7" FavoriteCount="4" />
  <row Id="14147" PostTypeId="2" ParentId="14146" CreationDate="2011-05-11T00:48:43.437" Score="1" ViewCount="" Body="&lt;p&gt;Draw a schematic, first, of the parts on the Arduino board that you are using, and any parts you have added, and how they are connected, and show us that. We can proceed from there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might need to get a PCB designed and made, and assemble it, or you could build the circuit on a prototyping board. Then you just plug the AVR from the Arduino into it, and it should start working just as the Arduino did.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-11T00:55:21.657" LastActivityDate="2011-05-11T00:55:21.657" />
  <row Id="14148" PostTypeId="2" ParentId="14136" CreationDate="2011-05-11T01:00:55.937" Score="1" ViewCount="" Body="&lt;p&gt;(this extra information doesn't really answer your question directly - but 'add comment' has broken on my browser since the last big UI change)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a trick - if you have a stepper with random colored wires you can easily find the pairs of wires that correspond to each wire - turn the stepper manually, feel how easily it moves, choose any wire, short it to other wires until you find one which makes the stepper harder to turn by hand - those two are wired to the same coil&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-05-11T01:00:55.937" CommentCount="1" />
  <row Id="14149" PostTypeId="1" CreationDate="2011-05-11T01:31:33.950" Score="1" ViewCount="70" Body="&lt;p&gt;Hi, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We have been working with servo's in some our field equipment, however require a slightly different application.  We will be deploying some underwater cameras for an extended period (3 months) and to prevent fouling of the camera face will need to make a wiper unit.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a product, or does anyone have a schematic which will allow for timed control of the servos? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;We are suggesting every hour for the servo to complete a return cycle or thereabouts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm sure this would be very straight forward for the right person, however i'm a bit lost.  I can make up a PCB if shown what needs to go where, but don't really understand the ins and outs of how it all works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for your assistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mark&lt;/p&gt;&#xA;" OwnerUserId="4206" LastActivityDate="2011-05-23T15:07:05.077" Title="Timed servo control" Tags="&lt;pcb&gt;&lt;servo&gt;&lt;timer&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="14150" PostTypeId="1" AcceptedAnswerId="14159" CreationDate="2011-05-11T01:34:30.280" Score="1" ViewCount="55" Body="&lt;p&gt;If I have a bipolar stepper motor driver (currently based on a L293, but I may be switching to a A4983) and I would like to control two 4 wire bipolar steppers from it (but not at the same time and the speed of the switching is irrelevant), can I just use a DPDT switch or relay to switch 1 wire of each pair between two motors on the output of the driver ?  Apart from just using another driver per motor, are there better options here?  &lt;/p&gt;&#xA;" OwnerUserId="3778" LastEditorUserId="3778" LastEditorDisplayName="" LastEditDate="2011-05-11T02:36:57.750" LastActivityDate="2011-05-11T05:20:39.087" Title="1 stepper motor driver using two motors" Tags="&lt;stepper&gt;" AnswerCount="2" />
  <row Id="14151" PostTypeId="2" ParentId="14146" CreationDate="2011-05-11T01:41:42.237" Score="2" ViewCount="" Body="&lt;p&gt;An easier way might be to make an arduino shield - you can get a prototype board in the shape of an arduino. Add whatever components you want to it and then simply plop it onto of the arduino. &lt;/p&gt;&#xA;" OwnerUserId="4201" LastActivityDate="2011-05-11T01:41:42.237" CommentCount="6" />
  <row Id="14152" PostTypeId="2" ParentId="13900" CreationDate="2011-05-11T01:59:35.623" Score="2" ViewCount="" Body="&lt;p&gt;How good a replacement is a rather complex question, mostly revolving around what you are looking to do with it. It looks from the datasheet that the 2n9013 has twice the Ic (continuous collector current) of 500mA, compared to a peak in the 3904 of 200mA. The 3904 is definitely intended to be a signal amplifier, and has a gain bandwidth product of 300MHz. The 9013 datasheet I found doesnt even have GBP, which to me tells me its much more intended as a current buffer, than as an amplifier. The fact that they tote the Hfe (essentially, but not the same as beta) as being linear suggests to me that it expects to have large signals fed into it, and not do much more than buffer an input to an output (hence the need for linear Hfe, but no mention of GBP). The other thing, that line &lt;em&gt;1W OUTPUT AMPLIFIER OF POTABLE RADIOS IN CLASS B PUSH-PULL OPERATION&lt;/em&gt; (I was as shocked to see the word potable is actually what they said on the datasheet. I'm like 90% sure they meant PORTABLE, not that its safe to DRINK the transistor). That line thats &quot;worse than Chinese&quot; means that its intended to be used with its PNP complimentary transistor the 2n9012 on the output stage (hence the class B push pull bit) of a power amplifier. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The long and short of it is this: its a good replacement as long as what you are replacing the 9013 with works the same for you as it did before. That is really all that matters. Generally tho, most designs are not THAT component parameter sensitive that they wont work with the wrong &lt;em&gt;VAGUELY&lt;/em&gt; similar part. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="4208" LastActivityDate="2011-05-11T01:59:35.623" CommentCount="2" />
  <row Id="14153" PostTypeId="1" CreationDate="2011-05-11T03:10:15.740" Score="0" ViewCount="71" Body="&lt;p&gt;I am using a GPS device. I'm told it's a WD-G-ZX4120, but on the actual device it says it's an ET-318. I heard from somewhere that this device uses 100 to 150mA. However the datasheets seem to say that it uses only a maximum of 42mA. So how much does it actually use?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=2&amp;amp;ved=0CB0QFjAB&amp;amp;url=http://gpsd.googlecode.com/files/WD-G-ZX4120.pdf&amp;amp;ei=Ef3JTa2nLPLYiAKHvIymBQ&amp;amp;usg=AFQjCNHf2NCixaifsKOGt9rGznbmzQz85Q&amp;amp;sig2=oq6gn-Frmq2kGJ5nUtRd3g&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is the datasheet for the WD-G-ZX4120, and &lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CBkQFjAA&amp;amp;url=http://www.globalsat.com.tw/globalsat_admin/new_file_download.php?Pact=FileDownLoad&amp;amp;Pval=1761&amp;amp;ei=afrJTaf3D43RiAKE9aybBQ&amp;amp;usg=AFQjCNFbdMkvavNBVrEeVofIE8k4Y7EmEw&amp;amp;sig2=SqFFisjQYrNboYPX9A2Jdw&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; is the datasheet for the ET-318. Are these the same thing?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-05-11T06:38:45.697" Title="How much current does this device draw?" Tags="&lt;current&gt;&lt;datasheet&gt;&lt;gps&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="14154" PostTypeId="1" CreationDate="2011-05-11T03:24:37.737" Score="2" ViewCount="54" Body="&lt;p&gt;The mbed has a pin which supplies 3.3V regulated current. I think it can supply up to 100mA. If this pin is used to power a device, and the device tries to draw 150mA, then what can happen? Is the mbed in danger of being damaged?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-05-11T04:18:11.320" Title="Can an mbed device be damaged by something drawing too much current?" Tags="&lt;current&gt;&lt;mbed&gt;" AnswerCount="1" />
  <row Id="14155" PostTypeId="2" ParentId="14153" CreationDate="2011-05-11T03:34:59.597" Score="2" ViewCount="" Body="&lt;p&gt;I highly recommend you &lt;em&gt;test&lt;/em&gt; the device to determine its draw. If you can measure it over 50mA while doing something, you have your answer pretty quickly. Besides, you might find out it's 500mA while you're at it, and wouldn't that be interesting!&lt;/p&gt;&#xA;" OwnerUserId="4209" LastActivityDate="2011-05-11T03:34:59.597" CommentCount="3" />
  <row Id="14156" PostTypeId="2" ParentId="14154" CreationDate="2011-05-11T04:18:11.320" Score="4" ViewCount="" Body="&lt;p&gt;The mbed wiki shows has a &lt;a href=&quot;http://mbed.org/cookbook/Reference-Design&quot; rel=&quot;nofollow&quot;&gt;(partial) schematic&lt;/a&gt; of the mbed module. It is using a &lt;a href=&quot;http://www.st.com/internet/analog/product/63477.jsp&quot; rel=&quot;nofollow&quot;&gt;LD1117S33&lt;/a&gt; 3.3v regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a 800mA regulator, but it is likely that the mbed's implementation is good for significantly less than that, given the apparent lack of any heatsinking on the voltage regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the LD1117 does have internal thermal and current limiting, so it should be pretty bulletproof with regard to damaging it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, if you draw too much current, the regulator will get hot, the thermal limiting will kick in, and it will reduce the output voltage until it no longer overheats. This &lt;em&gt;could&lt;/em&gt; cause unexpected/strange behavior in the LPC MCU (unless it has brownout detection), but it shouldn't damage anything.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, you don't need to worry about drawing too much current.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-05-11T04:18:11.320" CommentCount="3" />
  <row Id="14157" PostTypeId="2" ParentId="14150" CreationDate="2011-05-11T04:27:32.940" Score="0" ViewCount="" Body="&lt;p&gt;I don't see why not, as long as the switch you're using is rated for the amount of current that your motor is going to draw.  I also wouldn't switch over unless the driven motor is first stopped, so that you don't have any arcing in the switch.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-05-11T04:27:32.940" />
  <row Id="14158" PostTypeId="2" ParentId="14146" CreationDate="2011-05-11T04:42:24.873" Score="1" ViewCount="" Body="&lt;p&gt;Go take a look at the &lt;a href=&quot;http://metalab.at/wiki/Metaboard&quot; rel=&quot;nofollow&quot;&gt;MetaBoard&lt;/a&gt;. It's a &lt;em&gt;mostly&lt;/em&gt; arduino compatible board that you can etch at home on a single sided PCB. If you want to port what you've prototyped to a permanent board, this would be a good, well documented starting point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Along the way, you'll go grab a copy of &lt;a href=&quot;http://cadsoft.de&quot; rel=&quot;nofollow&quot;&gt;Eagle&lt;/a&gt; for editing the design to your needs and pickup an &lt;a href=&quot;http://www.adafruit.com/products/46&quot; rel=&quot;nofollow&quot;&gt;in circuit programmer&lt;/a&gt; that you'll need to program your homebrew board.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2011-05-11T04:42:24.873" CommentCount="3" />
  <row Id="14159" PostTypeId="2" ParentId="14150" CreationDate="2011-05-11T05:20:39.087" Score="1" ViewCount="" Body="&lt;p&gt;Having just addressed this myself I'd have to say separate drivers for each motor is the most sensible approach.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you remove the power from one motor, is has no holding torque and will 'flop' under any force.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may also have issues with the state of the outputs not being correct for the current rotor position, which will make the motor jump a bit when you switch it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And as Dave mentioned, if you have power on a coil when you switch it, it will arc inside the switch which will eventually destroy it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's also way more impressive to have both axes moving simultaneously if you can :)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your application may be able to cope with some of these issues, but if you need reliable accuracy then I'd recommend separate drivers.  The A4988 (update of the A4983) is only $3-4 from Digikey if you're building your own board.&lt;/p&gt;&#xA;" OwnerUserId="4211" LastActivityDate="2011-05-11T05:20:39.087" CommentCount="4" />
  <row Id="14160" PostTypeId="2" ParentId="14146" CreationDate="2011-05-11T05:40:52.067" Score="5" ViewCount="" Body="&lt;p&gt;Some others have mentioned the use of a shield.  I'm gonna suggest trying your hand at your own PCB :) Although this tends to be a pricey/difficult/frustrating route, it's easily the most educational.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Get yourself a copy of Eagle and have a play with the schematic editor.  You should be able to copy most of this from your prototype.  You'll also find the arduino schematic a good reference for the bits on the dev board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you've already written software on your development board, then you should have a good idea of what is required in terms of flash/RAM size, counters, IO pins etc.  It may take some digging to find out what the Arduino environment has actually used though, it tends to hide the technical details from the developer.  The easiest thing might be to just use the chip on the arduino which I believe is the &lt;a href=&quot;http://www.atmel.com/dyn/products/product_card.asp?part_id=3303&quot; rel=&quot;nofollow&quot;&gt;ATMega168&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Start browsing component supplier sites like &lt;a href=&quot;http://www.digikey.com&quot; rel=&quot;nofollow&quot;&gt;Digikey&lt;/a&gt; and &lt;a href=&quot;http://au.element14.com&quot; rel=&quot;nofollow&quot;&gt;Element14&lt;/a&gt; to find the components you need.  Try and use things already included in the Eagle libraries, or try your hand at drawing your own footprints.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you can have &lt;a href=&quot;http://batchpcb.com&quot; rel=&quot;nofollow&quot;&gt;BatchPCB&lt;/a&gt; fabricate your designs.  Order all the parts you chose.  Once everything has arrived, solder it together and pray it works when you switch it on :D&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course this sounds pretty daunting if you're new to electronic design, just keep asking questions the whole time!  Good luck ;)&lt;/p&gt;&#xA;" OwnerUserId="4211" LastActivityDate="2011-05-11T05:40:52.067" CommentCount="2" />
  <row Id="14161" PostTypeId="2" ParentId="14153" CreationDate="2011-05-11T06:38:45.697" Score="3" ViewCount="" Body="&lt;p&gt;Your link for the &lt;code&gt;ET-318&lt;/code&gt; doesn't work, but that doesn't matter. If I have contradicting information like this, what you've &lt;em&gt;been told&lt;/em&gt; (by whom?) and what the device &lt;em&gt;actually says&lt;/em&gt;, I'd believe the latter.&lt;br&gt;&#xA;If the device says &lt;code&gt;ET-318&lt;/code&gt; and the datasheet for the &lt;code&gt;ET-318&lt;/code&gt; says 42 mA, why not believe it? Otherwise you might as well never look at datasheets again.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-11T06:38:45.697" CommentCount="1" />
  <row Id="14162" PostTypeId="1" AcceptedAnswerId="14165" CreationDate="2011-05-11T07:22:32.960" Score="1" ViewCount="114" Body="&lt;p&gt;I have a beginner question about using multimeter to measure a current. I have dc motor, attached to 2 x AAA batteries. &#xA;Which reading I should use, 200 m under DCA or 2000 mA?&#xA;On 200 m, the current reads 15&#xA;On 2000 mA, the current reads 150.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Which one is the correct way of measuring the current?&#xA;For batteries current, do you use 200m or 2000mA?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/PDrjp.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="4185" LastActivityDate="2011-05-13T04:50:21.993" Title="Beginner question about measuring current using digital multimeter" Tags="&lt;multimeter&gt;&lt;current-measurement&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="14163" PostTypeId="2" ParentId="14162" CreationDate="2011-05-11T07:35:38.533" Score="2" ViewCount="" Body="&lt;p&gt;Notice the 2A range requires plugging the leads into a different jack than the other ranges.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both ranges should give you the same number.  Higher current ranges have lower shunt resistances, lower burden voltage, greater accuracy, less precision.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-05-11T07:35:38.533" CommentCount="1" />
  <row Id="14164" PostTypeId="2" ParentId="14162" CreationDate="2011-05-11T07:36:06.897" Score="1" ViewCount="" Body="&lt;p&gt;You should always use the lowest possible range. If you start at the 2000 mA range and it shows a value less than 200 mA, switch to the 200 mA range. But the reading should be the same for both ranges. Be sure you use the right jacks for each range.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-11T07:36:06.897" CommentCount="2" />
  <row Id="14165" PostTypeId="2" ParentId="14162" CreationDate="2011-05-11T08:08:36.290" Score="4" ViewCount="" Body="&lt;p&gt;General rule for measuring currents with multimeters:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Start with the highest range available (in you case: 2000 mA).&lt;/li&gt;&#xA;&lt;li&gt;If you read a value below the next lower range (in your case: 200 mA), change to this lower range.&lt;/li&gt;&#xA;&lt;li&gt;If the value is below the next available lower range, again, go one step down.&lt;/li&gt;&#xA;&lt;li&gt;...&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Here's &lt;a href=&quot;http://jbryant.eu/pages/DMM.htm&quot; rel=&quot;nofollow&quot;&gt;a very good article by Analog Devices' applications engineer James M. Bryant about using standard multimeters&lt;/a&gt; written for beginners with much attention to details.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-05-11T09:48:05.223" LastActivityDate="2011-05-11T09:48:05.223" CommentCount="4" />
  <row Id="14166" PostTypeId="2" ParentId="14144" CreationDate="2011-05-11T08:27:36.117" Score="3" ViewCount="" Body="&lt;p&gt;Use a high power resistor. For any given temperature, resistors will be more reliable than semiconductors, so there is no advantage in dissipating that power in a transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is common in power circuit design, for example dimmers and switched mode power supplies, you will need high power rated components because you are working at high voltages so even moderate currents produce high power dissipation. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I assume you are using a hard-fired technique, where you leave the gate current on continuously. In that case, the only way to reduce dissipation in the triac gate resistor is to use a more sensitive triac. But there is also the soft fired technique, where you only pulse the gate at the zero crossing and the triac stays latched on until the main current falls to zero. This is not suitable for all loads.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-05-11T08:27:36.117" CommentCount="7" />
  <row Id="14167" PostTypeId="2" ParentId="14133" CreationDate="2011-05-11T10:33:29.240" Score="3" ViewCount="" Body="&lt;p&gt;Your best bet is probably the &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0387740988&quot; rel=&quot;nofollow&quot;&gt;Reuse Methodology Manual for System-on-a-Chip Designs&lt;/a&gt; by Michael Keating and Pierre Bricaud.&lt;/p&gt;&#xA;" OwnerUserId="1933" LastEditorUserId="3441" LastEditorDisplayName="" LastEditDate="2011-05-11T16:04:09.587" LastActivityDate="2011-05-11T16:04:09.587" CommentCount="1" />
  <row Id="14168" PostTypeId="2" ParentId="14146" CreationDate="2011-05-11T10:36:25.257" Score="2" ViewCount="" Body="&lt;p&gt;Maybe go half way between Arduino shield and your own board using &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardPro&quot; rel=&quot;nofollow&quot;&gt;Arduino Pro&lt;/a&gt; or &lt;a href=&quot;http://arduino.cc/en/Main/ArduinoBoardProMini&quot; rel=&quot;nofollow&quot;&gt;Pro Mini&lt;/a&gt; board&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Pro - This board is designed for advanced users who want to leave a board embedded in a project: it's cheaper than a Diecimila and easily powered by a battery, but requires additional components and assembly. &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;You just add your additional components. &lt;/p&gt;&#xA;" OwnerUserId="3873" LastActivityDate="2011-05-11T10:36:25.257" />
  <row Id="14169" PostTypeId="2" ParentId="14133" CreationDate="2011-05-11T12:14:26.040" Score="1" ViewCount="" Body="&lt;p&gt;I found &lt;a href=&quot;http://www.gaisler.com/doc/vhdl2proc.pdf&quot; rel=&quot;nofollow&quot;&gt;A structured VHDL design method&lt;/a&gt; (pdf) interesting and useful, but it only covers a single design pattern.&lt;/p&gt;&#xA;" OwnerUserId="2395" LastActivityDate="2011-05-11T12:14:26.040" />
  <row Id="14171" PostTypeId="2" ParentId="11089" CreationDate="2011-05-11T13:21:45.160" Score="0" ViewCount="" Body="&lt;p&gt;you might want to have a look at &lt;a href=&quot;http://www.waitingforfriday.com/index.php/Building_a_PIC18F_USB_device&quot; rel=&quot;nofollow&quot;&gt;this website&lt;/a&gt;, which has a fairly recent proposition on how to make a low-cost usb interface, based on a pic. The code explains in full open source how to have bidirectionnal communication (blink a led from PC / respond to a button press), with both device and PC code.&lt;/p&gt;&#xA;" OwnerUserId="3991" LastActivityDate="2011-05-11T13:21:45.160" />
  <row Id="14172" PostTypeId="1" CreationDate="2011-05-11T13:58:41.443" Score="0" ViewCount="84" Body="&lt;p&gt;Hello everyone!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you please tell me the difference between DMOSFET and VMOSFET? &#xA; Or can suggest any good ebook regarding power MOSFET?&lt;/p&gt;&#xA;" OwnerUserId="4215" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-05-11T14:03:51.697" LastActivityDate="2011-05-13T06:47:49.443" Title="Different types of Power MOSFETS" Tags="&lt;power&gt;&lt;electronics&gt;" AnswerCount="1" />
  <row Id="14173" PostTypeId="2" ParentId="14089" CreationDate="2011-05-11T14:31:10.573" Score="0" ViewCount="" Body="&lt;p&gt;I got it figured out. I simple applied &quot;tubor J&quot; sugggestions ( who contributed above) and it worked good. Just ensure that you save all information when serial communication is going on, in a buffer. Then after, make use of the variables in the buffer. This prevents characters from been lost. &#xA;Thank to all!&lt;/p&gt;&#xA;" OwnerUserId="3632" LastActivityDate="2011-05-11T14:31:10.573" />
  <row Id="14174" PostTypeId="1" CreationDate="2011-05-11T14:36:53.360" Score="2" ViewCount="74" Body="&lt;p&gt;I recently bought 2 12V lead acid batteries (AGM type) for my mobile music needs where I need 24V, so I discharge them in series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the moment I charge both batteries separately, which is a bit annoying. So I would like to charge them in series, but I am not yet sure if this is a good idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When charging them separately I use a bench power supply with current and voltage control set to 14.1V. So, when charging them in series I would set my power supply to 28.2V, but then one of the batteries starts gassing and when measuring the individual batteries I see a voltage difference of about 0.3V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, am I doing something wrong here, is it just a bad measurement and nothing to worry about or is it generally a bad idea to charge batteries in series?&lt;/p&gt;&#xA;" OwnerUserId="4218" LastActivityDate="2011-05-11T22:43:36.653" Title="Charging lead acid batteries in series" Tags="&lt;battery&gt;&lt;battery-charging&gt;" AnswerCount="3" />
  <row Id="14175" PostTypeId="2" ParentId="14172" CreationDate="2011-05-11T14:41:01.610" Score="2" ViewCount="" Body="&lt;p&gt;Google turned this up in a couple of seconds:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.colorado.edu/physics/phys3330/phys3330_fa05/pdfdocs/AN101FETintro.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.colorado.edu/physics/phys3330/phys3330_fa05/pdfdocs/AN101FETintro.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks very good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both types are described.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-11T14:41:01.610" CommentCount="1" />
  <row Id="14176" PostTypeId="1" CreationDate="2011-05-11T14:58:06.760" Score="4" ViewCount="116" Body="&lt;p&gt;Wikipedia says that &lt;a href=&quot;http://en.wikipedia.org/wiki/Power_supply_rejection_ratio&quot; rel=&quot;nofollow&quot;&gt;power supply rejection ratio&lt;/a&gt; (PSRR) is the ratio of output noise &lt;em&gt;referred to the input&lt;/em&gt; vs noise at the power supply:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The PSRR is defined as the ratio of the change in supply voltage &lt;em&gt;to the equivalent (differential) input voltage&lt;/em&gt; it produces in the op-amp&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;Good Quality Design of Analog Cmos Integrated Circuits&lt;/em&gt; by Razavi seems to say the same thing:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The power supply rejection ratio (PSRR) is defined as the gain from the input to the output divided by the gain from the supply to the output.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;So the overall rejection from power supply to output vary with the closed-loop gain of the op-amp?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So an op-amp with +40 dB gain and 100 dB PSRR, with 0 dBV noise at the power supply would have -60 dBV noise at the output?  The Wikipedia example seems to say that it would be -120 dBV instead, which I don't understand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there also an output component of PSRR?  Like if you lower the gain of the amp, the input referred noise would decrease, right?  But is there then a constant component coupled from the power supply through the output stages that starts to dominate?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Analog Devices &lt;a href=&quot;http://www.analog.com/static/imported-files/tutorials/MT-043.pdf&quot; rel=&quot;nofollow&quot;&gt;MT-043&lt;/a&gt;, on the other hand, says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;PSRR or PSR can be referred either to the output (RTO) or the input (RTI). The RTI value can be obtained by dividing the RTO value by the amplifier gain. In the case of the traditional op amp, this would be the noise gain. The data sheet should be read carefully, because PSR can be expressed either as an RTO or RTI value.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Is this true?  How do you find out from the datasheet which method is used?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-11T21:03:13.697" LastActivityDate="2011-06-02T12:14:59.317" Title="Relationship between PSRR and gain" Tags="&lt;power-supply&gt;&lt;op-amp&gt;&lt;noise&gt;" AnswerCount="5" FavoriteCount="2" />
  <row Id="14177" PostTypeId="2" ParentId="14174" CreationDate="2011-05-11T15:06:16.767" Score="1" ViewCount="" Body="&lt;p&gt;I'll have a crack at answering, but I'm really not a reliable source here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My experience with LiPos in model aircraft says that series charging is fine, as they are usually a number of cells in series.  However it is required to keep the cells 'balanced' ie. the same voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Balancing is done by charging each cell individually.  This is a complex task in a LiPo as each cell remains in series.  It should be as simple as charging your batteries individually.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ideally the cells should remain at the same voltage after discharging in parallel, but this really depends on the quality/technology/relative-age of the batteries.  The further apart the voltages, the more you have to 'over-charge' one cell to get the other up to voltage.  Obviously there is only so far this can go before it starts gassing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It would also be a good idea to use a charger that adjusts voltage to maintain a constant current.  Typical lead acid batteries can be charged at 0.1C (a 1Ah cell can be charged at 0.1A).  A 'smart' charger will also make balancing the cells much easier.&lt;/p&gt;&#xA;" OwnerUserId="4211" LastActivityDate="2011-05-11T15:06:16.767" />
  <row Id="14178" PostTypeId="2" ParentId="14176" CreationDate="2011-05-11T15:07:59.153" Score="0" ViewCount="" Body="&lt;p&gt;The gain of your op-amp is not relevant, as the power supply voltage doesn't follow the signal path from input to output, but is coupled at various stages. So in your example, 0 dBV noise at the power supply and 100 dB PSRR the output will see -100 dBV of the power supply's noise.&lt;br&gt;&#xA;Note that noise is here not so important, noise levels are usually not so high on your power supply, and the noise on your input signal will be amplified and will be a lot higher at the output.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-11T15:56:41.497" LastActivityDate="2011-05-11T15:56:41.497" CommentCount="5" />
  <row Id="14179" PostTypeId="2" ParentId="14174" CreationDate="2011-05-11T15:17:28.723" Score="2" ViewCount="" Body="&lt;p&gt;This is a problem when series-charging lead-acid batteries and it is generally not recommended. The battery's condition is dependant on the specific gravity of the sulphuric acid electrolyte. Of course the 6 individual 2V cells in each battery share the same electrolyte which is why they can be charged in series but separate batteries can't.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-05-11T15:17:28.723" />
  <row Id="14180" PostTypeId="2" ParentId="14176" CreationDate="2011-05-11T15:43:18.857" Score="0" ViewCount="" Body="&lt;p&gt;There is a PDF of op-amp test procedures on Intersil's website &lt;a href=&quot;http://www.intersil.com/data/an/an551.pdf&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; which shows that PSRR is referred to the amplifier input. By my calculations, Wikipedia's 1uV output noise should read 1mV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$20 \log(\frac{1\mathrm V}{1\mathrm{mV}/100})\$ = 100dB&lt;/p&gt;&#xA;" OwnerUserId="2234" LastEditorUserId="2234" LastEditorDisplayName="" LastEditDate="2011-06-02T12:14:59.317" LastActivityDate="2011-06-02T12:14:59.317" CommentCount="2" />
  <row Id="14181" PostTypeId="2" ParentId="14176" CreationDate="2011-05-11T16:05:37.713" Score="1" ViewCount="" Body="&lt;p&gt;Gain is absolutely the ONLY important part of PSRR. Essentially what you are saying is how much can an op-amp when feeding back a signal cancel out any ripples introduced from the power supply, not from the input of the circuit..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lets take a simple example: an ideal (infinite open loop gain) voltage follower (output tied directly to the inverting input, fed from the non inverting input). The circuit has a closed loop gain of 1, but the feedback (since the overall gain is SOOO high) will mean that any power supply ripple will be canceled due to the feedback forcing the non inverting and inverting inputs to be in perfect lockstep..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But take the SAME example, but make the OPEN loop gain of the opamp 1, still with closed loop gain of 1, then suddenly the op amp cant keep up with the changes between the non-inverting input and the output-inverting input. And hence all ripple from the power supply would be visible on the output (essentially the op-amp would turn into a noise source with the noise being the coupled power supply ripple)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand HOW stevenvh could say that the gain is not meaningful, because he meant CLOSED loop gain... But the gain of question is OPEN loop gain, and YES, that is EVERYTHING in PSRR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;: And to answer your question, just to follow up slightly here, the PSRR is related to open loop gain, but the more closed loop gain you introduce, the more power supply ripple you will get on the output (hence the 60dB you reference above)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is why: Same example I give above, except this time you have a REAL op amp, (finite open loop gain), and resistors in your feedback path, meaning you have a closed loop gain of some value, say 6dB. Since the resistors behave as a voltage divider, the op-amp has to OVERCOMPENSATE for the power supply ripple being fed back to the non-inverting input. If it can only compensate for 100dB of power supply ripple, you will only get 94dB of rejection. The more closed loop gain you introduce, the less of the power supply ripple you are able to reject. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The whole conversation stems from the separate meanings of open loop and closed loop gain. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;2nd EDIT:&lt;/strong&gt; And the way that you get 60dB, or I get my 94dB is that you have to realize you have to convert dB BACK so for example you need to use &lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$&#xD;&#xA;20log10\left(\frac{10^\frac{100}{20}}{10^\frac{6}{20}}\right) = 94dB &#xD;&#xA;$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$&#xD;&#xA;20log10\left(\frac{10^\frac{100}{20}}{10^\frac{40}{20}}\right) = 60dB.&#xD;&#xA;$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And YES the other guy who said it should be 1mV not 1uV on Wikipedia is correct. &lt;/p&gt;&#xA;" OwnerUserId="4207" LastEditorUserId="4207" LastEditorDisplayName="" LastEditDate="2011-05-11T17:02:50.393" LastActivityDate="2011-05-11T17:02:50.393" />
  <row Id="14182" PostTypeId="2" ParentId="14176" CreationDate="2011-05-11T16:43:23.993" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/00722a.pdf&quot; rel=&quot;nofollow&quot;&gt;Microchip's op-amp topologies paper&lt;/a&gt; explains it this way:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&quot;In a closed-loop system, a less than ideal power supply rejection capability of an amplifier manifests itself as a offset voltage error...&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$ PSRR(dB) = 20 log \frac {\Delta V_{SUPPLY}}{\Delta V_{OS}} $&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$ PSR(\frac{V}{V}) = \frac {\Delta V_{OS}}{\Delta V_{SUPPLY}} $&lt;/p&gt;&#xA;&#xA;&lt;p&gt;where&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$ V_{SUPPLY} = V_{DD} - V_{SS}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$ \Delta V_{OS} = $ input offset voltage change due to PSR&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It also goes on to say that having bad PSR is not good for high-gain closed-loop amplifiers powered from batteries, as the DC change in supply voltage (as the battery discharges) will have a measurable affect on the output due to the input offset change.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-11T16:43:23.993" />
  <row Id="14183" PostTypeId="2" ParentId="14149" CreationDate="2011-05-11T17:18:55.460" Score="1" ViewCount="" Body="&lt;p&gt;Any of the popular small microcontroller boards would handle this easily. I don't know of anything prebuilt, but it should be a simple matter to find some e.g., Arduino code online to do what you need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want a simple, drop in solution and can wait a week or two, let me know and I can build you one. I did something similar for lighting not too long ago. I'm just pretty busy for the next week or so.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-05-11T17:18:55.460" />
  <row Id="14184" PostTypeId="2" ParentId="14176" CreationDate="2011-05-11T17:45:40.437" Score="0" ViewCount="" Body="&lt;p&gt;The confusion here is that PSRR (Power Supply Rejection Ratio) is a general term which in practice is actually used to refer to multiple things.  In general it is a ratio comparing a change in a parameter against a change in the supply's DC voltage level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, PSRR in an ADC is often used to refer to the ratio of the Gain Error to Change in DC Voltage of the Supply.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of this comes from confusing the acronym PSRR, which can be used as:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&quot;Power Supply Rejection Ratio&quot;&lt;/strong&gt; which is, as mentioned above, a ratio between a measured parameter and a change in the supply's &lt;strong&gt;DC voltage&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;&quot;Power Supply Ripple Rejection&quot;&lt;/strong&gt; which is the term which is, in general, the ratio of &lt;strong&gt;AC voltage&lt;/strong&gt; on the supply to &lt;strong&gt;AC voltage&lt;/strong&gt; on the input or output.  But, this can also be a ratio of an input to an output in the case of something like an Linear Regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lets look at an example: &lt;a href=&quot;http://focus.ti.com/lit/ds/symlink/opa121.pdf&quot; rel=&quot;nofollow&quot;&gt;http://focus.ti.com/lit/ds/symlink/opa121.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Here you'll see in the table on page 2 a value listed under the &quot;Offset Voltage&quot; section as &quot;Supply Rejection&quot;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a &quot;Power Supply Rejection Ratio&quot; comparing changes in the supply's DC level to shifts in the output's offset voltage.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;On page 3 a value listed under the &quot;Input Offset Voltage&quot; section as &quot;Supply Rejection&quot;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a &quot;Power Supply Rejection Ratio&quot; comparing changes in the supply level to shifts in the input offset voltage.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Looking at charts on page 4, we see a graph of &quot;Power Supply Rejection vs Frequency&quot;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a &quot;Power Supply Ripple Rejection&quot; measurement of AC ripple rejection which is the ratio of Supply Ripple to Input Ripple.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;This last one may be a bit confusing as for an op-amp the &quot;Power Supply Ripple Rejection&quot; is often specified as a ratio of the supply ripple to the input ripple.  This will generally be the case for devices with feedback or in the case of an op-amp, are generally used with feedback.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For devices without feedback, class D audio amplifiers for instance, &quot;Power Supply Ripple Rejection&quot; is usually just a ratio of the supply ripple to the output ripple and &quot;Power Supply Rejection Ratio&quot; is a measurement of the impact on the supply DC level to the output offset voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In summary there isn't really a hard and fast definition for 'PSRR' and often other terms are used such as 'Supply Rejection', 'Ripple Rejection', 'Power Supply Rejection', etc.  The important thing is that they are always measurements describing the effect of the power supply on the circuit in question.  To figure out what the measurement really means you have to consider the context of the measurement as well as the mode of operation of the device.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; Here are some examples of different uses by manufacturer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.national.com/nationaledge/apr01/ab102.html&quot; rel=&quot;nofollow&quot;&gt;National Semiconductor&lt;/a&gt;: Uses the terms &quot;Power Supply Rejection Ratio&quot; for AC and &quot;DC Power Supply Rejection Ratio&quot; for DC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.maxim-ic.com/glossary/definitions.mvp/term/PSRR/gpk/240&quot; rel=&quot;nofollow&quot;&gt;Maxim&lt;/a&gt;: Uses &quot;Power Supply Rejection Ratio&quot; for DC and &quot;Ripple Rejection&quot; for AC&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://focus.ti.com/lit/an/slyt202/slyt202.pdf&quot; rel=&quot;nofollow&quot;&gt;TI&lt;/a&gt;: Uses &quot;Power Supply Ripple Rejection (PSRR)&quot; LDOs and Various forms of &quot;Supply Rejection&quot; for Op-amps (see data sheet above).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.analog.com/static/imported-files/tutorials/MT-043.pdf&quot; rel=&quot;nofollow&quot;&gt;Analog Devices&lt;/a&gt;: Uses &quot;Power Supply Rejection Ratio&quot; defines it as relating to either the input or output, and even argues that the term PSRR shouldn't be used if its expressed in dB but rather PSR (Power Supply Rejection) should.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are many more examples but I'll leave it at that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So again, there really is no standardized definition here, its all up to context.&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2011-05-11T19:18:02.787" LastActivityDate="2011-05-11T19:18:02.787" CommentCount="4" />
  <row Id="14185" PostTypeId="1" AcceptedAnswerId="14232" CreationDate="2011-05-11T19:13:39.140" Score="0" ViewCount="77" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is;What is your concept of pinchoff voltage in an FET?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks in advance.&lt;/p&gt;&#xA;" OwnerUserId="3916" LastActivityDate="2011-05-12T16:36:56.920" ClosedDate="2011-05-13T04:23:18.367" Title="pinchoff voltage in an FET" Tags="&lt;voltage&gt;&lt;fet&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="14186" PostTypeId="1" CreationDate="2011-05-11T19:30:06.437" Score="1" ViewCount="116" Body="&lt;p&gt;Hello All :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to find a device with the following characteristics:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Programmable. A few kb of ROM will suffice.&lt;/li&gt;&#xA;&lt;li&gt;Can connect to a cellular data network.&lt;/li&gt;&#xA;&lt;li&gt;Has one digital pin input.&lt;/li&gt;&#xA;&lt;li&gt;Power consumption is not an issue, I can leave it connected to a power supply all day.&lt;/li&gt;&#xA;&lt;li&gt;Inexpensive, below USD$100 per unit.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;In other words, I'm looking for something similar to the PIC Ethernet Micro Web device described &lt;a href=&quot;http://www.sparkfun.com/products/8557&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; but with a cellular data modem instead of ethernet. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone suggest where to look for such devices and/or suggest a specific device? &lt;/p&gt;&#xA;" OwnerUserId="1346" LastEditorUserId="1346" LastEditorDisplayName="" LastEditDate="2011-05-11T22:41:54.823" LastActivityDate="2011-05-13T12:47:34.443" Title="Finding an inexpensive programmable, cellular data device." Tags="&lt;embedded&gt;&lt;device&gt;" AnswerCount="1" CommentCount="6" />
  <row Id="14187" PostTypeId="1" AcceptedAnswerId="14210" CreationDate="2011-05-11T19:40:22.070" Score="6" ViewCount="163" Body="&lt;p&gt;I know red LEDs have a higher forward voltage drop than a silicon diode; this leads to about 2.6x more power dissipation at a given current and so 2.6x less current rating, but 20mA is &lt;em&gt;way&lt;/em&gt; less than 1A. And yet, a humble 1N4001 won't complain about 1A but a 5mm LED (about the same size) will not last long at all. Why is this?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-05-11T20:16:37.423" LastActivityDate="2011-05-12T07:04:50.977" Title="Why can small LEDs only conduct ~20mA and a 1N4001 can conduct 1A?" Tags="&lt;led&gt;&lt;diode&gt;" AnswerCount="2" />
  <row Id="14188" PostTypeId="1" CreationDate="2011-05-11T19:46:01.440" Score="1" ViewCount="132" Body="&lt;p&gt;I am soldering a 10 lead MSOP (LMH1980) onto a PCB. Or trying to do so. The chip has a pitch of 0.5mm. I find that every time I use the &quot;tack and glob&quot; method I have been taught, I cannot remove the excess solder; it just sticks to the pins. (Tack and glob: pin a few crucial pins down, then glob solder over the pins. Wick away excess solder.) Tack and glob seems to work for a TQFP44 dsPIC and an TSOP16 ADG733 chip, but every time I do tack and glob on the LMH1980 I find that I cannot remove the excess solder, and in the process of trying to do so, I have damaged two PCBs (pulled the pads off) with components already on them. How can I solder this chip? BTW, I have only a basic temperature controlled soldering iron and hot air station (Aoyue 968.) Nothing fancy.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-05-11T19:56:37.340" LastActivityDate="2011-05-12T01:33:34.373" Title="How do I solder this tiny (0.5mm pitch) MSOP10?" Tags="&lt;soldering&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="14189" PostTypeId="2" ParentId="14188" CreationDate="2011-05-11T19:55:51.303" Score="2" ViewCount="" Body="&lt;p&gt;I've soldered similar devices without any problems. I use a very fine tip and a stereo microscope. I normally use drag-soldering with a mini-hoof cartridge and my Metcal system for fine-pitch devices, but I don't think it's suitable for one like that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can avoid damaging the PCB when removing parts like that by using &lt;a href=&quot;http://www.chipquikinc.com/&quot; rel=&quot;nofollow&quot;&gt;Chip Quik&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-12T00:28:44.863" LastActivityDate="2011-05-12T00:28:44.863" CommentCount="7" />
  <row Id="14190" PostTypeId="2" ParentId="14188" CreationDate="2011-05-11T19:58:56.917" Score="1" ViewCount="" Body="&lt;p&gt;Given that you have a hot air station, I think your best bet is to use a very thin layer of solder paste, preheat the board + chip (I used to have a recycled George Foreman grill for this) and then use the hot-air to push the solder past the melting point and allow it to flow.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, do you have solder mask on your boards?  At finer pitches, the solder mask can make a big difference on your success rate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are going to tack-and-glob, make sure your glob is much smaller than usual.  You might need to work with a much finer solder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;--&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, for solder already stuck beneath and under pins, sometimes hot air with high air flow can push the solder away from the pins enough to clear the short.  If your board is masked, there's a decent chance the resulting glob sitting under the IC will harmlessly stay put.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-11T19:58:56.917" CommentCount="1" />
  <row Id="14191" PostTypeId="2" ParentId="7979" CreationDate="2011-05-11T19:59:26.997" Score="3" ViewCount="" Body="&lt;p&gt;David May of XMOS presented an introduction to XMOS at the first OSHUG (Open Source Hardware) event last year: &lt;a href=&quot;http://www.vimeo.com/11624968&quot; rel=&quot;nofollow&quot;&gt;http://www.vimeo.com/11624968&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4222" LastActivityDate="2011-05-11T19:59:26.997" />
  <row Id="14192" PostTypeId="2" ParentId="14187" CreationDate="2011-05-11T20:06:27.467" Score="4" ViewCount="" Body="&lt;p&gt;It's primarily due to different junction areas, the power diode will have a much larger junction. A typical LED junction is 0.28mm x 0.28mm. Some LEDs take just as much current as power diodes.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-11T20:26:54.900" LastActivityDate="2011-05-11T20:26:54.900" CommentCount="3" />
  <row Id="14193" PostTypeId="2" ParentId="9322" CreationDate="2011-05-11T20:10:46.880" Score="1" ViewCount="" Body="&lt;p&gt;LI-Ion batteries are left with a charge of about 40% when they leave their factory. The discharge under storage is best then. This results in a voltage of about 3.7 for most types. When fully loaded or 100% charge the voltage is about 4.1V to 4.2V Do not charge them higher or they will lose their lifetime. They can be discharged until 3.3V or even lower but again lifetime is shortened when discharged too much.&#xA;I have much experience in charging an discharging as i am using solar cells to charge my li-ion batteries. I use for charging my mobile phone(s) &lt;/p&gt;&#xA;" OwnerUserId="4224" LastActivityDate="2011-05-11T20:10:46.880" />
  <row Id="14194" PostTypeId="2" ParentId="13662" CreationDate="2011-05-11T21:23:00.090" Score="0" ViewCount="" Body="&lt;p&gt;I now have this working. ADC10 part is now similar to TI's samples.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the code that can read successfully from 4 pins simultaneously:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;unsigned int res[5]; //for holding the conversion results&#xA;void main (void)&#xA;{ &#xA;&#xA;  //code for connecting to AP&#xA;&#xA;  //reading voltage&#xA;  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT&#xA;  ADC10CTL1 = INCH_4 + CONSEQ_1;            // A4/A3/A2/A1/A0, once multi channel&#xA;  ADC10CTL0 = REF2_5V + ADC10SHT_2 + MSC+ REFON + ADC10ON + ADC10IE; //2.5 reference voltage&#xA;  ADC10AE0 = 0x1F;                          // P2.0,1,2,3,4 ADC option select&#xA;  ADC10DTC1 = 0x5;                         // 5 conversions&#xA;  P1DIR |= 0x01;                            // Set P1.0 output&#xA;&#xA;  for (;;)&#xA;  {&#xA;    P1OUT |= 0x01;                          // Set P1.0 LED on&#xA;    ADC10CTL0 &amp;amp;= ~ENC;&#xA;    while (ADC10CTL1 &amp;amp; BUSY);               // Wait if ADC10 core is active&#xA;    ADC10SA = (int)res;                        // Data buffer start&#xA;    ADC10CTL0 |= ENC + ADC10SC;             // Sampling and conversion ready&#xA;    __bis_SR_register(CPUOFF + GIE);        // LPM0, ADC10_ISR will force exit&#xA;    P1OUT &amp;amp;= ~0x01;                         // Clear P1.0 LED off&#xA;  }&#xA;&#xA;}&#xA;&#xA;#pragma vector=ADC10_VECTOR&#xA;__interrupt void ADC10_ISR(void)&#xA;{&#xA;    //code from reading from res and sending it to AP&#xA;  __bic_SR_register_on_exit(CPUOFF);        // Clear CPUOFF bit from 0(SR)&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Thanks for the help!&lt;/p&gt;&#xA;" OwnerUserId="3852" LastActivityDate="2011-05-11T21:23:00.090" />
  <row Id="14195" PostTypeId="2" ParentId="14174" CreationDate="2011-05-11T22:43:36.653" Score="0" ViewCount="" Body="&lt;p&gt;My UPS uses 2 lead-acid sealed batteries in series. It charges them only to 27.4 Volts, and it does that rather slowly (IIRC ~8h charge time), but a charger of this type and voltage can stay connected to the batteries &quot;forever&quot; without damaging them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you try to charge them with higher currents the slight difference between the cells will be a problem, since one battery will have higher voltage and thus start gassing out at some point. A really inelligent desgin would measure the middle voltage between the batteries, but I have seen this only on high-power LiPo/Li-Ion chargers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, the answer is that if you have the time for slow charging, you can leave the batteries in series, but if you want to charge as fast as you can - separate them.&lt;/p&gt;&#xA;" OwnerUserId="1472" LastActivityDate="2011-05-11T22:43:36.653" />
  <row Id="14196" PostTypeId="1" AcceptedAnswerId="14205" CreationDate="2011-05-11T22:44:34.687" Score="3" ViewCount="149" Body="&lt;p&gt;I've read a lot about people cleaning keyboards in the dishwasher. But how does the water damage electronics? Does it cause shorts on the ICs on the internal circuitry or physically get in the IC(which I can't see happening). So what actually happens?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-05-12T09:15:35.340" Title="Water and Electronics?" Tags="&lt;damage&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="14197" PostTypeId="2" ParentId="14196" CreationDate="2011-05-11T22:52:27.993" Score="4" ViewCount="" Body="&lt;p&gt;If the device is off and you are just using plain water it's not going to harm the device as long as you dry it off again before turning it on. Dishwashers work quite well for this, but you shouldn't put much soap into it (too much and the residue could stick to the PCB and cause problems, as an insulator (not a conductor). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you run electronic equipment while it's wet then yes, it will short out. While water itself is not a conductor, any dissolved minerals/salts will make it very conductive. Since there are minerals in every form of tap or natural water it can be very bad for a computer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said I've literally spilled an entire glass of water onto a working motherboard and it continued to work for the next 5 minutes while I saved my work and shut down. Dried it off and there was no damage. &lt;/p&gt;&#xA;" OwnerUserId="4201" LastActivityDate="2011-05-11T22:52:27.993" CommentCount="3" />
  <row Id="14198" PostTypeId="1" AcceptedAnswerId="14199" CreationDate="2011-05-11T23:11:09.000" Score="1" ViewCount="43" Body="&lt;p&gt;Does anyone know of an online battery usage calculator for predicting the lifetime of low power systems?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(something simpler than doing the manual calculations).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;I have a microcontroller which is&#xA;  awake for 1ms in every 1000ms, during&#xA;  this time it consumes 5mA. I have an&#xA;  LED which is on for 2ms in every&#xA;  1000ms and it consumes 30mA. How long&#xA;  will my 2200mAh battery last?&quot;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-05-11T23:55:52.033" Title="Online battery usage calculator?" Tags="&lt;power&gt;&lt;battery&gt;" AnswerCount="1" />
  <row Id="14199" PostTypeId="2" ParentId="14198" CreationDate="2011-05-11T23:55:52.033" Score="4" ViewCount="" Body="&lt;p&gt;In the absence of an online tool, I can provide some alternatives.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As long as you're not considering any non-linear discharge effects, the following formula works fairly well:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$ I_\mbox{avg}=\sum{ I_{on} \times \frac{t_{on_j}}{t_{total}}} $&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And then to find total battery life, you can divide the energy of the battery by the average current to get a time figure. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;$t_{life} = \frac{Capacity}{I_{avg}} $&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if we take your example to run some numbers through the formula, then we get:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$ I_{avg} = (5mA\times\frac{1ms}{1000ms}) + (30mA\times\frac{2ms}{1000ms}) = 65\mu A$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$t_{life} = \frac{2200mAh}{65\mu A} = 33846 \mbox{ hours} \approx 3.8 \mbox{ years}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, before you down-vote me in a fit of rage for not having a link, I do know that this is not the question, and I strongly suspect that you understand how to run this calculation yourself. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I would suggest is that in the event that a handy internet reference is unavailable, that you would create a spreadsheet to calculate your power needs. This math is easily adapted to a spreadsheet calculation, and it allows real-time playing with the numbers. Given the simplicity, it may just be easiest to do things yourself. Arguably, it would take about the same amount of time, since the fundamental data must still be entered somehow into a computer.&lt;/p&gt;&#xA;" OwnerUserId="638" LastActivityDate="2011-05-11T23:55:52.033" CommentCount="1" />
  <row Id="14200" PostTypeId="2" ParentId="11089" CreationDate="2011-05-12T00:15:16.423" Score="0" ViewCount="" Body="&lt;p&gt;It is easy to connect DS18S20 temperature sensor to PC via USB as explained &lt;a href=&quot;http://www.obdev.at/products/vusb/prjdetail.php?pid=71&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-05-12T00:15:16.423" />
  <row Id="14201" PostTypeId="2" ParentId="14186" CreationDate="2011-05-12T00:49:02.620" Score="1" ViewCount="" Body="&lt;p&gt;From Sparkfun, the &lt;a href=&quot;http://www.sparkfun.com/products/8851&quot; rel=&quot;nofollow&quot;&gt;PIC GSM cellular development board&lt;/a&gt;   However, this will do SMS data, not 3G data which I'm guessing would be preferred?  Also, it's way outside your price range: $\$$250.  Judging by the fact that just the GSM cellular chips are about $\$$150 by themselves I don't think you're going to hit your price point, especially if you're looking for 3G data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now this idea isn't strictly in keeping with your ideal (from what I can tell, a 3G data unit with simple interface or built-in 8/16/32 bit microcontroller), another option might be a simple wireless router with host USB capabilities and a 3G USB modem.  I know that DD-WRT can support these, and probably OpenWRT and/or Tomato.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's also the &lt;a href=&quot;http://www.cutedigi.com/product_info.php?products_id=4445&quot; rel=&quot;nofollow&quot;&gt;Arduino wifi shield&lt;/a&gt; for $\$$55 if wifi is acceptable&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:  I looked into the Linux DIO thing, and on my router (Asus WL-500GPv2) there are digital I/O pins that can be accessed via /dev/gpio.  It looks like the setup involves an 'outen' file that specifies which lines are outputs, an 'out' file that lets you set DIO by writing a byte value to it and an 'in' file that can be read to view the current state of the GPIO.  There's a forum post describing it [here].&lt;a href=&quot;http://wl500g.info/showthread.php?t=19269&quot; rel=&quot;nofollow&quot;&gt;3&lt;/a&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone else find it fascinating how Linux accesses hardware by reading and writing to it like a bytestream?&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="249" LastEditorDisplayName="" LastEditDate="2011-05-13T12:47:34.443" LastActivityDate="2011-05-13T12:47:34.443" CommentCount="2" />
  <row Id="14202" PostTypeId="1" AcceptedAnswerId="14207" CreationDate="2011-05-12T01:11:42.987" Score="6" ViewCount="150" Body="&lt;p&gt;When wanting to look up a datasheet for a random part number I encounter in a circuit, say an AD9862, my first action is just to type it into google. For about half of the parts I encounter, particularly ones made by big respected brand names (like the Analog Devices example I used above) this gives me as a first hit the official manufacturer page and datasheet. Happy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But about half of the time, especially with commodity/generic parts, say a 7812, the top hits are all these garbage sites like alldatasheet, getdatasheet, or datasheetcatalog dot com (I'm not typing out their URLs, since I don't want to further increase the pagerank of these junk websites). These websites are ugly, crammed to the brim with ads, with bad search capabilities, lots of SEO to get them highly ranked by google, but often with very little in the way of useful content.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you have a favorite way to find datasheets online, that sidesteps these middle-man ad-crammed sites? Is there a nice, user-curated perhaps, clean, low-ad-content database of datasheets out there somewhere?&lt;/p&gt;&#xA;" OwnerUserId="3768" LastActivityDate="2011-05-12T02:17:32.607" Title="Online database of data sheets that isn't horrible?" Tags="&lt;electronics&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="14203" PostTypeId="2" ParentId="14188" CreationDate="2011-05-12T01:33:34.373" Score="7" ViewCount="" Body="&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/w6ngn.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;h2&gt;Flux!&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;Solder bridges mean you need more/better/fresh flux.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Either iron or hot air will work fine.  Heat is heat.  I prefer iron for clearing shorted pins:  wipe iron on sponge, apply to pins, repeat.  The excess solder will stick to the tip.)&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-05-12T01:33:34.373" CommentCount="4" />
  <row Id="14204" PostTypeId="2" ParentId="14202" CreationDate="2011-05-12T01:48:06.353" Score="3" ViewCount="" Body="&lt;p&gt;My favorite is alldatasheet.com because:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;they don't list parts they don't have datasheets for&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;they don't tease you and then try to charge for access (the expert-sexchange.com business model)&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;they let you actually download the pdf so you can Spotlight it next time and avoid the web entirely.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I think there will never be a great quality site for this because reproducing datasheets is kinda shady.  Although most manufacturers don't seem to mind, I believe most of these datasheets are scanned and redistributed in violation of copyright.  Although, I guess you could do extremely targeted advertisement. &quot;Looking at voltage regulators?  Click for a sample of our new XYZ regulator!&quot;&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-05-12T01:48:06.353" CommentCount="1" />
  <row Id="14205" PostTypeId="2" ParentId="14196" CreationDate="2011-05-12T02:03:02.760" Score="11" ViewCount="" Body="&lt;p&gt;Many electronic assembly lines have a water cleaning machine in them.  Basically it runs the PCB through it on a conveyor belt while spraying it with water.  One smaller contract manufacturer I visited actually used standard dishwashers to clean PCB's (but had a closed water system, so no bad stuff made it into the sewer).  In my lab, we use water soluble flux that must be cleaned with water, as the flux itself is very conductive.  I simply rinse the PCB in the sink and dry it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several important things to note when washing a PCB with water:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;The PCB should not be powered.  This seems obvious, but people often forget about batteries for the real-time-clock and stuff.  Sometimes the batteries will survive the washing step, but it's best to not tempt fate.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;The PCB should be completely dry before powering it up.  This is the tricky one, since there are many small nooks and crannies for water to go into, and it doesn't evaporate quickly in those tight spaces.   I'm in Colorado, where the humidity is often less than 30%, and I will either let the PCB drip dry for more than 24 hours or use a heat gun to speed things up.  If you're in a more humid climate then extend the drying time accordingly.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Some parts don't survive washing.  Speakers, buzzers, and microphones are the big ones.  Some switches and buttons don't like being washed either.  Of course there are always exceptions.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;If your water has a high mineral content then you might want to do a &quot;spot free rinse&quot; using deionized or reverse-osmosis-ized water.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;The #1 way water damages the electronics is by shorting things out while the power is on.  The #2 way is by corrosion.  Interestingly enough, it's not the water that does the damage but all the impurities that are dissolved in the water.  Pure water doesn't do much (but look at it wrong and it'll get impurities).  Of course, not powering on the device and drying it relatively quickly will prevent both of these problems.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-12T02:03:02.760" CommentCount="3" />
  <row Id="14206" PostTypeId="2" ParentId="14202" CreationDate="2011-05-12T02:13:18.913" Score="7" ViewCount="" Body="&lt;p&gt;I only get datasheets from the original manufacturer, and avoid all third-party datasheet sites.  With the manufacturer, you know that you're getting the latest, most up to date info.  I've been doing this long enough where I can locate the original manufacturer within a minute or two.  And places like Digikey will list the manufacturer and mfg part number so it's fairly painless.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For commodity parts, most of them are from National, TI, or On Semi so even then I can locate the original manufacture quickly.  Now that National was bought by TI, this will get even quicker.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also have another rule:  Don't use parts that I don't know the manufactures part number for.  That's the only way to know for sure what you're buying/using.  Anything else is too unreliable of a source to trust building an expensive PCB with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All of this works quite well, unless I'm trying to find a datasheet for an obsolete part or an oddball part.  In that case, Google it and search through all the hits.  But this only happens when I'm desperate anyway so a little Googling isn't the end of the world.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-12T02:13:18.913" />
  <row Id="14207" PostTypeId="2" ParentId="14202" CreationDate="2011-05-12T02:16:45.617" Score="7" ViewCount="" Body="&lt;p&gt;The others have made great recommendations.  I'll add one small google hack that I use a lot:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;[part number] datasheet filetype:pdf&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So let's say you're looking for the LM629 datasheet... you'll google&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;LM629 datasheet filetype:pdf&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;or maybe an 74LS04:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;74LS04 datasheet filetype:pdf&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This has always worked well for me, since I know that the datasheets are going to be in the PDF format.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-05-12T02:16:45.617" CommentCount="3" />
  <row Id="14208" PostTypeId="2" ParentId="14202" CreationDate="2011-05-12T02:17:32.607" Score="3" ViewCount="" Body="&lt;p&gt;My favorite method is to use supplier catalogues.  Granted I'm not working with many old parts so everything I'm interested in is still in their databases.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Digikey will link directly to the manufacturers datasheet (PDF) in almost all cases.  And their search features are much more useful than pure googling in a specific subject matter.&lt;/p&gt;&#xA;" OwnerUserId="4211" LastActivityDate="2011-05-12T02:17:32.607" CommentCount="1" />
  <row Id="14210" PostTypeId="2" ParentId="14187" CreationDate="2011-05-12T05:24:58.170" Score="5" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Packaging:&lt;/strong&gt; A power diode can have much material (Si and metal) to take the heat where an LED needs a transparent surface and housing to let the light out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Power dissipation:&lt;/strong&gt; As you say, Power diodes are trimmed for a low forward (conducting) voltage drop. Si diodes can go as low as maybe 300...500 mV, as opposed to the typical 650...750 mV for small signal diodes like the 1N4148.&#xA;LEDs have typical forward voltages in the range of 1600 mV...2400 mV.&#xA;What troubles the chip is the heat generated by the dissipated power: P=V*I.&#xA;Let's assume (for simplicity) that an LED and a power diode take the same amount of power. With an LED's forward voltage five times greater than that of an &quot;ordinary&quot; diode, the LED can handle only 1/5 of the current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Process trimming:&lt;/strong&gt; Also, LEDs are primarily trimmed for a good efficiency (Light output with respect to electrical power input) whereas power diodes are trimmed for maximum power handling capabilities. Power diodes can therefore usually be run at higher temperatures than LEDs. Actually, power diodes start to feel happy at temperatures where LEDs start to disintegrate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;These are just very rough approximations and the folks working on the research of better high-output LEDs probably cringe when they read this, but the examples still show the general answer for your question... And they show what LED research aims at: High-temp chips, innovative packaging techniques to conduct the heat away from the chip, low forward voltages (usually defined by the material and dopants involved in the process -- remember that the material defines the color and that not much stuff is available at all to build some colors), ...&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-05-12T07:04:50.977" LastActivityDate="2011-05-12T07:04:50.977" />
  <row Id="14211" PostTypeId="2" ParentId="10406" CreationDate="2011-05-12T06:10:22.593" Score="0" ViewCount="" Body="&lt;p&gt;MPS4355 if RS is low -- up to a few hundred ohms&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2N4250 is RS a few K ohms&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.thatcorp.com/THAT_IC_Selection_Guide.shtml#XsistorArrays&quot; rel=&quot;nofollow&quot;&gt;http://www.thatcorp.com/THAT_IC_Selection_Guide.shtml#XsistorArrays&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4228" LastActivityDate="2011-05-12T06:10:22.593" />
  <row Id="14212" PostTypeId="1" AcceptedAnswerId="14214" CreationDate="2011-05-12T06:31:47.327" Score="5" ViewCount="159" Body="&lt;p&gt;We purchased a number of stainless steel kiosk keyboards from a Chinese manufacturer a while back and have been seeing extraordinary failure rates (around 30%).  Groups of keys just stop working.  I've pulled several of them apart and traced the problem to plated through-holes / vias that have failed.  I've been repairing them by passing a small wire through the hole and soldering it directly to the trace or pad on either side.  Photos show what they look like when I pull them apart:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/5nyfS.jpg&quot; alt=&quot;Odd through-hole 1&quot;&gt;&#xA;&lt;img src=&quot;http://i.stack.imgur.com/t5Mdu.jpg&quot; alt=&quot;Odd through-hole 2&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given this information I have two questions:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;What's up with these?  Any theories on why they're failing?  Anything we can do to prevent it?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Is the repair method I mentioned earlier appropriate?  Is there a better way or anything specific I should be taking into consideration?&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="4227" LastActivityDate="2011-05-12T16:43:06.600" Title="What's up with these plated through-holes / vias?" Tags="&lt;pcb&gt;&lt;failure&gt;&lt;through-hole&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="14213" PostTypeId="1" AcceptedAnswerId="14220" CreationDate="2011-05-12T07:05:46.160" Score="4" ViewCount="105" Body="&lt;p&gt;Important note: You are not helping me do my homework. This is for a competition for engineering students, that encourages you to &quot;use your network&quot; ;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got this pattern for a frequency divider that divides the clock by 5. It's supposed to have one major problem, but I can't seem to figure out exactly what it is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/SMz1I.gif&quot; alt=&quot;enter image description here&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The options I have to fix this problem is:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;X==(000|001|100), Y==(001)&lt;/li&gt;&#xA;&lt;li&gt;X==(000|001|010|011), Y==(010|011)&lt;/li&gt;&#xA;&lt;li&gt;X==(001|010|011), Y==(000)&lt;/li&gt;&#xA;&lt;li&gt;Both a) and c) are correct!&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I've taken the time to map out the signals in the original design and in option number 3, as I thought that was the answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/sdkHx.png&quot; alt=&quot;http://imgur.com/dD30q&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've shifted the clock one half clock cycle, whoops. Shouldn't change anything though.&#xA;The rest is done by hand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone here have any good suggestions?&lt;/p&gt;&#xA;" OwnerUserId="4229" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-05-12T07:37:05.510" LastActivityDate="2011-05-12T15:35:00.803" Title="Odd number frequency divider" Tags="&lt;frequency&gt;&lt;digital&gt;&lt;clock&gt;&lt;divide&gt;" AnswerCount="2" />
  <row Id="14214" PostTypeId="2" ParentId="14212" CreationDate="2011-05-12T08:40:32.967" Score="5" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;What's up?&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, I assume your board has two layers only (top and bottom, no internal layers).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It may be the case that there is not enough copper in the vias. Copper is applied to vias in a galvanic or electro-chemical process. Maybe the solution used in the process was old, maybe the boards were not put into the process long enough, or maybe the board was not prepared or cleanded properly before they were put into the process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It also happens that during soldering, the board expands more than the vias can handle and the copper layer cracks (almost) open. This is especially tricky with boards containing a polyimide layer for rigid-flexible-combinations. After a while, the crack goes from almost open to open. These failures - like many other issues you can have with PCBs - are nasty, because they are hard to find while the boards are still tested. Instead, they occur after a while in the field...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My personal experience is that, however well your production tests are done, boards remain a case of trust between the manufacturer and the customer. Money spent on a good board manufacturer is money well spent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Repair:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For home brew devices, this would be the way to go. For mass production, you would have to rework all vias, because any via could be weak and almost fail open. This is likely not a practical solution, and also very likely not a repair method recommended by IPC guidelines...&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-05-12T08:40:32.967" CommentCount="2" />
  <row Id="14215" PostTypeId="2" ParentId="14212" CreationDate="2011-05-12T09:07:55.853" Score="3" ViewCount="" Body="&lt;p&gt;Could it be that the PCB is flexing when keys are pressed, leading to gradual cracking of the via plating as the copper work-hardens?&#xA;If so, a solution might be to improve how the PCB is supported, e.g. with high density foam and a metal plate.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-05-12T09:07:55.853" CommentCount="1" />
  <row Id="14216" PostTypeId="2" ParentId="14196" CreationDate="2011-05-12T09:15:35.340" Score="1" ViewCount="" Body="&lt;p&gt;Years ago a friend asked me for a way to slightly illuminate a small river in a miniature diorama. There was almost no space to hide the little circuit (it was a PIC with internal oscillator that handled 3 red leds) and no time to rebuild that diorama part, so with just 3V of supply (to limitate water electrolysis) we simply submerged the circuit in the water reservoir. And as all provisional hacks, it worked for years without problems :-)&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-05-12T09:15:35.340" />
  <row Id="14217" PostTypeId="2" ParentId="14146" CreationDate="2011-05-12T10:27:04.607" Score="4" ViewCount="" Body="&lt;p&gt;I assume from your question you want the essential parts of an Arduino along with your circuit in a permanent form.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my steps:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Build the entire circuit on a breadboard or two. Then you know it all works.&lt;/li&gt;&#xA;&lt;li&gt;Transfer it to a permanent form of circuit, testing as you go.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Take it a step at a time, and it'll work out nicely.&#xA;&lt;br&gt;&#xA;&lt;br&gt;&#xA;1. Build the entire circuit on a breadboard or two. Then you know it all works, and that you have all of the components ready to make your permanent circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This will involve making and programming part of your Arduino on the breadboard. I don't think you'll need the USB part, so it can be through-hole components which are relatively straightforward to begin with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's a link to instructions which show how to do make an Arduino without USB.&#xA;&lt;a href=&quot;http://appliedplatonics.com/breaduino/steps.html&quot; rel=&quot;nofollow&quot;&gt;http://appliedplatonics.com/breaduino/steps.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can be programmed using your existing Arduino, you don't need a programmer. For example:&#xA;&lt;a href=&quot;http://arduino.cc/en/Tutorial/ArduinoToBreadboard&quot; rel=&quot;nofollow&quot;&gt;http://arduino.cc/en/Tutorial/ArduinoToBreadboard&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd make a sketch of the circuit schematic to ensure I understood what I had on the breadboard, and to guide the next step.&#xA;&lt;br&gt;&#xA;&lt;br&gt;&#xA;2. I'd recommend you transfer the whole thing to 'veroboard' (stripboard) rather than make a PCB. Veroboard/stripboard will be much quicker and cheaper. You could easily spend 10x longer learning to use Eagle well enough to get a PCB made, than it would take to design and make the entire circuit on veroboard/stripboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can do a design on squared paper, but there are some CAD programs to help if you google for veroboard CAD. I have never used them, I use paper and a soft pencil or a vector drawing package. A friend used PowerPoint because that's what he had to hand.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's an example of someone who has built an Arduino on veroboard/stripboard&#xA;&lt;a href=&quot;http://icecreamterror.wordpress.com/2009/09/03/stripduino-v0-1-the-strip-board-arduino/&quot; rel=&quot;nofollow&quot;&gt;http://icecreamterror.wordpress.com/2009/09/03/stripduino-v0-1-the-strip-board-arduino/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It shows the design he produced for veroboard/stripboard. Try to get a reasonable layout for your design before making it. This is where the soft pencil and eraser come in :-) &#xA;Typically the first couple of attempts are too big or too small. Make it easy for yourself and get plenty of squared of graph paper :-)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This shows what the process will look like:&#xA;&lt;a href=&quot;http://www.zen22142.zen.co.uk/Prac/vero_circ/vero.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.zen22142.zen.co.uk/Prac/vero_circ/vero.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can follow veroboard/stripboard arduino design, and test that it works. Then focus on your extra circuit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Use a socket for the microcontroller, and so don't solder it in directly. Most of the other parts are a few $'s total, so I'd get a few of each part for spares and practice (To put it in context, some electronics companies charge more for delivery than those parts will cost, so getting several sets of parts makes sense, especially if you intend to make some more things).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Total cost for the Arduino part should be under $10.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck, and I hope you enjoy it.&lt;/p&gt;&#xA;" OwnerUserId="4231" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-05-12T11:48:57.783" LastActivityDate="2011-05-12T11:48:57.783" CommentCount="1" />
  <row Id="14218" PostTypeId="1" CreationDate="2011-05-12T10:50:30.243" Score="3" ViewCount="111" Body="&lt;p&gt;Hi all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using an Allegro 6280 PWM LED driver for a project. This is a cool little IC except for the fact that it is a 31 bit long input register.  This is no problem if I simply loop through my 31 bits and set the pin states accordingly, but I'm wanting to use the atmega's on-board SPI to speed things up a bit (the 6280 requires an external clock source for it's 10 bit long PWM cycle).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 31 bit long register looks like this in my application where R,G &amp;amp; B indicate the 10 bit PWM values for the attached LEDs.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;0BBBBBBBBBBGGGGGGGGGGRRRRRRRRRR&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;These shift registers are chainable, so I've built a linked list to represent them:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;struct Pixel {&#xA;  uint16_t red;&#xA;  uint16_t green;&#xA;  uint16_t blue;&#xA;  Pixel *next;&#xA;};&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;So, the idea is to set the latch pin low, iterate through all the Pixels and then after sending the last one set the latch high to latch the data into each register.  This would seem easy except that due to the uneven length of the register I have to construct nasty-looking code to be able to loop around to the beginning again so that it never sends any empty bits. Also, the latch might need to happen after an arbitrary number of bits are transmitted, not just the last one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any ideas on how to get this done, or am I simply barking up the wrong tree and stuck with manually twiddling the pin states?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks.&lt;/p&gt;&#xA;" OwnerUserId="4232" LastActivityDate="2011-06-01T09:52:00.533" Title="How to use ATmega328 SPI with a 31 bit shift register." Tags="&lt;avr&gt;&lt;atmega&gt;&lt;spi&gt;&lt;atmega328&gt;&lt;shift-register&gt;" AnswerCount="2" CommentCount="0" />
  <row Id="14220" PostTypeId="2" ParentId="14213" CreationDate="2011-05-12T13:06:00.823" Score="4" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;It's supposed to have one major problem&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The one possible problem that jumps out at me is glitch prevention. Your output is a clock signal, so it would be very sensitive to extra edges. But it is a combinational output, so it can be prone to glitches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just as an example, let's say you had this naive implementation of a full carry generator (at least 2 inputs of 3 are true), namely&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Y = ABC + AB(!C) + A(!B)C + (!A)BC&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;If your ABC signals switch from 111 to 011, there is a chance, depending on propagation delays, that the output Y, which should be a 1 the entire time, gives you a short glitch of 0. What's basically going on is that the output's trueness has to shift from one term to another: ABC -&gt; (!A)BC in this case. If the (!A)BC term has a longer propagation delay than the ABC term for the 1 -&gt; 0 transition on A, then both terms ABC and (!A)BC can be 0 for a short period of time, and you get a 0 as an output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A proper implementation is one where a single input bit change produces no glitches in the output: the output's level is shared by two terms as it transitions. In the case of a full-carry generator, this works:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Y = AB + BC + CA&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;In your case, there are two possible causes of glitches. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One is that X and Z change at nearly the same time -- but in your case, according to your timing diagrams, this shouldn't happen.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other is that the combinational logic that produces X is glitch-prone. We don't know how it's implemented, so that's hard to say.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The simplest solution in either case is to stick a flip-flop on the output, with the same clock input as your other flip-flops. Modern flip-flops have sample/hold specs such that any propagation delay &gt;= 0 and &amp;lt; (clock period - setup time) will produce stable, glitch-free outputs, so unless your clock period is really fast, any glitch on the input of the flip-flop will settle out by the start of its setup time window on the next clock edge.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't tolerate the delay of putting a flip-flop on the output, you need to guarantee that all combinational logic directly producing the output is glitch-free.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-05-12T13:06:00.823" CommentCount="1" />
  <row Id="14221" PostTypeId="1" CreationDate="2011-05-12T13:12:10.377" Score="3" ViewCount="81" Body="&lt;p&gt;Hello guys..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am a newbie to this MSP430. So, please tell me when I go wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a final project making MPPT (Maximum Power Point Tracker) using MSP430G2231. The basic idea is to measure to Analog input (voltage and current), then multiply it (power) and compare to the previous result. That's why, before going further to the algorithm of the MPPT itself, I am trying to use this MSP430G2231 to read 2 analog input and create PWM using it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I use two pins as an input, P1.0 and P1.1. Then, I use P1.2 to produce the PWM.&#xA;The coding that I made goes like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;i&gt;    &lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#include &amp;lt;msp430.h&amp;gt;&#xA;#include &quot;msp430g2231.h&quot;&#xA;&#xA;//Global Variable&#xA;unsigned int AdcData[2] ;                 // Store results A1,A0&#xA;unsigned int Current ;         // store value from P1.0&#xA;unsigned int Voltage ;         // store value from P1.1&#xA;&#xA;void main (void)&#xA;{&#xA;  WDTCTL = WDTPW + WDTHOLD;   // Stop WDT&#xA;&#xA;  BCSCTL1 = CALBC1_1MHZ;   // Set range&#xA;  DCOCTL = CALDCO_1MHZ;      // SMCLK = DCO = 1MHz &#xA;&#xA;  ADC10CTL1 = INCH_1 + CONSEQ_1;            // A1/A0, single sequence&#xA;  ADC10CTL0 = ADC10SHT_2 + MSC + ADC10ON + ADC10IE;&#xA;  ADC10DTC1 = 0x02;                         // 2 conversions&#xA;  ADC10AE0 |= 0x03;                         // P1.1,0 ADC10 option select&#xA;&#xA;  P1DIR |= BIT2;                            // P1.2 = output&#xA;  P1SEL |= BIT2;                            // P1.2 = TA1 output&#xA;  TACCR0 = 1024-1;                             // PWM Period&#xA;  TACCTL1 = OUTMOD_7;                       // TACCR1 reset/set&#xA;  AdcData[0]=32;&#xA;  AdcData[1]=16;&#xA;  Voltage = AdcData[0];&#xA;  Current = AdcData[1];             &#xA;  TACCR1 = (Voltage*0.04)*(Current*0.05);         // TACCR1 PWM Duty Cycle&#xA;  TACTL = TASSEL_2 + MC_1;                  // SMCLK, upmode&#xA;&#xA;&#xA;  while (1)&#xA;  {&#xA;  __bis_SR_register(LPM0_bits + GIE);     // LPM0, ADC10_ISR will force exit&#xA;   ADC10SA = (unsigned int)&amp;amp;AdcData;        // Data transfer location&#xA;   ADC10CTL0 |= ENC + ADC10SC;             // Start sampling&#xA;  }&#xA;}&#xA;&#xA;&#xA;// ADC10 interrupt service routine&#xA;#pragma vector=ADC10_VECTOR&#xA;__interrupt void ADC10_ISR(void)&#xA;{&#xA;  __bic_SR_register_on_exit(LPM0_bits);     // Exit LPM0&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;/i&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I try to trace it using &quot;step into&quot; in debugging mode. Everything seems goes well until it reach this line : &#xA;&lt;strong&gt;&lt;em&gt;ADC10SA = (unsigned int)&amp;AdcData;        // Data transfer location&lt;/em&gt;&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the pointer reach that line, the &quot;step into&quot; button is not active anymore which means there's something wrong. &#xA;Do I write the algorithm right, especially when assign the values from ADC to the AdcData?&#xA;And, I can multiply the output value from ADC right and then use it to generate PWM?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any helps are greatly appreciate.&#xA;Thank you.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;in response to jsolarski answer (thank you for giving me feedback)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Actually I've been writing the algorithm like you mention and it goes like these and it still not working &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;i&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; for (;;)&#xA;{&#xA;   ADC10CTL0 &amp;amp;= ~ENC;&#xA;   while (ADC10CTL1 &amp;amp; BUSY);               // Wait if ADC10 core is active&#xA;   ADC10SA = (unsigned int)&amp;amp;AdcData;        // Data transfer location &#xA;   ADC10CTL0 |= ENC + ADC10SC;             // Start sampling&#xA;   __bis_SR_register(CPUOFF + GIE);        // LPM0, ADC10_ISR will force exit  &#xA;  }&#xA;&#xA;&#xA;// ADC10 interrupt service routine&#xA;#pragma vector=ADC10_VECTOR&#xA;__interrupt void ADC10_ISR(void)&#xA;{&#xA;  //code from reading from res and sending it to AP&#xA;  __bic_SR_register_on_exit(CPUOFF);        // Clear CPUOFF bit from 0(SR)&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;/i&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't use this code : P1OUT |= 0x01;   because I use that Pin for ADC input.&#xA;And this line, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;ADC10SA = 0x200;                        // Data buffer start&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;ADC10SA means ADC10 Start Address right, where you want to transfer the ADC conversion value? So, when I want to transfer it to my AdcData array, is it okay to write it like it did?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks&lt;/p&gt;&#xA;" OwnerUserId="4234" LastEditorUserId="4234" LastEditorDisplayName="" LastEditDate="2011-05-12T14:08:29.270" LastActivityDate="2011-05-12T14:08:29.270" Title="Making PWM from 2 Analog input in MSP430G2231 ?" Tags="&lt;microcontroller&gt;&lt;electronics&gt;&lt;analog&gt;&lt;voltage-measurement&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="14222" PostTypeId="2" ParentId="11152" CreationDate="2011-05-12T13:19:10.540" Score="0" ViewCount="" Body="&lt;p&gt;The magic words to google are &quot;process calibrator&quot;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found the &lt;a href=&quot;http://www.tequipment.net/MartelElectronicsPSC-4010.html&quot; rel=&quot;nofollow&quot;&gt;Martel PSC-4010&lt;/a&gt; that retails for about US$1100 and has an RS232 connection.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fluke sells them too but they are more expensive.&lt;/p&gt;&#xA;" OwnerUserId="330" LastActivityDate="2011-05-12T13:19:10.540" />
  <row Id="14223" PostTypeId="1" AcceptedAnswerId="14226" CreationDate="2011-05-12T13:29:23.530" Score="3" ViewCount="104" Body="&lt;p&gt;We'd like to use several Kinects in a permanent exhibition. Does anyone have information on how long such a device might last? Could it maybe be compared to similar, older devices to estimate a failure-rate? Maybe it could be estimated by looking at the parts themselves like the IR lamp or the cameras? (We won't use the motors, so there won't really be mechanical problems.)&lt;/p&gt;&#xA;" OwnerUserId="4236" LastActivityDate="2011-05-12T21:49:38.663" ClosedDate="2011-05-12T23:17:16.170" Title="Longevity: using a Kinect in a permanent exhibition" Tags="&lt;sensor&gt;&lt;hardware&gt;&lt;ir&gt;&lt;lifetime&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="14224" PostTypeId="2" ParentId="14221" CreationDate="2011-05-12T13:45:44.177" Score="3" ViewCount="" Body="&lt;p&gt;You are not waiting for the ADC to finish the conversions. &#xA;You would have to do something like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt; for (;;)&#xA;{&#xA;  ADC10CTL0 &amp;amp;= ~ENC;&#xA;&#xA;  while (ADC10CTL1 &amp;amp; BUSY);                 // Wait if ADC10 core is active&#xA;    ADC10SA = 0x200;                        // Data buffer start&#xA;    P1OUT |= 0x01;                          // Set P1.0 LED on&#xA;    ADC10CTL0 |= ENC + ADC10SC;             // Sampling and conversion start&#xA;    __bis_SR_register(CPUOFF + GIE);        // LPM0, ADC10_ISR will force exit&#xA;    P1OUT &amp;amp;= ~0x01;                         // Clear P1.0 LED off&#xA; }&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;}&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should read the &lt;a href=&quot;http://focus.ti.com/mcu/docs/mcuprodtechdoc.tsp?sectionId=95&amp;amp;tabId=1201&amp;amp;familyId=342&amp;amp;techDoc=6&amp;amp;docCategoryId=6&amp;amp;viewType=mostviewed&quot; rel=&quot;nofollow&quot;&gt;user guide - chapter 20&lt;/a&gt; (I think) ADC10 and look at the &lt;a href=&quot;http://focus.ti.com/mcu/docs/mcuflashtools.tsp?sectionId=95&amp;amp;tabId=1538&amp;amp;familyId=342&quot; rel=&quot;nofollow&quot;&gt;code examples on ADC10 with DTC&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-12T13:57:59.870" LastActivityDate="2011-05-12T13:57:59.870" CommentCount="1" />
  <row Id="14225" PostTypeId="1" CreationDate="2011-05-12T14:13:17.947" Score="1" ViewCount="71" Body="&lt;p&gt;I am looking for help on an issue trying to read 2 level meters through rs-485 using kepserver.  Problem is when i run the program 1 out of 20 times it will work the rest of those 19 times if i do get good quality then one meter will cause the other meter go bad.  If i unplug the unit it might be working or have good quality or might not or one will have good and one will be bad.  when i put a 4-20ma signal to read level it seems to kick out one meter if i use it on the other in some cases.  we use 4-20 to read levels of liquid.&#xA;so in conclusion, on this unit 1 out of 20 times it will work.  the other times it either a. one will have a good quality of com and the other will have bad.  b. putting a 4-20 signal will cause the other level meter to kick out aka have bad quality.  again i'm using the kepserver 4-20 signal to read liquid levels with an adam 4510s repeater to boost.&lt;br&gt;&#xA;if anyone could have any input that would be awesome, hopefully i explained this issue good enough.&lt;/p&gt;&#xA;" OwnerUserId="4238" LastActivityDate="2011-05-12T14:13:17.947" ClosedDate="2011-05-13T00:18:18.187" Title="rs-485 quality problems" Tags="&lt;communication&gt;&lt;rs485&gt;" CommentCount="2" />
  <row Id="14226" PostTypeId="2" ParentId="14223" CreationDate="2011-05-12T14:51:37.277" Score="2" ViewCount="" Body="&lt;p&gt;As you have noticed the mechanical bits might be a weak point, as far as I know it also has a cooling fan, so if you have a dusty environment then that might pack up at some point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The next least reliable parts are electrolytic capacitors, I doubt they are very loaded, but they might still fail at some point.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After caps your IR leds might fail after 100k hours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;All in all I'd budget for replacing the Kinect every 5 years and buy an extra Kinect to store inside the piece as a spare for when the time comes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would not be surprised if the Kinect can last 10 years in a clean environment, but there is no way to tell other than to wait.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-05-12T14:51:37.277" CommentCount="2" />
  <row Id="14227" PostTypeId="2" ParentId="14213" CreationDate="2011-05-12T15:35:00.803" Score="0" ViewCount="" Body="&lt;p&gt;I'd suggest starting with a divide-by-five counter, one of whose bits is high for two counts and low for three.  For example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;Q0 := !Q1 &amp; !Q2;&#xA;Q1 := Q0;&#xA;Q2 := Q1;&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;This counter will go through the sequence: 000 001 011 110 100 (a value of 101 will reach a valid state after two clocks; 010 or 111 will reach a valid state after one clock).  Any bit of it may be used as a two-hot output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Take the output of this counter and feed it into a latch which is triggered by the opposite clock edge.  The &quot;OR&quot; of this counter output with the first one would yield the desired waveform.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-12T15:35:00.803" />
  <row Id="14228" PostTypeId="5" CreationDate="2011-05-12T16:28:23.453" Score="0" ViewCount="" Body="&lt;p&gt;The CPU is a 32-bit RISC core. It is divided up into several separate threads, where each thread has it its own set of registers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The architecture is very oriented towards concurrency with its many high-frequency threads which is why it can compete with FPGAs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;See also&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/XCore&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-05-12T16:32:58.850" LastActivityDate="2011-05-12T16:32:58.850" />
  <row Id="14229" PostTypeId="4" CreationDate="2011-05-12T16:28:23.453" Score="0" ViewCount="" Body="Xmos as a unique CPU/chip architecture placing itself between microcontrollers and FPGAs." OwnerUserId="-1" LastEditorUserId="2395" LastEditorDisplayName="" LastEditDate="2011-05-12T16:33:04.497" LastActivityDate="2011-05-12T16:33:04.497" />
  <row Id="14230" PostTypeId="1" AcceptedAnswerId="14582" CreationDate="2011-05-12T16:32:46.190" Score="2" ViewCount="85" Body="&lt;p&gt;I have some lipo batteries I'd like to test.  Ideally it would do the following:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;how much time does it take to discharge to minimum allowed voltage?&lt;/li&gt;&#xA;&lt;li&gt;how flat is the discharge curve?&lt;/li&gt;&#xA;&lt;li&gt;how many mAh were discharged?&lt;/li&gt;&#xA;&lt;li&gt;what's the maximum discharge rate?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For my own educational purposes, I'd like to try an arduino-based project to gather the raw data, sending the data to a connected computer for analysis.  Doing this for a single cell would be fine... I'm assuming I would just repeat the circuit for the maximum number of cells in the battery to be tested.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any pointers to such a circuit?  What components would be used to:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;put a steady load on the cell?  Nice if it were easy to change the amp draw.&lt;/li&gt;&#xA;&lt;li&gt;measure the cell voltage&lt;/li&gt;&#xA;&lt;li&gt;measure the current flow&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Ideally, each of these components would be readable, and the project would be mainly reading values from the components and sending the data over the serial line.&lt;/p&gt;&#xA;" OwnerUserId="1756" LastActivityDate="2011-05-23T17:06:45.143" Title="Circuit for testing LiPo batteries?" Tags="&lt;arduino&gt;&lt;voltage&gt;&lt;current&gt;&lt;measurement&gt;&lt;lipo&gt;" AnswerCount="2" FavoriteCount="2" />
  <row Id="14231" PostTypeId="2" ParentId="14223" CreationDate="2011-05-12T16:34:18.000" Score="0" ViewCount="" Body="&lt;p&gt;I would not expect a long MTBF (mean time between failures) for the Kinect for several reasons:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;the device is consumer-grade (not industrial) i.e. not intended for 8 hours-per-day, 5 days-per-week usage&lt;/li&gt;&#xA;&lt;li&gt;the device is a combination of electrical and mechanical items&lt;/li&gt;&#xA;&lt;li&gt;structurally, the device is mainly plastic&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Ultimately, I would agree with drek.dk and make sure you have at least one spare at all times.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-12T16:34:18.000" CommentCount="1" />
  <row Id="14232" PostTypeId="2" ParentId="14185" CreationDate="2011-05-12T16:36:56.920" Score="1" ViewCount="" Body="&lt;p&gt;My concept of pinch-off is the minimum gate-source threshold needed for conduction to start - if the voltage is below this, the channel is 'pinched off', so to speak.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-12T16:36:56.920" CommentCount="1" />
  <row Id="14233" PostTypeId="2" ParentId="14212" CreationDate="2011-05-12T16:43:06.600" Score="1" ViewCount="" Body="&lt;p&gt;I don't have anything to add to the cause explanations; I think all the bases are covered in the earlier posts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your repair method will work as long as there aren't any interconencts to the repaired vias on internal PCB layers. If your keyboard is a two-layer PCB, your fix is just fine.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-12T16:43:06.600" />
  <row Id="14234" PostTypeId="5" CreationDate="2011-05-12T17:08:11.640" Score="0" ViewCount="" Body="" OwnerUserId="-1" LastEditorUserId="-1" LastEditorDisplayName="" LastEditDate="2011-05-12T17:08:11.640" LastActivityDate="2011-05-12T17:08:11.640" />
  <row Id="14235" PostTypeId="4" CreationDate="2011-05-12T17:08:11.640" Score="0" ViewCount="" Body="A battery stores electrical energy using chemical energy. Common types of batteries include Lead-Acid, Alkaline, NiCd, NiMH, and Lithium-Ion." OwnerUserId="-1" LastEditorUserId="638" LastEditorDisplayName="" LastEditDate="2011-05-12T17:34:34.883" LastActivityDate="2011-05-12T17:34:34.883" />
  <row Id="14236" PostTypeId="1" AcceptedAnswerId="14238" CreationDate="2011-05-12T18:24:00.903" Score="2" ViewCount="134" Body="&lt;p&gt;Hi, i have a problem with this circuit.&lt;br&gt;&#xA;I am trying to calculate all the voltages and currents but i think i did something wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the voltages $U_L$ and $U_C$ are wrong because they seem a bit high and i am also not sure if the formulas used are the right ones in this case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/j8jgS.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$ Z = j\omega L + \frac{1}{\frac{1}{R} + j\omega C} =11.57 e^{j62.16&amp;#176;}$$&#xA;$$ I = 19.02 e^{-j112.16&amp;#176;}A$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;corrected:&#xA;$$ U_L = I\omega L = 646.66e^{-j22.16&amp;#176;}V$$&#xA;$$ U_C = U_0 - U_L = 463.6 e^{-j189.36&amp;#176;}V$$&lt;/p&gt;&#xA;" OwnerUserId="3817" LastEditorUserId="3817" LastEditorDisplayName="" LastEditDate="2011-05-13T08:35:35.637" LastActivityDate="2011-05-13T18:13:12.703" Title="How to calculate the voltage of the capacitor in this circuit?" Tags="&lt;capacitor&gt;&lt;circuit&gt;&lt;homework&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="14237" PostTypeId="1" AcceptedAnswerId="14239" CreationDate="2011-05-12T19:25:35.587" Score="0" ViewCount="60" Body="&lt;p&gt;This MOSFET is from a good board for an RC plane. On a bad board, the MOSFET is completely fried and the number is not visible. The MOSFET drives a motor, and the motor stalled during a crash repair, which caused the MOSFET to pop, as well as damaging a diode (probably the catch/flywheel diode as it is across the motor.) In future, I will add a fast blow ~10A fuse to the motor line to protect the MOSFET.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can replace the diode with any fast Schottky but I need to know the ratings of the MOSFET and I cannot find a datasheet &lt;em&gt;anywhere&lt;/em&gt;. I suspect the pin out is gate, drain, source from left to right, but I cannot be certain. I'm not even sure if it is actually a MOSFET; for all I know, it could be a power NPN transistor. It has no heatsink on it (likely what caused it to fry when the motor stalled) and looks like a TO263 package. The numbers on it are &quot;U438&quot; and &quot;BA8112&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/RutkF.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-12T20:42:35.020" Title="Help identifying this power MOSFET" Tags="&lt;mosfet&gt;&lt;repair&gt;" AnswerCount="1" />
  <row Id="14238" PostTypeId="2" ParentId="14236" CreationDate="2011-05-12T20:30:56.847" Score="2" ViewCount="" Body="&lt;p&gt;Your $\mathbf{I_L}$ is correct, but your phase angle for $\mathbf{U_L}$ is wrong. An inductor's voltage leads the current by 90 degrees; you subtracted. The voltages are larger than the input because the circuit is reactive, but total power is conserved and you can check that $\mathbf{U_q} = \mathbf{U_L} + \mathbf{U_C}$ by cross-verifying $\mathbf{U_C}=\mathbf{I_L}(\mathbf{Z_C} \parallel R)$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Here are the values I calculated with Python:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;from math import pi, e    &#xA;w = 2 * pi * 636.62&#xA;R = 0.11e3&#xA;ZL =  1j * w * 8.5e-3&#xA;ZC = -1j / w / 10e-6&#xA;Z = ZL + (R * ZC) / (R + ZC)&#xA;U = 220 * e ** (1j * pi * -50 / 180)&#xA;I = U / Z&#xA;UL = I * ZL&#xA;UC = U - UL&#xA;IC = UC / ZC&#xA;&#xA;def polar_str(x):&#xA;    from math import atan2&#xA;    angle = atan2(x.imag, x.real) / pi * 180&#xA;    return &quot;({:7.3f}, {:8.3f})&quot;.format(abs(x), angle)&#xA;&#xA;print('\n'.join(v + ' = ' + polar_str(eval(v)) for v in &#xA;      [' R','ZL', 'ZC', ' Z', ' U', ' I', 'UL', 'UC', 'IC']))&#xA;&#xA;output: (mag, phase)&#xA;&#xA; R = (110.000,    0.000)&#xA;ZL = ( 34.000,   90.000)&#xA;ZC = ( 25.000,  -90.000)&#xA; Z = ( 11.567,   62.155)&#xA; U = (220.000,  -50.000)&#xA; I = ( 19.019, -112.155)&#xA;UL = (646.657,  -22.155)&#xA;UC = (463.659,  170.649)&#xA;IC = ( 18.546,  -99.351)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="721" LastEditorUserId="721" LastEditorDisplayName="" LastEditDate="2011-05-13T18:13:12.703" LastActivityDate="2011-05-13T18:13:12.703" CommentCount="7" />
  <row Id="14239" PostTypeId="2" ParentId="14237" CreationDate="2011-05-12T20:32:28.623" Score="1" ViewCount="" Body="&lt;p&gt;AOU438L from Alpha Omega semiconductor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.alldatasheet.com/datasheet-pdf/pdf/135752/AOSMD/AOU438L.html&quot; rel=&quot;nofollow&quot;&gt;http://www.alldatasheet.com/datasheet-pdf/pdf/135752/AOSMD/AOU438L.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;VDS (V) = 30V&#xA;ID = 85A (VGS = 10V)&#xA;RDS(ON) &amp;lt; 4.5mΩ (VGS = 10V)&#xA;RDS(ON) &amp;lt; 6.5mΩ (VGS = 4.5V)&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Datasheet mentions it is designed for low-side switching in CPU power conversion.  So you could probably scavenge a suitable replacement from an old motherboard.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="411" LastEditorDisplayName="" LastEditDate="2011-05-12T20:42:35.020" LastActivityDate="2011-05-12T20:42:35.020" CommentCount="4" />
  <row Id="14240" PostTypeId="1" CreationDate="2011-05-12T20:42:22.383" Score="4" ViewCount="62" Body="&lt;p&gt;I have a BLDC motor on an autopiloted model airplane, running with an ordinary PWM-controlled ESC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a feature I'd like to add which the ESC I have doesn't support, so I either want to find one that does or to learn enough to build one that is integrated with the rest of my (mostly home cooked) autopilot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The feature I'd like to add is a mode that stops the prop and holds it in a horizontal position (it is a 2-blade prop) both to reduce drag during glides and for landing so that the pusher prop on my flying wing won't be as easily damaged by the ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I understand of how these motors work, it should be possible for the usual 6-MOSFET driver circuit to hold the output shaft in any of 6 (maybe even 12, if you leave one high side and the other two low sides on etc?) positions. Of course, without sensors, I'm not sure if it is possible to get it to that position in the first place? (I mean, if the motor were entirely off and I just connected certain leads and left them on -- with appropriate current -- would the shaft spin to that position? Or might it not have enough torque to move at all from some starting positions?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anyone tried this? Thoughts or advice?&lt;/p&gt;&#xA;" OwnerUserId="4217" LastActivityDate="2011-05-12T21:44:38.267" Title="Stopping a brushless DC motor in a specific position" Tags="&lt;brushless&gt;&lt;esc&gt;" AnswerCount="1" />
  <row Id="14241" PostTypeId="2" ParentId="14218" CreationDate="2011-05-12T21:27:48.397" Score="1" ViewCount="" Body="&lt;p&gt;I've been monitoring this question, and since no one has answered yet, I'm going to take a stab at it.  I apologize in advance if my reasoning ends up being flawed, but I'll do my best.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think the possibility of making your project work depends upon how many RGB LEDs you plan on using.  I've been going over the Allegro datasheet, and it looks like you need to pair one IC with one each of red, green, and blue LEDs (i.e. one RGB pixel).  All of the data gets transmitted down the chain of 6280s.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to only have one RGB pixel, or more specifically, N pixels displaying the same temporal information, then I think you might be able to get away with using SPI.  I think your linked list idea is the right way to go, but obviously the key is to latch LI at the right time (every 31 bits), and it won't be on 8 bit boundaries.  The only SPI libraries I've ever used on micros take a byte, clock out the data and read the response byte.  In your case, you'll need to figure out how to make an SPI function that can trigger LI during a byte transfer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since SPI requires transferring one byte at a time, you'll be forced to send 32 bits when you only want 31.  So the 32nd bit will actually be the first bit of your second set of RGB data.  You'll set LI before clocking out the 32nd bit.  For the next round of data, you'll trigger LI before clocking out the 31st bit.  You might be able to do this without writing your own SPI library, but I'm not sure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to support scrolling data, then things look like they will be a bit trickier.  I'm having a hard time formulating the explanation, but timing LI will be interesting.  LI determines how quickly your display is going to scroll, since it dictates when one 6280 outputs the data to the next.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For the first set of RGB data, you will trigger LI as soon as you've clocked out 31 bits.  You've also clocked out 1 bit for the next set of data.  You will then clock out another 3 bytes of data, plus 6 more before triggering LI.  But if your scroll time is slow, you can't send out the byte that contains the last 6 bits &lt;em&gt;until you are ready to trigger LI&lt;/em&gt;, because you don't want to overflow the shift register buffer!  But once you are ready to trigger LI, you'll send out this byte.  Now 2 bits for the next set of data is already in the serial buffer.  Send out another 3 bytes (26 bits total), and wait until you need to trigger LI.  When it is time, send out the next byte (that has the remaining 5 bits).  Repeat this over and over again.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this makes sense.  Like I said, I don't have experience with this chip, but what I've written here is at least the first step I'd take to trying to solve this problem using SPI.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck, and keep us posted!&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-05-12T21:27:48.397" CommentCount="5" />
  <row Id="14242" PostTypeId="1" AcceptedAnswerId="14247" CreationDate="2011-05-12T21:34:36.950" Score="5" ViewCount="156" Body="&lt;p&gt;I am interested in controlling an RC helicopter using a desktop/laptop computer. I see two possible approaches for such a project: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Wire the RF remote to a PC either directly or through some microcontroller.&lt;/li&gt;&#xA;&lt;li&gt;Install a microcontroller directly on the helicopter and use Wi-Fi, Bluetooth, or Zigbee to communicate with the microcontroller.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;My end goal is to use motion tracking data from a system of IR cameras piped into a feedback control system to develop algorithms to control flight paths. The motion data will come from a separate system, but what I am looking for here is a 'best practices' approach for physicality wiring (or wirelessly linking) the low-level control of the helicopter to a computer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What would be the most efficient way to approach this problem?&lt;/p&gt;&#xA;" OwnerUserId="3174" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-14T06:11:47.047" LastActivityDate="2011-05-14T06:11:47.047" Title="Computer control of RC helicopter" Tags="&lt;microcontroller&gt;&lt;wireless&gt;" AnswerCount="1" CommentCount="5" FavoriteCount="1" />
  <row Id="14243" PostTypeId="2" ParentId="14240" CreationDate="2011-05-12T21:44:38.267" Score="1" ViewCount="" Body="&lt;p&gt;I think if the speed controller was completely off, and you connect it to the battery, it would snap to some position. However, depending on the number of poles in the motor, you might find that it's not just one of six positions, but one of a multiple of six positions. In other words, you could get it to snap into line with one of the phases, but there may be multiple points that represent that phase, and the motor will likely just seek the nearest one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, if the ESC were to become activated while you had this alternate connection in place, you'd probably smoke at least a couple of the MOSFETs, so, hazard there to worry about. As long as it's off though, I don't think the speed controller would be harmed, b/c if you think about it, those MOSFETS routinely switch the battery voltage to make approximately 3-phase AC out of it. There should be protection diodes in the 6-way bridge that will protect it from the inductive kick-back when you break your alternate connection, too.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-12T21:44:38.267" CommentCount="3" />
  <row Id="14244" PostTypeId="2" ParentId="14223" CreationDate="2011-05-12T21:49:38.663" Score="1" ViewCount="" Body="&lt;p&gt;Reliability shouldn't be a big deal. If you're not using the sound processor, it won't get hot enough for the fan to come on or cook the  electrolytics, and if one does fail, replacements aren't exactly hard to come by.&#xA;The only part that may have an inherent lifetime is the laser diode, and even that is probably a few years.&#xA;Just make sure the exhibit design allows easy access for maintainance, and instractions for replacement are provided. And if necessary add an allowance for a spare or two the budget &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-05-12T21:49:38.663" CommentCount="1" />
  <row Id="14246" PostTypeId="2" ParentId="1940" CreationDate="2011-05-12T22:35:48.800" Score="0" ViewCount="" Body="&lt;p&gt;PIR, small PIC, and a Nordic nRF24L01+ module. About 12 dollars for the latter two items. An nRF24L01+ module can be interfaced to a PC using a USB PIC, to collect data from multiple remote PIRs.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-12T22:44:20.077" LastActivityDate="2011-05-12T22:44:20.077" />
  <row Id="14247" PostTypeId="2" ParentId="14242" CreationDate="2011-05-12T23:42:23.390" Score="4" ViewCount="" Body="&lt;p&gt;Since you are trying to create a control system that will control the helicopter in real time, one of your biggest things to look for is low latency links. This pretty much will throw out WiFi as an option unless you are able to guarantee that your WiFi network will be fast enough and wont be dropping any packets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So options left are XBee, Bluetooth, hacking the current controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hacking the controller will probably provide for the lowest latency link since it is a wireless connection that was specifically designed to fly the helicopter. This will require you to do some reverse engineering of the controller unless the controller already provides some information on how to interact with it. The hacking involved here might be simple. You will just have to make the controller think that a human is actually moving the controls. This can either be done by physically interacting with the controller, or you can look to see what signal the controller is using for each control, and then just fake that signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;XBee and Bluetooth can perform in pretty similar manners. Many modules will build a buffer before sending a packet on, you will need to program the modules to not buffer too much. With this option the reverse engineering will be on the plane instead of the controller. Depending on how nice this helicopter is, there might be a prebuilt control system on the plane in order to keep it flying easier. If this is the case it might be difficult to figure out how to add XBee or Bluetooth to it. If it is a simple helicopter and/or you want to hack this side, it would probably be easiest to just find out where the wires for the motors are and control them directly with your microcontroller. This will give you lots of flexibility on what you want to do; however, flexibility does also result in the possibility of more work for you.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope this helps you out. There is no &quot;right&quot; answer here, it is just where your comfort lies and how much control you want.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-12T23:42:23.390" />
  <row Id="14248" PostTypeId="1" CreationDate="2011-05-12T23:53:53.837" Score="7" ViewCount="118" Body="&lt;p&gt;I wish I knew more about this stuff, but alas I do not.  I have a radial lead aluminum electrolytic capacitor (rated 470mF and 25v) that died on me.  Can I swap it out with one rated at 35V, or do I need to get one matching it completely?  It is for a plasma, so if there is chance that 35V could cause more damage, then I would like to know!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="4243" LastActivityDate="2011-05-13T16:45:28.587" Title="Can I swap an electrolytic capacitor with one with a higher voltage?" Tags="&lt;capacitor&gt;&lt;voltage&gt;&lt;repair&gt;&lt;ratings&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="14249" PostTypeId="2" ParentId="14248" CreationDate="2011-05-12T23:58:02.563" Score="3" ViewCount="" Body="&lt;p&gt;The rating is a maximum voltage rating. It is not like the current rating of a fuse, the higher the rating, the better. There is normally an increase in cost from the person building them, this increase is negligible to you as a person purchasing only a couple.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can place that one in and should actually have a smaller chance of blowing it again, this is a good thing.&lt;/p&gt;&#xA;" OwnerUserId="230" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-13T00:11:55.387" LastActivityDate="2011-05-13T00:11:55.387" CommentCount="3" />
  <row Id="14250" PostTypeId="1" AcceptedAnswerId="14252" CreationDate="2011-05-13T00:56:30.010" Score="11" ViewCount="190" Body="&lt;p&gt;I found a circuit where in the classical Graetz rectifier capacitors were added in parallel to each diode. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looked something like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/N7MJa.png&quot; alt=&quot;mysterious rectifier&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After the rectifier itself, there was the usual huge capacitor and regulator and so on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So why the smaller capacitors near the diodes?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-05-13T03:23:18.417" Title="What are the advantages of full wave bridge rectifier with capacitors parallel to diodes?" Tags="&lt;rectifier&gt;" AnswerCount="1" CommentCount="2" FavoriteCount="1" />
  <row Id="14251" PostTypeId="2" ParentId="14230" CreationDate="2011-05-13T02:47:32.307" Score="0" ViewCount="" Body="&lt;p&gt;While there are some ICs that are designed for monitoring batteries, all of your requirements could be accomplished with single resistor (or potentiometer) and an ADC input on the Arduino. The only problem is that for your first task, &quot;put a steady load on the cell,&quot; the current draw would reduce as the cell voltage went down. All you need to do is measure the cell voltage at the positive terminal. The current will be just I = V/R.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're interesting in a more complicated solution, maybe something like the TI &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/bq2018.html&quot; rel=&quot;nofollow&quot;&gt;BQ2018&lt;/a&gt; would work?&lt;/p&gt;&#xA;" OwnerUserId="2827" LastActivityDate="2011-05-13T02:47:32.307" />
  <row Id="14252" PostTypeId="2" ParentId="14250" CreationDate="2011-05-13T03:23:18.417" Score="17" ViewCount="" Body="&lt;p&gt;Power supply transformers have leakage inductance and parasitic capacitance, and when the diodes in a bridge rectifier switch off these &quot;non-ideal&quot; elements form a resonant circuit that can oscillate at high frequency.  This high frequency oscillation can then couple into the rest of the circuitry.  Snubber circuits are used in an attempt to mitigate this problem.  Just using capacitors doesn't damp the ringing completely, but does cause it to drop to a lower frequency where the coupling effect is less.  An RC circuit across the diodes can damp the ringing almost completely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can read more in the following excellent paper:&#xA;&lt;a href=&quot;http://www.hagtech.com/pdf/snubber.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.hagtech.com/pdf/snubber.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4129" LastActivityDate="2011-05-13T03:23:18.417" CommentCount="2" />
  <row Id="14254" PostTypeId="2" ParentId="12960" CreationDate="2011-05-13T05:07:38.617" Score="0" ViewCount="" Body="&lt;p&gt;That often happens when you connect two transmitters together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, when you are looping back Knowing which one is the TX and which one is the RX is not a major concern. Either the FT232 or the pic is trying to be helpful and when the device uses TX it means the other devices TX. This is one of the many reasons naming conventions cause war.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try swapping the TX and RX line and see if the line starts following the voltage you are expecting. If everything else is working it is going to be a hardware issue, and this would both cause the line not to go to 0V and no signal to be transmitted between the chips.&lt;/p&gt;&#xA;" OwnerUserId="230" LastActivityDate="2011-05-13T05:07:38.617" CommentCount="2" />
  <row Id="14256" PostTypeId="1" AcceptedAnswerId="14257" CreationDate="2011-05-13T08:46:01.137" Score="3" ViewCount="88" Body="&lt;p&gt;My Nokia cell phone is charged with a very lightweight compact charger similar to &lt;a href=&quot;http://www.nokia.co.uk/find-products/accessories/all-accessories/power/chargers/nokia-fast-charger-ac-15&quot; rel=&quot;nofollow&quot;&gt;this AC-15&lt;/a&gt; (can't find the one I actually use).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;While the battery is close to empty the charger works silently - just heats up a little. Then, as the battery charges it starts to produce silent yet audible chirps and the more the battery charges the more time these chirps take and less time the charger is silent - something like one chirp with duration of one second, then one second of silence. Finally as charging stops and the phone says &quot;charging complete&quot; the charger starts producing a continuous tone of the same frequency as those chirps. When I unplug the charger the sound fades within about two seconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What component of the charger circuitry produces those chirps and why and also why would chirping pattern change as battery charges?&lt;/p&gt;&#xA;" OwnerUserId="3552" LastEditorUserId="3552" LastEditorDisplayName="" LastEditDate="2011-05-13T09:15:47.530" LastActivityDate="2011-05-13T09:37:01.643" Title="What component of my phone charger produces chirps and how does it do that?" Tags="&lt;power-supply&gt;&lt;power&gt;&lt;battery-charging&gt;&lt;charging&gt;&lt;charger&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="14257" PostTypeId="2" ParentId="14256" CreationDate="2011-05-13T09:37:01.643" Score="5" ViewCount="" Body="&lt;p&gt;As long as the battery is nearly empty, your charger produces its nominal current and runs constantly at a frequency that is likely around 100 kHz &gt; 15...20 kHz = your audible range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once the battery is nearly full, the charger goes into burst mode. This means that it switches at 100 kHz, stops switching entirely, and then produces some more cycles at 100 kHz (i.e. the next burst), stops again, ... (repeat).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you hear is not the main switching frequency, but the frequency of the bursts. You can think of this like an amplitude modulation between 0% and 100% with an inaudible carrier of 100 kHz and a signal of the burst frequency, likely of some kHz and in the audible range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason this is done is that you are able to greatly reduce the standby power consumption of a charger using burst mode. (A nearly full battery looks to the charger like &quot;almost standby&quot;.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For further reading, you can search for keywords like &quot;burst mode&quot; and &quot;switch mode power supply&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The components producing the noise are the transformer, and maybe the EMI filter chokes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It could also be the case that the charging circuit inside the cell phone modulates its current consumption and thereby imposes an audible modulation onto the switch-mode power supply inside of the charger device.&lt;/p&gt;&#xA;" OwnerUserId="930" LastActivityDate="2011-05-13T09:37:01.643" CommentCount="1" />
  <row Id="14258" PostTypeId="1" AcceptedAnswerId="14261" CreationDate="2011-05-13T09:40:13.343" Score="2" ViewCount="46" Body="&lt;p&gt;I'm trying to get my head around the DAC-08.  I have so far come up with this circuit as a test:&#xA;&lt;img src=&quot;http://i.stack.imgur.com/r3ttP.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However - it is not producing the results I would expect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's what it does:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;U1 created a square-wave clock signal to drive U2 which is a binary counter.  The output of this heads into the DAC-08's (U4) data inputs.  I have buffered the signal through U3 because I noticed during my experimentations that the outputs of U2 don't always have the exact same voltage.  U3 should be redundant in this circuit.  I had it there mainly when I replaced the DAC-08 with am R/2R ladder to test the rest of the circuit.  The output of the DAC-08 is then fed through an op-amp in voltage follower mode.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, I'd expect a nice triangle wave form out of this, and that is (roughly) what I got with the R/2R ladder.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, what I get from the DAC-08 is something more like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/LneeP.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;img src=&quot;http://i.stack.imgur.com/Hvqev.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried playing around with the order of the data pins, and it seems to always come up with the same (or similar) waveform.  Now, I'm new to the DAC-08, and I don't fully understand what all the pins do - and the data sheet fails to mention it either, so there is something I am missing.  I have gone through a number of example applications, but none of them have shed any light on this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any experience with the DAC-08?  Can anyone point out where I am going wrong?&lt;/p&gt;&#xA;" OwnerUserId="4245" LastActivityDate="2011-05-13T10:33:47.980" Title="Trying to get to grips with the DAC-08" Tags="&lt;dac&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="14259" PostTypeId="1" CreationDate="2011-05-13T09:49:14.363" Score="1" ViewCount="59" Body="&lt;p&gt;I'm trying to design a smart card interface using one 8051 UART and a &lt;a href=&quot;http://en.wikipedia.org/wiki/Pierce_oscillator&quot; rel=&quot;nofollow&quot;&gt;Pierce oscillator&lt;/a&gt; circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The project seems to be working, because I'm getting response from the smart card. However, I'm having difficulty controlling the clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sequence after card insertion is:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;power the card. I'm using &lt;code&gt;p3.3&lt;/code&gt; for this;&lt;/li&gt;&#xA;&lt;li&gt;take reset pin high. I'm using &lt;code&gt;p3.6&lt;/code&gt;;&lt;/li&gt;&#xA;&lt;li&gt;start the clock.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I'm using a NOT gate to power the oscillator circuit. The &lt;code&gt;pin3.7&lt;/code&gt; is connected to the input of the gate, and the output is connected to the VCC of the &lt;a href=&quot;http://en.wikipedia.org/wiki/Pierce_oscillator&quot; rel=&quot;nofollow&quot;&gt;Pierce oscillator&lt;/a&gt; circuit (which also consists of a NOT gate which drives the output high).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also tried a ULN2003, with a pull-up at the output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, this sequence doesn't seem to work fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But, if I disconnect the VCC of the oscillator while the code is waiting for response, and connect it again, I get full response, which is consistent over many tries, and valid according to 7816 protocol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That made me believe that the circuit that turns the clock on and off is not working fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've attached the two circuits I'm using, I want to know if there is a better way, or if maybe, I'm doing something wrong&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://I.stack.imgur.com/biiYB.jpg&quot; alt=&quot;VCC circuit for the oscillator&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="3632" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T10:51:14.537" LastActivityDate="2011-05-13T10:51:14.537" Title="8051 SMARTCARD DESIGN" Tags="&lt;oscillator&gt;&lt;8051&gt;&lt;smart-card&gt;" />
  <row Id="14260" PostTypeId="2" ParentId="14258" CreationDate="2011-05-13T10:12:34.287" Score="2" ViewCount="" Body="&lt;p&gt;I'm not sure you can leave /IOUT output dangling. Actually IOUT is a current output, so you also need some resistor to ground from IOUT. Take a look at the &lt;a href=&quot;http://people.scs.carleton.ca/~barbeau/SDR/BF537/DAC08.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;, figures 30 and 31 - one of these applications is what you need. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I don't think that VREF+/- can be directly tied to VCC/GND - see figure 24. You need to connect these pins via resistors, controlling the reference current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You may also want to take a look at a complete &lt;a href=&quot;http://www.filety.pl/arty/sprzet/edw/covox/rys2.png&quot; rel=&quot;nofollow&quot;&gt;application&lt;/a&gt;. It's a good, old Covox sound &quot;card&quot;, I had one attached to my 286 long ago :)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;: useful app notes:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.national.com/an/AN/AN-1525.pdf&quot; rel=&quot;nofollow&quot;&gt;AN-1525 from National&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.analog.com/static/imported-files/application_notes/80635169AN17.pdf&quot; rel=&quot;nofollow&quot;&gt;AN-17 from Analog Devices&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3564" LastEditorUserId="3564" LastEditorDisplayName="" LastEditDate="2011-05-13T10:33:47.980" LastActivityDate="2011-05-13T10:33:47.980" CommentCount="6" />
  <row Id="14261" PostTypeId="2" ParentId="14258" CreationDate="2011-05-13T10:33:23.670" Score="1" ViewCount="" Body="&lt;p&gt;The DAC08 also won't work properly without a negative supply voltage, in addition to the above mentioned problem.  The '08 output sinks current, so ideally it should drive a transimpedance amplifier, which you can make by connecting IOUT to the inverting input, noninverting to ground, and a gain resistor between the output and the inverting input. The output voltage will then be IOUT*R, where IOUT is set by the reference current and the binary input as described in the datasheet. If the output op amp being used in a transimpedance configuration isn't going to share the negative supply, it needs to have a common mode input voltage range that includes ground.&lt;/p&gt;&#xA;" OwnerUserId="4129" LastActivityDate="2011-05-13T10:33:23.670" />
  <row Id="14262" PostTypeId="1" CreationDate="2011-05-13T13:00:09.133" Score="7" ViewCount="189" Body="&lt;p&gt;Most sources on the internet discuss routing signals over a split power plane and how to do this properly. The main solution here is to create a short return current path.&#xA;&lt;strong&gt;I'm wondering whether routing signals over a split power supply plane (not ground plane) will have any noticeable effect on the signal integrity and if i should take measures.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My situation:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4-layer PCB:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Top layer: signal &lt;/li&gt;&#xA;&lt;li&gt;Internal plane:&#xA;splitted ground (analog/digital)&lt;/li&gt;&#xA;&lt;li&gt;Internal Plane: splitted power supply&#xA;plane (3.3V digital and 3.3V analog&#xA;are relevant in this case)&lt;/li&gt;&#xA;&lt;li&gt;Bottom layer: signal&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;I'm routing a few clock signals at the bottom layer starting from the digital section to the analog section. The signals will cross the power plane split between the digital and analog section (gap is 0.5mm wide). I will provide a solid current return path on the ground plane (bridge between digital and analog) so return currents shouldn't be an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The clock signal is just above 12MHz, the traces are 0.2mm wide and a maximum length of 13.4cm. The traces are terminated with a series resistor.&lt;/p&gt;&#xA;" OwnerUserId="4176" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T17:33:16.733" LastActivityDate="2011-05-14T15:06:31.513" Title="Trace crossing splitted power plane" Tags="&lt;signal-integrity&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="3" />
  <row Id="14263" PostTypeId="2" ParentId="14262" CreationDate="2011-05-13T14:42:40.507" Score="9" ViewCount="" Body="&lt;p&gt;The quick answer:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any signal that crosses a split in the power &lt;em&gt;OR&lt;/em&gt; ground plane is bad.  The higher the switching rate (and the faster the signal edges are), the worse the effects will be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The long answer:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you say, &quot;I will provide a solid current return path on the ground plane (bridge between digital and analog) so return currents shouldn't be an issue&quot;, either you don't understand the issues, or I didn't understand your statement.  The reason that I say this is that you can't have a &quot;solid current return path&quot; and still have a split plane.  There has to be some non-solid-ness in there.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The return currents will flow on the closest power &lt;em&gt;OR&lt;/em&gt; ground plane to the signal.  So in your case, if your signal is on the the top layer then the return currents will be on your ground layer.  But if your signal is on the bottom layer then the return currents will be on the power layer.  For most medium to high speed signals, the return current will follow the signal trace, and not take the shortest path.  To put it another way, the return currents will try to minimize the &quot;loop area&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your signal switches from the bottom to top (or vise versa) then the return currents will also switch, flowing through a decoupling cap.  This is why it is important to sprinkle decoupling caps all over the PCB, even when it's too far away from a chip to make any difference on power.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Minimizing the loop area is critical for signal integrity, minimizing EMI, and reducing the effects of ESD.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your signal cuts across a split in the power/ground plane then the return currents are forced to take a detour.  In some cases, this detour can increase the loop area by 2x or even 10x!  The most simple and best way to avoid this is to not run a signal across a split.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some boards have mixed analog and digital planes, or on some systems have multiple power rails.  Here's a list of things that might help out in these circumstances:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;For things like clocks or active data lines, you really don't want to cross a split.  Some creative PCB routing is the best solution, although sometimes you just have to have a combined analog/digital plane instead of splitting it.  &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;For low-speed signals, or signals that are mostly DC, you can cross a split but be careful and selective about it.  If you can, slow down the edge rate using a resistor and maybe a cap.  Usually the resistor would be physically bridging the split.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Things like 0-ohm resistors, or caps, can be used to provide for a signal return path between two planes.  For example, if a signal does jump the split, adding a cap between the two planes near the signal can help.  But beware, if this is not done well then it could negate any positive effects of having a split in the first place (I.E., keeping the digital noise from going to the analog plane).  The nice thing about using caps or 0-ohm resistors for this is that it allows you to play around with the design after the PCB has been made.  You can always stuff or unstuff parts to see what happens.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;While many PCB designs will involve some sort of compromise, try not to compromise unless you absolutely have to.  You'll have less headaches, and loose less hair, by doing that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should also point out that I completely glossed over the issue of impedance changes due to the split, and what that would mean.  While important, it's not as important as minimizing the loop area and stuff.  And understanding the loop area is much easier than understanding how the impedance changes will effect the signal integrity.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-13T14:42:40.507" CommentCount="3" />
  <row Id="14264" PostTypeId="2" ParentId="3146" CreationDate="2011-05-13T14:56:44.150" Score="0" ViewCount="" Body="&lt;p&gt;If you are talking about attachment for electrical interconnection, soldering or strong mechanical metal-to-metal contact  (think sockets, tightly wrapped wire-wrap, or wire-nuts) are the two most common reliable methods.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sometimes, adhesives are used to temporarily tack the components in place under they are soldered in.  It's important that these adhesives are not too rigid - you want some &quot;give&quot; so that the chip can be removed for rework.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, if you're talking about soldering for, say, building up your mechanical enclosures, then there are definitely other methods that you can use.  Soldering is clearly good for solderable metal pieces.  Cementing is good for compatible plastics.  And for quick mcguyvering, duct tape is your friend! :)&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-05-13T15:06:51.643" LastActivityDate="2011-05-13T15:06:51.643" CommunityOwnedDate="2011-05-13T14:56:44.150" />
  <row Id="14265" PostTypeId="1" CreationDate="2011-05-13T14:59:06.703" Score="3" ViewCount="135" Body="&lt;p&gt;I'm experimenting with trying to reflow a 0.8mm BGA myself for prototypes/repairs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've solved the main problem: alignment. I've used my 3D printer to print custom board guides that align on large through-hole pads and guide the BGAs into place. So far, I'm 100% on alignment for the 4 BGAs I've done so far.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, I'm trying to reflow it with my hot air system. I've got a BGA tip that fits over the part, and I have followed some general advice from a tech who told me to set it to 450 degC and put the BGA head down just about on the PCB totally covering the BGA for no more than 20 seconds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm noticing that even the outer row of pads (All I can examine) are not shiny. They've reflowed beautifully, but all the flux has not burned off. I notice that paste pads that have been under the hot air long enough go completely shiny, and many other pads never quite burn off the flux (I assume) and remain somewhat dull. Is this fine, or does that indicate it didn't reflow properly?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How well does the air from these hot air BGA heads penetrate to the inner pads of a medium sized (14mm square) BGA?  Should I bump up to my maximum 480 degC and/or heat it longer...  ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After noticing the dull pads on my first board, I attempted to reflow it for a longer period (40 sec) and pretty much burned the board. So, I know how far NOT to take it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any advice on the actual reflow of these?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt;  I forgot to mention I am using an IR preheating unit. (I actually use the hot air gun with the board on the preheating unit) I leave the preheating unit at about 250 degC for a couple minutes before starting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am seeing some videos online showing the use of a hot air gun and sort of following a real reflow oven profile at lower temperatures. Should I be doing that? I was thinking the hot air was not going to be as efficient and needed to be somewhat higher.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT 2:&lt;/strong&gt; I've tried following a profile used on a Youtube video for reflowing an XBox chipset, and even the paste on the surface of the board doesn't reflow. I guess if I really want to do this right I need to get some thermocouples and measure this directly. I re-ran the Youtube profile with 460C instead of 360C, and it looks good visually. I'll complete that board and see if it works.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT 3:&lt;/strong&gt; It works! An i.MX283 ARM processor running full Linux @ 454Mhz. 0.5-1 watt w/Ethernet. I'll get these 6 BGAs (3 boards, 2 BGAs each) X-rayed and see how I did.&lt;/p&gt;&#xA;" OwnerUserId="1270" LastEditorUserId="1270" LastEditorDisplayName="" LastEditDate="2011-05-15T03:24:16.670" LastActivityDate="2011-05-15T03:24:16.670" Title="Hot air lead-free BGA reflow" Tags="&lt;reflow&gt;&lt;bga&gt;&lt;hot-air&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="3" />
  <row Id="14266" PostTypeId="2" ParentId="14262" CreationDate="2011-05-13T15:40:46.653" Score="0" ViewCount="" Body="&lt;p&gt;One might ask - why is a clock signal going into the analog region?  Perhaps you need to gerrymander your planes to bring digital ground to the digital sides of your DAC/ADC's (I'm assuming that' what's going on here.)&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-13T15:40:46.653" CommentCount="4" />
  <row Id="14267" PostTypeId="2" ParentId="3027" CreationDate="2011-05-13T15:46:14.863" Score="1" ViewCount="" Body="&lt;p&gt;There are some features of C++ which are useful in embedded systems.  There are others, like exceptions, which can be expensive, and whose costs may not always be apparent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I had my druthers, there would be a popular language which combined the best of both worlds, and included some features which are lacking in both languages; some vendors include a few such features, but there are no standards.  A few things I'd like to see:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Exception handling a little more like Java, where functions which can throw or leak exceptions must be declared as such.  While a requirement for such declarations may be somewhat annoying from a programming perspective, it would improve the clarity of code in cases where a function may return an arbitrary integer if it succeeds, but may also fail.  Many platforms could handle this inexpensively in code by e.g. having the return value in a register and success/failure indication in the carry flag.&#xA;&lt;li&gt;Overloading of static and inline functions only; my understanding is that the standards bodies for C have avoided function overloading so as to avoid a need for name mangling.  Allowing overloads of static and inline functions only would avoid that problem, and would give 99.9% of the benefit of overloading external functions (since .h files could define inline overloads in terms of differently-named external functions)&#xA;&lt;li&gt;Overloads for arbitrary or specific compile-time-resolvable constant parameter values.  Some functions may inline very efficiently when passed with any constant value, but inline very poorly if passed a variable.  Other times code which may be an optimization if a value is constant may be a pessimization if it isn't.  For example:&#xA;&lt;pre&gt;&#xA;inline void copy_uint32s(uint32_t *dest, const uint32_t *src, __is_const int n)&#xA;{&#xA;  if (n &amp;lt;= 0) return;&#xA;  else if (n == 1) {dest[0] = src[0];}&#xA;  else if (n == 2) {dest[0] = src[0]; dest[1] = src[1];}&#xA;  else if (n == 3) {dest[0] = src[0]; dest[1] = src[1]; dest[2] = src[2];}&#xA;  else if (n == 4) {dest[0] = src[0]; dest[1] = src[1]; dest[2] = src[2]; dest[3] = src[3];}&#xA;  else memcpy((void*)dest, (const void*)src, n*sizeof(*src));&#xA;}&#xA;&lt;/pre&gt;&#xA;If 'n' can be evaluated at compile time, the above code will be more efficient than a call to memcpy, but if 'n' can't be evaluated at compile time the generated code would be much bigger and slower than code which simply called memcpy.&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;I know the father of C++ isn't too keen on an embedded-only version of C++, but I would think it could offer some considerable improvements over just using C.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone know if anything like the above are being considered for any type of standard?&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-05-13T16:06:01.193" LastActivityDate="2011-05-13T16:06:01.193" CommunityOwnedDate="2011-05-13T15:46:14.863" CommentCount="2" />
  <row Id="14268" PostTypeId="1" CreationDate="2011-05-13T10:49:26.520" Score="0" ViewCount="50" Body="&lt;p&gt;Hi, I have 12AMP /12 volts solar charge controller,&#xA;and i am using to charge 5 amp 12 volt battery.&#xA;Is this ok? or will it damage the battery?&lt;/p&gt;&#xA;" LastActivityDate="2011-05-13T16:37:02.707" ClosedDate="2011-05-13T19:56:24.140" Title="Using 12AMP /12 volts solar charge controller to charge 5 amp 12 volt battery" Tags="&lt;voltage&gt;&lt;charger&gt;&lt;current&gt;" CommentCount="5" />
  <row Id="14269" PostTypeId="2" ParentId="14248" CreationDate="2011-05-13T16:45:28.587" Score="6" ViewCount="" Body="&lt;p&gt;Make sure that the replacement part is comparable in terms of ESR (equivalent series resistance), rated ripple current and rated hours. Don't use a general-purpose cap (usually rated for 1000 hrs or less, with ripple current specified at 120Hz) instead of a high-performance cap (ripple current specified at 100kHz, ESR in milliohms)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the original capacitor was used in a high-frequency application (i.e. a capacitor on the output of a switching regulator) putting in a part that is not suited for the task will result in a severely shortened life for the cap and the need to replace it again once it blows up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, going from 25V to 35V won't cause you a problem as long as the above parameters are comparable. Once you start getting above 35V, you'll find less and less high-performance capacitors available (the majority of low ESR parts tend to be 25V or lower).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-13T16:45:28.587" CommentCount="2" />
  <row Id="14270" PostTypeId="2" ParentId="14262" CreationDate="2011-05-13T17:28:41.683" Score="0" ViewCount="" Body="&lt;p&gt;Clocks should not go through vias.  There's an inductance and capacitance price that you pay when you use vias and as your clock frequency increases this will eventually bite you.  It also forces the clock's return currents through a decoupling cap.  It really is just best practice to keep the clock all on one layer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is in addition to the advice above.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-05-13T17:28:41.683" CommentCount="1" />
  <row Id="14271" PostTypeId="2" ParentId="8042" CreationDate="2011-05-13T17:30:28.680" Score="1" ViewCount="" Body="&lt;p&gt;Inherently unsafe?  Not necessarily.  It could be a conforming product that was not labeled because the OEM relied on the reseller to test and label the product for specific markets.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That said, it's also possible that the product is made with unsafe components, or will fail some hazard condition that a certified product would have been tested for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In some jurisdictions, you cannot use a non-UL (or equivalent like CSA) product.  If an inspector finds a non-certified equipment, he could order you immediately discontinue its use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lack of labeling on the immediate product does not necessarily mean that the product is not certified -- in rare instances (a product that is &quot;too small&quot; to carry the mark, for example), the there is a separate, valid documentation of its certificated status.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The collection of relevant standards make up a large binder...  You have to buy (&lt;a href=&quot;http://webstore.ansi.org/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, &lt;a href=&quot;http://webstore.iec.ch/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, &lt;a href=&quot;https://www.standardsstore.ca/eSpecs/index.jsp&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, ...) the standards books (or, rather, gain access to the electronic versions of the same) - and it is definitely not cheap.  If you are developing a product, talking to a test lab and &quot;pre evaluating&quot; the product will usually yield some of the relevant details; and when you fail a test, they'll usually give you a copy of the rule that you failed for...&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-05-13T17:36:18.197" LastActivityDate="2011-05-13T17:36:18.197" />
  <row Id="14272" PostTypeId="2" ParentId="12960" CreationDate="2011-05-13T18:04:01.733" Score="0" ViewCount="" Body="&lt;p&gt;While this doesn't directly apply to your problem with voltages, one common issue with not getting data into a PIC's UART is that you must remember to clear the OERR bit.  If it ever gets set, the PIC will ignore all further incoming data until OERR is cleared.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-05-13T18:04:01.733" />
  <row Id="14273" PostTypeId="1" CreationDate="2011-05-13T19:19:06.047" Score="0" ViewCount="141" Body="&lt;p&gt;Is it possible to construct a simple circuit (sans transistors) that would cause a short circuit between two points when a switch is opened? My intuition says no, but I don't have any proof for such a claim.&lt;/p&gt;&#xA;" OwnerUserId="4252" LastActivityDate="2011-05-14T06:56:28.020" Title="Can Opening a Switch Cause a Short Circuit?" Tags="&lt;switch&gt;&lt;ground&gt;&lt;short-circuit&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="14274" PostTypeId="2" ParentId="616" CreationDate="2011-05-13T20:10:20.723" Score="1" ViewCount="" Body="&lt;p&gt;If you want a very affordable and welcoming book rather than a college textbook, I highly suggest &lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0470289619&quot; rel=&quot;nofollow&quot;&gt;All New Electronics Self-Teaching Guide&lt;/a&gt;.  It's a gentle introduction to electronics that has you work through examples so that you grasp the concepts.  It will get you through the basics: DC, diodes, BJTs, FETs, AC, oscillators, resonant networks, transformers, etc.  I used the original version years ago and it helped start me on the path to where I could work with the more comprehensive (and technical) textbooks like Sedra &amp;amp; Smith.&lt;/p&gt;&#xA;" OwnerUserId="2059" LastActivityDate="2011-05-13T20:10:20.723" CommunityOwnedDate="2011-05-13T20:10:20.723" />
  <row Id="14275" PostTypeId="1" CreationDate="2011-05-13T21:16:12.020" Score="0" ViewCount="80" Body="&lt;p&gt;I gotta get a &lt;a href=&quot;http://www.irobot.com/&quot; rel=&quot;nofollow&quot;&gt;Roomba&lt;/a&gt; because the dog hair builds up faster than I can get to vacuum it but I also want to make a beer bot that can go and fetch beer from the &lt;a href=&quot;http://www.kegerator.com/&quot; rel=&quot;nofollow&quot;&gt;kegorator&lt;/a&gt;. Seems the &lt;a href=&quot;http://www.irobot.com/&quot; rel=&quot;nofollow&quot;&gt;Roomba&lt;/a&gt; is the perfect base and since I usually only drink on special occasions (read: the weekend) I think a dual purpose &lt;a href=&quot;http://www.irobot.com/&quot; rel=&quot;nofollow&quot;&gt;Roomba&lt;/a&gt; would be perfect. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know there is a &quot;developer Roomba&quot; but it doesn't come with a vacuum. Is it (relatively) easy to add a usb connector to any &lt;a href=&quot;http://www.irobot.com/&quot; rel=&quot;nofollow&quot;&gt;Roomba&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="3534" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-13T22:52:39.323" LastActivityDate="2011-05-14T02:31:16.417" Title="What is the most hackable Roomba?" Tags="&lt;robotics&gt;&lt;roomba&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="14276" PostTypeId="2" ParentId="14275" CreationDate="2011-05-13T21:40:37.670" Score="3" ViewCount="" Body="&lt;p&gt;The 4000 series has a serial port that uses a special connector (it looks like an SVideo port) that is easily accessible.  On the newer ones you have to remove the cover it looks like.  &lt;a href=&quot;http://hobbymechatronics.com/projects/30-robotics/8-diy-roomba-usb-interface-cable&quot; rel=&quot;nofollow&quot;&gt;Website descriptions here&lt;/a&gt;. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.irobot.com/images/consumer/hacker/Roomba_SCI_Spec_Manual.pdf&quot; rel=&quot;nofollow&quot;&gt;commands can be found here.&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll probably want something wireless to control it remotely and it looks like &lt;a href=&quot;http://www.sparkfun.com/products/684&quot; rel=&quot;nofollow&quot;&gt;Sparkfun has you covered for $100&lt;/a&gt;.That will present itself as a serial port via bluetooth if I read it correctly.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure your Roomba will be able to get the beer though, but that's just a few dozen hacks away :)&lt;/p&gt;&#xA;" OwnerUserId="249" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-14T02:31:16.417" LastActivityDate="2011-05-14T02:31:16.417" CommentCount="2" />
  <row Id="14277" PostTypeId="1" CreationDate="2011-05-13T23:50:48.603" Score="4" ViewCount="129" Body="&lt;p&gt;Is there a website which lists/rates electronics stores by geographic location?&lt;/p&gt;&#xA;" OwnerUserId="4255" LastActivityDate="2011-05-14T16:30:40.927" CommunityOwnedDate="2011-05-14T05:43:56.810" ClosedDate="2011-05-16T13:03:27.797" Title="Where can I find a list of electronics parts stores in my area?" Tags="&lt;electronics&gt;&lt;parts&gt;&lt;buying&gt;" AnswerCount="3" CommentCount="4" FavoriteCount="1" />
  <row Id="14278" PostTypeId="2" ParentId="14273" CreationDate="2011-05-14T00:07:25.180" Score="0" ViewCount="" Body="&lt;p&gt;No.  Not without a transistor, relay, or something similar.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-14T00:07:25.180" CommentCount="1" />
  <row Id="14279" PostTypeId="1" CreationDate="2011-05-14T00:57:45.770" Score="1" ViewCount="57" Body="&lt;p&gt;I built the TDA 7052 circuit from the datasheet and connected it to my computer's sound card and a 50 $\Omega$ speaker. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the circuit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/PCHqE.png&quot; alt=&quot;circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The $R_s$ is the source impedance, which I can't measure and sound card manufacturer isn't providing any useful information. I also used 100 nF electrolytic capacitor, since I don't have any ceramic at the moment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I already know that the speaker and the amplifier can work well together, because they were salvaged from another circuit. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now about my problems: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First problem is that the amplifier won't work on voltages above 3.1 V. The minimal voltage listed in the datasheet is 3 V, typical is 6 V and maximum is 18 V, so this looks a bit strange.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The next problem is that I get crackling and noise when I set the computer volume to more than 50%. The speaker is quiet (&lt;strong&gt;much more&lt;/strong&gt; than in the radio I got the amplifier and speaker form) and from time to time it seems as if the amplifier is clipping (I'm not sure if that's the right word. The peaks seem to get distorted). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the effect of increasing volume on a sine wave:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/4UPkX.jpg&quot; alt=&quot;should have been a sine&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should also mention that this is my first circuit on a breadboard, so it could be causing problems too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So where do I start fixing this?&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-05-14T10:59:12.943" Title="Unexpected results with TDA 7052" Tags="&lt;amplifier&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="14280" PostTypeId="2" ParentId="14262" CreationDate="2011-05-14T02:25:26.940" Score="1" ViewCount="" Body="&lt;p&gt;I've got to kick some conventional wisdom to the curb. At least for the RF boards I've done, I've found that performance is improved by not having split grounds for analog and digital. Instead, using a solid ground plane and doing ground pours to keep a low inductance/low resistance path to a single unified ground node has worked better for the types of products I've done, primarly small size (handheld) and RF heavy (receivers and transmitters in the 500 MHz range and up. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I typically don't use Power planes, as it doesn't take much trace width to drop any trace IR voltage drop to the microvolt range, and I'd rather have ground there. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just another approach. &lt;/p&gt;&#xA;" OwnerUserId="2148" LastActivityDate="2011-05-14T02:25:26.940" CommentCount="4" />
  <row Id="14281" PostTypeId="2" ParentId="14279" CreationDate="2011-05-14T03:19:07.680" Score="1" ViewCount="" Body="&lt;p&gt;Why are you using a 50 ohm speaker? The TDA7062 was designed for an 8 ohm unit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are probably overdriving the amplifier by using a sound card for testing. Try a few mV input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Try putting a pot on the input, as a volume control. Sound cards have a low impedance output, so 10k (log) will be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a high-gain amplifier and might be oscillating if you built the circuit on a breadboard. Put it on a PCB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've never had any problems with the TDA7052.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-14T10:59:12.943" LastActivityDate="2011-05-14T10:59:12.943" CommentCount="1" />
  <row Id="14283" PostTypeId="2" ParentId="14277" CreationDate="2011-05-14T05:17:37.997" Score="5" ViewCount="" Body="&lt;p&gt;Mighy Ohm wiki maintains a list: &lt;a href=&quot;http://mightyohm.com/wiki/resources:surplus&quot; rel=&quot;nofollow&quot;&gt;http://mightyohm.com/wiki/resources:surplus&lt;/a&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Notice links to other lists at the bottom of that page.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Mighty Ohm has another list for suppliers of new components, but it's not as thorough.&lt;/p&gt;&#xA;" OwnerUserId="411" LastEditorUserId="3624" LastEditorDisplayName="" LastEditDate="2011-05-14T16:30:40.927" LastActivityDate="2011-05-14T16:30:40.927" CommunityOwnedDate="2011-05-14T05:43:56.810" CommentCount="7" />
  <row Id="14284" PostTypeId="2" ParentId="14273" CreationDate="2011-05-14T06:56:28.020" Score="1" ViewCount="" Body="&lt;p&gt;Put an inductor in the circuit, and some device that fails as a short circuit on overvoltage.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-05-14T06:56:28.020" CommentCount="1" />
  <row Id="14285" PostTypeId="1" CreationDate="2011-05-14T10:05:17.550" Score="1" ViewCount="95" Body="&lt;p&gt;Just wondering if I'm implementing a finite state machine in VHDL whether or not I need to state what &lt;strong&gt;all&lt;/strong&gt; of the outputs are in every possible state? Even if I know that some outputs won't change from one state to the other and I know that the order of the states will also be in the same order?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, in this (forced) example:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;entity test is&#xA;    port (&#xA;        clk : in std_logic;&#xA;        a : in std_logic;&#xA;        b: out std_logic;&#xA;        c: out std_logic;&#xA;    );&#xA;end test;&#xA;&#xA;architecture Behavioral of test is&#xA;&#xA;type executionStage is (s1,s2,s3);&#xA;signal currentstate, nextstate: executionStage;&#xA;&#xA;begin&#xA;    process (clk)&#xA;    begin&#xA;          if(rising_edge(clk)) then&#xA;                 currentstate &amp;lt;= nextstate;&#xA;          else &#xA;                 currentstate &amp;lt;= currentstate;&#xA;          end if;&#xA;    end process;&#xA;&#xA;    process(currentstate)&#xA;    begin&#xA;        case currentstate is&#xA;            when s1 =&amp;gt;&#xA;                if (a = '1') then&#xA;                    b &amp;lt;= '1';&#xA;                    c &amp;lt;= '0';&#xA;                else&#xA;                    b &amp;lt;= '1';&#xA;                    c &amp;lt;= '1';&#xA;                end if;&#xA;&#xA;                nextstate &amp;lt;= s2;&#xA;&#xA;            when s2 =&amp;gt;&#xA;                -- b doesnt change state from s1 to here, do I need to define what it is here?&#xA;                if (a = '1') then&#xA;                    b &amp;lt;= '1';&#xA;                    c &amp;lt;= '1';&#xA;                else&#xA;                    b &amp;lt;= '1';&#xA;                    c &amp;lt;= '0';&#xA;                end if;&#xA;&#xA;                nextstate &amp;lt;= s3;&#xA;&#xA;            when s3 =&amp;gt;&#xA;                iif (a = '1') then&#xA;                    b &amp;lt;= '0';&#xA;                    c &amp;lt;= '0';&#xA;                else&#xA;                    b &amp;lt;= '1';&#xA;                    c &amp;lt;= '1';&#xA;                end if;&#xA;&#xA;                nextstate &amp;lt;= s1;&#xA;        end case;&#xA;    end process;&#xA;end Behavioural;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;From my understanding if I don't do this then latches are created?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's not a big deal in something like that example but if I have a machine with more than 10 outputs and more than 10 states then my VHDL files start to look incredibly messy and I'm sure it must be bad practice to copy and paste the same thing over and over. Is there a better way of doing this?&lt;/p&gt;&#xA;" OwnerUserId="4257" LastActivityDate="2011-05-14T10:05:17.550" ClosedDate="2011-05-14T10:11:24.550" Title="Implementing a FSM in VHDL?" Tags="&lt;vhdl&gt;" CommentCount="8" />
  <row Id="14286" PostTypeId="1" AcceptedAnswerId="14317" CreationDate="2011-05-14T11:49:34.163" Score="3" ViewCount="102" Body="&lt;p&gt;Ceramic capacitors have this unfortunate property which can cause spikes in voltage when live batteries are connected to boards (hot-plugging), due to the inductance of the wires to the batteries and the very low inductance of the capacitors. It can create spikes of more than double the supply voltage. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;On my first board which used entirely ceramic capacitors on the input, I read up on this in detail in the &lt;a href=&quot;http://www.google.com/url?sa=t&amp;amp;source=web&amp;amp;cd=1&amp;amp;ved=0CBsQFjAA&amp;amp;url=http://cds.linear.com/docs/Datasheet/1933fe.pdf&amp;amp;rct=j&amp;amp;q=lt1933&amp;amp;ei=tWrOTamHEsyFhQfuvLn5DA&amp;amp;usg=AFQjCNEeTNBXcRPm_8n6oLiahd5TN6NjiQ&amp;amp;sig2=8wWPX6dT7jZwvjZ5yhn0kA&amp;amp;cad=rja&quot; rel=&quot;nofollow&quot;&gt;LT1933 datasheet&lt;/a&gt; (See page 14) and the recommendation was to use a 1 ohm series resistor, in a 1206 package, because it may dissipate up to 0.2W, and a 0.1µF cap directly on the input to reduce input ripple. However, I am now working on a project which has a 2A buck converter. That poor 1 ohm resistor, at a low input voltage, could be dissipating 4 watts! That is way too much. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The datasheet also recommends using an aluminium electrolytic capacitor, I'm currently using this. However, it is pretty big and ideally, I would like to eliminate it from my board. Also, being an electrolytic makes it sensitive to environmental conditions a lot more than ceramics, and it reduces the lifespan of the device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, what are my options for limiting hot-plug spikes?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-15T18:30:04.973" Title="Best options for limiting input ringing with ceramic capacitors" Tags="&lt;power&gt;&lt;ringing&gt;&lt;hot-plug&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="14288" PostTypeId="2" ParentId="14262" CreationDate="2011-05-14T15:06:31.513" Score="0" ViewCount="" Body="&lt;p&gt;Depending upon the speed of the clock and its routing, I would expect that you might benefit from passing it through a device at the boundary of the two planes, the input of which is relative to the digital plane and the output of which is relative to the analog plane.  If the clock is used for many purposes, you could also gate it there so that only the clock pulses that were actually relevant to the ADC would pass through the boundary.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-14T15:06:31.513" />
  <row Id="14289" PostTypeId="1" CreationDate="2011-05-14T15:10:18.400" Score="0" ViewCount="108" Body="&lt;p&gt;I am experimenting with a PIC16F84A at the moment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can get this working fine using an RC network for the clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When I switch to using a crystal (the usual xtal across pins 15&amp;amp;16 with 2 caps going to ground from the same pins) I am not getting any clock at all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PIC is the 20MHz version, and I have tried all the crystals I have - 4MHz, 14.3MHz and 25MHz, and numerous different capacitors rangeing from 22pf right up into the uF range, but all I get is what appears to be a logic high on pin 15 and a logic low on pin 16.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yes, I have changed the program config to be _XT_OSC (I have tried them all), but to no avail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using gpasm to assemble the program and pk2cmd to flash the PIC in circuit under Ubuntu.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any clues?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: diagram:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;            22pf&#xA;16 o----+---||----+&#xA;        |         |&#xA;        -         |&#xA;       |=|Xtal    +---+&#xA;        -         |   |&#xA;        |         |   _&#xA;15 o----+---||----+   - GND&#xA;            22pf&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;(a little crude, I know ;) )&lt;/p&gt;&#xA;" OwnerUserId="4245" LastEditorUserId="4245" LastEditorDisplayName="" LastEditDate="2011-05-14T15:41:47.843" LastActivityDate="2011-05-14T17:25:19.047" Title="Crystal oscilator not oscilating on a PIC" Tags="&lt;pic&gt;&lt;oscillator&gt;&lt;crystal&gt;" AnswerCount="0" CommentCount="19" />
  <row Id="14290" PostTypeId="2" ParentId="14277" CreationDate="2011-05-14T15:26:18.590" Score="2" ViewCount="" Body="&lt;p&gt;I might be voted down to infinity for this... but there's always Radio Shack.  If you have a good one that has components the selection is basic but fairly complete.  And as for me I haven't found another local place that carries PCB etchtant consistently except for Radio Shack.  Plus I &lt;em&gt;hear&lt;/em&gt; that they're trying to refocus on the hobbyist market (although who knows if this push will reach the physical stores or just online).  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-14T15:26:18.590" CommunityOwnedDate="2011-05-14T15:26:18.590" CommentCount="4" />
  <row Id="14291" PostTypeId="1" CreationDate="2011-05-14T16:13:57.480" Score="0" ViewCount="36" Body="&lt;p&gt;I am trying to get the eZDSP module from TI working on my computer using &lt;a href=&quot;http://support.spectrumdigital.com/boards/usbstk5505/revb/files/TMS320VC5505_eZDSP_USB_STICK_QuickStartGuide_spruf73a.pdf&quot; rel=&quot;nofollow&quot;&gt;this quickstart guide&lt;/a&gt;. I have installed CCS from the included DVD and fully updated it. On page 4, it describes building a configuration file. The device I have (TMS320C5505) does not appear in the drop down menus (Page 5). Has anyone else had this problem? How did you fix it? Development machine is running Windows 7 Ultimate x64 with all updates.&lt;/p&gt;&#xA;" OwnerUserId="3906" LastActivityDate="2011-05-14T16:13:57.480" Title="TI eZDSP configuration issues." Tags="&lt;usb&gt;&lt;dsp&gt;&lt;programming&gt;&lt;ide&gt;&lt;ccs&gt;" CommentCount="3" />
  <row Id="14292" PostTypeId="2" ParentId="14277" CreationDate="2011-05-14T16:21:41.963" Score="0" ViewCount="" Body="&lt;p&gt;Google &quot;electronics hobby&quot; + your city and you can see them on google maps.&lt;/p&gt;&#xA;" OwnerUserId="3906" LastActivityDate="2011-05-14T16:21:41.963" CommunityOwnedDate="2011-05-14T16:21:41.963" />
  <row Id="14293" PostTypeId="2" ParentId="14286" CreationDate="2011-05-14T16:52:31.083" Score="1" ViewCount="" Body="&lt;p&gt;The big electrolytic is helping because its high ESR is absorbing some of the ringing.  You could try simulating this by adding additional ceramic capacitance, with 1 or 4.7 ohms in series. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Otherwise, a zener across the supply might do what you want. Just make sure it won't be leaking too much at the battery's highest voltage.&lt;/p&gt;&#xA;" OwnerUserId="411" LastActivityDate="2011-05-14T16:52:31.083" />
  <row Id="14294" PostTypeId="1" AcceptedAnswerId="14299" CreationDate="2011-05-14T17:10:41.607" Score="4" ViewCount="89" Body="&lt;p&gt;I am trying to build my own H-bridge to drive a DC motor (12 volt, 25 amp stall). This is one of my first attempts ever at making my own circuit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to use the HIP4080A to control four N-channel MOSFETs, and the &lt;a href=&quot;http://www.intersil.com/data/fn/fn3658.pdf&quot; rel=&quot;nofollow&quot;&gt;datasheet for the HIP4080A&lt;/a&gt; is clear about the basic setup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have read that Schottky diodes should be used to deal with EMF from the motor. I do not know how to determine what kind of Schottky diode to get, or even if it's really necessary.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will be using PWM to drive the motor at varying speeds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is &lt;a href=&quot;http://www.datasheetcatalog.org/datasheet/microsemi/COC-46.pdf&quot; rel=&quot;nofollow&quot;&gt;this diode&lt;/a&gt; ok? I don't really understand how to know.&lt;/p&gt;&#xA;" OwnerUserId="4209" LastEditorUserId="4209" LastEditorDisplayName="" LastEditDate="2011-05-14T17:34:49.423" LastActivityDate="2011-05-14T20:48:30.927" Title="How do I determine the Schottky diodes to use with my H-bridge?" Tags="&lt;schottky&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="14296" PostTypeId="1" AcceptedAnswerId="14781" CreationDate="2011-05-14T20:36:55.827" Score="4" ViewCount="192" Body="&lt;p&gt;I am using an optocoupler and a power triac to switch 120VAC supply to an ~108 watt fan. &lt;a href=&quot;http://www.fairchildsemi.com/ds/MO/MOC3010M.pdf&quot; rel=&quot;nofollow&quot;&gt;The datasheet for my optocoupler&lt;/a&gt; requires me to snub the optocoupler output when I'm switching an inductive load (which I'm guessing an AC fan is). Why?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can see you might want to snub the fan itself if you're switching off/on frequently and you don't want the initial voltage and resulting EM spike, but I don't know why I should care to snub the relatively low current through the optocoupler outputs.&lt;/p&gt;&#xA;" OwnerUserId="2172" LastEditorUserId="2172" LastEditorDisplayName="" LastEditDate="2011-05-15T01:29:53.967" LastActivityDate="2011-05-28T18:29:47.187" Title="Why Snub an Optoisolator?" Tags="&lt;triac&gt;&lt;opto-isolator&gt;" AnswerCount="2" />
  <row Id="14297" PostTypeId="1" AcceptedAnswerId="14300" CreationDate="2011-05-14T20:43:08.870" Score="1" ViewCount="102" Body="&lt;p&gt;Can anyone shed some light on the naming conventions used by Texas Instruments manuals/guides/documents. For example slaa490, slau337. Is there a pattern hidden? Anyway to tell, just by looking at the name of the file, what product family it refers to? &lt;/p&gt;&#xA;" OwnerUserId="4260" LastActivityDate="2011-06-02T19:38:04.757" Title="TI manual naming conventions?" Tags="&lt;code-convention&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="14298" PostTypeId="2" ParentId="14296" CreationDate="2011-05-14T20:48:07.790" Score="2" ViewCount="" Body="&lt;p&gt;The snubbers are to minimise the effect of high voltages when the inductive load is switched. In some circumstances a voltage can be fed back to the opto-coupler output via the triac connections, hence the second snubber. The note does say that the snubber might not be needed, but I'd be inclined to include it, anyway. The parts are cheap and will avoid zapping the opto-coupler.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-14T22:26:40.513" LastActivityDate="2011-05-14T22:26:40.513" CommentCount="1" />
  <row Id="14299" PostTypeId="2" ParentId="14294" CreationDate="2011-05-14T20:48:30.927" Score="2" ViewCount="" Body="&lt;p&gt;The Intersil HIP4080A controller chip doesn't appear to need the normal &quot;freewheeling diodes&quot; that are sometimes seen in motor driving circuits.  The diodes in parallel with the MOSFET's in Figure 33, Page 14, are integral to the N-Channel MOSFET itself and not a separate component.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If, for whatever reason you decide that you need to use freewheeling diodes, you would put them in parallel with the ones integrated with the MOSFET's.  I would recommend diodes with a reverse voltage of at least double your motor voltage and 1x, and preferably 2x of the stall current of the motor.  Since your motor is 12 volts @ 25 amps, I would recommend diodes of at least 24 volts and 50 amps.  These are not small diodes.  The diodes in the datasheet you linked to are not even close to handling 50 amps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In Figure 33, there are two more diodes, CR1 and CR2, but the datasheet doesn't say how to spec these.  The diodes are located between +12v and AHB/BHB pins.  On page 4 the datasheet says that the absolute max voltage on those pins is 80v+VDD, and since VDD is 12v then the max voltage is 92v.  Therefore, without going through all the little details you'll need a diode that is spec'd for a reverse voltage of at least 92 volts.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(Note:  I'm doing a very rough analysis to come up with 92 volts, and I'm being very conservative too.  If you get a diode that goes to 92 volts then it'll work.  It very well might work with a diode rated at only 25 volts, but it's impossible to tell just from this datasheet.  To be sure, you'd either have to get more info from the chip manufacturer, simulate it, or build it and measure the thing.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's also really hard to tell from the datasheet what the current ratings on CR1&amp;amp;2 need to be.  It is mostly going to be determined by the values of C3 and C4-- values that they don't give.  Here again you'll either need more info from Intersil or you'll have to build it, measure it, and then change the diodes accordingly.  As a rough starting point I would go with diodes in the 1 or 2 amp range, but keep in mind that I could be as much as 10x high or 10x low.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-14T20:48:30.927" CommentCount="1" />
  <row Id="14300" PostTypeId="2" ParentId="14297" CreationDate="2011-05-14T20:57:44.687" Score="4" ViewCount="" Body="&lt;p&gt;There is no rhyme or reason to their naming conventions.  Keep in mind that the TI of today is the result of at least 7 acquisitions in the last 15 years, and probably several dozen over the whole lifetime of the company.  Each time they buy a new company they inherit their naming conventions.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might see some resemblance of reason within a small product line (their audio ADC/DAC's, for example), but that will not extend to their other product lines.  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-14T20:57:44.687" />
  <row Id="14301" PostTypeId="2" ParentId="14297" CreationDate="2011-05-14T21:35:08.427" Score="1" ViewCount="" Body="&lt;p&gt;Naming conventions on chips can be very inconvenient. National has some data converter sets that are logic: like the ADC121S021 is a 1x 12-bit 200ksps A/D where the ADC102S051 is a 2x 10-bit 500ksps ADC. But you still need to know which digit stands for 12-bit, and what '021' is.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;TI has many brands merged into their productline.You may see some burr brown products between their normal instrumentation amplifiers. Also TPS and TLV seem to be used a lot for power products, but TLV is also used on some opamps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just type the 'generic' name (prefix + number) in google , and you usually will see what it is.&lt;/p&gt;&#xA;" OwnerUserId="1476" LastActivityDate="2011-05-14T21:35:08.427" CommentCount="1" />
  <row Id="14302" PostTypeId="2" ParentId="14265" CreationDate="2011-05-14T21:38:26.757" Score="3" ViewCount="" Body="&lt;p&gt;Honestly, I wouldn't try to solder my own BGA's.  I know this doesn't directly address your issues, but hear me out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It takes a lot of work and effort to solder a BGA.  There's a lot of trial and error.  A lot of messed up test boards.  But then it's soldered.  Now what?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you have to prove that it's soldered correctly.  For that you need one or more of the following:  JTAG test (US\$10k, never has 100\% coverage), optical inspection (US\$20k for the equipment), or X-Rays (US\$500k).  The cost of doing these tests is too much for the normal hobbyist, and is even beyond many small companies.  So the tests are simply not done.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Skipping those tests, you proceed with debugging your PCB.  And let's say that the BGA is a complex CPU.  Inevitably you'll find a bug.  The CPU will randomly crash.  Is it your software, your electrical design, or the soldering on the BGA that's causing the problem?  Debugging this, in light of some possibly problematic soldering, is going to be terrible.  It will add a lot of time to your debug process, possibly months, and you'll loose a lot of hair on your head.  And then you can repeat this for the next major bug.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without confidence that your soldering is perfect, you will always have this dark cloud over your head.  Every little bug that shows up &quot;could be a BGA soldering problem&quot;.  This is made worse if you have multiple engineers working on the same PCB since the software guy will be questioning the hardware guy, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, even if the BGA soldering is perfect, did the chip get too hot?  Did you destroy the chip by getting it to hot?  Even on modern assembly lines this is an issue.  But with the proper equipment you can adjust and measure the temperature profiles to at least get you in the right ballpark.  On one board I did recently, the BGA's were being damaged.  The solder balls looked great, but under a very nice X-Ray machine we could see that the gold bond wires melted from the heat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've been there.  Not at the hobbiest level, but professionally as we were bringing up new boards while the assembly shop was learning to do BGA's.  We had no JTag.  No optical inspection.  And the X-Rays were terrible.  Our PCB had 11 BGA's on them.  That was 2 years of hell I don't wish to repeat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, here's my recommendation:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Get someone who has the proper equipment, training, and experience to solder your BGA's.  There are a lot of contract manufacturers that'll do a single BGA.  It takes money, but that's way less than the time you'll spend trying to debug your own soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you must do it yourself, then you should get the proper equipment, training, and figure out how to get the experience required.  For this to pay off in the end, you need to have a large enough company and need to justify the huge amount of time and money that you'll put into this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I would never try to just kludge something together.  That's a recipe for, um, bad stuff.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-14T21:38:26.757" CommentCount="8" />
  <row Id="14303" PostTypeId="1" AcceptedAnswerId="14306" CreationDate="2011-05-14T22:49:27.913" Score="2" ViewCount="162" Body="&lt;p&gt;I'm working on a project that involves swapping out a couple of pots of a circuit board for a couple of digital potentiomters. I'm trying to make sure that I'm using the right resistance values, so I'm measuring the resistance of the old pots. These are standard 3-terminal pots. I'm calling the terminals &lt;code&gt;A&lt;/code&gt;, &lt;code&gt;WIPER&lt;/code&gt;, and &lt;code&gt;B&lt;/code&gt;.For the first one, these are the values I'm getting:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;A to B: 4.84k&#xA;&#xA;CENTER:&#xA;A to WIPER: 1.66k&#xA;B to WIPER: 3.55k&#xA;            -----&#xA;            5.21k&#xA;&#xA;FORWARD DIRECTION:&#xA;A to WIPER: 2.333k&#xA;B to WIPER: 2.785k&#xA;            -----&#xA;            5.118k&#xA;&#xA;BACKWARDS DIRECTION:&#xA;A to WIPER: 1.00k&#xA;B to WIPER: 4.16k&#xA;            -----&#xA;            5.16k&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I had always understood that the resistance from &lt;code&gt;A&lt;/code&gt; to &lt;code&gt;WIPER&lt;/code&gt; + the resistance from &lt;code&gt;WIPER&lt;/code&gt; to &lt;code&gt;B&lt;/code&gt; should add up to equal the resistance from &lt;code&gt;A&lt;/code&gt; to &lt;code&gt;B&lt;/code&gt;, but no matter how many times I measure the &lt;code&gt;A&lt;/code&gt; to &lt;code&gt;B&lt;/code&gt; resistance is not 5.2k.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Obviously there is something that I'm not understanding correctly. What is it?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks!&lt;/p&gt;&#xA;" OwnerUserId="4261" LastActivityDate="2011-05-15T19:43:43.843" Title="Potentiometer values don't add up" Tags="&lt;potentiometer&gt;&lt;resistance&gt;" AnswerCount="2" CommentCount="14" />
  <row Id="14304" PostTypeId="1" CreationDate="2011-05-15T00:03:10.923" Score="3" ViewCount="111" Body="&lt;p&gt;Reading through &lt;a href=&quot;http://electronics.stackexchange.com/questions/5095/whats-the-best-way-to-protect-a-board-from-corrosion-in-a-hot-moist-environment&quot;&gt;What&amp;#39;s the best way to protect a board from corrosion in a hot/moist environment?&lt;/a&gt; it has specific advice for a board/project that will be used in a harsh environment.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How important is sealing a board for use in a &lt;em&gt;normal&lt;/em&gt; or even a &lt;em&gt;kind&lt;/em&gt; environment?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do people assembling DYI kits generally worry about it?&lt;/p&gt;&#xA;" OwnerUserId="2117" LastActivityDate="2011-05-15T17:35:39.487" Title="How important is it to seal/coat a PCB project for *normal* conditions?" Tags="&lt;pcb&gt;&lt;assembly&gt;" AnswerCount="2" />
  <row Id="14305" PostTypeId="2" ParentId="14304" CreationDate="2011-05-15T00:12:50.807" Score="8" ViewCount="" Body="&lt;p&gt;Do hobbyists worry about it?  Heck no.  At best I might put a clearcoat on a homemade PCB to keep the copper from oxidizing (looks bad, but that's it).  Some people at large companies don't even worry about it.  I've put unsealed professionally made boards in test equipment that's being used in a factory floor environment.  In fact I'd say boards aren't typically sealed or protected at all unless they're going into an environment that's known to be difficult.  This might include engine controllers (grease, carbon deposits), anything going on a ship (salt spray, salt fog), any overly dusty area - particularly metal particles I'd imagine.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-15T00:12:50.807" CommentCount="3" />
  <row Id="14306" PostTypeId="2" ParentId="14303" CreationDate="2011-05-15T02:48:04.073" Score="11" ViewCount="" Body="&lt;p&gt;This is expected behavior. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So I rummaged around my old parts bin and found similar behavior on most old potentiometers. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There wasn't have a big enough sample of newer ones to see a difference. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Possible reasons for this behavior: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Oxidation on the resistor track and / or wiper. There was one potentiometer where the resistance sum changed  wildly over one sweep, up to twice the nominal value, but became better with exercise. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Construction: The resistor itself is a flat band that the sweeping contact travels across. If the contact does not reach across the whole width of the band, or is not correctly aligned, the resistances will not add up. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;One of the more consistent potentiometers gave its life for geekness: There were two sweeping contacts, each about one quarter width of the resistor, one traveling along the inner edge, one traveling along the middle. This means, when you measure across the resistor, you measure all along the whole width of the resistor. On the dot of the sweeper, you measure only a tapering part of the resistor, which does not have as much resistor in parallel. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Trying to visualize: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;A-B resistance is like this: o========o; &lt;/li&gt;&#xA;&lt;li&gt;To the wiper it is like this: o==&gt;&amp;lt;=====o.&lt;/li&gt;&#xA;&lt;li&gt;It is the taper of the current distribution that leads to the increase in resistance.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Do I care about this? No. First, we only care about the relation of the two resistances. Second, we are dealing with 10% accuracy devices. Third, if precise control over the parameter was required, one would have chosen a different tool. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ms. Ohm and Ms. Kirchhoff can safely put away their husband's heart medicine. &lt;/p&gt;&#xA;" OwnerUserId="3438" LastEditorUserId="3438" LastEditorDisplayName="" LastEditDate="2011-05-15T07:20:32.117" LastActivityDate="2011-05-15T07:20:32.117" />
  <row Id="14307" PostTypeId="1" AcceptedAnswerId="14310" CreationDate="2011-05-15T09:14:54.127" Score="3" ViewCount="131" Body="&lt;p&gt;In my case I am using PIC24F and dsPIC33F microcontrollers, but where is the on-state resistance of an IO port for a PIC stated in the datasheet? I cannot find it anywhere. And how does this apply for other processors - 16F/12F PICs, PIC32, MSP430's, AVR's etc. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason I ask this is because I am designing a sensitive circuit which changes the range of an ADC input by leaving a 10k resistor floating or grounded. If the on resistance is in the 100's of ohms, this will introduce a 1% or more error term.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-15T18:03:42.207" Title="What is the typical on-resistance of an MCU output?" Tags="&lt;microcontroller&gt;&lt;resistance&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="14308" PostTypeId="2" ParentId="14307" CreationDate="2011-05-15T10:22:23.527" Score="1" ViewCount="" Body="&lt;p&gt;It's probably not specified because of the very wide range and variability with things like supply voltage and load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For something critical like that I'd use an analogue switch. They have a well-defined low on-resistance. You might be able to use a MOSFET as a switch, if you are short of room.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-15T11:35:05.373" LastActivityDate="2011-05-15T11:35:05.373" CommentCount="2" />
  <row Id="14310" PostTypeId="2" ParentId="14307" CreationDate="2011-05-15T14:19:38.757" Score="6" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Short answer:&lt;/strong&gt;&lt;br&gt;&#xA;Assuming &quot;regular cmos&quot; IO driver structure value of the output resistance can be estimated indirectly. Most of the DS provide data for &quot;DC IO characteristics&quot; from which you can calculate this parameter. Most of the time following is given:&lt;br&gt;&#xA;a) Supply voltage (Vcc)&lt;br&gt;&#xA;b) Load current (Iload)&lt;br&gt;&#xA;c) Voltage drop @ load current (Vdrop)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The static resistance is straight forward Vdrop/Iload   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example &lt;a href=&quot;http://ww1.microchip.com/downloads/en/DeviceDoc/39937b.pdf&quot; rel=&quot;nofollow&quot; title=&quot;PIC24F&quot;&gt;PIC24F&lt;/a&gt; on table 26-10 for Vcc=2V and Vdrop=0.4V manufacturer specifies Iload=3.5mA (worst case). This gives ~114 Ohm. Note that increasing supply voltage to 3.6V will increase Iload to 6.5mA at the same voltage drop giving ~62 Ohm.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Long answer&lt;/strong&gt;:&lt;br&gt;&#xA;&lt;strong&gt;I.&lt;/strong&gt; First of all one need to check if in fact is dealing with &quot;regular CMOS IO structure&quot; which should be similar to following:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.stack.imgur.com/9L6YE.png&quot; alt=&quot;CMOS output driver&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately uC manufacturers rarely provide this info (it is provided if you are dealing with discrete gates - such as 74HC family). However I would claim this is most common structure and there are tell-tell signs if it is actually used (more on this later).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;II.&lt;/strong&gt; If above is true one cane observe that on resistance would be in fact &quot;on resistance&quot; of the NMOS. In this case the VGS would be equal to supply voltage, VDS the Vdrop voltage and ID the Iload current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now what is left is to establish if data provided in manufacturer DS are from linear region or from saturation region. If data from DS Are from linear region the &quot;static resistance&quot; calculated in very fist point is pretty good approximation and be also valid for much smaller current. If the data are from saturation region the calculated resistance will be too pessimistic for smaller currents. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Above is illustrated by this &lt;a href=&quot;http://en.wikipedia.org/wiki/File%3aIvsV_mosfet.png&quot; rel=&quot;nofollow&quot;&gt;characteristics&lt;/a&gt; from Wikipedia. Also whole article on &lt;a href=&quot;http://en.wikipedia.org/wiki/MOSFET&quot; rel=&quot;nofollow&quot;&gt;MOSFETs&lt;/a&gt; is worth checking.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When VGS &gt; Vth and VDS &amp;lt; VGS - VTH the transistor is in linear region. It is pretty safe assumption that for CMOS technologies in which uC are manufactured the Vth is anywhere between 0.5V - 1.5V volts. So taking into account previous PIC24F example one can conclude with good probability that NMOS is in linear region -&gt; VGS (2V) &gt; VTH (~1.5V) and VDS (0.4) &amp;lt; VGS(2V)-VTH(1.5V).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: the MOS device even in so called &quot;linear region&quot; is non linear one. So quality of approximating it with linear device (resistor) will depend on the point where the approximation was taken (operating point). In the examples above approximation is taken at pretty large current so it will be not very accurate at very low currents (actually it sets upper boundary for resistance).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;III.&lt;/strong&gt; So what are tell-tell signs that you are dealing with regular CMOS IO circuitry?&lt;br&gt;&#xA;a) If you are lucky - there will be equivalent output stage schematic in DS&lt;br&gt;&#xA;b) If you are lucky - as in case of &lt;a href=&quot;http://focus.ti.com/lit/ds/slas694f/slas694f.pdf&quot; rel=&quot;nofollow&quot;&gt;MSP430G2231 on page 20&lt;/a&gt; one will find Vdrop versus iload characteristics that is awfully similar to NMOS ID versus VDS characteristic. And as a plus from this characteristic one directly get &quot;static resistance&quot; and tell if data provided by manufacturer are from linear or saturation region.&lt;br&gt;&#xA;c) In other case one can bet this is a case. Your odds for correct bet rise if ones data show that driving current rises significantly with rising supply voltage.      &lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="1471" LastEditorDisplayName="" LastEditDate="2011-05-15T16:06:41.070" LastActivityDate="2011-05-15T16:06:41.070" CommentCount="5" />
  <row Id="14311" PostTypeId="1" CreationDate="2011-05-15T15:58:19.177" Score="0" ViewCount="167" Body="&lt;p&gt;Can PC work with either 12V or 24V. I am not Electrical or Electronic engineer or technician. But I have two 12V SPV (74A+74A). It is feeding my PC in radiation period I don't want to convert DC which is obtained from SPV to AC. But want to run the PC with the available DC supply.  Can it possible? Is there any SMPS or Choopers or any equipments. Please guide me.&lt;/p&gt;&#xA;" OwnerUserId="4265" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T13:00:49.300" LastActivityDate="2011-05-16T13:00:49.300" Title="Can a computer work in 12V or 24V DC?" Tags="&lt;power&gt;&lt;dc&gt;&lt;smps&gt;&lt;supply&gt;" AnswerCount="5" />
  <row Id="14312" PostTypeId="2" ParentId="14311" CreationDate="2011-05-15T16:29:39.617" Score="4" ViewCount="" Body="&lt;p&gt;No, it's not directly possible without a device to convert voltages.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whilst 12V is one voltage required by a computer, 24V is not. In fact 24V will likely let the smoke out of components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other voltages required are 5V, 3.3V and -12V. Some legacy PCs also require -5V. Usually, 10-15 amps will be drawn on each 5V and 3.3V rail for a small computer and a few hundred milliamps on the -12V rail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could use a car PSU.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-15T16:29:39.617" />
  <row Id="14314" PostTypeId="2" ParentId="14304" CreationDate="2011-05-15T17:35:39.487" Score="3" ViewCount="" Body="&lt;p&gt;Here are some reasons &lt;em&gt;NOT&lt;/em&gt; to coat your board:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;the coating will thermally insulate the board.  Components that need to dissipate heat, like voltage regulators and PTC's, won't work as well, or may fail sooner.&lt;/li&gt;&#xA;&lt;li&gt;The coated board is harder to modify.  If this is a prototype, or other DIY project, you probably do want to have the option of making changes later.&lt;/li&gt;&#xA;&lt;li&gt;The kind of coatings that will actually protect the board from a harsh environment without running the risk of trapping undesirable material against the board (doing more harm than good) aren't terribly cheap.  A good coating may represent a substantial fraction of the total cost.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1325" LastActivityDate="2011-05-15T17:35:39.487" CommentCount="1" />
  <row Id="14315" PostTypeId="2" ParentId="14311" CreationDate="2011-05-15T17:55:28.940" Score="3" ViewCount="" Body="&lt;p&gt;The original IBM PC power supply output -12V, -5V, +5V, and +12V.  Generally, the -12V was used along with +12 for serial communication; I don't know what -5 was used for originally (a lot of audio circuitry uses it, but none was even considered when the PC was invented).  +5 was used to drive most of the logic, and +12 for drive disk drive motors and serial communication.  A few PC-compatible machines (Tandy 1000, e.g.) left off the -5V supply, making it incompatible with some cards like an internal modem that expected that voltage (fortunately, adding a 7905 to the modem solved that problem).  Later machines have all required those voltages, along with +3.3V.  Generally, computers expect those supply voltages to be exactly as specified, within a small tolerance, and are not equipped to handle any deviation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is possible to design a computer to operate off a single voltage, and generate any and all other required voltages internally.  Practically every battery-powered computer has operated that way.  Generally, such computers are prepared to accept some variation in the supplied voltage, and will use some sort of regulating circuitry to precisely derive all required voltages from it, evening out any irregularities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are two general designs for devices to convert higher voltages to lower ones: linear regulators, and switching regulators.  Both types have an upper voltage limit, which will if exceeded cause immediate damage.  Linear regulators also have another constraint: the amount of heat generated will be proportional to the difference between the supply voltage and the output voltage.  If a particular device is designed to run off 9V and uses 5V internally, the regulator will produce 75% more heat if the device is run off 12V (since the regulator will drop 7 volts rather than 4).  The regulator might be able to accommodate voltages up to 35 volts without immediate damage, but even 24V would quickly cause it to overheat (and hopefully shut down rather than melt) since the regulator would be producing almost five times as much much heat as designed (19 volts rather than 4).  Switching supplies do not have this limitation; provided the input voltage does not exceed the maximum, they will generate no more heat when run off higher voltages than lower ones.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A typical desktop PC motherboard will require many different voltage supplies.  A laptop machine will generally require a single supply.  Modern laptops can actually tolerate a considerable range of voltages on their power-supply inputs; unfortunately, very of them specify the range.  I would guess that a typical laptop would probably be happy with 24 volts, but I'm not sure of any that are actually spec'ed for that.  Your best bet might be to use a buck-mode switching power supply to convert your 24 volts nominal into 18.5 or whatever your favorite laptop requires.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-15T17:55:28.940" CommentCount="6" />
  <row Id="14316" PostTypeId="2" ParentId="14307" CreationDate="2011-05-15T18:03:42.207" Score="0" ViewCount="" Body="&lt;p&gt;A typical CMOS output will not have a single measurable &quot;resistance&quot; value as such--instead it will behave as something resembling a constant current source/sink in series with a resistor, with another resistor in parallel.  More accurately, it will behave as a parallel combination of a bunch of different current sources/sinks with different series resistors.  Device manufacturers will typically supply some graphs which state the output voltage at different levels of output current, but I've never seen one specify that a device will actually meet the graphed behavior with any particular degree of accuracy.  On the other hand, device manufacturers will frequently specify a guaranteed voltage for a lightly-loaded output.  If the current drawn by your 10K resistor does not exceed the value listed for that spec, you can expect the output voltage to meet the indicated specification.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-15T18:03:42.207" CommentCount="3" />
  <row Id="14317" PostTypeId="2" ParentId="14286" CreationDate="2011-05-15T18:30:04.973" Score="3" ViewCount="" Body="&lt;p&gt;You can consider an &lt;a href=&quot;http://www.intersil.com/products/deviceinfo.asp?pn=ISL6115&quot; rel=&quot;nofollow&quot;&gt;active hot-plug controller&lt;/a&gt; which solves the spike problem by controlling the charge-up of the input caps. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also consider a passive &lt;a href=&quot;http://www.epcos.com/web/generator/Web/Sections/ProductCatalog/ProtectionDevices/InrushCurrentLimiters/NTCInrushCurrentLimiters/Page,locale=en.html&quot; rel=&quot;nofollow&quot;&gt;NTC inrush limiter&lt;/a&gt; which remains in the circuit all the time. It will dissipate power constantly like the 1206 resistor in your example, but if chosen appropriately will dissipate much less power (it will be high resistance during startup, and reduce during steady-state operation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another technique used when connectors are involved is a precharge pin. The connector is designed such that the first power pins that make contact have a resistance in series, to &quot;slowly&quot; charge the caps. When the rest of the power pins make contact, the precharge resistance is shorted out and doesn't burn any power. &lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-15T18:30:04.973" />
  <row Id="14318" PostTypeId="2" ParentId="14311" CreationDate="2011-05-15T18:31:17.903" Score="3" ViewCount="" Body="&lt;p&gt;Any standard computer uses several supply voltages: +/- 5V, +3.3 V, +/-12V, 5V standby. All of these voltages have to be supplied by the PSU, or some other means.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your computer uses less than 120 W total, you want to use a picoPSU: &lt;a href=&quot;http://www.mini-box.com/s.nl/it.A/id.417/.f&quot; rel=&quot;nofollow&quot;&gt;http://www.mini-box.com/s.nl/it.A/id.417/.f&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If it uses more than 120W, you probably are best off with a DC/AC inverter and the normal PSU. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A few mainboards for small form factor computers come with a built-in power supply that can be driven with 12V DC. Mind you, if you use 120W, thats 10A @ 12V DC. Not every cable or plug can drive this load. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also the possibility of using a premade small computer, like a Mac Mini, or a Fujitsu Q9000, after adapting its power supply. Or, as supercat says, any laptop. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There's plenty websites out there which look at DC driven computers. One of the best sources is &lt;a href=&quot;http://www.mini-itx.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.mini-itx.com/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can also check a variety of websites concerning computing aboard yachts.&lt;/p&gt;&#xA;" OwnerUserId="3438" LastEditorUserId="3438" LastEditorDisplayName="" LastEditDate="2011-05-15T18:57:06.633" LastActivityDate="2011-05-15T18:57:06.633" />
  <row Id="14319" PostTypeId="2" ParentId="14311" CreationDate="2011-05-15T19:01:54.990" Score="5" ViewCount="" Body="&lt;p&gt;If you want to run a PC off of 12V or 24V DC, you MUST replace the PSU with one designed to use that input voltage. These are not uncommon in industrial systems, and shouldn't be that hard to obtain (google around a bit and I bet you can come up with one).&lt;/p&gt;&#xA;" OwnerUserId="259" LastActivityDate="2011-05-15T19:01:54.990" />
  <row Id="14320" PostTypeId="2" ParentId="14303" CreationDate="2011-05-15T19:43:43.843" Score="2" ViewCount="" Body="&lt;p&gt;In general, the resistance of a pot will have three components: the resistance from the contact point to the clockwise end, the resistance from the contact point to the counter-clockwise end, and the resistance from the contact point to the wiper terminal.  The first two resistances almost always add up to the resistance between the two ends of the pot, and if one doesn't draw any current through the wiper, the voltage between the wiper terminal and one of the end terminals will be a suitable ratio of the voltage between the two ends.  That is by far the preferred way to use the pot.  If there is no current flowing through the wiper terminal, its resistance won't matter.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the circuit requires drawing a non-trivial amount of current through the wiper terminal, things will generally get quite a bit nastier.  Unlike the first two resistances I mentioned, which nicely vary as the pot is turned, the resistance between the contact point and the wiper is arbitrarily variable.  Sometimes it may be 5 ohms, sometimes 500.  On older pots, it may even get to be 50,000.  Different spots on a potentiometer may have widely varying amounts of contact resistance, depending upon how the pot has been used and low long it has sat in different positions.  If one is going to use a pot to generate a resistance rather than a ratiometric voltage, one should design one's circuit to use the largest value pot one can practically manage (the Atari 2600 Video Computer System's &quot;paddle&quot; controllers, for example, use 1-meg pots wired as rheostats).  Unless the pots are clean, the &quot;jitter&quot; caused by varying wiper resistance will cause the game to respond somewhat erratically to small amounts of rotation, but unless the controls haven't been cleaned in ages it usually won't be too bad.  Had the console's circuitry been designed for lower-resistance pots, though, even small amounts of wiper resistance variation would have been intolerable.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-15T19:43:43.843" />
  <row Id="14322" PostTypeId="2" ParentId="7979" CreationDate="2011-05-16T06:39:13.430" Score="0" ViewCount="" Body="&lt;p&gt;I'm also interested in this processor and am poking around their site.  I wouldn't mind spending $100 for the bare minimum to get started, as Leon had mentioned.  However, I wasn't sure what to buy -- their development board page talks about different chips, but I couldn't figure out the differences between them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.xmos.com/technology/silicon-technology&quot; rel=&quot;nofollow&quot;&gt;Here's a helpful link&lt;/a&gt; that outlines the types of XMOS processors.  I wasn't able to find it by clicking around their website.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a nutshell, it looks like they have 4 different processors:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;XS1-G4: 4 cores&#xA;XS1-G2: 2 cores&#xA;XS1-L1: 1 core&#xA;XS1-L2: 2 cores&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The strange thing is that, for beginners, I would expect the XS1-L1 to be the best choice, as you can still learn how to leverage multithreading, but possibly save a little money on the development board.  However, this doesn't seem to be the case.  Both the &lt;a href=&quot;http://www.xmos.com/xk-1a&quot; rel=&quot;nofollow&quot;&gt;XK-1A&lt;/a&gt; and &lt;a href=&quot;http://www.xmos.com/products/development-kits/xc-1a-development-kit&quot; rel=&quot;nofollow&quot;&gt;XC-1A&lt;/a&gt; are $99, and include JTAG hardware.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Maybe Leon can add a comment here and let us know what he thinks is the best starter kit for those interested in getting into XMOS.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-05-16T06:39:13.430" CommentCount="2" />
  <row Id="14323" PostTypeId="1" AcceptedAnswerId="14325" CreationDate="2011-05-16T10:40:44.023" Score="3" ViewCount="140" Body="&lt;p&gt;I have an electret microphone pre amplifier and peak detector circuit that's working great. The microphone picks up sounds and I get a steady DC voltage that, depending on the volume of the sound the microphone is listening to, is somewhere between 0 and ~3.5v&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I need to feed this into an ADC pin on a AVR microcontroller though so that I can read in the relative volume that the microphone is getting. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only problem is that when I connect the circuit to the ADC pin on the microcontroller, my peak voltage drops from 3.5v to about 100mV.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm connecting the pre amp and peak detector circuit to an STK board that the chip is running off. When the board is powered off the peak voltage I'm reading with an oscilliscope (and with a multimeter) is correct but it massively drops down when I power it on. I still does exhibit the same sort of behaviour as it should though (the peak rises when there's noise) but I need the peak to be around 3.5v (not 100mV) as I need to a great resolution in the ADC value I read in in my software.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have connected the grounds of both circuits to the STK board's ground so I don't think that that is the issue. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anyone give me any sort of idea about what might be going wrong? Is it something to do with the internal resistance of the microcontroller? Am I perhaps putting too much current into the ADC pin? I'd really appreciate any help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit: I'm using pin A7 on an atmega16.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;edit 2: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is the pre amp circuit I'm using: &lt;a href=&quot;http://www.zen22142.zen.co.uk/Circuits/Audio/lf071_mic.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.zen22142.zen.co.uk/Circuits/Audio/lf071_mic.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and this is the peak detector/rectifier:&#xA;&lt;img src=&quot;http://i.stack.imgur.com/UMduM.jpg&quot; alt=&quot;peak detector&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;and the code to get the ADC value:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;unsigned int ADC_read(unsigned char ch)&#xA;{&#xA;    ADMUX = 0b11000111;&#xA;&#xA;    ADCSRA|=(1&amp;lt;&amp;lt;ADSC); // start conversion&#xA;&#xA;    while(!(ADCSRA &amp;amp; (1&amp;lt;&amp;lt;ADIF))); // waiting for ADIF, conversion complete&#xA;    {&#xA;        ADCSRA|=(1&amp;lt;&amp;lt;ADIF); // clearing of ADIF, it is done by writing 1 to it&#xA;    }&#xA;&#xA;    return (ADC);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I can't see how the code would have any effect though.&lt;/p&gt;&#xA;" OwnerUserId="4257" LastEditorUserId="4257" LastEditorDisplayName="" LastEditDate="2011-05-16T11:48:34.900" LastActivityDate="2011-05-16T18:05:30.863" Title="Huge drop in voltage when connecting output to pin of microcontroller?" Tags="&lt;avr&gt;&lt;voltage&gt;&lt;microphone&gt;" AnswerCount="3" CommentCount="10" />
  <row Id="14324" PostTypeId="2" ParentId="14323" CreationDate="2011-05-16T10:53:08.863" Score="1" ViewCount="" Body="&lt;p&gt;Check so there is not a internal pull-down inside the mcu that is enabled for that pin?&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2011-05-16T10:53:08.863" CommentCount="3" />
  <row Id="14325" PostTypeId="2" ParentId="14323" CreationDate="2011-05-16T12:04:25.730" Score="3" ViewCount="" Body="&lt;p&gt;Are you absolutely sure the pin/port is configured as an analog input, and not a digital output that's been set low?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An accidental digital low on the port could be what's loading the peak detector output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not an expert on your particular architecture, but in general, micro I/O pins are multiplexed - you need to explicitly set registers to configure them as inputs, outputs or ADC channels. Setting up an internal ADC still requires you to manually configure its input pin appropriately.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-05-16T16:29:53.790" LastActivityDate="2011-05-16T16:29:53.790" CommentCount="6" />
  <row Id="14326" PostTypeId="2" ParentId="14311" CreationDate="2011-05-16T12:22:20.673" Score="1" ViewCount="" Body="&lt;p&gt;There are industrial PCs designed for embedded applications that use 24 VDC directly, &lt;a href=&quot;http://www.men.de/products/computer-on-modules.html#t=general&quot; rel=&quot;nofollow&quot;&gt;MEN&lt;/a&gt; is a German company that sells such devices. They are more expensive that traditional PC mother boards. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a most PC hardware you will need a conventional PSU, but there are a wide variety of input voltages available.&lt;/p&gt;&#xA;" OwnerUserId="1810" LastActivityDate="2011-05-16T12:22:20.673" />
  <row Id="14327" PostTypeId="1" CreationDate="2011-05-16T13:15:10.840" Score="1" ViewCount="82" Body="&lt;p&gt;Studying for an exam&#xA;Looking at Data buses using Wired AND and Wired OR configurations.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using tristate logic, a device is able to gain control of the bus and transmit anything down it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't understand Wired AND or Wired OR.&#xA;The way I understand Wired AND at the moment - no device has control of the Bus and the output stays at a constant voltage (say 5V) if no devices are attempting to use the bus.&#xA;However when a device attempts to use the bus the line will be pulled to 0V.&#xA;Now if any device attempts to use the bus at the same time, it will never be clear which device is transmitting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also Wired AND is supposed to be active high however when a device uses the bus the line goes low. I would have thought this was active low.&lt;/p&gt;&#xA;" OwnerUserId="4275" LastActivityDate="2011-05-16T16:32:36.830" Title="How Does a Wired AND/OR Bus work" Tags="&lt;logic&gt;&lt;homework&gt;&lt;bus&gt;" AnswerCount="2" />
  <row Id="14328" PostTypeId="2" ParentId="14327" CreationDate="2011-05-16T13:50:09.103" Score="2" ViewCount="" Body="&lt;p&gt;&quot;However when a device attempts to use the bus the line will be pulled to 0V.&quot;&lt;br&gt;&#xA;That's it exactly: the bus is high only if all devices set it high. Just like in an AND gate the output is high only if all inputs are high.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Tri-state logic is not the way to control the bus; if one device sets it high, and another sets it low, you have a short circuit. Usually there's a passive pullup, which keeps the bus at its high level. Each device controls an open drain FET to pull it low.&lt;br&gt;&#xA;Like you said, in this setup there's no way to determine how many devices are pulling it low simultaneously.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is indeed active high logic: for the AND function the bus is active (high) if all inputs are active (high). If a device pulls the bus low it's just putting a low level on it.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-16T14:08:11.597" LastActivityDate="2011-05-16T14:08:11.597" />
  <row Id="14330" PostTypeId="2" ParentId="14323" CreationDate="2011-05-16T15:16:46.583" Score="3" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;If &lt;code&gt;DDRA = 0xFF&lt;/code&gt; it is all outputs.&lt;/li&gt;&#xA;&lt;li&gt;If you haven't written to &lt;code&gt;PORTA&lt;/code&gt; it will default to &lt;code&gt;0x00&lt;/code&gt; so all pins will be low.&lt;/li&gt;&#xA;&lt;li&gt;The ADC just works (TM) so it will happily read the result of the low output fighting with the preamp/rectifier just as happily as it would read any other voltage on the pin.&lt;/li&gt;&#xA;&lt;li&gt;You don't have to do anything to make the &lt;code&gt;ADC&lt;/code&gt; work, except make the pins inputs...&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="4278" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-16T18:05:30.863" LastActivityDate="2011-05-16T18:05:30.863" />
  <row Id="14331" PostTypeId="2" ParentId="14023" CreationDate="2011-05-16T16:01:31.020" Score="1" ViewCount="" Body="&lt;p&gt;There is only one answer - you will need a LOT more solar power generation than simple calculations will suggest:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;48 watts  for 15 hours (assuming a 60% on time averaged over night and day) is ~700 watt hours. With nominal 12V batteries call that 60 amp-hours capacity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget that in the day you need to be able to charge the battery and run the incubator at the same time so a nominal output of 100W minimum is needed (unless the incubator heater is off most of the time).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1 Solar cells rarely achieve their full rated output which assumes they are exactly normal to the incident light (pointing straight at the sun, in English)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2 The batteries won't be 100% effceint in taking or yielding up their charge&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3 You will need lead acid batteries designed for deep discharge - i.e. leisure batteries. Even then remember you won't be able to use part of their capacity&lt;/p&gt;&#xA;&#xA;&lt;p&gt;4 Even in Ethiopia you can't guarantee day-long sunshine&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Though you may get away with one, I would suggest using two 60Ah leisure batteries (to be on the safe side). If you have 10 hours sun and achieve 50% of nominal output you will need ~1400 watt-hours or 140 watts of panel capacity. So go with the BP 160W panel here or similar:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.windandsun.co.uk/Solar/BP_Solar_modules.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.windandsun.co.uk/Solar/BP_Solar_modules.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So even if the sun isn't full on to the panel it should make 100W - worst case 50W incubator and 50W for the battery.&lt;/p&gt;&#xA;" OwnerUserId="4278" LastActivityDate="2011-05-16T16:01:31.020" />
  <row Id="14332" PostTypeId="2" ParentId="10128" CreationDate="2011-05-16T16:06:55.540" Score="0" ViewCount="" Body="&lt;p&gt;Two answers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1 - read the datasheets, sorry but that is what they are for. Where else is a manufacturer gong to put their chip-specific information? This is the asy, fast way to get just the data you need for your project.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2 Not convinced? Get a copy of 'The Art of Electronics' by Horovitz and Hill and read it from cover to cover, and again until you can work out why all their 'bad examples' are bad. This is a way to learn general principles e.g. how to connect digital I/O for different types of chip.&lt;/p&gt;&#xA;" OwnerUserId="4278" LastActivityDate="2011-05-16T16:06:55.540" />
  <row Id="14333" PostTypeId="2" ParentId="14327" CreationDate="2011-05-16T16:32:36.830" Score="1" ViewCount="" Body="&lt;p&gt;In a common usage case for a wired-AND/wired-OR bus, there exists some means other than the bus by which devices can indicate whether they want attention.  If there are five devices which may require attention but a processor has a single interrupt pin, a common solution would be to have the interrupt pin trigger some code that will ask each device in turn if it wants attention (and if so, service it).  If the pin is still driven low after all devices have been polled, the polling cycle will repeat (in case a device which didn't want attention when it was first polled decides it wants attention while a later device is being serviced).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, a wired-AND/wired-OR bus will be used when there will often be zero devices wanting attention, and when it is useful to optimize for that case.  It would be possible to forgo interrupts and simply have code repeatedly query every I/O device to see if it wants attention even when none do, but it is often far more useful to have code doing other things when no devices need attention.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, another approach for using a bus that's electrically configured for wired-AND/wired-OR operation is to have devices only drive the line when explicitly addressed and asked to do so.  Despite the electrical similarity, though, such configurations are often not referred to as wired-AND/wired-OR buses, since there's no possibility (when things are working as expected) of combining signals from unknown sources.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-16T16:32:36.830" CommentCount="2" />
  <row Id="14334" PostTypeId="2" ParentId="2283" CreationDate="2011-05-16T17:20:55.527" Score="3" ViewCount="" Body="&lt;p&gt;One advantage not yet mentioned for using pull-ups rather than pull-downs is that when using a pull-up, one end of the switch must be tied to ground; when using a pull-down, it must be tied to VDD.  Exposing ground or VDD means there's some possibility something else might get shorted to it.  Generally, shorting something to VDD is apt to be more damaging than shorting it to ground.  Further, exposed connections run the risk of electrostatic discharge; discharge into VDD is often more damaging than discharge into ground.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-16T17:20:55.527" />
  <row Id="14335" PostTypeId="1" CreationDate="2011-05-16T18:20:51.460" Score="4" ViewCount="84" Body="&lt;p&gt;On various places across the net, I read that (some) synthesis tools do not respect VHDL libraries. These tools just throw all entities and packages into a single namespace, so that you cannot have &lt;code&gt;mylib.someEntity&lt;/code&gt; and &lt;code&gt;yourLib.someEntity&lt;/code&gt; in the same project. I know that Altera Quartus used to have that problem last time I checked (but that was a while ago). I'm afraid that some of the info on usenet archives might be outdated, so I'm looking for up-to-date info. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also believe &lt;em&gt;most&lt;/em&gt; simulators support libraries today.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;My question&lt;/strong&gt;: Which synthesis tools do support VHDL libraries and which don't? If there are any simulators that do not support libraries, I'd also like to hear that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you please also mention the &lt;em&gt;version numbers&lt;/em&gt; of the tools, for future reference?&lt;/p&gt;&#xA;" OwnerUserId="3145" LastActivityDate="2011-05-24T16:53:01.003" Title="Which synthesis tools support VHDL libraries?" Tags="&lt;vhdl&gt;&lt;synthesis&gt;" AnswerCount="3" CommentCount="0" />
  <row Id="14336" PostTypeId="2" ParentId="14335" CreationDate="2011-05-16T18:45:25.803" Score="1" ViewCount="" Body="&lt;p&gt;Quartus uses a single library by default, but different libraries can be used if required:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://quartushelp.altera.com/9.1/mergedProjects/hdl/vhdl/vhdl_pro_libraries.htm&quot; rel=&quot;nofollow&quot;&gt;http://quartushelp.altera.com/9.1/mergedProjects/hdl/vhdl/vhdl_pro_libraries.htm&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Two or more entities with the same name cannot be used, however, only packages.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-16T20:21:42.297" LastActivityDate="2011-05-16T20:21:42.297" CommentCount="3" />
  <row Id="14337" PostTypeId="1" CreationDate="2011-05-16T19:43:02.933" Score="2" ViewCount="75" Body="&lt;p&gt;Many laptop batteries have a button on the bottom that will light up 1-4 LEDs to indicate how much power is remaining.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd love to build something like that into my own device, which is powered by 2 18650 LIon batteries in series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a simple way to build a circuit that will light up different LEDs depending on the voltage of the battery pack?  Or a ready made IC that does something like this I could easily use?&lt;/p&gt;&#xA;" OwnerUserId="4280" LastActivityDate="2011-05-16T20:34:58.717" Title="Battery charge indicator LEDs" Tags="&lt;power&gt;&lt;battery&gt;&lt;charge&gt;" AnswerCount="2" />
  <row Id="14338" PostTypeId="2" ParentId="14337" CreationDate="2011-05-16T20:18:02.717" Score="3" ViewCount="" Body="&lt;p&gt;TI/Benchmarq makes battery fuel gauge devices, a typical one for two Li-Ion cells is the &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/bq28400.html?DCMP=npl_pmp_en_211_BQ28400&amp;amp;HQS=Other%20OT%20BQ28400npl&quot; rel=&quot;nofollow&quot;&gt;BQ28400&lt;/a&gt;. You will need to interface it to a suitable MCU that drives the LEDs. This technique should give an accurate indication of battery life, which you won't get simply by using the voltage.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-16T20:31:11.183" LastActivityDate="2011-05-16T20:31:11.183" />
  <row Id="14339" PostTypeId="2" ParentId="14337" CreationDate="2011-05-16T20:28:21.730" Score="2" ViewCount="" Body="&lt;p&gt;One simple way to do this is to use a series of comparators that power LEDs. You will need a stable voltage to compare against so you would need to place a voltage regulator on the batteries with a voltage out that is lower then what you plan on the batter being.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You then can use some voltage dividers off of the battery to get different voltages to compare the battery to. Since you have already stepped down the battery voltage with the voltage regulator you will also need to use a voltage divider on the battery to get it in the range that you are comparing against.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically if you have a battery that ranges between 6v and 10v, you will want a voltage regulator around 5v. You can then set the comparator voltages to be 3v, 3.5v, 4v, 4.5v and then use a resistor divider to divide the batter voltage by 2. So your new range is 3v - 5v and if it is  above the 3, 3.5, 4, 4.5 then the LED associated with that comparator will turn on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NOTE: 6-10v is just a random range I picked to illustrate my example, don't expect for your batteries to be like that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The biggest problem with this method is the poor accuracy you get. Batteries don't discharge with a linear voltage drop, so it can be hard to perfect what is considered 25% charge, or 50% charge, or what ever values it is you are looking for.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The nice thing about this method is it is very simple to understand and build.&lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-05-16T20:34:58.717" LastActivityDate="2011-05-16T20:34:58.717" />
  <row Id="14340" PostTypeId="1" AcceptedAnswerId="14341" CreationDate="2011-05-16T20:55:17.023" Score="3" ViewCount="73" Body="&lt;p&gt;I'm working on an AVR/JTAG/whatever programmer. The programmer will interface with chips running at various voltage levels, ranging from 1.8V to 5V. The programmer runs at 3.3V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The programmer interfaces with the programee through four 3-state pins, which I control from the 3.3V chip, and I need those pins to provide logic levels supplied by the user. I've tried the following (VDD is the user-supplied voltage), but unfortunately, with R1 = 220, the switching was too slow; I'd like to communicate at up to 10MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/aOXPP.png&quot; alt=&quot;level shifter&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've looked at voltage-translator ICs, but the best that I found was &lt;a href=&quot;http://uk.farnell.com/texas-instruments/sn74lvc8t245rhlr/ic-74lvc-translator-qfn24/dp/1601177&quot; rel=&quot;nofollow&quot;&gt;SN74LVC8T245&lt;/a&gt;, which won't however allow me to tristate each pin separately.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What should I use to perform the voltage translation?&lt;/p&gt;&#xA;" OwnerUserId="1850" LastActivityDate="2011-05-17T09:21:26.200" Title="How do I translate voltages to user-supplied levels?" Tags="&lt;voltage&gt;&lt;output&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="14341" PostTypeId="2" ParentId="14340" CreationDate="2011-05-16T21:41:18.683" Score="2" ViewCount="" Body="&lt;p&gt;Here's what you need:  T.I. &lt;a href=&quot;http://focus.ti.com/docs/prod/folders/print/sn74lvc1g125.html&quot; rel=&quot;nofollow&quot;&gt;SN74LVC1G125&lt;/a&gt;.  It's a single tri-state buffer in a 5 pin package.  It takes input voltages up to 5v, and spits out a voltage that's basically the same as VCC.  And VCC can be 1.65 to 5.0v.   &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-16T21:41:18.683" CommentCount="5" />
  <row Id="14342" PostTypeId="1" CreationDate="2011-05-16T21:48:58.837" Score="0" ViewCount="57" Body="&lt;p&gt;I am doing a “thought experiment” and wish to know:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How much do single chip Gyroscope cost?  (In the 100s)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How good are there results measurements of 3d direction?   &lt;/p&gt;&#xA;&#xA;&lt;p&gt;How hard are they to interface to?&lt;/p&gt;&#xA;" OwnerUserId="3879" LastEditorUserId="712" LastEditorDisplayName="" LastEditDate="2011-05-16T21:59:55.397" LastActivityDate="2011-05-16T21:59:55.397" ClosedDate="2011-05-16T22:12:39.283" Title="How much do single chip Gyroscope cost and how good are they?" Tags="&lt;sensor&gt;" CommentCount="3" />
  <row Id="14343" PostTypeId="2" ParentId="14340" CreationDate="2011-05-16T21:49:37.250" Score="3" ViewCount="" Body="&lt;p&gt;The Bus Pirate does voltage translation using 4066 Analog Bus Switches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The clearest example is in the &lt;a href=&quot;http://dangerousprototypes.com/docs/images/9/94/Cct-BusPirate-Shield-v1.0.png&quot; rel=&quot;nofollow&quot;&gt;Bus Pirate Arduino Shield schematic&lt;/a&gt;:&#xA;&lt;img src=&quot;http://i.stack.imgur.com/JwMy4.png&quot; alt=&quot;enter image description here&quot;&gt; &lt;/p&gt;&#xA;" OwnerUserId="566" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-17T09:21:26.200" LastActivityDate="2011-05-17T09:21:26.200" CommunityOwnedDate="2011-05-16T23:57:08.903" CommentCount="3" />
  <row Id="14344" PostTypeId="1" AcceptedAnswerId="14363" CreationDate="2011-05-16T22:16:06.977" Score="4" ViewCount="171" Body="&lt;p&gt;Someone asked me the other day how an FTDI USB to serial UART works, and I realized I didn't know. I looked at the datasheet for the FT232R and the block diagram didn't really help me. Can anyone explain or link me to a good explanation? &lt;/p&gt;&#xA;" OwnerUserId="2993" LastEditorUserId="4172" LastEditorDisplayName="" LastEditDate="2011-05-17T15:40:47.280" LastActivityDate="2011-05-18T01:16:44.457" Title="How does an FTDI chip work?" Tags="&lt;usb&gt;&lt;uart&gt;&lt;ftdi&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="14345" PostTypeId="1" CreationDate="2011-05-17T01:16:26.727" Score="0" ViewCount="20" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to buy a soldering tips for Aoyue 2900.&#xA;It uses the LF type soldering tips which are quite expensive.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it possible to use the Hakko T12 tips for this purpose?&lt;/p&gt;&#xA;" OwnerUserId="4095" LastActivityDate="2011-05-17T01:16:26.727" Title="Do Hakko T12 soldering tips match for Aoyue 2900?" Tags="&lt;soldering&gt;" />
  <row Id="14346" PostTypeId="1" AcceptedAnswerId="14369" CreationDate="2011-05-17T01:19:54.523" Score="2" ViewCount="67" Body="&lt;p&gt;Is it possible to construct an adjustable output switching power supply based on the MC34063? I read over the On Semi &lt;a href=&quot;http://www.onsemi.com/pub/Collateral/MC34063A-D.PDF&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt; and &lt;a href=&quot;http://www.onsemi.com/pub/Collateral/AN920-D.PDF&quot; rel=&quot;nofollow&quot;&gt;app notes&lt;/a&gt; but didn't see any examples of an adjustable output application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it just a matter of replacing the &quot;R1&quot; and &quot;R2&quot; resistors with a potentiometer and then &lt;a href=&quot;http://dics.voicecontrol.ro/tutorials/mc34063/&quot; rel=&quot;nofollow&quot;&gt;calculating&lt;/a&gt; the other components values based on a Vout in the &lt;em&gt;middle&lt;/em&gt; of the the target Vout range (i.e. so for a Vout of 5-12V, you'd base calculations on 8.5V)?&lt;/p&gt;&#xA;" OwnerUserId="2654" LastEditorUserId="2654" LastEditorDisplayName="" LastEditDate="2011-05-17T01:25:17.047" LastActivityDate="2011-05-17T16:48:38.433" Title="Adjustable SMPS using MC34063?" Tags="&lt;power-supply&gt;&lt;voltage-regulator&gt;&lt;smps&gt;&lt;switching-voltage-reg&gt;" AnswerCount="2" />
  <row Id="14347" PostTypeId="1" CreationDate="2011-05-17T01:42:45.627" Score="2" ViewCount="79" Body="&lt;p&gt;Hello Stack!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have had it with commercials on cable TV being a lot louder than the program I happen to be watching. I have also had the reverse where the program switches scenes and you cannot make out what the whispering actress is saying.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know products are already on the market that take care of this problem, but I thought it would be fun to fix it myself. I come from the microprocessor/digital side of things so I really have not played with audio a whole lot.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I current use RCA audio cables between my cable box and sound system. I would like to plug my device between those two devices so that my amplifier receives the modified normalized audio signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So far I have been looking at Automatic Gain Control circuits as a solution. Is this the right way to go or should I be looking at something else?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If possible, please include links to schematics, components, etc with your post. Thank you in advance for your help.&lt;/p&gt;&#xA;" OwnerUserId="1575" LastActivityDate="2011-05-17T12:29:43.883" Title="How Would I Nomalize Cable TV Volume Between Commercials and Programming" Tags="&lt;audio&gt;&lt;circuit&gt;&lt;op-amp&gt;&lt;agc&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="14348" PostTypeId="2" ParentId="14346" CreationDate="2011-05-17T03:44:54.923" Score="2" ViewCount="" Body="&lt;p&gt;For large output voltage ranges, you could replace R1/R2 with a pot (digital or otherwise).  You can also use a DAC (hooked up to a microcontroller) and an op-amp as a sort of voltage comparator.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main problem that you'll find is that the switching DC/DC converter is optimized for a certain input to output voltage ratio at a given current.  As you stray away from that optimized operation point the converter will degrade in performance.  And by degrade, I mean that at best it will loose efficiency and at worst it will cease to function.  In between those two extremes, you'll have increased ripple, increased noise, and possibly unstable operation.  All switching DC/DC converter chips will have these issues, but some will have them worse than others.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-17T03:44:54.923" CommentCount="2" />
  <row Id="14349" PostTypeId="3" CreationDate="2011-05-17T04:06:17.270" Score="0" ViewCount="" Body="&lt;p&gt;OMG retag me. I shouldn't exist. Make it stop.&lt;/p&gt;&#xA;" OwnerUserId="-1" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-17T08:03:27.660" LastActivityDate="2011-05-17T08:03:27.660" />
  <row Id="14350" PostTypeId="3" CreationDate="2011-05-17T04:06:17.270" Score="0" ViewCount="" Body="OMG retag me. I shouldn't exist." OwnerUserId="-1" LastEditorUserId="1227" LastEditorDisplayName="" LastEditDate="2011-05-17T08:03:30.607" LastActivityDate="2011-05-17T08:03:30.607" />
  <row Id="14351" PostTypeId="2" ParentId="3423" CreationDate="2011-05-17T05:33:36.270" Score="1" ViewCount="" Body="&lt;p&gt;I would like to add C# using the .NET Micro Framework.  There are many ARM ports in use and it is well supported and documented. &lt;a href=&quot;http://msdn.microsoft.com/en-us/library/cc533001.aspx&quot; rel=&quot;nofollow&quot;&gt;http://msdn.microsoft.com/en-us/library/cc533001.aspx&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of the well known development boards out there:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Fez Panda/Domino&#xA;Netduino and Netduino plus&lt;/p&gt;&#xA;" OwnerUserId="4172" LastActivityDate="2011-05-17T05:33:36.270" CommunityOwnedDate="2011-05-17T05:33:36.270" />
  <row Id="14352" PostTypeId="1" CreationDate="2011-05-17T08:26:00.493" Score="0" ViewCount="87" Body="&lt;p&gt;I am considering buying an electric bicycle using brushless DC Hub Motor.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;What is the difference between 24V Vs 36V motor?&lt;/li&gt;&#xA;&lt;li&gt;Is it related to maximum torque produced by the motor?&lt;/li&gt;&#xA;&lt;li&gt;If yes, what does that mean to a bike rider?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Sorry if this question sounds trivial. I have little knowledge in electrical engineering.&lt;/p&gt;&#xA;" OwnerUserId="4283" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-17T13:08:46.937" LastActivityDate="2011-05-17T13:08:46.937" ClosedDate="2011-05-18T19:02:48.220" Title="24V Vs 36 Brushless DC HUB Motor For Electric Bike" Tags="&lt;dc-motor&gt;&lt;brushless&gt;" CommentCount="5" />
  <row Id="14353" PostTypeId="2" ParentId="14347" CreationDate="2011-05-17T09:41:44.587" Score="1" ViewCount="" Body="&lt;p&gt;Typical electroacoustic systems use &lt;a href=&quot;http://en.wikipedia.org/wiki/Dynamic_range_compression&quot; rel=&quot;nofollow&quot;&gt;compressors&lt;/a&gt; (and variants - &lt;a href=&quot;http://en.wikipedia.org/wiki/Limiter&quot; rel=&quot;nofollow&quot;&gt;limiters&lt;/a&gt; and &lt;a href=&quot;http://en.wikipedia.org/wiki/Leveler&quot; rel=&quot;nofollow&quot;&gt;levelers&lt;/a&gt;) for exactly that - controlling the dynamic range of the signal. Those devices are used in audio production, by musicians, or e.g. to limit the modulation depth of a radio transmitter. Analogue compressors are still in wide use (I'd even say analogue compressors are more common in professional recording studios, not to mention vacuum tube ones).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What you need is basically a limiter or leveler, googling around for 'audio limiter schematics' yields a lot of results, I'd start the research from there. E.g. &lt;a href=&quot;http://www.repeater-builder.com/projects/limiter.html&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; looks reasonably simple. There are also many circuits like &lt;a href=&quot;http://www.seekic.com/forum/22_circuit_diagram/15583_AUDIO_LEVELER.html&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;, based on NE577 or NE572 or similar compander chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope that helps!&lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-05-17T09:41:44.587" />
  <row Id="14354" PostTypeId="2" ParentId="3260" CreationDate="2011-05-17T09:45:30.300" Score="0" ViewCount="" Body="&lt;p&gt;A normal Varicap (or Varactor) diode is a component that change his capacity by varying the voltage across the junction. Just control that voltage with a DAC and the varicap becomes &quot;programmable&quot; (its capacity can be changed via software). &#xA;Or by &quot;programmable&quot; you mean something else?&lt;/p&gt;&#xA;" OwnerUserId="244" LastEditorUserId="244" LastEditorDisplayName="" LastEditDate="2011-05-17T10:20:11.080" LastActivityDate="2011-05-17T10:20:11.080" />
  <row Id="14355" PostTypeId="1" AcceptedAnswerId="14424" CreationDate="2011-05-17T10:33:21.847" Score="-3" ViewCount="93" Body="&lt;p&gt;I am looking for .lbr file of Female header(thin type, varies from usual dimension) used in xbee modules ..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/6GRTk.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I had downloaded  microbuilder.lbr earlier which had the footprint of male header(usual dimension) for Eagle Schematic.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance..&lt;/p&gt;&#xA;" OwnerUserId="1484" LastActivityDate="2011-05-19T06:20:04.680" Title="Schematic Editor - Library files_part2" Tags="&lt;pcb&gt;&lt;schematics&gt;" AnswerCount="1" CommentCount="9" />
  <row Id="14356" PostTypeId="2" ParentId="2616" CreationDate="2011-05-17T11:52:37.270" Score="0" ViewCount="" Body="&lt;p&gt;Removing leadless packages is easy with a good hot air station. To speed removal up, it helps to set the temperature high - I work around 420 to 480 deg C. Don't worry about overheating it: You're not often bothered with saving a dead part and a voltage regulator is cheap, anyway. Also, I set airflow rate to near maximum. I choose a nozzle which covers the chip entirely. If such a nozzle does not exist (i.e. the chip is too big - I had to remove a 208 pin TQFP once) I work around the edges of the chip until it shows signs of moving. If the nozzle does cover the chip, I just put it over, wait a few seconds and the chip will usually come off when you remove the nozzle. Remove it quickly or the solder may solidify and stick to the board. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be careful with hot air, as it will often remove other components. 0603's don't stand a chance if exposed for more than a few seconds and then you'll have to solder more.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My hot air station is built into my soldering station, an Aoyue 968. But you can get a cheaper hot air only station. &lt;a href=&quot;http://www.eevblog.com/2011/04/25/eevblog-167-atten-858d-hot-air-rework-review/&quot; rel=&quot;nofollow&quot;&gt;Dave Jones of EEVBlog did a review of one recently&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-17T11:52:37.270" />
  <row Id="14357" PostTypeId="2" ParentId="14335" CreationDate="2011-05-17T12:03:53.770" Score="1" ViewCount="" Body="&lt;p&gt;Synplify E2010.09-SP1-1 is OK: you can tell it what library to compile each file into in the project file&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sample code follows for others to try (not my normal coding style, I'd normally not use positional mapping, but in this simple situation it looked a bit cleaner).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The gate-view shows two LUTs one with an AND and one with an XOR.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;lib1.vhd&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;library ieee;&#xA;use ieee.std_logic_1164.all;&#xA;entity test is&#xA;    port (a, b : in  std_logic;&#xA;          o    : out std_logic);&#xA;end entity test;&#xA;architecture a1 of test is&#xA;begin&#xA;    o &amp;lt;= a and b;&#xA;end architecture a1;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;lib2.vhd&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;library ieee;&#xA;use ieee.std_logic_1164.all;&#xA;entity test is&#xA;    port (&#xA;        c, d : in  std_logic;&#xA;        o    : out std_logic);&#xA;end entity test;&#xA;architecture a1 of test is&#xA;begin&#xA;    o &amp;lt;= c xor d;&#xA;end architecture a1;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;top.vhd&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;library ieee;&#xA;use ieee.std_logic_1164.all;&#xA;&#xA;library lib1;&#xA;library lib2;&#xA;&#xA;entity top is&#xA;    port (&#xA;        a, b, c, d : in std_logic;&#xA;        o1, o2     : out std_logic);&#xA;end entity top;&#xA;&#xA;architecture a1 of top is&#xA;begin  -- architecture a1&#xA;    test_1: entity lib1.test port map (a, b, o1);&#xA;    test_2: entity lib2.test port map (c, d, o2);&#xA;end architecture a1;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-05-17T12:03:53.770" CommentCount="1" />
  <row Id="14358" PostTypeId="2" ParentId="14347" CreationDate="2011-05-17T12:29:43.883" Score="1" ViewCount="" Body="&lt;p&gt;The big issue with commercials aren't their peak volume.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Advertisers use &lt;a href=&quot;http://www.ehow.com/about_6531457_tv-commercials-loud_.html&quot; rel=&quot;nofollow&quot;&gt;tricky techniques&lt;/a&gt; to keep the overall peak below the prescribed legal limit, but the quiet spots are boosted so that the whole commercial stays near peak.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whatever circuit you're going to build may have to calculate an average volume over a certain time interval to be able to detect a commercial (or an excessively loud TV scene) and attenuate accordingly.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-17T12:29:43.883" />
  <row Id="14359" PostTypeId="2" ParentId="14344" CreationDate="2011-05-17T13:43:44.163" Score="2" ViewCount="" Body="&lt;p&gt;There's a USB microcontroller inside which talks a proprietary protocol over USB (hence the need for drivers) and converts that into &quot;normal&quot; UART signals and back again.&lt;/p&gt;&#xA;" OwnerUserId="763" LastActivityDate="2011-05-17T13:43:44.163" />
  <row Id="14360" PostTypeId="2" ParentId="1011" CreationDate="2011-05-17T14:11:36.667" Score="0" ViewCount="" Body="&lt;p&gt;You may have already figured out that the answer depends heavily on the individual.  Some individuals carry work around with them mentally and physically, I have seen some engineers go so far as to have a computer at home but almost never touch it (I use a computer all day long why would I want to at home all night long).  I see a number of folks that cant wait to get home and get in a boat or on a bike and get outside.  Some just want to play with their kids and/our hang out with spouse.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a double edged sword.  If you do nothing work like at home on your own time, basically keeping up with the trends of the business or technology or keeping your programming or designing skills sharp, or learning the next new thing you will fall behind in your profession and your salary and position will reflect that.  At the same time if you are always the one that caves in to work the weekend or nights, management will walk all over you and expect you to put in double time for free, and you wont progress professionally.  Something that I feel has changed quite a bit since my father was an engineer to the present is the opposite of your question.  Professionals taking time off of work to go to get their kids, bringing their kids to work when they cant find someone to watch them, one or two part or full days a week working from home so they can watch the kids as the spouse or daytime caregiver is not available.   You as an individual and professional have to balance work time, personal time, and family time.  We work to make the money we need to do the things we do when we are not at work.  So you should do the work and not blow off that profession, at the same time dont blow off your family or your personal time.  In the US it is expected that a salaried engineer from time to time will put in extra hours to make a deadline of some sort without any additional compensation.  It is somewhat of a cultural thing.  I have read that in other certain countries under no circumstance that professional engineers will put in extra time without compensation.  I have no other direct experience to know more than that, if you live in the US, expect a late night or weekend every now and again, perhaps once every quarter or two if nothing else.  And some professional advice, take some of your personal time and surf or partake in hobbies related to your profession to keep your tools up to date and sharpened, it will definitely help your career, sometimes that involves doing actual work, sometimes you can borrow or use company equipment (scopes, etc), depends on the company.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-05-17T14:11:36.667" CommunityOwnedDate="2011-05-17T14:11:36.667" />
  <row Id="14361" PostTypeId="1" AcceptedAnswerId="14364" CreationDate="2011-05-17T14:37:05.663" Score="0" ViewCount="67" Body="&lt;p&gt;Does anyone know of a chip which can extract the colour burst from a PAL or NTSC video signal? Then, I would need to start an oscillator of the right frequency (4.43361875 MHz for PAL, and 3.579545 MHz for NTSC) and keep it oscillating once this frequency is established. If the signal is PAL, I would also need to phase shift this oscillator on every other line. Ideally, I would use just one crystal for both but I don't think the two frequencies could be derived from one crystal. It is required that the module support both PAL and NTSC; I'd like to avoid producing two types for different systems. In other words, I need some way to synchronise to a colour burst. I'm sure such devices must exist; most broadcast PAL/NTSC TVs would use one, but I'm having no luck.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-17T17:20:32.757" Title="Synchronising to a colour burst" Tags="&lt;video&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="14362" PostTypeId="2" ParentId="2245" CreationDate="2011-05-17T15:27:31.003" Score="0" ViewCount="" Body="&lt;p&gt;I'm a fan of the &lt;a href=&quot;http://freaklabs.org/&quot; rel=&quot;nofollow&quot;&gt;freaklabs&lt;/a&gt; &lt;a href=&quot;http://www.freaklabsstore.com/index.php?main_page=product_info&amp;amp;products_id=188&quot; rel=&quot;nofollow&quot;&gt;freakduino&lt;/a&gt; since it's an &lt;a href=&quot;http://www.arduino.cc/&quot; rel=&quot;nofollow&quot;&gt;Arduino&lt;/a&gt; compatible board that includes the ability to &lt;a href=&quot;http://freaklabs.org/index.php/Tutorials/Software/Feeding-the-Shark-Turning-the-Freakduino-into-a-Realtime-Wireless-Protocol-Analyzer-with-Wireshark.html&quot; rel=&quot;nofollow&quot;&gt;sniff 802.15.4 traffic&lt;/a&gt; for easy diagnosis of problems. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have two freakduinos and an XBee Pro module with AdaFruit's XBee breakout board.&#xA;I've honestly found the freakduinos easiest for getting started.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Even better, the &lt;a href=&quot;http://freaklabs.org/index.php/Forum/&quot; rel=&quot;nofollow&quot;&gt;freaklabs forums&lt;/a&gt; see many ZigBee/XBee/802.15.4 related questions and answers.&lt;/p&gt;&#xA;" OwnerUserId="1650" LastActivityDate="2011-05-17T15:27:31.003" />
  <row Id="14363" PostTypeId="2" ParentId="14344" CreationDate="2011-05-17T15:29:00.907" Score="4" ViewCount="" Body="&lt;p&gt;Word of warning, this will be a pretty high level explanation, for something more nitty gritty, I would suggest looking up the USB protocol. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The FTDI chips implement the USB protocol stack.  The responsibility of this hardware is to tell your PC what it is (using some identification information) such that your computer can load the right driver for it, and also to manage the data transactions with the PC there-on after - look up USB endpoints for a better explanation of these processes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once those drivers are loaded, this would sort of specify a command set that your PC can use to query the chip.  This hardware takes care of one side of the equation (communication with your PC).  The other side of it would be some dedicated hardware to manage the UART protocol which includes logic, buffers and line drivers and the sorts.  The command set that I mentioned earlier would be used to read from or write to the UART hardware.  It should probably be mentioned that USB devices are polled by the PC, so in instances where you are using code which is event based, your PC is actually doing some polling to determine that new data has arrived - this may be different than a native serial port, I wouldn't know.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The above logic can be implemented either as a dedicated ASIC or by using a stripped down microcontroller core which executes firmware on ROM.  If it is indeed a microcontroller core, then I imagine the UART is connected to it as a peripheral.&lt;/p&gt;&#xA;" OwnerUserId="4172" LastEditorUserId="4172" LastEditorDisplayName="" LastEditDate="2011-05-18T01:16:44.457" LastActivityDate="2011-05-18T01:16:44.457" CommentCount="3" />
  <row Id="14364" PostTypeId="2" ParentId="14361" CreationDate="2011-05-17T15:32:40.487" Score="1" ViewCount="" Body="&lt;p&gt;I would guess you're trying to upgrade your video overlay projects for color?  A tough job.  One difficulty you're apt to encounter is that while a 100ns jitter on a luminance signal is annoying but tolerable, and 50ns would be barely noticeable, even a 25ns jitter on your chroma signal will be clearly visible (it's about the difference between red and orange).  For luminance, it's fine to derive your dot clock by passing a free-running clock running at 24+ MHz through a counter that's held in reset during HSync, thus keeping all of your timing in the digital domain.  Chroma timing is sufficiently tight that such an approach will only yield good results if you have a really fast clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can't think of any consumer-electronics product I've ever seen which could overlay a color image onto a composite video signal which they did not either generate or decode internally.  There's probably a reason.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;b&gt;Edit&lt;/b&gt;&#xA;If you really want to forge ahead, your best bet may be to clock some logic with a precise multiple of the chroma frequency (e.g. 57.272727MHz if you can get it--chroma * 16), and then have fine-pitched variable delay using something like:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&#xA;Out0 = MyRef&#xA;Out1 = Out0 | (MyRef &amp; (PhaseDelay == 14))&#xA;Out2 = Out1 | (MyRef &amp; (PhaseDelay == 13))&#xA;Out3 = Out2 | (MyRef &amp; (PhaseDelay == 12))&#xA;...&#xA;Out14 = Out13 | (MyRef &amp; (PhaseDelay == 1))&#xA;Out15 = Out14 | (MyRef &amp; (PhaseDelay == 0))&#xA;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Ideally, each stage should delay by about 2.5ns, so the total delay would be 40ns, or a fair bit longer than the period of your clock.  On each scan line, determine whether you're lagging or leading the chroma signal.  If you're lagging, use a lower PhaseDelay value next line; if you're leading, use a higher one.  If you fall off the end, add or delete a clock cycle and adjust PhaseDelay by a self-tuning amount; use the lagging or leading phase next line to determine whether to increase or decrease that amount.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The logic could perhaps be simplified slightly if your reference chroma were guaranteed to be a tiny bit slower than the original, even with both signals at the ends of their tolerance regions.  I'm not sure what the exact tolerance ranges are, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PS--Another simplification might be to say that if before you sample the first chroma pulse of a scan-line you're close to the end of your delay line, add/drop a cycle and adjust PhaseDelay by a suitable amount; don't add/drop a cycle at any other time.  There are probably about 4 &quot;trustworthy&quot; chroma samples per line (the front end end of the chroma burst are sometimes a little wonky), so if your initial estimate of how much to adjust your delay time is even close, you'll be able to adjust it by +/- 4.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;PPS: A further simplification if you figure there will always be (at least) five nice chroma cycles would be to drop the length of your delay line so it's just a smidgen over your fast clock cycle, then use the first chroma cycle to get within a fast clock of the right position, the second to select between two delay taps that are about half a cycle apart, the next to select between taps that are about a quarter cycle apart, etc.  &lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-05-17T17:20:32.757" LastActivityDate="2011-05-17T17:20:32.757" CommentCount="3" />
  <row Id="14365" PostTypeId="2" ParentId="14361" CreationDate="2011-05-17T15:42:21.603" Score="0" ViewCount="" Body="&lt;p&gt;A phase-locked loop (PLL) is the standard way to do that. A 74HC4046 is often used in that situation, and should work with both frequencies.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-17T15:42:21.603" CommentCount="1" />
  <row Id="14366" PostTypeId="1" AcceptedAnswerId="14367" CreationDate="2011-05-17T15:54:42.567" Score="3" ViewCount="82" Body="&lt;p&gt;I'm looking for a mechanical relay that can run 500 amps when closed. There are solid state solutions for switching such currents (SSRs, IGBTs, etc), and we do use them, but for a low speed H-bridge to polarity-invert some coils, I would rather avoid all the voltage drop of using IGBTs. I would not need to &quot;hot switch&quot; the full 500A, the switching would only take place when no current was running.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Parts that I've come across: &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Omron G9EC series: Rated to 200A, with an exhaustive datasheet that looks trustworthy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stinger &quot;SGP35&quot; relay: supposedly rated to 500A, but the datasheet doesn't instill much trust. See for yourself: &lt;a href=&quot;http://www.stingerelectronics.com/productDetails.aspx?ProductId=89&amp;amp;CategoryID=2&quot; rel=&quot;nofollow&quot;&gt;http://www.stingerelectronics.com/productDetails.aspx?ProductId=89&amp;amp;CategoryID=2&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Has anybody got experience with either of these, or with other high current mechanical relays?&lt;/p&gt;&#xA;" OwnerUserId="3768" LastActivityDate="2011-05-17T16:35:48.930" Title="High current mechanical relays" Tags="&lt;power&gt;&lt;relay&gt;" AnswerCount="2" />
  <row Id="14367" PostTypeId="2" ParentId="14366" CreationDate="2011-05-17T16:17:17.680" Score="7" ViewCount="" Body="&lt;p&gt;You're looking for a &quot;contactor&quot; rather than a relay at those current levels. Tyco are a trustworthy brand, see the &lt;a href=&quot;http://relays.tycoelectronics.com/datasheets/MAP200.pdf&quot; rel=&quot;nofollow&quot;&gt;MAP200&lt;/a&gt;. Other places to look are the companies that make MCBs and other industrial automation controls such as Hager, ABB, GE, Moeller, Schneider, Eaton Cutler-Hammer &lt;a href=&quot;http://www.galco.com/scripts/cgiip.exe/wa/wcat/itemdtl.htm?pnum=XTCS500M22B-CHGP&quot; rel=&quot;nofollow&quot;&gt;XTCS500M22B&lt;/a&gt; etc.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastEditorUserId="2110" LastEditorDisplayName="" LastEditDate="2011-05-17T16:22:55.063" LastActivityDate="2011-05-17T16:22:55.063" CommentCount="1" />
  <row Id="14368" PostTypeId="2" ParentId="14366" CreationDate="2011-05-17T16:35:48.930" Score="3" ViewCount="" Body="&lt;p&gt;Also consider the &lt;a href=&quot;https://www.batteryspace.com/productimages/bms/Relayev200.pdf&quot; rel=&quot;nofollow&quot;&gt;Tyco EV200&lt;/a&gt;, rated for 500A continuous (2000A interruption).&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-17T16:35:48.930" CommentCount="1" />
  <row Id="14369" PostTypeId="2" ParentId="14346" CreationDate="2011-05-17T16:48:38.433" Score="3" ViewCount="" Body="&lt;p&gt;It is fairly trivial to make a power supply adjustable - as you said, the voltage feedback divider can be modified to give you a range of output.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You have to decide on what adjustment range you want to have, and do calculations at both the maximum and minimum voltages to make sure the power train is capable of working.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're designing a buck, for example, the highest voltage you want will dictate the voltage rating of the output capacitors, rectification and series transistor / MOSFET; the lowest voltage will dictate the minimum duty cycle and peak current capabilities of the inductor / MOSFET as well as the capacitor ripple voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The exact point at which you're operating dictates how much conduction loss and switching loss you'll have - moving the output up and down will change the losses. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, in a nutshell, designing for the &quot;middle&quot; of the range is not a valid approach. You need to understand how your intended converter works and design such that at the worst corners of input and load, your devices are in safe operating areas.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-17T16:48:38.433" />
  <row Id="14370" PostTypeId="1" AcceptedAnswerId="14375" CreationDate="2011-05-17T17:20:29.670" Score="3" ViewCount="98" Body="&lt;p&gt;Hello, not a very experienced EE, but I was thinking about a system for high speed data transfer,&#xA;and it is fairly simple conceptually, so I imagine that there must be serious flaws with the method,&#xA;because to my knowledge it is not implemented, or at least not widespread. I apologize in advance for &#xA;my ignorance of the subject matter (I'm just starting my learning).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way I understand it, binary signals enclosed in a carrier wave are modulated/demodulated through a modem.&#xA;I understand why this was done in the past - processors weren't that hardcore, and the hardware can only&#xA;understand binary. I guess I just don't understand why it is still done this way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If we modulate the amplitude of a wave (I think by providing the oscillator different levels of current), &#xA;can we not sample this wave with some sort of analog to digital converter and process it on the CPU?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this is possible, why stick to base 2? If we can have a unique value for each measurable amplitude,&#xA;data transfer rates would skyrocket. Imagine transferring data with base 1024, or even higher. If we &#xA;could accurately sample the wave (each oscillation), I don't see why the rate of transfer could be equal &#xA;to the frequency of the wave times base divided by 2 bits per second (this is probably not correct mathing).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If we have a processor running in the gigahertz, and a signal in the low megahertz, it seems feasible that&#xA;the processor would be able to sample and translate the data to base 2 (possibly sending to another core &#xA;for translation). This way, the data rate would be limited by the processor (faster processors would lead&#xA;to the utilization of higher frequencies for transfer).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Limiting factors that I can think of are how fast the current to the oscillator can be changed (for TX), &#xA;how fast the analog to digital conversion can be done (read that accurate sampling is possible into the&#xA;hundreds of megahertz), and the range of measurable amplitudes. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm aware that this question probably contains an unusal amount of stupidity, but I want to build this &#xA;system and I'm wondering why I shouldn't. There has to be something major that I am missing here. What could it be? Thanks.&lt;/p&gt;&#xA;" OwnerUserId="3621" LastActivityDate="2011-05-18T01:48:41.763" Title="modem free high base AM data transfer possible?" Tags="&lt;wireless&gt;&lt;data&gt;&lt;modulation&gt;&lt;transmitter&gt;" AnswerCount="5" CommentCount="8" />
  <row Id="14371" PostTypeId="2" ParentId="14370" CreationDate="2011-05-17T17:35:12.360" Score="1" ViewCount="" Body="&lt;p&gt;Discrete time sampling and digital signal processing such as you describe is used in telephone-line modems, but on a telephone line one is allowed to output almost arbitrary waveforms in a bandwidth which is quite wide relative to the center frequency (typical range about 300-3,300Hz).  By contrast, radio transmissions must fit fit within a fairly small envelope around a center frequency.  If you owned the only radio transmission device in the world, you could indeed output quite a bit of data on a 1MHz carrier by modulating every wave, but your transmission would garble any transmissions anyone else might be attempting at many other frequencies.  If the transmitter is limited to outputting energy in the range 995,000-1,005,000Hz, sampling the signal a few million times per second and processing everything digitally might allow better reception than using an analog tuner, but there's going to be a pretty tight limit on how much data can usefully be transmitted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;b&gt;Addendum&lt;/b&gt;&#xA;Amplitude-modulating a sine-wave carrier with another sine-wave signal will generate signals with frequency equal to the sum and difference of the carrier and modulating signals.  Amplitude-modulating a sine-wave carrier with a signal that's the sum of two sine waves is equivalent to amplitude-modulating the two sine waves separately on the same carrier and combining the result.  The result of amplitude-modulating a sine-wave carrier with a complex waveform may be determined by separating out all the different frequency components of that waveform and figuring the effect of amplitude-modulating each.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If one amplitude-modulates a variety of voice frequencies in the range 0-5KHz on a 1MHz carrier, the result will be a mix of frequencies in the range 995,000-1,005,000Hz.  To tune an AM radio broadcast on channel 1000 (i.e. 1,000Khz or 1.00MHz), one should endeavor to have the tuner accept all frequencies in the above range and reject any outside it.  If one wanted to tune in channel 990, one should capture frequencies 985,000-995,000.  Note that if the broadcaster on channel 1,000 doesn't filter out all audio frequencies above 5KHz before transmission, those would spill onto the channel below (as well as the channel above).&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-05-17T23:20:44.803" LastActivityDate="2011-05-17T23:20:44.803" CommentCount="13" />
  <row Id="14372" PostTypeId="2" ParentId="14370" CreationDate="2011-05-17T17:35:36.733" Score="4" ViewCount="" Body="&lt;p&gt;If you send 1 bit simultaneously you need two different levels (for amplitude modulation). If you want to send 8 bits simultaneously you need 256 levels, which will result in a lot of read errors; a level may change due to noise.&lt;br&gt;&#xA;There are ways to send more than one bit simultaneously however, like QAM (Quadrature Amplitude Modulation). Part of the information is in the amplitude of the signal, like in ASK (Amplitude Shift Keying), and part is in the phase of the signal, like in PSK (Phase Shift Keying).&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-17T18:08:23.460" LastActivityDate="2011-05-17T18:08:23.460" CommentCount="1" />
  <row Id="14373" PostTypeId="2" ParentId="14370" CreationDate="2011-05-17T18:25:41.137" Score="2" ViewCount="" Body="&lt;p&gt;What you are asking for has been done, to some extent or another, and for different transmission mediums.  I started to write a short thing about different modulation schemes, but then ran across a &lt;a href=&quot;http://en.wikipedia.org/wiki/Modulation&quot; rel=&quot;nofollow&quot;&gt;Wikipedia page&lt;/a&gt; that covers them fairly well.  Just scroll down to the section marked &quot;List of common digital modulation techniques&quot;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Many modern systems operate on Quadrature Amplitude Modulation (QAM).   Ethernet uses Pulse Amplitude Modulation (PAM), which is not on that page.  And many radio based transmissions use some form of Trellis Coding.  So, looking at those will give you a good idea on what the common stuff is.  Looking at the older AM, PSK, etc will give you an idea about where we came from. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bottom line is this...  Almost every form of computer communications that goes more than about 10 feet involves some level of encoding and modulation.  It's basically what you were talking about in your question, but taken to extremes.  Much of it is very theoretical and math-intensive.  People use this kind of stuff for their Ph.D. thesis.  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-17T18:25:41.137" CommentCount="4" />
  <row Id="14374" PostTypeId="1" CreationDate="2011-05-17T19:08:20.290" Score="0" ViewCount="45" Body="&lt;p&gt;I know there are RFID devices that can scan a given radius.  So, you can walk around scanning items rather than doing a barcode scan.  What are these devices called?  links to a couple would be good.&lt;/p&gt;&#xA;" OwnerUserId="4287" LastActivityDate="2011-05-17T19:19:56.707" ClosedDate="2011-05-19T00:14:53.343" Title="What devices exist for bulk scanning RFID tags in a radius?" Tags="&lt;rfid&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="14375" PostTypeId="2" ParentId="14370" CreationDate="2011-05-17T19:15:43.410" Score="4" ViewCount="" Body="&lt;p&gt;You've just described two separate and entirely valid technologies used in communication theory today:  software-defined radio and (for lack of a good general term that I can remember) multi-symbol/level communication.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If we modulate the amplitude of a wave (I think by providing the oscillator different levels of current), can we not sample this wave with some sort of analog to digital converter and process it on the CPU?&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Yes - to a degree.  You've just described software-defined radio.  The basic idea is what you said: dispense with the majority of the radio frequency equipment and create the modulated sine wave directly from the output of a D/A converter and for the return path use a similarly fast A/D and plenty of DSP processing for both sides.  The current problem is that although processor speeds are measured in gigahertz nowadays, the interface with the analog world hasn't yet reached those speeds. This means that direct waveform creation is limited to low frequencies (which, for communications, is still fearfully high compared to frequencies 'normal' analog designers worry about).  However, if I read my articles correctly this as still allow removal of some of the intermediate-frequency hardware present in most radios.  In the future it may be possible to dispense with more of the hardware.&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;If this is possible, why stick to base 2? If we can have a unique value for each measurable amplitude, data transfer rates would skyrocket. Imagine transferring data with base 1024, or even higher. If we could accurately sample the wave (each oscillation), I don't see why the rate of transfer could be equal to the frequency of the wave times base divided by 2 bits per second (this is probably not correct mathing). &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;You're right that it's not perfect but you definitely have the basic idea down.  To give an example we'll stick with Amplitude Modulation.  When you're trying to transmit 0 or 1 using AM it's called &lt;a href=&quot;http://www.technologyuk.net/telecommunications/telecom_principles/amplitude_modulation.shtml&quot; rel=&quot;nofollow&quot;&gt;On-Off-Keying&lt;/a&gt; (link goes to a site with nice pictures and a description).  This works by modulating a pure digital signal - 5v is '1', 0v is '0'.  You're right that if you have a number of voltage levels you can send more data at once - this is called &lt;a href=&quot;http://setup-wireless.blogspot.com/2008/11/wireless-keying-methods.html&quot; rel=&quot;nofollow&quot;&gt;Amplitude Shift Keying&lt;/a&gt; (another nice description with picture).  As you can see, there's multiple levels of voltage for various combinations of bits - 2 bits gives four different voltage levels, 3 gives 8, etc.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The problem with this and other similar schemes is not theoretical but practical - in a communication channel with noise it's very likely you'll have trouble figuring out what exactly was sent.  It's just like with analog signals: if my only valid voltage levels are 0 and 5V then if I get 4.3V out I can be reasonably sure it should be 5V.  If I have 1024 valid voltage levels then it gets a lot harder to determine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also note that you're not limited to Amplitude Modulation - the same techniques can be applied to Phase Modulated signals (similar to FM) or you can step into the realm of Frequency Shift Keying where distinct frequencies represent bits (ie, if you want to transmit '3' in binary that might mean sending a 3KHz sine wave and a 6KHz sine wave, then separating them at the receiving end where sending '1' might just be the 3KHz sine wave). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And these techniques are already in wide use - GSM cell phones use a form of Frequency Shift Keying called Gaussian Minimum Shift Keying.  Although I do want to correct one incorrect idea you may have:  modulation is still used in all of these schemes.  The opposite of a modulated signal is a baseband signal (like a bitstream from a serial port).  To communicate at any distance over the air you need modulation, period.  It's not going away, but how we generate the modulated waveform will change.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suggest you take a class in Communication Theory if you can - it sounds like you've got the knack for it.  &lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-17T19:15:43.410" CommentCount="2" />
  <row Id="14376" PostTypeId="1" CreationDate="2011-05-17T19:18:28.673" Score="1" ViewCount="95" Body="&lt;p&gt;I'm trying to make a fully configurable stepper motor controller by directly driving the H-bridges with the MCU, like an Atmel Atmega or other MCU, and use current feedback with the built in ADC, while using the PWM to create a current feedback loop (the ADC would measure across a sense resistor). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to get the basics down of what is required to accomplish this. I need to be able to support microstepping as well. I've been looking at the datasheets of the Allegro and TI stepper controller IC's, and have a basic idea of what it needs to do, but the implementation confuses me a bit. I can't find any other projects that accomplish this. It seems that nobody else uses microstepping, or nobody uses a current feedback loop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any open source projects that accomplish this task? If so, where can I find the source code and schematics of these projects?&lt;/p&gt;&#xA;" OwnerUserId="4288" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-19T19:34:22.603" LastActivityDate="2011-05-19T19:34:22.603" Title="Stepper Motor Microstepping with an MCU or Arduino without dedicated Microstepping IC Controller" Tags="&lt;arduino&gt;&lt;microcontroller&gt;&lt;atmega&gt;&lt;stepper&gt;&lt;stepper-motor&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="14377" PostTypeId="2" ParentId="14374" CreationDate="2011-05-17T19:19:56.707" Score="0" ViewCount="" Body="&lt;p&gt;I found what I was looking for on Motorola&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.motorola.com/Business/US-EN/Business+Product+and+Services/RFID/RFID+Readers&quot; rel=&quot;nofollow&quot;&gt;http://www.motorola.com/Business/US-EN/Business+Product+and+Services/RFID/RFID+Readers&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4287" LastActivityDate="2011-05-17T19:19:56.707" CommentCount="1" />
  <row Id="14378" PostTypeId="2" ParentId="14376" CreationDate="2011-05-17T19:25:37.630" Score="1" ViewCount="" Body="&lt;p&gt;The Microchip dsPIC motor control DSCs support micro-stepping (down to 1/64 of a step):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/01307A.pdf&quot; rel=&quot;nofollow&quot;&gt;http://ww1.microchip.com/downloads/en/AppNotes/01307A.pdf&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Closed loop current control is supported.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-17T20:05:49.497" LastActivityDate="2011-05-17T20:05:49.497" />
  <row Id="14380" PostTypeId="1" AcceptedAnswerId="14382" CreationDate="2011-05-17T21:37:04.217" Score="-1" ViewCount="103" Body="&lt;p&gt;Has anyone hacked an IOS cable and knows what data is going in and out of which wire. Maybe a diagram of an iphone cut cable?&lt;/p&gt;&#xA;" OwnerUserId="3947" LastActivityDate="2011-05-27T01:09:41.617" Title="Ipod/Iphone/Ipad cable hack" Tags="&lt;usb&gt;&lt;data&gt;&lt;iphone&gt;" AnswerCount="1" CommentCount="4" FavoriteCount="1" />
  <row Id="14381" PostTypeId="2" ParentId="13985" CreationDate="2011-05-17T21:59:47.683" Score="2" ViewCount="" Body="&lt;p&gt;Sometimes the artwork is related to the codename of the project.  Like maybe this power supply project was called &quot;pacific storm&quot; or something like that.&lt;/p&gt;&#xA;" OwnerUserId="3726" LastActivityDate="2011-05-17T21:59:47.683" />
  <row Id="14382" PostTypeId="2" ParentId="14380" CreationDate="2011-05-17T22:05:12.290" Score="3" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://pinouts.ru/PortableDevices/ipod_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;Pinouts.ru&lt;/a&gt; has a great description of the connector.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://ipl.derpapst.eu/wiki/Apple_Accessory_Protocol&quot; rel=&quot;nofollow&quot;&gt;iPodLinux wiki&lt;/a&gt; has a great page describing the serial protocol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the connector diagram (with the blank side of the connector facing up):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/lJlR4.gif&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Pins 12 and 13 are Tx and Rx, respectively. Rx and Tx are TTL level. Pin 1 is GND, and pin 21 is serial enable. To enable the serial port, tie a 6.8 kΩ resistor to GND.&lt;/p&gt;&#xA;" OwnerUserId="3556" LastEditorUserId="3556" LastEditorDisplayName="" LastEditDate="2011-05-27T01:09:41.617" LastActivityDate="2011-05-27T01:09:41.617" CommentCount="6" />
  <row Id="14383" PostTypeId="1" CreationDate="2011-05-18T00:40:46.163" Score="0" ViewCount="41" Body="&lt;p&gt;Does anyone know where to order the two wire connectors apple uses on its motherboards for e.g. the hard-drive temperature sensor or power button on the mac mini.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think I can just make out the part number mxl-71, but I haven't found any listings where I can buy them,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks,&lt;/p&gt;&#xA;" OwnerUserId="4293" LastActivityDate="2011-05-18T00:40:46.163" ClosedDate="2011-05-18T00:42:28.340" Title="Apple 2 wire connectors" Tags="&lt;connector&gt;" CommentCount="3" />
  <row Id="14384" PostTypeId="2" ParentId="14370" CreationDate="2011-05-18T01:48:41.763" Score="1" ViewCount="" Body="&lt;p&gt;You probably mean like &lt;a href=&quot;http://en.wikipedia.org/wiki/Constellation_diagram&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Having more than 2 signal levels is a very well known technique, the drawback is the lower signal-to-noise ratio.  But a good error-correcting scheme can use the extra bits to remove more errors than were added by the decreased signal-to-noise ratio, so this definitely can increase performance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;No clue why you say modems don't do this, they most certainly do.  V.90 has a HUGE constellation.&lt;/p&gt;&#xA;" OwnerUserId="1743" LastActivityDate="2011-05-18T01:48:41.763" />
  <row Id="14385" PostTypeId="1" AcceptedAnswerId="14389" CreationDate="2011-05-18T02:48:53.130" Score="1" ViewCount="82" Body="&lt;p&gt;From what I know, potentiometers vary an analog current with an input usually in the form of a knob. And transistors vary an analog current with an input in the form of a smaller current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any practical difference between the two other than one varies between the position of a knob and the other varies between a smaller current?&lt;/p&gt;&#xA;" OwnerUserId="4161" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-18T03:30:26.680" LastActivityDate="2011-05-18T08:39:58.837" Title="Potentiometer vs. Transistor" Tags="&lt;transistor&gt;&lt;potentiometer&gt;" AnswerCount="3" FavoriteCount="1" />
  <row Id="14386" PostTypeId="2" ParentId="14385" CreationDate="2011-05-18T03:34:24.270" Score="1" ViewCount="" Body="&lt;p&gt;A potentiometer varies a voltage, rather than a current. You presumably mean a rheostat, a BJT is a current-operated device. The word transistor was coined from &quot;transfer resistor&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transistor operation is a bit more complex than simply varying the setting of a rheostat. The Art of Electronics uses &lt;a href=&quot;http://books.google.com/books?id=bkOMDgwFA28C&amp;amp;pg=PA64&amp;amp;lpg=PA64&amp;amp;dq=art%20of%20electronics%20transistor%20man&amp;amp;source=bl&amp;amp;ots=F38kVKf-Yt&amp;amp;sig=wbtHVRb3Buh9WB6KQKbp2xDX-0c&amp;amp;hl=en&amp;amp;ei=Mz3TTf29LZCp8APGsuHjCg&amp;amp;sa=X&amp;amp;oi=book_result&amp;amp;ct=result&amp;amp;resnum=1&amp;amp;ved=0CBkQ6AEwAA#v=onepage&amp;amp;q&amp;amp;f=false&quot; rel=&quot;nofollow&quot;&gt;this cartoon&lt;/a&gt; with a &quot;Transistor man&quot; to explain how a transistor works:&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-18T08:39:58.837" LastActivityDate="2011-05-18T08:39:58.837" CommentCount="2" />
  <row Id="14387" PostTypeId="1" CreationDate="2011-05-17T20:07:31.620" Score="2" ViewCount="60" Body="&lt;p&gt;I'm trying to evaluate the quality of an 8b/10b encoded data stream (Gigabit Ethernet, 1.25 gigabits/sec). Without doing clock recovery from the data stream, I want to measure jitter (et al) with a plain oscilliscope. Is there any 8b data stream I can send which ends up as a regular square wave in 10b format? I don't care it's divided or uneven duty cycle, as long as it's a regular grouping of 0's and 1's.&lt;/p&gt;&#xA;" OwnerUserId="4290" LastActivityDate="2011-05-18T14:03:28.020" Title="Alternating patterns in 8b/10b encoding" Tags="&lt;hardware&gt;&lt;clock&gt;&lt;ethernet&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="14388" PostTypeId="2" ParentId="14385" CreationDate="2011-05-18T04:12:52.800" Score="1" ViewCount="" Body="&lt;p&gt;Yes, a transistor is like a variable resistor, in that the resistance between collector-emitter or drain-source is variable.   It's like a valve, and either allows current to flow or blocks it from flowing.  (I don't like it when people say &quot;transistors are amplifiers&quot;.  They're a part used &lt;em&gt;to build&lt;/em&gt; amplifiers, but they can't do anything themselves, without a power supply, biasing circuitry, etc.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The difference from a potentiometer is that the resistance of the output is not directly proportional to the current.  It's more like a current-regulating valve.  It adjusts its resistance as well as possible so that the current at the output is proportional to the input.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-05-18T04:12:52.800" />
  <row Id="14389" PostTypeId="2" ParentId="14385" CreationDate="2011-05-18T04:57:14.903" Score="1" ViewCount="" Body="&lt;p&gt;They are entirely different. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any resistor is a linear device, a transistor is nonlinear. A linear device has a linear relationship between voltage and current, simply put. Transistors show very much more complex behavior. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One is an interface, the other not. You cannot twiddle a transistor to change its characteristics. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A potentiometer is used to change a setting of a device, permanently at production, or during use. As long as it is not touched, the setting stays the same, being a passive device. Transistors can't be used to do that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A transistor, being an active device, puts some of its characteristics, say the output resistance in relation to one of its inputs, say the collector current. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A transistor does exhibit resistance in the sense there is a voltage and a current, and when I measure those, it looks like a resistance. But when you change the CE-voltage, the current will not change in the same ratio. Say, you double CE-voltage, you will not get double the current, but rather nearly the same current mostly, making it a differential resistance. On any resistor, you would get a linear response, double voltage ==&gt; double current. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This leads to the possibility of self-feedback on a transistor, making it possible to really regulate something, say in a constant current source. Twice the voltage, same current? Completely impossible with only passive devices, no resistor can do that. &lt;/p&gt;&#xA;" OwnerUserId="3438" LastActivityDate="2011-05-18T04:57:14.903" CommentCount="1" />
  <row Id="14390" PostTypeId="1" CreationDate="2011-05-18T05:31:01.550" Score="0" ViewCount="38" Body="&lt;p&gt;Hi, i am trying to control intensity of a 20-50W halogen lamp operating at 24V through a POT. my concerned is current passing through POT (which would be between 1A to 2.5A). what kind of POT should i look for? also how can i identify the POT's current rating?&lt;/p&gt;&#xA;" OwnerUserId="4296" LastActivityDate="2011-05-18T10:32:30.013" Title="Potentiometer current rating" Tags="&lt;potentiometer&gt;&lt;current-measurement&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="14391" PostTypeId="1" AcceptedAnswerId="14403" CreationDate="2011-05-18T05:37:00.360" Score="1" ViewCount="56" Body="&lt;p&gt;I am trying to repair a Nokia X6 headset in which one earpiece is not working. Any help on the questions below would be greatly appreciated.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is there a way to test the earpieces with a multimeter to identify whether it has a problem?&lt;/li&gt;&#xA;&lt;li&gt;How can I check the connectivity from earpiece to the headphone jack? Can I simply check this by connecting one end of multimeter to the wire at the earpiece and the other end to the TRS connector?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="4295" LastEditorUserId="1486" LastEditorDisplayName="" LastEditDate="2011-05-18T18:46:47.857" LastActivityDate="2011-05-27T20:46:52.547" Title="Nokia X6 headphone not working" Tags="&lt;audio&gt;&lt;speakers&gt;" AnswerCount="2" />
  <row Id="14392" PostTypeId="2" ParentId="14387" CreationDate="2011-05-18T06:57:14.520" Score="1" ViewCount="" Body="&lt;p&gt;Alternating pattern for 8b10b encoding is D10.2 symbol. &lt;a href=&quot;http://en.wikipedia.org/wiki/8b/10b_encoding&quot; rel=&quot;nofollow&quot;&gt;Check out table in wikipedia&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However this may not be what you want as for example gigabit Ethernet of the 1000BASE-T flavor uses PAM-5 modulation with data scrambling instead of NRZ with 8b10b encoding (again &lt;a href=&quot;http://en.wikipedia.org/wiki/Gigabit_Ethernet&quot; rel=&quot;nofollow&quot;&gt;Wikipedia is helpful&lt;/a&gt;). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also end result will depend in which protocol layer you are injecting test data as different protocol layers will add/remove/modify data.&lt;/p&gt;&#xA;" OwnerUserId="1471" LastEditorUserId="1471" LastEditorDisplayName="" LastEditDate="2011-05-18T07:02:16.603" LastActivityDate="2011-05-18T07:02:16.603" CommentCount="3" />
  <row Id="14393" PostTypeId="1" CreationDate="2011-05-18T07:10:51.047" Score="4" ViewCount="232" Body="&lt;p&gt;Hi Guys,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm doing a project where it requires to control 10,000 I/O.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5000 output - For 5000 LED, where only 1 LED will be light up at one time&lt;/p&gt;&#xA;&#xA;&lt;p&gt;5000 input - For 5000 sensor, where it'll sense the presence of an object.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically , i'm doing a storage system (something similar to pigeon hole) whereby, small box will be placed in this pigeon hole. Currently i have about 5000 boxes placed over 20 racks. Each rack has 250 hole (10 coloumns x 25 rows). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each of this holes will have one LED and one sensor. therefore, i need 5000 LED &amp;amp; 5000 sensors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;all sensors and LED will be connected to a system. When i need to place the box in the pigeon hole, i'll scan the barcode of the box and register it in the system. The system will then look for empty slot in any racks and light up the LED. I'll placed the box in the pigeon hole and the LED turn off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If i need to retrieve any box, i would then enter the box number and the LED of the exact location would light up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Not really sure how to start. Would like to know what kind of hardware that have such quantity of I/O ports.&lt;/p&gt;&#xA;" OwnerUserId="4297" LastEditorUserId="4297" LastEditorDisplayName="" LastEditDate="2011-05-19T03:38:44.180" LastActivityDate="2011-05-19T05:28:03.263" Title="Controlling 5000 LED" Tags="&lt;led&gt;&lt;multiplexing&gt;" AnswerCount="6" CommentCount="2" />
  <row Id="14394" PostTypeId="2" ParentId="14390" CreationDate="2011-05-18T07:21:27.663" Score="3" ViewCount="" Body="&lt;p&gt;I doubt you will find a suitable potmeter. Standard carbon potmeters allow only a few mA, and even wirewound potmeters won't take 10 W. Because that's what we're talking about. The power dissipated in the potmeter will be at a maximum when the lamp power is set to 25%, but the current will be at a maximum when the lamp power is set to 99%. Also control is anything but linear.&lt;br&gt;&#xA;A (linear or rotation) rheostat may work, but they're expensive and not easy to use.&lt;br&gt;&#xA;I'd suggest to look for a low voltage dimmer, that's what they're for.  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-18T10:32:30.013" LastActivityDate="2011-05-18T10:32:30.013" />
  <row Id="14395" PostTypeId="2" ParentId="14393" CreationDate="2011-05-18T07:42:38.893" Score="1" ViewCount="" Body="&lt;p&gt;It's really hard to come up with clear recommendations without a more precise idea of what the entire system is supposed to be doing, or how the leds and sensors should be arranged, but I'll give it a try.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are not going to find a single component with 10000 digital IO ports, and even if you did the driver/buffering/biasing circuitry for the leds and sensors would take up a huge amount of real estate on the board. Your best bet is to divide and conquer -- create a number of &quot;tiles&quot; that handle a specific subtask and connect them together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, if the leds and the sensors need to be co-located, each tile could have say 100 leds and 100 sensors, (de)-multiplexers and a simple microcontroller. Then you'd assemble 50 of these tiles, bringing the total up to 5000 leds and 5000 sensors. Then you connect each of these tiles to a &quot;mother board&quot; that can address the individual boards, talk to the microprocessor on them and write/read the leds and the sensor values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the main design decisions will be the &quot;power&quot; of the mother system, as well as the interconnection circuit. For example, if you are willing to control the thing from a laptop (or similar), you could use USB as interconnection. You can then run a software USB stack such as VUSB on the tiles to keep the cost down. Other options could be CAN, I2C and even Ethernet. Again, the specifics of your system dictate what to use.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For specific uses there are significant shortcuts available. For example, if the leds are used as a display, you can probably drive them from a single microcontroller using a matrix set-up and a simple frame-buffer.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-05-18T07:42:38.893" CommentCount="1" />
  <row Id="14396" PostTypeId="2" ParentId="14393" CreationDate="2011-05-18T07:43:12.623" Score="7" ViewCount="" Body="&lt;p&gt;The best approach is to place your LEDs in a 71x71 matrix. Since only 1 LED needs to be lit at any time you can use demultiplexers for both rows and columns. For the rows you want 1 line low, for the columns 1 line high.&lt;br&gt;&#xA;One solution is to use nine 74HC138s for the rows, controlled by 7 address lines (2^6 &amp;lt; 71 &amp;lt; 2^7). You'll need some additional logic to derive the control inputs for each 74HC138 from this address. For the columns you'll need 74HC238s, which is similar to the 74HC138, but with its output active high. So you'll have a total of 14 address lines.&lt;br&gt;&#xA;Another approach is to use a CPLD. 14 address lines in, 71 columns + 71 rows out. That's 156 I/Os. Altera has a few MAX3000 devices that fit the bill.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;If you don't have a compact presentation for the LEDs like a synoptical panel, you may want to drive them with a higher current for better visibility. In that case you'll need extra transistors on the outputs.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-18T08:47:50.290" LastActivityDate="2011-05-18T08:47:50.290" CommentCount="3" />
  <row Id="14397" PostTypeId="2" ParentId="14393" CreationDate="2011-05-18T08:43:56.250" Score="2" ViewCount="" Body="&lt;p&gt;Whooo, boy... This will not be a cheap project!  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I agree with Ranieri on the general concept of breaking the project down into repeated &quot;tiles&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given that you have 20 racks of 10 columns x 25 rows; I suspect what you'll want is a master controller for each rack (which would also deal with power distribution) paired with a &quot;shelf unit&quot; for each row, responsible for driving LED's for the 10 columns and to sense the box.  The master controller could also drive a master light at the top of the rack, so that the destination rack could easily be spotted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Considering the distances involved, I don't think you should use USB as your interconnect to the racks -- USB doesn't like to drive long distances.  Instead, an isolated interface like Ethernet, or opto-isolated ala MIDI is probably the better bet.  Interfacing within the rack, however, could be done with pretty much any approach.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-18T08:43:56.250" CommentCount="2" />
  <row Id="14398" PostTypeId="1" CreationDate="2011-05-18T08:44:56.403" Score="0" ViewCount="66" Body="&lt;p&gt;I just obtained o solar panel which shows a max output of about 18-19 votlts . I put it in partial shade to get an output of about 2.7 volts and connected it to an LED ensuring the correct positive and negative legs. But the LED failed to light. Other small appliances and toys using 3-6 volts also failed to work. Any suggestions ?&lt;/p&gt;&#xA;" OwnerUserId="4298" LastActivityDate="2011-05-18T10:22:26.010" Title="Solar panel and LED" Tags="&lt;solar-cell&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="14399" PostTypeId="2" ParentId="14398" CreationDate="2011-05-18T09:01:20.167" Score="2" ViewCount="" Body="&lt;p&gt;Use a series resistor with the LED to limit the current (220R, say), you could damage it otherwise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Measure the panel voltage when you have the item connected to it. You will probably find that it drops well below the 2.7V you were getting with no load. and is too low for it to work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Assuming that the panel has enough output in full sunlight, you will need a suitable regulator to power low voltage items. Switchers are often used, because of their high efficiency.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-18T09:52:41.423" LastActivityDate="2011-05-18T09:52:41.423" />
  <row Id="14400" PostTypeId="2" ParentId="11355" CreationDate="2011-05-18T09:34:59.390" Score="0" ViewCount="" Body="&lt;p&gt;One test worth trying is to remove the battery from your laptop and then see if your laptop will run from the power supply. If it does work your battery may be faulty and causing the problem.&lt;/p&gt;&#xA;" OwnerUserId="4299" LastActivityDate="2011-05-18T09:34:59.390" />
  <row Id="14401" PostTypeId="2" ParentId="14393" CreationDate="2011-05-18T09:48:07.743" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;https://www.xmos.com/applications/led-signs-and-displays&quot; rel=&quot;nofollow&quot;&gt;XMOS devices&lt;/a&gt; are often used to control very large arrays of LEDs. The LEDs are grouped into &quot;tiles&quot;, with each tile controlled by an XMOS chip and suitable shift registers. The XMOS devices can be connected to each other via high-speed XLinks or Ethernet, and can communicate with a host system via Ethernet or USB. XMOS devices can implement high-speed USB and Ethernet in software, just requiring suitable PHY chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 5,000 inputs can be interfaced in a similar fashion.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-18T10:03:38.173" LastActivityDate="2011-05-18T10:03:38.173" />
  <row Id="14402" PostTypeId="2" ParentId="14398" CreationDate="2011-05-18T10:22:26.010" Score="2" ViewCount="" Body="&lt;p&gt;Make sure the panel is supplying enough current. Current is what determines if an LED lights up, not voltage. That is to say, even if you have 1.7V (enough volts) but are only able to supply 0.3mA your LED won't light if it needs 1mA.&lt;/p&gt;&#xA;" OwnerUserId="4096" LastActivityDate="2011-05-18T10:22:26.010" />
  <row Id="14403" PostTypeId="2" ParentId="14391" CreationDate="2011-05-18T11:26:45.703" Score="1" ViewCount="" Body="&lt;ol&gt;&#xA;&lt;li&gt;You could identify whether there is any level of conductivity across the earpiece. This would tell you if something was definitively broken, but not definitively that it was working. You should compare values to the other working earpiece to know what you are looking for.&lt;/li&gt;&#xA;&lt;li&gt;Yes.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1486" LastActivityDate="2011-05-18T11:26:45.703" />
  <row Id="14404" PostTypeId="1" AcceptedAnswerId="14416" CreationDate="2011-05-18T11:32:37.103" Score="1" ViewCount="99" Body="&lt;p&gt;I have seen a few different ways of adding DC bias to an audio signal. I have simulated them and they all give me similar results, but I cant Figure out is why choose A over B or C. My audio source will be a Line Level Audio -2V to +2V AC passed through a 220uF coupling cap and then a low pass filter(RC, 2 pole). &#xA;edit -The signal will be read by an ADC&lt;/p&gt;&#xA;&#xA;&lt;p&gt;First way is using a Voltage divider, &lt;a href=&quot;http://electronics.stackexchange.com/questions/9160/simple-biasing-circuit&quot;&gt;Simple Biasing Circuit&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/zi93G.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is pretty self explanatory and i understand how it work. I have also seen this same design using Diode but could not find the example.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next example - &lt;a href=&quot;http://electronics.stackexchange.com/questions/5315/how-to-read-an-audio-signal-using-atmega328&quot;&gt;How to read an audio signal using ATMega328?&lt;/a&gt; - picture is from endolith's answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/qFZtK.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;another one that i have seen is &lt;a href=&quot;http://electronics.stackexchange.com/questions/2239/i-dont-quite-understand-this-fet-bjt-preamp-circuit&quot;&gt;I don&amp;#39;t quite understand this FET-BJT preamp circuit&lt;/a&gt;&#xA;And the schematic is for a pre-amp, and there are 2 versions and both add a bias.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/wWB8h.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is what is the best practice for adding the bias to an audio signal? what are some of the other ways to add a DC bias to the signal? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit/update&lt;/strong&gt; Looking at the answers - using the second one looks like it will work best for my application, using something like this- is there any other improvements I can make? other then Stable Vref/power rails.&lt;img src=&quot;http://i.stack.imgur.com/QNBaJ.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2060" LastEditorDisplayName="" LastEditDate="2011-05-19T07:58:41.237" LastActivityDate="2011-05-19T07:58:41.237" Title="DC biasing audio signal" Tags="&lt;audio&gt;&lt;dc&gt;&lt;bias&gt;" AnswerCount="3" CommentCount="6" />
  <row Id="14405" PostTypeId="1" AcceptedAnswerId="14408" CreationDate="2011-05-18T12:43:50.930" Score="4" ViewCount="83" Body="&lt;p&gt;I want to convert a $12V_{AC}$ power supply output to use $12V_{DC}$ to power some outdoor LEDs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The power supply as it stands will light the LEDs (with a slight flicker from the reverse polarity portion of the AC) but I have been told this may reduce the life of the LEDs having them reverse polarity for a long time. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So can someone suggest a simple rectifier circuit I could build or point me in the right direction of which one of these &lt;a href=&quot;http://www.maplin.co.uk/bridge-rectifiers-19088&quot; rel=&quot;nofollow&quot;&gt;Maplin rectifiers&lt;/a&gt; is suitable (I'm not sure what the specifications refer to exactly)?&lt;/p&gt;&#xA;" OwnerUserId="4301" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-18T12:54:53.123" LastActivityDate="2011-05-18T13:23:10.923" Title="Simple $12V_{AC}$ to $12V_{DC}$ Rectifier" Tags="&lt;power-supply&gt;&lt;diode&gt;&lt;rectifier&gt;&lt;convert&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="14406" PostTypeId="2" ParentId="14404" CreationDate="2011-05-18T13:08:04.787" Score="2" ViewCount="" Body="&lt;p&gt;The first circuit, the simple resistor divider, is by far the easiest, quickest, and cheapest solution.  It is also the solution that most audio circuits use.  Unless you are wanting pro-audio levels of performance, this is the method that I would recommend.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;correct&quot; solution would be to have a separate power rail that is at the bias voltage.  Run your audio signal through a DC blocking cap then have a resistor to the bias power rail.  This approach has less noise and harmonic distortion than the simple resistor-divider-- although the difference in performance is only important for those in the pro-audio world and not worth bothering with for most.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One case where the &quot;correct&quot; solution is worth the trouble for the average circuit is when the ADC itself provides the bias voltage rail.   Some ADC's will output that voltage and all you have to do is use it.  This is nice because you can get better precision than any other solution.  Sometimes I have had issues, however, where I had to take this output from the ADC and run it through a unity gain op-amp based buffer so it had the drive strength to work properly.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other two solutions you mention would work, but I wouldn't bother.  They are somewhat tweaky and don't offer any important benefits that the simple resistor-divider or the &quot;correct&quot; solutions provide.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-18T13:08:04.787" />
  <row Id="14407" PostTypeId="2" ParentId="14404" CreationDate="2011-05-18T13:08:30.997" Score="0" ViewCount="" Body="&lt;p&gt;The simplest method is the first image you linked to. It will do the job, but has a big draw back for your application. If your supply lines have any noise on them, the noise will be added to the signal you are trying to measure.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second method is almost identical to the first method. It's big advantage over the first method is that noise on the supply lines wont have as big of an effect on the signal itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The third method is over kill for what you are wanting to do. It is designed to give higher power outputs, but since you are just reading it with an ADC there is no reason you need it.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-18T13:08:30.997" CommentCount="1" />
  <row Id="14408" PostTypeId="2" ParentId="14405" CreationDate="2011-05-18T13:09:21.387" Score="6" ViewCount="" Body="&lt;p&gt;You may want to have a look at the answers to &lt;a href=&quot;http://electronics.stackexchange.com/questions/12390/using-a-transformer-to-step-down-230v-to-12v&quot;&gt;this question&lt;/a&gt;.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Applying AC to a LED is not a good idea. The flicker is not the main problem (may be hardly visible), but LEDs have a limited reverse voltage, usually about 5V. So the 12V you're using is way too high and may destroy your LED.&lt;br&gt;&#xA;What you need is a rectifier, followed by a capacitor (to flatten out the rectified voltage). You can use a rectifier like in your Maplin link, or use discrete diodes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/rbHb2.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;br&gt;&#xA;1A diodes like 1N4001 are standard and will do nicely for a few standard LEDs. For the capacitor I use 2000uF/A as a rule of thumb, so if your LEDs consume 100mA you could use a 220uF/25V electrolytic capacitor. Be sure to place the capacitor correctly; it may explode if you reverse it.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DC voltage will be about 15V (12V * sqrt(2) - 2V), so depending on the type of LED you're using it's a good idea to place a number of them in series, otherwise you'll have a big voltage drop over your series resistor = less efficient.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-18T13:23:10.923" LastActivityDate="2011-05-18T13:23:10.923" />
  <row Id="14409" PostTypeId="2" ParentId="2086" CreationDate="2011-05-18T13:12:59.847" Score="0" ViewCount="" Body="&lt;p&gt;I haven't any of these toys but I saw this requirement for a  TFT/LCD module including an SD slot :&#xA;&quot;You must use a micro SD card that supports the SPI interface, and is 2GB or less. Please note that not all uSD cards support SPI.&quot;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.robotshop.com/eu/4d-systems-3-2-qvga-touch-screen-lcd-3.html&quot; rel=&quot;nofollow&quot;&gt;http://www.robotshop.com/eu/4d-systems-3-2-qvga-touch-screen-lcd-3.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4302" LastActivityDate="2011-05-18T13:12:59.847" />
  <row Id="14410" PostTypeId="2" ParentId="14393" CreationDate="2011-05-18T13:21:57.743" Score="0" ViewCount="" Body="&lt;p&gt;There are alternatives&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;you can make separate modules for each rack, and interconnect them via LAN. Each module will control 250 LEDs.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;and / or&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;you can control LEDsin a 3D matrix. Since each LED has only 2 terminals, you can add a third one by using a transistor. The led will light up only if the the collector, emitter and the base are correctly powered. The 3D matrix requires only 52 I/Os (17 * 17 * 18) for controlling 5000 LEDs, instead of 142 (71 * 71).&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;In the meanwhile I think you can play with the &lt;a href=&quot;http://www.seeedstudio.com/depot/rainbowduino-led-driver-platform-plug-and-shine-p-371.html&quot; rel=&quot;nofollow&quot;&gt;Rainbowduino&lt;/a&gt; and the &lt;a href=&quot;http://www.seeedstudio.com/depot/60mm-square-88-led-matrix-super-bright-rgb-p-113.html?cPath=163_165&quot; rel=&quot;nofollow&quot;&gt;8*8 RGB LED Matrix&lt;/a&gt; which controls 192 LEDs (3 * 8 * 8).&lt;/p&gt;&#xA;" OwnerUserId="1298" LastActivityDate="2011-05-18T13:21:57.743" />
  <row Id="14411" PostTypeId="1" CreationDate="2011-05-18T13:45:04.380" Score="4" ViewCount="113" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm designing a little dev board for FPGA experimentation using the Cyclone IV EP4CE10 but I am having a bit of trouble estimating the power requirements. I understand this depends almost completely on the usage and configuration of the device but since I'm a bit new to this and really have no idea how and what I'm going to be using it for, (because, you know, it's a dev board) I could use some advice on what would be &quot;enough&quot; for the different power rails. I won't be doing anything extreme, I believe, but I would like to have a bit of headroom for experimentation.&lt;/p&gt;&#xA;" OwnerUserId="4303" LastActivityDate="2011-05-18T14:34:15.683" Title="How can I design my FPGA power supply if I don't know how it will be used exactly?" Tags="&lt;power&gt;&lt;fpga&gt;&lt;current&gt;" AnswerCount="3" />
  <row Id="14412" PostTypeId="2" ParentId="14387" CreationDate="2011-05-18T14:03:28.020" Score="0" ViewCount="" Body="&lt;p&gt;I think that I've found that the 10b words are selected specifically to avoid this kind of pattern. I looked at the 8b/10b tables for an hour or so before I gave up and determined it was going to have a very similar solution as the MU puzzle.&lt;/p&gt;&#xA;" OwnerUserId="4290" LastActivityDate="2011-05-18T14:03:28.020" CommentCount="2" />
  <row Id="14413" PostTypeId="2" ParentId="14411" CreationDate="2011-05-18T14:08:33.137" Score="0" ViewCount="" Body="&lt;p&gt;National Semi's &lt;a href=&quot;http://www.national.com/analog/power/simple_switcher&quot; rel=&quot;nofollow&quot;&gt;SIMPLE SWITCHER online tool&lt;/a&gt; (&quot;WEBENCH designer&quot;) allows you to design a power supply for a specific FPGA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Beyond that you could search online for designs/schematics of other similar dev boards to see what they used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, I have a mini/barebones FPGA board based on the EP2C5T144 (from eBay); I believe the 3.3V regulator it uses is rated at around 800mA. Compared to the big Altera DE2 board I have which is loaded full of all sorts of I/O devices, it uses an LM2676 3.3V switching regulator rated at 3A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm still pretty new to this too so I don't know all the fancy equations to calculate FPGA power requirements. Also, I believe there's some sort of power estimator tool in Quartus II, but that's proably specific to a specific design/configuration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hopefully the above gives you some frame of reference.&lt;/p&gt;&#xA;" OwnerUserId="2654" LastActivityDate="2011-05-18T14:08:33.137" CommentCount="4" />
  <row Id="14414" PostTypeId="2" ParentId="14411" CreationDate="2011-05-18T14:12:27.363" Score="3" ViewCount="" Body="&lt;p&gt;How about using Altera's tools for that? I've no practical experience here (I've some minor experience with Xilinx), but &lt;a href=&quot;http://www.altera.com/support/devices/estimator/pow-powerplay.jsp&quot; rel=&quot;nofollow&quot;&gt;PowerPlay Early Power Estimator&lt;/a&gt; seems helpful. You can chose &lt;code&gt;Maximum&lt;/code&gt; for the &lt;code&gt;Power Characteristic&lt;/code&gt;, if you want some headroom for experiments.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a real design for which you want to estimate the power consumption, you can use PowerPlay Power Analyzer, part of the Altera Quartus II system. They claim it has 20% accuracy. &lt;/p&gt;&#xA;" OwnerUserId="3564" LastActivityDate="2011-05-18T14:12:27.363" CommentCount="2" />
  <row Id="14415" PostTypeId="2" ParentId="14411" CreationDate="2011-05-18T14:34:15.683" Score="0" ViewCount="" Body="&lt;p&gt;You could use bench supplies for your prototype during development. When you know how much current the various supplies require you can design them for your production board, adding a bit of capacity for future enhancements.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-18T14:34:15.683" CommentCount="1" />
  <row Id="14416" PostTypeId="2" ParentId="14404" CreationDate="2011-05-18T15:12:06.320" Score="3" ViewCount="" Body="&lt;p&gt;Don't use the first circuit.  Any noise or spikes on the power supply will be mixed with your signal.  Because the bias point is connected directly to the signal, you can't filter out power supply noise without also filtering out the signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do use the second circuit.  It produces a mid-point voltage that is tightly coupled to ground, so the DC component is half the supply, but the AC component (noise and spikes) is filtered out by the capacitor.  That's not a complete circuit, though, you still need to connect it to your signal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+51.8012824668342+50+5.0+50%0Ar+288+64+288+160+0+10000.0%0Ac+288+64+432+64+0+1.0E-5+-2.5784348823538754%0Ar+432+64+432+160+0+10000.0%0AR+288+64+240+64+0+1+40.0+2.0+0.0+0.0+0.5%0AO+432+64+480+64+0%0Ag+288+160+288+176+0%0Ax+185+69+216+73+0+15+input%0AR+432+160+432+192+0+0+40.0+2.5+0.0+0.0+0.5%0Ao+3+64+0+34+2.0458691299350886+3.1966705155235764E-4+0+-1%0Ao+4+64+0+34+8.183476519740355+4.8828125000000005E-155+1+-1%0A&quot; rel=&quot;nofollow&quot;&gt;This is what you're trying to do&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/w2ntG.png&quot; alt=&quot;simple DC biasing&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The output is the same as the input, just shifted upward by 2.5 V.  The resistor on the input ensures that the input side of the capacitor is at 0 VDC, to prevent pops during connection.  The resistor on the output side of the AC coupling cap biases that side to the DC bias voltage.  If your circuit already has a clean, low impedance DC bias voltage source, connect to that.  Otherwise, you can use circuit #2 to generate the bias, &lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+51.8012824668342+50+5.0+50%0Ar+288+64+288+160+0+10000.0%0Ac+288+64+432+64+0+1.0E-5+-2.4847108304232224%0Ar+432+64+432+160+0+10000.0%0AR+288+64+240+64+0+1+40.0+2.0+0.0+0.0+0.5%0AO+432+64+480+64+0%0Ag+288+160+288+176+0%0Ar+352+240+352+304+0+10000.0%0Ar+352+304+352+368+0+10000.0%0AR+352+240+352+208+0+0+40.0+5.0+0.0+0.0+0.5%0Ag+352+368+352+384+0%0Ac+400+304+400+368+0+1.0E-5+2.521324539263428%0Aw+352+304+400+304+0%0Aw+352+368+400+368+0%0Aw+400+304+432+304+0%0Aw+432+160+432+304+0%0Ax+442+310+491+315+0+20+Vbias%0Ax+176+70+217+75+0+20+input%0Ao+3+64+0+34+2.187250724783012+3.4175792574734563E-4+0+-1%0Ao+4+64+0+34+8.749002899132048+4.8828125E-105+1+-1%0A&quot; rel=&quot;nofollow&quot;&gt;like this&lt;/a&gt;:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/d5GGK.png&quot; alt=&quot;Circuit showing DC biasing of an AC signal&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(The simulation takes a loong time to reach the DC bias value, though.)  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The DC bias voltage is produced by a voltage divider and capacitor to filter out power supply noise.  Note that if you use the same Vbias point for multiple signals, they can crosstalk through this point.  Larger bias cap reduces crosstalk.  Larger coupling capacitor improves low frequency response.  But make them too large and they'll take a long time to charge when you flip the power switch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 3rd diagram is not a biasing circuit; it's a microphone preamplifier.&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-18T15:30:00.407" LastActivityDate="2011-05-18T15:30:00.407" CommentCount="5" />
  <row Id="14417" PostTypeId="1" CreationDate="2011-05-18T16:20:55.950" Score="1" ViewCount="112" Body="&lt;p&gt;I need to provide a 60V/1A power source from a 12-24V input, -40 to 85 degC temperature range. Parametric searches for DC/DC converters at a couple online vendors don't seem to be turning up much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd prefer a simple chassis mount module of some kind, really.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there (readily available) DC/DC converters out there that satify these criteria? If not, how can I go about designing something that will work?&lt;/p&gt;&#xA;" OwnerUserId="1270" LastActivityDate="2011-05-25T07:35:16.460" Title="Step up DC voltage from 12-24V to 60V" Tags="&lt;power-supply&gt;&lt;smps&gt;" AnswerCount="2" />
  <row Id="14418" PostTypeId="2" ParentId="14417" CreationDate="2011-05-18T16:34:33.957" Score="4" ViewCount="" Body="&lt;p&gt;Nat Semi Simple Switcher? Try the on-line design software &lt;a href=&quot;http://www.national.com/analog/power/simple_switcher&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-18T16:34:33.957" CommentCount="2" />
  <row Id="14419" PostTypeId="2" ParentId="14417" CreationDate="2011-05-18T16:40:33.250" Score="4" ViewCount="" Body="&lt;p&gt;If you don't mind building the SMPS yourself, &lt;a href=&quot;http://tinyurl.com/69cnrm3&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; is a list of Linear Technology devices that match your criteria.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-18T16:40:33.250" CommentCount="2" />
  <row Id="14420" PostTypeId="2" ParentId="11048" CreationDate="2011-05-18T16:48:43.403" Score="2" ViewCount="" Body="&lt;p&gt;One difference not yet mentioned between devices intended for rheostats versus those intended for use as pots: if a device will be used as a rheostat, it is important that the wiper resistance be fairly small, and even more important that it be 'well-behaved'.  If the device will be used as a pot, and the amount of current flowing through the wiper will be minimal, wiper resistance is relatively unimportant.  A 100-ohm rheostat with a wiper resistance that had a wiper resistance of 10 ohms in some spots and 1,000 ohms in other spots would be totally useless.  A 100-ohm pot with such behavior could be just fine, however, if it was being used to drive a high-impedance input.  Note that such a pot would be roughly equivalent to a 1,000-ohm pot in parallel that had a 110-ohm fixed resistor tied between the ends.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-18T16:48:43.403" />
  <row Id="14421" PostTypeId="1" AcceptedAnswerId="14423" CreationDate="2011-05-18T18:53:36.340" Score="2" ViewCount="158" Body="&lt;p&gt;In an exam today I was asked to design 2 circuits that would keep an output turned on for 10 minutes. I used a 555 Timer and a PIC, but neither are the best solution if the time delay needs to increase. So what other options are there for creating long time delays, many hours/days of timing to a few milliseconds accuracy(1000's of a second)?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-05-18T19:18:07.580" LastActivityDate="2011-05-22T14:10:39.353" Title="Long Accurate Time Delay" Tags="&lt;timing&gt;" AnswerCount="3" CommentCount="2" />
  <row Id="14422" PostTypeId="1" CreationDate="2011-05-18T19:12:25.793" Score="2" ViewCount="111" Body="&lt;p&gt;I got a new camera, a Pentax KX, and am enjoying the movie mode, which not surprisingly eats batteries at a rate of about 1 alkaline AA per minute!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can you point to any examples on the web of people building a circuit to patch some large rechargeable battery (say my laptops Li-Ion) to an AA battery compartment?&lt;/p&gt;&#xA;" OwnerUserId="2375" LastActivityDate="2011-05-18T22:54:34.930" Title="Building an AA battery replacement" Tags="&lt;battery&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="14423" PostTypeId="2" ParentId="14421" CreationDate="2011-05-18T19:38:00.583" Score="7" ViewCount="" Body="&lt;p&gt;The best option for long time delays are Microcontrollers.  The are simple, inexpensive, and relatively easy to use.  Doing millisecond accuracy over days is easy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only trick to doing a multi-day timer is that you need to use two timers:  a hardware timer and a software timer.  For example:  Set the hardware timer to generate an IRQ every 1.0 mS.  In the ISR (interrupt service routine) increment a 32-bit counter on each IRQ.  So when this software counter gets to 1000 then 1 second has gone by.  Doing this will mean that the 32-bit counter will roll over at about 49.7 days.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can go longer than 49.7 days if you use a larger counter, like 48 or 64 bits.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The accuracy of this system will depend on the accuracy of the clock used for the microcontroller.  Most quartz crystal oscillators are good to about 100 ppm (parts per million), although 20 ppm crystals are readily available.  More accurate than 20 ppm is doable, but the cost goes up and the availability of parts goes down.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-18T19:38:00.583" CommentCount="3" />
  <row Id="14424" PostTypeId="2" ParentId="14355" CreationDate="2011-05-18T20:06:39.390" Score="3" ViewCount="" Body="&lt;p&gt;The headers used with XBee's are 2 mm pitch, instead of the more standard 0.100 inch pitch. Here's an example &lt;a href=&quot;http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtmXMEm8TaEVuQEcuZgVs6EVs6E666666--&quot; rel=&quot;nofollow&quot;&gt;datasheet&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://www.opencircuits.com/SFE_Footprint_Library_Eagle&quot; rel=&quot;nofollow&quot;&gt;Sparkfun Eagle library&lt;/a&gt; has footprints for both the 2mm 10 pin header and the actual XBee. The header part is M10 and the package is M102MM.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, &lt;a href=&quot;http://www.sparkfun.com/tutorials/110&quot; rel=&quot;nofollow&quot;&gt;this tutorial&lt;/a&gt; from Sparkfun shows step by step how to create a new part in Eagle.&lt;/p&gt;&#xA;" OwnerUserId="2827" LastEditorUserId="2827" LastEditorDisplayName="" LastEditDate="2011-05-19T06:20:04.680" LastActivityDate="2011-05-19T06:20:04.680" />
  <row Id="14425" PostTypeId="2" ParentId="14421" CreationDate="2011-05-18T20:12:27.480" Score="7" ViewCount="" Body="&lt;p&gt;The microcontroller is the way to go. Quartz crystals are known for their accuracy, but even that is relative. Standard crystals are 100 ppm, you pay extra for 20 ppm. 100 ppm doesn't sound too bad, but it's only 0.01%, and may give you an error of up to 8 seconds a day. Even the 20 ppm results in an error of 2 seconds.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The solution for timing long periods is to synchronize your timer to a high precision clock. DCF77 (Europe) and WWVB (North America) send a pulse every second, a timing derived from an atomic clock. You could count these second pulses for timing the longer periods and for sub-second timing rely on the crystal.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-18T20:12:27.480" CommentCount="1" />
  <row Id="14426" PostTypeId="2" ParentId="14422" CreationDate="2011-05-18T20:14:46.917" Score="2" ViewCount="" Body="&lt;p&gt;What you want to do is create a &quot;dummy battery&quot; that will fit inside the camera in place of the AA batteries and make contact with the battery contacts in that compartment. Here's an example of someone doing something similar: &lt;a href=&quot;http://www.lumika.org/gear_a2e_batts.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.lumika.org/gear_a2e_batts.htm&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Building the dummy battery for your camera is really just a mechanical issue. The electronics design part could come in if you were trying to supply power with a higher voltage and needed to regulate it down to match the voltage output from the AA batteries (most likely this is 3 V for the two AA batteries in series). This will depend on your camera and the external power source you decide to use.&lt;/p&gt;&#xA;" OwnerUserId="2827" LastActivityDate="2011-05-18T20:14:46.917" />
  <row Id="14427" PostTypeId="2" ParentId="14422" CreationDate="2011-05-18T22:40:28.670" Score="1" ViewCount="" Body="&lt;p&gt;Your K-x supports a AC adapter plug.  Find the appropriate plug, wire it up to any proper DC voltage (check the K-AC84 accessory to see what voltage it runs at) battery you like and go nuts.&lt;/p&gt;&#xA;" OwnerUserId="3778" LastEditorUserId="3778" LastEditorDisplayName="" LastEditDate="2011-05-18T22:54:34.930" LastActivityDate="2011-05-18T22:54:34.930" CommentCount="1" />
  <row Id="14428" PostTypeId="1" CreationDate="2011-05-18T23:05:42.717" Score="-1" ViewCount="45" Body="&lt;p&gt;Can anyone suggest a RF Front end operating in the 902-928MHz range with support for frequency hopping and preferably low cost development board? I know there are a lot more parameters involved than the ones mentioned, but I would like something well supported and with lots of code available online, like the nrf24l01 for the 2.4GHz range. Ultimately this front end would be connected to a FPGA, which will do the decoding, encoding and other DSP.&lt;/p&gt;&#xA;" OwnerUserId="4260" LastActivityDate="2011-05-18T23:05:42.717" ClosedDate="2011-05-19T00:13:17.323" Title="Suggestions for 902-928MHz RF Front end" Tags="&lt;rf&gt;" CommentCount="5" />
  <row Id="14429" PostTypeId="2" ParentId="14421" CreationDate="2011-05-18T23:35:34.100" Score="4" ViewCount="" Body="&lt;p&gt;Accuracy requires stability and calibration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Typically, you'll start out with a crystal that is already calibrated to a some degree of accuracy, with a known stability characteristic.  You then have to ensure that the accuracy and stability errors will meet your performance requirements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With a 100ppm device, you get up to roughly 5 minutes of drift per month.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you read various datasheets on battery-backed RTC's, they all will emphasize the need to choose a clock source that is stable over temperature, age, and voltage; and for long-term accuracy, the completed system should be calibrated to a know reference time source and adjusted -- many RTC's have a &quot;trim&quot; register that lets you add/subtract a few &quot;ticks&quot; over a period of time to adjust for the small variations between units.  You can use this technique with a MCU as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Separately, if your accuracy resolution is measured in terms of seconds, over a very long period of time, you can get reliable 60 Hz from the power line.  &lt;a href=&quot;http://en.wikipedia.org/wiki/Utility_frequency#Long-term_stability_and_clock_synchronization&quot; rel=&quot;nofollow&quot;&gt;(Wikipedia)&lt;/a&gt; - just make sure there's a secondary counter to handle blackouts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT --&lt;/p&gt;&#xA;&#xA;&lt;p&gt;BTW, I thought I recently saw a news article about NIST having developed a super-stable transportable atomic clock that sat inside the rear cargo space of a minivan; but I couldn't find it.  But during that process, I came across this &lt;a href=&quot;http://www.gizmag.com/portable-chip-scale-atomic-clock/18580/&quot; rel=&quot;nofollow&quot;&gt;interesting &quot;atomic clock&quot;&lt;/a&gt; that was recently announced.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT --&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Ah, I found the article &lt;a href=&quot;http://www.rdmag.com/News/2011/05/Manufacturing-Lasers-Super-Stable-Laser-Shines-In-Minivan-Experiment/?et_cid=1527169&amp;amp;et_rid=123697963&amp;amp;linkid=http://www.rdmag.com/News/2011/05/Manufacturing-Lasers-Super-Stable-Laser-Shines-In-Minivan-Experiment/&quot; rel=&quot;nofollow&quot;&gt;about a portable super-stable laser that would be used for a portable atomic clock&lt;/a&gt;!  This is not very practical for the most of us, but I thought it was an interesting piece.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastEditorUserId="3308" LastEditorDisplayName="" LastEditDate="2011-05-22T14:10:39.353" LastActivityDate="2011-05-22T14:10:39.353" CommentCount="10" />
  <row Id="14430" PostTypeId="1" CreationDate="2011-05-19T01:20:41.793" Score="5" ViewCount="128" Body="&lt;p&gt;I am a growing frustrated with the Art of Electronics.  It is such an approachable book in Chapter 1, and then in Chapter 2 it seems like the authors wanted to make it more textbook-like and they start dropping information in lieu of exercises.  I suppose this is really not a self-study book...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately I am one of those guys who has to understand the concepts, I cannot just blindly follow a formula.  In particular I am trying to understand output and input impedance of the emitter-follower.  The text gives a good breakdown of how the input impedance, the impedance looking into the base, is derived.  It then plops down the formula for output and says that it can also be computed...and then an exercise appears asking one to prove it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$Zout = \frac{(Zsource)}{(h_{fe} + 1)}$&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Show that the preceding relationship is correct.  &#xA;Hint: Hold the sourdce voltage fixed, and find &#xA;the change in output currrent for a given change&#xA;in output voltage.  Remember that the source voltage &#xA;is connected to the base through a series resistor.&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I don't really even know where to start.  I just jotted down a few formulas and started substituting...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$\begin{eqnarray*}&#xD;&#xA;  r_{out} &amp;amp;=&amp;amp; \frac{(\Delta V_{out})}{(\Delta I_{out})}\\&#xD;&#xA; &#xD;&#xA;      &amp;amp;=&amp;amp; \frac{(\Delta V_e) }{ (\Delta I_e)} \\&#xD;&#xA;&#xD;&#xA;      &amp;amp;=&amp;amp; \frac{(\Delta V_b - 0.6V) }{ (\Delta I_e)}\\ &#xD;&#xA;\end{eqnarray*}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$\begin{eqnarray*}&#xD;&#xA;  I_e &amp;amp;=&amp;amp; I_c + I_b \\&#xD;&#xA;     &amp;amp;=&amp;amp; (h_{fe} * I_b) + I_b\\ &#xD;&#xA;     &amp;amp;=&amp;amp; (h_{fe}+1) * I_b\\&#xD;&#xA;\end{eqnarray*}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$\Delta I_e = (h_{fe}+1) * \Delta I_b$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$r_{out} = \frac{(\Delta V_b) - 0.6 V } {(h_{fe} + 1) * \Delta I_b}$&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;Can I assume that 0.6 V is negligible and can I drop it?  If so,&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;$\begin{eqnarray*}&#xD;&#xA;    r_{out} &amp;amp;=&amp;amp;       \frac{(\Delta V_b)}{ (h_{fe} + 1) * (\Delta I_b)}\\&#xD;&#xA;&#xD;&#xA;     &amp;amp;=&amp;amp; \frac{(\Delta V_b)}{(\Delta I_b)} * \frac{1}{(h_{fe} + 1)} \\&#xD;&#xA;      &amp;amp;=&amp;amp; \frac{r_{source} }{ (h_{fe} + 1)}&#xD;&#xA;\end{eqnarray*}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I any where close in my derivation?  Are my assumptions about [$V_{out} = V_e$] and [$I_{out} = I_e$]valid?  And is it acceptable to drop the base-emitter junction voltage drop in my derivation?&lt;/p&gt;&#xA;" OwnerUserId="2059" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-19T01:49:03.823" LastActivityDate="2011-06-02T12:09:53.767" Title="Art of Electronics: Emitter-Follwer Zout" Tags="&lt;impedance&gt;&lt;emitter-follower&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="2" />
  <row Id="14431" PostTypeId="2" ParentId="14393" CreationDate="2011-05-19T05:28:03.263" Score="1" ViewCount="" Body="&lt;p&gt;Since you need to transfer the barcode to the central computing station, you have to set up a bus. Depending on how big your boxes are, distance plays a role in selection of the bus. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Analog cabling with LED multiplexing is no good idea on large area setups where the LEDs are not near each other (cabling effort, differing cabling resistance etc).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's suppose you want to keep it cheap. Maybe try I2C, and make it hierarchical. There would be router nodes that talk to the master computer, and route messages to and from the leaf nodes, of which there would be one per box. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;A leaf node can read the barcode, light a led, and perform various other features if needed, reading or sending messages to its router node. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This setup is probably in the same financial league as a central cabling for 5k LEDs, 5k Sensors, even if modularized. The cheapest AVR ATtiny4 with 4 GPIOs costs 0.6 EUR in numbers. &lt;/p&gt;&#xA;" OwnerUserId="3438" LastActivityDate="2011-05-19T05:28:03.263" />
  <row Id="14432" PostTypeId="2" ParentId="14430" CreationDate="2011-05-19T07:19:48.713" Score="3" ViewCount="" Body="&lt;p&gt;The standard way of doing this is to use small-signal AC analysis. Assume the transistor is biased in the forward-active region. Use the hybrid-pi model. Then place a test voltage/current source at the output node and ground the input. Measure the current/voltage of your test source and that tells you the output impedance. You can also find the input impedance that way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is basically the same as what the book is telling you to do, except that using the small signal model of the BJT allows you to turn problem into a linear circuit analysis problem which should be easy to do mechanically.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure what is wrong with your derivation but the 0.6V should somehow drop out because you're looking at the change in voltages and currents.&lt;/p&gt;&#xA;" OwnerUserId="3953" LastActivityDate="2011-05-19T07:19:48.713" CommentCount="3" />
  <row Id="14433" PostTypeId="1" AcceptedAnswerId="14531" CreationDate="2011-05-19T09:52:58.883" Score="4" ViewCount="132" Body="&lt;p&gt;When I read about Segway I always wonder how such precise control over the wheel motors can be achieved.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mean if the rider wants to go one foot forward, then one foot back, he leans forward, the motors start rotating the wheels, then he leans back and the motors change direction instantly and then when he's back he stands straight and the motors stop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Again, to achieve balancing motors will rotate in perfectly controlled manner at whatever speed is needed to balance the Segway.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From my experience with electric motors found on various stuff like power tools and sewing machines those are pretty hard to control precisely. For example, when a variable speed drill is started it just accelerates at whatever rate and actual rotation rate will largely depend on the load - whether I drill wood with a 2 millimeters bit  or hard steel with a 10 millimeters bit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How do systems like Segway achieve such precise control over electric motors?&lt;/p&gt;&#xA;" OwnerUserId="3552" LastActivityDate="2011-05-21T09:28:37.257" Title="How is precise control over motor as in Segway achieved?" Tags="&lt;motor&gt;&lt;control&gt;" AnswerCount="3" />
  <row Id="14434" PostTypeId="1" CreationDate="2011-05-19T10:43:50.383" Score="-1" ViewCount="37" Body="&lt;p&gt;Square up (https://squareup.com/) reads magnetic stripe cards through headphone jack on both Android and iOS.&#xA;I want to capture fingerprints on an Android phone. Can I capture fingerprints in the same way using a fingerprint scanner (UART/Serial)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am software engineer, but I have never done hardware programing. If this is achievable, whats the right methodology?&lt;/p&gt;&#xA;" OwnerUserId="4314" LastActivityDate="2011-05-19T10:43:50.383" ClosedDate="2011-05-19T11:07:36.237" Title="Can I connect fingerprint scanner (UART, Serial) through a headphone jack on Android?" Tags="&lt;serial&gt;&lt;uart&gt;&lt;android&gt;" CommentCount="4" />
  <row Id="14435" PostTypeId="1" AcceptedAnswerId="14446" CreationDate="2011-05-19T10:51:19.737" Score="3" ViewCount="116" Body="&lt;p&gt;My EDA software (PCAD, but I guess others do this too) adds thermal reliefs on vias in a copper pour. What's the use? Vias aren't soldered. (I &lt;em&gt;know&lt;/em&gt; why you use them on regular PTH pads) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/5Dj51.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-19T11:44:16.837" LastActivityDate="2011-05-19T13:00:25.600" Title="Why thermal reliefs on vias?" Tags="&lt;pcb&gt;" AnswerCount="3" />
  <row Id="14436" PostTypeId="2" ParentId="14435" CreationDate="2011-05-19T10:59:01.487" Score="2" ViewCount="" Body="&lt;p&gt;To ensure that the copper pour doesn't conduct the heat away when the board is soldered, which will result in bad solder joints. Vias are sometimes filled with solder, to increase reliability.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thermal reliefs are optional with the software I use; you can probably make them ordinary vias, if you wish. Tent them, if you don't want them soldered.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-19T11:39:46.630" LastActivityDate="2011-05-19T11:39:46.630" CommentCount="9" />
  <row Id="14437" PostTypeId="2" ParentId="12939" CreationDate="2011-05-19T11:38:02.733" Score="1" ViewCount="" Body="&lt;p&gt;This antenna is a modified form of the Yagi-Uda antenna.  A basic Yagi antenna consists of three sections.  A reflector, a driven element and a director.  This is illustrated here &lt;a href=&quot;http://www.eng.newcastle.edu.au/eecs/fyweb/Archives/1998/Macnamara/Image8.gif&quot; rel=&quot;nofollow&quot;&gt;http://www.eng.newcastle.edu.au/eecs/fyweb/Archives/1998/Macnamara/Image8.gif&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can clearly see each of these basic elements in the antenna you have purchased.  The reflector at the left of your image serves to increase the directivity of the antenna by focusing the beam pattern towards and along the axis of the smaller directors.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The driven element is the somewhat circular section in the middle that attaches to the Balun.  This element actually conducts the signal down the attached fly lead.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The directors are the short parallel elements that extend away from the driven element.  The width of the directors determines the frequency at which they enhance the directivity of the antenna.  A wideband antenna has many different width, parallel elements.  The spacing between the elements affects the phase and hence the beam pattern of the antenna.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Yagi's rely on the principles of phased arrays for the large directivity (apparent gain) that they offer.  The antenna you have purchased has taken this principle even further with its triple boom design.  The addition of more directors to the system with a phase difference in two axis allows greater manipulation of the beam pattern and directivity of the antenna.  The net result is an increase in the level of the received signal.&lt;/p&gt;&#xA;" OwnerUserId="4311" LastActivityDate="2011-05-19T11:38:02.733" />
  <row Id="14438" PostTypeId="1" CreationDate="2011-05-19T11:44:57.273" Score="1" ViewCount="51" Body="&lt;p&gt;Reviewing some material I thought I understood, but it turns out there's some subtlety I'm not getting.  The usual formula for calculating the Q of a non-ideal inductor is \$\frac{Xs}{Rs}\$, where Xs is the series reactance and Rs is the series resistance.  For a &lt;em&gt;parallel&lt;/em&gt; circuit, it's the inverse,  \$\frac{Rp}{Xp}\$.  The two are related by the equation \$Rp = (Q^2 +1)Rs\$, where Q is the unloaded Q of the element.  Consider a &lt;em&gt;non ideal&lt;/em&gt; parallel LC circuit.  You have an R and L in series, and this series combination is itself in parallel with a capacitor.  Using the above transformations, one can convert the series resistance into a value of parallel resistance, and then using the value of parallel resistance solve for a value of parallel inductance using the second formula above.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But then, what is the resonant frequency of the tuned circuit? Is it given by the original value of &lt;em&gt;series&lt;/em&gt; inductance, or the new value of &lt;em&gt;parallel&lt;/em&gt; inductance?  The texts I've read make the assumption that the reactance of the parallel inductance is the same as the series inductance, and working out the equations with the Laplace transform of the original circuit shows that the resonant frequency is solely determined by the value of the original capacitance and non-lossy inductance.  Indeed, it would hardly make sense to try to calculate a new resonant frequency based on this equivalent parallel inductance value, because the transformation is only valid at one frequency! So what's the significance of this new value of parallel inductance, then?  For low Qs it can be significantly larger than the original series value.  Does any of this make sense?&lt;/p&gt;&#xA;" OwnerUserId="4129" LastEditorUserId="3028" LastEditorDisplayName="" LastEditDate="2011-06-01T14:52:43.077" LastActivityDate="2011-06-02T12:13:55.963" Title="Series to Parallel inductance conversion" Tags="&lt;circuit&gt;&lt;rf&gt;&lt;analysis&gt;&lt;indutance&gt;" AnswerCount="1" />
  <row Id="14439" PostTypeId="2" ParentId="14433" CreationDate="2011-05-19T11:45:55.480" Score="-2" ViewCount="" Body="&lt;p&gt;According to &lt;a href=&quot;http://forums.segwaychat.com/archive/index.php/t-19196.html&quot; rel=&quot;nofollow&quot;&gt;this thread&lt;/a&gt; they use &lt;a href=&quot;http://en.wikipedia.org/wiki/Stepper_motor&quot; rel=&quot;nofollow&quot;&gt;stepper motors&lt;/a&gt;. That is, those found in printers, disk drivers, etc, but obviously as quite beefy versions, combined with accelerometers and some smart controller logic.&lt;/p&gt;&#xA;" OwnerUserId="1410" LastActivityDate="2011-05-19T11:45:55.480" CommentCount="2" />
  <row Id="14440" PostTypeId="1" CreationDate="2011-05-19T11:47:41.523" Score="4" ViewCount="208" Body="&lt;p&gt;Can someone care to explain - in plain English - what a transistor is and how it works. I know computers are full of these but don't know much about them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;P.S. I know about this site from another one in the family of StackExchange (I have no engineering background) and hoped someone might help me with this. Please don't link to the &lt;a href=&quot;http://en.wikipedia.org/wiki/Transistor&quot; rel=&quot;nofollow&quot;&gt;wiki&lt;/a&gt; explanation. I've read that and I'm more confused. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking for a 7 year old explanation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you!&lt;/p&gt;&#xA;" OwnerUserId="4315" LastActivityDate="2011-05-19T15:04:44.717" Title="Explain what is a transistor in plain English!" Tags="&lt;electronics&gt;&lt;transistor&gt;&lt;computers&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="3" />
  <row Id="14441" PostTypeId="2" ParentId="14435" CreationDate="2011-05-19T11:50:09.677" Score="1" ViewCount="" Body="&lt;p&gt;IPC2221 Section 9.1.3 says:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;9.1.3 Thermal Relief in Conductor Planes&lt;/strong&gt; Thermal relief is only&#xA;  required for holes that are subject to&#xA;  soldering in large conductor areas&#xA;  (ground planes, voltage planes,&#xA;  thermal planes, etc.). Relief is&#xA;  required to reduce soldering dwell&#xA;  time by providing thermal resistance&#xA;  during the soldering process&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I think most of times is not necessary to thermally relive a via.&lt;/p&gt;&#xA;" OwnerUserId="938" LastActivityDate="2011-05-19T11:50:09.677" />
  <row Id="14442" PostTypeId="1" CreationDate="2011-05-19T12:01:11.970" Score="5" ViewCount="95" Body="&lt;p&gt;&lt;a href=&quot;https://squareup.com/&quot; rel=&quot;nofollow&quot;&gt;Square up&lt;/a&gt; reads magnetic stripe cards through headphone jack on both Android and iOS. I want to capture fingerprints on an Android phone. Can I develop a hardware to capture fingerprints in the same way using a fingerprint scanner (UART/Serial)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to develop such hardware (like square) which can be used to capture fingerprints through the headphone jack. If it possible? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The fingerprint scanners are available with UART communication protocol. So is there a way to send the fingerprint image through the headphone jack by developing such connector?&lt;/p&gt;&#xA;" OwnerUserId="4314" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-05-19T12:45:40.560" LastActivityDate="2011-05-19T12:45:40.560" Title="How to make a fingerprint scanner (UART, Serial) for a headphone jack on Android?" Tags="&lt;serial&gt;&lt;uart&gt;&lt;android&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="14443" PostTypeId="2" ParentId="14440" CreationDate="2011-05-19T12:31:39.853" Score="6" ViewCount="" Body="&lt;p&gt;At a 7 year old level, a transistor is like a controllable valve or tap (or faucet for our US friends)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A small turn of the tap (or small increase in voltage between the base and the emitter) creates a large flow (or large voltage between the collector and emitter)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So at a very basic level it acts as an amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, in a computer it is generally used as a switch. Outside the small region where varying the base voltage drives a larger variation in the collector voltage it is effectively binary, so for allowed input voltages the output is always 0v or Vmax (this value depends on the power supply, type of transistor and circuit etc)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A bit more detail, while still not being too technical is on &lt;strong&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Transistor&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;&lt;/strong&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(and yes, I know I used flow and voltage in the same sentence:-)&lt;/p&gt;&#xA;" OwnerUserId="3525" LastActivityDate="2011-05-19T12:31:39.853" CommentCount="5" />
  <row Id="14444" PostTypeId="2" ParentId="14438" CreationDate="2011-05-19T12:33:23.753" Score="0" ViewCount="" Body="&lt;p&gt;You are confusing the Q of the inductance with the Q of the circuit. In a series LCR circuit, the Q of the inductor is the ratio of the voltage across the inductor to the voltage across the circuit. As you say, this is also the ratio of the inductive reactance to the resistance. In a circuit with series R &amp;amp; L in parallel with C, this relation also holds.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a parallel LCR circuit, the resistance is no longer a property of the inductor itself which is why you get a different definition for Q. The Q in this case is more a property of the circuit than the inductor. You cannot convert one circuit to the other although you could find two circuits with identical Q.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Laplace transforms of the impedance for (r + L) // C is ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$\frac{\frac{r}{LC}+\mathrm s\frac{1}{C}}{\mathrm s^2+\mathrm s\frac{r}{L}+\frac{1}{LC}}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;for which Q=\$\frac{1}{r}\sqrt{\frac{L}{C}}\$ (at resonance)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Laplace transform of the impedance for R // L // C is ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$\frac{\mathrm s\frac{1}{C}}{\mathrm s^2+\mathrm s\frac{1}{RC}+\frac{1}{LC}}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;for which Q=\$R\sqrt{\frac{C}{L}}\$ (at resonance)&lt;/p&gt;&#xA;" OwnerUserId="2234" LastEditorUserId="2234" LastEditorDisplayName="" LastEditDate="2011-06-02T12:13:55.963" LastActivityDate="2011-06-02T12:13:55.963" CommentCount="6" />
  <row Id="14445" PostTypeId="2" ParentId="14442" CreationDate="2011-05-19T12:45:02.153" Score="5" ViewCount="" Body="&lt;p&gt;It sounds like your question is, how do you go from a UART device to something that can be plugged into a microphone jack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://electronics.stackexchange.com/questions/12498/what-protocol-does-a-headphone-jack-use/12504#12504&quot;&gt;What protocol does a headphone jack use?&lt;/a&gt; should help you understand what is being done on the existing device that you are talking about.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is still a link missing for you though, that is the ability of turning UART into the audio itself. The easiest way to do this is to buy a microcontroller that you will place between the UART device and the Android device. All the microcontroller will do is read in any UART data and then convert it to what ever form you want the headphone jack to receive. You may also need to implement some handshaking between the microcontroller and the phone in order to know that the device you think is plugged in.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-19T12:45:02.153" CommentCount="6" />
  <row Id="14446" PostTypeId="2" ParentId="14435" CreationDate="2011-05-19T13:00:25.600" Score="5" ViewCount="" Body="&lt;p&gt;What the other guys have said is very true.  I'll add that about 10 or 15 years ago I stopped using thermal reliefs.  Since that time, maybe 30-50K PCB's have been manufactured and I've never had a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In a production environment soldering to pins/pads/vias/holes directly connected to large planes isn't really an issue due to the temperature profile of the ovens, and that the ovens tend to heat the whole board and not just the pads that are being soldered.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When hand soldering on a PCB without thermal reliefs there can be an issue, as the others have pointed out, but in my opinion the advantages of no thermal reliefs are far greater than easier hand soldering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's some of the advantages of no thermal reliefs:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Greater heat transfer to the planes on the PCB.  You see this the most on QFN's and other packages that have a ground pad on the bottom of the part in the center.  This pad is intended to transfer heat to vias and then to the ground plane.  &lt;/li&gt;&#xA;&lt;li&gt;Easier routing and fan-out of BGAs and other dense parts.  Particularly when putting planes under the BGA.&lt;/li&gt;&#xA;&lt;li&gt;Less chance for the via to get messed up due to plating, or drill accuracy issues, or other PCB manufacturing problems (not a huge benefit, but a benefit none the less).&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;So, in the end, I don't use thermal reliefs and I've had zero problems (other than the occasional hand-solder issue which is easy to overcome).&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-19T13:00:25.600" CommentCount="3" />
  <row Id="14447" PostTypeId="2" ParentId="14433" CreationDate="2011-05-19T13:03:35.367" Score="5" ViewCount="" Body="&lt;p&gt;Pretty much everything that requires precision movement incorporates a feedback loop into a control system. This feedback can be things like the feedback from stepper motors, or encoders, or accelerometers, or what ever the designer can imagine to be able to help them know what their system is doing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is lots of research and engineering that goes into how to optimize these systems for the application that they need.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the simplest control systems that people can understand is cruse control in a car. There are basically 3 things that are usually taken into account when designing the systems.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Overshoot. In the terms of the car, this is if you are at a different speed then your cruse control is set at, how much over the speed can the system go and be considered acceptable. Is 1 MPH ok? How about 2?, etc.&lt;/li&gt;&#xA;&lt;li&gt;Ripple. Once you get to your set speed, how much are you ok with it varying. Lets say it is set at 65 MPH, are you ok with it going up to 70 and then down to 60 or would you rather it stay +/- 0.5 MPH&lt;/li&gt;&#xA;&lt;li&gt;Settling/Rise Time. If your car is at 45 MPH and you want it to be at 65 MPH, how fast do you want it to get there?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Changing one of these effects the others. In the case of the Segway, they have refined their control system well enough to be able to do what you see it doing. Not an easy task at all though.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-19T13:03:35.367" CommentCount="1" />
  <row Id="14448" PostTypeId="1" AcceptedAnswerId="14457" CreationDate="2011-05-19T13:28:42.890" Score="2" ViewCount="84" Body="&lt;p&gt;I'm currently writing a physics report of an experiment, which is about optical fiber.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of experiments was about compare input &amp;amp; output signal of optical fiber, and the result was this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/YY3b4.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As you can see, there's difference (6ms) between input and output signal, and one question on the experiment instruction was to explain this delay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I found that two things can affect this delay - optical fiber itself and delay happened at light source: LED. However, I can't sure about both things..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the delay between electric current and light intensity of LED significant?&lt;/p&gt;&#xA;" OwnerUserId="4317" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T13:31:52.683" LastActivityDate="2011-05-19T18:01:56.653" Title="Delay between electric current and light intensity of LED" Tags="&lt;led&gt;&lt;homework&gt;" AnswerCount="2" CommentCount="3" />
  <row Id="14449" PostTypeId="2" ParentId="14430" CreationDate="2011-05-19T14:10:55.323" Score="1" ViewCount="" Body="&lt;p&gt;This is what I get using a hybrid-pi model with a base resistor of Rin and an emitter load of Re ...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$$v_o=v_{in}-\frac{(v_{in}+i_oR_e)(R_{in}+r_\pi)}{(R_{in}+r_\pi+R_e(1+\beta))}$$&#xA;$$\frac{\mathrm dv_o}{\mathrm di_o}=\frac{R_e(R_{in}+r_\pi)}{(R_{in}+r_\pi)+R_e(1+\beta)}$$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now if \$R_e\$ is large and \$R_{in}\$ &gt;&gt; \$r_\pi\$, this approximates to \$\frac{R_{in}}{1+\beta}\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(\$\beta\$ is so much quicker to LaTex than \$h_{fe}\$ :)&lt;/p&gt;&#xA;" OwnerUserId="2234" LastEditorUserId="2234" LastEditorDisplayName="" LastEditDate="2011-06-02T12:09:53.767" LastActivityDate="2011-06-02T12:09:53.767" />
  <row Id="14450" PostTypeId="1" AcceptedAnswerId="14451" CreationDate="2011-05-19T14:28:57.703" Score="4" ViewCount="143" Body="&lt;p&gt;I recently got a car lighter to USB adapter which I planned to use to charge my mobile phone. Unfortunately, the phone won't charge (and I know that the phone is capable of charging over USB port), so I opened it to see what could be the reason. The charger itself is pretty simple. It has a rectifier, MC34063A regulator and needed components, an LED and resistor and USB port. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of particular interest to me was the USB port itself. If I remember correctly, for USB chargers, there should be a 220 $\Omega$ resistor between data lines to signal to the device that the host is a charger. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In my case there was this circuit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/0ONKq.png&quot; alt=&quot;Circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I used black rectangles to mark junctions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if I'm reading this correctly, the D- and D+ lines are connected via pull-up resistors to Vcc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm thinking of removing these resistors and putting a 220$\Omega$ resistor between the data lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are: &lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Is there any obvious reason why should the data lines be connected to Vcc through this complicated system of resistors?&lt;/li&gt;&#xA;&lt;li&gt;Is there any reason why I shouldn't remove those resistors and just put a 220$\Omega$ resistor between the data lines?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-05-19T14:41:28.237" LastActivityDate="2011-05-19T16:24:00.823" Title="Why are these USB data lines conned to pull-up resistors?" Tags="&lt;usb&gt;&lt;charger&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="14451" PostTypeId="2" ParentId="14450" CreationDate="2011-05-19T15:04:10.450" Score="7" ViewCount="" Body="&lt;p&gt;If I am not getting confused, this system of resistors is required by &lt;a href=&quot;http://www.ladyada.net/make/mintyboost/icharge.html&quot; rel=&quot;nofollow&quot;&gt;iPhones and other i-Devices to charge at different current levels&lt;/a&gt;. Otherwise an error message will pop up. If you don't have an iPhone you can quite safely remove these and replace them.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-19T15:04:10.450" CommentCount="2" />
  <row Id="14452" PostTypeId="2" ParentId="14440" CreationDate="2011-05-19T15:04:44.717" Score="9" ViewCount="" Body="&lt;p&gt;For the moment, I'm going to lump together transistors, FET's (Field Effect Transistors), and relays.  There are some other devices that could be lumped in there as well, but...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;At the most basic level, all of these devices operate as a switch.  Do something, and electricity will start or stop flowing.  Stop doing something, and the electricity flow will change.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A relay is the easiest for beginners to understand.  Current flowing through the coil causes an electromagnet to become magnetized.  This makes a mechanical switch &quot;flip&quot;.  Turn off the current in the coil and the switch flips the other way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the case of a transistor, when &lt;strong&gt;current&lt;/strong&gt; flows through one of the pins (called the &quot;base&quot;) it causes more current to flow through the other two pins (the pins are called the collector and emitter).  No current through the base means that there is no current flowing through the other two pins.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A FET is similar to a transistor, but instead of a &lt;strong&gt;current&lt;/strong&gt; flowing through the base, it is a &lt;strong&gt;voltage&lt;/strong&gt; on the base.  And just to confuse matters the pins are not called Base, Emitter, and Collector.  Instead they are called Gate, Source, and Drain.  But the operation is very similar.  Have the correct voltage on the Gate and electricity will flow through the other two pins.  Don't have the correct voltage and the flow will stop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another important detail is that the transistor or FET doesn't have to be &quot;fully on&quot; or &quot;fully off&quot;.  If the Base or Gate is somewhere in between fully on &amp;amp; off, then the flow of electricity through the device will be &quot;a little on&quot; or &quot;a little off&quot;.  This doesn't work for relays.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And that's the beginner level explanation.  Of course I glossed over a lot of details, but they are not important at this stage.  What is important is that you can take Transistors and FET's and combine them in interesting ways to make all the cool electrical devices that we can't live without.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-19T15:04:44.717" CommentCount="1" />
  <row Id="14453" PostTypeId="2" ParentId="14450" CreationDate="2011-05-19T16:02:51.363" Score="7" ViewCount="" Body="&lt;p&gt;The resistors aren't really complicated, it's a simple &lt;a href=&quot;http://en.wikipedia.org/wiki/Voltage_divider&quot; rel=&quot;nofollow&quot;&gt;Voltage Divider&lt;/a&gt;. It's meant to take the voltage difference between Vcc and GND, and divide it to some particular voltage for the D+ and D- lines. Thomas O is correct in saying this is to support Apple products but there are some other devices that use a similar, sometimes slightly conflicting, set up to determine if the devices is a charger.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In essence this is a hack to avoid putting a USB enumerator in charging devices. The enumerator is used to make a device act as Host. It negotiates current requirements and capabilities between a host and device to ensure compatibility, announces the device's successful connection to the host, etc. The strict USB spec states that a device should connect at some very low current draw - enough to power its own logic - and negotiate for more current.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is overkill for a simple charger since there is no need to ever care about real data or communication. Some industry people decided to put in some &quot;dumb&quot; settings to allow a device to detect a connection to a simple charger, determine what current it is safe to draw and react all on its own without instruction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a couple &lt;a href=&quot;http://www.ladyada.net/make/mintyboost/icharge.html&quot; rel=&quot;nofollow&quot;&gt;places&lt;/a&gt; to find what the voltages should be to specify, say, 100mA, 250mA, 500mA or 1000mA capability. If you decide to modify your charger, make sure you know exactly what the safe output current is and that you're not advertising more capability than you can provide. This could cause your charger to fail in unexpected ways and possibly damage your connected device. Or it might just melt the plastic and release awful fumes.&lt;/p&gt;&#xA;" OwnerUserId="4319" LastEditorUserId="4319" LastEditorDisplayName="" LastEditDate="2011-05-19T16:24:00.823" LastActivityDate="2011-05-19T16:24:00.823" CommentCount="2" />
  <row Id="14454" PostTypeId="1" AcceptedAnswerId="14455" CreationDate="2011-05-19T16:26:12.397" Score="2" ViewCount="69" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Reading a question on SuperUser where someone received an electric shock from a modem made me curious, how much power can a phone line provide? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I'm not looking to do anything dodgy like try to power something, this is just out of curiously/amusement; in the UK phone lines operate at ~50v (up to 100 with an incoming call) enough to overcome the resistance of human skin in the right conditions. 10mA would give a nasty shock but 100-200mA has a high chance of fatality - in theory could someone actually be &lt;em&gt;electrocuted&lt;/em&gt; by a phone line?)&lt;/p&gt;&#xA;" OwnerUserId="4184" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-19T16:34:01.533" LastActivityDate="2011-05-19T17:11:59.550" Title="Max current draw from a UK Phone Line?" Tags="&lt;power&gt;&lt;telephone&gt;&lt;phone&gt;&lt;consumer-electronics&gt;&lt;uk&gt;" AnswerCount="1" />
  <row Id="14455" PostTypeId="2" ParentId="14454" CreationDate="2011-05-19T17:11:59.550" Score="2" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.cycom.co.uk/howto/bttelephone40macurrentsource.html&quot; rel=&quot;nofollow&quot;&gt;This source&lt;/a&gt; states that BT provides 40mA when the phone is off the hook.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.epanorama.net/circuits/telephone_ringer.html&quot; rel=&quot;nofollow&quot;&gt;This other source&lt;/a&gt; talks about the expectations of the ringer circuit:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;less than or equal to 5mA draw at 35V/25Hz ring signal&lt;/li&gt;&#xA;&lt;li&gt;less than or equal to 10.5mA draw at 75V/25Hz ring signal&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.microsemi.com/datasheets/pcr-sin06series.pdf&quot; rel=&quot;nofollow&quot;&gt;PowerDsine's&lt;/a&gt; North America ring module generator appears to be limited to 3W, so I would expect the PSTN provider's capabilities to be similar. This signal gets shorted out when the phone goes on-hook, so the source can't be too stiff.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-19T17:11:59.550" CommentCount="1" />
  <row Id="14456" PostTypeId="2" ParentId="14448" CreationDate="2011-05-19T17:15:39.283" Score="0" ViewCount="" Body="&lt;p&gt;LEDs switch very fast, typically faster than a microsecond. If they are special-purpose LEDs for communication they should even be much faster than that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As always you should take a look into the data sheet for the LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So compared to 6ms this is insignificant.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-05-19T17:15:39.283" />
  <row Id="14457" PostTypeId="2" ParentId="14448" CreationDate="2011-05-19T17:54:08.530" Score="2" ViewCount="" Body="&lt;p&gt;How long is your fiber, what is the switching time of your emitter and where are you measuring?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You would get a 6ms delay on a 1800km long fiber due to the speed of light. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another source of delay is afterburn in the LED phosphor. If you are using LEDs designed for fiberoptic transmission they would typically have switching speeds down in the low ns range. There are slower/low cost ones with switching times up to 1us. I work with visible light LED for photography and they exhibit an afterburn in the hundreds of ns. It seems like delay in the LED itself is unlikely.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The speed of your photodetector could of course be a factor. The one I use has a 1 ns rise time and it is hard to imagine the detector itself causing a 6ms delay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where are you measuring? I would look at the circuitry that is driving the LED. &lt;/p&gt;&#xA;" OwnerUserId="3876" LastEditorUserId="3876" LastEditorDisplayName="" LastEditDate="2011-05-19T18:01:56.653" LastActivityDate="2011-05-19T18:01:56.653" CommentCount="4" />
  <row Id="14458" PostTypeId="1" AcceptedAnswerId="14459" CreationDate="2011-05-19T18:36:54.237" Score="3" ViewCount="118" Body="&lt;p&gt;(NB: I feel this is better here than super-user because it is hardware based)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Trying to connect my laptop's S/PDIF output to some headphones. Setup is:&#xA;Laptop -&gt; 3.5mm to RCA cable -&gt; Co-ax to Toslink converter -&gt; toslink optical cable -&gt; headphone decoder box -&gt; headphones&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Everything from the Co-ax to toslink converter works fine from an alternate source RCA S/PDIF connector on my desktop's motherboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using a random 3.5mm mono jack to RCA cable works but it is &lt;em&gt;very&lt;/em&gt; quiet (as in laptop volume settings maxed out, and headphone volume control (active (yes they need their own power supply!)) also maxed out and I can barely hear the sound above the noise.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would a genuine 75 ohm cable (eg. &lt;a href=&quot;http://www.ramelectronics.net/audio-video/custom-audio-and-video-cables/rca-to-3-5mm-s-pdif-cables/custom-spdif-cable-digital-audio-3-5mm-to-rca/prodSPDIF.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;) sort out the attenuation issue?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am thinking that the laptop lacks the impedance matching output system my desktop has, so the laptop is setup for:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;spdif ----&#xA;        |&#xA;      ----&#xA;      |  | 75 ohm&#xA;      |  |&#xA;      |  |&#xA;      ----&#xA;        |&#xA;      ---- GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;hence provides \$I=\frac{V}{R}=\frac{0.5}{75}\simeq6.7\mbox{ mA}\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but because of my random cable (which multimeter measured at ~2 ohms)&#xA;sees:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;spdif ----&#xA;        |&#xA;       ----&#xA;       |  | 2 ohm&#xA;       |  |&#xA;       |  |&#xA;       ----&#xA;        |&#xA;       ---- GND&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;hence the voltage across the load (the converter box) is \$V=IR=13\mbox{ mV}\$ instead of the \$0.5\mbox{ V}\$ it should be.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is this anywhere near correct? And is a proper 75 ohm cable the solution?&lt;/p&gt;&#xA;" OwnerUserId="4324" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-01T11:36:52.183" LastActivityDate="2011-06-01T11:36:52.183" Title="Necessity of 75 ohm cable?" Tags="&lt;audio&gt;&lt;digital&gt;&lt;rca&gt;" AnswerCount="1" />
  <row Id="14459" PostTypeId="2" ParentId="14458" CreationDate="2011-05-19T18:50:33.257" Score="6" ViewCount="" Body="&lt;p&gt;'75ohm cable' refers to a reactive load - it's the capacitance and inductance of the cable, not the resistance end to end &lt;/p&gt;&#xA;&#xA;&lt;p&gt;spdif is a digital thing - 2 ohms from one end to the other of a digital cable sounds high if anything but shouldn't be an issue - because it's a digital signal loss will cause noise, not loss of volume &lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-05-19T18:50:33.257" CommentCount="2" />
  <row Id="14460" PostTypeId="1" AcceptedAnswerId="14461" CreationDate="2011-05-19T20:06:16.280" Score="1" ViewCount="60" Body="&lt;p&gt;This is a real odd thing I have here.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I picked up a PIC16F628 this morning to play with, and I am having a very strange issue with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have written a very simple program which should light 2 LEDs in this sequence: (* = on, o = off)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;RA0 RA1&#xA; *   o&#xA; *   *&#xA; o   *&#xA; o   o&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;But what actually happens is:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;RA0 RA1&#xA; *   o&#xA; o   *&#xA; o   o&#xA; o   o&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;When RA1 turns on, RA0 turns off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The exact same code run on an '84a works perfectly.  Snippet:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;loop&#xA;    BSF     PORTA,0&#xA;    CALL    delay&#xA;    BSF     PORTA,1&#xA;    CALL    delay&#xA;    BCF     PORTA,0&#xA;    CALL    delay&#xA;    BCF     PORTA,1&#xA;    CALL    delay&#xA;    GOTO    loop&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;My only thoughts are that it has something to do with the comparators that share the pins (should be disabled by default) which I have tried manually disabling but it has had no effect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, one more thing to add confusion...  If I send absolute values to PORTA (0x01, 0x03, 0x02, 0x00) it works correctly.  Why should the bitwise operations work so strangely?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Oh, and I don't have any issue at all working with PORTB - only PORTA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any clues or ideas? Because I have run out.&lt;/p&gt;&#xA;" OwnerUserId="4245" LastActivityDate="2011-05-19T21:27:18.940" Title="PIC16F628 PORTA Behaving oddly." Tags="&lt;pic&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="14461" PostTypeId="2" ParentId="14460" CreationDate="2011-05-19T20:25:22.567" Score="2" ViewCount="" Body="&lt;p&gt;Your problem is probably caused by the Read-Modify-Write effect, see page 31 of the data sheet. You should use a shadow register, set and reset the bits in that, and write it to the port. Delays usually help, so I find it surprising that it caused you problems. The fact that you could write bytes to the port and it works as expected indicates that it probably is an R-M-W effect.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/93009A.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a good description of the problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The 18F PICs have latch registers for the ports, and don't suffer from the R-M-W problem.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-19T21:27:18.940" LastActivityDate="2011-05-19T21:27:18.940" CommentCount="4" />
  <row Id="14462" PostTypeId="1" AcceptedAnswerId="14467" CreationDate="2011-05-19T20:34:38.410" Score="1" ViewCount="144" Body="&lt;p&gt;When you add energy to a capacitor, you say that you are &quot;charging it&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;s&gt;This is kind of a misnomer, since the total amount of charge in the capacitor is the same, but whatever.&lt;/s&gt; (&lt;a href=&quot;http://www.etymonline.com/index.php?term=charge&quot; rel=&quot;nofollow&quot;&gt;'charge' etymology&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But what do you call it when you put current through an inductor, and it &lt;strong&gt;&lt;em&gt;_&lt;/em&gt;____&lt;/strong&gt; up and forms a magnetic field?&lt;/p&gt;&#xA;" OwnerUserId="142" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-20T20:23:09.507" LastActivityDate="2011-05-20T20:23:09.507" Title="What do you call it when you add energy to an inductor?" Tags="&lt;capacitor&gt;&lt;inductor&gt;&lt;charging&gt;&lt;terminology&gt;" AnswerCount="5" CommentCount="5" />
  <row Id="14464" PostTypeId="2" ParentId="14462" CreationDate="2011-05-19T20:48:30.813" Score="0" ViewCount="" Body="&lt;p&gt;At first I was going to suggest 'currenting' since it's somewhat the opposite of 'charging' (current vs. voltage).  That doesn't sound right as a verb though.  I want to go with 'spin' since it connotes a continuous movement (of current) through the device.&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-19T20:48:30.813" CommentCount="3" />
  <row Id="14465" PostTypeId="2" ParentId="14462" CreationDate="2011-05-19T20:59:05.800" Score="1" ViewCount="" Body="&lt;p&gt;There is energy stored in an inductor, namely $1/2 * L * I^2$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For instance, it is used as energy storage in switching power supplies. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For lack of a better word, I would choose to call it charging. Also, wikipedia does not discern between capacitance and inductance in the article time_constant, which relates to the process of releasing charge. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;see &lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indeng.html&quot; rel=&quot;nofollow&quot;&gt;http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indeng.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3438" LastEditorUserId="3438" LastEditorDisplayName="" LastEditDate="2011-05-19T21:04:50.163" LastActivityDate="2011-05-19T21:04:50.163" CommentCount="1" />
  <row Id="14466" PostTypeId="2" ParentId="14462" CreationDate="2011-05-19T21:22:18.133" Score="3" ViewCount="" Body="&lt;p&gt;Putting energy into an inductor is called &quot;energizing&quot;, and removing energy from it is &quot;de-energizing&quot;.  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-19T21:22:18.133" />
  <row Id="14467" PostTypeId="2" ParentId="14462" CreationDate="2011-05-19T21:23:20.350" Score="9" ViewCount="" Body="&lt;p&gt;The word is simply &lt;em&gt;energizing&lt;/em&gt;. It is actually used quite often when referring to superconducting magnets, which are nothing but inductors.&#xA;&lt;a href=&quot;http://en.wikipedia.org/wiki/Superconducting_magnet#Persistent_mode&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Superconducting_magnet#Persistent_mode&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4327" LastActivityDate="2011-05-19T21:23:20.350" CommentCount="2" />
  <row Id="14468" PostTypeId="2" ParentId="10636" CreationDate="2011-05-19T21:49:20.420" Score="0" ViewCount="" Body="&lt;p&gt;CB will work with 1200 baud with a TNC2S modem, but highly restricted in the U.S. However I don't see an issue with sideband, but I am not a lawful expert either.&lt;/p&gt;&#xA;" OwnerUserId="4328" LastActivityDate="2011-05-19T21:49:20.420" />
  <row Id="14469" PostTypeId="1" AcceptedAnswerId="14473" CreationDate="2011-05-19T22:21:42.077" Score="2" ViewCount="74" Body="&lt;p&gt;The device is supposed to beep loudly if the network is down, a particular port on an Internet host doesn't respond or a socket connection is made on a specific local port.&#xA;Is an Arduino Ethernet shield enough? I am guessing i will also need an Arduino board and software? Are there non-Arduino solutions that are cheaper or easier to code for? This will never leave the working prototype stage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am a total newbie when it comes to electronics, so I am looking for a kit that covers all the hardware/software needs, excluding the speaker itself. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks in advance&lt;/p&gt;&#xA;" OwnerUserId="4329" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-05-19T23:08:26.607" LastActivityDate="2011-05-20T08:06:49.887" Title="Want to build an ethernet-connected USB or battery powered piezo alarm gizmo -- what's a good kit ?" Tags="&lt;arduino&gt;&lt;ethernet&gt;&lt;kit&gt;" AnswerCount="5" CommentCount="3" />
  <row Id="14470" PostTypeId="2" ParentId="14469" CreationDate="2011-05-19T22:43:15.413" Score="3" ViewCount="" Body="&lt;p&gt;The hardware you suggested sounds right for the job, given your skill level as well.  Are there non-arduino solutions? Yes. Would they be easier to code on?  Probably not.  Given that this is your first venture into electronics, I highly recommend the route that you've already suggested.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will need the arduino board as well.  That is where your program will go.  The ethernet shield is an add on peripheral.  The software to write the programs (&quot;sketches&quot;) is free as well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Happy hacking! &lt;a href=&quot;http://www.arduino.cc/en/Reference/Ethernet&quot; rel=&quot;nofollow&quot;&gt;http://www.arduino.cc/en/Reference/Ethernet&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4172" LastActivityDate="2011-05-19T22:43:15.413" />
  <row Id="14471" PostTypeId="2" ParentId="3760" CreationDate="2011-05-19T23:00:21.090" Score="0" ViewCount="" Body="&lt;p&gt;I have a tendency to only buy American for prototypes because I believe you get what you pay for.. So far, I have purchased from various PCB Fab companies and their are two that come to mine when dealing with &quot;Made in USA&quot; PCB companies. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;-Custom Circuit Boards (Link: &lt;a href=&quot;http://www.customcircuitboards.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.customcircuitboards.com/&lt;/a&gt;)&#xA;-Sunstone, like mentioned above (Link:http://www.sunstone.com/)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both have always produced quality boards ONTIME!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Best of luck.&lt;/p&gt;&#xA;" OwnerUserId="4331" LastActivityDate="2011-05-19T23:00:21.090" CommunityOwnedDate="2011-05-20T11:44:01.827" />
  <row Id="14472" PostTypeId="1" CreationDate="2011-05-19T23:02:30.997" Score="0" ViewCount="139" Body="&lt;p&gt;I have a Netduino Plus and I am trying to put together a shopping list to one of my usual vendors for digital &quot;glue&quot; parts I can use with it.  I am experienced in electronics but I haven't bought IC's (other than regulators) in a while.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is a difficult question, but what digital chips are people using?  I'm not referring to specialized chips, such as an RTC (that is on my shopping list for other reasons) but to the glue chips I need to make things work with a microcontroller.  (I have several other boards, including some MSP430 boards so my question is applicable to these too.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I'm not considering analog or RF chips for the moment;  I have plenty of 555's and 741's;  they're like mice!)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an example, I am looking at an 74LS595 shift register so I can use a few surplus Hitachi-based LCD's I have without the hassle of finding enough pins to directly drive it from the Netduino.  Is the 595 tolerant in the modern 3.3V logic environment?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know, too, that I will probably use chips like the 4066 switches, so those are on the list.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another example:  What is a good binary/BCD 7-segment driver for use these days?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's been years since &lt;strong&gt;anyone&lt;/strong&gt; could just run down the catalog of Mouser or Digi-Key and get 2 of everything with a 74/74LS or 4000 prefix and I don't expect to be able to do the same.  I'd just hate unpacking my order and finding another neat project on the net that I must have but didn't order in the box.&lt;/p&gt;&#xA;" OwnerUserId="3983" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-05-20T12:36:24.127" LastActivityDate="2011-05-29T00:21:39.993" Title="Common digital &quot;glue&quot; chips used with Arduino/Netduino?" Tags="&lt;arduino&gt;&lt;msp430&gt;&lt;netduino&gt;&lt;parts&gt;" AnswerCount="3" />
  <row Id="14473" PostTypeId="2" ParentId="14469" CreationDate="2011-05-19T23:07:15.580" Score="0" ViewCount="" Body="&lt;p&gt;This should have been a comment, but I fear it's too big for comment field.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A major part of the design can be the speaker, so you should pay considerable attention to that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are several options you could use and the best depends on the type of sound you want to achieve.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll first talk about the easiest option to set up. That would be a self-oscillating buzzer. In &lt;a href=&quot;http://electronics.stackexchange.com/q/10157/1240&quot;&gt;this&lt;/a&gt; question I got some nice answers on how to connect one to an AVR microcontroller (of same family as ones used in Arduino). The downside of this is that the buzzer produces only one frequency and all you can do is turn it on or off. On the other hand for a simple alarm, it should probably be good enough. The plus side is alto that you can only turn it on or off. This makes it very easy to program the microcontroller. The buzzer shouldn't be too expensive. The price will of course depend on the size and power, but for this type of application, 2€ or 3€ would be more than enough for the speaker and the transistor needed to drive it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second option is to use a piezoelectric sound source. The downside of them is that you must create your own driving circuit for the speaker. You could make an oscillator or you could use the Arduino to create square waves and then using a transistor and a resistor drive the sound source. I don't know how much this would cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another option is to use a real speaker. The easiest way to do this is to get a cheap amplifier chip and connect it to the speaker. You'd also need electronics for the amplifier (but that could be just a couple capacitors for some amplifiers). Another problem is that you'd need to use the Arduino to generate audio signal which will drive the amplifier, making the programming a bit more complicated. A positive side is that you can (with right amplifier choice) easily control volume. expect high price. The speaker could easily cost couple of Euros and so could the amplifier. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-05-19T23:07:15.580" CommentCount="1" />
  <row Id="14474" PostTypeId="2" ParentId="14472" CreationDate="2011-05-20T00:40:11.863" Score="1" ViewCount="" Body="&lt;p&gt;One thing I can recommend that I do think a lot of people eventually end up using is a MAX232 or equivalent, so you can talk to a device over RS-232.  Sure, you could count on being able to use the USB connection, but I always end up with a situation where I need to talk to another device (e.g. a touchscreen controller like Amulet's) and that device doesn't use TTL serial levels.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-05-20T00:40:11.863" CommentCount="3" />
  <row Id="14475" PostTypeId="2" ParentId="13190" CreationDate="2011-05-20T00:40:35.560" Score="1" ViewCount="" Body="&lt;p&gt;What about the TI Chronos?&lt;a href=&quot;http://focus.ti.com/docs/toolsw/folders/print/ez430-chronos.html#buy&quot; rel=&quot;nofollow&quot;&gt;1&lt;/a&gt;  I've considered buying one for its large display, which would be very nerdy but also very practical with my poor eyes.  It's relatively inexpensive, too.  &lt;/p&gt;&#xA;" OwnerUserId="3983" LastActivityDate="2011-05-20T00:40:35.560" />
  <row Id="14476" PostTypeId="2" ParentId="14462" CreationDate="2011-05-20T00:41:09.857" Score="1" ViewCount="" Body="&lt;p&gt;I've heard the term &quot;excitation&quot; with respect to magnetics ... I personally use the term &quot;ramping&quot;, as in current ramping up and ramping down.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-20T00:41:09.857" />
  <row Id="14477" PostTypeId="2" ParentId="14472" CreationDate="2011-05-20T03:52:07.877" Score="2" ViewCount="" Body="&lt;p&gt;If you want to switch power, a few triac optocouplers (like TLP3063, MOC302x). Some Triacs, MOSFETs, transisitor optocouplers. Latches.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Various assorted toys: LCD display. Sensors, digital or analog. For temperature DS18B20+, PTC.LDR. &lt;/p&gt;&#xA;" OwnerUserId="3438" LastActivityDate="2011-05-20T03:52:07.877" CommentCount="1" />
  <row Id="14478" PostTypeId="1" CreationDate="2011-05-20T04:10:24.037" Score="0" ViewCount="74" Body="&lt;p&gt;I have 6 IR LEDs that I want to run off a cigarette lighter outlet in a car.&#xA;(High output infrared LED 5mm 1.2VDC 100mA 940nm)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Currently I have all six in series with a 100ohm 1w 5% resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am going to use the Arduino Uno as a timer. Output on Pin 2.&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;int led = 2;&#xA;&#xA;void setup() {&#xA;  pinMode(led, OUTPUT);     &#xA;}&#xA;void loop() {&#xA;  digitalWrite(led, HIGH);&#xA;  delay(35);&#xA;  delayMicroseconds(544);&#xA;  digitalWrite(led, LOW);&#xA;  delay(35);&#xA;  delayMicroseconds(552);&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/wsWkU.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My 6 leds are in the place of &quot;M&quot;. But for some reason this is not working for me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The leds are sometimes off, blink at the inncorrect freq, or just stay lit.&lt;/p&gt;&#xA;" OwnerUserId="4333" LastActivityDate="2011-05-20T07:23:10.470" Title="Arduino LED strobe light with a MOSFET" Tags="&lt;arduino&gt;&lt;led&gt;" AnswerCount="2" CommentCount="4" />
  <row Id="14479" PostTypeId="2" ParentId="14478" CreationDate="2011-05-20T05:44:06.700" Score="1" ViewCount="" Body="&lt;p&gt;what is the source voltage?  In your diagram, you have +5 to +24 V feeding into a motor...  You mentioned car power, and an arduino - so I'm guessing you're either supplying ~ 12V or 5V; also, are you driving the output high/low?  Or is it setup to be open source?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;And, are you sure that your city still uses strobed IR bulbs without a special pattern to control its traffic lights?&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-20T05:44:06.700" />
  <row Id="14480" PostTypeId="2" ParentId="14469" CreationDate="2011-05-20T06:22:58.383" Score="1" ViewCount="" Body="&lt;p&gt;Once you stack a communications shield on an arduino, you generally lose the cost advantage over a different micro with that peripheral (ethernet, usb, whatever) built in.  And you can't quite fully leverage the peripheral since it's comparatively &quot;at arms length&quot; from the processor core.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But it obviously does work for many purposes, and lets you stay in the same software environment if you are familiar with that.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-05-20T06:22:58.383" />
  <row Id="14481" PostTypeId="2" ParentId="14478" CreationDate="2011-05-20T07:23:10.470" Score="2" ViewCount="" Body="&lt;p&gt;I assume you get 12V from your car? In that case your resistor should be 56 ohm if you want 100mA LED current. You don't want the kickback diode. It is required for inductive loads, but LEDs are a resistive load.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You risk burning the Arduino pin. I believe it is 5.5V tolerant? You should put a Zener diode on the gate of the MOSFET to limit its voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also check that the FET you are using turns fully on with 5V at the gate.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastActivityDate="2011-05-20T07:23:10.470" />
  <row Id="14482" PostTypeId="2" ParentId="14469" CreationDate="2011-05-20T07:45:54.863" Score="1" ViewCount="" Body="&lt;p&gt;Another good low-cost option is the &lt;a href=&quot;http://mbed.org/&quot; rel=&quot;nofollow&quot;&gt;mbed&lt;/a&gt;. It comes with an ethernet controller on-board, as well as a bunch of other bells and whistles. It is ARM based, so quite a bit beefier than the AVR on the arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will need to add an RJ45 magjack though.&lt;/p&gt;&#xA;" OwnerUserId="1802" LastActivityDate="2011-05-20T07:45:54.863" />
  <row Id="14483" PostTypeId="2" ParentId="14469" CreationDate="2011-05-20T08:06:49.887" Score="1" ViewCount="" Body="&lt;p&gt;I would hack some USB ready linux router. It has all the hardware you need if you add USB sound card and loud speakers to it. The other way would be to make sirene electronics triggered by some digital output pin from router.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-05-20T08:06:49.887" CommentCount="1" />
  <row Id="14484" PostTypeId="1" CreationDate="2011-05-20T08:12:24.627" Score="0" ViewCount="91" Body="&lt;p&gt;In college I had a small form factor media PC. One day some of us were watching a DIVX movie on that PC via a large TV, when another roommate came home.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For some reason known only to him, flipping the living room's breaker switch at the fusebox seemed like a really cool idea.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Everything shut off, and when we restored power we found (after some testing, of course) that the PC's video card had been fried. All other components were undamaged. I yanked the AGP card, tossed in another, and on we went with our lives less one asshole roommate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I always wondered &lt;em&gt;why&lt;/em&gt; that happened. Why would breaking the circuit damage the hardware?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Was damaging the videocard simply bad luck?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or was &lt;em&gt;only&lt;/em&gt; damaging the videocard simply good luck?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know nothing about real nuts and bolts electronics, so please try and explain it using plain English!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you!&lt;/p&gt;&#xA;" OwnerUserId="4312" LastActivityDate="2011-05-20T12:58:51.280" ClosedDate="2011-05-20T15:24:04.983" Title="threw circuit breaker, dead video card - what actually happened?" Tags="&lt;circuit&gt;&lt;pc&gt;&lt;damage&gt;" AnswerCount="4" CommentCount="1" />
  <row Id="14485" PostTypeId="2" ParentId="2245" CreationDate="2011-05-20T08:43:00.403" Score="0" ViewCount="" Body="&lt;p&gt;If you are into the home automation, why don't you opt for real thing? It's called &lt;strong&gt;Z-Wave&lt;/strong&gt;, a the facto industry standard for wireless home automation (the next X10), and there are hundreds of products Z-Wave enabled. Digikey has boards and dev kits, and there is even a small power plug linux box with Z-Wave and ethernet embedded.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.z-wave.com/modules/Products/?id=66&amp;amp;chk=94b8927269761c1a0c94de9268724ddb&quot; rel=&quot;nofollow&quot;&gt;http://www.z-wave.com/modules/Products/?id=66&amp;amp;chk=94b8927269761c1a0c94de9268724ddb&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://web1.zen-sys.com/modules/Products&amp;amp;Techonology/?id=33&amp;amp;chk=7c18247ff46da755b3d1753888e2a342&quot; rel=&quot;nofollow&quot;&gt;http://web1.zen-sys.com/modules/Products&amp;amp;Techonology/?id=33&amp;amp;chk=7c18247ff46da755b3d1753888e2a342&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.tricklestar.com/US/300ZW_US_W.html&quot; rel=&quot;nofollow&quot;&gt;http://www.tricklestar.com/US/300ZW_US_W.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ionicsplug.com/stratusplusplus.html&quot; rel=&quot;nofollow&quot;&gt;http://www.ionicsplug.com/stratusplusplus.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.digiwave.dk/en/programming/an-introduction-to-the-z-wave-protocol/&quot; rel=&quot;nofollow&quot;&gt;http://www.digiwave.dk/en/programming/an-introduction-to-the-z-wave-protocol/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.digiwave.dk/en/programming/an-introduction-to-z-wave-programming-in-c/&quot; rel=&quot;nofollow&quot;&gt;http://www.digiwave.dk/en/programming/an-introduction-to-z-wave-programming-in-c/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.smarthome-products.com/p-625-homepro-zcu201-z-wave-usb-interface-euro.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.smarthome-products.com/p-625-homepro-zcu201-z-wave-usb-interface-euro.aspx&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://plugcomputer.org/plugforum/index.php?topic=1462.0&quot; rel=&quot;nofollow&quot;&gt;http://plugcomputer.org/plugforum/index.php?topic=1462.0&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-05-20T08:43:00.403" />
  <row Id="14486" PostTypeId="1" AcceptedAnswerId="14487" CreationDate="2011-05-20T08:58:39.643" Score="1" ViewCount="70" Body="&lt;p&gt;I'm using a touch LCD whose content I want to change if the user moves toward it. For this I'm looking for an SMT proximity sensor with a 40~50 cm detection range. Space above the PCB is only 3 mm, so Sharp GP2D12 and the like are out.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;note&lt;/em&gt; - I'm not looking for shopping advice (&quot;where can I buy part xyz?&quot;), but rather design advice (&quot;How can I solve this design problem?&quot;)&lt;/p&gt;&#xA;" OwnerUserId="3920" LastEditorUserId="3920" LastEditorDisplayName="" LastEditDate="2011-05-23T07:57:46.447" LastActivityDate="2011-05-23T10:18:11.143" Title="SMT proximity sensor" Tags="&lt;sensor&gt;&lt;proximity-sensor&gt;" AnswerCount="1" CommentCount="5" FavoriteCount="1" />
  <row Id="14487" PostTypeId="2" ParentId="14486" CreationDate="2011-05-20T09:12:13.917" Score="4" ViewCount="" Body="&lt;p&gt;Mouser's latest mailing mentioned this one: &lt;a href=&quot;http://www.vishay.com/docs/83798/vcnl4000.pdf&quot; rel=&quot;nofollow&quot;&gt;Vishay VCNL4000&lt;/a&gt;. For the price of the proximity sensor you also get an ambient light sensor. 4mm x 4mm, 0.75mm high, though it has three blobs on it which make it somewhat higher. Still looks like it's less than 3mm.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/2lnzi.png&quot; alt=&quot;enter image description here&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Detection range for the proximity sensor is only 20cm, though.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;disclaimer: the mention of Mouser is not a shopping advice :-)&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-23T10:18:11.143" LastActivityDate="2011-05-23T10:18:11.143" />
  <row Id="14488" PostTypeId="2" ParentId="14484" CreationDate="2011-05-20T09:25:29.023" Score="0" ViewCount="" Body="&lt;p&gt;It sounds to me that the video card output driver chip was damaged by a surge coming back from the monitor along the video cable. Capacitors in the monitor which are fully charged at the point that the power starts to go off have to discharge somewhere, in this case back into the video card. To prevent similar damage occuring during normal switch off of the monitor, there would be a staged shutdown sequence that the monitor would use, but if the mains disappeared quickly it wouldn't be able to run that sequence.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-05-20T09:25:29.023" />
  <row Id="14489" PostTypeId="2" ParentId="14484" CreationDate="2011-05-20T09:27:49.223" Score="0" ViewCount="" Body="&lt;p&gt;It's possible that the video card was damaged because of the lack of extra power. On one video card I had, when the extra ATX power connector was disconnected, it becme damaged (magic smoke leaked out of what looked like an inductor.) I suspect that it drew too much current from the AGP port. But it struggle to see that this damage would occur in about 20 ms of hold up time for a good power supply; mine took about 30 seconds before it was fried. So just a theory. Do you still have the card?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-20T09:27:49.223" />
  <row Id="14490" PostTypeId="2" ParentId="14484" CreationDate="2011-05-20T10:14:20.730" Score="2" ViewCount="" Body="&lt;p&gt;Well, nothing is certain, but it's likely that that the card overheated (yep, even thought there was no longer any power). Playing a movie would have put the card under a fair load (since this was a few years ago), and the fan would most likely been at full speed trying to keep it cool. Cut the power, and the fan stops dead - of course so does the load on the graphics CPU, but there is still a lot of heat that has built up inside the chip and needs to be shifted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You see this effect most often in projectors, where the manual has lots of warning in big letters about the consequences of switching the power off at the mains - they need to keep the fan running for several minutes after the lamp is out to prevent thermal failure of the lamp. &lt;/p&gt;&#xA;" OwnerUserId="2540" LastActivityDate="2011-05-20T10:14:20.730" />
  <row Id="14491" PostTypeId="1" CreationDate="2011-05-20T12:48:11.953" Score="2" ViewCount="133" Body="&lt;p&gt;What can I use to recognize if a surface in touched or not?&#xA;What kind of sensor I need to do this?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I want to detect if an object is on the table or the object touch and go out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using Arduino board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any idea?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit&lt;/strong&gt;: My object is a ball and my surface is a 4 person kitchen wood table.&lt;/p&gt;&#xA;" OwnerUserId="3359" LastEditorUserId="3359" LastEditorDisplayName="" LastEditDate="2011-05-21T14:21:06.680" LastActivityDate="2011-05-27T15:03:04.527" Title="Detect touches on a surface" Tags="&lt;arduino&gt;&lt;sensor&gt;&lt;electronics&gt;" AnswerCount="2" CommentCount="6" />
  <row Id="14492" PostTypeId="2" ParentId="14484" CreationDate="2011-05-20T12:58:51.280" Score="1" ViewCount="" Body="&lt;p&gt;There may well have been some sort of inductive load on the living room circuit, which rang up after the circuit was interrupted (the breaker opening) causing a surge that propagated through the PC power supply and blew the 'weakest' downstream device, which happened to be the video card.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A normal power interruption should not blow up anything, &lt;em&gt;if&lt;/em&gt; the power supply is earthed properly and has some surge protection. These days, with cheaply-made commodity power supplies, there are no guarantees of robustness.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-20T12:58:51.280" />
  <row Id="14493" PostTypeId="1" CreationDate="2011-05-20T13:10:17.893" Score="14" ViewCount="380" Body="&lt;p&gt;The title is probably good enough, but I've always wondered why decoupling caps aren't built into the chip or at least the IC packaging? &lt;/p&gt;&#xA;" OwnerUserId="2157" LastActivityDate="2011-05-23T20:07:48.820" Title="Why aren't decoupling caps built into the IC or IC package?" Tags="&lt;decoupling-capacitor&gt;&lt;decoupling&gt;" AnswerCount="4" CommentCount="3" FavoriteCount="2" />
  <row Id="14495" PostTypeId="2" ParentId="14493" CreationDate="2011-05-20T13:15:18.733" Score="17" ViewCount="" Body="&lt;p&gt;Integrating capacitors on a chip is expensive (they need a lot of space) and not very efficient (you're limited to extremely small capacitors).&lt;br&gt;&#xA;The packaging doesn't offer the room neither, the capacitor would be in the way of the bonding.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;IC package miniaturization is driven by the cellphone market (hundreds of megadevices a year, if not a gigadevice). We always want smaller packages, both in area and in height. Just open your cellphone to see what the problem is. (My phone is 1 cm thin, which includes housing top and bottom, a display, a 5 mm thick battery, and between that there's a PCB with components.) You can find BGA packages less than a mm high (&lt;a href=&quot;http://www.samsung.com/global/system/business/semiconductor/product/2007/7/19/265070ds_k6r4016v1d_rev40.pdf&quot; rel=&quot;nofollow&quot;&gt;this SRAM package&lt;/a&gt; is 0.55 mm(!)). That's less than the height of a 0402 100 nF decoupling capacitor.&lt;br&gt;&#xA;Also typical of SRAM is that package size isn't standard. You find 8 mm * 6 mm, but also 9 mm * 6 mm. That's because the package fits the die as closely as possible. Just the die plus on each side a fraction of a mm for the bonding. (BTW, BGA dies are bonded on an integrated PCB, which routes the signals from the edges to the ball grid.)&lt;br&gt;&#xA;This is an extreme example, but other packages like TQFP don't leave much more room.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's also much cheaper to pick and place a capacitor on the PCB; you're doing this anyway for the other components.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-21T10:19:03.823" LastActivityDate="2011-05-21T10:19:03.823" CommentCount="5" />
  <row Id="14497" PostTypeId="1" CreationDate="2011-05-20T13:25:29.713" Score="1" ViewCount="102" Body="&lt;p&gt;Does a synchronous shift register put out its result at the same time as it gets its input, or does it output it at the next rising edge?&lt;/p&gt;&#xA;" OwnerUserId="1657" LastActivityDate="2011-05-20T23:05:33.330" Title="Output from a shift register" Tags="&lt;shift-register&gt;" AnswerCount="4" CommentCount="5" FavoriteCount="0" />
  <row Id="14498" PostTypeId="1" AcceptedAnswerId="14525" CreationDate="2011-05-20T14:02:14.917" Score="3" ViewCount="55" Body="&lt;p&gt;I have an Arduino UNO dev board with a blank atmega328 chip (no arduino bootloader, the chip that came with the unit is soldered in a separate standalone project so that I can use the arduino board for more than one instance :) )&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So looking &lt;a href=&quot;http://electronics.stackexchange.com/questions/10587/how-to-burn-atmega328-chip-via-arduino-uno-as-isp&quot;&gt;here&lt;/a&gt;, the UNO isn't able to program the chip as it cannot be used as an ISP (yet?).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would I be able to use avrdude in a bit-bang programmer mode and hook up the atmega's spi lines to my serial port (using the correct lines obviously) and program the bootloader? I've seen topics on the web that say this is possible to do with other AVR chips, but I'm just really a noob here trying to get by. I understand that I can purchase an AVR ISP for ~$20 to do so but I was hoping to get started on a project tomorrow/tonight and do not want this weekend to go wasted (waiting for it to arrive...). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone have a good reference on how to proceed?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: To clear up some confusion, I am trying to program an atmega328 with an arduino bootloader. I only have the UNO dev board and a blank atmega328. I do have a serial port and really do not want to wait for an AVRISP to come in as I would like to get started sooner rather than later. Is this possible with the atmega328? How would I proceed?&#xA;Thanks :)&lt;/p&gt;&#xA;" OwnerUserId="2833" LastEditorUserId="2833" LastEditorDisplayName="" LastEditDate="2011-05-20T14:43:45.267" LastActivityDate="2011-05-21T00:56:03.813" Title="bitbang atmega328 with arduino bootloader using avrdude" Tags="&lt;arduino&gt;&lt;avr&gt;&lt;avrdude&gt;&lt;bootloader&gt;&lt;atmega328&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="14500" PostTypeId="1" CreationDate="2011-05-20T14:26:35.180" Score="2" ViewCount="73" Body="&lt;p&gt;I have an Arduino project which takes three variable voltage inputs (in the range 0.43V to 0.63V) to a 4051 multiplexer (FAIRCHILD SEMICONDUCTOR CD4051BCN).  Each input is selected sequentially and passed through an OpAmp to the Arduino and on to the PC for logging and analysis.  DC5V is taken from the Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I can control the multiplexer input voltages fairly accurately for testing purposes with a variable resistance and multimeter, also I can test the OpAmp is working ok and stable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My problem is that the output from the multiplexer is hopelessly unstable and varies by +/- 20% or more from the input voltage and does not stabilise over time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried change the sampling rate and allowing more time for the output to settle before reading it - but no good!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As an electronics newbie I may have picked the wrong multiplexer - there seems to be a load of products available but not clear to me which is best for my application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any insight or guidance appreciated.&lt;/p&gt;&#xA;" OwnerUserId="4339" LastActivityDate="2011-05-20T22:21:06.113" Title="Multiplexer output is unstable and inaccurate - what am I doing wrong?" Tags="&lt;arduino&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="14501" PostTypeId="2" ParentId="14497" CreationDate="2011-05-20T14:31:52.893" Score="1" ViewCount="" Body="&lt;p&gt;Normally the outputs of a Synchronous Shift Register will change in response to a clock edge.  Of course the exact details will depend on exactly what shift register you're trying to use.  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-20T14:31:52.893" CommentCount="2" />
  <row Id="14502" PostTypeId="2" ParentId="14500" CreationDate="2011-05-20T14:42:04.733" Score="1" ViewCount="" Body="&lt;p&gt;I have a few general suggestions, based on my company's usage of the 74HC4051. &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Make sure that you're changing the address lines in a single operation, if possible. If all of the address lines are on the same physical micro I/O port, you can do this fairly easily.&lt;/li&gt;&#xA;&lt;li&gt;Make sure that under &lt;em&gt;no&lt;/em&gt; conditions there is an input signal higher than the supply of the IC, or below ground. Use resistor dividers and schottky diode clamps to keep signals in check.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;We use a small 10R + 33pF filter on the output as well.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-05-20T14:59:45.547" LastActivityDate="2011-05-20T14:59:45.547" />
  <row Id="14503" PostTypeId="2" ParentId="10587" CreationDate="2011-05-20T15:11:11.940" Score="2" ViewCount="" Body="&lt;p&gt;As of now, you can.&#xA;Actually, apparently the &lt;a href=&quot;http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267120897/15&quot; rel=&quot;nofollow&quot;&gt;big problem with the UNO is the auto reset&lt;/a&gt; - if you put about a 120 Ohm resistor from reset to 5v on the UNO then it'll work.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Load the ISP sketch, disable the auto reset with the resistor, and then follow the normal directions.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I just burned 3 chips last week from my UNO - so I &lt;em&gt;know&lt;/em&gt; this works).&lt;/p&gt;&#xA;" OwnerUserId="3778" LastActivityDate="2011-05-20T15:11:11.940" CommentCount="2" />
  <row Id="14504" PostTypeId="2" ParentId="14146" CreationDate="2011-05-20T15:16:35.093" Score="0" ViewCount="" Body="&lt;p&gt;My method is not far behind Cogsy's. Instead of deep diving into eagle and the such, goto your local Radioshack, pick up some of there perf boards (curcuit boards with a ton of holes in them). Setup the atmega328 with the necessary extras (1 external crystal with 2 capacitors, capcitor for power line filtering and resistor to pull reset pin high). Solder the chip/circuit to the perf board.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This method is a lot less daunting than starting off with a custom pcb. I recently just got started with electronics as well and this method was my next step. Now i do my own etching but that is the progression that most easily taken.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="2833" LastActivityDate="2011-05-20T15:16:35.093" />
  <row Id="14505" PostTypeId="2" ParentId="14491" CreationDate="2011-05-20T16:16:57.610" Score="1" ViewCount="" Body="&lt;p&gt;Arduino has a Capsense library. If your object is not metallic then it can be the perfect answer. Its cheap and easy to make too. You just need two arduino pins, few high value registers,aluminum foil and some capacitors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This thing works on the principle that the aluminum foil works as a capacitor and combined with resistor it charges in time equal to the RC time constant. You send a signal to one of the pin and wait to get the signal of second pin. As a human being starts to put their hand close to it the time constant changes and you can detect that see if a human being is near by.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is a &lt;a href=&quot;http://www.arduino.cc/playground/Main/CapSense&quot; rel=&quot;nofollow&quot;&gt;link&lt;/a&gt; to the arduino library.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt; Sorry I think I was hasty in posting. This is only applicable if you are detecting humans or anything that imitates human skin.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastEditorUserId="1200" LastEditorDisplayName="" LastEditDate="2011-05-20T17:04:36.727" LastActivityDate="2011-05-20T17:04:36.727" />
  <row Id="14506" PostTypeId="2" ParentId="12953" CreationDate="2011-05-20T17:19:46.137" Score="1" ViewCount="" Body="&lt;p&gt;You might want to look into GDTs.  Gas Discharge Tubes.  These are often used in telecom to buffer sensitive circuits from lightning strikes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistance when under their rated voltages (varies from 50v to over 200v) is many megaohms.  When the voltage reaches a higher level, the device will move into a glow range (think neon lamp).  This is good for small spikes.  When it gets hit with REAL voltage, like 40 kV from a strike, it converts into an arc phase, where the resistance is very small and lines are shorted together, protecting the sensitive components.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You still need something to handle the low danger voltages of a couple hundred, but after that the GDT takes over.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;None of these will protect you from a direct strike to the board.  Hopefully you have grounding path so a roof hit will mainly be taken to ground and all you are protecting is incidental voltage spikes and not a true lighting current path.  But a GDT across your thermistor might be the thing.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastEditorUserId="4342" LastEditorDisplayName="" LastEditDate="2011-05-20T21:09:39.653" LastActivityDate="2011-05-20T21:09:39.653" />
  <row Id="14507" PostTypeId="2" ParentId="14497" CreationDate="2011-05-20T18:02:13.423" Score="0" ViewCount="" Body="&lt;p&gt;In addition to David Kessner's answer, some serial-in-parallel-out shift registers have an Output Latch Enable.  This allows you to shift e.g. 8 bits into the shift register without the inputs &quot;sliding&quot; across the output.  Once you get all your bits in, then you assert OLE during a clock edge, and all 8 output bits are updated simultaneously.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-05-20T18:02:13.423" />
  <row Id="14508" PostTypeId="1" AcceptedAnswerId="14517" CreationDate="2011-05-20T18:11:02.073" Score="4" ViewCount="116" Body="&lt;p&gt;If the pickups are just electromagnets detecting vibrations in metal strings, what effect does the guitar (size, shape, type of wood, solid body, hollow body) have on the pickups?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most argue that the pickups are similar to microphones. However, direct contact with the pickup by material other than metal does not produce any significant sound from an amplifier.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can wood vibrations from the body effectively transfer to the electromagnetic pickup to affect tone in a significant way?&lt;/p&gt;&#xA;" OwnerUserId="4345" LastActivityDate="2011-05-21T01:28:38.180" Title="How does a guitar body affect electromagnetic pickups?" Tags="&lt;electromagnetism&gt;" AnswerCount="4" />
  <row Id="14509" PostTypeId="1" AcceptedAnswerId="14514" CreationDate="2011-05-20T18:11:30.870" Score="-2" ViewCount="123" Body="&lt;p&gt;Is there such a thing as a small self-contained, self-powered LED light?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example: Imagine that I want to put an ultra-bright 5mm LED light into a glass bottle, put a cap on the bottle, and have the LED light up (and just stay lit). Obviously, there's no simple way to feed wiring into the bottle, so the LED would need to be self-powered and fully &quot;self-contained&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note: I don't need a power switch. Once the LED is powered (&quot;turned on&quot;), it can remain on &quot;forever&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does such a thing exist? If not, is it be possible to make it on my own relatively cheaply/easily?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit (to clarify a few things):&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A friend of mine just showed me these:&#xA;&lt;a href=&quot;http://www.instructables.com/id/LED-Throwies/&quot; rel=&quot;nofollow&quot;&gt;http://www.instructables.com/id/LED-Throwies/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That's sort of what I'm looking for, but it looks like those are only good for 1-2 weeks. I'd like something that would last closer to 6-12 months.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I understand that there's a trade-off between size/brightness/life, so let's assume that the following is the list of priorities, in order of importance:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Self-contained (no external wiring needed).&lt;/li&gt;&#xA;&lt;li&gt;Life. Needs to last a long time.&lt;/li&gt;&#xA;&lt;li&gt;Size. As small as possible, once the above two requirements have been met.&lt;/li&gt;&#xA;&lt;li&gt;Brightness. Least important.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Can anyone recommend a specific self-contained solution that will keep a light lit for 6 months? As small as possible, and as bright as possible, but I understand there are limits.&lt;/p&gt;&#xA;" OwnerUserId="4343" LastEditorUserId="4343" LastEditorDisplayName="" LastEditDate="2011-05-20T18:44:08.997" LastActivityDate="2011-05-20T20:02:38.823" Title="Self-contained, self-powered LED: does such a thing exist?" Tags="&lt;led&gt;" AnswerCount="3" CommentCount="8" />
  <row Id="14511" PostTypeId="2" ParentId="14508" CreationDate="2011-05-20T18:28:08.700" Score="0" ViewCount="" Body="&lt;p&gt;An electric guitar doesn't have a resonance box like an acoustic guitar. As a matter of fact, it's rather massive (heavy) and quite stiff. And since, like you said, the pickups are electromagnetic the shape of the guitar doesn't have any influence on the sound. That's why electric guitars can exist in any shape, even just the neck, no body.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-20T18:36:44.730" LastActivityDate="2011-05-20T18:36:44.730" CommentCount="4" />
  <row Id="14512" PostTypeId="2" ParentId="14508" CreationDate="2011-05-20T19:09:02.540" Score="6" ViewCount="" Body="&lt;p&gt;One of the major ways the vibrations can affect the sound of the guitar is by allowing greater feedback influence (most especially with hollow-body electric guitars). Example, &lt;a href=&quot;http://en.wikipedia.org/wiki/Trey_Anastasio#Guitar_playing_style&quot; rel=&quot;nofollow&quot;&gt;Trey Anastasio&lt;/a&gt; has several extremely resonant guitars, and that controlled feedback is a signature of his sound.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for actual EM influence in this case, there isn't any; but that doesn't mean the body of the guitar can't have a tremendous effect on the guitar's sound and playability.&lt;/p&gt;&#xA;" OwnerUserId="1269" LastActivityDate="2011-05-20T19:09:02.540" CommentCount="2" />
  <row Id="14513" PostTypeId="2" ParentId="14493" CreationDate="2011-05-20T19:15:16.237" Score="3" ViewCount="" Body="&lt;p&gt;There used to be IC sockets with decoupling capacitors built in. Haven't seen them in years, tho  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/Smlbg.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2255" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-21T08:23:41.007" LastActivityDate="2011-05-21T08:23:41.007" CommentCount="5" />
  <row Id="14514" PostTypeId="2" ParentId="14509" CreationDate="2011-05-20T19:17:52.200" Score="1" ViewCount="" Body="&lt;p&gt;There are several ways to approach this.  The approach I'm going to take is by emphasizing the &quot;forever&quot; aspect of it.  Basically, you need some sort of &quot;input&quot; to power an LED forever.  Normally the input would be some wires with power, or a supply of fresh batteries.  Failing that, the best thing would be to use solar power.  I have seen several projects where someone took a solar outdoor light (the kind you stake into the ground in your garden) and modifies them to fit inside a jar or bottle.  This can then sit on your patio table or in a window and provides light at night.  These lights are fairly inexpensive so it's not too bad hacking these up for a project like this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another approach is to make a blinking LED.  There are lots of circuits on the web that do this, with either a battery or a solar panel to power it.  Some circuits can run for 1-2 years on a single AA battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another idea that you didn't mention is that you can encase the whole thing in &quot;casting resin&quot;.  This is basically a water-clear epoxy available from craft/hobby stores.  Normally you'd see things like dried flowers or insects put inside this.  But you can also put electronics if you're careful.  It's cool to have a solid brick of clear stuff with a light in it and no outside connections.  There is a trick to using this, however.  Like all epoxies, there are two parts that you mix together.  Depending on the ratio, the epoxy will set quickly or slowly.  You want slowly.  Very slowly.  And then even slower than that.  The quicker it sets, the hotter it gets (it is an exothermic chemical reaction, meaning it gives off heat).  If you're using a lot of it, which you will be, it will get very hot.  Hot enough to destroy electronics.  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-20T19:17:52.200" />
  <row Id="14515" PostTypeId="2" ParentId="1842" CreationDate="2011-05-20T19:18:01.230" Score="0" ViewCount="" Body="&lt;p&gt;This may be a bit pedantic, but (in the interest of not misleading newcomers) don't imply that thermistors are imprecise. I work with thermistors that are specified +/- 0.2 degC out of the box.&lt;/p&gt;&#xA;" OwnerUserId="2255" LastActivityDate="2011-05-20T19:18:01.230" />
  <row Id="14516" PostTypeId="2" ParentId="14497" CreationDate="2011-05-20T19:36:47.117" Score="1" ViewCount="" Body="&lt;p&gt;There are two common shift register designs with regard to the shift inputs and outputs.  On some shift registers, the shift-input sampling and shift-output change happen on the same clock edge; on others, they happen on opposite clock edges.  Generally, it's better for the sampling and change to happen on opposite clock edges &lt;i&gt;unless&lt;/i&gt; it can be guaranteed that the recipient of the data will receive the clock before the sender does (e.g. because the data recipient is generating the clock).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From what I can tell, it seems a lot of logic is implemented on the principle that all inputs and outputs change on the same clock edge, though I would tend to think that in many cases it would be better to use opposite clock edges.  If everything uses the same clock edge, clock matching is critical, even at clock rates down to DC.  By contrast, if outputs change on one edge and inputs are sampled on another, clock rates may not be able to go as fast as when using one edge for everything, but clock skew will merely limit the top usable clock speed, rather than rendering the device unusable at any speed.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-20T19:36:47.117" />
  <row Id="14517" PostTypeId="2" ParentId="14508" CreationDate="2011-05-20T19:40:27.123" Score="6" ViewCount="" Body="&lt;p&gt;I think the best way to think about this is to not only think about the wire (moving guitar string) cutting through the magnetic field of the pick-ups (stationary) but also to think about the pick-ups themselves moving with the resonance of the wood that they are fixated to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now you must consider the frequency response of the instrument as a whole and this would definitely be affected by the choice of wood.  How &lt;em&gt;much&lt;/em&gt; it affects the sound is another question.  I personally believe the subtle differences end up being audible due to the degree of amplification.  But in the grand scheme of things, this is just a part of the entire signal chain that can effect your sound.&lt;/p&gt;&#xA;" OwnerUserId="4172" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-21T01:28:38.180" LastActivityDate="2011-05-21T01:28:38.180" CommentCount="2" />
  <row Id="14518" PostTypeId="2" ParentId="14509" CreationDate="2011-05-20T19:40:57.017" Score="3" ViewCount="" Body="&lt;p&gt;The only way this could last virtually forever would be a nuclear power source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only &lt;em&gt;realistic&lt;/em&gt; way it can last forever is to feed in the energy in by some other means than wiring, the most obvious possibility being a transformator with the primary coil outside and the secondary coil inside the bottle. The energy is then fed in invisibly through the alternating magnetic field.&lt;/p&gt;&#xA;" OwnerUserId="4327" LastActivityDate="2011-05-20T19:40:57.017" />
  <row Id="14519" PostTypeId="2" ParentId="14509" CreationDate="2011-05-20T20:02:38.823" Score="0" ViewCount="" Body="&lt;p&gt;Can you post a picture or more information about this bottle?  Is there a specific kind, or will any bottle work?  I only ask because there are several drinks out there that come in a clear wide-mouth bottle.  That means feeding a self-contained LED + resistor + battery should be trivial.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there an aesthetic aspect to this project of yours?  Perhaps you don't want the LED assembly to be large, and prefer it to lay inconspicuously at the bottom of the bottle.  If you don't care, then you could make the unit serviceable by creating a column of these LED assemblies that just sit in the center of the bottle (picture a long rod going through the mouth of the bottle).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or you can form the LED assembly in a small football shape, so that when the batter does wear out, you can shake the bottle and the &quot;football&quot; will have more of a tendency to wiggle its way through the mouth.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bigger you can make the assembly, the larger the battery, and the longer the life.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Additionally, do you really need the light on 24/7/365?  If not, you can stick some small electronics in there to switch on based on ambient light levels.&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-05-20T20:02:38.823" CommentCount="2" />
  <row Id="14520" PostTypeId="2" ParentId="14508" CreationDate="2011-05-20T20:03:22.973" Score="5" ViewCount="" Body="&lt;p&gt;Of course it does not affect the &quot;sound of the pickups&quot;, but the pickups don't have any sound to themselves anyway: they only &lt;em&gt;pick up&lt;/em&gt; the sound that's coming from the guitar strings and modify it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The sound of the strings, on the other hand, is affected quite a lot by the mechanical resonances of the guitar, in particular by the neck but also by the body. Because on a frequency the guitar can easily resonate to, the strings are able to release much more energy into the environment than for a frequency where the body does not move along at all. And which frequencies these are depends on a lot of parameters, which are different for every guitar type and even for guitars built in exactly the same way but from different types of wood.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So if you equip, for instance, a Les Paul and a tele with exactly the same pickups an circuitry, you will still get very notably different sounds. The difference is even more obvious when you also consider hollow-body guitars: quite a lot of these actually do have the same pickups and circuitry on them as Les Pauls, but still sound completely different.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;hr&gt;&#xA;To make the point about the mechanical resonances a little clear: if you built a guitar by spanning one string across a plastic broomstick, no matter what pickup you equip it with, it will always sound like just what it is. That's because the material is so light and soft that it can resonate to virtually any frequency and absorb a lot of energy.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, if you use a massive block of granite, which is so heavy and hard that it will resonate but very little, you get a very long sustain (most damping is then due to string stiffness and perhaps even air friction) and a literally very hard sound, because none of the overtones are filtered particularly strong.&lt;/p&gt;&#xA;" OwnerUserId="4327" LastEditorUserId="4327" LastEditorDisplayName="" LastEditDate="2011-05-20T20:15:02.433" LastActivityDate="2011-05-20T20:15:02.433" CommentCount="3" />
  <row Id="14521" PostTypeId="2" ParentId="10150" CreationDate="2011-05-20T21:14:36.903" Score="1" ViewCount="" Body="&lt;p&gt;1/8&quot; and 1/4&quot; would be electrically equivalent.  Even if the 1/4&quot; is a TRS (Tip, Ring, Sleeve) instead of just a TS (Tip, Sleeve), you can get the same electrical balanced connection from an 1/8&quot; stereo plug hooked up for balanced mono audio.  If you support balanced audio, you could even get an adapter from XLR to 1/8&quot;.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastEditorUserId="4342" LastEditorDisplayName="" LastEditDate="2011-05-20T23:59:43.093" LastActivityDate="2011-05-20T23:59:43.093" />
  <row Id="14522" PostTypeId="2" ParentId="14500" CreationDate="2011-05-20T22:21:06.113" Score="2" ViewCount="" Body="&lt;p&gt;This is just a general technique that might apply here. One thing that beginners often do is to try to start and end a conversion in a single pass. For example,&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;start the conversion&#xA;kill some time&#xA;read the input&#xA;use the data&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The problem with this is that you need to wait long enough for the inputs to become stable, but you don't want to wait too long because doing so eats into your periodic's time slice. The usual solution is to turn things around, like so -&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;read the input&#xA;use the data&#xA;start a conversion&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;it looks backwards, but what it does is let the hardware do its thing for the entire length of the periodic. For example, let's say a conversion takes 50 usec (for argument's sake, combine the time to select an input and the ADC time), and you're trying to read the device every 1 msec. The first way, assuming you wait the bare minimum 50 usec, then 5% of every 1 msec interval is wasted, and the hardware has only the minimal allowable settling time. Done the second way, by the time you read the input, the hardware has had a full millisecond to do its thing, the data is available immediately at the start of the periodic, and the processor can get back to doing whatever it does between times with no cycle wasting delay loops. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course you do take a latency hit this way; in the example, all your data is 1 msec old, but usually the latency incurred this way is acceptable. In return you tend to get more stable input and more efficient cpu usage.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-20T22:21:06.113" />
  <row Id="14523" PostTypeId="2" ParentId="14497" CreationDate="2011-05-20T23:05:33.330" Score="1" ViewCount="" Body="&lt;p&gt;It depends on the device you are using.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, it will never be &quot;at the same time&quot;.&#xA; &lt;strong&gt;Nothing happens in zero amount of time.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your device datasheet will have the information you need. For example...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/GAVEK.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.onsemi.com/pub/Collateral/74HC595-D.PDF&quot; rel=&quot;nofollow&quot;&gt;Datasheet: 74HC595: 8-Bit Shift Register w/Output Storage Register (3-State)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sections of interest in the datasheet    &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Function Table&lt;/li&gt;&#xA;&lt;li&gt;Timing Requirements&lt;/li&gt;&#xA;&lt;li&gt;Timing Diagram&lt;/li&gt;&#xA;&lt;li&gt;Switching Waveforms&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;From this data we can determine things like...&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Data is shifted into the register on a rising edge of the shift clock.&lt;/li&gt;&#xA;&lt;li&gt;The serial input must be present for &lt;strong&gt;t&lt;/strong&gt;&lt;sub&gt;su&lt;/sub&gt; before switch clock goes high (fiq.5).&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;t&lt;/strong&gt;&lt;sub&gt;su&lt;/sub&gt; is in nanoseconds.&lt;/li&gt;&#xA;&lt;li&gt;&lt;strong&gt;t&lt;/strong&gt;&lt;sub&gt;su&lt;/sub&gt; could be as long as 75ns depending on V&lt;sub&gt;cc&lt;/sub&gt; and temperature.&lt;/li&gt;&#xA;&lt;li&gt;And more...&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/tZR88.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/FfkLd.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/eMM4s.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1419" LastActivityDate="2011-05-20T23:05:33.330" CommentCount="1" />
  <row Id="14524" PostTypeId="2" ParentId="11914" CreationDate="2011-05-20T23:54:07.500" Score="1" ViewCount="" Body="&lt;p&gt;Your dumb charger is just providing a slightly regulated voltage.  It works due to the combined resistances of the charger and battery limiting the current.  As the battery voltage gets close to the charger, the voltage potential is less.  So with a fixed resistance, the current drops.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I doubt that you can modify your current charger to push 38 A up to 14.4 V.  This could only happen if the combined resistances and voltage difference allow sufficient current flow.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most likely you will need a higher voltage source and then circuitry to make a constant current source to provide a fixed amperage.  Shutting it off can be done with a simple comparator circuit.  Put a 10k trimmer pot across the battery voltage and run it into a comparator along with voltage from a zener regulator.  Then you just adjust the voltage divider from the pot till it trips at the correct battery voltage.  Use that to turn off a high current MOSFET or something similar.  (Might use the same MOSFET to control the constant current.)&lt;/p&gt;&#xA;" OwnerUserId="4342" LastEditorUserId="4342" LastEditorDisplayName="" LastEditDate="2011-05-21T13:29:22.673" LastActivityDate="2011-05-21T13:29:22.673" />
  <row Id="14525" PostTypeId="2" ParentId="14498" CreationDate="2011-05-21T00:56:03.813" Score="2" ViewCount="" Body="&lt;p&gt;How about making one of the countless serial AVR programmers and using it to write the Arduino firmware? &lt;a href=&quot;http://electronics-diy.com/avr_programmer.php&quot; rel=&quot;nofollow&quot;&gt;This&lt;/a&gt; one worked for me, but I have USB to serial converter, so it works at amazing 3 B/s. If the programer lines on your other project are available, you can dump firmware using AVRdude. You could also probably get it form the Internet, but I don't know where to look&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-05-21T00:56:03.813" CommentCount="2" />
  <row Id="14526" PostTypeId="2" ParentId="5010" CreationDate="2011-05-21T06:45:25.567" Score="3" ViewCount="" Body="&lt;p&gt;I think the best solution is to use CD4060 with a crystal oscillator which can produced 1Hz pulses. Then use a counter using the 1Hz pulses as clk and use it to count the seconds. There are problems with 555 timer approach. The resistors and capacitors use to set the frequency are not all that accurate, and they drift with temperature. Actually the 555 Chip itself can drift with temperature. Check this site: &lt;a href=&quot;http://hackersbench.com/Projects/1Hz/&quot; rel=&quot;nofollow&quot;&gt;hackersbench.com&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4277" LastEditorUserId="4277" LastEditorDisplayName="" LastEditDate="2011-05-22T18:27:02.787" LastActivityDate="2011-05-22T18:27:02.787" />
  <row Id="14527" PostTypeId="1" AcceptedAnswerId="14538" CreationDate="2011-05-21T07:01:19.703" Score="4" ViewCount="368" Body="&lt;p&gt;Pardon my naïveté, but it seems like most programmable devices (FPGAs, PLCs, PICs, etc.) are programmable using the C or C++ languages, or a variant of one of these. Are there any devices out there that use something like D, Mozilla Rust, or Google Go? I realize that the latter two, especially, are immature languages; but surely someone, somewhere has released an experimental product.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone have any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="4349" LastActivityDate="2011-05-24T21:54:47.820" Title="Any programmable devices available for more modern languages?" Tags="&lt;programmable-logic&gt;" AnswerCount="7" CommentCount="12" FavoriteCount="1" />
  <row Id="14528" PostTypeId="2" ParentId="14493" CreationDate="2011-05-21T07:44:40.187" Score="5" ViewCount="" Body="&lt;p&gt;Oversimplified, one could say: &lt;em&gt;Capacitor designers don't like to use advanced 45 nm processing, and IC designers have little to no idea about how to get an extremely big $\epsilon_r$ out of barium titanate.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The materials used in chips are optimized for semiconductors, not for things needed in capacitors (i.e. extremely high dielectric constants). And even if they were, on-chip capacitors would still use a lot of space, making the chips very expensive. The relatively large area for an on-chip capacitor would have to go through all the tricky process steps needed for the original chip functionality. Therefore, the only capacitors built onto the chip structure are those that can be very small anyway or those that are required to be trimmed very precisely to what the IC is intended to to, e.g. the charge redistribution capacitors of a successive-approximation analog-to-digital converter that must even be trimmed while the chip is still being manufactured.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For things like decoupling of the chip's supply rails or buffering its reference node, where the precise value of the capacitor doesn't matter too much but where a high C*V product is needed, it is way better to place some capacitors next to the ICs. These can be made of electrolytic or ceramic material trimmed for much capacitance*voltage in a small volume, and fabricated in a process ideal for these requirements.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, there are of course some hybrid packaging techniques where ceramic capacitors are placed onto or into the same package with an IC, but these are exceptions where either the length of the connectors from the die through a standard IC package and socket to a cap on the board would already be too long and have too much inductance, or where the IC manufacturer doesn't want to rely on the board designers to actually read their data sheets and application notes about where the caps must be placed so the IC can meet its specifications.&lt;/p&gt;&#xA;" OwnerUserId="930" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-05-21T08:17:51.657" LastActivityDate="2011-05-21T08:17:51.657" CommentCount="2" />
  <row Id="14529" PostTypeId="2" ParentId="14527" CreationDate="2011-05-21T09:06:00.070" Score="2" ViewCount="" Body="&lt;p&gt;Devices have been designed to use other languages efficiently, such as LISP/Scheme, Forth and Java. I don't believe that any have been designed for those languages you mentioned, perhaps they are not suitable for embedded systems (apart from D which should run efficiently on anything designed for C/C++). They could, presumably, be implemented on any suitable MCU, if someone wished to do so.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-21T09:24:32.333" LastActivityDate="2011-05-21T09:24:32.333" CommentCount="1" />
  <row Id="14530" PostTypeId="2" ParentId="14527" CreationDate="2011-05-21T09:08:15.120" Score="3" ViewCount="" Body="&lt;p&gt;You are pardoned.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason that C, and less C++, (among other language as VHDL) is used for these kinds of devices is that it is easy to translate from the language constructs to the underlying hardware. C is considered lingua franca, understood by many and to port a new language to the device, especially if reading/writing to registers is awkward, is not worth the effort if the language isn't much better at expressing useful constructs.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The examples that you use as newer, shinier languages, D, for example, could be a candidate for a &quot;low-level&quot; language if more programmers use it. D is touted a the modern C++ without all the compromise with C and implemented right from the start. Unfortunately without all the C++ libraries. I think you can call C libs from D.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The question isn't if it is newer, the question is if they are better tools. As far as I can see, it isn't the case.&lt;br&gt;&#xA;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;When I have written embedded code (in C) I have wished for a better macros/templates than C can offer. As it is a compile time construct, it really has nothing to do with the underlying hardware. But much more complicated to implement in a compiler.&lt;/p&gt;&#xA;" OwnerUserId="3882" LastEditorUserId="3882" LastEditorDisplayName="" LastEditDate="2011-05-21T10:23:26.550" LastActivityDate="2011-05-21T10:23:26.550" CommentCount="2" />
  <row Id="14531" PostTypeId="2" ParentId="14433" CreationDate="2011-05-21T09:28:37.257" Score="5" ViewCount="" Body="&lt;h1&gt;By using closed-loop motion control and a lot of math.&lt;/h1&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;...variable speed drill is started it&#xA;  just accelerates at whatever rate and&#xA;  actual rotation rate will largely&#xA;  depend on the load...&quot;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;What we need here is something that would regulate the rotation rate for us and eliminate its dependence on foreign load. Something like a government, they are good a regulating things...&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;A GOVERNOR is a part of a machine by means of which the velocity of the&#xA;  machine is kept nearly uniform,&#xA;  notwithstanding variations in the&#xA;  driving-power or the resistance.        &lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;I propose at present, without entering into any details of mechanism&#xA;  to direct the attention of engineers&#xA;  and mathematicians to the dynamical&#xA;  theory of such governors.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;- &lt;a href=&quot;http://en.wikipedia.org/wiki/James_Clerk_Maxwell&quot; rel=&quot;nofollow&quot;&gt;James Clerk Maxwell&lt;/a&gt;. &lt;sub&gt;&lt;sup&gt;On Governors,&#xA;  Proceedings of Royal Society, vol. 16&#xA;  (1867–1868)&lt;/sub&gt;&lt;/sup&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The motion control systems in a Segway &quot;govern&quot; motor speeds and positions by &quot;&lt;a href=&quot;http://en.wikipedia.org/wiki/Control_loop&quot; rel=&quot;nofollow&quot;&gt;closing the loop&lt;/a&gt;&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Open-loop&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/rJihU.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Closed-loop&lt;/strong&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/qq0Lk.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;One small part of the loop found in a Segway.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/mAPim.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;More...&lt;br&gt;&#xA;&lt;a href=&quot;http://web.mit.edu/first/segway/&quot; rel=&quot;nofollow&quot;&gt;The DIY Segway&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.netrino.com/Embedded-Systems/How-To/PID-Closed-Loop-Control&quot; rel=&quot;nofollow&quot;&gt;Introduction to Closed-Loop Control&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.freepatentsonline.com/6302230.html&quot; rel=&quot;nofollow&quot;&gt;United States Patent 6302230 : Personal mobility vehicles and methods&lt;/a&gt;&lt;br&gt;&#xA;&lt;a href=&quot;http://www.freepatentsonline.com/6799649.html&quot; rel=&quot;nofollow&quot;&gt;United States Patent 6799649 : Control of a balancing personal vehicle&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1419" LastActivityDate="2011-05-21T09:28:37.257" />
  <row Id="14532" PostTypeId="1" AcceptedAnswerId="14535" CreationDate="2011-05-21T10:24:37.960" Score="2" ViewCount="84" Body="&lt;p&gt;I have seen circuits involving crystal oscillators connecting two capacitors between each of the crystal legs and ground. I would like to know how to design the value of these capacitors for different crystal frequencies. &lt;/p&gt;&#xA;" OwnerUserId="4277" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-21T17:35:11.953" LastActivityDate="2011-05-21T17:35:11.953" Title="How to design the capacitors used with Crystal Oscillators?" Tags="&lt;capacitor&gt;&lt;oscillator&gt;&lt;crystal&gt;" AnswerCount="1" CommentCount="3" FavoriteCount="1" />
  <row Id="14533" PostTypeId="1" AcceptedAnswerId="14537" CreationDate="2011-05-21T10:35:24.453" Score="2" ViewCount="112" Body="&lt;p&gt;I want to switch ON and OFF an incandescent bulb using MCU. Please suggest an electric switch (like relay or something) for 220V 50Hz AC line which can be used here. I would prefer something very cheap to keep the total project cost minimum.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT&lt;/strong&gt;: Don't limit this to incandescent bulb. The solution should be applicable to every daily life electrical appliances. &lt;/p&gt;&#xA;" OwnerUserId="4277" LastEditorUserId="4277" LastEditorDisplayName="" LastEditDate="2011-05-21T18:05:56.023" LastActivityDate="2011-05-21T18:05:56.023" Title="Control 220V AC line using MCU" Tags="&lt;microcontroller&gt;&lt;switch&gt;&lt;ac&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="14535" PostTypeId="2" ParentId="14532" CreationDate="2011-05-21T10:38:45.373" Score="4" ViewCount="" Body="&lt;p&gt;The frequency is irrelevant, what matters is the load capacitance of the crystal. It's specified by the crystal manufacturer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most MCUs use a Pierce oscillator with two feedback capacitors, which are effectively in series, although they look as though they might be in parallel. You therefore need to select the capacitors that, in series, and accounting for some stray capacitance, give the required crystal load capacitance. Most MCU manufacturers have application notes on capacitor selection, as do most crystal suppliers. &lt;a href=&quot;http://ww1.microchip.com/downloads/en/AppNotes/00826a.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a typical example.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-21T10:54:18.900" LastActivityDate="2011-05-21T10:54:18.900" CommentCount="1" />
  <row Id="14536" PostTypeId="2" ParentId="14533" CreationDate="2011-05-21T10:41:14.037" Score="5" ViewCount="" Body="&lt;p&gt;The best solution for an incandescent lamp is a SSR (Solid State Relay) with zero-crossing detection. (Zero-crossing switching increases the bulb's life.) An SSR module is the most convenient, but they're not cheap. If price is an issue you can better build the SSR from discrete components. Below is an example using the MOC3041 as opto-triac.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/DcMqM.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Despite Leon's comment this &lt;em&gt;is&lt;/em&gt; an inexpensive solution. In &lt;a href=&quot;http://electronics.stackexchange.com/questions/7516/why-do-solid-state-relays-cost-so-much&quot;&gt;this thread&lt;/a&gt; I calculated the cost as 2.10 euros; an electromechanical relay (+ transistor, diode, ...) often costs more.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-21T15:21:26.227" LastActivityDate="2011-05-21T15:21:26.227" CommentCount="3" />
  <row Id="14537" PostTypeId="2" ParentId="14533" CreationDate="2011-05-21T10:44:58.130" Score="3" ViewCount="" Body="&lt;p&gt;The cheapest solution is an ordinary mains relay with normally open contacts. Put the bulb in series with the contacts and the mains supply, and control it with a low voltage on the relay coil. Relays with coils that can be switched with the output from an MCU are readily available. Don't forget to put a diode or snubber across the relay coil. If you use a transistor driver, you can probably use a very cheap, less sensitive relay.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-21T11:20:48.393" LastActivityDate="2011-05-21T11:20:48.393" CommentCount="4" />
  <row Id="14538" PostTypeId="2" ParentId="14527" CreationDate="2011-05-21T12:12:20.157" Score="11" ViewCount="" Body="&lt;p&gt;You don't need different devices to use these languages, you just need the appropriate software system.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The main issues why this is not done more often are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;These languages typically need more resources (memory, runtime) for the same task.  For large volumes the reduced effort in programming would be more than offset by higher hardware costs.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Most higher-level languages need dynamic memory allocation with garbage collection, which is hard to do in a real-time setting.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;It is harder to get embedded developers for these languages.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;That said, there are such things as &lt;a href=&quot;http://www.rtsj.org/&quot; rel=&quot;nofollow&quot;&gt;Real-Time Java&lt;/a&gt;, which are used in &lt;a href=&quot;http://www.aicas.com/jamaica.html&quot; rel=&quot;nofollow&quot;&gt;real embedded systems&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-05-21T12:12:20.157" CommentCount="1" />
  <row Id="14539" PostTypeId="2" ParentId="14527" CreationDate="2011-05-21T12:18:43.087" Score="4" ViewCount="" Body="&lt;p&gt;There are open source projects working on such goals.  There is a project for Ada on Atmel MCUs (though I couldn't get it to work).  One of my coworkers is programming his 68HC11 MCU with a scaled down version of Ruby he has been working on himself.  And there is a company, BlueSpec, that has a new HDL for FPGAs/ASICs that is based on Haskell.  But it is not a tool that most would have access to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Vendors tend to stick with C because there is a large audience for C and it is widely accepted.  Likewise, for FPGAs/PLDs, VHDL/Verilog are widely accepted and proven.  Instead of having to support many different languages, most prefer to focus on their chips, trying to improve the performance of their C compilers and offer better tools for configuring and managing resources on their chips.  I kind of agree with this approach myself.  I much prefer that Texas Instruments improves their tools for configuring advanced peripherals on their chips than implementing advanced template metaprogramming on their minimal C++ compiler.&lt;/p&gt;&#xA;" OwnerUserId="2059" LastActivityDate="2011-05-21T12:18:43.087" />
  <row Id="14540" PostTypeId="1" CreationDate="2011-05-21T13:01:14.673" Score="2" ViewCount="71" Body="&lt;p&gt;FeRAM and MRAM have almost the same characteristics from electronic point of view although the physics behind is different - feroelectric material and magnetoresistive material. Their properties: non-volatile, write/read cycles number, write/read speeds etc are almost the same. Then why a company is choosing to use FeRAM instead of MRAM, or MRAM instead of FeRAM?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do you think that this are the future memories?&lt;/p&gt;&#xA;" OwnerUserId="4353" LastActivityDate="2011-05-21T13:36:32.323" Title="What is better to use, FeRAM or MRAM? Why?" Tags="&lt;memory&gt;" AnswerCount="1" />
  <row Id="14541" PostTypeId="2" ParentId="14527" CreationDate="2011-05-21T13:03:20.787" Score="1" ViewCount="" Body="&lt;p&gt;You are looking for a microprocessor. Intel sells them, so do AMD and ARM. You can use any programming langue on these devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for FPGA's: your choice of languages is limited. This is because you need a synthesis tool that will translate your code to a netlist. In addition to VHDL, Verilog and (restricted C), you can go with more modern languages like MyHDL (built on Python) or Bluespec (Haskell-like).&lt;/p&gt;&#xA;" OwnerUserId="3145" LastActivityDate="2011-05-21T13:03:20.787" CommentCount="2" />
  <row Id="14542" PostTypeId="2" ParentId="14540" CreationDate="2011-05-21T13:36:32.323" Score="2" ViewCount="" Body="&lt;p&gt;It seems like the only disadvantage of MRAM is more power for writes.  Unless things have changed, write speed is faster on MRAM and there is infinite endurance, unlike the limited number of cycles for FeRAM.  The issue is if MRAM can get into the main stream and get anywhere close to Flash as far as cell size.  Without the same yield, prices can't be competitive.  That drives most things.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-21T13:36:32.323" />
  <row Id="14543" PostTypeId="1" AcceptedAnswerId="14549" CreationDate="2011-05-21T16:15:14.737" Score="7" ViewCount="182" Body="&lt;p&gt;Hi, i'm currently making a geiger-counter and therefor I need to crank my 5VDC up to around 400 VDC, the current is very low, around 0.015-0.02 mA. What would be the best way to generate 400VDC from my 5v source? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks in advance! &lt;/p&gt;&#xA;" OwnerUserId="4354" LastActivityDate="2011-05-21T21:54:34.370" Title="Convert 5VDC to 400VDC" Tags="&lt;inverter&gt;&lt;5v&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="14544" PostTypeId="2" ParentId="14543" CreationDate="2011-05-21T16:50:10.430" Score="4" ViewCount="" Body="&lt;p&gt;Maxim has a design for a G-M tube power supply that takes a 5V input:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.maxim-ic.com/app-notes/index.mvp/id/3757&quot; rel=&quot;nofollow&quot;&gt;http://www.maxim-ic.com/app-notes/index.mvp/id/3757&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It looks easy to make, and should be quite cheap and very compact.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-21T17:33:34.043" LastActivityDate="2011-05-21T17:33:34.043" CommentCount="4" />
  <row Id="14545" PostTypeId="2" ParentId="14149" CreationDate="2011-05-21T19:09:39.397" Score="1" ViewCount="" Body="&lt;p&gt;I would suggest using a 555 timer with a 1-5% duty cycle and a T of one hour. Some 555 are not capable of less than 50% duty cycle, in which case you'll want to make the duty cycle 95-99% and the servo be active low. This website is an excellent reference for 555 timers with schematics - &lt;a href=&quot;http://www.kpsec.freeuk.com/555timer.htm#astable&quot; rel=&quot;nofollow&quot;&gt;http://www.kpsec.freeuk.com/555timer.htm#astable&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's a fairly simple circuit and you can easily play with it on a breadboard before making your PCB.&lt;/p&gt;&#xA;" OwnerUserId="4355" LastActivityDate="2011-05-21T19:09:39.397" />
  <row Id="14547" PostTypeId="1" CreationDate="2011-05-21T20:35:31.460" Score="2" ViewCount="86" Body="&lt;p&gt;I have a small form factor Lenovo IdeaCentre PC that I would like to use as the primary controller for a large scale tanked robot. I've ironed out the accessory connections using usb-&gt;server controllers and usb-&gt;motor controllers. However I am not certain how best to power the actual PC using LIPO batteries. The power supply/brick that shipped with the PC is a standard AC-&gt;DC 19v 3.42amp power supply. I'd like to power the robot and pc using ThunderPower lipo's, what type of regulator/converter is available for purchase? Or am I completely wrong in what I need? Any help would be greatly appreciated. Thanks!&lt;/p&gt;&#xA;" OwnerUserId="4356" LastActivityDate="2011-05-30T02:17:32.320" Title="DC-DC Regulator/Converter" Tags="&lt;power&gt;&lt;dc&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="14548" PostTypeId="2" ParentId="14472" CreationDate="2011-05-21T21:35:00.810" Score="3" ViewCount="" Body="&lt;p&gt;OK, this is what I wound up ordering from two vendors. This isn't a plug;  these are just two that I usually order from.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From SparkFun:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;BOB-10402 EM-406 Connector Breakout &lt;/li&gt;&#xA;&lt;li&gt;COM-00312 Darlington Driver 8-Channel ULN2803 DIP&lt;/li&gt;&#xA;&lt;li&gt;DEV-07914 Arduino ProtoShield Kit &lt;/li&gt;&#xA;&lt;li&gt;DEV-10059 Arduino and Breadboard Holder&lt;/li&gt;&#xA;&lt;li&gt;GPS-09123 Interface Cable for EM401 and EM406&lt;/li&gt;&#xA;&lt;li&gt;PRT-09279 Arduino Stackable Header - 8 Pin &lt;/li&gt;&#xA;&lt;li&gt;PRT-09389 Jumper Wires Premium 12&quot; F/F Pack of 10&lt;/li&gt;&#xA;&lt;li&gt;PRT-10158 Break Away Headers - Long&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;From Mouser:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;DS1822+PAR Board Mount Temperature Sensors 1-Wire Digital Thermometer&lt;/li&gt;&#xA;&lt;li&gt;SA612AD Up-Down Converters DOUBLE BAL MIXER/OSCILLATOR&lt;/li&gt;&#xA;&lt;li&gt;74HCT4066N Analog Switch ICs QUAD BILATERAL SWITCH&lt;/li&gt;&#xA;&lt;li&gt;MAX232ECNE4 RS-232 Interface IC RS232 Line Driver/Receiver&lt;/li&gt;&#xA;&lt;li&gt;122-0421-GR BAT HLDR 2XAAA 6 LDS NKL PLTD 6 LDS 26AWG&lt;/li&gt;&#xA;&lt;li&gt;AB38T-32.768KHZ Crystals 32.768KHz&lt;/li&gt;&#xA;&lt;li&gt;Desc.: Board to Board / Mezzanine Connectors HDR VT 1X09P .1 230/110 30AU&lt;/li&gt;&#xA;&lt;li&gt;SN74LS247N Encoders, Decoders, Multiplexers &amp;amp; Demultiplexers BCD to 7 Segment&lt;/li&gt;&#xA;&lt;li&gt;SN74LS595N Counter Shift Registers Serial-in shift Register&lt;/li&gt;&#xA;&lt;li&gt;DS1307+ Real Time Clock 64x8 Serial I2C RTC&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The SA612 seems like an odd choice for general tinkering;  I'm a ham radio operator, though.  I did decide to get the temperature sensor; we have a 600 dollar IT environment monitor at work and it is tempting to replicate that with a 59 dollar dev board for my personal server.  The battery holders are related to the RTC I'm planning to use, and I've gotten an assortment of 74LS logic so I can interface an LCD (Hitachi-based) and some seven-segment displays I have.  The GPS parts are for the specific module (EM406A) I got from SparkFun.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To broaden this for other experimenters, I'd also recommend the following things I have in my parts bins:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Small-signal NPN and PNP bipolar transistors--get bunches of each&lt;/li&gt;&#xA;&lt;li&gt;small-signal diodes of the 1N4148 variety&lt;/li&gt;&#xA;&lt;li&gt;for radio experimenting, 1N34 germanium diodes if they even still sell them&lt;/li&gt;&#xA;&lt;li&gt;1N4001 small switching diodes&lt;/li&gt;&#xA;&lt;li&gt;Zener diodes of 5.1V, 7.1V etc.&lt;/li&gt;&#xA;&lt;li&gt;LM7805, 7812 regulators.&lt;/li&gt;&#xA;&lt;li&gt;LED's (naw really!)&lt;/li&gt;&#xA;&lt;li&gt;breadboards, protoboards and jumper sets&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The &lt;a href=&quot;http://makershed.com&quot; rel=&quot;nofollow&quot;&gt;Maker Shed&lt;/a&gt; has a &lt;a href=&quot;https://www.makershed.com/ProductDetails.asp?ProductCode=MSUMP&amp;amp;Click=37845&quot; rel=&quot;nofollow&quot;&gt;nice starter kit&lt;/a&gt; for $120 with an option to get it with your choice of Arduino, Netdunio or Netduino Plus, which covers many of the items on my list. &lt;/p&gt;&#xA;" OwnerUserId="3983" LastEditorUserId="3983" LastEditorDisplayName="" LastEditDate="2011-05-29T00:21:39.993" LastActivityDate="2011-05-29T00:21:39.993" CommunityOwnedDate="2011-05-21T21:35:00.810" />
  <row Id="14549" PostTypeId="2" ParentId="14543" CreationDate="2011-05-21T21:54:34.370" Score="2" ViewCount="" Body="&lt;p&gt;An LM641 with a suitable FET, see for example &lt;a href=&quot;http://www.ludlums.com/images/stories/product_manuals/M2401PEWEC2ECmar97.pdf&quot; rel=&quot;nofollow&quot;&gt;this circuit&lt;/a&gt; of a Geiger counter (p 34/39).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incidentally, one of my current projects is to build a Geiger counter for LEGO Mindstorms NXT with a Soviet SBM-20 tube, which needs 400V and at most 50µA.  The power supply is 4.3V at 20mA, and I plan to use an LM641 with a BSP126 or BSP130.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also &lt;a href=&quot;http://www.mikrocontroller.net/topic/210725#new&quot; rel=&quot;nofollow&quot;&gt;this thread (in german) about circuits for an SBM-20&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="339" LastActivityDate="2011-05-21T21:54:34.370" />
  <row Id="14550" PostTypeId="1" CreationDate="2011-05-21T23:46:24.007" Score="0" ViewCount="61" Body="&lt;p&gt;I've got an Arduino Uno and I'm relatively new to electronics / I'd like to connect it to a serial receipt printer and an ethernet switch. For all the research that I've done, I've found a number of serial and ethernet shields, but I'm not sure if I can use them both together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any help would be greatly appreciated.&lt;/p&gt;&#xA;" OwnerUserId="4358" LastActivityDate="2011-05-22T00:46:13.113" Title="How to hook up an Arduino Uno to serial and ethernet" Tags="&lt;arduino&gt;&lt;serial&gt;&lt;ethernet&gt;" AnswerCount="1" />
  <row Id="14551" PostTypeId="2" ParentId="14550" CreationDate="2011-05-22T00:46:13.113" Score="1" ViewCount="" Body="&lt;p&gt;I believe the USART on the 328P is connected to the AT8U2 Micro, which is doing the USB to Serial conversion.  You my be able to use these same pins for another serial device, as long as you aren't connected to USB.  If this is the case, then you should have no conflicts from the Ethernet shield.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to roll your own serial using other pins, just look at the ethernet shield first to determine what pins it is using.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-22T00:46:13.113" />
  <row Id="14552" PostTypeId="1" CreationDate="2011-05-22T02:42:26.460" Score="-1" ViewCount="97" Body="&lt;p&gt;In the event that there is no power or voltage rating on an appliance, I was wondering how does one determine if the appliance works with 110V or 220V without damaging it. Does anyone have any suggestions?&lt;/p&gt;&#xA;" OwnerUserId="1863" LastActivityDate="2011-05-22T03:47:34.803" ClosedDate="2011-05-23T00:18:25.507" Title="How to differentiate 110V and 220V appliances?" Tags="&lt;power-supply&gt;&lt;voltage&gt;&lt;consumer-electronics&gt;" AnswerCount="2" CommentCount="9" />
  <row Id="14553" PostTypeId="2" ParentId="14552" CreationDate="2011-05-22T03:11:52.417" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Mains_electricity_by_country&quot; rel=&quot;nofollow&quot;&gt;Look at the plug&lt;/a&gt;?&lt;/p&gt;&#xA;" OwnerUserId="906" LastActivityDate="2011-05-22T03:11:52.417" CommentCount="4" />
  <row Id="14554" PostTypeId="2" ParentId="14552" CreationDate="2011-05-22T03:47:34.803" Score="1" ViewCount="" Body="&lt;p&gt;A couple of things come to mind.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-- Ask for a datasheet. Search the internet for the datasheet&lt;/p&gt;&#xA;&#xA;&lt;p&gt;-- Take it apart and see whats inside&lt;/p&gt;&#xA;" OwnerUserId="1927" LastActivityDate="2011-05-22T03:47:34.803" />
  <row Id="14555" PostTypeId="1" AcceptedAnswerId="14558" CreationDate="2011-05-22T09:28:24.987" Score="3" ViewCount="150" Body="&lt;p&gt;Reading the &lt;a href=&quot;http://en.wikipedia.org/wiki/Mains_electricity_by_country&quot; rel=&quot;nofollow&quot;&gt;list of standard plug and socket types on Wikipedia&lt;/a&gt;, I see that countries have made their mains voltage higher or lower. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, in Mainland Britain (Wales, Scotland, England) the voltage has been lowered to 230V from 240V.  On the other hand, in Northern Island it has increased from 220V to 230V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Have they just moved the voltage to informally meet the rest of the world? As the vast majority of countries are either 230V or 120V. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are there any other things that could be gained from this? I understand that lowering the voltage could decrease power dissipation because $P=VI$, but increasing the voltage?  What is there to gain other than more losses?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-22T12:24:55.943" LastActivityDate="2011-05-22T12:24:55.943" Title="What have countries gained by increasing/decreasing mains voltage by 10V?" Tags="&lt;line-power&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="14556" PostTypeId="1" AcceptedAnswerId="14569" CreationDate="2011-05-22T09:46:50.250" Score="0" ViewCount="178" Body="&lt;p&gt;I am a little weak in analog circuits even though electronics is my subject (Engineering course). Transistor is like a Pandora box to me. Last day I read a question about how to use transistor as switch in this site. It made complete sense to me. That gave me confidence to learn more about transistors. I want learn deep about that now. Deep enough so that I can even do analysis myself without referring any textbooks. So please explain me about transistor models in plain English.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know what transistor is. What I dont know is about its models for circuit design like hybrid model, small signal model etc. I dont what equations (I got books for that). Tell something in plain language.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: Explain about &lt;strong&gt;Small signal model&lt;/strong&gt;.&lt;/p&gt;&#xA;" OwnerUserId="4277" LastEditorUserId="4277" LastEditorDisplayName="" LastEditDate="2011-05-23T01:50:28.383" LastActivityDate="2011-05-23T01:50:28.383" Title="Explain small signal  model of transistor to a beginner." Tags="&lt;transistor&gt;" AnswerCount="4" CommentCount="5" FavoriteCount="1" />
  <row Id="14557" PostTypeId="2" ParentId="14555" CreationDate="2011-05-22T10:32:17.807" Score="2" ViewCount="" Body="&lt;p&gt;Europe switched from 220V to 230V in the nineties. Advantage: you need less current for the same power, making that you need less copper for distribution, but it's only 5%. And if increasing the voltage offers an advantage it can't be an advantage in the countries where the voltage is decreased.&lt;br&gt;&#xA;IMO it's been done to have more of a standard. Nowadays you can have universal power supplies which are as happy with 115V as with 230V, but in the past a 220V appliance may have had a switch to select between 220V and 240V. Now that everybody uses the same 230V you don't need that anymore. &lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-22T10:32:17.807" CommentCount="1" />
  <row Id="14558" PostTypeId="2" ParentId="14555" CreationDate="2011-05-22T11:12:02.433" Score="4" ViewCount="" Body="&lt;p&gt;It is to standardise everything on a single fixed voltage. But in practice, mains voltage &lt;em&gt;isn't&lt;/em&gt; 230V. It is standardised at 230V +10% -6%, or 216V to 253V. Here, mains voltage measures 249V, which is on the high end of the scale - but we're on a small farm road with not many other customers. Away from home I have measured it at 233V, due to resistive losses from greater demand. Countries have &lt;strong&gt;not&lt;/strong&gt; changed the actual voltage - that would require changing all the generators or all the transformers in the country (at a substantial cost), merely, the allowable range has changed.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-22T11:12:02.433" CommentCount="1" />
  <row Id="14559" PostTypeId="1" CreationDate="2011-05-22T11:16:56.320" Score="1" ViewCount="54" Body="&lt;p&gt;i'm constructing a simple portable speaker/amplifier and want it to contain am integrated rechargeable power source.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What's the best/safest way to integrate a rechargeable battery?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;i want it to work much like an electric shaver or mobile phone would, with a transformer integrated into the plug, and with a coaxial power connector used to transfer electricity to the unit.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;thanks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;battery type: probably ni-mh i think? i need something with plenty of ampere-hours, but am concerned about making it safe enough to leave charging overnight. also i need a simple and cheap solution!&lt;/p&gt;&#xA;" OwnerUserId="4360" LastEditorUserId="4360" LastEditorDisplayName="" LastEditDate="2011-05-22T11:43:47.980" LastActivityDate="2011-05-22T11:51:29.243" Title="how to implement an integrated rechargable battery in my project?" Tags="&lt;power-supply&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="14560" PostTypeId="1" CreationDate="2011-05-22T11:50:39.180" Score="3" ViewCount="79" Body="&lt;p&gt;Hello,&#xA;here is the schematic for LFSR polynomial division by $w(x) = n_3x^3 + n_2x^2 + n_1x + n_0$ (I wanted to post image but I don't have enough reputation :P)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/0i2v2.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;$\oplus$ denotes adder without carry logic, (nx) denotes multiplicator by $n_x$ coefficient and boxes are flip-flops.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The drawback of this solution is that polynomial $w(x)$ have to be of constant degree, otherwise circuit will not work. Are there are any solutions to build LFSR division unit which is able to divide by polynomial of non-constant-degree (there is specified maximally allowed degree)? Or maybe some not-LFSR units?&lt;/p&gt;&#xA;" OwnerUserId="4359" LastEditorUserId="142" LastEditorDisplayName="" LastEditDate="2011-05-22T12:32:07.403" LastActivityDate="2011-05-23T17:54:36.677" Title="Polynomial division LFSR" Tags="&lt;digital-logic&gt;" AnswerCount="1" CommentCount="6" />
  <row Id="14561" PostTypeId="2" ParentId="14559" CreationDate="2011-05-22T11:51:29.243" Score="1" ViewCount="" Body="&lt;p&gt;Your best bet is to use a battery management IC.  Searching Digikey for &quot;Battery management&quot; and then filtering by battery chemistry and then price, gave me the TSM101/A.  For less than a dollar, it seems to be capable of what you want.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just replace the mains and rectifier portion of the circuit with a wall wart.  There are some examples with charge status LEDs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here is the data sheet: &lt;a href=&quot;http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00001116.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00001116.pdf&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-22T11:51:29.243" />
  <row Id="14562" PostTypeId="2" ParentId="14556" CreationDate="2011-05-22T11:54:03.587" Score="2" ViewCount="" Body="&lt;p&gt;A BJT(bipolar junction transistor) is a device that can amplify current. They have a gain($h_{fe}$ when referring to BJTs) which is what the current on the base is times by to get the current through the collector. They have 3 legs:&lt;br&gt;&#xA; - Base&lt;br&gt;&#xA; - Emitter&lt;br&gt;&#xA; - Collector&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are 2 types of BJTs:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;NPN - current goes in to the base allowing current to from from the collector to the emitter.&lt;/li&gt;&#xA;&lt;li&gt;PNP - current comes out of the base allowing current to flow from the emitter to the collector. &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;For a NPN Transistor with gain of 400 and Current on the base is 0.05mA. The current then going through the collector is:  &lt;/p&gt;&#xA;&#xA;$I_{c} = h_{fe} * I_{b}$  &lt;br/&gt;&#xA;$I_{c} = 400 * 0.05$ &lt;br /&gt;  &#xA;$I_{c} = 20mA$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The emitter current can be calculated by adding the collector current and the base current:&lt;br&gt;&#xA;$I_{e} = I_{c} + I_{b}$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When using a BJT it is important to have a resistor in series with the base between 1k and 2k2 as too much current can cause damage to the BJT. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;To turn the transistor on a voltage of around 0.6V to 0.8V needs to be applied to the base($V_{be}$), this is so that current can flow.&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-05-22T11:54:03.587" CommentCount="4" />
  <row Id="14563" PostTypeId="2" ParentId="14556" CreationDate="2011-05-22T12:02:37.063" Score="0" ViewCount="" Body="&lt;p&gt;I got about 1/4 of the way typing up what Dean just posted.  So I'll pull that out and just respond with this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One of the best things you can do for your understanding is to pick up a copy of The Art of Electronics 2nd Edition.  It is a pricey book, but has a great chapter walking through transistors that would be of great help to you.  &lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-22T12:02:37.063" />
  <row Id="14564" PostTypeId="2" ParentId="14556" CreationDate="2011-05-22T13:03:01.927" Score="1" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://users.ece.gatech.edu/~alan/ECE3040/Lectures/Lecture20-BJT%20Small%20Signal%20Model.pdf&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; is a good description of the small-signal BJT model. Some maths is inevitable in electronics, if modeling is involved. If you don't understand something in the presentation, ask about it, and an answer might be forthcoming.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-22T14:05:45.970" LastActivityDate="2011-05-22T14:05:45.970" />
  <row Id="14565" PostTypeId="1" CreationDate="2011-05-22T14:49:39.877" Score="2" ViewCount="191" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/5556/is-fcc-testing-necessary-for-all-devices&quot;&gt;Is FCC testing necessary for all devices?&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Hi everyone,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've had a couple ideas floating around of some electronics devices that I could build, and I finally decided to go ahead with one of them and try to make a product. I would first make a couple and try to sell them on EBAY or Amazon. If they actually sold and people were happy with them, I would make a larger batch. If that still worked out, then I would try to mass produce it and start a company.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The reason for this long introduction is that I started trying to do some research about how viable this is, and what kind of other types of certifications, hidden costs, etc, there might be associated with doing something like this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After trying to research what exactly the FCC is, what their requirements are, and where to find them (geee, you think they would make it easy) I finally pieced together that there is a part 15 that you need to take care of.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Unfortunately, this seems to cost in the $10,000 range and take very long to do. I must be missing something, since if I had a microcontroller that blinked two LEDs, first of all, that will not make enough profit to even cover FCC testing, and second of all, it will need the testing since the micro will most definitely have an oscillator higher than 9 kHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my long winded question is this: Is there any power threshold, loophole, or any way to get by without doing FCC testing for some low power device you want to make that probably isn't even going to sell much?&lt;/p&gt;&#xA;" OwnerUserId="4362" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-22T23:43:07.330" LastActivityDate="2011-05-22T23:43:07.330" ClosedDate="2011-05-24T19:40:56.843" Title="Does every electronics device need to be FCC certified ?" Tags="&lt;fcc&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="0" />
  <row Id="14566" PostTypeId="2" ParentId="14565" CreationDate="2011-05-22T15:07:02.663" Score="5" ViewCount="" Body="&lt;p&gt;The $10,000 is probably about right. There isn't any way round it, if you want to sell the product legally in the USA. if the product is designed properly in the first place it will minimise the cost, and the procedure shouldn't take long. It's fixing problems and retesting that takes time and pushes the cost up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Testing for CE conformity for sale in the EU will be even more expensive, as immunity to external fields is also required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;We saved money on CE and FCC testing where I used to work by hiring the facility for a half-day (it was quite cheap), doing our own preliminary testing and fixing any problems that arose, before the formal testing. A system I designed for them was found to have a VHF emission from the RS-232 cable that connected it to the PC. The addition of some simple filters on an add-on PCB by the connector fixed that problem, and it sailed through the formal testing.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-22T15:13:46.970" LastActivityDate="2011-05-22T15:13:46.970" CommentCount="0" />
  <row Id="14567" PostTypeId="2" ParentId="14565" CreationDate="2011-05-22T17:32:10.993" Score="3" ViewCount="" Body="&lt;p&gt;The &quot;loop hole&quot; would be to use an oscillator lower then 9 kHz. If it is just a microcontroller that blinks 2 LEDs, 9 KHz should be plenty fast.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also the cost of FCC testing is not a fixed cost. It is possible that since it is such a simple design that you could get it certified for much cheaper.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-22T17:32:10.993" CommentCount="13" />
  <row Id="14569" PostTypeId="2" ParentId="14556" CreationDate="2011-05-22T19:25:24.563" Score="3" ViewCount="" Body="&lt;p&gt;These small signal models are important if you want to characterize the &lt;strong&gt;frequency response&lt;/strong&gt; of whatever amplifier you end up building with these transistors.  In a lot of applications, it is not enough to just know the gain for a given DC input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Suppose I have built myself a common-emitter amplifier out of a BJT for the purpose of amplifying an audio signal.  Let's say I've added my decoupling and bypass capacitors and biasing circuit as well.  How would I go about determining whether or not my amplifier ends up attenuating 15 KHz signals?  How would I determine if my signal output at 40 Hz is strong enough? For the purpose of amplifying audio, these frequencies are important to consider. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;The gain is not uniform across all frequencies&lt;/strong&gt; and this is due to the inherent capacitance and resistances inside the BJT itself.  Thus we need to construct these models that closely resembles the transistor's internals for the purpose of performing circuit analysis on paper (or in CAD, if your tools allow) that will tell us if our amplifier design is suitable for our application or not.  The parameters you speak of are usually given in the transistor's datasheet such that you can plug them in to one of the commonly accepted small signal models and perform your calculations.&lt;/p&gt;&#xA;" OwnerUserId="4172" LastEditorUserId="4172" LastEditorDisplayName="" LastEditDate="2011-05-23T00:02:33.600" LastActivityDate="2011-05-23T00:02:33.600" />
  <row Id="14570" PostTypeId="1" CreationDate="2011-05-22T20:56:16.450" Score="2" ViewCount="182" Body="&lt;p&gt;I have a schematic of some electrical components and something is marked +9/7.2V.  What exactly does that mean?  I presume the 7.2V means 7.2 volts, but what about the +9/ part?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is a PB Board for powering some fans in a plasma television.  The number is for the connection of the fans to a small board.  Since i am not a great expert on these things (hence the possibly simple question), I don't really know how else to explain it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any information would be greatly appreciated!&lt;/p&gt;&#xA;" OwnerUserId="4243" LastEditorUserId="4243" LastEditorDisplayName="" LastEditDate="2011-05-23T02:17:02.573" LastActivityDate="2011-05-23T19:05:28.633" Title="What does +9/7.2V mean?" Tags="&lt;voltage&gt;&lt;schematics&gt;" AnswerCount="1" CommentCount="9" />
  <row Id="14571" PostTypeId="1" AcceptedAnswerId="14572" CreationDate="2011-05-22T23:00:07.073" Score="0" ViewCount="97" Body="&lt;p&gt;I recently purchased a power brick (&lt;a href=&quot;http://www.amazon.com/VCT-VM-80W12-Universal-Converter/dp/B001QX6CK2/ref=sr_1_1?ie=UTF8&amp;amp;qid=1306105075&amp;amp;sr=8-1&quot; rel=&quot;nofollow&quot;&gt;VM-80W12&lt;/a&gt;) and I've been trying to test it with the multimeter to determine the polarity. It however registers 0 Volts continusly (yes I plugged it in) I've heard that sometimes a power supply will only switch on when it get's a load resistance on it's output and I was wondering if that was true. If so then how do I go about testing the power brick?&lt;/p&gt;&#xA;" OwnerUserId="3045" LastActivityDate="2011-05-23T03:41:34.247" Title="I can't get my switching power supply to turn on!" Tags="&lt;power-supply&gt;" AnswerCount="1" CommentCount="6" />
  <row Id="14572" PostTypeId="2" ParentId="14571" CreationDate="2011-05-22T23:37:08.447" Score="2" ViewCount="" Body="&lt;p&gt;Try plugging in a 1W 288ohm resistor across the load. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should do the trick and turn the power supply on!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: A 270ohm resistor would be much easier to find&lt;/p&gt;&#xA;" OwnerUserId="4201" LastEditorUserId="4201" LastEditorDisplayName="" LastEditDate="2011-05-23T03:41:34.247" LastActivityDate="2011-05-23T03:41:34.247" CommentCount="4" />
  <row Id="14573" PostTypeId="2" ParentId="13302" CreationDate="2011-05-23T01:44:25.040" Score="0" ViewCount="" Body="&lt;p&gt;In the old days, you could hold a scope probe or (my favorite) audible logic probe on the select output of the '138 decode chip, and hear it fire when you hit the right address, or at least hear it fire more frequently if you wrote a tight loop with debug to just read the address over and over again...  but with the CPLD on there the decode signal is probably buried inside.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could approach the output side first - you can write a program to try toggling the relays at all of the possible addresses.  Though it appears the input and output sides have separate address selection?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could also test your software against another I/O device, for example reading the status lines of a (true ISA bus hardware, not USB) parallel port, either on the PC104 system if it has one, or a different vintage PC...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You might also simply have a bad board or an address conflict with another module - do try putting the board at a different address.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-05-23T01:44:25.040" CommentCount="2" />
  <row Id="14574" PostTypeId="1" CreationDate="2011-05-23T05:15:27.337" Score="2" ViewCount="100" Body="&lt;p&gt;I recently started experimenting with DIY guitar pedals and I have been wanting to try to modify some of the schematics I have found, and eventually, design some of my own.  I'm not an electrical engineer, but I have done a fair amount of circuit building/designing, however nothing having to do with an audio signal.  I've been looking all over to try to find some resources on how different components affect an audio signal.  Can anyone give me a run down, or know of any resources that might be helpful?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="4366" LastActivityDate="2011-05-27T07:50:55.173" Title="Can anyone give me a brief overview or links to articles that might explain how different components might affect a sound signal?" Tags="&lt;audio&gt;&lt;circuit-design&gt;" AnswerCount="3" CommentCount="1" FavoriteCount="1" />
  <row Id="14576" PostTypeId="1" CreationDate="2011-05-23T08:21:49.553" Score="1" ViewCount="72" Body="&lt;p&gt;Hello people,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm new to electronics and trying to build a land-rover caaar. I found out Arduino Uno and quite understand the initial steps I need to take to get started with it and go on to build my car.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I learnt that Arduino Uno isn't available locally and is too costly when I order it from another city (I'm in India). But while checking a local shop, the guy showed me the P89V51RD2 ( 8051 ) controller. I didn't buy it right away but came to do a bit research. My initial findings were that it's quite more powerful than the Arduino Uno. I bought it for Rs. 1000 (~$25).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now I am sitting on my desk thinking about what I am supposed to do with this. What I basically plan is to hookup this board, a breadboard, an L293DNE IC and two motors together.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I can't understand where should I start. Answering a few questions would aid me a lot :&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;What's difference between the 89V51RD2 I bought and Arduino Uno?&lt;/li&gt;&#xA;&lt;li&gt;What should I do to start porgramming ( in C? I'm familiar with programming languages so this part isn't the problem at all )?&lt;/li&gt;&#xA;&lt;li&gt;The board has a serial port. I tried to connect it with the SERIAL PORT-USB converter I bought but windows isn't showing anything other than &quot;Unknown device found&quot; even after I installed the drivers for the converter.&lt;/li&gt;&#xA;&lt;li&gt;I am supposed to connect some power supply to the board before starting to work on it. I can see three 4-pin terminals labelled 5V,GND 12V. I have three 9V batteries. I can adjust the voltage with resistors, that's not the problem, but how exactly am I supposed to connect the supply? There are 4 pins for each of them. Can I connect the positive terminal to &quot;5V&quot; and negative to GND and leave the &quot;12V&quot; open?&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Thank you, all!&lt;/p&gt;&#xA;" OwnerUserId="4369" LastActivityDate="2011-05-23T13:28:41.763" Title="89V51RD2 (8051) and Arduino Uno" Tags="&lt;arduino&gt;&lt;pcb&gt;&lt;circuit&gt;&lt;voltage&gt;&lt;8051&gt;" AnswerCount="1" CommentCount="11" />
  <row Id="14577" PostTypeId="2" ParentId="14576" CreationDate="2011-05-23T09:06:59.700" Score="5" ViewCount="" Body="&lt;p&gt;1 - The 89V51RD2 is based on an age-old 8051 design, while the Arduino uses a more modern AVR RISC (ATmega328). The original 8051 used 12 clock cycles per machine cycle. The 89V51RD2 improved a bit on this, but still needs 6 clock cycles per machine cycle. That means that your 40MHz clock will give you only 6.67 mega machine cycles, and most instructions need more than 1 machine cycle, so in practice you'll only achieve a few millions of instructions per second. The ATmega328 on the other hand is a RISC controller which can do most instructions in 1 clock cycle. So the AVR at 16MHz should perform better than the 8051 derivative.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;4 - Don't! Don't use resistors to adjust power supply voltage. The voltage drop the give will depend on the load, and with smaller loads your 5V may become something like 7V, which may damage the electronics on your board. Better use a three-legged voltage regulator like the &lt;a href=&quot;http://www.fairchildsemi.com/ds/LM/LM7805.pdf&quot; rel=&quot;nofollow&quot;&gt;LM7805&lt;/a&gt;.&lt;br&gt;&#xA;The 12V may be used to drive motors and the like, most logic doesn't use that kind of voltage. The 9V batteries (2 in series, followed by an LM7812) are not a good solution, because they will drain rather quickly. The same goes probably for your 5V. For a car you can't use a mains power supply, but you may consider higher capacity batteries, like NiMH.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-23T13:28:41.763" LastActivityDate="2011-05-23T13:28:41.763" CommentCount="0" />
  <row Id="14578" PostTypeId="2" ParentId="14574" CreationDate="2011-05-23T09:40:27.283" Score="0" ViewCount="" Body="&lt;p&gt;On the question of how different components affect an audio signal, the veteran audio engineer &lt;a href=&quot;http://en.wikipedia.org/wiki/John_Linsley_Hood&quot; rel=&quot;nofollow&quot;&gt;John Linsley Hood&lt;/a&gt;'s books eg &lt;a href=&quot;http://www.amazon.co.uk/Audio-Electronics-Second-Edition/dp/B001LDJHCW/ref=sr_1_4?ie=UTF8&amp;amp;qid=1306143559&amp;amp;sr=8-4&quot; rel=&quot;nofollow&quot;&gt;The Art of Linear Electronics&lt;/a&gt;, who has been designing amplifiers since the '60s, would be a good start. Chapter 2 goes through passive components in detail, Chapter 8 covers frequency modification circuits, there is a chapter on audio amplifiers and the pros and cons of different circuits including distortion. Noise and hum are covered in chapter 8, and you may find aspects of chapter 10 on low frequency oscillators and waveform generators relevant.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whilst this doesn't give you circuits for deliberate distortion, many guitar effects also require/use dramatic levels of equiliser, and the chapter on amplifiers does cover valve configurations, so there is relevance to guitarists. I'd say overall it would give you a good grounding in the principles of analogue circuits so you can design your own with understanding rather than it being a receipe book.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastEditorUserId="2110" LastEditorDisplayName="" LastEditDate="2011-05-27T07:50:55.173" LastActivityDate="2011-05-27T07:50:55.173" CommentCount="2" />
  <row Id="14579" PostTypeId="2" ParentId="14574" CreationDate="2011-05-23T10:37:02.307" Score="4" ViewCount="" Body="&lt;p&gt;Instead of messing about with components, the modern way to modify sounds is in the digital domain, with digital signal processing (DSP). The audio is digitised by sampling with an ADC, modified with software running on a PC or DSP chip, and then converted back to analogue using a DAC. The ADC and DAC are usually combined in a codec chip.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An ideal device for experimenting with this technique is one of the Microchip 16-bit dsPICs. A few years ago I designed &lt;a href=&quot;http://www.leonheller.com/Audio%20Processor/AP.pdf&quot; rel=&quot;nofollow&quot;&gt;this low-cost audio processor&lt;/a&gt; based on one. It was intended for speech processing for amateur radio, but it would work equally well for guitar effects. PCB Gerber and drill files are available &lt;a href=&quot;http://tech.groups.yahoo.com/group/radio_dspic/&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt;, in the Files section. You need to join the group to access them.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-23T10:42:44.297" LastActivityDate="2011-05-23T10:42:44.297" CommentCount="1" />
  <row Id="14580" PostTypeId="1" CreationDate="2011-05-23T12:57:36.367" Score="1" ViewCount="87" Body="&lt;p&gt;I need 12Vdc 3.33A source power for &lt;a href=&quot;http://en.wikipedia.org/wiki/SGI_1600SW&quot; rel=&quot;nofollow&quot;&gt;Silicon Graphics 1600sw&lt;/a&gt; display, I have two &lt;a href=&quot;http://en.wikipedia.org/wiki/Power_supply_unit_%28computer%29&quot; rel=&quot;nofollow&quot;&gt;ATX computer power supply&lt;/a&gt;. Is it possible to use these PSU as replace for broken 12Vdc 3.33A adapter ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;UPDATE:&lt;/strong&gt; I connected the 12v 35w halogen lamp for provide a small load to &lt;em&gt;+12 VDC(Yellow)&lt;/em&gt; and &lt;em&gt;Ground(Black)&lt;/em&gt;, then I turn on the PSU by shorting the &lt;em&gt;PS-ON#(Green)&lt;/em&gt; and &lt;em&gt;Ground(Black)&lt;/em&gt;, DCV show about 11,43 V, so I connected the monitor and it works!&lt;/p&gt;&#xA;" OwnerUserId="4372" LastEditorUserId="4372" LastEditorDisplayName="" LastEditDate="2011-05-24T05:51:13.723" LastActivityDate="2011-05-24T05:51:13.723" Title="Use PSU as replace for broken source +12Vdc 3.33A ?" Tags="&lt;power-supply&gt;&lt;dc&gt;&lt;display&gt;&lt;atx&gt;&lt;12v&gt;" AnswerCount="3" />
  <row Id="14581" PostTypeId="2" ParentId="14580" CreationDate="2011-05-23T13:29:40.253" Score="1" ViewCount="" Body="&lt;p&gt;It should be possible and not too complicated. There are many guides explaining the process. &lt;a href=&quot;http://www.instructables.com/id/ATX--%3E-Lab-Bench-Power-Supply-Conversion/&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt;'s one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;UPDATE:&lt;br&gt;&#xA;To complement the other answer:&lt;br&gt;&#xA;Some computer PSUs may already have needed load installed and can provide stable voltages out of the box, but you can't rely on that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The instructable recommends use of $10\mbox{ }\Omega\mbox{, 10 W}$ resistors for $\mbox{+5 V, +12 V}$ and $\mbox{-12 V}$. The $\mbox{12 V}$ resistors are going to be dissipating around $\mbox{14,4 W}$, so my recommendation is to get some bigger resistors, just in case.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other option would be to use resistors with higher resistance for the 12 V lines, for example $22\mbox{ }\Omega$. They'll use less current, but I think that it won't be a major problem because the screen will use considerable amount of power too. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This isn't mentioned in the instructable, but I'd put some $10\mbox{ }\Omega$ or $22\mbox{ }\Omega$ resistors on the $\mbox{+3.3 V}$ line too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another part that has been omitted is how to locate the power supply rails inside the power supply itself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://pinouts.ru/Power/atx_v2_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; you can find the color code for computer supply wires. Just follow the wires inside the case of the supply and see where they end. The wires you're interested in are yellow for $\mbox{+12 V}$, orange for $\mbox{+3.3 V}$ and red for $\mbox{+5 V}$. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Don't forget the LEDs for gray and purple wires. You can use tool like &lt;a href=&quot;http://ledcalc.com/&quot; rel=&quot;nofollow&quot;&gt;http://ledcalc.com/&lt;/a&gt; to get the correct resistor for the LED. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-23T17:17:27.383" LastActivityDate="2011-05-23T17:17:27.383" CommentCount="4" />
  <row Id="14582" PostTypeId="2" ParentId="14230" CreationDate="2011-05-23T13:32:35.160" Score="3" ViewCount="" Body="&lt;p&gt;I was actually planning on building one of these.  I decided that it would be easiest to start with a USB Arduino to have easy data logging to the PC.  I figured I'd use an Uno, even if I wrote the code in native AVR C, rather than Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For this, you are looking for a constant current sink.  Something that will pull a constant current, even as the voltage of the battery drops.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You need two ADCs to measure voltage.  First will measure the actual battery voltage.  Depending on how accurate you want to be, you can either use the 5V power as the ADC reference or use a more accurate ref chip.  You will need some type of shunt to measure current.  (A shunt is a known resistance.  So by measuring voltage across it, you can know the current flowing through it via Ohm's Law.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Lets work backwards from the battery.  If we have a logic level N Channel MOSFET as a controller and an accurate resistor in series with the Drain/Source.  The resistor will work as our current shunt.  The battery + connects to the source of the MOSFET, then the resistor connects the drain to ground.  The battery - is also to ground.  If you have 1 Ohm resistor, and measure 1 V across it, you know that 1 A is flowing through it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(A Logic Level MOSFET is one that will turn on with a gate voltage in the normal range of logic chips, generally fully on before +5V.  It is useful for driving heavier loads from low current capable logic.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;OK, now we need to control the MOSFET.  Hook up an Op Amp as a voltage follower, with the + input for setting the voltage (more about that later) and the - connecting to the drain/resistor junction.  The output of the Op Amp goes to the gate of the MOSFET.  The Op Amp will adjust the gate of the MOSFET, until the voltage at the drain (and across the resistor) meets the voltage presented at the + input of the Op Amp.  This means it will consume a variable amount of voltage to maintain maintain a constant voltage across the resistor and therefore a constant current through the resistor.  (And a constant current draw from the battery.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Remember that the ideal Op Amp model is such that voltage between + and - is 0V.  In reality, there is a little, but you will be compensating for this so it doesn't matter unless you try to drive it too close to the rail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So we now have a circuit that will draw a current in amps equal to the voltage in volts that you provide to the + of the Op Amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The last things we need is to measure voltage and current and generate that voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can use the PWM output of the micro to generate an analog voltage.  You would hook a resistor in series with the pin and a capacitor from the end of the resistor to ground.  This junction will feed the + input of the Op Amp.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now we need to feed the voltage across the shunt resistor into one ADC input.  This will read discharge current in Amps if you use a 1 Ohm resistor.  Use this to drive the PWM output until you are pulling the desired current from the battery.  It may be better to drive a voltage divider with a trimmer resistor, so you can tweak the circuit to give outputs that correspond to given PWM duty cycles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The last hookup is an ADC input from the battery itself.  If you are using a battery that is over your supply voltage, you will have to use a voltage divider to get it down to a range that the ADC can handle.  You may need a switch to have a few different dividers, based on the number of cells you will hook up.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Once you have registered a voltage down as low as the battery should drain, set the PWM output to ground and this will turn the MOSFET off and stop draining the battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Add the associated logging to the PC and you are done.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/lTHq4.png&quot; alt=&quot;Rough Sketch of Circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure you get proper power rated MOSFET and shunt resistor.  If you are driving 5A through the 1 Ohm resistor, you will need 5W resistor.  It might be easier to put a few in parallel to get to the desired value and power.  You also need a MOSFET with enough power handling to sink the voltage difference between the battery and resistor at that current.  And you will need a good heat sink for running higher power.  The MOSFET and shunt are the only parts of the circuit that will be handing large currents.  All the others should be fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With this circuit, you can use it for more than just battery testing.  If you are developing a power supply and want a 1A load on it to see how bad the ripple looks, hook it up.  As long as you don't exceed the power ratings of the MOSFET or Resistor and stay within the proper bounds of the ADC inputs, it will work.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastEditorUserId="4342" LastEditorDisplayName="" LastEditDate="2011-05-23T17:06:45.143" LastActivityDate="2011-05-23T17:06:45.143" CommentCount="4" />
  <row Id="14583" PostTypeId="2" ParentId="14580" CreationDate="2011-05-23T14:28:04.220" Score="1" ViewCount="" Body="&lt;p&gt;The biggest problem with using the 12v rail on the PSU is that it is designed to pump out a lot of current, and as a result wont provide stable power at lower currents. However, 3.33A is a pretty sizable amount of current and will probably work out just fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am not sure about details of the graphics display, but I would recommend you look at the datasheet to see if there are any specifics on the amount of voltage swing it is able to handle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to double check your PSU before you plug it into your display, you could get yourself a high wattage resistor, plug it into the PSU, and then measure the voltage. 12v/3.33a = 3.6 Ohms at 39.96 Watts. On second thought, that is a lot of watts to put in a resistor and you will probably have a hard time easily finding one. You might have better luck finding an 8 Ohm 18+ watt resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other issue at hand is being able to turn on the PSU. PSU's are designed to be turned on by the motherboard, and so you will need to fake the PSU. The way that you do this is by shorting the PS_ON# pin to a COM pin. Usually the PS_ON# wire is green and all of the COM pins are black. It will probably be beneficial to put a switch here instead of a wire so that you can easily switch it on and off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You also mentioned that you have two PSUs. I am not sure if you were thinking about using both together, or just saying you have some extra. Just in case you were thinking about it, I would not try connecting the two together. Depending on the design of the PSUs they can end up fighting each other some, and bad things happen when electronics fight. &lt;/p&gt;&#xA;" OwnerUserId="319" LastEditorUserId="319" LastEditorDisplayName="" LastEditDate="2011-05-23T14:43:03.413" LastActivityDate="2011-05-23T14:43:03.413" CommentCount="1" />
  <row Id="14584" PostTypeId="2" ParentId="14574" CreationDate="2011-05-23T14:53:54.883" Score="2" ViewCount="" Body="&lt;p&gt;Sadly, most of the effects that have been made using analog components were done by playing. Basically someone sat there and switched components around until they got a &quot;cool&quot; effect. Many of these configurations were then patented and not tons published about them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best place to start is probably to learn about &lt;a href=&quot;http://electronics.stackexchange.com/questions/tagged/op-amp&quot;&gt;Op Amps&lt;/a&gt;. They are the building block for almost any type of analog signal processing. At first you will just be doing basic things like filters. Filters are like EQ. I bet you will be amazed at what you can do with very simple circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You mentioned you have some schematics, learn what is actually going on with it. If you are confused and have the ability, you can come back here and ask what a particular block is doing. Once you learn what is going on in prior schematics, you might start getting some ideas of things to play with.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As @Leon Heller mentioned, DSP is where most of the market is going. DSP can be a much more difficult field to really understand, but if you have the will and desire, you should defiantly check it out.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-23T14:53:54.883" />
  <row Id="14585" PostTypeId="2" ParentId="14580" CreationDate="2011-05-23T14:55:47.117" Score="0" ViewCount="" Body="&lt;p&gt;One other problem I've seen with switching PSUs is subtle high voltage spikes in the output.  The quick and easy way to deal with this is a neon lamp across the output.  If it lights even dimly, you HAD a problem and are dealing with it.  I've seen this on many PSUs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An easy way to test it would be automotive headlights at similar wattage.  These are much easier to obtain than power resistors of that size.  Get a replacement headlamp for your car that you will eventually use or something like that.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastEditorUserId="4342" LastEditorDisplayName="" LastEditDate="2011-05-23T17:15:33.667" LastActivityDate="2011-05-23T17:15:33.667" CommentCount="1" />
  <row Id="14586" PostTypeId="2" ParentId="14149" CreationDate="2011-05-23T15:07:05.077" Score="1" ViewCount="" Body="&lt;p&gt;By taking an hour to complete the full cycle, it sounds like you want the setup to continuously wipe at the speed of once an hour?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you design the wiper to just rotate, it would be easy to just use a low speed DC motor to continuously turn and gear down to a very slow speed.  This gives you the torque to push through the long rubber water seal.  On the inside part of the shaft, you can mount a sensor to detect position.  Now let a micro count to the time, turn on for a certain time, then stop when the sensor is tripped, meaning the wiper is not obstructing any sensors or cameras.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can do the same thing with a servo, but it seems like the accuracy of position control and complexity of a servo is over kill in this situation.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-23T15:07:05.077" />
  <row Id="14587" PostTypeId="2" ParentId="13984" CreationDate="2011-05-23T15:18:07.777" Score="2" ViewCount="" Body="&lt;p&gt;Temperature is a measure of the average thermal energy.  A temp sensor will not tell you if we are talking a dry or wet bulb temp.  The temperature is the same for both.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Wet or dry comes into play when you start thinking about how much thermal energy would be required to change the temperature of the air or how much condensation you will have if you lower the temperature of the air, etc.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To measure wet bulb, you need temperature and relative humidity.  With those two sensors, you should have what you need.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-23T15:18:07.777" />
  <row Id="14588" PostTypeId="2" ParentId="14570" CreationDate="2011-05-23T17:17:46.270" Score="1" ViewCount="" Body="&lt;p&gt;7.2V at 1.2V per cell is a 6 cell battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;9V at 1.5V per cell is a 6 cell battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It is most likely able to handle that range, so it can deal with NiCd/NiMH cell or standard Alkaline cells on battery powered instances. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: Looks like this is a duplicate of what supercat posted in the comments.  Sorry I missed that.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastEditorUserId="4342" LastEditorDisplayName="" LastEditDate="2011-05-23T19:05:28.633" LastActivityDate="2011-05-23T19:05:28.633" CommentCount="1" />
  <row Id="14589" PostTypeId="1" CreationDate="2011-05-23T17:32:05.487" Score="0" ViewCount="49" Body="&lt;p&gt;(Already posted this on the TI forums, no responses yet)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Using the hwafft.asm source file that came in sprabb6a.zip, and the assembler says it is full of syntax errors. Here is a link to the assembler output (quite long)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://pastebin.com/Nwrtqxkh&quot; rel=&quot;nofollow&quot;&gt;http://pastebin.com/Nwrtqxkh&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;hwafft.asm: &lt;a href=&quot;http://pastebin.com/511K7qGy&quot; rel=&quot;nofollow&quot;&gt;http://pastebin.com/511K7qGy&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3906" LastActivityDate="2011-05-23T19:21:20.117" Title="Tons of assembler errors using TI example code in CCS4" Tags="&lt;assembly&gt;&lt;ezdsp&gt;" AnswerCount="0" CommentCount="4" />
  <row Id="14590" PostTypeId="1" CreationDate="2011-05-23T17:38:38.413" Score="0" ViewCount="57" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/616/basic-electronics-book&quot;&gt;Basic Electronics Book&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;Hello there.&#xA;So, I'm  just now web developer. But I'm interested during many years microprocessor programming and generally electronic engineering.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, I want start learning and working with this direction. I need your help and consultation, I need books for starting.&lt;/p&gt;&#xA;" OwnerUserId="4370" LastActivityDate="2011-05-23T17:38:38.413" ClosedDate="2011-05-23T18:16:21.177" Title="Need Consultation / Beginner In Electronic Engineering + Microprocessor Programming" Tags="&lt;electronics&gt;&lt;microprocessor&gt;" CommentCount="0" />
  <row Id="14591" PostTypeId="2" ParentId="14560" CreationDate="2011-05-23T17:54:36.677" Score="1" ViewCount="" Body="&lt;p&gt;I think what you want is to have a multiplexer between the IN bit and the LFSR which will route the input bit around unneeded LFSR stages. This would require lines to not only deactivate unused stages but to reroute the output bit from one stage to another. It's possible but is going to be fairly hardware expensive. What is the purpose of having a variable-degree LFSR in hardware? &lt;/p&gt;&#xA;" OwnerUserId="3906" LastActivityDate="2011-05-23T17:54:36.677" CommentCount="1" />
  <row Id="14592" PostTypeId="1" AcceptedAnswerId="14599" CreationDate="2011-05-23T18:23:50.440" Score="2" ViewCount="122" Body="&lt;p&gt;Flash memory cells are erased for reprogramming not individually, but in large units of certain size. &lt;a href=&quot;http://www.ti.com/litv/pdf/slaa334a&quot; rel=&quot;nofollow&quot;&gt;Here&lt;/a&gt; they are called &lt;em&gt;segments&lt;/em&gt;, &lt;a href=&quot;http://www.micron.com/get-document/?documentId=5981&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; — &lt;em&gt;sectors&lt;/em&gt;, and &lt;a href=&quot;http://en.wikipedia.org/wiki/Flash_memory#Block_erasure&quot; rel=&quot;nofollow&quot;&gt;here&lt;/a&gt; — simply &lt;em&gt;blocks&lt;/em&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What is the correct term for the smallest erasable unit of flash memory? If there is no official one, which word could be used in vendor-neutral text?&lt;/p&gt;&#xA;" OwnerUserId="4350" LastEditorUserId="4350" LastEditorDisplayName="" LastEditDate="2011-05-24T18:18:50.563" LastActivityDate="2011-05-24T18:18:50.563" Title="How is the smallest erasable unit of flash memory called?" Tags="&lt;memory&gt;&lt;flash&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="14593" PostTypeId="1" CreationDate="2011-05-23T19:05:23.283" Score="-1" ViewCount="67" Body="&lt;p&gt;So, I'm a software engineer that's looking for a new hobby and decided to pick up a netduino.  According to UPS it's sitting at my door right now and I'll get to putz with it in a few hours.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That being said, looking for advice on where to start with things.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where do people usually buy parts?  LEDS/LCD Screens/sensors/etc?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Should I buy a breadboard?  What's generally in everyone's toolbox as it were?  I already have a soldering iron so I don't need that.  But I'm really green with everything else.&lt;/p&gt;&#xA;" OwnerUserId="4375" LastActivityDate="2011-05-23T19:17:00.243" ClosedDate="2011-05-23T19:21:44.810" Title="CS guy just bought a netduino, looking for advice" Tags="&lt;netduino&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="14594" PostTypeId="2" ParentId="14593" CreationDate="2011-05-23T19:17:00.243" Score="1" ViewCount="" Body="&lt;p&gt;There are a bunch of good parts suppliers.  My main go to places are DigiKey, Mouser, and Jameco.  With All Electronics a fun place to get sometimes unique items.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Specific to experimenting with more prebuild pieces: SparkFun, AdaFruit, and tons of others I'm forgetting about.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-23T19:17:00.243" CommentCount="2" />
  <row Id="14596" PostTypeId="2" ParentId="14493" CreationDate="2011-05-23T20:07:48.820" Score="-1" ViewCount="" Body="&lt;p&gt;If the question is why decoupling cap's aren't encapsulated along with the die in the packaging, I would say that the main reason is economics -- in most cases, there's not much of a performance gain to bring the chip onboard (instead of having it on the PCB) - so the extra cost (in process development, testing, and cost of goods) brings no benefit to the consumer and just adds to the cost of the device.  The packaging machines along would probably require millions of dollars in changes to support encapsulated caps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As for placing capacitors directly on the die -- that die space is more valuable as transistors than as capacitors.&lt;/p&gt;&#xA;" OwnerUserId="3308" LastActivityDate="2011-05-23T20:07:48.820" />
  <row Id="14597" PostTypeId="2" ParentId="13912" CreationDate="2011-05-23T20:20:21.740" Score="4" ViewCount="" Body="&lt;p&gt;If a diode is conducting in a forward condition and immediately switched to a reverse condition, the diode will conduct in a reverse condition for a shot time as the forward voltage bleeds off.  The current through the diode will be fairly large in a reverse direction during this small recovery time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;After the carriers have been flushed and the diode is acting as a normal blocking device in the reversed condition, the current flow should drop to leakage levels.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This is just a generic description reverse recovery time.  It can affect quite a few things, depending on context, as mentioned in the comments.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-23T20:20:21.740" CommentCount="2" />
  <row Id="14598" PostTypeId="1" CreationDate="2011-05-23T20:26:14.977" Score="4" ViewCount="143" Body="&lt;p&gt;Hi-&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please forgive this ultra-noob question, but I'm a bit confused. I've been reading about how neither voltage nor current alone constitute power in a DC circuit. Instead, power is a combination of both voltage and current. Alright... But if current is the flow rate of electrons through a circuit and if it's true that voltage causes current, then doesn't current alone already imply voltage? Why doesn't this mean then that current on its own indicates power?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Muchas gracias.&lt;/p&gt;&#xA;" OwnerUserId="4376" LastEditorUserId="4376" LastEditorDisplayName="" LastEditDate="2011-05-24T22:27:14.263" LastActivityDate="2011-05-25T00:59:06.750" Title="Trying to understand the relationship between voltage, current, and power..." Tags="&lt;power&gt;&lt;voltage&gt;&lt;current&gt;" AnswerCount="6" CommentCount="7" FavoriteCount="1" />
  <row Id="14599" PostTypeId="2" ParentId="14592" CreationDate="2011-05-23T20:30:47.063" Score="5" ViewCount="" Body="&lt;p&gt;On the NAND flash chips I've seen, a page is the amount of information that is typically written at a time, and a block is the smallest amount that can be erased.  Some chips have sectors which consist of multiple blocks, and provide commands to erase an entire sector at once.  I've never found such commands very useful, though, since they seem to take almost as long as erasing blocks individually.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would suggest using terms &quot;programmable page&quot; and &quot;erasable block&quot; to refer to those two different sizes of entity.  The term &quot;sector&quot; would not generally be used in vendor-independent discussion, since different vendors define sectors differently.  While programmable pages are usually of one uniform size, and erasable blocks are usually of another, many manufacturers use a mixture of large and small sectors, even within the same device.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-23T20:30:47.063" />
  <row Id="14600" PostTypeId="1" AcceptedAnswerId="14601" CreationDate="2011-05-23T20:56:47.090" Score="4" ViewCount="76" Body="&lt;p&gt;The LPC13xx datasheet suggests some clock setup is necessary to use USB. Does the chip's built in boot loader make it possible to load the initial program over USB, or do the clock multipliers have to be configured with JTAG first?&lt;/p&gt;&#xA;" OwnerUserId="1363" LastEditorUserId="1363" LastEditorDisplayName="" LastEditDate="2011-05-27T22:34:55.397" LastActivityDate="2011-05-27T22:34:55.397" Title="Can an LPC1343 accept its initial program over USB?" Tags="&lt;usb&gt;&lt;lpc&gt;&lt;nxp&gt;&lt;lpc13xx&gt;" AnswerCount="1" FavoriteCount="0" />
  <row Id="14601" PostTypeId="2" ParentId="14600" CreationDate="2011-05-23T21:17:04.273" Score="6" ViewCount="" Body="&lt;p&gt;Details of USB booting are provided in the User Manual on page 294:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The LPC134x is enumerated as a Mass Storage Class (MSC) device to a PC or another&#xA;embedded system. In order to connect via the USB interface, the LPC134x must use the&#xA;external crystal at a frequency of 12 MHz. The MSC device presents an easy integration&#xA;with the PC’s Windows operating system. The LPC134x flash memory space is&#xA;represented as a drive in the host file system. The entire available user flash is mapped to&#xA;a file of the size of the LPC134x flash in the host’s folder with the default name&#xA;‘firmware.bin’. The ‘firmware.bin’ file can be deleted and a new file can be copied into the&#xA;directory, thereby updating the user code in flash. Note that the filename of the new flash&#xA;image file is not important. After a reset or a power cycle, the new file is visible in the&#xA;host’s file system under it’s default name ‘firmware.bin.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Page 291 describes how to connect the device pins to ensure that USB booting takes place.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-23T21:17:04.273" CommentCount="2" />
  <row Id="14602" PostTypeId="1" CreationDate="2011-05-23T21:51:41.167" Score="1" ViewCount="136" Body="&lt;p&gt;It's the one dead center of the circle that exploded. I was thinking it was either a diode or a capacitor of some kind, but I don't know how to tell its value from its markings. This picture is of a motherboard that came out of an Acer netbook (Acer One D255E). I'm assuming that the wrong type of charger was plugged into this netbook to cause the damage. This also seems to be the only noticeable damage. Does anyone have experience with repairing this? Or at least what it is?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/GLb0Y.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If any more info is needed just ask.&lt;/p&gt;&#xA;" OwnerUserId="4378" LastEditorUserId="1623" LastEditorDisplayName="" LastEditDate="2011-05-23T22:47:06.150" LastActivityDate="2011-05-23T22:47:06.150" Title="What is this component(pic)?" Tags="&lt;components&gt;&lt;computers&gt;&lt;repair&gt;&lt;component&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="14603" PostTypeId="2" ParentId="14598" CreationDate="2011-05-23T22:08:16.250" Score="3" ViewCount="" Body="&lt;p&gt;I'm assuming we are talking in terms of DC here to keep things simple. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Voltage is a measure of how much a single electron's energy changes across the circuit.  Current is how many electrons are flowing through a circuit.  Multiply those two values to get the rate of energy transfer, or power.  If all you have is a measure of current, you know how many electrons are flowing through the circuit, but not how much their energy is changing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You are correct that voltage induces current, and that voltage and current are interrelated.  Ohm's law is the simplest case of that.  You can derive a circuit's power from current and it's resistance using known formulas.  And even more simply, if you know current is flowing you know the circuit is dissipating power, even if you don't know how much (as the other commenters have said)&lt;/p&gt;&#xA;" OwnerUserId="4379" LastActivityDate="2011-05-23T22:08:16.250" CommentCount="4" />
  <row Id="14604" PostTypeId="2" ParentId="14598" CreationDate="2011-05-23T22:12:34.673" Score="0" ViewCount="" Body="&lt;p&gt;With DC electronics, there are rarely situations where current and voltage don't mean power.  (I can't think of any off hand.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With AC electronics, you can have current flowing due to capacitive or inductive reactance.  These can cancel out and not truly consume any power from the source.  Any purely resistive load, P = IV should be true.  However, when you bring in power factor, things change.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;That may be more complex than you are thinking.  If you are talking only DC power, then current can imply power.  You can take V = IR and P = IV and get power from any two factors.  You cannot get power just from current.  How much power is consumed if 1 A is flowing through a huge diameter wire?  Almost nothing. It is just on its way to power something else. How much power is consumed if 1 A is flowing from a 10 V battery or across a 0.1 Ohm resistor?  Now you can say 10 W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It isn't that you NEED voltage, but that without two of the three items with DC electronics, you can't tell how much work is being done.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-23T22:12:34.673" />
  <row Id="14605" PostTypeId="2" ParentId="14602" CreationDate="2011-05-23T22:18:08.707" Score="6" ViewCount="" Body="&lt;p&gt;It looks like a tantalum capacitor to me. It's the wrong shape for a diode, and they usually have the cathode marked with a line.Tantalums usually have the positive terminal identified with a line or a '+' like that, and are encapsulated in plastic. Electrolytics usually have the negative terminal identified with a line, and aren't usually encapsulated.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-23T22:18:08.707" CommentCount="4" />
  <row Id="14606" PostTypeId="2" ParentId="14602" CreationDate="2011-05-23T22:25:01.603" Score="2" ViewCount="" Body="&lt;p&gt;Definitely a capacitor - could be tantalum or aluminium polymer - the latter are being increasingly used due to ultra-low ESR.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-05-23T22:25:01.603" />
  <row Id="14607" PostTypeId="2" ParentId="14592" CreationDate="2011-05-23T22:27:32.897" Score="1" ViewCount="" Body="&lt;p&gt;There is no 'correct' term  - different manufacturers have different conventions. The most common one I've seen is sector for erase and page for program, but this is by no means universal. &lt;/p&gt;&#xA;" OwnerUserId="1681" LastActivityDate="2011-05-23T22:27:32.897" />
  <row Id="14608" PostTypeId="1" AcceptedAnswerId="14636" CreationDate="2011-05-23T22:44:08.360" Score="1" ViewCount="54" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using the Arduino Servo library to control two servo's on a RC-car. One of the servo's (for steering) is without ESC (as it should be), so easy to connect and power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, the motor that provides the speed uses a ESC with BEC. Which means that the 3 wires coming out of the ESC (red, black and white, which I need to send pulses to) are providing me with current. This would be fine, I could use BEC to power my Arduino, but I like battery life and I have a totally different plan..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So now my actual question; how do I connect the ESC so that I would not have to use the BEC's power supply. I can not imagine only connecting the ground and signal wires, so I need a little help :-)&lt;/p&gt;&#xA;" OwnerUserId="4381" LastActivityDate="2011-05-24T13:40:02.763" Title="Connect Arduino to ESC with BEC (without using its power)" Tags="&lt;arduino&gt;&lt;power&gt;&lt;servo&gt;&lt;esc&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="14609" PostTypeId="1" CreationDate="2011-05-23T22:59:46.737" Score="1" ViewCount="66" Body="&lt;p&gt;I fly model aircraft as a hobby. On some model aircraft the battery connectors can be reversed especially the cheap JST ones with a broken or missing polarity locking tab. Or, the batteries can be mis-wired or a soldering mishap can lead to the poles being swapped. The classic solution to a problem like this would be a diode, probably a Schottky one. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But on a system where currents can exceed 100A, a diode is simply not practical; cooling and size constraints come to mind, as well as the wasted power being approximately &lt;em&gt;0.4 x I&lt;/em&gt;. If the power to an ESC is reversed, it may cause the body diode of the MOSFETs to conduct, leading to very high currents, immediately destroying the ESC. That sucks, of course. But it may be worse; if the ESC has a BEC output (a voltage regulator), the reversed polarity could break down the regulator and fry attached devices, such as servos, receivers, cameras and the like. Which would make for a &lt;em&gt;really&lt;/em&gt; bad day.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Being an RC aircraft application, this needs to be reliable, crash-resistant (i.e. relays are probably &lt;em&gt;not&lt;/em&gt; an option due to their mechanical nature), small in size, and low in cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what solutions for this problem are there?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-05-23T23:12:44.467" LastActivityDate="2011-05-24T07:25:25.833" Title="Reverse polarity protection on model RC aircraft" Tags="&lt;power&gt;&lt;diode&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="1" />
  <row Id="14610" PostTypeId="1" CreationDate="2011-05-23T23:21:29.980" Score="0" ViewCount="96" Body="&lt;p&gt;I have a 19V 4A laptop charger. I was wondering could I convert this into 8v 6A psu for my LEDs. They're parallel-only colour LEDs hence the high current demand. &lt;/p&gt;&#xA;" OwnerUserId="4382" LastEditorUserId="3028" LastEditorDisplayName="" LastEditDate="2011-06-02T11:21:20.813" LastActivityDate="2011-06-02T11:21:20.813" Title="How to build my own 8V 6A PSU using laptop charger" Tags="&lt;circuit-design&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="14611" PostTypeId="2" ParentId="14609" CreationDate="2011-05-23T23:30:36.317" Score="1" ViewCount="" Body="&lt;p&gt;I don't have any experiences with RC aircrafts, but I understand your concerns. I have seen some ideas about a polarity protection circuits using MOSFET's or even something called HEXFET's on battery controlled applications. I know these would, at least, last longer than diodes emitting heat.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(just another thought)&#xA;I was trying to think of a way to add a LED as a reverse polarity indicator so you could quickly unplug it, but nothing came to mind.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I hope these can help point you in the right direction:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.irf.com/technical-info/designtp/dt94-8.pdf&quot; rel=&quot;nofollow&quot;&gt;HEXFET&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.geofex.com/Article_Folders/mosswitch/mosswitch.htm&quot; rel=&quot;nofollow&quot;&gt;MOSFET&lt;/a&gt; - This one is specifically for guitar effects petals, but uses similar concepts.&lt;/p&gt;&#xA;" OwnerUserId="4378" LastActivityDate="2011-05-23T23:30:36.317" CommentCount="1" />
  <row Id="14612" PostTypeId="1" AcceptedAnswerId="14642" CreationDate="2011-05-23T23:50:37.587" Score="4" ViewCount="160" Body="&lt;p&gt;First of all I need to say that I have almost no experience with programming microcontrollers (aside for some Arduino stuff). I have worked with C (and x86 ASM) on some low level projects (think of kernel stuff, embedded systems) so I think the software part should not be an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since I'm trying to learn something about microcontrollers I figured the best way to do it is to take a pet project. I made up my mind and I want to implement &lt;a href=&quot;http://en.wikipedia.org/wiki/Spacewar!&quot; rel=&quot;nofollow&quot;&gt;Spacewar!&lt;/a&gt; on a microcontroller. If it was able to run on a PDP1 in the 60's should run on a microcontroller (I think).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So here's my question, could you recommend any particular development board that would have a VGA port for me to display (just black/white) the game. I am planning to use a usb keyboard for the controls.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Would the VGA displaying (i need only b/w, 640x480 would be more than enough, I would go for even less) be out of the reach for a cheap board (&amp;lt;=100$)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any recommendations for the board? Any other issues you think I might encounter?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you! &lt;/p&gt;&#xA;" OwnerUserId="2717" LastEditorUserId="2717" LastEditorDisplayName="" LastEditDate="2011-05-24T00:21:09.343" LastActivityDate="2011-05-24T15:01:46.280" Title="Spacewar on microcontroller" Tags="&lt;arduino&gt;&lt;microcontroller&gt;&lt;vga&gt;" AnswerCount="5" CommentCount="4" />
  <row Id="14613" PostTypeId="2" ParentId="14610" CreationDate="2011-05-24T01:54:57.000" Score="2" ViewCount="" Body="&lt;p&gt;It would be harder than starting from scratch.  Dropping 19V to 8V is fairly easy.  Increasing 4A to 6A is harder.  You would need DC to DC conversion circuit.  This is not easy and less so at that power level.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;LEDs don't need real great power regulation.  You can run a transformer with enough current capacity to drive the LEDs and a full wave rectifier.  You can probably get by with very little if any filter caps.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-24T01:54:57.000" CommentCount="2" />
  <row Id="14614" PostTypeId="2" ParentId="14612" CreationDate="2011-05-24T01:55:05.687" Score="1" ViewCount="" Body="&lt;p&gt;I wouldnt necessarily call a board that has a video interface a microcontroller.  I dont (yet) know enough about how spacewar interfaced to the display, you could try an asteroids approach where the program created a list of instructions for the vector graphics engine which itself was a processor of sorts with instructions and subroutine calls, etc.  Periodically send a list of video instructions across a serial port to a host, like a dumb terminal, that displays the video.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another approach might be to just get a gameboy advance, 16mhz ARM7, has a display, has pushbuttons.  Cost about $\$$30 or $\$$40 on ebay.  At places like realhotstuff.com you can get a flash cartridge or easier to use an sd (mini, micro or full size) card based one.  Shop around some are harder to use than others.  I also recommend getting a game link cable only so that you can cut it and make two serial cables, use something like this perhaps&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/718&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/718&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;or this is the one I normally use&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/449&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/449&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Write a bootloader and have it boot off the cartridge, then you can download programs via serial into ram and run them there, saves enormous amounts of time pulling the cartridge out then the sd card then mounting it copying the new file, unmount put it in the cartridge cartridge in the gba boot and wait, fail, start again.  With the serial bootloader you can off and on or follow the devr's page instructions and add a reset button.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Probably worth spending just a few bucks more and using a gba sp.  You get a backlit display and a power cord to leave it plugged in all the time.  An NDS will work from a cartridge and developers perspective but is more painful than the GBA for getting your feet wet.  yes in both cases you can simply fall into one of the existing sandboxes and really learn nothing about the embedded part of it.  I wouldnt bother doing anything embedded in that case just write an app on your computer and be done with it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you dont like the gba path you might consider a microcontroller and buy a display separately, earthlcd or sparkfun or someplace like that, easy to come by.  The oled on the stellaris eval boards is probably too small, but oled would be really cool.  You might also look at some of the fpga boards, they often have things like vga ports or lcd control, etc and you can put a mico8 or microblaze or other processor in there.  A bigger project than just writing software for an eval board yes, but puts you in the category of a microcontroller with a vga port.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have not looked at the details but adding something like this to some other microcontroller board may give you the package you are looking for&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.sparkfun.com/products/10329&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/10329&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or perhaps a stellaris board with usb otg, and get some sort of usb based video driver.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are you using as your baseline source?  Having done a static binary translation of asteroids myself, first an emulation then a translation from the pdp1 sources/binary sounds like a very fun project.&lt;/p&gt;&#xA;" OwnerUserId="985" LastEditorUserId="230" LastEditorDisplayName="" LastEditDate="2011-05-24T15:01:46.280" LastActivityDate="2011-05-24T15:01:46.280" CommentCount="1" />
  <row Id="14616" PostTypeId="2" ParentId="14612" CreationDate="2011-05-24T03:02:11.837" Score="6" ViewCount="" Body="&lt;p&gt;One MCU that should be suitable for implementing Spacewar is the 32-bit eight-core &lt;a href=&quot;http://www.parallax.com/tabid/407/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;Parallax Propeller&lt;/a&gt;, as each core has a video and VGA interface. What appear to be equally complex games have been ported to it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I remember playing Spacewar on a DEC PDP-12 where I once worked, many years ago.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-24T03:02:11.837" CommentCount="2" />
  <row Id="14617" PostTypeId="2" ParentId="14527" CreationDate="2011-05-24T04:18:51.410" Score="1" ViewCount="" Body="&lt;p&gt;There's always &lt;a href=&quot;http://www.netduino.com/&quot; rel=&quot;nofollow&quot;&gt;netduino&lt;/a&gt;, which lets you code in .NET.&lt;/p&gt;&#xA;" OwnerUserId="4232" LastActivityDate="2011-05-24T04:18:51.410" CommentCount="1" />
  <row Id="14619" PostTypeId="1" CreationDate="2011-05-24T05:15:23.980" Score="1" ViewCount="239" Body="&lt;p&gt;As legend goes &lt;a href=&quot;http://skeptics.stackexchange.com/q/3520/666&quot;&gt;it is maybe possible to steal electricity from power lines&lt;/a&gt; in a wireless way (also see &lt;a href=&quot;http://electronics.stackexchange.com/q/4664/3552&quot;&gt;this&lt;/a&gt; and &lt;a href=&quot;http://electronics.stackexchange.com/q/8337/3552&quot;&gt;this&lt;/a&gt; related questions). The legend continues that once someone does that he gets caught by the electric company.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Suppose I actually do it - dig enough wire under a power line, plant some fast growing weeds so that the fact of digging is concealed so that there's no obvious disruption and this way steal say one kilowatt of power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How would the electric company detect that wireless theft?&lt;/p&gt;&#xA;" OwnerUserId="3552" LastActivityDate="2011-05-25T02:10:39.850" Title="How would an electric company detect wireless theft of electricity?" Tags="&lt;power&gt;&lt;wireless&gt;&lt;powerline&gt;" AnswerCount="3" CommentCount="6" FavoriteCount="2" />
  <row Id="14620" PostTypeId="2" ParentId="14619" CreationDate="2011-05-24T07:07:53.997" Score="4" ViewCount="" Body="&lt;p&gt;They can't. They monitor the line and notice that a very small fraction of the produced power doesn't arrive at the transformer at the end of the line. Conclusion: over those several kilometers there's a leakage. There's no way to know where. BTW, the amount of power they lose this way is probably far less than cable and transformer losses.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-24T07:07:53.997" CommentCount="5" />
  <row Id="14621" PostTypeId="2" ParentId="14609" CreationDate="2011-05-24T07:25:25.833" Score="3" ViewCount="" Body="&lt;p&gt;Any reverse polarity protection you add will add to the complexity, weight, loss and unreliability of the system, so it's probably not worth it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In short: you can't really add reverse polarity protection in this case without compromising normal operations, so it's better to be careful to never reverse the polarity in the first place.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Make sure you use polarized connectors like Deans Ultra plug in stead of crappy ones that can be reversed with a little man-handling.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Be careful to put the connectors on the batteries correctly.&lt;/p&gt;&#xA;" OwnerUserId="1675" LastActivityDate="2011-05-24T07:25:25.833" CommentCount="1" />
  <row Id="14622" PostTypeId="2" ParentId="14612" CreationDate="2011-05-24T07:40:48.510" Score="3" ViewCount="" Body="&lt;p&gt;If you &lt;strong&gt;already have Arduino board&lt;/strong&gt;, then you can use some &lt;strong&gt;TV out library&lt;/strong&gt; like &lt;strong&gt;&lt;a href=&quot;http://www.batsocks.co.uk/products/Shields/TellyMate%20Shield.htm&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;&lt;/strong&gt;,  &lt;strong&gt;&lt;a href=&quot;http://www.arduino.cc/playground/Main/TVout&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;&lt;/strong&gt;, or &lt;strong&gt;&lt;a href=&quot;http://nootropicdesign.com/ve/projects.html&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt;&lt;/strong&gt;. As you can see you can also order or make your self these cheap boards.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-05-24T07:40:48.510" CommentCount="3" />
  <row Id="14623" PostTypeId="1" CreationDate="2011-05-24T09:11:45.640" Score="3" ViewCount="69" Body="&lt;p&gt;Hi can anyone help me figure out the truth table for this circuit? The output is w and the inputs are p, q, s, t. I have provided my answer for the truth table below, but I itit probably wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/R2Xu4.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/FaQQU.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can someone explain to me how this works? I know in nmos 0 opens switch and 1 closes, and a pmos is the reverse of this. My problem is, I am not sure what happens if:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;1) s &amp;amp; q are open (at the bottom)? Am i right in thinking if only one is open, w will be 0 providing p &amp;amp; t are shut (at the bottom)...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;2) can current still flow if the top T is open? or in fact if any one of the top switches are open?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;3) what will W be if current doesn't flow from bottom or top?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT: OK I think I get it now. I basically end up with 9 5V outputs for w and the rest (7) 0V outputs. basically when T = 0, output will equal 1. When T = 1 output will equal 0 except for when PQS are open at the bottom (that is when PQS are all equal to 1).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks for your help,&lt;/p&gt;&#xA;" OwnerUserId="4386" LastEditorUserId="4386" LastEditorDisplayName="" LastEditDate="2011-05-24T10:25:21.437" LastActivityDate="2011-05-24T10:57:47.287" Title="Boolean Logic Help" Tags="&lt;logic&gt;&lt;digital-logic&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="14624" PostTypeId="2" ParentId="14623" CreationDate="2011-05-24T09:56:08.393" Score="1" ViewCount="" Body="&lt;p&gt;The P, Q, S at the bottom form an OR gate; there's a path if either input is 1. But it's ANDed with T, so that W = 0 if (T = 1) AND (P = 1 OR Q = 1 OR S = 1). The top part is just the De Morgan dual of this: W = 1 if (T = 0) OR (P = 0 AND Q = 0 AND S = 0).&lt;br&gt;&#xA;So W = NOT (T AND (P OR Q OR S)).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The P, Q, S at the bottom look more complicated than they are. They're drawn as P OR (Q OR S) but that's the same as (P OR Q OR S).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Your truth table may be easier to interpret if you list the resp. inputs in binary counting order: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;T P Q S&lt;br&gt;&#xA;  0 0 0 0&lt;br&gt;&#xA;  0 0 0 1&lt;br&gt;&#xA;  0 0 1 0&lt;br&gt;&#xA;  0 0 1 1&lt;br&gt;&#xA;  0 1 0 0&lt;br&gt;&#xA;  0 1 0 1&lt;br&gt;&#xA;  etc.  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Some relationships between a certain input and the output may become more clear, in this case only in the bottom half of the table the output will be zero. The bottom half is when T = 1.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-24T10:13:29.823" LastActivityDate="2011-05-24T10:13:29.823" CommentCount="4" />
  <row Id="14625" PostTypeId="1" CreationDate="2011-05-24T09:57:03.620" Score="2" ViewCount="62" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have heard that mosfets can be converted into resistors if they are &quot;depleted&quot;. Can somebody explain how this is done as simply as possible...I don't have an EE background.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="4386" LastActivityDate="2011-05-24T14:46:03.630" Title="NMOS TO Resistor conversion" Tags="&lt;circuit&gt;&lt;mosfet&gt;" AnswerCount="3" />
  <row Id="14626" PostTypeId="2" ParentId="14625" CreationDate="2011-05-24T10:21:36.597" Score="5" ViewCount="" Body="&lt;p&gt;MOSFETs &lt;em&gt;are&lt;/em&gt; resistors. By how much the channel conducts current is determined by construction of the MOSFET and the voltage on the gate. A depletion type MOSFET will conduct with no voltage applied to the gate, and require a voltage to increase the channel's resistance, while for an enhancement type it's just the other way around.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-24T10:21:36.597" />
  <row Id="14627" PostTypeId="2" ParentId="14623" CreationDate="2011-05-24T10:40:35.857" Score="1" ViewCount="" Body="&lt;p&gt;I didnt quite understand your question clearly. But I will try to answer from my limited knowledge. This circuit is based on CMOS logic. In this logic, PMOS is used as pull up and NMOS is used as pull down. That circuit is an implementation of &lt;code&gt;~[(P+Q+S).T]&lt;/code&gt; which is also can be written as &lt;br&gt;&lt;code&gt;![(P | Q | S) &amp;amp; T]&lt;/code&gt; = &lt;code&gt;(!P &amp;amp; !Q &amp;amp; !S) | T&lt;/code&gt; . Now lets answer your question.&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Yes, &lt;strong&gt;W&lt;/strong&gt; will be pulled down. ie &lt;strong&gt;W&lt;/strong&gt; will be 0V.&lt;/li&gt;&#xA;&lt;li&gt;In CMOS logic, current will flow only when the logic changes. That is only when &lt;strong&gt;W&lt;/strong&gt; changes for 1 to 0 or when it changes from 0 to 1. Thats why CMOS is power efficient. When &lt;strong&gt;T&lt;/strong&gt; switch is closed, &lt;strong&gt;W&lt;/strong&gt; is pulled to Vdd.&lt;/li&gt;&#xA;&lt;li&gt;Like I explained for 2nd question, current will not flow always. &lt;strong&gt;W&lt;/strong&gt; will just be pulled to Vdd or to Vss corresponding to the inputs applied.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Here in this circuit Vdd = 5V and Vss = 0V.&lt;/p&gt;&#xA;" OwnerUserId="4277" LastEditorUserId="4277" LastEditorDisplayName="" LastEditDate="2011-05-24T10:57:47.287" LastActivityDate="2011-05-24T10:57:47.287" CommentCount="3" />
  <row Id="14628" PostTypeId="2" ParentId="14335" CreationDate="2011-05-24T10:50:42.970" Score="1" ViewCount="" Body="&lt;p&gt;I use the following tools which all have full library support:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Riviera-PRO (from at least version 2006.02 onwards)&lt;/li&gt;&#xA;&lt;li&gt;Xilinx ISE (from at least version 10 onwards)&lt;/li&gt;&#xA;&lt;li&gt;Quartus (from at least version 10.0 onwards)&lt;/li&gt;&#xA;&lt;li&gt;Synplify (from at least version 9.0 onwards)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The only caveat is that the &lt;strong&gt;XST&lt;/strong&gt; tool in the Xilinx toolchain is incapable of performing automatic file ordering on projects where entity names exist in multiple libraries (it ungraciously gets stuck looping forever trying to resolve dependencies).&lt;/p&gt;&#xA;" OwnerUserId="4387" LastEditorUserId="4387" LastEditorDisplayName="" LastEditDate="2011-05-24T16:53:01.003" LastActivityDate="2011-05-24T16:53:01.003" CommentCount="1" />
  <row Id="14629" PostTypeId="2" ParentId="14625" CreationDate="2011-05-24T11:22:30.450" Score="2" ViewCount="" Body="&lt;p&gt;A voltage applied to the gate will reduce the width of source-drain channel. Less width/space to flow means less current. That's same as the function of a resistor. Its simple as that.&lt;/p&gt;&#xA;" OwnerUserId="4277" LastActivityDate="2011-05-24T11:22:30.450" />
  <row Id="14630" PostTypeId="1" AcceptedAnswerId="14654" CreationDate="2011-05-24T12:30:24.713" Score="2" ViewCount="89" Body="&lt;p&gt;Title itself is explanatory. Also tell me what are the things I should take care of when I connect other IC's to it? With AVR's I never had to deal with these things. But now when dealing with ARM MCU's I think I have to consider these stuffs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will rephrase the question. Tell me, is it safe to connect LPC MCU to other common IC's like an AVR or L293D diver IC or 74xx series IC's etc without any interfacing circuits?&lt;/p&gt;&#xA;" OwnerUserId="4277" LastEditorUserId="4277" LastEditorDisplayName="" LastEditDate="2011-05-24T14:30:25.827" LastActivityDate="2011-05-24T21:42:21.030" Title="What logic family does NXP 1114 MCU belongs to?" Tags="&lt;microcontroller&gt;&lt;arm&gt;&lt;digital-logic&gt;" AnswerCount="4" CommentCount="0" />
  <row Id="14631" PostTypeId="2" ParentId="14619" CreationDate="2011-05-24T12:35:56.167" Score="-2" ViewCount="" Body="&lt;p&gt;Whatever you try, you cant harvest a considerable amount of power from these lines. These lines have shields that reduces electromagnetic loses, even though they may not be implemented specifically to stop wireless theft.&lt;/p&gt;&#xA;" OwnerUserId="4277" LastActivityDate="2011-05-24T12:35:56.167" CommentCount="3" />
  <row Id="14632" PostTypeId="2" ParentId="14630" CreationDate="2011-05-24T12:42:25.440" Score="1" ViewCount="" Body="&lt;p&gt;The LPC1114 is a Cortex-M0 controller. Cortex (ARMv7, not to be confused with ARM7) is the latest generation of 32-bit ARM controllers.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure what you're thinking of when you say &quot;connect other ICs to it&quot;. The main thing to consider is the voltage the peripherals need/supply, which should match the controller's $V_{DD}$, 3.3V typical according to the datasheet.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-24T12:42:25.440" CommentCount="3" />
  <row Id="14633" PostTypeId="2" ParentId="14630" CreationDate="2011-05-24T13:16:23.163" Score="3" ViewCount="" Body="&lt;p&gt;The digital interface pins are defined as:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;logic low output as maximum $0.4V$, and logic high output as minimum $V_{DD} - 0.4V$&lt;/li&gt;&#xA;&lt;li&gt;logic low input as maximum $0.3 \times V_{DD}$,  and logic high input as maximum $0.7 \times V_{DD}$&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;At a glance, the voltage levels appear similar to LVCMOS.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-24T13:16:23.163" CommentCount="1" />
  <row Id="14634" PostTypeId="2" ParentId="14630" CreationDate="2011-05-24T13:17:54.583" Score="1" ViewCount="" Body="&lt;p&gt;First half of your question:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stevenvh is close, the NXP 1114 is a Cortex-M0 that is a class ARMv6-M based MCU.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Both the Cortex-M0 and Cortex-M1 is based on ARMv6-M. (The Cortex-M3 is based on ARMv7-M).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please note that in the arm world the M more or less stands for a core that fits well in a MCU. (Then there is the R and A series for Application and more hardtime Real time demands).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Cortex-M is a replacement for ARM7 that was based on ARMv4 or ARMv5, and the Cortex-A is kind of a replacement for ARM9 and ARM11. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;But this answer is very academic, just remember that ARM7 and ARMv7 is not the same thing. One is a type of MCU and the other is the core inside a MCU... &lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2011-05-24T13:29:44.023" LastActivityDate="2011-05-24T13:29:44.023" />
  <row Id="14635" PostTypeId="2" ParentId="4724" CreationDate="2011-05-24T13:21:08.793" Score="0" ViewCount="" Body="&lt;p&gt;I've been in a similar boat and I can recommend two books that have been assisting me in getting &quot;up-to-speed&quot;.  Both books were recommended from friends that have spent years developing VHDL.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0471386782&quot; rel=&quot;nofollow&quot;&gt;Embedded System Design: A Unified Hardware/Software Introduction&lt;/a&gt; - Provides a great bottom-up discussion of hardware logic and embedded software.  Related lab-style examples can also be found at this website:  &lt;a href=&quot;http://esd.cs.ucr.edu/labs/tutorial/&quot; rel=&quot;nofollow&quot;&gt;http://esd.cs.ucr.edu/labs/tutorial/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0201895730&quot; rel=&quot;nofollow&quot;&gt;VHDL for Programmable Logic&lt;/a&gt; is another highly recommended book.&lt;/p&gt;&#xA;" OwnerUserId="923" LastActivityDate="2011-05-24T13:21:08.793" />
  <row Id="14636" PostTypeId="2" ParentId="14608" CreationDate="2011-05-24T13:40:02.763" Score="1" ViewCount="" Body="&lt;p&gt;You state that you like battery life.  The Arduino will take a miniscule amount of power compared to the motor on the car.  It will probably take less current then even running the steering servo.  There are reasons for not using  the BEC power, but those are usually related to noise from that power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regardless, if you want to power the Arduino from a separate power source you need to make sure to use close voltage levels.  (RC can usually tolerate 4.8-6.0V or what was 4-5 NiCd/NiMh before LiPo became more popular.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your servo connection will just be Vcc, Ground, and signal.  The signal is the only thing connected to an Arduino pin, so we don't have to worry about how much power pins can provide.  The Vcc and ground will provide the actual energy to turn the steering servo, which can be quite high depending on the performance of the servo used.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For connecting with the ESC, you need to tie your Arduino ground to the ESC ground through the BEC circuit.  You will leave the power coming from the BEC open.  Then you provide the signal to control it.  By tying the grounds together, they are now at the same potential.  Even though you are using different power sources, you are providing pulses that will be understood by the ESC, because they are both referenced from the same point (ground.)&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-24T13:40:02.763" CommentCount="3" />
  <row Id="14637" PostTypeId="2" ParentId="14527" CreationDate="2011-05-24T13:47:53.190" Score="1" ViewCount="" Body="&lt;p&gt;Firstly your examples are small devices that has a limited set of resources, then the old languages that is close to hardware like c and vhdl does the job well.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The new &quot;cool&quot; languages need more resources to run well, so my guess is that what you are seeking will come quite soon since the MCU is getting more powerful over time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My point is that right most MCU:s is still programmed in C, and the cool guy has just started to play with C++ on those devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But if you have a look at the 32-bit ARM based MCU that has a lot more resources than the old 8-bit onces you can find crazy project like &lt;a href=&quot;http://www.eluaproject.net/en_tc_cortex.html&quot; rel=&quot;nofollow&quot;&gt;eLua&lt;/a&gt;, that tries to run the script language lua on a Cortex-M3 based mcu... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So we will get there, but it is going to take a couple of more years.&#xA;And I don't think that any of those crazy project is ready for production use (yet), but some of them will be since it is faster do develop in languages with s higher abstraction level.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2011-05-24T13:47:53.190" />
  <row Id="14638" PostTypeId="1" AcceptedAnswerId="14646" CreationDate="2011-05-24T14:26:07.247" Score="1" ViewCount="92" Body="&lt;p&gt;I am hacking a vacuum cleaner robot by trying to control the motors with an Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have then two &lt;strong&gt;8V motors&lt;/strong&gt;, each one needing from &lt;strong&gt;50mA&lt;/strong&gt; (when the wheel is turning free) to more than &lt;strong&gt;1A&lt;/strong&gt; (when the wheel is blocked).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The robot battery provides &lt;strong&gt;16V&lt;/strong&gt; (and I know it can provide enough current for the motors because that is the original battery).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, how can I &lt;strong&gt;connect the battery to the motor&lt;/strong&gt; ?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I guess once that is done I can just add a transistor to control it with my Arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="4389" LastActivityDate="2011-05-24T17:13:26.960" Title="Connect a 8 V motor to a 16 V battery" Tags="&lt;battery&gt;&lt;motor&gt;&lt;voltage&gt;" AnswerCount="3" />
  <row Id="14639" PostTypeId="2" ParentId="14638" CreationDate="2011-05-24T14:42:42.467" Score="0" ViewCount="" Body="&lt;p&gt;For that small of a current draw motor, I would think about just using an LM7808 Positive 8V regulator to generate the 8V from the 16V.  Then use a logic level N-channel MOSFET to drive the motor from the Arduino.  This only works for always turning one direction.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need to reverse the directions of the motors, then you need to look into driving an H-bridge or other method of reversing the motor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The easiest might be to look into the original control circuitry and see if you can tie into it at the logic level.  I'm betting they have a simple H-bridge in place to control these (which I assume is a Roomba.)  The engineers that designed it probably spent a good bit of time figuring this out, so it is probably a great thing to borrow.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-24T14:42:42.467" CommentCount="3" />
  <row Id="14640" PostTypeId="2" ParentId="14625" CreationDate="2011-05-24T14:46:03.630" Score="3" ViewCount="" Body="&lt;p&gt;Depletion-mode MOSFETs are devices that will provide a voltage drop when current is drawn through them.  They can be used in places where something like a pull-up resistor would be required, but they don't act like a typical resistor.  A typical resistor will, throughout its useful operating range, drop a voltage proportional to current.  A 10Kohm resistor will drop ten volts per milliamp, or ten millivolts per microamp.  By contrast, a depletion-mode MOSFET might drop one volt at 100uA, but drop 0.5 volts at 75uA, or 3 volts at 120uA.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-24T14:46:03.630" />
  <row Id="14641" PostTypeId="2" ParentId="14612" CreationDate="2011-05-24T14:48:38.030" Score="1" ViewCount="" Body="&lt;p&gt;If you have access to an analog scope, I'd suggest wiring a microcontroller with a couple DACs to the XY of the scope.  If you can control the Z (brightness) as well, that would be even better; otherwise if your DACs are fast enough you can simply let the beam dwell on the points that are supposed to be lit.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-24T14:48:38.030" />
  <row Id="14642" PostTypeId="2" ParentId="14612" CreationDate="2011-05-24T14:49:22.980" Score="3" ViewCount="" Body="&lt;p&gt;The Hackvision is essentially an Arduino designed for retro game development.  You program it with ordinary Arduino IDE, and it uses the TVout library.  The output is composite video, so you can hook it up to any TV.  &lt;a href=&quot;http://nootropicdesign.com/hackvision/&quot; rel=&quot;nofollow&quot;&gt;http://nootropicdesign.com/hackvision/&lt;/a&gt;.  See examples of games here: &lt;a href=&quot;http://nootropicdesign.com/hackvision/games.html&quot; rel=&quot;nofollow&quot;&gt;http://nootropicdesign.com/hackvision/games.html&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(full disclosure: I designed Hackvision)&lt;/p&gt;&#xA;" OwnerUserId="4390" LastActivityDate="2011-05-24T14:49:22.980" CommentCount="5" />
  <row Id="14643" PostTypeId="1" CreationDate="2011-05-24T14:54:07.970" Score="0" ViewCount="50" Body="&lt;p&gt;Hi,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is; How can I write equations the following in the circuit?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/lGO5G.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;" OwnerUserId="3916" LastActivityDate="2011-05-24T14:54:07.970" ClosedDate="2011-05-24T15:58:37.457" Title="Magnetic Coupled Circuit Analysis Question" Tags="&lt;circuit&gt;&lt;homework&gt;" CommentCount="3" />
  <row Id="14644" PostTypeId="1" CreationDate="2011-05-24T15:10:58.953" Score="2" ViewCount="146" Body="&lt;p&gt;I am trying to interface micro SD card with PIC MCU using SPI-mode of SD protocol.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Being a beginner, I tried to get the R1 response from the SD card by sending the command '0' through SPI ie.,&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;0x40&#xA;0x00&#xA;0x00&#xA;0x00&#xA;0x00&#xA;0x95&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;But I am not getting the response as &lt;code&gt;0x01&lt;/code&gt; (in Idle mode)..&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The source code is as follows (the PIC MCU I am using is &lt;a href=&quot;http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en532441&quot; rel=&quot;nofollow&quot;&gt;PIC32mx360f512l&lt;/a&gt;)&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/*********************************************************************&#xA; *&#xA; *                 PIC32 - SD card interface&#xA; *&#xA; *********************************************************************&#xA; *&#xA; * Dependencies:    p32xxxx.h&#xA; *&#xA; *&#xA; * Processor:       PIC32&#xA; *&#xA; * Complier:        MPLAB C32&#xA; *                  MPLAB IDE v8.0+&#xA; * Company:         Microchip Technology Inc.&#xA; *&#xA; * Software License Agreement&#xA; *&#xA; *&#xA; ********************************************************************/&#xA;&#xA;&#xA;#include &amp;lt;p32xxxx.h&amp;gt;&#xA;#include &amp;lt;plib.h&amp;gt;&#xA;&#xA;// Config settings&#xA;// POSCMOD = HS, FNOSC = PRIPLL, FWDTEN = OFF&#xA;// PLLIDIV = DIV_2, PLLMUL = MUL_16&#xA;// PBDIV = 8 (default)&#xA;// Main clock = 8MHz /2 * 16    = 80MHz&#xA;// Peripheral clock = 80MHz /8  =  10MHz&#xA;&#xA;// Configuration Bit settings&#xA;// SYSCLK = 80 MHz (8MHz Crystal/ FPLLIDIV * FPLLMUL / FPLLODIV)&#xA;// PBCLK = 10 MHz&#xA;// Primary Osc w/PLL (XT+,HS+,EC+PLL)&#xA;// WDT OFF&#xA;// Other options are don't care&#xA;//&#xA;#pragma config FPLLMUL = MUL_20, FPLLIDIV = DIV_2, FPLLODIV = DIV_1, FWDTEN = OFF&#xA;#pragma config POSCMOD = HS, FNOSC = PRIPLL, FPBDIV = DIV_8&#xA;&#xA;#define SYS_FREQ            (40000000L)&#xA;void initialize();&#xA;void delay(double k);&#xA;void write_byte();&#xA;&#xA;&#xA;int delay_count,loop;&#xA;double d1,d2,d3;&#xA;int loop_var01 = 0;&#xA;int loop_var02 = 0;&#xA;int loop_var03 = 0;&#xA;int success_flag=0;&#xA;int i , j , k , l , m , n , o;&#xA;unsigned char  char_01,char_02 , char_03 , char_04 , char_05 , char_06 ,char_07, response_01;&#xA;char read_byte();&#xA;void toggle_clock();&#xA;&#xA;&#xA;int main(void)&#xA;{&#xA;    int delay;&#xA;    delay = 250;&#xA;    SYSTEMConfig(SYS_FREQ, SYS_CFG_WAIT_STATES | SYS_CFG_PCACHE);&#xA;    initialize();&#xA;    if(TRISDbits.TRISD2 == 1)       // if rd2 ie., DO is 1, check for flags&#xA;&#xA;    while( 1)&#xA;    {&#xA;    }&#xA;&#xA;}&#xA;&#xA;void initialize()&#xA;{&#xA;&#xA;// initialize the port pin directions&#xA;TRISDbits.TRISD0 = 0;&#xA;TRISDbits.TRISD1 = 0;&#xA;TRISDbits.TRISD2 = 1;&#xA;TRISDbits.TRISD3 = 0;&#xA;&#xA;// initialize the SPI card to SPI mode&#xA;delay(10);&#xA;PORTDbits.RD3 = 1;&#xA;PORTDbits.RD1 = 1;&#xA;&#xA;&#xA;// do this a minimum of 74 times&#xA;for(loop_var01=0;loop_var01&amp;lt;80;loop_var01++)&#xA;{&#xA; toggle_clock();&#xA;}&#xA;PORTDbits.RD1 = 0;&#xA;&#xA;write_byte(0x44);&#xA;write_byte(0x00);&#xA;write_byte(0x00);&#xA;write_byte(0x00);&#xA;write_byte(0x00);&#xA;write_byte(0x95);&#xA;&#xA;&#xA;response_01 = read_byte();&#xA;&#xA;if (response_01 == 0x01)&#xA;    success_flag=1;&#xA;&#xA;else&#xA;    success_flag=0;  &#xA;&#xA;}&#xA;&#xA;//write byte ++++++++++++++++++++++++++++++++++&#xA;&#xA;  void write_byte(char_02)&#xA;  {&#xA;    for(n=7;n&amp;gt;=0;n--)&#xA;    {&#xA;      if (char_02 &amp;amp; (1&amp;lt;&amp;lt;n))&#xA;         {PORTDbits.RD3 = 1;}&#xA;      else &#xA;         {PORTDbits.RD3 = 0;}&#xA;      toggle_clock();&#xA;     } &#xA;&#xA;  }&#xA;&#xA;//read byte +++++++++++++++++++++++++++++++++++&#xA;&#xA;  char read_byte()&#xA;  {&#xA;    while(PORTDbits.RD2)   // read the DO input till the the bit becomes 0&#xA;    {  &#xA;     toggle_clock();&#xA;    }&#xA;&#xA;    for (n=0;n&amp;lt;7;n++)&#xA;    { if (PORTDbits.RD2)&#xA;         { char_03 |=(1&amp;lt;&amp;lt;n); }&#xA;      else&#xA;         { char_03 &amp;amp;=~(1&amp;lt;&amp;lt;n); }&#xA;      toggle_clock();&#xA;    }&#xA;    return char_03;&#xA;&#xA;  }&#xA;&#xA;//toggle clock +++++++++++++++++++++++++++++++++&#xA;void toggle_clock()&#xA;{&#xA;delay(100000);&#xA;PORTDbits.RD0 = 0;&#xA;delay(100000);&#xA;PORTDbits.RD0 = 1;&#xA;delay(100000);&#xA;}&#xA;&#xA;//delay ++++++++++++++++++++++++++++++++++++++++&#xA;void delay(double k)&#xA;{ &#xA;  for(k=0;k&amp;lt;delay_count;k++)&#xA;  { for (l=0;l&amp;lt;1000;l++){}}&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Please help me to figure out why I am getting junk or no response&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sub-Question:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How to pass the next command (say command24)?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I mean what is the hex value for command 24? I learnt that every command should begin with 01 followed by 'six bis' corresponding to the command number(in this case it is 24)??&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What should be filled inside the quotes 0x&quot;&quot; for command 24??&lt;/p&gt;&#xA;&#xA;&lt;p&gt;how to pass arguments?? what is its hex value?? Is it 0x00 again or something else??&lt;/p&gt;&#xA;" OwnerUserId="1484" LastEditorUserId="1484" LastEditorDisplayName="" LastEditDate="2011-05-25T15:21:27.570" LastActivityDate="2011-05-25T15:21:27.570" Title="SD Card Interface with Pic Mcu - Part_1" Tags="&lt;pic&gt;&lt;microsd&gt;" CommentCount="7" FavoriteCount="2" />
  <row Id="14645" PostTypeId="2" ParentId="13038" CreationDate="2011-05-24T15:28:24.670" Score="1" ViewCount="" Body="&lt;p&gt;I'm not totally up to speed on SWR bridges, but currently learning to make my own antenna tuner system.  This isn't a complete answer, but more of me thinking through this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The bottom diodes and capacitors are generally called a Peak Detection circuit.  Think of it like a half wave rectifier of the signals of forward and reverse power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;C1 and C2 are forming an AC voltage divider.  The signal coming from the capacitors is the forward primary signal.  This is reinforced on the forward side of the peak detector and subtracted from the reversed side of the peak detector.  Reversed power then is accumulated by the reversed peak detector (this is the part I'm still trying to wrap my mind around.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For calculating the values to use, I would take the expected frequencies and calculate Capacitive reactance.  The ratio of the current ranges should predict the smaller ranges. I would expect it to be linear as we are talking about scaling essentially AC power.  I think we need a full schematic including the meter shunt.  Then we can start figuring out where the reactances are in parallel that make this look nonlinear with the change of one.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What are the values of C2 and R1?   I'm also not quite understanding where in the schematic you are talking about for the series resistors.  Is that after the FWD and REF connection in the schematic?&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-24T15:28:24.670" />
  <row Id="14646" PostTypeId="2" ParentId="14638" CreationDate="2011-05-24T16:41:44.220" Score="1" ViewCount="" Body="&lt;p&gt;Use PWM to provide 8V to the motors from the 16V supply via suitable drivers. Adafruit supplies &lt;a href=&quot;http://www.adafruit.com/products/81&quot; rel=&quot;nofollow&quot;&gt;this motor control shield kit&lt;/a&gt; that you could use, with software that you can adapt.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-24T16:41:44.220" CommentCount="4" />
  <row Id="14647" PostTypeId="2" ParentId="14598" CreationDate="2011-05-24T16:44:10.117" Score="0" ViewCount="" Body="&lt;p&gt;Power $P = I^{2} R$. This means that to have power you need both current and some resistance. Now even a copper wire has a resistance, so there will be power dissipation in the wire, but often both resistance and (thus) power are neglectable.&lt;br&gt;&#xA;There is a special condition, though, when you have a current in a superconductor. In that case resistance is indeed zero, so there will be no power dissipation, even if there is a nonzero current. Since $V = I R$ the current won't generate a voltage either.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-24T17:27:02.940" LastActivityDate="2011-05-24T17:27:02.940" />
  <row Id="14648" PostTypeId="2" ParentId="14638" CreationDate="2011-05-24T17:13:26.960" Score="0" ViewCount="" Body="&lt;p&gt;What kind of motors are there?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If they are using stepper motors (which is extremely common these days, as stepper motors offer superior torque, and are much more reliable), the answer might be surprisingly simple - they could've used 'universal' motors - 6 or 8-lead ones, that can be wired in series to operate directly at 16V.&lt;/p&gt;&#xA;" OwnerUserId="2292" LastActivityDate="2011-05-24T17:13:26.960" CommentCount="4" />
  <row Id="14649" PostTypeId="2" ParentId="14598" CreationDate="2011-05-24T19:54:30.040" Score="1" ViewCount="" Body="&lt;p&gt;@echobase: though it's an imperfect analogy, it is sometimes helpful to compare voltage to &quot;water pressure&quot;, current as &quot;rate of flow&quot; and power as &quot;force of flow&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To flesh that out: imagine you have a water wheel, and you need power to turn it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have really high water pressure, but it's coming through a tiny hole (high voltage, low current), you won't get much power.  If you have a big pipe but low pressure (high current but low voltage), you won't get much power either.  It takes both pressure (voltage) and flow (current) to get work done (power).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you're attracted to the water-as-electricity analogy, you'll probably enjoy &lt;a href=&quot;http://hyperphysics.phy-astr.gsu.edu/hbase/electric/watcir.html&quot; rel=&quot;nofollow&quot;&gt;this link from Georgia State University&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4393" LastActivityDate="2011-05-24T19:54:30.040" />
  <row Id="14650" PostTypeId="2" ParentId="10639" CreationDate="2011-05-24T20:11:58.660" Score="0" ViewCount="" Body="&lt;p&gt;RunDeep's answer is very good.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Only thing I would like to add is i've heard that some insurance policies will not cover your house from fire if it was started by a device that wasn't NRTL approved.&lt;/p&gt;&#xA;" OwnerUserId="4391" LastActivityDate="2011-05-24T20:11:58.660" />
  <row Id="14651" PostTypeId="1" CreationDate="2011-05-24T20:32:26.920" Score="1" ViewCount="41" Body="&lt;p&gt;There are lots of resources on emissions testing.  CE Testing for emissions is similar to FCC part 15 testing (cept it goes higher) so that is not the intention of this page.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm interested in knowing things that you might not have put into your circuit if you designed your subsystems based around the product datasheets which typically try to show as few parts as possible for marketing reasons.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example: My circuit has a standard MAX232 circuit consisting of the max232 chip, the required caps and a DB9 connector.  Will the default circuit pass the IEC 61000-4-4, Burst-Electrical Fast Transients (EFT) test?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another Example: My input voltage regulator has a Maximum input of 30V.  If my product is connected to mains through a step-down transformer (120VAC to 24VAC)... when they do the burst testing 4kV injected onto the power lines seems like it's going to destroy my voltage regulator...  Is it such low energy that typically this isn't an issue?  Or should you always have some type of zener diode on the input side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks&lt;/p&gt;&#xA;" OwnerUserId="4391" LastEditorUserId="4391" LastEditorDisplayName="" LastEditDate="2011-05-24T20:39:14.167" LastActivityDate="2011-05-24T20:39:14.167" ClosedDate="2011-05-24T21:28:37.000" Title="CE mark, Immunity Testing - What are common pitfalls/solutions?" Tags="&lt;markings&gt;&lt;production-testing&gt;" CommentCount="3" FavoriteCount="2" />
  <row Id="14652" PostTypeId="2" ParentId="14598" CreationDate="2011-05-24T21:03:57.863" Score="0" ViewCount="" Body="&lt;p&gt;I'll try to add a practical example to this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One situation where you can have current and no voltage in DC electronics is with solar cells. As light hits a solar cell an energy transfer occurs that causes a current, if the cell has a wire attached connecting the positive and negative (ground) terminals then this current will travel along the wire and back into the cell. There can be quite a lot of current but no voltage, as the wire has no resistance.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If we go to the other extreme and remove the wire from the solar cell, the energy transfer from light to electricity still occurs but the current gets &quot;stuck&quot; at the terminals of the device. This current builds up (almost instantly) to a set voltage. In this case the voltage can be measured but there is no current flow because the resistance between the terminals is infinite.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, if we attached a resistor across the solar cell (lets make it a big one) some of the current is able to flow through it and back to the cell. Assuming the resistance is large the current flow will be small and the voltage won't reduce very much.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If we added a much smaller resistance then it is really easy for the current to flow out of the solar cell and back to the other side. Not all of the current can get through at once though, so we can still see a small voltage across the solar cell (caused by some &quot;stuck&quot; current).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;By changing the resistance we put across the solar cell we can change the relationship between the current and voltage, as you have seen power = current x voltage so if we have 0 current and lots of voltage (or the other way round) you can see how we have 0 power. By adding resistance we get a little bit of both and as such we get power. That power is quite literally heat lost in the resistor in case you were wondering where the energy goes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NB: This is a hugely simplified example and explanation but if you are as noob as you claim then this should do the trick.&lt;/p&gt;&#xA;" OwnerUserId="4096" LastActivityDate="2011-05-24T21:03:57.863" />
  <row Id="14653" PostTypeId="1" AcceptedAnswerId="14655" CreationDate="2011-05-24T21:06:47.827" Score="5" ViewCount="112" Body="&lt;p&gt;In this diagram&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/3uRhL.gif&quot; alt=&quot;http://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/R-S_mk2.gif/220px-R-S_mk2.gif&quot;&gt; &lt;/p&gt;&#xA;&#xA;&lt;p&gt;what would be the beginning state for Q?  Since the first NOR for S and R rely on previous results, there must be something for the first iteration?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;NOTE:&#xA;I'm in a first year digital logic class, so the question is for theoretical use (table making, various homework problems it applies to, etc.), not actual implementation.  Just for things like &quot;if R is __ and S is __ what is Q?&quot;  Simple things like that.&lt;/p&gt;&#xA;" OwnerUserId="4396" LastEditorUserId="4396" LastEditorDisplayName="" LastEditDate="2011-05-25T19:52:06.147" LastActivityDate="2011-05-25T19:52:06.147" Title="What is the beginning state for Q in a SR latch?" Tags="&lt;circuit&gt;&lt;logic&gt;&lt;digital-logic&gt;&lt;flipflop&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="14654" PostTypeId="2" ParentId="14630" CreationDate="2011-05-24T21:42:21.030" Score="1" ViewCount="" Body="&lt;p&gt;The LPC1xxx family has 3.3V IO but it is 5V tolerant. This means that it will only give 3.3V when you output '1' but it will tolerate up to 5V when the pin is configured as an input. Many other 3.3V MCUs/logic chips are not so convenient.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;What this means in practice is that you can connect to almost any standard 5V logic chip. You lose a a bit of noise resistance but I never found this to be a problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The thing to remember is that you will need two supplies: one 3.3V for the LPC1xxx and another 5V one if you wish to use some 5V chips. You cannot run the LPC1xxx from 5V! (but you can use just a simple low drop-out regulator to get from 5V you have to 3.3V you need)&lt;/p&gt;&#xA;" OwnerUserId="659" LastActivityDate="2011-05-24T21:42:21.030" />
  <row Id="14655" PostTypeId="2" ParentId="14653" CreationDate="2011-05-24T21:42:49.317" Score="8" ViewCount="" Body="&lt;p&gt;If you just powered that on, the initial state would be the outcome of a race condition, depending on which gate output can become high first. In actuality, one gate or the other would tend to have a faster rise time, so it probably would tend to come up in one state or the other, but there'd be no guarantee. &lt;/p&gt;&#xA;" OwnerUserId="740" LastEditorUserId="740" LastEditorDisplayName="" LastEditDate="2011-05-25T12:04:14.613" LastActivityDate="2011-05-25T12:04:14.613" CommentCount="6" />
  <row Id="14656" PostTypeId="1" AcceptedAnswerId="14659" CreationDate="2011-05-24T21:47:28.597" Score="4" ViewCount="257" Body="&lt;p&gt;I read somewhere that LEDs could self limit current up to a certain point and had a few lying around in my box so I decided to test this statement. Its true for roughly the voltage drop across the LED. But the question comes is what happened when I applied 20V to the LED? It made a loud popping sound. What happened to the internals of the LED?&lt;/p&gt;&#xA;" OwnerUserId="1623" LastActivityDate="2011-06-03T19:10:26.150" Title="What happens to my LED when I supply too much current?" Tags="&lt;led&gt;" AnswerCount="3" CommentCount="6" FavoriteCount="1" />
  <row Id="14658" PostTypeId="2" ParentId="14656" CreationDate="2011-05-24T22:11:23.177" Score="3" ViewCount="" Body="&lt;p&gt;The weakest electrical portion of the LED fused.  That part would vary based on LED construction.  I've had this happen and blow off the tip of a 3mm LED with surprising energy, when I was young and messing with such questions.  It hit the ceiling pretty hard.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-24T22:11:23.177" />
  <row Id="14659" PostTypeId="2" ParentId="14656" CreationDate="2011-05-24T22:30:35.103" Score="8" ViewCount="" Body="&lt;p&gt;Increasing heat from power dissipation causes a failure of the LED die.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The change in colour, e.g. red and green LEDs going yellow at high currents, is probably because the die is actually glowing hot, i.e. near failure. Note that the red LED has a fall in wavelength, but the green one has an increase in wavelength. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;White LEDs going blue could be explained by the yellow-emitting phosphor in the LED being less effective at high currents. White LEDs are often constructed from a blue LED coated with a special phosphor which emits yellow light when blue light hits it creating a fairly even white light. So perhaps you are seeing more blue than the yellow phosphor can convert.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-24T22:30:35.103" CommentCount="1" />
  <row Id="14660" PostTypeId="1" CreationDate="2011-05-24T23:43:58.117" Score="4" ViewCount="195" Body="&lt;p&gt;I have an almost dead laptop battery and read in &lt;a href=&quot;http://forums.appleinsider.com/showthread.php?t=82905&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; forum that&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;&quot;The problem with most of the broken&#xA;  batterys is that they are exhaustive&#xA;  discharged. the trick to solve this is&#xA;  to give them a high voltage&#xA;  electricity source like a laptop&#xA;  charger (20V). I did that to all the 3&#xA;  lion batteries I found inside the&#xA;  macbook battery but just for a few&#xA;  seconds to reactivate them and now&#xA;  they are working fine&quot;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;I am curious whether this is theoretically possible if nothing else.&lt;/p&gt;&#xA;" OwnerUserId="4397" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-25T00:41:30.770" LastActivityDate="2011-05-25T15:55:14.033" Title="Is it possible to revive a dead battery by passing a high voltage through it?" Tags="&lt;battery&gt;&lt;battery-charging&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="2" />
  <row Id="14661" PostTypeId="2" ParentId="14660" CreationDate="2011-05-25T00:00:43.183" Score="0" ViewCount="" Body="&lt;p&gt;I don't know about theory, but in a company I worked for, we used to have hundreds of 3000$ mobile devices in use and every month we had 3-4 with a dead NiMH battery. It was strange since we knew that most batteries were quite new, and it was pretty much expensive to send them for a repair and wait for their return. Luckily we found an electrician who &quot;repaired them&quot; in a day very cheaply, and he mentioned using some short time high voltage shock.&lt;/p&gt;&#xA;" OwnerUserId="1129" LastActivityDate="2011-05-25T00:00:43.183" />
  <row Id="14662" PostTypeId="2" ParentId="14598" CreationDate="2011-05-25T00:59:06.750" Score="0" ViewCount="" Body="&lt;p&gt;Another water example.  voltage is the water in the tank in the water tower, current is the rate of flow of that water through the pipe to the ground, power is the current slamming into resistance (the inertia from the mass could be the voltage and the rate the mass is moving the current).  from ohms law as stated in another answer you can derive power from current and resistance alone (p=i*i*r).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;think about static electricity and the shock you get from it, the voltage numbers are huge, but the power isnt there, voltage or current by itself is not enough you need a supply of both to really do something and that is why the combination is needed to get power.  A really fast drop of water isnt going to do much, you need some voltage behind it.  Think of a water balloon and a water bed, they may fall at the same rate but only one will total your car when it hits the street.  The combination mass being the voltage and current being the rate the mass is moving, voltage being the multiplication of the two very similar to the way that that force is mass times acceleration, one without the other doesnt do much.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-05-25T00:59:06.750" />
  <row Id="14664" PostTypeId="2" ParentId="14619" CreationDate="2011-05-25T02:10:39.850" Score="2" ViewCount="" Body="&lt;p&gt;There are several problems here:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;p&gt;Power-theft in this manner is not feasible: Even if you had a couple kilometers of wire paralleling the power lines, you would only get a few watts of energy. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;Furthermore, the inverse-square law comes into play. Mythbusters tested this, and cot a few milliwatts with a great big wire coil right up against the wires. This would be rather noticeable, however. The available energy at the base of the tower is much less.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Note: It's possible to harvest a bit more power from the fields of a power line if you have a circuit that wraps completely around the power line (therefore basically acting like a 1-turn transformer). However, you are stuck with capacitive coupling if you cannot wrap entirely around the wire. (This is how parasitic power monitors work, like the one AngryEE mentions. Also, most parasitic monitors use microwatts of power anyways, so they don't need much power to work.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, the only real way the power company can find you did something like what is described in the question is to physically observe it. Realistically, if you did what you describe, the company would pretty much come after you for trespass and (maybe) vandalization, not theft.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;sup&gt;Interestingly enough, on some power lines, there is no way to tap the line &lt;strong&gt;at all&lt;/strong&gt; without a physical connection - On some long distance transmission power lines, they use high-voltage DC to reduce losses. On those power lines, there is no way to capacitively or inductively couple power out of the wires.&lt;/sup&gt;&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-05-25T02:10:39.850" CommentCount="4" />
  <row Id="14665" PostTypeId="2" ParentId="14660" CreationDate="2011-05-25T03:11:17.590" Score="11" ViewCount="" Body="&lt;p&gt;This is a &lt;em&gt;known effect&lt;/em&gt; of &lt;strong&gt;NiCad/NiMH&lt;/strong&gt; batteries.&lt;br&gt;&#xA;Doing it to any other battery risks setting something on fire.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically, Nickel-metal batteries, when over-discharged, can grow little metal whiskers or &quot;dendrites&quot; between the internal plates, shorting the cell out. Applying a high voltage to the cell causes enough current to flow that the dendrite fuses and melts, and therefore, the cell is not longer internally shorted, and can hold a charge. (This is what the guy in avra's response was doing to the batteries)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, letting a cell go completely flat (0V) is quite bad for it, so the battery will never completely recover. However, it may hold some charge afterwards.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;Note that what the guy in the quote is doing is &lt;strong&gt;not&lt;/strong&gt; applying a &lt;em&gt;high voltage&lt;/em&gt; to the cells, but applying a &lt;em&gt;high charge-current&lt;/em&gt; to the cells he is referring to. The laptop charger he describes is likely only good for a few amps, and the output voltage is probably dropping massively when it is connected.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The only thing I can think of is that some laptop batteries have a built-in protection system. If the battery is discharged fully, and then let sit and self-discharge for a while, the protection system may not even get enough power to turn itself on, and therefore, the laptop will not realize a battery is even present.&lt;br&gt;&#xA;When he manually charges the batteries a small amount with his external adapter, by taking the battery apart, it may be just enough to activate the battery protection circuit, so it can charge normally afterwards.&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Applying a significant over-voltage to ANY cell chemistries for any period of time can be dangerous.&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;On lithium cells, you will get metallic lithium plating out of the electrolyte when the cell voltage is above 4.3V. Metallic lithium can catch on fire when exposed to (the moisture in) the air.&lt;/li&gt;&#xA;&lt;li&gt;In Lead-Acid batteries, you will begin to electrolyze the electrolyte, causing the battery to vent hydrogen and oxygen. This is EXTREMELY EXPLOSIVE.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-05-25T03:11:17.590" CommentCount="4" />
  <row Id="14666" PostTypeId="2" ParentId="14660" CreationDate="2011-05-25T03:39:38.237" Score="5" ViewCount="" Body="&lt;p&gt;Lithium batteries have around 1/6th the energy in them as TNT.  Do not mess around with over powering the battery unless you like fires or explosions.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The method was used to clear shorting in NiCd batteries but should never be used for Lithium without understanding all the risks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As with many of the responses, it is possible that it will do what you want.  Just understand that there is a possibility of the pack exploding or burning and take precautions for that.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastEditorUserId="4342" LastEditorDisplayName="" LastEditDate="2011-05-25T15:55:14.033" LastActivityDate="2011-05-25T15:55:14.033" CommentCount="2" />
  <row Id="14667" PostTypeId="1" CreationDate="2011-05-25T05:22:15.220" Score="3" ViewCount="84" Body="&lt;p&gt;I have used Altera FPGAs from last year and I would like to know how the PLLs inside works.&#xA;Mainly, really have any kind of analog circuitry inside in order to measure phase-offset between VCO and external signal?&#xA;This pretty pieces are so reliable along wide freq range (currently 100MHz and beyond even on cheapest models) that I am impressed.&lt;/p&gt;&#xA;" OwnerUserId="4401" LastActivityDate="2011-05-25T10:50:03.323" Title="How work a PLL inside a FPGA?" Tags="&lt;fpga&gt;&lt;pll&gt;" AnswerCount="1" />
  <row Id="14669" PostTypeId="2" ParentId="14660" CreationDate="2011-05-25T09:32:58.700" Score="2" ViewCount="" Body="&lt;p&gt;Messing with lithium ion (LiIon) and lithium ion polymer (LiPo) batteries is a very dangerous thing to do and will likely result in fire and flames. LiPo and LiIon fires are VERY dangerous.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/i9F5J.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Attempting this will probably result in catastrophe. This guy got lucky. Another guy &lt;a href=&quot;http://www.helifreak.com/showthread.php?t=194957&quot; rel=&quot;nofollow&quot;&gt;had his house burn to the ground&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-25T09:32:58.700" CommentCount="3" />
  <row Id="14670" PostTypeId="2" ParentId="14667" CreationDate="2011-05-25T10:50:03.323" Score="4" ViewCount="" Body="&lt;p&gt;It's a conventional PLL with a VCO, a PFD, filter and dividers:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.altera.com/support/devices/pll_clock/basics/pll-basics.html&quot; rel=&quot;nofollow&quot;&gt;http://www.altera.com/support/devices/pll_clock/basics/pll-basics.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-25T10:50:03.323" />
  <row Id="14671" PostTypeId="1" CreationDate="2011-05-25T13:42:17.990" Score="2" ViewCount="65" Body="&lt;p&gt;I want to use a triac controlled by a suitable optoisolator such as a MOC3020 to switch a single phase AC motor on and off, like the ones you'd find in a typical desk fan or a blender or similar.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't want speed control... just on or off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've used triacs in the past to switch resistive loads, which have worked with no problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there anything special or different I need to do to switch an inductive load? Do I need to include any kind of protection or noise suppression? If so what additional components are needed, and how are they implemented?&lt;/p&gt;&#xA;" OwnerUserId="2426" LastActivityDate="2011-05-25T13:42:17.990" Title="Using a triac to switch on/off a single phase AC motor" Tags="&lt;motor&gt;&lt;ac&gt;&lt;triac&gt;" CommentCount="1" />
  <row Id="14672" PostTypeId="2" ParentId="14653" CreationDate="2011-05-25T14:51:15.917" Score="3" ViewCount="" Body="&lt;p&gt;An RS latch has a stable Q high state and a stable !Q high state, but it also has an essentially infinite number of metastable states.  When the latch is in a metastable state, the outputs may arbitrarily switch high and low for an arbitrary length of time, though in practice most metastable states fairly quickly resolve into a stable state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Suppose that each gate had an output propagation time of precisely one nanosecond, both inputs simultaneously switched from high to low.  While the inputs were high, both outputs would be low.  Then one nanosecond after they switched, both outputs would be high.  A nanosecond later, both outputs would be low, then both high, etc.  In practice, the gates aren't going to behave in such perfectly-balanced fashion, of course, but simply imbalancing things won't entirely prevent metastability.  No matter how one might try to tweak the circuit, were it not for quantum limitations, it would be theoretically possible to construct a stimulus with one input leading the other by just the right amount to throw the thing into a metastable state for an arbitrary length of time.  In practice, one can construct circuits so that extended metastability would require such a precise stimulus that the probability of such a stimulus actually occurring would be infinitesimal.  Nonetheless, it's important to be aware of metastability, since it can cause weird and unexpected behaviors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just about &lt;i&gt;any&lt;/i&gt; latch can be thrown into a metastable state if VDD rises and falls in just the right pattern.  Such metastable states will usually resolve pretty quickly, but it's important to note that it's possible for the output of a metastable latch to seem to switch one way and then some time later switch to the opposite state.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-25T14:51:15.917" />
  <row Id="14673" PostTypeId="1" CreationDate="2011-05-25T15:09:39.930" Score="0" ViewCount="45" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;&lt;strong&gt;Possible Duplicate:&lt;/strong&gt;&lt;br&gt;&#xA;  &lt;a href=&quot;http://electronics.stackexchange.com/questions/14644/sd-card-interface-with-pic-mcu-part-1&quot;&gt;SD Card Interface with Pic Mcu - Part_1&lt;/a&gt;  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&#xA;&#xA;&lt;p&gt;The DO line(pin no 2 of microsd card) never becomes high. What could be the reason?? ShouldI use Pullup resistor??&lt;/p&gt;&#xA;" OwnerUserId="1484" LastEditorUserId="1484" LastEditorDisplayName="" LastEditDate="2011-05-25T15:12:01.427" LastActivityDate="2011-05-25T15:12:01.427" ClosedDate="2011-05-25T15:21:56.387" Title="SD Card Interface with Pic Mcu - Part_2" Tags="&lt;pic&gt;&lt;microsd&gt;" CommentCount="6" />
  <row Id="14675" PostTypeId="1" CreationDate="2011-05-25T17:30:42.983" Score="-2" ViewCount="39" Body="&lt;p&gt;Hello people,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd like to know if there's a working ISP for 89S52 using RS232 (connected over USB converter).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can anybody be of help?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you,all.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Update&lt;/strong&gt;: I hadn't looked at the official page. Found this one - bit.ly/mErRez and it seems working. But I am not able to flash anything. I keep getting &quot;Target communication failure. Make sure that your development board has power and is connected to the selected port&quot; error and so unable to do anything. I'm pretty sure I have everything setup correctly. Also, I tried this on both WinXP x86 and Win7 x64. Getting the same message. Anybody?&lt;/p&gt;&#xA;" OwnerUserId="4369" LastEditorUserId="4369" LastEditorDisplayName="" LastEditDate="2011-05-25T18:12:29.797" LastActivityDate="2011-05-25T18:12:29.797" Title="ISP for 89S52 using RS232" Tags="&lt;avr&gt;&lt;pic&gt;&lt;rs232&gt;&lt;isp&gt;" CommentCount="1" />
  <row Id="14676" PostTypeId="1" CreationDate="2011-05-25T18:16:10.873" Score="0" ViewCount="50" Body="&lt;p&gt;Where can I buy a female connector for a &lt;a href=&quot;http://cgi.ebay.com/AWM-RIBBON-FLEX-CABLE-1-00-mm-pitch-16-PIN-230-mm-16PIN-/320662694046?pt=LH_DefaultDomain_0&amp;amp;hash=item4aa8fc689e&quot; rel=&quot;nofollow&quot;&gt;AWM ribbon flex cable 1.00 mm pitch 16 pin&lt;/a&gt;. Its about 17.00 mm wide. I need this for connecting this cable to a patch panel with 2.54 mm spacing. &lt;/p&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="3130" LastEditorDisplayName="" LastEditDate="2011-05-26T08:35:43.020" LastActivityDate="2011-05-27T19:04:50.853" Title="Flexible flat cable AWM 20798 female connector? (16 pin/1mm pitch)" Tags="&lt;connector&gt;&lt;buying&gt;&lt;ribbon-cable&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="14677" PostTypeId="2" ParentId="8767" CreationDate="2011-05-25T18:47:02.537" Score="0" ViewCount="" Body="&lt;p&gt;Avoid git. It doesn't handle large repositories well. And your repositories will get large unless you&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;Have binary schematic files that only change somewhat when they change&lt;/li&gt;&#xA;&lt;li&gt;Turn on treat binaries as text.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="206" LastActivityDate="2011-05-25T18:47:02.537" CommentCount="2" />
  <row Id="14678" PostTypeId="1" AcceptedAnswerId="14683" CreationDate="2011-05-25T18:47:13.103" Score="0" ViewCount="151" Body="&lt;p&gt;I'm trying to teach myself electronics and my goal is to create a digital clock with 4 digits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have  an MSP430G2231 which has only 8 available ports as far as I can tell.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I saw some methods for driving multiple seven segment displays, like using a multiplexer or transistors. But it doesn't seem possible with MSP430G2231 because of it's lack of ports.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Am I wrong? Or could it be done? If yes, how?&lt;/p&gt;&#xA;" OwnerUserId="4412" LastEditorUserId="930" LastEditorDisplayName="" LastEditDate="2011-05-25T20:43:13.360" LastActivityDate="2011-05-31T14:06:40.997" Title="Is it possible to drive 4 seven segment display with MSP430G2231?" Tags="&lt;msp430&gt;&lt;multiplexing&gt;&lt;7segmentdisplay&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="14679" PostTypeId="2" ParentId="14678" CreationDate="2011-05-25T19:04:54.120" Score="0" ViewCount="" Body="&lt;p&gt;I think it actually has 8 I/O pins (not ports, it has one port) available if you use a crystal, which is plenty for four multiplexed seven-segment displays if you use a suitable port expander. It might be sensible to use a device with more I/Os, though.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A suitable port expander is the PCF8575, which can be interfaced to the MSP430G2231 via I2C. It will give you 16 I/Os. It costs under $2.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-25T21:25:53.217" LastActivityDate="2011-05-25T21:25:53.217" CommentCount="6" />
  <row Id="14680" PostTypeId="1" CreationDate="2011-05-25T19:08:29.423" Score="4" ViewCount="142" Body="&lt;p&gt;I hope this is the right place to ask this. But my friend is just learning about electronics and just was given an old vacuum tube. Just because I'm curious, is there any technical information on the computer systems used for the apollo space missions? (Not a system diagram, just an overall summary). Specifically, I was just curious as to the number of vacuum tubes used in both the apollo spacecraft as well as the mission control computers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'd just like a high level description if possible. I'm an EE grad but I'm explaining transistors and digital electronic systems to my friend who's not an Engineer, but is a bio researcher. &lt;/p&gt;&#xA;" OwnerUserId="1360" LastActivityDate="2011-05-26T12:46:34.330" Title="Vacuum tube systems in apollo era space missions" Tags="&lt;transistor&gt;&lt;switch&gt;" AnswerCount="3" CommentCount="1" />
  <row Id="14681" PostTypeId="2" ParentId="14680" CreationDate="2011-05-25T19:12:20.593" Score="5" ViewCount="" Body="&lt;p&gt;The only place where valves were used might have been in the final stages of the various transmitters and radars. The spacecraft and mission control computers would have been solid-state systems; the Apollo guidance computer was one of the first to use ICs. Mainframe computers at the time used transistors, I worked for a company that built them.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-25T19:18:46.603" LastActivityDate="2011-05-25T19:18:46.603" CommentCount="1" />
  <row Id="14682" PostTypeId="2" ParentId="14680" CreationDate="2011-05-25T19:12:53.903" Score="3" ViewCount="" Body="&lt;p&gt;Not sure it did use vacuum tubes. Maybe the soviets used them? Anyway, according to &lt;a href=&quot;http://ed-thelen.org/comp-hist/vs-mit-apollo-guidance.html&quot; rel=&quot;nofollow&quot;&gt;this site&lt;/a&gt;,&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;&quot;The Apollo Guidance Computer (AGC) was built by Raytheon and used &#xA;approximately 4000 discrete integrated circuits from Fairchild Semiconductor.&quot;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-25T19:12:53.903" />
  <row Id="14683" PostTypeId="2" ParentId="14678" CreationDate="2011-05-25T20:14:05.117" Score="2" ViewCount="" Body="&lt;p&gt;Like Leon says you can use an I/O expander, or even better a LED display driver. In the past I've used the MAX7219, but this is a 5V device, for 3.3V you have to go to MAX6950.  This can drive up to five 7-segment digits (the 6951 can do 8), so that may be suitable for your clock. It's controlled via SPI, so you only need 3 I/O pin of your controller. The driver does the multiplexing for you, has a BCD to 7-segment decoder and you can control brightness via software. One minor issue may be the package. The 7219 was available in DIL, but the 6950 only comes in a 0.635 mm pitch TSOP.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/SDkfv.png&quot; alt=&quot;enter image description here&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You say you don't want a crystal (why not?). For a clock you normally would use a crystal to get the required accuracy. But you can also work with the mains frequency, which over long term like months is even more accurate.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;edit&lt;/strong&gt;&lt;br&gt;&#xA;Leon rightfully remarks on the high price for the MAX6950. The MAX7219 is more affordable, but like I said it's a 5V device. Since you only need 3 lines to drive it you could easily add a few level shifters. A transistor will suffice, at least if you don't mind bit-banging the SPI (because it inverts the signal). If you want to use the on-chip SPI you need a non-inverting level shifter, like the &lt;a href=&quot;http://www.fairchildsemi.com/pf/FX/FXL4T245.html&quot; rel=&quot;nofollow&quot;&gt;FXL4T245&lt;/a&gt; (difficult package though).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, just buy an MSP430 with more I/O pins :-)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-26T13:54:08.207" LastActivityDate="2011-05-26T13:54:08.207" CommentCount="5" />
  <row Id="14684" PostTypeId="2" ParentId="14676" CreationDate="2011-05-25T20:15:33.133" Score="2" ViewCount="" Body="&lt;p&gt;I believe what you are looking for are called FFC, FPC (Flat Flexible) connectors.  It looks like DigiKey has quite a few at 0.039&quot; (1.0mm) pitch and 16 conductor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have a surface mount 1mm plug, this is what you need:&#xA;&lt;a href=&quot;http://www.proto-advantage.com/store/product_info.php?products_id=3400022&quot; rel=&quot;nofollow&quot;&gt;http://www.proto-advantage.com/store/product_info.php?products_id=3400022&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you use a through hole 1mm plug, you need something like this (much cheaper and easier):&#xA;&lt;a href=&quot;http://www.proto-advantage.com/store/product_info.php?products_id=3800027&quot; rel=&quot;nofollow&quot;&gt;http://www.proto-advantage.com/store/product_info.php?products_id=3800027&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Never dealt with this company, so this isn't an endorsement.  You may find more by searching for Pitch Changer.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastEditorUserId="4342" LastEditorDisplayName="" LastEditDate="2011-05-27T19:04:50.853" LastActivityDate="2011-05-27T19:04:50.853" CommentCount="4" />
  <row Id="14685" PostTypeId="2" ParentId="14676" CreationDate="2011-05-25T22:22:27.287" Score="0" ViewCount="" Body="&lt;p&gt;I found something at &lt;a href=&quot;http://digikey.de&quot; rel=&quot;nofollow&quot;&gt;digikey&lt;/a&gt;, since there is no URL for search results these are the steps to reproduce my results:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://digikey.de&quot; rel=&quot;nofollow&quot;&gt;http://digikey.de&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;Search for &quot;FFC&quot;&lt;/li&gt;&#xA;&lt;li&gt;Click &quot;FFC, FPC (flach, flexibel) - Steckverbinder - Kartenmontage (X items)&quot;&lt;/li&gt;&#xA;&lt;li&gt;Select then Positionsanzahl: 16 &lt;/li&gt;&#xA;&lt;li&gt;and Neigung (pitch): 1mm&lt;/li&gt;&#xA;&lt;li&gt;and Montagetyp: Durchführungsloch, Durchführungsloch rechtwinklig, Kartenrand Ausschnitt&lt;/li&gt;&#xA;&lt;li&gt;and select &quot;Artikel auf Lager&quot;&lt;/li&gt;&#xA;&lt;li&gt;then click &quot;Filter anwenden&quot;&lt;/li&gt;&#xA;&lt;li&gt;If the product list does not show up select &quot;Seite aufrufen&quot;&lt;/li&gt;&#xA;&lt;li&gt;In the column &quot;Einheitspreis&quot; click the ascending icon and enter 10 for &quot;Teilemenge (erforderlich)&quot; since I'm looking for at least 10 connectors, sorted by the cheapest.&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Update: Digikey told me that there is flex cable 1mm connector for 2.54 mm bread board. :(&lt;/p&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="3130" LastEditorDisplayName="" LastEditDate="2011-05-26T23:45:36.923" LastActivityDate="2011-05-26T23:45:36.923" />
  <row Id="14686" PostTypeId="1" AcceptedAnswerId="14994" CreationDate="2011-05-25T22:41:19.167" Score="0" ViewCount="110" Body="&lt;p&gt;Good day,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm currently getting into DIY electronics and Netduino programming and there's this one personal project that I want to do but I'm hesitant because of lack of information. Basically this is what I want to do:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;Use a mobile phone, in my case an Android tablet (Galaxy Tab) and maybe a WP7 handset in the future, to communicate with a Netduino via a makeshift serial connection using the audio (headphone) port and a custom app. I have found a circuit that I could use and modify for my needs so this part can be considered solved... apart from the app, that is, but that's a different story.&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;So with that, I also wish to be able to transmit information to the Galaxy Tab via the tablet's microphone input by designing a DAC circuit to emulate an electret mic. Is this even possible? I am no electrical engineer but I do have electronics know-how (although that's with regards to high-voltages) because of my line of work but I have little experience working with digital/analog conversion circuits. I don't want to fry my Galaxy Tab's innards because of assumptions so I've been searching for information around the net to no avail. I hope someone can point me to the right direction. Will really appreciate it!&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Thanks a bunch,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Dan&lt;/p&gt;&#xA;" OwnerUserId="4414" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-27T11:20:48.820" LastActivityDate="2011-06-04T09:26:18.173" Title="Emulating an electret microphone with a DAC circuit.." Tags="&lt;voltage&gt;&lt;current&gt;&lt;microphone&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="14687" PostTypeId="1" CreationDate="2011-05-25T23:30:15.530" Score="1" ViewCount="50" Body="&lt;p&gt;I'm trying to do some homework involving this circuit diagram:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/dF8eu.jpg&quot; alt=&quot;Image&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But I'm confused as to what the input would be for building a state table.  Would I have to use the states of the flip flops as the input variables?&lt;/p&gt;&#xA;" OwnerUserId="4396" LastEditorUserId="1374" LastEditorDisplayName="" LastEditDate="2011-05-26T07:10:56.907" LastActivityDate="2011-05-26T10:32:31.313" Title="What happens when there's no specific input variable on a logic diagram using a JK flip flop?" Tags="&lt;logic&gt;&lt;homework&gt;&lt;digital-logic&gt;&lt;flipflop&gt;&lt;state-machines&gt;" AnswerCount="2" CommentCount="4" FavoriteCount="1" />
  <row Id="14688" PostTypeId="1" CreationDate="2011-05-26T01:17:36.513" Score="1" ViewCount="202" Body="&lt;p&gt;As we know CPU is pretty much millions of transistors on a single thumbnail,what if one of the transistors is broken?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does CPU have any auto-recovery mechanism?&lt;/p&gt;&#xA;" OwnerUserId="4418" LastActivityDate="2011-05-26T20:13:36.500" Title="How's CPU supposed to be stable with so many transistors?" Tags="&lt;transistor&gt;&lt;cpu&gt;" AnswerCount="5" CommentCount="1" FavoriteCount="1" />
  <row Id="14689" PostTypeId="2" ParentId="14688" CreationDate="2011-05-26T02:23:15.393" Score="0" ViewCount="" Body="&lt;p&gt;It may seem like a miracle but there are a number of mechanisms used to reduce the amount of transistor failures. However, depending on the type of failure experienced by the transistor and where, the CPU may or may not still be usable sometimes under certain conditions. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;At present, there is often no auto-recovery mechanism built in but there is a lot of research into reconfigurable computing, redundancy and other techniques to minimise this problem.&lt;/p&gt;&#xA;" OwnerUserId="1938" LastActivityDate="2011-05-26T02:23:15.393" />
  <row Id="14690" PostTypeId="2" ParentId="8767" CreationDate="2011-05-26T03:12:03.597" Score="1" ViewCount="" Body="&lt;p&gt;svn, hg, and git all work just fine.&lt;/p&gt;&#xA;" OwnerUserId="985" LastActivityDate="2011-05-26T03:12:03.597" />
  <row Id="14691" PostTypeId="2" ParentId="14688" CreationDate="2011-05-26T04:34:26.340" Score="1" ViewCount="" Body="&lt;p&gt;Most modern processor transistors are FETs.  These have the advantage of gaining source/drain resistance when starting to overload.  This is one factor that allows high power MOSFETs to be made by putting many in parallel.  The load automatically distributes.  That may be a factor to help distribute issues.  But I think it is really simpler than that.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As with most electronic parts, if you drive them within spec, they will last for quite a while.  When a microprocessor is made, there are two factors for the cost.  Just the space on the silicon and, due to complexity, the actual yield.  Not all chips work after manufacturing.  However, once it is made and pasts the validation, you know the transistors are good.  If driven within spec, chances are that they will stay good.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-26T04:34:26.340" />
  <row Id="14692" PostTypeId="2" ParentId="14686" CreationDate="2011-05-26T04:40:52.243" Score="0" ViewCount="" Body="&lt;p&gt;It should be possible, but you need to match the power and impedance expected.  An electret mic will have power running to it.  You might find it easiest to use a 1:1 audio transformer to isolate each sides and allow the signal to carry the voltage of the electret.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will most likely need to run something to give attenuation.  This could be either just a divider or an Op Amp with a gain less than one.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-26T04:40:52.243" CommentCount="3" />
  <row Id="14693" PostTypeId="2" ParentId="14678" CreationDate="2011-05-26T04:46:07.210" Score="1" ViewCount="" Body="&lt;p&gt;I would use 2 x 74HC 595 shift registers &#xA;I have tried the code example and schematic Here &lt;a href=&quot;http://www.43oh.com/forum/viewtopic.php?f=9&amp;amp;t=255&quot; rel=&quot;nofollow&quot;&gt;http://www.43oh.com/forum/viewtopic.php?f=9&amp;amp;t=255&lt;/a&gt; and it works with out an issue - I would suggest replacing the uln2003 with a few 2n2222 or 2n3909 npn transistor&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/jHc25.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;    #include &amp;lt;msp430g2231.h&amp;gt;&#xA;&#xA;unsigned int counter = 0;                   // Counter variable&#xA;unsigned int digitCounter = 0;            // Digit counter&#xA;unsigned char digit = 0;               // Single digit to be displayed&#xA;unsigned char bcd7digit[10] = {0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F}; // BCD to 7 digit map&#xA;unsigned char digitSelector[4] = {0x01, 0x02, 0x04, 0x08}; // Digit selector map&#xA;&#xA;void main(void)&#xA;{&#xA;  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT&#xA;&#xA;  P1OUT |= 0x01;                      // Port P1.0 will be used to latch&#xA;  P1DIR |= 0x01;&#xA;&#xA;  USICTL0 |= USIPE6 + USIPE5 + USIMST + USIOE; // Out &amp;amp; clk enable, SPI Master&#xA;  USICTL1 |= USICKPH + USIIE;               // Counter interrupt, flag remains set&#xA;  USICKCTL = USIDIV_7 + USISSEL_2;          // /128 SMCLK&#xA;  USICTL0 &amp;amp;= ~USISWRST;                     // USI released for operation&#xA;  USICNT = USI16B;                           // Enable 16 bit&#xA;&#xA;  CCTL0 = CCIE;                             // CCR0 interrupt enabled&#xA;  CCR0 = 500;                        //&#xA;  TACTL = TASSEL_2 + MC_1 + ID_3;           // SMCLK, upmode&#xA;&#xA;  _bis_SR_register(LPM0_bits + GIE);        // Enter LPM0 w/ interrupt&#xA;}&#xA;&#xA;// Timer A0 interrupt service routine&#xA;#pragma vector = TIMERA0_VECTOR&#xA;__interrupt void Timer_A (void)&#xA;{   &#xA;  digitCounter++;                       // Increase digit counter&#xA;  digitCounter &amp;amp;= 0x03;                // Mask, counter range is 0-3&#xA;  digit = counter&amp;gt;&amp;gt;(4 * digitCounter);       // Shift digits right&#xA;  digit &amp;amp;= 0x0F;                      // Mask, we need first digit only&#xA;  USISRL = bcd7digit[digit];             // Get segments from the map&#xA;  USISRH = digitSelector[digitCounter];    //&#xA;  if(digitCounter == 0) {&#xA;     counter = _bcd_add_short(counter, 0x01);// Decimally increase counter's when on first digit&#xA;  }&#xA;  USICNT |= 16;                              // Start USI&#xA;}&#xA;&#xA;// USI interrupt service routine&#xA;#pragma vector = USI_VECTOR&#xA;__interrupt void USI_TXRX (void)&#xA;{&#xA;  USICTL1 &amp;amp;= ~USIIFG;                     // Clear pending flag&#xA;  P1OUT &amp;amp;= ~0x01;                     // Latch data&#xA;  P1OUT |= 0x01;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Another Option would be using 4 x 74HC595 and use one each, for every 7segment you have this cuts the multiplexing and you can just send a serial string through the SPI interface or bit bang it. very similar as above. but uses less pins. Just an Idea &lt;/p&gt;&#xA;" OwnerUserId="2060" LastEditorUserId="2060" LastEditorDisplayName="" LastEditDate="2011-05-26T08:39:56.813" LastActivityDate="2011-05-26T08:39:56.813" />
  <row Id="14694" PostTypeId="2" ParentId="9722" CreationDate="2011-05-26T05:30:19.263" Score="0" ViewCount="" Body="&lt;p&gt;I agree with Brian on this one.  I have just recently had to modify a design to replace a particularly static sensitive Ethernet PHY IC from Davicom.  This part failed constantly and the only thing we could pin it down to was static.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The new design moved to a National Semi part which incorporated static protection in the IC plus we added an ethernet specific tranzorb style device right at the jack input.  This drove the cost up by more than $15USD so it's easy to believe that inexpensive routers / switches deliberately leave these components out.&lt;/p&gt;&#xA;" OwnerUserId="4311" LastActivityDate="2011-05-26T05:30:19.263" />
  <row Id="14695" PostTypeId="1" CreationDate="2011-05-26T06:14:29.530" Score="4" ViewCount="93" Body="&lt;p&gt;Hello there,&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am in my evil mad scientist mode right now, partly due to the finals tomorrow. Yesterday I was reading about those new consumer devices which allow one to sense brain waves. Somebody even interfaced those with an arduino (man they are everywhere) and a computer. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This got me thinking, can I make such a device at home? I know they could be bought for relatively cheap right now but I am in India and most of them cost more than I would ever have in one year.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does anyone know of any diy transducers which could sense brianwaves using parts I could acquire easily? I am not looking for neurofeedback. That can be dangerous (for no openEEG for me). I just want to sense, not give signals back to my brain.&lt;/p&gt;&#xA;" OwnerUserId="1200" LastActivityDate="2011-05-26T22:53:43.650" Title="Transducers for sensing brain waves which can be made at home?" Tags="&lt;brainwaves&gt;&lt;transducers&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="2" />
  <row Id="14696" PostTypeId="2" ParentId="14687" CreationDate="2011-05-26T07:13:31.663" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+10.20027730826997+50+5.0+43%0A152+352+240+464+240+0+2+5.0%0A152+352+432+464+432+0+2+0.0%0A156+688+240+800+240+0+5.0%0A156+688+432+736+432+0+0.0%0Aw+464+432+640+432+0%0Aw+640+432+640+496+0%0Aw+640+496+688+496+0%0Aw+688+432+640+432+0%0Aw+688+304+640+304+0%0Aw+640+304+640+240+0%0Aw+640+240+688+240+0%0Aw+640+240+464+240+0%0Aw+784+432+832+432+0%0Aw+832+432+832+368+0%0Aw+832+368+320+368+0%0Aw+320+368+320+416+0%0Aw+320+416+352+416+0%0Aw+352+448+320+448+0%0Aw+320+448+320+560+0%0Aw+320+560+896+560+0%0Aw+896+560+896+304+0%0Aw+896+304+784+304+0%0Aw+784+240+896+240+0%0Aw+896+240+896+160+0%0Aw+352+256+320+256+0%0Aw+320+256+320+368+0%0Aw+352+224+320+224+0%0Aw+896+160+320+160+0%0Aw+320+160+320+224+0%0Aw+688+272+576+272+0%0Aw+576+272+576+464+0%0Aw+576+464+688+464+0%0Aw+576+464+576+624+0%0Aw+576+624+464+624+0%0AR+464+624+432+624+0+2+40.0+5.0+0.0+0.0+0.5%0A&quot; rel=&quot;nofollow&quot;&gt;So I was bored&lt;/a&gt;, and Falstad Sim is Awesome.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This should get you started.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.falstad.com/circuit/#%24+1+5.0E-6+10.20027730826997+50+5.0+43%0A152+352+240+464+240+0+2+5.0%0A152+352+432+464+432+0+2+0.0%0A156+688+240+800+240+0+5.0%0A156+688+432+736+432+0+0.0%0Aw+464+432+640+432+0%0Aw+640+432+640+496+0%0Aw+640+496+688+496+0%0Aw+688+432+640+432+0%0Aw+688+304+640+304+0%0Aw+640+304+640+240+0%0Aw+640+240+688+240+0%0Aw+640+240+464+240+0%0Aw+784+432+832+432+0%0Aw+832+432+832+368+0%0Aw+832+368+320+368+0%0Aw+320+368+320+416+0%0Aw+320+416+352+416+0%0Aw+352+448+320+448+0%0Aw+320+448+320+560+0%0Aw+320+560+896+560+0%0Aw+896+560+896+304+0%0Aw+896+304+784+304+0%0Aw+784+240+896+240+0%0Aw+896+240+896+160+0%0Aw+352+256+320+256+0%0Aw+320+256+320+368+0%0Aw+352+224+320+224+0%0Aw+896+160+320+160+0%0Aw+320+160+320+224+0%0Aw+688+272+576+272+0%0Aw+576+272+576+464+0%0Aw+576+464+688+464+0%0Aw+576+464+576+624+0%0Aw+576+624+464+624+0%0AR+464+624+432+624+0+2+40.0+5.0+0.0+0.0+0.5%0A&quot; rel=&quot;nofollow&quot;&gt;&lt;img src=&quot;http://i.stack.imgur.com/ohpJe.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The Falstad Circuit Simulator applet is great for doing little logic proof-of-concepts, or other similar idea verification tasks. Like any circuit simulator, it will have situations where it does not behave exactly like the real-world circuit would, but with logic, it is certainly close enough.&lt;/p&gt;&#xA;" OwnerUserId="1374" LastActivityDate="2011-05-26T07:13:31.663" />
  <row Id="14697" PostTypeId="2" ParentId="14688" CreationDate="2011-05-26T07:52:48.333" Score="5" ViewCount="" Body="&lt;p&gt;To expand a bit on what others have said: There is validation and after that there is classification of chips. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Transistors in CPUs tend to show their problems at higher frequencies, so it is common to make one CPU and then market it as several different products. The cheaper CPUs are actually damaged versions of the expensive CPU. Another option is disabling certain parts of the CPU. For example, AMD made processors with BArton core. It also sold processors with Thorton core. Thorton wasn't a new core. Instead, half of L2 cache was defective and disabled. This way, AMD made some recovery on the CPUs that would have been otherwise wasted.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Same thing happened with AMD's 3 core processors. They were originally 4 core processors, but one of the cores was determined to be defective, so it was disabled.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-05-26T07:52:48.333" />
  <row Id="14698" PostTypeId="2" ParentId="14680" CreationDate="2011-05-26T07:59:21.223" Score="4" ViewCount="" Body="&lt;p&gt;Start from this page and drool :-) &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://klabs.org/history/build_agc/&quot; rel=&quot;nofollow&quot;&gt;http://klabs.org/history/build_agc/&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Abstract of the page: &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;This report describes my successful&#xA;  project to build a working&#xA;  reproduction of the 1964 prototype for&#xA;  the Block I Apollo Guidance Computer.&#xA;  The AGC is the flight computer for the&#xA;  Apollo moon landings, with one unit in&#xA;  the command module and one in the LEM.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;I built it in my basement. It took me&#xA;  4 years.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;If you like, you can build one too. It&#xA;  will take you less time, and yours&#xA;  will be better than mine.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;" OwnerUserId="244" LastEditorUserId="244" LastEditorDisplayName="" LastEditDate="2011-05-26T12:46:34.330" LastActivityDate="2011-05-26T12:46:34.330" CommentCount="3" />
  <row Id="14699" PostTypeId="1" AcceptedAnswerId="14717" CreationDate="2011-05-26T08:07:28.403" Score="3" ViewCount="118" Body="&lt;p&gt;I keep frying resistors in the following optocoupler and triac snubber circuit, and I'm not sure whether to attribute this to bad design, or to faulty components.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;There are no observable sparks at turn-on, but the 680-ohm resistor burns out within seconds.&lt;/li&gt;&#xA;&lt;li&gt;I'm using 1/4W through-hole resistors.&lt;/li&gt;&#xA;&lt;li&gt;The power triac gate triggers at &amp;lt;= 35mA.&lt;/li&gt;&#xA;&lt;li&gt;The load is a ~50W fan that runs on mains power.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/QQGys.gif&quot; alt=&quot;Switcher circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If my understanding is correct, the steady-state (ON) power dissipation of the 680-ohm resistor should be less than 0.1W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you agree that my design is reasonable, then what component do you suspect is faulty, and why?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also tried the following circuit, but again, the 680-ohm resistor smoked when I put the optocoupler in the ON state:&#xA;&lt;img src=&quot;http://i.stack.imgur.com/QldxP.gif&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2172" LastEditorUserId="2172" LastEditorDisplayName="" LastEditDate="2011-05-26T18:28:22.683" LastActivityDate="2011-06-01T23:27:27.473" Title="Sanity-check on snubber design" Tags="&lt;triac&gt;&lt;opto-isolator&gt;" AnswerCount="4" CommentCount="2" FavoriteCount="1" />
  <row Id="14700" PostTypeId="2" ParentId="8767" CreationDate="2011-05-26T08:49:30.007" Score="1" ViewCount="" Body="&lt;p&gt;Not a real version control system but Dropbox handles also revision of files an makes them available for different people on different OSes. - poor mans version control system ;)&lt;/p&gt;&#xA;" OwnerUserId="3130" LastActivityDate="2011-05-26T08:49:30.007" />
  <row Id="14701" PostTypeId="2" ParentId="10615" CreationDate="2011-05-26T08:54:11.717" Score="2" ViewCount="" Body="&lt;p&gt;A good documentation on the official Arduino Wiki: &lt;a href=&quot;http://www.arduino.cc/playground/Learning/WhatAdapter&quot; rel=&quot;nofollow&quot;&gt;arduino.cc/playground/Learning/WhatAdapter&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;+ is the center contact&lt;br&gt;&#xA;- is the outer contact&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;         .---.&#xA; -  ----&amp;lt;  O----  +&#xA;         `---´&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;DC should be between 9V and 12V (20V max)&lt;/li&gt;&#xA;&lt;li&gt;It's a 2.1mm power plug&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3130" LastEditorUserId="3130" LastEditorDisplayName="" LastEditDate="2011-05-26T09:14:50.023" LastActivityDate="2011-05-26T09:14:50.023" />
  <row Id="14702" PostTypeId="2" ParentId="14688" CreationDate="2011-05-26T09:53:15.717" Score="5" ViewCount="" Body="&lt;p&gt;It's simple, we test them before we sell them and throw the bad ones out.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are lots of ways to do this - different people do different thing, often use a combination of: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;p&gt;some tests are at speed to make sure they go fast enough. &lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;other tests involve a mode that turns some or all of the flipflops in the chip into giant serial shift registers, we clock known data into those chains, then run the chip for one clock and then scan the new results back out and check that they match our predicted results - automatic test tools generate a minimum set of &quot;scan vectors&quot; that will test every random gate or transistor on the chip - other vectors do special tests of ram blocks,&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;others test that the external wires are all bonded correctly&lt;/p&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;p&gt;we make sure it's not pulling an unhealthy amount of current&lt;/p&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;Testing time costs money, we sometimes do some simple testing for obvious dead chips before they are packaged to discard the bad ones and then more testing after the packaging is done&lt;/p&gt;&#xA;" OwnerUserId="3190" LastActivityDate="2011-05-26T09:53:15.717" />
  <row Id="14703" PostTypeId="2" ParentId="14687" CreationDate="2011-05-26T10:32:31.313" Score="0" ViewCount="" Body="&lt;p&gt;Your instinct is correct - assign labels to the FF outputs, e.g., Q1 and Q2. To form a state table, on the left side, list the the four possible states of Q1, Q2; on the right side, write the values that Q1 and Q2 will assume after the next clock pulse. The table will then contain a complete description of the state machine.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-26T10:32:31.313" />
  <row Id="14704" PostTypeId="2" ParentId="14699" CreationDate="2011-05-26T10:44:42.647" Score="1" ViewCount="" Body="&lt;p&gt;Put a much higher wattage resistor in that position and measure the current through it. You will find that your calculation is wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you read the data sheet you will see that the resistor in question and the 0.1 uF capacitor aren't necessarily needed (they constitute a snubber for the coupler). Try removing them.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-26T10:50:57.033" LastActivityDate="2011-05-26T10:50:57.033" CommentCount="4" />
  <row Id="14705" PostTypeId="1" AcceptedAnswerId="14733" CreationDate="2011-05-26T11:23:34.753" Score="2" ViewCount="70" Body="&lt;p&gt;I have a LPC1114 kit. Last few days I have been digging up CMSIS implementation of Cortex M0 to find how things are done in it. So far I understood how each registers are mapped and how I can access it. But still I dont know how interrupts are implemented in it. All I know about interrupts in CMSIS is there are some interrupt handler names mentioned in the startup file. And I can write my own handlers by simply writing a C function with the same names mentioned in the startup file. What confuses me is that in the user guide, it is told that all GPIO can be used as external interrupt sources. But there are only 4 PIO interrupts mentioned in the startup file. So tell me:&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;How can I implement external interrupt handlers for other GPIOs?&lt;/li&gt;&#xA;&lt;li&gt;Where is the interrupt table mapped in the CMSIS?&lt;/li&gt;&#xA;&lt;li&gt;What are the major differences between NVIC and the interrupt implementation in AVRs/PICs? (except NVIC can be mapped anywhere in the flash)&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;" OwnerUserId="4277" LastActivityDate="2011-05-27T00:18:40.910" Title="How are interrupt handlers implemented in CMSIS of Cortex M0?" Tags="&lt;arm&gt;&lt;interrupt&gt;" AnswerCount="2" FavoriteCount="1" />
  <row Id="14706" PostTypeId="1" CreationDate="2011-05-26T11:41:27.843" Score="0" ViewCount="42" Body="&lt;pre&gt;&lt;code&gt;PORTB = (PORTB &amp;amp; ~0xfc) | (b &amp;amp; 0xfc);&#xA;PORTD = (PORTD &amp;amp; ~0x30) | ((b &amp;lt;&amp;lt; 4) &amp;amp; 0x30);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Hi AFAIK the 0xFC is a hex value. Is that basically saying &#xA;11111100 hence PORTD0-PORTD1 are outputs but the rest are inputs.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you give a full explaination of that code. I'm not too sure I've understood it.&lt;/p&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="2288" LastEditorDisplayName="" LastEditDate="2011-05-26T13:26:33.717" LastActivityDate="2011-05-26T13:26:33.717" ClosedDate="2011-05-26T16:40:40.397" Title="Explain this code avr port setup" Tags="&lt;avr-gcc&gt;&lt;bitmask&gt;&lt;bitwise-operation&gt;" AnswerCount="0" CommentCount="1" />
  <row Id="14708" PostTypeId="1" CreationDate="2011-05-26T11:58:48.440" Score="0" ViewCount="44" Body="&lt;p&gt;How do I maximise the Q-factor of the low pass sallen and key design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have this equation: \$Q = \sqrt{ \frac {(R1 \times R2 \times C1 \times C2)} {R1 \times C1 \times (1-A) + (R1 \times C2) + (R2 \times C2)}} \$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;but I'm not sure of the best way to maximise it!&lt;/p&gt;&#xA;" OwnerUserId="4422" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-06-02T17:37:46.003" LastActivityDate="2011-06-02T17:37:46.003" Title="Maximise Q factor in low pass Sallen and Key Filter" Tags="&lt;filter&gt;" AnswerCount="1" />
  <row Id="14709" PostTypeId="2" ParentId="14705" CreationDate="2011-05-26T12:08:05.137" Score="4" ViewCount="" Body="&lt;p&gt;(Please note that points 1 and 2 are implementation details and not architectural limitations.)&lt;/p&gt;&#xA;&#xA;&lt;ol&gt;&#xA;&lt;li&gt;In bigger NXP chips (such as LPC17xx) there are a couple of dedicated interrupt pins (EINTn) which have their own interrupt handler. The rest of GPIOs have to use one common interrupt (EINT3). You can then poll the interrupt status register to see which pins have triggered the interrupt.&lt;/li&gt;&#xA;&lt;li&gt;I'm not very familiar with LPC11xx but it &lt;strong&gt;seems&lt;/strong&gt; that it has one interrupt per GPIO port. You again will have to check the status register to figure out the specific pins. There are also up to 12 pins that can act as wakeup sources. I'm not sure if you can hijack them as general interrupts (i.e. they will probably only be triggered when in sleep state).&lt;/li&gt;&#xA;&lt;li&gt;The default handler table is placed at the address 0 (which is in flash). The first entry is the reset value for the SP register, the second is the reset vector, and the rest are other exceptions and interrupt vectors. A couple of the first ones (such as NMI and HardFault) are fixed by ARM, the rest are chip-specific. If you need to change the vectors at runtime, you can remap it to RAM (you first need to copy the table). In LPC11xx the remapping is fixed to the start of SRAM (0x10000000), other chips can be more flexible.&lt;/li&gt;&#xA;&lt;li&gt;The NVIC is optimized for efficient interrupt handling:&#xA;&lt;ul&gt;&#xA;&lt;li&gt;programmable priority level of 0-3 for each interrupt. A higher-priority interrupt preempts lower-priority ones (nesting). The execution of the lower priority one resumes when the higher-priority interrupt is finished.&lt;/li&gt;&#xA;&lt;li&gt;automatic stacking of the processor state on interrupt entry; this allows writing interrupt handlers directly in C and removes the need for assembly wrappers.&lt;/li&gt;&#xA;&lt;li&gt;tail-chaining: instead of popping and pushing the state again, the next pending interrupt is handled immediately&lt;/li&gt;&#xA;&lt;li&gt;late-arriving: if a higher-priority interrupt arrives while stacking the processor state, it's executed immediately instead of the previously pending one.&lt;/li&gt;&#xA;&lt;/ul&gt;&lt;/li&gt;&#xA;&lt;/ol&gt;&#xA;&#xA;&lt;p&gt;Since you're familiar with PICs, have a look at this App Note:&#xA;&lt;a href=&quot;http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dai0234a/index.html&quot; rel=&quot;nofollow&quot;&gt;Migrating from PIC Microcontrollers to Cortex-M3&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's about M3, but most of the points apply to M0 too.&lt;/p&gt;&#xA;" OwnerUserId="1082" LastActivityDate="2011-05-26T12:08:05.137" />
  <row Id="14710" PostTypeId="1" AcceptedAnswerId="14711" CreationDate="2011-05-26T12:13:13.700" Score="4" ViewCount="109" Body="&lt;p&gt;Can anyone explain a little more about watchdogs, specifically in the circuitry level?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If there is some kind of problem in the chip, how can I guarantee that it will be kept running? It is implemented in a different silicon and later attached to the main chip circuit to avoid temperature problems? Which kind of interface circuit it is commonly used to avoid counting/resetting errors? It is common to implement any kind of redundancy?&lt;/p&gt;&#xA;" OwnerUserId="1757" LastActivityDate="2011-05-26T13:47:27.547" Title="Microcontroler's watchdog" Tags="&lt;microcontroller&gt;&lt;safety&gt;&lt;watchdog&gt;" AnswerCount="2" CommentCount="1" FavoriteCount="2" />
  <row Id="14711" PostTypeId="2" ParentId="14710" CreationDate="2011-05-26T12:22:21.427" Score="6" ViewCount="" Body="&lt;p&gt;The watchdog is just a timer on the same die as the rest of the microcontroller. It's mainly meant to catch software errors, there are no precautions for a malfunction of the watchdog itself. Typically one would reset the watchdog timer in the program's main loop. If for some reason the main loop will no longer be executed the controller will reset.&lt;br&gt;&#xA;If you don't trust the microcontroller hardware you can always add an external watchdog IC.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-26T12:54:25.677" LastActivityDate="2011-05-26T12:54:25.677" CommentCount="7" />
  <row Id="14713" PostTypeId="1" CreationDate="2011-05-26T13:07:54.933" Score="1" ViewCount="73" Body="&lt;p&gt;I'm looking for a simple, cheap device to detect low ac current. It will be used to detect irrigation valves. These valves operate @ 24 vac (60 hz) typically 100 - 200ma. I just need a go-no go signal, I'm not interested in the actual value. The device needs to be a &quot;clamp on&quot; type with no physical connections. I'm open to rolling my own, this is a one-off project.  Perhaps something with a hall sensor, clothes pin type of thing. Any ideas out there?&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-05-26T13:20:25.443" Title="Split core current transformer" Tags="&lt;pic&gt;&lt;sensor&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="14714" PostTypeId="2" ParentId="14708" CreationDate="2011-05-26T13:12:25.903" Score="3" ViewCount="" Body="&lt;p&gt;I'm not sure why you would want to do this - and presumably you have constraints such as  the cutoff frequency and LF gain, but with an LF gain of 1 you can obtain an arbitrarily large Q (theoretically) by making C1 much larger than C2 whilst maintaining the product C1C2 to preserve the cutoff frequency. There will of course be a practical limit to both capacitor values.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-05-26T13:12:25.903" />
  <row Id="14715" PostTypeId="2" ParentId="14713" CreationDate="2011-05-26T13:20:25.443" Score="1" ViewCount="" Body="&lt;p&gt;I have done this in the past using an old toroidal mains transformer. Just loop one of your valve leads once or twice round the transformer (not strictly &quot;clamp-on&quot; I know) and use the voltage induced in the primary. You should get sufficient voltage to rectify with a diode bridge and a capacitor/comparator will give you your output.&lt;/p&gt;&#xA;" OwnerUserId="2234" LastActivityDate="2011-05-26T13:20:25.443" CommentCount="3" />
  <row Id="14716" PostTypeId="2" ParentId="14710" CreationDate="2011-05-26T13:47:27.547" Score="1" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Watch Dog&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Like others have mentioned, the watchdog timer is able to catch &quot;odd&quot; errors that cause the program to go into an odd state. The microcontroller is reset and everything acts as if it had just been turned on again. For many applications this is the best solution. A consumer would be annoyed if their TV remote reset itself as they were trying to use it, but a watch dog timer would catch an odd even and reset it. I can assure you the consumer would be much more happier with a random reset then having to remove the batteries and putting back in before it recovers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is also situations where you might have no ability to reset the device, such as if it was in a sealed container or in some place that you just can't get to it. In these situations it would be much better to just reset instead of having to break into a container or what not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Safety Critical&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It sounds like you are looking for something that is more along the lines of safety critical in which you want a hardware failure to not cause something to go very wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are processors that are specifically designed for this. In general it is just able to alert you that an error has occurred, this alert can then be used to shut down your systems in a safe manner.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I saw a demo of a chip that did this, I think it was a TI ARM, maybe the &lt;a href=&quot;http://www.ti.com/ww/en/mcu/tms570/index.shtml&quot; rel=&quot;nofollow&quot;&gt;TMS570&lt;/a&gt;. But any ways, one method of protection is to have 2 parallel processing cores that are offset by half a clock cycle. The results of every operation can then be compared between the two cores. The offset makes it so that it is less likely that an external event would cause both of the cores to make the same exact error.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the comparison comes out true then you go on with life normally, if it were to be false then what you do would depend on your application. At least in this situation you will be made aware of an error and have full engineering control of how you want to recover from it.&lt;/p&gt;&#xA;" OwnerUserId="319" LastActivityDate="2011-05-26T13:47:27.547" CommentCount="1" />
  <row Id="14717" PostTypeId="2" ParentId="14699" CreationDate="2011-05-26T14:07:09.603" Score="4" ViewCount="" Body="&lt;p&gt;I suggest you read &lt;a href=&quot;http://focus.ti.com/lit/an/slup100/slup100.pdf&quot; rel=&quot;nofollow&quot;&gt;TI app note SLUP100&lt;/a&gt;, &quot;Snubber Design&quot; by Philip C. Todd for some good background on snubber design.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the triac is on, the dissipation through the snubbers will be low since they are 'shorted' by the triac.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the triac is off, load current is going to try and flow through both of your snubber circuits, and the resistors are going to see power dissipation.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Are you absolutely sure that the triac is firing each cycle?&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-26T14:07:09.603" CommentCount="1" />
  <row Id="14718" PostTypeId="2" ParentId="14695" CreationDate="2011-05-26T16:09:21.160" Score="2" ViewCount="" Body="&lt;p&gt;Neurofeedback doesn't push signals back into your brain - the feedback is you looking at the signal or hearing the noise that's created by reading the waves.  No signals return from the hardware direct to your brain so you're perfectly safe with something like OpenEEG - the electrodes are entirely passive (apart from signal amplification, but still no transmission into your head).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was semi-involved with electrodes for a fun project that wanted to measure electrical signals controlling muscles so they could turn a servo (bionic arm baby!).  I didn't do the procurement but one of the other people in the group said he got a good deal on disposable electrodes from the internet.  Most of the OpenEEG electrodes are not designed to be disposed, so their build quality is a bit better and (I think) doesn't require the yucky gel.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In general, the electrodes are thin silver plates with wires attached.  That's pretty much it - just have two so you can create a differential signal.  Be warned though: the primary problem we had was 60Hz interference from power lines.  The electrode cable made a decent enough antenna to pick up all of the interference around.  I suppose in India it will be 50Hz?  I'm not sure and too lazy to read Wikipedia at the moment, but it required some filtering because the signals we wanted were in the millivolt range.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good luck!&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-26T16:09:21.160" CommentCount="1" />
  <row Id="14719" PostTypeId="1" CreationDate="2011-05-26T16:24:02.043" Score="0" ViewCount="54" Body="&lt;p&gt;This appears to be a general classification of observers, but I can't find it in the index of my applicable texts:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0201361868&quot; rel=&quot;nofollow&quot;&gt;Mathematical Methods and Algorithims for Signal Processing (Moon and Stirling)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://rads.stackoverflow.com/amzn/click/0262570483&quot; rel=&quot;nofollow&quot;&gt;Applied Optimal Estimation (Gelb)&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If someone can provide a reference to classification of observer, that would be great.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, I'm not allowed to create and &quot;estimation&quot; tag, can someone with 300 reputation do that for me? Is there another applicable tag?&lt;/p&gt;&#xA;" OwnerUserId="4321" LastActivityDate="2011-05-26T17:18:51.647" Title="What is the definition of a complementary filter?" Tags="&lt;control&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="14720" PostTypeId="2" ParentId="14719" CreationDate="2011-05-26T17:18:51.647" Score="1" ViewCount="" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;A pair of filters are called complementary filters if their&#xA;  transfer functions sum to one at all frequencies in a complex&#xA;  sense, i.e. the phase is zero and the magnitude is&#xA;  one.  &lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.ligo.caltech.edu/docs/P/P040020-00.pdf&quot; rel=&quot;nofollow&quot;&gt;source&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-26T17:18:51.647" />
  <row Id="14721" PostTypeId="2" ParentId="8767" CreationDate="2011-05-26T18:05:22.790" Score="0" ViewCount="" Body="&lt;p&gt;I've been using multiple Mercurial (HG) repos (one per project) for this but as most Version Control Systems will experience, the repos are getting larger and larger.&lt;/p&gt;&#xA;" OwnerUserId="923" LastActivityDate="2011-05-26T18:05:22.790" />
  <row Id="14722" PostTypeId="1" CreationDate="2011-05-26T18:53:36.053" Score="0" ViewCount="31" Body="&lt;p&gt;I just got a brand new wd passport SE, took it home plugged it in, but nothing happened, or that is one thing happened, the LED on the disk lights up five times, then goes black for about two seconds and then blinks again. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've looked, and I'm not able to find the device in my USB list. I've even started the machine up in windows but no luck, does anyone have any ideas?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm testing on a pretty new macbook pro.&lt;/p&gt;&#xA;" OwnerUserId="4425" LastActivityDate="2011-05-26T18:53:36.053" ClosedDate="2011-05-26T19:31:21.557" Title="WD Passport Essential SE not able to connect to mac" Tags="&lt;usb&gt;&lt;mac&gt;" CommentCount="2" />
  <row Id="14723" PostTypeId="2" ParentId="14699" CreationDate="2011-05-26T19:36:56.063" Score="2" ViewCount="" Body="&lt;p&gt;The fact that your resistor blew a few seconds (versus milliseconds) after turn on, is a clue that you are exceeding wattage by at least a factor of 2, but probably less than a factor of 10.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The path through the triac should not affect the 680 Ohm R.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The path through the 0.1uF cap is not nearly high enough current to fry the 680 (assuming 60Hz power and a good cap).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the IC is sinking more than 19 mA through pin 6 at any time (I did not check the specs on this device) then you are exceeding the 1/4 W on your 680.  If the chip can sink much more 'I' than 19mA (like the 35 mA you mentioned... is that going through pin 6?), then I think we found your problem: Pick a resistor with a Power Rating (PR) and value (R) that satisfies PR &gt; Power=(I^2)R.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the triac triggers at 35ma through pin 6, then size R larger than (0.035^2)(680) = 0.833 Watts.  I'd select a 680 Ohm, 1W.&lt;/p&gt;&#xA;" OwnerUserId="4427" LastEditorUserId="4427" LastEditorDisplayName="" LastEditDate="2011-05-26T19:50:17.870" LastActivityDate="2011-05-26T19:50:17.870" />
  <row Id="14724" PostTypeId="1" AcceptedAnswerId="14726" CreationDate="2011-05-26T19:40:28.593" Score="2" ViewCount="35" Body="&lt;p&gt;I have a diode.  It has a forward current rating of 40 mA.  It has a surge current rating of 100 mA for t &amp;lt;= 10 usec.  There is no mention of a duty cycle in the datasheet.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a rule of thumb for determining what kind of off period I need in order to not kill the diode?  The naive assumption is that if I do 100 mA for 10 usec, and I need 40 mA forward current as an average, then I would need to use 10 usec on, 15 usec off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If that is the case, then my intuition would then suggest pushing 80 mA for 9 usec, and then double the off period to 30 usec minimum.  This would allow for overhead like temperature, lifespan, etc.&lt;/p&gt;&#xA;" OwnerUserId="1278" LastActivityDate="2011-05-26T20:23:05.643" Title="Diode IFSM to duty cycle extrapolation?" Tags="&lt;diode&gt;&lt;duty-cycle&gt;" AnswerCount="1" />
  <row Id="14725" PostTypeId="2" ParentId="14688" CreationDate="2011-05-26T20:13:36.500" Score="0" ViewCount="" Body="&lt;p&gt;The answer to your question is, &quot;No.&quot;  There are currently no auto-recovery methods, for hardware failures.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Manufacturers engineer their processes to get the best yield (dollars) possible from their wafers.  By shrinking the transistors, they can fit more functionality into less area.  This can be thought of as more chips (of the same functionality) per wafer.  As the chip size shrinks, you can get more of them out of a wafer, but as they shrink, more of them turn out bad.  Manufactures accept this, and are constantly pushing the envelope of technology to shrink chips.  The thing which tells them they ARE at the edge of the envelope is bad chips.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If a company can shrink feature size to 70% of the old feature size, they can get about 2 times the number of chips on a wafer.  If their yield on the old process was 95% (say, 95 good chips chips out of 100 on a wafer) and their yield on the new process is 75% (150 good chips out of 200 on a wafer) they made money going to the new process.&lt;/p&gt;&#xA;" OwnerUserId="4427" LastActivityDate="2011-05-26T20:13:36.500" CommentCount="1" />
  <row Id="14726" PostTypeId="2" ParentId="14724" CreationDate="2011-05-26T20:23:05.643" Score="3" ViewCount="" Body="&lt;p&gt;Your assumptions are basically correct.  100 mA for 10 uS, then off for 15 uS would provide for a 40 mA average and not exceed the specs. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's always good to &quot;derate&quot; your stuff.  A 1/4 watt resistor would normally not carry more than 1/8th watt in normal operation, and your 40 mA diode would carry maybe 20-30 mA on average.  There is no hard and fast rule to derating components, it's all a balance of cost, lifespan, availability of parts, PCB area, etc.  In the end, it is usually just a guess by the engineer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Resistors are often derated 50% on power, electrlytic caps are derated 30-50% on voltage, CPU's are almost never derated on clock frequency.  Diodes are derated in the neighborhood of 25-50% on power or voltage.  Of course, if this is a one-off project where failure isn't terrible then don't derate at all!  :)&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-26T20:23:05.643" CommentCount="3" />
  <row Id="14727" PostTypeId="2" ParentId="14656" CreationDate="2011-05-26T20:30:01.393" Score="2" ViewCount="" Body="&lt;p&gt;An LED is a Light Emitting Diode.  The key part of that name is &quot;Diode.&quot;  An LED is a diode.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Diodes do not limit forward current very well.  The extremely steep current/voltage curve (an exponential curve) is probably their second most important functional characteristic which results in sales of diodes.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;When you put a forward voltage on a diode (an LED, BE junction of a BJT, or whatever), it's current DOUBLES with each incremental 26mV of voltage.  So if you applied 0.7V (700mV) and got 50mA, then you should get about 100mA at 726mV, 200mA at 752mV, 400mA at 778mV, and so on.  So what would you expect at 20000mV?  The theoretical answer is about 7 times 10 to the 222nd power amps.  That is a '7' with about 222 zeros after it.  But your home's circuit breaker (thankfully) limits current draw to something less than Quadra-Bazillions of times the total of all power plants on planet Earth.  Your LED draws maybe 20 amps for a few microseconds, turning a very small volume inside it about as hot as the Sun, and then it is all over.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you do this with larger parts, the shrapnel can kill you.  An electrian, at a factory I worked at, had the misfortune of crossing two phases of industrial strength AC with his screwdriver.  As  far as could be figured out, he was not electricuted: the plastic screwdriver handle protected him from that.  However, the short instantly vaporized the metal in the screwdriver.  The resulting explosion killed him.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So provide external current limiting in line with your LED, or... wear safety goggles.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;EDIT:  I got carried away with the point I was trying to make and erroneously said current doubles with each 25 mV across the diode junction.  The actual factor is 'e', where 'e' = the base of the natural logarithm = about 2.7.  So the current would increase by a factor of 2.7, not 2, for each 25mV.  The damage to the device looks pretty much the same for large voltages, though....&lt;/p&gt;&#xA;" OwnerUserId="4427" LastEditorUserId="4427" LastEditorDisplayName="" LastEditDate="2011-06-03T19:10:26.150" LastActivityDate="2011-06-03T19:10:26.150" CommentCount="1" />
  <row Id="14728" PostTypeId="1" CreationDate="2011-05-26T21:13:44.493" Score="1" ViewCount="42" Body="&lt;p&gt;Do any companies offer devices to allow limited cellular internet connectivity for low bandwidth data transmission. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm imagining an embedded device that typically does not have (nor need) internet access but could access the internet via cellular networks to transmit error reports back to home base. Do any companies offer such systems without the need of a full blown data contract?&lt;/p&gt;&#xA;" OwnerUserId="2484" LastActivityDate="2011-05-26T21:19:32.070" Title="Adding Low Bandwidth 3G Internet Access to Embedded Device" Tags="&lt;electronics&gt;&lt;hardware&gt;&lt;embedded&gt;" AnswerCount="1" FavoriteCount="1" />
  <row Id="14729" PostTypeId="2" ParentId="14728" CreationDate="2011-05-26T21:19:32.070" Score="1" ViewCount="" Body="&lt;p&gt;If you don't need high data rates, then I think you want to look into GPRS, not 3G.  Google for &quot;free gprs&quot; and you should be able to come up with something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't played with one before, but Sparkfun has something that might work.  &lt;a href=&quot;http://www.sparkfun.com/products/9533&quot; rel=&quot;nofollow&quot;&gt;http://www.sparkfun.com/products/9533&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="2288" LastActivityDate="2011-05-26T21:19:32.070" CommentCount="3" />
  <row Id="14730" PostTypeId="1" CreationDate="2011-05-26T22:27:24.883" Score="0" ViewCount="90" Body="&lt;p&gt;What are some type of device that can cause electromagnetic interference ? I want to be able to make one myself with a low budget and as a small project. Thanks !&lt;/p&gt;&#xA;" OwnerUserId="4429" LastEditorUserId="1489" LastEditorDisplayName="" LastEditDate="2011-05-27T12:05:07.077" LastActivityDate="2011-05-27T12:05:07.077" ClosedDate="2011-05-27T12:05:16.453" Title="Electromagnetic interference devices" Tags="&lt;emi&gt;&lt;interference&gt;" AnswerCount="3" CommentCount="3" />
  <row Id="14731" PostTypeId="2" ParentId="14695" CreationDate="2011-05-26T22:53:43.650" Score="3" ViewCount="" Body="&lt;p&gt;It's not an EEG, but my experience building an EKG circuit from scratch might help you a bit. (Not sure if EEG is easier or harder). A few old OP27's configured as an &lt;a href=&quot;http://en.wikipedia.org/wiki/Instrumentation_amplifier&quot; rel=&quot;nofollow&quot;&gt;instrumentation amp (wikipedia)&lt;/a&gt; on a breadboard provided sufficient gain to get from sensors to an output comparator, which drove an LED. The power source was a 9V battery, both for safety and reduction of 60Hz noise input. The sensors were nothing more complicated than leads soldered onto two shiny new pennies. For contact gel, a mixture of alcohol hand-sanitizer with a little baking soda did the trick. Just the two sensors feeding the differential input of the instrumentation amp (and the usual fiddling with resistor values) was all it took to make the LED blink in sync with my actual heartbeat.  It was a quick, cheap, satisfying hack.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an EEG, you obviously want a more analog output than just the on/off from a comparator, so you'd want to run the amplifier output into an ADC. I'd say try running the signal into a PC sound-card input, but not sure that PC sound inputs have much response in the frequency range you want, which is probably in the 1Hz to 40Hz range. You'd probably also want more than a single pair of sensors. If you stick with a 9V battery for power, you will have a very hard time electrocuting yourself, and won't be able to drive any signals into your neural nets. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;btw, if you're really worried about signals going &lt;em&gt;into&lt;/em&gt; your brain, the only thing that does &lt;em&gt;that&lt;/em&gt; AFAIK is &quot;transcranial magnetic stimulation&quot;. You won't build that by accident.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-26T22:53:43.650" CommentCount="3" />
  <row Id="14732" PostTypeId="2" ParentId="14730" CreationDate="2011-05-26T23:42:49.943" Score="1" ViewCount="" Body="&lt;p&gt;Intentionally causing electromagnetic interefearance is illegal in most countries. A tesla coil or Van De Graf generator will unintentionally cause EMI. &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-26T23:42:49.943" CommentCount="6" />
  <row Id="14733" PostTypeId="2" ParentId="14705" CreationDate="2011-05-27T00:18:40.910" Score="4" ViewCount="" Body="&lt;p&gt;The following information is in addition to Igor's excellent answer.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From a C programming perspective, the interrupt handlers are defined in the cr_startup_xxx.c file (eg cr_startup_lpc13.c file for LPC1343).  All possible interrupt handlers are defined there as a WEAK alias.  If you do not define your own XXX_Handler() for an interrupt source, then the default interrupt handler function defined in this file will be used.  The linker will sort out which function to include in the final binary along with the interrupt vector table from cr_startup_xxx.c&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example of GPIO interrupts from ports are shown in the demo files in gpio.c.  There is one interrupt input to the NVIC per GPIO port.  Each individual bit in the port can be enabled/disabled to generate an interrupt on that port.  If you require interrupts on ports PIO1_4, and PIO1_5 for example, then you would enable the individual PIO1_4 and PIO1_5 interrupt bits in GPIO0IE.  When your PIOINT0_Handler() interrupt handler function fires, it's up to you to determine which of PIO1_4 or PIO1_5 (or both) interrupts are pending by reading the GPIO0RIS register and handling the interrupt appropriately.&lt;/p&gt;&#xA;" OwnerUserId="2308" LastActivityDate="2011-05-27T00:18:40.910" />
  <row Id="14734" PostTypeId="1" AcceptedAnswerId="14767" CreationDate="2011-05-27T00:26:15.773" Score="1" ViewCount="87" Body="&lt;p&gt;Hi, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have an Arduino + USB host shield. I would like to start developing with the Android Open Accessory Framework. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Can I connect my Arduino to the Android Emulator whilst developing? Or do I need to buy a compatible handset?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Cheers, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Marcus&lt;/p&gt;&#xA;" OwnerUserId="4430" LastActivityDate="2011-05-30T07:55:11.193" Title="Using the emulator with Android Open Accessory hardware" Tags="&lt;arduino&gt;&lt;android&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="14735" PostTypeId="2" ParentId="14730" CreationDate="2011-05-27T01:42:04.030" Score="0" ViewCount="" Body="&lt;p&gt;Can you be more specific with your problem statement?  What is the need for the interference?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Small appliance motors generate harmonics that can interfere with nearby devices, especially if they share a power source, and do not have good line filtering.&lt;/p&gt;&#xA;" OwnerUserId="4409" LastActivityDate="2011-05-27T01:42:04.030" CommentCount="1" />
  <row Id="14736" PostTypeId="1" CreationDate="2011-05-27T03:00:45.673" Score="4" ViewCount="102" Body="&lt;p&gt;I need to find a PID controller for a 12V 1hp DC motor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am currently building a tachometer for velocity feedback. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;My question is if anyone can suggest PID control hardware and software that is good for this type of motor? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I was thinking about using this driver from &lt;a href=&quot;http://www.pololu.com/catalog/product/1393&quot; rel=&quot;nofollow&quot;&gt;Pololu&lt;/a&gt; with an Arduino microcontroller but I am not sure if this is a robust enough solution. Also I dont believe that this can handle the current from the motor. Still doing calculations on that. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I will need to program a routine for the motor to run through. It will speed up, slow down, and change direction over time. Actually I will be using two motors but I figured it would be hard to find a dual motor PID controller. Any suggestion would be greatly appreciated. &lt;/p&gt;&#xA;" OwnerUserId="3267" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-27T10:33:14.150" LastActivityDate="2011-05-27T10:36:49.953" Title="Choosing a PID controller" Tags="&lt;dc-motor&gt;&lt;pid-controller&gt;&lt;control-system&gt;" AnswerCount="2" CommentCount="2" FavoriteCount="1" />
  <row Id="14737" PostTypeId="2" ParentId="14736" CreationDate="2011-05-27T03:17:05.747" Score="2" ViewCount="" Body="&lt;p&gt;Microchip dsPIC parts are among the cheapest parts capable of easily doing PID, and Microchip has a lot of application notes on the subject.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-27T03:17:05.747" CommentCount="2" />
  <row Id="14738" PostTypeId="1" CreationDate="2011-05-27T04:01:32.777" Score="0" ViewCount="56" Body="&lt;p&gt;I am currently looking for good online tutorials and reference code to understand SDIO bus interface, especially the i/o commands CMD52 &amp;amp; CMD53. I have gone through SDIO spec at sdcard.org, but its bit hard to follow. Any pointers would be helpful. &lt;/p&gt;&#xA;" OwnerUserId="4394" LastEditorUserId="206" LastEditorDisplayName="" LastEditDate="2011-05-27T15:19:04.217" LastActivityDate="2011-05-27T15:19:04.217" Title="What are good resources for learning SDIO bus interface?" Tags="&lt;bus&gt;&lt;tutorial&gt;&lt;sdio&gt;" CommentCount="5" />
  <row Id="14739" PostTypeId="2" ParentId="14736" CreationDate="2011-05-27T07:03:55.090" Score="2" ViewCount="" Body="&lt;p&gt;It sounds like you have some things there that makes it hard to find a ready device that can do the work (but I'm not sure).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It sounds like you have to either write a PID yourself, &#xA;or use a PID in some library (like the Arduino).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am unsure about the stability of the Arduino solutions, will this solution still be stable after a year? Or do you need to reboot it every day?&#xA;But maybe it is good enough? (Test it for a month a see what it can do)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you decide to write a PID yourself, the paper called PID-without-a-PhD is a good start: &lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.eetimes.com/design/embedded/4211211/PID-without-a-PhD&quot; rel=&quot;nofollow&quot;&gt;http://www.eetimes.com/design/embedded/4211211/PID-without-a-PhD&lt;/a&gt; or &lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.eetimes.com/ContentEETimes/Documents/Embedded.com/2000/f-wescot.pdf&quot; rel=&quot;nofollow&quot;&gt;http://www.eetimes.com/ContentEETimes/Documents/Embedded.com/2000/f-wescot.pdf&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;And you also have application notes on this topic from more or less every MCU maker out there. &lt;/p&gt;&#xA;" OwnerUserId="689" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-05-27T10:36:49.953" LastActivityDate="2011-05-27T10:36:49.953" />
  <row Id="14740" PostTypeId="2" ParentId="14730" CreationDate="2011-05-27T08:04:11.960" Score="0" ViewCount="" Body="&lt;p&gt;You could use commercial EMC test equipment, such as &lt;a href=&quot;http://www.teseq.com/com/en/products_solutions/emc_conducted_esd/burst_generators.php&quot; rel=&quot;nofollow&quot;&gt;Teseq Burst Noise generator&lt;/a&gt; if you have the budget, and RF amplifiers with sources if have even more budget, but they need to be used under controlled lab conditions. If you make your own device, it is unlikely to be repeatable or calibrateable.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;As others have said, it is illegal to place on the market (ie to sell) a device which intentionally or unintentionally radiates noise in specific bands and above specific power levels in most countries (with many caveats and provisos). In the EU it is also illegal to use contravening equipment. Even if you don't sell it, you could be in trouble for using it yourself, with the broadcasting authorities or regulators.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;With radiated RF testing, bear in mind that it is usually the modulation of the RF that causes the problem rather than the continuous carrier. For more information on EMC testing, see the &lt;a href=&quot;http://www.compliance-club.com/default.aspx?id=1&quot; rel=&quot;nofollow&quot;&gt;compliance-club website&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-05-27T08:04:11.960" />
  <row Id="14741" PostTypeId="1" AcceptedAnswerId="14742" CreationDate="2011-05-27T13:27:17.553" Score="2" ViewCount="97" Body="&lt;p&gt;I'm having trouble in explaining kirchoff's laws to my cousin who is studying in first year Engineering. &#xA;Can somebody explain me in simple plain english.&#xA;Thank you very much in advance :)&lt;/p&gt;&#xA;" OwnerUserId="4435" LastActivityDate="2011-05-27T14:05:55.840" Title="Explain kirchoff's law in Plain English" Tags="&lt;circuit&gt;&lt;kirchhoffs-laws&gt;" AnswerCount="1" />
  <row Id="14742" PostTypeId="2" ParentId="14741" CreationDate="2011-05-27T13:44:38.657" Score="8" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;Kirchhoff's current law&lt;/strong&gt;: the sum of the currents in a node is zero. Say you have 4 wires coming together in a node, and the first three supply currents I1, I2 and I3 to the node. This current has to go somewhere, and will go from the node by the fourth wire; I4 = -(I1 + I2 + I3), such that the I1 + I2 + I3 + I4 = 0.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Kirchhoff's voltage law&lt;/strong&gt;: the sum of the voltages in a closed circuit is zero. If you have a circuit consisting of a battery and a resistor as a load then the voltage over the resistor is -Vbat (the minus sign means that if you go clockwise through your circuit you go from - to + for the battery, but from + to - for the resistor). Total voltage: +Vbat - Vbat = 0.&lt;br&gt;&#xA;This goes for every closed loop path you can find in a design, no matter how complicated and how many branches there are.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-27T14:05:55.840" LastActivityDate="2011-05-27T14:05:55.840" CommentCount="2" />
  <row Id="14743" PostTypeId="1" CreationDate="2011-05-27T14:14:02.740" Score="8" ViewCount="107" Body="&lt;p&gt;Obviously the panel needs fiducials, and I also place three of them on each PCB. Some IC footprints however also show local fiducials. I've seen them for instance for certain TQFP footprints. When are they required?  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/yK1vx.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-27T14:34:14.960" LastActivityDate="2011-05-27T16:13:35.043" Title="When do I use fiducials for individual components on a PCB?" Tags="&lt;pcb&gt;&lt;fiducials&gt;" AnswerCount="2" CommentCount="3" FavoriteCount="1" />
  <row Id="14744" PostTypeId="2" ParentId="14743" CreationDate="2011-05-27T14:18:45.200" Score="0" ViewCount="" Body="&lt;p&gt;They are most often used with BGA devices, because the pads can't be seen when the chip is placed in position manually. Most assembly companies insist on them. I don't think I've seen them used with TQFP parts.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-27T16:13:35.043" LastActivityDate="2011-05-27T16:13:35.043" CommentCount="6" />
  <row Id="14745" PostTypeId="2" ParentId="14743" CreationDate="2011-05-27T14:49:07.250" Score="10" ViewCount="" Body="&lt;p&gt;Fiducials are used by the pick and place machine to provide better accuracy when placing components on the PCB.  There is a camera that recognizes the fiducials and uses it as a registration point to calibrate where the machine thinks it is on the PCB.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are two types of fiducials:  Global and Local.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally a PCB will have 3 global fiducials per side (top &amp;amp; bottom), and usually in the corners of the PCB.  This is so it can recognize the boards overall orientation and position.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Local fiducials are located near some of the critical parts.  Usually there are two fiducials for each part, in opposite corners.  IF you have several critical parts that are close together then a fiducial can be shared by two or more parts-- reducing the number of fiducials required and the the PCB space taken up by them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Where you need local fiducials really depends on the pick and place machine that will be used, and the placement accuracy required by the component.  Chips with a finer pin pitch will need fiducials more.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's interesting to note that TQFP's need fiducials more than most BGA's.  Most TQFP's have a pin pitch of around 0.5mm, while most BGA's are 0.8 to 1.27mm.  BGA's also have a cool ability to somewhat self-align due to the surface tension of the melted solder.  But I need to stress that this is very component and machine dependent, so check with your assembly shop.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also machine dependent is going to be the construction of the fiducial.  Things like how big the pad is, and how much the soldermask is pulled back.  Usually the fiducial is round, but sometimes square or bow-tie shaped.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing is that some assembly shops will request fiducials to just feel good about things-- but don't really need them.  My second to last PCB had had lots of fine pitch BGA's, QFN's, and TQFP's and had no fiducials on it, but there were no issues with parts placement.  My current board is nowhere near as difficult but they are requesting fiducials.  Go figure.  I'll humor them and put the fiducials on it.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-27T14:49:07.250" CommentCount="2" />
  <row Id="14746" PostTypeId="2" ParentId="14491" CreationDate="2011-05-27T15:03:04.527" Score="0" ViewCount="" Body="&lt;p&gt;I assume the ball is somewhat lightweight (like a beachball), so sensing pressure is not an option. In this case, I'd recommend to place ultrasonic transducers at the corners of the table. When the ball is on, it will reflect some of the sound waves back to the transducer. Take a look at:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://en.wikipedia.org/wiki/Ultrasonic_sensor&quot; rel=&quot;nofollow&quot;&gt;http://en.wikipedia.org/wiki/Ultrasonic_sensor&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.parallax.com/tabid/768/ProductID/92/Default.aspx&quot; rel=&quot;nofollow&quot;&gt;http://www.parallax.com/tabid/768/ProductID/92/Default.aspx&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="1078" LastActivityDate="2011-05-27T15:03:04.527" CommentCount="1" />
  <row Id="14747" PostTypeId="2" ParentId="12217" CreationDate="2011-05-27T15:57:10.407" Score="0" ViewCount="" Body="&lt;p&gt;&lt;a href=&quot;http://www.eetimes.com/design/programmable-logic/4216281/How-to-make-a-Geiger-counter-count?cid=NL_Embedded&amp;amp;Ecosystem=embedded&quot; rel=&quot;nofollow&quot;&gt;A recent write up of a repair of a geiger counter&lt;/a&gt; could be useful to your design process, if not for component selection.&lt;/p&gt;&#xA;" OwnerUserId="2110" LastActivityDate="2011-05-27T15:57:10.407" />
  <row Id="14748" PostTypeId="1" AcceptedAnswerId="14752" CreationDate="2011-05-27T16:50:08.053" Score="4" ViewCount="221" Body="&lt;p&gt;I've been creating a &lt;a href=&quot;http://10rem.net/blog/2011/05/25/building-a-midi-thru-box-part-1&quot; rel=&quot;nofollow&quot;&gt;MIDI Thru box project&lt;/a&gt; and was trying to avoid having so many resistors. Points A-G may (or may not) have a load connected to them. Are these equivalent, or do I really need to include a resistor on each branch?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's the circuit image&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/UdGQO.png&quot; alt=&quot;http://a.yfrog.com/img611/175/4rfk.png&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is the current/resistance/voltage equivalent from the DC supply to each lettered branch in each circuit? More importantly, can anyone explain (or provide a link that explains) how you came to the conclusion? I'm a developer just starting to learn electronics.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've gotten mixed responses on twitter, and someone mentioned asking here.&lt;/p&gt;&#xA;" OwnerUserId="4438" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-27T22:55:27.757" LastActivityDate="2011-05-27T22:55:27.757" Title="Are these MIDI circuits equivalent?" Tags="&lt;resistor&gt;&lt;voltage&gt;&lt;current-measurement&gt;&lt;midi&gt;" AnswerCount="5" CommentCount="3" FavoriteCount="2" />
  <row Id="14749" PostTypeId="2" ParentId="14748" CreationDate="2011-05-27T16:55:18.653" Score="3" ViewCount="" Body="&lt;p&gt;They are not equivalent.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Imagine placing a 1K resistor on point A to ground.  Also place a 10K resistor on point B to ground.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In Circuit A, a 220 resistor is in series with the 1K.  There is a separate 220 resistor in series with the 10K.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In Circuit B, the 1K and 10K would be in parallel.&lt;/p&gt;&#xA;" OwnerUserId="204" LastActivityDate="2011-05-27T16:55:18.653" CommentCount="6" />
  <row Id="14750" PostTypeId="1" CreationDate="2011-05-27T16:55:56.757" Score="-2" ViewCount="65" Body="&lt;p&gt;I'm having issues with the usb despite the gnd pin of the usb port is directly wired to my gnd pin of my 7805CV regulator. When I wire up my board to my programmer it works fine. I'm sure because i've tested it with my meter. &lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-05-27T16:55:56.757" Title="Usb gnd pin - where exactly shud it be connected" Tags="&lt;usb&gt;" CommentCount="6" FavoriteCount="1" />
  <row Id="14751" PostTypeId="2" ParentId="14748" CreationDate="2011-05-27T17:03:23.667" Score="4" ViewCount="" Body="&lt;p&gt;Suppose points A through G in circuit A are connected to ground. Then there's a current 5 V / 220 Ohm = 23 mA through every resistor for a total of 7 * 23 mA = 159 mA. In circuit B there's only one 23 mA current. They're not equivalent.&lt;br&gt;&#xA;Also, in circuit A the resistance between any two of the inputs is 440 Ohm, in circuit B this is 0 Ohm.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-27T17:03:23.667" />
  <row Id="14752" PostTypeId="2" ParentId="14748" CreationDate="2011-05-27T17:53:28.643" Score="2" ViewCount="" Body="&lt;p&gt;Pete, I don't know much about MIDI circuitry, but it appears that the outputs are simple open collector circuits with pull up resistors and inputs are opto-isolators. If that's not reasonably accurate, then somebody please correct me.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Given that understanding and assuming that the power supply you're using is adequately large so we can assume it'd capable of providing as much current as you want, then you could think of the two circuit options like this:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Circuit A is treating each of the inputs A-G independently and what's happening on input A isn't affecting what's happening on input B.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Circuit B is shorting all of the inputs A-G together and just happening to supply a bit of extra current to the mix. Anything happening on Input A is totally messing with what's happening on Input B. If Input A is trying to be +5 v and Input B is trying to be 0v, then you've got the outputs of two other boxes fighting each other and neither is working correctly any more.&lt;/p&gt;&#xA;" OwnerUserId="4441" LastActivityDate="2011-05-27T17:53:28.643" CommentCount="11" />
  <row Id="14753" PostTypeId="2" ParentId="14748" CreationDate="2011-05-27T18:04:41.887" Score="2" ViewCount="" Body="&lt;p&gt;This is like a fan-out circuit to drive multiple MIDI inputs?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I understand MIDI correctly, each of these outputs feeds directly into an LED, not a resistive load, &lt;a href=&quot;http://dernulleffekt.wolfgang-spahn.de/midi.html&quot; rel=&quot;nofollow&quot;&gt;like this&lt;/a&gt;:  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/CstFj.jpg&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the LEDs have a drop of 2 V, then circuit A would be applying (5 V - 2 V)/220 Ω into each LED = 14 mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Circuit B, on the other hand, puts all the LEDs in parallel, so they each get 1/7th of that current = 2 mA.  This could prevent them from lighting enough to register as signals.  Also, any variation in the voltage of the LEDs (if &lt;a href=&quot;http://www.oksolar.com/led/led_color_chart.htm&quot; rel=&quot;nofollow&quot;&gt;one optocoupler uses an IR LED and the others use green LEDs&lt;/a&gt;, for instance) would allow the lowest voltage LED to hog all the current and prevent the others from lighting at all.&lt;/p&gt;&#xA;" OwnerUserId="142" LastActivityDate="2011-05-27T18:04:41.887" CommentCount="2" />
  <row Id="14754" PostTypeId="2" ParentId="14748" CreationDate="2011-05-27T18:17:40.177" Score="0" ViewCount="" Body="&lt;p&gt;Yes. They could be equivalent. No, they aren't equivalent. It depends. &amp;lt;g&amp;gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(to clarify, they circuits aren't really equivalent - my response above is mostly in response to the implied question of, &quot;can I replace this part of a more complex circuit and get equivalent results)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I think a more interesting question is, in your particular circuit, would replacing the 5 resistors hanging off the 5v line with one resistor cause any problems? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;(it's been a really long time since I've done any kind of circuit analysis - and only in school - so I might have missed something below)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you look at the standard MIDI circuit (I used &lt;a href=&quot;http://www.midi.org/techspecs/electrispec.php&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; as an example) and compare it against your circuit diagram, you can see why it's designed the way it is. It appears as though the resistor is there to limit current. The MIDI output circuit has (2) 220 resistors while the input has just 1. When pin 5 of the output goes low current can flow across the opto-isolator from the +5 line on pin 4 (and passes through (3) 220 ohm resistors in series Ra, Rb, Rc in the diagram). If you short any of the lines the various resistors will keep too much current from flowing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you take a look at the datasheet for the inverter or the opto-isolator even if you removed the 220 ohm resistor on the +5v side of things you still be within tolerance of the parts (not flow too much current) (but don't do that - a short could cook parts in that case). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it looks like you could use just 1 resistor in your particular circuit so far. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What about power? How much power will this resistor need to handle? &lt;/p&gt;&#xA;&#xA;&lt;p&gt;In the original circuit you've got 5 resistors so if you replace them with a single one this resistor will need to handle 5X the amount of power. Does it matter? Power is P = I * V, and V = 5. To calculate &quot;I&quot;, first calculate the total circuit resistance, 220 (5v side) + 220 (pin 5 of the output) + 220 on the input side, so 5 / 660 (I'm going to ignore the 1.2/1.4 voltage drop of the opto; let's assume it shorted) = 7.5mA. P = 5 * 7.5mA = 37mW. 5 circuits * 37mW = 189mW. So it's less than a 1/4 of a watt even with all of them active (although that's not providing a ton of headroom, I'd probably use a 1/2 watt to be safe).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it looks like you could replace it with a single resistor. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;One other consideration - what happens if that 1 resistor fails? If it fails as an open circuit, all 5 ports would stop working. In the original circuit only a single port would be dead. If it shorted, the other resistors in the circuit would probably keep anything from cooking (so you're still safe there), although if you have multiple shorts (between equipment) you'd still cook things, as mentioned above.&lt;/p&gt;&#xA;" OwnerUserId="4440" LastEditorUserId="4440" LastEditorDisplayName="" LastEditDate="2011-05-27T19:14:37.713" LastActivityDate="2011-05-27T19:14:37.713" CommentCount="2" />
  <row Id="14755" PostTypeId="1" CreationDate="2011-05-27T18:18:16.367" Score="0" ViewCount="56" Body="&lt;p&gt;I have some confusion on how to power a 1 hp &lt;a href=&quot;http://www.superwinch.com/products/productdetail/part_number=1220210/4377.0.1.1&quot; rel=&quot;nofollow&quot;&gt;DC winch motor&lt;/a&gt; that is intended to run off a 12 V battery. I need to precisely control the velocity of the motor and will need a PID controller to do this. Since speed of the motor is proportional to the supply voltage, is 12 V the maximum voltage and corresponding speed that the motor can reach? Can I apply a voltage greater than 12 V to it? I need to find a motor driver/controller that can handle the current draw. Does anyone know of a controller that can run this motor. Ideally it would have PID  built in but it is not necessary. I believe my questions are from a lack of understanding of how voltage and current are related. Also the winch will not be spinning very fast(no more than a line speed of .5 feet per second). I am currently building a tachometer for the feedback control. Any help/suggestion is greatly appreciated. &lt;/p&gt;&#xA;" OwnerUserId="3267" LastActivityDate="2011-05-27T18:43:18.650" Title="Powering a dc motor." Tags="&lt;voltage&gt;&lt;dc-motor&gt;" AnswerCount="1" CommentCount="3" />
  <row Id="14756" PostTypeId="2" ParentId="14755" CreationDate="2011-05-27T18:43:18.650" Score="0" ViewCount="" Body="&lt;p&gt;Motor velocity control of motors is usually done through Pulse Width Modulation where the voltage remains constant but is switched off/on many times per second.  The more time it spends &quot;off&quot; the slower it goes.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A low-power PWM generator can be fed through something like one or more MOSFETs to switch the main load.  The &quot;duty cycle&quot;, or percentage of time the PWM generator spends in the &quot;on&quot; position, can be from any source you like - an analogue input (potentiometer), a PIC microcontroller or such (which often have a PWM controller built in), or whatever you like.&lt;/p&gt;&#xA;" OwnerUserId="4245" LastActivityDate="2011-05-27T18:43:18.650" />
  <row Id="14757" PostTypeId="1" AcceptedAnswerId="14764" CreationDate="2011-05-27T18:49:09.700" Score="1" ViewCount="80" Body="&lt;p&gt;Hello &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have 10 of these boards &lt;a href=&quot;http://macetech.com/store/index.php?main_page=product_info&amp;amp;products_id=12&quot; rel=&quot;nofollow&quot;&gt;OctoBright CYANEA v2.0&lt;/a&gt; connected in series, controlled by an Arduino. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Powering one or two off of the Arduino 5v pin has worked for testing. Now I want to scale it up to 10x boards. I been told that a computer power supply should be able to handle the load from all 10 of these boards in series. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Each board at max brightness consumes 500mA. 10 * 500mA = 5 Amps max&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My questions are;&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Do I need to add any power conditioning to the output of the computers power supply?&lt;/li&gt;&#xA;&lt;li&gt;Can I directly connect the 5v rails from the computer's power supply to these boards? &lt;/li&gt;&#xA;&lt;li&gt;Anything I should know before I wire this up?&lt;/li&gt;&#xA;&lt;li&gt;Can I power the Arduino from the same 5v rail of the computers power supply?&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3407" LastActivityDate="2011-05-27T20:52:29.750" Title="Powering LEDs with a computer's power supply" Tags="&lt;arduino&gt;&lt;led&gt;&lt;power&gt;" AnswerCount="2" CommentCount="2" />
  <row Id="14758" PostTypeId="2" ParentId="14757" CreationDate="2011-05-27T19:09:16.417" Score="3" ViewCount="" Body="&lt;p&gt;As you stated you have a total of 5Amps.  At 5 Volts thats 25 Watts which is a no-brainer for a typical computer power supply.  Be aware that even though a CPU power supply may have a given rating, say 200W, that doesn't mean you can load the entire 200 W onto a single voltage rail.  Having said that, you won't a problem with 25W on a single 5V rail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Regarding the use of the same 5v rail to supply for the Arduino, there won't be any problem with that either.  After all, the power supply is designed for the purpose of powering electronics.&lt;/p&gt;&#xA;" OwnerUserId="4437" LastActivityDate="2011-05-27T19:09:16.417" />
  <row Id="14759" PostTypeId="1" AcceptedAnswerId="14763" CreationDate="2011-05-27T20:09:43.360" Score="0" ViewCount="84" Body="&lt;p&gt;I have comfortably got to grips with the pic16's now, so I am moving on up to the pic18 series.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;However, I cannot get any joy from them.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have a pic18f4455 and a pic18f14k50 - neither of which I can get to work.  I really want to get the 4455 to go.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have the usual xtal+2cap oscillator circuit, which is oscillating happily.  I have the usual blinking-led program flashed into it.  But it's just not running the program.  My theory is that the overly-complex CONFIG registers aren't set right.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using sdcc on Ubuntu, and I have my config set up like this:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;__code char __at __CONFIG1L c1l = _USBPLL_CLOCK_SRC_FROM_96MHZ_PLL_2_1L &amp;amp; _CPUDIV__OSC1_OSC2_SRC___1__96MHZ_PLL_SRC___2__1L &amp;amp; _PLLDIV_NO_DIVIDE__4MHZ_INPUT__1L;&#xA;__code char __at __CONFIG1H c1h = _OSC_HS__HS_PLL__USB_HS_1H &amp;amp; _FCMEN_OFF_1H &amp;amp; _IESO_OFF_1H;&#xA;__code char __at __CONFIG2L c2l = _VREGEN_OFF_2L &amp;amp; _PUT_OFF_2L &amp;amp; _BODEN_OFF_2L;&#xA;__code char __at __CONFIG2H c2h = _WDT_DISABLED_CONTROLLED_2H;&#xA;__code char __at __CONFIG3H c3h = _PBADEN_PORTB_4_0__CONFIGURED_AS_DIGITAL_I_O_ON_RESET_3H &amp;amp; _LPT1OSC_OFF_3H &amp;amp; _MCLRE_MCLR_ON_RE3_OFF_3H;&#xA;__code char __at __CONFIG4L c4l = _LVP_OFF_4L &amp;amp; _ENHCPU_OFF_4L;                    // Disable LVP&#xA;__code char __at __CONFIG5L c5l = _CP_0_OFF_5L &amp;amp; _CP_1_OFF_5L &amp;amp; _CP_2_OFF_5L &amp;amp; _CP_3_OFF_5L;&#xA;__code char __at __CONFIG5H c5h = _CPD_OFF_5H &amp;amp; _CPB_OFF_5H;&#xA;__code char __at __CONFIG6L c6l = _WRT_0_OFF_6L &amp;amp; _WRT_1_OFF_6L &amp;amp; _WRT_2_OFF_6L &amp;amp; _WRT_3_OFF_6L;&#xA;__code char __at __CONFIG6H c6h = _WRTD_OFF_6H &amp;amp; _WRTB_OFF_6H &amp;amp; _WRTC_OFF_6H;&#xA;__code char __at __CONFIG7L c7l = _EBTR_0_OFF_7L &amp;amp; _EBTR_1_OFF_7L &amp;amp; _EBTR_2_OFF_7L &amp;amp; _EBTR_3_OFF_7L;&#xA;__code char __at __CONFIG7H c7h = _EBTRB_OFF_7H;&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;I know some of those aren't needed, but I have tried with nothing, just the needed ones, and with everything.  Nothing seems to work.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know what the best way of setting the config registers on this chip is in sdcc - g00gle doesn't seem to have much of a clue unless you're using MPLAB.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, any clues?  Anything I just haven't been able to see because it's so blindingly obvious?&lt;/p&gt;&#xA;" OwnerUserId="4245" LastActivityDate="2011-05-27T20:53:59.630" Title="Can't get pic18 running" Tags="&lt;pic&gt;" AnswerCount="1" />
  <row Id="14760" PostTypeId="1" AcceptedAnswerId="14762" CreationDate="2011-05-27T20:13:30.863" Score="1" ViewCount="79" Body="&lt;p&gt;I've got an old car radio that I've mounted in my backyard, with some speakers. Right now it's running off an old battery I have, with a solar panel that trickle charges it during the day. I want to know, how many watts/volts it's using and what the solar panel is producing. The goal, would be to add another panel, so it can supplement the power more.. because I'm thinking about expanding it. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've got a basic volt meter. If I have to buy something I will. I'm more cirious to learn about it then the &lt;/p&gt;&#xA;" OwnerUserId="4444" LastActivityDate="2011-05-27T20:52:47.537" Title="How to calculate DC power consumption of a device" Tags="&lt;radio&gt;&lt;solar-cell&gt;&lt;voltage-measurement&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="14761" PostTypeId="2" ParentId="8767" CreationDate="2011-05-27T20:16:37.153" Score="1" ViewCount="" Body="&lt;p&gt;I was at the Maker Faire in San Mateo this past weekend and met some reps from a new (to me) company called &lt;a href=&quot;http://upverter.com/&quot; rel=&quot;nofollow&quot;&gt;Up-Verter&lt;/a&gt;. They are basically building an electrical CAD tool that runs in &quot;the cloud&quot; (i.e. in your browser) and is conceptually built around collaboration, so should deal with merge/diff and the usual versioning stuff.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I haven't tried it yet, and it looks a little bit green still (don't think you can actually do pcb layout yet, just schematics), but it's kind of intriguing. They claimed they could import Eagle files, which is a plus.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I also talked to the Eagle reps at the Element 14 tent, and they indicated that they are moving to an XML format, which is kind of a big step toward making versioning of schematics and layout more plausible... all interesting advancements on this front!&lt;/p&gt;&#xA;" OwnerUserId="771" LastActivityDate="2011-05-27T20:16:37.153" />
  <row Id="14762" PostTypeId="2" ParentId="14760" CreationDate="2011-05-27T20:18:48.037" Score="3" ViewCount="" Body="&lt;p&gt;Watts = Volts x Amps&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, if you measure the amps flowing through the circuit, then multiply it by the voltage across the circuit, you will have the number of watts the system is using.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Switch your volt meter to a suitable voltage range and measure the voltage across the battery (should be somewhere around 12V).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Switch your volt meter to measure amps (if it can - if not get one that will) and connect it in between the battery and the stereo:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;  ----(meter)--------&#xA;  |                 |&#xA;  +                 |&#xA;Battery           Stereo&#xA;  -                 |&#xA;  |                 |&#xA;  -------------------&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;Multiply the two readings, and voila!&lt;/p&gt;&#xA;" OwnerUserId="4245" LastActivityDate="2011-05-27T20:18:48.037" CommentCount="5" />
  <row Id="14763" PostTypeId="2" ParentId="14759" CreationDate="2011-05-27T20:40:15.957" Score="0" ViewCount="" Body="&lt;p&gt;Remove all that config stuff, and just turn off the WDT. It should run off the 8 MHz internal oscillator, and flash your LED. I can do that with the similar PIC18F2455. If that doesn't work you might have a hardware problem.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You will find things much easier if you use MPLAB and the C18 compiler. If you don't want to use Windows you might be able to use the new MPLAB-X, there is a Linux version.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-27T20:53:59.630" LastActivityDate="2011-05-27T20:53:59.630" CommentCount="13" />
  <row Id="14764" PostTypeId="2" ParentId="14757" CreationDate="2011-05-27T20:43:23.670" Score="1" ViewCount="" Body="&lt;p&gt;The computer power supply is very likely to have a 3.3 Volt output, and you should use that for the LED power. Even the smallest ATX type power supply should have no problem delivering 5A on the 3.3 Volt rail (But check the specs).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you have to use a 5 Volt rail, the problem won't be your power supply, it will be the LED current sinks. The forward voltage drop of the LEDs will be between about 2.1 and 3.3 Volts depending on the color. If you apply 5 Volts, the 'extra' 1.7 to 2.9 volts are going to have to be lost as heat in the controller current sinks. The controller has 24 of these sinks and it is going to become very hot very soon.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you can't dissipate enough heat from the controllers, a simple fix could be to use one or more linear regulators to drop the voltage from 5 to 3.3 Volt or so. It might be easier to dissipate heat from the voltage regulators than from the controller chips.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastEditorUserId="3876" LastEditorDisplayName="" LastEditDate="2011-05-27T20:52:29.750" LastActivityDate="2011-05-27T20:52:29.750" />
  <row Id="14765" PostTypeId="2" ParentId="14391" CreationDate="2011-05-27T20:46:52.547" Score="0" ViewCount="" Body="&lt;p&gt;&lt;strong&gt;your earpiece wire is maybe broken from inside!&#xA;u can go to any nokia care for the help.u cannot repair it urself.&#xA;or u should check it.u can normally press its working pad and it will lose auto&#xA;u will open it easily and then only u ill check what is the xact proble.if its wire is broken from inside u can replace it.if urs hp is in warenty....&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;hr&gt;&#xA;" OwnerUserId="4445" LastActivityDate="2011-05-27T20:46:52.547" />
  <row Id="14766" PostTypeId="2" ParentId="14760" CreationDate="2011-05-27T20:52:47.537" Score="2" ViewCount="" Body="&lt;p&gt;The previous answer was great for measuring the radio power.  This is one reason why it is handy to own two meters.  You can hook one up for current and then the other across the load for voltage.  Now you can get power without changing the setup.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Connect the meter in amps mode in line with the solar cell charging the battery to get an idea of the charging current in full sunlight.  At the battery voltage, this is also the power that the solar cell is providing.  You will have some charging losses, so all of this power will not be available for using the radio.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You should also include a diode in line with the solar cell.  It needs to be rated at the current of the maximum number of solar cells you expect to hook up in parallel.  The reason for this diode is that a solar cell is a poor diode.  I will discharge the battery during dark times when it is not producing any voltage.  The diode prevents this at a cost of power during the charging (0.6V * Charging Current).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are manually attaching the solar panel on in the daylight, this diode is not needed.&lt;/p&gt;&#xA;" OwnerUserId="4342" LastActivityDate="2011-05-27T20:52:47.537" />
  <row Id="14767" PostTypeId="2" ParentId="14734" CreationDate="2011-05-28T00:45:17.807" Score="1" ViewCount="" Body="&lt;p&gt;The &lt;a href=&quot;http://developer.android.com/guide/developing/devices/emulator.html#limitations&quot; rel=&quot;nofollow&quot;&gt;emulator guide&lt;/a&gt; states:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;In this release [3.1, accessed 5/27/11], the limitations of the emulator include:  &lt;/p&gt;&#xA;  &#xA;  &lt;ul&gt;&#xA;  &lt;li&gt;No support for placing or receiving actual phone calls. You can simulate phone calls (placed and received) through the emulator console, however.  &lt;/li&gt;&#xA;  &lt;li&gt;&lt;strong&gt;No support for USB connections&lt;/strong&gt; [emphasis added]&lt;/li&gt;&#xA;  &lt;li&gt;No support for camera/video capture (input)   &lt;/li&gt;&#xA;  &lt;li&gt;No support for device-attached headphones  &lt;/li&gt;&#xA;  &lt;li&gt;No support for determining connected state  &lt;/li&gt;&#xA;  &lt;li&gt;No support for determining battery charge level and AC charging state  &lt;/li&gt;&#xA;  &lt;li&gt;No support for determining SD card insert/eject  &lt;/li&gt;&#xA;  &lt;li&gt;No support for Bluetooth  &lt;/li&gt;&#xA;  &lt;/ul&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;While the &quot;In this release&quot; clause might bring you some hope, I'm not sure that USB support for the ADK is likely in the near future.  USB host might happen, but I've not found any PCs that have the USB device port (micro USB) that you'd need to connect the ADK in a useful way.  The ADK doesn't use the Arduino's UBS type B device port, it uses a female USB A host.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, USB OTG would be perfect for this, but, as &lt;a href=&quot;http://www.youtube.com/watch?v=s7szcpXf2rE#t=2044s&quot; rel=&quot;nofollow&quot;&gt;the release video says at 34 minutes in&lt;/a&gt;, Android handsets all support USB device mode, while few to none support USB OTG.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, it seems the answer is &quot;No.&quot;  I'd love to see something to the contrary.  If you just want to get into development, but don't want to give up your current phone/plan, I'd suggest buying the cheapest Android tablet or unactivated cell phone (that can run a recent enough version of the OS) that you can find.  The emulator is fantastic for doing GUI tests for your apps, but you really need an Android device if you're serious about development.&lt;/p&gt;&#xA;" OwnerUserId="857" LastActivityDate="2011-05-28T00:45:17.807" CommentCount="2" />
  <row Id="14769" PostTypeId="1" CreationDate="2011-05-28T06:26:16.787" Score="1" ViewCount="41" Body="&lt;p&gt;I need a clean install of an iPod charger in my car. That means not a wire running from a 12 volt socket. I've looked at the Belkin flush chargers and they are beautiful, but require a socket.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm considering wiring one to a panel mount USB adaptor using a &lt;a href=&quot;http://www.dimensionengineering.com/DE-SW050.htm&quot; rel=&quot;nofollow&quot;&gt;DE-SW050 voltage regulator&lt;/a&gt;. It'll take up to 30 volts (so 12 is trivial) and outputs 5 volts at 1amp max (iPad compatible). The wiring seems trivial: An in, and out, and a common ground. With a &lt;a href=&quot;http://www.dimensionengineering.com/VregBreakout.htm&quot; rel=&quot;nofollow&quot;&gt;breakout board&lt;/a&gt; and the Cables to Go panel mount, (and a fuse in line with the 12 volts) this seems like a trivial solution.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is it viable and device-safe? It seems like such a clean design that there must be a catch.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other question I had was if it was possible to then add an LED to indicate that the 5 volts was being used. (Putting it in-line perhaps? But what about voltage drop?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Help would be much appreciated.&lt;/p&gt;&#xA;" OwnerUserId="4450" LastEditorUserId="4451" LastEditorDisplayName="" LastEditDate="2011-05-28T06:39:25.830" LastActivityDate="2011-05-28T07:22:30.007" Title="Using a DE-SW050 5volt regulator and a USB breakout board to charge an iPod in a car." Tags="&lt;voltage-regulator&gt;&lt;ipod&gt;" AnswerCount="2" CommentCount="1" />
  <row Id="14770" PostTypeId="2" ParentId="14769" CreationDate="2011-05-28T06:42:42.723" Score="2" ViewCount="" Body="&lt;p&gt;The automotive environment is electrically very noisy, with potentially large spikes on the 12 V power bus (especially during engine start). This can be mitigated through the use of large filtering capacitors, maybe an inductor inline on the supply, and perhaps a transorb or other protection device. I don't know enough about power supply filtering to tell you exactly what to do, but you might be able to Google &quot;automotive power supply filter&quot; or similar. Note that the regulator may require input and output bypass capacitors, too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then there's the issue of iPad fast charging. I'm not sure how it decides it can draw more current for charging than what is normally allowed by the USB spec. I think there are resistors of a specific value between certain pins on the supply side. If you don't care about fast charging (which I've heard the iPhone 4 also uses), then you can ignore this.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You don't want to put an LED inline in order to see that power is being drawn. An LED has a maximum forward current above which its lifespan is dramatically shortened. This forward voltage is typically 5 - 25 mA, far less than the 1000 mA your regulator is capable of delivering (and far less than the 500 mA the iPod will likely draw). An alternative would be to set up a high-side current sense resistor (inline on the +5V side) and high-side current sense amplifier, use the output of that to drive a MOSFET or other transistor to turn on an LED. There are probably other ways to do that, but that's what comes to mind.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It really is easier to buy an off-the-shelf USB charger with a suitable input voltage, and cut off the supply connector to wire it in (with a fuse!) to your car supply. As another commenter mentions later, it may still lack appropriate filtering. You should be able to buy an automotive power filter to put inline with the USB charger. Then plug the Cables to Go panel mount into the charger.&lt;/p&gt;&#xA;" OwnerUserId="4452" LastEditorUserId="4452" LastEditorDisplayName="" LastEditDate="2011-05-28T07:14:33.427" LastActivityDate="2011-05-28T07:14:33.427" CommentCount="3" />
  <row Id="14771" PostTypeId="2" ParentId="14769" CreationDate="2011-05-28T06:53:29.457" Score="1" ViewCount="" Body="&lt;p&gt;You're going to need voltage divider on the USB data lines as explained in &lt;a href=&quot;http://electronics.stackexchange.com/questions/14450/why-are-these-usb-data-lines-conned-to-pull-up-resistors/14451#14451&quot;&gt;this&lt;/a&gt; answer. This controls the charging modes for iDevics and is needed for them to start charging. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, the datasheet says that there are already integrated capacitors in the regulator, but I'd still recommend that you add some extra ones at the output. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another thing worth pointing out is the derating figure in the datasheet. Temperatures inside of the vehicle can get high, especially if you're going to place the regulator in an area with low ventilation. If you want to run it at 1 A, do take into account the graph. To me it seems that the maximum safe outside temperature would be around 35 degrees. You need to be sure that you have lower temperature when you're using the charger. Another problem is the unusual package. To me it looks like there's no easy way to add a heatsink to the device.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-05-28T07:22:30.007" LastActivityDate="2011-05-28T07:22:30.007" CommentCount="2" />
  <row Id="14772" PostTypeId="2" ParentId="11274" CreationDate="2011-05-28T07:03:58.803" Score="0" ViewCount="" Body="&lt;p&gt;Input voltage needs to be higher than 12V to charge the 12V lead acid battery.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Rather than crack your head, you can buy off the shelf 12V UPS with battery charger from&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.wegatech.com/charger.html&quot; rel=&quot;nofollow&quot;&gt;http://www.wegatech.com/charger.html&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4453" LastActivityDate="2011-05-28T07:03:58.803" />
  <row Id="14773" PostTypeId="1" CreationDate="2011-05-28T09:18:15.523" Score="1" ViewCount="210" Body="&lt;p&gt;From what i know, HDD is built on magnetic recording technology. My question is, is it possible to create a storage device from scratch (USB, HDD, etc.)? I'm just eager to try out building some electronic devices...&lt;/p&gt;&#xA;" OwnerUserId="4455" LastActivityDate="2011-05-29T23:09:43.630" Title="Is it possible to build homemade storage device?" Tags="&lt;hardware&gt;" AnswerCount="6" CommentCount="2" />
  <row Id="14774" PostTypeId="2" ParentId="14773" CreationDate="2011-05-28T09:26:49.210" Score="5" ViewCount="" Body="&lt;p&gt;A HDD is not a very good idea for a DIY project. You need lots of special parts which aren't available for DIY, like voice coil, the platters and the magnetic head. You'd also need clean room conditions. And of course it's all about high precision mechanics.&lt;br&gt;&#xA;Also, if you would succeed in constructing one it would probably cost 10 to 100 times more than what you pay for a commercial product.  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-28T09:39:31.393" LastActivityDate="2011-05-28T09:39:31.393" CommentCount="3" />
  <row Id="14775" PostTypeId="2" ParentId="3741" CreationDate="2011-05-28T09:27:42.253" Score="0" ViewCount="" Body="&lt;p&gt;We use .Net micro framework in production applications (precision measurement devices). It works fine. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Todays microprocessors reached the state when you can use 'create-see-profile-change-see...' paradigm. Memory amounts are quite big and chip now, so most probably you won't stack with out of memory. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;And as a C# developer you know, that adequate profiling to reach desired condition is a better way to live than guessing what else and more complicated you should do while creating your code to make your code (and maybe not) a bit faster. &lt;/p&gt;&#xA;" OwnerUserId="4454" LastActivityDate="2011-05-28T09:27:42.253" />
  <row Id="14777" PostTypeId="2" ParentId="14773" CreationDate="2011-05-28T14:19:46.113" Score="6" ViewCount="" Body="&lt;p&gt;Yes, you can do it-- but it's hard and it won't store very much.  I think the thing that makes it hard is that you need to know a lot of very specialized areas to make it works. Things like:  software, signal processing, electronics, electro-magnetism, metalworking, motors/gears/etc, and materials science (somewhat like chemistry).  While not impossible, it is rare to find someone who is proficient in all of those areas.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you want to make this easier, I would recommend starting with a standard cassette tape player/recorder.  Rip out all of the electronics and keep the motors, gears, mechanical stuff, and the read/write/erase heads.  Then add back in your own electronics.  This still offers a lot of challenges, but the odds of success go way up. Then, if you get that working you can take the knowledge you gained and go on to a hard drive or something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you go the cassette tape route, let me mention that if you Google that you'll find a lot of pages that do something similar, but without modifying the player much.  They do that by modulating the data into something that resembles audio and can be stored as audio.  That's not what I'm recommending. If you rip out the guts of the player/recorder then you can have direct control of the motors and heads, which opens up lots of possibilities.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hard drives will be harder, mostly because you'd have to figure out how to make the hard drive platters.  Meaning, you have to make the magnetic recording medium and somehow spread it out evenly and smoothly on the glass or aluminum platter &quot;base&quot;.  Making the heads isn't easy either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should point out, however, that a clean room is not required.  I remember playing with a &quot;removable hard drive&quot; on a DEC PDP-8 computer.  Instead of removing the whole drive, you only removed the platters.  The platters were about 12 inches across and contained in something like a piece of Tupperware that you'd carry a cake in.  About 6 or so platters per carrier.  Before putting the platters into the drive you would have to remove them from the Tupperware.  It was big, and didn't store a lot, but no clean room either.  Don't get me wrong, modern drives do need a clean room.  But a DIYer has little or no hope of building a modern drive in his home so it's not really an issue.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another form of storage that could be interesting is an optical fiber &quot;drive&quot;.  Light travels approximately 6 inches per nanosecond in a fiber optic.  So if you have a fiber that is 100 feet long and you're transmitting stuff at 1 gbps then you're really storing 200 bits of data in that fiber.  Make the fiber several kilometers long and you could store a barely useful amount of data.  Get a fiber transmitter and receiver set up so whatever is received will be retransmitted and your data will just recirculate endlessly.  Some extra stuff will then allow you to read/write the data.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Probably the most useful, and least satisfying, thing to build would be something like a USB thumb drive.  Basically you buy the flash chip, and the controller chip, connect them together and you're done.  To make it a little harder, replace the controller chip with a microcontroller and write lots of software.  It's not super interesting, in my opinion.  I don't think it offers the same sense of accomplishment that the other approaches offer-- even though the performance and capacity would be the highest this way.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-28T14:19:46.113" CommentCount="5" />
  <row Id="14778" PostTypeId="2" ParentId="14773" CreationDate="2011-05-28T15:02:32.137" Score="5" ViewCount="" Body="&lt;p&gt;A ferrite core memory is entirely buidable at home without specialized hardware or electronic parts... &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some kind of low density magnetic media storage could also be built with no custom parts. &lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-05-28T15:02:32.137" CommentCount="3" />
  <row Id="14779" PostTypeId="1" CreationDate="2011-05-28T15:11:21.877" Score="0" ViewCount="76" Body="&lt;p&gt;I don't really know how to describe what happened to my monitor, but I made a small video here: &lt;a href=&quot;http://www.youtube.com/watch?v=Gjh5crE-Zx4&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=Gjh5crE-Zx4&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In summary, the output of the monitor is all garbled, but still there (not dead) - but the OSD works fine.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have some knowledge of electronics - so I opened it up, checked the capacitors, didn't find anyone gone bad - but I'll check again, might have missed something.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any pointers as to how could this happen, and where should I focus my investigation? I guess it's something related to the VGA input, but what could it be? (So I should check only the vga board, not the power one?)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should note that I have another, identical monitor (it was a part of a dual-display setup): If I remove the faulty monitor and connect the good one, everything is fine - so it can't be the PC or the VGA or the cable, something has gone wrong in this particular monitor.&lt;/p&gt;&#xA;" OwnerUserId="4458" LastEditorUserId="4458" LastEditorDisplayName="" LastEditDate="2011-05-28T21:37:50.323" LastActivityDate="2011-05-30T00:48:52.993" Title="TFT Monitor output is blurry and weird looking - but OSD works fine" Tags="&lt;electronics&gt;&lt;problem&gt;&lt;monitor&gt;" AnswerCount="1" CommentCount="4" />
  <row Id="14780" PostTypeId="2" ParentId="14773" CreationDate="2011-05-28T18:14:42.240" Score="1" ViewCount="" Body="&lt;p&gt;Crazy idea&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you are really really bored. You could delve into organic storage. Slow but huge capacity.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.popsci.com/science/article/2011-01/biostorage-scheme-turns-e-coli-bacteria-data-storing-hard-drives&quot; rel=&quot;nofollow&quot;&gt;E Coli hard Disk&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="4459" LastActivityDate="2011-05-28T18:14:42.240" />
  <row Id="14781" PostTypeId="2" ParentId="14296" CreationDate="2011-05-28T18:29:47.187" Score="1" ViewCount="" Body="&lt;p&gt;The snubber on a triac helps the triac turn off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Whether you need a snubber has nothing to do with the how much power your load consumes. If you have an inductive load, you need a snubber to get that triac to turn off and stay off -- to avoid unwanted turn-on -- even when your load is very low power.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Typically the control circuit tries to turn off a triac by pulling the other end of a resistor tied to the triac gate &quot;up&quot; to VCC, the same voltage as the cathode A1.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The triac remains &quot;on&quot; until the current through the triac reaches zero, which may be as much as 10 ms later.&#xA;At that later time, there is zero current through an inductive load, and therefore zero energy stored in the magnetic field.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(When we use a NPN transistor or MOSFET transistor or a relay contact to turn off an inductive load, we have to somehow deal with the &quot;flyback voltage&quot; produced when the energy stored in the magnetic field in the load is dumped.&#xA;We don't have to deal with this energy dump when we use a triac, and so the complete system using a triac+snubber typically ends up simpler and cheaper than these other ways of switching AC mains power to a load).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;When the triac finally turns off, the voltage across the load rapidly changes to near zero, and the voltage across the triac rapidly changes to nearly the instantaneous mains voltage.&#xA;(At the instant the triac turns off, the instantaneous current through the load is near zero, but with an inductive load the instantaneous absolute voltage across the load is close to the maximum peak instantaneous mains voltage).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The voltage itself is not a problem -- before the triac turned on, and after the triac has been turned off for a while, the full mains voltage is applied across the triac A1 and A2 pins indefinitely, without any problems.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The rapid change in voltage causes problems -- the rapid change in voltage at the anode A2 is coupled through unwanted parasitic capacitance inside the triac to the gate of the triac, turning the triac back on.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To avoid this unwanted turn-on, we add a snubber to reduce the rate of the change in voltage at A2.&#xA;Lowering the change in voltage reduces the current through that parasitic internal capacitance.&#xA;We can't reduce that current to zero, but we can keep it low enough that the resistor connected to the gate terminal keeps the gate voltage close enough to A1 -- keeping the triac turned off when it is supposed to be off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Another way to avoid this unwanted turn-on is to choose one of the newer &quot;SNUBBERLESS&quot; triacs that have much smaller parasitic capacitance inside the triac.&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.st.com/stonline/products/literature/an/6785.pdf&quot; rel=&quot;nofollow&quot;&gt;ST AN437: RC snubber circuit design for TRIACs&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.thierry-lequeu.fr/data/AN437.pdf&quot; rel=&quot;nofollow&quot;&gt;T. Castagnet: New triacs: is the snubber circuit necessary?&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://www.nxp.com/documents/application_note/AN_GOLDEN_RULES.pdf&quot; rel=&quot;nofollow&quot;&gt;NXP application note: &quot;Thyristors &amp;amp; Triacs - Ten Golden Rules for success in your application&quot;&lt;/a&gt;&lt;/li&gt;&#xA;&lt;li&gt;&lt;a href=&quot;http://en.wikibooks.org/wiki/Power_Electronics#Triacs&quot; rel=&quot;nofollow&quot;&gt;Wikibooks Power Electronics: Triacs&lt;/a&gt;&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-05-28T18:29:47.187" />
  <row Id="14782" PostTypeId="1" AcceptedAnswerId="14790" CreationDate="2011-05-28T21:22:46.823" Score="3" ViewCount="63" Body="&lt;p&gt;First off, I'm very sorry if this is the wrong place, I thought that &lt;a href=&quot;http://superuser.com/&quot;&gt;Super User&lt;/a&gt; would be correct, then I thought that the &lt;a href=&quot;http://physics.stackexchange.com/&quot;&gt;physics&lt;/a&gt; might be correct, but I settled on here as it as a direct relation to electrical engineering and it's properties.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So to the background of my question, there has been a &lt;a href=&quot;http://arstechnica.com/apple/news/2011/05/intel-exec-throws-fuel-on-the-intel-to-fab-apple-chips-rumor-fire.ars&quot; rel=&quot;nofollow&quot;&gt;rumor around that Apple might use Intel's fab&lt;/a&gt; to manufacture their A4 or A5 chips as they no longer source them from Samsung. The article then goes on to state that Apple might then benefit from Intel's knowledge of a 22nm process and that would mean some power savings for them, giving them a quite a large amount of power savings over their current 45 nm process.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So my questions is in two parts; How much power saving does a die shrink offer all things being equal and Is there a mathematical formula for this for calculating the power consumption as a function of process size?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The last thing I would like to add, that is more conjecture then anything else, because we just don't know; that is, until Intel releases a product using their 3D transistor platform; how much benefit do 3D transistors add to the overall power efficacy of the chip?&lt;/p&gt;&#xA;" OwnerUserId="4460" LastActivityDate="2011-06-02T17:36:18.890" Title="Process Size and Power Consumption." Tags="&lt;power&gt;&lt;cpu&gt;&lt;efficiency&gt;" AnswerCount="1" />
  <row Id="14783" PostTypeId="1" CreationDate="2011-05-28T21:29:42.083" Score="3" ViewCount="231" Body="&lt;p&gt;After scoring a cheap not-powering-on LCD TV (£20 for a 42&quot; LCD) it got me thinking about how these TVs seem to be designed to fail.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, the capacitors on the power supply board are drastically undersized (10V on a 6.5V bus) and not designed to cope with the amount of ripple current (PSU is rated at ~5A on this rail, and they are using general purpose capacitors.)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there any evidence that these products have been designed to fail? I've noticed LCD monitors and TVs are affected by these problems almost universally. But maybe it is just negligence, or cost cutting.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-29T10:07:10.427" ClosedDate="2011-05-29T22:59:22.840" Title="Are products designed to fail?" Tags="&lt;consumer-electronics&gt;&lt;failure&gt;" AnswerCount="3" CommentCount="4" />
  <row Id="14784" PostTypeId="1" AcceptedAnswerId="14788" CreationDate="2011-05-28T21:58:11.760" Score="1" ViewCount="80" Body="&lt;p&gt;Hi!&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm a total beginner in hardware, but I'd like to build a piece of material that would make a real bell ring for a specific duration, or eventually instead of a bell, a light that would switch on based on a specific duration.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The start and duration would be triggered remotely via USB or Ethernet, coded in a Java language (part I'm most experienced with).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I thought about using an Arduino, but since I don't know anything in the hardware area, I'm asking you for your advice on how and what do buy for making this the cheaper way.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, it would be great if this device would be sell alimented, I'm most thinking about using an USB then, am I right?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you very much for your help :)&lt;/p&gt;&#xA;" OwnerUserId="4461" LastActivityDate="2011-05-30T07:49:29.980" Title="USB/Ethernet to a (real) bell based on a signal" Tags="&lt;usb&gt;&lt;ethernet&gt;" AnswerCount="3" />
  <row Id="14785" PostTypeId="2" ParentId="14773" CreationDate="2011-05-28T22:08:01.180" Score="1" ViewCount="" Body="&lt;p&gt;You can make magnetic tape from sticky tape and rust.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=YFRkhUMYiaY&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=YFRkhUMYiaY&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="566" LastActivityDate="2011-05-28T22:08:01.180" />
  <row Id="14786" PostTypeId="2" ParentId="14783" CreationDate="2011-05-28T22:09:12.380" Score="8" ViewCount="" Body="&lt;p&gt;There are two ways to interpret your question:  1.  Are things &lt;em&gt;deliberately&lt;/em&gt; designed to die?  and 2. Are things designed cheaply?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;1.  Are things deliberately designed to fail?&lt;/strong&gt;  This one would be hard to answer since it borders on a conspiracy theory or something.  It's also kind of like asking, &quot;Are you really that stupid?&quot;  That being said, my experience is that things are not intentionally designed to fail.  I base this statement on my experience working with many consumer and professional equipment manufacturers.  They might be lazy, stupid, etc., but I have not known any of them to be downright dishonest.  Of course, I have not personally talked with every consumer electronics company or engineer, so I can't speak for everyone.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;2.  Are things designed cheaply?&lt;/strong&gt;  Heck yes!  I've seen some very questionable design decisions that were entirely based on cost.  Things like using a series of diodes instead of a LDO regulator to take +3.3v down to 1.8v, simply because the diodes were cheaper than a 15 cent regulator.  There are countless examples of this kind of thing.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I should mention that your example of a 10v cap on a 6.5v rail isn't really that bad.  That puts that cap at a 65 percent derating, which is quite generous compared to a lot of stuff I've seen.  And there could be other issues that made the 10v cap appropriate, like PCB space constraints, etc.  Even using general purpose caps on a 5 amp rail isn't terrible, depending on the rest of the circuit.  For example, maybe there are a bunch of caps in parallel that effectively lower the ESR/ESL, and distributes the ripple current so that any one cap has reasonable current.  Or maybe there are other things with that +5v rail that minimize the ripple current.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Before someone gets all critical on me in the comments, I should also say that under-spec'ing the caps in a power supply is a common thing.  My point is, based on what the original poster put in the question, we cannot assume that the caps cannot handle the ripple current.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-28T22:09:12.380" CommentCount="3" />
  <row Id="14787" PostTypeId="2" ParentId="14784" CreationDate="2011-05-28T22:10:31.413" Score="2" ViewCount="" Body="&lt;p&gt;Personally I'd go about this using a small PIC microcontroller or similar.  The USB side of it can be quite a pain to program (on the PIC chip) for the beginner (I haven't fathomed it yet), so a USB to RS232 converter (either as a USB dongle or as a USB to RS232 chip) can make things an awful lot easier to handle.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The PIC16F88 is a good starting point if you don't want to program the USB yourself,  and is dirt cheap (you can get &lt;a href=&quot;http://www.microchip.com/samples&quot; rel=&quot;nofollow&quot;&gt;free samples from the manufacturer&lt;/a&gt;).  If you want USB then you should look at the PIC18F series of microcontrollers (I just got my first one working today - yippee).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't want to go about building your own hardware and programming the PIC yourself there are many DIY kits that come with a pre-programmed PIC (such as the &lt;a href=&quot;http://www.velleman.eu/distributor/products/view/?country=be&amp;amp;lang=en&amp;amp;id=351346&quot; rel=&quot;nofollow&quot;&gt;K8055 from Velleman&lt;/a&gt;) which often have the USB built into it already.&lt;/p&gt;&#xA;" OwnerUserId="4245" LastActivityDate="2011-05-28T22:10:31.413" CommentCount="1" />
  <row Id="14788" PostTypeId="2" ParentId="14784" CreationDate="2011-05-28T22:37:44.040" Score="3" ViewCount="" Body="&lt;p&gt;First thing first:&#xA;There is no way to cheaply do this in Java only. There are some chips that can execute Java, but I haven't heard of any which are accessible for beginners.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So it's either C or the Arduino's language if you go for that route. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, you're going to need a power source for the bell. This will depend on the bell and will make a major impact on the circuit you'll be making. You'll probably need a relay and protection circuit for it which will control the bell which will be powered from a separate power source (like for example mains power). You'll need to look up specifics for Arduino's (or whatever you want to use) pins and get a relay which can be triggered by such power source. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next, you'll need Ethernet or USB connection. Matt already recommended USB to RS-232 chips and that is an easy way to solve the problem. The chip will appear as a serial port and all you'll need to do is make a Java program which will send data to the port to the microcontroller. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The other more complicated option would be to use Ethernet. For Arduino, there's an already existing &lt;a href=&quot;http://www.arduino.cc/en/Main/ArduinoEthernetShield&quot; rel=&quot;nofollow&quot;&gt;Ethernet shield&lt;/a&gt; which is supported by its IDE. You could also pick up another Ethernet board like &lt;a href=&quot;http://www.sparkfun.com/products/200&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt; or &lt;a href=&quot;http://www.mikroe.com/eng/products/view/596/serial-ethernet-2-board/&quot; rel=&quot;nofollow&quot;&gt;this one&lt;/a&gt;. The positive side of Arduino shield is that you get to use existing library with it that could prove to be helpful. For a third-party solution, you'll have to write the code yourself.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also a bit of comparison between Arduino, bare AVR chips or PIC. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;First, today's PIC and AVR chips are more or less similar in price and capabilities. Some people will recommend PIC and some will recommend AVR. There are countless raging fanboys on each side, but my advice is to ignore them. If you're planning to seriously get into the microcontroller world, it would be good idea to get familiar with both families, because they are both very popular. The chips are generally programmed in C or assembly and there are many development tools (some of them free) available for both lines.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Next we have Arduino. First, it's not a chip. It's a development board line and that is an important difference. It uses AVR chips inside and a special bootloader to make them easier to program. With that you have packaged a nice IDE which uses a C++ like language for programming and may make some things easier for a beginner. Recently it has gained enormous popularity with beginners. Its main problem is that it hides some operational concepts of the chi[ from the user and at one point you may get the feeling that you're fighting the IDE and the language.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;On the other hand, we have also the PICAXE which are basically PIC version of Arduino. They also have IDE and programming language (a BASIC derivative) and bootloader. As far as I can see PICAXE boards aren't as popular as Arduino for some reason, but I don't have any experience with them, so I can't elaborate why. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;So to sum this up: If you want a single project, consider Arduino or PICAXE. This way, you won't have to pay for setup costs (like programmer, time needed for training and board design and so on) which working with single microcontroller brings. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you plan to seriously work with microcontrollers in the future, consider doing this with an AVR of PIC chip. It'll be much more educational experience but it could get too complicated if you just doing a one-off project.&lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-05-28T22:37:44.040" CommentCount="2" />
  <row Id="14789" PostTypeId="1" AcceptedAnswerId="14791" CreationDate="2011-05-28T23:32:36.013" Score="1" ViewCount="61" Body="&lt;p&gt;I'm hoping to find a piece of hardware that let's you simply activate/deactivate a power socket remotely (ideally using a mobile app or web function). &lt;/p&gt;&#xA;&#xA;&lt;p&gt;What I'm imagining would fit between the mains socket and device plug as to not require rewiring the house.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Anyone heard of such a device?&lt;/p&gt;&#xA;" OwnerUserId="4462" LastActivityDate="2011-05-29T01:00:53.787" ClosedDate="2011-05-29T22:56:50.627" Title="Anyone know of an mobile-controlled on/off for mains power" Tags="&lt;power&gt;&lt;electronics&gt;&lt;remote&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="14790" PostTypeId="2" ParentId="14782" CreationDate="2011-05-28T23:45:52.347" Score="5" ViewCount="" Body="&lt;p&gt;I can help to address the first part of your question.  As an abstraction of a single switching device inside a processor, imagine a MOSFET connected to ground with a load resistor to the power supply (in a real CMOS part there wouldn't be a load resistor, but another transistor, but this distinction is not important for the analysis).  Connected from the junction of the resistor and the transistor is a capacitor, representing all the input capacitances of the transistor that the transistor under discussion is &lt;em&gt;driving&lt;/em&gt;.  When the first transistor switches off, this capacitance will be charged up through the load resistor.  When the first transistor switches back on, the charge stored on the capacitor will be discharged through the first transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It can be shown that when a capacitor is charged through a load resistor, 1/2 of the energy used in charging the capacitor is lost in the resistor, for a total energy dissipation of \$\frac{1}{2}C{V_s}^2\$, where \$V_s\$ is the supply voltage.  When the switch then turns on, assuming the resistance of the switch is much less than the load resistance, that same energy will be dissipated in the switch, for a total energy of \$C{V_s}^2\$.  Dividing this by the switching period gives you the &lt;em&gt;dynamic&lt;/em&gt; power dissipation of the switch/capacitance combo, \$C{V_s}^2f\$.  Shrinking the die reduces the junction capacitances of the MOSFETS, so if you know the supply voltage, switching frequency, number of transistors and the approximate junction capacitances of a certain process, you could calculate a ballpark figure of what kind of power savings a process shrink entails, all other things being equal.&lt;/p&gt;&#xA;" OwnerUserId="4129" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-06-02T17:36:18.890" LastActivityDate="2011-06-02T17:36:18.890" CommentCount="2" />
  <row Id="14791" PostTypeId="2" ParentId="14789" CreationDate="2011-05-29T01:00:53.787" Score="0" ViewCount="" Body="&lt;p&gt;Check out Insteon or X10 gear. It'll take multiple pieces to get control from your mobile app, but it can be done.&lt;/p&gt;&#xA;" OwnerUserId="746" LastActivityDate="2011-05-29T01:00:53.787" />
  <row Id="14792" PostTypeId="2" ParentId="14783" CreationDate="2011-05-29T07:08:20.337" Score="5" ViewCount="" Body="&lt;p&gt;They're not deliberately designed to fail, though design decisions imply that product life will be limited. When a new mobile phone is being developed the question the team asks is not &quot;How can we limit the product life to 2 years?&quot; but rather &quot;How can we create a product that will last at least 2 years?&quot;&lt;br&gt;&#xA;It's perfectly feasible to design a phone which will last 15 years, but that will come at a price, and the customer isn't prepared to pay that price for a product he will replace after 2 years anyway. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;You often see 85° electrolytic capacitors in products where the temperature easily goes beyond that. Is this design for failure? Not necessarily. It's often the only way to reach the target price. And the designers have tools (FMEA, MTTF calculations) to estimate the risks.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-29T07:18:48.763" LastActivityDate="2011-05-29T07:18:48.763" />
  <row Id="14793" PostTypeId="2" ParentId="14783" CreationDate="2011-05-29T10:07:10.427" Score="0" ViewCount="" Body="&lt;p&gt;stevenvh is right about that they are not designed to break, &#xA;and that they are designed not to last forever.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;But some companies also think about that it should survive a &quot;normal user&quot; 2-3 years. And then the question comes how does a normal user use this device.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For a TV that could be &quot;how many hours will it be turned on during 3 years&quot;, and that is what the TV must survive. And if you have the option to select between two things the questions is if the cheaper will survive the &quot;normal&quot; user.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Or how many times will the normal user push this button.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How many times will the normal user turn on/off this device during 3 years.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So there may be &quot;power users&quot; that will use the device more than the &quot;normal user&quot; and in those cases, it is pure luck if it survives more that 3 years.&lt;/p&gt;&#xA;" OwnerUserId="689" LastActivityDate="2011-05-29T10:07:10.427" />
  <row Id="14794" PostTypeId="1" AcceptedAnswerId="14795" CreationDate="2011-05-29T11:19:10.833" Score="0" ViewCount="94" Body="&lt;p&gt;I know it's trivial for electronic's person. But I have difficulties with counting following task:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/A5wbw.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'll be thankful for any assistance.&lt;/p&gt;&#xA;" OwnerUserId="4464" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-05-31T12:19:54.443" LastActivityDate="2011-06-01T14:52:53.200" Title="Some simple calculations of current in circuit" Tags="&lt;resistor&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="14795" PostTypeId="2" ParentId="14794" CreationDate="2011-05-29T11:30:22.880" Score="3" ViewCount="" Body="&lt;p&gt;In the first circuit R2 and R3 are parallel, so you should be able to calculate their combined value (R23). Once you've done that there's only one path left: the voltage source with R1 and R23 in series, which should enable you to calculate the current and hence the voltage drop over R1 and R23. The voltage over R23 is the voltage over R2 and R3, so you can calculate the currents through each of them. And the current through R1 is just the sum of these.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The second circuit is more or less the same, but here it's R1 // R3.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;You get 5 givens, while only 4 are required&lt;/em&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;details&lt;/strong&gt;&lt;br&gt;&#xA;\$\frac{1}{R23} = \frac{1}{R2} + \frac{1}{R3} = \frac{1}{2} + \frac{1}{1} = 1.5\$. So \$R23 = \frac{1}{1.5} = 0.67 \Omega\$&lt;br&gt;&#xA;\$I_{E} = \frac{E}{R1 + R23} = \frac{11V}{3\Omega + 0.67\Omega}=3 A\$&lt;br&gt;&#xA;\$U_{R23} = I_{E} * R23 = 3 A * 0.67 \Omega = 2 V\$&lt;br&gt;&#xA;\$I_{R2} = \frac{U_{R23}}{R2} = \frac{2 V}{2 \Omega} = 1 A\$&lt;br&gt;&#xA;\$I_{R3} = I_{R23} - I_{R2} = 3 A - 1 A = 2 A\$  &lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="3028" LastEditorDisplayName="" LastEditDate="2011-06-01T14:52:53.200" LastActivityDate="2011-06-01T14:52:53.200" CommentCount="12" />
  <row Id="14797" PostTypeId="1" CreationDate="2011-05-29T12:19:02.023" Score="1" ViewCount="38" Body="&lt;p&gt;How can I find information about Wit Tognola Wavelet? I need the formula and description of it.&lt;/p&gt;&#xA;" OwnerUserId="4466" LastActivityDate="2011-05-29T12:19:02.023" ClosedDate="2011-05-29T15:16:43.440" Title="How can I find information about Wit Tognola Wavelet?" Tags="&lt;wave&gt;" CommentCount="1" FavoriteCount="1" />
  <row Id="14798" PostTypeId="1" CreationDate="2011-05-29T16:46:39.250" Score="1" ViewCount="60" Body="&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/enLeo.png&quot; alt=&quot;circuit diagram&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Hi I want to make sure I've not wired anything wrong here. My USB interface is working fine. However the 5 V from USB seems to be powering the led on my laptop power brick. Hence even when I switched the power brick off at the wall outlet, the led is still on. When I unplug the USB it goes off but comes back on again as soon as I plug it in. Do I just but a diode in?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm using this power brick because a part of my circuit draws a lot of current. &lt;/p&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="1240" LastEditorDisplayName="" LastEditDate="2011-05-29T17:23:37.260" LastActivityDate="2011-05-30T06:31:10.720" Title="Wiring diagram check up for usb interfaced avr" Tags="&lt;circuit&gt;&lt;circuit-design&gt;" AnswerCount="1" CommentCount="1" />
  <row Id="14799" PostTypeId="2" ParentId="11515" CreationDate="2011-05-29T17:04:22.083" Score="2" ViewCount="" Body="&lt;p&gt;If you only use the capacitor you would have a load, like a resistor, only this time frequency dependent. The thing is that this load doesn't change the signal.&lt;br&gt;&#xA;Enter the resistor. Now you have a &lt;strong&gt;voltage divider&lt;/strong&gt;. For low frequencies the capacitor's &quot;resistance&quot; will be high compared to the resistor, so most of the signal will arrive at the output. For high frequencies the capacitor's &quot;resistance&quot; is low compared to the resistor, and the divider will attenuate the input signal: only a small portion of it will appear at the output.&lt;br&gt;&#xA;&lt;em&gt;I put the capacitor's &quot;resistance&quot; in quotes because it's not just a real resistance, it's more complex, in every meaning of the word..&lt;/em&gt;&lt;/p&gt;&#xA;" OwnerUserId="2064" LastActivityDate="2011-05-29T17:04:22.083" CommentCount="3" />
  <row Id="14800" PostTypeId="1" CreationDate="2011-05-29T18:06:31.467" Score="4" ViewCount="183" Body="&lt;p&gt;For example, the passband of a LC resonant circuit is the differences of frequency at +3db and -3db.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Why do we prefer dB?&lt;/p&gt;&#xA;" OwnerUserId="493" LastEditorUserId="857" LastEditorDisplayName="" LastEditDate="2011-06-02T19:56:15.450" LastActivityDate="2011-06-02T19:56:15.450" Title="Why do we use dB to represent the difference between two voltages?" Tags="&lt;decibel&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="14801" PostTypeId="2" ParentId="14800" CreationDate="2011-05-29T18:13:11.287" Score="3" ViewCount="" Body="&lt;p&gt;dB are often used because the human senses have a logarithmic response, to increase the dynamic range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Around 3dB gives a sensation of doubling or halving the stimulus, as well as doubling or halving the physical value. That value seems to apply to all human senses, and is one reason why 3dB is so ubiquitous. Psychophysics, a branch of experimental psychology, has a long history of investigating this stuff. The minimal amount of change that can be detected is around 1dB (the Just Noticeable Difference or JND). 0dB is the absolute threshold, below which the stimulus isn't detected.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-29T18:28:29.950" LastActivityDate="2011-05-29T18:28:29.950" CommentCount="12" />
  <row Id="14802" PostTypeId="1" AcceptedAnswerId="14808" CreationDate="2011-05-29T18:22:53.567" Score="0" ViewCount="111" Body="&lt;p&gt;I am looking to interface a Casio 991es calculator's LCD to arduino. The LCD is just two bare glass plates glued together with lot of pins. I dont find any driver chip with it. How can I interface this LCD to arduino?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Edit: I think it is a dynamic LCD. This site has some info: &lt;a href=&quot;http://dataweek.co.za/article.aspx?pklArticleId=2382&amp;amp;pklCategoryId=31&quot; rel=&quot;nofollow&quot;&gt;http://dataweek.co.za/article.aspx?pklArticleId=2382&amp;amp;pklCategoryId=31&lt;/a&gt;&#xA;I dont understand the waveforms they provided. &lt;/p&gt;&#xA;" OwnerUserId="4277" LastEditorUserId="4277" LastEditorDisplayName="" LastEditDate="2011-05-31T04:53:05.730" LastActivityDate="2011-05-31T04:53:05.730" Title="How can I interface bare glass LCD to an arduino?" Tags="&lt;arduino&gt;&lt;lcd&gt;" AnswerCount="2" />
  <row Id="14803" PostTypeId="2" ParentId="14800" CreationDate="2011-05-29T18:24:56.013" Score="3" ViewCount="" Body="&lt;p&gt;dB is useful since it is a relative expression. +/-3dB is a doubling or halving of power.&lt;/p&gt;&#xA;" OwnerUserId="3876" LastActivityDate="2011-05-29T18:24:56.013" />
  <row Id="14804" PostTypeId="2" ParentId="14798" CreationDate="2011-05-29T18:33:51.703" Score="2" ViewCount="" Body="&lt;p&gt;You really need a switch to control where the power is coming from, at the very least you want some sort of current limiting.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without such control both the LDO and the USB bus can be providing +5V but there will be small offsets between the two +5V levels which can cause large currents to flow as the resistance between the supplies in your design is very low.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Current from the USB host controller should be limited to 100mA if you haven't requested more power but bouncing off that current limiter may cause issues depending on the implementation of the limiting.  This could be limited if the LDO has an internal protection diode or you supply one externally.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If the +5V is slightly higher on the board when being supplied from the jack, then current will flow back at the host controller, which appears to be the issue your seeing.  This could cause lots of issues of various forms on the host side.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Basically what you need is to OR the USB bus power with the output of LDO and prevent reverse current flow.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This can be done with a pair of diodes, one on each supply line, pointing toward the micro-controller.  However, the forward voltage drop from the diode is going to be roughly 0.5V.  With a USB input that can go as low as 4.75V your supply voltage at the micro-controller may be as low as 4.25V which may be outside the operational range of the micro-controller.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;In that case there are special devices designed for this purpose, here is an &lt;a href=&quot;http://www.linear.com/product/LTC4413&quot; rel=&quot;nofollow&quot;&gt;example&lt;/a&gt;.  Such a device will reduce your forward drop to 50mV or less in most cases.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you also need to support USB device suspend mode then you need to also handle a power limit of 500uA in this mode.  This will require an external power enable switch which basically shuts everything down, including the regulator.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT:&lt;/strong&gt; If you don't mind it not being automatic, you can just put a jumper on the board to pick between the power sources.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;EDIT2:&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Excuse the poor picture editing but hopefully this clears up what I'm saying.  This is what you would do to OR the two +5V rails with diodes:&#xA;&lt;img src=&quot;http://i.stack.imgur.com/RDNCR.png&quot; alt=&quot;diagram&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="1438" LastEditorUserId="1438" LastEditorDisplayName="" LastEditDate="2011-05-30T06:31:10.720" LastActivityDate="2011-05-30T06:31:10.720" CommentCount="3" />
  <row Id="14805" PostTypeId="1" CreationDate="2011-05-29T19:08:55.070" Score="-3" ViewCount="60" Body="&lt;p&gt;Hi,&#xA;I'm very interested in sending signals via TRS and TRRS, but I don't know anything about it.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I know basics about electric circuits and electromagnetism, but doesn't anything about connection between this what I know and what I want - sending and receiveing signals via TRS or TRRS.&#xA;Where should I start learning? (It doesn't matter how long will it last)&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thank you&lt;/p&gt;&#xA;" OwnerUserId="4468" LastActivityDate="2011-05-29T19:08:55.070" ClosedDate="2011-05-29T22:58:05.180" Title="What should I learn for playing with TRS and TRRS?" Tags="&lt;audio&gt;" CommentCount="5" FavoriteCount="0" />
  <row Id="14806" PostTypeId="2" ParentId="2010" CreationDate="2011-05-29T19:14:11.477" Score="4" ViewCount="" Body="&lt;p&gt;Yes, there are several ways to build an &quot;AC switch&quot; entirely out of transistors.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;two diodes and two transistors&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can put a diode in series with the collector of one (nFET or npn) transistor that conducts when the &quot;hot&quot; line of the mains is positive relative to &quot;neutral&quot;, so when the CPU turns on that transistor, the transistor turns on the light bulb during the positive half-cycles.&#xA;(zero electrons flow through this diode+transistor connection when the transistor is off, or during the negative half-cycles).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can put a diode in series with the collector of another (pFET or pnp) transistor that conducts when the &quot;hot&quot; line of the mains is negative relative to &quot;neutral&quot;, so when the CPU turns on that transistor, the transistor turns on the light bulb during the negative half-cycles.&#xA;(zero electrons flow through this diode+transistor connection when the transistor is off, or during the positive half-cycles).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Normally the CPU would either turn both transistors on, or both transistors off.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The &quot;neutral&quot; line and the emitter of each transistor are all connected, and the CPU power supply and the gate of each transistor stay within a few volts of neutral.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;This approach may be simplest to understand, but in practice other AC switches have lower net cost.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;two transistors and a bunch of diodes&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can put a pnp and a npn transistor together so the combination acts identical to a SCR.&#xA;(See the &lt;a href=&quot;http://en.wikipedia.org/wiki/Silicon-controlled_rectifier&quot; rel=&quot;nofollow&quot;&gt;Wikipedia SCR schematic&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then you can use a bunch of diodes to steer the current so the SCR can turn on and off both the positive and negative half-cycles.&#xA;(See the &lt;a href=&quot;http://en.wikipedia.org/wiki/Dimmer#Thyristor_dimmer&quot; rel=&quot;nofollow&quot;&gt;Wikipedia SCR dimmer schematic&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;four transistors&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You can build two SCRs out of a pnp and npn transistor each.&#xA;Then connect them in antiparallel so the combination acts as a triac.&#xA;(See &lt;a href=&quot;http://en.wikipedia.org/wiki/TRIAC&quot; rel=&quot;nofollow&quot;&gt;Wikipedia: TRIAC&lt;/a&gt; and &lt;a href=&quot;http://en.wikibooks.org/wiki/Power_Electronics#Triacs&quot; rel=&quot;nofollow&quot;&gt;Wikibooks: Power Electronics: Triac&lt;/a&gt;).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;details&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You'll need to use transistors that can handle voltages higher than your average mains voltage and also currents higher than your average load current.&#xA;Your &lt;a href=&quot;http://opencircuits.com/Supplier&quot; rel=&quot;nofollow&quot;&gt;favorite supplier&lt;/a&gt;&#xA;should be able to hook you up with several kinds of transistors that meet that criteria.&#xA;You might also look at a triac or IGBT or a solid-state relay -- they have (in effect) several transistors combined into a convenient package.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Timing the off-to-on transition or the on-to-off transition to occur close to the zero-crossing (when the voltage across the transistors is close to zero) puts less stress on the transistors, so they stay cooler.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Much like the acronym LASER has become an ordinary word &quot;laser&quot;, the acronym &quot;TRIAC&quot; has become ordinary word &quot;triac&quot; -- both &quot;TRIAC&quot; and &quot;triac&quot; refer to the same thing.&lt;/p&gt;&#xA;" OwnerUserId="813" LastActivityDate="2011-05-29T19:14:11.477" />
  <row Id="14807" PostTypeId="1" AcceptedAnswerId="14812" CreationDate="2011-05-29T20:09:29.967" Score="4" ViewCount="82" Body="&lt;p&gt;The way I understand it, the input value (D) of a D type flip-flop appears immediately on the output (Q) of a D type flip when triggered by a positive clock edge. If this is the case, then how can the value before the clock edge be used as an input to another clocked flip-flop? According to this model, there's no particular value at all right at the edge of the clock.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Of course, flip-flops &lt;em&gt;do&lt;/em&gt; work so it's my model of understanding which is wrong. So can anyone elaborate this a bit more?&lt;/p&gt;&#xA;" OwnerUserId="4303" LastActivityDate="2011-05-29T22:56:34.977" Title="If the output of a D type flip-flop appears immediately on the clock edge, how can the previous output be used?" Tags="&lt;clock&gt;&lt;flipflop&gt;&lt;setup&gt;" AnswerCount="3" />
  <row Id="14808" PostTypeId="2" ParentId="14802" CreationDate="2011-05-29T20:32:20.827" Score="1" ViewCount="" Body="&lt;p&gt;When I disassembled my Casio FX-85GT, I found that there were two main chips (both under epoxy blobs): what looked like a microcontroller, and a display controller. The display controller would drive the LCD directly. Unfortunately, driving a 128x64 pixel display without a dedicated driver will be next to impossible. A cheap solution is buying a ready-made display with a controller, e.g. &lt;a href=&quot;http://www.seeedstudio.com/depot/serial-graphic-lcd-12864-st756567-ctrl-black-and-white-p-287.html?cPath=163_164&quot; rel=&quot;nofollow&quot;&gt;this one from SeeedStudio&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I don't know about the 991es, but if it is just a character display you are after, &lt;a href=&quot;http://www.seeedstudio.com/depot/lcd-162-characters-green-yellow-back-light-p-62.html?cPath=163_164&quot; rel=&quot;nofollow&quot;&gt;they are even cheaper&lt;/a&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastEditorUserId="1225" LastEditorDisplayName="" LastEditDate="2011-05-29T20:42:45.010" LastActivityDate="2011-05-29T20:42:45.010" CommentCount="1" />
  <row Id="14809" PostTypeId="2" ParentId="14807" CreationDate="2011-05-29T21:12:30.987" Score="4" ViewCount="" Body="&lt;p&gt;If you scrutinize the data sheet for a real D-FF carefully, you will see an item called 'setup time'. In actuality, the FF doesn't grab the value at the exact time of the clock edge; the data has to be stable for the last 20 ns or so before the clock rises, and that's the value that gets transferred. Also, the value at the output takes a few ns to settle down to the (possibly) changed value. So if you daisy chain a string of D-FF's together, Q from one into the D of the next, everything works because during the critical time for each stage's D input, the Q's are stable; the Q's only change very shortly after the active clock edge.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-29T21:12:30.987" CommentCount="1" />
  <row Id="14810" PostTypeId="2" ParentId="14807" CreationDate="2011-05-29T21:51:20.417" Score="1" ViewCount="" Body="&lt;p&gt;Propagation delay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Just like an inverter or in fact any other logic gate the output does not change immediately with the input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, for the &lt;a href=&quot;http://www.nxp.com/documents/data_sheet/74F74.pdf&quot; rel=&quot;nofollow&quot;&gt;74F74&lt;/a&gt;, a dual D-type flip flop with dedicated S and R inputs, there are two propagation delays specified: &quot;Propagation delay CPn to Qn or Qn#&quot; and &quot;Propagation delay &quot;SDn#, RDn# to Qn or Qn#&quot;. Both take less than 11 ns worst case. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Now, it is fun to consider what would happen if logic gates had zero propagation delay. Let's take the D-type, set up as a binary counter. Assume Q = 0, Q# = 1. A rising edge occurs on the clock pin. Immediately (in zero time), Q# is transferred to Q. Now, with all logic gates, the rising edge detection logic can output a rising edge for some time, say a few ns. So for these few ns (required to be shorter than propagation delay for stability, but in this case greater) we get oscillations. Q# becomes 0, and gets transferred to Q. Then Q# becomes 1, and gets transferred to Q... and so on. The output is known as &lt;em&gt;indeterminate&lt;/em&gt;.&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-29T21:51:20.417" />
  <row Id="14811" PostTypeId="2" ParentId="14800" CreationDate="2011-05-29T22:37:29.673" Score="7" ViewCount="" Body="&lt;p&gt;Many processes in nature are either of logarithmic nature (like human senses) or have a great dynamic range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Describing them on a logarithmic scale and expressing differences in dB has several advantages:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;often the absolute difference doesn't matter, but the ratio (that's what dB is used for) does (e.g. signal-to-noise ratio)&lt;/li&gt;&#xA;&lt;li&gt;smaller numbers can be used&lt;/li&gt;&#xA;&lt;li&gt;there's an approximately linear relation between measurement and perceived sensation&lt;/li&gt;&#xA;&lt;li&gt;chained attenuations or amplifications can be expressed by addition instead of multiplication (easier to calculate in the head)&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.youtube.com/watch?v=mLMfUi2yVu8&quot; rel=&quot;nofollow&quot;&gt;Here's another video&lt;/a&gt; about it.&lt;/p&gt;&#xA;" OwnerUserId="1950" LastActivityDate="2011-05-29T22:37:29.673" />
  <row Id="14812" PostTypeId="2" ParentId="14807" CreationDate="2011-05-29T22:56:34.977" Score="3" ViewCount="" Body="&lt;p&gt;The setup and hold times of a D flip flop together specify an interval during which any change to the data input may cause arbitrary behavior.  If a flip-flop has a 7ns setup time and a 5ns hold time, that means that if a clock edge happens within 7ns after an input change, or the input changes within 5ns after a clock edge, the behavior of the latch is not guaranteed.  It is possible for either the setup or hold time (but not both) to be negative; the magnitude of the other time bust be greater than that of the negative time.  If a latch had, e.g. a specified setup time of 11ns and a hold time of -4ns, that would mean that the behavior of the latch would be guaranteed unless the clock input changed between 11 and 4ns after a change to the data input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Note that while setup and hold times are usually specified as maxima, they are in reality absolute worst-case values since the manufacturer makes no guarantee as to what would happen were they violated.  For example, suppose chip X has 10ns setup and hold times, while chip Y has 1ns setup and hold times, and that both chips are fed a data signal which changes 7ns before a clock edge.  Chip Y would be required to latch the data signal correctly; chip X could do just about anything--including latching the data signal correctly--and be deemed to meet spec.  It would be pointless for a manufacturer to specify that a minimum setup time (unless the intention was really to specify that the maximum hold time was negative, in which case that's what the spec should say).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Almost any process which is used to make flip flops will effectively guarantee that the shortest propagation time for any of the flip flops on the chip will be longer than the longest setup time for any similarly-specified flip flops.  In most cases, this guarantee effectively seems to extend to other chips in the same manufacturing lot, but it's unclear how far it really extends.  In many cases, manufacturers specify that a chip's hold time will be no longer than some amount, and that the propagation time will be no longer than a certain amount, but unless the hold time is zero or negative or a minimum propagation time is specified and it's longer than the required hold time, I don't think the data sheets actually specify correct operation for cascading latches.  Certainly it's possible to have trouble when feeding the data output of a very fast chip into the data input of a slow chip with a long hold time.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One approach that's used with some protocols like SPI, and it's an approach I'd like to see used more, is to have the output stage of each latch change on the opposite clock edge from the input.  I'm not sure why this approach isn't used more; while there are times when it would be unnecessary and wasteful (if one knows that the propagation time of the circuitry between two latches would be sufficient to satisfy the hold time of the downstream latch, having the output of the upstream latch change on the same clock edge as downstream latch is sampled would allow for higher clock speeds), it also makes it possible to guarantee the correctness of many circuits involving mixed logic families--something which may otherwise be difficult.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-29T22:56:34.977" CommentCount="3" />
  <row Id="14813" PostTypeId="2" ParentId="14800" CreationDate="2011-05-29T23:01:15.163" Score="2" ViewCount="" Body="&lt;p&gt;In many cases, voltage ratios are expressed in terms of dB rather than absolute numbers because there are many relationships which end up being linear when expressed in terms of dB.  It is simpler, for example, to say that an N-stage low-pass filter will attenuate frequencies above the cutoff by \$(6 \times N) \frac{dB}{octave}\$ than it is to say that it will attenuate frequencies above the cutoff by a ratio of \$({\frac{f_c}{f}})^N\$.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-06-02T17:35:35.987" LastActivityDate="2011-06-02T17:35:35.987" CommentCount="3" />
  <row Id="14814" PostTypeId="2" ParentId="14773" CreationDate="2011-05-29T23:09:43.630" Score="0" ViewCount="" Body="&lt;p&gt;If your goal is to build something to be interesting, rather than practical, there are variety of DIY-compatible ways one could store information electronically.  While it's extremely doubtful that one could achieve anything resembling cost-effective performance, it's entirely possible that one might be able to, with modern technology, achieve a level of performance for some techniques which would be significantly above what could have been achieved a few years ago with similar techniques.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For example, it might be interesting to play with acoustic delay lines.  Generally, their performance has been limited by the fact that signals will spread out a certain amount as they travel down the lines; if one tries to push the bandwidth too high, bits may blur into each other by the time they reach the far end.  Back in the days when delay lines were used for storage, that would have been an absolute limiting factor.  With today's DSP's, however, it may be possible to reconstruct waves which would have been unreadably blurry a few decades ago.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm not sure how many bits one could store in something like a spring reverb, but it might be interesting to play with one and find out.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-29T23:09:43.630" CommentCount="1" />
  <row Id="14815" PostTypeId="2" ParentId="4139" CreationDate="2011-05-29T23:26:55.603" Score="1" ViewCount="" Body="&lt;p&gt;If one builds a rectangular memory array which is read using a tri-state driver in each memory cell, then one decoder circuit can control all of the cells in a row.  One will need circuitry around the perimeter of the array to control it, but the amount of control circuitry will be proportional to sqrt(N)*lg(N).  By contrast, if one tried to feed all the memory cells into a multiplexer, one would end up needing a lot more circuitry.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The multiplexer-based approach does have some advantages.  If one built a one mega-word memory using two-way multiplexers, each bit would have to pass through 20 multiplexers, but one could achieve a very high-bandwidth pipelined memory system if each multiplexer included a latch.  It would take 20 cycles to perform any particular read operation, but in 100 cycles one could begin 100 different reads.  Since the signal wouldn't have to go very far in each cycle and wouldn't be driving any large buses, the cycle rate could be extremely high.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The issue of whether to use multiplexers or buses ends up being somewhat similar to the question of whether to use data repeaters when sending information over long distances.  On the one hand, data repeaters add delay.  On the other hand, the time required for a signal transition at one end of a stretch of copper to cause a transition at the other end is asymptotically proportional to the square of the length (since adding length adds both resistance and capacitance).  Adding a repeater in the middle of a long wire may end up improving speed since the long run will be replaced by two shorter ones with somewhere between a quarter and half of the longer delay.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If one were to double the width and length of a memory array without improving the 'oomph' of the row and column driver circuits, one would more than double the time required to switch the rows and columns.  By contrast, if one were to use four smaller memory arrays and multiplex the outputs, one would only add a constant to the access time.  Faster memories are subdivided into more small arrays connected by multiplexers; cheaper memories use fewer multiplexers but aren't as fast.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-29T23:26:55.603" CommentCount="1" />
  <row Id="14816" PostTypeId="1" AcceptedAnswerId="14820" CreationDate="2011-05-30T00:14:36.767" Score="4" ViewCount="141" Body="&lt;blockquote&gt;&#xA;  &lt;p&gt;Metastability in electronics is the&#xA;  ability of a digital electronic system&#xA;  to persist for an unbounded time in an&#xA;  unstable equilibrium or metastable&#xA;  state. In metastable states, the&#xA;  circuit may be unable to settle into a&#xA;  stable '0' or '1' logic level within&#xA;  the time required for proper circuit&#xA;  operation. As a result, the circuit&#xA;  can act in unpredictable ways, and may&#xA;  lead to a system failure. &#xA;  &lt;a href=&quot;http://en.wikipedia.org/wiki/Metastability_in_electronics&quot; rel=&quot;nofollow&quot;&gt;Wikipedia&lt;/a&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;That seems a good definition but what does it mean in application?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;From an electronics designer's standpoint, what are some examples of when this might occur and where should this type of failure be of concern?     &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could someone provide a more pragmatic or applied definition - something in more specific terms?&lt;/p&gt;&#xA;" OwnerUserId="1419" LastActivityDate="2011-05-30T17:55:24.463" Title="What is metastability?" Tags="&lt;design&gt;" AnswerCount="4" CommentCount="2" />
  <row Id="14817" PostTypeId="2" ParentId="14816" CreationDate="2011-05-30T00:29:33.457" Score="2" ViewCount="" Body="&lt;p&gt;The classic case is if you violate setup/hold times for a synchronous latch, and is an issue you need to be aware of when designing FPGAs (I'm sure Xilinx and Altera will have appnotes on this). If a signal can come along at any random time, you can never be sure that when you clock it, it isn't changing within the setup/hold time window spec. What can happen is instead of the latch output going high or low at the specified time after the clock edge, it can dither about for a while before settling at a stable state. &#xA;The normal way to prevent this is to use a 2-stage latch, either with  the  same clock or a delayed or out-of-phase clock depending on the balance between your latency requirements and probability of metastability. &#xA;This allows the first latch time to stabilise before the second latch latches a stable state. &#xA;Incidentally, this is something that microcontrollers have to deal with internally, as external I/O signals are usually asynchronous to the CPU clock, so I/O ports often have dual latching arrangements to avoid problems, and the software doesn't need to worry about it. &#xA;A vaguely recall reading many years ago about a problem with the 6502, where a bus read of data which changed outside the setup/hold time spec could cause a branch to an address that was neither the branch target nor the next instruction, as some internal state went metastable.&#xA;This video shows some examples : &lt;a href=&quot;http://www.youtube.com/watch?v=tKHCwjWMMyg&quot; rel=&quot;nofollow&quot;&gt;http://www.youtube.com/watch?v=tKHCwjWMMyg&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;An analogy is if you throw someone a ball -  they mostly either catch it or drop/miss it, so after a given time from throwing, they will either be holding it or not. But occasionally they will fumble for a while before either catching or dropping it, so their state is neither holding nor dropped - this is the metastable state!   &lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="1681" LastEditorDisplayName="" LastEditDate="2011-05-30T00:39:51.400" LastActivityDate="2011-05-30T00:39:51.400" CommentCount="5" />
  <row Id="14818" PostTypeId="2" ParentId="14779" CreationDate="2011-05-30T00:48:52.993" Score="0" ViewCount="" Body="&lt;p&gt;I'm guessing a bad pin - one of the syncs (either horizontal or vertical).  According to &lt;a href=&quot;http://pinouts.ru/Video/VGA15_pinout.shtml&quot; rel=&quot;nofollow&quot;&gt;pinouts.ru&lt;/a&gt; this could be either pin 10,12, or 13 (sync ground, horizontal or vertical sync).  If you can swap cables on your monitor try that.  If you can and that doesn't help, it's the connector on the monitor.  You could try to replace it - aim a heat gun at the connector and pull it when all the solder melts or use a hot air rework station or a solder wick, then replace it.  You can buy right angle HD-15 connectors like &lt;a href=&quot;http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;amp;name=A35119-ND&quot; rel=&quot;nofollow&quot;&gt;this&lt;/a&gt; one on Digikey or elsewhere.  Remember - it's a high-density 15 pin D-sub connector, female, through-hole and probably right-angle.  Should be cheap if that's the issue.  Good luck!&lt;/p&gt;&#xA;" OwnerUserId="249" LastActivityDate="2011-05-30T00:48:52.993" CommentCount="1" />
  <row Id="14819" PostTypeId="2" ParentId="14816" CreationDate="2011-05-30T00:58:33.843" Score="2" ViewCount="" Body="&lt;p&gt;A metastable signal is one which may arbitrarily appear to be high or low in any arbitrary pattern for some arbitrary length of time.  If the signal feeds multiple gates directly &lt;i&gt;or indirectly&lt;/i&gt; it's possible that some of those gates will &quot;see&quot; it high while others see it low.  Nasty stuff.&lt;p&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For systems with a single clock, metastable signals can often be dealt with by passing through two latches.  A trickier issue comes when gating clocks.  There are a lot of circuits (especially using RS latches) which would work wonderfully if metastability weren't possible, but which can, if metastability occurs, end up generating runt clock pulses (which in turn can cause downstream metastability).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Incidentally, another important point to make regarding metastability: a latch's propagation time indicates when, &lt;i&gt;if sample and hold times are met&lt;/i&gt;, the output will be stable at its new value.  If setup and hold times are not met, there is no guarantee as to if or when the output will or will not switch, until such time as the latch receives a valid clocking event.  Even if the output 'seems' to switch cleanly, there's no guarantee it won't spontaneously switch back.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastEditorUserId="3123" LastEditorDisplayName="" LastEditDate="2011-05-30T01:31:09.087" LastActivityDate="2011-05-30T01:31:09.087" />
  <row Id="14820" PostTypeId="2" ParentId="14816" CreationDate="2011-05-30T01:39:16.693" Score="8" ViewCount="" Body="&lt;p&gt;Quick Answer:  If you violate the setup and hold time on the input of a flip flop, then the output will be unpredictable for some amount of time.  That unpredictable output is called meta-stable (or metastability).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Long answer:  When the output is unpredictable, I mean that it's unpredictable.  It could be high, it could be low, it could be somewhere in between, or it could oscillate.  After this metastable period the output will be high or low, but we don't know which way it'll go until it happens.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The amount of time that it's unpredictable is somewhat predictable, however.  There are two main factors that determine the length of the metastable period:  The speed of the flip-flop, and how &quot;close to the edge&quot; you got the timing.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Most of the metastable times are quite short, although the probability of having a long time is non-zero.  Theoretically you could have a metastable time on the order of seconds, although the odds of that happening are incredibly rare.  As the speed of the flip-flop increases, the average metastable time decreases-- all other things being equal.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There is an &quot;imaginary&quot; time in the flip-flop, relative to the clock edge, where you're most susceptible to metastability issues.  Exactly when that is depends on lots of factors like temperature, voltage, process, phase of the moon, animal sacrifices, and what political party you affiliate with.  Whenever that time is, the closer your data input edge is to that time the longer the metastability time will be.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best way to deal with metastability is to make all of your logic synchronous, and not violate any of your setup and hold times.  This is, of course, difficult to impossible for circuits of any complexity.  So what we do is try to limit the places where metastability could be an issue and then deal with those places.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;The normal method would be to &quot;double-clock&quot; the data.  Meaning, have two D Flip-Flops in series with the output of the first feeding the input of the second.  The hope is that if the first flip-flop goes metastable then the metastable period would be over before it violates the setup/hold time of the second.  In practice this works fairly well.  In super critical applications there might be some &quot;triple-clocking&quot; going on.&lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-30T01:39:16.693" CommentCount="1" />
  <row Id="14821" PostTypeId="2" ParentId="14547" CreationDate="2011-05-30T02:17:32.320" Score="1" ViewCount="" Body="&lt;p&gt;You just need a regulator/converter that produces as a 19V output and can provide at least 3.42A.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;a href=&quot;http://www.batteryspace.com/dc-dcregulatormodulefrom222v-259vdcto19v4ampmax.aspx&quot; rel=&quot;nofollow&quot;&gt;This one&lt;/a&gt; should work provided you have enough batteries to give it a proper input.&lt;/p&gt;&#xA;" OwnerUserId="4470" LastActivityDate="2011-05-30T02:17:32.320" />
  <row Id="14822" PostTypeId="2" ParentId="14802" CreationDate="2011-05-30T04:32:06.723" Score="0" ViewCount="" Body="&lt;p&gt;When you want to interface any screen to an Arduino or other Microcontroller, you should make sure that the screen you intend to use has code libraries (in C, C++, Assembly, etc) for proper communication or else you will have a very difficult time with that screen. I would suggest you go on sparkfun and find an LCD screen + MC combo that have been tested to work nicely..&lt;/p&gt;&#xA;" OwnerUserId="4471" LastActivityDate="2011-05-30T04:32:06.723" />
  <row Id="14823" PostTypeId="1" AcceptedAnswerId="14824" CreationDate="2011-05-30T06:50:27.970" Score="1" ViewCount="55" Body="&lt;p&gt;In an answer to &lt;a href=&quot;http://electronics.stackexchange.com/questions/11515/novice-question-about-low-pass-filter&quot;&gt;this question&lt;/a&gt; Leon Heller links to a tutorial which includes the following graph:&lt;br&gt;&#xA;&lt;img src=&quot;http://i.stack.imgur.com/gPu9w.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;br&gt;&#xA;I'm a bit confused. Shouldn't the graph for an RC filter monotonously decrease, without the inflection point?&lt;/p&gt;&#xA;" OwnerUserId="3920" LastActivityDate="2011-05-30T13:34:50.873" Title="graph of transfer function for RC filter" Tags="&lt;filter&gt;" AnswerCount="1" />
  <row Id="14824" PostTypeId="2" ParentId="14823" CreationDate="2011-05-30T07:05:22.227" Score="6" ViewCount="" Body="&lt;p&gt;The graph is correct. The curve looks a bit unusual because the voltage scale is linear. The Bode plot will have a slope of 6dB/octave which will be a straight line on a logarithmic graph. But a straight line on a logarithmic graph is a hyperbola on a semi-logarithmic graph.&lt;br&gt;&#xA;If the curve were to approach a decreasing asymptote the voltage would eventually become negative. Not something you get from a divider.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-30T13:34:50.873" LastActivityDate="2011-05-30T13:34:50.873" CommentCount="1" />
  <row Id="14825" PostTypeId="2" ParentId="14784" CreationDate="2011-05-30T07:49:29.980" Score="0" ViewCount="" Body="&lt;p&gt;There are off the shelf solutions for USB controlled relays, usually with libraries for a variety of high level languages.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-05-30T07:49:29.980" CommentCount="2" />
  <row Id="14826" PostTypeId="2" ParentId="14734" CreationDate="2011-05-30T07:55:11.193" Score="1" ViewCount="" Body="&lt;p&gt;There are earlier, alternative implementations of ADK-like functionality using the ADB protocol built into almost all android devices instead of the ADB protocol only supported by a few.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your goal is to make actual ADK products, that may not help.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If your goal is to control something with your own current personal android device, it's probably the solution you want.&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-05-30T07:55:11.193" />
  <row Id="14827" PostTypeId="2" ParentId="14686" CreationDate="2011-05-30T08:02:00.577" Score="0" ViewCount="" Body="&lt;p&gt;I suppose there is some risk involved, but basically I think you want to wire up an audio-taper potentiometer from the output of the dac to ground, and then tap off the wiper with a series capacitor to inject the signal into the mic input.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I suppose it is possible you might need a resistor between the audio input and ground as well, but my guess is you will not.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Start with the potentiometer turned all the way down, and turn it up slowly until you get the cleanest signal (get a spectral fft type of app for your testing, and run your test modulation).&lt;/p&gt;&#xA;" OwnerUserId="2246" LastActivityDate="2011-05-30T08:02:00.577" />
  <row Id="14828" PostTypeId="1" AcceptedAnswerId="14830" CreationDate="2011-05-30T12:23:44.587" Score="2" ViewCount="76" Body="&lt;p&gt;If I want to have a resolution of X * Y pixels, updating in frequency f. How do I calculate the pixel clock speed?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Example:&#xA;1280 x 1024 @ 85Hz usually have a pixel clock of 157.5 MHz, but how do I calculate the needed pixel clock?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Need to know to select DAC and DSP.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;strong&gt;Edit:&lt;/strong&gt;&#xA;Usually the Front porch is: 16 pixels 1 line, Synch width: 144 pixels 3 lines. So this is a total of 1688 x 1066 @ 85Hz. But, still the pixel clock &lt;em&gt;formula&lt;/em&gt; should be the same regardless of the extra lines and pixels.&lt;/p&gt;&#xA;" OwnerUserId="4474" LastEditorUserId="3441" LastEditorDisplayName="" LastEditDate="2011-05-30T19:55:16.283" LastActivityDate="2011-05-30T19:55:16.283" Title="How do I calculate needed pixel clock frequency?" Tags="&lt;dsp&gt;&lt;clock&gt;&lt;dac&gt;&lt;clock-speed&gt;&lt;display-timings&gt;" AnswerCount="2" />
  <row Id="14829" PostTypeId="1" CreationDate="2011-05-30T12:48:29.773" Score="1" ViewCount="157" Body="&lt;p&gt;Hi &#xA;I made a school boy error in buying the BS170. It doesn't produce enough continuous current to power my leds. They're bicolour and can only be wired in parallel hence I would need at least 2 amps! &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Since I can't return them I was wondering can I just get some transistors to amplify the current up to 2.5 amps. Also would it have a knock on effect on the resistors am using? &#xA;&lt;img src=&quot;http://i.stack.imgur.com/s4nSt.png&quot; alt=&quot;enter image description here&quot;&gt;&#xA;I have 20 copies of this circuit on strip board. Some of the leds are grouped together and switched by one mosfet hence the 2amp&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Sorry the led is actually supplied by 5v regulator which isn't on the diagram&lt;/p&gt;&#xA;" OwnerUserId="2824" LastEditorUserId="2824" LastEditorDisplayName="" LastEditDate="2011-05-30T13:04:31.180" LastActivityDate="2011-06-05T11:31:05.373" Title="how to amplify current coming out of n channel mosfet" Tags="&lt;circuit-design&gt;" AnswerCount="5" CommentCount="7" />
  <row Id="14830" PostTypeId="2" ParentId="14828" CreationDate="2011-05-30T13:28:42.253" Score="2" ViewCount="" Body="&lt;p&gt;There is more pixels in the video signal than just the x * y * refresh_rate would imply.  Back in the bad old days of CRT's, it would take time for the electron beam to move from the end of the current line to beginning of the next.  Likewise, it would take time for the beam to move from the bottom of th screen to the top for the next frame.  The time it took was built into the video signaling standard, and essentially took the form of pixels that are never seen.  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Without knowing the info on these blank pixels (sometimes called &quot;overscan&quot;), you cannot calculate the pixel clock required.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The best way to figure this stuff out is to Google for the approximate video standard you're trying to do, or look at the datasheet for the screen you are trying to drive.  &lt;/p&gt;&#xA;" OwnerUserId="3624" LastActivityDate="2011-05-30T13:28:42.253" CommentCount="3" />
  <row Id="14831" PostTypeId="2" ParentId="14829" CreationDate="2011-05-30T13:56:12.257" Score="1" ViewCount="" Body="&lt;p&gt;I'm not really sure of what you mean with &quot;Amplify&quot; the current. You can't &quot;create&quot; more current from nowhere. All your current will be drawn from your power supply through your transistor, divide into 3 paths through your LEDs and then through your transistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A serial path has the same current, so your 3 LED's should together be \$ U = 2.5 \times 3 = 7.5V\$ drop and \$I = 0.03A\$. Then you have 3 of these paths in parallel creating 3 paths of current, \$0.03A\$ each \$= 0.03A \times 3 = 0.09A\$ through the resistor.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Your resistor is there to limit the current through your LEDs. If you Drive with 19v and have a drop of 7.5V over the LEDs you need to put the remaining V over R10 \$= 19-7.5 = 11.5V\$.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The resistance should be \$R = \frac{11.5V}{0.09A} = 127.8\Omega\$ and \$P = 11.5V \times 0.09A = 1.035W\$. Still the current through BS170 and R10 are the same, 90mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;You could either switch your transistor to a bigger one \$(20 \times 90mA = 1.8A)\$ or have the same pin (from your AVR) driving multiple transistor, each driving their own circuits.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I usually use biopolar transistors such as BD435 that can drive 4A Collector to Emitter. Just put a 1K resistor in series to the base and it will operate as a switch. You could dimm all your LEDs by feeding it with a PWM signal. But in this case the transistor must be placed close to ground so the AVR signal (5V) are above the transistors threshold (BE) 0.7V.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;(I might have forgot something in the formulas, but the principle is the same).&lt;/p&gt;&#xA;" OwnerUserId="4474" LastEditorUserId="1293" LastEditorDisplayName="" LastEditDate="2011-06-02T17:37:18.123" LastActivityDate="2011-06-02T17:37:18.123" CommentCount="1" />
  <row Id="14832" PostTypeId="2" ParentId="14829" CreationDate="2011-05-30T14:01:23.167" Score="3" ViewCount="" Body="&lt;p&gt;You don't need to &quot;amplify the current&quot;. It will flow automagically when you switch the LEDs on. The thing is that you need a switch (MOSFET or BJT) which can stand the 2A.&lt;br&gt;&#xA;A power MOSFET would be ideal, since they're available with very low \$R_{DS}(on)\$, so they won't get very hot. You can do a parametric search on &lt;a href=&quot;http://www.fairchildsemi.com/tree/power-semiconductors/mosfets/parametric-form/&quot; rel=&quot;nofollow&quot;&gt;this Fairchild page&lt;/a&gt;. For example the &lt;a href=&quot;http://www.fairchildsemi.com/ds/FD/FDN339AN.pdf&quot; rel=&quot;nofollow&quot;&gt;FDN339AN&lt;/a&gt; and &lt;a href=&quot;http://www.fairchildsemi.com/ds/FD/FDN359BN.pdf&quot; rel=&quot;nofollow&quot;&gt;FDN359BN&lt;/a&gt; have low \$R_{DS}(on)\$.&lt;br&gt;&#xA;An other option is to use a darlington transistor. They're not ideal though: \$V_{CEsat}\$ is rather high, often 2V, so when you run 2A through them you need some cooling.&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-06-01T15:03:57.287" LastActivityDate="2011-06-01T15:03:57.287" CommentCount="0" />
  <row Id="14833" PostTypeId="1" AcceptedAnswerId="14835" CreationDate="2011-05-30T17:33:26.210" Score="0" ViewCount="42" Body="&lt;p&gt;Greetings, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I bought a GM862 module some while ago, I introduced the SIM card and made all the necessary conf but I always get the:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;AT+CREG?&#xA;+CREG: 0,2&lt;/p&gt;&#xA;&#xA;&lt;p&gt;response, which means that is trying to get a network but can't succesfully connect. Now the question is: Do I need to install an antenna in order to work? (I didn't bought it I tought it &lt;/p&gt;&#xA;" OwnerUserId="170" LastActivityDate="2011-05-30T17:55:00.090" Title="Help with GSM Module from Telit GM862" Tags="&lt;gsm&gt;" AnswerCount="1" />
  <row Id="14834" PostTypeId="1" AcceptedAnswerId="14842" CreationDate="2011-05-30T17:44:57.967" Score="3" ViewCount="84" Body="&lt;p&gt;I have to amplify a microphone signal to be in the range -2.5 to +2.5V. It is currently providing a signal that has a peak amplitudes of around 2V. This, however, is highly dependent on the situation (how close you hold the microphone to your mouth etc.). I need to be able to variably amplify it somehow to make the signal be in the required range. Is there a method of achieving this? I have read a bit about automatic gain control. Do you think this is the way to go?&lt;/p&gt;&#xA;" OwnerUserId="4476" LastActivityDate="2011-05-31T21:16:22.530" Title="Analogue automatic gain control" Tags="&lt;analog&gt;&lt;amplifier&gt;&lt;control&gt;" AnswerCount="3" CommentCount="3" FavoriteCount="1" />
  <row Id="14835" PostTypeId="2" ParentId="14833" CreationDate="2011-05-30T17:45:26.740" Score="2" ViewCount="" Body="&lt;p&gt;An antenna is essential if you want to connect to the network! If you look at the unit you will see a tiny coaxial socket marked GSM on the bottom edge, where the antenna needs to be attached. A similar connector marked GPS is on the upper left side, for a GPS antenna. Your Telit distributor should be able supply suitable antennae.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-30T17:55:00.090" LastActivityDate="2011-05-30T17:55:00.090" CommentCount="2" />
  <row Id="14836" PostTypeId="2" ParentId="14816" CreationDate="2011-05-30T17:55:24.463" Score="4" ViewCount="" Body="&lt;p&gt;A metastable state is similar to an unstable equilibrium. A common example of an unstable equilibrium is an &lt;a href=&quot;http://en.wikipedia.org/wiki/Inverted_pendulum&quot; rel=&quot;nofollow&quot;&gt;inverted pendulum&lt;/a&gt;. If you can balance the pendulum in a vertical position, that is a stable state. However, if anything pushes the lever to either side (air currents or ground vibrations, for example), the pendulum will not restore itself to the vertical position, it will fall down. Contrast with a regular pendulum, which if pushed to one side, will eventually settle back to vertical.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Stable equilibria are used in electrical systems to create storage elements. Unstable equlibria don't make good storage elements (since they lose their state easily), but often exist as a parasitic state.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A common digital storage element is a pair of cross-coupled inverters:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/wDo3y.png&quot; alt=&quot;Two inverters connected in a loop, output-to-input&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The storage element has two stable states, one where the node on left is at the supply voltage and the node on the right is at ground, and the other in the opposite condition. There is also an unstable state, in which each node is at some intermediate voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To better understand how the unstable state arises, recall the transfer function for an inverter. The plot of the transfer function shows the output voltage of the inverter for a given input voltage.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/yY7ip.png&quot; alt=&quot;Inverter transfer function&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The inverter is non-linear; one simple way to obtain an approximate solution of a non-linear circuit is to plot the circuit characteristics; the intersections of the plots are the solutions, or in other words, the points where the electrical characteristics of all components of the circuit are satisfied. Normally this is done with i-v plots as in &lt;a href=&quot;http://en.wikipedia.org/wiki/Diode_modelling#Graphical_solution&quot; rel=&quot;nofollow&quot;&gt;this diode example at Wikipedia&lt;/a&gt;. However, for the inverters, we'll do it with v-v plots. Overlaying a second inverter transfer function on the plot (with the axes swapped, since the second inverter is backwards:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/SNaIO.png&quot; alt=&quot;Overlayed transfer functions for back-to-back inverters&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are three intersections of the plots: one at (0, Vs), one at (Vs, 0), and one at (Vs/2, Vs/2). The (Vs/2, Vs/2) state is metastable. After a small perturbation of either node, the circuit will almost always settle to one of the stable states rather than returning to (Vs/2, Vs/2).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The way to write a value to the dual-inverter storage element is to force one of the nodes to the desired value using a driver that is stronger than the inverters. One common way to do this is with a pass transistor:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/oXSVU.png&quot; alt=&quot;Cross-coupled inverters with pass transistor&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you connect the gate of the pass transistor to the clock, you have a D latch (I'm leaving out the output structure). When the clock is high, enabling the pass transistor, the latch is transparent &amp;mdash; input passes directly to output. When the clock is low, the latch holds the previous value. Metastability arises at the moment the latch samples. If the input is a stable high or low voltage when the latch samples, then it will work properly. However, if the input is around the Vs/2 point when the latch samples, there's a possibility the latch will end up in the metastable (Vs/2, Vs/2) state. Once it's in the metastable state, it can stay there indefinitely (assuming the latch isn't clocked again), but since it's an unstable equilibrium, something usually happens relatively quickly to knock it out of the metastable state. &lt;/p&gt;&#xA;&#xA;&lt;h2&gt;When to worry about metastability&lt;/h2&gt;&#xA;&#xA;&lt;p&gt;If your storage elements are going metastable, then you're at the very least losing some of the timing budget for the downstream logic. The logic can't perform the desired evaluation until the metastable state resolves. In the worst case, the metastable state persists or propagates through logic, and downstream storage elements also go metastable, or multiple related storage elements capture inconsistent values.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Properly designed and functioning synchronous logic doesn't have problems with metastability. The clock period is longer than the evaluation time for the logic, all the flip-flop inputs are stable at the next clock edge (setup requirement satisfied), and they all load a valid value.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some of the common situations where metastability is a concern are:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Logic sampling an external input, for example, a switch on the front panel, or the output of monitor circuits that may transition at any time (undervoltage, overtemp).&lt;/li&gt;&#xA;&lt;li&gt;Logic using multiple clocks that don't have a synchronous relationship. This often arises with I/O interfaces that have particular clock requirements, but also occurs internally when different parts of a chip have different performance requirements. For example, not all of the logic in your 3 GHz CPU is actually running at 3 GHz. (A CPU is not a great example, though, since many of the clocks in a CPU are synchronous multiples of each other.) &lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-05-30T17:55:24.463" CommentCount="2" />
  <row Id="14837" PostTypeId="1" CreationDate="2011-05-30T18:16:23.190" Score="1" ViewCount="72" Body="&lt;p&gt;I bought the Sparkfun's &lt;a href=&quot;http://www.sparkfun.com/products/555&quot; rel=&quot;nofollow&quot;&gt;Uberboard&lt;/a&gt; a while back and I was trying to run the &lt;a href=&quot;http://www.sparkfun.com/tutorials/94&quot; rel=&quot;nofollow&quot;&gt;&quot;Bootloader Tutorial&quot;&lt;/a&gt; I followed all the instructions, got the FW.SFE file, but when the Uberboard resets it does not load the code. I got the following:&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;SparkFun USB Bootloader v1.1 Boot up&#xA;  complete No USB Detected Failed&#xA;  Reading Header opening filesystem&#xA;  failed Root open &quot;UART0 setup...ing&#xA;  firmware...&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;The &quot;Failed reading header&quot; what does it means? help, anyone? :S&lt;/p&gt;&#xA;" OwnerUserId="170" LastActivityDate="2011-06-04T06:07:48.823" Title="Sparkfun's Uberboard HELP" Tags="&lt;arm7&gt;&lt;sparkfun&gt;" AnswerCount="1" CommentCount="2" />
  <row Id="14838" PostTypeId="2" ParentId="14828" CreationDate="2011-05-30T18:23:11.687" Score="0" ViewCount="" Body="&lt;p&gt;If you have a particular display you need to drive, then it is best to look for a spec for that display. Modern displays are reasonably forgiving, however.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are VESA standards for calculating display timings. The more recent standard is the CVT; it was preceded by the GTF. If you have access to a machine with X.org, there are command-line utilities to calculate the timings: &lt;a href=&quot;http://www.x.org/archive/X11R7.5/doc/man/man1/gtf.1.html&quot; rel=&quot;nofollow&quot;&gt;GTF&lt;/a&gt; &lt;a href=&quot;http://www.x.org/archive/X11R7.5/doc/man/man1/cvt.1.html&quot; rel=&quot;nofollow&quot;&gt;CVT&lt;/a&gt;. You may be able to get Excel calculators from VESA with a &lt;a href=&quot;http://www.vesa.org/vesa-standards/free-standards/&quot; rel=&quot;nofollow&quot;&gt;free registration&lt;/a&gt;, I haven't tried it though.&lt;/p&gt;&#xA;" OwnerUserId="3441" LastActivityDate="2011-05-30T18:23:11.687" />
  <row Id="14839" PostTypeId="1" CreationDate="2011-05-30T18:27:24.683" Score="3" ViewCount="73" Body="&lt;p&gt;I am designing my own MP3 player now. While decoding &amp;amp; all digital backend looks straightforward, I am only puzzled with audio output (i.e. DAC-&gt;Amplifier part). My goals are 1: sound quality 2: power efficiency. Price is not important.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My previous approach (looking for I2S DAC with integrated D-class amplifier) seems to be bad idea as for some reason there are just no low-power D-class amplifiers.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I see some DAC's have integrated headphones amplifiers (AB-class). I am scared a little, as they probably eat too much energy...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Other ways might be getting bare I2S DAC and building my own analog frontend on high-quality opamps. Power consumption is still a problem here (+all fun of having dual-rail power on battery powered device).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Any ideas? Or will I have to spend 80-100mW just to drive headphones at 40mW and have barely 10 hours of battery time...&lt;/p&gt;&#xA;" OwnerUserId="2062" LastEditorUserId="3028" LastEditorDisplayName="" LastEditDate="2011-05-31T06:36:19.630" LastActivityDate="2011-05-31T06:36:19.630" Title="DAC and/or output amplifier selection for a MP3 player?" Tags="&lt;audio&gt;&lt;amplifier&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" />
  <row Id="14840" PostTypeId="2" ParentId="14839" CreationDate="2011-05-30T19:29:22.060" Score="1" ViewCount="" Body="&lt;p&gt;How about &lt;a href=&quot;http://www.national.com/cat/index.cgi?i=i//268%3as//502//Class%20D%3am//502//18%3am//502//11%3am//502//3%3am//502//1%3am//501//17%3am//501//9%3am//501//2&quot; rel=&quot;nofollow&quot;&gt;one of these Class D amplifier parts&lt;/a&gt; which are very efficient?&lt;/p&gt;&#xA;" OwnerUserId="1225" LastActivityDate="2011-05-30T19:29:22.060" CommentCount="4" />
  <row Id="14841" PostTypeId="2" ParentId="14834" CreationDate="2011-05-30T20:09:24.777" Score="1" ViewCount="" Body="&lt;p&gt;Your instinct about automatic gain control (AGC) is correct. AGC is also sometimes known as 'compression' in the audio world. Essentially it is a variable gain amplifier, that conditions a signal to keep its overall level within some desired range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A signal that varies in intensity a lot is said to have a lot of 'dynamic range', which is often considered desirable when listening to music. However, broadcasters prefer to have a more level power output, and will typically compress the audio so that the modulated power output stays more constant. You'll also encounter AGC in shortwave radios, where atmospheric conditions can cause signal intensities of distant stations to fluctuate wildly.&lt;/p&gt;&#xA;" OwnerUserId="740" LastActivityDate="2011-05-30T20:09:24.777" />
  <row Id="14842" PostTypeId="2" ParentId="14834" CreationDate="2011-05-30T20:34:01.583" Score="1" ViewCount="" Body="&lt;p&gt;You need to rectify and filter the output, to get a DC signal that varies with the output level. A single-stage amplifier is often used before the rectifier. The DC signal is used to provide feedback to a gain control element at the amplifier input. Something like a FET is often used, with the feedback signal amplified by an op amp. The feedback has to be negative, of course. The system will need some tuning, to avoid problems with the gain rising when there are quiet periods, so that the first syllable of the next word comes out at high volume, before the AGC kicks in.&lt;/p&gt;&#xA;" OwnerUserId="305" LastEditorUserId="305" LastEditorDisplayName="" LastEditDate="2011-05-30T21:49:04.493" LastActivityDate="2011-05-30T21:49:04.493" />
  <row Id="14843" PostTypeId="1" CreationDate="2011-05-30T20:41:21.477" Score="-1" ViewCount="43" Body="&lt;p&gt;Hi,this is my first post.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm looking to develop a mobile application that interacts with a bluetooth module (ideally a credit card sized form factor), but small and thin of any kind of work. I have the mobile application development skills, but need some help on the bluetooth module.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The module can have a blinking light or beeper functionality based on proximity to paired devices, and should be able to interact with the phone app without requiring a heavy power source. A keypad for input on the bluetooth would be a nice to have, but something for later. I have found some modules, but they are all 2.5+ mm and ideally I would prefer something in the 0.5-1.5mm range.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;A simple use case would be to alert if the card moves out of a particular range set by the application.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If this question has already been answered, please direct me to the appropriate thread.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Please also let me know where I can buy such a module for developing my prototype, and any useful materials on programming for bluetooth devices.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Thanks,&lt;/p&gt;&#xA;" OwnerUserId="4478" LastActivityDate="2011-05-30T20:41:21.477" ClosedDate="2011-05-31T01:58:29.933" Title="credit card form factor for bluetooth module" Tags="&lt;bluetooth&gt;" CommentCount="2" />
  <row Id="14844" PostTypeId="1" CreationDate="2011-05-30T21:54:31.907" Score="0" ViewCount="38" Body="&lt;p&gt;I need to record whatever I am playing on my keyboard (CASIO CTK-5000) on my PC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've looked up the Web for a place I could buy a USB interface cable that would channel the output from the keyboard into a PC. I haven't found any.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've also looked in local stores. No luck there either.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Could you please help me if you know where I could find one?&lt;/p&gt;&#xA;" OwnerUserId="4479" LastActivityDate="2011-05-30T21:54:31.907" ClosedDate="2011-05-31T01:56:56.797" Title="Keyboard CASIO CTK-5000 to PC Line In" Tags="&lt;keyboard&gt;" CommentCount="2" />
  <row Id="14845" PostTypeId="1" AcceptedAnswerId="14856" CreationDate="2011-05-31T05:12:51.417" Score="3" ViewCount="104" Body="&lt;p&gt;I'm thinking of changing to lead-free solder. I've heard some people prefer a traditional Pb/Sn solder, but haven't heard any specific reasons why.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm mostly doing through-hole work, and I have a decent temperature-controlled iron.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, are there any issues I might encounter with changing over? And are there any situations where I'd want to use a particular type?&lt;/p&gt;&#xA;" OwnerUserId="3028" LastActivityDate="2011-05-31T12:37:22.320" Title="Any issues with changing to lead-free solder?" Tags="&lt;soldering&gt;&lt;rohs&gt;" AnswerCount="3" FavoriteCount="2" />
  <row Id="14846" PostTypeId="1" CreationDate="2011-05-31T07:20:00.893" Score="-4" ViewCount="111" Body="&lt;p&gt;hi&#xA;My circuit has a huge load and so the volts is dropping considerably hence each component isn't getting alot of potential.  I was wondering how difficult is it to build a multi rail psu? Could you post an example for me to have a go at.&lt;/p&gt;&#xA;" OwnerUserId="2824" LastActivityDate="2011-06-05T20:03:21.650" Title="how to build a multi rail psu 5v" Tags="&lt;circuit-design&gt;" AnswerCount="4" CommentCount="3" />
  <row Id="14847" PostTypeId="2" ParentId="14845" CreationDate="2011-05-31T08:42:26.237" Score="5" ViewCount="" Body="&lt;p&gt;DO not use lead free unless you really really need to. And even then consider if anyone's going to find out it's not leadfree. &#xA;Temeratures are higher, so more risk of part &amp;amp; PCB damage, and it doesn't flow as nicely. Desoldering through-holes with leadfree is a bitch, to the extent that it's easier to first flood it with leaded. It also eats through tips way faster than leaded. &#xA;The flux fumes are also more unpleasant than leaded fluxes. &#xA;If you really must do leadfree, use the stuff with 2% silver as this has a lower melting point and produces nicer joints.&lt;/p&gt;&#xA;" OwnerUserId="1681" LastEditorUserId="1681" LastEditorDisplayName="" LastEditDate="2011-05-31T11:42:24.683" LastActivityDate="2011-05-31T11:42:24.683" />
  <row Id="14848" PostTypeId="1" AcceptedAnswerId="14867" CreationDate="2011-05-31T08:56:35.327" Score="3" ViewCount="85" Body="&lt;p&gt;Ok, my next PIC18 problem...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;USART - I can't get it to transmit anything sensible.  All I get is random x's and inverted question marks.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I am using the same BAUD settings as I have used many times on PIC16s quite happily.  I have tried re-calculating the baud setting from the formula, I have tried different baud rates and different crystal frequencies to give different baud accuracies, but still all I get is the same two wrong characters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If I change the baud to something completely wrong it puts more random gibberish than just these two characters.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/ow7fW.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have tried this on 2 different PIC18s - both my '4455 and my '14K50 - both do exactly the same.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Here's my program:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;void main()&#xA;{&#xA;    OpenUSART ( USART_TX_INT_OFF &amp;amp;&#xA;                USART_RX_INT_OFF &amp;amp;&#xA;                USART_ASYNCH_MODE &amp;amp;&#xA;                USART_EIGHT_BIT &amp;amp;&#xA;                USART_BRGH_HIGH &amp;amp;&#xA;                USART_CONT_RX, 103);&#xA;    baudUSART(  BAUD_IDLE_CLK_HIGH &amp;amp;&#xA;                BAUD_8_BIT_RATE &amp;amp;&#xA;                BAUD_WAKEUP_OFF &amp;amp;&#xA;                BAUD_AUTO_OFF);&#xA;    while(1)&#xA;    {&#xA;&#xA;        WriteUSART('F');&#xA;        WriteUSART('o');&#xA;        WriteUSART('o');&#xA;        WriteUSART(13);&#xA;        WriteUSART(10);&#xA;    }&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;The 103 I caclulated from a 16MHz crystal at 9600 baud according to the formula in the data sheet for the PIC.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So what am I missing?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;&lt;strong&gt;UPDATE&lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Timing the data stream with a 'scope I have determined that it is infact running at 2400 baud (setting the computer to 2400 baud confirms it).&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I have checked and the crystal is oscillating at 16MHz.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The formula for calculating the BAUD is:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$\frac{F_{osc}}{(16*(n+1))}\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;where &lt;em&gt;Fosc&lt;/em&gt; is the is the oscillator frequency, and &lt;em&gt;n&lt;/em&gt; is the number passed to the baud rate generator. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$\frac{16,000,000}{(16*(103+1))} = \frac{16,000,000}{(16 * 104)} = \frac{16,000,000}{1664} = 9615.384615385\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So why is it actually running at 2400 baud???&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;em&gt;I know it's not my calculations - the table of bauds in the datasheet quotes 119 for a 9600 baud on an 18.432MHz crystal, so 103 for a 16MHz is perfectly reasonable.&lt;/em&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Things I have tried:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;Switch to BRGH=0 - slows the baud down even more&lt;/li&gt;&#xA;&lt;li&gt;Switch to 16-bit timer not 8-bit - slows the baud down to a crawl.&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;So what is strange about this UART then?&lt;/p&gt;&#xA;" OwnerUserId="4245" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-01T10:56:58.570" LastActivityDate="2011-06-01T10:56:58.570" Title="PIC18 USART problem" Tags="&lt;pic&gt;&lt;uart&gt;" AnswerCount="2" CommentCount="14" />
  <row Id="14849" PostTypeId="2" ParentId="14845" CreationDate="2011-05-31T09:23:44.193" Score="2" ViewCount="" Body="&lt;p&gt;Well... try by yourself and you'll discover the reason why peoples don't use lead free solder unless they're forced to.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;My supplier, when I go buy solder, always asks me &quot;Do you need lead-free solder or do you want the working one?&quot; :-)&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-05-31T09:23:44.193" />
  <row Id="14850" PostTypeId="2" ParentId="14848" CreationDate="2011-05-31T09:46:57.877" Score="1" ViewCount="" Body="&lt;p&gt;This test program worked OK with an 18F4520:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;/Test.c&#xA;//Tx RC6 (pin 44)&#xA;//Rx RC7 (pin 1)&#xA;&#xA;#include &amp;lt;p18cxxx.h&amp;gt;&#xA;#include &amp;lt;usart.h&amp;gt;&#xA;&#xA;#pragma config OSC = INTIO67, MCLRE = ON&#xA;&#xA;void main (void)&#xA;{&#xA;    char c;&#xA;&#xA;    TRISC = 0x80;       // RC6 output, RC7 input&#xA;&#xA;    // Internal osc. 8 MHz, PLL 4x&#xA;    OSCCON |= 0x72;&#xA;    OSCTUNEbits.PLLEN = 1;&#xA;&#xA;    // wait until IOFS = 1 (osc. stable)&#xA;    while (!OSCCONbits.IOFS)&#xA;        ;&#xA;&#xA;&#xA;/*&#xA;* Open the USART configured as&#xA;* 8N1, 2400 baud, in polled mode&#xA;*/&#xA;  OpenUSART (USART_TX_INT_OFF &amp;amp;&#xA;             USART_RX_INT_OFF &amp;amp;&#xA;             USART_ASYNCH_MODE &amp;amp;&#xA;             USART_EIGHT_BIT &amp;amp;&#xA;             USART_CONT_RX &amp;amp;&#xA;             USART_BRGH_HIGH, 103);&#xA;&#xA;    while (1)&#xA;    {&#xA;        putcUSART('1');&#xA;        c = 0;&#xA;        c = getcUSART();&#xA;        Nop();&#xA;    }&#xA;&#xA;}&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="305" LastEditorUserId="566" LastEditorDisplayName="" LastEditDate="2011-05-31T10:07:30.707" LastActivityDate="2011-05-31T10:07:30.707" CommentCount="2" />
  <row Id="14851" PostTypeId="2" ParentId="14610" CreationDate="2011-05-31T09:47:45.333" Score="2" ViewCount="" Body="&lt;p&gt;Linear Technology has a broad offer of SMPS controllers. Check &lt;a href=&quot;http://www.linear.com/products/step-down_%28buck%29_regulators&quot; rel=&quot;nofollow&quot;&gt;this page&lt;/a&gt; for a parametric search.&lt;br&gt;&#xA;One example which fits your requirements is the &lt;a href=&quot;http://www.linear.com/product/LTC3611&quot; rel=&quot;nofollow&quot;&gt;LTC3611&lt;/a&gt;. It comes in a (for a buck controller) rather unusual QFN64 package, but doesn't require any external active components (MOSFETs).  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/Zr2ud.png&quot; alt=&quot;enter image description here&quot;&gt;  &lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you don't like soldering QFN packages, Linear has an evaluation kit for this. (Hm, pretty steep price. I never took notice of price before, as Linear was always so generous as to give them to us for free.)&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-06-02T10:31:56.910" LastActivityDate="2011-06-02T10:31:56.910" />
  <row Id="14852" PostTypeId="1" AcceptedAnswerId="14853" CreationDate="2011-05-31T10:28:38.827" Score="3" ViewCount="193" Body="&lt;p&gt;I have a simple circuit:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/gwgWL.png&quot; alt=&quot;circuit&quot;&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;The max rating (current) of the LED is 30mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;How can I work out what the resistance of the resistor needs to be? By using ohm's law I found it to be &lt;code&gt;3/0.03 = 100 ohm&lt;/code&gt;. However using software called &lt;a href=&quot;http://www.yenka.com/&quot; rel=&quot;nofollow&quot;&gt;Yenka&lt;/a&gt;, and trial and error I got the minimum possible resistance to be 36 &amp;Omega;. However, if I use a 35 &amp;Omega; resistor, then the LED breaks. Is the software wrong, or (more likely) am I doing something wrong?&lt;/p&gt;&#xA;" OwnerUserId="1982" LastEditorUserId="689" LastEditorDisplayName="" LastEditDate="2011-06-01T10:54:18.867" LastActivityDate="2011-06-05T13:51:38.397" Title="How do I calculate the resistor value for a simple LED circuit?" Tags="&lt;led&gt;&lt;circuit&gt;&lt;resistance&gt;" AnswerCount="4" CommentCount="5" FavoriteCount="1" />
  <row Id="14853" PostTypeId="2" ParentId="14852" CreationDate="2011-05-31T10:38:52.617" Score="9" ViewCount="" Body="&lt;p&gt;You'll have to check the datasheet or measure it to know how much voltage drops over your LED. Let's say this is 2V. Then the voltage over the resistor is the difference between your power supply (3V) - voltage over the LED (2V) = 1V. To get 30 mA through the resistor (and thus also the LED) your resistor has to be 1V / 30 mA = 33 Ohm.&lt;br&gt;&#xA;If your LED voltage is lower the current will be somewhat higher, but the LED shouldn't break!&lt;/p&gt;&#xA;" OwnerUserId="2064" LastEditorUserId="2064" LastEditorDisplayName="" LastEditDate="2011-05-31T11:13:13.090" LastActivityDate="2011-05-31T11:13:13.090" CommentCount="10" />
  <row Id="14854" PostTypeId="2" ParentId="14852" CreationDate="2011-05-31T11:26:08.890" Score="5" ViewCount="" Body="&lt;p&gt;You have to take in count the \$V_{F_{typ}}\$ of the LED. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;Let's take a red LED as example:&lt;/p&gt;&#xA;&#xA;&lt;ul&gt;&#xA;&lt;li&gt;\$I_{F_{max}} = 30mA\$&lt;/li&gt;&#xA;&lt;li&gt;\$V_{F_{typ}} = 1.7V\$&lt;/li&gt;&#xA;&lt;li&gt;\$V_{F_{max}} = 2.1V\$&lt;/li&gt;&#xA;&lt;li&gt;\$V_{R_{max}} = 5V\$&lt;/li&gt;&#xA;&lt;/ul&gt;&#xA;&#xA;&lt;p&gt;The LED and the resistance (R) are in series. The source voltage (3V) is the summation of voltage across the LED (\$V_{F_{typ}}\$) and the voltage across the resistance (\$V_{Res}\$). To calculate R we need to know the voltage on the resistance. Let's use the maximum current, but normally is used 15mA.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$R = \frac{V_{Res}}{I_{F_{max}}}\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, &lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$V_{Res} = V - V_{F_{typ}}\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$V_{Res} = 3 - 1.7\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$V_{Res} = 1.3V\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$R = \frac{V_{Res}}{I_{F_{max}}} = \frac{1,3}{0,03} = 43,33\Omega\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It's important calculate power dissipation in the resistor, too:&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$P_{res} = V_{res} * I_{F_{max}}\$&lt;/p&gt;&#xA;&#xA;&lt;p&gt;\$P_{res} = 1.3 * 0,03 = 0,039W\$ (You can use 1/8W or 1/10W)&lt;/p&gt;&#xA;" OwnerUserId="938" LastEditorUserId="938" LastEditorDisplayName="" LastEditDate="2011-06-01T10:38:22.107" LastActivityDate="2011-06-01T10:38:22.107" CommentCount="3" />
  <row Id="14855" PostTypeId="1" CreationDate="2011-05-31T12:30:19.867" Score="-1" ViewCount="39" Body="&lt;p&gt;I drive stepper motor using 298 ic giving clock pulse using4151 ic . i connected the 120slot disc ti motor shaft using one opto coupler. output from the opto coupler give the frequency accirding to speed of motor. it is not giving linear frequency to output of the opto coupler. it fluctuate at the lower speed &lt;/p&gt;&#xA;" OwnerUserId="4485" LastActivityDate="2011-05-31T12:30:19.867" ClosedDate="2011-05-31T14:11:47.190" Title="stepper motor using opto disc" Tags="&lt;stepper-motor&gt;" CommentCount="1" />
  <row Id="14856" PostTypeId="2" ParentId="14845" CreationDate="2011-05-31T12:37:22.320" Score="4" ViewCount="" Body="&lt;p&gt;Workmanship is more challening with Pb-free solder, due to degraded wetting and a higher melt point. It is often more difficult to visually verify a cold-solder joint by visual inspection, because most Pb-free solder joints 'look' cold if you judge with the same criteria that is normally used to judge conventional solder joints.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Also, Pb-free is much more prone to &lt;a href=&quot;http://nepp.nasa.gov/whisker/background/&quot; rel=&quot;nofollow&quot;&gt;tin whiskers&lt;/a&gt; than conventional solder - in fact, way back in the day (decades ago) this was one of the reasons lead was added to solder (it's the most effective whiskering inhibitor known). Tin whisker-induced failures are more common with dense layouts and usually happen months or years after assembly.&lt;/p&gt;&#xA;" OwnerUserId="1293" LastActivityDate="2011-05-31T12:37:22.320" />
  <row Id="14857" PostTypeId="1" AcceptedAnswerId="14859" CreationDate="2011-05-31T13:05:15.037" Score="3" ViewCount="154" Body="&lt;p&gt;I'm trying my first real project with an arduino of my own design/idea.&#xA;I come from a CS background this EE stuff is both exciting and scary. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;I'm trying to wire up a 3.5mm female audio jack to the Arduino, via my breadboard.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I've just finished soldering some wires to the jack (my first time with the solder) but now I have hit an issue I didn't think of: the wire I'm using is made of 10's of little copper wires, this seems normal enough, but I've only ever plugged in larger solid single-thread wires in to my arduino.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Do I somehow have to fuse the little ones together to be able to plug this in? Or can I just kinda shove it in?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;END NOTE: Thanks every one for your suggestions!&#xA;Thanks guys, and sorry for the lack of proper terminology, as I said, I'm from CS and very new to any thing to do with EE.&lt;/p&gt;&#xA;" OwnerUserId="4486" LastEditorUserId="4486" LastEditorDisplayName="" LastEditDate="2011-06-01T16:04:37.013" LastActivityDate="2011-06-01T21:50:46.783" Title="How to fuse wires into single solid thread?" Tags="&lt;soldering&gt;&lt;wire&gt;" AnswerCount="6" CommentCount="3" />
  <row Id="14858" PostTypeId="2" ParentId="14857" CreationDate="2011-05-31T13:33:23.253" Score="3" ViewCount="" Body="&lt;p&gt;Heat the stranded wire from the end.  In a few seconds, dab at it with a bit of flux-cored solder.  You're trying to get a bit of flux to melt into the strands.  A couple of seconds later, the wire should be hot enough to melt the solder.  Dab it again and let just a tiny solder melt into the strands; it will be enough to bind them.&lt;/p&gt;&#xA;" OwnerUserId="3361" LastActivityDate="2011-05-31T13:33:23.253" CommentCount="1" />
  <row Id="14859" PostTypeId="2" ParentId="14857" CreationDate="2011-05-31T13:34:16.840" Score="8" ViewCount="" Body="&lt;p&gt;The best way to use stranded wire with a solderless breadboard is to solder the end to a short length of solid wire (the same stuff that you use for your normal connections), and plug that in. You need to remove the insulation from the solid wire, of course.&lt;/p&gt;&#xA;" OwnerUserId="305" LastActivityDate="2011-05-31T13:34:16.840" CommentCount="2" />
  <row Id="14860" PostTypeId="2" ParentId="14857" CreationDate="2011-05-31T13:50:37.027" Score="1" ViewCount="" Body="&lt;p&gt;The wire you're using is called &quot;stranded&quot;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;To use stranded wire in this application, you will need to tin the wire tip.  There are several places on the internet that describe how to do it.  This one has many pictures: &lt;a href=&quot;http://www.teamnovak.com/tech_info/how_to/solder/index.html&quot; rel=&quot;nofollow&quot;&gt;http://www.teamnovak.com/tech_info/how_to/solder/index.html&lt;/a&gt;.  This one has several good points: &lt;a href=&quot;http://www.kpsec.freeuk.com/solder.htm&quot; rel=&quot;nofollow&quot;&gt;http://www.kpsec.freeuk.com/solder.htm&lt;/a&gt;.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Some key points: cleanliness is key to a good solder joint.  Too much solder is just as bad as too little.  And be very mindful of the soldering iron tip.  I accidentally gave myself a nasty burn on my thumb when I was first learning to solder; it took a month to fully heal.&lt;/p&gt;&#xA;" OwnerUserId="4409" LastActivityDate="2011-05-31T13:50:37.027" />
  <row Id="14861" PostTypeId="2" ParentId="14857" CreationDate="2011-05-31T14:00:19.927" Score="5" ViewCount="" Body="&lt;p&gt;I usually solder the wire to the &quot;short&quot; part of a header strip pin. &#xA;&lt;img src=&quot;http://i.stack.imgur.com/IJ4ps.jpg&quot; alt=&quot;Strip Image&quot;&gt;&lt;/p&gt;&#xA;" OwnerUserId="244" LastActivityDate="2011-05-31T14:00:19.927" CommentCount="3" />
  <row Id="14863" PostTypeId="2" ParentId="14857" CreationDate="2011-05-31T15:59:51.310" Score="0" ViewCount="" Body="&lt;p&gt;Well, you can actually force a stranded wire into a breadboard or a socket such as the one in Arduino, but it will take some time and effort. If the wire isn't rigid enough to get in the socket, pushing it inside with another solid wire, like one form an end of a resistor helps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;One way I found useful was to use 3 $\Omega$ resistors which I had lying around. They are small enough that they won't make a major impact in most circuits. Just plug one side of the resistor into a socket and wrap the wire around the other side. For a better connection, bend the end of the resistor by say 90 degrees or more. This way, the wrapped wire won't just slide off. &lt;/p&gt;&#xA;&#xA;&lt;p&gt;This method won't actually modify a wire, won't require you to solder it or to try to shape a bit of molten solder, which could sometimes be a problem, and is relatively cheap and very quick. The downside is that you'll need resistors with low enough resistance which won't make a big impact on the circuit. &lt;/p&gt;&#xA;" OwnerUserId="1240" LastActivityDate="2011-05-31T15:59:51.310" CommentCount="1" />
  <row Id="14864" PostTypeId="2" ParentId="12312" CreationDate="2011-05-31T18:40:38.023" Score="1" ViewCount="" Body="&lt;p&gt;One point not yet mentioned about hysteresis: any circuit with hysteresis has some possibility of exhibiting metastability on either the rising or falling edge (circuits may be designed to eliminate the probability of metastability in one direction, at the expense of increasing it in the other).  For example, if an input is designed to switch high at precisely 2.10 volts and low at precisely 2.00 volts, one can pretty well figure that if the input goes to 2.15 volts, it will be regarded as high until it goes below 2.00 volts.  If, however, the input goes to precisely 2.10 volts and then down to 2.05, it's possible that the registered value might never go high, go high and stay high, go high and then low, or even start going randomly high and low until such time as the input goes above 2.10 or below 2.00 volts.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;There are a variety of ways to minimize the risk of an input gate going into a metastable state, but the possibility cannot be totally avoided.  One could have a three-state output with &quot;clean high&quot;, &quot;clean low&quot;, and &quot;uncertain&quot; states, and guarantee that if &quot;clean high&quot; was asserted, &quot;clean low&quot; could not be asserted unless the input fell below 2.0 volts, and likewise if &quot;clean low&quot; was asserted, &quot;clean high&quot; could not be asserted until the input rose above 2.10 volts.  Unfortunately, there'd be no way to prevent oscillation between &quot;clean high&quot; and &quot;uncertain&quot;, or between &quot;clean low&quot; and &quot;uncertain&quot;.  One could try to latch the &quot;clean high&quot; and &quot;clean low&quot; signals, but there'd be no way to guarantee that they wouldn't violate the setup/hold times of whatever latching circuit one tried to use.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-31T18:40:38.023" CommentCount="1" />
  <row Id="14865" PostTypeId="2" ParentId="10752" CreationDate="2011-05-31T19:31:12.917" Score="1" ViewCount="" Body="&lt;p&gt;If you do a 2 sided PCB and plan on doing one sided mounting all SMT except for minimal throughole.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Then, when you order your PCBs, you can order a solder paste template. You can put together a wooden holder with a bottom into which the board fits exactly. Pop in a PCB, place the solder template in there, then put some solder paste in there and use a squeegee (you can get them at a paint store) cut to fit it, and then just spread the paste over the board. Then remove the template and the PCB should have the correct paste on it (remember to clean the template). Then just place the components carefully.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For an oven, you can use the Black and Decker Infrawave series. It's important to get a good temperature profile (to not heat up too quickly or cool too quickly). There are many articles online on this oven. You can also use the Cuisinart convection toaster too.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, you can do 4 board easily at a time this way, easily in 10 minutes if they are small boards. Thats 24 per hour. You hire someone at $24/hour. Thats $1 per board!!!!!!!&#xA;It'll take one person a little over a week to do 1000 boards. Recommended you use diagnostics in your flash to test the board and light an LED. You can always load diagnostics, run the test, then load your desired code and lock the MCU....it you are trying to save space. Testing the boards is the slow part perhaps.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;For enclosure, you'll want to use an off the shelf plastic box. I don't know of a cheap fast way to do your own enclosures. Vacuum forming can work, but it's still slower than 24 per hour. Remember 24 per hour is $1 each, 12 per hour is $2 each, etc, etc...&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Good Luck. Post if you find other info.&lt;/p&gt;&#xA;" OwnerUserId="4492" LastActivityDate="2011-05-31T19:31:12.917" />
  <row Id="14866" PostTypeId="2" ParentId="14846" CreationDate="2011-05-31T20:05:35.443" Score="0" ViewCount="" Body="&lt;p&gt;If you need some 10-20A of total current, I would make boring 6V x20A DCDC PSU, and place separate linear regulator near each consumer. Cheap &amp;amp; easy. Each LDO eats just 1V, so total power dissipation is just 20W.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;If you need more than 20A, I would replace these individual LDOs with simple switch-mode DCDC's - choose any on your choose, with internal or external switch. This will be a little more tricky the do and more expensive, but much more efficient.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;So, the idea is that you have 1 BIG switch mode PSU, and several small LDO's or DCDC's to get required number independent voltages you need.&lt;/p&gt;&#xA;" OwnerUserId="2062" LastActivityDate="2011-05-31T20:05:35.443" />
  <row Id="14867" PostTypeId="2" ParentId="14848" CreationDate="2011-05-31T20:06:14.030" Score="3" ViewCount="" Body="&lt;p&gt;The problem here is that Microchip sneakily defaulted the CPUDIV to /4 meaning the internal clock of the PIC was running at a quarter of the expected frequency - thus the calculations were all wrong.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;It took some time to figure this out, but setting&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;#pragma config CPUDIV = NOCLKDIV&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;&#xA;&lt;p&gt;appears to fixed the problem.  Also, because I am using a MAX232 linked to the output I have to invert the signals:&lt;/p&gt;&#xA;&#xA;&lt;pre&gt;&lt;code&gt;baudUSART(BAUD_IDLE_CLK_LOW &amp;amp; &#xA;          BAUD_AUTO_OFF &amp;amp; &#xA;          BAUD_8_BIT_RATE &amp;amp; &#xA;          BAUD_IDLE_RX_PIN_STATE_HIGH);&#xA;&#xA;OpenUSART (USART_TX_INT_OFF &amp;amp;&#xA;           USART_RX_INT_OFF &amp;amp;&#xA;           USART_ASYNCH_MODE &amp;amp;&#xA;           USART_EIGHT_BIT &amp;amp;&#xA;           USART_CONT_RX &amp;amp;&#xA;           USART_ADDEN_OFF &amp;amp;&#xA;           USART_BRGH_HIGH, 103);&#xA;&lt;/code&gt;&lt;/pre&gt;&#xA;" OwnerUserId="4245" LastActivityDate="2011-05-31T20:06:14.030" />
  <row Id="14868" PostTypeId="2" ParentId="8164" CreationDate="2011-05-31T20:44:45.600" Score="0" ViewCount="" Body="&lt;p&gt;Yes, there is. It is &quot;Slot coupled waveguide&quot;. Though it is not as pure as just 2 coupled capacitors, but it is nearly 100% capacitance based, and involves inherent inductance and magnetic air core and more conductors.&lt;/p&gt;&#xA;" OwnerUserId="924" LastActivityDate="2011-05-31T20:44:45.600" CommentCount="2" />
  <row Id="14869" PostTypeId="2" ParentId="14834" CreationDate="2011-05-31T21:16:22.530" Score="0" ViewCount="" Body="&lt;p&gt;AGC is the way to go...&lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;Low frequency automatic gain control&#xA;  (AGC) circuits are used in audio and&#xA;  power equipment for applications such&#xA;  as sensitive microphone preamplifiers&#xA;  (preamps) and regulators. An AGC&#xA;  circuit, a closed-loop feedback&#xA;  system, is shown in Figure 1. The loop&#xA;  consists of a controllable gain&#xA;  element, a detector, a stable&#xA;  reference and a comparison circuit.&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;img src=&quot;http://i.stack.imgur.com/pqeqb.png&quot; alt=&quot;enter image description here&quot;&gt;&lt;/p&gt;&#xA;  &#xA;  &lt;p&gt;&lt;sub&gt;&lt;sup&gt;Source: &lt;a href=&quot;http://www.analog.com/static/imported-files/application_notes/AN_934.pdf&quot; rel=&quot;nofollow&quot;&gt;AN-934 60 dB Wide Dynamic Range, Low Frequency AGC Circuit Using a Single VGA&lt;/a&gt;&lt;/sup&gt;&lt;/sub&gt;&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;Fast and simple: &lt;a href=&quot;http://www.radio-kits.co.uk/radio-related/agc_amplifier/index.htm&quot; rel=&quot;nofollow&quot;&gt;Microphone AGC amplifier&lt;/a&gt;&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Datasheets can be a good source of information on a topic (even if you don't use the product specified). From Maxim... &lt;/p&gt;&#xA;&#xA;&lt;blockquote&gt;&#xA;  &lt;p&gt;The &lt;a href=&quot;http://www.maxim-ic.com/datasheet/index.mvp/id/5433&quot; rel=&quot;nofollow&quot;&gt;MAX9814&lt;/a&gt; is a low-cost,&#xA;  high-quality microphone amplifier with&#xA;  automatic gain control (AGC) and&#xA;  lownoise microphone bias.&lt;/p&gt;&#xA;&lt;/blockquote&gt;&#xA;&#xA;&lt;p&gt;AGC can also be implemented in software: &lt;a href=&quot;http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&amp;amp;nodeId=2680&amp;amp;dDocName=en542097&quot; rel=&quot;nofollow&quot;&gt;dsPIC DSC Automatic Gain Control Library&lt;/a&gt; &lt;/p&gt;&#xA;" OwnerUserId="1419" LastActivityDate="2011-05-31T21:16:22.530" />
  <row Id="14870" PostTypeId="2" ParentId="14846" CreationDate="2011-05-31T21:57:46.640" Score="0" ViewCount="" Body="&lt;p&gt;You could use a standard ATX 250 watt (or bigger) power supply. It has a maximum current of 12 amps @ 5 volts, and another 2.5 amps from the 5 vsb pin. The 5 Volt outputs on 5 pins of the power connector. You did not mention what your load requirements are, however the ATX power supplies are cheap and you may add several to meet your needs.&lt;a href=&quot;http://www.formfactors.org/developer/specs/ATX12V%20PSDG2.01.pdf&quot; rel=&quot;nofollow&quot;&gt;ATX specification&lt;/a&gt;&lt;/p&gt;&#xA;" OwnerUserId="3453" LastActivityDate="2011-05-31T21:57:46.640" />
  <row Id="14871" PostTypeId="2" ParentId="7129" CreationDate="2011-05-31T22:03:43.117" Score="2" ViewCount="" Body="&lt;p&gt;The best approach IMHO is to have one hardware timer which is never written to but simply free-runs.  This will allow one to easily emulate an arbitrary of poll-able timers for durations up to half the length of the hardware timer.  To &quot;start&quot; a timer, simply compute the value of the hardware timer when it should expire.  To see if a timer has expired yet, subtract the expected expiration time from the current time (regarding both quantities as unsigned), and see if the (unsigned) result exceeds half the maximum timer value.  If so, the timer has not expired.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Alternatively, if one wants a timer for measuring time since a certain event occurred, one can simply latch the timer value when the event occurred, and later compute the difference between the latched value and the present time.&lt;/p&gt;&#xA;" OwnerUserId="3123" LastActivityDate="2011-05-31T22:03:43.117" CommentCount="2" />
</posts>